Development Of Face Based Radiation Anthropomorphic Phantom And Applications In Dosimetric Study Of Proton Therapy And Space Radiation

Ionization radiation is a double-edged sword.It has been widely used in the field of energy,medicine,material science,et al,and also have the potential of risk for human health.In order to safely develop the applications,accurate radiation protection and dosimetry is critical.Computational human phantom,which denotes the kind of anthropomorphic model to mimic a human on the purpose of the dose calculation,plays an irreplaceable role in human dosimetry in the field of radiation protection.Looking back the past decades,it has been widely developed and innovated in different features in terms of both the construction method and the physiological characteristic.On the topic of development of surface based phantoms,a new generation of computational phantom,and its application,the thesis was comprised of the following contents.The first work was to develop a series of surface based Chinese reference radiation phantom based on the Chinese psychological character.The feature of the phantom is the combination of the flexibility of the stylized phantom and the reality of the voxelized phantom.Based on the established phantoms,a series of simulations were performed for external neutron irradiation environments.The results were compared with that based on the ICRP reference phantoms.The result of the Chinese phantom are always higher than that of the ICRP reference phantoms.The radioiodine internal dosimetry also considered for the dose calculation for the radioiodine carrier and surrouding individuals.Comparing with the result calculated with ICRP based phantoms,results in this study are closest to the hybrid UF phantom(comparing the difference among the Chinese phantom against the three generation of ICRP phantoms).Also the target organ S values and effective dose for surrounding individuals obey the inverse square law with the distance between source and target phantoms.The difference shows the necessary of establishment of reference phantoms with Chinese feature,and eventually performing more accurate dosimetric study.Secondly,two research topics on proton therapy were discussed using the computational phantom.The in-field and out-of-field secondary risk were compared for passive scattering and pencil beam scanning proton therapy.The dissertation validated the feasibility of using aperture for optimising the pernumbra in pencil beam scanning without increasing unaccessable out-of-field neutron dose,i.e.far lower than passive scattering proton therapy.Furthermore,the scattered and secondary dose to the fetus was calculated for the conventional photon therapy,passive scattering proton therapy and pencil beam scanning proton therapy.The attained dose to a fetus from the three modalities is far lower than the thresholds of malformation,severe mental retardation and lethal death.The childhood cancer excessive absolute risk was estimated using a linear no-threshold dose-response relationship.The risk would be 1.0(95%Cl:0.6,1.6)and 0.1(95%Cl:-0.01,0.52)in 105 for the 9-month fetus for PBS with a prescribed dose of 52.2 Gy(RBE).The increased risks for PPT and photon therapy are about two and one orders of magnitude larger than that for PBS,respectively.Last but not least,the dissertation developed a Monte Carlo-based approach to evaluating the shielding effectiveness of the active shielding technique using confined magnetic fields(CMFs)for space radiation.The penetrating primary particle fluence,organ-specific dose equivalent,and male effective dose were calculated for particles in galactic cosmic radiation(GCR)and solar particle events(SPEs).Results show that the SPE protons can be easily shielded against,even almost completely detected,by the toroidal magnetic field.GCR particles can also be more effectively shielded against by increasing the magnetic field strength.Our results also show that the introduction of a structural A1 wall in the CMF did not provide additional shielding for GCR;in fact it can weaken the total shielding effect of the CMF.This study demonstrated the feasibility of accurately determining the radiation field inside the environment and evaluating the organ dose equivalents for astronauts under active shielding using the CMF.