A pharmaceutical formulation including a chelator-somatostatin receptor ligand and a transchelator is provided. The chelator-somatostatin receptor ligand is conjugated with a metal source or a radionuclide source, whereas the transchelator is capable of capturing free metal source or radionuclide source that is not conjugated to the chelator-somatostatin receptor ligand. By using such pharmaceutical formulation, the preparation of radiolabeled somatostatin analogues could be made more efficient, and is feasible for imaging of SSTR pathway-activated systems in cancers and neurological diseases.
