Coronary arteriography is currently the only method which provides potentially precise information of in vivo coronary luminal dimensions. Objective methods which increase luminal image information may therefore expedite studies of atherosclerotic interventions. We have recently developed a rotating step-wedge technique which permits extraction of three-dimensional image information from single-plane cine-angiograms by calibrating film grey scale against relative arterial chord length in a manner which circumvents the problems of inhomogeneity of background radio-density, i.e., step-wedge movement is synchronized with film exposure so that steps appear one by one at the same location on successive frames. We will test a primary hypothesis that objective image analysis of films in which this technique is employed provides an accurate measure of coronary luminal volume (MCLV) from single plane angiograms. Accuracy of MCLV determined in a dog model, wherein a thin-walled replicate arterial phantom of known luminal dimensions will be positioned within a coronary artery as an inner sleeve. The inner surface of the phantom will reproduce exactly the topography of a non-axisymmetric atherosclerotic lumen. We will also test a secondary hypothesis that subtle, visually inapparent changes in luminal volume may be quantitated by MCLV. Subtle dynamic pressure and vasomotor tone related changes in MCLV in the dog will be compared to simultaneous changes in instantaneous external diameter of the exposed coronary artery as determined cinematographically. MCLV will be compared to visual estimates. Future clinical studies will parallel experimental objectives; rotational invariances as one measure of MCLV accuracy will be tested, and subtle, acute changes in MCLV will be compared to visual estimates. MCLV will be obtained from manual analysis of single line optical desity raster scans as well as from computer analysis of digitized images. Correction will be made for geometric distortion and response variation in x-ray and digitizing systems.