cialis online without The present invention includes all pharmaceutically acceptable radio isotope labeled peptide ligands of the invention, wherein one or more atoms are replaced by atoms having the same atomic number, but an atomic mass or mass number different from the atomic mass or mass number usually found in nature, and peptide ligands of the invention, wherein metal chelating groups are attached termed effector that are capable of holding relevant radio isotopes, and peptide ligands of the invention, wherein certain functional groups are covalently replaced with relevant radio isotopes or isotopically labelled functional groups