Figure 2

Illustration of the methods to evaluate the cranial-caudal heterogeneity of emphysematous change. Each lung was divided into 12 partitions with equal volumes (A), and LAV% values in 12 partitions were calculated (B). The top and basal partitions (open circles in C and D) were excluded to avoid volume partial effects. SD-LAV was defined as the standard deviation of LAV% values in the remaining 10 partitions. C and D showed examples of heterogeneous and homogeneous emphysema, respectively. While LAV% in C and D were almost similar (45.5 and 47.7%, respectively), SD-LAV in C was higher than in D (8.0 versus 2.8%).