Sequences: New Acquisition Strategies & Applications
Click on to view the abstract pdf. Click on to view the recorded presentation.
Tuesday 8 May 2012
Plenary Hall  16:00 - 18:00 Moderators: Charles H. Cunningham, Maxim Zaitsev

16:00 0285.   Radial-Cones: A New Sampling Scheme for Compressed Sensing Accelerated 3D Ultrashort Echo Time Imaging
Kevin Michael Johnson1
1Department of Medical Physics, University of Wisconsin-Madison, Madison, WI, United States

3D Ultra Short Echo Time (UTE) imaging holds the potential both to visualize rapidly decaying species that would not otherwise be visible1 and to dramatically improve sampling efficiency. Unfortunately, 3D imaging must be performed either with inefficiency but robust 3D radial sampling or highly efficient 3D twisting trajectories that are sensitive to structured artifacts. In this work, we embrace compressed sensing sampling theory to develop a hybrid 3D UTE trajectory, Radial Cones, that combines the efficiency of 3D cones with the robustness of 3D radial sampling.

16:12 0286.   MR cortical bone imaging using UTE for digitally-reconstructed radiographs and attenuation correction at 3.0T
Melanie S Kotys-Traughber1, Bryan J Traughber2, Michael Meltsner3, and Raymond F Muzic, Jr.2
1MR Clinical Science, Philips Healthcare, Cleveland, OH, United States, 2Department of Radiology, University Hospitals Case Medical Center, Cleveland, OH, United States, 3Philips Radiation Oncology Systems, Philips Healthcare, Fitchburg, WI, United States

Two emerging MR applications, MR-based radiation therapy planning (RTP) and hybrid PET/MR systems, require complete segmentation of cortical bone. We investigate a 3D UTE multi-echo acquisition and subtraction method for generation of MR-based digitally reconstructed radiographs (DRRs) and attenuation correction (AC) maps. After careful calibration of the gradient hardware, the method robustly segments cortical bone in the brain. The DRRs generated from the bone-enhanced images appear sufficient for 2D patient matching. The range of TEs tested, from 90-200µs, yielded excellent signal from cortical bone and the signal from bone, tissue and air were significantly different at all TEs.

16:24 0287.   
Two New 3D Spiral-Based Trajectories
Dallas C Turley1, Nicholas R Zwart1, and James G Pipe1
1Neuroimaging Research, Barrow Neurological Institute, Phoenix, Arizona, United States

This work presents two new 3D trajectories comparable to conventional Stack of Spirals (SOS), namely Golden EquiDistant Interleaves (GEDI) and Spherical-GEDI (S-GEDI). Both trajectories have non-Cartesian aliasing patterns in all three directions. S-GEDI collects a sphere in k-space, is not sensitive to 3D blurring, and its PSF shows less ringing than SOS or GEDI, whose PSF are identical. Both trajectories are comparable to SOS in terms of scan time, SNR efficiency and ease of implementation.

16:36 0288.   
MR Fingerprinting (MRF): a Novel Quantitative Approach to MRI
Dan Ma1, Vikas Gulani1,2, Nicole Seiberlich1, Jeffrey Duerk1, and Mark Griswold1,2
1Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States, 2Dept. of Radiology, University Hospitals of Cleveland and Case Western Reserve University, Cleveland, OH, United States

MR Fingerprinting is a completely novel approach to quantitative MRI. Instead of collecting a series of weighted images and fitting signal time courses to an exponential model, MRF eschews collection of traditional images and a model based approach altogether. A compressed sensing based approach is adopted where information about each voxel is collected with signal timecourses generated using variable TRs, flip angles, and inversion pulses to encode relaxation information into unique signal evolution curves. Matching these curves to a comprehensive dictionary using pattern matching provides multiple parameter mappings (T1, T2, proton density and off-resonance) and synthesized reconstructed images simultaneously.

16:48 0289.   Use of Simulated Annealing for the Design of Multiple TR bSSFP Sequences in Positive Contrast Imaging
Kuan J. Lee1, Hsu-Lei Lee1, Jürgen Hennig1, and Jochen Leupold1
1Medical Physics, University Medical Centre Freiburg, Freiburg, Baden-Württemberg, Germany

We introduce a novel multiple TR bSSFP sequence for positive contrast imaging. Using simulated annealing, the sequence has been designed for a spectral profile that has stopbands over both fat and water resonances. This enables simultaneous water and fat suppression, which improves contrast without requiring a second acquisition, as with for example, the PARTS (Positive Contrast with Alternating Repetition Time SSFP) technique.

17:00 0290.   
Fast, low SAR and off-resonance insensitive T2 weighted Variable Amplitude PSIF (T2 VAPSIF) imaging
Subashini Srinivasan1,2, Wesley D Gilson1, Aaron Flammang1, Dominik Paul3, and Sunil Patil1
1Center for Applied Medical Imaging, Siemens Corporation, Corporate Research, Baltimore, Maryland, United States, 2Biomedical Engineering Interdepartmental Program, University of California, Los Angeles, California, United States, 3Siemens AG, Erlangen, Germany

T2TIDE is a balanced SSFP based T2w single shot sequence which provides faster image acquisition, sharper edge resolution and lower SAR compared to HASTE. However, T2TIDE is sensitive to B0 inhomogeneities producing banding artifacts especially at higher field strengths. We present a sequence based on T2TIDE called T2w Variable Amplitude PSIF (T2VAPSIF) wherein a Kaiser-Bessel derived stabilization module and a PSIF acquisition are used. Phantom and volunteer images show that the T2VAPSIF has T2w similar to TSE and HASTE, is insensitive to B0 inhomogeneities and preserves the low SAR, sharper edge resolution and faster acquisition properties of T2TIDE.

17:12 0291.   Resolution-Related Diffusion Damping in Fast Spin Echo Sequences
Oliver Bieri1, Carl Ganter2, and Klaus Scheffler3,4
1Division of Radiological Physics, Department of Radiology and Nuclear Medicine, University of Basel Hospital, Basel, Switzerland, 2Department of Radiology, Klinikum rechts der Isar, Technische Universität München, Munich, Germany, 3High-Field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany, 4Department of Neuroimaging and MR-Physics, Centre for Integrative Neuroscience, University of Tübingen, Tübingen, Germany

We have recently shown that the tissue-fluid contrast of nonbalanced steady state free precession (SSFP) shows an unexpected strong sensitivity on resolution: an increase in the spatial resolution goes with an increase in spoiling moments leading to a pronounced diffusion damping of fluids. Clearly, this effect is not confined to SSFP, but can affect the contrast of other multi-pulse sequences that show resolution dependent spoiling moments, such as RARE (TSE, FSE). In this work, we will show that RARE sequences show a similar fluid-tissue contrast modulation as nonbalanced SSFP.

17:24 0292.   Simultaneous Linear and Nonlinear Encoding in a Single Shot
Daniel Gallichan1, Frederik Testud1, Christoph Barmet2, Chris A Cocosco1, Anna M Welz1, Klaas Prüssmann2, Juergen Hennig1, and Maxim Zaitsev1
1University Medical Center Freiburg, Freiburg, BW, Germany, 2Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland

In this work we seek to push the limits of a custom-built gradient insert which generates the two quadratic SEMs by performing a single-shot version of a 4-Dimensional Radial In/Out (4D-RIO) trajectory which simultaneously drives the linear and quadratic encoding fields, and testing this trajectory in-vivo. A field camera was used to track the actual encoding trajectory up to 3rd order to assist image reconstruction. We were able to reconstruct reasonable quality images, both in a phantom and in the human brain in vivo, using this novel single-shot higher-order encoding trajectory.

17:36 0293.   
Multi-Directional High Moment Encoded 3D PCMRA In-Vivo
Nicholas Ryan Zwart1, and James Grant Pipe1
1Neuroimaging Research, Barrow Neurological Institute, Phoenix, Arizona, United States

Signal to noise ratio gains in low VENC phase contrast MRI are limited by the ability to successfully unalias phase measurements that fall outside the -180 to 180 degree interval. A new time efficient acquisition and reconstruction method for unaliasing velocity encoded phase is compared to the well known 3-point (or dual-VENC) method in-vivo.

17:48 0294.   
Towards Dynamic 3D MRI of Speech
Yinghua Zhu1, Yoon-Chul Kim1, Michael Proctor1, Shrikanth Narayanan1, and Krishna Nayak1
1University of Southern California, Los Angeles, California, United States

MRI has a long history of informing basic research into speech production, and has included the use of static and dynamic 2D imaging and static 3D imaging. In this work, we report on our initial efforts towards real-time 3D imaging of speech using 3D stack-of-spirals gradient echo sequences at 1.5T. We characterize the trade-off between spatial and temporal resolution, and assess the image quality in the articulators (i.e. air-tissue boundaries in the tongue, lips, and velum) using a variety of the spiral readout durations and number of interleaves.