99mTc-SSS lipiodol: development and study of its biodistribution following injection intra-hepatic artery of healthy pigs

Aims. Intra-arterial metabolic radiotherapy with 131I-lipiodol is a therapeutic approach witch can be used for hepatocellular carcinoma, but several drawbacks limit its use. We report here the development of lipiodol labelling with 99mTc and its biodistribution after infusion in the hepatic artery in healthy pigs. In fact, labelling lipiodol with 99mTc is the first step towards the development of labelling Lipiodol with 188Re and 99mTc lipiodol could be used for dosimetric purpose. Method. The 99mTc lipiodol is obtained after dissolving in lipiodol a lipophilic chelating agent labelled with 99mTc: the 99mTc-(PhCS3)2(PhCS2). The radiochemical purity was assessed immediately after the labelling and 24 hours later. 99mTc-lipiodol was injected through the hepatic artery in 7 pigs. Scintigraphic acquisitions were performed 1 and 24 hours after injection. Pigs were killed after 1 or 24 hours for removal of organs and in vitro counting. Results. The labelling of lipiodol with 99mTc is achieved with a very high yield, 96 ± 0,8%. The radiochemical purity is satisfactory: 92 ± 2,6% immediately after labelling and at least 88 ± 3,5% at 24 hours. Scintigraphic acquisitions showed a predominant liver uptake and a faint lung uptake without other site of uptake at one hour and the apparition of a faint digestive elimination at 24 hours. Those results are confirmed by ex-vivo counting. Conclusion. This preliminary study point out that labelling lipiodol with 99mTc can be performed with a good yield and a good radiochemical purity. It's biodistribution in healthy pigs is satisfactory. Labelling lipiodol with 188Re is now under development with the same chelating agent. (author)