Radiotherapy is the most widely applied oncologic treatment modality utilizing ionizing radiation. A high degree of accuracy, reliability and reproducibility is required for a successful treatment outcome. Measurement...Radiotherapy is the most widely applied oncologic treatment modality utilizing ionizing radiation. A high degree of accuracy, reliability and reproducibility is required for a successful treatment outcome. Measurement using ionization chamber is a prerequisite for absorbed dose determination for external beam radiotherapy. Calibration coefficient is expressed in terms of air kerma and absorbed dose to water traceable to Secondary Standards Dosimetry Laboratory. The objective of this work was to evaluate the level of accuracy of ionization chamber used for clinical radiotherapy beam determination. Measurement and accuracy determination were carried out according to IAEA TRS 398 protocol. Clinical farmers type ionization chamber measurement and National Reference standard from Secondary Standards Dosimetry Laboratory were both exposed to cobalt-60 beam and measurement results compared under the same environmental conditions. The accuracy level between National Reference Standard and clinical radiotherapy standard was found to be −1.92% and −2.02% for air kerma and absorbed dose to water respectively. To minimize the effect of error and maximize therapeutic dose during treatment in order to achieve required clinical outcome, calibration factor was determined for air kerma (Nk) as 49.7 mGy/nC and absorbed dose to water ND, as 52.9 mGy/nC. The study established that radiotherapy beam measurement chain is prone to errors. Hence there is a need to independently verify the accuracy of radiation dose to ensure precision of dose delivery. The errors must be accounted for during clinical planning by factoring in calibration factor to minimize the systematic errors during treatment, and thereby providing enough room to achieve ±5% dose delivery to tumor target as recommended by ICRU.展开更多
In this paper,fast neutron inactivation effects of Bacillus subtilis were investigated with fission fast neutrons from CFBR-Ⅱreactor of INPC(Institute of Nuclear Physics and Chemistry)and mono-energetic neutrons from...In this paper,fast neutron inactivation effects of Bacillus subtilis were investigated with fission fast neutrons from CFBR-Ⅱreactor of INPC(Institute of Nuclear Physics and Chemistry)and mono-energetic neutrons from the Van de Graaff accelerator at Peking University.The method for determining the absorbed dose in the Bacillus subtilis suspension contained in test tubes is introduced.The absorbed dose,on account of its dependence on the volume and the form of confined state,was determined by combined experiments and Monte Carlo method.Using the calculation results of absorbed dose,the fast neutron inactivation effects on Bacillus subtilis were studied.The survival rates and absorbed dose curve was constructed.展开更多
As children are prone to be more radiosensitive than adults, it is imperative to assess the Entrance Skin Doses (ESDs) for patients being examined by X-rays, in order to ensure the optimization of dose while consideri...As children are prone to be more radiosensitive than adults, it is imperative to assess the Entrance Skin Doses (ESDs) for patients being examined by X-rays, in order to ensure the optimization of dose while considering a number of other fickles. The ESD received by 50 paediatrics (aged 1-13 years) undergoing 8 types of X-ray examinations were measured at Federal Teaching Hospital, Ido-Ekiti, Ekiti, Nigeria, within a period of February 2019 to March 2020 using thermoluminescent dosimeters. The mean ± SD of ESDs were 0.85 ± 0.32, 2.04 ± 0.75, 0.60 ± 0.07, 0.62 ± 0.22, 0.57 ± 0.24, 1.75 ± 0.76, 0.93 ± 0.31 and 0.63 ± 0.06 mGy for Chest, Skull, Hand, Forearm, Knee, Abdomen, Leg and Feet, respectively. The mean ESDs were found to be within the recommended reference dose in all examinations, except for the Chest examination which was higher. The data obtained in this study will serve as existing data in Nigeria for future research works, as it would assist in optimizing dose to patients, especially the paediatrics.展开更多
X-ray excited photodynamic therapy(X-PDT)is the bravo answer of photodynamic therapy(PDT)for deep-seated tumors,as it employs X-ray as the irradiation source to overcome the limitation of light penetration depth.Howev...X-ray excited photodynamic therapy(X-PDT)is the bravo answer of photodynamic therapy(PDT)for deep-seated tumors,as it employs X-ray as the irradiation source to overcome the limitation of light penetration depth.However,high X-ray irradiation dose caused organ lesions and side effects became the major barrier to X-PDT application.To address this issue,this work employed a classic-al co-precipitation reaction to synthesize NaLuF_(4):15%Tb^(3+)(NLF)with an average particle size of(23.48±0.91)nm,which was then coupled with the photosensitizer merocyanine 540(MC540)to form the X-PDT system NLF-MC540 with high production of singlet oxygen.The system could induce antitumor efficacy to about 24%in relative low dose X-ray irradiation range(0.1-0.3 Gy).In vivo,when NLF-MC540 irradiated by 0.1 Gy X-ray,the tumor inhibition percentage reached 89.5%±5.7%.The therapeutic mechanism of low dose X-PDT was found.A significant increase of neutrophils in serum was found on the third day after X-PDT.By immunohistochemical staining of tumor sections,the Ly6G^(+),CD8^(+),and CD11c^(+)cells infiltrated in the tumor microenvironment were studied.Utilizing the bilat-eral tumor model,the NLF-MC540 with 0.1 Gy X-ray irradiation could inhibit both the primary tumor and the distant tumor growth.De-tected by enzyme linked immunosorbent assay(ELISA),two cytokines IFN-γand TNF-αin serum were upregulated 7 and 6 times than negative control,respectively.Detected by enzyme linked immune spot assay(ELISPOT),the number of immune cells attributable to the IFN-γand TNF-αlevels in the group of low dose X-PDT were 14 and 6 times greater than that in the negative control group,respectively.Thus,it conclude that low dose X-PDT system could successfully upregulate the levels of immune cells,stimulate the secretion of cy-tokines(especially IFN-γand TNF-α),activate antitumor immunity,and finally inhibit colon tumor growth.展开更多
The effect of the size of radiotherapy photon beams on the absorbed dose to an Al2O3 dosimeter was investigated using the Monte Carlo method. The EGSnrc/DOSRZnrc program code was used to simulate the absorbed dose to ...The effect of the size of radiotherapy photon beams on the absorbed dose to an Al2O3 dosimeter was investigated using the Monte Carlo method. The EGSnrc/DOSRZnrc program code was used to simulate the absorbed dose to the Al2O3 dosimeter, as well as the absorbed dose to water at the corresponding position in the absence of the dosimeter. The incident beams were 60Co γ and 6 MV with a different beam radius ranging from 0.1 cm to 2 cm. Results revealed that the absorbed dose ratio factor depends on the size of the incident photon beam. When the radius of the incident beam is smaller than that of the dosimeter, the absorbed dose ratio factor decreases as the incident beam size increases. The absorbed dose ratio factor reaches its minimum when the radius of the incident beam is almost the same as that of the dosimeter. When the radius of the incident beam is larger than that of the dosimeter, the absorbed dose ratio factor increases as the incident beam size increases. The maximum difference among these absorbed dose ratio factors can be up to 14% in 60Co γ beams and 23% in 6 MV beams. However, when the size of the incident beam is much larger than that of the dosimeter, the effect of the incident beam size on the absorbed dose ratio factor becomes quite small. The maximum discrepancy between the absorbed dose ratio factors and the average value is not more than 1%.展开更多
The methods of determining the superficial absorbed dose distributions in a water phantom by means of the experiments and available theories have been reported. The distributions of beta dose were measured by an extra...The methods of determining the superficial absorbed dose distributions in a water phantom by means of the experiments and available theories have been reported. The distributions of beta dose were measured by an extrapolation ionization chamber at definite depthes corresponding to some superficial organs and tissues such as the radiosensitive layer of the skin, cornea, sclera, anterior chamber and lens of eyeball.The ratios among superficial absorbed dose D (0.07) and average absorbed doses at the depthes 1,2,3,4,5 and 6 mm are also obtained with Cross's methods. They can be used for confining the deterministic effects of some superficial tissues and organs such as the skin and the components of eyeball for weakly penetrating radiations.展开更多
Ensuring reliability and traceability of the unit of absorbed dose of intense photon and electron radiation, used in radiation technologies in industry, is based on the creation of a system of sample measures and meth...Ensuring reliability and traceability of the unit of absorbed dose of intense photon and electron radiation, used in radiation technologies in industry, is based on the creation of a system of sample measures and methods of transmission with minimal loss of dimensional accuracy of the unit of absorbed dose from the sample tools to working dosimeters and is a necessary basis of yield growth, of increase of labour productivity and the introduction of innovative products. The measuring capabilities of the State primary special standard of power unit of absorbed dose of intensity photon, electron and beta radiation for radiation technologies and of the standards of the absorbed dose of photon and electron radiation, used for radiation monitoring of radiation pro- cesses.展开更多
Cancer is a major societal public health and economic problem, responsible for one in every six deaths. Radiotherapy is the main technique of treatment for more than half of cancer patients. To achieve a successful ou...Cancer is a major societal public health and economic problem, responsible for one in every six deaths. Radiotherapy is the main technique of treatment for more than half of cancer patients. To achieve a successful outcome, the radiation dose must be delivered accurately and precisely to the tumor, within ± 5% accuracy. Smaller uncertainties are required for better treatment outcome. The objective of the study is to investigate the uncertainty of measurement of external radiotherapy beam using a standard ionization chamber under reference conditions. Clinical farmers type ionization chamber measurement was compared against the National Reference standard, by exposing it in a beam 60Co gamma source. The measurement set up was carried out according to IAEA TRS 498 protocol and uncertainty of measurement evaluated according to GUM TEDDOC-1585. Evaluation and analysis were done for the identified subjects of uncertainty contributors. The expanded uncertainty associated with 56 mGy/nC ND,W was found to be 0.9% corresponding to a confidence level of approximately 95% with a coverage factor of k = 2. The study established the impact of dosimetry uncertainty of measurement in estimating external radiotherapy dose. The investigation established that the largest contributor of uncertainty is the stability of the ionization chamber at 36%, followed by temperature at 22% and positioning of the chamber in the beam at 8%. The effect of pressure, electrometer, resolution, and reproducibility were found to be minimal to the overall uncertainty. The study indicate that there is no flawless measurement, as there are many prospective sources of variation. Measurement results have component of unreliability and should be regarded as best estimates of the true value. .展开更多
This work investigated the absorbed dose to water rate under reference conditions in a Cyberknife VSI system using radiochromic films EBT3 and MD-V3 and three ionization chambers: an Exradin A12 and two FC65P Welh&...This work investigated the absorbed dose to water rate under reference conditions in a Cyberknife VSI system using radiochromic films EBT3 and MD-V3 and three ionization chambers: an Exradin A12 and two FC65P Welhöfer Scanditronix with different serial numbers. The correction factor,, was studied using a Varian iX linac and the Cyberknife system. The measurements in the Varian iX were performed in a 10 × 10 cm2 field, 10 cm depth in liquid water at 90 cm and 70 cm SSD and in a 5.4 × 5.4 cm2 field, 10 cm depth at 70 cm SSD to simulate the Cyberknife conditions. In the Cyberknife system, measurements were performed using ionization chambers and both film types at 70 cm SSD and 10 cm depth in its 6 cm diameter reference field. The results indicate that ?is independent of the dosimeters and the evaluation methods. Maximum differences of 0.22% - 0.55% (combined uncertainties of 1.22% - 1.98%, k = 1) are obtained on ?using Varian iX, whereas discrepancies of 2.08% - 2.09% (combined uncertainties of 1.87% - 2.13%, k = 1) are observed using the Cyberknife system. Given the agreement between detectors and the combined standard uncertainties, the data from Varian iX could be considered the most accurate and consequently a weighted average factor of 0.902 ± 0.006 could be used for the Cyberknife VSI system reference field. Within measurement uncertainties, the absorbed dose rate measured in the Cyberknife VSI system reference field was found to be independent of the dosimeters used. These results suggest that the absorbed dose measured at a point within a given field size should be the same, regardless the dosimeter used, if their dosimetric characteristics are well known. This highlighted the importance of performing dosimetry by controlling all parameters that could affect the dosimeter response. One can conclude that radiochromic film dosimetry can be considered as an appropriate alternative for measuring absorbed dose to water rate.展开更多
Since the early times, radioprotection has been focused on the human being. Currently this approach has changed, being now also necessary to take care of the protection of the environment from unwanted effects of ioni...Since the early times, radioprotection has been focused on the human being. Currently this approach has changed, being now also necessary to take care of the protection of the environment from unwanted effects of ionizing radiation. To this end, several institutions (UNSCEAR, ICRP, IAEA, DOE, ACRP) and consortia of institutions (FASSET, ERICA) have established procedures in order to protect the biota of such effects. Developed procedures are based on the calculation of the absorbed dose in biota (ICRP, DOE, IAEA), or on environmental risk assessment―ERA (DOE, ACRP, FASSET, ERICA);but even in this latter approach the parameters used are related to the absorbed doses in biota. The calculation of dose is the standard procedure in human radioprotection, and this points such an approach as the most interesting for providing a convergence between human and nonhuman (= biota) radioprotections. On the other hand, the ERA approach is easier to apply, because this methodology is used in several countries for non-radioactive contamination assessments. Since the world radioprotection system follows a number of institutions (UNSCEAR, ICRP, IAEA and regulatory institutions of member countries) that use dose calculation, this appears to be the way for biota radioprotection. We here review and comment the evolution of the concepts and approaches of the recommendations for radioprotection of non-human biota.展开更多
Perovskite-type complex oxides ABO3 （A=Sr, La; B=Mn, Fe, Co） were prepared by citric acid method. The degradation of water-solubilized dyes was carried out using the mixed oxides as photocatalyst. The surface absorb...Perovskite-type complex oxides ABO3 （A=Sr, La; B=Mn, Fe, Co） were prepared by citric acid method. The degradation of water-solubilized dyes was carried out using the mixed oxides as photocatalyst. The surface absorbed oxygen was analyzed using X-ray photoelectron spectroscopy （XPS）. The results indicated that there was a relationship between the photocatalytic activity and the content of the surface absorbed oxygen. The higher the content of the surface absorbed oxygen was, the better the performance of the photocatalyst.展开更多
Objective: The current research study aims to calculate entrance surface air kerma for skull, chest, cervical spine, lumbar spine, and pelvic X-ray examinations in interior posterior and posterior interior positions a...Objective: The current research study aims to calculate entrance surface air kerma for skull, chest, cervical spine, lumbar spine, and pelvic X-ray examinations in interior posterior and posterior interior positions and generate a method for chest dose reduction to decrease radiation risk. Materials and Methods: The indirect dose measurement was used in the current research. The X-ray tube output was measured using RAD-CHECK Plus ionization chamber and the indirect entrance surface air kerma was calculated via applying physical acquisition parameters such as a focus on skin distance, tube current times exposure time (mAs), and applied tube voltage (kV), and applying a mathematical model. Results: The main findings were obtained from comparing the radiation doses with the reference levels of International organizations such as the American College of Radiology and the International Atomic Energy Authority. The mean entrance skin dose for the skull (AP), skull (PA), skull (LAT), cervical spine (PA), cervical spine (LAT), lumbar spine (AP), lumbar spine (LAT), pelvis (AP), and pelvis (LAT) of adult X-ray examinations was within the diagnostic reference dose level values obtained by ACR (2018) except for the ESD for chest (AP) which was 0.88 mGy. Conclusions: The results of the study concluded that by adjusting the applied tube voltage, kV, and tube current product time, mAs decreased the radiation dose to the chest X-ray by 58%.展开更多
目前国内大多数放射治疗剂量只能溯源到^(60)Co γ射线空气比释动能,与溯源至空气比释动能相比,将放射治疗剂量直接溯源至水吸收剂量的不确定度要小很多。为了解决^(60)Co γ射线水吸收剂量量值溯源与传递问题,进一步提升^(60)Co γ射...目前国内大多数放射治疗剂量只能溯源到^(60)Co γ射线空气比释动能,与溯源至空气比释动能相比,将放射治疗剂量直接溯源至水吸收剂量的不确定度要小很多。为了解决^(60)Co γ射线水吸收剂量量值溯源与传递问题,进一步提升^(60)Co γ射线水吸收剂量的量值溯源与传递能力,中国测试技术研究院(National Institute of Measurement and Testing Technology,NIMTT)采用水量热法建立了^(60)Co γ射线水吸收剂量绝对测量装置,实现了水吸收剂量的绝对测量,复现了^(60)Co γ射线水吸收剂量,其量值复现的相对标准不确定度为0.45%。为了进一步验证^(60)Co γ射线水吸收剂量复现结果的准确性与一致性,将NIMTT实验室与加拿大国家研究委员会(National Research Council,NRC)实验室的复现结果进行了实验室之间的比对,结果在相对标准不确定度0.71%以内呈现一致性,归一化误差En值为-0.45。表明NIMTT具有^(60)Co γ射线水吸收剂量量值溯源与传递的能力,本研究结果也为^(60)Co γ射线吸收剂量的绝对测量提供了参考。展开更多
The bulk peanuts were used as the materials. After ）,-ray irradiation of different doses, the peanuts were stored up at room temperature, and the degree of pest infection and gradient of mould infection were observed...The bulk peanuts were used as the materials. After ）,-ray irradiation of different doses, the peanuts were stored up at room temperature, and the degree of pest infection and gradient of mould infection were observed regularly. The results showed that insects began to appear in the unirradiated peanuts in 2 months, while after 4 months, the pest infection rate increased with the prolonged storage time, and the pest infection rate reached up to 58%-100% after 6 months of storage. However, the irradiated peanuts did not suffer from the pest infection throughout the storage. The unirradiated peanuts were contaminated by moulds after three months of storage, while the peanuts with an irradiation dose of 0.3-0.5 kGy were mildewed after 6 months of storage, while those with an irradiation dose of 1.0, 4.0 kGy had no mould after 12 months of storage. Combined with relevant international and national standards as well as the findings of scholars at home and abroad, the minimum effective irradiation dose for insect disinfestations of peanuts was 0,3 kGy, and the minimum effective irradiation dose for mildew control was 1.0 kGy, while the maximum tolerance dose was 4.0 kGy.展开更多
文摘Radiotherapy is the most widely applied oncologic treatment modality utilizing ionizing radiation. A high degree of accuracy, reliability and reproducibility is required for a successful treatment outcome. Measurement using ionization chamber is a prerequisite for absorbed dose determination for external beam radiotherapy. Calibration coefficient is expressed in terms of air kerma and absorbed dose to water traceable to Secondary Standards Dosimetry Laboratory. The objective of this work was to evaluate the level of accuracy of ionization chamber used for clinical radiotherapy beam determination. Measurement and accuracy determination were carried out according to IAEA TRS 398 protocol. Clinical farmers type ionization chamber measurement and National Reference standard from Secondary Standards Dosimetry Laboratory were both exposed to cobalt-60 beam and measurement results compared under the same environmental conditions. The accuracy level between National Reference Standard and clinical radiotherapy standard was found to be −1.92% and −2.02% for air kerma and absorbed dose to water respectively. To minimize the effect of error and maximize therapeutic dose during treatment in order to achieve required clinical outcome, calibration factor was determined for air kerma (Nk) as 49.7 mGy/nC and absorbed dose to water ND, as 52.9 mGy/nC. The study established that radiotherapy beam measurement chain is prone to errors. Hence there is a need to independently verify the accuracy of radiation dose to ensure precision of dose delivery. The errors must be accounted for during clinical planning by factoring in calibration factor to minimize the systematic errors during treatment, and thereby providing enough room to achieve ±5% dose delivery to tumor target as recommended by ICRU.
基金Supported by Science and Technology Foundation of China Academy of Engineering Physics(No.2008A0103002)
文摘In this paper,fast neutron inactivation effects of Bacillus subtilis were investigated with fission fast neutrons from CFBR-Ⅱreactor of INPC(Institute of Nuclear Physics and Chemistry)and mono-energetic neutrons from the Van de Graaff accelerator at Peking University.The method for determining the absorbed dose in the Bacillus subtilis suspension contained in test tubes is introduced.The absorbed dose,on account of its dependence on the volume and the form of confined state,was determined by combined experiments and Monte Carlo method.Using the calculation results of absorbed dose,the fast neutron inactivation effects on Bacillus subtilis were studied.The survival rates and absorbed dose curve was constructed.
文摘As children are prone to be more radiosensitive than adults, it is imperative to assess the Entrance Skin Doses (ESDs) for patients being examined by X-rays, in order to ensure the optimization of dose while considering a number of other fickles. The ESD received by 50 paediatrics (aged 1-13 years) undergoing 8 types of X-ray examinations were measured at Federal Teaching Hospital, Ido-Ekiti, Ekiti, Nigeria, within a period of February 2019 to March 2020 using thermoluminescent dosimeters. The mean ± SD of ESDs were 0.85 ± 0.32, 2.04 ± 0.75, 0.60 ± 0.07, 0.62 ± 0.22, 0.57 ± 0.24, 1.75 ± 0.76, 0.93 ± 0.31 and 0.63 ± 0.06 mGy for Chest, Skull, Hand, Forearm, Knee, Abdomen, Leg and Feet, respectively. The mean ESDs were found to be within the recommended reference dose in all examinations, except for the Chest examination which was higher. The data obtained in this study will serve as existing data in Nigeria for future research works, as it would assist in optimizing dose to patients, especially the paediatrics.
基金funded by the National Natural Science Foundation of China (Nos.81771972,52171243,and 52371256)the National Key Research and Development Program of China (No.2017YFC0107405).
文摘X-ray excited photodynamic therapy(X-PDT)is the bravo answer of photodynamic therapy(PDT)for deep-seated tumors,as it employs X-ray as the irradiation source to overcome the limitation of light penetration depth.However,high X-ray irradiation dose caused organ lesions and side effects became the major barrier to X-PDT application.To address this issue,this work employed a classic-al co-precipitation reaction to synthesize NaLuF_(4):15%Tb^(3+)(NLF)with an average particle size of(23.48±0.91)nm,which was then coupled with the photosensitizer merocyanine 540(MC540)to form the X-PDT system NLF-MC540 with high production of singlet oxygen.The system could induce antitumor efficacy to about 24%in relative low dose X-ray irradiation range(0.1-0.3 Gy).In vivo,when NLF-MC540 irradiated by 0.1 Gy X-ray,the tumor inhibition percentage reached 89.5%±5.7%.The therapeutic mechanism of low dose X-PDT was found.A significant increase of neutrophils in serum was found on the third day after X-PDT.By immunohistochemical staining of tumor sections,the Ly6G^(+),CD8^(+),and CD11c^(+)cells infiltrated in the tumor microenvironment were studied.Utilizing the bilat-eral tumor model,the NLF-MC540 with 0.1 Gy X-ray irradiation could inhibit both the primary tumor and the distant tumor growth.De-tected by enzyme linked immunosorbent assay(ELISA),two cytokines IFN-γand TNF-αin serum were upregulated 7 and 6 times than negative control,respectively.Detected by enzyme linked immune spot assay(ELISPOT),the number of immune cells attributable to the IFN-γand TNF-αlevels in the group of low dose X-PDT were 14 and 6 times greater than that in the negative control group,respectively.Thus,it conclude that low dose X-PDT system could successfully upregulate the levels of immune cells,stimulate the secretion of cy-tokines(especially IFN-γand TNF-α),activate antitumor immunity,and finally inhibit colon tumor growth.
基金supported by the Science and Technology Project for University and Research Institute of Dongguan of China (No. 200910814045)
文摘The effect of the size of radiotherapy photon beams on the absorbed dose to an Al2O3 dosimeter was investigated using the Monte Carlo method. The EGSnrc/DOSRZnrc program code was used to simulate the absorbed dose to the Al2O3 dosimeter, as well as the absorbed dose to water at the corresponding position in the absence of the dosimeter. The incident beams were 60Co γ and 6 MV with a different beam radius ranging from 0.1 cm to 2 cm. Results revealed that the absorbed dose ratio factor depends on the size of the incident photon beam. When the radius of the incident beam is smaller than that of the dosimeter, the absorbed dose ratio factor decreases as the incident beam size increases. The absorbed dose ratio factor reaches its minimum when the radius of the incident beam is almost the same as that of the dosimeter. When the radius of the incident beam is larger than that of the dosimeter, the absorbed dose ratio factor increases as the incident beam size increases. The maximum difference among these absorbed dose ratio factors can be up to 14% in 60Co γ beams and 23% in 6 MV beams. However, when the size of the incident beam is much larger than that of the dosimeter, the effect of the incident beam size on the absorbed dose ratio factor becomes quite small. The maximum discrepancy between the absorbed dose ratio factors and the average value is not more than 1%.
文摘The methods of determining the superficial absorbed dose distributions in a water phantom by means of the experiments and available theories have been reported. The distributions of beta dose were measured by an extrapolation ionization chamber at definite depthes corresponding to some superficial organs and tissues such as the radiosensitive layer of the skin, cornea, sclera, anterior chamber and lens of eyeball.The ratios among superficial absorbed dose D (0.07) and average absorbed doses at the depthes 1,2,3,4,5 and 6 mm are also obtained with Cross's methods. They can be used for confining the deterministic effects of some superficial tissues and organs such as the skin and the components of eyeball for weakly penetrating radiations.
文摘Ensuring reliability and traceability of the unit of absorbed dose of intense photon and electron radiation, used in radiation technologies in industry, is based on the creation of a system of sample measures and methods of transmission with minimal loss of dimensional accuracy of the unit of absorbed dose from the sample tools to working dosimeters and is a necessary basis of yield growth, of increase of labour productivity and the introduction of innovative products. The measuring capabilities of the State primary special standard of power unit of absorbed dose of intensity photon, electron and beta radiation for radiation technologies and of the standards of the absorbed dose of photon and electron radiation, used for radiation monitoring of radiation pro- cesses.
文摘Cancer is a major societal public health and economic problem, responsible for one in every six deaths. Radiotherapy is the main technique of treatment for more than half of cancer patients. To achieve a successful outcome, the radiation dose must be delivered accurately and precisely to the tumor, within ± 5% accuracy. Smaller uncertainties are required for better treatment outcome. The objective of the study is to investigate the uncertainty of measurement of external radiotherapy beam using a standard ionization chamber under reference conditions. Clinical farmers type ionization chamber measurement was compared against the National Reference standard, by exposing it in a beam 60Co gamma source. The measurement set up was carried out according to IAEA TRS 498 protocol and uncertainty of measurement evaluated according to GUM TEDDOC-1585. Evaluation and analysis were done for the identified subjects of uncertainty contributors. The expanded uncertainty associated with 56 mGy/nC ND,W was found to be 0.9% corresponding to a confidence level of approximately 95% with a coverage factor of k = 2. The study established the impact of dosimetry uncertainty of measurement in estimating external radiotherapy dose. The investigation established that the largest contributor of uncertainty is the stability of the ionization chamber at 36%, followed by temperature at 22% and positioning of the chamber in the beam at 8%. The effect of pressure, electrometer, resolution, and reproducibility were found to be minimal to the overall uncertainty. The study indicate that there is no flawless measurement, as there are many prospective sources of variation. Measurement results have component of unreliability and should be regarded as best estimates of the true value. .
文摘This work investigated the absorbed dose to water rate under reference conditions in a Cyberknife VSI system using radiochromic films EBT3 and MD-V3 and three ionization chambers: an Exradin A12 and two FC65P Welhöfer Scanditronix with different serial numbers. The correction factor,, was studied using a Varian iX linac and the Cyberknife system. The measurements in the Varian iX were performed in a 10 × 10 cm2 field, 10 cm depth in liquid water at 90 cm and 70 cm SSD and in a 5.4 × 5.4 cm2 field, 10 cm depth at 70 cm SSD to simulate the Cyberknife conditions. In the Cyberknife system, measurements were performed using ionization chambers and both film types at 70 cm SSD and 10 cm depth in its 6 cm diameter reference field. The results indicate that ?is independent of the dosimeters and the evaluation methods. Maximum differences of 0.22% - 0.55% (combined uncertainties of 1.22% - 1.98%, k = 1) are obtained on ?using Varian iX, whereas discrepancies of 2.08% - 2.09% (combined uncertainties of 1.87% - 2.13%, k = 1) are observed using the Cyberknife system. Given the agreement between detectors and the combined standard uncertainties, the data from Varian iX could be considered the most accurate and consequently a weighted average factor of 0.902 ± 0.006 could be used for the Cyberknife VSI system reference field. Within measurement uncertainties, the absorbed dose rate measured in the Cyberknife VSI system reference field was found to be independent of the dosimeters used. These results suggest that the absorbed dose measured at a point within a given field size should be the same, regardless the dosimeter used, if their dosimetric characteristics are well known. This highlighted the importance of performing dosimetry by controlling all parameters that could affect the dosimeter response. One can conclude that radiochromic film dosimetry can be considered as an appropriate alternative for measuring absorbed dose to water rate.
文摘Since the early times, radioprotection has been focused on the human being. Currently this approach has changed, being now also necessary to take care of the protection of the environment from unwanted effects of ionizing radiation. To this end, several institutions (UNSCEAR, ICRP, IAEA, DOE, ACRP) and consortia of institutions (FASSET, ERICA) have established procedures in order to protect the biota of such effects. Developed procedures are based on the calculation of the absorbed dose in biota (ICRP, DOE, IAEA), or on environmental risk assessment―ERA (DOE, ACRP, FASSET, ERICA);but even in this latter approach the parameters used are related to the absorbed doses in biota. The calculation of dose is the standard procedure in human radioprotection, and this points such an approach as the most interesting for providing a convergence between human and nonhuman (= biota) radioprotections. On the other hand, the ERA approach is easier to apply, because this methodology is used in several countries for non-radioactive contamination assessments. Since the world radioprotection system follows a number of institutions (UNSCEAR, ICRP, IAEA and regulatory institutions of member countries) that use dose calculation, this appears to be the way for biota radioprotection. We here review and comment the evolution of the concepts and approaches of the recommendations for radioprotection of non-human biota.
基金the National Natural Science Foundation of China (20671069)
文摘Perovskite-type complex oxides ABO3 （A=Sr, La; B=Mn, Fe, Co） were prepared by citric acid method. The degradation of water-solubilized dyes was carried out using the mixed oxides as photocatalyst. The surface absorbed oxygen was analyzed using X-ray photoelectron spectroscopy （XPS）. The results indicated that there was a relationship between the photocatalytic activity and the content of the surface absorbed oxygen. The higher the content of the surface absorbed oxygen was, the better the performance of the photocatalyst.
文摘Objective: The current research study aims to calculate entrance surface air kerma for skull, chest, cervical spine, lumbar spine, and pelvic X-ray examinations in interior posterior and posterior interior positions and generate a method for chest dose reduction to decrease radiation risk. Materials and Methods: The indirect dose measurement was used in the current research. The X-ray tube output was measured using RAD-CHECK Plus ionization chamber and the indirect entrance surface air kerma was calculated via applying physical acquisition parameters such as a focus on skin distance, tube current times exposure time (mAs), and applied tube voltage (kV), and applying a mathematical model. Results: The main findings were obtained from comparing the radiation doses with the reference levels of International organizations such as the American College of Radiology and the International Atomic Energy Authority. The mean entrance skin dose for the skull (AP), skull (PA), skull (LAT), cervical spine (PA), cervical spine (LAT), lumbar spine (AP), lumbar spine (LAT), pelvis (AP), and pelvis (LAT) of adult X-ray examinations was within the diagnostic reference dose level values obtained by ACR (2018) except for the ESD for chest (AP) which was 0.88 mGy. Conclusions: The results of the study concluded that by adjusting the applied tube voltage, kV, and tube current product time, mAs decreased the radiation dose to the chest X-ray by 58%.
文摘目前国内大多数放射治疗剂量只能溯源到^(60)Co γ射线空气比释动能,与溯源至空气比释动能相比,将放射治疗剂量直接溯源至水吸收剂量的不确定度要小很多。为了解决^(60)Co γ射线水吸收剂量量值溯源与传递问题,进一步提升^(60)Co γ射线水吸收剂量的量值溯源与传递能力,中国测试技术研究院(National Institute of Measurement and Testing Technology,NIMTT)采用水量热法建立了^(60)Co γ射线水吸收剂量绝对测量装置,实现了水吸收剂量的绝对测量,复现了^(60)Co γ射线水吸收剂量,其量值复现的相对标准不确定度为0.45%。为了进一步验证^(60)Co γ射线水吸收剂量复现结果的准确性与一致性,将NIMTT实验室与加拿大国家研究委员会(National Research Council,NRC)实验室的复现结果进行了实验室之间的比对,结果在相对标准不确定度0.71%以内呈现一致性,归一化误差En值为-0.45。表明NIMTT具有^(60)Co γ射线水吸收剂量量值溯源与传递的能力,本研究结果也为^(60)Co γ射线吸收剂量的绝对测量提供了参考。
基金Supported by the Special Fund for Agro-scientific Research in the Public Interest(201103007)~~
文摘The bulk peanuts were used as the materials. After ）,-ray irradiation of different doses, the peanuts were stored up at room temperature, and the degree of pest infection and gradient of mould infection were observed regularly. The results showed that insects began to appear in the unirradiated peanuts in 2 months, while after 4 months, the pest infection rate increased with the prolonged storage time, and the pest infection rate reached up to 58%-100% after 6 months of storage. However, the irradiated peanuts did not suffer from the pest infection throughout the storage. The unirradiated peanuts were contaminated by moulds after three months of storage, while the peanuts with an irradiation dose of 0.3-0.5 kGy were mildewed after 6 months of storage, while those with an irradiation dose of 1.0, 4.0 kGy had no mould after 12 months of storage. Combined with relevant international and national standards as well as the findings of scholars at home and abroad, the minimum effective irradiation dose for insect disinfestations of peanuts was 0,3 kGy, and the minimum effective irradiation dose for mildew control was 1.0 kGy, while the maximum tolerance dose was 4.0 kGy.
