Electronic Poster Session - Pulse Sequences & Reconstruction B
  Sequences, Eddy Currents, Water/Fat 4149-4172
  Sequences: New Acquistion Strategies Saturation Transfer Methodology 4173-4196
  Compressed Sensing/Sequences: Applications 4197-4220
  Compressed Sensing/Sequences: Applications 4221-4244
  Image Reconstruction & Saturation Transfer Imaging 4245-4268
  Tools to Map the Brain & for Small Scale & Education 4269-4289
     

Sequences, Eddy Currents, Water/Fat
Click on to view the abstract pdf and click on to view the video presentation. (Not all presentations are available.)
Thursday 10 May 2012
Exhibition Hall  10:30 - 11:30

  Computer #  
4149.   1 Aliasing separation in accelerated MR image acquisition by voxel modification
Min-Oh Kim1, Joonsung Lee1, Sang-Young Zho1, and Dong-Hyun Kim1
1Electrical and Electronic Engineering, Yonsei University, Seoul, Korea

 
Aliasings occurred due to undersampled phase-encodings in accelerated MR imaging are separated to readout direction by applying additional gradient along undersampled direction at readout timing. Resolution and FOV are redefined due to voxel modification as sheared form. With this method, 6x acceleration is achieved in high-resolution invivo 3D imaging with a partial loss of diagonal resolution. Further acceleration is possible by using parallel imaging techniques such as SENSE and GRAPPA.

 
4150.   
2 In-Vivo Curved Multi-Slice Imaging
Hans Weber1, Daniel Gallichan1, Anna M. Welz1, Chris A. Cocosco1, Sebastian Littin1, Jürgen Hennig1, and Maxim Zaitsev1
1Department of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany

 
ExLoc allows excitation and geometrically matched spatial encoding of curved slices by the application of a set of nonlinear, but locally orthogonal, encoding fields. In this work we explore ExLoc’s potential for multi-slice imaging. Stacks of curved slices result in improved relevant volume coverage for fewer excited slices and thus increase efficiency for particular applications. We present the results of experiments performed on a phantom, as well as a demonstration in vivo.

 
4151.   3 A new cascade-regularized spatial encoding technique using non-linear field disturbance of susceptibility markers
Hirad Karimi1, William Dominguez-Viqueira2, and Charles H. Cunningham1,2
1Dept. of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada, 2Imaging Research, Sunnybrook Research Institue, Toronto, Ontario, Canada

 
Conventional linear gradient fields generated using gradient coils usually perform spatial encoding in MRI. These coils are stationary relative to any physiological movements and this ultimately limits the spatial resolution. Some applications such as intravascular MR imaging (iMRI) could benefit from the high-resolution images that could result from new approaches. Here, a new encoding technique that allows encoding fields to move with physiological structures is investigated. The method uses only the field perturbations emanating from markers with different susceptibilities as the encoding fields. (The gradient coils on scanner are not used). Simulations and phantom studies were conducted to further validate the result.

 
4152.   4 B1-Gradient based MRI using a Single Surface Coil; RF-Encodig
Dominique M. R. Corteville1, Friedrich Wetterling1, and Lothar R. Schad1
1Computer Assisted Clinical Medicine, Heidelberg University, Mannheim, Germany

 
Traditionally RF-encoding is performed by modulating the magnetization along the longitudinal axis of the magnet and rotating it into the orthogonal plane. Recent hardware improvements made it possible to achieve encoding by direct usage of the excitation pulses. This study evaluates the possibilities and challenges of RF-encoding using a single transceiver surface coil, providing general information about the achievable speed and resolution. Sodium was chosen as imaging nucleus to outline the advantages of using nuclei with short relaxation times.

 
4153.   5 Reducing central brightening and increasing penetration depth with single-channel transmit systems at 7 Tesla using a TIAMO-like method
Stephan Orzada1,2, Sören Johst1,2, Andreas K. Bitz1,2, Oliver Kraff1,2, Mark E. Ladd1,2, and Stefan Maderwald1
1Erwin L. Hahn Institute for MRI, Essen, NRW, Germany, 2Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, NRW, Germany

 
At field strengths of 7 Tesla and above, severe B1 inhomogeneities cause problems due to non-uniform contrast and SNR distributions. Most methods proposed to mitigate these problems rely on multi-channel transmit systems. In this single-channel variant of TIAMO, we propose acquiring two images with different transmit amplitudes in an interleaved fashion. In this way the dark areas where the refocusing pulse does not achieve flip angles close to α = 180° + (n∙360°) are in different positions in the two images. The resulting combined images show less impact of the inhomogeneous transmit field.

 
4154.   6 Using the Binomial RF Pulses for Selective Excitation of the Ultra-shot T2 Component
Tiejun Zhao1, Hai Zheng2, Yongxian Qian2, Tamer S Ibrahim2, and Fernando Boada2
1Siemens Healthcare USA; Siemens Medical Solutions USA, Inc., Pittsburgh, PA, United States, 2University of Pittsburgh, Pittsburgh, PA, United States

 
Ultra-short echo imaging in the order of 100us achievable for clinical scanners allowed the detection of protons exhibiting very short T2 relaxation times, which is relevant for tendons, ligaments, or the periosteum. In this abstract, we proposed to use the Binomial pulse excite only the short T2 component and demonstrated that the new scheme helped for detecting fast relaxation tissues with the lower SNR that might be otherwise buried under various imaging artifacts.

 
4155.   7 Simultaneous echo refocused (SIR) EPI with constant TE
An Thanh Vu1,2, Audrey Chang1,2, Liyong Chen1,2, and David Feinberg1,2
1Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, CA, United States, 2Advanced MRI Technologies, Sebastopol, CA, United States

 
Simultaneous echo refocused (SIR) EPI has greatly accelerated the acquisition of both fMRI and DTI data sets. However, the effective echo time (TE) of each individual SIR slice can differ by several milliseconds, resulting in slice dependent signal intensity and BOLD contrast. Here, we propose a constant TE version of the SIR method that is able to use TR specific phase correction navigators while maintaining the minimum TE and TR of the original SIR method. SIR with and without constant TE is evaluated in both phantom and human fMRI experiments.

 
4156.   8 PACEUP-3DEPI: A highly Accelerated 3D-EPI Sequence for fMRI at 7T
Mayur Narsude1,2, José Marques1,2, Wietske van der Zwaag1,2, Tobias Kober1,2, and Rolf Gruetter1,2
1Laboratory for Functional and Metabolic Imaging, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, 2Department of Radiology, University of Lausanne, Lausanne, Switzerland

 
EPI acquisition times can be shortened by partial Fourier acquisition, parallel imaging and sparse data sampling. We present an approach to reduce the EPI volume acquisition time which accelerates in the slice-encode dimension of 3D-EPI enabling an up to 8 fold acceleration with an 8 channel coil at 7T with good image quality. In the PACEUP-3DEPI (ksPACE acqUisition Parallelized 3DEPI) pulse sequence 2 kspace planes are encoded per rf excitation. 96x96x40 matrix volumes were acquired in 0.9s. BOLD sensitivity was tested via resting state networks and found to be increased compared to 2D and 3D-EPI.

 
4157.   9 High-quality clinical MRI massively accelerated with segmented echo-planar readout and phase-cycled reconstruction
Nan-kuei Chen1
1Brain Imaging and Analysis Center, Duke University, Durham, North Carolina, United States

 
Every year millions of patients (e.g., children, seriously ill patients and claustrophobic individuals) cannot complete lengthy MRI procedures without sedation or anesthesia, which poses significant risks for serious adverse effects and harm to health. It is highly desirable to design a novel approach to enable millions of patients to complete clinical MRI without the risk of adverse effects associated with sedation / anesthesia. Here we demonstrate that many clinical MRI sequences may be massively accelerated with segmented echo-planar readout, and high-quality data can be reliably obtained by removing the echo-planar related phase errors with a novel phase-cycled reconstruction algorithm.

 
4158.   10 Extending HARP imaging by acquiring an overdetermined set of stripes
Lucilio Cordero-Grande1, and Carlos Alberola-López1
1University of Valladolid, Valladolid, Castilla y León, Spain

 
An extension of HARP reconstruction in tagged MR imaging is presented in which a number of stripe patterns greater than the dimension of the space are acquired in order to robustify the reconstruction of the local phase of the image. Reconstruction equations for the estimation of the deformation gradient tensor are presented and combined with a previous contribution which improves the original HARP method by using the windowed Fourier transform to better capture the spatio-spectral distribution of the magnetization pattern. Results on real images deformed by a synthetic pattern show the benefits of the proposed scheme in limiting the interferences in HARP reconstruction.

 
4159.   11 Time-Resolved Contrast-Enhanced Peripheral MRA in Patients with Low Contrast Doses Using VIPR-HYPR
L. Keith1, C. Francois2, M. Schiebler2, S. Reeder2,3, and F. Korosec1,2
1Medical Physics, University of Wisconsin - Madison, Madison, WI, United States, 2Radiology, University of Wisconsin - Madison, Madison, WI, United States, 3Biomedical Engineering, University of Wisconsin - Madison, Madison, WI, United States

 
We have previously introduced a method for acquisition of time-resolved contrast-enhanced MR angiography of the peripheral vasculature using fractional doses of contrast material (<0.1 mmol/kg). Undersampled 3D radial k-space trajectories (VIPR) and HYPR image processing are combined to provide distal time-resolved MRA with high spatial and temporal resolution while maintaining good image quality with contrast material injections as little as 0.025 mmol/kg in patients with known PVD. Using this method, it is possible to decease the dose of gadolinium-based contrast agents for time-resolved, contrast-enhanced peripheral MRA while maintaining high image quality and diagnostic confidence.

 
4160.   12 Optimized Gradient Echo Imaging for Hyperpolarised Nuclei - a Simulation Study
Sebastien Bär1, Robert Borowiak1, Jan-Bernd Hövener1, Jürgen Hennig1, Dominik von Elverfeldt1, and Jochen Leupold1
1Dept. of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany

 
The gradient echo (GRE) sequence is one of the standard means to image hyperpolarized nuclei. We show Bloch equation based simulations intending to exploit the decaying hyperpolarized signal over as much sequence cycles as possible. Simulations include both RF-spoiled and non-RFspoiled GRE. Parameters under examination are flip angle and the RF spoil increment. Best signal behaviour was obtained for a moderately small flip angle (approx. 10°) and a small spoil increment (approx. 1°).

 
4161.   13 Eddy Currents in MT Asymmetry Imaging with Alternate Ascending/Descending Directional Navigation (ALADDIN)
Sung-Hong Park1, Tiejun Zhao2, Jung-Hwan Kim1, Fernando E. Boada1,3, and Kyongtae Ty Bae1
1Radiology, University of Pittsburgh, Pittsburgh, PA, United States, 2MR Research Support, Siemens Healthcare, Pittsburgh, PA, United States,3Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States

 
ALADDIN is a new imaging technique that provides interslice perfusion-weighted and MT asymmetry images. We investigated the effects of gradient imperfections on ALADDIN MT asymmetry imaging in this study. Subtraction artifacts were detectable in ALADDIN MT asymmetry images from an agarose phantom but not from a water phantom, in agreement with the theoretical analysis that they were induced by mismatch in MT frequencies associated with readout eddy currents. The artifacts were suppressed by averaging signals over the readout gradient polarities independent of scan parameters. With suppression of the artifacts, ALADDIN signals of human brain were less dependent on scan conditions.

 
4162.   14 Reduction of Eddy-current-induced Distortion in Diffusion-weighted EPI using Spin-tagging
Kun Zhou1, and Wei Liu1
1Siemens (Shenzhen) Magnetic Resonance Ltd., Shenzhen, Guangdong, China

 
A spin-tagging based method is proposed to correct eddy currents induced distortions in DW-EPI images. In this method strips placed by tagging pulses are used to characterize image distortion. Parameters (scaling and shifting factors) describing distortion are derived by comparing strip images of distorted image and reference image (image with b = 0). After that pixel shifting map is calculated using these parameters and used to perform distortion correction.

 
4163.   15 Correcting High Order Eddy Currents for Diffusion Weighted Imaging with Arbitrary Scan Plane and Diffusion Direction
Dan Xu1, Joe K. Maier2, and Kevin F. King1
1Applied Science Lab, GE Healthcare, Waukesha, WI, United States, 2MR Engineering, GE Healthcare, Waukesha, WI, United States

 
An axial plane based high order eddy current correction (HOEC) method was previously proposed to mitigate diffusion gradient direction dependent image distortion often seen in images acquired with the Stejkal-Tanner diffusion sequence, which is known to produce images with higher signal-to-noise ratio than the corresponding dual spin echo images due to generally shorter echo time. In this paper, we show that HOEC correction can be extended to arbitrary scan plane with arbitrary diffusion direction through the application of gradient and polynomial basis rotation matrices.

 
4164.   16 Eddy-current-induced Artifact Suppression for b-SSFP via Through-slice Dephasing
Ozan Sayin1, John A. Derbyshire2, Liheng Guo1, and Daniel A. Herzka1
1Department of Biomedical Engineering, Johns Hopkins School of Medicine, Baltimore, MD, United States, 2Tornado Medical Systems, Toronto, Ontario, Canada

 
Recent advancements in parallel imaging and/or image reconstruction (e.g. Compressed Sensing) have led to the common employment of nonconventional and irregular phase encode ordering schemes. For balanced steady-state free precession (b-SSFP) MRI, such sequences can be problematic in terms of eddy current artifacts due to rapid jumps in k-space trajectories from one TR to the next. In this work, we explore and characterize a previously-proposed technique, through-slice dephasing, as an efficient technique for eddy current artifact suppression. We demonstrate the utility of the technique in vivo, and further analyze it via b-SSFP simulations.

 
4165.   17 Characterization and Compensation of Eddy Current Induced by Insertable dreMR Magnet
Ludovic de Rochefort1, Eddy S.M. Lee2, Matteo Polello3, Luc Darrasse1, Gianni Ferrante3, and Brian K. Rutt2
1UMR8081, IR4M (Imagerie par Résonance Magnétique Médicale et Multi-modalités), Univ. Paris-Sud, CNRS, Orsay, France, 2Radiology, Stanford University, Stanford, California, United States, 3Stelar s.r.l, Mede, Italy

 
Delta relaxation-enhanced magnetic resonance (dreMR) imaging is a B0-cycled technology producing contrast from intended targets only. While ÄB can be achieved with an insertable field-cycling magnet, mutual coupling induces eddy currents (EC) that change the main field. An imaging strategy is presented to characterize and compensate for the EC. A multiphase imaging sequence was modified to produce multiple images after a dreMR pulse. Results show that offset caused by EC is spatially homogeneous, proportional to ÄB and decays monoexponentially. Consequently, the EC induced spatial shifts in the frequency encoding direction which could be compensated for using sequence adaptation and post-processing.

 
4166.   18 Correction of Eddy Current Distortions in High b-value and High Angular Resolution Diffusion Imaging
Jiancheng Zhuang1, Zhong-Lin Lu1, Christine Bouteiller Vidal1, and Hanna Damasio1
1University of Southern California, Los Angeles, California, United States

 
High angular resolution diffusion images are susceptible to distortions caused by eddy currents induced by large diffusion gradients. A new post-acquisition correction algorithm is proposed which does not require any auxiliary reference scans. Image distortion parameters were obtained by image coregistration, performed only between diffusion weighted images with close diffusion gradient orientations. A linear model that describes distortion parameters (translation, scaling, and shear) as a function of diffusion gradient directions was numerically computed to allow individualized distortion correction for every diffusion-weighted image. The method avoids the problematic procedure of cross-correlating images with significantly different contrasts resulting from very different gradient orientations or strengths. Application of the proposed algorithm in high angular resolution diffusion images markedly reduced eddy current distortions, when compared to results obtained with previously published methods.

 
4167.   19 Two-Point Dixon Fat and Water Separation using 3D Dual-Echo SSFP Sequence in Breast Imaging
Yi Wang1,2, Emilee Minalga1,2, Allison Payne2, Glen Morrell2, and Dennis L. Parker1,2
1Bioengineering, University of Utah, Salt Lake City, UT, United States, 2Utah Center for Advanced Imaging Research, Salt Lake City, UT, United States

 
bSSFP sequences offer superior signal intensity in a relative short time. However, fat could appear very bright due to its high T2/T1 values. Fat signal suppression or elimination can be helpful to uncover information that might otherwise be obscured by fat, e.g., lesions and blood vessels in breast imaging. Initial work on achieving two-point Dixon fat and water separation in breast using the dual-echo SSFP sequence has been reported. In this work, we simulate the signal behavior of the dual-echo SSFP to assist in choosing the optimal flip angle for in vivo breast imaging in a breast-specific MR guided high intensity focused ultrasound system.

 
4168.   20 Simultaneous fat-water separated imaging using dual spatial-spectral RF pulses
Cheng-Chieh Cheng1,2, Hing-Chiu Chang1, Lawrence Panych2, Chun-Jung Juan3, Tzu-Cheng Chao4, and Hsiao-Wen Chung1
1Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan, 2Department of Radiology, Brigham and Women's Hospital, Boston, Massachusetts, United States, 3Department of Radiology, Tri-Service General Hospital, Taipei, Taiwan, 4Institute of Medical Informatics, National Cheng-Kung University, Tainan, Taiwan

 
Spatial-Spectral RF pulses have been widely adopted for many purposes, especially in the situation when fat-suppression is necessary. In this study, we utilized this idea to simultaneously generate fat-water separated imaging. For comparison, images with fat/water suppression were acquired using a conventional FLASH sequence. Our results showed these simultaneously acquired images have comparable contrast to the FLASH images. Consequently, our proposed method may be beneficial for studies that require dynamic information of both water and fat.

 
4169.   21 Robust Water-Fat Separation Using Binomial Rectangular Pulses
Yongquan Ye1, Jiani Hu1, and E.Mark Haacke1
1Radiology, Wayne State University, Detroit, MI, United States

 
In this study, a novel RF-based water-fat separation method is introduced, by utilizing the unique frequence response profile of a pair of opposite-phase rectangular pulses.Functioning as simutaneous excitation and selective suppression, the dual-rect pulses do not require extra scan time but come with low SAR level. With the simplicity and robust performance due to the broad passbands and stopbands, our method is especially advantageous for high field fast 3D imaging.

 
4170.   22 Accelerated Water-fat Separation Using Parallel Imaging, Compressed Sensing, and Multiscale Cubic B-splines
Samir D Sharma1, Houchun H Hu2, and Krishna S Nayak1
1Electrical Engineering, University of Southern California, Los Angeles, CA, United States, 2Radiology, Children's Hospital Los Angeles, Los Angeles, CA, United States

 
Chemical shift-encoded water-fat separation techniques are used in both research and clinical settings because they are highly robust to off-resonance. A tradeoff when using these techniques is a longer scan time since data must be collected at multiple echo-times. Previous works have proposed to use either parallel imaging or compressed sensing to shorten the scan time. In this work, we introduce a joint parallel imaging and compressed sensing approach for water-fat separation. The proposed approach is compared to an existing parallel imaging and water-fat separation method. We demonstrate 3.4x 1D acceleration with the proposed approach.

 
4171.   23 Water Fat Identification for Symmetically Acquired Dixon Method on Non-connected Body Regions
Cong Zhao1, and Andrew Liang2
1Siemens ShenZhen Magnetic Resonance, ShenZhen, GuangDong, China, 2School of Engineering and Applied Science, University of Pennsylvania

 
The work provides a post-processing algorithm classifying water and fat images generated by symetically acquired 2D/3D dixon techniques. It is also extended to work on imaging with non-connected body parts

 
4172.   24 Volumetric Fat Quantification of Intra-Abdominal Adipose Tissue from a Single Breath Hold Acquisition
Bryan T Addeman1, Abraam S Soliman2,3, Curtis N Wiens4, and Charles A McKenzie1,4
1Department of Medical Biophysics, University of Western Ontario, London, ON, Canada, 2The Robarts Research Institute, London, ON, Canada,3Biomedical Engineering, University of Western Ontario, London, ON, Canada, 4Department of Physics and Astronomy, University of Western Ontario, London, ON, Canada

 
Escalating interest in the studies of obesity and metabolic disease has created a demand for techniques to measure the regional distribution of adipose tissue. Current standards employ manual segmentation of fat on a single slice, and extrapolation to estimate total fat volumes. We propose a novel automated tissue segmentation technique on images acquired from the entire intra-abdominal cavity within a single breath-hold. Volunteers were imaged in less than 10 minutes, and the images were analyzed in under 2 minutes. Results are similar to those obtained by manual segmentation, but require no manual intervention and are calculated very rapidly.
 
Electronic Poster Session - Pulse Sequences & Reconstruction B

Sequences: New Acquistion Strategies Saturation Transfer Methodology
Click on to view the abstract pdf and click on to view the video presentation. (Not all presentations are available.)
Thursday 10 May 2012
Exhibition Hall  11:30 - 12:30

  Computer #  
4173.   1 Spin-Echo Propeller (SE-prop): T1-w single-echo motion robust imaging without inversion pulses
Stefan Skare1, and Anders Lilja1
1Dept of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden

 
A new propeller sequence has been implemented as a complement to existing T2-w and T2 FLAIR techniques. Based on the classical Spin-Echo sequence, the aim was to produce an image contrast before and after Gd administration that it familiar to the radiologists, while overcoming artifacts from flow and motion. Being a T1-w propeller acquisition, off-resonances from the signal-intense fat manifests as a swirly bright structures instead of a simple shift, why high bandwidths should be used, in particular at 3T.

 
4174.   2 Partial Fourier acquisition with centric circular reference lines in 3D MRI
Guobin Li1, Dominik Paul2, Iulius Dragonu1, Maxim Zaitsev1, Jürgen Hennig1, and Kuan Lee1
1University Medical Center Freiburg, Freiburg, Baden-Württemberg, Germany, 2Siemens Healthcare, Erlangen, Germany

 
Partial Fourier acquisition has been widely combined with other acceleration techniques, i.e. Parallel imaging, Compressed sensing etc., to reduce MR scanning time. The k-space central data used for phase correction are crucial for the reconstructed image quality. However, these central data are usually acquired in a simple rectangular pattern, which leads to some problems in 3D MRI. A round pattern for partial Fourier acquisition is presented. Its advantages are also shown with in vivo experiments.

 
4175.   3 Combination of consecutive interleaved EPI schemes and parallel imaging technique
Dae-Hun Kang1, Jun-Young Chung1, Da-Eun Kim1, Young-Bo Kim1, and Zang-Hee Cho1
1Neuroscience Research Institute, Gachon University of Medicine and Science, Incheon, Korea

 
Interleaved multi-shot EPI (iEPI) is able to provide the short echo time and the short echo train length, which lead to reduce geometric distortions. iEPI with a minimum intersegment delay was presented for reducing motion artifacts due to a long acquisition time of iEPI and imaging like ssEPI, namely consecutive interleaved EPI (ciEPI). In this paper, we propose the combination between ciEPI and parallel imaging.

 
4176.   4 An efficient EPI pulse sequence module for active marker motion correction acquisition for EPI scans
Erik B Beall1, and Mark J Lowe1
1Radiology, Cleveland Clinic, Cleveland, OH, United States

 
Head motion is a huge problem in many advanced MRI sequences. Previous reports of microcoil-based active marker motion correction are truly prospective but impose reductions in SNR and time-efficiency in the main sequence due the separate excitation. Anatomic sequences are largely insensitive to motion, but functional, perfusion and diffusion-weighted EPI presents intractable problems if there is more than minimal head motion. EPI in most uses requires a fat saturation pulse, and we present a method to use fat saturation with active markers to remove the SNR and time penalties and demonstrate proof-of-principle in human data.

 
4177.   5 Coded Spatial Localization using Rotating Nonlinear Sets of Gradient Fields and Continuous Readout
R. Todd Constable1, Leo Tam1, Jason Stockmann1, and Gigi Galiana1
1Diagnostic Radiology, Yale University School of Medicine, New Haven, CT, United States

 
In this work, a novel approach to spatial encoding that uses nonlinear gradients to impose a unique code on each voxel in the image is introduced. The data is readout in a continuous manner as combinations of linear and nonlinear gradients rotate refocusing different regions of the image at different times. This approach may yield advantages in terms of imaging speed, acoustic noise, and reduced gradient dB/dt, all while providing a high SNR fast acquisition strategy.

 
4178.   6 Variable-Density 3D Cones Trajectory Design with Compressed Sensing Reconstruction
Nii Okai Addy1, Holden H Wu1,2, and Dwight G Nishimura1
1Electrical Engineering, Stanford University, Stanford, CA, United States, 2Cardiovascular Medicine, Stanford University, Stanford, CA, United States

 

4179.   7 3D Cine Ultra-short TE (UTE) phase contrast imaging in carotid artery: comparison with conventional technique
Mo Kadbi1, Hui Wang1, Melanie Traughber2, Motaz Alshaher1, Andrea Yancey3, Jens Heidenreich1, and Amir A Amini1
1University of Louisville, Louisville, Kentucky, United States, 2Philips healthcare, Cleveland, United States, 3VA hospital, Louisville, Kentucky, United States

 
Phase contrast MRI is a non-invasive technique to assess cardiovascular blood flow. However, this technique is not accurate in cases where there is atherosclerotic disease and the blood flow is disturbed.. Carotid bifurcation is one of the main sites of atherosclerosis is and a good example of complex and disturbed blood flow due to atypical geometry of this branch site. Therefore, conventional PC MRI at the site of carotid bifuraction suffers from intravoxel dephasing and flow artifacts. In this work, a 3D UTE PC imaging method is designed to measure the blood velocity in carotid bifurcation using a center-out radial trajectory and short TE time compared to standard PC MRI sequences. With 3D UTE-PC combined quantification and visualization of blood flow in the region of interest is possible.

 
4180.   8 Spatially encoded high-resolution 2D correlation spectroscopy in inhomogeneous fields
Zhiyong Zhang1, Yulan Lin1, Shuhui Cai1, and Zhong Chen1
1Department of Electronic Science, Fujian Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, Fujian, China

 
To eliminate the influences of field inhomogeneity on the conventional 2D correlation spectroscopy (COSY), two schemes via spatially encoded intermolecular multiple-quantum coherences combined with Hadamard encoding and three-dimensional acquisition respectively were proposed to achieve high-resolution 2D COSY in inhomogeneous fields with high acquisition efficiency. Compared to the conventional method, the acquisition time is shortened by orders of magnitude. The new schemes may be useful for the study of chemical and biological materials.

 
4181.   9 Validation Of A Novel Fine Structure MRI Technique Using A Porcine Liver As Phantom For Liver Fibrosis
Samantha A. Telfer1, N.J. Taylor2, James Stirling2, Ian Simcock2, Anwar R. Padhani2, Gareth Thomas1, and T. W. James1
1Acuitas Medical, Swansea, West Glamorgan, United Kingdom, 2Paul Strickland Scanner Centre, Northwood, Middlesex, United Kingdom

 
Fine structure analysis (structural spectroscopy of fine textures below the resolution limit of clinical MR imaging) was applied to specially acquired MR data of ex-vivo livers from pigs and oxen to establish their utility as phantoms for characterising chronic liver disease (CLD). Porcine liver exhibits fibrotic structure similar to human CLD whilst ox liver has an appearance similar to healthy human liver. Whole liver lobules “decorated” with a fibrotic network exhibit a distinctly different spectral signature than the underlying vascular structure of the lobules - hence clearly distinguishing between the two livers and supporting use of fine structure analysis.

 
4182.   10 High-resolution imaging using partial separability of spatiotemporal signals with a novel data sampling scheme
Guoxi Xie1, Xiang Feng2, Xin Liu2, Bensheng Qiu2, and Anthony G. Christodoulou3
1Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China, 2Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, 3Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urban

 
The Partial Separability (PS) model allows sparse sampling for fast MRI. It is generally performed by sampling two datasets (navigator data and image data) to estimate the parameters of the model before reconstruction high spatiotemporal resolution MR images. Based on the theory of partially separable functions, the more spatial frequency components in (k-f) space the navigator data covers, the more accurately the PS model will capture object motion. To address this issue, we present a novel sampling method that uses radial sampling trajectories for navigator data sampling and Cartesian sampling trajectories for image data sampling. This covers more spatial frequency components of the navigator data without requiring re-gridding during image reconstruction.

 
4183.   11 An Analytic Description of Steady-State Imaging with Dual RF Pulses and Gradient Spoiling
Hao Sun1, Jeffrey Fessler1, and Jon Fredrik Nielsen2
1Electrical Engineering and Computer Science, University of Michigan - Ann Arbor, Ann Arbor, Michigan, United States, 2Biomedical Engineering, University of Michigan - Ann Arbor, Ann Arbor, Michigan, United States

 
Small-tip fast recovery (STFR) imaging is a recently proposed steady-state sequence that has similar T2/T1 contrast as bSSFP but has the potential to simultaneously remove banding artifacts and transient fluctuations. At the end of each TR, the STFR method tips the magnetization back to the longitudinal axis using a tailored RF pulse. After the tip-up pulse, a gradient spoiler is applied. In this abstract, we derived an analytic expression for the STFR signal and verified the equation with simulations and phantom data. This new signal equation is useful for analyzing STFR, and potentially could be used for quantitative imaging.

 
4184.   12 Linear Sweeps generate Extreme Echoes: explanation, generalization
Patrick H Le Roux1, and Brice Fernandez2
1Applied Science Lab, GE Healthcare, Palaiseau, France, 2Applied Science Lab, GE Healthcare, Munich, Germany

 
When a train of RF pulses with constant nutation is modulated in phase according to a periodic quadratic law, a refocusing for all the three components of magnetization (Extreme Echo) is generated at the end of the modulation or after two periods if the period is odd. This was first observed experimentally and also demonstrated mathematically . But that demonstration lacks any physical meaning. We propose here a simple geometrical explanation in which the symmetries of the echo to echo rotation plays an essential role. This remark leads to more general phase modulation having the same property.

 
4185.   13 Intrinsic Field Homogeneity Correction in Fast Spin Echo based Amide Proton Transfer MRI
Jochen Keupp1, and Holger Eggers1
1Philips Research, Hamburg, Germany

 
Amide proton transfer (APT), a powerful technique for molecular imaging of endogenous proteins, is based on an asymmetry analysis of RF saturation frequency offsets acquired around the water resonance, which needs precise B0 homogeneity correction. While fast spin-echo (FSE) based APT has superior contrast-to-noise ratio, the previously shown multi-echo APT acquisition with intrinsic Dixon-type B0 mapping/correction is restricted to gradient-echo sequences. We propose a FSE-Dixon APT technique with varied echo time shifts, using iterative Dixon reconstruction across different positive saturation frequency offsets for intrinsic B0 mapping and correction. Feasibility in the human head is demonstrated using a clinical 3T scanner.

 
4186.   14 B1 Inhomogeneity Correction of In-vivo CEST Contrast
Anup Singh1, Kejia Cai1, Mohammad Haris1, Hari Hariharan1, and Ravinder Reddy1
1Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, United States

 
In current study effect of B1 in-homogeneities on in vivo chemical-exchange-saturation-transfer(CEST) asymmetry contrast from human brain at 7T is studied and a procedure for correction of these in-homogeneities is presented. The z-spectral and CEST data (at 3ppm) at multiple saturation powers and fixed duration(1s) were obtained from brain of healthy human volunteers at 7T research scanner. These data were corrected for B0 in-homogeneities before generating z-spectral and CEST asymmetry contrast. B1 map from human brains were highly in-homogeneous (~50% variation) and CESTasy map without these corrections were difficult to interpret. Proposed calibration based approach resulted in B1-inhomogeneities corrected CESTasy map.

 
4187.   15 Chemical exchange sensitive imaging without a long irradiation pulse: irradiation with toggling inversion preparation
Tao Jin1, and Seong-Gi Kim1
1Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States

 
One practical issue for the chemical exchange (CE) based MRI techniques is that the conventional T1 and T2 relaxations often contaminate the CE imaging contrast. Another issue is that due to hardware or specific absorption rate limitations, CE-sensitive image often has to be acquired using a short irradiation pulse, although a long pulse reaching the steady state may simplify the quantification and sometimes results in better image contrast. Here we propose a novel acquisition method that can use a relatively short irradiation pulse to remove T1 and T2 effects in the CE contrasts, and also to obtain the steady-state imaging contrast.

 
4188.   16 Inversion preparation in magnetization transfer imaging reduces irradiation requirements in human brain at 3 T
Tae Kim1, Kristy Hendrich1, and Seong-Gi Kim1
1Radiology, University of Pittsburgh, Pittsburgh, PA, United States

 
We compare various strategies utilizing inversion prepulses applied at water proton frequency and/or off-resonance MT irradiation to obtain magnetization transfer ratio (MTR) maps. Our results demonstrate that MTR maps of similar quality can be obtained at significantly reduced irradiation times (i.e., much lower overall RF power deposition) when incorporating on-resonance inversion prepulses, as compared with steady-state MTR maps acquired with only off-resonance MT irradiation.

 
4189.   17 Exchange rate filtering of CEST agents using frequency-labeled exchange (FLEX) transfer
Nirbhay Yadav1,2, Amnon Bar-Shir1, Craig Jones1,2, Chien-Yuan Lin2,3, Jun Hua1,2, Assaf Gilad1, Michael McMahon1,2, and Peter van Zijl1,2
1Johns Hopkins University, Baltimore, MD, United States, 2KKI, Baltimore, MD, United States, 3UT Southwestern Medical Center, Dallas, TX, United States

 
In vivo CEST studies are complicated by multiple groups of protons that contribute to the exchange contrast. Here, we used the recently reported FLEX approach to measure the exchange-based proton-transfer ratio (PTR) from the imino protons of thymidine under conditions of different exchange rate due to a change in pH of the solution. Our results show that it is possible to weight exchange contrast in FLEX based on exchange rate. These methods can then be used to filter the contrast from protons with certain exchange rates.

 
4190.   18 Quantitative CEST imaging with Reduced MT Interference using Dual-frequency Irradiation
Xiaolei Song1,2, Amnon Bar-Shir1,3, Yajie Liang1,3, Guanshu Liu1,2, Assaf A Gilad1,3, Jeff W.M. Bulte1,3, Peter C.M. van Zijl1,2, and Michael T Mcmahon1,2
1Russell H. Morgan Department of Radiology and Radiological Sciences, Johns Hopkins University School, The Johns Hopkins University, Baltimore, MD, United States, 2F.M.Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States, 3Cellular Imaging Section, Institute for Cell Engineering, The Johns Hopkins University, Baltimore, MD, United States

 
CEST imaging is an emerging new technology with great promise for molecular imaging applications. Unfortunately, current CEST imaging schemes produce images with a large signal losses due to interference of conventional magnetization transfer and direct water saturation effects, especially for in vivo. We have developed a new method in which cosine-modulated dual-band pulses are inserted into the saturation module. These pulses shift the water-dip in Z-spectra, providing a reduction in conventional magnetization transfer effects. We have collected images on both DIACEST phantoms and 9L tumors in vivo, with the CNR of the resulting images improved over previous methods.

 
4191.   19 Studies of Quantum Mechanics/Molecular mechanics of small metabolites for quantification of chemical exchange saturation transfer
Olga Ivchenko1,2, Petra Imhof2, Moritz Zaiss1, and Peter Bachert1
1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, 2Molecular Biophysics, Interdisciplinary Center for Scientific Computing (IWR), Heidelberg, Germany

 
The chemical exchange rate was determined for creatine – NH2 group (kex =102.9 s-1) at the pH=6.5 using quantum mechanics/molecular mechanics simulations (QM/MM) in combination with umbrella sampling simulations. This value is in agreement with the value from CEST experiment. The chemical exchange rate was determining using Arrhenius equation: kex =Aexp(-Ea/KbT), where A is pre-exponential factor which determines the frequency of collusion ( calculated from classical MD simulations), and Ea is an activation energy characterizing the height of a barriers which protons need to overcome in order to transfer from solute to water and vice versa (determined from QM/MM simulations).

 
4192.   20 Chemical Exchange Contrast with Off-Resonance Spin Locking
Feliks Kogan1, Anup Singh1, Kejia Cai1, Mohammad Haris1, Hari Hariharan1, and Ravinder Reddy1
1Center for Magnetic Resonance and Optical Imaging, University of Pennsylvania, Philadelphia, PA, United States

 
Chemical Exchange Saturation Transfer (CEST) has become a popular method for measurement of metabolites with exchangeable protons. Current CEST methods are plagued by direct saturation of water protons which leads to decreased SNR and CEST contrast. In this work, we demonstrate the feasibility of using an off-resonance spin-lock (SL) pulse for generating the exchange mediated contrast. We showed in phantom experiments that this new method can decrease direct water saturation and increase chemical exchange contrast. We also demonstrated the feasibility of using the SL method in vivo in human patellar cartilage and showed that the SL method was 15% more sensitive than conventional CEST.

 
4193.   21 Altered CEST Spectrum with Different Imaging Readout Schemes
Sheng-Min Huang1, Shang-Yueh Tsai2, Teng-Yi Huang3, Yi-Chun Wu4, and Fu-Nien Wang1
1Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, Taiwan, 2Graduate Institute of Applied Physics, National Chengchi University, Taipei, Taiwan, 3Department of Electrical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan, 4Molecular Imaging Center, Chang Gung Memorial Hospital, Taoyuan, Taiwan

 
The effect of image acquisition RF pulses on CEST imaging was investigated in this study. RARE and spin-echo EPI were utilized on a phantom experiment. The spillover effect of multiple 180 refocusing RFs was confirmed on the observed Z-spectra. The asymmetry of magnetic transfer ratio was thus reduced while using RARE for imaging acquisition. It is suggested that care must be taken when using RF pulses train for image readout.

 
4194.   22 Spillover correction for quantification of pulsed-CEST experiments
Moritz Zaiss1, Olga Ivchenko1, and Peter Bachert1
1Dpt. of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Baden-Württemberg, Germany

 
Chemical exchange saturation transfer (CEST) effect of endogenous CEST agents with small frequency offset from water resonance like amide protons (APT) are always diluted by direct saturation of water protons (spillover effect). An analytical spillover correction is presented which allows reconstructing the unperturbed pulsed-proton transfer rate for different flip angles and B1 using only label and reference scan. Additionally, the artificial pulsed-proton transfer rate is shown to be correlated with the analytical cw proton transfer rate. Therefore, the spillover correction provides analytic quantification of pulsed saturation transfer experiments which are feasible in clinical scanners.

 
4195.   23 CEST Imaging with Alternating-Offset-Saturation bSSFP
Qi Liu1,2, Zhaoyang Fan2, Wafa Tawackoli2, Gadi Pelled2, Dan Gazit2, Yutaka Natsuaki3, and Debiao Li2,4
1Northwestern University, Chicago, IL, United States, 2Cedars-Sinai Medical Center, Los Angeles, CA, United States, 3Siemens Healthcare, Los Angeles, CA,4University of California, Los Angeles, CA, United States

 
Balanced steady-state-free-precession (bSSFP) allows rapid imaging with high SNR efficiency. However, it is sensitive to scanner frequency drift, especially when long imaging time is required such as in CEST imaging. We developed an alternating-offset-saturation bSSFP (AOS-bSSFP) technique for more accurate CEST detection, as demonstrated by excellent agreement with TSE CEST in MTR asym plot both in phantom and in vivo scans.

 
4196.   24 Rescalable spillover prediction for optimization of pulsed magnetization transfer and CEST experiments
Moritz Zaiss1, and Peter Bachert1
1Dpt. of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany

 
A rescaling property for simulated direct water saturation maps for pulsed RF irradiation at different frequency offsets is introduced. It allows prediction of regions of low spillover effect for a specific pulse train for all offsets of interests by simply rescaling one simulated spillover map. Additionally, for each simulated pulse power and duration the same map shows to provide the whole symmetric z-spectrum. This makes the search of low spillover regions quick and easy which is interesting for optimization of pulsed magnetization transfer and CEST experiments where small chemical shifts relative to the water protons lead to strong signal dilution by spillover effect.
 
Electronic Poster Session - Pulse Sequences & Reconstruction B

Compressed Sensing/Sequences: Applications
Click on to view the abstract pdf and click on to view the video presentation. (Not all presentations are available.)
Thursday 10 May 2012
Exhibition Hall  10:30 - 11:30

  Computer #  
4197.   25 k-t ISD compressed sensing reconstruction for T1ñ mapping: A study in rat brains at 3T
Jing Yuan1, Dong Liang2, Feng Zhao1, Yujia Li1, Yi-Xiang J Wang1, and Leslie Ying3
1Imaging and Interventional Radiology, The Chinese University of Hong Kong, Shatin, NT, Hong Kong, 2Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China, 3Department of Electrical Engineering and Computer Science, University of Wisconsin, Milwaukee, WI, United States

 
T1ñ relaxation has potentials for investigating low frequency motional physiological processes but suffers from long scan time, susceptibility to motion and high SAR. We present the use of k-t ISD, a recently proposed compressed-sensing method for T1ñ mapping. The T1ñ maps of rat brains derived with and without CS were compared. The results show that T1ñ map can be accurately estimated from the highly compressed data with the reduction factor up to 10 in brain ROIs and 6 in muscle ROIs without significant differences. This technique is promising for accurate T1ñ quantification with remarkably reduced scan time and SAR.

 
4198.   26 Local Temporal Point Spread Function for CS Reconstructions Exploiting x-f-sparsity
Tobias Wech1, Daniel Stäb1, Andre Fischer1, Dietbert Hahn1, and Herbert Köstler1
1Institute of Radiology, University of Würzburg, Würzburg, Germany

 
Compressed Sensing reconstructions exploiting spatio-temporal sparsity have successfully been applied to accelerate dynamic MRI. However, the non-linear and non-stationary CS algorithms prohibit the straightforward evaluation of the temporal resolution through a single global temporal point spread function. In this work a pixelwise perturbation strategy was utilized to assess local temporal point spread functions for every image pixel. The method therefore allows an appropriate assessment of the temporal resolution and can thus improve the choice of sampling patterns and algorithm settings.

 
4199.   27 Compressed Sensing with Prior Information for Time-Resolved TurboSPI
James A. Rioux1,2, Steven D. Beyea2,3, and Chris V. Bowen2,3
1Department of Physics, Dalhousie University, Halifax, Nova Scotia, Canada, 2Institute for Biodiagnostics (Atlantic), National Research Council, Halifax, Nova Scotia, Canada, 3Departments of Physics, Radiology and Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada

 
TurboSPI can be used to acquire a time series of images suitable for high temporal resolution relaxometry, but must be significantly accelerated to permit applications such as cellular imaging in vivo. The acquisition of a matched Fast Spin Echo image provides prior information to further sparsify the reconstructed image. We compare two approaches to incorporating this prior information, and show that a modified-CS reconstruction using the known support of the FSE template allows acceleration factors of up to 30 while retaining high image quality throughout the time series.

 
4200.   28 Combination of Compressed Sensing and Parallel Imaging with Adaptive Motion Compensation for Accelerated Dynamic MRI
Cagdas Bilen1, Ricardo Otazo2, Daniel K Sodickson2, Ivan Selesnick1, and Yao Wang1
1Department of Electrical Engineering, Polytechnic Institute of NYU, Brooklyn, NY, United States, 2Bernard and Irene Schwartz Center for Biomedical Imaging, NYU School of Medicine, New York, NY, United States

 
Video coding techniques such as motion compensation has been proposed to exploit temporal redundancy and improve compressed sensing reconstructions of undersampled dynamic MRI data. Many of these methods require reference frames and/or fully sampled low pass k-space data which limits the acceleration factor. We propose a regularization framework with motion compensating prior that adaptively estimates the motion field during the reconstruction iterations with no need for reference frames or fully sampled k-space data.

 
4201.   29 Limits of Acceleration for Combinations of Compressed Sensing and Parallel Imaging
Ricardo Otazo1, Riccardo Lattanzi1, and Daniel K Sodickson1
1Bernard and Irene Schwartz Center for Biomedical Imaging, NYU School of Medicine, New York, NY, United States

 
The limits of acceleration for combinations of compressed sensing and parallel imaging remain uncertain. In this work, we investigate the performance of the combined reconstruction with respect to the number of coils for truly-sparse and compressible MR images. A complete basis set of electromagnetic fields is employed as a hypothetical optimal coil array, which achieves the best possible SNR for parallel imaging reconstructions. We demonstrate that the minimum number of required k-space samples is bounded by the number of sparse coefficients, which removes the oversampling factor of 3-5 for compressed sensing alone and approximates the theoretical bounds of L0-norm minimization.

 
4202.   30 Applicability of k-t BLAST, k-t SENSE, k-t PCA and k-t PCA/SENSE for tissue phase mapping in a heart phantom at 3T
Anja Lutz1, Sebastian Kozerke2, Jan Paul1, Michael Schmucker1, Axel Bornstedt1, G Ulrich Nienhaus3, Wolfgang Rottbauer1, and Volker Rasche1
1University Hospital of Ulm, Ulm, BW, Germany, 2ETH Zürich, Institute for Biomedical Engineering, Zürich, Switzerland, 3Karlsruhe Institute of Technology, Karlsruhe, BW, Germany

 
Quantification of myocardial mechanics by tissue phase mapping (TPM) is supposed to provide an improved understanding of cardiac motion and to enable a detailed assessment of myocardial diseases such as cardiac asynchrony and dilated cardiomyopathy. A major limitation of TPM in clinical routine is the long acquisition time. In this study different reconstruction algorithms (k-t BLAST, k-t SENSE, k-t PCA and k-t PCA/SENSE) are investigated regarding their applicability to accelerated TPM data. For high acceleration factors, the use of sensitivity maps and principal component analysis improves the quality of velocity data.

 
4203.   31 Comparison of highly accelerated TV and low rank methods for breast DCE data
Haonan Wang1, Neal Kepler Bangerter1,2, Ganesh Adluru2, Matthias Schabel3, Glen R. Morrell2, and Edward V.R. DiBella2
1Electrical & Computer Engineering, Brigham Young University, Provo, UT, United States, 2Department of Radiology, University of Utah, Salt Lake City, UT, United States, 3Ohio State University

 
Dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) of breast tumors provides a promising method for the evaluation of vessel permeability in the tumor area. Recently, a number of constrained reconstruction algorithms using Total Variation (TV) and Low Rank (LR) have been proposed to mitigate the tradeoff between spatial and temporal resolution in DCE MRI. In this work, we compare two of these acceleration methods on DCE MRI of the breast. We demonstrate that high acceleration rates (R=13) are potentially feasible in DCE-MRI of the breast using both the TV and LR constrained reconstruction algorithms.

 
4204.   32 On Compressed sensing for phase-contrast velocity mapping
Claudio Santelli1,2, Sebastian Kozerke1,2, and Tobias Schaeffter2
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland, 2Division of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom

 
Among the various scan acceleration techniques available to Phase-Contrast(PC)-MRI, Compressed sensing (CS)has recently been demonstrated. In this work, it It is hypothesized that reconstruction accuracy with respect to object phase depends on inflow contrast. Using 2D and 3D in-vivo flow data acquired in the aortic arch it is demonstrated that reconstruction error varies significantly on the amplitude contrast.

 
4205.   33 Improved waveform fidelity of Hybrid HYPR with Compressed Sensing technique
Yijing Wu1, Kevin M Johnson1, Steven R Kecskemeti2, Patrick A Turski3, and Chuck A Mistretta4
1Medical Physics, University of Wisconsin, Madison, WI, United States, 2University of Wisconsin, 3Radiology, University of Wisconsin, Madison, WI, United States, 4Medical Physics and Radiology, University of Wisconsin, Madison, WI, United States

 
Hybrid HYPR-MRA utilizes a separately acquired high spatial resolution static MRA as a spatial constraint to reconstruct highly undersampled dynamic MRA to achieve high temporal and spatial resolution simultenously. However, for extremely high undersampling factor (>100) or/with reduced sparsity, severe undersampling artifacts not only contaminate the image, but also cause signal "crosstalk" from distant vessels, which appears as early enhanced veins or prolonged enhanced arteries. In this project, we integrate Parallel imaging and CS to eliminate undersampling artifacts before HYPR algorithm, such that the waveform fidelity of small vessels can be improved, at the same time, CS related artifacts and SNR can be improved by Hybrid HYPR technique.

 
4206.   34 Free-breathing dynamic contrast-enhanced MRI of the liver with radial golden-angle sampling scheme and advanced compressed-sensing reconstruction.
Hersh Chandarana1, Li Feng1, Tobias Kai Block1, Andrew B Rosenkrantz1, Ruth P Lim1, Dewey Chu1, Daniel K Sodickson1, and Ricardo Otazo1
1Radiology, NYU Langone Medical Center, New York, NY, United States

 
Dynamic post-contrast liver MR examination is performed with Cartesian k-space sampling in a breath-hold (BH). However, this results in non-diagnostic images in patients who cannot adequately breath-hold. Purpose of this study was to compare image quality of free-breathing radial (interleaved ‘angle-bisection’ and golden angle) acquisition schemes reconstructed with either view sharing (KWIC) or joint compressed-sensing and parallel imaging reconstruction (CS-PI), to conventional BH exam. Our results demonstrate that free-breathing radial golden angle trajectory continuous acquisition scheme with CS-PI reconstruction has image quality comparable to a breath-hold exam and significantly better than interleaved radial acquisition with KWIC or CS-PI reconstruction.

 
4207.   35 k-t CaLM: CALIBRATION-LESS MULTI-COIL DYNAMIC MRI RECONSTRUCTION
Angshul Majumdar1, Rabab K Ward2, and Tyseer Aboulnasr3
1Electrical and Computer Engineering, University of British Columbia, Vancouver, British Columbia, Canada, 2Electrical and Computer Engineering, University of British Columbia, Vancouver, BC, Canada, 3Electrical and Computer Engineering, University of British Columbia

 
A method for reconstructing dynamic MRI sequence, acquired via partial parallel imaging is proposed here. The novelty of the method is that it does not require explicit or implicit knowledge of the sensitivity maps. The method is compared against k-t BLAST and k-t GRAPPA - both of which the sensitivity profile in one form or the other. Our method is as good as k-t BLAST and better than k-t GRAPPA.

 
4208.   36 A Distributed Compressive Sensing Strategy for Non-Cartesian MRI: Applications to SWIRLS CE-MRA
Joshua D. Trzasko1, Yunhong Shu2, Armando Manduca1, John Huston III2, and Matt A Bernstein2
1Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States, 2Department of Radiology, Mayo Clinic, Rochester, MN, United States

 
In non-Cartesian image reconstruction, equality data constraints cannot be explicitly enforced, which limits the applicability of popular methods like projection-onto-convex-sets (POCS) to this area. In this work, we demonstrate that they can be implicitly enforced via a specific affine projection, and discuss numerical methods for efficiently imposing them. We use this construction to develop an efficient Compressive Sensing reconstruction based on block-wise redundant sparsity constraints, which results in strong reconstruction performance. We demonstrate the proposed reconstruction strategy for CE-MRA acquired using the 3D SWIRLS trajectory.

 
4209.   37 Pseudo golden-ratio spiral imaging with gradient acoustic noise cancellation: application to real-time MRI of fluent speech
Yoon-Chul Kim1, Nassos Katsamanis1, Michael Proctor1, Shrikanth Narayanan1, and Krishna S. Nayak1
1Electrical Engineering, University of Southern California, Los Angeles, CA, United States

 
In the context of vocal tract imaging during fluent speech, golden-ratio (GR) spiral imaging has been shown to provide improved depiction of articulators over conventional spiral imaging. However, one drawback of GR imaging is incompatibility with MRI-gradient noise cancellation methods because there is no periodicity in the gradient waveforms. We apply GR spiral view order with fixed number of interleaves (i.e. pseudo GR spiral) to promote periodicity. The proposed method is well-suited to parallel imaging for acceleration thus leading to improved image quality for selection of a small temporal window and also provides adequate sound quality (and/or comparable speech alignment accuracy) compared to the conventional method.

 
4210.   38 Towards real-time MR imaging of the soft palate for clinical evaluation of velopharyngeal closure
Andrew David Scott1, Redha Boubertakh1, Malcolm Birch1, and Marc Eric Miquel1
1Clinical Physics, Barts and the London NHS Trust, London, Greater London, United Kingdom

 
Previous real-time MR studies of soft palate motion have had limited frame-rates or used complex spiral techniques. We implement and compare high frame-rate (9-20fps) 1.5T bSSFP and 3.0T SSFP sequences. Comparisons were made in healthy subjects and images were synchronised with simultaneously acquired audio recordings. SNR was higher in 3.0T acquisitions at rest, but lower during speech compared to 1.5T. 3.0T images were reliably of diagnostic quality. 1.5T images were mostly of the highest quality but frequently undiagnostic. Comparison between sequences suggested that for the assessment of soft-palate motion, high frame-rates (~20fps) are desirable at the expense of some spatial-resolution.

 
4211.   
39 In vivo simultaneous multiple 19F marker tracking using an improved 3D Golden Angle sampling scheme
Tobias Hahn1, Sebastian Kozerke1, Ruben Pellicer Guridi1,2, Werner Schwizer3, Michael Fried3, Peter Boesiger1, and Andreas Steingoetter1
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland, 2Department of Biophysics and Bioengineering, University of Barcelona, Barcelona, Spain, 3Dep. of Internal Medicine, Division of Gastroenterology and Hepatology, Zurich, Switzerland

 
This study presents the simultaneous in vivo tracking of three identical fluorine labeled capsules using an improved 3D Golden Angle based sampling scheme. Liquid fluorine marker was Perfluoro-15-crown-5-ether and capsule filling was 65µl each. In vivo SNR for different reconstruction window sizes is given. Furthermore, the effect of constrained reconstruction onto the tracking reliability is studied, by multiplication of reconstructed 3D images covering a large temporal range with dynamic 19F images. SNR comparable to other tracking methods is found and good tracking reliability from a temporal resolution of 220 ms.

 
4212.   40 Comparison between EPI and RS-EPI at high acceleration factors
Samantha J Holdsworth1, Anh T Van1, Stefan Skare2, and Roland Bammer1
1'Center for Quantitative Neuroimaging, Department of Radiology, Stanford University, Palo Alto, CA, United States, 2Clinical Neuroscience, Karolinska Institute, Stockholm, Sweden

 
Readout-Segmented EPI (RS-EPI) has been proposed in a number of studies as a variant of EPI to reduce distortion in diffusion-weighted (DW) neuroimaging. With the increasing number of coils coming available with advanced phased-array technology that increases the capacity of EPI to achieve higher acceleration factors, and with advanced distortion-correction methodology, we present preliminary data that shows that EPI may be more useful for acquisition of DWI images in clinically-acceptable scan times. Here we compare EPI and RS-EPI data acquired with the highest acceptable GRAPPA-acceleration factor that we have been using with our 32-channel coil.

 
4213.   41 MR-microimaging on a 7T whole-body scanner featuring ultrashort detection times and magnetization transfer contrast
Christian Horn1,2, Vladimir Juras1,3, Stefan Ropele4, and Andreas Berg1,2
1MR-Center of Excellence, Medical University of Vienna, Vienna, Vienna, Austria, 2Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Vienna, Austria, 3Department of Radiology, Vienna General Hospital, Medical University of Vienna, Vienna, Vienna, Austria,4Department of Neurology, Medical University of Graz, Graz, Steiermark, Austria

 
The combination of special, radial pulse sequences designed for the detection of ultra-short echo times (UTE, TEmin = 0.07 ms) with the clinically more established technique of magnetization transfer contrast promises a new image contrast in semi-solid tissue components or implants with very short T2 times (< 1 ms). A corresponding pulse sequence was evaluated on a custom designed MR microscopy gradient insert on a 7T human scanner. BSA phantoms, with different BSA to water concentrations, and biological samples were used to demonstrate the practical applicability of the sequence ex vivo.

 
4214.   42 Signal amplitude dependence on object size and shape due to T2 decay during radial k-space readout in ultrashort TE sequences: A 2D ring model.
Jing-Tzyh Alan Chiang1, Michael Carl2, Jiang Du1, and Graeme Bydder1
1Radiology, University of California San Diego, San Diego, CA, United States, 2GE Healthcare

 
We investigate the signal amplitude relationships due to T2 decay during radial k-space readout in ultrashort TE sequences, via numerical simulations on 2D rings of varying inner and outer diameters. Decreasing inner and increasing outer diameters lead to increased signal amplitudes at any given T2 value, which demonstrate important dependencies of signal amplitude on object shape and size. These results on 2D rings also serve as numerical models for analyzing T2 dependent signal and contrast in quantitative UTE techniques that utilize axial imaging of tubular bones, such as in cortical bone water quantification.

 
4215.   43 Simultaneous Bright- and Black-Blood Imaging Acquisition for Contrast-Enhanced Brain Metastasis Screening
Masami Yoneyama1, Masanobu Nakamura1, Tomoyuki Okuaki1, Takashi Tabuchi1, Atsushi Takemura2, Tetsuo Ogino2, Makoto Obara2, Thomas Kwee3, and Taro Takahara4
1Yaesu Clinic, Tokyo, Japan, 2Philips Electronics Japan, Tokyo, Japan, 3University Medical Center Utrecht, Utrecht, Netherlands, 4Tokai University School of Engineering, Kanagawa, Japan

 
Contrast-enhanced 3D-T1-weighted imaging based on GRE is widely used for detecting small brain metastases, but since contrast materials remain in both blood and the tumor parenchyma and thus increase the signal intensity of both regions, it is often challenging to distinguish brain tumors from blood. To overcome this problem, "black-blood" version of T1 weighted images based on TSE with/without MSDE are used recently, but these methods are difficult to "perfect" suppression of whole-vessel signals, and therefore the differentiation of residual blood vessel and small brain metastasis is occasionally difficult. In this study, we propose a new scheme of fast, volumetric, high-resolution, bright- and black-blood imaging simultaneous acquisition (VISIBLE). This optimal sequence can be used for 3D volumetric T1 weighted bright- and black-blood imaging, and that is promising for detecting small brain metastases, by the differentiation improvement of blood vessel and small brain metastasis.

 
4216.   44 Optimized 3D Fast Spin Echo imaging at 7T
Manojkumar Saranathan1, Michael Zeineh1, Geoffrey A. Kerchner2, Mohammad Mehdi Khalighi3, Marcus T. Alley1, and Brian K. Rutt1
1Radiology, Stanford University, Stanford, CA, United States, 2Neurology and Neurological Sciences, Stanford University, Stanford, CA, United States,3Global Applied Science Labatory, GE Healthcare, Menlo Park, CA, United States

 
Fast Spin Echo (FSE) imaging is increasingly used for fast T2 weighted imaging applications. However, at 7T, the sequence is heavily limited by SAR considerations, severely reducing its time efficiency. Flip angle modulation schemes like SPACE and XETA [1-2], have been proposed for 3D FSE that enable the use of longer echo-train-lengths and help lower SAR due to reduced refocusing flip angles. We optimized the 3D XETA refocusing flip angle train for T2 weighted brain imaging at 7T based on SAR, signal intensity, contrast and point spread function (PSF) considerations, using T1 and T2 values of white/grey matter at 7T. Additionally, we explored the use of composite excitation pulses to mitigate signal loss from B1 inhomogeneity effects. Whole brain 3D T2 imaging was performed on patients using these modifications.

 
4217.   45 High-Resolution Magnetization Transfer Compensated Dynamic Angiography Imaging at 7 Tesla
Ann-Kathrin Homagk1, Alexander Radbruch2, and Wolfhard Semmler1
1Dept. of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, 2Dept. of Neuroradiology, University Heidelberg, Heidelberg, Germany

 
In this work, we investigate the suitability of different ASL techniques for high resolution dynamic angiography imaging of the cerebral vasculature at 7 Tesla. As the basic STAR sequence is prone to magnetization transfer effects, an additional inversion pulse was inserted prior to the acquisition of the control image. Furthermore, a PICORE, a FAIR and a FAIRER sequence were implemented. The cerebral vasculature of three volunteers was imaged with an in-plane resolution of 0.57x0.57mm² using all five sequences. The acquisition time for the magnetization transfer compensated techniques was increased by up to 20%; however the visibility of peripheral vessels was improved.

 
4218.   
46 Improving the inversion efficiency in regions of low lower case Greek gammaB1 for whole brain acquisitions
Kieran O'Brien1,2, Jean Delacoste1, Jose Marques1, Tobias Kober3, Francois Lazeyras2, Rolf Gruetter1, and Gunnar Krueger3
1LIFMET-CIBM, Ecole Polytechnique Fédéral de Lausanne, Lausanne, Switzerland, 2Department of Radiology-CIBM, Université de Genève, Geneva, Switzerland, 3Advanced Clinical Imaging Technology, Siemens Suisse, Switzerland

 
In whole brain acquisitions, such as MP2RAGE, large Capital Greek DeltaB0 offsets or regions of low lower case Greek gammaB1 can suffer from poor inversion. Optimisation of adiabatic pulses to work at lower lower case Greek gammaB1, allows for better inversion profiles extending the coverage of whole brain acquisitions.

 
4219.   47 A NOVEL PULSE SEQUENCE TO MEASURE OXYGEN EXTRACTION FRACTION IN THE BRAIN USING PARAMETER ASSESSMENT USING RETRIEVAL FROM SIGNAL ENCODING (PARSE) TECHNIQUES
Rajiv G Menon1, Bradley P Sutton2, Donald B Twieg3, and Timothy J Carroll1
1Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States, 2Bioengineering Department, University of Illinois at Urbana-Champaign, Urbana, IL, United States, 3Biomedical Engineering Department, University of Alabama at Birmingham, Birmingham, AL, United States

 
We propose a novel technique for the measurement of oxygen extraction fraction (OEF) using Parameter Assessment by Retrieval from Signal Encoding (PARSE) techniques. OEF is a key indicator of cerebral perfusion and gives crucial information regarding the stage of vascular compromise in patients with neurovascular disease. PARSE is an efficient, multi-parameter estimation technique, that uses a more accurate signal model to simultaneously measure M0, R2* and local frequency. By direct measurement of local frequency changes due to OEF related susceptibility changes using PARSE, we determine the feasibility of robustly estimating OEF in pathological situations.

 
4220.   48 Translating fMRI and DTI biomarkers from academic studies to global clinical trials in Alzheimer’s Disease
Lea E Marais1, Jean-François Mangin2,3, Cyril Poupon2,3, Urielle Thoprakarn2,3, Vincent Perlbarg4, Gareth J Barker5, Xavier Golay6, Joseph V Hajnal7, Adam J Schwarz 8, and Derek Hill1
1IXICO Ltd., London, United Kingdom, 2I²BM NeuroSpin, CEA, Gif-sur-Yvette, France, 3CATI, Gif-sur-Yvette, France, 4UMR-S 678, Laboratoire d'Imagerie Fonctionnelle, Inserm and UPMC Univ Paris06, Paris, France, 5Centre for Neuroimaging Sciences, King's College London, Institute of Psychiatry, London, United Kingdom, 6MR Neurophysics and Translational Neuroscience, UCL Institute of Neurology, National Hospital for Neurology & Neurosurgery, London, United Kingdom, 7Robert Steiner MRI Unit,Imaging Sciences Department, MRC Clinical Sciences, Hammersmith Hospital, Imperial College London, London, United Kingdom, 8Translational Medicine, Eli Lilly and Company, Indianapolis, United States

 
Diffusion Tensor Imaging (DTI) and resting state functional Magnetic Resonance Imaging (rs-fMRI) biomarkers correlate with Alzheimer’s Disease stage and provide additional information on the efficacy of new treatments. Multi-centre clinical studies are essential for rapid enrolment of a sufficient number of patients. We deployed ADNI-style fMRI and DTI sequences on Philips and Siemens 3T scanners and evaluated their repeatability and reproducibility on healthy volunteers. The variability across scanners was comparable to the within-scanner variability. These sequences are thus suitable for the acquisition of comparable data in multi-site, multi-vendor clinical trials.
 
Electronic Poster Session - Pulse Sequences & Reconstruction B

Compressed Sensing/Sequences: Applications
Click on to view the abstract pdf and click on to view the video presentation. (Not all presentations are available.)
Thursday 10 May 2012
Exhibition Hall  11:30 - 12:30

  Computer #  
4221.   25 Accelerating Dynamic Contrast-Enhanced MRI Using K-T ISD
Na Zhang1,2, Guanghua Song1,2, Weiqi Liao1,2, Weijie Tao1,2, Leslie Ying3, and Dong Liang1,2
1Paul C. Lauterbur Research Centre for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China, 2Key Laboratory of Health Informatics, Chinese Academy of Sciences, Shenzhen, Guangdong, China, 3Department of Electrical Engineering and Computer Science, University of Wisconsin-Milwaukee, Milwaukee, WI, United States

 
The emerging CS-based methods have shown promising performance for accelerating DCE-MRI. In this work, the potential of k-t Iterative Support Detection (k-t ISD, a recently proposed dynamic imaging method based on CS with partial known support theory) in accelerating DCE-MRI is investigated and compared to the sliding window (SW) method. The superiority of this method to conventional CS methods has been demonstrated on cardiac cine imaging. The reconstruction results and statistical analysis indicate that k-t ISD can faithfully reconstruct the uptake curves and improve temporal resolution of DCE-MRI without compromising the spatial resolution, when a high net reduction factor is used.

 
4222.   26 Investigation of Spatial and Temporal Fidelity of HYPR Processing Using a Motion Phantom
L. Keith1, M. Rahimi2, J. Holmes3, K. Wang3, J. Brittain3, and F. Korosec1,4
1Medical Physics, University of Wisconsin-Madison, Madison, WI, United States, 2Biomedical Engineering, University of Wisconsin - Madison, Madison, WI, United States, 3Global Applied Science Laboratory, GE Healthcare, 4Radiology, University of Wisconsin - Madison, Madison, WI, United States

 
In this work, an experimental setup has been designed in which a computer-controlled motion stage is used to translate an object through the imaging FOV during data acquisition in an attempt to mimic a bolus of contrast material traveling through vasculature. Since the motion is computer controlled and the dynamic elements of the phantom are well-defined with sharp edges, the input to the HYPR process is well-known. We conduct two experiments: Experiment 1 investigates the temporal and spatial fidelity of HYPR processing; Experiment 2 compares the fidelity of HYPR against that of current clinical MRA techniques.

 
4223.   27 Evaluation of Compressed Sensing MR Reconstruction Quality Using Signed Just Noticeable Difference (JND) Analysis
Michelle Yan1, Jeff Johnson1, Xiao Chen2, Li Pan2, Ti-Chiun Chang1, Yunqiang Chen1, and Tong Fang1
1Siemens Corporate Research, Princeton, NJ, United States, 2Center for Applied Medical Imaging, Siemens Corporate Research, Baltimore, MD, United States

 
We propose to incorporate human perception model into assessing the quality of compressed sensing MR reconstruction algorithms. More specifically, we seek to measure the perceptual changes or degradation in reconstructed MR images using the signed just noticeable difference (JND) analysis, providing an overall “quality” color map or score for each MR image under consideration. Red color indicates positive (added) changes; blue color indicates negative (lost) changes. The lighter a JND map in color, the better a reconstruction method performs. The result has demonstrated potential value of JND maps in assessing image quality and comparing the overall performance of MR reconstruction methods.

 
4224.   28 Comparison of Wavelet Subband Decomposition Methods for High-Frequency Subband CS
Kyunghyun Sung1, Anderson N Nnewihe1,2, Bruce L Daniel1, and Brian A Hargreaves1
1Radiology, Stanford University, Stanford, CA, United States, 2Bioengineering, Stanford University, Stanford, CA, United States

 
Compressed sensing (CS) is a technique that allows accurate reconstruction of images from a reduced set of acquired data. Here, we describe two wavelet subband decomposition methods for High-frequency Subband CS, which enable to employ selective application of different undersampling patterns and reconstructions in different k-space regions. Two wavelet decomposition methods are evaluated in high-resolution T1- and T2-weighted 3D breast imaging with extremely high acceleration factors.

 
4225.   29 A Novel Compressed Sensing Approach to Accelerated Quantitative MRI Using Model-Driven Adaptive Sparsifying Transforms
Julia V Velikina1, and Alexey A Samsonov2
1Medical Physics, University of Wisconsin - Madison, Madison, Wisconsin, United States, 2Radiology, University of Wisconsin - Madison

 
We propose a novel model-driven compressed sensing approach for T1 relaxometry. The proposed algorithm alternates signal estimation with adaptive update of sparsifying transform based both on the analytical signal model and current signal estimate. The proposed algorithm can also be used in other quantitative MRI applications.

 
4226.   30 Compressed Sensing Sodium MRI in Cartilage at 7T: Preliminary Study
Guillaume Madelin1, Gregory Chang1, Alexej Jerschow2, Ricardo Otazo1, and Ravinder R Regatte1
1Radiology Department, New York University Medical Center, New York, NY, United States, 2Chemistry Department, New York University, New York, NY, United States

 
Quantitative sodium MRI is highly specific to the glycosaminoglycan content in cartilage and could be used to assess the biochemical degradation of cartilage in early stages of osteoarthritis. However, due to low sodium NMR sensitivity and its low concentration, sodium images need long acquisition times (15 to 25 min, respectively without and with fluid suppression) at 7T and are typically of low resolution. In this preliminary study, we show that compressed sensing can be applied to reconstruct undersampled sodium images and reduce the acquisition time by a factor of 2 at 7T without losing sodium quantification accuracy.

 
4227.   31 A novel undersampling scheme for data acquisition in non k-space domains
Sebastian Weingärtner1, Friedrich Wetterling1, and Lothar R. Schad1
1Computer Assisted Clinical Medicine, University Medical Center Mannheim, University of Heidelberg, Mannheim, Germany

 
The purpose of this study was to develop a novel undersampling scheme, for the case that acquisition does not take place in the k-space. To achieve this, an acquisition scheme that parallels a binary search algorithm was developed. By scanning successively the sum of several coefficients in a sparse image transformation domain high undersampling factors can be reached. The algorithm was evaluated and showed only minor differences for undersampling with up to 4% of the data. These results can be achieved by an acquisition in a sparse-domain and do not need compressed sensing post-processing.

 
4228.   32 3D TV-Based Compressed MR Image Reconstruction Using a Primal Dual Algorithm
Abolfazl Mehranian1, Hamidreza Saligheh Rad1,2, Mohammadreza Ay1,2, and Arman Rahmim3
1Medical Physics and Biomedical Engineering Department, Tehran University of Medical Sciences of Medical Sciences, Tehran,Iran, Tehran, Tehran, Iran,2Research Center for Science and Technology in Medcine, Imam Hospital, Tehran, Tehran, Iran, 3Department of Radiology, School of Medicine, Johns Hopkins University, Baltimore, Maryland, United States

 
The compressive sensing (CS) of spirally encoded MR acquisitions makes it possible to significantly reduce the scanning time in 3D MR imaging techniques. In this work, we studied an efficient primal-dual algorithm for 3D total variation (TV) and Huber-based compressed MR image reconstruction. We tailored this algorithm for TV and Huber regularizations in 3D and made use of a stack of variable-density spiral trajectories for 80% k-space undersampling. In a volumetric cardiac dataset, it was demonstrated that the derived algorithm objectively outperforms several state-of-the-art algorithms and thus can have promising clinical implications in fast MR imaging.

 
4229.   33 A GA Guided K-space Sampling for Compressed Sensing MRI
Hua Wang1, Yeyang Yu1, Bing Keong Li1, Adnan Trakic1, Mingjian Hong2, Feng Liu1, and Stuart Crozier1
1The University of Queensland, Brisbane, QLD, Australia, 2ChongQing University, ChongQing, China

 
In this work, we presented a method to optimise the k-space sampling scheme for CS-MRI. The problem was simplified by treating the variable density functions in parts, and optimising the weighting factors with GA. A 2D brain and a 3D apple MRI image reconstruction illustrates an improved imaging quality with this method.

 
4230.   34 A multi-lattice sampling approach for highly undersampled phase contrast carotid blood velocity mapping
Gabriel Rilling1, Yuehui Tao2, Mike E. Davies1, and Ian Marshall2
1School of Engineering, University of Edinburgh, Edinburgh, Scotland, United Kingdom, 2Medical Physics, University of Edinburgh

 
A novel model-based undersampling and reconstruction framework is proposed for phase contrast carotid blood velocity mapping. It is based on splitting the space-frequency support of the signal into two elementary blocks and use a combination of two sampling lattices adapted to each block. This multi-lattice sampling approach is intermediate between lattice and random sampling, allowing more flexibility and acceleration than the former and better noise robustness than the latter. Combined with the "keyhole" technique, it allows up to 12X acceleration with limited distortion. Simulation and in vivo undersampling experiments at 12X and 8X acceleration validate the proposed method.

 
4231.   35 Optimizing Spars 3D-MRI using Cubic Compressed Sensing Reconstruction Method
Jian-Xiong Wang1
1Applied Science Laboratory, GE Healthcare, London, ON, Canada

 
This work demonstrated that true 3D, or Cubic, Compressed Sensing reconstruction method not only reduced the computation time by about a factor of two, but also greatly increased image quality for Sparse MRI.

 
4232.   36 Improved Compressed Sensing Reconstruction with Overcomplete Wavelet Transforms
Alicia W Yang1,2, Li Feng1,2, Jian Xu3,4, Ivan Selesnick4, Daniel K Sodickson1, and Ricardo Otazo1
1Department of Radiology, New York University School of Medicine, New York, NY, United States, 2Sackler Institute for Biomedical Sciences, New York University, New York, NY, United States, 3Siemens Medical Solution USA Inc, New York, United States, 4Polytechnic Institute of New York University, New York, United States

 
An adaptive decreasing thresholding method is developed to take into consideration the structure of overcomplete transforms by (1) using local thresholds that adapt to the signal power in each band and (2) decreasing the threshold for each step of the iterative reconstruction algorithm. The performance of this method in dual-tree wavelet transforms and curvelets was tested on compressed sensing reconstructions of retrospectively undersampled 3D coronary MRA and brain image datasets, and compared to that of standard Haar wavelet transforms.

 
4233.   37 Dynamic 3D MRI of upper airway collapse during inspiratory loading
Yoon-Chul Kim1, R. Marc Lebel1, Michael C.K. Khoo2, and Krishna S. Nayak1
1Electrical Engineering, University of Southern California, Los Angeles, CA, United States, 2Biomedical Engineering, University of Southern California, Los Angeles, CA, United States

 
Imaging of upper airway dynamics can give new insights into the mechanisms of airway obstruction and provide data for its modeling. Conventional MRI is not fast enough to capture the entire airway volume and its dynamics. We demonstrate dynamic 3D imaging of the airway during inspiratory loading using 3D Cartesian imaging with golden-angle temporal view order and L1-SPIRiT reconstruction, to achieve 1.6 mm isotropic spatial and sub-second temporal resolution. The end result is a first-ever visualization of airway collapse using real-time 3D MRI.

 
4234.   38 T1 Mapping of the Lungs Using DESPOT1 Approach with 3D Radial UTE Acquisition
L.C. Bell1, K.M. Johnson2, S.B. Fain1, S.J. Kruger1, and S.K. Nagle1,2
1Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, United States, 2Radiology, University of Wisconsin-Madison, Madison, Wisconsin, United States

 
Various techniques currently in place for T1 mapping of the lung parenchyma are limited by the low signal in the lungs. Recent developments have shown that sequences utilizing an ultra-short echo time are capable of acquiring MR signal in small animal lung parenchyma. We propose to use a 3D Radial UTE acquisition in conjunction with DESPOT1 to produce T1 maps of human lung parenchyma with sufficient signal while still maintaining high isotropic spatial resolution for functional and structural analysis.

 
4235.   39 Parallel imaging accelerated susceptibility imaging with no SNR penalty
Bing Wu1, Wei Li2, and Chunlei Liu2
1GE heathcare, Beijing, China, 2Brain Imaging and analysis center, Duke University

 
Susceptibility imaging with SPGR is a considerably long imaging process which limits its clinical feasibility. Acceleration with parallel imaging, however, degrades the SNR in the resulting susceptibility map. In this work, additional data acquisitions are made in the otherwise wasted empty echo space in front of the readout. The SNR improvement gained through multi-echo averaging has been shown to completely offset the SNR loss incurred at an acceleration factor of 4, showing visibly even better SNR than fully sampled dataset at a single TE.

 
4236.   40 Rapid and tissue specific susceptibility imaging with multi-echo multi-shot EPI acquisition
Bing Wu1, Wei Li2, Nankuei Chen2, and Chunlei Liu2
1GE heathcare, Beijing, China, 2Brain Imaging and analysis center, Duke University

 
Susceptibility imaging with standard SPGR is a considerably long imaging process which limits its clinical feasibility. Spiral acquisition has been proposed as an alternative to achieve rapid susceptibility imaging. However, spiral trajectory places demanding requirements on the gradient system and is not usually available on commercial scanners. In addition, spiral trajectory is very sensitive to susceptibility distortions. In this work, a multi-echo multi-shot EPI sequence is implemented and used for susceptibility imaging. The result shows that, given the same acquisition time, EPI leads to a susceptibility map with less distortion compared to that of spiral acquisition.

 
4237.   41 Optimisation of T2*-weighted MRI for differential diagnosis of MS at clinical field strengths
Jennifer E Dixon1, Ashley I Simpson2, Niraj Mistry2, Nikos Evangelou2, and Peter G Morris1
1Sir Peter Mansfield Magnetic Resonance Centre, University of Nottingham, Nottingham, Nottinghamshire, United Kingdom, 2Academic Division of Clinical Neurology, University of Nottingham, Nottingham, Nottinghamshire, United Kingdom

 
7T T2*-weighted MRI has been shown to allow differentiation between MS lesions and microangiopathic white-matter (WM) lesions by the presence of a visible vein, and accurately predicts eventual diagnosis in patients who were otherwise unable to be diagnosed without further testing; however, the limited availability of 7T systems necessitates the translation of this technique to lower field. The aim of this work is to increase its sensitivity at 3T and 7T, and to compare the optimised sequences theoretically and experimentally in order to quantify the benefit of imaging at higher field, and to enable its use at clinical field strengths.

 
4238.   42 Positive Contrast Imaging of Microhemorrhages in Patients with Traumatic Brain Injury
Wei Liu1,2, Qun Zhao3, Haiying Tang4, Binquan Wang1,2, Ping-Hong Yeh1,2, Dominic E Nathan1,2, John Graner1, Hai Pan1,2, Rachel Wolfowitz1,2, Jamie Harper1, Louis M French5, Terry R Oakes1, and Gerard Riedy1
1National Neuroimaging Consortium, National Intrepid Center of Excellence, Bethesda, MD, United States, 2Henry M Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, United States, 3Department of Physics and Astronomy, University of Georgia, Athens, GA, United States,4Uniformed Services University of the Health Sciences, Bethesda, MD, United States, 5Walter Reed National Military Medical Center, Bethesda, MD, United States

 
Two positive contrast techniques using phase gradient mapping (PGM) and susceptibility gradient mapping (SGM) were investigated as complementary approaches of susceptibility weighted imaging (SWI) for microhemorrhage detection in patients with combat related traumatic brain injury. The results demonstrated that PGM and SGM improved the CNR for the local regional of interest and might provide additional information for diagnosis.

 
4239.   43 Application of T1-weighted contrast enhancement in EPRI/MRI co-imaging of isolated rat heart
Ziqi Sun1, Sergey Petryakov1, Wael F Alzawahra1, and Jay L Zweier1
1Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio, United States

 
T1-weighted (T1W) contrast enhancement using free radical probe as the contrast agent is applied for EPRI/MRI co-imaging of isolated rat hearts. Hyper-intense signal intensity was observed in the right-ventricle of the rat heart in the 3D T1W image, which is consistent with the greater signal intensity shown in the low resolution 3D EPRI image overlaid onto the high resolution 3D T1W image. This result indicates that high resoltion T1-weighted MRI technique is useful in accurately dipicting free radical probe distribution within tissue in EPRI/MRI co-imaging experiments.

 
4240.   44 Practical multi-mode cardiac MRI of mice and rats on a 3T clinical scanner
Ronald J. Beyers1, Nouha Salibi1,2, Rajesh Amin3, John C Quindry4, and Thomas S Denney1
1MRI Research Center, Electrical Engineering, Auburn University, Auburn, AL, United States, 2Healthcare, USA, Siemens Corporation, United States,3Harrison School of Pharmacy, Auburn University, Auburn, AL, United States, 4Department of Kinesiology, Auburn University, Auburn, AL, United States

 
Introduction: Need for cardiac MRI in rodents on clinical scanner with: 1) bright & dark blood cine, and 2) inversion recovery (IR), late gadolinium enhanced (LGE) & look-locker (LL) T1-mapping. Methods: Sequence developed ran on a Siemens 3T Verio. Included adjustable TR loops, multislice GRE, and RF preparations including: 1) DIR for dark blood, and 2) IR prep. Imaged C57BL/6 mice and Wistar rats, anesthesized by isoflurane, and ECG/respiratory tiggered. Results: Cine time was approximately equal4-6 minutes. Wrist coil provided sufficient signal. Cine provided good volumetrics and wall thickness. IR LL on a water-deprived mouse estimated myocardial T1 = 662 ms. The IR LGE made 6-slice acquisition in approximately equal13 minutes.

 
4241.   45 Reproducibility of myocardial T1 estimation with modified CINE-IR in rat myocardium at 7T
Henk Smit1, A. Ruggiero1, G.N. Doeswijk1, M. Milanesi2,3, G.C. Houston4, M.R. Bernsen1, G.P. Krestin1, S. Klein1, and G. Kotek1
1Erasmus MC, Rotterdam, Zuid Holland, Netherlands, 2Agilent Technologies UK Ltd., 3MRI Lab, Fondazione G. Monasterio-CNR, Pisa, Italy, 4GE Healthcare, Netherlands

 
This work addresses the feasibility, accuracy and the sensitivity of a novel T1 mapping method in rat myocardium at 7.0 T. With the modified Cine Inversion Recovery (mCINE-IR), the effective TR can be adjusted to allow much higher longitudinal recovery between two subsequent inversions pulses than with conventional methods. Furthermore the magnetization recovery is monitored by the CINE loop acquisition for the entire number of RR intervals within the chosen TR. The results show that mCINE-IR offers a reproducible T1 estimation of both healthy tissue and injected Gd labelled cells in the rat myocardium at 7T making longitudinal studies feasible.

 
4242.   46 Residual blood signal elimination on T1W non-gated radial scan for MR carotid plaque imaging
Takashi Nishihara1, Hikaru Hanada1, Kuniharu Oka1, Masahiro Takizawa1, Chikako Moriwake2, Hiroyuki Itagaki1, Tetsuhiko Takahashi1, Yosuke Hirata3, and Makoto Sasaki4
1MRI System Division, Hitachi Medical Corporation, Kashiwa, Chiba, Japan, 2Marketing Division, Hitachi Medical Corporation, Tokyo, Japan, 3Center for Radiological Sciences, Iwate Medical University Hospital, Morioka, Iwate, Japan, 4Division of Ultrahigh Field MRI, Institute for Biomedical Sciences, Iwate Medical University, Morioka, Iwate, Japan

 
Non-gated T1W plaque imaging has been proposed for evaluating plaque characteristics. To improve image quality, we introduced flow dephasing pulses to eliminate residual blood signal and evaluated it. We determined the b value of flow dephasing pulses which can eliminate flow signal, and the ratio P of the asymmetric sampling that doesnft affect spatial resolution. We applied the determined P value of 8% and b value of 0.4s/mm2 to volunteer imaging. The residual flow signal in ICA was eliminated and image resolution was not affected. We achieved a good contrast for plaque imaging by using non-gated radial sampling SE sequence.

 
4243.   47 In Flow Effects in Alternating Differenced Balanced Steady State Free Precession Imaging: A Brain Study
Neville D Gai1, and John A Butman1
1Radiology & Imaging Sciences, National Institutes of Health, Bethesda, MD, United States

 
Alternating excitation and/or phase perturbed balanced SSFP provides highly localized variations in magnetization. The technique has been recently proposed as a means to provide positive contrast imaging. Here, the inflow effect is studied in relation to the technique. Simulations and in-vivo imaging in the brain show that blood as well as CSF pulsatility can be a confounding factor when using the sequence for positive contrast imaging. Means to reduce inflow effects need to be developed.

 
4244.   48 Assessing phase variations in gradient induced spatial modulation of magnetization (SPAMM)
Lukas Pirpamer1, Gernot Reishofer2, and Stefan Ropele1
1Department of Neurology, Medical University of Graz, Graz, Styria, Austria, 2Department of Radiology, Medical University of Graz, Graz, Styria, Austria

 
Non-linearities of gradient fields can cause a shift of the modulation function when SPAMM is used for image tagging. For certain application such as high resolution imaging with the microSPAMM technique, these shifts can seriously affect image reconstruction even if they are small. In this experimental work a new method for assessing these gradient induced variations of the modulation function is proposed. First phantom measurements demonstrate the feasibility and the advantage over existing methods.
 
Electronic Poster Session - Pulse Sequences & Reconstruction B

Image Reconstruction & Saturation Transfer Imaging
Click on to view the abstract pdf and click on to view the video presentation. (Not all presentations are available.)
Thursday 10 May 2012
Exhibition Hall  10:30 - 11:30

  Computer #  
4245.   49 Data Decoupling for Efficient Auto-Calibrating Parallel Imaging for Arbitrary Cartesian k-space Sampling: Application to Highly-Accelerated 3D Cardiac Cine MRI
Peng Lai1, and Anja C.S Brau1
1Global Applied Science Laboratory, GE Healthcare, Menlo Park, CA, United States

 
This work develops a novel source data decoupling method for computationally efficient auto-calibrating parallel imaging for arbitrary Cartesian sampling and validates its performance on 3D cardiac cine MRI with different acceleration factors and different coils. Our computation analysis shows that the proposed method can dramatically reduce calibration time compared to conventional autocalibrating parallel imaging methods, especially with large numbers of coil channels and synthesis patterns. Our invivo results on cardiac cine MRI also show the decoupling method preserves image quality of conventional kt GRAPPA and provides more accurate reconstruction and higher SNR than GRAPPA operator based methods due to its optimal combination of syntheses from different source data groups. The proposed data decoupling method is promising for online reconstruction for 3D cardiac cine MRI and other static 3D MRI applications.

 
4246.   50 High quality Real-Time Cardiac MRI using Self-Calibrating Radial GRAPPA with Sparsification
Felix Breuer1, Philipp Ehses2,3, Nicole Seiberlich4, Martin Blaimer1, Peter Jakob1,5, and Mark Griswold4
1Reserch Center Magnetic Resonance Bavaria, Würzburg, Germany, 2Max Planck Institute for Biological Cybernetics, Tübingen, Germany, 3Dept. for Neuroimaging, University Hospital Tübingen, Tübingen, Germany, Tübingen, Germany, 4Dept. of Radiology, Case Western Reserve University and University Hospitals of Cleveland, Cleveland, Ohio, United States, 5Experimental Physics 5, University of Würzburg, Würzburg, Germany

 
In this work an improved self-calibrating radial GRAPPA algorithm for real-time cardiac MRI is presented. It is shown that by subtracting the temporal average prior to the parallel MRI reconstruction significantly improved image quality can be achieved over pure radial GRAPPA. Real-time cardiac imaging data at a frame rate of 20fps in 2mm in-plane resolution are shown using only 16 radial projections per frame.

 
4247.   51 Parallel Reconstruction Observing Self consistency and Temporal smoothness (PROST)
Mitchell A Cooper1,2, Thanh D Nguyen2, Pascal Spincemaille2, Keigo Kawaji1,2, Jonathan W Weinsaft3, Martin R Prince2, and Yi Wang1,2
1Biomedical Engineering, Cornell University, Ithaca, New York, United States, 2Radiology, Weill Cornell Medical College, New York, New York, United States,3Cardiology, Weill Cornell Medical College, New York, New York, United States

 
PROST (Parallel Reconstruction Observing Self consistency and Temporal smoothness) is a SPIRiT based paralell imaging technique implemented by extending the SPIRiT self-consistency kernel to the time domain. PROST is based on the assumption that each temporal phase has small changes with respect to its neighbors (temporal smoothness). PCA is incorporated into PROST to further express the information redundancy in the temporal dimension. PROST improves error performance compared to regular SPIRiT. When used for CINE imaging, PROST gives similar ejection fraction values compared to fully sampled data.

 
4248.   52 Accelerated Dynamic MRI Using Multicoil Low-Rank Matrix Completion
Ricardo Otazo1, Cagdas Bilen2, Yao Wang2, Leon Axel1, and Daniel K Sodickson1
1Bernard and Irene Schwartz Center for Biomedical Imaging, NYU School of Medicine, New York, NY, United States, 2Department of Electrical Engineering, Polytechnic Institute of NYU, Brooklyn, NY, United States

 
Low-rank matrix completion is proposed as a new generalized approach to combining compressed sensing and parallel imaging by jointly exploiting implicit temporal and coil correlations without an explicit sparsifying transform or coil calibration procedure. A low-rank k-t matrix can be obtained by concatenating overlapping k-space blocks from consecutive time points and multiple coils to form the different columns. Reconstruction of k-t undersampled data is performed using an iterative singular value thresholding algorithm. We demonstrate the feasibility of reconstructing undersampled cardiac cine data.

 
4249.   53 Dynamic cardiac MRI reconstruction with weighted redundant Haar wavelets
Jun Liu1, Jeremy Rapin1, Ti-chiun Chang1, Alban Lefebvre1, Michael Zenge2, Edgar Mueller2, and Mariappan S. Nadar1
1Siemens Corporate Research, Princeton, NJ, United States, 2Siemens AG, Healthcare Sector, Erlangen, Germany

 
High temporal resolution is often desired in Cardiac Magnetic Resonance Imaging (CMRI). Parallel imaging enables the reconstruction with a reduced the number of acquired frequencies, hence accelerating the acquisition, and spiral sampling scheme is widely used in CMRI. In this work, a new approach was proposed for dynamic cardiac MRI reconstruction by applying an L1 regularization based on the weighted 3D redundant Haar wavele for incorporating the smoothness in both spatial and temporal directions. Experiments conducted on a CMRI data with only 15 spokes for each temporal phase demonstrated the effectiveness of the proposed approach.

 
4250.   54 Comparing k-t SENSE and Auto-Calibrating k-t SENSE Transfer Functions
Irene Paola Ponce Garcia1, Martin Blaimer2, Felix Breuer2, Peter M Jakob1,2, and Peter Kellman3
1Department of Experimental Physics 5, University of Würzburg, Würzburg, Bavaria, Germany, 2Research Center Magnetic Resonance Bavaria (MRB), Würzburg, Bavaria, Germany, 3Laboratory of Cardiac Energetics, National Institutes of Health, National Heart, Lung and Blood, Bethesda, Maryland, United States

 
In Dynamic Parallel Magnetic Resonance Imaging (pMRI) there are many reconstruction methods aiming to speed up acquisition and accurate reconstructions with high temporal and spatial resolution. It has been demonstrated that comparing to conventional k-t SENSE approach, Auto-Calibrating k-t SENSE saves acquisition time. Even though Auto-Calibrating k-t SENSE has been compared to conventional k-t SENSE, the comparison of the filter performing by both of them has not been jet evaluated. In this work, the performance in the temporal frequency of conventional and Auto-Calibrating k-t SENSE was evaluated using the 2-D Modulated Transfer Function (MTF).

 
4251.   55 Fast Approximators for Least-Norm Reconstructions of Undersampled Non-Cartesian MRI Data
Joshua D. Trzasko1, Yunhong Shu2, Armando Manduca1, and Matt A Bernstein2
1Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States, 2Department of Radiology, Mayo Clinic, Rochester, MN, United States

 
Least-norm reconstruction of undersampled Cartesian MRI data, often referred to a “zero filling”, remains a popular strategy due to its simple and efficient implementation, and readily-characterized behavior. For non-Cartesian MRI, however, determination of an analogous reconstruction is computationally demanding and requires iterative methods that may be impractical for clinical use. In this work, we propose a novel and efficient numerical framework based on positive semi-definite constrained least-squares regression for generating accurate, non-iterative (i.e., direct) approximators of least-norm reconstructions of non-Cartesian MRI data.

 
4252.   56 Noise from non-cone regions in segmented k-space contributes to artifacts in Quantitative Susceptibility Mapping
Shuai Wang1,2, Tian Liu3, Weiwei Chen4, Pascal Spincemaille2, and Yi Wang2,5
1University of Electronic Science and Technology of China, Cheng Du, Si Chuan, China, 2Radiology, Weill Cornell Medical College, New York, New York, United States, 3MedImageMetric LLC, New York, New York, United States, 4Radiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science&Technology, Wuhan, Hubei, China, 5Biomedical Engineering, Cornell University, Ithaca, New York, United States

 
Several Quantitative Susceptibility Mapping (QSM) methods have been proposed to obtain tissue magnetic susceptibility in vivo. We compared various QSM methods in order to identify a robust QSM for clinical applications. We found that noise from the non-cone region in k-pace where the dipole inversion has been regarded as well behaved can contribute to substantial streaking artifacts in QSM. An accurate QSM needs address noise in the entire k-space, and not just the cone region. Evaluation on 21 consecutive patients indicated that the image space based morphology enabled dipole inversion is the most robust among three evaluated methods.

 
4253.   57 Correlation-based reconstruction using coil sensitivity information and image content similarity
Yu Li1, Feng Huang2, Wei Lin2, Randy Duensing2, and Charles L. Dumoulin1
1Imaging Research Center, Radiology Department, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, United States, 2Invivo Diagnostic Imaging, Philips HealthCare, Gainesville, Florida, United States

 
The presented work aims to overcome the parallel imaging acceleration limit posed by spatial encoding capability of multi-channel coil sensitivity in clinical MRI. A previously reported framework of "correlation-based reconstruction" is used to convert high-speed imaging reconstruction to the estimation of correlation functions that may include multiple data correlation mechanisms underlying parallel acquisition. In the work presented here, we investigated whether coil sensitivity information and image content similarity can synergistically benefit correlation-based reconstruction for a static MRI scan.

 
4254.   58 Restoration of within-FOV aliasing in Propeller MRI using kt-Blast
Su-Chin Chiu1, Hing-Chiu Chang2, Tzu-Chao Chuang3, Fu-Nien Wang4, and Hsiao-Wen Chung1
1Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan, 2GE Healthcare, Taiwan, 3Electrical Engineering, National Sun Yat-Sen University, Taiwan, 4National Tsing Hua University, Taiwan

 
The FOV of Propeller MRI is approximately circular due to the rotating blade sampling pattern in the k-space, causing within-FOV aliasing artifact. In this article we proposed a self-training method similar to kt-Blast to restore the aliasing artifact to the conventional rectangular FOV. Phantom experiments were performed to verify the proposed method. Results show good agreement with conventional Cartesian sampling.

 
4255.   59 T1FLAIR PROPELLER with parallel imaging using simultaneous crossed blade calibration APPEAR
James H Holmes1, Philip J Beatty2,3, Howard A Rowley4, Zhiqiang Li5, and Jean H Brittain1
1Global Applied Science Laboratory, GE Healthcare, Madison, WI, United States, 2Global Applied Science Laboratory, GE Healthcare, Thornhill, ON, Canada,3Physical Sciences, Sunnybrook Research Institute, Toronto, Ontario, Canada, 4Radiology, University of Wisconsin-Madison, Madison, WI, United States,5MR Engineering, GE Healthcare, Phoenix, AZ, United States

 
PROPELLER imaging with external calibration data driven parallel imaging acceleration has been shown to generate high T1 contrast while yielding sufficient blade width for robust motion correction. In this work, we present a crossed blade calibration method that enables greater imaging blade accelerations and decreased acquired echo trains for improved T1 contrast. Results from a PROPELLER acquisition with blades using echo trains of 7 and 3x effective acceleration for an effective blade width of 19 phase encodes are demonstrated to provide improved T1 contrast while maintaining wide blades for motion correction.

 
4256.   60 Reconstruction of 3D Radial MRI with Linogram Sampling
Naoharu Kobayashi1, Djaudat Idiyatullin1, Curtis A Corum1, and Michael Garwood1
1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, United States

 
Linogram sampling, introduced to radial MRI about 20 years ago, is a “semi-Cartesian” k-space sampling method, where the sampling pattern is a concentric square (2D) or cubic grid (3D). For linogram sampling, there is a corresponding reconstruction algorithm known as linogram reconstruction that does not need explicit interpolation and simplifies the Jacobian calculation, i.e. density correction. Therefore, linogram reconstruction has potential to improve resolution, minimize interpolation errors, and reduce computational time. In this study, we show point spread functions and reconstructed images from 3D linogram data that were calculated with the three reconstruction methods: gridding, backprojection and linogram reconstruction.

 
4257.   61 Theoretical and Experimental Investigation of Imaging 2D Interslice MT Ratio Asymmetry
Sung-Hong Park1, Jeffrey W. Barker1,2, and Kyongtae Ty Bae1
1Radiology, University of Pittsburgh, Pittsburgh, PA, United States, 2Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States

 
Alternate Ascending/Descending Directional Navigation (ALADDIN) is a new imaging technique that provides interslice magnetization transfer (MT) asymmetry images with no separate preparation pulse. In this article, we investigated the ALADDIN MT asymmetry at various flip angles. The MT asymmetry signals peaked at around 60 degree. Centric phase encode order provided about twice higher MT asymmetry signals than linear phase encode order. Experimental results agreed with simulations results. The simulation results also showed that MT asymmetry signals decay with RF excitations faster at higher flip angle. The results of the study expand our knowledge on the interslice MT asymmetry signals.

 
4258.   62 Optimization of Saturation Pulse Length in Parallel Transmission based Amide Proton Transfer MRI for Oncology Applications
Jochen Keupp1, Osamu Togao2, Jinyuan Zhou3, Yuriko Suzuki4, and Takashi Yoshiura2
1Philips Research, Hamburg, Germany, 2Department of Clinical Radiology, Kyushu University, Fukuoka, Japan, 3Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States, 4Philips Electronics Japan, Tokyo, Japan

 
Amide proton transfer (APT) offers a novel route to sensitive MR molecular imaging of endogenous cytosolic proteins and is expected to play an important role in delineation/classification of active tumor tissue for therapy planning/monitoring. The length of RF saturation (Tsat) is a key for sensitivity, in particular at low protein concentrations. With novel parallel transmission based techniques, Tsat>1s is possible on clinical scanners. A thorough protocol optimization is needed for tumor contrast and contrast-to-noise ratio. In a phantom study and acquiring first exemplary clinical brain tumor data, the effect of Tsat on the APT contrast is studied in the range of Tsat=0.5s up to 4s.

 
4259.   63 An automatic real-time optimization of MT off-resonance frequency
Jyun-Ming Tsai1, Teng-Yi Huang1, Hsu-Hsia Peng2, Yi-Chun Wu3, and Fu-Nien Wang2
1Electrical Engineering, National Taiwan University of Science and Technology, Tapei, Taiwan, 2Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, Taiwan, 3Molecular Imaging Center, Chang Gung Memorial Hospital, Taoyuan, Taiwan

 
This study presents an automatically real-time feedback optimization for frequency adjustment of magnetization transfer imaging. We proposed a general framework that can automatically optimize MT frequency based on the obtain image. The optimization can account for a whole field-of-view or a specific region-of-interest (ROI). We demonstrate this system by an experiment calibrating the central frequency of MT pulse for a ROI. The system was tested on a rabbit leg muscle. The frequency obtained by the real-time system was consistent with that obtained by a long sweep frequency scan. We therefore concludes the proposed system is a potential useful tool for MT-related studies, such as APT imaging.

 
4260.   64 Analyzing the Minimum Discretization of Pulses Required to Speed Up Model-based Analysis for Pulsed CEST
Yee Kai Tee1, Alexandr A Khrapichev2, Manus J Donahue3, Nicola R Sibson2, Stephen J Payne1, and Michael A Chappell1,4
1Department of Engineering Science, Institute of Biomedical Engineering, University of Oxford, Oxford, Oxfordshire, United Kingdom, 2Department of Oncology, CR-UK/MRC Gray Institute for Radiation Oncology & Biology, University of Oxford, Oxford, Oxfordshire, United Kingdom, 3School of Medicine, Vanderbilt University, Nashville, Tennessee, United States, 4Oxford Centre for Functional MRI of the Brain, University of Oxford, Oxford, Oxfordshire, United Kingdom

 
Discretizing the Gaussian pulses in pulsed CEST has been used recently as a way to calculate stimulated spectra. So far, different number of discrete intervals has been applied to perform the task. Since the number of intervals correlates directly to the computational time required, it is important to use the minimal discretization for efficient processing. In this study, simulations were used to calculate the minimal intervals required across a range of pulse parameters and the optimal values were then used to fit both in vitro and in vivo data. Excellent fits were found with minimum processing time.

 
4261.   65 A simple and fast method for solving the time-dependent Bloch equations in spin-locked chemical exchange saturation transfer (CESTrho) magnetic resonance imaging
Kenya Murase1, and Shigeyoshi Saito1
1Department of Medical Physics and Engineering, Osaka University Graduate School of Medicine, Suita, Osaka, Japan

 
We present a simple and fast method for solving the time-dependent Bloch equations in spin-locked chemical exchange saturation transfer (CESTrho) MRI using the 2-pool CEST model, and for calculating the longitudinal relaxation time in the rotating frame (T1lower case Greek rho). When using the population-averaged longitudinal (R1) and transverse relaxation rates (R2), the T1lower case Greek rho values obtained by our method agreed with the approximate solutions given by Trott and Palmer, except for the on-resonance SL case. When the population-averaged R1 and R2 were not used, some differences were observed between them. Our method will be useful for better understanding and optimization of CESTrho MRI.

 
4262.   66 Analytical Description of Magnetization Transfer Effects on the Transient Phase of Balanced SSFP
Monika Gloor1, Klaus Scheffler2,3, and Oliver Bieri1
1University of Basel Hospital, Radiological Physics, Basel, Basel, Switzerland, 2MPI for Biological Cybernetics, MRC Department, Tübingen, Germany,3University of Tübingen, Neuroimaging and MR-Physics, Tübingen, Germany

 
An inversion recovery (IR) balanced steady-state free precession (bSSFP) sequence has been proposed for fast T1, T2, and spin density quantification. It has recently been shown that the presence of magnetization transfer (MT) effects on the transient phase of bSSFP experiments with short RF pulses leads to considerable deviations in calculated T1 and T2 values. In this work, an analytical expression of the two-pool IR bSSFP signal is presented taking MT effects into account. Numerical simulations of the Bloch equations are used to confirm the validity of the approximations made, and comparisons of the new equation to measurements are shown.

 
4263.   67 Double-angle Amide Proton Transfer Imaging: A New Chemical Exchange Saturation Transfer (CEST) Contrast
Zhongliang Zu1,2, Vaibhav Janve1,3, Junzhong Xu1,2, Mark D Does1,2, John Gore1,2, and Daniel Gochberg1,2
1Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States, 2Department of Radiology, Vanderbilt University, Nashville, TN, United States, 3Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, United States

 
APT imaging has shown promise in many clinical applications. However, the conventional CEST asymmetry analysis, by subtracting a label scan from a reference scan, is sensitive to confounding contributions from magnetic field inhomogeneities, inherently asymmetric macromolecular resonances, and lipid. In this study, we introduce a new CEST contrast that avoids these issues by creating label and reference scans based on varying the irradiation pulse turn angle (180 and 360 degree) instead of the frequency offset (3.5 and -3.5 ppm). Clear peak has been found at 3.5 ppm by using our method, but not by using the conventional asymmetry analysis.

 
4264.   68 Analyse the Important Fitted Parameters Using Pulsed Fitting and Continuous CEST Approximation for Pulsed CEST
Yee Kai Tee1, Alexandr A Khrapichev2, Nicola R Sibson2, Stephen J Payne1, and Michael A Chappell1,3
1Department of Engineering Science, Institute of Biomedical Engineering, University of Oxford, Oxford, Oxfordshire, United Kingdom, 2Department of Oncology, CR-UK/MRC Gray Institute for Radiation Oncology & Biology, University of Oxford, Oxford, Oxfordshire, United Kingdom, 3Oxford Centre for Functional MRI of the Brain, University of Oxford, Oxford, Oxfordshire, United Kingdom

 
Pulsed CEST (PC) is the only feasible irradiation scheme for clinical application as a result of SAR and hardware limitations but there is no simple analytical solution available. Thus, it is typically treated as continuous CEST (CC) by finding its equivalent average field or power to exploit the closed-form analytical solution of CC. Although fitting the data by discretizing the short pulses used by PC is able to produce smaller fitted errors, there is no significant difference found for the important fitted parameters such as amide proton exchange rate (related to pH) when CC approximation, which is fast, is used.

 
4265.   69 Optimization Strategies for Accurate Quantitative MT Imaging
Pouria Mossahebi1, and Alexey A. Samsonov2
1Biomedical Engineering, University of Wisconsin, Madison, WI, United States, 2Radiology, University of Wisconsin, Madison, WI, United States

 
We studied several ways to optimize efficiency of CRI at both 1.5 and 3T. We showed (for 3T case) that the CRI efficiency may be improved by including extra sample(s) from low Δ range (<1 kHz). Further, we demonstrated that SAR-efficient pulses may provide additional large efficiency gains in CRI. At the same time, high BW SAR-efficient pulses may lead to a significant error in qMT measures for the low offset frequency designs. One simple solution is to resort to longer SAR-efficient pulses.

 
4266.   70 Development of a 3D CEST Pulse Sequence with Embedded Field Map and Low SAR for pH-Weighted Contrast in Stroke Patients
Chao Xu1,2, Christian Labadie2,3, André Pampel2, Jochen B. Fiebach1, and Harald E. Möller2
1Center for Stroke Research Berlin (CSB), Charite-Universitaetsmedizin Berlin, Berlin, Germany, 2Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, 3Laboratoire de Spectrométrie Ionique et Moléculaire, Université Claude-Bernard Lyon 1, Villeurbanne, France

 
Chemical exchange saturation transfer (CEST) permits the detection of dilute labile proteins to allow pH-weighted imaging. However, clinical applications of the technique are currently limited due to time and specific absorption rate (SAR) restrictions. We developed a three-dimensional (3D) pulse sequence with low SAR and embedded field map information. Potential application for detecting ischemic acidosis is demonstrated in a stroke patient imaged on the second day after symptom onset.

 
4267.   71 Rapid and Accurate Variable Flip Angle T1 Mapping with Correction of On-Resonance MT Effects
Pouria Mossahebi1, and Alexey A Samsonov2
1Biomedical Engineering, University of Wisconsin, Madison, WI, United States, 2Radiology, University of Wisconsin Madison, Madison, WI, United States

 
Accurate estimation of T1 values from VFA measurements requires consideration of magnetization transfer effects, which may introduce T1 bias roughly proportional to the macromolecular content. The fast T1 correction protocol developed in this work (VFA-MT) requires a single MT scan in addition to regular VFA measurements for accurate T1 mapping. The presented approach is promising for fast high-resolution whole brain T1 mapping within clinically acceptable scan times.

 
4268.   72 Chemical Exchange Saturation Transfer (CEST) Imaging Using Interleaved Balanced Steady State Free Precession (SSFP)
Zhongliang Zu1,2, Ke Li1,2, Richard Dortch1,2, Seth Smith1,2, Mark D Does1,2, John Gore1,2, and Daniel Gochberg1,2
1Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States, 2Department of Radiology, Vanderbilt University, Nashville, TN, United States

 
Conventional CEST sequences contain a long saturation block (several seconds of continuous wave or pulsed irradiation) before acquisition. To fill k-space, several saturation blocks followed by acquisitions may be required, especially in high-resolution imaging. The long scan time limits CEST imaging in clinical applications. Here we present a new CEST imaging method using interleaved balanced steady state free precession (SSFP) acquisitions (named SSFP-CEST) to shorten imaging time. Experiments on creatine/agar phantom show that the SSFP-CEST has similar contrast as that of pulsed-CEST, but the total acquisition time decreases by a factor of ~6.
 
Electronic Poster Session - Pulse Sequences & Reconstruction B

Tools to Map the Brain & for Small Scale & Education
Click on to view the abstract pdf and click on to view the video presentation. (Not all presentations are available.)
Thursday 10 May 2012
Exhibition Hall  11:30 - 12:30

  Computer #  
4269.   49 Whole Cerebrum Myelin Water Imaging In Less Than 15 Minutes
Thomas Prasloski1, Alexander Rauscher2,3, Alex MacKay1,2, Madeleine Hodgson1, Irene Vavasour2, Corree Laule4, and Burkhard Mädler5
1Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada, 2Department of Radiology, University of British Columbia, 3UBC MRI Research Centre, University of British Columbia, 4Department of Pathology & Laboratory Medicine, University of British Columbia,5Department of Neurosurgery, University of Bonn

 
We present the application of an accelerated GRASE pulse sequence in the acquisition of data used to generate myelin water fraction maps. This sequence allows whole cerebrum coverage in scan times of less than 15 minutes. Further, the results of region of interest analysis indicate that myelin water fraction values correlate well with those of a previously validated sequence. Fast myelin water imaging could present new opportunities in both clinical and scientific research.

 
4270.   50 A 7min protocol for quantitative, whole-brain, accurate water mapping at 3T for neurological applications
Ana-Maria Oros-Peusquens1, Fabian Keil1, Zaheer Abbas1, Vincent Gras1, Klaus H.M. Möllenhoff1,2, and N. Jon Shah1,3
1Institute of Neuroscience and Medicine - 4, Forschungszentrum Jülich, Jülich, Germany, 2Department of Cognitive Neuroscience, University Maastricht, Maastricht, Netherlands, 3JARA - Faculty of Medicine, RWTH Aachen University, Aachen, Germany

 
The method proposed here is based on a long-TR multiple-echo GRE measurement with 7:21 minutes acquisition time. It has the advantage that all B1 corrections, which are large, are multiplicative and can be approached heuristically, using a bias field correction. A simple exponential fit of the signal decay with echo time is the other postprocessing ingredient. Well-separated distributions are found for the WM and GM and agree very well with previous ones obtained at 1.5T. It is anticipated that this easy to use, high-quality water mapping method will open the road to routine, widespread quantitative MR imaging of water content.

 
4271.   51 Including a Third, Non-Exchanging Water Component in mcDESPOT
Sean Deoni1
1School of Engineering, Brown University, Providence, RI, United States

 
Rapid Myelin Water imaging can provide important information in de-myelinating disease (Multiple Sclerosis) as well as neuropsychological disorders that may be associated with “disconnectivity”. Although mcDESPOT is a rapid myelin water imaging, it suffers from an implicit assumption of two-component relaxation, which may not be true in voxels bordering CSF or edema. Here we introduce a third, non-exchanging component to address this deficiency. Results show improved myelin water estimation in areas bordering the ventricles and the periphery of the brain.

 
4272.   52 Fast mapping of absolute water content in the human brain using TAPIR
Klaus H. M. Möllenhoff1,2, Fabian Keil1, Zaheer Abbas1, Vincent Gras1, Miriam Rabea Kubach1, Ana-Maria Oros-Peusquens1, and N. Jon Shah1,3
1Institute of Neuroscience and Medicine - 4, Forschungszentrum Jülich, Jülich, Germany, 2Department of Cognitive Neuroscience, University Maastricht, Maastricht, Netherlands, 3JARA - Faculty of Medicine, RWTH Aachen University, Aachen, Germany

 
Absolute water content in the human brain is highly regulated and shown to change in various diseases.Thus mapping of H2O values in clinical acceptable measurement times is of great interest. Here we present a fast and accurate method for mapping H2O values in vivo based on the 2D TAPIR approach.

 
4273.   53 Changes in T1ρ in Human Brain during Hypercapnic Challenge
Hye Young Heo1,2, Brian J Dlouhy3, Daniel R Thedens1, John Wemmie3,4, and Vincent Magnotta1,4
1Department of Radiology, University of Iowa, Iowa City, Iowa, United States, 2Department of Biomedical Engineering, University of Iowa, Iowa City, Iowa, United States, 3Department of Neurosurgery, University of Iowa, Iowa City, Iowa, United States, 4Department of Psychiatry, University of Iowa, Iowa City, Iowa, United States

 
The purpose of this study is to assess the ability of pH sensitive-T1ρ MRI to measure brain function. T1ρ contrast was compared with the BOLD contrast in the visual cortex during activation. In order to validate the specificity of T1ρ to pH changes, a sheep phantom study was performed, resulting in the double dissociation between T1ρ and T2* in acidified and oxygenated blood phantoms. In addition, we found that the release of the lactate by neural activity is consistent with the expected local acidosis.

 
4274.   54 A high-resolution large-scale 2D geometric magnetic susceptibility model of white matter microstructure
Way Cherng Chen1, Sean Foxley1, and Karla Miller1
1Centre for Functional MRI of the Brain (FMRIB), University of Oxford, Oxford, Oxfordshire, United Kingdom

 
Studies have shown that magnetic susceptibility introduces signal changes that are related to white matter tract structure. We previously presented a simple, small-scale 3D geometric model to estimate the microscopic field pattern that is driven by of various aspects of underlying tissue microstructure such as orientation to B0, myelin thickness and tissue iron concentration that can be used to predict susceptibility-based MR contrast. Here, a more robust and flexible 2D geometric model is introduced to allow more physiologically realistic representations of the actual WM microstructure.

 
4275.   55 Accelerated Variable Flip Angle T1 Mapping via View Sharing of Pseudo-Random Sampled Higher Order K-Space
Jason Su1, Manojkumar Saranathan1, and Brian Rutt1
1Department of Radiology, Stanford University, Stanford, CA, United States

 
A view-sharing methodology in which higher order k-space samples are shared between data frames is applied along the flip angle dimension of a variable flip angle T1 mapping sequence to achieve an acceleration of 2.3x with nearly negligible loss in T1 estimation. The composite-derived maps had a percent error median of 0.104% and a 5-to-95 percentile range of -5.216% to 5.192%. Composite image quality and T1 map fidelity was dramatically improved by correcting mixed data with a scale factor based on values in the fully sampled center of k-space. The 5-to-95 percent error range shrank by a factor of 1.67.

 
4276.   56 A rapid, spiral based VFA approach to simultaneous T1 and B1+ mapping
Christopher Sica1, and Christopher Collins1
1Radiology, Pennsylvania State University, Hershey, PA, United States

 
A method for simultaneous B1+ and T1 mapping is presented. The proposed method acquires a series of spoiled 3D GRE scans with fixed TR and variable flip angle between scans. A spiral acquisition with off-resonance correction is utilized to speed acquisition. Non-linear fitting is applied to the signal expression M 0 B1-(1-E1)sin[ FA(λθ, ∆B0) ] / (1 – E1cos[ FA(λθ, ∆B0) ]) to obtain B1+ and T1. This method is compared to an inversion recovery based method to measure T1 in a set of doped water tubes, and agreement is on the order of several percent. In-vivo results from this technique are also presented.

 
4277.   57 A high resolution high SNR 3D T2prep spiral protocol for robust whole brain myelin water quantification at 3 Tesla
Thanh D. Nguyen1, Mitchell Cooper1,2, Pascal Spincemaille1, Ashish Raj1, Yi Wang1,2, and Susan A Gauthier3
1Radiology, Weill Cornell Medical College, New York, NY, United States, 2Biomedical Engineering, Cornell University, 3Neurology and Neuroscience, Weill Cornell Medical College, New York, NY, United States

 
Conventional multi-component T2 relaxometry for myelin water fraction (MWF) mapping in the brain at 1.5T is time-consuming and has limited spatial coverage. The objective of this study is to develop a high resolution and high SNR 3D T2prep spiral protocol for whole brain myelin water mapping at 3T and to evaluate its performance in healthy volunteers by comparing with the conventional 1.5T acquisition. We found no significant changes in MWF between 1.5T and 3T. MWF maps obtained at 3T have lower coefficient of variance and better visualization of WM tracts.

 
4278.   58 Stimulated echo compensation enables accurate transverse relaxometry with short echo train multi-echo spin echo imaging.
Md. Nasir Uddin1, R. Marc Lebel1, and Alan H. Wilman1
1Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada

 
Standard transverse relaxometry makes use of a multi-echo spin echo sequence, typically with a large number of echoes to enable accurate T2 fitting. Reducing the number of echoes would enable substantially reduced RF heating and increased slice coverage. However, in the presence of spatially varying RF fields, across or within a slice, standard exponential fitting methods are shown to perform poorly with limited echo trains. We demonstrate the use of a stimulated echo correction to enable reduction of echo trains to as few as four echoes while retaining accurate T2 fits in the human brain.

 
4279.   59 Whole-Brain Tissue-Based Assessment of the Ultrashort T2 Component Using 3D UTE MRI Relaxometry
Ece Ercan1, Peter Börnert2, Andrew Webb1, and Itamar Ronen1
1C.J. Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center, Leiden, Netherlands, 2Philips Research Laboratories, Hamburg, Germany

 
We present a whole-brain tissue-based characterization of the ultrashort T2 components using 3D UTE MRI. Initial results show distinct distributions of ultrashort relaxation rates in gray and white matter. The estimated mean and distribution of the ultrashort T2 value for white matter is likely to contain contributions from cell membranes as well as from myelin, which is more ubiquitous in white matter than in gray matter. This implies that the actual ultrashort T2 value of myelin protons may be even shorter than the mean value found here and in previous works.

 
4280.   60 Iron quantification in normal aging brain accessed by the MR signal decay in the static spin dephasing regime of spherical perturbations
Jan Sedlacik1, Kai Boelmans2, Ulrike Löbel1, Brigitte Holst1, Susanne Siemonsen1, and Jens Fiehler1
1Neuroradiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany, 2Neurology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany

 
MRI is able to quantitatively detect iron deposition by changes in transverse relaxation rates and signal phase. Recently, quantitative susceptibility mapping was used to further extract the underlying magnetic susceptibility from the MR signal phase information. Purpose of this study was to demonstrate that true quantitative iron content can be derived from the transverse relaxation rates by using the analytical model of the static spin dephasing regimen of spherical perturbations. The established control values of iron content in the normal aging brain will serve as control for future clinical studies of neurodegenerative diseases at our institution.

 
4281.   
61 Imaging the whole life span of a Zebrafish with Magnetic Resonance Microscopy (MRM) using a standard bore 850 MHz system
Thomas Neuberger1,2, Tatjana Neuberger1, Darin Clark3, Victoria Braithwaite4,5, and Keith Cheng3
1Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA, United States, 2Department of Bioengineering, Pennsylvania State University, University Park, PA, United States, 3Department of Pathology, Penn State College of Medicine, Hershey, PA, United States, 4School of Forest Resources, Pennsylvania State University, University Park, PA, United States, 5Department of Biology, Pennsylvania State University, Univerity Park, PA, United States

 
The zebrafish is now widely recognized as a key model organism in biological research. Our study demonstrates that MRI can image the zebrafish in detail across its whole life span with an isotropic resolution of up to 8 microns. To perform these studies a standard bore 20 tesla system was utilized. Despite restricted space, we achieved a throughput of more than 60 specimens of early developmental stages. As the high resolution and contrast to noise ratio permits the identification of small details, we suggest that MRI could be a valuable tool to quantify the progression of disease in the zebrafish.

 
4282.   62 Cortical layers one by one: T2*, phase and susceptibility at 80μm resolution
Ana-Maria Oros-Peusquens1, Johannes Lindemeyer1, Alard Roebroeck2, Ralf A.W. Galuske3, Hansjuergen Bratzke4, and N. Jon Shah1
1INM-4, Research Centre Juelich, Juelich, Germany, 2Dept. of Psychology, University of Maastricht, Netherlands, 3Dept. of Biology, TU Darmstadt, Germany, 4Dept. of Forensic Medicine, Faculty of Medicine, JWG-University, Frankfurt/M, Germany

 
We report on a multiparametric, high-resolution study of the motor cortex at 9.4T. Two intracortical bands were visualised, with contrast strikingly different from that of the surrounding cortex. We observe orientation dependence of the contrast in both magnitude and phase images as well as T2* and susceptibility maps. Interestingly, the dependence of the visualisation of the cortical bands on direction is complementary in magnitude and phase. This is an indication of microstructure dependence of T2* and phase contrast.

 
4283.   63 Dichromate as an MR Microscopy Stain
Ian J Rowland1, McLean Gunderson2, Seth Dailey2, and Jose R Torrealba3
1Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin, United States, 2Department of Surgery, University of Wisconsin-Madison, United States, 3Department of Pathology and Laboratory Medicine, University of Wisconsin-Madison

 
Unlike optical microscopy, MR microscopy has few stains available to enhance contrast between tissue types. Whilst a significant number of MR microscopy studies use gadolinium based contrast agents to enhance available signal, enhanced tissue contrast is not guaranteed. In this study, we demonstrate that potassium dichromate may be utilized as a general MR histology stain to enhance contrast between a range of tissue types. The tissue specific generation of paramagnetic chromium species is responsible for the observed MR imaging contrast. Despite tissue oxidation, this study also demonstrates that standard histological procedures are unaffected following the chromium based MR staining.

 
4284.   
64 Quantitative in vivo Imaging of Low Concentrations of Iron Oxide Nanoparticles with Adiabatic Preparation Pulses
Steven Harris1, Liya Wang2, Jing Huang2, Lei Zhou1, Hui Mao2, and Xiaoping Hu1
1Department of Biomedical Engineering, Georgia Institute of Technology / Emory University, Atlanta, GA, United States, 2Department of Radiology, Emory University, Atlanta, GA, United States

 
Adiabatic preparation pulses and the failure of the adiabatic condition for spins diffusing near the iron oxide nanoparticles can be used to generate contrast that is linearly increasing with particle concentration. In this work, in vitro work is extended to an in vivo model of nanoparticle accumulation in the mouse liver. The adiabatic full passage contrast, as well as a magnetization transfer compensated approach, is shown to be linearly correlated with organ iron concentration by biochemical measurement. The low nanoparticle concentrations used in this study suggest the approach may be suitable for in vivo quantitative molecular imaging studies.

 
4285.   65 TOWARDS INTERACTIVE SUPER-RESOLUTION RECONSTRUCTION OF WHOLE-BODY MRI MOUSE DATA
Artem Khmelinskii1, Esben Plenge2, Peter Kok3,4, Dirk Poot2, Oleh Dzyubachyk3, Charl P. Botha4, Ernst Suidgeest5, Wiro Niessen2,6, Louise van der Weerd5,7, Erik Meijering2, and Boudewijn P. F. Lelieveldt3,4
1Division of Image Processing, Dept. of Radiology, LUMC, Leiden, The Netherlands, Leiden, Zuid-Holland, Netherlands, 2BIGR, Depts. of Radiology and Medical Informatics, ErasmusMC, Rotterdam, Netherlands, 3Division of Image Processing, Dept. of Radiology, LUMC, Leiden, Netherlands, 4Data Visualization Group, Dept. of Mediamatics, TU Delft, Netherlands, 5Dept. of Radiology, Molecular Imaging Laboratories Leiden, Section Nuclear Medicine, LUMC, Leiden, Netherlands, 6Quantitative Imaging Group, Dept. of Imaging Science & Technology, TU Delft, Netherlands, 7Depts. of Anatomy & Embryology, LUMC, Leiden, Netherlands

 
We present a new approach for producing highly resolved, localized isotropic volumes-of-interest in whole-body mouse MRI. This enables interactive HR visualization and exploration of anatomical structures in MRI. The idea is similar to that of well-known web-based geographical maps, where it is possible from a global overview image to zoom in on a detail of interest. Such functionality is relevant in a biomedical setting when working with high-resolution volumetric data. Using the method presented in this paper, from a global LR image the user can interactively zoom in on a sub-volume of interest.

 
4286.   66 An efficient reconstruction method for spatially encoded single-scan 2D MRI
Congbo Cai1, Ying Chen1, Jing Li1, Lin Chen1, Shuhui Cai1, Jianhui Zhong2, and Zhong Chen1
1Department of Electronics Science, Xiamen University, Xiamen, Fujian, China, 2Departments of Radiology and Physics and Astronomy, University of Rochester, Rochester, New York, United States

 
A new reconstruction algorithm based on generalized Fourier transform is explored for sequences with linear frequency-swept excitation. A hybrid-encoding sequence is tested. This algorithm improves the spatial resolution of the images while maintaining the excellent field perturbation immunity of the sequence. In vivo experiments are performed on coronal and sagittal planes of rat. Compared to the traditional gradient echo sequence and spin-echo EPI sequence, the artifacts induced by motion effects, susceptibility variation and Nyquist ghost are greatly relieved in the images produced by the hybrid-encoding sequence.

 
4287.   67 Correcting patient movement in Dynamic Contrast Enhanced MRI
Andrew Melbourne1
1University College London, London, United Kingdom

 
This work is a review of techniques for retrospective automatic image registration techniques in dynamic contrast enhanced (DCE) MRI. Due to the length of time required to obtain a DCE MRI series image registration techniques are used to correct subject movement between imaging volumes prior to physiological model-fitting to extract features of the enhancement pattern. These techniques are often modified for the DCE setting so that they separate motion artefacts from contrast enhancement. Due to the proliferation of techniques a review is worthwhile so that knowledge of the technical details of image registration can be made more widely available.

 
4288.   68 Signal-to-noise measurement methods in MR imaging
Elizabeth M Tunnicliffe1, Martin J Graves2,3, and Matthew D Robson4
1AVIC, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, United Kingdom, 2Department of Medical Physics & Clinical Engineering, Cambridge University Hospitals NHS Foundation Trust, Cambridge, United Kingdom, 3Department of Radiology, University of Cambridge, Cambridge, United Kingdom, 4OCMR, Department of Cardiovascular Medicine, University of Oxford, Oxford, United Kingdom

 
There are a multitude of different SNR methods in MRI. In this educational poster we provide an overview of different SNR methods and their applicability, including guidance on when different approaches may be most useful.

 
4289.   
69 Methods for quantitative magnetization transfer imaging
Ives R Levesque1, Nikola Stikov2, and G Bruce Pike2
1Electrical Engineering, Stanford University, Stanford, CA, United States, 2Montreal Neurological Institute, McGill University, Montreal, QC, Canada

 
This educational poster reviews the basic concepts of magnetization transfer and methods for quantitative MT imaging (QMTI). Various off- and on-resonance methods are discussed, along with their strengths and limitations for in vivo applications. General findings in neurological and muskuloskeletal imaging will also be discussed.