Physiological Animal Imaging with ⁶⁸Ga-Citrate

Background: Gallium-68 is an ideal research and hospital-based PET radioisotope. The uptake mechanism of Gallium citrate is a combination of specific and non-specific processes, for example, vasodilatation, increased vascular permeability, plasma transferrin binding and lactoferrin and siderophores. Objective: In this study, by applying the ⁶⁸Ge/⁶⁸Ga generator product, a simple technique for the synthesis and quality control of 68Ga-citrate was introduced and was followed by preliminary animal studies. Methods: The synthesis of ⁶⁸Ga-citrate was performed with a cationic method using the Scintomics automated synthesis system (Scintomics GmbH GRP module 4V). Since the standard procedure for quality control (QC) was not available, the definition of chemical and radiochemical purity of ⁶⁸Ga-citrate was carried out according to the ICH Q2(R1) guideline. The standard QC tests were analysed with Scintomics 8100 radio-HPLC system equipped with a radioactivity detector. In this study, a New Zealand rabbit weighing 2520 g was used for PET/CT images. Results: ⁶⁸Ga-citrate synthesis was performed by a cationic method without using organic solvents. The labelling efficiency was found to be >98% . The HPLC method used to assess the radiochemical purity of ⁶⁸Ga -citrate was validated as rapid, accurate and reproducible enough to apply it to patients safely. The physiological distribution of ⁶⁸Ga-citrate was investigated in a healthy rabbit. The blood pool, liver, spleen, kidneys and growth plates were the most common sites of ⁶⁸Ga-citrate involvement.