- All included patients under the standardized preoperative imaging staging, by written consent, will get an additional DECT scan of the pelvis, either with Gadovist 1.0 mmol / ml, 0.1 mg / kg iv, or after administration of standard CT contrast Omnipaque. DECT scans can be performed in the same scanner and at the same session as the conventional CT of the thorax and abdomen. Images should result in ongoing 3mm thick sections of the pelvis, perpendicular to the rectum wall, from the anorectal transition to promontory level.