title: Vaginal motion and bladder and rectal volumes during pelvic intensity-modulated radiation therapy after hysterectomy.
abstract: OBJECTIVE
  To evaluate variations in bladder and rectal volume and the position of the vaginal vault during a 5-week course of pelvic intensity-modulated radiation therapy (IMRT) after hysterectomy.
  
  
  METHODS
  Twenty-four patients were instructed how to fill their bladders before simulation and treatment. These patients underwent computed tomography simulations with full and empty bladders and then underwent rescanning twice weekly during IMRT; patients were asked to have full bladder for treatment. Bladder and rectal volumes and the positions of vaginal fiducial markers were determined, and changes in volume and position were calculated.
  
  
  RESULTS
  The mean full and empty bladder volumes at simulation were 480 cc (range, 122-1,052) and 155 cc (range, 49-371), respectively. Bladder volumes varied widely during IMRT: the median difference between the maximum and minimum volumes was 247 cc (range, 96-585). Variations in rectal volume during IMRT were less pronounced. For the 16 patients with vaginal fiducial markers in place throughout IMRT, the median maximum movement of the markers during IMRT was 0.59 cm in the right-left direction (range, 0-0.9), 1.46 cm in the anterior-posterior direction (range, 0.8-2.79), and 1.2 cm in the superior-inferior direction (range, 0.6-2.1). Large variations in rectal or bladder volume frequently correlated with significant displacement of the vaginal apex.
  
  
  CONCLUSIONS
  Although treatment with a full bladder is usually preferred because of greater sparing of small bowel, our data demonstrate that even with detailed instruction, patients are unable to maintain consistent bladder filling. Variations in organ position during IMRT can result in marked changes in the position of the target volume and the volume of small bowel exposed to high doses of radiation.
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA. ajhingra@mdanderson.org
authors.forename: Anuja
authors.initials: A
authors.lastname: Jhingran
authors.forename: Mohammad
authors.initials: M
authors.lastname: Salehpour
authors.forename: Marianne
authors.initials: M
authors.lastname: Sam
authors.forename: Larry
authors.initials: L
authors.lastname: Levy
authors.forename: Patricia J
authors.initials: PJ
authors.lastname: Eifel
mesh_terms: D000328:Adult; D003198:Computer Simulation; D060766:Drinking Water / Q000008:administration & dosage; D016889:Endometrial Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy* / Q000601:surgery; D005260:Female; D057918:Fiducial Markers; D006801:Humans; D007044:Hysterectomy; D007421:Intestine, Small / Q000000981:diagnostic imaging; D008875:Middle Aged; D009068:Movement; D009929:Organ Size; D011182:Postoperative Care / Q000379:methods; D011446:Prospective Studies; D050397:Radiotherapy, Intensity-Modulated; D012007:Rectum / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed; D014521:Urethra / Q000000981:diagnostic imaging; D001743:Urinary Bladder / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D002583:Uterine Cervical Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy* / Q000601:surgery; D014621:Vagina / Q000033:anatomy & histology / Q000000981:diagnostic imaging*
chemical_list: D060766:Drinking Water