Abstract: TRACE STUDY OF SLOW RELEASE ON GELATIN MICROSPHERETong Jian\ Li Yaoling\ Feng Yun(Stomatological Hospital of Tianjin Medical University, 300070)Li Huaifen\ Niu Huisheng(Institute of Radiation Medicine, Chinese Academy of Medical Sciences, 300192)ABSTRACTThe microsphere of the diameter of 40-80 μm is made of 125Ifibrinogen125IFG and gelatin. The encapsuled rate of 125IFG is over 90%.There is a 125IFG peak in blood after six days of subcutaneous injection and the microsphere is almost absorbed completely at the fifteenth day. There is no stimulative reaction in injection place. Gelatin microsphere is a ideal style of successful controlrelease drug.Key words gelatin microsphere slow release radioactive trace