Preparation and preliminary biological evaluation of 99Tcm-TADP as bone imaging agent

TADP, 2-(1H-1,2,4-triazol-1-yl)-1-hydroxyethane-1,1-diphosphonic acid, was synthesized by three step reactions from the raw material 1H-1,2,4-triazole. Tc-99(m)-TADP was prepared with 5 mg TADP at pH 7.0 by joining (TcO4-)-Tc-99-O-m with SnCl2 center dot 2H(2)O in aqueous solution for 10 min at room temperature. Both labeling yield and radiochemical purity of Tc-99(m)-TADP were more than 95%. The biodistribution in rats and bone scan in rabbits were also studied. The uptake of organ was expressed as %ID/g. The results showed that the bone uptake is up to 17.17%ID/g which is the maximum of bone uptake at 30 min after injection of Tc-99(m)-TADP in rats, bone-to-muscle and bone-to-blood uptake ratios were 61.32 and 13.21, respectively. The clear bone image of rabbit was obtained at 120 min after injection of Tc-99(m)-TADP and clearance in soft tissue was visible. The preparation of 99Tcm-TADP was convenient and Tc-99(m)-TADP exhibited high uptake in bone, and it would be a potential new bone imaging agent.