Mouse biodistribution and rabbit bone imaging of 99Tcm-Ibandronate

Abstract

Objective To prepare 99Tcm-Ibandronate (IBN) and explore the feasibility of 99Tcm-IBN as a radiopharmaceutical for bone imaging. Methods 99Tcm-IBN was synthesized by the stannous reduction method. The biodistribution in mice was observed and the bone imaging was performed in rabbits. Two-sample t test were used to analyze the data. Results The 99Tcm-IBN was highly stable in vitro, with a radiochemical purity of (98.24±0.24)%. The radiochemical purity was still >95% after 6 h at room temperature. In vivo distribution experiments showed that 99Tcm-IBN could be specifically and rapidly incepted by bones of mice, and the peak value ((9.85±0.51) percentage activity of injection dose per gram of tissue (%ID/g)) was observed at 30 min post-injection. The radioactivity was retained in bone for a long time. The uptake by the liver and spleen was low, and the radioactivity was eliminated rapidly from the blood and soft tissues, demonstrating a high bone/soft tissue ratio of radioactivity. Rabbit bone imaging showed that the background was nearly eliminated and the images of the spinal column, costal bones, and extremity bones were very distinct at 1 h post-injection. Compared to 99Tcm-methylene diphosphonate (MDP), 99Tcm-IBN was characterized by rapid and high uptake by bones, rapid elimination from soft tissues, and low uptake by the liver and spleen. The bone/soft tissue ratios of 99Tcm-IBN at each time point (10, 20, 30, 40, 50 min) were significantly higher than those of 99Tcm-MDP (t values: 2.867-5.426, all P<0.05). The imaging performance of 99Tcm-IBN was superior to 99Tcm-MDP at 1-2 h post-injection. Conclusions 99Tcm-IBN has good biological properties. Its imaging performance is comparable to that of 99Tcm-MDP and has shorten imaging waiting time. It might be a promising new bone imaging agent. Key words: Diphosphonates; Isotope labeling; Technetium; Skeleton; Mice; Rabbits