Synthesis, Characterization and Radiolabeling of Nitrilotris (methylenephosphonic) Acid As a model for Bone Imaging

The aim of this work was labeling of nitrilotris (methylenephosphonic) acid (NTMP) with technetium-99m and rhenium-188. Stannous chloride was used as a reducing agent for the reduction of 99mTcO4- and 188ReO4-. At ph 7, 99mTc-NTMP complex was obtained with a high radiochemical yield of 99.6±2.1 %, and high stability (up to 8 h) once by adding technetium-99m to the reaction mixture. Under optimum conditions, the labeling yield of 188Re-NTMP complex is 90% for the carrier-free 188Re but with the carrier-added 188Re the labeling yield is more than 97.5%. The studies of biodistribution in mice indicate that 99mTc-NTMP and 188ReNTMP complexes were highly selective accumulated in the bone at time interval lower than that of the commercially available 99mTc-MDP and rapid clearance from the soft tissues. 99mTcNTMP and 188Re-NTMP complexes could be used to scan body bones in time interval between injection and bone imaging equal to 15 min, minimizing the burden on patients in terms of the total length of the examination