Development Of Chinese Reference Adult Male Voxel Model And Its Application In Radiation Dose Measurement And Assessment

Human computational models play a central role in radiation dosimetry. Voxel models being the state-of-the-art can give a realistic anatomic description of human body, thus provide a more accurate dose evaluation than the previous mathematical models. Development of human voxel model and its application is one of the most dynamic research areas in radiation protection.A high-resolution Chinese reference adult male whole-body voxel model, called CRAM, was developed in this thesis. Then, the organ dose and effective-male-dose were calculated for Chinese adult male from photons and neutrons external exposure, respectively. The voxel model was also used to develop a so-called bio-dynamic virtual calibration technique for human internal contamination in-vivo monitoring. The main results are as follows:(1) Based on a previous Chinese individual voxel model (CNMAN), the CRAM model was developed according to Chinese reference data and the skeleton tissue distribution data from ICRP publications. The resultant model has a height of 170 cm and a weight of 60 kg. There are more than 80 organs and tissues in CRAM, including almost all radiation sensitive organs required by the ICRP new recommendation. The mass of individual organs has been adjusted to the Chinese reference value with the difference less than 5%. Special considerations were given to representing the spatial distribution of various bone constituents as realistically as possible during the construction of the site-specific skeleton voxel model, which is the method adopted by ICRP for its reference voxel model. With regarding to the key issue of voxel model adjustment, a new dilation and erosion method, called "neighbouring-field-proportional" method, was developed in this thesis, which has been proved to be better than the method used by ICRP.(2) The CRAM model has been used to calculate the external dose conversion coefficients for Chinese adult male by using Monte Carlo code MCNPX. The energy ranges of the dose coefficient data set are 10 keV-10 MeV, and 0.01 eV-20 MeV for photons and neutrons, respectively. The dosimetric difference between Chinese and Caucasian, the difference between mathematical and voxel models were discussed through a comprehensive comparison of the resultant dose coefficients with those from other models. In addition, some new or improved methods have been developed for more accurate dose calculation for special organs, such as skin, red bone marrow, and bone surface.(3) The CRAM voxel model, combined with ICRP bio-kinetics model, was also used to develop a so-called bio-dynamic virtual calibration method for in-vivo monitoring. By using the method, a comprehensive research was carried out to evaluate the influence of Am, U, and Co radionuclide bio-kinetics distribution on the measurement for lung counter and whole body counter, respectively. Meanwhile, it also has shown an excellent result for the participation in an international intercomparison program on the virtual calibration technique.