Fig. 4.

Mean lung attenuation (Hounsfield units [HU]) versus lung volume (liters [L]) with decaying exponential regression line. Automated measurements of mean lung attenuation and lung volume were obtained from CT lung segmentations. Individual data points indicate the patient age range. Mean lung attenuation decreases rapidly in infants and young children with lower lung volumes (<0.8 liters). The decaying exponential regression line shows that as age and lung volume increase, mean lung attenuation approaches a relatively constant adult value of −860 HU. mos months