Construction Of Stylized Model And Boundary-Representation Model Based On Visible Chinese Human And External Radiation Dosimetry Research

As the intrinsic features of the natural environment of the earth and the space, there are close relations between ionizing radiation and human. In the process of the continuous research and the use of all kinds of ionizing radiation sources, the cognitive degree of ionizing radiation dangers imposed on the of human body was deepened and extended. In order to protect mankind itself and the environment more effectively, it is needed to the understand the specific dose of the targeted object under radiation, and to determine energy transfer and energy deposition in the material during the ionizing radiation in the application of production, medical treatment, scientific research and so on. It is also required to master the radiation effects of objects and the potential harm as possible, and to guide the radiation protection plan and shielding equipment design through the objective index. In the nuclear radiation dose calculation using the Monte Carlo method and procedures, the phantom of the human body is indispensable and in important position. But among each kind of the existing computational human phantoms, phantom based on the characteristics of Chinese human anatomy has not been perfected yet, and can not meet the different needs for calculation modeling and radiation dose calculation in all kinds of actual application, and also remains to be further investigated in order to achieve human radiation dose assessment and protective study.In this work, the accurate Chinese male stylized phantom was constructed based on Visible Chinese Human (VCH) male voxel phantom and and the instauration process of the phantom was discussed in detail. And the whole body VCH female phantoms were developed using human body color section images from China’s digital woman dataset, including three kinds of radiation model (stylized model, voxel model and boundary-representation model), and the China digital human phantoms were further perfected. The existing problems in the modeling has been improved, moreover, the application foundation of the phantom simulation has been enhanced. Furthermore, on this basis, combining with the needs of the radiation dose calculation, MCNP Monte Carlo simulation calculations were implemented under irradiation of photon, neutron and proton to study the organ doses, the whole body effective doses and the radiation shielding. Through the dose comparison, several factors which affect the internal organ doses were discussed. For the problem about the dose evaluation of proton irradiation for female astronaut, rapid approximate calculation of on-orbit dose was obtained, the differences before and after shielding were compared, the anatomical factors were analyzed.The main research results and innovation are as follows:(1) During the construction of the stylized models, the parameters of tissue and organ are from the voxel model, with error within5%, in smaller level compared with other models. During the construction of boundary-representation models, the authenticity, accuracy and variability of the human anatomy structure were ensured.(2) Through the comparison of photon doses, we found that the curve of conversion coefficient of photon organ dose has the obvious directional features, and closely related to radiation directions. The obvious differences are not only numerical, but also exist in the shape of the curve. Through the comparison of the neutron irradiation dose, it is found that:for particle energy of different level, because of different penetrating power, the energy deposition is dissimilar, that is to say, the level of the relevant organ dose would be different. In the curve of organ absorbed dose for the VCH male stylized phantom, due to the different energy, values of organ absorbed dose form a plateau and a rising phase in two areas.(3) Through the comparison of the proton illuminate dose, this study found that, the way of proton incidence and energy deposition has many difference with photon and neutron. It indicates that the skin does not have large influence on the absorbed dose of the internal organs, but the Bragg Peak of breast shift to the high-energy period about20MeV. In the field of radiation protection study, shielding strategy is an important factor to be considered, especially for human space exploration. In the process of penetration under shielding conditions, there must be some energy loss, less radiation particles can pass through and reach of human organs, so organ doses decrease after shielding. Under shielding layer of1.35g/cm2thickness, the organ doses reduce by13.90%on average (from9.00%to24.20%range). An exception is the skin dose, with52.20%reduction.In this study, the established computational human phantom for radiation dose calculation is based on the VCH male NO.1and the VCH female NO.1, including three kinds of phantom, stylized phantom, the voxel phantom and NURBS surface phantom. It improves VCH computational human phantoms, and can be used as an adjustable template of radiation dose calculation and risk assessment. The data provided by this work will be helpful to the existing Chinese human dose data set, and to improve the calculation model in radiation protection applications. For all kinds of application and dose calculation of more complex illuminate circumstance, dose research on various body type and human body posture, as well as accurate radiation dose estimation and real-time radiation protection, are extremely important.