Assessment of implanted stent coverage of side-branches in intravascular optical coherence tomographic images

Coronary stents improve the blood flow by keeping narrowed vessels open, but small stent cells that overlay a side branch may cause restenosis and obstruct the blood flow to the side branch. There are increasing demands for precise measurement of the stent coverage of side branches for outcome evaluation and clinical research. Capturing micrometerresolution images, intravascular optical coherence tomography (IVOCT) allows proper visualization of the stent struts, which subsequently can be used for the coverage measurement purpose. In this paper, a new approach to compute the stent coverage of side branches in IVOCT image sequences is presented. The amount of the stent coverage of a side branch is determined by the ostial area of the stent cells that cover this side branch. First, the stent struts and the guide wires are detected to reconstruct the irregular stent surface and the stent cell contours are generated to segment their coverage area on the stent surface. Next, the covered side branches are detected and their lumen contours are projected onto the stent surface to specify the side branch areas. By assessing the common parts between the stent cell areas and the side branch areas, the stent cell coverage of side branches can be computed. The evaluation based on a phantom data set demonstrated that the average error of the stent coverage of side branches is 8.9% ± 7.0%. The utility of the presented approach for in-vivo data sets was also proved by the testing on 12 clinical IVOCT image sequences.