Dosimetrische auswirkungen der verwendung eines rektumhüllen-volumens für die bestrahlungsplanung fluenzmodulierter strahlentherapie von prostatakrebs

The present study evaluated a hull-volume definition strategy for the planning organ at risk volume (PRV) for the rectum in the planning of radiotherapy of prostate cancer. The bounding volumes of rectum contours of 1 to 5 CT scans were compared on the basis of the rectum coverage probabilities for 5 patients. In addition, IMRT treatment plans were optimized using the rectum hull PRV₅ of 5 CTs and each of the conventional rectum contours PRV₁. The plans were compared on the basis of the organ doses caused by the individual organ motion. PRV₅ allowed to cover the rectum with a probability of nearly 90% (PRV₁ 67%). Rectal wall dose showed a great variability for PRV₁, while planned and treatmend dose agreed well for PRV₅ due to the improved geometric information which resulted in a better rectal sparing. In conclusion, the rectum hull-volume PRV₅ is a well suited PRV for planning of IMRT dose distributions allowing dose escalation as well as rectal sparing.