Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is prominence of the aortic knob with mild calcification . The cardiomediastinal and hilar contours are otherwise within normal limits . Lungs are well expanded . Note is made of increased retrocardiac opacity and atelectasis at the right lung base . There is no significant pneumothorax or large pleural effusion in this single frontal chest radiograph .
    OUTPUT:
    
1 . No evidence of pneumothorax in this single frontal chest radiograph . 2 . Patchy left Retrocardiac opacity could reflect atelectasis versus aspiration . If clinical concern , dedicated chest radiograph with a lateral view can be considered for more complete evaluation and to help exclude the possibility of a developing infectious pneumonia at this site .