Ishita Raghuvanshi
BME MS Thesis Defense Presentation
Date: 2026-11-12
Time: 12:00 pm 
Location / Meeting Link: Room N600, Health Sciences Research Building II, 1750 Haygood Dr NE, Atlanta, GA 30322 

Committee Members:
Dr. Candace Fleischer (advisor); Dr. John Oshinski; Dr. David Reiter


Title: Tolerability, repeatability, and clinical application of brain thermometry at ultra-high magnetic resonance field strengths

Abstract:
Brain temperature is a tightly regulated physiological parameter, maintained by the balance between metabolic heat production and heat dissipation through cerebral blood flow. Deviations from healthy temperature ranges may indicate injury or disease. Chemical shift thermometry (CST) uses proton magnetic resonance spectroscopy (¹H MRS) to measure the chemical shift difference between water and a temperature insensitive metabolite to quantify absolute brain temperature noninvasively, and ultra-high field (7T) MRI provides greater signal-to-noise ratio and spectral resolution than conventional field strengths which may enable precise temperature measurement. CST has been developed and validated primarily at lower field strengths (≤3 T), and its use at 7T requires characterization of participant tolerability and field-specific values in healthy adults. Furthermore, applications in disease are largely unexplored. This thesis addresses the two gaps and demonstrates application of 7T CST in a disease model. Tolerability was assessed by comparing symptom prevalence in healthy adults scanned with both 3T and 7T MRI. Symptoms, predominantly dizziness, were reported by 61% of participants at 7T and 3% at 3T and were present on entry into the bore, independent of cumulative scan time. Subsequently, a mock 7T bore and head and neck coil was designed and 3D-printed as a low-cost, portable tool to help acclimate participants to ultra-high field MRI and was implemented to screen prospective clinical trial participants for comfort prior to a 7T MRI examination. The repeatability and healthy range of brain temperature measured with 7T CST were then characterized in healthy adults. Brain temperature demonstrated moderate repeatability in the posterior cingulate cortex (PCC) and high repeatability in the thalamus, with thalamic temperature exceeding cortical temperature. Brain temperature at 7T was approximately 0.8°C lower than at 3T despite comparable body temperature, indicating a field-strength dependence that precludes the direct application of 3T reference ranges at 7T and motivates further investigation into field strength dependent effects. Median brain temperature at 7T was 37.1°C and was not associated with age or sex. Finally, 7T CST was applied to assess brain temperature alterations in people with HIV (PWH). PCC temperature was lower in PWH than in healthy controls, and associations between brain temperature and myo-inositol and total choline, markers of glial activity and membrane turnover, were present in controls but absent in PWH. These findings suggest brain temperature, and its coupling to cerebral metabolism remains altered despite viral suppression. Collectively, this work characterizes participant experience at 7T and establishes field-specific reference values for CST. It also demonstrates that 7T CST is sensitive to disease-related alterations in brain physiology. Interpreted against field-specific reference values, 7T CST can serve as a noninvasive, quantitative marker of brain health that complements standard of care MRI parameters.