title: Radiation-induced reductions in regional lung perfusion: 0.1-12 year data from a prospective clinical study.
abstract: OBJECTIVE
  To assess the time and regional dependence of radiation therapy (RT)-induced reductions in regional lung perfusion 0.1-12 years post-RT, as measured by single photon emission computed tomography (SPECT) lung perfusion.
  
  
  METHODS
  Between 1991 and 2005, 123 evaluable patients receiving RT for tumors in/around the thorax underwent SPECT lung perfusion scans before and serially post-RT (0.1-12 years). Registration of pre- and post-RT SPECT images with the treatment planning computed tomography, and hence the three-dimensional RT dose distribution, allowed changes in regional SPECT-defined perfusion to be related to regional RT dose. Post-RT follow-up scans were evaluated at multiple time points to determine the time course of RT-induced regional perfusion changes. Population dose response curves (DRC) for all patients at different time points, different regions, and subvolumes (e.g., whole lungs, cranial/caudal, ipsilateral/contralateral) were generated by combining data from multiple patients at similar follow-up times. Each DRC was fit to a linear model, and differences statistically analyzed.
  
  
  RESULTS
  In the overall groups, dose-dependent reductions in perfusion were seen at each time post-RT. The slope of the DRC increased over time up to 18 months post-RT, and plateaued thereafter. Regional differences in DRCs were only observed between the ipsilateral and contralateral lungs, and appeared due to tumor-associated changes in regional perfusion.
  
  
  CONCLUSIONS
  Thoracic RT causes dose-dependent reductions in regional lung perfusion that progress up to approximately 18 months post-RT and persists thereafter. Tumor shrinkage appears to confound the observed dose-response relations. There appears to be similar dose response for healthy parts of the lungs at different locations.
authors.affiliation: Department of Radiation Oncology, Duke University Medical Center, Durham, NC 27710, USA. junan.zhang@duke.edu
authors.forename: Junan
authors.initials: J
authors.lastname: Zhang
authors.forename: Jinli
authors.initials: J
authors.lastname: Ma
authors.forename: Sumin
authors.initials: S
authors.lastname: Zhou
authors.forename: Jessica L
authors.initials: JL
authors.lastname: Hubbs
authors.forename: Terence Z
authors.initials: TZ
authors.lastname: Wong
authors.forename: Rodney J
authors.initials: RJ
authors.lastname: Folz
authors.forename: Elizabeth S
authors.initials: ES
authors.lastname: Evans
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Jaszczak
authors.forename: Robert
authors.initials: R
authors.lastname: Clough
authors.forename: Lawrence B
authors.initials: LB
authors.lastname: Marks
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D001943:Breast Neoplasms / Q000532:radiotherapy; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D016014:Linear Models; D008168:Lung / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000528:radiation effects*; D008175:Lung Neoplasms / Q000532:radiotherapy; D008223:Lymphoma / Q000532:radiotherapy; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011832:Radiation Injuries / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*; D014057:Tomography, X-Ray Computed; D055815:Young Adult