8. Agents for renal function Most important: 99m Tc -DMSA complex (dimercaptosuccinic acid)
9. 99m Tc -DMSA Mechanism of uptake: Accumulates in the kidneys and specially localizes in the proximal convoluted tubule In the proximal convoluted tubule most of the water and salts are reabsorbed Shows ability of the kidneys to filter the blood Nephron
10. Agents for renal function Most recent and now widely used anionic kidney imaging agent: 99m TcO-mercaptoacetyltriglycine Free carboxylic acid group is believed to be necessary for efficient renal excretion
11. Monoclonal antibodies or antibody fragments Monoclonal antibodies or their fragments are potentially ideal vehicles to carry radioisotopes to specific sites within the body But: radiolabel has to be inserted without affecting the binding site! elegant route to binding the antibody to the Tc is via a thiolactone which generates an N 2 S 2 diaminedithiol -forms a stable, neutral, square pyramidal Tc=O species with 99m Tc-[TcO4] - -the uptake of these antibodies is quite slow, it can take up to 20 hours
12. Recent development Very recently, there have been reports of the preparation of the 94 Tc isotope by irradiation of 94 Mo in a cyclotron 94m Tc as well as 94g Tc are positron emitters and could be also used for taking PET images But: Though the characteristics of 94 Tc are really good, you still need an expensive cyclotron to produce it; that limits its usage Future role -Monoclonal antibodies as tracers for all different kinds of tumors -SPECT/CT good method for better planning of surgery