The radioelement astatine and its prospects in nuclear medicine

Astatine is the fifth halogen and the earth's rarest naturally occurring element. It has no stable isotopes and its longest-lived radioactive isotopes with half-lives of several hours can be produced only via nuclear reactions. Its behaviour and properties can be studied only on a tracer scale, making use of radiochemical methods. The considerable attention paid to the chemistry of this element stems mainly from the potential application in tumour therapy of the α-emitting 221At-isotope whose half-life is 7.2 hours. Its tumour destroying effect, when administered locally, has been proved by utilizing 211At-tellurium colloid. Recently, the main efforts have been directed towards preparing such 211At-labelled carriers stabe in vivo, which metabolically could deliver and localize the α-emitter selectively to the tumour cells. (orig.)