Two different radiolabeled forms of the same mAb were injected into groups of LNCaP tumor-bearing mice and their tumor uptake kinetics compared by serial PET imaging: J591, a specific PSMA-targeted antibody that is known to be internalized after binding to extracellular antigen, labeled with either 89Zr, a residualizing PET isotope, or 124I, a non-residualizing PET isotope. The gene discussed is FOLH1; the disease is neoplasm.