Quantification of myocardial microcirculatory function with X-ray CT.

A mathematical model of the intramyocardial coronary microcirculation is used to explore the validity of a fast CT imaging method for characterizing the myocardial microcirculatory functional status. The fast CT method depends on the demonstrated CT-based estimation of myocardial perfusion (F) and the intramyocardial blood volume (B(v)). The observed curvilinear myocardial blood volume-to-flow relationship, empirically fitted to B(v) = a.F + b.F(0.5), is a signature of the underlying early pathophysiologic processes thought to be involved in systemic disease processes, such as atherosclerosis, hypertension, and diabetes mellitus. The sensitivity and specificity of the CT-based estimate of this characteristic relationship is explored by altering the characteristics of the vascular diameter-to-flow relationship and the variation in the fraction of capillaries perfused at different coronary flows. The simulation results also indicate that if the vascular diameters change so that the vascular resistance corresponds to the change in flow, then the empirically observed myocardial B(v)-to-F relationship holds well.