title: A novel method to incorporate the spatial location of the lung dose distribution into predictive radiation pneumonitis modeling.
abstract: OBJECTIVE
  Studies have proposed that patients who receive radiation therapy to the base of the lung are more susceptible to radiation pneumonitis than patients who receive therapy to the apex of the lung. The primary purpose of the present study was to develop a novel method to incorporate the lung dose spatial information into a predictive radiation pneumonitis model. A secondary goal was to apply the method to a 547 lung cancer patient database to determine whether including the spatial information could improve the fit of our model.
  
  
  METHODS
  The three-dimensional dose distribution of each patient was mapped onto one common coordinate system. The boundaries of the coordinate system were defined by the extreme points of each individual patient lung. Once all dose distributions were mapped onto the common coordinate system, the spatial information was incorporated into a Lyman-Kutcher-Burman predictive radiation pneumonitis model. Specifically, the lung dose voxels were weighted using a user-defined spatial weighting matrix. We investigated spatial weighting matrices that linearly scaled each dose voxel according to the following orientations: superior-inferior, anterior-posterior, medial-lateral, left-right, and radial. The model parameters were fit to our patient cohort with the endpoint of severe radiation pneumonitis. The spatial dose model was compared against a conventional dose-volume model to determine whether adding a spatial component improved the fit of the model.
  
  
  RESULTS
  Of the 547 patients analyzed, 111 (20.3%) experienced severe radiation pneumonitis. Adding in a spatial parameter did not significantly increase the accuracy of the model for any of the weighting schemes.
  
  
  CONCLUSIONS
  A novel method was developed to investigate the relationship between the location of the deposited lung dose and pneumonitis rate. The method was applied to a patient database, and we found that for our patient cohort, the spatial location does not influence the risk of pneumonitis.
authors: Department of Radiation Physics, University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA. yvinogra@mdanderson.org
authors: Yevgeniy
authors: Y
authors: Vinogradskiy
authors: Susan L
authors: SL
authors: Tucker
authors: Zhongxing
authors: Z
authors: Liao
authors: Mary K
authors: MK
authors: Martel
mesh_terms: D000465:Algorithms; D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology / Q000532:radiotherapy*; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D008168:Lung / Q000528:radiation effects*; D008175:Lung Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D008954:Models, Biological; D058958:Organs at Risk / Q000528:radiation effects; D017564:Radiation Pneumonitis / Q000209:etiology*; D011836:Radiation Tolerance; D011880:Radiotherapy Planning, Computer-Assisted; D012044:Regression Analysis; D012189:Retrospective Studies