共查询到18条相似文献,搜索用时 140 毫秒
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针对我国放疗水吸收剂量测量方法即将更新的现状,先后在北京多家医院放疗科的医用加速器下进行了200多次高能光子水吸收剂量量值验证实验。按照IAEA 277报告和IAEA 398报告的测量方法,测量高能光子最大剂量点处的水吸收剂量值并进行比较。统计2种方法测量结果的偏差,在NE2571电离室的实验结果中,398报告的测量结果比277报告的测量结果大0.23%;在PTW30013电离室的实验结果中,398报告的测量结果比277报告的测量结果测量结果大0.85%。实验表明,2种方法的测量结果在不确定度范围内一致,实验为398报告量值体系在我国的推行建立了实验基础。对结果的偏差做了分析,深入研究了相关因子的计算过程,从几个修正因子的角度探讨了偏差产生的原因。 相似文献
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《计量技术》2019,(10)
研究用IAEA TRS398的方法测量高能X射线和高能电子的水吸收剂量的测量方法和计算过程。按照398报告的对位和测量方法获得测量值,根据辐射质和电离室型号计算得到的k_(Q,Q0),测得各辐射质的PDD曲线,求出最大剂量点处的水吸收剂量,并与277报告的计算结果进行比较。在6MV、10MV高能X射线、18MeV高能电子下,按照398报告和277报告的方法测得最大剂量点处剂量分别为2. 251、2. 676、2. 243(Gy)和2. 251、2. 669、2. 254(Gy),相对偏差为0. 00%、0. 26%、-0. 49%。两种方法测量结果在不确定度范围内一致,且398方法更易于操作和计算。 相似文献
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为了建立医学、农业和辐射加工(~60Co γ射线)吸收剂量国家标准,精确测定了Frieke剂量计中Fe~(3+)离子摩尔消光系数ε_m值,着重研究了邮寄玻璃安瓿剂量计的制备方法和工艺,采用老化和预辐照剂量计溶液的办法进行质量控制,有效地清除了有害杂质的影响,使未辐照剂量计的本底读数十分稳定,提高了测量精度。同时,试验观察了影响吸收剂量测量的一些因素;考查了剂量计的复现性和长期稳定性;并进行了医用(限束)和工、农业(非限束)~(60)Co γ射线水模体中校准点处吸收剂量的测量以及与标准照射量计(Farmer 2560)的比对。结果表明,在测定~(60)Co γ射线(限束与非限束)水中吸收剂量量值,当剂量范围为(40~400)Gy时,测量的重复性有效地控制在±1.0%以内(95%置信度),总不确定度在±1.9%以内。 相似文献
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平行板电离室的检定与测量 总被引:1,自引:0,他引:1
本文较详细介绍了国际原子能机构(IAEA)第381号报告中60Coγ射线-空气法检定平行板电离室的方法和水中吸收剂量的测量,并对平行板电离室检定与测量进行讨论. 相似文献
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用于~(60)Coγ射线照射量基准的石墨空腔电离室的研制 总被引:1,自引:1,他引:0
本文报告了一种用于γ射线照射量基准的石墨空腔电离室,采取球-圆柱形状,结构设计和材料选择保证了电离室良好的测量性能和稳定性。采用水称重法和几何尺寸测量相结合。精确测定了电离室体积。电离室内电场的合理分布,保证了可以得到良好的饱和特性。根据“等效壁厚”来考虑室壁的减弱效应,采用对“等效壁厚”外推的方法来得到室壁修正。用此电离室进行~(60)Co γ射线照射量测量的标准化,得到了满意的结果。测量照射量的合成不确定度为±0.25%。与BIPM的~(60)Co γ射线照射量测量比对,结果在0.16%以内一致, 相似文献
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为实现加速器光子水吸收剂量绝对测量,研制了水量热计系统,在此基础上取得国际互认并建立加速器光子水吸收剂量基准,进一步提高了我国放疗剂量量值传递能力。通过水浴与半导体制冷系统二级控温,将量热计水模体的温度漂移控制在0.5μ℃/s。利用惠斯通交流电桥测量辐射所致的热敏探针阻值变化,逐次校准热敏探针和交流电桥,实现了医用加速器光子水吸收剂量的绝对测量,合成标准不确定度为0.30%。参加了国际计量局加速器光子水吸收剂量关键比对,复现的6MV和10MV光子水吸收剂量值与比对参考值之比分别为0.9917和0.9949,在不确定度允许的范围内一致。 相似文献
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γ射线辐照对PA6/PTFE合金吸水与力学性能的影响 总被引:1,自引:0,他引:1
为了探讨辐照对尼龙6(PA6)基共混材料吸水性能和力学性能的影响,制备了PA6和聚四氟乙烯(PTFE)共混合金并在室温下进行不同剂量的60Coγ射线辐照.通过吸水率测试、准静态拉伸和弯曲实验以及缺口冲击测试,研究了辐照对PA6/PTFE共混体系吸水性能以及吸收水和辐照剂量对共混合金动静态力学性能的影响.结果表明,辐照过程引发交联反应,共混合金的拉伸强度、拉伸模量和弯曲模量均随辐照剂量的增大而增大,而缺口冲击强度和吸水率则随之减小.吸收水对共混合金缺口冲击强度的影响与合金组分有关.PTFE含量较低时,吸收水抑制PTFE对合金冲击强度的减弱作用;当PTFE的质量分数大于7%时,吸收水反而加剧PTFE对材料冲击强度的减弱效应.此外,PA6/PTFE合金的吸水率随PTFE含量的增加而降低,而弯曲模量则先增后减. 相似文献
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Vynckier S;International Atomic Energy Agency;International Commission on Radiation Units Measurements 《Radiation protection dosimetry》2004,110(1-4):565-572
Neutron therapy beams are obtained by accelerating protons or deuterons on Beryllium. These neutron therapy beams present comparable dosimetric characteristics as those for photon beams obtained with linear accelerators; for instance, the penetration of a p(65)+Be neutron beam is comparable with the penetration of an 8 MV photon beam. In order to be competitive with conventional photon beam therapy, the dosimetric characteristics of the neutron beam should therefore not deviate too much from the photon beam characteristics. This paper presents a brief summary of the neutron beams used in radiotherapy. The dosimetry of the clinical neutron beams is described. Finally, recent and future developments in the field of physics for neutron therapy is mentioned. In the last two decades, a considerable number of centres have established radiotherapy treatment facilities using proton beams with energies between 50 and 250 MeV. Clinical applications require a relatively uniform dose to be delivered to the volume to be treated, and for this purpose the proton beam has to be spread out, both laterally and in depth. The technique is called 'beam modulation' and creates a region of high dose uniformity referred to as the 'spread-out Bragg peak'. Meanwhile, reference dosimetry in these beams had to catch up with photon and electron beams for which a much longer tradition of dosimetry exists. Proton beam dosimetry can be performed using different types of dosemeters, such as calorimeters, Faraday cups, track detectors and ionisation chambers. National standard dosimetry laboratories will, however, not provide a standard for the dosimetry of proton beams. To achieve uniformity on an international level, the use of an ionisation chamber should be considered. This paper reviews and summarises the basic principles and recommendations for the absorbed dose determination in a proton beam, utilising ionisation chambers calibrated in terms of absorbed dose to water. These recommendations are based on the recent IAEA TRS398 Code of Practice: 'Absorbed Dose Determination in External Beam Radiotherapy: An International Code of Practice for Dosimetry based on Standards of Absorbed Dose to Water'. 相似文献
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A thermoluminescent dosemeter (TLD) mailed dose audit programme was performed at five radiotherapy clinics in Turkey. The intercomparison was organised by the University of Wisconsin Radiation Calibration Laboratory (UWRCL), which was responsible for the technical aspects of the study including reference irradiations, distribution, collection and evaluation. The purpose of these audits was to perform an independent dosimetry check of the radiation beams using TLDs sent by mail. Acrylic holders, each with five TLD chips inside and instructions for their irradiation to specified absorbed dose to water of 2 Gy, were mailed to all participating clinics. TLD irradiations were performed with a 6 MV linear accelerator and (60)Co photon beams. The deviations from the TL readings of UWRCL were calculated. Discrepancies inside the limits of ±5 % between the participant-stated dose, and the TLD-measured dose were considered acceptable. One out of 10 beams checked was outside this limit, with a difference of 5.8 %. 相似文献
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Mingcheng YANG Hongyan SONG Chengshen ZHU Suqin HE Ya GAO 《材料科学技术学报》2007,23(2):182-184
By using a new method, ^60Co γ-ray irradiation, Fe3O4 magnetic nano-particles were successfully synthesized at room temperature under ambient pressure. The structure, morphology and magnetic properties of these nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and vibrating sample magnetometer (VSM), respectively. The radiation formation mechanism was also discussed. The results show that the absorbed dose can greatly influence the structure, morphology and magnetic properties of the products. XRD and TEM studies show that the product prepared by γ-ray irradiation (10 kGy) is pure FesO4 phase and the mean diameter of these nano-particles is about 21 nm. The Fe3O4 nano-particles synthesized by γ-ray irradiation (10 kGy) are mainly in small cubic shape and the size uniformity of these particles is good. 相似文献
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Marqarete Ehrlich Garv L. Welter 《Journal of research of the National Institute of Standards and Technology》1976,(4):663-668
The National Bureau of Standards is performing a study of the ability of radiation-therapy departments to deliver prescribed absorbed doses of 60Co gamma radiation to a water phantom. Batches of thermoluminescence dosimeters are mailed to participating therapy departments for irradiation under prescribed conditions. Upon return of the dosimeters, the participants’ computations are checked and the absorbed dose is evaluated from dosimeter response. The rugged dosimetry system was assembled mainly from commercial components adapted to the present requirements of relatively high flexibility of readout parameters and data-handling techniques, and of relatively high accuracy. The uncertainty in the dose interpretation inherent in the system is estimated to be about 4 percent.In order to illustrate the type of information that can be obtained from such a study, results of the first four mailings involving tests on 114 60Co gamma-ray beams are discussed. They show about 75 percent of the dose interpretations to be within 5 percent of the prescribed absorbed dose, and about 20 percent to be within 5 to 10 percent of this dose. Four dose interpretations showed discrepancies larger than 20 percent. Differences in the computations larger than 1 percent were observed in over one-half of the cases. 相似文献
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Baumgartner A Steurer A Tiefenböck W Gabris F Maringer FJ Kapsch RP Stucki G 《Radiation protection dosimetry》2011,145(1):3-12
The graphite calorimeter of the Federal Office of Metrology and Surveying (BEV-Bundesamt für Eich- und Vermessungswesen) was established in the 1980s as the primary standard for the absorbed dose to water for (60)Co gamma ray beams. To maintain the primary standard at an international level the graphite calorimeter and its corresponding components had to undergo a refurbishment and modernisation process. The correction factors of the graphite calorimeter were re-evaluated with Monte Carlo and experimental methods to obtain improved values. These are the correction for the effect of the gaps (1.0061), the scaling correction (0.9998), the correction for the difference in air attenuation (0.9971) and the corrections for the effective measurement depths in the graphite phantom for the graphite calorimeter (0.9886) and the CC01-105 ionisation chamber (0.9913). Consequently, it was necessary to change the reference value for the absorbed dose rate to water of the (60)Co teletherapy unit used for the calibration of secondary standard dosemeters. 相似文献