A convenient method for the preparation of 99mTc-labelled pentavalent DMSA and its evaluation as a tumour imaging agent.

A cold kit has been developed for the instant preparation of 99mTc-(V)-DMSA. The radiochemical purity of the radiopharmaceutical was determined by chromatography. A study of the effect of pH and stannous chloride concentrations on its labelling efficiency demonstrated that pH 8.5-9.0 and 0.2 mg stannous chloride for 1.1 mg DMSA provides the optimum formulation (98%). The addition of ascorbic acid stabilized the kit for up to 24 weeks under refrigerated temperatures. The radiopharmaceutical was found to concentrate in the bone and muscles in contrast to trivalent DMSA which accumulates in the liver and kidneys in normal mice. Studies in patients have shown its usefulness in the scintigraphy of thyroid medullary carcinoma and in the brain metastasis of breast carcinoma.