title: Gold marker displacement due to needle insertion during HDR-brachytherapy for treatment of prostate cancer: a prospective cone beam computed tomography and kilovoltage on-board imaging (kV-OBI) study.
abstract: OBJECTIVE
  To evaluate gold marker displacement due to needle insertion during HDR-brachytherapy for therapy of prostate cancer.
  
  
  METHODS
  18 patients entered into this prospective evaluation. Three gold markers were implanted into the prostate during the first HDR-brachytherapy procedure after the irradiation was administered. Three days after marker implantation all patients had a CT-scan for planning purpose of the percutaneous irradiation. Marker localization was defined on the digitally-reconstructed-radiographs (DRR) for daily (VMAT technique) or weekly (IMRT) set-up error correction. Percutaneous therapy started one week after first HDR-brachytherapy. After the second HDR-brachytherapy, two weeks after first HDR-brachtherapy, a cone-beam CT-scan was done to evaluate marker displacement due to needle insertion. In case of marker displacement, the actual positions of the gold markers were adjusted on the DRR.
  
  
  RESULTS
  The value of the gold marker displacement due to the second HDR-brachytherapy was analyzed in all patients and for each gold marker by comparison of the marker positions in the prostate after soft tissue registration of the prostate of the CT-scans prior the first and second HDR-brachytherapy. The maximum deviation was 5 mm, 7 mm and 12 mm for the anterior-posterior, lateral and superior-inferior direction. At least one marker in each patient showed a significant displacement and therefore new marker positions were adjusted on the DRRs for the ongoing percutaneous therapy.
  
  
  CONCLUSIONS
  Needle insertion in the prostate due to HDR-brachytherapy can lead to gold marker displacements. Therefore, it is necessary to verify the actual position of markers after the second HDR-brachytherapy. In case of significant deviations, a new DRR with the adjusted marker positions should be generated for precise positioning during the ongoing percutaneous irradiation.
authors.affiliation: Department of Radiotherapy, University of Goettingen, Goettingen, Germany. markusherrmann@med.uni-goettingen.de
authors.forename: Markus K A
authors.initials: MK
authors.lastname: Herrmann
authors.forename: Tereza
authors.initials: T
authors.lastname: Kertesz
authors.forename: Tammo
authors.initials: T
authors.lastname: Gsänger
authors.forename: Eugen
authors.initials: E
authors.lastname: Bloch
authors.forename: Gerhard
authors.initials: G
authors.lastname: Pollul
authors.forename: Mohamed
authors.initials: M
authors.lastname: Bouabdallaoui
authors.forename: Arne
authors.initials: A
authors.lastname: Strauss
authors.forename: Mareike
authors.initials: M
authors.lastname: Herrmann
authors.forename: Hans
authors.initials: H
authors.lastname: Christiansen
authors.forename: Hendrik A
authors.initials: HA
authors.lastname: Wolff
authors.forename: Clemens F
authors.initials: CF
authors.lastname: Hess
authors.forename: Andrea
authors.initials: A
authors.lastname: Hille
mesh_terms: D000368:Aged; D001918:Brachytherapy / Q000295:instrumentation*; D054893:Cone-Beam Computed Tomography; D006050:Gold Radioisotopes; D006801:Humans; D008297:Male; D008875:Middle Aged; D009339:Needles; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D019736:Prostheses and Implants; D011856:Radiographic Image Enhancement; D011880:Radiotherapy Planning, Computer-Assisted
chemical_list: D006050:Gold Radioisotopes