Undergraduate Honors Theses

Thesis Defended

Spring 2017

Document Type

Thesis

Type of Thesis

Departmental Honors

Department

Engineering Physics

First Advisor

Dr. Stephen Russek

Abstract

MRI is increasingly used in mapping tissue susceptibility to identify cerebral microbleeds associated with traumatic brain injury and pathological iron deposits associated with neurodegenerative diseases such as Parkinson's and Alzheimer's disease [1,2]. Accurate measurement is important for determining oxygen and iron content in blood vessels and tissue in the brain, which are in turn used for noninvasive clinical diagnosis and treatment assessments. Magnetic field distortions with a resolution of a few parts per billion can be measured using MRI phase maps. The field distortion map can then be inverted to obtain a quantitative susceptibility map. The primary focus of this thesis project is to determine the accuracy of these MRI-based susceptibility measurements and to demonstrate their ability to reliably measure the concentration of oxygenated hemoglobin in-vitro. The susceptibility of paramagnetic salts in cylindrical containers with varied temperature and orientation relative to the static MRI field were compared with theoretical predictions. The MRI susceptibility measurements were compared with SQUID magnetometry. Limitations of these measurements were investigated with Finite Element Method and Monte Carlo simulations of the macroscopic and microscopic field shifts in our samples, respectively. Measurements of oxygen concentration of bovine hemoglobin samples will be tested against optical absorption techniques to test the potential functionality of MRI oximetry in in-vivo diagnostics.