title: CT perfusion measurements of head and neck carcinoma from single section with largest tumor dimensions or average of multiple sections: agreement between the two methods and effect on intra- and inter-observer agreement.
abstract: OBJECTIVE
  To evaluate the agreement between quantitative CT perfusion measurements of head and neck squamous cell carcinoma (SCC) obtained from single section with maximal tumor dimension and from average values of multiple sections, and to compare intra- and inter-observer agreement of the two methods.
  
  
  METHODS
  Perfusion was measured for 28 SCC cases using a region of interest (ROI) inserted in the single dynamic CT section showing maximal tumor dimension, then using average values of multiple ROIs inserted in all tumor-containing sections. Agreement between values of blood flow (BF), blood volume (BV), mean transit time (MTT) and permeability surface area product (PS) calculated by the two methods was assessed. Intra-observer agreement was assessed by comparing repeated calculations done by the same radiologist using both methods after 2 months blinding period. Perfusion measurements were done by another radiologist independently to assess inter-observer agreement of both methods.
  
  
  RESULTS
  No significant differences were observed between the means of the 4 perfusion parameters calculated by both methods, all p values >0.05 The 95% limits of agreement between the two methods were (-33.9 to 43)ml/min/100g for BF, (-2.5 to 2.8)ml/100g for BV, (-4.9 to 3.9)s for MTT and (-17.5 to 18.6)ml/min/100g for PS. Narrower limits of agreement were obtained using average of multiple sections than with single section denoting improved intra- and inter-observer agreement.
  
  
  CONCLUSIONS
  Agreement between both methods is acceptable. Taking the average of multiple sections slightly improves intra- and inter-observer agreement.
authors.affiliation: Institut für Diagnostische und Interventionelle Radiologie, Klinikum der J.W.v. Goethe Universität Frankfurt am Main, Theodor-Stern-Kai 7 Frankfurt am Main 60590, Germany. ahm m tawfik@hotmail.com
authors.forename: Ahmed M
authors.initials: AM
authors.lastname: Tawfik
authors.forename: Nour-Eldin A
authors.initials: NE
authors.lastname: Nour-Eldin
authors.forename: Nagy N
authors.initials: NN
authors.lastname: Naguib
authors.forename: Ahmed Abdel
authors.initials: AA
authors.lastname: Razek
authors.forename: Adel T
authors.initials: AT
authors.lastname: Denewer
authors.forename: Sotirios
authors.initials: S
authors.lastname: Bisdas
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Vogl
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging*; D005260:Female; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging*; D006801:Humans; D008875:Middle Aged; D015588:Observer Variation; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*