title: High-dose-rate prostate brachytherapy based on registered transrectal ultrasound and in-room cone-beam CT images.
abstract: OBJECTIVE
  To present a high-dose-rate (HDR) brachytherapy procedure for prostate cancer using transrectal ultrasound (TRUS) to contour the regions of interest and registered in-room cone-beam CT (CBCT) images for needle reconstruction. To characterize the registration uncertainties between the two imaging modalities and explore the possibility of performing the procedure solely on TRUS.
  
  
  METHODS
  Patients were treated with a TRUS/CBCT-based HDR brachytherapy procedure. For 100 patients, dosimetric results were analyzed. For 40 patients, registration uncertainties were examined by determining differences in fiducial marker positions on TRUS and registered CBCT. The accuracy of needle reconstruction on TRUS was investigated by determining the position differences of needle tips on TRUS and CBCT. The dosimetric impact of reregistration and needle reconstruction on TRUS only was studied for 8 patients.
  
  
  RESULTS
  The average prostate V100 was 97.8%, urethra D10 was 116.3%, and rectum D1 cc was 66.4% of the prescribed dose. For 85% of the patients, registration inaccuracies were within 3 mm. Large differences were found between needle tips on TRUS and CBCT, especially in cranial-caudal direction, with a maximum of 10.4 mm. Reregistration resulted in a maximum V100 reduction of 0.9%, whereas needle reconstruction on TRUS only gave a maximum reduction of 9.4%.
  
  
  CONCLUSIONS
  HDR prostate brachytherapy based on TRUS combined with CBCT is an accurate method. Registration uncertainties, and consequently dosimetric inaccuracies, are small compared with the uncertainties of performing the procedure solely based on static TRUS images. CBCT imaging is a requisite in our current procedure.
authors.affiliation: Department of Medical Physics, Radiotherapeutic Institute RISO, Deventer, The Netherlands; MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, The Netherlands.
authors.forename: Aniek J G
authors.initials: AJ
authors.lastname: Even
authors.affiliation: Department of Medical Physics, Radiotherapeutic Institute RISO, Deventer, The Netherlands; Department of Radiation Oncology, Radiotherapeutic Institute RISO, Deventer, The Netherlands. Electronic address: t.nuver@risomail.nl.
authors.forename: Tonnis T
authors.initials: TT
authors.lastname: Nuver
authors.affiliation: Department of Medical Physics, Radiotherapeutic Institute RISO, Deventer, The Netherlands; Department of Radiation Oncology, Radiotherapeutic Institute RISO, Deventer, The Netherlands.
authors.forename: Hendrik
authors.initials: H
authors.lastname: Westendorp
authors.affiliation: Department of Radiation Oncology, Radiotherapeutic Institute RISO, Deventer, The Netherlands.
authors.forename: Carel J
authors.initials: CJ
authors.lastname: Hoekstra
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: Department of Medical Physics, Radiotherapeutic Institute RISO, Deventer, The Netherlands; Department of Radiation Oncology, Radiotherapeutic Institute RISO, Deventer, The Netherlands.
authors.forename: André W
authors.initials: AW
authors.lastname: Minken
mesh_terms: D001918:Brachytherapy / Q000379:methods*; D054893:Cone-Beam Computed Tomography; D006801:Humans; D008297:Male; D009339:Needles; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D011874:Radiometry / Q000379:methods; D012007:Rectum / Q000000981:diagnostic imaging / Q000528:radiation effects; D012189:Retrospective Studies; D014521:Urethra / Q000000981:diagnostic imaging / Q000528:radiation effects
keywords: Cone-beam CT; HDR brachytherapy; Prostate; Registration; Transrectal ultrasound