[1] Hlth Protect Agcy, Radiat Protect Div, Didcot OX11 0RQ, Oxon, England
[2] Nagoya Inst Technol, Showa Ku, Nagoya, Aichi 4668555, Japan
[3] Natl Inst Informat & Commun Technol, Appl Electromagnet Res Ctr, Electromagnet Compatibil Grp, Koganei, Tokyo 1848795, Japan