GATE/Geant4-based dosimetry for ex vivo in solution irradiation of blood with radionuclides

To establish a dose-response relationship between radiation-induced DNA damage and the corresponding absorbed doses in blood irradiated with radionuclides in solution under ex vivo conditions, the absorbed dose coefficient for 1 ml for 1 h internal ex vivo irradiation of peripheral blood (d(Blood)) must be determined. d(Blood) is specific for each radionuclide, and it depends on the irradiation geometry. Therefore, the aim of this study is to use the Monte Carlo radiation transport code GATE/Geant4 to calculate the mean absorbed dose rates for ex vivo irradiation of blood with several radionuclides used in Nuclear Medicine. METHODS: The Monte Carlo simulation reproduces the irradiation geometry of a blood sample of 7 ml mixed with 1 ml of a water equivalent radioactive solution in an 8 ml vial. The simulation was performed for ten different radionuclides: (18)F, (68)Ga, (90)Y, (99m)Tc, (123)I, (124)I, (131)I, (177)Lu, (223)Ra, and (225)Ac. Two sets of simulations for each radionuclide were performed with 1x10(9) histories. The first set was simulated with a mass density of 1.0525 g/cm(3) of the blood plus water mixture. The second set of simulations was performed with a mass density of 1 g/cm(3) for comparison with previous studies. RESULTS: The values of d(Blood) for ten radionuclides were calculated. The values range from 10.23 mGy∙ml∙MBq(−1) for (99m)Tc to 15632.02 mGy∙ml∙MBq(−1) for (225)Ac. The maximum relative change compared to previous studies was 13.0% for (124)I. CONCLUSION: This study provides a comprehensive set of absorbed dose coefficients for 1 ml for 1 h internal ex vivo irradiation of peripheral blood in a special vial geometry and radionuclides typically used in Nuclear Medicine. Furthermore, the method proposed by this work can be easily adapted to a variety of internal irradiation conditions and serve as a reference for future studies.