title: SPECT-based functional lung imaging for the prediction of radiation pneumonitis: a clinical and dosimetric correlation.
abstract: BACKGROUND
  When we irradiate lung cancer, the radiation dose that can be delivered safely is limited by the risk of radiation pneumonitis (RP) in the surrounding normal lung. This risk is dose-dependent and is commonly predicted using metrics such as the V20, which are usually formulated assuming homogeneous pulmonary function. Because in vivo pulmonary function is not homogeneous, if highly functioning lung can be identified beforehand and preferentially avoided during treatment, it might be possible to reduce the risk of RP, suggesting the utility of function-based prediction metrics.
  
  
  METHODS
  We retrospectively identified 26 patients who received ventilation and perfusion single photon emission computed tomography (SPECT-CT) immediately prior to curative-intent radiation therapy. Patients were separated into non-RP and RP groups. As-treated dose-volume histogram (DVH), perfusion-SPECT-based and ventilation-SPECT-based dose-function histogram (DFH) parameters were defined for each group and were tested for differences. The relative utilities of ventilation-based and perfusion-based DFH metrics were assessed using receiver operating characteristic (ROC) analysis.
  
  
  RESULTS
  The standard mean lung dose (MLD) was significantly higher in the RP group; the standard V20 and V30 were higher in the RP group but not significantly. Perfusion-weighted and ventilation-weighted values of the MLD, V20 and V30 were all significantly higher in the RP group. ROC analysis suggested that SPECT-based DFH parameters outperformed standard DVH parameters as predictors of RP.
  
  
  CONCLUSIONS
  SPECT-based DFH parameters appear to be useful as predictors of RP.
authors.affiliation: Department of Physics and Engineering, London Regional Cancer Program, University of Western Ontario, London, Ontario, Canada; Department of Oncology, University of Western Ontario, London, Ontario, Canada; Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada.
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Hoover
authors.forename: Robert H
authors.initials: RH
authors.lastname: Reid
authors.forename: Eugene
authors.initials: E
authors.lastname: Wong
authors.forename: Larry
authors.initials: L
authors.lastname: Stitt
authors.forename: Eric
authors.initials: E
authors.lastname: Sabondjian
authors.forename: George B
authors.initials: GB
authors.lastname: Rodrigues
authors.forename: Jasbir K
authors.initials: JK
authors.lastname: Jaswal
authors.forename: Brian P
authors.initials: BP
authors.lastname: Yaremko
mesh_terms: D000368:Aged; D006801:Humans; D008175:Lung Neoplasms / Q000150:complications / Q000532:radiotherapy*; D008297:Male; D011379:Prognosis; D017564:Radiation Pneumonitis / Q000175:diagnosis* / Q000209:etiology; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal / Q000009:adverse effects*; D015203:Reproducibility of Results; D012129:Respiratory Function Tests / Q000379:methods*; D012189:Retrospective Studies; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
keywords: DFH; SPECT; dose-function histogram; functional lung imaging; lung cancer