title: Electronic and film portal images: a comparison of landmark visibility and review accuracy.
abstract: OBJECTIVE
  To quantitatively compare a scanning liquid ion chamber electronic portal imaging device (SLIC-EPID) and an amorphous silicon flat panel (aSi) EPID with portal film in clinical applications using measures of landmark visibility and treatment review accuracy.
  
  
  METHODS
  Six radiation oncologists viewed 39 electronic portal images (EPIs) from the SLIC-EPID, 36 EPIs from the aSi-EPID, and portal films of each of these treatment fields. The physicians rated the clarity of anatomic landmarks in the portal images, and the scores were compared between EPID and film. Nine hundred portal image reviews were performed. EPID and film portal images were acquired with known setup errors in either phantom or cadaver treatments. Physicians identified the errors visually in portal films and with computerized analysis for EPID.
  
  
  RESULTS
  There were no statistically significant (p < 0.05) differences between film and SLIC-EPID in ratings of landmark clarity. Eleven of 12 landmarks were more visible in aSi-EPID than in film. Translational setup errors were identified with an average accuracy of 2.5 mm in film, compared to 1.5 mm with SLIC-EPID and 1.3 mm with aSi-EPID.
  
  
  CONCLUSIONS
  Both EPIDs are clinically viable replacements for film, but aSi-EPID represents a significant advancement in image quality over film.
authors.affiliation: Division of Radiation Oncology, Mayo Clinic, Rochester, MN 55905, USA.
authors.forename: Jon J
authors.initials: JJ
authors.lastname: Kruse
authors.forename: Michael G
authors.initials: MG
authors.lastname: Herman
authors.forename: Chris R
authors.initials: CR
authors.lastname: Hagness
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Davis
authors.forename: Yolanda I
authors.initials: YI
authors.lastname: Garces
authors.forename: Michael G
authors.initials: MG
authors.lastname: Haddock
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Olivier
authors.forename: Scott L
authors.initials: SL
authors.lastname: Stafford
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Pisansky
mesh_terms: D009068:Movement; D015588:Observer Variation; D019047:Phantoms, Imaging; D011856:Radiographic Image Enhancement / Q000379:methods / Q000592:standards*; D013679:Technology, Radiologic / Q000379:methods / Q000592:standards; D014962:X-Ray Film / Q000592:standards