Photon energy response optimization using few-channel spectroscopy dose method for Si-PIN photodetector applied in personal dose equivalent measurements

Si-PIN photodetectors having features such as low cost,small size,low weight,low voltage,and low power consumption are widely used as radiation detectors in electronic personal dosimeters(EPDs).The technical parameters of EPDs based on the Si-PIN photodetectors include photon energy response(PER),angular response,inherent error,and dose rate linearity.Among them,PER is a key parameter for evaluation of EPD measurement accuracy.At present,owing to the limitations of volume,power consumption,and EPD cost,the PER is usually corrected by a combination of single-channel counting techniques and filtering material methods.However,the above-mentioned methods have problems such as poor PER and low measurement accuracy.To solve such problems,in this study,a 1024-channel spectrometry system using a Si-PIN photodetector was developed and fullspectrum measurement in the reference radiation fields was conducted for radiation protection.The measurement results using the few-channel spectroscopy dose method showed that the PER could be controlled within±14%and±2%under the conditions of two and three energy intervals,respectively,with different channel numbers.The PER measured at 0°angle of radiation incidence meets the-29%to+67%requirements of IEC 61526:2010.Meanwhile,the channel number and counts-to-dose conversion factors formed in the experiment can be integrated into an EPD.

Measurement of air kerma rate and ambient dose equivalent rate using the G(E) function with hemispherical CdZnTe detector

Since the room-temperature detector CdZnTe(CZT) has advantages in terms of detection efficiency,energy resolution, and size, it has been extensively used to detect X-rays and gamma-rays. So far, nuclear radiation detectors such as cerium chloride doped with lanthanum bromide(LaBr_3(Ce)), thallium doped with cesium iodide(sI(Tl)), thallium doped with sodium iodide(NaI(Tl)),and high-purity germanium(HPGe) primarily use the spectroscopy-dose rate function(G(E)) to achieve the accurate measurement of air kerma rate(K_a) and ambient dose equivalent rate(H*(10)). However, the spectroscopy-dose rate function has been rarely measured for a CZT detector. In this study, we performed spectrum measurement using a hemispherical CZT detector in a radiation protection standards laboratory. The spectroscopy-dose rate function G(E) of the CZT detector was calculated using the least-squares method combined with the standard dose rate at the measurement position. The results showed that the hemispherical CZT detector could complete the measurement of air kerma rate(K_a) and ambient dose equivalent rate(H*(10)) by using the G(E) function at energies between 48 keV and 1.25 MeV, and the relative intrinsic errors were, respectively, controlled within ± 2. 3 and ± 2. 1%.

Estimation of the effect of target and normal tissue sparing based on equivalent uniform dose-based optimization in hypofractionated radiotherapy for lung cancer

Objective This study aims to investigate the dosimetric differences among four planning methods of physical and biological optimization in hypofractionated radiation therapy for non-small cell lung cancer(NSCLC).Methods Ten NSCLC patients receiving radiation therapy were chosen for this retrospective study.Volumetric modulated arc treatment plans for each patient were remade with dose-volume(DV)functions,biological-physical functions,and biological functions,using the same constraint parameters during optimization.The dosimetric differences between the four types of plans were calculated and analyzed.Results For the target,equivalent uniform dose(EUD)of the EUD and EUD+DV groups was approximately 2.8%–3.6%and 3.2%–3.7%higher than those of the DV and DV+EUD groups,respectively.The average tumor control probability(TCP)of the EUD and EUD+DV groups was also significantly higher than those of the other two groups(P<0.05).The difference in heterogeneity index(HI)among the four groups was also statistically significant(P<0.05),while the difference of conformity index(CI)was not significant(P>0.05).For the organs at risk,the differences of EUD,V5,V10,V20,V30 of normal lung tissues were not statistically significant(P>0.05);however,the mean lung dose of the EUD and EUD+DV groups was slightly lower than those of the other two groups.Conclusion The biological optimization method has obvious advantages of improving EUD and TCP of the target,while decreasing the exposed dose of normal lung.This result is meaningful in choosing plan optimization methods in routine work.

Assessment of Equivalent Radium Activity and Annual Effective Dose Due to Building Materials in Côte D’Ivoire by Gamma Spectrometry: Cases of Cement

Radioactivity is a natural phenomenon present in the universe. So, because of human life solidarity with a habitat, we are permanently in contact, especially through building materials. The objective of this work is the determination of the used cement radioactivity level in the buildings in Cote d'Ivoire. Thus, samples of grey and white cement currently used on Ivorian territory were taken. In order to determine the radioactivity level of this cement, samples were analyzed by using gamma spectrometry chain which contains a NaI (Tl) scintillation detector designed by the German manufacturer LD-DIDACTIC, coupled to a multichannel analyzer (AMC) using a Cassy Lab software. Thus, the specific activity of the primordial radionuclides 226Ra, 232Th and 40K, was able to be determined. The average values obtained are 29.66 Bq/kg, 34.88 Bq/kg and 178.424 Bq/kg respectively for 226Ra, 232Th and 40K. All average values are below the limit values recommended by UNSCEAR. However, we evaluated the radiological parameters such as the equivalent radium activity and the annual effective dose in order to translate the specific activity in terms of harmfulness. Values obtained for these parameters are below those recommended by ICRP and UNSCEAR. These results show that the risk incurred by the use of these different brands of cement is low.

Development of a spherical tissue equivalent proportional counter for neutron monitoring

A spherical tissue equivalent proportional counter(TEPC) for neutron monitoring has been developed. It was properly designed to produce a uniform electric field intensity around the anode wire. An internal ^(241)Am alpha source was adopted for lineal energy calibration. The TEPC was characterized in terms of dose equivalent response in a standard ^(252)Cf neutron field, and was tested with 2.45 MeV neutrons. Microdosimetric spectra, frequency mean lineal energy and dose-average mean lineal energy of 2.45 MeV neutrons were obtained and compared with FLUKA Monte Carlo simulation results. The measurement and simulation results agreed well. The mean quality factor and dose equivalent values evaluated from the 2.45 MeV neutron measurement were in good agreement with the recommended effective quality factor and ambient dose equivalent H*(10),respectively. Preliminary results have proved the availability of the developed TEPC for neutron monitoring.

不同性别和年龄的精神分裂症患者服用抗精神病药的等效剂量比较分析

目的:探讨不同性别和不同年龄的精神分裂症患者服用抗精神病药等效剂量的差异性。方法:对1552例精神分裂症住院患者的用药情况进行回顾性调查分析,按照服用的抗精神病药物分组,进行等效剂量换算,分别从性别和年龄对抗精神病药物治疗的等效剂量差异性进行分析。结果:性别分组结果显示女性精神分裂症患者的利培酮组、联合药物组以及氯氮平组的平均有效剂量分别为(10.53±2.57)mg、(18.45±7.08)mg、(6.54±2.58)mg,显著低于男性精神分裂症患者(P<0.01或P<0.05)。年龄分组结果显示55~66岁年龄段的平均有效剂量最低,16~55岁年龄段男性患者用药剂量显著高于女性患者,差异具有统计学意义(P<0.001或P=0.001)。结论:性别以及年龄因素均可能对精神分裂症患者抗精神病药治疗剂量产生影响。

土壤光释光测量方法在特拉敖包砂岩型铀矿产地的试验研究

文章以探索新型铀矿放射性勘查技术方法的试验效果为目的,在特拉敖包砂岩型铀矿产地开展了土壤光释光测量方法的试验研究。通过数据处理,综合地质、钻孔和物探相关先验信息,分析评价了土壤光释光测量方法在砂岩型铀矿勘查中的应用效果。试验结果显示:土壤光释光测量等效剂量数据非正态分布,不适宜采用逐步剔除法进行数据异常下限的计算;对数处理后的数据符合近似正态分布,可根据数据分布特征进行异常下限的估算。在铀矿体上方及其附近,存在土壤光释光测量等效剂量异常,表明该方法在砂岩型铀矿勘查领域具有较好的发展前景。通过对异常成因的分析,提出通过不同深度样品等效剂量差的矿致释光异常识别方法。

250~500 kV X射线窄谱辐射质空气比释动能测量及剂量当量转换系数研究

辐射剂量仪表的准确测量是开展辐射防护工作的重要保障,根据ICRU中规定的实用量要求,需要在特定的参考辐射场中对其进行检定或校准。参考ISO 4037-1:2019,建立250~500 kV X射线窄谱系列参考辐射质,对所建辐射场的均匀性以及相应辐射质下的能谱进行研究。将由EGSnrc模拟的X射线能谱得到所建辐射质下的平均能量、分辨率以及实验测量得到的半值层值与ISO标准推荐值进行比较,结果均满足规范要求,表明新建辐射质准确可靠。利用A5电离室对新建辐射场中的空气比释动能进行测量,再根据X射线能谱信息计算得到的空气比释动能到剂量当量的转换系数,实现空气比释动能到周围剂量当量和个人剂量当量的转换,从而为各类辐射剂量仪表在该高能段的能量响应评价提供了测量条件,保证了量值的准确与可靠。

多种水等效材料的医用电子束修正因子研究

针对水等效材料在医用电子束剂量测量中修正因子的测量和使用问题,通过扫描医用电子束在水中和水等效材料中的百分深度剂量(percentage depth dose,PDD)曲线,计算获得深度缩放因子c_(pl)、注量缩放因子h_(pl)及总修正因子k_(pl)的实验值。结果表明,通过c_(pl)和h_(pl)组合或仅使用k_(pl)均可将水等效材料测量结果转换为水吸收剂量。比较PDD曲线表明,在10~20 MeV电子能量下3种水等效材料通过c_(pl)-h_(pl)修正后的R_(50),较水中测量最大偏差分别为0.19%、0.28%、0.22%;经k_(pl)修正得到的R_(50),较水中测量最大偏差分别为0.23%、0.29%、0.18%。结论:研究提供了多种材料c_(pl)-h_(pl)、k_(pl)的实验值,可方便用户快速完成电子束水吸收剂量的测量,相比于c_(pl)-h_(pl),使用k_(pl)更加简单高效。

基于中子/瞬发γ射线联合测量的中子剂量监测模拟研究

辐射场下的中子周围剂量当量率监测具有重要意义,其可以反应核设施运行状况以及辐射防护信息。目前常用的监测仪器为基于单探测器、单慢化体的A-B型剂量当量率仪,其响应曲线与“中子注量-周围剂量当量转换系数”有较大的差异,导致测量结果误差较大。为提升中子剂量仪测量结果的准确性,对基于中子和瞬发γ射线联合监测中子剂量率开展研究。利用铅块、含硼聚乙烯、有机玻璃和氯化钠组合而成的转换材料,通过蒙特卡罗模拟计算B、H、Cl、Pb、C和O元素对不同能量中子的响应,利用响应曲线结合LB6411型剂量仪的响应曲线进行线性拟合,得到与“中子注量-周围剂量当量转换系数”更为接近的响应曲线。通过差分进化算法计算得到线性拟合系数,结果显示,新的响应曲线在1×10^(-8)~16 MeV能量区间内与h_(φ)响应曲线更贴近,二者的相对偏差在50%之内。联合测量中子与瞬发γ射线对中子周围剂量当量率进行监测可行,为中子剂量仪校准和研发提供了新的方向和支持。

中药联合多巴胺能药物对帕金森病运动症状及左旋多巴等效剂量影响的Meta分析

目的:系统评价中药联用多巴胺能药物对帕金森病(PD)运动症状及左旋多巴等效剂量的影响。方法:对已发表的中药治疗PD的随机临床对照试验(RCT)进行系统评价,通过统一帕金森病评分量表运动症状部分(UPDRSⅢ)评分和左旋多巴等效剂量(LED),对中药联用多巴胺能药物改善PD运动症状及治疗后多巴胺能药物用量变化进行Meta分析。结果:根据纳入与排除标准筛选文献,最终对6项RCT进行Meta分析。结果显示,中药联用多巴胺能药物能显著降低PD病人UPDRSⅢ评分,改善运动症状[MD=-4.03,95%CI(-4.93,-3.12),P<0.000 01];在排除异质性后发现联合中药治疗后能降低PD病人LED[MD=-55.35,95%CI(-86.17,-24.52),P=0.000 4]。对4项记录不良反应的RCT进行分析显示,中药联用多巴胺能药物的不良反应事件发生率较高[MD=2.41,95%CI(1.44,4.02),P=0.000 8]。结论:对纳入6篇文献的Meta分析结果显示,中药联用多巴胺能药物比单独运用多巴胺能药物能够在改善PD病人运动症状的同时减少治疗后LED,其轻度胃肠道症状反应的发生率较高,考虑与口服中药造成的胃肠道刺激相关。

广义等效均匀剂量生物优化法在食管癌调强计划的应用

目的探讨食管癌调强计划中广义等效均匀剂量生物优化法的应用。方法选取承德医学院附属医院8例食管癌患者。每位患者使用三种方式进行运算,分别是对心脏和肺采用单目标物理优化法(PlanA),多目标物理优化法(PlanB)以及广义等效均匀剂量生物优化法(PlanC)。脊髓及其外放的约束条件保持不变,对比3组计划的优劣。结果在靶区和脊髓以及脊髓外扩剂量没有发生明显变化时,用广义等效均匀剂量生物优化法设计的计划在肺和心脏的大部分均值都下降,Plan A与Plan C对比显示,肺的V5、V10、V20、V30及Dmean均有差异且具有统计学意义(P<0.05),心脏的V5、V10、V20及Dmean均有差异且具有统计学意义(P<0.05)。Plan B与PlanC对比显示,肺的V5、V10、V20、V30、V40及Dmean均有差异且具有统计学意义(P<0.05),心脏的V5、V20及Dmean均有差异且具有统计学意义(P<0.05)。在剂量体积直方图(DVH)的显示中,在计划靶区(PTV)曲线没有明显变化且脊髓及脊髓外扩也没有明显变化的情况下,肺和心脏的曲线均有不同程度的左移。并且肺的正常组织并发症概率(NTCP)下降且具有统计学意义(P<0.05)。结论采用广义等效均匀剂量生物优化法可以降低肺和心脏的照射剂量。广义等效剂量生物优化法要更优于多目标优化法和单目标优化法,可以更好的保护危及器官。

基于Eclipse计划系统等效均匀剂量在旋转调强放疗中的临床应用

目的对等效均匀剂量(equivalent uniform dose,EUD)在旋转调强放疗中的应用进行研究,探讨调强计划质量的优化方法。方法用Python分析EUD公式中a值对EUD曲线特征的影响。随机选取头颈部肿瘤、胸部肿瘤以及盆腔肿瘤各30例进行计划设计,分别用仅基于物理优化方式和物理约束条件配合EUD函数的优化方式对靶区和危及器官进行剂量优化,对两组计划的剂量分布、约束条件等指标进行比较,同时观察a的不同取值对计划结果的影响。结果a值对EUD曲线特征变化的影响与对EUD计划优化结果的影响一致,当-15≤a≤-5时,靶区剂量分布较均匀;当1≤a≤7时,约束危及器官的均匀剂量及低剂量区效果较明显;当10≤a≤30时,约束危及器官高剂量区效果明显,靶区和危及器官的EUD在不同a值下表达不同。研究还发现,采用EUD优化方式的计划组靶区的剂量分布和对危及器官的保护均优于仅用物理优化方法的计划组。结论a的取值对靶区和危及器官的剂量分布具有重要影响,为使用EUD优化调强计划时a值的设定提供了参考依据。EUD优化方法的使用能在保证靶区剂量分布的前提下,明显降低正常组织受量,减少并发症概率,具有一定临床应用价值。

晚更新世化石等效剂量标准生长曲线构建

通过分析牙釉质化石自然样品的电子自旋共振(Electron Spin Resonance,ESR)信号强度,可以构建牙釉质标准生长曲线(Standardised Growth Curve,SGC),用以直接获得样品等效剂量(DE)值。但由于不同时段的化石样品石化程度不同,其剂量响应特征也不尽相同,很难建立统一的化石标准生长曲线。本研究通过对32个中晚更新世阶段牙釉质样品ESR信号分析发现,这一时段的样品具有近似的剂量响应,因此在前期工作的基础上尝试采用三种不同方法构建晚更新世化石样品的标准生长曲线,并将获得的化石样品等效剂量与附加剂量法的结果进行了比较,最小偏差在26%内。本文还探讨了建立化石样品标准生长曲线的潜在优势。

儿童头颅CT检查不同辐射剂量衡量指标差异性比较及相关性分析

目的:比较容积CT剂量指数(volume CT dose index,CTDI_(VOL))及基于水当量直径的体型特异性剂量估计值(size-specific dose estimate based on water equivalent diameter,SSDE_(WED))在衡量儿童头颅CT辐射剂量中的差异性,并分析CTDI_(VOL)、SSDE_(WED)与曝光量、水当量直径(water equivalent diameter,WED)的相关性,以为临床检查中儿童头颅CT辐射剂量衡量提供参考。方法:回顾性分析2021年1—12月于某院进行头颅CT检查的1297例患儿的临床资料,根据年龄将患儿分为≤1个月组、>1个月~4岁组、>4~10岁组、>10~15岁组。记录患儿的曝光量、年龄、CTDI_(VOL)、剂量长度乘积,并计算WED、转换因子及SSDE_(WED)。比较CTDI_(VOL)与SSDE_(WED)的差异;建立CTDI_(VOL)、SSDE_(WED)与曝光量、WED的回归模型,并采用Pearson分析CTDI_(VOL)、SSDE_(WED)与曝光量、WED之间的相关性;对比国内诊断参考水平(diagnostic reference level,DRL)、欧盟DRL及本医疗机构诊断参考水平(local diagnostic reference level,LDRL)的差异。采用SPSS 25.0统计学软件进行分析。结果:患儿头颅CT的CTDI_(VOL)为(9.22±1.63)mGy,SSDE_(WED)为(8.14±0.84)mGy,CTDI_(VOL)较SSDE_(WED)高13.27%,差异有统计学意义(t=47.66,P<0.001)。CTDI_(VOL)、SSDE_(WED)与曝光量、WED均呈正相关关系(P<0.001);CTDI_(VOL)、SSDE_(WED)与曝光量、WED回归模型拟合性较强(R^(2)为0.58~0.99)。与国内DRL及欧盟DRL比较,LDRL均处于较低水平。结论:在儿童头颅CT辐射剂量衡量中,相较于CTDI_(VOL),SSDE_(WED)对辐射剂量的衡量更准确。同时定期对医疗机构的DRL值进行统计更新并优化检查参数,是减少辐射剂量的重要方式。

TEPC及其中子剂量测量应用研究进展

基于组织等效正比计数器(Tissue-Equivalent Proportional Counter,TEPC)的辐射监测装置在中子周围剂量当量测量领域展现出独特优势和应用潜力,成为各国新型中子剂量测量技术的研究热点。本文阐述了TEPC基本工作原理、各种技术路线的工作机理和特点优势,综述了基于TEPC的中子周围剂量当量测量技术的国内外研究和应用现状,并对关键技术的未来发展进行了展望。

关于近台操作的透视防护区检测平面上周围剂量当量率的探讨

目的分析介入放射诊疗的数字减影血管造影X射线设备(以下简称DSA设备)的放射卫生设备检测报告中的近台操作透视防护区检测平面上周围剂量当量率在验收检时的测情况和同一台设备的历年变化,针对近台工作人员受照剂量率与防护设施防护量的变化,进行讨论并提出建议。方法通过统计广州南方医大医疗设备综合检测有限责任公司近年来新验收的DSA设备和同一台设备三年间变化的透视防护区检测平面上周围剂量当量率,分析统计数据是否满足《医用X射线诊断设备质量控制检测规范》(WS 76—2020)的要求。结果新验收设备均能满足WS 76—2020要求,其中规范上所述的第二术者位的腹部位置的周围剂量当量率是其中较高的,同一设备连续三年的检测结果大部分未发生剧变。结论应加强关注第一术者位以外的其他近台工作人员的辐射防护量,要注意防护设施的日常维护和管理,增加个人防护用品的使用并增强个人防护意识,降低工作人员的受照剂量。

建筑火灾与人员疏散耦合模拟研究

为研究火灾环境下烟气对人员的影响,将火灾发展与人员疏散过程进行耦合。以某商场为研究对象,引入当量速度系数和有效剂量分数模型对商场火灾场景下的人员疏散速度进行修正,利用Pyrosim与Pathfinder建立更贴近真实火场的商场火灾与人员疏散耦合模型,得到火灾发展过程中的烟气浓度、温度、能见度与人员疏散过程的耦合时空分布图和烟气毒性对人员伤害的累积作用。模拟结果表明:通过对火灾发展与人员疏散的时空动态分析,在火灾发生380s后,商场剩余77人由于能见度下降不能完成疏散。相比于比较建筑内人员可用安全疏散时间(ASET)和必需安全疏散时间(RSET)的大小的传统判定方式,耦合模型更能直观准确地表现建筑物内火灾烟气对被疏散人员的实时影响。

Radiological characterization of building materials used in Malaysia and assessment of external and internal doses

In this study, the activity concentrations of ^(226)Ra,^(232)Th,^(222)Rn, and ^(40)K, emanation fractions(P),equilibrium equivalent concentration(EEC), and mass exhalation rates(E_m) of radon released from building materials used in Malaysia were studied using gamma-ray spectrometer with HPGe detector. Radiological parameters[activity concentration index(ACI), indoor air-absorbed dose rate(D_(in)), annual effective dose(AED_(in)) from external and internal(E_(Rn)), soft tissues(H_(ST)) and lung(H_L), and effective dose equivalent(H_(eff))] were estimated to evaluate radiological hazards due to the use of these building materials: sand, cement, gravel, bricks, tiles, fly ash, white cement, and ceramic raw materials. The measured P, EEC,and E_m vary from 10 to 30%, 0.9 to 22 Bq m^(-3), and 33 to 674 mBq h^(-1) kg^(-1), respectively, while the calculated ACI and AED_(in) vary from 0.1 ± 0.01 to 2.1 ± 0.1 and 0.1 ± 0.01 to 2.4 ± 0.6 mSv y^(-1), respectively. On the other hand, the internal annual effective dose ranges from 0.1 to 1.4 mSv y^(-1). The estimated radiological risk parameters were below the recommended maximum values, and radiological hazards associated with building materials under investigation are therefore negligible.

Natural radioactivity and the resulting radiation doses in some kinds of commercially marble collected from different quarries and factories in Egypt

Fourteen samples of marble were collected from different factories in Egypt. The samples were crushed, dried in controlled furnace for around twenty four hours, and then stored for five weeks in plastic Marinelli beakers. Concentrations and the U- and Th-bearing minerals were studied by scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS).The gamma radiation of the samples was measured, employing high resolution γ-ray spectroscopy with an accumulating time for about 80000 sec. each. From the measured γ -ray spectra, activity concentrations were determined for marble samples 226Ra (37. 6 ± 1.7 - 100.54 ± 3.2 Bq/kg), 232Th (3.57 ± 0.64 - 9.37 ± 1.80 Bq/kg) and 40K (30.68 ± 1.1 – 1196 ± 4.9 Bq/kg). The absorbed dose rates, annual effective dose rates, radium equivalent activities as well as the radiation hazard indices were estimated. The radium equivalent activities (Raeq) are lower than the limit of 370 Bq kg?1 set by the Organization for Economic Cooperation and Development (Exposure to radiation from the natural radioactivity in building materials. Report by a Group of Experts of the OECD, Nuclear Energy Agency, OECD, Paris, 1979) [1]. All obtained results referred to the fact that all the concentrations were within the allowed limits to domestic use. Comparing the results in this work with those published by International Atomic Energy Agency and local and universal researches, it was found that these concentrations were within the allowed limits for agricultural and domestic uses.