Shannon Helsper^1,2, Xuegang Yuan³, Richard Jeske², Li Sun⁴, David G. Meckes Jr.⁴, Yan Li², and Samuel C. Grant^1,2
1National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, United States, ²Chemical & Biomedical Engineering, FAMU-FSU College of Engineering, Tallahassee, FL, United States, ³University of California, Los Angeles, CA, United States, ⁴Department of Biomedical Sciences, Florida State University, Tallahassee, FL, United States

This study interrogates human mesenchymal stem cell (hMSC) derived treatments (cells versus secretome) in a preclinical transient ischemic stroke model. Biochemical markers of tissue recovery measured longitudinally over 21 d via sodium chemical shift imaging and proton relaxation-enhanced MR spectroscopy demonstrated that the arterial injection of extracellular vesicles produced in vitro by hMSC improved outcomes over ischemic stroke, albeit not to the level of direct cellular implantation. For the first time, novel MRI-compatible labeling provided the initial visualization of biodistribution and estimated permanence of hMSC-derived extracellular vesicles in the ischemic brain.

Mohamed Salah Khlif¹, Emilio Werden¹, Laura Bird², Natalia Brumley-Egorova¹, and Amy Brodtmann^1
1The Florey Institute of Neuroscience and Mental Health, Parkville, Australia, ²Turner Institute for Brain and Mental Health, Monash University, Clayton, Australia

Cortical thinning has been used both for diagnosis and disease monitoring. Few studies have examined longitudinal changes in cortical thickness following ischemic stroke. We compared cortical thinning, vortex-wise and region-wise, between ischemic stroke survivors and stroke-free control participants at 3 months and 3 years post-stroke using linear mixed-effect regression and correcting for age and sex. At 3 years, there was widespread cortical thinning in ischemic stroke, especially in the ipsilesional cortex, in lobes implicated in motor, sensory, and memory processing and recovery.

Jonathan Rafael-Patiño^1,2, Elda Fischi-Gomez¹, Sebastian Otálora³, Veronica Ravano^1,2,4, Guillaume Saliou¹, Steven David Hajdu¹, Tobias Kober^1,2,4, Roland Wiest³, Patrik Michel⁵, Richard McKinley³, and Jonas Richiardi^1
1Radiology Department, Centre Hospitalier Universitaire Vaudois and University of Lausanne., Lausanne, Switzerland, ²LTS5, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland, ³Support Center for Advanced Neuroimaging (SCAN), University Institute of Diagnostic and Interventional Neuroradiology, University of Bern, Inselspital, Bern University Hospital., Bern, Switzerland, ⁴Advanced Clinical Imaging Technology, Siemens Healthcare AG., Lausanne, Switzerland, ⁵Stoke Center, Neurology Service, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland

In acute stroke assessment, reference clinical trials such as DEFUSE-3 use absolute thresholds on ADC maps to define the infarct core. Yet, the variance of ADC values, but not the mean, change with the number of diffusion directions and the specific directions in a 4-directions sampling scheme. The resulting shifts in ADC distribution tails result in an overestimation of the infarct core. This has implications for multi-centric trials, where infarct sizes and locations may be biased simply due to diffusion protocol differences and/or different head positions with respect to B₀.

Mi Zhou¹, Robert Stobbe¹, Brian Buck², Ken Butcher², Paige Fairall², Annie Boyd¹, Derek Emery³, Thorsten Feiweier⁴, and Christian Beaulieu^1
1Biomedical Engineering, University of Alberta, Edmonton, AB, Canada, ²Neurology, University of Alberta, Edmonton, AB, Canada, ³Radiology and Diagnostic Imaging, University of Alberta, Edmonton, AB, Canada, ⁴Siemens Healthcare GmbH, Erlangen, Germany

Short diffusion time oscillating gradient spin echo (OGSE) showed less water diffusion reduction in acute human stroke lesions (n=28) than the typical clinically used long diffusion time pulsed gradient spin echo (PGSE) method. The diffusion time dependency is far greater in ischemic lesions, particularly white matter, than in contralateral healthy brain. These effects were heterogeneous across the lesion with larger OGSE-PGSE differences in regions indicative of larger axons. The range of MD decrease in lesions across patients as measured with OGSE and PGSE showed a linear correlation and is consistent with concomitant axon beading and swelling implied from prior simulations.

Giacomo Annio^1,2, Gabrielle Mangin¹, Marco Barbero-Mota¹, Giuseppina Caligiuri¹, Antonino Nicoletti¹, Katharina Schregel³, and Ralph Sinkus^1,4
1INSERM UMRS1148 - Laboratory for Vascular Translational Science, University Paris, Paris, France, ²School of Biomedical Engineering and Imaging Sciences, King’s College London, London, United Kingdom, ³Department of Neuroradiology, Heidelberg University Hospital, Heidelberg, Germany, ⁴School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom

Stroke is the leading cause of death globally. The infarcted area undergoes a deprivation of oxygen and energy, followed by multiple transient events and reorganization processes called ischemic cascade. MRI is the reference tool for accurate diagnosis, volumetric assessments and age determination of the lesion. The aim of the present study was to investigate the time course of changes in tissue biomechanics after an ischemic event in mice using MRE and study the relationship between stroke volume and tissue biomechanics, to explore a potential role of MRE in assessing the post stroke recovery.