Evaluation of a DMSA Kit for Instant Preparation of 99mTc(V)-DMSA for Tumour and Metastasis Scintigraphy

A kit has been developed to instantly prepare 99mTc(V)-DMSA. The freeze-dried kit consisting of DMSA, stannous chloride and ascorbic acid in appropriate proportions, produces quality 99mTc(V)-DMSA when mixed with 0.2 mL of 3.5% NaHCO3 solution and 2-4 mL of (99mTc)pertechnetate. The radiopharmaceutical characterized by chromatography with ITLC-SG in 0.9% saline and horizontal paper electrophoresis in 50 mM vernol buffer, pH 8.6, at a potential gradient of 15 V/cm showed a different mobility with respect to 99mTc(III)-DMSA, a known agent for kidney imaging. The new agent exhibited less plasma protein binding compared to that of 99mTc(III)-DMSA. Biodistribution of the pentavalent DMSA in mouse demonstrated greater uptake in bone and muscle and lower uptake in liver and kidney with respect to trivalent DMSA. The soft tissue tumour specificity and its suitability for tumour scintigraphy was apparent from the scintigrams of mammary carcinoma in a C3H Jax mouse and medullary carcinoma in a patient. Brain metastatic lesions were also visible in a breast carcinoma patient after administering him with the agent.