Figure 2.

The difference in texture (absolute value) between regions near and away from cysts can be used to measure the degradation of lung parenchyma and to control for technical differences resulting from type of CT scanner used. A, Comparison of cyst score and FEV₁ at 5 years before starting sirolimus treatment (t = –5) and at the start of sirolimus treatment (t = 0) in 14 patients using a paired t test. B, Comparison of energy near cysts (< 10 mm) and away from cysts (> 10 mm) at t = –5 and t = 0 in 14 patients using a paired t test. Energy is a texture property (co-occurrence matrix measure) with significant (P < .001) correlations to FEV₁, diffusion capacity for carbon monoxide, and cyst score (R = 0.79). Energy is used here for illustrative purposes; all 26 texture properties were examined, and stable areas far from cysts were found for each. NS = not significant.