Segmentation of the common carotid intima-media complex in ultrasound images using active contours

The segmentation of the intima-media complex (IMC) of the common carotid artery (CCA) wall is important for the evaluation of the intima media thickness (IMT) on B-mode ultrasound (US) images. The IMT is considered an important marker in the evaluation of the risk for the development of atherosclerosis. The fully automated segmentation algorithm presented in this article is based on active contours and active contours without edges and incorporates anatomical information to achieve accurate segmentation. The level set formulation by Chan and Vese using random initialization provides a segmentation of the CCA US images into different distinct regions, one of which corresponds to the carotid wall region below the lumen and includes the far wall IMC. The segmented regions are used to automatically achieve image normalization, which is followed by speckle removal. The resulting smoothed lumen-intima boundary combined with anatomical information provide an excellent initialization for parametric active contours that provide the final IMC segmentation. The algorithm is extensively evaluated on 100 different cases with ground truth (GT) segmentation available from two expert clinicians. The GT mean IMT value is 0.6679mm 0.1350mm and the corresponding automatically segmented (AS) mean IMT value is 0.6054mm 0.1464mm. The mean absolute difference between the GT IMT and the IMT evaluated from from the AS region is 0.095mm 0.0615mm. The polyline distance is 0.096mm 0.034mm while the Hausdorff distance is 0.176mm 0.047 mm. The algorithm compares favorably to both automatic and semiautomatic methods presented in the literature.