[The effect of different patient positions on overlapping volumes in radiotherapy of patients with high-risk prostate cancer].

The purpose of the study was to evaluate the relationship among planning target volumes (PTVs) and organs at risk (OARs) based on four different radiotherapy treatment plans for high-risk prostate cancer patients. CT scans were obtained in supine position with knee and ankle support (KAS) and in prone position with belly-board (BB) both with full bladder (FB) and empty bladder (EB). Overlapping volumes of the delineated PTVs and OARs on four different setup combinations (KAS-FB; BB-FB; KAS-EB; BB-EB) were analyzed according to the patient position, bladder filling and circumference of abdomen (CA).