title: Effect of rectal enema on intrafraction prostate movement during image-guided radiotherapy.
abstract: BACKGROUND
  Rectal volume and movement are major factors that influence prostate location. The aim of this study was to assess the effect of a rectal enema on intrafraction prostate motion.
  
  
  METHODS
  The data from 12 patients with localised prostate cancer were analysed. Each patient underwent image-guided radiotherapy (RT), receiving a total dose of 70 Gy in 28 fractions. Rectal enemas were administered to all of the patients before each RT fraction. The location of the prostate was determined by implanting three fiducial markers under the guidance of transrectal ultrasound. Each patient underwent preparation for IGRT twice before an RT fraction and in the middle of the fraction. The intrafraction displacement of the prostate was calculated by comparing fiducial marker locations before and in the middle of an RT fraction.
  
  
  RESULTS
  The rectal enemas were well tolerated by patients. The mean intrafraction prostate movement in 336 RT fractions was 1.11 ± 0.77 mm (range 0.08-7.20 mm). Intrafraction motions of 1, 2 and 3 mm were observed in 56.0%, 89.0% and 97.6% of all RT fractions, respectively. The intrafraction movements on supero-inferior and anteroposterior axes were larger than on the right-to-left axes (P < 0.05). The CTV-to-PTV margin necessary to allow for movement, calculated using the van Herk formula (2.5Σ + 0.7σ), was 1.50 mm.
  
  
  CONCLUSIONS
  A daily rectal enema before each RT fraction was tolerable and yielded little intrafraction prostate displacement. We think the use of rectal enemas is a feasible method to reduce prostate movement during RT.
authors.affiliation: Departments of Radiation Oncology, School of Medicine, Dong-A University Hospital, Busan, South Korea.
authors.forename: Youngmin
authors.initials: Y
authors.lastname: Choi
authors.forename: Dong-Won
authors.initials: DW
authors.lastname: Kwak
authors.forename: Hyung-Sik
authors.initials: HS
authors.lastname: Lee
authors.forename: Won-Joo
authors.initials: WJ
authors.lastname: Hur
authors.forename: Won-Yeol
authors.initials: WY
authors.lastname: Cho
authors.forename: Gyung Tak
authors.initials: GT
authors.lastname: Sung
authors.forename: Tae-Hyo
authors.initials: TH
authors.lastname: Kim
authors.forename: Soo-Dong
authors.initials: SD
authors.lastname: Kim
authors.forename: Seong-Guk
authors.initials: SG
authors.lastname: Yun
mesh_terms: D000368:Aged; D004733:Enema / Q000379:methods*; D006801:Humans; D008297:Male; D009068:Movement; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D000069473:Radiation Dose Hypofractionation; D011859:Radiography; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
keywords: enema; image-guided radiotherapy; movement; prostate neoplasm