title: Simulator verification of the accuracy of patient repositioning after virtual simulation. Is physical simulation still needed?
abstract: OBJECTIVE
  To evaluate the frequency and amount of displacements after repositioning a patient on the physical simulator following virtual simulation.
  
  
  METHODS
  After laser marking at the CT scanner and virtual simulation, patients were repositioned on the simulator. The isocenter obtained from the calculated table movements was checked by fluoroscopically measuring the distances to standardized anatomic landmarks and comparing them to the treatment plan.
  
  
  RESULTS
  In 86% of patients, displacements were < or = 0.5 cm. There was no significant difference between the supine and prone position, diagnosis categories or CT reconstruction indices. The use of immobilization devices and cranial versus body stem localization did make a significant difference. Rates of exact repositioning were high in brain and head and neck patients and comparatively low in abdominal tumors and breast cancer.
  
  
  CONCLUSIONS
  Immobilization devices play an important role for the precision of radiotherapy. Whenever precise positioning is possible (e. g. with a head mask), virtual simulation alone might be sufficient. Patients with abdominal and breast tumors, were repositioning precision is often suboptimal, might profit from an additional physical simulation.
authors.affiliation: Hospital and Outpatient Department for Radiotherapy - Radiooncology, University Hospital Münster, Germany. pschuel@uni-muenster.de
authors.forename: Patrick
authors.initials: P
authors.lastname: Schüller
authors.forename: Frank
authors.initials: F
authors.lastname: Bruns
authors.forename: Stefan
authors.initials: S
authors.lastname: Hesselmann
authors.forename: Kirsten
authors.initials: K
authors.lastname: Horn
authors.forename: Joan E
authors.initials: JE
authors.lastname: Panke
authors.forename: Andreas
authors.initials: A
authors.lastname: Schuck
authors.forename: Ulrich
authors.initials: U
authors.lastname: Schäfer
authors.forename: Oliver
authors.initials: O
authors.lastname: Micke
authors.forename: Normann
authors.initials: N
authors.lastname: Willich
mesh_terms: D000328:Adult; D000368:Aged; D016477:Artifacts; D002138:Calibration; D003198:Computer Simulation; D005260:Female; D005471:Fluoroscopy; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000532:radiotherapy*; D016684:Prone Position; D011880:Radiotherapy Planning, Computer-Assisted; D015203:Reproducibility of Results; D012984:Software; D016683:Supine Position; D014057:Tomography, X-Ray Computed; D014584:User-Computer Interface