Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Best seen on the lateral view a linear opacity projecting over the lower thoracic spine . This is not clearly localized frontal , potentially in the retrocardiac location on the left . Otherwise , the lungs remain clear . The cardiomediastinal silhouette is within normal limits . No acute osseous abnormalities identified .
    OUTPUT:
    
Linear opacity projecting over the lower lobes on the lateral view not clearly delineated on the frontal . This may be due to focal atelectasis although infection can not be excluded in the proper clinical setting .