title: Changes in rectal volume and prostate localization due to placement of a rectum-emptying tube.
abstract: OBJECTIVE
  Rectal volume variation has a crucial effect on prostate localization during external beam radiotherapy for prostate cancer. This study investigated the effect of rectal volume reduction by a rectum-emptying tube (RET) on prostate immobilization.
  
  
  METHODS
  The study group comprised 21 patients who underwent proton beam treatment for prostate cancer. Sigmoid-shaped flexible plastic RETs were used to drain gases from the rectum. Computed tomography (CT) was performed before and after RET placement at the treatment planning stage and at the beginning of treatment. Prostate displacement and changes in rectal volume were measured on the CT images. The feasibility of RET placement was evaluated during and after the procedure.
  
  
  RESULTS
  All 21 patients tolerated the procedure. The rectal volume was significantly lower with a RET than without a RET. The differences in rectal volume between the treatment planning stage and the beginning of treatment were significantly lower with a RET than without. RET placement significantly decreased prostate displacement in the anteroposterior and superoinferior directions but not in the left-right direction.
  
  
  CONCLUSIONS
  RET placement reduced both rectal volume and variation in rectal volume. The procedure reduced displacement of the prostate. RET placement thus appears to be an effective technique for immobilizing the prostate.
authors: Proton Therapy Division, Shizuoka Cancer Center, 1007 Shimonagakubo, Nagaizumi, Shizuoka 411-8777, Japan. h.fuji@scchr.jp.
authors: Hiroshi
authors: H
authors: Fuji
authors: Shigeyuki
authors: S
authors: Murayama
authors: Masashi
authors: M
authors: Niwakawa
authors: Raizou
authors: R
authors: Yamaguchi
authors: Ryou
authors: R
authors: Yamashita
authors: Takashi
authors: T
authors: Matsui
authors: Haruo
authors: H
authors: Yamashita
authors: Tetsuo
authors: T
authors: Nishimura
authors: Kenichi
authors: K
authors: Tobisu
mesh_terms: D000328:Adult; D006801:Humans; D007103:Immobilization / Q000295:instrumentation*; D008297:Male; D011467:Prostate / Q000000981:diagnostic imaging / Q000473:pathology; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D011857:Radiographic Image Interpretation, Computer-Assisted; D012007:Rectum / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed