title: Internal motion of the vagina after hysterectomy for gynaecological cancer.
abstract: OBJECTIVE
  The purpose of this study was to investigate position changes of the vagina after hysterectomy for early stage cervical or endometrial cancer and their impact on CTV-PTV margins. We also studied their correlation with surrounding organ filling.
  
  
  METHODS
  Fifteen patients underwent T2-weighted MR scans before and weekly during the course of their EBRT. The vaginal CTVs and the surrounding organs were delineated. PTV margins were derived from the boundaries of the CTVs in the main directions and correlated with changes in the volumes of organs at risk. Additionally we investigated the impact of margin sizes on CTV coverage.
  
  
  RESULTS
  The vaginal CTVs change their position in the pelvis during time with a maximum in anterior-posterior direction. The 95% confidence level was 2.3 cm into the anterior or posterior direction, 1.8 cm to left or right and 1.5 cm towards the cranial. With a homogenous 1.5 cm CTV-PTV margin ≥5% inadequately covered vaginal CTV was seen in only 3.3% of the measurements. This increased to 20.6% with a margin of 1.0 cm. Concerning the impact of organ filling on vaginal position changes we found the only significant correlation with rectal volume and shift of the vagina towards anterior-posterior.
  
  
  CONCLUSIONS
  To accommodate the changes in the position of the vaginal CTV inhomogeneous PTV margins should be generated with the largest size in the anterior-posterior direction. The position shifts were only weakly related to the volume of the rectum and not at all to the volumes of other parts of the bowel and the bladder.
authors.affiliation: Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, The Netherlands. i.m.schulz@umcutrecht.nl
authors.forename: Ina M
authors.initials: IM
authors.lastname: Jürgenliemk-Schulz
authors.forename: Malgorzata Z
authors.initials: MZ
authors.lastname: Toet-Bosma
authors.forename: Gérard A P
authors.initials: GA
authors.lastname: de Kort
authors.forename: Henk W R
authors.initials: HW
authors.lastname: Schreuder
authors.forename: Judith M
authors.initials: JM
authors.lastname: Roesink
authors.forename: Robbert J H A
authors.initials: RJ
authors.lastname: Tersteeg
authors.forename: Uulke A
authors.initials: UA
authors.lastname: van der Heide
mesh_terms: D016889:Endometrial Neoplasms / Q000473:pathology / Q000601:surgery*; D005260:Female; D006801:Humans; D007044:Hysterectomy; D008279:Magnetic Resonance Imaging; D009038:Motion; D002583:Uterine Cervical Neoplasms / Q000473:pathology / Q000601:surgery*; D014621:Vagina / Q000473:pathology*