[Geometry of eccentric vascular stenoses in various projections--significance for angiographic assessment of the degree of stenosis, especially using digital subtraction angiography].

A mathematical model is used to predict the angiographic appearance of plaque-like lesions and eccentric vascular stenoses. The virtual stenotic areas and the degree of stenosis are calculated for different projection angles varying between 0 degree--x-ray beam tangential to the lesion--and 90 degrees--x-ray beam incidental to the lesion. Eccentric stenoses are underestimated if the lesion is not tangential to the x-ray beam. Eccentric stenoses can be overestimated if automated programmes are based on a circular configuration of both the normal and the stenotic lumens. In this model the best estimation is obtained if the stenotic lumen is assumed to be elliptic, and if biplane rectangular projections are available.