title: Regional lung density changes after radiation therapy for tumors in and around thorax.
abstract: OBJECTIVE
  To study the temporal nature of regional lung density changes and to assess whether the dose-dependent nature of these changes is associated with patient- and treatment-associated factors.
  
  
  METHODS
  Between 1991 and 2004, 118 patients with interpretable pre- and post-radiation therapy (RT) chest computed tomography (CT) scans were evaluated. Changes in regional lung density were related to regional dose to define a dose-response curve (DRC) for RT-induced lung injury using three-dimensional planning tools and image fusion. Multiple post-RT follow-up CT scans were evaluated by fitting linear-quadratic models of density changes on dose with time as the covariate. Various patient- and treatment-related factors were examined as well.
  
  
  RESULTS
  There was a dose-dependent increase in regional lung density at nearly all post-RT follow-up intervals. The population volume-weighted changes evolved over the initial 6-month period after RT and reached a plateau thereafter (p < 0.001). On univariate analysis, patient age greater than 65 years (p = 0.003) and/or the use of pre-RT surgery (p < 0.001) were associated with significantly greater changes in CT density at both 6 and 12 months after RT, but the magnitude of this effect was modest.
  
  
  CONCLUSIONS
  There appears to be a temporal nature for the dose-dependent increases in lung density. Nondosimetric clinical factors tend to have no, or a modest, impact on these changes.
authors.affiliation: Department of Radiation Oncology, Duke University Medical Center, Durham, NC 27599-7512, USA.
authors.forename: Jinli
authors.initials: J
authors.lastname: Ma
authors.forename: Junan
authors.initials: J
authors.lastname: Zhang
authors.forename: Sumin
authors.initials: S
authors.lastname: Zhou
authors.forename: Jessica L
authors.initials: JL
authors.lastname: Hubbs
authors.forename: Rodney J
authors.initials: RJ
authors.lastname: Foltz
authors.forename: Donna R
authors.initials: DR
authors.lastname: Hollis
authors.forename: Kim L
authors.initials: KL
authors.lastname: Light
authors.forename: Terence Z
authors.initials: TZ
authors.lastname: Wong
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Kelsey
authors.forename: Lawrence B
authors.initials: LB
authors.lastname: Marks
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D000704:Analysis of Variance; D001943:Breast Neoplasms / Q000532:radiotherapy; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D016014:Linear Models; D008168:Lung / Q000000981:diagnostic imaging / Q000528:radiation effects*; D008175:Lung Neoplasms / Q000532:radiotherapy; D008223:Lymphoma / Q000532:radiotherapy; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011832:Radiation Injuries / Q000000981:diagnostic imaging*; D011880:Radiotherapy Planning, Computer-Assisted; D014057:Tomography, X-Ray Computed; D055815:Young Adult