Inherent variability of CT lung nodule measurements in vivo using semiautomated volumetric measurements

AJR Am J Roentgenol. 2006 Apr;186(4):989-94. doi: 10.2214/AJR.04.1821.


Objective: The objective of our study was to evaluate repeatability and reproducibility of lung nodule volume measurements using volumetric nodule-sizing software.

Materials and methods: Fifty nodules, less than 20 mm in diameter, in 29 patients were scanned with 1.25-mm collimation using MDCT (time 1 = T1). During the same session, two additional scans, using identical technique, were obtained through each nodule (T2, T3). Three observers working independently then obtained volumetric measurements using a semiautomated volumetric nodule-sizing software package. Qualitative nodule characterization was also performed. The Bland-Altman method for assessing measurement agreement was used to calculate the 95% limits for agreement for nodule volumes at T1, T2, and T3.

Results: Automated nodule segmentation was successful in 438 (97%) of 450 measurements. Forty-three nodules were available for final evaluation. Twenty-six nodules had well-defined edges, and 17 had irregular or spiculated margins. Seventeen were freestanding, 16 were juxtapleural, and 10 were juxtavascular in location. Average nodule volume was 345.5 mm(3) (range, 49.3-1,434 mm(3)). The mean interobserver variability (repeatability) was 0.018% (SD = 0.73%), and the SD of the mean for the three contemporaneous scans (reproducibility) was 13.1% (confidence limits, +/- 25.6%). SD and confidence limits narrowed as volumes increased.

Conclusion: Volumetric measurements show minimal interobserver variability (0.018%) but an interscan SEM of 13.1% (confidence limits, +/- 25.6%). Repeatability and reproducibility of volumetric measurements are better than those of linear measurements reported in the literature.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Female
  • Humans
  • Lung Neoplasms / diagnostic imaging*
  • Lung Neoplasms / pathology*
  • Male
  • Middle Aged
  • Observer Variation
  • Reproducibility of Results
  • Tomography, X-Ray Computed / statistics & numerical data*