Dissertations and Theses

Date of Award


Document Type



Biomedical Engineering

First Advisor

Lucas Parra

Second Advisor

Priti Balchandani


Magnetic resonance imaging, ultra-high field, depression, trigeminal neuralgia, spectroscopy, GABA


Neurological and neuropsychiatric diseases and disorders are a major burden on society, impairing the health and functioning of millions of people every year. There is a need to define the biological bases of these diseases and identify potential biomarkers to improve diagnosis, monitoring, and treatment efficacy across multiple diseases.

Magnetic resonance imaging (MRI) is a noninvasive imaging technique which facilitates detection of brain lesions and visualization of the brain overall. However, limitations in contrast and resolution at clinical field strengths may hinder investigation of the underlying biological mechanisms of these diseases. Ultra-high field MRI scanners, such as those at 7-Tesla, can enhance biomarker detection because they provide superior contrast, resolution, and signal-to-noise-ratio (SNR) in feasible scan times. Since ultra-high field systems come with their own unique set of technical challenges, especially as applied to brain imaging, technique optimization and development is often required.

To address these concerns while leveraging the advantages of 7-Tesla MRI, we have designed and conducted studies to provide high-resolution imaging of small structures and high spectral resolution of metabolite concentrations in clinically feasible scan times. As a group, these studies provide support for the usefulness of ultra-high field MRI for revealing disease pathophysiology through the detection of biomarkers, which may be unclear or below the threshold of detectability at clinical field strengths.

The purpose of this work was to investigate anatomical and spectroscopic biomarkers in the brain. Specifically, we analyzed limbic structure subfield volumes, including subfields of the hippocampus, amygdala, and thalamus, for diseases including major depressive disorder (MDD) and trigeminal neuralgia (TN). We found a significant reduction in the right CA2/3 subfield volume of the hippocampus in MDD patients compared to healthy controls. In TN, we found significant differences in subfield volumes between patients and controls, specifically in the nerve cross-sectional-area, in the basal and paralaminar subnuclei of the amygdala, and in the central lateral subnucleus and the inferior and lateral pulvinar subnuclei of the thalamus. We also developed a method for detecting gamma-Aminobutyric acid (GABA) with spectroscopic editing, with potential application to MDD. In summary, we have presented significant findings in biomarker detection and a novel method for spectroscopic signal editing of GABA at ultra-high field MRI.



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