Figure 2. Interactive refinement segmentation of the rectum from an intraoperative gynecological 3-Tesla magnetic resonance imaging dataset.

The leftmost image shows the native scan and the second image from the left presents the initial seed point (white) for the interactive segmentation placed by the user inside the rectum. The red dots present the segmentation outcome with regard to the current seed point position (note: for the interactive segmentation of the rectum, a triangle was used as template to construct the graph. Thereby, the center of the rectangle is the user-defined seed point and the yellow crosses display the three corners of the triangle). In the third image from the left, an additional seed point (white) has been placed in the upper left contour of the rectum. This additional seed forces the algorithm to perform the min-cut at this position. In the fourth image from the left, the user has interactively repositioned the initial seed point inside the rectum to find a better segmentation outcome. However, the additional seed at the contour stays fixed during the interactive repositioning of the initial seed and still forces the algorithm to perform the min-cut at its position in the upper left contour of the rectum. In the rightmost image, the user further refined the segmentation outcome with two additional seed points.