Grace McIlvain¹, Emily M Magoon², Rebecca Clements², Alexis Merritt², Lucy V Hiscox³, Hillary Schwarb⁴, and Curtis L Johnson^2
1Biomedical Engineering, University of Delaware, Newark, DE, United States, ²University of Delaware, Newark, DE, United States, ³University of Bath, Bath, United Kingdom, ⁴University of Illinois at Urbana-Champaign, Champaign, IL, United States

Here we use magnetic resonance elastography (MRE) to quantify brain mechanical properties of 30 individuals aged 19-30 immediately before a high intensity interval training (HIIT) exercise, immediately after exercise, and 1 hour after exercise. We additionally tested subjects’ cognitive performance at these time points through a memory task and two executive function tasks. We found that whole brain stiffness decreased in nearly all subjects immediately after exercise by an average of 4.2% (p<0.0001) and that whole brain damping ratio increased by an average of 3.1% (p=0.001). Performance on all three cognitive tasks improved immediately after exercise (p<0.05).

Matthew McGarry¹, John Weaver^1,2, and Keith Paulsen^1,2
1Dartmouth College, Hanover, NH, United States, ²Dartmouth-Hitchcock Medical Center, Lebanon, NH, United States

The pulsatile tissue motions from the cardiac cycle can be imaged using retrospectively gated phase contrast MRI. Modeling brain tissue as a poroelastic material allows a distribution of pulsatile fluid sources to be computed which reproduce the measured motions by estimating the RHS vector of a finite element representation of the poroelastic system. This Fluid source imaging (FSI) represents a completely new type of image parameterization that could offer unique diagnostic signatures. The associated pressure field gradients are also the driving force for interstitial fluid movement, where disruptions are thought to cause buildup of waste products which leads to dementia.

Jiahui Li¹, Zheng Zhu¹, Jingbiao Chen¹, Alina M Allen², Sudhakar K. Venkatesh¹, Taofic Mounajjed³, Kevin J. Glaser¹, Armando Manduca¹, Vijay H. Shah², Richard L. Ehman¹, and Meng Yin^1
1Radiology, Mayo Clinic, Rochester, MN, United States, ²Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN, United States, ³Anatomic Pathology, Mayo Clinic, Rochester, MN, United States

The water in hepatic tissue has intracellular, extracellular matrix bound, and extracellular interstitial free fluid components, which are affected by inflammation and fibrosis.  This study assessed longitudinal changes in MRE-based biomarkers and their relationship with hepatic water content in clinical and preclinical models.  In clinical studies, MRE-assessed loss modulus (LM) was elevated in obese patients and in NAFLD patients with severe inflammation. In preclinical models, changes in LM correlated with water content and disease progression in non-NAFLD mice. LM significantly increased with the development of NASH.  MRE-assessed viscoelasticity strongly reflects extracellular free fluid associated with inflammation.

Gwenaël Pagé¹, Philippe Garteiser¹, Valérie Paradis², Ralph Sinkus³, Valérie Vilgrain^1,4, and Bernard E. Van Beers^1,4
1Laboratory of imaging biomarkers, INSERM UMR 1149, Paris, France, ²Center for research on inflammation, INSERM UMR 1149, Paris, France, ³Laboratory for vascular translational science, INSERM UMR 1148, Paris, France, ⁴Department of Radiology, University Hospital Paris Nord, Clichy, France

The aim of this study was to investigate the value of compression MR elastography to assess microvascular invasion in hepatocellular carcinomas. MR elastographic and T2-weighted images were acquired at end expiration and end inspiration in 52 patients with hepatocellular carcinomas. The storage and loss moduli at inspiration did not differ between tumors with/without microvascular invasion. However, the compression stiffening rate, derived from the increase of tumor storage modulus between expiration and inspiration, had good diagnostic performance (area under the receiver operating characteristic curve 0.85) in detecting microvascular invasion.

Sevgi Gokce Kafali^1,2, Bradley D. Bolster Jr.³, Shu-Fu Shih^1,2, Grace J. Kim¹, Joanna Yeh⁴, Robert S. Venick⁴, Shahnaz Ghahremani¹, Kara L. Calkins⁴, and Holden H. Wu^1,2
1Radiological Sciences, University of California, Los Angeles, Los Angeles, CA, United States, ²Bioengineering, University of California, Los Angeles, Los Angeles, CA, United States, ³MR Collaborations, Siemens Medical Solutions, Inc., Salt Lake City, UT, United States, ⁴Pediatrics, University of California, Los Angeles, Los Angeles, CA, United States

Hepatic stiffness measured by magnetic resonance elastography (MRE) is a biomarker for hepatic fibrosis. Conventional Cartesian gradient-echo MRE requires breath-holding (BH), which can be challenging for children. While radial free-breathing (FB) MRE overcomes the challenge of BH, the scan time is relatively longer (163 seconds/slice). This study’s objective was to reduce radial FB-MRE scan time by a factor of two with rapid motion encoding (81 seconds/slice) and to improve robustness by performing self-navigated motion compensation. Compared to Cartesian BH-MRE in children at 3T, the proposed rapid radial FB-MRE technique quantified hepatic stiffness with close agreement and similar repeatability. 

Clementine Lesbats¹, Upasana Roy¹, Emma L. Reeves¹, Jessica K. R. Boult¹, Yann Jamin², Craig Cummings¹, James Sullivan³, Ralph Sinkus⁴, Erik Wennerberg¹, and Simon P. Robinson^2
1Division of Radiotherapy & Imaging, The Institute of Cancer Research, Sutton, United Kingdom, ²The Institute of Cancer Research, Sutton, United Kingdom, ³The Royal Marsden NHS Foundation Trust, Sutton, United Kingdom, ⁴School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom

Radiotherapy is widely used to treat cancer. In this study, we used MR elastography to evaluate early tumour response to radiation therapy. A significant increase in stiffness |G*| and elasticity G_d were determined 3 days after orthotopic 4T1 breast tumours were irradiated with a single 8Gy dose, compared to untreated control tumour-bearing mice. The increase in tumour stiffness was associated with an increased macromolecule pool measured by magnetisation transfer, and increased collagen deposition observed histologically.

Anne-Sophie van Schelt¹, Nienke P.M. Wassenaar¹, Jurgen H. Runge¹, Jules L. Nelissen¹, Marian Troelstra^1,2, Christian Guenthner³, Ralph Sinkus^2,4, Jaap Stoker¹, Aart J. Nederveen¹, and Eric M. Schrauben^1
1Radiology and Nuclear Medicine, Amsterdam UMC location AMC, Amsterdam, Netherlands, ²Department of Imaging Sciences and Biomedical Engineering, King’s College London, London, United Kingdom, ³Department of Biomed, ETH Zurich, Zurich, Switzerland, ⁴Inserm U1148, LVTS, Univeristy Paris Diderot, Paris, France

Magnetic resonance elastography (MRE) allows for non-invasive determination of pancreatic visco-elastic properties in four consecutive breath-holds. The aim of this study was to develop and test a single breath-hold MRE acquisition accelerated using prospective undersampling and compressed sensing (CS) reconstruction. Testing was done on a retrospective undersampled phantom dataset and in-vivo. These showed that CS accelerated (R< 8.7), single breath-hold MRE is feasible without hampering visco-elastic reconstruction in tissues with low shear stiffness (|G*|<1.6kPa). Further research is necessary to guarantee accuracy of the measured shear stiffness, notably for high stiffness tissues such as tumors, and at higher acceleration factors.