title: Exploring intra- and inter-reader variability in uni-dimensional, bi-dimensional, and volumetric measurements of solid tumors on CT scans reconstructed at different slice intervals.
abstract: OBJECTIVE
  Understanding magnitudes of variability when measuring tumor size may be valuable in improving detection of tumor change and thus evaluating tumor response to therapy in clinical trials and care. Our study explored intra- and inter-reader variability of tumor uni-dimensional (1D), bi-dimensional (2D), and volumetric (VOL) measurements using manual and computer-aided methods (CAM) on CT scans reconstructed at different slice intervals.
  
  
  METHODS
  Raw CT data from 30 patients enrolled in oncology clinical trials was reconstructed at 5, 2.5, and 1.25 mm slice intervals. 118 lesions in the lungs, liver, and lymph nodes were analyzed. For each lesion, two independent radiologists manually and, separately, using computer software, measured the maximum diameter (1D), maximum perpendicular diameter, and volume (CAM only). One of them blindly repeated the measurements. Intra- and inter-reader variability for the manual method and CAM were analyzed using linear mixed-effects models and Bland-Altman method.
  
  
  RESULTS
  For the three slice intervals, the maximum coefficients of variation for manual intra-/inter-reader variability were 6.9%/9.0% (1D) and 12.3%/18.0% (2D), and for CAM were 5.4%/9.3% (1D), 11.3%/18.8% (2D) and 9.3%/18.0% (VOL). Maximal 95% reference ranges for the percentage difference in intra-reader measurements for manual 1D and 2D, and CAM VOL were (-15.5%, 25.8%), (-27.1%, 51.6%), and (-22.3%, 33.6%), respectively.
  
  
  CONCLUSIONS
  Variability in measuring the diameter and volume of solid tumors, manually and by CAM, is affected by CT slice interval. The 2.5mm slice interval provides the least measurement variability. Among the three techniques, 2D has the greatest measurement variability compared to 1D and 3D.
authors.affiliation: Department of Radiology, Columbia University Medical Center, New York, NY 10032, USA. bz2166@columbia.edu
authors.forename: Binsheng
authors.initials: B
authors.lastname: Zhao
authors.forename: Yongqiang
authors.initials: Y
authors.lastname: Tan
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Bell
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Marley
authors.forename: Pingzhen
authors.initials: P
authors.lastname: Guo
authors.forename: Helen
authors.initials: H
authors.lastname: Mann
authors.forename: Marietta L J
authors.initials: ML
authors.lastname: Scott
authors.forename: Lawrence H
authors.initials: LH
authors.lastname: Schwartz
authors.forename: Dana C
authors.initials: DC
authors.lastname: Ghiorghiu
mesh_terms: D000465:Algorithms; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D009369:Neoplasms / Q000000981:diagnostic imaging*; D015588:Observer Variation; D011856:Radiographic Image Enhancement / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D047368:Tumor Burden