Fig. 1

Male patient 65 years old, chronic heavy smoker. Pulmonary function tests showed very severe obstructive pulmonary disease. a–d HRCT (axial, sagittal, and coronal images) revealed hyperinflated chest, mild bilateral diffuse emphysematous changes predominately the right upper lobe. e–g Images after applying density mask revealed emphysematous areas as black areas while normal lung density as gray. More pronounced bilateral diffuse emphysematous changes, more evident at the right upper lobe (Right upper lobe low density index 48.4%) and to a lesser degree, left upper lobe (left upper lobe low density index 33.1%). h, i Lung density histogram showing distribution of voxel density with respect to the whole lung volume: x-axis represents density range expressed in HU, whereas y-axis scales the relative number of voxels as a percentage of total lung volume. Evaluation of the histogram allowed quantification mean lung density (MLD), 15% percentile value (P15), and relative volume of parenchyma with density lower than – 950 HU. LAV, low attenuation volume. PD15% for right lung is 59, left lung 74, and both lungs 66. N.B: both upper lobes more emphysematous than both lower lobes as regarding the low-density index that of both upper lobes was 41.2%while that of both lower lobes was 25.7%