This invention relates to kits for tumor imaging and methods for preparing the kits using a composition having the structure— His-Ser-Asp-Gly-Ile-Phe-Thr-Asp-Ser-Tyr-Ser-Arg-Tyr-Arg-Lys-Gln-Met-Ala-Val-Lys-Lys-Tyr-Leu-Ala-Ala-Val-Leu-yAba-Lys (R) (SEQ ID NO:1), wherein the y-amino group of the lysine residue is coupled to a chelator disclosed in this application.