Objective The three-dimensional finite element model of the normal ankle joint was established to simulate the changes of stress and displacement under stress from different directions and of different magnitudes so as to provide a theoretical basis for the biomechanical mechanism of the ankle joint injury.Methods Spiral CT scan was performed on the left ankle of a 30 year old healthy male volunteer to obtain the original CT image data.The three-dimensional digital model of ankle joint generated by Mimics and Geomagic softwares was imported into the software Ansys.The three-dimensional finite element model of ankle joint with complete anatomical structure was obtained after the main steps of meshing,central node,element linking and module loading using finite element method.Stress from different directions and of different magnitudes were loaded unto the model.The stress changes were measured by foot stress distribution measurement system.The stress changes,displacement change distribution,the stress peak value of heel are,metatarsal stress,and plantar contact stress area as well as the maximum,minimum,and contact are of the tibial articular surface contact stress were compared between the finite element model and the volunteer himself to verify the consistency.Results For the finite element model of normal ankle joint,the plantar peak stress was [(0.33 ± 0.10) MPa],the metatarsal stress was [(0.13 ± 0.21)MPa],the foot contact stress area was [(78.60 ±0.32)mm2],the tibial articular surface maximum contact stress was [(2.72 ± 0.10) MPa],the minimum contact stress was [(1.35 ±0.12)MPa],and the contact stress area was [(79.1 ± 0.14)mm2].For the volunteer,double foot plantar peak stress was [(0.35 ± 0.12)MPa],the metatarsal stress [(0.13 ±0.16)MPa],the foot contact stress area was [(77.3 ± 0.42)mm2],the tibial articular surface maximum contact stress was [(2.79 ± 0.23) MPa],the minimum contact stress was [(1.37 ± 0.20) MPa],and the contact stress area was [(79.10 ±0.14)mm2] (P ＜0.05).Therefore,the three finite element model of ankle joint was basically consistent with the real human ankle joint because of the similiar distribution,trend,and values.Conclusion The three-dimensional finite element model of normal ankle joint can objectively reflect the anatomical structure and biomechanical characteristics of the joint,which is of great value to understand the changes of the internal mechanics and ankle joint injury.

Objective:To asscentain the 131I activity concentration in 131I treatment workplaces and to explore the method of estimating the internal dose to workers by air sampling and to analyze its influencing factors. Methods:Air sampling method was used to collect aerosols containing radioactivity in 10 randomly selected workplaces in Zhengzhou where 131I therapy was performed. Aactivity concentration of 131I in treatment workplace was measured for gamma emitters by gamma-ray spectrometry. The internal dose due to 131I inhalation was estimated based on measurement result and field investigation result. Results:The activity concentration of 131I in air samples from 19 subpacking rooms ranged from 0.087 to 570 Bq/m 3, with an average of (51.04 ± 128.58) Bq/m 3. Those from 11 wards ranged from 0.162 to 54.6 Bq/m 3, with an average of (7.97 ± 15.89) Bq/m 3. In terms of the work hours recommended by the national standard GBZ 129-2016 Specifications for individual monitoring of occupational internal exposure, the estimated annual effective dose to radiation workers due to the inhalation of 131I ranges from 0.002 to 10 mSv, with an average of (0.61 ± 1.80) mSv, below the dose limit specified in the national standards. Conclusions:The samples with high 131I activity concentration in nuclear medicine workplaces of 10 medical institutions selected in Zhengzhou are mostly distributed in tertiary class hospitals operating large amount of radionuclide with large numbers of thyroid cancer patients adimitted. The result ing internal dose to radiation workers cannot be ignored. Estimating the internal dose based on the measurement result of air samples has a large uncertainty.However, air sampling method can promptly detect radioactive contamination in case of abnormal events or accidents, providing early warning for workers to carry out dose measurement from external exposure and internal exposure assessment.