title: Dynamic contrast enhanced CT aiding gross tumor volume delineation of liver tumors: an interobserver variability study.
abstract: OBJECTIVE
  To evaluate the application of perfusion CT for gross tumor volume (GTV) delineation for radiotherapy of intrahepatic tumors.
  
  
  METHODS
  15 radiotherapy patients with confirmed liver tumors underwent contrast enhanced 4D-CT (Philips Brilliance Big-bore) as well as dynamic contrast enhanced (DCE) CT (GE 750HD). Perfusion maps were generated with CT perfusion v5 from GE. Five observers delineated GTVs of all intrahepatic foci on the 4D-CT, time-averaged DCE-CT and perfusion CT for every patient. STAPLE consensus contours were generated. Dice's coefficients were compared between GTVs generated by observers on each image set and the corresponding consensus GTVs. Comparisons were also performed with patients stratified by hepatocellular carcinoma (HCC) metastatic tumors, and by tumor volume.
  
  
  RESULTS
  Overall, mean Dice's coefficients were 0.81±0.14, 0.84±0.10, and 0.81±0.14 for 4D-CT, DCECT and perfusion. DCE-CT performed significantly better than 4D-CT and perfusion (p=0.005 and p=0.01 respectively). For patients with HCC, DCE-CT reduced interobserver variability significantly compared to 4D-CT (Dice's coefficients 0.87 vs. 0.84, p<0.05). For patients with metastatic disease time-averaged DCE-CT images decreased variability compared to 4D-CT (Dice's coefficient 0.81 vs. 0.76, p<0.05), especially true for tumors<100cc. The smaller tumors results are important to be included here.
  
  
  CONCLUSIONS
  DCE-CT imaging of liver perfusion reduced interobserver variability in GTV delineation for both HCC and metastatic liver tumors.
authors.affiliation: Physics & Engineering, London Regional Cancer Program, Canada.
authors.forename: Nikolaj K G
authors.initials: NK
authors.lastname: Jensen
authors.affiliation: Physics & Engineering, London Regional Cancer Program, Canada.
authors.forename: Danielle
authors.initials: D
authors.lastname: Mulder
authors.affiliation: Radiation Oncology, London Regional Cancer Program, Canada; Department of Oncology, University of Western Ontario, London, Canada.
authors.forename: Michael
authors.initials: M
authors.lastname: Lock
authors.affiliation: Radiation Oncology, London Regional Cancer Program, Canada; Department of Oncology, University of Western Ontario, London, Canada.
authors.forename: Barbara
authors.initials: B
authors.lastname: Fisher
authors.affiliation: Radiology, London Hospitals, Canada.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Zener
authors.affiliation: Physics & Engineering, London Regional Cancer Program, Canada.
authors.forename: Ben
authors.initials: B
authors.lastname: Beech
authors.affiliation: Radiology, St. Joseph's Health Care, London, Canada.
authors.forename: Roman
authors.initials: R
authors.lastname: Kozak
authors.affiliation: Physics & Engineering, London Regional Cancer Program, Canada; Department of Oncology, University of Western Ontario, London, Canada; Department of Medical Biophysics, University of Western Ontario, London, Canada.
authors.forename: Jeff
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Oncology, University of Western Ontario, London, Canada; Radiology, St. Joseph's Health Care, London, Canada; Imaging Research Lab, Robarts Research Institute, London, Canada; Department of Medical Biophysics, University of Western Ontario, London, Canada; Imaging Program, Lawson Health Research Institute, London, Canada.
authors.forename: Ting-Yim
authors.initials: TY
authors.lastname: Lee
authors.affiliation: Physics & Engineering, London Regional Cancer Program, Canada; Department of Oncology, University of Western Ontario, London, Canada; Department of Medical Biophysics, University of Western Ontario, London, Canada; Department of Physics & Astronomy, University of Western Ontario, London, Canada. Electronic address: ewong4@uwo.ca.
authors.forename: Eugene
authors.initials: E
authors.lastname: Wong
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D006528:Carcinoma, Hepatocellular / Q000473:pathology* / Q000532:radiotherapy*; D003287:Contrast Media; D005260:Female; D056973:Four-Dimensional Computed Tomography / Q000379:methods; D006801:Humans; D008113:Liver Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D036542:Tomography, Spiral Computed / Q000379:methods; D047368:Tumor Burden
chemical_list: D003287:Contrast Media
keywords: 4D-CT; CT perfusion; Contouring; Dynamic contrast enhanced CT; GTV delineation; Hepatocellular carcinoma