title: Quantitative evaluation of changes in irradiated lung fields after stereotactic irradiation by the Polygon Method.
abstract: OBJECTIVE
  To evaluate areas of change in lung after thoracic stereotactic irradiation (STI).
  
  
  METHODS
  We developed a method of evaluation named the Polygon Method, to measure the irradiated lung fields of 12 lung tumors treated by STI. Before treatment, each targeted field was divided into several circular zones of 2 cm in width centered at the tumor on high resolution computed tomography, and the areas of each zone before and after treatment were compared.
  
  
  RESULTS
  Six months after treatment, the areas of the zone within 2 cm from the tumor decreased, and the mean ratio of areas after and before STI was 0.849 (range, 0.515 to 1.052, p=0.0254). By contrast, the areas of zones located at 4 to 6, 6 to 8, 8 to 10, and more than 10 cm from the tumor tended to increase, with mean ratios of 1.059, 1.058, 1.089 (p=0.0374), and 1.084, respectively.
  
  
  CONCLUSIONS
  After thoracic STI, volume loss in the lung is limited to the field in close proximity to the tumor, while compensatory expansion of the lung occurs in fields distant from the tumor.
authors.affiliation: Division of Multidisciplinary Radiotherapy, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita-shi, Osaka 565-0871, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Yamada
authors.forename: Hiroya
authors.initials: H
authors.lastname: Shiomi
authors.forename: Iori
authors.initials: I
authors.lastname: Sumida
authors.forename: Osamu
authors.initials: O
authors.lastname: Suzuki
authors.forename: Fumiaki
authors.initials: F
authors.lastname: Isohashi
authors.forename: Ryoong-Jin
authors.initials: RJ
authors.lastname: Oh
authors.forename: Eiichi
authors.initials: E
authors.lastname: Tanaka
authors.forename: Takehiro
authors.initials: T
authors.lastname: Inoue
authors.forename: Hironobu
authors.initials: H
authors.lastname: Nakamura
mesh_terms: D000230:Adenocarcinoma / Q000000981:diagnostic imaging / Q000601:surgery*; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging / Q000601:surgery*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008168:Lung / Q000528:radiation effects*; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000556:secondary / Q000601:surgery*; D008297:Male; D017564:Radiation Pneumonitis / Q000000981:diagnostic imaging; D016634:Radiosurgery; D011879:Radiotherapy Dosage; D012984:Software; D014057:Tomography, X-Ray Computed / Q000379:methods*