Julia Velikina¹, Ruiyang Zhao^1,2, Collin J Buelo^1,2, Alexey A Samsonov¹, Scott B Reeder^1,2,3,4, and Diego Hernando^1,2
1Radiology, University of Wisconsin-Madison, Madison, WI, United States, ²Medical Physics, University of Wisconsin-Madison, Madison, WI, United States, ³Medicine, University of Wisconsin-Madison, Madison, WI, United States, ⁴Emergency Medicine, University of Wisconsin-Madison, Madison, WI, United States

Quantitative susceptibility mapping (QSM) is a promising non-invasive technique for assessment of liver iron concentration (LIC), necessary in a number of diseases. QSM solves an ill-conditioned inverse problem, whose performance depends on the chosen regularization. This work is the first to evaluate the accuracy, repeatability, and reproducibility of liver QSM for two regularized inversion methods in a large patient population with a wide range of LIC. Our results indicate that data-adaptive regularization shows higher correlation with reference LIC values and increases repeatability/reproducibility due to its reduced sensitivity to the field map errors and regularizing effect of anatomical priors.

Nan Wang¹, Fardad M. Serry², Tianle Cao², Fei Han³, Yibin Xie², Xiaodong Zhong³, Sen Ma², Xiaoming Bi³, Mazen Noureddin², Shehnaz Hussain⁴, Vibhas Deshpande⁵, Anthony G. Christodoulou², and Debiao Li^2
1Stanford University, Stanford, CA, United States, ²Cedars-Sinai Medical Center, Los Angeles, CA, United States, ³Siemens Medical Solutions, Los Angeles, CA, United States, ⁴University of California, Davis, Davis, CA, United States, ⁵Siemens Medical Solutions, Austin, TX, United States

Quantitative T1, fat fraction, and R2* show promise for characterizing chronic liver diseases. We develop a dual-flip-angle MultiTasking Multi-Echo (MT-ME-dFA) technique to achieve B1+ insensitive, whole-liver joint T1/water-specific T1(T1w), fat fraction(PDFF), and R2* quantification. Respiratory motion is resolved through multidimensional low-rank tensor imaging, and B1+ robustness is achieved by modeling the inversion recovery with two alternating flip angles. Compared to the previously published single-flip-angle MT-ME approach, intra-subject variation on T1/T1w maps was substantially reduced; stronger correlation was achieved for T1/T1w, PDFF and R2* with references on phantom; root-mean-square of intra-subject T1/T1w variation was substantially reduced from 72ms/63ms to 39ms/31ms.

Woowon Lee¹, Emily Y Miller², Hongtian Zhu¹, and Corey P Neu^1,2
1Paul M. Rady Department of Mechanical Engineering, University of Colorado, Boulder, CO, United States, ²Biomedical Engineering Program, University of Colorado, Boulder, CO, United States

Displacement encoding with stimulated echoes (DENSE) MRI is used to calculate pixel-level deformation maps of soft tissues under repetitive motion. It is a powerful technique that can quantify the mechanical behavior of tissues from displacement. We apply spiral DENSE MRI on human knees and obtain multi-frame displacement and strain maps during varus loading, leading to compressive motion on the medial condyle. Since high SNR DENSE images require long scanning time which is costly and less tolerable for participants, we additionally apply compressed sensing (CS) to reduce the imaging time to less than five minutes.

Mustafa Cavusoglu¹ and Christina Rossi^2
1University of Zurich, Zurich, Switzerland, ²University Hospital Zurich, Zurich, Switzerland

Monitoring the tissue sodium content (TSC) in the intervertebral disk geometry  by MRI is sensitive measure to diagnose degenerative disk disease (DDD) and of lumbar back pain (LBP) in intervertebral disks.  However, application of quantitative sodium concentration measurements in ²³Na-MRI  is highly challenging  due to the lower in vivo concentrations and smaller gyromagnetic ratio. Moreover, imaging the intervertebral disk geometry places higher demands because the necessary  RF volume coils produces highly inhomogenous transmit  field patterns.  In this study, we reported for the first time quantitative sodium concentration in the intervertebral disks at clinical field strengths (3T). 

Pierre Daudé^1,2, Frank Kober^1,2, Sylviane Confort Gouny^1,2, Monique Bernard^1,2, and Stanislas Rapacchi^1,2
1Aix-Marseille Univ, CNRS, CRMBM, Marseille, France, ²APHM, Hôpital Universitaire Timone, CEMEREM, Marseille, France

An open-source toolbox has been implemented to compare state-of-the-art open-source fat-water separation algorithms over synthetic multi-echo data. Data varied in fat-fraction, B0, SNR, number of echoes and echo spacings. Most algorithms proved to be biased for 3 echoes data. For 5 echoes and more, six algorithms were comparable, but two algorithms proved to be inaccurate. Echo spacing scheme impacted quantitative limits of agreements. For proton-density fat-fraction(PDFF) quantification in the extreme ranges, graph-cut approaches provided similar results while IDEAL-CE provided more reliable results. Interestingly, the toolbox also revealed PDFF/T2* quantification to be sensitive to the choice of the fat spectrum.

Adèle LC Mackowiak¹, Christopher W Roy¹, Mariana BL Falcaõ¹, Aurélien Bustin^1,2,3, Mario Bacher^1,4, Peter Speier⁴, Davide Piccini^1,5, Matthias Stuber^1,6, Naïk Vietti-Violi¹, and Jessica AM Bastiaansen^1,7,8
1Department of Radiology, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland, ²Department of Cardiovascular Imaging, Hôpital Cardiologique du Haut-Lévêque, CHU de Bordeaux, Bordeaux, France, ³IHU LIRYC, Electrophysiology and Heart Modeling Institute, INSERM U1045, Centre de Recherche Cardio-Thoracique de Bordeaux, Université de Bordeaux, Bordeaux, France, ⁴Siemens Healthcare GmbH, Erlangen, Germany, ⁵Advanced Clinical Imaging Technology, Siemens Healthcare AG, Lausanne, Switzerland, ⁶CIBM Center for Biomedical Imaging, Lausanne, Switzerland, ⁷Department of Diagnostic, Interventional and Pediatric Radiology (DIPR), Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland, ⁸Translational Imaging Center, sitem-insel, Bern, Switzerland

A free-breathing 3D radial multi-echo GRE acquisition for whole-liver fat-water separation and quantification was proposed, which integrated retrospective respiratory motion extraction with Pilot Tone and motion-compensated reconstruction with focused navigation. The proposed framework was tested in 10 healthy volunteers at 1.5T. Post-processing of the 8 reconstructed and denoised echoes with a graphcut algorithm provided fat-water separated images and fat fraction maps of isotropic resolution. Images and maps were compared to breath-held reference 3D and 2D Cartesian acquisitions for validation of the quality of both motion compensation and fat-water separation.

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, ³GE Healthcare, Waukesha, WI, United States, ⁴GE 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

T₁ relaxation is emerging as a quantitative biomarker for the diagnosis and staging of chronic liver disease. Conventional T₁ mapping methods such as variable flip angle and Modified Look-Locker Inversion Recovery, fail to address confounding factors such as B₁ inhomogeneities, the presence of fat, and motion. In this work, we propose a novel free-breathing T₁ mapping method that addresses multiple confounding factors, combining chemical shift encoded MRI, inversion recovery and stack-of-stars sampling strategy for abdominal T₁ mapping.

MungSoo Kang^1,2, Ramin Jafari¹, Gerald G. Behr³, Ricardo Otazo^1,3, and Youngwook Kee^1
1Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, United States, ²Department of Biomedical Engineering, Ulsan National Institute of Science and Technology, Ulsan, Korea, Republic of, ³Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, NY, United States

Liver quantitative susceptibility mapping (QSM) can provide a direct measurement of liver iron concentration (LIC). However, respiratory motion and rapid T₂^* decay are the major challenges in reliable liver QSM. To address these issues a motion-resolved multi-echo 3D cones MRI method with pseudo-random view ordering was implemented, which was then compared with a multi-echo Cartesian GRE sequence in a phantom and healthy volunteer. The proposed motion-resolved cones QSM presented strong motion-robustness in terms of image quality and ROI-based measurements in our phantom and in-vivo studies, demonstrating the feasibility of free-breathing liver QSM.