Cardiac 17O MRI: Toward Direct Quantification of Myocardial Oxygen Consumption

A new O-17-labeled blood contrast agent was injected intravenously in control dogs. Electrocardiogram (ECG)-triggered myocardial T-1 rho imaging was performed to obtain spin-locking T-1 rho-weighted myocardial signals for the detection of resultant metabolite (H2O)-O-17 water in the heart. Bolus and slow injection methods of various doses of the O-17-labeled and O-16-labeled agents were carried out in order to evaluate the sensitivity of this method and determine the optimal injection method. Bolus injection provided approximately 1% signal reduction, whereas slow injection with larger amount of agent yielded 11.9 +/- 0.6% signal reduction. Myocardial oxygen consumption rate was determined by a technique to quantify cerebral oxygenation consumption rate previously developed in O-17 brain studies. With either injection method, myocardial oxygen consumption rate at rest was 5.0 - 5.6 mu mol/g/min. Therefore, it appears feasible to detect metabolically generated (H2O)-O-17 water in vivo in the heart, using the O-17-labeled blood tracer. Myocardial oxygen consumption rate can then be quantified in vivo, which may open new doors for the assessment of myocardial metabolism. Magn Reson Med 63:1442-1447, 2010. (C) 2010 Wiley-Liss, Inc.