Recombinant Anti-CEA x Anti-DTPA Bispecific Antibody (Diabody-Fc) is a fusion protein of two diabodies connected together by an Fc region. In a diabody, the two scFvs with short linkers are from anti-CEA and anti-DTPA antibodies. The VH and VL domains form an inter-chain pairing. The diabody with different specificities is fused to the Fc fragment, which results in 2+2 antigen-binding valency and exerts Fc-mediated functions or just extends the half-life. 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.