Development of radiochemically pure antibodies.

There are presently three approaches to radiolabeling antibodies: direct radiolabeling; radiolabeling of a chelating agent conjugated to an antibody; and radiolabeling of a chelating agent before conjugation to an antibody. Using either the direct radiolabeling or radiolabeling of a chelating agent conjugated to an antibody has not led to a radiochemically pure 99mTc-labeled protein. High radiochemical purity is obtained using a prelabeled ligand; therefore this method is preferred.