Absolute flow measurements by computer analysis of coronary cineangiograms

Abstract

A new method was developed to measure absolute coronary blood flow in all major branches of the coronary circulation using computer analysis of conventional biplane coronary cineangiograms.Coronary cineangiograms were obtained at SO fps in any biplane projections.A cube with IS radioopaque beads was filmed in the same projections. Images were digitized into a 512x512 8-bit matrix. From the biplane images of the cube and the known location of the beads, 2 projection matrices were calculated describing projection parameters f o r both planes. Arterial edges were determined by the computer for all branches > I mm in diameter. From the 2 projection matrices, the artery was reconstructed in 3 -0 and its true volume calculated. Absolute flow was given by the coronary volume filled by contrast medium during the first cycle following the injection divided by the duration of that cycle.A good correlation was found between absolute flow in the LAD by this technique and great cardiac vein flow simultaneously measured by thermodilution in patients at baseline and during pacing-induced hyperemia (r = 0.82 and SEE = 9.8 mllmin). . IntroductionCoronary angiography provides important information on the location and severity of a coronary stenosis, but does not provide any information on its physiologic a1In the past few years, several groups have attempted to assess the physiological sign i fic anc e. significance of a coronary stenosis by measuring coronary flow reserve using computer analysis of coronary angiograms [l]. However, flow reserve is a relative index that depends on the level of resting flow and the achievement of maximal hyperemia [2]. Resting flow is influenced by a number of factors including the presence of LV hypertrophy, contractility, tachycardia, aortic and LV diastolic pressure. On the other hand, absolute coronary flow takes into account all factors affecting resting flow and does not depend on achieving maximal vasodilation.Several years ago, Rutishauser et al. determined absolute coronary flow by measuring the transit time of a contrast bolus between 2 points in a right coronary artery [3, 41. However, this approach was limited to large, proximal, non branching arteries parallel to the image intensifier.We extended this approach to measure absolute coronary blood flow in ml/min in all major branches of the coronary circulation using computer analysis of conventional coronary cineangiograms. . M e t h o dOur method has been described elsewhere in details [ 5 ] . Briefly, a conventional coronary cineangiogram is obtained in any biplane projections at 50 frames/sec by manual injection of 6-8 ml iopamidol. A 4 cm cube is filmed in the same biplane projections. This cube has 15 radioopaque beads placed at each comer, in the middle of each side and in the tenter. Images are digitized into a 512x512 8-bit matrix. From the biplane images of the 721 0-8186-2485-x192 $3.00 0 1992 IEEE