Volume-Doubling Time of Pulmonary Nodules with Ground Glass Opacity at Multidetector CT: Assessment with Computer-Aided Three-Dimensional Volumetry

Rationale and Objectives: To investigate the volume-doubling time (VDT) of histologically proved pulmonary nodules showing ground glass opacity (GGO) at multidetector CT (MDCT) using computer-aided three-dimensional volumetry. Materials and Methods: We retrospectively evaluated 47 GGO nodules (mixed n = 28, pure n = 19) that had been examined by thin-section helical CT more than once. They were histologically confirmed as atypical adenomatous hyperplasia (AAH, n = 13), bronchioloalveolar carcinoma (BAC, n = 22), and adenocarcinoma (AC, n = 12). Using computer-aided three-dimensional volumetry software, two radiologists independently performed volumetry of GGO nodules and calculated the VDT using data acquired from the initial and final CT study. We compared VDT among the three pathologies and also compared the VDT of mixed and pure GGO nodules. Results: The mean VDT of all GGO nodules was 486.4 +/- 368.6 days (range 89.0-1583.0 days). The mean VDT for AAH, BAC, and AC was 859.2 +/- 428.9, 421.2 +/- 228.4, and 202.1 +/- 84.3 days, respectively; there were statistically significant differences for all comparative combinations of AAH, BAC, and AC (Steel-Dwass test, P < .01). The mean VDT for pure and mixed GGO nodules was 628.5 +/- 404.2 and 276.9 +/- 155.9 days, respectively; it was significantly shorter for mixed than pure GGO nodules (Mann-Whitney U-test, P < .01). Conclusion: The evaluation of VDT using computer-aided volumetry may be helpful in assessing the histological entities of GGO nodules.