TECHNETIUM-99M-SULFUR COLLOID FOR LYMPHOSCINTIGRAPHY - EFFECTS OF PREPARATION PARAMETERS

There has been a resurgence in the use of lymphoscintigraphy for the e xternal detection of lymph nodes for metastatic melanoma and breast tu mors. Technetium-99m-antimony trisulfide colloid was the radiopharmace utical developed for this procedure and was found to have a narrow dis tribution of small particles, 0.003-0.03 mu m, but it was never approv ed by the FDA. Technetium-99m-sulfur colloid also forms particles and this article reports on the effects different preparation parameters h ave on its particle size distribution and stability. Methods: Four gro ups of kits were evaluated, kits which utilized: (a) a reduced heating protocol with a new Tc-99m-elution, (b) a reduced heating protocol wi th an old Tc-99m-elution, (c) a prolonged heating protocol with a new Tc-99m-elution and (d) a prolonged heating protocol with an old Tc-99m -elution. The particle size distribution and the stability of the diff erent Tc-99m-sulfur colloid kit preparations were evaluated over 6 hr utilizing polycarbonate filters ranging from 0.03 to 10 mu m. Results: In vitro studies demonstrated no significant change in the particle s ize distribution over a 6-hr period and all Tc-99m-sulfur colloid prep arations had a bimodal particle size distribution pattern. Importantly , heating the kit for shorter periods of times utilizing [Tc-99m]perte chnetate, which had a longer ingrowth of [Tc-99m]pertechnetate, produc ed a formulation which had the largest percentage of particles smaller than 0.03 mu m. Conclusion: In our clinical setting, Tc-99m-sulfur co lloid prepared with the reduced heating protocol and utilizing [Tc-99m ]pertechnetate, which has the highest ingrowth of [Tc-99m]pertechnetat e has proved to be an excellent agent for lymphoscintigraphy studies. This preparation has demonstrated rapid movement of the particles from the primary site to the lymph nodes in over 97% (106/109) of the pati ents we have studied.