ISMRM 21st Annual Meeting & Exhibition 20-26 April 2013 Salt Lake City, Utah, USA

3696 -3717 Pulse Sequences: Research
3718 -3719 Pulse Sequences: Education
3720 -3731 Advances in Image Analysis: Image Analysis
3732 -3743 Advances in Image Analysis: Image Reconstruction & Processing
3744 -3767 Artifacts & Correction: Motion
3768 -3791 Artifacts & Corrections: Off-Resonance & Eddy Currents
3792 -3815 Compressed Sensing
3816 -3839 Non-Cartesian & Parallel Imaging
3840 -3858 Susceptibility Contrast

Tuesday, 23 April 2013 (16:00-17:00) Exhibition Hall
Pulse Sequences: Research

  Computer #  
3696.   1 Real-Time MRI of Tablet Disintegration: Visualization and Quantification
Amir Moussavi1,2, Julian Quodbach3, Jens Frahm2,4, and Roland Tammer1,2
1Biomedizinische NMR Forschungs GmbH, am Max-Planck-Institut für biophysikalische Chemie, Göttingen, Niedersachsen, Germany, 2DFG Research Center for Molecular Physiology of the Brain (CMPB), Göttingen, Niedersachsen, Germany, 3Institut für Pharmazeutische Technologie und Biopharmazie, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, NRW, Germany, 4Biomedizinische NMR Forschungs GmbH, Max Planck Institute, Göttingen, Niedersachsen, Germany

The efficiency of orally administered pharmaceutical dosage forms depends on the disintegration characteristics of the tablet. In contrast to conventional approaches that only observe the surface of tablets during the disintegration process via CCD cameras, the real-time MRI-based method proposed in this work is able to visualize the interior of disintegrating tablets. The achieved spatiotemporal resolution with real-time MRI is sufficient to get a detailed representation of the disintegration dynamics. Furthermore, the introduced method is able to determine the disintegration time of tablets.

3697.   2 T1-W SE-Prop to Overcome Flow Artifacts in Post-Gd Brain Imaging
Stefan Skare1, Magnus Mårtensson2, Patrik Ring1, and Anders Lilja1
1Dept Neuroradiology, Karolinska University Hospital, Stockholm, Sweden, 2EMEA Research and Collaboration, Applied Science Laboratory, GE Healthcare, Stockholm, Sweden

T1-w Spin-Echo imaging of the brain after Gadolinium (Gd) administration to the patient suffers typically from significant flow artifacts, in particular in the basal parts of the brain. In this study we show that T1-w Spin-Echo Propeller acquisitions largely can solve these issues.

3698.   3 Mulit-Echo Averaging in MR Elastography for Improved SNR
Bing Wu1 and Yongchuan Lai1
1GE healthcare, Beijing, China

High spatial resolution and SNR in phase images are key factors for high quality elastogram in MR elastography and conflict with the scan time, which is a critical issue as breah hold is usually performed during the liver scan. The use of a fast acquisition strategy such as EPI partly solves this issue, but has its own limitations such as limited SNR and large distortions. In the method, we reduce the scan time by using a minimum TR and uses multi-echo acquisition to compensate for the loss of phase SNR due to shortened TR. Phantom and in vivo experiments have been performed to evaluate this method qualitatively and quantitatively.

3699.   4 Temporal Phase Transition Via Fractional Wave Cycle TR in MR Elastography
Bing Wu1 and Yongchuan Lai1
1GE healthcare, Beijing, China

In MR elastography (MRE), an external driver is used to generate a periodic wave and applied to the subject. A key factor for high quality elastogram is accurate synchronization of the external wave and the motion encoding gradient (MEG). To achieve this, a TR that is the multiple of the wave periods is usually used, which limits the flexibility for TR selection and requires additional discarded data acquisitions (DDA) in the scan. An improvement of the pulse sequence implementation of MRE is proposed. Instead of relying on re-triggering the external wave in every temporal phase, the transition from one temporal phase to the other is achieved by sliding the relative temporal positions of the external wave and MEG. In this way, the TR may be more flexibly selected and also eliminate the need of DDAs.

3700.   5 T1 Mapping in Real Time: Single Inversion-Recovery Radial FLASH with Nonlinear Inverse Reconstruction
Shuo Zhang1, Martin Uecker2, and Jens Frahm1
1Biomedizinische NMR Forschungs GmbH am Max-Planck-Institut fuer biophysikalische Chemie, Goettingen, Niedersachsen, Germany, 2Dept. of Electrical Engineering and Computer Sciences, University of California, Berkeley, California, United States

Previous MRI studies of quantitative T1 mapping are limited mainly by a long acquisition time for high resolution and sufficient spatial coverage. Here, we applied the recently introduced real-time MRI technique based on highly undersampled radial FLASH together with a single magnetization inversion pulse. Consecutive brain images with a spatial resolution of 0.5 multiplication sign 0.5 multiplication sign 5 mm3 covering typically 5 to 9 slices were acquired within 4 s and were reconstructed by regularized nonlinear inversion. Quantitative T1 maps were obtained through a pixel-by-pixel three parameter curve fitting, with T1 values of different tissues in good agreement with literature findings.

6 B1 Gradient Encoding with the Rotating RF Coil
Adnan Trakic1, Ewald Weber1, Ming Yan Li1, Jin Jin1, Feng Liu1, and Stuart Crozier1
1The School of ITEE, The University of Queensland, Brisbane, QLD, Australia

Magnetic resonance imaging (MRI) is achieved by pulsing gradient coils, which invariably leads to notable acoustic noise, eddy current induction in nearby conductors/ patient, and costly power and space requirements. We describe a new silent, B0 gradient-free MRI technique, B1 gradient encoding with a mechanically rotating RF coil (B1-RRFC), which facilitates a large number of B1 gradients over time. Preliminary results suggest that representative images with intensity deviations of < 5% from original image can be obtained using the new approach. Potential applications include silent, low-cost and simplified (gradient coil - free) MRI equipment.

7 Multidimensional Gradient Encoding: Artifacts Resulting from Destructive Signal Interference
Gerrit Schultz1, Stefan Kroboth2, Daniel Gallichan3, Jürgen Hennig1, and Maxim Zaitsev1
1University Medical Center Freiburg, Freiburg, Germany, 2Graz University of Technology, Graz, Austria, 3Center for Biomedical Imaging (CIBM), Lausanne, Switzerland

The researcher or engineer who is working with nonlinear gradient fields is addressed. Maybe the most challenging problem with multi-dimensional trajectories is that they tend to be extremely sensitive to calibration errors. In this abstract a band-shaped artifact that may result from miscalibration is investigated and explained. The analysis reveals how such an artifact can be avoided when designing new multi-dimensional encoding schemes.

8 Segmented Multi-Echo MPRAGE Acquisition for Accelerated T1-Weighted Brain Imaging
Pavel Falkovskiy1,2, Tobias Kober1,2, Denise Reyes3, Kaely Steinert3, Matthias Seeger4, Matthew Bernstein3, and Gunnar Krueger1,2
1Advanced Clinical Imaging Technology, Siemens Healthcare IM S AW, Lausanne, Switzerland, 2CIBM-AIT, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, 3Department of Radiology, Mayo Clinic, Rochester, MN, United States, 4Laboratory for Probabilistic Machine Learning, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland

Patient comfort and short scan times are crucial in clinical settings. The MP-RAGE pulse sequence produces an excellent T1-weighted contrast but has relatively long acquisition times. In contrast to conventional parallel imaging, this work accelerates the acquisition by using an EPI-type multi-echo k-space segmentation scheme. Obtained images were rated to appear with clinically useful image quality at up to 4x scan time reduction (9:14 to 2:20 min). The concept is independent of the coil design and could be applied in situations when parallel imaging technology is limited, e.g. when there are restrictions in imaging dimensions and coil geometry.

9 A Whole Brain High Temporal and Spatial Resolution SE Simultaneous Multislice Sequence for Task fMRI at 7T
Rasim Boyacioglu1, Jennifer Bersch1, Nils Müller1, Peter J. Koopmans1,2, Markus Barth1,2, and David Norris1,2
1Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, Netherlands, 2Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany

Simultaneous multi-slice (SMS) imaging enables 2D sequences to be accelerated in the slice direction. The power deposition however remains as the limiting factor for SE based SMS sequences. By using standard SMS excitation pulses and Power Independent Number of Slices (PINS) pulses for refocusing, we show that a whole brain high spatial (1.5 mm isotropic) resolution SE SMS acquisition can be achieved with a considerably short TR (1.97s) at 7T. We compare the SE SMS protocol with a matched GE SMS sequence in terms of tSNR and sensitivity with task (Stroop) fMRI.

10 Superior GRAPPA Reconstruction with Reduced G-Factor Noise Using 2D CAIPIRINHA for 3D EPI
Mayur Narsude1,2, José P. Marques1,2, Daniel Gallichan3, and Rolf Gruetter2,4
1Laboratory for Functional and Metabolic Imaging, Ecole Polytechnique Fédéral de Lausanne, Lausanne, Vaud, Switzerland, 2Department of Radiology, University of Lausanne, Lausanne, Vaud, Switzerland, 3Laboratory for Functional and Metabolic Imaging, Ecole Polytéchnique Fédérale de Lausanne, Lausanne, Vaud, Switzerland, 4Laboratory for Functional and Metabolic Imaging, École Polytechnique Fédérale de Lausanne, Lausanne, Vaud, Switzerland

Efficient GRAPPA or SENSE reconstruction is largely dependent on coil geometry in the direction in which phase encoding steps reduction is performed during partially parallel acquisition. In this study we demonstrate the ability to perform a 2D CAIPIRINHA trajectory in a 3D EPI sequence to reduce the geometry factor (g-factor) noise amplification in the reconstructed images for a predefined total acceleration. 2D CAIPIRINHA style k-space patterns provide improved reconstructions when using very large accelerations on one phase-encode direction, thanks to the ability to use the coil sensitivities along the other phase-encode direction to compensate the reduced coil sensitivity variation.

3706.   11 Reduced Scan Time 3D FLAIR Using Variable Repetition Time
Neville D. Gai1 and John Anthony Butman1
1Radiology & Imaging Sciences, National Institutes of Health, Bethesda, MD, United States

3D FLAIR now provides high resolution images of the entire brain in a clinically reasonable scan time using extended modulated refocusing trains. However, the repetition time still includes a relatively long dead time to allow for magnetization recovery. Here, we describe a technique that reduces the scan time by varying the repetition time in a predetermined fashion using a Blackman-Harris window function. As a result, the effective TR of the sequence is still maintained which results in comparable SNR and CNR while reducing the total scan time. Simulation and measurements in volunteers confirm the utility of the technique.

3707.   12 Short TR Resting State Data Acquired with a Simultaneous Multislice Multi-Echo Sequence at 7T, a Comparison with Multi-Echo
Rasim Boyacioglu1, Jennifer Bersch1, Benedikt A. Poser2, Peter J. Koopmans1,3, Markus Barth1,3, and David Norris1,3
1Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, Netherlands, 2John A. Burns School of Medicine, U. of Hawaii, Honolulu, HI, United States, 3Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany

Simultaneous multi-slice (SMS) imaging enables 2D sequences to be accelerated in the slice direction. We have implemented a short TR SMS multi-echo (ME) sequence to investigate the potential improvement in sensitivity compared to ME at 7T for resting state (RS) fMRI. We also explored different echo weighting schemes (TE vs. Average) as RS BOLD signal characteristics might impose different constraints than previously shown task fMRI results. We found that SMS acquisition improves sensitivity compared to a standard ME sequence and combining echoes by averaging might be more favourable than TE weighting at 7T for RS fMRI data.

3708.   13 Weighted Dual-Echo T1-W Spin-Echo Propeller with Mutual Cross-Calibration
Stefan Skare1, Magnus Mårtensson2, Ajit Shankaranarayanan3, Patrik Ring1, and Anders Lilja1
1Dept Neuroradiology, Karolinska University Hospital, Stockholm, Sweden, 2EMEA Research and Collaboration, Applied Science Laboratory, GE Healthcare, Stockholm, Sweden, 3Global Applied Science Laboratory, GE Healthcare, Menlo Park, CA, United States

A dual-echo (blade) Spin-Echo propeller is presented for motion and flow robust T1-w imaging. With the echoes are played out orthogonally to each other, a parallel imaging acceleration of R=2 is used relying on mutual cross-calibration. Shortening the blade acquisition time is important to avoid intra-blade head motion.

3709.   14 MP2RAGE Imaging at 9.4T Using a PTX System
Daniel Brenner1, Kaveh Vahedipour1, Tony Stöcker1, Jörg Felder1, Frank Geschewski1, Eberhard Daniel Pracht1, and Nadim Jon Shah1,2
1INM-4, Forschungszentrum Juelich, Juelich, Germany, 2JARA - Faculty of Medicine, RWTH Aachen University, Aachen, Germany

Conventional T1 weighted Neuroimaging at 9.4T (using the MP2RAGE sequence) is complicated by strong RF inhomogeneities that cause areas of contrast loss. These can be partially removed by utilising a pTX system with two distinct RF shims and efficient HSN inversion pulses.

3710.   15 Improved Compressed Sensing Reconstructions with MOET
Daniel Neumann1, Felix A. Breuer1, Peter M. Jakob1,2, and Mark A. Griswold3,4
1Research Center MR Bavaria (MRB), Würzburg, Germany, 2Experimental Physics 5, University of Würzburg, Würzburg, Germany, 3Radiology, University Hospitals, Cleveland, OH, United States, 4Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States

MOET is a 2D sampling scheme based on radial sampling combined with oscillating gradients providing incoherent aliasing artifacts. This is essential to the success of Compressed Sensing algorithms. Real-time in-vivo cardiac data along a MOET and a standard radial trajectory were acquired and reconstructed using CS exploiting sparsity in the frequency domain with a temporal resolution of 51.2ms per frame. The reconstructed MOET images exhibit an overall improved image quality with fewer residual aliasing artifacts compared to the radial trajectory.

3711.   16 Reducing Fluctuation of Train Trajectories in 3D TSE Imaging with Compressed Sampling
Guobin Li1, Maxim Zaitsev1, Esther Meyer2, Dominik Paul2, and Jürgen Hennig1
1University Medical Center Freiburg, Freiburg, Germany, 2Siemens Healthcare, Erlangen, Germany

In MR imaging using a 3D TSE sequence with long echo trains, k-space reordering is a critical part of the sequence design, especially when Compressed Sampling(CS) is applied, because the irregular distribution of sampled views in CS leads to dramatic fluctuation of the train trajectories. In this work, It is shown that the fluctuation of train trajectories can be dramatically reduced by introducing a concept of 'echo ambiguity'in the flexible k-space reordering.

3712.   17 Reducing Off-Resonance Artifacts in O-Space Imaging
Dana C. Peters1, Leo K. Tam1, Gigi Galiana2, and Robert Todd Constable2
1Diagnostic Radiology, Yale Medical School, New Haven, CT, United States, 2Diagnostic Radiology, Yale University, New Haven, CT, United States

In O-space, the z2 non-linear gradient generates a quadratic field, which at the center-placement, CP, has a very low effective magnetic field gradient (i.e Hz/pixel). Therefore off-resonant spins in the CP location will be inaccurately encoded based on their frequency. Here we explore the effects of off-resonant signal on O-space. The reconstruction was modified, based on the insight that the spatial encoding magnetic field has little information, and significant off-resonance error, in the location around the CP. In the modified ART reconstruction, for each CP, the image estimate in the neighborhood of the CP is not updated. Simulations show improvement.

3713.   18 Variable Flip Angle Balanced SSFP for Low SAR Cardiac Cine Imaging
Subashini Srinivasan1,2 and Daniel B. Ennis1,2
1Department of Bioengineering, University of California, Los Angeles, California, United States, 2Department of Radiological Sciences, University of California, Los Angeles, California, United States

Cardiac structural and functional imaging is routinely performed using balanced steady-state free precession (bSSFP) due to its high contrast and high SNR efficiency. Higher flip angles generate higher blood-myocardial contrast, but can result in substantially increased SAR, which may result in exceeding SAR limitations or limit its applicability in patients with implanted devices. In our work, we describe novel variable flip angle (VFA) scheme coupled with a k-space acquisition strategy for low SAR bSSFP cardiac cine imaging. Our results show that VFA-bSSFP cardiac cine imaging can reduce the SAR by at least 45% compared to conventional bSSFP, while maintaining blood myocardial SNR and CNR. VFA-bSSFP can also increase the CNR by at least 29% with SAR matched to a conventional bSSFP scheme.

3714.   19 Robust Dual-Contrast 3D Abdominal Imaging Within a Single Breath-Hold  -permission withheld
Nadine Gdaniec1, Peter Koken2, Peter Börnert3, Christian Stehning2, Holger Eggers2, Mariya Doneva4, and Alfred Mertins1
1University of Lübeck, Lübeck, Germany, 2Philips Research Laboratories, Hamburg, Germany, 3Philips Research Laboratory, Hamburg, Germany, 4Philips Research Europe, Hamburg, Germany

A method for dual-contrast imaging of the abdomen within one breath-hold is proposed, that is able to cope with potential premature breathing-onset. Because of ultra-fast sequence switching the scans are performed quasi-simultaneously and without spatial misregistration. The first scan is sampled conventional one, while the second is adapted to the breath-hold capabilities of the patient. An adaptive sampling pattern was chosen that enables flexible scan termination. Shorter breath-hold duration comes as a compromise at the cost of lower resolution.

3715.   20 K-Space Density Weighted Echo Planar Imaging
Mario Zeller1, Alexander Müller1, Marcel Gutberlet2, Andreas J. Bartsch3,4, Daniel Stäb1, Dietbert Hahn1, and Herbert Köstler1
1Institute of Radiology, University of Würzburg, Würzburg, Germany, 2Institute for Interventional and Diagnostic Radiology, Hannover Medical School, Hannover, Germany, 3Department of Neuroradiology, University of Heidelberg, Heidelberg, Germany, 4FMRIB Centre, Oxford University, Oxford, United Kingdom

In Cartesian imaging, optimal SNR can be achieved by filtering the k-space proportional to the signal (SNR matched filter). This however leads to Gibbs artifact amplification. In contrast, Gibbs artifacts are reduced by filters that apodize the k-space periphery, leading to non-optimal SNR. K-space density weighting allows combining both approaches. The application of an SNR matched filter ensures optimal SNR, while a non-Cartesian k-space sampling allows achieving a prospectively defined point spread function. In this work, k-space density weighting was applied to echo planar imaging. The results indicate significant SNR advantages of density weighting over Cartesian imaging with retrospective filtering.

3716.   21 A Systematic Approach to Design Flip Angle Modulation in Pseudo-Steady-State 3D Fast Spin Echo Acquisition
Weitian Chen1, Kristin Granlund2, Donglai Huo3, and Garry E. Gold2
1Applied Science Laboratory, GE Healthcare, Menlo Park, CA, United States, 2Radiology, Stanford University, Palo Alto, CA, United States, 3PSD Applications, GE Healthcare, Waukesha, WI, United States

Pseudo-steady state 3D fast spin echo acquisition has recently shown great promise in high-resolution 3D anatomical imaging. Flip angle modulation is used in these techniques to acquire data with very long echo train without excessive blurring. The flip angle modulation provides additional dimensions of freedom to achieve desired image quality. Different flip angle modulation can result in significant change of image contrast, sharpness, and SNR, which usually are tradeoffs among each other. Such flexibility imposes challenge but also opportunity to design flip angle modulation in 3DFSE to achieve desired image quality. In this work, we proposed a systematic approach to design flip angle train in 3DFSE to achieve desired image quality.

3717.   22 W=2 Acceleration Single Carrier Wideband MRI Technique and Blur Mitigation Method
Yun-An Huang1, Edzer L. Wu1,2, Tzi-Dar Chiueh1, and Jyh-Horng Chen1,2
1Dept. Electrical engineering, National Taiwan University, Taipei, Taipei, Taiwan, 2Institue of biomedical engineering, National Taiwan University, Taipei, Taipei, Taiwan

In this study, we demonstrate the Single carrier Wideband MRI technique and its associated blur mitigation method. The W=2 accelerated Single carrier Wideband MRI produced the same contrast comparable to the standard gradient echo imaging while reducing half the scan time. Our results suggest a potential to speed up scan time without losing image quality, which is valuable in clinical study.


Tuesday, 23 April 2013 (16:00-17:00) Exhibition Hall
Pulse Sequences: Education

  Computer #  
3718.   23 Using Extended Phase Graphs: Review and Examples
Brian Andrew Hargreaves1 and Karla L. Miller2
1Radiology, Stanford University, Stanford, CA, United States, 2FMRIB Centre, Oxford University, Oxford, United Kingdom

The extended-phase-graph (EPG) formalism, which allows efficient simulation of the signal from numerous commonly-used pulses sequences, is summarized intuitively, with example applications and software. EPG treats a group of spins within a voxel undergoing integer numbers of cycles of gradient dephasing by using a Fourier basis that reduces a large spin ensemble to a limited number of states. Effects of relaxation, RF nutation, gradient dephasing and rephasing, diffusion and static dephasing are easily included. Links to Matlab code with intuitive examples of how to build up pulse sequence simulations are provided.

3719.   24 arrayShow: A Guide to an Open Source Matlab Tool for Complex MRI Data Analysis
Tilman Johannes Sumpf1 and Markus Untenberger1
1Biomedizinische NMR Forschungs GmbH am Max-Planck-Institut fuer biophysikalische Chemie, Goettingen, Germany

Especially for development and testing of new reconstruction and post processing algorithms, the Matlab environment became a popular choice in the MRI community. However, the visualization and comparison of multidimensional complex MRI data arrays is still rather uncomfortable with standard Matlab routines. To overcome these limitations, we introduce a freely available tool which has been designed specifically for MRI data analysis. This e-poster gives a quick tour through the concepts and features of the tool and, therewith, offers practical solutions to some common MRI data visualization problems in Matlab.


Tuesday, 23 April 2013 (17:00-18:00) Exhibition Hall
Advances in Image Analysis: Image Analysis

  Computer #  
3720.   1 Fast and Robust Framework for PET-MR Attenuation Map Generation with Joint MR Bias Estimation and Tissue Segmentation
Dattesh D. Shanbhag1, Sheshadri Thiruvenkadam1, Sandeep Kaushik1, Gaspar Delso2, Scott D. Wollenweber3, Sonal Ambwani3, Rakesh Mullick1, and Florian Wiesinger4
1GE Global Research, Bangalore, Karanataka, India, 2GE Healthcare, Glattbrugg, Zurich, Switzerland, 3GE Healthcare, Waukesha, WI, United States, 4GE Global Research, Garching b. Munchen, Bavaria, Germany

MR-based PET attenuation correction (AC) is a prerequisite for quantitative PET and a key determining factor for the success of PET/MR. RF shading with phased array coils results in segmentation based MR-AC map generation failure. In this work we present a novel approach for MR-AC map generation within the phase field based framework based on joint estimation/correction of the RF shading and tissue segmentation maps using Dixon MRI images. The method provides for parameter variation resilient body contour and tissue class segmentation, obviates the need to “re-tune” the algorithm for specific cohort of data acquisition and coils and results in simplified workflow for PET-MR attenuation map generation.

3721.   2 Quantitative Oxygenation Venography from MRI Phase
Audrey Peiwen Fan1, Berkin Bilgic1, Louis O. Gagnon2,3, Thomas Witzel3, Himanshu Bhat3, Bruce R. Rosen2,3, and Elfar Adalsteinsson1,3
1Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, United States, 2Health Sciences and Technology, Harvard-MIT, Cambridge, MA, United States, 3Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, United States

Comprehensive venograms which map quantitative oxygenation along each vessel are shown for the first time. Susceptibility maps are created from MR phase images and cerebral veins are graphed into a node-edge representation. Quantitative oxygen saturation (SvO2) along each vessel is then displayed onto a 3D mesh generated from the graph to create oxygenation venograms. We probe the dependence of reconstructed SvO2 in vivo as a function of vein tilt angle relative to the main field, and found increased SvO2 at angles undersampled by the dipole imaging kernel. This observation motivates future work to incorporate vessel angle priors from graphing for more accurate model-based reconstruction of SvO2 venograms.

3722.   3 An MR Brain Image Classifier System Via Particle Swarm Optimization and Kernel Support Vector Machine  -permission withheld
Yudong Zhang1,2, Chuanmiao Xie1,3, Bradley S. Peterson1,2, and Zhengchao Dong1,2
1Columbia University, New York, NY, United States, 2New York State of Psychiatric Institute, New York, NY, United States, 3Department of Medical Imaging & Interventional Radiology, Sun Yat-Sen University, Guangzhou, Guangdong, China

We proposed a novel hybrid system to classify an MR brain image as either normal or abnormal. The method employed digital wavelet transform to extract features and used principal component analysis to reduce the dimensionality of the feature space. Afterwards, we constructed a kernel support vector machine with Radial Basis Function kernel, using particle swarm optimization to optimize the parameters in the training function. We tested the method with a dataset of 90 brain images consisting of 17 diseases. A 5-fold cross validation showed that our method achieved 97.78% classification accuracy, higher than 86.22% by BP-NN and 91.33% by RBF-NN.

3723.   4 Robust Reproducible Semi-Automated Perfusion-Diffusion Mismatch Assessment in Acute Ischemic Stroke Setting  -permission withheld
Venkata Veerendranadh Chebrolu1, Dattesh D. Shanbhag1, Arun Govinda Rao2, Patrice Hervo3, Marc-Antoine Labeyrie4, Catherine Oppenheim4,5, and Rakesh Mullick1
1Medical Image Analysis Lab, GE Global Research, Bangalore, Karnataka, India, 2GE Healthcare, Bangalore, Karnataka, India, 3GE Healthcare, Buc, France,4Departments of Radiology and Neurology, Centre Hospitalier, Sainte-Anne, Paris, France, 5Université Paris Descartes, Paris, France

In semi-automated stroke lesion segmentation based on user defined seed inputs, the location and shape of the input could vary. We developed robust and reproducible semi-automated DWI and PWI lesion segmentation algorithms and evaluated their performance and reproducibility in assessing perfusion-diffusion mismatch in a cohort of acute ischemic stroke patients. Repeated measures ANOVA did not show any statistically significant differences between ground-truth lesion volumes and those obtained using the semi-automated methods (p < 0.05). Mismatch agreement was achieved in 88% of the cases with a kappa (κ) of 0.766.

3724.   5 Myelin Water Fraction Using Multiple-Echo 2D and 3D GRE at 3T with Whole-Brain Coverage
Ana-Maria Oros-Peusquens1, Sandra M. Meyers2, Alex L. MacKay2, and Nadim Jon Shah1,3
1INM-4, Research Centre Jülich, Jülich, Germany, 2Department of Physics and Astronomy, University of British Columbia, Vancouver, B.C., Canada, 3Faculty of Medicine, JARA, RWTH Aachen University, Aachen, Germany

It is increasingly recognised that myelin is ubiquitous in determining MR contrast in the living brain, especially at high fields. Investigating its distribution is not only useful in the study of several neurodegenerative diseases but can also be used for the in vivo parcellation of the brain. The current “gold standard” method for characterisation of myelin content in vivo is based on the investigation of the water trapped between myelin layers. Separation of the myelin water and tissue water pools, which have different mobility, is possible with an NNLS-based analysis of T2 decay curves. We introduce here a method which allows for discrimination between the two water pools based on their T2* properties. The data are acquired at 3T with either a 2D or a 3D multiple-echo gradient echo sequence and analysed with NNLS. Evaluation of the raw data (no additional resampling or image filtering) allows for separation of myelin (T2* < 20ms) and tissue water (T2*> 20ms) in the majority of white matter voxels. The average value of brain myelin water fraction for 12 volunteers is found to be 6.4%. Several improvements in data analysis are suggested. The method is proposed as an alternative to (high-SAR) spin-echo based myelin water analysis for use with high-field systems.

3725.   6 Automated Bolus Tracker Positioning for MRI Liver Scans
Takao Goto1 and Hiroyuki Kabasawa1
1Global Science Laboratory, GE Healthcare, Hino-shi, Tokyo, Japan

We present a new method of the automated bolus tracker positioning for MRI liver scans. Bolus tracker is used to monitor bolus signal to know the arrival of the bolus. Placing the bolus tracker inside the aorta accurately with looking at scout images is complicated task and one of the factors making operatorfs workflow worse. In proposed method, the aorta was detected using AdaBoost by searching aorta around spine. 234 axial images of 64 volunteersf datasets were tested and showed 98.3 % success rate of the aorta detection. Automated size of the tracker will be necessarily towards practical use.

3726.   7 Streaking Artifact Reduction in Orthogonal Super Resolution Reconstruction of MRI Data Sets  -permission withheld
Niranchana Manivannan1, Bradley Dean Clymer1, Anna Bratasz2,3, and Kimerly A. Powell2,3
1Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH, United States, 2Small Animal Imaging Shared Resources, The Ohio State University, Columbus, OH, United States, 3Department of Biomedical Informatics, The Ohio State University, Columbus, OH, United States

The goal of this research is to explore the effect on image quality of including an additional LR view to the orthogonal super resolution geometry. The visual evaluation of this technique was performed in low resolution data sets simulated from isotropic high resolution data. The results of simulation indicate that the quality of an SRR image based on orthogonal acquisition may be improved by the addition of a fourth view acquired obliquely to the through-plane direction. Additionally, the observed increase in image quality would be worth the minimal increase in acquisition time required for one additional view.

3727.   8 Comparison of Bayesian and Linear Regression-Based Partial Volume Correction in Single Time Point ASL
Ruth Oliver1, Michael A. Chappell2,3, David Thomas1, and Xavier Golay1
1Institute of Neurology, University College London, London, United Kingdom, 2Institute of Biomedical Engineering, University of Oxford, Oxford, United Kingdom, 3FMRIB Centre, University of Oxford, Oxford, United Kingdom

Partial volume effects due to low spatial resolution are known to introduce errors in quantification of perfusion estimates using ASL. This is particularly problematic in patients where atrophy is present and cortical thinning occurs. A comparison is made for single-TI data of an existing method that employs adaptive spatial priors, and a linear regression approach that assumes constant perfusion for each tissue over a specified kernel area. Both methods offer good correction, increasing GM perfusion by a factor of 1.7 on average, although the adaptive spatial prior method introduces less smoothing and better preserves detail.

3728.   9 Computer Aided Diagnosis of Parkinson’s Disease from T1-Weighted MRI
Mohit Saxena1, Namita Aggarwal2, Bharti Rana2, S. Senthil Kumaran3, Ramesh Kumar Agrawal2, and Madhuri Behari1
1Department of Neurology, All India Institute of Medical Sciences, New Delhi, Delhi, India, 2School of Computer & Systems Sciences, Jawaharlal Nehru University, New Delhi, Delhi, India, 3Department of NMR, All India Institute of Medical Sciences, New Delhi, Delhi, India

Support vector machine (SVM) is used to distinguish PD from controls in terms of white matter changes in substantia nigra, thalamus and/ or combination of both areas from the T1-weighted MR images. We extracted voxels from white tissue probability maps of substantia nigra and thalamus region. The performance of the decision system was evaluated in terms of sensitivity, specificity and accuracy. Experimental results demonstrate the importance of white matter change in thalamus and effectiveness of SVM to automatically distinguish PD from controls.

3729.   10 3D Co-Registration of MRI and Histology in a Mouse Model of Obesity and Non-Alcoholic Fatty Liver Disease
Eli Gibson1,2, Lanette J. Friesen-Waldner2,3, Amanda M. Hamilton2, Emeline J. Ribot2, Trevor P. Wade2,3, Curtis N. Wiens4, Kundan Thind2,3, Jacqueline K. Harris3, Nica M. Borradaile5, Charles A. McKenzie1,3, and Aaron D. Ward1,2
1Biomedical Engineering, University of Western Ontario, London, Ontario, Canada, 2Robarts Research Institute, London, Ontario, Canada, 3Medical Biophysics, University of Western Ontario, London, Ontario, Canada, 4Physics and Astronomy, University of Western Ontario, London, Ontario, Canada, 5Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada

Validation of quantitative MRI for non-invasive quantification of liver fat ideally uses accurate registration to an accepted reference standard (e.g. histology). We demonstrate accurate co-registration of murine in vivo 3D whole-body water-only and fat-only images to stained histological liver images. Three 129/SVJ mice were fed a high fat diet to induce hepatic steatosis and obesity, imaged using 3D quantitative IDEAL MRI at 3T, then sectioned on a cryomicrotome, where 3D optical and histology images were collected. We successfully co-registered MR-optical images and optical-histology images interactively using thin-plate-spline transformations with mean target registration errors of 0.7 mm and 0.1 mm, respectively.

3730.   11 Non-Rigid Registration of Sequential DCE-MRI in the Assessment of Response to Neoadjuvant Chemotherapy in Breast Cancer
Tess E. Catherwood1, Andrew J. Patterson1, Kamarul Zaki2, Mahesh Iddawela2, Helena Earl2, Carlos Caldas3, Karen Sayal4, Martin John Graves1, and Fiona J. Gilbert1
1Radiology, University of Cambridge, NHS Foundation Trust, Cambridge, United Kingdom, 2Oncology, Addenbrooke's Hospital and University of Cambridge, NHS Foundation Trust, Cambridge, United Kingdom, 3Cancer Research UK Cambridge Institute, Cambridge, United Kingdom, 4University of Cambridge, Cambridge, United Kingdom

Tumor heterogeneity is well recognized in breast cancer and is associated with differential responses to chemotherapy. Voxel-wise analysis of sequential DCE-MRI requires that images be spatially registered. Patients were studied with 3T MRI during neoadjuvant chemotherapy. Mutual information-based rigid and non-rigid registration was used to align dynamic and sequential volumes to account for motion artifacts and larger inter-session deformations. Semi-quantitative perfusion metrics were extracted and generation of spatially registered parameter maps allowed voxel-wise assessment of treatment response. This approach provides an insight into tumor microstructure and physiology and developments will ideally increase statistical sensitivity in differentiating responders and non-responders.

3731.   12 Time Correlation of EPI Versus Real-Time fMRI Time Series
Radu Mutihac1,2, Allen Braun3, and Thomas J. Balkin2
1Department of Physics, University of Bucharest, Bucharest, Bucharest-Magurele, Romania, 2Psychiatry & Neuroscience, Department of Behavioral Biology, Walter Reed Army Institute of Research, Silver Spring, Maryland, United States, 3Language Section, NIDCD / National Institutes of Health, Bethesda, Maryland, United States

Analysis of real-time fMRI time series is subject to temporal dispersion of the hemodynamic response and aliasing of physiological noise. Echo-volumar imaging (EVI), inverse imaging (InI), highly undersampled projection imaging (PI), and compressed sensing (CS) imaging reconstruction enable temporal resolution down to 100 ms. Extremely short acquisition (TR) poses the problem of serial correlations among voxels studied here in the context of autoregressive (AR) models.


Tuesday, 23 April 2013 (17:00-18:00) Exhibition Hall
Advances in Image Analysis: Image Reconstruction & Processing

  Computer #  
3732.   13 Improving Through-Plane Resolution for Multi-Slice Acquisitions
Thomas A. Depew1 and Qing-San Xiang1,2
1Physics & Astronomy, University of BC, Vancouver, BC, Canada, 2Radiology, University of BC, Vancouver, BC, Canada

3D MRI is becoming increasingly popular in clinical diagnostic imaging and interventional studies. In multi-slice acquisitions, the through-plane resolution is limited by the slice selection profile. We present here a simple and scalable technique to improve through-plane resolution in 3D multi-slice acquisitions that can be employed on any set of MRI data by acquiring a few extra datasets.

3733.   14 An Exact Phase Unwrapping Method Based on FFT
Renjie He1, Joshua P. Yung1, David T. A. Fuentes1, R. Jason Stafford1, and John D. Hazle1
1Department of Imaging Physics, The University of Texas M. D. Anderson Cancer Center, Houston, Texas, United States

FFT Based phase unwrapping is a straight, flexible and fast method; however, it suffers from the phase distortion in practice. We tried to recover the phase unwrapping exactly by quantizing the dispersed integer filed into an integer field through Powell optimization. The exact phase unwrapping was obtained for phantom phase MR images. This approach is useful in quantitative analysis based on phase images.

3734.   15 A Bilinear Noise Transfer Model for SENSE Reconstruction
Yu Ding1, Rizwan Ahmad1, Hui Xue2, Lee C. Potter1, Samuel T. Ting1, Ning Jin3, and Orlando P. Simonetti1
1The Ohio State University, Columbus, OH, United States, 2Corporate Research, Siemens Corporation, Princeton, NJ, United States, 3Siemens Healthcare, Columbus, OH, United States

SENSE is a widely used parallel imaging technique. The so-called g-factor represents how noise in the raw data affects the noise in the reconstructed image. However, the g-factor calculation does not take into account the noise in the channel sensitivity map. In this abstract, we present a noise transfer model in SENSE reconstruction that takes into account the noise in both the raw data and the channel sensitivity map. A phantom study showed that the model has satisfactory accuracy. We observed that a large portion (> 35%) of the image noise originates from the noise in the sensitivity map.

3735.   16 An Efficient De-Convolution Reconstruction Method for Spatiotemporally-Encoded Single-Scan 2D MRI
Congbo Cai1, Jiyang Dong1, Shuhui Cai1, Jing Li1, Lin Chen1, and Zhong Chen2
1Department of Communication Engineer and Electronic Science, Xiamen university, Xiamen, Fujian, China, 2Department of Communication Engineer and Electronic Science, Xiamen University, Xiamen, Fujian, China

Spatiotemporally-encoded single-scan MRI method is relatively insensitive to field inhomogeneity compared to EPI method. Conjugate gradient (CG) method has been used to reconstruct super-resolved images from the original blurred ones. In this article, a new de-convolution reconstruction method is proposed. Through removing the quadratic phase modulation from the signal acquired with spatiotemporally-encoded MRI, the signal can be described as a convolution of desired super-resolved image and a point spread function. The de-convolution method proposed herein not only is simpler and more efficient than the CG method, but also provides super-resolved images with better quality.

17 Adaptive Synthesis of Prior Image and New Acquired Data in Repetitive 3D Examinations
Guobin Li1, Maxim Zaitsev1, Esther Meyer2, Dominik Paul2, and Jürgen Hennig1
1University Medical Center Freiburg, Freiburg, Germany, 2Siemens Healthcare, Erlangen, Germany

High resolution isotropic 3D MR imaging is often repeatedly performed for preoperative evaluation and postoperative follow-up. Usually only a little information is updated each time in a following examination compared to the previous one if neglecting the change of pose. an adaptive synthesis of the prior data and the new acquired data from separate 3D examinations is presented. It shows that the information synthesis can help to reduce residual aliasing artifacts in Compressed Sensing (CS) imaging with highly undersampled k-space.

3737.   18 Comparison of the Accuracy of PET/CT and PET/MR Spatial Registration in Multiple Metastatic Lesions
Linda DeMello1, Rajan Rakheja1, Christopher B. Glielmi2, Christian Geppert3, Hersh Chandarana4, and Kent Friedman1
1Radiology, New York University School of Medicine, New York, New York, United States, 2MR R&D Collaborations, Siemens Healthcare, New York, New York, United States, 3MR R&D Collaborations, Siemens Medical Systems, New York, New York, United States, 4Radiology, NYU Langone Medical Center, New York, New York, United States

This study was performed to compare the accuracy of spatial registration of PET/CT and PET/MR in patients with FDG-avid metastatic lesions. Thirteen patients underwent PET/CT followed by PET/MR, and the spatial coordinates of the visually estimated centers of nineteen metastatic lesions were measured. Total distance between the isocenters was calculated, along with averages and standard deviations. Morphologic PET/MR sequences showed significantly more accurate spatial registration than PET/CT, likely secondary to simultaneous acquisition of PET and MR data. However, EPI-based DWI sequences demonstrated significant misregistration compared to PET/CT, likely due to respiratory motion and the inherent spatial distortion of DWI.

3738.   19 Fast Platform Independent Web-Based Visualization of MRI Data for Computers, Tablets and Smartphones
Daniel Hähn1,2, Nicolas Rannou1,2, Thomas J. Re1,3, Patricia Ellen Grant1,2, and Rudolph Pienaar1,2
1Radiology, Boston Children's Hospital, Boston, MA, United States, 2Radiology, Harvard Medical School, Boston, MA, United States, 3Radiology, University of Milan, Milan, Italy

Recent advances in web browser technology enable fast loading and visualization of medical imaging data. We developed a parser for MR data in DICOM format which shows workstation-like performance while enabling access to such data across devices (smartphones, tablets, computers).

3739.   20 Optimal Phase Sensitive Combination of Multi-Channel, Multi-Echo Images
L. Martyn Klassen1 and Ravi S. Menon1
1Robarts Research Institute, The University of Western Ontario, London, ON, Canada

Increased use of multichannel coils and phase sensitive analysis requires coil combination techniques beyond the traditional square root of sum of squares. For multiple echo acquisitions used in B0 and quantitative susceptibility mapping, pixel wise singular value decomposition can be used to generate phase sensitive optimum, in a least squares sense, coil sensitivity and image magnetization estimates.

3740.   21 A Magnitude-Based Asymmetric Fourier Imaging (MagAFI)
Tokunori Kimura1 and Naho Imamura1
1MRI development department, Toshiba medical systems corp., Otawara, Tochigi, Japan

We proposed and assessed a new partial Fourier technique named MagAFI (Magnitude-based Asymmetric Fourier Imaging ) where only magnitude image with 0-filling is used and also it is possible to combine with POCS technique. MagAFI introduced smaller artifacts than standard homodyne method and the POCS combination sepecially in the portion of large and spatially high-frequency phase, reflecting the difference of residual phase errors after phase correction. Our proposed MagAFI is practically useful algorithm from the views of balancing image quality and simplicity. If allowing us to use phase information and to take processing time, MagAFI combining POCS is further better to improve image quality and robustness.

3741.   22 Measuring and Characterizing Short-Term High Order Eddy Currents with a Phantom
Dan Xu1, Joseph K. Maier1, Kevin F. King1, and R. Scott Hinks1
1GE Healthcare, Waukesha, WI, United States

Uncompensated high order eddy currents (HOEC) can cause various image artifacts, including image distortion in echo planar imaging (EPI) and phase errors in phase contrast imaging. While a recently proposed method is capable of measuring and correcting long term HOEC to minimize distortion in EPI, it cannot provide accurate characterization of short term HOEC, which is believed to be one of the main sources of phase errors in phase contrast imaging. In this paper, we propose to extend the Duyn’s method to 3D to measure and characterize short term HOEC with a phantom.

3742.   23 Navigators Improve Accuracy of Quantitative Sodium MR Imaging Compromised by Head Motion During with Long Acquisition Times
Aiming Lu1, Ian C. Atkinson1, and Keith R. Thulborn1
1Ctr Magnetic Resonance Research, University of Illinois, Chicago, IL, United States

Quantitative sodium MR imaging with flexible twisted projection imaging (flexTPI) provides valuable information about regional changes in tissue sodium concentration (TSC) in human brain tumors responsive to fractionated radiation treatment. The acquisition time of 10 minutes is at the upper limits for which a patient can be expected to remain stationary. Stimulations show that quantification of TSC is compromised by even small head motions without appreciable degradation of the visual impression of image quality. Navigators incorporated within the flexTPI sequence have been investigated as a means of detecting head motion during acquisition and then correcting the quantification of TSC.

3743.   24 Ultra-Low-Field MRI Noise Suppression Using a Data Consistency Constraint
Fa-Hsuan Lin1,2, Yi-Cheng Hsu3, Panu Vesanen2, Jaako O. Nieminen2, Koos C. J. Zevenhoven2, Juhani Dabek2, Lauri T. Parkkonen2, and Risto J. Ilmoniemi2
1Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan, 2Department of Biomedical Engineering and Computational Science, Aalto University, Espoo, Finland, 3Department of Mathematics, Nnational Taiwan University, Taipei, Taiwan

To mitigate the challenge of low SNR in ultra-low-field (ULF) MRI (typically B0 ~ 100 lower case Greek muT), we exploit the simultaneous measurements from multiple superconductive quantum interference device (SQUID) sensors to enforce a linear dependency among local k-space data points across coils. Experimental data using 47 SQUID sensors demonstrate that this data consistency (DC) constraint can improve the ULF MRI peak SNR by 2 fold.


Tuesday, 23 April 2013 (16:00-17:00) Exhibition Hall
Artifacts & Correction: Motion

  Computer #  
3744.   25 Retrospective Rigid Body Motion Correction of Interleaved Slice-Selective Acquisitions
Murat Aksoy1, Melvyn B. Ooi1, Anh Tu Van1, and Roland Bammer1
1Center for Quantitative Neuroimaging, Department of Radiology, Stanford University, Stanford, CA, United States

A method is described to retrospectively correct rigid body motion artifacts in interleaved slice-selective acquisitions. Instead of the conventional slice-by-slice reconstruction, the proposed method relies on reconstructing the 3D volume using all the slices simultaneously using an iterative technique. Simulations demonstrate that, if the motion information is known, it is possible to correct through-plane motion in an interleaved slice-selective acquisition.

3745.   26 T1- And T2-Weighted MR Acquisition for Bulk Motion Correction for Simultaneous PET-MR
Christoph Kolbitsch1, Claudia Prieto1, Charalampos Tsoumpas1, Christian Buerger1, and Tobias Schaeffter1
1Division of Imaging Sciences & Biomedical Engineering, King's College London, London, United Kingdom

Simultaneous PET-MR acquisition has recently been proposed to improve cancer diagnosis by combining metabolic information from PET-acquisitions with high-resolution MR-images. Since PET data is usually acquired in multi-stations, 3D MR-images need to be obtained during the PET scan. Bulk motion during acquisition can severely impair image quality of both techniques. Here we present an MR acquisition which acquires T1- and T2-weighted 3D images and allows for the estimation of bulk motion from the data itself. The motion information can be used to correct MR and PET-images. Our approach was successfully tested in healthy volunteers in real MR-acquisitions and PET simulations.

3746.   27 Motion-Robust Super-Resolution Reconstruction of Fetal Brain MRI
Ali Gholipour1, Judy A. Estroff1, and Simon K. Warfield1
1Department of Radiology, Boston Children's Hospital and Harvard Medical School, Boston, MA, United States

This educational E-Poster provides an overview of the recently developed motion-robust super-resolution volumetric MRI reconstruction methods with exemplary application in fetal MRI. The mathematical details of the methods will be discussed and illustrated with visual examples.

3747.   28 Cardiac Functional Assessment Without ECG Using Physiological Self-Navigation
Christoph Kolbitsch1, Claudia Prieto1, and Tobias Schaeffter1
1Division of Imaging Sciences & Biomedical Engineering, King's College London, London, United Kingdom

ECG-gated cine MRI provides accurate functional information on the heart, however reliable ECG signals are not always available. We propose a novel framework to assess heart function based on physiological information obtained from MR images without an ECG. A Golden-Angle radial acquisition is used to obtain quantitative cardiac gating signals from blood volume changes in real-time images. This is used for reconstruction of retrospectively gated 2D multi-slice cine images. Finally, information on heart valve closure is used for slice synchronisation. Functional assessment of the left ventricle in five volunteers showed deviations less than 5% compared to standard ECG-gated Cartesian approach.

3748.   29 SPIRiTmc - Autocalibrating Parallel Imaging with Non-Rigid Motion Correction
Claudio Santelli1,2, Johannes F.M. Schmidt2, Tobias Schaeffter1, and Sebastian Kozerke1,2
1Imaging Sciences and Biomedical Engineering, King’s College London, London, United Kingdom, 2Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland

Scan acceleration and motion compensating techniques are invaluable to reduce acquisition times and breathing artifacts in cardiac imaging. Respiratory motion compensation with navigator based gating or breathholding is widely used, but may be limited in non-compliant patients. In this work, the SPIRiT reconstruction framework is extended by incorporating linear motion operators into the signal model allowing for scanning during the entire breathing cycle in cardiac imaging. Simulation and in-vivo phase-contrast data demonstrate the benefits of the technique: Results show reduction in blurring artifacts for magnitude and velocity induced phase.

3749.   30 Optimal Channel Selection for Respiratory Self-Gating Signals
Robert Grimm1, Simon Bauer2, Berthold Kiefer2, Joachim Hornegger1, and Kai Tobias Block3
1Pattern Recognition Lab, FAU Erlangen-Nuremberg, Erlangen, Germany, 2Siemens Healthcare, Erlangen, Germany, 3Department of Radiology, NYU Langone Medical Center, New York City, NY, United States

In most respiratory self-gating techniques, the self-gating signal can be derived from all acquired channels. However, only coil elements close to the diaphragm deliver a reliable signal. Therefore, previous approaches usually required manual selection of an appropriate coil element or fixed scan protocols, both of which is infeasible for clinical routine applications. This work proposes a fully automatic method for this task, based on a score to characterize how well the self-gating signal shape resembles physiological respiration.

3750.   31 Fast, Robust and Self-Navigated 3D Cylindrical Imaging: MP-RAGE and FLAIR
Wei Lin1, Qin Qin2,3, Stewart H. Mostofsky4,5, and George Randy Duensing1
1Invivo Corporation, Philips Healthcare, Gainesville, Florida, United States, 2Radiology, The Johns Hopkins University, Baltimore, Maryland, United States, 3F.M. Kirby Research Center, Kennedy Krieger Institute, Baltimore, Maryland, United States, 4Neurology and Psychiatry, The Johns Hopkins University, Baltimore, Maryland, United States, 5Kennedy Krieger Institute, Baltimore, Maryland, United States

A fast, robust and self-navigated 3D imaging method is proposed, based on sampling k-space with pairs of orthogonal view planes forming a cylinder. Rotation around its main axis is corrected in real-time, while other motions are corrected retrospectively at a temporal resolution of every 1-2 second. The method achieves the same off-resonance behavior and reconstruction speed as the conventional 3D Cartesian imaging. When array coil is used, scan time can be reduced significantly by acquiring less view planes. The efficacy of the proposed technique is demonstrated in healthy volunteers using a T1-weighted MP-RAGE sequence and a T2-weighted FLAIR sequence.

3751.   32 Real-Time Motion Correction in 2D Multi-Slice Imaging with Through-Plane Navigator
Wei Lin1, Tim Nielsen2, Qin Qin3,4, Stewart H. Mostofsky5,6, and George Randy Duensing1
1Invivo Corporation, Philips Healthcare, Gainesville, Florida, United States, 2Philips Research Europe, Hamburg, Germany, 3Radiology, The Johns Hopkins University, Baltimore, Maryland, United States, 4F.M. Kirby Research Center, Kennedy Krieger Institute, Baltimore, Maryland, United States, 5Neurology and Psychiatry, The Johns Hopkins University, Baltimore, Maryland, United States, 6Kennedy Krieger Institute, Baltimore, Maryland, United States

A real-time strategy for 3D rigid-body motion correction in 2D multi-slice multi-shot MRI scans is proposed. Two through-plane navigator (tNav) echoes are collected on each imaging slice to derive two tNav projection images within each TR. Rotation/translation within each tNav image plane is detected using an image correlation measure. Rotation within the imaging plane is detected by replacing tNav with an orbital navigator on one slice. The proposed method does not introduce any additional 3D RF excitation, and does not require any additional hardware. The efficacy of the proposed method is demonstrated with in vivo brain studies.

3752.   33 Free Breathing Abdominal Imaging Via Self-Navigation and Subvolume Registration
Gregory R. Lee1,2, Yong Chen3,4, Nicole Seiberlich4,5, Mark A. Griswold3,4, and Vikas Gulani4,6
1Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, United States, 2Radiology, University of Cincinnati, Cincinnati, OH, United States,3Radiology, Case Western Reserve University, Cleveland, OH, United States, 4Radiology, University Hospitals of Cleveland, Cleveland, OH, United States,5Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States, 6Radiology, University Hospitals Case Medical Center, Cleveland, OH, United States

Dynamic contrast enhanced imaging of the abdomen is complicated by respiratory motion and often requires multiple breath-holds to be completed. In this work, the properties of a recently developed multi-echo 3D radial acquisition are leveraged to develop a method of self-navigation and subvolume registration. Self-navigation was performed by reconstructing low resolution images every 0.5 seconds to allow the extraction of a pencil-beam navigator. Nonlinear registration of extended duration images corresponding to each respiratory position was performed. Subsequent combination of undersampled images using the corresponding registration parameters allowed rapid, free breathing dynamic abdominal exams to be performed.

3753.   34 Motion-Immune Structural MRI Based on Repeated K-T-Subsampling and Artifact-Minimization (REKAM)
Mei-Lan Chu1,2 and Nan-Kuei Chen3
1Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan, 2Brain Imaging and Analysis Center, Duke University Medical Center, Durham, NC, United States, 3Brain Imaging and Analysis Center, Duke University, Durham, NC, United States

A robust motion-immune MRI acquisition and reconstruction strategy is presented in this study. The experimental results indicate that the proposed REKAM method can effectively suppress motion-related artifacts even for highly challenging cases, such as continual head tremor during scans. As compared with the conventional SPGR that is highly susceptible to intra-scan motion, the REKAM method can produce artifact-free images of the same spatial resolution within the same scan time. Even though the REKAM method is demonstrated here with T2*-weighted imaging, the developed technique can be applied to structural MRI pulse sequences of other weightings and contrasts.

3754.   35 Compressive Manifold Learning Respiratory Self-Gated Liver MRI: Estimating the Respiratory Motion Directly from Undersampled K-Space
Muhammad Usman1, Paul Aljabar1, Tobias Schaeffter1, and Claudia Prieto1,2
1King's College London, London, United Kingdom, 2Pontificia Universidad Catolica de Chile, Santiago, Chile

Manifold learning approaches can be applied in MRI to extract meaningful patterns of variation from the high-dimensional set of images. An example is respiratory self-gating where the low dimensional respiratory signal can be extracted from a set of free breathing images. In this work, we propose Compressive Manifold learning for respiratory self-gated MRI. This approach estimates the respiratory signal directly from undersampled k-space data, without the need for image reconstruction. Results from simulated free-breathing liver MR data show that the respiratory signal can be accurately extracted from highly undersampled k-space samples using the proposed method. Free-breathing acquisitions, performed prospectively in 3 volunteers, also demonstrate the feasibility of CML respiratory self-gating in k-space.

3755.   36 Bringing Prospective Motion Correction to Clinical Routine - Fast Camera Calibration
Cris Lovell-Smith1, Julian R. Maclaren2, Michael Herbst1, Ilja Kadashevich3, K.A. Danishad3, Oliver Speck3, and Maxim Zaitsev1
1Department of Radiology, University Medical Center Freiburg, Freiburg, Germany, 2Department of Radiology, Stanford University, Stanford, California, United States, 3Faculty of Natural Sciences, Institute of Experimental Physics (IEP), Magdeburg, Germany

Motion-induced artefacts in MR images degrade quality. The use of an optical tracking system to prospectively compensate for head movement during brain imaging has been shown to reduce these artefacts. To successfully apply motion correction, the cross-calibration matrix defining the transform between tracking system coordinates and scanner coordinates must be accurately known. We previously reported a method to determine this transform, however it required two experienced MR technicians upward of 20 minutes to perform. We present two newly developed methods that accurately calculate the cross-calibration within two minutes with one operator, thereby reducing the system setup time considerably. This is a major step in bringing prospective motion correction to clinical routine.

3756.   37 Cross-Calibration Accuracy Requirements for Prospective Motion Correction
Murat Aksoy1, Melvyn B. Ooi1, Julian R. Maclaren1, and Roland Bammer1
1Center for Quantitative Neuroimaging, Department of Radiology, Stanford University, Stanford, CA, United States

Cross-calibration of the optical tracking system and the scanner is an essential step in prospective motion correction. Errors in cross-calibration cause inaccuracies in motion correction and subsequent motion artifacts in the image. In this study, we assessed the accuracy requirement of cross-calibration for robust motion tracking and correction. Simulations show that for a maximum of 0.5mm pixel position error and in the presence of 10° head rotation, the cross-calibration has to be accurate up to 0.3° and 3 mm. The required accuracy of cross-calibration depends on the maximum motion that needs to be corrected and the baseline position of the camera in the scanner.

3757.   38 2D Nose Navigators (NoseNav) for Real-Time Correction of Nodding Motion in Brain MRI
Axel Hartwig1, Magnus Mårtensson2, and Stefan Skare1
1Neuroradiology, Karolinska University Hospital, Stockholm, Sweden, 2EMEA Research and Collaboration, Applied Science Laboratory, GE Healthcare, Stockholm, Sweden

A new image based navigation sequence is proposed to overcome nodding motion in MRI, where a thick coronal excitation plane over the patient’s nose followed by a sagittal EPI readout tracks the nose in real time - NoseNav. This sequence module will be used in a real-time setting and update the prescribed slices over the brain so that they follow the nodding motion of the patient, which also is the direction that is hardest to restrain in practice.

3758.   39 High-Resolution Multi-Shot Spiral Diffusion Tensor Imaging with Inherent Correction of Motion-Induced Phase Errors
Trong-Kha Truong1 and Arnaud Guidon1
1Brain Imaging and Analysis Center, Duke University, Durham, NC, United States

In multi-shot spiral diffusion tensor imaging, subject motion causes phase errors among different shots, leading to signal loss and aliasing artifacts. A novel method is proposed to inherently correct for these errors without requiring a variable-density spiral trajectory or a navigator echo. This method uses a sensitivity encoding reconstruction algorithm to estimate the phase error for each shot and a conjugate gradient algorithm to correct for them. In vivo experiments were performed to demonstrate that it can inherently and efficiently correct for phase errors caused by rigid and nonrigid motion, without increasing the scan time or reducing the signal-to-noise ratio.

3759.   40 Prospective Motion Correction Reduces the Number of False Positive Activations in an fMRI Group Study Involving Task-Correlated Motion
Jessica Schulz1, Thomas Siegert1, Pierre-Louis Bazin1, Julian R. Maclaren2, Michael Herbst3, Maxim Zaitsev3, and Robert Turner1
1Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, 2Stanford University, Stanford, CA, United States, 3Radiology, University Medical Center Freiburg, Freiburg, Germany

This study compared the rate of false positive activations in an fMRI group study with and without slice-by-slice prospective motion correction using an optical tracking system. The paradigm involved strong task-correlated motion - a major cause of false positive activations in fMRI. The number of voxels with T-values higher than 5 outside of grey matter – i.e. activations that are obviously false positive - was strongly reduced using prospective motion correction. Additionally, the statistical power of the analysis increased. Therefore, we suggest that prospective correction techniques should be used whenever available.

3760.   41 Characterizing Respiratory Motion of the Major Abdominal Vessels
Ashley Gould Anderson III1, Christopher J. François2, and Oliver Wieben1,2
1Medical Physics, University of Wisconsin, Madison, Wisconsin, United States, 2Radiology, University of Wisconsin, Madison, Wisconsin, United States

A detailed analysis of the motion of 11 segments of major abdominal vessels (renal, hepatic, mesenteric, splenic arteries, aorta) during free breathing, as well as during inspiration and expiration breath holds was conducted. The results form a comprehensive reference for motion of the abdominal vasculature that extends the knowledge from previous motion studies. These data should be valuable for those interested in imaging the abdominal vasculature using respiratory-gated or breath-held acquisitions.

3761.   42 Generalized Multiple Averages (GRAMA) for Motion Compensation
Shujing Cao1, Feng Huang2, Rui Li1, and Chun Yuan3
1Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, Beijing, China, 2Philips Healthcare, Beijing, Beijing, China, 3Department of Radiology, University of Washington, Seattle, WA, United States

A new retrospective motion compensation method named as GeneRAlized Multiple Averages (GRAMA) is proposed. GRAMA synthesizes two copies of original k-space with relative consistency using a couple of optimized convolution kernel. Based on the interleaved data acquisition manner, error in different k-space copies is inherent. Instead of average with original k-space like that in conventional multiple averages method, GRAMA directly use the average of two synthetic k-space to reconstruct motion corrected image. Volunteer experiments indicate GRAMA effectively balances SNR preservation and artifact reduction.

3762.   43 Abdominal Fat-Water Separation in High Temporal and Spatial Resolution During Free Breathing
Riad Ababneh1, Thomas Benkert2, Martin Blaimer2, and Felix A. Breuer2
1Physics, Yarmouk University, Irbid, Jordan, 2Research Center Magnetic Resonance Bavaria, Würzburg, Bavaria, Germany

We present a robust approach to separate fat and water signals in the abdomen during free breathing. The approach combined with the k-space-weighted image contrast (KWIC) technique of different respiratory phases in free-breathing. In this study a radial TrueFISP sequence was modified, wherein TE was made to vary between subsequent readouts. Good separation without streaking artifacts or blurring due to respiratory motion was obtained in all studied cases.

3763.   44 Prospective Real Time Correction of Head Motion Using NMR Probes at 7 Tesla
Saikat Sengupta1, Sasidhar Tadanki2, John C . Gore1, and E. Brian Welch1
1Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States, 2Vanderbilt University, Nashville, TN, United States

In this abstract, we report the use of NMR probes for prospective motion corrections of head motion in high-resolution gradient echo (GRE) imaging at high field of 7 Tesla. 3 NMR probes mounted on a volunteer’s head are used in conjunction with a linear navigator sequence to measure and correct for head motion in real time. The system is evaluated with 1 mm3 isotropic voxel GRE scans with a series of motion patterns on normal volunteers. Effective real time compensation is demonstrated for each type of motion tested.

3764.   45 Hybrid MP-RAGE Trajectory with FID Motion Detection and Self-Navigated Motion Correction (MoCoRAGE)
Tobias Kober1,2, Davide Piccini1,2, Christoph Forman3,4, Thorsten Feiweier5, and Gunnar Krueger1,2
1Advanced Clinical Imaging Technology, Siemens Healthcare IM S AW, Lausanne, Switzerland, 2CIBM - AIT, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, 3Pattern Recognition Lab, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany, 4Erlangen Graduate School in Advanced Optical Technologies, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany, 5Siemens AG, Erlangen, Germany

The Magnetisation-Prepared Rapid Acquisition Gradient Echo (MP-RAGE) sequence is widely used in clinical routine and research. However, its comparably long acquisition times render MP-RAGEs susceptible to motion artefacts. The present work explores the feasibility of mitigating the motion susceptibility of MP-RAGEs. While a free-induction-decay navigator is used for motion detection, the self-navigating properties of a hybrid acquisition trajectory are exploited to perform motion correction directly from portions of the imaging data. The motion detection and correction performance was tested in five volunteers proving the feasibility of this concept.

3765.   46 Inherent Correction of Artifacts from Large-Scale Patient Motion in High-Resolution Multishot Diffusion-Weighted EPI
Shayan Guhaniyogi1, Allen Song1, Jeffrey Petrella2, and Nan-Kuei Chen1
1Brain Imaging and Analsyis Center, Duke University, Durham, NC, United States, 2Department of Radiology, Duke University, Durham, NC, United States

Multishot EPI in diffusion weighted imaging allows improved spatial resolution and reduced geometric distortions compared to single-shot acquisitions. However, multishot EPI acquisitions are very sensitive to patient motion. To overcome this limitation we present a technique which inherently corrects motion-induced artifacts and blurring in multishot diffusion-weighted EPI images using only the originally acquired data, without needing navigator echoes. The technique is shown to greatly reduce artifacts and blurring, enabling visual identification of small structures such as the optic nerve fibers. This method is anticipated to be valuable in clinical and neuroscience investigations requiring high resolution images with detailed microstructure information.

3766.   47 On the Robustness of Prospective Motion Correction for Clinical Routine
Michael Herbst1, Cris Lovell-Smith1, Benjamin Haeublein1, Rebecca Sostheim1, Julian R. Maclaren2, Jan G. Korvink3, and Maxim Zaitsev1
1Department of Radiology, University Medical Center Freiburg, Freiburg, Germany, 2Department of Radiology, Stanford University, Stanford, California, United States, 3Laboratory for Simulation, IMTEK - Institute of Microsystem Technology, Freiburg, Germany

Despite the recent advances in prospective motion correction (PMC) for the correction of rigid body motion, the application of this technique to clinical routine still lacks behind. External tracking and motion correction has been shown to be applicable to a wide range of sequences and to provide sufficient accuracy and precision to improve even data from cooperative volunteers. However, when used in patients, problems such as marker fixation and involuntary skin motion limit the abilities of PMC and can even lead to additional motion artifacts. The aim of this work was to address this last key barrier to help bring PMC to clinical routine.

3767.   48 Non-Rigid Motion-Corrected Averaging for Improved Pelvic MRI
Patrick J. Bolan1, Xiufeng Li1, and Gregory J. Metzger1
1Radiology, CMRR, University of Minnesota, Minneapolis, MN, United States

While strategies for handling cardiac and respiratory motion are well established for cardiac and abdominal imaging, the aperiodic and non-rigid deformations from bowel contractions can limit the ability to perform high-resolution imaging in the lower abdomen and pelvis. This work assesses the feasibility of using a retrospective, non-rigid motion-corrected averaging approach to reduce the impact of involuntary motion on anatomical MRI of the pelvis.


Tuesday, 23 April 2013 (17:00-18:00) Exhibition Hall
Artifacts & Corrections: Off-Resonance & Eddy Currents

  Computer #  
3768.   49 Improved RF Pulses for 3D SSFP with Minimised Off-Resonance Out-Of-Slab Corruption
Anthony N. Price1, Shaihan J. Malik1, and Joseph V. Hajnal1
1Division of Imaging Sciences and Biomedical Engineering, King's College London, London, United Kingdom

Balanced SSFP provides excellent contrast and SNR efficiency, however, its familiar off-resonance characteristics result in black-band artefacts, which are particularly problematic at higher field strengths. Less well-known, but also significant to image quality, are the unwanted signal fluctuations arising from out-off-slice contributions, which are folded back into the imaging plane. Here we design a new RF pulse specifically for 3D SSFP that has very low stopband ripple. When compared to the standard truncated sinc pulse typically used, it yields effective suppression of off-resonance signal ripple whilst achieving a more homogeneous slab profile.

3769.   50 Using Spatio-Temporal Duality for Memory-Efficient Non-Uniform Fourier Transformation with Field Correction
Kaveh Vahedipour1,2 and Nadim Jon Shah1,3
1Juelich Research Centre, Juelich, Germany, 2Maastricht University, Maastricht, Netherlands, 3RWTH Aachen University, Aachen, Germany

The spatio-temporal duality of the Fourier transform, the time-reveral parity of Bloch equation without T1 and T2* relaxation as well as the principle of reciprocity can be used to rewind the physical process of gradient encoding along the time axis to obtain images from signals acquired along arbitrary k-space trajectories. In this work we show advantages of such a reconstruction scheme when compared to the state of the art non-uniform FFT solutions. The algorithm can be implemented in a very efficient way with respect to memory as well as processing complexity. It is discussed why this algorithm behaves favourably particularly for larger number of receive elements and large image matrices.

3770.   51 An Extended PSF Mapping Method for Distortion Correction in DW-EPI with Both Forward and Reverse Phase-Encoding Polarity at UHF
Myung-Ho In1, Oleg Posnansky1, Erik B. Beall2, Mark J. Lowe3, and Oliver Speck1
1Biomedical Magnetic Resonance, Otto-von-Guericke University, Magdeburg, Germany, 2Radiology, Cleveland Clinic, Cleveland, OH, United States,3Radiology, Imaging Institute, Cleveland Clinic, Cleveland, OH, United States

The geometric distortion correction quality is important to generate a distortion free diffusion weighted echo planar image (DW-EPI) without loss of spatial information. To recover spatial information in strongly compressed areas, two sets of DWIs with opposite phase-encoding (PE) polarities have been measured and combined after distortion correction. The point spread function (PSF) mapping method was used for correction due to its very high accuracy and robustness. To reduce PSF scan time, the PSF method was extended to correct distortions in both DW-EPIs with opposite PE polarities from a single PSF reference.

3771.   52 Phase-Labeled Reference EPI for Frequency-Segmented Inhomogeneity Corrections (PREFICS)
Mario Zeller1, Alexander Müller1, Dietbert Hahn1, and Herbert Köstler1
1Institute of Radiology, University of Würzburg, Würzburg, Germany

Artifacts induced by field inhomogeneities in non-Cartesian EPI acquisitions typically cannot be corrected by simple pixel-shifting. Instead, conjugate phase based methods can be applied. These methods require the acquisition of a separate gradient-echo field map. The acquisition of such a map is relatively time-consuming, as multiple radiofrequency pulses are applied. In this work, a method is described, which allows deriving the field map from a phase-labeled reference EPI scan comprising of only two fast EPI acquisitions. With this map, geometric distortions arising in non-Cartesian EPI can be successfully corrected.

3772.   53 Parallel Transmission Z-Shimming to Compensate GE-EPI Signal Voids at 7 Tesla
Benedikt A. Poser1, Soeren Johst2, Weiran Deng1, Stephan Orzada2, Mark E. Ladd2,3, and Victor Andrew Stenger1
1John A Burns School of Medicine, University of Hawaii, Honolulu, Hawaii, United States, 2Erwin L Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany, 3Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany

Gradient-echo BOLD fMRI suffers signal voids in regions of strong susceptibility variation e.g. near ear canals and frontal sinuses. “z-shimming” can correct this by applying a z-gradient moment to counteract the local background gradient. The global correction affects all spins and dephases originally intact signal, hence an intermediate compromise is required. Timeshifting an RF pulse equivalently creates a shim. This gives “pTX z-shimming” some spatial selectivity following each channel’s sensitivity profile. pTX z-shimming is explored at 7T, using EPI with slice and channel specific corrections and breathold fMRI. Signal recovery was seen near ear canals, but not the frontal cortex.

3773.   54 VOI-Based Fourier Transform Method for Rapid Partial Calculation of B0 Maps from Sparse Susceptibility Distributions
Rahul Dewal1 and Qing X. Yang1
1Radiology, Pennsylvania State University, Hershey, PA, United States

Calculation of B0 field inhomogeneity maps from susceptibility models via convolution with dipole kernels is limited by computer memory (RAM) and calculation time requirements in the case of large data matrices. In some applications, only small portions of the full matrix may be of interest as a susceptibility perturbation source or as a volume of interest (VOI). A VOI-based approach is here proposed that can reduce memory usage or calculation time in this sparse case. The method can be expected to accelerate various applications, such as passive shimming simulations and patient-specific B0 field calculations derived from anatomic scans.

3774.   55 Gradient Nonlinearity Terms in the Concomitant Field for Quantitative Phase Contrast Correction
Ek T. Tan1, Christopher J. Hardy1, and John F. Schenck1
1Diagnostics and Biomedical Technologies, GE Global Research, Niskayuna, NY, United States

The correction of residual phase intrinsic to phase-contrast velocity measurements remains a challenging problem, and affects accurate flow quantitation in imaging of congenital heart disease. A high degree of correlation between the residual phase and the concomitant field motivated an investigation into an improved concomitant field correction that accounts for gradient nonlinearity. The nonlinear correction resulted in a residual phase that was more quadratic in shape, but did not affect the residual phase near the vessels of interest. However, the incorporation of nonlinear concomitant fields into a hybrid-fitting method showed an improvement in the fitted result over the linear correction.

3775.   56 Temporal Unwrapping of Highly Wrapped Multi-Echo Phase Images at Ultra-High Field: UMPIRE
Simon P. Robinson1, Horst Schödl1, and Siegfried Trattnig1
1Department of Radiology, Medical University of Vienna, Vienna, Vienna, Austria

We describe a temporal phase unwrapping method applicable to multi-echo data called UMPIRE. This uses unequal spacings between echoes and an assessment of phase evolution in the time difference between the echo spacings to allow - uniquely amongst temporal unwrapping approaches - a number of wraps between echoes to be resolved. UMPIRE successfully resolved wraps in complicated simulated shapes which could not be unwrapped with prior temporal methods or the spatial methods PRELUDE and PHUN. UMPIRE also outperformed spatial methods in unwrapping in-vivo data and was faster than spatial methods.

3776.   57 Correction of Gradient-Induced Phase Errors in Radial MRI
Amir Moussavi1,2, Markus Untenberger1, Martin Uecker3, and Jens Frahm1,2
1Biomedizinische NMR Forschungs GmbH, am Max-Planck-Institut für biophysikalische Chemie, Göttingen, Niedersachsen, Germany, 2DFG Research Center for Molecular Physiology of the Brain (CMPB), Göttingen, Niedersachsen, Germany, 3Dept. of Electrical Engineering and Computer Sciences, University of California, Berkeley, California, United States

Gradient-induced eddy currents affect the MRI data acquisition by gradient delays and phase errors that may lead to severe image artifacts. This work introduces a robust method for quantifying and correcting phase errors in radial MRI without the need of complementary measurements. The proposed method yields a specific phase error per gradient that can be used for correcting the raw data. It is also able to distinguish between and separately correct for phase errors due to eddy currents caused by the in-plane gradients and other phase alterations which are constant for an image and that may carry relevant physiologic information.

3777.   58 Measurement of Short Time Constant Eddy Currents with Zero TE Imaging
Kevin F. King1, Graeme C. McKinnon1, Xu Dan1, and Joseph K. Maier1
1GE Healthcare, Waukesha, WI, United States

Eddy currents are typically measured using small samples with a special fixture. As part of an image-based tool without a special fixture, we propose to measure eddy currents with time constants of a few hundred microseconds or less with ultrashort TE imaging. A spherical phantom was scanned with eddy current generating preparation gradients followed by readouts at increasing delays. The image phase was fit to spatially linear terms which were then fit to sums of decaying exponentials. Reasonable agreement with fixture-based decay curves and comparable correction for ghosting in single-shot EPI and spectral-spatial RF pulse banding was found.

3778.   59 Correction Method for Thin Slice Spectral Spatial RF Pulses
Yuval Zur1
1GE Healthcare, Haifa, Israel

Spectral spatial (spsp) RF pulses are used for simultaneous fat suppression and slice selective excitation. However, spsp pulses are very sensitive to RF gradient delay and eddy currents. We present a correction method, such that spsp pulses are, in practice, not sensitive to system imperfections. This correction enables practical use of spsp RF pulses with slice width of 1.5 mm at high field strength (3T).

3779.   60 A Novel Approach in the Network Analysis of Eddy Current Induced by Planar Z Gradient Coil
Md. Shahadat Hossain Akram1 and Katsumi Kose1
1Institute of Applied Physics, University of Tsukuba, Ibaraki, Tsukuba, Japan

Transient response of eddy currents generated by planar z gradient coil in the local Rf shielding box of a 0.3T permanent magnet MRI system are simulated by applying a novel approach in the network analysis of electromagnetic system. Magnetic scalar potential of Biot Savart’s law is implemented in the calculation of mutual inductances between the z gradient coil and the conducting structure in interest, which is always the most crucial part in network analysis method. This very unique and efficient method would be possible to implement in network analysis of eddy current generated by any type of planar gradient coil.

61 Correction of RF Spike Noise in MR Images Using Robust Principal Component Analysis
Adrienne E. Campbell-Washburn1,2, David Atkinson3, Oliver Josephs4, Mark F. Lythgoe5, Roger J. Ordidge6, and David L. Thomas7
1Centre for Advnaced Biomedical Imaging, University College London, London, London, United Kingdom, 2Department of Medical Physics and Bioengineering, University College London, London, United Kingdom, 3Centre for Medical Imaging and Centre for Medical Image Computing, University College London, London, United Kingdom, 4University College London and Birkbeck College, London, United Kingdom, 5Centre for Advanced Biomedical Imaging, Division of Medicine and Institute of Child Health, University College London, London, United Kingdom, 6Centre for Neuroscience, University of Melbourne, Melbourne, Victoria, Australia, 7Department of Brain Repair and Rehabilitation, UCL Institute of Neurology, University College London, London, United Kingdom

RF spike noise, caused by hardware problems, can lead to striping artefacts in MR images. These artefacts affect the image quality and quantitative information from the MRI data, and often must be removed in post-processing. This abstract presents an algorithm for semi-automated detection and correction of RF spike noise based on Robust Principal Component Analysis (RPCA). RPCA is used to decompose the measured k-space into low-rank (artefact-free) and sparse (RF spike) matrix components, including an automatic correction for the misidentification of the central k-space cluster. This algorithm is demonstrated to efficiently and effectively recover artefact-free data and regain quantitative information.

3781.   62 DC Artifact Correction for Arbitrary Phase-Cycling Sequence
Paul Kyu Han1, Jong Chul Ye1, HyunWook Park2, and Sung-Hong Park1
1Bio and Brain Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Daejeon, Korea, 2Electrical Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Daejeon, Korea

We proposed a new technique that allows for the correction of DC artifact for any phase-cycled pulse sequence. The proposed method includes receiver phase unification and its reversal before and after the application of a usual DC artifact removal technique in the specifically phase-cycled pulse sequence. Results show complete removal of the DC artifact for phase cycling angles of 0¡Æ, 90¡Æ, 180¡Æ, 270¡Æ in the phase-cycled bSSFP sequence, and provides useful insight for the application of DC artifact removal in other phase-cycled pulse sequences.

3782.   63 Fast, Parallelized Implementation of a Novel Temporal Phase Unwrapping Method, and Comparison with Spatial Approaches  -permission withheld
Horst Schödl1, Siegfried Trattnig1, and Simon Robinson1
1Department of Radiology, Medical University Vienna, Vienna, Vienna, Austria

Phase images can be unwrapped with spatial or temporal approaches. A new and fast temporal approach, suited to highly wrapped phase images at ultra-high field, is UMPIRE. It is based on a multi-echo acquisition with unequal echo spaces, and uses the difference between phase difference images (essentially a wrap-free estimation of B0) to unwrap phase images. UMPIRE was implemented in C using parallelization. The performance of UMPIRE was compared with region growing methods PHUN and PRELUDE using simulated data with complicated shapes and in-vivo images. UMPIRE was dramatically faster than the spatial methods PHUN and PRELUDE in all tests.

3783.   64 Nonlinear Phase Correction of Multi-Shot Diffusion Weighted EPI Using Parallel Imaging Estimated Phase Cycled Reconstruction (PIPCR) Method
Wentao Liu1, Xin Tang1, Yajun Ma1, and Jia-Hong Gao1,2
1MRI Research Center and Beijing City Key Lab for Medical Physics and Engineering, Peking University, Beijing, China, 2Brain Research Imaging Center and Department of Radiology, The University of Chicago, Chicago, Illinois, United States

Multi-shot echo-planar imaging (msEPI) has advantages of high spatial resolution and less distortion when comparing to single-shot EPI (ssEPI). However, in the application of diffusion imaging, msEPI often suffers ghosting artifacts due to phase shifts from shot to shot. A recently proposed phase cycled reconstruction (PCR) method can correct 2D linear phase errors in msEPI efficiently using a search algorithm, but phase shifts caused by the pulsing of cerebrospinal fluid (CSF) are nonlinear and hard to be compensated by PCR method directly. In this study, an efficient parallel imaging estimated phase cycled reconstruction (PIPCR) method is introduced. The inter-shot phase maps are estimated from the parallel imaging (PI) reconstruction of the subset k-space of msEPI data. After a smoothing process, these phase maps are utilized as nonlinear phase compensation for PCR msEPI reconstruction. The proposed PIPCR is a fast and robust method to correct arbitrary inter-shot phase errors of diffusion weighted msEPI and the reconstruction result is demonstrated in the report.

3784.   65 Removing Echo Planar Imaging Banding Artifact Using Phase Matching
Dan Xu1, Kenichi Kanda1, Kevin F. King1, Zhenghui Zhang1, and Robert D. Peters1
1GE Healthcare, Waukesha, WI, United States

Conventional echo planar imaging (EPI) phase correction can introduce a channel dependent phase which could conflict with parallel imaging unaliasing especially for high channel count coils, leading to banding or residual aliasing artifacts in the final images. In this paper we propose a phase matching method to remove the incompatibility by introducing a channel dependent phase while retaining the odd-even phase correction capability, thereby producing images free of banding and aliasing artifacts, in addition to minimizing EPI Nyquist ghost.

66 Robust Estimation of True K-Space Center Position for Radial Center-Out Trajectories
Martin Krämer1, Karl-Heinz Herrmann1, and Jürgen R. Reichenbach1
1Medical Physics Group, Institute of Diagnostic and Interventional Radiology I, Jena University Hospital - Friedrich Schiller University Jena, Jena, Germany

Radial center-out trajectories are extremely sensitive towards imperfections in the gradient and data sampling hardware. Even the smallest jitter between data sampling and gradient onset must be compensated during image reconstruction in order to obtain images free of delay artifacts. We propose to estimate such delays with a template scan using a very short additional dephaser. The delay is given from the difference between the expected k-space center position along the template readouts and the actual center crossing. We shot that a very robust estimation of the true k-space center crossing can be made by analyzing k-space phase directly.

3786.   67 Fast Automatic Coil Selection for Radial Stack-Of-Stars GRE Imaging
Robert Grimm1, Christoph Forman2, Jana Hutter1, Berthold Kiefer3, Joachim Hornegger1, and Kai Tobias Block4
1Pattern Recognition Lab, FAU Erlangen-Nuremberg, Erlangen, Germany, 2Pattern Recognition Lab, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany, 3Siemens Healthcare, Erlangen, Germany, 4Department of Radiology, NYU Langone Medical Center, New York City, NY, United States

In radial stack-of-stars GRE imaging, distortions of the magnetic B0 field and gradient fields distant from the isocenter can cause significant streaking artifacts. The image quality can be severely degraded by coils that contribute mostly artifacts but little image information. Here, an efficient, k-space-based score is proposed as an indicator for channels that are corrupted by streaking artifacts. A k-means clustering algorithm is employed to detect affected channels in order to exclude them from reconstruction. The method requires no manual training and, therefore, can be applied easily to different scan protocols.

3787.   68 Intensity Inhomogeneity Correction in Human Brain Imaging at 7 Tesla Using SPM8
Ikuko Uwano1, Kohsuke Kudo1, Fumio Yamashita1, Jonathan Goodwin1, Tsuyoshi Metoki1, Satomi Higuchi1, Kenji Ito1, and Makoto Sasaki1
1Division of Ultrahigh Field MRI, Institute for Biomedical Sciences, Iwate Medical University, Morioka, Iwate, Japan

In ultra-high field 7 Tesla (T) MRI, signal intensity variation or inhomogeneity are caused by main magnetic field (B0) and RF field (B1) inhomogeneity, susceptibility effects, and inhomogeneous coil sensitivity. We tested a post-processing technique available with SPM8, for signal intensity correction of various scan sequences on 7 T MRI. We found that by using SPM8, signal inhomogeneity was successfully corrected and a reduction in signal non-uniformity between the subcortical and deep white matter was observed.

3788.   69 A Retrospective, Fully Automated and Fast Method for Intensity Inhomogeneity Correction in 7T MRI
Sven Jaeschke1,2, Robin Martin Heidemann2, and Aleksandar Petrovic2
1HAW Hamburg, Hamburg, Germany, 2Healthcare Sector, Siemens AG, Erlangen, Germany

Ultra high field (UHF) MRI offers improved image contrast and higher SNR enabling isotropic, high-resolution in vivo anatomical imaging. However, image quality is affected by bias fields, which can be a hindrance for tissue segmentation or classification. In this study, we propose a novel, fast and fully automated image inhomogeneity correction method, which is well suited for UHF applications. In comparison to former methods, we employ a bounded Nelder-Mead simplex optimizer and use a joint intensity-gradient histogram to calculate entropy. We show that our approach outperforms other methods in UHF-MRI in terms of processing speed and promises better inhomogeneity correction.

3789.   70 A Clinical Evaluation of a Novel, Retrospective and Entropy-Based Intensity Inhomogeneity Correction Method in 3T MRI
Sven Jaeschke1,2, Alexander Hubert3, Andreas J. Bartsch4, Antje Kickhefel2, and Aleksandar Petrovic2
1HAW Hamburg, Hamburg, Germany, 2Healthcare Sector, Siemens AG, Erlangen, Germany, 3Neuroradiology, Universitätsklinikum Heidelberg, Heidelberg, Germany, 4Neuroradiology, University of Heidelberg, Heidelberg, Germany

Intensity inhomogeneities remain an issue in high-field MRI and can degrade clinical interpretability of images. To improve image quality in a fast, robust and fully automated fashion, we developed and clinically validated a novel image inhomogeneity correction method, based on entropy minimization. A wide range of different MR-contrasts/sequences in healthy-control and images with pathological findings were assessed. Two trained radiologists evaluated each image in a blind fashion and both agreed on each rating. We show that the combination of the 3D implementation of our method and the current built-in Siemens solution significantly improves the clinical impression of 3T neuroradiological MRI.

3790.   71 N/2 Ghosting Artifacts in a Radial 3D EPI Pulse Sequence
Sumeeth Vijay Jonathan1, Parmede Vakil1, Yong Jeong1, and Timothy J. Carroll1,2
1Biomedical Engineering, Northwestern University, Chicago, IL, United States, 2Radiology, Northwestern University, Chicago, IL, United States

We characterize and introduce a phase correction scheme for N/2 ghosting artifacts in 3D RAZIR, a new radial 3D GRE-EPI pulse sequence. Phase modulations between alternating echoes in our radial 3D EPI acquisition are dependent on radial view. Our phase correction scheme measures phase modulations for each radial view without the need for a separate reference scan. N/2 ghosting artifacts that occur in radial 3D multiecho acquisitions like 3D RAZIR can be corrected with our technique.

3791.   72 Eye Movement Artifact Suppression Via 2D Spatially Selective RF-Excitation
Paul Wighton1, Matthew Dylan Tisdall1, and André J. W. van der Kouwe1
1Department of Radiology, MGH, Martinos Center for Biomedical Imaging, Charlestown, Massachusetts, United States

In this abstract, we explore the suppression of eye-movement artifacts using a subject-specific, spatially-selective RF-excitation pulse designed to excite only the subject's brain, ensuring no signal (and therefore no artifact) originates from the eyes. A 3D-encoded FLASH sequence was augmented with a 2D-selective RF-excitation pulse. A subject specific 2D brain-excitation shape was generated using a FreeSurfer segmentation of the subject acquired in a previous scan. Compared to a conventional FLASH scan, eye-motion artifacts were significantly suppressed with our modified spatially-selective RF-excitation scan.


Tuesday, 23 April 2013 (16:00-17:00) Exhibition Hall
Compressed Sensing

  Computer #  
3792.   49 Iterative Hard Thresholding and Matrix Shrinkage (IHT+MS) for Low-Rank Recovery of K-T Undersampled MRI Data
Mark Chiew1, Karla L. Miller1, Peter J. Koopmans2, Elizabeth M. Tunnicliffe3, Stephen M. Smith1, and Thomas Blumensath4
1FMRIB Centre, University of Oxford, Oxford, United Kingdom, 2Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, Netherlands, 3AVIC, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, United Kingdom, 4ISVR, University of Southampton, Southampton, Hampshire, United Kingdom

In matrices that are low rank or approximately so, matrix completion strategies can be used to recover data in the presence of undersampling. Here we present a novel algorithm, iterative hard thresholding + matrix shrinkage (IHT+MS), for the recovery of low rank approximations to k-t undersampled MRI data. Performance of the IHT+MS algorithm is compared to other matrix completion techniques in retrospectively undersampled cardiac cine and fMRI data. Results indicate that good reconstruction fidelity is observed in both cardiac and fMRI data, even at high undersampling factors, and that IHT+MS produces the best results in many cases.

3793.   50 Fast Compressed Sensing Reconstruction Using a Direct Fourier-Wavelet Transform
KyungHyun Sung1 and Brian Andrew Hargreaves2
1Radiological Sciences, UCLA, Los Angeles, California, United States, 2Radiology, Stanford University, Stanford, CA, United States

High computational complexity is one major issue for compressed sensing (CS) reconstruction. We present a new way to reduce the computational complexity for the CS reconstruction by directly transforming between k-space and wavelet domains. This replaces FIR filtering in the image domain with a multiplication in k-space and can reduce computational complexity. This efficient computation can benefit almost all CS methods that exploit the wavelet sparsity, and we have shown the actual CS reconstruction time can be reduced by 46% on MATLAB.

51 AMP-SENSE: Parallel Imaging Compressed Sensing with Approximate Message Passing
Evan Levine1,2, Kyunghyun Sung3, Manojkumar Saranathan2, Bruce Daniel2, and Brian Andrew Hargreaves2
1Electrical Engineering, Stanford University, Palo Alto, CA, United States, 2Radiology, Stanford University, Palo Alto, CA, United States, 3Radiological Sciences, University of California, Los Angeles, Los Angeles, CA, United States

Iterative Soft Thresholding (IST) and a more recent method, Approximate Message Passing (AMP) are promising techniques for fast compressed sensing (CS) reconstruction. Combining CS, parallel imaging, partial-Fourier, and other techniques is still being investigated, and the reconstruction time is critical. The AMP method, as is currently implemented on a single coil basis, does not exploit known dependencies among coil images. We have developed a novel reconstruction method, AMP-SENSE, that incorporates coil sensitivity information into AMP to address the combined CS and parallel imaging problem, improving both performance and computational efficiency. We demonstrate an application to dynamic contrast-enhanced (DCE) breast MRI.

3795.   52 Improving Compressed Sensing Initialization and Convergence Using an Efficient Auto-Calibrating Parallel Imaging Method
Peng Lai1, Shreyas S. Vasanawala2, Michael Lustig3, Kang Wang4, and Anja C.S Brau5
1MR Applications & Workflow, GE Healthcare, Menlo Park, CA, United States, 2Radiology, Stanford University, Stanford, CA, United States, 3Electrical Engineering & Computer Science, University of California, Berkeley, CA, United States, 4MR Applications & Workflow, GE Healthcare, Madison, WI, United States, 5MR Applications & Workflow, GE Healthcare, Garching, Munchen, Germany

Compressed sensing reconstruction requires many iterations to converge. This work developed an auto-calibrating parallel imaging method that can efficiently reconstruct coil-combined k-space data from random k-space sampling. Our preliminary results show that the proposed method can provide similar reconstruction accuracy with much faster computation compared to conventional auto-calibrating parallel imaging and can significantly improve the initial condition and convergence of compressed sensing reconstruction.

3796.   53 CIRcular Cartesian UnderSampling (CIRCUS): A Variable Density 3D Cartesian Undersampling Strategy for Compressed Sensing and Parallel Imaging  -permission withheld
Jing Liu1 and David A. Saloner1
1University of California San Francisco, San Francisco, CA, United States

Compressed sensing (CS) and parallel imaging (PI) have been exploited to reduce scan time by undersampling k-space data, which is highly desirable for 3D applications that usually involve unreasonably long scan times. This study proposes a novel method for generating undersampling patterns for 3D Cartesian acquisition, providing easy implementation, flexible sampling patterns, and high accuracy of image reconstruction with CS&PI.

3797.   54 Highly Accelerated 3D Dynamic Imaging with Variable Density Golden Angle Stack-Of-Stars Sampling
Zhitao Li1, Benjamin Paul Berman2, Maria I. Altbach3, Jean-Philippe Galons3, Diego R. Martin3, Bin Dong4, Puneet Sharma3, Natarajan Raghunand3, and Ali Bilgin1,5
1Electrical and Computer Engineering, University of Arizona, Tucson, Arizona, United States, 2Applied Mathematics, University of Arizona, Tucson, Arizona, United States, 3Medical Imaging, University of Arizona, Tucson, Arizona, United States, 4Mathematics, University of Arizona, Tucson, Arizona, United States, 5Biomedical Engineering, University of Arizona, Tucson, Arizona, United States

High spatial and temporal resolution in DCE are desirable. High temporal resolution is needed for accurate kinetic data analysis and high spatial resolution contributes to small structures identification. Radial DCE techniques have been combined with CS to accelerate DCE. Radial trajectories provide desirable attributes: Oversampling of the center k-space, incoherent artifacts from undersampled trajectories can be exploited in CS. Radial trajectories are also less sensitive to motion. A dynamic MRI technique using 3D stack-of-stars was proposed for free breathing 3D liver perfusion MRI. We propose a highly accelerated 3D dynamic MRI technique which uses 3D stack-of-stars with non-uniform kz sampling.

3798.   55 Optimising for Eddy Currents in Compressed Sensing Spiral Acquisitions
Kaveh Vahedipour1,2 and Nadim Jon Shah1,3
1Juelich Research Centre, Juelich, Germany, 2Maastricht University, Maastricht, Netherlands, 3RWTH Aachen University, Aachen, Germany

Combination of non-Cartesian data sampling and Compressed Sensing is an obvious way to go for approaching to the best SNR per unit time. Here, the non-Cartesian sampling strategy must incorporate the random sampling paradigm in the most efficient way in multiple facets. In general, one would like to acquire as much signal amplitude as possible per image while achieving as much randomness as possible of the sampling footprint and thus as little coherences in the artifact domain as achievable. However, a third aspect, which has thus far remained unconsidered, is that of induction of Eddy-currents and their effect on the image quality.

3799.   56 Evaluation of Sparse K-Space Sampling Schemes for Fast Cardiac MRI Using Compressed Sensing Reconstruction Technique
Youngseob Seo1,2, Jonathan M. Chia3, Nancy K. Rollins2,4, and Zhiyue J. Wang2,4
1Division of Convergence Technology, Korea Research Institute of Standards and Science, Daejeon, Korea, 2Radiology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States, 3Philips Healthcare, Cleveland, Ohio, United States, 4Radiology, Children's Medical Center Dallas, Dallas, Texas, United States

Using compressed sensing reconstruction method for fast cardiac MRI, we shows how the number of central k-space lines with varying k-space sampling schemes affects sparsely sampled reconstructed image quality.

3800.   57 Unifying Compressed-Sensing Reconstruction Framework for Multidimensional MRI: Combining Novel Dictionary Models with Frame-Based Sparsity and Flexible Undersampling Schemes
Suyash P. Awate1 and Edward V.R. DiBella2
1Scientific Computing and Imaging (SCI) Institute, University of Utah, Salt Lake City, Utah, United States, 2Utah Center for Advanced Imaging Research (UCAIR), University of Utah, Salt Lake City, Utah, United States

We propose a novel unified framework for compressed-sensing reconstruction of multidimensional magnetic resonance imaging (MRI) including dynamic MRI and high angular resolution diffusion imaging (HARDI). This brand-new framework incorporates a novel formulation for the compressed-sensing reconstruction problem which makes it very flexible with regards to (i) the kinds of imaging or undersampling strategies that can be exploited as well as (ii) the kinds of sparse models that need to be enforced on the data, allowing a variety of wavelet-frame models, total-variation models, and novel dictionary models.

3801.   58 Region of Interest Compressive Sensing (ROICS)
Amaresha Sridhar Konar1, Steen Moeller2, Julianna Czum3, Barjor Gimi3, and Sairam Geethanath1
1Biomedical Research Center, Dayananda Sagar Institutions, Bangalore, Karnataka, India, 2Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, United States, 3Dept. of Radiology, Giesel School of Medicine at Dartmouth, Lebanon, New Hampshire, United States

Compressed sensing (CS) performance depends significantly on sparsity of the image data.The current work aims at providing additional sparsity regardless of the transform chosen to achieve increased acceleration than the conventional CS approach, usinga novel technique called “Region of Interest Compressed Sensing” (ROICS). ROICS allows for enhanced sparsity by decreasing the number of non-zero coefficients to be estimated by restricting the CS reconstruction to a ROI. This work demonstrates that ROICS outperforms CS at higher acceleration factors, quantified through reduced normalized root mean square error, as applied to cardiac MRI frames.

3802.   59 Blind Compressive Sensing Dynamic MRI with Sparse Dictionaries
Sajan Goud Lingala1 and Mathews Jacob1
1The University of Iowa, Iowa city, IA, United States

We propose an sparse blind compressive algorithm to learn dictionary atoms that are constrained to be sparse for accelerated dynamic MRI reconstruction. The sparsity promoting norm on the dictionary atoms penalizes the learning of noisy basis functions. We demonstrate through examples on free breathing cardiac data, that the proposed scheme results in superior image quality in comparison to the conventional blind CS scheme and methods with fixed dictionaries.

3803.   60 Motion Residual Reconstruction Using Low Rank Property of Similarity Patches in Motion Compensated Compressed Sensing Dynamic MRI
Huisu Yoon1, Daniel Kim2, Kyung Sang Kim1, and Jong Chul Ye1
1KAIST, Daejeon, Korea, 2The University of Utah, Salt Lake City, Utah, United States

Recently, many compressed sensing (CS) based algorithms have been developed for dynamic MR imaging applications by exploiting sparsity in temporal transform domain. For example, in k-t FOCUSS with motion estimation and compensation (ME/MC), when a high resolution reference frame is available, ME/MC is shown a quite effective sparsifying transforms. However, one of the limitations of ME/MC is that the energy of the residual measurement after motion compensation is significantly reduced compared to the original k-space measurement. Hence, a new reconstruction algorithm for motion residual is required that judiciously reconstructs geometrically meaningful features. One of main contributions of this paper is a novel patch-based signal processing algorithm for motion residual reconstruction that overcomes the limitation of the existing k-t FOCUSS with ME/MC. More specifically, we impose a non-convex patch-based low-rank penalty that exploits self-similarities within the residual images. This penalty is shown to favor capturing geometric features such as edges rather than reconstructing the background noises. To solve the resulting non-convex optimization problem, we propose a globally convergent concave-convex procedure (CCCP)2 using convex conjugate, which has closed form solution at each sub-iteration.

3804.   61 Accelerating Dynamic MRI Using Patch-Based Spatiotemporal Dictionaries
Yanhua Wang1 and Leslie Ying1
1Department of Biomedical Engineering, Department of Electrical Engineering, The State University of New York at Buffalo, Buffalo, New York, United States

We propose a patch-based dictionary learning model for dynamic MRI reconstruction. The image sequence is divided into overlapping patches along both spatial and temporal directions. A set of temporal dependent dictionaries with three-dimensional atoms are adopted to provide sparse representations for compressed sensing reconstruction. This model adapts to specific local spatial-temporal features. Results on cardiac cine dataset demonstrate that the proposed method is capable of preserving both spatial structures and temporal variations.

3805.   62 Cardiovascular MRI Reconstruction with Data-Driven Sparsifying Transform
Qiu Wang1, Jun Liu1, Nirmal Janardhanan1, and Mariappan S. Nadar1
1Imaging and Computer Vision, Siemens Corporation, Corporate Technology, Princeton, NJ, United States

Dynamic cardiovascular MRI facilitates the assessment of the structure and function of the cardiovascular system. To fit the data acquisition time, the data must be highly undersampled. Compressed sensing or sparsity based MR reconstruction takes advantage of the fact that the image is compressible in some transform domain, and enables reconstruction based on under-sampled k-space data thereby reducing the acquisition time. The design of such transform is a key to the success of the reconstruction. In this paper, we propose to use tight frame learning for computing data-driven transforms. Empirical results demonstrate improvement over the transform associated with the redundant Haar Wavelets.

3806.   63 Dictionary Based Reconstruction of Dynamic Complex MRI Data
Jose Caballero1, Anthony Price2, Daniel Rueckert1, and Joseph V. Hajnal2
1Department of Computing, Imperial College London, London, United Kingdom, 2Division of Imaging Sciences and Biomedical Engineering Department, King's College London, London, United Kingdom

The reconstruction of MR data from undersampled observations has been studied as a solution to the acceleration of MR acquisition and shown to have great potential. Nonetheless, exploration of sparsity models has been somewhat limited, particularly in the case of dynamic MRI. Here we propose a combination of dictionary learning techniques and temporal gradient sparsity for the reconstruction of cardiac cine sequences. A comparison with an established method enforcing x-f support sparsity shows the benefits of carefully choosing a model. The technique presented is able to reconstruct the full complex data with an independent treatment of real and imaginary components.

64 Investigating Spatiotemporal Sparse SENSE Reconstruction to Preserve Geometric and Temporal Fidelity
Jerome Yerly1,2, Mari Elyse Boesen2,3, Michel Louis Lauzon2,4, and Richard Frayne2,4
1Electrical and Computer Engineering, University of Calgary, Calgary, AB, Canada, 2Seaman Family MR Research Centre, Foothills Medical Centre, Calgary, AB, Canada, 3Physics and Astronomy, University of Calgary, Calgary, AB, Canada, 4Radiology and Clinical Neurosciences, University of Calgary, Calgary, AB, Canada

Prospectively gated FSE sequence for time-resolved imaging of physiological motion is often prohibitively lengthy. In this study, we propose to use a sparse SENSE approach with spatial and temporal constraints to reconstruct dynamic retrospectively gated undersampled FSE carotid images. Our spatiotemporal sparse SENSE reconstruction yielded readily interpretable and quantifiable vessel wall motion. We measured a maximum change in diameter of approximately 0.5 mm over a cardiac cycle. Our approach enables time-resolved characterization of the motion of the carotid vessel wall. To measure small changes more precisely, however, an increase in spatial resolution is necessary.

3808.   65 Ultrashort Echo Time (UTE) Imaging with a Time Frame Regularized Compressive Sensing (TF-CS)
Xun Jia1, Yifei Lou2, and Jiang Du3
1Radiation Medicine and Applied Sciences, University of California, San Diego, La Jolla, CA, United States, 2Mathematics, University of California, Irvine, Irvine, CA, United States, 3Radiology, University of California, San Diego, San Diego, CA, United States

Regular two-dimensional (2D) UTE imaging sequences employ half pulse excitations followed by radial ramp sampling. The 2D UTE sequence requires the summation of two acquisitions which adds a significant penalty to the total scan time. 3D UTE imaging employs a short rectangular pulse excitation followed by 3D radial ramp sampling, which is even more time consuming. Both 2D and 3D UTE sequences typically require undersampling to reduce scan time, but this produces streak artifacts. Recent advances in compressive sensing (CS) permits data recovery from extremely under-sampled measurements. In this study we aimed to reconstruct UTE image from the understampled data using a tight-frame (TF) regularized compressive sensing (TF-CS) technique.

3809.   66 Bringing Compressed Sensing to Clinical Reality: Prototypic Setup for Evaluation in Routine Applications
Kai Tobias Block1, Robert Grimm2, Li Feng3, Ricardo Otazo1, Hersh Chandarana1, Mary Bruno1, Christian Geppert4, and Daniel K. Sodickson1
1Center for Biomedical Imaging, NYU Langone Medical Center, New York, NY, United States, 2Pattern Recognition Lab, University of Erlangen-Nuremberg, Erlangen, Germany, 3Center for Biomedical Imaging, New York University Langone Medical Center, New York, NY, United States, 4Siemens Medical Systems, New York, NY, United States

Compressed sensing is a promising technique for MRI reconstruction from incomplete data, but the feasibility and reliability for clinical routine applications have not been verified. Here, we present a prototypic setup that allows evaluating a recently proposed CS approach for motion-robust dynamic T1-weighted imaging in daily patient exams. It consists of a 3D stack-of-stars GRE sequence, a fully-automatic service for raw-data transfer to a multi-core server, and a highly parallelized implementation of the reconstruction algorithm. Images are saved in DICOM format and forwarded to the PACS archive, which enables our radiologists to read the images along with the conventional exams.

67 SWIRLS 3D CE-MRA with Field-Corrected Sparse SENSE Reconstruction
Joshua D. Trzasko1, Yunhong Shu1, Armando Manduca1, John Huston III1, and Matthew A. Bernstein1
1Mayo Clinic, Rochester, MN, United States

In this work, we describe a sparsity-driven reconstruction framework for single-phase (non-Cartesian) SWIRLS 3D CE-MRA that incorporates both sensitivity encoding and off-resonance correction. As demonstrated, the proposed framework substantially reduces both noise amplification and geometric distortion that are routinely present in, and can compromise the diagnostic utility of, standard gridding reconstruction images.

3811.   68 Highly Undersampled Time Resolved Phase-Contrast MRA with Flow-Adapted Compressed Sensing Reconstruction
Jana Hutter1,2, Andreas Greiser3, Robert Grimm1, Christoph Forman2,4, Joachim Hornegger1,2, and Peter Schmitt5
1Pattern Recognition Lab, Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Erlangen, Germany, 2School of Advanced Optical Technologies, Erlangen, Germany, 3Siemens AG, Erlangen, Germany, 4Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany, 5MR Application & Workflow Development, Siemens Healthcare, Erlangen, Germany

The proposed compressed sensing based algorithm for velocity-encoded phase contrast MRA combines an incoherent interleaved undersampling pattern in both velocity-encoding and temporal dimension with a flow-adapted temporal resolution. High undersampling factors are supported while preserving the contrast and temporal resolution. Results are compared with state-of-the-art Grappa and Sense methods and the fully sampled reference.

3812.   69 Motion-Dependent L1 Minimization for Dynamic Cardiac MRI Reconstruction
Qiu Wang1, Jun Liu1, Zhili Yang1, Nicolas Chesneau1, Michael O. Zenge2, Michaela Schmidt2, Nirmal Janardhanan1, Edgar Mueller2, and Mariappan S. Nadar1
1Imaging and Computer Vision, Siemens Corporation, Corporate Technology, Princeton, NJ, United States, 2MR Application & Workflow Development, Siemens AG, Healthcare Sector, Erlangen, Bavaria, Germany

High temporal resolution is often desired in Cardiac Magnetic Resonance Imaging (CMRI). Compressed sensing has enables the reconstruction with a reduced the number of acquired frequencies, hence accelerating the acquisition. Spatial-temporal regularization has been proven effective for enforcing the smoothness. However, the fine details of the heart such as valve leaflets can be eliminated by strong regularization. In this work, a new approach was proposed for dynamic cardiac MRI reconstruction by setting the motion-dependent L1 regularization. Experiments conducted on CMRI data demonstrate the effectiveness of the proposed approach in preserving fine details of the heart.

3813.   70 S-SPIRiT: An Iterative/Shrinkage Approach to SPIRiT for Real-Time Cardiac MRI
Samuel T. Ting1, Rizwan Ahmad1, Yu Ding1, Hui Xue2, Lee C. Potter1, and Orlando P. Simonetti1
1The Ohio State University, Columbus, Ohio, United States, 2Siemens Corporate Research, Princeton, New Jersey, United States

We propose shrinkage SPIRiT (S-SPIRiT), an application of the fast iterative shrinkage-thresholding algorithm (FISTA) to SPIRiT that results in an L1-regularized implementation of SPIRiT that is more efficient than typical nonlinear conjugate gradient (NLCG) approaches and exhibits robustness to suboptimal parameter tuning and presence of noise. This approach may be especially applicable to cardiac magnetic resonance imaging, where kernel mismatch due to breathing motion can impact image quality.

71 Denoising Image Sequences: Algorithm and Application to Quantitative MR Imaging
Fan Lam1,2, Bo Zhao1,2, Michael Weiner3,4, Norbert Schuff3,4, and Zhi-Pei Liang1,2
1Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States, 2Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, United States, 3Center for Imaging of Neurodegenerative Diseases, Department of Veteran Affairs Medical Center, San Francisco, CA, United States, 4Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, United States

We propose a new method to jointly denoise a sequence of noisy images typically acquired in quantitative imaging experiments. The proposed method uses a penalized maximum likelihood estimation formalism, integrating two modeling constraints: a low-rank model that captures any correlation in the edge structures from one frame to another and a penalty function that promotes sparse edge structures. A computationally efficient algorithm is developed to solve the associated optimization problem. Representative results from a parametric mapping experiment are presented to demonstrate the performance of the proposed method.

3815.   72 From Matrix to Tensor: Compressed Sensing Dynamic MRI Using Tensor Based Sparsity
Yeyang Yu1, Jin Jin1, Feng Liu1, Stuart Crozier1, and Mingjian Hong2
1The School of Information Technology and Electrical and Engineering, The University of Queensland, Brisbane, QLD, Australia, 2School of Software Engineering, Chongqing Univeristy, Chongqing, Chongqing, China

In this work, we introduce the conception of tensor sparsity for Compressed Sensing dynamic MRI. Conventionally, the spatial and temporal information were then sparsified independently and sequentially. Therefore the spatial-temporal correlation may not be sufficiently exploited. This work applys the Tucker model based Higher-order Singular Value Decomposition (HOSVD) in the Compressed Sensing dynamic MRI framework. Instead of treating the 3D/4D data as series of 2D images, HOSVD inherits the high-dimensional data format, leading to significantly improved dMRI reconstructions compared with those well-established CS-dMRI methods. The advantages of the tensor sparsity in terms of reconstruction accuracy have been demonstrated in a given cardiac dynamic MRI study.


Tuesday, 23 April 2013 (17:00-18:00) Exhibition Hall
Non-Cartesian & Parallel Imaging

  Computer #  
73 Taming an Ill-Conditioned SPIRiT: Improved Iterative Image Reconstruction for Real-Time Cardiac MRI
Samuel T. Ting1, Yu Ding1, Rizwan Ahmad1, Hui Xue2, and Orlando P. Simonetti1
1The Ohio State University, Columbus, Ohio, United States, 2Siemens Corporate Research, Princeton, New Jersey, United States

We seek to address the ill-conditioned properties of the SPIRiT reconstruction method when applied in scenarios requiring highly accelerated acquisitions, as is the case in real-time cardiac imaging under free-breathing conditions. We show that the use of a suitable data initialization in the POCS implementation of SPIRiT can help alleviate the issues resulting from the ill-conditioned properties of SPIRiT.

3817.   74 Suppressing Mulit-Channel Diffusion Tensor Imaging Noise Using the Data Consistency Constraint
Ying-Hua Chu1, Shang-Yueh Tsai2, Yi-Cheng Hsu3, Wen-Jui Kuo4, and Fa-Hsuan Lin1,5
1Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan, 2Graduate Institute of Applied Physics, National Cheng-Chi University, Taipei, Taiwan, 3Department of Mathematics, Nnational Taiwan University, Taipei, Taiwan, 4Institute of Neuroscience, National Yang-Ming University, Taipei, Taiwan, 5Department of Biomedical Engineering and Computational Science, Aalto University, Espoo, Finland

We exploit the redundancy among channels of a receiver coil array to improve the SNR of DTI. Our method uses a universal kernel to enforce the data-consistency (DC) among k-space data across receiver coils. This DC constraint was then applied to all diffusion-weighted images to suppress noise disturbing the data consistency required by the parallel MRI theory. Experimental results at 3T with b = 4,000 s/mm2 demonstrate that the SNR can be improved by approximately 40% by applying this constraint to DTI reconstructions.

75 TRIPLET: Transmit and Receive Fields Reconstruction from a Single Low-Tip-Angle Gradient-Echo Scan.
Alessandro Sbrizzi1, Alexander Raaijmakers1, Cornelis A.T. van den Berg1, Jan J.W. Lagendijk1, Peter R. Luijten1, and Hans Hoogduin1
1Imaging Division, UMC Utrecht, Utrecht, Utrecht, Netherlands

It is shown how the fields derived upon singular value decomposition are related to the true receive and transmit fields maps of a pTx coil array. TRIPLET produces all necessary RF field maps for a parallel transmit and parallel imaging experiment in a very short time and with use of minimal RF power. In addition, the methods results in receive sensitivity maps per channel without the need for a homogeneous receive reference. The method is generic and will also work in case of a single transmit channel combined with several receive channels.

76 Efficient Hybrid Parallel Imaging Reconstruction with Rotating Radiofrequency Coil Array
Mingyan Li1, Jin Jin1, Feng Liu1, Adnan Trakic1, and Stuart Crozier1
1School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, Queensland, Australia

With the ability of encoding larger number of sensitivity profiles, the novel 4-element rotating radiofrequency coil array (RRFCA) has better imaging acceleration performance than stationary phased-array coils (PACs). However, with more time-varying sensitivity encoding, the system matrix of RRFCA is more complex and leads to a longer reconstruction time. In this work, while maintaining the same acceleration capability, the fast hybrid image reconstruction strategy reduces the number of sensitivity encodings and obtains the fast initial estimation to improve the efficiency and accuracy of accelerated image reconstruction with RRFCA.

3820.   77 Combining Coil Compression and Direct Virtual Coil for Dynamic MRI Using Auto-Calibrating Parallel Imaging
Kang Wang1, Tao Zhang2, Philip J. Beatty3, Dan W. Rettmann4, Ersin Bayram5, and James H. Holmes1
1Global Applied Science Laboratory, GE Healthcare, Madison, WI, United States, 2Electrical Engineering, Stanford University, Stanford, CA, United States,3Sunnybrook Research Institute, Toronto, ON, Canada, 4Global Applied Science Laboratory, GE Healthcare, Rochester, Minnesota, United States, 5GE Healthcare, Waukesha, WI, United States

Auto-calibrating parallel imaging (acPI) methods have advantages over physically-modeled methods in reduced FOV applications or when it is difficult to accurately measure coil sensitivity maps, such as breath-hold exams. However, for challenging clinical protocols that use large channel counts, big matrix sizes and high parallel imaging factors, conventional channel-by-channel acPI methods may still have long reconstruction latency. To address this issue, Coil Compression (CC) and Direct Virtual Coil (DVC) techniques have been proposed independently. This work is to demonstrate the feasibility of combining the two techniques to achieve even higher reduction in computation without compromise in image quality.

3821.   78 k-T Accelerated 4D Flow MRI in the Aorta: Effect on Scan Time, Flow Quantification and Analysis of Wall Shear Stress
Bernd A. Jung1, Michael Markl2, Pegah Entezaril2, Riti J. Mahadevia2, and Susanne Schnell2
1Dept. of Radiology, Medical Physics, University Medical Center, Freiburg, Germany, 2Dept. of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States

The purpose of this study was to evaluate the utility of k-t parallel imaging for the acceleration of aortic 4D-flow MRI by systematically investigating the impact of different acceleration factors R and coil elements on quantification of hemodynamics parameters such as blood flow and wall shear stress. K-t accelerated 4D-flow MRI was performed in 10 healthy volunteers with R=3, 5 and 8 using a 12-channel and a 32-channel receiver coil and compared to conventional parallel imaging (GRAPPA, R=2). Data analysis included 3D blood flow visualization and quantification of peak velocities, flow rates and wall shear stress in different aortic locations.

3822.   79 Denoising in Parallel Imaging Via Structured Low-Rank Matrix Approximation
Derya Gol1 and Lee C. Potter1
1Electrical & Computer Engineering and Davis Heart & Lung Institute, The Ohio State University, Columbus, OH, United States

Interpolation approaches in parallel MRI exhibit a noise amplification effect that may be mitigated via regularization techniques which are computationally expensive. In this study, we propose a pre-processing technique based on structured low-rank matrix approximation via truncated singular value decomposition (TSVD), which is able to suppress noise and ghost artifacts efficiently. TSVD method has been previously used in parallel MRI to improve the conditioning of the system matrix and to reconstruct k-space via matrix completion. In contrast to previous work, here rank properties are used to denoise acquired data in a computationally simple preprocessing for GRAPPA reconstruction.

3823.   80 Differential Energy: A K-Space PPI Reconstruction Optimization Metric
Thomas A. Depew1 and Qing-San Xiang1,2
1Physics & Astronomy, University of BC, Vancouver, BC, Canada, 2Radiology, University of BC, Vancouver, BC, Canada

Partial Parallel Imaging (PPI) is a popular choice for performing accelerated acquisitions in MRI. PPI algorithms that use calibration and fitting to recreate the omitted k-space signals are candidates for using the Differential Energy (ED) as a metric for optimizing reconstruction parameters. ED provides a measure of the accuracy of the reconstruction and can be calculated without a fully sampled reference image. The ED reliably predicted optimal RW for a regionally tuned GRAPPA algorithm (r-GRAPPA).

3824.   81 Self-Calibrating Stack-Of-Stars (SOS)-CAIPIRINHA for Improved Parallel Imaging
Felix A. Breuer1, Simon Bauer2, and Martin Blaimer1
1Research Center Magnetic Resonance Bavaria, Würzburg, Bavaria, Germany, 2Siemens Healthcare, Erlangen, Bavaria, Germany

In this work, the concept of CAIPIRINHA is applied to 3D stack-of-stars (SOS) VIBE liver imaging. It is demonstrated that by rotating the stars by Δφ with respect to each other significantly improved parallel imaging performance is achieved compared to standard acceleration in only the radial direction. pMRI reconstruction was performed using a novel self-calibrating segmented radial GRAPPA algorithm tailored to the individual CAIPIRINHA undersampling schemes eliminating the need of an extra calibration scan. This allows for robust high resolution 3D liver imaging within a 12s breath-hold.

3825.   82 Accelerated MRI Through Aliased and Sub-Sampled K-Space Acquisitions
Arjun Arunachalam1
1Electrical Engineering, Indian Institute of Technology Bombay, Mumbai, Maharashtra, India

A method for restoring aliased, sub-sampled k-space for a multiplicative increase in scan acceleration is presented. Recently, the RATE method for accelerating dynamic MRI by acquiring and then restoring aliased k-space through a Fourier transformation was presented. In this work, it’s shown that for normal and dynamic MRI, receiver sensitivities can be used to restore aliased k-space. Also, if aliased k-space is sub-sampled, Parallel Imaging is used first to synthesize the un-acquired samples. Next, the coil sensitivities are used again with the acquired, synthesized samples in an iterative reconstruction to enable acceleration factors as high as 12 for 2D scans.

3826.   83 L1-Regularized GRAPPA Kernel Estimate
Yu Ding1, Rizwan Ahmad1, Hui Xue2, Samuel T. Ting1, Ning Jin3, and Orlando P. Simonetti1
1The Ohio State University, Columbus, OH, United States, 2Corporate Research, Siemens Corporation, Princeton, NJ, United States, 3Siemens Healthcare, Columbus, OH, United States

SENSE is a widely used parallel imaging technique. The so-called g-factor represents how noise in the raw data affects the noise in the reconstructed image. However, the g-factor calculation does not take into account the noise in the channel sensitivity map. In this abstract, we present a noise transfer model in SENSE reconstruction that takes into account the noise in both the raw data and the channel sensitivity map. A phantom study showed that the model has satisfactory accuracy. We observed that a large portion (> 35%) of the image noise originates from the noise in the sensitivity map.

3827.   84 Image Reconstruction of Single-Shot North West EPI Data Acquired with PatLoc Gradients Using Magnetic Field Monitoring and Total Generalized Variation – Conjugate Gradient
Stefan Kroboth1, Frederik Testud2, Kristian Bredies3, Kelvin J. Layton4, Daniel Gallichan5, Chris A. Cocosco2, Gerrit Schultz2, Florian Knoll1, Christoph Barmet6,7, Klaas P. Pruessmann8, Maxim Zaitsev2, and Rudolf Stollberger1
1Institute of Medical Engineering, Graz University of Technology, Graz, Austria, 2Medical Physics, University Medical Center Freiburg, Freiburg, Germany,3Institute for Mathematics and Scientific Computing, University of Graz, Graz, Austria, 4Department of Electrical and Electronic Engineering, University of Melbourne, Parkville, Victoria, Australia, 5LIFMET, Ecole Polytéchnique Fédérale de Lausanne, Lausanne, Switzerland, 6Institute for Biomedical Engineering, University and ETH Zurich, Zürich, Switzerland, 7Skope Magnetic Resonance Technologies, Zürich, Switzerland, 8Institute for Biomedical Engineering, University of Zürich and ETH Zürich, Zürich, Switzerland

This work investigates the reconstruction of single shot North-West Echo Planar Imaging (NW-EPI) data with estimated trajectories using field cameras. NW-EPI is a multidimensional trajectory designed to improve the resolution in a selected region by exploiting the spatially varying resolution characteristic of nonlinear PatLoc fields. Reconstruction with Total Generalized Variation (TGV) was successfully applied to PatLoc imaging with 2D trajectories to reduce noise, Gibbs ringing and undersampling artifacts. However, for multidimensional trajectories, TGV converges very slowly. We therefore present a new concept of numerically solving the inverse problem, called Total Generalized Variation - Conjugate Gradient (TGV-CG) to increase convergence speed.

3828.   85 Real-Time Cardiac MRI Using a Golden-Ratio-Ordered Spiral Trajectory and Self-Consistent Parallel Imaging
Holden H. Wu1,2 and Dwight G. Nishimura3
1Radiological Sciences, UCLA, Los Angeles, CA, United States, 2Cardiovascular Medicine, Stanford University, Stanford, CA, United States, 3Electrical Engineering, Stanford University, Stanford, CA, United States

A new real-time cardiac MRI technique combining the advantages of spiral imaging with flexible golden-ratio acquisition ordering and acceleration from self-consistent parallel imaging is presented in this work. The scan acceleration achieved by the proposed technique is used to acquire free-breathing real-time images at a relatively high in-plane resolution of 1.6 mm and expanded field of view of 40 cm. Adequate temporal resolution is maintained to visualize cardiac and respiratory motion.

3829.   86 How to Stack the Stars: A Variable Center-Dense K-Space Trajectory for 3D MRI
Benjamin Paul Berman1, Zhitao Li2, Maria I. Altbach3, Jean-Philippe Galons3, Diego R. Martin3, Bin Dong4, Puneet Sharma3, Bobby T. Kalb3, and Ali Bilgin2,5
1Applied Mathematics, University of Arizona, Tucson, Arizona, United States, 2Electrical and Computer Engineering, University of Arizona, Tucson, Arizona, United States, 3Medical Imaging, University of Arizona, Tucson, Arizona, United States, 4Mathematics, University of Arizona, Tucson, Arizona, United States, 5Biomedical Engineering, University of Arizona, Tucson, Arizona, United States

There is constant demand for high quality images and short data acquisition times for MRI. Traditionally, a choice is made for one or the other, but due to the development of CS theory, it is often possible to have both. For 3D MR imaging, various trajectories are used to undersample in Fourier space including Cartesian, radial, and cylindrical. The cylindrical trajectory – or stack-of-stars – is used for dynamic and motion sensitive 3D imaging. For CS it is crucial that each measurement contain as much information as possible. We show that the 3D stack-of-stars trajectory benefits from a center-dense sampling scheme.

3830.   87 Iterative Auto-Calibrated Reconstruction of 3D Non-Cartesian Trajectories
Daniel Kopeinigg1, Murat Aksoy1, Samantha J. Holdsworth1, Rafael O'Halloran1, and Roland Bammer1
1Center for Quantitative Neuroimaging, Department of Radiology, Stanford University, Stanford, CA, United States

An iterative POCS algorithm for reconstructing arbitrary 3D k-space data is introduced and applied to undersampled 3D Cones trajectories. Our results indicate that the algorithm can greatly reduce aliasing artifacts after only 3-5 iterations.

3831.   88 Highly Accelerated Projection Imaging (HAPI) with Coil Sensitivity Encoding
Ali Ersoz1, Volkan Emre Arpinar2, and L. Tugan Muftuler2,3
1Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI, United States, 2Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, WI, United States, 3Center for Imaging Research, Medical College of Wisconsin, Milwaukee, WI, United States

We developed a new technique, named Highly Accelerated Projection Imaging (HAPI) with coil sensitivity encoding, which is capable of reconstructing a 2D image using fewer projections than the previous reports. The essence of this new technique is to sample each spoke more densely than the conventional scheme. The feasibility of this new technique was investigated with realistic simulations and experimental phantom studies. Simulation results show that 1-2 projections might be sufficient to reconstruct a 2D image. Experimental results demonstrated that HAPI is a promising new technique for fast imaging.

3832.   89 Direct Virtual Coil (DVC) Coil Combination for Non-Cartesian 4D Flow Imaging
Kang Wang1, Ann Shimakawa2, Kevin M. Johnson3, Philip J. Beatty4, Oliver Wieben3,5, and James H. Holmes1
1Global Applied Science Laboratory, GE Healthcare, Madison, WI, United States, 2Global Applied Science Laboratory, GE Healthcare, Menlo Park, CA, United States, 3Medical Physics, University of Wisconsin-Madison, Madison, WI, United States, 4Sunnybrook Research Institute, Toronto, ON, Canada, 5Radiology, University of Wisconsin-Madison, Madison, WI, United States

Multi-channel non-Cartesian phase contrast imaging has been demonstrated with great capability for various 4D flow MRI applications. However, reconstruction latency has been challenging, as well as the need for a robust phase preserving coil combination algorithm. Among several recently reported algorithms, the Direct Virtual Coil (DVC) technique provides great potential to address both challenges simultaneously. This work is to demonstrate the usage of the DVC technique for non-Cartesian phase-contrast imaging, specifically, PC-VIPR.

3833.   90 Super-Resolved Two-Dimensional Spatiotemporally-Encoded Single-Scan MRI with Spiral Sampling
Jing Li1, Lin Chen1, Congbo Cai2, Shuhui Cai1, and Zhong Chen1
1Department of Electronic Science, Xiamen University, Xiamen, Fujian, China, 2Department of Communication Engineering, Xiamen University, Xiamen, Fujian, China

Last decades have witnessed a continuous growth of single-scan MRI, both in scientific research and clinical application. Spatiotemporally encoded (SPEN) MRI has an intrinsic immunity to field inhomogeneity. However, its phase encoding dimension is always sub-Nyquist sampling for ultrafast acquisition, which leads to aliasing artifacts. In this study, we propose a spiral sampling method for two-dimensional SPEN single-scan MRI. It can not only maintain the advantages of SPEN method, but also eliminate the aliasing artifacts due to undersampling. In combination with a super-resolved reconstruction based on the singular value decomposition, images with good quality can be obtained.

3834.   91 Golden Angle Through-Time Radial GRAPPA for Real-Time Cardiac MRI
Xu Han1, Katherine L. Wright1, Vikas Gulani2,3, and Nicole Seiberlich1
1Dept. of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States, 2Dept. of Radiology, Case Western Reserve University, Cleveland, Ohio, United States, 3Dept. of Radiology, University Hospitals, Cleveland, Ohio, United States

The goal of this work is to demonstrate that undersampled golden angle radial data can be reconstructed using through-time radial GRAPPA. The golden-angle trajectory is advantageous when it is not clear what acceleration factor is desired, as any subset of temporally adjacent k-space lines can be used for the reconstruction. This abstract describes two approaches for through-time radial GRAPPA weight calibration: using an additional sequentially ordered golden angle calibration dataset and a self-calibrating golden angle technique. Using these formulations, real-time free-breathing cardiac images can be reconstructed at retrospectively selected temporal resolutions from the same golden angle dataset.

92 Iterative K-T PCA with Motion Corrected Training Regularization for 3D Myocardial Perfusion Imaging
Johannes F.M. Schmidt1, Lukas Wissmann1, Robert Manka1,2, and Sebastian Kozerke1,3
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland, 2University Hospital Zurich, Zurich, Switzerland, 3Imaging Sciences and Biomedical Engineering, King's College London, London, United Kingdom

In this work, an iterative k-t PCA algorithm is proposed where an additional spatial transformation is used to further sparsify the data. Training data based regularization is performed in a motion corrected x-pc domain where each time frame is warped to a reference respiratory position. Spatial transformations are derived from frame-by-frame composite images using atlas-based image registration. Using 3D perfusion data acquired in vivo it is demonstrated that this approach successfully corrects for incomplete unfolding due to respiratory bulk motion.

3836.   93 Self-Calibrating Interleaved Reconstruction for Through-Time Non-Cartesian GRAPPA
Jesse I. Hamilton1, Katherine L. Wright1, Mark A. Griswold2, and Nicole Seiberlich1
1Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States, 2Radiology, Case Western Reserve University, Cleveland, OH, United States

Despite the high acceleration factors that are achievable with through-time non-Cartesian GRAPPA, the major limitation of this method is the need for a separate fully-sampled calibration scan. Here we present a self-calibrating method for through-time non-Cartesian GRAPPA using interleaved trajectories. In free breathing, non-gated cardiac scans, the self-calibrating reconstruction with both interleaved radial and interleaved variable density spiral trajectories produced images with higher quality and less blurring compared to view-sharing without parallel imaging reconstruction. Due to its shorter temporal footprint, less blurring was observed with self-calibrating through-time non-Cartesian GRAPPA using an undersampled spiral trajectory than the radial trajectory.

3837.   94 Retrospective Self-Gated MRI of the TMJ Dynamics During Mastication
Stefan Wundrak1,2, Jan Paul1, Johannes Ulrici2, Erich Hell2, and Volker Rasche1
1Klinik für Innere Medizin II, Ulm University, Ulm, Germany, 2Sirona Dental Systems, Bensheim, Germany

We introduce a retrospective self-gated MRI reconstruction method for the imaging of the temporomandibular joint dynamics. Compared to real-time imaging the proposed technique shows an improved tempo-spatial resolution and allows for the first time the imaging of the TMJ dynamics under a continuous mastication.

3838.   95 A Generic, Multi-Node, Multi-GPU Reconstruction Framework for Online, Real-Time, Low-Latency MRI
Haris Saybasili1, Daniel A. Herzka2, Kestutis Barkauskas3, Nicole Seiberlich3, and Mark A. Griswold1
1Radiology, Case Western Reserve University, Cleveland, OH, United States, 2Biomedical Engineering, Johns Hopkins University, Baltimore, MD, United States, 3Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States

In the recent years, many research oriented, customizable, external MR image reconstruction frameworks have been presented. To the best of our knowledge, none of these frameworks provided fully automated, remotely and locally distributed (multi-node, and multi-GPU) image reconstruction capabilities. Additionally, these frameworks may depend on high-level software libraries that make it difficult to maintain, debug and update the existing code. In this work, we present a highly customizable, automatically distributed, multi-threaded image reconstruction environment, built using only low-level system libraries for improved performance and portability. Our framework utilizes multiple GPUs and multiple workstations (nodes) by transparently distributing reconstruction tasks.  

3839.   96 Method for Estimating K-T Sensitivity from Under-Sampled Data with No Training Scans
Hidenori Takeshima1, Shuhei Nitta1, Taichiro Shiodera1, Tomoyuki Takeguchi1, Masao Yui2, and Shigehide Kuhara2
1Corporate Research & Development Center, Toshiba Corporation, Kawasaki, Kanagawa, Japan, 2MRI Systems Division, Toshiba Medical Systems Corporation, Otawara-shi, Tochigi, Japan

The number of calibration samples is relatively high when the number of phase encodes is small or when the reduction factor is high. To reduce the acquisition time, we have developed a novel method for estimating k-t coil sensitivity maps from only the k-t data to be reconstructed. The images reconstructed by the proposed method are as clear as those reconstructed by k-t SENSE. The processing time of the proposed method is about 11.6 seconds for data scanned with reduction factor R = 4, 256 readout encoding steps, 96/R phase encoding steps, 32 coils, and 96 frames.


Tuesday, 23 April 2013 (16:00-17:00) Exhibition Hall
Susceptibility Contrast

  Computer #  
3840.   73 Regularized Susceptibility Tensor Imaging for Generating White Matter Fiber Color Maps in Human Brain
Xu Li1,2, Issel Anne L. Lim1,2, Craig K. Jones1,2, and Peter C.M. van Zijl1,2
1F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, United States, 2Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States

We propose regularization strategies for susceptibility tensor imaging (STI) based on a combination of structural information and the values of mean magnetic susceptibility (MMS) and magnetic susceptibility anisotropy (MSA). The goal is to generate color maps of fiber tracts using MR phase data from a small number of orientations. Human brain imaging data acquired at 7 Tesla using six head orientations with rotation angles of absolute magnitude 5° to 15° show that the principle eigenvector (PEV) map obtained from the regularized STI method resembles the PEV map from DTI, whereas the PEV map from the non-regularized STI method does not.

3841.   74 Measurement Precision of Contrast Agent with R2* (Magnitude) and Quantitative Susceptibility Mapping (Phase)
Hongchen Wang1, Xavier Maître1, Jean-Pierre Ruaud1, Luc Darrasse1, and Ludovic De Rochefort2
1Imagerie par Résonance Magnétique Médicale et Multi-Modalités (UMR8081) IR4M, CNRS, Univ. Paris-Sud, Orsay, France, 2Univ Paris-Sud, Orsay, France

Apparent transverse relaxation rate R2* and magnetic susceptibility χ are distinct measurable parameters that can be used to quantify paramagnetic and superparamagnetic materials. R2* mapping requires several echoes times in a gradient-echo scan and is based on the analysis of signal amplitude decrease. Magnetic Susceptibility mapping uses field mapping that can be measured from the same multi-echo dataset using phase images. Here, phantom experiments are done to compare the precision of R2* and susceptibility methods for quantifying contrast agent concentration.

3842.   75 Multi-Echo Susceptibility-Weighted Imaging Using an Adaptive Frequency Mask
Junmin Liu1, David A. Rudko1,2, Joseph S. Gati1, Ravi S. Menon1,2, and Maria Drangova1,2
1Imaging Research Laboratories, Robarts Research Institute, Shulich School of Medicine & Dentistry, University of Western Ontario, London, ONtario, Canada, 2Department of Medical Biophysics, Shulich School of Medicine & Dentistry, University of Western Ontario, London, Ontario, Canada

When a frequency mask (FM) is used for generating multi-echo susceptibility-weighted images, a cutoff frequency value (fth) must be defined for the frequency image at each echo. In this work, we present a new FM generation method which determines fth by using the criterion 2π×|fth|×TE =π. The performance of the proposed technique is evaluated with a set of volunteer brain images acquired at 7 T, and the results are compared with the standard frequency normalization approach, which uses the lowest frequency value in the image as fth. The proposed method produces a more robust FM and higher contrast SW images.

76 Diffusion-Guided Quantitative Susceptibility Mapping
Amanda C. L. Ng1,2, David K. Wright3,4, Parnesh Raniga2,5, Stephen Moore6, Gary F. Egan2, and Leigh A. Johnston4,7
1Dept of Electrical & Electronic Engineering, The University of Melbourne, Melbourne, VIC, Australia, 2Monash Biomedical Imaging, Monash University, Melbourne, VIC, Australia, 3Centre for Neuroscience, The University of Melbourne, Melbourne, VIC, Australia, 4Florey Institute of Neuroscience and Mental Health, The University of Melbourne, VIC, Australia, 5The Australian e-Health Research Centre-BioMedIA The Australian e-Health Research Centre-BioMedIA, CSIRO Preventative Health National Research Flagship ICTC, Herston, QLD, Australia, 6IBM Research Collaboratory for Life Sciences-Melbourne, Victorian Life Sciences Computing Initiative, The University of Melbourne, VIC, Australia, 7NeuroEngineering Laboratory, Dept. Electrical & Electronic Engineering, The University of Melbourne, Melbourne, VIC, Australia

Quantitative Susceptibility Mapping (QSM) aims to derive reliable estimates of the magnetic susceptibility of voxels from phase data arising from 3D gradient-echo MRI acquisitions. Current methods compute the contribution of all tissue types using a spherical model, however research has shown that white matter is better modelled as cylinders. We present a method for deriving susceptibility maps from MRI phase data that combines both spherical and cylindrical models. We use MR diffusion data to identify voxels best modelled as cylinders and to determine the orientation of those cylinders. Our results demonstrated improved accuracy and robustness compared to conventional methods.

77 Anisotropic Magnetic Susceptibility Induced R2* Anisotropy of Human Brain in vivo
Wei Li1, Bing Wu2, and Chunlei Liu1,3
1Brain Imaging & Analysis Center, Duke University, Durham, North Carolina, United States, 2GE Healthcare China, Beijing, China, 3Radiology, Duke University, Durham, North Carolina, United States

The dependence of R2* on fiber orientation was evaluated using multi-orientation brain images. The significant derivation from sine squared relationship between R2* and fiber orientation indicated the contribution of anisotropic magnetic susceptibility. Assuming a constant ratio of -0.4 between isotropic and anisotropic susceptibility contributions, R2* anisotropy were estimated on a voxel-by-voxel basis. R2* anisotropy due to anisotropic susceptibility accounted for approximately 10~30% of the total R2* of white matter, and is highly correlated with diffusion anisotropy. These results suggested the importance of anisotropic magnetic susceptibility induced R2* variations and its value for the study of white matter microstructure and composition.

3845.   78 Quantitative Susceptibility Mapping Reconstruction with Spatial Prior: Shortening Reconstruction Time and Choosing Regularization Parameters Automatically
Hongchen Wang1, Jean-Sébastien Raynaud2, and Ludovic De Rochefort3
1Univ. Paris Sud - CNRS, UMR 8081, IR4M, Orsay, France, 2Experimental Imaging, MRI unit, Research Division, Guerbet, Aulnay-sous-bois, France, 3Univ Paris-Sud, Orsay, France

Quantitative susceptibility mapping (QSM) provides a way to quantify bulk magnetic susceptibility distribution from field inhomogeneity images. It involves phase unwrapping, background filtering and source reconstruction. QSM reconstruction with spatial priors can be performed to solve this ill-posed problem. However, the iterative procedure is limited by a long calculation time, and multiple iterations are needed to choose adequate regularization parameters. Here we accelerate QSM using a rapid estimation in k-space and introduce a general and efficient parameter search method.

3846.   79 Simulations Show Tumor Vascular Morphology Affects the Accuracy of Steady-State Susceptibility Contrast MRI Biomarkers of Angiogenesis
Eugene Kim1, B. Douglas Ward2, and Arvind P. Pathak3
1Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, United States, 2Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI, United States, 3Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, United States

The finite perturber method (FPM) and Monte Carlo simulations were used to compute steady-state susceptibility contrast (SSC)-MRI biomarkers of fractional blood volume (FBV), vessel size (VSI), and vessel density (N) for tumor vasculature from μCT data and for an ensemble of randomly oriented cylinders (RC). For the μCT data, the correlations between simulated and true biomarker values were lower and the median errors greater compared to the RC data, indicating that vascular morphology significantly affects the accuracy of these biomarkers. The FPM can be used to elucidate how various biophysical factors affect the SSC-MRI signal and help develop more accurate imaging biomarkers of angiogenesis.

80 Dynamic Quantitative Susceptibility Mapping for Contrast Agent Concentration
Bo Xu1, Tian Liu2, Pascal Spincemaille2, Nanda Deepa Thimmappa2, Martin R. Prince2, and Yi Wang1
1Biomedical Engineering, Cornell University, Ithaca, New York, United States, 2Weill Cornell Medical College, New York, New York, United States

A dynamic quantitative susceptibility imaging method is presented for 3D imaging of Gadolinium concentration at sub-second frame rate. A multi-echo flow compensated spiral gradient echo is used for data acquisition. Temporal resolution acceleration with constrained evolution reconstruction is used to generate high temporal frame rate. A morphology enabled dipole inversion with nonlinear formulation is used to generate quantitative susceptibility mapping from complex frame images.

3848.   81 Magnetic Susceptibility as a Field-Independent MRI Biomarker of Liver Iron Overload
Diego Hernando1 and Scott B. Reeder1,2
1Radiology, University of Wisconsin-Madison, Madison, WI, United States, 2Medical Physics, University of Wisconsin-Madison, Madison, WI, United States

MR-based quantification of liver magnetic susceptibility may enable field strength-independent quantification of liver iron concentration (LIC), for diagnosis, staging and treatment monitoring of hepatic iron overload. However, susceptibility measurement is challenging, due to the non-local effect of the susceptibility distribution on the measured B0. The purpose of this work is to demonstrate feasibility of MR-based LIC quantification using a fat-referenced approach to estimate liver susceptibility from the measured B0 field map. The proposed method is validated at 1.5T and 3T using an R2-based LIC measurement (Ferriscan) as the reference standard.

3849.   82 Quantification of Blood Oxygen-Level Dependent Signal Changes of Rat Brain by Using Quantitative Susceptibility Mapping
Meng-Chi Hsieh1,2 and Jyh-Horng Chen1,2
1Institute of Biomedical Electronic and Bioinformatics, National Taiwan University, Taipei, Taiwan, 2Interdisciplinary MRI/MRS Lab, Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan

Functional MRI measures brain activity and relative blood flow using blood-oxygen-level-dependent (BOLD) contrast. However, the mechanism of BOLD contrast is caused by intrinsic susceptibility change. A recent MRI approach, referred to as quantitative susceptibility mapping (QSM), has been proposed to have the potential to quantify the susceptibility within tissues, which may be also capable of improving the measurement of oxygenation-dependent susceptibility changes. To understand the relationship between tissue oxygenation and resulting susceptibility changes, in this study, we aimed to employ QSM technique on rats with different oxygenation levels and investigate the susceptibility changes within different regions of the brain.

3850.   83 Intracerebral Microbleed Assessment by Using Quantitative Susceptibility Mapping
Meng-Chi Hsieh1,2, Jyh-Horng Chen1,2, and Hon-Man Liu3
1Institute of Biomedical Electronic and Bioinformatics, National Taiwan University, Taipei, Taiwan, 2Interdisciplinary MRI/MRS Lab, Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan, 3Department of Medical Imaging, National Taiwan University Hospital and College of Medicine, Taipei, Taiwan

Cerebral hemorrhage is a common cerebrovascular disease in elderly people and associated with hypertension cerebral amyloid angiopathy. However, the amount of interacerebral microbleeding is strongly and dependently relate to incidence of cerebral hemorrhage and its effect on treatment decision. In this study, we accessed the quantity of microbleed using quantitative susceptibility mapping technique to provide a possible quantified approach for medical diagnosis.

3851.   84 Temporal Susceptibility Variations with Multi-Echo Quantitative Susceptibility Mapping (QSM)
Sung-Min Gho1, Yoonho Nam1, Dongyeob Han1, and Dong-Hyun Kim1
1Electrical and Electronic Engineering, Yonsei University, Seodaemun-gu, Seoul, Korea

Quantitative susceptibility mapping (QSM) methods determined from the image phase have been developed for description of tissue anatomy, structure and susceptibility. MR image and its phase value, however, represent the combined signal of sub-voxel components. In addition, image voxel signal at an echo times (TE) represents signal contributions of various T2 and/or T2* value components. For example, myelin, one of major sub-voxel components in white matter regions, is hard to obtain at long TEs because of its very short T2 relaxation times. A QSM, if determined at different TEs, therefore, would represent different characters even in the same voxels. We estimated the temporal variations of QSM images at different TEs using multi-echo gradient echo data.

3852.   85 Macroscopic B0 Inhomogeneity Corrected QSM Based on a Field Mapping Algorithm Using a Single-Scan 3D Z-Shim Multi-Echo GRE.
Dongyeob Han1, Yoonho Nam1, Sung-Min Gho1, and Dong-Hyun Kim1
1Electrical & Electronic Engineering, Yonsei University, Seoul, Korea

Quantitative Susceptibility Mapping (QSM) based on phase data of gradient echo (GRE) is a novel technique for measuring susceptibility differences of the tissue. However, the macroscopic B0 inhomogeneity due to air/tissue boundary causes artifacts which is a common drawback of the GRE1. Furthermore, the effect of the macroscopic B0 inhomogeneity become worse as the echo time increases, and this is critical to QSM studies which have long echo times. To overcome this problem, we propose a 3D z-shim multi-echo GRE pulse sequence which can generate B0 inhomogeneity compensated QSM and a simple robust algorithm for B0 inhomogeneity compensated field map.

3853.   86 Categorization of Various Methods for Quantititative Susceptibility Mapping (QSM) and Their Noise Properties
Shuai Wang1, Tian Liu2, Weiwei Chen3, Cynthia Wisnieff2, Pascal Spincemaille2, Apostolos John Tsiouris2, and Yi Wang2
1School of Electronic and Engineering, University of Electronic Science and Technology of China, Chengdu, Sichuan, China, 2Department of Radiology, Weill Cornell Medical College, New York, New York, United States, 3Department of Radiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China

To help understand various QSM methods, we propose the following categorization: Non-Bayesian approach with alteration of the dipole kernel or approximation of the dipole kernel to overcome ill condition, and Bayesian approach using a general mathematical prior or a specific physical structure prior. We also examine the noise modeling error in QSM methods.

3854.   87 Quantitive Proton Resonance Frequency Imaging Using Fast Multi-Echo Gradient-Echo
Wolfgang Stefan1, Erol Yeniaras1, Ken-Pin Hwang2, Linda Chi3, Ed Jackson1, John D. Hazle1, and R. Jason Stafford1
1Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas, United States, 2Applied Science Laboratory, Healthcare Technologies, WI, Hosuton, Texas, United States, 3Diagnostic & Radiology, The University of Texas MD Anderson Cancer Center, Houston, Texas, United States

We have developed a new background suppression technique that can be used to suppress the background in MR phase images and PRF measurements. In contrast to the most common approach of high pass filtering, our approach leaves the low frequency components of the tissue intact, which enables us to make quantitative measurements of the PRF. The method separates sparse structures in the PRF from the non-sprase background by means of non-convex optimization similar to compressed sensing.

3855.   88 A Quantitative Susceptibility Mapping (QSM) Analysis in Subjects with Alzheimer’s Diseases and Mild Cognitive Impairment -permission withheld
Eo-Jin Hwang1, Min-Ji Kim2, Hyug-gi Kim3, Kyung-Mi Lee4, Ji-Seon Park5, Wook Jin2, Dal-Mo Yang2, and Geon-Ho Jahng2
1Kyung Hee University Hospital at Gangdong, Seoul, Seoul, Korea, 2KyungHee University Hospital at GangDong, Seoul, Seoul, Korea, 3KyungHee University, YoungIn, Gyeonggi-do, Korea, 4Department of Radiology, Kyung Hee University Hospital, Seoul, Seoul, Korea, 5Kyung Hee University Hospital, Seoul, Seoul, Korea

The objective of this study was to apply voxel-based analyses to compare the susceptibility changes among three different groups, cognitive normal (CN), mild cognitive impairment (MCI), and Alzheimer’s disease (AD) using a quantitative susceptibility mapping (QSM) technique. The QSM images were produced by implementing a Morphology Enabled Dipole Inversion (MEDI) method, and the direct comparisons of the whole brains between CN and MCI, CN and AD, and MCI and AD subjects were performed. Throughout the study, the brain regions where different susceptibility effects existed were identified, and the effects of both paramagnetic and diamagnetic substances were visible in all comparisons.

3856.   89 SHARP Edges: Recovering Cortical Phase Contrast Through Harmonic Extension
Ryan Topfer1,2, Ferdinand Schweser3, Andreas Deistung4, Alan H. Wilman1,2, and Jürgen R. Reichenbach3
1Department of Physics, University of Alberta, Edmonton, AB, Canada, 2Department of Biomedical Engineering, University of Alberta, Edmonton, AB, Canada, 3Medical Physics Group, Institute of Diagnostic and Interventional Radiology I, Jena University Hospital - Friedrich Schiller University, Jena, Thuringia, Germany, 4Medical Physics Group, Institute of Diagnostic and Interventional Radiology I, Jena University Hospital - Friedrich Schiller University Jena, Jena, Thuringia, Germany

SHARP and PDF, two recently proposed techniques for filtering B0 field (phase) maps, share a common pitfall: failure to accurately filter background field near the edges of the brain (e.g. cortex). This study presents an adaptation to conventional SHARP whereby the analyticity of the harmonic background field is exploited to recover local phase contrast (that which pertains to tissue magnetic susceptibility) of the hitherto lost edge voxels. The method is quantitatively assessed with a “field-forward” experiment and qualitatively demonstrated using in vivo data.

3857.   90 Background Field Removal Through Infinite Spherical Mean Value Operation
Yan Wen1,2, Tian Liu1,3, and Yi Wang1,3
1Department of Radiology, Weill Cornell Medical College, New York, NY, United States, 2Department of Physics and Astronomy, SUNY at Stony Brook, Stony Brook, NY, United States, 3Department of Biomedical Engineering, Cornell University, Ithaca, NY, United States

A background removal procedure removes background fields to isolate local fields, which is essential for susceptibility calculation. A previous method based on spherical mean value (SMV) principle, Sophisticated Harmonic Artifact Reduction on Phase Data (SHARP), has shown promising results but its result depends on the radius of the sphere and requires a subjective selection of truncation threshold for the deconvolution procedure. Here, we present an infinite SMV algorithm to reduce the dependence of radius and eliminates the need of deconvolution.

3858.   91 Fat-Constrained QSM for Abdominal Applications
Debra E. Horng1,2, Diego Hernando1, Samir D. Sharma1, and Scott B. Reeder1,2
1Radiology, University of Wisconsin-Madison, Madison, WI, United States, 2Medical Physics, University of Wisconsin-Madison, Madison, WI, United States

Quantitative Susceptibility Mapping (QSM), which has been employed in brain applications to measure iron, also has the potential to quantify liver iron overload. However, unlike in the brain, the presence of abdominal fat provides a unique opportunity to constrain the ill-posed QSM estimation problem. In this work, we constrain the QSM estimation by assuming that the magnetic susceptibility of fat (and air) is constant in the presence of iron overload. Comparison of a conventional QSM constraint (ℓ1-regularization) to the proposed fat/air-constraint shows that the latter is more accurate even in the presence of background field variation and noise.