3D-reconstruction of coronary arteries in view of flow measurement.

An angiographic method for measurement of absolute coronary blood flow in patients was developed. It is based on 3D-reconstruction of the left or right coronary tree from digitized biplane coronary cineangiograms. The apparatus is presently composed of a 35 mm cinefilm projector with a video camera and a 512 x 512 x 8 bits image array processor controlled by a VAX-11/750 computer. First, the parameters of the two angiographic projections are determined in form of two 4 x 3 matrices from a pair of cineframes showing a 4 cm cube bearing markers. The cube is filmed after the coronary injection, with unchanged geometric configuration. The coronary arteries of interest are then 3D-reconstructed from a pair of cineframes showing them fully opacified. This allows to compute the intravascular volumes needed for flow determination. In vitro experiments showed that the obtained volume are reasonably accurate. For the measurement of coronary flow, the concentration of contrast medium along the involved arteries is computed (in arbitrary units) from two cineframes taken one (or two) cardiac cycle after onset of the injection. This yields a 'concentration-distance' curve per artery. The volume of fluid (contrast medium mixed with blood) which flows into the arteries during this (or these two) cardiac cycle is determined by applying a concentration threshold to the obtained concentration-distance curves. Measurements performed on a constant flow model were satisfying. Preliminary measurements in 12 patients showed that flow values obtained angiographically into the left anterior descending coronary artery correlate well with the values measured simultaneously by thermodilution in the great cardiac vein (Qangio = 0.83 x Qthermo + 16.1 ml, r = 0.87, n = 29).