Automated extraction of pelvic features in portal and simulation images

A new approach, a pyramid template matching as guided by a snake, is developed for the extraction of pelvic features in both portal and simulation images. Initially, the treatment field edge was extracted using a Canny edge detector. A template modeled using a polynomial function for the typical pelvic structures was used as the initial approximation for the anterioposterior (AP) pelvic brim. Several energies were defined to search the actual bony structures as guided by the snake in a larger range. In this study, a double-snake model coupled with a spring was developed to define the external constraint force. The image force was calculated from various processed images using different edge detection algorithms. The criterion used for search termination was to find the locations where the overall energy was at its minimum. The result of the initial search was fit using a polynomial function as the second approximation for the pelvic bony structure. Snake searching technique was repeated in a smaller range around the initial identified features for fine search of pelvic bony structure. This technique has shown to be very promising for extracting pelvic features.