[Quantitative coronary angiography: methodologic principles of a densitometric procedure].

In a defined short segment of a coronary artery, the amount of contrast medium depends on the cross-sectional area of the artery. The density of the coronary angiogram in the corresponding region reflects the amount of contrast medium. During projection of a single coronary angiographic frame, light intensity at the respective region can be measured by means of a light sensor. In phantom studies, light intensity was proportional to the amount of contrast medium in the corresponding area. This was the case even after dilution of the contrast medium (correlation coefficient r = 0.96-0.99). In a concentric stenosis model, a good correlation was found between the real cross-sectional area and the cross-sectional area measured by densitometric analysis (r = 0.97). Even in the model of eccentric stenoses, the correlation was linear (r = 0.96). Thus, it seems basically possible to densitometrically measure the cross-section of a coronary stenosis in relation to a normal segment. Unlike video densitometry, this method requires only very little apparatus.