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@#With the utilization of more types of radiation with a wider energy range, the application scope of the currently valid operational quantities is limited due to some conceptual defects, so a new group of operational quantities was proposed recently by the International Commission on Radiation Units and Measurements. The unification of protection quantities and operational ones is achieved in conceptual and physical sense. However, to achieve the comprehensive application of these new operational quantities in China, such preliminary work should be done as computational model construction and built-in of a calibration system in monitoring equipment, which depends on the collaborative development of multi-parties.
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@#<b>Objective</b> To investigate the dose level of pediatric CT scan in one hospital, and to provide recommendations for optimized scanning. <b>Methods</b> The CT scan data of children were collected from this hospital to analyze the differences in typical dose values and typical scanning parameters between different age groups and different scanning parts. <b>Results</b> The sample size was >10 for routine cranial scan, routine maxillary sinus scan, and routine chest scan in each age group, and the 1-year-old group and the 5-year-old group had the same kV, mA, and CTDIvol values of routine cranial scan and maxillary sinus scan, but with relatively great differences in the parameters of chest scan. <b>Conclusion</b> Scanning parameters in this hospital can be further optimized, and optimization measures should be adopted continuously.
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Objective To analyze the room layout and shielding of three types of self-shielded accelerators, and to provide a basis for optimizing the shielding design of rooms for self-shielded accelerators. Methods We compared the radiation shielding levels (transmitted radiation dose rate outside the primary barrier and scattered radiation dose rate outside the secondary barrier) of three self-shielded accelerator rooms by Monte Carlo simulation and empirical formula calculation. Results According to Monte Carlo simulation and empirical formula calculation, for the Unity MR Linac accelerator, the scatter radiation dose rate outside the secondary barrier was significantly higher (up to five times) than the transmitted primary radiation dose rate outside the primary barrier. The scatter radiation dose rate of the cross section was significantly higher than that of the sagittal section for both Unity MR Linac and TOMO accelerators. Conclusion The differences in the shape, material, and thickness of self-shielding structures complicate the shielding calculation and design for accelerator rooms. The shielding calculation method should be improved to optimize the radiation shielding of novel accelerator rooms.
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@#<b>Objective</b> To discuss the shielding calculation method for proton therapy room, and to provide a scientific basis for shielding design of proton therapy room and improvement of existing national standards. <b>Methods</b> Using the calculation formula and key characteristic parameters from national standards and Chinese and foreign literature, combining with the FLUKA Monte Carlo method, empirical formula calculation and Monte Carlo simulation were conducted for the neutron ambient dose equivalent rates of the focuses outside the shielding of proton therapy room. The estimation results of the two methods were analyzed. <b>Results</b> Relative to the calculation results of the single exponential formula in the two directions of 0° and 50° in the beam loss point of divergence slit (0.13 and 12.4), the calculation results of the double exponential formula (0.40 and 17.9) were more consistent with the Monte Carlo simulation results (0.32 ± 0.19 and 18.2 ± 4.98). The Monte Carlo simulation results of copper target and nickel target were similar, suggesting that the key characteristic parameters of concrete shielding for copper target could be well applied to the calculation of nickel target, but the neutron ambient dose equivalent rates were underestimated when applied to tantalum target, with a difference of 5.7 times and 1.3 times in the two directions of 0° and 40°, respectively. <b>Conclusion</b> The dose rate estimates based on the calculation formula and key characteristic parameters from Chinese and foreign literature are consistent with FLUKA simulation results, and this method can be used in the shielding design of proton therapy room as a supplement and improvement to the existing national standards.
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Objective To observe the osteogenic and/or chondrogenic differentiation potential of cartilage endplate derived stem cells ( CESCs) .Methods The cartilage endplate ( CEP) was obtained from 5 patients who underwent posterior discectomy procedure for the lumber degenerative disease.The agarose culture was used to select CESCs.The expanded CESCs were injected into the hydroxyapatite ceram-ic(HA) and incubated for 7 days.After that,the HA contained CESCs were implanted into the subcutaneous of nude mouse for 7 weeks.Then the HA was obtained and sliced for the specific stain and immunohistochemisty.The expanded CESCs were injected into the degenerated in-tervertebral disk of the rabbit for 16 weeks.Then MRI was used to detect the repair of the degenerated disc.Results The metachromasia of toluidin blue indicated that cartilage matrix was formed in the vacant space of HA.Mallory stain indicated that there was bone matrix was formed.The results of immunohistochemistry indicated that there was more collageⅠand collageⅩ,and a small quantity of collage Ⅱ.MRI results indicated that the CESCs could be induced into the chondrocyte-like cells in the rabbit intervertebral disk.Conclusion The CESCs could be induced into the bone/cartilage in vivo.
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Objective To analyze the influence of ionizing radiation on the lymphocytes and its regulatory T cells in mice.Methods Mice were administered with whole body irradiation of γ-rays at different doses,and lymphocytes were separated from thymus and spleen,then the number of total cells were counted and the percentages of CD4 + T and CD4 + FOXP3 + CD25 + Treg lymphocytes were analyzed by using FACS.Results The lymphocyte numbers in thymus and spleen decreased in dosedependent manner and reached to the minimum at 4 d after irradiation (F =118.08,144.01,P ＜ 0.05).Exposure to higher dose(more than 1 Gy) decreased Treg number time-dependently in thymus,however increased it in spleen.On the contrary,exposure to lower dose (less than 0.75 Gy) increased Treg number in thymus.Besides,the percentage of Treg cells increased dose-dependently(in thymus,F =5.16,89.44,3.01,P ＜ 0.05 ; in spleen,F =52.02,32.13,27.45,P ＜ 0.05).Conclusions The radiation responses of lymphocytes and their Treg subpopulation vary with the different doses.Treg cells are resistant to high dose irradiation,however,their differentiation could be induced by low dose irradiation.In addition,the different time-dependent responses of lymphocytes and their subpopulation to ionizing radiation indicate the difference of lymphocyte maturation,differentiation and emigration.
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Objective To analyze the influence of ionizing radiation on the viability of the regulatory T cells and the relationship between the expression of CD39 and apoptosis related factors in mice Treg cells.Methods Mice were administered to whole body irradiation with 2 Gy of γ-rays,then lymphocytes were separated from thymus and spleen.The percentages of CD4 + T and CD4 + FOXP3 +CD25 + Treg lymphocytes,apoptosis related genes of Bax,Bcl-2 and CD39 were analyzed with FACS.Results Treg cells had a higher survival fraction than CD4 + FOXP3-Tcon cells after irradiation,and the time-responses of Treg cells in thymus and spleen were different.The apoptosis rate of Treg cells increased at 4 d after irradiation(t =-3.6,-7.4,P ＜0.05).The Bax/Bcl-2 ratio and the CD39 expression were increased in thymus Treg cells (t =-3.4,-6.6,P ＜ 0.05),but decreased in spleen Treg cells (t =2.4,2.6,P ＜0.05).Conclusions Thechanges of apoptosis and Bax/Bcl-2 are in consistent with the expression of CD39 in the irradiated Treg cells.