title: Bladder extension variability during pelvic external beam radiotherapy with a full or empty bladder.
abstract: OBJECTIVE
  Varying bladder fillings during radiotherapy lead to a changing dose-volume load to the bladder and adjacent structures. The aim of the study was to compare the extent of bladder wall movements during parallel series with full bladder (FB) and empty bladder (EB).
  
  
  METHODS
  Three hundred and forty serial computed tomography (CT) scans were performed in 50 patients scheduled for primary and postoperative radiotherapy for prostate cancer. Each patient underwent two CT scans (with FB and EB) before and 2-3 times during radiotherapy. Displacements of the bladder wall were compared and correlated with changing bladder fillings.
  
  
  RESULTS
  The variability of FB was larger compared to EB volume (standard deviation of 124 cc and 56 cc; p<0.01), but significant bladder wall displacement variabilities were only found at the anterior and superior borders. Within a bladder volume range between -100 and +200 ml relative to the FB planning scan, the mean bladder wall displacement remained < 5 mm at the inferior, lateral, and posterior borders - as opposed to 15 and 21 mm at the anterior and superior borders.
  
  
  CONCLUSIONS
  Treating the pelvis with EB compared to FB, bladder wall displacement can be only reduced at the superior and anterior borders. FB wall displacements are comparable with EB displacements at all other borders.
authors.affiliation: Department of Radiation Oncology, RWTH Aachen University, Aachen, Germany. MPinkawa@ukaachen.de
authors.forename: Michael
authors.initials: M
authors.lastname: Pinkawa
authors.forename: Branka
authors.initials: B
authors.lastname: Asadpour
authors.forename: Jaroslav
authors.initials: J
authors.lastname: Siluschek
authors.forename: Bernd
authors.initials: B
authors.lastname: Gagel
authors.forename: Marc D
authors.initials: MD
authors.lastname: Piroth
authors.forename: Cengiz
authors.initials: C
authors.lastname: Demirel
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Eble
mesh_terms: D016009:Chi-Square Distribution; D006801:Humans; D008297:Male; D009068:Movement; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed; D001743:Urinary Bladder / Q000000981:diagnostic imaging / Q000502:physiology*; D014556:Urine