THE EFFECT OF VASCULAR CURVATURE ON 3-DIMENSIONAL RECONSTRUCTION OF INTRAVASCULAR ULTRASOUND IMAGES

Objective: To characterize the effect of vessel curvature on the geome tric accuracy of conventional three-dimensional reconstruction (3DR) a lgorithms for intravascular ultrasound image data. Background: A commo n method of 3DR for intravascular ultrasound image data involves geome tric reassembly and volumetric interpolation of a spatially related se quence of tomographic cross sections generated by an ultrasound cathet er withdrawn at a constant rate through a vascular segment of interest . The resulting 3DR is displayed as a straight segment, with inherent vascular curvature neglected. Most vascular structures, however, are n ot straight but curved to some degree. For this reason, vascular curva ture may influence the accuracy of computer-generated 3DR. Methods: We collected image data using three different intravascular ultrasound c atheters (2.9 Fr, 4.3 Fr, 8.0 Fr) during a constant-rate pullback of 1 mm/sec through tubing of known diameter with imposed radii of curvatu re ranging from 2 to 10 cm. Image data were also collected from straig ht tubing. Image data were digitized at 1.0-mm intervals through a len gth of 25 mm. Two passes through each radius of curvature were perform ed with each intravascular ultrasound catheter. 3DR lumen volume for e ach radius of curvature was compared to that theoretically expected fr om a straight cylindrical segment. Differences between 3DR lumen volum e of theoretical versus curved (actual) tubes were quantified as absol ute percentage error and categorized as a function of curvature. Tubin g deformation error was quantified by quantitative coronary angiograph y (QCA). Results: Volumetric errors ranged from 1% to 35%, with an inv erse relationship demonstrated be tween 3DR lumen volume and segmental radius of curvature. Higher curvatures (r < 6.0 cm) induced greater l umen volume error when compared to lower curvatures (r > 6.0 cm). This trend was exhibited for all three catheters and was shown to be indep endent of tubing deformation artifacts. QCA-determined percentage diam eter stenosis indicated no deformation error as a function of curvatur e. Total volumetric error contributed by tubing deformation was estima ted to be 0.05%. Conclusions: Catheter-dependent geometrical error ari ses in three-dimensionally reconstructed timed linear pullbacks of int ravascular ultrasound images due in part to uniplanar vascular curvatu re. Three-dimensional reconstruction of timed linear pullbacks is robu st for vessels with low radii of curvature; however, careful interpret ation of three-dimensional reconstructions from timed linear pullbacks for higher radii of curvature is warranted. These data suggest that m ethods of spatially correct three-dimensional reconstruction of intrav ascular ultrasound images should be considered when more pronounced va scular curvature is present.