16-BETA-[F-18]FLUOROMOXESTROL - A POTENT, METABOLICALLY STABLE POSITRON EMISSION TOMOGRAPHY IMAGING AGENT FOR ESTROGEN-RECEPTOR POSITIVE HUMAN BREAST-TUMORS

16beta-[F-18]Fluoromoxestrol (betaFMOX, 1) is a highly selective, meta bolically stable estrogen with potential as a receptor imaging agent. It demonstrates receptor-mediated uptake in the immature rat in the es trogen receptor-rich primary target tissues, uterus and ovaries, as we ll as, in receptor-poor secondary target tissues, muscle, thymus and k idneys; uptake in the uterus is nearly four times that of the clinical ly useful 16alpha-[F-18] fluoroestradiol (FES), most likely due to the extended lifetime of the labeled betaFMOX in the blood afforded by it s relatively slow metabolism. In vivo and in vitro studies demonstrate a nearly four-fold decrease in metabolism rate between betaFMOX and F ES. Dosimetry studies indicate radiation absorbed doses comparable to FES. BetaFMOX possesses desirable imaging characteristics and may prov e to be a clinically useful imaging agent.