The invention provides A compound of the formula L-Xwherein L is selected from folate, folinic acid, pteropolyglutamic acid, a tetrahydropterin, a dihydrofolate, a tetrahydrofolate, a 1-deaza folate, a 3-deaza folate, a 5-deaza folate, an 8-deaza folate, a 10-deaza folate, a 1,5 dideaza folate, a 5,10-dideaza folate, an 8,10-dideaza folate, a 5,8-dideaza folate, aminopterin, amethopterin, N10 -methylfolate, 2-deamino-hydroxyfolate, 1-deazamethopterin, 3-deazamethopterin, and 3'5'-dichloro-4-amino-4-deoxy-N10 -methylpteroylglutamic acid,wherein X comprises a radiophore comprising a radioisotope；wherein the radiophore comprises a group selected from a benzamidyl, a benzylic, a phenyl, a naphthyl, and a benzoxazolyl group； andwherein the radioisotope is 18F.
