Recombinant Anti-CEA x Anti-DTPA Bispecific Antibody (IgG-scFv) is designed to be expressed as a LC and an extended HC with scFv moiety linked to the C terminus. It is a symmetric bispecific and tetravalent molecule, bivalent for each antigen specificity, 2+2 antigen-binding valency. This BsAb can be used in pretargeting system of PET, radioimaging or radiotherapy. It can mediate targeting of radioactivity to tumor cells. It is designed for the research of Breast cancer; Ovary cancer; Colon cancer; Lung cancer imaging and therapy.