Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Frontal and lateral views of the chest demonstrate mild cardiomegaly , predominantly left atrial . The mediastinal and hilar contours are unremarkable . There is dense aortic arch calcification . The lungs are clear , without pneumothorax , vascular congestion , or pleural effusion .
    OUTPUT:
    
Mild left atrial enlargement . No acute cardiopulmonary process .