Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Previously seen left upper lobe nodular opacity is not as well seen in this exam , but it probably represents focal calcification at the first rib costochondral cartilage . There is mild atelectasis at the left lung base , similar to prior . There is no pleural effusion or pneumothorax . Cardiomediastinal silhouette is within normal limits and unchanged .
    OUTPUT:
    
Previously seen left upper lobe nodular opacity is not as well seen in this exam , but it probably represents focal calcification at the first rib costochondral cartilage . Lordotic view chest radiograph is recommended to better evaluate whether the opacity is parenchymal or skeletal in origin .