Preparation and clinical evaluation of technetium-99m dimercaptosuccinic acid for tumour scintigraphy

We describe a simple method of pentavalent technetium-99m dimercaptosuccinic acid [^99mTc(V)-DMSA] preparation for the imaging of medullary carcinoma of the thyroid using commercially available kits. ^99mTc(V)-DMSA is available at high pH (approximately 7.5) by adding NaHCO₃ solution in the presence of a small amout of reducing agent (SnCl₂). On the other hand, trivalent ^99mTc-DMSA [^99m-Tc(III)-DMSA] can be obtained at low pH (below 3) in the presence of an excess amount of reducing agent. In the clinical evaluation of a patient with a medullary carcinoma of the thyroid, only ^99mTc(V)-DMSA revealed an area of intense accumulation.