Doctoral Dissertation Defense – Peyton Lian Delgorio

BME PhD Candidate Peyton Lian Delgorio will be defending her dissertation:


High-Resolution Magnetic Resonance Elastography of Human Hippocampal Subfields



Alzheimer’s disease (AD) causes widespread neurodegeneration, leading to cognitive dysfunction and interruptions in functions of daily living. Studying the early stages of AD, including amnestic mild cognitive impairment (aMCI), may assist in early detection of AD and provide new opportunities for treatments and pharmaceutical interventions. To better understand and target these diseases, investigating the aging brain is crucial for providing insights into methods for combating the long-term effects of neurodegeneration. The hippocampal subfields (HCsf) have recently been targeted as they each have unique roles in memory processing, are cytoarchitecturally distinct, and may show differential sensitivity to aging and disease. However, metrics of HCsf atrophy, which are typically estimated with volumetric measures, are only indirectly related to tissue health and results have been inconsistent across studies. Magnetic resonance elastography (MRE) is a non-invasive MRI-based technique that sensitively assesses the microstructural tissue health of the brain. Prior limitations on high-resolution MRE methods have hindered the ability to properly investigate the HCsf. Thus, the goal of this thesis is to provide the first high-resolution MRE protocol for assessing HCsf viscoelasticity in aging and disease, as well as their associations with memory performance. This work consists of three main aims: (1) Establish a high-resolution, HCsf-specific MRE protocol and determine the effect of normal aging on their individual viscoelastic properties; (2) identify the unique structure-function relationships between the regions and different memory domains across the lifespan; and (3) determine the differential effects of aMCI on the individual HCsf properties and showcase the value of MRE measures in aMCI classification beyond established volume measures. In all, this work utilized high-resolution MRE to study a relevant and important clinical topic: the development and biological mechanisms behind AD pathophysiology in the HCsf. Furthermore, the HCsf viscoelastic measures may be used as clinical biomarkers in detecting and differentiating between different disease states such as normal aging, aMCI, and AD. Future research will expand this work to studying HCsf viscoelasticity in later stages of AD to capture how the specific HCsf mechanical properties change in AD progression.