Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: As before , tip of right IJ central line lies at SVC / RA junction . The cardiomediastinal silhouette is unchanged , allowing for differences in positioning . Minimal upper zone redistribution , without overt CHF . Patchy opacity in the retrocardiac region is improved compared with ___ not clearly changed from ___ . Minimal atelectasis at the right lung base is slightly improved . As before , there is interruption of the right fifth rib posteriorly , which appears old and mild undulation of the lower right chest rib .
    OUTPUT:
    
Mild left base patchy opacity is similar to the most recent prior film , but improved compared with ___ . Minimal atelectasis at the right base is unchanged . Minimal upper zone redistribution , without overt CHF .