Motion compensation method for quantification of neovascularization in carotid atherosclerotic plaques with contrast enhanced ultrasound (CEUS)

Several studies have linked intraplaque neovascularization (IPN) with progressive atherosclerotic disease and plaque instability. An accurate quantification of IPN may allow early detection of vulnerable plaques. In this study, a dedicated motion compensation method was developed for quantification of IPN in small plaques (<30% diameter stenosis). Motion compensation is a prerequisite to analyze identical regions of interest (ROI) for accurate quantification of IPN. Side-by-side CEUS and B-mode ultrasound images of carotid arteries were acquired by a Philips iU22 system with a L9-3 linear array probe. The motion pattern for the plaque region was obtained from the B-mode images with a tuned speckle tracking (ST) method with subpixel precision and applied to contrast images. In-vivo validation was done by comparing ST to manual tracking by two experts for multibeat image sequences (MIS) of 11 plaques. In the in-vivo validation, error was 51.4 ± 91 μm for X (longitudinal) and 18.7 ± 39.8 μm for Y (radial). The ST success rate was visually assessed on 67 atherosclerotic wall plaque MIS. The tracking was considered failed if the ST deviated > 2 pixels from true motion in any frame. Tracking was scored as fully successful in 52 MIS (78%). The proposed motion tracking is sufficiently accurate and successful for in vivo application.