1Department of Occupational Medicine, Pohang Sunrin Hospital, Korea.
2Department of Radiology, Pohang Sunrin Hospital, Korea.
3Department of Neurology, Pohang Sunrin Hospital, Korea.
4Department of Preventive Medicine, College of Medicine, Dongguk University, Korea.
5Department of Preventive Medicine, College of Medicine, Yeungnam University, Korea.
6Department of Preventive Medicine, College of Medicine, Dong-A University, Korea.
7Department of Industrial Medicine Research Institute, College of Medicine, Dong-A University, Korea.