The following analyses are performed on segmented lung images, using VIDA software (VIDA Diagnostics, http://www.vidadiagnostics.com): total inspiratory and expiratory lung volumes, mean lung attenuation, and relative lung volumes (for the whole lung, and for each lobe) falling below attenuation thresholds of −950, −910 and −856 HU. Emphysema distribution is assessed by comparing percent emphysema in central vs. peripheral lung and upper vs. lower lobes. Automated airway segmentation and quantification are performed, as discussed by Hoffman et al 15. For each bronchial tree, multiple parameters are calculated for third, fourth, fifth, and sixth generation bronchi, including wall area, lumen area, wall thickness, and luminal diameter. Parallel imaging analyses of percent emphysema and percent gas trapping are also being done using 3D Slicer (http://www.slicer.org/).
