title: Reproducibility of CT perfusion parameters in liver tumors and normal liver.
abstract: OBJECTIVE
  To assess the reproducibility of computed tomographic (CT) perfusion measurements in liver tumors and normal liver and effects of motion and data acquisition time on parameters.
  
  
  METHODS
  Institutional review board approval and written informed consent were obtained for this prospective study. The study complied with HIPAA regulations. Two CT perfusion scans were obtained 2-7 days apart in seven patients with liver tumors with two scanning phases (phase 1: 30-second breath-hold cine; phase 2: six intermittent free-breathing cines) spanning 135 seconds. Blood flow (BF), blood volume (BV), mean transit time (MTT), and permeability-surface area product (PS) for tumors and normal liver were calculated from phase 1 with and without rigid registration and, for combined phases 1 and 2, with manually and rigid-registered phase 2 images, by using deconvolution modeling. Variability was assessed with within-patient coefficients of variation (CVs) and Bland-Altman analyses.
  
  
  RESULTS
  For tumors, BF, BV, MTT, and PS values and reproducibility varied by analytical method, the former by up to 11%, 23%, 21%, and 138%, respectively. Median PS values doubled with the addition of phase 2 data to phase 1 data. The best overall reproducibility was obtained with rigidly registered phase 1 and phase 2 images, with within-patient CVs for BF, BV, MTT, and PS of 11.2%, 14.4%, 5.5% and 12.1%, respectively. Normal liver evaluations were similar, except with marginally lower variability.
  
  
  CONCLUSIONS
  Absolute values and reproducibility of CT perfusion parameters were markedly influenced by motion and data acquisition time. PS, in particular, probably requires data acquisition beyond a single breath hold, for which motion-correction techniques are likely necessary.
authors.affiliation: Department of Diagnostic Radiology, University of Texas M. D. Anderson Cancer Center, 1400 Pressler St, Unit 1473, Houston, TX 77030-4009, USA. cng@mdanderson.org
authors.forename: Chaan S
authors.initials: CS
authors.lastname: Ng
authors.forename: Adam G
authors.initials: AG
authors.lastname: Chandler
authors.forename: Wei
authors.initials: W
authors.lastname: Wei
authors.forename: Delise H
authors.initials: DH
authors.lastname: Herron
authors.forename: Ella F
authors.initials: EF
authors.lastname: Anderson
authors.forename: Razelle
authors.initials: R
authors.lastname: Kurzrock
authors.forename: Chusilp
authors.initials: C
authors.lastname: Charnsangavej
mesh_terms: D000368:Aged; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008099:Liver / Q000000981:diagnostic imaging*; D008107:Liver Diseases / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology*; D008111:Liver Function Tests / Q000379:methods*; D008113:Liver Neoplasms / Q000000981:diagnostic imaging*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D055420:Perfusion Imaging / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: C073590:gadolinium ethoxybenzyl DTPA; D019786:Gadolinium DTPA