1. Department of Respiratory Medicine, Tokyo Metropolitan Bokutoh Hospital , Tokyo 130-1022 , Japan
2. Department of Respiratory Medicine, Kashiwa City Hospital , Chiba 277-0825 , Japan
3. Department of Respiratory Medicine, Tokyo Medical and Dental University , Tokyo 113-8519 , Japan
4. Department of Radiology, Tokyo Metropolitan Bokutoh Hospital , Tokyo 130-1022 , Japan