Automatic extraction of local axis of bone symmetry in CT images

We present an algorithm that extracts local axis of symmetry in CT images automatically. The proposed method combines registration and extraction of bone contours to generate the desired symmetry axis. The method consists of several stages: first extracting the bone contours of the images by using an active contour method, then finding grossly an axis that allows the division of the image into two parts, loosely called “half” images, but with the understanding that they are not exactly the two halves of the image but rather the two halves of the depicted object. After that, finding a mapping that aligns the first half of the image with the second half and finally, finding the local axis of symmetry from corresponding contours.