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Proceedings Paper

Curvature-vector pair and its application in displaying CT colon data
Author(s): Zhan Zhang; Kenneth R. Hoffmann; Alan Walczak
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Paper Abstract

To facilitate early detection and removal of colonic polyps, we have developed a method to present the whole colon surface in a single 2D image. To improve detection sensitivity and lower false positives while using the 2D image, we utilize curvature-vector pair and curvature-images to construct a candidate-point image to indicate possible locations of polyps in the 2D image. Planes perpendicular to the centerline are generated. On each plane, equiangularly spaced radial rays are generated, which intersect the colon surface, generating sample points. The centerline index of the planes and the angular index of the radial rays on each plane define the x and y coordinates of a 2D array, respectively. At each sample point, four curves are constructed along the x, the y, and the two diagonal directions, for which four curvatures are calculated. The curvature vectors which pointing into the lumen are set to zero. Then, at each sample point, the values of the maximum and minimum curvature are assigned to the corresponding element in the 2D array. Using this 2D array and a two-step thresholding method, a so-called candidate-point image, which indicates possible locations of polyps, is generated. In the two-step thresholding method, the thresholds are determined by using a five training colon-data sets. This candidate-point image can be used in conjunction with other analyses in polyp detection.