title: Superficial doses in breast cancer radiotherapy using conventional and IMRT techniques: a film-based phantom study.
abstract: OBJECTIVE
  Superficial doses in radiotherapy are affected by the treatment technique. The implications for breast cancer treatments were evaluated.
  
  
  METHODS
  Four treatment techniques relevant for breast cancer irradiation were evaluated; tangential standard, tangential IMRT, 7-field IMRT (arc-like field arrangement) and hybrid IMRT (an IMRT plan mixed with non-modulated fields). Only 6MV photons were used. GafChromic EBT film was used for dose measurements at the surface, in the skin (0-5mm depth) and in the superficial parts of CTV (5-10mm depth) of an anthropomorphic thorax phantom.
  
  
  RESULTS
  Only small differences in superficial doses were observed between tangential standard and tangential IMRT. Compared to the tangential standard plan, the surface and skin doses were reduced with the 7-field IMRT plan, on average by 20% and 5%, respectively, while hybrid IMRT reduced the surface and skin doses medially (by 44% and 8%, respectively) and increased the surface and skin dose laterally (by 40% and 15%, respectively). Minimum superficial CTV doses varied between regions, but were mainly between 90% and 95% of the target dose for all plans, only the hybrid IMRT plan resulted in a region with minimum dose below 90%.
  
  
  CONCLUSIONS
  Compared to tangential irradiation, skin sparing was achieved by the 7-field IMRT plan. The minimum dose in the superficial parts of the CTV was below 95% of the target dose for all plans investigated.
authors.affiliation: Department of Physics, The Norwegian University of Science and Technology, Trondheim, Norway. sigrun.saur@ntnu.no
authors.forename: Sigrun Saur
authors.initials: SS
authors.lastname: Almberg
authors.forename: Tore
authors.initials: T
authors.lastname: Lindmo
authors.forename: Jomar
authors.initials: J
authors.lastname: Frengen
mesh_terms: D001940:Breast / Q000528:radiation effects; D001943:Breast Neoplasms / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D019047:Phantoms, Imaging; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012867:Skin / Q000528:radiation effects