Liver Dose Deposition (mGy) Optimization of Image-based Dosimetry in Y90 Radioembolization: a Monte Carlo approach using the GATE simulation toolkit K. Mountris1, A. Autret2, P. Papadimitroulas1, G. Loudos3, D. Visvikis2, G. Nikiforidis1 1 Department of Medical Physics, School of Medicine, University of Patras, Rion, GR 265 04, 2 LaTIM, UMR 1101 INSERM, CHRU Brest, Brest, France 3 Department of Biomedical Engineering, Technological Educational institute of Athens, Ag. Spyridonos Street, Egaleo GR 122 10, Athens, Greece Introduction: Y90 Radioembolization is a selective internal radiation therapy based on the heterogeneous distribution of Y90 microspheres in the target area through the hepatic artery, exploiting the unique blood flow of the human liver. Purpose: The improvement of the pretreatment image-based (IB) dosimetry using as imaging surrogate macroaggregated albumin (MAA) labeled with Ga68 or Cu64 instead of Tc99m was investigated according to the correlation with the follow up image-based dosimetric results of Y90 microspheres PET acquisition , using Monte Carlo (MC) simulations. Methods: Results: Divergence (%) Tc99m-MAA Ga68-MAA Cu64-MAA IB tumor dose +1.58% -2.61% -0.36% IB liver dose +12.77% +4.26% +3.29% XCAT phantom generation with tumor of 0.178 kg MC simulations with GATE open source toolkit Y90 IB tumor dose: 147.28 Gy Y90 IB liver dose: 62.94 Gy 52.31 mGy liver dose deposition from 200 MBq Tc99m-MAA Liver Dose Deposition (mGy) Tc99m-MAA Ga68-MAA Cu64-MAA 52.31 33.35 66.01 OPL-EM / ML-EM reconstruction Y90 kernel convolution MC estimation of imaging surrogates’ dose deposition in liver 36.2 % decrease in dose for 100 MBq of Ga68-MAA 26.2 % increase in dose for 100 MBq of Cu64-MAA Conclusions: Ability to simulate PET-based follow up dosimetry exploiting the tiny branch of positron emission of Y90. Improvement in correlation with the pre-treatment planning using PET imaging surrogates. Ga68-MAA showed dosimetric improvement and decrease in dose deposition supports further research. The radiochemical stability of Cu64-MAA has to be investigated due to it’s appealing dosimetric results. References: Konstantinos Mountris et al. “Liver Radioembolization with microspheres Y90: Method Investigation and dosimetry improvement using Monte Carlo Simulations”, Master Thesis University of Patras, Greece.