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.</p

S1 Data -

This study aimed to determine the optimal conditions to measure the percentage of the area considered as pneumonia (pneumonia volume ratio [PVR]) and the computed tomography (CT) score due to coronavirus disease 2019 (COVID-19) using the Ziostation2 image analysis software (Z2; Ziosoft, Tokyo, Japan), which is popular in Japan, and to evaluate its usefulness for assessing the clinical severity. We included 53 patients (41 men and 12 women, mean age: 61.3 years) diagnosed with COVID-19 using polymerase chain reaction who had undergone chest CT and were hospitalized between January 2020 and January 2021. Based on the COVID-19 infection severity, the patients were classified as mild (n = 38) or severe (n = 15). For 10 randomly selected samples, the PVR and CT scores by Z2 under different conditions and the visual simple PVR and CT scores were compared. The conditions with the highest statistical agreement were determined. The usefulness of the clinical severity assessment based on the PVR and CT scores using Z2 under the determined conditions was statistically evaluated. The best agreement with the visual measurement was achieved by the Z2 measurement condition of ≥–600 HU. The areas under the receiver operating characteristic curves, Youden’s index, and the sensitivity, specificity, and p-values of the PVR and CT scores by Z2 were as follows: PVR: 0.881, 18.69, 66.7, 94.7, and </div

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.</p

Cut-off values for pneumonia volume ratio and blood test to differentiate the mild and severe groups.

Cut-off values for pneumonia volume ratio and blood test to differentiate the mild and severe groups.</p

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.</p

The flow chart shows the process of determining the number of study cases to 53.

The flow chart shows the process of determining the number of study cases to 53.</p

S3 File -

This study aimed to determine the optimal conditions to measure the percentage of the area considered as pneumonia (pneumonia volume ratio [PVR]) and the computed tomography (CT) score due to coronavirus disease 2019 (COVID-19) using the Ziostation2 image analysis software (Z2; Ziosoft, Tokyo, Japan), which is popular in Japan, and to evaluate its usefulness for assessing the clinical severity. We included 53 patients (41 men and 12 women, mean age: 61.3 years) diagnosed with COVID-19 using polymerase chain reaction who had undergone chest CT and were hospitalized between January 2020 and January 2021. Based on the COVID-19 infection severity, the patients were classified as mild (n = 38) or severe (n = 15). For 10 randomly selected samples, the PVR and CT scores by Z2 under different conditions and the visual simple PVR and CT scores were compared. The conditions with the highest statistical agreement were determined. The usefulness of the clinical severity assessment based on the PVR and CT scores using Z2 under the determined conditions was statistically evaluated. The best agreement with the visual measurement was achieved by the Z2 measurement condition of ≥–600 HU. The areas under the receiver operating characteristic curves, Youden’s index, and the sensitivity, specificity, and p-values of the PVR and CT scores by Z2 were as follows: PVR: 0.881, 18.69, 66.7, 94.7, and </div

S1 File -

This study aimed to determine the optimal conditions to measure the percentage of the area considered as pneumonia (pneumonia volume ratio [PVR]) and the computed tomography (CT) score due to coronavirus disease 2019 (COVID-19) using the Ziostation2 image analysis software (Z2; Ziosoft, Tokyo, Japan), which is popular in Japan, and to evaluate its usefulness for assessing the clinical severity. We included 53 patients (41 men and 12 women, mean age: 61.3 years) diagnosed with COVID-19 using polymerase chain reaction who had undergone chest CT and were hospitalized between January 2020 and January 2021. Based on the COVID-19 infection severity, the patients were classified as mild (n = 38) or severe (n = 15). For 10 randomly selected samples, the PVR and CT scores by Z2 under different conditions and the visual simple PVR and CT scores were compared. The conditions with the highest statistical agreement were determined. The usefulness of the clinical severity assessment based on the PVR and CT scores using Z2 under the determined conditions was statistically evaluated. The best agreement with the visual measurement was achieved by the Z2 measurement condition of ≥–600 HU. The areas under the receiver operating characteristic curves, Youden’s index, and the sensitivity, specificity, and p-values of the PVR and CT scores by Z2 were as follows: PVR: 0.881, 18.69, 66.7, 94.7, and </div

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.</p