This thesis describes the development of new magnetic resonance imaging (MRI) methods to characterize cardiac tissue with myocardial infarction (MI). Wall motion imaging (for visualizing myocardial contraction) and viability imaging (to identify MI) are two components of cardiac tissue characterization used for prognosis and treatment planning. MRI-based wall motion and viability methods are considered the gold standard in imaging, and characterization of MRI viability images has been correlated with inducibility for ventricular tachycardia (VT). However, viability imaging with MRI has limitations such as difficulty visualizing the blood-infarct border. Wall motion and viability images are acquired separately, each requiring cardiac gating and breath holds, leading to long scan times. A novel multi-contrast delayed enhancement (MCDE) sequence was developed that simultaneously acquires wall motion and viability images. In a patient study, the MCDE sequence was demonstrated to provide improved visualization of MI compared to the conventional inversion-recovery gradient echo (IR-GRE) sequence, particularly for small infarcts adjacent to the blood pool. MCDE images also provided accurate wall motion images that could be used to calculate the left ventricular ejection fraction. An image processing algorithm was developed to analyze MCDE images to segment and classify the infarct gray zone, which is hypothesized to represent heterogeneous infarct responsible for causing VT. In a study of 15 patients with MI, the MCDE-derived gray zone was shown to be less sensitive to image noise than the IR-GRE-derived gray zone, and did not require manual contours of the blood pool which contributes to additional variability in the IR-GRE gray zone analysis. Finally, a real-time delayed enhancement (RT-DE) method was developed to provide black-blood viability images without requiring cardiac gating or breath holds. RT-DE imaging was shown to have a high sensitivity for detecting MI in a study of 23 patients. The methods described in this thesis help expand the patient population that can undergo a cardiac viability exam and help improve the visualization of myocardial infarct. Further modifications in the pulse sequences to improve the temporal and spatial resolutions are proposed with the goal of predicting and guiding treatment of ventricular tachycardia resulting from myocardial infarct.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/16782 |
| Date | 20 January 2009 |
| Creators | Detsky, Jay |
| Contributors | Wright, Graham |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
| Format | 4854231 bytes, application/pdf |
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