title: Cine-magnetic resonance imaging assessment of intrafraction motion for prostate cancer patients supine or prone with and without a rectal balloon.
abstract: OBJECTIVE
  Determine prostate intrafraction motion with Cine-magnetic resonance imaging (MRI) and deformable registration.
  
  
  METHODS
  A total of 68 cine-MRI studies were done in 17 different series with 4 scans per series in 7 patients. In without rectal balloon (WORB) scans, 100 mL of water was infused in the rectum. Each series consisted of supine and prone, with a rectal balloon (WRB) and WORB. Each scan was performed over 4 minutes. Automatic deformable registration software developed by View Ray, Inc., Cleveland, Ohio was employed to segment the prostate for each cine-MRI image. A time-based analysis was done for the different positions and the use of the rectal balloon.
  
  
  RESULTS
  The variation/standard deviation of the prostate position during 240 seconds was: supine WRB: 0.55 mm, WORB: 1.2 mm, and prone WRB: 1.48 mm, WORB: 2.15 mm (P < 0.001). A strong relationship was observed between time and prostate motion. For the initial 120 s the standard deviation was smaller than for the second 120 s supine WRB 0.54 mm versus 1.37 mm; supine WORB 0.61 mm versus 1.70 mm; prone WRB 0.85 mm versus 1.85 mm; and prone WORB 1.60 mm versus 2.56 mm. The probabilities for prostate staying within +/-2 mm to its initial position are: 94.8% supine WRB; 91.5% supine WORB; 92.3% prone WRB; 79.2% prone WORB.
  
  
  CONCLUSIONS
  Intrafraction prostate motion was found dependent on time, patient position, and the use of a rectal balloon. Relatively stable positions can be obtained for 4 minutes or less especially in the supine position with a rectal balloon.
authors.affiliation: Boca Radiation Oncology Associates, Boca Raton, FL, USA.
authors.forename: Carlos
authors.initials: C
authors.lastname: Vargas
authors.forename: Anneyuko I
authors.initials: AI
authors.lastname: Saito
authors.forename: Wen Chien
authors.initials: WC
authors.lastname: Hsi
authors.forename: Daniel
authors.initials: D
authors.lastname: Indelicato
authors.forename: Aaron
authors.initials: A
authors.lastname: Falchook
authors.forename: Qingguo
authors.initials: Q
authors.lastname: Zengm
authors.forename: Kenneth
authors.initials: K
authors.lastname: Oliver
authors.forename: Sameer
authors.initials: S
authors.lastname: Keole
authors.forename: Jim
authors.initials: J
authors.lastname: Dempsey
mesh_terms: D002404:Catheterization / Q000379:methods*; D006801:Humans; D019028:Magnetic Resonance Imaging, Cine; D008297:Male; D009038:Motion; D016684:Prone Position; D011471:Prostatic Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000517:prevention & control*; D012007:Rectum / Q000473:pathology / Q000528:radiation effects*; D016683:Supine Position