title: Bowel exposure in rectal cancer IMRT using prone, supine, or a belly board.
abstract: OBJECTIVE
  To investigate bowel exposure using prone, supine, or two different belly boards for rectal cancer intensity modulated RT plans using a full bladder protocol.
  
  
  METHODS
  For 11 volunteers four MR scans were acquired, on a flat table in prone, supine, and on two different belly boards (IT-V Medizintechnik GmbH® (BB1) and CIVCO® (BB2)), using a full bladder protocol. On each scan a 25×2 Gy IMRT plan was calculated.
  
  
  RESULTS
  BB2 led to an average bowel area volume reduction of 20-30% at any dose level compared to prone. BB1 showed a smaller dose reduction effect, while no differences between prone and supine were found. Differences between BB2 and prone, supine or BB1 were significant up to a level of respectively, 45, 35, and 30 Gy. The reducing effect varied among individuals, except for the 50 Gy region, where no effect was found. An increase in bladder volume of 100 cc led to a significant bowel area V15 reduction of 16% independent of scan type.
  
  
  CONCLUSIONS
  In the low and intermediate dose region a belly board still attributes to a significant bowel dose reduction when using IMRT and a full bladder protocol. A larger bladder volume resulted in a significant decreased bowel area dose.
authors: Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
authors: Jasper
authors: J
authors: Nijkamp
authors: Barry
authors: B
authors: Doodeman
authors: Corrie
authors: C
authors: Marijnen
authors: Andrew
authors: A
authors: Vincent
authors: Corine
authors: C
authors: van Vliet-Vroegindeweij
mesh_terms: D005260:Female; D006801:Humans; D007422:Intestines / Q000528:radiation effects*; D008279:Magnetic Resonance Imaging; D008297:Male; D056888:Patient Positioning; D016684:Prone Position; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods; D011874:Radiometry; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012004:Rectal Neoplasms / Q000532:radiotherapy*; D016683:Supine Position