Fig 1.
Images displayed on the console of the Z2.
Z2 monitor screen. The PVR above a certain concentration is displayed in the upper right corner (red square). LAV, low attenuation volume; LL, left lower lobe; LU, left upper lobe; nLAV, not LAV (lung volume other than LAV); PVR, pneumonia volume ratio; RL, right lower lobe; RM, right middle lobe; RU, right upper lobe; Z2, Ziostation2.
Fig 2.
Visual measurement of the PVR.
Two radiologists independently selected the entire lung field and pneumonia area every 1.5 cm on the coronal view using a drawing tool on the PACS (PSP Corporation, Tokyo, Japan) and added these up to measure the PVR. The blue line indicates the entire lung field (mm2), and the yellow line indicates the pneumonia area (mm2). The minimum and maximum in the figure represent CT values in the region. CT, computed tomography; max, maximum; min, minimum; PACS, report picture archiving and communication system; PVR, pneumonia volume ratio; SD, standard deviation.
Fig 3.
Dorsal subpleural consolidations are not recognized as part of the lung and require manual correction.
The white arrows indicate the areas that need to be manually corrected.
Fig 4.
The flow chart shows the process of determining the number of study cases to 53.
Table 1.
Patient background, blood test, and CT findings.
Table 2.
Results of the Spearman’s test of the PVR and CT scores by two radiologists and Ziostation2 of five/two conditions in the 10 selected patients.
Fig 5.
ROC curves for the PVR, CT score, CRP, and LDH.
ROC curve for a. PVR using Z2 (≥–600 HU) and b. CT scores using Z2 (≥–600 HU), c. CRP, and d. LDH. CRP, C-reactive protein; CT, computed tomography; LDH, lactate dehydrogenase; PVR, pneumonia volume ratio; ROC, receiver operating characteristic; SD, standard deviation; Z2, Ziostation2.
Fig 6.
Boxplots of the PVR, CT score, and CRP.
Boxplots for a. The PVR using Z2 (≥–600 HU), b. CT scores using Z2 (≥–600 HU), c. CRP, and d. LDH. 1: Mild group, 2: Severe group. Error bars indicate outliers. CRP, C-reactive protein; CT, computed tomography; LDH, lactate dehydrogenase; PVR, pneumonia volume ratio; ROC, receiver operating characteristic; Z2, Ziostation2.
Table 3.
Cut-off values for pneumonia volume ratio and blood test to differentiate the mild and severe groups.
Table 4.
Bivariable logistic regression of the PVR (≥–600 HU) according to age, sex, number of days from onset to CT, and comorbidities.