title: Target delineation in post-operative radiotherapy of brain gliomas: interobserver variability and impact of image registration of MR(pre-operative) images on treatment planning CT scans.
abstract: OBJECTIVE
  To investigate the interobserver variability of intracranial tumour delineation on computed tomography (CT) scans using pre-operative MR hardcopies (CT+MR(conv)) or CT-MR (pre-operative) registered images (CT+MR(matched)).
  
  
  METHODS
  Five physicians outlined the 'initial' clinical tumour volume (CTV0) of seven patients affected by HGG and candidates for radiotherapy (RT) after radical resection. The observers performed on screen-tumour delineation using post-operative CT images of the patients in the treatment position and pre-operative MR radiographs (CT+MR(conv)); they also outlined CTV0 with both CT and corresponding MR axial image on screen (CT+MR(matched)). The accuracy of the image fusion was quantitatively assessed. An analysis was conducted to assess the variability among the five observers in CT+MR(conv) and CT+MR(matched) modality.
  
  
  RESULTS
  The registration accuracy in 3D space is always less than 3.7 mm. The concordance index was significantly better in CT+MR(matched) (47.4+/-12.4%) than in CT+MR(conv) (14.1+/-12.7%) modality (P<0.02). The intersecting volumes represent 67+/-15 and 24+/-18% of the patient mean volume for CT+MR(matched) and CT+MR(conv), respectively (P<0.02).
  
  
  CONCLUSIONS
  The use of CT and MR registered imaging reduces interobserver variability in target volume delineation for post-operative irradiation of HGG; smaller margins around target volume could be adopted in defining irradiation technique.
authors.affiliation: Medical Physics, Scientific Institute, H.S. Raffaele, Milano, Italy. cattaneo.mauro@hsr.it
authors.forename: Giovanni Mauro
authors.initials: GM
authors.lastname: Cattaneo
authors.forename: Michele
authors.initials: M
authors.lastname: Reni
authors.forename: Giovanna
authors.initials: G
authors.lastname: Rizzo
authors.forename: Pietro
authors.initials: P
authors.lastname: Castellone
authors.forename: Giovanni Luca
authors.initials: GL
authors.lastname: Ceresoli
authors.forename: Cesare
authors.initials: C
authors.lastname: Cozzarini
authors.forename: Andrés José Maria
authors.initials: AJ
authors.lastname: Ferreri
authors.forename: Paolo
authors.initials: P
authors.lastname: Passoni
authors.forename: Riccardo
authors.initials: R
authors.lastname: Calandrino
mesh_terms: D000328:Adult; D000368:Aged; D001932:Brain Neoplasms / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery*; D003131:Combined Modality Therapy; D019583:Dose Fractionation, Radiation; D005260:Female; D005910:Glioma / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery*; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging / Q000592:standards*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000592:standards*