MORPHOMETRIC ANALYSIS IN 3-DIMENSIONAL INTRACORONARY ULTRASOUND - AN IN-VITRO AND IN-VIVO STUDY PERFORMED WITH A NOVEL SYSTEM FOR THE CONTOUR-DETECTION OF LUMEN AND PLAQUE

Currently, automated systems for quantitative analysis by intracoronar y ultrasound (ICUS) are restricted to the detection of the lumen. The aim of this study was to determine the accuracy and reproducibility of a new semiautomated contour detection method, providing off-line iden tification of the intimal leading edge and external contour of the ves sel in three-dimensional ICUS. The system allows cross-sectional and v olumetric quantification of lumen and of plaque. It applies a minimum- cost algorithm and the concept that edge points derived from previousl y detected longitudinal contours guide and facilitate the contour dete ction in the cross-sectional images. A tubular phantom with segments o f various luminal dimensions was examined in vitro during five cathete r pull-backs (1 mm/sec), and subsequently 20 diseased human coronary a rteries were studied in vivo with 2.9F 30 MHz mechanical ultrasound ca theters (200 images per 20 mm segment). The ICUS measurements of phant om lumen area and volume revealed a high correlation with the true pha ntom areas and volumes (r = 0.99); relative mean differences were -0.6 5% to 3.86% for the areas and 0.25% to 1.72% for the volumes of the va rious segments. Intraobserver and interobserver comparisons showed hig h correlations (r = 0.95 to 0.98 for area and r = 0.99 for volume) and small mean relative differences (-0.87% to 1.08%), with SD of lumen, plaque, and total vessel measurements not exceeding 7.28%, 10.81%, and 4.44% (area) and 2.66%, 2.81%, and 0.67% (volume), respectively. Thus the proposed analysis system provided accurate measurements of phanto m dimensions and can be used to perform highly reproducible area and v olume measurements in three-dimensional ICUS in vivo.