title: [Evaluation of a method for correcting systematic setup error in external-beam radiation therapy].
abstract: OBJECTIVE
  We verified the propriety of our systematic error reduction strategy by means of a computer simulation based on our data of position error with a prone fixation device for prostate IMRT.
  
  
  METHODS
  Computer simulations of the off-line correction method for systematic setup errors based on the portal imaging taken on the first several days of the treatment session were performed. Using the computer simulations, an optimal number of portal images were evaluated for the SD value, from 0.5 mm to 1.5 mm at a 0.25 mm interval, and the respective required setup margins were calculated.
  
  
  RESULTS
  The value of systematic error was reduced as the frequency of data obtained increased. Moreover, the reduction rate was so remarkable that random error was large.
authors.affiliation: Clinical Radiology Service, Kyoto University Hospital, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Takakura
authors.forename: Kana
authors.initials: K
authors.lastname: Matsubara
authors.forename: Takashi
authors.initials: T
authors.lastname: Mizowaki
authors.forename: Manabu
authors.initials: M
authors.lastname: Nakata
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Yano
authors.forename: Takashi
authors.initials: T
authors.lastname: Okada
authors.forename: Takahiro
authors.initials: T
authors.lastname: Fujimoto
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kamomae
authors.forename: Rie
authors.initials: R
authors.lastname: Tanaka
authors.forename: Kichiro
authors.initials: K
authors.lastname: Koshida
authors.forename: Yuzo
authors.initials: Y
authors.lastname: Kikuchi
mesh_terms: D003198:Computer Simulation; D006801:Humans; D009010:Monte Carlo Method; D011878:Radiotherapy / Q000379:methods*; D012189:Retrospective Studies