Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: A frontal supine view of the chest was obtained portably . The lungs are well expanded and clear without focal consolidation , pleural effusion , or pneumothorax . Linear atelectasis in the left lower lung is similar to prior studies . Heart size is normal . Mediastinal silhouette and hilar contours are within normal limits with mild aortic knob calcifications . No acute displaced rib fracture is seen , old left lateral rib fractures again seen . Degenerative change is seen in the shoulder girdle girdles bilaterally .
    OUTPUT:
    
No evidence of acute intrathoracic injury .