Gamma Low-Dose-Rate Ionizing Radiation Stimulates Adaptive Functional and Molecular Response in Human Aortic Endothelial Cells in a Threshold-, Dose-, and Dose Rate–Dependent Manner

Science.gov (United States)

Vieira Dias, Juliana; Gloaguen, Celine; Kereselidze, Dimitri; Manens, Line; Tack, Karine; Ebrahimian, Teni G

2018-01-01

A central question in radiation protection research is whether low-dose and low-dose-rate (LDR) exposures to ionizing radiation play a role in progression of cardiovascular disease. The response of endothelial cells to different LDR exposures may help estimate risk of cardiovascular disease by providing the biological mechanism involved. We investigated the effect of chronic LDR radiation on functional and molecular responses of human aorta endothelial cells (HAoECs). Human aorta endothelial cells were continuously irradiated at LDR (6 mGy/h) for 15 days and analyzed at time points when the cumulative dose reached 0.05, 0.5, 1.0, and 2.0 Gy. The same doses were administered acutely at high-dose rate (HDR; 1 Gy/min). The threshold for the loss of angiogenic capacity for both LDR and HDR radiations was between 0.5 and 1.0 Gy. At 2.0 Gy, angiogenic capacity returned to normal only for HAoEC exposed to LDR radiation, associated with increased expression of antioxidant and anti-inflammatory genes. Pre-LDR, but not pre-HDR, radiation, followed by a single acute 2.0 Gy challenge dose sustained the expression of antioxidant and anti-inflammatory genes and stimulated angiogenesis. Our results suggest that dose rate is important in cellular response and that a radioadaptive response is involved for a 2.0 Gy dose at LDR. PMID:29531508

Dose-rate effects on mammalian cells exposed to ionizing radiation

International Nuclear Information System (INIS)

Mitchell, J.B.

1978-01-01

The effect of irradiation on the life cycle and on cell survival was studied for a range of different dose rates. Log phase, plateau phase and synchronized cultures of different mammalian cells were used. Cell cycle redistribution during the radiation exposure was found to be a very important factor in determining the overall dose-rate effect for log phase and synchronized cells. In fact, cell cycle redistribution during the exposure, in some instances, resulted in a lower dose rate being more effective in cell killing per unit dose than a higher dose rate. For plateau phase cultures, where cell cycle times are greatly lengthened, the effects of redistribution in regard to cell killing was virtually eliminated. Both fed and unfed plateau phase cultures exhibited a dose-rate effect, but it was found that below dose rates of 154 rad/h there is no further loss in effectiveness

Exposure to low doses of ionizing radiations

International Nuclear Information System (INIS)

Le Guen, B.

2008-01-01

The author discusses the knowledge about the effects of ionizing radiations on mankind. Some of them have been well documented (skin cancer and leukaemia for the pioneer scientists who worked on radiations, some other types of cancer for workers who handled luminescent paints, rock miners, nuclear explosion survivors, patients submitted to radiological treatments). He also evokes the issue of hereditary cancers, and discusses the issue of low dose irradiation where some surveys can now be performed on workers. He discusses the biological effects of these low doses. He outlines that many questions remain about these effects, notably the influence of dose level and of dose rate level on the biological reaction

The health effects of low-dose ionizing radiation

International Nuclear Information System (INIS)

Dixit, A.N.; Dixit, Nishant

2012-01-01

It has been established by various researches, that high doses of ionizing radiation are harmful to health. There is substantial controversy regarding the effects of low doses of ionizing radiation despite the large amount of work carried out (both laboratory and epidemiological). Exposure to high levels of radiation can cause radiation injury, and these injuries can be relatively severe with sufficiently high radiation doses. Prolonged exposure to low levels of radiation may lead to cancer, although the nature of our response to very low radiation levels is not well known at this time. Many of our radiation safety regulations and procedures are designed to protect the health of those exposed to radiation occupationally or as members of the public. According to the linear no-threshold (LNT) hypothesis, any amount, however small, of radiation is potentially harmful, even down to zero levels. The threshold hypothesis, on the other hand, emphasizes that below a certain threshold level of radiation exposure, any deleterious effects are absent. At the same time, there are strong arguments, both experimental and epidemiological, which support the radiation hormesis (beneficial effects of low-level ionizing radiation). These effects cannot be anticipated by extrapolating from harmful effects noted at high doses. Evidence indicates an inverse relationship between chronic low-dose radiation levels and cancer incidence and/or mortality rates. Examples are drawn from: 1) state surveys for more than 200 million people in the United States; 2) state cancer hospitals for 200 million people in India; 3) 10,000 residents of Taipei who lived in cobalt-60 contaminated homes; 4) high-radiation areas of Ramsar, Iran; 5) 12 million person-years of exposed and carefully selected control nuclear workers; 6) almost 300,000 radon measurements of homes in the United States; and 7) non-smokers in high-radon areas of early Saxony, Germany. This evidence conforms to the hypothesis that

Health hazards of low doses of ionizing radiations. Vo. 1

International Nuclear Information System (INIS)

El-Naggar, M.A.

1996-01-01

Exposure to high doses of ionizing radiation results in clinical manifestations of several disease entities that may be fatal. The onset and severity of these acute radiation syndromes are deterministic in relation to dose magnitude. Exposure to ionizing radiations at low doses and low dose rates could initiate certain damage in critical molecules of the cell, that may develop in time into serious health effects. The incidence of such delayed effects in low, and is only detectable through sophisticated epidemiological models carried out on large populations. The radiation damage induced in critical molecules of cells may develop by stochastic biochemical mechanisms of repair, residual damage, adaptive response, cellular transformation, promotion and progression into delayed health effects, the most important of which is carcinogenesis. The dose response relationship of probabilistic stochastic delayed effects of radiation at low doses and low dose rates, is very complex indeed. The purpose of this review is to provide a comprehensive understanding of the underlying mechanisms, the factors involved, and the uncertainties encountered. Contrary to acute deterministic effects, the occurrence of probabilistic delayed effects of radiation remains to be enigmatic. 7 figs

Biological effects of low doses of ionizing radiation

International Nuclear Information System (INIS)

Gonzalez, A.J.

1994-01-01

Few weeks ago, when the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) submitted to the U.N. General Assembly the UNSCEAR 1994 report, the international community had at its disposal a broad view of the biological effects of low doses of ionizing radiation. The 1994 report (272 pages) specifically addressed the epidemiological studies of radiation carcinogenesis and the adaptive responses to radiation in cells and organisms. The report was aimed to supplement the UNSCEAR 1993 report to the U.N. General Assembly- an extensive document of 928 pages-which addressed the global levels of radiation exposing the world population, as well as some issues on the effects of ionizing radiation, including: mechanisms of radiation oncogenesis due to radiation exposure, influence of the level of dose and dose rate on stochastic effects of radiation, hereditary effects of radiation effects on the developing human brain, and the late deterministic effects in children. Those two UNSCEAR reports taken together provide an impressive overview of current knowledge on the biological effects of ionizing radiation. This article summarizes the essential issues of both reports, although it cannot cover all available information. (Author)

The limiting dose rate and its importance in radiation protection

International Nuclear Information System (INIS)

Bakkiam, D.; Sonwani, Swetha; Arul Ananthakumar, A.; Mohankumar, Mary N.

2012-01-01

The concept of defining a low dose of ionizing radiation still remains unclear. Before attempting to define a low dose, it is more important to define a low-dose rate since effects at low dose-rates are different from those observed at higher dose-rates. Hence, it follows that low dose-rates rather than a low dose is an important criteria to determine radio-biological effects and risk factors i.e. stochastic health effects. Chromosomal aberrations induced by ionizing radiations are well fitted by quadratic model Y= áD + âD 2 + C with the linear coefficient of dose predominating for high LET radiations and low doses of low LET. At higher doses and dose rates of sparsely ionizing radiation, break pairs produced by inter-track action leads to the formation of exchange type aberrations and is dependent on dose rate. Whereas at lower doses and dose rates, intra-track action produces break pairs and resulting aberrations are in direct proportion to absorbed dose and independent of dose rate. The dose rate at which inter-track ceases to be observable and where intra-track action effectively becomes the sole contributor of lesion-pair formation is referred to as limiting dose rate (LDR). Once the LDR is reached further reduction in dose rates will not affect the slope of DR since breaks produced by independent charged particle tracks are widely separated in time to interact with each other for aberration yield. This linear dependency is also noticed for acute exposures at very low doses. Existing reports emphasizes the existence of LDR likely to be e6.3cGyh -1 . However no systematic studies have been conducted so far to determine LDR. In the present investigation DR curves were constructed for the dose rates 0.002 and 0.003 Gy/min and to define LDR at which a coefficient approaches zero. Extrapolation of limiting low dose rate data can be used to predict low dose effects regardless of dose rate and its definition ought to serve as a useful index for studies pertaining

Dose-rate dependent stochastic effects in radiation cell-survival models

International Nuclear Information System (INIS)

Sachs, R.K.; Hlatky, L.R.

1990-01-01

When cells are subjected to ionizing radiation the specific energy rate (microscopic analog of dose-rate) varies from cell to cell. Within one cell, this rate fluctuates during the course of time; a crossing of a sensitive cellular site by a high energy charged particle produces many ionizations almost simultaneously, but during the interval between events no ionizations occur. In any cell-survival model one can incorporate the effect of such fluctuations without changing the basic biological assumptions. Using stochastic differential equations and Monte Carlo methods to take into account stochastic effects we calculated the dose-survival rfelationships in a number of current cell survival models. Some of the models assume quadratic misrepair; others assume saturable repair enzyme systems. It was found that a significant effect of random fluctuations is to decrease the theoretically predicted amount of dose-rate sparing. In the limit of low dose-rates neglecting the stochastic nature of specific energy rates often leads to qualitatively misleading results by overestimating the surviving fraction drastically. In the opposite limit of acute irradiation, analyzing the fluctuations in rates merely amounts to analyzing fluctuations in total specific energy via the usual microdosimetric specific energy distribution function, and neglecting fluctuations usually underestimates the surviving fraction. The Monte Carlo methods interpolate systematically between the low dose-rate and high dose-rate limits. As in other approaches, the slope of the survival curve at low dose-rates is virtually independent of dose and equals the initial slope of the survival curve for acute radiation. (orig.)

Effects of prolonged irradiation by low dose-rate ionizing radiation on the production of growth factors in murine bone marrow cells

Energy Technology Data Exchange (ETDEWEB)

Saitou, Mikio; Sirata, Katsutoshi; Yanai, Takanori; Tanaka, Satoshi; Onodera, Junichi; Otsu, Hiroshi; Sato, Fumiaki [Institute for Environmental Sciences, Department of Radiobiology, Rokkasho, Aomori (Japan)

1999-07-01

To evaluate effects of prolonged irradiation by low dose-rate ionizing radiation on the production of growth factors of cells, the dose dependency of the expression of cytokines, interleukin-6 (IL-6) and granulocyte-macrophage colony stimulating factor (GM-CSF), of mice is being measured at accumulated doses between 1 and 8 Gy, with the dose interval of 1 Gy. In the present work, specific-pathogen-free (SPF) C3H-HeN female mice were irradiated by {sup 137}Cs {gamma}-rays with the doses of 5-8 Gy at the dose rate of 20 mGy (22 h-day){sup -1}, and the expression of IL-6 and GM-CSF in bone marrow and spleen cells from the mice were measured semiquantitatively by the reverse transcriptase-polymerase chain reaction (RT-PCR) method. (author)

Reducing ionizing radiation doses during cardiac interventions in pregnant women.

Science.gov (United States)

Orchard, Elizabeth; Dix, Sarah; Wilson, Neil; Mackillop, Lucy; Ormerod, Oliver

2012-09-01

There is concern over ionizing radiation exposure in women who are pregnant or of child-bearing age. Due to the increasing prevalence of congenital and acquired heart disease, the number of women who require cardiac interventions during pregnancy has increased. We have developed protocols for cardiac interventions in pregnant women and women of child-bearing age, aimed at substantially reducing both fluoroscopy duration and radiation doses. Over five years, we performed cardiac interventions on 15 pregnant women, nine postpartum women and four as part of prepregnancy assessment. Fluoroscopy times were minimized by simultaneous use of intracardiac echocardiography, and by using very low frame rates (2/second) during fluoroscopy. The procedures most commonly undertaken were closure of atrial septal defect (ASD) or patent foramen ovale (PFO) in 16 women, coronary angiograms in seven, right and left heart catheters in three and two stent placements. The mean screening time for all patients was 2.38 minutes (range 0.48-13.7), the median radiation dose was 66 (8.9-1501) Gy/cm(2). The median radiation dose to uterus was 1.92 (0.59-5.47) μGy, and the patient estimated dose was 0.24 (0.095-0.80) mSv. Ionizing radiation can be used safely in the management of severe cardiac structural disease in pregnancy, with very low ionizing radiation dose to the mother and extremely low exposure to the fetus. With experience, ionizing radiation doses at our institution have been reduced.

Effects of prolonged irradiation by low dose-rate ionizing radiation on the production of growth factors in murine bone marrow cells

Energy Technology Data Exchange (ETDEWEB)

Saitou, Mikio; Yamada, Yutaka; Shirata, Katsutoshi; Yanai, Takanori; Izumi, Jun; Tanaka, Satoshi; Onodera, Jun' ichi; Otsu, Hiroshi; Sato, Fumiaki [Institute for Environmental Sciences, Rokkasho, Aomori (Japan)

2000-07-01

To evaluate effects of prolonged irradiation by low dose-rate ionizing radiation on the production of growth factors of cells, the expression of cytokines, interleukin-6 (IL-6) and granulocyte-macrophage colony stimulating factor (GM-CSF), of mice is being measured at accumulated doses between 1 and 8 Gy, with the dose interval of 1 Gy. In the present work, ten specific-pathogen-free (SPF) C3H/HeN female mice per experimental group were irradiated with {sup 137}Cs {gamma}-rays with the doses of 1-4 Gy at the dose rate of 20 mGy/(22 h-day), and the expression of IL-6 and GM-CSF in bone marrow and spleen cells from the mice was measured semiquantitatively by the reverse transcriptase-polymerase chain reaction (RT-PCR) method. (author)

Effects of prolonged irradiation by low dose-rate ionizing radiation on the production of growth factors in murine bone marrow cells

International Nuclear Information System (INIS)

Saitou, Mikio; Yamada, Yutaka; Shirata, Katsutoshi; Yanai, Takanori; Izumi, Jun; Tanaka, Satoshi; Onodera, Jun'ichi; Otsu, Hiroshi; Sato, Fumiaki

2000-01-01

To evaluate effects of prolonged irradiation by low dose-rate ionizing radiation on the production of growth factors of cells, the expression of cytokines, interleukin-6 (IL-6) and granulocyte-macrophage colony stimulating factor (GM-CSF), of mice is being measured at accumulated doses between 1 and 8 Gy, with the dose interval of 1 Gy. In the present work, ten specific-pathogen-free (SPF) C3H/HeN female mice per experimental group were irradiated with 137 Cs γ-rays with the doses of 1-4 Gy at the dose rate of 20 mGy/(22 h-day), and the expression of IL-6 and GM-CSF in bone marrow and spleen cells from the mice was measured semiquantitatively by the reverse transcriptase-polymerase chain reaction (RT-PCR) method. (author)

Evaluation of quality characteristics and functional properties of mechanically deboned chicken meats treated with different dose rates of ionizing radiation and use of antioxidants

International Nuclear Information System (INIS)

Brito, Poliana de Paula

2012-01-01

The Mechanically Deboned chicken meat (MDCM) is used in traditional meat products, in greater proportion in those emulsified, replacing meat raw materials more expensive. The raw material can have high MDCM the microbial load, as a result of contamination during processing or failure during the evisceration. The irradiation process is accepted as one of the most effective technologies when compared to conventional techniques of preservation, to reduce contamination of pathogens and spoilage. However, little information is available about the use and effects of different dose rates of ionizing radiation processing. Irradiation causes chemical changes in food, a major cause of deterioration of quality of raw or cooked meat products during refrigerated storage, frozen. The objective of this study was to evaluate the effects of different dose rates of ionizing radiation on the production of Thiobarbituric Acid Reactive Substances (TBARS), color, microbiological and sensory characteristics of mechanically deboned chicken added or without added antioxidants, during the cold storage and evaluation of functional properties. The results showed that among the tested dose rates using cobalt-60 source, dose rate of 4.04 kGy.h-1 was the best for processing MDCM. Furthermore, the use of the combination of rosemary antioxidant and α-tocopherol were able to reduce lipid oxidation generated by irradiation of the samples, showed a synergistic effect to the processing with ionizing radiation in reduction of psychrotrophic bacteria count and contributed to a better sensory quality. The use of radiation in the processing FDMI did not adversely affect the functional properties studied. (author)

A graphical review of radiogenic animal cancer data using the 'dose and dose-rate map'

International Nuclear Information System (INIS)

Yoshida, Kazuo; Hoshi, Yuko; Sakai, Kazuo

2008-01-01

We have been investigating the effects of low dose or low dose rate irradiation on mice, using our low dose-rate irradiation facilities. In these studies, we found that the effects were highly dependent on both total dose and dose rate. To show this visually, we proposed the 'dose/dose rate map', and plotted the results of our laboratory and our co-workers. The map demonstrated that dose/dose rate plane could be divided into three areas; 1) An area where harmful effects are observed, 2) An area where no harmful effects are observed, and 3) Another area, between previous two areas, where certain protective functions are enhanced. As this map would be a powerful tool to find some trend among the vast numbers of data relating the biological effects of ionizing radiation, we have developed a computer program which plots the collected data on the dose/dose rate map sorting by experimental conditions. In this study, we graphically reviewed and analyzed the data relating to the lifespan studies of animals with a view to determining the relationships between doses and dose rates of ionizing radiation and cancer incidence. The data contains about 800 sets of experiments, which concerns 187,000 animals exposed to gamma ray or X-ray and their 112,000 controls, and total of about 30,000 cancers in exposed animals and 14,000 cancers in controls. About 800 points of data were plotted on the dose/dose rate map. The plot showed that 1) The divided three areas in the dose/dose rate map were generally confirmed by these 800 points of data, and 2) In some particular conditions, e.g. sarcoma by X-rays, the biologically effective area is extended to relatively high dose/dose rate area. (author)

Biological effects of low doses of radiation at low dose rate

International Nuclear Information System (INIS)

1996-05-01

The purpose of this report was to examine available scientific data and models relevant to the hypothesis that induction of genetic changes and cancers by low doses of ionizing radiation at low dose rate is a stochastic process with no threshold or apparent threshold. Assessment of the effects of higher doses of radiation is based on a wealth of data from both humans and other organisms. 234 refs., 26 figs., 14 tabs

Radiation dose rate measuring device

International Nuclear Information System (INIS)

Sorber, R.

1987-01-01

A portable device is described for in-field usage for measuring the dose rate of an ambient beta radiation field, comprising: a housing, substantially impervious to beta radiation, defining an ionization chamber and having an opening into the ionization chamber; beta radiation pervious electrically-conductive window means covering the opening and entrapping, within the ionization chamber, a quantity of gaseous molecules adapted to ionize upon impact with beta radiation particles; electrode means disposed within the ionization chamber and having a generally shallow concave surface terminating in a generally annular rim disposed at a substantially close spacing to the window means. It is configured to substantially conform to the window means to define a known beta radiation sensitive volume generally between the window means and the concave surface of the electrode means. The concave surface is effective to substantially fully expose the beta radiation sensitive volume to the radiation field over substantially the full ambient area faced by the window means

Transition of some type of integrated circuits into latch-up mode under effect of ionizing radiation of large dose rate

International Nuclear Information System (INIS)

Berdichevskij, B.E.; Madzharova, T.B.

1986-01-01

Some types of integrated circuits (IC) are almost short-circuit, i.e. they transit to the latch-up regime under the effect of ionizing radiation pulses of large dose rate. The results of investigation into IC under their transition into the latch-up regime at supply voltage of 10 V are presented. It is shown that IC stably transit to the latch-up regime if the dinistor current becomes at least equal to the photocurrent. At bias reduction from 15 to 6 V the dose rate at which the latch-up arises grows from 2.5x10 9 to 3.5x10 9 rad (Si)/s. Burn-out of supply busbar is the usual type of IC failure at latch-up arising. Measures for IC protection from latch-up are shown. In some IC the latch-up is formed beginning from a certain critical value of dose rate, the so-called ''windows'' of latch-up

Oligodendroglial response to ionizing radiation: Dose and dose-rate response

International Nuclear Information System (INIS)

Levy, R.P.

1991-12-01

An in vitro system using neuroglia from neonatal rat brain was developed to examine the morphologic, immunocytochemical and biochemical response of oligodendroglia to ionizing radiation. Following acute γ-irradiation at day-in-culture (DIC) 8, oligodendrocyte counts at DIC 14 were 55% to 65% of control values after 2 Gy, and 29% to 36% after 5 Gy. Counts increased to near-normal levels at DIC 21 in the 2 Gy group and to 75% of normal in the 5 Gy group. Myelin basic protein levels (MBP) at DIC 14 were 60% of control values after 2 Gy, and 40% after 5 Gy. At DIC 21, MBP after 2 Gy was 45% greater than that observed at DIC 14, but MBP, as a fraction of age-matched control values, dropped from 60% to 50%. Following 5 Gy, absolute MBP changed little between DIC 14 and DIC 21, but decreased from 40% to 25% of control cultures. The response to split-dose irradiation indicated that nearly all sublethal damage in the oligodendrocyte population (and its precursors) was repaired within 3 h to 4 h. A new compartmental cell model for radiation response in vitro of the oligodendrocyte population is proposed and examined in relation to the potential reaction to radiation injury in the brain

Oligodendroglial response to ionizing radiation: Dose and dose-rate response

Energy Technology Data Exchange (ETDEWEB)

Levy, Richard P. [Univ. of California, Berkeley, CA (United States)

1991-12-01

An in vitro system using neuroglia from neonatal rat brain was developed to examine the morphologic, immunocytochemical and biochemical response of oligodendroglia to ionizing radiation. Following acute γ-irradiation at day-in-culture (DIC) 8, oligodendrocyte counts at DIC 14 were 55% to 65% of control values after 2 Gy, and 29% to 36% after 5 Gy. Counts increased to near-normal levels at DIC 21 in the 2 Gy group and to 75% of normal in the 5 Gy group. Myelin basic protein levels (MBP) at DIC 14 were 60% of control values after 2 Gy, and 40% after 5 Gy. At DIC 21, MBP after 2 Gy was 45% greater than that observed at DIC 14, but MBP, as a fraction of age-matched control values, dropped from 60% to 50%. Following 5 Gy, absolute MBP changed little between DIC 14 and DIC 21, but decreased from 40% to 25% of control cultures. The response to split-dose irradiation indicated that nearly all sublethal damage in the oligodendrocyte population (and its precursors) was repaired within 3 h to 4 h. A new compartmental cell model for radiation response in vitro of the oligodendrocyte population is proposed and examined in relation to the potential reaction to radiation injury in the brain.

Oligodendroglial response to ionizing radiation: Dose and dose-rate response

Energy Technology Data Exchange (ETDEWEB)

Levy, R.P.

1991-12-01

An in vitro system using neuroglia from neonatal rat brain was developed to examine the morphologic, immunocytochemical and biochemical response of oligodendroglia to ionizing radiation. Following acute {gamma}-irradiation at day-in-culture (DIC) 8, oligodendrocyte counts at DIC 14 were 55% to 65% of control values after 2 Gy, and 29% to 36% after 5 Gy. Counts increased to near-normal levels at DIC 21 in the 2 Gy group and to 75% of normal in the 5 Gy group. Myelin basic protein levels (MBP) at DIC 14 were 60% of control values after 2 Gy, and 40% after 5 Gy. At DIC 21, MBP after 2 Gy was 45% greater than that observed at DIC 14, but MBP, as a fraction of age-matched control values, dropped from 60% to 50%. Following 5 Gy, absolute MBP changed little between DIC 14 and DIC 21, but decreased from 40% to 25% of control cultures. The response to split-dose irradiation indicated that nearly all sublethal damage in the oligodendrocyte population (and its precursors) was repaired within 3 h to 4 h. A new compartmental cell model for radiation response in vitro of the oligodendrocyte population is proposed and examined in relation to the potential reaction to radiation injury in the brain.

Field measurement and interpretation of beta doses and dose rates

International Nuclear Information System (INIS)

Selby, J.M.; Swinth, K.L.; Hooker, C.D.; Kenoyer, J.L.

1983-01-01

A wide variety of portable survey instruments employing GM, ionization chamber and scintillation detectors exist for the measurement of gamma exposure rates. Often these same survey instruments are used for monitoring beta fields. This is done by making measurements with and without a removable shield which is intended to shield out the non-penetrating component (beta) of the radiation field. The difference does not correspond to an absorbed dose rate for the beta field due to a variety of factors. Among these factors are the dependence on beta energy, source-detector geometries, mixed fields and variable ambient conditions. Attempting to use such measurements directly can lead to errors as high as a factor of 100. In many instances correction factors have been derived, that if properly applied, can reduce these errors substantially. However, this requires some knowledge of the beta spectra, calibration techniques and source geometry. This paper discusses some aspects of the proper use of instruments for beta measurements including the application of appropriate correction factors. Ionization type instruments are commonly used to measure beta dose rates. Through design and calibration these instruments will give an accurate reading only for uniform irradiation of the detection volume. Often in the field it is not feasible to meet these conditions. Large area uniform distributions of activity are not generally encountered and it is not possible to use large source-to-detector distances due to beta particle absorption in air. An example of correction factors required for various point sources is presented when a cutie pie ionization chamber is employed. The instrument reading is multiplied by the appropriate correction factor to obtain the dose rate at the window. When a different detector is used or for other geometries, a different set of correction factors must be used

Time- and dose-dependent effects of total-body ionizing radiation on muscle stem cells

Science.gov (United States)

Masuda, Shinya; Hisamatsu, Tsubasa; Seko, Daiki; Urata, Yoshishige; Goto, Shinji; Li, Tao-Sheng; Ono, Yusuke

2015-01-01

Exposure to high levels of genotoxic stress, such as high-dose ionizing radiation, increases both cancer and noncancer risks. However, it remains debatable whether low-dose ionizing radiation reduces cellular function, or rather induces hormetic health benefits. Here, we investigated the effects of total-body γ-ray radiation on muscle stem cells, called satellite cells. Adult C57BL/6 mice were exposed to γ-radiation at low- to high-dose rates (low, 2 or 10 mGy/day; moderate, 50 mGy/day; high, 250 mGy/day) for 30 days. No hormetic responses in proliferation, differentiation, or self-renewal of satellite cells were observed in low-dose radiation-exposed mice at the acute phase. However, at the chronic phase, population expansion of satellite cell-derived progeny was slightly decreased in mice exposed to low-dose radiation. Taken together, low-dose ionizing irradiation may suppress satellite cell function, rather than induce hormetic health benefits, in skeletal muscle in adult mice. PMID:25869487

Macroarray analysis of gene expression in hematopoietic tissues from mice continuously irradiated by low dose-rate ionizing radiation

Energy Technology Data Exchange (ETDEWEB)

Saitou, Mikio; Nakamura, Shingo; Shirata, Katsutoshi; Yanai, Takanori; Izumi, Jun; Sugihara, Takashi; Tanaka, Satoshi; Tanaka, Kimio; Otsu, Hiroshi; Sato, Fumiaki [Inst. for Environmental Sciences, Rokkasho, Aomori (Japan)

2002-07-01

We found that the number of hematopoietic progenitor cells in bone marrow and spleen from 4 - 8 Gy-irradiated mice decreased about 50%, in spite of no change in the number of peripheral blood cells. To evaluate the effects of chronic irradiation by low dose-rate ionizing radiation on the gene expression in mice hematopoietic cells from bone marrow and spleen, the RNA expressions of more than 500 genes such as cytokine genes and oncogenes were measured on the membranes by the RNA macroarray analysis method at accumulated doses at 4.7 and 8 Gy in specific-pathogen-free (SPF) C3H/HeN female mice irradiated by {sup 137}Cs {gamma}-rays with the dose rate of 20 mGy/day. The RNA macroarray analysis in spleens from 8 Gy-irradiated mice showed that the expressions in 16 genes including noggin were more than 1.5 times larger than that of control, while those in 64 genes including shh (sonic hedgehog) and BMP-4 (bone morphogenesis protein 4) were more than 1.5 times smaller than that of control. (author)

Mortality from diseases other than cancer following low doses of ionizing radiation

DEFF Research Database (Denmark)

Vrijheid, M; Cardis, E; Ashmore, P

2007-01-01

BACKGROUND: Ionizing radiation at very high (radio-therapeutic) dose levels can cause diseases other than cancer, particularly heart diseases. There is increasing evidence that doses of the order of a few sievert (Sv) may also increase the risk of non-cancer diseases. It is not known, however......, whether such effects also occur following the lower doses and dose rates of public health concern. METHODS: We used data from an international (15-country) nuclear workers cohort study to evaluate whether mortality from diseases other than cancer is related to low doses of external ionizing radiation....... Analyses included 275 312 workers with adequate information on socioeconomic status, over 4 million person-years of follow-up and an average cumulative radiation dose of 20.7 mSv; 11 255 workers had died of non-cancer diseases. RESULTS: The excess relative risk (ERR) per Sv was 0.24 [95% CI (confidence...

Investigation of the dose rate dependency of the PAGAT gel dosimeter at low dose rates

International Nuclear Information System (INIS)

Zehtabian, M.; Faghihi, R.; Zahmatkesh, M.H.; Meigooni, A.S.; Mosleh-Shirazi, M.A.; Mehdizadeh, S.; Sina, S.; Bagheri, S.

2012-01-01

Medical physicists need dosimeters such as gel dosimeters capable of determining three-dimensional dose distributions with high spatial resolution. To date, in combination with magnetic resonance imaging (MRI), polyacrylamide gel (PAG) polymers are the most promising gel dosimetry systems. The purpose of this work was to investigate the dose rate dependency of the PAGAT gel dosimeter at low dose rates. The gel dosimeter was used for measurement of the dose distribution around a Cs-137 source from a brachytherapy LDR source to have a range of dose rates from 0.97 Gy h −1 to 0.06 Gy h −1 . After irradiation of the PAGAT gel, it was observed that the dose measured by gel dosimetry was almost the same at different distances (different dose rates) from the source, although the points nearer the source had been expected to receive greater doses. Therefore, it was suspected that the PAGAT gel is dose rate dependent at low dose rates. To test this further, three other sets of measurements were performed by placing vials containing gel at different distances from a Cs-137 source. In the first two measurements, several plastic vials were exposed to equal doses at different dose rates. An ionization chamber was used to measure the dose rate at each distance. In addition, three TLD chips were simultaneously irradiated in order to verify the dose to each vial. In the third measurement, to test the oxygen diffusion through plastic vials, the experiment was repeated again using plastic vials in a nitrogen box and glass vials. The study indicates that oxygen diffusion through plastic vials for dose rates lower than 2 Gy h −1 would affect the gel dosimeter response and it is suggested that the plastic vials or (phantoms) in an oxygen free environment or glass vials should be used for the dosimetry of low dose rate sources using PAGAT gel to avoid oxygen diffusion through the vials.

Low doses effects of ionizing radiation on Saccharomyces cerevisiae

International Nuclear Information System (INIS)

Durand, J.; Broock, M. van; Gillette, V.H.

2000-01-01

The exposure of living cells to low doses of ionizing radiation induce in response the activation of cellular protection mechanisms against subsequent larger doses of radiation. This cellular adaptive response may vary depending on radiation intensity and time of exposure, and also on the testing probes used whether they were mammalian cells, yeast, bacteria and other organisms or cell types. The mechanisms involved are the genome activation, followed by DNA repair enzymes synthesis. Due to the prompt cell response, the cell cycle can be delayed, and the secondary detoxification of free radicals and/or activation of membrane bound receptors may proceed. All these phenomena are submitted to intense scientific research nowadays, and their elucidation will depend on the complexity of the organism under study. In the present work, the effects of low doses of ionizing radiation (gamma rays) over a suspension of the yeast Saccharomyces cerevisiae (Baker's yeast) was studied, mainly in respect to survival rate and radio-adaptive response. At first, the yeast surviving curve was assessed towards increasing doses, and an estimation of Lethal Dose 50 (LD50) was made. The irradiation tests were performed at LINAC (electrons Linear Accelerator) where electron energy reached approximately 2.65 MeV, and gamma-radiation was produced for bremsstrahlung process over an aluminium screen target. A series of experiments of conditioning doses was performed and an increment surviving fraction was observed when the dose was 2.3 Gy and a interval time between this and a higher dose (challenging dose) of 27 Gy was 90 minutes. A value of 58 ± 4 Gy was estimated for LD50, at a dose rate of 0.44 ± 0.03 Gy/min These quantities must be optimized. Besides data obtained over yeast survival, an unusual increasing amount of tiny yeast colonies appeared on the agar plates after incubation, and this number increased as increasing the time exposure. Preliminary results indicate these colonies as

Effects of low doses of ionizing radiation

International Nuclear Information System (INIS)

Anon.

2008-01-01

Ionizing radiation of cosmic or terrestrial origin is part of the environment in which all living things have evolved since the creation of the universe. The artificial radioactivity generated by medical diagnostic and treatment techniques, some industrial activities, radioactive fallout, etc. has now been added to this natural radioactivity. This article reviews the biological effects of the low doses of ionizing radiation to which the population is thus exposed. Their carcinogenic risk cannot simply be extrapolated from what we know about high-dose exposure. (author)

Dose-rate effect of adaptive response of apoptosis and cell cycle progression induced by low-dose ionizing radiation in EL-4 lymphoma cells in vitro

International Nuclear Information System (INIS)

Liu Shuchun; Lu Zhe; Li Yanbo; Kang Shunai; Gong Shouliang; Zhao Wenju

2008-01-01

Objective: To observe the dose-rate effect of adaptive response of apoptosis and cell cycle progression induced by low-dose ionizing radiation in EL-4 lymphoma cells in vitro in order to reveal the possible mechanism of biological effect and adaptive response induced by low dose radiation. Methods: The experiment was divided into D2 (challenging dose), D1 (inductive dose) + D2 and sham-irradiation groups. EL-4 lymphoma cells were irradiated with D1 (75 mGy, 6.25-200.00 mGy·mm -1 ) and D2(1.5 Gy, 287 mGy·min -1 ), the time interval between D1 and D2 was 6 h. The percentage of apoptosis and each cell cycle phase were measured with flow cytometry. Results: When the dose rates of D1 were 6.25-50.00 mGy·min -1 , the percentages of apoptosis in the D1 + D2 group were significantly lower than those in the D2 group (P 0 /G 1 phase cells decreased significantly (P -1 , D2 is 1.5 Gy (287 mGy·min -1 ), and the time interval between D1 and D2 is 6 h, the adaptive response of apoptosis and cell cycle progression in EL-4 lymphoma cells in vitro could be induced. (authors)

Cancer risk of low dose/low dose rate radiation: a meta-analysis of cancer data of mammals exposed to low doses of radiation

International Nuclear Information System (INIS)

Ogata, Hiromitsu; Magae, Junji

2008-01-01

Full text: Linear No Threshold (LNT) model is a basic theory for radioprotection, but the adaptability of this hypothesis to biological responses at low doses or at low dose rates is not sufficiently investigated. Simultaneous consideration of the cumulative dose and the dose rate is necessary for evaluating the risk of long-term exposure to ionizing radiation at low dose. This study intends to examine several numerical relationships between doses and dose rates in biological responses to gamma radiation. Collected datasets on the relationship between dose and the incidence of cancer in mammals exposed to low doses of radiation were analysed using meta-regression models and modified exponential (MOE) model, which we previously published, that predicts irradiation time-dependent biological response at low dose rate ionizing radiation. Minimum doses of observable risk and effective doses with a variety of dose rates were calculated using parameters estimated by fitting meta-regression models to the data and compared them with other statistical models that find values corresponding to 'threshold limits'. By fitting a weighted regression model (fixed-effects meta-regression model) to the data on risk of all cancers, it was found that the log relative risk [log(RR)] increased as the total exposure dose increased. The intersection of this regression line with the x-axis denotes the minimum dose of observable risk. These estimated minimum doses and effective doses increased with decrease of dose rate. The goodness of fits of MOE-model depended on cancer types, but the total cancer risk is reduced when dose rates are very low. The results suggest that dose response curve for cancer risk is remarkably affected by dose rate and that dose rate effect changes as a function of dose rate. For scientific discussion on the low dose exposure risk and its uncertainty, the term 'threshold' should be statistically defined, and dose rate effects should be included in the risk

Low doses effects and gamma radiations low dose rates; Les effets des faibles doses et des faibles debits de doses de rayons gamma

Energy Technology Data Exchange (ETDEWEB)

Averbeck, D [Institut Curie, CNRS UMR 2027, 75 - Paris (France)

1999-07-01

This expose wishes for bringing some definitions and base facts relative to the problematics of low doses effects and low dose rates effects. It shows some already used methods and some actual experimental approaches by focusing on the effects of ionizing radiations with a low linear energy transfer. (N.C.)

Atmospheric radiation flight dose rates

Science.gov (United States)

Tobiska, W. K.

2015-12-01

Space weather's effects upon the near-Earth environment are due to dynamic changes in the energy transfer processes from the Sun's photons, particles, and fields. Of the domains that are affected by space weather, the coupling between the solar and galactic high-energy particles, the magnetosphere, and atmospheric regions can significantly affect humans and our technology as a result of radiation exposure. Space Environment Technologies (SET) has been conducting space weather observations of the atmospheric radiation environment at aviation altitudes that will eventually be transitioned into air traffic management operations. The Automated Radiation Measurements for Aerospace Safety (ARMAS) system and Upper-atmospheric Space and Earth Weather eXperiment (USEWX) both are providing dose rate measurements. Both activities are under the ARMAS goal of providing the "weather" of the radiation environment to improve aircraft crew and passenger safety. Over 5-dozen ARMAS and USEWX flights have successfully demonstrated the operation of a micro dosimeter on commercial aviation altitude aircraft that captures the real-time radiation environment resulting from Galactic Cosmic Rays and Solar Energetic Particles. The real-time radiation exposure is computed as an effective dose rate (body-averaged over the radiative-sensitive organs and tissues in units of microsieverts per hour); total ionizing dose is captured on the aircraft, downlinked in real-time, processed on the ground into effective dose rates, compared with NASA's Langley Research Center (LaRC) most recent Nowcast of Atmospheric Ionizing Radiation System (NAIRAS) global radiation climatology model runs, and then made available to end users via the web and smart phone apps. Flight altitudes now exceed 60,000 ft. and extend above commercial aviation altitudes into the stratosphere. In this presentation we describe recent ARMAS and USEWX results.

Comparison of the measured radiation dose-rate by the ionization chamber and G (Geiger-Mueller) counter after radioactive lodine therapy in differentiated thyroid cancer patients

Energy Technology Data Exchange (ETDEWEB)

Park, Kwang Hun [Dept. of Nuclear Medicine, Kyungbuk National University Hospital, Daegu (Korea, Republic of); Kim, Kgu Hwan [Dept. of Radiological Technology, Daegu Health College, Daegu (Korea, Republic of)

2016-12-15

Radioactive iodine(131I) treatment reduces recurrence and increases survival in patients with differentiated thyroid cancer. However, it is important in terms of radiation safety management to measure the radiation dose rate generated from the patient because the radiation emitted from the patient may cause the exposure. Research methods, it measured radiation dose-rate according to the elapsed time from 1 m from the upper abdomen of the patient by intake of radioactive iodine. Directly comparing the changes over time, high dose rate sensitivity and efficiency is statistically significant, and higher chamber than GM counter(p<0.05). Low dose rate sensitivity and efficiency in the chamber had lower levels than gm counter, but not statistically significant(p>0.05). In this study confirmed the characteristics of calibrated ionization chamber and GM counter according to the radiation intensity during high-dose radioactive iodine therapy by measuring the accurate and rapid radiation dose rate to the patient explains, discharged patients will be reduced to worry about radiation hazard of family and others person.

Calibration procedure for thermoluminescent dosemeters in water absorbed doses for Iridium-192 high dose rate sources

International Nuclear Information System (INIS)

Reyes Cac, Franky Eduardo

2004-10-01

Thermoluminescent dosimeters are used in brachytherapy services quality assurance programs, with the aim of guaranteeing the correct radiation dose supplied to cancer patients, as well as with the purpose of evaluating new clinical procedures. This work describes a methodology for thermoluminescent dosimeters calibration in terms of absorbed dose to water for 192 Ir high dose rate sources. The reference dose used is measured with an ionization chamber previously calibrated for 192 Ir energy quality, applying the methodology proposed by Toelli. This methodology aims to standardizing the procedure, in a similar form to that used for external radiotherapy. The work evolves the adaptation of the TRS-277 Code of the International Atomic Energy Agency, for small and big cavities, through the introduction for non-uniform experimental factor, for the absorbed dose in the neighborhood of small brachytherapy sources. In order to simulate a water medium around the source during the experimental work, an acrylic phantom was used. It guarantees the reproducibility of the ionization chamber and the thermoluminescent dosimeter's location in relation to the radiation source. The values obtained with the ionization chamber and the thermoluminescent dosimeters, exposed to a 192 Ir high dose rate source, were compared and correction factors for different source-detector distances were determined for the thermoluminescent dosimeters. A numeric function was generated relating the correction factors and the source-detector distance. These correction factors are in fact the thermoluminescent dosimeter calibration factors for the 192 Ir source considered. As a possible application of this calibration methodology for thermoluminescent dosimeters, a practical range of source-detector distances is proposed for quality control of 192 Ir high dose rate sources. (author)

Mammalian Tissue Response to Low Dose Ionizing Radiation: The Role of Oxidative Metabolism and Intercellular Communication

Energy Technology Data Exchange (ETDEWEB)

Azzam, Edouard I

2013-01-16

The objective of the project was to elucidate the mechanisms underlying the biological effects of low dose/low dose rate ionizing radiation in organs/tissues of irradiated mice that differ in their susceptibility to ionizing radiation, and in human cells grown under conditions that mimic the natural in vivo environment. The focus was on the effects of sparsely ionizing cesium-137 gamma rays and the role of oxidative metabolism and intercellular communication in these effects. Four Specific Aims were proposed. The integrated outcome of the experiments performed to investigate these aims has been significant towards developing a scientific basis to more accurately estimate human health risks from exposures to low doses ionizing radiation. By understanding the biochemical and molecular changes induced by low dose radiation, several novel markers associated with mitochondrial functions were identified, which has opened new avenues to investigate metabolic processes that may be affected by such exposure. In particular, a sensitive biomarker that is differentially modulated by low and high dose gamma rays was discovered.

Annual individual doses for personnel dealing with ionizing radiation sources

International Nuclear Information System (INIS)

Poplavskij, K.K.

1982-01-01

Data on annual individual doses for personnel of national economy enterprises, research institutes, high schools, medical establishments dealing with ionizing radiation sources are presented. It is shown that radiation dose for the personnel constitutes only shares of standards established by sanitary legislation. Numeral values of individual doses of the personnel are determined by the type, character and scope of using ionizing radiation sources

In situ measurements of dose rates from terrestrial gamma rays

International Nuclear Information System (INIS)

Horng, M.C.; Jiang, S.H.

2002-01-01

A portable, high purity germanium (HPGe) detector was employed for the performance of in situ measurements of radionuclide activity concentrations in the ground in Taiwan, at altitudes ranging from sea level to 3900 m. The absolute peak efficiency of the HPGe detector for a gamma-ray source uniformly distributed in the semi-infinite ground was determined using a semi-empirical method. The gamma-ray dose rates from terrestrial radionuclides were calculated from the measured activity levels using recently published dose rate conversion factors. The absorbed dose rate in air due to cosmic rays was derived by subtracting the terrestrial gamma-ray dose rate from the overall absorbed dose rate in air measured using a high-pressure ionization chamber. The cosmic-ray dose rate calculated as a function of altitude, was found to be in good agreement with the data reported by UNSCEAR. (orig.)

Radiation response of industrial materials: Dose-rate and morphology implications

International Nuclear Information System (INIS)

Berejka, Anthony J.

2007-01-01

Industrial uses of ionizing radiation mostly rely upon high current, high dose-rate (100 kGy/s) electron beam (EB) accelerators. To a lesser extent, industry uses low dose-rate (2.8 x 10 -3 kGy/s) radioactive Cobalt-60 as a gamma source, generally for some rather specific purposes, as medical device sterilization and the treatment of food and foodstuffs. There are nearly nine times as many (∼1400) high current EB units in commercial operation than gamma sources (∼160). However, gamma sources can be easily scaled-down so that much research on materials effects is conducted using gamma radiation. Likewise, laboratories are more likely to have very low beam current and consequently low dose-rate accelerators such as Van de Graaff generators and linear accelerators. With the advent of very high current EB accelerators, X-ray processing has become an industrially viable option. With X-rays from high power sources, dose-rates can be modulated based upon accelerator power and the attenuation of the X-ray by the distance of the material from the X-ray target. Dose and dose-rate dependence has been found to be of consequence in several commercial applications which can employ the use of ionizing radiation. The combination of dose and dose-rate dependence of the polymerization and crosslinking of wood impregnants and of fiber composite matrix materials can yield more economically viable results which have promising commercial potential. Monomer and oligomer structure also play an important role in attaining these desirable results. The influence of morphology is shown on the radiation response of olefin polymers, such as ethylene, propylene and isobutylene polymers and their copolymers. Both controlled morphology and controlled dose-rate have commercial consequences. These are also impacted both by the adroit selection of materials and through the possible use of X-ray processing

Effect of different ionizing radiation doses and dose rates, using Cobalt-60 and electrons beam sources, on the staphylococcal enterotoxin inoculated in mechanically deboned chicken meat

International Nuclear Information System (INIS)

Pomarico Neto, Walter; Brito, Poliana de Paula; Azevedo, Heliana de; Roque, Claudio Vitor; Fukuma, Henrique Takuji; Kodama, Yasko; Miya, Norma Terugo Nago; Pereira, Jose Luiz

2011-01-01

The purpose of food irradiation is the destruction of present pathogenic microorganisms and the increase of shelf life of foods. To achieve this process, the source of cobalt-60 and the electron accelerator can be used. The mechanically deboned chicken meat (MDCM) is used for the production of traditional meat products, and it may come to present pathogenic microorganisms such as staphylococcus aureus, a bacterium that produces enterotoxin, which causes food poisoning. The objective of this study is to analyze the effect of ionizing irradiation with different doses and dose rates, deriving from different radiation sources, on staphylococcal enterotoxin type B (SEB) in the MDCM. 50 g samples of MDCM were prepared in a batch of 6 kg of MDCM. The samples were contaminated, with the exception of the control, with SEB in amounts of about 100 ng. Then they were conditioned in a transparent bag made of low density polyethylene, frozen at -18±1 deg C overnight and irradiated in these conditions with doses of 0.0 kGy (control), 1.5 kGy and 3.0 kGy, and with three different dose rates, both in the Cobalt-60 and the electron accelerator. The experiments were conducted in quintuplicate. The SEB extraction from the MDCM was performed according to the protocol recommended by the manufacturer of the kit VIDAS Staph Enterotoxin II (bioMerrieux). The principle of mass balance was used to determine the actual amount of SEB removed by irradiation. The treatment that presented the best results was the one with a dose of 1.5 kGy, high dose rate of the electron accelerator. (author)

Effect of different ionizing radiation doses and dose rates, using Cobalt-60 and electrons beam sources, on the staphylococcal enterotoxin inoculated in mechanically deboned chicken meat

Energy Technology Data Exchange (ETDEWEB)

Pomarico Neto, Walter; Brito, Poliana de Paula; Azevedo, Heliana de; Roque, Claudio Vitor; Fukuma, Henrique Takuji, E-mail: pbrito@cnen.gov.br, E-mail: hazevedo@cnen.gov.br, E-mail: cvroque@cnen.gov.br, E-mail: htfukuma@cnen.gov.br [Brazilian Nuclear Energy Commission (LAPOC/CNEN), Pocos de Caldas, MG (Brazil); Kodama, Yasko, E-mail: ykodama@ipen.br [Nuclear and Energy Research Institute (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Miya, Norma Terugo Nago; Pereira, Jose Luiz, E-mail: miya@fea.unicamp.br, E-mail: pereira@fea.unicamp.br [Campinas State University (UNICAMP), SP (Brazil). Dept. of Food Sciences

2011-07-01

The purpose of food irradiation is the destruction of present pathogenic microorganisms and the increase of shelf life of foods. To achieve this process, the source of cobalt-60 and the electron accelerator can be used. The mechanically deboned chicken meat (MDCM) is used for the production of traditional meat products, and it may come to present pathogenic microorganisms such as staphylococcus aureus, a bacterium that produces enterotoxin, which causes food poisoning. The objective of this study is to analyze the effect of ionizing irradiation with different doses and dose rates, deriving from different radiation sources, on staphylococcal enterotoxin type B (SEB) in the MDCM. 50 g samples of MDCM were prepared in a batch of 6 kg of MDCM. The samples were contaminated, with the exception of the control, with SEB in amounts of about 100 ng. Then they were conditioned in a transparent bag made of low density polyethylene, frozen at -18{+-}1 deg C overnight and irradiated in these conditions with doses of 0.0 kGy (control), 1.5 kGy and 3.0 kGy, and with three different dose rates, both in the Cobalt-60 and the electron accelerator. The experiments were conducted in quintuplicate. The SEB extraction from the MDCM was performed according to the protocol recommended by the manufacturer of the kit VIDAS Staph Enterotoxin II (bioMerrieux). The principle of mass balance was used to determine the actual amount of SEB removed by irradiation. The treatment that presented the best results was the one with a dose of 1.5 kGy, high dose rate of the electron accelerator. (author)

CARCINOGENIC EFFECTS OF LOW DOSES OF IONIZING RADIATION

Science.gov (United States)

Carcinogenic Effects of Low Doses of Ionizing RadiationR Julian Preston, Environmental Carcinogenesis Division, NHEERL, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711The form of the dose-response curve for radiation-induced cancers, particu...

Fiber optical dose rate measurement based on the luminescence of beryllium oxide

Directory of Open Access Journals (Sweden)

Teichmann Tobias

2018-01-01

Full Text Available This work presents a fiber optical dose rate measurement system based on the radioluminescence and optically stimulated luminescence of beryllium oxide. The system consists of a small, radiation sensitive probe which is coupled to a light detection unit with a long and flexible light guide. Exposing the beryllium oxide probe to ionizing radiation results in the emission of light with an intensity which is proportional to the dose rate. Additionally, optically stimulated luminescence can be used to obtain dose and dose rate information during irradiation or retrospectively. The system is capable of real time dose rate measurements in fields of high dose rates and dose rate gradients and in complex, narrow geometries. This enables the application for radiation protection measurements as well as for quality control in radiotherapy. One inherent drawback of fiber optical dosimetry systems is the generation of Cherenkov radiation and luminescence in the light guide itself when it is exposed to ionizing radiation. This so called “stem” effect leads to an additional signal which introduces a deviation in the dose rate measurement and reduces the spatial resolution of the system, hence it has to be removed. The current system uses temporal discrimination of the effect for radioluminescence measurements in pulsed radiation fields and modulated optically stimulated luminescence for continuous irradiation conditions. This work gives an overview of the major results and discusses new-found obstacles of the applied methods of stem discrimination.

Study of genomic instability induced by low dose ionizing radiation

International Nuclear Information System (INIS)

Seoane, A.; Crudeli, C.; Dulout, F.

2006-01-01

The crews of commercial flights and services staff of radiology and radiotherapy from hospitals are exposed to low doses of ionizing radiation. Genomic instability includes those adverse effects observed in cells, several generations after the exposure occurred. The purpose of this study was to analyze the occurrence of genomic instability by very low doses of ionizing radiation [es

Measurement of air kerma rate for Cs-137 using different ionization chambers

International Nuclear Information System (INIS)

Mohammed, K. T. A.

2013-07-01

Due to the importance of radiation doses in medical field quality assurance should be established in order to maintain a reasonable balance between the purpose of application and exposure. This study had been carried out to achieve quality control for protection based on air kerma rate. Measurements were performed by using Cs-137 for the comparison of two working ionization chambers in secondary standard dosimetry laboratory of Sudan. Spherical ionization chamber L S-01 1000 cc S/N 912 and Farmer ionization chamber 2675 A 600 cc S/N 0511, respectively. The results obtained from this study have been represented as mean and their standard deviations shown in most cases remains at 5% uncertainly. Comparison between kinetic energy released per unit mass in air rate (air kerma rate) were obtained by using spherical ionization chamber L S-01 1000 cc S/N 912 and results have been determined using inverse square law. The differences have been represented as means and standard deviations with significant P-value less than 0.05. Spherical ionization chamber gives accurate, reproducible results with acceptable uncertainty which is more suitable for calibration of radiation detectors.(Author)

Problems linked to effects of ionizing radiations low doses

International Nuclear Information System (INIS)

Anon.

1995-10-01

The question of exposure to ionizing radiations low doses and risks existing for professional and populations has been asked again, with the recommendations of the International Commission of Radiation Protection (ICRP) to lower the previous standards and agreed as guides to organize radiation protection, by concerned countries and big international organisms. The sciences academy presents an analysis which concerned on epidemiological and dosimetric aspects in risk estimation, on cellular and molecular aspects of response mechanism to irradiation. The observation of absence of carcinogen effects for doses inferior to 200 milli-sieverts and a re-evaluation of data coming from Nagasaki and Hiroshima, lead to revise the methodology of studies to pursue, to appreciate more exactly the effects of low doses, in taking in part, particularly, the dose rate. The progress of molecular and cellular biology showed that the extrapolation from high doses to low doses is not in accordance with actual data. The acknowledge of DNA repair and carcinogenesis should make clearer the debate. (N.C.). 61 refs., 9 annexes

Low dose irradiation reduces cancer mortality rates

International Nuclear Information System (INIS)

Luckey, T.D.

2000-01-01

Low doses of ionizing radiation stimulate development, growth, memory, sensual acuity, fecundity, and immunity (Luckey, T.D., ''Radiation Hormesis'', CRC Press, 1991). Increased immune competence reduces cancer mortality rates and provides increased average lifespan in animals. Decreased cancer mortality rates in atom bomb victims who received low dose irradiation makes it desirable to examine populations exposed to low dose irradiation. Studies with over 300,000 workers and 7 million person-years provide a valid comparison of radiation exposed and control unclear workers (Luckey, T.D., Nurture with Ionizing Radiation, Nutrition and Cancer, 34:1-11, 1999). Careful selection of controls eliminated any ''healthy worker effect''. The person-year corrected average indicated the cancer mortality rate of exposed workers was only 51% that of control workers. Lung cancer mortality rates showed a highly significant negative correlation with radon concentrations in 272,000 U.S. homes (Cohen, B.L., Health Physics 68:157-174, 1995). In contrast, radon concentrations showed no effect on lung cancer rates in miners from different countries (Lubin, J.H. Am. J. Epidemiology 140:323-332, 1994). This provides evidence that excessive lung cancer in miners is caused by particulates (the major factor) or toxic gases. The relative risk for cancer mortality was 3.7% in 10,000 Taiwanese exposed to low level of radiation from 60 Co in their steel supported homes (Luan, Y.C. et al., Am. Nuclear Soc. Trans. Boston, 1999). This remarkable finding needs further study. A major mechanism for reduced cancer mortality rates is increased immune competence; this includes both cell and humoral components. Low dose irradiation increases circulating lymphocytes. Macrophage and ''natural killer'' cells can destroy altered (cancer) cells before the mass becomes too large. Low dose irradiation also kills suppressor T-cells; this allows helper T-cells to activate killer cells and antibody producing cells

Single event effects and total ionizing dose effects of typical VDMOSFET devices

International Nuclear Information System (INIS)

Lou Jianshe; Cai Nan; Liu Jiaxin; Wu Qinzhi; Wang Jia

2012-01-01

In this work, single event effects and total ionizing dose effects of typical VDMOSFET irradiated by 60 Co γ-rays and 252 Cf source were studied. The single event burnout and single event gate rupture (SEB/SEGR) effects were investigated, and the relationship between drain-source breakdown voltage and ionizing dose was obtained. The results showed that the VDMOSFET devices were sensitive to SEB and SEGR, and measures to improve their resistance to SEB and SEGR should be considered seriously for their space applications. The drain-source breakdown voltage was sensitive to total ionizing dose effects as the threshold voltage. In assessing the devices' resistance to the total ionizing dose effects, both the threshold voltage and the drain-source breakdown voltage should be taken into account. (authors)

Biological effects of low-dose ionizing radiation exposure

International Nuclear Information System (INIS)

Reinoehl-Kompa, Sabine; Baldauf, Daniela; Heller, Horst

2009-01-01

The report on the meeting of the Strahlenschutzkommission 2007 concerning biological effects of low-dose ionizing radiation exposure includes the following contributions: Adaptive response. The importance of DNA damage mechanisms for the biological efficiency of low-energy photons. Radiation effects in mammography: the relative biological radiation effects of low-energy photons. Radiation-induced cataracts. Carcinomas following prenatal radiation exposure. Intercellular apoptosis induction and low-dose irradiation: possible consequences for the oncogenesis control. Mechanistic models for the carcinogenesis with radiation-induced cell inactivation: application to all solid tumors in the Japanese atomic bomb survivors. Microarrays at low radiation doses. Mouse models for the analysis of biological effects of low-dose ionizing radiation. The bystander effect: observations, mechanisms and implications. Lung carcinoma risk of Majak workers - modeling of carcinogenesis and the bystander effect. Microbeam studies in radiation biology - an overview. Carcinogenesis models with radiation-induced genomic instability. Application to two epidemiological cohorts.

Low-dose ionizing radiation limitations to seed germination: Results from a model linking physiological characteristics and developmental-dynamics simulation strategy.

Science.gov (United States)

Liu, Hui; Hu, Dawei; Dong, Chen; Fu, Yuming; Liu, Guanghui; Qin, Youcai; Sun, Yi; Liu, Dianlei; Li, Lei; Liu, Hong

2017-08-01

There is much uncertainty about the risks of seed germination after repeated or protracted environmental low-dose ionizing radiation exposure. The purpose of this study is to explore the influence mechanism of low-dose ionizing radiation on wheat seed germination using a model linking physiological characteristics and developmental-dynamics simulation. A low-dose ionizing radiation environment simulator was built to investigate wheat (Triticum aestivum L.) seeds germination process and then a kinetic model expressing the relationship between wheat seed germination dynamics and low-dose ionizing radiation intensity variations was developed by experimental data, plant physiology, relevant hypotheses and system dynamics, and sufficiently validated and accredited by computer simulation. Germination percentages were showing no differences in response to different dose rates. However, root and shoot lengths were reduced significantly. Plasma governing equations were set up and the finite element analysis demonstrated H 2 O, CO 2 , O 2 as well as the seed physiological responses to the low-dose ionizing radiation. The kinetic model was highly valid, and simultaneously the related influence mechanism of low-dose ionizing radiation on wheat seed germination proposed in the modeling process was also adequately verified. Collectively these data demonstrate that low-dose ionizing radiation has an important effect on absorbing water, consuming O 2 and releasing CO 2 , which means the risk for embryo and endosperm development was higher. Copyright © 2017 Elsevier Ltd. All rights reserved.

Secondary standard dosimetry system with automatic dose/rate calculation

International Nuclear Information System (INIS)

Duftschmid, K.E.; Bernhart, J.; Stehno, G.; Klosch, W.

1980-01-01

A versatile and automated secondary standard instrument has been designed for quick and accurate dose/rate measurement in a wide range of radiation intensity and quality (between 1 μR and 100 kR; 0.2 nC/kg - 20C/kg) for protection and therapy level dosimetry. The system is based on a series of secondary standard ionization chambers connected to a precision digital current integrator with microprocessor circuitry for data evaluation and control. Input of measurement parameters and calibration factors stored in an exchangeable memory chip provide computation of dose/rate values in the desired units. The ionization chambers provide excellent long-term stability and energy response and can be used with internal check sources to test validity of calibration. The system is a useful tool particularly for daily measurements in a secondary standard dosimetry laboratory or radiation therapy center. (H.K.)

Modeling of transient ionizing radiation effects in bipolar devices at high dose-rates

International Nuclear Information System (INIS)

FJELDLY, T.A.; DENG, Y.; SHUR, M.S.; HJALMARSON, HAROLD P.; MUYSHONDT, ARNOLDO

2000-01-01

To optimally design circuits for operation at high intensities of ionizing radiation, and to accurately predict their a behavior under radiation, precise device models are needed that include both stationary and dynamic effects of such radiation. Depending on the type and intensity of the ionizing radiation, different degradation mechanisms, such as photoelectric effect, total dose effect, or single even upset might be dominant. In this paper, the authors consider the photoelectric effect associated with the generation of electron-hole pairs in the semiconductor. The effects of low radiation intensity on p-II diodes and bipolar junction transistors (BJTs) were described by low-injection theory in the classical paper by Wirth and Rogers. However, in BJTs compatible with modem integrated circuit technology, high-resistivity regions are often used to enhance device performance, either as a substrate or as an epitaxial layer such as the low-doped n-type collector region of the device. Using low-injection theory, the transient response of epitaxial BJTs was discussed by Florian et al., who mainly concentrated on the effects of the Hi-Lo (high doping - low doping) epilayer/substrate junction of the collector, and on geometrical effects of realistic devices. For devices with highly resistive regions, the assumption of low-level injection is often inappropriate, even at moderate radiation intensities, and a more complete theory for high-injection levels was needed. In the dynamic photocurrent model by Enlow and Alexander. p-n junctions exposed to high-intensity radiation were considered. In their work, the variation of the minority carrier lifetime with excess carrier density, and the effects of the ohmic electric field in the quasi-neutral (q-n) regions were included in a simplified manner. Later, Wunsch and Axness presented a more comprehensive model for the transient radiation response of p-n and p-i-n diode geometries. A stationary model for high-level injection in p

Risks to health from radiation at low dose rates

International Nuclear Information System (INIS)

Gentner, N.E.; Osborne, R.V.

1997-01-01

Our focus is on whether, using a balance-of-evidence approach, it is possible to say that at a low enough dose, or at a sufficiently low dose rate, radiation risk reduces to zero in a population. We conclude that insufficient evidence exists at present to support such a conclusion. In part this reflects statistical limitations at low doses, and in part (although mechanisms unquestionably exist to protect us against much of the damage induced by ionizing radiation) the biological heterogeneity of human populations, which means these mechanisms do not act in all members of the population at all times. If it is going to be possible to demonstrate that low doses are less dangerous than we presently assume, the evidence, paradoxically, will likely come from studies of higher dose and dose rate scenarios than are encountered occupationally. (author)

Problems in continuous dose rate measurement

International Nuclear Information System (INIS)

Yoshioka, Mitsuo

1983-01-01

The system of continuous dose rate measurement in Fukui Prefecture is described. A telemeter system was constructed in October, 1976, and it has been operated since 1977. Observation has been made at 11 observation stations in the Prefecture. In addition to the continuous measurement of dose rate by using NaI(T1)-DBM systems, the ionization chambers for high dose rate were installed, and also meteorological data have been collected. The detectors are covered with 1 mm thick aluminum designed so that the absorption of external radiation is kept as small as possible. To keep the environmental temperature of the detectors constant, constant temperature wind blow is made. With these consideration, the measurement of Xe-133 is possible, and the standard deviation of yearly dose is around 0.4 mR/Y. By measuring DBM transmission rate, the contribution of Xe-133, which comes from the exhaust pumps in power plants, can be detected. The problems of this system are as follows. First of all, the characteristics of the system must meet the purpose of dose monitoring. The system must detect the dose less than the target value to be achieved. The second is the selection of measuring systems to be set. The system is still not unified, and it is difficult to exchange data between different stations. Finally, the method of data analysis is not yet unified. Manuals or guide-books for this purpose are necessary for the mutual comparison of the data from the stations in different districts. (Kato, T.)

Calibration of working standard ionization chambers and dose standardization

International Nuclear Information System (INIS)

Abd Elmahoud, A. A. B.

2011-01-01

Measurements were performed for the calibration of two working standard ionization chambers in the secondary standard dosimetry laboratory of Sudan. 600 cc cylindrical former type and 1800 cc cylindrical radical radiation protection level ionization chambers were calibrated against 1000 cc spherical reference standard ionization chamber. The chamber were calibrated at X-ray narrow spectrum series with beam energies ranged from (33-116 KeV) in addition to 1''3''7''Cs beam with 662 KeV energy. The chambers 0.6 cc and 0.3 cc therapy level ionization were used for dose standardization and beam output calibrations of cobalt-60 radiotherapy machine located at the National Cancer Institute, University of Gazira. Concerning beam output measurements for 6''0''Co radiotherapy machine, dosimetric measurements were performed in accordance with the relevant per IAEA dosimetry protocols TRS-277 and TRS-398. The kinetic energy released per unit mass in air (air kerma) were obtained by multiplying the corrected electrometer reading (nC/min) by the calibration factors (Gy/n C) of the chambers from given in the calibration certificate. The uncertainty of measurements of air kerma were calculated for the all ionization chambers (combined uncertainty) the calibration factors of these ionization chambers then were calculated by comparing the reading of air kerma of secondary standard ionization chambers to than from radical and farmer chambers. The result of calibration working standard ionization chambers showed different calibration factors ranged from 0.99 to 1.52 for different radiation energies and these differences were due to chambers response and specification. The absorbed dose to to water calculated for therapy ionization chamber using two code of practice TRS-277 and TRS-398 as beam output for 6''0''Co radiotherapy machine and it can be used as a reference for future beam output calibration in radiotherapy dosimetry. The measurement of absorbed dose to water showed that the

Low-dose ionizing radiation alleviates Aβ42-induced defective phenotypes in Drosophila Alzheimer's disease models

International Nuclear Information System (INIS)

Hwang, SooJin; Jeong, Hae Min; Nam, Seon Young

2017-01-01

Alzheimer's disease (AD) is the most common neurodegenerative disease that is characterized by amyloid plaques, progressive neuronal loss, and gradual deterioration of memory. Amyloid imaging using positron emission tomography (PET) radiotracers have been developed and approved for clinical use in the evaluation of suspected neurodegenerative disease, including AD. Particularly, previous studies involving low-dose ionizing radiation on Aβ 42-treated mouse hippocampal neurons have suggested a potential role for low-dose ionizing radiation in the treatment of AD. However, associated in vivo studies involving the therapy effects of low-dose ionizing radiation on AD are still insufficient. As a powerful cell biological system, Drosophila AD models have been generated and established a useful model organism for study on the etiology of human AD. In this study, we investigated the hormesis effects of low-dose ionizing radiation on Drosophila AD models. Our results suggest that low-dose ionizing radiation have the beneficial effects on not only the Aβ42-induced developmental defective phenotypes but also motor defects in Drosophila AD models. These results might be due to a regulation of apoptosis, and provide insight into the hormesis effects of low-dose ionizing radiation. Our results suggest that low-dose ionizing radiation have the beneficial effects on not only the Aβ42-induced developmental defective phenotypes but also motor defects in Drosophila AD models. These results might be due to a regulation of apoptosis, and provide insight into the hormesis effects of low-dose ionizing radiation.

Double ionization chamber survey meter for the separate measurement of penetrating and non-penetrating dose

International Nuclear Information System (INIS)

Lucas, A.C.

1987-01-01

The full capabilities of an advanced 8-bit microprocessor have been utilized in construction of a wide range, multiplexing survey meter based on dual electrometers and ionization chambers. The ionization chambers are constructed of modular conducting and non-conducting parts in such a way that the angular dependence for measurement of beta radiation is controlled by design. Display functions for the high range instrument include logarithmic or linear analog display, digital display of rate or dose, SI or English units, optionally for either total, penetrating, or non-penetrating dose. The instrument is presently configured to operate in the range 0.1 R/hr to 50,000 R/hr in support of the requirements of Regulatory Guide 19.7

Development of Real-Time Measurement of Effective Dose for High Dose Rate Neutron Fields

CERN Document Server

Braby, L A; Reece, W D

2003-01-01

Studies of the effects of low doses of ionizing radiation require sources of radiation which are well characterized in terms of the dose and the quality of the radiation. One of the best measures of the quality of neutron irradiation is the dose mean lineal energy. At very low dose rates this can be determined by measuring individual energy deposition events, and calculating the dose mean of the event size. However, at the dose rates that are normally required for biology experiments, the individual events can not be separated by radiation detectors. However, the total energy deposited in a specified time interval can be measured. This total energy has a random variation which depends on the size of the individual events, so the dose mean lineal energy can be calculated from the variance of repeated measurements of the energy deposited in a fixed time. We have developed a specialized charge integration circuit for the measurement of the charge produced in a small ion chamber in typical neutron irradiation exp...

CANCER RISKS ATTRIBUTABLE TO LOW DOSES OF IONIZING RADIATION - ASSESSING WHAT WE REALLY KNOW?

Science.gov (United States)

Cancer Risks Attributable to Low Doses of Ionizing Radiation - What Do We Really Know?AbstractHigh doses of ionizing radiation clearly produce deleterious consequences in humans including, but not exclusively, cancer induction. At very low radiation doses the situatio...

Studies on the radicidation of natural food colorants. Effects of electron energy (accelerating voltages) and dose rate of ionizing radiation on functional properties of beet red colorant

International Nuclear Information System (INIS)

Higashimura, Yutaka; Tada, Mikiro; Furuta, Masakazu

2003-01-01

In order to the practical use of radicidation of beet red, natural food colorant with low heat stability and high possibility of microbe contamination, we studied on the energy dependency and dose rate effect for the influence on functional properties of the beet red colorant. For the elucidation of energy dependency, the γ-ray (1.33 MeV) and electron beams with different accelerating voltages (0.75, 1, 2.5, 5 and 10 MeV) were used. The dose rate effect was studied under the different dose rate by using γ-ray (0.723, 1.91 and 4.55 kGy/h) and electron beams with accelerating voltage of 10 MeV (1.0 x 10 3 , 2.6 x 10 3 , 7.0 x 10 3 , 7.0 x 10 3 , 2.0 x 10 4 and 5.0 x 10 4 kGy/h). The results obtained in this study showed that regardless of these energy and dose rate, the functional properties of the beet red colorant were little affected by irradiation less than 25 kGy of ionizing radiations. (author)

Occupational radiation exposure to low doses of ionizing radiation and female breast cancer

International Nuclear Information System (INIS)

Adelina, P.; Bliznakov, V.; Bairacova, A.

2003-01-01

The aim of this study is to examine the relationship between past occupational radiation exposure to low doses of ionizing radiation and cases of diagnosed and registered breast cancer [probability of causation - PC] among Bulgarian women who have used different ionizing radiation sources during their working experience. The National Institute of Health (NIH) in US has developed a method for estimating the probability of causation (PC) between past occupational radiation exposure to low doses of ionizing radiation and cases of diagnosed cancer. We have used this method. A group of 27 women with diagnosed breast cancer has been studied. 11 of them are former workers in NPP - 'Kozloduy', and 16 are from other sites using different sources of ionizing radiation. Analysis was performed for 14 women, for whom full personal data were available. The individual radiation dose for each of them is below 1/10 of the annual dose limit, and the highest cumulative dose for a period of 14 years of occupational exposure is 50,21 mSv. The probability of causation (PC) values in all analyzed cases are below 1%, which confirms the extremely low probability of causation (PC) between past occupational radiation exposure to low doses of ionizing radiation and occurring cases of breast cancer. (orig.)

Prototype Operational Advances for Atmospheric Radiation Dose Rate Specification

Science.gov (United States)

Tobiska, W. K.; Bouwer, D.; Bailey, J. J.; Didkovsky, L. V.; Judge, K.; Garrett, H. B.; Atwell, W.; Gersey, B.; Wilkins, R.; Rice, D.; Schunk, R. W.; Bell, D.; Mertens, C. J.; Xu, X.; Crowley, G.; Reynolds, A.; Azeem, I.; Wiltberger, M. J.; Wiley, S.; Bacon, S.; Teets, E.; Sim, A.; Dominik, L.

2014-12-01

Space weather's effects upon the near-Earth environment are due to dynamic changes in the energy transfer processes from the Sun's photons, particles, and fields. The coupling between the solar and galactic high-energy particles, the magnetosphere, and atmospheric regions can significantly affect humans and our technology as a result of radiation exposure. Space Environment Technologies (SET) has developed innovative, new space weather observations that will become part of the toolset that is transitioned into operational use. One prototype operational system for providing timely information about the effects of space weather is SET's Automated Radiation Measurements for Aerospace Safety (ARMAS) system. ARMAS will provide the "weather" of the radiation environment to improve aircraft crew and passenger safety. Through several dozen flights the ARMAS project has successfully demonstrated the operation of a micro dosimeter on commercial aviation altitude aircraft that captures the real-time radiation environment resulting from Galactic Cosmic Rays and Solar Energetic Particles. The real-time radiation exposure is computed as an effective dose rate (body-averaged over the radiative-sensitive organs and tissues in units of microsieverts per hour); total ionizing dose is captured on the aircraft, downlinked in real-time via Iridium satellites, processed on the ground into effective dose rates, compared with NASA's Langley Research Center (LaRC) most recent Nowcast of Atmospheric Ionizing Radiation System (NAIRAS) global radiation climatology model runs, and then made available to end users via the web and smart phone apps. We are extending the dose measurement domain above commercial aviation altitudes into the stratosphere with a collaborative project organized by NASA's Armstrong Flight Research Center (AFRC) called Upper-atmospheric Space and Earth Weather eXperiment (USEWX). In USEWX we will be flying on the ER-2 high altitude aircraft a micro dosimeter for

Effects of high dose rate gamma radiation on survival and reproduction of Biomphalaria glabrata

Energy Technology Data Exchange (ETDEWEB)

Cantinha, Rebeca S.; Nakano, Eliana [Instituto Butantan, Sao Paulo, SP (Brazil). Lab. de Parasitologia], e-mail: rebecanuclear@gmail.com, e-mail: eliananakano@butantan.gov.br; Borrely, Sueli I. [Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN/SP), Sao Paulo, SP (Brazil). Centro de Tecnologia das Radiacoes], e-mail: sborrely@ipen.br; Amaral, Ademir; Melo, Ana M.M.A. [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Dept. de Energia Nuclear. Grupo de Estudos em Radioprotecao e Radioecologia (GERAR)], e-mail: amaral@ufpe.br; Silva, Luanna R.S. [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Dept. de Biofisica e Radiobiologia. Lab. de Radiobiologia], e-mail: amdemelo@hotmail.com, e-mail: luannaribeiro_lua@hotmail.com

2009-07-01

Ionizing radiations are known as mutagenic agents, causing lethality and infertility. This characteristic has motivated its application on animal biological control. In this context, the freshwater snail Biomphalaria glabrata can be considered an excellent experimental model to study effects of ionizing radiations on lethality and reproduction. This work was designed to evaluate effects of {sup 60}Co gamma radiation at high dose rate (10.04 kGy/h) on B. glabrata. For this purpose, adult snails were selected and exposed to doses ranging from 20 to 100 Gy, with 10 Gy intervals; one group was kept as control. There was not effect of dose rate in the lethality of gamma radiation; the value of 64,3 Gy of LD{sub 50} obtained in our study was similar to that obtained by other authors with low dose rates. Nevertheless, our data suggest that there was a dose rate effect in the reproduction. On all dose levels, radiation improved the production of embryos for all exposed individuals. However, viability indexes were below 6% and, even 65 days after irradiation, fertility was not recovered. These results are not in agreement with other studies using low dose rates. Lethality was obtained in all groups irradiated, and the highest doses presented percentiles of dead animals above 50%. The results demonstrated that doses of 20 and 30 Gy were ideal for population control of B. glabrata. Further studies are needed; nevertheless, this research evidenced great potential of high dose rate gamma radiation on B. glabrata reproductive control. (author)

Effects of high dose rate gamma radiation on survival and reproduction of Biomphalaria glabrata

International Nuclear Information System (INIS)

Cantinha, Rebeca S.; Nakano, Eliana; Silva, Luanna R.S.

2009-01-01

Ionizing radiations are known as mutagenic agents, causing lethality and infertility. This characteristic has motivated its application on animal biological control. In this context, the freshwater snail Biomphalaria glabrata can be considered an excellent experimental model to study effects of ionizing radiations on lethality and reproduction. This work was designed to evaluate effects of 60 Co gamma radiation at high dose rate (10.04 kGy/h) on B. glabrata. For this purpose, adult snails were selected and exposed to doses ranging from 20 to 100 Gy, with 10 Gy intervals; one group was kept as control. There was not effect of dose rate in the lethality of gamma radiation; the value of 64,3 Gy of LD 50 obtained in our study was similar to that obtained by other authors with low dose rates. Nevertheless, our data suggest that there was a dose rate effect in the reproduction. On all dose levels, radiation improved the production of embryos for all exposed individuals. However, viability indexes were below 6% and, even 65 days after irradiation, fertility was not recovered. These results are not in agreement with other studies using low dose rates. Lethality was obtained in all groups irradiated, and the highest doses presented percentiles of dead animals above 50%. The results demonstrated that doses of 20 and 30 Gy were ideal for population control of B. glabrata. Further studies are needed; nevertheless, this research evidenced great potential of high dose rate gamma radiation on B. glabrata reproductive control. (author)

Up-regulation of calreticulin in mouse liver tissues after long-term irradiation with low-dose-rate gamma rays.

Science.gov (United States)

Yi, Lan; Hu, Nan; Yin, Jie; Sun, Jing; Mu, Hongxiang; Dai, Keren; Ding, Dexin

2017-01-01

The biological effects of low-dose or low-dose-rate ionizing radiation on normal tissues has attracted attention. Based on previous research, we observed the morphology of liver tissues of C57BL/6J mice that received irradiation dose rates increased. Additionally, differential protein expression in liver tissues was analyzed using a proteomics approach. Compared with the matched group in the 2D gel analysis of the irradiated groups, 69 proteins had ≥ 1.5-fold changes in expression. Twenty-three proteins were selected based on ≥2.5-fold change in expression, and 22 of them were meaningful for bioinformatics and protein fingerprinting analysis. These molecules were relevant to cytoskeleton processes, cell metabolism, biological defense, mitochondrial damage, detoxification and tumorigenesis. The results from real-time PCR and western blot (WB) analyses showed that calreticulin (CRT) was up-regulated in the irradiated groups, which indicates that CRT may be relevant to stress reactions when mouse livers are exposed to low-dose irradiation and that low-dose-rate ionizing radiation may pose a cancer risk. The CRT protein can be a potential candidate for low-dose or low-dose-rate ionizing radiation early-warning biomarkers. However, the underlying mechanism requires further investigation.

Anomalous effect of small doses of ionizing radiation on metals and alloys

International Nuclear Information System (INIS)

Chernov, I.P.; Mamontov, A.P.; Botaki, A.A.; Cherdantsev, P.A.; Chakhlov, B.V.; Sharov, S.R.; Timoshnikov, Yu.A.; Filipenko, L.A.

1986-01-01

The effect of small doses of 60 Co gamma rays on copper, tungsten, and WCo alloys has been investigated. A decrease in the concentration of material defects under the influence of small doses of ionizing radiation was found. Also the structural rearrangement of the crystal was found to be still in progress after irradiation ceased. The mechanism of the anomalous effect of small doses of ionizing radiation on metals and alloys is discussed in terms of the electron energy scheme. (U.K.)

Impact of total ionizing dose on the electromagnetic susceptibility of a single bipolar transistor

International Nuclear Information System (INIS)

Doridant, A.; Jarrix, S.; Raoult, J.; Blain, A.; Dusseau, L.; Chatry, N.; Calvel, P.; Hoffmann, P.

2012-01-01

Space or military electronic components are subject to both electromagnetic fields and total ionizing dose. This paper deals with the electromagnetic susceptibility of a discrete low frequency transistor subject to total ionizing dose deposition. The electromagnetic susceptibility is investigated on both non-irradiated and irradiated transistors mounted in common emitter configuration. The change in susceptibility to 100 MHz-1.5 GHz interferences lights up a synergy effect between near field electromagnetic waves and total ionizing dose. Physical mechanisms leading to changes in signal output are detailed. (authors)

On the common mechanism for initiation of different effects of low doses of ionizing radiations

International Nuclear Information System (INIS)

Ehjdus, L.Kh.

1996-01-01

Main regularities of different endpoints of ionizing radiation low dose effects (adaptive response, stimulation of proliferation, special radiosensitivity of lymphoid cells, and others) have been examined. It has been shown that these endpoints have a commonness for the dose interval, the shape of the dose-response curve, the reverse effect of dose rate, non-specificity toward initiating agents, and others. An explanation is suggested for the common mechanism of the initiation of all the studied low dose effects, basing on the theory of the non-specific reaction of cell to external influences. It is concluded that initiation of the low dose effects is conditioned by radiation induced damage of functions of plasmic and internal membranes

Effect of different ionizing radiation dose rates on the Staphylococcal enterotoxin in mechanically deboned chicken meat

International Nuclear Information System (INIS)

Azevedo, Heliana de; Brito, Poliana de Paula; Fukuma, Henrique Takuji; Roque, Claudio Vitor; Custodio, Wilson; Kodama, Yasko; Miya, Norma Terugo Nago; Pereira, Jose Luiz

2009-01-01

Samples weighing 50g each were prepared from allotments of back with skin MDCM, to the EEB contamination or not (control). Each sample of MDCM contaminated or not with EEB was conditioned in low density polyethylene bag, frozen (-18 ± 1 deg C) for one night in a tunnel and irradiated with gamma rays from 60 Co source in this state with doses of 0.0 kGy (control), 1.5 kGy (5.7 kGy.h -1 - higher dose rate, 1.8 kGy.h -1 - intermediary dose rate and 0.6 kGy.h -1 - lower dose rate) and 3.0 kGy (8.4 kGy.h - '1 - higher dose rate, 2.4 kGy.h -1 - intermediary dose rate and 0.6 kGy.h -1 - lower dose rate). Irradiated or non irradiated MDCM samples were processed to the EEB extraction, according to the VIDAS Staph enterotoxin II kit (bioMerieux) manufacturer protocol. The calculation to determinate the MDCM EEB recovery after the sample (control or irradiated) processing were carried out applying the principle of mass balance, along the whole process. Described experiment was performed in triplicate. Results showed that the irradiation process was effective to remove the MDCM EEB, to both 1.5 kGy and 3.0 kGy. According to the expected, doses of 3.0 kGy showed the highest values of MDCM EEB removal. Regarding the effect of dose rate of radiation on the removal of EEB of the MDCM, it could be observed only for samples irradiated with 1.5 kGy radiation dose; in these processing conditions, the highest value of EEB removal was obtained for samples processed with low radiation dose rate. (author)

The revision of dose limits for exposure to ionizing radiation

International Nuclear Information System (INIS)

Hughes, D.

1990-01-01

The paper reviews the current dose limits for exposure to ionizing radiations and the risk factors on which they are based, and summarizes the revised risk factors and the draft proposals for new dose limits published by the International Commission on Radiological Protection. (author)

Pressurized ionization chamber dose ratemeter for enviromental radiation measaurement

Energy Technology Data Exchange (ETDEWEB)

Qingyu, Yue; Hua, Jin; Youling, Jiang

1986-01-01

The dose ratemeter, mainly used for measuring absorbed doserate of environmental gamma radiation and the charged particle components of cosmic-rays in /sup f/ree-air/sup ,/ consists of an energy compensated spherical pressurized ionization chamber, a MOS electrometer and a digital voltmeter. The flat energy response of the pressurized ionization chamber ranges from 60 keV to 1250 keV. It has good stability and higher sensitivity, and weights 6 kg.

Low-dose ionizing radiation alleviates Aβ42-induced defective phenotypes in Drosophila Alzheimer's disease models

Energy Technology Data Exchange (ETDEWEB)

Hwang, SooJin; Jeong, Hae Min; Nam, Seon Young [Low-dose Radiation Research Team, Radiation Health Institute, Korea Hydro & Nuclear Power Co. Ltd., Daejeon (Korea, Republic of)

2017-04-15

Alzheimer's disease (AD) is the most common neurodegenerative disease that is characterized by amyloid plaques, progressive neuronal loss, and gradual deterioration of memory. Amyloid imaging using positron emission tomography (PET) radiotracers have been developed and approved for clinical use in the evaluation of suspected neurodegenerative disease, including AD. Particularly, previous studies involving low-dose ionizing radiation on Aβ 42-treated mouse hippocampal neurons have suggested a potential role for low-dose ionizing radiation in the treatment of AD. However, associated in vivo studies involving the therapy effects of low-dose ionizing radiation on AD are still insufficient. As a powerful cell biological system, Drosophila AD models have been generated and established a useful model organism for study on the etiology of human AD. In this study, we investigated the hormesis effects of low-dose ionizing radiation on Drosophila AD models. Our results suggest that low-dose ionizing radiation have the beneficial effects on not only the Aβ42-induced developmental defective phenotypes but also motor defects in Drosophila AD models. These results might be due to a regulation of apoptosis, and provide insight into the hormesis effects of low-dose ionizing radiation. Our results suggest that low-dose ionizing radiation have the beneficial effects on not only the Aβ42-induced developmental defective phenotypes but also motor defects in Drosophila AD models. These results might be due to a regulation of apoptosis, and provide insight into the hormesis effects of low-dose ionizing radiation.

Influence of low dose ionizing radiation on amplification and antitumor activity of LAK/TIL cells

International Nuclear Information System (INIS)

Liu Wei; Hou Dianjun; Qiao Jianwei; Shang Ximei; Li Jieqing

2000-01-01

Objective: To study the influence of low dose ionization on amplification and antitumor activity of LAK/TIL cells. Methods: TIL cells isolated from Lewis lung cancer tissues and LAK cells from spleen of tumor-bearing mouse were irradiated with different low doses of X-rays and were cultured after irradiation. Results: Low dose ionizing radiation improved the amplification volume of LAK/TIL cells, decreased the cell death ratio in amplification process, and increased the toxicity of LAK/TIL cells, Conclusions: Low dose ionizing radiation can result in amplification of biologically activated lymphocytes, and decreases the death ratio of the cells in amplification process

Adaptive response to ionizing radiation in normal human skin fibroblasts. Enhancement of DNA repair rate and modulation of gene expression

International Nuclear Information System (INIS)

Toledo, S.M. de; Mitchel, R.E.J.; Azzam, E.; Ottawa Univ., ON; Raaphorst, G.P.

1994-01-01

Low doses and dose rates of ionizing radiation enhance the rate of DNA repair in human fibroblasts and protect the cells against radiation-induced micronucleus formation. Chronic exposures reduce the mRNA levels of the genes topoisomerase II and FACC-1 (Fanconi's anemia, group C). (authors). 11 refs., 1 tab., 2 figs

Late biological effects of ionizing radiation as influenced by dose, dose rate, age at exposure, and genetic sensitivity to neoplastic transformation

International Nuclear Information System (INIS)

Spalding, J.F.; Prine, J.R.; Tietjen, G.L.

1978-01-01

A most comprehensive investigation is in progress at the Los Alamos Scientific Laboratory to study the late biological effects of whole-body exposure to gamma irradiation as they may be influenced by total dose, dose rate, age at exposure, and genetic background. Strain C57B1/6J mice of four age groups (newborn, 2, 6, and 15 months) were given five doses (20, 60, 180, 540, and 1620 rad) of gamma rays, with each dose being delivered at six dose rates (0.7, 2.1, 6.3, 18.9, 56.7 rad/day and 25 rad/min). Forty to sixty mice were used in each of the approximately 110 dose/dose-rate and age combinations. The study was done in two replications with an equal number of mice per replication. Strain RF/J mice were used in a companion study to investigate the influence of genetic background on the type and magnitude of effect. Results of the first and second replications of the 15-month-old age group and data on the influence of genetic background on biological response have been completed, and the results show no significant life shortening within the dose and dose-rate range used

Plastic packaging and burn-in effects on ionizing dose response in CMOS microcircuits

International Nuclear Information System (INIS)

Clark, S.D.; Bings, J.P.; Maher, M.C.; Williams, M.K.; Alexander, D.R.; Pease, R.L.

1995-01-01

Results are reported from an investigation of the effects of packaging and burn-in on the post-irradiation performance of National Semiconductor 54AC02 Quad 2-input NOR gates. The test population was drawn from a single wafer fabricated in the National process qualified under Mil-Prf-38535 to an ionizing radiation hardness of 100 krads(Si). The test sample was divided between plastic and ceramic packages. Additionally, half of the plastic samples and half of the two ceramic samples received a 168 hour/125 C burn-in. Two irradiation schemes were used. The first followed Mil-Std-883 Method 1019.4 (dose rate = 50 rads(Si)/s). The second used a low dose rate (0.1 rads(Si)/s). AC, DC, transfer function and functional behavior were monitored throughout the tests. Significant differences among the package types and burn-in variations were noted with the plastic, burned-in components demonstrating enhanced degradation. They show the worst post-irradiation parameter values as well as very broad post-irradiation parameter distributions. Degradation is highly dependent upon dose rate and anneal conditions. Two different radiation induced leakage paths have been identified, and their characteristics have been correlated to variations in high dose rate and low dose rate circuit performance. Caution is recommended for system developers to ensure that radiation hardness characterization is performed for the same package/burn-in configuration to be used in the system

Development of Real-Time Measurement of Effective Dose for High Dose Rate Neutron Fields

International Nuclear Information System (INIS)

Braby, L. A.; Reece, W. D.; Hsu, W. H.

2003-01-01

Studies of the effects of low doses of ionizing radiation require sources of radiation which are well characterized in terms of the dose and the quality of the radiation. One of the best measures of the quality of neutron irradiation is the dose mean lineal energy. At very low dose rates this can be determined by measuring individual energy deposition events, and calculating the dose mean of the event size. However, at the dose rates that are normally required for biology experiments, the individual events can not be separated by radiation detectors. However, the total energy deposited in a specified time interval can be measured. This total energy has a random variation which depends on the size of the individual events, so the dose mean lineal energy can be calculated from the variance of repeated measurements of the energy deposited in a fixed time. We have developed a specialized charge integration circuit for the measurement of the charge produced in a small ion chamber in typical neutron irradiation experiments. We have also developed 4.3 mm diameter ion chambers with both tissue equivalent and carbon walls for the purpose of measuring dose mean lineal energy due to all radiations and due to all radiations except neutrons, respectively. By adjusting the gas pressure in the ion chamber, it can be made to simulate tissue volumes from a few nanometers to a few millimeters in diameter. The charge is integrated for 0.1 seconds, and the resulting pulse height is recorded by a multi channel analyzer. The system has been used in a variety of photon and neutron radiation fields, and measured values of dose and dose mean lineal energy are consistent with values extrapolated from measurements made by other techniques at much lower dose rates. It is expected that this technique will prove to be much more reliable than extrapolations from measurements made at low dose rates because these low dose rate exposures generally do not accurately reproduce the attenuation and

Low Dose Ionizing Radiation Modulates Immune Function

International Nuclear Information System (INIS)

Nelson, Gregory A.

2016-01-01

In order to examine the effects of low dose ionizing radiation on the immune system we chose to examine an amplified adaptive cellular immunity response. This response is Type IV delayed-type hypersensitivity also called contact hypersensitivity. The agent fluorescein isothiocyanate (FITC) is a low molecular weight, lipophilic, reactive, fluorescent molecule that can be applied to the skin where it (hapten) reacts with proteins (carriers) to become a complete antigen. Exposure to FITC leads to sensitization which is easily measured as a hypersensitivity inflammatory reaction following a subsequent exposure to the ear. Ear swelling, eosinophil infiltration, immunoglobulin E production and cytokine secretion patterns characteristic of a 'Th2 polarized' immune response are the components of the reaction. The reaction requires successful implementation of antigen processing and presentation by antigen presenting Langerhans cells, communication with naïve T lymphocytes in draining lymph nodes, expansion of activated T cell clones, migration of activated T cells to the circulation, and recruitment of memory T cells, macrophages and eosinophils to the site of the secondary challenge. Using this model our approach was to quantify system function rather than relying only on indirect biomarkers of cell. We measured the FITC-induced hypersensitivity reaction over a range of doses from 2 cGy to 2 Gy. Irradiations were performed during key events or prior to key events to deplete critical cell populations. In addition to quantifying the final inflammatory response, we assessed cell populations in peripheral blood and spleen, cytokine signatures, IgE levels and expression of genes associated with key processes in sensitization and elicitation/recall. We hypothesized that ionizing radiation would produce a biphasic effect on immune system function resulting in an enhancement at low doses and a depression at higher doses and suggested that this transition would occur in

Low Dose Ionizing Radiation Modulates Immune Function

Energy Technology Data Exchange (ETDEWEB)

Nelson, Gregory A. [Loma Linda Univ., CA (United States)

2016-01-12

In order to examine the effects of low dose ionizing radiation on the immune system we chose to examine an amplified adaptive cellular immunity response. This response is Type IV delayed-type hypersensitivity also called contact hypersensitivity. The agent fluorescein isothiocyanate (FITC) is a low molecular weight, lipophilic, reactive, fluorescent molecule that can be applied to the skin where it (hapten) reacts with proteins (carriers) to become a complete antigen. Exposure to FITC leads to sensitization which is easily measured as a hypersensitivity inflammatory reaction following a subsequent exposure to the ear. Ear swelling, eosinophil infiltration, immunoglobulin E production and cytokine secretion patterns characteristic of a “Th2 polarized” immune response are the components of the reaction. The reaction requires successful implementation of antigen processing and presentation by antigen presenting Langerhans cells, communication with naïve T lymphocytes in draining lymph nodes, expansion of activated T cell clones, migration of activated T cells to the circulation, and recruitment of memory T cells, macrophages and eosinophils to the site of the secondary challenge. Using this model our approach was to quantify system function rather than relying only on indirect biomarkers of cell. We measured the FITC-induced hypersensitivity reaction over a range of doses from 2 cGy to 2 Gy. Irradiations were performed during key events or prior to key events to deplete critical cell populations. In addition to quantifying the final inflammatory response, we assessed cell populations in peripheral blood and spleen, cytokine signatures, IgE levels and expression of genes associated with key processes in sensitization and elicitation/recall. We hypothesized that ionizing radiation would produce a biphasic effect on immune system function resulting in an enhancement at low doses and a depression at higher doses and suggested that this transition would occur in the

Effect of γ-dose rate and total dose interrelation on the polymeric hydrogel: A novel injectable male contraceptive

International Nuclear Information System (INIS)

Jha, Pradeep K.; Jha, Rakhi; Gupta, B.L.; Guha, Sujoy K.

2010-01-01

Functional necessity to use a particular range of dose rate and total dose of γ-initiated polymerization to manufacture a novel polymeric hydrogel RISUG (reversible inhibition of sperm under guidance) made of styrene maleic anhydride (SMA) dissolved in dimethyl sulphoxide (DMSO), for its broad biomedical application explores new dimension of research. The present work involves 16 irradiated samples. They were tested by fourier transform infrared spectroscopy, matrix assisted laser desorption/ionization-TOF, field emission scanning electron microscopy, high resolution transmission electron microscopy, etc. to see the interrelation effect of gamma dose rates (8.25, 17.29, 20.01 and 25.00 Gy/min) and four sets of doses (1.8, 2.0, 2.2 and 2.4 kGy) on the molecular weight, molecular weight distribution and porosity analysis of the biopolymeric drug RISUG. The results of randomized experiment indicated that a range of 18-24 Gy/min γ-dose rate and 2.0-2.4 kGy γ-total doses is suitable for the desirable in vivo performance of the contraceptive copolymer.

The Increase in Animal Mortality Risk following Exposure to Sparsely Ionizing Radiation Is Not Linear Quadratic with Dose

OpenAIRE

Haley, Benjamin M.; Paunesku, Tatjana; Grdina, David J.; Woloschak, Gayle E.

2015-01-01

Introduction The US government regulates allowable radiation exposures relying, in large part, on the seventh report from the committee to estimate the Biological Effect of Ionizing Radiation (BEIR VII), which estimated that most contemporary exposures- protracted or low-dose, carry 1.5 fold less risk of carcinogenesis and mortality per Gy than acute exposures of atomic bomb survivors. This correction is known as the dose and dose rate effectiveness factor for the life span study of atomic bo...

Conversion of ionization measurements to radiation absorbed dose in non-water density material

International Nuclear Information System (INIS)

El-Khatib, E.; Connors, S.

1992-01-01

In bone-equivalent materials two different calculations of absorbed dose are possible: the absorbed dose to soft tissue plastic (polystyrene) within bone-equivalent material and the dose to the bone-equivalent material itself. Both can be calculated from ionization measurements in phantoms. These two calculations result in significantly different doses in a heterogeneous phantom composed of polystyrene and aluminium (a bone substitute). The dose to a thin slab of polystyrene in aluminium is much higher than the dose to the aluminium itself at the same depth in the aluminium. Monte Carlo calculations confirm that the calculation of dose to polystyrene in aluminium can be accurately carried out using existing dosimetry protocols. However, the conversion of ionization measurements to absorbed dose to high atomic number materials cannot be accurately carried out with existing protocols and appropriate conversion factors need to be determined. (author)

Compendium of Single Event Effects, Total Ionizing Dose, and Displacement Damage for Candidate Spacecraft Electronics for NASA

Science.gov (United States)

LaBel, Kenneth A.; OBryan, Martha V.; Chen, Dakai; Campola, Michael J.; Casey, Megan C.; Pellish, Jonathan A.; Lauenstein, Jean-Marie; Wilcox, Edward P.; Topper, Alyson D.; Ladbury, Raymond L.;

A pressurized ionization chamber dose ratemeter for enviromental radiation measaurement

International Nuclear Information System (INIS)

Yue Qingyu; Jin Hua

1986-01-01

The dose ratemeter, mainly used for measuring absorbed doserate of environmental gamma radiation and the charged particle components of cosmic-rays in f ree-air , consists of an energy compensated spherical pressurized ionization chamber, a MOS electrometer and a digital voltmeter. The flat energy response of the pressurized ionization chamber ranges from 60 keV to 1250 keV. It has good stability and higher sensitivity, and weights 6 kg

Late biological effects of ionizing radiation as influenced by dose, dose rate, age at exposure and genetic sensitivity to neoplastic transformation

International Nuclear Information System (INIS)

Spalding, J.F.; Prine, J.R.; Tietjen, G.L.

1978-01-01

A most comprehensive investigation is in progress at the Los Alamos Scientific Laboratory to study the late biological effects of whole-body exposure to gamma irradiation as they may be influenced by total dose, dose rate, age at exposure and genetic background. Strain C57B1/6J mice of four age groups (newborn, 2, 6 and l5 months) were given five doses (20, 60, 180, 540, and 1620 rads) of gamma rays, with each dose being delivered at six dose rates (0.7, 2.1, 6.3, 18.9, 56.7 rads/day and 25 rads/min). Forty to sixty mice were used in each of the approximately 119 dose/dose-rate and age combinations. The study was done in two replications with an equal number of mice per replicaton. Strain RF/J mice were used in a companion study to investigate the influence of genetic background on the type and magnitude of effect. Results of the first and second replications of the l5-month-old age group and data on the influence of genetic background on biological response have been completed, and the results show no significant life shortening within the dose and dose-rate range used. It was also concluded that radiaton-induced neoplastic transformaton was significantly greater in mice with a known genetic sensitivity to neoplastic disease than in mammals which do not normally have a significant incidence of tumours. (author)

Application of accelerated evaluation method of alteration temperature and constant dose rate irradiation on bipolar linear regulator LM317

International Nuclear Information System (INIS)

Deng Wei; Wu Xue; Wang Xin; Zhang Jinxin; Zhang Xiaofu; Zheng Qiwen; Ma Wuying; Lu Wu; Guo Qi; He Chengfa

2014-01-01

With different irradiation methods including high dose rate irradiation, low dose rate irradiation, alteration temperature and constant dose rate irradiation, and US military standard constant high temperature and constant dose rate irradiation, the ionizing radiation responses of bipolar linear regulator LM317 from three different companies were investigated under the operating and zero biases. The results show that compared with constant high temperature and constant dose rate irradiation method, the alteration temperature and constant dose rate irradiation method can not only very rapidly and accurately evaluate the dose rate effect of three bipolar linear regulators, but also well simulate the damage of low dose rate irradiation. Experiment results make the alteration temperature and constant dose rate irradiation method successfully apply to bipolar linear regulator. (authors)

Field measurement and interpretation of beta doses and dose rates

International Nuclear Information System (INIS)

Selby, J.M.; Swinth, K.L.; Hooker, C.D.; Kenoyer, J.L.

1983-01-01

A large number of portable survey instruments employing G.M., ionization chamber, and scintillation detectors used for gamma measurements are also used for monitoring in beta fields by using removable shields to separate the beta and gamma components of the radiation field. The difference does not correspond to an absorbed dose rate for the beta field due to a variety of factors. Among these factors are the dependence on beta energy, source-detector geometries, mixed fields and variable ambient conditions. Attempting to use such measurements directly can lead to errors as high as a factor of 100. Appropriate calibrations and correction factors can be used to reduce the errors in beta measurements to a tolerable level

Evaluation of quality characteristics and functional properties of mechanically deboned chicken meats treated with different dose rates of ionizing radiation and use of antioxidants; Avaliacao de caracteristicas de qualidade e propriedades funcionais da carne mecanicamente separada de frango tratada com diferentes taxas de dose de radiacao ionizante e uso de antioxidantes

Energy Technology Data Exchange (ETDEWEB)

Brito, Poliana de Paula

2012-07-01

The Mechanically Deboned chicken meat (MDCM) is used in traditional meat products, in greater proportion in those emulsified, replacing meat raw materials more expensive. The raw material can have high MDCM the microbial load, as a result of contamination during processing or failure during the evisceration. The irradiation process is accepted as one of the most effective technologies when compared to conventional techniques of preservation, to reduce contamination of pathogens and spoilage. However, little information is available about the use and effects of different dose rates of ionizing radiation processing. Irradiation causes chemical changes in food, a major cause of deterioration of quality of raw or cooked meat products during refrigerated storage, frozen. The objective of this study was to evaluate the effects of different dose rates of ionizing radiation on the production of Thiobarbituric Acid Reactive Substances (TBARS), color, microbiological and sensory characteristics of mechanically deboned chicken added or without added antioxidants, during the cold storage and evaluation of functional properties. The results showed that among the tested dose rates using cobalt-60 source, dose rate of 4.04 kGy.h-1 was the best for processing MDCM. Furthermore, the use of the combination of rosemary antioxidant and α-tocopherol were able to reduce lipid oxidation generated by irradiation of the samples, showed a synergistic effect to the processing with ionizing radiation in reduction of psychrotrophic bacteria count and contributed to a better sensory quality. The use of radiation in the processing FDMI did not adversely affect the functional properties studied. (author)

Ionizing radiation population doses at Sao Paulo city, Brazil: open-pit gamma dose measurement

International Nuclear Information System (INIS)

Oliveira, Raimundo Enoch Rodrigues

2001-01-01

The effects of ionizing radiation to the human beings are well known for high and intermediate doses. As far as low level) radiation doses are concerned, there is no consensus. In order to get a better understanding of such effects it is necessary to assess the low doses with better accuracy. In this work, it was made an estimate of the annual ambient dose equivalent (H * (10)) to which the people are exposed in the city of Sao Paulo. Until now there are no data about it available in the literature. For the purpose of this evaluation, a map with various routes covering the largest and more representative area of the city was designed. The choice of points for data collection was made taking into account mainly the occupancy of the region. A portable gamma spectrometry system was used. It furnishes the rate of H * (10) and the measured gamma spectrum (in the range from 50 to 1670 keV) in the place of interest. The measurements were performed in a short time interval, since the gamma radiation arrives from a great extent of soil. Each measurement was done 1 m above the soil during 300 s. The rates of H * (10) varied from 33.1 to 152.3 nSv.h -1 , net values, obtained after subtraction of the cosmic rays contribution. The standard deviation was 22 n Sv.h -1 for an average for the city of Sao Paulo of 96.1(24) nSv.h -1 . In addition, average values of H * (10) rates for the city Health Divisions were calculated. Those values are not statistically equivalent and the whole set of data could not be treated as one, as the statistical Student test indicated a non homogeneity of the group of data. Hence it is necessary the accomplishment of a more detailed survey in order to verify the origin of the discrepancy. The mean value of H * (10) rate obtained for the city of Sao Paulo as converted to effective dose. in order to be compared with other places results It could be noticed that the annual average of effective dose for the city of Sao Paulo, 0.522(13) mSv, is superior to

Alteration of cytokine profiles in mice exposed to chronic low-dose ionizing radiation

Energy Technology Data Exchange (ETDEWEB)

Shin, Suk Chul [Radiation Health Research Institute, Korea Hydro and Nuclear Power Co., Ltd., 388-1, Ssangmun-dong, Dobong-gu, Seoul 132-703 (Korea, Republic of); Lee, Kyung-Mi [Global Research Lab, BAERI Institute, Department of Biochemistry and Molecular Biology, Korea University College of Medicine, Seoul 136-705 (Korea, Republic of); Kang, Yu Mi [Radiation Health Research Institute, Korea Hydro and Nuclear Power Co., Ltd., 388-1, Ssangmun-dong, Dobong-gu, Seoul 132-703 (Korea, Republic of); Kim, Kwanghee [Global Research Lab, BAERI Institute, Department of Biochemistry and Molecular Biology, Korea University College of Medicine, Seoul 136-705 (Korea, Republic of); Kim, Cha Soon; Yang, Kwang Hee; Jin, Young-Woo [Radiation Health Research Institute, Korea Hydro and Nuclear Power Co., Ltd., 388-1, Ssangmun-dong, Dobong-gu, Seoul 132-703 (Korea, Republic of); Kim, Chong Soon [Department of Nuclear Medicine, Haeundae Paik Hospital, Inje University, Busan 612-030 (Korea, Republic of); Kim, Hee Sun, E-mail: hskimdvm@khnp.co.kr [Radiation Health Research Institute, Korea Hydro and Nuclear Power Co., Ltd., 388-1, Ssangmun-dong, Dobong-gu, Seoul 132-703 (Korea, Republic of)

2010-07-09

While a high-dose of ionizing radiation is generally harmful and causes damage to living organisms, a low-dose of radiation has been shown to be beneficial in a variety of animal models. To understand the basis for the effect of low-dose radiation in vivo, we examined the cellular and immunological changes evoked in mice exposed to low-dose radiation at very low (0.7 mGy/h) and low (3.95 mGy/h) dose rate for the total dose of 0.2 and 2 Gy, respectively. Mice exposed to low-dose radiation, either at very low- or low-dose rate, demonstrated normal range of body weight and complete blood counts. Likewise, the number and percentage of peripheral lymphocyte populations, CD4{sup +} T, CD8{sup +} T, B, or NK cells, stayed unchanged following irradiation. Nonetheless, the sera from these mice exhibited elevated levels of IL-3, IL-4, leptin, MCP-1, MCP-5, MIP-1{alpha}, thrombopoietin, and VEGF along with slight reduction of IL-12p70, IL-13, IL-17, and IFN-{gamma}. This pattern of cytokine release suggests the stimulation of innate immunity facilitating myeloid differentiation and activation while suppressing pro-inflammatory responses and promoting differentiation of naive T cells into T-helper 2, not T-helper 1, types. Collectively, our data highlight the subtle changes of cytokine milieu by chronic low-dose {gamma}-radiation, which may be associated with the functional benefits observed in various experimental models.

Present status of ambient dose equivalent rate and radioactive substance concentration measurements in working environment. (3) Measuring instruments for ionizing radiation in working environments

International Nuclear Information System (INIS)

Matsubara, Shohei

2006-01-01

In order to measure the airborne radioactive substance concentration in working environments, some kinds of sampler such as dust sampler and iodine sampler, measuring instruments (alpha and beta spectrometer, and liquid scintillation counter), monitor (dust-, iodine- and gas-monitor), survey meter for measuring gamma ray dose rate are stated. The measurement method of α, β and γ-ray nuclides and ambient dose-equivalent at 10 mm was explained. Some examples of the list of dust sampler, filter, tritium sampler, dust monitor, iodine monitor, gas monitor, and survey meter on the market are shown. There are so many kinds of measuring instruments for ionizing radiation in working environment that the best instrument for measurement should be selected. The environment conditions such as sample form, temperature and humidity have to be considered in order to evaluate the measurement values. (S.Y.)

Analytical models for total dose ionization effects in MOS devices.

Energy Technology Data Exchange (ETDEWEB)

Campbell, Phillip Montgomery; Bogdan, Carolyn W.

2008-08-01

MOS devices are susceptible to damage by ionizing radiation due to charge buildup in gate, field and SOI buried oxides. Under positive bias holes created in the gate oxide will transport to the Si / SiO{sub 2} interface creating oxide-trapped charge. As a result of hole transport and trapping, hydrogen is liberated in the oxide which can create interface-trapped charge. The trapped charge will affect the threshold voltage and degrade the channel mobility. Neutralization of oxidetrapped charge by electron tunneling from the silicon and by thermal emission can take place over long periods of time. Neutralization of interface-trapped charge is not observed at room temperature. Analytical models are developed that account for the principal effects of total dose in MOS devices under different gate bias. The intent is to obtain closed-form solutions that can be used in circuit simulation. Expressions are derived for the aging effects of very low dose rate radiation over long time periods.

Effects of total dose of ionizing radiation on integrated circuits

Energy Technology Data Exchange (ETDEWEB)

Silveira, Marcilei A.G.; Cirne, K.H.; Gimenez, S.; Santos, R.B.B. [Centro Universitario da FEI, Sao Bernardo do Campo, SP (Brazil); Added, N.; Barbosa, M.D.L.; Medina, N.H.; Tabacniks, M.H. [Universidade de Sao Paulo (IF/USP), SP (Brazil). Inst. de Fisica; Lima, J.A. de; Seixas Junior, L.E.; Melo, W. [Centro de Tecnologia da Informacao Paulo Archer, Sao Paulo, SP (Brazil)

2011-07-01

Full text: The study of ionizing radiation effects on materials used in electronic devices is of great relevance for the progress of global technological development and, particularly, it is a necessity in some strategic areas in Brazil. Electronic circuits are strongly influenced by radiation and the need for IC's featuring radiation hardness is largely growing to meet the stringent environment in space electronics. On the other hand, aerospace agencies are encouraging both scientific community and semiconductors industry to develop hardened-by-design components using standard manufacturing processes to achieve maximum performance, while significantly reducing costs. To understand the physical phenomena responsible for changes in devices exposed to ionizing radiation several kinds of radiation should then be considered, among them alpha particles, protons, gamma and X-rays. Radiation effects on the integrated circuits are usually divided into two categories: total ionizing dose (TID), a cumulative dose that shifts the threshold voltage and increases transistor's off-state current; single events effects (SEE), a transient effect which can deposit charge directly into the device and disturb the properties of electronic circuits. TID is one of the most common effects and may generate degradation in some parameters of the CMOS electronic devices, such as the threshold voltage oscillation, increase of the sub-threshold slope and increase of the off-state current. The effects of ionizing radiation are the creation of electron-hole pairs in the oxide layer changing operation mode parameters of the electronic device. Indirectly, there will be also changes in the device due to the formation of secondary electrons from the interaction of electromagnetic radiation with the material, since the charge carriers can be trapped both in the oxide layer and in the interface with the oxide. In this work we have investigated the behavior of MOSFET devices fabricated with

Comparative investigation of three dose rate meters for their viability in pulsed radiation fields

International Nuclear Information System (INIS)

Gotz, M; Karsch, L; Pawelke, J

2015-01-01

Pulsed radiation fields, characterized by microsecond pulse duration and correspondingly high pulse dose rates, are increasingly used in therapeutic, diagnostic and research applications. Yet, dose rate meters which are used to monitor radiation protection areas or to inspect radiation shielding are mostly designed, characterized and tested for continuous fields and show severe deficiencies in highly pulsed fields. Despite general awareness of the problem, knowledge of the specific limitations of individual instruments is very limited, complicating reliable measurements. We present here the results of testing three commercial dose rate meters, the RamION ionization chamber, the LB 1236-H proportional counter and the 6150AD-b scintillation counter, for their response in pulsed radiation fields of varied pulse dose and duration. Of these three the RamION proved reliable, operating in a pulsed radiation field within its specifications, while the other two instruments were only able to measure very limited pulse doses and pulse dose rates reliably. (paper)

Effect of low dose rate irradiation on doped silica core optical fibers

International Nuclear Information System (INIS)

Friebele, E.J.; Askins, C.G.; Gingerich, M.E.

1984-01-01

The optical attenuation induced in multimode doped silica core optical fiber waveguides by a year's exposure to low dose rate (1 rad/day) ionizing radiation was studied, allowing a characterization of fibers deployed in these environments and a determination of the permanent induced loss in the waveguides. Variations in the induced attenuation at 0.85 μm have been observed with changes in the dose rate between 1 rad/day and 9000 rads/min. These dose rate dependences have been found to derive directly from the recovery that occurs during the exposure; the recovery data predict little or no dose rate dependence of the damage at 1.3 μm. The low dose rate exposure has been found to induce significant permanent attenuation in the 0.7-1.7-μm spectral region in all fibers containing P in the core, whether doped uniformly across the diameter or constrained to a narrow spike on the centerline. Whereas permanent loss was induced at 0.85 μm in a P-free binary Ge-doped silica core fiber by the year's exposure, virtually no damage was observed at 1.3 μm

Reduction of the dose of ionizing radiation: progressions in TC

International Nuclear Information System (INIS)

Orlacchio, A.; Costanzo, E.; Chegai, F.; Simonetti, G.

2014-01-01

The optimization of the dose of ionizing radiation in CT, it is a very important matter that can be reach avoiding unnecessary examinations, using un appropriate report KV / mAs reducing the rotation time, determining the field of study, using a high pitch using equipment that provide systems with dose reduction, through proper education of the staff that interacts with machinery and using radioprotective compounds.

Study on ionizing radiation to the workers' lymphocyte micronucleus rate and chromosome aberrations

International Nuclear Information System (INIS)

Li Jianhua; Wang Linchao; He Wei

2007-01-01

Objective: To study lymphocyte genetic material of an iron and steel enterprise workers exposed to the ionizing radiation, find out measures to protect their health and reduce ionizing radiation occupation harm. Methods: 342 workers were choseh as the exposed group who worked in an iron and steel enterprise in the beam installment operation, to examine their circumference blood lymphocyte micronucleus rate and the chromosome aberrations, simultaneously select 280 chefs as the control group, The irradiation dosage was determined and statistical analysis was carded out wich the consideration of their length of work and differences in work post. Results: Exposed group: the micronucleus rate masculine gender (MNR), 4 people, the masculine gender pick out rate is 12.87%. The chromosome aberration factor masculine gender (CAF), 12 people, the masculine rate is 3.51%. Control group: MNR 3 people, the asculine gender pick out rate is 1.07%; CAF 2 people, masculine gender rate is 0.72%. Comparing the two groups, every item has the significant difference. Workers in is the exposed group workers have the average exposure dose of 6.73mSv/a, MNR,CAF are illuminated to the dosage have a positive line correlation. They become increased as the job lenght prolongs. The nucleon name, the material calculation and the medical X-radial are responsible for the highest ratio. Conclusion: In iron and steel enterprises, long-time ionizing radiation can cause the workers' circumference blood lymphocyte micronucleus rate and the chromosome aberrations obvious to rise. The beam protection measures strengthened so as to reduce the harms to workers. (authors)

Effect of dose rate and exposure time on the stimulation effect of tube growth of Pinus sylvestris pollen

International Nuclear Information System (INIS)

Zelles, L.; Fendrik, I.; Technische Univ. Hannover

1975-01-01

The stimulating effect of ionizing radiation in respect to dose rate and exposure time was studied using the tube growth of Pinus silvestris pollen. Stimulation was registered with a small dose (50 rad) supplied at low dose rates (0.5; 1.0; 3.0 and 5.0 rad/sec) and with higher doses (300; 800 and 1,400 rad) supplied at higher dose rates (10; 40 and 50 rad/sec). This suggests that only the exposure time is of importance for radiation-induced stimulation provided that the exposure time does not exceed 100 sec. (orig.) [de

Dose rate constants for new dose quantities

International Nuclear Information System (INIS)

Tschurlovits, M.; Daverda, G.; Leitner, A.

1992-01-01

Conceptual changes and new quantities made is necessary to reassess dose rate quantities. Calculations of the dose rate constant were done for air kerma, ambient dose equivalent and directional dose equivalent. The number of radionuclides is more than 200. The threshold energy is selected as 20 keV for the dose equivalent constants. The dose rate constant for the photon equivalent dose as used mainly in German speaking countries as a temporary quantity is also included. (Author)

The influence of low doses of ionizing radiation on biological systems

International Nuclear Information System (INIS)

Kwiecinska, T.

1986-11-01

Recent results concerning possible beneficial effects of low doses of ionizing radiation on biological systems are summarized. It is also pointed out on the basis of existing evidence that harmful effects on living organisms take place not only in the case of excess but also in the case of deficiency of ionizing radiation. Possibility of using radio-enhanced ultralow luminescence for studying hormesis phenomena is discussed. 24 refs., 4 figs. (author)

Circuitry for use with an ionizing-radiation detector

International Nuclear Information System (INIS)

Marshall, J.H. III; Harrington, T.M.

1976-01-01

An improved system of circuitry for use in combination with an ionizing-radiation detector over a wide range of radiation levels includes a current-to-frequency converter together with a digital data processor for respectively producing and measuring a pulse repetition frequency which is proportional to the output current of the ionizing-radiation detector, a dc-to-dc converter for providing closely regulated operating voltages from a rechargeable battery and a bias supply for providing high voltage to the ionization chamber. The ionizing-radiation detector operating as a part of this system produces a signal responsive to the level of ionizing radiation in the vicinity of the detector, and this signal is converted into a pulse frequency which will vary in direct proportion to such level of ionizing-radiation. The data processor, by counting the number of pulses from the converter over a selected integration interval, provides a digital indication of radiation dose rate, and by accumulating the total of all such pulses provides a digital indication of total integrated dose. Ordinary frequency-to-voltage conversion devices or digital display techniques can be used as a means for providing audible and visible indications of dose and dose-rate levels

Dose response of tracheal epithelial cells to ionizing radiation in air-liquid interface cultures

International Nuclear Information System (INIS)

Fukutsu, K.; Yamada, Y.; Shimo, M.

2002-01-01

The dose-response relationships of tracheal epithelial cells to ionizing radiation was examined in air-liquid interface cultures, which were developed for the purpose of simulating in vivo conditions. The cultures investigated in this study were expected to be advantageous for the performance of irradiation experiments using short-range α rays. The level of dose response of air-liquid interface cultures to ionizing radiation proved to be the same as that for in vivo conditions. This result indicates that air-liquid interface cultures will prove most useful, to facilitate future studies for the investigation of the biological effects induced in tracheal epithelial cells by ionizing radiation, especially by α-rays. (orig.)

The Effects of Low Dose-Rate Ionizing Radiation on the Shapes of Transients in the LM124 Operational Amplifier

Science.gov (United States)

Buchner, Stephen; McMorrow, Dale; Roche, Nicholas; Dusseau, Laurent; Pease, Ron L.

2008-01-01

Shapes of single event transients (SETs) in a linear bipolar circuit (LM124) change with exposure to total ionizing dose (TID) radiation. SETs shape changes are a direct consequence of TID-induced degradation of bipolar transistor gain. A reduction in transistor gain causes a reduction in the drive current of the current sources in the circuit, and it is the lower drive current that most affects the shapes of large amplitude SETs.

Wound trauma alters ionizing radiation dose assessment

Directory of Open Access Journals (Sweden)

Kiang Juliann G

2012-06-01

Full Text Available Abstract Background Wounding following whole-body γ-irradiation (radiation combined injury, RCI increases mortality. Wounding-induced increases in radiation mortality are triggered by sustained activation of inducible nitric oxide synthase pathways, persistent alteration of cytokine homeostasis, and increased susceptibility to bacterial infection. Among these factors, cytokines along with other biomarkers have been adopted for biodosimetric evaluation and assessment of radiation dose and injury. Therefore, wounding could complicate biodosimetric assessments. Results In this report, such confounding effects were addressed. Mice were given 60Co γ-photon radiation followed by skin wounding. Wound trauma exacerbated radiation-induced mortality, body-weight loss, and wound healing. Analyses of DNA damage in bone-marrow cells and peripheral blood mononuclear cells (PBMCs, changes in hematology and cytokine profiles, and fundamental clinical signs were evaluated. Early biomarkers (1 d after RCI vs. irradiation alone included significant decreases in survivin expression in bone marrow cells, enhanced increases in γ-H2AX formation in Lin+ bone marrow cells, enhanced increases in IL-1β, IL-6, IL-8, and G-CSF concentrations in blood, and concomitant decreases in γ-H2AX formation in PBMCs and decreases in numbers of splenocytes, lymphocytes, and neutrophils. Intermediate biomarkers (7 – 10 d after RCI included continuously decreased γ-H2AX formation in PBMC and enhanced increases in IL-1β, IL-6, IL-8, and G-CSF concentrations in blood. The clinical signs evaluated after RCI were increased water consumption, decreased body weight, and decreased wound healing rate and survival rate. Late clinical signs (30 d after RCI included poor survival and wound healing. Conclusion Results suggest that confounding factors such as wounding alters ionizing radiation dose assessment and agents inhibiting these responses may prove therapeutic for radiation combined

Using RADFET for the real-time measurement of gamma radiation dose rate

Science.gov (United States)

Andjelković, Marko S.; Ristić, Goran S.; Jakšić, Aleksandar B.

2015-02-01

RADFETs (RADiation sensitive Field Effect Transistors) are integrating ionizing radiation dosimeters operating on the principle of conversion of radiation-induced threshold voltage shift into absorbed dose. However, one of the major drawbacks of RADFETs is the inability to provide the information on the dose rate in real-time using the conventional absorbed dose measurement technique. The real-time monitoring of dose rate and absorbed dose can be achieved with the current mode dosimeters such as PN and PIN diodes/photodiodes, but these dosimeters have some limitations as absorbed dose meters and hence they are often not a suitable replacement for RADFETs. In that sense, this paper investigates the possibility of using the RADFET as a real-time dose rate meter so that it could be applied for simultaneous online measurement of the dose rate and absorbed dose. A RADFET sample, manufactured by Tyndall National Institute, Cork, Ireland, was tested as a dose rate meter under gamma irradiation from a Co-60 source. The RADFET was configured as a PN junction, such that the drain, gate and source terminals were grounded, while the radiation-induced current was measured at the bulk terminal, whereby the bulk was successively biased with 0 , 10 , 20  and 30 V. In zero-bias mode the radiation-induced current was unstable, but in the biased mode the current response was stable for the investigated dose rates from 0.65  to 32.1 Gy h-1 and up to the total absorbed dose of 25 Gy. The current increased with the dose rate in accordance with the power law, whereas the sensitivity of the current read-out was linear with respect to the applied bias voltage. Comparison with previously analyzed PIN photodiodes has shown that the investigated RADFET is competitive with PIN photodiodes as a gamma radiation dose rate meter and therefore has the potential to be employed for the real-time monitoring of the dose rate and absorbed dose.

Using RADFET for the real-time measurement of gamma radiation dose rate

International Nuclear Information System (INIS)

Andjelković, Marko S; Ristić, Goran S; Jakšić, Aleksandar B

2015-01-01

RADFETs (RADiation sensitive Field Effect Transistors) are integrating ionizing radiation dosimeters operating on the principle of conversion of radiation-induced threshold voltage shift into absorbed dose. However, one of the major drawbacks of RADFETs is the inability to provide the information on the dose rate in real-time using the conventional absorbed dose measurement technique. The real-time monitoring of dose rate and absorbed dose can be achieved with the current mode dosimeters such as PN and PIN diodes/photodiodes, but these dosimeters have some limitations as absorbed dose meters and hence they are often not a suitable replacement for RADFETs. In that sense, this paper investigates the possibility of using the RADFET as a real-time dose rate meter so that it could be applied for simultaneous online measurement of the dose rate and absorbed dose. A RADFET sample, manufactured by Tyndall National Institute, Cork, Ireland, was tested as a dose rate meter under gamma irradiation from a Co-60 source. The RADFET was configured as a PN junction, such that the drain, gate and source terminals were grounded, while the radiation-induced current was measured at the bulk terminal, whereby the bulk was successively biased with 0 , 10 , 20  and 30 V. In zero-bias mode the radiation-induced current was unstable, but in the biased mode the current response was stable for the investigated dose rates from 0.65  to 32.1 Gy h −1 and up to the total absorbed dose of 25 Gy. The current increased with the dose rate in accordance with the power law, whereas the sensitivity of the current read-out was linear with respect to the applied bias voltage. Comparison with previously analyzed PIN photodiodes has shown that the investigated RADFET is competitive with PIN photodiodes as a gamma radiation dose rate meter and therefore has the potential to be employed for the real-time monitoring of the dose rate and absorbed dose. (paper)

Biological effects of very low doses of ionizing radiation

International Nuclear Information System (INIS)

Evseev, V.S.

1987-01-01

The paper deals with a qualitative microdosimetric analysis of a new radiobiological phenomenon (physiological reaction of the cell as a whole to very low doses of ionizing radiations). The analysis is aimed at identifying the type of the primary interaction of radiation with the cell and finding its place in the cell

Mutation induction in cultured human cells after low-dose and low-dose-rate γ-ray irradiation. Detection by LOH analysis

International Nuclear Information System (INIS)

Umebayashi, Yukihiro; Iwaki, Masaya; Yatagai, Fumio; Honma, Masamitsu; Suzuki, Masao; Suzuki, Hiromi; Shimazu, Toru; Ishioka, Noriaki

2007-01-01

To study the genetic effects of low-doses and low-dose-rate ionizing radiation (IR), human lymphoblastoid TK6 cells were exposed to 30 mGy of γ-rays at a dose-rate of 1.2 mGy/hr. The frequency of early mutations (EMs) in the thymidine kinase (TK) gene locus was determined to be 1.7 x 10 -6 , or 1.9-fold higher than the level seen in unirradiated controls. These mutations were analyzed with a loss of heterozygosity (LOH) detection system, a methodology which has been shown to be sensitive to the effects of radiation. Among the 15 EMs observed after IR exposure, 8 were small interstitial-deletion events restricted to the TK gene locus. However, this specific type of event was not found in unirradiated controls. Although these results were observed under the limited conditions, they strongly suggest that the LOH detection system can be used for estimating the genetic effects of a low-dose IR exposure delivered at a low-dose-rate. (author)

Assessment of the radiological impact of gamma and radon dose rates at former U mining sites in Tajikistan

International Nuclear Information System (INIS)

Lespukh, E.; Stegnar, P.; Yunusov, M.; Tilloboev, H.; Zyazev, G.; Kayukov, P.; Hosseini, A.; Strømman, G.; Salbu, B.

2013-01-01

An assessment of the radiological situation due to exposure to gamma radiation, radon ( 222 Rn) and thoron ( 220 Rn) was carried out at former uranium (U) mining and processing sites in Taboshar and at Digmai in Tajikistan. Gamma dose rate measurements were made using various field instruments. 222 Rn/ 220 Rn measurements were carried out with field instruments for instantaneous measurements and then discriminative 222 Rn/ 220 Rn solid state nuclear track detectors (SSNTD) were used for longer representative measurements. The detectors were exposed for an extended period of time in different outdoor and indoor public and residential environments at the selected U legacy sites. The results showed that gamma, 222 Rn and 220 Rn doses were in general low, which consequently implies a low to relatively low radiological risk. The radiation doses deriving from external radiation (gamma dose rate), indoor 222 Rn and 220 Rn with their short-lived progenies did not exceed national or international standards. At none of the sites investigated did the average individual annual effective doses exceed 10 mSv, the recommended threshold value for the general public. A radiation hazard could be associated with exceptional situations, such as elevated exposures to ionizing radiation at the Digmai tailings site and/or in industrial facilities, where gamma and 222 Rn/ 220 Rn dose rates could reach values of several 10 mSv/a. Current doses of ionizing radiation do not represent a hazard to the health of the resident public, with the exception of some specific situations. These issues should be adequately addressed to further reduce needless exposure of the resident public to ionizing radiation

Mutational influences of low-dose and high let ionizing radiation in drosophila melanogaster

Science.gov (United States)

Lei, Huang; Fanjun, Kong; Sun, Yeqing

For cosmic environment consists of a varying kinds of radiation particles including high Z and energy ions which was charactered with low-dose and high RBE, it is important to determine the possible biofuctions of high LET radiation on human beings. To analyse the possible effectes of mutational influences of low-dose and high-LET ionizing radiation, wild fruit flies drosophila melanogaster were irradiated by 12C6+ ions in two LET levels (63.3 and 30 keV/µum) with different low doses from 2mGy to 2000mGy (2, 20, 200, 2000mGy) in HIRFL (Heavy ion radiation facility laboratory, lanzhou, China).In the same LET value group, the average polymorphic frequency was elevated along with adding doses of irradation, the frequency in 2000 mGy dose samples was significantly higher than other samples (p<0.01).These results suggest that genomic DNA sequence could be effected by low-dose and high-LET ionizing radiation, the irradiation dose is an important element in genomic mutation frequency origination.

[Influence of low doses of ionizing radiation on tenascin expression in hybridoma cell systems].

Science.gov (United States)

Lunga, I N

2003-01-01

One of the achievements of the modern radiation ecology is the preparation and application of stable eukariotic cell lines to solve various problems occurring under exposure to ionizing radiation, especially to low doses. The detection of onco-fetal protein--tenascin in different embryonic and tumor cells of humans and animals supposes the probability of appropriate gene expression in lymphoid cells, including hybridomal cells. Using the immunochemical method, the study of tenascin expression in two mouse hybridomal lines was carried out. Tenascin was revealed in hybridomal lines MLC-1 and K-48. Further hybridomal cell lines were exposed to X-ray radiation (120 KV) with doses 2.10,15 cGy. The obtained results demonstrated the sensitivity of tenascin expression to low doses of ionizing radiation, that may be used as a convenient model of studying of genotoxic effects of various damaging ionizing agents on a cell level.

Clustered DNA damages induced in human hematopoietic cells by low doses of ionizing radiation

Science.gov (United States)

Sutherland, Betsy M.; Bennett, Paula V.; Cintron-Torres, Nela; Hada, Megumi; Trunk, John; Monteleone, Denise; Sutherland, John C.; Laval, Jacques; Stanislaus, Marisha; Gewirtz, Alan

2002-01-01

Ionizing radiation induces clusters of DNA damages--oxidized bases, abasic sites and strand breaks--on opposing strands within a few helical turns. Such damages have been postulated to be difficult to repair, as are double strand breaks (one type of cluster). We have shown that low doses of low and high linear energy transfer (LET) radiation induce such damage clusters in human cells. In human cells, DSB are about 30% of the total of complex damages, and the levels of DSBs and oxidized pyrimidine clusters are similar. The dose responses for cluster induction in cells can be described by a linear relationship, implying that even low doses of ionizing radiation can produce clustered damages. Studies are in progress to determine whether clusters can be produced by mechanisms other than ionizing radiation, as well as the levels of various cluster types formed by low and high LET radiation.

Hormesis of Low Doses of Ionizing Radiation Exposure on Immune System

International Nuclear Information System (INIS)

Ragab, M.H.; Abbas, M.O.; El-Asady, R.S.; Amer, H.A.; El-Khouly, W.A.; Shabon, M.H.

2015-01-01

The effect of low doses of ionizing radiation on the immune system has been a controversial subject. To evaluate the effect of low-doses γ-irradiation exposure on immune system. An animal model, using Rattus Rattus rats was used. The rats were divided into groups exposed to either continuous or fractionated 100, 200, 300, 400 and 500 mSv of radiation and compared to control rats that did not receive radiation. All groups were exposed to a total white blood count (Wcs), lymphocyte count and serum IgG level measurement, as indicators of the function of the cell-mediated (T lymphocytes) and the humoral (B lymphocytes) immune system. The results of the current study revealed that the counts of total leukocytes (WBCs) and lymphocytes, as well as the serum level of IgG were increased significantly in rats receiving low dose radiation, indicating enhancement of immune system. The data suggests that low-dose gamma-radiation improved hematological parameters and significantly enhances immune response indices of the exposed rats. These findings are similar to the radiation adaptive responses in which a small dose of pre irradiation would induce certain radiation resistance and enhances the cell response after exposure to further irradiation doses The applied low doses used in the present study may appear effective inducing the radio adaptive response. Farooqi and Kesavan (1993) and Bravard et al. (1999) reported that the adaptive response to ionizing radiation refers to the phenomenon by which cells irradiated with low (cGy) or sublethal doses (conditioning doses) become less susceptible to genotoxic effects of a subsequent high dose (challenge dose, several Gy).

Dose rate effect on the yield of radiation induced response with thermal fading

International Nuclear Information System (INIS)

Chernov, V.; Rogalev, B.; Barboza-Flores, M.

2005-01-01

A model describing the dependences of the accumulation of thermally unstable radiation induced defects on the dose and dose rate is proposed. The model directly takes into account the track nature of the ionizing radiation represented as accumulation processes of defects in tracks averaged over a crystal volume considering various degrees of overlapping in space and time. The accumulation of the defects in the tracks is phenomenologically described. General expressions are obtained that allows radiation yield simulation of defects involving known creation and transformation processes. The cases considered, of linear accumulation (constant increment of the defects in tracks) and accumulation with saturation (complete saturation of the defects in one track), lead to a set of linear dose dependences with saturation, which are routinely used in luminescence and ESR dating. The accumulation, with increase of sensitivity in regions overlapped by two or more tracks, gave a set of dose dependences, from linear-sublinear-linear-saturation, distinctive of quartz up to linear-supralinear-linear-saturation. It is shown that the effect of the dose rate on dose dependences is determined by a dimensionless parameter a=Pτ/D0, where P is the dose rate, τ is the defect lifetime and D0 is the track dose. At a-bar 1 the dose rate influences basically the accumulation of thermally unstable defects. In the reverse case the dose dependences did not seems to be influenced by the dose rate

Model predictions and analysis of enhanced biological effectiveness at low dose rates

International Nuclear Information System (INIS)

Watt, D.E.; Sykes, C.E.; Younis, A.-R.S.

1988-01-01

A severe challenge to all models purporting to describe the biological effects of ionizing radiation has arisen with the discovery of two phenomena: the anomalous trend with dose rate of the frequency of neoplastic transformation of mammalian cells and the apparent excessive damaging power of electron-capture radionuclides when incorporated into cell nuclei. A new model is proposed which predicts and enables interpretation of these phenomena. Radiation effectiveness is found to be expressible absolutely in terms of the geometrical cross-sectional area of the radiosensitive sites. The duration of the irradiation, the mean free path for ionization, the influence of particles in the slowing-down spectrum perrtaining in the medium and two collective time factors determining the mean repair rate and the mean lifetime of unidentified reactive chemical species [pt

Simulation experiment on total ionization dose effects of linear CCD

International Nuclear Information System (INIS)

Tang Benqi; Zhang Yong; Xiao Zhigang; Wang Zujun; Huang Shaoyan

2004-01-01

We carry out the ionization radiation experiment of linear CCDs operated in unbiased, biased, biased and driven mode respectively by Co-60 γ source with our self-designed test system, and offline test the Dark signal and Saturation voltage and SNR varied with total dose for TCD132D, and get some valuable results. On the basis of above work, we set forth a primary experiment approaches to simulate the total dose radiation effects of charge coupled devices. (authors)

Dose rate correction in medium dose rate brachytherapy for carcinoma cervix

International Nuclear Information System (INIS)

Patel, F.D.; Negi, P.S.; Sharma, S.C.; Kapoor, R.; Singh, D.P.; Ghoshal, S.

1998-01-01

Purpose: To establish the magnitude of brachytherapy dose reduction required for stage IIB and III carcinoma cervix patients treated by external radiation and medium dose rate (MDR) brachytherapy at a dose rate of 220±10 cGy/h at point A.Materials and methods: In study-I, at the time of MDR brachytherapy application at a dose rate of 220±10 cGy/h at point A, patients received either 3060 cGy, a 12.5% dose reduction (MDR-12.5), or 2450 cGy, a 30% dose reduction (MDR-30), to point A and they were compared to a group of previously treated LDR patients who received 3500 cGy to point A at a dose rate of 55-65 cGy/h. Study-II was a prospective randomized trial and patients received either 2450 cGy, a 30% dose reduction (MDR-II (30)) or 2800 cGy, a 20% dose reduction (MDR-II (20)), at point A. Patients were evaluated for local control of disease and morbidity. Results: In study-I the 5-year actuarial local control rate in the MDR-30 and MDR-12.5 groups was 71.7±10% and 70.5±10%, respectively, compared to 63.4±10% in the LDR group. However, the actuarial morbidity (all grades) in the MDR-12.5 group was 58.5±14% as against 34.9±9% in the LDR group (P 3 developed complication as against 62.5% of those receiving a rectal BED of (140 3 (χ 2 =46.43; P<0.001). Conclusion: We suggest that at a dose rate of 220±10 cGy/h at point A the brachytherapy dose reduction factor should be around 30%, as suggested by radiobiological data, to keep the morbidity as low as possible without compromising the local control rates. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

Low doses of ionizing radiation and hydrogen peroxide stimulate plant growth

International Nuclear Information System (INIS)

Korystov, Y.; Narimanov, A.

1997-01-01

The present study shows that low-dose oxidative stress induced by ionizing radiation (10-20 cGy) and hydrogen peroxide (1-100 pmol per litre) stimulates germination of seeds and growth of sprouts and roots. The growth of seedlings can be stimulated by treatment of seeds as well as seedlings but in the latter case it needs lower doses. The stimulation effect is observed in a narrow dose interval which is the same for the plant species studied: barley, wheat, pea, maize and melon

Late effects of low-dose ionizing radiation on man

International Nuclear Information System (INIS)

Brilliant, M.D.; Vorob'ev, A.I.; Gogin, E.E.

1987-01-01

One of the most important problems, being stated before the medicine by the accident, which took place in Chernobyl in 1986- the problem of the so-called ionizing radiation low dose effect on a man's organism, is considered because a lot of people were subjected to low dose action. The concept of low doses of radiaion action and specificity of its immediate action in comparison with high dose action is considered. One of the most important poit while studying low dose action is the necessity to develop a system including all irradiated people and dosimetry, and espicially to study frequencies and periods of tumor appearance in different irradiated tissues. The results obtained when examining people who survived the atomic explosion in Japan and on the Marshall islands are analyzed. They testify to the fact that radiation affets more tissues than the clinical picture about the acute radiation sickness tells, and that tumors developing in them many years after radiation action tell about radiosensitivity in some tissues

Chromosomal Aberrations in Normal and AT Cells Exposed to High Dose of Low Dose Rate Irradiation

Science.gov (United States)

Kawata, T.; Shigematsu, N.; Kawaguchi, O.; Liu, C.; Furusawa, Y.; Hirayama, R.; George, K.; Cucinotta, F.

2011-01-01

Ataxia telangiectasia (A-T) is a human autosomally recessive syndrome characterized by cerebellar ataxia, telangiectases, immune dysfunction, and genomic instability, and high rate of cancer incidence. A-T cell lines are abnormally sensitive to agents that induce DNA double strand breaks, including ionizing radiation. The diverse clinical features in individuals affected by A-T and the complex cellular phenotypes are all linked to the functional inactivation of a single gene (AT mutated). It is well known that cells deficient in ATM show increased yields of both simple and complex chromosomal aberrations after high-dose-rate irradiation, but, less is known on how cells respond to low-dose-rate irradiation. It has been shown that AT cells contain a large number of unrejoined breaks after both low-dose-rate irradiation and high-dose-rate irradiation, however sensitivity for chromosomal aberrations at low-dose-rate are less often studied. To study how AT cells respond to low-dose-rate irradiation, we exposed confluent normal and AT fibroblast cells to up to 3 Gy of gamma-irradiation at a dose rate of 0.5 Gy/day and analyzed chromosomal aberrations in G0 using fusion PCC (Premature Chromosomal Condensation) technique. Giemsa staining showed that 1 Gy induces around 0.36 unrejoined fragments per cell in normal cells and around 1.35 fragments in AT cells, whereas 3Gy induces around 0.65 fragments in normal cells and around 3.3 fragments in AT cells. This result indicates that AT cells can rejoin breaks less effectively in G0 phase of the cell cycle? compared to normal cells. We also analyzed chromosomal exchanges in normal and AT cells after exposure to 3 Gy of low-dose-rate rays using a combination of G0 PCC and FISH techniques. Misrejoining was detected in the AT cells only? When cells irradiated with 3 Gy were subcultured and G2 chromosomal aberrations were analyzed using calyculin-A induced PCC technique, the yield of unrejoined breaks decreased in both normal and AT

Low-Dose, Ionizing Radiation and Age-Related Changes in Skeletal Microarchitecture

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Joshua S. Alwood

2012-01-01

Full Text Available Osteoporosis can profoundly affect the aged as a consequence of progressive bone loss; high-dose ionizing radiation can cause similar changes, although less is known about lower doses (≤100 cGy. We hypothesized that exposure to relatively low doses of gamma radiation accelerates structural changes characteristic of skeletal aging. Mice (C57BL/6J-10 wk old, male were irradiated (total body; 0-sham, 1, 10 or 100 cGy 137Cs and tissues harvested on the day of irradiation, 1 or 4 months later. Microcomputed tomography was used to quantify microarchitecture of high turnover, cancellous bone. Irradiation at 100 cGy caused transient microarchitectural changes over one month that were only evident at longer times in controls (4 months. Ex vivo bone cell differentiation from the marrow was unaffected by gamma radiation. In conclusion, acute ionizing gamma irradiation at 100 cGy (but not at 1 cGy or 10 cGy exacerbated microarchitectural changes normally found during progressive, postpubertal aging prior to the onset of age-related osteoporosis.

Quantitative analysis of biological responses to low dose-rate γ-radiation, including dose, irradiation time, and dose-rate

International Nuclear Information System (INIS)

Magae, J.; Furukawa, C.; Kawakami, Y.; Hoshi, Y.; Ogata, H.

2003-01-01

Full text: Because biological responses to radiation are complex processes dependent on irradiation time as well as total dose, it is necessary to include dose, dose-rate and irradiation time simultaneously to predict the risk of low dose-rate irradiation. In this study, we analyzed quantitative relationship among dose, irradiation time and dose-rate, using chromosomal breakage and proliferation inhibition of human cells. For evaluation of chromosome breakage we assessed micronuclei induced by radiation. U2OS cells, a human osteosarcoma cell line, were exposed to gamma-ray in irradiation room bearing 50,000 Ci 60 Co. After the irradiation, they were cultured for 24 h in the presence of cytochalasin B to block cytokinesis, cytoplasm and nucleus were stained with DAPI and propidium iodide, and the number of binuclear cells bearing micronuclei was determined by fluorescent microscopy. For proliferation inhibition, cells were cultured for 48 h after the irradiation and [3H] thymidine was pulsed for 4 h before harvesting. Dose-rate in the irradiation room was measured with photoluminescence dosimeter. While irradiation time less than 24 h did not affect dose-response curves for both biological responses, they were remarkably attenuated as exposure time increased to more than 7 days. These biological responses were dependent on dose-rate rather than dose when cells were irradiated for 30 days. Moreover, percentage of micronucleus-forming cells cultured continuously for more than 60 days at the constant dose-rate, was gradually decreased in spite of the total dose accumulation. These results suggest that biological responses at low dose-rate, are remarkably affected by exposure time, that they are dependent on dose-rate rather than total dose in the case of long-term irradiation, and that cells are getting resistant to radiation after the continuous irradiation for 2 months. It is necessary to include effect of irradiation time and dose-rate sufficiently to evaluate risk

Direct determination of the absorbed dose to water from 125I low dose-rate brachytherapy seeds using the new absorbed dose primary standard developed at ENEA-INMRI

International Nuclear Information System (INIS)

Toni, M.P.; Pimpinella, M.; Pinto, M.; Quini, M.; Cappadozzi, G.; Silvestri, C.; Bottauscio, O.

2012-01-01

Low-intensity radioactive sources emitting low-energy photons are used in the clinic for low dose-rate brachytherapy treatments of tumours. The dosimetry of these sources is based on reference air kerma rate measurements. The absorbed dose rate to water at the reference depth d 0 = 1 cm, D w , 1 cm, is then obtained by a conversion procedure with a large relative standard uncertainty of about 5%. This paper describes a primary standard developed at ENEA-INMRI to directly measure D w , 1 cm due to LDR sources. The standard is based on a large-angle and variable-volume ionization chamber, embedded in a graphite phantom and operating under 'wall-less air chamber' conditions. A set of correction and conversion factors, based on experiments and Monte Carlo simulations, are determined to obtain the value of D w , 1 cm from measurements of increment of ionization current with increasing chamber volume. The relative standard uncertainty on D w , 1 cm is 2.6%, which is appreciably lower than the current uncertainty. Characteristics of the standard, its associated uncertainty budget, and some experimental results are given for 125 I BEBIG I25.S16.C brachytherapy seeds. Finally, results of the experimental determination of the dose-rate constant 1 cm, traceable to the D w , 1 cm and the low-energy air kerma ENEA-INMRI standards, are given. The relative standard uncertainty on 1 cm is 2.9%, appreciably lower than the typical uncertainty (4.8%) of the values available in the literature. (authors)

Campylobacter radicidation of poultry meat by means of low dose ionizing radiation

International Nuclear Information System (INIS)

Tarjan, Veronika

1984-01-01

The effect of ionizing radiation on the number of sprouts of pathogenic Campylobacter was studied in the function of time, storage temperature and radiation dose. Culture-media and minced poultry meat treated with isolated bacteria were irradiated by sup(60)Co up to a dose of 1 kGy. It would be established that low irradiation doses of 3-5 kGy used to eliminate Salmonella infection satisfactorily destroy Campylobacter in chilled meat. (V.N.)

Dose rate and total dose dependence of the 1/f noise performance of a GaAs operational amplifier during irradiation

International Nuclear Information System (INIS)

Hiemstra, D.M.

1995-01-01

A pictorial of a sectioned view of the torus of the International Thermonuclear Experimental Reactor (ITER) is shown. Maintenance and inspection of the reactor are required to be performed remotely. This is due to the high gamma radiation environment in vessel during inspection and maintenance activities. The custom GaAs operational amplifier is to be used to readout sensors on the in-vessel manipulator and inspection equipment. The gamma dose rate during maintenance and inspection is anticipated to be 3 Mrad(GaAs)/hour. Here, dose rate and total dose dependence of the 1/f noise performance of a custom GaAs MESFET operational amplifier during irradiation are presented. Dose rate dependent 1/f noise degradation during irradiation is believed to be due to electron trapping in deep levels, enhanced by backgating and shallow traps excited during irradiation. The reduction of this affect with accumulated total dose is believed to be due a reduction of deep level site concentration associated with substitutional oxygen. Post irradiation 1/f noise degradation is also presented.The generation-recombination noise observed post irradiation can be attributed to the production of shallow traps due to ionizing radiation

Influence of the dose rate in the PVDF degradation processes

Energy Technology Data Exchange (ETDEWEB)

Batista, Adriana S.M.; Pereira, Claubia, E-mail: adriananuclear@yahoo.com.br, E-mail: claubia@nuclear.ufmg.br [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil); Gual, Maritza R., E-mail: maritzargual@gmail.com [Instituto Superior de Tecnologias y Ciencias Aplicadas (InsTEC), Departamento de Ingenieria Nuclear, La Habana (Cuba); Faria, Luiz O., E-mail: farialo@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

2015-07-01

Modification in polymeric structure of plastic material can be brought either by conventional chemical means or by exposure to ionization radiation from gamma radioactive sources or highly accelerated electrons. The prominent drawbacks of chemical cross-linking typically involve the generation by products such as peroxide degradation. Radiation cross-linking technologies include: application in cable and wire, application in rubber tyres, radiation vulcanization of rubber latex, polymer recycling, hydrogels etc. The degradation of PVDF polymer exposed to gamma irradiation in oxygen atmosphere in high dose rate has been studied and compared to obtained under smaller dose rates. The samples were irradiated with a Co-60 source at constant dose rate (12 kGy/h and 2,592 kGy/h), with doses ranging from 100 kGy to 3,000 kGy. Different dose rate determine the prevalence of the processes being evaluated in this work by thermal measurements and infrared spectroscopy. It is shown that the degradation processes involve chain scissions and crosslink formation. The formation of oxidation products was shown at the surface of the irradiated film. The FTIR data revealed absorption bands at 1730 and 1853 cm{sup -1} which were attributed to the stretch of C=O bonds, at 1715 and 1754 cm{sup -1} which were attributed to the C=C stretching and at 3518, 3585 and 3673 cm{sup -1} which were associated with NH stretch of NH{sub 2} and OH. Thermogravimetric studies reveal that the irradiation induced the increasing residues and decrease of the temperature of the decomposition start. (author)

Influence of the dose rate in the PVDF degradation processes

International Nuclear Information System (INIS)

Batista, Adriana S.M.; Pereira, Claubia; Gual, Maritza R.; Faria, Luiz O.

2015-01-01

Modification in polymeric structure of plastic material can be brought either by conventional chemical means or by exposure to ionization radiation from gamma radioactive sources or highly accelerated electrons. The prominent drawbacks of chemical cross-linking typically involve the generation by products such as peroxide degradation. Radiation cross-linking technologies include: application in cable and wire, application in rubber tyres, radiation vulcanization of rubber latex, polymer recycling, hydrogels etc. The degradation of PVDF polymer exposed to gamma irradiation in oxygen atmosphere in high dose rate has been studied and compared to obtained under smaller dose rates. The samples were irradiated with a Co-60 source at constant dose rate (12 kGy/h and 2,592 kGy/h), with doses ranging from 100 kGy to 3,000 kGy. Different dose rate determine the prevalence of the processes being evaluated in this work by thermal measurements and infrared spectroscopy. It is shown that the degradation processes involve chain scissions and crosslink formation. The formation of oxidation products was shown at the surface of the irradiated film. The FTIR data revealed absorption bands at 1730 and 1853 cm -1 which were attributed to the stretch of C=O bonds, at 1715 and 1754 cm -1 which were attributed to the C=C stretching and at 3518, 3585 and 3673 cm -1 which were associated with NH stretch of NH 2 and OH. Thermogravimetric studies reveal that the irradiation induced the increasing residues and decrease of the temperature of the decomposition start. (author)

Scintillation detectors, applications in ambient dose rate measurement of ionizing radiation

International Nuclear Information System (INIS)

Harja, C.

1997-01-01

For the task of developing an ambient dose rate measuring probe, the company MAB decided for a design combining an organic plastic scintillator and a secondary electron multiplier. MAB tested a range of available plastic scintillators suitable for this task, and one proved to be particularly good for the intended purpose. This scintillator is a product of the British company NE Technology Ltd. and was specially developed for dosimetry applications, offering the following advantages: The response within the range from 33 keV to 1.3 MeV (Co-60) is much more constant than with combined-design types; there is no afterglow under conditions of excessive load. (orig./CB) [de

Dose-rate models for human survival after exposure to ionizing radiation

International Nuclear Information System (INIS)

Jones, T.D.; Morris, M.D.; Young, R.W.

1987-01-01

This paper reviews new estimates of the LD 50 in man by Mole and by Rotblat, the biological processes contributing to hematologic death, the collection of animal experiments dealing with hematologic death, and the use of regression analysis to make new estimates of human mortality based on all relevant animal studies. Regression analysis of animal mortality data has shown that mortality is dependent strongly on dose rate, species, body weight, and time interval over which the exposure is delivered. The model has predicted human LD 50 s of 194, 250, 310, and 360 rad to marrow when the exposure time is a minute, an hour, a day, and a week, respectively

Dose-rate models for human survival after exposure to ionizing radiation

International Nuclear Information System (INIS)

Jones, T.D.; Morris, M.D.; Young, R.W.

1986-01-01

This paper reviews new estimates of the L 50 in man by Mole and by Rotblat, the biological processes contributing to hematologic death, the collection of animal experiments dealing with hematologic death, and the use of regression analysis to make new estimates of human mortality based on all relevant animal studies. Regression analysis of animal mortality data has shown that mortality is dependent strongly on dose rate, species, body weight, and time interval over which the exposure is delivered. The model has predicted human LD 50 s of 194, 250, 310, and 360 rad to marrow when the exposure time is a minute, an hour, a day, and a week, respectively

Inconsistencies and open questions regarding low-dose health effects of ionizing radiation

International Nuclear Information System (INIS)

Nussbaum, R.H.; Koehnlein, W.

1994-01-01

The state of knowledge of health effects from low-dose exposures to ionizing radiation has recently been reviewed in extensive reports by three prestigious national and international commissions of scientific and medical experts with partially overlapping membership, known by their acronyms UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation), BEIR V (Biological Effects of Ionizing Radiation), and ICRP (International Commission on Radiological Protection). Publication of these reports was followed by a number of summaries in scientific journals, authored by recognized radiation experts, that purport to present a scientific consensus of low-dose effects in a more accessible format for health professionals. A critical comparison between various presentations of accepted views, however, reveals inconsistencies regarding open-quotes establishedclose quotes facts and unsettled questions

Calibration of ionization chamber and GM counter survey meters, (1)

International Nuclear Information System (INIS)

Bingo, Kazuyoshi; Kajimoto, Yoichi; Suga, Shin-ichi

1978-01-01

Three types of ionization chamber survey meters and a type of GM counter survey meter were calibrated for measuring the β-ray absorbed dose rate in a working area. To estimate the β-ray absorbed dose rate, a survey meter was used without and with a filter. A reading of survey meter's indicator measured with the filter was subtracted from a reading measured without the filter, and then the absorbed dose rate was obtained by multiplying this remainder by a conversion coefficient. The conversion coefficients were roughly constant with distance more than 8 cm (ionization chamber survey meters) and with distance more than 5 cm (GM counter survey meter). The conversion coefficient was dependent on β-ray energies. In order to measure the absorbed dose rate of tissue whose epidermal thickness is 40 mg/cm 2 , the constant value, 4 (mrad/h)/(mR/h), was chosen independently of β-ray energies as the conversion coefficient of three types of ionization chamber survey meters. The conversion coefficient of the GM counter survey meter was more energy dependent than that of every type of ionization chamber survey meter. (author)

Three-dimensional spatial imaging in multiphoton ionization rate measurements

International Nuclear Information System (INIS)

Bredy, Richard; Camp, Howard A.; Nguyen, Hai; Awata, Takaaki; Shan Bing; Chang Zhenghu; DePaola, B.D.

2004-01-01

An experiment is described in which an apparatus is used to demonstrate the feasibility of measuring multiphoton photoionization rates in the interaction of short pulsed lasers with atoms or molecules. With this methodology, the ionization rate is measured as a function of the spatial position in the beam-waist region of the laser through the direct three-dimensional spatial imaging of the ionization events. Thus, if the spatial dependence of the laser beam intensity were known, a series of experiments could yield the intensity dependence of multiphoton ionization without the assumptions or errors that are generally inherent in the integration over one or more dimensions in the laser focal volume

Radiobiological aspects of continuous low dose-rate irradiation and fractionated high dose-rate irradiation

International Nuclear Information System (INIS)

Turesson, I.

1990-01-01

The biological effects of continuous low dose-rate irradiation and fractionated high dose-rate irradiation in interstitial and intracavitary radiotherapy and total body irradiation are discussed in terms of dose-rate fractionation sensitivity for various tissues. A scaling between dose-rate and fraction size was established for acute and late normal-tissue effects which can serve as a guideline for local treatment in the range of dose rates between 0.02 and 0.005 Gy/min and fraction sizes between 8.5 and 2.5 Gy. This is valid provided cell-cycle progression and proliferation can be ignored. Assuming that the acute and late tissue responses are characterized by α/β values of about 10 and 3 Gy and a mono-exponential repair half-time of about 3 h, the same total doses given with either of the two methods are approximately equivalent. The equivalence for acute and late non-hemopoietic normal tissue damage is 0.02 Gy/min and 8.5 Gy per fraction; 0.01 Gy/min and 5.5 Gy per fraction; and 0.005 Gy/min and 2.5Gy per fraction. A very low dose rate, below 0.005 Gy/min, is thus necessary to simulate high dose-rate radiotherapy with fraction sizes of about 2Gy. The scaling factor is, however, dependent on the repair half-time of the tissue. A review of published data on dose-rate effects for normal tissue response showed a significantly stronger dose-rate dependence for late than for acute effects below 0.02 Gy/min. There was no significant difference in dose-rate dependence between various acute non-hemopoietic effects or between various late effects. The consistent dose-rate dependence, which justifies the use of a general scaling factor between fraction size and dose rate, contrasts with the wide range of values for repair half-time calculated for various normal-tissue effects. This indicates that the model currently used for repair kinetics is not satisfactory. There are also few experimental data in the clinical dose-rate range, below 0.02 Gy/min. It is therefore

Dose rate dependence for different dosimeters and detectors: TLD, OSL, EBT films, and diamond detectors

International Nuclear Information System (INIS)

Karsch, L.; Beyreuther, E.; Burris-Mog, T.; Kraft, S.; Richter, C.; Zeil, K.; Pawelke, J.

2012-01-01

Purpose: The use of laser accelerators in radiation therapy can perhaps increase the low number of proton and ion therapy facilities in some years due to the low investment costs and small size. The laser-based acceleration technology leads to a very high peak dose rate of about 10 11 Gy/s. A first dosimetric task is the evaluation of dose rate dependence of clinical dosimeters and other detectors. Methods: The measurements were done at ELBE, a superconductive linear electron accelerator which generates electron pulses with 5 ps length at 20 MeV. The different dose rates are reached by adjusting the number of electrons in one beam pulse. Three clinical dosimeters (TLD, OSL, and EBT radiochromic films) were irradiated with four different dose rates and nearly the same dose. A faraday cup, an integrating current transformer, and an ionization chamber were used to control the particle flux on the dosimeters. Furthermore two diamond detectors were tested. Results: The dosimeters are dose rate independent up to 410 9 Gy/s within 2% (OSL and TLD) and up to 1510 9 Gy/s within 5% (EBT films). The diamond detectors show strong dose rate dependence. Conclusions: TLD, OSL dosimeters, and EBT films are suitable for pulsed beams with a very high pulse dose rate like laser accelerated particle beams.

Assessment of dose level of ionizing radiation in army scrap

International Nuclear Information System (INIS)

Abdel Hamid, S. M.

2010-12-01

Radiation protection is the science of protecting people and the environment from the harmful effects of ionizing radiation, which includes both particle radiation and high energy radiation. Ionizing radiation is widely used in industry and medicine. Any human activity of nuclear technologies should be linked to the foundation of scientific methodology and baseline radiation culture to avoid risk of radiation and should be working with radioactive materials and expertise to understand, control practices in order to avoid risks that could cause harm to human and environment. The study was conducted in warehouses and building of Sudan air force Khartoum basic air force during September 2010. The goal of this study to estimate the radiation dose and measurement of radioactive contamination of aircraft scrap equipment and increase the culture of radiological safety as well as the concept of radiation protection. The results showed that there is no pollution observed in the contents of the aircraft and the spire part stores outside, levels of radiation dose for the all contents of the aircraft and spire part within the excitable level, except temperature sensors estimated radiation dose about 43 μSv/h outside of the shielding and 12 μSv/h inside the shielding that exceeded the internationally recommended dose level. One of the most important of the identification of eighteen (18) radiation sources used in temperature and fuel level sensors. These are separated from the scrap, collected and stored in safe place. (Author)

Low-dose ionizing radiation – is it harmful to health?

Energy Technology Data Exchange (ETDEWEB)

Sullivan, A. H. [CERN Radiation Protection Group (European Organization for Nuclear Research (CERN))

1987-09-15

A conference on the health effects of low-dose ionizing radiation organized in London earlier this year by the British Nuclear Energy Society brought together epidemiologists who have been investigating the mortality of workers from the nuclear industry in an attempt to put low-level radiation risk estimates on a scientific basis.

Study of total ionization dose effects in electronic devices

International Nuclear Information System (INIS)

Nidhin, T.S.; Bhattacharyya, Anindya; Gour, Aditya; Behera, R.P.; Jayanthi, T.

2018-01-01

Radiation effects in electronic devices are a major challenge in the dependable application developments of nuclear power plant instrumentation and control systems. The main radiation effects are total ionization dose (TID) effects, displacement damage dose (DDD) effects and single event effects (SEE). In this study, we are concentrating on TID effects in electronic devices. The focus of the study is mainly on SRAM based field programmable gate arrays (FPGA) along with that the devices of our interest are voltage regulators, flash memory and optocoupler. The experiments are conducted by exposing the devices to gamma radiation in power off condition and the degradation in the performances are analysed

Epidemiology and effects on health of low ionizing radiation doses

International Nuclear Information System (INIS)

Rodriguez Artalejo, F.; Andres Manzano, B. de; Rel Calero, J. del

1997-01-01

This article describes the concept and aims of epidemiology, its methods and contribution to the knowledge of the effects of low ionizing radiation doses on health. The advantages of epidemiological studies for knowing the consequences of living near nuclear facilities and the effects of occupational exposure to radiations are also described. (Author) 43 refs

Low dose ionizing radiation exposure and cardiovascular disease mortality: cohort study based on Canadian national dose registry of radiation workers

International Nuclear Information System (INIS)

Zielinski, J. M.; Band, P. R.; Ashmore, P. J.; Jiang, H.; Shilnikova, N. S.; Tait, V. K.; Krewski, D.

2009-01-01

The purpose of our study was to assess the risk of cardiovascular disease (CVD) mortality in a Canadian cohort of 337 397 individuals (169 256 men and 168 141 women) occupationally exposed to ionizing radiation and included in the National Dose Registry (NDR) of Canada. Material and Methods: Exposure to high doses of ionizing radiation, such as those received during radiotherapy, leads to increased risk of cardiovascular diseases. The emerging evidence of excess risk of CVDs after exposure to doses well below those previously considered as safe warrants epidemiological studies of populations exposed to low levels of ionizing radiation. In the present study, the cohort consisted of employees at nuclear power stations (nuclear workers) as well as medical, dental and industrial workers. The mean whole body radiation dose was 8.6 mSv for men and 1.2 mSv for women. Results: During the study period (1951 - 1995), as many as 3 533 deaths from cardiovascular diseases have been identified (3 018 among men and 515 among women). In the cohort, CVD mortality was significantly lower than in the general population of Canada. The cohort showed a significant dose response both among men and women. Risk estimates of CVD mortality in the NDR cohort, when expressed as excess relative risk per unit dose, were higher than those in most other occupational cohorts and higher than in the studies of Japanese atomic bomb survivors. Conclusions: The study has demonstrated a strong positive association between radiation dose and the risk of CVD mortality. Caution needs to be exercised when interpreting these results, due to the potential bias introduced by dosimetry uncertainties, the possible record linkage errors, and especially by the lack of adjustment for non-radiation risk factors. (authors)

Dose-rate models for human survival after exposure to ionizing radiation

Energy Technology Data Exchange (ETDEWEB)

Jones, T.D.; Morris, M.D.; Young, R.W.

1986-01-01

This paper reviews new estimates of the L/sub 50/ in man by Mole and by Rotblat, the biological processes contributing to hematologic death, the collection of animal experiments dealing with hematologic death, and the use of regression analysis to make new estimates of human mortality based on all relevant animal studies. Regression analysis of animal mortality data has shown that mortality is dependent strongly on dose rate, species, body weight, and time interval over which the exposure is delivered. The model has predicted human LD/sub 50/s of 194, 250, 310, and 360 rad to marrow when the exposure time is a minute, an hour, a day, and a week, respectively.

Method for measuring and evaluation dose equivalent rate from fast neutrons in mixed gamma-neutron fields around particles accelerators

International Nuclear Information System (INIS)

Cruceru, I.; Sandu, M.; Cruceru, M.

1994-01-01

A method for measuring and evaluation of doses and dose equivalent rate in mixed gamma- neutron fields is discussed in this paper. The method is basedon a double detector system consist of an ionization chamber with components made from a plastic scintillator, coupled to on photomultiplier. Generally the radiation fields around accelerators are complex, often consisting of many different ionizing radiations extending over a broad range of energies. This method solve two major difficulties: determination of response functions of radiation detectors; interpretation of measurement and determination of accuracy. The discrimination gamma-fast neutrons is assured directly without a pulse shape discrimination circuit. The method is applied to mixed fields in which particle energies are situated in the energy range under 20 MeV and an izotropic emision (Φ=10 4 -10 11 n.s -1 ). The dose equivalent rates explored is 0.01mSV--0.1SV

SU-F-T-16: Experimental Determination of Ionization Chamber Correction Factors for In-Phantom Measurements of Reference Air Kerma Rate and Absorbed Water Dose Rate of Brachytherapy 192Ir Source

International Nuclear Information System (INIS)

Chan, M; Lee, V; Wong, M; Leung, R; Law, G; Lee, K; Cheung, S; Tung, S

2016-01-01

Purpose: Following the method of in-phantom measurements of reference air kerma rate (Ka) at 100cm and absorbed water dose rate (Dw1) at 1cm of high-dose-rate 192Ir brachytherapy source using 60Co absorbed-dose-to-water calibrated (ND,w,60Co) ionization chamber (IC), we experimentally determined the in-phantom correction factors (kglob) of the PTW30013 (PTW, Freiburg, Germany) IC by comparing the Monte Carlo (MC)-calculated kglob of the other PTW30016 IC. Methods: The Dw1 formalism of in-phantom measurement is: M*ND,w,60Co*(kglob)Dw1, where M is the collected charges, and (kglob)Dw1 the in-phantom Dw1 correction factor. Similarly, Ka is determined by M*ND,w,60Co*(kglob)ka, where (kglob)ka the in-phantom Ka correction factor. Two thimble ICs PTW30013 and another PTW30016 having a ND,w,60Co from the German primary standard laboratory (PTB) were simultaneously exposed to the microselectron 192Ir v2 source at 8cm in a PMMA phantom. A reference well chamber (PTW33004) with a PTB transfer Ka calibration Nka was used for comparing the in-phantom measurements to derive the experimental (kglob)ka factors. We determined the experimental (kglob)Dw1 of the PTW30013 by comparing the PTW30016 measurements with MC-calculated (kglob)Dw1. Results: Ka results of the PTW30016 based on ND,w,60Co and MC-calculated (kglob)ka differ from the well chamber results based on Nka by 1.6% and from the manufacturer by 1.0%. Experimental (kglob)ka factors for the PTW30016 and two other PTW30013 are 0.00683, 0.00681 and 0.00679, and vary <0.5% with 1mm source positioning uncertainty. Experimental (kglob)Dw1 of the PTW30013 ICs are 75.3 and 75.6, and differ by 1.6% from the conversion by dose rate constant from the AAPM report 229. Conclusion: The 1.7% difference between MC and experimental (kglob)ka for the PTW30016 IC is within the PTB 2.5% expanded uncertainty in Ka calibration standard. Using a single IC with ND,w,60Co to calibrate the brachytherapy source and dose output in external

Modeling dose-rate on/over the surface of cylindrical radio-models using Monte Carlo methods

International Nuclear Information System (INIS)

Xiao Xuefu; Ma Guoxue; Wen Fuping; Wang Zhongqi; Wang Chaohui; Zhang Jiyun; Huang Qingbo; Zhang Jiaqiu; Wang Xinxing; Wang Jun

2004-01-01

Objective: To determine the dose-rates on/over the surface of 10 cylindrical radio-models, which belong to the Metrology Station of Radio-Geological Survey of CNNC. Methods: The dose-rates on/over the surface of 10 cylindrical radio-models were modeled using the famous Monte Carlo code-MCNP. The dose-rates on/over the surface of 10 cylindrical radio-models were measured by a high gas pressurized ionization chamber dose-rate meter, respectively. The values of dose-rate modeled using MCNP code were compared with those obtained by authors in the present experimental measurement, and with those obtained by other workers previously. Some factors causing the discrepancy between the data obtained by authors using MCNP code and the data obtained using other methods are discussed in this paper. Results: The data of dose-rates on/over the surface of 10 cylindrical radio-models, obtained using MCNP code, were in good agreement with those obtained by other workers using the theoretical method. They were within the discrepancy of ±5% in general, and the maximum discrepancy was less than 10%. Conclusions: As if each factor needed for the Monte Carlo code is correct, the dose-rates on/over the surface of cylindrical radio-models modeled using the Monte Carlo code are correct with an uncertainty of 3%

Biological effects of low-dose ionizing radiation exposure; Biologische Wirkungen niedriger Dosen ionisierender Strahlung

Energy Technology Data Exchange (ETDEWEB)

Reinoehl-Kompa, Sabine; Baldauf, Daniela; Heller, Horst (comps.)

2009-07-01

The report on the meeting of the Strahlenschutzkommission 2007 concerning biological effects of low-dose ionizing radiation exposure includes the following contributions: Adaptive response. The importance of DNA damage mechanisms for the biological efficiency of low-energy photons. Radiation effects in mammography: the relative biological radiation effects of low-energy photons. Radiation-induced cataracts. Carcinomas following prenatal radiation exposure. Intercellular apoptosis induction and low-dose irradiation: possible consequences for the oncogenesis control. Mechanistic models for the carcinogenesis with radiation-induced cell inactivation: application to all solid tumors in the Japanese atomic bomb survivors. Microarrays at low radiation doses. Mouse models for the analysis of biological effects of low-dose ionizing radiation. The bystander effect: observations, mechanisms and implications. Lung carcinoma risk of Majak workers - modeling of carcinogenesis and the bystander effect. Microbeam studies in radiation biology - an overview. Carcinogenesis models with radiation-induced genomic instability. Application to two epidemiological cohorts.

Evaluation of experimental animal biological state at exposure to low-dose ionizing radiation

International Nuclear Information System (INIS)

Rozanov, V.A.; Rejtarova, T.Je.; Chernyikov, G.B.; Timoshevs'ka, Je.V.; Kozozojeva, O.O.

1997-01-01

New approaches to quantitative evaluation of ionizing radiation absorbed dose within the low-dose range (up to 400 mGy) according to the degree of the organism biological response was developed. The purpose of the stage of the work published in Communication 1 is to evaluate the shifts in the animal behaviour and cellular composition of the blood at irradiation by the dose of 100,200 and 400 mGy. Distinct dose dependence of behaviour reactions and hematological indices within the dose range of 100-400 mGy was not noted

Dose and dose rate monitor

International Nuclear Information System (INIS)

Novakova, O.; Ryba, J.; Slezak, V.; Svobodova, B.; Viererbl, L.

1984-10-01

The methods are discussea of measuring dose rate or dose using a scintillation counte. A plastic scintillator based on polystyrene with PBD and POPOP activators and coated with ZnS(Ag) was chosen for the projected monitor. The scintillators were cylindrical and spherical in shape and of different sizes; black polypropylene tubes were chosen as the best case for the probs. For the counter with different plastic scintillators, the statistical error 2σ for natural background was determined. For determining the suitable thickness of the ZnS(Ag) layer the energy dependence of the counter was measured. Radioisotopes 137 Cs, 241 Am and 109 Cd were chosen as radiation sources. The best suited ZnS(Ag) thickness was found to be 0.5 μm. Experiments were carried out to determine the directional dependence of the detector response and the signal to noise ratio. The temperature dependence of the detector response and its compensation were studied, as were the time stability and fatigue manifestations of the photomultiplier. The design of a laboratory prototype of a dose rate and dose monitor is described. Block diagrams are given of the various functional parts of the instrument. The designed instrument is easiiy portable, battery powered, measures dose rates from natural background in the range of five orders, i.e., 10 -2 to 10 3 nGy/s, and allows to determine a dose of up to 10 mGy. Accouracy of measurement in the energy range of 50 keV to 1 MeV is better than +-20%. (E.S.)

Biochemical and immunological responses to low doses of ionizing radiation

International Nuclear Information System (INIS)

Shabon, M.H.; Sayed, Z.S.; Mahdy, E.M.; El-Gawish, M.A.; Shosha, W.

2006-01-01

Malondialdehyde, lactate dehydrogenase, iron concentration, IL-6 and IL-1b concentration, hemoglobin content, red cells, white cells and platelet counts were determined in seventy-two male albino rats divided into two main groups. The first one was subdivided into 7 subgroups; control and 6 irradiated subgroups with 0.1, 0.2, 0.3, 0.5, 0.7 and 1 Gy single dose of gamma radiation. The other was subdivided into 4 subgroups irradiated with fractionated doses of gamma radiation; three groups were irradiated with 0.3, 0.7 and 1 Gy (0.1 Gy/day) and the last subgroup with 1 Gy (0.2 Gy/day). All animals were sacrificed after three days of the last irradiation dose. The results revealed that all biochemical parameters were increased in rats exposed to fractionated doses more than the single doses. Hematological parameters were decreased in rats exposed to single doses more than the fractionated ones. In conclusion, the data of this study highlights the stimulatory effect of low ionizing radiation doses (= 1 Gy), whether single or fractionated, on some biochemical and immunological parameters

Mutation frequencies in male mice and the estimation of genetic hazards of radiation in men: (specific-locus mutations/dose-rate effect/doubling dose/risk estimation)

International Nuclear Information System (INIS)

Russell, W.L.; Kelly, E.M.

1982-01-01

Estimation of the genetic hazards of ionizing radiation in men is based largely on the frequency of transmitted specific-locus mutations induced in mouse spermatogonial stem cells at low radiation dose rates. The publication of new data on this subject has permitted a fresh review of all the information available. The data continue to show no discrepancy from the interpretation that, although mutation frequency decreases markedly as dose rate is decreased from 90 to 0.8 R/min (1 R = 2.6 X 10 -4 coulombs/kg) there seems to be no further change below 0.8 R/min over the range from that dose rate to 0.0007 R/min. Simple mathematical models are used to compute: (a) a maximum likelihood estimate of the induced mutation frequency at the low dose rates, and (b) a maximum likelihood estimate of the ratio of this to the mutation frequency at high dose rates in the range of 72 to 90 R/min. In the application of these results to the estimation of genetic hazards of radiation in man, the former value can be used to calculate a doubling dose - i.e., the dose of radiation that induces a mutation frequency equal to the spontaneous frequency. The doubling dose based on the low-dose-rate data compiled here is 110 R. The ratio of the mutation frequency at low dose rate to that at high dose rate is useful when it becomes necessary to extrapolate from experimental determinations, or from human data, at high dose rates to the expected risk at low dose rates. The ratio derived from the present analysis is 0.33

Physiological benefits from low levels of ionizing radiation

International Nuclear Information System (INIS)

Luckey, T.D.

1982-01-01

Extensive literature indicates that minute doses of ionizing radiation benefit animal growth and development, fecundity, health and longevity. Specific improvements appear in neurologic function, growth rate and survival of young, wound healing, immune competence, and resistance to infection, radiation morbidity, and tumor induction and growth. Decreased mortality from these debilitating factors results in increased average life span following exposure to minute doses of ionizing radiation. The above phenomena suggest the possibility that ionizing radiation may be essential for life. Limited data with protozoa suggest that reproduction rates decrease when they are maintained in subambient radiation environments. This may be interpreted to be a radiation deficiency. Evidence must now be obtained to determine whether or not ionizing radiation is essential for growth, development, nutrient utilization, fecundity, health and longevity of higher animals. Whether or not ionizing radiation is found to be essential for these physiologic functions, the evidence reviewed indicates that the optimal amount of this ubiquitous agent is imperceptibly above ambient levels. (author)

Transient Genome-Wide Transcriptional Response to Low-Dose Ionizing Radiation In Vivo in Humans

International Nuclear Information System (INIS)

Berglund, Susanne R.; Rocke, David M.; Dai Jian; Schwietert, Chad W.; Santana, Alison; Stern, Robin L.; Lehmann, Joerg; Hartmann Siantar, Christine L.; Goldberg, Zelanna

2008-01-01

Purpose: The in vivo effects of low-dose low linear energy transfer ionizing radiation on healthy human skin are largely unknown. Using a patient-based tissue acquisition protocol, we have performed a series of genomic analyses on the temporal dynamics over a 24-hour period to determine the radiation response after a single exposure of 10 cGy. Methods and Materials: RNA from each patient tissue sample was hybridized to an Affymetrix Human Genome U133 Plus 2.0 array. Data analysis was performed on selected gene groups and pathways. Results: Nineteen gene groups and seven gene pathways that had been shown to be radiation responsive were analyzed. Of these, nine gene groups showed significant transient transcriptional changes in the human tissue samples, which returned to baseline by 24 hours postexposure. Conclusions: Low doses of ionizing radiation on full-thickness human skin produce a definable temporal response out to 24 hours postexposure. Genes involved in DNA and tissue remodeling, cell cycle transition, and inflammation show statistically significant changes in expression, despite variability between patients. These data serve as a reference for the temporal dynamics of ionizing radiation response following low-dose exposure in healthy full-thickness human skin

Sensors of absorbed dose of ionizing radiation based on mosfet

Directory of Open Access Journals (Sweden)

Perevertaylo V. L.

2010-10-01

Full Text Available The requirements to technology and design of p-channel and n-channel MOS transistors with a thick oxide layer designed for use in the capacity of integral dosimeters of absorbed dose of ionizing radiation are defined. The technology of radiation-sensitive MOS transistors with a thick oxide in the p-channel and n-channel version is created.

High dose-per-pulse electron beam dosimetry - A model to correct for the ion recombination in the Advanced Markus ionization chamber.

Science.gov (United States)

Petersson, Kristoffer; Jaccard, Maud; Germond, Jean-François; Buchillier, Thierry; Bochud, François; Bourhis, Jean; Vozenin, Marie-Catherine; Bailat, Claude

2017-03-01

The purpose of this work was to establish an empirical model of the ion recombination in the Advanced Markus ionization chamber for measurements in high dose rate/dose-per-pulse electron beams. In addition, we compared the observed ion recombination to calculations using the standard Boag two-voltage-analysis method, the more general theoretical Boag models, and the semiempirical general equation presented by Burns and McEwen. Two independent methods were used to investigate the ion recombination: (a) Varying the grid tension of the linear accelerator (linac) gun (controls the linac output) and measuring the relative effect the grid tension has on the chamber response at different source-to-surface distances (SSD). (b) Performing simultaneous dose measurements and comparing the dose-response, in beams with varying dose rate/dose-per-pulse, with the chamber together with dose rate/dose-per-pulse independent Gafchromic™ EBT3 film. Three individual Advanced Markus chambers were used for the measurements with both methods. All measurements were performed in electron beams with varying mean dose rate, dose rate within pulse, and dose-per-pulse (10 -2  ≤ mean dose rate ≤ 10 3 Gy/s, 10 2  ≤ mean dose rate within pulse ≤ 10 7  Gy/s, 10 -4  ≤ dose-per-pulse ≤ 10 1  Gy), which was achieved by independently varying the linac gun grid tension, and the SSD. The results demonstrate how the ion collection efficiency of the chamber decreased as the dose-per-pulse increased, and that the ion recombination was dependent on the dose-per-pulse rather than the dose rate, a behavior predicted by Boag theory. The general theoretical Boag models agreed well with the data over the entire investigated dose-per-pulse range, but only for a low polarizing chamber voltage (50 V). However, the two-voltage-analysis method and the Burns & McEwen equation only agreed with the data at low dose-per-pulse values (≤ 10 -2 and ≤ 10 -1  Gy, respectively). An empirical

Single Low-Dose Ionizing Radiation Induces Genotoxicity in Adult Zebrafish and its Non-Irradiated Progeny.

Science.gov (United States)

Lemos, J; Neuparth, T; Trigo, M; Costa, P; Vieira, D; Cunha, L; Ponte, F; Costa, P S; Metello, L F; Carvalho, A P

2017-02-01

This study investigated to what extent a single exposure to low doses of ionizing radiation can induce genotoxic damage in irradiated adult zebrafish (Danio rerio) and its non-irradiated F1 progeny. Four groups of adult zebrafish were irradiated with a single dose of X-rays at 0 (control), 100, 500 and 1000 mGy, respectively, and couples of each group were allowed to reproduce following irradiation. Blood of parental fish and whole-body offspring were analysed by the comet assay for detection of DNA damage. The level of DNA damage in irradiated parental fish increased in a radiation dose-dependent manner at day 1 post-irradiation, but returned to the control level thereafter. The level of DNA damage in the progeny was directly correlated with the parental irradiation dose. Results highlight the genotoxic risk of a single exposure to low-dose ionizing radiation in irradiated individuals and also in its non-irradiated progeny.

THE IMPLICATIONS OF A HIGH COSMIC-RAY IONIZATION RATE IN DIFFUSE INTERSTELLAR CLOUDS

International Nuclear Information System (INIS)

Indriolo, Nick; Fields, Brian D.; McCall, Benjamin J.

2009-01-01

Diffuse interstellar clouds show large abundances of H + 3 which can only be maintained by a high ionization rate of H 2 . Cosmic rays are the dominant ionization mechanism in this environment, so the large ionization rate implies a high cosmic-ray flux, and a large amount of energy residing in cosmic rays. In this paper, we find that the standard propagated cosmic-ray spectrum predicts an ionization rate much lower than that inferred from H + 3 . Low-energy (∼10 MeV) cosmic rays are the most efficient at ionizing hydrogen, but cannot be directly detected; consequently, an otherwise unobservable enhancement of the low-energy cosmic-ray flux offers a plausible explanation for the H + 3 results. Beyond ionization, cosmic rays also interact with the interstellar medium by spalling atomic nuclei and exciting atomic nuclear states. These processes produce the light elements Li, Be, and B, as well as gamma-ray lines. To test the consequences of an enhanced low-energy cosmic-ray flux, we adopt two physically motivated cosmic-ray spectra which by construction reproduce the ionization rate inferred in diffuse clouds, and investigate the implications of these spectra on dense cloud ionization rates, light-element abundances, gamma-ray fluxes, and energetics. One spectrum proposed here provides an explanation for the high ionization rate seen in diffuse clouds while still appearing to be broadly consistent with other observables, but the shape of this spectrum suggests that supernovae remnants may not be the predominant accelerators of low-energy cosmic rays.

The effects of low doses of ionizing radiation - A question of ethics

International Nuclear Information System (INIS)

Tschaeche, A.N.

1996-01-01

Three ethical questions are asked and answered about the current state of affairs concerning how those in power manipulate public understanding of the effects of low doses of ionizing radiation. The questions are as follows: (1) Is it ethical to frighten people when you do not know that there is anything to be frightened of? (2) Is it ethical to be so conservative that resources are spent to solve a problem that may not exist? (3) Is it ethical not to tell the whole truth about the effects of low levels of ionizing radiation?

Degradation and annealing studies on gamma rays irradiated COTS PPD CISs at different dose rates

International Nuclear Information System (INIS)

Wang, Zujun; Ma, Yingwu; Liu, Jing; Xue, Yuan; He, Baoping; Yao, Zhibin; Huang, Shaoyan; Liu, Minbo; Sheng, Jiangkun

2016-01-01

The degradation and annealing studies on Colbalt-60 gamma-rays irradiated commercial-off-the-shelf (COTS) pinned photodiode (PPD) CMOS image sensors (CISs) at the various dose rates are presented. The irradiation experiments of COTS PPD CISs are carried out at 0.3, 3.0 and 30.0 rad(Si)/s. The COTS PPD CISs are manufactured using a standard 0.18-μm CMOS technology with four-transistor pixel PPD architecture. The behavior of the tested CISs shows a remarkable degradation after irradiation and differs in the dose rates. The dark current, dark signal non-uniformity (DSNU), random noise, saturation output, signal to noise ratio (SNR), and dynamic range (DR) versus the total ionizing dose (TID) at the various dose rates are investigated. The tendency of dark current, DSNU, and random noise increase and saturation output, SNR, and DR to decrease at 3.0 rad(Si)/s are far greater than those at 0.3 and 30.0 rad(Si)/s. The damage mechanisms caused by TID irradiation at the various dose rates are also analyzed. The annealing tests are carried out at room temperature with unbiased conditions after irradiation.

Degradation and annealing studies on gamma rays irradiated COTS PPD CISs at different dose rates

Science.gov (United States)

Wang, Zujun; Ma, Yingwu; Liu, Jing; Xue, Yuan; He, Baoping; Yao, Zhibin; Huang, Shaoyan; Liu, Minbo; Sheng, Jiangkun

2016-06-01

The degradation and annealing studies on Colbalt-60 gamma-rays irradiated commercial-off-the-shelf (COTS) pinned photodiode (PPD) CMOS image sensors (CISs) at the various dose rates are presented. The irradiation experiments of COTS PPD CISs are carried out at 0.3, 3.0 and 30.0 rad(Si)/s. The COTS PPD CISs are manufactured using a standard 0.18-μm CMOS technology with four-transistor pixel PPD architecture. The behavior of the tested CISs shows a remarkable degradation after irradiation and differs in the dose rates. The dark current, dark signal non-uniformity (DSNU), random noise, saturation output, signal to noise ratio (SNR), and dynamic range (DR) versus the total ionizing dose (TID) at the various dose rates are investigated. The tendency of dark current, DSNU, and random noise increase and saturation output, SNR, and DR to decrease at 3.0 rad(Si)/s are far greater than those at 0.3 and 30.0 rad(Si)/s. The damage mechanisms caused by TID irradiation at the various dose rates are also analyzed. The annealing tests are carried out at room temperature with unbiased conditions after irradiation.

Health consequences of ionizing radiation exposure

International Nuclear Information System (INIS)

Dalci, D.; Dorter, G.; Guclu, I.

2004-01-01

The increasing use of ionizing radiations all over the world induces an ever increasing interest of the professionals as well as of the whole society in health protection and the risk due to these practices. Shortly after its discovery, it was recognized that ionizing radiation can have adverse health effects and knowledge of its detrimental effects has accumulated. The fact that ionizing radiation produces biological damage has been known for many years. The biological effects of ionizing radiation for radiation protection considerations are grouped into two categories: The deterministic and the stochastic ones. Deterministic radiation effects can be clinically diagnosed in the exposed individual and occur when above a certain 'threshold' an appropriately high dose is absorbed in the tissues and organs to cause the death of a large number of cells and consequently to impair tissue or organ functions early after exposure. A clinically observable biological effect (Acute Radiation Syndromes, ARS) that occurs days to months after an acute radiation dose. ARS is a complex of acute injury manifestations that occur after a sufficiently large portion of a person's body is exposed to a high dose of ionizing radiation. Such irradiation initially injures all organs to some extent, but the timing and extent of the injury manifestations depend upon the type, rate, and dose of radiation received. Stochastic radiation effects are the chronic effects of radiation result from relatively low exposure levels delivered over long periods of time. These are sort of effects that might result from occupational exposure, or to the background exposure levels (includes radioactive pollution). Such late effects might be the development of malignant (cancerous) disease and of the hereditary consequences. These effects may be observed many years after the radiation exposure. There is a latent period between the initial radiation exposure and the development of the biological effect. In this

Low doses of ionizing radiation: Biological effects and regulatory control. Invited papers and discussions. Proceedings of an international conference

International Nuclear Information System (INIS)

1998-01-01

The levels and biological effects resulting from exposure to ionizing radiation are continuously reviewed by the United Nations Committee on the Effects of Atomic Radiation (UNSCEAR). Since its creation in 1928, the International Commission on Radiological Protection (ICRP) has issued recommendations on protection against ionizing radiation. The UNSCEAR estimates and the ICRP recommendations have served as the basis for national and international safety standards on radiation safety, including those developed by the International Atomic Energy Agency (IAEA) and the World Health Organization (WHO). Concerning health effects of low doses of ionizing radiation, the international standards are based on the plausible assumption that, above the unavoidable background radiation dose, the probability of effects increases linearly with dose, i.e. on a 'linear, no threshold' (LNT) assumption. However, in recent years the biological estimates of health effects of low doses of ionizing radiation and the regulatory approach to the control of low level radiation exposure have been much debated. To foster information exchange on the relevant issues, an International Conference on Low Doses of Ionizing Radiation: Biological Effects and Regulatory Control, jointly sponsored by the IAEA and WHO in co-operation with UNSCEAR, was held from 17-21 November 1997 at Seville, Spain. These Proceedings contain the invited special reports, keynote papers, summaries of discussions, session summaries and addresses presented at the opening and closing of the Conference

High and Low Doses of Ionizing Radiation Induce Different Secretome Profiles in a Human Skin Model

Energy Technology Data Exchange (ETDEWEB)

Zhang, Qibin; Matzke, Melissa M.; Schepmoes, Athena A.; Moore, Ronald J.; Webb-Robertson, Bobbie-Jo M.; Hu, Zeping; Monroe, Matthew E.; Qian, Weijun; Smith, Richard D.; Morgan, William F.

2014-03-18

It is postulated that secreted soluble factors are important contributors of bystander effect and adaptive responses observed in low dose ionizing radiation. Using multidimensional liquid chromatography-mass spectrometry based proteomics, we quantified the changes of skin tissue secretome – the proteins secreted from a full thickness, reconstituted 3-dimensional skin tissue model 48 hr after exposure to 3, 10 and 200 cGy of X-rays. Overall, 135 proteins showed statistical significant difference between the sham (0 cGy) and any of the irradiated groups (3, 10 or 200 cGy) on the basis of Dunnett adjusted t-test; among these, 97 proteins showed a trend of downregulation and 9 proteins showed a trend of upregulation with increasing radiation dose. In addition, there were 21 and 8 proteins observed to have irregular trends with the 10 cGy irradiated group either having the highest or the lowest level among all three radiated doses. Moreover, two proteins, carboxypeptidase E and ubiquitin carboxyl-terminal hydrolase isozyme L1 were sensitive to ionizing radiation, but relatively independent of radiation dose. Conversely, proteasome activator complex subunit 2 protein appeared to be sensitive to the dose of radiation, as rapid upregulation of this protein was observed when radiation doses were increased from 3, to 10 or 200 cGy. These results suggest that different mechanisms of action exist at the secretome level for low and high doses of ionizing radiation.

Influence mechanism of low-dose ionizing radiation on Escherichia coli DH5α population based on plasma theory and system dynamics simulation

International Nuclear Information System (INIS)

Sun, Yi; Hu, Dawei; Li, Liang; Jing, Zheng; Wei, Chuanfeng; Zhang, Lantao; Fu, Yuming

2016-01-01

It remains a mystery why the growth rate of bacteria is higher in low-dose ionizing radiation (LDIR) environment than that in normal environment. In this study, a hypothesis composed of environmental selection and competitive exclusion was firstly proposed from observed phenomena, experimental data and microbial ecology. Then a LDIR environment simulator (LDIRES) was built to cultivate a model organism of bacteria, Escherichia coli (E. coli) DH5α, the accurate response of bacterial population to ionizing radiation intensity variation was measured experimentally, and then the precise relative dosage of ionizing radiation E. coli DH5α population received was calculated by finite element analysis based on drift-diffusion equations of plasma. Finally, a highly valid mathematical model expressing the relationship between E. coli DH5α population and LDIR intensity was developed by system dynamics based on hypotheses, experimental data and microbial ecology. Both experiment and simulation results clearly showed that the E. coli DH5α individuals with greater specific growth rate and lower substrate consumption coefficient would adapt and survive in LDIR environment and those without such adaptability were finally eliminated under the combined effects of ionizing radiation selection and competitive exclusion. - Highlights: • Establishment of a low-dose ionizing radiation (LDIR) environment simulator. • Escherichiacoli DH5α was selected as a bacterial representative for investigation. • Precise LDIR intensity for E. coli DH5α was calculated by FEA and plasma theory. • Development of system dynamics model of LDIR influence on E. coli DH5α population. • Mechanism of bacterial boom in LDIR environment was elucidated by computer simulation.

Effect of the rate and dose rate of irradiation on the quality of mushrooms, shrimps and marinated poultry

International Nuclear Information System (INIS)

Lacroix, M.; Mahrour, A.; Beaulieu, M.; Jobin, M.; Nketsa-Tabiri, J.; Gagnon, M.

1998-01-01

In this research programme, three investigations involving irradiation in combination with other preservation treatments are described. The first study evaluated the effect of the gamma irradiation dose rate combined with control storage at 15 deg. C and 90% relative humidity on the biochemical, microbiological and physical quality of mushrooms (Agaricus bisporus). A 2 kGy dose was necessary to control the pathogenic microorganisms and to decrease the ageing process of mushrooms. The shelf-life of the mushrooms, as assessed by colour, was extended by 4 days at the lower dose rate (4.5 kGy/h) and by only 2 days at the higher dose rate (32 kGy/h). The higher dose rate caused stress to the cells and altered cell permeability. The second study was to verify the efficacy of ionizing radiation ( 60 Co) on frozen shrimps in eliminating or reducing the pathogenic bacteria that may occasionally be present and to increase the cold storage life of thawed shrimps. A dose of 2.5 kGy permitted storage at 4 deg. C for 1 month without affecting the quality of the product. The third study investigated the anti-oxidant and anti-microbial properties of the natural substances added to fresh poultry before irradiation. Irradiation of poultry at 5 kGy was found to be highly effective in eliminating Salmonella and reducing the number of spoilage microorganisms to ensure safety and quality. Moreover, use of marinating techniques had a synergistic effect with irradiation in reducing the microbial load and the oxidation rate of unsaturated fatty acids, particularly C18:2. The essential oils in rosemary and thyme were the most potent anti-microbial agents investigated and prevented the deterioration of stored foods by bacteria. Several phenolic compounds with anti-oxidant activities were also isolated from rosemary. (author)

Cancer radiotherapy based on femtosecond IR laser-beam filamentation yielding ultra-high dose rates and zero entrance dose.

Science.gov (United States)

Meesat, Ridthee; Belmouaddine, Hakim; Allard, Jean-François; Tanguay-Renaud, Catherine; Lemay, Rosalie; Brastaviceanu, Tiberius; Tremblay, Luc; Paquette, Benoit; Wagner, J Richard; Jay-Gerin, Jean-Paul; Lepage, Martin; Huels, Michael A; Houde, Daniel

2012-09-18

Since the invention of cancer radiotherapy, its primary goal has been to maximize lethal radiation doses to the tumor volume while keeping the dose to surrounding healthy tissues at zero. Sadly, conventional radiation sources (γ or X rays, electrons) used for decades, including multiple or modulated beams, inevitably deposit the majority of their dose in front or behind the tumor, thus damaging healthy tissue and causing secondary cancers years after treatment. Even the most recent pioneering advances in costly proton or carbon ion therapies can not completely avoid dose buildup in front of the tumor volume. Here we show that this ultimate goal of radiotherapy is yet within our reach: Using intense ultra-short infrared laser pulses we can now deposit a very large energy dose at unprecedented microscopic dose rates (up to 10(11) Gy/s) deep inside an adjustable, well-controlled macroscopic volume, without any dose deposit in front or behind the target volume. Our infrared laser pulses produce high density avalanches of low energy electrons via laser filamentation, a phenomenon that results in a spatial energy density and temporal dose rate that both exceed by orders of magnitude any values previously reported even for the most intense clinical radiotherapy systems. Moreover, we show that (i) the type of final damage and its mechanisms in aqueous media, at the molecular and biomolecular level, is comparable to that of conventional ionizing radiation, and (ii) at the tumor tissue level in an animal cancer model, the laser irradiation method shows clear therapeutic benefits.

Compendium of Total Ionizing Dose and Displacement Damage for Candidate Spacecraft Electronics for NASA

Science.gov (United States)

Cochran, Donna J.; Boutte, Alvin J.; Chen, Dakai; Pellish, Jonathan A.; Ladbury, Raymond L.; Casey, Megan C.; Campola, Michael J.; Wilcox, Edward P.; Obryan, Martha V.; LaBel, Kenneth A.;

Ionizing radiation dose due to the use of agricultural fertilizers

International Nuclear Information System (INIS)

Umisedo, Nancy Kuniko

2007-01-01

Among several agents that exist in the environment which can expose to different risks and effects, there is the ionizing radiation whose knowledge of dose is of importance to the effective control and prevention of possible damages to human beings and to the environment. The transfer of radionuclides from fertilizers to/and soils to the foodstuffs can result as an increment in the internal dose when they are consumed by the human beings. This work evaluates the contribution of fertilizers to the ionizing radiation dose in the environment and in the human being. Samples of fertilizers, soils and vegetables produced in fertilized soils were analysed through gamma spectrometry with the use of a hyper pure germanium detector. Measurements of ambient dose with thermoluminescent dosimeters were also performed. In the fertilized soil samples values of specific activities from 36 to 342 Bq/kg for K-40, from 42 to 142 Bq/kg for U-238 and from 36 to 107 Bq/kg for Th-232 were obtained. In the vegetables the values varied from 21 to 118 Bq/kg for K-40 and for the elements of uranium and thorium series the values were less than 2 Bq/kg. In fertilizers the maximum value of 5800 Bq/kg was obtained for K-40, 430 Bq/kg for U-238 and 230 Bq/kg for Th-232. The average values of soil to plant transfer factor were not significantly different among the types of vegetables. The annual committed effective dose of 0.882 μSv due to the ingestion of K-40 from the analysed vegetables is very small if compared to the reference value of 170 μv given by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR, 2000). The thermoluminescent dosimetry provided the annual ambient dose equivalent from 1.5 to 1.8 mSv without differences between cultivated and non cultivated fields. Through the results obtained, it was not observed a significant transfer of radionuclides from fertilizers to soils and to foodstuffs in the conditions adopted in this work and consequently there

High dose-per-pulse electron beam dosimetry: Usability and dose-rate independence of EBT3 Gafchromic films.

Science.gov (United States)

Jaccard, Maud; Petersson, Kristoffer; Buchillier, Thierry; Germond, Jean-François; Durán, Maria Teresa; Vozenin, Marie-Catherine; Bourhis, Jean; Bochud, François O; Bailat, Claude

2017-02-01

The aim of this study was to assess the suitability of Gafchromic EBT3 films for reference dose measurements in the beam of a prototype high dose-per-pulse linear accelerator (linac), capable of delivering electron beams with a mean dose-rate (Ḋ m ) ranging from 0.07 to 3000 Gy/s and a dose-rate in pulse (Ḋ p ) of up to 8 × 10 6 Gy/s. To do this, we evaluated the overall uncertainties in EBT3 film dosimetry as well as the energy and dose-rate dependence of their response. Our dosimetric system was composed of EBT3 Gafchromic films in combination with a flatbed scanner and was calibrated against an ionization chamber traceable to primary standard. All sources of uncertainties in EBT3 dosimetry were carefully analyzed using irradiations at a clinical radiotherapy linac. Energy dependence was investigated with the same machine by acquiring and comparing calibration curves for three different beam energies (4, 8 and 12 MeV), for doses between 0.25 and 30 Gy. Ḋ m dependence was studied at the clinical linac by changing the pulse repetition frequency (f) of the beam in order to vary Ḋ m between 0.55 and 4.40 Gy/min, while Ḋ p dependence was probed at the prototype machine for Ḋ p ranging from 7 × 10 3 to 8 × 10 6 Gy/s. Ḋ p dependence was first determined by studying the correlation between the dose measured by films and the charge of electrons measured at the exit of the machine by an induction torus. Furthermore, we compared doses from the films to independently calibrated thermo-luminescent dosimeters (TLD) that have been reported as being dose-rate independent up to such high dose-rates. We report that uncertainty below 4% (k = 2) can be achieved in the dose range between 3 and 17 Gy. Results also demonstrated that EBT3 films did not display any detectable energy dependence for electron beam energies between 4 and 12 MeV. No Ḋ m dependence was found either. In addition, we obtained excellent consistency between films and TLDs over the entire Ḋ p

Tank Z-361 dose rate calculations

International Nuclear Information System (INIS)

Richard, R.F.

1998-01-01

Neutron and gamma ray dose rates were calculated above and around the 6-inch riser of tank Z-361 located at the Plutonium Finishing Plant. Dose rates were also determined off of one side of the tank. The largest dose rate 0.029 mrem/h was a gamma ray dose and occurred 76.2 cm (30 in.) directly above the open riser. All other dose rates were negligible. The ANSI/ANS 1991 flux to dose conversion factor for neutrons and photons were used in this analysis. Dose rates are reported in units of mrem/h with the calculated uncertainty shown within the parentheses

Bayesian estimation of dose rate effectiveness

International Nuclear Information System (INIS)

Arnish, J.J.; Groer, P.G.

2000-01-01

A Bayesian statistical method was used to quantify the effectiveness of high dose rate 137 Cs gamma radiation at inducing fatal mammary tumours and increasing the overall mortality rate in BALB/c female mice. The Bayesian approach considers both the temporal and dose dependence of radiation carcinogenesis and total mortality. This paper provides the first direct estimation of dose rate effectiveness using Bayesian statistics. This statistical approach provides a quantitative description of the uncertainty of the factor characterising the dose rate in terms of a probability density function. The results show that a fixed dose from 137 Cs gamma radiation delivered at a high dose rate is more effective at inducing fatal mammary tumours and increasing the overall mortality rate in BALB/c female mice than the same dose delivered at a low dose rate. (author)

Comparison of the dose-effect relationship for UV radiation and ionizing radiation

International Nuclear Information System (INIS)

Leenhouts, H.P.; Sijsma, M.J.; Chadwick, K.H.

1990-06-01

Ionizing radiation and ultraviolet radiation (UV) are both physical agents with mutagenic and carcinogenic properties. However, there are some basic differences in the fundamental mechanism of their interaction with biological material that may have consequences for risk assessment. In this paper the dose-effect relationships for gamma radiation and UV at cellular level will be used to demonstrate the different radio-biological effectiveness of both agents. The results will be discussed in the framework of a biophysical model, based on the assumption that DNA doublestranded lesions are crucial for the cytotoxic action. After exposure to ionizing radiation, the lesions are fixed immediately following irradiation, but after UV exposure the lethal lesions are recognized only in the next DNA synthesis phase. The combination of this concept with the mechanism of lesion induction and the possibility of repair, leads to different dose and time relationships for the radiation effects of both agents. The possible consequences for risk assessment at low levels will be discussed. (author). 9 refs.; 5 figs

Advanced Computational Approaches for Characterizing Stochastic Cellular Responses to Low Dose, Low Dose Rate Exposures

Energy Technology Data Exchange (ETDEWEB)

Scott, Bobby, R., Ph.D.

2003-06-27

applications of NEOTRANS2, indicate that nonlinear threshold-type, dose-response relationships for excess stochastic effects (problematic nonlethal mutations, neoplastic transformation) should be expected after exposure to low linear energy transfer (LET) gamma rays or gamma rays in combination with high-LET alpha radiation. Similar thresholds are expected for low-dose-rate low-LET beta irradiation. We attribute the thresholds to low-dose, low-LET radiation induced protection against spontaneous mutations and neoplastic transformations. The protection is presumed mainly to involve selective elimination of problematic cells via apoptosis. Low-dose, low-LET radiation is presumed to trigger wide-area cell signaling, which in turn leads to problematic bystander cells (e.g., mutants, neoplastically transformed cells) selectively undergoing apoptosis. Thus, this protective bystander effect leads to selective elimination of problematic cells (a tissue cleansing process in vivo). However, this protective bystander effects is a different process from low-dose stimulation of the immune system. Low-dose, low-LET radiation stimulation of the immune system may explain why thresholds for inducing excess cancer appear much larger (possibly more than 100-fold larger) than thresholds for inducing excess mutations and neoplastic transformations, when the dose rate is low. For ionizing radiation, the current risk assessment paradigm is such that the relative risk (RR) is always ¡Ý 1, no matter how small the dose. Our research results indicate that for low-dose or low-dose-rate, low-LET irradiation, RR < 1 may be more the rule than the exception. Directly tied to the current RR paradigm are the billion-dollar cleanup costs for radionuclide-contaminated DOE sites. Our research results suggest that continued use of the current RR paradigm for which RR ¡Ý 1 could cause more harm than benefit to society (e.g., by spreading unwarranted fear about phantom excess risks associated with low-dose low

Impact of the Revised 10 CFR 835 on the Neutron Dose Rates at LLNL

International Nuclear Information System (INIS)

Radev, R.

2009-01-01

In June 2007, 10 CFR 835 (1) was revised to include new radiation weighting factors for neutrons, updated dosimetric models, and dose terms consistent with the newer ICRP recommendations. A significant aspect of the revised 10 CFR 835 is the adoption of the recommendations outlined in ICRP-60 (2). The recommended new quantities demand a review of much of the basic data used in protection against exposure to sources of ionizing radiation. The International Commission on Radiation Units and Measurements has defined a number of quantities for use in personnel and area monitoring (3,4,5) including the ambient dose equivalent H*(d) to be used for area monitoring and instrument calibrations. These quantities are used in ICRP-60 and ICRP-74. This report deals only with the changes in the ambient dose equivalent and ambient dose rate equivalent for neutrons as a result of the implementation of the revised 10 CFR 835. In the report, the terms neutron dose and neutron dose rate will be used for convenience for ambient neutron dose and ambient neutron dose rate unless otherwise stated. This report provides a qualitative and quantitative estimate of how much the neutron dose rates at LLNL will change with the implementation of the revised 10 CFR 835. Neutron spectra and dose rates from selected locations at the LLNL were measured with a high resolution spectroscopic neutron dose rate system (ROSPEC) as well as with a standard neutron rem meter (a.k.a., a remball). The spectra obtained at these locations compare well with the spectra from the Radiation Calibration Laboratory's (RCL) bare californium source that is currently used to calibrate neutron dose rate instruments. The measurements obtained from the high resolution neutron spectrometer and dose meter ROSPEC and the NRD dose meter compare within the range of ±25%. When the new radiation weighting factors are adopted with the implementation of the revised 10 CFR 835, the measured dose rates will increase by up to 22%. The

On possible risks of low-dose irradiation

International Nuclear Information System (INIS)

Hug, O.; Gesellschaft fuer Strahlen- und Umweltforschung m.b.H., Neuherberg/Muenchen

1974-01-01

The survey on more recent experimental and epidemiological data and newer concepts for a realistic estimation of the radiation risk leads to the conclusion that for radiation late damages and possibly also for genetic damages with a chronical radiation exposure in the order of magnitude of the natural radiation exposure and probably also in the order of magnitude of the maximum permissible radiation dose, the risk is very probably lower than is to be expected based on the findings after relatively high doses and dose rates. A few less direct comparative studies have detected a time factor of 3 to 5. Considering the analysis of the RBW demely ionizing radiation which at high doses is not greater than 3, increases with decreasing dose and according to biophysical considerations, can possibly reach a value of 30, an effectiveness reduced by a factor of 10 of small doses and dose rates of loosely ionizing radiation would be even to be expected. All radiobiological knowledge on the effect of ionizing radiation allows one to expect that even smallest radiation doses can cause cellular damages due to the linear irreversable components of the radiation effect and probably that these damages can even be the starting point of a malignant tumour. Regarding this cancer-initiating effect however, the effectiveness of loosely ionizing radiation per rad in the region of natural radiation exposure lie considerably below that existing at high doses and dose rates. Whether however this initial carcinogenic effect of very small doses is at all noticeable during the average life duration in an increase of the spontaneous age-specific tumour rate is questionable if the assumption is confirmed that with decreasing dose, the time manifestation of the radiation induced tumours is delayed. (orig./LH) [de

Dose/dose-rate responses of shrimp larvae to UV-B radiation

International Nuclear Information System (INIS)

Damkaer, D.M.

1981-01-01

Previous work indicated dose-rate thresholds in the effects of UV-B on the near-surface larvae of three shrimp species. Additional observations suggest that the total dose response varies with dose-rate. Below 0.002 Wm -2 sub([DNA]) irradiance no significant effect is noted in activity, development, or survival. Beyond that dose-rate threshold, shrimp larvae are significantly affected if the total dose exceeds about 85 Jm -2 sub([DNA]). Predictions cannot be made without both the dose-rate and the dose. These dose/dose-rate thresholds are compared to four-year mean dose/dose-rate solar UV-B irradiances at the experimental site, measured at the surface and calculated for 1 m depth. The probability that the shrimp larvae would receive lethal irradiance is low for the first half of the season of surface occurrence, even with a 44% increase in damaging UV radiation. (orig.)

Dose/dose-rate responses of shrimp larvae to UV-B radiation

Energy Technology Data Exchange (ETDEWEB)

Damkaer, D.M.; Dey, D.B.; Heron, G.A.

1981-01-01

Previous work indicated dose-rate thresholds in the effects of UV-B on the near-surface larvae of three shrimp species. Additional observations suggest that the total dose response varies with dose-rate. Below 0.002 Wm/sup -2/sub((DNA)) irradiance no significant effect is noted in activity, development, or survival. Beyond that dose-rate threshold, shrimp larvae are significantly affected if the total dose exceeds about 85 Jm/sup -2/sub((DNA)). Predictions cannot be made without both the dose-rate and the dose. These dose/dose-rate thresholds are compared to four-year mean dose/dose-rate solar UV-B irradiances at the experimental site, measured at the surface and calculated for 1 m depth. The probability that the shrimp larvae would receive lethal irradiance is low for the first half of the season of surface occurrence, even with a 44% increase in damaging UV radiation.

Calibration of ionization chambers and determination of the absorbed doses

International Nuclear Information System (INIS)

RANDRIANTSEHENO, H.F

1996-01-01

In order to further improve the accuracy of dosimetric measurements in radiation therapy, the IAEA and WHO supported the establishment of Secondary Standard Dosimetry Laboratory (SSDLs). These SSDLs bridge the gap between the primary measurement standards and the user of ionizing radiation by providing the latter with calibrations against the SSDLs' secondary standards and by giving technical advice and assistance. However, a properly calibrated dosimeter is just necessary first condition for the determination of the dose. It has been demonstrated that the success or failure of radiation treatment depends on the absorbed dose delivered to the tumour and that this should not vary by more than a few per cent from described values. [fr

Cancer risk at low doses of ionizing radiation. Artificial neural networks inference from atomic bomb survivors

International Nuclear Information System (INIS)

Sasaki, Masao S.; Tachibana, Akira; Takeda, Shunichi

2014-01-01

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 (1) the presence of a threshold that varied with organ, gender and age at exposure, and (2) a small but significant bumping increase in cancer risk at low doses in Nagasaki that probably reflects internal exposure to 239 Pu. 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. (author)

Disordered redox metabolism of brain cells in rats exposed to low doses of ionizing radiation or UHF electromagnetic radiation.

Science.gov (United States)

Burlaka, A P; Druzhyna, M O; Vovk, A V; Lukin, S М

2016-12-01

To investigate the changes of redox-state of mammalian brain cells as the critical factor of initiation and formation of radiation damage of biological structures in setting of continuous exposure to low doses of ionizing radiation or fractionated ultra high frequency electromagnetic radiation (UHF EMR) at non-thermal levels. The influence of low-intensity ionizing radiation was studied on outbred female rats kept for 1.5 years in the Chernobyl accident zone. The effects of total EMR in the UHF band of non-thermal spectrum were investigated on Wistar rats. The rate of formation of superoxide radicals and the rate of NO synthesis in mitochondria were determined by the EPR. After exposure to ionizing or UHF radiation, the levels of ubisemiquinone in brain tissue of rats decreased by 3 and 1.8 times, respectively. The content of NO-FeS-protein complexes in both groups increased significantly (р < 0.05). In the conditions of ionizing or EMR the rates of superoxide radical generation in electron-transport chain of brain cell mitochondria increased by 1.5- and 2-fold, respectively (р < 0.05). In brain tissue of rats kept in the Chernobyl zone, significant increase of NO content was registered; similar effect was observed in rats treated with UHFR (р < 0.05). The detected changes in the electron transport chain of mitochondria of brain cells upon low-intensity irradiation or UHF EMR cause the metabolic reprogramming of cell mitochondria that increases the rate of superoxide radical generation and nitric oxide, which may initiate the development of neurodegenerative diseases and cancer. This article is part of a Special Issue entitled "The Chornobyl Nuclear Accident: Thirty Years After".

Demonstration of a stimulating effect of natural ionizing radiation and of very low radiation doses on cell multiplication

International Nuclear Information System (INIS)

Planel, G.; Soleilhavoup, J.P.; Tixador, R.; Croute, F.; Richoilley, G.

1976-01-01

Experiments have been carried out to demonstrate a possible effect of natural ionizing radiation. Using lead shielding devices or an underground laboratory, it was shown that a decrease in background irradiation induces a decrease in cell growth rate (experiments carried out on Paramecia). On the other hand, the recovery of a normal irradiation level in shielding devices induces a quite normal cell proliferation. Moreover, small doses of γ rays from 60 Co exhibit a stimulating effect. Variations in cell radiosensitivity to these low doses are reported. Experiments carried out in the underground laboratory and at high altitude show that both telluric radioactivity and cosmic rays contribute to this stimulating effect on cell multiplication. (author)

Biological effects of low-level ionizing and non-ionizing radiation

International Nuclear Information System (INIS)

Upton, A.C.

1986-01-01

Early in this century it was recognized that large doses of ionizing radiation could injure almost any tissue in the body, but small doses were generally thought to be harmless. By the middle of the century however it came to be suspected that even the smallest doses of ionizing radiation to the gonads might increase the risk of hereditary disease in subsequently-conceived offspring. Since then the hypothesis that carcinogenic and teratogenic effects also have no threshold has been adopted for purposes of radiological protection. It is estimated nevertheless that the risks that may be associated with natural background levels of ionizing irradiation are too small to be detectable. Hence validation of such risk estimates will depend on further elucidation of the dose-effect relationships and mechanisms of the effects in question, through studies at higher dose levels. In contrast to the situation with ionizing radiation, exposure to natural background levels of ultraviolet radiation has been implicated definitively in the etiology of skin cancers in fair-skinned individuals. Persons with inherited effects in DNA repair capacity are particularly susceptible. Non-ionizing radiations of other types can also affect health at high dose levels, but whether they can cause injury at low levels of exposure is not known

Cancer risk from low doses of ionizing radiation

Energy Technology Data Exchange (ETDEWEB)

Auvinen, A

1997-06-01

The aim of the study was to estimate cancer risk from small doses of ionizing radiation from various sources, including both external and internal exposure. The types of radiation included alpha, gamma, and neutron radiation. A nationwide follow-up study covering the years up to 1992 revealed no significant association between fallout from the Chernobyl accident and incidence of childhood leukemia. An excess of eight cases or more per year could be excluded. However, some indication of an increase was evident in the most heavily affected areas. Furthermore, the risk estimates were in accordance with those reported from Hiroshima and Nagasaki, although the confidence intervals were wide. (282 refs.).

Cancer risk from low doses of ionizing radiation

International Nuclear Information System (INIS)

Auvinen, A.

1997-06-01

The aim of the study was to estimate cancer risk from small doses of ionizing radiation from various sources, including both external and internal exposure. The types of radiation included alpha, gamma, and neutron radiation. A nationwide follow-up study covering the years up to 1992 revealed no significant association between fallout from the Chernobyl accident and incidence of childhood leukemia. An excess of eight cases or more per year could be excluded. However, some indication of an increase was evident in the most heavily affected areas. Furthermore, the risk estimates were in accordance with those reported from Hiroshima and Nagasaki, although the confidence intervals were wide. (282 refs.)

Ionizing radiation and non-ionizing radiation in educational environment

International Nuclear Information System (INIS)

Matsuzawa, Takao; Otsubo, Tomonobu; Ikke, Satoshi; Taguchi, Noriko; Takeda, Rie

2005-01-01

By chance, we measured gamma dose rates in our school, and around the JCO Tokai Plant during the criticality on September 30 in 1999, with our GM survey meter. At that time, we made sure to estimate the position of criticality reaction (source point), and the source intensity of criticality reaction, with our own data, measured along the public roads, route 6 and local road 62. The intensity of gamma dose rates along the road was analyzed as Lorentz functions. At the time, there were no environmental radiation data about the criticality accident, or all the data, especially radioactivity and dose rates around the JCO Tokai Plant, was closed to the public. Recently, we are interested in the intensity of non-ionizing radiation, especially extremely low frequency (ELF) magnetic field, and electric field, in our environment. We adopted the same method to analyze the source position and source intensity of an ELF magnetic field and electric behind a wall. (author)

Ionization of bovine meat products. Microbiological, nutritional and organoleptic consequences

International Nuclear Information System (INIS)

Desmonts, M.H.

1991-01-01

In this thesis, the author analyses simultaneously the characteristics of sliced beef steaks, of minced beef steaks from industrial making and of beef and calf ionized liver rounds: microbiological quality, nutritional quality, and organoleptic quality. These analyses are systematically effected during 3 to 4 weeks on vacuum packaged products and stored at 3-4 deg C. The influence of ionization on microbiological, nutritional and organoleptic qualities is studied. These products are vacuum packaged in oxygen-porous films, ionized under accelerated electron with radiation doses from 1 to 5 kGy and stored at 3-4 deg C during 3-4 weeks. Then, other parameters are studied : fats rate of minced steaks (5 and 10%), packing quality (oxygen-tight packing and oxygen-porous film) and finally, the radiation dose rate (X or gamma-radiation and accelerated electrons). In conclusion, the ionization allows to improve the preservation time of vacuum packaged beef and calf liver rounds. Meat can be preserved during 10-14 days after having received a radiation dose of 3-4 kGy, without nutritional quality alteration

Audits in high dose rate brachytherapy in Brazil

International Nuclear Information System (INIS)

Marechal, M.H.; Rosa, L.A.; Velasco, A.; Paiva, E. de; Goncalves, M.; Castelo, L.C.

2002-01-01

The lack of well established dosimetry protocols for HDR sources is a point of great concern regarding the uniformity of procedures within a particular country. The main objective of this paper is to report the results of an implementation of the audit program in dosimetry of high dose rate brachytherapy sources used by the radiation therapy centers in Brazil. In Brazil, among 169 radiotherapy centers, 35 have HDR brachytherapy systems. This program started in August 2001 and until now eight radiotherapy services were audited. The audit program consists of the visit in loco to each center and the evaluation of the intensity of the source with a well type chamber specially design for HDR 192 Ir sources. The measurements was carried out with a HDR1000PLUS Brachytherapy Well Type Chamber and a MAX 4000 Electrometer, both manufactured by Standard Imaging Inc. The chamber was calibrated in air kerma strength by the Accredited Dosimetry Calibration Laboratory, Department of Medical Physics, University of Wisconsin in the USA. The same chamber was calibrated in Brazil using a 192 lr high dose rate source whose intensity was determined by 60 Co gamma rays and 250 kV x rays interpolation methodology. The Nk of 60 Co and 250 kV x rays were provided by the Brazilian National Standard Laboratory for Ionizing Radiation (LMNRI)

Effect of low doses of ionizing radiation on the thymus-dependent humoral immune response and the polyclonal activation of B-lymphocytes

International Nuclear Information System (INIS)

Sharetskij, A.N.; Surinov, B.P.; Abramova, M.R.

2000-01-01

The results of studies on the effect of the low-dose (10 cGy with the dose rate of 1cGy/min) γ-radiation on the indices of the mice system and local immune response are presented. The sheep erythrocytes were used as a thymus-dependent antigen. It is shown that the total irradiation with the above dose rate induced the increase in the primary thymus-dependent humoral immune response on the sheep erythrocytes and polyclonal activation of the B-lymphocytes. The sharp oppression of the antibody formation was observed in the immune response dynamics after the phase of the radiation-induced elevation. The injection of hydroquinone right after the irradiation resulted in elimination of the radiation stimulation of the polyclonal response of the B-cells. The essential decrease in the immunoantilogarithmic radiation effect took place in the animals treated with thymogen. The possible negative consequences of the low-dose ionizing radiation impact on the body immune system are discussed [ru

Ionizing radiation dose control for workers in a nuclear plant working with unsealed sources

International Nuclear Information System (INIS)

Gerulis, Eduardo

2006-01-01

With the liberation of the use of the nuclear energy for peaceful applications, International Commission Radiological Protection, ICRP, founded in 1928, created a system of protection of the undesirable doses of ionizing radiation in 1958. This has been received by workers, members of the public and environment and hence it became possible for the introduction of these applications. This protection system is adopted by the International Agency of Energy Atomic, IAEA, that publishes recommendations in safety series, 88 and by the Comissao Nacional de Energia Nuclear, CNEN, which publishes these regulations. The international recommendations and national regulations were adapted and they need to be applied in this way. The present paper uses recommendations of the publication 75 from ICRP, of the publication 115 from 88 and regulations of the regulation NN 3.01 from CNEN to present, through radiological protection measures, the ionizing radiation dose control for workers in a nuclear plant that works in the research, production, division and packing of unsealed sources to be used in clinical applications. In that way it is possible to prevent appropriately the undesirable doses and to confirm the received doses. (author)

Dose-rate and oxygen effects in models of lipid membranes: linoleic acid

Energy Technology Data Exchange (ETDEWEB)

Raleigh, J A; Kremers, W; Gaboury, B [Atomic Energy of Canada Ltd., Pinawa, Manitoba. Whiteshell Nuclear Research Establishment

1977-03-01

Cellular membranes have been suggested as possible loci for the development of the oxygen effect in radiobiology. Unsaturated lipids from membranes are subject to very efficient radiation-induced peroxidation, and the deleterious effects generally associated with lipid autoxidation could be initiated by ionizing radiation. Oxidative damage in lipids was characterized not only by high yields but also by a profound dose-rate effect. At dose-rates of x irradiation below 100 rad/min, a very sharp rise occurred in oxidative damage. This damage has been quantified spectrophotometrically in terms of diene conjugation (O.D. 234 mm) and chromatographically in terms of specific 9- and 13-hydroperoxide formation in linoleic acid micelles. Radical scavenging experiments indicated that hydroxyl radical attack initiated the oxidative damage. Dimethyl sulphoxide is exceptional in that it did not protect, but sensitized, linoleic acid to radiation-induced peroxidation. The yields of hydroperoxides were substantial (G = 10 to 40) and could be related to biological changes known to be effected by autoxidizing lipids.

III. Penning ionization, associative ionization and chemi-ionization processes

International Nuclear Information System (INIS)

Cermak, V.

1975-01-01

Physical mechanisms of three important ionization processes in a cold plasma and the methods of their experimental study are discussed. An apparatus for the investigation of the Penning ionization using ionization processes of long lived metastable rare gas atoms is described. Methods of determining interaction energies and ionization rates from the measured energy spectra of the originating electrons are described and illustrated by several examples. Typical associative ionization processes are listed and the ionization rates are compared with those of the Penning ionization. Interactions with short-lived excited particles and the transfer of excitation without ionization are discussed. (J.U.)

MCNPX calculations of dose rate distribution inside samples treated in the research gamma irradiating facility at CTEx

Energy Technology Data Exchange (ETDEWEB)

Rusin, Tiago; Rebello, Wilson F.; Vellozo, Sergio O.; Gomes, Renato G., E-mail: tiagorusin@ime.eb.b, E-mail: rebello@ime.eb.b, E-mail: vellozo@cbpf.b, E-mail: renatoguedes@ime.eb.b [Instituto Militar de Engenharia (IME), Rio de Janeiro, RJ (Brazil). Dept. de Engenharia Nuclear; Vital, Helio C., E-mail: vital@ctex.eb.b [Centro Tecnologico do Exercito (CTEx), Rio de Janeiro, RJ (Brazil); Silva, Ademir X., E-mail: ademir@con.ufrj.b [Universidade Federal do Rio de Janeiro (PEN/COPPE/UFRJ), RJ (Brazil). Coordenacao dos Programas de Pos-Graduacao de Engenharia. Programa de Engenharia Nuclear

2011-07-01

A cavity-type cesium-137 research irradiating facility at CTEx has been modeled by using the Monte Carlo code MCNPX. The irradiator has been daily used in experiments to optimize the use of ionizing radiation for conservation of many kinds of food and to improve materials properties. In order to correlate the effects of the treatment, average doses have been calculated for each irradiated sample, accounting for the measured dose rate distribution in the irradiating chambers. However that approach is only approximate, being subject to significant systematic errors due to the heterogeneous internal structure of most samples that can lead to large anisotropy in attenuation and Compton scattering properties across the media. Thus this work is aimed at further investigating such uncertainties by calculating the dose rate distribution inside the items treated such that a more accurate and representative estimate of the total absorbed dose can be determined for later use in the effects-versus-dose correlation curves. Samples of different simplified geometries and densities (spheres, cylinders, and parallelepipeds), have been modeled to evaluate internal dose rate distributions within the volume of the samples and the overall effect on the average dose. (author)

MCNPX calculations of dose rate distribution inside samples treated in the research gamma irradiating facility at CTEx

International Nuclear Information System (INIS)

Rusin, Tiago; Rebello, Wilson F.; Vellozo, Sergio O.; Gomes, Renato G.; Silva, Ademir X.

2011-01-01

A cavity-type cesium-137 research irradiating facility at CTEx has been modeled by using the Monte Carlo code MCNPX. The irradiator has been daily used in experiments to optimize the use of ionizing radiation for conservation of many kinds of food and to improve materials properties. In order to correlate the effects of the treatment, average doses have been calculated for each irradiated sample, accounting for the measured dose rate distribution in the irradiating chambers. However that approach is only approximate, being subject to significant systematic errors due to the heterogeneous internal structure of most samples that can lead to large anisotropy in attenuation and Compton scattering properties across the media. Thus this work is aimed at further investigating such uncertainties by calculating the dose rate distribution inside the items treated such that a more accurate and representative estimate of the total absorbed dose can be determined for later use in the effects-versus-dose correlation curves. Samples of different simplified geometries and densities (spheres, cylinders, and parallelepipeds), have been modeled to evaluate internal dose rate distributions within the volume of the samples and the overall effect on the average dose. (author)

INTERSTELLAR METASTABLE HELIUM ABSORPTION AS A PROBE OF THE COSMIC-RAY IONIZATION RATE

International Nuclear Information System (INIS)

Indriolo, Nick; McCall, Benjamin J.; Hobbs, L. M.; Hinkle, K. H.

2009-01-01

The ionization rate of interstellar material by cosmic rays has been a major source of controversy, with different estimates varying by three orders of magnitude. Observational constraints of this rate have all depended on analyzing the chemistry of various molecules that are produced following cosmic-ray ionization, and in many cases these analyses contain significant uncertainties. Even in the simplest case (H + 3 ), the derived ionization rate depends on an (uncertain) estimate of the absorption path length. In this paper, we examine the feasibility of inferring the cosmic-ray ionization rate using the 10830 A absorption line of metastable helium. Observations through the diffuse clouds toward HD 183143 are presented, but yield only an upper limit on the metastable helium column density. A thorough investigation of He + chemistry reveals that only a small fraction of He + will recombine into the triplet state and populate the metastable level. In addition, excitation to the triplet manifold of helium by secondary electrons must be accounted for as it is the dominant mechanism which produces He* in some environments. Incorporating these various formation and destruction pathways, we derive new equations for the steady state abundance of metastable helium. Using these equations in concert with our observations, we find ζ He -15 s -1 , an upper limit about 5 times larger than the ionization rate previously inferred for this sight line using H + 3 . While observations of interstellar He* are extremely difficult at present, and the background chemistry is not nearly as simple as previously thought, potential future observations of metastable helium would provide an independent check on the cosmic-ray ionization rate derived from H + 3 in diffuse molecular clouds, and, perhaps more importantly, allow the first direct measurements of the ionization rate in diffuse atomic clouds.

Charophyte electrogenesis as a biomarker for assessing the risk from low-dose ionizing radiation to a single plant cell

International Nuclear Information System (INIS)

Sevriukova, Olga; Kanapeckaite, Auste; Lapeikaite, Indre; Kisnieriene, Vilma; Ladygiene, Rima; Sakalauskas, Vidmantas

2014-01-01

The impact of low-dose ionizing radiation on the electrical signalling pattern and membrane properties of the characea Nitellopsis obtusa was examined using conventional glass-microelectrode and voltage-clamp techniques. The giant cell was exposed to a ubiquitous radionuclide of high biological importance – tritium – for low-dose irradiation. Tritium was applied as tritiated water with an activity concentration of 15 kBq L −1 (an external dose rate that is approximately 0.05 μGy h −1 above the background radiation level); experiments indicated that this was the lowest effective concentration. Investigating the dynamics of electrical excitation of the plasma membrane (action potential) showed that exposing Characeae to tritium for half an hour prolonged the repolarization phase of the action potential by approximately 35%: the repolarization rate decreased from 39.2 ± 3.1 mV s −1 to 25.5 ± 1,8 mV s −1 due to tritium. Voltage-clamp measurements showed that the tritium exposure decreased the Cl – efflux and Ca 2+ influx involved in generating an action potential by approximately 27% (Δ = 12.4 ± 1.1 μA cm −2 ) and 64% (Δ = −5.3 ± 0.4 μA cm −2 ), respectively. The measured alterations in the action potential dynamics and in the chloride and calcium ion transport due to the exogenous low-dose tritium exposure provide the basis for predicting possible further impairments of plasma membrane regulatory functions, which subsequently disturb essential physiological processes of the plant cell. - Highlights: • We show some cellular details of the impact of low-dose ionizing radiation on biota. • Giant green algae cells provides a useful tool for studying HTO toxicity to a single plant cell. • Rapid real-time electrophysiological methods allowed to determine low dose tritium effect on transmembrane ion fluxes. • Pattern of charophyte cell membrane electrical excitation encodes tritium-caused alteration in cell homeostasis

Evaluation of absorbed radiation dose rate in a didactic X-ray equipment

International Nuclear Information System (INIS)

Costa, Phelipe Amaral Ferreira; Perini, Ana Paula; Neves, Lucio Pereira

2016-01-01

This work was performed in order to create a new didactic experiment in the X-ray apparatus of PHYWE, where the saturation current was obtained through a free air ionization chamber. The values of saturation currents were obtained in two ways. Initially, the anodic DDP was kept constant and the anodic current was varied. In the second way, the anodic current was kept constant while the anodic DDP was varied. Therefore, we were able to evaluate the dependence of the absolved dose rate in relation to the DDP and the tube current. (author)

Effects of a prolonged irradiation with low dose-rate ionizing radiation on the hemopoiesis of mice

Energy Technology Data Exchange (ETDEWEB)

Yanai, Takanori; Shirata, Katsutoshi; Saitou, Mikio; Tanaka, Satoshi; Onodera, Jun' ichi; Izumi, Jun; Otsu, Hiroshi; Sato, Fumiaki [Inst. for Environmental Sciences, Rokkasho, Aomori (Japan); Kanaiwa-Kudo, Syouko

2000-07-01

SPF C3H/HeN female mice were irradiated with {sup 137}Cs {gamma}-rays at doses of 1-8 Gy at the dose rate of 20 mGy/22 h/day. After irradiation, the numbers of CFU-S and CFU-GM in the bone marrow were determined. Number of peripheral blood cells was also counted. The day 12-CFU-S, which is in the earliest stage of differentiation, decreased as the dose increased. Decreases in the numbers of day 7-CFU-S and CFU-GM were also observed. Regardless of the severe decrease in the number of hemopoietic stem cells, no remarkable changes were observed in the number of peripheral blood cells, indicating an enhanced differentiation of the precursor cells. (author)

Outdoor γ-ray dose rate in Shariki Village and environmental factors affecting outdoor γ-ray dose rate in IES

International Nuclear Information System (INIS)

Iyogi, Takashi; Hisamatsu, Shun'ichi; Inaba, Jiro

2000-01-01

Previously, we surveyed the outdoor γ-ray dose rate throughout Aomori Prefecture from 1992 to 1995, and found an annual mean dose rate of 51 nGy h -1 . Relatively high dose rates were also observed in several areas (municipalities) of the survey locations. In this study, we examined the detailed distribution of the γ-ray dose rate in one such high dose rate area, Shariki Village. Glass dosemeters were used for the monitoring of cumulative γ-ray dose rate at 10 locations in the village. The dose rate from each radioactive nuclide in the ground at the monitoring locations was measured by using an in situ γ-ray spectrometer with a Ge detector. The results obtained with the glass dosemeters showed that the γ-ray dose rates in Shariki Village varied from 49 to 55 nGy h -1 . Although the dose rates were generally higher than the mean dose in Aomori Prefecture (1992-1995), the rates were lower than other high dose rate areas which had already been measured. The in situ γ-ray spectrometry revealed that these relatively high dose rates were mainly caused by 40 K and Th series radionuclides in the village. The effect of meteorological conditions on the γ-ray dose rate was studied at a monitoring station in the IES site. The dose rate was continuously recorded by a DBM NaI(Tl) scintillation detector system. The mean dose rate obtained when precipitation was sensed was 27 nGy h -1 and higher than when no precipitation was sensed (25 nGy h -1 ). (author)

Outdoor γ-ray dose rate in Mutsu city and environmental factors affecting outdoor γ-ray dose rate in IES

International Nuclear Information System (INIS)

Iyogi, Takashi; Hisamatsu, Shun'ichi; Inaba, Jiro

2001-01-01

Previously, we surveyed outdoor γ-ray dose rates throughout Aomori Prefecture from 1992 to 1995, and found a mean annual dose rate of 28 nGy h -1 . Relatively high dose rates were also observed in several areas (municipalities) of the survey locations. In this study, we examined the detailed distribution of the γ-ray dose rate in one such high dose rate area, Mutsu City. Glass dosemeters were used for the monitoring of cumulative γ-ray dose rate at 10 locations in the city. The dose rate from each radioactive nuclide in the ground at the monitoring locations was measured by using an in situ γ-ray spectrometer with a Ge detector. The results obtained with the glass dosemeters showed that the γ-ray dose rates in Mutsu City varied from 17 to 32 nGy h -1 . Although the dose rates were almost the same as the mean dose in Aomori Prefecture (1992-1995), the rates were lower than other high dose rate areas which had already been measured. The in situ γ-ray spectrometry revealed that these relatively high dose rates were mainly caused by 40 K and Th series radionuclides in the local ground. The effect of meteorological conditions on the γ-ray dose rate was studied at a monitoring station in the IES site. The dose rate was continuously recorded by a DBM NaI(Tl) scintillation detector system. The mean dose rate obtained when precipitation was sensed was 26 nGy h -1 and higher than when no precipitation was sensed (24 nGy h -1 ). (author)

Spontaneous mutation rates and the rate-doubling dose

International Nuclear Information System (INIS)

Von Borstel, R.C.; Moustaccki, E.; Latarjet, R.

1978-01-01

The amount of radiation required to double the frequency of mutations or tumours over the rate of those that occur spontaneously is called the rate-doubling dose. An equivalent concept has been proposed for exposure to other environmental mutagens. The doubling dose concept is predicated on the assumption that all human populations have the same spontaneous mutation rate, and that this spontaneous mutation rate is known. It is now established for prokaryotes and lower eukaryotes that numerous genes control the spontaneous mutation rate, and it is likely that the same is true for human cells as well. Given that the accepted mode of evolution of human populatons is from small, isolated groups of individuals, it seems likely that each population would have a different spontaneous mutation rate. Given that a minimum of twenty genes control or affect the spontaneous mutation rate, and that each of these in turn is susceptible to spontaneously arising or environmentally induced mutations, it seems likely that every individual within a population (except for siblings from identical multiple births) will have a unique spontaneous mutation rate. If each individual in a population does have a different spontaneous mutation rate, the doubling dose concept, in rigorous terms, is fallacious. Therefore, as with other concepts of risk evaluation, the doubling dose concept is subject to criticism. Nevertheless, until we know individual spontaneous mutation rates with precision, and can evaluate risks based on this information, the doubling dose concept has a heuristic value and is needed for practical assessment of risks for defined populations. (author)

Effects of proton radiation dose, dose rate and dose fractionation on hematopoietic cells in mice

International Nuclear Information System (INIS)

Ware, J.H.; Rusek, A.; Sanzari, J.; Avery, S.; Sayers, C.; Krigsfeld, G.; Nuth, M.; Wan, X.S.; Kennedy, A.R.

2010-01-01

The present study evaluated the acute effects of radiation dose, dose rate and fractionation as well as the energy of protons in hematopoietic cells of irradiated mice. The mice were irradiated with a single dose of 51.24 MeV protons at a dose of 2 Gy and a dose rate of 0.05-0.07 Gy/min or 1 GeV protons at doses of 0.1, 0.2, 0.5, 1, 1.5 and 2 Gy delivered in a single dose at dose rates of 0.05 or 0.5 Gy/min or in five daily dose fractions at a dose rate of 0.05 Gy/min. Sham-irradiated animals were used as controls. The results demonstrate a dose-dependent loss of white blood cells (WBCs) and lymphocytes by up to 61% and 72%, respectively, in mice irradiated with protons at doses up to 2 Gy. The results also demonstrate that the dose rate, fractionation pattern and energy of the proton radiation did not have significant effects on WBC and lymphocyte counts in the irradiated animals. These results suggest that the acute effects of proton radiation on WBC and lymphocyte counts are determined mainly by the radiation dose, with very little contribution from the dose rate (over the range of dose rates evaluated), fractionation and energy of the protons.

Effects of proton radiation dose, dose rate and dose fractionation on hematopoietic cells in mice.

Science.gov (United States)

Ware, J H; Sanzari, J; Avery, S; Sayers, C; Krigsfeld, G; Nuth, M; Wan, X S; Rusek, A; Kennedy, A R

2010-09-01

The present study evaluated the acute effects of radiation dose, dose rate and fractionation as well as the energy of protons in hematopoietic cells of irradiated mice. The mice were irradiated with a single dose of 51.24 MeV protons at a dose of 2 Gy and a dose rate of 0.05-0.07 Gy/min or 1 GeV protons at doses of 0.1, 0.2, 0.5, 1, 1.5 and 2 Gy delivered in a single dose at dose rates of 0.05 or 0.5 Gy/min or in five daily dose fractions at a dose rate of 0.05 Gy/min. Sham-irradiated animals were used as controls. The results demonstrate a dose-dependent loss of white blood cells (WBCs) and lymphocytes by up to 61% and 72%, respectively, in mice irradiated with protons at doses up to 2 Gy. The results also demonstrate that the dose rate, fractionation pattern and energy of the proton radiation did not have significant effects on WBC and lymphocyte counts in the irradiated animals. These results suggest that the acute effects of proton radiation on WBC and lymphocyte counts are determined mainly by the radiation dose, with very little contribution from the dose rate (over the range of dose rates evaluated), fractionation and energy of the protons.

Review of techniques and detectors used in instruments for field measurement of beta doses and dose rates

International Nuclear Information System (INIS)

Jones, A.R.

1983-01-01

Generally, field measurements are required to assess the hazard from #betta#-rays before personnel are allowed to occupy a working space or perform a task. Occasionally, the measurements are required for an assessment after a #betta#-ray exposure is suspected to have occurred. Until recently the dose or dose rate have been the quantities of interest but there is now felt to be a need to characterize the energies and directions of the #betta#-rays as well. The purpose of #betta#-dosimetry is the assessment of hazard to superficial tissues (within approx. 10 mm of the surface) and that these tissues may also be exposed simultaneously to other ionizing radiations. The #betta#-dosimetry technique must take account of this. With these uses of field instruments in mind the following detectors, and associated techniques will be discussed in terms of the measurement principles, advantages and limitations: thin-walled ion chambers (sometimes in combination with thick-walled ones or with covers thick enough to prevent penetration of #betta#-particles); thin scintillators, nearly tissue equivalent, to provide a detector analogous to skin; scintillators, thick enough to absorb all the energy of the #betta#-particles (circuitry is required to count pulses according to size to permit calculation of dose or dose rate); silicon diodes with thin detection layers operated as photocurrent generators; silicon diodes, reversed biassed, with pulses counted according to size; and simple pulse counters (e.g., GM counters or silicon diodes with thin windows)

Brachytherapy. High dose rate brachytherapy - Radiation protection: medical sheet ED 4287

International Nuclear Information System (INIS)

Celier, D.; Aubert, B.; Vidal, J.P.; Biau, A.; Lahaye, T.; Gauron, C.; Barret, C.; Boisserie, G.; Branchet, E.; Gambini, D.; Gondran, C.; Le Guen, B.; Guerin, C.; Nguyen, S.; Pierrat, N.; Sarrazin, T.; Donnarieix, D.

2010-02-01

After having indicated the required authorization to implement brachytherapy techniques, this document presents the various aspects and measures related to radiation protection when performing high-dose-rate brachytherapy treatments. It presents the concerned personnel, describes the operational process, indicates the associated hazards and the risk related to ionizing radiation, and describes how the risk is to be assessed and how exposure levels are to be determined (elements of risk assessment, delimitation of controlled and monitored areas, personnel classification, and choice of the dose monitoring method). It describes the various components of a risk management strategy (risk reduction, technical measures regarding the installation and the personnel, training and information, prevention and medical monitoring). It briefly presents how risk management is to be assessed, and mentions other related risks (biological risk, handling and posture, handling of heavy loads, mental workload, chemical risk)

Brachytherapy. Pulsed dose rate brachytherapy - Radiation protection: medical sheet ED 4250

International Nuclear Information System (INIS)

Celier, D.; Aubert, B.; Vidal, J.P.; Biau, A.; Lahaye, T.; Gauron, C.; Barret, C.; Boisserie, G.; Branchet, E.; Gambini, D.; Gondran, C.; Le Guen, B.; Guerin, C.; Nguyen, S.; Pierrat, N.; Sarrazin, T.; Donnarieix, D.

2009-06-01

After having indicated the required authorization to implement brachytherapy techniques, this document presents the various aspects and measures related to radiation protection when performing pulsed-dose-rate brachytherapy treatments. It presents the concerned personnel, describes the operational process, indicates the associated hazards and the risk related to ionizing radiation, and describes how the risk is to be assessed and how exposure levels are to be determined (elements of risk assessment, delimitation of controlled and monitored areas, personnel classification, and choice of the dose monitoring method). It describes the various components of a risk management strategy (risk reduction, technical measures regarding the installation and the personnel, training and information, prevention and medical monitoring). It briefly presents how risk management is to be assessed, and mentions other related risks (biological risk, handling and posture, handling of heavy loads, mental workload, chemical risk)

Evaluation of low dose ionizing radiation effect on some blood components in animal model

OpenAIRE

El-Shanshoury, H.; El-Shanshoury, G.; Abaza, A.

2016-01-01

Exposure to ionizing radiation is known to have lethal effects in blood cells. It is predicted that an individual may spend days, weeks or even months in a radiation field without becoming alarmed. The study aimed to discuss the evaluation of low dose ionizing radiation (IR) effect on some blood components in animal model. Hematological parameters were determined for 110 animal rats (divided into 8 groups) pre- and post-irradiation. An attempt to explain the blood changes resulting from both ...

Ionizing radiation

International Nuclear Information System (INIS)

Kruger, J.

1989-01-01

Ionizing radiation results in biological damage that differs from other hazardous substances and is highly dangerous to man. Ionizing radiation cannot be perceived by man's sense organs and the biological damage cannot be detected immediately afterwards (except in very high doses). Every human being is exposed to low doses of radiation. The structure of the atom; sources of ionizing radiation; radiation units; biological effects; norms for radiation protection; and the national control in South Africa are discussed. 1 fig., 5 refs

Experimental research on transient ionizing radiation effects of CMOS microcontroller

International Nuclear Information System (INIS)

Jin Xiaoming; Fan Ruyu; Chen Wei; Wang Guizhen; Lin Dongsheng; Yang Shanchao; Bai Xiaoyan

2010-01-01

This paper presents an experimental test system of CMOS microcontroller EE80C196KC20. Based on this system, the transient ionizing radiation effects on microcontroller were investigated using 'Qiangguang-I' accelerator. The gamma pulse width was 20 ns and the dose rate (for the Si atom) was in the range of 6.7 x 10 6 to 2.0 x 10 8 Gy/s in the experimental study. The disturbance and latchup effects were observed at different dose rate levels. Latchup threshold of the microcontroller was obtained. Disturbance interval and the system power supply current have a relationship with the dose rate level. The transient ionizing radiation induces photocurrent in the PN junctions that are inherent in CMOS circuits. The photocurrent is responsible for the electrical and functional degradation. (authors)

Increased ionization rate in laser enrichment

International Nuclear Information System (INIS)

Janes, G.S.; Pike, G.T.

1977-01-01

A system employing multiple, upper excitation levels in a technique for isotopically selective ionization to improve the ionization efficiency is described. Laser radiation is employed to excite particles with isotopic selectivity. Excitation is produced to a plurality of excited states below the ionization level with the result of increasing the number of available excited particles for ionization and thereby increasing the ionization cross section for improved system efficiency

Recent Total Ionizing Dose and Displacement Damage Compendium of Candidate Electronics for NASA Space Systems

Science.gov (United States)

Cochran, Donna J.; Boutte, Alvin J.; Campola, Michael J.; Carts, Martin A.; Casey, Megan C.; Chen, Dakai; LaBel, Kenneth A.; Ladbury, Raymond L.; Lauenstein, Jean-Marie; Marshall, Cheryl J.;

Foundations of ionizing radiation dosimetry

International Nuclear Information System (INIS)

Denisenko, O.N.; Pereslegin, I.A.

1985-01-01

Foundations of dosimetry in application to radiotherapy are presented. General characteristics of ionizing radiations and main characteristics of ionizing radiation sources, mostly used in radiotherapy, are given. Values and units for measuring ionizing radiation (activity of a radioactive substance, absorbed dose, exposure dose, integral dose and dose equivalent are considered. Different methods and instruments for ionizing radiation dosimetry are discussed. The attention is paid to the foundations of clinical dosimetry (representation of anatomo-topographic information, choice of radiation conditions, realization of radiation methods, corrections for a configuration and inhomogeneity of a patient's body, account of biological factors of radiation effects, instruments of dose field formation, control of irradiation procedure chosen)

Low doses of ionizing radiation: Biological effects and regulatory control. Contributed papers

International Nuclear Information System (INIS)

1997-11-01

The International Atomic Energy Agency and the World Health Organization, in cooperation with the United Nations Scientific Committee on the Effects of Atomic Radiation, organized an international conference on Low Doses of Ionizing Radiation: Biological Effects and Regulatory Control, held in seville, Spain, from 17 to 21 November 1997. This technical document contains concise papers submitted to the conference

High Total Ionizing Dose and Temperature Effects on Micro- and Nano-electronic Devices

International Nuclear Information System (INIS)

Gaillardin, M.; Martinez, M.; Paillet, P.; Leray, J.L.; Marcandella, C.; Duhamel, O.; Raine, M.; Richard, N.; Girard, S.; Ouerdane, Y.; Boukenter, A.; Goiffon, V.; Magnan, P.; Andrieu, F.; Barraud, S.; Faynot, O.

2013-06-01

This paper investigates the vulnerability of several micro- and nano-electronic technologies to a mixed harsh environment including high total ionizing dose at MGy levels and high temperature. Such operating conditions have been revealed recently for several applications like new security systems in existing or future nuclear power plants, fusion experiments, or deep space missions. In this work, the competing effects already reported in literature of ionizing radiations and temperature are characterized in elementary devices made of MOS transistors from several technologies. First, devices are irradiated using a radiation laboratory X-ray source up to MGy dose levels at room temperature. Devices are grounded during irradiation to simulate a circuit which waits for a wake up signal, representing most of the lifetime of an integrated circuit operating in a harsh environment. Devices are then annealed at several temperatures to discuss the post-irradiation behavior and to determine whether an elevated temperature is an issue or not for circuit function in mixed harsh environments. (authors)

High dose rate (HDR) and low dose rate (LDR) interstitial irradiation (IRT) of the rat spinal cord

International Nuclear Information System (INIS)

Pop, Lucas A.M.; Plas, Mirjam van der; Skwarchuk, Mark W.; Hanssen, Alex E.J.; Kogel, Albert J. van der

1997-01-01

Purpose: To describe a newly developed technique to study radiation tolerance of rat spinal cord to continuous interstitial irradiation (IRT) at different dose rates. Material and methods: Two parallel catheters are inserted just laterally on each side of the vertebral bodies from the level of Th 10 to L 4 . These catheters are afterloaded with two 192 Ir wires of 4 cm length each (activity 1-2.3 mCi/cm) for the low dose rate (LDR) IRT or connected to the HDR micro-Selectron for the high dose rate (HDR) IRT. Spinal cord target volume is located at the level of Th 12 -L 2 . Due to the rapid dose fall-off around the implanted sources, a dose inhomogeneity across the spinal cord thickness is obtained in the dorso-ventral direction. Using the 100% reference dose (rate) at the ventral side of the spinal cord to prescribe the dose, experiments have been carried out to obtain complete dose response curves at average dose rates of 0.49, 0.96 and 120 Gy/h. Paralysis of the hind-legs after 5-6 months and histopathological examination of the spinal cord of each irradiated rat are used as experimental endpoints. Results: The histopathological damage seen after irradiation is clearly reflected the inhomogeneous dose distribution around the implanted catheters, with the damage predominantly located in the dorsal tract of the cord or dorsal roots. With each reduction in average dose rate, spinal cord radiation tolerance is significantly increased. When the dose is prescribed at the 100% reference dose rate, the ED 50 (induction of paresis in 50% of the animals) for the HDR-IRT is 17.3 Gy. If the average dose rate is reduced from 120 Gy/h to 0.96 or 0.49 Gy/h, a 2.9- or 4.7-fold increase in the ED 50 values to 50.3 Gy and 80.9 Gy is observed; for the dose prescribed at the 150% reference dose rate (dorsal side of cord) ED 50 values are 26.0, 75.5 and 121.4 Gy, respectively. Using different types of analysis and in dependence of the dose prescription and reference dose rate, the �

Dosimetry of ionizing radiation

International Nuclear Information System (INIS)

Musilek, L.; Seda, J.; Trousil, J.

1992-01-01

The publication deals with a major field of ionizing radiation dosimetry, viz., integrating dosimetric methods, which are the basic means of operative dose determination. It is divided into the following sections: physical and chemical effects of ionizing radiation; integrating dosimetric methods for low radiation doses (film dosimetry, nuclear emulsions, thermoluminescence, radiophotoluminescence, solid-state track detectors, integrating ionization dosemeters); dosimetry of high ionizing radiation doses (chemical dosimetric methods, dosemeters based on the coloring effect, activation detectors); additional methods applicable to integrating dosimetry (exoelectron emission, electron spin resonance, lyoluminescence, etc.); and calibration techniques for dosimetric instrumentation. (Z.S.). 422 refs

Atmospheric Ionizing Radiation (AIR) ER-2 Preflight Analysis

Science.gov (United States)

Tai, Hsiang; Wilson, John W.; Maiden, D. L.

1998-01-01

Atmospheric ionizing radiation (AIR) produces chemically active radicals in biological tissues that alter the cell function or result in cell death. The AIR ER-2 flight measurements will enable scientists to study the radiation risk associated with the high-altitude operation of a commercial supersonic transport. The ER-2 radiation measurement flights will follow predetermined, carefully chosen courses to provide an appropriate database matrix which will enable the evaluation of predictive modeling techniques. Explicit scientific results such as dose rate, dose equivalent rate, magnetic cutoff, neutron flux, and air ionization rate associated with those flights are predicted by using the AIR model. Through these flight experiments, we will further increase our knowledge and understanding of the AIR environment and our ability to assess the risk from the associated hazard.

Gamma dose rate effect on JFET transistors

International Nuclear Information System (INIS)

Assaf, J.

2011-04-01

The effect of Gamma dose rate on JFET transistors is presented. The irradiation was accomplished at the following available dose rates: 1, 2.38, 5, 10 , 17 and 19 kGy/h at a constant dose of 600 kGy. A non proportional relationship between the noise and dose rate in the medium range (between 2.38 and 5 kGy/h) was observed. While in the low and high ranges, the noise was proportional to the dose rate as the case of the dose effect. This may be explained as follows: the obtained result is considered as the yield of a competition between many reactions and events which are dependent on the dose rate. At a given values of that events parameters, a proportional or a non proportional dose rate effects are generated. No dependence effects between the dose rate and thermal annealing recovery after irradiation was observed . (author)

Long-term biological effects induced by ionizing radiation--implications for dose mediated risk.

Science.gov (United States)

Miron, S D; Astărăstoae, V

2014-01-01

Ionizing radiations are considered to be risk agents that are responsible for the effects on interaction with living matter. The occurring biological effects are due to various factors such as: dose, type of radiation, exposure time, type of biological tissue, health condition and the age of the person exposed. The mechanisms involved in the direct modifications of nuclear DNA and mitochondrial DNA are reviewed. Classical target theory of energy deposition in the nucleus that causes DNA damages, in particular DNA double-strand breaks and that explanation of the biological consequences of ionizing radiation exposure is a paradigm in radiobiology. Recent experimental evidences have demonstrated the existence of a molecular mechanism that explains the non-targeted effects of ionizing radiation exposure. Among these novel data, genomic instability and a variety of bystander effects are discussed here. Those bystander effects of ionizing radiation are fulfilled by cellular communication systems that give rise to non-targeted effects in the neighboring non irradiated cells. This paper provides also a commentary on the synergistic effects induced by the co-exposures to ionizing radiation and various physical agents such as electromagnetic fields and the co-exposures to ionizing radiation and chemical environmental contaminants such as metals. The biological effects of multiple stressors on genomic instability and bystander effects are also discussed. Moreover, a brief presentation of the methods used to characterize cyto- and genotoxic damages is offered.

Biological influence from low dose and low-dose rate radiation

International Nuclear Information System (INIS)

Magae, Junji

2007-01-01

Although living organisms have defense mechanisms for radioadaptive response, the influence is considered to vary qualitatively and quantitatively for low dose and high dose, as well as for low-dose rate and high-dose rate. This article describes the bioresponse to low dose and low-dose rate. Among various biomolecules, DNA is the most sensitive to radiation, and accurate replication of DNA is an essential requirement for the survival of living organisms. Also, the influence of active enzymes resulted from the effect of radiation on enzymes in the body is larger than the direct influence of radiation on the body. After this, the article describes the carcinogenic risk by low-dose radiation, and then so-called Hormesis effect to create cancer inhibition effect by stimulating active physiology. (S.K.)

Epidemiological studies on disturbances of human fetal development in areas with various doses of natural background radiation. I. Relationship between incidences of Down's syndrome or visible malformation and gonad dose equivalent rate of natural background radiation

International Nuclear Information System (INIS)

Ujeno, Y.

1985-01-01

The relationship between environmental radiation to the gonads and incidences of Down's syndrome and visible malformation was analyzed using Kendall's rank correlation method. The subjects, studied during a 3-yr period (1979-1981), were inhabitants of 46 prefectures in Japan that had various dose rates of natural background ionizing radiation. Results showed that the natural background very low-dose radiation rate was not a predominant factor responsible for inducing Down's syndrome or other visible malformations

Dose rate measuring device and dose rate measuring method using the same

International Nuclear Information System (INIS)

Urata, Megumu; Matsushita, Takashi; Hanazawa, Sadao; Konno, Takahiro; Chiba, Yoshinori; Yumitate, Tadahiro

1998-01-01

The device of the present invention comprises a scintillation fiber scope having a shape elongated in the direction of the height of a pressure vessel and emitting light by incident of radiation to detect radiation, a radioactivity measuring device for measuring a dose rate based on the detection of the fiber scope and a reel means for dispensing and taking up the fiber scope, and it constituted such that the dose rate of the pressure vessel and that of a shroud are determined independently. Then, when the taken out shroud is contained in an container, excessive shielding is not necessary, in addition, this device can reliably be inserted to or withdrawn from complicated places between the pressure vessel and the shroud, and further, the dose rate of the pressure vessel and that of the shroud can be measured approximately accurately even when the thickness of them is different greatly. (N.H.)

Dose rate measuring device and dose rate measuring method using the same

Energy Technology Data Exchange (ETDEWEB)

Urata, Megumu; Matsushita, Takashi; Hanazawa, Sadao; Konno, Takahiro; Chiba, Yoshinori; Yumitate, Tadahiro

1998-11-13

The device of the present invention comprises a scintillation fiber scope having a shape elongated in the direction of the height of a pressure vessel and emitting light by incident of radiation to detect radiation, a radioactivity measuring device for measuring a dose rate based on the detection of the fiber scope and a reel means for dispensing and taking up the fiber scope, and it constituted such that the dose rate of the pressure vessel and that of a shroud are determined independently. Then, when the taken out shroud is contained in an container, excessive shielding is not necessary, in addition, this device can reliably be inserted to or withdrawn from complicated places between the pressure vessel and the shroud, and further, the dose rate of the pressure vessel and that of the shroud can be measured approximately accurately even when the thickness of them is different greatly. (N.H.)

Ion collection efficiency of ionization chambers in electron beams

International Nuclear Information System (INIS)

Garcia, S.; Cecatti, E.R.

1984-01-01

When ionization chambers are used in pulsed radiation beams the high-density of ions produced per pulse permits ion recombination, demanding the use of a correction factor. An experimental technique using the charge collected at two different voltages permits the calculation of the ion collection efficiency. The ion collection efficiency of some common ionization chambers in pulsed electron beams were studied as a function of electron energy, dose rate and depth. Accelerators with magnetic scanning system, in which the instantaneous dose rate is much greater than the average dose rate, present a smaller collection efficiency than accelerators with scattering foil. The results lead to the introduction of a correction factor for ion recombination that is the reciprocal of the ion collection efficiency. It is also suggested a simple technique to connect an external variable DC power supply in a Baldwin Farmer dosemeter. (Author) [pt

Low dose rate and high dose rate intracavitary treatment for cervical cancer

International Nuclear Information System (INIS)

Hareyama, Masato; Oouchi, Atsushi; Shidou, Mitsuo

1997-01-01

From 1984 through 1993, 144 previous untreated patients with carcinoma of uterine cervix were treated with either low dose rate 137 Cs therapy (LDR) or high dose rate 60 Co therapy (HDR). The local failure rates for more than 2-years for the primary lesions were 11.8% (8 of 63 patients) for LDR and 18.0% (11 of 61 patients). Rectal complication rates were significantly lower for HDR versus LDR (14.3% VS. 32.8%. p<0.01). Also, bladder complication rates were significantly lower for HDR versus LDR (0% VS. 10.4%, p<0.005). Treatment results in term of local control were equivalent for HDR and LDR treatment. However, the incidence of complications was higher for the LDR group than for the HDR group. (author)

Influence mechanism of low-dose ionizing radiation on Escherichia coli DH5α population based on plasma theory and system dynamics simulation.

Science.gov (United States)

Sun, Yi; Hu, Dawei; Li, Liang; Jing, Zheng; Wei, Chuanfeng; Zhang, Lantao; Fu, Yuming; Liu, Hong

2016-01-01

It remains a mystery why the growth rate of bacteria is higher in low-dose ionizing radiation (LDIR) environment than that in normal environment. In this study, a hypothesis composed of environmental selection and competitive exclusion was firstly proposed from observed phenomena, experimental data and microbial ecology. Then a LDIR environment simulator (LDIRES) was built to cultivate a model organism of bacteria, Escherichia coli (E. coli) DH5α, the accurate response of bacterial population to ionizing radiation intensity variation was measured experimentally, and then the precise relative dosage of ionizing radiation E. coli DH5α population received was calculated by finite element analysis based on drift-diffusion equations of plasma. Finally, a highly valid mathematical model expressing the relationship between E. coli DH5α population and LDIR intensity was developed by system dynamics based on hypotheses, experimental data and microbial ecology. Both experiment and simulation results clearly showed that the E. coli DH5α individuals with greater specific growth rate and lower substrate consumption coefficient would adapt and survive in LDIR environment and those without such adaptability were finally eliminated under the combined effects of ionizing radiation selection and competitive exclusion. Copyright © 2015 Elsevier Ltd. All rights reserved.

Structure factors for tunneling ionization rates of molecules

DEFF Research Database (Denmark)

Madsen, L.B.; Jensen, F.; Tolstikhin, O.I.

2013-01-01

Within the weak-field asymptotic theory, the dependence of the tunneling ionization rate of a molecule in a static electric field on its orientation with respect to the field is determined by the structure factor for the highest occupied molecular orbital (HOMO). An accurate determination...

Low doses of ionizing radiation: Biological effects and regulatory control. Contributed papers

Energy Technology Data Exchange (ETDEWEB)

NONE

1997-11-01

The International Atomic Energy Agency and the World Health Organization, in cooperation with the United Nations Scientific Committee on the Effects of Atomic Radiation, organized an international conference on Low Doses of Ionizing Radiation: Biological Effects and Regulatory Control, held in seville, Spain, from 17 to 21 November 1997. This technical document contains concise papers submitted to the conference. Refs, figs, tabs.

Dependence of total dose response of bipolar linear microcircuits on applied dose rate

International Nuclear Information System (INIS)

McClure, S.; Will, W.; Perry, G.; Pease, R.L.

1994-01-01

The effect of dose rate on the total dose radiation hardness of three commercial bipolar linear microcircuits is investigated. Total dose tests of linear bipolar microcircuits show larger degradation at 0.167 rad/s than at 90 rad/s even after the high dose rate test is followed by a room temperature plus a 100 C anneal. No systematic correlation could be found for degradation at low dose rate versus high dose rate and anneal. Comparison of the low dose rate with the high dose rate anneal data indicates that MIL-STD-883, method 1019.4 is not a worst-case test method when applied to bipolar microcircuits for low dose rate space applications

Compendium of Current Total Ionizing Dose and Displacement Damage Results from NASA GSFC and NEPP

Science.gov (United States)

Topper, Alyson D.; Campola, Michael J.; Chen, Dakai; Casey, Megan C.; Yau, Ka-Yen; Label, Kenneth A.; Cochran, Donna J.; O'Bryan, Martha V.

2017-01-01

Total ionizing dose and displacement damage testing was performed to characterize and determine the suitability of candidate electronics for NASA space utilization. Devices tested include opto-electronics, digital, analog, linear bipolar devices, and hybrid devices.

Effect of low dose ionizing radiation upon concentration of

International Nuclear Information System (INIS)

Viliae, M.; Kraljeviae, P.; Simpraga, M.; Miljaniae, S.

2004-01-01

It is known that low dose ionizing radiation might have stimulating effects (Luckey, 1982, Kraljeviae, 1988). This fact has also been confirmed in the previous papers of Kraljeviae et al. (2000-2000a; 2001). Namely, those authors showed that irradiation of chicken eggs before incubation by a low dose of 0.15 Gy gamma radiation increases the activity aspartateaminotrasferases (AST) and alanine-aminotransferases (ALT) in blood plasma of chickens hatched from irradiated eggs, as well as growth of chickens during the fattening period. Low doses might also cause changes in the concentration of some biochemical parameters in blood plasma of the same chickens such as changes in the concentration of total proteins, glucose and cholesterol. In this paper, an attempt was made to investigate the effects of low dose gamma radiation upon the concentration of sodium and potassium in the blood plasma of chickens which were hatched from eggs irradiated on the 19th day of incubation by dose of 0.15 Gy. Obtained results were compared with the results from the control group (chickens hatched from nonirradiated eggs). After hatching, all other conditions were the same for both groups. Blood samples were drawn from heart, and later from the wing vein on days 1, 3, 5, 7, 10, 20, 30 and 42. The concentration of sodium and potassium was determined spectrophotometrically by atomic absorbing spectrophotometer Perkin-Elmer 1100B. The concentration of sodium and potassium in blood plasma of chickens hatched from eggs irradiated on the 19th day of incubation by dose of 0.15 Gy indicated a statistically significant increase (P>0.01) only on the first day of the experiment. Obtained results showed that irradiation of eggs on the 19th day of incubation by dose of 0.15 Gy gamma radiation could have effects upon the metabolism of electrolytes in chickens. (Author)

Clustered DNA damages induced in isolated DNA and in human cells by low doses of ionizing radiation

Science.gov (United States)

Sutherland, B. M.; Bennett, P. V.; Sidorkina, O.; Laval, J.; Lowenstein, D. I. (Principal Investigator)

2000-01-01

Clustered DNA damages-two or more closely spaced damages (strand breaks, abasic sites, or oxidized bases) on opposing strands-are suspects as critical lesions producing lethal and mutagenic effects of ionizing radiation. However, as a result of the lack of methods for measuring damage clusters induced by ionizing radiation in genomic DNA, neither the frequencies of their production by physiological doses of radiation, nor their repairability, nor their biological effects are known. On the basis of methods that we developed for quantitating damages in large DNAs, we have devised and validated a way of measuring ionizing radiation-induced clustered lesions in genomic DNA, including DNA from human cells. DNA is treated with an endonuclease that induces a single-strand cleavage at an oxidized base or abasic site. If there are two closely spaced damages on opposing strands, such cleavage will reduce the size of the DNA on a nondenaturing gel. We show that ionizing radiation does induce clustered DNA damages containing abasic sites, oxidized purines, or oxidized pyrimidines. Further, the frequency of each of these cluster classes is comparable to that of frank double-strand breaks; among all complex damages induced by ionizing radiation, double-strand breaks are only about 20%, with other clustered damage constituting some 80%. We also show that even low doses (0.1-1 Gy) of high linear energy transfer ionizing radiation induce clustered damages in human cells.

Compendium of Current Total Ionizing Dose and Displacement Damage Results from NASA Goddard Space Flight Center and NASA Electronic Parts and Packaging Program

Science.gov (United States)

Topper, Alyson D.; Campola, Michael J.; Chen, Dakai; Casey, Megan C.; Yau, Ka-Yen; Cochran, Donna J.; Label, Kenneth A.; Ladbury, Raymond L.; Mondy, Timothy K.; O'Bryan, Martha V.;

Assessment of health risks from exposure to ionizing radiation

International Nuclear Information System (INIS)

Beebe, G.W.

1982-01-01

Rapid development in the assessment of health risks from exposure to ionizing radiation has produced an impressive array of risk differentials of presumed biologic significance. In the human data these differentials involve: (1) the variety of cancer, especially its size; (2) host factors, especially age; (3) time following exposure; (4) magnitude of dose; and (5) type of radiation. From experimental work we may presume that dose-rate also plays a role, especially for sparsely ionizing radiation. Current research is extending the scope of differentials with respect to these and other variables, including cell type and concomitant environmental risk factors, and testing dose-response models suggested by experimental and theoretical work. As facts to be explained, differentials in risk may lead to hypotheses to be explored experimentally and improve our understanding of how ionizing radiation causes cancer. 74 references

Brachytherapy for early oral tongue cancer. Low dose rate to high dose rate

International Nuclear Information System (INIS)

Yamazaki, Hideya; Inoue, Takehiro; Yoshida, Ken; Yoshioka, Yasuo; Shimizutani, Kimishige; Inoue, Toshihiko; Furukawa, Souhei; Kakimoto, Naoya

2003-01-01

To examine the compatibility of low dose rate (LDR) with high dose rate (HDR) brachytherapy, we reviewed 399 patients with early oral tongue cancer (T1-2N0M0) treated solely by brachytherapy at Osaka University Hospital between 1967 and 1999. For patients in the LDR group (n=341), the treatment sources consisted of Ir-192 pin for 227 patients (1973-1996; irradiated dose, 61-85 Gy; median, 70 Gy), Ra-226 needle for 113 patients (1967-1986; 55-93 Gy; median, 70 Gy). Ra-226 and Ir-192 were combined for one patient. Ir-192 HDR (microSelectron-HDR) was used for 58 patients in the HDR group (1991-present; 48-60 Gy; median, 60 Gy). LDR implantations were performed via oral and HDR via a submental/submandibular approach. The dose rates at the reference point for the LDR group were 0.30 to 0.8 Gy/h, and for the HDR group 1.0 to 3.4 Gy/min. The patients in the HDR group received a total dose of 48-60 Gy (8-10 fractions) during one week. Two fractions were administered per day (at least a 6-h interval). The 3- and 5-year local control rates for patients in the LDR group were 85% and 80%, respectively, and those in the HDR group were both 84%. HDR brachytherapy showed the same lymph-node control rate as did LDR brachytherapy (67% at 5 years). HDR brachytherapy achieved the same locoregional result as did LDR brachytherapy. A converting factor of 0.86 is applicable for HDR in the treatment of early oral tongue cancer. (author)

Studies of absorbed dose determinations and spatial dose distributions for high energy proton beams

International Nuclear Information System (INIS)

Hiraoka, Takeshi

1982-01-01

Absolute dose determinations were made with three types of ionization chamber and a Faraday cup. Methane based tissue equivalent (TE) gas, nitrogen, carbon dioxide, air were used as an ionizing gas with flow rate of 10 ml per minute. Measurements were made at the entrance position of unmodulated beams and for a beam of a spread out Bragg peak at a depth of 17.3 mm in water. For both positions, the mean value of dose determined by the ionization chambers was 0.993 +- 0.014 cGy for which the value of TE gas was taken as unity. The agreement between the doses estimated by the ionization chambers and the Faraday cup was within 5%. Total uncertainty estimated in the ionization chamber and the Faraday cup determinations is 6 and 4%, respectively. Common sources of error in calculating the dose from ionization chamber measurements are depend on the factors of ion recombination, W value, and mass stopping power ratio. These factors were studied by both experimentally and theoretically. The observed values for the factors show a good agreement to the predicted one. Proton beam dosimetry intercomparison between Japan and the United States was held. Good agreement was obtained with standard deviation of 1.6%. The value of the TE calorimeter is close to the mean value of all. In the proton spot scanning system, lateral dose distributions at any depth for one spot beam can be simulated by the Gaussian distribution. From the Gaussian distributions and the central axis depth doses for one spot beam, it is easy to calculate isodose distributions in the desired field by superposition of dose distribution for one spot beam. Calculated and observed isodose curves were agreed within 1 mm at any dose levels. (J.P.N.)

Radiology Residents' Awareness about Ionizing Radiation Doses in Imaging Studies and Their Cancer Risk during Radiological Examinations

International Nuclear Information System (INIS)

Goekce, Senem Divrik; Gekce, Erkan; Coskun, Melek

2012-01-01

Imaging methods that use ionizing radiation have been more frequent in various medical fields with advances in imaging technology. The aim of our study was to make residents be aware of the radiation dose they are subjected to when they conduct radiological imaging methods, and of cancer risk. A total of 364 residents participated in this descriptive study which was conducted during the period between October, 2008 and January, 2009. The questionnaires were completed under strict control on a one-to-one basis from each department. A X 2 -test was used for the evaluation of data obtained. Only 7% of residents correctly answered to the question about the ionizing radiation dose of a posteroanterior (PA) chest X-ray. The question asking about the equivalent number of PA chest X-rays to the ionizing dose of a brain CT was answered correctly by 24% of residents; the same question regarding abdominal CT was answered correctly by 16% of residents, thorax CT by 16%, thyroid scintigraphy by 15%, intravenous pyelography by 9%, and lumbar spine radiography by 2%. The risk of developing a cancer throughout lifetime by a brain and abdominal CT were 33% and 28%, respectively. Radiologic residents should have updated knowledge about radiation dose content and attendant cancer risks of various radiological imaging methods during both basic medical training period and following practice period.

Radiation safety program in a high dose rate brachytherapy facility

International Nuclear Information System (INIS)

Rodriguez, L.V.; Hermoso, T.M.; Solis, R.C.

2001-01-01

The use of remote afterloading equipment has been developed to improve radiation safety in the delivery of treatment in brachytherapy. Several accidents, however, have been reported involving high dose-rate brachytherapy system. These events, together with the desire to address the concerns of radiation workers, and the anticipated adoption of the International Basic Safety Standards for Protection Against Ionizing Radiation (IAEA, 1996), led to the development of the radiation safety program at the Department of Radiotherapy, Jose R. Reyes Memorial Medical Center and at the Division of Radiation Oncology, St. Luke's Medical Center. The radiation safety program covers five major aspects: quality control/quality assurance, radiation monitoring, preventive maintenance, administrative measures and quality audit. Measures for evaluation of effectiveness of the program include decreased unnecessary exposures of patients and staff, improved accuracy in treatment delivery and increased department efficiency due to the development of staff vigilance and decreased anxiety. The success in the implementation required the participation and cooperation of all the personnel involved in the procedures and strong management support. This paper will discuss the radiation safety program for a high dose rate brachytherapy facility developed at these two institutes which may serve as a guideline for other hospitals intending to install a similar facility. (author)

The study of hemopoietic cells. Effect of prolonged irradiation by low dose rate radiation on the hemopoiesis in the spleen of mice

Energy Technology Data Exchange (ETDEWEB)

Shirata, Katsutoshi; Yanai, Takanori; Yamada, Yutaka; Saitou, Mikio; Izumi, Jun; Tanaka, Satoshi; Otsu, Hiroshi; Sato, Fumiaki [Inst. for Environmental Sciences, Dept. of Radiobiology, Rokkasho, Aomori (Japan)

2001-07-01

For evaluation of effects of prolonged irradiation by low dose-rate ionizing radiation on the hemopoiesis of mice, SPF C3H/HeN female mice were irradiated with {sup 137}Cs {gamma}-rays with doses of 5-8 Gy at the dose rate of 20 mGy/22h-day. After irradiation, the number of hemopoietic cells contained in spleen was determined by the methods of CFU-S and CFU-GM assays, and the number of peripheral blood cells was counted. It was shown that the number of hemopoietic cells (CFU-S colonies and CFU-GM colonies) decreased as dose increased. No remarkable changes in the number of peripheral blood cells, however, were observed. (author)

Ionizing radiation biomarkers for potential use in epidemiological studies

International Nuclear Information System (INIS)

Pernot, Eileen; Cardis, Elisabeth; Hall, Janet; Baatout, Sarah; El Saghire, Houssein; Mohammed Abderrafi Benotmane; Roel Quintens; Blanchardon, Eric; Bouffler, Simon; Gomolka, Maria; Guertler, Anne; Kreuzer, Michaela; Harms-Ringdahl, Mats; Jeggo, Penny; Laurier, Dominique; Lindholm, Carita; Mkacher, Radhia; Sabatier, Laure; Tapio, Soile; De Vathaire, Florent

2012-01-01

Ionizing radiation is a known human carcinogen that can induce a variety of biological effects depending on the physical nature, duration, doses and dose-rates of exposure. However, the magnitude of health risks at low doses and dose-rates (below 100 mSv and/or 0.1 mSv min -1 ) remains controversial due to a lack of direct human evidence. It is anticipated that significant insights will emerge from the integration of epidemiological and biological research, made possible by molecular epidemiology studies incorporating biomarkers and bioassays. A number of these have been used to investigate exposure, effects and susceptibility to ionizing radiation, albeit often at higher doses and dose rates, with each reflecting time-limited cellular or physiological alterations. This review summarises the multidisciplinary work undertaken in the framework of the European project DoReMi (Low Dose Research towards Multidisciplinary Integration) to identify the most appropriate biomarkers for use in population studies. In addition to logistical and ethical considerations for conducting large-scale epidemiological studies, we discuss the relevance of their use for assessing the effects of low dose ionizing radiation exposure at the cellular and physiological level. We also propose a temporal classification of biomarkers that may be relevant for molecular epidemiology studies which need to take into account the time elapsed since exposure. Finally, the integration of biology with epidemiology requires careful planning and enhanced discussions between the epidemiology, biology and dosimetry communities in order to determine the most important questions to be addressed in light of pragmatic considerations including the appropriate population to be investigated (occupationally, environmentally or medically exposed), and study design. The consideration of the logistics of biological sample collection, processing and storing and the choice of biomarker or bioassay, as well as awareness of

Biological effects of ionizing radiation

International Nuclear Information System (INIS)

Gisone, Pablo; Perez, Maria R.

2001-01-01

It has been emphasised the importance of DNA as the main target for ionizing radiation, that can induce damage by its direct action on this molecule or by an indirect effect mediated by free-radicals generated by water radiolysis. Biological effects of ionizing radiation are influenced not only by the dose but also by the dose-rate and the radiation quality. Radiation induced damage, mainly DNA single and double strand breaks, is detected by molecular sensors which in turn trigger signalling cascades leading to cell cycle arrest to allow DNA repair or programmed cell death (apoptosis). Those effects related with cell death, named deterministic, exhibits a dose-threshold below which they are not observed. Acute radiation syndrome and radiological burns are examples of this kind of effects. Other radiation induced effects, called stochastic, are the consequence of cell transformation and do not exhibit a dose-threshold. This is the case of cancer induction and hereditary effects. The aim of this presentation is briefly describe the main aspects of deterministic and stochastic effects from the point of view of radiobiology and radio pathology. (author)

Dose Rate Effects in Linear Bipolar Transistors

Science.gov (United States)

Johnston, Allan; Swimm, Randall; Harris, R. D.; Thorbourn, Dennis

2011-01-01

Dose rate effects are examined in linear bipolar transistors at high and low dose rates. At high dose rates, approximately 50% of the damage anneals at room temperature, even though these devices exhibit enhanced damage at low dose rate. The unexpected recovery of a significant fraction of the damage after tests at high dose rate requires changes in existing test standards. Tests at low temperature with a one-second radiation pulse width show that damage continues to increase for more than 3000 seconds afterward, consistent with predictions of the CTRW model for oxides with a thickness of 700 nm.

Dose rate visualization of radioisotope thermoelectric generators

International Nuclear Information System (INIS)

Schwarz, R.A.; Kessler, S.F.; Tomaszewski, T.A.

1995-09-01

Advanced visualization techniques can be used to investigate gamma ray and neutron dose rates around complex dose rate intensive operations. A method has been developed where thousands of dose points are calculated using the MCNP(Monte Carlo N-Particle) computer code and then displayed to create color contour plots of the dose rate for complex geometries. Once these contour plots are created, they are sequenced together creating an animation to dynamically show how the dose rate changes with changes in the geometry or source over time

Biological responses to low dose rate gamma radiation

International Nuclear Information System (INIS)

Magae, Junji; Ogata, Hiromitsu

2003-01-01

Linear non-threshold (LNT) theory is a basic theory for radioprotection. While LNT dose not consider irradiation time or dose-rate, biological responses to radiation are complex processes dependent on irradiation time as well as total dose. Moreover, experimental and epidemiological studies that can evaluate LNT at low dose/low dose-rate are not sufficiently accumulated. Here we analyzed quantitative relationship among dose, dose-rate and irradiation time using chromosomal breakage and proliferation inhibition of human cells as indicators of biological responses. We also acquired quantitative data at low doses that can evaluate adaptability of LNT with statistically sufficient accuracy. Our results demonstrate that biological responses at low dose-rate are remarkably affected by exposure time, and they are dependent on dose-rate rather than total dose in long-term irradiation. We also found that change of biological responses at low dose was not linearly correlated to dose. These results suggest that it is necessary for us to create a new model which sufficiently includes dose-rate effect and correctly fits of actual experimental and epidemiological results to evaluate risk of radiation at low dose/low dose-rate. (author)

Review of low dose-rate epidemiological studies and biological mechanisms of dose-rate effects on radiation induced carcinogenesis

International Nuclear Information System (INIS)

Iwasaki, Toshiyasu; Otsuka, Kensuke; Yoshida, Kazuo

2015-01-01

Radiation protection system adopts the linear non-threshold model with using dose and dose-rate effectiveness factor (DDREF). The dose-rate range where DDREF is applied is below 100 mGy per hour, and it is regarded that there are no dose-rate effects at very low dose rate, less than of the order of 10 mGy per year, even from the biological risk evaluation model based on cellular and molecular level mechanisms for maintenance of genetic integrity. Among low dose-rate epidemiological studies, studies of residents in high natural background areas showed no increase of cancer risks at less than about 10 mGy per year. On the other hand, some studies include a study of the Techa River cohort suggested the increase of cancer risks to the similar degree of Atomic bomb survivor data. The difference of those results was supposed due to the difference of dose rate. In 2014, International Commission on Radiological Protection opened a draft report on stem cell biology for public consultations. The report proposed a hypothesis based on the new idea of stem cell competition as a tissue level quality control mechanism, and suggested that it could explain the dose-rate effects around a few milligray per year. To verify this hypothesis, it would be needed to clarify the existence and the lowest dose of radiation-induced stem cell competition, and to elucidate the rate of stem cell turnover and radiation effects on it. As for the turnover, replenishment of damaged stem cells would be the important biological process. It would be meaningful to collect the information to show the difference of dose rates where the competition and the replenishment would be the predominant processes. (author)

Dose rate visualization of radioisotope thermoelectric generators

International Nuclear Information System (INIS)

Schwarz, R.A.; Kessler, S.F.; Tomaszewski, T.A.

1996-01-01

Advanced visualization techniques can be used to investigate gamma ray and neutron dose rates around complex dose rate intensive operations. A method has been developed where thousands of dose points are calculated using the MCNP (Monte Carlo N-Particle) computer code (Briesmeister 1993) and then displayed to create color contour plots of the dose rate for complex geometries. Once these contour plots are created, they are sequenced together creating an animation to dynamically show how the dose rate changes with changes in the geometry or source over time. copyright 1996 American Institute of Physics

Decomposition of persistent pharmaceuticals in wastewater by ionizing radiation

Science.gov (United States)

Kimura, Atsushi; Osawa, Misako; Taguchi, Mitsumasa

2012-09-01

Pharmaceuticals in wastewater were treated by the combined method of activated sludge and ionizing radiation in laboratory scale. Oseltamivir, aspirin, and ibuprofen at 5 μmol dm-3 in wastewater were decomposed by the activated sludge at reaction time for 4 h. Carbamazepine, ketoprofen, mefenamic acid, clofibric acid, and diclofenac were not biodegraded completely, but were eliminated by γ-ray irradiation at 2 kGy. The rate constants of the reactions of these pharmaceuticals with hydroxyl radicals were estimated by the competition reaction method to be 4.0-10×109 mol-1 dm3 s-1. Decompositions of the pharmaceuticals in wastewater by ionizing radiation were simulated by use of the rate constants and the amount of total organic carbon as parameters. Simulation curves of concentrations of these pharmaceuticals as a function of dose described the experimental data, and the required dose for the elimination of them in wastewater by ionizing radiation can be estimated by this simulation.

The effects of ionizing radiation on man

International Nuclear Information System (INIS)

Watson, G.M.

1975-08-01

This paper describes the major effects of ionizing radiation on man and the relationship between such effects and radiation dose, with the conclusion that standards of radiological safety must be based on the carcinogenetic and mutagenic properties of ionizing radiation. Man is exposed to radiation from natural sources and from man-made sources. Exposure from the latter should be regulated but, since there is little observational or experimental evidence for predicting the effects of the very small doses likely to be required for adequate standards of safety, it is necessary to infer them from what is seen at high doses. Because the formal relationship between dose and effect is not fully understood, simplifying assumptions are necessary to estimate the effects of low doses. Two such assumptions are conventionally used; that there is a linear relationship between dose and effect at all levels of dose, and that the rate at which a dose of radiation is given does not alter the magnitude of the effect. These assumptions are thought to be conservative, that is they will not lead to an underestimation of the effects of small radiation doses although they may give an over-estimate. (author)

Absolute absorbed dose measurements with an array of ionization chambers as part of a routine procedure of quality control for the VMAT technique

International Nuclear Information System (INIS)

Clemente Gutierrez, F.; Cabello Murillo, E.; Ramirez Ros, J. C.; Casa de Julian, M. A. de la

2011-01-01

Arcotheraphy techniques volumetric modulated (VMAT) treatments involve continuous variation of the gantry rotation speed, positions of the sheets and dose rate. Since all treatments are administered by continuous arcs, these techniques require quality control procedures to ensure quick and easy constancy of the calibration factor (total absorbed dose) for any gantry angle. We report here a simple method of quality control for the measurement of the calibration factor using an array of ionization chambers. The measurements were performed on a unit of 6 MV Elekta Synergy with VMAT, belonging to the Radiation Oncology service of the Defense Central Hospital Gomez Ulla.

Adaptive answer to low ionizing radiation doses in Saccharomyces cerevisiae; Respuesta adaptativa a bajas dosis de radiacion ionizante en Saccharomyces cerevisiae

Energy Technology Data Exchange (ETDEWEB)

Durand, Jorge L. [Comision Nacional de Energia Atomica, San Carlos de Bariloche (Argentina). Inst. Balseiro; Frati, Diego Libkind; Broock, Maria Van [Universidad Nacional del Comahue, Bariloche (Argentina). Centro Regional Universitario Bariloche; Gillette, Victor [Comision Nacional de Energia Atomica, San Carlos de Bariloche (Argentina). Centro Atomico

2001-07-01

The aim of this work is to verify the existence of the adaptive response phenomenon induced by low doses of ionizing radiation in living cells. It is known that low doses of ionizing radiation, called conditioning doses, may induce resistance in exposed organisms to higher doses, called challenging doses, which are applied after a period of time. The involved mechanisms in this phenomenon, called Adaptive Response, are diverse and complex. Among them, the most important are the activation of DNA-repair enzymes and nuclear recombination process. As the 'target' sample, it was utilized a 'wild type' strain of Saccharomyces cerevisiae in aqueous suspension. Adaptive Response was verified in a wide range of challenging doses. Conditioning doses, inductors of radio-resistance, were (0.44{+-}0.03) Gy and the waiting time between them and challenging doses was 2 hours at room temperature.(author)

The system for automatic dose rate measurements by mobile groups in field

International Nuclear Information System (INIS)

Drabova, D.; Filgas, R.; Cespirova, I.; Ejemova, M.

1998-01-01

The comparison of characteristics between a pressurized ionization chamber, plastic scintillator and proportional counter is given. Based on requirements and comparison of properties of various probes, the system for automatic dose rate measurement and integration of geographic co-ordinates in field was designed and tested.The system consists of proportional counter. This is so-called intelligent probe can be easily connected to a personal computer. The probe measures in the energy range 30 keV - 1.3 MeV with reasonable energy and angular response, it can measure the dose rate in the range 50 nSv/h - 1 Sv/h with the typical efficiency 9.5 imp/s/μSv/h. The probe is fixed in the holder placed on the front mask of a car. For the simultaneous determination of geographical co-ordinates the personal GPS navigator Garmin 95 is used. Both devices are controlled by a notebook via two serial ports. The second serial port that is not quite common in notebook can be easily realised by a PCMCIA card. The notebook is used in the field by a mobile group can be transmitted to the assessment centre by the cellular GSM phone. The system Nokia 2110 connected to notebook by PCMCIA card is used. The whole system is powered up from the car battery. The system is controlled by specially developed software. The software was developed in the FoxPro 2.5 environment and works under MS-DOS 6.22. It has no problems to work in Windows 95 DOS window. The results of dose rate measurements obtained during route monitoring are stored in files. They can be displayed on a graphic screen, presenting the geographical distribution of the dose rate values colour coded on a map and the time sequence of the measured data. (authors)

Probing background ionization: positive streamers with varying pulse repetition rate and with a radioactive admixture

International Nuclear Information System (INIS)

Nijdam, S; Van Veldhuizen, E M; Ebert, U; Wormeester, G

2011-01-01

Positive streamers need a source of free electrons ahead of them to propagate. A streamer can supply these electrons by itself through photo-ionization, or the electrons can be present due to external background ionization. Here we investigate the effects of background ionization on streamer propagation and morphology by changing the gas composition and the repetition rate of the voltage pulses, and by adding a small amount of radioactive 85 Kr. We find that the general morphology of a positive streamer discharge in high-purity nitrogen depends on background ionization: at lower background ionization levels the streamers branch more and have a more feather-like appearance. This is observed both when varying the repetition rate and when adding 85 Kr, though side branches are longer with the radioactive admixture. But velocities and minimal diameters of streamers are virtually independent of the background ionization level. In air, the inception cloud breaks up into streamers at a smaller radius when the repetition rate and therefore the background ionization level is higher. When measuring the effects of the pulse repetition rate and of the radioactive admixture on the discharge morphology, we found that our estimates of background ionization levels are consistent with these observations; this gives confidence in the estimates. Streamer channels generally do not follow the paths of previous discharge channels for repetition rates of up to 10 Hz. We estimate the effect of recombination and diffusion of ions and free electrons from the previous discharge and conclude that the old trail has largely disappeared at the moment of the next voltage pulse; therefore the next streamers indeed cannot follow the old trail.

Radiology Residents' Awareness about Ionizing Radiation Doses in Imaging Studies and Their Cancer Risk during Radiological Examinations

Science.gov (United States)

Divrik Gökçe, Senem; Coşkun, Melek

2012-01-01

Objective Imaging methods that use ionizing radiation have been more frequent in various medical fields with advances in imaging technology. The aim of our study was to make residents be aware of the radiation dose they are subjected to when they conduct radiological imaging methods, and of cancer risk. Materials and Methods A total of 364 residents participated in this descriptive study which was conducted during the period between October, 2008 and January, 2009. The questionnaires were completed under strict control on a one-to-one basis from each department. A χ2-test was used for the evaluation of data obtained. Results Only 7% of residents correctly answered to the question about the ionizing radiation dose of a posteroanterior (PA) chest X-ray. The question asking about the equivalent number of PA chest X-rays to the ionizing dose of a brain CT was answered correctly by 24% of residents; the same question regarding abdominal CT was answered correctly by 16% of residents, thorax CT by 16%, thyroid scintigraphy by 15%, intravenous pyelography by 9%, and lumbar spine radiography by 2%. The risk of developing a cancer throughout lifetime by a brain and abdominal CT were 33% and 28%, respectively. Conclusion Radiologic residents should have updated knowledge about radiation dose content and attendant cancer risks of various radiological imaging methods during both basic medical training period and following practice period. PMID:22438688

Three-dimensional Finite Elements Method simulation of Total Ionizing Dose in 22 nm bulk nFinFETs

Energy Technology Data Exchange (ETDEWEB)

Chatzikyriakou, Eleni, E-mail: ec3g12@soton.ac.uk; Potter, Kenneth; Redman-White, William; De Groot, C.H.

2017-02-15

Highlights: • Simulation of Total Ionizing Dose using the Finite Elements Method. • Carrier generation, transport and trapping in the oxide. • Application in three-dimensional bulk FinFET model of 22 nm node. • Examination of trapped charge in the Shallow Trench Isolation. • Trapped charge dependency of parasitic transistor current. - Abstract: Finite Elements Method simulation of Total Ionizing Dose effects on 22 nm bulk Fin Field Effect Transistor (FinFET) devices using the commercial software Synopsys Sentaurus TCAD is presented. The simulation parameters are extracted by calibrating the charge trapping model to experimental results on 400 nm SiO{sub 2} capacitors irradiated under zero bias. The FinFET device characteristics are calibrated to the Intel 22 nm bulk technology. Irradiation simulations of the transistor performed with all terminals unbiased reveal increased hardness up to a total dose of 1 MRad(SiO{sub 2}).

Detection limits of absorbed dose of ionizing radiation in molluscan shells as determined by e.p.r. spectroscopy

International Nuclear Information System (INIS)

Stachowicz, W.; Michalik, J.; Burlinska, G.; Sadlo, J.; Dziedzic-Goclawska, A.; Ostrowski, K.

1995-01-01

The exposure of waters to ionizing radiation from radionuclides imprisoned in dumped nuclear waste containers, freed in nuclear submarine accidents or released in underwater magma eruptions are difficult to be evaluated by conventional radiometric methods. Ionizing radiation evokes stable paramagnetic centers in crystalline lattice of mineral components in bone skeletons of mammals and fishes as well as in exoskeletons of mollusca. They give rise in e.p.r. to specific, extremely stable signals which are proposed to be applied as indicators of radiation exposure levels. In the present study the e.p.r. detection limits of the dose of ionizing radiation absorbed in shells of fresh water and marine mollusca (selected species) have been estimated. It has been found that with fresh water mollusca the dose of 1-2 Gy can be detected, while the sea water mollusca by one order of magnitude lower, i.e. about 0.1 Gy. (author)

The effect of extreme ionization rates during the initial collapse of a molecular cloud core

Science.gov (United States)

Wurster, James; Bate, Matthew R.; Price, Daniel J.

2018-05-01

What cosmic ray ionization rate is required such that a non-ideal magnetohydrodynamics (MHD) simulation of a collapsing molecular cloud will follow the same evolutionary path as an ideal MHD simulation or as a purely hydrodynamics simulation? To investigate this question, we perform three-dimensional smoothed particle non-ideal MHD simulations of the gravitational collapse of rotating, one solar mass, magnetized molecular cloud cores, which include Ohmic resistivity, ambipolar diffusion, and the Hall effect. We assume a uniform grain size of ag = 0.1 μm, and our free parameter is the cosmic ray ionization rate, ζcr. We evolve our models, where possible, until they have produced a first hydrostatic core. Models with ζcr ≳ 10-13 s-1 are indistinguishable from ideal MHD models, and the evolution of the model with ζcr = 10-14 s-1 matches the evolution of the ideal MHD model within 1 per cent when considering maximum density, magnetic energy, and maximum magnetic field strength as a function of time; these results are independent of ag. Models with very low ionization rates (ζcr ≲ 10-24 s-1) are required to approach hydrodynamical collapse, and even lower ionization rates may be required for larger ag. Thus, it is possible to reproduce ideal MHD and purely hydrodynamical collapses using non-ideal MHD given an appropriate cosmic ray ionization rate. However, realistic cosmic ray ionization rates approach neither limit; thus, non-ideal MHD cannot be neglected in star formation simulations.

Shift in imaging modalities of the spine through 25 years and its impact on patient ionizing radiation doses

Energy Technology Data Exchange (ETDEWEB)

Borgen, Lars [Department of Radiology, Hospital of Buskerud, Dronning gaten 28, 3004 Drammen (Norway)]. E-mail: lars.borgen@sb-hf.no; Ostensen, Harald [Diagnostic Imaging and Laboratory Technology, World Health Organization, 20 Avenue Appia, CH-1211 Geneva 27 (Switzerland); Stranden, Erling [Buskerud University College, Konggate 51, 3019 Drammen (Norway); Olerud, Hilde Marie [Norwegian Radiation Protection Authority, PO Box 55, 1332 Osteras (Norway); Gudmundsen, Tor Erik [Department of Radiology, Hospital of Buskerud, Dronning gaten 28, 3004 Drammen (Norway); Buskerud University College, Konggate 51, 3019 Drammen (Norway)

2006-10-15

Study design: Retrospective. Objective: To explore the shift in modalities when diagnosing the spine in the years 1979-2003. To see how this shift, together with a radiation protective policy, have influenced on the ionizing radiation doses. Summary of background data: The shift from CT/myelography to MR when diagnosing the spine is well known. To what extent this has changed the radiation doses has to our knowledge not yet been published. Methods: Activity reports from a department of radiology have been reviewed. Relevant radiation doses estimates have been obtained from the Norwegian Radiation Protection Authority. Results: MRI was introduced in 1992 and has been used increasingly since then. Conventional X-ray to the spine has been practically unchanged. Myelography and CT decreased markedly after the introduction of MRI. The total number of examinations of the spine has increased, but the radiation doses given have decreased since 1993. Conclusions: The introduction of MRI together with a radiation protective policy have reduced the ionizing radiation doses given to this population, in spite of an increase in the total number of examinations of the spine.

The effect of low dose rate on metabolomic response to radiation in mice

International Nuclear Information System (INIS)

Goudarzi, Maryam; Mak, Tytus D.; Chen, Congju; Smilenov, Lubomir B.; Brenner, David J.; Fornace, Albert J.

2014-01-01

Metabolomics has been shown to have utility in assessing responses to exposure by ionizing radiation (IR) in easily accessible biofluids such as urine. Most studies to date from our laboratory and others have employed γ-irradiation at relatively high dose rates (HDR), but many environmental exposure scenarios will probably be at relatively low dose rates (LDR). There are well-documented differences in the biologic responses to LDR compared to HDR, so an important question is to assess LDR effects at the metabolomics level. Our study took advantage of a modern mass spectrometry approach in exploring the effects of dose rate on the urinary excretion levels of metabolites 2 days after IR in mice. A wide variety of statistical tools were employed to further focus on metabolites, which showed responses to LDR IR exposure (0.00309 Gy/min) distinguishable from those of HDR. From a total of 709 detected spectral features, more than 100 were determined to be statistically significant when comparing urine from mice irradiated with 1.1 or 4.45 Gy to that of sham-irradiated mice 2 days post-exposure. The results of this study show that LDR and HDR exposures perturb many of the same pathways such as TCA cycle and fatty acid metabolism, which also have been implicated in our previous IR studies. However, it is important to note that dose rate did affect the levels of particular metabolites. Differences in urinary excretion levels of such metabolites could potentially be used to assess an individual's exposure in a radiobiological event and thus would have utility for both triage and injury assessment. (orig.)

Dose-rate dependence of thermoluminescence response

International Nuclear Information System (INIS)

McKeever, S.W.S.; Chen, R.; Groom, P.J.; Durrani, S.A.

1980-01-01

The previously observed dose-rate effect of thermoluminescence in quartz at high dose-rates is given at theoretical formulation. Computer calculations simulating the experimental conditions yield similar results to the experimental ones. (orig.)

Radiology Residents' Awareness about Ionizing Radiation Doses in Imaging Studies and Their Cancer Risk during Radiological Examinations

Energy Technology Data Exchange (ETDEWEB)

Goekce, Senem Divrik [I. Ikad Community Health Center, Health Directorate, Samsun (Turkmenistan); Gekce, Erkan [Samsun Maternity and Women' s Disease and Pediatrics Hospital, Samsun (Turkmenistan); Coskun, Melek [Faculty of Medicine, Ondokuz May' s University, Samsun (Turkmenistan)

2012-03-15

Imaging methods that use ionizing radiation have been more frequent in various medical fields with advances in imaging technology. The aim of our study was to make residents be aware of the radiation dose they are subjected to when they conduct radiological imaging methods, and of cancer risk. A total of 364 residents participated in this descriptive study which was conducted during the period between October, 2008 and January, 2009. The questionnaires were completed under strict control on a one-to-one basis from each department. A X{sup 2}-test was used for the evaluation of data obtained. Only 7% of residents correctly answered to the question about the ionizing radiation dose of a posteroanterior (PA) chest X-ray. The question asking about the equivalent number of PA chest X-rays to the ionizing dose of a brain CT was answered correctly by 24% of residents; the same question regarding abdominal CT was answered correctly by 16% of residents, thorax CT by 16%, thyroid scintigraphy by 15%, intravenous pyelography by 9%, and lumbar spine radiography by 2%. The risk of developing a cancer throughout lifetime by a brain and abdominal CT were 33% and 28%, respectively. Radiologic residents should have updated knowledge about radiation dose content and attendant cancer risks of various radiological imaging methods during both basic medical training period and following practice period.

Non-targeted effects of low dose ionizing radiation act via TGF-beta to promote mammary carcinogenesis

Data.gov (United States)

National Aeronautics and Space Administration — This is a genome-wide approach to identifying genes persistently induced in the mouse mammary gland by acute whole body low dose ionizing radiation (10cGy) 1 and 4...

Recent Total Ionizing Dose Results and Displacement Damage Results for Candidate Spacecraft Electronics for NASA

Science.gov (United States)

Cochran, Donna J.; Buchner, Stephen P.; Irwin, Tim L.; LaBel, Kenneth A.; Marshall, Cheryl J.; Reed, Robert A.; Sanders, Anthony B.; Hawkins, Donald K.; Flanigan, Ryan J.; Cox, Stephen R.

2005-01-01

We present data on the vulnerability of a variety of candidate spacecraft electronics to total ionizing dose and displacement damage. Devices tested include optoelectronics, digital, analog, linear bipolar devices, hybrid devices, Analog-to- Digital Converters (ADCs), and Digital-to-Analog Converters (DACs), among others. T

Low and high dose rate heavy ion radiation-induced intestinal and colonic tumorigenesis in APC1638N/+ mice

Science.gov (United States)

Suman, Shubhankar; Kumar, Santosh; Moon, Bo-Hyun; Fornace, Albert J.; Datta, Kamal

2017-05-01

Ionizing radiation (IR) is a recognized risk factor for colorectal cancer (CRC) and astronauts undertaking long duration space missions are expected to receive IR doses in excess of permissible limits with implications for colorectal carcinogenesis. Exposure to IR in outer space occurs at low doses and dose rates, and energetic heavy ions due to their high linear energy transfer (high-LET) characteristics remain a major concern for CRC risk in astronauts. Previously, we have demonstrated that intestinal tumorigenesis in a mouse model (APC1638N/+) of human colorectal cancer was significantly higher after exposure to high dose rate energetic heavy ions relative to low-LET γ radiation. The purpose of the current study was to compare intestinal tumorigenesis in APC1638N/+ mice after exposure to energetic heavy ions at high (50 cGy/min) and relatively low (0.33 cGy/min) dose rate. Male and female mice (6-8 weeks old) were exposed to either 10 or 50 cGy of 28Si (energy: 300 MeV/n; LET: 70 keV/μm) or 56Fe (energy: 1000 MeV/n; LET: 148 keV/μm) ions at NASA Space Radiation Laboratory in Brookhaven National Laboratory. Mice (n = 20 mice/group) were euthanized and intestinal and colon tumor frequency and size were counted 150 days after radiation exposure. Intestinal tumorigenesis in male mice exposed to 56Fe was similar for high and low dose rate exposures. Although male mice showed a decreasing trend at low dose rate relative to high dose rate exposures, the differences in tumor frequency between the two types of exposures were not statistically significant after 28Si radiation. In female mice, intestinal tumor frequency was similar for both radiation type and dose rates tested. In both male and female mice intestinal tumor size was not different after high and low dose rate radiation exposures. Colon tumor frequency in male and female mice after high and low dose rate energetic heavy ions was also not significantly different. In conclusion, intestinal and colonic tumor

Consequences of low dose ionizing radiation exposure on the hippocampal microenvironment.

Directory of Open Access Journals (Sweden)

Munjal M Acharya

Full Text Available The response of the brain to irradiation is complex, involving a multitude of stress inducible pathways that regulate neurotransmission within a dynamic microenvironment. While significant past work has detailed the consequences of CNS radiotherapy following relatively high doses (≥ 45 Gy, few studies have been conducted at much lower doses (≤ 2 Gy, where the response of the CNS (like many other tissues may differ substantially from that expected from linear extrapolations of high dose data. Low dose exposure could elicit radioadaptive modulation of critical CNS processes such as neurogenesis, that provide cellular input into hippocampal circuits known to impact learning and memory. Here we show that mice deficient for chemokine signaling through genetic disruption of the CCR2 receptor exhibit a neuroprotective phenotype. Compared to wild type (WT animals, CCR2 deficiency spared reductions in hippocampal neural progenitor cell survival and stabilized neurogenesis following exposure to low dose irradiation. While radiation-induced changes in microglia levels were not found in WT or CCR2 deficient animals, the number of Iba1+ cells did differ between each genotype at the higher dosing paradigms, suggesting that blockade of this signaling axis could moderate the neuroinflammatory response. Interestingly, changes in proinflammatory gene expression were limited in WT animals, while irradiation caused significant elevations in these markers that were attenuated significantly after radioadaptive dosing paradigms in CCR2 deficient mice. These data point to the importance of chemokine signaling under low dose paradigms, findings of potential significance to those exposed to ionizing radiation under a variety of occupational and/or medical scenarios.

Novel approach to analyzing the carcinogenic effect of ionizing radiations.

Science.gov (United States)

Gregoire, O; Cleland, M R

2006-01-01

Cancer incidence of ionizing radiations exposure is considered to be proportional to the absorbed dose. However, there are disagreements between substantial amounts of epidemiological studies. In this study, we question the basic relationship of the risk estimate with total accumulated dose, and reanalyse available data on the basis of a daily dose concept. The data analysed were relative mortality risk from all cancers vs. total-body dose on a daily basis. References have been selected on the basis of objective criteria. We found that this relationship removes major discrepancies. It revises estimates of low-level exposures, with consequences regarding nuclear power plants safety, wastes management, medical applications or homeland security. The idea that the dose rate may have a significant impact on health effects of ionizing radiations is not new, but has always been considered as a parameter in models based on integrated dose. The novel approach in this paper is to consider the primary relevant parameter as an average of dose rate over a time period of one day. This is an argument to revise the whole philosophy in radioprotection, and place regulatory limits on specific locations instead of annual limits relevant to individual persons.

A study of the effects of therapeutic doses of ionizing radiation in vitro on Lactobacillus isolates originating from the vagina - a pilot study.

Science.gov (United States)

Gosiewski, Tomasz; Mróz, Tomasz; Ochońska, Dorota; Pabian, Wojciech; Bulanda, Malgorzata; Brzychczy-Wloch, Monika

2016-05-31

Ionizing radiation is used as a therapeutic option in the treatment of certain neoplastic lesions located, among others, in the pelvic region. The therapeutic doses of radiation employed often result in adverse effects manifesting themselves primarily in the form of genital tract infections in patients or diarrhea. The data available in the literature indicate disorders in the microbial ecosystem caused by ionizing radiation, which leads to the problems mentioned above. In the present study, we examined the influence of ionizing radiation on 52 selected strains of bacteria: Lactobacillus crispatus, L. fermentum, L. plantarum, L. reuteri, L. acidophilus L. amylovorus, L. casei, L. helveticus, L. paracasei, L. rhamnosus, L. salivarius and L. gasseri. This collection of Lactobacillus bacteria isolates of various species, obtained from the genital tract and gastrointestinal tract of healthy women, was tested for resistance to therapeutic doses of ionizing radiation. The species studied, were isolated from the genital tract (n = 30) and from the anus (n = 22) of healthy pregnant women. Three doses of 3 Gy (fractionated dose) and 50 Gy (total dose of the whole radiotherapy cycle) were applied. The greatest differences in survival of the tested strains in comparison to the control group (not subjected to radiation) were observed at the dose of 50 Gy. However, the results were not statistically significant. Survival decrease to zero was not demonstrated for any of the tested strains. Therapeutic doses of radiation do not affect the Lactobacillus bacteria significantly.

The possibility of the dose limitation system application non-ionizing radiation protection

International Nuclear Information System (INIS)

Ranisavljevic, M., Markovic, S.

1997-01-01

Modern conception of the ionizing radiation protection is based on Dose Limitation System. In the base of every human decision lies compromise. Balance between positive and negative factors, benefit and detriment, profit and expense includes the decision about possibilities for realization any defined radiation practice. The optimal option for the given value of the varying parameter gives the maximum benefit and the minimum detriment. In radiation protection field, detriment is related with human health or expenses, and varying parameter is level of radiation protection (for example dimensions of the installed shielding). The problem lies in fact that for the given value of the varying shielding parameter the maximum benefit and the minimum detriment are not achievable simultaneously because the greater benefit includes the greater expense. The problems which have to be solved because of introducing Dose Limitation System, in regard to create Modified Dose Limitation System, are presented. (author)

Determination of dose components in mixed gamma neutron fields by use of high pressure ionization chambers

International Nuclear Information System (INIS)

Golnik, N.; Pliszczynski, T.; Wysocka, A.; Zielczynski, M.

1985-01-01

The two ionization chamber method for determination of dose components in mixed γ-neutron field has been improved by increasing gas pressure in the chambers up to some milions pascals. Advantages of high pressure gas filling are the followings: 1) significant reduction of the ratio of neutron-to gamma sensitivity for the hydrogen-free chamber, 2) possibility of sensitivity correction for both chambers by application of appropriate voltage, 3) high sensitivity for small detectors. High-pressure, pen-like ionization chambers have been examined in fields of different neutron sources: a TE-chamber, filled with 0.2 MPa of quasi-TE-gas and a conductive PTFE chamber, filled with 3.1 MPa of CO 2 . The ratio of neutron-to-gamma sensitivity for the PTFE chamber, operated at electrical field strength below 100 V/cm, has not exceeded 0.01 for neutrons with energy below 8 MeV. Formula is presented for calculation of this ratio for any high-pressure, CO 2 -filled ionization chamber. Contribution of gamma component to total tissue dose in the field of typical neutron sources has been found to be 3 to 70%

External dose-rate conversion factors for calculation of dose to the public

Energy Technology Data Exchange (ETDEWEB)

1988-07-01

This report presents a tabulation of dose-rate conversion factors for external exposure to photons and electrons emitted by radionuclides in the environment. This report was prepared in conjunction with criteria for limiting dose equivalents to members of the public from operations of the US Department of Energy (DOE). The dose-rate conversion factors are provided for use by the DOE and its contractors in performing calculations of external dose equivalents to members of the public. The dose-rate conversion factors for external exposure to photons and electrons presented in this report are based on a methodology developed at Oak Ridge National Laboratory. However, some adjustments of the previously documented methodology have been made in obtaining the dose-rate conversion factors in this report. 42 refs., 1 fig., 4 tabs.

Gas-phase reaction rate constants for atmospheric pressure ionization in ion-mobility spectrometry

International Nuclear Information System (INIS)

Vandiver, V.J.

1987-01-01

Ion-mobility spectrometry (IMS) is an instrumental technique in which gaseous ions are formed from neutral molecules by proton and charge transfer from reactant ions through collisional ionization. An abbreviated rate theory has been proposed for atmospheric pressure ionization (API) in IMS, but supporting experimental measurements have not been reported. The objectives of this thesis were (1) assessment of existing API rate theory using positive and negative product ions in IMS, (2) measurement of API equilibria and kinetics for binary mixtures, and (3) investigating of cross-ionizations with multiple-product ions in API reactions. Although IMS measurements and predictions from rate theory were comparable, shapes and slopes of response curves for both proton transfer and electron capture were not described exactly by existing theory. In particular, terms that are needed for calculation of absolute rate constants were unsuitable in the existing theory. These included recombination coefficients,initial number of reactant ions, and opposing ion densities

Radiobiological modelling of dose-gradient effects in low dose rate, high dose rate and pulsed brachytherapy

International Nuclear Information System (INIS)

Armpilia, C; Dale, R G; Sandilos, P; Vlachos, L

2006-01-01

This paper presents a generalization of a previously published methodology which quantified the radiobiological consequences of dose-gradient effects in brachytherapy applications. The methodology uses the linear-quadratic (LQ) formulation to identify an equivalent biologically effective dose (BED eq ) which, if applied uniformly to a specified tissue volume, would produce the same net cell survival as that achieved by a given non-uniform brachytherapy application. Multiplying factors (MFs), which enable the equivalent BED for an enclosed volume to be estimated from the BED calculated at the dose reference surface, have been calculated and tabulated for both spherical and cylindrical geometries. The main types of brachytherapy (high dose rate (HDR), low dose rate (LDR) and pulsed (PB)) have been examined for a range of radiobiological parameters/dimensions. Equivalent BEDs are consistently higher than the BEDs calculated at the reference surface by an amount which depends on the treatment prescription (magnitude of the prescribed dose) at the reference point. MFs are closely related to the numerical BED values, irrespective of how the original BED was attained (e.g., via HDR, LDR or PB). Thus, an average MF can be used for a given prescribed BED as it will be largely independent of the assumed radiobiological parameters (radiosensitivity and α/β) and standardized look-up tables may be applicable to all types of brachytherapy treatment. This analysis opens the way to more systematic approaches for correlating physical and biological effects in several types of brachytherapy and for the improved quantitative assessment and ranking of clinical treatments which involve a brachytherapy component

Radiation hormesis: an outcome of exposure to low level ionizing radiation

International Nuclear Information System (INIS)

Kant, Krishan

2012-01-01

Ionizing radiation is a benign environmental agent at background levels. Human population is always exposed to ionizing radiation from natural sources. Important sources are cosmic rays which come from outer space and from the surface of the sun, terrestrial radionuclides which occur in the earths crust in various geological formations in soils, rocks, building materials, plants, water, food, air and in the human body itself. With the increasing use of radiation in health facilities, scientific research, industry and agriculture, the study of impact of low-level ionizing radiation on environment and possible health effects on future generations has been a cause of concern in recent years. As regards the effects, it is established fact that high doses of ionizing radiation are harmful to health, there exists, however, a substantial controversy regarding the effects of low doses of ionizing radiation (LLIR). In the present paper, brief review of the available literature, data and reports on stimulation by low-dose irradiation and recent data supporting radiation hormesis. A linear quadratic model has been given illustrating the validity of radiation hormesis, besides the comparison of the dose rates arising from natural and manmade sources to the Indian population. This overview summarizes various reports

Pulsed dose rate and fractionated high dose rate brachytherapy: choice of brachytherapy schedules to replace low dose rate treatments

International Nuclear Information System (INIS)

Visser, Andries G.; Aardweg, Gerard J.M.J. van den; Levendag, Peter C.

1996-01-01

Purpose: Pulsed dose rate (PDR) brachytherapy is a new type of afterloading brachytherapy (BT) in which a continuous low dose rate (LDR) treatment is simulated by a series of 'pulses,' i.e., fractions of short duration (less than 0.5 h) with intervals between fractions of 1 to a few hours. At the Dr. Daniel den Hoed Cancer Center, the term 'PDR brachytherapy' is used for treatment schedules with a large number of fractions (at least four per day), while the term 'fractionated high dose rate (HDR) brachytherapy' is used for treatment schedules with just one or two brachytherapy fractions per day. Both treatments can be applied as alternatives for LDR BT. This article deals with the choice between PDR and fractionated HDR schedules and proposes possible fractionation schedules. Methods and Materials: To calculate HDR and PDR fractionation schedules with the intention of being equivalent to LDR BT, the linear-quadratic (LQ) model has been used in an incomplete repair formulation as given by Brenner and Hall, and by Thames. In contrast to earlier applications of this model, both the total physical dose and the overall time were not kept identical for LDR and HDR/PDR schedules. A range of possible PDR treatment schedules is presented, both for booster applications (in combination with external radiotherapy (ERT) and for BT applications as a single treatment. Because the knowledge of both α/β values and the half time for repair of sublethal damage (T (1(2)) ), which are required for these calculations, is quite limited, calculations regarding the equivalence of LDR and PDR treatments have been performed for a wide range of values of α/β and T (1(2)) . The results are presented graphically as PDR/LDR dose ratios and as ratios of the PDR/LDR tumor control probabilities. Results: If the condition that total physical dose and overall time of a PDR treatment must be exactly identical to the values for the corresponding LDR treatment regimen is not applied, there appears

Development of a phoswich detector for neutron dose rate measurements in the Earth's atmosphere

International Nuclear Information System (INIS)

Doensdorf, Esther Miriam

2014-01-01

The Earth is constantly exposed to a stream of energetic particles from outer space. Through the interaction of this radiation with the Earth's magnetosphere and atmosphere a complex radiation field is formed which varies with the location inside the Earth's atmosphere. This radiation field consists of charged and uncharged particles leading to the constant exposure of human beings to radiation. As this ionizing radiation can be harmful for humans, it is necessary to perform dose rate measurements in different altitudes in the Earth's atmosphere. Due to their higher biological effectiveness the exposure to neutrons is more harmful than the exposure to γ-rays and charged particles, which is why the determination of neutron dose rates is the focus of this work. In this work the prototype of a Phoswich detector called PING (Phoswich Instrument for Neutrons and Gammas) is developed to determine dose rates caused by neutrons in the Earth's atmosphere and to distinguish these from γ-rays. The instrument is composed of two different scintillators optically coupled to each other and read out by one common photomultiplier tube. The scintillator package consists of an inner plastic scintillator made of the material BC-412 and a surrounding anti-coincidence made of sodium doped caesium iodide (CsI(Na)). In this work the instrument is calibrated, tested and flown and a procedure for a pulse shape analysis for this instrument is developed. With this analysis it is possible to distinguish pulses from the plastic scintillator and pulses from the CsI(Na). The pulses from the plastic scintillator are mainly due to the interaction of neutrons but there is an energy-dependent contribution of γ-rays to these events. Measurements performed on board an airplane show that the dose rates measured with the developed detector are in the same order of magnitude as results of other instruments. During measurements on board stratospheric balloons the altitude dependence of count rates and

The effects of low dose ionizing radiation on the development of rat cerebral cortex, (2)

International Nuclear Information System (INIS)

Matsushita, Koji

1993-01-01

In order to study the molecular mechanisms of neuronal migration on developing rat cerebral cortex, we need a tissue culture system in which neuronal migration can be observed. We prepared a tissue culture system of embryonic rat cerebral cortex starting on embryonic day 16 and cultivating it for 48 hours. The autoradiographic study in this system revealed not only the migration of 3 H-thymidine labeled neurons but also neuronal migration delays from low doses of ionizing radiation of more than 10 cGy. In addition, on immunohistochemical study, cell-cell adhesion molecule N-CAM staining was remarkably decreased in the matrix cell layer. In the tissue culture system where monoclonal anti-N-CAM antibodies were added, neuronal migration delay comparable to that of 20 cGy radiation was found. In conclusion, it was speculated that neuronal migration delay might be caused by disturbed N-CAM synthesis in matrix cells after low dose ionizing radiation. (author)

Dose rate effect on low-dose hyper-radiosensitivity with cells in vitro

Energy Technology Data Exchange (ETDEWEB)

Kim, Geon-Min; Kim, Eun-Hee [Seoul National University, Seoul (Korea, Republic of)

2016-10-15

Low-dose hyper-radiosensitivity (HRS) is the phenomenon that mammalian cells exhibit higher sensitivity to radiation at low doses (< 0.5 Gy) than expected by the linear-quadratic model. At doses above 0.5Gy, the cellular response is recovered to the level expected by the linear-quadratic model. This transition is called the increased radio-resistance (IRR). HRS was first verified using Chinese hamster V79 cells in vitro by Marples and has been confirmed in studies with other cell lines including human normal and tumor cells. HRS is known to be induced by inactivation of ataxia telangiectasia-mutated (ATM), which plays a key role in repairing DNA damages. Considering the connection between ATM and HRS, one can infer that dose rate may affect cellular response regarding HRS at low doses. In this study, we quantitated the effect of dose rate on HRS by clonogenic assay with normal and tumor cells. The HRS of cells at low dose exposures is a phenomenon already known. In this study, we observed HRS of rat normal diencephalon cells and rat gliosarcoma cells at doses below 1 Gy. In addition, we found that dose rate mattered. HRS occurred at low doses, but only when total dose was delivered at a rate below certain level.

Definition of the roentgen in connection with this unit's application for all ionizing radiations

Energy Technology Data Exchange (ETDEWEB)

Poroikov, I. V.

1956-07-01

Revision of the All-union State Standard for the roentgen is discussed. It is recommended that the roentgen be considered a unit of ionization and roentgen/sec should be called increment of ionization instead of dose rate. (J.R.D.)

Use of BEIR V and UNSCEAR 1988 in radiation risk assessment: Lifetime total cancer mortality risk estimates at low doses and low dose rates for low-LET radiation

International Nuclear Information System (INIS)

1992-12-01

In November 1986, the Department of Defense (DoD) asked the Committee on Interagency Radiation Research and Policy Coordination (CIRRPC) to develop a coordinated Federal position on risk assessment for low levels of ionizing radiation. Since Federal risk assessment activities are based primarily on the scientific data and analyses in authoritative review documents prepared by groups like the National Academy of Sciences' Committee on the Biological Effects of Ionizing Radiation (BEIR), the National Council on Radiation Protection and Measurements (NCRP) and the United Nations' Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), DoD proposed that the CIRRPC Science Panel undertake the task of providing coordinated interagency positions on the use of information in the reports of such groups. The practice has been for individual Federal agencies to interpret and decide independently how to use the information provided in such reports. As a result of its deliberations, the Subpanel recommends two nominal risk estimates for lifetime total cancer mortality following whole-body exposure to low levels of low-LET ionizing radiation, one for the general population and one for the working-age population (see Section II). The recommended risk estimates reflect the general agreement of information in BEIR V and UNSCEAR 1988 for total cancer mortality. The Subpanel's risk estimates and associated statements are intended to meet the needs of the Federal agencies for: (a) values that are current; (b) values that are relevant to the low-dose and low dose-rate ionizing radiation exposures principally encountered in carrying out Federal responsibilities; (c) a statement of the change in the estimates of lifetime total cancer mortality relative to estimates in previous authoritative review documents; and (d) a practical statement on the scientific uncertainty associated with applying the lifetime total cancer mortality values at very low doses

DNA excision repair as a component of adaptation to low doses of ionizing radiation Escherichia coli

International Nuclear Information System (INIS)

Huang, H.; Claycamp, H.G.

1993-01-01

In this study the authors examined whether or not DNA excision repair is a component of adaptation induced by very low-dose ionizing radiation in Escherichia coli, a well-characterized prokaryote, and investigated the relationship between enhanced excision repair and the SOS response. Their data suggest that there seems to be narrow 'windows' of dose-effect for the induction of SOS-independent DNA excision repair. Being similar to mammalian cell studies, the dose range for this effect was about 200-fold less than D 37 for radiation survival. (author)

Effect of low doses of ionizing radiation on human health

International Nuclear Information System (INIS)

Kovalenko, A.N.

1990-01-01

Data are reported on the possible mechanism of biological effects of low doses of ionizing radiation on the human body. The lesioning effect of this radiation resulted in some of the persons in the development of disorders of the function of information and vegetative-regulatory systems determined as a desintegration syndrome. This syndrome is manifested in unspecific neuro-vegetative disorders of the function of most important physiological and homeostatic system of the body leading to weakening of the processes of compensation and adaptation. This condition is characterized by an unspecific radiation syndrome as distinct from acute or chronic radiation disease which is a specific radiation syndrome

Analysis of the health of a group exposed to low doses of ionizing radiation

International Nuclear Information System (INIS)

Diaz Ledesma, F.; Crespo, H.

1997-01-01

In order to evaluate the effects of exposure to low radiation doses, the health status of professional staff exposed to ionizing radiation is investigated. Based on archived material of medical and radiation exposure records taken over a time span of 13 years, a variety of medical parameters are explored. Findings of surveys made are given. (author)

Possible radioprotective effect of folic acid supplementation on low dose ionizing radiation-induced genomic instability in vitro.

Science.gov (United States)

Padula, Gisel; Ponzinibbio, María Virginia; Seoane, Analia I

2016-08-01

Ionizing radiation (IR) induces DNA damage through production of single and double-strand breaks and reactive oxygen species (ROS). Folic acid (FA) prevents radiation-induced DNA damage by modification of DNA synthesis and/or repair and as a radical scavenger. We hypothesized that in vitro supplementation with FA will decrease the sensitivity of cells to genetic damage induced by low dose of ionizing radiation. Annexin V, comet and micronucleus assays were performed in cultured CHO cells. After 7 days of pre-treatment with 0, 100, 200 or 300 nM FA, cultures were exposed to radiation (100 mSv). Two un-irradiated controls were executed (0 and 100 nM FA). Data were statistically analyzed with X2-test and linear regression analysis (P 0.05). We observed a significantly decreased frequency of apoptotic cells with the increasing FA concentration (P <0.05). The same trend was observed when analyzing DNA damage and chromosomal instability (P <0.05 for 300 nM). Only micronuclei frequencies showed significant differences for linear regression analysis (R2=94.04; P <0.01). Our results have demonstrated the radioprotective effect of folic acid supplementation on low dose ionizing radiation-induced genomic instability in vitro; folate status should be taken into account when studying the effect of low dose radiation in environmental or occupational exposure.

Air dose rate in Aichi Prefecture

International Nuclear Information System (INIS)

Ohnuma, Shoko; Chaya, Kunio; Tomita, Banichi; Aoyama, Kan; Yamada, Naoki; Yamada, Masuo; Hamamura, Norikatsu

1985-01-01

We have carried out the observations of air dose rate during 1964--1983 at the fixed points of Aichi Prefecture and investigated the distribution of air dose rate in this prefecture during 1979--1983. The results of these researches are as follows. 1) The apparent half time of radiation dose from the earth and the atmosphere during the last 20 years was about 9.7 years and it was longer than the apparent half time of fallout total β radioactivity in every rainfall that was about 3.2 years. 2) The influence of nuclear explosion test in China on the measurements of air does rate did not existed directly during the latter half of 20 years, not so as during the former and it was keeping decreasing. It was expected that the air dose rate would begin to indicate the natural radiation dose from the earth and the atmosphere in the near future. 3) The distribution of air dose rate in this prefecture depended strongly on the geology. The maximum value was 5.6 μR/hr (except cosmic rays) in Fujioka Cho, the minimum value was 1.9 μR/hr (except cosmic rays) in Tahara Cho and the average in the whole prefecture was 3.5+-0.7 μR/hr (except cosmic rays). 4) It was estimated that the radiation dose which the inhabitants received from the earth and the atmosphere was 17--52 m rem a year and the average was 31 m rem a year. (author)

Air dose rate in Aichi Prefecture

Energy Technology Data Exchange (ETDEWEB)

Ohnuma, Shoko; Chaya, Kunio; Tomita, Banichi; Aoyama, Kan; Yamada, Naoki; Yamada, Masuo; Hamamura, Norikatsu

1985-03-01

We have carried out the observations of air dose rate during 1964-1983 at the fixed points of Aichi Prefecture and investigated the distribution of air dose rate in this prefecture during 1979-1983. The results of these researches are as follows. 1) The apparent half time of radiation dose from the earth and the atmosphere during the last 20 years was about 9.7 years and it was longer than the apparent half time of fallout total ..beta.. radioactivity in every rainfall that was about 3.2 years. 2) The influence of nuclear explosion test in China on the measurements of air does rate did not existed directly during the latter half of 20 years, not so as during the former and it was keeping decreasing. It was expected that the air dose rate would begin to indicate the natural radiation dose from the earth and the atmosphere in the near future. 3) The distribution of air dose rate in this prefecture depended strongly on the geology. The maximum value was 5.6 ..mu..R/hr (except cosmic rays) in Fujioka Cho, the minimum value was 1.9 ..mu..R/hr (except cosmic rays) in Tahara Cho and the average in the whole prefecture was 3.5 +- 0.7 ..mu..R/hr (except cosmic rays). 4) It was estimated that the radiation dose which the inhabitants received from the earth and the atmosphere was 17-52 m rem a year and the average was 31 m rem a year.

Dose rate and dose fractionation studies in total body irradiation of dogs

International Nuclear Information System (INIS)

Kolb, H.J.; Netzel, B.; Schaffer, E.; Kolb, H.

1979-01-01

Total body irradiation (TBI) with 800-900 rads and allogeneic bone marrow transplantation according to the regimen designated by the Seattle group has induced remissions in patients with otherwise refractory acute leukemias. Relapse of leukemia after bone marrow transplantation remains the major problem, when the Seattle set up of two opposing 60 Co-sources and a low dose rate is used in TBI. Studies in dogs with TBI at various dose rates confirmed observations in mice that gastrointestinal toxicity is unlike toxicity against hemopoietic stem cells and possibly also leukemic stem cells depending on the dose rate. However, following very high single doses (2400 R) and marrow infusion acute gastrointestinal toxicity was not prevented by the lowest dose rate studied (0.5 R/min). Fractionated TBI with fractions of 600 R in addition to 1200 R (1000 rads) permitted the application of total doses up to 300 R followed by marrow infusion without irreversible toxicity. 26 dogs given 2400-3000 R have been observed for presently up to 2 years with regard to delayed radiation toxicity. This toxicity was mild in dogs given single doses at a low dose rate or fractionated TBI. Fractionated TBI is presently evaluated with allogeneic transplants in the dog before being applied to leukemic patients

Decomposition of persistent pharmaceuticals in wastewater by ionizing radiation

International Nuclear Information System (INIS)

Kimura, Atsushi; Osawa, Misako; Taguchi, Mitsumasa

2012-01-01

Pharmaceuticals in wastewater were treated by the combined method of activated sludge and ionizing radiation in laboratory scale. Oseltamivir, aspirin, and ibuprofen at 5 μmol dm −3 in wastewater were decomposed by the activated sludge at reaction time for 4 h. Carbamazepine, ketoprofen, mefenamic acid, clofibric acid, and diclofenac were not biodegraded completely, but were eliminated by γ-ray irradiation at 2 kGy. The rate constants of the reactions of these pharmaceuticals with hydroxyl radicals were estimated by the competition reaction method to be 4.0–10×10 9 mol −1 dm 3 s −1 . Decompositions of the pharmaceuticals in wastewater by ionizing radiation were simulated by use of the rate constants and the amount of total organic carbon as parameters. Simulation curves of concentrations of these pharmaceuticals as a function of dose described the experimental data, and the required dose for the elimination of them in wastewater by ionizing radiation can be estimated by this simulation. - Highlights: ► We treat pharmaceuticals in wastewater by activated sludge and ionizing radiation. ► Activated sludge decreases the amounts of total organic carbons in wastewater. ► Pharmaceuticals were decomposed by γ-ray irradiation at 2 kGy. ► We construct simulation for treatment of pharmaceuticals by ionizing radiation.

Compensation for damage to workers health exposed to ionizing radiation in Argentina

CERN Document Server

Sobehart, L J

2003-01-01

The objective of this report is to analyze the possibility to establish a scheme to compensate damage to workers health exposed to ionizing radiation in Argentina for those cases in which it is possible to assume that the exposure to ionizing radiation is the cause of the cancer suffered by the worker. The proposed scheme is based on the recommendations set out in the 'International Conference on Occupational Radiation Protection: Protecting Workers against Exposure to Ionization Radiation, held in Geneva, Switzerland, August 26-30, 2002. To this end, the study analyzes the present state of scientific knowledge on cancer causation due to genotoxic factors, and the accepted form of the doses-response curve, for the human beings exposure to ionization radiation at low doses with low doses rates. Finally, the labor laws and regulations related to damage compensation; in particular the present Argentine Labor Law; the National Russian Federal Occupational Radiological Health Impairment and Workmen Compensation, t...

Dosimetric systems of high dose, dose rate and dose uniformity in food and medical products

International Nuclear Information System (INIS)

Vargas, J.; Vivanco, M.; Castro, E.

2014-08-01

In the Instituto Peruano de Energia Nuclear (IPEN) we use the chemical dosimetry Astm-E-1026 Fricke as a standard dosimetric system of reference and different routine dosimetric systems of high doses, according to the applied doses to obtain the desired effects in the treated products and the doses range determined for each type of dosimeter. Fricke dosimetry is a chemical dosimeter in aqueous solution indicating the absorbed dose by means an increase in absorbance at a specific wavelength. A calibrated spectrophotometer with controlled temperature is used to measure absorbance. The adsorbed dose range should cover from 20 to 400 Gy, the Fricke solution is extremely sensitive to organic impurities, to traces of metal ions, in preparing chemical products of reactive grade must be used and the water purity is very important. Using the referential standard dosimetric system Fricke, was determined to March 5, 2013, using the referential standard dosimetric system Astm-1026 Fricke, were irradiated in triplicate Fricke dosimeters, to 5 irradiation times (20; 30; 40; 50 and 60 seconds) and by linear regression, the dose rate of 5.400648 kGy /h was determined in the central point of the irradiation chamber (irradiator Gamma cell 220 Excel), applying the decay formula, was compared with the obtained results by manufacturers by means the same dosimetric system in the year of its manufacture, being this to the date 5.44691 kGy /h, with an error rate of 0.85. After considering that the dosimetric solution responds to the results, we proceeded to the irradiation of a sample of 200 g of cereal instant food, 2 dosimeters were placed at the lateral ends of the central position to maximum dose and 2 dosimeters in upper and lower ends as minimum dose, they were applied same irradiation times; for statistical analysis, the maximum dose rate was 6.1006 kGy /h and the minimum dose rate of 5.2185 kGy /h; with a dose uniformity of 1.16. In medical material of micro pulverized bone for

Effects of low doses of ionizing radiation

International Nuclear Information System (INIS)

Masse, R.

2006-01-01

Several groups of human have been irradiated by accidental or medical exposure, if no gene defect has been associated to these exposures, some radioinduced cancers interesting several organs are observed among persons exposed over 100 to 200 mSv delivered at high dose rate. Numerous steps are now identified between the initial energy deposit in tissue and the aberrations of cell that lead to tumors but the sequence of events and the specific character of some of them are the subject of controversy. The stake of this controversy is the risk assessment. From the hypothesis called linear relationship without threshold is developed an approach that leads to predict cancers at any tiny dose without real scientific foundation. The nature and the intensity of biological effects depend on the quantity of energy absorbed in tissue and the modality of its distribution in space and time. The probability to reach a target (a gene) associated to the cancerating of tissue is directly proportional to the dose without any other threshold than the quantity of energy necessary to the effect, its probability of effect can be a more complex function and depends on the quality of the damage produced as well as the ability of the cell to repair the damage. These two parameters are influenced by the concentration of initial injuries in the target so by the quality of radiation and by the dose rate. The mechanisms of defence explain the low efficiency of radiation as carcinogen and then the linearity of effects in the area of low doses is certainly the least defensible scientific hypothesis for the prediction of the risks. (N.C.)

Development of special ionization chambers for a quality control program in mammography

International Nuclear Information System (INIS)

Silva, Jonas Oliveira da

2013-01-01

Mammography is an imaging method that uses X-rays. The use of ionization chambers in mammography quality control programs presents an essential role which is to verify whether the parameters of the patient exposure are correct. However, the commercial ionization chambers for dosimetry in mammography represent a high cost for small and medium size clinics that wish to have this equipment or for professionals that work with quality control programs. The innovative feature of this work was to develop ionization chambers for this purpose. In this work ionization chambers for X radiation beams in the mammography energy range were designed, constructed and characterized. The ionization chambers were tested in standard X radiation beams at the LCI/IPEN. The main characterization tests performed with the ionization chambers were: saturation curve, linearity of response, angular and energy dependence. The response stability tests of the ionization chambers were also conducted at the LCI, presenting results within 2.0 % for long-term stability. The results of the remaining tests are in accordance with international standards. These ionization chambers were also submitted to quality control tests of mammography equipment: linearity of the air kerma rates, determination of half-value layers and mean glandular doses. The results for air kerma rate linearity were less than 10 %, as recommended in international standards. The mean glandular dose obtained with the developed chambers presented values comparable to those of commercial ionization chambers tested, with an estimated variation within international standards. (author)

Ionization chambers

International Nuclear Information System (INIS)

Boag, J.W.

1987-01-01

Although a variety of solid-state and chemical methods for measuring radiation dose have been developed in recent decades and calorimetry can now provide an absolute standard of reference, ionization dosimetry retains its position as the most widely used, most convenient, and, in most situations, most accurate method of measuring either exposure or absorbed dose. The ionization chamber itself is the central element in this system of dosimetry. In this chapter the principles governing the construction and operation of ionization chambers of various types are examined. Since the ionization chambers now in general use are nearly all of commercial manufacture, the emphasis is on operating characteristics and interpretation of measurements rather than on details of construction, although some knowledge of the latter is often required when applying necessary corrections to the measured quantities. Examples are given of the construction of typical chambers designed for particular purposes, and the methods of calibrating them are discussed

Simulation studies on a prototype ionization chamber for measurement of personal dose equivalent, Hp(10)

International Nuclear Information System (INIS)

Cardoso, J.; Oliveira, C.; Carvalho, A.F.

2005-01-01

Full text: The Metrological Laboratory of lonizing Radiation and Radioactivity (LMRIR) of Nuclear and Technological Institute (ITN) has designed and constructed a prototype ionization chamber for direct measurement of the personal dose equivalent, H p (10), similar to the developed by the Physikalisch-Technische Bundesanstalt (PTB) and now commercialized by PTW. Tests already performed had shown that the behaviour of this chamber is very close to the PTB chamber, namely the energy dependence for the x-ray radiation qualities of the ISO 4037-1 narrow series N-30, N-40, N-60, N-80, N-100 and N-120 and also for gamma radiation of 137 Cs and 60 Co. However, the results obtained also show a high dependence on the energy for some incident radiation angles and a low magnitude of the electrical response of the ionization chamber. In order to try to optimize the performance of the chamber, namely to decrease the energy dependence and to improve the magnitude of the electrical response of the ionization chamber, the LMRIR initiated numerical simulation of this ionization chamber using a Monte-Carlo method for simulation of radiation transport using, in a first step, the MCNPX code. So, simulation studies of some physical parameters are been performed in order to optimize the response of the ionization chamber, namely the diameter of the central electrode of the ionization chamber, the thickness of the front wall of the ionization chamber, among others. Preliminary results show that probably the actual geometry of the ionization chamber is not yet the optimized configuration. The simulation study will carry on in order to find the optimum geometry. (author)

Dose-rate effects in external beam radiotherapy redux

International Nuclear Information System (INIS)

Ling, C. Clifton; Gerweck, Leo E.; Zaider, Marco; Yorke, Ellen

2010-01-01

Recent developments in external beam radiotherapy, both in technical advances and in clinical approaches, have prompted renewed discussions on the potential influence of dose-rate on radio-response in certain treatment scenarios. We consider the multiple factors that influence the dose-rate effect, e.g. radical recombination, the kinetics of sublethal damage repair for tumors and normal tissues, the difference in α/β ratio for early and late reacting tissues, and perform a comprehensive literature review. Based on radiobiological considerations and the linear-quadratic (LQ) model we estimate the influence of overall treatment time on radio-response for specific clinical situations. As the influence of dose-rate applies to both the tumor and normal tissues, in oligo-fractionated treatment using large doses per fraction, the influence of delivery prolongation is likely important, with late reacting normal tissues being generally more sensitive to the dose-rate effect than tumors and early reacting tissues. In conventional fractionated treatment using 1.8-2 Gy per fraction and treatment times of 2-10 min, the influence of dose-rate is relatively small. Lastly, the dose-rate effect in external beam radiotherapy is governed by the overall beam-on-time, not by the average linac dose-rate, nor by the instantaneous dose-rate within individual linac pulses which could be as high as 3 x 10 6 MU/min.

Dose-rate effects and chronological changes of chromosome aberration rates in spleen cells from mice that are chronically exposed to gamma-ray at low dose rates

International Nuclear Information System (INIS)

Tanaka, Kimio; Kohda, Atsushi; Ichinohe, Kazuaki; Matsumoto, Tsuneya; Oghiso, Yoichi

2006-01-01

Dose-rate effects have not been examined in the low dose-rate regions of less than 60-600 mGy/h. Mice were chronically exposed to gamma-ray at 20 mGy/day (approximately 1 mGy/h) up to 700 days and at 1 mGy/day (approximately 0.05 mGy/h) for 500 days under SPF conditions. Chronological changes of chromosome aberration rates in spleen cells were observed along with accumulated doses at both low dose-rates. Unstable aberrations increased in a biphasic manner within 0-2 Gy and 4-14 Gy in 20 mGy/day irradiation. They slightly increased up to 0.5 Gy in 1 mGy/day irradiation. Chromosome aberration rates at 20 mGy/day and 1 mGy/day were compared at the same total doses of 0.5 Gy and 0.25 Gy. They were 2.0 vs. 0.53, and 1.0 vs. 0.47 respectively. Thus, dose-rate effects were observed in these low dose-rate regions. (author)

Absorbed dose rate meter for β-ray

International Nuclear Information System (INIS)

Bingo, K.

1977-01-01

The absorbed dose of β-ray depends on the energy of β-rays and the epidermal thickness of tissue in interest. In order to measure the absorbed dose rate at the interested tissue directly, the ratio of counting rate to absorbed dose should be constant independent of β-ray energy. In this purpose, a thin plastic scintillator was used as a detector with a single channel analyzer. The pulse height distribution, obtained using the scintillator whose thickness is less than the range of β-rays, shows a peak at a particular pulse height depending on the thickness of scintillator used. This means an increase of the number of pulses at lower pulse height. The lower level of discrimination and window width of the single channel analyzer are chosen according to the epidermal thickness of the tissue. In the experiment, scintillators of 0.5, 1, 2, 3, 5 and 10 mm thick were tested. It was found that desirable pulse height distribution, to obtain a constant dose sensitivity, could be obtained using the 2 mm thick scintillator. The sensitivity of the absorbed dose rate meter is constant within +-15% for β-ray with maximum energy from 0.4 to 3.5 MeV, when the absorbed dose rate for skin (epidermal thickness 7mg/cm 2 ) is measured. In order to measure the dose rate for a hand (epithermal thickness 40mg/cm 2 ) the lower level of discrimination is changed to be higher and at the same time the window width is also changed. Combining these techniques, one can get an absorbed dose rate meter for the tissue dose of various thickness, which has the constant dose sensitivity within +-15% for β-rays with maximum energy from 0.4 to 3.5 MeV

Pressing problems of measurement of ionizing radiations

International Nuclear Information System (INIS)

Fominykh, V.I.; Yudin, M.F.

1993-01-01

The current system for ensuring the unity of measurements in the Russian Federation and countries of the former Soviet Union ensures a high quality of dosimetric, radiometric, and spectrometric measurements in accordance with the recommendations of the Consulative Committee on Standards for Measurements of Ionizing Radiations of the International Bureau of Weights and Measures (IBWM), International Organization on Radiological Units (ICRU), International Commission on Radiological Protection (ICRP), International Organization on Legislative Metrology (IOLM), International Atomic Energy Agency (IAEA), World Health Organization (WHO), etc. Frequent collation of the national primary and secondary standards of Russia with those of IBWM and the leading national laboratories of the world facilitate mutual verification of the measurements of ionizing radiations. The scope of scientific and scientific-technical problems that can be solved by using ionizing radiations has expanded significantly in recent years. In this paper the authors consider some pressing problems of the metrology of ionizing radiations which have arisen as a result of this expansion. These include the need for unity and reliability of measurements involved in radiation protection, the measurement of low doses involving low dose rates, ensuring the unity of measurements when monitoring the radiological security of the population, the need for more uniformity on an international scale regarding the basic physical quantities and their units for characterizing radiation fields, determination of the accuracy of measurement of the radiation dose absorbed by an irradiated tissue or organ, and the development of complex standards for ionizing radiations. 5 refs., 1 tab

Health effects of low dose exposures to external ionizing radiation in the French cohort of nuclear workers CEA-AREVA-EDF - 5287

International Nuclear Information System (INIS)

Leuraud, K.; Fournier, L.; Samson, E.; Caer-Lorho, S.; Laurier, D.; Laroche, P.; Le Guen, B.

2015-01-01

Populations of nuclear workers are particularly relevant to study health effects of low dose and low dose-rate exposures to ionizing radiation. In France, a cohort of nuclear workers employed by CEA, AREVA NC, or EDF, and badge-monitored for radiation exposure, has been followed-up. Annual exposure to penetrating photons was reconstructed for each worker. Standardized mortality ratios were calculated using national mortality rates as the reference. Estimates of radiation dose-mortality associations were obtained using a linear excess relative risk (ERR) model. A total of 59,004 workers were followed-up between 1968 and 2004, for an average of 25 years. The mean cumulative photons dose was 16.1 mSv. At the end of the follow-up, workers were 56 years old and 6,310 workers had died. A strong healthy worker effect was observed. Positive but imprecise estimates of ERR/Sv were observed for all solid cancers and leukemia excluding chronic lymphocytic leukemia. A significant ERR/Sv was found for myeloid leukemia. This cohort study is the most informative ever conducted in France among nuclear workers. Results confirmed a healthy worker effect due to selection at hiring and health monitoring from occupational medicine. Observed dose-risk relationships were consistent with risks estimated in other studies, even if they remained associated to a large uncertainty. (authors)

Optimal treatment scheduling of ionizing radiation and sunitinib improves the antitumor activity and allows dose reduction

International Nuclear Information System (INIS)

Kleibeuker, Esther A; Hooven, Matthijs A ten; Castricum, Kitty C; Honeywell, Richard; Griffioen, Arjan W; Verheul, Henk M; Slotman, Ben J; Thijssen, Victor L

2015-01-01

The combination of radiotherapy with sunitinib is clinically hampered by rare but severe side effects and varying results with respect to clinical benefit. We studied different scheduling regimes and dose reduction in sunitinib and radiotherapy in preclinical tumor models to improve potential outcome of this combination treatment strategy. The chicken chorioallantoic membrane (CAM) was used as an angiogenesis in vivo model and as a xenograft model with human tumor cells (HT29 colorectal adenocarcinoma, OE19 esophageal adenocarcinoma). Treatment consisted of ionizing radiation (IR) and sunitinib as single therapy or in combination, using different dose-scheduling regimes. Sunitinib potentiated the inhibitory effect of IR (4 Gy) on angiogenesis. In addition, IR (4 Gy) and sunitinib (4 days of 32.5 mg/kg per day) inhibited tumor growth. Ionizing radiation induced tumor cell apoptosis and reduced proliferation, whereas sunitinib decreased tumor angiogenesis and reduced tumor cell proliferation. When IR was applied before sunitinib, this almost completely inhibited tumor growth, whereas concurrent IR was less effective and IR after sunitinib had no additional effect on tumor growth. Moreover, optimal scheduling allowed a 50% dose reduction in sunitinib while maintaining comparable antitumor effects. This study shows that the therapeutic efficacy of combination therapy improves when proper dose-scheduling is applied. More importantly, optimal treatment regimes permit dose reductions in the angiogenesis inhibitor, which will likely reduce the side effects of combination therapy in the clinical setting. Our study provides important leads to optimize combination treatment in the clinical setting

Biological effects of low doses of ionizing radiation: Conflict between assumptions and observations

International Nuclear Information System (INIS)

Kesavan, P.C.; Devasagayam, T.P.A.

1997-01-01

Recent epidemiological data on cancer incidence among the A-bomb survivors and more importantly experimental studies in cell and molecular radiobiology do not lend unequivocal support to the ''linear, no threshold'' (LNT) hypothesis; in fact, the discernible evidence that low and high doses of ionizing radiations induce qualitatively different/opposite effects cannot be summarily rejected. A time has come to examine the mechanistic aspects of ''radiation hormesis'' and ''radioadaptive response'' seriously rather than proclaiming one's profound disbelief about these phenomena. To put the discussion in a serious scientific mode, we briefly catalogue here reports in the literature on gene expression differentially influenced by low and high doses. These are not explicable in terms of the current radiation paradigm. (author)

Choosing populations to study the health effects of low-dose ionizing radiation

International Nuclear Information System (INIS)

Dreyer, N.A.; Loughlin, J.E.; Friedlander, E.R.; Clapp, R.W.; Fahey, F.H.

1981-01-01

In January 1978, the United States Congress requested information about the utility of additional epidemiologic studies for quantifying the health effects of low-dose ionizing radiation. In our judgment, no single population can be recommended for study on purely scientific grounds, since the largest group offers only a small chance to obtain a definitive result. On the other hand, if social pressures and regulatory agencies mandate that such studies be attempted, we would recommend prospective cohort studies of occupational populations. We propose that a national worker registry be developed using ionizing radiation as the prototype for studying other occupational exposures. The problems related to studying low-level radiation are not unique, but apply equally to investigations dealing with a great variety of toxic agents. A national plan for collecting information on workers' exposure and health could provide a cost-efficient means to answer public health questions posed by the Congress, scientists and the public

Biology of dose rate in brachytherapy

International Nuclear Information System (INIS)

Brenner, David J.

1995-01-01

Purpose: This course is designed for practitioners and beginners in brachytherapy. The aim is to review biological principles underlying brachytherapy, to understand why current treatment regimes are the way they are, and to discuss what the future may hold in store. Brachytherapy has a long history. It was suggested as long ago as 1903 by Alexander Graham Bell, and the optimal application of this technique has been a subject of debate ever since. 'Brachy' means 'short', and the essential features of conventional brachytherapy are: positioning of the source a short distance from, or in, the tumor, allowing good dose distributions; short overall treatment times, to counter tumor repopulation; low dose rate, enabling a good therapeutic advantage between tumor control and damage to late-responding tissue. The advantages of good dose distributions speak for themselves; in some situations, as we shall see, computer-based dose optimization can be used to improve them still further. The advantages of short overall times stem from the fact that accelerated repopulation of the tumor typically begins a few weeks after the start of a radiation treatment. If all the radiation can be crammed in before that time, the risks of tumor repopulation can be considerably reduced. In fact even external-beam radiotherapy is moving in this direction, with the use of highly accelerated protocols. The advantages of low dose rate stem from the differential response to fractionation of early- and late-responding tissues. Essentially, lowering the dose rate spares late-responding tissue more than it does early-responding tissue such as tumors. We shall also discuss some recent innovations in the context of the general principles that have been outlined. For example, High dose rate brachytherapy, particularly for the uterine cervix: Does it work? If so, when and why? Use of Ir-192 sources, with a half life of 70 days: Should corrections be made for changing biological effectiveness as the dose

Comparison of depth-dose distributions of proton therapeutic beams calculated by means of logical detectors and ionization chamber modeled in Monte Carlo codes

Energy Technology Data Exchange (ETDEWEB)

Pietrzak, Robert [Department of Nuclear Physics and Its Applications, Institute of Physics, University of Silesia, Katowice (Poland); Konefał, Adam, E-mail: adam.konefal@us.edu.pl [Department of Nuclear Physics and Its Applications, Institute of Physics, University of Silesia, Katowice (Poland); Sokół, Maria; Orlef, Andrzej [Department of Medical Physics, Maria Sklodowska-Curie Memorial Cancer Center, Institute of Oncology, Gliwice (Poland)

2016-08-01

The success of proton therapy depends strongly on the precision of treatment planning. Dose distribution in biological tissue may be obtained from Monte Carlo simulations using various scientific codes making it possible to perform very accurate calculations. However, there are many factors affecting the accuracy of modeling. One of them is a structure of objects called bins registering a dose. In this work the influence of bin structure on the dose distributions was examined. The MCNPX code calculations of Bragg curve for the 60 MeV proton beam were done in two ways: using simple logical detectors being the volumes determined in water, and using a precise model of ionization chamber used in clinical dosimetry. The results of the simulations were verified experimentally in the water phantom with Marcus ionization chamber. The average local dose difference between the measured relative doses in the water phantom and those calculated by means of the logical detectors was 1.4% at first 25 mm, whereas in the full depth range this difference was 1.6% for the maximum uncertainty in the calculations less than 2.4% and for the maximum measuring error of 1%. In case of the relative doses calculated with the use of the ionization chamber model this average difference was somewhat greater, being 2.3% at depths up to 25 mm and 2.4% in the full range of depths for the maximum uncertainty in the calculations of 3%. In the dose calculations the ionization chamber model does not offer any additional advantages over the logical detectors. The results provided by both models are similar and in good agreement with the measurements, however, the logical detector approach is a more time-effective method. - Highlights: • Influence of the bin structure on the proton dose distributions was examined for the MC simulations. • The considered relative proton dose distributions in water correspond to the clinical application. • MC simulations performed with the logical detectors and the

High Dose-Rate Versus Low Dose-Rate Brachytherapy for Lip Cancer

Energy Technology Data Exchange (ETDEWEB)

Ghadjar, Pirus, E-mail: pirus.ghadjar@insel.ch [Department of Radiation Oncology, Inselspital, Bern University Hospital, and University of Bern (Switzerland); Bojaxhiu, Beat [Department of Radiation Oncology, Inselspital, Bern University Hospital, and University of Bern (Switzerland); Simcock, Mathew [Swiss Group for Clinical Cancer Research Coordinating Center, Bern (Switzerland); Terribilini, Dario; Isaak, Bernhard [Division of Medical Radiation Physics, Inselspital, Bern University Hospital, and University of Bern, Bern (Switzerland); Gut, Philipp; Wolfensberger, Patrick; Broemme, Jens O.; Geretschlaeger, Andreas; Behrensmeier, Frank; Pica, Alessia; Aebersold, Daniel M. [Department of Radiation Oncology, Inselspital, Bern University Hospital, and University of Bern (Switzerland)

2012-07-15

Purpose: To analyze the outcome after low-dose-rate (LDR) or high-dose-rate (HDR) brachytherapy for lip cancer. Methods and Materials: One hundred and three patients with newly diagnosed squamous cell carcinoma of the lip were treated between March 1985 and June 2009 either by HDR (n = 33) or LDR brachytherapy (n = 70). Sixty-eight patients received brachytherapy alone, and 35 received tumor excision followed by brachytherapy because of positive resection margins. Acute and late toxicity was assessed according to the Common Terminology Criteria for Adverse Events 3.0. Results: Median follow-up was 3.1 years (range, 0.3-23 years). Clinical and pathological variables did not differ significantly between groups. At 5 years, local recurrence-free survival, regional recurrence-free survival, and overall survival rates were 93%, 90%, and 77%. There was no significant difference for these endpoints when HDR was compared with LDR brachytherapy. Forty-two of 103 patients (41%) experienced acute Grade 2 and 57 of 103 patients (55%) experienced acute Grade 3 toxicity. Late Grade 1 toxicity was experienced by 34 of 103 patients (33%), and 5 of 103 patients (5%) experienced late Grade 2 toxicity; no Grade 3 late toxicity was observed. Acute and late toxicity rates were not significantly different between HDR and LDR brachytherapy. Conclusions: As treatment for lip cancer, HDR and LDR brachytherapy have comparable locoregional control and acute and late toxicity rates. HDR brachytherapy for lip cancer seems to be an effective treatment with acceptable toxicity.

Human papillomavirus E6 and E7 oncoproteins alter cell cycle progression but not radiosensitivity of carcinoma cells treated with low-dose-rate radiation

International Nuclear Information System (INIS)

DeWeese, Theodore L.; Walsh, Jonathan C.; Dillehay, Larry E.; Kessis, Theodore D.; Hedrick, Lora; Cho, Kathleen R.; Nelson, William G.

1997-01-01

Purpose: Low-dose-rate radiation therapy has been widely used in the treatment of urogenital malignancies. When continuously exposed to low-dose-rate ionizing radiation, target cancer cells typically exhibit abnormalities in replicative cell-cycle progression. Cancer cells that arrest in the G2 phase of the cell cycle when irradiated may become exquisitely sensitive to killing by further low-dose-rate radiation treatment. Oncogenic human papillomaviruses (HPVs), which play a major role in the pathogenesis of uterine cervix cancers and other urogenital cancers, encode E6 and E7 transforming proteins known to abrogate a p53-dependent G1 cell-cycle checkpoint activated by conventional acute-dose radiation exposure. This study examined whether expression of HPV E6 and E7 oncoproteins by cancer cells alters the cell-cycle redistribution patterns accompanying low-dose-rate radiation treatment, and whether such alterations in cell-cycle redistribution affect cancer cell killing. Methods and Materials: RKO carcinoma cells, which contain wild-type P53 alleles, and RKO cell sublines genetically engineered to express HPV E6 and E7 oncoproteins, were treated with low-dose-rate (0.25-Gy/h) radiation and then assessed for p53 and p21WAF1/CIP1 polypeptide induction by immunoblot analysis, for cell-cycle redistribution by flow cytometry, and for cytotoxicity by clonogenic survival assay. Results: Low-dose-rate radiation of RKO carcinoma cells triggered p53 polypeptide elevations, p21WAF1/CIP1 induction, and arrest in the G1 and G2 phases of the cell cycle. In contrast, RKO cells expressing E6 and E7 transforming proteins from high-risk oncogenic HPVs (HPV 16) arrested in G2, but failed to arrest in G1, when treated with low-dose-rate ionizing radiation. Abrogation of the G1 cell-cycle checkpoint activated by low-dose-rate radiation exposure appeared to be a characteristic feature of transforming proteins from high-risk oncogenic HPVs: RKO cells expressing E6 from a low

Inhibition of gastric secretion in guinea pig by relatively low dose ionizing radiation

International Nuclear Information System (INIS)

Batzri, S.; Catravas, G.

1988-01-01

We evaluated the effect of a single dose of ionizing radiation on gastric secretion in awake guinea pigs equipped with a permanent gastric cannula. Changes in gastric secretion were measured using a dye dilution technique. Infusion of histamine increased acid and fluid output and there was a positive correlation (r = 0.93) between the two. Total body irradiation with 400 cGy, like cimetidine, suppressed acid and fluid secretion under basal conditions and during histamine stimulation by 50-90%. Recovery from the radiation damage was only partial after one week. Irradiation inhibited the rise in gastric juice volume during histamine stimulation and also reduced the normal gain in body weight of the guinea pig. These results demonstrate that ionizing radiations have an immediate and long lasting effects on the gastric mucosal function of the guinea pig

Low-Dose Ionizing Radiation Exposure, Oxidative Stress and Epigenetic Programing of Health and Disease.

Science.gov (United States)

Tharmalingam, Sujeenthar; Sreetharan, Shayenthiran; Kulesza, Adomas V; Boreham, Douglas R; Tai, T C

2017-10-01

Ionizing radiation exposure from medical diagnostic imaging has greatly increased over the last few decades. Approximately 80% of patients who undergo medical imaging are exposed to low-dose ionizing radiation (LDIR). Although there is widespread consensus regarding the harmful effects of high doses of radiation, the biological effects of low-linear energy transfer (LET) LDIR is not well understood. LDIR is known to promote oxidative stress, however, these levels may not be large enough to result in genomic mutations. There is emerging evidence that oxidative stress causes heritable modifications via epigenetic mechanisms (DNA methylation, histone modification, noncoding RNA regulation). These epigenetic modifications result in permanent cellular transformations without altering the underlying DNA nucleotide sequence. This review summarizes the major concepts in the field of epigenetics with a focus on the effects of low-LET LDIR (stress on epigenetic gene modification. In this review, we show evidence that suggests that LDIR-induced oxidative stress provides a mechanistic link between LDIR and epigenetic gene regulation. We also discuss the potential implication of LDIR exposure during pregnancy where intrauterine fetal development is highly susceptible to oxidative stress-induced epigenetic programing.

Mapping the terrestrial air-absorbed gamma dose rate based on the data of airborne gamma-ray spectrometry in southern cities of China

International Nuclear Information System (INIS)

Xiong Shengqing; Fan Zhengguo; Wu Qifan; Wan Jianhua; Wang Nanping; Chu Xingming; Pei Shaoying; Zeng Lihui

2012-01-01

An environmental radioactivity survey by Airborne Gamma-ray Spectrometry (AGS) on a large scale was undertaken in Zhuhai Zone (ZZ) and Shenzhen Zone (SZ), which include major cities in southern China, covering areas of 3800 km 2 and 4660 km 2 , respectively. The estimated dose rates by AGS have been compared with observed results by ionization chamber and portable dosemeter. Maps of the terrestrial dose rate at 1m above ground level have been calculated based on the data of AGS. The mean dose rates are 84.37 ± 51.69 and 82.10 ± 32.98 nGy/h in ZZ and SZ, and the maximum rates are 343.11 and 368.36 nGy/h, respectively. Dose rates in some places are above 180 nGy/h; the areas covered where 149 km 2 in ZZ and 43 km 2 in SZ. The dominant geological conditions that evidently contribute to the radioactive anomalies are outcrops of Middle and Late Jurassic and Cretaceous biotitic-granite. The growth of industrialization and urbanization has dramatically altered radiation background. Stone mining results in the increase of radiation levels with maximum dose rates approaching 368.36 nGy/h in an open pit. The investigation results provide valuable background data and give a good example for mapping nationwide natural radiation terrestrial dose rates in China by AGS. (author)

Dose Response Model of Biological Reaction to Low Dose Rate Gamma Radiation

International Nuclear Information System (INIS)

Magae, J.; Furikawa, C.; Hoshi, Y.; Kawakami, Y.; Ogata, H.

2004-01-01

It is necessary to use reproducible and stable indicators to evaluate biological responses to long term irradiation at low dose-rate. They should be simple and quantitative enough to produce the results statistically accurate, because we have to analyze the subtle changes of biological responses around background level at low dose. For these purposes we chose micronucleus formation of U2OS, a human osteosarcoma cell line, as indicators of biological responses. Cells were exposed to gamma ray in irradiation rom bearing 50,000 Ci 60Co. After irradiation, they were cultured for 24 h in the presence of cytochalasin B to block cytokinesis, and cytoplasm and nucleus were stained with DAPI and prospidium iodide, respectively. the number of binuclear cells bearing micronuclei was counted under a fluorescence microscope. Dose rate in the irradiation room was measured with PLD. Dose response of PLD is linear between 1 mGy to 10 Gy, and standard deviation of triplicate count was several percent of mean value. We fitted statistically dose response curves to the data, and they were plotted on the coordinate of linearly scale response and dose. The results followed to the straight line passing through the origin of the coordinate axes between 0.1-5 Gy, and dose and does rate effectiveness factor (DDREF) was less than 2 when cells were irradiated for 1-10 min. Difference of the percent binuclear cells bearing micronucleus between irradiated cells and control cells was not statistically significant at the dose above 0.1 Gy when 5,000 binuclear cells were analyzed. In contrast, dose response curves never followed LNT, when cells were irradiated for 7 to 124 days. Difference of the percent binuclear cells bearing micronucleus between irradiated cells and control cells was not statistically significant at the dose below 6 Gy, when cells were continuously irradiated for 124 days. These results suggest that dose response curve of biological reaction is remarkably affected by exposure

On determining dose rate constants spectroscopically

International Nuclear Information System (INIS)

Rodriguez, M.; Rogers, D. W. O.

2013-01-01

Purpose: To investigate several aspects of the Chen and Nath spectroscopic method of determining the dose rate constants of 125 I and 103 Pd seeds [Z. Chen and R. Nath, Phys. Med. Biol. 55, 6089–6104 (2010)] including the accuracy of using a line or dual-point source approximation as done in their method, and the accuracy of ignoring the effects of the scattered photons in the spectra. Additionally, the authors investigate the accuracy of the literature's many different spectra for bare, i.e., unencapsulated 125 I and 103 Pd sources. Methods: Spectra generated by 14 125 I and 6 103 Pd seeds were calculated in vacuo at 10 cm from the source in a 2.7 × 2.7 × 0.05 cm 3 voxel using the EGSnrc BrachyDose Monte Carlo code. Calculated spectra used the initial photon spectra recommended by AAPM's TG-43U1 and NCRP (National Council of Radiation Protection and Measurements) Report 58 for the 125 I seeds, or TG-43U1 and NNDC(2000) (National Nuclear Data Center, 2000) for 103 Pd seeds. The emitted spectra were treated as coming from a line or dual-point source in a Monte Carlo simulation to calculate the dose rate constant. The TG-43U1 definition of the dose rate constant was used. These calculations were performed using the full spectrum including scattered photons or using only the main peaks in the spectrum as done experimentally. Statistical uncertainties on the air kerma/history and the dose rate/history were ⩽0.2%. The dose rate constants were also calculated using Monte Carlo simulations of the full seed model. Results: The ratio of the intensity of the 31 keV line relative to that of the main peak in 125 I spectra is, on average, 6.8% higher when calculated with the NCRP Report 58 initial spectrum vs that calculated with TG-43U1 initial spectrum. The 103 Pd spectra exhibit an average 6.2% decrease in the 22.9 keV line relative to the main peak when calculated with the TG-43U1 rather than the NNDC(2000) initial spectrum. The measured values from three different

Late effects of low doses and dose rates

International Nuclear Information System (INIS)

Paretzke, H.G.

1980-01-01

This paper outlines the spectrum of problems and approaches used in work on the derivation of quantitative prognoses of late effects in man of low doses and dose rates. The origins of principal problems encountered in radiation risks assessments, definitions and explanations of useful quantities, methods of deriving risk factors from biological and epidemiological data, and concepts of risk evaluation and problems of acceptance are individually discussed

Quantification of gene expression modulation at the human genome wide induced by low doses of ionizing radiations

International Nuclear Information System (INIS)

Nosel, Ingrid

2013-01-01

The main goal of this study is to identify the molecular mechanisms involved in the response to low doses of ionizing radiation by using oligonucleotide micro-arrays. The results presented in this study demonstrate the relevance of this tool in the characterization of changes in gene expression at low doses of g radiation. All experimentations conducted were conducted on T CD4+ human lymphocytes. From this model we tried to characterize in 600 minutes after irradiation the molecular players in response to a dose range of 5 and 500 mGy. In this study, we highlight two types of molecular response. First, a dose-dependent response to irradiation involving groups of genes whose proteins are implicated in the response to DNA damage and in the p53 signaling pathway. The expression of the majority of the genes is modulated from 100 mGy. The second type of response is independent of the irradiation dose and the proteins encoded are involved in the mechanism of oxidative phosphorylation. Some of these genes could potentially be regulated by a family of transcription factor with an ETS domain. These ETS factors are known to be potential targets of the MAPKinase pathway. All these genes are modulated from 5 mGy and are therefore potential molecular players involved in the cellular response to ionizing stress with a low intensity. (author)

Quality control of 192Ir high dose rate after loading brachytherapy dose veracity

International Nuclear Information System (INIS)

Feng Zhongsu; Xu Xiao; Liu Fen

2008-01-01

Recently, 192 Ir high dose rate (HDR) afterloading are widely used in brachytherapy. The advantage of using HDR systems over low dose rate systems are shorter treatment time and higher fraction dose. To guarantee the veracity of the delivery dose, several quality control methods are deseribed in this work. With these we can improve the position precision, time precision and dose precision of the brachytherapy. (authors)

Effect of ''pasteurizing'' doses of ionizing radiations on drug sensitivity of microbes isolated at pharmacentical factory

International Nuclear Information System (INIS)

Pavlov, E.P.; Shcheglova, S.G.; Sedov, V.V.

1978-01-01

The effect of ionizing radiations on drug sensitivity of microorganisms has been investigated, particularly, the influence of pasteurizing'' doses of ionizing radia''ons on the drug sensitivity of microorganisms isolated at a Moscow pharmaceutical factory to a number of widely used antibiotics. 250 krad single irradiation of dry microbial culture resulted in a change of the antibiotic sensitivity in 0.5% of 686 strains studied. All changes were toward the appearance of sensitivity to one or several antibiotics. When cultures were irradiated 3 times, this value increased up to 9%. In no case the appearance of resistance to antibiotics was observed

Low doses of ionizing radiation and risk of cardiovascular disease: A review of epidemiological studies

International Nuclear Information System (INIS)

Metz-Flamant, C.; Bonaventure, A.; Tirmarche, M.; Laurier, D.; Bernier, M.O.; Milliat, F.

2009-01-01

Background While cardiovascular risks associated with high level of ionizing radiation are well-established, long-term effects of low and medium levels of exposure, between 0 and 5 gray (Gy), on the cardiovascular system are debated. Methods Available literature was reviewed considering various populations, such as survivors of atomic bombs, nuclear workers, Chernobyl liquidators, radiologists and radiological technologists and patients exposed for medical reasons. Results A significant increased risk of cardiovascular diseases associated with low doses of ionizing radiation was observed in 13 studies among the 27 analyzed. The ischemic heart diseases risk was detailed in 16 studies and seven of them showed a significant increase. The cerebrovascular risk was significantly increased in five studies among the 12 considered. Conclusion Some epidemiological and experimental data are clearly in favour of an increased cardiovascular risk associated with exposure to low doses. However, given the multi-factorial origin of cardiovascular diseases and the lack of a clear pathophysiologic mechanism, epidemiological results have to be carefully interpreted. Further research should be conducted in this area. (authors)

Evaluation of absorbed radiation dose rate in a didactic X-ray equipment; Avaliacao da taxa de dose absorvida em um equipamento de raios-X didatico

Energy Technology Data Exchange (ETDEWEB)

Costa, Phelipe Amaral Ferreira; Perini, Ana Paula; Neves, Lucio Pereira, E-mail: lucio.neves@ufu.br [Universidade Federal de Uberlandia (UFU), MG (Brazil). Instituto de Fisica

2016-07-01

This work was performed in order to create a new didactic experiment in the X-ray apparatus of PHYWE, where the saturation current was obtained through a free air ionization chamber. The values of saturation currents were obtained in two ways. Initially, the anodic DDP was kept constant and the anodic current was varied. In the second way, the anodic current was kept constant while the anodic DDP was varied. Therefore, we were able to evaluate the dependence of the absolved dose rate in relation to the DDP and the tube current. (author)

Carcinogenesis in mice after low doses and dose rates

International Nuclear Information System (INIS)

Ullrich, R.L.

1979-01-01

The results from the experimental systems reported here indicate that the dose-response curves for tumor induction in various tissues cannot be described by a single model. Furthermore, although the understanding of the mechanisms involved in different systems is incomplete, it is clear that very different mechanisms for induction are involved. For some tumors the mechanism of carcinogenesis may be mainly a result of direct effects on the target cell, perhaps involving one or more mutations. While induction may occur, in many instances, through such direct effects, the eventual expression of the tumor can be influenced by a variety of host factors including endocrine status, competence of the immune system, and kinetics of target and interacting cell populations. In other tumors, indirect effects may play a major role in the initiation or expression of tumors. Some of the hormone-modulated tumors would fall into this class. Despite the complexities of the experimental systems and the lack of understanding of the types of mechanisms involved, in nearly every example the tumorigenic effectiveness per rad of low-LET radiation tends to decrease with decreasing dose rate. For some tumor types the differences may be small or may appear only with very low dose rates, while for others the dose-rate effects may be large

Ionizing and non-ionizing radiation and the risk of childhood cancer-illustrated with domestic radon and radio frequency electromagnetic field exposure

OpenAIRE

Hauri, Dimitri

2013-01-01

Background Children are exposed to many different environmental factors, including exposure to low-dose ionizing radiation and to non-ionizing radiation. Low-dose ionizing radiation comprises anthropogenic modified radiation and natural ionizing radiation from cosmic rays from the atmosphere, terrestrial gamma radiation from radionuclides in rocks and soils and radiation from radon. Non-ionizing radiation comprises optical radiation and radiation from electromagnetic fields. The la...

Radiation dose rate meter

International Nuclear Information System (INIS)

Kronenberg, S.; Siebentritt, C.R.

1981-01-01

A combined dose rate meter and charger unit therefor which does not require the use of batteries but on the other hand produces a charging potential by means of a piezoelectric cylinder which is struck by a manually triggered hammer mechanism. A tubular type electrometer is mounted in a portable housing which additionally includes a geiger-muller (Gm) counter tube and electronic circuitry coupled to the electrometer for providing multi-mode operation. In one mode of operation, an rc circuit of predetermined time constant is connected to a storage capacitor which serves as a timed power source for the gm tube, providing a measurement in terms of dose rate which is indicated by the electrometer. In another mode, the electrometer indicates individual counts

A study on gamma dose rate in Seoul (I)

International Nuclear Information System (INIS)

Kim, You Hyun; Kim, Chang Kyun; Choi, Jong Hak; Kim, Jeong Min

2001-01-01

This study was conducted to find out gamma dose rate in Seoul, from January to December in 2000, and the following results were achieved : The annual gamma dose rate in Seoul was 17.24 μR/hr as average. The annual gamma dose rate in subway of Seoul was 14.96 μR/hr as average. The highest annual gamma dose rate was Dong-daemon ku. Annual gamma dose rate in Seoul was higher autumn than winter

Radioactivities (dose rates) of rocks in Japan

International Nuclear Information System (INIS)

Matsuda, Hideharu; Minato, Susumu

1995-01-01

The radioactive distribution (radiation doses) of major rocks in Japan was monitored to clarify the factors influencing terrestrial gamma-ray absorbed dose rates. The rock samples were reduced to powder and analyzed by well-type NaI(Tl) scintillation detector and pulse height analyzer. Terrestrial gamma-ray dose rates were estimated in terms of gamma radiation dose rate 1 m above the ground. The radioactivity concentration was highest in acidic rock which contains much SiO 2 among igneous rock, followed by neutral rock, basic rock, and ultrabasic rock. The radioactive concentration was 30-40% lower in acidic and clastic rocks than those of the world average concentration. Higher radioactive concentration was observed in soils than the parent rocks of sedimentary rock and metamorphic rock. The gamma radiation dose rate was in proportion to the radioactive concentration of the rocks. To clarify the radioactive effect in the change course of rocks into soils, comparative measurement of outcrop and soil radioactive concentrations is important. (S.Y.)

Ageing effects of polymers at very low dose-rates

International Nuclear Information System (INIS)

Chenion, J.; Armand, X.; Berthet, J.; Carlin, F.; Gaussens, G.; Le Meur, M.

1987-10-01

The equipment irradiation dose-rate into the containment is variable from 10 -6 to 10 -4 gray per second for the most exposed materials. During qualification, safety equipments are submitted in France to dose-rates around 0.28 gray per second. This study purpose is to now if a so large irradiation dose-rate increase is reasonable. Three elastomeric materials used in electrical cables, o'rings seals and connectors, are exposed to a very large dose-rates scale between 2.1.10 -4 and 1.4 gray per second, to 49 KGy dose. This work was carried out during 3.5 years. Oxygen consumption measurement of the air in contact with polymer materials, as mechanical properties measurement show that: - at very low dose-rate, oxygen consumption is maximum at the same time (1.4 year) for the three elastomeric samples. Also, mechanical properties simultaneously change with oxygen consumption. At very low dose-rate, for the low irradiation doses, oxygen consumption is at least 10 times more important that it is showed when irradiation is carried out with usual material qualification dose-rate. At very low dose-rate, oxygen consumption decreases when absorbed irradiation dose by samples increases. The polymer samples irradiation dose is not still sufficient (49 KGy) to certainly determine, for the three chosen polymer materials, the reasonable irradiation acceleration boundary during nuclear qualification tests [fr

Recommended de minimis radiation dose rates for Canada

International Nuclear Information System (INIS)

1990-07-01

A de minimis dose or dose rate as used in this report represents a level of risk which is generally accepted as being of no significance to an individual, or in the case of a population, of no significance to society. The doses corresponding to these levels of risk are based on current scientific knowledge. Dose rates recommended in this report are as follows: a de minimis individual dose rate of 10 μSv a -1 , based on a risk level that would generally be regarded as negligible in comparison with other risks; and a de minimis collective dose rate of 1 person-Sv a -1 , based on an imperceptible increase above the normal incidences of cancer and genetic defects in the exposed population. The concept of de minimis is to be distinguished from 'exempt from regulation' (below regulatory concern). The latter involves broader social and economic factors which encompass but are not limited to the purely risk-based factors addressed by the de minimis dose. De minimis is one of the factors that determine the exemption of sources or practices that may result in doses below or above the de minimis level. Although these de minimis dose rates should be considered in developing criteria and guidelines for deriving quantities and concentrations of radioactive substances that may be exempted from regulation, this document is only concerned with establishing de minimis dose rates, not with exempting sources and practices

The calculation of dose rates from rectangular sources

International Nuclear Information System (INIS)

Hartley, B.M.

1998-01-01

A common problem in radiation protection is the calculation of dose rates from extended sources and irregular shapes. Dose rates are proportional to the solid angle subtended by the source at the point of measurement. Simple methods of calculating solid angles would assist in estimating dose rates from large area sources and therefore improve predictive dose estimates when planning work near such sources. The estimation of dose rates is of particular interest to producers of radioactive ores but other users of bulk radioactive materials may have similar interest. The use of spherical trigonometry can assist in determination of solid angles and a simple equation is derived here for the determination of the dose at any distance from a rectangular surface. The solid angle subtended by complex shapes can be determined by modelling the area as a patchwork of rectangular areas and summing the solid angles from each rectangle. The dose rates from bags of thorium bearing ores is of particular interest in Western Australia and measured dose rates from bags and containers of monazite are compared with theoretical estimates based on calculations of solid angle. The agreement is fair but more detailed measurements would be needed to confirm the agreement with theory. (author)

Changes in the Number of Double-Strand DNA Breaks in Chinese Hamster V79 Cells Exposed to γ-Radiation with Different Dose Rates

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Andreyan N. Osipov

2013-07-01

Full Text Available A comparative investigation of the induction of double-strand DNA breaks (DSBs in the Chinese hamster V79 cells by γ-radiation at dose rates of 1, 10 and 400 mGy/min (doses ranged from 0.36 to 4.32 Gy was performed. The acute radiation exposure at a dose rate of 400 mGy/min resulted in the linear dose-dependent increase of the γ-H2AX foci formation. The dose-response curve for the acute exposure was well described by a linear function y = 1.22 + 19.7x, where “y” is an average number of γ-H2AX foci per a cell and “x” is the absorbed dose (Gy. The dose rate reduction down to 10 mGy/min lead to a decreased number of γ-H2AX foci, as well as to a change of the dose-response relationship. Thus, the foci number up to 1.44 Gy increased and reached the “plateau” area between 1.44 and 4.32 Gy. There was only a slight increase of the γ-H2AX foci number (up to 7 in cells after the protracted exposure (up to 72 h to ionizing radiation at a dose rate of 1 mGy/min. Similar effects of the varying dose rates were obtained when DNA damage was assessed using the comet assay. In general, our results show that the reduction of the radiation dose rate resulted in a significant decrease of DSBs per cell per an absorbed dose.

Methodology for calibration of ionization chambers for X-ray of low energy in absorbed dose to water

International Nuclear Information System (INIS)

Oliveira, C.T.; Vivolo, V.; Potiens, M.P.A.

2015-01-01

The beams of low energy X-ray (10 to 150 kV) are used in several places in the world to treat a wide variety of surface disorders, and between these malignancies. As in Brazil, at this moment, there is no calibration laboratory providing the control service or calibration of parallel plate ionization chambers, the aim of this project was to establish a methodology for calibration of this kind of ionization chambers at low energy X-ray beams in terms of absorbed dose to water using simulators in the LCI. (author)

Estimation of dose from chromosome aberration rate

International Nuclear Information System (INIS)

Li Deping

1990-01-01

The methods and skills of evaluating dose from correctly scored shromsome aberration rate are presented, and supplemented with corresponding BASIC computer code. The possibility and preventive measures of excessive probability of missing score of the aberrations in some of the current routine score methods are discussed. The use of dose-effect relationship with exposure time correction factor G in evaluating doses and their confidence intervals, dose estimation in mixed n-γ exposure, and identification of high by nonuniform acute exposure to low LET radiation and its dose estimation are discussed in more detail. The difference of estimated dose due to whether the interaction between subleisoms produced by n and γ have been taken into account is examined. In fitting the standard dose-aberration rate curve, proper weighing of experiment points and comparison with commonly accepted values are emphasised, and the coefficient of variation σ y √y of the aberration rate y as a function of dose and exposure time is given. In appendix I and II, the dose-aberration rate formula is derived from dual action theory, and the time variation of subleisom is illustrated and in appendix III, the estimation of dose from scores of two different types of aberrations (of other related score) is illustrated. Two computer codes are given in appendix IV, one is a simple code, the other a complete code, including the fitting of standard curve. the skills of using compressed data storage, and the production of simulated 'data ' for testing the curve fitting procedure are also given

High Dose-Rate Versus Low Dose-Rate Brachytherapy for Lip Cancer

International Nuclear Information System (INIS)

Ghadjar, Pirus; Bojaxhiu, Beat; Simcock, Mathew; Terribilini, Dario; Isaak, Bernhard; Gut, Philipp; Wolfensberger, Patrick; Brömme, Jens O.; Geretschläger, Andreas; Behrensmeier, Frank; Pica, Alessia; Aebersold, Daniel M.

2012-01-01

Purpose: To analyze the outcome after low-dose-rate (LDR) or high-dose-rate (HDR) brachytherapy for lip cancer. Methods and Materials: One hundred and three patients with newly diagnosed squamous cell carcinoma of the lip were treated between March 1985 and June 2009 either by HDR (n = 33) or LDR brachytherapy (n = 70). Sixty-eight patients received brachytherapy alone, and 35 received tumor excision followed by brachytherapy because of positive resection margins. Acute and late toxicity was assessed according to the Common Terminology Criteria for Adverse Events 3.0. Results: Median follow-up was 3.1 years (range, 0.3–23 years). Clinical and pathological variables did not differ significantly between groups. At 5 years, local recurrence-free survival, regional recurrence-free survival, and overall survival rates were 93%, 90%, and 77%. There was no significant difference for these endpoints when HDR was compared with LDR brachytherapy. Forty-two of 103 patients (41%) experienced acute Grade 2 and 57 of 103 patients (55%) experienced acute Grade 3 toxicity. Late Grade 1 toxicity was experienced by 34 of 103 patients (33%), and 5 of 103 patients (5%) experienced late Grade 2 toxicity; no Grade 3 late toxicity was observed. Acute and late toxicity rates were not significantly different between HDR and LDR brachytherapy. Conclusions: As treatment for lip cancer, HDR and LDR brachytherapy have comparable locoregional control and acute and late toxicity rates. HDR brachytherapy for lip cancer seems to be an effective treatment with acceptable toxicity.

Radiobiological responses for two cell lines following continuous low dose-rate (CLDR) and pulsed dose rate (PDR) brachytherapy

International Nuclear Information System (INIS)

Hanisch, Per Henrik; Furre, Torbjoern; Olsen, Dag Rune; Pettersen, Erik O.

2007-01-01

The iso-effective irradiation of continuous low-dose-rate (CLDR) irradiation was compared with that of various schedules of pulsed dose rate (PDR) irradiation for cells of two established human lines, T-47D and NHIK 3025. Complete single-dose response curves were obtained for determination of parameters α and β by fitting of the linear quadratic formula. Sublethal damage repair constants μ and T 1/2 were determined by split-dose recovery experiments. On basis of the acquired parameters of each cell type the relative effectiveness of the two regimens of irradiation (CLDR and PDR) was calculated by use of Fowler's radiobiological model for iso-effect irradiation for repeated fractions of dose delivered at medium dose rates. For both cell types the predicted and observed relative effectiveness was compared at low and high iso-effect levels. The results indicate that the effect of PDR irradiation predicted by Fowler's model is equal to that of CLDR irradiation for both small and large doses with T-47D cells. With NHIK 3025 cells PDR irradiation induces a larger effect than predicted by the model for small doses, while it induces the predicted effect for high doses. The underlying cause of this difference is unclear, but cell-cycle parameters, like G2-accumulation is tested and found to be the same for the two cell lines

Dose and dose rate effects of whole-body gamma-irradiation: I. Lymphocytes and lymphoid organs

Science.gov (United States)

Pecaut, M. J.; Nelson, G. A.; Gridley, D. S.

2001-01-01

The major goal of part I of this study was to compare varying doses and dose rates of whole-body gamma-radiation on lymphoid cells and organs. C57BL/6 mice (n = 75) were exposed to 0, 0.5, 1.5, and 3.0 Gy gamma-rays (60Co) at 1 cGy/min (low-dose rate, LDR) and 80 cGy/min (high-dose rate, HDR) and euthanized 4 days later. A significant dose-dependent loss of spleen mass was observed with both LDR and HDR irradiation; for the thymus this was true only with HDR. Decreasing leukocyte and lymphocyte numbers occurred with increasing dose in blood and spleen at both dose rates. The numbers (not percentages) of CD3+ T lymphocytes decreased in the blood in a dose-dependent manner at both HDR and LDR. Splenic T cell counts decreased with dose only in HDR groups; percentages increased with dose at both dose rates. Dose-dependent decreases occurred in CD4+ T helper and CD8+ T cytotoxic cell counts at HDR and LDR. In the blood the percentages of CD4+ cells increased with increasing dose at both dose rates, whereas in the spleen the counts decreased only in the HDR groups. The percentages of the CD8+ population remained stable in both blood and spleen. CD19+ B cell counts and percentages in both compartments declined markedly with increasing HDR and LDR radiation. NK1.1+ natural killer cell numbers and proportions remained relatively stable. Overall, these data indicate that the observed changes were highly dependent on the dose, but not dose rate, and that cells in the spleen are more affected by dose rate than those in blood. The results also suggest that the response of lymphocytes in different body compartments may be variable.

Determination of high level absorbed dose in a 60Co gamma ray field with ionization chambers

International Nuclear Information System (INIS)

Zhongying Li; Benjiang Mao; Lu Zhang

1995-01-01

This paper relates to the principles and methods for determining the absorbed dose of high energy photons radiation with ionization chambers, and its shows the doserate results of high level 60 Co γ-rays in water measured with Farmer chambers. The results with two kinds of chambers at a same point are consistent within 0.3%, and the total uncertainty is less than ± 4%. In the domestic intercomparison on determining high level absorbed dose in which 12 laboratories participated, the deviation of our result from the mean result of the intercomparison is -0.04% [Chen Yundong (1992). Summing up report on a high level absorbed dose intercomparison (in Chinese)]. (author)

Femtosecond Coherent Spectroscopy at 800nm: MI-FROG Measures High-Field Ionization Rates in Gases

International Nuclear Information System (INIS)

Siders, C.W.; Siders, J.L.W.; Taylor, A.J.

1999-01-01

The authors report the first quantitative phase-sensitive measurement of ultrafast ionization rates in gases using Multi-phase Interferometric Frequency-Resolved Optical Gating. Ultrafast probe depletion via frequency mixing in the ionization front is observed

MONTEC, an interactive fortran program to simulate radiation dose and dose-rate responses of populations

International Nuclear Information System (INIS)

Perry, K.A.; Szekely, J.G.

1983-09-01

The computer program MONTEC was written to simulate the distribution of responses in a population whose members are exposed to multiple radiation doses at variable dose rates. These doses and dose rates are randomly selected from lognormal distributions. The individual radiation responses are calculated from three equations, which include dose and dose-rate terms. Other response-dose/rate relationships or distributions can be incorporated by the user as the need arises. The purpose of this documentation is to provide a complete operating manual for the program. This version is written in FORTRAN-10 for the DEC system PDP-10

Myeloid leukaemia frequency after protracted exposure to ionizing radiation: experimental confirmation of the flat dose-response found in ankylosing spondylitis after a single treatment course with x-rays

Energy Technology Data Exchange (ETDEWEB)

Mole, R H; Major, I R [Medical Research Council, Harwell (UK). Radiobiological Research Unit

1983-01-01

The dose-response for leukaemia induction by exposure to ionizing radiation protracted over several weeks was largely independent of dose not only in X-rayed patients with ankylosing spondylitis but also in experimentally ..gamma..-rayed CBA/H mice. In the experiment the induced leukaemia frequency of acute myeloid leukaemia was independent of a several thousand-fold variation in physical dose rate. Any difference in leukaemia induction between brief and protracted exposures must therefore depend on specifically biological consequences of protracted exposures. Experimental analysis is required to provide the guides for inference about risks of low level exposure from observations on relatively heavily irradiated populations.

Expression of Cellular Isoform of Prion Protein on the Surface of Peripheral Blood Lymphocytes Among Women Exposed to Low Doses of Ionizing Radiation

International Nuclear Information System (INIS)

Klucinski, P.; Martirosian, G.; Mazur, B.; Kaufman, J.; Hrycek, A.; Masluch, E.; Cieslik, P.

2007-01-01

Ionizing radiation affect the expression of adhesive and co-stimulation molecules in lymphocytes. The objective of this study was to determinate the effect of low doses of ionizing radiation on the expression of prion protein PrPc on the surface peripheral blood lymphocytes in the women operating X-ray equipment. In female workers and persons of the control group the PrPc expression on CD3 (T-lymphocytes), Cd4 (T-helper), CD8 (T-cytotoxic) and CD19 (B- lymphocytes), were tested. We conclude that in women operating X-ray equipment the relationship between low doses of ionizing radiation and expression of PrPc on lymphocytes does exist concerning CD3, CD4 and CD lymphocytes. (author)

Compensation for damage to workers health exposed to ionizing radiation in Argentina

International Nuclear Information System (INIS)

Sobehart, Leonardo J.

2003-01-01

The objective of this report is to analyze the possibility to establish a scheme to compensate damage to workers health exposed to ionizing radiation in Argentina for those cases in which it is possible to assume that the exposure to ionizing radiation is the cause of the cancer suffered by the worker. The proposed scheme is based on the recommendations set out in the 'International Conference on Occupational Radiation Protection: Protecting Workers against Exposure to Ionization Radiation, held in Geneva, Switzerland, August 26-30, 2002. To this end, the study analyzes the present state of scientific knowledge on cancer causation due to genotoxic factors, and the accepted form of the doses-response curve, for the human beings exposure to ionization radiation at low doses with low doses rates. Finally, the labor laws and regulations related to damage compensation; in particular the present Argentine Labor Law; the National Russian Federal Occupational Radiological Health Impairment and Workmen Compensation, the United Kingdom Compensation Scheme for Radiation-linked Diseases and the United States Energy Employees Occupational Illness Compensation Program are described. (author)

DOSIS: a computer program for the calculation of absorbed dose in photon and electron beams from ionization measurements in a phantom

Energy Technology Data Exchange (ETDEWEB)

Andreo, P [Kungliga Karolinska Mediko-Kirurgiska Inst., Stockholm (Sweden). Radiofysiska Institutionen; Zaragoza Univ. (Spain). Dept. de Radiologia)

1983-06-15

A computer program has been developed to facilitate the calculation of the absorbed dose in photon and electron beams from measurements with an ionization chamber in a phantom. The generalized Bragg-Gray theory, introduced in the latest recommendations of the Nordic Association of Clinical Physics (NACP), is used throughout the code, including more updated parameter values than those included in the NACP protocol. The calibration factor of the ionization chamber in units of absorbed dose in the air of the cavity can be derived for most of the chambers available today by using experimental data or fitted relations to Monte Carlo results.

Effect of dose rate on residual γ-H2AX levels and frequency of micronuclei in X-irradiated mouse lymphocytes.

Science.gov (United States)

Turner, H C; Shuryak, I; Taveras, M; Bertucci, A; Perrier, J R; Chen, C; Elliston, C D; Johnson, G W; Smilenov, L B; Amundson, S A; Brenner, D J

2015-03-01

The biological risks associated with low-dose-rate (LDR) radiation exposures are not yet well defined. To assess the risk related to DNA damage, we compared the yields of two established biodosimetry end points, γ-H2AX and micronuclei (MNi), in peripheral mouse blood lymphocytes after prolonged in vivo exposure to LDR X rays (0.31 cGy/min) vs. acute high-dose-rate (HDR) exposure (1.03 Gy/min). C57BL/6 mice were total-body irradiated with 320 kVP X rays with doses of 0, 1.1, 2.2 and 4.45 Gy. Residual levels of total γ-H2AX fluorescence in lymphocytes isolated 24 h after the start of irradiation were assessed using indirect immunofluorescence methods. The terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay was used to determine apoptotic cell frequency in lymphocytes sampled at 24 h. Curve fitting analysis suggested that the dose response for γ-H2AX yields after acute exposures could be described by a linear dependence. In contrast, a linear-quadratic dose-response shape was more appropriate for LDR exposure (perhaps reflecting differences in repair time after different LDR doses). Dose-rate sparing effects (P effect across the dose range 24 h or 7 days post exposure. In conclusion, the γ-H2AX biomarker showed higher sensitivity to measure dose-rate effects after low-dose LDR X rays compared to MNi formation; however, confounding factors such as variable repair times post exposure, increased cell killing and cell cycle block likely contributed to the yields of MNi with accumulating doses of ionizing radiation.

Total Ionizing Dose Effects on Threshold Switching in 1T-Tantalum Disulfide Charge-Density-Wave Devices

OpenAIRE

Liu, G.; Zhang, E. X.; Liang, C. D.; Bloodgood, M. A.; Salguero, T. T.; Fleetwood, D. M.; Balandin, A. A.

2017-01-01

The 1T polytype of TaS2 exhibits voltage-triggered threshold switching as a result of a phase transition from nearly commensurate to incommensurate charge density wave states. Threshold switching, persistent above room temperature, can be utilized in a variety of electronic devices, e.g., voltage controlled oscillators. We evaluated the total-ionizing-dose response of thin film 1T-TaS2 at doses up to 1 Mrad(SiO2). The threshold voltage changed by less than 2% after irradiation, with persisten...

Protection of wood with ionizing radiation

International Nuclear Information System (INIS)

Jokel, J.; Paserin, V.

1975-01-01

The method is described of accelerated killing of wood cells by ionizing radiation. From the conducted experiments the relation was derived for the resistance of these cells to the effects of high-energy gamma radiation and a relationship was ascertained between the level of the irradiation of live cells and the spread of tylosis in beech trees. Live wood cells may be killed by doses of up to 25 J/g (2.5 Mrad). The occurrence and formation rate of tylosis is restricted by doses between 0.25 J/g to 4.5 J/g. Doses of more than 4.5 J/g prevent the occurrence of tylosis. (J.K.)

Ionizing radiations simulation on bipolar components

International Nuclear Information System (INIS)

Montagner, X.

1999-01-01

This thesis presents the ionizing radiation effects on bipolar components and more specially their behavior facing the total dose. The first part is devoted to the radiation environments with a special attention to the spatial environments and new emergent environments. The specificities of bipolar components are then presented and their behavior facing the interactions. The physical mechanisms bound to the dose rate are also discussed. The second part presents a physical analysis of degradations induced by the cumulated dosimetry on bipolar components and simulation with the ATLAS code. The third part exposes an electric empirical simulation induced by the cumulated dose in static conditions. (A.L.B.)

Radiation shielding and dose rate distribution for the building of the high dose rate accelerator

International Nuclear Information System (INIS)

Matsuda, Koji; Takagaki, Torao; Nakase, Yoshiaki; Nakai, Yohta.

1984-03-01

A high dose rate electron accelerator was established at Osaka Laboratory for Radiation Chemistry, Takasaki Establishment, JAERI in the fiscal year of 1975. This report shows the fundamental concept for the radiation shielding of the accelerator building and the results of their calculations which were evaluated through the model experiments. After the construction of the building, the leak radiation was measured in order to evaluate the calculating method of radiation shielding. Dose rate distribution of X-rays was also measured in the whole area of the irradiation room as a data base. (author)

Measurement of nonlinear refractive index and ionization rates in air using a wavefront sensor.

Science.gov (United States)

Schwarz, Jens; Rambo, Patrick; Kimmel, Mark; Atherton, Briggs

2012-04-09

A wavefront sensor has been used to measure the Kerr nonlinear focal shift of a high intensity ultrashort pulse beam in a focusing beam geometry while accounting for the effects of plasma-defocusing. It is shown that plasma-defocusing plays a major role in the nonlinear focusing dynamics and that measurements of Kerr nonlinearity and ionization are coupled. Furthermore, this coupled effect leads to a novel way that measures the laser ionization rates in air under atmospheric conditions as well as Kerr nonlinearity. The measured nonlinear index n₂ compares well with values found in the literature and the measured ionization rates could be successfully benchmarked to the model developed by Perelomov, Popov, and Terentev (PPT model) [Sov. Phys. JETP 50, 1393 (1966)].

Effects of ionizing radiation on aquatic organisms and ecosystems

International Nuclear Information System (INIS)

1976-01-01

A panel of experts in November 1971 specifically considered the effects of ionizing radiation on aquatic organisms and ecosystems and formulated detailed suggestions for research in the area. A further panel meeting took place in April 1974. The results of the work are presented in this report which is divided into 3 chapters in the first chapter the concentrations of natural and artificial radionuclides in aquatic environments and the radiation dose rates received by aquatic organisms are discussed. In particular, simple dosimetry models for phytoplankton, zooplankton, mollusca, crustacea and fish are presented which permit the estimation of the dose rates from incorporated radionuclides and from radionuclides in the external environment. In the second chapter the somatic and genetic effects of ionizing radiation on aquatic organisms are reviewed. Somatic effects are discussed separately as effects due to short-term (acute) exposure to near-lethal doses of radiation. Great attention is paid to the effects due to long-term (chronic) exposure at lower doses rates. Consideration is given to behaviour, repair mechanisms and metabolic stimulation after exposure, and also the influence of environmental factors on radiation effects. In the third chapter the potential effects of low-level irradiation on aquatic populations are considered. First, the possible consequences of somatic effects on egg and larval mortality, stock-recruitment, fecundity and ecosystem stability are discussed. Subsequently, the assessment of genetic effects as they relate to population genetics and increased mutation rates are considered

Male gonadal dose of ionizing radiation delivered during X-ray examinations and monthly probability of pregnancy: a population-based retrospective study

Directory of Open Access Journals (Sweden)

Slama Remy

2006-03-01

Full Text Available Abstract Background Male gonadal exposure to ionizing radiation may disrupt spermatogenesis, but its influence on the fecundity of couples has been rarely studied. We aimed to characterize the influence of male gonadal dose of ionizing radiation delivered during radiodiagnostic on the monthly probability of pregnancy. Methods We recruited a random sample of women who retrospectively described 1110 periods of unprotected intercourse beginning between 1985 and 1999 and leading either to a live birth or to no pregnancy; their duration was censored after 13 months. The male partner answered a telephone questionnaire on radiodiagnostic examinations. We assigned a mean gonadal dose to each type of radiodiagnostic examination. We defined male dose for each period of unprotected intercourse as the sum of the gonadal doses of the X-ray examinations experienced between 18 years of age and the date of discontinuation of contraception. Time to pregnancy was analysed using a discrete Cox model with random effect allowing to estimate hazard ratios of pregnancy. Results After adjustment for female factors likely to influence fecundity, there was no evidence of an association between male dose and the probability of pregnancy (test of homogeneity, p = 0.55. When compared to couples with a male gonadal dose between 0.01 and 0.20 milligrays (n = 321 periods of unprotected intercourse, couples with a gonadal dose above 10 milligrays had a hazard ratio of pregnancy of 1.44 (95% confidence interval, 0.73–2.86, n = 31. Conclusion Our study provides no evidence of a long-term detrimental effect of male gonadal dose of ionizing radiation delivered during radiodiagnostic on the monthly probability of pregnancy during the year following discontinuation of contraceptive use. Classification errors due to the retrospective assessment of male gonadal exposure may have limited the statistical power of our study.