Design and evaluation of portable shielding case for thyroid 131I monitoring by imaging plate

A portable shielding case was designed and evaluated for thyroid I-131 monitoring by imaging plate (IP) under storage temperature of 0 and 25 A degrees C. The background count with shielding case was 20 % of that without shielding case in 25 A degrees C after 7 day. The fading rate decreased to 85.3 and 66.4 % after 7 day with and without shielding case. The detection limit was low by shielding and storing at low temperature and the lower detection limits of the IP system are less than the screening level even 7 day after irradiation. The use of shielding case and a low temperature is effective in reducing the fading rate of IP.