title: Doubling time calculations for lung cancer by three-dimensional computer-aided volumetry: effects of inter-observer differences and nodule characteristics.
abstract: BACKGROUND
  The purpose of this study was to investigate doubling time (DT) differences among solid, part-solid (PS) and non-solid (NS) types of lung cancers. We also compared inter-observer differences in size measurements between diameter and three-dimensional (3D) volume measurements of lung cancers, including PS- and NS-type nodules, using 3D computer-aided volumetry (3D-CAV).
  
  
  METHODS
  The long-axis diameters and 3D volumes of lung tumours were measured using CAV by two chest radiologists for 71 consecutive patients with peripheral lung cancer who underwent at least two CT examinations before surgical resection. We evaluated the inter-observer variability for the ratio of diameter change (RCdiameter) and volume change (RCvolume), which were based on two CT images obtained at different times prior to resection. Inter-observer agreement was evaluated by Bland-Altman plots. Based on the volumes obtained from 3D-CAV, we calculated the DTs and compared DT differences between solid, PS and NS types of lung tumours.
  
  
  RESULTS
  The inter-observer Spearman's rank correlation coefficients were 0.87 for RCvolume and 0.64 for RCdiameter (p < 0.001). For all internal appearance types, the rs values for RCvolume were greater than those for RCdiameter. The median DT values for solid, PS and NS were 278, 347 and 584 days, respectively. NS- and PS-type tumours had significantly longer DTs (p = 0.024; by Spearman's rank correlation coefficient).
  
  
  CONCLUSIONS
  DT determinations using 3D-CAV had good correlations with the internal appearances of lung cancers. Lung tumour volume measurements by 3D-CAV exhibited better inter-observer correlations than did diameter measurements.
authors.affiliation: Department of Radiology, Nagoya University Graduate School of Medicine, Nagoya, Japan; Department of Radiology, Gifu Prefectural Tajimi Hospital, Tajimi, Japan.
authors.forename: Wataru
authors.initials: W
authors.lastname: Koike
authors.forename: Shingo
authors.initials: S
authors.lastname: Iwano
authors.forename: Keiji
authors.initials: K
authors.lastname: Matsuo
authors.forename: Mariko
authors.initials: M
authors.lastname: Kitano
authors.forename: Kenichi
authors.initials: K
authors.lastname: Kawakami
authors.forename: Shinji
authors.initials: S
authors.lastname: Naganawa
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008175:Lung Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; 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; D003074:Solitary Pulmonary Nodule / Q000000981:diagnostic imaging*; D013382:Subtraction Technique; D014057:Tomography, X-Ray Computed / Q000379:methods*; D047368:Tumor Burden
keywords: computer tomography; computer-aided diagnosis; doubling time; lung cancer; volumetry