3D Slicer 5.0.3 software was used to import the chest CT data set, which consisted of 1.25mm thick continuous CT slices obtained by a multi-slice spiral CT scanner under a conventional dose protocol (120Kv,150mA, pitch 1.0), and then the ''Lung CT Segment'' extension program was used. The lung regions were segmented by manually marking 13 marker points. After marking, all the lung regions were visually displayed, and then the region range was manually corrected using the tools selected in the ''Segment editor''. The ''Lung CT Analyzer'' extension program was then used to quantify the lung zones of ''hyperventilation'', ''normal ventilation'', ''hypoventilation'', and ''no ventilation'', and the proportion of no ventilation areas was obtained by software analysis.