Department of Radioisotope, Nuclear Research Center, AOEI, Tehran, Iran
When Tc-99m-sulfur colloid was introduced as an ideal liver-spleen agent in nuclear medicine, many other types of colloids followed by different manufacturers. They hoped to find a suitable colloidal agent, contrary to sulfur colloid, which is easy to use, and less sensitive to the low contamination of aluminum ions. One of this type of colloid agents, is Tc-99-tin-colloid which is prepared by reduction of pertechnetate ion with stannous ion. In such process the Tc-99m-Tc04 is reduced by stannous ions and in the next step combines with the same stannous ions to form insoluble complex Tc(OH)4, Sn(OH)2. The percipitate, is then converted to colloidal form by using suitable stabilizing agent. To make a suitable colloidal form, the quality and quantity of stabilizing agent play an important role in forming optimum diameters needed for maximum uptake in liver and spleen. In our investigation, PVP-360 and PVP-40t with different molecular weights were used as stabilizing agents. By mixing the above two chemical stabilizers with proper ratios, we obtained a reasonable viscosity necessary for preparing colloids of optimum size particles.