Construction of hybrid Chinese reference adult phantoms and estimation of dose conversion coefficients for muons

Calculation of the Photon Dose Conversion Coefficient Based on Boundary Representation Phantoms of Different Postures

Based on the hybrid Chinese reference adult female phantom, the Chinese reference female boundary representation (BREP) phantoms involving sitting, walking, and squatting postures were established. The photon effective dose conversion coefficient (ECCK) and some organ absorbed dose conversion coefficients (DCCK) were calculated under six standard irradiation geometries, and the irradiation source included 20 monoenergetic photon energies ranging from 0.01 MeV to 10 MeV. The results indicate that the postures, location of the organs, and irradiation geometries have an impact on the dose conversion coefficients. With the same irradiation geometry, the DCCKs of different organs are different; when the photon energy is from 0.02 MeV to 0.1 MeV, significant differences exist in the DCCK of phantoms of various postures, and the maximum relative deviation is 80%. For the ECCKs, there are greater differences among phantoms of various postures with the same irradiation geometry when the photon energy is from 0.02 MeV to 0.05 MeV, and the maximum relative deviation is about 20%.

The influence of physique on dose conversion coefficients for idealised external photon exposures: a comparison of doses for Chinese male phantoms with 10th, 50th and 90th percentile anthropometric parameters

For evaluating radiation risk, the construction of anthropomorphic computational phantoms with a variety of physiques can help reduce the uncertainty that is due to anatomical variation. In our previous work, three deformable Chinese reference male phantoms with 10th, 50th and 90th percentile body mass indexes and body circumference physiques (DCRM-10, DCRM-50 and DCRM-90) were constructed to represent underweight, normal weight and overweight Chinese adult males, respectively. In the present study, the phantoms were updated by correcting the fat percentage to improve the precision of radiological dosimetry evaluations. The organ dose conversion coefficients for each phantom were calculated and compared for four idealized external photon exposures from 15 keV to 10 MeV, using the Monte Carlo method. The dosimetric results for the three deformable Chinese reference male phantom (DCRM) phantoms indicated that variations in physique can cause as much as a 20% difference in the organ dose conversion coefficients. When the photon energy was <50 keV, the discrepancy was greater. The irradiation geometry and organ position can also affect the difference in radiological dosimetry between individuals with different physiques. Hence, it is difficult to predict the conversion coefficients of the phantoms from the anthropometric parameters alone. Nevertheless, the complex organ conversion coefficients presented in this report will be helpful for evaluating the radiation risk for large groups of people with various physiques.

Development of Chinese reference man deformable surface phantom and its application to the influence of physique on electromagnetic dosimetry

A reference man is a theoretical individual that represents the average anatomical structure and physiological and metabolic features of a specific group of people and has been widely used in radiation safety research. With the help of an advantage in deformation, the present work proposed a Chinese reference man adult-male polygon-mesh surface phantom based on the Visible Chinese Human segment image dataset by surface rendering and deforming. To investigate the influence of physique on electromagnetic dosimetry in humans, a series of human phantoms with 10th, 50th and 90th body mass index and body circumference percentile physiques for Chinese adult males were further constructed by deforming the Chinese reference man surface phantom. All the surface phantoms were then voxelized to perform electromagnetic field simulation in a frequency range of 20 MHz to 3 GHz using the finite-difference time-domain method and evaluate the whole-body average and organ average specific absorption rate and the ratios of absorbed energy in skin, fat and muscle to the whole body. The results indicate thinner physique leads to higher WBSAR and the volume of subcutaneous fat, the penetration depth of the electromagnetic field in tissues and standing-wave occurrence may be the influence factors of physique on electromagnetic dosimetry.