Nan Wang¹, Tianle Cao^1,2, Fei Han³, Yibin Xie¹, Xiaodong Zhong³, Sen Ma¹, Xinheng Zhang^1,2, Xiaoming Bi³, Mazen Noureddin⁴, Vibhas Deshpande³, Anthony G Christodoulou¹, and Debiao Li^1
1Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, CA, United States, ²Bioengineering, University of California, Los Angeles, Los Angeles, CA, United States, ³Siemens Medical Solutions USA, Inc., Los Angeles, CA, United States, ⁴Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA, United States

Chronic liver disease has been a leading cause of mortality worldwide. Multiparametric MRI is a promising tool for non-invasive characterization of liver disease, but has yet to be widely used in clinical practice due to demanding technical challenges. In this work, we proposed a 6D Multitasking multi-echo (MT-ME) technique that allows free-breathing acquisition, whole-liver coverage, and simultaneous T1, PDFF, R2*, and water-specific T1 (T1_w) quantification. Phantom study and in vivo studies with 14 volunteers and 1 patient with NAFLD were performed. The quantitative parameters measured from MT-ME were repeatable and showed good agreement with the reference methods.

Zhitao Li^1,2, John M Pauly², and Shreyas Vasanawala^1
1Department of Radiology, Stanford University, Palo Alto, CA, United States, ²Electrical Engineering, Stanford University, Palo Alto, CA, United States

A radial IR-SPGR pulse sequence with bipolar readouts is demonstrated along with a model-based iterative reconstruction to simultaneously map high resolution composite and water-only T₁ and proton density fat fraction (PDFF) in the abdomen. The proposed pulse sequence and reconstruction algorithm can yield high-quality T₁ and PDFF maps in 2.5 seconds/slice. The resulting maps have an in-plane resolution of 1.25mm and through-plane resolution of 5.00mm. When combined with selective inversion pulse, the technique achieves multi-slice imaging for breath-hold studies.

Yavuz Muslu^1,2, Ty A. Cashen³, Sagar Mandava⁴, and Scott B. Reeder^1,2,5,6,7
1Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States, ²Department of Radiology, University of Wisconsin-Madison, Madison, WI, United States, ³Global MR Applications and Workflow, GE Healthcare, Madison, WI, United States, ⁴Global MR Applications and Workflow, GE Healthcare, Atlanta, GA, United States, ⁵Department of Medical Physics, University of Wisconsin-Madison, Madison, WI, United States, ⁶Department of Medicine, University of Wisconsin-Madison, Madison, WI, United States, ⁷Department of Emergency Medicine, University of Wisconsin-Madison, Madison, WI, United States

Quantitative T1 mapping in the liver is an emerging biomarker of hepatic fibrosis and characterization of liver function. The variable flip angle approach with Cartesian sampling is among the most popular T1 mapping methods used in the abdomen. A major drawback of this approach is that T1 estimations are highly sensitive to B1 inhomogeneities. Furthermore, Cartesian sampling suffers from motion related ghosting artifacts and requires breath-holding acquisitions. In this study, we propose to combine stack-of-stars radial sampling with dual-echo inversion recovery (IR-SoS) MRI for confounder corrected T1 mapping in the abdomen.

Eze Ahanonu¹, Zhiyang Fu^1,2, Kevin Johnson², Maria Altbach^2,3, and Ali Bilgin^1,2,3
1Electrical and Computer Engineering, University of Arizona, Tucson, AZ, United States, ²Medical Imaging, University of Arizona, Tucson, AZ, United States, ³Biomedical Engineering, University of Arizona, Tucson, AZ, United States

Abdominal T1 mapping is important for quantitative evaluation of various pathologies. A recent inversion recovery radial balanced-SSFP (IR-radSSFP) technique allows high resolution T1 mapping of ten slices within a single breath hold period (BHP), but requires multiple BHPs for full abdominal coverage. We propose an accelerated T1 mapping framework which utilizes deep learning to estimate T1 using a fraction of the T1 recovery curve (T1RC). In vivo experiments demonstrate that the proposed framework achieves less than 6% T1 error while using only 25% of the T1RC of the earlier IR-radSSFP technique. This enables full abdominal coverage within a single BHP.

Mahesh Bharath Keerthivasan^1,2, Lavanya Umapathy^2,3, Jean-Philippe Galons², Diego Martin⁴, Ali Bilgin^2,3,4, and Maria Altbach^2
1Siemens Medical Solutions USA Inc, New York, NY, United States, ²Medical Imaging, University of Arizona, Tucson, AZ, United States, ³Electrical and Computer Engineering, University of Arizona, Tucson, AZ, United States, ⁴Biomedical Engineering, University of Arizona, Tucson, AZ, United States

Radial TSE techniques have been proposed for abdominal T2-weighted (T2w) imaging and T2 mapping. Slice efficiency of breath-held RADTSE is limited by the specific absorption rate (SAR). We present a reduced SAR variable refocusing flip angle RADTSE (RADTSE-VFA) technique designed for efficient slice coverage and improved T2 estimation. The flip angles are designed to (1) minimize T2 estimation error, (2) improve lesion-liver relative contrast, and (3) minimize SAR. RADTSE-VFA generated T2w images with comparable contrast as constant flip angle RADTSE while resulting in a 60% increase in slice coverage at a 1.5x reduction in SAR.

Kelvin Chow¹, Genevieve Hayes², Jacqueline Flewitt², Patricia Feuchter², Carmen Lydell², Andrew Howarth², Joseph Pagano³, Richard Thompson⁴, Peter Kellman⁵, and James White^2
1Cardiovascular MR R&D, Siemens Medical Solutions USA, Inc., Chicago, IL, United States, ²Stephenson Cardiac Imaging Centre, University of Calgary, Calgary, AB, Canada, ³Division of Pediatric Cardiology, University of Alberta, Edmonton, AB, Canada, ⁴Biomedical Engineering, University of Alberta, Edmonton, AB, Canada, ⁵National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, United States

A novel multi-parametric cardiac mapping sequence, mSASHA, is proposed to calculate T₁ and T₂ maps in a single breath-hold.  mSASHA is validated against spin-echo in phantoms with -0.7±0.4% T₁ error and -1.3±1.3% T₂ error.  In 10 healthy volunteers at 3T, mSASHA had similar T₁ values to SASHA in the myocardium (1523±18 ms vs. 1520±18, p>0.05) and blood pool (2054±61 ms vs. 2060±65 ms, p>0.05).  mSASHA had similar myocardial T₁ coefficient of variation (CoV) to SASHA and MOLLI and similar myocardial T₂ CoV to T₂p-bSSFP (p>0.05).  mSASHA provides accurate and precise T₁ and T₂ maps in a single breath-hold.

Carlos Velasco¹, Giorgia Milotta¹, Alina Hua¹, Karl Kunze^1,2, Radhouene Neji^1,2, Tevfik Ismail¹, Claudia Prieto¹, and René M. Botnar^1
1School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom, ²MR Research Collaborations, Siemens Healthcare Limited, Frimley, United Kingdom

Myocardial tissue characterization, such as quantification of fibrosis and oedema plays an important role in many myocardial diseases. T₁ and T₂ maps are typically acquired sequentially in 2D under several breath-holds. However, they achieve limited spatial resolution and coverage. To overcome these limitations, a high resolution, motion compensated joint T₁/T₂ water/fat sequence has been recently proposed and validated in phantom and healthy subjects. In this study, we demonstrate the capability of the proposed approach to obtain whole-heart, motion-compensated, simultaneous and co-registered T₁, T₂ maps and water and fat images in ~9min in patients with cardiovascular disease.

Ingo Hermann^1,2, Daiki Tamada³, Scott Reeder³, Lothar Schad², and Sebastian Weingärtner^1
1Magnetic Resonance Systems Lab, Department of Imaging Physics, Delft University of Technology, Delft, Netherlands, ²Computer Assisted Clinical Medicine, Medical Faculty Mannheim, University Heidelberg, Mannheim, Germany, ³Department of Radiology, University of Wisconsin, Madison, WI, United States

In this study we explore the use of the signal phase of RF phase modulated gradient echo imaging during steady state for rapid T₂ mapping in the myocardium. RF phase modulated GRE images were obtained with quadratic phase increments of ±2° and T₂ times were extracted by matching the phase evolution. B₁+ sensitivity was incorporated in the reconstruction based on separately acquired Bloch-Siegert maps. Good correlation was found in phantom measurements (R>0.95; p<0.0001) and high visual image quality in vivo.

Qi Liu¹, Yuan Zheng¹, Jingyuan Lyu¹, Zhongqi Zhang², Yanqun Teng², Shuheng Zhang², Jian Xu¹, and Weiguo Zhang^1
1UIH America, Inc., Houston, TX, United States, ²United Imaging Healthcare, Shanghai, China

Multiband (MB) technique is combined with multitasking for increased spatial coverage of the heart without prolonging scan time. Two different MB multitasking implementations were developed and compared with the conventional multitasking technique on volunteers and phantoms. Both methods demonstrated similar capabilities in solving multiple ‘tasks’ when compared with the reference method and exhibited good agreement in T1 mapping values. MB multitasking is a promising technique for cardiac MR.

Jochen Keupp¹, Petra J. v. Houdt², Jakob Meineke¹, Paul de Bruin³, Johannes M. Peeters³, Leon ter Beek⁴, and Mariya Doneva^1
1Philips Research, Hamburg, Germany, ²Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, Netherlands, ³Philips Healthcare, Best, Netherlands, ⁴Department of Medical Physics, The Netherlands Cancer Institute, Amsterdam, Netherlands

T2w-MRI plays an important role in prostate cancer providing information on the location and aggressiveness in diagnosis and therapy. T2-mapping may provide objective characterization, but is hampered by long acquisition time, which has been addressed by dedicated acceleration techniques (e.g. k-t T2-mapping). We investigated T2-mapping in a prostate cancer patient based on a 4-minute protocol with Poisson-disk prospective irregular sub-sampling in the k_y-TE domain in combination with a low rank and sparsity constraint compressed sensing reconstruction. The regularization parameters were investigated, and compressed sensing results were compared to separately acquired k-t T2-maps with respect to quality and noise.