The physicochemical properties of [18F]rucaparib, as an isotopologue of FDA-approved PARP inhibitor, rucaparib, may potentially allow real-time direct imaging of the whole body, and extraction of critical bio-information by interrogating PARP expressions, probing drug-target engagement and drug distribution and in-depth investigating off-binding effects, which may meet the current clinical needs in cancer imaging and therapy. The gene discussed is PARP1; the disease is cancer.