2.2. Chest MDCT protocol and assessment

All patients were assigned to a 64-slice multidetector CT scanner (Somatom® go.All; Siemens Healthineers, Forchheim, Germany). This scanner is reserved for COVID-19 suspected patients only. The CT room was disinfected after the examination of each patient was completed. All patients were examined in the supine position. MDCT images were then acquired during a single inspiratory breath-hold. The scanning range was from the apex of the lung to the costophrenic angle. Scan parameters were as follows: X-ray tube parameters 110 kVp, 76 mAs; rotation time 0.5 s; pitch 0,7; z cover 32 × 0,7 mm and a slice thickness of 3 mm with 1 mm reconstructions.

Chest MDCT imaging findings such as pleural thickening, subpleural lines, pleural effusion, pericardial effusion, mediastinal lymphadenopathy; parenchymal infiltration pattern as peripheral, peripheral-central, ground glass opacities, crazy paving pattern, consolidation and reverse halo sign were noted for all patients.

Image analyses for pneumonic severity score was made by an automated lung opacity analysis program “CT Pneumonia Analysis” which is provided by (Siemens Healthineers, Forchheim, Germany), The CT Pneumonia Analysis prototype was performed on a non-contrast Chest MDCT axial data with 1 mm reconstructed slice thicknesses. Multiplanar reconstruction (MPR) images were obtained which contain lung segmentations and opacity areas with percentage of pneumonic infiltration and an opacity score. The algorithm automatically detects and quantifies abnormal tomographic patterns commonly present in lung infections, namely ground glass opacities (GGO) and consolidations. Based on 3D segmentations of lesions, lungs, and lobes, the algorithm quantifies the extent of overall abnormalities and the presence of high opacity abnormalities, both globally and lobe-wise. The severity of COVID-19 pneumonia was measured by measuring percentage of ground glass opacity (PO), percentage of high opacity (PHO, consolidation), total opacity score (TOS) which refers lobe-wise involvement of pneumonia for each 5 lobes and ranges between 0–4 for each lobe and totally ranges between 0–20 for all lung parenchyma (Fig. 1 ) [⁷]. Data process and calculation results take 1–2 min. After automatically measurement, the program allows the user to correct manually lung segment borders and false positive or false negative pneumonic opacities (Fig. 1).

A 52 years old woman presented with cough weakness and fatigue. Layout image of CT Pneumonia Analysis contains, axial, sagittal, coronal reformat images of lung parenchyma with color-coded lines (yellow - RUL, pink - ML, dark green - RLL, light green - LUL, blue - LLL) mark the borders of lung lobes and red lines which presents in both lungs, mark opacity areas of lung. Volume rendering image (right lower) demonstrates the spatial distribution of the opacities as red areas which involves both lungs. Summary tables of quantitative results show lung segmentations and opacity areas with percentage of pneumonic infiltration and an opacity score (TOS). On the left upper corner of the image lung segmentations and opacity areas editing tools are also available. (For interpretation of the references to colour in the Figure, the reader is referred to the web version of this article).

- Score 0: lobe is not affected

- Score 1: 0–25 % of the lobe affected

- Score 2: 25–50 % of the lobe affected

- Score 3: 50–75 % of the lobe affected

- Score 4: 75–100 % of the lobe affected

All CT examinations were independently reviewed by two chest radiologists with experience in Syngo via workstation (Siemens Healthineers, Forchheim, Germany). After automatically measurement of lung opacities, radiologists reviewed all results and edited images if needed. Although only in a few patients required minor contour adjustments to exclude hilar vascularities in images obtained after automated measurement, they were not large enough to affect scoring results.