title: Interobserver-variability of lung nodule volumetry considering different segmentation algorithms and observer training levels.
abstract: OBJECTIVE
  The aim of this study was to investigate the interobserver variability of CT based diameter and volumetric measurements of artificial pulmonary nodules. A special interest was the consideration of different measurement methods, observer experience and training levels.
  
  
  METHODS
  For this purpose 46 artificial small solid nodules were examined in a dedicated ex-vivo chest phantom with multislice-spiral CT (20 mAs, 120 kV, collimation 16 mm x 0.75 mm, table feed 15 mm, reconstructed slice thickness 1mm, reconstruction increment 0.7 mm, intermediate reconstruction kernel). Two observer groups of different radiologic experience (0 and more than 5 years of training, 3 observers each) analysed all lesions with digital callipers and 2 volumetry software packages (click-point depending and robust volumetry) in a semi-automatic and manually corrected mode. For data analysis the variation coefficient (VC) was calculated in per cent for each group and a Wilcoxon test was used for analytic statistics.
  
  
  RESULTS
  Click-point robust volumetry showed with a VC of <0.01% in both groups the smallest interobserver variability. Between experienced and un-experienced observers interobserver variability was significantly different for diameter measurements (p=0.023) but not for semi-automatic and manual corrected volumetry. A significant training effect was revealed for diameter measurements (p=0.003) and semi-automatic measurements of click-point depending volumetry (p=0.007) in the un-experienced observer group.
  
  
  CONCLUSIONS
  Compared to diameter measurements volumetry achieves a significantly smaller interobserver variance and advanced volumetry algorithms are independent of observer experience.
authors: Department of Diagnostic Radiology, University Hospital Schleswig-Holstein Campus Kiel, Arnold-Heller Strasse 9, 24105 Kiel, Germany. hendrikbolte@rad.uni-kiel.de
authors: H
authors: H
authors: Bolte
authors: T
authors: T
authors: Jahnke
authors: F K W
authors: FK
authors: Schäfer
authors: R
authors: R
authors: Wenke
authors: B
authors: B
authors: Hoffmann
authors: S
authors: S
authors: Freitag-Wolf
authors: V
authors: V
authors: Dicken
authors: J M
authors: JM
authors: Kuhnigk
authors: J
authors: J
authors: Lohmann
authors: S
authors: S
authors: Voss
authors: N
authors: N
authors: Knöss
authors: M
authors: M
authors: Heller
authors: J
authors: J
authors: Biederer
mesh_terms: D000465:Algorithms; D000818:Animals; D002138:Calibration; D004195:Disease Models, Animal; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008171:Lung Diseases / Q000000981:diagnostic imaging*; D015588:Observer Variation; D011871:Radiology / Q000193:education*; D011873:Radiology Information Systems; D012984:Software; D013552:Swine; D036542:Tomography, Spiral Computed / Q000379:methods / Q000706:statistics & numerical data*