Measurement of total myocardial blood flow in dogs with 43K and the scintillation camera.

To establish an innocuous method for evaluating myocardial ischemia, a technique was devised utilizing a scintillation camera to record the distribution of K in the myocardium following an intravenous injection of the tracer. The objective was achieved by determining with the camera the fraction of the total amount of injected material deposited in the myocardium and calculating the total myocardial blood flow as a fraction of cardiac output according to the indicator fractionation principle. Following in vivo measurements in dogs, the entire heart was excised, compared with an aliquot of the injected dose as a standard, and assayed by a well scintillation counter. Reasonable agreement was achieved between estimations determined in vivo and those determined in vitro. Because of difficulties in ascertaining the heart border on the scans, a deconvolution program which used a digital computer was applied to the 40 X 40 matrix of digitized scan data to sharpen the transition between counting levels and improve the distributional image of K deposition in the myocardium.