Impact of Catheter Shaft Angulation on the Accuracy of Atherosclerotic Plaque Volume Measurement by Three-Dimensional Intravascular Ultrasound

Abstract

Computerized three-dimensional reconstruction of intravascular ultrasound (IVUS) images is a relatively new imaging modality for the study of atheromatous coronary disease with particular use in serial study of atheroma regression. Distortion of the acquired IVUS images has an important influence on the quality and accuracy of volume measurements made from the 3-D reconstruction. We evaluated the impact of commonly encountered sources of image distortion, catheter shaft angulation and luminal transducer position, on the accuracy of plaque and vessel volume measurements. A segment of diseased post-mortem human coronary artery was studied in a specially designed water bath, which enabled IVUS examination. A number of angulations of the arterial segment and the IVUS catheter were made to reproduce the areas of tortuousity encountered in the in vivo setting. Nine conformations were made. Following acquisition of IVUS images the segment was fixed in formalin and sectioned. Vessel, lumen and plaque volumes were determined by histomorphometry. These were compared to volume measurements made from 3-D reconstruction of the IVUS images in each conformation. Minimal catheter angulation produced acceptable variability for vessel (–7.9%), lumen (–6.0%) and plaque volume (-8.5%). Proximal angulations significantly over-estimated vessel, lumen and plaque volumes. Variability was greatest when multiple, severe angulations were applied (–17.7 to –21.3%). Eccentric catheter tip positioning produced greater variability in vessel (mean 16.8 ± 2.6 v. 14.2 ± 3.1%, p < 0.01) and plaque volume (18.1 ± 2.8 v. 15.3 ± 3.5%, p < 0.01). Technical factors, such as catheter shaft angulation and transducer tip position, significantly influence the degree of image distortion and subsequent volume measurement by computerized three-dimensional reconstruction of IVUS images. Recognition of these factors is important particularly in longitudinal studies of atheroma regression.