The present disclosure provides immunes cells comprising a radiolabeled tracer useful in imaging tests such as positron emission topography (PET)/computed tomography (CT) scans. The present disclosure further includes engineered cells comprising a chimeric antigen receptor (CAR) further comprising a nucleic acid molecule comprising a ligand binding domain capable of binding to radiolabeled tracer. This disclosure also includes methods for assessing the efficacy or toxicity of an adoptive cell therapy in a subject, methods for detecting the quantity of engineered T cells in a subject, methods for monitoring an immunotherapy treatment in a subject and methods of imaging engineered T cells in a subject. In some embodiments, the radiolabeled tracer is [18F]fluoropropyl-trimethoprim ([18F]FPTMP).
