The present application is directed to radiolabeled imaging agents comprising a radiolabel, and a substrate, pharmaceutical compositions comprising radiolabeled imaging agents, and methods of using the radiolabeled imaging agents. The present application is further directed to methods of preparing the radiolabeled imaging agent. Such imaging agents can used in imaging studies, such as Positron Emitting Tomography (PET) or Single Photon Emission Computed Tomography (SPECT).