Coronary artery disease (CAD) remains the leading cause of death in industrialized nations. Under normal physiological conditions, myocardial blood flow (MBF), oxygen consumption (MVO2), and myocardial mechanical function are intimately related. CAD manifests as imbalances between myocardial oxygen supply and demand. MVO2 directly reflects the balance of oxygen supply and demand of myocardium. Accurate assessment of myocardial ischemic status, particularly myocardial viability, is of paramount importance for selection of patients likely to benefit from coronary revascularization. However, detection of this status in myocardium remains an important clinical problem, partially owning to the inherent difficulty of direct measurement of MVO2 in vivo, particularly on a non-invasive and regional basis. In response to this need, our laboratory is developing a new technique to directly quantify MVO2 using non-invasive magnetic resonance imaging (MRI) T1rho techniques and 17O-enriched blood tracer. However, this technique has not been optimized and needs rigorous validation. Therefore, our overall objective is to optimize and validate this clinically viable MRI technique to measure MVO2 reliably and consistently. The goal of the application will be accomplished by pursuing a series of experiments in phantoms and a canine model. Accuracy of MVO2 measurement by MRI will be determined by comparing with gold standards such as microsphere for blood flow measurements and simultaneous blood sampling from artery and coronary sinus for the determination of myocardial global OEF. Pharmaceutical interventions will be performed to alter MVO2 in dogs. This direct assessment of metabolic activity in the myocardium may significantly improve the accuracy and precision of measurement of MVO2. Ultimately, the proposed methods may facilitate comprehensive MRI assessments of CAD and other cardiac diseases. PUBLIC HEALTH RELEVANCE: This project is to develop a new magnetic resonance imaging technique for direct quantification of myocardial oxygen consumption ratio. The technique will use T1rho imaging method and the injection of 17O-labeled blood contrast agent. Direct measurement of the oxygen consumption ratio may facilitate comprehensive evaluations of patients with a variety of cardiac diseases.