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Objective:To study the healthcare level (HCL) in China and its influencing factors.Methods:By using the data reported in the China statistical yearbook published by the National Bureau of Statistics and in other public literature, HCL was calculated in terms of the number of population and physicians in the whole country and various provinces. Multiple regression was used to analyze the relationship between HCL and regional population, area, number of administrative divisions and gross domestic product (GDP). Pearson correlation analysis was applied to analyze the relationship between healthcare level and medical radiation frequency. Results:Since 2015, Chinese HCL value was lower than 1 000, but there were two provinces with HCL value greater than 1 000 in 2019. Population and GDP were the influencing factors for the HCL, with correlation coefficients of 0.416 and -0.583, respectively. There was a correlation between HCL and medical exposure frequency of Chinese population( r= -0.620, P=0.028). Conclusions:Chinese HCL value was 542 in 2020, but there has been great differences between various provinces. HCL as an indicator of medical exposure assessment needs further research in China.
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In recent years, the diagnostic radiology, especially CT scanning, has a rapidly increased frequency in our country, becoming the largest artificial radiation source to the average individual doses to the population. In clinical diagnosis and treatment activities, the examined patients and individuals may undergo multiple procedures and multiple frequencies of medical imaging in a short period of time and receive high cumulative radiation doses even exceeding 50 or 100 mSv in a single day, posing a potential risk to their health. Therefore, it is necessary to carry out statistical analysis and management of diagnostic radiation dose information to minimize the probability of excessive dose and associated radiation risk. In this paper, the international cognition of radiation risks in diagnostic radiology, diagnostic equipment and medical imaging frequency, radiation dose and its management status are described. Four countermeasures for radiation dose management are put forward to provide reference for further improving radiation protection in clinical practice.
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Radon is the second largest environmental factor inducing lung cancer after smoking. In recent years, with the deeper epidemiological investigation on radon and lung cancer and the further improvement of its methodology, new progress has been made in the research on risk assessment models. This paper reviews the relative risk models of radon-induced lung cancer developed by several international academic organizations or research teams, and briefly introduces the background information on the models and the main factors considered. Based on the indoor radon concentrations in different decades in China, the relative risks of radon-induced lung cancer were estimated and analyzed, together with some suggestions given for more accurate evaluation of lung cancer induced by indoor radon in the future.
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Objective:To construct a system for evaluating the professional capability of provincial radiological health institutions.Methods:Based on the Donabedian model and the main professional responsibilities of provincial radiological health institutions, the logical framework and indicator database of the capability evaluation system were initially constructed, the Delphi expert consultation method and analytic hierarchy process were further used to determine each indicator and its weight. The self-assessment test was carried out throughout the provincial radiological health institutions by using the system established in this study.Results:The evaluation system included 3 primary-class indicators, 11 second-class indicators, 30 third-class indicators and 76 fourth-class indicators. Taking 100 points as the full score, the self-assessment scores of the 29 provincial institutions ranged from 28.7 to 97.7 with an average of 78.7, and the scores conform to the normal distribution.Conclusions:The system established in this study are scientific, comprehensive and operable, which can be used as an effective tool to evaluate the professional capability of provincial radiological health institutions.
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Objective:To estimate the attribution share of residents′lung cancer caused by indoor Radon.Methods:Based on the 2015 lung cancer mortality, all-cause mortality from China together with nationally representative smoking rate and the average indoor radon concentration of 30 Bq/m 3, the relatively authoritative and applicable EPA/BEIR-VI risk model was used to predict the lung cancer mortality caused by indoor radon exposure. Results:The excess relative risk (ERR) of indoor radon-related lung cancer mortality among the male non-smokers is higher than that of smokers. For the age-group above 50, the male smokers and male non-smokers have the highest ERR values, which were 0.511 and 0.230, respectively. Assuming the exposure incurred starting at age 0 with the same radon concentration, the lifetime risk of men and women non-smokers is higher than that of the smokers of the same gender. The higher the radon concentration, the higher the lifetime risk of lung cancer. Assuming that the radon concentration level in China is 30 Bq/m 3, the number of deaths from indoor radon-related lung cancer in 2015 is about 55 512. According to this, about 6.62% of lung cancers are caused by indoor radon exposure. If we assume that radon concentration levels are 40 Bq/m 3and 70 Bq/m 3 in China, approximately 8.82% and 15.38% of lung cancer deaths can be attributed to indoor radon exposure. Conclusions:Indoor radon exposure is an important environmental factor that causes Chinese residential lung cancer. Effective measures should be taken to prevent and control the increasing indoor radon levels. In order to accurately assess risk of lung cancer morality caused by indoor radon, more detailed data such as the indoor radon level in China are needed.
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Objective:To simulate the effects of different thyroid-neck phantoms and monitoring positions on the detection efficiency of portable γ spectrometer, and to provide guidance for more accurate on-site measurement of 131I activity in the human thyroid. Methods:Based on the models of 4 typical thyroid-neck phantoms and a 3-inch NaI (TI) γ spectrometer used for the measurement of 131I in the thyroid and combined with the possible field monitoring scenarios, the Monte Carlo method was used to simulate and calculate the detection efficiency of the spectrometer under different conditions of monitoring distance, thyroid depth and thyroid volume. Results:The detection efficiency decreased significantly with the increase in the distance between the detector and the neck surface. The efficiency close to the neck surface was about 15 times that at 15 cm away from the neck surface. The detection efficiency decreased significantly with the increase in thyroid depth. When it was measured at the surface of the neck, the detection efficiency of thyroid at depth of 2 mm was about 3.6 times that of 30 mm. The detection efficiency decreases with the increase in thyroid volume. When it was measured at the neck surface, the detection efficiency of thyroid with 1 ml volume was 1.71 times that with 30 ml. The detection efficiency decreased with the center-point offset of the detector, especially at the neck surface, an offset of 2 cm would reduce the detection efficiency by about 15%.Conclusions:Not only the measurement distance used in calibration, but also the information of the depth and volume of thyroid in the neck-thyroid phantom, is important to know in advance for an accurate measurement of 131I activity in thyroid by using a portable gamma spectrometer.
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@#<b>Objective</b> To compare the precision and efficiency of computing the specific absorbed fraction (SAF) of a reference human with two grid methods in MCNP6.0. <b>Methods</b> Based on the adult female reference voxel phantom provided by the International Commission on Radiological Protection, assuming the liver as the source organ emitting single-energy photons (0.5 MeV), the SAF of each target organ/tissue was calculated by using the mesh method and repeated structure lattice method with the F4, F6, and *F8 tally cards in MCNP6.0. We compared the methods by assessing the relative deviation of SAF and computing time for 27 organs/tissues. <b>Results</b> Compared with reported data, the absolute values of relative deviations of SAF values for all the organs/tissues were less than 5%, except for the eye lens and skin. By using the repeated structure lattice-based *F8 tally, the relative deviations of SAF values of the organs/tissues were all smallest, but with the longest computing time. The computing time of the mesh-based F4 tally was slightly longer than that of the repeated structure lattice-based F6 tally, which was shortest. <b>Conclusion</b> The *F8 tally simultaneously simulating primary and secondary particle transport showed the highest precision. The mesh tally requireda longer computing time than the lattice tally when using the same tally card.
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@#The radiation risk caused by CT examination is of great concern. Organ dose is considered to be the most significant technical parameter for quantifying the patient radiation dose and assessing the corresponding risk. At present, the methods to obtain patient organ dose caused by CT examination mainly include physical phantom measurement, direct human body measurement, dose conversion coefficient, Monte Carlo simulation, and dose calculation software. Although different methods have their own characteristics and application, the individualization of organ dose is always the goal of radiation protection and dosimetry research. Patient-specific phantom developed with artificial intelligence and GPU-accelerated Monte Carlo simulation make it possible to calculate the patient-specific organ dose, and the patient-specific organ dose extrapolated by the CT detector signal provides a new solution.
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Objective:To estimate the organ doses and effective doses to different-age children during cardiovascular interventional radiological procedures under some specific exposure conditions, and explore the main influencing factors on the doses.Methods:Based on the paediatric reference computational phantoms recommended in the ICRP Publication 143, several specific exposure models of cardiovascular intervention were built, and the Monte Carlocook MCNPX 2.7.0, was used to calculate the organ doses and effective doses for 1-, 5-, 10- and 15-year-old children. To validate the simulation result , an experiment was implemented by putting the thermoluminescent dosimeters in a 5-y old phantom (ATOM 705-D) manufactured by the CIRS Inc. in the USA.Results:Both the height and weight of the reference children for 1-, 5- and 10-year-old provided for by Chinese national standards are nearly in consistency with those recommended by ICRP, and even for the 15-year-old, the maximum relative deviations of the height and weight are only -1.9% and -5.7%, respectively. Under the exposure condition where the focal spot to image receptor distance (SID) was 90 cm, the length of square field of view (FOV) was 30 cm with a dose area product (DAP) of 45 Gy·cm 2, the relative deviations between simulated and measured doses to main organs/tissues within the irradiation filed were within ±6.7%. Under the same exposure conditions, the younger the children, the larger the organ doses and effective doses, and the effective doses could vary by a factor of about 5 among the 4 age groups. The conversion coefficient between the organ dose and the value of DAP was not only closely related to the age of children, but also affected by the FOV. Conclusions:In combination with the paediatric reference computational phantoms and the exposure models of cardiovascular intervention, the Monte Carlo method can be used to calculate the doses to children undergoing cardiovascular interventional radiological procedures. The information on the values of DAP and FOV as well as the directions of projection are needed for more accurate estimation of the exposure doses.
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Objective:In order to make up for the gap in the digital model of twins in the study of fetal radiation dosimetry, this study intends to construct a computational twins phantom based on low-dose CT images.Methods:The low-dose CT images of a pregnant patient were segmented by the combination of threshold automatic segmentation and manual segmentation, which were derived into stereolithography files. The maternal contour, fetal contour and bone structure were constructed using 3D modeling software, and the organ mass was adjusted according to the reference values of ICRP Publication 89 and WHO report after the organs were scaled on a specific scale.Results:The first set of Non-Uniform Rational B-Splines (NURBS) surface phantom of twins in China was established. The external contours, bones, size, position and posture of the phantom were completely consistent with those of the real human body. Each fetus had 25 organs or tissues. After optimization and adjustment, the relative deviation between the twin phantom and the reference value of organ mass was less than 10%.Conclusions:In this study, a personalized computational phantom of twins based on low-dose CT images is constructed, which fills the gap in the twin model. It is helpful in estimating the dose by the fetus from ionizing radiation received in the process of radiation diagnosis of pregnant women with twins.
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Objective:The Chinese pediatric mesh-type reference phantoms were developed and applied in the dose assessment of X-ray radiography.Methods:The 5- and 10-year-old Chinese pediatric mesh-type reference phantoms were developed based on the CT data. Based on the phantoms, the Monte Carlo method was applied to simulate the X-ray radiography to calculate the organ dose conversion coefficient and the effective dose conversion coefficient in different radiography conditions.Results:The 5- and 10-year-old Chinese pediatric mesh-type reference phantoms were developed, and the physical parameters were consistent with the national standard. The differences of the organ mass between the established phantoms and reference data were within 2%. The database of the pediatric chest posteroanterior projection and abdominal anteroposterior projection, tube voltage 60-90 kVp, total filtration 2.5~4 mmAl were simulated, and the difference between the effective dose conversion factor and the literature result was within 3%.Conclusions:The established Chinese pediatric mesh-type reference phantoms can be applied in the studies of radiation protection and clinical medicine and their result can provide an important reference for the dose assessment of the pediatric X-ray radiography.
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Objective:To explore the method for estimating the energy and angle of incident protons based on the nuclear track morphology on CR-39.Methods:The CR-39 was irradiated with different energies and angles of incident protons and the morphology of nuclear tracks was scanned and read out by both the atomic force microscope and optical microscope after chemical etching. Through out quantitative analyses of the two-dimensional morphology of the nuclear tracks, an attempt was made to establish the method for estimating the energy and angle of incident particles.Results:As the increase of incident proton energy, the nuclear track became smaller and shallower. In the case of vertical incidence, the track opening was close to a circle. As the incident angle increases, the track opening gradually changed into an ellipse shape. The diameter of the circular nuclear track and the minor axis or the equivalent diameter of the elliptical nuclear track both decrease exponentially ( E= Ae - Bx) with the increase of the incident energy of protons. The fitting coefficients A and B were 15.763 and 0.305, and 15.886 and 0.320 by using the diameter/equivalent diameter and the minor axis of tracks. There also existed a relatively fixed quantitative relationship between the angle of the incident particle and the ratios of the major and minor axes of the elliptical nuclear track. For protons incident at 10° and 20°, the average ratios of the major and minor axes of the nuclear track were 1.10-1.15 and 1.35-1.37, respectively. Conclusions:Based on the diameter or minor axis of the nuclear track formed on CR-39, the energy of incident particles can be estimated, and the angle of incident particles can also be estimated by using the ratio of the major and minor axes of the nuclear track.
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Objective To investigate the feasibility and plan quality of the image-guided volumetric modulated arc therapy (VMAT) based voluntary deep exhale breath-holding technique in the stereotactic ablative body radiotherapy (SABR) for liver tumors.Methods Fifteen patients with liver tumors were involved in this study.All patients were immobilized with voluntary deep exhale breath hold (vDEBH) combined with real-time position management (RPM) respiratory gating system.Treatment was planned using VMAT with 2 modified partial arc and re-planned using intensity modulated radiation therapy (IMRT) technique for comparison.Dosimetric parameters were calculated for plan quality assessment.Quality assurance studies included absolute dose and multiple planar dose verifications,total monitor units and delivery time analysis.Daily cone beam computed tomography imaging was used to verify the motions.Results There were no significant dosimetric differences between VMAT and conventional IMRT plans (P ＞0.05).Both techniques were able to minimize doses to organs at risk including normal liver,kidneys,spinal cord,and stomach.However,the average monitor units with VMAT were significantly lower 28.1％ than those with IMRT(t =3.064,P ＜0.05).The average beam-on time in VMAT plans was 31.6％ shorter than that in IMRT plans(t =2.278,P ＜ 0.05).Conclusions The utilization of VMAT in the treatment planning of SABR for liver tumors under breath control mode has better dosimetrics.In comparison to conventional IMRT plans,VMAT plans have higher efficiency and feasibility.
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Objective To analyze the radiation dose to contra-lateral breasts and estimate the incidence risk of contra-lateral breast cancer for women undergone unilateral breast cancer radiotherapy.Methods The radiation doses of contra-lateral breasts for 49 patients were counted and analyzed in a hospital,and the risk of contra-lateral breast cancer in different age groups that induced by radiotherapy was estimated based on BEIR Ⅶ model combined with the Chinese lifetime table.Results The prescribed doses for the patients were all 50 Gy.The mean dose to contra-lateral breasts ranged from 0.14 Gy to 3.59 Gy,with an average of (1.21 ±0.89) Gy,and the maximum point dose varied from 0.98 Gy to 45.27 Gy,with the average of (17.42 ±13.20) Gy.Both the maximum point dose and the mean dose obviously varied among the patients,and their correlation was significant (R =0.527,P =0.000).Furthermore,no significant differences of the mean dose was found among the ages (P ＞ 0.05).The lifetime attribute risks of contra-lateral breast cancer were estimated to be 2 449,1 857,994,446,173 and 55 for per 100 thousand women corresponding to the ages of 35,40,50,60,70 and 80,respectively.Conclusions In the radiotherapy for unilateral breast cancer,the dose delivered to the contra-lateral breast is about 1 Gy order of magnitude,the risk of contra-lateral breast cancer cannot be ignored for young women.Therefore,the irradiation dose of contra-lateral breasts should be controlled as less as possible in planning the treatment.
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Objective To evaluate the influence of indoor air filtration by air purifier on the behavior of indoor radon progeny and estimate its effects on indoor radon exposure to residents.Methods The concentrations of indoor radon progeny with and without the air filtration were calculated by the theoretical model developed in this study.Based on the dose conversion factors of attached and unattached radon progeny,the mitigation effects of indoor radon exposure due to the air filtration were estimated.Verification experiments were conducted in an airtight room.Results With the air filtration rate increased,the removal efficiency of indoor radon progeny would appear more obvious.For an airtight room with its initial aerosol concentration of 10 000 cm-3,the concentration of total radon progeny would decrease by more than 90％ when the air filtration rate exceeded 10 h-1.But the concentrations of indoor unattached radon progeny would increase by using the air purifier in different extents.The variations of radon progeny concentrations and the decrease of internal doses were closely related to the filtration rate of air purifier.With the air filtration rates increased,the mitigation effects would be better and faster.The internal dose would reduce by more than 70％ when the filtration rate exceeded 5 h-1.Conclusions Although the indoor concentration of unattached radon progeny will increase by using the air purifier,it is still effective in reducing the exposure dose to residents due to the inhalation of radon progeny.
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Objective To compare patient organ doses and entrance surface dose conversion coefficients in conventional radiography using medical internal radiation dose (MIRD) phantom and voxel human phantom.Methods The voxel phantom was adapted to the Monte Carlo transport code to simulate the organ doses and entrance surface dose in five common projections, and thus the dose conversion coefficients between the entrance skin dose and organ dose were calculated.The results were compared with the reported mean values which were simulated using MIRD phantom.Results The dose conversion coefficients values of organs covered or partially covered by the X-ray field ranged from 0.149-0.650 in chest postero-anterior projection, 0.067-0.382 in chest left lateral projection, 0.023-0.374 in chest right lateral projection, 0.035-0.431 in abdominal antero-posterior projection, 0.083-0.432 in lumbar spine antero-posterior projection.In chest postero-anterior projection, significant differences were most obviously observed in lung, the dose conversion coefficients difference was 54.3％.In chest left lateral projection, the dose conversion coefficients difference of liver was greatest, which was 54.5％.In chest right lateral projection, the dose conversion coefficients differences of stomach wall was most obviously 63.8％.In abdominal antero-posterior projection, dose conversion coefficients discrepancy was most obviously observed in spleen, with the value of 65.0％;while in lumbar spine antero-posterior projection, the dose conversion coefficients differences of stomach wall was most obviously 43.7％.Conclusions Compared with the stylized MIRD phantoms, the anatomical realism in voxel phantom is evident.Therefore, the dose conversion coefficients calculated by voxel phantoms are more accurate and scientific in conventional radiology.
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Objective To establish an accurate method for estimating the indoor gamma dose rate from decorative stones.Methods Combining a room model with decorating conditions,the gamma dose rates and dose rate conversion factors (DCF) at 1 m above the floor in the room center were calculated with the Monte Carlo simulations,and the calculation results were verified through experiments.Based on the results,the limit of radionuclide contents in stone materials was further discussed.Results The DCF increases with the increase of area or thickness of decorative stones in the same room.The increase of DCF with the thickness of decorative stone is approximately linear.The DCF also increases with the area of decorative stones,but the increasing trend slows down.For the same decorative stones,the smaller the room,the larger the increase of gamma dose rate.Experimental results were consistent with the simulation results within ± 20％.Conclusions The increase of indoor gamma dose rate depends not only on the radionuclide contents,but also on the area and thickness of the decorative stones as well as the room size.The method used in this study can be used to estimate,more accurately than ever,the additional external exposure to residents due to decorative stones,and it provides a theoretical basis for revising the limit standard on radionuclide contents in decorative materials.
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Objective To investigate the methods and effects of abdominal and pelvic shielding for pediatric chest CT examinations.Methods The 705-D phantom made by Computerized Imaging Reference Systems (CIRS) was used to replace a 5-year-old child,thermoluminescent dosimeters were set in the abdomen and pelvis to measure the organ and tissue doses.Chest scans were conducted with the routine protocol for pediatric chest CT examinations.Doses to main organs and tissues in the abdomen and pelvis were measured after chest CT scans without lead apron,with lead apron covering anterior of the abdomen and pelvis and with apron wrapping same part,respectively.Results Absorbed doses to some abdominal organs near the irradiation field were up to several mGy in a procedure of pediatric chest CT examination.There were statistically significant differences among the dose values for three different scans at the same location (x2 =16.00,P ＜ 0.05).Statistically significant difference was also found between the dose values for scans,which were measured with wrapping and covering approaches (Z =-2.52,P ＜ 0.05).Compared to the doses in the condition of no shielding,the doses in testis and colon reduced by 71.2％ and 42.3％,respectively,if the abdomen and pelvis was wrapped with a lead apron (0.35 mm Pb),and reduced by 55.9％ and 26.1％,respectively,if the same lead apron was used to cover the anterior of the abdomen and pelvis.Conclusions In pediatric chest CT examinations,the use of a lead apron can effectively shield the abdomen and pelvis,and plays an important role in protection of the gonad and colon.The wrapping measure is worth being recommended.
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Objective To study the shielding effect of equivalent thickness and size of lead glasses on eye lens of interventional radiologists.Methods Based on the human voxel phantom and MCNPX software,doses to eye lens of radiologists were simulated under different conditions of wearing lead glasses and beam projections,and measurements were performed with anthropomorphic phantom placed with eye lens dosimeters to verify simulation results.Results The results showed that the dose to eye lens reduced by a factor from 3 to 9 when the equivalent thickness of glasses ranged from 0.1 to 1.0 mm Pb with a len size of 20 cm2.The dose reduction factors (DRF) not only depended on the lead equivalent,but also on the beam projection of X-rays.However,the increase in DRF was not significant whenever the lead equivalent of glasses was larger than 0.35 mm.Furthermore,the DRF was proportional to the size of glass lens from 6 to 30 cm2 with the same lead equivalent.The simulation results were in well agreement with the measured ones.Conclusions For more reasonable and effective protection of the eye lens of interventional radiologists,a pair of glasses with a lead equivalent of 0.5 mm and large-sized lens is recommended.
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Objective To study the relationship between the dose indicator of computed radiography (CR) and the entrance surface dose (ESD),and to build a model for estimating ESD based on this relationship.Methods Taking Kodak CR system as the research object,a theoretical model for estimating the ESD was established according to theoretical derivations,and the key parameters in the model were determined through experiments in a CR system.Further experiments in another CR system were also conducted to verify the model.Results The ESDs were not only dependent on the dose indicator provided by the CR system,but also influenced by other factors,such as tube potential,patient's body thickness and energy response of the imaging plate.The estimation results of the model agreed well with the experiment results,and the relative deviation was confirmed within 20％.Conclusions The dose indicator based model can provide a relatively fast and easy way for evaluating the doses of patients undergoing X-ray diagnoses with the CR system.