Monitoring of smoking-induced emphysema with CT in a lung cancer screening setting: Detection of real increase in extent of emphysema

Purose: To retrospectively establish the minimum increase in emphysema score (ES) required for detection of real Increased extent of emphysema with 95% confidence by using multi-detector row computed tomography (CT) in a lung cancer screening setting. Materials and Methods The study was a substudy of the NELSON project that was approved by the Dutch Ministry of Health and the ethics committee of each participating hospital, with patient informed consent. For this substudy, original approval and informed consent allowed use of data for future research. Among 1684 men screened with low-dose multi-detector row CT (30 mAs, 16 detector rows, 0.75-mm section thickness) between April 2004 and March 2005,only participants who underwent repeat multi the same scanner after 3 months because of an indeterminate the pulmonary nodule were included. Extent of emphysema,was considered to remain stable in this short 4 period. Extent or low-attenuation areas representing emphysema was computed for repeat and baseline scans as percentage of lung volume below three attenuation threshold values (-910 HU, -930 1115, -950 HU). Limits of agreement were determined with Bland-Altman approach; limits were used to deduce the minimum increase inupper ES required for detecting increased extent of emphysema with 95% probability. Factors influencing the limits of agreement were determined. Results In total, 157 men (mean age, 60 years) were included in the study. Limits of agreement for differences in total king volume between repeat and baseline scans were -13.4% to +12.6% at -910 HU, -4.7% to +4.2% at -930 HU, and -1.3% to +1.1% at -950 HU. Differences in ES showed weak to moderate correlation with variation in level of inspiration (r = 0.20-0.49, P < .05). Scanner contributing could be excluded as a factor contributing to variation in ES. Conclusion Increase in ES required to detect increased extent of smoking-related emphysema with 95% probability varies between 1.1% of total lung volume at -950 HU and +12.6% at -910 HU for tow-dose multi-detector row CT.