Technetium-99m labelled pyrophosphate

A simple method for the preparation of 99Tcm-pyrophosphate has been developed. A 1 per cent solution of sodium pyrophosphate in isotonic saline was added to a 1 per cent solution of stannous chloride in 1/3 N HCl in 10:1 ratio, pH automatically adjusted to 5. An adequate amount of 99TcmO4− eluate was added to 1 ml. of this mixture for bone scanning. Tissue distribution studies in mice showed rapid accumulation of the radiopharmaceutical in the bone. A higher value of the two-hour ratio of femur to liver specific activity was found suitable for the comparative evaluation of pyrophosphate preparations. Over 90 per cent of the radioactivity cleared from the blood in 30 minutes in dogs, and the urinary excretion was about 40 per cent in two hours. Serial scans in dogs showed an optimal visualization of the skeleton at about three hours. Good bone scans of adult patients were obtained in three to four hours using a tracer dose of the present radiopharmaceutical containing 5–10 mCi of 99Tcm along with 2–6 mg of pyrophosphate and 0·1–0·3 mg of tin.