Tagging & Water/Fat
Friday 7 May 2010
Room A9 10:30-12:30 Moderators: Diego Hernando and Scott B. Reeder

10:30 764. 

Super-Resolution MRI Using Microscopic Spatial Modulation of Magnetization (MicroSPAMM)
Stefan Ropele1, Gernot Reishofer2
Department of Neurology, Medical University of Graz, Graz, Austria; 2Department of Radiology, Medical University of Graz, Graz, Austria

A new super-resolution (SR) method for field of view (FOV) shifted MRI is presented. In contrast to previous attempts that are based on simple FOV shifts only, the new method additionally modulates the longitudinal magnetization within the imaging plane for each shift, thus allowing the acquisition of new and independent k-space data. First SR experiments in a geometric phantom and in brain tissue of two healthy volunteers clearly demonstrate the feasibility and advantages of the new method, which has the capability to break current resolution limits in MRI.

10:42 765. 

Experimental Validation of SPAMM Tagged Magnetic Resonance Imaging Based Measurement of Non-Uniform 3D Soft Tissue Deformation
Kevin Mattheus Moerman1,2, Ciaran Knut Simms1, Andre M. J. Sprengers2, J. Stoker2, Aart J. Nederveen2
Trinity Centre for Bioengineering, Trinity College Dublin, Dublin, Ireland; 2Radiology, Academic Medical Centre, Amsterdam, Netherlands

Analysis of human soft tissue motion and deformation is vital in diverse applications from constitutive modelling in biomechanics to the study of bowel motility. Post-processing Magnetic Resonance Imaging (MRI) to derive soft tissue deformation challenging and requires validation. For this study a novel MRI sequence, based on SPAtial Modulation of the Magnetization (SPAMM) designed for real-time measurement of non-periodic movements was evaluated for its ability to measure 3D soft tissue deformation using marker tracking in a silicone gel phantom. The mean error of the SPAMM based non-invasive deformation measurement technique was found to be 0.75mm.

10:54 766. 

Radial Tagging of MR Images: A Continuous RF Excitation Approach
Abbas Nasiraei Moghaddam1,2, Yutaka Natsuaki3, J. Paul Finn1
Radiology, UCLA, Los Angeles, CA, United States; 2Caltech, Pasadena, CA, United States; 3Siemens Medical Solutions, Los Angeles, CA, United States

MRI tagging is a well established method for non-invasive measurement of deformation and strain. Radial tagging is a pattern of interest that facilitates the measurement of angular information reflected in shear and twist of the left ventricle. In this work we describe a continuous RF approach for radial tagging that acts on a rotating excitation plane. The sequence has been successfully tested on phantom and also used to acquire short axis images of the left ventricle. The spatial resolution and density of taglines are considerably higher in this approach compared to previous schemes of the radial tagging.

11:06 767.  

Single Coil PILS Imaging Using Phase-Scrambling Fourier Transform Technique
Satoshi Ito1, Yoshifumi Yamada1
Research Division of Intelligence and Information Sciences, Utsunomiya University, Utsunomiya, Tochigi, Japan

Parallel image reconstruction using local sensitivities (PILS) accelerate MR scan time by using multiple receiver coil in parallel scan time. We propose a novel imaging technique which is based on the PILS, but uses only a single set of signals. The signal obtained in the phase-scrambling Fourier Transform imaging (PSFT) can be transformed into the signal described by the Fresnel transform of the objects, in which alias-less images can be obtained by optionally scaling the object images. The reconstructed alias-less image has lower resolution than the original image which has aliasing artifact since aliasing is avoided by shrinking the image to fit in the given data size. In this paper, we propose PILS like reconstruction method which can improve the resolution of images by using the up-scaling of alias-less reconstruction and signal band extrapolation technique of PSFT signal.

11:18 768.

A Reliable, Efficient and Flexible Multi-Echo FSE Based Water-Fat Separation Method
Huanzhou Yu1, Ann Shimakawa1, Sabina Prato2, Scott B. Reeder3, Charles A. McKenzie4, Jean H. Brittain5
Applied Science Laboratory, GE Healthcare, Menlo Park, CA, United States; 2GE Healthcare, Waukesha, WI, United States; 3Departments of Radiology, Medical Physics, Biomedical Engineering and Medicine, University of Wisconsin, Madison, Madison, WI, United States; 4Department of Medical Biophysics, University of Western Ontario, London, ON, Canada; 5Applied Science Laboratory, GE Healthcare, Madison, WI, United States

Three-point IDEAL water-fat separation techniques have been applied to FSE sequences, however, minimum scan time is tripled. Therefore, it is desirable to collect all 3 echoes in one repetition, an approach that brings unique challenges. In this work, we present a multi-echo FSE-IDEAL implementation that offers superior noise performance, high quality water-fat separation and flexible echo shift choices. The bipolar acquisition with high order phase correction allows efficient acquisition and uniform water-fat separation. Echo shifts are adapted to the desired resolution with best tradeoff in SNR. The technique is demonstrated in volunteer scanning in a variety of anatomic regions.

11:30 769

Ultrafast Near-Isotropic Spatial Resolution 3D Balanced-SSFP Dixon Imaging in the Breast
Manojkumar Saranathan1, Ersin Bayram2, Christine Lee3
Applied Science Lab, GE Healthcare, Rochester, MN, United States; 2MR Engineering, GE Healthcare, Waukesha, WI, United States; 3Radiology, Mayo Clinic, Rochester, MN, United States

T2 imaging in the breast is most commonly performed using a 2D Fast Spin Echo (FSE) pulse sequence with a high in-plane spatial resolution and 3-4 mm slice thickness. Balanced steady-state free precession (b-SSFP) techniques yield high SNR images in short scan times with a T2-like image contrast. We investigated a new 3D technique that combines balanced steady-state free precession imaging with a two-point Dixon fat-water reconstruction algorithm [2] for robust fat-separated volumetric imaging of the breast with near isotropic spatial resolution in short scan times.

11:42 770

Dual-Echo Dixon Imaging with Unrestricted Choice of Echo Times
Holger Eggers1, Bernhard Brendel1, Adri Duijndam2, Gwenael Herigault2
Philips Research, Hamburg, Germany; 2Philips Healthcare, Best, Netherlands

Existing two-point Dixon methods require at least one echo time being in phase. Thus, they restrict flexibility in the selection of protocol parameters and compromise scan efficiency. In this work, a novel two-point Dixon method is outlined that removes restrictions on the echo times. It is characterized in terms of noise propagation, and it is demonstrated to enable shorter scan times, higher spatial resolution, and increased signal-to-noise ratio in abdominal imaging in single breathholds.

11:54 771

Exploiting the Spectral Complexity of Fat for Robust Multi-Point Water-Fat Separation
Huanzhou Yu1, Ann Shimakawa1, Jean H. Brittain2, Charles A. McKenzie3, Scott B. Reeder4
Applied Science Laboratory, GE Healthcare, Menlo Park, CA, United States; 2Applied Science Laboratory, GE Healthcare, Madison, WI, United States; 3Department of Medical Biophysics, University of Western Ontario, London, ON, Canada; 4Departments of Radiology, Medical Physics, Biomedical Engineering and Medicine, University of Wisconsin, Madison, Madison, WI, United States

Multi-point water-fat separation methods must address the challenge of water-fat ambiguity that arises from the signal behavior of water and fat which, when both modeled with a single spectral peak, may appear identical in the presence of Bo off-resonance. Water-fat ambiguity is typically removed by enforcing field- or phase-map smoothness using region growing based algorithms.  However, the fat spectrum actually has multiple spectral peaks. In this work, a novel algorithm to identify water and fat for multi-point acquisitions is introduced by exploiting the spectral differences between water and fat. New opportunities arise to design algorithms for highly robust water-fat separation.

12:06 772.

Extending Performance of Fat-Water Separated Alternating TR SSFP: Ultra-High 0.29 Mm Isotropic Resolution
Jessica Leigh Klaers1, Ethan K. Brodsky1,2, Richard Kijowski2, Walter F. Block1,3

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

The alternating TR (ATR) balanced SSFP technique has proven to be useful for suppression of unwanted species while extending the TR interval available for increased spatial resolution.  Ultra-high 0.29 mm isotropic resolution has been achieved by extending the performance of the multi-acquisition fat-water separation ATR SSFP sequence through the implementation of a 3D radial trajectory.  Applications in cartilage assessment and vasculature imaging are demonstrated in the knee joint.

12:18 773

Three-Point Dixon Method for Whole-Body Water/fat Imaging
Johan Berglund1, Lars Johansson1, Håkan Ahlström1, Joel Kullberg1
Department of Radiology, Uppsala University, Uppsala, Sweden

A three-point Dixon method applicable for water/fat separation of whole-body datasets is presented. In each voxel, two alternative error phasors are found analytically. The correct error phasor is identified by imposing spatial smoothness in a 3D multi-seed region growing scheme with a dynamic path. After removing the phase errors, water and fat signal components are found in each voxel by least squares fitting. Whole-body water and fat images were reconstructed from 39 volunteer subjects, and the images were subjectively graded by two radiologists. The method was found to achieve fast and accurate whole-body water/fat separation.



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