Contrast medium concentration threshold for angiographic measurements of absolute coronary blood flow

In this method for measurement of mean coronary flow from biplane angiograms, one has to threshold curves obtained by computing the intra-arterial contrast medium concentration along the arterial branches. To find the appropriate threshold value, the spreading of contrast medium injected continuously in a straight and rigid coronary artery was computer simulated. The theoretical investigation reveals the utmost importance of injecting the contrast medium at a rate roughly equal to or greater than peak coronary flow. The ratio of injection rate to peak coronary flow has a major impact. If this ratio is about 1 or greater, a concentration threshold of 50% seems to be a good choice