Master of Science (MS)
Physics and Astronomy
Magnetic resonance elastography (MRE) allows the visualization of displacement patterns from induced harmonic mechanical waves propagating in tissue. Strain and mechanical properties can be computed from these displacement patterns. Mechanical properties of tissue are affected by various disease processes. MRE has shown brain tumor to differ in stiffness in comparison to normal tissue. MRE is currently being offered as an upgrade on most conventional MRI scanners. However, the actuator supplied by vendors is a drum driver designed primarily for hepatic MRE scan. The goals of the project was to design and build an ergonomic flexible driver for use in MRE of the brain, to assess the Scan-Rescan reproducibility of shear modulus measurements, and to investigate the relationship between shear modulus measurements and driver frequency. An ergonomic flexible driver was constructed to induce mechanical waves in the brain. MRE of the brain was performed in 10 healthy volunteers. MRE data was collected at frequencies of 60 Hz, 50 Hz, and 40 Hz. After the scans were completed, the subjects were removed from the table, and then repositioned and rescanned using the same process. All subjects were scanned and rescanned within an hour. The within-subject coefficient of variance (CV) and inter-subject CV were calculated for shear modulus measurements of white matter, grey matter, and whole brain. A one-way analysis of variance (ANOVA) was applied to test for any difference between shear modulus measurements made at different frequencies. The within-subject CVs of white matter, grey matter, and whole brain shear modulus measurements for all frequencies ranged from 3.7-4.1%, 4.7-6.0%, and 1.8-3.5% respectively. A significant statistical difference was found between measurements made at different frequencies. This study demonstrated the ability to make in vivo shear modulus measurements of brain tissue. MRE was shown to be able to differentiate white matter from grey matter using the shear modulus. Measured white and grey matter shear modulus values were within the range of values reported in literature. A dependence of shear modulus measurements on frequency was observed; Standardization of MRE imaging parameters is recommended to facilitate the interpretation of brain MRE results.
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Chafi, Hatim, "Magnetic Resonance Elastography of the Brain Using an Ergonomic Driver: Assessment of Scan-Rescan Reproducibility" (2015). LSU Master's Theses. 2496.