Radiopharmaceutical scanning agents

A dispersion useful in forming an injectable radiopharmaceutical scanning agent prepared by the method comprising

• a. forming a dispersion containing a sulfur colloid by reacting in an aqueous medium a thiosulfate with a pharmaceutically acceptable acid,
• b. interacting a pharmaceutically acceptable stannous salt with the dispersion of (a) and thereafter buffering the resulting dispersion.

method for preparing a dispersion of a stannous sulfur colloid in an aqueous buffer solution which is useful in forming an injectable radiopharmaceutical scanning agent comprising

• a. forming a dispersion containing a sulfur colloid by reacting in an aqueous medium a thiosulfate with a pharmaceutically acceptable acid,
• b. interacting a pharmaceutically acceptable stannous salt with the dispersion of (a) to form a dispersion containing a stannous sulfur colloid and buffering said dispersion contaning said stannous sulfur colloid.

An injectable radiopharmaceutical scanning agent comprising a technetium-99m labelled sulfur colloid to which stannous ions are attached dispersed in an aqueous buffer solution.