title: Accuracy of deformable image registration for contour propagation in adaptive lung radiotherapy.
abstract: BACKGROUND
  Deformable image registration (DIR) is an attractive method for automatic propagation of regions of interest (ROIs) in adaptive lung radiotherapy. This study investigates DIR for automatic contour propagation in adaptive Non Small Cell Lung Carcinoma patients.
  
  
  METHODS
  Pre and mid-treatment fan beam 4D-kVCT scans were taken for 17 NSCLC patients. Gross tumour volumes (GTV), nodal-GTVs, lungs, esophagus and spinal cord were delineated on all kVCT scans. ROIs were propagated from pre- to mid-treatment images using three DIR algorithms. DIR-propagated ROIs were compared with physician-drawn ROIs on the mid-treatment scan using the Dice score and the mean slicewise Hausdorff distance to agreement (MSHD). A physician scored the DIR-propagated ROIs based on clinical utility.
  
  
  RESULTS
  Good agreement between the DIR-propagated and physician drawn ROIs was observed for the lungs and spinal cord. Agreement was not as good for the nodal-GTVs and esophagus, due to poor soft-tissue contrast surrounding these structures. 96% of OARs and 85% of target volumes were scored as requiring no or minor adjustments.
  
  
  CONCLUSIONS
  DIR has been shown to be a clinically useful method for automatic contour propagation in adaptive radiotherapy however thorough assessment of propagated ROIs by the treating physician is recommended.
authors.affiliation: Department of Physical Sciences, Peter MacCallum Cancer Centre, East Melbourne, VIC 3002, Australia. nicholas.hardcastle@petermac.org.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Hardcastle
authors.forename: Wouter
authors.initials: W
authors.lastname: van Elmpt
authors.forename: Dirk
authors.initials: D
authors.lastname: De Ruysscher
authors.forename: Karl
authors.initials: K
authors.lastname: Bzdusek
authors.forename: Wolfgang A
authors.initials: WA
authors.lastname: Tomé
mesh_terms: D000465:Algorithms; D002289:Carcinoma, Non-Small-Cell Lung / Q000532:radiotherapy*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008175:Lung Neoplasms / Q000532:radiotherapy*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*