title: Dosimetric impact of contouring and image registration variability on dynamic125I prostate brachytherapy.
abstract: The quality of permanent prostate brachytherapy can be increased by addition of imaging modalities in the intraoperative procedure. This addition involves image registration, which inherently has inter- and intraobserver variabilities. We sought to quantify the inter- and intraobserver variabilities in geometry and dosimetry for contouring and image registration and analyze the results for our dynamic125I brachytherapy procedure.
  
  
  
  Five observers contoured 11 transrectal ultrasound (TRUS) data sets three times and 11 CT data sets one time. The observers registered 11 TRUS and MRI data sets to cone beam CT (CBCT) using fiducial gold markers. Geometrical and dosimetrical inter- and intraobserver variabilities were assessed. For the contouring study, structures were subdivided into three parts along the craniocaudal axis.
  
  
  
  We analyzed 165 observations. Interobserver geometrical variability for prostate was 1.1 mm, resulting in a dosimetric variability of 1.6% for V100and 9.3% for D90. The geometric intraobserver variability was 0.6 mm with a V100of 0.7% and D90of 1.1%. TRUS-CBCT registration showed an interobserver variability in V100of 2.0% and D90of 3.1%. Intraobserver variabilities were 0.9% and 1.6%, respectively. For MRI-CBCT registration, V100and D90were 1.3% and 2.1%. Intraobserver variabilities were 0.7% and 1.1% for the same.
  
  
  
  Prostate dosimetry is affected by interobserver contouring and registration variability. The observed variability is smaller than underdosages that are adapted during our dynamic brachytherapy procedure.
authors.affiliation: Radiotherapiegroep behandellocatie Deventer, Deventer, The Netherlands. Electronic address: r.westendorp@radiotherapiegroep.nl.
authors.forename: Hendrik
authors.initials: H
authors.lastname: Westendorp
authors.affiliation: Radiotherapiegroep behandellocatie Deventer, Deventer, The Netherlands; MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, The Netherlands.
authors.forename: Kathrin
authors.initials: K
authors.lastname: Surmann
authors.affiliation: Radiotherapiegroep behandellocatie Deventer, Deventer, The Netherlands.
authors.forename: Sandrine M G
authors.initials: SMG
authors.lastname: van de Pol
authors.affiliation: Radiotherapiegroep behandellocatie Deventer, Deventer, The Netherlands.
authors.forename: Carel J
authors.initials: CJ
authors.lastname: Hoekstra
authors.affiliation: Radiotherapiegroep behandellocatie Deventer, Deventer, The Netherlands.
authors.forename: Robert A J
authors.initials: RAJ
authors.lastname: Kattevilder
authors.affiliation: Radiotherapiegroep behandellocatie Deventer, Deventer, The Netherlands.
authors.forename: Tonnis T
authors.initials: TT
authors.lastname: Nuver
authors.affiliation: Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Marinus A
authors.initials: MA
authors.lastname: Moerland
authors.affiliation: MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, The Netherlands.
authors.forename: Cornelis H
authors.initials: CH
authors.lastname: Slump
authors.affiliation: Radiotherapiegroep behandellocatie Deventer, Deventer, The Netherlands.
authors.forename: André W
authors.initials: AW
authors.lastname: Minken
mesh_terms: D001918:Brachytherapy / Q000379:methods*; D054893:Cone-Beam Computed Tomography; D057918:Fiducial Markers; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D008279:Magnetic Resonance Imaging; D008297:Male; D015588:Observer Variation; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D061089:Radiotherapy, Image-Guided / Q000379:methods; D014463:Ultrasonography
chemical_list: D007457:Iodine Radioisotopes; C000614960:Iodine-125
keywords: Brachytherapy; Contouring; Low-dose rate; Prostate; Registration; Variability