Deformable registration of prone and supine colons for CT colonography.

CT colonography (CTC) is a non-invasive technique for detecting colorectal polyps and colon cancer. Through the addition of the prone scanning with the original supine scanning, the possibility of detecting the polyps is increased. The registration process for this application requires the comparison between the prone and supine colons for diagnosis. A level-set representation of the object boundary using a distance map is presented in this paper as an input to demons registration algorithm for supine and prone CT colonography image data. After first aligning the colon volumes based on the patient's anus position, distances inside and outside the objects' boundary are computed. The level-set from the distance map allows the demons algorithm to decide the moving direction for the initial demons' force between the two colons. We present a result with a 3 dimensional volume of a patient's colon. The results suggest that our method has excellent registration performance with high confidence even with considerable deformation of the colon lumen in 3 dimensional case.