Labeling procedures for the preparation of sup(188)Re-DMSA(V)

Abstract

188Re has received a lot of attention in the past decade, due to its favorable nuclear characteristics [t1/2 16.9 h, Eβ max 2.12 MeV and Eγ 155 keV (15%) suitable for imaging], including the fact that it is carrier-free and can be obtained cost-effectively through the generator 188W-188Re. Besides the therapeutic usefulness of 188Re, the emission of the 155 keV gamma photon is an added advantage since the biodistribution of 188Re-labeled agents can be evaluated in vivo with a gamma camera. Biodistribution studies of 188Re-DMSA(V) have shown that its general pharmacokinetic properties are similar to that of 99mTc-DMSA(V), so this agent could be used for targeted radiotherapy of the same tumors, i.e., medullary thyroid carcinoma, bone metastases, soft tissue, head and neck tumors. The aim of this work is to evaluate two labeling procedures for the preparation of 188ReDMSA(V). 188Re-DMSA(V) was prepared by two methods. The first method was prepared using a commercial kit of DMSA(III) for labeling with 99mTc, at high temperature (100oC). The second method was prepared in a vial containing 2.5 mg of DMSA, 1.00 mg of SnCl2.2H2O and 30 mg of sodium oxalate, in a total volume of 1.1 mL. The pH was adjusted to 5 with 37% HCl. After labeling the solution was stirred and incubated for 15 min at room temperature. The radiochemical purity was determined using TLC-SG developed with two different solvent systems. Preliminary results for both methods of labeling 188Re-DMSA(V) showed that the labeling yield was >90%.