Quantification of relative coronary arterial stenosis by cinevideodensitometric analysis of coronary arteriograms

Abstract

A computerized method for measuring relative coronary arterial stenosis by cinevideodensitometric analysis of 35 mm coronary arteriograms was developed and validated. Video images of projected coronary arteriographic frames were digitized into a 512 x 512 matrix (256 gray levels) by computer analysis that compared integrated contrast density measured over stenotic and normal arterial segments after background substraction. Pixel density was 70 to 80 pixels/mm2 actual area. In phantom studies performed on plexiglass cylinders, cinevideodensitometric measurements correlated linearly with concentration of contrast medium (r=.99), with cross-sectional areas (r=.99) of contrast-filled cylinders 1 to 4 mm in diameter over a wide range of contrast concentrations (25% to 100%), and with relative stenosis of eccentric lesions in the cylinders (r=.99, SEE=3.9%). In postmortem studies of patients who died after undergoing coronary arteriography, videodensitometric measurements of relative stenosis correlated highly (r=.97, SEE=7.0%) with percentage stenosis based on actual area measurements obtained histologically with computer-assisted microscopic planimetry. Cinevideodensitometric analysis of coronary arteriograms was reproducible (r=.92, SEE=7.7%), and interobserver variability was low (r=.99, SEE=4.3%). In addition, videodensitometry provided comparably values for eccentric coronary lesions filmed in right anterior oblique and left anterior oblique projections (r=.99, SEE=1/9%). Cinevideodensitometric analysis is an accurate, rapid method for quantifying the relative stenosis of eccentric coronary lesions without manual tracing of arterial borders.