MODELING THE MYOCARDIAL DILUTION CURVE OF A PURE INTRAVASCULAR INDICATOR

The dispersion and dilution of contrast medium through the myocardial vasculature is examined first with a serial model comprised of arteria l, capillary, and venous components in series to determine their time- concentration curves (TCC) and the myocardial dilution curve (MDC). An alysis of general characteristics shows that the first moment of the M DC, adjusted for that of the aortic TCC and mean transit time (MTT) fr om the aorta to the first intramyocardial artery, is one-half the MTT of the myocardial vasculature and that the ratio of the area of the MD C and aortic TCC is the fractional myocardial blood volume (MBV). The use of known coronary vascular morphometry and a set of transport func tions indicates that the temporal change in MDC is primarily controlle d by the MTT. An analysis of several models with heterogeneous flow di stributions justifies the procedures to calculate MTT and MBV from the measured MDC. Compared with previously described models, the present model is more general and provides a physical basis for the effects of flow dispersion and heterogeneity on the characteristics of the MDC.