Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Since the prior study , there has been slight decrease in conspicuity of the left lower lobe opacity . The lungs are otherwise clear , heart size is stable , and there is no pleural effusion or pneumothorax .
    OUTPUT:
    
Slight interval decrease in conspicuity of the left lower lobe opacity , which may reflect resolving atelectasis or response of focal pneumonia to therapy ( if receiving antibiotics ) .