title: Quantitative assessment of lung cancer perfusion using MDCT: does measurement reproducibility improve with greater tumor volume coverage?
abstract: OBJECTIVE
  To date, quantitative assessment of tumor vascularity using perfusion CT has been limited to a single tumor level, with the potential for measurement error in heterogeneous tumors. We aimed to determine if greater z-axis tumor coverage improves the reproducibility of perfusion CT measurements in lung cancer.
  
  
  METHODS
  Paired perfusion studies were performed on 10 patients who had histologically confirmed advanced non-small cell lung cancer. Using 16-MDCT, multiple sequential volumetric acquisitions encompassing the entire tumor were acquired after infusion of i.v. contrast material. Using Patlak analysis, median values of tumor permeability (mL/100 mL/min) and blood volume (mL/100 mL) were measured for 10-mm z-axis coverage, and for 40-mm z-axis coverage in each of the paired perfusion studies. Measurement reproducibility was evaluated using Bland-Altman statistics.
  
  
  RESULTS
  Mean difference (95% limits of agreement) for tumor permeability was 1.4 (-4.0 to 6.8) for 10-mm coverage and 0.8 (-3.6 to 5.2) for 40-mm coverage. Mean difference (95% limits of agreement) for blood volume was 1.9 (-5.1 to 8.9) for 10-mm coverage and 1.4 (-3.7 to 6.6) for 40-mm coverage. The coefficient of variation for permeability was 18.7% for 10-mm coverage, improving to 11.9% for 40-mm coverage. The coefficient of variation for blood volume was 41.7% for 10-mm coverage, improving to 32.6% for 40-mm coverage.
  
  
  CONCLUSIONS
  Our results show that an improvement in tumor perfusion measurement reproducibility may be achieved with greater z-axis coverage.
authors.affiliation: Marie Curie Research Wing, Mount Vernon Hospital, Northwood, Middlesex, United Kingdom.
authors.forename: Quan Sing
authors.initials: QS
authors.lastname: Ng
authors.forename: Vicky
authors.initials: V
authors.lastname: Goh
authors.forename: Ernst
authors.initials: E
authors.lastname: Klotz
authors.forename: Heinz
authors.initials: H
authors.lastname: Fichte
authors.forename: Michele I
authors.initials: MI
authors.lastname: Saunders
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Hoskin
authors.forename: Anwar R
authors.initials: AR
authors.lastname: Padhani
mesh_terms: D000368:Aged; D001810:Blood Volume; D002289:Carcinoma, Non-Small-Cell Lung / Q000098:blood supply* / Q000000981:diagnostic imaging* / Q000473:pathology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008175:Lung Neoplasms / Q000098:blood supply* / Q000000981:diagnostic imaging* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden