Provided are a compound represented by formula (1) or a salt thereof, and a medicine including the same. [In the formula, X1 represents a hydrogen atom or a halogen atom, X2 represents a fluorine atom or a nitrile group, and X3 represents a radioactive halogen atom].提供下述化學式(1)所表示的化合物或其鹽類,以及,包含該化合物或其鹽類的藥物。《化學式中,X1係表示氫原子或鹵素原子,X2係表示氟原子或腈基(nitrile group),X3係表示放射性鹵素原子。》