title: [Use of IGRT for prostate cancers (OBI-CBCT Varian, ExacTrac BrainLAB and MVCT TomoTherapy)].
abstract: BACKGROUND
  The aim of this work was to report the experience of image-guided radiotherapy at the CLCC Nantes-Atlantique using three repositioning imaging devices, the ExacTrac (BrainLAB), the OBI-CBCT (Varian) and the MVCT (Tomotherapy Inc), in the case of prostate external radiotherapy.
  
  
  METHODS
  For each linac and its imaging device, a treatment plan was described. Moreover, studies concerning calculated shifts after imaging sessions were achieved. Using ExacTrac, for eight patients, a study compared daily shifts based on bony anatomy or on implanted markers. Considering mean values of displacements over a course of radiotherapy, dosimetric impact was evaluated. With the OBI-CBCT, two imaging modalities were used, kV-kV (0 degrees and 270 degrees ) and CBCT. Up to now, whatever the images, displacements were calculated using the bony anatomy. For both modalities and for 26 patients, shifts were compared. Since the beginning of the Tomotherapy HiArt use, MVCT was performed for each session of each patient. For 12 patients, mean displacements were calculated after five fractions. Then the deviations to those values were calculated. This was done to show the relevance of daily MVCT.
  
  
  CONCLUSIONS
  This work allows us to report the use of three repositioning imaging devices in the radiotherapy department. At least they provide an efficient positioning tool. And they let us see the future radiotherapy which would probably be the dose-guided radiotherapy.
authors.affiliation: Service de physique médicale, centre René-Gauducheau, CLCC Nantes Atlantique, 44805 Nantes Saint-Herblain cedex, France. g-delpon@nantes.fnclcc.fr
authors.forename: G
authors.initials: G
authors.lastname: Delpon
authors.forename: C
authors.initials: C
authors.lastname: Llagostera
authors.forename: M
authors.initials: M
authors.lastname: Le Blanc
authors.forename: E
authors.initials: E
authors.lastname: Rio
authors.forename: S
authors.initials: S
authors.lastname: Supiot
authors.forename: M-A
authors.initials: MA
authors.lastname: Mahé
authors.forename: A
authors.initials: A
authors.lastname: Lisbona
mesh_terms: D002173:Cancer Care Facilities; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D004867:Equipment Design; D005602:France; D006801:Humans; D008297:Male; D010315:Particle Accelerators / Q000295:instrumentation; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D019736:Prostheses and Implants; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation / Q000379:methods*