Pharmacokinetic studies and human absorbed dose estimation of 68Ga-(4 {[(bis (phosphonomethyl)) carbamoyl] methyl}-7,10-bis(carboxymethy l) -1,4,7,10-tetraazacyclododec-1-yl) acetic acid

Background: In this study, human absorbed dose of a newly introduced bone imaging agent, 68Ga-(4-{[(bis(phosphonomethyl))carbamoyl]methyl}-7,10-bis(carboxymethyl)-1,4,7,10-tetraazacyclododec-1-yl) acetic acid (68Ga-BPAMD), was estimated based on the rats data. Materials and Methods: 68Ga was obtained from the 68Ge/68Ga generator and it's radionuclidic and radiochemical purities were investigated. 68Ga-BPAMD complex was prepared at optimal conditions and the radiochemical purity was studied using instant thin layer chromatography (ITLC) method. The final preparation was injected to the normal rats and the biodistribution of the complex was followed up to 120 min post injection. The accumulated activity for animal organs was calculated. Finally, the human absorbed dose of the complexes was estimated by RADAR method. Results: 68Ga-BPAMD complex was prepared in high radiochemical purity (>99%, ITLC) at optimal conditions. The biodistribution of the complex demonstrated that the main remained radioactivity would considerably accumulate into the bones. The results showed the highest amounts of absorbed dose on the bone surface (0.253 mGy/MBq) and in the bone marrow (0.250 mGy/MBq), while the other organs would receive an insignificant absorbed dose after injection of the 68Ga-BPAMD complex. Conclusion: The comparison of dosimetric results for 68Ga-BPAMD with other complexes shows this complex is a safer agent for bone scanning. This property as well as other characteristics such as the high resolution images of the positron emission tomography (PET) scanning and the availability of 68Ga in the form of 68Ge/68Ga generator, make this complex as a suitable agent for PET bone imaging.