Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: PA and lateral views of the chest . No prior . A new opacity identified at the left lung base laterally and posteriorly , potentially due to atelectasis versus scarring . Elsewhere , the left lung and the right lung are clear . There is no evidence of pulmonary vascular congestion . The cardiomediastinal silhouette is within normal limits . Osseous and soft tissue structures are unremarkable .
    OUTPUT:
    
Left basilar atelectasis versus scarring , but no other acute cardiopulmonary process or evidence of failure .