Abstract: A zoledronic acid derivative, 1-hydroxy-5-(2-ethyl-1H-imidazol-1-yl)pentane-1,1-diphosphonic acid(EIPeDP), was synthesized using 2-ethylimidazole， 5-bromo valeric acid ethyl ester and PCl3 as the starting material and further labeled with 99mTc. The influence of the amount of EIPeDP and the pH value of the reaction system on the labeling yield of 99mTc-EIPeDP has been studied. Satisfactory radiolabelling yield(RLY) and the radiochemical purity(RCP)(over 97％) were obtained when the pH was 5~6 and the amount of EIPeDP, SnCl2·2H2O and Na99mTcO4 were 5 mg, 100 μg and 92.5 MBq, respectively. The radiolabeled complex was very stable in vitro. In vivo SPECT bone imaging of rabbit showed that a clearer image can be obtained from 99mTc-EIPeDP at 1 h post injection, which is superior to 99mTc-ZL and 99mTc-MDP. These results showed that 99mTc-EIPeDP is a potential bone imaging agent with advantages of simple preparation, good stability and superior bone imaging characteristics.

Key words: zoledronic acid derivative, 99mTc radiolabeling, quality control, stability, bone imaging