Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Study is essentially unchanged from prior . The lungs are well inflated and clear bilaterally with no masses or lesions identified . There is no pleural effusion or pneumothorax . The aorta is slightly tortuous . Otherwise , the cardiomediastinal silhouette is within normal limits . Hilar contour is normal . Pleural surfaces are unremarkable . Stable mild degenerative changes of the thoracic spine are seen .
    OUTPUT:
    
No evidence of malignancy or infection .