60 year old patient with complaints of shortness of breath

Chest Radiograph shows reticular opacities in the bilateral lungs with peripheral dominance. No cardiomegaly is noted. Axial CT scan lung window(3) of lower thorax shows interlobular septal thickening with honeycombing in the periphery of the bilateral lower lobes. Similar section at the level of upper thorax(3) shows milder changes suggestive of lower lobe dominance. Axial CECT images show no dilatation of the main pulmonary artery(4) or cardiomegaly/straightening of the interventricular septum(5). No significant mediastinal lymphadenopathy is noted(6).