title: Reproducibility of perfusion parameters obtained from perfusion CT in lung tumors.
abstract: OBJECTIVE
  The purpose of this article is to assess the variability of perfusion CT measurements in lung tumors and the effects of motion and duration of data acquisition on perfusion CT parameter values.
  
  
  METHODS
  Two perfusion CT scans were obtained in 11 patients with lung tumors, 2-7 days apart, using phase 1 scans (30-second breath-hold cine) followed by phase 2 scans (six intermittent helical breath-holds), spanning 125 seconds. Tumor blood flow (BF), blood volume (BV), mean transit time (MTT), and permeability were calculated for phase 1 using all-cine and motion-corrected (rigidly registered) images, both with and without matching phase 2 images (manually or rigidly registered). Variability was assessed by the within-patient coefficient of variation (CV) and Bland-Altman analyses.
  
  
  RESULTS
  BF, BV, MTT, and permeability values varied widely by method of analysis (median BF, 45.3-65.1 mL/min/100 g; median BV, 2.6-3.8 mL/100 g; median MTT, 3.6-4.1 seconds, and median permeability, 13.7-39.3 mL/min/100 g), as did within-patient CVs (10.9-114.4%, 25.3-117.6%, 22.3-51.5%, and 29.6-134.9%, respectively). Parameter values and variability were affected by motion and duration of data analyzed: permeability values doubled when phase 2 images were added to phase 1 data. Overall, the best reproducibility was obtained with registered phase 1 and 2 data, with within-patient CVs of 11.6%, 26.5%, 45.4%, and 30.2%, respectively.
  
  
  CONCLUSIONS
  The absolute values and reproducibility of perfusion parameters in lung tumors are markedly influenced by motion and duration of data acquisition. Permeability, in particular, probably requires data acquisition beyond a single breath-hold. The smallest variability in parameter values was obtained with motion correction and extended acquisition durations.
authors.affiliation: Department of Diagnostic Radiology, The University of Texas M. D. Anderson Cancer Center, Houston, 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: Ella F
authors.initials: EF
authors.lastname: Anderson
authors.forename: Delise H
authors.initials: DH
authors.lastname: Herron
authors.forename: Chusilp
authors.initials: C
authors.lastname: Charnsangavej
authors.forename: Razelle
authors.initials: R
authors.lastname: Kurzrock
mesh_terms: D000328:Adult; D000368:Aged; D016477:Artifacts; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D055420:Perfusion Imaging / Q000379:methods*; D011652:Pulmonary Circulation; D014057:Tomography, X-Ray Computed / Q000379:methods*; D055815:Young Adult