Longitudinal Motion Assessment of the Carotid Artery Using Speckle Tracking and Scale-Invariant Feature Transform

The purpose of this work is to present and validate a novel approach for ultra-sound-based speckle tracking to measure the carotid artery longitudinal displacement, and to assess the apparent sliding between of Intima-Media Complex (IMC) and Adventitia (Ad) layers. This method utilizes feature detectors and descriptors to localize and track keypoints for local motion quantification. The procedure was tested and validated on an in silico dataset and on 18 heathy volunteers and 16 patients. Accuracy measured on in silico data gave a mean ± standard deviation of 23 ± 15 and 19 ± 18 μm for IMC and Ad respectively, and thus smaller than the pixel size (0.0925 mm). Robustness analysis was performed on in vivo images, obtaining a maximum variation coefficient, over 5 repeated measures, of 9.5 and 13.8% for IMC and Ad, respectively. The novel method capability for detecting the relative motion of IMC vs. Ad was compared with visual assessment performed by 2 physicians, leading to a correlation coefficient R of 0.7 in the worst case. (Healthy group scored by rater #1.) In conclusion, our results provide evidence that the novel method is able to accurately and reliably track carotid artery layer motion and that it overcomes limitations currently present in the literature, therefore providing an automatic tool for clinical evaluation of IMC vs. Ad relative displacement.