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Sample records for dose rate ionizing

  1. Properties of liquid ionization chambers at LDR brachytherapy dose rates.

    PubMed

    Johansson, B; Wickman, G; Holmström, T

    1995-04-01

    Properties such as sensitivity, general recombination and reproducibility of liquid-filled parallel-plate ionization chambers for dosimetry in low-dose-rate brachytherapy radiation fields have been evaluated. Two different dielectric liquids, isooctane (C8H(1)8) and tetramethylsilane (Si(CH3)4), have been used as sensitive media in chambers having a coin-shaped sensitive volume of 3 mm in diameter and 1 mm thickness. An electric field strength of 300 kV m-1 was found to be optimal with respect to sensitivity, leakage current and general recombination. At absorbed dose rates from 0.1-100 mGy min-1 the ionization charge measurements at an irradiation time of 1 min showed a reproducibility better than 1%, and a general recombination not exceeding 0.5%. The calibration--absorbed dose to water against ionization charge at a 60Co reference source--did not show any significant change over an observation time of one year for any of the chambers.

  2. The susceptibility of TaOx-based memristors to high dose rate ionizing radiation and total ionizing dose

    DOE PAGES

    McLain, Michael Lee; Sheridan, Timothy J.; Hjalmarson, Harold Paul; ...

    2014-11-11

    This paper investigates the effects of high dose rate ionizing radiation and total ionizing dose (TID) on tantalum oxide (TaOx) memristors. Transient data were obtained during the pulsed exposures for dose rates ranging from approximately 5.0 ×107 rad(Si)/s to 4.7 ×108 rad(Si)/s and for pulse widths ranging from 50 ns to 50 μs. The cumulative dose in these tests did not appear to impact the observed dose rate response. Static dose rate upset tests were also performed at a dose rate of ~3.0 ×108 rad(Si)/s. This is the first dose rate study on any type of memristive memory technology. Inmore » addition to assessing the tolerance of TaOx memristors to high dose rate ionizing radiation, we also evaluated their susceptibility to TID. The data indicate that it is possible for the devices to switch from a high resistance off-state to a low resistance on-state in both dose rate and TID environments. The observed radiation-induced switching is dependent on the irradiation conditions and bias configuration. Furthermore, the dose rate or ionizing dose level at which a device switches resistance states varies from device to device; the enhanced susceptibility observed in some devices is still under investigation. As a result, numerical simulations are used to qualitatively capture the observed transient radiation response and provide insight into the physics of the induced current/voltages.« less

  3. Total ionizing dose effects of domestic SiGe HBTs under different dose rates

    NASA Astrophysics Data System (ADS)

    Liu, Mo-Han; Lu, Wu; Ma, Wu-Ying; Wang, Xin; Guo, Qi; He, Cheng-Fa; Jiang, Ke; Li, Xiao-Long; Xun, Ming-Zhu

    2016-03-01

    The total ionizing radiation (TID) response of commercial NPN silicon germanium hetero-junction bipolar transistors (SiGe HBTs) produced domestically are investigated under dose rates of 800 mGy(Si)/s and 1.3 mGy(Si)/s with a Co-60 gamma irradiation source. The changes of transistor parameters such as Gummel characteristics, and excess base current before and after irradiation, are examined. The results of the experiments show that for the KT1151, the radiation damage is slightly different under the different dose rates after prolonged annealing, and shows a time dependent effect (TDE). For the KT9041, however, the degradations of low dose rate irradiation is higher than for the high dose rate, demonstrating that there is a potential enhanced low dose rate sensitivity (ELDRS) effect for the KT9041. The possible underlying physical mechanisms of the different dose rates responses induced by the gamma rays are discussed.

  4. Low-dose or low-dose-rate ionizing radiation–induced bioeffects in animal models

    PubMed Central

    Loke, Weng Keong; Khoo, Boo Cheong

    2017-01-01

    Abstract Animal experimental studies indicate that acute or chronic low-dose ionizing radiation (LDIR) (≤100 mSv) or low-dose-rate ionizing radiation (LDRIR) (<6 mSv/h) exposures may be harmful. It induces genetic and epigenetic changes and is associated with a range of physiological disturbances that includes altered immune system, abnormal brain development with resultant cognitive impairment, cataractogenesis, abnormal embryonic development, circulatory diseases, weight gain, premature menopause in female animals, tumorigenesis and shortened lifespan. Paternal or prenatal LDIR/LDRIR exposure is associated with reduced fertility and number of live fetuses, and transgenerational genomic aberrations. On the other hand, in some experimental studies, LDIR/LDRIR exposure has also been reported to bring about beneficial effects such as reduction in tumorigenesis, prolonged lifespan and enhanced fertility. The differences in reported effects of LDIR/LDRIR exposure are dependent on animal genetic background (susceptibility), age (prenatal or postnatal days), sex, nature of radiation exposure (i.e. acute, fractionated or chronic radiation exposure), type of radiation, combination of radiation with other toxic agents (such as smoking, pesticides or other chemical toxins) or animal experimental designs. In this review paper, we aimed to update radiation researchers and radiologists on the current progress achieved in understanding the LDIR/LDRIR-induced bionegative and biopositive effects reported in the various animal models. The roles played by a variety of molecules that are implicated in LDIR/LDRIR-induced health effects will be elaborated. The review will help in future investigations of LDIR/LDRIR-induced health effects by providing clues for designing improved animal research models in order to clarify the current controversial/contradictory findings from existing studies. PMID:28077626

  5. Low-dose or low-dose-rate ionizing radiation-induced bioeffects in animal models.

    PubMed

    Tang, Feng Ru; Loke, Weng Keong; Khoo, Boo Cheong

    2017-03-01

    Animal experimental studies indicate that acute or chronic low-dose ionizing radiation (LDIR) (≤100 mSv) or low-dose-rate ionizing radiation (LDRIR) (<6 mSv/h) exposures may be harmful. It induces genetic and epigenetic changes and is associated with a range of physiological disturbances that includes altered immune system, abnormal brain development with resultant cognitive impairment, cataractogenesis, abnormal embryonic development, circulatory diseases, weight gain, premature menopause in female animals, tumorigenesis and shortened lifespan. Paternal or prenatal LDIR/LDRIR exposure is associated with reduced fertility and number of live fetuses, and transgenerational genomic aberrations. On the other hand, in some experimental studies, LDIR/LDRIR exposure has also been reported to bring about beneficial effects such as reduction in tumorigenesis, prolonged lifespan and enhanced fertility. The differences in reported effects of LDIR/LDRIR exposure are dependent on animal genetic background (susceptibility), age (prenatal or postnatal days), sex, nature of radiation exposure (i.e. acute, fractionated or chronic radiation exposure), type of radiation, combination of radiation with other toxic agents (such as smoking, pesticides or other chemical toxins) or animal experimental designs. In this review paper, we aimed to update radiation researchers and radiologists on the current progress achieved in understanding the LDIR/LDRIR-induced bionegative and biopositive effects reported in the various animal models. The roles played by a variety of molecules that are implicated in LDIR/LDRIR-induced health effects will be elaborated. The review will help in future investigations of LDIR/LDRIR-induced health effects by providing clues for designing improved animal research models in order to clarify the current controversial/contradictory findings from existing studies. © The Author 2017. Published by Oxford University Press on behalf of The Japan Radiation Research

  6. Evaluation of High Performance Converters Under Low Dose Rate Total Ionizing Dose (TID) Testing for NASA Programs

    NASA Technical Reports Server (NTRS)

    Sharma, Ashok K.; Sahu, Kusum

    1998-01-01

    This paper reports the results of low dose rate (0.01-0.18 rads(Si)/sec) total ionizing dose (TID) tests performed on several types of high performance converters. The parts used in this evaluation represented devices such as a high speed flash converter, a 16-bit ADC and a voltage-to-frequency converter.

  7. The susceptibility of TaOx-based memristors to high dose rate ionizing radiation and total ionizing dose

    SciTech Connect

    McLain, Michael Lee; Sheridan, Timothy J.; Hjalmarson, Harold Paul; Mickel, Patrick R.; Hanson, Donald J.; McDonald, Joseph K.; Hughart, David Russell; Marinella, Matthew J.

    2014-11-11

    This paper investigates the effects of high dose rate ionizing radiation and total ionizing dose (TID) on tantalum oxide (TaOx) memristors. Transient data were obtained during the pulsed exposures for dose rates ranging from approximately 5.0 ×107 rad(Si)/s to 4.7 ×108 rad(Si)/s and for pulse widths ranging from 50 ns to 50 μs. The cumulative dose in these tests did not appear to impact the observed dose rate response. Static dose rate upset tests were also performed at a dose rate of ~3.0 ×108 rad(Si)/s. This is the first dose rate study on any type of memristive memory technology. In addition to assessing the tolerance of TaOx memristors to high dose rate ionizing radiation, we also evaluated their susceptibility to TID. The data indicate that it is possible for the devices to switch from a high resistance off-state to a low resistance on-state in both dose rate and TID environments. The observed radiation-induced switching is dependent on the irradiation conditions and bias configuration. Furthermore, the dose rate or ionizing dose level at which a device switches resistance states varies from device to device; the enhanced susceptibility observed in some devices is still under investigation. As a result, numerical simulations are used to qualitatively capture the observed transient radiation response and provide insight into the physics of the induced current/voltages.

  8. Effects of Martian dust storms on ionization profiles and surface dose rates from cosmic rays

    NASA Astrophysics Data System (ADS)

    Norman, R. B.; Gronoff, G.; Mertens, C. J.

    2012-12-01

    Global dust storms can engulf Mars and distribute dust throughout the atmosphere. The change in composition and density of the atmosphere due to dust storms affects the ionization rate due to cosmic rays impingent on Mars. To model the effect of dust storms on the Martian ionization profile, the Badhwar-O'Neill cosmic ray spectrum model has been adapted to Mars and used as an input in the NAIRAS model. NAIRAS is a cosmic ray irradiation model adapted for fast computations and has been applied to the Martian atmosphere. Full atmosphere ionization profiles for solar maximum and solar minimum conditions during both dust storms and quiet times are reported. The contribution of heavy ions and secondary particles to the ionization profile are also reported. Dose rates at the surface due to cosmic radiation are shown to not vary significantly due to the dust storms.

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

    SciTech Connect

    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.

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

    SciTech Connect

    Levy, Richard 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.

  11. Multi-Level Effects of Low Dose Rate Ionizing Radiation on Southern Toad, Anaxyrus [Bufo] terrestris

    PubMed Central

    Stark, Karolina; Scott, David E.; Tsyusko, Olga; Coughlin, Daniel P.; Hinton, Thomas G.

    2015-01-01

    Despite their potential vulnerability to contaminants from exposure at multiple life stages, amphibians are one of the least studied groups of vertebrates in ecotoxicology, and research on radiation effects in amphibians is scarce. We used multiple endpoints to assess the radiosensitivity of the southern toad (Anaxyrus [Bufo] terrestris) during its pre-terrestrial stages of development –embryonic, larval, and metamorphic. Toads were exposed, from several hours after oviposition through metamorphosis (up to 77 days later), to four low dose rates of 137Cs at 0.13, 2.4, 21, and 222 mGy d-1, resulting in total doses up to 15.8 Gy. Radiation treatments did not affect hatching success of embryos, larval survival, or the length of the larval period. The individual family variation in hatching success of embryos was larger than the radiation response. In contrast, newly metamorphosed individuals from the higher dose-rate treatments had higher mass and mass/length body indices, a measure which may relate to higher post-metamorphic survival. The increased mass and index at higher dose rates may indicate that the chronic, low dose rate radiation exposures triggered secondary responses. Additionally, the increases in growth were linked to a decrease in DNA damage (as measured by the Comet Assay) in red blood cells at a dose rate of 21 mGy d-1 and a total dose of 1.1 Gy. In conclusion, the complex effects of low dose rates of ionizing radiation may trigger growth and cellular repair mechanisms in amphibian larvae. PMID:25927361

  12. Multi-level effects of low dose rate ionizing radiation on southern toad, Anaxyrus [Bufo] terrestris

    DOE PAGES

    Stark, Karolina; Scott, David E.; Tsyusko, Olga; ...

    2015-04-30

    Despite their potential vulnerability to contaminants from exposure at multiple life stages, amphibians are one of the least studied groups of vertebrates in ecotoxicology, and research on radiation effects in amphibians is scarce. We used multiple endpoints to assess the radiosensitivity of the southern toad (Anaxyrus [Bufo] terrestris) during its pre-terrestrial stages of development –embryonic, larval, and metamorphic. Toads were exposed, from several hours after oviposition through metamorphosis (up to 77 days later), to four low dose rates of ¹³⁷Cs at 0.13, 2.4, 21, and 222 mGy d⁻¹, resulting in total doses up to 15.8 Gy. Radiation treatments did notmore » affect hatching success of embryos, larval survival, or the length of the larval period. The individual family variation in hatching success of embryos was larger than the radiation response. In contrast, newly metamorphosed individuals from the higher dose-rate treatments had higher mass and mass/length body indices, a measure which may relate to higher post-metamorphic survival. The increased mass and index at higher dose rates may indicate that the chronic, low dose rate radiation exposures triggered secondary responses. Additionally, the increases in growth were linked to a decrease in DNA damage (as measured by the Comet Assay) in red blood cells at a dose rate of 21mGy d⁻¹ and a total dose of 1.1 Gy. In conclusion, the complex effects of low dose rates of ionizing radiation may trigger growth and cellular repair mechanisms in amphibian larvae.« less

  13. Multi-Level Effects of Low Dose Rate Ionizing Radiation on Southern Toad, Anaxyrus [Bufo] terrestris.

    PubMed

    Stark, Karolina; Scott, David E; Tsyusko, Olga; Coughlin, Daniel P; Hinton, Thomas G

    2015-01-01

    Despite their potential vulnerability to contaminants from exposure at multiple life stages, amphibians are one of the least studied groups of vertebrates in ecotoxicology, and research on radiation effects in amphibians is scarce. We used multiple endpoints to assess the radiosensitivity of the southern toad (Anaxyrus [Bufo] terrestris) during its pre-terrestrial stages of development -embryonic, larval, and metamorphic. Toads were exposed, from several hours after oviposition through metamorphosis (up to 77 days later), to four low dose rates of 137Cs at 0.13, 2.4, 21, and 222 mGy d-1, resulting in total doses up to 15.8 Gy. Radiation treatments did not affect hatching success of embryos, larval survival, or the length of the larval period. The individual family variation in hatching success of embryos was larger than the radiation response. In contrast, newly metamorphosed individuals from the higher dose-rate treatments had higher mass and mass/length body indices, a measure which may relate to higher post-metamorphic survival. The increased mass and index at higher dose rates may indicate that the chronic, low dose rate radiation exposures triggered secondary responses. Additionally, the increases in growth were linked to a decrease in DNA damage (as measured by the Comet Assay) in red blood cells at a dose rate of 21 mGy d-1 and a total dose of 1.1 Gy. In conclusion, the complex effects of low dose rates of ionizing radiation may trigger growth and cellular repair mechanisms in amphibian larvae.

  14. Critical target and dose and dose-rate responses for the induction of chromosomal instability by ionizing radiation

    NASA Technical Reports Server (NTRS)

    Limoli, C. L.; Corcoran, J. J.; Milligan, J. R.; Ward, J. F.; Morgan, W. F.

    1999-01-01

    To investigate the critical target, dose response and dose-rate response for the induction of chromosomal instability by ionizing radiation, bromodeoxyuridine (BrdU)-substituted and unsubstituted GM10115 cells were exposed to a range of doses (0.1-10 Gy) and different dose rates (0.092-17.45 Gy min(-1)). The status of chromosomal stability was determined by fluorescence in situ hybridization approximately 20 generations after irradiation in clonal populations derived from single progenitor cells surviving acute exposure. Overall, nearly 700 individual clones representing over 140,000 metaphases were analyzed. In cells unsubstituted with BrdU, a dose response was found, where the probability of observing delayed chromosomal instability in any given clone was 3% per gray of X rays. For cells substituted with 25-66% BrdU, however, a dose response was observed only at low doses (<1.0 Gy); at higher doses (>1.0 Gy), the incidence of chromosomal instability leveled off. There was an increase in the frequency and complexity of chromosomal instability per unit dose compared to cells unsubstituted with BrdU. The frequency of chromosomal instability appeared to saturate around approximately 30%, an effect which occurred at much lower doses in the presence of BrdU. Changing the gamma-ray dose rate by a factor of 190 (0.092 to 17.45 Gy min(-1)) produced no significant differences in the frequency of chromosomal instability. The enhancement of chromosomal instability promoted by the presence of the BrdU argues that DNA comprises at least one of the critical targets important for the induction of this end point of genomic instability.

  15. Critical target and dose and dose-rate responses for the induction of chromosomal instability by ionizing radiation

    NASA Technical Reports Server (NTRS)

    Limoli, C. L.; Corcoran, J. J.; Milligan, J. R.; Ward, J. F.; Morgan, W. F.

    1999-01-01

    To investigate the critical target, dose response and dose-rate response for the induction of chromosomal instability by ionizing radiation, bromodeoxyuridine (BrdU)-substituted and unsubstituted GM10115 cells were exposed to a range of doses (0.1-10 Gy) and different dose rates (0.092-17.45 Gy min(-1)). The status of chromosomal stability was determined by fluorescence in situ hybridization approximately 20 generations after irradiation in clonal populations derived from single progenitor cells surviving acute exposure. Overall, nearly 700 individual clones representing over 140,000 metaphases were analyzed. In cells unsubstituted with BrdU, a dose response was found, where the probability of observing delayed chromosomal instability in any given clone was 3% per gray of X rays. For cells substituted with 25-66% BrdU, however, a dose response was observed only at low doses (<1.0 Gy); at higher doses (>1.0 Gy), the incidence of chromosomal instability leveled off. There was an increase in the frequency and complexity of chromosomal instability per unit dose compared to cells unsubstituted with BrdU. The frequency of chromosomal instability appeared to saturate around approximately 30%, an effect which occurred at much lower doses in the presence of BrdU. Changing the gamma-ray dose rate by a factor of 190 (0.092 to 17.45 Gy min(-1)) produced no significant differences in the frequency of chromosomal instability. The enhancement of chromosomal instability promoted by the presence of the BrdU argues that DNA comprises at least one of the critical targets important for the induction of this end point of genomic instability.

  16. Influence of low-dose and low-dose-rate ionizing radiation on mutation induction in human cells

    NASA Astrophysics Data System (ADS)

    Yatagai, F.; Umebayashi, Y.; Suzuki, M.; Abe, T.; Suzuki, H.; Shimazu, T.; Ishioka, N.; Iwaki, M.; Honma, M.

    This is a review paper to introduce our recent studies on the genetic effects of low-dose and low-dose-rate ionizing radiation (IR). Human lymphoblastoid TK6 cells were exposed to γ-rays at a dose-rate of 1.2 mGy/h (total 30 mGy). The frequency of early mutations (EMs) in the thymidine kinase ( TK) gene locus was determined to be 1.7 × 10 -6, or 1.9-fold higher than the level seen in unirradated controls [Umebayashi, Y., Honma, M., Suzuki, M., Suzuki, H., Shimazu, T., Ishioka, N., Iwaki, M., Yatagai, F., Mutation induction in cultured human cells after low-dose and low-dose-rate γ-ray irradiation: detection by LOH analysis. J. Radiat. Res., 48, 7-11, 2007]. These mutants were then analyzed for loss of heterozygosity (LOH) events. Small interstitial-deletion events were restricted to the TK gene locus and were not observed in EMs in unirradated controls, but they comprised about half of the EMs (8/15) after IR exposure. Because of the low level of exposure to IR, this specific type of event cannot be considered to be the direct result of an IR-induced DNA double strand break (DSB). To better understand the effects of low-level IR exposure, the repair efficiency of site-specific chromosomal DSBs was also examined. The pre γ-irradiation under the same condition did not largely influence the efficiency of DSB repair via end-joining, but enhanced such efficiency via homologous recombination to an about 40% higher level (unpublished data). All these results suggest that DNA repair and mutagenesis can be indirectly influenced by low-dose/dose-rate IR.

  17. Modeling ion recombination in liquid ionization chambers - Improvement and analysis of the two-dose-rate method.

    PubMed

    Andersson, Jonas; Tölli, Heikki

    2017-08-12

    The use of liquid ionization chambers can provide useful information to endeavors with radiation dosimetry for highly modulated beams. Liquid ionization chambers may be particularly suitable for computed tomography applications where conventional ionization chambers do not present a high enough sensitivity for the spatial resolution required to characterize common X-ray beams. Due to the sensitivity, which leads to high charge densities, liquid ionization chambers can suffer from large recombination losses leading to degradation in signal to dose rate linearity. To solve this problem, a two-dose-rate method for general recombination correction has been proposed for liquid ionization chambers. However, the valid range of recombination losses that the method can accurately account for has been found to vary depending on radiation quality. The present work provides an in-depth analysis of the performance of the two-dose-rate method. Furthermore, the soundness of applying gas theory to liquids is investigated by using the two-dose-rate method. In the present work, the two-dose-rate method for general recombination correction of liquid ionization chambers used in continuous beams is studied by employing theory for gas-filled ionization chambers. An approximate relation for the general collection efficiency containing a material-specific parameter that is traceable to liquids has been derived for theoretical and experimental investigation alongside existing theory. Furthermore, the disassociation between initial and general recombination in the method is analyzed both theoretically and experimentally. The results indicate that liquids and gases share general recombination characteristics, where the liquids investigated (isooctane and tetramethylsilane) to a large extent mimic the behavior theoretically expected in gases. Furthermore, it is shown that the disassociation between initial and general recombination in the two-dose-rate method is an approximation that depends

  18. Ion-recombination correction for different ionization chambers in high dose rate flattening-filter-free photon beams.

    PubMed

    Lang, Stephanie; Hrbacek, Jan; Leong, Aidan; Klöck, Stephan

    2012-05-07

    Recently, there has been an increased interest in flattening-filter-free (FFF) linear accelerators. Removal of the filter results in available dose rates up to 24 Gy min(-1) (for nominal energy 10 MV in depth of maximum dose, a source-surface distance of 100 cm and a field size of 10×10 cm2). To guarantee accurate relative and reference dosimetry for the FFF beams, we investigated the charge collection efficiency of multiple air-vented and one liquid ionization chamber for dose rates up to 31.9 Gy min(-1). For flattened beams, the ion-collection efficiency of all air-vented ionization chambers (except for the PinPoint chamber) was above 0.995. By removing the flattening filter, we found a reduction in collection efficiency of approximately 0.5-0.9% for a 10 MV beam. For FFF beams, the Markus chamber showed the largest collection efficiency of 0.994. The observed collection efficiencies were dependent on dose per pulse, but independent of the pulse repetition frequency. Using the liquid ionization chamber, the ion-collection efficiency for flattened beams was above 0.990 for all dose rates. However, this chamber showed a low collection efficiency of 0.940 for the FFF 10 MV beam at a dose rate of 31.9 Gy min(-1). All investigated air-vented ionization chambers can be reliably used for relative dosimetry of FFF beams. The order of correction for reference dosimetry is given in the manuscript. Due to their increased saturation in high dose rate FFF beams, liquid ionization chambers appear to be unsuitable for dosimetry within these contexts.

  19. Ion-recombination correction for different ionization chambers in high dose rate flattening-filter-free photon beams

    NASA Astrophysics Data System (ADS)

    Lang, Stephanie; Hrbacek, Jan; Leong, Aidan; Klöck, Stephan

    2012-05-01

    Recently, there has been an increased interest in flattening-filter-free (FFF) linear accelerators. Removal of the filter results in available dose rates up to 24 Gy min-1 (for nominal energy 10 MV in depth of maximum dose, a source-surface distance of 100 cm and a field size of 10×10 cm2). To guarantee accurate relative and reference dosimetry for the FFF beams, we investigated the charge collection efficiency of multiple air-vented and one liquid ionization chamber for dose rates up to 31.9 Gy min-1. For flattened beams, the ion-collection efficiency of all air-vented ionization chambers (except for the PinPoint chamber) was above 0.995. By removing the flattening filter, we found a reduction in collection efficiency of approximately 0.5-0.9% for a 10 MV beam. For FFF beams, the Markus chamber showed the largest collection efficiency of 0.994. The observed collection efficiencies were dependent on dose per pulse, but independent of the pulse repetition frequency. Using the liquid ionization chamber, the ion-collection efficiency for flattened beams was above 0.990 for all dose rates. However, this chamber showed a low collection efficiency of 0.940 for the FFF 10 MV beam at a dose rate of 31.9 Gy min-1. All investigated air-vented ionization chambers can be reliably used for relative dosimetry of FFF beams. The order of correction for reference dosimetry is given in the manuscript. Due to their increased saturation in high dose rate FFF beams, liquid ionization chambers appear to be unsuitable for dosimetry within these contexts.

  20. Evaluation of GaAs low noise and power MMIC technologies to neutron, ionizing dose and dose rate effects

    SciTech Connect

    Derewonko, H.; Bosella, A.; Pataut, G.; Perie, D.; Pinsard, J.L.; Sentubery, C.; Verbeck, C.; Bressy, P.; Augier, P.

    1996-06-01

    An evaluation program of Thomson CSF-TCS GaAs low noise and power MMIC technologies to 1 MeV equivalent neutron fluence levels, up to 1 {times} 10{sup 15} n/cm{sup 2}, ionizing 1.17--1.33 MeV CO{sup 60} dose levels in excess of 200 Mrad(GaAs) and dose rate levels reaching 1.89 {times} 10{sup 11} rad(GaAs)/s is presented in terms of proper components and parameter choices, DC/RF electrical measurements and test methods under irradiation. Experimental results are explained together with drift analyses of electrical parameters that have determined threshold limits of component degradations. Modelling the effects of radiation on GaAs components relies on degradation analysis of active layer which appears to be the most sensitive factor. MMICs degradation under neutron fluence was simulated from irradiated FET data. Finally, based on sensitivity of technological parameters, rad-hard design including material, technology and MMIC design enhancement is discussed.

  1. A two-dose-rate method for general recombination correction for liquid ionization chambers in pulsed beams

    NASA Astrophysics Data System (ADS)

    Tölli, Heikki; Sjögren, Rickard; Wendelsten, Mikael

    2010-08-01

    The correction for general recombination losses in liquid ionization chambers (LICs) is more complex than that in air-filled ionization chambers. The reason for this is that the saturation charge in LICs, i.e. the charge that escapes initial recombination, depends on the applied voltage. This paper presents a method, based on measurements at two different dose rates in a pulsed beam, for general recombination correction in LICs. The Boag theory for pulsed beams is used and the collection efficiency is determined by numerical methods which are equivalent to the two-voltage method used in dosimetry with air-filled ionization chambers. The method has been tested in experiments in water in a 20 MeV electron beam using two LICs filled with isooctane and tetramethylsilane. The dose per pulse in the electron beam was varied between 0.1 mGy/pulse and 8 mGy/pulse. The relative standard deviations of the collection efficiencies determined with the two-dose-rate method ranged between 0.1% and 1.5%. The dose-rate variations of the general recombination corrected charge measured with the LICs are in excellent agreement with the corresponding values obtained with an air-filled plane parallel ionization chamber.

  2. Application of the two-dose-rate method for general recombination correction for liquid ionization chambers in continuous beams

    NASA Astrophysics Data System (ADS)

    Andersson, Jonas; Tölli, Heikki

    2011-01-01

    A method to correct for the general recombination losses for liquid ionization chambers in continuous beams has been developed. The proposed method has been derived from Greening's theory for continuous beams and is based on measuring the signal from a liquid ionization chamber and an air filled monitor ionization chamber at two different dose rates. The method has been tested with two plane parallel liquid ionization chambers in a continuous radiation x-ray beam with a tube voltage of 120 kV and with dose rates between 2 and 13 Gy min-1. The liquids used as sensitive media in the chambers were isooctane (C8H18) and tetramethylsilane (Si(CH3)4). The general recombination effect was studied using chamber polarizing voltages of 100, 300, 500, 700 and 900 V for both liquids. The relative standard deviation of the results for the collection efficiency with respect to general recombination was found to be a maximum of 0.7% for isooctane and 2.4% for tetramethylsilane. The results are in excellent agreement with Greening's theory for collection efficiencies over 90%. The measured and corrected signals from the liquid ionization chambers used in this work are in very good agreement with the air filled monitor chamber with respect to signal to dose linearity.

  3. Application of the two-dose-rate method for general recombination correction for liquid ionization chambers in continuous beams.

    PubMed

    Andersson, Jonas; Tölli, Heikki

    2011-01-21

    A method to correct for the general recombination losses for liquid ionization chambers in continuous beams has been developed. The proposed method has been derived from Greening's theory for continuous beams and is based on measuring the signal from a liquid ionization chamber and an air filled monitor ionization chamber at two different dose rates. The method has been tested with two plane parallel liquid ionization chambers in a continuous radiation x-ray beam with a tube voltage of 120 kV and with dose rates between 2 and 13 Gy min(-1). The liquids used as sensitive media in the chambers were isooctane (C(8)H(18)) and tetramethylsilane (Si(CH(3))(4)). The general recombination effect was studied using chamber polarizing voltages of 100, 300, 500, 700 and 900 V for both liquids. The relative standard deviation of the results for the collection efficiency with respect to general recombination was found to be a maximum of 0.7% for isooctane and 2.4% for tetramethylsilane. The results are in excellent agreement with Greening's theory for collection efficiencies over 90%. The measured and corrected signals from the liquid ionization chambers used in this work are in very good agreement with the air filled monitor chamber with respect to signal to dose linearity.

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

    SciTech Connect

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

    2000-04-25

    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

  5. Expression of cytoskeletal and matrix genes following exposure to ionizing radiation: Dose-rate effects and protein synthesis requirements

    SciTech Connect

    Woloschak, G.E. |; Felcher, P.; Chang-Liu, Chin-Mei

    1994-05-01

    Experiments were designed to examine the effects Of radiation dose-rate and of the protein synthesis inhibitor cycloheximide on expression of cytoskeletal elements ({gamma}- and {beta}-actin and {alpha}-tubulin) and matrix elements (fibronectin) in Syrian hamster embryo cells. Past work from our laboratory had already demonstrated optimum time points and doses for examination of radiation effects on accumulation of specific transcripts. Our results here demonstrated little effect of dose-rate for JANUS fission spectrum neutrons when comparing expression of either {alpha}-tubulin or fibronectin genes. Past work had already documented similar results for expression of actin transcripts. Effects of cycloheximide revealed that cycloheximide repressed accumulation of {alpha}-tubulin following exposure to high dose-rate neutrons or {gamma} rays; this did not occur following similar low dose-rate exposure. (2) Cycloheximide did not affect accumulation of MRNA for actin genes; and that cycloheximide abrogated the moderate induction of fibronectin-mRNA which occurred following exposure to {gamma} rays and high dose-rate neutrons. These results suggest a role for labile proteins in the maintenance of {alpha}-tubulin and fibronectin MRNA accumulation following exposure to ionizing radiation. in addition, they suggest that the cellular/molecular response to low dose-rate neutrons may be different from the response to high dose-rate neutrons.

  6. Expression of cytoskeletal and matrix genes following exposure to ionizing radiation: Dose-rate effects and protein synthesis requirements

    SciTech Connect

    Woloschak, G.E. |; Felcher, P.; Chang-Liu, Chin-Mei

    1992-12-31

    Experiments were designed to examine the effects of radiation dose-rate and of the protein synthesis inhibitor cycloheximide on expression of cytoskeletal elements ({gamma}- and {beta}-actin and {alpha}-tubulin) and matrix elements (fibronectin) in Syrian hamster embryo cells. Past work from our laboratory had already demonstrated optimum time points and doses for examination of radiation effects on accumulation of specific transcripts. Our results here demonstrated little effect of dose-rate for JANUS fission spectrum neutrons when comparing expression of either {alpha}-tubulin or fibronectin genes. Past work had already documented similar results for expression of actin transcripts. Effects of cycloheximide, however, revealed several interesting and novel findings: (1) Cycloheximide repressed accumulation of {alpha}-tubulin following exposure to high dose-rate neutrons or {gamma} rays; this did not occur following similar low dose-rate exposure (2) Cycloheximide did not affect accumulation of mRNA for actin genes. Cycloheximide abrogated the moderate induction of fibronectin-mRNA which occurred following exposure to {gamma} rays and high dose-rate neutrons. These results suggest a role for labile proteins in the maintenance of {alpha}-tubulin and fibronectin mRNA accumulation following exposure to ionizing radiation. In addition, they suggest that the cellular/molecular response to low dose-rate neutrons may be different from the response to high dose-rate neutrons.

  7. Expression of cytoskeletal and matrix genes following exposure to ionizing radiation: Dose-rate effects and protein synthesis requirements

    SciTech Connect

    Woloschak, G.E. |; Felcher, P.; Chang-Liu, Chin-Mei

    1993-12-31

    Experiments were designed to examine the effects of radiation dose-rate and of the protein synthesis inhibitor cycloheximide on expression of cytoskeletal elements ({gamma}- and {beta}-actin and {alpha}-tubulin) and matrix elements (fibronectin) in Syrian hamster embryo cells. Results demonstrated little effect of dose-rate for JANUS fission-spectrum neutrons when comparing expression of either a-tubulin or fibronectin genes. Past work had already documented similar results for expression of actin transcripts. Cycloheximide, however, repressed accumulation of {alpha}-tubulin following exposure to high dose-rate neutrons or {gamma} rays; this did not occur following similar low dose-rate exposures. Cycloheximide did not affect accumulation of mRNA for actin genes. Cycloheximide abrogated the moderate induction of fibronectin-mRNA which occurred following exposure to {gamma} rays and high dose-rate neutrons. These results suggest a role for labile proteins in the maintenance of {alpha}-tubulin and fibronectin mRNA accumulation following exposure to ionizing radiation and that the cellular/molecular response to low dose-rate neutrons may be different from the response to high dose-rate neutrons.

  8. Ionizing radiation sensitivity of the ocular lens and its dose rate dependence.

    PubMed

    Hamada, Nobuyuki

    2017-10-01

    In 2011, the International Commission on Radiological Protection reduced the threshold for the lens effects of low linear energy transfer (LET) radiation. On one hand, the revised threshold of 0.5 Gy is much lower than previously recommended thresholds, but mechanisms behind high radiosensitivity remain incompletely understood. On the other hand, such a threshold is independent of dose rate, in contrast to previously recommended separate thresholds each for single and fractionated/protracted exposures. Such a change was made predicated on epidemiological evidence suggesting that a threshold for fractionated/protracted exposures is not higher than an acute threshold, and that a chronic threshold is uncertain. Thus, the dose rate dependence is still unclear. This paper therefore reviews the current knowledge on the radiosensitivity of the lens and the dose rate dependence of radiation cataractogenesis, and discusses its mechanisms. Mounting biological evidence indicates that the lens cells are not necessarily radiosensitive to cell killing, and the high radiosensitivity of the lens thus appears to be attributable to other mechanisms (e.g., excessive proliferation, abnormal differentiation, a slow repair of DNA double-strand breaks, telomere, senescence, crystallin changes, non-targeted effects and inflammation). Both biological and epidemiological evidence generally supports the lack of dose rate effects. However, there is also biological evidence for the tissue sparing dose rate (or fractionation) effect of low-LET radiation and an enhancing inverse dose fractionation effect of high-LET radiation at a limited range of LET. Emerging epidemiological evidence in chronically exposed individuals implies the inverse dose rate effect. Further biological and epidemiological studies are warranted to gain deeper knowledge on the radiosensitivity of the lens and dose rate dependence of radiation cataractogenesis.

  9. Multi-level effects of low dose rate ionizing radiation on southern toad, Anaxyrus [Bufo] terrestris

    SciTech Connect

    Stark, Karolina; Scott, David E.; Tsyusko, Olga; Coughlin, Daniel P.; Hinton, Thomas G.; Amendola, Roberto

    2015-04-30

    Despite their potential vulnerability to contaminants from exposure at multiple life stages, amphibians are one of the least studied groups of vertebrates in ecotoxicology, and research on radiation effects in amphibians is scarce. We used multiple endpoints to assess the radiosensitivity of the southern toad (Anaxyrus [Bufo] terrestris) during its pre-terrestrial stages of development –embryonic, larval, and metamorphic. Toads were exposed, from several hours after oviposition through metamorphosis (up to 77 days later), to four low dose rates of ¹³⁷Cs at 0.13, 2.4, 21, and 222 mGy d⁻¹, resulting in total doses up to 15.8 Gy. Radiation treatments did not affect hatching success of embryos, larval survival, or the length of the larval period. The individual family variation in hatching success of embryos was larger than the radiation response. In contrast, newly metamorphosed individuals from the higher dose-rate treatments had higher mass and mass/length body indices, a measure which may relate to higher post-metamorphic survival. The increased mass and index at higher dose rates may indicate that the chronic, low dose rate radiation exposures triggered secondary responses. Additionally, the increases in growth were linked to a decrease in DNA damage (as measured by the Comet Assay) in red blood cells at a dose rate of 21mGy d⁻¹ and a total dose of 1.1 Gy. In conclusion, the complex effects of low dose rates of ionizing radiation may trigger growth and cellular repair mechanisms in amphibian larvae.

  10. Dose-rate dependent effects of ionizing radiation on vascular reactivity.

    PubMed

    Suvorava, T; Luksha, L; Bulanova, K Ya; Lobanok, L M

    2006-01-01

    This study was designed to investigate the dose-rate dependent effects of ionising radiation on endothelium- and NO-mediated reactivity of aorta and coronary vessels. Rats were exposed to acute ((137)Cs, 9 x 10(-4) Gy s(-1), 18 min) and chronic ((137)Cs, 2.8 x 10(-7) Gy s(-1), 41 days) radiation in 1 Gy dose. Acute irradiation transiently increased coronary flow in eNOS-activity-dependent manner on day 3 after exposure. In striking contrast, chronic irradiation caused a significant depression of coronary flow even on day 90 after irradiation and abolished the effects of NO-synthase inhibitor N-nitro-L-arginine methyl ester (10 micromol l(-1)). Furthermore, low intensity radiation strongly diminished the vasodilator properties of NO-donor sodium nitroprusside (5 micromol l(-1)). A similar pattern was observed in aortic rings. Endothelium-dependent vasodilation was increased on days 3 and 10 after acute irradiation, but strongly inhibited following chronic exposure for the entire post-radiation period. This was accompanied by a diminished vasodilator response to NO-donor on days 3, 10 and 30 of post-radiation but not on day 90. The data suggest that ionising radiation in 1 Gy induces changes of aortic and coronary vessels reactivity depending on the dose-rate and the interval after exposure.

  11. Health Risks From Low Doses and Low Dose-Rates of Ionizing Radiation. Session 5: Future of Radiation Protection Regulations.

    PubMed

    Cool, Donald A

    2016-03-01

    The system of radiological protection is a prospective approach to protection of individuals in all exposure situations. It must be applied equitably across all age groups and all populations. This is a very different circumstance from dose assessment for a particular individual where the unique characteristics of the individual and the exposure can be taken into account. Notwithstanding the ongoing discussions on the possible shape of the dose response at low doses and dose rates, the prospective system of protection has therefore historically used a linear assumption as a pragmatic, prudent and protective approach. These radiation protection criteria are not intended to be a demarcation between "safe" and "unsafe" and are the product of a risk-informed judgement that includes inputs from science, ethics, and experience. There are significant implications for different dose response relationships. A linear model allows for equal treatment of an exposure, irrespective of the previously accumulated exposure. In contrast, other models would predict different implications. Great care is therefore needed in separating the thinking around risk assessment from risk management, and prospective protection for all age groups and genders from retrospective assessment for a particular individual. In the United States, the prospective regulatory structure functions effectively because of assumptions that facilitate independent treatment of different types of exposures, and which provide pragmatic and prudent protection. While the a linear assumption may, in fact, not be consistent with the biological reality, the implications of a different regulatory model must be considered carefully.

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

    SciTech Connect

    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.

  13. Long-term stability of liquid ionization chambers with regard to their qualification as local reference dosimeters for low dose-rate absorbed dose measurements in water.

    PubMed

    Bahar-Gogani, J; Grindborg, J E; Johansson, B E; Wickman, G

    2001-03-01

    The long-term sensitivity and calibration stability of liquid ionization chambers (LICs) has been studied at a local and a secondary standards dosimetry laboratory over a period of 3 years. The chambers were transported several times by mail between the two laboratories for measurements. The LICs used in this work are designed for absorbed dose measurements in the dose rate region of 0.1-100 mGy min(-1) and have a liquid layer thickness of 1 mm and a sensitive volume of 16.2 mm3. The liquids used as sensitive media in the chambers are mixtures of isooctane (C8H18) and tetramethylsilane (Si(CH3)4) in different proportions (about 2 to 1). Operating at a polarizing voltage of 300 V the leakage current of the chambers was stable and never exceeded 3% of the observable current at a dose rate of about 1 mGy min(-1). The volume sensitivity of the chambers was measured to be of the order of 10(-9) C Gy(-1) mm3. No systematic changes in the absorbed dose to water calibration was observed for any of the chambers during the test period (sigma < 0.2%). Variations in chamber dose response with small changes in the polarizing voltage as well as sensitivity changes with accumulated absorbed dose were also investigated. Measurements showed that the LIC response varies by 0.15% per 1% change in applied voltage around 300 V. No significant change could be observed in the LIC sensitivity after a single absorbed dose of 15 kGy. The results indicate that the LIC can be made to serve as a calibration transfer instrument and a reference detector for absorbed dose to water determinations providing good precision and long-term reproducibility.

  14. A new re-entrant ionization chamber for the calibration of iridium-192 high dose rate sources.

    PubMed

    Goetsch, S J; Attix, F H; DeWerd, L A; Thomadsen, B R

    1992-01-01

    A re-entrant (well-type) ionization chamber has been designed and fabricated at the University of Wisconsin for use with iridium-192 high dose-rate (HDR) remote after-loading brachytherapy devices. The chamber was designed to provide an ionization current of about 10(-8) ampere with a nominal 10 curie iridium-192 source. A narrow opening is provided into the sensitive volume of the chamber to insert a Nucletron MicroSelectron catheter, or catheters with similar diameters from other HDR manufacturers. The chamber exhibits a flat response (+/- 0.1%) for any source position within +/-4 mm of the chamber center. A 300 volt chamber bias yields a 99.96% ion collection efficiency. The chamber is capable of being calibrated directly with an iridium-192 source which has in turn been calibrated with thimble-type ion chambers. Reproducibility for readings in the current mode for 10 consecutive insertions of the MicroSelectron iridium-192 HDR source is within 0.02% or less. Two thimble chambers calibrated by the U.S. National Institute of Standards and Technology provide calibration traceability of iridium-192 HDR sources and re-entrant chambers to a primary national standards laboratory. Results of activity measurements of 6 commercial iridium-192 HDR sources are reported.

  15. Experimental derivation of wall correction factors for ionization chambers used in high dose rate 192Ir source calibration.

    PubMed

    Maréchal, M H; de Almeida, C E; Ferreira, I H; Sibata, C H

    2002-01-01

    At present there are no specific primary standards for 192Ir high dose rate sources used in brachytherapy. Traceability to primary standards is guaranteed through the method recommended by the AAPM that derives the air kerma calibration factor for the 192Ir gamma rays as the average of the air kerma calibration factors for x-rays and 137Cs gamma-rays or the Maréchal et al. method that uses the energy-weighted air kerma calibration factors for 250 kV x rays and 60Co gamma rays as the air kerma calibration factor for the 192Ir gamma rays. In order to use these methods, it is necessary to use the same buildup cap for all energies and the appropriate wall correction factor for each chamber. This work describes experimental work used to derive the A(W) for four different ionization chambers and different buildup cap materials for the three energies involved in the Maréchal et al. method. The A(W) for the two most common ionization chambers used in hospitals, the Farmer NE 2571 and PTW N30001 is 0.995 and 0.997, respectively, for 250 kV x rays, 0.982 and 0.985 for 192Ir gamma rays, and 0.979 and 0.991 for 60Co gamma rays, all for a PMMA build-up cap of 0.550 gm cm(-2). A comparison between the experimental values and Monte Carlo calculations shows an agreement better than 0.9%. Availability of the A(W) correction factors for all commercial chambers allows users of the in-air calibration jig, provided by the manufacturer, to alternatively use the Maréchal et al. method. Calibration laboratories may also used this method for calibration of a well-type ionization chamber with a comparable accuracy to the AAPM method.

  16. Assessment of dose and DNA damages in individuals exposed to low dose and low dose rate ionizing radiations during computed tomography imaging.

    PubMed

    Kanagaraj, Karthik; Abdul Syed Basheerudeen, Safa; Tamizh Selvan, G; Jose, M T; Ozhimuthu, Annalakshmi; Panneer Selvam, S; Pattan, Sudha; Perumal, Venkatachalam

    2015-08-01

    Computed tomography (CT) is a frequently used imaging modality that contributes to a tenfold increase in radiation exposure to the public when compared to other medical imaging modalities. The use of radiation for therapeutic need is always rationalized on the basis of risk versus benefit thereby increasing concerns on the dose received by patients undergoing CT imaging. Therefore, it was of interest to us to investigate the effects of low dose and low dose-rate X-irradiation in patients who underwent CT imaging by recording the doses received by the eye, forehead and thyroid, and to study the levels of damages in the lymphocytes in vivo. Lithium manganese borate doped with terbium (LMB:Tb) thermo luminescence dosimeters (TLD) were used to record the doses in the patient's (n = 27) eye, forehead, and thyroid and compared with the dose length product (DLP) values. The in vivo DNA damages measured were compared before and after CT imaging using chromosomal aberration (CA) and micronucleus (MN) assays. The overall measured organ dose ranged between 2 ± 0.29 and 520 ± 41.63 mGy for the eye, 0.84 ± 0.29 and 210 ± 20.50 mGy for the forehead, and 1.79 ± 0.43 and 185 ± 0.70 mGy for the thyroid. The in vivo damages measured from the blood lymphocytes of the subjects showed an extremely significant (p < 0.0001) increase in CA frequency and significant (p < 0.001) increase in MN frequency after exposure, compared to before exposure. The results suggest that CT imaging delivers a considerable amount of radiation dose to the eye, forehead, and thyroid, and the observed increase in the CA and MN frequencies show low dose radiation effects calling for protective regulatory measures to increase patient's safety. This study is the first attempt to indicate the trend of doses received by the patient's eye, forehead and thyroid and measured directly in contrast to earlier values obtained by extrapolation from phantoms, and to assess the in vivo low dose effects in an Indian

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

    NASA Technical Reports Server (NTRS)

    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.

  18. Acceleration of atherogenesis in ApoE−/− mice exposed to acute or low-dose-rate ionizing radiation

    PubMed Central

    Mancuso, Mariateresa; Pasquali, Emanuela; Braga-Tanaka, Ignacia; Tanaka, Satoshi; Pannicelli, Alessandro; Giardullo, Paola; Pazzaglia, Simonetta; Tapio, Soile; Atkinson, Michael J.; Saran, Anna

    2015-01-01

    There is epidemiological evidence for increased non-cancer mortality, primarily due to circulatory diseases after radiation exposure above 0.5 Sv. We evaluated the effects of chronic low-dose rate versus acute exposures in a murine model of spontaneous atherogenesis. Female ApoE−/− mice (60 days) were chronically irradiated for 300 days with gamma rays at two different dose rates (1 mGy/day; 20 mGy/day), with total accumulated doses of 0.3 or 6 Gy. For comparison, age-matched ApoE−/− females were acutely exposed to the same doses and sacrificed 300 days post-irradiation. Mice acutely exposed to 0.3 or 6 Gy showed increased atherogenesis compared to age-matched controls, and this effect was persistent. When the same doses were delivered at low dose rate over 300 days, we again observed a significant impact on global development of atherosclerosis, although at 0.3 Gy effects were limited to the descending thoracic aorta. Our data suggest that a moderate dose of 0.3 Gy can have persistent detrimental effects on the cardiovascular system, and that a high dose of 6 Gy poses high risks at both high and low dose rates. Our results were clearly nonlinear with dose, suggesting that lower doses may be more damaging than predicted by a linear dose response. PMID:26359350

  19. Expression of cytoskeletal and matrix genes following exposure to ionizing radiation: Dose-rate effects and protein synthesis requirements

    SciTech Connect

    Woloschak, G.E. |; Felcher, P.; Chin-Mei Chang-Liu

    1995-06-01

    Experiments examined the effects of radiation dose-rate and protein synthesis inhibition expression of cytoskeletal and matrix elements in Syrian hamster embryo cells. Results demonstrated little effect of dose-rate for neutrons when comparing expression of {alpha}-tubulin and fibronectin genes. Cycloheximide repressed accumulation of {alpha}-tubulin-mRNA following exposure to high dose-rate neutrons or {gamma} rays. Cycloheximide did not affect accumulation of actin mRNA. Cycloheximide abrogated induction of fibronectin-mRNA which occurred following exposure to {gamma} rays and high dose-rate neutrons. These results suggest a role for labile proteins in the maintenance of {alpha}-tubulin and fibronectin mRNA accumulation following exposure to radiation. 24 refs., 3 tabs.

  20. Evidence That Lifelong Low Dose Rates of Ionizing Radiation Increase Lifespan in Long- and Short-Lived Dogs

    PubMed Central

    Feinendegen, Ludwig E.; Socol, Yehoshua

    2017-01-01

    After the 1956 radiation scare to stop weapons testing, studies focused on cancer induction by low-level radiation. Concern has shifted to protecting “radiation-sensitive individuals.” Since longevity is a measure of health impact, this analysis reexamined data to compare the effect of dose rate on the lifespans of short-lived (5% and 10% mortality) dogs and on the lifespans of dogs at 50% mortality. The data came from 2 large-scale studies. One exposed 10 groups to different γ dose rates; the other exposed 8 groups to different lung burdens of plutonium. Reexamination indicated that normalized lifespans increased more for short-lived dogs than for average dogs, when radiation was moderately above background. This was apparent by interpolating between the lifespans of nonirradiated dogs and exposed dogs. The optimum lifespan increase appeared at 50 mGy/y. The threshold for harm (decreased lifespan) was 700 mGy/y for 50% mortality dogs and 1100 mGy/y for short-lived dogs. For inhaled α-emitting particulates, longevity was remarkably increased for short-lived dogs below the threshold for harm. Short-lived dogs seem more radiosensitive than average dogs and they benefit more from low radiation. If dogs model humans, this evidence would support a change to radiation protection policy. Maintaining exposures “as low as reasonably achievable” (ALARA) appears questionable. PMID:28321175

  1. Evidence That Lifelong Low Dose Rates of Ionizing Radiation Increase Lifespan in Long- and Short-Lived Dogs.

    PubMed

    Cuttler, Jerry M; Feinendegen, Ludwig E; Socol, Yehoshua

    2017-01-01

    After the 1956 radiation scare to stop weapons testing, studies focused on cancer induction by low-level radiation. Concern has shifted to protecting "radiation-sensitive individuals." Since longevity is a measure of health impact, this analysis reexamined data to compare the effect of dose rate on the lifespans of short-lived (5% and 10% mortality) dogs and on the lifespans of dogs at 50% mortality. The data came from 2 large-scale studies. One exposed 10 groups to different γ dose rates; the other exposed 8 groups to different lung burdens of plutonium. Reexamination indicated that normalized lifespans increased more for short-lived dogs than for average dogs, when radiation was moderately above background. This was apparent by interpolating between the lifespans of nonirradiated dogs and exposed dogs. The optimum lifespan increase appeared at 50 mGy/y. The threshold for harm (decreased lifespan) was 700 mGy/y for 50% mortality dogs and 1100 mGy/y for short-lived dogs. For inhaled α-emitting particulates, longevity was remarkably increased for short-lived dogs below the threshold for harm. Short-lived dogs seem more radiosensitive than average dogs and they benefit more from low radiation. If dogs model humans, this evidence would support a change to radiation protection policy. Maintaining exposures "as low as reasonably achievable" (ALARA) appears questionable.

  2. Ion recombination and polarity corrections for small-volume ionization chambers in high-dose-rate, flattening-filter-free pulsed photon beams.

    PubMed

    Hyun, Megan A; Miller, Jessica R; Micka, John A; DeWerd, Larry A

    2017-02-01

    To investigate ion recombination and polarity effects in scanning and microionization chambers when used with digital electrometers and high-dose-rate linac beams such as flattening-filter-free (FFF) fields, and to compare results against conventional pulsed and continuous photon beams. Saturation curves were obtained for one Farmer-type ionization chamber and eight small-volume chamber models with volumes ranging from 0.01 to 0.13 cm(3) using a Varian TrueBeam™ STx with FFF capability. Three beam modes (6 MV, 6 MV FFF, and 10 MV FFF) were investigated, with nominal dose-per-pulse values of 0.0278, 0.0648, and 0.111 cGy/pulse, respectively, at dmax . Saturation curves obtained using the Theratronics T1000 (60) Co unit at the UWADCL and a conventional linear accelerator (Varian Clinac iX) were used to establish baseline behavior. Jaffé plots were fitted to obtain Pion , accounting for exponential effects such as charge multiplication. These values were compared with the two-voltage technique recommended in TG-51, and were plotted as a function of dose-per-pulse to assess the ability of small-volume chambers to meet reference-class criteria in FFF beams. Jaffé- and two-voltage-determined Pion values measured for high-dose-rate beams agreed within 0.1% for the Farmer-type chamber and 1% for scanning and microionization chambers, with the exception of the CC01 which agreed within 2%. With respect to ion recombination and polarity effects, the Farmer-type chamber, scanning chambers and the Exradin A26 microchamber exhibited reference-class behavior in all beams investigated, with the exception of the IBA CC04 scanning chamber, which had an initial recombination correction that varied by 0.2% with polarity. All microchambers investigated, with the exception of the A26, exhibited anomalous polarity and ion recombination behaviors that make them unsuitable for reference dosimetry in conventional and high-dose-rate photon beams. The results of this work demonstrate that

  3. Total Ionizing Dose Response of Hafnium-Oxide Based MOS Devices to Low-Dose-Rate Gamma Ray Radiation Observed by Pulse CV and On-Site Measurements

    NASA Astrophysics Data System (ADS)

    Mu, Yifei; Zhao, Ce Zhou; Lu, Qifeng; Zhao, Chun; Qi, Yanfei; Lam, Sang; Mitrovic, Ivona Z.; Taylor, Stephen; Chalker, Paul R.

    2017-01-01

    This paper reports on the low-dose-rate radiation response of Al-HfO2/SiO2-Si MOS devices, where the gate dielectric was formed by atomic layer deposition with 4.7 nm equivalent oxide thickness. The degradation of the devices was characterized by a pulse capacitance-voltage (CV) and on-site radiation response techniques under continuous gamma (γ) ray exposure at a relatively low-dose-rate of 0.116 rad(HfO2)/s. A significant variation of the flat-band voltage shift of up to ± 1.1 V under positive and negative biased irradiation, with the total dose of up to 40 krad (HfO2) and the electric field of 0.5 MV/cm, has been measured on the HfO2-based MOS devices using the proposed techniques, not apparent by conventional CV measurements. The large flat-band voltage shift is mainly attributed to the radiation-induced oxide trapped charges, which are not readily compensated by bias-induced charges produced over the measurement timescales of less than 5 ms. Analysis of the experimental results suggest that both hole and electron trapping can dominate the radiation response performance of the HfO2-based MOS devices depending on the applied bias. No distinct loop width variation has been found with irradiation in all cases.

  4. Risk of Low Dose/Low Dose Rate Ionizing Radiation to Humans Symposium Annual Meeting of the Environmental Mutagen Society: Agenda and Abstracts

    SciTech Connect

    Veigl, Martina L.; Morgan, William F.; Schwartz, Jeffrey L.

    2009-11-11

    The low dose symposium thoughtfully addressed controversy of risk from low dose radiation exposure, hormesis and radon therapy. The stem cell symposium cogently considered the role of DNA damage and repair in hematopoietic stem cells underlying aging and malignancy and provocatively presented evidence that stem cells may have distinct morphologies and replicative properties, as well as special roles in cancer initiation. In the epigenetics symposium, studies illustrated the long range interaction of epigenetic mechanisms, the roles of CTCF and BORIS in region/specific regulation of epigenetic processes, the impact of DNA damage on epigenetic processes as well as links between epigenetic mechanisms and early nutrition and bystander effects. This report shows the agenda and abstracts for this symposium.

  5. The total ionizing dose effect in 12-bit, 125 MSPS analog-to-digital converters

    NASA Astrophysics Data System (ADS)

    Xue, Wu; Wu, Lu; Yudong, Li; Qi, Guo; Xin, Wang; Xingyao, Zhang; Xin, Yu; Wuying, Ma

    2014-04-01

    This paper presents the total ionizing dose test results at different biases and dose rates for AD9233, which is fabricated using a modern CMOS process. The experimental results show that the digital parts are more sensitive than the other parts. Power down is the worst-case bias, and this phenomenon is first found in the total ionizing dose effect of analog-to-digital converters. We also find that the AC as well as DC parameters are sensitive to the total ionizing dose at a high dose rate, whereas none of the parameters are sensitive at a low dose rate. The test facilities, results and analysis are presented in detail.

  6. Atmospheric radiation flight dose rates

    NASA Astrophysics Data System (ADS)

    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.

  7. Total Ionizing Dose Test Report for the UC1823A Pulse Width Modulator

    NASA Technical Reports Server (NTRS)

    Chen, Dakai; Forney, James

    2017-01-01

    The purpose of this study is to examine the total ionizing dose susceptibility for the UC1823A pulse width modulator manufactured by Texas Instruments, Inc. The part is suspected to be vulnerable to enhanced low dose rate sensitivity (ELDRS).

  8. Low Dose Ionizing Radiation Modulates Immune Function

    SciTech Connect

    Nelson, Gregory A.

    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

  9. Iron ionization and recombination rates and ionization equilibrium

    NASA Technical Reports Server (NTRS)

    Arnaud, M.; Raymond, J.

    1992-01-01

    In the past few years important progress has been made on the knowledge of ionization and recombination rates of iron, an astrophysically abundant heavy element and a major impurity in laboratory fusion devices. We make a critical review of the existing data on ionization and dielectronic recombination and present new computations of radiative recombination rate coefficients of Fe(+14) through Fe(+25) using the photoionization cross sections of Clark et al. (1986). We provide analytical fits to the recommended data (direct ionization and excitation-autoionization cross sections; radiative and dielectronic recombination rate coefficients). Finally we determine the iron ionic fractions at ionization equilibrium and compare them with previous computations as well as with observational data.

  10. Iron ionization and recombination rates and ionization equilibrium

    NASA Technical Reports Server (NTRS)

    Arnaud, M.; Raymond, J.

    1992-01-01

    In the past few years important progress has been made on the knowledge of ionization and recombination rates of iron, an astrophysically abundant heavy element and a major impurity in laboratory fusion devices. We make a critical review of the existing data on ionization and dielectronic recombination and present new computations of radiative recombination rate coefficients of Fe(+14) through Fe(+25) using the photoionization cross sections of Clark et al. (1986). We provide analytical fits to the recommended data (direct ionization and excitation-autoionization cross sections; radiative and dielectronic recombination rate coefficients). Finally we determine the iron ionic fractions at ionization equilibrium and compare them with previous computations as well as with observational data.

  11. [Functioning of the antioxidant system in epithelial cells of small intestine under the influence of ionizing radiation of low dose rate].

    PubMed

    Khizhniak, S V; Prokhorova, A A; Stepanova, L I; Voĭtsitskiĭ, V M

    2011-01-01

    The investigations of the functional state of the antioxidant system in epithelial cells from rat small intestine in dynamics after X-ray irradiation (0.1; 0.5 and 1.0 Gy) at a low absorbed dose rate (55 mGy/min) were performed. The obtained results point out the ambiguity of the antioxidant system reaction to the activation of oxidative processes at different doses of irradiation. The multidirectional changes of these antioxidant enzymatic activities whose functioning is characterized by the early post-irradiation recovery depending on the value of the absorbed dose were observed. The sensitivity of superoxide dismutase, glutathione transferase and glutathione peroxidase in mitochondria of epithelial cells to the irradiation exposure in the investigated range of absorbed doses was shown.

  12. Acoustic dose and acoustic dose-rate.

    PubMed

    Duck, Francis

    2009-10-01

    Acoustic dose is defined as the energy deposited by absorption of an acoustic wave per unit mass of the medium supporting the wave. Expressions for acoustic dose and acoustic dose-rate are given for plane-wave conditions, including temporal and frequency dependencies of energy deposition. The relationship between the acoustic dose-rate and the resulting temperature increase is explored, as is the relationship between acoustic dose-rate and radiation force. Energy transfer from the wave to the medium by means of acoustic cavitation is considered, and an approach is proposed in principle that could allow cavitation to be included within the proposed definitions of acoustic dose and acoustic dose-rate.

  13. LTC1877 High Efficiency Regulator Total Ionizing Dose Test Report

    NASA Technical Reports Server (NTRS)

    Oldham, Timothy; Pellish, Jonathan; Boutte, Alvin

    2012-01-01

    This report presents total ionizing dose evaluation data for the Linear Technology Corporation LTC1877 high efficiency monolithic synchronous step-down regulator. Data sheet parameters were tracked as a function of ionizing dose up to a total of 20 krad(SiO2). Control devices were also used.

  14. The galactic cosmic ray ionization rate

    PubMed Central

    Dalgarno, A.

    2006-01-01

    The chemistry that occurs in the interstellar medium in response to cosmic ray ionization is summarized, and a review of the ionization rates that have been derived from measurements of molecular abundances is presented. The successful detection of large abundances of H3+ in diffuse clouds and the recognition that dissociative recombination of H3+ is fast has led to an upward revision of the derived ionization rates. In dense clouds the molecular abundances are sensitive to the depletion of carbon monoxide, atomic oxygen, nitrogen, water, and metals and the presence of large molecules and grains. Measurements of the relative abundances of deuterated species provide information about the ion removal mechanisms, but uncertainties remain. The models, both of dense and diffuse clouds, that are used to interpret the observations may be seriously inadequate. Nevertheless, it appears that the ionization rates differ in dense and diffuse clouds and in the intercloud medium. PMID:16894166

  15. The galactic cosmic ray ionization rate.

    PubMed

    Dalgarno, A

    2006-08-15

    The chemistry that occurs in the interstellar medium in response to cosmic ray ionization is summarized, and a review of the ionization rates that have been derived from measurements of molecular abundances is presented. The successful detection of large abundances of H(3)(+) in diffuse clouds and the recognition that dissociative recombination of H(3)(+) is fast has led to an upward revision of the derived ionization rates. In dense clouds the molecular abundances are sensitive to the depletion of carbon monoxide, atomic oxygen, nitrogen, water, and metals and the presence of large molecules and grains. Measurements of the relative abundances of deuterated species provide information about the ion removal mechanisms, but uncertainties remain. The models, both of dense and diffuse clouds, that are used to interpret the observations may be seriously inadequate. Nevertheless, it appears that the ionization rates differ in dense and diffuse clouds and in the intercloud medium.

  16. On line high dose static position monitoring by ionization chamber detector for industrial gamma irradiators.

    PubMed

    Rodrigues, Ary A; Vieira, Jose M; Hamada, Margarida M

    2010-01-01

    A 1 cm(3) cylindrical ionization chamber was developed to measure high doses on line during the sample irradiation in static position, in a (60)Co industrial plant. The developed ionization chamber showed to be suitable for use as a dosimeter on line. A good linearity of the detector was found between the dose and the accumulated charge, independently of the different dose rates caused by absorbing materials.

  17. Chronic Low Dose Rate Ionizing Radiation Exposure Induces Premature Senescence in Human Fibroblasts that Correlates with Up Regulation of Proteins Involved in Protection against Oxidative Stress

    PubMed Central

    Loseva, Olga; Shubbar, Emman; Haghdoost, Siamak; Evers, Bastiaan; Helleday, Thomas; Harms-Ringdahl, Mats

    2014-01-01

    The risks of non-cancerous diseases associated with exposure to low doses of radiation are at present not validated by epidemiological data, and pose a great challenge to the scientific community of radiation protection research. Here, we show that premature senescence is induced in human fibroblasts when exposed to chronic low dose rate (LDR) exposure (5 or 15 mGy/h) of gamma rays from a 137Cs source. Using a proteomic approach we determined differentially expressed proteins in cells after chronic LDR radiation compared to control cells. We identified numerous proteins involved in protection against oxidative stress, suggesting that these pathways protect against premature senescence. In order to further study the role of oxidative stress for radiation induced premature senescence, we also used human fibroblasts, isolated from a patient with a congenital deficiency in glutathione synthetase (GS). We found that these GS deficient cells entered premature senescence after a significantly shorter time of chronic LDR exposure as compared to the GS proficient cells. In conclusion, we show that chronic LDR exposure induces premature senescence in human fibroblasts, and propose that a stress induced increase in reactive oxygen species (ROS) is mechanistically involved. PMID:28250385

  18. The Inhibitory Effects of Low-Dose Ionizing Radiation in IgE-Mediated Allergic Responses

    PubMed Central

    Nam, Seon Young; Yang, Kwang Hee; Kim, Cha Soon; Lee, In Kyung; Kim, Ji Young

    2015-01-01

    Ionizing radiation has different biological effects according to dose and dose rate. In particular, the biological effect of low-dose radiation is unclear. Low-dose whole-body gamma irradiation activates immune responses in several ways. However, the effects and mechanism of low-dose radiation on allergic responses remain poorly understood. Previously, we reported that low-dose ionizing radiation inhibits mediator release in IgE-mediated RBL-2H3 mast cell activation. In this study, to have any physiological relevance, we investigated whether low-dose radiation inhibits allergic responses in activated human mast cells (HMC-1(5C6) and LAD2 cells), mouse models of passive cutaneous anaphylaxis and the late-phase cutaneous response. High-dose radiation induced cell death, but low-dose ionizing radiation of <0.5 Gy did not induce mast cell death. Low-dose ionizing radiation that did not induce cell death significantly suppressed mediator release from human mast cells (HMC-1(5C6) and LAD2 cells) that were activated by antigen-antibody reaction. To determine the inhibitory mechanism of mediator released by low-dose ionizing radiation, we examined the phosphorylation of intracellular signaling molecules such as Lyn, Syk, phospholipase Cγ, and protein kinase C, as well as the intracellular free Ca2+ concentration ([Ca2+]i). The phosphorylation of signaling molecules and [Ca2+]i following stimulation of FcεRI receptors was inhibited by low dose ionizing radiation. In agreement with its in vitro effect, ionizing radiation also significantly inhibited inflammatory cells infiltration, cytokine mRNA expression (TNF-α, IL-4, IL-13), and symptoms of passive cutaneous anaphylaxis reaction and the late-phase cutaneous response in anti-dinitrophenyl IgE-sensitized mice. These results indicate that ionizing radiation inhibits both mast cell-mediated immediate- and delayed-type allergic reactions in vivo and in vitro. PMID:26317642

  19. The Inhibitory Effects of Low-Dose Ionizing Radiation in IgE-Mediated Allergic Responses.

    PubMed

    Joo, Hae Mi; Kang, Su Jin; Nam, Seon Young; Yang, Kwang Hee; Kim, Cha Soon; Lee, In Kyung; Kim, Ji Young

    2015-01-01

    Ionizing radiation has different biological effects according to dose and dose rate. In particular, the biological effect of low-dose radiation is unclear. Low-dose whole-body gamma irradiation activates immune responses in several ways. However, the effects and mechanism of low-dose radiation on allergic responses remain poorly understood. Previously, we reported that low-dose ionizing radiation inhibits mediator release in IgE-mediated RBL-2H3 mast cell activation. In this study, to have any physiological relevance, we investigated whether low-dose radiation inhibits allergic responses in activated human mast cells (HMC-1(5C6) and LAD2 cells), mouse models of passive cutaneous anaphylaxis and the late-phase cutaneous response. High-dose radiation induced cell death, but low-dose ionizing radiation of <0.5 Gy did not induce mast cell death. Low-dose ionizing radiation that did not induce cell death significantly suppressed mediator release from human mast cells (HMC-1(5C6) and LAD2 cells) that were activated by antigen-antibody reaction. To determine the inhibitory mechanism of mediator released by low-dose ionizing radiation, we examined the phosphorylation of intracellular signaling molecules such as Lyn, Syk, phospholipase Cγ, and protein kinase C, as well as the intracellular free Ca2+ concentration ([Ca2+]i). The phosphorylation of signaling molecules and [Ca2+]i following stimulation of FcεRI receptors was inhibited by low dose ionizing radiation. In agreement with its in vitro effect, ionizing radiation also significantly inhibited inflammatory cells infiltration, cytokine mRNA expression (TNF-α, IL-4, IL-13), and symptoms of passive cutaneous anaphylaxis reaction and the late-phase cutaneous response in anti-dinitrophenyl IgE-sensitized mice. These results indicate that ionizing radiation inhibits both mast cell-mediated immediate- and delayed-type allergic reactions in vivo and in vitro.

  20. Resource Letter EIRLD-1: Effects of ionizing radiation at low doses

    NASA Astrophysics Data System (ADS)

    Wilson, Richard

    1999-05-01

    This Resource Letter provides a guide to the literature on the effects of ionizing radiation on people at low doses. Journal articles, books, and web pages are provided for the following: data at high dose levels, effects of moderate to high doses (leukemia, solid cancer, lung cancer, childhood cancer and noncancer outcomes), effects of dose rate, relationship to background, supra linearity and homesis, and policy implications.

  1. Resource Letter EIRLD-2: Effects of Ionizing Radiation at Low Doses

    NASA Astrophysics Data System (ADS)

    Wilson, Richard

    2012-04-01

    This Resource Letter provides a guide to the literature on the effects of ionizing radiation on people at low doses. Journal articles, books and web pages are provided for the following: data at high dose levels, effects of moderate to high doses (leukemia, solid cancer, lung cancer, childhood cancer, and non-cancer outcomes), effects of dose rate, relationship to background, supra linearity and hormesis, and policy implications.

  2. CARCINOGENIC EFFECTS OF LOW DOSES OF IONIZING RADIATION

    EPA Science Inventory

    Carcinogenic Effects of Low Doses of Ionizing Radiation

    R Julian Preston, Environmental Carcinogenesis Division, NHEERL, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

    The form of the dose-response curve for radiation-induced cancers, particu...

  3. CARCINOGENIC EFFECTS OF LOW DOSES OF IONIZING RADIATION

    EPA Science Inventory

    Carcinogenic Effects of Low Doses of Ionizing Radiation

    R Julian Preston, Environmental Carcinogenesis Division, NHEERL, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

    The form of the dose-response curve for radiation-induced cancers, particu...

  4. Photo-ionization rate coefficients for the rare gases

    NASA Astrophysics Data System (ADS)

    Pang, Xuexia

    2005-01-01

    By introducing the converting method from electron-impact ionization cross sections to rate coefficients through using a semi-experiential formula, we try to probe a semi-experiential formula for converting the photo-ionization cross sections into photo-ionization rate coefficient. It"s found that photo-ionization rate coefficient is direct proportion to photo-ionization cross sections, the rate S is related with light resource.

  5. Effects Of Dose Rates On Radiation Damage In CMOS Parts

    NASA Technical Reports Server (NTRS)

    Goben, Charles A.; Coss, James R.; Price, William E.

    1990-01-01

    Report describes measurements of effects of ionizing-radiation dose rate on consequent damage to complementary metal oxide/semiconductor (CMOS) electronic devices. Depending on irradiation time and degree of annealing, survivability of devices in outer space, or after explosion of nuclear weapons, enhanced. Annealing involving recovery beyond pre-irradiation conditions (rebound) detrimental. Damage more severe at lower dose rates.

  6. Analytical models for total dose ionization effects in MOS devices.

    SciTech Connect

    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.

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

    SciTech Connect

    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.

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

    PubMed Central

    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

  9. Micro RNA responses to chronic or acute exposures to low dose ionizing radiation

    PubMed Central

    Chaudhry, M. Ahmad; Omaruddin, Romaica A.; Kreger, Bridget; de Toledo, Sonia M.; Azzam, Edouard I.

    2014-01-01

    Human health risks of exposure to low dose ionizing radiation remain ambiguous and are the subject of intense debate. A wide variety of biological effects are induced after cellular exposure to ionizing radiation, but the underlying molecular mechanism(s) remain to be completely understood. We hypothesized that low dose c-radiation-induced effects are controlled by the modulation of micro RNA (miRNA) that participate in the control of gene expression at the posttranscriptional level and are involved in many cellular processes. We monitored the expression of several miRNA in human cells exposed to acute or chronic low doses of 10 cGy or a moderate dose of 400 cGy of 137Cs γ-rays. Dose, dose rate and time dependent differences in the relative expression of several miRNA were investigated. The expression patterns of many miRNA differed after exposure to either chronic or acute 10 cGy. The expression of miRNA let-7e, a negative regulator of RAS oncogene, and the c-MYC miRNA cluster were upregulated after 10 cGy chronic dose but were downregulated after 3 h of acute 10 cGy. The miR-21 was upregulated in chronic or acute low dose and moderate dose treated cells and its target genes hPDCD4, hPTEN, hSPRY2, and hTPM1 were found to be downregulated. These findings provide evidence that low dose and dose rate c-irradiation dictate the modulation of miRNA, which can result in a differential cellular response than occurs at high doses. This information will contribute to understanding the risks to human health after exposure to low dose radiation. PMID:22367372

  10. Detecting ionizing radiation with optical fibers down to biomedical doses

    NASA Astrophysics Data System (ADS)

    Avino, S.; D'Avino, V.; Giorgini, A.; Pacelli, R.; Liuzzi, R.; Cella, L.; De Natale, P.; Gagliardi, G.

    2013-10-01

    We report on a passive ionizing radiation sensor based on a fiber-optic resonant cavity interrogated by a high resolution interferometric technique. After irradiation in clinical linear accelerators, we observe significant variations of the fiber thermo-optic coefficient. Exploiting this effect, we demonstrate an ultimate detection limit of 160 mGy with an interaction volume of only 6 × 10-4 mm3. Thanks to its reliability, compactness, and sensitivity at biomedical dose levels, our system lends itself to real applications in radiation therapy procedures as well as in radiation monitoring and protection in medicine, aerospace, and nuclear power plants.

  11. Tank Z-361 dose rate calculations

    SciTech Connect

    Richard, R.F.

    1998-09-30

    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.

  12. Estimation of the Dose and Dose Rate Effectiveness Factor

    NASA Technical Reports Server (NTRS)

    Chappell, L.; Cucinotta, F. A.

    2013-01-01

    Current models to estimate radiation risk use the Life Span Study (LSS) cohort that received high doses and high dose rates of radiation. Transferring risks from these high dose rates to the low doses and dose rates received by astronauts in space is a source of uncertainty in our risk calculations. The solid cancer models recommended by BEIR VII [1], UNSCEAR [2], and Preston et al [3] is fitted adequately by a linear dose response model, which implies that low doses and dose rates would be estimated the same as high doses and dose rates. However animal and cell experiments imply there should be curvature in the dose response curve for tumor induction. Furthermore animal experiments that directly compare acute to chronic exposures show lower increases in tumor induction than acute exposures. A dose and dose rate effectiveness factor (DDREF) has been estimated and applied to transfer risks from the high doses and dose rates of the LSS cohort to low doses and dose rates such as from missions in space. The BEIR VII committee [1] combined DDREF estimates using the LSS cohort and animal experiments using Bayesian methods for their recommendation for a DDREF value of 1.5 with uncertainty. We reexamined the animal data considered by BEIR VII and included more animal data and human chromosome aberration data to improve the estimate for DDREF. Several experiments chosen by BEIR VII were deemed inappropriate for application to human risk models of solid cancer risk. Animal tumor experiments performed by Ullrich et al [4], Alpen et al [5], and Grahn et al [6] were analyzed to estimate the DDREF. Human chromosome aberration experiments performed on a sample of astronauts within NASA were also available to estimate the DDREF. The LSS cohort results reported by BEIR VII were combined with the new radiobiology results using Bayesian methods.

  13. Total Ionizing Dose Test of Microsemi's Silicon Switching Transistors JANTXV2N2222AUB and 2N2907AUB

    NASA Technical Reports Server (NTRS)

    Campola, M.; Freeman, B.; Yau, K.

    2017-01-01

    Microsemi's silicon switching transistors, JANTXV2N2222AUB and 2N2907AUB, were tested for total ionizing dose (TID) response beginning on July 11, 2016. This test served as the radiation lot acceptance test (RLAT) for the lot date code (LDC) tested. Low dose rate (LDR) irradiations were performed in this test so that the device susceptibility to enhanced low dose rate sensitivity (ELDRS) could be determined.

  14. Total Dose Effects on Error Rates in Linear Bipolar Systems

    NASA Technical Reports Server (NTRS)

    Buchner, Stephen; McMorrow, Dale; Bernard, Muriel; Roche, Nicholas; Dusseau, Laurent

    2007-01-01

    The shapes of single event transients in linear bipolar circuits are distorted by exposure to total ionizing dose radiation. Some transients become broader and others become narrower. Such distortions may affect SET system error rates in a radiation environment. If the transients are broadened by TID, the error rate could increase during the course of a mission, a possibility that has implications for hardness assurance.

  15. Dose rate mapping of VMAT treatments

    NASA Astrophysics Data System (ADS)

    Podesta, Mark; Antoniu Popescu, I.; Verhaegen, Frank

    2016-06-01

    Human tissues exhibit a varying response to radiation dose depending on the dose rate and fractionation scheme used. Dose rate effects have been reported for different radiations, and tissue types. The literature indicates that there is not a significant difference in response for low-LET radiation when using dose rates between 1 Gy min-1 and 12 Gy min-1 but lower dose rates have an observable sparing effect on tissues and a differential effect between tissues. In intensity-modulated radiotherapy such as volumetric modulated arc therapy (VMAT) the dose can be delivered with a wide range of dose rates. In this work we developed a method based on time-resolved Monte Carlo simulations to quantify the dose rate frequency distribution for clinical VMAT treatments for three cancer sites, head and neck, lung, and pelvis within both planning target volumes (PTV) and normal tissues. The results show a wide range of dose rates are used to deliver dose in VMAT and up to 75% of the PTV can have its dose delivered with dose rates  <1 Gy min-1. Pelvic plans on average have a lower mean dose rate within the PTV than lung or head and neck plans but a comparable mean dose rate within the organs at risk. Two VMAT plans that fulfil the same dose objectives and constraints may be delivered with different dose rate distributions, particularly when comparing single arcs to multiple arc plans. It is concluded that for dynamic plans, the dose rate range used varies to a larger degree than previously assumed. The effect of the dose rate range in VMAT on clinical outcome is unknown.

  16. Dose rate mapping of VMAT treatments.

    PubMed

    Podesta, Mark; Popescu, I Antoniu; Verhaegen, Frank

    2016-06-07

    Human tissues exhibit a varying response to radiation dose depending on the dose rate and fractionation scheme used. Dose rate effects have been reported for different radiations, and tissue types. The literature indicates that there is not a significant difference in response for low-LET radiation when using dose rates between 1 Gy min(-1) and 12 Gy min(-1) but lower dose rates have an observable sparing effect on tissues and a differential effect between tissues. In intensity-modulated radiotherapy such as volumetric modulated arc therapy (VMAT) the dose can be delivered with a wide range of dose rates. In this work we developed a method based on time-resolved Monte Carlo simulations to quantify the dose rate frequency distribution for clinical VMAT treatments for three cancer sites, head and neck, lung, and pelvis within both planning target volumes (PTV) and normal tissues. The results show a wide range of dose rates are used to deliver dose in VMAT and up to 75% of the PTV can have its dose delivered with dose rates  <1 Gy min(-1). Pelvic plans on average have a lower mean dose rate within the PTV than lung or head and neck plans but a comparable mean dose rate within the organs at risk. Two VMAT plans that fulfil the same dose objectives and constraints may be delivered with different dose rate distributions, particularly when comparing single arcs to multiple arc plans. It is concluded that for dynamic plans, the dose rate range used varies to a larger degree than previously assumed. The effect of the dose rate range in VMAT on clinical outcome is unknown.

  17. Modeling Dose-response at Low Dose: A Systems Biology Approach for Ionization Radiation.

    PubMed

    Zhao, Yuchao; Ricci, Paolo F

    2010-03-18

    For ionization radiation (IR) induced cancer, a linear non-threshold (LNT) model at very low doses is the default used by a number of national and international organizations and in regulatory law. This default denies any positive benefit from any level of exposure. However, experimental observations and theoretical biology have found that both linear and J-shaped IR dose-response curves can exist at those very low doses. We develop low dose J-shaped dose-response, based on systems biology, and thus justify its use regarding exposure to IR. This approach incorporates detailed, molecular and cellular descriptions of biological/toxicological mechanisms to develop a dose-response model through a set of nonlinear, differential equations describing the signaling pathways and biochemical mechanisms of cell cycle checkpoint, apoptosis, and tumor incidence due to IR. This approach yields a J-shaped dose response curve while showing where LNT behaviors are likely to occur. The results confirm the hypothesis of the J-shaped dose response curve: the main reason is that, at low-doses of IR, cells stimulate protective systems through a longer cell arrest time per unit of IR dose. We suggest that the policy implications of this approach are an increasingly correct way to deal with precautionary measures in public health.

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

    EPA Science Inventory

    Cancer Risks Attributable to Low Doses of Ionizing Radiation - What Do We Really Know?

    Abstract
    High doses of ionizing radiation clearly produce deleterious consequences in humans including, but not exclusively, cancer induction. At very low radiation doses the situatio...

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

    EPA Science Inventory

    Cancer Risks Attributable to Low Doses of Ionizing Radiation - What Do We Really Know?

    Abstract
    High doses of ionizing radiation clearly produce deleterious consequences in humans including, but not exclusively, cancer induction. At very low radiation doses the situatio...

  20. Dose Rate Effects in Linear Bipolar Transistors

    NASA Technical Reports Server (NTRS)

    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.

  1. Dose Rate Effects in Linear Bipolar Transistors

    NASA Technical Reports Server (NTRS)

    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.

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

    NASA Technical Reports Server (NTRS)

    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.; hide

    2012-01-01

    Vulnerability of a variety of candidate spacecraft electronics to total ionizing dose and displacement damage is studied. Devices tested include optoelectronics, digital, analog, linear, and hybrid devices.

  3. Total ionizing dose radiation effects on NMOS parasitic transistors in advanced bulk CMOS technology devices

    NASA Astrophysics Data System (ADS)

    Baoping, He; Zujun, Wang; Jiangkun, Sheng; Shaoyan, Huang

    2016-12-01

    In this paper, total ionizing dose effect of NMOS transistors in advanced CMOS technology are examined. The radiation tests are performed at 60Co sources at the dose rate of 50 rad (Si)/s. The investigation's results show that the radiation-induced charge buildup in the gate oxide can be ignored, and the field oxide isolation structure is the main total dose problem. The total ionizing dose (TID) radiation effects of field oxide parasitic transistors are studied in detail. An analytical model of radiation defect charge induced by TID damage in field oxide is established. The I - V characteristics of the NMOS parasitic transistors at different doses are modeled by using a surface potential method. The modeling method is verified by the experimental I - V characteristics of 180 nm commercial NMOS device induced by TID radiation at different doses. The model results are in good agreement with the radiation experimental results, which shows the analytical model can accurately predict the radiation response characteristics of advanced bulk CMOS technology device. Project supported by the National Natural Science Foundation of China (No. 11305126).

  4. Evaluation of Rectal Dose During High-Dose-Rate Intracavitary Brachytherapy for Cervical Carcinoma

    SciTech Connect

    Sha, Rajib Lochan; Reddy, Palreddy Yadagiri; Rao, Ramakrishna; Muralidhar, Kanaparthy R.; Kudchadker, Rajat J.

    2011-01-01

    High-dose-rate intracavitary brachytherapy (HDR-ICBT) for carcinoma of the uterine cervix often results in high doses being delivered to surrounding organs at risk (OARs) such as the rectum and bladder. Therefore, it is important to accurately determine and closely monitor the dose delivered to these OARs. In this study, we measured the dose delivered to the rectum by intracavitary applications and compared this measured dose to the International Commission on Radiation Units and Measurements rectal reference point dose calculated by the treatment planning system (TPS). To measure the dose, we inserted a miniature (0.1 cm{sup 3}) ionization chamber into the rectum of 86 patients undergoing radiation therapy for cervical carcinoma. The response of the miniature chamber modified by 3 thin lead marker rings for identification purposes during imaging was also characterized. The difference between the TPS-calculated maximum dose and the measured dose was <5% in 52 patients, 5-10% in 26 patients, and 10-14% in 8 patients. The TPS-calculated maximum dose was typically higher than the measured dose. Our study indicates that it is possible to measure the rectal dose for cervical carcinoma patients undergoing HDR-ICBT. We also conclude that the dose delivered to the rectum can be reasonably predicted by the TPS-calculated dose.

  5. Breast cancer mortality between 1950 and 1987 after exposure to fractionated moderate-dose-rate ionizing radiation in the Canadian fluoroscopy cohort study and a comparison with breast cancer mortality in the atomic bomb survivors study.

    PubMed

    Howe, G R; McLaughlin, J

    1996-06-01

    The relationship between exposure to low-linear energy transfer ionizing radiation and subsequent breast cancer mortality risk is reported based on a further 7 years of follow-up in the Canadian fluoroscopy study. Amongst 31,917 women first treated for tuberculosis in a Canadian institution between 1930 and 1952, a total of 688 breast cancer deaths were observed between 1950 and 1987. There is a strong linear trend of increasing risk with increasing dose (P < 0.0001), with the excess relative risk per sievert decreasing with age at exposure (P = 0.0003). The excess relative risk is approximately constant between 5 and 39 years after exposure, with a suggestion of a decrease between 40 and 57 years after exposure, though this could be a chance effect (P = 0.22). Combined analyses of the Canadian fluoroscopy data and the data for the atomic bomb survivors with respect to breast cancer mortality are also reported. In general the two studies are reasonably consistent, the only distinct difference being the much greater excess relative risk per sievert amongst women exposed to very high doses in the province of Nova Scotia (P, heterogeneity <0.0001). Based on the combined data sets a simple relative risk (RR) model for the effect of a dose of D sieverts at age A years is developed: RR(D) = 1.0 + 0.52D exp[-0.10(A-15)]. This model fits the combined data well, and is used to predict excess lifetime risks of breast cancer mortality after radiation exposure from routine annual mammography.

  6. Quantitative modeling of total ionizing dose reliability effects in device silicon dioxide layers

    NASA Astrophysics Data System (ADS)

    Rowsey, Nicole L.

    The electrical breakdown of oxides and oxide/semiconductor interfaces is one of the main reasons for device failure in integrated circuits, especially devices under high-stress conditions. One high-stress environment of interest is the space environment. All electronics are vulnerable to ionizing radiation; any high-energy particle that passes through an insulating layer will deposit unwanted charge there, causing shifts in device characteristics. Designing electronics for use in space can be a challenge, because much more energetic radiation exits in space than on Earth, as there is no atmosphere in space to collide with, and thereby reduce the energy of, energetic particles. Although oxide charging due to ionizing radiation creates well-known changes in device characteristics, or total ionizing dose effects, it is still poorly-understood exactly how these changes come about. There are many theories that draw upon a large body of both experimental work and, more recently, quantum-mechanical first principles calculations at the molecular level. This work uses FLOODS, a 3D object-oriented device simulator with multi-physics capability, to investigate these theories, by simulating oxide degradation in realistic device geometries, and comparing the subsequent degradation in device characteristics to experimental measurements. The charge trapping and defect-modulated transport models developed and implemented here have resulted in the first quantitative account of the enhanced low-dose-rate sensitivity effect, and are applicable in a comprehensive range of hydrogen environments. Measurements show that devices exposed to ionizing radiation at high dose rates exhibit less degradation that those exposed at low dose rates. Furthermore, the observed trend differs depending on the amount of hydrogen available before, during, and after irradiation. It is therefore important to understand and take into account the effects of dose rate and hydrogen when developing accelerated

  7. Assessing dose rate distributions in VMAT plans

    NASA Astrophysics Data System (ADS)

    Mackeprang, P.-H.; Volken, W.; Terribilini, D.; Frauchiger, D.; Zaugg, K.; Aebersold, D. M.; Fix, M. K.; Manser, P.

    2016-04-01

    Dose rate is an essential factor in radiobiology. As modern radiotherapy delivery techniques such as volumetric modulated arc therapy (VMAT) introduce dynamic modulation of the dose rate, it is important to assess the changes in dose rate. Both the rate of monitor units per minute (MU rate) and collimation are varied over the course of a fraction, leading to different dose rates in every voxel of the calculation volume at any point in time during dose delivery. Given the radiotherapy plan and machine specific limitations, a VMAT treatment plan can be split into arc sectors between Digital Imaging and Communications in Medicine control points (CPs) of constant and known MU rate. By calculating dose distributions in each of these arc sectors independently and multiplying them with the MU rate, the dose rate in every single voxel at every time point during the fraction can be calculated. Independently calculated and then summed dose distributions per arc sector were compared to the whole arc dose calculation for validation. Dose measurements and video analysis were performed to validate the calculated datasets. A clinical head and neck, cranial and liver case were analyzed using the tool developed. Measurement validation of synthetic test cases showed linac agreement to precalculated arc sector times within  ±0.4 s and doses  ±0.1 MU (one standard deviation). Two methods for the visualization of dose rate datasets were developed: the first method plots a two-dimensional (2D) histogram of the number of voxels receiving a given dose rate over the course of the arc treatment delivery. In similarity to treatment planning system display of dose, the second method displays the dose rate as color wash on top of the corresponding computed tomography image, allowing the user to scroll through the variation over time. Examining clinical cases showed dose rates spread over a continuous spectrum, with mean dose rates hardly exceeding 100 cGy min-1 for conventional

  8. Potential Treatment of Inflammatory and Proliferative Diseases by Ultra-Low Doses of Ionizing Radiations

    PubMed Central

    Sanders, Charles L.

    2012-01-01

    Ultra-low doses and dose- rates of ionizing radiation are effective in preventing disease which suggests that they also may be effective in treating disease. Limited experimental and anecdotal evidence indicates that low radiation doses from radon in mines and spas, thorium-bearing monazite sands and enhanced radioactive uranium ore obtained from a natural geological reactor may be useful in treating many inflammatory conditions and proliferative disorders, including cancer. Optimal therapeutic applications were identified via a literature survey as dose-rates ranging from 7 to 11μGy/hr or 28 to 44 times world average background rates. Rocks from an abandoned uranium mine in Utah were considered for therapeutic application and were examined by γ-ray and laser-induced breakdown fluorescence spectroscopy. The rocks showed the presence of transuranics and fission products with a γ-ray energy profile similar to aged spent uranium nuclear fuel (93% dose due to β particles and 7% due to γ rays). Mud packs of pulverized uranium ore rock dust in sealed plastic bags delivering bag surface β,γ dose-rates of 10–450 μGy/h were used with apparent success to treat several inflammatory and proliferative conditions in humans. PMID:23304108

  9. Potential treatment of inflammatory and proliferative diseases by ultra-low doses of ionizing radiations.

    PubMed

    Sanders, Charles L

    2012-12-01

    Ultra-low doses and dose- rates of ionizing radiation are effective in preventing disease which suggests that they also may be effective in treating disease. Limited experimental and anecdotal evidence indicates that low radiation doses from radon in mines and spas, thorium-bearing monazite sands and enhanced radioactive uranium ore obtained from a natural geological reactor may be useful in treating many inflammatory conditions and proliferative disorders, including cancer. Optimal therapeutic applications were identified via a literature survey as dose-rates ranging from 7 to 11μGy/hr or 28 to 44 times world average background rates. Rocks from an abandoned uranium mine in Utah were considered for therapeutic application and were examined by γ-ray and laser-induced breakdown fluorescence spectroscopy. The rocks showed the presence of transuranics and fission products with a γ-ray energy profile similar to aged spent uranium nuclear fuel (93% dose due to β particles and 7% due to γ rays). Mud packs of pulverized uranium ore rock dust in sealed plastic bags delivering bag surface β,γ dose-rates of 10-450 μGy/h were used with apparent success to treat several inflammatory and proliferative conditions in humans.

  10. Oxygen ionization rates at Mars and Venus - Relative contributions of impact ionization and charge exchange

    NASA Technical Reports Server (NTRS)

    Zhang, M. H. G.; Luhmann, J. G.; Nagy, A. F.; Spreiter, J. R.; Stahara, S. S.

    1993-01-01

    Oxygen ion production rates above the ionopauses of Venus and Mars are calculated for photoionization, charge exchange, and solar wind electron impact ionization processes. The latter two require the use of the Spreiter and Stahara (1980) gas dynamic model to estimate magnetosheath velocities, densities, and temperatures. The results indicate that impact ionization is the dominant mechanism for the production of O(+) ions at both Venus and Mars. This finding might explain both the high ion escape rates measured by Phobos 2 and the greater mass loading rate inferred for Venus from the bow shock positions.

  11. Dose rate assessment in tooth enamel

    NASA Astrophysics Data System (ADS)

    Wieser, A.; Göksu, H. Y.; Regulla, D. F.; Vogenauer, A.

    A mammoth found in the southern part of Germany was dated by ESR spectroscopy. This dating method is based on the measurement of the accumulated dose in tooth enamel and assessment of the annual dose. The accumulated dose is obtained from the radiation induced ESR signal at g = 2.0018 of the enamel. The annual dose was first determined by measuring the 238U, 232Th and 40K content of the tooth and of the surrounding soil. As a crosscheck, the dose rate from the tooth was measured by inserting TL dosimeters in the dentine and storing them at 'zero' background in a salt mine. The cosmic dose rate and the gamma dose rate from the soil was evaluated from TL dosimeters buried at the excavation site. The results are discussed with respect to the applicability of ESR dating on teeth.

  12. Cardiovascular Risks Associated with Low Dose Ionizing Particle Radiation

    PubMed Central

    Yan, Xinhua; Sasi, Sharath P.; Gee, Hannah; Lee, JuYong; Yang, Yongyao; Mehrzad, Raman; Onufrak, Jillian; Song, Jin; Enderling, Heiko; Agarwal, Akhil; Rahimi, Layla; Morgan, James; Wilson, Paul F.; Carrozza, Joseph; Walsh, Kenneth; Kishore, Raj; Goukassian, David A.

    2014-01-01

    Previous epidemiologic data demonstrate that cardiovascular (CV) morbidity and mortality may occur decades after ionizing radiation exposure. With increased use of proton and carbon ion radiotherapy and concerns about space radiation exposures to astronauts on future long-duration exploration-type missions, the long-term effects and risks of low-dose charged particle irradiation on the CV system must be better appreciated. Here we report on the long-term effects of whole-body proton (1H; 0.5 Gy, 1 GeV) and iron ion (56Fe; 0.15 Gy, 1GeV/nucleon) irradiation with and without an acute myocardial ischemia (AMI) event in mice. We show that cardiac function of proton-irradiated mice initially improves at 1 month but declines by 10 months post-irradiation. In AMI-induced mice, prior proton irradiation improved cardiac function restoration and enhanced cardiac remodeling. This was associated with increased pro-survival gene expression in cardiac tissues. In contrast, cardiac function was significantly declined in 56Fe ion-irradiated mice at 1 and 3 months but recovered at 10 months. In addition, 56Fe ion-irradiation led to poorer cardiac function and more adverse remodeling in AMI-induced mice, and was associated with decreased angiogenesis and pro-survival factors in cardiac tissues at any time point examined up to 10 months. This is the first study reporting CV effects following low dose proton and iron ion irradiation during normal aging and post-AMI. Understanding the biological effects of charged particle radiation qualities on the CV system is necessary both for the mitigation of space exploration CV risks and for understanding of long-term CV effects following charged particle radiotherapy. PMID:25337914

  13. Cardiovascular risks associated with low dose ionizing particle radiation.

    PubMed

    Yan, Xinhua; Sasi, Sharath P; Gee, Hannah; Lee, JuYong; Yang, Yongyao; Mehrzad, Raman; Onufrak, Jillian; Song, Jin; Enderling, Heiko; Agarwal, Akhil; Rahimi, Layla; Morgan, James; Wilson, Paul F; Carrozza, Joseph; Walsh, Kenneth; Kishore, Raj; Goukassian, David A

    2014-01-01

    Previous epidemiologic data demonstrate that cardiovascular (CV) morbidity and mortality may occur decades after ionizing radiation exposure. With increased use of proton and carbon ion radiotherapy and concerns about space radiation exposures to astronauts on future long-duration exploration-type missions, the long-term effects and risks of low-dose charged particle irradiation on the CV system must be better appreciated. Here we report on the long-term effects of whole-body proton ((1)H; 0.5 Gy, 1 GeV) and iron ion ((56)Fe; 0.15 Gy, 1GeV/nucleon) irradiation with and without an acute myocardial ischemia (AMI) event in mice. We show that cardiac function of proton-irradiated mice initially improves at 1 month but declines by 10 months post-irradiation. In AMI-induced mice, prior proton irradiation improved cardiac function restoration and enhanced cardiac remodeling. This was associated with increased pro-survival gene expression in cardiac tissues. In contrast, cardiac function was significantly declined in (56)Fe ion-irradiated mice at 1 and 3 months but recovered at 10 months. In addition, (56)Fe ion-irradiation led to poorer cardiac function and more adverse remodeling in AMI-induced mice, and was associated with decreased angiogenesis and pro-survival factors in cardiac tissues at any time point examined up to 10 months. This is the first study reporting CV effects following low dose proton and iron ion irradiation during normal aging and post-AMI. Understanding the biological effects of charged particle radiation qualities on the CV system is necessary both for the mitigation of space exploration CV risks and for understanding of long-term CV effects following charged particle radiotherapy.

  14. Cardiovascular Risks Associated with Low Dose Ionizing Particle Radiation

    DOE PAGES

    Yan, Xinhua; Sasi, Sharath P.; Gee, Hannah; ...

    2014-10-22

    Previous epidemiologic data demonstrate that cardiovascular (CV) morbidity and mortality may occur decades after ionizing radiation exposure. With increased use of proton and carbon ion radiotherapy and concerns about space radiation exposures to astronauts on future long-duration exploration-type missions, the long-term effects and risks of low-dose charged particle irradiation on the CV system must be better appreciated. Here we report on the long-term effects of whole-body proton (1H; 0.5 Gy, 1 GeV) and iron ion (56Fe; 0.15 Gy, 1GeV/nucleon) irradiation with and without an acute myocardial ischemia (AMI) event in mice. We show that cardiac function of proton-irradiated mice initiallymore » improves at 1 month but declines by 10 months post-irradiation. In AMI-induced mice, prior proton irradiation improved cardiac function restoration and enhanced cardiac remodeling. This was associated with increased pro-survival gene expression in cardiac tissues. In contrast, cardiac function was significantly declined in 56Fe ion-irradiated mice at 1 and 3 months but recovered at 10 months. In addition, 56Fe ion-irradiation led to poorer cardiac function and more adverse remodeling in AMI-induced mice, and was associated with decreased angiogenesis and pro-survival factors in cardiac tissues at any time point examined up to 10 months. This is the first study reporting CV effects following low dose proton and iron ion irradiation during normal aging and post-AMI. Finally, understanding the biological effects of charged particle radiation qualities on the CV system is necessary both for the mitigation of space exploration CV risks and for understanding of long-term CV effects following charged particle radiotherapy.« less

  15. Cardiovascular Risks Associated with Low Dose Ionizing Particle Radiation

    SciTech Connect

    Yan, Xinhua; Sasi, Sharath P.; Gee, Hannah; Lee, JuYong; Yang, Yongyao; Mehrzad, Raman; Onufrak, Jillian; Song, Jin; Enderling, Heiko; Agarwal, Akhil; Rahimi, Layla; Morgan, James; Wilson, Paul F.; Carrozza, Joseph; Walsh, Kenneth; Kishore, Raj; Goukassian, David A.

    2014-10-22

    Previous epidemiologic data demonstrate that cardiovascular (CV) morbidity and mortality may occur decades after ionizing radiation exposure. With increased use of proton and carbon ion radiotherapy and concerns about space radiation exposures to astronauts on future long-duration exploration-type missions, the long-term effects and risks of low-dose charged particle irradiation on the CV system must be better appreciated. Here we report on the long-term effects of whole-body proton (1H; 0.5 Gy, 1 GeV) and iron ion (56Fe; 0.15 Gy, 1GeV/nucleon) irradiation with and without an acute myocardial ischemia (AMI) event in mice. We show that cardiac function of proton-irradiated mice initially improves at 1 month but declines by 10 months post-irradiation. In AMI-induced mice, prior proton irradiation improved cardiac function restoration and enhanced cardiac remodeling. This was associated with increased pro-survival gene expression in cardiac tissues. In contrast, cardiac function was significantly declined in 56Fe ion-irradiated mice at 1 and 3 months but recovered at 10 months. In addition, 56Fe ion-irradiation led to poorer cardiac function and more adverse remodeling in AMI-induced mice, and was associated with decreased angiogenesis and pro-survival factors in cardiac tissues at any time point examined up to 10 months. This is the first study reporting CV effects following low dose proton and iron ion irradiation during normal aging and post-AMI. Finally, understanding the biological effects of charged particle radiation qualities on the CV system is necessary both for the mitigation of space exploration CV risks and for understanding of long-term CV effects following charged particle radiotherapy.

  16. Comparison of TID Effects in Space-Like Variable Dose Rates and Constant Dose Rates

    NASA Technical Reports Server (NTRS)

    Harris, Richard D.; McClure, Steven S.; Rax, Bernard G.; Evans, Robin W.; Jun, Insoo

    2008-01-01

    The degradation of the LM193 dual voltage comparator has been studied at different TID dose rate profiles, including several different constant dose rates and a variable dose rate that simulates the behavior of a solar flare. A comparison of results following constant dose rate vs. variable dose rates is made to explore how well the constant dose rates used for typical part testing predict the performance during a simulated space-like mission. Testing at a constant dose rate equal to the lowest dose rate seen during the simulated flare provides an extremely conservative estimate of the overall amount of degradation. A constant dose rate equal to the average dose rate is also more conservative than the variable rate. It appears that, for this part, weighting the dose rates by the amount of total dose received at each rate (rather than the amount of time at each dose rate) results in an average rate that produces an amount of degradation that is a reasonable approximation to that received by the variable rate.

  17. Ionization dynamics of small water clusters: Proton transfer rate

    NASA Astrophysics Data System (ADS)

    Tachikawa, Hiroto; Takada, Tomoya

    2016-08-01

    The surfaces of icy planets and comets are composed of frozen water (H2O), carbon dioxide (CO2), and methane (CH4). These surfaces are irradiated by solar wind and cosmic rays from the interstellar space and they cause ionization of surface molecules. In this report, the effects of ionization of cold water clusters have been investigated using a direct ab initio molecular dynamics (AIMD) method to elucidate the rate of proton transfer (PT) in cations of small water clusters (H2O)n (n = 2-7). After ionization of the water clusters, PT occurred in all the cluster cations, and dissociation of the OH radical occurred for n = 4-7. The time of PT decreased with increasing the cluster size at n = 2-5 and reached a limiting value at n = 6 and 7. The mechanism of the PT process in ionized water clusters was discussed based on the theoretical results.

  18. Simulating total-dose and dose-rate effects on digital microelectronics timing delays using VHDL

    SciTech Connect

    Brothers, C.P. Jr.; Pugh, R.D.

    1995-12-01

    This paper describes a fast timing simulator based on Very High Speed Integrated Circuit (VHSIC) Hardware Description Language (VHDL) for simulating the timing of digital microelectronics in pre-irradiation, total dose, and dose-rate radiation environments. The goal of this research is the rapid and accurate timing simulation of radiation-hardened microelectronic circuits before, during, and after exposure to ionizing radiation. The results of this research effort were the development of VHDL compatible models capable of rapid and accurate simulation of the effect of radiation on the timing performance of microelectronic circuits. The effects of radiation for total dose at 1 Mrad(Si) and dose rates up to 2 {times} 10{sup 12} rads(Si) per second were modeled for a variety of Separation by IMplantion of OXygen (SIMOX) circuits. In all cases tested, the VHDL simulations ran at least 600 times faster than SPICE while maintaining a timing accuracy to within 15% of SPICE values.

  19. Dose rate in brachytherapy using after-loading machine: pulsed or high-dose rate?

    PubMed

    Hannoun-Lévi, J-M; Peiffert, D

    2014-10-01

    Since February 2014, it is no longer possible to use low-dose rate 192 iridium wires due to the end of industrial production of IRF1 and IRF2 sources. The Brachytherapy Group of the French society of radiation oncology (GC-SFRO) has recommended switching from iridium wires to after-loading machines. Two types of after-loading machines are currently available, based on the dose rate used: pulsed-dose rate or high-dose rate. In this article, we propose a comparative analysis between pulsed-dose rate and high-dose rate brachytherapy, based on biological, technological, organizational and financial considerations.

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

    PubMed Central

    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 (i) the presence of a threshold that varied with organ, gender and age at exposure, and (ii) a small but significant bumping increase in cancer risk at low doses in Nagasaki that probably reflects internal exposure to 239Pu. The threshold was distinct from the canonical definition of zero effect in that it was manifested as negative excess relative risk, or suppression of background cancer rates. Such a unique tissue response at low doses of radiation exposure has been implicated in the context of the molecular basis of radiation–environment interplay in favor of recently emerging experimental evidence on DNA double-strand break repair pathway choice and its epigenetic memory by histone marking. PMID:24366315

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

    PubMed

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

    2014-05-01

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

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

    SciTech Connect

    Shin, Suk Chul; Lee, Kyung-Mi; Kang, Yu Mi; Kim, Kwanghee; Kim, Cha Soon; Yang, Kwang Hee; Jin, Young-Woo; Kim, Chong Soon; Kim, Hee Sun

    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.

  3. Effects of Proton Radiation Dose, Dose Rate and Dose Fractionation on Hematopoietic Cells in Mice

    PubMed Central

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

    2012-01-01

    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. PMID:20726731

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

    PubMed

    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.

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

    SciTech Connect

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

  6. Dose rate profile surrounding a repository

    SciTech Connect

    Parson, J.; Brandl, A.; Zoeger, N.; Koppitsch, R.

    2013-07-01

    The focus of this research was to analyze the dose rate profile around a waste repository using Monte Carlo techniques. Dose rates at various heights and distances were analyzed outside of the waste repository using MCNPX [1]. The heights measured extended the height of the building and the distances varied between 0 and 22 m away from the waste repository. The simulation data were fitted by smooth analytical functions for different height levels and distances, such that vertical and horizontal dose rates as functions of source-detector distance were achieved. (authors)

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

    PubMed

    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 H2O, CO2, O2 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 O2 and releasing CO2, which means the risk for embryo and endosperm development was higher. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Radiation Leukemogenesis at Low Dose Rates

    SciTech Connect

    Weil, Michael; Ullrich, Robert

    2013-09-25

    The major goals of this program were to study the efficacy of low dose rate radiation exposures for the induction of acute myeloid leukemia (AML) and to characterize the leukemias that are caused by radiation exposures at low dose rate. An irradiator facility was designed and constructed that allows large numbers of mice to be irradiated at low dose rates for protracted periods (up to their life span). To the best of our knowledge this facility is unique in the US and it was subsequently used to study radioprotectors being developed for radiological defense (PLoS One. 7(3), e33044, 2012) and is currently being used to study the role of genetic background in susceptibility to radiation-induced lung cancer. One result of the irradiation was expected; low dose rate exposures are ineffective in inducing AML. However, another result was completely unexpected; the irradiated mice had a very high incidence of hepatocellular carcinoma (HCC), approximately 50%. It was unexpected because acute exposures are ineffective in increasing HCC incidence above background. This is a potential important finding for setting exposure limits because it supports the concept of an 'inverse dose rate effect' for some tumor types. That is, for the development of some tumor types low dose rate exposures carry greater risks than acute exposures.

  9. [Radiation situation prognosis for deep space: reactions of water and living systems to chronic low-dose ionizing irradiation].

    PubMed

    Ushakov, I B; Tsetlin, V V; Moisa, S S

    2013-01-01

    The authors review the findings of researches into the effects of low-dose ionizing irradiation on diverse biological objects (embryonic Japanese quails, Aspergillus niger, Spirostomum ambiguum Ehrbg., mesenchymal stem cells from mouse marrow, dry higher plants seeds, blood lymphocytes from pilots and cosmonauts). Model experiments with chronic exposure to ionizing radiation doses comparable with the measurements inside orbital vehicles and estimations for trips through the interplanetary space resulted in morphological disorders (embryonic Japanese quails, Aspergillus niger), radiation hormesis (Aspergillus niger, MSCs from mouse marrow), increase in the seed germination rate, inhibition of Spirostomum spontaneous activity, DNA damages, chromosomal aberrations, and increase of the blood lymphocytes reactivity to additional radiation loading. These facts give grounds to assume that the crucial factor in the radiation outcomes is changes in liquid medium. In other words, during extended orbiting within the magnetosphere region and interplanetary missions ionizing radiation affects primarily liquids of organism and, secondarily, its morphofunctional structures.

  10. Test Results of Total Ionizing Dose Conducted at the Jet Propulsion Laboratory

    NASA Technical Reports Server (NTRS)

    Rivas, Rosa M.; Johnston, Allan H.; Miyahira, Tetsuo F.; Rax, Bernard G.; Wiedeman, Michael D.

    2004-01-01

    This paper reports recent Total Ionizing Dose (TID) test results obtained at JPL. Several device samples were analyzed exhibiting significant failure levels and ELDRS effects under biased and unbiased condition.

  11. Test Results of Total Ionizing Dose Conducted at the Jet Propulsion Laboratory

    NASA Technical Reports Server (NTRS)

    Rivas, Rosa M.; Johnston, Allan H.; Miyahira, Tetsuo F.; Rax, Bernard G.; Wiedeman, Michael D.

    2004-01-01

    This paper reports recent Total Ionizing Dose (TID) test results obtained at JPL. Several device samples were analyzed exhibiting significant failure levels and ELDRS effects under biased and unbiased condition.

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

    NASA Technical Reports Server (NTRS)

    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.

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

    NASA Technical Reports Server (NTRS)

    Cochran, Donna J.; Chen, Dakai; Oldham, Timothy R.; Sanders, Anthony B.; Kim, Hak S.; Campola, Michael J.; Buchner, Stephen P.; LaBel, Kenneth A.; Marshall, Cheryl J.; Pellish, Jonathan A.; Carts, Martin A.; O'Bryan, Martha V.

    2010-01-01

    Vulnerability of a variety of candidate spacecraft electronics to total ionizing dose and displacement damage is studied. Devices tested include optoelectronics, digital, analog, linear bipolar devices, and hybrid devices.

  14. The ionization rate inversion of H? induced by the single and double UV photon(s)

    NASA Astrophysics Data System (ADS)

    He, Pei-Lun; He, Feng

    2013-11-01

    The ionization of H? in the strong UV laser pulse is studied by numerically solving the time-dependent Schrödinger equation. In analogy to Young's double-slit interference, the ionized electron originating from two nuclei will constructively, or destructively interfere, depending on the UV frequencies. The fluctuation of the ionization rate as a function of the laser frequency is observed. The destructive interference suppresses the single-photon ionization rate, so that the double-photon ionization rate can be larger than the single-photon ionization rate. When such an ionization-rate inversion happens, the electron momentum spectra splits into several peaks.

  15. Construction of an ionization chamber for the measurement of dose of low energy x-rays

    SciTech Connect

    Perez, Y. B. Alcantara; Jimenez, F. J. Ramirez

    2008-08-11

    We designed and constructed the prototype of an ionization chamber to measure the dose of an X-ray tube with Molybdenum anode. This X-ray tube is located in the Physics department at CINVESTAV and is used for medical physics purposes in the imaging area. The ionization chamber is designed to measure doses on biological samples exposed to X-rays and will be applied in radiation protection studies.

  16. Extended range radiation dose-rate monitor

    DOEpatents

    Valentine, Kenneth H.

    1988-01-01

    An extended range dose-rate monitor is provided which utilizes the pulse pileup phenomenon that occurs in conventional counting systems to alter the dynamic response of the system to extend the dose-rate counting range. The current pulses from a solid-state detector generated by radiation events are amplified and shaped prior to applying the pulses to the input of a comparator. The comparator generates one logic pulse for each input pulse which exceeds the comparator reference threshold. These pulses are integrated and applied to a meter calibrated to indicate the measured dose-rate in response to the integrator output. A portion of the output signal from the integrator is fed back to vary the comparator reference threshold in proportion to the output count rate to extend the sensitive dynamic detection range by delaying the asymptotic approach of the integrator output toward full scale as measured by the meter.

  17. Historical river flow rates for dose calculations

    SciTech Connect

    Carlton, W.H.

    1991-06-10

    Annual average river flow rates are required input to the LADTAP Computer Code for calculating offsite doses from liquid releases of radioactive materials to the Savannah River. The source of information on annual river flow rates used in dose calculations varies, depending on whether calculations are for retrospective releases or prospective releases. Examples of these types of releases are: Retrospective - releases from routine operations (annual environmental reports) and short term release incidents that have occurred. Prospective - releases that might be expected in the future from routine or abnormal operation of existing or new facilities (EIS`s, EID`S, SAR`S, etc.). This memorandum provides historical flow rates at the downstream gauging station at Highway 301 for use in retrospective dose calculations and derives flow rate data for the Beaufort-Jasper and Port Wentworth water treatment plants.

  18. Quantitative estimation of UV light dose concomitant to irradiation with ionizing radiation

    NASA Astrophysics Data System (ADS)

    Petin, Vladislav G.; Morozov, Ivan I.; Kim, Jin Kyu; Semkina, Maria A.

    2011-01-01

    A simple mathematical model for biological estimation of UV light dose concomitant to ionizing radiation was suggested. This approach was applied to determine the dependency of equivalent UV light dose accompanied by 100 Gy of ionizing radiation on energy of sparsely ionizing radiation and on volume of the exposed cell suspension. It was revealed that the relative excitation contribution to the total lethal effect and the value of UV dose was greatly increased with an increase in energy of ionizing radiation and volume of irradiated suspensions. It is concluded that these observations are in agreement with the supposition that Čerenkov emission is responsible for the production of UV light damage and the phenomenon of photoreactivation observed after ionizing exposure of bacterial and yeast cells hypersensitive to UV light. A possible synergistic interaction of the damages produced by ionizations and excitations as well as a probable participation of UV component of ionizing radiation in the mechanism of hormesis and adaptive response observed after ionizing radiation exposure is discussed.

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

    PubMed Central

    Nussbaum, R H; Köhnlein, W

    1994-01-01

    The effects on human health of exposures to ionizing radiation at low doses have long been the subject of dispute. In this paper we focus on open questions regarding the health effects of low-dose exposures that require further investigations. Seemingly contradictory findings of radiation health effects have been reported for the same exposed populations, or inconsistent estimates of radiation risks were found when different populations and exposure conditions were compared. Such discrepancies may be indicative of differences in sensitivities among the applied methods of epidemiological analysis or indicative of significant discrepancies in health consequences after comparable total exposures of different populations under varying conditions. We focus first on inconsistencies and contradictions in presentations of the state of knowledge by different authoritative experts. We then review studies that found positive associations between exposure and risks in dose ranges where traditional notions (generalized primarily from high-dose studies of A-bomb survivors or exposed animals) would have predicted negligible effects. One persistent notion in many reviews of low-dose effects is the hypothesis of reduced biological effectiveness of fractionated low-dose exposures, compared to that of the same acute dose. This assumption is not supported by data on human populations. From studies of populations that live in contaminated areas, more and more evidence is accumulating on unusual rates of various diseases other than radiation-induced malignancies, health effects that are suspected to be associated with relatively low levels of internal exposures originating from radioactive fallout. Such effects include congenital defects, neonatal mortality, stillbirths, and possibly genetically transmitted disease. A range of open questions challenges scientists to test imaginative hypotheses about induction of disease by radiation with novel research strategies. Images Figure 1. PMID

  20. Dose rate calculations for a reconnaissance vehicle.

    PubMed

    Grindrod, L; Mackey, J; Salmon, M; Smith, C; Wall, S

    2005-01-01

    A Chemical Nuclear Reconnaissance System (CNRS) has been developed by the British Ministry of Defence to make chemical and radiation measurements on contaminated terrain using appropriate sensors and recording equipment installed in a land rover. A research programme is under way to develop and validate a predictive capability to calculate the build-up of contamination on the vehicle, radiation detector performance and dose rates to the occupants of the vehicle. This paper describes the geometric model of the vehicle and the methodology used for calculations of detector response. Calculated dose rates obtained using the MCBEND Monte Carlo radiation transport computer code in adjoint mode are presented. These address the transient response of the detectors as the vehicle passes through a contaminated area. Calculated dose rates were found to agree with the measured data to be within the experimental uncertainties, thus giving confidence in the shielding model of the vehicle and its application to other scenarios.

  1. Enhanced Low Dose Rate Effects in Bipolar Circuits: A New Hardness Assurance Problem for NASA

    NASA Technical Reports Server (NTRS)

    Johnston, A.; Barnes, C.

    1995-01-01

    Many bipolar integrated circuits are much more susceptible to ionizing radiation at low dose rates than they are at high dose rates typically used for radiation parts testing. Since the low dose rate is equivalent to that seen in space, the standard lab test no longer can be considered conservative and has caused the Air Force to issue an alert. Although a reliable radiation hardness assurance test has not yet been designed, possible mechanisms for low dose rate enhancement and hardness assurance tests are discussed.

  2. Enhanced Low Dose Rate Effects in Bipolar Circuits: A New Hardness Assurance Problem for NASA

    NASA Technical Reports Server (NTRS)

    Johnston, A.; Barnes, C.

    1995-01-01

    Many bipolar integrated circuits are much more susceptible to ionizing radiation at low dose rates than they are at high dose rates typically used for radiation parts testing. Since the low dose rate is equivalent to that seen in space, the standard lab test no longer can be considered conservative and has caused the Air Force to issue an alert. Although a reliable radiation hardness assurance test has not yet been designed, possible mechanisms for low dose rate enhancement and hardness assurance tests are discussed.

  3. Enhanced Low Dose Rate Sensitivity at Ultra-Low Dose Rates

    NASA Technical Reports Server (NTRS)

    Chen, Dakai; Pease, Ronald; Forney, James; Carts, Martin; Phan, Anthony; Cox, Stephen; Kruckmeyer, Kriby; Burns, Sam; Albarian, Rafi; Holcombe, Bruce; Little, Bradley; Salzman, James; Chaumont, Geraldine; Duperray, Herve; Ouellet, Al; Buchner, Stephen; LaBel, Kenneth

    2011-01-01

    We have presented results of ultra-low dose rate irradiations (< or = 10 mrad(Si)/s) for a variety of radiation hardened and commercial linear bipolar devices. We observed low dose rate enhancement factors exceeding 1.5 in several parts. The worst case of dose rate enhancement resulted in functional failures, which occurred after 10 and 60 krad(Si), for devices irradiated at 0.5 and 10 mrad(Si)/s, respectively. Devices fabricated with radiation hardened processes and designs also displayed dose rate enhancement at below 10 mrad(Si)/s. Furthermore, the data indicated that these devices have not reached the damage saturation point. Therefore the degradation will likely continue to increase with increasing total dose, and the low dose rate enhancement will further magnify. The cases presented here, in addition to previous examples, illustrate the significance and pervasiveness of low dose rate enhancement at dose rates lower than 10 mrad(Si). These results present further challenges for radiation hardness assurance of bipolar linear circuits, and raise the question of whether the current standard test dose rate is conservative enough to bound degradations due to ELDRS.

  4. Behavioral Incapacitation from a High Dose of Ionizing Radiation

    DTIC Science & Technology

    1993-11-01

    1983. (UNCLASSIFIED) SMcMillan, G., Falkenberg , S., and Thompson, WI Early behavioral effects of ionizing radiation on fou• r species pf subhuman...aspect of Os, collection of iformatlort, indudkg Suggestions for reducing ttds burden, to Wahs ton HeadQuarters Services Directoralte f r infomratlon...wiere employed at the AFRRI in 1981 when the research was completed. R . W. Young and C. G. Franz were investigators in the Behavioral Science Department

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

    NASA Technical Reports Server (NTRS)

    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

  6. Total Ionizing Dose Effects in Bipolar and BiCMOS Devices

    NASA Technical Reports Server (NTRS)

    Chavez, Rosa M.; Rax, Bernard G.; Scheick, Leif Z.; Johnston, Allan H.

    2005-01-01

    This paper describes total ionizing dose (TID) test results performed at JPL. Bipolar and BiCMOS device samples were tested exhibiting significant degradation and failures at different irradiation levels. Linear technology which is susceptible to low-dose dependency (ELDRS) exhibited greater damage for devices tested under zero bias condition.

  7. Prototype Operational Advances for Atmospheric Radiation Dose Rate Specification

    NASA Astrophysics Data System (ADS)

    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

  8. Cervix cancer brachytherapy: high dose rate.

    PubMed

    Miglierini, P; Malhaire, J-P; Goasduff, G; Miranda, O; Pradier, O

    2014-10-01

    Cervical cancer, although less common in industrialized countries, is the fourth most common cancer affecting women worldwide and the fourth leading cause of cancer death. In developing countries, these cancers are often discovered at a later stage in the form of locally advanced tumour with a poor prognosis. Depending on the stage of the disease, treatment is mainly based on a chemoradiotherapy followed by uterovaginal brachytherapy ending by a potential remaining tumour surgery or in principle for some teams. The role of irradiation is crucial to ensure a better local control. It has been shown that the more the delivered dose is important, the better the local results are. In order to preserve the maximum of organs at risk and to allow this dose escalation, brachytherapy (intracavitary and/or interstitial) has been progressively introduced. Its evolution and its progressive improvement have led to the development of high dose rate brachytherapy, the advantages of which are especially based on the possibility of outpatient treatment while maintaining the effectiveness of other brachytherapy forms (i.e., low dose rate or pulsed dose rate). Numerous innovations have also been completed in the field of imaging, leading to a progress in treatment planning systems by switching from two-dimensional form to a three-dimensional one. Image-guided brachytherapy allows more precise target volume delineation as well as an optimized dosimetry permitting a better coverage of target volumes.

  9. Ionization rate in the presence of runaway electrons

    SciTech Connect

    Bulanov, S.V.; Lontano, M.; Sasorov, P.V.

    1997-04-01

    The role of a fast electron population, produced by the strong electric field driving the axial current in a capillary discharge, can be essential in order to justify the appreciable concentration of highly charged C ions (C{sup 5+}, C{sup 6+}) as observed in many experiments with low electron temperature. Under the assumption that a quasistationary state is established during the discharge, the runaway electron distribution function is determined analytically for Z{sub eff}{gt}1, following the approximated method developed by Lebedev [A. N. Lebedev, Sov. Phys. JETP {bold 21}, 931 (1965)]. The strong enhancement of the ionization rate, due to the presence of an electron tail in the energy range of the ionization potential, is then demonstrated. {copyright} {ital 1997 American Institute of Physics.}

  10. On determining dose rate constants spectroscopically

    SciTech Connect

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

    2013-01-15

    Purpose: To investigate several aspects of the Chen and Nath spectroscopic method of determining the dose rate constants of {sup 125}I and {sup 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 {sup 125}I and {sup 103}Pd sources. Methods: Spectra generated by 14 {sup 125}I and 6 {sup 103}Pd seeds were calculated in vacuo at 10 cm from the source in a 2.7 Multiplication-Sign 2.7 Multiplication-Sign 0.05 cm{sup 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 {sup 125}I seeds, or TG-43U1 and NNDC(2000) (National Nuclear Data Center, 2000) for {sup 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 Less-Than-Or-Slanted-Equal-To 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 {sup 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 {sup 103}Pd spectra exhibit an average 6.2% decrease in the 22.9 keV line relative to the main peak when

  11. The coagulation rate of charged aerosols in ionized gases

    SciTech Connect

    Matsoukas, T.

    1997-03-15

    The charging of aerosols occurs by natural or artificial means in many systems, for example, in electrostatic precipitators and radioactive ionizers, in flames and glow discharges, in ambient air, and in outer space. The author obtains analytical expressions for the coagulation rate of aerosols in ionized gases taking into account the statistical distribution of the aerosol charge due to the random nature the charging process. Depending on the asymmetry of the ionic environment, the charge distribution may be bipolar (symmetric charging) or unipolar (highly asymmetric charging). In symmetric charging the attraction between opposite charges is almost exactly counterbalanced by repulsion between like charges and the net effect is a slight increase in the overall coagulation rate. In asymmetric charging all particles carry charges of the same polarity, interparticle interactions are repulsive, and the rate of coagulation decreases. However, the effect of the charge distribution in these systems is to increase the rate of coagulation above the rate that would be obtained if all particles carried the mean charge. This increase is substantial for larger particles in highly asymmetric ionic environments.

  12. [Hopes of high dose-rate radiotherapy].

    PubMed

    Fouillade, Charles; Favaudon, Vincent; Vozenin, Marie-Catherine; Romeo, Paul-Henri; Bourhis, Jean; Verrelle, Pierre; Devauchelle, Patrick; Patriarca, Annalisa; Heinrich, Sophie; Mazal, Alejandro; Dutreix, Marie

    2017-04-01

    In this review, we present the synthesis of the newly acquired knowledge concerning high dose-rate irradiations and the hopes that these new radiotherapy modalities give rise to. The results were presented at a recent symposium on the subject. Copyright © 2017. Published by Elsevier Masson SAS.

  13. [Rapid dicentric assay of human blood lymphocytes after exposure to low doses of ionizing radiation].

    PubMed

    Repin, M V; Repina, L A

    2011-01-01

    The probability of losses of different chromosome aberrations during the dicentric chromosome assay of metaphase cells with incomplete sets of chromosome centromeres was estimated using a mathematical model for low doses of ionizing radiation. A dicentric assay of human blood lymphocytes without determination of the total amount of chromosome centromeres in cells without chromosome aberrations (rapid dicentric assay) has been proposed. The rapid dicentric analysis allows to register chromosome aberrations in full compliance with the conventional classification. The experimental data have shown no statistically significant difference between the frequencies of dicentric chromosomes detected by rapid and classical dicentric chromosome assays of human lymphocytes exposed to 0.5 Gy of 60Co gamma-rays. The rate of the rapid dicentric assay was almost twice as high as that of the classical dicentric assay.

  14. Low dose ionizing radiation detection using conjugated polymers

    SciTech Connect

    Silva, E.A.B.; Borin, J.F.; Nicolucci, P.; Graeff, C.F.O.; Netto, T. Ghilardi; Bianchi, R.F.

    2005-03-28

    In this work, the effect of gamma radiation on the optical properties of poly[2-methoxy-5-(2{sup '}-ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV) is studied. The samples were irradiated at room temperature with different doses from 0 Gy to 152 Gy using a {sup 60}Co gamma ray source. For thin films, significant changes in the UV-visible spectra were only observed at high doses (>1 kGy). In solution, shifts in absorption peaks are observed at low doses (<10 Gy), linearly dependent on dose. The shifts are explained by conjugation reduction, and possible causes are discussed. Our results indicate that MEH-PPV solution can be used as a dosimeter adequate for medical applications.

  15. An Introduction to Multiphoton Ionization and Study of Ionization Rate of Hydrogen Atom

    SciTech Connect

    Shrestha, N.; Nakarmi, J. J.; Jha, L. N.

    2009-04-19

    From a semiclassical point of view, we discuss the problem of nonlinear interaction between electromagnetic radiation and atoms. The time-dependent Schroedinger equation for single electron systems is solved using perturbative technique to obtain transition probability. We also discuss higher order perturbation used in multiple processes where two or more quanta are emitted instead of a single photon. The approach is based on the assumption that the perturbation is small. From the transition probability ionization rate and absorption, the cross-section of hydrogen atoms is calculated. Variation in photon energy and field strength is analyzed. Variation of cross-section with photon energy is discussed.

  16. High dose rate brachytherapy for oral cancer

    PubMed Central

    YamazakI, Hideya; Yoshida, Ken; Yoshioka, Yasuo; Shimizutani, Kimishige; Furukawa, Souhei; Koizumi, Masahiko; Ogawa, Kazuhiko

    2013-01-01

    Brachytherapy results in better dose distribution compared with other treatments because of steep dose reduction in the surrounding normal tissues. Excellent local control rates and acceptable side effects have been demonstrated with brachytherapy as a sole treatment modality, a postoperative method, and a method of reirradiation. Low-dose-rate (LDR) brachytherapy has been employed worldwide for its superior outcome. With the advent of technology, high-dose-rate (HDR) brachytherapy has enabled health care providers to avoid radiation exposure. This therapy has been used for treating many types of cancer such as gynecological cancer, breast cancer, and prostate cancer. However, LDR and pulsed-dose-rate interstitial brachytherapies have been mainstays for head and neck cancer. HDR brachytherapy has not become widely used in the radiotherapy community for treating head and neck cancer because of lack of experience and biological concerns. On the other hand, because HDR brachytherapy is less time-consuming, treatment can occasionally be administered on an outpatient basis. For the convenience and safety of patients and medical staff, HDR brachytherapy should be explored. To enhance the role of this therapy in treatment of head and neck lesions, we have reviewed its outcomes with oral cancer, including Phase I/II to Phase III studies, evaluating this technique in terms of safety and efficacy. In particular, our studies have shown that superficial tumors can be treated using a non-invasive mold technique on an outpatient basis without adverse reactions. The next generation of image-guided brachytherapy using HDR has been discussed. In conclusion, although concrete evidence is yet to be produced with a sophisticated study in a reproducible manner, HDR brachytherapy remains an important option for treatment of oral cancer. PMID:23179377

  17. Investigation of DNA Damage Dose-Response Kinetics after Ionizing Radiation Schemes Similar to CT Protocols.

    PubMed

    Elgart, S Robin; Bostani, Maryam; Mok, Karen C; Adibi, Ali; Ruehm, Stefan; Enzmann, Dieter; McNitt-Gray, Michael; Iwamoto, Keisuke S

    2015-06-01

    Although there has been extensive research done on the biological response to doses of ionizing radiation relevant to radiodiagnostic procedures, very few studies have examined radiation schemes similar to those frequently utilized in CT exams. Instead of a single exposure, CT exams are often made up of a series of scans separated on the order of minutes. DNA damage dose-response kinetics after radiation doses and schemes similar to CT protocols were established in both cultured (ESW-WT3) and whole blood lymphocytes and compared to higher dose exposures. Both the kinetics and extent of H2AX phosphorylation were found to be dose dependent. Damage induction and detection showed a clear dose response, albeit different, at all time points and differences in the DNA repair kinetics of ESW-WT3 and whole blood lymphocytes were characterized. Moreover, using a modified split-dose in vitro experiment, we show that phosphorylation of H2AX is significantly reduced after exposure to CT doses fractionated over a few minutes compared to the same total dose delivered as a single exposure. Because the split-dose exposures investigated here are more similar to those experienced during a CT examination, it is essential to understand why and how these differences occur. This work provides compelling evidence supporting differential biological responses not only between high and low doses, but also between single and multiple exposures to low doses of ionizing radiation.

  18. Ionizing Radiation Dose Due to the Use of Agricultural Fertilizers

    NASA Astrophysics Data System (ADS)

    Umisedo, Nancy K.; Okuno, Emico; Colacioppo, Sérgio; Medina, Nilberto H.; Hiodo, Francisco Y.

    2008-08-01

    The transference of radionuclides from the fertilizers to/and from soils to the foodstuffs can represent an increment in the internal dose when the vegetables are consumed by the human beings. This work evaluates the contribution of fertilizers to the increase of radiation level in the environment and of dose to the people. Samples of fertilizers, soils and vegetables produced in farms located in the neighbourhood of São Paulo city in the State of São Paulo, Brazil were analysed through gamma spectroscopy. The values of specific activity of 40K, 238U and 232Th show that there is no significant transference of natural radionuclides from fertilizers to the final product of the food chain. The annual committed effective dose due to the ingestion of 40K contained in the group of consumed vegetables analysed in this work resulted in the very low value of 0.882 μSv.

  19. Ionizing Radiation Dose Due to the Use of Agricultural Fertilizers

    SciTech Connect

    Umisedo, Nancy K.; Okuno, Emico; Medina, Nilberto H.; Colacioppo, Sergio; Hiodo, Francisco Y.

    2008-08-07

    The transference of radionuclides from the fertilizers to/and from soils to the foodstuffs can represent an increment in the internal dose when the vegetables are consumed by the human beings. This work evaluates the contribution of fertilizers to the increase of radiation level in the environment and of dose to the people. Samples of fertilizers, soils and vegetables produced in farms located in the neighbourhood of Sao Paulo city in the State of Sao Paulo, Brazil were analysed through gamma spectroscopy. The values of specific activity of {sup 40}K, {sup 238}U and {sup 232}Th show that there is no significant transference of natural radionuclides from fertilizers to the final product of the food chain. The annual committed effective dose due to the ingestion of {sup 40}K contained in the group of consumed vegetables analysed in this work resulted in the very low value of 0.882 {mu}Sv.

  20. Proteomic Analysis of Low Dose Arsenic and Ionizing Radiation Exposure on Keratinocytes

    PubMed Central

    Berglund, Susanne R.; Santana, Alison R.; Li, Dan; Rice, Robert H.; Rocke, David M.; Goldberg, Zelanna

    2008-01-01

    Human exposure to arsenic and ionizing radiation occur environmentally at low levels. While the human health effects of arsenic and ionizing radiation have been examined separately, there is little information regarding their combined effects at doses approaching environmental levels. Arsenic toxicity may be affected by concurrent ionizing radiation especially given their known individual carcinogenic actions at higher doses. We found that keratinocytes responded to either low dose arsenic and/or low dose ionizing radiation exposure, resulting in differential proteomic expression based on 2DGE, immunoblotting and statistical analysis. Seven proteins were identified that passed a rigorous statistical screen for differential expression in 2DGE and also passed a strict statistical screen for follow-up immunoblotting. These included: α-enolase, epidermal-fatty acid binding protein, heat shock protein 27, histidine triad nucleotide-binding protein 1, lactate dehydrogenase A, protein disulfide isomerase precursor and S100A9. Four proteins had combined effects that were different than would be expected based on the response to either individual toxicant. These data demonstrate a possible reaction to the combined insult that is substantially different from that of either separate treatment. Several proteins had different responses than what has been seen from high dose exposures, adding to the growing literature suggesting that the cellular responses to low dose exposures are distinct. PMID:19294697

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

    NASA Technical Reports Server (NTRS)

    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.

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

    NASA Technical Reports Server (NTRS)

    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.

  3. Total ionizing dose effects in multiple-gate field-effect transistor

    NASA Astrophysics Data System (ADS)

    Gaillardin, Marc; Marcandella, Claude; Martinez, Martial; Raine, Mélanie; Paillet, Philippe; Duhamel, Olivier; Richard, Nicolas

    2017-08-01

    This paper focuses on total ionizing dose (TID) effects induced in multiple-gate field-effect transistors. The impact of device architecture, geometry and scaling on the TID response of multiple-gate transistors is reviewed in both bulk and silicon-on-insulator (SOI) complementary metal-oxide-semiconductor (CMOS) technologies. These innovating devices exhibit specific ionizing dose responses which strongly depend on their three-dimensional nature. Their TID responses may look like the one usually observed in planar two-dimensional bulk or SOI transistors, but multiple-gate devices can also behave like any other CMOS device.

  4. [Absorbed dose measurement of photon beam with Farmer-type ionization chambers in Japanese dosimetry protocols].

    PubMed

    Fujisaki, Tatsuya; Hiraoka, Takeshi; Osawa, Atsushi; Nakajima, Masaru; Kuwabara, Akio; Yokoyama, Koichi; Saitoh, Hidetoshi; Tomaru, Teizo; Inada, Tetsuo

    2004-01-01

    The Japan Society of Medical Physics (JSMP) has published a new dosimetry protocol "JSMP-01" (standard dosimetry of absorbed dose in external beam radiotherapy) which conforms to the recommendations of the International Atomic Energy Agency (IAEA TRS-398) and the American Association of Physicists in Medicine (AAPM TG-51) protocols for the calibration of radiotherapy beams. Since the new protocol offers the physical data for the Famer-type ionization chambers of the various wall materials, the user can measure the absorbed dose at reference point (D(r)) using most of the commercially available Famer-type ionization chambers. In this paper, the six Famer-type ionization chambers of the various wall materials are examined for photon beam by two ways. To verify the JSMP-01 protocol as the first way, D(r) was cross-measured based on the JSMP-01 protocol using a Farmer-type ionization chamber of the acrylic wall material which is called "JARP-chamber" and the Farmer-type ionization chambers of the various wall materials, and compared. To compare the basic data in previous and new protocols as the second way, D(r) was measured based on the previous protocol (JSMP-86) and the JSMP-01 protocol using the Farmer-type ionization chambers of the various wall materials. Dose calculation was made using common exposure calibration factor for (60)Co gamma-rays (Nc) for each of the Farmer-type ionization chambers. Measurement was made with each ionization chamber for 6 and 10 MV photon beams in two facilities. D(r) were found to agree to that of JARP-chamber within about +/- 1% despite significant differences of ratio of calibration factor (k(D,X)) and beam quality conversion factor (k(Q)) for photon beams. The ratios JSMP-01/JSMP-86 of the reference dose were found to lie on between 0.999 and 1.004 for 6 MV and on between 0.999 and 1.005 for 10 MV depending upon the Farmer-type ionization chambers used. The largest discrepancies between the previous and new protocols arise from

  5. Structure factors for tunneling ionization rates of molecules

    NASA Astrophysics Data System (ADS)

    Madsen, Lars Bojer; Jensen, Frank; Tolstikhin, Oleg I.; Morishita, Toru

    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 of this factor, and hence the ionization rate, requires accurate values of the HOMO in the asymptotic region. Techniques for calculating the structure factors for molecules in the Hartree-Fock approximation are discussed. For diatomics, grid-based numerical Hartree-Fock calculations which reproduce the correct asymptotic tail of the HOMO are possible. However, for larger molecules, to solve the Hartree-Fock equations one should resort to basis-based approaches with too rapidly decaying Gaussian basis functions. A systematic study of the possibility to reproduce the asymptotic tail of the HOMO in calculations with Gaussian basis sets is presented. We find that polarization-consistent basis sets with quadruple or pentuple-zeta quality greatly improve the tail of the HOMO, but only when used with variationally optimized exponents. This methodology is validated by considering the CO molecule for which reliable grid-based calculations can be performed. The optimized Gaussian basis sets are used to calculate the structure factors for the triatomic molecules CO2 and OCS. The results are compared with available experimental and theoretical results.

  6. Patient-specific dose calculation methods for high-dose-rate iridium-192 brachytherapy

    NASA Astrophysics Data System (ADS)

    Poon, Emily S.

    In high-dose-rate 192Ir brachytherapy, the radiation dose received by the patient is calculated according to the AAPM Task Group 43 (TG-43) formalism. This table-based dose superposition method uses dosimetry parameters derived with the radioactive 192Ir source centered in a water phantom. It neglects the dose perturbations caused by inhomogeneities, such as the patient anatomy, applicators, shielding, and radiographic contrast solution. In this work, we evaluated the dosimetric characteristics of a shielded rectal applicator with an endocavitary balloon injected with contrast solution. The dose distributions around this applicator were calculated by the GEANT4 Monte Carlo (MC) code and measured by ionization chamber and GAFCHROMIC EBT film. A patient-specific dose calculation study was then carried out for 40 rectal treatment plans. The PTRAN_CT MC code was used to calculate the dose based on computed tomography (CT) images. This study involved the development of BrachyGUI, an integrated treatment planning tool that can process DICOM-RT data and create PTRAN_CT input initialization files. BrachyGUI also comes with dose calculation and evaluation capabilities. We proposed a novel scatter correction method to account for the reduction in backscatter radiation near tissue-air interfaces. The first step requires calculating the doses contributed by primary and scattered photons separately, assuming a full scatter environment. The scatter dose in the patient is subsequently adjusted using a factor derived by MC calculations, which depends on the distances between the point of interest, the 192Ir source, and the body contour. The method was validated for multicatheter breast brachytherapy, in which the target and skin doses for 18 patient plans agreed with PTRAN_CT calculations better than 1%. Finally, we developed a CT-based analytical dose calculation method. It corrects for the photon attenuation and scatter based upon the radiological paths determined by ray tracing

  7. Total Ionizing Dose Effects in MOS Oxides and Devices

    NASA Technical Reports Server (NTRS)

    Oldham, Timothy R.; McLean, F. B.

    2003-01-01

    The development of military and space electronics technology has traditionally been heavily influenced by the commercial semiconductor industry. The development of MOS technology, and particularly CMOS technology, as dominant commercial technologies has occurred entirely within the lifetime of the NSREC. For this reason, it is not surprising that the study of radiation interactions with MOS materials, devices and circuits has been a major theme of this conference for most of its history. The basic radiation problem in a MOS transistor is illustrated. The application of an appropriate gate voltage causes a conducting channel to form between the source and drain, so that current flows when the device is turned on. In Fig. lb, the effect of ionizing radiation is illustrated. Radiation-induced trapped charge has built up in the gate oxide, which causes a shift in the threshold voltage (that is, a change in the voltage which must be applied to turn the device on). If this shift is large enough, the device cannot be turned off, even at zero volts applied, and the device is said to have failed by going depletion mode.

  8. The Effect of High-Dose Ionizing Radiation on the Astrobiological Model Lichen Circinaria gyrosa.

    PubMed

    de la Torre, Rosa; Miller, Ana Zélia; Cubero, Beatriz; Martín-Cerezo, M Luisa; Raguse, Marina; Meeßen, Joachim

    2017-02-01

    The lichen Circinaria gyrosa is an astrobiological model defined by its high capacity of resistance to space conditions and to a simulated martian environment. Therefore, it became part of the currently operated BIOMEX experiment on board the International Space Station and the recent STARLIFE campaign to study the effects of four types of space-relevant ionizing radiation. The samples were irradiated with helium and iron ions at doses up to 2 kGy, with X-rays at doses up to 5 kGy and with γ rays at doses from 6 to 113 kGy. Results on C. gyrosa's resistance to simulated space ionizing radiation and its post-irradiation viability were obtained by (i) chlorophyll a fluorescence of photosystem II (PSII), (ii) epifluorescence microscopy, (iii) confocal laser scanning microscopy (CLSM), and (iv) field emission scanning electron microscopy (FESEM). Results of photosynthetic activity and epifluorescence show no significant changes up to a dose of 1 kGy (helium ions), 2 kGy (iron ions), 5 kGy (X-rays)-the maximum doses applied for those radiation qualities-as well as a dose of 6 kGy of γ irradiation, which was the lowest dose applied for this low linear energy transfer (LET) radiation. Significant damage in a dose-related manner was observed only at much higher doses of γ irradiation (up to 113 kGy). These data corroborate the findings of the parallel STARLIFE studies on the effects of ionizing radiation on the lichen Circinaria gyrosa, its isolated photobiont, and the lichen Xanthoria elegans. Key Words: Simulated space ionizing radiation-Gamma rays-Extremotolerance-Lichens-Circinaria gyrosa-Photosynthetic activity. Astrobiology 17, 145-153.

  9. Cardiovascular diseases related to ionizing radiation: The risk of low-dose exposure (Review)

    PubMed Central

    Baselet, Bjorn; Rombouts, Charlotte; Benotmane, Abderrafi Mohammed; Baatout, Sarah; Aerts, An

    2016-01-01

    Traditionally, non-cancer diseases are not considered as health risks following exposure to low doses of ionizing radiation. Indeed, non-cancer diseases are classified as deterministic tissue reactions, which are characterized by a threshold dose. It is judged that below an absorbed dose of 100 mGy, no clinically relevant tissue damage occurs, forming the basis for the current radiation protection system concerning non-cancer effects. Recent epidemiological findings point, however, to an excess risk of non-cancer diseases following exposure to lower doses of ionizing radiation than was previously thought. The evidence is the most sound for cardiovascular disease (CVD) and cataract. Due to limited statistical power, the dose-risk relationship is undetermined below 0.5 Gy; however, if this relationship proves to be without a threshold, it may have considerable impact on current low-dose health risk estimates. In this review, we describe the CVD risk related to low doses of ionizing radiation, the clinical manifestation and the pathology of radiation-induced CVD, as well as the importance of the endothelium models in CVD research as a way forward to complement the epidemiological data with the underlying biological and molecular mechanisms. PMID:27748824

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

    SciTech Connect

    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.

  11. The increase in animal mortality risk following exposure to sparsely ionizing radiation is not linear quadratic with dose

    DOE PAGES

    Haley, Benjamin M.; Paunesku, Tatjana; Grdina, David J.; ...

    2015-12-09

    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 bomb survivors (DDREFLSS). As a result, it was calculated by applying a linear-quadratic dose response model to data from Japanese atomic bomb survivors and a limitedmore » number of animal studies.« less

  12. The increase in animal mortality risk following exposure to sparsely ionizing radiation is not linear quadratic with dose

    SciTech Connect

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

    2015-12-09

    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 bomb survivors (DDREFLSS). As a result, it was calculated by applying a linear-quadratic dose response model to data from Japanese atomic bomb survivors and a limited number of animal studies.

  13. Fast-neutron and photon doses determined with proportional counters and ionization chambers

    SciTech Connect

    DeLuca, P.M. Jr.; Higgins, P.D.; Schell, M.C.; Pearson, D.W.

    1981-01-01

    A /sup 60/Co teletherapy source has recently been coupled to an existing source of fast neutrons. These sources may be operated to provide precise and controlled mixtures of photons and neutrons. In this work we report the application of paired miniature proportional counters to n/..gamma.. dose separation. Graphite- and A150 plastic-walled proportional counters were employed. Results are compared to dose values deduced from a cnventional A150 plastic ionization chamber and a neutron insensitive GM counter.

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

    PubMed

    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 relationships 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.

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

    NASA Technical Reports Server (NTRS)

    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.; Berg, Melanie D.; Gigliuto, Robert A.; Boutte, Alvin J.; Cochran, Donna J.; Buchner, Stephen P.; Violette, Daniel P.

    2014-01-01

    We present results and analysis investigating the effects of radiation on a variety of candidate spacecraft electronics to proton and heavy ion induced single event effects (SEE), proton-induced displacement damage (DD), and total ionizing dose (TID). Introduction: This paper is a summary of test results.NASA spacecraft are subjected to a harsh space environment that includes exposure to various types of ionizing radiation. The performance of electronic devices in a space radiation environment is often limited by its susceptibility to single event effects (SEE), total ionizing dose (TID), and displacement damage (DD). Ground-based testing is used to evaluate candidate spacecraft electronics to determine risk to spaceflight applications. Interpreting the results of radiation testing of complex devices is quite difficult. Given the rapidly changing nature of technology, radiation test data are most often application-specific and adequate understanding of the test conditions is critical. Studies discussed herein were undertaken to establish the application-specific sensitivities of candidate spacecraft and emerging electronic devices to single-event upset (SEU), single-event latchup (SEL), single-event gate rupture (SEGR), single-event burnout (SEB), single-event transient (SET), TID, enhanced low dose rate sensitivity (ELDRS), and DD effects.

  16. Absorbed dose dependence of the correction factors for ionization chamber cable irradiation effects.

    PubMed

    Campos, L L; Caldas, L V

    1991-03-01

    A simple method was developed, for possible use by hospital physicists, to evaluate the irradiation effects on cables and connectors during large-radiation-field dosimetry with ionization chambers and to determine correction factors for the used system or geometry. This method was based on the absorbed dose dependence of the correction factor.

  17. Current Total Ionizing Dose Results and Displacement Damage Results for Candidate Spacecraft Electronics for NASA

    NASA Technical Reports Server (NTRS)

    Cochran, Donna J.; Kniffin, Scott D.; LaBel, Kenneth A.; OBryan, Martha V.; Reed, Robert A.; Ladbury, Ray L.; Howard, James W., Jr.; Poivey, Christian; Buchner, Stephen P.; Marshall, Cheryl J.

    2004-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Cochran, Donna J.; Kniffin, Scott D.; LaBel, Kenneth A.; OBryan, Martha V.; Reed, Robert A.; Ladbury, Ray L.; Howard, James W., Jr.; Poivey, Christian; Buchner, Stephen P.; Marshall, Cheryl J.

    2003-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    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

  20. The Effect of Total Ionizing Dose Degradation of Laptop Hard Disks

    NASA Technical Reports Server (NTRS)

    Nguyen, D. N.; Guertin, S. M.; Patterson, J. D.

    2005-01-01

    A series of total ionizing dose (TID) measurements were performed on commercial hard drives to explore the possible uses of the devices for the high radiation mission, and to help the understanding of the reliability of current hard drive technology. Three different models from three major manufacturers were tested with the aid of a commercial hard drive test system.

  1. The Effect of Total Ionizing Dose Degradation of Laptop Hard Disks

    NASA Technical Reports Server (NTRS)

    Nguyen, D. N.; Guertin, S. M.; Patterson, J. D.

    2005-01-01

    A series of total ionizing dose (TID) measurements were performed on commercial hard drives to explore the possible uses of the devices for the high radiation mission, and to help the understanding of the reliability of current hard drive technology. Three different models from three major manufacturers were tested with the aid of a commercial hard drive test system.

  2. The Effect of High-Dose Ionizing Radiation on the Astrobiological Model Lichen Circinaria gyrosa

    NASA Astrophysics Data System (ADS)

    de la Torre, Rosa; Zélia Miller, Ana; Cubero, Beatriz; Martín-Cerezo, M. Luisa; Raguse, Marina; Meeßen, Joachim

    2017-02-01

    The lichen Circinaria gyrosa is an astrobiological model defined by its high capacity of resistance to space conditions and to a simulated martian environment. Therefore, it became part of the currently operated BIOMEX experiment on board the International Space Station and the recent STARLIFE campaign to study the effects of four types of space-relevant ionizing radiation. The samples were irradiated with helium and iron ions at doses up to 2 kGy, with X-rays at doses up to 5 kGy and with γ rays at doses from 6 to 113 kGy. Results on C. gyrosa's resistance to simulated space ionizing radiation and its post-irradiation viability were obtained by (i) chlorophyll a fluorescence of photosystem II (PSII), (ii) epifluorescence microscopy, (iii) confocal laser scanning microscopy (CLSM), and (iv) field emission scanning electron microscopy (FESEM). Results of photosynthetic activity and epifluorescence show no significant changes up to a dose of 1 kGy (helium ions), 2 kGy (iron ions), 5 kGy (X-rays) - the maximum doses applied for those radiation qualities - as well as a dose of 6 kGy of γ irradiation, which was the lowest dose applied for this low linear energy transfer (LET) radiation. Significant damage in a dose-related manner was observed only at much higher doses of γ irradiation (up to 113 kGy). These data corroborate the findings of the parallel STARLIFE studies on the effects of ionizing radiation on the lichen Circinaria gyrosa, its isolated photobiont, and the lichen Xanthoria elegans.

  3. Investigation of an apparent protective effect of occupational exposure to low doses of ionizing radiation on mortality

    SciTech Connect

    Schwartzbaum, J.; Shy, C.

    1986-09-01

    To examine the effect of occupational exposure to low doses of ionizing radiation on the length of survival after the start of employment, 8375 employees at a nuclear scientific research and development laboratory were followed from 1943 until 1977. Nine hundred sixty-six deaths from all causes were observed. The total cumulative dose of ionizing radiation in rems as measured by film badges was divided into four categories, 0, 0.01-0.99, 1-4.9, greater than or equal to5 rems. When adjusted for the year of first employment and the age at death (using the Cox proportional hazards regression model) the risks of death from all causes at each dose per unit time relative to the risk at the 0 dose level (the hazard ratios - from the lowest to the highest dose) were 1.00, 0.97 (95% confidence interval (CI), 0.82-1.14), 0.75 (95% CI, 0.73-0.89), and 0.46 (95% CI, 0.34-0.61). The hypothesis of a linear relationship between the log of the hazard rate and dose was not rejected (x/sub 2/ = 1.34, p > 0.05). The hazard ratios for deaths due to cancer were similar: 1.00, 1.19 (95% CI, 0.80-1.75, 1.01 (95% CI, 0.64-1.50), and 0.58 (95% CI, 0.31-1.10). This unexpected inverse association is being examined by 1) treating radiation dose as a time dependent covariate; 2) investigating the effect of adding several potentially confounding and effect modifying variables; and 3) determining the survival-dose association within subsets of causes of death.

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

    PubMed

    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.

  5. Ionizing Radiation Doses Detected at the Eye Level of the Primary Surgeon During Orthopaedic Procedures.

    PubMed

    Cheriachan, Deepak; Hughes, Adrian M; du Moulin, William S M; Williams, Christopher; Molnar, Robert

    2016-07-01

    To evaluate the ionizing radiation dose received by the eyes of orthopaedic surgeons during various orthopaedic procedures. Secondary objective was to compare the ionizing radiation dose received between differing experience level. Prospective comparative study between January 2013 and May 2014. Westmead Hospital, a Level 1 Trauma Centre for Greater Western Sydney. A total of 26 surgeons volunteered to participate within the study. Experience level, procedure performed, fluoroscopy time, dose area product, total air kerma, and eye dose received was recorded. Participants were evaluated on procedure and experience level. Radiation dose received at eye level by the primary surgeon during an orthopaedic procedure. Data from a total of 131 cases was recorded and included for analysis. The mean radiation dose detected at the eye level of the primary surgeon was 0.02 mSv (SD = 0.05 mSv) per procedure. Radiation at eye level was only detected in 31 of the 131 cases. The highest registered dose for a single procedure was 0.31 mSv. Femoral nails and pelvic fixation procedures had a significantly higher mean dose received than other procedure groups (0.04 mSv (SD = 0.07 mSv) and 0.04 mSv (SD = 0.06 mSv), respectively). Comparing the eye doses received by orthopaedic consultants and trainees, there was no significant difference between the 2 groups. The risk of harmful levels of radiation exposure at eye level to orthopaedic surgeons is low. This risk is greatest during insertion of femoral intramedullary nails and pelvic fixation, and it is recommended that in these situations, surgeons take all reasonable precautions to minimize radiation dose. The orthopaedic trainees in this study were not subjected to higher doses of radiation than their consultant trainers. On the basis of these results, most of the orthopaedic surgeons remain well below the yearly radiation dose of 20 mSv as recommended by the International Commission on Radiological Protection.

  6. Dose rate, dose-equivalent rate, and quality factor in SLS-1

    NASA Technical Reports Server (NTRS)

    Badhwar, G. D.; Braby, L. A.; Cucinotta, F. A.; Atwell, W.

    1992-01-01

    A tissue-equivalent proportional counter (TEPC) sensitive to the lineal energy range of 0.26-300 keV micrometer-1 was flown on STS-40 (39 degrees x 278 km x 296 km) inside the Spacelab. This instrument was previously flown on STS-31 but was modified to provide a finer resolution at lower lineal energies to better map the South Atlantic Anomaly (SAA) protons. The instrument was turned on 6 June 1991, and operated for 7470 min (124.5 h). The flight duration was characterized by a very large number of X-ray solar flares and enhanced magnetic field fluctuations; however, no significant dose from the solar particles was measured at the location of this instrument. The flight data can be separated into trapped and galactic cosmic radiation parts. The dose rate, dose-equivalent rate and quality factor for trapped radiation were 4.21 +/- 0.03 mrad day-1, 7.72 +/- 0.05 mrem day-1, and 1.83 +/- 0.1, respectively. The dose rate, dose-equivalent rate, and quality factor for galactic cosmic radiation were 5.34 +/- 0.03 mrad day-1, 14.63 +/- 0.06 mrem day-1, and 2.74 +/- 0.1, respectively. The overall quality factor for the flight was 2.38. The dose from the GCR is higher than from SAA protons because of the high inclination and low altitude of this flight. The AP8MAX model of the trapped radiation gives a dose rate of 2.43 mrad day-1 and a quality factor of 1.77. The CREME solar maximum model of galactic cosmic radiation gives a dose rate of 2.54 mrad day-1 and a quality factor of 2.91. Thus the AP8MAX model underestimates the dose by a factor of 1.8 whereas the CREME model leads to an underestimation of the dose by a factor of 2. A comparison of the LET spectra using the AP8MAX model and galactic cosmic radiation transport codes shows only a qualitative agreement.

  7. Annual effective dose of ionizing radiation from natural sources received by airline aircrew members compared with that received by non-flying residents of the United States

    NASA Astrophysics Data System (ADS)

    Friedberg, W.; Copeland, K.; O'Brien, K., III

    In evaluating health aspects of the ionizing radiation exposure of aircrews, risk estimates are normally based on the amount of cosmic radiation received in flight. Not considered is that aircrews spend most of their time on the ground. In this report, annual total effective doses of ionizing radiation from natural sources received by aircrews on and off the job, flying between Los Angeles and Tokyo or Chicago and London, are compared with doses to non-flying residents of the United States and non-flying residents of Environmental Protection Agency Region 8 (Montana, North Dakota, South Dakota, Wyoming, Utah, Colorado --- the region in the United States with the highest dose rates of natural ionizing radiation at ground level). Occupational exposure of aircrews to ionizing radiation is thought to increase their risk of fatal cancer. It may not be a significant concern if one considers: (a) the annual dose of ionizing radiation to the crewmembers in our study is only 7-41% higher than that received by non-flying residents of Region 8 (terrestrial gamma and cosmic radiation in the Denver, Colorado, area of Region 8); (b) the dose to non-flying residents of Region 8 is 87% higher than the average dose to non-flying residents of the United States; and (c) the estimated death rate from cancer in the six states in Region 8 is 3-26% lower than the average for the United States. When considering health concerns of aircrew members, one should recognize that the standard risk coefficient for radiation-induced fatal cancer is derived primarily from studies on individuals exposed to radiation at higher doses and dose rates and of generally lower energy, than the galactic cosmic radiation to which aircrews are exposed. These differences are a major reason that epidemiology studies are important in evaluating health aspects of the occupational radiation exposure of aircrews.

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

    SciTech Connect

    Tschaeche, A.N.

    1996-12-31

    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?

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

    SciTech Connect

    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

  10. [Evaluation of absorbed doses of ionizing radiation by milk teeth enamel in children living in the Belarus Republic].

    PubMed

    Mel'nichenko, E M; Kushner, A N; Miliutin, A A; Mashevskiĭ, A A; Muravskiĭ, V A

    2002-01-01

    Mean doses of ionizing radiation, absorbed by children in the Byelarus Republic, were evaluated by EPR dosimetry of tableted samples of milk teeth enamel. A relationship between the doses absorbed by the children and density of radionuclide contamination of the territory of residence was detected. Based on the mean absorbed doses, doses which can be absorbed during 70 years of life were estimated.

  11. Cell-density dependent effects of low-dose ionizing radiation on E. coli cells.

    PubMed

    Alipov, E D; Shcheglov, V S; Sarimov, R M; Belyaev, I Ya

    2003-01-01

    The changes in genome conformational state (GCS) induced by low-dose ionizing radiation in E. coli cells were measured by the method of anomalous viscosity time dependence (AVTD) in cellular lysates. Effects of X-rays at doses 0.1 cGy--1 Gy depended on post-irradiation time. Significant relaxation of DNA loops followed by a decrease in AVTD. The time of maximum relaxation was between 5-80 min depending on the dose of irradiation. U-shaped dose response was observed with increase of AVTD in the range of 0.1-4 Gy and decrease in AVTD at higher doses. No such increase in AVTD was seen upon irradiation of cells at the beginning of cell lysis while the AVTD decrease was the same. Significant differences in the effects of X-rays and gamma-rays at the same doses were observed suggesting a strong dependence of low-dose effects on LET. Effects of 0.01 cGy gamma-rays were studied at different cell densities during irradiation. We show that the radiation-induced changes in GCS lasted longer at higher cell density as compared to lower cell density. Only small amount of cells were hit at this dose and the data suggest cell-to-cell communication in response to low-dose ionizing radiation. This prolonged effect was also observed when cells were irradiated at high cell density and diluted to low cell density immediately after irradiation. These data suggest that cell-to-cell communication occur during irradiation or within 3 min post-irradiation. The cell-density dependent response to low-dose ionizing radiation was compared with previously reported data on exposure of E. coli cells to electromagnetic fields of extremely low frequency and extremely high frequency (millimeter waves). The body of our data show that cells can communicate in response to electromagnetic fields and ionizing radiation, presumably by reemission of secondary photons in infrared-submillimeter frequency range.

  12. Radiation quality and the shape of dose-effect curves at low doses of ionizing radiation for eukaryotic cells.

    PubMed

    Petin, V G; Kapultcevich, Yu G

    2014-06-01

    To explain different yeast and mammalian cell response to low and high linear energy transfer (LET) radiation in low dose region, the dependence of fine target structure on the stage of cell growth was supposed. Theoretical consideration based on this suggestion was carried out. Results of calculations are qualitatively in agreement with experimental data under assuming that hit-event for both mammalian and yeast cells is a group of ionizations produced by the same ionizing particle. In the dependence of cell cycle phase, sensitive sites (presumable the vulnerable sections of chromosomes) can be located either in periphery of cell nucleus forming a thin layer inside the nucleus or distributed evenly over the whole nucleus. Such rearrangement of the target results in the alteration of the dependence of both survival curve shape and the relative biological effectiveness values on radiation quality. Copyright © 2014 Elsevier Inc. All rights reserved.

  13. [Effects of low doses of ionizing radiation on substrate and germination of higher plants seeds].

    PubMed

    Tsetlin, V V; Levinskikh, M A; Nefedova, E L; Derendiaeva, T A; Fedotova, I V

    2008-01-01

    The investigation had the aim to evaluate the effects of low doses (< 1-10 cGy) of ionizing radiation on the physical-chemical qualities of high-purification water. It had also the goal to study germination rate and energy and sprouting of four species of higher plants exposed directly and indirectly (watering) to alpha- and beta-radiation from radionuclids sources. When compared with intact water, after exposure to beta-particles electrical currents in water-filled containers consistently tended upward and downward after exposure to alpha-particles. Radiation-induced changes in water parameters were observed throughout the experiment with higher plant seeds. Evaluation of the effect of irradiated water on sprouting showed that plant sensitivity varied with species and depended on type of radiation particles. Neither alpha- nor beta particles affected the wheat sprouts; however, both types of particles inhibited growth of mustard and accelerated growth of lentil and haricot Mash as compared with control crops. The investigation suggests that plant species for space greenhouses should be selected with account of their radioresistance and radiosensitivity.

  14. Boosting the total ionizing dose tolerance of digital switches by using OCTO SOI MOSFET

    NASA Astrophysics Data System (ADS)

    Navarenho de Souza Fino, Leonardo; Davini Neto, Enrico; Aparecida Guazzelli da Silveira, Marcilei; Renaux, Christian; Flandre, Denis; Pinillos Gimenez, Salvador

    2015-10-01

    This paper performs an experimental comparative study of the total ionizing dose effects due to the x-ray radiation between the silicon-on-insulator (SOI) metal-oxide semiconductor field-effect transistors (MOSFETs) manufactured with octagonal gate geometry and the standard counterpart. Our main focus is on integrated transceivers for wireless communications and smart-power dc/dc converters for mobile electronics, where the transistor is used as the key switching element. It is shown that this innovative layout can reduce the total ionizing dose (TID) effects due to the special characteristics of the OCTO SOI MOSFET bird’s beak regions, where longitudinal electrical field lines in these regions are not parallel to the drain and source regions. Consequently, the parasitic MOSFETs associated with these regions are practically deactivated.

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

    PubMed

    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".

  16. The biobehavioral and neuroimmune impact of low-dose ionizing radiation

    PubMed Central

    York, Jason M; Blevins, Neil A; Meling, Daryl D; Peterlin, Molly B; Gridley, Daila S; Cengel, Keith A; Freund, Gregory G

    2011-01-01

    In the clinical setting, repeated exposures (10–30) to low-doses of ionizing radiation (≤ 200 cGy), as seen in radiotherapy for cancer, causes fatigue. Almost nothing is known, however, about the fatigue inducing effects of a single exposure to environmental low-dose ionizing radiation that might occur during high-altitude commercial air flight, a nuclear reactor accident or a solar particle event (SPE). To investigate the short-term impact of low-dose ionizing radiation on mouse biobehaviors and neuroimmunity, male CD-1 mice were whole body irradiated with 50 cGy or 200 cGy of gamma or proton radiation. Gamma radiation was found to reduce spontaneous locomotor activity by 35% and 36%, respectively, 6 h post irradiation. In contrast, the motivated behavior of social exploration was un-impacted by gamma radiation. Examination of pro-inflammatory cytokine gene transcripts in the brain demonstrated that gamma radiation increased hippocampal TNF-α expression as early as 4 h post-irradiation. This was coupled to subsequent increases in IL-1RA (8 h and 12 h post irradiation) in the cortex and hippocampus and reductions in activity-regulated cytoskeleton-associated protein (Arc) (24 h post irradiation) in the cortex. Finally, restraint stress was a significant modulator of the neuroimmune response to radiation blocking the ability of 200 cGy gamma radiation from impairing locomotor activity and altering the brain-based inflammatory response to irradiation. Taken together, these findings indicate that low-dose ionizing radiation rapidly activates the neuroimmune system potentially causing early onset fatigue-like symptoms in mice. PMID:21958477

  17. Total ionizing dose effects in high voltage devices for flash memory

    NASA Astrophysics Data System (ADS)

    Liu, Zhangli; Hu, Zhiyuan; Zhang, Zhengxuan; Shao, Hua; Chen, Ming; Bi, Dawei; Ning, Bingxu; Wang, Ru; Zou, Shichang

    2010-12-01

    The effect of size and substrate bias conditions after irradiation on the total ionizing dose response of high voltage devices for flash memory has been investigated. Different sensitivity of transistors with different gate width was observed, which is well known as the radiation induced narrow channel effect. A charge sharing model was used to explain this effect. The negative substrate bias voltage after irradiation showed considerable impact on the parasitic transistor's response by suppressing leakage current.

  18. Strong field ionization rates simulated with time-dependent configuration interaction and an absorbing potential

    SciTech Connect

    Krause, Pascal; Sonk, Jason A.; Schlegel, H. Bernhard

    2014-05-07

    Ionization rates of molecules have been modeled with time-dependent configuration interaction simulations using atom centered basis sets and a complex absorbing potential. The simulations agree with accurate grid-based calculations for the ionization of hydrogen atom as a function of field strength and for charge resonance enhanced ionization of H{sub 2}{sup +} as the bond is elongated. Unlike grid-based methods, the present approach can be applied to simulate electron dynamics and ionization in multi-electron polyatomic molecules. Calculations on HCl{sup +} and HCO{sup +} demonstrate that these systems also show charge resonance enhanced ionization as the bonds are stretched.

  19. Non-targeted effects of ionizing radiation–implications for low dose risk

    PubMed Central

    Kadhim, Munira; Salomaa, Sisko; Wright, Eric; Hildebrandt, Guido; Belyakov, Oleg V.; Prise, Kevin M.; Little, Mark P.

    2014-01-01

    Non-DNA targeted effects of ionizing radiation, which include genomic instability, and a variety of bystander effects including abscopal effects and bystander mediated adaptive response, have raised concerns about the magnitude of low-dose radiation risk. Genomic instability, bystander effects and adaptive responses are powered by fundamental, but not clearly understood systems that maintain tissue homeostasis. Despite excellent research in this field by various groups, there are still gaps in our understanding of the likely mechanisms associated with non-DNA targeted effects, particularly with respect to systemic (human health) consequences at low and intermediate doses of ionizing radiation. Other outstanding questions include links between the different non-targeted responses and the variations in response observed between individuals and cell lines, possibly a function of genetic background. Furthermore, it is still not known what the initial target and early interactions in cells are that give rise to non-targeted responses in neighbouring or descendant cells. This paper provides a commentary on the current state of the field as a result of the Non-targeted effects of ionizing radiation (NOTE) Integrated Project funded by the European Union. Here we critically examine the evidence for non-targeted effects, discuss apparently contradictory results and consider implications for low-dose radiation health effects. PMID:23262375

  20. TRANSIENT GENOME-WIDE TRANSCRIPTIONAL RESPONSE TO LOW-DOSE IONIZING RADIATION IN VIVO IN HUMANS

    PubMed Central

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

    2009-01-01

    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. PMID:17996396

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

    SciTech Connect

    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.

  2. The measuring of the absorbed dose in human tissue that underwent irradiation with ionizing radiation

    NASA Astrophysics Data System (ADS)

    Bercea, S.; Nikolic, A.; Cenusa, C.; Celarel, A.

    2010-07-01

    Ionizing radiations are radiations of atomic origin (X) or nuclear origin (α, β, γ). They are composed of either subatomic particles (α, β) or electromagnetic waves (X, γ) which possess enough energy to remove electrons from the atoms and molecules of the medium with which particles interact. They thus generate ionizing processes. The effects that are produced by the interaction of the ionizing radiations with a particular medium (which could be human tissue) have different intensities depending on the nature of the incident radiations, on the rate in which these radiations release energy to the medium and on the total amount of energy released to the medium. For this reason, the energy released by a particular type of ionizing radiations to a particular type of medium has become of great interest both for researchers and for specialists who deal with using ionizing radiations in different fields, such as the biomedical one. The aim of the present paper is to briefly present some of the aspects connected to the way certain quantities are defined, quantities which are specific to the interaction of ionizing particles with the medium they pass through and which are also connected to the energy released in the medium. The paper also describes methods of measuring these quantities.

  3. Effect of ionizing radiation at low dose on transgenerational carcinogenesis by epigenetic regulation.

    PubMed

    Li, Lan; Kim, Jong-Hyun; Park, Hee-Tae; Lee, Jae-Hoon; Park, Min-Koo; Lee, Ji-Won; Lee, Jeong-Chan; Lee, Min-Jae

    2017-06-01

    The objective of this study was to determine the effect of ionizing radiation (IR) exposure of parents on carcinogenesis of the next generation focusing on the epigenetic perspective to clarify the relationship between radiation dose and carcinogenesis in F1 generation SD rats. F1 generations from pregnant rats (F0) who were exposed to gamma rays were divided into three groups according to the dose of radiation: 10 rad, 30 rad, and untreated. They were intraperitoneally injected with 50 mg/kg of diethylnitrosamine (DEN). Carcinogenesis was analyzed by examining expression levels of tumor suppressor genes (TSG) and other related genes by methylation-specific polymerase chain reaction (MSP). DNA methylation in liver tissues was evaluated to discern epigenetic regulation of transgenerational carcinogenesis vulnerability following IR exposure. Numerous studies have proved that transcriptional inactivation due to hypermethylation of TSG preceded carcinogenesis. Results of this study revealed hypermethylation of tumor suppressor gene SOCS1 in group treated with 30 rad. In addition, genes related to DNA damage response pathway (GSTP1, ATM, DGKA, PARP1, and SIRT6) were epigenetically inactivated in all DEN treated groups. In the case of proto-oncogene c-Myc, DNA hypermethylation was identified in the group with low dose of IR (10 rad). Results of this study indicated that each TSG had different radiation threshold level (dose-independent way) and DEN treatment could affect DNA methylation profile irrelevant of ionizing radiation dose.

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

    NASA Astrophysics Data System (ADS)

    Berejka, Anthony J.

    2007-08-01

    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 × 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.

  5. Electron impact ionization rates for interstellar H and He atoms near interplanetary shocks: Ulysses observations

    SciTech Connect

    Feldman, W.C.; Phillips, J.L.; Gosling, J.T.; Isenberg, P.A.

    1996-07-01

    Solar wind plasma data measured during the near-ecliptic phase of the Ulysses mission between October, 1990 and January, 1993 were studied to determine the relative importance of electron-impact ionization to the total ionization rates of interstellar hydrogen and helium atoms. During times of quiet flow conditions electron-impact ionization rates were found to be generally low, of the order of 1{percent} of the total ionization rates. However, just downstream of the strongest CME- and CIR-driven shock waves encountered by Ulysses, the electron impact-ionization rate at times was more than 10{percent} that of the charge-exchange rate for hydrogen and more than 100{percent} that of the photoionization rate for helium. {copyright} {ital 1996 American Institute of Physics.}

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

    SciTech Connect

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

    2012-05-15

    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{sup 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{sup 9} Gy/s within 2% (OSL and TLD) and up to 1510{sup 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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

    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.

  8. Effects of ISS equivalent ionizing radiation dose on Human T-lymphocytes

    NASA Astrophysics Data System (ADS)

    Meloni, Maria Antonia; Pani, Giuseppe; Benotmane, Rafi; Mastroleo, Felice; Aboul-El-Ardat, Khalil; Janssen, Ann; Leysen, Liselotte; Vanhavere, Filip; Leys, Natalie; Galleri, Grazia; Pippia, Proto; Baatout, Sarah

    One of the objectives of the current international space programs is to investigate the effects of cosmic environment on Humans. It is known that during a long exposure to the space conditions, including ionizing radiations and microgravity, the immune system of the astronauts is impaired. In past years several experiments were performed to identify responsible factors of in vitro mitogenic activation process in human T-lymphocytes under simulated microgravity effect and during dedicated space missions. It come out that the lack of immune response in microgravity occurs at the cellular and molecular level. In order to evaluate effects on pure primary T-lymphocytes from peripheral blood exposed to International Space Station (ISS)-like ionizing radiation, we applied a mixture of Cesium-137, as representative of low energy particles, and Californium-252, as representative of hight energy particles, with rate similar to those monitored inside the ISS during previous space mission (Goossens et all. 2006). This facility is available at SCK•CEN (Belgium) (Mastroleo et al., 2009). Although the dose received by the cells was relatively low, flow cytometry analysis 24 hours after irradiation showed a decrease in cell viability coupled with the increase of the caspase-3 activity. However, Bcl-2 activity did not seem to be affected by the radiation. Furthermore, activation of cells induced an increase of the cell size and alteration of cellular morphology. Cell cycle as well as 8-oxo-G were also modified upon radiation and activation. Gene expression analysis shows a modulation of genes rather as a consequence of exposure than with the activation status. 330 genes have been identified to be significantly modulated in function of the time and have been grouped in four different cluster representing significant expression profiles. Preliminary functional analysis shows mainly genes involved in the immune response and inflammatory diseases as well as oxidative stress and

  9. Dose rate and annealing effects on total dose response of MOS and bipolar circuits

    SciTech Connect

    Carriere, T.; Beaucour, J.; Gach, A.; Johlander, B.; Adams, L.

    1995-12-01

    Different part types of major technology families were irradiated in order to study dose rate and post irradiation annealing effects. Results confirm that degradation of MOS technologies at low dose rates can be predicted from high dose rate and annealing measurements, while this is not possible for bipolar linear IC`s. The ESA/SCC22900 test method is discussed.

  10. Compendium of Current Total Ionizing Dose Results and Displacement Damage Results for Candidate Spacecraft Electronics for NASA

    NASA Technical Reports Server (NTRS)

    Cochran, Donna J.; O'Bryan, Martha V.; Buchner, Stephen P.; Poivey, Christian; Ladbury, Ray L.; LaBel, Kenneth A.

    2007-01-01

    Sensitivity of a variety of candidate spacecraft electronics to total ionizing dose and displacement damage is studied. Devices tested include optoelectronics, digital, analog, linear bipolar devices, and hybrid devices.

  11. Cancer risks attributable to low doses of ionizing radiation: assessing what we really know.

    PubMed

    Brenner, David J; Doll, Richard; Goodhead, Dudley T; Hall, Eric J; Land, Charles E; Little, John B; Lubin, Jay H; Preston, Dale L; Preston, R Julian; Puskin, Jerome S; Ron, Elaine; Sachs, Rainer K; Samet, Jonathan M; Setlow, Richard B; Zaider, Marco

    2003-11-25

    High doses of ionizing radiation clearly produce deleterious consequences in humans, including, but not exclusively, cancer induction. At very low radiation doses the situation is much less clear, but the risks of low-dose radiation are of societal importance in relation to issues as varied as screening tests for cancer, the future of nuclear power, occupational radiation exposure, frequent-flyer risks, manned space exploration, and radiological terrorism. We review the difficulties involved in quantifying the risks of low-dose radiation and address two specific questions. First, what is the lowest dose of x- or gamma-radiation for which good evidence exists of increased cancer risks in humans? The epidemiological data suggest that it is approximately 10-50 mSv for an acute exposure and approximately 50-100 mSv for a protracted exposure. Second, what is the most appropriate way to extrapolate such cancer risk estimates to still lower doses? Given that it is supported by experimentally grounded, quantifiable, biophysical arguments, a linear extrapolation of cancer risks from intermediate to very low doses currently appears to be the most appropriate methodology. This linearity assumption is not necessarily the most conservative approach, and it is likely that it will result in an underestimate of some radiation-induced cancer risks and an overestimate of others.

  12. Benchmark Experiment of Dose Rate Distributions Around the Gamma Knife Medical Apparatus

    SciTech Connect

    Oishi, K.; Kosako, K.; Kobayashi, Y.; Sonoki, I.

    2014-06-15

    Dose rate measurements around a gamma knife apparatus were performed by using an ionization chamber. Analyses have been performed by using the Monte Carlo code MCNP-5. The nuclear library used for the dose rate distribution of {sup 60}Co was MCPLIB04. The calculation model was prepared with a high degree of fidelity, such as the position of each Cobalt source and shielding materials. Comparisons between measured results and calculated ones were performed, and a very good agreement was observed. It is concluded that the Monte Carlo calculation method with its related nuclear data library is very effective for such a complicated radiation oncology apparatus.

  13. Benchmark Experiment of Dose Rate Distributions Around the Gamma Knife Medical Apparatus

    NASA Astrophysics Data System (ADS)

    Oishi, K.; Kosako, K.; Kobayashi, Y.; Sonoki, I.

    2014-06-01

    Dose rate measurements around a gamma knife apparatus were performed by using an ionization chamber. Analyses have been performed by using the Monte Carlo code MCNP-5. The nuclear library used for the dose rate distribution of 60Co was MCPLIB04. The calculation model was prepared with a high degree of fidelity, such as the position of each Cobalt source and shielding materials. Comparisons between measured results and calculated ones were performed, and a very good agreement was observed. It is concluded that the Monte Carlo calculation method with its related nuclear data library is very effective for such a complicated radiation oncology apparatus.

  14. Update on the biological effects of ionizing radiation, relative dose factors and radiation hygiene.

    PubMed

    White, Stuart C; Mallya, S M

    2012-03-01

    Diagnostic imaging is an indispensable part of contemporary medical and dental practice. Over the last few decades there has been a dramatic increase in the use of ionizing radiation for diagnostic imaging. The carcinogenic effects of high-dose exposure are well known. Does diagnostic radiation rarely cause cancer? We don't know but we should act as if it does. Accordingly, dentists should select patients wisely - only make radiographs when there is patient-specific reason to believe there is a reasonable expectation the radiograph will offer unique information influencing diagnosis or treatment. Low-dose examinations should be made: intraoral imaging - use fast film or digital sensors, thyroid collars, rectangular collimation; panoramic and lateral cephalometric imaging - use digital systems or rare-earth film screen combinations; and cone beam computed tomography - use low-dose machines, restrict field size to region of interest, reduce mA and length of exposure arc as appropriate. © 2012 Australian Dental Association.

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

    SciTech Connect

    Batzri, S.; Catravas, G.

    1988-11-01

    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.

  16. Compact modeling of total ionizing dose and aging effects in MOS technologies

    SciTech Connect

    Esqueda, Ivan S.; Barnaby, Hugh J.; King, Michael Patrick

    2015-06-18

    This paper presents a physics-based compact modeling approach that incorporates the impact of total ionizing dose (TID) and stress-induced defects into simulations of metal-oxide-semiconductor (MOS) devices and integrated circuits (ICs). This approach utilizes calculations of surface potential (ψs) to capture the charge contribution from oxide trapped charge and interface traps and to describe their impact on MOS electrostatics and device operating characteristics as a function of ionizing radiation exposure and aging effects. The modeling approach is demonstrated for bulk and silicon-on-insulator (SOI) MOS device. The formulation is verified using TCAD simulations and through the comparison of model calculations and experimental I-V characteristics from irradiated devices. The presented approach is suitable for modeling TID and aging effects in advanced MOS devices and ICs.

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

    PubMed Central

    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. PMID:7294269

  18. Compact modeling of total ionizing dose and aging effects in MOS technologies

    DOE PAGES

    Esqueda, Ivan S.; Barnaby, Hugh J.; King, Michael Patrick

    2015-06-18

    This paper presents a physics-based compact modeling approach that incorporates the impact of total ionizing dose (TID) and stress-induced defects into simulations of metal-oxide-semiconductor (MOS) devices and integrated circuits (ICs). This approach utilizes calculations of surface potential (ψs) to capture the charge contribution from oxide trapped charge and interface traps and to describe their impact on MOS electrostatics and device operating characteristics as a function of ionizing radiation exposure and aging effects. The modeling approach is demonstrated for bulk and silicon-on-insulator (SOI) MOS device. The formulation is verified using TCAD simulations and through the comparison of model calculations and experimentalmore » I-V characteristics from irradiated devices. The presented approach is suitable for modeling TID and aging effects in advanced MOS devices and ICs.« less

  19. Dose equivalence for high-dose-rate to low-dose-rate intracavitary irradiation in the treatment of cancer of the uterine cervix

    SciTech Connect

    Akine, Y.; Tokita, N.; Ogino, T.; Kajiura, Y.; Tsukiyama, I.; Egawa, S. )

    1990-12-01

    By comparing the incidence of major radiation injury, we estimated doses clinically equivalent for high-dose-rate (HDR) to conventional low-dose-rate (LDR) intracavitary irradiation in patients with Stages IIb and IIIb cancer of the uterine cervix. We reviewed a total of 300 patients who were treated with external beam therapy to the pelvis (50 Gy in 5 weeks) followed either by low-dose-rate (253 patients) or high-dose-rate (47 patients) intracavitary treatment. The high-dose-rate intracavitary treatment was given 5 Gy per session to point A, 4 fractions in 2 weeks, with a total dose of 20 Gy. The low-dose-rate treatment was given with one or two application(s) delivering 11-52 Gy to the point A. The local control rates were similar in both groups. The incidence of major radiation injury requiring surgical intervention were 5.1% (13/253) and 4.3% (2/47) for low-dose-rate and high-dose-rate groups, respectively. The 4.3% incidence corresponded to 29.8 Gy with low-dose-rate irradiation, thus, it was concluded that the clinically equivalent dose for high-dose-rate irradiation was approximately 2/3 (20/29.8) of the dose used in low-dose-rate therapy.

  20. Mitochondrial-Derived Oxidants and Cellular Responses to Low Dose/Low LET Ionizing Radiation

    SciTech Connect

    Spitz, Douglas R.

    2009-11-09

    Exposure to ionizing radiation results in the immediate formation of free radicals and other reactive oxygen species (ROS). It has been assumed that the subsequent injury processes leading to genomic instability and carcinogenesis following radiation, derive from the initial oxidative damage caused by these free radicals and ROS. It is now becoming increasingly obvious that metabolic oxidation/reduction (redox) reactions can be altered by irradiation leading to persistent increases in steady-state levels of intracellular free radicals and ROS that contribute to the long term biological effects of radiation exposure by causing chronic oxidative stress. The objective during the last period of support (DE-FG02-05ER64050; 5/15/05-12/31/09) was to determine the involvement of mitochondrial genetic defects in metabolic oxidative stress and the biological effects of low dose/low LET radiation. Aim 1 was to determine if cells with mutations in succinate dehydrogenase (SDH) subunits C and D (SDHC and SDHD in mitochondrial complex II) demonstrated increases in steady-state levels of reactive oxygen species (ROS; O2•- and H2O2) as well as demonstrating increased sensitivity to low dose/low LET radiation (10 cGy) in cultured mammalian cells. Aim #2 was to determine if mitochondrially-derived ROS contributed to increased sensitivity to low dose/low LET radiation in mammalian cells containing mutations in SDH subunits. Aim #3 was to determine if a causal relationship existed between increases in mitochondrial ROS production, alterations in electron transport chain proteins, and genomic instability in the progeny of irradiated cells. Evidence gathered in the 2005-2009 period of support demonstrated that mutations in genes coding for mitochondrial electron transport chain proteins (ETC); either Succinate Dehydrogenase (SDH) subunit C (SDHC) or subunit D (SDHD); caused increased ROS production, increased genomic instability, and increased sensitivity to low dose/low LET radiation

  1. Dose Response of MTLn3 Cells to Serial Dilutions of Arsenic Trioxide and Ionizing Radiation.

    PubMed

    Raja, Waseem Khan; Satti, Jahangir; Liu, Gang; Castracane, James

    2013-01-01

    MTLn3 cells derived from mouse mammary epithelium are known to be highly malignant and are resistant to both radio- and chemo-therapy. We exposed MTLn3 cells to various doses of inorganic Arsenic trioxide (As2O3) in combination with ionizing radiation. Cells were treated with a series of As2O3 concentrations ranging from 20 μM to 1.22 nM for 8 hour, 24 hour and 48 hour periods. Post-treated cell proliferation was quantified by measuring mitochondrial activity and DNA analysis. Cells exposed to radiation and As2O3 at concentration greater than 1.25 μM showed apoptosis and radiations alone treated cells were statistically not different from the control. Hormesis was observed for As2O3 concentrations in the range of 0.078 μM to 0.625 μM while the combined chemo and radiation treatments of the cells did not affect the hormetic effect. We have demonstrated that As2O3 (in the presence and absence of ionizing radiation) in specific low concentrations induced apoptosis in the otherwise chemoresistant cancer cells. This low concentration-mediated cell death is immediately followed by a surge in cell survival. Low dosing dosimetry is highly desirable in metronomic therapy however, it has a narrow window since necrosis, hormesis, apoptosis and other dose-dependent biological processes take place in this region. Further quantifiable dosimetry is highly desired for routine clinical practice.

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

    DOE PAGES

    Alwood, Joshua S.; Kumar, Akhilesh; Tran, Luan H.; ...

    2012-01-01

    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 137 Cs) 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 evidentmore » 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.« less

  3. Dose-dependent changes in the antigenicity of bacterial endotoxin exposed to ionizing radiation. Report No. 2, 1986-1987

    SciTech Connect

    Csako, G.; Suba, E.A.; Tsai, C.M.; Mocca, L.F.; Elin, R.J.

    1987-01-01

    The antigenic properties of the highly purified US reference standard endotoxin (RSE) exposed to varying doses of ionizing radiation were studied with double immuno-diffusion, immunoelectrophoresis, and immunoblotting. Rabbit RSE antisera identified 2 distinct major antigenic components for untreated RSE: one related to the O-polysaccharide side chain (O-antigenic specificity), the other to the R-core. Based on a serologic cross-reactivity of R-core of RSE (Escherichia coli 0113) with the R-core of the lipopolysaccharide from E. coli 0111, the core type of E. coli 0113 was identified as coli R3. Increasing exposure of RSE to ionizing radiation progressively destroyed all antigenic reactivities; at lower doses of radiation the rate of elimination differed for the 2 antigen classes. The O-polysaccharide was more sensitive to gamma radiation than the R-core and the O-antigenicity was lost before that of the R-core. Endotoxin molecules containing incomplete R-core (radiation-induced or mutant) did not react with the RSE antiserum. Keywords: Antigenicity, Reprints. (KT/KR)

  4. The Effects of ELDRS at Ultra-Low Dose Rates

    NASA Technical Reports Server (NTRS)

    Chen, Dakai; Forney, James; Carts, Martin; Phan, Anthony; Pease, Ronald; Kruckmeyer, Kirby; Cox, Stephen; LaBel, Kenneth; Burns, Samuel; Albarian, Rafi; Holcombe, Bruce; Little, Bradley; Salzman, James; Chaumont, Geraldine; Duperray, Herve; Ouellet, Al

    2011-01-01

    We present results on the effects on ELDRS at dose rates of 10, 5, 1, and 0.5 mrad(Si)/s for a variety of radiation hardened and commercial devices. We observed low dose rate enhancement below 10 mrad(Si)/s in several different parts. The magnitudes of the dose rate effects vary. The TL750L, a commercial voltage regulator, showed dose rate dependence in the functional failures, with initial failures occurring after 10 krad(Si) for the parts irradiated at 0.5 mrad(Si)/s. The RH1021 showed an increase in low dose rate enhancement by 2x at 5 mrad(Si)/s relative to 8 mrad(Si)/s and high dose rate, and parametric failure after 100 krad(Si). Additionally the ELDRS-free devices, such as the LM158 and LM117, showed evidence of dose rate sensitivity in parametric degradations. Several other parts also displayed dose rate enhancement, with relatively lower degradations up to approx.15 to 20 krad(Si). The magnitudes of the dose rate enhancement will likely increase in significance at higher total dose levels.

  5. A systematic review of epidemiological associations between low and moderate doses of ionizing radiation and late cardiovascular effects, and their possible mechanisms.

    PubMed

    Little, M P; Tawn, E J; Tzoulaki, I; Wakeford, R; Hildebrandt, G; Paris, F; Tapio, S; Elliott, P

    2008-01-01

    Little, M. P., Tawn, E. J., Tzoulaki, I., Wakeford, R., Hildebrandt, G., Paris, F., Tapio, S. and Elliott, P. A Systematic Review of Epidemiological Associations Between Low and Moderate Doses of Ionizing Radiation and Late Cardiovascular Effects, and Their Possible Mechanisms. Radiat. Res. 169, 99-109 (2008). The link between high doses of ionizing radiation and damage to the heart and coronary arteries is established. In this paper, we systematically review the epidemiological evidence for associations between low and moderate doses (<5 Gy) of ionizing radiation and late-occurring cardiovascular disease. Risks per unit dose in epidemiological studies vary over at least two orders of magnitude, possibly a result of confounding factors. An examination of possible biological mechanisms indicates that the most likely causative effect of radiation exposure is damage to endothelial cells and subsequent induction of an inflammatory response, although it seems unlikely that this would extend to low-dose and low-dose-rate exposure. However, a role for somatic mutation has been proposed that would indicate a stochastic effect. In the absence of a convincing mechanistic explanation of epidemiological evidence that is less than persuasive at present, a cause-and-effect interpretation of the reported statistical associations cannot be reliably inferred, although neither can it be reliably excluded. Further epidemiological and biological evidence will allow a firmer conclusion to be drawn.

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

    SciTech Connect

    Radev, R

    2009-01-13

    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

  7. Quantitative Proteomic Profiling of Low Dose Ionizing Radiation Effects in a Human Skin Model

    SciTech Connect

    Hengel, Shawna; Aldrich, Joshua T.; Waters, Katrina M.; Pasa-Tolic, Ljiljana; Stenoien, David L.

    2014-07-29

    To assess molecular responses to low doses of radiation that may be encountered during medical diagnostic procedures, nuclear accidents, or terrorist acts, a quantitative global proteomic approach was used to identify protein alterations in a reconstituted human skin tissue treated with 10 cGy of ionizing radiation. Subcellular fractionation was employed to remove highly abundant structural proteins and provide insight on radiation induced alterations in protein abundance and localization. In addition, peptides were post-fractionated using high resolution 2-dimensional liquid chromatography to increase the dynamic range of detection of protein abundance and translocation changes. Quantitative data was obtained by labeling peptides with 8-plex isobaric iTRAQ tags. A total of 207 proteins were detected with statistically significant alterations in abundance and/or subcellular localization compared to sham irradiated tissues. Bioinformatics analysis of the data indicated that the top canonical pathways affected by low dose radiation are related to cellular metabolism. Among the proteins showing alterations in abundance, localization and proteolytic processing was the skin barrier protein filaggrin which is consistent with our previous observation that ionizing radiation alters profilaggrin processing with potential effects on skin barrier functions. In addition, a large number of proteases and protease regulators were affected by low dose radiation exposure indicating that altered proteolytic activity may be a hallmark of low dose radiation exposure. While several studies have demonstrated altered transcriptional regulation occurs following low dose radiation exposures, the data presented here indicates post-transcriptional regulation of protein abundance, localization, and proteolytic processing play an important role in regulating radiation responses in complex human tissues.

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

    PubMed Central

    Kleibeuker, Esther A; ten Hooven, Matthijs A; 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. PMID:25828633

  9. Dynamic changes in the proteome of human peripheral blood mononuclear cells with low dose ionizing radiation.

    PubMed

    Nishad, S; Ghosh, Anu

    2016-02-01

    Humans are continually exposed to ionizing radiation from natural as well as anthropogenic sources. Though biological effects of high dose radiation exposures have been well accepted, studies on low-to-moderate dose exposures (in the range of 50-500 mGy) have been strongly debated even as researchers continue to search for elusive 'radiation signatures' in humans. Proteins are considered as dynamic functional players that drive cellular responses. However, there is little proteomic information available in context of human exposure to ionizing radiation. In this study, we determined differential expressed proteins in G0 peripheral blood mononuclear cells (PBMCs) from healthy individuals 1h and 4h after 'ex vivo' exposure with two radiation doses (300 mGy and 1 Gy). Twenty-three proteins were found to be significantly altered in irradiated cells when compared to sham irradiated cells with fold change ± 1.5-fold (p ≤ 0.05), with only three proteins showing ≥ 2.5-fold change, either with dose or with time. Mass spectrometry analyses identified redox sensor protein, chloride intracellular channel protein 1 (CLIC-1), the antioxidant protein, peroxiredoxin-6 and the pro-survival molecular chaperone 78 KDa glucose regulated protein (GRP78) among the 23 modulated proteins. The mean coefficient of variation (CV) for the twenty-three radiation responsive protein spots was found to be 33.7% for 300 mGy and 48.3% for 1 Gy. We thus, conclude that the radiation proteomic response of G0 human PBMCs, which are in the resting stage of the cell cycle, involves moderate upregulation of protective mechanisms, with low inter-individual variability. This study will help further our understanding of cellular effects of low dose acute radiation in humans and contribute toward differential biomarker discovery. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. Ionizing radiation doses during lower limb torsion and anteversion measurements by EOS stereoradiography and computed tomography.

    PubMed

    Delin, Cyrille; Silvera, Stéphane; Bassinet, Céline; Thelen, Philippe; Rehel, Jean-Luc; Legmann, Paul; Folinais, Dominique

    2014-02-01

    To calculate and compare the doses of ionizing radiation delivered to the organs by computed tomography (CT) and stereoradiography (SR) during measurements of lower limb torsion and anteversion. A Rando anthropomorphic phantom (Alderson RANDO phantom, Alderson Research Laboratories Inc., Stanford, Conn) was used for the dose measurements. The doses were delivered by a Somatom 16-slice CT-scanner (Siemens, Erlangen) and an EOS stereoradiography unit (EOS-Imaging, Paris) according to the manufacturers' acquisition protocols. Doses to the surface and deeper layers were calculated with thermoluminiscent GR207P dosimeters. Dose uncertainties were evaluated and assessed at 6% at k=2 (that is, two standard deviations). The absorbed doses for the principal organs assessed were as follows: for the ovaries, 0.1 mGy to the right ovary and 0.5 mGy to the left ovary with SR versus 1.3 mGy and 1.1 mGy with CT, respectively; testes, 0.3 mGy on the right and 0.4 mGy on the left with SR versus 8.5 mGy and 8.4 mGy with CT; knees, 0.4 mGy to the right knee and 0.8 mGy to the left knee with SR versus 11 mGy and 10.4 mGy with CT; ankles, 0.5 mGy to the right ankle and 0.8 mGy to the left with SR versus 15 mGy with CT. The SR system delivered substantially lower doses of ionizing radiation doses than CT to all the organs studied: CT doses were 4.1 times higher to the ovaries, 24 times higher for the testicles, and 13-30 times higher for the knees and ankles. The use of the SR system to study the torsion of lower limbs makes it possible to reduce the amount of medical irradiation that patients accumulate. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  11. Hydrocarbon rate coefficients for proton and electron impact ionization, dissociation, and recombination in a hydrogen plasma.

    SciTech Connect

    Alman, D.A.; Brooks, J.N.; Ruzic, D.N.; Wang, Z.

    1999-07-21

    We estimate cross sections and rate coefficients for proton and electron impact ionization, dissociation, and recombination of neutral and ionized hydrocarbon molecules and fragments of the form C{sub x}H{sub y}{sup k}, x = 1-3, y = 1-6, k = 0,1 in a thermalized hydrogen-electron plasma.

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

    SciTech Connect

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

    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.

  13. Inter-Individual Variability in Human Response to Low-Dose Ionizing Radiation, Final Report

    SciTech Connect

    Rocke, David

    2016-08-01

    In order to investigate inter-individual variability in response to low-dose ionizing radiation, we are working with three models, 1) in-vivo irradiated human skin, for which we have a realistic model, but with few subjects, all from a previous project, 2) ex-vivo irradiated human skin, for which we also have a realistic model, though with the limitations involved in keeping skin pieces alive in media, and 3) MatTek EpiDermFT skin plugs, which provides a more realistic model than cell lines, which is more controllable than human samples.

  14. An investigation of the reaction kinetics of luciferase and the effect of ionizing radiation on the reaction rate.

    PubMed

    Berovic, Nikolas; Parker, David J; Smith, Michael D

    2009-04-01

    The bioluminescence produced by luciferase, a firefly enzyme, requires three substrates: luciferin, ATP and oxygen. We find that ionizing radiation, in the form of a proton beam from a cyclotron, will eliminate dissolved oxygen prior to any damage to other substrates or to the protein. The dose constant for removal of oxygen is 70 +/- 20 Gy, a much smaller dose than required to cause damage to protein. Removal of oxygen, which is initially in excess, leads to a sigmoidal response of bioluminescence to radiation dose, consistent with a Michaelis-Menten relationship to substrate concentration. When excess oxygen is exhausted, the response becomes exponential. Following the irradiation, bioluminescence recovers due to a slow leak of oxygen into the solution. This may also explain previous observations on the response of bioluminescent bacteria to radiation. We have studied the dependence of the reaction rate on enzyme and substrate concentration and propose a model for the reaction pathway consistent with this data. The light output from unirradiated samples decreases significantly with time due to product inhibition. We observe that this inhibition rate changes dramatically immediately after a sample is exposed to the beam. This sudden change of the inhibition rate is unexplained but shows that enzyme regulatory function responds to ionizing radiation at a dose level less than 0.6 Gy.

  15. The effect of dose rate dependence of p-type silicon detectors on linac relative dosimetry.

    PubMed

    Wilkins, D; Li, X A; Cygler, J; Gerig, L

    1997-06-01

    Cumulative radiation damage to silicon semiconductor diode detectors can induce dose rate dependent sensitivity, a concern in the pulsed beam of a linac. Two p-Si diode photon detectors were used in this study, diodes A and B. Both were preirradiated by the supplier to 5 kGy, with diode A receiving an estimated 8 kGy from measurements, and diode B, 25 kGy. At 6 MV, the PDD measured with diode B was lower (by 4.4% at a depth of 25 cm) than diode A. Using SSD to vary the dose per pulse from 0.02 to 0.64 mGy/pulse, diode A was dose rate independent (within 2%), while the sensitivity of diode B changed by 13%. Silicon diode detectors should be checked regularly against ionization chambers in the pulsed beam of a linac, especially older high-resistivity diodes that have accumulated dose from high-energy photon beams.

  16. Radiation dose rates from UF{sub 6} cylinders

    SciTech Connect

    Friend, P.J.

    1991-12-31

    This paper describes the results of many studies, both theoretical and experimental, which have been carried out by Urenco over the last 15 years into radiation dose rates from uranium hexafluoride (UF{sub 6}) cylinders. The contents of the cylinder, its history, and the geometry all affect the radiation dose rate. These factors are all examined in detail. Actual and predicted dose rates are compared with levels permitted by IAEA transport regulations.

  17. Correlation of dose rate and spectral measurements in the Inner Van Allen Belt.

    PubMed

    Thede, A L; Radke, G E

    1968-01-01

    Dose rate measurements and the charged particle environment of the Inner Van Allen Belt have been correlated using recent data obtained from the radiation research satellite, OV3-4. Six tissue equivalent ionization chambers, constructed of a material which simulates the muscle tissue response to ionizing radiation, measured the dose rate behind various types and thicknesses of material. The specific shields used for several of the chambers were 0.192 g/cm2 aluminum, 0.797 g/cm2 Lucite and 4.485 g/cm2 brass. The proton and electron spectra were determined with an omnidirectional spectrometer using solid state detectors. The spectral measurements discussed here include geomagnetically trapped protons with energies in the range of 15 to 200 MeV. The proton spectra and dose rates are presented as profiles in terms of the McIlwain parameters of L (1.5, 2.0 and 2.5 earth radii) and the magnetic field B (0.050 to 0.250 gauss). The excellent agreement between the measured dose rate and the theoretically predicted dose rate based on the measured spectra provides justification for the radiation transport techniques now being employed to predict the doses to be encountered during future manned space missions. It was found, however, that a more adequate description of the proton fluxes for energies greater than 50 MeV will be necessary to predict dose rate accurately behind shields of 2.5 g/cm2 thickness or greater.

  18. Consequences of Low Dose Ionizing Radiation Exposure on the Hippocampal Microenvironment

    PubMed Central

    Acharya, Munjal M.; Patel, Neal H.; Craver, Brianna M.; Tran, Katherine K.; Giedzinski, Erich; Tseng, Bertrand P.; Parihar, Vipan K.; Limoli, Charles L.

    2015-01-01

    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. PMID:26042591

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

    PubMed

    Acharya, Munjal M; Patel, Neal H; Craver, Brianna M; Tran, Katherine K; Giedzinski, Erich; Tseng, Bertrand P; Parihar, Vipan K; Limoli, Charles L

    2015-01-01

    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.

  20. Total Ionizing Dose Effects on High Resolution (12-/14-bit) Analog-to-Digital Converters

    NASA Technical Reports Server (NTRS)

    Lee, C. I.; Rax, B. G.; Johnson, A. H.

    1994-01-01

    This paper reports total dose radiation test results for high resolution 12-/14-bit A/D converters. Small changes in internal components can cause these devices to fail their specifications at relatively low total dose levels. Degradation of signal-to-noise ratio becomes increasingly importamt for high accuracy converters. Rebound effects in the thick-oxide MOS devices causes these responses to be different at low and high dose rates, which is a major concern for space applications.

  1. Dose rate effects in radiation degradation of polymer-based cable materials

    NASA Astrophysics Data System (ADS)

    Plaček, V.; Bartoníček, B.; Hnát, V.; Otáhal, B.

    2003-08-01

    Cable ageing under the nuclear power plant (NPP) conditions must be effectively managed to ensure that the required plant safety and reliability are maintained throughout the plant service life. Ionizing radiation is one of the main stressors causing age-related degradation of polymer-based cable materials in air. For a given absorbed dose, radiation-induced damage to a polymer in air environment usually depends on the dose rate of the exposure. In this work, the effect of dose rate on the degradation rate has been studied. Three types of NPP cables (with jacket/insulation combinations PVC/PVC, PVC/PE, XPE/XPE) were irradiated at room temperature using 60Co gamma ray source at average dose rates of 7, 30 and 100 Gy/h with the doses up to 590 kGy. The irradiated samples have been tested for their mechanical properties, thermo-oxidative stability (using differential scanning calorimetry, DSC), and density. In the case of PVC and PE samples, the tested properties have shown evident dose rate effects, while the XPE material has shown no noticeable ones. The values of elongation at break and the thermo-oxidative stability decrease with the advanced degradation, density tends to increase with the absorbed dose. For XPE samples this effect can be partially explained by the increase of crystallinity. It was tested by the DSC determination of the crystalline phase amount.

  2. Metabolomic Response of Human Skin Tissue to Low Dose Ionizing Radiation

    SciTech Connect

    Hu, Zeping; Kim, Young-Mo; Sowa, Marianne B.; Robinson, Robert J.; Gao, Xiaoli; Metz, Thomas O.; Morgan, William F.; Zhang, Qibin

    2012-05-18

    Understanding how human organs respond to ionizing radiation (IR) at a systems biology level and identifying biomarkers for IR exposure at low doses can help provide a scientific basis for establishing radiation protection standards. Little is known regarding the physiological responses to low dose IR at the metabolite level, which represents the end-point of biochemical processes inside cells. Using a full thickness human skin tissue model and GC-MS-based metabolomics analysis, we examined the metabolic perturbations at three time points (3, 24 and 48 hr) after exposure to 3, 10 and 200 cGy of X-rays. PLS-DA score plots revealed dose- and time-dependent clustering between sham and irradiated groups. Importantly, a comparable number of metabolites were detected to have significant change 48 hr after exposure to 3 and 10 cGy of irradiation, when compared with the high dose of 200 cGy. Biochemical pathway analysis showed perturbations to DNA/RNA damage and repair, lipid and energy metabolisms, even at low doses of IR.

  3. Identifying the health risks from very low-dose sparsely ionizing radiation.

    PubMed Central

    Dreyer, N A; Friedlander, E

    1982-01-01

    The health risks from low-dose sparsely ionizing (low-LET) radiation have been the subject of continued debate. At present, quantitative estimates of risk are extremely uncertain due to the controversy surrounding both the dosimetry for A-bomb survivor data and the choice of mathematical models for extrapolating risk from high to low doses. Nevertheless, much can be learned about the nature of the health risks by reviewing the epidemiologic literature. We present a summary of diseases which have been associated with low-LET radiation (less than 1000 rad) in at least two independent studies, according to the mean cumulative organ dose at which the disease was observed. At organ doses of less than or equal to 50 rad, the only diseases that have been reported consistently are thyroid cancer, salivary gland tumors, and leukemia. The first two diseases were observed in association with x-ray epilation of the scalp for tinea capitis, a therapy which is no longer employed. On the other hand, leukemia has been observed repeatedly to occur at cumulative doses of greater than or equal to 30 rad low-LET radiation. PMID:7041660

  4. [Pulsed-dose rate brachytherapy in cervical cancers: why, how?].

    PubMed

    Mazeron, R; Dumas, I; Martin, V; Martinetti, F; Benhabib-Boukhelif, W; Gensse, M-C; Chargari, C; Guemnie-Tafo, A; Haie-Méder, C

    2014-10-01

    The end of the production of 192 iridium wires terminates low dose rate brachytherapy and requires to move towards pulsed-dose rate or high-dose rate brachytherapy. In the case of gynecological cancers, technical alternatives exist, and many teams have already taken the step of pulsed-dose rate for scientific reasons. Using a projector source is indeed a prerequisite for 3D brachytherapy, which gradually installs as a standard treatment in the treatment of cervical cancers. For other centers, this change implies beyond investments in equipment and training, organizational consequences to ensure quality.

  5. The estimation of galactic cosmic ray penetration and dose rates

    NASA Technical Reports Server (NTRS)

    Burrell, M. O.; Wright, J. J.

    1972-01-01

    This study is concerned with approximation methods that can be readily applied to estimate the absorbed dose rate from cosmic rays in rads - tissue or rems inside simple geometries of aluminum. The present work is limited to finding the dose rate at the center of spherical shells or behind plane slabs. The dose rate is calculated at tissue-point detectors or for thin layers of tissue. This study considers cosmic-rays dose rates for both free-space and earth-orbiting missions.

  6. Space Radiation Quality Factors and the Delta Ray Dose and Dose-Rate Reduction Effectiveness Factor.

    PubMed

    Cucinotta, Francis A; Cacao, Eliedonna; Alp, Murat

    2016-03-01

    In this paper, the authors recommend that the dose and dose-rate effectiveness factor used for space radiation risk assessments should be based on a comparison of the biological effects of energetic electrons produced along a cosmic ray particles path in low fluence exposures to high dose-rate gamma-ray exposures of doses of about 1 Gy. Methods to implement this approach are described.

  7. Study of total ionizing dose radiation effects on enclosed gate transistors in a commercial CMOS technology

    NASA Astrophysics Data System (ADS)

    Li, Dong-Mei; Wang, Zhi-Hua; Huangfu, Li-Ying; Gou, Qiu-Jing

    2007-12-01

    This paper studies the total ionizing dose radiation effects on MOS (metal-oxide-semiconductor) transistors with normal and enclosed gate layout in a standard commercial CMOS (compensate MOS) bulk process. The leakage current, threshold voltage shift, and transconductance of the devices were monitored before and after γ-ray irradiation. The parameters of the devices with different layout under different bias condition during irradiation at different total dose are investigated. The results show that the enclosed layout not only effectively eliminates the leakage but also improves the performance of threshold voltage and transconductance for NMOS (n-type channel MOS) transistors. The experimental results also indicate that analogue bias during irradiation is the worst case for enclosed gate NMOS. There is no evident different behaviour observed between normal PMOS (p-type channel MOS) transistors and enclosed gate PMOS transistors.

  8. Mechanistic Modeling of Dose and Dose Rate Dependences of Radiation-Induced DNA Double Strand Break Rejoining Kinetics in Saccharomyces cerevisiae

    PubMed Central

    Shuryak, Igor

    2016-01-01

    Mechanistic modeling of DNA double strand break (DSB) rejoining is important for quantifying and medically exploiting radiation-induced cytotoxicity (e.g. in cancer radiotherapy). Most radiation-induced DSBs are quickly-rejoinable and are rejoined within the first 1–2 hours after irradiation. Others are slowly-rejoinable (persist for several hours), and yet others are essentially unrejoinable (persist for >24 hours). The dependences of DSB rejoining kinetics on radiation dose and dose rate remain incompletely understood. We hypothesize that the fraction of slowly-rejoinable and/or unrejoinable DSBs increases with increasing dose/dose rate. This radiation-dependent (RD) model was implemented using differential equations for three DSB classes: quickly-rejoinable, slowly-rejoinable and unrejoinable. Radiation converts quickly-rejoinable to slowly-rejoinable, and slowly-rejoinable to unrejoinable DSBs. We used large published data sets on DSB rejoining in yeast exposed to sparsely-ionizing (electrons and γ-rays, single or split-doses, high or low dose rates) and densely-ionizing (α-particles) radiation to compare the performances of the proposed RD formalism and the established two-lesion kinetic (TLK) model. These yeast DSB rejoining data were measured within the radiation dose range relevant for clonogenic cell survival, whereas in mammalian cells DSB rejoining is usually measured only at supra-lethal doses for technical reasons. The RD model described both sparsely-ionizing and densely-ionizing radiation data much better than the TLK model: by 217 and 14 sample-size-adjusted Akaike information criterion units, respectively. This occurred because: the RD (but not the TLK) model reproduced the observed upwardly-curving dose responses for slowly-rejoinable/unrejoinable DSBs at long times after irradiation; the RD model adequately described DSB yields at both high and low dose rates using one parameter set, whereas the TLK model overestimated low dose rate data

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

    NASA Astrophysics Data System (ADS)

    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.

  10. Electron Impact Ionization Cross Sections and Rate Coefficients for Single Carbon Freon Molecules

    NASA Astrophysics Data System (ADS)

    Pal, Satyendra; Kumar, Neeraj

    2015-09-01

    Single carbon Freon molecules or chlorofluorocarbons (CFCs) are important industrial material with wide-ranging applications as refrigerant, aerosol propellant and semiconductor etchant, etc. The large-scale industrial consumption is of particular environmental concern because of its potential for ozone destruction in the stratosphere. In the present work, we have extended and generalized the modified Jain-Khare (JK) semi-empirical formalism for the evaluation of the total ionization cross sections corresponding to the formation of the cations in the electron impact ionization of molecules to the electron impact ionization of single carbon freon molecules, viz. CFCl3, CF2Cl2 and CF3Cl. The integral partial and the total ionization cross sections as function of incident electron energy are evaluated in the energy range varying from ionization threshold to 1000 eV. In absence of available differential cross sections, the corresponding derived partial and total ionization cross sections revealed a reasonably good agreement with the experimental and theoretical data, wherever available. In addition to the differential and integral ionization cross sections, we have also calculated the ionization rate coefficients using the evaluated partial ionization cross sections and the Maxwell-Boltzmann distribution as a function of electron temperature/energy. The work is supported by DST, New Delhi, India.

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

    PubMed

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

    2017-07-28

    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 (<100 mGy) and oxidative 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.

  12. First observations of enhanced low dose rate sensitivity (ELDRS) in space: One part of the MPTB experiment

    SciTech Connect

    Titus, J.L.; Combs, W.E.; Turflinger, T.L.; Krieg, J.F.; Tausch, H.J.; Brown, D.B.; Campbell, A.B.; Pease, R.L.

    1998-12-01

    Bipolar devices, most notably circuits fabricated with lateral PNP transistors (LPNP) and substrate PNP transistors (SPNP), have been observed to exhibit an enhanced low dose rate sensitivity when exposed to ionizing radiation. These dose rate sensitive bipolar devices exhibited enhanced degradation of base current in transistors and of input bias current, offset current, and/or offset voltage in linear circuits at dose rates greater than 1 rd(Si)/s. The total dose responses of several bipolar transistors and linear circuits in a space environment are demonstrated to exhibit enhanced degradation comparable, in magnitude, to ground-based data irradiated at a dose rate of 10 mrd(Si)/s indicating that enhanced low dose rate sensitivities (ELDRS) do indeed exist in space.

  13. Impact of Drug Therapy, Radiation Dose, and Dose Rate on Renal Toxicity Following Bone Marrow Transplantation

    SciTech Connect

    Cheng, Jonathan C.; Schultheiss, Timothy E. Wong, Jeffrey Y.C.

    2008-08-01

    Purpose: To demonstrate a radiation dose response and to determine the dosimetric and chemotherapeutic factors that influence the incidence of late renal toxicity following total body irradiation (TBI). Methods and Materials: A comprehensive retrospective review was performed of articles reporting late renal toxicity, along with renal dose, fractionation, dose rate, chemotherapy regimens, and potential nephrotoxic agents. In the final analysis, 12 articles (n = 1,108 patients), consisting of 24 distinct TBI/chemotherapy conditioning regimens were included. Regimens were divided into three subgroups: adults (age {>=}18 years), children (age <18 years), and mixed population (both adults and children). Multivariate logistic regression was performed to identify dosimetric and chemotherapeutic factors significantly associated with late renal complications. Results: Individual analysis was performed on each population subgroup. For the purely adult population, the only significant variable was total dose. For the mixed population, the significant variables included total dose, dose rate, and the use of fludarabine. For the pediatric population, only the use of cyclosporin or teniposide was significant; no dose response was noted. A logistic model was generated with the exclusion of the pediatric population because of its lack of dose response. This model yielded the following significant variables: total dose, dose rate, and number of fractions. Conclusion: A dose response for renal damage after TBI was identified. Fractionation and low dose rates are factors to consider when delivering TBI to patients undergoing bone marrow transplantation. Drug therapy also has a major impact on kidney function and can modify the dose-response function.

  14. Effect of a finite ionization rate on the radiative heating of outer planet atmospheric entry probes

    NASA Technical Reports Server (NTRS)

    Nelson, H. F.

    1981-01-01

    The influence of finite rate ionization in the inviscid gas just behind the stagnation shock wave on the radiation heating of probes entering the hydrogen helium atmospere of the major planets was investigated. At the present time, there is disagreement as to whether the radiative flux increases or decreases relative to its equilibrium value when finite rate ionization is considered. Leibowitz and Kuo content that the finite rate ionization in the hydrogen gas just behind the shock wave reduces the radiative flux to the probe, whereas Tiwari and Szema predict that it increases the radiative flux. The radiation modeling used in the calculations of both pairs of these investigators was reviewed. It is concluded that finite rate ionization in the inviscid region of the shock layer should reduce the cold wall radiative heating below the values predicted by equilibrium chemistry assumptions.

  15. Electron impact ionization rates for interstellar neutral H and He atoms near interplanetary shocks: Ulysses observations

    NASA Technical Reports Server (NTRS)

    Feldman, W. C.; Phillips, J. L.; Gosling, J. T.; Isenberg, P. A.

    1995-01-01

    During average solar wind flow conditions at 1 AU, ionization rates of interstellar neutrals that penetrate into the inner heliosphere are dominated by charge exchange with solar wind protons for H atoms, and by photoionization for He atoms. During occurrences of strong, coronal mass ejection (CME)-driven interplanetary shock waves near 1 AU, electron impact ionization can make substantial, if not dominating, contributions to interstellar neutral ionization rates in the regions downstream of the shocks. However, electron impact ionization is expected to be relatively less important with increasing heliocentric distance because of the decrease in electron temperature. Ulysses encountered many CME-driven shocks during its journey to and beyond Jupiter, and in addition, encountered a number of strong corotating interaction region (CIR) shocks. These shocks generally occur only beyond approximately 2 AU. Many of the CIR shocks were very strong rivalling the Earth's bow shock in electron heating. We have compared electron impact ionization rates calculated from electron velocity distributions measured downstream from CIR shocks using the Ulysses SWOOPS experiment to charge-exchange rates calculated from measured proton number fluxes and the photoionization rate estimated from an assumed solar photon spectrum typical of solar maximum conditions. We find that, although normally the ratio of electron-impact ionization rates to charge-exchange (for H) and to photoionization (for He) rates amounts to only about one and a few tens of percent, respectively, downstream of some of the stronger CIR shocks they amount to more than 10% and greater than 100%, respectively.

  16. Effect of a finite ionization rate on the radiative heating of outer planet atmospheric entry probes

    NASA Technical Reports Server (NTRS)

    Nelson, H. F.

    1982-01-01

    The influence of finite rate ionization in the inviscid gas just behind the stagnation shock wave on the radiative heating of probes entering the hydrogen-helium atmosphere of the major plants was investigated. Two opposing conclusions were reached as to how the ionization rate assumption affects the radiative transfer. Hydrogen-helium shock waves with a cold nonblowing wall boundary condition at the probe heat shield are emphasized. The study is limited to the stagnation shock layer.

  17. Estimation of Weapon Yield From Inversion of Dose Rate Contours

    DTIC Science & Technology

    2009-03-01

    Zucchini .................................................................................... 76 Operation PLUMBBOB—Priscilla...Appendix E: ESS FOM ....................................................................................................112 Appendix F: Zucchini FOM...Relationship of Dose Rate Contour Area, Weather Grid, and AOI ............... 57 23. Zucchini FDC, DNA-EX, and HPAC Dose Rate Contours at 28KT

  18. Low doses ionizing radiation enhances the invasiveness of breast cancer cells by inducing epithelial-mesenchymal transition

    SciTech Connect

    Zhang, Xin; Li, Xiaoyan; Zhang, Ning; Yang, Qifeng; Moran, Meena S.

    2011-08-19

    Highlights: {yields} Low doses ionizing irradiation would enhance the invasiveness of breast cancer cells by inducing EMT. {yields} Low doses ionizing radiation induced morphologic changes in breast cancer cells. {yields} Low doses ionizing radiation led to upregulation of mesenchymal markers and down-regulation of epithelial markers. {yields} Low doses ionizing radiation increased migration and invasion of breast cancer cells. -- Abstract: Epithelial-mesenchymal transition (EMT) is a process cellular morphologic and molecular alterations facilitate cell invasion. We hypothesized that low dose ionizing irradiation (LDIR) enhances the invasiveness of breast cancer cells by inducing EMT. The effects of LDIR on cellular morphology and the EMT markers of MCF-7 breast cancer cells were analyzed by western blot/RT-PCR and migration/invasion was examined using the transwell assay. We found that LDIR led to the phenotypic changes of EMT in MCF-7 cells and down-regulation of epithelial differentiation markers and transcriptional induction of mesenchymal markers. Furthermore, the radiated cells demonstrated enhanced migration/invasion MCF-7 cells compared with non-radiated cells. In summary, LDIR promotes the invasiveness of breast cancer cells through epithelial to mesenchymal transition. These findings may ultimately provide a new targeted approach for improving the therapeutic effectiveness of radiation in breast cancer.

  19. Observed rate of ionization in shaped-charge releases of barium in the ionosphere

    NASA Technical Reports Server (NTRS)

    Hallinan, Thomas J.

    1988-01-01

    Data from 36 Ba shaped-charge releases carried out at an angle of less than 25 deg to the magnetic field, by the technique of Wescott et al. (1972) and Michel (1974), were examined for evidence of a sustained rate of ionization in excess of that attributable to sunlight. In four of the experiments, the time constant for the decay of the neutrals was measured using an ultrasensitive color TV camera and was found to have a value of about 30 sec, consistent with slow (solar) ionization. Although the qualitative appearance of most jets was found to be consistent with a slow process of ionization, some releases produced a thin confined jet that was suggestive of rapid ionization. Two of these jets were analyzed in detail, but no evidence of anomalous ionization was produced. The data obtained in this work agree with the geometrical predictions of the Swift model.

  20. Review and meta-analysis of epidemiological associations between low/moderate doses of ionizing radiation and circulatory disease risks, and their possible mechanisms.

    PubMed

    Little, M P; Tawn, E J; Tzoulaki, I; Wakeford, R; Hildebrandt, G; Paris, F; Tapio, S; Elliott, P

    2010-05-01

    Although the link between high doses of ionizing radiation and damage to the heart and coronary arteries has been well established for some time, the association between lower-dose exposures and late occurring cardiovascular disease has only recently begun to emerge, and is still controversial. In this paper, we extend an earlier systematic review by Little et al. on the epidemiological evidence for associations between low and moderate doses of ionizing radiation exposure and late occurring blood circulatory system disease. Excess relative risks per unit dose in epidemiological studies vary over at least two orders of magnitude, possibly a result of confounding and effect modification by well-known (but unobserved) risk factors, and there is statistically significant (p < 0.00001) heterogeneity between the risks. This heterogeneity is reduced, but remains significant, if adjustments are made for the effects of fractionated delivery or if there is stratification by endpoint (cardiovascular disease vs. stroke, morbidity vs. mortality). One possible biological mechanism is damage to endothelial cells and subsequent induction of an inflammatory response, although it seems unlikely that this would extend to low-dose and low-dose-rate exposure. A recent paper of Little et al. proposed an arguably more plausible mechanism for fractionated low-dose effects, based on monocyte cell killing in the intima. Although the predictions of the model are consistent with the epidemiological data, the experimental predictions made have yet to be tested. Further epidemiological and biological evidence will allow a firmer conclusion to be drawn.

  1. Effects of orientation of substrate on the enhanced low-dose-rate sensitivity (ELDRS) in NPN transistors

    NASA Astrophysics Data System (ADS)

    Lu, Wu; Zheng, Yu-Zhan; Wang, Yi-Yuan; Ren, Di-Yuan; Guo, Qi; Wang, Zhi-Kuan; Wang, Jian-An

    2011-02-01

    The radiation effects and annealing characteristics of two types of domestic NPN bipolar junction transistors, fabricated with different orientations, were investigated under different dose-rate irradiation. The experimental results show that both types of the NPN transistors exhibit remarkable Enhanced Low-Dose-Rate Sensitivity (ELDRS). After irradiation at high or low dose rate, the excess base current of NPN transistors obviously increased, and the current gain would degrade rapidly. Moreover, the decrease of collector current was also observed. The NPN transistor with <111> orientation was more sensitive to ionizing radiation than that with <100> orientation. The underlying mechanisms of various experimental phenomena are discussed in detail in this paper.

  2. Absorbed dose thresholds and absorbed dose rate limitations for studies of electron radiation effects on polyetherimides

    NASA Technical Reports Server (NTRS)

    Long, Edward R., Jr.; Long, Sheila Ann T.; Gray, Stephanie L.; Collins, William D.

    1989-01-01

    The threshold values of total absorbed dose for causing changes in tensile properties of a polyetherimide film and the limitations of the absorbed dose rate for accelerated-exposure evaluation of the effects of electron radiation in geosynchronous orbit were studied. Total absorbed doses from 1 kGy to 100 MGy and absorbed dose rates from 0.01 MGy/hr to 100 MGy/hr were investigated, where 1 Gy equals 100 rads. Total doses less than 2.5 MGy did not significantly change the tensile properties of the film whereas doses higher than 2.5 MGy significantly reduced elongation-to-failure. There was no measurable effect of the dose rate on the tensile properties for accelerated electron exposures.

  3. GAMMA DOSE RATE NEAR A NEW (252)Cf BRACHYTHERAPY SOURCE

    SciTech Connect

    Fortune, Eugene C; Gauld, Ian C; Wang, C

    2011-01-01

    A new generation of medical grade (252)Cf sources was developed in 2002 at the Oak Ridge National Laboratory. The combination of small size and large activity of (252)Cf makes the new source suitable to be used with the conventional high-dose-rate remote afterloading system for interstitial brachytherapy. A recent in-water calibration experiment showed that the measured gamma dose rates near the new source are slightly greater than the neutron dose rates, contradicting the well established neutron-to-gamma dose ratio of approximately 2:1 at locations near a (252)Cf brachytherapy source. Specifically, the MCNP-predicted gamma dose rate is a factor of two lower than the measured gamma dose rate at the distance of I cm, and the differences between the two results gradually diminish at distances farther away from the source. To resolve this discrepancy, we updated the source gamma spectrum by including in the ORIGEN-S data library the experimentally measured (252)Cf prompt gamma spectrum as well as the true (252)Cf spontaneous fission yield data to explicitly model delayed gamma emissions from fission products. We also investigated the bremsstrahlung X-rays produced by the beta particles emitted from fission product decays. The results show that the discrepancy of gamma dose rates is mainly caused by the omission of the bremsstrahlung X-rays in the MCNP runs. By including the bremsstrahlung X-rays, the MCNP results show that the gamma dose rates near a new (252)Cf source agree well with the measured results and that the gamma dose rates are indeed greater than the neutron dose rates.

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

    SciTech Connect

    Not Available

    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.

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

    PubMed

    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 (Ḋm ) ranging from 0.07 to 3000 Gy/s and a dose-rate in pulse (Ḋp ) 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. Ḋm dependence was studied at the clinical linac by changing the pulse repetition frequency (f) of the beam in order to vary Ḋm between 0.55 and 4.40 Gy/min, while Ḋp dependence was probed at the prototype machine for Ḋp ranging from 7 × 10(3) to 8 × 10(6) Gy/s. Ḋp 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 Ḋm dependence was found either. In addition, we obtained excellent consistency between films and TLDs over the entire Ḋp range

  6. Activation of the Fanconi anemia/BRCA pathway at low doses of ionization radiation.

    PubMed

    Bosch, Pau Castillo; Bogliolo, Massimo; Surrallés, Jordi

    2015-11-01

    Fanconi anemia (FA) is a rare, clinically heterogeneous autosomal recessive or X-linked genetic disease characterized by chromosome fragility, congenital malformations and cancer susceptibility. FA patients are usually radiosensitive when exposed to radiotherapy but the role of the FA in response to ionizing radiation (IR) is controversial. Here we have investigated IR-induced activation of the FA pathway by systematically analyzing monoubiquitination of the central protein FANCD2 and subsequent recruitment to stalled replication forks in primary fibroblasts. We developed an immunolabelling method to simultaneously visualize IR-induced FANCD2 and γH2AX foci in S-phase. We observed FANCD2 foci formation in a subset of IR-induced γH2AX foci in S-phase cells. This was observed at doses of IR ranging from 0.1 to 5.0Gy in a dose dependent non-threshold fashion. Our results indicate that minimum doses of IR can produce replication fork stalling and FA pathway activation during S-phase in primary cells.

  7. Strategy for stochastic dose-rate induced enhanced elimination of malignant tumour without dose escalation.

    PubMed

    Paul, Subhadip; Roy, Prasun Kumar

    2016-09-01

    The efficacy of radiation therapy, a primary modality of cancer treatment, depends in general upon the total radiation dose administered to the tumour during the course of therapy. Nevertheless, the delivered radiation also irradiates normal tissues and dose escalation procedure often increases the elimination of normal tissue as well. In this article, we have developed theoretical frameworks under the premise of linear-quadratic-linear (LQL) model using stochastic differential equation and Jensen's inequality for exploring the possibility of attending to the two therapeutic performance objectives in contraposition-increasing the elimination of prostate tumour cells and enhancing the relative sparing of normal tissue in fractionated radiation therapy, within a prescribed limit of total radiation dose. Our study predicts that stochastic temporal modulation in radiation dose-rate appreciably enhances prostate tumour cell elimination, without needing dose escalation in radiation therapy. However, constant higher dose-rate can also enhance the elimination of tumour cells. In this context, we have shown that the sparing of normal tissue with stochastic dose-rate is considerably more than the sparing of normal tissue with the equivalent constant higher dose-rate. Further, by contrasting the stochastic dose-rate effects under LQL and linear-quadratic (LQ) models, we have also shown that the LQ model over-estimates stochastic dose-rate effect in tumour and under-estimates the stochastic dose-rate effect in normal tissue. Our study indicates the possibility of utilizing stochastic modulation of radiation dose-rate for designing enhanced radiation therapy protocol for cancer.

  8. Role of AKT and ERK pathways in controlling sensitivity to ionizing radiation and adaptive response induced by low-dose radiation in human immune cells.

    PubMed

    Park, Hyung Sun; You, Ga Eun; Yang, Kwang Hee; Kim, Ji Young; An, Sungkwan; Song, Jie-Young; Lee, Su-Jae; Lim, Young-Khi; Nam, Seon Young

    2015-12-01

    Despite many studies of the effect of ionizing radiation, biological mechanisms of action might differ greatly depend on dose, dose rate, and cell type. This study was performed to explore the effects of low- and high-dose radiation in human immune cell lines. We examined cell sensitivity after irradiation with 0.05, 0.1, or 2Gy in two normal cell lines and three tumor cell lines. Low-dose radiation of 0.05 and 0.1Gy had no effect on cell survival in any tested cell line, with the exception of IM-9 cells, whose viability was transiently increased. However, IM-9 and C1R-sB7 cells were very sensitive to high-dose radiation-induced cell death, whereas Jurkat and JM1 cells showed moderate sensitivity, and THP-1 cells were completely resistant. This radiosensitivity was correlated with basal AKT activation, which is induced by phosphorylation. In radiosensitive IM-9 cells, priming with chronic low-dose irradiation blocked cell death induced by high-dose radiation challenge via inhibition of caspase activation and PARP cleavage. AKT phosphorylation was not altered in IM-9 cells, but ERK phosphorylation was greatly elevated immediately after chronic low-dose irradiation. Taken together, our results suggest that the different responses of normal and tumor cells to low-dose and high-dose radiation depend on AKT activation, which is regulated by protein phosphatase 2 (PP2A). In radiosensitive normal cells lacking basal AKT activity, chronic low-dose radiation increases activation of the ERK pathway, which plays an important role in the adaptive response to radiation, providing a very important insight into understanding the effects of ionizing radiation on health. Copyright © 2015 Elsevier GmbH. All rights reserved.

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

    PubMed

    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.

  10. Genetic background modulates lncRNA-coordinated tissue response to low dose ionizing radiation

    DOE PAGES

    Tang, Jonathan; Huang, Yurong; Nguyen, David H.; ...

    2015-02-04

    Long noncoding RNAs (lncRNAs) are emerging as key regulators of diverse cell functions and processes. However, the relevance of lncRNAs in the cell and tissue response to ionizing radiation has not yet been characterized. Here we used microarray profiling to determine lncRNA and mRNA expression in mammary glands of BALB/c and SPRET/EiJ mice after low-dose ionizing radiation (LDIR) exposure. We found that unirradiated mammary tissues of these strains differed significantly in baseline expressions of 290 lncRNAs. LDIR exposure (10 cGy) induced a significant change in the expression of many lncRNAs. The vast majority of lncRNAs identified to be differentially expressed aftermore » LDIR in either BALB/c or SPRET/EiJ had a significantly correlated expression pattern with at least one LDIR responsive mRNA. Functional analysis revealed that the response to LDIR in BALB/c mice is highly dynamic with enrichment for genes involved in tissue injury, inflammatory responses, and mammary gland development at 2, 4, and 8 weeks after LDIR, respectively. Our study demonstrates that genetic background strongly influences the expression of lncRNAs and their response to radiation and that lncRNAs may coordinate the tissue response to LDIR exposure via regulation of coding mRNAs.« less

  11. Genetic Background Modulates lncRNA-Coordinated Tissue Response to Low Dose Ionizing Radiation

    PubMed Central

    Tang, Jonathan; Huang, Yurong; Nguyen, David H.; Costes, Sylvain V.; Snijders, Antoine M.; Mao, Jian-Hua

    2015-01-01

    Long noncoding RNAs (lncRNAs) are emerging as key regulators of diverse cell functions and processes. However, the relevance of lncRNAs in the cell and tissue response to ionizing radiation has not yet been characterized. Here we used microarray profiling to determine lncRNA and mRNA expression in mammary glands of BALB/c and SPRET/EiJ mice after low-dose ionizing radiation (LDIR) exposure. We found that unirradiated mammary tissues of these strains differed significantly in baseline expressions of 290 lncRNAs. LDIR exposure (10 cGy) induced a significant change in the expression of many lncRNAs. The vast majority of lncRNAs identified to be differentially expressed after LDIR in either BALB/c or SPRET/EiJ had a significantly correlated expression pattern with at least one LDIR responsive mRNA. Functional analysis revealed that the response to LDIR in BALB/c mice is highly dynamic with enrichment for genes involved in tissue injury, inflammatory responses, and mammary gland development at 2, 4, and 8 weeks after LDIR, respectively. Our study demonstrates that genetic background strongly influences the expression of lncRNAs and their response to radiation and that lncRNAs may coordinate the tissue response to LDIR exposure via regulation of coding mRNAs. PMID:25802832

  12. Quantitative Proteomic Profiling of Low-Dose Ionizing Radiation Effects in a Human Skin Model

    PubMed Central

    Hengel, Shawna M.; Aldrich, Joshua T.; Waters, Katrina M.; Pasa-Tolic, Ljiljana; Stenoien, David L.

    2014-01-01

    To assess responses to low-dose ionizing radiation (LD-IR) exposures potentially encountered during medical diagnostic procedures, nuclear accidents or terrorist acts, a quantitative proteomic approach was used to identify changes in protein abundance in a reconstituted human skin tissue model treated with 0.1 Gy of ionizing radiation. To improve the dynamic range of the assay, subcellular fractionation was employed to remove highly abundant structural proteins and to provide insight into radiation-induced alterations in protein localization. Relative peptide quantification across cellular fractions, control and irradiated samples was performing using 8-plex iTRAQ labeling followed by online two-dimensional nano-scale liquid chromatography and high resolution MS/MS analysis. A total of 107 proteins were detected with statistically significant radiation-induced change in abundance (>1.5 fold) and/or subcellular localization compared to controls. The top biological pathways identified using bioinformatics include organ development, anatomical structure formation and the regulation of actin cytoskeleton. From the proteomic data, a change in proteolytic processing and subcellular localization of the skin barrier protein, filaggrin, was identified, and the results were confirmed by western blotting. This data indicate post-transcriptional regulation of protein abundance, localization and proteolytic processing playing an important role in regulating radiation response in human tissues. PMID:28250387

  13. Total Ionizing Dose Test Report BFR92A NPN 5 GHz Wide Band Transistor from NXP

    NASA Technical Reports Server (NTRS)

    Phan, Anthony M.; Oldham, Timothy R.

    2011-01-01

    The purpose of this test was to characterize the Philips/NXP BFR92A NPN 5 gigahertz wide band silicon transistor for total dose response. This test shall serves as the radiation lot acceptance test (RLAT) for the lot date code (LDC) 1027. The BFR92A is packaged in a 3-pin plastic SOT23 package. Low dose rate (LDR/ELDRS) irradiations was performed.

  14. Total Ionizing Dose Effects on Strained Ge pMOS FinFETs on Bulk Si

    DOE PAGES

    Zhang, En Xia; Fleetwood, Daniel M.; Hachtel, Jordan A.; ...

    2016-12-02

    In this paper, we have characterized the total ionizing dose response of strained Ge p MOS FinFETs built on bulk Si using a fin replacement process. Devices irradiated to 1.0 Mrad(SiO2) show minimal transconductance degradation (less than 5%), very small Vth shifts (less than 40 mV in magnitude) and very little ON/OFF current ratio degradation (<5%), and only modest variation in radiation response with transistor geometry (typically less than normal part-to-part variation). Both before and after irradiation, the performance of these strained Ge p MOS FinFETs is far superior to that of past generations of planar Ge p MOS devices.more » Finally, these improved properties result from significant improvements in processing technology, as well as the enhanced gate control provided by the strained Ge FinFET technology.« less

  15. Effects of low doses of ionizing radiation upon the micromorphology and functional state of cell surface

    SciTech Connect

    Somosy, Z.; Kubasova, T.; Koeteles, G.J.

    1987-09-01

    The cellular membrane as one of the targets of ionizing radiation might play an important role in the development and modification of radiation-induced alterations after low doses. The present paper reviews the micromorphological and functional changes of plasma membranes of irradiated blood and cultured cells with special emphasis on the surface conditions: lectin binding, negative surface charges. The review is completed by our own studies on distribution of positive surface charges and the bindings of two lectins, the Concanavalin A and the wheat germ agglutinin. It was found that the decrease of negative surface charges is unconcomitant with appearance of domains exposing positive ones, particularly on the surfaces of rufflings. The distribution of Concanavalin A binding sites turned from a uniform distribution to a polarized one, especially on apical regions where it appeared in large aggregates. The polarity in localization of wheat germ agglutinin on untreated fibroblasts observed in our experiments ceased shortly after irradiation. 72 references.

  16. Total Ionizing Dose Effects on Strained Ge pMOS FinFETs on Bulk Si

    SciTech Connect

    Zhang, En Xia; Fleetwood, Daniel M.; Hachtel, Jordan A.; Oak Ridge National Lab. , Oak Ridge, TN ; Liang, Chundong; Reed, Robert A.; Alles, Michael L.; Schrimpf, Ronald D.; Linten, Dimitri; Mitard, Jerome; Chisholm, Matthew F.; Pantelides, Sokrates T.; Oak Ridge National Lab. , Oak Ridge, TN

    2016-12-02

    In this paper, we have characterized the total ionizing dose response of strained Ge p MOS FinFETs built on bulk Si using a fin replacement process. Devices irradiated to 1.0 Mrad(SiO2) show minimal transconductance degradation (less than 5%), very small Vth shifts (less than 40 mV in magnitude) and very little ON/OFF current ratio degradation (<5%), and only modest variation in radiation response with transistor geometry (typically less than normal part-to-part variation). Both before and after irradiation, the performance of these strained Ge p MOS FinFETs is far superior to that of past generations of planar Ge p MOS devices. Finally, these improved properties result from significant improvements in processing technology, as well as the enhanced gate control provided by the strained Ge FinFET technology.

  17. Total Ionizing Dose Response of Multiple-Gate Nanowire Field Effect Transistors

    NASA Astrophysics Data System (ADS)

    Gaillardin, M.; Marcandella, C.; Martinez, M.; Duhamel, O.; Lagutere, T.; Paillet, P.; Raine, M.; Richard, N.; Andrieu, F.; Barraud, S.; Vinet, M.

    2017-08-01

    This paper investigates the total ionizing dose (TID) response of nanoscaled field-effect transistors (FET) made of silicon multiple-gate nanowire (NW). The NWFET architecture relies on its remarkable electrostatic properties to push “silicon”-based technologies much deeper into device scaling than present FinFETs. However, as commonly observed when a new device or technology concept is proposed, such as shallow trench isolation and silicon-on-insulator or FinFET, TID effects reveal unexpected behaviors that can permanently modify pristine device electrical characteristics. This is why this paper discusses the impact of several parameters including the NWFET design and the transistor's type to get thorough insights into the NWFET TID behavior.

  18. Characterization of total ionizing dose damage in COTS pinned photodiode CMOS image sensors

    SciTech Connect

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

    2016-03-15

    The characterization of total ionizing dose (TID) damage in COTS pinned photodiode (PPD) CMOS image sensors (CISs) is investigated. The radiation experiments are carried out at a {sup 60}Co γ-ray source. The CISs are produced by 0.18-μm CMOS technology and the pixel architecture is 8T global shutter pixel with correlated double sampling (CDS) based on a 4T PPD front end. The parameters of CISs such as temporal domain, spatial domain, and spectral domain are measured at the CIS test system as the EMVA 1288 standard before and after irradiation. The dark current, random noise, dark signal non-uniformity (DSNU), photo response non-uniformity (PRNU), overall system gain, saturation output, dynamic range (DR), signal to noise ratio (SNR), quantum efficiency (QE), and responsivity versus the TID are reported. The behaviors of the tested CISs show remarkable degradations after radiation. The degradation mechanisms of CISs induced by TID damage are also analyzed.

  19. Measurements of neutron dose rates with a balloon in Japan.

    PubMed

    Nagaoka, K; Hiraide, I; Sato, K; Yamagami, T; Nakamura, T; Yabutani, T

    2007-01-01

    Measurements of cosmic-ray neutron dose rates with a balloon in Sanriku, Japan (geographic location: 39 degrees N, 142 degrees E; corresponding geomagnetic latitude: 30 degrees N) were conducted at an altitude from 0.2 to 25 km on 25-26 August 2004 when solar activity was at an average level. Neutron dose rates given as ambient dose equivalent rates (H(10)) were measured with high-sensitive neutron dose equivalent counters and electronic silicon personal dosimeters (EPDs). The neutron dose rates increased with increasing altitude, but they were saturated around 15-20 km and decreased with increasing altitude beyond 20 km. The neutron ambient dose equivalent rate was 1.5 microSv/h(- 1) at 20 km. Measured values were corrected for the deviation of the energy response of the dose equivalent counter from the fluence-to-ambient dose equivalent conversion coefficient, and the corrected values were very close to the calculated values with EPCARD. On the other hand, neutron measurements by the EPDs gave about 10 times overestimation because of the high sensitivity to cosmic-ray protons.

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

    SciTech Connect

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

    2009-10-01

    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{sup +} {sub 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{sup +} chemistry reveals that only a small fraction of He{sup +} 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 zeta{sub He} < 1.2 x 10{sup -15} s{sup -1}, an upper limit about 5 times larger than the ionization rate previously inferred for this sight line using H{sup +} {sub 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{sup +} {sub 3} in diffuse molecular clouds, and, perhaps more importantly, allow the first direct measurements of the ionization rate in diffuse atomic clouds.

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

    SciTech Connect

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

    1999-05-24

    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.

  2. Dose integration and dose rate characteristics of a NiPAM polymer gel MRI dosimeter system

    NASA Astrophysics Data System (ADS)

    Waldenberg, C.; Karlsson Hauer, A.; Gustafsson, C.; Ceberg, S.

    2017-05-01

    The normoxic polymer gel dosimeter based on N-isopropyl acrylamide (NiPAM) is a promising full 3D-dosimeter with high spatial resolution and near tissue equivalency. NiPAM gel samples were irradiated to different doses using a linear accelerator. The absorbed dose was evaluated using MRI and statistical significance of the analysed data was calculated. The analysis was carried out using an in-house developed software. It was found that the gel dosimeter responded linearly to the absorbed dose. The gel exhibited a dose rate dependence, as well as a dependence on the sequential beam irradiation scheme. A higher dose rate, as well as a higher dose per sequential beam, resulted in a lower dose response.

  3. High dose rate brachytherapy source measurement intercomparison.

    PubMed

    Poder, Joel; Smith, Ryan L; Shelton, Nikki; Whitaker, May; Butler, Duncan; Haworth, Annette

    2017-06-01

    This work presents a comparison of air kerma rate (AKR) measurements performed by multiple radiotherapy centres for a single HDR (192)Ir source. Two separate groups (consisting of 15 centres) performed AKR measurements at one of two host centres in Australia. Each group travelled to one of the host centres and measured the AKR of a single (192)Ir source using their own equipment and local protocols. Results were compared to the (192)Ir source calibration certificate provided by the manufacturer by means of a ratio of measured to certified AKR. The comparisons showed remarkably consistent results with the maximum deviation in measurement from the decay-corrected source certificate value being 1.1%. The maximum percentage difference between any two measurements was less than 2%. The comparisons demonstrated the consistency of well-chambers used for (192)Ir AKR measurements in Australia, despite the lack of a local calibration service, and served as a valuable focal point for the exchange of ideas and dosimetry methods.

  4. Comparative dosimetry of GammaMed Plus high-dose rate 192Ir brachytherapy source

    PubMed Central

    Patel, N. P.; Majumdar, B.; Vijayan, V.

    2010-01-01

    The comparative dosimetry of GammaMed (GM) Plus high-dose rate brachytherapy source was performed by an experiment using 0.1-cc thimble ionization chamber and simulation-based study using EGSnrc code. In-water dose measurements were performed with 0.1-cc chamber to derive the radial dose function (r = 0.8 to 20.0 cm) and anisotropy function (r = 5.0 cm with polar angle from 10° to 170°). The nonuniformity correction factor for 0.1-cc chamber was applied for in-water measurements at shorter distances from the source. The EGSnrc code was used to derive the dose rate constant (Λ), radial dose function gL(r) and anisotropy function F(r, θ) of GM Plus source. The dosimetric data derived using EGSnrc code in our study were in very good agreement relative to published data for GM Plus source. The radial dose function up to 12 cm derived from measured dose using 0.1-cc chamber was in agreement within ±3% of data derived by the simulation study. PMID:20927220

  5. Cytogenetic monitoring by use of the micronucleus assay among hospital workers exposed to low doses of ionizing radiation.

    PubMed

    Sari-Minodier, I; Orsière, T; Auquier, P; Martin, F; Botta, A

    2007-05-18

    The aim of this study was to assess occupationally induced chromosomal damage in a large population of hospital workers exposed to low doses of ionizing radiation. We used the cytokinesis-block micronucleus (CBMN) assay in the peripheral lymphocytes of 132 exposed workers compared with 69 controls matched for gender, age and smoking habits. The CBMN assay was combined with fluorescence in situ hybridization with a human pan-centromeric DNA probe in 32 exposed subjects and 30 controls randomly chosen from the initial populations. Occupational dosimetry records were collected over the last 10-year period and revealed very low exposure levels. The average binucleated micronucleated cell rate (BMCR) was significantly higher in the exposed subjects than in the controls (14.9 per thousand+/-8.1 versus 11.8 per thousand+/-6.5; P=0.011). About one-third of the micronuclei were centromere-negative in the exposed and control groups. BMCR significantly positively correlated with donor age in the exposed population; this correlation was at the border of significance in the control group. In the two groups, BMCR was significantly greater in females than in males, and the significant correlation between age and BMCR was observed in the female population, but not in the male one. No effect of smoking habits emerged. Univariate analysis revealed a possible influence of familial cancer history and diagnostic medical radiation dose (estimated from examinations reported in the questionnaire) on BMCR. Multiple regression analysis, taking into account all the previous confounding factors, showed that only occupational exposure status, gender and age had a significant effect on BMCR. In conclusion, the present study shows that chromosomal damage leading to micronucleated lymphocytes is more frequent in hospital workers exposed to ionizing radiation than in controls, despite the very low levels of exposure.

  6. Measurement for the dose-rates of the cosmic-ray components on the ground.

    PubMed

    Rasolonjatovo, Danielle A H; Suzuki, Hiroyuki; Hirabayashi, Naoya; Nunomiya, Tomoya; Nakamura, Takashi; Nakao, Noriaki

    2002-12-01

    In this study, we aimed to measure the directly ionizing component (muons and photons) and the indirectly ionizing component (neutrons) of the cosmic-ray spectra and evaluate their dose rate contribution to the total dose rate on a ground level in Japan. Measurements were carried out in Tohoku University, Japan, from October 2000. The pulse-height spectra of the cosmic-ray photons and muons were measured with a 12.7 cm diameter and 12.7 cm long NaI(Tl) scintillation detector. In order to measure energy spectra of cosmic-ray photons and muons, response functions of the detector to photons and muons were determined by the Monte Carlo simulation codes. The cosmic-ray photon dose was evaluated directly from the measured pulse-height spectrum by using the spectrum weight function, and the cosmic-ray muon dose was evaluated by converting the measured pulse height spectrum into deposited energy within the detector. The quantity of the cosmic-ray electrons is estimated to be very small and is not taken into account in this study. The cosmic-ray neutron spectrum and the neutron dose were measured by using a multi-moderator spectrometer (Bonner ball) and a rem counter. The measurements could finally give the annual absorbed dose in tissue of the cosmic-ray muons of 315 microSv/y and annual ambient doses of the cosmic-ray photons and neutrons on the ground in Japan of 55 microSv/y and 31 microSv/y, respectively.

  7. Effects of fractionated doses of ionizing radiation on small intestinal motor activity

    SciTech Connect

    Otterson, M.F.; Sarna, S.K.; Moulder, J.E.

    1988-11-01

    The small intestinal motor effects of fractionated doses of ionizing radiation were studied in 6 conscious dogs. Eight strain-gauge transducers were implanted on the small intestine and a single gauge on the ascending colon, of each dog. After control recordings, an abdominal dose of 250 cGy was administered three times a week on alternate days for 3 successive weeks (total dose, 2250 cGy). Recordings were then made for 4 wk of follow-up. Giant migrating contractions occurred 11 times in 520 h of control recordings in the fasted and fed state, with a mean distance of origin of 55 +/- 16 cm from the ileocolonic junction. Abdominal field irradiation significantly increased the incidence and distance of origin of these giant contractions to 438 in 745 recording hours and 158 +/- 7 cm from the ileocolonic junction, respectively. The incidence of giant migrating contractions peaked after the second dose of radiation. The amplitude ratio of radiation-induced giant migrating contractions to phase III contractions, and their duration and velocity of migration, were similar to the control state. The dogs developed diarrhea and vomiting as early as the first fraction of radiation. Irradiation also increased the incidence of retrograde giant contractions from 8 in 520 h of control recording to 42 in 745 h of recording during the radiation schedule. The radiation-induced retrograde giant contractions peaked in incidence on the day of the first fraction of radiation and were more likely to be associated with a vomiting episode than those occurring in the control period. Migrating motor complex cycling persisted during radiation and its cycle length was not different from the control or postradiation values.

  8. Dose-Rate Dependence of High-Dose Health Effects in Humans from Photon Radiation with Application to Radiological Terrorism

    SciTech Connect

    Strom, Daniel J.

    2005-01-14

    In 1981, as part of a symposium entitled ''The Control of Exposure of the Public to Ionizing Radiation in the Event of Accident or Attack,'' Lushbaugh, H?bner, and Fry published a paper examining ''radiation tolerance'' of various human health endpoints as a function of dose rate. This paper may not have received the notice it warrants. The health endpoints examined by Lushbaugh et al. were the lethal dose that will kill 50% of people within 60 days of exposure without medical care (LD50/60); severe bone marrow damage in healthy men; severe bone marrow damage in leukemia patients; temporary sterility (azoospermia); reduced male fertility; and late effects such as cancer. Their analysis was grounded in extensive clinical experience and anchored to a few selected data points, and based on the 1968 dose-rate dependence theory of J.L. Bateman. The Lushbaugh et al. paper did not give predictive equations for the relationships, although they were implied in the text, and the relationships were presented in a non-intuitive way. This work derives the parameters needed in Bateman's equation for each health endpoint, tabulates the results, and plots them in a more conventional manner on logarithmic scales. The results give a quantitative indication of how the human organism can tolerate more radiation dose when it is delivered at lower dose rates. For example, the LD50/60 increases from about 3 grays (300 rads) when given at very high dose rates to over 10 grays (1,000 rads) when given at much lower dose rates over periods of several months. The latter figure is borne out by the case of an individual who survived for at least 19 years after receiving doses in the range of 9 to 17 grays (900-1700 rads) over 106 days. The Lushbaugh et al. work shows the importance of sheltering when confronted with long-term exposure to radiological contamination such as would be expected from a radiological dispersion event, reactor accident, or ground-level nuclear explosion.

  9. Ionization cross sections and rate coefficients for CFCl3 molecule by electron impact

    NASA Astrophysics Data System (ADS)

    Pal, Satyendra; Kumar, Neeraj

    2013-09-01

    Chlorofluorocarbons (CFCs) or freons are important industrial material with wide-ranging applications as refrigerant, aerosol propellant and semiconductor etchant, etc. The large-scale industrial consumption is of particular environmental concern because of its potential for ozone destruction in the stratosphere. The present work reports the calculations for differential cross sections as a function of secondary/ ejected electron energy and the scattering angle in the ionization of CFCl3 by electron collision leading to the production of various cations viz. CCl3+,CFCl2+,CCl2+,CFCl+, CCl+, Cl+, CF+, F+, and C+ through direct and dissociative ionization processes at a fixed incident electron energy of 200 eV. A modified Jain-Khare semi-empirical formalism based on oscillator strength has been employed. To the best of our knowledge, no experimental and/or theoretical data is available for comparison of the present results for differential cross sections. The corresponding derived integral cross sections in terms of the partial ionization cross sections corresponding to these cations, in the energy range varying from ionization threshold to 1000 eV, revealed a reasonably good agreement with the experimental and theoretical data, wherever available. In addition to the differential and integral ionization cross sections, we have also calculated the ionization rate coefficients using the evaluated partial ionization cross sections and the Maxwell-Boltzmann distribution as a function of electron energy.

  10. Microfluidic Thrombosis under Multiple Shear Rates and Antiplatelet Therapy Doses

    PubMed Central

    Ku, David N.; Forest, Craig R.

    2014-01-01

    The mainstay of treatment for thrombosis, the formation of occlusive platelet aggregates that often lead to heart attack and stroke, is antiplatelet therapy. Antiplatelet therapy dosing and resistance are poorly understood, leading to potential incorrect and ineffective dosing. Shear rate is also suspected to play a major role in thrombosis, but instrumentation to measure its influence has been limited by flow conditions, agonist use, and non-systematic and/or non-quantitative studies. In this work we measured occlusion times and thrombus detachment for a range of initial shear rates (500, 1500, 4000, and 10000 s−1) and therapy concentrations (0–2.4 µM for eptifibatide, 0–2 mM for acetyl-salicylic acid (ASA), 3.5–40 Units/L for heparin) using a microfluidic device. We also measured complete blood counts (CBC) and platelet activity using whole blood impedance aggregometry. Effects of shear rate and dose were analyzed using general linear models, logistic regressions, and Cox proportional hazards models. Shear rates have significant effects on thrombosis/dose-response curves for all tested therapies. ASA has little effect on high shear occlusion times, even at very high doses (up to 20 times the recommended dose). Under ASA therapy, thrombi formed at high shear rates were 4 times more prone to detachment compared to those formed under control conditions. Eptifibatide reduced occlusion when controlling for shear rate and its efficacy increased with dose concentration. In contrast, the hazard of occlusion from ASA was several orders of magnitude higher than that of eptifibatide. Our results show similar dose efficacy to our low shear measurements using whole blood aggregometry. This quantitative and statistically validated study of the effects of a wide range of shear rate and antiplatelet therapy doses on occlusive thrombosis contributes to more accurate understanding of thrombosis and to models for optimizing patient treatment. PMID:24404131

  11. A standard graphite calorimeter for dosimetry in brachytherapy with high dose rate 192Ir sources

    NASA Astrophysics Data System (ADS)

    Guerra, A. S.; Loreti, S.; Pimpinella, M.; Quini, M.; D'Arienzo, M.; Astefanoaei, I.; Caporali, C.; Bolzan, C.; Pagliari, M.

    2012-10-01

    Within the framework of the JRP06 European project ‘Increasing Cancer Treatment Efficacy Using 3D Brachytherapy’, a prototype of a graphite standard calorimeter for the measurement of the absorbed dose rate to water, \\dot {D}_w , for 192Ir sources used in high dose rate (HDR) brachytherapy has been developed at the Italian National Institute of Ionizing Radiation Metrology (ENEA-INMRI). The calorimeter was tested at the Sant'Andrea Hospital in Rome, where \\dot {D}_w measurements were performed in the quasi-adiabatic mode of operation using an 192Ir MicroSelectron® HDR V2 source. The \\dot {D}_w measurements showed a reproducibility of about 1%, while the combined standard uncertainty on the \\dot {D}_w value at the distance of 1 cm from the source was estimated as 1.4%, lower than the uncertainty of \\dot {D}_w determined from the reference air-kerma rate.

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

    NASA Technical Reports Server (NTRS)

    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.

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

    NASA Technical Reports Server (NTRS)

    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.

  14. VMATc: VMAT with constant gantry speed and dose rate

    NASA Astrophysics Data System (ADS)

    Peng, Fei; Jiang, Steve B.; Romeijn, H. Edwin; Epelman, Marina A.

    2015-04-01

    This article considers the treatment plan optimization problem for Volumetric Modulated Arc Therapy (VMAT) with constant gantry speed and dose rate (VMATc). In particular, we consider the simultaneous optimization of multi-leaf collimator leaf positions and a constant gantry speed and dose rate. We propose a heuristic framework for (approximately) solving this optimization problem that is based on hierarchical decomposition. Specifically, an iterative algorithm is used to heuristically optimize dose rate and gantry speed selection, where at every iteration a leaf position optimization subproblem is solved, also heuristically, to find a high-quality plan corresponding to a given dose rate and gantry speed. We apply our framework to clinical patient cases, and compare the resulting VMATc plans to idealized IMRT, as well as full VMAT plans. Our results suggest that VMATc is capable of producing treatment plans of comparable quality to VMAT, albeit at the expense of long computation time and generally higher total monitor units.

  15. Response of human fibroblasts to low dose rate gamma irradiation

    SciTech Connect

    Dritschilo, A.; Brennan, T.; Weichselbaum, R.R.; Mossman, K.L.

    1984-11-01

    Cells from 11 human strains, including fibroblasts from patients with the genetic diseases of ataxia telangiectasia (AT), xeroderma pigmentosum (XP), and Fanconi's anemia (FA), were exposed to ..gamma.. radiation at high (1.6-2.2 Gy/min) and at low (0.03-0.07 Gy/min) dose rates. Survival curves reveal an increase inthe terminal slope (D/sub 0/) when cells are irradiated at low dose rates compared to high dose rates. This was true for all cell lines tested, although the AT, FA, and XP cells are reported or postulated to have radiation repair deficiencies. From the response of these cells, it is apparent that radiation sensitivities differ; however, at low dose rate, all tested human cells are able to repair injury.

  16. Failures Of CMOS Devices At Low Radiation-Dose Rates

    NASA Technical Reports Server (NTRS)

    Goben, Charles A.; Price, William E.

    1990-01-01

    Method for obtaining approximate failure-versus-dose-rate curves derived from experiments on failures of SGS 4007 complementary metal oxide/semiconductor (CMOS) integrated circuits irradiated by Co60 and Cs137 radioactive sources.

  17. Radiation-induced 1/f noise degradation of PNP bipolar junction transistors at different dose rates

    NASA Astrophysics Data System (ADS)

    Qi-Feng, Zhao; Yi-Qi, Zhuang; Jun-Lin, Bao; Wei, Hu

    2016-04-01

    It is found that ionizing-radiation can lead to the base current and the 1/f noise degradations in PNP bipolar junction transistors. In this paper, it is suggested that the surface of the space charge region of the emitter-base junction is the main source of the base surface 1/f noise. A model is developed which identifies the parameters and describes their interactive contributions to the recombination current at the surface of the space charge region. Based on the theory of carrier number fluctuation and the model of surface recombination current, a 1/f noise model is developed. This model suggests that 1/f noise degradations are the result of the accumulation of oxide-trapped charges and interface states. Combining models of ELDRS, this model can explain the reason why the 1/f noise degradation is more severe at a low dose rate than at a high dose rate. The radiations were performed in a Co60 source up to a total dose of 700 Gy(Si). The low dose rate was 0.001 Gy(Si)/s and the high dose rate was 0.1 Gy(Si)/s. The model accords well with the experimental results. Project supported by the National Natural Science Foundation of China (Grant Nos. 61076101 and 61204092).

  18. Model of radiation-induced gain degradation of NPN bipolar junction transistor at different dose rates

    NASA Astrophysics Data System (ADS)

    Qifeng, Zhao; Yiqi, Zhuang; Junlin, Bao; Wei, Hu

    2015-06-01

    Ionizing-radiation-induced current gain degradation in NPN bipolar junction transistors is due to an increase in base current as a result of recombination at the surface of the device. A model is presented which identifies the physical mechanism responsible for current gain degradation. The increase in surface recombination velocity due to interface states results in an increase in base current. Besides, changing the surface potential along the base surface induced by the oxide-trapped charges can also lead to an increased base current. By combining the production mechanisms of oxide-trapped charges and interface states, this model can explain the fact that the current gain degradation is more severe at a low dose rate than at a high dose rate. The radiations were performed in a Co60 source up to a total dose of 70 krad(Si). The low dose rate was 0.1 rad(Si)/s and the high dose rate was 10 rad(Si)/s. The model accords well with the experimental results. Project supported by the National Natural Science Foundation of China (Nos. 61076101, 61204092).

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

    NASA Astrophysics Data System (ADS)

    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.

  20. Medical imaging using ionizing radiation: Optimization of dose and image quality in fluoroscopy

    SciTech Connect

    Jones, A. Kyle; Balter, Stephen; Rauch, Phillip; Wagner, Louis K.

    2014-01-15

    The 2012 Summer School of the American Association of Physicists in Medicine (AAPM) focused on optimization of the use of ionizing radiation in medical imaging. Day 2 of the Summer School was devoted to fluoroscopy and interventional radiology and featured seven lectures. These lectures have been distilled into a single review paper covering equipment specification and siting, equipment acceptance testing and quality control, fluoroscope configuration, radiation effects, dose estimation and measurement, and principles of flat panel computed tomography. This review focuses on modern fluoroscopic equipment and is comprised in large part of information not found in textbooks on the subject. While this review does discuss technical aspects of modern fluoroscopic equipment, it focuses mainly on the clinical use and support of such equipment, from initial installation through estimation of patient dose and management of radiation effects. This review will be of interest to those learning about fluoroscopy, to those wishing to update their knowledge of modern fluoroscopic equipment, to those wishing to deepen their knowledge of particular topics, such as flat panel computed tomography, and to those who support fluoroscopic equipment in the clinic.

  1. Which molecular features affect the intrinsic hepatic clearance rate of ionizable organic chemicals in fish?

    EPA Science Inventory

    Greater knowledge of biotransformation rates for ionizable organic compounds (IOCs) in fish is required to properly assess the bioaccumulation potential of many environmentally relevant contaminants. In this study we measured in vitro hepatic clearance rates for 50 IOCs using a p...

  2. Which molecular features affect the intrinsic hepatic clearance rate of ionizable organic chemicals in fish?

    EPA Science Inventory

    Greater knowledge of biotransformation rates for ionizable organic compounds (IOCs) in fish is required to properly assess the bioaccumulation potential of many environmentally relevant contaminants. In this study we measured in vitro hepatic clearance rates for 50 IOCs using a p...

  3. Rapid Measurement of Neutron Dose Rate for Transport Index

    SciTech Connect

    Morris, R.L.

    2000-02-27

    A newly available neutron dose equivalent remmeter with improved sensitivity and energy response has been put into service at Rocky Flats Environmental Technology Site (RFETS). This instrument is being used to expedite measurement of the Transport Index and as an ALARA tool to identify locations where slightly elevated neutron dose equivalent rates exist. The meter is capable of measuring dose rates as low as 0.2 {mu}Sv per hour (20 {mu}rem per hour). Tests of the angular response and energy response of the instrument are reported. Calculations of the theoretical instrument response made using MCNP{trademark} are reported for materials typical of those being shipped.

  4. Shock tube study of ionization rates of NaCl-contaminated argon

    NASA Technical Reports Server (NTRS)

    Schneider, K.-P.; Park, C.

    1975-01-01

    Electron density, electron temperature, and concentration of excited sodium atoms are measured in the weakly ionized regime behind a shock wave in impure argon in a shock tube using microwave techniques and spectrally resolved radiometry. Evidence is presented to show that an apparent increase in the rate of ionization is due to electron detachment of negative chlorine ions produced from sodium chloride vapor contained as an impurity. To be consistent with this chemical model, rate coefficients are found in the temperature range between 5500 and 8600 K for the dissociation of NaCl into an ion pair, dissociation of NaCl into a neutral pair, and electron detachment of a negative chlorine ion. Electron temperature is lower than heavy-particle temperature by roughly 1000 K. The electron-argon impact-ionization rate coefficient is a weak function of electron temperature in contradiction to expectation.

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

    NASA Technical Reports Server (NTRS)

    LaBel, Kenneth A.; O'Bryan, 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.; Berg, Melanie D.; Gigliuto, Robert A.; Boutte, Alvin J.; Cochran, Donna J.; Buchner, Stephen P.; Violette, Daniel P.

    2014-01-01

    We present results and analysis investigating the effects of radiation on a variety of candidate spacecraft electronics to proton and heavy ion-induced single-event effects (SEE), proton-induced displacement damage (DD), and total ionizing dose (TID). This paper is a summary of test results.

  6. High temperature electronic excitation and ionization rates in gases

    NASA Technical Reports Server (NTRS)

    Hansen, Frederick

    1991-01-01

    The relaxation times for electronic excitation due to electron bombardment of atoms was found to be quite short, so that electron kinetic temperature (T sub e) and the electron excitation temperature (T asterisk) should equilibrate quickly whenever electrons are present. However, once equilibrium has been achieved, further energy to the excited electronic states and to the kinetic energy of free electrons must be fed in by collisions with heavy particles that cause vibrational and electronic state transitions. The rate coefficients for excitation of electronic states produced by heavy particle collision have not been well known. However, a relatively simple semi-classical theory has been developed here which is analytic up to the final integration over a Boltzmann distribution of collision energies; this integral can then be evaluated numerically by quadrature. Once the rate coefficients have been determined, the relaxation of electronic excitation energy can be evaluated and compared with the relaxation rates of vibrational excitation. Then the relative importance of these two factors, electronic excitation and vibrational excitation by heavy particle collision, on the transfer of energy to free electron motion, can be assessed.

  7. Dose rate effects during damage accumulation in silicon

    SciTech Connect

    Caturla, M.J.; Diaz de la Rubia, T.

    1997-01-01

    We combine molecular dynamics and Monte Carlo simulations to study damage accumulation and dose rate effects during irradiation of Silicon. We obtain the initial stage of the damage produced by heavy and light ions using classical molecular dynamics simulations. While heavy ions like As or Pt induce amorphization by single ion impact, light ions like B only produce point defects or small clusters of defects. The amorphous pockets generated by heavy ions are stable below room temperature and recrystallize at temperatures below the threshold for recrystallization of a planar amorphous-crystalline interface. The damage accumulation during light ion irradiation is simulated using a Monte Carlo model for defect diffusion. In this approach, we study the damage in the lattice as a function of dose and dose rate. A strong reduction in the total number of defects left in the lattice is observed for lower dose rates.

  8. Environmental exposure to low-doses of ionizing radiation. Effects on early nephrotoxicity in mice.

    PubMed

    Bellés, Montserrat; Gonzalo, Sergio; Serra, Noemí; Esplugas, Roser; Arenas, Meritxell; Domingo, José Luis; Linares, Victoria

    2017-03-31

    Nuclear accidents of tremendous magnitude, such as those of Chernobyl (1986) and Fukushima (2011), mean that individuals living in the contaminated areas are potentially exposed to ionizing radiation (IR). However, the dose-response relationship for effects of low doses of radiation is not still established. The present study was aimed at investigating in mice the early effects of low-dose internal radiation exposure on the kidney. Adult male (C57BL/6J) mice were divided into three groups. Two groups received a single subcutaneous (s.c.) doses of cesium ((137)Cs) with activities of 4000 and 8000Bq/kg bw. A third group (control group) received a single s.c. injection of 0.9% saline. To evaluate acute and subacute effects, mice (one-half of each group) were euthanized at 72h and 10 days post-exposure to (137)Cs, respectively. Urine samples were collected for biochemical analysis, including the measurement of F2-isoprostane (F2-IsoP) and kidney injury molecule-1 (KIM-1) levels. Moreover, the concentrations of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a sensitive marker of oxidative DNA damage, were measured in renal tissue. Urinary excretion of total protein significantly increased at 72h in mice exposed to Cs4000. Uric acid and lactate dehydrogenase (LDH) decreased significantly at both times post-exposure in animals exposed to Cs8000. After 72h and 10d of exposure to Cs4000, a significant increase in the γ-glutamil transferase (GGT) and N-acetyl-β-D-glucosaminidase (NAG) activities was observed. In turn, F2-IsoP levels increased -mainly in the Cs4000 group- at 72h post-exposure. Following irradiation ((137)Cs), the highest level of KIM-1 was corresponded to the Cs4000 group at 72h. Likewise, the main DNA damage was detected in mice exposed to Cs4000, mainly at 10d after irradiation. The alterations observed in several biomarkers suggest an immediate renal damage following exposure to low doses of IR (given as (137)Cs). Further investigations are required to clarify

  9. Strong effects of ionizing radiation from Chernobyl on mutation rates

    NASA Astrophysics Data System (ADS)

    Møller, Anders Pape; Mousseau, Timothy A.

    2015-02-01

    In this paper we use a meta-analysis to examine the relationship between radiation and mutation rates in Chernobyl across 45 published studies, covering 30 species. Overall effect size of radiation on mutation rates estimated as Pearson's product-moment correlation coefficient was very large (E = 0.67; 95% confidence intervals (CI) 0.59 to 0.73), accounting for 44.3% of the total variance in an unstructured random-effects model. Fail-safe calculations reflecting the number of unpublished null results needed to eliminate this average effect size showed the extreme robustness of this finding (Rosenberg's method: 4135 at p = 0.05). Indirect tests did not provide any evidence of publication bias. The effect of radiation on mutations varied among taxa, with plants showing a larger effect than animals. Humans were shown to have intermediate sensitivity of mutations to radiation compared to other species. Effect size did not decrease over time, providing no evidence for an improvement in environmental conditions. The surprisingly high mean effect size suggests a strong impact of radioactive contamination on individual fitness in current and future generations, with potentially significant population-level consequences, even beyond the area contaminated with radioactive material.

  10. Strong effects of ionizing radiation from Chernobyl on mutation rates

    PubMed Central

    Møller, Anders Pape; Mousseau, Timothy A.

    2015-01-01

    In this paper we use a meta-analysis to examine the relationship between radiation and mutation rates in Chernobyl across 45 published studies, covering 30 species. Overall effect size of radiation on mutation rates estimated as Pearson's product-moment correlation coefficient was very large (E = 0.67; 95% confidence intervals (CI) 0.59 to 0.73), accounting for 44.3% of the total variance in an unstructured random-effects model. Fail-safe calculations reflecting the number of unpublished null results needed to eliminate this average effect size showed the extreme robustness of this finding (Rosenberg's method: 4135 at p = 0.05). Indirect tests did not provide any evidence of publication bias. The effect of radiation on mutations varied among taxa, with plants showing a larger effect than animals. Humans were shown to have intermediate sensitivity of mutations to radiation compared to other species. Effect size did not decrease over time, providing no evidence for an improvement in environmental conditions. The surprisingly high mean effect size suggests a strong impact of radioactive contamination on individual fitness in current and future generations, with potentially significant population-level consequences, even beyond the area contaminated with radioactive material. PMID:25666381

  11. Strong effects of ionizing radiation from Chernobyl on mutation rates.

    PubMed

    Møller, Anders Pape; Mousseau, Timothy A

    2015-02-10

    In this paper we use a meta-analysis to examine the relationship between radiation and mutation rates in Chernobyl across 45 published studies, covering 30 species. Overall effect size of radiation on mutation rates estimated as Pearson's product-moment correlation coefficient was very large (E = 0.67; 95% confidence intervals (CI) 0.59 to 0.73), accounting for 44.3% of the total variance in an unstructured random-effects model. Fail-safe calculations reflecting the number of unpublished null results needed to eliminate this average effect size showed the extreme robustness of this finding (Rosenberg's method: 4135 at p = 0.05). Indirect tests did not provide any evidence of publication bias. The effect of radiation on mutations varied among taxa, with plants showing a larger effect than animals. Humans were shown to have intermediate sensitivity of mutations to radiation compared to other species. Effect size did not decrease over time, providing no evidence for an improvement in environmental conditions. The surprisingly high mean effect size suggests a strong impact of radioactive contamination on individual fitness in current and future generations, with potentially significant population-level consequences, even beyond the area contaminated with radioactive material.

  12. Accurate transition rates for intercombination lines of singly ionized nitrogen

    NASA Astrophysics Data System (ADS)

    Tayal, S. S.

    2011-01-01

    The transition energies and rates for the 2s22p2 3P1,2-2s2p3 5S2o and 2s22p3s-2s22p3p intercombination transitions have been calculated using term-dependent nonorthogonal orbitals in the multiconfiguration Hartree-Fock approach. Several sets of spectroscopic and correlation nonorthogonal functions have been chosen to describe adequately term dependence of wave functions and various correlation corrections. Special attention has been focused on the accurate representation of strong interactions between the 2s2p3 1,3P1o and 2s22p3s 1,3P1olevels. The relativistic corrections are included through the one-body mass correction, Darwin, and spin-orbit operators and two-body spin-other-orbit and spin-spin operators in the Breit-Pauli Hamiltonian. The importance of core-valence correlation effects has been examined. The accuracy of present transition rates is evaluated by the agreement between the length and velocity formulations combined with the agreement between the calculated and measured transition energies. The present results for transition probabilities, branching fraction, and lifetimes have been compared with previous calculations and experiments.

  13. Accurate transition rates for intercombination lines of singly ionized nitrogen

    SciTech Connect

    Tayal, S. S.

    2011-01-15

    The transition energies and rates for the 2s{sup 2}2p{sup 2} {sup 3}P{sub 1,2}-2s2p{sup 3} {sup 5}S{sub 2}{sup o} and 2s{sup 2}2p3s-2s{sup 2}2p3p intercombination transitions have been calculated using term-dependent nonorthogonal orbitals in the multiconfiguration Hartree-Fock approach. Several sets of spectroscopic and correlation nonorthogonal functions have been chosen to describe adequately term dependence of wave functions and various correlation corrections. Special attention has been focused on the accurate representation of strong interactions between the 2s2p{sup 3} {sup 1,3}P{sub 1}{sup o} and 2s{sup 2}2p3s {sup 1,3}P{sub 1}{sup o}levels. The relativistic corrections are included through the one-body mass correction, Darwin, and spin-orbit operators and two-body spin-other-orbit and spin-spin operators in the Breit-Pauli Hamiltonian. The importance of core-valence correlation effects has been examined. The accuracy of present transition rates is evaluated by the agreement between the length and velocity formulations combined with the agreement between the calculated and measured transition energies. The present results for transition probabilities, branching fraction, and lifetimes have been compared with previous calculations and experiments.

  14. Construction of a fast ionization chamber for high-rate particle identification

    NASA Astrophysics Data System (ADS)

    Chae, K. Y.; Ahn, S.; Bardayan, D. W.; Chipps, K. A.; Manning, B.; Pain, S. D.; Peters, W. A.; Schmitt, K. T.; Smith, M. S.; Strauss, S. Y.

    2014-07-01

    A new gas-filled ionization chamber for high count rate particle identification has been constructed and commissioned at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory (ORNL). To enhance the response time of the ionization chamber, a design utilizing a tilted entrance window and tilted electrodes was adopted, which is modified from an original design by Kimura et al. [1]. A maximum counting rate of 700 , 000 particles per second has been achieved. The detector has been used for several radioactive beam measurements performed at the HRIBF.

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

    PubMed

    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.

  16. Investigations on MGy ionizing dose effects in thin oxides of micro-electronic devices

    SciTech Connect

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

    2015-07-01

    Total ionizing dose (TID) effects have been studied for a long time in micro-electronic components designed to operate in natural and artificial environments. In most cases, TID induces both charge trapping in the bulk of irradiated oxides and the buildup of interface traps located at semiconductor/dielectric interfaces. Such effects result from basic mechanisms driven by both the shape of the electric field which stands into the oxide and by fabrication process parameters inducing pre-existing traps in the oxide's bulk. From the pioneering studies based on 'thick' oxide technologies to the most recent ones dedicated to innovative technologies, most studies concluded that the impact of total ionizing dose effects reduces with the oxide thinning. This is specifically the case for the gate-oxide of Metal-Oxide-Semiconductor Field Effect Transistors (MOSFET) for which it is generally considered that TID is not a major issue anymore at kGy dose ranges. TID effects are now mainly due to charge trapping in the field oxides such as Shallow Trench Isolation. This creates either parasitic conduction paths or Radiation-Induced Narrow Channel Effects (RINCE). Static current-voltage (I-V) electrical characteristics are then modified through a significant increase of the off-current of NMOS transistors or by shifting the whole I-V curves (of both NMOS and PMOS transistors). Based on these assumptions, no significant shift of I-V curves should be observed in modern bulk CMOS technologies. However, such phenomenon may not be directly extrapolated to higher TID ranges, typically of several MGy for which only few data are available in the literature. This paper presents evidences of large threshold voltage shifts measured at MGy dose levels despite the fact that transistors are designed in a submicron bulk technology which features a 7-nm thin gate-oxide on GO2 transistors dedicated to mixed analog/digital integrated circuits. Such electrical shifts are encountered on PMOS

  17. Electron Impact Ionization cross sections and rate coefficients for α-tetra hydro furfuryl alcohol

    NASA Astrophysics Data System (ADS)

    Kumar, Neeraj; Pal, Satyendra

    2013-09-01

    α - tetrahydrofurfuryl alcohol (THFA; C5H10O2) is an aromatic compound having the molecular structure similar to that of 2-deoxy-D-ribose (deoxyribose). This molecule has attracted enormous interest in the field of research because its electron charge cloud possesses a quite significant spatial extent (dipole polarizability, α = 70.18 au) and has a relatively strong permanent dipole moment (μ ~ 2D). In the present work, we have extended and generalized the modified Jain-Khare semi-empirical formalism for the evaluation of the total ionization cross sections corresponding to the formation of the cations in the electron impact ionization of molecules to the electron impact ionization of α-tetrahydrofurfuryl alcohol (THFA; C5H10O2) , in the energy range varying from ionization threshold to 1000 eV. The evaluated cross sections revealed a reasonably good agreement with the experimental and theoretical data, wherever available. We have also calculated the ionization rate coefficients as a function of electron energy, using the evaluated total ionization cross sections and the Maxwell-Boltzmann distribution.

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

    NASA Technical Reports Server (NTRS)

    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.; hide

    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 optoelectronics, digital, analog, linear bipolar devices, and hybrid devices. Displacement Damage, Optoelectronics, Proton Damage, Single Event Effects, and Total Ionizing Dose.

  19. Extreme variations of air dose rates in east Fukushima.

    PubMed

    Akimoto, Kazuhiro

    2015-11-01

    This report analyses the data of air (ambient) dose rates measured at 164 points in eastern Fukushima during a period of half a year after 10 June 2011. It is found that at some locations the values decreased or increased extraordinarily although on average the overall dose rates decreased significantly faster than the theoretically predicted rate. Among them the nine most extreme points are selected and analysed. It is found that behind these extraordinary behaviours of air dose rates there exists the combination of wind/rain and artificial structures such as sloped pavements. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  20. Calculation of the biological effective dose for piecewise defined dose-rate fits

    SciTech Connect

    Hobbs, Robert F.; Sgouros, George

    2009-03-15

    An algorithmic solution to the biological effective dose (BED) calculation from the Lea-Catcheside formula for a piecewise defined function is presented. Data from patients treated for metastatic thyroid cancer were used to illustrate the solution. The Lea-Catcheside formula for the G-factor of the BED is integrated numerically using a large number of small trapezoidal fits to each integral. The algorithmically calculated BED is compatible with an analytic calculation for a similarly valued exponentially fitted dose-rate plot and is the only resolution for piecewise defined dose-rate functions.

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

    PubMed

    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)].

  2. Equivalent dose rate by muons to the human body.

    PubMed

    Băcioiu, I

    2011-11-01

    In this paper, the relative sensitivity from different human tissues of the human body, at a ground level, from muon cosmic radiation has been studied. The aim of this paper was to provide information on the equivalent dose rates received from atmospheric muons to human body, at the ground level. The calculated value of the effective dose rate by atmospheric muons plus the radiation levels of the natural annual background radiation dose, at the ground level, in the momentum interval of cosmic ray muon (0.2-120.0 GeV/c) is about 2.106±0.001 mSv/y, which is insignificant in comparison with the values of the doses from the top of the atmosphere.

  3. FT-IR spectroscopy assessment of aesthetic dental materials irradiated with low-dose therapeutic ionizing radiation

    NASA Astrophysics Data System (ADS)

    Cruz, A. D.; Almeida, S. M.; Rastelli, A. N. S.; Bagnato, V. S.; Byscolo, F. N.

    2009-03-01

    The aim of the present study was to evaluate the effects of low-dose therapeutic ionizing radiation on different aesthetic dental materials. Forty five specimens ( n = 45) of three different aesthetic restorative materials were prepared and randomly divided into five groups: G1 (control group); G2, G3, G4, G5 experimental groups irradiated respectively with 0.25, 0.50, 0.75, and 1.00 Gy of gamma radiation by the 60Co teletherapy machine. Chemical analyses were performed using a FT-IR Nicolet 520 spectrophotometer with reflectance diffuse technique. Even a minimal exposition at ionizing radiation in therapeutic doses can provide chemical changes on light-cured composite resins. The three studied restorative materials showed changes after exposure at gamma radiation, however the increase of the radiation dose did not contribute to an increase in this effect.

  4. PRECEDENTS FOR AUTHORIZATION OF CONTENTS USING DOSE RATE MEASUREMENTS

    SciTech Connect

    Abramczyk, G.; Bellamy, S.; Nathan, S.; Loftin, B.

    2012-06-05

    For the transportation of Radioactive Material (RAM) packages, the requirements for the maximum allowed dose rate at the package surface and in its vicinity are given in Title 10 of the Code of Federal Regulations, Section 71.47. The regulations are based on the acceptable dose rates to which the public, workers, and the environment may be exposed. As such, the regulations specify dose rates, rather than quantity of radioactive isotopes and require monitoring to confirm the requirements are met. 10CFR71.47 requires that each package of radioactive materials offered for transportation must be designed and prepared for shipment so that under conditions normally incident to transportation the radiation level does not exceed 2 mSv/h (200 mrem/h) at any point on the external Surface of the package, and the transport index does not exceed 10. Before shipment, the dose rate of the package is determined by measurement, ensuring that it conforms to the regulatory limits, regardless of any analyses. This is the requirement for all certified packagings. This paper discusses the requirements for establishing the dose rates when shipping RAM packages and the precedents for meeting these requirements by measurement.

  5. Total Ionizing Dose Effects in 12-Bit Successive-Approximation Analog-To-Digital Converters

    NASA Technical Reports Server (NTRS)

    Lee, C. I.; Rax, B. G.; Johnston, A. H.

    1993-01-01

    Analog-to-digital (A/D) converters are critical components in many space and military systems, and there have been numerous advances in A/D converter technology that have increased the resolution and conversion time. The increased performance is due to two factors: (1) advances in circuit design and complexity, which have increased the number of components and the integration density; and (2) new process technologies, such as BiCMOS, which provide better performance, cost, and smaller size in mixed-signal circuits. High-speed A/D converters, with conversion rates above 1 MHz, present a challenge to circuit designers and test engineers. Their complex architectures and high-performance specifications result in numerous possible failure modes when they are subjected to ionizing radiation. The dominant failure mode may depend on the specific application because the fundamental effects on MOS and bipolar transistors are strongly affected by bias conditions.

  6. Total Ionizing Dose Effects in 12-Bit Successive-Approximation Analog-To-Digital Converters

    NASA Technical Reports Server (NTRS)

    Lee, C. I.; Rax, B. G.; Johnston, A. H.

    1993-01-01

    Analog-to-digital (A/D) converters are critical components in many space and military systems, and there have been numerous advances in A/D converter technology that have increased the resolution and conversion time. The increased performance is due to two factors: (1) advances in circuit design and complexity, which have increased the number of components and the integration density; and (2) new process technologies, such as BiCMOS, which provide better performance, cost, and smaller size in mixed-signal circuits. High-speed A/D converters, with conversion rates above 1 MHz, present a challenge to circuit designers and test engineers. Their complex architectures and high-performance specifications result in numerous possible failure modes when they are subjected to ionizing radiation. The dominant failure mode may depend on the specific application because the fundamental effects on MOS and bipolar transistors are strongly affected by bias conditions.

  7. Performance Improvement of Total Ionization Dose Radiation Sensor Devices Using Fluorine-Treated MOHOS

    PubMed Central

    Hsieh, Wen-Ching; Lee, Hao-Tien Daniel; Jong, Fuh-Cheng; Wu, Shich-Chuan

    2016-01-01

    Fluorine-treated titanium nitride–silicon oxide–hafnium oxide–silicon oxide–silicon devices (hereafter F-MOHOS) are candidates for total ionization dose (TID) radiation sensor applications. The main subject of the study reportedherein is the performance improvement in terms of TID radiation-induced charge generation effect and charge-retention reliability characterization for F-MOHOS devices. In the case of F-MOHOS TID radiation sensors, the gamma radiation induces a significant decrease of threshold voltage VT and the radiation-induced charge density is nearly six times larger than that of standard metal–oxide–nitride–oxide–silicon MONOS devices. The decrease of VT for F-MOHOS after gamma irradiation has a strong correlation to the TID up to 5 Mrad gamma irradiation as well. The improvement of charge retention loss for F-MOHOS devices is nearly 15% better than that of metal–oxide–hafnium oxide–oxide–silicon MOHOS devices. The F-MOHOS device described in this study demonstrates better feasibility for non-volatile TID radiation sensing in the future. PMID:27043560

  8. Performance Improvement of Total Ionization Dose Radiation Sensor Devices Using Fluorine-Treated MOHOS.

    PubMed

    Hsieh, Wen-Ching; Lee, Hao-Tien Daniel; Jong, Fuh-Cheng; Wu, Shich-Chuan

    2016-03-29

    Fluorine-treated titanium nitride-silicon oxide-hafnium oxide-silicon oxide-silicon devices (hereafter F-MOHOS) are candidates for total ionization dose (TID) radiation sensor applications. The main subject of the study reportedherein is the performance improvement in terms of TID radiation-induced charge generation effect and charge-retention reliability characterization for F-MOHOS devices. In the case of F-MOHOS TID radiation sensors, the gamma radiation induces a significant decrease of threshold voltage VT and the radiation-induced charge density is nearly six times larger than that of standard metal-oxide-nitride-oxide-silicon MONOS devices. The decrease of VT for F-MOHOS after gamma irradiation has a strong correlation to the TID up to 5 Mrad gamma irradiation as well. The improvement of charge retention loss for F-MOHOS devices is nearly 15% better than that of metal-oxide-hafnium oxide-oxide-silicon MOHOS devices. The F-MOHOS device described in this study demonstrates better feasibility for non-volatile TID radiation sensing in the future.

  9. Transcriptional response of ex vivo human skin to ionizing radiation: comparison between low- and high-dose effects.

    PubMed

    Albrecht, Huguette; Durbin-Johnson, Blythe; Yunis, Reem; Kalanetra, Karen M; Wu, Shiquan; Chen, Rachel; Stevenson, Thomas R; Rocke, David M

    2012-01-01

    Although human exposure to low-dose ionizing radiation can occur through a variety of sources, including natural, medical, occupational and accidental, the true risks of low-dose ionizing radiation are still poorly understood in humans. Here, the global transcriptional responses of human skin after ex vivo exposure to low (0.05 Gy) and high (5 Gy) doses of X rays and of time in culture (0 Gy) at 0, 2, 8 and 30 h postirradiation were analyzed and compared. Responses to low and high doses differed quantitatively and qualitatively. Differentially expressed genes fell into three groups: (1) unique genes defined as responsive to either 0.05 or 5 Gy but not both and also responsive to time in culture, (2) specific genes defined as responsive to either 0.05 or 5 Gy but not both and not responsive to time in culture, and (3) dose-independent responsive genes. Major differences observed in ex vivo irradiated skin between transcriptional responses to low or high doses were twofold. First, gene expression modulated by 0.05 Gy was transient, while in response to 5 Gy persistence of modified gene expression was observed for a limited number of genes. Second, neither TP53 nor TGFβ target genes were modulated after exposure to an acute low dose, suggesting that the TP53-dependent DNA damage response either was not triggered or was triggered only briefly.

  10. Transcriptional Response of Ex Vivo Human Skin to Ionizing Radiation: Comparison Between Low- and High-Dose Effects

    PubMed Central

    Albrecht, Huguette; Durbin-Johnson, Blythe; Yunis, Reem; Kalanetra, Karen M.; Wu, Shiquan; Chen, Rachel; Stevenson, Thomas R.; Rocke, David M.

    2013-01-01

    Although human exposure to low-dose ionizing radiation can occur through a variety of sources, including natural, medical, occupational and accidental, the true risks of low-dose ionizing radiation are still poorly understood in humans. Here, the global transcriptional responses of human skin after ex vivo exposure to low (0.05 Gy) and high (5 Gy) doses of X rays and of time in culture (0 Gy) at 0, 2, 8 and 30 h postirradiation were analyzed and compared. Responses to low and high doses differed quantitatively and qualitatively. Differentially expressed genes fell into three groups: (1) unique genes defined as responsive to either 0.05 or 5 Gy but not both and also responsive to time in culture, (2) specific genes defined as responsive to either 0.05 or 5 Gy but not both and not responsive to time in culture, and (3) dose-independent responsive genes. Major differences observed in ex vivo irradiated skin between transcriptional responses to low or high doses were twofold. First, gene expression modulated by 0.05 Gy was transient, while in response to 5 Gy persistence of modified gene expression was observed for a limited number of genes. Second, neither TP53 nor TGFβ target genes were modulated after exposure to an acute low dose, suggesting that the TP53-dependent DNA damage response either was not triggered or was triggered only briefly. PMID:22029842

  11. Impact of Spacecraft Shielding on Direct Ionization Soft Error Rates for sub-130 nm Technologies

    NASA Technical Reports Server (NTRS)

    Pellish, Jonathan A.; Xapsos, Michael A.; Stauffer, Craig A.; Jordan, Michael M.; Sanders, Anthony B.; Ladbury, Raymond L.; Oldham, Timothy R.; Marshall, Paul W.; Heidel, David F.; Rodbell, Kenneth P.

    2010-01-01

    We use ray tracing software to model various levels of spacecraft shielding complexity and energy deposition pulse height analysis to study how it affects the direct ionization soft error rate of microelectronic components in space. The analysis incorporates the galactic cosmic ray background, trapped proton, and solar heavy ion environments as well as the October 1989 and July 2000 solar particle events.

  12. Absorbed dose-to-water protocol applied to synchrotron-generated x-rays at very high dose rates

    NASA Astrophysics Data System (ADS)

    Fournier, P.; Crosbie, J. C.; Cornelius, I.; Berkvens, P.; Donzelli, M.; Clavel, A. H.; Rosenfeld, A. B.; Petasecca, M.; Lerch, M. L. F.; Bräuer-Krisch, E.

    2016-07-01

    Microbeam radiation therapy (MRT) is a new radiation treatment modality in the pre-clinical stage of development at the ID17 Biomedical Beamline of the European synchrotron radiation facility (ESRF) in Grenoble, France. MRT exploits the dose volume effect that is made possible through the spatial fractionation of the high dose rate synchrotron-generated x-ray beam into an array of microbeams. As an important step towards the development of a dosimetry protocol for MRT, we have applied the International Atomic Energy Agency’s TRS 398 absorbed dose-to-water protocol to the synchrotron x-ray beam in the case of the broad beam irradiation geometry (i.e. prior to spatial fractionation into microbeams). The very high dose rates observed here mean the ion recombination correction factor, k s , is the most challenging to quantify of all the necessary corrections to apply for ionization chamber based absolute dosimetry. In the course of this study, we have developed a new method, the so called ‘current ramping’ method, to determine k s for the specific irradiation and filtering conditions typically utilized throughout the development of MRT. Using the new approach we deduced an ion recombination correction factor of 1.047 for the maximum ESRF storage ring current (200 mA) under typical beam spectral filtering conditions in MRT. MRT trials are currently underway with veterinary patients at the ESRF that require additional filtering, and we have estimated a correction factor of 1.025 for these filtration conditions for the same ESRF storage ring current. The protocol described herein provides reference dosimetry data for the associated Treatment Planning System utilized in the current veterinary trials and anticipated future human clinical trials.

  13. Low-dose-rate or high-dose-rate brachytherapy in treatment of prostate cancer – between options

    PubMed Central

    2013-01-01

    Purpose Permanent low-dose-rate (LDR-BT) and temporary high-dose-rate (HDR-BT) brachytherapy are competitive techniques for clinically localized prostate radiotherapy. Although a randomized trial will likely never to be conducted comparing these two forms of brachytherapy, a comparative analysis proves useful in understanding some of their intrinsic differences, several of which could be exploited to improve outcomes. The aim of this paper is to look for possible similarities and differences between both brachytherapy modalities. Indications and contraindications for monotherapy and for brachytherapy as a boost to external beam radiation therapy (EBRT) are presented. It is suggested that each of these techniques has attributes that advocates for one or the other. First, they represent the extreme ends of the spectrum with respect to dose rate and fractionation, and therefore have inherently different radiobiological properties. Low-dose-rate brachytherapy has the great advantage of being practically a one-time procedure, and enjoys a long-term follow-up database supporting its excellent outcomes and low morbidity. Low-dose-rate brachytherapy has been a gold standard for prostate brachytherapy in low risk patients since many years. On the other hand, HDR is a fairly invasive procedure requiring several sessions associated with a brief hospital stay. Although lacking in significant long-term data, it possesses the technical advantage of control over its postimplant dosimetry (by modulating the source dwell time and position), which is absent in LDR brachytherapy. This important difference in dosimetric control allows HDR doses to be escalated safely, a flexibility that does not exist for LDR brachytherapy. Conclusions Radiobiological models support the current clinical evidence for equivalent outcomes in localized prostate cancer with either LDR or HDR brachytherapy, using current dose regimens. At present, all available clinical data regarding these two techniques

  14. An overview of zinc addition for BWR dose rate control

    SciTech Connect

    Marble, W.J.

    1995-03-01

    This paper presents an overview of the BWRs employing feedwater zinc addition to reduce primary system dose rates. It identifies which BWRs are using zinc addition and reviews the mechanical injection and passive addition hardware currently being employed. The impact that zinc has on plant chemistry, including the factor of two to four reduction in reactor water Co-60 concentrations, is discussed. Dose rate results, showing the benefits of implementing zinc on either fresh piping surfaces or on pipes with existing films are reviewed. The advantages of using zinc that is isotopically enhanced by the depletion of the Zn-64 precursor to Zn-65 are identified.

  15. Radiation damage in single-particle cryo-electron microscopy: effects of dose and dose rate

    PubMed Central

    Karuppasamy, Manikandan; Karimi Nejadasl, Fatemeh; Vulovic, Milos; Koster, Abraham J.; Ravelli, Raimond B. G.

    2011-01-01

    Radiation damage is an important resolution limiting factor both in macromolecular X-ray crystallography and cryo-electron microscopy. Systematic studies in macromolecular X-ray crystallography greatly benefited from the use of dose, expressed as energy deposited per mass unit, which is derived from parameters including incident flux, beam energy, beam size, sample composition and sample size. In here, the use of dose is reintroduced for electron microscopy, accounting for the electron energy, incident flux and measured sample thickness and composition. Knowledge of the amount of energy deposited allowed us to compare doses with experimental limits in macromolecular X-ray crystallography, to obtain an upper estimate of radical concentrations that build up in the vitreous sample, and to translate heat-transfer simulations carried out for macromolecular X-ray crystallography to cryo-electron microscopy. Stroboscopic exposure series of 50–250 images were collected for different incident flux densities and integration times from Lumbricus terrestris extracellular hemoglobin. The images within each series were computationally aligned and analyzed with similarity metrics such as Fourier ring correlation, Fourier ring phase residual and figure of merit. Prior to gas bubble formation, the images become linearly brighter with dose, at a rate of approximately 0.1% per 10 MGy. The gradual decomposition of a vitrified hemoglobin sample could be visualized at a series of doses up to 5500 MGy, by which dose the sample was sublimed. Comparison of equal-dose series collected with different incident flux densities showed a dose-rate effect favoring lower flux densities. Heat simulations predict that sample heating will only become an issue for very large dose rates (50 e−Å−2 s−1 or higher) combined with poor thermal contact between the grid and cryo-holder. Secondary radiolytic effects are likely to play a role in dose-rate effects. Stroboscopic data collection

  16. Ensemble Monte Carlo calculation of the hole initiated impact ionization rate in bulk GaAs and silicon using a k-dependent, numerical transition rate formulation

    NASA Technical Reports Server (NTRS)

    Oguzman, Ismail H.; Wang, Yang; Kolnik, Jan; Brennan, Kevin F.

    1995-01-01

    The hole initiated impact ionization rate in bulk silicon and GaAs is calculated using a numerical formulation of the impact ionization transition rate incorporated into an ensemble Monte Carlo simulation. The transition rate is calculated from Fermi's golden rule using a two-body screened Coulomb interaction including a wavevector dependent dielectric function. It is found that the effective threshold for hole initiated ionization is relatively soft in both materials, that the split-off band dominates the ionization process in GaAs. and that no clear dominance by any one band is observed in silicon, though the rate out of the light hole band is greatest.

  17. Direct measurement of absorbed dose to water in HDR {sup 192}Ir brachytherapy: Water calorimetry, ionization chamber, Gafchromic film, and TG-43

    SciTech Connect

    Sarfehnia, Arman; Kawrakow, Iwan; Seuntjens, Jan

    2010-04-15

    Purpose: Gafchromic film and ionometric calibration procedures for HDR {sup 192}Ir brachytherapy sources in terms of dose rate to water are presented and the experimental results are compared to the TG-43 protocol as well as with the absolute dose measurement results from a water calorimetry-based primary standard. Methods: EBT-1 Gafchromic films, an A1SL Exradin miniature Shonka thimble type chamber, and an SI HDR 1000 Plus well-type chamber (Standard Imaging, Inc., Middleton, WI) with an ADCL traceable S{sub k} calibration coefficient (following the AAPM TG-43 protocol) were used. The Farmer chamber and Gafchromic film measurements were performed directly in water. All results were compared to direct and absolute absorbed dose to water measurements from a 4 deg. C stagnant water calorimeter. Results: Based on water calorimetry, the authors measured the dose rate to water to be 361{+-}7 {mu}Gy/(h U) at a 55 mm source-to-detector separation. The dose rate normalized to air-kerma strength for all the techniques agree with the water calorimetry results to within 0.83%. The overall 1-sigma uncertainty on water calorimetry, ionization chamber, Gafchromic film, and TG-43 dose rate measurement amounts to 1.90%, 1.44%, 1.78%, and 2.50%, respectively. Conclusions: This work allows us to build a more realistic uncertainty estimate for absorbed dose to water determination using the TG-43 protocol. Furthermore, it provides the framework necessary for a shift from indirect HDR {sup 192}Ir brachytherapy dosimetry to a more accurate, direct, and absolute measurement of absorbed dose to water.

  18. [New dosimetry system based on the thermoluminescence method for evaluation of ionizing radiation doses to workers of the health centers].

    PubMed

    Urban, Paweł; Skubacz, Krystian

    2015-01-01

    In different areas of industry, science and in the greater extend medicine, plenty of devices intended for production of ionizing radiation or containing sources of such radiation found application. Such situation causes the necessity to control such kind of hazards. Currently, the most popular technique for detection of ionizing radiation is the method based on the thermoluminescence phenomena. Within the frame of this work, a new Panasonic's dosimetry system based on thermoluminescence dosimeters, intended for assessment of doses in mixed radiation fields of various energies is presented. In addition, the measured dosimetry quantities and problems connected with monitoring of radiation hazard in mixed fields (commonly present in medical sector) are characterized. In orderto verify measurement capabilities of the new system the irradiations of dosimeters with ionizing radiation of different energies have been done.

  19. Investigation of pulsed low dose rate radiotherapy using dynamic arc delivery techniques

    NASA Astrophysics Data System (ADS)

    Ma, C.-M.; Lin, M. H.; Dai, X. F.; Koren, Sion; Klayton, T.; Wang, L.; Li, J. S.; Chen, L.; Price, R. A.

    2012-07-01

    There has been no consensus standard of care to treat recurrent cancer patients who have previously been irradiated. Pulsed low dose rate (PLDR) external beam radiotherapy has the potential to reduce normal tissue toxicities while still providing significant tumor control for recurrent cancers. This work investigates the dosimetry feasibility of PLDR treatment using dynamic arc delivery techniques. Five treatment sites were investigated in this study including breast, pancreas, prostate, head and neck, and lung. Dynamic arc plans were generated using the Varian Eclipse system and the RapidArc delivery technique with 6 and 10 MV photon beams. Each RapidArc plan consisted of two full arcs and the plan was delivered five times to achieve a daily dose of 200 cGy. The dosimetry requirement was to deliver approximately 20 cGy/arc with a 3 min interval to achieve an effective dose rate of 6.7 cGy min-1. Monte Carlo simulations were performed to calculate the actual dose delivered to the planning target volume (PTV) per arc taking into account beam attenuation/scattering and intensity modulation. The maximum, minimum and mean doses to the PTV were analyzed together with the dose volume histograms and isodose distributions. The dose delivery for the five plans was validated using solid water phantoms inserted with an ionization chamber and film, and a cylindrical detector array. Two intensity-modulated arcs were used to efficiently deliver the PLDR plans that provided conformal dose distributions for treating complex recurrent cancers. For the five treatment sites, the mean PTV dose ranged from 18.9 to 22.6 cGy/arc. For breast, the minimum and maximum PTV dose was 8.3 and 35.2 cGy/arc, respectively. The PTV dose varied between 12.9 and 27.5 cGy/arc for pancreas, 12.6 and 28.3 cGy/arc for prostate, 12.1 and 30.4 cGy/arc for H&N, and 16.2 and 27.6 cGy/arc for lung. Advanced radiation therapy can provide superior target coverage and normal tissue sparing for PLDR

  20. Total dose and dose rate models for bipolar transistors in circuit simulation.

    SciTech Connect

    Campbell, Phillip Montgomery; Wix, Steven D.

    2013-05-01

    The objective of this work is to develop a model for total dose effects in bipolar junction transistors for use in circuit simulation. The components of the model are an electrical model of device performance that includes the effects of trapped charge on device behavior, and a model that calculates the trapped charge densities in a specific device structure as a function of radiation dose and dose rate. Simulations based on this model are found to agree well with measurements on a number of devices for which data are available.

  1. [Side effects of postoperative irradiation of uterine cancer with high dose rate iridium and low dose rate radium].

    PubMed

    Kucera, H; Unel, N; Weghaupt, K

    1986-02-01

    A report is given about reversible and irreversible complications following postoperative irradiation in cases of endometrial carcinoma. Intravaginal brachytherapy was performed. In advanced cases or in cases with poor prognosis (tumor grading) percutaneous irradiation was added (Co60). In 156 cases low-dose-rate irradiation (Ra226) and in 143 cases high-dose-rate irradiation (Ir192) was applied intravaginally. Reversible complications (cystitis, proctitis) could be observed following Radium in 7%, following Iridium in 14%. Irreversible complications (fistulas, stenoses): 1.9% following Radium and 3.5% following Iridium. When high-dose-rate irradiation was combined with percutaneous Co60 therapy, reversible complications occurred in 22.8%. After changing the Iridium-therapy scheme (reduction of dose from 10 to 7 Gy and irradiation only of the upper two thirds of the vagina) complications only could be observed in the same level as in Radium-therapy. High-dose-rate irradiation does not need hospitalization of the patients.

  2. Patient release criteria for low dose rate brachytherapy implants.

    PubMed

    Boyce, Dale E; Sheetz, Michael A

    2013-04-01

    A lack of consensus regarding a model governing the release of patients following sealed source brachytherapy has led to a set of patient release policies that vary from institution to institution. The U.S. Nuclear Regulatory Commission has issued regulatory guidance on patient release in NUREG 1556, Volume 9, Rev. 2, Appendix U, which allows calculation of release limits following implant brachytherapy. While the formalism presented in NUREG is meaningful for the calculation of release limits in the context of relatively high energy gamma emitters, it does not estimate accurately the effective dose equivalent for the common low dose rate brachytherapy sources Cs, I, and Pd. NUREG 1556 states that patient release may be based on patient-specific calculations as long as the calculation is documented. This work is intended to provide a format for patient-specific calculations to be used for the consideration of patients' release following the implantation of certain low dose rate brachytherapy isotopes.

  3. Radiosensitization of Human Cervical Cancer Cells by Inhibiting Ribonucleotide Reductase: Enhanced Radiation Response at Low-Dose Rates

    SciTech Connect

    Kunos, Charles A.; Colussi, Valdir C.; Pink, John; Radivoyevitch, Tomas; Oleinick, Nancy L.

    2011-07-15

    Purpose: To test whether pharmacologic inhibition of ribonucleotide reductase (RNR) by 3-aminopyridine-2-carboxaldehyde thiosemicarbazone (3-AP, NSC no. 663249) enhances radiation sensitivity during low-dose-rate ionizing radiation provided by a novel purpose-built iridium-192 cell irradiator. Methods and Materials: The cells were exposed to low-dose-rate radiation (11, 23, 37, 67 cGy/h) using a custom-fabricated cell irradiator or to high-dose-rate radiation (330 cGy/min) using a conventional cell irradiator. The radiation sensitivity of human cervical (CaSki, C33-a) cancer cells with or without RNR inhibition by 3-AP was evaluated using a clonogenic survival and an RNR activity assay. Alteration in the cell cycle distribution was monitored using flow cytometry. Results: Increasing radiation sensitivity of both CaSki and C33-a cells was observed with the incremental increase in radiation dose rates. 3-AP treatment led to enhanced radiation sensitivity in both cell lines, eliminating differences in cell cytotoxicity from the radiation dose rate. RNR blockade by 3-AP during low-dose-rate irradiation was associated with low RNR activity and extended G{sub 1}-phase cell cycle arrest. Conclusions: We conclude that RNR inhibition by 3-AP impedes DNA damage repair mechanisms that rely on deoxyribonucleotide production and thereby increases radiation sensitivity of human cervical cancers to low-dose-rate radiation.

  4. ACDOS2: an improved neutron-induced dose rate code

    SciTech Connect

    Lagache, J.C.

    1981-06-01

    To calculate the expected dose rate from fusion reactors as a function of geometry, composition, and time after shutdown a computer code, ACDOS2, was written, which utilizes up-to-date libraries of cross-sections and radioisotope decay data. ACDOS2 is in ANSI FORTRAN IV, in order to make it readily adaptable elsewhere.

  5. Predicted and observed therapeutic dose exceedances of ionizable pharmaceuticals in fish plasma from urban coastal systems.

    PubMed

    Scott, W Casan; Du, Bowen; Haddad, Samuel P; Breed, Christopher S; Saari, Gavin N; Kelly, Martin; Broach, Linda; Chambliss, C Kevin; Brooks, Bryan W

    2016-04-01

    Instream flows of the rapidly urbanizing watersheds and estuaries of the Gulf of Mexico in Texas (USA) are increasingly dominated by reclaimed waters. Though ionizable pharmaceuticals have received increasing attention in freshwaters, many research questions remain unanswered, particularly in tidally influenced urban coastal systems, which experience significant spatiotemporal variability in pH that influences bioavailability and bioaccumulation. The authors coupled fish plasma modeling of therapeutic hazard values with field monitoring of water chemistry variability and pharmaceutical occurrence to examine whether therapeutic hazards to fish existed within these urban coastal ecosystems and whether therapeutic hazards differed within and among coastal locations and seasons. Spatial and temporal fluctuations in pH within study sites altered the probability of encountering pharmaceutical hazards to fish. Significant water quality differences were consistently observed among traditional parameters and pharmaceuticals collected from surface and bottom waters, which are rarely sampled during routine surface water quality assessments. The authors then compared modeling predictions of fish plasma concentrations of pharmaceuticals to measured plasma levels from various field-collected fish species. Diphenhydramine and diltiazem were observed in plasma of multiple species, and diltiazem exceeded human therapeutic doses in largemouth bass, catfish, and mullet inhabiting these urban estuaries. Though the present study only examined a small number of target analytes, which represent a microcosm of the exposome of these fish, coastal systems are anticipated to be more strongly influenced by continued urbanization, altered instream flows, and population growth in the future. Unfortunately, aquatic toxicology information for diltiazem and many other pharmaceuticals is not available for marine and estuarine organisms, but such field observations suggest that potential adverse

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

    PubMed

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

    2013-12-01

    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.

  7. Kinetic effects on parallel heat flow and ionization rate in divertor plasmas

    NASA Astrophysics Data System (ADS)

    Allais, Fabrice; Kim, Chang-Geun; Alouani Bibi, Fathallah; Matte, Jean-Pierre; Stotler, Daren; Rognlien, Thomas

    2004-11-01

    1-D simulations of parallel heat flow in divertor plasmas, with and without recycling are made with the UEDGE fluid code, comparing runs using classical flux limited heat flow to nonlocal heat transport [1], now implemented in UEDGE. Comparative simulations are made with the electron kinetic code FPI. For the latter, we prescribe the power input source, which emulates cross field transport, to be identical to that of our UEDGE runs. But, the temperature profile computed by FPI is found to depend very strongly on the assumed velocity dependence of this source, even if the integrated power is the same. The atomic hydrogen ionization module in FPI uses cross sections such that, for Maxwellian plasmas, the rates are the same as those used by UEDGE and DEGAS; this is necessary because step-wise ionization is dominant. There is strong enhancement of the total ionization rate (including stepwise ionization) in cold, detached plasmas, due to nonlocal transport effects. [1] F. Alouani Bibi and J.P. Matte, Phys. Rev. E 66, 066414 (2002)

  8. Effect of high dose natural ionizing radiation on the immune system of the exposed residents of Ramsar Town, Iran.

    PubMed

    Attar, Massoud; Molaie Kondolousy, Yaghob; Khansari, Nemat

    2007-06-01

    Iran is one of several countries that has regions of high dose natural ionizing radiation. Two well-known villages in the suburb of Ramsar Town in the Caspian Sea strip, Taleshmahaleh and Chaparsar, have background radiation that is 13 times higher than normal. This radiation is the result of Radium 226 and Radon gas both of which are highly water soluble. While people living in these regions do not suffer from any major health problems, we decided to study the their immune responses to infection and inflammation in order to determine if their habitat affects their immune defense mechanisms as a way of compensating for their exposure to high dose environmental ionizing radiation. Our results showed that the total serum antioxidant level in the exposed people was significantly lower than the individuals not exposed to high dose natural ionizing radiation. The exposed individuals also had higher lymphocyte-induced IL-4 and IL-10 production, and lower IL-2 and IFN-gamma production. In addition, neutrophil NBT, phagocytosis, and locomotion were higher in the exposed group. In contrast, lymphocyte proliferation in response to PHA was unaffected. We conclude that the immune system of individuals exposed to high dose ionizing radiation has adapted to its environment by shifting from a Type 1 to a Type 2 response to promote anti-inflammation. This may be because inflammatory Type 1 responses generate more free radicals than Type 2 responses, in addition to the free radicals generated as a result of high environmental radiation. Thus, the serum total antioxidant level in the exposed residents was lower than the unexposed group.

  9. Induction of transcription of {open_quotes}Immediate early genes{close_quotes} by low-dose ionizing radiation

    SciTech Connect

    Prasad, A.V.; Mohan, N.; Chandrasekar, B.; Meltz, M.L.

    1995-09-01

    The induction of transition of specific genes after exposure to ionizing radiation has previously been reported after lethal doses of radiation (2-50 Gy). Little attention has been focused on expression of {open_quotes}immediate early genes{close_quotes} after low doses of ionizing radiation, where cell viability remains high. This dose range (0.25-2.0 Gy) is above the diagnostic dose level but at or below the doses typical for a single exposure in fractionated radiotherapy treatment of cancer. In this study, it was observed that doses in the range of 0.25-2.0 Gy induced different amounts of the mRNAs of the proto-oncogenes c-fos, c-jun, c-myc and c-Ha-ras at a given dose and time in Epstein-Barr virus-transformed human lymphoblastoid 244B cells. A maximum response was seen after a dose of 0.5 Gy for all but c-fos, which showed a maximum response after exposure to 0.25 Gy. Time-course studies demonstrated that the induction was transient, reaching a maximum at 1 h and declining to the constitutive level at 4 h after irradiation. Using second-messenger specific inhibitors, the signaling pathways involved in the induction of these proto-oncogenes was also investigated. The results showed that all four of the proto-oncogenes induced after 0.5 Gy shared a common pathway of tyrosine kinase activation. Other signaling pathways included protein kinase C, reactive oxygen intermediates and calcium-dependent kinases; these were found to be differentially involved in the induction of transcription of the individual proto-oncogenes. In summary, this study suggests that low-dose ionizing radiation (0.25-2.0 Gy) can modulate expression of immediate early genes. Secondly, the activation of immediate early genes after low-dose exposure involves multiple second-messenger signaling pathways. Third, the magnitude of involvement of the different signaling pathways after low-dose radiation is different for each proto-oncogene expressed. 43 refs., 6 figs., 1 tab.

  10. Ethylene oxide dose and dose-rate effects in the mouse dominant-lethal test

    SciTech Connect

    Generoso, W.M.; Cain, K.T.; Hughes, L.A.; Sega, G.A.; Braden, P.W.; Gosslee, D.G.; Shelby, M.D.

    1986-01-01

    In the dose-response study, male mice were exposed by inhalation to ethylene oxide (EtO) for 4 consecutive days. Mice were exposed for 6 hr per day to 300 ppm, 400 ppm, or 500 ppm EtO for a daily total of 1800, 2400, or 3000 ppm X hr (total exposures of 7200, 9600 and 12,000 ppm X hr), respectively. In the dose-rate study, mice were given a total exposure of 1800 ppm X hr per day, also for 4 consecutive days, delivered either at 300 ppm in 6 hr, 600 ppm in 3 hr, or 1200 ppm in 1.5 hr. Quantitation of dominant-lethal responses was made on matings involving sperm exposed as late spermatids and early spermatozoa, the most sensitive stages to EtO. In the dose-response study, a dose-related increase in dominant-lethal mutations was observed, the dose-response curve proved to be nonlinear. In the dose-rate study, increasing the exposure concentrations resulted in increased dominant-lethal responses.

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

    NASA Astrophysics Data System (ADS)

    Chatzikyriakou, Eleni; Potter, Kenneth; Redman-White, William; De Groot, C. H.

    2017-02-01

    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 SiO2 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(SiO2).

  12. SU-E-T-145: Beam Characteristics of Flattening Filter Free Beams Including Low Dose Rate Setting

    SciTech Connect

    Uehara, K; Ogata, T; Nakayama, M; Shinji, T; Nishimura, H; Masutani, T; Ishihara, T; Ejima, Y; Sasaki, R

    2015-06-15

    Purpose: In commissioning of volumetric modulated arc therapy (VMAT), it is necessary to evaluate the beam characteristics of various dose rate settings with potential to use. The aim of this study is to evaluate the beam characteristics of flattened and flattening filter free (FFF) including low dose rate setting. Methods: We used a Varian TrueBeam with Millennium 120 MLC. Both 6 and 10 MV beams with or without flattening filter were used for this study. To evaluate low-dose rate FFF beams, specially-designed leaf sequence files control out-of-field MLC leaf pair at constant dose rate ranging from 80 to 400 MU/min. For dose rate from 80 MU/min to the maximum usable value of all energies, beam output were measured using ionization chamber (CC04, IBA). The ionization chamber was inserted into water equivalent phantom (RT3000-New, R-tech), and the phantom was set with SAD of 100cm. The beam profiles were performed using the 2D diode array (Profiler2, Sun Nuclear). The SSD was set to 90cm and a combined 30cmx30cmx9cm phantom which consisted of solid water slabs was put on the device. All measurement were made using 100MU irradiation for 10cmx10cm jaw-defined field size with a gantry angle of 0°. Results: In all energies, the dose rate dependences with beam output and variation coefficient were within 0.2% and 0.07%, respectively. The flatness and symmetry exhibited small variations (flatness ≤0.1 point and symmetry≤0.3 point at absolute difference). Conclusion: We had studied the characteristics of flattened and FFF beam over the 80 MU/min. Our results indicated that the beam output and profiles of FFF of TrueBeam linac were highly stable at low dose rate setting.

  13. Membrane Signaling Induced by High Doses of Ionizing Radiation in the Endothelial Compartment. Relevance in Radiation Toxicity

    PubMed Central

    Corre, Isabelle; Guillonneau, Maëva; Paris, François

    2013-01-01

    Tumor areas can now be very precisely delimited thanks to technical progress in imaging and ballistics. This has also led to the development of novel radiotherapy protocols, delivering higher doses of ionizing radiation directly to cancer cells. Despite this, radiation toxicity in healthy tissue remains a major issue, particularly with dose-escalation in these new protocols. Acute and late tissue damage following irradiation have both been linked to the endothelium irrigating normal tissues. The molecular mechanisms involved in the endothelial response to high doses of radiation are associated with signaling from the plasma membrane, mainly via the acid sphingomyelinase/ceramide pathway. This review describes this signaling pathway and discusses the relevance of targeting endothelial signaling to protect healthy tissues from the deleterious effects of high doses of radiation. PMID:24252908

  14. Absolute dose measurements by means of a small cylindrical ionization chamber for very high dose per pulse high energy electron beams

    SciTech Connect

    Karaj, E.; Righi, S.; Di Martino, F.

    2007-03-15

    Very high dose per pulse (3-13 cGy/pulse) high energy electron beams are currently produced by special linear accelerators (linac) dedicated to Intra Operative Radiation Therapy (IORT). The electron beams produced by such linacs are collimated by special Perspex applicators of various size and cylindrically shaped. The biggest problems from the dosimetric point of view are caused by the high dose-per-pulse values and the use of inclined applicators. In this work measurements of absolute dose for the inclined applicators were done by using a small cylindrical ionization chamber, type CC01 (Wellhofer), a parallel plane ionization chamber type Markus (PTW 23343) and radiochromic films type EBT. We show a method which allows calculating the quality correction factors for CC01 chamber with an uncertainty of 1% and the absolute dose value for the inclined applicators using CC01 with an uncertainty of 3.1% for electron beams of energy of 6 and 7 MeV produced by the linac dedicated to IORT Novac7.

  15. Radiobiological evaluation of low dose-rate prostate brachytherapy implants

    NASA Astrophysics Data System (ADS)

    Knaup, Courtney James

    Low dose-rate brachytherapy is a radiation therapy treatment for men with prostate cancer. While this treatment is common, the use of isotopes with varying dosimetric characteristics means that the prescription level and normal organ tolerances vary. Additionally, factors such as prostate edema, seed loss and seed migration may alter the dose distribution within the prostate. The goal of this work is to develop a radiobiological response tool based on spatial dose information which may be used to aid in treatment planning, post-implant evaluation and determination of the effects of prostate edema and seed migration. Aim 1: Evaluation of post-implant prostate edema and its dosimetric and biological effects. Aim 2: Incorporation of biological response to simplify post-implant evaluation. Aim 3: Incorporation of biological response to simplify treatment plan comparison. Aim 4: Radiobiologically based comparison of single and dual-isotope implants. Aim 5: Determine the dosimetric and radiobiological effects of seed disappearance and migration.

  16. Preliminary Radiation Analysis of the Total Ionizing Dose for the Resource Prospector Mission

    NASA Technical Reports Server (NTRS)

    Rojdev, Kristina; Tylka, Allan J.; Atwell, William

    2015-01-01

    NASA's Resource Prospector (RP) is a collaborative project between multiple centers and institutions to search for volatiles at the polar regions of the Moon as a potential resource for oxygen and propellant production. The mission is rated Class D and will be the first In-Situ Resource Utilization (ISRU) demonstration on the lunar surface and at the lunar poles. Given that this mission is rated Class D, the project is considering using commercial off the shelf (COTS) electronics parts to reduce cost. However, COTS parts can be more susceptible to space radiation than typical aerospace electronic parts and carry some additional risk. Thus, prior to parts selection, having a better understanding of the radiation environment can assist designers in the parts selection process. The focus of this paper is to provide a preliminary analysis of the radiation environment from launch, through landing on the surface, and some surface stay as an initial step in determining worst case mission doses to assist designers in screening out electronic parts that would not meet the potential dose levels experienced on this mission.

  17. Radiation-induced failures and degradation of wireless real-time dosimeter under high-dose-rate irradiation

    NASA Astrophysics Data System (ADS)

    Tsuchiya, K.; Kuroki, K.; Akiba, N.; Kurosawa, K.; Matsumoto, T.; Nishiyama, J.; Harano, H.

    2010-04-01

    Radiation-induced malfunction and degradation of electronic modules in certain operating conditions are described in this report. The cumulative radiation effects on Atmel AVR microcontrollers, and 2.4 GHz and 303 MHz wireless network devices were evaluated under gamma ray irradiation with dose rates of 100, 10 and 3 Gy/h. The radiation-induced malfunctions occurred at doses of 510+/-22 Gy for AVR microcontrollers, and 484+/-111 and 429+/-14 Gy for 2.4 GHz and 303 MHz wireless network devices, respectively, under a 100 Gy/h equivalent dose rate. The degradation of microcontrollers occurred for total ionizing doses between 400 and 600 Gy under X-ray irradiation. In addition, we evaluated the reliability of neutron dosimeters using a standard neutron field. One of the neutron dosimeters gave a reading that was half of the standard field value.

  18. Dosimetric Study of a Low-Dose-Rate Brachytherapy Source

    NASA Astrophysics Data System (ADS)

    Rodríguez-Villafuerte, M.; Arzamendi, S.; Díaz-Perches, R.

    Carcinoma of the cervix is the most common malignancy - in terms of both incidence and mortality - in Mexican women. Low dose rate (LDR) intracavitary brachytherapy is normally prescribed for the treatment of this disease to the vast majority of patients attending public hospitals in our country. However, most treatment planning systems being used in these hospitals still rely on Sievert integral dose calculations. Moreover, experimental verification of dose distributions are hardly ever done. In this work we present a dosimetric characterisation of the Amersham CDCS-J 137Cs source, an LDR brachytherapy source commonly used in Mexican hospitals. To this end a Monte Carlo simulation was developed, that includes a realistic description of the internal structure of the source embedded in a scattering medium. The Monte Carlo results were compared to experimental measurements of dose distributions. A lucite phantom with the same geometric characteristics as the one used in the simulation was built. Dose measurements were performed using thermoluminescent dosimeters together with commercial RadioChromic dye film. A comparison between our Monte Carlo simulation, the experimental data, and results reported in the literature is presented.

  19. Structure factors for tunneling ionization rates of molecules: General Hartree-Fock-based integral representation

    NASA Astrophysics Data System (ADS)

    Madsen, Lars Bojer; Jensen, Frank; Dnestryan, Andrey I.; Tolstikhin, Oleg I.

    2017-07-01

    In the leading-order approximation of the weak-field asymptotic theory (WFAT), the dependence of the tunneling ionization rate of a molecule in an electric field on its orientation with respect to the field is determined by the structure factor of the ionizing molecular orbital. The WFAT yields an expression for the structure factor in terms of a local property of the orbital in the asymptotic region. However, in general quantum chemistry approaches molecular orbitals are expanded in a Gaussian basis which does not reproduce their asymptotic behavior correctly. This hinders the application of the WFAT to polyatomic molecules, which are attracting increasing interest in strong-field physics. Recently, an integral-equation approach to the WFAT for tunneling ionization of one electron from an arbitrary potential has been developed. The structure factor is expressed in an integral form as a matrix element involving the ionizing orbital. The integral is not sensitive to the asymptotic behavior of the orbital, which resolves the difficulty mentioned above. Here, we extend the integral representation for the structure factor to many-electron systems treated within the Hartree-Fock method and show how it can be implemented on the basis of standard quantum chemistry software packages. We validate the methodology by considering noble-gas atoms and the CO molecule, for which accurate structure factors exist in the literature. We also present benchmark results for CO2 and for NH3 in the pyramidal and planar geometries.

  20. Limitations of the TG-43 formalism for skin high-dose-rate brachytherapy dose calculations

    SciTech Connect

    Granero, Domingo; Perez-Calatayud, Jose; Vijande, Javier; Ballester, Facundo; Rivard, Mark J.

    2014-02-15

    Purpose: In skin high-dose-rate (HDR) brachytherapy, sources are located outside, in contact with, or implanted at some depth below the skin surface. Most treatment planning systems use the TG-43 formalism, which is based on single-source dose superposition within an infinite water medium without accounting for the true geometry in which conditions for scattered radiation are altered by the presence of air. The purpose of this study is to evaluate the dosimetric limitations of the TG-43 formalism in HDR skin brachytherapy and the potential clinical impact. Methods: Dose rate distributions of typical configurations used in skin brachytherapy were obtained: a 5 cm × 5 cm superficial mould; a source inside a catheter located at the skin surface with and without backscatter bolus; and a typical interstitial implant consisting of an HDR source in a catheter located at a depth of 0.5 cm. Commercially available HDR{sup 60}Co and {sup 192}Ir sources and a hypothetical {sup 169}Yb source were considered. The Geant4 Monte Carlo radiation transport code was used to estimate dose rate distributions for the configurations considered. These results were then compared to those obtained with the TG-43 dose calculation formalism. In particular, the influence of adding bolus material over the implant was studied. Results: For a 5 cm × 5 cm{sup 192}Ir superficial mould and 0.5 cm prescription depth, dose differences in comparison to the TG-43 method were about −3%. When the source was positioned at the skin surface, dose differences were smaller than −1% for {sup 60}Co and {sup 192}Ir, yet −3% for {sup 169}Yb. For the interstitial implant, dose differences at the skin surface were −7% for {sup 60}Co, −0.6% for {sup 192}Ir, and −2.5% for {sup 169}Yb. Conclusions: This study indicates the following: (i) for the superficial mould, no bolus is needed; (ii) when the source is in contact with the skin surface, no bolus is needed for either {sup 60}Co and {sup 192}Ir. For

  1. Limitations of the TG-43 formalism for skin high-dose-rate brachytherapy dose calculations

    SciTech Connect

    Granero, Domingo; Perez-Calatayud, Jose; Vijande, Javier; Ballester, Facundo; Rivard, Mark J.

    2014-02-15

    Purpose: In skin high-dose-rate (HDR) brachytherapy, sources are located outside, in contact with, or implanted at some depth below the skin surface. Most treatment planning systems use the TG-43 formalism, which is based on single-source dose superposition within an infinite water medium without accounting for the true geometry in which conditions for scattered radiation are altered by the presence of air. The purpose of this study is to evaluate the dosimetric limitations of the TG-43 formalism in HDR skin brachytherapy and the potential clinical impact. Methods: Dose rate distributions of typical configurations used in skin brachytherapy were obtained: a 5 cm × 5 cm superficial mould; a source inside a catheter located at the skin surface with and without backscatter bolus; and a typical interstitial implant consisting of an HDR source in a catheter located at a depth of 0.5 cm. Commercially available HDR{sup 60}Co and {sup 192}Ir sources and a hypothetical {sup 169}Yb source were considered. The Geant4 Monte Carlo radiation transport code was used to estimate dose rate distributions for the configurations considered. These results were then compared to those obtained with the TG-43 dose calculation formalism. In particular, the influence of adding bolus material over the implant was studied. Results: For a 5 cm × 5 cm{sup 192}Ir superficial mould and 0.5 cm prescription depth, dose differences in comparison to the TG-43 method were about −3%. When the source was positioned at the skin surface, dose differences were smaller than −1% for {sup 60}Co and {sup 192}Ir, yet −3% for {sup 169}Yb. For the interstitial implant, dose differences at the skin surface were −7% for {sup 60}Co, −0.6% for {sup 192}Ir, and −2.5% for {sup 169}Yb. Conclusions: This study indicates the following: (i) for the superficial mould, no bolus is needed; (ii) when the source is in contact with the skin surface, no bolus is needed for either {sup 60}Co and {sup 192}Ir. For

  2. Activity concentrations and dose rates from decorative granite countertops.

    PubMed

    Llope, W J

    2011-06-01

    The gamma radiation emitted from a variety of commercial decorative granites available for use in U.S. homes has been measured with portable survey meters as well as an NaI(Th) gamma spectrometer. The (40)K, U-nat, and (232)Th activity concentrations were determined using a full-spectrum analysis. The dose rates that would result from two different arrangements of decorative granite slabs as countertops were explored in simulations involving an adult anthropomorphic phantom.

  3. NAC-1 cask dose rate calculations for LWR spent fuel

    SciTech Connect

    CARLSON, A.B.

    1999-02-24

    A Nuclear Assurance Corporation nuclear fuel transport cask, NAC-1, is being considered as a transport and storage option for spent nuclear fuel located in the B-Cell of the 324 Building. The loaded casks will be shipped to the 200 East Area Interim Storage Area for dry interim storage. Several calculations were performed to assess the photon and neutron dose rates. This report describes the analytical methods, models, and results of this investigation.

  4. Ambient dose and dose rate measurements in the vicinity of Elekta Precise accelerators for radiation therapy.

    PubMed

    Zutz, H; Hupe, O

    2014-12-01

    In radiation therapy, commercially available medical linear accelerators (LINACs) are used. At high primary beam energies in the 10-MeV range, the leakage dose of the accelerator head and the backscatter from the room walls, the air and the patient become more important. Therefore, radiation protection measurements of photon dose rates in the treatment room and in the maze are performed to quantify the radiation field. Since the radiation of the LINACs is usually pulsed with short radiation pulse durations in the microsecond range, there are problems with electronic dose (rate) meters commonly used in radiation protection. In this paper measurements with ionisation chambers are presented and electronic dosemeters are used for testing at selected positions. The measured time-averaged dose rate ranges from a few microsieverts per hour in the maze to some millisieverts per hour in the vicinity of the accelerator head and up to some sieverts per hour in the blanked primary beam and several hundred sieverts per hour in the direct primary beam.

  5. Blackbody-induced decay, excitation and ionization rates for Rydberg states in hydrogen and helium atoms

    NASA Astrophysics Data System (ADS)

    Glukhov, I. L.; Nekipelov, E. A.; Ovsiannikov, V. D.

    2010-06-01

    New features of the blackbody-induced radiation processes on Rydberg atoms were discovered on the basis of numerical data for the blackbody-induced decay Pdnl(T), excitation Penl(T) and ionization Pionnl(T) rates of nS, nP and nD Rydberg states calculated together with the spontaneous decay rates Pspnl in neutral hydrogen, and singlet and triplet helium atoms for some values of the principal quantum number n from 10 to 500 at temperatures from T = 100 K to 2000 K. The fractional rates Rd(e, ion)nl(T) = Pnld(e, ion)(T)/Pspnl equal to the ratio of the induced decay (excitation, ionization) rates to the rate of spontaneous decay were determined as functions of T and n in every series of states with a given angular momentum l = 0, 1, 2. The calculated data reveal an essential difference between the asymptotic dependence of the ionization rate Pionnl(T) and the rates of decay and excitation Pd(e)nl(T)~T/n2. The departures appear in each Rydberg series for n > 100 and introduce appreciable corrections to the formula of Cooke and Gallagher. Two different approximation formulae are proposed on the basis of the numerical data, one for Rd(e)nl(T) and another one for Rionnl(T), which reproduce the calculated values in wide ranges of principal quantum number from n = 10 to 1000 and temperatures between T = 100 K and T = 2000 K with an accuracy of 2% or better. Modified Fues' model potential approach was used for calculating matrix elements of bound-bound and bound-free radiation transitions in helium.

  6. Total ionizing dose effects on a radiation-induced BiMOS analog-to-digital converter

    NASA Astrophysics Data System (ADS)

    Xue, Wu; Wu, Lu; Yiyuan, Wang; Jialing, Xu; Leqing, Zhang; Jian, Lu; Xin, Yu; Xingyao, Zhang; Tianle, Hu

    2013-01-01

    The total dose effect of an AD678 with a BiMOS process is studied. We investigate the performance degradation of the device in different bias states and at several dose rates. The results show that an AD678 can endure 3 krad(Si) at low dose rate and 5 krad(Si) at a high dose rate for static bias. The sensitive parameters to the bias states also differ distinctly. We find that the degradation is more serious on static bias. The underlying mechanisms are discussed in detail.

  7. Mass-loss rates, ionization fractions, shock velocities, and magnetic fields of stellar jets

    NASA Technical Reports Server (NTRS)

    Hartigan, Patrick; Morse, Jon A.; Raymond, John

    1994-01-01

    In this paper we calculate emission-line ratios from a series of planar radiative shock models that cover a wide range of shock velocities, preshock densities, and magnetic fields. The models cover the initial conditions relevant to stellar jets, and we show how to estimate the ionization fractions and shock velocities in jets directly from observations of the strong emission lines in these flows. The ionization fractions in the HH 34, HH 47, and HH 111 jets are approximately 2%, considerably smaller than previous estimates, and the shock velocities are approximately 30 km/s. For each jet the ionization fractions were found from five different line ratios, and the estimates agree to within a factor of approximately 2. The scatter in the estimates of the shock velocities is also small (+/- 4 km/s). The low ionization fractions of stellar jets imply that the observed electron densities are much lower than the total densities, so the mass-loss rates in these flows are correspondingly higher (approximately greater than 2 x 10(exp -7) solar mass/yr). The mass-loss rates in jets are a significant fraction (1%-10%) of the disk accretion rates onto young stellar objects that drive the outflows. The momentum and energy supplied by the visible portion of a typical stellar jet are sufficient to drive a weak molecular outflow. Magnetic fields in stellar jets are difficult to measure because the line ratios from a radiative shock with a magnetic field resemble those of a lower velocity shock without a field. The observed line fluxes can in principle indicate the strength of the field if the geometry of the shocks in the jet is well known.

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

    NASA Technical Reports Server (NTRS)

    Topper, Alyson D.; Campola, Michael J.; Chen, Dakai; Casey, Megan C.; Yau, Ka-Yen; Cochran, Donna J.; LaBel, Kenneth A.; Ladbury, Raymond L.; Lauenstein, Jean-Marie; Mondy, Timothy K.; hide

    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 optoelectronics, digital, analog, linear bipolar devices, and hybrid devices.

  9. Measurements with a Ge detector and Monte Carlo computations of dose rate yields due to cosmic muons.

    PubMed

    Clouvas, A; Xanthos, S; Antonopoulos-Domis, M; Silva, J

    2003-02-01

    The present work shows how portable Ge detectors can be useful for measurements of the dose rate due to ionizing cosmic radiation. The methodology proposed converts the cosmic radiation induced background in a Ge crystal (energy range above 3 MeV) to the absorbed dose rate due to muons, which are responsible for 75% of the cosmic radiation dose rate at sea level. The key point is to observe in the high energy range (above 20 MeV) the broad muon peak resulting from the most probable energy loss of muons in the Ge detector. An energy shift of the muon peak was observed, as expected, for increasing dimensions of three Ge crystals (10%, 20%, and 70% efficiency). Taking into account the dimensions of the three detectors the location of the three muon peaks was reproduced by Monte Carlo computations using the GEANT code. The absorbed dose rate due to muons has been measured in 50 indoor and outdoor locations at Thessaloniki, the second largest town of Greece, with a portable Ge detector and converted to the absorbed dose rate due to muons in an ICRU sphere representing the human body by using a factor derived from Monte Carlo computations. The outdoor and indoor mean muon dose rate was 25 nGy h(-1) and 17.8 nGy h(-1), respectively. The shielding factor for the 40 indoor measurements ranges from 0.5 to 0.9 with a most probable value between 0.7-0.8.

  10. Low-dose ionizing radiation-induced blood plasma metabolic response in a diverse genetic mouse population.

    PubMed

    Lee, Do Yup; Bowen, Benjamin P; Nguyen, David H; Parsa, Sara; Huang, Yurong; Mao, Jian-Hua; Northen, Trent R

    2012-12-01

    Understanding the biological effects and biochemical mechanisms of low-dose ionizing radiation (LDIR) is important for setting exposure limits for the safe use of nuclear power and medical diagnostic procedures. Although several studies have highlighted the effects of ionizing radiation on metabolism, most studies have focused on uniform genetic mouse populations. Here, we report the metabolic response to LDIR (10 cGy X ray) on a genetically diverse mouse population (142 mice) generated from a cross of radiation-sensitive (BALB/c) and radiation-resistant (SPRET/EiJ) parental strains. GC-TOF profiling of plasma metabolites was used to compare exposed vs. sham animals. From this, 16 metabolites were significantly altered in the LDIR treated vs. sham group. Use of two significantly altered metabolites, thymine and 2-monostearin, was found to effectively segregate the two treatments. Multivariate statistical analysis was used to identify genetic polymorphisms correlated with metabolite abundance (e.g., amino acids, fatty acids, nucleotides and TCA cycle intermediates). Genetic analysis of metabolic phenotypes showed suggestive linkages for fatty acid and amino acid metabolism. However, metabolite abundance was found to be a function of low-dose ionizing radiation exposure, and not of the underlying genetic variation.

  11. Construction and validation of a dose-response curve using the comet assay to determine human radiosensitivity to ionizing radiation.

    PubMed

    Güerci, A; Zúñiga, L; Marcos, R

    2011-01-01

    Individual radiosensitivity is an individual characteristic associated with an increased reaction to ionizing radiation. The purpose of our work is to establish a dose-response curve useful to classify individuals as radiosensitive or radioresistant. Thus, a dose-response curve was constructed by measuring in vitro responses to increasing doses (0 to 8 Gy) of gamma radiation in the comet assay. The obtained curve fit well with a linear equation in the range of 0 to 8 Gy. The overall dose-response curve was constructed for percent DNA in tail, as a measure of the genetic damage induced by irradiation. To probe the goodness of the constructed curve, a validation study was carried out with whole blood from two donors in a blind study. Results show that, for the two applied doses (2 and 6 Gy), the obtained values fit well inside the interval of confidence of the curve. In conclusion, our results demonstrate the usefulness of the comet assay in determining individual responses to defined doses of gamma radiation. The standard dose-response curve constructed may be used to detect individuals departing from reference values.

  12. Design and characterization of a new high-dose-rate brachytherapy Valencia applicator for larger skin lesions.

    PubMed

    Candela-Juan, C; Niatsetski, Y; van der Laarse, R; Granero, D; Ballester, F; Perez-Calatayud, J; Vijande, J

    2016-04-01

    The aims of this study were (i) to design a new high-dose-rate (HDR) brachytherapy applicator for treating surface lesions with planning target volumes larger than 3 cm in diameter and up to 5 cm in size, using the microSelectron-HDR or Flexitron afterloader (Elekta Brachytherapy) with a (192)Ir source; (ii) to calculate by means of the Monte Carlo (MC) method the dose distribution for the new applicator when it is placed against a water phantom; and (iii) to validate experimentally the dose distributions in water. The penelope2008 MC code was used to optimize dwell positions and dwell times. Next, the dose distribution in a water phantom and the leakage dose distribution around the applicator were calculated. Finally, MC data were validated experimentally for a (192)Ir mHDR-v2 source by measuring (i) dose distributions with radiochromic EBT3 films (ISP); (ii) percentage depth-dose (PDD) curve with the parallel-plate ionization chamber Advanced Markus (PTW); and (iii) absolute dose rate with EBT3 films and the PinPoint T31016 (PTW) ionization chamber. The new applicator is made of tungsten alloy (Densimet) and consists of a set of interchangeable collimators. Three catheters are used to allocate the source at prefixed dwell positions with preset weights to produce a homogenous dose distribution at the typical prescription depth of 3 mm in water. The same plan is used for all available collimators. PDD, absolute dose rate per unit of air kerma strength, and off-axis profiles in a cylindrical water phantom are reported. These data can be used for treatment planning. Leakage around the applicator was also scored. The dose distributions, PDD, and absolute dose rate calculated agree within experimental uncertainties with the doses measured: differences of MC data with chamber measurements are up to 0.8% and with radiochromic films are up to 3.5%. The new applicator and the dosimetric data provided here will be a valuable tool in clinical practice, making treatment of

  13. Design and characterization of a new high-dose-rate brachytherapy Valencia applicator for larger skin lesions

    SciTech Connect

    Candela-Juan, C.; Niatsetski, Y.; Laarse, R. van der; Granero, D.; Ballester, F.; Perez-Calatayud, J.; Vijande, J.

    2016-04-15

    Purpose: The aims of this study were (i) to design a new high-dose-rate (HDR) brachytherapy applicator for treating surface lesions with planning target volumes larger than 3 cm in diameter and up to 5 cm in size, using the microSelectron-HDR or Flexitron afterloader (Elekta Brachytherapy) with a {sup 192}Ir source; (ii) to calculate by means of the Monte Carlo (MC) method the dose distribution for the new applicator when it is placed against a water phantom; and (iii) to validate experimentally the dose distributions in water. Methods: The PENELOPE2008 MC code was used to optimize dwell positions and dwell times. Next, the dose distribution in a water phantom and the leakage dose distribution around the applicator were calculated. Finally, MC data were validated experimentally for a {sup 192}Ir mHDR-v2 source by measuring (i) dose distributions with radiochromic EBT3 films (ISP); (ii) percentage depth–dose (PDD) curve with the parallel-plate ionization chamber Advanced Markus (PTW); and (iii) absolute dose rate with EBT3 films and the PinPoint T31016 (PTW) ionization chamber. Results: The new applicator is made of tungsten alloy (Densimet) and consists of a set of interchangeable collimators. Three catheters are used to allocate the source at prefixed dwell positions with preset weights to produce a homogenous dose distribution at the typical prescription depth of 3 mm in water. The same plan is used for all available collimators. PDD, absolute dose rate per unit of air kerma strength, and off-axis profiles in a cylindrical water phantom are reported. These data can be used for treatment planning. Leakage around the applicator was also scored. The dose distributions, PDD, and absolute dose rate calculated agree within experimental uncertainties with the doses measured: differences of MC data with chamber measurements are up to 0.8% and with radiochromic films are up to 3.5%. Conclusions: The new applicator and the dosimetric data provided here will be a valuable

  14. Genome Wide Evaluation of Normal Human Tissue in Response to Controlled, In vivo Low-Dose Low LET Ionizing Radiation Exposure: Pathways and Mechanisms Final Report, September 2013

    SciTech Connect

    Rocke, David M.

    2013-09-09

    During course of this project, we have worked in several areas relevant to low-dose ionizing radiation. Using gene expression to measure biological response, we have examined the response of human skin exposed in-vivo to radation, human skin exposed ex-vivo to radiation, and a human-skin model exposed to radiation. We have learned a great deal about the biological response of human skin to low-dose ionizing radiation.

  15. Core hole screening and decay rates of double core ionized first row hydrides.

    PubMed

    Inhester, L; Groenhof, G; Grubmüller, H

    2013-04-28

    Because of the high intensity, X-ray free electron lasers allow one to create and probe double core ionized states in molecules. The decay of these multiple core ionized states crucially determines the evolution of radiation damage in single molecule diffractive imaging experiments. Here we have studied the Auger decay in hydrides of first row elements after single and double core ionization by quantum mechanical ab initio calculations. In our approach the continuum wave function of the emitted Auger electron is expanded into spherical harmonics on a radial grid. The obtained decay rates of double K-shell vacancies were found to be systematically larger than those for the respective single K-shell vacancies, markedly exceeding the expected factor of two. This enhancement is attributed to the screening effects induced by the core hole. We propose a simple model, which is able to predict core hole decay rates in molecules with low Z elements based on the electron density in the vicinity of the core hole.

  16. Does non-ionizing radiant energy affect determination of the evaporation rate by the gradient method?

    PubMed

    Kjartansson, S; Hammarlund, K; Oberg, P A; Sedin, G

    1991-01-01

    A study was performed to investigate whether measurements of the evaporation rate from the skin of newborn infants by the gradient method are affected by the presence of non-ionizing radiation from phototherapy equipment or a radiant heater. The evaporation rate was measured experimentally with the measuring sensors either exposed to or protected from non-ionizing radiation. Either blue light (phototherapy) or infrared light (radiant heater) was used; in the former case the evaporation rate was measured from a beaker of water covered with a semipermeable membrane, and in the latter case from the hand of an adult subject, aluminium foil or with the measuring probe in the air. No adverse effect on the determinations of the evaporation rate was found in the presence of blue light. Infrared radiation caused an error of 0.8 g/m2h when the radiant heater was set at its highest effect level or when the ambient humidity was high. At low and moderate levels the observed evaporation rate was not affected. It is concluded that when clinical measurements are made from the skin of newborn infants nursed under a radiant heater, the evaporation rate can appropriately be determined by the gradient method.

  17. High doses of ionizing radiation on bone repair: is there effect outside the irradiated site?

    PubMed

    Rocha, Flaviana Soares; Dias, Pâmella Coelho; Limirio, Pedro Henrique Justino Oliveira; Lara, Vitor Carvalho; Batista, Jonas Dantas; Dechichi, Paula

    2017-03-01

    Local ionizing radiation causes damage to bone metabolism, it reduces blood supply and cellularity over time. Recent studies indicate that radiation promotes biological response outside the treatment field. The aim of this study was to investigate the effects of ionizing radiation on bone repair outside the irradiated field. Ten healthy male Wistar rats were used; and five animals were submitted to radiotherapy on the left femur. After 4 weeks, in all animals were created bone defects in the right and left femurs. Seven days after surgery, animals were euthanized. The femurs were removed and randomly divided into 3 groups (n=5): Control (C) (right femur of the non-irradiated animals); Local ionizing radiation (IR) (left femur of the irradiated animals); Contralateral ionizing radiation (CIR) (right femur of the irradiated animals). The femurs were processed and embedded in paraffin; and bone histologic sections were evaluated to quantify the bone neoformation. Histomorphometric analysis showed that there was no significant difference between groups C (24.6±7.04) and CIR (25.3±4.31); and IR group not showed bone neoformation. The results suggest that ionizing radiation affects bone repair, but does not interfere in bone repair distant from the primary irradiated site.

  18. Static field ionization rates for multi-electron atoms and small molecules

    NASA Astrophysics Data System (ADS)

    Pramod Majety, Vinay; Scrinzi, Armin

    2015-12-01

    We present an application of the hybrid anti-symmetrized coupled channels approach to compute static field ionization rates for multi-electron atoms (He, Ne, Ar) and small molecules (H2, N2, CO). While inert gas atoms behave as effective single electron systems, molecules exhibit multi-electron effects in the form of core polarization. It is shown that at moderate field strengths, these effects can be modeled to about 10% accuracy using a few (5-6) channel ansatz. In the case of the CO molecule, description of core polarization is essential for the correct prediction of the maximum ionization direction and our converged results are in good agreement with the experimental measurements.

  19. [Metabolic effect of amaranth oil and impulse hypoxic training under chronic fluoride intoxication and small doses of ionizing radiation].

    PubMed

    Konyk, U V; Hzhehots'kyĭ, M P; Koval'chuk, S M

    2002-01-01

    Lipid peroxidation and antioxidative defence system in blood, liver and heart tissues, nitric oxide metabolites content in brain tissue of rats under binary action of small-doses of ionizing radiation and fluoride intoxication treated by amaranth oil and interval hypoxic training have been studied. Complex using of amaranth oil and interval hypoxic training result in increase both enzymatic, as nonezymatic links of antioxidant defence in all investigated tissues. It was revealed also enhance of NO system metabolites content in brain gomogenate. In this conditions lipid peroxidation processes in liver and heart tissues normalize comparison with essential increase level LPO under binary action influence. On the basis of obtained results LPO metabolites content we can suppossed that complex using of amaranth oil and interval hypoxic training result in increase of organism adaptative possibility. This complex can be using for binary action of ionizing radiation and fluoride intoxication correction.

  20. What Have "Omics" Taught Us about the Health Risks Associated with Exposure to Low Doses of Ionizing Radiation

    SciTech Connect

    Morgan, William F.; Sowa, Marianne B.

    2011-04-27

    There is a plethora of data available on the DNA damages associated with exposures to ionizing radiation and the subsequent cellular responses. Indeed, much of radiation research has focused on these initial insults and induced responses, particularly DNA repair, cell signaling pathways, cell cycle checkpoint control, mutation induction, chromosomal rearrangements, transformation and apoptosis etc. While many of these endpoints correlate with exposure dose, few, if any, provide substantive information on human health risk(s) associated with radiation exposure. Here the contribution of recent advances in high throughput ‘omics technologies are evaluated to examine what they have taught us about health risk(s) to humans associated with exposure to ionizing radiation.

  1. Total ionizing dose and single-event effect in vertical channel double-gate nMOSFETs

    NASA Astrophysics Data System (ADS)

    Tan, Fei; An, Xia; Xue, Shoubin; Huang, Liangxi; Wu, Weikang; Zhang, Xing; Huang, Ru

    2013-05-01

    In this paper, the total ionizing dose (TID) and single-event effect (SEE) in vertical channel double-gate (DG) nMOSFETs are comprehensively investigated. Due to the vertical channel structure and the excellent gate control capability, the vertical channel DG transistor is relatively resistant to TID and transient ionization effect. However, the dc characteristics of vertical channel DG device are very sensitive to permanent damage induced by a few ions hitting the device. The on-state current and transconductance of the vertical channel DG MOSFETs show significant degradation after exposure to heavy ions, which is attributed to the formation of displacement damage in the channel. As the device feature size scales down to the deca-nanometer regime, the influence of permanent damage induced by a few ions striking the device static performance cannot be ignored and should be seriously considered in radiation-hardened technologies.

  2. Low-dose-rate, low-dose irradiation delays neurodegeneration in a model of retinitis pigmentosa.

    PubMed

    Otani, Atsushi; Kojima, Hiroshi; Guo, Congrong; Oishi, Akio; Yoshimura, Nagahisa

    2012-01-01

    The existence of radiation hormesis is controversial. Several stimulatory effects of low-dose (LD) radiation have been reported to date; however, the effects on neural tissue or neurodegeneration remain unknown. Here, we show that LD radiation has a neuroprotective effect in mouse models of retinitis pigmentosa, a hereditary, progressive neurodegenerative disease that leads to blindness. Various LD radiation doses were administered to the eyes in a retinal degeneration mouse model, and their pathological and physiological effects were analyzed. LD gamma radiation in a low-dose-rate (LDR) condition rescues photoreceptor cell apoptosis both morphologically and functionally. The greatest effect was observed in a condition using 650 mGy irradiation and a 26 mGy/minute dose rate. Multiple rounds of irradiation strengthened this neuroprotective effect. A characteristic up-regulation (563%) of antioxidative gene peroxiredoxin-2 (Prdx2) in the LDR-LD-irradiated retina was observed compared to the sham-treated control retina. Silencing the Prdx2 using small-interfering RNA administration reduced the LDR-LD rescue effect on the photoreceptors. Our results demonstrate for the first time that LDR-LD irradiation has a biological effect in neural cells of living animals. The results support that radiation exhibits hormesis, and this effect may be applied as a novel therapeutic concept for retinitis pigmentosa and for other progressive neurodegenerative diseases regardless of the mechanism of degeneration involved.

  3. Light dose versus rate of delivery: implications for macroalgal productivity.

    PubMed

    Desmond, Matthew J; Pritchard, Daniel W; Hepburn, Christopher D

    2017-04-07

    The role of how light is delivered over time is an area of macroalgal photosynthesis that has been overlooked but may play a significant role in controlling rates of productivity and the structure and persistence of communities. Here we present data that quantify the relative influence of total quantum dose and delivery rate on the photosynthetic productivity of five ecologically important Phaeophyceae species from southern New Zealand. Results suggested that greater net oxygen production occurs when light is delivered at a lower photon flux density (PFD) over a longer period compared to a greater PFD over a shorter period, given the same total dose. This was due to greater efficiency (α) at a lower PFD which, for some species, meant a compensatory effect can occur. This resulted in equal or greater productivity even when the total quantum dose of the lower PFD was significantly reduced. It was also shown that light limitation at Huriawa Peninsula, where macroaglae were sourced, may be restricting the acclimation potential of species at greater depths, and that even at shallow depth periods of significant light limitation are likely to occur. This research is of particular interest as the variability of light delivery to coastal reef systems increases as a result of anthropogenic disturbances, and as the value of in situ community primary productivity estimates is recognised.

  4. Differential Response and Priming Dose Effect on the Proteome of Human Fibroblast and Stem Cells Induced by Exposure to Low Doses of Ionizing Radiation.

    PubMed

    Hauptmann, Monika; Haghdoost, Siamak; Gomolka, Maria; Sarioglu, Hakan; Ueffing, Marius; Dietz, Anne; Kulka, Ulrike; Unger, Kristian; Babini, Gabriele; Harms-Ringdahl, Mats; Ottolenghi, Andrea; Hornhardt, Sabine

    2016-03-01

    It has been suggested that a mechanistic understanding of the cellular responses to low dose and dose rate may be valuable in reducing some of the uncertainties involved in current risk estimates for cancer- and non-cancer-related radiation effects that are inherited in the linear no-threshold hypothesis. In this study, the effects of low-dose radiation on the proteome in both human fibroblasts and stem cells were investigated. Particular emphasis was placed on examining: 1. the dose-response relationships for the differential expression of proteins in the low-dose range (40-140 mGy) of low-linear energy transfer (LET) radiation; and 2. the effect on differential expression of proteins of a priming dose given prior to a challenge dose (adaptive response effects). These studies were performed on cultured human fibroblasts (VH10) and human adipose-derived stem cells (ADSC). The results from the VH10 cell experiments demonstrated that low-doses of low-LET radiation induced unique patterns of differentially expressed proteins for each dose investigated. In addition, a low priming radiation dose significantly changed the protein expression induced by the subsequent challenge exposure. In the ADSC the number of differentially expressed proteins was markedly less compared to VH10 cells, indicating that ADSC differ in their intrinsic response to low doses of radiation. The proteomic results are further discussed in terms of possible pathways influenced by low-dose irradiation.

  5. Dosimetry Modeling for Focal Low-Dose-Rate Prostate Brachytherapy

    SciTech Connect

    Al-Qaisieh, Bashar; Mason, Josh; Bownes, Peter; Henry, Ann; Dickinson, Louise; Ahmed, Hashim U.; Emberton, Mark; Langley, Stephen

    2015-07-15

    Purpose: Focal brachytherapy targeted to an individual lesion(s) within the prostate may reduce side effects experienced with whole-gland brachytherapy. The outcomes of a consensus meeting on focal prostate brachytherapy were used to investigate optimal dosimetry of focal low-dose-rate (LDR) prostate brachytherapy targeted using multiparametric magnetic resonance imaging (mp-MRI) and transperineal template prostate mapping (TPM) biopsy, including the effects of random and systematic seed displacements and interseed attenuation (ISA). Methods and Materials: Nine patients were selected according to clinical characteristics and concordance of TPM and mp-MRI. Retrospectively, 3 treatment plans were analyzed for each case: whole-gland (WG), hemi-gland (hemi), and ultra-focal (UF) plans, with 145-Gy prescription dose and identical dose constraints for each plan. Plan robustness to seed displacement and ISA were assessed using Monte Carlo simulations. Results: WG plans used a mean 28 needles and 81 seeds, hemi plans used 17 needles and 56 seeds, and UF plans used 12 needles and 25 seeds. Mean D90 (minimum dose received by 90% of the target) and V100 (percentage of the target that receives 100% dose) values were 181.3 Gy and 99.8% for the prostate in WG plans, 195.7 Gy and 97.8% for the hemi-prostate in hemi plans, and 218.3 Gy and 99.8% for the focal target in UF plans. Mean urethra D10 was 205.9 Gy, 191.4 Gy, and 92.4 Gy in WG, hemi, and UF plans, respectively. Mean rectum D2 cm{sup 3} was 107.5 Gy, 77.0 Gy, and 42.7 Gy in WG, hemi, and UF plans, respectively. Focal plans were more sensitive to seed displacement errors: random shifts with a standard deviation of 4 mm reduced mean target D90 by 14.0%, 20.5%, and 32.0% for WG, hemi, and UF plans, respectively. ISA has a similar impact on dose-volume histogram parameters for all plan types. Conclusions: Treatment planning for focal LDR brachytherapy is feasible. Dose constraints are easily met with a notable

  6. Low and high dose rate heavy ion radiation-induced intestinal and colonic tumorigenesis in APC(1638N/+) mice.

    PubMed

    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 (APC(1638N/+)) 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 APC(1638N/+) mice after exposure to energetic heavy ions at high (50cGy/min) and relatively low (0.33cGy/min) dose rate. Male and female mice (6-8 weeks old) were exposed to either 10 or 50cGy of (28)Si (energy: 300MeV/n; LET: 70keV/μm) or (56)Fe (energy: 1000MeV/n; LET: 148keV/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 150days after radiation exposure. Intestinal tumorigenesis in male mice exposed to (56)Fe 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 (28)Si 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

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

    NASA Astrophysics Data System (ADS)

    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

  8. Numerical Study of the Wave-Vector Dependence of the Electron Interband Impact Ionization Rate in Bulk GaAs

    NASA Technical Reports Server (NTRS)

    Wang, Yang; Brennan, Kevin F.

    1994-01-01

    Ensemble Monte Carlo calculations of the electron interband impact ionization rate in bulk GaAs are presented using a wave-vector (k)-dependent formulation of the ionization transition rate. The transition rate is evaluated through use of numerically generated wavefunctions determined via a k-p calculation within the first two conduction bonds at numerous points within a finely spaced three-dimensional grid in k space. The transition rate is determined to be greatest for states within the second conduction band. It is found that the interband impact ionization transition rate in bulk GaAs is best characterized as having an exceedingly "soft" threshold energy. As a consequence, the dead space, defined as the distance over which the ionization probability for a given carrier is assumed to be zero, is estimated to be-much larger than that estimated using a "harder" threshold. These results have importance in the design of multiquantum-well avalanche photodiodes.

  9. Numerical study of the wave-vector dependence of the electron interband impact ionization rate in bulk GaAs

    NASA Technical Reports Server (NTRS)

    Wang, Yang; Brennan, Kevin F.

    1994-01-01

    Ensemble Monte Carlo calculations of the electron interband impact ionization rate in bulk GaAs are presented using a wave-vector (k)-dependent formulation of the ionization transition rate. The transition rate is evaluated through the use of numerically generated wavefunctions determined via a k-p calculation within the first two conduction bands at numerous points within a finely spaced three-dimensional grid in k space. The transition rate is determined to be greatest for states within the second conduction band. Is is found that the interband impact ionization transition rate in bulk GaAs is best characterized as having an exceedingly soft threshold energy. As a consequence, the dead space, defined as the distance over which the ionization probability for a given carrier is assumed to be zero, is estimated to be much larger than that estimated using a harder threshold. These results have importance in the design of the multiquantum-well avalanche photodiodes.

  10. The doubling dose of ionizing radiation for drosophilia, mice, and humans

    SciTech Connect

    Neel, J.V.

    1997-10-01

    It is part of the lore of radiation genetics that Drosophila is much more resistant to the genetic effects of radiation than the mouse. For across-species comparisons and risk setting, an estimate of the mutational doubling dose (DD) for human germ cells (immature oocytes and spermatogonia) was approximately 2 Sv equivalents. Neel and Lewis suggested that the population DD for mouse spermatogonia was approximately 1.3 Sv equivalents, with the rate for immature oocytes even higher, because of the failure to recover mutations in the late litters of radiated females. With the incorporation of cluster mutations into the mouse DD estimate, as discussed by Selby here last year, these mouse DD can only go higher. Given the relative agreement between these two mammals, I have now reviewed all the pertinent Drosophila data, the results of which review will be presented. There are many difficulties to combining the results of the various relevant Drosophila studies, but, to a first approximation, a population DD of approximately 4 Gy emerges. There is, thus, given the uncertainties in such estimates, agreement within a factor of 2 between the three species, with such different life histories. The coincidence, to what extent a simple function of target size, and to what extent the result of an evolutionary adjustment by virtue of which induced mutation rates (i.e., repair inefficiencies) are proportional to generation length rather than absolute time.

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

    NASA Technical Reports Server (NTRS)

    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.

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

    NASA Technical Reports Server (NTRS)

    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.

  13. Determination of surface dose rate of indigenous (32)P patch brachytherapy source by experimental and Monte Carlo methods.

    PubMed

    Kumar, Sudhir; Srinivasan, P; Sharma, S D; Saxena, Sanjay Kumar; Bakshi, A K; Dash, Ashutosh; Babu, D A R; Sharma, D N

    2015-09-01

    Isotope production and Application Division of Bhabha Atomic Research Center developed (32)P patch sources for treatment of superficial tumors. Surface dose rate of a newly developed (32)P patch source of nominal diameter 25 mm was measured experimentally using standard extrapolation ionization chamber and Gafchromic EBT film. Monte Carlo model of the (32)P patch source along with the extrapolation chamber was also developed to estimate the surface dose rates from these sources. The surface dose rates to tissue (cGy/min) measured using extrapolation chamber and radiochromic films are 82.03±4.18 (k=2) and 79.13±2.53 (k=2) respectively. The two values of the surface dose rates measured using the two independent experimental methods are in good agreement to each other within a variation of 3.5%. The surface dose rate to tissue (cGy/min) estimated using the MCNP Monte Carlo code works out to be 77.78±1.16 (k=2). The maximum deviation between the surface dose rates to tissue obtained by Monte Carlo and the extrapolation chamber method is 5.2% whereas the difference between the surface dose rates obtained by radiochromic film measurement and the Monte Carlo simulation is 1.7%. The three values of the surface dose rates of the (32)P patch source obtained by three independent methods are in good agreement to one another within the uncertainties associated with their measurements and calculation. This work has demonstrated that MCNP based electron transport simulations are accurate enough for determining the dosimetry parameters of the indigenously developed (32)P patch sources for contact brachytherapy applications.

  14. The Dose Rate Conversion Factors for Nuclear Fallout

    SciTech Connect

    Spriggs, G D

    2009-02-13

    In a previous paper, the composite exposure rate conversion factor (ECF) for nuclear fallout was calculated using a simple theoretical photon-transport model. The theoretical model was used to fill in the gaps in the FGR-12 table generated by ORNL. The FGR-12 table contains the individual conversion factors for approximate 1000 radionuclides. However, in order to calculate the exposure rate during the first 30 minutes following a nuclear detonation, the conversion factors for approximately 2000 radionuclides are needed. From a human-effects standpoint, it is also necessary to have the dose rate conversion factors (DCFs) for all 2000 radionuclides. The DCFs are used to predict the whole-body dose rates that would occur if a human were standing in a radiation field of known exposure rate. As calculated by ORNL, the whole-body dose rate (rem/hr) is approximately 70% of the exposure rate (R/hr) at one meter above the surface. Hence, the individual DCFs could be estimated by multiplying the individual ECFs by 0.7. Although this is a handy rule-of-thumb, a more consistent (and perhaps, more accurate) method of estimating the individual DCFs for the missing radionuclides in the FGR-12 table is to use the linear relationship between DCF and total gamma energy released per decay. This relationship is shown in Figure 1. The DCFs for individual organs in the body can also be estimated from the estimated whole-body DCF. Using the DCFs given FGR-12, the ratio of the organ-specific DCFs to the whole-body DCF were plotted as a function of the whole-body DCF. From these plots, the asymptotic ratios were obtained (see Table 1). Using these asymptotic ratios, the organ-specific DCFs can be estimated using the estimated whole-body DCF for each of the missing radionuclides in the FGR-12 table. Although this procedure for estimating the organ-specific DCFs may over-estimate the value for some low gamma-energy emitters, having a finite value for the organ-specific DCFs in the table is

  15. Radon exhalation rates and gamma doses from ceramic tiles.

    PubMed

    O'Brien, R S; Aral, H; Peggie, J R

    1998-12-01

    This study was carried out to assess the possible radiological hazard resulting from the use of zircon in glaze applied to tiles used in buildings. The 226Ra content of various stains and glazing compounds was measured using gamma spectroscopy and the 222Rn exhalation rates for these materials were measured using adsorption on activated charcoal. The radon exhalation rates were found to be close to or less than the minimum detectable values for the equipment used. This limit was much lower than the estimated exhalation rates, which were calculated assuming that the parameters controlling the emanation and diffusion of 222Rn in the materials studied were similar to those of soil. This implied that the 222Rn emanation coefficients and/or diffusion coefficients for most of the materials studied were very much lower than expected. Measurements on zircon powders showed that the 222Rn emanation coefficient for zircon was much lower than that for soil, indicating that only a small fraction of the 222Rn produced by the decay of 226Ra was able to escape from the zircon grains. The estimated increase in radon concentration in room air and the estimated external gamma radiation dose resulting from the use of zircon glaze are both much lower than the relevant action level and dose limit.

  16. [An investigation of ionizing radiation dose in a manufacturing enterprise of ion-absorbing type rare earth ore].

    PubMed

    Zhang, W F; Tang, S H; Tan, Q; Liu, Y M

    2016-08-20

    Objective: To investigate radioactive source term dose monitoring and estimation results in a manufacturing enterprise of ion-absorbing type rare earth ore and the possible ionizing radiation dose received by its workers. Methods: Ionizing radiation monitoring data of the posts in the control area and supervised area of workplace were collected, and the annual average effective dose directly estimated or estimated using formulas was evaluated and analyzed. Results: In the control area and supervised area of the workplace for this rare earth ore, α surface contamination activity had a maximum value of 0.35 Bq/cm(2) and a minimum value of 0.01 Bq/cm(2); β radioactive surface contamination activity had a maximum value of 18.8 Bq/cm(2) and a minimum value of 0.22 Bq/cm(2). In 14 monitoring points in the workplace, the maximum value of the annual average effective dose of occupational exposure was 1.641 mSv/a, which did not exceed the authorized limit for workers (5 mSv/a) , but exceeded the authorized limit for general personnel (0.25 mSv/a) . The radionuclide specific activity of ionic mixed rare earth oxides was determined to be 0.9. Conclusion: The annual average effective dose of occupational exposure in this enterprise does not exceed the authorized limit for workers, but it exceeds the authorized limit for general personnel. We should pay attention to the focus of the radiation process, especially for public works radiation.

  17. SOD2-mediated adaptive responses induced by low-dose ionizing radiation via TNF signaling and amifostine.

    PubMed

    Murley, J S; Baker, K L; Miller, R C; Darga, T E; Weichselbaum, R R; Grdina, D J

    2011-11-15

    Manganese superoxide dismutase (SOD2)-mediated adaptive processes that protect against radiation-induced micronucleus formation can be induced in cells after a 2-Gy exposure by previously exposing them to either low-dose ionizing radiation (10cGy) or WR1065 (40μM), the active thiol form of amifostine. Although both adaptive processes culminate in elevated levels of SOD2 enzymatic activity, the underlying pathways differ in complexity, with the tumor necrosis factor α (TNFα) signaling pathway implicated in the low-dose radiation-induced response, but not in the thiol-induced pathway. The goal of this study was the characterization of the effects of TNFα receptors 1 and 2 (TNFR1, TNFR2) on the adaptive responses induced by low-dose irradiation or thiol exposure using micronucleus formation as an endpoint. BFS-1 wild-type cells with functional TNFR1 and 2 were exposed 24h before a 2-Gy dose of ionizing radiation to either 10cGy or a 40μM dose of WR1065. BFS2C-SH02 cells, defective in TNFR1, and BFS2C-SH22 cells, defective in both TNFR1 and TNFR2 and generated from BFS2C-SH02 cells by transfection with a murine TNFR2-targeting vector and confirmed to be TNFR2 defective by quantitative PCR, were also exposed under similar conditions for comparison. A 10-cGy dose of radiation induced a significant elevation in SOD2 activity in BFS-1 (P<0.001) and BFS2C-SH02 (P=0.005) but not BFS2C-SH22 cells (P=0.433), compared to their respective untreated controls. In contrast, WR1065 significantly induced elevations in SOD2 activity in all three cell lines (P=0.001, P=0.007, P=0.020, respectively). A significant reduction in the frequency of radiation-induced micronuclei was observed in each cell line when exposure to a 2-Gy challenge dose of radiation occurred during the period of maximal elevation in SOD2 activity. However, this adaptive effect was completely inhibited if the cells were transfected 24h before low-dose radiation or thiol exposure with SOD2 siRNA. Under the

  18. Probabilistic models and uncertainty quantification for the ionization reaction rate of atomic Nitrogen

    NASA Astrophysics Data System (ADS)

    Miki, K.; Panesi, M.; Prudencio, E. E.; Prudhomme, S.

    2012-05-01

    The objective in this paper is to analyze some stochastic models for estimating the ionization reaction rate constant of atomic Nitrogen (N + e- → N+ + 2e-). Parameters of the models are identified by means of Bayesian inference using spatially resolved absolute radiance data obtained from the Electric Arc Shock Tube (EAST) wind-tunnel. The proposed methodology accounts for uncertainties in the model parameters as well as physical model inadequacies, providing estimates of the rate constant that reflect both types of uncertainties. We present four different probabilistic models by varying the error structure (either additive or multiplicative) and by choosing different descriptions of the statistical correlation among data points. In order to assess the validity of our methodology, we first present some calibration results obtained with manufactured data and then proceed by using experimental data collected at EAST experimental facility. In order to simulate the radiative signature emitted in the shock-heated air plasma, we use a one-dimensional flow solver with Park's two-temperature model that simulates non-equilibrium effects. We also discuss the implications of the choice of the stochastic model on the estimation of the reaction rate and its uncertainties. Our analysis shows that the stochastic models based on correlated multiplicative errors are the most plausible models among the four models proposed in this study. The rate of the atomic Nitrogen ionization is found to be (6.2 ± 3.3) × 1011 cm3 mol-1 s-1 at 10,000 K.

  19. Global rate coefficients for ionization and recombination of carbon, nitrogen, oxygen, and argon

    NASA Astrophysics Data System (ADS)

    Annaloro, Julien; Morel, Vincent; Bultel, Arnaud; Omaly, Pierre

    2012-07-01

    The flow field modeling of planetary entry plasmas, laser-induced plasmas, inductively coupled plasmas, arcjets, etc., requires to use Navier-Stokes codes. The kinetic mechanisms implemented in these codes involve global (effective) rate coefficients. These rate coefficients result from the excited states coupling during a quasi-steady state. In order to obtain these global rate coefficients over a wide electron temperature (Te) range for ionization and recombination of carbon, nitrogen, oxygen, and argon, the behavior of their excited states is investigated using a zero-dimensional (time-dependent) code. The population number densities of these electronic states are considered as independent species. Their relaxation is studied within the range 3000 K ≤Te≤20 000 K and leads to the determination of the ionization (ki) and recombination (kr) global rate coefficients. Comparisons with existing data are performed. Finally, the ratio ki/kr is compared with the Saha equilibrium constant. This ratio increases more rapidly than the equilibrium constant for Te>15 000 K.

  20. Global rate coefficients for ionization and recombination of carbon, nitrogen, oxygen, and argon

    SciTech Connect

    Annaloro, Julien; Morel, Vincent; Bultel, Arnaud; Omaly, Pierre

    2012-07-15

    The flow field modeling of planetary entry plasmas, laser-induced plasmas, inductively coupled plasmas, arcjets, etc., requires to use Navier-Stokes codes. The kinetic mechanisms implemented in these codes involve global (effective) rate coefficients. These rate coefficients result from the excited states coupling during a quasi-steady state. In order to obtain these global rate coefficients over a wide electron temperature (T{sub e}) range for ionization and recombination of carbon, nitrogen, oxygen, and argon, the behavior of their excited states is investigated using a zero-dimensional (time-dependent) code. The population number densities of these electronic states are considered as independent species. Their relaxation is studied within the range 3000 K{<=}T{sub e}{<=}20 000 K and leads to the determination of the ionization (k{sub i}) and recombination (k{sub r}) global rate coefficients. Comparisons with existing data are performed. Finally, the ratio k{sub i}/k{sub r} is compared with the Saha equilibrium constant. This ratio increases more rapidly than the equilibrium constant for T{sub e}>15 000 K.

  1. High-dose-rate and pulsed-dose-rate brachytherapy for oral cavity cancer and oropharynx cancer

    PubMed Central

    2010-01-01

    Interstitial brachytherapy represents the treatment of choice for small tumours, regionally localized in the oral cavity and the oropharynx. In the technical setting, continuous low-dose-rate (LDR) brachytherapy represented for many years the gold standard for administering radiation in head and neck brachytherapy. Large series of head and neck cancer patients treated with LDR brachytherapy have been reported, constituting an invaluable source of clinical data and the gold standard to compare results of new techniques. Nowadays, LDR brachytherapy competes with fractionated HDR and hyperfractionated PDR. In the paper an overview of the different time-dose-fraction alternatives to LDR brachytherapy in head and neck cancer is presented, as well as the radiobiological basis of different dose-rate schedules, the linear-quadratic model, interconversion of fractionation schedules and the repair half-times for early- and late-responding tissues. In subsequent sections essentials of switching from LDR to HDR and from LDR to PDR are discussed. Selected clinical results using HDR and PDR brachytherapy in oral cavity and oropharynx cancer are presented. PMID:28050175

  2. Radiological mapping of Kelantan, Malaysia, using terrestrial radiation dose rate.

    PubMed

    Garba, Nuraddeen Nasiru; Ramli, Ahmad Termizi; Saleh, Muneer Aziz; Sanusi, Syazwan Mohd; Gabdo, Hamman Tukur

    2016-06-01

    Measurements of the environmental terrestrial gamma radiation dose rate (TGRD) in each district of Kelantan state, Malaysia, were carried out using a portable hand-held radiation survey meter and global positioning system. The measurements were done based on geology and soil types of the area. The mean TGRD was found to be 209 nGy h(-1). Few areas of relatively enhanced activity were observed in Pasir Mas, Tanah Merah and Jeli districts, which have a mean TGRD between 300 and 500 nGy h(-1). An isodose map of the area was produced using ArcGIS software version 9.3.

  3. Optimized source selection for intracavitary low dose rate brachytherapy

    SciTech Connect

    Nurushev, T.; Kim, Jinkoo

    2005-05-01

    A procedure has been developed for automating optimal selection of sources from an available inventory for the low dose rate brachytherapy, as a replacement for the conventional trial-and-error approach. The method of optimized constrained ratios was applied for clinical source selection for intracavitary Cs-137 implants using Varian BRACHYVISION software as initial interface. However, this method can be easily extended to another system with isodose scaling and shaping capabilities. Our procedure provides optimal source selection results independent of the user experience and in a short amount of time. This method also generates statistics on frequently requested ideal source strengths aiding in ordering of clinically relevant sources.

  4. Risk of solid cancer in low dose-rate radiation epidemiological studies and the dose-rate effectiveness factor.

    PubMed

    Shore, Roy; Walsh, Linda; Azizova, Tamara; Rühm, Werner

    2017-10-01

    Estimated radiation risks used for radiation protection purposes have been based primarily on the Life Span Study (LSS) of atomic bomb survivors who received brief exposures at high dose rates, many with high doses. Information is needed regarding radiation risks from low dose-rate (LDR) exposures to low linear-energy-transfer (low-LET) radiation. We conducted a meta-analysis of LDR epidemiologic studies that provide dose-response estimates of total solid cancer risk in adulthood in comparison to corresponding LSS risks, in order to estimate a dose rate effectiveness factor (DREF). We identified 22 LDR studies with dose-response risk estimates for solid cancer after minimizing information overlap. For each study, a parallel risk estimate was derived from the LSS risk model using matching values for sex, mean ages at first exposure and attained age, targeted cancer types, and accounting for type of dosimetric assessment. For each LDR study, a ratio of the excess relative risk per Gy (ERR Gy(-1)) to the matching LSS ERR risk estimate (LDR/LSS) was calculated, and a meta-analysis of the risk ratios was conducted. The reciprocal of the resultant risk ratio provided an estimate of the DREF. The meta-analysis showed a LDR/LSS risk ratio of 0.36 (95% confidence interval [CI] 0.14, 0.57) for the 19 studies of solid cancer mortality and 0.33 (95% CI 0.13, 0.54) when three cohorts with only incidence data also were added, implying a DREF with values around 3, but statistically compatible with 2. However, the analyses were highly dominated by the Mayak worker study. When the Mayak study was excluded the LDR/LSS risk ratios increased: 1.12 (95% CI 0.40, 1.84) for mortality and 0.54 (95% CI 0.09, 0.99) for mortality + incidence, implying a lower DREF in the range of 1-2. Meta-analyses that included only cohorts in which the mean dose was <100 mGy yielded a risk ratio of 1.06 (95% CI 0.30, 1.83) for solid cancer mortality and 0.58 (95% CI 0.10, 1.06) for mortality

  5. Strong-field ionization rates of linear polyenes simulated with time-dependent configuration interaction with an absorbing potential.

    PubMed

    Krause, Pascal; Schlegel, H Bernhard

    2014-11-07

    The strong field ionization rates for ethylene, trans 1,3-butadiene, and trans,trans 1,3,5-hexatriene have been calculated using time-dependent configuration interaction with single excitations and a complex absorbing potential (TDCIS-CAP). The calculations used the aug-cc-pVTZ basis set with a large set of diffuse functions (3 s, 2 p, 3 d, and 1 f) on each atom. The absorbing boundary was placed 3.5 times the van der Waals radius from each atom. The simulations employed a seven-cycle cosine squared pulse with a wavelength of 800 nm. Ionization rates were calculated for intensities ranging from 0.3 × 10(14) W/cm(2) to 3.5 × 10(14) W/cm(2). Ionization rates along the molecular axis increased markedly with increasing conjugation length. By contrast, ionization rates perpendicular to the molecular axis were almost independent of the conjugation length.

  6. Strong-field ionization rates of linear polyenes simulated with time-dependent configuration interaction with an absorbing potential

    NASA Astrophysics Data System (ADS)

    Krause, Pascal; Schlegel, H. Bernhard

    2014-11-01

    The strong field ionization rates for ethylene, trans 1,3-butadiene, and trans,trans 1,3,5-hexatriene have been calculated using time-dependent configuration interaction with single excitations and a complex absorbing potential (TDCIS-CAP). The calculations used the aug-cc-pVTZ basis set with a large set of diffuse functions (3 s, 2 p, 3 d, and 1 f) on each atom. The absorbing boundary was placed 3.5 times the van der Waals radius from each atom. The simulations employed a seven-cycle cosine squared pulse with a wavelength of 800 nm. Ionization rates were calculated for intensities ranging from 0.3 × 1014 W/cm2 to 3.5 × 1014 W/cm2. Ionization rates along the molecular axis increased markedly with increasing conjugation length. By contrast, ionization rates perpendicular to the molecular axis were almost independent of the conjugation length.

  7. Micron MT29F128G08AJAAA 128GB Asynchronous Flash Memory Total Ionizing Dose Characterization Test Report

    NASA Technical Reports Server (NTRS)

    Campola, Michael; Wyrwas, Edward

    2017-01-01

    The purpose of this test was to characterize the Micron MT29F128G08AJAAAs parameter degradation for total dose response and to evaluate and compare lot date codes for sensitivity. In the test, the device was exposed to both low dose and high dose rate (HDR) irradiations using gamma radiation. Device parameters such as leakage currents, quantity of upset bits and overall chip and die health were investigated to determine which lot is more robust.

  8. Low-dose ionizing radiation induces mitochondrial fusion and increases expression of mitochondrial complexes I and III in hippocampal neurons

    PubMed Central

    Chang, Chuang-Rung; Kao, Mou-Chieh; Chen, Kuan-Wei; Chiu, Shih-Che; Hsu, Ming-Ling; Hsiang, I-Chou; Chen, Yu-Jen; Chen, Linyi

    2015-01-01

    High energy ionizing radiation can cause DNA damage and cell death. During clinical radiation therapy, the radiation dose could range from 15 to 60 Gy depending on targets. While 2 Gy radiation has been shown to cause cancer cell death, studies also suggest a protective potential by low dose radiation. In this study, we examined the effect of 0.2-2 Gy radiation on hippocampal neurons. Low dose 0.2 Gy radiation treatment increased the levels of MTT. Since hippocampal neurons are post-mitotic, this result reveals a possibility that 0.2 Gy irradiation may increase mitochondrial activity to cope with stimuli. Maintaining neural plasticity is an energy-demanding process that requires high efficient mitochondrial function. We thus hypothesized that low dose radiation may regulate mitochondrial dynamics and function to ensure survival of neurons. Our results showed that five days after 0.2 Gy irradiation, no obvious changes on neuronal survival, neuronal synapses, membrane potential of mitochondria, reactive oxygen species levels, and mitochondrial DNA copy numbers. Interestingly, 0.2 Gy irradiation promoted the mitochondria fusion, resulting in part from the increased level of a mitochondrial fusion protein, Mfn2, and inhibition of Drp1 fission protein trafficking to the mitochondria. Accompanying with the increased mitochondrial fusion, the expressions of complexes I and III of the electron transport chain were also increased. These findings suggest that, hippocampal neurons undergo increased mitochondrial fusion to modulate cellular activity as an adaptive mechanism in response to low dose radiation. PMID:26415228

  9. Low-dose ionizing radiation induces mitochondrial fusion and increases expression of mitochondrial complexes I and III in hippocampal neurons.

    PubMed

    Chien, Ling; Chen, Wun-Ke; Liu, Szu-Ting; Chang, Chuang-Rung; Kao, Mou-Chieh; Chen, Kuan-Wei; Chiu, Shih-Che; Hsu, Ming-Ling; Hsiang, I-Chou; Chen, Yu-Jen; Chen, Linyi

    2015-10-13

    High energy ionizing radiation can cause DNA damage and cell death. During clinical radiation therapy, the radiation dose could range from 15 to 60 Gy depending on targets. While 2 Gy radiation has been shown to cause cancer cell death, studies also suggest a protective potential by low dose radiation. In this study, we examined the effect of 0.2-2 Gy radiation on hippocampal neurons. Low dose 0.2 Gy radiation treatment increased the levels of MTT. Since hippocampal neurons are post-mitotic, this result reveals a possibility that 0.2 Gy irradiation may increase mitochondrial activity to cope with stimuli. Maintaining neural plasticity is an energy-demanding process that requires high efficient mitochondrial function. We thus hypothesized that low dose radiation may regulate mitochondrial dynamics and function to ensure survival of neurons. Our results showed that five days after 0.2 Gy irradiation, no obvious changes on neuronal survival, neuronal synapses, membrane potential of mitochondria, reactive oxygen species levels, and mitochondrial DNA copy numbers. Interestingly, 0.2 Gy irradiation promoted the mitochondria fusion, resulting in part from the increased level of a mitochondrial fusion protein, Mfn2, and inhibition of Drp1 fission protein trafficking to the mitochondria. Accompanying with the increased mitochondrial fusion, the expressions of complexes I and III of the electron transport chain were also increased. These findings suggest that, hippocampal neurons undergo increased mitochondrial fusion to modulate cellular activity as an adaptive mechanism in response to low dose radiation.

  10. Simulated Space Radiation: Impact of Four Different Types of High-Dose Ionizing Radiation on the Lichen Xanthoria elegans.

    PubMed

    Brandt, Annette; Meeßen, Joachim; Jänicke, Reiner U; Raguse, Marina; Ott, Sieglinde

    2017-02-01

    This study addresses the viability of the lichen Xanthoria elegans after high-dose ionizing irradiation in the frame of the STARLIFE campaign. The first set of experiments was intended to resemble several types of galactic cosmic radiation (GCR) as present beyond the magnetic shield of Earth. In the second set of experiments, γ radiation up to 113 kGy was applied to test the limit of lichen resistance to ionizing radiation. Entire thalli of Xanthoria elegans were irradiated in the anhydrobiotic state. After STARLIFE 1, the metabolic activity of both symbionts was quantified by live/dead staining with confocal laser scanning microscopy. The photosynthetic activity was measured after the respective irradiation to assess the ability of the symbiotic green algae to restore photosynthesis after irradiation. The STARLIFE campaign complements the results of the LIFE experiments at the EXPOSE-E facility on the International Space Station by testing the model organism Xanthoria elegans on its resistance to hazardous radiation that might be accumulated during long-term space exposure. In addition, the photosynthetic activity of metabolically active lichen was investigated after X-ray irradiation up to 100 Gy (3.3 Gy/min). Since previous astrobiological experiments were mostly performed with anhydrobiotic lichen, these experiments will broaden our knowledge on the correlation of physiological state and astrobiological stressors. Key Words: Astrobiology-Extremotolerance-Gamma rays-Ionizing radiation-Lichens-Viability. Astrobiology 17, 136-144.

  11. PFP vertical calciner shield wall dose rate calculations using MCNP

    SciTech Connect

    Wittekind, W.D.

    1997-08-21

    This report yields a neutron shield wall design for a full time occupancy dose rate of 0.25 mrem/h. ORIGEN2 generated gamma ray spectrum and neutron intensity for plutonium. MCNP modeled the calciner glovebox and room for reflection of neutrons off concrete walls and ceiling. Neutron calculations used MCNP in mode n, p to include neutron capture gammas. Photon calculations used MCNP in mode p for gamma rays. Neutron shield with lower 137.16 cm (4.5 feet) of 12.7 cm (5 inch) thick Lucite{reg_sign} and 0.3175 cm (0.125 inch) stainless steel on both sides, and upper 76.2 cm (2.5 feet) of 10.16 cm (4 inch) thick Lucite{reg_sign} and 1.905 cm (0.75 inch) thick glass on each side gave a total weighted dose rate of 0.23 mrem/h, fulfilling the design goal. Lucite{reg_sign} is considered to be equivalent to Plexiglas{reg_sign} since both are methylmethacrylate polymers.

  12. Reporting small bowel dose in cervix cancer high-dose-rate brachytherapy.

    PubMed

    Liao, Yixiang; Dandekar, Virag; Chu, James C H; Turian, Julius; Bernard, Damian; Kiel, Krystyna

    2016-01-01

    Small bowel (SB) is an organ at risk (OAR) that may potentially develop toxicity after radiotherapy for cervix cancer. However, its dose from brachytherapy (BT) is not systematically reported as in other OARs, even with image-guided brachytherapy (IGBT). This study aims to introduce consideration of quantified objectives for SB in BT plan optimization and to evaluate the feasibility of sparing SB while maintaining adequate target coverage. In all, 13 patients were included in this retrospective study. All patients were treated with external beam radiotherapy (EBRT) 45Gy in 25 fractions followed by high dose rate (HDR)-BT boost of 28Gy in 4 fractions using tandem/ring applicator. Magnetic resonance imaging (MRI) and computed tomographic (CT) images were obtained to define the gross tumor volume (GTV), high-risk clinical target volume (HR-CTV) and OARs (rectum, bladder, sigmoid colon, and SB). Treatment plans were generated for each patient using GEC-ESTRO recommendations based on the first CT/MRI. Treatment plans were revised to reduce SB dose when the [Formula: see text] dose to SB was > 5Gy, while maintaining other OAR constraints. For the 7 patients with 2 sets of CT and MRI studies, the interfraction variation of the most exposed SB was analyzed. Plan revisions were done in 6 of 13 cases owing to high [Formula: see text] of SB. An average reduction of 19% in [Formula: see text] was achieved. Meeting SB and other OAR constraints resulted in less than optimal target coverage in 2 patients (D90 of HR-CTV < 77Gyαβ10). The highest interfraction variation was observed for SB at 16 ± 59%, as opposed to 28 ± 27% for rectum and 21 ± 16% for bladder. Prospective reporting of SB dose could provide data required to establish a potential correlation with radiation-induced late complication for SB.

  13. High-rate axial-field ionization chamber for particle identification of radioactive beams

    NASA Astrophysics Data System (ADS)

    Vadas, J.; Singh, Varinderjit; Visser, G.; Alexander, A.; Hudan, S.; Huston, J.; Wiggins, B. B.; Chbihi, A.; Famiano, M.; Bischak, M. M.; deSouza, R. T.

    2016-11-01

    The design, construction and performance characteristics of a simple axial-field ionization chamber suitable for identifying ions in a radioactive beam are presented. Optimized for use with low-energy radioactive beams (< 5 MeV / A) the detector presents only three 0.5 μm/cm2 foils to the beam in addition to the detector gas. A fast charge sensitive amplifier (CSA) integrated into the detector design is also described. Coupling this fast CSA to the axial field ionization chamber produces an output pulse with a risetime of 60-70 ns and a fall time of 100 ns, making the detector capable of sustaining a relatively high rate and providing a time resolution of 6-8 ns. Tests with an α source establish the detector energy resolution as ∼ 8 % for an energy deposit of ∼3.5 MeV. The energy resolution with beams of 2.5 and 4.0 MeV/A 39K ions and the dependence of the energy resolution on beam intensity is measured. At an instantaneous rate of 3×105 ions/s the energy resolution has degraded to 14% with a pileup of 12%. The good energy resolution of this detector at rates up to 3×105 ions/s makes it an effective tool in the characterization of low-energy radioactive beams.

  14. The Analysis on Space Radiation Environment and Effect of the KOMPSAT-2 Spacecraft(I): Total Ionizing Dose Effect

    NASA Astrophysics Data System (ADS)

    Baek, Myung-Jin; Kim, Hak-Jung

    2001-11-01

    In this paper, space radiation environment and total ionizing dose(TID) effect have been analyzed for the KOMPSAT-2 operational orbit. It has been revealed that the trapped protons are concentrated in the SAA(South Atlantic Anomaly) area and that the trapped protons and electrons, and solar protons are main factors affecting TID. It turned out that low energy particles can be effectively blocked by aluminum shielding thickness, but high energy particles can not be effectively blocked by increasing aluminum shielding thickness. KOMPSAT-2 total radiation dose which is accumulated continuously to spacecraft electronics has been expressed as the function of aluminum thickness. These values can be used as the criteria for the selection of electronic parts and shielding thinkness of the KOMPSAT-2 structure or electronic box.

  15. Monte Carlo Study of Radiation Dose Enhancement by Gadolinium in Megavoltage and High Dose Rate Radiotherapy

    PubMed Central

    Zhang, Daniel G.; Feygelman, Vladimir; Moros, Eduardo G.; Latifi, Kujtim; Zhang, Geoffrey G.

    2014-01-01

    MRI is often used in tumor localization for radiotherapy treatment planning, with gadolinium (Gd)-containing materials often introduced as a contrast agent. Motexafin gadolinium is a novel radiosensitizer currently being studied in clinical trials. The nanoparticle technologies can target tumors with high concentration of high-Z materials. This Monte Carlo study is the first detailed quantitative investigation of high-Z material Gd-induced dose enhancement in megavoltage external beam photon therapy. BEAMnrc, a radiotherapy Monte Carlo simulation package, was used to calculate dose enhancement as a function of Gd concentration. Published phase space files for the TrueBeam flattening filter free (FFF) and conventional flattened 6MV photon beams were used. High dose rate (HDR) brachytherapy with Ir-192 source was also investigated as a reference. The energy spectra difference caused a dose enhancement difference between the two beams. Since the Ir-192 photons have lower energy yet, the photoelectric effect in the presence of Gd leads to even higher dose enhancement in HDR. At depth of 1.8 cm, the percent mean dose enhancement for the FFF beam was 0.38±0.12, 1.39±0.21, 2.51±0.34, 3.59±0.26, and 4.59±0.34 for Gd concentrations of 1, 5, 10, 15, and 20 mg/mL, respectively. The corresponding values for the flattened beam were 0.09±0.14, 0.50±0.28, 1.19±0.29, 1.68±0.39, and 2.34±0.24. For Ir-192 with direct contact, the enhanced were 0.50±0.14, 2.79±0.17, 5.49±0.12, 8.19±0.14, and 10.80±0.13. Gd-containing materials used in MRI as contrast agents can also potentially serve as radiosensitizers in radiotherapy. This study demonstrates that Gd can be used to enhance radiation dose in target volumes not only in HDR brachytherapy, but also in 6 MV FFF external beam radiotherapy, but higher than the currently used clinical concentration (>5 mg/mL) would be needed. PMID:25275550

  16. Radiation dose-rate meter using an energy-sensitive counter

    DOEpatents

    Kopp, Manfred K.

    1988-01-01

    A radiation dose-rate meter is provided which uses an energy-sensitive detector and combines charge quantization and pulse-rate measurement to monitor radiation dose rates. The charge from each detected photon is quantized by level-sensitive comparators so that the resulting total output pulse rate is proportional to the dose-rate.

  17. Meta-analysis of non-tumour doses for radiation-induced cancer on the basis of dose-rate.

    PubMed

    Tanooka, Hiroshi

    2011-07-01

    Quantitative analysis of cancer risk of ionising radiation as a function of dose-rate. Non-tumour dose, D(nt), defined as the highest dose of radiation at which no statistically significant tumour increase was observed above the control level, was analysed as a function of dose-rate of radiation. An inverse correlation was found between D(nt) and dose-rate of the radiation. D(nt) increased 20-fold with decreasing dose-rate from 1-10(-8) Gy/min for whole body irradiation with low linear energy transfer (LET) radiation. Partial body radiation also showed a dose-rate dependence with a 5- to 10-fold larger D(nt) as dose rate decreased. The dose-rate effect was also found for high LET radiation but at 10-fold lower D(nt) levels. The cancer risk of ionising radiation varies 1000-fold depending on the dose-rate of radiation and exposure conditions. This analysis explains the discrepancy of cancer risk between A-bomb survivors and radium dial painters.

  18. Dose measurement using Al2O3 dosimeter in comparison to LiF:Mg,Ti dosimeter and ionization chamber at low and high energy x-ray

    NASA Astrophysics Data System (ADS)

    Yusof, Mohd Fahmi Mohd; Yahya, Muhammad Hadzmi; Rosnan, Muhammad Syazwan; Abdullah, Reduan; Kadir, Ahmad Bazlie Abdul

    2017-01-01

    The dose measurement using Al2O3 OSL dosimeter (OSLD) was carried out at low and high energy x-ray. The dose at low energy x-ray was measured at 40, 71 and 125 kVp x-ray energies. The dose ar high energy x-ray was measured at 6 and 10 MV x-ray energies measured at the depth of maximum dose (Zmax). The results were compared to that in ionization chamber and LiF: Mg,Ti thermoluminescent dosimeters (TLD100). The results showed that the dose of OSLD were less in agreement to ionization chamber compared to that in TLD100. The dose of OSLD however was in good agreement to that in ionization chamber at high energy x-ray. The dose measured using OSLD were found to be more consistence at high energy x-ray shown by the standard deviation of the readings. The measurement of x2 showed that the readings of OSLD were close to that in ionization chamber with values of 2.21 and 4.63 for 6 and 10 MV respectively. The results indicated that OSLD is more suitable for dose measurement at high energy x-ray.

  19. Variations of the ambient dose equivalent rate in the ground level air.

    PubMed

    Lebedyte, M; Butkus, D; Morkŭnas, G

    2003-01-01

    The ambient dose equivalent rate is caused by ionizing radiation of radionuclides in the atmosphere and on the ground surface as well as by cosmic radiation. Seasonal and diurnal variations of the ambient dose equivalent rate (ADER) in the ground level air are influenced by the concentration of 222Rn daughters. The 222Rn concentration in the ground level atmosphere, in turn, depends on the rate of the 222Rn exhalation from soil and turbulent air mixing. Its diurnal and seasonal variations depend on meteorological conditions. The aim of this study is to estimate the influence of variations of the rate of the 222Rn exhalation from soil and its concentrations in the ground level air on variations of ADER in the ground level air, as well as the dependence of these parameters on meteorological conditions. The 222Rn diffusion coefficient and its exhalation rate in undisturbed loamy soil have been determined. The 222Rn concentration in the soil air and its concentration in the ground level air correlate inversely (correlation coefficient is r = -0.62). The main factors determining the 222Rn exhalation from soil are: the soil temperature (r = 0.64), the difference in temperature of soil and air (r = 0.57), and the precipitation amount (r = 0.50). The intensity of gamma radiation in the ground level air is mostly related to the 222Rn concentration in the air (r = 0.62), while the effect of the exhalation rate from soil is relatively low (r = 0.36). It has been shown that ADER due to 222Rn progeny causes only 7-16% of the total ADER and influences its variation. The comparison of variations of ADER due to 222Rn progeny and the total ADER during several years shows that these parameters correlate positively.

  20. The Effect of High-Dose Ionizing Radiation on the Isolated Photobiont of the Astrobiological Model Lichen Circinaria gyrosa.

    PubMed

    Meeßen, Joachim; Backhaus, Theresa; Brandt, Annette; Raguse, Marina; Böttger, Ute; de Vera, Jean-Pierre; de la Torre, Rosa

    2017-02-01

    Lichen symbioses between fungi and algae represent successful life strategies to colonize the most extreme terrestrial habitats. Consequently, space exposure and simulation experiments have demonstrated lichens' high capacity for survival, and thus, they have become models in astrobiological research with which to discern the limits and limitations of terrestrial life. In a series of ground-based irradiation experiments, the STARLIFE campaign investigated the resistance of astrobiological model organisms to galactic cosmic radiation, which is one of the lethal stressors of extraterrestrial environments. Since previous studies have identified that the alga is the more sensitive lichen symbiont, we chose the isolated photobiont Trebouxia sp. of the astrobiological model Circinaria gyrosa as a subject in the campaign. Therein, γ radiation was used to exemplify the deleterious effects of low linear energy transfer (LET) ionizing radiation at extremely high doses up to 113 kGy in the context of astrobiology. The effects were analyzed by chlorophyll a fluorescence of photosystem II (PSII), cultivation assays, live/dead staining and confocal laser scanning microscopy (CLSM), and Raman laser spectroscopy (RLS). The results demonstrate dose-dependent impairment of photosynthesis, the cessation of cell proliferation, cellular damage, a decrease in metabolic activity, and degradation of photosynthetic pigments. While previous investigations on other extraterrestrial stressors have demonstrated a high potential of resistance, results of this study reveal the limits of photobiont resistance to ionizing radiation and characterize γ radiation-induced damages. This study also supports parallel STARLIFE studies on the lichens Circinaria gyrosa and Xanthoria elegans, both of which harbor a Trebouxia sp. photobiont. Key Words: Astrobiology-Gamma rays-Extremotolerance-Ionizing radiation-Lichens-Photobiont. Astrobiology 17, 154-162.

  1. Retrospective Biological Dosimetry at Low and High Doses of Radiation and Radioiodine Impact on Individual Susceptibility to Ionizing Radiation

    PubMed Central

    Cebulska-Wasilewska, Antonina; Krzysiek, Mateusz; Krajewska, Grażyna; Stępień, Artur; Krajewski, Paweł

    2017-01-01

    Iodine-131 (I-131) is often used in thyroid diagnostics and therapy. External and internal exposure to radioiodine can lead to molecular and cellular damage in peripheral blood lymphocytes. The aim of this study was to explore the influence of low and high doses of I-131 on susceptibility to ionizing radiation. Study groups consisted of 30 individuals free of thyroid diseases, 41 patients exposed diagnostically to low doses of I-131, and 37 hyperthyroidism patients exposed therapeutically to high doses. The standardized DNA repair competence assay was used to test the efficacy of the fast DNA repair process in G0 cells. Cytogenetic preparations were made in fresh blood samples before and after challenging cells in vitro with X-ray dose. The frequency of sister chromatid exchanges (SCE) and percentage of cells with significantly elevated numbers of SCE were used as cytogenetic biomarkers associated to homologous recombination and compared to reported earlier cytogenetic biomarkers of cancer risk. Strong individual variation in the biomarkers is observed in all investigated groups before and after challenging. Nevertheless, the efficiency of post challenging fast repair is significantly high in the patients exposed to diagnostic I-131 doses than in unexposed control group and linked to decreased cytogenetic damage. However, 5 weeks after administration of therapeutic doses, significant increases of unrepaired post challenging DNA and cytogenetic damages were observed indicating a health risk. Results also suggest that the appearance of cancers in immediate families might influence DNA repair differently in patients exposed to low than to high doses. PMID:28250909

  2. Reaction rate theory of radiation exposure:Effects of dose rate on mutation frequency

    NASA Astrophysics Data System (ADS)

    Bando, Masako; Nakamura, Issei; Manabe, Yuichiro

    2014-03-01

    We revisit the linear no threshold (LNT) hypothesis deduced from the prominent works done by H. J. Muller for the DNA mutation induced by the artificial radiation and by W. L. Russell and E. M. Kelly for that of mega-mouse experiments, developing a new kinetic reaction theory. While the existing theoretical models primarily rely on the dependence of the total dose D on the mutation frequency, the key ingredient in our theory is the dose rate d(t) that accounts for decrease in the mutation rate during the time course of the cellular reactions. The general form for the mutation frequency with the constant dose rate d is simply expressed as, dFm(t)/dt = A - BFm(t) , with A =a0 +a1(d +deff) and B =b0 +b1(d +deff) . We discuss the solution for a most likely case with B > 0 ; Fm(t) = [A/B -Fm(0) ] (1 -e-Bt) +Fm(0) with the control value Fm(0) . We show that all the data of mega-mouse experiments by Russel with different dose rates fall on the universal scaling function Φ(τ) ≡ [Fm(τ) -Fm(0) ]/[ A / B -Fm(0) ] = 1 - exp(- τ) with scaled time τ = Bt . The concept of such a scaling rule provides us with a strong tool to study different species in a unified manner.

  3. Angle-dependent strong-field molecular ionization rates with tuned range-separated time-dependent density functional theory

    NASA Astrophysics Data System (ADS)

    Sissay, Adonay; Abanador, Paul; Mauger, François; Gaarde, Mette; Schafer, Kenneth J.; Lopata, Kenneth

    2016-09-01

    Strong-field ionization and the resulting electronic dynamics are important for a range of processes such as high harmonic generation, photodamage, charge resonance enhanced ionization, and ionization-triggered charge migration. Modeling ionization dynamics in molecular systems from first-principles can be challenging due to the large spatial extent of the wavefunction which stresses the accuracy of basis sets, and the intense fields which require non-perturbative time-dependent electronic structure methods. In this paper, we develop a time-dependent density functional theory approach which uses a Gaussian-type orbital (GTO) basis set to capture strong-field ionization rates and dynamics in atoms and small molecules. This involves propagating the electronic density matrix in time with a time-dependent laser potential and a spatial non-Hermitian complex absorbing potential which is projected onto an atom-centered basis set to remove ionized charge from the simulation. For the density functional theory (DFT) functional we use a tuned range-separated functional LC-PBE*, which has the correct asymptotic 1/r form of the potential and a reduced delocalization error compared to traditional DFT functionals. Ionization rates are computed for hydrogen, molecular nitrogen, and iodoacetylene under various field frequencies, intensities, and polarizations (angle-dependent ionization), and the results are shown to quantitatively agree with time-dependent Schrödinger equation and strong-field approximation calculations. This tuned DFT with GTO method opens the door to predictive all-electron time-dependent density functional theory simulations of ionization and ionization-triggered dynamics in molecular systems using tuned range-separated hybrid functionals.

  4. Dose estimation outside radiation field using Pinpoint and Semiflex ionization chamber detectors

    NASA Astrophysics Data System (ADS)

    Abdelaal, Ahmed M.; Attalla, Ehab M.; Elshemey, Wael M.

    2017-10-01

    This work aims to provide a comparison between two important detectors (Pinpoint and Semiflex) that are frequently used in radiation dosimetery in radiotherapy. This is carried out through the employment of both detectors in a quantitative estimation of the change in out-of-field dose with important dosimetric parameters such as field size (from 5×5 cm2 to 30×30 cm2) and depth (from 1.5 cm to 30 cm) at two different energies (6 MV and 15 MV) and two different collimator angles (0-90°). The change in out-of-field dose with Source-Skin-Distance (SSD) from 80 to 115 cm is also studied using both detectors. Results show that, the Pinpoint and Semiflex detectors both reported an increase in out-of-field dose with field size, depth, energy and SSD. In almost all measurements, Pinpoint detector reported considerably higher out-of-field dose values compared to Semiflex. For 6 MV and 0° collimator angle, the out-of-field dose at field size of 30×30 cm2 and at a depth of 1.5 cm is 7.3% for Pinpoint detector compared to 4.3% for Semiflex. At collimator angle of 90°, the out-of-field dose is 6.5% for Pinpoint detector compared to 5.5% for semiflex. The out-of-field dose for a depth of 30 cm and field size of 10×10 cm is 7.9% for Pinpoint detector compared to 5.9% for Semiflex. For 15 MV and 0° collimator angle, the out-of-field dose at field size of 30×30 cm2 and at a depth of 1.5 cm is 7.5% for Pinpoint detector compared 5.1% for Semiflex. At 6 MV, field size of 10×10 cm2 and depth of 1.5 cm, the out-of-field dose at SSD 115 cm is 3.7% for Pinpoint detector compared to 3.4% for Semiflex. The considerably higher out-of-field dose values reported by Pinpoint detector compared to Semiflex may be attributed to the relatively higher sensitivity of Pinpoint detector for low doses (such as out-of-field doses). Therefore, for reliable out-of-field dose measurements a Pinpoint detector is highly recommended.

  5. Spectrum and ionization rate of low-energy Galactic cosmic rays

    NASA Astrophysics Data System (ADS)

    Nath, Biman B.; Gupta, Nayantara; Biermann, Peter L.

    2012-09-01

    We consider the rate of ionization of diffuse and molecular clouds in the interstellar medium by Galactic cosmic rays (GCRs) in order to constrain its low-energy spectrum. We extrapolate the GCR spectrum obtained from PAMELA at high energies (≥200 GeV nucleon-1) and a recently derived GCR proton flux at 1-200 GeV from observations of gamma-rays from molecular clouds, and find that the observed average Galactic ionization rate can be reconciled with this GCR spectrum if there is a low-energy cut-off for protons at 10-100 MeV. We also identify the flattening below a few GeV as being due to (a) decrease of the diffusion coefficient and dominance of convective loss at low energy and (b) the expected break in energy spectrum for a constant spectral index in momentum. We show that the inferred CR proton spectrum of ? for Ekin≤ few GeV is consistent with a power-law spectrum in momentum p-2.45± 0.4, which we identify as the spectrum at source. Diffusion loss at higher energies then introduces a steepening by E-α with α˜ 1/3, making it consistent with high-energy measurements.

  6. Dielectronic recombination rates, ionization equilibrium, and radiative emission rates for Mn ions in low-density high-temperature plasmas

    NASA Technical Reports Server (NTRS)

    Jacobs, V. L.; Davis, J.

    1983-01-01

    The analysis of optically-thin far-ultraviolet and X-ray emission lines of multiply-charged ions is one of the basic methods for determining the temperatures and densities of laboratory and astrophysical plasmas. In addition, the energy balance in these plasmas can be significantly influenced by the emission of radiation from relatively low concentrations of multiple-charged atomic ions. Because the populations of the excited levels are expected to depart substantially from their local thermodynamic equilibrium values a detailed treatment of the elementary collisional and radiative processes must be employed in order to predict the emission line intensities. In this investigation the authors present the results of calculations based on a corona equilibrium model in which a detailed evaluation is made of the dielectronic recombination rate coefficients. The ionization and autoionization following inner-shell electron excitation from each ground state are balanced by direct radiative and dielectronic recombination. The spectral line intensities emitted by the low-lying excited states, which are assumed to undergo spontaneous radiative decay in times that are short compared with the collision time, are evaluated in terms of the corona ionization equilibrium distributions of the ground states and their electron-impact excitation states.

  7. Long-term effects of acute low-dose ionizing radiation on the neonatal mouse heart: a proteomic study.

    PubMed

    Bakshi, Mayur V; Barjaktarovic, Zarko; Azimzadeh, Omid; Kempf, Stefan J; Merl, Juliane; Hauck, Stefanie M; Eriksson, Per; Buratovic, Sonja; Atkinson, Michael J; Tapio, Soile

    2013-11-01

    Epidemiological studies establish that children and young adults are especially susceptible to radiation-induced cardiovascular disease (CVD). The biological mechanisms behind the elevated CVD risk following exposure at young age remain unknown. The present study aims to elucidate the long-term effects of ionizing radiation by studying the murine cardiac proteome after exposure to low and moderate radiation doses. NMRI mice received single doses of total body (60)Co gamma-irradiation on postnatal day 10 and were sacrificed 7 months later. Changes in cardiac protein expression were quantified using isotope-coded protein label and tandem mass spectrometry. We identified 32, 31, 66, and 34 significantly deregulated proteins after doses of 0.02, 0.1, 0.5, and 1.0 Gy, respectively. The four doses shared 9 deregulated proteins. Bioinformatics analysis showed that most of the deregulated proteins belonged to a limited set of biological categories, including metabolic processes, inflammatory response, and cytoskeletal structure. The transcription factor peroxisome proliferator-activated receptor alpha was predicted as a common upstream regulator of several deregulated proteins. This study indicates that both adaptive and maladaptive responses to the initial radiation damage persist well into adulthood. It will contribute to the understanding of the long-term consequences of radiation-induced injury and developmental alterations in the neonatal heart.

  8. Variable dose rate single-arc IMAT delivered with a constant dose rate and variable angular spacing

    NASA Astrophysics Data System (ADS)

    Tang, Grace; Earl, Matthew A.; Yu, Cedric X.

    2009-11-01

    Single-arc intensity-modulated arc therapy (IMAT) has gained worldwide interest in both research and clinical implementation due to its superior plan quality and delivery efficiency. Single-arc IMAT techniques such as the Varian RapidArc™ deliver conformal dose distributions to the target in one single gantry rotation, resulting in a delivery time in the order of 2 min. The segments in these techniques are evenly distributed within an arc and are allowed to have different monitor unit (MU) weightings. Therefore, a variable dose-rate (VDR) is required for delivery. Because the VDR requirement complicates the control hardware and software of the linear accelerators (linacs) and prevents most existing linacs from delivering IMAT, we propose an alternative planning approach for IMAT using constant dose-rate (CDR) delivery with variable angular spacing. We prove the equivalence by converting VDR-optimized RapidArc plans to CDR plans, where the evenly spaced beams in the VDR plan are redistributed to uneven spacing such that the segments with larger MU weighting occupy a greater angular interval. To minimize perturbation in the optimized dose distribution, the angular deviation of the segments was restricted to <=± 5°. This restriction requires the treatment arc to be broken into multiple sectors such that the local MU fluctuation within each sector is reduced, thereby lowering the angular deviation of the segments during redistribution. The converted CDR plans were delivered with a single gantry sweep as in the VDR plans but each sector was delivered with a different value of CDR. For four patient cases, including two head-and-neck, one brain and one prostate, all CDR plans developed with the variable spacing scheme produced similar dose distributions to the original VDR plans. For plans with complex angular MU distributions, the number of sectors increased up to four in the CDR plans in order to maintain the original plan quality. Since each sector was delivered

  9. Variable dose rate single-arc IMAT delivered with a constant dose rate and variable angular spacing.

    PubMed

    Tang, Grace; Earl, Matthew A; Yu, Cedric X

    2009-11-07

    Single-arc intensity-modulated arc therapy (IMAT) has gained worldwide interest in both research and clinical implementation due to its superior plan quality and delivery efficiency. Single-arc IMAT techniques such as the Varian RapidArc deliver conformal dose distributions to the target in one single gantry rotation, resulting in a delivery time in the order of 2 min. The segments in these techniques are evenly distributed within an arc and are allowed to have different monitor unit (MU) weightings. Therefore, a variable dose-rate (VDR) is required for delivery. Because the VDR requirement complicates the control hardware and software of the linear accelerators (linacs) and prevents most existing linacs from delivering IMAT, we propose an alternative planning approach for IMAT using constant dose-rate (CDR) delivery with variable angular spacing. We prove the equivalence by converting VDR-optimized RapidArc plans to CDR plans, where the evenly spaced beams in the VDR plan are redistributed to uneven spacing such that the segments with larger MU weighting occupy a greater angular interval. To minimize perturbation in the optimized dose distribution, the angular deviation of the segments was restricted to dose distributions to the original VDR plans. For plans with complex angular MU distributions, the number of sectors increased up to four in the CDR plans in order to maintain the original plan quality. Since each sector was

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

    PubMed

    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.

  11. Bronchoscopic phototherapy at comparable dose rates: Early results

    SciTech Connect

    Pass, H.I.; Delaney, T.; Smith, P.D.; Bonner, R.; Russo, A.

    1989-05-01

    Photodynamic therapy is a recently introduced treatment for surface malignancies. Since January 1987, 10 patients with endobronchial neoplasms have had bronchoscopic photodynamic therapy at similar dose rates (400 mW/cm) for total atelectasis (2), carinal narrowing with respiratory insufficiency (2), or partial obstruction without collapse (4). Two patients underwent photodynamic therapy as a preliminary to immunotherapy. Histologies included endobronchial metastases (colon, ovary, melanoma, and sarcoma, 1 each; and renal cell, 3) and primary lung cancer (3). The 2 patients with total atelectasis had complete reexpansion after photodynamic therapy, which permitted eventual sleeve lobectomy in 1. Carinal narrowing was ameliorated in the 2 patients seen with inspiratory stridor, thereby permitting hospital discharge. Endoscopically resected fragments after photodynamic therapy exhibited avascular necrosis. These data support further controlled studies of photodynamic therapy by thoracic surgical oncologists to define its limitations as well as to improve and expand its efficacy as a palliative or surgical adjuvant.

  12. ACDOS3: a further improved neutron dose-rate code

    SciTech Connect

    Martin, C.S.

    1982-07-01

    ACD0S3 is a computer code designed primarily to calculate the activities and dose rates produced by neutron activation in a variety of simple geometries. Neutron fluxes, in up to 50 groups and with energies up to 20 MeV, must be supplied as part of the input data. The neutron-source strength must also be supplied, or alternately, the code will compute it from neutral-beam operating parameters in the case where the source is a fusion-reactor injector. ACD0S3 differs from the previous version ACD0S2 in that additional geometries have been added, the neutron cross-section library has been updated, an estimate of the energy deposited by neutron reactions has been provided, and a significant increase in efficiency in reading the data libraries has been incorporated.

  13. Epinephrine at doses used in dentistry deteriorates platelet retention rate.

    PubMed Central

    Ichinohe, T.; Fukuda, K.; Kaneko, Y.

    1997-01-01

    Epinephrine promotes platelet aggregation through alpha 2 receptor-mediated mechanisms. In this study, the change in the platelet retention rate (PRR) was investigated before and after submucosal epinephrine injection with or without lidocaine in oral surgical patients during isoflurane-nitrous oxide anesthesia. Thirty-nine consenting patients participated in this study. Subjects were allocated in one of five groups depending on the solution injected, the diclofenac supplement, and the patients' age. PRR was measured immediately before and 5 min after epinephrine injection using a modified form of Saltzman's method. Injection of epinephrine with lidocaine deteriorated PRR, although epinephrine without lidocaine produced no PRR change. Epinephrine at doses used in routine dental practices may activate the platelet aggregating function. Dentists should keep in mind that epinephrine elicits both hemodynamic and platelet-activating effects. The latter may be of clinical importance in some situations. PMID:9481962

  14. Dosimetry modeling for focal high-dose-rate prostate brachytherapy.

    PubMed

    Mason, Josh; Al-Qaisieh, Bashar; Bownes, Peter; Thwaites, David; Henry, Ann

    2014-01-01

    The dosimetry of focal high-dose-rate prostate brachytherapy was assessed. Dose volume histogram parameters, robustness to source position errors, and Monte Carlo (MC) simulations were compared for whole-gland (WG), hemi-gland (HEMI), and ultra-focal (UF) treatment plans. Tumor volumes were delineated based on MRI and template biopsy results for 9 patients. WG, HEMI, and UF plans were produced assuming 19 Gy single fraction monotherapy treatments. For UF plans, a 6-mm margin was applied to the visible tumor to create a focal-planning target volume (F-PTV). Systematic source position shifts of 1-4 mm were applied to assess plan robustness. The dosimetric impact of steel catheters was assessed using MC simulation. Mean D90 and V100 were 20.4 Gy and 97.9% for prostate in WG plans, 22.2 Gy and 98.1% for hemi-prostate in HEMI plans, and 23.0 Gy and 98.2% for F-PTV in UF plans. Mean urethra D10 was 20.3, 19.7, and 9.2 Gy in WG, HEMI, and UF plans, respectively. Mean rectal D2cc was 12.5, 9.8, and 4.6 Gy in WG, HEMI, and UF plans, respectively. Focal treatment plans were sensitive to source position errors-2 mm systematic shifts reduced mean prostate D90 by 0.7%, hemi-prostate D90 by 2.6%, and F-PTV D90 by 8.3% in WG, HEMI, and UF plans, respectively. MC simulation results were similar for all plan types with most dose volume histogram parameters reduced by <2%. HEMI and UF treatments can achieve higher D90 values compared with WG treatments with reduced organ at risk dose. Focal treatments are more sensitive to systematic source position errors than WG treatments. Copyright © 2014 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

  15. Low doses of ionizing radiation to mammalian cells may rather control than cause DNA damage

    SciTech Connect

    Feinendegen, L.E.; Bond, V.P.; Sondhaus, C.A.; Altman, K.I.

    1998-12-31

    This report examines the origin of tissue effects that may follow from different cellular responses to low-dose irradiation, using published data. Two principal categories of cellular responses are considered. One response category relates to the probability of radiation-induced DNA damage. The other category consists of low-dose induced metabolic changes that induce mechanisms of DNA damage mitigation, which do not operate at high levels of exposure. Modeled in this way, tissue is treated as a complex adaptive system. The interaction of the various cellular responses results in a net tissue dose-effect relation that is likely to deviate from linearity in the low-dose region. This suggests that the LNT hypothesis should be reexamined. This paper aims at demonstrating tissue effects as an expression of cellular responses, both damaging and defensive, in relation to the energy deposited in cell mass, by use of microdosimetric concepts.

  16. An assessment of immediate DNA damage to occupationally exposed workers to low dose ionizing radiation by using the comet assay.

    PubMed

    Martínez, Angélica; Coleman, Matthew; Romero-Talamás, Carlos Alejandro; Frias, Sara

    2010-01-01

    Several cytogenetic studies have shown an increased frequency of chromosomal aberrations for workers exposed to low dose ionizing radiation, however the dose, type of radiation and management vary among the areas of work; it is possible that this variation may generate different quantity of DNA damage, detectable within the first hours after exposure of the personnel. In this study we assessed early DNA lesions caused by exposure to low doses of ionizing radiation in 41 workers from the departments of Radiology, Nuclear Medicine and Radiotherapy and a group of 20 healthy unexposed individuals, all from the same Institution. Blood samples were obtained from exposed and unexposed subjects for analysis of DNA damage using the comet assay. The migration of the comet's tail was compared before and after the workday, as well as among the groups; the relationship between DNA migration and the exposure dose of the month was also obtained. A significant increase in damage to DNA was seen after workday for the occupationally exposed group (p < 0.01) as compared with the samples before workday as well as with those from the unexposed group. A positive correlation was found between the monthly dose of radiation and the migration length of DNA before and after the workday (p < 0.01). There were significant differences in the length of the comet tails among workers from different departments: workers from Radiology (28.6 microm) have less DNA damage than those from Nuclear Medicine and Radiotherapy (92.5 microm, 63.4 microm respectively) departments. All the workers occupationally exposed showed an increase in DNA fragmentation after the workday. The amount of radiation in all three services is different, in Nuclear Medicine and Radiotherapy the workers showed a greater monthly dose of exposure and greater DNA damage than the Radiology workers. The longer tails were observed in Nuclear Medicine where radionuclides are used; these radioactive substances are handled and

  17. Neonatal exposure to a moderate dose of ionizing radiation causes behavioural defects and altered levels of tau protein in mice.

    PubMed

    Buratovic, Sonja; Stenerlöw, Bo; Fredriksson, Anders; Sundell-Bergman, Synnöve; Viberg, Henrik; Eriksson, Per

    2014-12-01

    Medical use of ionizing radiation (IR) has great benefits for treatment and diagnostic imaging, but procedures as computerized tomography (CT) may deliver a significant radiation dose to the patient. Recently, awareness has been raised about possible non-cancer consequences from low dose exposure to IR during critical phases of perinatal and/or neonatal brain development. In the present study neonatal NMRI mice were whole body irradiated with a single dose of gamma radiation (0; 350 and 500 mGy) on postnatal day 10 (PND 10). At 2 and 4 months of age, mice of both sexes were observed for spontaneous behaviour in a novel home environment. The neuroproteins CaMKII, GAP-43, synaptophysin and total tau in male mouse cerebral cortex and hippocampus were analysed 24h post-irradiation and in adults at 6 months of age exposed to 0 or 500 mGy on PND 10. A significantly dose-response related deranged spontaneous behaviour in 2- and 4-month-old mice was observed, where both males and females displayed a modified habituation, indicating reduced cognitive function. The dose of 350 mGy seems to be a tentative threshold. Six-month-old male mice showed a significantly increased level of total tau in cerebral cortex after irradiation to 500 mGy compared to controls. This demonstrates that a single moderate dose of IR, given during a defined critical period of brain development, is sufficient to cause persistently reduced cognitive function. Moreover, an elevation of tau protein was observed in male mice displaying reduced cognitive function.

  18. Cancer and non-cancer brain and eye effects of chronic low-dose ionizing radiation exposure

    PubMed Central

    2012-01-01

    Background According to a fundamental law of radiobiology (“Law of Bergonié and Tribondeau”, 1906), the brain is a paradigm of a highly differentiated organ with low mitotic activity, and is thus radio-resistant. This assumption has been challenged by recent evidence discussed in the present review. Results Ionizing radiation is an established environmental cause of brain cancer. Although direct evidence is lacking in contemporary fluoroscopy due to obvious sample size limitation, limited follow-up time and lack of focused research, anecdotal reports of clusters have appeared in the literature, raising the suspicion that brain cancer may be a professional disease of interventional cardiologists. In addition, although terminally differentiated neurons have reduced or mild proliferative capacity, and are therefore not regarded as critical radiation targets, adult neurogenesis occurs in the dentate gyrus of the hippocampus and the olfactory bulb, and is important for mood, learning/memory and normal olfactory function, whose impairment is a recognized early biomarker of neurodegenerative diseases. The head doses involved in radiotherapy are high, usually above 2 Sv, whereas the low-dose range of professional exposure typically involves lifetime cumulative whole-body exposure in the low-dose range of < 200 mSv, but with head exposure which may (in absence of protection) arrive at a head equivalent dose of 1 to 3 Sv after a professional lifetime (corresponding to a brain equivalent dose around 500 mSv). Conclusions At this point, a systematic assessment of brain (cancer and non-cancer) effects of chronic low-dose radiation exposure in interventional cardiologists and staff is needed. PMID:22540409

  19. Radiative Rates for Forbidden Transitions in Doubly-Ionized Fe-Peak Elements

    NASA Astrophysics Data System (ADS)

    Fivet, Vanessa; Quinet, P.; Bautista, M.

    2012-05-01

    Accurate and reliable atomic data for lowly-ionized Fe-peak species (Sc, Ti, V, Cr, Mn, Fe, Co, Ni and Cu) are of paramount importance for the analysis of the high resolution astrophysical spectra currently available. The third spectra of several iron group elements have been observed in different galactic sources like Herbig-Haro objects in the Orion Nebula [1] and stars like Eta Carinae [2]. However, forbidden transitions between low-lying metastable levels of doubly-ionized iron-peak ions have been very little investigated so far and radiative rates for those lines remain sparse or inexistent. We are carrying out a systematic study of the electronic structure of doubly-ionized iron-peak elements. The magnetic dipole (M1) and electric quadrupole (E2) transition probabilities are computed using the pseudo-relativistic Hartree-Fock (HFR) code of Cowan [3] and the central Thomas-Fermi-Dirac potential approximation implemented in AUTOSTRUCTURE [4]. This multi-platform approach allows for consistency checks and intercomparison and has proven very successful in the study of the complex Fe-peak species where many different effects contribute [5]. References [1] A. Mesa-Delgado et al., MNRAS 395 (2009) 855 [2] S. Johansson et al., A&A 361 (2000) 977 [3] R.D. Cowan, The Theory of Atomic Structure and Spectra, Berkeley: Univ. California Press (1981) [4] N.R. Badnell, J. Phys. B: At. Mol. Opt. Phys. 30 (1997) 1 [5] M. Bautista et al., ApJ 718 (2010) L189

  20. Exposure to ionizing radiation reveals global dose- and time-dependent changes in the urinary metabolome of rat

    PubMed Central

    Mak, Tytus D.; Tyburski, John B.; Krausz, Kristopher W.; Kalinich, John F.; Gonzalez, Frank J.; Fornace, Albert J.

    2014-01-01

    The potential for exposures to ionizing radiation has increased in recent years. Although advances have been made, understanding the global metabolic response as a function of both dose and exposure time is challenging considering the complexity of the responses. Herein we report our findings on the dose- and time-dependency of the urinary response to ionizing radiation in the male rat using radiation metabolomics. Urine samples were collected from adult male rats, exposed to 0.5 to 10 Gy γ–radiation, both before from 6 to 72 h following exposures. Samples were analyzed by liquid chromatography coupled with time-of-flight mass spectrometry, and deconvoluted mass chromatographic data were initially analyzed by principal component analysis. However, the breadth and complexity of the data necessitated the development of a novel approach to summarizing biofluid constituents after exposure, called Visual Analysis of Metabolomics Package (VAMP). VAMP revealed clear urine metabolite profile differences to as little as 0.5 Gy after 6 h exposure. Via VAMP, it was discovered that the response to radiation exposure found in rat urine is characterized by an overall net down-regulation of ion excretion with only a modest number of ions excreted in excess over pre-exposure levels. Our results show both similarities and differences with the published mouse urine response and a dose- and time-dependent net decrease in urine ion excretion associated with radiation exposure. These findings mark an important step in the development of minimally invasive radiation biodosimetry. VAMP should have general applicability in metabolomics to visualize overall differences and trends in many sample sets. PMID:26557048

  1. Calculated ionization rates, ion densities, and airglow emission rates due to precipitating electrons in the nightside ionosphere of Mars

    NASA Technical Reports Server (NTRS)

    Haider, S. A.; Kim, J.; Nagy, A. F.; Keller, C. N.; Verigin, M. I.; Gringauz, K. I.; Shutte, N. M.; Szego, K.; Kiraly, P.

    1992-01-01

    The calculations presented in this paper clearly establish that the electron fluxes measured by the HARP instrument, carried on board Phobos 2, could cause significant electron impact ionization and excitation in the nightside atmosphere of Mars, if these electrons actually do precipitate. The calculated peak electron densities were found to be about a factor of 2 larger than the mean observed nightside densities, indicating that if a significant fraction of the measured electrons actually precipitate, they could be the dominant mechanism responsible for maintaining the nightside ionosphere. The calculated zenith column emission rates of the O I 5577-A and 6300-A and CO Cameron band emissions, due to electron impact and dissociative recombination mechanisms, were found to be significant.

  2. Calculated ionization rates, ion densities, and airglow emission rates due to precipitating electrons in the nightside ionosphere of Mars

    NASA Technical Reports Server (NTRS)

    Haider, S. A.; Kim, J.; Nagy, A. F.; Keller, C. N.; Verigin, M. I.; Gringauz, K. I.; Shutte, N. M.; Szego, K.; Kiraly, P.

    1992-01-01

    The calculations presented in this paper clearly establish that the electron fluxes measured by the HARP instrument, carried on board Phobos 2, could cause significant electron impact ionization and excitation in the nightside atmosphere of Mars, if these electrons actually do precipitate. The calculated peak electron densities were found to be about a factor of 2 larger than the mean observed nightside densities, indicating that if a significant fraction of the measured electrons actually precipitate, they could be the dominant mechanism responsible for maintaining the nightside ionosphere. The calculated zenith column emission rates of the O I 5577-A and 6300-A and CO Cameron band emissions, due to electron impact and dissociative recombination mechanisms, were found to be significant.

  3. Connecting the dots: a correlation between ionizing radiation and cloud mass-loss rate traced by optical integral field spectroscopy

    NASA Astrophysics Data System (ADS)

    McLeod, A. F.; Gritschneder, M.; Dale, J. E.; Ginsburg, A.; Klaassen, P. D.; Mottram, J. C.; Preibisch, T.; Ramsay, S.; Reiter, M.; Testi, L.

    2016-11-01

    We present an analysis of the effect of feedback from O- and B-type stars with data from the integral field spectrograph Multi Unit Spectroscopic Explorer (MUSE) mounted on the Very Large Telescope of pillar-like structures in the Carina Nebular Complex, one of the most massive star-forming regions in the Galaxy. For the observed pillars, we compute gas electron densities and temperatures maps, produce integrated line and velocity maps of the ionized gas, study the ionization fronts at the pillar tips, analyse the properties of the single regions, and detect two ionized jets originating from two distinct pillar tips. For each pillar tip, we determine the incident ionizing photon flux Q0, pil originating from the nearby massive O- and B-type stars and compute the mass-loss rate dot{M} of the pillar tips due to photoevaporation caused by the incident ionizing radiation. We combine the results of the Carina data set with archival MUSE data of a pillar in NGC 3603 and with previously published MUSE data of the Pillars of Creation in M16, and with a total of 10 analysed pillars, find tight correlations between the ionizing photon flux and the electron density, the electron density and the distance from the ionizing sources, and the ionizing photon flux and the mass-loss rate. The combined MUSE data sets of pillars in regions with different physical conditions and stellar content therefore yield an empirical quantification of the feedback effects of ionizing radiation. In agreement with models, we find that dot{M}∝ Q_0,pil^{1/2}.

  4. Excess processing of oxidative damaged bases causes hypersensitivity to oxidative stress and low dose rate irradiation.

    PubMed

    Yoshikawa, Y; Yamasaki, A; Takatori, K; Suzuki, M; Kobayashi, J; Takao, M; Zhang-Akiyama, Q-M

    2015-10-01

    Ionizing radiations such as X-ray and γ-ray can directly or indirectly produce clustered or multiple damages in DNA. Previous studies have reported that overexpression of DNA glycosylases in Escherichia coli (E. coli) and human lymphoblast cells caused increased sensitivity to γ-ray and X-ray irradiation. However, the effects and the mechanisms of other radiation, such as low dose rate radiation, heavy-ion beams, or hydrogen peroxide (H2O2), are still poorly understood. In the present study, we constructed a stable HeLaS3 cell line overexpressing human 8-oxoguanine DNA N-glycosylase 1 (hOGG1) protein. We determined the survival of HeLaS3 and HeLaS3/hOGG1 cells exposed to UV, heavy-ion beams, γ-rays, and H2O2. The results showed that HeLaS3 cells overexpressing hOGG1 were more sensitive to γ-rays, OH(•), and H2O2, but not to UV or heavy-ion beams, than control HeLaS3. We further determined the levels of 8-oxoG foci and of chromosomal double-strand breaks (DSBs) by detecting γ-H2AX foci formation in DNA. The results demonstrated that both γ-rays and H2O2 induced 8-oxoguanine (8-oxoG) foci formation in HeLaS3 cells. hOGG1-overexpressing cells had increased amounts of γ-H2AX foci and decreased amounts of 8-oxoG foci compared with HeLaS3 control cells. These results suggest that excess hOGG1 removes the oxidatively damaged 8-oxoG in DNA more efficiently and therefore generates more DSBs. Micronucleus formation also supported this conclusion. Low dose-rate γ-ray effects were also investigated. We first found that overexpression of hOGG1 also caused increased sensitivity to low dose rate γ-ray irradiation. The rate of micronucleus formation supported the notion that low dose rate irradiation increased genome instability.

  5. High-rate axial-field ionization chamber for particle identification of Radioactive beams

    NASA Astrophysics Data System (ADS)

    Desouza, Romualdo; Vadas, Justin; Singh, Varinderjit; Visser, G.; Alexander, A.; Hudan, S.; Huston, J.; Wiggins, B.; Chbihi, A.; Famiano, M.; Bischak, M.

    2017-01-01

    The design, construction and performance characteristics of a simple axial-field ionization chamber suitable for identifying ions in a radioactive beam are presented. The detector is optimized for use with low-energy radioactive beams (<) 5 MeV/A. A fast charge sensitive amplifier (CSA) integrated into the detector design is also described. Coupling this fast CSA to the axial field ionization chamber produces an output pulse with a rise-time of 60 to 70 ns and a fall time of 100 ns, making the detector capable of sustaining a relatively high rate while providing a time resolution of 6 to 8 ns. Tests with an α source establish the detector energy resolution as 8 % for an energy deposit of 3.5 MeV. Beam tests indicate that the detector is an effective tool for the characterization of low-energy radioactive beams at beam intensities up to 3 x 105 ions/s. Supported by the U.S. DOE under Award # DE-FG02-88ER-40404 and the NSF under Grant No. 1342962.

  6. Dose and dose rate dependency of lipid peroxide formation in rat tissues by low level contamination with tritiated water

    NASA Astrophysics Data System (ADS)

    Moisoi, N.; Petcu, I.

    1999-01-01

    The changes in peroxide level in different tissues (liver, kidney, small intestine, spleen, bone marrow) of rats exposed to low levels of tritiated water were investigated in relation to tissue radiosensitivity, the irradiation dose and the dose rate domain. The radiation exposure was performed by internal contamination of rats with tritiated water, in the 0 50cGy dose domain, with dose rates in the range of 0.01 2cGy/day. For the lower dose rates (< 0.35cGy/day) the peroxide levels did not increase for doses up to 10cGy, while a dose rate of 1 1.75cGy/day induced an increase in peroxide levels starting at 5cGy. The increases were more significant for the tissues with higher radiosensitivity: spleen, small intestine and bone marrow. For the 4.2 7cGy dose domain and very low dose rates, up to 0.1cGy/day, the peroxide level seemed to have an inverse dose rate dependency. Nous avons étudié la modification du niveau des peroxydes lipidiques pour des tissus ayant des radiosensibilités différentes (foie, rein, rate, intestin grêle, moelle osseuse) après irradiation de rats par contamination interne à l'eau tritiée dans le domaine des faibles doses (0 - 50 cGy) et faibles débits de doses (0,01 - 2 cGy/jour). L'irradiation au débit de dose inférieure à 0,35 cGy/jour, n'augmente le niveau de peroxydation que pour des doses supérieures à 10 cGy. Par contre, le débit de 1-1.75 cGy/jour induit une augmentation significative du paramètre étudié à partir de la dose de 5 cGy. Cette augmentation est plus accentuée pour la rate, l'intestin grêle et la moelle osseuse. Aux doses de 4,2-7 cGy et débits de doses très faibles (< 0.1 cGy), le niveau de peroxydation montre une dépendance inverse par rapport au débit de dose.

  7. Biodosimetry of Persons Chronically Exposed to Low and Therapeutic Doses of Ionizing Radiation

    PubMed Central

    Zedginidze, Alla; Namchevadze, Ema; Ormocadze, George; Kapanadze, Archil; Nikuradze, Tamara; Lomidze, Darejan

    2016-01-01

    Dynamic changes of the chromosomal aberrations and the DNA damage were analyzed in individuals exposed to low and therapeutic doses of radiation. The investigation included 37 persons living in areas where the radioactive sources were discovered 10–12 years ago. It was established by biodosimetry methods that the examined persons had absorbed dose of 0.2–0.7 Gy or had increased number of chromosomal aberrations, though insufficient to determine a dose. Clinical examination, chromosomal analysis, and assay of DNA damage by the comet (single-cell gel electrophoresis) assay were carried out. There was no correlation between the doses received 10 years ago and the cytogenetic changes with clinical outcome. The effect of the local fractionated gamma-irradiation with doses of 40–70 Gy was studied in cancer patients with localized head and neck tumors. The study of chromosomal abnormalities, the DNA damages by the comet assay, and the micronuclei detection of the buccal cells revealed a statistically significant correlation between the initial cytogenetic indices in cancer patients and their dynamic changes during and after the radiation exposure. In addition, the correlation was detected between the initial cytogenetic parameters and the functional stage of red blood system. Our results allow us to conclude that there is a need for further research to estimate the individual radiation risk to optimize and individualize the subsequent medical management of radiotherapy. PMID:28217288

  8. Single cell ionization by a laser trap: a preliminary study in measuring radiation dose and charge in BT20 breast carcinoma cells

    PubMed Central

    Kelley, Michele; Gao, Ying; Erenso, Daniel

    2016-01-01

    In this work, a preliminary study in the application of a laser trap for ionization of living carcinoma cells is presented. The study was conducted using BT20 breast carcinoma cells cultured and harvested in our laboratory. Each cell, for a total of 50 cells, was trapped and ionized by a high intensity infrared laser at 1064 nm. The threshold radiation dose and the resultant charge from the ionization for each cell were determined. With the laser trap serving as a radiation source, the cell underwent dielectric breakdown of the membrane. When this process occurs, the cell becomes highly charged and its dielectric susceptibility changes. The charge creates an increasing electrostatic force while the changing dielectric susceptibility diminishes the strength of the trapping force. Consequently, at some instant of time the cell gets ejected from the trap. The time inside the trap while the cell is being ionized, the intensity of the radiation, and the post ionization trajectory of the cell were used to determine the threshold radiation dose and the charge for each cell. The measurement of the charge vs ionization radiation dose at single cell level could be useful in the accuracy of radiotherapy as the individual charges can collectively create a strong enough electrical interaction to cause dielectric breakdown in other cells in a tumor. PMID:27699110

  9. High-dose-rate brachytherapy in uterine cervical carcinoma

    SciTech Connect

    Patel, Firuza D. . E-mail: patelfd@glide.net.in; Rai, Bhavana; Mallick, Indranil; Sharma, Suresh C.

    2005-05-01

    Purpose: High-dose-rate (HDR) brachytherapy is in wide use for curative treatment of cervical cancer. The American Brachytherapy Society has recommended that the individual fraction size be <7.5 Gy and the range of fractions should be four to eight; however, many fractionation schedules, varying from institution to institution, are in use. We use 9 Gy/fraction of HDR in two to five fractions in patients with carcinoma of the uterine cervix. We found that our results and toxicity were comparable to those reported in the literature and hereby present our experience with this fractionation schedule. Methods and Materials: A total of 121 patients with Stage I-III carcinoma of the uterine cervix were treated with HDR brachytherapy between 1996 and 2000. The total number of patients analyzed was 113. The median patient age was 53 years, and the histopathologic type was squamous cell carcinoma in 93% of patients. The patients were subdivided into Groups 1 and 2. In Group 1, 18 patients with Stage Ib-IIb disease, tumor size <4 cm, and preserved cervical anatomy underwent simultaneous external beam radiotherapy to the pelvis to a dose of 40 Gy in 20 fractions within 4 weeks with central shielding and HDR brachytherapy of 9 Gy/fraction, given weekly, and interdigitated with external beam radiotherapy. The 95 patients in Group 2, who had Stage IIb-IIIb disease underwent external beam radiotherapy to the pelvis to a dose of 46 Gy in 23 fractions within 4.5 weeks followed by two sessions of HDR intracavitary brachytherapy of 9 Gy each given 1 week apart. The follow-up range was 3-7 years (median, 36.4 months). Late toxicity was graded according to the Radiation Therapy Oncology Group criteria. Results: The 5-year actuarial local control and disease-free survival rate was 74.5% and 62.0%, respectively. The actuarial local control rate at 5 years was 100% for Stage I, 80% for Stage II, and 67.2% for Stage III patients. The 5-year actuarial disease-free survival rate was 88.8% for

  10. Estimation of annual occupational effective doses from external ionizing radiation at medical institutions in Kenya

    NASA Astrophysics Data System (ADS)

    Korir, Geoffrey; Wambani, Jeska; Korir, Ian

    2011-04-01

    This study details the distribution and trends of doses due to occupational radiation exposure among radiation workers from participating medical institutions in Kenya, where monthly dose measurements were collected for a period of one year ranging from January to December in 2007. A total of 367 medical radiation workers were monitored using thermoluminescent dosemeters. They included radiologists (27%), oncologists (2%), dentists (4%), Physicists (5%), technologists (45%), nurses (4%), film processor technicians (3%), auxiliary staff (4%), and radiology office staff (5%). The average annual effective dose of all categories of staff was found to range from 1.19 to 2.52 mSv. This study formed the initiation stage of wider, comprehensive and more frequent monitoring of occupational radiation exposures and long-term investigations into its accumulation patterns in our country.

  11. Caffeine induces a second wave of apoptosis after low dose-rate gamma radiation of HL-60 cells.

    PubMed

    Vávrová, Jirina; Mareková-Rezácová, Martina; Vokurková, Doris; Szkanderová, Sylva; Psutka, Jan

    2003-10-01

    Most cell lines that lack functional p53 protein are arrested in the G(2) phase of the cell cycle due to DNA damage. It was previously found that the human promyelocyte leukemia cells HL-60 (TP53 negative) that had been exposed to ionizing radiation at doses up to 10 Gy were arrested in the G(2) phase for a period of 24 h. The radioresistance of HL-60 cells that were exposed to low dose-rate gamma irradiation of 3.9 mGy/min, which resulted in a pronounced accumulation of the cells in the G(2) phase during the exposure period, increased compared with the radioresistance of cells that were exposed to a high dose-rate gamma irradiation of 0.6 Gy/min. The D(0) value (i.e. the radiation dose leading to 37% cell survival) for low dose-rate radiation was 3.7 Gy and for high dose-rate radiation 2.2 Gy. In this study, prevention of G(2) phase arrest by caffeine (2 mM) and irradiation of cells with low dose-rate irradiation in all phases of the cell cycle proved to cause radiosensitization (D(0)=2.2 Gy). The irradiation in the presence of caffeine resulted in a second wave of apoptosis on days 5-7 post-irradiation. Caffeine-induced apoptosis occurring later than day 7 post-irradiation is postulated to be a result of unscheduled DNA replication and cell cycle progress.

  12. Mutant frequency of radiotherapy technicians appears to be associated with recent dose of ionizing radiation

    SciTech Connect

    Messing, K.; Ferraris, J.; Bradley, W.E.; Swartz, J.; Seifert, A.M. )

    1989-10-01

    The frequency of hypoxanthine phosphoribosyl transferase (HPRT) mutants among peripheral T-lymphocytes of radiotherapy technicians primarily exposed to 60Co was measured by the T-cell cloning method. Mutant frequencies of these technicians in 1984 and 1986 were significantly higher than those of physiotherapy technicians who worked in a neighboring service, and correlated significantly with thermoluminescence dosimeter readings recorded during the 6 mo preceding mutant frequency determination. Correlations decreased when related to dose recorded over longer time intervals. HPRT mutant frequency determination in peripheral lymphocytes is a good measure of recently received biologically effective radiation dose in an occupationally exposed population.

  13. Dose-effect relation of interstitial low-dose-rate radiation (Ir192) in an animal tumor model

    SciTech Connect

    Ruifrok, A.C.; Levendag, P.C.; Lakeman, R.F.; Deurloo, I.K.; Visser, A.G. )

    1990-01-01

    One way to deliver high doses of radiation to deep seated tumors without damaging the surrounding tissue is by interstitial techniques. This is commonly applied clinically; however, biological data of tumor response to interstitial low-dose-rate gamma irradiation are scarce. Therefore, we have studied the response of rhabdomyosarcoma R1 tumors implanted in the flanks of female Wag/Rij rats using an interstitial Ir192 afterloading system. A template was developed by which four catheters can be implanted in a square geometry with a fixed spacing. Subsequently four Ir192 wires of 2 cm length each are inserted. For dose prescription the highest isodose enveloping the tumor volume was chosen. Interstitial irradiation was performed using tumor volumes of 1500-2000 mm3. A range of minimum tumor doses of 20 up to 115 Gy were given at a mean dose-rate of 48 cGy/hr. Dose-effect relations were obtained from tumor growth curves and tumor cure data, and compared to data from external irradiation. The dose required for 50% cures with interstitial irradiation (TCD50) appears to be 95 +/- 9 Gy. The TCD50 for low-dose-rate interstitial gamma irradiation is 1.5 times the TCD50 for single dose external X ray irradiation at high dose rates, but is comparable to the TCD50 found after fractionated X ray irradiation at high dose rate. Sham treatment of the tumors had no effect on the time needed to reach twice the treatment volume. The growth rate of tumors regrowing after interstitial radiotherapy is not markedly different from the growth rate of untreated (control) tumors (volume doubting time 5.6 +/- 1 day), in contrast to the decreased growth rate after external X ray irradiation.

  14. New model for assessing dose, dose rate, and temperature sensitivity of radiation-induced absorption in glasses

    SciTech Connect

    Gilard, Olivier; Quadri, Gianandrea; Caussanel, Matthieu; Duval, Herve; Reynaud, Francois

    2010-11-15

    A new theoretical approach is proposed to explain the dose, dose rate and temperature sensitivity of the radiation-induced absorption (RIA) in glasses. In this paper, a {beta}{sup th}-order dispersive kinetic model is used to simulate the growth of the density of color centers in irradiated glasses. This model yields an explanation for the power-law dependence on dose and dose rate usually observed for the RIA in optical fibers. It also leads to an Arrhenius-like relationship between the RIA and the glass temperature during irradiation. With a very limited number of adjustable parameters, the model succeeds in explaining, with a good agreement, the RIA growth of two different optical fiber references over wide ranges of dose, dose rate and temperature.

  15. Simulated Space Radiation: Impact of Four Different Types of High-Dose Ionizing Radiation on the Lichen Xanthoria elegans

    NASA Astrophysics Data System (ADS)

    Brandt, Annette; Meeßen, Joachim; Jänicke, Reiner U.; Raguse, Marina; Ott, Sieglinde

    2017-02-01

    This study addresses the viability of the lichen Xanthoria elegans after high-dose ionizing irradiation in the frame of the STARLIFE campaign. The first set of experiments was intended to resemble several types of galactic cosmic radiation (GCR) as present beyond the magnetic shield of Earth. In the second set of experiments, γ radiation up to 113 kGy was applied to test the limit of lichen resistance to ionizing radiation. Entire thalli of Xanthoria elegans were irradiated in the anhydrobiotic state. After STARLIFE 1, the metabolic activity of both symbionts was quantified by live/dead staining with confocal laser scanning microscopy. The photosynthetic activity was measured after the respective irradiation to assess the ability of the symbiotic green algae to restore photosynthesis after irradiation. The STARLIFE campaign complements the results of the LIFE experiments at the EXPOSE-E facility on the International Space Station by testing the model organism Xanthoria elegans on its resistance to hazardous radiation that might be accumulated during long-term space exposure. In addition, the photosynthetic activity of metabolically active lichen was investigated after X-ray irradiation up to 100 Gy (3.3 Gy/min). Since previous astrobiological experiments were mostly performed with anhydrobiotic lichen, these experiments will broaden our knowledge on the correlation of physiological state and astrobiological stressors.

  16. Dosimetry for quantitative analysis of low dose ionizing radiation effects on humans in radiation therapy patients

    SciTech Connect

    Lehmann, J; Stern, R L; Daly, T P; Schwieter, C W; Jones, G E; Arnold, M L; Hartmann-Siantar, C L; Goldberg, Z

    2004-04-20

    We have successfully developed a practical approach to predicting the location of skin surface dose at potential biopsy sites that receive 1 cGy and 10 cGy, respectively, in support of in vivo biologic dosimetry in humans. This represents a significant technical challenge as the sites lie on the patient surface out side the radiation fields. The PEREGRINE Monte Carlo simulation system was used to model radiation dose delivery and TLDs were used for validation on a phantom and confirmation during patient treatment. In the developmental studies the Monte Carlo simulations consistently underestimated the dose at the biopsy site by approximately 15% for a realistic treatment configuration, most likely due to lack of detail in the simulation of the linear accelerator outside the main beam line. Using a single, thickness-independent correction factor for the clinical calculations, the average of 36 measurements for the predicted 1 cGy point was 0.985 cGy (standard deviation: 0.110 cGy) despite patient breathing motion and other real world challenges. Since the 10 cGy point is situated in the region of high dose gradient at the edge of the field, patient motion had a greater effect and the six measured points averaged 5.90 cGy (standard deviation: 1.01 cGy), a difference that is equivalent to approximately a 6 mm shift on the patient's surface.

  17. Accurate Structure Parameters for Tunneling Ionization Rates of Gas-Phase Linear Molecules

    NASA Astrophysics Data System (ADS)

    Zhao, Song-Feng; Li, Jian-Ke; Wang, Guo-Li; Li, Peng-Cheng; Zhou, Xiao-Xin

    2017-03-01

    In the molecular Ammosov-Delone-Krainov (MO-ADK) model of Tong et al. [Phys. Rev. A 66 (2002) 033402], the ionization rate depends on the structure parameters of the molecular orbital from which the electron is removed. We determine systematically and tabulate accurate structure parameters of the highest occupied molecular orbital (HOMO) for 123 gas-phase linear molecules by solving time-independent Schrödinger equation with B-spline functions and molecular potentials which are constructed numerically using the modified Leeuwen-Baerends (LBα) model. Supported by National Natural Science Foundation of China under Grant Nos. 11664035, 11674268, 11465016, 11364038, 11364039, the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No. 20116203120001 and the Basic Scientific Research Foundation for Institution of Higher Learning of Gansu Province

  18. Treating Alzheimer's Dementia With CT-Induced Low-Dose Ionizing Radiation: Problematic, Yet Potential for More Precise Inquiry.

    PubMed

    Raynor, Stephanie; Giordano, James

    2017-01-01

    This commentary evaluates a recent single-case study by Cuttler et al that posits that a series of computerized tomographic (CT) scans ameliorated symptoms and signs of advanced Alzheimer's dementia in an elderly female patient. The report proposes that CT scanning delivered low-dose ionizing radiation (LDIR) that activated adaptive mechanisms in the brain to induce the effects observed and reported. However, the report evidenced methodologic problems that threaten the validity and value of its approach, stated results, and conclusions. We provide discussion of these issues, with view and intent toward developing more precise investigations of the potential mechanisms and utility of LDIR in treating Alzheimer's dementia and possibly other neurodegenerative disorders.

  19. Dose rate dependence of the PTW 60019 microDiamond detector in high dose-per-pulse pulsed beams

    NASA Astrophysics Data System (ADS)

    Brualla-González, Luis; Gómez, Faustino; Pombar, Miguel; Pardo-Montero, Juan

    2016-01-01

    Recombination effects can affect the detectors used for the dosimetry of radiotherapy fields. They are important when using ionization chambers, especially in liquid-filled ionization chambers, and should be corrected for. The introduction of flattening-filter-free accelerators increases the typical dose-per-pulse used in radiotherapy beams, which leads to more important recombination effects. Diamond detectors provide a good solution for the dosimetry and quality assurance of small radiotherapy fields, due to their low energy dependence and small volume. The group of Università di Roma Tor Vergata has developed a synthetic diamond detector, which is commercialized by PTW as microDiamond detector type 60019. In this work we present an experimental characterization of the collection efficiency of the microDiamond detector, focusing on high dose-per-pulse FFF beams. The collection efficiency decreases with dose-per-pulse, down to 0.978 at 2.2 mGy/pulse, following a Fowler-Attix-like curve. On the other hand, we have found no significant dependence of the collection efficiency on the pulse repetition frequency (or pulse period).

  20. The Effect of High-Dose Ionizing Radiation on the Isolated Photobiont of the Astrobiological Model Lichen Circinaria gyrosa

    NASA Astrophysics Data System (ADS)

    Meeßen, Joachim; Backhaus, Theresa; Brandt, Annette; Raguse, Marina; Böttger, Ute; de Vera, Jean-Pierre; de la Torre, Rosa

    2017-02-01

    Lichen symbioses between fungi and algae represent successful life strategies to colonize the most extreme terrestrial habitats. Consequently, space exposure and simulation experiments have demonstrated lichens' high capacity for survival, and thus, they have become models in astrobiological research with which to discern the limits and limitations of terrestrial life. In a series of ground-based irradiation experiments, the STARLIFE campaign investigated the resistance of astrobiological model organisms to galactic cosmic radiation, which is one of the lethal stressors of extraterrestrial environments. Since previous studies have identified that the alga is the more sensitive lichen symbiont, we chose the isolated photobiont Trebouxia sp. of the astrobiological model Circinaria gyrosa as a subject in the campaign. Therein, γ radiation was used to exemplify the deleterious effects of low linear energy transfer (LET) ionizing radiation at extremely high doses up to 113 kGy in the context of astrobiology. The effects were analyzed by chlorophyll a fluorescence of photosystem II (PSII), cultivation assays, live/dead staining and confocal laser scanning microscopy (CLSM), and Raman laser spectroscopy (RLS). The results demonstrate dose-dependent impairment of photosynthesis, the cessation of cell proliferation, cellular damage, a decrease in metabolic activity, and degradation of photosynthetic pigments. While previous investigations on other extraterrestrial stressors have demonstrated a high potential of resistance, results of this study reveal the limits of photobiont resistance to ionizing radiation and characterize γ radiation-induced damages. This study also supports parallel STARLIFE studies on the lichens Circinaria gyrosa and Xanthoria elegans, both of which harbor a Trebouxia sp. photobiont.

  1. Dosis: A computer program for the calculation of absorbed dose in photon and electron beams from ionization measurements in a phantom

    NASA Astrophysics Data System (ADS)

    Andreo, Pedro

    1983-06-01

    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.

  2. Multiple-estimate Monte Carlo calculation of the dose rate constant for a cesium-131 interstitial brachytherapy seed

    SciTech Connect

    Wittman, Richard S.; Fisher, Darrell R.

    2007-01-03

    The purpose of this study was to calculate a more accurate dose rate constant for the Cs-131 (model CS-1, IsoRay Medical, Inc., Richland, Washington) interstitial brachytherapy seed. Previous measurements of the dose rate constant for this seed have been reported by others with incongruity. Recent direct measurements by thermoluminescence dosimetry and by gamma-ray spectroscopy were about 15 percent greater than earlier thermoluminescence dosimetry measurements. Therefore, we set about to calculate independent values by a Monte Carlo approach that combined three estimates as a consistency check, and to quantify the computational uncertainty. The calculated dose rate constant for the Cs-131 seed was 1.040 cGy h^{-1} U^{-1} for an ionization chamber model and 1.032 cGy h^{-1} U^{-1} for a circular ring model. A formal value of 2.2% uncertainty was calculated for both values. The range of our multi-estimate values were from 1.032 cGy h^{-1} U^{-1} to 1.061 cGy h^{-1} U^{-1}. We also modeled three I-125 seeds with known dose rate constants to test the accuracy of this study's approach.

  3. Gamma irradiation: Effect of dose and dose rate on development of mature codling moth larvae and adult eclosion

    NASA Astrophysics Data System (ADS)

    Burditt, Arthur K.; Hungate, Frank P.; Toba, H. Harold

    Codling moth, Cydia pomonella (L.), larvae infest apples, pears and many other fruits and nuts. Mature, nondiapausing, cocooned larvae in fiberboard strips were exposed to γ-irradiation at applied doses ranging from 0 to 98 Gy and dose rates from 0.77 to 204.4 Gy/min and subsequently held to permit further development, pupation and adult emergence. At or above an applied dose of 58 Gy, many of the adults that emerged were physically deformed and most were males. As the applied dose increased from 44 to 98 Gy, the percentage of normal adults decreased, the primary effect shifting from a higher percentage of abnormal adults, pupal mortality, to larval mortility. The effects were more pronounced at higher than at lower dose rates. Insect development apparently was not affected when larvae were irradiated at applied doses up to 31.7 Gy. Significantly more adults emerged when larvae were treated at low dose rates (1.0 Gy/min) than at higher dose rates (204 Gy/min). A rate of 52.2 Gy/min was more effective at preventing adult emergence than rates of 1, 4.4 or 201.5 Gy/min.

  4. Morphological transformation of Syrian hamster embryo cells by low doses of fission neutrons delivered at different dose rates

    SciTech Connect

    Jones, C.A.; Sedita, B.A. ); Hill, C.K. . Cancer Research Lab.); Elkind, M.M. . Dept. of Radiology and Radiation Biology)

    1991-01-01

    Both induction of cell transformation and killing were examined with Syrian hamster embryo (SHE) fibroblasts exposed to low doses of JANUS fission-spectrum neutrons delivered at high (10.3 cGy/min) and low (0.43 and 0.086 cGy/min) dose rates. Second-passage cells were irradiated in mass cultures, then cloned over feeder cells. Morphologically transformed colonies were identified 8-10 days later. Cell killing was independent of dose rate, but the yield of transformation was greater after low-dose-rate irradiations. Decreasing the neutron dose-rate from 10.3 to 0.086 cGy/min resulted in a two- to threefold increase in the yield of transformation for neutron exposures below 50 cGy, and enhancement which was consistently observed in repetitive experiments in different radiosensitive SHE cell preparations. 43 refs., 5 figs., 1 tab.

  5. Ionizing radiation fluxes and dose measurements during the Kosmos 1887 satellite flight.

    PubMed

    Charvat, J; Spurny, F; Kopecka, B; Votockova, I

    1990-01-01

    The results of dosimetric experiments performed during the flight of Kosmos 1887 biosatellite are presented. Two kinds of measurements were performed on the external surface of the satellite. First, the fluences and spectra of low energy charged particles were established. It was found that most of the particles registered by means of solid state nuclear track detectors are helium nuclei. Tracks of oxygen nuclei and some heavier charged particles were also observed. Thermoluminescent detectors were used to establish absorbed doses in open space on the satellite's surface and behind thin shielding. It was found that these doses were rather high; nevertheless, their decrease with shielding thickness is very rapid. Dosimetric and other consequences of the results obtained are analyzed and discussed.

  6. Dose reconstruction for individuals exposed to ionizing radiation using chromosome painting

    NASA Technical Reports Server (NTRS)

    Lucas, J. N.; Cox, A. B. (Principal Investigator)

    1997-01-01

    To be most useful, a biomarker for dose reconstruction should employ an end point that is highly quantitative, stable with time and easily measured. Reciprocal translocations have been shown to be a promising biomarker that is linked to both prior exposure and risk, and they can be measured easily and quantitatively using fluorescence in situ hybridization. In contrast to other biomarkers that are available, the frequency of reciprocal translocations in individuals exposed to whole-body radiation is stable with time after exposure, has rather small interindividual variability and can be measured accurately at low levels of exposure. Results from recent studies demonstrate that measurements of reciprocal translocation frequencies, facilitated by chromosome painting, can be used to reconstruct radiation dose for individuals exposed in the distant past.

  7. Cosmic ray ionization and dose at Mars: Benchmarking deterministic and Monte Carlo methods

    NASA Astrophysics Data System (ADS)

    Norman, R. B.; Gronoff, G.; Mertens, C. J.

    2014-12-01

    The ability to evaluate the cosmic ray environment at Mars is of interest for future manned exploration. To support exploration, tools must be developed to accurately access the radiation environment in both free space and on planetary surfaces. The primary tool NASA uses to quantify radiation exposure behind shielding materials is the space radiation transport code, HZETRN. In order to build confidence in HZETRN, code benchmarking against Monte Carlo radiation transport codes is often used. This work compares the dose calculations at Mars by HZETRN and the GEANT4 application, Planetocosmics. The dose at ground and the energy deposited in the atmosphere by galactic cosmic ray protons and alpha particles has been calculated for the Curiosity landing conditions. In addition, this work has considered Solar Energetic Particle events, which allows for a better understanding of the spectral form in the comparison. The results for protons and alpha particles show very good agreement between HZETRN and Planetocosmics.

  8. Estimating the Effects of Astronaut Career Ionizing Radiation Dose Limits on Manned Interplanetary Flight Programs

    NASA Technical Reports Server (NTRS)

    Koontz, Steven L.; Rojdev, Kristina; Valle, Gerard D.; Zipay, John J.; Atwell, William S.

    2013-01-01

    The Hybrid Inflatable DSH combined with electric propulsion and high power solar-electric power systems offer a near TRL-now solution to the space radiation crew dose problem that is an inevitable aspect of long term manned interplanetary flight. Spreading program development and launch costs over several years can lead to a spending plan that fits with NASA's current and future budgetary limitations, enabling early manned interplanetary operations with space radiation dose control, in the near future while biomedical research, nuclear electric propulsion and active shielding research and development proceed in parallel. Furthermore, future work should encompass laboratory validation of HZETRN calculations, as previous laboratory investigations have not considered large shielding thicknesses and the calculations presented at these thicknesses are currently performed via extrapolation.

  9. Dose reconstruction for individuals exposed to ionizing radiation using chromosome painting

    NASA Technical Reports Server (NTRS)

    Lucas, J. N.; Cox, A. B. (Principal Investigator)

    1997-01-01

    To be most useful, a biomarker for dose reconstruction should employ an end point that is highly quantitative, stable with time and easily measured. Reciprocal translocations have been shown to be a promising biomarker that is linked to both prior exposure and risk, and they can be measured easily and quantitatively using fluorescence in situ hybridization. In contrast to other biomarkers that are available, the frequency of reciprocal translocations in individuals exposed to whole-body radiation is stable with time after exposure, has rather small interindividual variability and can be measured accurately at low levels of exposure. Results from recent studies demonstrate that measurements of reciprocal translocation frequencies, facilitated by chromosome painting, can be used to reconstruct radiation dose for individuals exposed in the distant past.

  10. Effect of low-dose ionizing radiation on luminous marine bacteria: radiation hormesis and toxicity.

    PubMed

    Kudryasheva, N S; Rozhko, T V

    2015-04-01

    The paper summarizes studies of effects of alpha- and beta-emitting radionuclides (americium-241, uranium-235+238, and tritium) on marine microorganisms under conditions of chronic low-dose irradiation in aqueous media. Luminous marine bacteria were chosen as an example of these microorganisms; bioluminescent intensity was used as a tested physiological parameter. Non-linear dose-effect dependence was demonstrated. Three successive stages in the bioluminescent response to americium-241 and tritium were found: 1--absence of effects (stress recognition), 2--activation (adaptive response), and 3--inhibition (suppression of physiological function, i.e. radiation toxicity). The effects were attributed to radiation hormesis phenomenon. Biological role of reactive oxygen species, secondary products of the radioactive decay, is discussed. The study suggests an approach to evaluation of non-toxic and toxic stages under conditions of chronic radioactive exposure.

  11. Dose and dose rate effects of whole-body proton-irradiation on lymphocyte blastogenesis and hematological variables: part II

    NASA Technical Reports Server (NTRS)

    Pecaut, Michael J.; Gridley, Daila S.; Smith, Anna L.; Nelson, Gregory A.

    2002-01-01

    The goal of part II of this study was to evaluate functional characteristics of leukocytes and circulating blood cell parameters after whole-body proton irradiation at varying doses and at low- and high-dose-rates (LDR and HDR, respectively). C57BL/6 mice (n=51) were irradiated and euthanized at 4 days post-exposure for assay. Significant radiation dose- (but not dose-rate-) dependent decreases were observed in splenocyte responses to T and B cell mitogens when compared to sham-irradiated controls (P<0.001). Spontaneous blastogenesis, also significantly dose-dependent, was increased in both blood and spleen (P<0.001). Red blood cell counts, hemoglobin concentration, and hematocrit were decreased in a dose-dependent manner (P<0.05), whereas thrombocyte numbers were only slightly affected. Comparison of proton- and gamma-irradiated groups (both receiving 3 Gy at HDR) showed a higher level of spontaneous blastogenesis in blood leukocytes and a lower splenocyte response to concanavalin A following proton irradiation (P<0.05). There were no dose rate effects. Collectively, the data demonstrate that the measurements in blood and spleen were largely dependent upon the total dose of proton radiation and that an 80-fold difference in the dose rate was not a significant factor. A difference, however, was found between protons and gamma-rays in the degree of change induced in some of the measurements.

  12. Dose and dose rate effects of whole-body proton-irradiation on lymphocyte blastogenesis and hematological variables: part II

    NASA Technical Reports Server (NTRS)

    Pecaut, Michael J.; Gridley, Daila S.; Smith, Anna L.; Nelson, Gregory A.

    2002-01-01

    The goal of part II of this study was to evaluate functional characteristics of leukocytes and circulating blood cell parameters after whole-body proton irradiation at varying doses and at low- and high-dose-rates (LDR and HDR, respectively). C57BL/6 mice (n=51) were irradiated and euthanized at 4 days post-exposure for assay. Significant radiation dose- (but not dose-rate-) dependent decreases were observed in splenocyte responses to T and B cell mitogens when compared to sham-irradiated controls (P<0.001). Spontaneous blastogenesis, also significantly dose-dependent, was increased in both blood and spleen (P<0.001). Red blood cell counts, hemoglobin concentration, and hematocrit were decreased in a dose-dependent manner (P<0.05), whereas thrombocyte numbers were only slightly affected. Comparison of proton- and gamma-irradiated groups (both receiving 3 Gy at HDR) showed a higher level of spontaneous blastogenesis in blood leukocytes and a lower splenocyte response to concanavalin A following proton irradiation (P<0.05). There were no dose rate effects. Collectively, the data demonstrate that the measurements in blood and spleen were largely dependent upon the total dose of proton radiation and that an 80-fold difference in the dose rate was not a significant factor. A difference, however, was found between protons and gamma-rays in the degree of change induced in some of the measurements.

  13. Molecular Mechanisms of Nonlinearity in Response to Low Dose Ionizing Radiation

    DTIC Science & Technology

    2007-10-12

    reducing the cell lethality have not been sensitive enough to show any radiation-absorbed dose uncertainty in the sample. The biopsy site was biological...shown. the patient skin. TLD and/or MOSFET microdosimeters were placed on However, such responses are often subtle and inconsistent the marked sites to...sets of circumstances (6, 7). Another group has examined brain radiation at sites determined to have received 1, 10, or 100 cGy point samples from

  14. SU-E-T-165: Characterization of Dose Distributions in High-Dose-Rate Surface Brachytherapy

    SciTech Connect

    Buzurovic, I; Hansen, J; Bhagwat, M; O’Farrell, D; Damato, A; Friesen, S; Devlin, P; Cormack, R

    2015-06-15

    Purpose: To characterize dose distributions in high-dose-rate(HDR) surface brachytherapy using an Ir-125 source for different geometries, field sizes and topology of the clinical targets(CT). To investigate the depth doses at the central axis(CAX), edges of the treatment fields(E), and lateral dose distributions(L) present when using flap applicators in skin cancer treatments. Methods: When malignancies diagnosed on the skin are treated, various geometries of the CT require proper adaptation of the flap or custom-made applicators to the treatment site. Consequently, the dose at the depth on CAX and field edges changes with variation of the curvatures and size of the applicators. To assess the dose distributions, we created a total of 10 treatment plans(TP) for 10×10 and 20×20 field sizes(FS) with a step size of 1cm. The geometry of the applicators was: planar(PA), curved to 30(CA30) and 60(CA60) degrees with respect to the CAX, half-cylinder(HC), and cylindrical shape(CS). One additional TP was created in which the applicators were positioned to form a dome shape(DS) with a diameter of 16cm. This TP was used to emulate treatment of the average sized scalp. All TPs were optimized to deliver a prescription dose at 8mm equidistantly from the planes containing the dwell positions. This optimization is equivalent to the clinical arrangement since the SSD for the flap applicators is 5mm and the prescription depth is 3mm in the majority of clinical cases. Results: The depths (in mm) of the isodose lines were: FS(10×10):PA[90%(9.1CAX,8.0E,7.6L),50%(28.3CAX,20E,17.3L), 25%(51.1CAX,40E,27L)],CA30[90%(10.3CAX,8.2E,7.9L),50%(32.1CAX, 16.2E,15.8L),25%(61.3CAX,36.7E,31.8L)],CA60[90%(12.2CAX,6.1E,6.3L ),50%(47CAX,14E,16.6L),25%(70.8CAX,31.9E,35.4L)],HC[90%(11.1CA X,6.3E,7.3L),50%(38.3CAX,14.6E,16.1L),25%(66.2CAX,33.8E,34.2L)];FS (20×20):PA[90%(11.1CAX,9.0E,7.0L),50%(34.4CAX,21.9E,15.3L),25%(7 0.4CAX,50.9E,34.8L)],CA30[90%(10.9CAX,7.5E,7.1L),50%(38.8CAX,16. 7E,15.4L),25

  15. Dose rate effect of pulsed electron beam on micronucleus frequency in human peripheral blood lymphocytes.

    PubMed

    Acharya, Santhosh; Sanjeev, Ganesh; Bhat, Nagesh N; Narayana, Yerol

    2010-03-01

    The micronucleus assay in human peripheral blood lymphocytes is a sensitive indicator of radiation damage and could serve as a biological dosimeter in evaluating suspected overexposure to ionising radiation. Micronucleus (MN) frequency as a measure of chromosomal damage has also extensively been employed to quantify the effects of radiation dose rate on biological systems. Here we studied the effects of 8 MeV pulsed electron beam emitted by Microtron electron accelerator on MN induction at dose rates between 35 Gy min-1 and 352.5 Gy min-1. These dose rates were achieved by varying the pulse repetition rate (PRR). Fricke dosimeter was employed to measure the absorbed dose at different PRR and to ensure uniform dose distribution of the electron beam. To study the dose rate effect, blood samples were irradiated to an absorbed dose of (4.7+/-0.2) Gy at different rates and cytogenetic damage was quantified using the micronucleus assay. The obtained MN frequency showed no dose rate dependence within the studied dose rate range. Our earlier dose effect study using 8 MeV electrons revealed that the response of MN was linear-quadratic. Therefore, in the event of an accident, dose estimation can be made using linear-quadratic dose response parameters, without adding dose rate as a correction factor.

  16. SU-E-T-561: Development of Depth Dose Measurement Technique Using the Multilayer Ionization Chamber for Spot Scanning Method

    SciTech Connect

    Takayanagi, T; Fujitaka, S; Umezawa, M; Ito, Y; Nakashima, C; Matsuda, K

    2014-06-01

    Purpose: To develop a measurement technique which suppresses the difference between profiles obtained with a multilayer ionization chamber (MLIC) and with a water phantom. Methods: The developed technique multiplies the raw MLIC data by a correction factor that depends on the initial beam range and water equivalent depth. The correction factor is derived based on a Bragg curve calculation formula considering range straggling and fluence loss caused by nuclear reactions. Furthermore, the correction factor is adjusted based on several integrated depth doses measured with a water phantom and the MLIC. The measured depth dose profiles along the central axis of the proton field with a nominal field size of 10 by 10 cm were compared between the MLIC using the new technique and the water phantom. The spread out Bragg peak was 20 cm for fields with a range of 30.6 cm and 6.9 cm. Raw MLIC data were obtained with each energy layer, and integrated after multiplying by the correction factor. The measurements were performed by a spot scanning nozzle at Nagoya Proton Therapy Center, Japan. Results: The profile measured with the MLIC using the new technique is consistent with that of the water phantom. Moreover, 97% of the points passed the 1% dose /1mm distance agreement criterion of the gamma index. Conclusion: We have demonstrated that the new technique suppresses the difference between profiles obtained with the MLIC and with the water phantom. It was concluded that this technique is useful for depth dose measurement in proton spot scanning method.

  17. LDR brachytherapy: can low dose rate hypersensitivity from the "inverse" dose rate effect cause excessive cell killing to peripherial connective tissues and organs?

    PubMed

    Leonard, B E; Lucas, A C

    2009-02-01

    Examined here are the possible effects of the "inverse" dose rate effect (IDRE) on low dose rate (LDR) brachytherapy. The hyper-radiosensitivity and induced radioresistance (HRS/IRR) effect benefits cell killing in radiotherapy, and IDRE and HRS/IRR seem to be generated from the same radioprotective mechanisms. We have computed the IDRE excess cell killing experienced in LDR brachytherapy using permanent seed implants. We conclude, firstly, that IDRE is a dose rate-dependent manifestation of HRS/IRR. Secondly, the presence of HRS/IRR or IDRE in a cell species or tissue must be determined by direct dose-response measurements. Thirdly, a reasonable estimate is that 50-80% of human adjoining connective and organ tissues experience IDRE from permanent implanted LDR brachytherapy. If IDRE occurs for tissues at point A for cervical cancer, the excess cell killing will be about a factor of 3.5-4.0 if the initial dose rate is 50-70 cGy h(-1). It is greater for adjacent tissues at lower dose rates and higher for lower initial dose rates at point A. Finally, higher post-treatment complications are observed in LDR brachytherapy, often for unknown reasons. Some of these are probably a result of IDRE excess cell killing. Measurements of IDRE need be performed for connective and adjacent organ tissues, i.e. bladder, rectum, urinary tract and small bowels. The measured dose rate-dependent dose responses should extended to <10 cGy h(-1) and involve multiple patients to detect patient variability. Results may suggest a preference for high dose rate brachytherapy or LDR brachytherapy without permanent retention of the implant seeds (hence the dose rates in peripheral tissues and organs remain above IDRE thresholds).

  18. Effect of absorbed dose of ionizing radiation on the decomposition of rare earth nitrates placed in cellular corundum

    SciTech Connect

    Zakharov, M.A.; Kryukov, E.B.; Kuranov, K.V.

    1994-11-01

    The effect of irradiation at different dose rates on the decomposition of a rare earth (Nd) nitrate in cellular corundum is studied. Thermal analysis showed that irradiation lowers the decomposition temperature of Nd nitrate. Increasing the dose rate increases the extent of Nd(NO{sub 3}){sub 3}{center_dot}nH{sub 2}O decomposition (including denitration). The presence of the {Chi}-phase of Al{sub 2}O{sub 3} in the samples facilitates the irreversible immobilization of fission products by considerably lowering the reaction temperature of the matrix with deposited Nd nitrate to form NdAlO{sub 3}.

  19. Dose-effect relation of interstitial low-dose-rate radiation (Ir192) in an animal tumor model.

    PubMed

    Ruifrok, A C; Levendag, P C; Lakeman, R F; Deurloo, I K; Visser, A G

    1990-01-01

    One way to deliver high doses of radiation to deep seated tumors without damaging the surrounding tissue is by interstitial techniques. This is commonly applied clinically; however, biological data of tumor response to interstitial low-dose-rate gamma irradiation are scarce. Therefore, we have studied the response of rhabdomyosarcoma R1 tumors implanted in the flanks of female Wag/Rij rats using an interstitial Ir192 afterloading system. A template was developed by which four catheters can be implanted in a square geometry with a fixed spacing. Subsequently four Ir192 wires of 2 cm length each are inserted. For dose prescription the highest isodose enveloping the tumor volume was chosen. Interstitial irradiation was performed using tumor volumes of 1500-2000 mm3. A range of minimum tumor doses of 20 up to 115 Gy were given at a mean dose-rate of 48 cGy/hr. Dose-effect relations were obtained from tumor growth curves and tumor cure data, and compared to data from external irradiation. The dose required for 50% cures with interstitial irradiation (TCD50) appears to be 95 +/- 9 Gy. The TCD50 for low-dose-rate interstitial gamma irradiation is 1.5 times the TCD50 for single dose external X ray irradiation at high dose rates, but is comparable to the TCD50 found after fractionated X ray irradiation at high dose rate. Sham treatment of the tumors had no effect on the time needed to reach twice the treatment volume. The growth rate of tumors regrowing after interstitial radiotherapy is not markedly different from the growth rate of untreated (control) tumors (volume doubting time 5.6 +/- 1 day), in contrast to the decreased growth rate after external X ray irradiation. It is argued that the absence of a clear tumor bed effect may be explained by some sparing of the stroma by the low-dose-rate of the interstitial irradiation per se as well as by the physical dose distribution of the interstitial Ir192 sources, giving a relative low dose of radiation to the surrounding

  20. Verification of difference of ion-induced nucleation rate for kinds of ionizing radiation

    NASA Astrophysics Data System (ADS)

    Suzuki, A.; Masuda, K.; Takeuchi, Y.; Itow, Y.; Sako, T.; Matsumi, Y.; Nakayama, T.; Ueda, S.; Miura, K.; Kusano, K.

    2014-12-01

    Correlation between the global cloud cover and the galactic cosmic rays intensity has been pointed out. So as one of hypotheses, the promotion of creation of cloud condensation nuclei by cosmic rays can be considered. In this study, we have carried out verification experiment of this hypothesis using an atmospheric reaction chamber at room temperature focusing on the kind of ionizing radiation. We introduced pure air, a trace of water vapor, ozone and sulfur dioxide gas in a chamber with a volume of 75[L]. The sulfur dioxide reacts chemically in the chamber to form sulfate aerosol. After introducing the mixed gas into the chamber, it was irradiated with ultraviolet light, which simulate solar ultraviolet radiation and with anthropogenic ionizing radiation for cosmic rays, particles and new particle formation due to ion-induced nucleation was observed by measuring and recording the densities of ions and aerosol particles, the particle size distribution, the concentrations of ozone and sulfur dioxide, the temperature and the relative humidity. Here, the experimental results of aerosol nucleation rate for different types of radiation are reported. In this experiment, we conducted experiments of irradiation with heavy ions and β-rays. For ionizing radiation Sr-90 β-rays with an average energy of about 1[MeV] and a heavy ion beam from a particle accelerator facility of HIMAC at NIRS (Heavy Ion Medical Accelerator in Chiba, National Institute of Radiological Sciences) were used. The utilized heavy ion was 14N ions of 180[MeV/n] with intensities from 200[particles/spill] to 10000[particles/spill]. In this experimental run the chamber was irradiated for 10 hours and, the relationship between aerosol particle density for the particle size of > of 2.5[nm] and the generated ion density was verified. In the middle, the chamber was irradiated with β-rays for comparison. Increases in the ion density with the increase of the beam intensity were confirmed. Also, a rise in the

  1. Genetic Factors Affecting Susceptibility to Low Dose & Low Dose-Rate Radiation

    SciTech Connect

    Bedford, Joel

    2014-04-18

    Our laboratory has, among other things, developed and used the gamma H2AX focus assay and other chromosomal and cell killing assays to show that differences in this DNA double strand break (dsb) related response can be clearly and distinctly demonstrated for cells which are mildly hyper-radiosensitive such as those associated with A-T heterozygosity. We have found this level of mild hypersensitivity for cells from some 20 to 30 % of apparently normal individuals and from apparently normal parents of Retinoblastoma patients. We found significant differences in gene expression in somatic cells from unaffected parents of Rb patients as compared with normal controls, suggesting that these parents may harbor some as yet unidentified genetic abnormality. In other experiments we sought to determine the extent of differences in normal human cellular reaponses to radiation depending on their irradiation in 2D monolayer vs 3D organized acinar growth conditions. We exmined cell reproductive death, chromosomal aberration induction, and the levels of γ-H2AX foci in cells after single acute gamma-ray doses and immediately after 20 hours of irradiation at a dose rate of 0.0017 Gy/min. We found no significant differences in the dose-responses of these cells under the 2D or 3D growth conditions. While this does not mean such differences cannot occur in other situations, it does mean that they do not generally or necessarily occur. In another series of studies in collaboration with Dr Chuan Li, with supprt from this current grant. We reported a role for apoptotic cell death in promoting wound healing and tissue regeneration in mice. Apoptotic cells released growth signals that stimulated the proliferation of progenitor or stem cells. In yet another collaboration with Dr, B. Chen with funds from this grant, the relative radiosensitivity to cell killing as well as chromosomal instability of 13 DNA-PKcs site-directed mutant cell lines (defective at phosphorylation sites or kinase

  2. Modeling Low-Dose-Rate Effects in Irradiated Bipolar-Base Oxides

    SciTech Connect

    Cirba, C.R.; Fleetwood, D.M.; Graves, R.J.; Michez, A.; Milanowski, R.J.; Saigne, F.; Schrimpf, R.D.; Witczak, S.C.

    1998-10-26

    A physical model is developed to quantify the contribution of oxide-trapped charge to enhanced low-dose-rate gain degradation in bipolar junction transistors. Multiple-trapping simulations show that space charge limited transport is partially responsible for low-dose-rate enhancement. At low dose rates, more holes are trapped near the silicon-oxide interface than at high dose rates, resulting in larger midgap voltage shifts at lower dose rates. The additional trapped charge near the interface may cause an exponential increase in excess base current, and a resultant decrease in current gain for some NPN bipolar technologies.

  3. Retrospective Dosimetric Comparison of Low-Dose-Rate and Pulsed-Dose-Rate Intracavitary Brachytherapy Using a Tandem and Mini-Ovoids

    SciTech Connect

    Mourtada, Firas Gifford, Kent A.; Berner, Paula A.; Horton, John L.; Price, Michael J.; Lawyer, Ann A.; Eifel, Patricia J.

    2007-10-01

    The purpose of this study was to compare the dose distribution of Iridium-192 ({sup 192}Ir) pulsed-dose-rate (PDR) brachytherapy to that of Cesium-137 ({sup 137}Cs) low-dose-rate (LDR) brachytherapy around mini-ovoids and an intrauterine tandem. Ten patient treatment plans were selected from our clinical database, all of which used mini-ovoids and an intrauterine tandem. A commercial treatment planning system using AAPM TG43 formalism was used to calculate the dose in water for both the {sup 137}Cs and {sup 192}Ir sources. For equivalent system loadings, we compared the dose distributions in relevant clinical planes, points A and B, and to the ICRU bladder and rectal reference points. The mean PDR doses to points A and B were 3% {+-} 1% and 6% {+-} 1% higher than the LDR doses, respectively. For the rectum point, the PDR dose was 4% {+-} 3% lower than the LDR dose, mainly because of the {sup 192}Ir PDR source anisotropy. For the bladder point, the PDR dose was 1% {+-} 4% higher than the LDR dose. We conclude that the PDR and LDR dose distributions are equivalent for intracavitary brachytherapy with a tandem and mini-ovoids. These findings will aid in the transfer from the current practice of LDR intracavitary brachytherapy to PDR for the treatment of gynecologic cancers.

  4. Dose equivalent rate constants and barrier transmission data for nuclear medicine facility dose calculations and shielding design.

    PubMed

    Kusano, Maggie; Caldwell, Curtis B

    2014-07-01

    A primary goal of nuclear medicine facility design is to keep public and worker radiation doses As Low As Reasonably Achievable (ALARA). To estimate dose and shielding requirements, one needs to know both the dose equivalent rate constants for soft tissue and barrier transmission factors (TFs) for all radionuclides of interest. Dose equivalent rate constants are most commonly calculated using published air kerma or exposure rate constants, while transmission factors are most commonly calculated using published tenth-value layers (TVLs). Values can be calculated more accurately using the radionuclide's photon emission spectrum and the physical properties of lead, concrete, and/or tissue at these energies. These calculations may be non-trivial due to the polyenergetic nature of the radionuclides used in nuclear medicine. In this paper, the effects of dose equivalent rate constant and transmission factor on nuclear medicine dose and shielding calculations are investigated, and new values based on up-to-date nuclear data and thresholds specific to nuclear medicine are proposed. To facilitate practical use, transmission curves were fitted to the three-parameter Archer equation. Finally, the results of this work were applied to the design of a sample nuclear medicine facility and compared to doses calculated using common methods to investigate the effects of these values on dose estimates and shielding decisions. Dose equivalent rate constants generally agreed well with those derived from the literature with the exception of those from NCRP 124. Depending on the situation, Archer fit TFs could be significantly more accurate than TVL-based TFs. These results were reflected in the sample shielding problem, with unshielded dose estimates agreeing well, with the exception of those based on NCRP 124, and Archer fit TFs providing a more accurate alternative to TVL TFs and a simpler alternative to full spectral-based calculations. The data provided by this paper should assist

  5. Dose and dose rate effects of whole-body gamma-irradiation: II. Hematological variables and cytokines

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    The goal of part II of this study was to evaluate the effects of gamma-radiation on circulating blood cells, functional characteristics of splenocytes, and cytokine expression after whole-body irradiation at varying total doses and at low- and high-dose-rates (LDR, HDR). Young adult C57BL/6 mice (n = 75) were irradiated with either 1 cGy/min or 80 cGy/min photons from a 60Co source to cumulative doses of 0.5, 1.5, and 3.0 Gy. The animals were euthanized at 4 days post-exposure for in vitro assays. Significant dose- (but not dose-rate-) dependent decreases were observed in erythrocyte and blood leukocyte counts, hemoglobin, hematocrit, lipopolysaccharide (LPS)-induced 3H-thymidine incorporation, and interleukin-2 (IL-2) secretion by activated spleen cells when compared to sham-irradiated controls (p < 0.05). Basal proliferation of leukocytes in the blood and spleen increased significantly with increasing dose (p < 0.05). Significant dose rate effects were observed only in thrombocyte counts. Plasma levels of transforming growth factor-beta 1 (TGF-beta 1) and splenocyte secretion of tumor necrosis factor-alpha (TNF-alpha) were not affected by either the dose or dose rate of radiation. The data demonstrate that the responses of blood and spleen were largely dependent upon the total dose of radiation employed and that an 80-fold difference in the dose rate was not a significant factor in the great majority of measurements.

  6. Dose and dose rate effects of whole-body gamma-irradiation: II. Hematological variables and cytokines

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    The goal of part II of this study was to evaluate the effects of gamma-radiation on circulating blood cells, functional characteristics of splenocytes, and cytokine expression after whole-body irradiation at varying total doses and at low- and high-dose-rates (LDR, HDR). Young adult C57BL/6 mice (n = 75) were irradiated with either 1 cGy/min or 80 cGy/min photons from a 60Co source to cumulative doses of 0.5, 1.5, and 3.0 Gy. The animals were euthanized at 4 days post-exposure for in vitro assays. Significant dose- (but not dose-rate-) dependent decreases were observed in erythrocyte and blood leukocyte counts, hemoglobin, hematocrit, lipopolysaccharide (LPS)-induced 3H-thymidine incorporation, and interleukin-2 (IL-2) secretion by activated spleen cells when compared to sham-irradiated controls (p < 0.05). Basal proliferation of leukocytes in the blood and spleen increased significantly with increasing dose (p < 0.05). Significant dose rate effects were observed only in thrombocyte counts. Plasma levels of transforming growth factor-beta 1 (TGF-beta 1) and splenocyte secretion of tumor necrosis factor-alpha (TNF-alpha) were not affected by either the dose or dose rate of radiation. The data demonstrate that the responses of blood and spleen were largely dependent upon the total dose of radiation employed and that an 80-fold difference in the dose rate was not a significant factor in the great majority of measurements.

  7. Rate coefficient for the chemi-ionization in slow Li*(n)+Li and Na*(n)+Na collisions

    SciTech Connect

    Ignjatovic, Lj.M.; Mihajlov, A.A.

    2005-08-15

    The chemi-ionization processes in slow-atom-Rydberg-atom collisions are considered in this paper. A version of the semiclassical method of rate coefficient calculation that is free of the presumptions which significantly limited its applicability previously is presented. The method is applied to the cases of Li*(n)+Li and Na*(n)+Na collisions for the principal quantum numbers 5{<=}n{<=}25 and temperatures 600{<=}T{<=}1200 K. The results of calculation of the rate coefficients of the corresponding chemi-ionization processes are compared to the existing experimental data from the literature.

  8. Urinary bladder carcinogenesis induced by chronic exposure to persistent low-dose ionizing radiation after Chernobyl accident.

    PubMed

    Romanenko, Alina; Kakehashi, Anna; Morimura, Keiichirou; Wanibuchi, Hideki; Wei, Min; Vozianov, Alexander; Fukushima, Shoji

    2009-11-01

    Urinary bladder urothelium as well as cells in the microenvironment of lamina propria (endothelial elements, fibroblasts and lymphocytes) demonstrate a number of responses to chronic persistent long-term, low-dose ionizing radiation (IR). Thus, oxidative stress occurs, accompanied by up-regulation of at least two signaling pathways (p38 mitogen-activated protein kinase and nuclear factor-kappaB cascades) and activation of growth factor receptors, in the bladder urothelium of people living in Cesium 137-contaminated areas of Ukraine, resulting in chronic inflammation and the development of proliferative atypical cystitis, so-called Chernobyl cystitis, which is considered a possible pre-neoplastic condition in humans. Furthermore, significant alterations in regulation of cell cycle transitions are associated with increased cell proliferation, along with up-regulated ubiquitination and sumoylation processes as well as inefficient DNA repair (base and nucleotide excision repair pathways) in the affected urothelium. The microenvironmental changes induced by chronic long-term, low-dose IR also appear to promote angiogenesis and remodeling of the extracellular matrix that could facilitate invasion as well as progression of pre-existing initiated cells to malignancy. Based on the available findings, new strategies have been developed for predicting and treatment of Chernobyl cystitis-a first step in urinary bladder carcinogenesis in humans.

  9. Apoptotic activity of 5-fluorouracil in breast cancer cells transformed by low doses of ionizing α-particle radiation.

    PubMed

    Ponce-Cusi, Richard; Calaf, Gloria M

    2016-02-01

    Globally, breast cancer in women is the leading cause of cancer death. This fact has generated an interest to obtain insight into breast tumorigenesis and also to develop drugs to control the disease. Ras is a proto-oncogene that is activated as a response to extracellular signals. As a member of the Ras GTPase superfamily, Rho-A is an oncogenic and a critical component of signaling pathways leading to downstream gene regulation. In chemotherapy, apoptosis is the predominant mechanism by which cancer cells die. However, even when the apoptotic machinery remains intact, survival signaling may antagonize the cell death by signals. The aim of this study was to evaluate 5-fluorouracil (5-FU) in cells transformed by low doses of ionizing α-particle radiation, in breast cancer cell lines on these genes, as well as apoptotic activity. We used two cell lines from an in vitro experimental breast cancer model. The MCF-10F and Tumor2 cell lines. MCF-10F was exposed to low doses of high linear energy transfer (LET) α-particles radiation (150 keV/µm). Tumor2, is a malignant and tumorigenic cell line obtained from Alpha5 (60cGy+E/60cGy+E) injected into the nude mice. Results indicated that 5-FU decreased H-ras, Rho-A, p53, Stat1 and increased Bax gene expression in Tumor2 and decreased Rac1, Rho-A, NF-κB and increased Bax and caspase-3 protein expression in Tumor2. 5-FU decreased H-ras, Bcl-xL and NF-κB and increased Bax gene expression. 5-FU decreased Rac1, Rho-A protein expression and increased Bax and caspase-3 protein expression in MDA-MB-231. Flow cytometry indicated 21.5% of cell death in the control MCF-10F and 80% in Tumor2 cell lines. It can be concluded that 5-FU may exert apoptotic activity in breast cancer cells transformed by low doses of ionizing α-particles in vitro regulating genes of Ras family and related to apoptosis such as Bax, Bcl-xL and NF-κB expression.

  10. Antioxidant protection against curative and palliative doses of ionizing irradiation in human blood decreases with aging.

    PubMed

    Kasapović, Jelena; Stojiljković, Vesna; Gavrilović, Ljubica; Popović, Nataša; Milićević, Zorka

    2012-01-01

    Reactive oxygen species (ROS) are independently recognized to play a significant role in radiation-induced damage on healthy tissue and in aging process. However, an age-related alteration of antioxidant (AO) system in radiation response in humans is poorly investigated. The aim of this paper was to evaluate the irradiation effects on the activities and expression of AO system in the blood of healthy women during aging. Blood samples were irradiated with curative and palliative doses of 2 Gy or 9 Gy γ-rays. AO capacity for detoxification of O(2)•(-) and H(2)O(2) in response to 2 Gy γ-irradiation decreases in women above 58 years, while in response to 9 Gy shows signs of weakening after 45 years of age. Due to reduction of AO capacity during aging, cytotoxic effects of curative and palliative doses of irradiation, mediated by ROS, may significantly increase in older subjects, while removal of H(2)O(2) excess could reduce them.

  11. Dose specification for 192Ir high dose rate brachytherapy in terms of dose-to-water-in-medium and dose-to-medium-in-medium

    NASA Astrophysics Data System (ADS)

    Paiva Fonseca, Gabriel; Carlsson Tedgren, Åsa; Reniers, Brigitte; Nilsson, Josef; Persson, Maria; Yoriyaz, Hélio; Verhaegen, Frank

    2015-06-01

    Dose calculation in high dose rate brachytherapy with 192Ir is usually based on the TG-43U1 protocol where all media are considered to be water. Several dose calculation algorithms have been developed that are capable of handling heterogeneities with two possibilities to report dose: dose-to-medium-in-medium (Dm,m) and dose-to-water-in-medium (Dw,m). The relation between Dm,m and Dw,m for 192Ir is the main goal of this study, in particular the dependence of Dw,m on the dose calculation approach using either large cavity theory (LCT) or small cavity theory (SCT). A head and neck case was selected due to the presence of media with a large range of atomic numbers relevant to tissues and mass densities such as air, soft tissues and bone interfaces. This case was simulated using a Monte Carlo (MC) code to score: Dm,m, Dw,m (LCT), mean photon energy and photon fluence. Dw,m (SCT) was derived from MC simulations using the ratio between the unrestricted collisional stopping power of the actual medium and water. Differences between Dm,m and Dw,m (SCT or LCT) can be negligible (<1%) for some tissues e.g. muscle and significant for other tissues with differences of up to 14% for bone. Using SCT or LCT approaches leads to differences between Dw,m (SCT) and Dw,m (LCT) up to 29% for bone and 36% for teeth. The mean photon energy distribution ranges from 222 keV up to 356 keV. However, results obtained using mean photon energies are not equivalent to the ones obtained using the full, local photon spectrum. This work concludes that it is essential that brachytherapy studies clearly report the dose quantity. It further shows that while differences between Dm,m and Dw,m (SCT) mainly depend on tissue type, differences between Dm,m and Dw,m (LCT) are, in addition, significantly dependent on the local photon energy fluence spectrum which varies with distance to implanted sources.