Electronic Theses and Dissertations

Identifier

2510

Date

2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Biomedical Engineering

Committee Chair

Eugene Eckstein

Committee Member

Amy de Jongh Curry

Committee Member

Esra Roan

Abstract

The characterization and quantification of cerebral hemodynamics can provide critical biological information of current physiology. Divergent hemodynamic processes can provide integral knowledge into different pathophysiologies and aid in the diagnosis and evaluation of treatment. A variety of different magnetic resonance (MR) imaging techniques were implemented to quantify cerebral hemodynamics in a diverse set of neurological conditions. The first study investigated the association of blood flow and blood volume of a diffuse intrinsic pontine glioma tumor by arterial spin labeling (ASL) and dynamic susceptibility weighted contrast MR as a predictive marker of survival. Higher tumor blood flow and maintenance of higher blood flow was associated with longer progression free survival. In the following study, ASL was used to evaluate the association of resting state perfusion and neurocognitive impairment in long-term survivors of pediatric acute lymphoblastic leukemia and Hodgkin lymphoma. Systematic differences in resting state perfusion and neurocognitive performance was observed between the cancer survivor groups. In the last few studies, a variety of different MR techniques were implemented to investigate the hemodynamic properties of Sickle cell disease (SCD). Susceptibility weighed imaging (SWI) was used to investigate difference in the cerebral venous vascular system integrity between SCD patients and healthy controls. A segmentation procedure was introduced to quantify the normalized visible venous volume (NVVV). The study showed that SCD effects SWI venous conspicuity by having a lower NVVV with a global isointense venous contrast. A follow-up study improved the accuracy of the NVVV quantification by removing hypointese arterial vessel contamination. This new segmentation framework combined information from SWI and MR angiography. In the final study, intracranial blood velocity measurements made by MRI and transcranial Doppler ultrasound were compared in a cohort of SCD patients. Excessive intracranial blood velocity is a clinical indicator of elevated stroke risk in SCD patients. Blood velocities correlated well between the different modalities, however, MR systematically underestimated the blood velocity. The ability to noninvasively image, quantify, and monitor biological processed represents a powerful diagnostic toolkit for physiological evaluation. Characterizing cerebral hemodynamics only represents a small but vital tool for the future of medicine.

Comments

Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to the local University of Memphis Electronic Theses & dissertation (ETD) Repository.

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