title: Integrated (18)F-FDG PET/CT and perfusion CT of primary colorectal cancer: effect of inter- and intraobserver agreement on metabolic-vascular parameters.
abstract: OBJECTIVE
  The purpose of this article is to assess the effect of observers on combined metabolic-vascular parameters in colorectal cancer.
  
  
  METHODS
  Twenty-five prospective patients (12 men and 13 women; mean age, 66.9 years) with proven primary colorectal adenocarcinoma underwent integrated (18)F-FDG PET/perfusion CT to assess tumor metabolism (mean and maximum standardized uptake value [SUV(mean) and SUV(max), respectively]) and vascularization (blood flow [BF], blood volume [BV], permeability surface-area product, and standardized perfusion value). Intra- and interobserver agreement for PET, perfusion CT, and combined metabolic-flow parameters were determined by Bland-Altman statistics and intraclass correlation coefficients (ICCs).
  
  
  RESULTS
  The mean tumor size was 3.8 ± 1.6 cm; there were five stage IA/B, six stage IIA/B, eight stage IIIA/B, and six stage IV tumors. Intra- and interobserver agreement for individual parameters was fair to good, with mean differences between observers of -0.74 for SUV(max), -0.16 for SUV(mean), 9.72 for BF, 0.15 for BV, -0.76 for permeability surface-area product, and 0.09 for standardized perfusion value. ICCs were 0.44-0.99 and 0.38-0.89 for intra- and interobserver agreement, respectively. Interobserver agreement was variable for combined metabolic-flow parameters but better for metabolic-flow difference than for metabolic-flow ratio: ICCs were 0.69-0.88 for the metabolic-flow difference and 0.44-0.94 for the metabolic-flow ratio.
  
  
  CONCLUSIONS
  Combined parameters to assess the metabolic-flow relationship are influenced by observer variation. Intra- and interobserver agreement are better for the metabolic-flow differences than for the ratios, suggesting that metabolic-flow differences may be a more robust parameter for clinical practice.
authors.affiliation: Division of Imaging Sciences and Biomedical Engineering, King's College London, Imaging 2, Level 1, Lambeth Wing, St. Thomas' Hospital, Lambeth Palace Rd, Middlesex, London SE1 7EH, United Kingdom. vicky.goh@kcl.ac.uk
authors.forename: Vicky
authors.initials: V
authors.lastname: Goh
authors.forename: Manu
authors.initials: M
authors.lastname: Shastry
authors.forename: Alec
authors.initials: A
authors.lastname: Engledow
authors.forename: Robert
authors.initials: R
authors.lastname: Kozarski
authors.forename: Jacqui
authors.initials: J
authors.lastname: Peck
authors.forename: Raymondo
authors.initials: R
authors.lastname: Endozo
authors.forename: Manuel
authors.initials: M
authors.lastname: Rodriguez-Justo
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Taylor
authors.forename: Steve
authors.initials: S
authors.lastname: Halligan
authors.forename: Ashley M
authors.initials: AM
authors.lastname: Groves
mesh_terms: D000230:Adenocarcinoma / Q000098:blood supply / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology; D000368:Aged; D015179:Colorectal Neoplasms / Q000098:blood supply / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D009367:Neoplasm Staging; D015588:Observer Variation; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18