Magnetic-susceptibility-based functional MRI for heart disease
By: Rohan Dharmakumar.
Published: 2004
Language: eng
Number of pages: 168
Description: Heart disease is the primary cause of mortality in the western world. A common feature among several cardiac pathologies is the disruption of hemodynamic and/or oxygen metabolism/delivery homeostasis. The major hemodynamic variables of interest in the clinical assessment of heart disease are blood pressure and flow. While the noninvasive assessment of flow and systemic pressures are easily obtained, the measurement of pulmonary arterial pressure (PAP) is challenging. Since a small change in PAP (5mmHg) defines pulmonary hypertension (PH), for early detection of PH, a highly sensitive technique is needed. Since PH is progressive in nature, in time, right ventricular failure will cause death. Currently existing diagnostic techniques are limited either by their invasiveness to the body or by their inability to provide a quantitative measure of PAP, even for moderate PH. Further, impairments in oxygen metabolism/delivery mechanisms are also critical in many serious heart conditions. Magnetic resonance imaging (MRI) is being developed around the world as a potential methodology for the assessment of oxygen-related functional changes in the cardiovascular system. However, the scan times associated with commonly employed MRI measurement methods are prohibitively long for some cardiac applications.This dissertation focuses on using MRI to develop noninvasive methods that can provide accurate measurements of pressure and fast measurements of blood oxygen saturations. Both techniques were developed by exploiting the unique ability of MRI to detect changes in field perturbation due to magnetic susceptibility differences in the vicinity of different probing media---a novel pressure-sensitive contrast agent for manometry and deoxygenated red blood cells for oximetry. The first two contributions are theoretical studies aimed at improving the microbubble-based manometry technique. The first of these works explores the parameter space of microbubble-based MR manometry. Based on the conclusions derived, the second work proposes a novel microbubble construct and shows theoretically how such a construct may be useful in improving the sensitivity. The following chapter forms the basis for improving the temporal sensitivity of the oximetry technique. The final chapter concludes with the discussion of future directions on how the magnetic-susceptibility-based functional measures need to be developed further to become clinically useful.
Notes: Adviser:  Graham Wright.

Thesis (Ph.D.)--University of Toronto, 2004.

Electronic version licensed for access by U. of T. users.

Source: Dissertation Abstracts International, Volume: 65-10, Section: B, page: 5033.