“…To date, a variety of urea-based PSMA inhibitors have been developed and labeled with different SPECT ( 99m Tc, 111 In), PET ( 68 Ga, 64 Cu), and therapeutic ( 177 Lu) radiometals using several chelators and showed great promise not only preclinicaly but also in the clinical assessment. Apart from the radiometals to be used as the cytotoxic units, a considerable amount of urea-based PSMA inhibitors labeled with 11 C, 125 I, 124 I, 131 I and 18 F, have also been reported [ 19 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 , 95 , 96 ]. These radiotracers were also able to successfully image PSMA-expressing xenografted mice, but since this is beyond the focus of this review no further information will be given here with regard to this topic.…”