Dosimetry of 175Ytterbium-poly (amidoamine) therapy for humans' organs

Purpose: This investigation focuses on biodistribution of irradiated dendrimer encapsulated ytterbium-175 ( 175 Yb) and to estimate the absorbed dose from intravenous injection of PAMAM encapsulated 175 Yb to human organs. Methods: A dendrimer compound containing an average of 55 Yb +3 ions per dendrimer was prepared and irradiated with neutrons for 2h at 3×10 11 n.cm- 2 s- 1 neutron flux. The resulting mixture was injected into a group of tumor bearing mice and the mice were excised, weighed and counted at certain times to study the biodistribution. The human organs absorbed dose was assessed by MIRD schema and MCNP simulation. Results: The specific activity and radiochemical purity of the irradiated nano-composite were 7MBq/mg and >99% respectively. The rapid up take of dendrimer was in liver, lung, and, spleen. MIRD and MCNPX were applied for dose estimation. The human absorbed dose in liver, lung, spleen, kidney and bone that simulated by MCNP are 1.266, 0.8081, 0.8347, 0.03979 and 0.01706 mGy/MBq respectively and these values for MIRD schema are 1.351, 0.73, 1.03, 0.039, and 0.0097 mGy/MBq respectively. Conclusion: The results showed that 175 Yb-PAMAM nano-radiopharmaceutical has potential of application for liver and lung tumors.