title: Inter- and intra-fractional bladder motion during radiotherapy for bladder cancer: a comparison of full and empty bladders.
abstract: OBJECTIVE
  To compare inter- and intra-fraction bladder volume variations and bladder wall motion during radiotherapy (RT) for bladder cancer with full and empty bladder protocols.
  
  
  METHODS
  Bladder volumes, filling rates and bladder wall movement were retrospectively analyzed for 24 patients with at least 4 sets of delineable pre and post treatment cone beam CT (CBCT)-scans. Eight patients were treated with an 'empty bladder' (EB) protocol and sixteen patients with a 'full bladder' (FB) protocol.
  
  
  RESULTS
  24 planning CT-scans and 356 CBCT-scans (178 sets) were analyzed. The average time between pre and post irradiation CBCT was 8min (range 6-18min). Median filling rate was 1.94ml/min and did not differ between EB and FB. Random variation in bladder volume and inter-fraction wall movement was slightly but not significantly larger for FB, whereas intra-fraction bladder wall movement was slightly but not significantly smaller for FB. The largest inter- and intra-fraction bladder wall movement was found in the cranial anterior direction.
  
  
  CONCLUSIONS
  Empty and full bladder protocols show similar inter- and intra-fraction wall motion, and therefore treatment choices could be purely based on organ at risk criteria.
authors.affiliation: Department of Radiation Oncology, The Netherlands Cancer Institute - Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands. Electronic address: h.ribbers@nki.nl.
authors.forename: Hermine M
authors.initials: HM
authors.lastname: Dees-Ribbers
authors.affiliation: Department of Radiation Oncology, The Netherlands Cancer Institute - Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands.
authors.forename: Anja
authors.initials: A
authors.lastname: Betgen
authors.affiliation: Department of Radiation Oncology, The Netherlands Cancer Institute - Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands.
authors.forename: Floris J
authors.initials: FJ
authors.lastname: Pos
authors.affiliation: Department of Radiation Oncology, The Netherlands Cancer Institute - Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands.
authors.forename: Thelma
authors.initials: T
authors.lastname: Witteveen
authors.affiliation: Department of Radiation Oncology, The Netherlands Cancer Institute - Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands.
authors.forename: Peter
authors.initials: P
authors.lastname: Remeijer
authors.affiliation: Department of Radiation Oncology, The Netherlands Cancer Institute - Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands. Electronic address: portal@nki.nl.
authors.forename: Marcel
authors.initials: M
authors.lastname: van Herk
mesh_terms: D054893:Cone-Beam Computed Tomography; D005260:Female; D006801:Humans; D008297:Male; D009068:Movement; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D001749:Urinary Bladder Neoplasms / Q000503:physiopathology / Q000532:radiotherapy*
keywords: Bladder filling; Bladder radiotherapy; Full or empty bladder; Inter-fractional bladder motion; Intra-fractional bladder motion