title: Pulmonary tumor measurements from x-ray computed tomography in one, two, and three dimensions.
abstract: OBJECTIVE
  We evaluated the accuracy and reproducibility of three-dimensional (3D) measurements of lung phantoms and patient tumors from x-ray computed tomography (CT) and compared these to one-dimensional (1D) and two-dimensional (2D) measurements.
  
  
  METHODS
  CT images of three spherical and three irregularly shaped tumor phantoms were evaluated by three observers who performed five repeated measurements. Additionally, three observers manually segmented 29 patient lung tumors five times each. Follow-up imaging was performed for 23 tumors and response criteria were compared. For a single subject, imaging was performed on nine occasions over 2 years to evaluate multidimensional tumor response. To evaluate measurement accuracy, we compared imaging measurements to ground truth using analysis of variance. For estimates of precision, intraobserver and interobserver coefficients of variation and intraclass correlations (ICC) were used. Linear regression and Pearson correlations were used to evaluate agreement and tumor response was descriptively compared.
  
  
  RESULTS
  For spherical shaped phantoms, all measurements were highly accurate, but for irregularly shaped phantoms, only 3D measurements were in high agreement with ground truth measurements. All phantom and patient measurements showed high intra- and interobserver reproducibility (ICC >0.900). Over a 2-year period for a single patient, there was disagreement between tumor response classifications based on 3D measurements and those generated using 1D and 2D measurements.
  
  
  CONCLUSIONS
  Tumor volume measurements were highly reproducible and accurate for irregular, spherical phantoms and patient tumors with nonuniform dimensions. Response classifications obtained from multidimensional measurements suggest that 3D measurements provide higher sensitivity to tumor response.
authors.affiliation: Imaging Research Laboratories, Robarts Research Institute, London, Canada N6A 5K8.
authors.forename: Lauren
authors.initials: L
authors.lastname: Villemaire
authors.forename: Amir M
authors.initials: AM
authors.lastname: Owrangi
authors.forename: Roya
authors.initials: R
authors.lastname: Etemad-Rezai
authors.forename: Laura
authors.initials: L
authors.lastname: Wilson
authors.forename: Elaine
authors.initials: E
authors.lastname: O'Riordan
authors.forename: Harry
authors.initials: H
authors.lastname: Keller
authors.forename: Brandon
authors.initials: B
authors.lastname: Driscoll
authors.forename: Glenn
authors.initials: G
authors.lastname: Bauman
authors.forename: Aaron
authors.initials: A
authors.lastname: Fenster
authors.forename: Grace
authors.initials: G
authors.lastname: Parraga
mesh_terms: D000704:Analysis of Variance; D006801:Humans; D021621:Imaging, Three-Dimensional; D008175:Lung Neoplasms / Q000000981:diagnostic imaging*; D019047:Phantoms, Imaging; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed