Variability of semiautomated volume measurements between different versions of the same CT lung nodule volumetry software.

Purpose of the Study: To test the variability of semiautomated volume measurements of pulmonary nodules between two different versions of the same CT lung nodule volumetry software. Methods: The volumes of 100 intraparenchymal solid noncalcified nodules (mean volume 88.10 mm³; range 7.36 - 595.25 mm³) studied with the same CT protocol were calculated using two different versions of the same software (LungCARE 2006G and LungCARE 2007S). The 2006G version is based on a single segmentation algorithm, whereas the newer version is featured by two available algorithms called SmallSizeNodule and AllSizeNodule. 2006G version results were compared with those from the 2007S version obtained with the SmallSizeNodule algorithm as suggested by the user manual. Then, we also compared the volumetric measurements obtained by the two different algorithms of the 2007S version. Results:2006G and 2007S version with SmallSizeNodule algorithm agreed in only 2 cases and showed an overall mean volume variability of 1.66% (range 0 - 8.78%). A significant discrepancy was observed between the two different algorithms of the 2007S version, with larger volumes obtained by the AllSizeNodule algorithm (mean variation 71.08%; range 6.02 - 218.80%). Conclusions: Variability of results exists even between different versions of the same nodule volumetry software and may influence doubling time calculation. Computer-aided growth assessment of lung nodules detected on MDCT should always be performed by the same software version, using with the same segmentation algorithm in repeated MDCT scans.