Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: In comparison to the chest radiograph obtained 1 week prior , the right hemidiaphragm is slightly more elevated with new partial collapse of the right middle lobe . Lungs are otherwise clear without focal consolidations . No pleural effusions or pneumothorax . Mild cardiomegaly is unchanged . Cardiomediastinal hilar silhouettes are otherwise normal . Mild calcification of the aortic knob is unchanged .
    OUTPUT:
    
New , partial , right middle lobe collapse can possibly caused by pneumonia or airway obstruction .