Fig. 5

Example of quantitative lung CT analysis for a patient with severe COVID-19 with no steroid therapy. A 57-year-old male complained of fever for 12 days accompanied with dyspnea. After admission to hospital, he received high-flow nasal cannula oxygen therapy and arbidol, but without steroid therapy. Chest CT scans were performed at admission (A), day 5 (B), day 13 (C), day 19 (D), and day 21 (E). Chest CT scans (a), illustration of automated lung segmentation (b), 3D volumetric representation of the bilateral lungs (c), and comparison among different quantitative CT parameters (d) are shown in Fig. 4 at each time point. Yellow areas represent hyperinflated regions (%HI, − 901 to − 1000 HU); blue areas indicate normally aerated regions (%NAL, − 501 to − 900 HU); green areas represent poorly aerated regions (%PAL, − 101 to − 500 HU); red areas indicate nonaerated regions (%NNL, 100 to − 100 HU). The compromised lung volume was calculated as the sum of NNL and PAL. During the treatment process, the compromised lung volume showed no significant change over time from 25.6% (A-d) at admission to 23.14% (E-d) at stage 5