Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Cardiomediastinal silhouette and hilar contours are normal . Two subcentimeter elliptical nodular opacities overlying the posterolateral aspect of the left fourth rib are most likely rib based . Lungs are otherwise clear . There is no pleural effusion or pneumothorax . A mild anterior wedge compression of one of the lower thoracic vertebral bodies is noted .
    OUTPUT:
    
1 . Two subcentimeter elliptical nodular opacities overlying the posterolateral aspect of the left fourth rib are likely rib based , but can be further evaluated by CT if there is clinical suspicion for metastatic disease . 2 . Mild anterior wedge compression of a lower thoracic vertebral body of unclear chronicity without comparison .