The Effect of Lung Volume on the Size and Volume of Pulmonary Subsolid Nodules on CT: Intraindividual Comparison between Total Lung Capacity and Tidal Volume

PURPOSE: To examine the effect of lung volume on the size and volume of pulmonary subsolid nodules (SSNs) measured on CT. MATERIALS AND METHODS: A total of 42 SSNs from 31 patients were included. CT examination was first performed at total lung capacity (TLC), and a section containing the nodule was additionally scanned at tidal volume (TV). The diameter and volume of each SSN, as well as the cross-sectional lung area containing the nodule, were measured. The significance of the changes in measurements between TLC and TV within the same individuals was evaluated. RESULTS: The lung area and the diameter and volume of SSNs decreased significantly at TV by 12.7 cm(2), 0.5 mm, and 46.4 mm(3) on average, respectively (p < 0.001), compared to those at TLC. Changes in lung area between TV and TLC were positively correlated with the change in SSN diameter (p = 0.027) and volume (p = 0.014). However, after correction (by considering the change in lung area), the changes in SSN diameter (p = 0.124) and volume (p = 0.062) were not significantly different. CONCLUSION: SSN size and volume can be significantly affected by lung volume during CT scans of the same individuals.