Preparation and biodistribution of rhenium-188 ECD/lipiodol in rats following hepatic arterial injection

Radiolabeled Lipiodol has been used in hepatoma therapy. In our previous studies, EDTB was used in the syntheses of 188Re-Lipiodol. However, the toxicity of EDTB is unknown and therefore is an obstacle for further clinical trial since EDTB has not been approved for use in human beings. In this report, we attempted to develop a new 188Re-ECD/Lipiodol radiopharmaceutical in which the chelating agent, ECD (ethyl cyteinate dimer), is the constituent of the known brain perfusion agent, 99mTc-ECD, and to evaluate its stability and biodistribution in rats with hepatic tumors. Firstly, 188Re-ECD was prepared in a vial, followed by extraction with Lipiodol to get the final product, 188Re-ECD/Lipiodol. The optimal labeling conditions for 188Re-ECD were: (1) tartaric acid which is better than EDTA as a weak chelating agent; and (2) 15 mg of SnC12, as the reducing agent, and 5-10 mg of tartaric acid in each vial had a better labeling yield. The radiochemical purity of 188Re-ECD/Lipiodol was more than 94%. Twenty-four male Sprague-Dawley rats with liver tumors were sacrificed at 1, 24, and 48 hrs (eight rats each time) after an injection of approximately 7.4 MBq of 188Re-ECD/Lipiodol via the hepatic artery. The radioactivity in the liver tumor is significant higher following therapeutic arterial injection, and relatively low in other organs including the bone, spleen, brain, thyroid, stomach, muscle, blood and testis throughout this study. In Conclusion, the new preparation of 188Re-ECD/Lipiodol is a candidate agent for the treatment of liver cancer. (authors)