title: [Optimization of MVCT imaging schedule in prostate cancer treatment using helical tomotherapy].
abstract: OBJECTIVE
  Megavoltage CT (MVCT) study on helical tomotherapy permits to verify and correct the patient setup by coregistration with the planning kVCT. This process is time-consuming and our objective is to investigate a possibility of using a smaller number of imaging studies in the case of patients with prostate cancer.
  
  
  METHODS
  The interfraction shifts of 20 patients (about 700 MVCT studies) treated in our institution have been recorded and analyzed. A new reference position has been calculated as an average of shifts observed during different initial number of fractions imaged.
  
  
  RESULTS
  The analysis of the reference position obtained for the set of 20 patients as a function of the number of imaging sessions has shown that MVCT studies during first four fractions are sufficient for the majority of patients.
  
  
  CONCLUSIONS
  Imaging during the first four fractions can be used to determine a reference position for patients with prostate cancer treated on helical tomotherapy. A study on Planned Adaptive (TomoTherapy Inc., Madison, WI, USA) software to evaluate the clinical significance of this scenario is currently in process in our institution.
authors.affiliation: Programme régional de cancérologie de London, London Health Sciences Centre, 790, Commissioners Road East, London, Ontario N6A 4L6, Canada.
authors.forename: G
authors.initials: G
authors.lastname: Beldjoudi
authors.forename: S
authors.initials: S
authors.lastname: Yartsev
authors.forename: J J
authors.initials: JJ
authors.lastname: Battista
authors.forename: J
authors.initials: J
authors.lastname: Van Dyk
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D006801:Humans; D008297:Male; D008875:Middle Aged; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D014057:Tomography, X-Ray Computed / Q000379:methods*