Measurement of Regional

We measured blood flow within each of eight segments of the left ventricular myocardium in dogs by an Ultrafast CT scanner. The results were compared with flow determined by radiolabeled microspheres. Computed tomography (CT) flow was measured by an intravenous injection of nonionic contrast agent done simultaneously with the left atrial injection of microspheres. We calculated flow from the CT data by obtaining CT number versus time curves for regions of interest in the myocardium and by using a formula that related flow to both the time and value of the peak enhancement. Measurements were obtained in five dogs at rest and during hyperperfusion induced by chromonar. Based on 169 regional measurements, the Ultrafast CT and microsphere-determined flows correlated moderately (r = 0.68) over a range of 0.4 to 8 mL/min/g. However, when the data were divided into resting and hyperperfusion (ie, 20 to 30 minutes after the injection of the chromonar) states, a significant (P less than .001) increase in regional flow was determined from the CT measurements. The conclusion was that Ultrafast CT can distinguish between low and high myocardial flow states in dogs and has considerable potential for evaluating coronary flow reserve.