title: Validation of an elastic registration technique to estimate anatomical lung modification in non-small-cell lung cancer tomotherapy.
abstract: BACKGROUND
  The study of lung parenchyma anatomical modification is useful to estimate dose discrepancies during the radiation treatment of Non-Small-Cell Lung Cancer (NSCLC) patients. We propose and validate a method, based on free-form deformation and mutual information, to elastically register planning kVCT with daily MVCT images, to estimate lung parenchyma modification during Tomotherapy.
  
  
  METHODS
  We analyzed 15 registrations between the planning kVCT and 3 MVCT images for each of the 5 NSCLC patients. Image registration accuracy was evaluated by visual inspection and, quantitatively, by Correlation Coefficients (CC) and Target Registration Errors (TRE). Finally, a lung volume correspondence analysis was performed to specifically evaluate registration accuracy in lungs.
  
  
  RESULTS
  Results showed that elastic registration was always satisfactory, both qualitatively and quantitatively: TRE after elastic registration (average value of 3.6 mm) remained comparable and often smaller than voxel resolution. Lung volume variations were well estimated by elastic registration (average volume and centroid errors of 1.78% and 0.87 mm, respectively).
  
  
  CONCLUSIONS
  Our results demonstrate that this method is able to estimate lung deformations in thorax MVCT, with an accuracy within 3.6 mm comparable or smaller than the voxel dimension of the kVCT and MVCT images. It could be used to estimate lung parenchyma dose variations in thoracic Tomotherapy.
authors.affiliation: Istituto di Bioimmagini e Fisiologia Molecolare, CNR, via Fratelli Cervi 93 Segrate (Milan), 20090, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Faggiano
authors.forename: Giovanni M
authors.initials: GM
authors.lastname: Cattaneo
authors.forename: Cristina
authors.initials: C
authors.lastname: Ciavarro
authors.forename: Italo
authors.initials: I
authors.lastname: Dell'Oca
authors.forename: Diego
authors.initials: D
authors.lastname: Persano
authors.forename: Riccardo
authors.initials: R
authors.lastname: Calandrino
authors.forename: Giovanna
authors.initials: G
authors.lastname: Rizzo
mesh_terms: D000465:Algorithms; D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008168:Lung / Q000528:radiation effects*; D008175:Lung Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D009367:Neoplasm Staging; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated; D036542:Tomography, Spiral Computed / Q000379:methods