99m

Tc labeled human serum albumin (HSA) kit using stannous chloride (SnCl

2

) as a reductant

is usually not stable. The purpose of this research is to provide a stable and convenient equilibrium tracer for cardiovascular nuclear medical studies.

This paper consists of titrating Sn

(11)

of storage solution; choosing chemical analysis methods and evaluating the labeling efficiency application of "Latin—square design" experiment to obtain the optimum labeling condition; the compositions of the kit-HSA 7mg

tartrate 1.08mg

SnCl

2

•2H

2

O 0.16mg

at pH3.5; and the test of the frozen kits (in five batches)showing labeling rate 95%

blood clearance rate-0.0026 (mean slope)

effective shelf live 6 monthes.

Conclusion: adopting indirect labeling technique (adding the chelating agent—tartrate)in stead of direct labeling

the stability of

99m

Tc-HSA kit increases significantly both in vitro and in vivo. The labeling rate of the kit can further increase when the amount of tartrate is much larger than that of SnCl

2

. Combining the use of the kit in the nuclear stethoscope to study left ventricular function has proved satisfactory.