title: Evidence of limited motion of the prostate by carefully emptying the rectum as assessed by daily MVCT image guidance with helical tomotherapy.
abstract: OBJECTIVE
  To assess setup and organ motion error by means of analysis of daily megavoltage computed tomography (MVCT) of patients treated with hypofractionated helical tomotherapy (71.4-74.2 Gy in 28 fractions).
  
  
  METHODS
  Data from 21 patients were analyzed. Patients were instructed to empty the rectum carefully before planning CT and every morning before therapy by means of a self-applied rectal enema. The position of the prostate was assessed by means of automatic bone matching (BM) with the planning kilovoltage CT (BM, setup error) followed by a direct visualization (DV) match on the prostate. Deviations between planning and therapy positions referred to BM and BM + DV were registered for the three main axes. In case of a full rectum at MVCT with evident shift of the prostate, treatment was postponed until after additional rectal emptying procedures; in this case, additional MVCT was performed before delivering the treatment. Data for 522 fractions were available; the impact of post-MVCT procedure was investigated for 17 of 21 patients (410 fractions).
  
  
  RESULTS
  Prostate motion relative to bony anatomy was limited. Concerning posterior-anterior shifts, only 4.9% and 2.7% of fractions showed deviation of 3 mm or greater of the prostate relative to BM without and with consideration of post-MVCT procedures, respectively. Interobserver variability for BM + DV match was within 0.8 mm (1 SD).
  
  
  CONCLUSIONS
  Daily MVCT-based correction is feasible. The BM + DV matching was found to be consistent between operators. Rectal emptying using a daily enema is an efficient tool to minimize prostate motion, even for centers that have not yet implemented image-guided radiotherapy.
authors: Medical Physics, S. Raffaele Institute, Milano, Italy. florino.claudio@hsr.it
authors: Claudio
authors: C
authors: Fiorino
authors: Nadia
authors: N
authors: Di Muzio
authors: Sara
authors: S
authors: Broggi
authors: Cesare
authors: C
authors: Cozzarini
authors: Eleonora
authors: E
authors: Maggiulli
authors: Filippo
authors: F
authors: Alongi
authors: Riccardo
authors: R
authors: Valdagni
authors: Ferruccio
authors: F
authors: Fazio
authors: Riccardo
authors: R
authors: Calandrino
mesh_terms: D003672:Defecation; D019583:Dose Fractionation, Radiation; D004733:Enema / Q000379:methods*; D006801:Humans; D008297:Male; D009068:Movement; D015588:Observer Variation; D010384:Pelvic Bones / Q000000981:diagnostic imaging; D011467:Prostate / Q000000981:diagnostic imaging*; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated; D012007:Rectum / Q000000981:diagnostic imaging; D036542:Tomography, Spiral Computed