The influence of the method of preparation of the bone scanning agent 99mTc(Sn)EHDP on its tissue distribution in the rat.

The tissue distribution in the rat of the bone scanning agent 99mTc(Sn)EHDP is investigated by three methods, viz. by dissecting the animals 3 and 24 h post injection, by scanning the animals with a rectilinear scanner and by whole body autoradiography, particular of micro-sections of the skeleton. The effect of varying the experimental conditions in the preparation of the bone scanning agent (pH and concentrations of Sn(II) and EHDP) is investigated. In some of the experiments additional amounts of Sn(II) and EHDP are added to the reaction mixture after the preparation of the bone scanning agent. In this way the influence of the Sn(II) and EHDP concentrations on the composition of the bone scanning agent, and their influence as such on tissue uptake can be separately investigated. The 99mTc-uptake in bone is compared with the distribution of the 99mTc over the two main products in the reaction mixture, viz. 99mTc(IV)-Sn-EHDP2 and 99mTc(IV)-Sn-EHDP. In addition, the stability in vitro of some of the preparations in urine and plasma and the in vivo binding of the 99mTc to plasma proteins are determined. A procedure for the preparation of the bone scanning agent is recommended.