Technetium or rhenium radionuclide labelled chelate-hexapeptide complexes are useful for the selective detection or treatment of tumors with somatostatin receptors. In particular, the hexapeptide of formula (I) (wherein R<3> is as defined herein) may be attached to an N3S2 chelate and labelled with a radionuclide. The resulting complex is useful as a radioimaging agent or as a radiopharmaceutical for the treatment of certain tumors.
TC OR RE RADIOLABELLED SOMATOSTATIN ANALOGS