Dose Coefficients for Monoclonal Antibodies and Antibody Fragments Labeled by Zirconium-89

The purpose was to assess the behavior of monoclonal antibodies (MAb) and their fragments labeled by 89 Zr after injecting them into the human body for the purpose of positron emission tomography (PET), as well as to assess absorbed doses in organs and tissues with maximum radiation exposure. The biokinetic model has been built on the base reference data about the behavior of MAb and their fragments and on the literature data on the excretion of chelate complexes from the human body. The cumulative activity of 89 Zr in organs and tissues per Bq of administered activity was calculated. For the most exposed organs, average absorbed doses for organs and tissues were calculated. The organs which had the highest doses, when 89 Zr was injected into the human body associated with intact monoclonal antibodies, are the spleen, the liver, and the heart wall. The estimated doses on these organs are 1.69, 1.48 and 1.08 mGy/MBq, respectively. When the injection associated with the fragments of monoclonal antibodies is considered, the most exposed organs are the kidneys with the doses of 0.939 mGy/MBq for F(ab')) and 0.920 mGy/MBq for F(ab')2.