Coupling of 11C-acetate and 13N-ammonia for measurement of myocardial blood flow in normal rats using the Sherbrooke PET scanner

Regional myocardial blood flow (MBF) can be assessed non-invasively with dynamic PET and ¹³N-ammonia or ¹¹C-acetate. The latter can also be used to estimate the myocardial oxygen consumption (MVO2) from the same time-activity curve. In this work, we explore the feasibility of such techniques for evaluating myocardial parameters in normal rats (∼350 g) using the Sherbrooke small animal PET scanner. Scans were acquired in list mode for ¹³N-ammonia and ¹¹C-acetate as two consecutive 15 minute dynamic scans separated by a 5 minute interval, without moving the rat from the scanner. Three-compartment models were applied to regions of interest (ROIs) defined on four segments of the myocardium. ¹³N-ammonia and ¹¹C-acetate time-activity curves were fitted for three and four rate constants, respectively, plus blood volume. A reasonable agreement is observed between MBF estimates extracted from ¹³N-ammonia and ¹¹C-acetate. MVO2 estimates, as given by the k₂ rate constant, were obtained with good reproducibility, indicating that myocardial metabolism can reliably be assessed concurrently with MBF using ¹¹C-acetate. In conclusion, it is demonstrated that myocardial blood flow and oxygen consumption can be evaluated in rats with the Sherbrooke small animal PET scanner through high-rate, list-mode, dynamic imaging and kinetic modeling of ¹³N-ammonia and ¹¹C-acetate.