title: Intra- and interobserver agreement and impact of arterial input selection in perfusion CT measurements performed in squamous cell carcinoma of the upper aerodigestive tract.
abstract: OBJECTIVE
  CT Perfusion (CTP) has shown potential for assessing head and neck tumors. Our purposes were to assess the inter- and intraobserver agreement of CTP measurements and to investigate whether the selection of arterial input, ipsilateral versus contralateral to the tumor or left-versus-right external carotid artery (ECA), may affect CTP measurements in patients with squamous cell carcinoma (SCCA) of the upper aerodigestive tract.
  
  
  METHODS
  Twenty-six patients with SCCA were enrolled in this prospective study and underwent CTP. Data were analyzed by 2 expert readers and by an inexperienced reader for interobserver agreement and by the 2 expert readers for intraobserver agreement assessment, by using the ECA ipsilateral to tumor site as arterial input. All 3 readers repeated their analysis by using the ECA contralateral to tumor site as arterial input. Inter- and intraobserver agreement was assessed by using the Bland-Altman approach; CTP measurements by using ipsilateral-versus-contralateral or left-versus-right ECA were compared by using the Wilcoxon signed rank test.
  
  
  RESULTS
  The geometric mean of the ratios (95% limits of agreement) for inter- and intraobserver agreement ranged from 0.96 (0.75-1.23) to 1.00 (0.92-1.10) for blood flow (BF), from 0.88 (0.63-1.21) to 1.00 (0.88-1.14) for blood volume (BV), from 0.96 (0.64-1.44) to 0.98 (0.76-1.27) for mean transit time (MTT), and from 0.85 (0.41-1.76) to 1.14 (0.70-1.86) for permeability surface area product (PS). Significantly higher tumor PS and MTT for 2 readers and lower tumor BF for 1 of 3 readers were observed when the arterial input was placed in the left ECA.
  
  
  CONCLUSIONS
  BF, BV, and MTT demonstrated higher inter- and intraobserver agreement than PS. The selection of arterial input, right-versus-left ECA, may determine changes in CTP measurements in patients with SCCA of the upper aerodigestive tract.
authors.affiliation: Department of Radiology, European Institute of Oncology, Milan, Italy. giuseppe.petralia@ieo.it
authors.forename: G
authors.initials: G
authors.lastname: Petralia
authors.forename: L
authors.initials: L
authors.lastname: Preda
authors.forename: S
authors.initials: S
authors.lastname: Raimondi
authors.forename: G
authors.initials: G
authors.lastname: D'Andrea
authors.forename: P
authors.initials: P
authors.lastname: Summers
authors.forename: G
authors.initials: G
authors.lastname: Giugliano
authors.forename: F
authors.initials: F
authors.lastname: Chiesa
authors.forename: M
authors.initials: M
authors.lastname: Bellomi