Computer-Assisted, Operator-Interactive Technique for Calculating Pulmonary Arterial Taper

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Abstract
A computer-assisted, operator-interactive technique was developed which performs fast, precise computations of pulmonary artery taper. Individual 35-mm cineframes from balloon occlusion pulmonary arteriograms are digitized into a 640 .times. 480 matrix in 8-bit depth and loaded into a VAX 11/780 computer for analysis. After operator identification of the arterial segment, an automated process of caliber analysis is initiated. By fitting a cubic spline function to the densitometric profiles extracted from the arterial segment, serial arterial cross-sectional diameters are calculated from the mathematically-derived points along the fitted curves. Spurious profiles, caused by sectioning at bifurcations, can be overridden by an operator-interactive subroutine. Taper is derived from the slope of the least-squares fit of vessel caliber with respect to its distance along the arterial segment. Results obtained by calculations from the computer-assisted caliber measurements were compared with those obtained by hand-tracing the same vessel segments. Correlation between computer-traced inflection points and hand-traced taper was very significant (r = 0.96, n = 13, P < 0.001).