Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Heart size is normal . The aorta is mildly tortuous . Minimal atherosclerotic calcifications are noted at the aortic knob . Pulmonary vasculature is normal . Minimal streaky atelectasis is seen in the retrocardiac region . No focal consolidation , pleural effusion or pneumothorax is seen . Multilevel mild degenerative changes are noted in the thoracic spine .
    OUTPUT:
    
Mild retrocardiac atelectasis .