title: Analysis of interfraction and intrafraction variation during tangential breast irradiation with an electronic portal imaging device.
abstract: OBJECTIVE
  To evaluate the daily setup variation and the anatomic movement of the heart and lungs during breast irradiation with tangential photon beams, as measured with an electronic portal imaging device.
  
  
  METHODS
  Analysis of 1,709 portal images determined changes in the radiation field during a treatment course in 8 patients. Values obtained for every image included central lung distance (CLD) and area of lung and heart within the irradiated field. The data from these measurements were used to evaluate variation from setup between treatment days and motion due to respiration and/or patient movement during treatment delivery.
  
  
  RESULTS
  The effect of respiratory motion and movement during treatment was minimal: the maximum range in CLD for any patient on any day was 0.25 cm. The variation caused by day-to-day setup variation was greater, with CLD values for patients ranging from 0.59 cm to 2.94 cm. Similar findings were found for heart and lung areas.
  
  
  CONCLUSIONS
  There is very little change in CLD and corresponding lung and heart area during individual radiation treatment fractions in breast tangential fields, compared with a relatively greater amount of variation that occurs between days.
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Ryan P
authors.initials: RP
authors.lastname: Smith
authors.forename: Peter
authors.initials: P
authors.lastname: Bloch
authors.forename: Eleanor E
authors.initials: EE
authors.lastname: Harris
authors.forename: James
authors.initials: J
authors.lastname: McDonough
authors.forename: Abhirup
authors.initials: A
authors.lastname: Sarkar
authors.forename: Alireza
authors.initials: A
authors.lastname: Kassaee
authors.forename: Steven
authors.initials: S
authors.lastname: Avery
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Solin
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy* / Q000601:surgery; D005260:Female; D006321:Heart; D006801:Humans; D008168:Lung; D015412:Mastectomy, Segmental; D008875:Middle Aged; D009068:Movement; D019095:Point-of-Care Systems; D011859:Radiography; D011879:Radiotherapy Dosage; D012119:Respiration; D014894:Weights and Measures