Guanhua Wang¹, Tianrui Luo¹, Jon-Fredrik Nielsen¹, Jeffrey A. Fessler², and Douglas C. Noll^1
1Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States, ²Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, United States

The proposed approach, BJORK, provides a robust and generalizable workflow to jointly optimize non-Cartesian sampling patterns and a physics-informed reconstruction. Several approaches, including re-parameterization of trajectories, multi-level optimization, and non-Cartesian unrolled neural networks, are introduced to improve training effect and avoid sub-optimal local minima. The in-vivo experiments show that the networks and trajectories learned on simulation dataset are transferable to the real acquisition even with different parameter-weighted MRI contrasts and noise-levels, and demonstrate improved image quality compared with previous learning-based and model-based trajectory optimization methods.

Qingfei Luo¹, Zheng Zhong^1,2, Kaibao Sun¹, and Xiaohong Joe Zhou^1,2,3
1Center for MR Research, University of Illinois at Chicago, Chicago, IL, United States, ²Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, United States, ³Departments of Radiology and Neurosurgery, University of Illinois at Chicago, Chicago, IL, United States

It has been reported that a new sequence, epi-SPEEDI, can offer sub-millisecond temporal resolution, but its scan time is relatively long due to phase-encoding. In this study we propose an accelerated version of epi-SPEEDI (named epi-SPEEDI-kt) that improves the acquisition efficiency of epi-SPEEDI by randomly undersampling the k-space, followed by image reconstruction using joint spatiotemporal partial separability and sparsity constraints. Through a human imaging example for visualizing the dynamics of aortic valve, we demonstrated that epi-SPEEDI-kt can provide comparable image quality to epi-SPEEDI and reduce the scan time by ~50% concurrently. This acceleration is expected to enhance SPEEDI applications.

Antoine Klauser^1,2,3, Bernhard Strasser^2,4, Wolfgang Bogner⁴, Lukas Hingerl⁴, Claudiu Schirda⁵, Bijaya Thapa², Daniel Cahill⁶, Tracy Batchelor⁷, François Lazeyras^1,3, and Ovidiu Andronesi^2
1Radiology and Medical Informatics, University of Geneva, Geneva, Switzerland, ²Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States, ³CIBM Center for Biomedical Imaging, Geneva, Switzerland, ⁴High‐Field MR Center, Department of Biomedical Imaging and Image‐guided Therapy, Medical University of Vienna, Vienna, Austria, ⁵Department of Radiology, University of Pittsburgh, Pittsburgh, PA, United States, ⁶Department of Neurosurgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States, ⁷Department of Neurology, Brigham and Women, Harvard Medical School, Boston, MA, United States

A new encoding trajectory for magnetic resonance spectroscopic imaging was developed and implemented on a 7T human scanner. ECcentric Circle ENcoding TRajectorIes for Compressed-sensing (ECCENTRIC) is a spatial-spectral encoding strategy optimized for random non-Cartesian sparse Fourier domain sampling. Acceleration by undersampling ECCENTRIC prevents coherent aliasing artefacts in the spatial response function. ECCENTRIC allows smaller circles to avoid temporal interleaving for large matrix size, which is beneficial for spectral quality. Circle trajectories need limited gradient slewrate without rewinding deadtime, and are robust to timing imperfection and eddy-current delays.

Thomas A Roberts¹, Laurence H Jackson¹, Joshua FP van Amerom², Alena Uus¹, Anthony N Price¹, Johannes K Steinweg¹, David FA Lloyd^1,3, Milou PM van Poppel¹, Kuberan Pushparajah³, Mary A Rutherford¹, Reza Razavi^1,3, Maria Deprez¹, and Joseph V Hajnal^1
1Biomedical Engineering Department, School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom, ²Division of Pediatric Cardiology, The Hospital for Sick Children, Toronto, ON, Canada, ³Department of Congenital Heart Disease, Evelina Children's Hospital, London, United Kingdom

MRI of the fetal heart is challenging due to fetal motion and its small size. Previously, we have demonstrated a method for simultaneous 4D anatomical and blood flow imaging of the whole fetal heart. However, the acquisition takes at least 14 minutes, which is unfavourable for routine clinical usage. Here, we combine k-t SENSE with SWEEP excitation to acquire a continuous sequence of images through the heart. The removal of dummy pulses due to SWEEP excitation reduces our acquisition time by 17%. We also acquire one-third fewer frames compared to our conventional method, resulting in a 45% faster acquisition time.

Zhixing Wang¹, Steven Allen¹, Xue Feng¹, John P. Mugler², and Craig H. Meyer^1
1Biomedical Engineering, University of Virginia, Charlottesville, VA, United States, ²Radiology & Medical Imaging, University of Virginia, Charlottesville, VA, United States

This study presents a new approach to 2D TSE imaging using annular spiral rings with a retraced in/out trajectory, dubbed “SPRING-RIO TSE”, for fast T2-weighted brain imaging. Annular rings with retraced in/out segments offer benefits for reducing T2 decay induced artifacts and self-correction of moderate off-resonance effects. Phantom and human results show that high-quality T2-weighted images can be acquired with higher scan efficiency and reduced SAR, when compared with Cartesian TSE imaging.

Myung-Ho In¹, Norbert G Campeau¹, John III Huston¹, Zijing Dong^2,3, Kawin Setsompop^4,5, Daehun Kang¹, Uten Yarach⁶, Yunhong Shu¹, Joshua D Trzasko¹, and Matt A Bernstein^1
1Department of Radiology, Mayo Clinic, Rochester, MN, United States, ²A. A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, ³Department of Electrical Engineering and Computer Science, MIT, Cambridge, MA, United States, ⁴Department of Radiology, Stanford University, Stanford, CA, United States, ⁵Stanford University, Stanford, CA, United States, ⁶Department of Radiologic Technology, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai, Thailand

 Rapid high-resolution echo-planar-imaging (EPI) with improved image quality could conceivably be utilized as a high-speed alternative to conventional T2-weighted fast-spin-echo imaging (T2-FSE). A variant of multi-shot EPI, DIADEM (distortion-free imaging: a double encoding method), was recently described (5) and shown to yield high quality, high resolution images free of spatial distortion. In this work, a T2-weighted DIADEM pulse sequence was optimized with self-calibrated, tilted-CAIPI reconstruction scheme and then comparatively evaluated to T2-FSE images of the brain in 24 human subjects by two neuroradiologists.

Michael Schär^1
1Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States

Recently, it was shown that phase-modulated balanced steady-state free precession (bSSFP) offers banding-free radial cine bSSFP images. Because this novel approach for bSSFP overcomes the need for short repetition times (TR), this work proposes to use more efficient spiral readouts with long TR of 15 ms. Banding free bSSFP cine images are demonstrated for either high temporal or high spatial resolution. The long TR furthermore facilitates fat suppression with spatial-spectral water-only excitation pulses which could improve depiction of the coronary arteries. Out of slice signal pileup at dark band frequencies is shown to be reduced with pre-saturation of those frequencies.

Kaibao Sun¹, Zheng Zhong^1,2, Kezhou Wang¹, and Xiaohong Joe Zhou^1,2,3
1Center for MR Research, University of Illinois at Chicago, Chicago, IL, United States, ²Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, United States, ³Departments of Radiology and Neurosurgery, University of Illinois at Chicago, Chicago, IL, United States

Golden-angle radial sampling based on single-echo bSSFP has been increasingly used in MRI. In a method known as ETGAR (echo-train golden-angle radial), a series of spokes separated by a golden angle are acquired within a TR to accelerate data sampling. A main disadvantage is that the large inter-echo steering gradients can lead to a longer TR and trigger eddy currents. We herein demonstrate an alternative golden-angle radial sequence – ETGAR-II – to overcome the afore-mentioned issues. This novel sequence, together with an integrated phase-correction algorithm has been demonstrated on phantoms and human to obtain high quality images with 36% scan time reduction.

Zhiqiang Li¹, Melvyn B Ooi², and John P Karis^1
1Neuroradiology, Barrow Neurological Institute, Phoenix, AZ, United States, ²Philips Healthcare, Gainesville, FL, United States

DW-MRI is an invaluable technique for the diagnosis of neurological disorders. ssEPI is time efficient but suffers from geometric distortions. DW-PROPELLER and its variants, including turboPROP, have been proposed for generating distortion-free images. This project proposes a new whole-blade acquisition mode with phase correction in reconstruction to increase the blade width and consequently reduce the scan time by a factor of ~2, relative to the original turboPROP. Furthermore, the increased blade width allows for robust motion correction, which was typically not performed in PROPELLER-based DWI. In vivo results demonstrate advantages over ssEPI, and recently released product msEPI and SPLICE-PROPELLER.

Edwin Versteeg¹, Sarah M. Jacobs¹, Ícaro A.F. Oliveira², Dennis W.J. Klomp¹, and Jeroen C.W. Siero^1,2
1Radiology, University Medical Center Utrecht, Utrecht, Netherlands, ²Spinoza centre for neuroimaging Amsterdam, Amsterdam, Netherlands

Sound levels in MRI can be reduced by switching a silent gradient axis beyond the hearing threshold. In this work, we implemented a silent readout module that applies such a silent gradient axis (at 7T) to a 3D MPRAGE sequence. This resulted in a sequence that featured a much lower peak sound level (26 dB reduction), similar image contrast and imaging time compared to a conventional MPRAGE-scan.  This shows that a silent gradient axis provides a pathway to fast and quiet brain imaging with the potential to translate to other field strengths.