Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Single frontal view of the chest demonstrates normal heart size and mild unfolding of the thoracic aorta . Dense atherosclerotic calcifications are seen in the aortic arch . The lungs are clear with the exception of a trace subsegmental atelectasis in the left base . There is no pneumothorax , vascular congestion , or pleural effusion .
    OUTPUT:
    
Subsegmental atelectasis in the left base . No acute cardiopulmonary process .