STUDIES IN THE RAT WITH 4-FLUORO-ESTRADIOL-F-18 AND 4-FLUORO-ESTRONE-F-18 AS POTENTIAL PROSTATE SCANNING AGENTS - COMPARISON WITH 2,4-DI-IODO-ESTRADIOL-I-125

18F-4-Fluoro-oestradiol, 18F-4-fluoro-oestrone, 125I-2-iodo-oestradiol and 125I-2,4-di-iodo-oestradiol were synthesised and the distribution of the radioactivity was studied following injection into male rats. The uptake of all of these compounds by the ventral prostate was very low with considerable levels of activity being excreted in the bile. No evidence of defluorination of the fluorosteroids was found while there appeared to be a slow, progressive de-iodinisation of the iodooestradiols. It was concluded that failure to localise in the prostate was due primarily to the compounds being of insufficient specific activity. © 1979.