The effect of late-phase contrast enhancement on semi-automatic software measurements of CT attenuation and volume of part-solid nodules in lung adenocarcinomas.

ABSTRACT

OBJECTIVES: To evaluate the differences in semi-automatic measurements of CT attenuation and volume of part-solid nodules (PSNs) between unenhanced and enhanced CT scans. MATERIALS AND METHODS: CT scans including unenhanced and enhanced phases (slice thickness 0.625 and 1.25mm, respectively) for 53 adenocarcinomas presenting as PSNs in 50 patients were retrospectively evaluated. For each nodule, semi-automatic segmentation provided the diameter, mean attenuation, mass, and volume of a whole nodule and its solid component. Interscan variability and statistical significance of the differences in those measures according to the adenocarcinoma category were evaluated by one reader. RESULTS: All parameters except for the mean attenuation of the solid components, were significantly increased on enhanced CT (p<0.05). For the whole nodule, the mean relative differences were as follows the longest diameter, 1.4% (limits of agreement, -6.2-9.1); volume, 2.4% (-26.7-31.4); mass, 7.0% (-11.3-25.2); mean attenuation, 2.7% (-5.6-11). For the nodule's solid component, those differences were as follow the longest diameter, 6.9% (-34.4-48.2); volume, 17.9% (-77.8-113.7); mass, 18.8% (-77.8-115.4). The differences of measures between the unenhanced and enhanced CT were not significantly different between two groups of adenocarcinoma in situ/minimally invasive adenocarcinomas and invasive adenocarcinomas (p>0.05). CONCLUSIONS: As most volumetric and attenuation measurements changed significantly after contrast enhancement, care should be taken in comparing unenhanced and enhanced CT in the evaluation of PSNs.