玻璃电子自旋共振剂量学特性的研究进展

辐照后的玻璃可经电子自旋共振（ESR）波谱仪检测出ESR信号,包括本底信号、机械信号和辐射信号。ESR信号的大小与受照剂量基本成正比。当发生核事故或突发辐射意外时,可以通过对受照人员随身携带物品或事故区域内的玻璃进行ESR测量,快速估算事故剂量,评价事故的严重程度,并对受照人员进行及时的医学救治。玻璃具有廉价、化学惰性、刚度好、易于处理、普遍易得等特点,是一种很有前景的剂量估算物理剂量计。笔者主要对玻璃构成、剂量估算原理、ESR信号组成及其剂量学特性进行了探讨。     

正常人牙釉ESR信号强度水平及其影响因素

最近电子共振自旋(ＥＳＲ)方法越来越多地被用于事故剂量的估算,所应用的材料很广泛,如人和某些动物的骨[1,2]、牙齿、头发、佩带的手表[3]、环境材料(如水泥、花岗岩、石英、玻璃、陶瓷等)、贝壳、鸡蛋壳[4]等。但应用最多的是用牙釉作剂量估算,如广岛和长崎的原爆幸存者[5]、切尔诺贝利核事故周边居民及救灾人员[6]、前苏联Ｍａｙａｋ核设施的工作人员[7]。对事故人员的危险度估计以及受照剂量在低剂量范围时,事故剂量就需要进行准确估算。准确可靠而具有代表性的本底信号水平是进行剂量估算的基础;在慢性低水平辐射剂量范围内,本底的准确…     

辐照后硅掺杂羟基磷灰石顺磁性变化及其剂量学性能初步研究

目的 通过分析辐照后硅掺杂羟基磷灰石(Si?HAP)的顺磁性变化,研究Si?HAP材料的剂量学特性,为新型电离辐射剂量测量材料研究提供参考.方法 采用化学沉淀法合成Si?HAP样品,利用不同光子能量射线源照射,采用电子自旋共振(ESR)波谱技术分析辐射相关信号的变化.结果 合成的样品为Si?HAP,硅元素以Si?O基团...     

用电子顺磁共振波谱拟合方法估算牙釉质辐射剂量

目的 探讨运用电子顺磁共振(electron paramagnetic resonance, EPR)波谱拟合技术估算牙釉质EPR辐射剂量的准确性。方法 编制多成分叠加型EPR粉末波谱拟合软件,分别拟合牙齿本底信号(background signal,BS)和辐照诱发信号(radiation-induced signal,RS)的EPR波谱模型,用波谱模型叠加计算方法拟合出实际辐照后牙釉质的EPR波谱,从复合谱中提取出RS成分并计算其相对强度,建立剂量响应曲线,估算样品剂量,并将剂量估算结果与传统的波谱强度测量方法进行比较。结果 拟合获得的BS信号为单峰高斯线形粉末谱,g=2.0035,线宽Hpp=0.650-1.100 mT; RS信号为轴对称多晶粉末谱线形,其g_⊥=2.0018,g_‖＝1.9965,线宽Hpp=0.335-0.400 mT;分离BS与RS后得到的RS相对强度与辐照剂量呈线性相关,剂量响应方程为:y=240.74x+76 724(R²=0.9947),剂量估算结果相对误差期望值为0.13。结论 EPR波谱拟合方法在一定程度上提高了牙釉质辐射剂量估计的准确性和可信度。     

石英的辐射剂量学特性研究

电子自旋共振 (ESR)技术现已广泛应用于辐射剂量测量 ,近年来人们试图寻找更多的环境和生物材料做为辐射事故剂量计 ,估算事故剂量。国内外对石英受大剂量照射后的稳定信号做了一些研究[1,2 ]。本实验以一批熔融石英样品作为实验对象 ,研究其经6 0 Coγ照射在 0～ 6Gy剂量范围内的剂量学特性。一、材料和方法1 材料 :选用纯度约为 99 99%的直径为 3mm熔融石英棒 ,加工成长为 10mm的石英样品。2 实验方法 :①分散性 :实验选用不同批次的 5种石英样品 ,用6 0 Coγ射线源照射 ,吸收剂量 2 0Gy ,照射后 10min内用ESR仪测量其信号。②剂量响…     

核事故体内污染的评价方法

主要以ICRP近年公布的有关报告为依据,并结合1998年以来这方面的研究成果,总结出在目前情况下核事故体内污染评价的较为有效的方法。对核事故体内污染评价的一般程序、评价的剂量学量和剂量估算方法以及估算摄入量的主要方法进行了描述。重点介绍了用剂量系数h_T(τ)和e(τ)估算待积当量剂量H_T(τ)和待积有效剂量E(τ)的方法。也对通过环境物质检测、体外直接测量的生物样品检测进行摄入量估算等主要方法进行了介绍。     

蒙特卡罗模拟方法结合不同体模在剂量估算中的应用

随着核与辐射在人们日常生活中的应用越来越广泛,其所带来的危害也备受关注。剂量估算是辐射技术应用的重要一环,估算出人体所受的剂量对评价辐射造成的确定效应与随机效应起着重要作用。蒙特卡罗（MC）模拟与人体参考模型结合可对核事故、医疗照射和环境的辐射剂量进行估算,是一种快速且对硬件要求较少的剂量估算方法,目前正面临模型开发和计算耗时的瓶颈,笔者对此现状进行综述。     

强碱变性法制备电子自旋共振剂量测定用的牙釉质样品

牙釉质的电子自旋共振 (ESR)剂量测定技术是当前用来估算核事故受照射人员辐射剂量的重要方法。使用传统的机械法制样不能彻底除去牙本质 ,笔者探讨了用强碱变性法制备用于ESR剂量测定的牙釉质样品的新方法[1 ] ,报道如下。牙釉质是由羟基磷灰石构成 (99 5 % ) ,具有较强的化学稳定性 ,而牙本质则含有大约 2 0 %的胶原物质 ,因此可用强碱溶液对牙样进行选择性的变性处理。一、材料和方法1 样品预处理 :收集成人磨牙 2 0颗 ,剔除残留的软组织 ,洗净 ,在 5 0℃烘箱中干燥后 ,将每颗磨牙按纵向切成两半。再将牙根部分切掉 ,所保留的牙冠即为…     

浙江和广东省部分砖样的剂量学研究

随着我国放射源的应用日益广泛，以及核电站的不断发展，急待建立和完善与核能、核技术发展相适应的各种医学应急救援手段和方法。而核事故后的核设施周围环境的剂量估算，对于事故的处理具有非常重要的意义。人们试图在核事故现场寻找一些可用来估算核事故剂量的物质，为事故的剂量估算提供较为客观的数据。研究发现广泛用于建筑材料的砖和瓦中，含有可用于辐射剂量响应的热释光物质。砖和瓦中经过化学前处理后，从中提取石英样品可作为热释光剂量计，用于照射后剂量估算。笔者主要将广东和浙江两省的砖样作为研究对象，对其剂量学性能进行了研究。研究方法直接采用将砖和瓦样品粉碎后，未经化学处理直接进行热释光测量。     

日射量的估算及其对牙釉质电子自旋共振剂量学的影响

目的 探讨日射量的估算方法及太阳光辐射对牙釉质电子自旋共振(ESR)剂量学的影响。方法 用机械方法获得11个牙釉质样品。用照度计测量太阳光的照度,通过比较日本气象厅在广岛市测得的瞬时日射量和相同时刻所测得的照度,计算出转换系数,然后估算出照射在牙釉质样品的累积日射量。用⁶⁰⁶⁰Co γ射线和太阳光分别照射牙釉质样品,使用ESR波谱仪测量不同辐射后牙釉质样品的ESR信号。结果 照度与瞬时日射量的转换系数为(8.67±0.22) W·m^-2klx。照射在牙釉质样品上的累积日射量为(580±16) MJm²。太阳光辐射也引起γ射线照射产生的剂量学信号,而且随累积日射量而线性增强,太阳光辐射还产生一个紧邻本底的信号,当累积日射量大于某一值时,该信号趋于饱和状态。结论 用剂量学信号对所受辐射剂量进行评价,本研究中每MJm²的太阳光辐射的影响相当于(7.7±1.4) mGy的γ射线辐射。紧邻本底的ESR信号可作为太阳光辐射的标志峰,有助于判断所收集的样品是否受到太阳光辐射,从而提高小剂量重建的准确度。     

用牙釉电子自旋共振方法估算慢性辐射损伤人员的受照剂量

目的 用于牙釉电子自旋共振对慢性辐射损伤人员的受照剂量进行估算的方法。方法 用电子自旋共振仪测定慢性辐射损伤人员牙釉电子自旋共振信号强度，用剂量－效应曲线法和附加剂量法来重建辐射损伤人员的受照剂量，探讨牙釉电子自旋共振法估算受照剂量的可行性；并比较了不同能量的射线（1.25MeV的γ射线和6MeV的X射线）对牙釉电子自旋共振信号强度的影响。结果 用两种方法估算的辐射损伤人员受照剂量基本一致；对能量1.25MeV的γ射线和6MeV的X射线进行比较，无论从剂量－效应曲线的直线系数，还是用混合照射后的剂量估算，两者差别不大。结论 慢性辐射损伤人员的受照剂量可以用于牙釉电子自旋共振方法进行估算，射线能量在1.25MeV-6MeV范围内对牙釉电子自旋共振信号强度影响不大。     

Dosimetry for radiation emergencies: Radiation-induced free radicals in sugar of various countries and the effect of pulverizing on the ESR signal

Household sugar has been proposed as a dosimeter for radiation emergencies, since radiation-induced free radicals in sucrose are known to be relatively stable and can readily be analyzed by the electron spin resonance (ESR) method. Elemental impurities in crystalline sugar produced in 19 countries were investigated with ESR spectroscopy. Certain characteristic contributions to the ESR signal from trace elements were not detected in any of the sugar samples. No difference in the radiation-induced properties, i.e. ESR sensitivity and decay of the ESR signal intensity, was observed with sugar produced in any of 19 countries. The induction of free radicals when sugar crystals are ground into fine powder or are irradiated by γ rays was compared by ESR spectroscopy, as a means of testing the possible differences between the response of sugars in the various sugar-producing countries. The maximum equivalent radiation absorbed dose caused by the powdering of sugar reached about 10 Gy. The precision of the ESR measurement observed with only one sample tube is much greater than the precision between several different samples. Furthermore, it was found that both the radiation-induced and pulverization-induced free radicals in sugar are quite stable, even when heated to near the melting point.     

核事故剂量的顺磁分析方法研究与应用

目的建立电离辐射事故剂量的实际测量方法。方法用电子自旋共振（ＥＳＲ）技术，在人体骨髓型急性放射病阈剂量以上范围，对人体生物样品及可能的随身佩带材料的剂量响应特性，信号稳定性，本底均一性，可测剂量下限及辐射条件和环境影响因素等基本剂量学特性进行了实验研究。结果建立了多项适于实际事故剂量测量的顺磁剂量测量指标和方法，并在包括切尔诺贝利事故在内的三起辐射事故剂量评估中得到了成功的应用。结论这项工作进一步证实了ＥＳＲ在事故剂量评估中的重要作用。     

The use of organic substances as emergency dosimeters

In unexpected encounters with ionizing radiation, it is possible to monitor absorbed exposure or absorbed dose by ESR analysis of incidental organic materials carried by both workers and non-workers with radiations. Materials of interest include plastics, paper, clothing, buttons, human hair and nail. The concept is to correlate with dose the quantity of free radicals generated in organic materials by irradiation. The experiments were aimed at determining the sensitivity, the fading, the effects of differences in conditions of storage such as temperature, illumination, and washing before ESR analysis. The method should prove useful for estimating the extent of radiation exposure at strategic locations on the body.     

Dose control in the semi-industrial irradiation plant at Ezeiza Atomic Center

High-dose dosimetry is carried out at Ezeiza Atomic Center (CAE) on a routine basis, within the absorbed dose range 10²–10⁵ Gy using potassium nitrate dosimeters (Dorda and Muñoz, 1985). The reference dosimeter is Fricke and Super Fricke. The next inauguration of a private irradiation plant and the increasing interest for a new technology in the industry led us to use a dosimeter easy to be read, without need for wet chemical analysis: the alanine dosimeter (Regulla and Deffner, 1982). Under the influence of ionizing radiation, the alanine in the crystalline state forms stable paramagnetic free radicals. The radical concentration of irradiated alanine, which is proportional to the absorbed dose, can be measured using electron spin resonance (ESR) spectroscopy. The pellets are made of 90% alanine and 10% paraffin. The procedure for mixing is not simple: temperature control is used to get an homogenous mass. The dose evaluation is performed for the ESR signal by measuring the maximum peak-to-peak amplitude. Intercomparison studies were made between the alanine and potassium nitrate dosimeter with good results. The relative standard deviation of our alanine dosimeter at doses of 25 and 32 kGy and 25°C temperature is 4%.     

In vivo ESR dosimetry in total body irradiation

Total body irradiation (TBI) using high doses (about 10 Gy) with photons in the range between 1 and 10 MV combined with intensive chemotherapy has been used successfully in treatment of acute and chronic leukemia before bone marrow transplantation. One of the principal international guidelines in TBI is to use in vivo dosimetry in order to compare the prescribed dose with that absorbed. The use of in vivo dosimetry is also useful as a retrospective evaluation of any deviation from the prescribed dose greater than +/- 5% for relevant parts of the body, especially in the lung and in other organs at risk. In this paper, Electron Spin Resonance (ESR), using alanine dosimeters, is demonstrated to be a powerful tool for absorbed dose evaluation in TBI by detection of free radicals produced in alanine by ionizing radiation. In this study, we present the results obtained using ESR dosimetry in eleven patients undergoing TBI. The major advantages appear to be: 1. the ESR signal in alanine dosimetry is stable for years without fading: 2. the detection of the ESR signal does not destroy the information and so enables a retrospective judgment of the TBI plan adopted.     

ESR dosimetry using inorganic materials: a case study of Li2CO3 and CaSO4:Dy as prospective dosimeters.

The CO2- radical ion, detected by ESR technique in bones and teeth enamel, was proved to be invaluable in high level and retrospective dosimetry. In these matrices, impurity carbonate (at phosphate sites) was the precursor to CO2-. With a view to investigate the possibility of using inorganic materials such as lithium carbonate as ESR dosimeters, studies were carried out on gamma-irradiated Li2CO3. The intensity of radiation-induced ESR signals of Li2CO3 at g = 2.0036 (CO3-) and g = 2.0006 (CO2-) was followed as a function of gamma dose in the low dose range of 1-1350 Gy. It was observed that the intensity of the ESR signal at g = 2.0036 (CO3-) was in a linear relation with the radiation dose in the dose range 10-800 Gy and the signal at g = 2.0006 (CO2-) showed linear response in the dose range 5-800 Gy. The lowest dose that could be detected in the present studies using the signal of CO2- in Li2CO3 powder samples (approximately 50 mg) is 3.2 Gy. ESR studies were also carried out on the widely used TL dosimetric material CaSO4:Dy and in pure CaSO4 after gamma irradiation. The TL materials were used in powder as well as pellet forms. The linearity of ESR response with dose for powder and pellet forms of CaSO4: Dy was also studied using the signals at g = 2.0030 (SO3-) and at g = 2.0139 (SO4-). It was observed that the range of linearity of dose response extended between 20 and 1200 Gy, for SO3- signals. The results of dosimetric study indicate that the ESR-Li2CO3 system could be used in dosimetric applications in radiotherapy. However, for the actual applications further advancement is needed to lower the detection limit. The TL phosphor, CaSO4:Dy in powder and pellet forms, could be used as ESR dosimeter in the dose range 20-600 Gy.     

Ammonium tartrate as an ESR dosimeter material

This study is one step in the search for an ESR dosimeter material with a higher signal intensity than the commonly used l-α-alanine, to be useful in the clinical dose range (approximately 0.1–20 Gy). The substance ammonium tartrate was found and investigated regarding signal intensity, radical stability, dose response and dose resolution. The ESR signal intensity of ammonium tartrate was shown to be more than twice the intensity of the alanine signal. The data indicate that an unstable radiation induced radical contributes to the ESR signal initially; after a couple of hours it has converted to a secondary radical which has a decay slow enough to be considered stable during the first two weeks after irradiation. Ammonium tartrate has a linear dose response in the investigated range of 0.5–4000 Gy and a dose resolution of 0.1 Gy at the 0.5 Gy level where, as a comparison, the corresponding value for alanine is 0.3 Gy. We thus find the substance suitable for clinical dosimetry.     

A comparative study based on dosimetric properties of different sugars.

Measurements of free radical densities in sugar by electron spin resonance (ESR) constitute a useful method for determining the dose received in the case of accidental irradiation because this material retains its radiation history. The aim of this work is to establish methods for practical dose assessment of people involved in ionising irradiation accidents, using two types of sugar: sucrose and dextrose. In this regard, practical considerations of sample preparation, grain size, ESR spectrum and spurious mechanical-induced ESR signal are discussed. Also presented are results for signal reproducibility, radiation response, signal stability and low-dose values. Studies on irradiated samples were carried out to explain the complex spectra derived from different paramagnetic species.