Kevin Michael Johnson^1
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.

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.

Dallas C Turley¹, Nicholas R Zwart¹, and James G Pipe^1
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.

Dan Ma¹, Vikas Gulani^1,2, Nicole Seiberlich¹, Jeffrey Duerk¹, and Mark Griswold^1,2
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.

Kuan J. Lee¹, Hsu-Lei Lee¹, Jürgen Hennig¹, and Jochen Leupold^1
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.

Subashini Srinivasan^1,2, Wesley D Gilson¹, Aaron Flammang¹, Dominik Paul³, and Sunil Patil^1
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.

Oliver Bieri¹, Carl Ganter², and Klaus Scheffler^3,4
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.

Daniel Gallichan¹, Frederik Testud¹, Christoph Barmet², Chris A Cocosco¹, Anna M Welz¹, Klaas Prüssmann², Juergen Hennig¹, and Maxim Zaitsev^1
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.

Nicholas Ryan Zwart¹, and James Grant Pipe^1
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.

Yinghua Zhu¹, Yoon-Chul Kim¹, Michael Proctor¹, Shrikanth Narayanan¹, and Krishna Nayak^1
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.