Giacomo Annio^1,2, Omar Darwish², Elijah Van Houten³, Knut Solna⁴, Sverre Holm⁵, and Ralph Sinkus^1,2
1LVTS, INSERM U1148, Paris, France, ²Department of Biomedical Engineering, King's College London, London, United Kingdom, ³Département de Génie Mécanique, Université de Sherbrooke, Sherbrooke, QC, Canada, ⁴Department of Mathematics, University of California at Irvine, Irvine, CA, United States, ⁵Department of Physics, University of Oslo, Oslo, Norway

MRE is a novel tool to study in-vivo biomechanics. Recently, the diagnostic value of viscosity has been explored. However, its physical origin as intrinsic absorption or due to scattering is yet unknown. This work shows that the majority of viscosity at about 100Hz is apparent, thus originating mainly from scattering. Moreover, we observed that the classical springpot model fails to describe the dispersion properties of complex media containing scattering structures. We propose a nonlocal viscoelastic model that can ultimately disentangle intrinsic loss effects from scattering-induced ones. This changes dramatically the way we interpret viscous changes for therapies impacting on vasculature.

Runke Wang¹, Suhao Qiu¹, Zhiyong Zhang¹, and Yuan Feng^1
1School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China

Accelerating magnetic resonance elastography (MRE) is desired for improved patient care and image quality. In this study, we proposed a multiphase radial DENSE MRE (MRD-MRE) sequence, and a compressed sensing based reconstruction algorithm using the sparsity of harmonic motion. A spatial modulation of magnetization (SPAMM) shot was applied for motion encoding together with a radial sampling scheme for acceleration. Reconstruction accuracy was improved by utilizing the temporal sparsity of harmonic motion. Phantom and brain imaging showed that an acceleration factor up to 4 could be reached.

Yi Sui¹, Jiahui Li¹, Joshua D. Trzasko¹, Arvin Arani¹, Kevin Glaser¹, Phillip J. Rossman¹, Ziying Yin¹, Meng Yin¹, and Richard L. Ehman^1
1Radiology, Mayo Clinic, Rochester, MN, United States

A free-breathing hybrid radial-cartesian 3D MRE technique (TURBINE-MRE) was developed for MR elastography of the liver. This technique provides motion-resolved wave images and stiffness maps in single 4-minute free breathing acquisition. The feasibility of the new technique was demonstrated in healthy volunteers and a NASH patient with hepatic cirrhosis.

Tanguy Boucneau¹, Brice Fernandez², Luc Darrasse¹, and Xavier Maître^1
1Université Paris-Saclay, CEA, CNRS, Inserm, BioMaps, Orsay, France, ²Applications & Workflow, GE Healthcare, Orsay, France

By decoupling motion and spatial encoding, magnitude contrast MR Elastography could be performed for the first time at ultrashort echo times (12 µs). On the basis of a motion-sensitizing magnetization preparation, the available total magnetic moment is sensitized to the motion induced in the tissues so the information can be efficiently carried over by the MR signal magnitude when the selected imaging pulse sequence is applied. The new paradigm allows also for shorter total acquisition times as demonstrated here in a set of homogeneous and heterogeneous phantoms with up to 5-fold acceleration factors.

Grace McIlvain ¹, Julie M Schneider², Melanie A Matyi ³, Melissa S DiFabio¹, Peyton L Delgorio¹, Matthew DJ McGarry ⁴, Jeffrey M Spielberg³, Zhenghan Qi², and Curtis L Johnson^1
1Biomedical Engineering, University of Delaware, Newark, DE, United States, ²Department of Linguistics, University of Delaware, Newark, DE, United States, ³Department of Psychology, University of Delaware, Newark, DE, United States, ⁴Thayer School of Engineering, Dartmouth College, Hanover, NH, United States

Brain mechanical properties are markers of microstructural health and have been extensively studied in neurodegeneration using MR elastography. However, brain mechanical changes during maturation have yet to be comprehensively explored. Here we present preliminary findings from an ongoing study which uses OSCILLATE, a fast acquisition, high-resolution sequence to characterize brain mechanical properties in people ages 5-21. We present notable regional brain mechanical property differences during development and aim to categorize brain mechanical property developmental trajectories in major anatomical structures. This data will provide a platform for brain mechanical property comparison when studying atypical maturation.

Anna Sophie Wittgenstein¹, Marco Barbero Mota², Giacomo Annio², Guillaume Rucher², Rachida Aid-Launais², Rami Mustapha³, David Alexander Nordsletten^1,4, and Ralph Sinkus^1,2
1School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom, ²INSERM-Université de Paris, Paris, France, ³chool of Cancer and Pharmaceutical Sciences, King's College London, London, United Kingdom, ⁴Department of Biomedical Engineering and Cardiac Surgery, University of Michigan, Ann Habor, MI, United States

In vivo assessment of biomechanical properties in the left ventricle carries substantial promises for disease characterization. Its proper quantification, however, is far from straightforward. We propose an ECG-gated 3D CINE GRE sequence with motion encoding gradients (TR=7ms) and time-shifted mechanical excitation to quantify the propagation of transient shear waves at a temporal resolution of 0.7ms. In-vivo results in anesthetised rats show apparent shear waves speeds around 8m/s at mid diastole, compatible with recent human in-vivo data.

Rolf Reiter¹, Mehrgan Shahryari¹, Heiko Tzschätzsch¹, Matthias Haas¹, Christian Bayerl¹, Britta Siegmund², Bernd Hamm¹, Patrick Asbach¹, Jürgen Braun¹, and Ingolf Sack^1
1Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany, ²Gastroenterology, Charité - Universitätsmedizin Berlin, Berlin, Germany

We aimed to investigate the solid-fluid behavior of hepatic fibrosis and cirrhosis using multifrequency MR elastography. Despite the success of stiffness-based assessment of hepatic fibrosis, little is known about tissue’s solid-fluid behavior upon fibrosis. Although cirrhosis is associated with liver stiffening and, intuitively, transition towards more rigid material properties, the observed increases in fluidity and slope of shear-wave-speed-dispersion indicate abnormally high mechanical friction in cirrhotic livers. This biophysical signature might provide a prognostic imaging marker for the detection of end-stage fibrosis independent of stiffness. 

Jie Chen^1,2, Alina Allen³, Terry Therneau⁴, Jun Chen², Jiahui Li², Jingbiao Chen², Xin Lu², Zheng Zhu², safa Hoodeshenas², Sudhakar Venkatesh², Bin Song¹, Richard Ehman², and Meng Yin^2
1Department of Radiology, West China Hospital, Sichuan University, Chengdu, China, ²Department of Radiology, Mayo Clinic, Rochester, MN, United States, ³Devision of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN, United States, ⁴Devision of Biomedical Statistics and Informatics, Mayo Clinic, Rochester, MN, United States

In a cross-sectional study, we investigated the relationship between pathology-assessed hepatic steatosis, MRI-assessed PDFF, and LSM with MRE in a large NAFLD population. No significant differences in LSM was found between patients with S1, S2, and S3 steatosis, and between all steatosis grades after patients were grouped according to fibrosis stage. After adjusting with fibrosis stage and age, there was no statistically significant relationship between liver stiffness and PDFF in patients with diagnosed steatosis (i.e., PDFF≥5%). LSM by MRE is not biased by increased liver fat content.

Paul Kennedy¹, Muhammed Shareef¹, Octavia Bane¹, Guillermo Carbonell¹, Elizabeth Miller², Israel Lowy², Stephen Ward¹, M. Isabel Fiel¹, Miriam Merad¹, Thomas Marron¹, and Bachir Taouli^1
1Icahn School of Medicine at Mount Sinai, New York, NY, United States, ²Regeneron Pharmaceuticals Inc., Tarrytown, NY, United States

In this prospective study we correlated tumor stiffness measured in hepatocellular carcinoma with density of tumor infiltrating lymphocytes and  assessed the changes in tumor stiffness in patients undergoing neoadjuvant immunotherapy prior to liver resection. We found that tumor stiffness strongly correlates with grade of tumor infiltrating lymphocytes, and that changes in tumor stiffness correlate with histopathologic response.

Jingbiao Chen¹, Mahmoud Adam Tahboub Amawi², Xin Lu², Jie Chen³, Jiahui Li², Zheng Zhu², Safa Hoodeshenas², Jin Wang⁴, Douglas A Simonetto², Vijay H Shah², Richard L Ehman², and Meng Yin^2
1Radiology, the Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China, ²Mayo Clinic, Rochester, MN, United States, ³West China Hospital, Chengdu, China, ⁴the Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China

Identifying those at high risk for the development of end-stage liver disease in patients with alcohol-associated liver disease (ALD) is of great clinical importance. We retrospectively investigated the role of MR elastography (MRE) in predicting cirrhosis or decompensated cirrhosis on a cohort of 182 ALD patients. Our preliminary results indicated that liver stiffness measured by 2D-MRE is a significant and independent prognostic factor for the future development of cirrhosis or decompensated cirrhosis. These results echoed the previous findings in other etiologies and reinforced the prognostic value of MRE in predicting advanced liver disease, which facilitates early intervention for ALD.