Applications of anisotropic magnetic resonance elastography
| Author(s) | Caban-Rivera, Diego A. | |
| Date Accessioned | 2025-05-07T15:49:38Z | |
| Date Available | 2025-05-07T15:49:38Z | |
| Publication Date | 2025 | |
| SWORD Update | 2025-04-28T04:02:57Z | |
| Abstract | Magnetic resonance elastography (MRE) is a noninvasive imaging technique that characterizes the mechanical properties of soft tissues in vivo. While conventional MRE assumes isotropic material behavior, tissues such as white matter and skeletal muscle exhibit strongly anisotropic structure, with mechanical properties that vary by fiber orientation, density, and extracellular interactions. This dissertation applies a transversely isotropic nonlinear inversion (TI-NLI) framework to quantify direction-dependent tissue stiffness in the brain and lower limb, establishing the biological sensitivity and translational potential of anisotropic MRE across development, aging, and disease. ☐ In Aim 1, multi-excitation MRE was used to assess age-related differences in white matter anisotropy. Older adults exhibited significantly reduced shear and tensile anisotropy across nearly all major tracts, particularly in anterior regions. Logistic regression and voxel-wise analyses demonstrated that anisotropic MRE parameters provide complementary and distinct information relative to diffusion tensor imaging (DTI), supporting their utility for assessing microstructural integrity in aging. ☐ Aim 2 extended the TI-NLI framework to multifrequency MRE, validating it as a hardware-simplified alternative for estimating anisotropy from a single external actuation source. Simulations and in vivo data revealed strong agreement between multi-excitation and multifrequency estimates, with some regional variability in deeper tracts. Findings from this larger cohort replicated Aim 1 results and revealed developmental increases in anisotropy among younger participants, consistent with known patterns of white matter maturation. ☐ In Aim 3, MRE was applied to assess passive stiffness and composition in children with spastic hemiplegic cerebral palsy. The more affected leg exhibited significantly lower cross-sectional area and contractile tissue ratio relative to typically developing controls, and higher normalized shear stiffness in the soleus compared to the less affected side. Additionally, shear anisotropy in the gastrocnemius was significantly reduced in the more affected leg. These findings highlight the potential of anisotropic MRE to detect clinically relevant differences in muscle structure and mechanics in pediatric neuromuscular disorders. ☐ Collectively, this work demonstrates that anisotropic MRE using TI-NLI is a reproducible and biologically sensitive approach for probing microstructural differences in fibrous tissues. By establishing tract-level benchmarks across the lifespan and applying this framework to skeletal muscle in cerebral palsy, this dissertation supports the broader integration of anisotropic MRE into neuroimaging and musculoskeletal research, with promising applications in clinical diagnosis, monitoring, and intervention. | |
| Advisor | Johnson, Curtis L. | |
| Degree | Ph.D. | |
| Department | University of Delaware, Department of Biomedical Engineering | |
| Unique Identifier | 1518701507 | |
| URL | https://udspace.udel.edu/handle/19716/36109 | |
| Language | en | |
| Publisher | University of Delaware | |
| URI | https://www.proquest.com/pqdtlocal1006271/dissertations-theses/applications-anisotropic-magnetic-resonance/docview/3195958934/sem-2?accountid=10457 | |
| Keywords | Anisotropy | |
| Keywords | Cerebral palsy | |
| Keywords | Magnetic resonance elastography | |
| Keywords | White matter | |
| Title | Applications of anisotropic magnetic resonance elastography | |
| Type | Thesis |