外照射小剂量电离辐射所致器官剂量的估算应用研究

目的：探索一种可行的γ能谱分析用于辐射流行病学调查现场常见场景情况下外照射所致器官剂量的估算方法,并展望此方法在器官剂量估算中的应用前景。方法：采用无源效率刻度方法对阳江高本底地区居民居住环境所测量的γ能谱进行分析,根据已有的转换系数对居民器官剂量进行估算和分析,并和对应位置所测量的空气比释动能所估算出来的全身有效剂量进行对比。结果：采用无源效率刻度方法,分析阳江高本底地区和对照地区居民(成年男性)包括红骨髓、结肠(壁)、甲状腺及眼晶体等30个人体器官的年器官吸收剂量和全身有效剂量。高本底地区居民全身有效剂量的估算结果(不含宇宙射线)为1.97～2.93 mSv/a,计算得到的测量点的空气比释动能和在同一测量点实测的结果相一致。结论：该实验设计方案合理,其结果可信,同时表明该方法在小剂量电离辐射所致器官剂量估算中的应用可行。     

Analysis of the effects of low doses of ionizing radiation

The paper analyzes the data available in the literature and the authors' own findings relating to the effects of low-dose ionizing radiation on biological objects, which confirm a higher likelihood of general somatic diseases upon exposure to small dosages (as low as 200 meq).     

Analysis in changes in health status as a result of irradiation with low doses of ionizing radiation

The first part of this paper is published in the journal "Meditsinskaya Tekhnika" (Medical Engineering), No. 2, 2002. The paper analyzes the data available in the literature and the authors' own findings relating to the effects of small-dosage ionizing radiation on the human health status and on biological objects.     

Possible discrepancies between dicentric chromosome frequencies and recorded ionizing radiation doses: in vivo study.

BACKGROUND: The available data on the effects of radiation on humans are limited to the reports of accidental exposure or studies of patients under diagnostic and therapeutic treatment; few reports refer to a occupationally exposed population groups. METHODS: The research was conducted on 66 subjects employed in the Department of Nuclear Medicine and 41 nonemployed controls. For each of them chromosomal analysis and gamma-spectrometer analysis of 24-hour urine were carried out. Exposure doses were measured using film-badge dosimetry. RESULTS: The comparison of dosimetric data obtained by film-badge measurements and the frequency of dicentric chromosomes in each subject revealed no correlation between the two observed parameters. CONCLUSIONS: In view of the above results, the subjects should be studied within job/task groups as they are far more likely to receive comparable doses.     

Cancer risk at low doses of ionizing radiation: artificial neural networks inference from atomic bomb survivors

Cancer risk at low doses of ionizing radiation remains poorly defined because of ambiguity in the quantitative link to doses below 0.2 Sv in atomic bomb survivors in Hiroshima and Nagasaki arising from limitations in the statistical power and information available on overall radiation dose. To deal with these difficulties, a novel nonparametric statistics based on the ‘integrate-and-fire’ algorithm of artificial neural networks was developed and tested in cancer databases established by the Radiation Effects Research Foundation. The analysis revealed unique features at low doses that could not be accounted for by nominal exposure dose, including (i) the presence of a threshold that varied with organ, gender and age at exposure, and (ii) a small but significant bumping increase in cancer risk at low doses in Nagasaki that probably reflects internal exposure to ²³⁹Pu. The threshold was distinct from the canonical definition of zero effect in that it was manifested as negative excess relative risk, or suppression of background cancer rates. Such a unique tissue response at low doses of radiation exposure has been implicated in the context of the molecular basis of radiation–environment interplay in favor of recently emerging experimental evidence on DNA double-strand break repair pathway choice and its epigenetic memory by histone marking.     

电离辐射对放射工作人员细胞遗传学的影响

目的 通过对放射工作人员辐射剂量进行监测,探讨电离辐射对放射工作人员细胞遗传学的影响.方法 采用流行病学中队列研究的方法,选取唐山市内1 392名放射工作人员作为观察组,选取无射线接触史且其他条件与观察组具有可比性的143名身体健康者为对照组.分别行一般情况调查、放射剂量测量、微核检测、染色体畸变检测.结果 放射线接触组微核率和染色体畸变率均明显高于对照组.按不同工种分组,观察组微核率和染色体畸变率依照医学放射诊断组、工业探伤组、工业用放射源组、医学放免放疗组的次序呈现出一定程度的递增趋势.按不同工龄分析,＜10、10～ 20和＞20a工龄组的放射工作人员细胞微核异常率分别为10.8％、16.2％、24.8％,对照组为2.1％,差异均有统计学意义(P ＜0.05或0.01);染色体畸变异常率亦随放射工龄的增加而升高.差异均有统计学意义(P＜0.05).随着累积辐射剂量的增加,放射工作人员累积微核异常率、累积染色体畸变异常率也随之增加.结论 电离辐射对放射工作人员健康状况产生一定程度的影响,淋巴细胞微核率和染色体畸变率将会有所增高.从事不同放射工种的放射工作人员受到的辐射损伤不同,放射工作人员受到的辐射损伤与接触射线年限有关,放射工龄越长,累积电离辐射剂量越高,细胞微核率和染色体畸变率越高,其对机体造血系统的损伤越严重,细胞微核率、染色体畸变率与累积辐射剂量均具有一定程度的关联.     

电离辐射和非电离辐射复合作用的生物学效应

在现实环境中，我们有时可能受到的不止是1种而是2种或多种环境因素的影响，因此，在积极探讨电磁波损伤的规律与机制的同时，电磁波与其他形式的损伤因子，比如与低温、缺氧、射线等的复合效应，也渐渐引起人们的关注，在军事领域，有专家甚至提出了电磁复合伤的概念。其中，电离辐射和非电离辐射的复合效应尤为引人瞩目。     

低剂量电离辐射对放射工作人员细胞遗传学影响

目的 分析低剂量电离辐射对放射工作人员细胞遗传学影响.方法 采用放射场所辐射剂量、个人剂量、细胞遗传学指标检测及流行病学横断面调查研究方法.结果 射线接触组染色体畸变率(0.16%)高于对照组(0.04%),染色体畸变检出率(17.05%)高于对照组(5.1%),微核率(1.03‰)高于对照组(0.2‰),微核检出率(48.06%)高于对照组(12.25%),差异均有统计学意义(χ²=8.45,P<0.01;χ²=7.59,P<0.01;χ²=57.23,P<0.01;χ²=32.52,P<0.01);不同年剂量、累积剂量组染色体畸变率、微核率与对照组比较,差异均有统计学意义;随着个人年剂量、累积剂量水平的增加,染色体畸变率、微核率、微核阳性检出率有增高趋势.结论 长期低剂量电离辐射,对淋巴细胞产生的辐射效应导致的染色体畸变率、微核率的增加并与放射人员个人累积吸收剂量密切相关.     

Interaction of ionizing radiation with matter

The basic physical mechanisms by which different kinds of ionizing radiation interact with matter are described. Understanding of these processes, coupled with detailed knowledge of atomic structure, provides much of the foundation for the theory and practice of radiological health protection today.     

Interaction of ionizing radiation with matter

The basic physical mechanisms by which different kinds of ionizing radiation interact with matter are described. Understanding of these processes, coupled with detailed knowledge of atomic structure, provides much of the foundation for the theory and practice of radiological health protection today.     

Toward improved ionizing radiation safety standards

Ionizing radiation safety standards developed by the International Commission on Radiological Protection (ICRP) during the past 50-plus years have provided guidance for effective protection of workers and the public from the potentially harmful effects of exposure to ionizing radiation, including cancer. Earlier standards were based primarily on radiation dose rate to organs of the body. More recent recommendations have calculated cancer risk as a function of cumulative dose using a linear no-threshold cancer risk model based on the acute high dose rate exposures received by the Japanese atomic bomb survivors. The underlying assumption in these current recommendations is that risk of radiation-induced cancer is proportional to cumulative dose without threshold. In conflict with this position are the studies of protracted exposures from internally-deposited radionuclides in people and laboratory animals that have demonstrated that cancer induction risk is a function of average dose rate for protracted exposures to ionizing radiation. At lower average dose rates, cancer latency can exceed natural lifespan leading to a virtual threshold. This forum statement proposes that the conflict of these two cancer risk models is explained by the fact that the increased risk of cancer observed in the atomic bomb survivor studies was primarily the result of acute high dose rate promotion of ongoing biological processes that lead to cancer rather than cancer induction. In addition, ionizing radiation-induced cancer is not the result of a simple stochastic event in a single living cell but rather a complex deterministic systemic effect in living tissues. It is recommended that the ICRP consider revising its position in light of this important distinction between cancer promotion and cancer induction.