Animal studies of 99mTc–i-PIDP: A new bone imaging agent

This study was to investigate the preparation and biodistribution of 99mTc-labeled novel zoledronic acid derivative 1-hydroxy-2-(2-isopropyl-1H-imidazole-1-yl) ethylidene-1,1-bisphosphonic (99mTc–i-PIDP) as a potential bone imaging agent. Satisfactory labeling results (radiochemical purity over 95%) were obtained when the amount of i-PIDP, Na99mTcO4, and SnCl2·2H2O, were 5 mg, 37 MBq, and 100 μg, respectively, the pH value was between 4.0 and 6.0, and the labeling reaction continued for 30 min. The labeled complex was stable at least up to 6 h in vitro. The biodistribution and pharmacokinetics studies in mice and single photon emission computed tomography (SPECT) bone scan in rabbit of 99mTc–i-PIDP were systematically studied. The results showed that the bone uptake is up to 9.63%ID/g at 60 min after injection of 99mTc–i-PIDP. The pharmacokinetic studies indicate that the data can be fitted to a two-compartment model with the equation of C=5.80e−0.20t+2.66e−0.01t. A plain bone image was obtained at 1 h. All of the results suggested that 99mTc–i-PIDP is worthy of future investigation as a novel bone imaging agent.