(3S,7S,22S)-26-Amino-5,13,20-trioxo-4,6,12,21-tetraazahexacosane-1,3,7,22-tetracarboxylic Acid, can be used in preparation of GdIII-Based Magnetic Resonance contrast agents, that have been evaluated to have relaxometric properties for molecular Imaging of Prostate-Specific Membrane Antigen (PSMA).