Effect of vessel orientation on videodensitometry quantitative coronary arteriography

Cross-sectional area measurement using videodensitometry coronary arteriography is a function of the out-of-plane angle of the vessel segment with respect to the face of the image intensifier. Therefore, absolute cross-sectional area measurement using videodensitometry requires correction for the out-of-plane angle. In this study, a simple technique to measure the out-of-plane angle of a vessel segment using images from two different projections is presented. The technique was tested using vessel phantoms imaged at different out-of-plane angles. A vessel segment with an out-of-plane angle of less than 20 degrees introduces less than 5% error in the cross-sectional area measurements. However, an out-of-plane angle of 60 degrees can introduce more than 90% error. The results of the measurements show that correction for the out-of-plane angle reduces the error in cross-sectional area measurement to less that 5%. The correction for the out-of-plane angle makes it possible to measure the absolute cross-sectional area using videodensitometery, which can be used to assess a diseased vessel segment with any complex geometry.