CT chest in our institution will be done with standard high resolution protocol . No I.V contrast will be given. Scans will be obtained during full inspiration in supine position from the thoracic inlet to the level of the diaphragm.

Patients with CT chest performed outside our institution will be reviewed in DICOM format and assessed for its compatibility to be integrated into the computer-based analysis software.

Spirometry will be performed using standard techniques according to ATS-ERS criteria 2019 . Spirometry device (Zan 300, NSPIRE HEALTH GMBH Co.) will be used. Percentage predicted values (%pred) will be calculated based on reference values for healthy adults. All patients will be required to undergo spirometry in a reproducible way, and the best values will be reported. Spirometry should meet international acceptability and repeatability standards

Warrick score is calculated as follow : A point value will be given to each abnormality i.e ground-glass appearance (areas of hazy opacity in the lung that do not obscure the underlying bronchial structures) = 1, irregular pleural margins = 2, septal/subpleural lines = 3, honeycombing (usually 3-10 mm in diameter and have thick walls) = 4, and subpleural cysts = 5. In each patient, the "severity of disease" score will be obtained by adding single point values (maximal severity score 15).

An "extent of disease" score is obtained by counting the number of bronchopulmonary segments involved for each abnormality as follows ; one to three segments scored as 1, four to nine segments scored as 2, and more than nine segments scored as 3 (maximal extent score 15).

The severity and extent of disease will be then calculated as the total Warrick score (range from 0 to 30)

Total lung volume , volume of the lung occupied by low attenuation areas (attenuation values from -1024 to -950 HU; representing emphysema), volume of normally attenuated lung (from -949 to -700 HU; corresponds to healthy lung tissue) and volume of the lung occupied by high attenuation areas (between - 699 and - 250 HU) ; it represents the lung parts which are more dense than healthy lung); volume of lung with density from -249 to +40 HU, this group corresponds to areas with further increase in density, including the semi-consolidation and consolidation.

Percentage of the lung occupied by low attenuation areas (attenuation values from -1024 to -950 HU), percentage of normal lung (from -949 to -700 HU), percentage of the lung occupied by high attenuation areas (between - 699 and - 250 HU) and percentage of consolidation areas (from -249 to +40 HU) in each lung and in each lobe.