Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: PA and lateral views of the chest provided . Lungs are well inflated . A focal opacity posteriorly overlying the lower spine on the lateral view likely corresponds to the posterior basilar segment of the right lower lobe given a patchy opacity in this region on the frontal view . . No pneumothorax . No pleural effusion . Allowing for patient rotation , the cardiomediastinal contours are upper limits of normal .
    OUTPUT:
    
Focal right lower lobe posterior basal segment opacity , concerning for focal pneumonia . Differential diagnosis includes focal atelectasis and aspiration .