title: Evaluation of the respiratory prostate motion with four-dimensional computed tomography scan acquisitions using three implanted markers.
abstract: OBJECTIVE
  During the irradiation of the prostate cancer, it is crucial to take into account the possible displacements in defining the planning target volume. The objective of this study was to specifically analyze the respiratory-induced prostate motion using a four-dimensional CT scan (4DCT).
  
  
  METHODS
  Ten patients have been treated for prostate cancer in the supine position and with three implanted gold markers; they underwent a 4DCT using a GE LightSpeed16 CT scan (slice thickness 2.5mm). This acquisition was divided into 10 phases over the respiratory cycle using the Advantage4D software. For each phase, digitally-reconstructed radiographs (DRRs) were created at 0° and 90° with the view of the markers. The coordinates of each marker center were generated from the scan isocenter. The motion amplitude was: visually analyzed on the dynamic 4DCT sequences and then more precisely calculated by comparing the marker coordinates on the 10 scans.
  
  
  RESULTS
  There was not any difficulty in defining the coordinates of the markers on each series. No prostate motion was observed on a simple visual analysis of the dynamic 4DCT sequences. After a more specific analysis, using the coordinates of the fiducials on the 10 phases, the prostate motion remained below 1mm in all directions, except for the cranio-caudal, where it was undetectable (thereby below the slice thickness of 2.5mm).
  
  
  CONCLUSIONS
  To our knowledge, this is the first study that evaluates the respiratory-induced prostate motion, using a 4DCT scan. Even if important prostate displacement can occur during the prostate treatment, because of the bladder or rectum filling, in the present study no respiratory-induced prostate motion was observed.
authors.affiliation: Department of Radiation Oncology, Centre Hospitalier Lyon Sud, Pierre Benite, France.
authors.forename: Corina
authors.initials: C
authors.lastname: Udrescu
authors.forename: Patrice
authors.initials: P
authors.lastname: Jalade
authors.forename: Berardino
authors.initials: B
authors.lastname: de Bari
authors.forename: Géraldine
authors.initials: G
authors.lastname: Michel-Amadry
authors.forename: Olivier
authors.initials: O
authors.lastname: Chapet
mesh_terms: D056973:Four-Dimensional Computed Tomography / Q000379:methods*; D006801:Humans; D008297:Male; D009038:Motion; D016684:Prone Position; D011467:Prostate / Q000000981:diagnostic imaging*; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D012119:Respiration; D016683:Supine Position