UCLA

Cardiovascular diseases are the leading cause of death in the United States, translating to a high cost burden on the healthcare system. Noninvasive imaging can play a significant role in the diagnosis and triaging of cardiovascular diseases. Cardiac MRI is a noninvasive imaging technique becoming more prevalent due to its advantage of providing excellent soft-tissue contrast and high spatial resolution without the use of ionizing radiation; however, major challenges exist including respiratory and cardiac motion. One emerging application of cardiac MRI is myocardial tissue characterization using quantitative mapping techniques. Current mapping techniques rely on electrocardiogram (ECG)-gating which assumes normal sinus rhythm, as well as breath-holds or respiratory monitoring which preclude some patients from scans or prolong scan time. Quantification of spin-lattice relaxation times (or T1 mapping) of the myocardium has been shown to enable detection of diffuse myocardial fibrosis, a key feature in the progression of many cardiac diseases. The main focus of this dissertation is to remove the limitations of ECGs and respiratory monitoring from cardiac MRI to enable free-breathing, non-ECG T1 mapping.

The first objective of this dissertation was to develop a two-dimensional, free-breathing, non-ECG, continuous T1 mapping technique and validate it in imaging phantoms using a gold-standard technique. We compare the T1 and extracellular volume (ECV) values to a conventional breath-hold, ECG-gated, T1 mapping technique in healthy subjects. The repeatability and accuracy of the technique were assessed for different length scans. The second objective was to demonstrate the feasibility of quantifying T1 values throughout the cardiac cycle and to assess cardiac function simultaneously with a method free of ECG and prospective respiratory monitoring. The third objective of this dissertation was to develop a three-dimensional free-breathing, non-ECG T1 mapping technique capable of providing T1 and ECV maps with full coverage of the left ventricle.

This dissertation lays the groundwork for quantitative cardiac MRI with no reliance on prospective respiratory monitoring or ECGs. The removal of these limitations makes cardiac MRI accessible to all types of patients and provides a comfortable scan environment with no breath-holding. This dissertation represents a move toward a “push-button” cardiac MRI paradigm, wherein one scan with minimal setup can provide information comparable to a complex standard-of-care cardiac MRI scan.