Cardiac 17O MRI: Toward direct quantification of myocardial oxygen consumption

Abstract

A new ¹⁷O‐labeled blood contrast agent was injected intravenously in control dogs. Electrocardiogram (ECG)‐triggered myocardial T ₁ρ imaging was performed to obtain spin‐locking T ₁ρ‐weighted myocardial signals for the detection of resultant metabolite H₂¹⁷O water in the heart. Bolus and slow injection methods of various doses of the ¹⁷O‐labeled and ¹⁶O‐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 ¹⁷O brain studies. With either injection method, myocardial oxygen consumption rate at rest was 5.0 – 5.6 μmol/g/min. Therefore, it appears feasible to detect metabolically generated HO water in vivo in the heart, using the ¹⁷O‐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.