Figure 3

The IST heterogeneity indices in human data. Panels (a) and (b) show unpaired Student’s t test of the IST ventilation (\({\sigma }_{V}\)) and perfusion heterogeneity (\({\sigma }_{P}\)) indices. Panel (c) shows the linear regression of the IST heterogeneity indices versus ages in healthy people. Panel (d) shows the receiver operating characteristic curve of the COPD classification using only IST heterogeneity indices. *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001.