Evaluation of Human Organ Estimated Absorbed Dose After 67Ga-Citrate and 68Ga-citrate (Radiopharmaceutics) Injection Based on Biodistribution Data in Rats

Abstract: Gallium-68 citrate has become known as an alternative radioisotope in nuclear medicine recently. As for its influences, Ga68-based tracers have already been proposed as positron emission tomography agents. In this study, the human absorbed dose of 68Ga -Citrate and 67Ga-citrate was estimated based on biodistribution data in rats with medical internal radiation dose (MIRD) method. 68Ga-citrate was prepared from eluted 68Ga-Cl3 and sodium citrate under multiple reaction form. In order to investigate the bio-distribution of 68Ga/67Ga –Citrate, five male rats with approximately the same weight were killed by CO2 asphyxiation, at several specific times after injection. Then the organs of the rats were removed, and counted by HPGe to determine the percentage of injected dose per gram. Finally, the human radiation absorbed dose was calculated. The extraction/purification process causes a radionuclide purity of higher than 97% ITLC and 98% HPLC, leading to a specific activity of about 4-6 GBq/Mm and reaching high chemical purity (Sn, Fe<0.3 PPM and Zn<0.2 ppm) within 15-30 minutes. The results of estimating human absorbed dose illustrate that this agent caused much lower human absorbed dose in comparison with 67Ga-citrate. According to the results, it may be concluded that 68Ga-citrate is a more appropriate agent than 67Ga-citrate and it was generally revealed as a potential compound for imaging applications.

Keywords:

Radiopharmaceutical biodistribution , Internal radiation dose , 68Ga-citrate , 67Ga-citrate , positron emission tomography