title: Quantification of variability in breath-hold perfusion CT of hepatocellular carcinoma: a step toward clinical use.
abstract: OBJECTIVE
  To assess the variability of breath-hold perfusion computed tomography (CT) parameters and to investigate whether these measurements are affected by a commercial software upgrade in patients with hepatocellular carcinoma (HCC).
  
  
  METHODS
  Written informed consent was obtained from all participants in this institutional ethics committee-approved study. Perfusion CT examinations in HCC patients were prospectively analyzed by three readers. Two readers repeated their analysis after an interval of at least 4 weeks. Inter- and intraobserver agreement, as well as intersoftware agreement, were assessed with intraclass correlation coefficients (ICCs) and Bland-Altman limits of agreement (LoA), with adjustment for correlation between repeated measures.
  
  
  RESULTS
  Ninety-three breath-hold perfusion CT examinations were included from 23 HCC patients. The ICC between readers was very high (>0.91) for blood flow (BF), high (>0.84) for blood volume (BV), and lower (>0.30 and >0.39) for mean transit time (MTT) and permeability surface area product (PS), respectively, while ICC between readings was high (>0.80) for BF and BV, good (>0.75) for PS, and lower (>0.38) for MTT, irrespective of software version. By using the current software, the clinically relevant percentage of LoA between readers for BF were -33%; for BV, -39%; for MTT, 55%; and for PS, -93%. Between readings by the most expert reader, the clinically relevant LoA were -35% for BF,-43% for BV, 33% for MTT, and -79% for PS. BF, BV, and PS values were significantly higher and MTT values were significantly lower (P<.01) with the current software version relative to the previous version.
  
  
  CONCLUSIONS
  With the current CT perfusion software, only decreases between scans of HCC lesions of more than 35% for BF and 43% for BV, or an increase of more than 55% for MTT, could be considered beyond the analysis variability. The perfusion parameters obtained with the current and previous software versions were not exchangeable. The results of this study are specific for breath-hold perfusion CT of HCC and may not apply to different acquisition protocols and tumors.
authors.affiliation: Department of Radiology and Division of Epidemiology and Biostatistics, European Institute of Oncology, Via Ripamonti 435, 20141 Milan, Italy. giuseppe.petralia@ieo.it
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Petralia
authors.forename: Paul
authors.initials: P
authors.lastname: Summers
authors.forename: Stefano
authors.initials: S
authors.lastname: Viotti
authors.forename: Roberta
authors.initials: R
authors.lastname: Montefrancesco
authors.forename: Sara
authors.initials: S
authors.lastname: Raimondi
authors.forename: Massimo
authors.initials: M
authors.lastname: Bellomi
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D062485:Breath Holding; D006528:Carcinoma, Hepatocellular / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008113:Liver Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D055420:Perfusion Imaging / Q000379:methods*; D011856:Radiographic Image Enhancement / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012984:Software; D014057:Tomography, X-Ray Computed / Q000379:methods*