Detection of Focal Contour Abnormality

A focal contour abnormality is said to occur when the local curvature is large compared to the average lumen curvature. The curvature, x y - yx c = (x2 + 02)3/2 (8.60)

is calculated for a small segment of the lumen and its ratio to the average curvature for the whole lumen is assigned to the point in the center of that segment. In order to obtain gradient and curvature parameters for the same point, the TOF contour and BB contour are brought into correspondence by registering the centroids of their convex hulls. With this definition any sharp change in curvature is detected. It becomes significant only when associated with the absence of a dark rim. However, it has to be noted that this could lead to some false classifications especially around the bifurcation.

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