Development and biodistribution of 188Re-SSS lipiodol following injection into the hepatic artery of healthy pigs

Although intra-arterial radiotherapy with 131I-labelled lipiodol is a useful therapeutic approach in the treatment of hepatocellular carcinomas, various disadvantages limit its use. Here we describe the development of 188Re-SSS lipiodol, as well as its biodistribution in the healthy pig after injection into the hepatic artery. The 188Re-SSS lipiodol was obtained after dissolving a chelating agent, previously labelled with 188Re, in cold lipiodol. The radiochemical purity (RCP) of the labelling was checked immediately and at 24 and 48 h. The 188Re-SSS lipiodol was injected into the hepatic artery of six healthy pigs. They were killed 1, 24 and 48 h post injection, for ex vivo counting. An autoradiographic study was performed in three cases. 188Re-SSS lipiodol was obtained with a yield of 87%±9.1%. The immediate RCP was 93%±3.4%. This radiolabelling was reproducible and stable at 48 h in plasma: 90.6%±1.5% of the activity remained in the lipiodol with an RCP of 91%±4%. Ex vivo counting confirmed the predominantly hepatic uptake and revealed weak lung and intestinal uptake. There was very weak urinary elimination (2.3%±0.5% at 48 h) and a slightly higher level of intestinal elimination (4.8%±1.9% at 48 h). The autoradiographic studies showed 188Re-SSS lipiodol to be located mainly in sinusoids, like 131I-lipiodol. By using the method described here, 188Re-SSS lipiodol can be obtained with a very high yield and a satisfactory RCP. Its biodistribution in the healthy pig is in agreement with data published elsewhere concerning other types of radiolabelling used for lipiodol, except for the very weak urinary and intestinal elimination, which probably indicates better stability of 188Re-SSS labelling.