Disclosed herein are novel radiolabeled nucleosides and methods for detecting cellular proliferation in a mammal, the method comprising administrating an effective amount of a radiolabeled nucleoside; the method comprising: a) administering to the mammal a diagnostically effective amount of the nucleoside to the mammal; b) allowing the nucleoside to distribute into the effective tissue; and c) imaging the tissue, wherein an increase in binding of the compound to tissue compared to a normal control level of binding indicates that the mammal is suffering from a disease involving cellular proliferation.