Compressed Sensing I

Hall B                        Monday 14:00-16:00                                                                           Computer 110           

14:00         4847.     Compressive Sensing and Low Contrast Detectability

Joshua D. Trzasko1, Armando Manduca1, Matt A. Bernstein1

1Mayo Clinic, Rochester, MN, United States

To date, the most successful applications of Compressive Sensing (CS) to MRI have focused on situations like contrast-enhanced MR angiography where the information of interest is represented by high-contrast features.  However, many diagnostic tasks in clinical MRI are more closely related to low-contrast object detectability (LCOD) than high-contrast detectablility.  In this work, we investigate the potential of the CS paradigm for LCOD and compare its performance against more widely-used approaches based on of zero-filling.

14:30         4848.     High-Frequency Subband Compressed Sensing MRI

Kyunghyun Sung1, Brian A. Hargreaves1

1Radiology, Stanford University, Stanford, CA, United States

Compressed sensing (CS) is a technique that allows accurate reconstruction of images from a reduced set of acquired data. Here, we present a new method, which applies CS to only high-frequency subbands to maximally utilize the wavelet characteristics while minimizing reconstruction artifacts, and allowing easy incorporation of other rapid imaging techniques.

15:00         4849.     The Influence of Various Adaptive Radial Undersampling Schemes on Compressed-Sensing L1-Regularized Reconstruction

Rachel Wai-chung Chan1, Elizabeth Anne Ramsay2, Donald Bruce Plewes2

1Medical Biophysics, University of Toronto, Toronto, ON, Canada; 2Imaging Research, University of Toronto, Toronto, ON, Canada

Adaptive radial imaging allows multiple images to be retrospectively reconstructed from the same dataset, each with a different spatial-temporal balance. It has been shown that compressed sensing reconstruction can be used reduce streak artifacts in high-temporal-resolution images created by radial undersampling. Here, we compare the effect of 3 adaptive sampling schemes (golden angle, bit-reversed, and random sampling scheme) on the ability of CS reconstruction to reduce streak artifacts, at various spatiotemporal resolutions. Results show that CS reconstruction lowers the degree of error and mostly preserves the differences among sampling schemes compared to Fourier reconstruction.

15:30         4850.     Efficient Non-Contrast-Enhanced MRA with Inflow Inversion Recovery by Skipped Phase Encoding and Edge Deghosting (SPEED)

Zheng Chang1, Qing-San Xiang2,3, Hao Shen4, Fang-Fang Yin1

1Department of Radiation Oncology, Duke University, Durham, NC, United States; 2Department of Physics and Astronomy, University of British Columbia, Vancouver, bc, Canada; 3Department of Radiology, University of British Columbia, Vancouver, BC, Canada; 4Applied Science Laboratory, GE Healthcare, Beijing, China

Skipped Phase Encoding and Edge Deghosting (SPEED) has been demonstrated effective in accelerating typical MRI. In this work, SPEED is further developed to achieve higher efficiency in accelerating non-contrast-enhanced MRA with inflow inversion recovery (IFIR). IFIR employs an inversion recovery pulse to suppress signals from static tissue, while leaving inflow arterial blood unaffected, resulting in visible vasculature on modest tissue background.  By taking advantages of sparsity of vasculature, SPEED with a single-layer-model can achieve higher efficiency than that achievable with a double-layer-model. The technique is demonstrated with a 3D renal IFIR study achieving undersmapling factors up to 5.

                                   Tuesday 13:30-15:30                                                                          Computer 110           

13:30         4851.     Partial Fourier Compressed Sensing

Mariya Doneva1, Peter Börnert2, Holger Eggers2, Alfred Mertins1

1University of Lübeck, Lübeck, Germany; 2Philips Research Europe, Hamburg, Germany

This work considers an extension of the frequently used partial Fourier imaging to a combination with compressed sensing and parallel imaging. The sampling pattern and the reconstruction have been adjusted to allow a combined multi-coil partial Fourier compressed sensing reconstruction, which could benefit from the different  fast imaging methods, potentially achieving even higher acceleration factors. The basic feasibility of the proposed method has been demostrated on in vivo brain data.

14:00         4852.     Non-Convex Greedy Compressed Sensing for Phase Contrast MRI

Daehyun Yoon1, Jeffrey Fessler1, Jon-Fredrik Nielsen2, Anna Gilbert3, Douglas Noll2

1Electrical Engineering, University of Michigan, Ann Arbor, MI, United States; 2Biomedical Engineering, University of Michigan; 3Mathematics, University of Michigan

We propose a novel, non-convex greedy compressed sensing algorithm for phase-contrast MRI. Because the blood vessel distributions are sparse in the image domain, we model that the velocity encoded image has only sparse phase changes compared to the reference image without velocity encoding. Exploiting this sparsity in the velocity encoding phase, we developed a non-convex greedy compressed sensing algorithm to highly undersample the acquisition of the velocity encoded object. We also compared our proposed method to a convex optimization method and found out from the simulations that our method can achieve higher undersampling rates.

14:30         4853.     Fast Time-Resolved 3D Single Point Imaging with Compressed Sensing

James A. Rioux1,2, Steven D. Beyea2,3, Chris V. Bowen2,3

1Department of Physics, Dalhousie University, Halifax, Nova Scotia, Canada; 2National Research Council - Institute for Biodiagnostics (Atlantic), Halifax, Nova Scotia, Canada; 3Departments of Physics, Radiology and Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada

Single Point Imaging sequences are well suited to acceleration with Compressed Sensing (CS), allowing the lengthy acquisition times associated with these sequences to be shortened considerably.  We demonstrate such acceleration with 128x128x16 3D TurboSPI images, which also contain time course information for quantification of relaxation parameters.  Acceleration factors of 6-10 are readily achievable, with further improvements possible at larger matrix sizes.  CS reconstruction retains overall image quality and preserves time course information to within a few percent, allowing SPI to be more readily used for in vivo imaging, or studying dynamic systems.

15:00         4854.     Clinically Feasible Reconstruction Time for L1-SPIRiT Parallel Imaging and Compressed Sensing MRI

Mark Murphy1, Kurt Keutzer1, Shreyas Vasanawala2, Michael Lustig1

1EECS, UC Berkeley, Berkeley, CA, United States; 2Radiology, Stanford University, Stanford, CA, United States

We have optimized for GPUs the L1-minimization for reconstruction of Parallel Imaging and Compressed Sensing MRI, reducing the runtime to 97 seconds. This is the first clinically-feasible runtime reported for Compressed Sensing MRI reconstruction.

                                   Wednesday 13:30-15:30                                                                     Computer 110           

13:30         4855.     Total Generalized Variation (TGV) for MRI

Florian Knoll1, Kristian Bredies2, Thomas Pock3, Rudolf Stollberger1

1Institute of Medical Engineering, Graz University of Technology, Graz, Austria; 2Institute for Mathematics and Scientific Computing, University of Graz, Graz, Austria; 3Institute for Computer Graphics and Vision, Graz University of Technology, Austria

Total Variation was recently introduced in many different MRI applications. The assumption of TV is that images consist of areas which are piecewise constant. However, in many practical MRI situations, this assumption is not valid due to the existence of smooth signal inhomogeneities originating from the exiting b1 field or the receive coils. This work introduces the new concept of Total Generalized Variation for MRI, a new mathematical framework which is a generalization of the TV theory and which eliminates these restrictions. Two important applications are considered in this paper, image denoising and iterative image reconstruction from undersampled radial data sets with multiple coils. Apart from simulations, experimental results from in vivo measurements are presented where TGV yielded improved image quality over conventional TV in all cases.

14:00         4856.     Wavelet-Based Compressed Sensing Using Gaussian Scale Mixtures

Yookyung Kim1, Mariappan S. Nadar2, Ali Bilgin, 1,3

1Electrical and Computer Engineering, University of Arizona, Tucson, AZ, United States; 2Siemens Corporation, Corporate Research, Princeton, NJ, United States; 3Biomedical Engineering, University of Arizona, Tucson, AZ, United States

While initial Compressed Sensing (CS) techniques assumed that sparsity transform coefficients are independently distributed, recent results indicate that dependencies between transform coefficients can be exploited for improved performance. In this paper, we propose the use of a Gaussian Scale Mixture (GSM) model for exploiting the dependencies between wavelet coefficients in CS MRI. Our results indicate that the proposed model can significantly reduce the reconstruction artifacts and reconstruction time in wavelet-based CS MRI.

14:30         4857.     Accelerated Compressed Sensing of Diffusion-Inferred Intra-Voxel Structure Through Adaptive Refinement

Bennett Allan Landman1,2, Hanlin Wan2,3, John A. Bogovic3, Peter C. M. van Zijl4,5, Pierre-Louis Bazin6, Jerry L. Prince, 23

1Electrical Engineering, Vanderbilt University, Nashville, TN, United States; 2Biomedical Engineering, Johns Hopkins University, Baltimore, MD, United States; 3Electrical and Computer Engineering, Johns Hopkins University, Baltimore, MD, United States; 4F.M. Kirby Center, Kennedy Krieger Institute, Baltimore, MD, United States; 5Biomedical Engineering, Johns Hopkins University, Nashville, TN, United States; 6Radiology, Johns Hopkins University, Baltimore, MD, United States

Compressed sensing is a promising technique to estimate intra-voxel structure with traditional DTI data and avoid many of the practical constraints (e.g., long scan times, low signal-to-noise ratio) that plague more detailed, high b-value studies. However, computational complexity is a major limitation of compressed sensing techniques as currently proposed. We demonstrate a novel technique for accelerated compressed sensing of diffusion-inferred intra-voxel structure utilizing adaptive refinement of a multi-resolution basis set. Our approach achieves a tenfold reduction in computational complexity and enables more practical consideration of intra-voxel orientations in time-sensitive settings, routine data analysis, or in large studies.

15:00         4858.     Optimal Single-Shot K-Space Trajectory Design for Non-Cartesian Sparse MRI

Yong Pang1, Bing Wu2, Xiaoliang Zhang2,3

1Radiology and Biomedical imaging, University of California San Francisco, San Francisco, CA , United States; 2Radiology and Biomedical imaging, University of California San Francisco, San Francisco, CA, United States; 3 UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco & Berkeley, CA, United States

Sparse MRI can reduce the acquisition time and raw data size using significantly undersampled k-space. However, conventional k-trajectories waste much time in traveling useless k-space samples. In this work the optimal k-space trajectory design for sparse MRI is addressed. After sampling the k-space using Monto-Carlo sampling schemes, the graphic theory is applied to design an optimal shingle-shot k-trajectory traveling through all these samples, which can further decrease the acquisition time. To demonstrate the feasibility and efficiency, conventional Cartesian EPI and spiral trajectories, as well as their gradients are designed to be compared with those of the optimal k-trajectory.

                                   Thursday 13:30-15:30                                                                        Computer 110           

13:30         4859.     A Novel Compressed Sensing (CS) Method for B1+ Mapping in 7T

Joonsung Lee1, Elfar Adalsteinsson1,2

1Electrical engineering and computer science, Massachusetts Institute of Technology, Cambridge, MA, United States; 2Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, United States

We have developed a novel CS algorithm for B1+ mapping. By imposing smoothness constraint on the B1+ map, we are able to determine B1+ with highly under-sampled data. The method is applied to any kind of B1+ mapping methods.

14:00         4860.     Direct Reconstruction of B1 Maps from Undersampled Acquisitions

Francesco Padormo1, Shaihan J. Malik1, Jo V. Hajnal1

1Robert Steiner MRI Unit, Imaging Sciences Department, MRC Clinical Sciences Centre, Hammersmith Hospital, Imperial College London, London, United Kingdom

We present a method utilizing the smoothness of the B1+ field to accelerate flip angle mapping. By randomly undersampling k-space and using a Compressed Sensing type reconstruction, we show that accurate flip angle distributions can be found with only 40% of the original data.

14:30         4861.     Compressed Sensing Reconstruction in the Presence of a Reference Image

Fan Lam1, Diego Hernando1, Kevin F. King2, Zhi-Pei Liang1

1Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States; 2Global Applied Science Lab, GE Healthcare, Waukesha, WI, United States

In this work, we are addressing the problem on improving compressed sensing reconstruction in the presence of a reference image. A novel algorithm is developped to generate a motion compensated reference image to further improve signal sparsity for a difference image between the reference and the target image to be reconstructed. A compressed sensing reconstruction scheme is proposed to reconstruct the difference image and then the overal reconstruction is constructed by adding the difference image with the reference. The final reconstruction outperforms conventional CS-based reconstruction. The comparison is shown for an interventional imaging experiment.

15:00         4862.     Autocalibrated Approach for the Combination of Compressed Sensing and SENSE

Claudia Prieto1, Benjamin R. Knowles1, Muhammad Usman1, Philip G. Batchelor1, Freddy Odille2, David Atkinson2, Tobias Schaeffter1

1Division of Imaging Sciences, King's College London, London, United Kingdom; 2Centre for Medical Image Computing, University College London, London, United Kingdom

An autocalibrated approach for the combination of Compressed Sensing (CS) and SENSE is proposed. This method is based on the sequential estimation of the coil sensitivity maps using distributed CS followed by image reconstruction using SparseSENSE (or its equivalents), from the same data set. The proposed approach was tested in 2D black-blood atrial wall images with undersampling factors up to 5, showing good image quality. This method does not require extra reference scans and avoids the acquisition of the fully sampled k-space center, which could limit the maximum achievable undersampling factor.

Compressed Sensing II

Hall B                        Monday 14:00-16:00                                                                           Computer 111           

14:00         4863.     Compressed Sensing FMRI Using Optimized Temporal Basis

Hong Jung1, Jong Chul Ye1

1KAIST, Yuseong-Gu, Daejon, Korea, Republic of

Functional MRI (fMRI) has become popular with the developments of echo planar imaging (EPI) sequences. However, EPI needs more image quality improvements for some applications. For example, EPI images suffer from field inhomogeneity artifacts resulting from signal losses in some areas especially around air-tissue interfaces. These artifacts can be minimized with, for example, thin slice thickness. This strategy, however, requires more acquisition time so that temporal resolution or field of view should be sacrificed. In this paper, to address this problem, we applied a compressed sensing dynamic MR imaging algorithm called k-t FOCUSS to fMRI. To resolve degradation of SNR at accelerated acquisition, more number of repetitions of tasks were conducted. Then, from down-sampled k-space data, we obtained accurate brain activation maps for right finger tapping experiments. We verified the reliability of our results by plotting receiver operating characteristic (ROC) curve.

14:30         4864.     Improving the Achievable Temporal Resolution of Compressed Sensing in CE MRA

Bing Wu1,2, Philip Bones1, Anthony Butler1, Richard Watts3, Rick Millane1

1Electrical and computer engineering, University of Canterbury, Christchurch, Canterbury, New Zealand; 2Brain Imaging and Analysis Center, School of Medicine, Duke University, Durham, NC, United States; 3Physics and Astronomy, University of Canterbury, New Zealand

A new data acquisition and image reconstruction method for contrast enhanced (CE) MRA is presented. It is based on Cartesian compressed sensing and incorporates image prior knowledge embedded in the composite data set obtained from time resolved data acquisition.  An acceleration factor that is comparable to that offered by HYPR has been achieved with this new method, on a Cartesian grid.

15:00         4865.     Design of Temporally Constrained Compressed Sensing Methods for Accelerated Dynamic MRI

Julia V. Velikina1, Kevin M. Johnson1, Walter F. Block1, Alexey A. Samsonov1

1University of Wisconsin - Madison, Madison, WI, United States

We present a novel temporally constrained method for reconstruction of dynamic MRI images from undersampled data using second temporal difference. The proposed method is compared to the previously described temporal compressed sensing approaches, including k-t FOCUSS. Performance comparison is done in a series of experiments in digital phantoms and in vivo human volunteer data for phase contrast and contrast-enhanced imaging. The proposed method provided higher accuracy of flow waveform estimations for acceleration factors 8-13.

15:30         4866.     Compressed Sensing Reconstruction with Retrospectively Gated Sampling Patterns for Velocity Measurement of Carotid Blood Flow

Yuehui Tao1, Gabriel Rilling2, Mike Davies2, Ian Marshall1

1Medical Physics, University of Edinburgh, Edinburgh, United Kingdom; 2School of Engineering and Electronics, University of Edinburgh, Edinburgh, United Kingdom

Due to unpredictable heart rate variability, sampling patterns recorded in retrospectively gated dynamic scans appears to be incoherent, which suits the Compressed Sensing framework. Three such sampling patterns recorded in real scans are tested in Compressed Sensing reconstruction with in vivo data from 2D cine phase contrast velocity measurement of carotid blood flow. Both intensity and phase (velocity) errors are examined.

                                   Tuesday 13:30-15:30                                                                          Computer 111           

13:30         4867.     Adaptive Compressed Sensing MRI

Ricardo Otazo1, Daniel K. Sodickson1

1Center for Biomedical Imaging, New York University School of Medicine, New York, NY, United States

A method to adapt the sparsifying transform in order to increase image sparsity for compressed sensing (CS) is presented. The method updates the sparsifying transform and computes the corresponding sparse coefficient simultaneously using image examples from the undersampled data. We demonstrate improved performance of adaptive CS over standard CS with a pre-defined wavelet transform on a brain imaging example

14:00         4868.     Phase-Sensitive Reconstruction Based on the Orthogonality (PRO) of Under-Sampled MRI

Nan-kuei Chen1

1Brain Imaging and Analysis Center, Duke University, Durham, NC, United States

To improve the scan efficiency of dynamic MRI, the k-space data may be undersampled and then reconstructed using one or more of the conventional strategies: e.g., parallel imaging, partial Fourier method, and 3) UNFOLD technique. Here we report a new algorithm to reconstruct under-sampled data, based on the orthogonality of signals from voxels separated by half of the FOV. The new technique, termed Phase-sensitive Reconstruction based on the Orthogonality (PRO),  performs well for data acquired from single-channel or multi-channel coils, and is complementary to existing fast MRI techniques, enabling further reduction of aliasing artifacts in under-sampled MRI data.

14:30         4869.     A Hybrid L0-L1 Minimization Algorithm for Compressed Sensing MRI

Dong Liang1, Leslie Ying2

1Department of Electrical Engineering and Computer Science , University of Wisconsin-Milwaukee, Milwaukee, WI, United States; 2Department of Electrical Engineering and Computer Science, University of Wisconsin-Milwaukee, Milwaukee, WI, United States

Both L1 and homotopic L0 minimizations have been used in compressed-sensing MRI reconstruction. In this abstract, we propose a homotopic L0-L1 hybrid minimization algorithm such that it has the benefit of both L1 and homotopic L0 minimizations. The proposed algorithm minimizes the L0 quasi-norm of large transform coefficients but the L1 norm of small transform coefficients for the image to be reconstructed. The simulation results show the proposed algorithm outperforms both L1 and homotopic L0 minimization algorithms when the same reduction factor is used.

15:00         4870.     Impact of Coil Sensitivity Estimation on MRI Reconstruction Methods Combining Compressed Sensing and Parallel MRI

Seunghoon Nam1,2, Mehmet Akçakaya1,2, Peng Hu2, Warren Manning2, Vahid Tarokh1, Reza Nezafat2

1Harvard University, Cambridge, MA, United States; 2Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States

MRI reconstruction methods combining parallel MRI and compressed sensing (CS) have been recently proposed to accelerate image acquisition and showed great promise. Inherited from parallel MRI, these techniques utilize the coil sensitivity information in their reconstruction procedure. The quality of reconstructed image is affected by the quality of coil sensitivity estimation and different reconstruction methods have different susceptibilities to the coil sensitivity estimation depending on how the coil sensitivity is used in their reconstruction. In this study, we investigate the impact of coil sensitivity estimation on two reconstruction methods: SparseSENSE and distributed CS-SENSE.

                                   Wednesday 13:30-15:30                                                                     Computer 111           

13:30         4871.     Improved K-T FOCUSS Using a Sparse Bayesian Learning

Hong Jung1, Jong Chul Ye1

1KAIST, Yuseong-Gu, Daejon, Korea, Republic of

In dynamic MRI, spatio-temporal resolution is a very important issue. Recently, compressed sensing approach has become a highly attracted imaging technique since it enables accelerated acquisition without aliasing artifacts. Our group has proposed an l1-norm based compressed sensing dynamic MRI called k-t FOCUSS which outperforms the existing methods. However, it is known that the restrictive conditions for l1 exact reconstruction usually cost more measurements than l0 minimization. In this paper, we adopt a sparse Bayesian learning approach to improve k-t FOCUSS and achieve l0 solution. We demonstrated the improved image quality using cardiac cine imaging.

14:00         4872.     Breath-Held Highly-Accelerated 2D Fourier-Velocity Encoded MRI Using Compressed Sensing

Luca Marinelli1, Kedar Khare1, Kevin F. King2, Christopher J. Hardy1

1GE Global Research Center, Niskayuna, NY, United States; 2GE Healthcare, Waukesha, WI, United States

We optimized a  pulse sequence for accelerated 2D Fourier-velocity-encoded (FVE) MRI to measure blood-velocity in disturbed flows using compressed sensing and developed a fast and accurate reconstruction algorithm. 2D Fourier-velocity-encoded M-mode MRI provides a non-invasive probe of 2D velocity distributions that cannot be measured by other modalities such as Doppler ultrasound but can be exceedingly time consuming. Unlike conventional imaging, parallel imaging cannot be utilized to reduce number of velocity encoding steps. Scan time was reduced enough to fit the acquisition in a single breath-hold, achieving a 20x overall scan-time reduction relative to the fully sampled acquisition.

14:30         4873.     Parameter-Free Reconstruction of Highly Undersampled MR Angiography  Images Using Gradient Descent with Sparsification

Nicole Seiberlich1, Hyun J. Jeong2, Timothy J. Carroll2, Mark A. Griswold1,3

1Radiology, Case Western Reserve University, Cleveland, OH, United States; 2Radiology, Northwestern University, Chicago, IL, United States; 3Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States

Gradient Descent with Sparsification, a novel image reconstruction technique, has been applied to the generation of images from highly undersampled MR Angiography data. Unlike other techniques, this method can be implemented using no external para-meters, allowing completely unsupervised reconstructions. The extremely high acceleration factors shown here are made possible by initializing a given time frame with the previous frame, such that only differences must be reconstructed. Temporal resolutions of 180ms/frame have been achieved by undersampling the collected data by a factor of R~75 (using 4 projections per partition per frame) with no venous contamination and little residual streaking or blurring.

15:00         4874.     Clinical Image Quality Assessment of CS-Reconstructed Brain Images

Samir D. Sharma1, Caroline Fong2, Brian Tzung2, Krishna S. Nayak1, Meng Law2

1Department of Electrical Engineering, University of Southern California, Los Angeles, CA, United States; 2Department of Radiology, University of Southern California, Los Angeles, CA, United States

Compressed Sensing (CS) is a relatively new method for MR image reconstruction from undersampled k-space data.  While other acceleration techniques, like parallel imaging, are common in clinical protocols, the role of CS in clinical imaging remains an open question.  In this work we perform a double-blind assessment of CS-MRI image quality by neuroradiologists.  Preliminary results suggest the potential for at least 3x acceleration without significant loss in image quality.

                                   Thursday 13:30-15:30                                                                        Computer 111           

13:30         4875.     Novel Algorithm for L1 Wavelet-Based MR Image Reconstruction

Matthieu Guerquin-Kern1, Maximilian Häberlin2, Michael Unser1, Klaas P. Pruessmann2

1Biomedical Imaging Group, Ecole polytechnique fédérale de Lausanne, Lausanne, Vaud, Switzerland; 2Institute for Biomedical Engineering, University and ETH Zurich, Zürich, Switzerland

The wavelet-based reconstruction that is proposed yields encouraging results compared to more popular reconstructions and is optimized to reduce reconstruction duration.

14:00         4876.     Accelerated Serial MR Imaging in Multiple Sclerosis Using Baseline Scan Information

Alexey A. Samsonov1, Julia V. Velikina2, John O. Fleming3, Mark L. Schiebler1, Aaron S. Field1

1Department of Radiology, University of Wisconsin, Madison, WI, United States; 2Department of Medical Physics, University of Wisconsin, Madison, WI, United States; 3Department of Neurology, University of Wisconsin, Madison, WI, United States

In this work, we present a method to accelerate MS imaging in longitudinal studies through acquisition of fully sampled images at the baseline scan and accelerated undersampled data at follow-ups.  W investigated feasibility to accelerate serial scanning of MS patients with 3D pulse sequences (T2 FLAIR and T1 weighted after Gd administration).  Our results indicate that the proposed technique has a potential to produce high-quality images from significantly accelerated reduced follow-up acquisition (up to 8 times) and correctly depict T2 and Gd+ lesion load and anatomical content.

14:30         4877.     A New Approach to Incorporate Image  Prior Estimate in Compressed Sensing

Bing Wu1,2, Philip Bones1, Richard Watts3, Rick Millane1

1Electrical and computer engineering, University of Canterbury, Christchurch, Canterbury, New Zealand; 2Brain Imaging and Analysis Center, School of Medicine, Duke University, Durham, NC, United States; 3Physics and Astronomy, University of Canterbury, New Zealand

The success level of compressed sensing (CS) reconstruction is fundamentally limited by the sparsity of the underlying image. A data sorting process can be incorporated in the CS recovery to improve the sparsity of the underlying image based on the knowledge of an image prior estimate. We here show that performing a data sorting effectively incorporates the image prior estimate in the CS reconstruction.

15:00         4878.     Improved Coil Sensitivity Estimation for SENSE Using Compressed Sensing

Bing Wu1, Chunlei Liu1

1Brain Imaging and Analysis Center, School of Medicine, Duke University, Durham, NC, United States

The conventional approach of deriving coil sensitivity profile for SENSE reconstruction using a small number of auto-calibration scan lines limits the fidelity of the coil sensitivity estimate, and hence the quality of SENSE reconstructions.  However estimating coil sensitivity from under-sampled k-space data set is an under-determined problem, and previous attempts resort to additional regularizing terms that may affect the accuracy of the outcome. We present a new compress sensing based approach that allows the coil sensitivity profile to be estimated using all the acquired data measurements to achieve improved coil sensitivity estimate, which in turn leads to an improved SENSE reconstruction.

Parallel Imaging & Compressed Sensing

Hall B                        Monday 14:00-16:00                                                                           Computer 112           

14:00         4879.     Toward Clinically Applicable Highly-Accelerated SENSE

Feng Huang1, Yunmei Chen2, Xiaojing Ye2, Wei Lin1, Yu Li1, Arne Reykowski1

1Invivo Corporation, Gainesville, FL, United States; 2Department of Mathematics, University of Florida, Gainesville, FL, United States

Recently, many advanced technologies have been proposed to improve the quality of images reconstructed by SENSE with high acceleration factors. However, success of these methods needs one or more following conditions: long reconstruction time, special acquisition trajectory, or expertise on parameter choice. These requirements have hindered their clinical applicability. In this work, a novel technique based on variable splitting is proposed to tackle these problems. Mathematical proof and experimental results demonstrate that the proposed method significantly improves the clinical applicability of highly-accelerated SENSE because of low reconstruction error, fast reconstruction, insensitivity to the choice of parameters, and regular Cartesian trajectory

14:30         4880.     Combining Nonconvex Compressed Sensing and GRAPPA Using the Nullspace Method

Daniel Stuart Weller1, Jonathan R. Polimeni2,3, Leo J. Grady4, Lawrence L. Wald2,3, Elfar Adalsteinsson1, Vivek K. Goyal1

1Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA, United States; 2A.A. Martinos Center, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States; 3Harvard Medical School, Boston, MA, United States; 4Imaging and Visualization, Siemens Corporate Research, Princeton, NJ, United States

This work combines GRAPPA, a parallel image reconstruction method, with compressed sensing in a joint optimization framework.  To enforce consistency with the acquired data, the optimization problem operates in the nullspace of the sampling pattern, which more accurately preserves the acquired data than a data feasibility penalty in the objective.  The L0 penalty was approximated using a continuation procedure with a differentiable nonconvex regularizer.  The proposed method was implemented using an iterative reweighted least squares routine.  The combined method was applied to highly under-sampled MPRAGE data.  This approach reconstructed images at higher quality than GRAPPA and CS alone.

15:00         4881.     A New Combination of Compressed Sensing and Data Driven Parallel Imaging

Kevin King1, Dan Xu1, Anja CS Brau2, Peng Lai2, Philip J. Beatty2, Luca Marinelli3

1Global Applied Science Lab, GE Healthcare, Waukesha, WI, United States; 2Global Applied Science Lab, GE Healthcare, Menlo Park, CA, United States; 3Global Research Center, General Electric, Niskayuna, NY, United States

Compressed sensing and data driven parallel imaging can be combined in a serial approach in which randomly undersampled data are reconstructed onto a uniformly undersampled k-space grid using compressed sensing.  Parallel imaging uses this uniformly undersampled data plus the auto-calibration data to create a fully sampled k-space grid.  The serial approach allows the acceleration to be split between compressed sensing and parallel imaging.  Each method solves a problem with better conditioning than if the full acceleration were used.  Any data driven parallel imaging method, such as GRAPPA, ARC or SPIRIT can be used without modification using this approach.

15:30         4882.     Improved Compressed Sensing Reconstruction for Equidistant K-Space by Sampling Decomposition and Its Application in Parallel MR Imaging

Jun Miao1,2, Weihong Guo3, David L. Wilson1,4

1Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States; 2Siemens Corporate Research, Princeton, NJ, United States; 3Mathematics, Case Western Reserve University, Cleveland, OH, United States; 4Radiology, University Hospitals of Cleveland

Incoherent sampling requirement is a bottleneck for application of compressed sensing (CS) in parallel MR imaging. Thus, a direct plug-in of CS to parallel imaging, especially in the case of equidistant k-space sampling, is not feasible. We propose a simple method to eliminate this problem by sampling decomposition and illustrate the idea using GRAPPA reconstruction. Significant improvement in image quality can be achieved with even less k-space acquisition.

                                   Tuesday 13:30-15:30                                                                          Computer 112           

13:30         4883.     l1-Denoised Autocalibrating Parallel Imaging

Tao Zhang1, Michael Lustig1,2, Shreyas Vasanawala3, John Mark Pauly1

1Electrical Engineering, Stanford University, Stanford, CA, United States; 2Electrical Engineering and Computer Science, UC Berkeley, Berkeley, CA, United States; 3Radiology, Stanford University, Stanford, CA, United States

In this study, sequential parallel imaging and compressed sensing (CS) are applied to suppress noise and improve image quality. A noise covariance matrix constructed from the GRAPPA interpolation kernels are used to "intelligently inform" the CS optimization about the confidence level of each GRAPPA reconstructed entry. The experiment results show that the proposed method can efficiently suppress noise.

14:00         4884.     Acceleration of IDEAL Water-Fat Imaging Using Compressed Sensing

Samir D. Sharma1, Harry H. Hu1, Krishna S. Nayak1

1Department of Electrical Engineering, University of Southern California, Los Angeles, CA, United States

IDEAL is a robust iterative technique for estimating water and fat signals on a voxel-basis, based on multi-echo data.  In each iteration, two least-squares problems are solved.  In this work, we reformulate each of the least-squares problems and solve them via Compressed Sensing (CS).  We exploit the compressibility of both the water and fat images as well as smoothness of the field map to regularize our underdetermined systems of equations.  The result is an up to 3x acceleration from the conventional IDEAL method.

14:30         4885.     Image Quality Parameters in MR Images, Reconstructed by Using Compressed Sensing

Tobias Wech1, Marcel Gutberlet1, Daniel Stäb1, Dietbert Hahn1, Herbert Köstler1

1Institute of Radiology, University of Wuerzburg, Wuerzburg, Bavaria, Germany

Compressed sensing allows reconstructing undersampled data in the presence of sparse or compressible signals. However, up to now there are no studies that examine basic imaging parameters like image noise and spatial resolution for compressed sensing. In this work, methods were introduced to determine image quality parameters suitable for compressed sensing reconstructions and applied to to the compressed sensing of cardiac CINE imaging.

15:00         4886.     Spike Artifact Reduction in Nonconvex Compressed Sensing

Thomas Christian Basse-Luesebrink1,2, Thomas Kampf1, Andre Fischer1,3, Gesa Ladewig2, Guido Stoll2, Peter Michael Jakob1,3

1Experimental Physics 5, University of Wuerzburg, Wuerzburg, Germany; 2Neurology, University of Wuerzburg, Wuerzburg, Germany; 3Research Center for Magnetic Resonance Bavaria (MRB), Wuerzburg, Germany

Compressed sensing (CS), a reconstruction method for undersampled MR data, allows a significant reduction in experiment time. 19F MR is a suitable target for CS since the 19F signal distribution in vivo is sparse. However, spike artifacts appear highly pronounced in nonconvex CS reconstructions of noisy 19F MR data. The present study focuses on the reduction of spike artifacts in these CS reconstructions. Therefore, a post-processing "de-spike algorithm" is proposed, using the fact that the spatial position of spike artifacts depends on the chosen sampling pattern. Numerical phantom simulations as well as ex- and in-vivo 19F CSI experiments were performed.

                                   Wednesday 13:30-15:30                                                                     Computer 112           

13:30         4887.     Dictionary Design for Compressed Sensing MRI

Ali Bilgin1,2, Yookyung Kim2, Feng Liu2, Mariappan S. Nadar3

1Biomedical Engineering, University of Arizona, Tucson, AZ, United States; 2Electrical and Computer Engineering, University of Arizona, Tucson, AZ, United States; 3Siemens Corporation, Corporate Research, Princeton, NJ, United States

The recently introduced Compressed Sensing (CS) theory promises to accelerate data acquisition in MRI. In this work, we propose a framework for designing and utilizing sparse dictionaries in CS MRI applications. Reconstruction results demonstrate that the proposed technique can yield significantly improved image quality compared to commonly used sparsity transforms in CS MRI.

14:00         4888.     19F-Compressed-Sensing-CISS: Elimination of Banding Artifacts in 19F Bssfp MRI/CSI Without Sacrificing Time

Thomas Christian Basse-Luesebrink1,2, Andre Fischer1,3, Thomas Kampf1, Volker Sturm1, Gesa Ladewig2, Guido Stoll2, Peter Michael Jakob1,3

1Experimental Physics 5, University of Wuerzburg, Wuerzburg, Germany; 2Neurology, University of Wuerzburg, Wuerzburg, Germany; 3Research Center for Magnetic Resonance Bavaria (MRB), Wuerzburg, Germany

Balanced ssfp (bssfp) MRI and CSI sequences show banding artifacts in either the image domain or the spectral domain. Those artifacts can be eliminated using a constructive interference in the steady state (CISS) technique. This, however, prolongs experiment times due to the need of additional experiments with different phase cycles. Compressed sensing (CS), a reconstruction method for undersampled MR data allows reduction in measurement time. The present study focuses on the application of CS in bssfp 19F-MRI/CSI in order to gain enough time for the acquisition of additional experiments with different phase cycles for CISS reconstruction.

14:30         4889.     Compressed Sensing with a Priori Information for Reconstruction of Remotely Detected Microfluidic Devices

Thomas Z. Teisseyre1,2, Jeffrey Paulsen2, Vik Bajaj2, Nicholas Halpern-Manners2,3, Alexander Pines2,3

1Bioengineering, UC Berkeley/UCSF, Berkeley, CA, United States; 2Materials Sciences Division, Lawrence Berkeley National Lab, Berkeley, CA, United States; 3Chemistry, UC Berkeley, Berkeley, CA, United States

We developed a novel reconstruction technique for remotely detected microfluidic NMR using prior knowledge about the chip geometry. This technique allows significant amounts of subsampling for shorter acquisition times.

15:00         4890.     MR Rician Noise Reduction in Diffusion Tensor Imaging Using Compressed Sensing by Sampling Decomposition

Jun Miao1, Wen Li1, Sreenath Narayan1, Xin Yu1, David L. Wilson1,2

1Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States; 2Radiology, University Hospitals of Cleveland

Reduction of Rician noise in MRI is very much desired, particularly in low signal-to-noise ratio (SNR) images such as diffusion tensor imaging. We used compressed sensing to reduce noise by decomposing full k-space data into multiple sets of incoherent subsamples, reconstructing full k-space individually, and aggregate them to be the final k-space data. Noise can be significantly suppressed in image and fractional anisotropy (FA) estimation can be significantly improved.

                                   Thursday 13:30-15:30                                                                        Computer 112           

13:30         4891.     Feasibility Study of Combining CS with SENSE for Catheter Visualization in MR Endovascular Intervention

Jérôme Yerly1,2, Michel Louis Lauzon, 23, Richard Frayne, 23

1Department of Electrical and Computer Engineering, University of Calgary, Calgary, Alberta, Canada; 2Seaman Family MR Research Centre, Foothills Medical Centre, Calgary, Alberta, Canada; 3Departments of Radiology, and Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada

MR imaging is a promising alternative to x-ray fluoroscopy for guiding/monitoring catheters in endovascular intervention by offering many advantages. Conventional MR imaging has insufficient temporal resolution, but accelerated approaches such as sensitivity encoding (SENSE) and compressed sensing (CS) prove favorable via accurate reconstruction of undersampled k-space datasets. Since SENSE relies on coil sensitivity whereas CS depends on sparsity to recover the missing information, it may be advantageous to combine these two different methodologies. Previously, we demonstrated that CS alone accurately reconstructs catheter images. Here, we extend our catheter image reconstructions and investigate the potential of sequentially combining CS with SENSE.

14:00         4892.     Coarse-To-Fine Iterative Reweighted L1-Norm Compressed Sensing for Dynamic Imaging

Michael Lustig1,2, Julia Velikina3, Alexey Samsonov3, Chuck Mistretta3,4, John Mark Pauly2, Michael Elad5

1Electrical Engineering and Computer Science, University of California Berkeley, Berkeley, CA, United States; 2Electrical Engineering, Stanford University, Stanford, CA, United States; 3Medical Physics, University of Wisconsin-Madison, Madison, WI, United States; 4Radiology, University of Wisconsin-Madison, Madison, WI, United States; 5Computer Science, Technion IIT, Haifa, Israel

A coarse-to-fine compressed sensing (CS) reconstruction for dynamic imaging is presented. It is inspired by the composite image constraint in HYPR-like processing. At each temporal scale, a “composite” image is reconstructed using a CS reconstruction.  The result is used as an initial image for the next finer scale. In addition it is used to generate weighting of the l1-norm in the CS reconstruction, promoting sparsity at locations that appear in the composite.  Reconstruction from highly undersampled DCE-MRA is demonstrated.

14:30         4893.     Efficient Randomly Encoded Data Acquisition for Compressed Sensing

Eric C. Wong1

1Radiology and Psychiatry, UC San Diego, La Jolla, CA, United States

Compressed sensing (CS) allows for efficient extraction of information from MR data, and benefits from incoherent sampling.  We propose here an imaging strategy that simultaneously produces high steady state signal, high A/D duty cycle, and pseudo-random sampling functions, and is therefore both SNR efficient and amenable to CS reconstruction.  The method uses rapid low flip angle pulses of random phase, along with a rosette gradient trajectory to produce an array of coherence pathways.  Simulated data and reconstruction demonstrate simultaneous estimation of proton density, T2, and field maps from under-sampled data.

15:00         4894.     Faster Acquisition of MR Images with Double Quantum Filtering by Regularization

Genevieve Guillot1, Yongchao Xu1, Slawomir Kusmia1, Hadia Hanachi1, Jean-François Giovannelli2, Alain Herment3

1U2R2M UMR8081 CNRS, Orsay, France, France; 2LAPS / IMS UMR5218, Bordeaux, France, France; 33-           LIF U678 INSERM / UMR-S UPMC, Paris, France, France

MRI with Double Quantum Filter (DQF) gives a direct access to water linked to macromolecules, but requires 16 up to 64 repetitions of the acquisition scheme with different phases of the RF pulses in the DQ filter to select the DQ signal. We reduced the number of phase encoding lines kept in the data for each DQF step, employing a regularization method to compute each image. The acquisition time could be reduced by 2/3 without any significant loss of contrast and minor loss of contrast on contours. Even faster acquisition should be possible with radial or spiral k-space trajectories.

Topics in Parallel Imaging

Hall B                        Monday 14:00-16:00                                                                           Computer 113           

14:00         4895.     Noise-Facilitated GRAPPA Reconstruction for FMRI

Hu Cheng1, Wei Lin2, Feng Huang2

1Indiana University, Bloomington, IN, United States; 2Invivo Diagnostic Imaging, Gainesville, FL, United States

In fMRI, temporal SNR is the main concern in the optimization of parallel imaging algorithms such as GRAPPA. It is shown in this work that adding noise to the auto-calibration signal (ACS) region of GRAPPA data can increase the temporal SNR of fMRI series, with a minimal impact on image quality.  Simulation on the EPI images of a phantom and human subject demonstrated that image quality can be improved by adding a certain amount of noise to the raw data of reference scans, while the temporal SNR can be further improved with a higher level of additive ACS noise.

14:30         4896.     Undersampled Multi Coil Image Reconstruction for Fast FMRI Using Adaptive Linear Neurons

Thimo Grotz1, Benjamin Zahneisen1, Marco Reisert1, Maxim Zaitsev1, Jürgen Hennig1

1Dept. of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany

Standard fMRI experiments have a rather limited temporal resolution of 1-3s. The temporal resolution of fMRI experiments can be increased by an order of magnitude by acquiring less k-space and using a high number of receive channels. Image reconstruction is thus an ill-posed inverse problem. Here we would like to introduce a new approach, based on neural networks, to reconstruct the undersampled fMRI data that offers a significantly improved point spread function with reduced spatial spread and hence improved spatial localization of activation.

15:00         4897.     Time Dependent Regularization for Functional Magnetic Resonance Inverse Imaging

Aapo Nummenmaa1,2, Matti S. Hamalainen1, Fa-Hsuan Lin1,3

1MGH-MIT-HMS Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, United States; 2Department of Biomedical Engineering and Computational Science, Helsinki University of Technology, Espoo, Finland; 3Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan

We propose a novel method for time dependent regularization of functional magnetic resonance Inverse Imaging (InI). A Variational Bayesian approximation with a dynamic model for the regularization is constructed to obtain an automatic, temporally adaptive estimation algorithm. The proposed method is compared with the standard Minimum-Norm Estimate (MNE) by using simulated InI data. The dynamic dMNE shows significant improvements in determining the activation onset from the baseline period.

15:30         4898.     Magnetic Resonance Multi-View Inverse Imaging (MV InI) for Human Brain

Kevin Wen-Kai Tsai1, Thomas Witzel2, Fa-Hsuan Lin1,3

1Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan; 2A. A. Martinos Center; 3A. A. Martinos Center, Massachusetts General Hospital, Charlestown, MA, United States

To solve the anisotropic spatial resolution of MR inverse imaging (InI) reconstruction method, we propose the multi-view InI (MV InI) to using a few projections and a highly parallel detection to achieve high spatiotemporal MR dynamic imaging. Specifically, we used three orthogonal projections and a 32-channel head coil array to achieve the effective TR of 300 ms and 4 mm3 isotropic spatial resolution. We demonstrated the acquisitions and reconstruction of MV InI using in vivo data. This method achieved a 8 times faster temporal resolution than conventional multi-slice EPI acquisitions.

                                   Tuesday 13:30-15:30                                                                          Computer 113           

13:30         4899.     Homotopic l0 Minimization Technique Applied to Dynamic Cardiac MR Imaging

Muhammad Usman1, Philip G. Batchelor1

1King's College London, London, United Kingdom

The L1 minimization technique has been empirically demonstrated to exactly recover an S-sparse signal with about 3S-5S measurements. In order to get exact reconstruction with smaller number of measurements, recently, for static images, Trzasko has proposed homotopic L0 minimization technique. Instead of minimizing the L0 norm which achieves best possible theoretical bound (approximately 2S measurements) but is a NP hard problem or L1 norm which is a convex optimization problem but requires more measurements, the homotopic technique minimizes iteratively the continuous approximations of the L0 norm. In this work, we have extended the use of homotopic L0 method to dynamic MR imaging. For dynamic 2D CINE data, using five different non-convex functional approximations to L0 norm, we have compared the performance of homotopic L0 minimization technique with the standard L1 method.

14:00         4900.     Fast Time-Resolved Cine Sequence Using Temporal Regularization for Small Animal Cardiac Imaging on a Clinical 3T Scanner

Bénédicte Delattre1, Vincent Braunersreuther2, Jean-Noël Hyacinthe1, Jean-Paul Vallée1, Dimitri Van De Ville3,4

1University of Geneva - Faculty of medicine, Geneva, Switzerland; 2Division of Cardiology - Department of Medicine, Geneva University Hospital - Foundation for medical researchers, Geneva, Switzerland; 3Department of Radiology and Medical Informatics - University of Geneva, Geneva, Switzerland; 4Institute of Bioengineering - Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland

Small animal cardiac imaging on clinical scanners allows contributing effectively to translational medicine. However, hardware limitations prevent obtaining the same space and time resolution than with dedicated instrumentation. Here, we propose a novel method to improve time resolution for cardiac mouse imaging. By combining two fast repetitions with temporal regularization based on l1-minimization in the Fourier domain, we achieve a TR=6.5 ms with an in-plane resolution of 257 μm2 and reduce efficiently artifacts resulting from the combination of the two repetitions.

14:30         4901.     Four-Dimensional Analytical Cardiac Magnetic Resonance Imaging Phantom in the Fourier Domain

David Moratal1, Lei Hou Hamilton2, Senthil Ramamurthy3, Marijn Eduard Brummer3

1Universitat Politècnica de València, Valencia, Spain; 2Georgia Institute of Technology, Atlanta, GA, United States; 3Emory University, Atlanta, GA, United States

The value of a standardized simulation phantom to test and compare reconstruction methods for cardiac imaging has become evident during last years. In this work, a 4D analytical phantom in the Fourier domain is proposed, aimed to serve as a flexible, objective, standardized benchmark for evaluation and comparison of different image reconstruction techniques in dynamic 3D MRI. It can be used to compare different non-Cartesian encoding schemes and reconstruction methods, as well as different cardiac MRI acceleration strategies. The k-space signal for the 4D phantom can be evaluated analytically and sampled accordingly to any chosen k-space trajectory or encoding scheme.

15:00         4902.     RF Excitation Encoding: A Fast Imaging Technique for Dynamic Studies

Yanle Hu1, Gary H. Glover2

1Imaging Research Center, University of Texas at Austin, Austin, TX, United States; 2Department of Radiology, Stanford University, Stanford, CA, United States

Fast imaging techniques based on under-sampling are all approaching the problem from the acquisition side. Less effort has been involved in exploring the possibility of speeding up image acquisition from the excitation side. Although parallel excitation is focused on the excitation side, it is typically used to reduce the RF pulse duration rather than accelerate image acquisition. In this work, a new technique is introduced to speed up image acquisition from the excitation side. This technique is independent of other techniques focused on the acquisition side and thus may be combined with them to achieve a higher acceleration factor.

                                   Wednesday 13:30-15:30                                                                     Computer 113           

13:30         4903.     Analytic Image SENSE Reconstruction for Dynamic PMRI

Josiane Yankam Njiwa1, Christof Baltes1, Markus Rudin1,2

1ETH-University Zurich, Institute for Biomedical Engineering, Zurich, Switzerland; 2University Zurich, Institute of Pharmacology & Toxicology, Zurich, Switzerland

Dynamic susceptibility (DSC) MRI is increasingly being used to evaluate cerebral microcirculation. In this study is proposed an acquisition scheme, combining partial k-space sampling and pMRI, allowing higher gains for DSC perfusion measurements in small animals. Three male Lewis rats were imaged and a T2*- weighted FLASH sequence was performed for data acquisition. The results show that the used method satisfactory reconstruct DSC-MRI while preserving a good reconstruction quality and image characteristics compared to the non-accelerated and SENSE reconstructed image series. The combination of an Analytic Image based reconstruction with SENSE to reconstruct the images series increase the temporal resolution.

14:00         4904.     Application of Hybrid Through-Time/k-Space Radial GRAPPA Calibration to Real-Time Cardiac Imaging

Nicole Seiberlich1, Philipp Ehses2, Jeffrey L. Duerk, 1,3, Robert Gilkeson1, Mark A. Griswold1,3

1Radiology, Case Western Reserve University, Cleveland, OH, United States; 2Experimentelle Physik V, Universitaet Wuerzburg, Wuerzburg, Germany; 3Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States

While standard radial GRAPPA can be used to reconstruct images with low undersampling factors, its primary assumption (that segments of the radial lines can be approximated as Cartesian) breaks down at high acceleration factors. A new through-time calibration method has recently been proposed; this method yields high image quality, but requires large numbers of calibration frames. The method proposed here uses through-k-space segments as well as repetitions through time to reduce the number of calibration frames needed while maintaining image quality. This hybrid radial GRAPPA calibration method is demonstrated for real-time, ungated cardiac acquisitions with frame rates of 43 ms.

14:30         4905.     On the Optimal Acceleration of Time-Resolved 3D Imaging Using GRAPPA

Bernd André Jung1, Simon Bauer1, Michael Markl1

1Dept. of Diagnostic Radiology, Medical Physics, University Hospital, Freiburg, Germany

The aim of this work was to explore how to optimally undersample and reconstruct time-resolved 3D data using GRAPPA. Two different data sets were acquired in a moving phantom with isotropic and anisotropic data matrices. Reconstruction was performed with 3D- (kx,ky,t) and 4D-kernel (kx,ky,kz,t) configurations. For the symmetric data matrix, it was demonstrated that the 4D-kernel configuration leads to better results in terms of error behaviour. However, in a more realistic anisotropic data matrix typically used in clinical applications the different kernel configurations show an opposite behaviour. Furthermore, noise enhancement for 4D-kernel configuration was more pronounced compared to 3D-configurations.

15:00         4906.     A Nonlinear GRAPPA Method for Improving SNR

Yuchou Chang1, Dong Liang1, Leslie Ying1

1Electrical Engineering and Computer Science, University of Wisconsin-Milwaukee, Milwaukee, WI, United States

This abstract presents a nonlinear GRAPPA method to address the poor SNR of GRAPPA at high reduction factors. The method is motivated by the fact that nonlinear filtering usually outperforms linear ones in denoising. The proposed method uses a nonlinear combination of the acquired k-space data to estimate the missing data. The experimental results demonstrate that the proposed method is able to improve the SNR of GRAPPA at high reduction factors.

                                   Thursday 13:30-15:30                                                                        Computer 113           

13:30         4907.     Generalized PRUNO Kernel Selection by Using Singular Value Decomposition (SVD)

Jian Zhang1, Chunlei Liu2, Michael Moseley3

1Department of Electrical Engineering, Stanford University, Stanford, CA, United States; 2Brain Imaging and Analysis Center, Duke University Medical Center, Durham, NC, United States; 3Department of Radiology, Stanford University, Stanford, CA, United States

Parallel Reconstruction Using Null Operations (PRUNO) is an iterative k-space based reconstruction method for Cartesian parallel imaging. One particular challenge in PRUNO is to select a set of proper nulling kernels. In this work, we demonstrate an improved kernel selection strategy to create generalized PRUNO kernels from the Singular Value Decomposition (SVD) of calibration data. Furthermore, by introducing composite kernels prior to the conjugate-gradient (CG) reconstruction, the reconstruction time wouldn’t increase much when a large number of kernels are used. These new strategies boost the robustness of PRUNO with faster algorithm convergence and lower noise sensitivity.

14:00         4908.     Image Reconstruction from Phased-Array Mri Data Based on Multichannel Blind Deconvolution

Huajun She1, RongRong Chen1, Dong Liang2, Yuchou Chang2, Leslie Ying2

1Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT, United States; 2Department of Electrical Engineering and Computer Science, University of Wisconsin-Milwaukee, Milwaukee, WI, United States

In this abstract we consider image reconstruction from multichannel phased array MRI data without prior knowledge of the coil sensitivity functions. A new framework based on multichannel blind deconvolution (MBD) is developed for joint estimation of the image function and the sensitivity functions in k-space. By exploiting the smoothness of the image and sensitivity functions in the spatial domain, we develop a regularized MBD method to obtain both the image function and sensitivity functions. Simulation and in vivo experimental results demonstrate that the proposed method reconstructs images with more uniform intensity than the SoS method does.

14:30         4909.     KLT-GRAPPA: A New Method to Estimate Auto-Calibration Signal in Dynamic Parallel Imaging

Yu Ding1, Mihaela Jekic1, Yiu-Cho Chung2, Orlando P. Simonetti1

1The Ohio State University, Columbus, OH, United States; 2Siemens Medical Solutions, Columbus, OH, United States

TSENSE and TGRAPPA are widely used parallel acquisition methods that can dynamically update the sensitivity map to accommodate variations caused by physiological motion. These methods use temporal low-pass filtering or sliding window averaging  to estimate a dynamically changing sensitivity map. We propose to use the Karhunen-Loeve Transform filter to generate a frame-by-frame estimate of the time-varying channel sensitivity. In-vivo experiments showed that the new method significantly reduces the artifact level in TGRAPPA reconstruction compared to traditional approaches.

15:00         4910.     Auto-Calibrated Parallel Imaging Using a Distortion-Optimal Filter-Bank

Behzad Sharif1, Yoram Bresler1

1Electrical and Computer Engineering, Coordinated Science Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL, United States

We presented a k-space-based self-calibrating parallel MRI reconstruction technique, dubbed ACSIOM, which estimates a GRAPPA-type interpolation kernel by jointly minimizing data inconsistency and aliasing distortion. In imaging scenarios where high effective acceleration is desired, the capability to reconstruct artifact-free images with minimal amount of reference (auto-calibration scan) data is needed. In such cases, we have shown that ACSIOM outperforms two different implementations of GRAPPA. The results indicate that improved image quality, and thus greater scan time reductions compared to GRAPPA can be achieved.

RF Shimming & Parallel RF

Hall B                        Monday 14:00-16:00                                                                           Computer 114           

14:00         4911.     Combination of Basic and Tailored RF Shimming Using Curved Spoke Trajectories

Ulrich Katscher1, Peter Börnert1

1Philips Research Europe, Hamburg, Germany

Generally, two RF shimming approaches are reported. The first approach, "basic" RF shimming via adjusting the channels’ drive weights, is stable and fast, however, has limited shimming potential. The second approach, "tailored" RF shimming via multidimensional RF pulses, is more complex and requires significant sequence modifications, however, has superior shimming potential. This study investigates a compromise combining the advantages of both approaches. It applies a slight curvature of the "straight" k-space trajectory of standard slice selective excitation, maintaining short pulse durations, and sharp slice profiles. Simultaneously, it allows higher freedom for in-plane B1 variation, yielding an enhanced shimming potential.

14:30         4912.     A New Class of Encoding Techniques Using a Transmit Array: Illustration with Cylindrical Encoding

Emre Kopanoglu1,2, Adil Firat Yilmaz1,2, Taner Demir2, Vakur B. Erturk1, Ergin Atalar1,2

1Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey; 2UMRAM - National Research Center for Magnetic Resonance , Ankara, Turkey

In nearly all magnetic resonance imaging applications, data encoding is made by gradient coils, which limit the slice to a plane and the field-of-view (FOV) to a rectangle although the region-of-interest (ROI) can have an arbitrary shape. In this paper we propose a novel encoding scheme for arbitrarily shaped slices, so that the need to get unnecessary data from outside the ROI is eliminated. The proposed method uses multi-dimensional pulses for slice selection and RF pulses to encode the data instead of gradient coils, hence a slice with an arbitrary shape and FOV can be selected.

15:00         4913.     Comparison of Whole Body Transmit Coil Configurations for RF Shimming at 3T

Kay Nehrke1, Ulrich Katscher1, Peter Börnert1, Ingmar Graesslin1

1Philips Research Europe, Hamburg, Germany

Whole body MRI at 3T may be impeded by B1 transmit field inhomogeneities caused by the dielectric shortening of the RF wavelength. RF shimming techniques based on parallel transmission can strongly improve the image quality in clinical whole body applications. In this context, it is an important question, how the RF shimming performance depends on the chosen coil topology and, in particular, on the number of transmit channels. In the present work, an 8-channel transmit system is used for B1 mapping and shimming, providing the flexibility of emulating different coil configurations and comparing their RF shimming performance.

15:30         4914.     T1 Weighted Whole Brain Imaging with Uniform Contrast at 3T Using Parallel Transmission

Shaihan J. Malik1, Shiva Keihaninejad2, Alexander Hammers2,3, Joseph V. Hajnal4

1Robert Steiner MRI Unit, Imaging Sciences Department, MRC Clinical Sciences Centre, Hammersmith Hospital, Imperial College London, London, United Kingdom; 2Division of Neuroscience and Mental Health, Imperial College London, London, United Kingdom; 3Neurodis Foundation, CERMEP - Imagerie du Vivant, Lyon, France; 4Robert Steiner MRI Unit, Imaging Sciences Department, MRC Clinical Sciences Centre, Hammersmith Hospital, Imperial College London, United Kingdom

T1 weighted brain imaging at 3T suffers from contrast variation caused by B1 field inhomogeneity. This can lead to reduced conspicuity of key anatomical structures; particularly the deep grey matter nuclei. We present a 3D tailored RF pulse using parallel transmission which produces uniform excitation over the whole brain incorporated into a standard MPRAGE sequence.  The resulting images demonstrate more uniform contrast than those acquired with standard RF pulses and result in more accurate depiction and automated segmentation of deep grey matter structures.

                                   Tuesday 13:30-15:30                                                                          Computer 114           

13:30         4915.     Image Quality Improvements for Balanced TFE at 3.0T Using a Clinical Parallel RF Transmission MR System

Trevor Andrews1,2, Melanie Kotys1, Marc Kouwenhoven3, Jay Gonyea2, Takamaru Ashikaga2, George Gentchos, 2,4

1Philips Healthcare, Cleveland, OH, United States; 2College of Medicine, University of Vermont, Burlington, VT, United States; 3Philips Healthcare, Best, Netherlands; 4Radiology, Fletcher Allen Health Care, Burlington, VT, United States

Cardiac MR imaging with steady state free precession sequences suffer from at least two image quality problems at 3T: excessive banding artifacts and suboptimal contrast due to inadequate flip angle.  In this study RF shimming was utilized to address these issues.  Results from 8 subjects demonstrated improved blood-to-septum contrast and radiologist-assessed image quality.  For one choice of parameters banding artifacts were effectively eliminated in all subjects while maintaining good overall image quality.

14:00         4916.     Multi-Slice Parallel Excitation Reduced FOV Imaging for Rodent EPI Applications - not available

Denis Kokorin1,2, Martin Haas1, Maxim Zaitsev1

1Dept. of Diagnostic Radiology, University Hospital Freiburg, Freiburg, Germany; 2International Tomography Center, Novosibirsk, Russian Federation

The technique of parallel transmission in combination with spatially selective excitation allows for reduction of the field of view in the phase encoding direction. In this study the novel principle of multi-slice inner volume imaging is presented and the advantages are illustrated when combined with single shot EPI. The method was implemented successfully in DWI applications on the Bruker BioSpec animal system.

14:30         4917.     Parallel Excitation of a 3D ROI Inside a Post Mortem Brain

Kaveh Vahedipour1, Tony Stöcker1, Daniel Brenner1, N Jon Shah1,2

1Institute of Neuroscience and Medicine, Forschungszentrum Jülich, Jülich, Germany; 2Department of Neurology, RWTH Aachen University, Aachen, Germany

This work demonstrates the excitation of a 3D ROI within a post mortem brain by parallel RF transmission at 4T.

15:00         4918.     A Simple and Analytical Way to Correct for δB0 Inhomogeneity in the Evaluation of B1 Maps Relying on Flip Angle Measurements and Non-Selective Square Pulses

Nicolas Boulant1, Martijn Cloos1, Alexis Amadon1

1NeuroSpin, CEA, Gif sur Yvette, France

Efficient mitigation of the radiofrequency inhomogeneity at high field using coil arrays relies on the accurate knowledge of the individual B1 maps. To date, no simple recipe has been formulated to correct for B0 inhomogeneity in the evaluation of the B1 maps themselves. Here we derive a simple analytical approximation to increase the accuracy of the B1 mapping techniques which rely on the measurement of the flip angle using non-selective square pulses, in the presence of B0 variations. In some possibly encountered cases, applying the correction reduces the error of the estimated B1 amplitude from 13 % to 0.2 %.

                                   Wednesday 13:30-15:30                                                                     Computer 114           

13:30         4919.     Improving RF Shimming Via Non-Linear Sub-Image Combination

Ulrich Katscher1, Peter Vernickel1, Kay Nehrke1, Ingmar Graesslin1

1Philips Research Europe, Hamburg, Germany

RF shimming is able to overcome B1 inhomogeneities at high main fields via optimizing the drive weights of multiple transmit channels. However, due to the limited degrees of freedom in this approach, residual B1 inhomogeneities might occur for particular anatomies. This study tries to mitigate residual B1 inhomogeneities by a suitable, non-linear combination of images obtained from different sub-images. The sub-images have been acquired using different drive weights of the transmit channels, leading to complementary inhomogeneities in the different sub-images. The subsequent combination of the sub-images can be optimized with respect to constant total B1 and constant image contrast.

14:00         4920.     Enhanced Slab Selective Brain Imaging at 3T Using Wide Band Tailored RF Pulses

Shaihan J. Malik1, Joseph V. Hajnal1

1Robert Steiner MRI Unit, Imaging Sciences Department, MRC Clinical Sciences Centre, Hammersmith Hospital, Imperial College London, London, United Kingdom

Short (~2ms) 2DRF B1 inhomogeneity mitigation pulses designed to give broadband uniformity with a controlled excitation in fat were integrated into a T1 weighted MPRAGE sequence. No SAR increase was experienced compared with a standard sequence, but improved grey/white matter contrast was observed.

14:30         4921.     Sparse Parallel Transmission Using Optimized Sparse K-Space Trajectory by Simulated Annealing

Yong Pang1, Xiaoliang Zhang2,3

1Radiology and Biomedical imaging, University of California San Francisco, San Francisco, CA , United States; 2Radiology and Biomedical imaging, University of California San Francisco, San Francisco, CA, United States; 3UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco & Berkeley, CA, United States

The combination of parallel transmission and sparse pulse is able to shorten the excitation duration by using both the coil sensitivity and sparse k-space. In this work, a novel sparse parallel transmission design based on optimal k-space trajectory is proposed. After undersampling the k-space, the simulated annealing (SA) algorithm is applied to design a short k-trajectory traveling through all the sparse samples. Almost without sampling useless k-space data, this k-trajectory is shorter than conventional trajectories and thus shortening the pulse width. Bloch simulation of 90O excitation has been performed to demonstrate the feasibility of this method.

15:00         4922.     Improved SNR/g Using Small FOV Spatially Selective Pulses with Parallel Excitation

Mike J. Smith1, Scott B. King1, Matthew Sodomsky1, Peter Latta1, Jarod Matwiy1, Ulrich Fontius2, Franz Schmitt2, Boguslaw Tomanek1

1National Research Council, Winnipeg, Manitoba, Canada; 2Siemens Medical Solutions, Erlangen, Germany

Transmit array systems generate improved spatially selective excitation profiles while mitigating RF power disposition. We used our 3T Siemens 8-channel transmit system for small FOV excitation to improve parallel imaging SNR when the sample exceeds the ROI. We ensure that excitation artifact signals are below the image noise level, making the g-factor maps ideal (unity) and effective reduction factors greater than what would typically be used for a particular array become possible.

                                   Thursday 13:30-15:30                                                                        Computer 114           

13:30         4923.     Eddy-Current-Compensated RF Pulse Design for Parallel Excitation

Hai Zheng1, Tiejun Zhao2, Tamer Ibrahim1, Fernando Emilio Boada1

1MR Research Center, University of Pittsburgh, Pittsburgh, PA, United States; 2Siemens Medical Systems, Malvern, PA, United States

High-performance RF coils for high or ultra high field MRI often require the use of RF shields that are in close proximity to the imaged volume. These shields can sometimes generate Eddy-currents that are not adequately compensated for using the pre-emphasis algorithm of the scanner and lead to severe distortions in the desired excitation pattern. In this work, we introduce a simple yet effective method for designing eddy-current-compensated parallel transmit RF pulses and demonstrate its effectiveness using simulations as well as experimental data at 7T.

14:00         4924.     VERSE-Guided Numerical RF Pulse Design

Daeho Lee1, William Allyn Grissom1, Michael Lustig1, John Mark Pauly1

1Electrical Engineering, Stanford University, Stanford, CA, United States

Numerical optimization-based RF pulse design methods are widely used to incorporate system non-idealities and non-linearities such as field inhomogeneities, coil sensitivities, and signal decay. These approaches often lead to RF pulses with high peak RF magnitude exceeding the hardware or safety limits and the variable-rate selective excitation (VERSE) principle can be utilized to directly constrain the peak RF power on-the-fly. However, discrete-time implementations of VERSE may not preserve spins' rotational behavior due to the imperfect system modeling and sampling. Also, the excitation profile of reshaped pulses is affected by time-dependencies that are not accounted for in VERSE. To effectively correct these errors while achieving a fast peak RF power control, VERSE-guided numerical RF pulse design framework is introduced for parallel transmit applications.

14:30         4925.     GrIP: Gradient Iterative Predistortion for Multidimensional and Parallel Excitation

William A. Grissom1, Adam B. Kerr1, Pascal P. Stang1, Michael Lustig2, Greig C. Scott1, John M. Pauly1

1Electrical Engineering, Stanford University, Stanford, CA, United States; 2Electrical Engineering, University of California, Berkeley, Berkeley, CA, United States

Multidimensional and parallel excitation pulses are highly sensitive to trajectory imperfections resulting from eddy currents and gradient amplifier nonlinearity. It has been recently proposed to solve this by redesigning RF pulses on measured trajectories; however, this approach is not compatible with RF pulse design methods in which the RF and gradients are designed jointly. We introduce an iterative technique for gradient preemphasis for multidimensional and parallel excitation. The method is capable of overcoming gradient amplifier non-linearities, and obviates the need to redesign pulses on a measured trajectory.

15:00         4926.     Using Dedicated Fieldprobes for Trajectory Measurements in Parallel Excitation Experiments

Johannes Thomas Schneider1, Christoph Barmet2, Wolfgang Ruhm1, Klaas Paul Pruessmann2, Peter Ullmann1

1Bruker BioSpin MRI GmbH, Ettlingen, Germany; 2Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland

Several studies have demonstrated the benefit of measuring actually traversed k-space trajectories and incorporating this information into the design process of parallel spatially-selective excitation (PEX) pulses. However, most of the applied measurement techniques are based on phase evolutions in situ within the object. This leads to a strong dependency of data-quality and -reliability on the imaged objects. To overcome these limitations, a newly developed D2O-fieldprobe was used in this study in order to acquire object-independent trajectory data. This allows robust measurements of calibration data for the calculation of PEX pulses and results in high excitation accuracy under various experimental conditions.

Large-tip-angle & SAR in Parallel RF Contrast Agents & Their Detection

Hall B                        Monday 14:00-16:00                                                                           Computer 115           

14:00         4927.     Bloch Simulation Acceleration for Fast Pulse Design in Parallel Transmit

Seung-Kyun Lee1, Dan Xu2, Silke M. Lechner3,4, Mika W. Vogel3

1GE Global Research, Niskayuna, NY, United States; 2Applied Science Laboratory, GE Healthcare, Waukesha, WI; 3Advanced Medical Applications Laboratory, GE Global Research, Munich, Bavaria, Germany; 4Department of Scientific Computing in Computer Science, Technical University Munich, Munich, Bavaria, Germany

Analytical and computational methods are presented to accelerate Bloch simulation for optimal control-based RF pulse design in parallel transmit. In the first method, the cost and steepest descent calculation in optimal control theory is performed in a frame of reference in which local longitudinal magnetic fields are transformed away analytically. In the second method we demonstrate an order-of-magnitude enhancement in iterative calculation speed as we shift the calculation load from the conventional Central Processing Unit to a Graphics Processing Unit. Both methods were tested in simulated 8-channel pTx pulse design.

14:30         4928.     Optimized Chemical Shift Selective Suppression for PTx Systems at 7T

Rene Gumbrecht1,2, Borjan Gagoski1, Elfar Adalsteinsson1,3

1Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, United States; 2Department of Physics, Friedrich-Alexander-University, Erlangen, Germany; 3Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, United States

Parallel RF transmission offers flexible control of magnetization generation and has been successfully applied at 7T for spatially tailored excitations and mitigation of in-plane B1+ inhomogeneity for slice-selection. CHESS pulses are known to provide good frequency selective suppression in proton spectroscopy as long as B1+ inhomogeneity is small. We propose an optimized CHESS pulse design for pTx systems with high variation in peak-to-trough excitation field magnitude.

15:00         4929.     Large Tip Angle Parallel Excitation Using Nonlinear Non-Bijective PatLoc Encoding Fields

Martin Haas1, Peter Ullmann2, Johannes T. Schneider, 1,2, Wolfgang Ruhm2, Jürgen Hennig1, Maxim Zaitsev1

1Dept. of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany; 2Bruker BioSpin MRI GmbH, Ettlingen, Germany

The nonlinear non-bijective "PatLoc" fields recently proposed for anatomically tailored readout encoding are examined in combination with RF transmission for 2D spatially selective excitation. It is shown that parallel transmission is necessary to resolve encoding ambiguities but that PatLoc encoding allows for higher resolution magnetization patterns to be generated locally as compared to conventional linear encoding fields. The RF pulse design is based on the optimal control algorithm introduced by D. Xu et al. MRM 59, 547 (2008), which has been generalized to the regime of nonlinear non-bijective encoding fields.

15:30         4930.     SAR Benefits of Including E-Field Interactions in Parallel RF Pulse Design

Cem Murat Deniz1,2, Leeor Alon1,2, Riccardo Lattanzi1,2, Daniel K. Sodickson1, Yudong Zhu1

1Center for Biomedical Imaging, Department of Radiology, NYU School of Medicine, New York, NY, United States; 2Sackler Institute of Graduate Biomedical Sciences, NYU School of Medicine, New York, NY, United States

SAR management and excitation homogeneity are critical aspects of RF pulse design at ultra-high magnetic field strength. We investigated the effects on SAR behavior of incorporating measurable E-field interactions into parallel transmission RF pulse design. We simulated three different transmit coil array configurations using two different coil loadings, a human mesh and a homogeneous water phantom. Small-tip-angle and linear class large-tip-angle pulses were employed. We found that global SAR during parallel excitation decreases when  E-field interactions are included in RF pulse design optimization. Larger global SAR benefits were achieved for lower accelerations and for human mesh data.

                                   Tuesday 13:30-15:30                                                                          Computer 115           

13:30         4931.     A Fast Algorithm for Local-1gram-SAR Optimized Parallel-Transmit RF-Pulse Design

Alessandro Sbrizzi1, Hans Hoogduin2, Jan J. Lagendijk2, Peter Luijten2, Gerard Sleijpen3, Cornelis A. van den Berg2

1Imaging Division, UMC utrecht, Utrecht, Netherlands; 2UMC Utrecht; 3Mathematics, Utrecht University

In this paper we present a novel approach to the fast design of local SAR optimized multidimensional spatially selective RF pulses. It is based on the application of a multi-shift Conjugate Gradients (mCGLS) algorithm for computing RF pulses whose resulting local 1 gram SAR is more uniformly distributed, lowering the maximal value over the whole 3D spatial domain. The method was validated by simulations showing a reduction of 23% of the maximal SAR.

14:00         4932.     Local SAR Constrained Hotspot Reduction by Temporal Averaging

Ingmar Graesslin1, Christian Steiding1, Bjoern Annighoefer2, Julia Weller1, Sven Biederer3, David Brunner4, Hanno Homann1, Ferdinand Schweser5, Ulrich Katscher1, Klaas Pruessmann4, Peter Boernert1

1Philips Research Europe, Hamburg, Germany; 2TU Hamburg-Harburg, Hamburg, Germany; 3Institute of Medical Engineering, University of Lübeck, Lübeck, Germany; 4University and ETH Zurich, Zurich, Switzerland; 5IDIR / University Clinics, Jena, Germany

With increasing field strength the local specific absorption rate (SAR) becomes a limiting factor for many MR imaging applications. Minimal SAR RF pulses can be selected from the large solution space due to the extra degrees of freedom in the RF pulse design. This paper extends the recently proposed temporal averaging approach for local SAR reduction with multiple local SAR constraints. It successively applies multiple RF pulses with similar target excitation patterns, but different spatial SAR distributions, for averaging out local hotspots. The concept was validated by simulations and initial experiments on an 8-channel TX MRI system.

14:30         4933.     Characterization of Adiabatic Pulse Prepared Cell Imaging of Iron Oxide Nanoparticles

Steven Harris1, Chase Kessinger2, Jinming Gao2, Hongwei Chen3, Hui Mao3, Xiaoping Hu1

1Biomedical Engineering, Georgia Institute of Technology / Emory University, Atlanta, GA, United States; 2Simmons Comprehensive Cancer Center, University of Texas Southwestern  Medical Center, Dallas, TX, United States; 3Department of Radiology, Emory University School of Medicine, Atlanta, GA, United States

An adiabatic preparation pulse is used to produce an increasing contrast with increasing iron oxide nanoparticle concentration in cell and tumor models.  The adiabatic condition has been shown to fail leading to a contrast for spins diffusing near the nanoparticles.  We show that the adiabatic contrast is linearly correlated with R2 over the range of iron loading tested. Also, increasing contrast is observed in a tumor region confirmed by histology to contain nanoparticles in a model of tumor angiogenesis.  This technique has the potential for cellular imaging and quantification as it is less sensitive magnetization transfer and B0 homogeneity.

15:00         4934.     Local SAR Reduction Based on Channel-Dependent Tikhonov Parameters

Martijn Anton Cloos1, Michel Luong2, Guillaume Ferrand2, Alexis Amadon1, Dennis Le Bihan1, Nicolas Boulant1

1CEA, DSV, I2BM, NeuroSpin, LRMN, Gif-sur-Yvette, France; 2CEA, DSM, IRFU, SACM, Gif-sur-Yvette, France

The possibility of high local SAR values can be a limiting factor to in-vivo transmit-SENSE applications at high field. In this work we introduce a novel method to reduce the local SAR and demonstrate its application based on simulations. When considering the human head at 7T, the proposed method demonstrates local SAR reductions up to a factor of 6.

                                   Wednesday 13:30-15:30                                                                     Computer 115           

13:30         4935.     Selective Positive Contrast of Subvoxel Field-Disturbers Using Off-Resonance Excitation

Gerrit Hendrik van de Maat1, Hendrik de Leeuw1, Peter R. Seevinck1, Chris J.G Bakker2

1Image Sciences Institute, Utrecht, Netherlands; 2Department of Radiology, University Medical Center, Utrecht, Netherlands

It is feasible to excite protons that reside in the vicinity of Holmium loaded microspheres inside a voxel by shifting the center frequency f0 of the rf-excitation pulse. Due to this frequency shift, on-resonance protons are not excited and signal is only generated by protons strongly influenced by the dipole fields invoked by the microspheres. The total signal intensity of a voxel is related to the concentration HoMS in that voxel. The resulting positive contrast can be manipulated by the user since it will depend on the excitation bandwidth and profile and on the f0 frequency shift.

14:00         4936.     Combined Off-Resonance Imaging and Relaxation in the Rotating Frame for Positive Contrast Imaging of Infection in a Murine Burn Model

Valeria Righi1,2, Dionyssios Mintzopoulos1,2, Ovidiu C. Andronesi1,2, Jianxin He3, George Dai2, Laurence G. Rahme3, A Aria Tzika1,2

1NMR Surgical Laboratory, Department of Surgery, Massachusetts General Hospital and Shriners Burns Institute, Harvard Medical School, Boston, MA, United States; 2Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Athinoula A. Martinos Center for Biomedical Imaging, Boston, MA, United States; 3Molecular Surgery Laboratory, Department of Surgery, Massachusetts General Hospital and Shriners Burns Institute, Harvard Medical School, Boston, MA, United States

We employed positive-contrast MRI in a murine model of burn and infection. We used off-resonance imaging (ORI) and a novel method of combining off-resonance imaging and relaxation in the rotating frame (ORI-T2ρ). We imaged accumulation of ultra-small super-paramagnetic iron oxide (USPIO) nanoparticle-labeled macrophages at the infection site in mice, which were burned and infected with Pseudomona aeruginosa. We concluded that ORI-T2ρ is more sensitive than ORI in detecting USPIOs and that we can successfully detect infection with positive contrast imaging, which opens up perspectives for monitoring infection and testing anti-infectives.

14:30         4937.     Quantification of Bound Contrast Agent Concentration Using Delta Relaxation Enhanced MR

Jamu K. Alford1, Blaine A. Chronik1

1Physics and Astronomy, The University of Western Ontario, London, ON, Canada

Delta relaxation enhanced magnetic resonance (dreMR) is an emerging method for performing molecular imaging, which utilizes a removable electromagnetic coil to modify the strength of the main magnetic field during an MRI pulse sequence.  The purpose of this field-cycling method is to acquire information about the binding state of targeted contrast agents that is not obtainable with static-field MRI methods.  This work describes a method for advancing dreMR from qualitative imaging to quantitative measurement of contrast agent binding.  By measuring the concentration of bound agent, the corresponding concentration of the target molecule can determined.

15:00         4938.     Rigidity of the Microscopic Environment Surrounding the Binding Site of Magnetic Nanoparticles

John B. Weaver1, Adam M. Rauwerdink2

1Radiology, Dartmouth-Hitchcock Medical Center, Lebanon, NH, United States; 2Thayer School of Engineering, Dartmouth College, Hanover, NH, United States

The microscopic stiffness of cellular cytoskeleton and the extracellular matrix have been very important in understanding metastasis and angiogenesis but no methods capable of in vivo measurement exist.  We show that a new method related to magnetic particle imaging (MPI) called magnetic spectroscopy of nanoparticle Brownian motion (MSB) is sensitive to the stiffness of the microscopic environment surrounding the binding sites of the streptavidin functionalized nanoparticles.  The matrix consisted of gels made with mixtures of gelatin and biotinated BSA.  Gel stiffness was changed by varying the concentration of gelatin.  MSB showed significant differences between each of the gels.

                                   Thursday 13:30-15:30                                                                        Computer 115           

13:30         4939.     Unambiguous Localization of Contrast Agents Via B0-Field-Cycling

Uvo Christoph Hoelscher1, Steffen Lother1, Florian Fidler1, Matin Blaimer1, Peter Jakob1,2

1Research Center Magnetic Resonance Bavaria (MRB), Wuerzburg, Germany; 2Department for Experimental Physics 5, University of Wuerzburg, Wuerzburg, Germany

This work presents a setup and analysis algorithm for unambiguous localization of contrast agents via a cycled magnetic field inside a clinical scanner. The algorithm detects contrasts agents with high relaxivity dispersion and suppresses signal from pure tissue. Data for the contrast agent Vasovist is shown and compared to theoretical results.

14:00         4940.     Contrast Agents:  the Effect of Relaxation on Magnetic Particle Imaging

Yong Wu1, Zhen Yao1, Gareth Kafka1, David Farrell1, Mark Griswold2, Robert Brown1

1Department of Physics, Case Western Reserve University, Cleveland, OH, United States; 2Department of Radiology, Case Western Reserve University, Cleveland, OH, United States

Magnetic particle imaging (MPI) is a new tomographic technique that allows fast, inexpensive imaging of MRI contrast ferrofluid agents with submillimeter resolution.  Selection fields combined with oscillating driving fields can move unsaturated field-free-points so as to cover the field of view.  In previous studies, the average magnetization is assumed to respond instantaneously to changes in the applied field.  Realistically, however, a finite relaxation time slows the magnetic response.  The present simulation demonstrates that, for contrast agents of interest, the choice of an optimal particle size is strongly dependent on this effect.  A trade-off thus exists between sensitivity and resolution.

 

14:30       4941        A Fast Optimization Algorithm for Multi-Dimensional RF-Pulse Design under Multiple Constraints

A. Sbrizzi1, H. Hoogduin2, P. Luijten2, J. J. Lagendijk2, G. Sleijpen3, and C. A. van den Berg4

1Imaging Division, UMC utrecht, Utrecht, Utrecht, Netherlands, 2UMC Utrecht, 3Mathematics, Utrecht University, 4Radiotherapy, UMC Utrecht

 

Multi dimensional spatially selective excitation (mDSSE) RF pulse design aims to homogenize the magnetization over a given region of interest. After discretizing the solution of the Bloch Equation under the small flip angle approximation, the problem is to find an optimal numerical solution to the least squares problem argmin{||Ax-b||2 } (1) where the matrix A is the discretization of the integral operator as in [1], x and b the vectors corresponding to the requested RF pulses and desired magnetization respectively. In this paper we present an algorithm to solve (1) in a fast and stable way. From recent works it appears that a smooth RF pulse profile improves accuracy in the magnetization obtained from a transmit system. The speed achieved by the algorithm is exploited to add regularization terms to (1) in order to optimize the smoothness of the solution.

 

15:00         4942.     Detection of Human Mononuclear Cells Labelled with Micron-Sized Iron Oxide Particles Using the Sub-Pixel Enhancement of Nonuniform Tissue (SPENT) Sequence

Bernard Siow1, David W. Carmichael2,3, Johannes Riegler4, Daniel Alexander1, Mark Lythgoe4, Roger Ordidge3

1Centre for Medical Image Computing, University College London, London, United Kingdom; 2Institute of Neurology, University College London, United Kingdom; 3Department of Medical Physics and Bioengineering, University College London, United Kingdom; 4Centre for Advanced Biomedical Imaging, University College London, United Kingdom

The Sub-pixel Enhancement of Nonuniform Tissue (SPENT) sequence applies a 2pi phase dispersion across each voxel: the net phase of spins in magnetically homogeneous voxels would be equal to zero and thus no signal would be generated. If there are sub-pixel inhomogeneities, then the net phase of spins in a voxel is not zero and thus signal is seen. In this study, human mononuclear cells labelled with micron-sized iron oxide particles, which creates sub-voxel perturbations in the field, are scanned with a spin-echo SPENT sequence producing positive contrast images. SPENT provides directional information, as well as the potential for quantification.

Topics in RF Design

Hall B                        Monday 14:00-16:00                                                                           Computer 116           

14:00         4943.     ΦFA CUP: PHase Based Flip Angle Calibration Using the P0 Pulse for Proton MRI at 7T

Davide Santoro1, Tomasz Lindel, 1,2, Matthias Dieringer, 1,3, Wolfgang Renz, 1,4, Thoralf Niendorf, 1,5

1Berlin Ultrahigh Field Facility, Max-Delbrueck Center for Molecular Medicine, Berlin, Germany; 2 (PTB), Physikalisch Technische Bundesanstalt, Berlin, Germany; 3Franz-Volhard Klinik, Clinic for Cardiology, Charité Berlin, University Medicine, Berlin, Germany; 4Siemens Healthcare, Erlangen, Germany; 5Experimental and Clinical Research Center (ECRC), Charité Campus Buch, Humboldt-University, Berlin, Germany

We demonstrate the applicability of a rapid 3D-B1+ mapping method  for proton MRI at 7T. The method is based on the acquisition of two phase images where the effective flip angle is encoded in the phase of the non-slice selective rectangular composite pulse used as excitation in a gradient recall echo. On phantoms our method compares well with the double angle method, and is approximately 40 times faster. 3D FA map of human brain acquired in 102s are presented.

14:30         4944.     Spatial RF Pulse Design in Local Rotating Frame

Seung-Kyun Lee1

1GE Global Research, Niskayuna, NY, United States

In magnetic resonance, a gradient- and voxel-dependent rotating frame, which we call a “local rotating frame” can eliminate all longitudinal magnetic fields in magnetization dynamics and therefore significantly simplifies the theory and practice of spatial RF pulse design. When the gradient waveform is pre-determined, as is the case in most existing numerical  RF design methods, the frame transformation is completely straightforward, and removes need for repeated calculation of the same gradient effects as RF pulse is iteratively updated. After introducing basic theoretical elements of the new frame approach, we demonstrate its usefulness in two examples. First, we demonstrate calculation of the residual dephasing in slice selective excitation caused by nonlinearity of the Bloch equations by analytical integration of the equations in the local rotating frame. Second, we show that numerical integration of the Bloch equations is made significantly faster in the new frame due to the lack of strong longitudinal field. We discuss the relevance of the new approach in the context of iterative RF design in parallel transmit.

15:00         4945.     RF Concatenation with Spiral In-And-Out Trajectory for Two-Dimensional Large-Tip-Angle Excitation

Seung-Kyun Lee1, Dan Xu2, W A. Grissom3, Ileana Hancu1, Mika W. Vogel4

1GE Global Research, Niskayuna, NY, United States; 2Applied Science Laboratory, GE Healthcare, Waukesha, WI; 3Department of Electrical Engineering and Radiology, Stanford University, Stanford, CA; 4GE Global Research, Munich, Bavaria, Germany

We demonstrate that the time-reversed RF concatenation principle, which was previously considered in one-dimensional non-adiabatic inversion pulse design, can be extended to multi-dimensional and multi-coil excitation pulses. We present general analytical formulation of the concatenation principle, and demonstrate its use in (i) simulated inversion in 8-channel parallel transmit, and (ii) in-vivo inversion experiment on a single channel system with a human subject. The off-resonance field sensitivity, which is a drawback of the concatenation method in one dimension, is significantly reduced for two-dimensional excitation when a spiral in- and out- trajectory is employed.

15:30         4946.     Design of Velocity Selective Inversion Pulse for VSASL Using the Shinnar-Le Roux Algorithm

Kangrong Zhu1, Kui Ying1, Xinlu Xu1, William Grissom2, Michael Lustig2, John Pauly2

1Tsinghua University, Beijing, China; 2Stanford University, Stanford, CA, United States

A new method which employs the SLR algorithm to generate velocity selective inversion pulse is presented and a design example is shown. Simulation results demonstrate that the slice profile of the designed inversion pulse is very smooth and that the pulse has good resistance to B1 inhomogeneity. Phantom studies verified the frequency selectivity and the velocity selectivity of the pulse. All results imply that the pulse is potentially suitable for use as a tagging pulse in VSASL. The design method enables the pulse designer to explicitly trade off among important parameters such as slice thickness, pulse duration and pass-band ripple.

                                   Tuesday 13:30-15:30                                                                          Computer 116           

13:30         4947.     Combined Excitation and Partial Saturation to Reduce Inflow Enhancement

Misung Han1,2, Brian A. Hargreaves1

1Radiology, Stanford University, Stanford, CA, United States; 2Electrical Engineering, Stanford University, Stanford, CA, United States

Partially saturating outer slab upstream can reduce inflow enhancement and pulsatile ghost artifacts by preparing flowing spins to a steady state before entering the imaging slab. However, adding another RF pulse and spoilers increases scan time. Here, we present a short RF pulse that simultaneously excites the imaging slab and partially saturates the outer slab. This pulse was designed and demonstrated by phantom and in vivo experiments for the RF-spoiled gradient echo sequence.

14:00         4948.     Partial Fourier Accelerated Selective Excitation Improves Pattern Fidelity at 9.4 Tesla

Kaveh Vahedipour1, Tony Stöcker1, N Jon Shah1,2

1Institute of Neuroscience and Medicine, Forschungszentrum Jülich, Jülich, Germany; 2Department of Neurology, RWTH Aachen University, Aachen, Germany

Partial Fourier Spatially has so far been only investigated in 1 dimension in form of asymmetric echoes. Recently, we have prposed to use partial Fourier excitations for higher dimension. This work encloses recent results and considerations.

14:30         4949.     T2-Weighted Spin Echo Pulse Sequence That Is Sensitive to Restricted Diffusion

Ziqi Sun1, Robert Bartha2

1The Ohio State University, Columbus, OH, United States; 2Robarts Research Institute, London, Ontario, Canada

A spin-echo (SE) pulse sequence incorporated with two selective adiabatic full passage (AFP) pulse trains separated by a time delay tau (varying with TE) and located symmetrically on both sides of an amplitude modulated 180 degree refocusing pulse. Apparent T2 and diffusion measurements on a phantom of multi-medium and multi-compartment demonstrated that the customized SE sequence generated T2-weighted contrast that is specifically sensitive to restricted diffusion in the phantom media in comparison to those of the conventional SE and CPMG pulse sequences.

15:00         4950.     On the Generation of Half-Sinc Pulses for Optimal Excitation Profile

Keith Wachowicz1, B. Gino Fallone2,3

1Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada; 2Medical Physics, Cross Cancer Institute, Canada; 3University of Alberta

In this work, we perform simulations to explore the effects of fast T2 relaxation on excitation with half-sinc pulses.  The generation of pulses for optimal excitation profiles is explored in terms of optimal flip angle, for which standard reasoning used for longer T2 species will no longer hold.  Also, the number of side lobes to generate an optimal excitation profile was investigated, since, unlike the case of longer T2, using more side-lobes does not necessarily result in a better profile.

                                   Wednesday 13:30-15:30                                                                     Computer 116           

13:30         4951.     Arbitrary Shape Excitation Using a 2D SPOKE Pulse at 7T

Christopher Joseph Wargo1, Marcin Jankiewicz1, Huairen Zeng1, John C. Gore1

1Vanderbilt University Institute of Imaging Science, Nashville, TN, United States

Arbitrarily shaped volume excitation has a variety of potential MRI applications.   By restricting the FOX, the information obtained is isolated to particular anatomical or functional regions.  Faster acquisitions can also be enabled for high resolutions due to fewer collected points.   To accomplish this, multi-pulse composites can be applied at various excitation k-space points, with simulations used to define RF and gradient waveforms for a specific desired excitation pattern. B1 inhomogeneity effects, prevalent at ultra-high field strengths such as 7T, can also be accounted for.   Here we demonstrate the performance of a SPOKE based arbitrary shape excitation at 7T in phantoms.

14:00         4952.     Multi-Voxel Excitation Using Sparse Pulse on Significantly Undersampled K-Space

Yong Pang1, Xiaoliang Zhang2,3

1Radiology and Biomedical imaging, University of California San Francisco, San Francisco, CA , United States; 2Radiology and Biomedical imaging, University of California San Francisco, San Francisco, CA, United States; 3UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco & Berkeley, CA, United States

Multi-dimensional spatial selective excitation and parallel transmission have been applied to single- and multi-voxel MR spectroscopy to excite arbitrarily shaped region and shorten the pulse width. Recently the sparse pulse has been developed to shorten the excitation duration by using significantly undersampled k-space. Taking the advantage of this new technique, an example of multi-voxel excitation using sparse pulse is presented. Bloch simulation results demonstrate that each voxel can be well localized within the Field of View and the in-slice error can be controlled within 5%.

14:30         4953.     Refine Phase Modulation Function Sampling Step Size in Off-Center Variable-Rate Selective Excitation with Rf Pulse Magnitude Replication

Leping Zha1, Mitsue Miyazaki1

1Toshiba Medical Research Institute USA, Vernon Hills, IL, United States

Optimized rf waveforms are often designed under the “hard pulse approximation”, and come with a small number of wave points and singular features.  When the original designs are converted to variable-rate pulses, the small number of points often causes the often required variable-rate phase modulation function to be inadequately sampled, resulting in selection profile degeneration in off-center slices.  The piece-wise-constant amplitude function should be preserved, with the proposed simple pulse magnitude replication method which enables much finer phase sampling step size to better mimic the continuous phase function, and to help maintain the selection quality of the original pulse design.

15:00         4954.     Optimization of RF Excitation to Maximize Signal and T2 Contrast of Tissues with Rapid Transverse Relaxation

Michael Carl1, Mark Bydder2, Jiang Du2, Atsushi Takahashi1, Eric Han1, Graeme Bydder2

1GE Healthcare, Waukesha, WI, United States; 2University of California, San Diego

We present experimental data to verify theoretical findings on how to select the RF parameters of a non-selective SPGR pulse train to maximize signal amplitude and T2 contrast in tissues with fast transverse relaxation. The experimental data very closely matched the theory so that our results may directly be implemented to maximize the scan efficiency of UTE acquisitions.

                                   Thursday 13:30-15:30                                                                        Computer 116           

13:30         4955.     Reduction of Slice Select Artifacts in Half Pulse Excitations Used in Ultrashort TE (UTE) Imaging

Atsushi M. Takahashi1

1Applied Science Laboratory, GE Healthcare, Menlo Park, CA, United States

In ultra short TE (UTE) imaging, so-called “half pulses” are used because they do not require a refocusing gradient, thus reducing the echo time.  Two half pulses are required and cancellation of signal outside the desired slice desired.  Poor cancellation results in artifacts generated by signals from out of slice.  Here we present a method for improving the cancellation of out-of-slice signal to improve slice selection.

14:00         4956.     "MY Way" – a New Construction Technique for Broadband Slice-Selective Refocusing Pulses

James B. Murdoch1

1Toshiba Medical Research Institute USA, Mayfield Village, OH, United States

High-bandwidth slice-selective refocusing pulses are important for proton spectroscopy at 3T and above, but they are not easy to construct.  Previously it has been proposed to combine a self-refocused 90° excitation pulse with a time-reversed version of itself to create a suitably spin-flipping 180° waveform.  However, the 90° pulse need not be wholly slice-selective:  MX and MZ can vary outside the desired slice width so long as MY≈0.  Both AM and PM excitation pulses have therefore been optimized for the proper MY response and then combined to spawn new refocusing pulses (with a PM second-component phase flip for overall antisymmetry).

14:30         4957.     A Study of Wideband MR Imaging: SNR and CNR

Edzer Lienson Wu1,2, Jyh-Horng Chen, 23, Tzi-Dar Chiueh3

1Biomedical Engineering, National Taiwan University, Taipei, Taiwan; 2Interdisciplinary MRI/MRS  Lab, Taipei, Taiwan; 3Electrical Engineering, National Taiwan University, Taipei, Taiwan

Most of the MR image accelerating methods suffer from degradation of acquired images, which is often correlated with the degree of acceleration. However, Wideband MRI is a novel technique that transcends such flaws. In this study we demonstrate that Wideband MRI is capable of obtaining images with identical quality as conventional MR images in terms of SNR, CNR (contrast-to-noise ratio) and image sharpness, while using only half the total scan time (Wideband factor W=2) of normal MRI sequence.

15:00         4958.     High Fidelity Imaging Using Frequency Sweep Encoding

Jun Shen1

1NIMH, Bethesda, MD, United States

Recently Frydman et al proposed a mechanism for directly forming images in k space using frequency sweep encoding. It relies on the quadratic dependence of magnetization phase on position. In combination with EPI-type readout, this method has found applications in single-shot spin-echo imaging. Its sequential excitation of magnetization may also be used for novel image contrast generation. Fidelity of images directly formed in k space, however, is significantly degraded. Here we show that fidelity of this type of images can be restored and we also extend this method to susceptibility-weighted imaging.

Non-Cartesian Imaging Methods

Hall B                        Monday 14:00-16:00                                                                           Computer 117           

14:00         4959.     Fast Regridding Using LSQR on Graphics Hardware

Gerald Buchgraber1, Florian Knoll2, Manuel Freiberger2, Christian Clason3, Markus Grabner1, Rudolf Stollberger2

1Institute for Computer Graphics and Vision, Graz University of Technology, Graz, Austria; 2Institute of Medical Engineering, Graz University of Technology, Graz, Austria; 3Institute of Mathematics and Scientific Computing, University of Graz, Graz, Austria

Iterative image reconstruction methods have become increasingly popular for parallel imaging or constrained reconstruction methods, but the main drawback of these methods is the long reconstruction time. In the case of non-Cartesian imaging, resampling of k-space data between Cartesian and non-Cartesian grids has to be performed in each iteration step. Therefore the gridding procedure tends to be the time limiting step in these reconstruction strategies. With the upcoming parallel computing toolkits (such as CUDA) for graphics processing units image reconstruction can be accelerated in a tremendous way. In this work, we present a fast GPU based gridding method and a corresponding inverse-gridding procedure by reformulating the gridding procedure as a linear problem with a sparse system matrix.

14:30         4960.     A General Trajectory Tester

Lawrence Frank1,2, Greg Balls1, Souheil Inati3, Leslie Greengard4

1Radiology, UCSD, La Jolla, CA, United States; 2Radiology, VASDHS, San Diego, CA, United States; 3Dept of Psychology, NYU, New York; 4Courant Institute, NYU, New York, United States

We present a software platform called the General Trajectory Tester (GTT) that allows users to input arbitrary 3D k-space trajectories, in an arbitrary number of interleaves, which are then used to sample and reconstruct a known 3D analytical phantom.  The GTT can also simulate diffusion weighting, including arbitrary diffusion angular encoding schemes for DTI, multiple b-values, eddy current and motion induced artifacts and self-navigation, and so is a natural platform to test efficient DTI acquisition and self-navigation schemes.

15:00         4961.     Nonlinear Inverse Reconstruction for Real-Time MRI of the Human Heart Using Undersampled Radial FLASH

Martin Uecker1, Shuo Zhang1, Jens Frahm1

1Biomedizinische NMR Forschungs GmbH, Max-Planck-Institut für biophysikalische Chemie, Göttingen, Germany

A previously proposed algorithm for autocalibrated parallel imaging simultaneously estimates image content and coil sensitivities by inverting a nonlinear equation. Here, this algorithm is extended to non-Cartesian encodings and applied to real-time MRI. The method takes advantage of a convolution-based technique to simplify the implementation on a graphical processing unit (GPU) for reduced reconstruction times. The method is validated for real-time MRI of the human heart at 3 T using RF-spoiled radial FLASH. The results demonstrate artifact-free reconstructions for acquisitions with only 65 – 85 spokes corresponding to imaging times of 130 – 170 ms.

15:30         4962.     Improved BPE Reconstruction Using FOCUSS

Hisamoto Moriguchi1, Yutaka Imai1

1Radiology, Tokai University, Isehara, Kanagawa, Japan

Bunched Phase Encoding (BPE) is a new type of fast data acquisition method in MRI that takes advantage of zigzag k-space trajectories. A primary disadvantage of BPE is that images reconstructed using matrix inversion methods are sometimes affected by high levels of noise. In this study, a novel framework to reduce SNR loss in BPE reconstruction is presented. In this technique, high frequency k-space data are processed using regularization and the focal underdetermined system solver (FOCUSS). The newly proposed method is referred to as eBPE-FOCUSSf. Noise levels in the images of BPE-FOCUSS are substantially reduced from those of BPE.

                                   Tuesday 13:30-15:30                                                                          Computer 117           

13:30         4963.     Accurate Iterative Reconstruction Algorithm from Undersampled Radial Trajectory

Sung-Min Gho1, Dong-Hyun Kim1,2

1Electrical and Electronic Engineering, Yonsei University, Shinchon-Dong, Seoul, Korea, Republic of; 2Radiology, Yonsei University, Shinchon-Dong, Seoul, Korea, Republic of

Radial k-space sampled data can be reconstructed using a variety of schemes such as gridding, filtered back-projection (FBP), etc. Recently, the iterative next-neighbor regridding (INNG) algorithm was proposed as a means for accurate reconstruction. However, these algorithms have drawbacks in their ability to reconstruct image from undersampled radial trajectory. Therefore, we propose a new algorithm to reconstruct accurate images from undersampled radial trajectory.

14:00         4964.     Sampling Density-Adaption for Directly Filtered Projection Reconstruction - not available

Armin Michael Nagel1, Frederik Bernd Laun1, Christian Matthies1, Armin Biller2,3, Michael Bock1

1Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany; 2Radiology, German Cancer Research Center, Germany; 3Department of Diagnostic and Interventional Radiology, University Hospital Heidelberg, Germany

To minimize ringing artifacts apodization functions are often used. In this work a sampling density weighted apodization (SW) with a Hamming-window was implemented for 3D projection reconstruction trajectories (3DPR). This pulse sequence was compared with two post-acquisition filtered 3DPR-sequences, a conventional 3DPR-sequence and a sampling density adapted sequence (3DPR-UPF). Both, the 3DPR-UPF- and the 3DPR-SW-sampling scheme show a much better performance when compared to a conventional post-acquisition filtered 3DPR-sequence. Comparing the 3DPR-SW- and the post-acquisition filtered 3DPR-UPF-sequence, the SNR-benefits of the SW approach competes against the better artifact-behavior of the post-filtered technique.

14:30         4965.     2D Radial Acquisition Technique with Density Adaption in Sodium MRI

Simon Konstandin1, Armin Michael Nagel2, Patrick Michael Heiler1, Lothar Rudi Schad1

1Computer Assisted Clinical Medicine, Heidelberg University, Mannheim, Germany; 2Department of Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany

A 2D projection reconstruction method with variable gradient amplitudes is proposed to cover the k-space uniformly. Simulations and sodium measurements were performed to compare a non-adapted with a density adapted radial sequence scheme in regard to SNR and blurring. A total SNR benefit of 1.37 for the adapted sequence can be reached. The new density adapted 2D radial sampling scheme provides higher SNR and less artifacts in the presence of magnetic field inhomogeneities than conventional projection reconstruction methods.

15:00         4966.     Anisotropic Twisted Projection Sodium MRI of Articular Cartilage in the Human Knee

Alexander Watts1, Robert Stobbe1, Christian Beaulieu1

1Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada

3D projection imaging has potential benefits in sodium MRI due to ultra-low echo times, but the spherical sampling of k-space leads to isotropic voxels which may not be ideal for imaging thin structures such as cartilage in the knee. Oblate-spheroidal twisted projection imaging, which yields anisotropic voxels, was compared to isotropic acquisition; both projection acquisitions had equal voxel volume (2.56 mm3), twist, readout length, and scan time.  The anisotropic projection acquisition had better effective in-plane resolution in a saline resolution phantom and yielded sharper, higher quality sagittal sodium images of human knee cartilage (n=3) in 9 min at 4.7T.

                                   Wednesday 13:30-15:30                                                                     Computer 117           

13:30         4967.     Flexible Retrospective Selection of Temporal Resolution in Real-Time Speech MRI Using a Golden-Ratio Spiral View Order

Yoon-Chul Kim1, Shrikanth S. Narayanan1, Krishna S. Nayak1

1Ming Hsieh Department of Electrical Engineering, University of Southern California, Los Angeles, CA, United States

In speech research using real-time MRI, the analysis of vocal tract dynamics is performed retrospectively after acquiring data in real-time. A flexible selection of temporal resolution is desirable because of natural variations in speaking rate and variations in the speed of different articulators. In this work, a golden ratio temporal view order was applied. Compared to a traditional spiral acquisition, the proposed method can provide an improved aliasing artifact reduction for static postures (e.g. pause, vowel sound) and an improved temporal resolution for capturing the dynamics of rapid articulator movement (e.g. consonant to vowel transition).

14:00         4968.     Efficient T2*- Contrast Manipulations in 3D Abdominal Imaging Using Autocorrected Forward/Reverse Spiral MRI

Peter Börnert1, Peter Koken1, Holger Eggers1

1Philips Research Europe, Hamburg, Germany

Large volume coverage, short total scan time, robust fat suppression and dedicated measures to varyimage contrast are important issues in abdominal MRI. To manipulate T2* weighting from very weak to very strong, 3D single breath-hold forward and reverse spiral imaging is performed in combination with three-point chemical-shift imaging (IDEAL) for high quality fat suppression and off-resonance artifact correction. Parallel imaging was employed to improve SNR, sampling efficiency and to achieve an up-front data compression during image reconstruction and correction. The combination of forward/reverse spiral signal sampling, IDEAL and SENSE could pave the way for interesting future water / fat resolved clinical applications.

14:30         4969.     Spiral MRI Trajectory Design with Frequency Constraint

Thomas Oberhammer1,2, Markus Weiger, 1,2, Franciszek Hennel3

1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland; 2Bruker BioSpin AG, Faellanden, Switzerland; 3Bruker BioSpin MRI GmbH, Ettlingen, Germany

An improved, 3-domain design for Archimedean spiral trajectories is proposed, utilising the instantaneous frequency for taking into account frequency limitations of the gradient system. It is demonstrated by simulations and experiments that the new layout enables creating trajectories with high fidelity and efficiency, leading to improved spiral image quality.

15:00         4970.     A Comparison of Spiral-Out, Spiral-In/out and Radial Balanced SSFP Sequences for Dynamic Cardiac Imaging

Xue Feng1, Michael Salerno2, Christopher M. Kramer, 23, Craig H. Meyer1,3

1Biomedical Engineering, University of Virginia, Charlottesville, VA, United States; 2Medicine, University of Virginia, Charlottesville, VA, United States; 3Radiology, University of Virginia, Charlottesville, VA, United States

Cartesian and radial balanced SSFP (bSSFP) sequences are widely used clinically for dynamic cardiac imaging. Dynamic spiral sequences have been used in many research studies, but clinical adoption has been slow.  One goal of this study is to compare radial and spiral dynamic balanced SSFP scanning. The other goal is to develop a new spiral-in/spiral-out bSSFP pulse sequence to achieve flow compensation through symmetry and to exploit the bSSFP refocusing mechanism at TE = TR/2.  We compared this new sequence to radial bSSFP and spiral-out bSSFP with flow-compensated rewinders.

                                   Thursday 13:30-15:30                                                                        Computer 117           

13:30         4971.     3D Cardiac Cine Imaging Using a 3D Cones Trajectory

Holden H. Wu1,2, Bob S. Hu3, Dwight G. Nishimura2, Michael V. McConnell1

1Cardiovascular Medicine, Stanford University, Stanford, CA, United States; 2Electrical Engineering, Stanford University, Stanford, CA, United States; 3Palo Alto Medical Foundation, Palo Alto, CA, United States

In this work, we present a 3D cardiac cine sequence based on the 3D cones non-Cartesian trajectory which can resolve multiple cardiac phases for a 3D volume within a single breath-held scan. The 3D cones trajectory is a fast sampling method that enables a high degree of scan time reduction. Furthermore, its robust motion and flow properties are beneficial for cardiac imaging. We implement the 3D cones cine sequence using a prospectively cardiac-triggered segmented SSFP sequence. Experimental results demonstrate that 12 cardiac phases can be resolved for 10 contiguous slices within a single 30-second breath-held scan.

14:00         4972.     Spiral Phyllotaxis: A Better Way to Construct a 3D Radial Trajectory in MRI - not available

Davide Piccini1, Arne Littmann2, Peter Schmitt2, Michael O. Zenge2

1Pattern Recognition Lab,, University Erlangen-Nuernberg, Erlangen, Germany; 2MR Applications and Workflow Development, Healthcare Sector, Siemens AG, Erlangen, Germany

In order to exploit the self-navigating properties of 3D radial MRI, the trajectory has to be arranged so that the first readout of each interleave is oriented in superior-inferior direction. If this is done sub-optimally, image quality is degraded. Hence, an innovative trajectory based on spiral phyllotaxis featuring optimized interleaving properties is presented. The trajectory was compared to an Archimedean spiral in phantom experiments and in-vivo. The smooth gradient waveforms of the novel trajectory avoided eddy currents effects and, thus, allowed for whole-heart coronary imaging with highly undersampled data. Moreover, the presented method is intrinsically prepared for self-gated cardiac MRI.

14:30         4973.     Fast 3D SSFP Imaging Using a Concentric Cylinders Trajectory

Kie Tae Kwon1, Holden H. Wu, 1,2, Dwight G. Nishimura1

1Electrical Engineering, Stanford University, Stanford, CA, United States; 2Cardiovascular Medicine, Stanford University, Stanford, CA, United States

A 2D concentric rings trajectory is inherently centric-ordered, provides a smooth weighting in k-space, and enables shorter scan times.  Extensions of this trajectory for 3D imaging include: stack-of-rings and concentric cylinders. 3D stack-of-rings trajectory directly inherits flexible trade-offs property from 2D concentric rings. 3D concentric cylinders trajectory is similar to stack-of-rings, but it also has a unique property that leads to fewer excitations and benign off-resonance effects. In this work, we revisited the 3D concentric cylinders trajectory and have implemented an SSFP version of this sequence. Among the potential applications of this sequence is non-contrast MR angiography based on SSFP.

15:00         4974.     A Fast 3D Trajectory with Orthogonal Oversampling

James Grant Pipe1, Ryan K. Robison1, Ajit Devaraj1, Nicholas Zwart1, Kenneth Otho Johnson1

1Neuroimaging Research, Barrow Neurological Institute, Phoenix, AZ, United States

This work presents a new, center-out, rapid 3D trajectory based on spirals.  It has very uniform sampling density, and good suppression of aliasing and motion artifacts.  A unique feature is that, with little penalty in time, it samples most of k-space twice, in orthogonal directions, making it a good method undersampling for parallel imaging or compressed sensing.

Quantitative Imaging

Hall B                        Monday 14:00-16:00                                                                           Computer 118           

14:00         4975.     A Technique for Rapid Single-Echo Spin Echo T2 Mapping

Marshall S. Sussman1, Logi Vidarsson2, John M. Pauly3, Hai-Ling Margaret Cheng4,5

1Medical Imaging, University Health Network, Toronto, Ontario, Canada; 2Diagnostic Imaging, The Hospital for Sick Children, Toronto, Ontario, Canada; 3Electrical Engineering, Stanford University, Stanford, CA, United States; 4Research Institute & Diagnostic Imaging, The Hospital for Sick Children, Toronto, Ontario, Canada; 5Medical Biophysics, University of Toronto, Toronto, Ontario, Canada

Rapid T2 mapping is conventionally performed using multi-echo spin-echo imaging. However, due to errors arising from stimulated echoes and limited availability, the traditional but much slower single-echo spin-echo approach is often preferred. In this work, a rapid and accurate T2 mapping method based on single-echo spin-echo imaging is presented. Acquisition times are significantly reduced by employing a short repetition time (TR) together with a constant TR-TE difference to maintain monoexponential decay. Accuracy of the proposed method is demonstrated in phantom results and in-vivo imaging of the healthy human knee cartilage and brain.

14:30         4976.     Transverse Relaxation of Tissue Water in Human Brain: Relative Contributions of Iron and Macromolecules

Fumiyuki Mitsumori1, Hidehiro Watanabe1, Nobuhiro Takaya1, Michael Garwood2, Edward Auerbach2

1National Inst. Environmental Studies, Tsukuba, Ibaraki, Japan; 2University of Minnesota, United States

Apparent transverse relaxation rate (R2†) of the tissue water was measured in various regions of healthy human brain at four different fields of 1.9, 3, 4.7, and 7T using a multi-echo adiabatic spin echo (MASE) sequence. The R2† increased with field strength (B0).  Distribution of R2† in various regions is well explained by contributions from regional non-hemin iron concentration ([Fe]) and macromolecular mass fraction defined by 1 – water fraction. Assuming an equation of R2† = α[Fe] + βfM + γ, the coefficient α increased linearly with B0, as previously observed in ferritin solution.

15:00         4977.     Iron Accumulation and Transverse Relaxation Rates: A Quantitative Postmortem Study

Christian Langkammer1,2, Nikolaus Krebs2, Walter Goessler3, Eva Scheurer2, Kathrin Yen2, Franz Fazekas1, Stefan Ropele1

1Department of Neurology, Medical University of Graz, Graz, Austria; 2Ludwig Boltzmann Institute for Clinical-Forensic Imaging, Graz, Austria; 3Institute of Chemistry - Analytical Chemistry, University of Graz, Graz, Austria

Iron deposition in human brain tissue is commonly assessed by mapping R2 or R2* relaxation rates. The goal of our study was to validate if transverse relaxation rates can be used as sensitive and linear measures for iron concentration. R2 and R2* mapping was done in human post-mortem brains in situ. After brain extraction and fixation iron concentrations were determined in selected grey and white matter regions using inductively coupled plasma mass spectrometry. We found that both, R2 and R2* are strongly correlated with iron concentration and therefore can be used as a surrogate marker for iron deposition.

15:30         4978.     In Vivo Comparison of Three Quantitative MRI Techniques to Measure Brain Iron

Catherine Anusha Mallik1, Gareth J. Barker1, David J. Lythgoe1

1Centre for Neuroimaging Sciences, Institute of Psychiatry, London, United Kingdom

Correlation of quantitative MRI with brain iron may prove a useful tool in the diagnosis and prognosis of associated neuropathology. Sequences required for three of the most promising measures were implemented: transverse relaxation rate, magnetic susceptibility and magnetic field correlation (MFC) mapping. Protocols for each technique were standardised for brain coverage under the constraint of approximately equal, patient tolerable, scan times. Data collected on three control subjects at 3T in six brain regions indicated that magnetic susceptibly is the most closely correlated with reference brain iron of the three techniques.

                                   Tuesday 13:30-15:30                                                                          Computer 118           

13:30         4979.     Automated Calculation of T2* Mapping for MR Images with Application of Certainty Criterion for Enhanced Display - not available

Oyinlolu Adeyanju1, Einar Heirberg2, Jane Sjögren3

1Biomedical Engineering, Northwestern University, Chicago, IL, United States; 2Clinical Physiology, Lund University, Lund, Sweden; 3Engineering, Medviso AB, Lund, Sweden

T2* mapping is a broadly-applied MRI measurement technique with various applications in many areas of MRI, including fMRI, molecular cell tracking, and the in vivo quantification of superparamagnetic contrast agents. This study assessed the validity of a T2* mapping module implemented in Segment (Medviso, AB). The T2* mapping module employs a linear least squares fitting algorithm with a goodness of fit certainty criterion for enhancing the accuracy of T2* maps. When compared with standard methods of T2* mapping, Segment showed an improved correlation with concentration over standard methods in phantom measurements, with a much shorter time of T2* map creation.

14:00         4980.     Influence of Stimulated Echoes on Iron Quantification with Multi-Echo Spin-Echo Pulse Sequences

Christina Louise Tosti1, Haiying Tang2, Srirama V. Swaminathan3, Sujit S. Sheth2, Jens H. Jensen4, Alvaro Nunez4, Kristi Hultman5, Daniel Kim4, Ed X. Wu6, Gary M. Brittenham2, Truman R. Brown2

1The Ohio State University, Columbus, OH, United States; 2Columbia University, New York, NY, United States; 3Philips Healthcare, Andover, MA, United States; 4New York University, New York, NY, United States; 5Mayo Clinic, Rochester, MN, United States; 6The University of Hong Kong, Hong Kong, Hong Kong

Phantoms that simulate the iron in tissue have been measured using a theoretical model that can separately quantify dispersed (ferritin-like) and aggregated (hemosiderin-like) iron using multiple spin echo (MSE) based R2 images. Here, we examine a large range of these heterogeneous phantoms and a preliminary patient population to determine the effects of stimulated echo (STE) contamination in MSE sequences on the iron quantification.

14:30         4981.     Cramer-Rao Lower Bounds for Assessment of Precision in T2* Value Evaluation by GRE Multiecho Sequence: Application to Iron Overload Measurements in Thalassemia Patients

Vincenzo Positano1, Luca Menichetti1, Alessia Pepe1, Antonella Meloni1, Daniele De Marchi1, Matteo Milanesi1, Maria Filomena Santarelli1, Giovanni Palazzi2, Massimo Lombardi1, Luigi Landini1,3

1MRI Lab, "G. Monasterio" Foundation and Institute of Clinical Physiology, Pisa, Italy; 2Oncoematologia Pediatrica, Policlinico di Modena, Modena, Italy; 3Department of Information Engineering, University of Pisa, Pisa, Italy

T2* multiecho magnetic resonance is an established methodology for assessment of iron overload in heart, liver, and other organs by evaluation of the T2* value. However, the dependence of the expected error from T2* value and acquisition parameters is unknown. This study demonstrate that evaluation of Cramer-Rao lower bounds allows to quantify the precision limits of T2* assessment for various schema of TEs. CRLB approach was applied to evaluate the T2* measurement quality in thalassemia patients.

15:00         4982.     MR Iron Quantification of Soluble (Ferritin-Like) and Insoluble (Hemosiderin-Like) Iron: A Biochemical Validation in Human Liver Explants

Christina Louise Tosti1, Boguslaw S. Wojczyk2, Sujit S. Sheth2, Daniel Kim3, Haiying Tang2, Jens H. Jensen3, Gary M. Brittenham2, Truman R. Brown2

1The Ohio State University, Columbus, OH, United States; 2Columbia University, New York, NY, United States; 3New York University, New York, NY, United States

A theoretical MR model has been proposed that separately quantifies dispersed (soluble, ferritin-like) and aggregated (insoluble, hemosiderin-like) iron by distinguishing their effects on R2 relaxation curves.  In this study, we examine human liver explants with this non-invasive MR iron measurement technique.  We compare the results of iron quantification using this model to the tissue concentrations of ferritin and hemosiderin iron determined by biochemical analysis.

                                   Wednesday 13:30-15:30                                                                     Computer 118           

13:30         4983.     Real-Time EPI T1, T2 and T2* Mapping at 3T

Cyril Poupon1, Jessica Dubois1, Linda Marrakchi1, Veronique Brion1, Jean-Francois Mangin1, Fabrice Poupon1

1CEA I2BM NeuroSpin, Gif-sur-Yvette, F91191, France

Besides their usual methodological use to characterize the NMR characteristics of specific chemical drugs, T1, T2 or T2* mapping is now progressively used in neuro-scientific studies, for instance to better understand the structural modifications occurring during brain development. Despite major improvements using DESPOT1 and DESPOT2 pulse sequences, mapping the whole brain relaxometry still requires scan durations not always compatible with clinical use. In this abstract, we present a novel solution dedicated to perforrm rho, T1, T2, and T2* mapping of the human brain in real-time with a low scan duration and a 1.5mm isotropic resolution.

14:00         4984.     Rapid and Simultaneous Measurements of T1, T2 and Relative Proton Density (M0) for Dynamic Musculoskeletal Studies

Paulo Loureiro de Sousa1,2, Alexandre Vignaud3, Servanne Fleury1,2, Pierre G. Carlier1,2

1Institut de Myologie, Laboratoire de RMN, Paris, France; 2CEA, I2BM, Paris, France; 3Siemens Healthcare, Saint Denis, France

Skeletal muscle functional imaging can provide valuable information on the physiological changes accompanying muscle activation  Because skeletal muscle physiological adaptations can simultaneously impact several NMR physical parameters (T1, T2, T2*, relative spin density (M0)), mono-parametric NMR imaging may not be able to describe adequately the complex behavior of stressed or exercised muscle. We investigated the feasibility of fast simultaneous measurements of T1, T2 and M0 using an Inversion Recovery TrueFISP (IR-TrueFISP) sequence. The main advantage of this method is the possibility of performing dynamic T1, T2 and M0 measurements in a single multi-parametric acquisition protocol, with relatively high temporal resolution.

14:30         4985.     Correction for T1 Determined Using Rapid Look-Locker B-SSFP  and a Simple Two Parameter Model Fit

Neville D. Gai1, John A. Butman1

1Radiology & Imaging Sciences, National Institutes of Health, Bethesda, MD, United States

A correction scheme for modulated longitudinal magnetization and incomplete inversion recovery Look-Locker sequence with  balanced SSFP acquisition is described. Correction for such a scheme typically uses a three parameter model which requires acquisition of several (6 to 10) phases. It is shown that the two parameter inversion recovery model provides excellent fit over a wide range of TR/T1 and flip angle parameter space.  The T1* obtained is easily corrected using a linear model. The correction was tested in phantoms and in head scans of several volunteers and shown to be accurate. Use of the two parameter model requires fewer acquisition phases (3 to 5) leading to improved temporal and spatial resolution.

15:00         4986.     T1 Error Analysis for Double Angle Technique and Comparison to Inversion Recovery B-SSFP Look-Locker Acquisition

Neville D. Gai1, John A. Butman

1Radiology & Imaging Sciences, National Institutes of Health, Bethesda, MD, United States

The dual flip angle technique (DAT) with short TRs is widely used to derive T1 maps rapidly. DAT offers a relatively faster alternative to typical Look-Locker based schemes. The optimal flip angles required, the effect of field inhomogeneity and, more recently, the effect of spoiling for DAT have been described in literature. In this work, we systematically study various sources of errors through simulations and error propagation analysis. DAT accuracy and repeatability of T1 calculations is shown to be substantially affected as a result of these sources of errors especially when compared with inversion recovery based schemes. Experimental results in phantoms and head scans in several volunteers confirm relatively poorer repeatability and accuracy in calculated T1 values especially when compared with recently described rapid Look-Locker technique with similar temporal and spatial resolution.

                                   Thursday 13:30-15:30                                                                        Computer 118           

13:30         4987.     General Formulas for Optimizing Two-Point Saturation-Recovery Measurements

Jung-Jiin Hsu1, Gary H. Glover2, Greg Zaharchuk2

1Department of Radiology, University of Miami School of Medicine, Miami, FL, United States; 2Lucas Center for Imaging, Stanford University, Stanford, CA, United States

Saturation-recovery (SR) method is a popular technique for the longitudinal relaxation rate measurement, in which the relaxation rate is derived from separate measurements of at least two different recovery times.  An interesting and long-standing question in clinical applications is, given a limited amount of time, how the recovery times should be allocated to minimize the uncertainty of the measurement.  In this work, a systematic Monte Carlo computation for the SR method is carried out and general formulas are derived to answer this question.

14:00         4988.     Fast Two-Dimensional Relaxometric Characterisation of Brain Tissue in Vivo: Is T1 Relaxation Multi-Component?

Ana-Maria Oros-Peusquens1, Fabian Keil1, N Jon Shah1,2

1Institute of Neuroscience and Medicine 4, Medical Imaging Physics, Forschungszentrum Juelich GmbH, Juelich, Germany; 2Faculty of Medicine, RWTH Aachen University, Aachen, Germany

T1 mapping is performed with a spoiled 3D multiple-echo gradient echo sequence, from two acquisitions with same TR and different flip angles. At each different echo time, an independent T1 map is produced. Apart from small variations due to decreasing SNR with echo time, no dependence of T1 on TE is expected from the theoretical description of the method. However, a systematic increase of T1 with echo time is observed in the white matter, and interpreted as an indication for multi-component T1 decay due to the presence of multiple and distinct water environments.

14:30         4989.     Rapid T1 Determination with Optimized Inversion Recovery Sequence

Ke Li1,2, Junzhong Xu1,2, Zhongliang Zu1,2, John C. Gore1,2, Mark D. Does1,2, Daniel F. Gochberg1,2

1Vanderbilt University Institute of Imaging Science, Nashville, TN, United States; 2Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States

In this work, the inversion recovery sequence was optimized for T1 measurements, by varying both the inversion recovery time (ti) and pre-delay (td). Comparing to conventional acquisition scheme, which uses logarithmic spacing ti and long td (> 5T1), the optimized sequence has precision efficiency of ~ 2.5 times greater than the conventional scheme.

15:00         4990.     A Field Comparison of R1 and R2* Relaxivities of Gd-DTPA in Aqueous Solution and Whole Blood: 3T Versus 7T

Chaitanya Kalavagunta1, Gregory John Metzger1

1Center of Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States

The goal of this study was to measure r1 and r2* relaxivity of Gd-DTPA in bovine blood and aqueous solution at 3T and 7T. To our knowledge this is the first time that the r2* characteristic for blood has been measured at 7T.

Susceptibility Mapping

Hall B                        Monday 14:00-16:00                                                                           Computer 119           

14:00         4991.     Advantages of a Local Polynomial Filter with Moving Window for Phase Reconstruction in Susceptibility Weighted Imaging

Sandra M. Meyers1, Amir Eissa2, Alan H. Wilman3

1Physics, University of Alberta, Edmonton, AB, Canada; 2Physics, Univeristy of Alberta, Edmonton, AB, Canada; 3Biomedical Engineering, University of Alberta, Edmonton, AB, Canada

Phase images produced from susceptibility-weighted images require extensive reconstruction.  In this work we compare a moving window, local polynomial approach to a standard method, demonstrating significant differences in phase unwrapping and contrast.

14:30         4992.     Improving SWI Contrast

Kai Zhong1, Oliver Speck1

1Biomedical Magnetic Resonance, Otto-von-Guericke University, Magdeburg, Saxon-Anhalt, Germany

Susceptibility Weighted Imaging (SWI) has been proposed to enhance the image contrast, especially between small veins and surrounding tissues and has received wide acceptance in clinical MR studies. On the other hand, it was not discussed in detail whether the original SWI filter indeed optimally exploits magnitude and phase information. A generalized filter based on the sigmoidal function was applied for SWI contrast and showed higher contrast compared to the original SWI filter. The new filter can be parameterized and thus can be dynamically adapted to the data input to improve the overall SWI contrast and therefore should improve the outcome of future studies utilizing SWI contrast.

15:00         4993.     A Comparison of T2* Magnitude, SWI, K-Division Susceptibility Map, Maxwell Equation Regularized Quantitative Susceptibility Map for Brain Iron Mapping

James R. Ledoux1, Tian Liu1, Jing Liu1, Ildar Khalidov1, Martin Prince1, Yi Wang1

1Weill Cornell Medical Center, New York, NY, United States

The reconstruction methods of Quantitative Susceptability Mapping (QSM), Susceptability Weighted Imaging (SWI), and truncated k-space division all desire to reveal an image of susceptability sources. It is difficult to directly find susceptability sources from the magnetic field map (obtained by phase information) as the dipole convolution kernel has zeros in k-space.  However, the inversion problem can be regularized to provide a solution as shown in the QSM method.  We compare this to direct inversion of the convolution by truncating the convolution kernel near ill-conditioned values, and with SWI which is a phase-masked T2* image.

15:30         4994.     Eliminating Streaking Artifacts in Quantitative Susceptibility Mapping Using L1 Norm Minimization - not available

Ildar Khalidov1, Tian Liu1, Xiaoyue Chen2, Moonsoo Jin2, Martin Prince1, Yi Wang1

1Radiology, Weill Cornell Medical College, NYC, NY, United States; 2Biomedical Engineering, Cornell University, Ithaca, NY, United States

Quantitative susceptibility mapping (QSM) has been developed as a technique that uses the phase information from the MRI measurements to estimate susceptibility changes in the imaged object. Moreover, it is possible to estimate the magnetic moment of the region of interest, which gives way to quantitative imaging of tracer particles in MRI. However, the inverse problem that needs to be solved to recover the susceptibility map from the phase image is ill-posed: 1), the dipole kernel that links the two maps has a cone of zeros in Fourier domain, and 2), regions of strong susceptibility change have low intensity (and hence, unreliable phase data) due to T2* dephasing. In this work, we use total variation-based regularization to tackle the inverse problem. Compared to original weighted quadratic regularization in [1], the proposed TV regularization significantly reduces the streaking artifacts from the areas of susceptibility change. This is particularly important in animal imaging where eventual air bubbles and/or voxel misclassifications at the segmentation stage could lead to strong under-estimation of the quantities of particles of interest.

                                   Tuesday 13:30-15:30                                                                          Computer 119           

13:30         4995.     Quantitative Susceptibility Mapping: A Comparison Between COSMOS and Weighted L1 Regularization from Single Orientation

Tian Liu1, Jing Liu2, James Ledoux2, Martin R. Prince2, Yi Wang1

1Biomedical Engineering, Cornell University, New York, NY, United States; 2Radiology, Weill Cornell Medical College, New York, NY, United States

Quantitative Susceptibility Mapping (QSM) provides both visualization and quantification of endogenous and exogenous susceptibility contrasts. In this study, we compared two validated reconstruction techniques, COSMOS and weighted L1, on a phantom experiment and on healthy volunteer brain scans.

14:00         4996.     Quantitative Susceptibility Mapping by Regulating the Field to Source Inverse Problem with a Sparse Prior Derived from the Maxwell Equation: Validation and Application to Brain - not available

Jing Liu1, Tian Liu2, Ludovic de Rochefort3, Ildar Khalidov1, Martin Prince1, Yi Wang1,2

1Radiology, Weill Cornell Medical College, New York, NY, United States; 2Biomedical Engineering, Cornell University, Ithaca, NY, United States; 3MIRCen, I2BM, DSV, CEA, Fontenay-aux-roses, France

Quantitative susceptibility mapping (QSM) is a promising technique for quantifying endogenous and exogenous susceptibility contrasts. The problem of deriving QSM from the measured field is under-determined and can be solved by optimization minimization programming. The prior information of the MR image magnitude can be used for promoting the sparsity of the minimization problem. The proposed method was validated by phantom experiments with high accuracy and good image quality. Brain susceptibility mapping provides good visualization as well as valuable quantification of iron accumulation in the brain.

14:30         4997.     Quantitative Susceptibility Mapping in Vivo in the Rat Brain

Ludovic de Rochefort1, Aurélie Delzor1, Martine Guillermier1, Diane Houitte1, Marion Chaigneau1, Nicole Déglon1, Philippe Hantraye1, Vincent Lebon1

1MIRCen, I2BM, DSV, CEA, Fontenay-aux-Roses, France

Molecular and cellular imaging is seeing a growing interest, but applicability to MRI relies on the ability to be specific, sensitive and quantifiable. Superparamagnetic iron oxides are good candidates as they produce a strong magnetic field creating signal voids in gradient echo images. Quantitative susceptibility mapping (QSM) additively uses the magnetic field to quantify the magnetic sources. In this study we apply QSM in the preclinical context of the rat brain using a reconstruction algorithm that includes unwrapping, removing background effects and inverting the field map. The technique demonstrates its ability to quantify SPIO amounts injected in the brain.

15:00         4998.     Susceptibility Phase Imaging of the Basal Ganglia: Effects of Phase Filtering, Slice Orientation and ROI Selection with Comparison to T2* Mapping

Andrew Walsh1, Marguerite Wieler2, Wayne Martin2, Alan Wilman1

1Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada; 2Division of Adult Neurology, University of Alberta, Edmonton, Alberta, Canada

We examined the effectiveness of current methods in susceptibility phase imaging of basal ganglia structures using computer simulations and invivo data. The effects of phase filtering reconstruction, slice orientation and ROI selection with comparison to T2* mapping are examined in this study.  These investigations showed that measured phase can be substantially influenced by filtering, slice orientation and ROI selection which can confound phase data acquired in cross sectional or longitudinal studies.  We have proposed techniques to optimize phase value acquisition for the consistent evaluation of phase in future studies.

                                   Wednesday 13:30-15:30                                                                     Computer 119           

13:30         4999.     Accurate Susceptibility Quantification from MR Phase Data Through the Least Squares Fit Method: Phantom Validation

Jaladhar Neelavalli1,2, Yu-Chung Norman Cheng3, Mudassar Kamran2, James V. Byrne2, Ewart Mark Haacke3

1The MRI Institute for Biomedical Research, Detroit, MI, United States; 2Nuffield Department of Surgery, University of Oxford, Oxford, Oxfordshire, United Kingdom; 3Academic Radiology, Wayne State University, Detroit, MI, United States

We utilize a Fourier based method of quantifying the magnetic susceptibilities of arbitrarily shaped objects with medium sizes in a phantom. The method uses the phase images and an iterative 3D least-squares fitting algorithm. The quantified susceptibility has an 11% uncertainty, which is due to the pixelization (or systematic) error.

14:00         5000.     Multi Echo Susceptibility Weighted Imaging: Improving Image Contrast by Applying the Susceptibility Weighted Phase Mask to Maps of the R2* Decay

Christian Denk1, Alexander Rauscher1

1UBC MRI Research Centre, University of British Columbia, Vancouver, BC, Canada

Maps of R2* relaxation computed from multi echo susceptibility weighted images (SWI) were multiplied with phase mask obtained from the same data. This procedure leads to an improved contrast between grey matter and white matter compared to standard SWI data processing.

14:30         5001.     Susceptibility Weighted Imaging (SWI) of the Kidney at 3T – Initial Results

Moritz Mie1, Johanna C. Nissen2, Frank G. Zöllner1, Melanie Heilmann1, Henrik J. Michaely2, Stefan O. Schönberg2, Lothar R. Schad1

1Department of Computer Assisted Clinical Medicine, Heidelberg University, Mannheim, Germany; 2Institute of Clinical Radiology and Nuclear Medicine, Heidelberg University, Mannheim, Germany

SWI has been investigated for its applicability to renal imaging. To handle the problems of organ motion and a higher oxygenation level of the kidneys compared to the brain, the acquisition time has been cut down to allow for breath-hold examinations and different post-processing methods were investigated. Results showed that our new post-processing strategy could produce a susceptibility weighted contrast enhancement by a factor of 1.5 compared to the standard approach. The results represent initial experiences with the SWI for abdominal imaging which proof the principal feasibility.

15:00         5002.     Field-Corrected 3D Multiecho Gradient Echo: Simultaneous Extraction of Quantitative R2*, T2* Weighting, SWI, and Venography

Robert Marc Lebel1, Alan W. Wilman1

1Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada

Susceptibility weighted imaging incorporates phase information to enhance image contrast. We employ multiecho 3D gradient-echo, with a rapid pre-scan to minimize diverging phase ramps in the readout direction, with advanced post-processing techniques to correct for macroscopic field gradients to generate multiple high quality data sets from a single scan. Ultimately this technique yields the following low-artifact, high-resolution data sets: (1) T2*-weighted images, (2) quantitative R2* maps, (3) SWI, and (4) venography.

                                   Thursday 13:30-15:30                                                                        Computer 119           

13:30         5003.     Resolving Phase: Inversion of SWI-Phase Data in Order to Obtain Its Sources Utilizing the Concept of a Generalized Lorentzian Approximation

Ferdinand Schweser1, Moritz Hütten2, Berengar Wendel Lehr2, Andreas Deistung2, Daniel Güllmar2, Jürgen Rainer Reichenbach2

1Medical Physics Group, Department of Diagnostic and Interventional Radiology , Jena University Hospital, Jena, Germany; 2Medical Physics Group, Department of Diagnostic and Interventional Radiology, Jena University Hospital, Jena, Germany

Phase data acquired at multiple orientations with respect to the magnetic field was inverted to susceptibility, rotation-invariant local shift, and anisotropy-related susceptibility. Results indicate that gray-to-white matter contrast in phase images is dominated by sources from magnetic susceptibilities rather than macro-molecular exchange processes.

14:00         5004.     Reconstruction of Multi-Echo High-Resolution T2* and Phase Imaging Data Acquired at 3 Tesla Using a 32 Channel Head Coil

Claudiu Schirda1, Anthony Vu2, Robert Zivadinov1

1Buffalo Neuroimaging Analysis Center, University at Buffalo, Buffalo, NY, United States; 2GE Healthcare, Milwaukee,, WI, United States

Susceptibility weighted imaging (SWI) has been shown to be a useful technique for visualization of small veins, of iron deposits and micro bleeds in vivo brain, among other applications. Because the susceptibility effects present in the image are dependent on the echo time, a multi-echo acquisition like SWAN, even when using just the magnitude information, will be able to provide complimentary information. Using the free (no extra acquisition time) information that is found in the phase image, thus SWAN with phase reconstruction, enables one to obtain a wealth of information. A number of challenges are presented when using a 32 channel coil for data acquisition and we present solutions to these challenges.

14:30         5005.     Order of Magnitude Speedup for Iterative Algorithms in Quantitative Susceptibility Mapping Using Multi-Core Parallel Programming

Deqi Cui1,2, Tian Liu1, Pascal Spincemaille3, Yi Wang

1Biomedical Engineering, Cornell University, New York, NY, United States; 2Optic electronics, Beijing Institute of Technology, Beijing, China; 3Radiology, Weill Cornell Medical College, New York, NY, United States

Iterative susceptibility reconstructions requires four Fast Fourier Transforms in every iteration and hundreds of iterations to converge. Although the iteration is hard to disperse, FFT can be computed in parallel. In this study, a parallelized FFT based on OpenMP was implemented to achieve quasi real-time susceptibility map reconstructions.

15:00         5006.     A T2* Selective Higher-Order Soliton Preparation Pulse for MRI

Marcin Jankiewicz1,2, Jay Moore1,3, Adam W. Anderson1,4, John C. Gore1,4

1Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States; 2Department of Radiology, Vanderbilt University, Nashville, TN, United States; 3Department of Physics, Vanderbilt University; 4Department of Biomedical Engineering, Vanderbilt University

The soliton pulses represent a promising solution to the problem of designing T2* selective preparation pulses. The pulses are characterized by a set of complex parameters. Their interpretation is only partially understood in the context of MRI. For example, some of them correspond to values of relaxation times for which the magnetization vector will be nulled. A preliminary analysis of the behavior of such pulses is presented here with the goal of demonstrating the versatility of such pulses in producing a range of T2* contrasts.

Gating & Triggering

Hall B                        Monday 14:00-16:00                                                                           Computer 120           

14:00         5007.     Rapid Frame-Rate MR Acquisitions to Reveal Mechanisms of Circular Breathing and Sound Production in the Australian Aboriginal Didgeridoo

Graham Charles Wiggins1, Pippa Storey1

1Radiology, NYU Medical Center, New York, NY, United States

The Australian Aboriginal wind instrument known as the didgeridoo is played using techniques that are unusual in Western music. A continuous sound is maintained through circular breathing, in which the mouth is used as a pump to keep air flowing into the instrument while inhaling through the nose. Traditional playing technique involves interdental articulation that differs from Western tonguing. We used rapid FLASH acquisitions to capture the circular breathing cycle and reveal the mechanics involved. This may serve as an aid to teaching proper playing technique.

14:30         5008.     Cardiac Imaging at 7.0T: Comparison of Pulse Oximetry, Electrocardiogram and Phonocardiogram Triggered 2D CINE for Left Ventricular Function Assessment

Tobias Frauenrath1, Fabian Hezel1, Wolfgang Renz2, Florian von Knobelsdorff-Brenkenhoff3, Thibaut de Geyer d’Orth1, Marcel Prothmann3, Matthias Dieringer1, Kerstin Kretschel3, Jeanette Schulz-Menger3,4, Thoralf Niendorf1,4

1Berlin Ultrahigh Field Facility, Max-Delbrueck Center for Molecular Medicine, Berlin, Germany; 2Siemens Medical Solutions, Erlangen, Germany; 3Franz-Volhard-Klinik for Cardiology, Helios Klinikum Berlin-Buch, Charité Campus Buch, Germany; 4Experimental and Clinical Research Center (ECRC), Charité Campus Buch, Humboldt-University, Berlin, Germany

As ultrahigh field cardiac MRI becomes more widespread in the (pre)clinical research arena the propensity of ECG recordings to interference from electromagnetic fields and magneto-hydrodynamic effects increases and with it the motivation for a practical gating/triggering alternative. This study compares the feasibility, efficacy and reliability phonocardiogram (ACT), vector electrocardiogram (VCG) and traditional pulse oximetry (pO2) triggered MRI for left ventricular function assessment at 7.0T. ACT’s intrinsic insensitivity to interference from electro-magnetic fields and magneto-hydrodynamic effects results in an excellent trigger reliability and renders it suitable for global cardiac function assessment at ultrahigh magnetic field strengths.

15:00         5009.     Magnetic Field Gradient Artifact Reduction on ECG for Improved Triggering

Julien Oster1,2, Olivier Pietquin1,3, Michel Kraemer4, Jacques Felblinger1,2

1U947, Inserm, Vandoeuvre-les-Nancy, France; 2IADI, Nancy-Université, Nancy, France; 3IMS Research Group, Supelec Metz Campus, Metz, France; 4Schiller Médical, Wissembourg, France

Cardiac MR Acquisitions have to be synchronized with heart activity to prevent from motion artifacts. Electrocardiogram (ECG) is therefore the most accurate tool. Magnetic Field Gradients (MFG) artifacts are unfortunately induced on ECG signals. In this paper a new real-time MFG artifact reduction method is presented. This technique is based on the merging of both ECG and MFG artifact models. An estimation of the model parameters is recursively updated by nonlinear Bayesian filtering. The MFG signals can then be filtered with the MFG artifact model parameters in real-time. The herein presented method outperforms state-of-the-art algorithms and enables accurate triggering.

15:30         5010.     High Resolution, Free-Breathing Coronary Artery Imaging with >99% Respiratory Efficiency:  Comparing Beat to Beat Respiratory Motion Correction with Navigator Gating

Andrew David Scott1,2, Jennifer Keegan, 1,2, David N. Firmin, 1,2

1National Heart and Lung Institute, Imperial College, London, Greater London, United Kingdom; 2Cardiovascular Magnetic Resonance Unit, The Royal Brompton Hospital, London, Greater London, United Kingdom

Respiratory motion correction using highly efficient localized beat-to-beat epicardial fat tracking was compared to standard navigator gating using high resolution right coronary artery imaging.  Beat-to-beat corrections were applied to 3D spiral acquisitions (99.3% respiratory efficiency) and navigator gating applied to 3D magnetization-prepared balanced steady-state-free-precession acquisitions (44% efficient) in ten healthy subjects.  Quantitative comparison was performed using vessel diameter and vessel sharpness.  Results were not substantially different between techniques and the study highlights the importance of the localized nature of the beat-to-beat respiratory-motion-correction.

                                   Tuesday 13:30-15:30                                                                          Computer 120           

13:30         5011.     Efficient Navigator-Gated Acquisition of Different Breathing Positions During Free Breathing Applied to Flow Measurements in the Great Vessels

Sebastian Gruhlke1, Michael Markl1, Bernd André Jung1

1University Hospital Freiburg, Freiburg, Germany

To investigate physiological effects of the breathing position on blood flow, a double navigator-gated sequence was implemented defining two acceptance windows during expiration and inspiration. The method permitted to acquire flow sensitive phase contrast MRI data during both in- and expiration within a single scan with optimal scan efficiency. The sequence was applied to measure the dependency of time resolved blood flow on in- and expiration during breath-hold and free breathing as well as valsalva maneuver in the major vessels. In-vivo measurements could detect respiration related difference in blood flow even during free breathing

14:00         5012.     Retrospective Bellows-Based Reconstruction for Cardiac MRI: Preliminary Experience

Claudio Santelli1, Reza Nezafat1, Warren J. Manning1,2, Sebastian Kozerke3, Dana C. Peters1

1Cardiology, Beth Israel Deaconess Medical Center, Boston, MA , United States; 2Radiology, Beth Israel Deaconess Medical Center, Boston, MA, United States; 3D-ITET, ETH Zurich, Institute for Biomedical Engineering, Zurich, Switzerland

We evaluated the relationship between the respiratory bellows, placed on the chest, and the abdomen, and the superior-inferior displacement of the navigator signal, the lung-liver interface, and the heart, in single-heart-beat ECG-gated images.  The diaphragmatic  bellows correlated better than the chest wall bellows, and bellows correlated best with the navigator.  Using a bellows based criteria, 3D coronary MRI was reconstructed retrospectively, based on the bellows data only.  Our preliminary experience suggests that bellows-gating should be revisited.

14:30         5013.     Prospective Diaphragm Position Prediction for Cardiac MR Using Multiple Navigators

Ian Hamilton Burger1, Jennifer Keegan2,3, Ernesta Meintjes1, David Firmin2,3

1Human Biology, University of Cape Town, Cape Town, Western Cape, South Africa; 2CMR Unit, Royal Brompton Hospital Trust, London, United Kingdom; 3Imperial College London

Prediction of the diaphragm position during imaging segments by multiple navigators and a predictor estimator during the preceding systole. The control system compares the navigator records to a model and feeds back the difference between the model and recorded value to prevent the model from diverging. This data can then be used to improve prospective slice following and increase acceptance window and increase respiratory efficiency.

15:00         5014.     Motion Compensated Reconstruction for Thoracoabdominal Dynamic Contrast-Enhanced MRI in Free-Breathing

Marina Filipovic1,2, Pierre-André Vuissoz1,2, Andrei Codreanu3, Michel Claudon4, Jacques Felblinger1,5

1INSERM-U947, Nancy, France; 2Laboratory IADI, Nancy-Université, Nancy, France; 3Centre Hospitalier de Luxembourg; 4University Hospital Nancy; 5INSERM-CIC801

Physiological motion often impairs the analysis of abdominal and thoracic dynamic contrast-enhanced MRI, by causing motion-induced artefacts and misregistration. A previously published reconstruction algorithm, GRICS, corrects for motion-induced artifacts in a single image reconstruction. A novel method has been developed by modifying GRICS with the purpose of performing whole motion compensation in dynamic contrast-enhanced MRI. The performance is demonstrated on 6 myocardial perfusion MRI data sets and on one simulated data set. The results present elastic registration and motion-artefact correction of the image series, in order to allow for more accurate time-intensity curves analysis and for a simplified post-processing.

                                   Wednesday 13:30-15:30                                                                     Computer 120           

13:30         5015.     3D Free-Breathing Cardiac Cine Imaging with Respiratory and Cardiac Self-Gating and 3D Motion Correction - not available

Jing Liu1, Thanh D. Nguyen1, Pascal Spincemaille1, Noel CF Codella1, Martin R. Prince1, Yi Wang1

1Radiology, Weill Cornell Medical College, New York, NY, United States

A 3D radial cardiac cine imaging technique provides reliable 3D motion tracking from the data acquisition for image reconstruction. 3D tracked motions are used for robust respiratory and cardiac self-gating and also allows 3D motion correction. 

14:00         5016.     High Spatial and Temporal Resolution Free Breathing Cardiac CINE-GRICS :  512x512 Vs 128x128 Matrix

Pierre-André Vuissoz1,2, Freddy Odille3, Brice Fernandez, 1,4, Maelene Lohezic, 1,4, Adnane Benhadid1,2, Damien Mandry2,5, Jacques Felblinger1,6

1Imagerie Adaptative Diagnostique et Interventionnelle, Nancy-Université, Nancy, France; 2U947, INSERM, Nancy, France; 3Centre for Medical Image Computing, University College London, London, United Kingdom; 4Global Applied Science Lab., GE healthcare, Nancy, France; 5Departments of Radiology, University Hospital Nancy, Nancy, France; 6CIC801, INSERM, Nancy, France

In cardiac MRI, myocardium function is usually studied through breath hold acquisitions, limiting the achievable spatial and temporal resolution. The recently proposed CINE-GRICS algorithm allows reconstructing cardiac cine images from free-breathing scans without any limitation regarding spatial resolution, as motion is corrected for by a motion model. In 2D short axis balanced-SSFP scans, we assess the benefit of using the motion-compensated strategy for high spatial and temporal resolution CINE, with matrix sizes from 128x128 to 512x512. Resulting images were assessed visually and using entropy-based metrics, and showed improved sharpness and better depiction of fine cardiac structures.

14:30         5017.     Reducing the Sensitivity to Respiratory Motion of Modified Look-Locker with Saturation Recovery for Cardiac T1 Mapping

Ting Song1,2, Vincent B. Ho2,3, Glenn Slavin1, Maureen N. Hood2,3, Jeffrey A. Stainsby4

1GE Healthcare Applied Science Laboratory, Bethesda, MD, United States; 2Radiology, Uniformed Services University of the Health Sciences, Bethesda, MD, United States; 3Radiology, National Navy Medical Center, Bethesda, MD, United States; 4GE Healthcare Applied Science Laboratory, Toronto, ON, Canada

To address cardiac motion, data acquisition is limited to quiescent periods of the cardiac cycle necessitating a segmented method. However, respiratory motion resulting from failed breath holding remains an issue. If a subject fails to maintain a consistent breath hold throughout the entire scan the acquired K-space data is not consistent across segments and this can result in motion artifacts. A new scheme of segment arrangement is proposed in this context. Phantom and human studies were evaluated with the two schemes.

15:00         5018.     Simulation of Motion-Induced Dark-Rim Artifacts for Cartesian and Spiral Pulse Sequences

Michael Salerno1, Christopher M. Kramer2, Craig H. Meyer3

1Department of Medicine, Cardiology, University of Virginia, Charlottesville, VA, United States; 2Department of Radiology, University of Virginia, Charlottesville, VA; 3Biomedical Engineering, University of Virginia, Charlottesville, VA

Simulation of interleaved spiral data acquisition demonstrates reduced sensitivity to motion-induced dark-rim artifacts as compared to conventional Cartesian data acquisition.  Thus, spiral data acquisition strategies may be advantageous for first-pass myocardial perfusion imaging.

                                   Thursday 13:30-15:30                                                                        Computer 120           

13:30         5019.     Combination of Motion Adapted Gating with Non-Rigid Motion Correction for Free-Breathing MRI

Yuji Iwadate1, Yoshihiro Tomoda2, Yoshikazu Ikezaki2, Tetsuji Tsukamoto1

1MR Applied Science Laboratory, GE Healthcare Japan, Hino, Tokyo, Japan; 2MR Engineering, GE Healthcare Japan, Hino, Tokyo, Japan

The motion adapted gating (MAG) approach accelerates respiratory gating but still requires considerably longer scan time compared to a single breath-hold scan. In this work, we combined the non-rigid motion correction technique with the MAG approach to reduce scan time to the level comparable to breath-hold. A volunteer study showed that the scan time was less than 1.1-fold longer than non-gating scan and motion artifacts remaining with the MAG were reduced by non-rigid motion correction. This technique can be applied to various abdominal applications such as free-breathing dynamic contrast enhanced imaging.

14:00         5020.     Using Respiratory Biofeedback Games in Pediatric MRI Examinations to Increase Patient Comfort and Facilitate Scanning – a Pilot Study

Lena Douglas1, Rose-Marie Claesson2, Bo Ehnmark2, Thröstur Finnbogason2, Anna-Märta Lång2, Bo Nordell1, Morten Bruvold3, Jouke Smink3, Permjit Jhooti4

1Department of Medical Physics, Karolinska University Hospital, Stockholm, Sweden; 2Department of Pediatric Radiology, Astrid Lindgren Children's Hospital, Karolinska University Hospital, Stockholm, Sweden; 3Philips Healthcare, Best, Netherlands; 4Radiological Physics, University Hospital of Basel, Basel, Switzerland

MRI examinations of pediatric patients can be challenging partly because many children have difficulties in lying still. The aim of this work is to introduce in respiratory controlled sequences a biofeedback game in which the child can control the flight of an airplane on a screen through the diaphragm position, as registered by standard navigator echoes. Given a task to focus on children are less likely to move during scanning leading to less motion artifacts. When playing the game the breathing pattern also becomes smoother with a more regular end-expiratory position, leading to more efficient and shorter examinations.

14:30         5021.     Self-Gating Reconstruction of Multiple Respiratory Phases Using Undersampled Golden-Radial Phase Encoding Trajectory

Christian Buerger1, Tobias Schaeffter1, Claudia Prieto1

1Division of Imaging Sciences, King's College London, London, United Kingdom

A new self-gating acquisition scheme allowing the retrospective reconstruction of several respiratory phases is proposed. This approach takes advantage of the recently introduced Golden-Radial Phase Encoding (G-RPE) trajectory and uses the, inherently acquired, central k-space profiles to derive the respiratory motion signal. The method was tested in in-vivo data using a 32-channel coil and 3 different respiratory phases were reconstructed from undersampled data using non-Cartesian SENSE reconstruction.

15:00         5022.     Phase Navigator for Respiratory Triggering

Alto Stemmer1, Berthold Kiefer1

1Healthcare Sector, Siemens AG, Erlangen, Germany

In this work the signal for respiratory triggering is derived with a navigator that measures respiratory induced off-resonance effects. The advantages compared to a liver dome navigator are the compatibility with short bore scanners and that no navigator positioning is necessary.

Prospective Motion Correction

Hall B                        Monday 14:00-16:00                                                                           Computer 121           

14:00         5023.     Combination of Prospective and Retrospective Motion Correction for Multi-Channel MRI

Chaiya Luengviriya1,2, Jian Yun1, Oliver Speck1

1Department of Biomedical Magnetic Resonance, Otto-von-Guericke University, Magdeburg, Germany; 2Department of Physics, Kasetsart University, Bangkok, Thailand

Real-time prospective correction is a very promising method to avoid image quality degradation caused by subject motion in MRI of human brain. The inaccuracy of measured motion data is limiting the efficiency. Simulations showed that residual motion artifacts after a prospective correction increased with the level of inaccuracy. Even for an ideal accurate case, artifacts can appear in multi-channel MRI because of coil sensitivity map errors. A retrospective correction was proposed and showed that the image quality can be further improved, especially for strong motion. In all cases, smooth motion resulted in fewer artifacts than abrupt motion.

14:30         5024.     MR Compatible Sensor for Motion Artifact Corrected Reconstruction Method  - not available

Laure Rousselet1,2, Maélène Lohezic, 23, Damien Mandry, 2,4, Cédric Pasquier5, Jacques Felblinger1,2

1IADI, Nancy-Université, Nancy, France; 2U947, Inserm, Nancy, France; 3Global Applied Science Lab., GE Healthcare, Nancy, France; 4CHU de Nancy, Nancy, France; 5CIC801, INSERM, Nancy, France

The goal of this work was to develop a MR compatible sensor which aims at measuring the acceleration of a localized region of the body. It has been integrated to a motion compensated reconstruction (GRICS) as a physiological input to reduce respiratory artifacts and improve image quality.

GRICS reconstructions, performed with respiratory belt and with accelerometer, were compared to breath-hold images and averaged free breathing acquisitions. Accelerometer gives similar results to respiratory belts and to breath-hold. Moreover, it is easier to install on patient.

15:00         5025.     Self-Encoded Marker Design for Adaptive Optical Real-Time Motion Correction

Christoph Forman1, Murat Aksoy2, Matus Straka2, Joachim Hornegger1, Roland Bammer2

1Pattern Recognition Lab, Department of Computer Science, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany; 2Department of Radiology, Stanford University, Stanford, CA, United States

Patient motionis one of the unsolved problems in MRI. In this study, we propose a novel large field of view marker design to be used with a monovision based system to correct for rigid head motion. The proposed marker design has gives better accuracy and can correct for larger patient head motion.

15:30         5026.     Fast Cross-Calibration Between MR Scanner and Optical System for Prospective Motion Correction

Murat Aksoy1, Christoph Forman1, Matus Straka1, Samantha Jane Holdsworth1, Stefan Tor Skare1,2, Joachim Hornegger3, Roland Bammer1

1Department of Radiology, Stanford University, Stanford, CA, United States; 2Karolinska Institute, Stockholm, Sweden; 3Computer Science, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany

Optical systems have been proposed as a way to achieve rigid head motion correction with minimal changes to the pulse sequence. However, the usability of these systems in clinical practice have been limited mostly due to the tedious scanner-optical system cross-calibration routine that is required to link the frame of references of the optical system and the MR scanner. In this study, we propose a fast cross-calibration routine that is easy and takes only a couple of seconds. The variability of the scanner-camera cross calibration parameters with varying sequence parameters was investigated.

                                   Tuesday 13:30-15:30                                                                          Computer 121           

13:30         5027.     Prospective Motion Correction for MRI with a Single Retro-Grate Reflector Target and a Single Camera

Maxim Zaitsev1, Brian S. R. Armstrong2, Brian Andrews-Shigaki3, Todd P. Kusik2, Robert T. Barrows2, Kazim Gumus3, Ilja Y. Kadashevich4, Thomas Prieto5, Oliver Speck4, Thomas M. Ernst3

1Dept. of Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany; 2Electrical Engineering and Computer Science, UW-Milwaukee, Milwaukee, WI, United States; 3John A. Burns School of Medicine, University of Hawaii, Honolulu, HI, United States; 4Biomedical Magnetic Resonance, Otto-von-Guericke University,, Magdeburg, Germany; 5Medical College of Wisconsin, Milwaukee, WI, United States

Even subtle motions degrade MR image quality. With optical stereoscopic motion tracking it is possible to correct for head motion in 6 degrees of freedom. However, it is extremely difficult to realise in the tight geometric constraints of the MR scanner, while keeping up with comfort and handling requirements of the clinical routine. Optical motion tracking with a single retro-grate reflector (RGR) target and a single camera has a great potential due to its versatility and accuracy. Reported here is the successful implementation of a prospective real time motion correction with RGR tracking, aiming at developing easy-to-handle motion correction strategies.

14:00         5028.     Breathing Motion Artifact Reduction for MRI with Continuously Moving Table Using Motion Consistent Retrospective Data Selection

Matthias Honal1, Jochen Leupold1, Tobias Baumann2

1Dept. of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany; 2Dept. of Diagnostic Radiology, University Hospital Freiburg, Freiburg, Germany

A retrospective breathing motion compensation technique for axial MRI with continuously moving table is proposed. Redundant free breathing acquisitions are performed and motion consistent undersampled k-spaces are retrospectively extracted for parallel imaging reconstruction. Compared to a conventional reconstruction from free breathing data artifacts are significantly reduced. Except for increased noise, the achieved image quality is comparable to a reconstruction from a breath-hold acquisition.

14:30         5029.     3D PROMO MRI with Online Automatic Slice Positioning

Nathan Scott White1, Josh Kuperman2, Beth Ripley2, Ajit Shankaranarayanan3, Eric Han3, Anders Dale2,4

1Dept. of Cognitive Science, University of California, San Diego, La Jolla, CA, United States; 2Dept. of Radiology, University of California, San Diego, La Jolla, CA, United States; 3Global Applied Science Lab, GE Healthcare, Menlo Park, CA, United States; 4Dept. of Neuroscience, University of California, San Diego, La Jolla, CA, United States

We present an extension to the real-time 3D "PROspective MOtion correction" (PROMO) framework for online correction of between-scan motion in 3D sequences through automatic slice plane positioning. Initial results demonstrate an intra-subject alignment precision of better than 1 mm/deg, despite initial position/landmark differences of over 13 mm. Given current scanner and computer hardware capabilities, the alignment procedure can be done in about a second or two, making it suitable to be integrated as part of a routine automatic pre-scan procedure.

15:00         5030.     Motion-Induced Frequency and Shim Variations During Localized 1H MR Spectroscopy with Prospective Motion Correction

Brian Keating1, Thomas Ernst1

1Department of Medicine, John. A. Burns School of Medicine, University of Hawaii, Honolulu, HI, United States

Motion during brain 1H MR spectroscopy may cause susceptibility-induced changes in B0. We used a PRESS sequence with prospective motion correction (PMC) to quantify the effects of motion on center frequency and shim quality. Subjects performed x- and z-head rotations while the MRS voxel tracked head motion. The center frequency displays a linear dependence on both θx (0.01ppm/deg) and θz (0.002ppm/deg). The FWHM is approximately a quadratic function of the θx, but is largely independent of θz. Our results indicate that PMC requires real-time frequency and shim updates in order to recover high-quality spectra in the presence of subject motion.

                                   Wednesday 13:30-15:30                                                                     Computer 121           

13:30         5031.     Head Pose Prediction for Prospectively-Corrected EPI During Rapid Subject Motion

Julian Maclaren1, Rainer Boegle1, Michael Herbst1, Jürgen Hennig1, Maxim Zaitsev1

1Medical Physics, Dept. of Diagnostic Radiology, University Hospital Freiburg, Freiburg, Germany

The final goal of this project is fMRI of moving subjects using prospective motion correction. An optical tracking system provides head pose data in six degrees of freedom, which are used to prospectively update the imaging volume. However, latency delays in the tracking system, and the effective echo time of the sequence, result in a time lag between position measurement and the acquisition of the central k-space line. This causes in errors in slice registration. This work shows that motion prediction using a Kalman filter can solve this problem.

14:00         5032.     Prospective Motion Correction for Single-Voxel 1H MR Spectroscopy

Brian Keating1, Weiran Deng1, J Cooper Roddey2, Nathan White3, Anders Dale2, V Andrew Stenger1, Thomas Ernst1

1Department of Medicine, University of Hawaii, Honolulu, HI, United States; 2Department of Neuroscience, University of California at San Diego, La Jolla, CA, United States; 3Department of Cognitive Science, University of California at San Diego, La Jolla, CA, United States

Motion during brain 1H MR spectroscopy acquisitions can compromise spectral quality. We adapted an image-based adaptive motion correction module for use with a PRESS sequence. Sets of three orthogonal spiral navigator images are acquired in each TR period, to estimate head motion in real-time.  By applying the appropriate rotations and translations, the voxel can be made to remain stationary with respect to the brain. Adaptive motion correction recovered original metabolite values (Cho/Cr ratio) to within a few percent even for extensive head movements (20-30°), whereas non-navigated spectra showed marked changes in metabolite levels as well as increased variability.

14:30         5033.     PROspective MOtion Correction (PROMO) Results in Improved Image and Segmentation Quality of High-Resolution MRI Scans of Children

Joshua M. Kuperman1,2, Timothy T. Brown, 23, Matthew J. Erhart, 23, J Cooper Roddey, 23, Nathan Cooper White, 2,4, Ajit Shankaranarayanan5, Eric T. Han5, Daniel Rettmann6, Anders M. Dale, 23

1Radiology, UCSD, La Jolla, CA, United States; 2Multimodal Imaging Lab, UCSD, La Jolla, CA, United States; 3Neurosciences, UCSD, La Jolla, CA, United States; 4Cognitive Science, UCSD, La Jolla, CA, United States; 5Applied Science Lab, GE Healthcare, Menlo Park, CA, United States; 6Applied Science Lab, GE Healthcare, Rochester, MN, United States

In order to test the utility of PROspective MOtion correction (PROMO) for pediatric MRI research, nine children, ages 9-12, were scanned four times with a high-resolution T1-weighted sequence.  For each subject, PROMO on and off scans were collected in a counterbalanced alternating pattern.  Results show a qualitative enhancement in image clarity and reduction of apparent motion artifacts with the use of PROMO.  Furthermore, automated segmentations of PROMO-enabled images show significant improvements in quality and reliability as compared to PROMO-off images.  Volumetric segmentations of structures show consistently greater percent volume overlap when PROMO is enabled.

15:00         5034.     Pulsed Continuous Arterial Spin Labeling (PCASL) with Prospective Motion Correction (PROMO)

Jian Zhang1,2, Greg Zaharchuk2, Michael Moseley2, Eric Han3, Nate White4, Cooper Roddey4, Daniel Rettmann5, Anders Dale4, Joshua Kuperman4, Ajit Shankaranarayanan3

1Department of Electrical Engineering, Stanford University, Stanford, CA, United States; 2Department of Radiology, Stanford University, Stanford, CA, United States; 3Global Applied Science Lab, GE Healthcare, Menlo Park, CA, United States; 4Department of Neuroscience, University of California, San Diego, La Jolla, CA, United States; 5Global Applied Science Lab, GE Healthcare, Rochester, MN, United States

Pulsed Continuous Arterial Spin Labeling (PCASL) is a promising whole-brain perfusion imaging technique, with good properties such as high efficiency, 3D multi-slice capability, and low hardware demands. However, this sequence is vulnerable to patient motions due to its long scan time. We demonstrate an improved perfusion imaging strategy by integrating the original PCASL sequence with a PROspective MOtion (PROMO) correction module. The new sequence is much more robust against brain motion with little interference between the imaging volume and PROMO navigators.

                                   Thursday 13:30-15:30                                                                        Computer 121           

13:30         5035.     Catadioptric RGR Motion Tracking for Prospective Motion Compensation in MR Acquisitions

Brian S. R. Armstrong1, Todd P. Kusik1, Robert T. Barrows1, Brian Andrews-Shigaki2, Julian Maclaren3, Maxim Zaitsev3, Oliver Speck4, Thomas Prieto5, Thomas Ernst2

1Electrical Engineering, Univ. Wisc.-Milwaukee, Milwaukee, WI, United States; 2Medicine, University of Hawaii, Honolulu, HI, United States; 3Dept. of Diagnostic Radiology, University Hospital Freiburg, Freiburg, Germany; 4Biomedical Magnetic Resonance, Otto-von-Guericke University; 5Neurology, Medical College of Wisconsin, Wauwatosa, WI, United States

A retro-grate reflector (RGR) optical system for tracking motion in an MR bore is presented, including an RGR motion tracking camera comprising a camera, lighting system and custom drive electronics in an RF enclosure, and a rib that has been engineered to grip the inside surface of the MR bore and support a mirror, which permits viewing through a head coil opening with the RGR camera positioned outside the head end of the MR bore.  Evaluations of RF interference, mirror stability and tracking system noise are presented.

14:00         5036.     Real-Time Motion Correction for High-Resolution Imaging of the Larynx: Implementation and Initial Results

Joëlle Karine Barral1, Juan M. Santos1, Dwight G. Nishimura1

1Electrical Engineering, Stanford University, Stanford, CA, United States

Respiratory motion is currently the main limitation to high-resolution MR imaging of the larynx. A novel algorithm integrating Compressed Sensing and the Diminishing Variance Algorithm is proposed and implemented within the framework of the real-time system RTHawk. The effectiveness of the approach is demonstrated on phantoms and in vivo.

14:30         5037.     Real-Time Motion Detection for Structural Brain Imaging Using Multi-Coil FID Navigators

Tobias Kober1,2, José P. Marques1,3, Rolf Gruetter1,4, Gunnar Krueger2

1Laboratory for functional and metabolic imaging, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland; 2Advanced Clinical Imaging Technology, Siemens Suisse SA - CIBM, Lausanne, Switzerland; 3Department of Radiology, University of Lausanne, Switzerland; 4Departments of Radiology, Universities of Lausanne and Geneva, Switzerland

Subject motion is often affecting the quality of MRI data. In this work, we investigate the feasibility to detect motion by monitoring repetitive FID navigator signals from arrays of receive coils. Object motion is shown to induce changes in the FID signal intensity. For proof of concept, the technique was applied to structural MP-RAGE scans of the brain. Subject motion was reliably detected. The technique has the potential to provide a scan quality measure and motion parameters for real-time or retrospective correction. It could be used in other MR sequences without time or signal penalty.

15:00         5038.     Real-Time Intra-Volume Motion Correction in EPI Using Active Markers

Melvyn Boon King Ooi1,2, Sascha Krueger3, William J. Thomas2, Truman R. Brown1,2

1Biomedical Engineering, Columbia University, New York, NY, United States; 2Radiology, Columbia University, New York, NY, United States; 3Philips Research Europe, Hamburg, Germany

Head motion is a fundamental problem in fMRI. A prospective, slice-by-slice compensation strategy for rigid-body motion is presented for EPI sequences. Before the acquisition of each EPI-slice, a short tracking pulse-sequence is used to measure the positions of three micro RF-coil "active markers" integrated into a headband worn by the subject. During head motion, the rigid-body transformation that realigns these markers to their initial positions is fed back to update the image-plane – maintaining it at a fixed orientation relative to the head – before the next EPI-slice is acquired. EPI time-series are obtained that demonstrate real-time image-plane realignment during volunteer motion.

Image Correction - Non-Motion

Hall B                        Monday 14:00-16:00                                                                           Computer 122           

14:00         5039.     Application of K-Space Energy Spectrum Analysis for Inherent and Dynamic B0 Mapping and Distortion Correction in DTI

Trong-Kha Truong1, Nan-kuei Chen1, Allen W. Song1

1Brain Imaging and Analysis Center, Duke University, Durham, NC, United States

Diffusion tensor imaging (DTI) is vulnerable to spatial and temporal B0 variations due to susceptibility effects, eddy currents, subject motion, physiological noise, and system instabilities, resulting in geometric distortions and subsequent errors in the derivation of the diffusion tensor. Here, we propose a novel method based on k-space energy spectrum analysis, which can inherently and dynamically generate a B0 map from the k-space data for each baseline (b = 0) and diffusion-weighted image, without requiring any additional data acquisition, to effectively and efficiently correct for such artifacts and achieve a high spatial fidelity and accuracy.

14:30         5040.     A Blood Flow Navigator for Assessing Physiologic Noise in EPI Data

Andre van der Kouwe1, Matthew Dylan Tisdall1, Oliver Hinds1, Aaron Hess2, David Salat1, Douglas Greve1

1Radiology, Massachusetts General Hospital, Charlestown, MA, United States; 2Biomedical Engineering, University of Cape Town, Cape Town, South Africa

A rapid single slice EPI acquisition (neck blood flow navigator) is interleaved between slices of a conventional multislice 2D BOLD EPI acquisition in a single sequence that provides information with high temporal resolution describing blood flow in the major arteries of the neck. This signal is tightly coupled to blood flow in the brain and may be used to assess and correct for physiologic noise in the BOLD signal. Navigator images are reconstructed in real-time during acquisition and it is shown that the timing of the cardiac signal derived from the navigators closely matches the timing of the photoplethysmograph.

15:00         5041.     CINE Images of a Beating Rodent Cardiac Phantom

Steven Fortune1, Ian Marshall1, Maurits A. Jansen1, Peter R. Hoskins1, Tom Anderson1

1Medical Physics, University of Edinburgh, Edinburgh, United Kingdom

Small animal cardiac MRI is challenging due to small dimensions and fast heart rates. In order to assist in the development and testing of MRI sequences a rodent cardiac phantom has been designed and tested. It consists of a single chamber of PVAC housed in a water bath, expanded by an external pump. Initial CINE images of the phantom show this phantom functions with similar parameters to a rat left ventricle. Strong flow artefacts are present in the image. Thus this phantom could be used for the development of flow compensation methods as well as fast imaging methods.

15:30         5042.     ECG-Triggered FASTERMAP Shimming Allows for Reproducible Shim Convergence in Spinal Cord Spectroscopy

Andreas Hock1, Anke Henning2, Michael Schär3,4, Alexander Fuchs1, Spyros Kollias5, Peter Boesiger1

1University and ETH Zurich, Institute for Biomedical Engineering, Zurich, Switzerland; 2University Hospital of Zurich, Institute for Biomedical Engineering, Zurich, Switzerland; 3The Johns Hopkins University School of Medicine, 1Russel H. Morgan Department of Radiology and Radiological Science, Baltimore, MD, United States; 4Philips Healthcare, Cleveland, OH, United States; 5University Hospital of Zurich, Institute of Neuroradiology, Zurich, Switzerland

ECG-triggered FASTERMAP shimming is introduced and compared to conventional FASTERMAP shimming and shimming based on ECG-triggered B0 field mapping for single voxel proton spectroscopy at 3T. This investigation shows that the use of ECG-triggered FASTERMAP seems to be a robust and applicable method for clinical spinal cord spectroscopy. It is significantly faster than ECG-triggered B0 mapping and in contrast to the conventional FASTERMAP shimming artifacts due to pulsatile CSF flow introduced by cardiac motion may have less influence.

                                   Tuesday 13:30-15:30                                                                          Computer 122           

13:30         5043.     A Three-Dimensional Magnetic Resonance Imaging Geometric Distortion Correction Algorithm for Radiotherapy

Scott Hanvey1, John Foster2

1Radiotherapy Physics, Beatson West of Scotland Cancer Centre, Glasgow, Lanarkshire, United Kingdom; 2MRI Physics, Beatson West of Scotland Cancer Centre, Glasgow, United Kingdom

The following article describes the testing of a three-dimensional geometric distortion correction algorithm, with applications in radiotherapy planning. Magnetic resonance imaging is well known to suffer from geometric distortion and although in-plane distortion is now routinely corrected, in general, through-plane distortion remains uncorrected. This study investigates a three-dimensional and a two geometric distortion correction algorithm using a variety of test objects to establish their accuracy in the axial and coronal planes. An acceptable clinical range for radiotherapy is established for the two-dimensional and three-dimensional distortion correction algorithms using three slices and many slices.

14:00         5044.     Evaluation of Geometrical Distortion in a Head-Sized Phantom at Ultra-High-Field (7 Tesla) MRI

Philipp Dammann1, Oliver Kraff, Stefan Maderwald, Elke Gizewski2, Mark Ladd, Thomas Gasser3

1Neurosurgery, University of Duisburg-Essen, Germany and Erwin L. Hahn Institute for Magnetic Resonance Imaging, Essen, NRW, Germany; 2Department for Diagn. and Interv. Radiology and Neuroradiology, University of Duisburg-Essen, Germany; 3Department of Neurosurgery, University of Duisburg-Essen, Germany

In this study we assess geometrical distortion over a head-sized phantom at ultra-high-field MRI (7 Tesla). As field inhomogenity is proportional to B0, system-related distortions of spatial encoding are expected to increase with the field strength. This may interfere with potential image-guided applications in ultra-high-field MRI. This study revealed that distortion is lower than expected, showing no significant difference in distortion at 7 Tesla compared to lower field strength within a range of 91 mm from the magnetic center. Image distortion correction reduced local distortion maxima but didn`t significantly reduce mean distortion over the whole volume.

14:30         5045.     Accuracy the Spatial Position of Gold Markers in MR Images

Tufve Nyholm1, Joakim Jonsson1, Magnus G. Karlsson1, Mikael Karlsson1

1Umeå University, Umeå, Sweden

MR has potential to replace CT as basis for radiotherapy of prostate cancer. To be able to use the MR images for patient positioning at treatment, the position of the internal gold markers needs to be correct in the MR images. A phantom was created and scanned to evaluate the dependence between the apparent position and relevant sequence parameters. It was found that use of 2D sequences introduces errors in the position, and that the apparent marker position is dependent on the tissue type surrounding the marker. The apparent position is not dependent on band-width or frequency encoding direction.

15:00         5046.     Attenuation Correction of a Simple Phantom from Simultaneous SPECT and MR Imaging

Mark Jason Hamamura1, Seunghoon Ha1, Werner W. Roeck1, Lufti Tugan Muftuler1, Douglas J. Wagenaar2, Dirk Meier2, Bradley E. Patt2, Orhan Nalcioglu1

1Tu & Yuen Center for Functional Onco-Imaging, University of California, Irvine, CA, United States; 2Gamma Medica-Ideas, Inc., Northridge, CA, United States

Accurate SPECT imaging requires attenuation correction (AC) of the nuclear projection data.  In this study, we simultaneously acquired SPECT and MRI data of a simple cylindrical phantom using a novel MR-SPECT system.  This MRI data was then used to perform the AC of the SPECT data.  The results demonstrate the feasibility of performing AC using data acquired from simultaneous MR and SPECT imaging.

                                   Wednesday 13:30-15:30                                                                     Computer 122           

13:30         5047.     Application of IDEAL for the Correction of Chemical Shift Artifacts in MREIT

Mark Jason Hamamura1, Orhan Nalcioglu1, Lufti Tugan Muftuler1

1Tu & Yuen Center for Functional Onco-Imaging, University of California, Irvine, CA, United States

Chemical shift artifacts in magnetic resonance electrical impedance tomography (MREIT) degrade the accuracy of the reconstructed conductivity.  In this study, we investigated the use of the iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) algorithm to remove these artifacts in a simple fat/water phantom.  The results demonstrate that this technique can be used to correct for chemical shift artifacts in MREIT.

14:00         5048.     SSFP Banding Artefact Removal in Large FOV Images at 3T

Sonia I. Gonçalves1, Maria L.W. Ziech1, Jaap Stoker1, Aart J. Nederveen1

1Radiology, AMC, Amsterdam, Netherlands

Banding artefacts are a serious obstacle to the use of B-FFE sequences in large FOV images and (ultra-)high field strengths. It is more so because the shortening of TR to minimize this type of artefacts is often not possible because of SAR constraints. In this work, it is shown that by combining scans with different phase cycling schemes one is able to correct for banding artefacts in large FOV abdominal images at 3 T, with as few as 6 different phase cycling schemes, independently of the chosen TR.

14:30         5049.     Ramp Sampling Strageties for High Resolution Single-Pass Dixon Imaging at 3T

Ken-Pin Hwang1, Basak E. Dogan2, Zachary W. Slavens3, Anthony T. Vu3, Wei Tse Yang2, Jingfei Ma2

1MR Applied Science Laboratory, General Electric Healthcare, Houston, TX, United States; 2Department of Diagnostic Radiology, University of Texas MD Anderson Cancer Center, Houston, TX, United States; 3GE Healthcare, Waukesha, WI, United States

Errors in Dixon fat-water separation may occur when acquired echo times deviate far from those expected by the separation algorithm.  Single pass, dual-echo sequences are particularly vulnerable when pursuing high resolution at higher field strengths, where the increased frequency shift of lipid demands shorter in- and out-of-phase echo times.  This study examines the effect of improper echo times on a Dixon algorithm and corrects them with the use of ramp sampling methods.  Suppression is improved and artifacts are reduced by aligning the echo times closer to those expected by the algorithm, with no observable degradation of image quality.

15:00         5050.     SERA: A Technique to Improve the Performance of the 3D Sequence by Reducing Aliasing Artifacts in Edge Slices

Yanle Hu1

1Imaging Research Center, University of Texas at Austin, Austin, TX, United States

When the object being imaged is larger than the field of view in slice-selection direction (zFOV), wrap-around aliasing artifacts will be observed in 3D sequences even with the use of a high performance excitation pulse. Although throwing away a couple of edge slices can solve the problem, it reduces the efficiency of the 3D method. In this work, a new technique is introduced. It excites and saturates spins in two thin slices immediately outside of zFOV before the slab excitation. As a result, aliasing artifacts in edge slices can be suppressed and the efficiency of 3D acquisition can be preserved.

                                   Thursday 13:30-15:30                                                                        Computer 122           

13:30         5051.     An A-Priori Supported Image Correction Method for Severe Intensity Non-Uniformities at 3 T

Christian Würslin1, Fritz Schick1

1Department of Diagnostical and Interventional Radiology, Section on Experimental Radiology, University Hospital Tübingen, 72076 Tübingen, Germany

Images, acquired at high field strengths usually suffer from a high amount of image non-uniformities (INUs), which cause a large amount of automatic post-processing techniques (e.g. for quantification) to fail. This applies especially for abdominal image slices, where INUs are particularly strong and common INU correction schemes do not apply. The authors therefore propose a correction algorithm which incorporates anatomic information for the compensation of heavily corrupted images. The algorithm was validated on real and simulated image data and showed a high potential in the reduction of INUs, enabling further post-processing procedures, such as thresholding, at high field strengths.

14:00         5052.     A Robust and Simple Technique for the Suppression of Artifacts Arising from Long T1 Species in Segmented Inversion Recovery Sequences

Wolfgang Gerhard Rehwald1, Pooja Aggarwal2, Igor Klem2, Han Kim2, Raymond J. Kim2

1Siemens Healthcare, Chicago, IL, United States; 2Duke Cardiovascular MR Center, United States
 

14:30         5053.     Improvement of the Arterial Input Function Considering B1-Inhomogeneities

Robert Merwa1, Karin Kapp2, Franz Ebner3, Thorsten Feiweier4, Gernot Reishofer3, Rudolf Stollberger5

1Medical Engineering, FH OÖ - Upper Austria University of Applied Sciences, Linz, Austria; 2Department of Radiation Therapy, Medical University of Graz, Graz, Austria; 3Department of Radiology, Medical University of Graz, Graz, Austria; 4Healthcare, Siemens AG, Germany; 5Institute of Medical Engineering, Graz University of Technology, Graz, Austria

DCE MRI was performed at 3 T in combination with a special sequence in order to determine B1 inhomogenities. AIF and tissue concentrations were calculated and the kinetic parameters Ktrans and Ve were determined with a generalized kinetic model. The absolute deviation of the maximum value of two comparable AIFs can be improved by a factor up to 70 and the root mean square deviation concerning the two AIFs can be decreased by a factor up to 30 if B1 inhomogeneities are corrected. Also the deviations of Ktrans and Ve in respect of the two AIFs are significantly lower.

15:00         5054.     Stent Imaging Using Metal Artifact Reduction Sequence

Sang-Young Zho1, Min Oh Ghim1, Dong Joon Kim2, Dong-Hyun Kim1,2

1Electrical and Electronic Engineering, Yonsei University, Seoul, Korea, Republic of; 2Radiology, Yonsei University College of Medicine, Seoul, Korea, Republic of

We examine a method for high-resolution stent imaging using metal artifact correction sequence and parallel imaging technique.

EPI Correction

Hall B                        Monday 14:00-16:00                                                                           Computer 123           

14:00         5055.     Robust Elimination of EPI Nyquist Ghosts Via Spatial and Temporal Encoding

W Scott Hoge1, Huan Tan2, Robert A. Kraft2

1Radiology, Brigham and Women's Hospital, Boston, MA, United States; 2Virgina-Tech Wake Forest School of Biomedical Engineering, Winston-Salem, NC, United States

Nyquist ghosts are an inherent artifact in EPI acquisitions. We propose here a method that fuses ghost correctuion methods based on spatial encoding (via multiple coils) and temporal encoding (via cyclic variations in the acquisition sequence). Post acquisition, PLACE is employed to cancel ghosting artifacts in data used to estimate self-referenced parallel MR imaging reconstruction coefficients.  The improved pMRI reconstruction coefficients are then employed on each frame, to reconstruct a ghost free image.  We demonstrate that this self-referenced approach significantly reduces Nyquist ghosts, and is robust to temporal variations such as magnetic field drift with minimal latency.

14:30         5056.     Optimized Acquisition Strategy for Reference-Free Reduction of Nyquist Ghosting in EPI at 7 T

Benedikt A. Poser1,2, Pål Erik Goa, 1,3, Markus Barth, 1,2

1Erwin L Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany; 2Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, Netherlands; 3Department of Medical Imaging, St. Olavs University Hospital, Trondheim, Norway

Nyquist (N/2) ghosting in EPI tends to become particularly problematic at ultra-high field. Strongly dependent on imaging parameters –especially echo spacing and readout bandwidth– ghosting may pose considerable practical limitations when setting up fMRI protocols at 7 T and above.

We here show that residual ghosting is caused by an often appreciable mismatch between phase correction and imaging data. We propose a small but powerful sequence modification, namely an optimized timing of the phase-correction navigators, to overcome this problem and thereby remove the practical restrictions due to ghosting. Phantom and in vivo results demonstrate ghost reductions by up to factor four.

15:00         5057.     Robust Method for EPI Ghost Correction

Frank Godenschweger1, Myung-Ho In1, Oliver Speck1

1Biomedical Magnetic Resonance, Institute for Experimental Physics, Otto-von-Guericke University, Magdeburg, Germany

A Nyquist ghost correction of EPI is propose, which determines the phase correction differences between channels and slices with high accuracy in a preparation step from a set of navigator echoes. Taking this calibration into account, only one single correction needs to be determined dynamically for all slices and channels during the EPI series, greatly improving stability.

   The robustness of the proposed technique was tested on phantom and in-vivo data. The proposed technique for EPI ghost correction dramatically improves the image quality.

15:30         5058.     Reducing Ghosting in EPI Using Trajectory Based Reconstruction with Dixon Method Fat Suppressed Navigator Echoes at 7T

Oliver Josephs1, Chloe Hutton1, Joerg Stadler2, Johannes Bernarding3, Oliver Speck3, Nikolaus Weiskopf1

1Wellcome Trust Centre for Neuroimaging, University College London, London, United Kingdom; 2Leibniz Institute for Neurobiology, Magdeburg; 3Otto-von-Guericke University, Magdeburg

At 7T, navigator echoes, acquired at short TE, and used in EPI to reduce Nyquist ghosting, can be significantly compromised by fat signal. Usually, in EPI, fat is suppressed by applying a fat saturation pulse before slice selective excitation but at 7T this significantly increases the required SAR. We present a two point Dixon technique for suppressing the fat signal in the navigator echoes and demonstrate its effectiveness in human brain imaging. The new technique is an efficient alternative for improving phase navigators and can be used in additon to fat saturation and other artifact suppression methods.

                                   Tuesday 13:30-15:30                                                                          Computer 123           

13:30         5059.     Navigator-Free Dynamic Phase Correction for Echo-Planar Imaging Based Functional MRI

Dan Xu1, R. Scott Hinks1, Bruce D. Collick

1Applied Science Laboratory, GE Healthcare, Waukesha, WI, United States

In echo-planar imaging based functional MRI, non-phase-encoded navigator echoes are sometimes collected to enable correction of temporal frame dependent even-odd-echo phase modulation. However, the navigator-based method assumes that the additional modulation that the center echoes experience is the same as that predicted by navigator echoes, which is not true when there is additional modulation building up across echoes. Therefore, the modulation of the center echoes would not be well corrected, leading to ghost drift. We propose a method to use scan data itself to more faithfully estimate the per-temporal-frame modulation than the navigator-based method, which significantly reduces ghost drift.

14:00         5060.     Robust 2D Phase Correction for Echo-Planar Imaging Under a Tight Field-Of-View

Dan Xu1, Kevin F. King1, Yuval Zur2, R. Scott Hinks1

1Applied Science Laboratory, GE Healthcare, Waukesha, WI, United States; 2GE Healthcare, Haifa, Israel

The existing 2D phase correction methods to reduce Nyquist ghost in echo-planar imaging (EPI) have several unaddressed issues that largely affect their practicality. These issues include uncharacterized noise behavior, image artifact due to unoptimized phase estimation, and most seriously a new image artifact under tight FOV. We propose a modified, more robust method that addresses all the abovementioned issues. Various EPI results show that the proposed method can robustly generate images free of Nyquist ghost and some other image artifacts even in oblique scans or when cross-term eddy current terms are significant.

14:30         5061.     Comparison of Applying 1D Phase and 2D Phase N/2 Ghost Correction Prior to PROPELLER-EPI Reconstruction

Hing-Chiu Chang1,2, Chun-Jung Juan3, Tzu-Chao Chuang4, Yi-Jui Liu5, Chao-Chun Lin2,6, Hsiao-Wen Chung2

1Applied Science Laboratory, GE Healthcare Taiwan, Taipei, Taiwan; 2Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan; 3Department of Radiology, Tri-Service General Hospital, Taipei, Taiwan; 4Electrical Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan; 5Department of Automatic Control Engineering, Feng Chia University, Taichung, Taiwan; 6Department of Radiology, China Medical University Hospital, Taichung, Taiwan

PROPELLER-EPI consists of EPI signal readout with alternative echoes, thereby the phase inconsistencies between odd and even echoes generate N/2 ghost artifact in each rotating blade as well as conventional EPI imaging. The 1D correction method fails in oblique scan (rotating blades) because the phase inconsistencies along both readout and phase direction. A 2D phase correction method can overcome this problem by modifying the reference scan manner. In this work, we compare the quality of reconstructed PROPELLER-EPI images by applying 1D phase and 2D phase N/2 ghost correction prior to PROPELLER-EPI reconstruction.

15:00         5062.     In FMRI a Dual Echo Time EPI Pulse Sequence Can Induce Sources of Error in Dynamic Magnetic Field Maps

Andrew Hahn1, Andrew Nencka1, Daniel Rowe, 1,2

1Biophysics, Medical College of Wisconsin, Milwaukee, WI, United States; 2Mathematics, Statistics, and Computer Science, Marquette University, Milwaukee, WI

Estimations of main magnetic field inhomogeneity are often acquired for correction of image warping in echo planar images (EPI) resulting from vulnerability to off-resonance effects of EPI.  Many established methods exist for field estimation, one of which involves two EPI acquisitions with different echo times.  The method is fast, easily implemented and can be performed in-line with fMRI experiments.  However, inconsistencies in the MRI scanner hardware, specifically with the RF pulse, as well as physiologic phenomena that alter the off-resonance characteristics between image acquisitions such as motion or respiration can induce errors in field maps estimated in this manner.

                                   Wednesday 13:30-15:30                                                                     Computer 123           

13:30         5063.     Jacobian Weighting of Distortion Corrected EPI Data

Stefan Skare1,2, Roland Bammer1

1Radiology, Stanford University, Stanford, CA, United States; 2MR Center, Clinical Neuroscience, Karolinska Institute, Stockholm, Sweden

By acquiring EPI data both with positive and negative phase encoding blips one obtains two oppositely distorted images.  The reversed gradient polarity (RGPM) method can be used to correct these images by searching for a displacement field that explains their difference. However, even if the estimated displacement field is adequate, the two corrected EPI images have a very low resolution in anatomical regions that have been too compressed. In this work, we use a Jacobian weighting scheme to make an informative choice about the combination of the two images that avoids the inclusion of signals from very compressed regions.

14:00         5064.     Using PLACE for EPI Distortion Correction of Diffusion Weighted Images (DWIs)

Sofia Chavez1, Elizabeth Ramsay1, Donald Plewes1,2, Greg Stanisz1,2, Q-San Xiang3

1Imaging Research, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; 2Medical Biophysics, University of Toronto, Toronto, Ontario, Canada; 3Department of Radiology, University of British Columbia, Vancouver, B.C., Canada

A feasibility study for the application of  PLACE, an EPI distortion correction, to diffusion weighted images (DWIs) is presented. PLACE requires a minimum of two input images which differ by an extra “blip” along the phase encode (PE) direction. The phase relation between the images encodes the PE coordinate, allowing for correction of the EPI-based distortion along the PE direction. Results show successful distortion correction for DWIs of a phantom despite the lower SNR, partial k-space and ramp sampling typical of standard DWI sequences. In vivo application of PLACE to DWI is currently under investigation.

14:30         5065.     Accelerating Phase Modulation for Correcting EPI Geometry Distortion by Modern GPGPU Parallel Computation. - not available

Yao-Hao Yang1, Teng-Yi Huang, Fu-Nien Wang2, Nan-Kuei Chen3

1National Taiwan University of Science and Technology, Taipei, Taiwan; 2Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua university; 3Brain Imaging and Analysis Center, Duke University Medical Center

Phase modulation combined with field mapping can correct the EPI geometry distortion but it is a time-consuming algorithm. We proposed to incorporate the GPGPU technique into phase-modulation calculation to reduce the whole computation time. Applying on the PROPELLER EPI data set, the parallel algorithm reduced the computation time from ~1750 seconds to ~100 seconds. We conclude that the GPU computing is a promising method to accelerate EPI geometry correction.

15:00         5066.     Probabilistic Reconstruction of Undistorted EPI Images Using a Rician Noise Model

Jesper Leif Roger Andersson1, Mark Jenkinson1

1fMRIB, Oxford University, Oxford, Oxfordshire, United Kingdom

We have developed a method for estimating and correcting distortions from reverse-blip data with poor SNR. It is based on a forward model that allows us to make predictions about the images and a Rician noise model that enables us to calculate the probability of observed images. Bayesian inversion is used to find the most probable distortion-free image and field. It performs well even on data with very poor SNR.

                                   Thursday 13:30-15:30                                                                        Computer 123           

13:30         5067.     New Calculation Method of Pixel Shift Map on PSF Mapping Technique: A Study on 7T MRI

Se-Hong Oh1, Jun-Young Chung1, Myung-Ho In2, Maxim Zaitsev3, Oliver Speck2, Young-Bo Kim1, Zang-Hee Cho1

1Neuroscience Research Institute, Gachon University of Medicine and Science, Incheon, Korea, Republic of; 2Department of Biomedical Magnetic Resonance, Institute for Experimental Physics, Otto-von-Guericke University Magdeburg, Magdeburg, Germany; 3Department of Radiologic Research, Medical Physics, University Hospital of Freiburg, Freiburg, Germany

Echo-planar imaging (EPI) is one of the fastest and most widely used MRI pulse sequences in the field of MRI. Compared to conventional imaging sequence, EPI is more prone to a variety of artifacts. A prominent EPI artifact is geometric distortion due to strong magnetic field inhomogeneity and susceptibility. Previous PSF mapping method, which was implemented by Zaitsev et al. used GE (Gradient Echo) StdDev (standard deviation) image as a base and produced a ¡°mask¡± to extrapolate pixel shift map. Flow artifact as well as setting of the parameters (i.e. threshold value) can affect the result of mask. And the extrapolated shift map which resulting shift maps with extrapolation eventually have error. Consequently corrected images will also have errors induced by mask errors and flow artifacts. So we propose new mask calculation method based on using a 2D PSF data based, not based on the GE StdDev image as previously used. This method is capable of making automatic mask calculation procedure, along with the advantage of eliminating flow induced ghost artifact all together.

14:00         5068.     Accelerated Point Spread Function Mapping Using Compressed Sensing for EPI Geometric Distortion Correction

Iulius Dragonu1, Juergen Hennig1, Maxim Zaitsev1

1Diagnostic Radiology, University Hospital Freiburg, Freiburg, Baden Wuerttemberg, Germany

Single-shot echo-planar imaging (EPI) is a fast technique allowing the acquisition of an image following a single RF excitation. The high temporal resolution of EPI makes it the method of choice for applications such as fMRI or diffusion tensor imaging. However, EPI is prone to geometric and intensity distortions in the presence of magnetic field inhomogeneities. Several correction techniques have been proposed in the past based on field map acquisitions or point spread function (PSF) acquisitions. Parallel imaging techniques were employed for accelerating the PSF data acquisition. In this work we demonstrate that compressed sensing (CS) reconstruction can be used for acquiring the PSF data set with high acceleration factors for accurate geometric distortion corrections.

14:30         5069.     Distortion Correction for Echo Planar MR Imaging Using the Point Spread Function (PSF) Map with Bregman Iteration

Yu Cai1, Weili Lin, Qingwei Liu, Craig Hamilton2, Hongyu An

1Department of Radiology, University of North Carolina-Chapel Hill, Chapel Hill, NC, United States; 2Wake Forest University

Point Spread Function (PSF) mapping techniques have shown promise for geometric distortion correction in Echo Planar Imaging (EPI)(1), where the distortion information is mapped by applying additional phase encoding gradients with a constant time (PSF encoding).  Cai et al(2)  introduced the inverse solution of the PSF map with the Tikhonov regularization method for EPI distortion correction. The smoothness penalty in the Tikhonov regularization causes it sensitive to the aliasing artifact in its reconstructed image and fine textile structure blurring.  Here we apply the total variation (TV) regularization with Bregman iteration method(3) to the PSF map in which the penalty term is adaptively updated based on the Bregman distance, which is immune to the above effects. The proposed approach compared with the Tikhonov regularization methods were evaluated at 3.0T with human subjects while at 9.4T with rats.

15:00         5070.     Improved PSF-Based EPI Distortion Correction in Human Imaging at 7 Tesla

Myung-Ho In1, Jun-Young Jung2, Se-Hong Oh2, Maxim Zaitsev3, Zang-Hee Cho2, Oliver Speck1

1Department Biomedical Magnetic Resonance, Institute for Experimental Physics, Otto-von-Guericke University Magdeburg, Magdeburg, Germany; 2Neuroscience Research Institute, Gachon University of Medicine and Science, Inchoen, Korea, Republic of; 3Department of Radiologic Research, Medical Physics, University Hospital Freiburg, Freiburg, Germany

This method proposes an improved method with which distortions in EPI images in the ultra high field MRI such as 7.0 Tesla can be correct automatically and with high fidelity. The correction is a modification and extension of the point spread function (PSF) method previously developed. In addition to more precise mapping and correction of blurring, the method removes flow induced artifacts which can cause errors in the shift map derived from the PSF. The advantages of the proposed method for the correction of geometric distortions in EPI are demonstrated in human brain in vivo at 7.0 Tesla.

Topics in Image Analysis

Hall B                        Monday 14:00-16:00                                                                           Computer 124           

14:00         5071.     Automated Analysis of ACR Phantom Data as an Adjunct to a Regular MR Quality Assurance Program

Lawrence P. Panych1,2, Lisa Bussolari1, Robert V. Mulkern, 23

1Radiology, Brigham and Women's Hospital, Boston, MA, United States; 2Radiology, Harvard Medical School, Boston, MA, United States; 3Radiology, Children's Hospital, Boston, MA, United States

A Matlab-based package for automatic analysis of phantom images was developed. The package analyzes images of the American College of Radiology (ACR) phantom, performing measurements similar to those required as part of the ACR accreditation program along with other useful measures. Analysis of the data from five 1.5T MR systems acquired during weekly QA scans was performed. Such data can be help to identify potential system problems, such as lower than usual SNR, and serve as an adjunct to a regular program of quality assurance.

14:30         5072.     Weisskoff Stability Metrics Dependence on K-Space Trajectory

E. Brian Welch1,2, Ad Moerland3, Elizabeth A. Moore3, J. Christopher Gatenby1, John C. Gore1

1Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, TN, United States; 2MR Clinical Science, Philips Healthcare, Highland Heights, OH, United States; 3MR Clinical Science, Philips Healthcare, Best, Netherlands

Measurement of an MR scanner’s signal stability is important for clinical and research sites acquiring data known to be adversely affected by system instabilities such as functional MRI.  In particular, the Weisskoff plot and its associated radius of decorrelation (RDC) metric are often used to compare systems.  The RDC is known to be influenced by the noise level of the data.  However, it has not been widely reported that the observed RDC is also affected by k-space trajectory.  Here we present stability measurements from a single scanner collected using four distinct k-space acquisition trajectories: Cartesian, multivane (propeller), spiral and radial.

15:00         5073.     Array Coil Signal-To-Noise Ratio Measurement: A Comparison of Methods

Elizabeth M. Tunnicliffe1, Martin J. Graves1

1Department of Medical Physics and Clinical Engineering, Cambridge University Hospitals, Cambridge, CB2 0QQ, United Kingdom

This phantom study compares six signal-to-noise ratio (SNR) measurement methods in two eight-channel head arrays. While the methods are equivalent for well de-coupled elements, this is not the case once noise correlations exist, which can indicate that an array is failing. In the absence of longitudinal SNR data, a comparison between the background region standard deviation SNR method and the noise power SNR method can provide evidence of array failure. In this situation the noise power method provides the most accurate estimate of the underlying SNR in a single image acquisition.

15:30         5074.     Protocol for Regular Quality Control of MRI Scanners in a Clinical Setting

Joost Kuijer1, Erwin Kist2, Mark Hofman1

1Physics and Medical Technology, VU University Medical Center, Amsterdam, Netherlands; 2Radiology, VU University Medical Center, Amsterdam, Netherlands

A protocol for MRI Quality Control (QC) testing within 15 minutes was developed in a clinical setting including phantom positioning and image evaluation. The set-up consisted of a scan protocol using the ACR phantom, based on the ACR 2004 QC Manual. The images were sent from the scanner to a central server using a DICOM transfer, automatically analysed and compared to predefined action limits, based on clinical relevance and short-term reproducibility. Parameters included SNR, ghosting, image homogeneity and 3D geometric accuracy. Web-based reporting allowed direct feedback at the scanner, while trend plots provide insight in long-term stability.

                                   Tuesday 13:30-15:30                                                                          Computer 124           

13:30         5075.     On Accelerated Dynamic Contrast-Enhanced Lung Perfusion Using K-T BLAST

Jia-Shuo Hsu1, Shang-Yueh Tsai2, Yi-Ru Lin3, Hsiao-Wen Chung1

1Institute of Biomedical Electronics and BioInformatics, National Taiwan University, Taipei, Taiwan; 2Dept. of Electrical Engineering, Chang-Gung University, Taoyuan, Taiwan; 3Dept. of Electronic Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan

k-t BLAST accelerates dynamic contrast-enhanced lung imaging with only limited penalty in RMS error. Yet its restrictions including initial-overshooting and temporal-smoothing cast uncertainties on perfusion quantifications and corresponding studies. This work shows that while those restrictions  influence intensity estimation on patient images as predicted, little impact is inflicted on the corresponding perfusion quantification, suggesting feasibility of accelerated lung images in clinical studies.

14:00         5076.     Nonrigid Registration Based Segmentation for the Analysis of Real-Time Cardiac Flow Images.

Freddy Odille1, Jennifer Steeden1, Vivek Muthurangu2, David Atkinson1

1Centre for Medical Image Computing, University College London, London, United Kingdom; 2Centre for Cardiovascular MR, UCL Institute of Child Health, London, United Kingdom

Cardiac flow measurements can be obtained from real-time phase contrast MRI. Due to the compromised spatial resolution and signal-to-noise ratio, automatic segmentation of great vessels is challenging. Here, we propose to use nonrigid registration of the time series of magnitude images (148 frames) to propagate the segmentation performed  manually in a reference frame. The registration, based on optical flow,  includes smoothness constraints in both space and time, and is computationally very efficient. Flow measurements generated by manual and registration-based segmentations, as well as stroke volumes, were compared in data from 10 volunteers (rest and physical exercise), and showed good agreement.

14:30         5077.     Center Point Trajectory Model for Cardiac Wall Motion Abnormality Assessment Compared with Echocardiography Strain

Ting Song1,2, Alexander I. Bustamante3, Jeffrey A. Stainsby4, Maureen N. Hood2,5, Vincent B. Ho2,5

1GE Healthcare Applied Science Laboratory, Bethesda, MD, United States; 2Radiology, Uniformed Services University of the Health Sciences, Bethesda, MD, United States; 3Cardiology, National Navy Medical Center, Bethesda, MD, United States; 4GE Healthcare Applied Science Laboratory, Toronto, ON, Canada; 5Radiology, National Navy Medical Center, Bethesda, MD, United States

A quantitative method, Central Point Trajectory (CPT), of assessing myocardial wall motion is evaluated in this paper. This center point trajectory method is compared and validated against echocardiography systolic peak strain maps and myocardial delayed enhancement images, which shows strong correlation in terms of detection of abnormal regions with reduced wall motion.

15:00         5078.     Postprocessing Tool for 3D Strain Quantification from 3D Tagging Data

Marco Piccirelli1, Roger Luechinger1, Peter Boesiger1

1Institute for biomedical Engineering, University & ETH Zurich, Zurich, Switzerland

Tagging acquisition of the orbit during eye movement have proven to give new inside into the mechanical properties of orbital tissues, and to be a valuable tool for investigating ocular diseases etiologies. 3D tagging acquisition have been shown to be feasible. We present here a model-free method enabling to quantify out of 3D tagging data the inhomogeneous deformation along extraocular muscles. This tool able 3D strain quantification and is adaptable to other tissues, like the heart.

                                   Wednesday 13:30-15:30                                                                     Computer 124           

13:30         5079.     Quantitative Analysis of Projection Breast Density Changes at Different Compression Angles Based on 3D MRI

Tzu-Ching Shih1,2, Jeon-Hor Chen2,3, D Chang3, K Nie3, M Lin3, O Nalcioglu3, Min-Ying Lydia Su3

1Department of Biomedical Imaging and Radiological Science, China Medical University, Taichung, Taiwan; 2Department of Radiology, China Medical University Hospital, Taichung, Taiwan; 3Tu & Yuen Center for Functional Onco-Imaging, University of California, Irvine, CA, United States

This study aims to demonstrate the effect of compression angle on the projection breast density at different compression ratios based on the patient-specific three-dimensional MR images. The fibroglandular tissue and tatty tissue were described by 3,488 and 11,803 tetrahedral elements. Within 50% to 70% compression ratio, the variation of the measured projection breast density was approximately 7%. In contrast, the variation of the projection breast density was nearly 11% for MOL view compression. This study provides a novel computer simulation approach to simulate the large deformation of breast compression. Compression angle of deviation may affect the measured projection breast density.

14:00         5080.     Interactive Intensity Thresholding Based Breast Density Assessment in Sequential MR Examinations

Sadie Nicola Reed1, Gokhan Ertas1, Martin O. Leach1

1Cancer Research UK and EPSRC Cancer Imaging Centre, Institute of Cancer Research, Sutton, Surrey, United Kingdom

Breast density has been shown to be a strong risk factor for breast cancer. MR imaging allows direct volume estimation of the fibroglandular breast tissues providing an accurate breast density assessment. In this study, we investigate the value of interactive intensity thresholding in the assessment of breast density from sequential MR examinations. The results have shown a good consistency between the left and right breasts and a high level of reproducibility for sequential patient visits. The ability of the technique to highlight variations from normal breast development in sequential images could give valuable information in assessment of breast cancer risk.

14:30         5081.     A Maximum Likelihood Method for Partial Volume Segmentation of Magnitude Breast MR Data

Melanie Freed1,2, Christian Graff1, Maria I. Altbach3, Jacco A. de Zwart4, Jeff H. Duyn4, Aldo Badano1

1CDRH/OSEL/DIAM, FDA, Silver Spring, MD, United States; 2Department of Bioengineering, University of Maryland, College Park, MD, United States; 3Department of Radiology, University of Arizona, Tucson, AZ, United States; 4NINDS/LFMI/Advanced MRI Section, National Institutes of Health, Bethesda, MD, United States

We apply maximum likelihood estimation techniques to magnitude MR images as a method for partial volume segmentation. The method is validated on noisy inversion recovery and saturation recovery images of a simulated MR breast phantom created from human CT data and then applied to inversion recovery images of a physical breast phantom.  The segmentation algorithm is able to successfully separate tissue types in both simulated and phantom MR images.

15:00         5082.     DIVA+QUADRANT: Novel Visualisation Software for DCE-MRI to Aid Breast Cancer Diagnosis and Neoadjuvant Chemotherapy Monitoring

Martin Lowry1, David John Manton1, Martin D. Pickles1, Lindsay W. Turnbull1

1YCR Centre for MR Investigations, Hull-York Medical School, Hull, East Yorkshire, United Kingdom

The clinical utility of dynamic contrast-enhanced MRI (DCE-MRI) is well established, but the analysis of data by radiologists can be time-consuming.  Novel visualisation software, called DIVA+QUADRANT, has been developed which quickly and clearly indicates those regions within a tumour which display the highest contrast agent enhancement (uptake) rate and the greatest degree of contrast agent wash out (signal decay); both well-established indicators of malignancy following the BIRADS-MRI lexicon.  The software can also be used to monitor response to chemotherapy as it can map out areas where enhancement and washout rates have decreased, i.e. areas where vasculature shutdown is occurring.

                                   Thursday 13:30-15:30                                                                        Computer 124           

13:30         5083.     Local Rigid and Volume Preserving Deformable Registration Method with Applications to Liver MR Data

Atilla Peter Kiraly1, Christophe Chefd'Hotel1, Clifford R. Weiss2, Ralph Strecker3

1Imaging and Visualization, Siemens Corporate Research, Princeton, NJ, United States; 2Department of Radiology, The Johns Hopkins Univeristy School of Medicine, Baltimore, MD, United States; 3MR Oncology, Siemens Healthcare, Erlangen, Germany

A novel approach to ensure local rigidity and volume preservation with existing registration methods is presented. A modification to the deformation field is performed before application to the moving image. It adds little additional runtime and can be quickly implemented. Results are shown on T1 MR liver data with simulated enhancing structures to demonstrate the volume preserving properties.

14:00         5084.     Non-Rigid Motion Compensation in MR Prostate Perfusion Imaging

Gert Wollny1, Isabel Casanova1, Thomes Hambrock2, Andres Santos1, Maria Jesus Ledesma-Carbayo1

1BIT-DIE, ETSI Telecomunicación, UPM, Madrid, Spain; 2Department of Radiology, Radboud University Nijmegen Medical Centre, Nijmegen, Netherlands

Dynamic Contrast enhance MRI has been established as accurate method in detection and localization of prostate cancer.  Time series of three-dimensional datasets of the prostate are acquired and used to obtain  per-voxel signal-intensity vs. time curves. These are then used to differentiate cancerous from non-cancerous tissue. However,  rectal peristalsis and patient movement may result in spatial-mismatching of the serial datasets and, therefore, incorrect enhancement curves. In this work, we present a method based on image registration  to compensate for these movements, and validate the method by comparing pre-and postregistration intensity time curves to manually obtained ones.

14:30         5085.     Validation of Deformable Registration of Prostate MRI with and Without Endorectal Coil for IMRT Planning

Marnix Christiaan Maas1, Corijn Kamerling1, Simon van Kranen1, Sara Muller2, Jelle Teertstra2, Floris Pos1, Christoph Schneider1, Jan Jakob Sonke1, Marcel van Herk1

1Radiotherapy, NKI-AVL, Amsterdam, Netherlands; 2Radiology, NKI-AVL, Amsterdam, Netherlands

Using an endorectal coil (ERC) greatly improves the quality of prostate MR images, but results in displacements and deformations of the organ and its surrounding tissues, causing systematic errors in intensity modulated radiation therapy (IMRT) planning. We have implemented an image based method for the deformable registration of endorectal to non-endorectal MR images. Here we present a validation of this method using markers placed on corresponding anatomical structures in pairs of fixed and deformed images. The registration method was found to be feasible, and our results suggest that sufficient accuracy for use in radiotherapy planning is attainable.

15:00         5086.     Automatic Segmentation of the Prostate in MR Images Using a Prior Knowledge of Shape, Geometry and Gradient Information

Yujin Jang1, Helen Hong1, Hak Jong Lee2, Sung Il Hwang2

1Division of Multimedia Engineering, Seoul Women's University, Seoul, Korea, Republic of; 2Department of Radiology, Seoul National University Hospital of Bundang, Seongnam-si, Korea, Republic of

To segment the prostate in MR images with a poor tissue contrast and shape variation, we propose a reliable and reproducible segmentation method using a prior knowledge of shape, geometry and gradient information. The prostate surface is generated by 3D active shape model using adaptive density profile and multiresolution technique. To prevent holes from occurring by the convergence of the surface shape on the local optima, the hole is eliminated by 3D shape correction using geometry information. In the apex of the prostate which has a large anatomical variation, the boundary is refined by 2D contour correction using gradient information.

Image Analysis

Hall B                        Monday 14:00-16:00                                                                           Computer 125           

14:00         5087.     Automated Assessment of Ghost Artifacts in MRI

Sotirios A. Tsaftaris1,2, Xiangzhi Zhou2, Rohan Dharmakumar2

1Electrical Engineering and Computer Science, Northwestern University, Evanston, IL, United States; 2Radiology, Northwestern University, Chicago, IL, United States

Flow artifacts in MR images can appear as image ghosts within and outside the body cavity. Technical improvements to suppress these ghosts often rely on expert scoring or on semi-automated methods demanding tissue segmentation to evaluate the efficacy of the methods. These approaches can be labor/computation intensive, introduce observer bias, or error-prone if tissue segmentation is used. Herein we propose two fully automated image-processing methods relying on the statistical properties of background pixels to assess the presence of flow artifacts (appearing as image ghosts) without requiring segmentation. We demonstrate that the automated methods are as effective as image scoring approaches that rely on expert reviewers.

14:30         5088.     Total Variation Denoising with Spatially Dependent Regularization

Florian Knoll1, Yiqiu Dong2, Christian Langkammer3, Michael Hintermüller2,4, Rudolf Stollberger1

1Institute of Medical Engineering, Graz University of Technology, Graz, Austria; 2Institute of Mathematics and Scientific Computing, University of Graz, Graz, Austria; 3Department of Neurology, Medical University Graz, Graz, Austria; 4Department of Mathematics, Humboldt-University of Berlin, Berlin, Germany

The Total Variation regularization model is popular in MR research. In this model, a regularization parameter controls the trade-off between noise elimination, and preservation of image details. However, MR images are comprised of multiple details. This indicates that different amounts of regularization are desirable for regions with fine image details in order to obtain better restoration results. This work introduces spatially dependent regularization parameter selection for TV based image restoration. With this technique, the regularization parameter is adapted automatically based on the details in the images, which improves the reconstruction of details as well as providing an adequate smoothing for the homogeneous parts.

15:00         5089.     Modeling Non-Central Chi Distributed Noise in T1-Weighted MR Images: Brain Tissue Segmentation Using Partial Volume Densities

Hugo Gerard Schnack1, Rachel Brouwer1, Hilleke Hulshoff Pol1

1Psychiatry, UMC Utrecht, Utrecht, Netherlands

A brain tissue segmentation algorithm is developed that includes a non-central Chi description of the MR scanner noise. It is applied to a set of MR images of 16 healthy human volunteers and found to produce significantly different tissue volume estimates, when compared to models incorporating Gaussian noise.

15:30         5090.     Automatic Quality Assessment for Multi-Slice 2D FLAIR MR Imaging

Bénédicte Mortamet1, Matt A. Bernstein2, Clifford R. Jack2, Jeffrey L. Gunter2, Maria Shiung2, Reto Meuli3, Jean-Philippe Thiran4, Gunnar Krueger1

1Advanced Clinical Imaging Technology, Siemens Healthcare Sector IM&WS S - CIBM, Lausanne, Switzerland; 2Mayo Clinic, Rochester, MI, United States; 3CHUV, Radiology, Lausanne, Switzerland; 4Signal Processing Laboratory (LTS5) Ecole Polytechnique Fédérale de Lausanne

The FLAIR contrast is increasingly used as part of routine protocol for brain MRI. It provides high sensitivity to a wide range of disease but is susceptible to patient motion. Resulting artifacts may obscure the pathology or mislead automated image analysis algorithms. We propose a method that automates quality classification of T2w 2D-FLAIR data. The validation based on 99 head scans confirms the robustness and reliability of the method. It could greatly improve clinical workflow as, in particular if integrated in online image reconstruction, it could provide immediate feedback to the MR technologist to repeat low-quality scans within the same session.

                                   Tuesday 13:30-15:30                                                                          Computer 125           

13:30         5091.     A Fully Automatic Cerebellum Segmentation Method Using an Active Contour Model with Shape Prior

Jinyoung Hwang1, Junmo Kim1, HyunWook Park1

1Department of Electrical Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Korea, Republic of

The segmentation of cerebellum in human brain is not widely used since the boundary between cerebrum and cerebellum is indistinguishable due to the partial volume effect. Although some literatures proposed the methodology in cerebellum segmentation, they are not the purpose of the cerebellum segmentation. In this work, we present fully automatic cerebellum segmentation method using shape priors in brain MR images, which already skull-stripped volume. We evaluated the proposed method to images from BrainWeb, 1.5T, and 3T MR scanner. The proposed method shows fine segmentation results, and it could be used for cerebellum generation in human brain.

14:00         5092.     A Fully Automated White Matter / Gray Matter Segmentation of Mice Spinal Cord on DTI Images

Michaël Sdika1, Virginie Callot1, Mathias Hebert1, Guillaume Duhamel1, Patrick J. Cozzone1

1CRMBM/CNRS UMR6612, Faculté de médecine, Université de la Méditérranée, Marseille, France, France

In this work, a fully automated method is proposed to segment mice SC white matter (WM) and gray matter (GM) tissues on Diffusion Tensor Imaging (DTI) images. The proposed method is based on three main step: first a small patch containing the SC is detected using a machine learning procedure, then a mask of the SC is computed within this patch and finally WM/GM segmentation is performed. Specific attention has been paid to choose an appropriate modality for each steps. The segmentation results has been evaluated by visual assessment by two experts on the images of 13 mice.

14:30         5093.     Extracellular Fluid Volume Measurements with Complex Signal Analysis

John David Dickson1, Guy Barnett Williams2, Thomas Adrian Carpenter2, Richard E. Ansorge1

1Department of Physics, Cambridge University, Cambridge, Cambridgeshire, United Kingdom; 2Wolfson Brain Imaging Centre, Cambridge University, Cambridge, Cambridgeshire, United Kingdom

It has been suggested that extracellular fluid spins undergo bulk dephasing from those in intracellular fluid. This study provides direct evidence for this phenomenon and exploits it to make quantitative measurements of both the intra/extracellular fluid volume fractions and precession frequencies. This is achieved by fitting the data from a Gradient Echo Sampling of a Free Induction Decay (GESFID) sequence with a complex signal model.

15:00         5094.     Automatic Segmentation of Brain Tumors on Non-Contrast-Enhanced Magnetic Resonance Images Using Fuzzy Clustering

Yi-Min Liu1, Chun-Chih Liao1,2, Furen Xiao1,3, Jau-Min Wong1, I-Jen Chiang1,4

1Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan; 2Department of Neurosurgery, Taipei Hospital, Department of Health, Taipei, Taiwan; 3Department of Neurosurgery, National Taiwan University Hospital; 4Institute of Biomedical Informatics, Taipei Medical University, Taipei, Taiwan

An automated brain tumor segmentation method is desirable for helping human experts to obtain tumor location and volume estimation. This study was aimed to automatically segment brain tumor with two non-contrast-enhanced MR images, T1 and T2 images, via an unsupervised fuzzy c-means clustering method combined with region merging and knowledge-based analysis. The overall quantitative results percent match and correspondence ratio of this system are 0.842 and 0.716, respectively.

                                   Wednesday 13:30-15:30                                                                     Computer 125           

13:30         5095.     Modeling of T2* Decay in Water/fat Imaging: Comparison of One-Decay and Two-Decay Models

Diego Hernando1, Zhi-Pei Liang1, Peter Kellman2

1Electrical and Computer Engineering, University of Illinois, Urbana, IL, United States; 2National Institutes of Health, Bethesda, MD, United States

In quantitative water/fat imaging, modeling the T2* decay of the signal is necessary in order to avoid significant bias. A two-decay model with separate decay rates for water and fat has recently been proposed as an alternative to the one-decay model where water and fat share a common decay rate. Even though the two-decay model is more realistic, it suffers from increased noise sensitivity with respect to the one-decay model. In this work, we analyze quantitatively this tradeoff between bias and standard deviation using simulation, phantom and in vivo data. Our results show that a one-decay model is preferable for a clinically relevant range of fat fractions and SNRs.

14:00         5096.     A Method for De-Scalping Human Brain MRI Data Using Lipid Ratio Map - not available

Anup Singh1, Mohammad Haris1, Kejia Cai1, Ari Borthakur1, Hari Hariharan1, Ravinder Reddy1

1CMROI, Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States

De-scalping the brain data is a very critical step in MRI data post-processing and analyzing. Many applications related to brain MRI either require, or benefits from the ability to accurately segment brain from the non-brain tissue. Here we present a simple, fast and robust technique for brain de-scalping. Current de-scalping procedure utilizes lipid ratio map obtained from MRI images without and with lipid saturation pulse, which are normally acquired at clinical scanners. MRI  whole brain data from different clinical scanners was successfully de-scalped using current procedure.

14:30         5097.     Chemical Shift-Based Water/fat Separation: Comparison of Fitting Models

Diego Hernando1, Zhi-Pei Liang1, Peter Kellman2

1Electrical and Computer Engineering, University of Illinois, Urbana, IL, United States; 2National Institutes of Health, Bethesda, MD, United States

Quantitative water/fat separation in MRI requires careful modeling of the acquired signal. Multiple signal models have been proposed in recent years, but their relative performance has not yet been established. This abstract presents a comparative study of 12 signal models for water/fat separation. The models were selected according to three criteria: magnitude or complex fitting, single-peak or multi-peak fat spectrum, and modeling of T2* decay. Our results show that a complex-fitting, multi-peak fat, one-decay model is preferable over a wide range of clinically relevant fat fractions and SNRs.

15:00         5098.     Comparison of Magnitude and Complex Data Fitting for Quantitative Water/fat Imaging

Diego Hernando1, Zhi-Pei Liang1, Peter Kellman2

1Electrical and Computer Engineering, University of Illinois, Urbana, IL, United States; 2National Institutes of Health, Bethesda, MD, United States

Magnitude fitting has been proposed as an alternative to complex data fitting for quantitative chemical shift-encoded water/fat imaging. Potential advantages of magnitude fitting include the removal of sensitivity to phase errors in the signal and suppression of B0 field inhomogeneity effects. However, the noise performance of magnitude fitting, relative to complex fitting, has not been established. In this abstract, we present a quantitative comparison of both methods, based on the bias and standard deviation of their estimates. Our results show that complex fitting is preferable to magnitude fitting for quantitative water/fat imaging, both in theory and in practice.

                                   Thursday 13:30-15:30                                                                        Computer 125           

13:30         5099.     Correction of the Kinetic Parameters of Human Tissue Considering RF-Field Inhomogeneities

Robert Merwa1, Gernot Reishofer2, Thorsten Feiweier3, Karin Kapp4, Franz Ebner2, Rudolf Stollberger5

1Medical Engineering, FH OÖ - Upper Austria University of Applied Sciences, Linz, Austria; 2Department of Radiology, Medical University of Graz, Graz, Austria; 3Healthcare, Siemens AG, Germany; 4Department of Radiation Therapy, Medical University of Graz, Graz, Austria; 5Institute of Medical Engineering, Graz University of Technology, Graz, Austria

Dynamic contrast-enhanced MRI was performed at 3 T in combination with a flip angle mapping sequence in order to correct the kinetic parameters of human tissue. Due to the local magnitude of these inhomogenities the values for the AIF and tissue concentrations are widespread which lead to an overestimation or underestimation of Ktrans and Ve. The peak of the arterial input function decreases of about 60 % and the absolute difference of Ktrans and Ve obtained with the AIF in two comparable arteries can be improved by a factor up to 33 if the dynamic data are corrected accordingly.

14:00         5100.     Registration of Histology and MR Images Using Local Rigid Registration and Differential Evolution

Zhengyi Yang1, Viktor Vegh1, Deming Wang1, David Charles Reutens1,2

1University of Queensland, Brisbane, Queensland, Australia; 2Royal Brisbane and Women's Hospital, Brisbane, Queensland, Australia

Registration of histological sections and the corresponding MR images is a critical step in MR constrained histology volume reconstruction. Histological sections with dislocated segments are problematic. This issue is addressed by employing a local rigid registration method. The dislocated segments are identified by morphological operations and connectivity analysis. These segments are treated as rigid bodies having independent degree-of-freedom of motion. The registration was to find the transformation matrix for each segment to maximize the similarity, which was normal mutual information, between the transformed histological section and target MR image. The method of differential evolution was used to find optimal registrations.

14:30         5101.     A Method for Planning Interventions in the Brain with Straight Access Paths - not available

Nikhil Navkar1, Zhigang Deng1, Jason Stafford2, Jeffrey Weinberg3, Nikolaos V. Tsekos1

1Computer Science, University fo Houston, Houston, TX, United States; 2Imaging Physics, MD Anderson, United States; 3Neurosurgery, MD Anderson, United States

The aim of the work is to designed visualization techniques for preoperative planning of neurosurgical interventional procedures using straight tabular tool.  The visualization techniques include calculation of access maps on the surface of patient head, which help the neurosurgeon in selecting the optimum point for insertion. The preliminary results show that it is possible to plan the trajectory of the interventional tool to hit a target in such a way that it minimizes the trauma to vital structures inside the brain.

15:00         5102.     Input Function Detection in MR Brain Perfusion Using a Blood Circulatory Model Based Algorithm

Azimeh Noorizadeh1, Hassan Bagher-Ebadian2,3, Reza Faghihi1, Jayant Narang4, Rajan Jain4, James Russel Ewing2,3

1Department of Nuclear Engineering, Shiraz University, Shiraz, Fars, Iran; 2Department of Neurology, Henry Ford Hospital, Detroit, MI, United States; 3Department of Physics, Oakland University, Rochester, MI, United States; 4Department of Radiology, Henry Ford Hospital, Detroit, MI, United States

MR Quantification of the hemodynamic maps such as Cerebral Blood Volume, Mean Transit Time, and Cerebral Blood Flow in perfusion studies is highly susceptible to selection of the correct Arterial Input Function (AIF) and a correct AIF selection could substantially reduce bias in hemodynamic parameters. This study uses a blood circulatory model to construct an automatic and model-based algorithm for AIF detection in MR perfusion studies. The algorithm is used to detect the AIF from MR perfusion of four patients with 19 slices. This study introduces a new and reliable (performance: 84%) algorithm for AIF detection in MR perfusion studies.

Novel Image Analysis Techniques

Hall B                        Monday 14:00-16:00                                                                           Computer 126           

14:00         5103.     DIR Imaging Using GRAPPA for Cortical Thickness Estimation

Narae Choi1, Yoonho Nam1, Dong-Hyun Kim1,2

1Electrical and Electronic Engineering, Yonsei University, Sinchon dong, Seoul, Korea, Republic of; 2Radiology, Yonsei University, Sinchon dong, Seoul, Korea, Republic of

Most gray matter volumetric studies use T1-weighted imaging such as MP-RAGE because it provides good contrast between white matter and cortex. However, due to susceptibility artifact coming from the air-tissue interface, a reliable and accurate measurement is difficult in the regions near the air-bone interface for T1-wieghted schemes. One way to alleviate this problem is to perform gray matter spin-echo imaging through DIR sequence. One drawback of the DIR sequence, however, is its long scan time. We applied one of the parallel imaging reconstruction schemes, GRAPPA scheme, to DIR imaging to evaluate measurement changes as a function of reduction factor.

14:30         5104.     Enhancing Subcortical Image Segmentation Based on Age Dependent Intensity Normalization

Mustafa Ulas Ciftcioglu1, Didem Gokcay1

1Medical Informatics Department, Informatics Institute, Middle East Technical University, Ankara, Turkey

Automatic algorithms for subcortical segmentation often suffer due to the complex anatomic structure of this area and intersubject variability. To overcome this problem, a method that incorporates age dependent tissue volume statistics with atlas based intensity normalization is proposed. Age dependent regression equations for volumetric ratios of the tissues are constructed and included in a segmentation performed by Maximum Likelihood (ML) approach. For intensity normalization, the intensity distribution from a single subject atlas is utilized, after registering the given image with the atlas image. Improvement on the proposed method is documented by comparison with a widely accepted segmentation tool.

15:00         5105.     Automated Evaluation of Structural Characteristics and Extension of Cerebral Gliomas Using DTI-MR 3D Texture Analysis

Giorgio De Nunzio1,2, Antonella Castellano3,4, Gabriella Pastore, 1,2, Marina Donativi2, Giuseppe Scotti3, Lorenzo Bello5, Andrea Falini6

1INFN (National Institute of Nuclear Physics), Lecce, Italy; 2Department of Materials Science, University of Salento, Lecce, Italy; 3Neuroradiology Unit and CERMAC, Scientific Institute and University Vita-Salute San Raffaele, Milan, Italy; 4Institute of Radiological Sciences, University of Milano, Milan, Italy; 5Neurosurgery, Department of Neurological Sciences, University of Milano, Milan, Italy; 6Neuroradiology Unit and CERMAC, , Scientific Institute and University Vita-Salute San Raffaele, Milan, Italy

This work illustrates the development and validation of a semi-automated Computer-Assisted Detection technique (CAD) for the recognition of cerebral glioma in Diffusion Tensor MR images (DTI-MR). The described system adheres to the classic scheme of a CAD software tool, with a data preprocessing step followed by feature calculation and supervised tissue classification. The chosen discriminating features come from 3D statistical Texture Analysis. Segmentation results are also correlated with histopathological findings from specimens obtained from image-guided tumor biopsies.

15:30         5106.     Texture Analysis of MRI of Juvenile Myoclonic Epilepsy Patients

Márcia Silva de Oliveira1,2, Luiz Eduardo Betting, 23, Fernando Cendes, 23, Gabriela Castellano1,2

1Neurophysics Group, State University of Campinas (Unicamp), Campinas, SP, Brazil; 2CInAPCe (Cooperação Interinstitucional de Apoio a Pesquisas sobre o Cérebro), São Paulo State, Brazil; 3NeuroImage Laboratory, State University of Campinas (Unicamp), Campinas, SP, Brazil

Juvenile myoclonic epilepsy (JME) is the most frequent subsyndrome of the idiopathic generalized epilepsies. Experimental investigations support that the thalamus is a key structure in the mechanisms of JME. The objective of this study was to investigate the thalamus of patients with JME using texture analysis, a quantitative neuroimaging technique. Patients and controls were submitted to MRI investigation. The T1 volumetric sequence was used for thalamic segmentation and extraction of texture parameters. Texture analysis revealed differences between the thalamus of patients and controls. The present investigation supports the participation of the thalamus in the mechanisms of JME.

                                   Tuesday 13:30-15:30                                                                          Computer 126           

13:30         5107.     Impact of Motion and Symmetry Correction on Perfusion Lesion Segmentation in Acute Ischemic Stroke: Quantitative Evaluation - not available

Dattesh D. Shanbhag1, Rakesh Mullick1, Sumit K. Nath1, Catherine Oppenheim2, Marie Luby3, Katherine D. Ku3, Lawrence L. Latour3, Steven Warach3, - NINDS Natural History of Stroke Investigators3

1Imaging Technologies, GE Global Research, Bangalore, Karnataka, India; 2Department of Neuroradiology, Université Paris-Descartes, Paris, France; 3NINDS, NIH, Bethesda, MD, United States

In context of acute ischemic stroke, we demonstrate that motion correction on PWI data should be used only if motion is detected, rather than as a standard pre-processing recipe in analysis pipeline. A motion detection scheme based on image moments is shown to be effective in capturing motion during phase volumes. Since the motion correction is the “rate-limiting” step in PWI data analysis pipeline, moment based motion detection and selective motion correction can result in significant time saving for processing PWI data. Symmetry correction, a step commonly used for contralateral analysis, produces lower estimates of perfusion lesion volumes if applied retrospectively on quantitative maps rather than on bolus signal volumes.

14:00         5108.     Correction Algorithm for Singular Value Decomposition Artifact in Quantitative Cerebral Perfusion Images Using SCALE-PWI

Jessy J. Mouannes1, Wanyong Shin2, Saurabh Shah3, Anindya Sen4, Sameer Maheshwari1, Timothy Carroll1,4

1Biomedical Engineering, Northwestern University, Chicago, IL, United States; 2National Institute on Drug Abuse, National Institute of Health, Baltimore, MD, United States; 3Siemens Medical Solutions USA, Chicago, IL, United States; 4Radiology, Northwestern University, Chicago, IL, United States

Self-CALibrated Epi Perfusion Weighted Imaging (SCALE-PWI) MRI pulse sequence produces quantitative cerebral perfusion images in a single MRI scan, using dynamic susceptibility contrast (DSC) and T1 changes in normal white matter in relation to changes  in the blood pool after contrast injection. A singular value decomposition algorithmic artifact results in alternating signal intensity modulation in the reconstructed quantitative perfusion maps of consecutive slices. A correction method to eliminate this artifact is presented in this study at 1.5T. The results show a significant effect of this correction on the resulting quantitative maps, which become more accurate and suitable for clinical diagnosis.

14:30         5109.     Pharmacokinetic Modelling of DCE-MRI at Moderate Temporal Resolution: Dealing with Tumours Which Wash Out Extremely Fast

David John Manton1, Martin D. Pickles1, Martin Lowry1, Lindsay W. Turnbull1

1YCR Centre for MR Investigations, Hull-York Medical School, Hull, East Yorkshire, United Kingdom

Dynamic, contrast-enhanced MRI was carried out with a temporal resolution of approximately 30 s.  When a simple, two-compartment pharmacokinetic model without a significant signal contribution from blood plasma (SSCP) was utilised, the quality of fit was poor in breast tumours demonstrating extremely rapid contrast wash-out.  More sophisticated models were then investigated with the best performance being achieved by a Tofts-Kermode-Kety model with an SSCP as modelled by a bi-exponential fit to the latter part of the Parker population arterial input function (i.e. ignoring early bolus peaks and assuming instantaneous mixing).  This model also yielded parameters which are more physiologically realistic.

15:00         5110.     A Self Automated Normalization Algorithm of CBV Maps for Glioma Grading

Ravi Teja Seethamraju1, Hui You2,3, Jinrong Qu4,5, Eric A. Macklin6, Geoffrey S. Young

1MR R and D, Siemens Medical Solutions, USA Inc., Charlestown, MA, United States; 2Radiology, Peking Union Medical College Hospital, Beijing, China; 3Neuro Radiology, Brigham and Women's Hospital, Boston, MA, United States; 4Radiology, Tiantan Hospital, Beijing, China; 5Radiology, Henan Tumor Hospital, Zhengzhou, China; 6Biostatistics Center, Massachusetts General Hospital, Boston, MA, United States

The hot spot method is the most widely used technique for analysis of DSC PWI maps. Here, ROIs are selected on the relCBV maps in the portion of tumor that appears to have the highest relCBV. This value is divided by the relCBV of ROI selected in the contralateral normal appearing white matter (NAWM), to yield the normalized CBV (nCBV). The measured nCBV is highly operator dependent, so we present a method for automating the determination of NAWM relCBV in order to reduce the operator dependence of the hot spot and other analytic methods.

                                   Wednesday 13:30-15:30                                                                     Computer 126           

13:30         5111.     Automated Phase-Based Segmentation of the Cerebral Cortex in 7T MR Images of the Elderly

Nhat Trung Doan1, Maarten J. Versluis2, Sanneke van Rooden, Jeroen van der Grond, Andrew Webb2, Mark A. van Buchem, Johan H.C. Reiber1, Julien Milles1

1LKEB - Department of Radiology, Leiden University Medical Center, Leiden, Zuid Holland, Netherlands; 2CJ Gorter Center - Department of Radiology, Leiden University Medical Center, Leiden, Zuid Holland, Netherlands

The aim of this work is to implement a phase-based approach for the automated segmentation of the cerebral cortex in T2* data of elderly patients acquired using a 7T MR scanner. These data show essentially no gray/white matter contrast on magnitude images. The method is divided into two stages. The first step makes use of k-means clustering to segment the outer layer of the cortex. The obtained contour is subsequently deformed to match the gray/white matter interface based on the improved contrast in phase images, thereby resulting in a full segmentation of the cerebral cortex.

14:00         5112.     Classification of Calcium Salts:  Correlation of Magnetic Susceptibility with Susceptibility Weighted Imaging (SWI)

Ali Fatemi1, E Mark Haacke2,3, Michael D. Noseworthy4

1Medical Physics and Applied Radiation Sciences, McMaster University, Hamilton, Ontario, Canada; 2Radiology, Wayne State University, Detroit, MI, United States; 3The MRI Institute for Biomedical Research, Detroit, MI, United States; 4Electrical and Computer Engineering, School of Biomedical Engineering, McMaster University, Hamilton, Ontario, Canada

We propose that by looking at the local magnetic field pattern of corrected phase images, it is possible to quantify local magnetic susceptibility, which is equivalent to classifying different calcium salts.  This may lead to not only identification of breast cancer calcification but their biochemical characterization.

14:30         5113.     Dipole Matched  Filter with SWIFT

Curtis Andrew Corum1,2, Djaudat Idiyatullin1, Steen Moeller1, Ryan Chamberlain1, Michael Garwood1,2

1Center for Magnetic Resonance Research, Dept. of Radiology, Medical School, University of Minnesota, Minneapolis, MN, United States; 2Cancer Center, Medical School, University of Minnesota, Minneapolis, MN, United States

The combination of the SWIFT sequence and a secular dipole matched filter give positive contrast at dipole sites.

15:00         5114.     Forward-Field Calculations Improve Contrast of Unwrapped MR Phase Images

Martijn D. Steenwijk1, Maarten J. Versluis2, Mark A. van Buchem, Johan H C Reiber1, Andrew Webb2, Julien Milles1

1Division of Image Processing, Leiden University Medical Center, Leiden, Zuid-Holland, Netherlands; 2CJ Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center, Leiden, Zuid-Holland, Netherlands

The aim of this work is to evaluate the gray matter / white matter (GM/WM) contrast improvement obtained by using forward-field calculations when unwrapping MR phase images of the brain. Standard phase unwrapping methods, such as high-pass filtering, prove sub-optimal in eliminating phase wraps with high spatial frequencies. Forward-field calculations can be used to compute geometry-dependent artifact-corrected (GDAC) images in which the residual phase wrapping is reduced significantly. We applied this technique to a high-resolution T2*-weighted sequence at 7T to study its effects on GM/WM contrast. The GDAC technique results in a more favourable trade-off between unwrapping and GM/WM contrast.

                                   Thursday 13:30-15:30                                                                        Computer 126           

13:30         5115.     Segmentation of the Structure of the Mouse Spinal Cord on DTI Images

Michaël Sdika1, Virginie Callot1, Mathias Hebert1, Guillaume Duhamel1, Patrick J. Cozzone1

1CRMBM/CNRS UMR6612, Faculté de médecine, Université de la Méditérranée, Marseille, France, France

In this work, a fully automated method is proposed to segment the sub-structures of the mouse spinal Cord. WM/GM segmentation is used as input of the proposed method and on output, the GM substructures are distributed in Left Ventral and Dorsal GM and Right ventral and dorsal GM whereas substructures of WM were distributed into Left Lateral WM, Right Lateral WM, Ventral WM and Dorsal WM. The method has been evaluated by visual assessment and correlation with manual segmentation on 10 DTI images of mice acquired at 11.75T and show promising results.

14:00         5116.     Longitudinal Changes of White Matter Lesions

Snehashis Roy1, Aaron Carass1, Navid Shiee1, Dzung L. Pham2, Susan Resnick3, Jerry L. Prince1,2

1Electrical and Computer Engg, Johns Hopkins University, Baltimore, MD, United States; 2Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, MD, United States; 3Laboratory of Personality and Cognition, National Institute on Aging, Baltimore, MD, United States

Progression of white matter lesions are important for early detection and monitoring of diseases like Alzheimer's or Multiple Sclerosis. FLAIR images provide superior contrast for lesions compared to traditional T1 or T2 weighted images. But they are often not acquired for time and cost constraints. We developed an atlas based method to synthesize FLAIR images from T1 and T2 acquisitions. We use this method to quantify the progression of lesions on a pool of 20 subjects. Synthesizing FLAIRs can be seen as a potential way to reduce unnecessary data acquisition.

14:30         5117.     Accurate Adipose Tissue Segmentation from Single Gradient Echo Phase Images by Adaptive Local Thresholding

Christian Würslin1, Frank Eibofner1, Fabian Springer1, Fritz Schick1

1Department of Diagnostical and Interventional Radiology, Section on Experimental Radiology, University Hospital Tübingen, 72076 Tübingen, Germany

In many applications, a quantification of fat is desired. Most (semi-)automatic procedures use T1-weighted spin echo images to accomplish this. These approaches are time-consuming and a precise quantification is usually complicated by a high amount of partial volume effects. We propose a quantification procedure based on one single phase image, acquired with a gradient echo technique and opposed-phase condition. This maximizes the contrast in between fat- and water- dominated tissues and is less time-consuming. The phase divergence, arising from inhomogeneities, is compensated for using an automated algorithm, enabling a precise fat quantification by thresholding. Phantom measurements show a high precision.

15:00         5118.     Improving Robustness of Cartilage Segmentation Using IDEAL Water and Fat Images

Raghu Kokku1

1MR SW & Apps , GTO-I, Wipro GE Healthcare, Bangalore, Karnataka, India

Accurate and reliable quantification of cartilage volume in MRI is required for diagnosis of many degenerative and inflammatory diseases such as osteoarthritis or rheumatoid arthritis. A Novel approach to segment the anatomical structures and cartilage using IDEAL knee MRI data is proposed. Variation in the characteristics of similar structures in IDEAL water and fat images is used to generate the guidance map for automated segmentation. Segmented structures are analyzed qualitatively and quantitatively with manually segmented datasets from GE 1.5T scanner. Reported DSC with the experimental datasets (>85%) indicates that the proposed solution improved the robustness of segmentation.

Contrast Mechanisms

Hall B                        Monday 14:00-16:00                                                                           Computer 127           

14:00         5119.     The Effect of NMR-Invisible Susceptibility Inclusions on Phase Maps.

Samuel James Wharton1, Richard Bowtell1

1Sir Peter Mansfield Magnetic Resonance Centre, University of Nottingham, Nottingham, United Kingdom

Phase images generated at high field show exquisite anatomical contrast resulting from small changes of the NMR frequency linked to variation of the local magnetic susceptibility across tissues.  When a significant contribution to the average susceptibility comes from NMR-invisible inclusions, the average NMR frequency offset is not however simply proportional to the average susceptibility. Here, we derive a simple expression based on the use of the conventional sphere of Lorentz, which allows the average NMR frequency offset to be calculated for compartments containing inclusions of varying shape and concentration. The expression is tested by comparison with the results of simulations.

14:30         5120.     MRI Signal Response Mapping (SIRMA) to Dephaser to Quantify Susceptibility Gradient - not available

florence franconi1, Jean-Jacques Le Jeune2, Pascal Richomme1, Laurent Lemaire2

1PIAM, Université d'Angers, Angers, France, Metropolitan; 2UMR-S646, INSERM, Angers, France

SIgnal Response MApping to dephaser (SIRMA) method is proposed to quantify susceptibility gradient. In gradient echo acquisitions, the SIRMA method measures the echo shifts in k-space of susceptibility affected spins from a series of dephased images collected with additional incremental slice refocusing gradient offset or incremental reconstruction window off-centering. SIRMA applicability and performances have been demonstrated in vitro through quantization of susceptibility gradient induced in a cylinder model and in vivo through the quantitative detection of SPIO distribution volume. With respect to its quantitative nature, its computational simplicity, this method deserves further attention for application in molecular or cellular imaging.

15:00         5121.     Simultaneous δR1 and δR2* Quantification in 5s to Monitor Blood and Tissue Oxygenation with Dynamic (C)O2 Enhanced MRI

Stefanie Remmele1, Tobias Voigt2, Jochen Keupp1, Christian Stehning1, Julien Sénégas1

1Philips Research Europe, Hamburg, Germany; 2University of Karlsruhe, Karlsruhe, Germany

This work presents an approach to simultaneous and dynamic dR1, dR2* estimation that combines the beneficial features of currently used techniques for dynamic R1 quantification in DCE-MRI and for dynamic R2*-quantification in D(C)O2E-MRI. The technique aims at increasing the specificity of R2* BOLD imaging during respiratory challenges. Its accuracy and sensitivity is evaluated in phantom and breathold experiments.

15:30         5122.     Susceptibility Weighted Imaging and Susceptibility Mapping (SWIM): A New Means to Visualize Veins and Quantify Susceptibility

Ewart Mark Haacke1,2, Jin Tang3, Yu-Chung Norman Cheng1, Jaladhar Neelavalli2,4

1Academic Radiology, Wayne State University, Detroit, MI, United States; 2The MRI Institute for Biomedical Research, Detroit, MI, United States; 3McMaster University, Hamilton, Ontario, Canada; 4Nuffield Department of Surgery, University of Oxford, Oxford, United Kingdom

A new means of visualizing veins which is independent of orientation of vessels (or the head) relative to the main magnetic field is presented. This new venous imaging method is based on direct mapping of the susceptibility using the inverse Green’s function approach.

                                   Tuesday 13:30-15:30  Computer 127                                                                       

13:30         5123.     Feasibility of Brain Lesion Characterization at 1.5T – Whole-Brain Susceptibility Mapping Using A Homogeneous Lesion Constraint

Ferdinand Schweser1, Andreas Deistung2, Berengar Wendel Lehr2, Jürgen Rainer Reichenbach2

1Medical Physics Group, Department of Diagnostic and Interventional Radiology , Jena University Hospital, Jena, Germany; 2Medical Physics Group, Department of Diagnostic and Interventional Radiology, Jena University Hospital, Jena, Germany

A method is presented for high-quality whole-brain susceptibility mapping based on standard clinical single-shot low-field SWI-data. Feasibility of in-vivo lesion characterization is demonstrated for clinical patient data.

14:00         5124.     Towards an In-Vivo and Post-Mortem Characterization of Chronic Multiple Sclerosis Lesions Using Susceptibility Related Mechanisms of Contrast at Ultra-High Field MRI with R2* and Phase Images

Bing Yao1, Francesca Bagnato2, Eiji Matsuura2, Hellmut Merkle1, Peter van Gelderen1, Henry McFarland2, Jeff H. Duyn1

1AMRI, NINDS, National Institutes of Health, Bethesda, MD, United States; 2Neuroimmunology Branch, NINDS, National Institutes of Health

High field magnetic susceptibility-weighted MRI provides information on healthy and diseased human brain. Although the sources that contribute to the R2* and frequency shifts associated with susceptibility contrast are not fully understood, previous studies suggest that iron and myelin content may contribute. In this study, we used in-vivo and post-mortem brain tissues of multiple sclerosis (MS) as a model of disease to investigate the contribution of tissue iron and myelin content to the image contrast. We found that the iron and myelin may affect phase and R2* differently.

14:30         5125.     Non-Lorentzian Sphere Behavior of Magnetic Susceptibility Induced MR Signal Frequency Shift in White Matter: Validation Study

Xiang He1, Jie Luo2, Dmitriy A. Yablonskiy1

1Mallinckrodt Institute of Radiology, Washington University in St Louis, School of Medicine, St. Louis, MO, United States; 2Department of Chemistry, Washington University in St Louis, St Louis, MO, United States

Previously proposed generalized Lorentzian approach that allows evaluation of magnetic susceptibility induced MR signal frequency shift in brain tissue is validated here using ex vivo fresh rat optic nerve positioned in the buffer solution. The frequency shift within and around the optic nerve is measured using double-echo gradient echo MRI at two orientations of optic nerve – parallel and perpendicular to the external magnetic field. Our results demonstrate that generalized Lorentzian approach, which takes into account cellular anisotropic microstructure of axons, provides satisfactory explanation of experimental data while Lorentzian sphere approximation fails to describe experimental measurements.

15:00         5126.     Very Fast T2* Imaging by Using Improved Echo-Shifted Gradient-Recalled-Echo (IESGRE)

Jian Zhang1,2, Chunlei Liu3, Michael Moseley2

1Department of Electrical Engineering, Stanford University, Stanford, CA, United States; 2Department of Radiology, Stanford University, Stanford, CA, United States; 3Brain Imaging and Analysis Center, Duke University Medical Center, Durham, NC, United States

Echo-Shifted Gradient-Recalled-Echo (ESGRE) can be used to acquire GRE images at TE>TR.  This property makes it an appealing approach for fast T2* imaging. However, the original method didn’t work well with multiple-echo shift due to the ghosting artifacts. We demonstrate an improved ESGRE method here, in which extra crusher gradients are introduced to help establish a single steady-state among all phase encodes. By using this approach, high quality T2* images can be acquired with an arbitrary echo shift index. Very fast 2D/3D T2* imaging can be achieved with iESGRE.

                                   Wednesday 13:30-15:30                                                                     Computer 127           

13:30         5127.     T2 Contrast Due to Signal Decay During Radial Readout in UTE (Ultrashort TE) Sequences

Jing-Tzyh Alan Chiang1, Michael Carl2, Jiang Du1, Mark Bydder1, Nick Szeverenyi1, Robert F. Mattrey1, Graeme Bydder1

1Radiology, University of California, San Diego, CA, United States; 2GE Healthcare

When imaging short T2 objects using ultrashort TE (UTE) pulse sequences, significant T2 decay can occur during radial readout for T2s comparable or less than the readout duration (typically ~1 ms), leading to signal amplitude loss in the image.  Here, we study the relationship between T2 and the amount of signal amplitude loss – i.e. T2 contrast due to signal decay during radial readout in UTE.  Significant T2 contrast is present, especially for T2s in the 0.1 to 1 millisecond range.  We also observe important dependencies of this T2 contrast on object size as well as gradient parameters.

14:00         5128.     3D Radial UTE MRI for Serial Assessment of Fibrosis Development and Silicone Implant Distortion in Rat.

Lindsey Alexandra Crowe1, Giorgio Petramaggiori2, Sonia Nielles-Vallespin3, Peter Speier3, Enrico Vigato4, Hicham Majd4, Jean-Paul Vallée1

1Department of Radiology, Geneva University Hospital, University of Geneva, Faculty of Medicine, Geneva, Switzerland; 2Department of Surgery, Geneva University Hospital, Geneva, Switzerland; 3Siemens AG Medical Solutions, Erlangen, Germany; 4Department of Surgery, University of Geneva, Faculty of Medicine, Geneva, Switzerland

Fibrotic reaction around implantable medical devices is an increasingly important problem, limiting function and causing pain. Up to 10-15% of silicone breast implants develop capsular contraction, necessitating replacement.  A 3D radial MRI technique with ultrashort TE is proposed as an early, pre-clinical quantification method and to serially assess the formation of capsular tissue. With the reduction of chemical shift effect and motion artifacts, and high isotropic resolution, distortion, rupture and tissue build-up around the implants can be segmented and quantified. Results may lead to standardized methods for early detection of excessive capsular formation, decreasing complication rates in patients.

14:30         5129.     Design of Iron Sensitivity Phantom Suitable for Quantitative MRI and Atomic Spectrometry

Catherine Anusha Mallik1, David Bellis2, David J. Lythgoe1, Rebeca Santamaria-Fernandez2, Gareth J. Barker1

1Centre for Neuroimaging Sciences, Institute of Psychiatry, London, United Kingdom; 2Laboratory of Government Chemists, Teddington, Middlesex, United Kingdom

There is a growing body of MRI research on the effects of abnormal levels of iron in the brain.  Validation of quantitative MRI with a phantom of known iron concentrations, is necessary for comparing different MRI measures. To allow cross-validation with Atomic spectrometry (AS) three different AS and MRI compatible phantoms were manufactured using various substrates and concentrations of iron. Phantoms were imaged at 3T with three different iron-sensitive MRI techniques. Imaging results show that a thrombin-fibrinogen gel doped with ferritin is a suitable phantom for both MRI and AS.

15:00         5130.     Liposome-Loaded Microspheres as a Magnetic Susceptibility Agent for PH Sensing

Kannie W. Y. Chan1,2, April M. Chow1,2, Ed X. Wu1,2

1Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China; 2Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong SAR, China

MR susceptibility contrast agents have been used for imaging of vasculature and tumors, such as microbubbles and iron oxides. We have developed a susceptibility agent for pH sensing, especially for acidic tumor environment, increasing sensitivity around physiological pH using liposome-loaded microspheres. Our in vitro data showed that both R2 and R2* decreased at low pH, and the percentage change in R2* is larger when compared to controls at pH 6.8-7.2. Liposome-loaded microspheres showed a substantial increase in pH-dependence of R2*, which favoured by localization of liposomes on microspheres, and is first demonstrated to an improve pH sensitivity at 7T.

                                   Thursday 13:30-15:30                                                                        Computer 127           

13:30         5131.     Experimental Investigation of the Relationship Between Phase Contrast and Orientation of White-Matter Fiber Orientation

Ferdinand Schweser1, Berengar Wendel Lehr1, Andreas Deistung1, Jürgen Rainer Reichenbach1, Daniel Güllmar1

1Medical Physics Group, Department of Diagnostic and Interventional Radiology, Jena University Hospital, Jena, Germany

Based on a recently published theoretical framework, we investigate experimentally, the relationship between phase images and white matter fiber orientation with respect to the orientation of the magnetic field of the MR scanner system. A volunteer was scanned in four different positions with respect to the external magnetic field. Phase information was plotted against the different fiber orientation settings and we found that the obtained correlation reflects at least in parts the proposed theoretical dependency.

14:00         5132.     Phase Derived Frequency Shift Mapping and DTI of White Matter Regions at 3T

Gisela E. Hagberg1, Andrea Cherubini1, Umberto Sabatini1, Carlo Caltagirone1

1Santa Lucia Scientific Foundation, Rome, Italy

Frequency shift, R2* and DTI-derived parameters (FA,MD) were evaluated in automatically parcellated white matter. The type of phase pre-processing affected the range and spatial contiguity of FS. The rank order of the 48 structures was significantly different between the evaluated parameters. The anterior and posterior limbs of the internal capsule had similar FA and MD, while the FS decreased and the R2* increased. In the commissural fibers, FS and MD values decreased from anterior to posterior while FA increased and T2* was greatest in the callosal body. The combined informational content thus depended both on fiber orientation and myelin density.

14:30         5133.     Maximal Contrasts Using MR Complex Data: With an Application to Visualise Cortical Structure

Zhaolin Chen1, Leigh A. Johnston2, Gary F. Egan3

1Florey Neuroscience Institutes, Carlton, VIC, Australia; 2Electrical and Electronic Engineering, University of Melbourne; 3Centre for Neuroscience, University of Melbourne

Recent developments in MR phase imaging enable analyses of MR signals in the complex domain. However, in clinical diagnoses and anatomical studies, it is necessary to objectively map complex MR signals to a one-dimensional signal for visualisation. The Susceptibility Weighted Imaging (SWI) method uses the phase image to calculate a phase mask that is multiplied with the magnitude image to enhance the contrast caused by tissue susceptibility. SWI has demonstrated great advantage in contrast enhancement for various applications. In this work, we introduce a new method called Maximum Contrast Image (MCI) to further improve the image contrast from complex MR signals. Enhanced image contrasts obtained with the new method have been demonstrated using a 3T dataset of a cortical brain section. Furthermore, in contrast to the nonlinear operation in SWI, the MCI method uses a linear operation, which permits meaningful quantification of the MCI signals.

15:00         5134.     Phase-Imaging Study in Restless Legs Syndrome

David Neil Manners1, Giovanni Rizzo1,2, Claudia Testa1, Caterina Tonon1, Roberto Vetrugno2, Sara Marconi2, Giuseppe Plazzi2, Fabio Pizza2, Federica Provini2, Emil Malucelli1, Bruno Barbiroli1, Pasquale Montagna2, Raffaele Lodi1

1Spectroscopy Unit, Department of Internal Medicine, Aging and Nephrology, Università di Bologna, Bologna, BO, Italy; 2Neurological Sciences, University of Bologna, Bologna, BO, Italy

Objectives. To apply phase imaging to the evaluation of brain iron content in patients with Restless Legs Syndrome. Methods. 11 RLS patients and 11 controls were studied using gradient echo imaging, and localised and whole brain ROIs selected on derived phase maps, sensitive to paramagnetic tissue. Results. In the whole brain analysis, RLS patients showed 10th and 90th percentile phase values significantly different from controls. The 10th percentile for RLS patients correlated with disease duration. Conclusions. Whole brain phase analysis is a suitable technique to study brain iron content and disclose reduced cerebral iron in RLS patients.

Magnetization Transfer

Hall B                        Monday 14:00-16:00   Computer 128                                                                       

14:00         5135.     Magnetization Transfer Contrast MRI in GFP-Tagged Live Bacteria

Valeria Righi1,2, Melissa Starkey3, George Dai2, Laurence G. Rahme3, A Aria Tzika1,2

1NMR Surgical Laboratory, Department of Surgery, Massachusetts General Hospital and Shriners Burns Institute, Harvard Medical School, Boston, MA, United States; 2Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Athinoula A. Martinos Center for Biomedical Imaging, Boston, MA, United States; 3Molecular Surgery Laboratory, Department of Surgery, Massachusetts General Hospital and Shriners Burns Institute, Harvard Medical School, Boston, MA, United States

We compared wild-type and GFP-tagged cells of Pseudomonas aeruginosa and Escherichia coli bacteria using MRI with Magnetization Transfer Contrast (MTC). This method was sensitive enough to distinguish between GFP-tagged and non-tagged cells at cell concentrations relevant to those used in animal infection models. The significance of this method is that it can be used to visualize bacterial infections in vivo in real time without being restricted to the use of transparent tissue necessary for optical imaging. This method provides a valuable tool to study the impact of novel antibacterial therapeutics.

14:30         5136.     Enhancement of MT and CEST Contrast Via Heuristic Fitting of Z-Spectra

Moritz Wilhelm Zaiss1, Benjamin Schmitt1, Bram Stieltjes, Peter Bachert1

1Medical Physics in Radiology, DKFZ, Heidelberg, Germany

Magnetizations transfer processes are quantified by the evaluation of z-spectra. A superposition of Lorentzian line shape functions, a solution of Bloch equations, is discussed as a heuristic but parametric model for z-spectrum fitting. Numerical, phantom and in vivo studies demonstrate the functionality of this method which is less dependent on exact knowledge of the system and provides enhanced contrast through parameter maps compared to standard asymmetry analysis. The heuristic fit is also less dependent on B0 inhomogeneities and its parameters can be assigned to physical parameters such as concentration and transfer rates, which are markers for tumour activity.

15:00         5137.     A New, 3D GRE Based CEST Imaging Method for Clinical Application and Verification with GagCEST in Articular Cartilage

Benjamin Schmitt1, Michael Bock1, Bram Stieltjes, Peter Bachert1

1Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany

CEST imaging has been introduced as a new method to generate a various number of contrasts for MRI. However, the application of CEST imaging for clinical application has so far been limited by extensive scan-times. These long scan times were necessary to generate reproducible CEST images and often restricted to single-slice acquisitions. We introduce a new, 3D CEST imaging sequence based on RF-spoiled gradient echo which can theoretically be used in a various number of CEST applications. The functionality is exemplified using gagCEST to determine the vitality of knee cartilage in a 3D volume.

15:30         5138.     A Comparison of Three CEST Imaging Methods

Zhongliang Zu1, Ke Li1, Daniel Frank Gochberg1

1Radiology, Vanderbilt University, Nashville, TN, United States

Three CEST imaging methods including continuous-wave, pulsed-, and spoiled gradient recalled CEST are numerically optimized and compared using simulations and a creatine/agarose tissue phantom. We found that the average irradiation power is a more meaningful sequence metric than is the average irradiation field; We also found that the SPGR-CEST provides an alternative to the EPI based CW- and pulsed-CEST imaging methods that avoids the artifacts inherent to multi-echo acquisitions, though at the cost of lower CNR.

                                   Tuesday 13:30-15:30                                                                          Computer 128           

13:30         5139.     Improved CEST Detection in Frequency Domain Using the Length and Offset VARiation of Saturation (LOVARS-CEST) Acquisition Scheme

Xiaolei Song1,2, Assaf A. Gilad1,2, Guanshu Liu1,3, Peter C.M. Van Zijl1,3, Jeff W.M. Bulte1,2, Michael T. McMahon1,3

1Division of MR Research, Russel H. Morgan Dept. of Radiology and Radiological Science, Johns Hopkins University, Baltimore, MD, United States; 2Cellular Imaging Section, Institute for Cell Engineering, Johns Hopkins University, Baltimore, MD, United States; 3F.M. Kirby Center, Kennedy Krieger Institute, Baltimore, MD, United States

We have developed a new acquisition scheme designed to improve CEST contrast  detection. In this scheme a series of saturation transfer images are collected using a regular pattern of length and offsets for the saturation pulse in order to generate different waveforms for CEST and non-CEST saturation contrast. The images can be Fourier transformed along this series and the types of saturation contrast separated out by the modulation frequency. We demonstrate how this method can be applied on a phantom. This new method can potentially improve the detection of small amounts of CEST agent in vivo.

14:00         5140.     Highly Accelerated 3D Amide Proton Transfer (APT) Imaging of the Whole Brain at 3T Using a 32-Channel Phased-Array Coil

He Zhu1,2, Craig K. Jones1,2, Jun Hua1,2, Ronald Ouwerkerk1, Peter C.M. van Zijl1,2, Peter Barker1,2, Jinyuan Zhou1,2

1Department of Radiology, Johns Hopkins University, Baltimore, MD, United States; 2F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States

We presented a fast 3D APT imaging approach with whole-brain coverage. The sequence employs a gradient and spin echo (GRASE) readout, combined with parallel imaging. The results show that the GRASE 3D APT approach largely reduced the scanning time and the RF power deposition. Data from normal volunteers clearly show the presence of the lipid artifacts and the artifacts caused by B0 inhomogeneity, and the feasibility of their corrections. The preliminary results show that GRASE 3D APT imaging can be acquired within a clinically feasible time.

14:30         5141.     CEST Imaging at 7 Tesla: Comparison of the WASSR and Higher Order Polynomial Fit to Determine Center Frequency

Adrienne N. Dula1, Richard D. Dortch1, Bennett A. Landman2, Edward B. Welch, 1,3, John C. Gore1, Seth A. Smith1

1Vanderbilt Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States; 2Radiology and Radiological Sciences, Vanderbilt Medical Center, Nashville, TN, United States; 33MR Clinical Science, Philips Healthcare, Cleveland, OH, United States

Chemical exchange saturation transfer (CEST) imaging is a molecular MRI technique that detects endogenous mobile protons via saturation transfer. Amide proton transfer (APT), a type of CEST imaging, probes amide protons in the peptide bondsallowing MRI quantification through asymmetry analysis of the z-spectrum. Translation to 7T  brings sensitivity to magnetic field inhomogeneities. Water saturation shift referencing (WASSR) uses direct water saturation to determine  the frequency shift due to field inhomogeneities producing symmetric spectra with negligible field inhomogeneities, MT, or CEST interference. This study evaluates compares WASSR to high-order fitting to determine the center frequency at 7T.

15:00         5142.     Amide Proton Transfer Imaging with Improved Robustness to Magnetic Field Inhomogeneity

Rachel Scheidegger1,2, Elena Vinogradov1,3, David C. Alsop1,3

1Radiology, Beth Israel Deaconess Medical Center, Boston, MA, United States; 2Health Sciences and Technology, Harvard-MIT, Cambridge, MA, United States; 3Radiology, Harvard Medical School, Boston, MA, United States

Amide Proton Transfer (APT) imaging is readily contaminated by asymmetric magnetization transfer and off-resonance errors. Improved robustness to these errors can be achieved using a 3-way subtraction between positive frequency, negative frequency, and combined frequency RF irradiation. Whole slice APT imaging using this approach and without additional acquisitions or corrections is demonstrated in-vivo in human volunteers. The 3-way subtraction was found to significantly improve the APT map homogeneity by reducing susceptibility artifacts and MT asymmetry effects. This method may improve the feasibility of APT imaging for clinical applications.

                                   Wednesday 13:30-15:30                                                                     Computer 128           

13:30         5143.     Finite RF Pulse Effects on Quantitative Magnetization Transfer Imaging Using Balanced SSFP - not available

Monika Gloor1, Klaus Scheffler1, Oliver Bieri1

1Radiological Physics, University of Basel Hospital, Basel, Switzerland

It has recently been shown that the effect of finite RF pulses can lead to considerable balanced SSFP (bSSFP) signal modulations. As bSSFP-based quantitative magnetization transfer imaging (qMTI) uses RF pulse modifications, a correction for these effects has to be included. In this work, a modification to the two-pool bSSFP equation is presented and effects on the parameter maps are assessed in human brain. This finite RF pulse correction improves the fitting quality considerably and reduces the values of the bound pool fraction F, the exchange rate kf and the transverse relaxation time of the free pool T2,f by about 10%.

14:00         5144.     Quantitative Magnetization Transfer Imaging in Postmortem Brain at 3T Using BSSFP

Michaela Soellinger1, Christian Langkammer1,2, Thomas Seifert-Held1, Nikolaus Krebs2, Monika Gloor3, Eva Scheurer2, Klaus Scheffler3, Franz Fazekas1, Stefan Ropele1

1Department of Neurology, Medical University of Graz, Graz, Austria; 2Ludwig Boltzmann Institute for Clinical-Forensic Imaging, Graz, Austria; 3Department of Radiology, University Hospital Basel, Basel, Switzerland

A crucial issue in determining quantitative magnetization transfer (qMT) parameters using balanced steady state free precession (bSSFP) is the estimation of the on-resonant singularity of the superlorentzian absorption line shape G0. We present an empirical G0 calibration method for postmortem in-situ brain scans at 3T using cross-linked BSA (bovine serum albumin) probes.  For the investigated temperature range from 6-20°C G0 resulted in 2.0*10-5. First qMT results of three postmortem in-situ brain scans revealed decreased bound pool size ratios f in white matter compared to in-vivo scans.

14:30         5145.     Correction and Normalization of Magnetization Transfer Ratio Maps for Quantitative Analysis - not available

Steffen Volz1, Ulrike Nöth1, Anna Rotarska-Jagiela2, Ralf Deichmann1

1Brain Imaging Center (BIC), Goethe University Frankfurt, Frankfurt am Main, Germany; 2Department of Neurophysiology, Max Planck Institute for Brain Research, Frankfurt am Main, Germany

Imaging of the Magnetization Transfer Ratio (MTR) is of increasing interest in neuroimaging, yielding important information, e.g. about myelin integrity. However, a quantitative analysis is affected by B1 biased MTR values and high specific absorption rates may require a reduction of the saturation angle for individual subjects, impairing comparability of results in longitudinal studies. Purpose of this study was to determine calibration parameters to correct for B1 bias in MTR maps at 3 Tesla, and to test if MTR data acquired at reduced MT saturation angles can be normalized to allow for comparison with data acquired at the full angle.

15:00         5146.     Susceptibility-Corrected Magnetization Transfer Contrast in a Mouse Model of Glioblastoma Multiforme at 9.4 T

David Rudko1,2, Martyn Klassen2, Susan Meakin2, Ravi Menon2

1Department of Physics and Astronomy, University of Western Ontario, London, Ontario, Canada; 2Robarts Research Institute, London, Ontario, Canada

In this study, magnetization transfer (MT) imaging was applied to a mouse model of GBM at 9.4 T. The goals of this work were: a) to quantify the MT effect in tumour core and in normal-appearing white matter and (b) to compensate for susceptibility differences which alter the MT effect at 9.4 T. The MTR in tumour core was observed to increase significantly from 14.6±0.5% to 15.3±0.6% using a field-map based static field correction. Further, the MTR asymmetry increased in two disparate regions of tumour to values of 15.3±0.6% and 13.2±0.5%  relative to in normal-appearing white matter (MTRasym = 10.7±1.6%)

                                   Thursday 13:30-15:30                                                                        Computer 128           

13:30         5147.     The Effect of Tissue Erosions and Segmentation Probability Thresholds on Magnetisation Transfer Ratio Histograms

Daniel J. Tozer1, Sameeha Fallatah1, Leonora Finisku1, David H. Miller1

1NMR Unit, Department of Neuroinflammation, UCL Institute of Neurology, London, United Kingdom

Magnetisation transfer ratio histograms are widely used in the study of multiple sclerosis. Histogram generation methods may affect the parameters extracted. This work investigates whether the tissue probability threshold used in segmentation and the number of erosions applied to the tissue segments effect the histogram parameters and whether this differs between healthy controls and multiple sclerosis patients. It is found that the number of erosions has more of an effect on the histogram parameters than the probability threshold used, in particular the first erosion. There were some differences between the behaviour in patients and controls, but this was not systematic.

14:00         5148.     Fast Bound Pool Fraction Quantification Using Stimulated Echoes

Michaela Soellinger1, Christian Langkammer1, Thomas Seifert-Held1, Franz Fazekas1, Stefan Ropele1

1Department of Neurology, Medical University of Graz, Graz, Austria

The bound proton pool fraction is linked to the lipid and protein content of myelin. Therefore, fast mapping methods are required for patient studies and clinical routine. We introduce a sequence allowing whole brain BPF determination in within clinically feasible time (~5 min for 11 slices). The method is based on the labelling of the free water pool with stimulated echo amplitude modulation (STEAM). The herewith presented approach was validated with bovine serum albumin (BSA) probes and successfully tested in three healthy volunteers. Regional analysis of white matter was in good agreement with published BPF values.

14:30         5149.     Correlation Time Diffusion MRI of Mouse Liver at 11.7T: Magnetization Transfer Effects

Hernan Jara1, Stephan W. Anderson1, Osamu Sakai1, Jorge A. Soto1

1Boston University School of Medicine, Boston, MA, United States

Purpose: To map the correlation time diffusion coefficient (CT-D) of ex vivo liver samples imaged at 11.7T and to compare results quantitatively vs. the standard pulsed-field gradient (PFG-D) diffusion MRI. Methods: A CT-D algorithm was applied to mouse liver images obtained with Tandem-TSE at 11.7T. Results: Excellent quantitative agreement was found between this non-PFG diffusion technique vs. the standard PFG diffusion technique. Conclusion: CT-D diffusion MRI is a viable alternative to standard PFG-diffusion MRI that produces higher SNR and is less demanding on the imaging gradients. This work could have implications for diffusion MRI microscopy.

15:00         5150.     Novel Magnetization-Prepared Multi-Slice Multi-Shot EPI Pulse Sequence for T1rho Quantitation - not available

Eric T. Han1, Weitian Chen1, Ajit Shankaranarayanan1

1Applied Science Laboratory, GE Healthcare, Menlo Park, CA, United States

There are numerous clinical scenarios where evaluation of T1ñ in a focal region-of-interest is desired.  In such cases, a quantitative multi-slice 2D T1ñ approach may be more appropriate and time-efficient than a 3D technique.  We propose a novel 2D multi-slice T1ñ imaging sequence that overcomes many of the shortcomings of current multi-slice T1ñ methods. Using this sequence, in vivo T1ñ maps of the knee, spine, and brain are acquired.