**Abbreviations**

Cholecystokinin-2 (CCK-2), cholecystokinin-2 receptor (CCK-2R), nastorazepide (Z-360), cholecystokinin-1 receptor (CCK-1R), 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA), 1,10 carbonyldiimidazole (CDI), *tert*-butoxycarbonyl (Boc-), trifluoroacetic acid (TFA), dichloromethane (DCM), fluorenylmethoxycarbonyl (Fmoc-), dimethylformamide (DMF), nuclear magnetic resonance (NMR), high-resolution mass spectrometry (HRMS), Wildman's logP (W-logP), topological polar surface area (TPSA), predicted solubility (log scale) computed according to the Estimated aqueous SOLubility (ESOL) model (LogS (ESOL)), gastrointestinal (GI), blood brain barrier (BBB), P-glycoprotein (P-gp), P-cytochrome (CYP), solid phase extraction (SPE), radiochemical purity (RCP), high-performance liquid chromatography (HPLC), thin-layer chromatography (TLC), 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES), ethylenediaminetetraacetic acid (EDTA), acetonitrile (MeCN), single photon emission tomography (SPECT), computed tomography (CT), tumor to muscle (T/M), tumor to blood (T/B), maximum intensity projection (MIP), injected dose per cube centimeter (ID/cc), tetramethylsilane (TMS), matrix-assisted laser desorption/ionization time of flight (MALDI TOF/TOF), triethylamine (TEA), ethyl acetate (EtOAc), benzotriazol-1-yloxytris(dimethylamino)phosphonium hexafluorophosphate (BOP), human serum (HS), human blood (HB), 40 ,6-diamidino-2-phenylindole (DAPI), phosphate buffer saline (PBS), maximum-likelihood expectation-maximization (MLEM), and iterative image space reconstruction algorithm (ISRA).
