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
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
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
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
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
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
We irradiated pea seeds with neutrons from a ^(252)Cf source and studied the radiation dose effects on various morphological development parameters during the growth of M_(1) generation peas.We found that in the dose ...We irradiated pea seeds with neutrons from a ^(252)Cf source and studied the radiation dose effects on various morphological development parameters during the growth of M_(1) generation peas.We found that in the dose range of 0.51-9.27 Gy,with the increase in neutron-absorbed dose,the morphological development parameters of M_(1) generation peas at the initial seedling stage showed an obvious trend with three fluctuations.With the development of pea,this trend gradually weakened.Further analysis and verification showed that the main trend in the M_(1) generation of pea seeds was an inhibitory effect induced by neutron irradiation and there was a good linear correlation between the inhibitory effect and neutron absorption dose We successfully demonstrated the background removal of mutant plants and defined morphological developmen parameters for peas that match the overall development of plants.Our results will positively impact neutron mutation breeding and automatic agriculture.展开更多
Natural radioactivity radionuclides in building materials, such as^(226)Ra,^(232)Th and^(40)K, cause indoor exposure due to their gamma-rays. In this research, in a standard dwelling room(5.0 m 9 4.0 m 9 2.8 m), with ...Natural radioactivity radionuclides in building materials, such as^(226)Ra,^(232)Th and^(40)K, cause indoor exposure due to their gamma-rays. In this research, in a standard dwelling room(5.0 m 9 4.0 m 9 2.8 m), with the floor covered by various granite stones, was set up to simulate the dose rates from the radionuclides using MCNP4 C code. Using samples of granite building products in Iran, activities of the^(226)Ra,^(232)Th and^(40)K were measured at 3.8–94.2, 6.5–172.2 and 556.9–1529.2 Bq kg^(-1),respectively. The simulated dose rates were26.31–184.36 n Gy h^(-1), while the measured dose rates were 27.70–204.17 n Gy h^(-1). With the results in good agreement, the simulation is suitable for any kind of dwelling places.展开更多
For precise and accurate patient dose delivery,the dosimetry system must be calibrated properly according to the recommendations of standard dosimetry protocols such as TG-51 and TRS-398. However, the dosimetry protoc...For precise and accurate patient dose delivery,the dosimetry system must be calibrated properly according to the recommendations of standard dosimetry protocols such as TG-51 and TRS-398. However, the dosimetry protocol followed by a calibration laboratory is usually different from the protocols that are followed by different clinics, which may result in variations in the patient dose.Our prime objective in this study was to investigate the effect of the two protocols on dosimetry measurements.Dose measurements were performed for a Co-60 teletherapy unit and a high-energy Varian linear accelerator with 6 and 15 MV photon and 6, 9, 12, and 15 MeV electron beams, following the recommendations and procedures of the AAPM TG-51 and IAEA TRS-398 dosimetry protocols. The dosimetry systems used for this study were calibrated in a Co-60 radiation beam at the Secondary Standard Dosimetry Laboratory(SSDL) PINSTECH,Pakistan, following the IAEA TRS-398 protocol. The ratio of the measured absorbed doses to water in clinical setting,D_w(TG-51/TRS-398), was 0.999 and 0.997 for 6 and15 MV photon beams,whereas these ratios were 1.013,1.009, 1.003, and 1.000 for 6, 9, 12, and 15 MeV electron beams, respectively. This difference in the absorbed dosesto-water D_w ratio may be attributed mainly due to beam quality(K_Q) and ion recombination correction factor.展开更多
<span><b><span style="font-family:"">Introduction: </span></b></span><span><span><span style="font-family:"">Radiotherapy is one of t...<span><b><span style="font-family:"">Introduction: </span></b></span><span><span><span style="font-family:"">Radiotherapy is one of the important treatment modalities in cancer treatment. To maintain the treatment procedure accuracy, the phantom is an essential tool for absolute dosimetry conformation and Quality Assurance routine cheek up. This work aims to study the absorbed dose of various phantoms and hence to make a comparison of the result with the IAEA recommendation (TRS 398) for daily QA of Linac. <b>Materials and Methods: </b>The experiment has been done at the Institute of Nuclear Medical Physics (INMP), AERE, Savar, Dhaka, under the Bangladesh Atomic Energy Commission. For external beam radiation, 6 MV and 15 MV photon beams of Varian Clinac iX Linear Accelerator (Linac) were used. One dimensional (1D) water phantom, solid water phantom, and MatriXX with MULTICube phantom and associate accessories were used to experiment. <b>Results: </b>We have measured and compared the absorbed dose data of the phantoms. The variation of sold water phantom from the 1D water phantom is +2.8% at 6 MV and +3.5% at 15 MV. The variation MatriXX with MULTIcube phantom from the 1D water phantom is +8.0% at 6 MV and +3.2% at 15 MV. This study revealed that the 1D water phantom was the best absolute dose conformation among the other phantoms and the deviation was within the acceptable limit (±5%), except MatriXX with MULTICube Phantom for low energy beam (8%). <b>Conclusion:</b> It was observed that the accuracy of dose estimation was better in the 1D water phantom rather than the other two. It is also known that the 1D water phantom is low cost but needs a long time to set up for the experimental arrangement. Solid water or MatriXX with MULTICube phantom can be used to overcome this problem, which takes only a few minutes for setup and is comparatively faster than 1D water phantom.展开更多
The radiation therapy is applied on around 50% of the cancer patients. As we know, before implementing a radiation treatment planning system in the clinic, the dose-calculation measurement must be validated using rigo...The radiation therapy is applied on around 50% of the cancer patients. As we know, before implementing a radiation treatment planning system in the clinic, the dose-calculation measurement must be validated using rigorous, clinically relevant criteria [1]. Percent Depth Doses (PDD), Dose Profile (DP), Open Collimator Factor (OCF) etc., are measured for all numbers of square fields for Treatment Planning System XiO, version 4.7, for 6 and 15 MV photons energies and for 15°, 30°, 45°, 60° wedge, which were employed to obtain the profiles in any depth. The measurements were conducted also for different energies of electron beam and TPS calculation algorithms.展开更多
Maximum Likelihood (MLH) supervised classification of atmospherically corrected Landsat 8 imagery was applied successfully for delineating main geologic units with a good accuracy (about 90%) according to reliable gro...Maximum Likelihood (MLH) supervised classification of atmospherically corrected Landsat 8 imagery was applied successfully for delineating main geologic units with a good accuracy (about 90%) according to reliable ground truth areas, which reflected the ability of remote sensing data in mapping poorly-accessed and remote regions such as playa (Sabkha) environs, subdued topography and sand dunes. Ground gamma-ray spectrometric survey was to delineate radioactive anomalies within Quaternary sediments at Wadi Diit. The mean absorbed dose rate (D), annual effective dose equivalent (AEDE) and external hazard index (H<sub>ex</sub>) were found to be within the average worldwide ranges. Therefore, Wadi Diit environment is said to be radiological hazard safe except at the black-sand lens whose absorbed dose rate of 100.77 nGy/h exceeds the world average. So, the inhabitants will receive a relatively high radioactive dose generated mainly by monazite and zircon minerals from black-sand lens.展开更多
The specific radioactivity of several building materials used in France, which is considered a direct exposure to radiation, has been assessed by γ-ray spectrometry. Corrected for coincidence summing and self-absorpt...The specific radioactivity of several building materials used in France, which is considered a direct exposure to radiation, has been assessed by γ-ray spectrometry. Corrected for coincidence summing and self-absorption effects, the values for 226Ra, 232Th and 40K were in the ranges 4 - 56, 3 - 72 and 9 - 1136 Bq·kg-1, respectively. The samples were found to have radium-equivalent activities between 5 and 245 Bq·kg-1. Values of 0.02 - 0.67 for the external and 0.03 - 0.82 for the internal hazard indexes were estimated. The calculated absorbed dose in air agrees closely with MCNPX simulations. The conversion of absorbed dose to annual effective dose gave values between 0.03 - 1.09 mSv·y-1. All these values are below action limits recommended by the International Commission on Radiological Protection. The materials examined would not contribute a significant radiation exposure for an occupant and thus are acceptable for construction.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
本文旨在比较常规直线加速器与射波刀在治疗大体积肺癌患者立体定向中央消融放疗(Stereotactic Central Ablative Radiotherapy,SCART)计划中的性能差异。通过深入分析两种技术的剂量学特性及执行效率,为大体积肺癌患者及其他类似大体...本文旨在比较常规直线加速器与射波刀在治疗大体积肺癌患者立体定向中央消融放疗(Stereotactic Central Ablative Radiotherapy,SCART)计划中的性能差异。通过深入分析两种技术的剂量学特性及执行效率,为大体积肺癌患者及其他类似大体积肿瘤的消融放疗提供优化的治疗策略与临床指导。采用回顾性分析方法,选取2023年至2024年间接受SCART放疗的20例大体积肺癌患者(肿瘤三维尺寸均大于5 cm),分别使用常规直线加速器和射波刀计划系统进行治疗计划设计。比较两种技术在处方剂量覆盖体积(STV)、靶区适形指数、靶区梯度指数、危及器官剂量、机器跳数及治疗时间等关键参数上的差异,全面评估两种技术的计划质量和执行效率。结果显示在消融剂量的STV处方剂量覆盖体积方面,射波刀相较于常规加速器展现出显著优势(P=0.005)。对于STV靶区,常规加速器的CI值表现更佳(P=0.004),但在GTV靶区,射波刀则优于常规加速器(P=0.02)。在GI方面,无论是STV还是GTV靶区,射波刀均显著优于常规加速器(P值分别为0.025和0.02)。在危及器官保护方面,射波刀在食管、心脏的平均剂量和剂量体积参数D_(5CC),以及双肺的D_(950cc)上均优于常规加速器。尽管最大剂量点限值无显著差异,但根据剂量云图和DVH图,射波刀在实际应用中可能更具优势。在所有计划中,常规加速器的MU值和治疗时间都远小于射波刀。两种技术均能满足大肿瘤患者的临床SCART放疗需求。从计划质量和执行效率来看,对于身体状况良好、呼吸稳定且能长时间保持平躺的患者,推荐使用射波刀进行SCART治疗,以提高治疗精度并减少对正常器官的毒副反应。对于身体状况较差、呼吸不规律或难以长时间保持同一姿势的患者,建议选择常规加速器,以确保治疗的舒适性和顺利完成,减少治疗过程中的误差。未来研究需扩大病例数量并结合辅助资料,以评估更深层次的剂量学差异及治疗后的疗效,并进行长期随访,收集应用SCART技术患者的肿瘤控制率和不良反应数据,为临床决策提供支持。展开更多
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.
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.
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.
基金supported by the National Natural Science Foundation of China(Nos.11675069 and 12075106)the Natural Science Foundation of Gansu Province(No.20JR10RA607)the Fundamental Research Funds for the Central Universities of China(No.lzujbky-2020-kb09)。
文摘We irradiated pea seeds with neutrons from a ^(252)Cf source and studied the radiation dose effects on various morphological development parameters during the growth of M_(1) generation peas.We found that in the dose range of 0.51-9.27 Gy,with the increase in neutron-absorbed dose,the morphological development parameters of M_(1) generation peas at the initial seedling stage showed an obvious trend with three fluctuations.With the development of pea,this trend gradually weakened.Further analysis and verification showed that the main trend in the M_(1) generation of pea seeds was an inhibitory effect induced by neutron irradiation and there was a good linear correlation between the inhibitory effect and neutron absorption dose We successfully demonstrated the background removal of mutant plants and defined morphological developmen parameters for peas that match the overall development of plants.Our results will positively impact neutron mutation breeding and automatic agriculture.
文摘Natural radioactivity radionuclides in building materials, such as^(226)Ra,^(232)Th and^(40)K, cause indoor exposure due to their gamma-rays. In this research, in a standard dwelling room(5.0 m 9 4.0 m 9 2.8 m), with the floor covered by various granite stones, was set up to simulate the dose rates from the radionuclides using MCNP4 C code. Using samples of granite building products in Iran, activities of the^(226)Ra,^(232)Th and^(40)K were measured at 3.8–94.2, 6.5–172.2 and 556.9–1529.2 Bq kg^(-1),respectively. The simulated dose rates were26.31–184.36 n Gy h^(-1), while the measured dose rates were 27.70–204.17 n Gy h^(-1). With the results in good agreement, the simulation is suitable for any kind of dwelling places.
文摘For precise and accurate patient dose delivery,the dosimetry system must be calibrated properly according to the recommendations of standard dosimetry protocols such as TG-51 and TRS-398. However, the dosimetry protocol followed by a calibration laboratory is usually different from the protocols that are followed by different clinics, which may result in variations in the patient dose.Our prime objective in this study was to investigate the effect of the two protocols on dosimetry measurements.Dose measurements were performed for a Co-60 teletherapy unit and a high-energy Varian linear accelerator with 6 and 15 MV photon and 6, 9, 12, and 15 MeV electron beams, following the recommendations and procedures of the AAPM TG-51 and IAEA TRS-398 dosimetry protocols. The dosimetry systems used for this study were calibrated in a Co-60 radiation beam at the Secondary Standard Dosimetry Laboratory(SSDL) PINSTECH,Pakistan, following the IAEA TRS-398 protocol. The ratio of the measured absorbed doses to water in clinical setting,D_w(TG-51/TRS-398), was 0.999 and 0.997 for 6 and15 MV photon beams,whereas these ratios were 1.013,1.009, 1.003, and 1.000 for 6, 9, 12, and 15 MeV electron beams, respectively. This difference in the absorbed dosesto-water D_w ratio may be attributed mainly due to beam quality(K_Q) and ion recombination correction factor.
文摘<span><b><span style="font-family:"">Introduction: </span></b></span><span><span><span style="font-family:"">Radiotherapy is one of the important treatment modalities in cancer treatment. To maintain the treatment procedure accuracy, the phantom is an essential tool for absolute dosimetry conformation and Quality Assurance routine cheek up. This work aims to study the absorbed dose of various phantoms and hence to make a comparison of the result with the IAEA recommendation (TRS 398) for daily QA of Linac. <b>Materials and Methods: </b>The experiment has been done at the Institute of Nuclear Medical Physics (INMP), AERE, Savar, Dhaka, under the Bangladesh Atomic Energy Commission. For external beam radiation, 6 MV and 15 MV photon beams of Varian Clinac iX Linear Accelerator (Linac) were used. One dimensional (1D) water phantom, solid water phantom, and MatriXX with MULTICube phantom and associate accessories were used to experiment. <b>Results: </b>We have measured and compared the absorbed dose data of the phantoms. The variation of sold water phantom from the 1D water phantom is +2.8% at 6 MV and +3.5% at 15 MV. The variation MatriXX with MULTIcube phantom from the 1D water phantom is +8.0% at 6 MV and +3.2% at 15 MV. This study revealed that the 1D water phantom was the best absolute dose conformation among the other phantoms and the deviation was within the acceptable limit (±5%), except MatriXX with MULTICube Phantom for low energy beam (8%). <b>Conclusion:</b> It was observed that the accuracy of dose estimation was better in the 1D water phantom rather than the other two. It is also known that the 1D water phantom is low cost but needs a long time to set up for the experimental arrangement. Solid water or MatriXX with MULTICube phantom can be used to overcome this problem, which takes only a few minutes for setup and is comparatively faster than 1D water phantom.
文摘The radiation therapy is applied on around 50% of the cancer patients. As we know, before implementing a radiation treatment planning system in the clinic, the dose-calculation measurement must be validated using rigorous, clinically relevant criteria [1]. Percent Depth Doses (PDD), Dose Profile (DP), Open Collimator Factor (OCF) etc., are measured for all numbers of square fields for Treatment Planning System XiO, version 4.7, for 6 and 15 MV photons energies and for 15°, 30°, 45°, 60° wedge, which were employed to obtain the profiles in any depth. The measurements were conducted also for different energies of electron beam and TPS calculation algorithms.
文摘Maximum Likelihood (MLH) supervised classification of atmospherically corrected Landsat 8 imagery was applied successfully for delineating main geologic units with a good accuracy (about 90%) according to reliable ground truth areas, which reflected the ability of remote sensing data in mapping poorly-accessed and remote regions such as playa (Sabkha) environs, subdued topography and sand dunes. Ground gamma-ray spectrometric survey was to delineate radioactive anomalies within Quaternary sediments at Wadi Diit. The mean absorbed dose rate (D), annual effective dose equivalent (AEDE) and external hazard index (H<sub>ex</sub>) were found to be within the average worldwide ranges. Therefore, Wadi Diit environment is said to be radiological hazard safe except at the black-sand lens whose absorbed dose rate of 100.77 nGy/h exceeds the world average. So, the inhabitants will receive a relatively high radioactive dose generated mainly by monazite and zircon minerals from black-sand lens.
文摘The specific radioactivity of several building materials used in France, which is considered a direct exposure to radiation, has been assessed by γ-ray spectrometry. Corrected for coincidence summing and self-absorption effects, the values for 226Ra, 232Th and 40K were in the ranges 4 - 56, 3 - 72 and 9 - 1136 Bq·kg-1, respectively. The samples were found to have radium-equivalent activities between 5 and 245 Bq·kg-1. Values of 0.02 - 0.67 for the external and 0.03 - 0.82 for the internal hazard indexes were estimated. The calculated absorbed dose in air agrees closely with MCNPX simulations. The conversion of absorbed dose to annual effective dose gave values between 0.03 - 1.09 mSv·y-1. All these values are below action limits recommended by the International Commission on Radiological Protection. The materials examined would not contribute a significant radiation exposure for an occupant and thus are acceptable for construction.
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. .
文摘本文旨在比较常规直线加速器与射波刀在治疗大体积肺癌患者立体定向中央消融放疗(Stereotactic Central Ablative Radiotherapy,SCART)计划中的性能差异。通过深入分析两种技术的剂量学特性及执行效率,为大体积肺癌患者及其他类似大体积肿瘤的消融放疗提供优化的治疗策略与临床指导。采用回顾性分析方法,选取2023年至2024年间接受SCART放疗的20例大体积肺癌患者(肿瘤三维尺寸均大于5 cm),分别使用常规直线加速器和射波刀计划系统进行治疗计划设计。比较两种技术在处方剂量覆盖体积(STV)、靶区适形指数、靶区梯度指数、危及器官剂量、机器跳数及治疗时间等关键参数上的差异,全面评估两种技术的计划质量和执行效率。结果显示在消融剂量的STV处方剂量覆盖体积方面,射波刀相较于常规加速器展现出显著优势(P=0.005)。对于STV靶区,常规加速器的CI值表现更佳(P=0.004),但在GTV靶区,射波刀则优于常规加速器(P=0.02)。在GI方面,无论是STV还是GTV靶区,射波刀均显著优于常规加速器(P值分别为0.025和0.02)。在危及器官保护方面,射波刀在食管、心脏的平均剂量和剂量体积参数D_(5CC),以及双肺的D_(950cc)上均优于常规加速器。尽管最大剂量点限值无显著差异,但根据剂量云图和DVH图,射波刀在实际应用中可能更具优势。在所有计划中,常规加速器的MU值和治疗时间都远小于射波刀。两种技术均能满足大肿瘤患者的临床SCART放疗需求。从计划质量和执行效率来看,对于身体状况良好、呼吸稳定且能长时间保持平躺的患者,推荐使用射波刀进行SCART治疗,以提高治疗精度并减少对正常器官的毒副反应。对于身体状况较差、呼吸不规律或难以长时间保持同一姿势的患者,建议选择常规加速器,以确保治疗的舒适性和顺利完成,减少治疗过程中的误差。未来研究需扩大病例数量并结合辅助资料,以评估更深层次的剂量学差异及治疗后的疗效,并进行长期随访,收集应用SCART技术患者的肿瘤控制率和不良反应数据,为临床决策提供支持。
