1. Faculty of Biomedical Engineering, Kim Chaek University of Technology, Pyongyang, Democratic People’s Republic of Korea
2. Neurology Department, Pyongyang Medical College Hospital, Pyongyang, Democratic People’s Republic of Korea
3. Chongjin Medical College Hospital, Chongjin, Democratic People’s Republic of Korea
4. Institute of Engineering, Kim Chaek University of Technology, Pyongyang, Democratic People’s Republic of Korea