Studies on optimal utilization conditions of methylenediphosphonate-sup(99m)Tc

For an effective preparation and utilization of methylenediphosphonate (MDP)-sup(99m)Tc, a typical radioactive bone imaging agent, methods of radiochemical purity determination, labelling yields under various conditions, in-vitro stabilities, and relations between the radiochemical purity and bio-distributions have been studied. It has been confirmed that the paper chromatography using 1 M-acetate buffer (pH 4.75) and Whatman 3 MM paper is quite effective for radiochemical purity determination in simplicity and resolution points of view. Freeze-dried labelling vial consists of 13 mg MDP, 1 mg SnCl2-2H2O, pH adjusted to 4.8-5.0, showed more than 98% labelling yield by reconstitution with 1 ml Na sup(99m)TcO4 solution. The compound maintained more than 95% radiochemical purity at room temperature until two hours from the instant labelling. One hundred twenty (sometimes one hundred fifty) minutes after the I.V. injection of MDP-sup(99m)Tc to mice, the radioactivities accumulated at the three organs such as stomach, liver and femur were counted. The radioactivity distribution patterns were correlated with the injected volume, injected radioactivities and the radiochemical purity of the injected MDP-sup(99m)Tc. The results indicated that the use of small amount of MDP-sup(99m)Tc having high radioactivity concentration and high radiochemical purity is preferred for an efficient bone imaging. The B/S ratios were sharply decreased with increasing radioactivity and the volume of injection while the B/L ratios were rather in increasing tendency with increasing the afore-described parameters. Such a tendency has been explained in terms of organ characteristics. (author)