共查询到17条相似文献,搜索用时 171 毫秒
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<正>X射线半值层是指一束X射线的空气比释动能减弱到其初始值一半所需的标准物质的厚度。它直观的反映了X射线束的穿透能力,是医用X射线诊断辐射源的重要性能指标。根据JJG744-2004《医用诊断X射线辐射源检定规程》,半值层对于所有的X射线辐射源的首次和后续检定都是必检项目。但遗憾的是,JJG744-2004中对 相似文献
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随着国内X光机数量的迅速增多,简易有效的X光机半值层(HVL)质量检测方法也越来越重要。使用Penelope软件模拟N80(65keV)、N100(83 keV)、N150(118keV)、N200(164keV)重过滤窄谱辐照场中氟化锂热释光(LiF(Mg,Cu,P))剂量计在不同铜过滤片厚度下的能量沉积,分析计算得到X光机HVL; 通过实验测量LiF在N100(83keV)3m处窄谱标准辐照场的X光机HVL,对模拟程序进行了验证。对模拟结果与标准实验室电离室测量结果进行比较表明:对于低能N80(65keV)、N100(83keV)辐照场,LiF剂量计测量X射线半值层的方法具有可行性;N150(118keV)、N200(164keV)辐照场中模拟结果与实验室给出电离法测量得到的半值层值相对误差较大,不建议直接使用LiF测量半值层。 相似文献
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一、概述 1.测量标准和设备 依据JJG744-2004<医用诊断X射线辐射源>检定规程,在规定的测最条件下,使用不确定度小于5%的医用诊断X射线辐射源检定装置(其配套设备有非介入电压表、非介入电流表、半值层仪、星卡、分辨力卡、空盒气压表等),对工作级医用诊断X射线辐射源进行检定. 相似文献
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文章详细的介绍了医用电子直线加速器X射线辐射源在检定过程中的原理,方法。阐述了规程中对于剂量计算中的计算方法,介绍了治疗水平电离室剂量校正因子(Nx、ND、DW)。结合实例对加速器X射线吸收剂量测量及其计算问题进行探讨。 相似文献
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X光机的管电压、管电流及固有过滤是X射线光机质量控制的重要参数。X光机管电压、管电流以及固有过滤的测量,对于X光机的性能评价和参考辐射质的建立是非常必要的。以一台管电压上限为225kV的X光机为例,用能谱终点法测量对X光机的管电压进行测量,得出X光机能在±0.2%的范围内显示管电压值;用指型电离室PTW30013测量了高能X光机管电流的线性,测量得到的X光机的的管电流性能良好;用半值层法测量X光机的固有过滤,固有过滤为0.058mmAl. 相似文献
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一、概述1.测量依据JJG744-2004《医用诊断X射线辐射源》检定规程。2.环境条件检定的环境温度是诊断X射线机的常规使用条件,相对湿度:<85%。3.测量标准剂量计和电离室的不确定度Urel=2.0%,包含因子kp=2。4.被测对象医用诊断X射线辐射源空气比释动能率,X射线管的峰值电压范围为(30~150)kV,空气比释动能的不确 相似文献
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Hemdal B 《Radiation protection dosimetry》2011,147(1-2):196-201
From major protocols on dosimetry in mammography, there is no doubt that the incident air kerma should be evaluated without backscattered radiation to the dosemeter. However, forward-scattered radiation from the compression paddle is neglected. The aim of this work was to analyse the contribution of forward-scattered radiation for typical air kerma measurements. Measurements of forward-scatter were performed with a plane-parallel ionisation chamber on four mammography units. The forward-scatter contribution to the air kerma was 2-10 % and increased with the compression paddle thickness, but also with the half-value layer value. For incident air kerma in mammography, it can be as important to consider forward-scattered as backscattered radiation. If an ionisation chamber is used, the compression paddle should be in contact with the chamber; otherwise the air kerma and absorbed dose will be underestimated. If a dosemeter based on semiconductors with much less sensitivity to scattered radiation is used, it is suggested that a forward-scatter factor (FSF) is applied. Based on the results of this work, FSF = 1.06 will lead to a maximum error of ~4 %. 相似文献
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运用紫外光辐射的方法对超细羊毛纤维表面进行刻蚀、糙化, 并在其表面接枝载银纳米SiO2 抗菌剂制备抗菌羊毛纤维。通过SEM、IR 等, 对其物理性能进行了表征; 同时测试了其抗菌和耐洗涤性能。结果表明, 制备的抗菌羊毛纤维表面形成了约200 nm 的抗菌层, 羊毛纤维与纳米抗菌剂以价键形式结合而非单纯的物理吸附,其对大肠杆菌和金黄色葡萄球菌的抗菌率达96 %以上, 经20 次以上洗涤, 抗菌率仍能达到90 %以上。 相似文献
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In diagnostic radiology, the tube voltage [peak kilovoltage (kV(p))] is one of the most important parameter affecting both radiation exposure and image contrast. So, an accurate kV(p) meter is necessary to control kV(p) in the medical radiography practice with the overall uncertainty less than ± 5 % according to IEC 61676. Therefore, both invasive and non-invasive calibration methods of kV(p) meter were established and applied to different kinds of commercial quality control instruments for diagnostic radiology. Calibration of kV(p) meter by the invasive method is the most accurate (with uncertainty of 1.67 %, k=2); however, the non-invasive method also provides good results (with uncertainty of 3.12 %, k=2). Due to their detailed design, the commercial kV(p) meters have various responses with X-ray beam, so the working regime of a particular device type must be appropriately selected with a specific X-ray machine used for calibration of kV(p) meter. 相似文献
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Patient exposure in medical X-ray imaging in Europe 总被引:6,自引:0,他引:6
Patients are exposed to X rays when undergoing medical examinations in diagnostic radiology. Exposure data acquired and assessed in Germany for the year 1997 resulted in a mean annual effective dose of 2 +/- 0.5 mSv per head of the population, thereby reaching or exceeding the average level of environmental radiation in many cases. The underlying frequency of medical X-ray examinations was approximately 136 million, i.e. approximately 1.7 examinations annually per head of the population. For comparison, corresponding data of other countries were extracted from the UNSCEAR 2000 report or originate from the literature. Data analysis shows significant differences in national radiological practices and a very uneven distribution of patient doses amongst the world population. The mean annual effective dose per head of the population varies by up to a factor of 60 between health care level I and IV countries, and still by a factor of approximately 6 within health care level I countries. While projection radiography has succeeded in reducing dose consumption, computed tomography and radiological interventions have given rise to a significant growth of patient exposure, and interventional radiology can even exceed thresholds for deterministic radiation effects. Patient exposure is further shown to result from misadministration and retakes of X-ray examinations, usually not registered, as well as from technical failures of X-ray facilities, which can cause significantly enhanced exposure times. Corresponding data are presented and comments are made on the international situation of non-harmonised data collection on patient exposure as well as of parameters affecting the assessment of exposure and risk. 相似文献
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Kang HY Park S Hwangbo CK Seo HS Kim SS Cho HK 《Journal of nanoscience and nanotechnology》2012,12(4):3330-3333
In this study, we propose a new extreme ultraviolet (EUV) binary mask with an indium tin oxide (ITO) absorber. The optical constant of ITO film at 13.5 nm wavelength in the EUV regime was determined by means of X-ray reflectivity measurements and the chemical composition was determined using Rutherford backscattering spectrometry. The reflectance of a binary mask with an ITO absorber layer at various thicknesses was also measured to investigate the optical performance in the EUV regime. It was found that the extinction coefficient of ITO film is higher than that of a typical absorber layer, TaN, and that the reflectance of the ITO absorber in the binary mask at a wavelength of 13.5 nm is reduced to 0.62% at a thickness of 45 nm. Therefore, it is expected that the ITO film can be employed as a thin absorber of a binary mask to reduce the geometrical shadow effect in extreme ultraviolet lithography. 相似文献