4D MRI Development for Cardiovascular Imaging

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DESCRIPTION (provided by applicant): Assessments of coronary artery disease and ventricular function are crucial elements for heart health evaluation. The goal of this research is to develop 4D magnetic resonance imaging (MRI) techniques that provide a non-invasive and effective cardiac imaging examination, including assessing coronary artery disease (CAD) and both left (LV) and right ventricular (RV) function. Echocardiography (ECHO) is widely used to assess function but is limited to 2D views of the anatomy. It has poor ability to measure RV dimensions given the position, trabeculations, and complex anatomy of the RV. CT angiography (CTA) provides non-invasive assessment of CAD and ventricular function, however it involves exposure to ionizing radiation and risk of nephrotoxicity from iodinated contrast agents. Adequate CTA generally requires the use of beta blockers and is improved by the administration of nitroglycerin, both of which are contraindicated for certain patients. Coronary angiography (CA) is the definitive study for identifying the presence of CAD, but it is invasive, costly in bot dollar terms and patient morbidity, and provides no assessment of ventricular function. Cardiac magnetic resonance imaging (MRI) offers several powerful capabilities. It is the gold standard for quantitating ventricular function with 2D breath-hold cine acquisitions. Whole-heart coronary MRA centered on mid-diastole has also been demonstrated without contrast injection. However, both applications are limited by the challenges posed by cardiac and breathing motion. Cardiac function quantitation on 2D MRI suffers from breathing inconsistencies and consequent slice-to-slice spatial misregistration, particularly when patients, such as lung transplantation candidates, are unable to perform even a short breath-hold. Inconsistent breathing and selection of a fixed window at mid-diastole results in unacceptable scan times and reduces image quality in coronary studies since some coronary segments are not quiescent at that time. In this research we aim to: 1) develop self-gated free-breathing 4D cardiac MRI with novel self-gating, motion correction, and advanced image reconstruction methods; 2) optimize a 4D MRI protocol for cardiac function imaging and coronary artery imaging; and 3) implement the optimized methods in assessment of cardiac patients. Successful implementation of the proposed 4D cardiac MRI will not only be important for assessing CAD and ventricular function, but will be generalizable to conditions requiring similar capabilities, such as evaluation of valve disease, enhanced imaging of ischemic myocardium and assessment of vascular compliance. This will offer improved care for the vast population of patients with these conditions and financial benefits for the health car system.