~(60)Coγ射线单次和分次照射对兔外周血T淋巴细胞DNA合成影响的动态观察

本文报道长耳白兔受单次与分次~(60)Coγ线不同剂量照射后一个月外周血 T 淋巴细胞 DNA 的合成能力。结果表明,单次照射各剂量组均在照后第1天 DNA 合成受抑最严重,照后第3天各组开始恢复,第7天各组都恢复到照前水平。当剂量率、累积剂量均相同,仅分次照射的次数不同时,0.05Gy/d 组受抑恢复比0.10Gy/d 组慢。     

γ射线照射人肝细胞对BMP信号通路相关基因表达的影响

利用实时荧光定量PCR技术对人肝细胞株受不同剂量(0.1、0.2、0.5、1.0、2.0、4.0 Gy)⁶⁰Co γ射线照后不同时间点(6、12、24 h)的骨形成蛋白(BMP)信号通路相关基因表达的剂量和时间效应关系进行研究。结果显示,不同剂量照后不同时间点,BMP信号通路相关基因骨形成蛋白2(BMP2)、骨形成蛋白7(BMP7)、骨形成蛋白受体1A(BMPR1A)、骨形成蛋白受体1B(BMPR1B)、骨形成蛋白受体2(BMPR2)的溶解曲线均为单峰,均为特异性扩增产物。在不同照射剂量点BMP2的表达水平与照后时间呈正相关;BMP7在0.1、0.2、0.5 Gy的表达水平与照后时间呈负相关,在照后12和24 h的表达水平与照射剂量呈正相关;BMPR1A在0.1、0.2、1.0 Gy的表达水平与照后时间呈正相关;BMPR1B在0.2、0.5、1.0 Gy的表达水平与照后时间呈正相关,在4.0 Gy的表达水平与照后时间呈负相关;BMPR2在照后12 h的表达水平与照射剂量呈负相关。     

利用人外周血淋巴细胞染色体畸变估算离体模拟局部照射剂量

多数电离辐射事故均为局部照射。对于局部照射剂量估算,国际原子能机构(IAEA)推荐采用Dolphin's 模型,该模型需推算出照射部位染色体畸变率,再代入离体均匀照射情况下建立的剂量效应曲线来估算局部照射剂量。准确推算照射部位染色体畸变率对于估算剂量十分重要,选用合适的剂量效应曲线对估算剂量也同样重要,而对于局部照射,关于不同剂量率剂量效应曲线对估算结果影响的报道还十分有限。基于此本研究利用人外周血淋巴细胞染色体畸变估算离体模拟局部照射剂量,分析不同剂量率剂量效应曲线对估算结果的影响。利用⁶⁰Co γ射线离体照射人外周血样品(样本A和样本B),剂量分别为1 Gy和5 Gy。将照射血与未照射血按25%和75%比例混合以模拟局部照射,分析混合血样中淋巴细胞的双着丝粒染色体(dicentric chromosome,dic)加着丝粒环(r),利用Dolphin's模型估算局部照射dic+r率,并用剂量率不同的两种剂量效应曲线估算局部照射剂量。结果显示,大部分混合血样dic+r分布不符合泊松分布,为过离散分布。利用与实际照射剂量率一致的剂量效应曲线估算的样品受照剂量大多与实际照射剂量比较接近,相对偏差在10%以内,但两样本的1 Gy 25%组的估算受照剂量与实际照射剂量偏差较大。利用与实际照射剂量率不一致的剂量效应曲线估算的样品受照剂量与实际照射剂量相对偏差均超过10%。结果表明dic+r分析用于估算离体模拟局部照射的剂量有可行性,采用剂量率和照射剂量率一致的剂量效应曲线估算的结果更为准确。     

两例~(60)Co源事故受照病人的剂量估计

1986年5月26日,河南省开封市辐照厂两名工作人员进入了正在照射的~(60)Co 源(～0.3PBq)辐照室。通过模拟试验、辐射场分布测量和受照者左裤袋内手表红宝石的辐射热释光信号的测定,确定了事故照射的几何条件和受照时间。估计了受照病人的全身剂量和器官剂量,其中全身剂量包括造血干细胞活存计权等效剂量、红骨髓计权平均剂量和全身平均吸收剂盈。这些剂量估计结果与染色体畸变分析所估计的剂量值符合得很好。     

急性、分次及慢性γ线照射诱发猕猴生物效应的比较研究

本文就高剂量率急性一次(223mGy/min)、分次累积(223mGy/min,每周照射一次,0.25Gy/次)及低剂量率慢性连续(每周照射5天,50mGy/d)γ射线照射时,在0—2Gy 累积剂量范围内,对猕猴造血、免疫及细胞遗传学方面某些生物效应进行了比较研究。不同方式照射时机体损伤程度和特性不一,急性照射组各类效应均比其它受照组明显;而分次和慢性照射组的剂量-效应规律则比较相似。在低剂量率慢性照射情况下,PHA 激活淋巴细胞微核、淋巴细胞染色体无着丝点断片及总断裂数在累积剂量为0.25Gy 时就出现了明显增高(p<0.05),且与受照剂量呈线性正相关。它们的剂量-效应曲线尾部(在1—2Gy 区)均呈现有“坪”的现象。停照后一年中动态观察的结果表明,各照射组动物受照时所诱发的效应,绝大多数是可恢复的。急性组恢复至正常所需时间较其它组长,其中免疫和造血机能的恢复呈显著波动性,而细胞遗传学效应随停照后时间的延长逐步恢复。     

出生前受照的电离辐射效应

出生前电离辐射照射诱发的生物效应,有些在出生时就能观察到,有些直至生命晚期尚不能检测到。来自广岛和长崎原爆幸存者的数据表明,在怀孕四周内受照使生育率下降。虽然在动物实验中用同样剂量的X射线照射发现了大量的先天性畸形,而在人类只观察到小头畸形(怀孕4—17周受照)和先天性智力障碍(在怀孕8—15周受照)。在广岛数据中受照0.10—0.19Gy以上剂量照射引起小头畸形,受0.2—0.4Gy以上剂量照射导致超额先天性智力障碍。在怀孕8—15周受照的原爆幸存者中,智力测试成绩每Gy下降21至29个智商点。原爆所致的其它的宫内受照效应还包括各种持久的染色体畸变。     

乳腺癌术后放疗时靶外组织剂量的研究

本文借助非均匀组织等效拟人体模型,模拟成年女性左侧乳腺癌术后放疗,研究了医用电子直线加速器产生的９ＭｅＶ电子束和６ＭＶ Ｘ射线对乳腺癌放疗时靶外组织的受照剂量。结果表明,单次照射剂量２．０Ｇｙ时,在胸壁照射区域,电子束照射时体表的受照剂量较高,位于野内左后壁的剂量明显低于野外右乳腺的剂量,野外组织受照剂量波动较大,Ｘ射线照射时野外组织受照剂量波动较小,受照剂量最高的具有一定深度的纵隔;     

蒙特卡罗法估算中子受照剂量

根据中国人人体特征和MIRD模型,构建符合中国成年男性人体特征的数学模型(CRHMIRD模型);然后基于MCNP 4C,利用CRH-MIRD模型,针对0-10 Me V的中子能量和不同照射方式,研究得到不同能量中子所致吸收剂量与人体24Na比活度的比值系数;应用中,根据照射情景查得中子所致吸收剂量与人体24Na比活度的比值系数,通过测量人体24Na比活度即可估算中子受照剂量。此方法适用中子能量范围广,应用便捷,可用于事故现场中子辐射损伤伤员的受照剂量估算,为伤员救治及时提供支持。     

四君子汤对受照小鼠体重及外周血象的影响

采用CCK-8试剂盒检测不同终浓度(0、5、25、50、250和500μg/m L)四君子汤及其单味组份作用48 h对AHH-1细胞的毒性作用,以及不同终浓度(0、0.4、2、10和50μg/m L)四君子汤及其单味组份预处理AHH-1细胞2 h后对经4 Gy60Coγ射线照射的细胞存活的影响。将BALB/c小鼠80只,雌雄各半,随机分为阴性对照组、照射对照组、四君子汤低剂量组(0.75 g/kg)、四君子汤中剂量组(2.25 g/kg)、四君子汤高剂量组(6.75 g/kg),检测各组照后3天和7天的外周血白细胞、红细胞、血红蛋白、血小板数量,以及照前7天至照后7天小鼠体重的变化,研究四君子汤对60Coγ射线照射引起的小鼠体重及外周血象的影响。结果显示,与对照细胞相比,5、25和50μg/m L四君子汤及其单味组份作用于AHH-1细胞48 h对细胞存活无明显影响(p0.05),但50μg/m L四君子汤可显著提高受照后24 h AHH-1细胞的存活率(p0.05)。四君子汤中剂量组小鼠外周血白细胞数与照射对照组相比显著升高(p0.01),并且四君子汤中剂量组能明显减弱受照小鼠外周血血小板数的降低,同时四君子汤可以减轻辐射损伤所致的体重下降。上述研究结果表明,四君子汤对受照射AHH-1细胞具有一定的辐射损伤防护作用;四君子汤通过影响受照射后小鼠造血系统,促进体重恢复,减轻辐射所致损伤。     

不同剂量γ射线照射诱发CHL细胞基因组不稳定性的研究

采用单细胞凝胶电泳技术和微核检测技术对60Coγ射线照射诱发中国仓鼠肺细胞(CHL细胞)产生的直接效应、基因组不稳定性进行了初步探讨.将对数生长期的细胞分成不同的剂量组,经γ射线照射后,对受照存活细胞进行单细胞凝胶电泳(SCGE)和微核发生率(MF)的测定.同时,将一部分受照存活细胞继续传代培养,待其传至33代时,再给予2 Gy的照射剂量进行二次照射,然后再进行单细胞凝胶电泳和MF的测定.结果表明,首次照射剂量与子代二次照射后的损伤程度存在剂量-效应关系.本实验为探讨辐射诱发基因组不稳定性的研究提供了实验基础.     

Assessing dose of the representative person for the purpose of radiation protection of the public. ICRP publication 101. Approved by the Commission in September 2005

The Commission intended that its revised recommendations should be based on a simple, but widely applicable, system of protection that would clarify its objectives and provide a basis for the more formal systems needed by operating managers and regulators. The recommendations would establish quantified constraints, or limits, on individual dose from specified sources. These dose constraints apply to actual or representative people who encounter occupational, medical, and public exposures. This report updates the previous guidance for estimating dose to the public. Dose to the public cannot be measured directly and, in some cases, it cannot be measured at all. Therefore, for the purpose of protection of the public, it is necessary to characterise an individual, either hypothetical or specific, whose dose can be used for determining compliance with the relevant dose constraint. This individual is defined as the 'representative person'. The Commission's goal of protection of the public is achieved if the relevant dose constraint for this individual for a single source is met and radiological protection is optimised. This report explains the process of estimating annual dose and recognises that a number of different methods are available for this purpose. These methods range from deterministic calculations to more complex probabilistic techniques. In addition, a mixture of these techniques may be applied. In selecting characteristics of the representative person, three important concepts should be borne in mind: reasonableness, sustainability, and homogeneity. Each concept is explained and examples are provided to illustrate their roles. Doses to the public are prospective (may occur in the future) or retrospective (occurred in the past). Prospective doses are for hypothetical individuals who may or may not exist in the future, while retrospective doses are generally calculated for specific individuals. The Commission recognises that the level of detail afforded by its provision of dose coefficients for six age categories is not necessary in making prospective assessments of dose, given the inherent uncertainties usually associated with estimating dose to the public and with identification of the representative person. It now recommends the use of three age categories for estimating annual dose to the representative person for prospective assessments. These categories are 0-5 years (infant), 6-15 years (child), and 16-70 years (adult). For practical implementation of this recommendation, dose coefficients and habit data for a 1-year-old infant, a 10-year-old child, and an adult should be used to represent the three age categories. In a probabilistic assessment of dose, whether from a planned facility or an existing situation, the Commission recommends that the representative person should be defined such that the probability is less than about 5% that a person drawn at random from the population will receive a greater dose. If such an assessment indicates that a few tens of people or more could receive doses above the relevant constraint, the characteristics of these people need to be explored. If, following further analysis, it is shown that doses to a few tens of people are indeed likely to exceed the relevant dose constraint, actions to modify the exposure should be considered. The Commission recognises the role that stakeholders can play in identifying characteristics of the representative person. Involvement of stakeholders can significantly improve the quality, understanding, and acceptability of the characteristics of the representative person and the resulting estimated dose.     

Age-dependent dose conversion coefficients for external exposure to radioactive cesium in soil

To estimate effective doses for members of the public exposed to external radiation from radioactive cesium (¹³⁴Cs and ¹³⁷Cs) deposited on the ground by the Fukushima nuclear accident, we calculate the conversion coefficients for converting activity concentration to effective dose rate by using the Particle and Heavy Ion Transport Code System. The data were produced from different age groups within the public (newborns; 1-, 5-, 10-, and 15-year-old children; and adults) for the situations in which radioactive cesium is distributed uniformly in the soil over a planar area and at specific depths of 0.0, 0.5, 2.5, 5.0, 10.0, and 50.0 g/cm². On the basis of the results, we also derive the conversion coefficients for exponentially distributed volumetric sources. In addition, we obtain the conversion coefficients that give the effective dose accumulated over the first and second months, the first year, and over a lifetime (50 years) because of the contamination remaining on the ground. These calculations indicate that the conversion coefficients to obtain the effective dose rate are higher for the younger ages compared with adults, but do not exceed the ambient dose equivalent rate. Furthermore, we find that the difference between the calculated effective dose rates according to the International Commission on Radiological Protection 1990 and 2007 Recommendations is small (7% maximum) for a ground contamination of radioactive cesium.     

Annals of the ICRP. A report of: doses to infants from ingestion of radionuclides in mothers' milk

In the present report, ICRP provides information on radiation doses to the infant due to intakes of radionuclides in maternal milk. As in Publication 88 (ICRP, 2001) on doses to the embryo and fetus following intakes of radionuclides by the mother, intakes by female members of the public and female workers are addressed. Acute and chronic intakes are considered at various times before and during pregnancy as well as during the period of breastfeeding. Dose coefficients per unit intake by the mother (Sv/Bq) are given for the selected radionuclides of the same 31 elements for which age-specific biokinetic models were given in Publications 56, 67, 69, and 71 (ICRP, 1989, 1993, 1995a,b). For these elements, doses were calculated for the most radiologically significant natural or artificial radionuclides that might be released into the environment due to various human activities. Dose coefficients are also given in this report for radionuclides of an additional four elements: sodium, magnesium,phosphorus, and potassium. Relevant human and animal data on elemental and radionuclide transfer to milk are reviewed. The biokinetic models for adults given in earlier ICRP publications are adapted to include transfer to milk. Model predictions of fractional transfer of ingested or inhaled activity to milk are discussed in the report, and the corresponding dose coefficients for the infant are compared with dose coefficients for in utero exposure, as given in Publication 88 (ICRP, 2001). Illustrative information is also given on doses to the female breast from radionuclides in breastmilk, and external doses received by the child from radionuclides retained in the tissues of the mother. For the additional elements considered in this report, but not in Publication 88 (ICRP,2001), information is also given on doses to the embryo and fetus following maternal intakes of radioisotopes during or before pregnancy. A CD-ROM is to be issued giving data that will supplement the information given in this report. In addition to the dose coefficients given here, committed equivalent doses to the various organs and tissues of the offspring will be given. Dose coefficients will also be given for inhalation of a range of aerosol sizes for the selected radionuclides of the elements covered by this report.     

Ambient dose equivalent conversion coefficients for radionuclides exponentially distributed in the ground

Conversion coefficients of radionuclide deposition density to the ambient dose equivalent rate at 1 m height above ground were calculated for exponentially distributed sources in the ground. First, Monte Carlo transport simulations assuming exponential distributions in the ground were performed to obtain ambient dose equivalent for mono-energetic gamma-ray sources having different relaxation depths; next, on the basis of the simulated data, conversion coefficients for radionuclides were composed considering recent nuclear decay data. The ambient dose equivalent rates were then compared to the effective dose rates for reference adults and a new-born baby as well as to air kerma rates quoted from previous studies. It was confirmed that the ambient dose equivalent sufficiently overestimates effective doses, independently of age, for sources exponentially distributed in the ground. Furthermore, the air kerma was found to also overestimate the effective doses for all ages in the same conditions. In order to verify the computed conversion coefficients, the ratio of ambient dose equivalent to air kerma obtained by simulation was compared to the ratios measured at hundreds of locations in Japan which have been contaminated with radioactive cesium after the accident at the nuclear power plant in Fukushima Prefecture, Japan, in 2011; a good agreement was observed.     

氚的内照射剂量转换系数研究

不同的生物动力学模型给出的氚的摄入量滞留函数和剂量转换系数存在明显的差别。Crawford-Brown模型在氚化学形态转化描述和年龄段剂量转换系数分析上具有独特优势,本文在比较不同模型研究进展的基础上,重点对Crawford-Brown模型进行计算,给出不同年龄段的氚滞留函数和剂量转换系数,并同其他模型计算结果进行了详细的比较。结果显示,除了成人摄入氚水情况,Crawford-Brown模型计算给出的不同年龄段人群摄入氚水和有机氚的剂量转换系数都会比ICRP模型的高。随着年龄的减小,氚水和有机氚的相互转换愈发明显,剂量转换系数上的差别愈发明显。成人氚水摄入量滞留函数的比较表明,几种模型在100 d内的滞留函数曲线几乎完全相同,只在长期滞留项上存在显著差别。     

基于蒙特卡罗数学模型评价不同螺距冠状动脉CCTA受检者辐射剂量的特点与验证

收集61例采用双源CT Flash大螺距冠状动脉CCTA (Coronary Computed Tomography Angiography,CCTA)受检者资料,按WHO亚洲人体质量指数(BMI )标准将研究对象分为三组:正常组(12例)、超重组(41例)和肥胖组(8例),应用蒙特卡罗(Monte Carlo)数学模型软件计算三组受检者大螺距与常规螺距行CCTA的器官剂量,比较两种螺距CCTA时受检者的器官剂量分布特点及两种螺距CCTA的有效剂量变化幅度,并与大螺距模式下CT设备直接读取法所得有效剂量值进行比较。结果表明,用蒙特卡罗软件计算的双源CT大螺距CCTA受检者的器官剂量比常规螺距技术的剂量降低约70%,其中心脏、胸腺的器官剂量下降最为明显,降幅最大约80%;三组CCTA受检者大螺距较常规螺距的有效剂量(E)均降低明显(p<0.05),正常组使用大螺距技术后有效剂量E降幅最为明显;大螺距模式下数学模型软件模拟有效剂量E与CT设备所测有效剂量E间的偏差度小于50%。说明Monte Carlo数学模型软件可用于检查前预估或回顾性分析CCTA扫描时受检者的器官剂量与有效剂量的分布情况,并预判CCTA大螺距模式对受检者的胸部器官剂量和有效剂量,从而达到了降低辐射剂量的目的,尤其对BMI较小的受检者(如儿童)控制辐射风险更具意义。对开展低剂量CT技术具有一定实际意义。     

利用蒙特卡罗建模及估算儿童X-CT检查受照剂量

在儿科X射线-CT检查迅速增加的当下,尤其对电离辐射敏感的儿童,其所致医疗照射剂量的评估是十分重要和迫切的课题。本文结合已建立的1岁儿童体素体模,利用蒙特卡罗技术建立扫描模型,进行CT检查所致儿童受检者的医疗照射剂量估算。建立了CT单层轴向扫描时对1岁儿童36个器官或组织所产生医疗照射剂量的数据库,利用该数据库,可快速估算1岁儿童受检者接受CT扫描时的医疗照射剂量。并与同样扫描条件下的实验测量值进行了比较,结果显示二者相对偏差在25%以内。     

甲癌患者131I治疗后手及颈部剂量当量率的监测与临床意义

为监测分化型甲癌(differentiated thyroid carcinoma,DTC)患者¹³¹I治疗后手及颈部近距离剂量当量率变化情况,指导患者如何进行最优化的辐射防护。以100例DTC患者按治疗次数分为两组,每组各50例,组1为首次行¹³¹I清甲治疗患者(服用¹³¹I剂量3 700～4 440 MBq),组2为再次行¹³¹I清灶治疗患者(服用¹³¹I剂量6 660～8 140 MBq),采用Inspector Alert γ射线检测仪分别对两组患者于¹³¹I治疗后出院时、出院后1周、2周、1个月及2个月进行双手及颈前部剂量当量率测量,测量距离包括颈前部、手掌部30 cm处及紧贴皮肤处。结果表明,(1)随着时间的延后,各监测时间点剂量当量率逐渐降低。患者出院后1个月距患者颈部、手掌部30 cm处剂量当量率、出院后2个月各监测部位剂量当量率均值均在天然本底范围内( 0.25 μSv/h) 。(2)¹³¹I治疗出院时,患者颈部剂量当量率均值均大于手掌部位,但出院后1周、2周及1个月,患者手掌部位剂量当量率均大于颈部。(3)出院后1个月内,一疗程患者颈部各时间点剂量当量率均值均大于二疗程(p＜ 0.05),二疗程患者紧贴手部各时间点剂量当量率均值明显大于一疗程(p＜ 0.05)。¹³¹I治疗患者刚出院时,各监测部位剂量当量率均较高(＞20 μSv/h),建议患者出院后1周内避免与他人亲密接触,2周内避免长时间超亲密接触,避免与特殊人群(如婴幼儿、孕妇等)零距离接触(如拥抱、亲吻等),出院后1个月距离患者≥30 cm的社交活动和出院后2个月的社交活动可完全不受限制。患者手部容易被污染导致剂量当量率较高,尤其是二疗程患者,应做好辐射防护隔离措施。     

Simulation study of personal dose equivalent for external exposure to radioactive cesium distributed in soil

The personal dose equivalent was calculated for the public (newborns; 1-, 5-, 10-, and 15-year-old children; and adults) in an environment contaminated with radioactive cesium (¹³⁴Cs and ¹³⁷Cs) distributed in a soil at specific depths of 0.0, 0.5, 2.5, 5.0, 10.0, and 50.0 g/cm², and the conversion coefficients for converting activity concentration to personal dose equivalent rate were provided for each age group. Monte Carlo calculations were performed using pediatric and adult computational phantoms incorporated into a particle and heavy ion transport code system. Compared with the effective dose and ambient dose equivalent at a height of 100 cm above the ground, the personal dose equivalent was found to provide a good estimate as a measurable quantity for the effective dose and did not exceed the ambient dose equivalent even in the environmental radiation fields, while the personal dose equivalent values increased for younger subjects. The weighted-integral method to obtain the personal dose equivalent for a volumetric source was applied to the analysis of exponential radioactive cesium distributions in the soil observed in Fukushima, and the calculation results successfully reproduced the measured data.     

国际放射防护委员会的剂量系数的可靠性

在评价公众成员摄入放射性核素的辐射危害时，需估算每单位摄入量所致的剂量。摄入放射性素后器官或民受到的剂量是受到的剂量是通过生物学模型和剂量学模型来确定的，因此剂量也必须根据模型来确定。文中初步探讨了国际放射防护委员会给出的剂量系数的可靠性问题。文中首先说明了估算剂量系数的概念和方法，然后分析了剂量系数估算中，采用胃肠道模型，呼吸道模型，系统生物动力学模型和剂量学模型所遇到的不确定度的各种主要来源。