Abstract: PRELIMINARY STUDY ON A POTENTIAL TUMORRADIOTHERAPY AGENT——188ReRHENIUM SULFIDE SUSPENSION Yu Junfeng\ Yin Duanzhi\ Min Xiaofeng\ Zhang Jiong\ Guo Zili\ Wang Yon gxian(Shanghai Institute of Nuclear Research, Academia Sinica, Shanghai 201800)F. F. Knapp, Jr(Oak Ridge National Laboratory, P. O. Box 2008, Oak Ridge, US A)Abstract 188Rerhenium sulfide suspension is formed by acid reduction of Na2S2O3 in the presence of KReO4 including Na 188ReO4. The radiochemical yield is more than 96%. The in vitro stability studies reveal that more than 99% of 188Re remains in sulfide form in 3 days. The major particle size is 1～5 μm. 188 Rerhenium sulfide suspension is injected into tumors of mice and the tumorb ea ring mice are killed in certain interval. The results of the biodistribution stu dy show that the mean retention percentages of 188Re in tumors are about 90% in 3 days. Compared with the control which is injected the inactive r henium sulfide suspension or normal saline, the tumor inhibiting ratio by intra tumor injection of 188Rerhenium sulfide suspension is about 96%.