title: Tumour delineation in oesophageal cancer - A prospective study of delineation in PET and CT with and without endoscopically placed clip markers.
abstract: OBJECTIVE
  The objective was to analyse the value of F-18-fluorodesoxyglucose (FDG)-positron emission tomography/computed tomography (PET/CT) for delineation of the Gross Tumour Volumes (GTVs) in primary radiotherapy of oesophageal cancer.
  
  
  METHODS
  20 consecutive and prospective patients (13 men, 7 women) underwent FDG-PET/CT for initial staging and radiation treatment planning. After endoscopy-guided clipping of the tumour another CT study was acquired. The CT and the FDG-PET/CT were registered with a rigid and a non-rigid registration algorithm to compare the overlap between GTV contours defined with the following methods: manual GTV definition in (1) the CT image of the FDG-PET/CT, (2) the PET image of the FDG-PET/CT, (3) the CT study based on endoscopic clips (CT clip), and (4) in the PET-data using different semi-automatic PET segmentation algorithms including a gradient-based algorithm. The absolute tumour volumes, tumour length in cranio-caudal direction, as well as the overlap with the reference volume (CT-clip) were compared for all lesions and separately for proximal/distal tumours.
  
  
  RESULTS
  In 6 of the patients, FDG-PET/CT discovered previously unknown tumour locations, which resulted in either altered target volumes (n=3) or altered intent of treatment from curative to palliative (n=3) by upstaging to stage IV. For tumour segmentation a large variability between all algorithms was found. For the absolute tumour volumes with CT-clip as reference, no single PET-based segmentation algorithm performed better compared to using the manual CT delineation alone. The best correlation was found between the CT-clip and the gradient based segmentation algorithm (PET-edge, R(2)=0.84) as well as the manual CT-delineation (CT-manual R(2)=0.89). Non-rigid registration between CT and image FDG-PET/CT did not decrease variability between segmentation methods compared to rigid registration statistically significant. For the analysis of tumour length no homogeneous correlation was found.
  
  
  CONCLUSIONS
  Whereas FDG-PET was highly relevant for staging purposes, CT imaging with clipping of the tumour extension remains the gold standard for GTV delineation.
authors.affiliation: Klinik und Poliklinik für Nuklearmedizin, Universitätsklinikum Würzburg, Germany; Klinik und Poliklinik für Strahlentherapie, Universitätsklinikum Würzburg, Germany; Klinik und Poliklinik für Nuklearmedizin, Universitätsklinikum Bonn, Germany. Electronic address: Lena.Thomas@ukb.uni-bonn.de.
authors.forename: Lena
authors.initials: L
authors.lastname: Thomas
authors.affiliation: Klinik und Poliklinik für Nuklearmedizin, Universitätsklinikum Würzburg, Germany.
authors.forename: Constatin
authors.initials: C
authors.lastname: Lapa
authors.affiliation: Klinik und Poliklinik für Nuklearmedizin, Universitätsklinikum Würzburg, Germany; Klinik und Poliklinik für Nuklearmedizin, Universitätsklinikum Bonn, Germany.
authors.forename: Ralph Alexander
authors.initials: RA
authors.lastname: Bundschuh
authors.affiliation: Klinik und Poliklinik für Strahlentherapie, Universitätsklinikum Würzburg, Germany.
authors.forename: Bülent
authors.initials: B
authors.lastname: Polat
authors.affiliation: Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, Netherlands.
authors.forename: Jan-Jakob
authors.initials: JJ
authors.lastname: Sonke
authors.affiliation: Klinik und Poliklinik für Strahlentherapie, Universitätsklinikum Würzburg, Germany; Klinik für Radioonkologie, Universitätsspital Zürich, Switzerland.
authors.forename: Matthias
authors.initials: M
authors.lastname: Guckenberger
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D004938:Esophageal Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods; D011446:Prospective Studies; D019275:Radiopharmaceuticals; D013525:Surgical Instruments; D014057:Tomography, X-Ray Computed / Q000379:methods; D047368:Tumor Burden
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: Biological target volume; Endoscopic clipping; Oesophageal cancer; PET/CT