title: Bladder distension improves the dosimetry of organs at risk during intracavitary cervical high-dose-rate brachytherapy.
abstract: OBJECTIVE
  To evaluate dose-volume histograms (DVHs) and dose-surface histograms (DSHs) to analyze bladder distension during cervical brachytherapy.
  
  
  METHODS
  Twenty brachytherapy fractions from five cervical cancer patients were selected. For each fraction, empty and full (200cc of contrasted saline) bladder simulation CT scans existed, one of which was used to plan treatment. An alternative plan was then created with the unused scan. DVH for each fraction was generated for the bladder, rectum, sigmoid colon, and small bowel. Mean DVH dose, D0.1cc, and D2cc were calculated for each organ at risk. Plans were then exported to a MATLAB-based program to generate a DSH.
  
  
  RESULTS
  Full bladder plans showed no difference in bladder D2cc or D0.1cc compared with empty bladder plans; however, bladder mean DVH dose and DSH dose were both significantly reduced. Full bladder plans showed a significant reduction in small intestine D2cc from 2.81 Gy to 1.83 Gy and reduction in D0.1cc from 4.07 Gy to 2.57 Gy (p < 0.05); similarly, sigmoid D2cc was significantly reduced from 4.24 Gy to 3.87 Gy (p < 0.05) and D0.1cc was reduced from 6.12 Gy to 5.61 Gy (p < 0.05) in full bladder plans. Both small intestine and sigmoid also showed reduced mean DVH and DSH dose in full bladder plans. The rectum showed no significant difference in D2cc, D0.1cc, mean DVH, or DSH dose between plans.
  
  
  CONCLUSIONS
  Bladder distension during cervical brachytherapy significantly reduced dose in all DVH and DSH parameters for sigmoid and small intestine with no change in bladder parameters. It reduces dose to organ at risk, but the correlation to toxicity requires further investigation.
authors.affiliation: Department of Radiation Oncology, Loyola University Hospital, Maywood, IL.
authors.forename: Grant
authors.initials: G
authors.lastname: Harmon
authors.affiliation: Department of Radiation Oncology, Loyola University Hospital, Maywood, IL.
authors.forename: Bonnie
authors.initials: B
authors.lastname: Chinsky
authors.affiliation: Department of Radiation Oncology, Loyola University Hospital, Maywood, IL.
authors.forename: Murat
authors.initials: M
authors.lastname: Surucu
authors.affiliation: Department of Radiation Oncology, Loyola University Hospital, Maywood, IL.
authors.forename: Matthew
authors.initials: M
authors.lastname: Harkenrider
authors.affiliation: Department of Radiation Oncology, Loyola University Hospital, Maywood, IL. Electronic address: wmsmall@lumc.edu.
authors.forename: William
authors.initials: W
authors.lastname: Small
mesh_terms: D001918:Brachytherapy / Q000379:methods; D012809:Colon, Sigmoid; D005260:Female; D006801:Humans; D007421:Intestine, Small; D058958:Organs at Risk; D011829:Radiation Dosage; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D012007:Rectum; D014057:Tomography, X-Ray Computed; D001743:Urinary Bladder / Q000000981:diagnostic imaging; D002583:Uterine Cervical Neoplasms / Q000532:radiotherapy*
keywords: Bladder distension; Cervical cancer; Dose-surface histogram; HDR brachytherapy