Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is hyperinflation of the lungs , which is unchanged from prior . Linear opacities in the left lung base correspond with atelectasis . No confluent consolidation is identified . There is no vascular congestion or pulmonary edema . No large effusions are evident . Cardiomediastinal and hilar contours are within normal limits . On the lateral projection , there is a linear lucency posterior to the sternum which is of uncertain etiology , though pneumothorax can not be entirely excluded . Followup inspiratory and expiratory radiographs are recommended for further characterization .
    OUTPUT:
    
1 . Linear lucency posterior to the sternum on the lateral projection of uncertain etiology . Pneumothorax can not be excluded . Followup radiographs are recommended . 2 . No evidence of pneumonia or pulmonary edema .