Estimation of Brain Biomechanics using MRI

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Abstract

In FY23, we have scanned 12 subjects (5 Male, 7 Female), with 12 tagged MRI scans under neck rotation, 5 tagged MRI scans under next extension, and 7 MRE scans. A total of 6 subjects underwent all 3 scans, including one subject initially scanned in the previous year. Most of the scans were from the 22-49 age group, with one subject from the over 50 group. In addition to scanning, we continued to optimize the acquisition protocol 1, particularly since transitioning to a 1.5T scanner in the previous year due to the retirement of the Siemens Biograph mMR 3T scanner. At the lower field strength, we have observed that tag fading occurs more rapidly, leading to noisier measurements at later timepoints during the acquisition. We are also applying these techniques to characterize the biomechanical properties of a gyrencephalic phantom 2, as well as a novel skull-brain phantom 3. This novel brain-skull phantom uses a cylindrical shape composed of polyacrylamide gel, and additionally has small, evenly spaced slots around the perimeter that can be filled with a fat simulant to simulate skull marrow. We have continued to evaluate the biomechanics in post-mortem specimens. We have acquired tagged MRI and MRE longitudinally from a cadaver head specimen spanning 48 hours to 72 days after death. This data set will allow us to not only compare the material properties and brain deformation following impulsive loading between cadavers and humans, but it will also enable characterization of how the cadaver properties evolve over time. Because post-mortem studies remain an integral part of TBI biomechanical studies, the biofidelity of its response as the brain tissue degrades is an important consideration. We have submitted two conference abstracts on this data set 4, 5. 1. Lu YC, Knutsen AK, Alshareef A, Wang WT, Mojumder J, Prince JL, Bayly PV, Butman JA, Pham DL. Late triggering of tagged MRI for measurement of in vivo brain deformation during head rotation. Summer Biomechanics, Bioengineering and Biotransport Conference (SB3C). Jun 4-8, 2023, Vail, CO. 2. Knutsen AK, Vidhate S, McIlvain G, Luster J, Galindo EJ, Johnson CL, Pham DL, Butman JA, Mejia-Alvarez R, Tartis M, Willis AM. Characterization of material properties and deformation in the ANGUS phantom during mild head impacts using MRI. J Mech Behav Biomed Mater. 2023 Feb;138:105586. doi: 10.1016/j.jmbbm.2022.105586. PMID: 36516544. NIHMSID: 1895812. 3. Mojumder J, Vidhate S, Lu YC, Alshareef A, Johnson CL, Pham DL, Butman JA. Novel MRI phantoms for investigating skull-brain mechanics. Summer Biomechanics, Bioengineering and Biotransport Conference (SB3C). Jun 4-8, 2023, Vail, CO. 4. Lu YC, Mojumder J, Alshareef A, Prince JL, Bayly PV, Butman JA, Pham DL. Quantifying biomechanical property changes of the human cadaver brain using tagged magnetic resonance imaging. Submitted to the Annual Meeting of the Biomedical Engineering Society (BMES) Oct 11-14, 2023. Seattle, WA. 5. Mojumder J, Lu YC, Diano A, Alshareef A, Johnson CL, Pham DL, Butman JA. Relating tissue properties of post-mortem brain to time from death using magnetic resonance elastography. Submitted to the Annual Meeting of the Biomedical Engineering Society (BMES) Oct 11-14, 2023. Seattle, WA.