1. Department of Radiation Medicine, Fourth Military Medical University, Xi'an, P.R. China.
2. Health and Epidemic Prevention Team, Navy General Hospital, Beijing, P.R. China.
3. Insititute of Disease Control and Prevention, Academy of Military Science, Beijing, P.R. China.
4. Department of Radiotherapy, Tangdu Hospital, Fourth Military Medical University, Xi'an, P.R. China.
5. Central Laboratory, General Hospital of the Air Force, Beijing, P.R. China.