Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Frontal and lateral chest radiographs demonstrate clear , well - expanded lungs . There is moderate hyperexpansion and lucency consistent with emphysema . There is no pleural effusion or pneumothorax . Minimal linear atelectasis or scar is noted in the left mid lung . The cardiac silhouette is top normal in size , the mediastinal contours are normal , with calcification of the aortic knob present . Pleural thickening or effusion is present on the left .
    OUTPUT:
    
Emphysema . Atelectasis is a non-specific finding ; the examination neither suggests nor excludes the diagnosis of acute pulmonary embolus .