Intraplaque neovascularization (IPN) has been linked with progressive atherosclerotic disease and plaque instability in several studies. Quantification of IPN may allow early detection of vulnerable plaques. A dedicated motion compensation method with normalized-cross-correlation (NCC) block matching combined with multidimensional (2D+time) dynamic programming (MDP) was developed for quantification of IPN in small plaques (<30% diameter stenosis). The method was compared to NCC block matching without MDP (forward tracking (FT)) and showed to improve motion tracking. 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 Bmode images with MDP. MDP results were evaluated in-vitro by a phantom and in-vivo by comparing to manual tracking of three experts for multibeat-image-sequences (MIS) of 11 plaques. In the in-vivo images, the absolute error was 72±55μm (mean±SD) for X (longitudinal) and 34±23μm for Y (radial). The method's success rate was visually assessed on 67 MIS. The tracking was considered failed if it deviated >2 pixels (~200μm) from true motion in any frame. Tracking was scored as fully successful in 63 MIS (94%) for MDP vs. 52(78%) for FT. The range of displacement over these 63 was 1045±471μm (X) and 395±216μm (Y). The tracking sporadically failed in 4 MIS (6%) due to poor image quality, jugular vein proximity and out-of-plane motion. Motion compensation showed improved lumen-plaque contrast separation. In conclusion, the proposed method is sufficiently accurate and successful for in vivo application.

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doi.org/10.1117/12.912468, hdl.handle.net/1765/60409
Medical Imaging 2012: Ultrasonic Imaging, Tomography, and Therapy
Department of Cardio-Thoracic Surgery

Akkus, Z., Hoogi, A., Renaud, G., Sijbrands, E., van den Oord, S., Schinkel, A., … Bosch, H. (2012). Motion compensation method using dynamic programming for quantification of neovascularization in carotid atherosclerotic plaques with contrast enhanced ultrasound (CEUS). Presented at the Medical Imaging 2012: Ultrasonic Imaging, Tomography, and Therapy. doi:10.1117/12.912468