Optimized geometry of the carotid artery cross-section: Comparison between circular and elliptical approximations in B-mode ultrasound images

Abstract

Cross-sectional area (CSA) measurement obtained from transverse ultrasound images is the general method used for carotid artery stenosis calculation which assumes a circular CS, however, atherosclerotic stenosis may change the CSA geometry and lead to miscalculation. This study aims to determine the accuracy of circular or elliptical approximation of the normal and stenosed carotid artery CSA. Sixty transverse B-mode ultrasound images (30 from healthy and 30 from stenosed carotid arteries) were recorded. Contours of the internal lumen of the arteries were segmented and the encompassed lumen area was calculated. Based on the fitting accuracy and computational cost effectiveness, pattern search (PS) optimization algorithm was selected by which the parameterized equations of the circular and elliptical geometries were fitted to the segmented point clouds. Goodness of fit analysis of two geometries was carried out using root mean square error (RMSE) and the relative deviation of the approximated CSA. Results of this study showed that elliptical approximation better fits to the artery CS of carotid arteries, with the average RMSE of [Formula: see text] and [Formula: see text] pixels in healthy and [Formula: see text] and [Formula: see text] pixels in stenosed carotid arteries, respectively, for circle and ellipse approximation. Mean values of the relative deviation of the approximated CSA by circle and ellipse geometries were 5.14%[Formula: see text]±[Formula: see text]4.53% and 3.89%[Formula: see text]±[Formula: see text]4.19% in normal arteries; and 12.18%[Formula: see text]±[Formula: see text]10.94% and 4.59%[Formula: see text]±[Formula: see text]3.75% in stenosed arteries, respectively. This study represented that elliptical approximation provides increased accuracy for carotid artery CSA for both normal and stenosed carotid arteries.