A new formulation of Tc-99m colloid is described. The new colloid contains
a high ratio of perrhenate to thiosulphate, cysteine, and a prepared
higher final pH than found previously. In preparing the colloid preferred
rhenium sulfide is not used as an ingredient. The pH of the final
formulation and can be between about 5.5 an about 8.0, and the ratio of
rhenium to sulfur is from about 0.05 to about 1.2. In addition, the new
colloid has excellent radiochemical purity, and a much smaller particle
size distribution than has generally been previously available for sulfur
colloid preparations.
