Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Frontal and lateral views of the chest . The lungs are clear without focal opacity , pleural effusion or pneumothorax . The heart size is normal . There is calcification of the left aortic knob . Old left posterior rib fracture .
    OUTPUT:
    
No acute intrathoracic process . Conventional chest radiographs are not sensitive for detecting subtle chest wall trauma . If there are focal findings , dedidcated views of those areas are recommended .