Comparison of three software systems for semi-automatic volumetry of pulmonary nodules on baseline and follow-up CT examinations

Abstract

Background

Early diagnosis of lung cancer in a treatable stage is the main purpose of lung cancer screening by computed tomography (CT). Accurate three-dimensional size and growth measurements are essential to assess the risk of malignancy. Nodule volumes can be calculated by using semi-automated volumetric software. Systematic differences in volume measurements between packages could influence nodule categorization and management decisions.

Purpose

To compare volumetric measurements of solid pulmonary nodules on baseline and follow-up CT scans as well as the volume doubling time (VDT) for three software packages.

Material and Methods

From a Lung Cancer Screening study (NELSON), 50 participants were randomly selected from the baseline round. The study population comprised participants with at least one pulmonary nodule at the baseline and consecutive CT examination. The volume of each nodule was determined for both time points using three semi-automated software packages (P₁, P₂, and P₃). Manual modification was performed when automated assessment was visually inaccurate. VDT was calculated to evaluate nodule growth. Volume, VDT, and nodule management were compared for the three software packages, using P₁ as the reference standard.

Results

In 25 participants, 147 nodules were present on both examinations (volume: 12.0–436.6 mm³). Initial segmentation at baseline was evaluated to be satisfactory in 93.9% of nodules for P₁, 84.4 % for P₂, and 88.4% for P₃. Significant difference was found in measured volume between P₁ and the other two packages (P < 0.001). P₂ overestimated the volume by 38 ± 24%, and P₃ by 50 ± 22%. At baseline, there was consensus on nodule size categorization in 80% for P₁&P₂ and 74% for P₁&P₃. At follow-up, consensus on VDT categorization was present in 47% for P₁&P₂ and 44% for P₁&P₃.

Conclusion

Software packages for lung nodule evaluation yield significant differences in volumetric measurements and VDT. This variation affects the classification of lung nodules, especially in follow-up examinations.

Keywords

Pulmonary nodule lung neoplasms NELSON study software

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