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Sample records for absolute dose rate

  1. Absolute depth-dose-rate measurements for an {sup 192}Ir HDR brachytherapy source in water using MOSFET detectors

    SciTech Connect

    Zilio, Valery Olivier; Joneja, Om Parkash; Popowski, Youri; Rosenfeld, Anatoly; Chawla, Rakesh

    2006-06-15

    Reported MOSFET measurements concern mostly external radiotherapy and in vivo dosimetry. In this paper, we apply the technique for absolute dosimetry in the context of HDR brachytherapy using an {sup 192}Ir source. Measured radial dose rate distributions in water for different planes perpendicular to the source axis are presented and special attention is paid to the calibration of the R and K type detectors, and to the determination of appropriate correction factors for the sensitivity variation with the increase of the threshold voltage and the energy dependence. The experimental results are compared with Monte Carlo simulated dose rate distributions. The experimental results show a good agreement with the Monte Carlo simulations: the discrepancy between experimental and Monte Carlo results being within 5% for 82% of the points and within 10% for 95% of the points. Moreover, all points except two are found to lie within the experimental uncertainties, confirming thereby the quality of the results obtained.

  2. Absolute rate theories of epigenetic stability

    NASA Astrophysics Data System (ADS)

    Walczak, Aleksandra M.; Onuchic, José N.; Wolynes, Peter G.

    2005-12-01

    Spontaneous switching events in most characterized genetic switches are rare, resulting in extremely stable epigenetic properties. We show how simple arguments lead to theories of the rate of such events much like the absolute rate theory of chemical reactions corrected by a transmission factor. Both the probability of the rare cellular states that allow epigenetic escape and the transmission factor depend on the rates of DNA binding and unbinding events and on the rates of protein synthesis and degradation. Different mechanisms of escape from the stable attractors occur in the nonadiabatic, weakly adiabatic, and strictly adiabatic regimes, characterized by the relative values of those input rates. rate theory | stochastic gene expression | gene switches

  3. [High dose rate brachytherapy].

    PubMed

    Aisen, S; Carvalho, H A; Chavantes, M C; Esteves, S C; Haddad, C M; Permonian, A C; Taier, M do C; Marinheiro, R C; Feriancic, C V

    1992-01-01

    The high dose rate brachytherapy uses a single source os 192Ir with 10Ci of nominal activity in a remote afterloading machine. This technique allows an outpatient treatment, without the inconveniences of the conventional low dose rate brachytherapy such as use of general anesthesia, rhachianesthesia, prolonged immobilization, and personal exposition to radiation. The radiotherapy department is now studying 5 basic treatment schemes concerning carcinomas of the uterine cervix, endometrium, lung, esophagus and central nervous system tumors. With the Micro Selectron HDR, 257 treatment sessions were done in 90 patients. Mostly were treated with weekly fractions, receiving a total of three to four treatments each. No complications were observed neither during nor after the procedure. Doses, fraction and ideal associations still have to be studied, so that a higher therapeutic ratio can be reached.

  4. The Absolute Rate of LGRB Formation

    NASA Astrophysics Data System (ADS)

    Graham, J. F.; Schady, P.

    2016-06-01

    We estimate the long-duration gamma-ray burst (LGRB) progenitor rate using our recent work on the effects of environmental metallically on LGRB formation in concert with supernovae (SNe) statistics via an approach patterned loosely off the Drake equation. Beginning with the cosmic star formation history, we consider the expected number of broad-line Type Ic events (the SNe type associated with LGRBs) that are in low-metallicity host environments adjusted by the contribution of high-metallicity host environments at a much reduced rate. We then compare this estimate to the observed LGRB rate corrected for instrumental selection effects to provide a combined estimate of the efficiency fraction of these progenitors to produce LGRBs and the fraction of which are beamed in our direction. From this we estimate that an aligned LGRB occurs for approximately every 4000 ± 2000 low-metallically broad-lined SNe Ic. Therefore, if one assumes a semi-nominal beaming factor of 100, then only about one such supernova out of 40 produce an LGRB. Finally, we propose an off-axis LGRB search strategy of targeting only broad-line Type Ic events that occur in low-metallicity hosts for radio observation.

  5. Measurement of Disintegration Rates and Absolute {gamma}-ray Intensities

    SciTech Connect

    DeVries, Daniel J.; Griffin, Henry C.

    2006-03-13

    The majority of practical radioactive materials decay by modes that include {gamma}-ray emission. For questions of 'how much' or 'how pure', one must know the absolute intensities of the major radiations. We are using liquid scintillation counting (LSC) to measurements of disintegration rates, coupled with {gamma}-ray spectroscopy to measure absolute {gamma}-ray emission probabilities. Described is a study of the 227Th chain yielding absolute {gamma}-ray intensities with {approx}0.5% accuracy and information on LSC efficiencies.

  6. Flow rate calibration for absolute cell counting rationale and design.

    PubMed

    Walker, Clare; Barnett, David

    2006-05-01

    There is a need for absolute leukocyte enumeration in the clinical setting, and accurate, reliable (and affordable) technology to determine absolute leukocyte counts has been developed. Such technology includes single platform and dual platform approaches. Derivations of these counts commonly incorporate the addition of a known number of latex microsphere beads to a blood sample, although it has been suggested that the addition of beads to a sample may only be required to act as an internal quality control procedure for assessing the pipetting error. This unit provides the technical details for undertaking flow rate calibration that obviates the need to add reference beads to each sample. It is envisaged that this report will provide the basis for subsequent clinical evaluations of this novel approach. PMID:18770842

  7. Comprehensive fluence model for absolute portal dose image prediction

    SciTech Connect

    Chytyk, K.; McCurdy, B. M. C.

    2009-04-15

    Amorphous silicon (a-Si) electronic portal imaging devices (EPIDs) continue to be investigated as treatment verification tools, with a particular focus on intensity modulated radiation therapy (IMRT). This verification could be accomplished through a comparison of measured portal images to predicted portal dose images. A general fluence determination tailored to portal dose image prediction would be a great asset in order to model the complex modulation of IMRT. A proposed physics-based parameter fluence model was commissioned by matching predicted EPID images to corresponding measured EPID images of multileaf collimator (MLC) defined fields. The two-source fluence model was composed of a focal Gaussian and an extrafocal Gaussian-like source. Specific aspects of the MLC and secondary collimators were also modeled (e.g., jaw and MLC transmission factors, MLC rounded leaf tips, tongue and groove effect, interleaf leakage, and leaf offsets). Several unique aspects of the model were developed based on the results of detailed Monte Carlo simulations of the linear accelerator including (1) use of a non-Gaussian extrafocal fluence source function, (2) separate energy spectra used for focal and extrafocal fluence, and (3) different off-axis energy spectra softening used for focal and extrafocal fluences. The predicted energy fluence was then convolved with Monte Carlo generated, EPID-specific dose kernels to convert incident fluence to dose delivered to the EPID. Measured EPID data were obtained with an a-Si EPID for various MLC-defined fields (from 1x1 to 20x20 cm{sup 2}) over a range of source-to-detector distances. These measured profiles were used to determine the fluence model parameters in a process analogous to the commissioning of a treatment planning system. The resulting model was tested on 20 clinical IMRT plans, including ten prostate and ten oropharyngeal cases. The model predicted the open-field profiles within 2%, 2 mm, while a mean of 96.6% of pixels over

  8. 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.

  9. Rate Change Graph Technology: Absolute Value Point Methodology

    NASA Astrophysics Data System (ADS)

    Strickland, Ken; Duvernois, Michael

    2011-10-01

    Absolute Value Point Methodology (AVPM) is a new theoretical tool for science research centered on Rate Change Graph Technology (RCGT). The modeling techniques of AVPM surpass conventional methods by extending the geometrical rules of mathematics. Exact geometrical structures of matter and energy become clearer revealing new ways to compile advanced data. RCGT mechanics is realized from geometrical intersections that are the result of plotting changing value vs. changing geometry. RCGT methods ignore size and value to perform an objective analysis in geometry. Value and size are then re-introduced back into the analytical system for a clear and concise solution. Available AVPM applications reveal that a massive amount of data from the Big Bang to vast super-clusters is untouched by human thought. Once scientists learn to design tools from RCGT Mechanics, new and formidable approaches to experimentation and theory may lead to new discoveries. In the creation of AVPM, it has become apparent there is a particle-world that exists between strings and our familiar universe. These unrealized particles in their own nature exhibit inflation like properties and may be the progenitor of the implements of our universe. Thus space, time, energy, motion, space-time and gravity are born from its existence and decay. This announcement will be the beginning of many new ideas from the study of RCGT mechanics.

  10. 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.

  11. 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.

  12. 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.

  13. Dose rate mapping of VMAT treatments.

    PubMed

    Podesta, Mark; Popescu, I Antoniu; 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.

  14. 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.

  15. A Program for Calculating Radiation Dose Rates.

    1986-01-27

    Version 00 SMART calculates radiation dose rate at the center of the outer cask surface. It can be applied to determine the radiation dose rate on each cask if source conditions, characteristic function, and material conditions in the bottle regions are given. MANYCASK calculates radiation dose rate distribution in a space surrounded by many casks. If the dose rate on each cask surface can be measured, MANYCASK can be applied to predict dose spatial dosemore » rate distribution for any case of cask configuration.« less

  16. Assessing dose rate distributions in VMAT plans.

    PubMed

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

    2016-04-21

    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 fractionation

  17. 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

  18. Using a dose-area product for absolute measurements in small fields: a feasibility study.

    PubMed

    Dufreneix, S; Ostrowsky, A; Le Roy, M; Sommier, L; Gouriou, J; Delaunay, F; Rapp, B; Daures, J; Bordy, J-M

    2016-01-21

    To extend the dosimetric reference system to field sizes smaller than 2 cm × 2 cm, the LNE-LNHB laboratory is studying an approach based on a new dosimetric quantity named the dose-area product instead of the commonly used absorbed dose at a point. A graphite calorimeter and a plane parallel ion chamber with a sensitive surface of 3 cm diameter were designed and built for measurements in fields of 2, 1 and 0.75 cm diameter. The detector surface being larger than the beam section, most of the issues linked with absolute dose measurements at a point could be avoided. Calibration factors of the plane parallel ionization chamber were established in terms of dose-area product in water for small fields with an uncertainty smaller than 0.9%. PMID:26690271

  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. Absolute calibration of the Gamma Knife{sup ®} Perfexion™ and delivered dose verification using EPR/alanine dosimetry

    SciTech Connect

    Hornbeck, Amaury E-mail: tristan.garcia@cea.fr; Garcia, Tristan E-mail: tristan.garcia@cea.fr; Cuttat, Marguerite; Jenny, Catherine

    2014-06-15

    Purpose: Elekta Leksell Gamma Knife{sup ®} (LGK) is a radiotherapy beam machine whose features are not compliant with the international calibration protocols for radiotherapy. In this scope, the Laboratoire National Henri Becquerel and the Pitié-Salpêtrière Hospital decided to conceive a new LKG dose calibration method and to compare it with the currently used one. Furthermore, the accuracy of the dose delivered by the LGK machine was checked using an “end-to-end” test. This study also aims to compare doses delivered by the two latest software versions of the Gammaplan treatment planning system (TPS). Methods: The dosimetric method chosen is the electron paramagnetic resonance (EPR) of alanine. Dose rate (calibration) verification was done without TPS using a spherical phantom. Absolute calibration was done with factors calculated by Monte Carlo simulation (MCNP-X). For “end-to-end” test, irradiations in an anthropomorphic head phantom, close to real treatment conditions, are done using the TPS in order to verify the delivered dose. Results: The comparison of the currently used calibration method with the new one revealed a deviation of +0.8% between the dose rates measured by ion chamber and EPR/alanine. For simple fields configuration (less than 16 mm diameter), the “end-to-end” tests showed out average deviations of −1.7% and −0.9% between the measured dose and the calculated dose by Gammaplan v9 and v10, respectively. Conclusions: This paper shows there is a good agreement between the new calibration method and the currently used one. There is also a good agreement between the calculated and delivered doses especially for Gammaplan v10.

  1. 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

  2. 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.

  3. Explaining the Relative and Absolute LGRB Rate with Metallically

    NASA Astrophysics Data System (ADS)

    Graham, John

    2016-01-01

    There is now strong evidence that Long-duration Gamma-Ray Bursts (LGRBs) have an intrinsic preference for low-metallicity environments despite the existence of some exceptions to this trend (Graham & Fruchter 2013). Here I will present a pair of results expanding on this work. First, a detailed effort to quantize magnitude of this effect, and characterized its change as a function of metallicity. Thus we directly address a fundamental question of this subfield: how much more likely is an LGRB to form at one metallicity as compared with another? Then, employing these results, we relate the LGRB rate as a function of redshift to the cosmic star-formation rate and provide a detailed breakdown of the intervening steps and their rate of occurrence. This provides interesting implications for radio search efforts to detect off axis LGRB events which will be discussed.

  4. Resource utilization. High dose rate versus low dose rate brachytherapy for gynecologic cancer.

    PubMed

    Bastin, K; Buchler, D; Stitt, J; Shanahan, T; Pola, Y; Paliwal, B; Kinsella, T

    1993-06-01

    A comparative analysis of anesthesia use, perioperative morbidity and mortality, capital, and treatment cost of high dose rate versus low dose rate intracavitary brachytherapy for gynecologic malignancy is presented. To assess current anesthesia utilization, application location, and high dose rate afterloader availability for gynecologic brachytherapy in private and academic practices, a nine-question survey was sent to 150 radiotherapy centers in the United States, of which 95 (63%) responded. Of these 95 respondents, 95% used low dose rate brachytherapy, and 18% possessed high dose rate capability. General anesthesia was used in 95% of programs for tandem + ovoid and in 31% for ovoids-only placement. Differences among private and academic practice respondents were minimal. In our institution, a cost comparison for low dose rate therapy (two applications with 3 hospital days per application, operating and recovery room use, spinal anesthesia, radiotherapy) versus high dose rate treatment (five outpatient departmental applications, intravenous anesthesia without an anesthesiologist, radiotherapy) revealed a 244% higher overall charge for low dose rate treatment, primarily due to hospital and operating room expenses. In addition to its ability to save thousands of dollars per intracavitary patient, high dose rate therapy generated a "cost-shift," increasing radiotherapy departmental billings by 438%. More importantly, perioperative morbidity and mortality in our experience of 500+ high dose rate applications compared favorably with recently reported data using low dose rate intracavitary treatment. Capital investment, maintenance requirements, and depreciation costs for high dose rate capability are reviewed. Application of the defined "revenue-cost ratio" formula demonstrates the importance of high application numbers and consistent reimbursement for parity in high dose rate operation. Logically, inadequate third-party reimbursement (e.g., Medicare) reduces high

  5. An absolute dose determination of helical tomotherapy accelerator, TomoTherapy High-Art II

    SciTech Connect

    Bailat, Claude J.; Buchillier, Thierry; Pachoud, Marc; Moeckli, Raphaeel; Bochud, Francois O.

    2009-09-15

    Purpose: A helical tomotherapy accelerator presents a dosimetric challenge because, to this day, there is no internationally accepted protocol for the determination of the absolute dose. Because of this reality, we investigated the different alternatives for characterizing and measuring the absolute dose of such an accelerator. We tested several dosimetric techniques with various metrological traceabilities as well as using a number of phantoms in static and helical modes. Methods: Firstly, the relationship between the reading of ionization chambers and the absorbed dose is dependent on the beam quality value of the photon beam. For high energy photons, the beam quality is specified by the tissue phantom ratio (TPR{sub 20,10}) and it is therefore necessary to know the TPR{sub 20,10} to calculate the dose delivered by a given accelerator. This parameter is obtained through the ratio of the absorbed dose at 20 and 10 cm depths in water and was measured in the particular conditions of the tomotherapy accelerator. Afterward, measurements were performed using the ionization chamber (model A1SL) delivered as a reference instrument by the vendor. This chamber is traceable in absorbed dose to water in a Co-60 beam to a water calorimeter of the American metrology institute (NIST). Similarly, in Switzerland, each radiotherapy department is directly traceable to the Swiss metrology institute (METAS) in absorbed dose to water based on a water calorimeter. For our research, this traceability was obtained by using an ionization chamber traceable to METAS (model NE 2611A), which is the secondary standard of our institute. Furthermore, in order to have another fully independent measurement method, we determined the dose using alanine dosimeters provided by and traceable to the British metrology institute (NPL); they are calibrated in absorbed dose to water using a graphite calorimeter. And finally, we wanted to take into account the type of chamber routinely used in clinical

  6. Sampling and recording dose rate meter

    SciTech Connect

    Kronenberg, S.

    1984-04-06

    A wide range radiation dose rate for civil defense use, including a Geiger-Mueller tube used in a continuous counting mode and for measuring dose rates from the natural background to about 30. rads/hr., with an ion chamber arranged to measure higher dose rates up to 10,000 rads/hr. The instrument has a sample and record capability in which the selected radiation detector will have its output connected to a selected storage capacitor for a precise interval of time determined by a timing circuit and the storage capacitor will accumulate and hold a voltage proportional to the dose rate, which can be read by means of an electrometer at a later time. The instrument has a self contained hand cranked power supply and all components are selected for long shelf life.

  7. 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.

  8. Single- and Multiple-Dose Pharmacokinetics and Absolute Bioavailability of Tedizolid

    PubMed Central

    Flanagan, Shawn; Fang, Edward; Muñoz, Kelly A; Minassian, Sonia L; Prokocimer, Philippe G

    2014-01-01

    Objectives Tedizolid phosphate is a novel antibacterial under investigation for the treatment of gram-positive infections. This study was conducted to assess the pharmacokinetics, safety, and tolerability of intravenous tedizolid phosphate as well as the oral bioavailability of tedizolid phosphate. Design Double-blind, single-ascending dose, multiple-dose pharmacokinetics study, as well as tolerability and open-label crossover studies. Setting Single center in the United States (Covance Clinical Research Unit, Madison, WI) between September 2009 and January 2010. Participants Ninety healthy volunteers. Intervention Single intravenous (IV) doses of tedizolid phosphate 50 mg (lead-in) and 100–400 mg. Single oral and IV dose of tedizolid phosphate 200 mg in crossover fashion. Multiple IV doses of tedizolid phosphate 200 and 300 mg for up to 7 days. Measurements and Main Results A dose-dependent increase was observed in the maximum plasma concentration (1.2–5.1 μg/ml) and the area under the concentration-time curve (17.4–58.7 μg × hr/ml) of tedizolid (the microbiologically active moiety of tedizolid phosphate) after single IV doses of tedizolid phosphate 100–400 mg. Administration of IV tedizolid phosphate 200 mg once/day for 7 days resulted in minimal (28%) tedizolid accumulation. The absolute oral bioavailability of tedizolid after a single 200-mg dose of tedizolid phosphate was 91%; pharmacokinetic parameters of tedizolid were similar with oral and IV administration. Treatment-related adverse events occurred in 41% of subjects. Most adverse events were related to infusion site and became more frequent with multiple dosing. In an additional 3-day tolerability study, IV tedizolid phosphate 200 mg and placebo were similarly tolerated, based on visual infusion phlebitis scores. Conclusion These results from a population of healthy volunteers support once/day dosing of tedizolid phosphate 200 mg with both the oral and IV formulations, without the

  9. Dose and dose rate effectiveness of space radiation.

    PubMed

    Schimmerling, W; Cucinotta, F A

    2006-01-01

    Dose and dose rate effectiveness factors (DDREF), in conjunction with other weighting factors, are commonly used to scale atomic bomb survivor data in order to establish limits for occupational radiation exposure, including radiation exposure in space. We use some well-known facts about the microscopic pattern of energy deposition of high-energy heavy ions, and about the dose rate dependence of chemical reactions initiated by radiation, to show that DDREF are likely to vary significantly as a function of particle type and energy, cell, tissue, and organ type, and biological end point. As a consequence, we argue that validation of DDREF by conventional methods, e.g. irradiating animal colonies and compiling statistics of cancer mortality, is not appropriate. However, the use of approaches derived from information theory and thermodynamics is a very wide field, and the present work can only be understood as a contribution to an ongoing discussion. PMID:17169950

  10. 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.

  11. 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.

  12. TU-A-12A-09: Absolute Blood Flow Measurement in a Cardiac Phantom Using Low Dose CT

    SciTech Connect

    Ziemer, B; Hubbard, L; Lipinski, J; Molloi, S

    2014-06-15

    Purpose: To investigate a first pass analysis technique to measure absolute flow from low dose CT images in a cardiac phantom. This technique can be combined with a myocardial mass assignment to yield absolute perfusion using only two volume scans and reduce the radiation dose to the patient. Methods: A four-chamber cardiac phantom and perfusion chamber were constructed from poly-acrylic and connected with tubing to approximate anatomical features. The system was connected to a pulsatile pump, input/output reservoirs and power contrast injector. Flow was varied in the range of 1-2.67 mL/s with the pump operating at 60 beats/min. The system was imaged once a second for 14 seconds with a 320-row scanner (Toshiba Medical Systems) using a contrast-enhanced, prospective-gated cardiac perfusion protocol. Flow was calculated by the following steps: subsequent images of the perfusion volume were subtracted to find the contrast entering the volume; this was normalized by an upstream, known volume region to convert Hounsfield (HU) values to concentration; this was divided by the subtracted images time difference. The technique requires a relatively stable input contrast concentration and no contrast can leave the perfusion volume before the flow measurement is completed. Results: The flow calculated from the images showed an excellent correlation with the known rates. The data was fit to a linear function with slope 1.03, intercept 0.02 and an R{sup 2} value of 0.99. The average root mean square (RMS) error was 0.15 mL/s and the average standard deviation was 0.14 mL/s. The flow rate was stable within 7.7% across the full scan and served to validate model assumptions. Conclusion: Accurate, absolute flow rates were measured from CT images using a conservation of mass model. Measurements can be made using two volume scans which can substantially reduce the radiation dose compared with current dynamic perfusion techniques.

  13. The impact of water temperature on the measurement of absolute dose

    NASA Astrophysics Data System (ADS)

    Islam, Naveed Mehdi

    To standardize reference dosimetry in radiation therapy, Task Group 51 (TG 51) of American Association of Physicist's in Medicine (AAPM) recommends that dose calibration measurements be made in a water tank at a depth of 10 cm and at a reference geometry. Methodologies are provided for calculating various correction factors to be applied in calculating the absolute dose. However the protocol does not specify the water temperature to be used. In practice, the temperature of water during dosimetry may vary considerably between independent sessions and different centers. In this work the effect of water temperature on absolute dosimetry has been investigated. Density of water varies with temperature, which in turn may impact the beam attenuation and scatter properties. Furthermore, due to thermal expansion or contraction air volume inside the chamber may change. All of these effects can result in a change in the measurement. Dosimetric measurements were made using a Farmer type ion chamber on a Varian Linear Accelerator for 6 MV and 23 MV photon energies for temperatures ranging from 10 to 40 °C. A thermal insulation was designed for the water tank in order to maintain relatively stable temperature over the duration of the experiment. Dose measured at higher temperatures were found to be consistently higher by a very small magnitude. Although the differences in dose were less than the uncertainty in each measurement, a linear regression of the data suggests that the trend is statistically significant with p-values of 0.002 and 0.013 for 6 and 23 MV beams respectively. For a 10 degree difference in water phantom temperatures, which is a realistic deviation across clinics, the final calculated reference dose can differ by 0.24% or more. To address this effect, first a reference temperature (e.g.22 °C) can be set as the standard; subsequently a correction factor can be implemented for deviations from this reference. Such a correction factor is expected to be of similar

  14. 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.

  15. 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

  16. ISFSI site boundary radiation dose rate analyses.

    PubMed

    Hagler, R J; Fero, A H

    2005-01-01

    Across the globe nuclear utilities are in the process of designing and analysing Independent Spent Fuel Storage Installations (ISFSI) for the purpose of above ground spent-fuel storage primarily to mitigate the filling of spent-fuel pools. Using a conjoining of discrete ordinates transport theory (DORT) and Monte Carlo (MCNP) techniques, an ISFSI was analysed to determine neutron and photon dose rates for a generic overpack, and ISFSI pad configuration and design at distances ranging from 1 to -1700 m from the ISFSI array. The calculated dose rates are used to address the requirements of 10CFR72.104, which provides limits to be enforced for the protection of the public by the NRC in regard to ISFSI facilities. For this overpack, dose rates decrease by three orders of magnitude through the first 200 m moving away from the ISFSI. In addition, the contributions from different source terms changes over distance. It can be observed that although side photons provide the majority of dose rate in this calculation, scattered photons and side neutrons take on more importance as the distance from the ISFSI is increased. PMID:16604670

  17. 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

  18. Absolute and Relative Reliability of Percentage of Syllables Stuttered and Severity Rating Scales

    ERIC Educational Resources Information Center

    Karimi, Hamid; O'Brian, Sue; Onslow, Mark; Jones, Mark

    2014-01-01

    Purpose: Percentage of syllables stuttered (%SS) and severity rating (SR) scales are measures in common use to quantify stuttering severity and its changes during basic and clinical research conditions. However, their reliability has not been assessed with indices measuring both relative and absolute reliability. This study was designed to provide…

  19. Effective light absorption and absolute electron transport rates in the coral Pocillopora damicornis.

    PubMed

    Szabó, Milán; Wangpraseurt, Daniel; Tamburic, Bojan; Larkum, Anthony W D; Schreiber, Ulrich; Suggett, David J; Kühl, Michael; Ralph, Peter J

    2014-10-01

    Pulse Amplitude Modulation (PAM) fluorometry has been widely used to estimate the relative photosynthetic efficiency of corals. However, both the optical properties of intact corals as well as past technical constrains to PAM fluorometers have prevented calculations of the electron turnover rate of PSII. We used a new Multi-colour PAM (MC-PAM) in parallel with light microsensors to determine for the first time the wavelength-specific effective absorption cross-section of PSII photochemistry, σII(λ), and thus PAM-based absolute electron transport rates of the coral photosymbiont Symbiodinium both in culture and in hospite in the coral Pocillopora damicornis. In both cases, σII of Symbiodinium was highest in the blue spectral region and showed a progressive decrease towards red wavelengths. Absolute values for σII at 440 nm were up to 1.5-times higher in culture than in hospite. Scalar irradiance within the living coral tissue was reduced by 20% in the blue when compared to the incident downwelling irradiance. Absolute electron transport rates of P. damicornis at 440 nm revealed a maximum PSII turnover rate of ca. 250 electrons PSII(-1) s(-1), consistent with one PSII turnover for every 4 photons absorbed by PSII; this likely reflects the limiting steps in electron transfer between PSII and PSI. Our results show that optical properties of the coral host strongly affect light use efficiency of Symbiodinium. Therefore, relative electron transport rates do not reflect the productivity rates (or indeed how the photosynthesis-light response is parameterised). Here we provide a non-invasive approach to estimate absolute electron transport rates in corals.

  20. Absolute rate of the reaction of hydrogen atoms with ozone from 219-360 K

    NASA Technical Reports Server (NTRS)

    Lee, J. H.; Michael, J. V.; Payne, W. A.; Stief, L. J.

    1978-01-01

    Absolute rate constants for the reaction of atomic hydrogen with ozone were obtained over the temperature range 219-360 K by the flash photolysis-resonance fluorescence technique. The results can be expressed in Arrhenius form by K = (1.33 plus or minus 0.32)x10 to the minus 10 power exp (-449 plus or minus 58/T) cu cm/molecule/s (two standard deviations). The present work is compared to two previous determinations and is discussed theoretically.

  1. Absolute Density Calibration Cell for Laser Induced Fluorescence Erosion Rate Measurements

    NASA Technical Reports Server (NTRS)

    Domonkos, Matthew T.; Stevens, Richard E.

    2001-01-01

    Flight qualification of ion thrusters typically requires testing on the order of 10,000 hours. Extensive knowledge of wear mechanisms and rates is necessary to establish design confidence prior to long duration tests. Consequently, real-time erosion rate measurements offer the potential both to reduce development costs and to enhance knowledge of the dependency of component wear on operating conditions. Several previous studies have used laser-induced fluorescence (LIF) to measure real-time, in situ erosion rates of ion thruster accelerator grids. Those studies provided only relative measurements of the erosion rate. In the present investigation, a molybdenum tube was resistively heated such that the evaporation rate yielded densities within the tube on the order of those expected from accelerator grid erosion. This work examines the suitability of the density cell as an absolute calibration source for LIF measurements, and the intrinsic error was evaluated.

  2. Absolute rate coefficients for the recombination of open f-shell tungsten ions

    NASA Astrophysics Data System (ADS)

    Krantz, C.; Spruck, K.; Badnell, N. R.; Becker, A.; Bernhardt, D.; Grieser, M.; Hahn, M.; Novotný, O.; Repnow, R.; Savin, D. W.; Wolf, A.; Müller, A.; Schippers, S.

    2014-04-01

    We have carried out direct measurements of the absolute recombination rate coefficients of four charge states of tungsten in the range from W18+ to W21+ in a heavy ion storage ring. We find that the rich atomic fine structure of the open f-shell leads to very high resonant enhancement of the recombination rate at energies below ~50 eV. Even in the higher energy domain relevant to fusion plasma this leads to a recombination rate coefficient that is more than four times higher than predicted by the commonly used ADAS database of recombination rates. In addition to the experimental measurements we have carried out theoretical calculations using Autostructure. For W20+ these predict a plasma recombination rate coefficient that agrees much better with the measurement than the ADAS model but still fail to reproduce the experimental data in detail.

  3. Brachytherapy for early oral tongue cancer: low dose rate to high dose rate.

    PubMed

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

    2003-03-01

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

  4. Evaluation of clinical IMRT treatment planning using the GATE Monte Carlo simulation platform for absolute and relative dose calculations

    SciTech Connect

    Benhalouche, S.; Le Maitre, A.; Visvikis, D.; Pradier, O.; Boussion, N.

    2013-02-15

    Purpose: The objective of this study was to evaluate and validate the use of the Geant4 application for emission tomography (GATE) Monte Carlo simulation platform for clinical intensity modulated radiotherapy (IMRT) dosimetry studies. Methods: The first step consisted of modeling a 6 MV photon beam linear accelerator (LINAC), with its corresponding validation carried out using percent depth dose evaluation, transverse profiles, tissue phantom ratio, and output factor on water phantom. The IMRT evaluation was performed by comparing simulation and measurements in terms of absolute and relative doses using IMRT dedicated quality assurance phantoms considering seven different patient datasets. Results: Concerning the LINAC simulated model validation tissue phantom ratios at 20 and 10 cm in water TPR{sub 10}{sup 20} obtained from GATE and measurements were 0.672 {+-} 0.063 and 0.675, respectively. In terms of percent depth dose and transverse profiles, error ranges were, respectively: 1.472%{+-} 0.285% and 4.827%{+-} 1.323% for field size of 4 Multiplication-Sign 4, 5 Multiplication-Sign 5, 10 Multiplication-Sign 10, 15 Multiplication-Sign 15, 20 Multiplication-Sign 20, 25 Multiplication-Sign 25, 30 Multiplication-Sign 30, and 40 Multiplication-Sign 40 cm{sup 2}. Most errors were observed at the edge of radiation fields because of higher dose gradient in these areas. Output factors showed good agreement between simulation and measurements with a maximum error of 1.22%. Finally, for IMRT simulations considering seven patient datasets, GATE provided good results with a relative error of 0.43%{+-} 0.25% on absolute dose between simulated and measured beams (measurements at the isocenter, volume 0.125 cm{sup 3}). Planar dose comparisons were also performed using gamma-index analysis. For the whole set of beams considered the mean gamma-index value was 0.497 {+-} 0.152 and 90.8%{+-} 3.6% of the evaluated dose points satisfied the 5%/ 4 mm criterion. Conclusions: These

  5. 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.

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

    SciTech Connect

    Levy, R.P.

    1991-01-01

    An in vitro system using neuroglia from neonatal rat brain was developed to examining the morphologic, immunocytochemical and biochemical response of oligodendroglia to ionizing radiation. Following acute [gamma]-radiation 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. It was concluded that oligodendrocytes in irradiated cultures had significantly lower functional capacity than did unirradiated controls. 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. At DIC 14, the group irradiated in a single fraction had significantly lower oligodendrocyte counts than any group given split doses; all irradiated cultures had marked depression of MBP synthesis, but to significant differences referable to time interval between doses. At DIC 21, cultures irradiated at intervals of 0 h to 2 h had similar oligodendrocyte counts to one another, but these counts were significantly lower than in cultures irradiated at intervals of 4 h to 6 h; MBP levels remained depressed at DIC 21 for all irradiated cultures. The oligodendrocyte response to dose rate (0.03 to 1.97 Gy/min) was evaluated at DIC 14 and DIC 21. Exposure at 0.03 Gy/min suppressed oligodendrocyte counts at DIC 21 less than did higher dose rates in 5-Gy irradiated cultures.

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

    NASA Astrophysics Data System (ADS)

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

    2006-09-01

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

  8. 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.

  9. The Br+HO 2 reaction revisited: Absolute determination of the rate constant at 298 K

    NASA Astrophysics Data System (ADS)

    Laverdet, G.; Le Bras, G.; Mellouki, A.; Poulet, G.

    1990-09-01

    The absolute determination of the rate constant for the reaction Br+HO 2→HBr+O 2 has been done at 298 K using the discharge-flor EPR method. The value k1 = (1.5±0.2) × 10 -12 cm 3 molecule -1 s -1 was obtained. Previous indirect measurements of k1 from a discharge-flow, LIF/mass spectrometric study of the Br/H 2CO/O 2 system have been reinterpreted, leading to values for k1 ranging from 1.0 × 10 -12 to 2.2 × 10 -12 cm 3 molecule -1 s -1 at 298 K. These results are discussed and compared with other literature values.

  10. 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.

  11. Method to determine the position-dependant metal correction factor for dose-rate equivalent laser testing of semiconductor devices

    DOEpatents

    Horn, Kevin M.

    2013-07-09

    A method reconstructs the charge collection from regions beneath opaque metallization of a semiconductor device, as determined from focused laser charge collection response images, and thereby derives a dose-rate dependent correction factor for subsequent broad-area, dose-rate equivalent, laser measurements. The position- and dose-rate dependencies of the charge-collection magnitude of the device are determined empirically and can be combined with a digital reconstruction methodology to derive an accurate metal-correction factor that permits subsequent absolute dose-rate response measurements to be derived from laser measurements alone. Broad-area laser dose-rate testing can thereby be used to accurately determine the peak transient current, dose-rate response of semiconductor devices to penetrating electron, gamma- and x-ray irradiation.

  12. 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.

  13. Study on improving the turbidity measurement of the absolute coagulation rate constant.

    PubMed

    Sun, Zhiwei; Liu, Jie; Xu, Shenghua

    2006-05-23

    The existing theories dealing with the evaluation of the absolute coagulation rate constant by turbidity measurement were experimentally tested for different particle-sized (radius = a) suspensions at incident wavelengths (lambda) ranging from near-infrared to ultraviolet light. When the size parameter alpha = 2pi a/lambda > 3, the rate constant data from previous theories for fixed-sized particles show significant inconsistencies at different light wavelengths. We attribute this problem to the imperfection of these theories in describing the light scattering from doublets through their evaluation of the extinction cross section. The evaluations of the rate constants by all previous theories become untenable as the size parameter increases and therefore hampers the applicable range of the turbidity measurement. By using the T-matrix method, we present a robust solution for evaluating the extinction cross section of doublets formed in the aggregation. Our experiments show that this new approach is effective in extending the applicability range of the turbidity methodology and increasing measurement accuracy.

  14. 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.

  15. 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. PMID:26808878

  16. 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.

  17. 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.

  18. Effect of various methods for rectum delineation on relative and absolute dose-volume histograms for prostate IMRT treatment planning.

    PubMed

    Kusumoto, Chiaki; Ohira, Shingo; Miyazaki, Masayoshi; Ueda, Yoshihiro; Isono, Masaru; Teshima, Teruki

    2016-01-01

    Several reports have dealt with correlations of late rectal toxicity with rectal dose-volume histograms (DVHs) for high dose levels. There are 2 techniques to assess rectal volume for reception of a specific dose: relative-DVH (R-DVH, %) that indicates relative volume for a vertical axis, and absolute-DVH (A-DVH, cc) with its vertical axis showing absolute volume of the rectum. The parameters of DVH vary depending on the rectum delineation method, but the literature does not present any standardization of such methods. The aim of the present study was to evaluate the effects of different delineation methods on rectal DVHs. The enrollment for this study comprised 28 patients with high-risk localized prostate cancer, who had undergone intensity-modulated radiation therapy (IMRT) with the prescription dose of 78Gy. The rectum was contoured with 4 different methods using 2 lengths, short (Sh) and long (Lg), and 2 cross sections, rectum (Rec) and rectal wall (Rw). Sh means the length from 1cm above the seminal vesicles to 1cm below the prostate and Lg the length from the rectosigmoid junction to the anus. Rec represents the entire rectal volume including the rectal contents and Rw the rectal volume of the area with a wall thickness of 4mm. We compared dose-volume parameters by using 4 rectal contour methods for the same plan with the R-DVHs as well as the A-DVHs. For the high dose levels, the R-DVH parameters varied widely. The mean of V70 for Sh-Rw was the highest (19.4%) and nearly twice as high as that for Lg-Rec (10.4%). On the contrary, only small variations were observed in the A-DVH parameters (4.3, 4.3, 5.5, and 5.5cc for Sh-Rw, Lg-Rw, Sh-Rec, and Lg-Rec, respectively). As for R-DVHs, the parameters of V70 varied depending on the rectal lengths (Sh-Rec vs Lg-Rec: R = 0.76; Sh-Rw vs Lg-Rw: R = 0.85) and cross sections (Sh-Rec vs Sh-Rw: R = 0.49; Lg-Rec vs Lg-Rw: R = 0.65). For A-DVHs, however, the parameters of Sh rectal A-DVHs hardly changed regardless of

  19. SU-E-J-85: Leave-One-Out Perturbation (LOOP) Fitting Algorithm for Absolute Dose Film Calibration

    SciTech Connect

    Chu, A; Ahmad, M; Chen, Z; Nath, R

    2014-06-01

    Purpose: To introduce an outliers-recognition fitting routine for film dosimetry. It cannot only be flexible with any linear and non-linear regression but also can provide information for the minimal number of sampling points, critical sampling distributions and evaluating analytical functions for absolute film-dose calibration. Methods: The technique, leave-one-out (LOO) cross validation, is often used for statistical analyses on model performance. We used LOO analyses with perturbed bootstrap fitting called leave-one-out perturbation (LOOP) for film-dose calibration . Given a threshold, the LOO process detects unfit points (“outliers”) compared to other cohorts, and a bootstrap fitting process follows to seek any possibilities of using perturbations for further improvement. After that outliers were reconfirmed by a traditional t-test statistics and eliminated, then another LOOP feedback resulted in the final. An over-sampled film-dose- calibration dataset was collected as a reference (dose range: 0-800cGy), and various simulated conditions for outliers and sampling distributions were derived from the reference. Comparisons over the various conditions were made, and the performance of fitting functions, polynomial and rational functions, were evaluated. Results: (1) LOOP can prove its sensitive outlier-recognition by its statistical correlation to an exceptional better goodness-of-fit as outliers being left-out. (2) With sufficient statistical information, the LOOP can correct outliers under some low-sampling conditions that other “robust fits”, e.g. Least Absolute Residuals, cannot. (3) Complete cross-validated analyses of LOOP indicate that the function of rational type demonstrates a much superior performance compared to the polynomial. Even with 5 data points including one outlier, using LOOP with rational function can restore more than a 95% value back to its reference values, while the polynomial fitting completely failed under the same conditions

  20. 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.

  1. 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.

  2. Subjective evaluation of HDTV stereoscopic videos in IPTV scenarios using absolute category rating

    NASA Astrophysics Data System (ADS)

    Wang, K.; Barkowsky, M.; Cousseau, R.; Brunnström, K.; Olsson, R.; Le Callet, P.; Sjöström, M.

    2011-03-01

    Broadcasting of high definition (HD) stereobased 3D (S3D) TV are planned, or has already begun, in Europe, the US, and Japan. Specific data processing operations such as compression and temporal and spatial resampling are commonly used tools for saving network bandwidth when IPTV is the distribution form, as this results in more efficient recording and transmission of 3DTV signals, however at the same time it inevitably brings quality degradations to the processed video. This paper investigated observers quality judgments of state of the art video coding schemes (simulcast H.264/AVC or H.264/MVC), with or without added temporal and spatial resolution reduction of S3D videos, by subjective experiments using the Absolute Category Rating method (ACR) method. The results showed that a certain spatial resolution reduction working together with high quality video compressing was the most bandwidth efficient way of processing video data when the required video quality is to be judged as "good" quality. As the subjective experiment was performed in two different laboratories in two different countries in parallel, a detailed analysis of the interlab differences was performed.

  3. 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.

  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. Dose characterization in the near-source region for two high dose rate brachytherapy sources.

    PubMed

    Wang, Ruqing; Li, X Allen

    2002-08-01

    High dose rate (HDR) 192Ir sources are currently used in intravascular brachytherapy (IVB) for the peripheral arterial system. This poses a demand on evaluating accurate dose parameters in the near-source region for such sources. The purpose of this work is to calculate the dose parameters for the old VariSource HDR 192Ir source and the new microSelectron HDR 192Ir source, using Monte Carlo electron and photon transport simulation. The two-dimensional (2D) dose rate distributions and the air kerma strengths for the two HDR sources were calculated by EGSnrc and EGS4 Monte Carlo codes. Based on these data, the dose parameters proposed in the AAPM TG-60 protocol were derived. The dose rate constants obtained are 13.119+/-0.028 cGy h(-1) U(-1) for the old VariSource source, and 22.751+/-0.031 cGy h(-1) U(-1) for the new microSelectron source at the reference point (r0 = 2 mm, theta = pi/2). The 2D dose rate distributions, the radial dose functions, and the anisotropy functions presented for the two sources cover radial distances ranging from 0.5 to 10 mm. In the near-source region on the transverse plane, the dose effects of the charged particle nonequilibrium and the beta-particle dose contribution were studied. It is found that at radial distances ranging from 0.5 to 2 mm, these effects increase the calculated dose rates by up to 29% for the old VariSource source, and by up to 12% for the new microSelectron source, which, in turn, change values of the radial dose function and the anisotropy function. The present dose parameters, which account for the charged particle nonequilibrium and the beta particle contribution, may be used for accurate IVB dose calculation. PMID:12201413

  6. 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.

  7. 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.

  8. Current Absolute Plate Velocities Inferred from Hotspot Tracks, Comparison with Absolute Velocities Inferred from Seismic Anisotropy, and Bounds on Rates of Motion Between Groups of Hotspots

    NASA Astrophysics Data System (ADS)

    Wang, C.; Gordon, R. G.; Zheng, L.

    2015-12-01

    Hotspot tracks have been widely used to estimate the velocities of the plate relative to the lower mantle. Here we analyze the hotspot azimuth data set of Morgan and Phipps Morgan [2007] and show that the errors in plate velocity azimuths inferred from hotspot tracks in any one plate are correlated with the errors of other azimuths in the same plate. We use a two-tier analysis to account for this correlated error. First, we determine an individual best-fitting pole for each plate. Second, we determine the absolute plate velocity by minimizing the misfit while constrained by the MORVEL relative plate velocities [DeMets et al. 2010]. Our preferred model, HS4-MORVEL, uses azimuths from 9 major plates, which are weighted equally. We find that the Pacific plate rotates 0.860.016°Ma-1 right handed about 63.3°S, 96.1°E. Angular velocities of four plates (Amur, Eurasia, Yangtze and Antarctic) differ insignificantly from zero. The net rotation of the lithosphere is 0.24°±0.014° Ma-1 right handed about 52.3S, 56.9E. The angular velocities differ insignificantly from the absolute angular velocities inferred from the orientation of seismic anisotropy [Zheng et al. 2014]. The within-plate dispersion of hotspot track azimuths is 14°, which is comparable to the within-plate dispersion found from orientations of seismic anisotropy. The between-plate dispersion is 6.9±2.4° (95% confidence limits), which is smaller than that found from seismic anisotropy. The between-plate dispersion of 4.5° to 9.3° can be used to place bounds on how fast hotspots under one plate move relative to hotspots under another plate. For an average plate absolute speed of ≈50 mm/yr, the between-plate dispersion indicates a rate of motion of 4 mm/yr to 8 mm/yr for the component of hotspot motion perpendicular to plate motion. This upper bound is consistent with prior work that indicated upper bounds on motion between Pacific hotspots and Indo-Atlantic hotspots over the past 48 Ma of 8-13 mm

  9. Effect of low dose rate radiation on cell growth kinetics.

    PubMed Central

    Gregg, E C; Yau, T M; Kim, S C

    1979-01-01

    Experimental determinations were made of cell number as a function of time for two strains of L5178Y mammalian cells maintained continuously in various environments of radiation. One strain possessed a shoulder in its dose response curve whereas the other did not. Neither strain showed any significant difference in growth rate for interdivision doses on the order of the median lethal dose or less delivered continuously at a low dose rate or pulsed every 4 h at a high instantaneous dose rate. It was also shown that large numbers of dead cells have little effect on growth rate and that these dead cells last as discrete entities for many days. A simple theory of growth rate in the presence of radiation is presented, and the agreement with the observations implies that there is no effect of any sublethal low dose rate radiation received in one generation on the growth rate or radiation sensitivity of the succeeding generation. Further analysis of the data also showed that for the no-shoulder cells at 37 degrees C, tritiated water had a relative biological effect close to unity for cell sterilization. PMID:262446

  10. 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.

  11. Dose Rate Calculations for Rotary Mode Core Sampling Exhauster

    SciTech Connect

    FOUST, D.J.

    2000-10-26

    This document provides the calculated estimated dose rates for three external locations on the Rotary Mode Core Sampling (RMCS) exhauster HEPA filter housing, per the request of Characterization Field Engineering.

  12. Dose rate distribution from a standard waste drum arrangement.

    PubMed

    Zoeger, N; Brandl, A

    2011-11-01

    The evaluation of the dose rate distributions from radioactive sources, together with the specific detector locations with respect to those sources, in many cases presents a significant analytical challenge. With the exception of a few, simple source-detector geometries, it is not possible to find an analytical expression for these dose rate distributions as functions of detector location. In this paper, the dose rate distributions due to the arrangement of radiological waste drums on a standard wooden transport and storage pallet are investigated. The dose rates at various distances, ranging from 5 cm to 20 m, from the waste drum assembly have been evaluated by Monte Carlo calculations. The simulation data are fitted by smooth analytical functions in two independent regions, the waste drum near zone, where a logarithmic function best described the data, and the far zone, where the functional dependence closely approximates the 1/r2-law for point sources. PMID:21968820

  13. SU-E-T-189: First Experimental Verification of the Accuracy of Absolute Dose Reconstruction From PET-CT Imaging of Yttrium 90 Microspheres

    SciTech Connect

    Veltchev, I; Fourkal, E; Doss, M; Ma, C; Meyer, J; Yu, M; Horwitz, E

    2014-06-01

    Purpose: In the past few years there have been numerous proposals for 3D dose reconstruction from the PET-CT imaging of patients undergoing radioembolization treatment of the liver with yttrium-90 microspheres. One of the most promising techniques uses convolution of the measured PET activity distribution with a pre-calculated Monte Carlo dose deposition kernel. The goal of the present study is to experimentally verify the accuracy of this method and to analyze the significance of various error sources. Methods: Optically stimulated luminescence detectors (OSLD) were used (NanoDot, Landauer) in this experiment. Two detectors were mounted on the central axis of a cylinder filled with water solution of yttrium-90 chloride. The total initial activity was 90mCi. The cylinder was inserted in a larger water phantom and scanned on a Siemens Biograph 16 Truepoint PET-CT scanner. Scans were performed daily over a period of 20 days to build a calibration curve for the measured absolute activity spanning 7 yttrium-90 half-lives. The OSLDs were mounted in the phantom for a predetermined period of time in order to record 2Gy dose. The measured dose was then compared to the dose reconstructed from the activity density at the location of each dosimeter. Results: Thorough error analysis of the dose reconstruction algorithm takes into account the uncertainties in the absolute PET activity, branching ratios, and nonlinearity of the calibration curve. The measured dose for 105-minute exposure on day 10 of the experiment was 219(11)cGy, while the reconstructed dose at the location of the detector was 215(47)cGy. Conclusion: We present the first experimental verification of the accuracy of the convolution algorithm for absolute dose reconstruction of yttrium-90 microspheres. The excellent agreement between the measured and calculated point doses will encourage the broad clinical adoption of the convolution-based dose reconstruction algorithm, making future quantitative dose

  14. Dose rate dependency of micelle leucodye 3D gel dosimeters

    NASA Astrophysics Data System (ADS)

    Vandecasteele, J.; Ghysel, S.; De Deene, Y.

    2010-11-01

    Recently a novel 3D radiochromic gel dosimeter was introduced which uses micelles to dissolve a leucodye in a gelatin matrix. Experimental results show that this 3D micelle gel dosimeter was found to be dose rate dependent. A maximum difference in optical dose sensitivity of 70% was found for dose rates between 50 cGy min-1 and 400 cGy min-1. A novel composition of 3D radiochromic dosimeter is proposed composed of gelatin, sodium dodecyl sulphate, chloroform, trichloroacetic acid and leucomalachite green. The novel gel dosimeter formulation exhibits comparable radio-physical properties in respect to the composition previously proposed. Nevertheless, the novel formulation was found to be still dose rate dependent. A maximum difference of 33% was found for dose rates between 50 cGy min-1 and 400 cGy min-1. On the basis of these experimental results it is concluded that the leucodye micelle gel dosimeter is still unsatisfactory for clinical radiation therapy dose verifications. Some insights in the physico-chemical mechanisms were obtained and are discussed.

  15. 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.

  16. 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.

  17. Calculating lens dose and surface dose rates from 90Sr ophthalmic applicators using Monte Carlo modeling.

    PubMed

    Gleckler, M; Valentine, J D; Silberstein, E B

    1998-01-01

    Using a 90Sr applicator for brachytherapy for the reduction of recurrence rates after pterygium excisions has been an effective therapeutic procedure. Accurate knowledge of the dose being applied to the affected area on the sclera has been lacking, and for decades inaccurate estimates for lens dose have thus been made. Small errors in the assumptions which are required to make these estimates lead to dose rates changing exponentially because of the attenuation of beta particles. Monte Carlo simulations have been used to evaluate the assumptions that are now being used for the calculation of the surface dose rate and the corresponding determination of lens dose. For an ideal 90Sr applicator, results from this study indicate dose rates to the most radiosensitive areas of the lens ranging from 8.8 to 15.5 cGy/s. This range is based on different eye dimensions that ultimately corresponds to a range in distance between the applicator surface and the germinative epithelium of the lens of 2-3 mm. Furthermore, the conventional 200 cGy threshold for whole lens cataractogenesis is questioned for predicting complications from scleral brachytherapy. The dose to the germinative epithelium should be used for studying radiocataractogenesis.

  18. 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.

  19. Statistical variability and confidence intervals for planar dose QA pass rates

    SciTech Connect

    Bailey, Daniel W.; Nelms, Benjamin E.; Attwood, Kristopher; Kumaraswamy, Lalith; Podgorsak, Matthew B.

    2011-11-15

    Purpose: The most common metric for comparing measured to calculated dose, such as for pretreatment quality assurance of intensity-modulated photon fields, is a pass rate (%) generated using percent difference (%Diff), distance-to-agreement (DTA), or some combination of the two (e.g., gamma evaluation). For many dosimeters, the grid of analyzed points corresponds to an array with a low areal density of point detectors. In these cases, the pass rates for any given comparison criteria are not absolute but exhibit statistical variability that is a function, in part, on the detector sampling geometry. In this work, the authors analyze the statistics of various methods commonly used to calculate pass rates and propose methods for establishing confidence intervals for pass rates obtained with low-density arrays. Methods: Dose planes were acquired for 25 prostate and 79 head and neck intensity-modulated fields via diode array and electronic portal imaging device (EPID), and matching calculated dose planes were created via a commercial treatment planning system. Pass rates for each dose plane pair (both centered to the beam central axis) were calculated with several common comparison methods: %Diff/DTA composite analysis and gamma evaluation, using absolute dose comparison with both local and global normalization. Specialized software was designed to selectively sample the measured EPID response (very high data density) down to discrete points to simulate low-density measurements. The software was used to realign the simulated detector grid at many simulated positions with respect to the beam central axis, thereby altering the low-density sampled grid. Simulations were repeated with 100 positional iterations using a 1 detector/cm{sup 2} uniform grid, a 2 detector/cm{sup 2} uniform grid, and similar random detector grids. For each simulation, %/DTA composite pass rates were calculated with various %Diff/DTA criteria and for both local and global %Diff normalization

  20. HDRMC, an accelerated Monte Carlo dose calculator for high dose rate brachytherapy with CT-compatible applicators

    SciTech Connect

    Chibani, Omar C-M Ma, Charlie

    2014-05-15

    Purpose: To present a new accelerated Monte Carlo code for CT-based dose calculations in high dose rate (HDR) brachytherapy. The new code (HDRMC) accounts for both tissue and nontissue heterogeneities (applicator and contrast medium). Methods: HDRMC uses a fast ray-tracing technique and detailed physics algorithms to transport photons through a 3D mesh of voxels representing the patient anatomy with applicator and contrast medium included. A precalculated phase space file for the{sup 192}Ir source is used as source term. HDRM is calibrated to calculated absolute dose for real plans. A postprocessing technique is used to include the exact density and composition of nontissue heterogeneities in the 3D phantom. Dwell positions and angular orientations of the source are reconstructed using data from the treatment planning system (TPS). Structure contours are also imported from the TPS to recalculate dose-volume histograms. Results: HDRMC was first benchmarked against the MCNP5 code for a single source in homogenous water and for a loaded gynecologic applicator in water. The accuracy of the voxel-based applicator model used in HDRMC was also verified by comparing 3D dose distributions and dose-volume parameters obtained using 1-mm{sup 3} versus 2-mm{sup 3} phantom resolutions. HDRMC can calculate the 3D dose distribution for a typical HDR cervix case with 2-mm resolution in 5 min on a single CPU. Examples of heterogeneity effects for two clinical cases (cervix and esophagus) were demonstrated using HDRMC. The neglect of tissue heterogeneity for the esophageal case leads to the overestimate of CTV D90, CTV D100, and spinal cord maximum dose by 3.2%, 3.9%, and 3.6%, respectively. Conclusions: A fast Monte Carlo code for CT-based dose calculations which does not require a prebuilt applicator model is developed for those HDR brachytherapy treatments that use CT-compatible applicators. Tissue and nontissue heterogeneities should be taken into account in modern HDR

  1. 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.

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

    PubMed

    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

    2016-07-21

    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. PMID:27366861

  3. Equilibration Rates and Negative Absolute Temperatures for Ultracold Atoms in Optical Lattices

    NASA Astrophysics Data System (ADS)

    Rapp, Akos; Mandt, Stephan; Rosch, Achim

    2010-11-01

    As highly tunable interacting systems, cold atoms in optical lattices are ideal to realize and observe negative absolute temperatures, T<0. We show theoretically that, by reversing the confining potential, stable superfluid condensates at finite momentum and T<0 can be created with low entropy production for attractive bosons. They may serve as “smoking gun” signatures of equilibrated T<0. For fermions, we analyze the time scales needed to equilibrate to T<0. For moderate interactions, the equilibration time is proportional to the square of the radius of the cloud and grows with increasing interaction strengths as atoms and energy are transported by diffusive processes.

  4. 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

  5. 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

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

    PubMed

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

    2011-05-01

    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 combined with

  7. 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.

  8. 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.

  9. 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. PMID:23439145

  10. High-Dose-Rate 192Ir Brachytherapy Dose Verification: A Phantom Study

    PubMed Central

    Nikoofar, Alireza; Hoseinpour, Zohreh; Rabi Mahdavi, Seied; Hasanzadeh, Hadi; Rezaei Tavirani, Mostafa

    2015-01-01

    Background: The high-dose-rate (HDR) brachytherapy might be an effective tool for palliation of dysphagia. Because of some concerns about adverse effects due to absorbed radiation dose, it is important to estimate absorbed dose in risky organs during this treatment. Objectives: This study aimed to measure the absorbed dose in the parotid, thyroid, and submandibular gland, eye, trachea, spinal cord, and manubrium of sternum in brachytherapy in an anthropomorphic phantom. Materials and Methods: To measure radiation dose, eye, parotid, thyroid, and submandibular gland, spine, and sternum, an anthropomorphic phantom was considered with applicators to set thermoluminescence dosimeters (TLDs). A specific target volume of about 23 cm3 in the upper thoracic esophagus was considered as target, and phantom planned computed tomography (CT) for HDR brachytherapy, then with a micro-Selectron HDR (192Ir) remote after-loading unit. Results: Absorbed doses were measured with calibrated TLDs and were expressed in centi-Gray (cGy). In regions far from target (≥ 16 cm) such as submandibular, parotid and thyroid glands, mean measured dose ranged from 1.65 to 5.5 cGy. In closer regions (≤ 16 cm), the absorbed dose might be as high as 113 cGy. Conclusions: Our study showed similar depth and surface doses; in closer regions, the surface and depth doses differed significantly due to the role of primary radiation that had imposed a high-dose gradient and difference between the plan and measurement, which was more severe because of simplifications in tissue inhomogeneity, considered in TPS relative to phantom. PMID:26413250

  11. Absolute rate constant of the reaction between chlorine /2P/ atoms and hydrogen peroxide from 298 to 424 K

    NASA Technical Reports Server (NTRS)

    Keyser, L. F.

    1980-01-01

    The absolute rate constant of the reaction between chlorine (2P) atoms and hydrogen peroxide was determined from 298 to 424 K, using the discharge flow resonance fluorescence technique. Pseudo-first-order conditions were used with hydrogen peroxide in large excess. A fast flow-sampling procedure limited hydrogen peroxide decomposition to less than 5% over the temperature range studied. At 298 K, the rate constant is (4.1 plus or minus 0.2) x 10 to the minus 13th cu cm/molecule-sec.

  12. 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.

  13. 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.

  14. Absolute Rate Constants for the Reaction of OH with [|#11#|]Cyclopentane and Cycloheptane from 230-350 K

    NASA Astrophysics Data System (ADS)

    Dransfield, T. J.; Gennaco, M. M.; Huang, Y.; Hannun, R. A.

    2011-12-01

    We report absolute measurements of the rate constants of the reaction of hydroxyl radical (OH) with cyclopentane and cycloheptane in 6-8 Torr of nitrogen from 230-350 K using Harvard's High Pressure Flow System. Ethane's reactivity was simultaneously measured as a test of experimental performance. Hydroxyl concentrations were measured using Laser-Induced Fluorescence, and alkane concentrations were measured using Fourier-Transform Infrared Spectroscopy. Recent work on this flow system has suggested that cyclohexane has a significantly higher activation energy to reaction with OH than does cyclo-octane, a result which is not suggested by our understanding of hydrocarbon reactivity nor predicted by structure-activity relationships. This work examines the temperature dependent rates for two other similarly-sized cycloalkanes to determine whether they behave as cyclohexane or as cyclooctane. While several previous experiments have studied the reaction with cyclopentane, there is significant scatter in the room temperature rates, and only four absolute rate measurements are available at non-ambient temperatures. There are only two absolute rate measurements available for the reaction with cycloheptane; only one of these reports a temperature dependence, and that study is limited to temperatures above 298 K. Thus, this work significantly expands the available data set for both reactions. The data for the reactions of OH with ethane, cyclopentane, cyclohexane, and cycloheptane are all modeled using a simple Arrhenius fit, and also with a modified Arrhenius equation based on transition state theory, ignoring tunneling. Results from the latter fit indicate that the activation barriers for both title reactions are greater than that of OH + cyclo-octane. The measured activation energy for OH + cyclopentane actually exceeds that of OH + cyclohexane.

  15. TH-E-BRE-09: TrueBeam Monte Carlo Absolute Dose Calculations Using Monitor Chamber Backscatter Simulations and Linac-Logged Target Current

    SciTech Connect

    A, Popescu I; Lobo, J; Sawkey, D; Svatos, M

    2014-06-15

    Purpose: To simulate and measure radiation backscattered into the monitor chamber of a TrueBeam linac; establish a rigorous framework for absolute dose calculations for TrueBeam Monte Carlo (MC) simulations through a novel approach, taking into account the backscattered radiation and the actual machine output during beam delivery; improve agreement between measured and simulated relative output factors. Methods: The ‘monitor backscatter factor’ is an essential ingredient of a well-established MC absolute dose formalism (the MC equivalent of the TG-51 protocol). This quantity was determined for the 6 MV, 6X FFF, and 10X FFF beams by two independent Methods: (1) MC simulations in the monitor chamber of the TrueBeam linac; (2) linac-generated beam record data for target current, logged for each beam delivery. Upper head MC simulations used a freelyavailable manufacturer-provided interface to a cloud-based platform, allowing use of the same head model as that used to generate the publicly-available TrueBeam phase spaces, without revealing the upper head design. The MC absolute dose formalism was expanded to allow direct use of target current data. Results: The relation between backscatter, number of electrons incident on the target for one monitor unit, and MC absolute dose was analyzed for open fields, as well as a jaw-tracking VMAT plan. The agreement between the two methods was better than 0.15%. It was demonstrated that the agreement between measured and simulated relative output factors improves across all field sizes when backscatter is taken into account. Conclusion: For the first time, simulated monitor chamber dose and measured target current for an actual TrueBeam linac were incorporated in the MC absolute dose formalism. In conjunction with the use of MC inputs generated from post-delivery trajectory-log files, the present method allows accurate MC dose calculations, without resorting to any of the simplifying assumptions previously made in the True

  16. Solar modulation of dose rate onboard the Mir station.

    PubMed

    Badhwar, G D; Shurshakov, V A; Tsetlin, V V

    1997-12-01

    Models of the radiation belts that are currently used to estimate exposure for astronauts describe the environment at times of either solar minimum or solar maximum. Static models, constructed using data acquired prior to 1970 during a solar cycle with relatively low solar radio flux, have flux uncertainties of a factor of two to live and dose-rate uncertainties of a factor of about two. The inability of these static models to provide a dynamic description of the radiation belt environment limits our ability to predict radiation exposures for long-duration missions in low earth orbits. In an attempt to add some predictive capability of these models, we studied the measured daily absorbed dose rate on the Mir orbital station over roughly the complete 22nd solar cycle that saw some of the highest solar flux values in the last 40 y. We show that the daily trapped particle dose rate is an approximate power law function of daily atmospheric density. Atmospheric density values are in turn obtained from standard correlation with observed solar radio noise flux. This correlation improves, particularly during periods of high solar activity, if the density at roughly 400 days earlier time is used. This study suggests the possibility of a dose- and flux-predictive trapped-belt model based on atmospheric density.

  17. Easy Absolute Values? Absolutely

    ERIC Educational Resources Information Center

    Taylor, Sharon E.; Mittag, Kathleen Cage

    2015-01-01

    The authors teach a problem-solving course for preservice middle-grades education majors that includes concepts dealing with absolute-value computations, equations, and inequalities. Many of these students like mathematics and plan to teach it, so they are adept at symbolic manipulations. Getting them to think differently about a concept that they…

  18. 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.

  19. Measurement verification of dose distributions in pulsed-dose rate brachytherapy in breast cancer

    PubMed Central

    Mantaj, Patrycja; Zwierzchowski, Grzegorz

    2013-01-01

    Aim The aim of the study was to verify the dose distribution optimisation method in pulsed brachytherapy. Background The pulsed-dose rate brachytherapy is a very important method of breast tumour treatment using a standard brachytheraphy equipment. The appropriate dose distribution round an implant is an important issue in treatment planning. Advanced computer systems of treatment planning are equipped with algorithms optimising dose distribution. Materials and methods The wax-paraffin phantom was constructed and seven applicators were placed within it. Two treatment plans (non-optimised, optimised) were prepared. The reference points were located at a distance of 5 mm from the applicators’ axis. Thermoluminescent detectors were placed in the phantom at suitable 35 chosen reference points. Results The dosimetry verification was carried out in 35 reference points for the plans before and after optimisation. Percentage difference for the plan without optimisation ranged from −8.5% to 1.4% and after optimisation from −8.3% to 0.01%. In 16 reference points, the calculated percentage difference was negative (from −8.5% to 1.3% for the plan without optimisation and from −8.3% to 0.8% for the optimised plan). In the remaining 19 points percentage difference was from 9.1% to 1.4% for the plan without optimisation and from 7.5% to 0.01% for the optimised plan. No statistically significant differences were found between calculated doses and doses measured at reference points in both dose distribution non-optimised treatment plans and optimised treatment plans. Conclusions No statistically significant differences were found in dose values at reference points between doses calculated by the treatment planning system and those measured by TLDs. This proves the consistency between the measurements and the calculations. PMID:24416545

  20. 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

  1. 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.

  2. High dose rate (HDR) brachytherapy quality assurance: a practical guide

    PubMed Central

    Wilkinson, DA

    2006-01-01

    The widespread adoption of high dose rate brachytherapy with its inherent dangers necessitates adoption of appropriate quality assurance measures to minimize risks to both patients and medical staff. This paper is aimed at assisting someone who is establishing a new program or revising one already in place into adhere to the recently issued Nuclear Regulatory Commission (USA) regulations and the guidelines from the American Association of Physicists in Medicine. PMID:21614233

  3. 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.

  4. Pressure dependence of the absolute rate constant for the reaction OH + C2H2 from 228 to 413 K

    NASA Technical Reports Server (NTRS)

    Michael, J. V.; Nava, D. F.; Payne, W. A.; Stief, L. J.; Borkowski, R. P.

    1980-01-01

    The pressure dependence of the absolute rate constant for the reaction of the hydroxyl radical with acetylene, important in both atmospheric and combustion chemistry, is determined for temperatures between 228 and 413 K. The flash photolysis-resonance fluorescence technique was employed at five temperatures over wide ranges of pressure and acetylene concentrations, with the OH produced by water photolysis and hydroxyl resonance fluorescent photons measured by multiscaling techniques. Results indicate that, except at the lowest temperature, the bimolecular rate constant for the reaction depends strongly on total pressure, with the pressure effect becoming more pronounced with increasing temperature. At limiting high pressures, the rate constant is found to be equal to 6.83 + or - 1.19 x 10 to the -12th exp (-646 + or - 47/T) cu cm/molecule per sec, where T is the temperature. Results thus demonstrate the importance of environmental conditions in theoretical studies of atmospheric and combustion product compositions

  5. Interaction of 2-Gy Equivalent Dose and Margin Status in Perioperative High-Dose-Rate Brachytherapy

    SciTech Connect

    Martinez-Monge, Rafael; Cambeiro, Mauricio; Moreno, Marta; Gaztanaga, Miren; San Julian, Mikel; Alcalde, Juan; Jurado, Matias

    2011-03-15

    Purpose: To determine patient, tumor, and treatment factors predictive of local control (LC) in a series of patients treated with either perioperative high-dose-rate brachytherapy (PHDRB) alone (Group 1) or with PHDRB combined with external-beam radiotherapy (EBRT) (Group 2). Patient and Methods: Patients (n = 312) enrolled in several PHDRB prospective Phase I-II studies conducted at the Clinica Universidad de Navarra were analyzed. Treatment with PHDRB alone, mainly because of prior irradiation, was used in 126 patients to total doses of 32 Gy/8 b.i.d. or 40 Gy/10 b.i.d. treatments after R0 or R1 resections. Treatment with PHDRB plus EBRT was used in 186 patients to total doses of 16 Gy/4 b.i.d. or 24 Gy/6 b.i.d. treatments after R0 or R1 resections along with 45 Gy of EBRT with or without concomitant chemotherapy. Results: No dose-margin interaction was observed in Group 1 patients. In Group 2 patients there was a significant interaction between margin status and 2-Gy equivalent (Eq2Gy) dose (p = 0.002): (1) patients with negative margins had 9-year LC of 95.7% at Eq2Gy = 62.9Gy; (2) patients with close margins of >1 mm had 9-year LC of 92.4% at Eq2Gy = 72.2Gy, and (3) patients with positive/close <1-mm margins had 9-year LC of 68.0% at Eq2Gy = 72.2Gy. Conclusions: Two-gray equivalent doses {>=}70 Gy may compensate the effect of close margins {>=}1 mm but do not counterbalance the detrimental effect of unfavorable (positive/close <1 mm) resection margins. No dose-margin interaction is observed in patients treated at lower Eq2Gy doses {<=}50 Gy with PHDRB alone.

  6. 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

  7. Commissioning and Implementation of an EPID Based IMRT QA System "Dosimetry Check" for 3D Absolute Dose Measurements and Quantitative Comparisons to MapCheck

    NASA Astrophysics Data System (ADS)

    Patel, Jalpa A.

    The software package "Dosimetry Check" by MathResolutions, LLC, provides an absolute 3D volumetric dose measurement for IMRT QA using the existing Electronic Portal Imaging Device (EPID) mounted on most linear accelerators. This package provides a feedback loop using the patient's treatment planning CT data as the phantom for dose reconstruction. The aim of this work is to study the difference between point, planar and volumetric doses with MapCheck and Dosimetry Check via the use of the EPID and the diode array respectively. Evaluating tools such as point doses at isocenter, 1-D profiles, gamma volume histograms, and dose volume histograms are used for IMRT dose comparison in three types of cases: head and neck, prostate, and lung. Dosimetry Check can be a valuable tool for IMRT QA as it uses patient specific attenuation corrections and the superiority of the EPID as compared to the MapCheck diode array. This helps reduce the uncertainty in dose for less variability in delivery and a more realistic measured vs computed dose verification system as compared to MapCheck.

  8. Absolute rate parameters for the reaction of ground state atomic oxygen with carbonyl sulfide

    NASA Technical Reports Server (NTRS)

    Klemm, R. B.; Stief, L. J.

    1974-01-01

    The rate parameters for the reaction of O(3P) with carbonyl sulfide, O(3P) + OCS yields CO + SO, have been determined directly by monitoring O(3P) using the flash photolysis-resonance fluorescence technique. The value for reaction rate was measured over a temperature range of 263-502 K and the data were fitted to an Arrhenius expression with good linearity. A comparison of the present results with those from previous studies of this reaction is also presented.

  9. 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.

  10. SU-E-T-244: Motion Control Challenges in High Dose Rate Brachytherapy

    SciTech Connect

    Hyvarinen, M; Leventouri, T; Pella, S; Dumitru, N

    2014-06-01

    Purpose: High dose rate (HDR) brachytherapy dose distribution is highly localized and has a very sharp fall-off. Thus the one of the most important part of the treatment is the localization and immobilization of the applicator from the implantation to the setup verification to the treatment delivery. The smallest motions of the patient can induce a small rotation, tilt, or translational movement of the applicator that can convert into miss of a significant part of the tumor or to over irradiating a nearby critical organ.The purpose of this study is to revise most of the HDR types of treatments with their applicators and their localization challenges. Since every millimeter of misplacement counts the study will look into the necessity of increasing the immobilization for several types of applicators. Methods: The study took over 136 plans generated by the treatment planning system (TPS) looking into the applicator placement in regard to the organs at risk (OR) and simulated the three possible displacements at the hottest dose point on the critical organ for several accessories to evaluate the variation of the delivered dose at the point due to the displacement. Results: Many of the present immobilization devices produced for external radiotherapy can be used to improve the localization of HDR applicators during transportation of the patient and during treatment. Conclusion: This study data indicates that an improvement of the immobilization devices for HDR is absolutely necessary. Better applicator fixation devices are required too. Developing new immobilization devices for all the applicators is recommended.

  11. Modelling evolution of air dose rates in river basins in Fukushima Prefecture affected by sediment-sorbed radiocesium redistribution

    NASA Astrophysics Data System (ADS)

    Malins, A.; Sakuma, K.; Nakanishi, T.; Kurikami, H.; Machida, M.; Kitamura, A.; Yamada, S.

    2015-12-01

    The radioactive 134Cs and 137Cs isotopes deposited over Fukushima Prefecture by the Fukushima Daiichi nuclear disaster are the predominant radiological concern for the years following the accident. This is because the energetic gamma radiation they emit on decay constitutes the majority of the elevated air dose rates that now afflict the region. Therefore, we developed a tool for calculating air dose rates from arbitrary radiocesium spatial distributions across the land surface and depth profiles within the ground. As cesium is strongly absorbed by clay soils, its primary redistribution mechanism within Fukushima Prefecture is by soil erosion and water-borne sediment transport. Each year between 0.1~1% of the total radiocesium inventory in the river basins neighboring Fukushima Daiichi is eroded from the land surface and enters into water courses, predominantly during typhoon storms. Although this is a small amount in relative terms, in absolute terms it corresponds to terabecquerels of 134Cs and 137Cs redistribution each year and this can affect the air dose rate at locations of high erosion and sediment deposition. This study inputs the results of sediment redistribution simulations into the dose rate evaluation tool to calculate the locations and magnitude of air dose rate changes due to radiocesium redistribution. The dose rate calculations are supported by handheld survey instrument results taken within the Prefecture.

  12. Comparison of dose distributions around the pulsed-dose-rate Fletcher Williamson and the low-dose-rate Fletcher Suit Delclos ovoids: a Monte Carlo study

    NASA Astrophysics Data System (ADS)

    Price, Michael J.; Gifford, Kent A.; Horton, John; Lawyer, Ann; Eifel, Patricia; Mourtada, Firas

    2006-08-01

    We performed a Monte Carlo study to compare dose distributions for a Fletcher-Suit-Delclos (FSD) ovoid used with 137Cs low-dose-rate (LDR) sources with those for a Fletcher-Williamson (FW) ovoid used with an 192Ir pulsed-dose-rate (PDR) source for intracavitary brachytherapy of cervical cancer. We recently reported on extensive validation of Monte Carlo MCNPX models of these ovoids using radiochromic film measurements. Here, we compared these models assuming identical loading of 10, 15 and 20 mgRaEq (72, 108 and 145 cGy cm2 h-1, respectively) in three dose mesh planes: one perpendicular to the ovoid long axis bisecting the ovoid, one parallel to and displaced 2 cm medially from the long axis of the ovoid, and a 'rectal' plane perpendicular to the long axis located 1 cm distal to the distal face of the ovoid cap. The FW ovoid delivered slightly higher doses (within 10%) over all loadings to regions away from the bladder and rectal shields when compared to the FSD ovoid. However, the FW ovoid delivered much higher doses (>50%) in regions near these shields. In the rectal plane, the FW ovoid delivered a slightly higher dose, but within the region directly behind the rectal shield, the FW ovoid delivered a dose ranging from +35% to -35% of the FSD dose distribution. We attribute these differences to intrinsic differences in source characteristics (radial dose function and anisotropy factors) and extrinsic factors such as the solid-angle effect between sources and shields and applicator design.

  13. Comparison of high-dose-rate and low-dose-rate brachytherapy in the treatment of endometrial carcinoma

    SciTech Connect

    Fayed, Alaa; Mutch, David G.; Rader, Janet S.; Gibb, Randall K. |; Powell, Matthew A. |; Wright, Jason D.; El Naqa, Issam; Zoberi, Imran |; Grigsby, Perry W. |||. E-mail: pgrigsby@wustl.edu

    2007-02-01

    Purpose: To compare the outcomes for endometrial carcinoma patients treated with either high-dose-rate (HDR) or low-dose-rate (LDR) brachytherapy. Methods and Materials: This study included 1,179 patients divided into LDR (1,004) and HDR groups (175). Patients with International Federation of Gynecology and Obstetrics (FIGO) surgical Stages I-III were included. All patients were treated with postoperative irradiation. In the LDR group, the postoperative dose applied to the vaginal cuff was 60-70 Gy surface doses to the vaginal mucosa. The HDR brachytherapy prescription was 6 fractions of 2 Gy each to a depth of 0.5 cm from the surface of the vaginal mucosa. Overall survival, disease-free survival, local control, and complications were endpoints. Results: For all stages combined, the overall survival, disease-free survival, and local control at 5 years in the LDR group were 70%, 69%, and 81%, respectively. For all stages combined, the overall survival, disease-free survival, and local control at 5 years in the HDR group were 68%, 62%, and 78%, respectively. There were no significant differences in early or late Grade III and IV complications in the HDR or LDR groups. Conclusion: Survival outcomes, pelvic tumor control, and Grade III and IV complications were not significantly different in the LDR brachytherapy group compared with the HDR group.

  14. Performance assessment of the BEBIG MultiSource high dose rate brachytherapy treatment unit.

    PubMed

    Palmer, Antony; Mzenda, Bongile

    2009-12-21

    A comprehensive system characterisation was performed of the Eckert & Ziegler BEBIG GmbH MultiSource High Dose Rate (HDR) brachytherapy treatment unit with an (192)Ir source. The unit is relatively new to the UK market, with the first installation in the country having been made in the summer of 2009. A detailed commissioning programme was devised and is reported including checks of the fundamental parameters of source positioning, dwell timing, transit doses and absolute dosimetry of the source. Well chamber measurements, autoradiography and video camera analysis techniques were all employed. The absolute dosimetry was verified by the National Physical Laboratory, UK, and compared to a measurement based on a calibration from PTB, Germany, and the supplied source certificate, as well as an independent assessment by a visiting UK centre. The use of the 'Krieger' dosimetry phantom has also been evaluated. Users of the BEBIG HDR system should take care to avoid any significant bend in the transfer tube, as this will lead to positioning errors of the source, of up to 1.0 mm for slight bends, 2.0 mm for moderate bends and 5.0 mm for extreme curvature (depending on applicators and transfer tube used) for the situations reported in this study. The reason for these errors and the potential clinical impact are discussed. Users should also note the methodology employed by the system for correction of transit doses, and that no correction is made for the initial and final transit doses. The results of this investigation found that the uncorrected transit doses lead to small errors in the delivered dose at the first dwell position, of up to 2.5 cGy at 2 cm (5.6 cGy at 1 cm) from a 10 Ci source, but the transit dose correction for other dwells was accurate within 0.2 cGy. The unit has been mechanically reliable, and source positioning accuracy and dwell timing have been reproducible, with overall performance similar to other existing HDR equipment. The unit is capable of high

  15. Noninvasive optical quantification of absolute blood flow, blood oxygenation, and oxygen consumption rate in exercising skeletal muscle

    NASA Astrophysics Data System (ADS)

    Gurley, Katelyn; Shang, Yu; Yu, Guoqiang

    2012-07-01

    This study investigates a method using novel hybrid diffuse optical spectroscopies [near-infrared spectroscopy (NIRS) and diffuse correlation spectroscopy (DCS)] to obtain continuous, noninvasive measurement of absolute blood flow (BF), blood oxygenation, and oxygen consumption rate (\\Vdot O2) in exercising skeletal muscle. Healthy subjects (n=9) performed a handgrip exercise to increase BF and \\Vdot O2 in forearm flexor muscles, while a hybrid optical probe on the skin surface directly monitored oxy-, deoxy-, and total hemoglobin concentrations ([HbO2], [Hb], and THC), tissue oxygen saturation (StO2), relative BF (rBF), and relative oxygen consumption rate (r\\Vdot O2). The rBF and r\\Vdot O2 signals were calibrated with absolute baseline BF and \\Vdot O2 obtained through venous and arterial occlusions, respectively. Known problems with muscle-fiber motion artifacts in optical measurements during exercise were mitigated using a novel gating algorithm that determined muscle contraction status based on control signals from a dynamometer. Results were consistent with previous findings in the literature. This study supports the application of NIRS/DCS technology to quantitatively evaluate hemodynamic and metabolic parameters in exercising skeletal muscle and holds promise for improving diagnosis and treatment evaluation for patients suffering from diseases affecting skeletal muscle and advancing fundamental understanding of muscle and exercise physiology.

  16. Absolute rate coefficients for photorecombination of beryllium-like and boron-like silicon ions

    NASA Astrophysics Data System (ADS)

    Bernhardt, D.; Becker, A.; Brandau, C.; Grieser, M.; Hahn, M.; Krantz, C.; Lestinsky, M.; Novotný, O.; Repnow, R.; Savin, D. W.; Spruck, K.; Wolf, A.; Müller, A.; Schippers, S.

    2016-04-01

    We report measured rate coefficients for electron-ion recombination of Si10+ forming Si9+ and of Si9+ forming Si8+, respectively. The measurements were performed using the electron-ion merged-beams technique at a heavy-ion storage ring. Electron-ion collision energies ranged from 0 to 50 eV for Si9+ and from 0 to 2000 eV for Si10+, thus, extending previous measurements for Si10+ (Orban et al 2010 Astrophys. J. 721 1603) to much higher energies. Experimentally derived rate coefficients for the recombination of Si9+ and Si10+ ions in a plasma are presented along with simple parameterizations. These rate coefficients are useful for the modeling of the charge balance of silicon in photoionized plasmas (Si9+ and Si10+) and in collisionally ionized plasmas (Si10+ only). In the corresponding temperature ranges, the experimentally derived rate coefficients agree with the latest corresponding theoretical results within the experimental uncertainties.

  17. Sci—Fri PM: Dosimetry — 03: Delta4 diode absolute dose response for large and small target volume IMRT QA

    SciTech Connect

    Simard, D; Thakur, V

    2014-08-15

    The goal of this project was to quantify the over-response/under-response of the Delta4 diodes for Helical Tomotherapy plans on extreme target volume sizes. A custom Delta4 phantom quarter with a hole to insert an ionisation chamber (IC) close to the center of the phantom have been used to acquire simultaneous IC and diodes absolute dose measurements. Eight plans for different target volumes were created from 20cm to 1cm diameter. Diodes dose measurements in the target were compared with IC measurement, to quantify absolute dose accuracy. IC measurements show a good agreement with planned dose (±2%). Diode measurements demonstrate a good agreement with IC for regular target size of 5 and 10cm (0 to 1%). For larger targets, an over-response is observed for FW 25mm and 10mm (2 to 3%). for small target of 1cm diameter, a major under-response is observed for FW 25mm and 10mm (−8 and −36%). The over-response could to be due to the extra amount of scattered radiation and the opposite for under-response. Although this scatter hypothesis still has to be proven, early testing demonstrates an over-response of 40%/20% of the central diodes compare to IC when an open helical rotational beam is delivered 75mm/25mm away from the center of the phantom. These results are in agreement with the real patient Delta4 DQA results at our center.

  18. 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

  19. A Simple Apparatus for Screening Absolute Photosynthetic Rates of Single Algal Colonies in an Anoxic Atmosphere 1

    PubMed Central

    Graves, D. A.; Greenbaum, E.

    1989-01-01

    Photosynthetically generated O2 was measured from single algal colonies in a He atmosphere, using an enhanced Hersch galvanic cell. The enhancement consisted of using ultrapure potassium hydroxide as the electrolyte and ultrapure lead as the anode. The galvanic cell was placed in a regulated helium-flow system containing a reaction cuvette with the colonies and an electrolysis cell for calibration. Colonies were individually irradiated using a He-Ne laser. Data collection and laser positioning for colony irradiation were microcomputer controlled. This assay system was capable of detecting O2 production rates of 500 femtomoles per second with a signal to noise ratio of 2, a level of sensitivity that permitted the detection of photoevolved O2 from single algal colonies. This capability provides, for the first time, an approach for quantitatively measuring the absolute rate of photosynthetic O2 evolution from a single algal colony. PMID:16666743

  20. Absolute rate of the reaction of bromine atoms with ozone from 200-360 K

    NASA Technical Reports Server (NTRS)

    Michael, J. V.; Lee, J. H.; Payne, W. A.; Stief, L. J.

    1978-01-01

    The rate constant for the reaction Br + O3 yields BrO + O2 was measured from 200 to 360 K by the technique of flash photolysis coupled to time resolved detection of bromine atoms by resonance fluorescence (FP-RF). Br atoms were produced by the flash photolysis of CH3Br at lambda 165nm.O3 was monitored continuously under reaction conditions by absorption at 253.7 nm. At each of five temperatures the results were independent of substantial variations in O3, total pressure and limited variations in flash intensity. The measured rate constants obeyed the Arrhenius expression, where the error quoted is two standard deviations. Results are compared with previous determinations which employed the discharge flow-mass spectrometric technique.

  1. Absolute rate of the reaction of bromine atoms with ozone from 200 to 360 K

    NASA Technical Reports Server (NTRS)

    Michael, J. V.; Lee, J. H.; Payne, W. A.; Stief, L. J.

    1978-01-01

    The rate constant for the reaction Br + O3 yields BrO + O2 has been measured from 200 to 360 K by the technique of flash photolysis coupled to time resolved detection of bromine atoms by resonance fluorescence (FP-RF). Br atoms were produced by the flash photolysis of CH3Br at a wavelength of 165 nm. O3 concentration was monitored continuously under reaction conditions by absorption at 253.7 nm. At each of five temperatures the results were independent of substantial variations in O3 concentration, total pressure (Ar), and limited variations in flash intensity (i.e., initial Br concentration). The measured rate constants obey the Arrhenius expression, k = (7.74 plus or minus 0.50) x 10 to the -12th exp(-603 plus or minus 16/T) cu cm/molecule/sec, where the error quoted is two standard deviations.

  2. Absolute rate constants for the reaction of atomic hydrogen with ketene from 298 to 500 K

    NASA Technical Reports Server (NTRS)

    Michael, J. V.; Nava, D. F.; Payne, W. A.; Stief, L. J.

    1979-01-01

    Rate constants for the reaction of atomic hydrogen with ketene have been measured at room temperature by two techniques, flash photolysis-resonance fluorescence and discharge flow-resonance fluorescence. The measured values are (6.19 + or - 1.68) x 10 to the -14th and (7.3 + or - 1.3) x 10 to the -14th cu cm/molecule/s, respectively. In addition, rate constants as a function of temperature have been measured over the range 298-500 K using the FP-RF technique. The results are best represented by the Arrhenius expression k = (1.88 + or - 1.12) x 10 to the -11th exp(-1725 + or - 190/T) cu cm/molecule/s, where the indicated errors are at the two standard deviation level.

  3. Clinical implementation of a novel applicator in high-dose-rate brachytherapy treatment of esophageal cancer

    PubMed Central

    Hansen, Jorgen L.; Bhagwat, Mandar S.; O'Farrell, Desmond A.; Friesen, Scott; Harris, Thomas C.; Damato, Antonio L.; Cormack, Robert A.; Martin, Neil E.; Devlin, Phillip M.

    2016-01-01

    Purpose In this study, we present the clinical implementation of a novel transoral balloon centering esophageal applicator (BCEA) and the initial clinical experience in high-dose-rate (HDR) brachytherapy treatment of esophageal cancer, using this applicator. Material and methods Acceptance testing and commissioning of the BCEA were performed prior to clinical use. Full performance testing was conducted including measurements of the dimensions and the catheter diameter, evaluation of the inflatable balloon consistency, visibility of the radio-opaque markers, congruence of the markers, absolute and relative accuracy of the HDR source in the applicator using the radiochromic film and source position simulator, visibility and digitization of the applicator on the computed tomography (CT) images under the clinical conditions, and reproducibility of the offset. Clinical placement of the applicator, treatment planning, treatment delivery, and patient's response to the treatment were elaborated as well. Results The experiments showed sub-millimeter accuracy in the source positioning with distal position at 1270 mm. The digitization (catheter reconstruction) was uncomplicated due to the good visibility of markers. The treatment planning resulted in a favorable dose distribution. This finding was pronounced for the treatment of the curvy anatomy of the lesion due to the improved repeatability and consistency of the delivered fractional dose to the patient, since the radioactive source was placed centrally within the lumen with respect to the clinical target due to the five inflatable balloons. Conclusions The consistency of the BCEA positioning resulted in the possibility to deliver optimized non-uniform dose along the catheter, which resulted in an increase of the dose to the cancerous tissue and lower doses to healthy tissue. A larger number of patients and long-term follow-up will be required to investigate if the delivered optimized treatment can lead to improved

  4. Clinical implementation of a novel applicator in high-dose-rate brachytherapy treatment of esophageal cancer

    PubMed Central

    Hansen, Jorgen L.; Bhagwat, Mandar S.; O'Farrell, Desmond A.; Friesen, Scott; Harris, Thomas C.; Damato, Antonio L.; Cormack, Robert A.; Martin, Neil E.; Devlin, Phillip M.

    2016-01-01

    Purpose In this study, we present the clinical implementation of a novel transoral balloon centering esophageal applicator (BCEA) and the initial clinical experience in high-dose-rate (HDR) brachytherapy treatment of esophageal cancer, using this applicator. Material and methods Acceptance testing and commissioning of the BCEA were performed prior to clinical use. Full performance testing was conducted including measurements of the dimensions and the catheter diameter, evaluation of the inflatable balloon consistency, visibility of the radio-opaque markers, congruence of the markers, absolute and relative accuracy of the HDR source in the applicator using the radiochromic film and source position simulator, visibility and digitization of the applicator on the computed tomography (CT) images under the clinical conditions, and reproducibility of the offset. Clinical placement of the applicator, treatment planning, treatment delivery, and patient's response to the treatment were elaborated as well. Results The experiments showed sub-millimeter accuracy in the source positioning with distal position at 1270 mm. The digitization (catheter reconstruction) was uncomplicated due to the good visibility of markers. The treatment planning resulted in a favorable dose distribution. This finding was pronounced for the treatment of the curvy anatomy of the lesion due to the improved repeatability and consistency of the delivered fractional dose to the patient, since the radioactive source was placed centrally within the lumen with respect to the clinical target due to the five inflatable balloons. Conclusions The consistency of the BCEA positioning resulted in the possibility to deliver optimized non-uniform dose along the catheter, which resulted in an increase of the dose to the cancerous tissue and lower doses to healthy tissue. A larger number of patients and long-term follow-up will be required to investigate if the delivered optimized treatment can lead to improved

  5. Absolute vertical uplift rates in western Washington inferred from historical leveling and tide gauge data

    NASA Astrophysics Data System (ADS)

    Alba, S.; Weldon, R.; Livelybrooks, D.; Schmidt, D. A.

    2009-12-01

    We present a new uplift rate map for western Washington based on reanalysis of water levels from the 12 major NOAA tide gauges, three new water level series that combine NOAA’s historical records and our temporarily deployed gauges (at Cape Disappointment, Olympia, and Point Grenville), and reinterpretation of repeated 1st and 2nd order NGS leveling lines. As previous studies have concluded, EW gradients in the vertical deformation field are consistent with strain accumulation across the Cascadia subduction zone interface; however, uplift rates are highly variable along the outer Washington coast, ranging from approximately +4 to -2 mm/yr, suggesting significant changes in the depth of locking along strike. Improved measure of uplift rates from water level changes are accomplished by aggressively editing available hourly data and applying a transfer function approach to better remove tides, ocean and atmospheric “noise”. The analysis allows uplift to be determined from shorter and less complete records and in some cases permits the identification of transients like slow earthquakes. As we found in a similar study in Oregon (Burgette et al, JGR, 2009), releveled lines need to be anchored to as many tide gauges as possible to remove systematic error, and repeated releveling (especially of tidal benchmarks) is required to identify the few stable benchmarks that link water levels at the tidal stations to each other through time and to the regional NGS leveling lines. A portion of the westernmost Washington coast, from an approximate latitude of 47.4 to 47.9 N, is subsiding, and tilts suggest that the peak in uplift rate is well onshore, indicating that the locked zone extends onshore, in contrast to most previous studies. To the north, the peak in uplift approximately passes through Neah Bay (the NW corner of the Olympic Peninsula, lat. 48.3 N), and to the south the peak is offshore from Grays Harbor (lat. 47 N) to the Columbia River (lat. 46.2 N). A north

  6. 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.

  7. 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

  8. 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.

  9. Absolute rate constant determinations for the deactivation of O/1D/ by time resolved decay of O/1D/ yields O/3P/ emission

    NASA Technical Reports Server (NTRS)

    Davidson, J. A.; Sadowski, C. M.; Schiff, H. I.; Howard, C. J.; Schmeltekopf, A. L.; Jennings, D. A.; Streit, G. E.

    1976-01-01

    Absolute rate constants for the deactivation of O(1D) atoms by some atmospheric gases have been determined by observing the time-resolved emission of O(1D) at 630 nm. O(1D) atoms were produced by the dissociation of ozone via repetitive laser pulses at 266 nm. Absolute rate constants for the relaxation of O(1D) at 298 K are reported for N2, O2, CO2, O3, H2, D2, CH4, HCl, NH3, H2O, N2O, and Ne. The results obtained are compared with previous relative and absolute measurements reported in the literature.

  10. 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

  11. Radiation dose rates from commercial PWR and BWR spent fuel elements

    SciTech Connect

    Willingham, C.E.

    1981-10-01

    Data on measurements of gamma dose rates from commercial reactor spent fuel were collected, and documented calculated gamma dose rates were reviewed. As part of this study, the gamma dose rate from spent fuel was estimated, using computational techniques similar to previous investigations into this problem. Comparison of the measured and calculated dose rates provided a recommended dose rate in air versus distance curve for PWR spent fuel.

  12. 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.

  13. Absolute rate calculations: atom and proton transfers in hydrogen-bonded systems.

    PubMed

    Barroso, Mónica; Arnaut, Luis G; Formosinho, Sebastião J

    2005-02-01

    We calculate energy barriers of atom- and proton-transfer reactions in hydrogen-bonded complexes in the gas phase. Our calculations do not involve adjustable parameters and are based on bond-dissociation energies, ionization potentials, electron affinities, bond lengths, and vibration frequencies of the reactive bonds. The calculated barriers are in agreement with experimental data and high-level ab initio calculations. We relate the height of the barrier with the molecular properties of the reactants and complexes. The structure of complexes with strong hydrogen bonds approaches that of the transition state, and substantially reduces the barrier height. We calculate the hydrogen-abstraction rates in H-bonded systems using the transition-state theory with the semiclassical correction for tunneling, and show that they are in excellent agreement with the experimental data. H-bonding leads to an increase in tunneling corrections at room temperature. PMID:15751360

  14. Temperature and pressure dependence of the absolute rate constant for the reactions of NH2 radicals with acetylene and ethylene

    NASA Technical Reports Server (NTRS)

    Bosco, S. R.; Nava, D. F.; Brobst, W. D.; Stief, L. J.

    1984-01-01

    The absolute rate constants for the reaction between the NH2 free radical and acetylene and ethylene is measured experimentally using a flash photolysis technique. The constant is considered to be a function of temperature and pressure. At each temperature level of the experiment, the observed pseudo-first-order rate constants were assumed to be independent of flash intensity. The results of the experiment indicate that the bimolecular rate constant for the NH2 + C2H2 reaction increases with pressure at 373 K and 459 K but not at lower temperatures. Results near the pressure limit conform to an Arrhenius expression of 1.11 (+ or -) 0.36 x 10 to the -13th over the temperature range from 241 to 459 K. For the reaction NH2 + C2H4, a smaller rate of increase in the bimolecular rate constant was observed over the temperature range 250-465 K. The implications of these results for current theoretical models of NH2 + C2H2 (or H4) reactions in the atmospheres of Jupiter and Saturn are discussed.

  15. 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.

  16. SU-D-BRE-04: Evaluating the Dose Accuracy of a 2D Ion Chamber Array in High Dose Rate Pencil Beam Scanning Proton Beam

    SciTech Connect

    Perles, L; Mascia, A; Piskulich, F; Lepage, R; Zhang, Y; Giebeler, A; Dong, L

    2014-06-01

    Purpose: To evaluate the absolute dose accuracy of the PTW Octavius 729 XDR 2D ion chamber array at a high dose rate pencil beam scanning proton therapy facility. Methods: A set of 18 plans were created in our treatment planning system, each of which comprising a unique combination of field sizes (FS), length of spread out of Bragg peaks (SOBP) and depths. The parameters used were: FS of 5×5cm{sup 2}, 10×10cm{sup 2} and 15×15cm{sup 2}; flat SOBP of 5cm and 10cm; and isocenter depths of 10cm, 15cm and 20cm, which coincides with the center of the SOBP. The 2D array detector was positioned at the machine isocenter and the appropriate amount of solid water was used to match the planned depths of 10, 15 and 20 cm water equivalent depth. Subsequently, we measured the absolute dose at isocenter using a CC04 ion chamber in a 1D water tank. Both 2D array and CC04 were previously cross calibrated. We also collected the MU rates used by our proton machine from the log files. Results: The relative differences between the CC04 and the 2D array can be summarized into two groups, one with 5 cm SOBP and another with 10 cm SOBP. Plotting these datasets against FS shows that the 2D array response for high dose rate fields (FS of 5×5cm{sup 2} and 5cm SOBP) can be up to 2% lower. Similarly, plotting them against isocenter depths reveals the detector's response can be up to 2% lower for higher energy beams (about 200MeV nominal). The MU rate found in the machine log files for 5cm SOBP's were as high as twice the MU rate for the 10cm SOBP. Conclusion: The 2D array dose response showed a dose rate effect in scanning pencil beam delivery, which needs to be corrected to achieve a better dose accuracy.

  17. Dose and dose-rate effects of ionizing radiation: a discussion in the light of radiological protection.

    PubMed

    Rühm, Werner; Woloschak, Gayle E; Shore, Roy E; Azizova, Tamara V; Grosche, Bernd; Niwa, Ohtsura; Akiba, Suminori; Ono, Tetsuya; Suzuki, Keiji; Iwasaki, Toshiyasu; Ban, Nobuhiko; Kai, Michiaki; Clement, Christopher H; Bouffler, Simon; Toma, Hideki; Hamada, Nobuyuki

    2015-11-01

    The biological effects on humans of low-dose and low-dose-rate exposures to ionizing radiation have always been of major interest. The most recent concept as suggested by the International Commission on Radiological Protection (ICRP) is to extrapolate existing epidemiological data at high doses and dose rates down to low doses and low dose rates relevant to radiological protection, using the so-called dose and dose-rate effectiveness factor (DDREF). The present paper summarizes what was presented and discussed by experts from ICRP and Japan at a dedicated workshop on this topic held in May 2015 in Kyoto, Japan. This paper describes the historical development of the DDREF concept in light of emerging scientific evidence on dose and dose-rate effects, summarizes the conclusions recently drawn by a number of international organizations (e.g., BEIR VII, ICRP, SSK, UNSCEAR, and WHO), mentions current scientific efforts to obtain more data on low-dose and low-dose-rate effects at molecular, cellular, animal and human levels, and discusses future options that could be useful to improve and optimize the DDREF concept for the purpose of radiological protection. PMID:26343037

  18. Dose and dose-rate effects of ionizing radiation: a discussion in the light of radiological protection.

    PubMed

    Rühm, Werner; Woloschak, Gayle E; Shore, Roy E; Azizova, Tamara V; Grosche, Bernd; Niwa, Ohtsura; Akiba, Suminori; Ono, Tetsuya; Suzuki, Keiji; Iwasaki, Toshiyasu; Ban, Nobuhiko; Kai, Michiaki; Clement, Christopher H; Bouffler, Simon; Toma, Hideki; Hamada, Nobuyuki

    2015-11-01

    The biological effects on humans of low-dose and low-dose-rate exposures to ionizing radiation have always been of major interest. The most recent concept as suggested by the International Commission on Radiological Protection (ICRP) is to extrapolate existing epidemiological data at high doses and dose rates down to low doses and low dose rates relevant to radiological protection, using the so-called dose and dose-rate effectiveness factor (DDREF). The present paper summarizes what was presented and discussed by experts from ICRP and Japan at a dedicated workshop on this topic held in May 2015 in Kyoto, Japan. This paper describes the historical development of the DDREF concept in light of emerging scientific evidence on dose and dose-rate effects, summarizes the conclusions recently drawn by a number of international organizations (e.g., BEIR VII, ICRP, SSK, UNSCEAR, and WHO), mentions current scientific efforts to obtain more data on low-dose and low-dose-rate effects at molecular, cellular, animal and human levels, and discusses future options that could be useful to improve and optimize the DDREF concept for the purpose of radiological protection.

  19. Solid-state track recorder dosimetry device to measure absolute reaction rates and neutron fluence as a function of time

    DOEpatents

    Gold, Raymond; Roberts, James H.

    1989-01-01

    A solid state track recording type dosimeter is disclosed to measure the time dependence of the absolute fission rates of nuclides or neutron fluence over a period of time. In a primary species an inner recording drum is rotatably contained within an exterior housing drum that defines a series of collimating slit apertures overlying windows defined in the stationary drum through which radiation can enter. Film type solid state track recorders are positioned circumferentially about the surface of the internal recording drum to record such radiation or its secondary products during relative rotation of the two elements. In another species both the recording element and the aperture element assume the configuration of adjacent disks. Based on slit size of apertures and relative rotational velocity of the inner drum, radiation parameters within a test area may be measured as a function of time and spectra deduced therefrom.

  20. Metabolically consistent breathing rates for use in dose assessments

    SciTech Connect

    Layton, D.W. )

    1993-01-01

    Assessments of doses resulting from exposures to airborne gases and particles are based almost exclusively on inhalation rates that are inconsistent with the quantities of oxygen needed to metabolize dietary intakes of fats, carbohydrates, and protein. This inconsistency leads to erroneous estimates of inhalation exposures and can distort the relative importance of inhalation and ingestion-based exposures to environmental contaminants that are present in foods, air, and water. As a means of dealing with this problem, a new methodology for estimating breathing rates is presented that is based on the oxygen uptake associated with energy expenditures and a ventilatory equivalent that relates minute volume to oxygen uptake. Three alternative energy-based approaches for estimating daily inhalation rates are examined: (1) average daily intakes of food energy from dietary surveys, adjusted for under reporting of foods; (2) average daily energy expenditure calculated from ratios of total daily expenditure to basal metabolism; and (3) daily energy expenditures determined from a time-activity survey. Under the first two approaches, inhalation rates for adult females in different age cohorts ranged from 9.7 to 11 m3 d-1, whereas for adult males the range was 13 to 17 m3 d-1. Inhalation rates for adults determined from activity patterns were higher (i.e., 13 to 18 m3 d-1), however, those rates were shown to be quite sensitive to the energy expenditures used to represent light and sedentary activities. In contrast to the above estimates, the ICRP 23 reference values for adult females and males are 21 and 23 m3 d-1 (Snyder et al. 1975). Finally, the paper provides a technique for determining the short-term breathing rates of individuals based on their basal metabolic rate and level of physical activity.

  1. 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.

  2. 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.

  3. High-dose-rate prostate brachytherapy inverse planning on dose-volume criteria by simulated annealing

    NASA Astrophysics Data System (ADS)

    Deist, T. M.; Gorissen, B. L.

    2016-02-01

    High-dose-rate brachytherapy is a tumor treatment method where a highly radioactive source is brought in close proximity to the tumor. In this paper we develop a simulated annealing algorithm to optimize the dwell times at preselected dwell positions to maximize tumor coverage under dose-volume constraints on the organs at risk. Compared to existing algorithms, our algorithm has advantages in terms of speed and objective value and does not require an expensive general purpose solver. Its success mainly depends on exploiting the efficiency of matrix multiplication and a careful selection of the neighboring states. In this paper we outline its details and make an in-depth comparison with existing methods using real patient data.

  4. High-dose-rate prostate brachytherapy inverse planning on dose-volume criteria by simulated annealing.

    PubMed

    Deist, T M; Gorissen, B L

    2016-02-01

    High-dose-rate brachytherapy is a tumor treatment method where a highly radioactive source is brought in close proximity to the tumor. In this paper we develop a simulated annealing algorithm to optimize the dwell times at preselected dwell positions to maximize tumor coverage under dose-volume constraints on the organs at risk. Compared to existing algorithms, our algorithm has advantages in terms of speed and objective value and does not require an expensive general purpose solver. Its success mainly depends on exploiting the efficiency of matrix multiplication and a careful selection of the neighboring states. In this paper we outline its details and make an in-depth comparison with existing methods using real patient data. PMID:26760757

  5. Dose rate properties of NIPAM-based x-ray CT polymer gel dosimeters

    NASA Astrophysics Data System (ADS)

    Jirasek, A.; Johnston, H.; Hilts, M.

    2015-06-01

    In this work we investigate radiation dose rate dependencies of N-isopropylacrylamide (NIPAM) based polymer gel dosimeters (PGDs) used in conjunction with x-ray computed tomography imaging for radiotherapy dose verification. We define four primary forms of dose rate variation: constant mean dose rate where beam on and beam off times both vary, variable mean dose rate where beam on time varies, variable mean dose rate where beam off time varies and machine dose rate (MU min-1). We utilize both small (20 mL) vials and large volume (1L) gel containers to identify and characterize dose rate dependence in NIPAM PGDs. Results indicate that all investigated constant and variable mean dose rates had negligible affect on PGD dose response with the exception of machine dose rates (100-600 MU min-1) which produced variations in dose response significantly lower than previously reported. Explanations of the reduced variability in dose response are given. It is also shown that NIPAM PGD dose response is not affected by variations in dose rate that may occur in modulated treatment deliveries. Finally, compositional changes in NIPAM PGDs are investigated as potential mitigating strategies for dose rate-dependent response variability.

  6. 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

  7. Monte Carlo study of radiation dose enhancement by gadolinium in megavoltage and high dose rate radiotherapy.

    PubMed

    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.

  8. Indirectly estimated absolute lung cancer mortality rates by smoking status and histological type based on a systematic review

    PubMed Central

    2013-01-01

    Background National smoking-specific lung cancer mortality rates are unavailable, and studies presenting estimates are limited, particularly by histology. This hinders interpretation. We attempted to rectify this by deriving estimates indirectly, combining data from national rates and epidemiological studies. Methods We estimated study-specific absolute mortality rates and variances by histology and smoking habit (never/ever/current/former) based on relative risk estimates derived from studies published in the 20th century, coupled with WHO mortality data for age 70–74 for the relevant country and period. Studies with populations grossly unrepresentative nationally were excluded. 70–74 was chosen based on analyses of large cohort studies presenting rates by smoking and age. Variations by sex, period and region were assessed by meta-analysis and meta-regression. Results 148 studies provided estimates (Europe 59, America 54, China 22, other Asia 13), 54 providing estimates by histology (squamous cell carcinoma, adenocarcinoma). For all smoking habits and lung cancer types, mortality rates were higher in males, the excess less evident for never smokers. Never smoker rates were clearly highest in China, and showed some increasing time trend, particularly for adenocarcinoma. Ever smoker rates were higher in parts of Europe and America than in China, with the time trend very clear, especially for adenocarcinoma. Variations by time trend and continent were clear for current smokers (rates being higher in Europe and America than Asia), but less clear for former smokers. Models involving continent and trend explained much variability, but non-linearity was sometimes seen (with rates lower in 1991–99 than 1981–90), and there was regional variation within continent (with rates in Europe often high in UK and low in Scandinavia, and higher in North than South America). Conclusions The indirect method may be questioned, because of variations in definition of smoking and

  9. A rare gas optics-free absolute photon flux and energy analyzer to provide absolute photoionization rates of inflowing interstellar neutrals

    NASA Technical Reports Server (NTRS)

    Judge, Darrell L.

    1994-01-01

    A prototype spectrometer has been developed for space applications requiring long term absolute EUV photon flux measurements. The energy spectrum of the incoming photons is transformed directly into an electron energy spectrum by taking advantage of the photoelectric effect in one of several rare gases at low pressures. Using an electron energy spectrometer, followed by an electron multiplier detector, pulses due to individual electrons are counted. The overall efficiency of this process can be made essentially independent of gain drifts in the signal path, and the secular degradation of optical components which is often a problem in other techniques is avoided. A very important feature of this approach is its freedom from the problem of overlapping spectral orders that plagues grating EUV spectrometers. An instrument with these features has not been flown before, but is essential to further advances in our understanding of solar EUV flux dynamics, and the coupled dynamics of terrestrial and planetary atmospheres. The detailed characteristics of this optics-free spectrometer are presented in the publications section.

  10. Pressure dependence of the absolute rate constant for the reaction OH + C2H2 from 228 to 413K

    NASA Technical Reports Server (NTRS)

    Michael, J. V.; Nava, D. F.; Borokowski, R. P.; Payne, W. A.; Stief, L. J.

    1980-01-01

    The pressure dependence of absolute rate constants for the reaction of OH + C2H2 yields products has been examined at five temperatures ranging from 228 to 413 K. The experimental techniques which was used is flash photolysis-resonance fluoresence. OH was produced by water photolysis and hydroxyl resonance fluorescent photons were measured by multiscaling techniques. The results indicate that the low pressure bimolecular rate constant is 4 x 10 the the minus 13th power cu cm molecule (-1) s(-1) over the temperature range studied. A substantial increase in the bimolecular rate constant with an increase in pressure was observed at all temperatures except 228 K. This indicates the importance of initial adduct formation and subsequent stablization. The high pressure results are well represented by the Arrhenius expression (k sub bi) sub infinity = (6.83 + or - 1.19) x 10 to the minus 12th power exp(-646 + or - 47/T)cu cm molecule (-1) s(-1). The results are compared to previous investigated and are theoretically discussed. The implications of these results on modeling of terrestrial and planetary atmospheres and also in combustion chemistry are discussed.

  11. The reaction H + C4H2 - Absolute rate constant measurement and implication for atmospheric modeling of Titan

    NASA Technical Reports Server (NTRS)

    Nava, D. F.; Mitchell, M. B.; Stief, L. J.

    1986-01-01

    The absolute rate constant for the reaction H + C4H2 has been measured over the temperature (T) interval 210-423 K, using the technique of flash photolysis-resonance fluorescence. At each of the five temperatures employed, the results were independent of variations in C4H2 concentration, total pressure of Ar or N2, and flash intensity (i.e., the initial H concentration). The rate constant, k, was found to be equal to 1.39 x 10 to the -10th exp (-1184/T) cu cm/s, with an error of one standard deviation. The Arrhenius parameters at the high pressure limit determined here for the H + C4H2 reaction are consistent with those for the corresponding reactions of H with C2H2 and C3H4. Implications of the kinetic carbon chemistry results, particularly those at low temperature, are considered for models of the atmospheric carbon chemistry of Titan. The rate of this reaction, relative to that of the analogous, but slower, reaction of H + C2H2, appears to make H + C4H2 a very feasible reaction pathway for effective conversion of H atoms to molecular hydrogen in the stratosphere of Titan.

  12. DuraSeal as a spacer to reduce rectal doses in low-dose rate brachytherapy for prostate cancer.

    PubMed

    Heikkilä, Vesa-Pekka; Kärnä, Aarno; Vaarala, Markku H

    2014-08-01

    The purpose of this study was to evaluate the utility of off-label use of DuraSeal polyethylene glycol (PEG) gel in low-dose rate (LDR) prostate brachytherapy seed implantation to reduce rectal doses. Diluted DuraSeal was easy to use and, in spite of a clearance effect, useful in decreasing D₂cc rectal doses. PMID:25201125

  13. 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

  14. 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.

  15. 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; 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. 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

  16. Optical factors determined by the T-matrix method in turbidity measurement of absolute coagulation rate constants.

    PubMed

    Xu, Shenghua; Liu, Jie; Sun, Zhiwei

    2006-12-01

    Turbidity measurement for the absolute coagulation rate constants of suspensions has been extensively adopted because of its simplicity and easy implementation. A key factor in deriving the rate constant from experimental data is how to theoretically evaluate the so-called optical factor involved in calculating the extinction cross section of doublets formed during aggregation. In a previous paper, we have shown that compared with other theoretical approaches, the T-matrix method provides a robust solution to this problem and is effective in extending the applicability range of the turbidity methodology, as well as increasing measurement accuracy. This paper will provide a more comprehensive discussion of the physical insight for using the T-matrix method in turbidity measurement and associated technical details. In particular, the importance of ensuring the correct value for the refractive indices for colloidal particles and the surrounding medium used in the calculation is addressed, because the indices generally vary with the wavelength of the incident light. The comparison of calculated results with experiments shows that the T-matrix method can correctly calculate optical factors even for large particles, whereas other existing theories cannot. In addition, the data of the optical factor calculated by the T-matrix method for a range of particle radii and incident light wavelengths are listed.

  17. 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.

  18. 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.

  19. Continuous, online measurement of the absolute plasma refill rate during hemodialysis using feedback regulated ultrafiltration: preliminary results.

    PubMed

    Brummelhuis, Walter J; van Schelven, Leonard J; Boer, Walther H

    2008-01-01

    Methods to continuously measure absolute refill during dialysis are not available. It would be useful to have such a method because it would allow investigating the mechanism of refill the effect of interventions. We designed a feedback algorithm that adjusts ultrafiltration rate (QUF) according to hemoglobin (Hb) concentration changes in such a way that relative blood volume (BV) remains constant within a narrow target range. In this situation, the generated QUF quantitatively reflects refill. Refill patterns were studied in five hypotension prone patients. In addition, on separate occasions, we studied the effect of antiembolism stockings (AES) and infusion of hydroxy-ethylated starch (HAES) on refill in these patients. Refill during the first hour fell significantly from 21 +/- 3 ml/min to 9 +/- 2 ml/min (p < 0.05). In the second hour, refill decreased further and became zero in four out of five patients. Neither AES nor HAES measurably affected refill. The marked and rapid fall in refill in the early stages of dialysis suggests untimely depletion of the interstitial compartment and underestimation of dry weight. We propose that continuous, online measurement of refill patterns may be of value for accurate estimation of dry weight in dialysis patients. PMID:18204322

  20. 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.

  1. 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.

  2. A patient-specific quality assurance study on absolute dose verification using ionization chambers of different volumes in RapidArc treatments

    SciTech Connect

    Syam Kumar, S.A.; Sukumar, Prabakar; Sriram, Padmanaban; Rajasekaran, Dhanabalan; Aketi, Srinu; Vivekanandan, Nagarajan

    2012-01-01

    The recalculation of 1 fraction from a patient treatment plan on a phantom and subsequent measurements have become the norms for measurement-based verification, which combines the quality assurance recommendations that deal with the treatment planning system and the beam delivery system. This type of evaluation has prompted attention to measurement equipment and techniques. Ionization chambers are considered the gold standard because of their precision, availability, and relative ease of use. This study evaluates and compares 5 different ionization chambers: phantom combinations for verification in routine patient-specific quality assurance of RapidArc treatments. Fifteen different RapidArc plans conforming to the clinical standards were selected for the study. Verification plans were then created for each treatment plan with different chamber-phantom combinations scanned by computed tomography. This includes Medtec intensity modulated radiation therapy (IMRT) phantom with micro-ionization chamber (0.007 cm{sup 3}) and pinpoint chamber (0.015 cm{sup 3}), PTW-Octavius phantom with semiflex chamber (0.125 cm{sup 3}) and 2D array (0.125 cm{sup 3}), and indigenously made Circular wax phantom with 0.6 cm{sup 3} chamber. The measured isocenter absolute dose was compared with the treatment planning system (TPS) plan. The micro-ionization chamber shows more deviations when compared with semiflex and 0.6 cm{sup 3} with a maximum variation of -4.76%, -1.49%, and 2.23% for micro-ionization, semiflex, and farmer chambers, respectively. The positive variations indicate that the chamber with larger volume overestimates. Farmer chamber shows higher deviation when compared with 0.125 cm{sup 3}. In general the deviation was found to be <1% with the semiflex and farmer chambers. A maximum variation of 2% was observed for the 0.007 cm{sup 3} ionization chamber, except in a few cases. Pinpoint chamber underestimates the calculated isocenter dose by a maximum of 4.8%. Absolute dose

  3. 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

  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 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

  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. Novel brachytherapy treatment planning system utilizing dose rate dependent average cell survival, CT-simulator, and dose-volume histogram

    SciTech Connect

    Mayer, R.; Fong, W.; Frankel, T.

    1995-12-31

    This report describes a new brachytherapy planning program that provides an evaluation of a given low or high dose rate treatment taking into account spatial dose heterogeneity and cell response to radiation. This brachytherapy scheme uses the images from a CT-Simulator (AcQSim, Picker International, Cleveland, Ohio) to simultaneously localize the seed positions and to axially scan the patient. This procedure helps to ensure accurate registration of the putative seed positions with the patient tissues and organs. The seed positions are determined by back-projecting positions of seeds or dummy seeds from the CT-Simulator setup scout images. Physicians delineate the tissues of interest on the axial slices. Dose is computed after assigning activity (low dose rate) of dwell times (high dose rate) to the Ir{sup 192} or I{sup 125} seed. The planar isodose distribution is superimposed onto axial cuts of the tissues and onto coronal or sagital views of the tissues following image reconstruction. Areal or volumetric calculations of the dose distribution within a given tissue are computed from the tissue outlines. The treatment plan computes (1) volume differential and cummulative dose histograms of the dose delivered to individual tissues, (2) the average, standard deviation, and coefficient of skewness of the dose distribution delivered to the individual tissues, (3) the average survival probability for a given radiation treatment.

  8. Inverse modelling of radionuclide release rates using gamma dose rate observations

    NASA Astrophysics Data System (ADS)

    Hamburger, Thomas; Stohl, Andreas; von Haustein, Christoph; Thummerer, Severin; Wallner, Christian

    2014-05-01

    Severe accidents in nuclear power plants such as the historical accident in Chernobyl 1986 or the more recent disaster in the Fukushima Dai-ichi nuclear power plant in 2011 have drastic impacts on the population and environment. The hazardous consequences reach out on a national and continental scale. Environmental measurements and methods to model the transport and dispersion of the released radionuclides serve as a platform to assess the regional impact of nuclear accidents - both, for research purposes and, more important, to determine the immediate threat to the population. However, the assessments of the regional radionuclide activity concentrations and the individual exposure to radiation dose underlie several uncertainties. For example, the accurate model representation of wet and dry deposition. One of the most significant uncertainty, however, results from the estimation of the source term. That is, the time dependent quantification of the released spectrum of radionuclides during the course of the nuclear accident. The quantification of the source terms of severe nuclear accidents may either remain uncertain (e.g. Chernobyl, Devell et al., 1995) or rely on rather rough estimates of released key radionuclides given by the operators. Precise measurements are mostly missing due to practical limitations during the accident. Inverse modelling can be used to realise a feasible estimation of the source term (Davoine and Bocquet, 2007). Existing point measurements of radionuclide activity concentrations are therefore combined with atmospheric transport models. The release rates of radionuclides at the accident site are then obtained by improving the agreement between the modelled and observed concentrations (Stohl et al., 2012). The accuracy of the method and hence of the resulting source term depends amongst others on the availability, reliability and the resolution in time and space of the observations. Radionuclide activity concentrations are observed on a

  9. 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.

  10. 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.

  11. Facility for gamma irradiations of cultured cells at low dose rates: design, physical characteristics and functioning.

    PubMed

    Esposito, Giuseppe; Anello, Pasquale; Pecchia, Ilaria; Tabocchini, Maria Antonella; Campa, Alessandro

    2016-09-01

    We describe a low dose/dose rate gamma irradiation facility (called LIBIS) for in vitro biological systems, for the exposure, inside a CO2 cell culture incubator, of cells at a dose rate ranging from few μGy/h to some tens of mGy/h. Three different (137)Cs sources are used, depending on the desired dose rate. The sample is irradiated with a gamma ray beam with a dose rate uniformity of at least 92% and a percentage of primary 662keV photons greater than 80%. LIBIS complies with high safety standards. PMID:27423023

  12. Comparison of Hydrogen Atom Abstraction Rates of Terminal and Bridging Hydrides in Triosmium Clusters: Absolute Abstraction Rate Constants for Benzyl Radical

    SciTech Connect

    Franz, James A.; Kolwaite, Douglas S.; Linehan, John C.; Rosenberg, Edward

    2004-02-02

    Absolute rate constants for hydrogen atom abstraction by benzyl radical from Os3(m-H)2 (CO)9PPh3(1), Os3 (m-H)(H)(CO)10PPh3(2), Os3(m-H)(CO)9(m3-h2-C9H6N)(3), Os3(m-H)(CO)9(m-h2-C9H6N)PPh3 (5) and Os3(m-H)(CO)10(m-h2-C9H6N) (4) were determined in benzene by competition of the abstraction reaction with the self termination of benzyl radical. Thus, experimental values of kabs/kt1/2 were combined with rate constants for self-termination of benzyl radical in benzene from the expression ln(2kt/M-1s-1= 27.23 - 2952.4/RT), RT in cal/mol, to give absolute rate constants for abstraction, kabs: for Os3(m-H)2 (CO)9PPh3(1) in benzene, log (kabs/M-1s-1)= (8.86 .20) - (6.90 .31)/q; for Os3 (m-H)(H)(CO)(10PPh3) (2) log (kabs/M-1s-1)= (8.15 .49) - (4.41 .72)/q; for Os3(m-H)(CO)9(m3-h2-C9H6N) (3) log (kabs/M-1s-1)= (8.9 2) (8.8 3)/q; value for 4 and for Os3(m-H)(CO9)(m-h2-C9H6N)(PPh3) (5) log (kabs/M-1s-1)= (7.0 .38) - (4.15 .56)/q, q= 2.303RT kcal/mol. The terminal hydride on the Os3 c luster 2 is about 10 times more reactive than bridging hydride in 1. The results show that while m-H bridging retards the rate of hydrogen abstraction relative to terminal hydrogen, the bridging hydrogen remains appreciably reactive in the m-H form. In fact, the highest rate observed was for the bridging hydride in 4, Os3(m-H)(CO)10(m-h2-C9H6N). Temperature dependent kinetics for compound 4 were not determined because of significant CO loss above room temperature. However at 293 K the rate constant of hydrogen atom abstraction from this electron-rich cluster, 5 2 x 104 M-1s-1, is at least twice as fast as that for the terminal hydrogen atom cluster, 2, Os3 (m-H)(H)(CO)10PPh3, kabs (298 K)= 1.8 x 104 M-1s-1. The rate constants for hydrogen atom abstraction by benzyl radical from these osmium clusters increase with increasing electron density on the osmium cluster and decrease with increasing steric bulk of the ligands.

  13. Spatial variations in natural background radiation: absorbed dose rates in air in Colorado.

    PubMed

    Stone, J M; Whicker, R D; Ibrahim, S A; Whicker, F W

    1999-05-01

    Large and small-scale spatial variations in natural ambient background radiation dose rates in Colorado were investigated at 1,150 specific locations with particular attention to 40 of the more populated areas along the Front Range of the Rocky Mountains. Total dose rates (including cosmic and terrestrial components) in Front Range communities below 2,000 m elevation averaged 135 nGy h(-1). Terrestrial dose rates had a coefficient of variation of 17%. Communities above 2,000 m had a mean total dose rate of 196 nGy h(-1), and a terrestrial dose rate coefficient of variation of 17%. Across all Front Range communities, the coefficient of variation for terrestrial dose rates was 22%. Within individual communities, coefficient of variation values for terrestrial dose rates ranged from 3 to 21%. Smaller-scale spatial variability (to within a few meters) was relatively small (coefficient of variation values generally ranged from 3 to 7%). A significant linear relationship (r2 = 0.83) between the size of area surveyed (km2) and coefficient of variation value for terrestrial dose rates was found. West of the Continental Divide, the terrestrial component accounted for roughly 60% of total measured dose rates, while east of the Continental Divide, where enriched granitic source rocks and associated soils are prevalent, the terrestrial component generally accounted for two-thirds or more of total dose rates. PMID:10201565

  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. Dose-Dependent Mutation Rates Determine Optimum Erlotinib Dosing Strategies for EGFR Mutant Non-Small Cell Lung Cancer Patients

    PubMed Central

    Liu, Lin L.; Li, Fei; Pao, William; Michor, Franziska

    2015-01-01

    Background The advent of targeted therapy for cancer treatment has brought about a paradigm shift in the clinical management of human malignancies. Agents such as erlotinib used for EGFR-mutant non-small cell lung cancer or imatinib for chronic myeloid leukemia, for instance, lead to rapid tumor responses. Unfortunately, however, resistance often emerges and renders these agents ineffective after a variable amount of time. The FDA-approved dosing schedules for these drugs were not designed to optimally prevent the emergence of resistance. To this end, we have previously utilized evolutionary mathematical modeling of treatment responses to elucidate the dosing schedules best able to prevent or delay the onset of resistance. Here we expand on our approaches by taking into account dose-dependent mutation rates at which resistant cells emerge. The relationship between the serum drug concentration and the rate at which resistance mutations arise can lead to non-intuitive results about the best dose administration strategies to prevent or delay the emergence of resistance. Methods We used mathematical modeling, available clinical trial data, and different considerations of the relationship between mutation rate and drug concentration to predict the effectiveness of different dosing strategies. Results We designed several distinct measures to interrogate the effects of different treatment dosing strategies and found that a low-dose continuous strategy coupled with high-dose pulses leads to the maximal delay until clinically observable resistance. Furthermore, the response to treatment is robust against different assumptions of the mutation rate as a function of drug concentration. Conclusions For new and existing targeted drugs, our methodology can be employed to compare the effectiveness of different dose administration schedules and investigate the influence of changing mutation rates on outcomes. PMID:26536620

  16. Relative contributions of galactic cosmic rays and lunar proton "albedo" to dose and dose rates near the Moon

    NASA Astrophysics Data System (ADS)

    Spence, Harlan E.; Golightly, Michael J.; Joyce, Colin J.; Looper, Mark D.; Schwadron, Nathan A.; Smith, Sonya S.; Townsend, Lawrence W.; Wilson, Jody; Zeitlin, Cary

    2013-11-01

    use validated radiation transport models of the Cosmic Ray Telescope for the Effects of Radiation instrument and its response to both primary galactic cosmic rays (GCR) and secondary radiation, including lunar protons released through nuclear evaporation, to estimate their relative contributions to total dose rate in silicon (372 μGy/d) and dose equivalent rate at the skin (2.88 mSv/d). Near the Moon, we show that GCR accounts for ~91.4% of the total absorbed dose, with GCR protons accounting for ~42.8%, GCR alpha particles for ~18.5%, and GCR heavy ions for ~30.1%. The remaining ~8.6% of the dose at Lunar Reconnaissance Orbiter altitudes (~50 km) arises from secondary lunar species, primarily "albedo" protons (3.1%) and electrons (2.2%). Other lunar nuclear evaporation species contributing to the dose rate are positrons (1.5%), gammas (1.1%), and neutrons (0.7%). Relative contributions of these same species to the total dose equivalent rate in skin, a quantity of more direct biological relevance, favor those with comparatively high quality factors. Consequently, the primary GCR heavy ion components dominate the estimated effective skin dose. Finally, we note that when considering the lunar radiation environment, although the Moon blocks approximately half of the sky, thus essentially halving the absorbed dose rate near the Moon relative to deep space, the secondary radiation created by the presence of the Moon adds back a small, but measurable, absorbed dose (~8%) that can and should be now accounted for quantitatively in radiation risk assessments at the Moon and other similar exploration targets.

  17. Chromosome aberrations in human lymphocytes induced by 250 MeV protons: effects of dose, dose rate and shielding

    NASA Technical Reports Server (NTRS)

    George, K.; Willingham, V.; Wu, H.; Gridley, D.; Nelson, G.; Cucinotta, F. A.

    2002-01-01

    Although the space radiation environment consists predominantly of energetic protons, astronauts inside a spacecraft are chronically exposed to both primary particles as well as secondary particles that are generated when the primary particles penetrate the spacecraft shielding. Secondary neutrons and secondary charged particles can have an LET value that is greater than the primary protons and, therefore, produce a higher relative biological effectiveness (RBE). Using the accelerator facility at Loma Linda University, we exposed human lymphocytes in vitro to 250 MeV protons with doses ranging from 0 to 60 cGy at three different dose rates: a low dose rate of 7.5 cGy/h, an intermediate dose rate of 30 cGy/h and a high dose rate of 70 cGy/min. The effect of 15 g/cm2 aluminum shielding on the induction of chromosome aberrations was investigated for each dose rate. After exposure, lymphocytes were incubated in growth medium containing phytohemagglutinin (PHA) and chromosome spreads were collected using a chemical-induced premature chromosome condensation (PCC) technique. Aberrations were analyzed using the fluorescence in situ hybridization (FISH) technique with three different colored chromosome-painting probes. The frequency of reciprocal and complex-type chromosome exchanges were compared in shielded and unshielded samples. c2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

  18. Dose and dose rate effects of whole-body proton irradiation on leukocyte populations and lymphoid organs: part I

    NASA Technical Reports Server (NTRS)

    Gridley, Daila S.; Pecaut, Michael J.; Dutta-Roy, Radha; Nelson, Gregory A.

    2002-01-01

    The goal of part I of this study was to evaluate the effects of whole-body proton irradiation on lymphoid organs and specific leukocyte populations. C57BL/6 mice were exposed to the entry region of the proton Bragg curve to total doses of 0.5 gray (Gy), 1.5 Gy, and 3.0 Gy, each delivered at a low dose rate (LDR) of 1 cGy/min and high dose rate (HDR) of 80 cGy/min. Non-irradiated and 3 Gy HDR gamma-irradiated groups were included as controls. At 4 days post-irradiation, highly significant radiation dose-dependent reductions were observed in the mass of both lymphoid organs and the numbers of leukocytes and T (CD3(+)), T helper (CD3(+)/CD4(+)), T cytotoxic (CD3(+)/CD8(+)), and B (CD19(+)) cells in both blood and spleen. A less pronounced dose effect was noted for natural killer (NK1.1(+) NK) cells in spleen. Monocyte, but not granulocyte, counts in blood were highly dose-dependent. The numbers for each population generally tended to be lower with HDR than with LDR radiation; a significant dose rate effect was found in the percentages of T and B cells, monocytes, and granulocytes and in CD4(+):CD8(+) ratios. These data indicate that mononuclear cell response to the entry region of the proton Bragg curve is highly dependent upon the total dose and that dose rate effects are evident with some cell types. Results from gamma- and proton-irradiated groups (both at 3 Gy HDR) were similar, although proton-irradiation gave consistently lower values in some measurements.

  19. Assessment of gamma-dose rate in city of Kermanshah

    PubMed Central

    Tavakoli, Mohamad Bagher; Kodamoradi, Ehsan; Shaneh, Zahra

    2012-01-01

    Introduction: Environmental natural radiation measurement is of great importance and interest especially for human health. The induction of genetic disorder and cancer appears to be the most important in an exposed population. Materials and Methods: Measurements of background gamma rays were performed using a mini-rad environmental survey meter at 25 different locations around the city of Kermanshah (a city in the west of Iran). The measurements were also performed at two different time of day one in the morning and the other in the afternoon. At each location and time measurements were repeated for five times and the mean was considered as the background dose at that location. Results and Discussions: Comparison between the measured results in the morning and afternoon has not shown any significant difference (P > 0.95). The maximum and minimum obtained results were 2.63 mSv/y and 1.49 mSv/y, respectively. From the total measurements at 25 sites mean and SD background radiation dose to the population is 2.24 ± 0.25 mSv. Conclusion: The mean radiation dose to the population is about 2.5 times of the world average total external exposure cosmic rays and terrestrial gamma rays dose reported by UNSCEAR. PMID:23555133

  20. Correlation of Point B and Lymph Node Dose in 3D-Planned High-Dose-Rate Cervical Cancer Brachytherapy

    SciTech Connect

    Lee, Larissa J.; Sadow, Cheryl A.; Russell, Anthony; Viswanathan, Akila N.

    2009-11-01

    Purpose: To compare high dose rate (HDR) point B to pelvic lymph node dose using three-dimensional-planned brachytherapy for cervical cancer. Methods and Materials: Patients with FIGO Stage IB-IIIB cervical cancer received 70 tandem HDR applications using CT-based treatment planning. The obturator, external, and internal iliac lymph nodes (LN) were contoured. Per fraction (PF) and combined fraction (CF) right (R), left (L), and bilateral (Bil) nodal doses were analyzed. Point B dose was compared with LN dose-volume histogram (DVH) parameters by paired t test and Pearson correlation coefficients. Results: Mean PF and CF doses to point B were R 1.40 Gy +- 0.14 (CF: 7 Gy), L 1.43 +- 0.15 (CF: 7.15 Gy), and Bil 1.41 +- 0.15 (CF: 7.05 Gy). The correlation coefficients between point B and the D100, D90, D50, D2cc, D1cc, and D0.1cc LN were all less than 0.7. Only the D2cc to the obturator and the D0.1cc to the external iliac nodes were not significantly different from the point B dose. Significant differences between R and L nodal DVHs were seen, likely related to tandem deviation from irregular tumor anatomy. Conclusions: With HDR brachytherapy for cervical cancer, per fraction nodal dose approximates a dose equivalent to teletherapy. Point B is a poor surrogate for dose to specific nodal groups. Three-dimensional defined nodal contours during brachytherapy provide a more accurate reflection of delivered dose and should be part of comprehensive planning of the total dose to the pelvic nodes, particularly when there is evidence of pathologic involvement.

  1. A graphite calorimeter for absolute measurements of absorbed dose to water: application in medium-energy x-ray filtered beams

    NASA Astrophysics Data System (ADS)

    Pinto, M.; Pimpinella, M.; Quini, M.; D'Arienzo, M.; Astefanoaei, I.; Loreti, S.; Guerra, A. S.

    2016-02-01

    The Italian National Institute of Ionizing Radiation Metrology (ENEA-INMRI) has designed and built a graphite calorimeter that, in a water phantom, has allowed the determination of the absorbed dose to water in medium-energy x-rays with generating voltages from 180 to 250 kV. The new standard is a miniaturized three-bodies calorimeter, with a disc-shaped core of 21 mm diameter and 2 mm thickness weighing 1.134 g, sealed in a PMMA waterproof envelope with air-evacuated gaps. The measured absorbed dose to graphite is converted into absorbed dose to water by means of an energy-dependent conversion factor obtained from Monte Carlo simulations. Heat-transfer correction factors were determined by FEM calculations. At a source-to-detector distance of 100 cm, a depth in water of 2 g cm-2, and at a dose rate of about 0.15 Gy min-1, results of calorimetric measurements of absorbed dose to water, D w, were compared to experimental determinations, D wK, obtained via an ionization chamber calibrated in terms of air kerma, according to established dosimetry protocols. The combined standard uncertainty of D w and D wK were estimated as 1.9% and 1.7%, respectively. The two absorbed dose to water determinations were in agreement within 1%, well below the stated measurement uncertainties. Advancements are in progress to extend the measurement capability of the new in-water-phantom graphite calorimeter to other filtered medium-energy x-ray qualities and to reduce the D w uncertainty to around 1%. The new calorimeter represents the first implementation of in-water-phantom graphite calorimetry in the kilovoltage range and, allowing independent determinations of D w, it will contribute to establish a robust system of absorbed dose to water primary standards for medium-energy x-ray beams.

  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. Absorbed dose simulations in near-surface regions using high dose rate Iridium-192 sources applied for brachytherapy

    NASA Astrophysics Data System (ADS)

    Moura, E. S.; Zeituni, C. A.; Sakuraba, R. K.; Gonçalves, V. D.; Cruz, J. C.; Júnior, D. K.; Souza, C. D.; Rostelato, M. E. C. M.

    2014-02-01

    Brachytherapy treatment with Iridium-192 high dose rate (HDR) sources is widely used for various tumours and it could be developed in many anatomic regions. Iridium-192 sources are inserted inside or close to the region that will be treated. Usually, the treatment is performed in prostate, gynaecological, lung, breast and oral cavity regions for a better clinical dose coverage compared with other techniques, such as, high energy photons and Cobalt-60 machines. This work will evaluate absorbed dose distributions in near-surface regions around Ir-192 HDR sources. Near-surface dose measurements are a complex task, due to the contribution of beta particles in the near-surface regions. These dose distributions should be useful for non-tumour treatments, such as keloids, and other non-intracavitary technique. For the absorbed dose distribution simulations the Monte Carlo code PENELOPE with the general code penEasy was used. Ir-192 source geometry and a Polymethylmethacrylate (PMMA) tube, for beta particles shield were modelled to yield the percentage depth dose (PDD) on a cubic water phantom. Absorbed dose simulations were realized at the central axis to yield the Ir-192 dose fall-off along central axis. The results showed that more than 99.2% of the absorbed doses (relative to the surface) are deposited in 5 cm depth but with slower rate at higher distances. Near-surface treatments with Ir-192 HDR sources yields achievable measurements and with proper clinical technique and accessories should apply as an alternative for treatment of lesions where only beta sources were used.

  4. Absorbed dose rate in air in metropolitan Tokyo before the Fukushima Daiichi Nuclear Power Plant accident.

    PubMed

    Inoue, K; Hosoda, M; Fukushi, M; Furukawa, M; Tokonami, S

    2015-11-01

    The monitoring of absorbed dose rate in air has been carried out continually at various locations in metropolitan Tokyo after the accident of the Fukushima Daiichi Nuclear Power Plant. While the data obtained before the accident are needed to more accurately assess the effects of radionuclide contamination from the accident, detailed data for metropolitan Tokyo obtained before the accident have not been reported. A car-borne survey of the absorbed dose rate in air in metropolitan Tokyo was carried out during August to September 2003. The average absorbed dose rate in air in metropolitan Tokyo was 49±6 nGy h(-1). The absorbed dose rate in air in western Tokyo was higher compared with that in central Tokyo. Here, if the absorbed dose rate indoors in Tokyo is equivalent to that outdoors, the annual effective dose would be calculated as 0.32 mSv y(-1).

  5. Changes in ambient dose equivalent rates around roads at Kawamata town after the Fukushima accident.

    PubMed

    Kinase, Sakae; Sato, Satoshi; Sakamoto, Ryuichi; Yamamoto, Hideaki; Saito, Kimiaki

    2015-11-01

    Changes in ambient dose equivalent rates noted through vehicle-borne surveys have elucidated ecological half-lives of radioactive caesium in the environment. To confirm that the ecological half-lives are appropriate for predicting ambient dose equivalent rates within living areas, it is important to ascertain ambient dose equivalent rates on/around roads. In this study, radiation monitoring on/around roads at Kawamata town, located about 37 km northwest of the Fukushima Daiichi Nuclear Power Plant, was performed using monitoring vehicles and survey meters. It was found that the ambient dose equivalent rates around roads were higher than those on roads as of October 2012. And withal the ecological half-lives on roads were essentially consistent with those around roads. With dose predictions using ecological half-lives on roads, it is necessary to make corrections to ambient dose equivalent rates through the vehicle-borne surveys against those within living areas. PMID:25953794

  6. Absorbed dose rate in air in metropolitan Tokyo before the Fukushima Daiichi Nuclear Power Plant accident.

    PubMed

    Inoue, K; Hosoda, M; Fukushi, M; Furukawa, M; Tokonami, S

    2015-11-01

    The monitoring of absorbed dose rate in air has been carried out continually at various locations in metropolitan Tokyo after the accident of the Fukushima Daiichi Nuclear Power Plant. While the data obtained before the accident are needed to more accurately assess the effects of radionuclide contamination from the accident, detailed data for metropolitan Tokyo obtained before the accident have not been reported. A car-borne survey of the absorbed dose rate in air in metropolitan Tokyo was carried out during August to September 2003. The average absorbed dose rate in air in metropolitan Tokyo was 49±6 nGy h(-1). The absorbed dose rate in air in western Tokyo was higher compared with that in central Tokyo. Here, if the absorbed dose rate indoors in Tokyo is equivalent to that outdoors, the annual effective dose would be calculated as 0.32 mSv y(-1). PMID:25944962

  7. ``In Vivo'' Dosimetry in High Dose Rate Brachytherapy for Cervical Cancer Treatments

    NASA Astrophysics Data System (ADS)

    González-Azcorra, S. A.; Mota-García, A.; Poitevín-Chacón, M. A.; Santamaría-Torruco, B. J.; Rodríguez-Ponce, M.; Herrera-Martínez, F. P.; Gamboa de Buen, I.; Ruíz-Trejo, C.; Buenfil, A. E.

    2008-08-01

    In this prospective study, rectal dose was measured "in vivo" using TLD-100 crystals (3×3×1 mm3), and it has been compared to the prescribed dose. Measurements were performed in patients with cervical cancer classified in FIGO stages IB-IIIB and treated with high dose rate brachytherapy (HDR BT) at the Instituto Nacional de Cancerología (INCan).

  8. 'In vivo' Dose Measurements in High-Dose-Rate Brachytherapy Treatments for Cervical Cancer: A Project Proposal

    SciTech Connect

    Reynoso Mejia, C. A.; Buenfil Burgos, A. E.; Ruiz Trejo, C.; Mota Garcia, A.; Trejo Duran, E.; Rodriguez Ponce, M.; Gamboa de Buen, I.

    2010-12-07

    The aim of this thesis project is to compare doses calculated from the treatment planning system using computed tomography images, with those measured 'in vivo' by using thermoluminescent dosimeters placed at different regions of the rectum and bladder of a patient during high-dose-rate intracavitary brachytherapy treatment of uterine cervical carcinoma. The experimental dosimeters characterisation and calibration have concluded and the protocol to carry out the 'in vivo' measurements has been established. In this work, the calibration curves of two types of thermoluminescent dosimeters (rods and chips) are presented, and the proposed protocol to measure the 'in vivo' dose is fully described.

  9. Dose-rate conversion factors for external exposure to photons and electrons

    SciTech Connect

    Kocher, D.C.

    1981-08-01

    Dose-rate conversion factors for external exposure to photons and electrons have been calculated for approximately 500 radionuclides of potential importance in environmental radiological assessments. The dose-rate factors were obtained using the DOSFACTER computer code. The results given in this report incorporate calculation of electron dose-rate factors for radiosensitive tissues of the skin, improved estimates of organ dose-rate factors for photons, based on organ doses for monoenergetic sources at the body surface of an exposed individual, and the spectra of scattered photons in air from monoenergetic sources in an infinite, uniformly contaminated atmospheric cloud, calculation of dose-rate factors for other radionuclides in addition to those of interest in the nuclear fuel cycle, and incorporation of updated radioactive decay data for all radionuclides. Dose-rate factors are calculated for three exposure modes - immersion in contaminated air, immersion in contaminated water, and exposure at a height of 1 m above a contaminated ground surface. The report presents the equations used to calculate the external dose-rate factors for photons and electrons, documentation of the revised DOSFACTER computer code, and a complete tabulation of the calculated dose-rate factors. 30 refs., 12 figs.

  10. Life span of C57 mice as influenced by radiation dose, dose rate, and age at exposure

    SciTech Connect

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

    1982-10-01

    This study was designed to measure the life shortening of C57BL/6J male mice as a result of exposure to five external doses from /sup 60/Co gamma radiation delivered at six different dose rates. Total doses ranged from 20 to 1620 rad at exposure rates ranging from 0.7 to 36,000 R/day. The ages of the mice at exposure were newborn, 2, 6, or 15 months. Two replications were completed. Although death was the primary endpoint, we did perform gross necropsies. The life span findings are variable, but we found no consistent shortening compared to control life spans. Therefore, we cannot logically extrapolate life shortening to lower doses, from the data we have obtained. In general, the younger the animals were at the beginning of exposure, the longer their life spans were compared to those of controls. This relationship weakened at the higher doses and dose rates, as mice in these categories tended not to have significantly different life spans from controls. Using life span as a criterion, we find this study suggests that some threshold dosage may exist beyond which effects of external irradiation may be manifested. Up to this threshold, there is no shortening effect on life span compared to that of control mice. Our results are in general agreement with the results of other researchers investigating human and other animal life span effects on irradiation.

  11. 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.

  12. Treatment system for whole bladder wall photodynamic therapy with in vivo monitoring and control of light dose rate and dose

    SciTech Connect

    Marynissen, J.P.; Jansen, H.; Star, W.M. )

    1989-11-01

    A system is described for in vivo monitoring and control of light dose rate and dose during whole bladder photodynamic therapy (PDT). A modified cystoscope admits an isotropic light source (fiber with diffusing tip, connected to a dye laser) and three translucent nylon catheters that are unfolded in three directions along the bladder wall. An isotropic light detector (0.8 mm. diameter probe on 200 microns. fiber) is inserted into each catheter and connected to an amplifier displaying light dose rate (in mW/cm.2) and integrated light dose (in J/cm.2) for each probe. Before treatment a low light level is used to optimize the position of the light source, requiring equal readings by each of the three dosimetry probes. Uniformity of irradiation is checked by moving the probes through their respective catheters along the bladder wall. With red light (wavelength 630 nm.) a dose rate uniformity of {plus minus} 20% could be achieved in vivo in dog bladder. With green light (514.5 nm.) uniform irradiation was difficult, most likely due to a much smaller contribution of scattered light. Measurements during clinical PDT show that optimizing the light source position by suprapubic transvesical ultrasound may not secure uniform irradiation. Half-way into the treatment a difference of 100% between the readings of two probes was noted. Adjusting the position of the light source resulted in integrated light dose variations of less than 20% among the three probes at the end of treatment.

  13. The effect of dose, dose rate, route of administration, and species on tissue and blood levels of benzene metabolites.

    PubMed Central

    Henderson, R F; Sabourin, P J; Bechtold, W E; Griffith, W C; Medinsky, M A; Birnbaum, L S; Lucier, G W

    1989-01-01

    Studies were completed in F344/N rats and B6C3F1 mice to determine the effect of dose, dose rate, route of administration, and rodent species on formation of total and individual benzene metabolites. Oral doses of 50 mg/kg or higher saturated the capacity for benzene metabolism in both rats and mice, resulting in an increased proportion of the administered dose being exhaled as benzene. The saturating air concentration for benzene metabolism during 6-hr exposures was between 130 and 900 ppm. At the highest exposure concentration, rats exhaled approximately half of the internal dose retained at the end of the 6-hr exposure as benzene; mice exhaled only 15% as benzene. Mice were able to convert more of the inhaled benzene to metabolites than were rats. In addition, mice metabolized more of the benzene by pathways leading to the putative toxic metabolites, benzoquinone and muconaldehyde, than did rats. In both rats and mice, the effect of increasing dose, administered orally or by inhalation, was to increase the proportion of the total metabolites that were the products of detoxification pathways relative to the products of pathways leading to putative toxic metabolites. This indicates low-affinity, high-capacity pathways for detoxification and high-affinity, low-capacity pathways leading to putative toxic metabolites. If the results of rodent studies performed at high doses were used to assess the health risk at low-dose exposures to benzene, the toxicity of benzene would be underestimated. PMID:2792053

  14. Dosimetric and radiobiological comparison of volumetric modulated arc therapy, high-dose rate brachytherapy, and low-dose rate permanent seeds implant for localized prostate cancer.

    PubMed

    Yang, Ruijie; Zhao, Nan; Liao, Anyan; Wang, Hao; Qu, Ang

    2016-01-01

    To investigate the dosimetric and radiobiological differences among volumetric modulated arc therapy (VMAT), high-dose rate (HDR) brachytherapy, and low-dose rate (LDR) permanent seeds implant for localized prostate cancer. A total of 10 patients with localized prostate cancer were selected for this study. VMAT, HDR brachytherapy, and LDR permanent seeds implant plans were created for each patient. For VMAT, planning target volume (PTV) was defined as the clinical target volume plus a margin of 5mm. Rectum, bladder, urethra, and femoral heads were considered as organs at risk. A 78Gy in 39 fractions were prescribed for PTV. For HDR and LDR plans, the dose prescription was D90 of 34Gy in 8.5Gy per fraction, and 145Gy to clinical target volume, respectively. The dose and dose volume parameters were evaluated for target, organs at risk, and normal tissue. Physical dose was converted to dose based on 2-Gy fractions (equivalent dose in 2Gy per fraction, EQD2) for comparison of 3 techniques. HDR and LDR significantly reduced the dose to rectum and bladder compared with VMAT. The Dmean (EQD2) of rectum decreased 22.36Gy in HDR and 17.01Gy in LDR from 30.24Gy in VMAT, respectively. The Dmean (EQD2) of bladder decreased 6.91Gy in HDR and 2.53Gy in LDR from 13.46Gy in VMAT. For the femoral heads and normal tissue, the mean doses were also significantly reduced in both HDR and LDR compared with VMAT. For the urethra, the mean dose (EQD2) was 80.26, 70.23, and 104.91Gy in VMAT, HDR, and LDR brachytherapy, respectively. For localized prostate cancer, both HDR and LDR brachytherapy were clearly superior in the sparing of rectum, bladder, femoral heads, and normal tissue compared with VMAT. HDR provided the advantage in sparing of urethra compared with VMAT and LDR.

  15. Induction of reciprocal translocations in rhesus monkey stem-cell spermatogonia: effects of low doses and low dose rates

    SciTech Connect

    van Buul, P.P.; Richardson, J.F. Jr.; Goudzwaard, J.H.

    1986-01-01

    The induction of reciprocal translocation in rhesus monkey spermatogonial stem cells was studied following exposure to low doses of acute X rays (0.25 Gy, 300 mGy/min) or to low-dose-rate X rays (1 Gy, 2 mGy/min) and gamma rays (1 Gy, 0.2 mGy/min). The results obtained at 0.25 Gy of X rays fitted exactly the linear extrapolation down from the 0.5 and 1.0 Gy points obtained earlier. Extension of X-ray exposure reduced the yield of translocations similar to that in the mouse by about 50%. The reduction to 40% of translocation rate after chronic gamma exposure was clearly less than the value of about 80% reported for the mouse over the same range of dose rates. Differential cell killing with ensuing differential elimination of aberration-carrying cells is the most likely explanation for the differences between mouse and monkey.

  16. Inverse modelling of radionuclide release rates using gamma dose rate observations

    NASA Astrophysics Data System (ADS)

    Hamburger, Thomas; Evangeliou, Nikolaos; Stohl, Andreas; von Haustein, Christoph; Thummerer, Severin; Wallner, Christian

    2015-04-01

    Severe accidents in nuclear power plants such as the historical accident in Chernobyl 1986 or the more recent disaster in the Fukushima Dai-ichi nuclear power plant in 2011 have drastic impacts on the population and environment. Observations and dispersion modelling of the released radionuclides help to assess the regional impact of such nuclear accidents. Modelling the increase of regional radionuclide activity concentrations, which results from nuclear accidents, underlies a multiplicity of uncertainties. One of the most significant uncertainties is the estimation of the source term. That is, the time dependent quantification of the released spectrum of radionuclides during the course of the nuclear accident. The quantification of the source term may either remain uncertain (e.g. Chernobyl, Devell et al., 1995) or rely on estimates given by the operators of the nuclear power plant. Precise measurements are mostly missing due to practical limitations during the accident. The release rates of radionuclides at the accident site can be estimated using inverse modelling (Davoine and Bocquet, 2007). The accuracy of the method depends amongst others on the availability, reliability and the resolution in time and space of the used observations. Radionuclide activity concentrations are observed on a relatively sparse grid and the temporal resolution of available data may be low within the order of hours or a day. Gamma dose rates, on the other hand, are observed routinely on a much denser grid and higher temporal resolution and provide therefore a wider basis for inverse modelling (Saunier et al., 2013). We present a new inversion approach, which combines an atmospheric dispersion model and observations of radionuclide activity concentrations and gamma dose rates to obtain the source term of radionuclides. We use the Lagrangian particle dispersion model FLEXPART (Stohl et al., 1998; Stohl et al., 2005) to model the atmospheric transport of the released radionuclides. The

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

    PubMed

    Gotz, M; Karsch, L; Pawelke, J

    2015-06-01

    Pulsed radiation fields, characterized by microsecond pulse duration and correspondingly high pulse dose rates, are increasingly used in therapeutic, diagnostic and research applications. Yet, dose rate meters which are used to monitor radiation protection areas or to inspect radiation shielding are mostly designed, characterized and tested for continuous fields and show severe deficiencies in highly pulsed fields. Despite general awareness of the problem, knowledge of the specific limitations of individual instruments is very limited, complicating reliable measurements. We present here the results of testing three commercial dose rate meters, the RamION ionization chamber, the LB 1236-H proportional counter and the 6150AD-b scintillation counter, for their response in pulsed radiation fields of varied pulse dose and duration. Of these three the RamION proved reliable, operating in a pulsed radiation field within its specifications, while the other two instruments were only able to measure very limited pulse doses and pulse dose rates reliably. PMID:25978117

  18. Low-dose-rate extrapolation using the multistage model

    SciTech Connect

    Portier, C.; Hoel, D.

    1983-12-01

    The distribution of the maximum likelihood estimates of virtually safe levels of exposure to environmental chemicals is derived by using large-sample theory and Monte Carlo simulation according to the Armitage-Doll multistage model. Using historical dose-response we develop a set of 33 two-stage models upon which we base our conclusions. The large-sample distributions of the virtually safe dose are normal for cases in which the multistage-model parameters have nonzero expectation, and are skewed in other cases. The large-sample theory does not provide a good approximation of the distribution observed for small bioassays when Monte Carlo simulation is used. The constrained nature of the multistage-model parameters leads to bimodal distributions for small bioassays. The two modes are the direct result of estimating the linear parameter in the multistage model; the lower mode results from estimating this parameter to be nonzero, and the upper mode from estimating it to be zero. The results of this research emphasize the need for incorporation of the biological theory in the model-selection process.

  19. 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

  20. In situ gamma-ray spectrometry in the environment using dose rate spectroscopy

    NASA Astrophysics Data System (ADS)

    Ji, Young-Yong; Kim, Chang-Jong; Chung, Kun Ho; Choi, Hee-Yeoul; Lee, Wanno; Kang, Mun Ja; Park, Sang Tae

    2016-02-01

    In order to expand the application of dose rate spectroscopy to the environment, in situ gamma-ray spectrometry was first conducted at a height of 1 m above the ground to calculate the ambient dose rate and individual dose rate at that height, as well as the radioactivity in the soil layer for the detected gamma nuclides from the dose rate spectroscopy. The reliable results could be obtained by introducing the angular correction factor to correct the G-factor with respect to incident photons distributed in a certain range of angles. The intercomparison results of radioactivity using ISOCS software, an analysis of a sample taken from the soil around a detector, and dose rate spectroscopy had a difference of <20% for 214Pb, 214Bi, 228Ac, 212Bi, 208Tl, and 40K, except for 212Pb with low-energy photons, that is, <300 keV. In addition, the drawback of using dose rate spectroscopy, that is, all gamma rays from a nuclide should be identified to accurately assess the individual dose rate, was overcome by adopting the concept of contribution ratio of the key gamma ray to the individual dose rate of a nuclide, so that it could be accurately calculated by identifying only a key gamma ray from a nuclide.

  1. Measured absorbed dose rates from semi-infinite hemispherical volumes of 133Xe.

    PubMed

    Munyon, W J; Barber, D E; Howley, J R

    1986-07-01

    Surface absorbed dose rates from different hemispheric volumes of 133Xe have been measured directly with an extrapolation chamber. The results indicate that a linear relationship exists between the radius of the cloud volume and the surface absorbed dose rate for radii between 0 and 23 cm. If cloud volumes with radii larger than 23 cm are taken to be infinite with respect to the range of the charged particles emitted, the absorbed dose rate calculated based on that assumption will be within the uncertainty of any measurement of absorbed dose rate that might be made. For hemispheric volumes having radii less than or equal to 23 cm, the surface absorbed dose rate in tissue-equivalent material, in mGy h-1, is approximated (+/- 20%) by the product of [1.30 mGy h-1 cm-1 kBq-1 cm3] X [cloud radius, cm] X [cloud activity concentration, kBq cm-3].

  2. Interplanetary crew dose rates for the August 1972 solar particle event.

    PubMed

    Parsons, J L; Townsend, L W

    2000-06-01

    Parsons, J. L. and Townsend, L. W. Interplanetary Crew Dose Rates for the August 1972 Solar Particle Event. Using the coupled neutron-proton space radiation transport computer code (BRYNTRN), estimates of dose rates of protons in the skin, ocular lens and bone marrow, behind various thicknesses of aluminum shielding, for crews on space missions outside the Earth's magnetosphere, are made for the large solar particle event (SPE) of August 1972. Overall, the August 1972 dose rates are significantly higher than those estimated for any of the events that occurred in August-December 1989. The dose rates in the August 1972 SPE are not low dose rates as specified by the major national and international advisory bodies and committees. PMID:10825747

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

    PubMed

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

    2012-09-18

    Since the invention of cancer radiotherapy, its primary goal has been to maximize lethal radiation doses to the tumor volume while keeping the dose to surrounding healthy tissues at zero. Sadly, conventional radiation sources (γ or X rays, electrons) used for decades, including multiple or modulated beams, inevitably deposit the majority of their dose in front or behind the tumor, thus damaging healthy tissue and causing secondary cancers years after treatment. Even the most recent pioneering advances in costly proton or carbon ion therapies can not completely avoid dose buildup in front of the tumor volume. Here we show that this ultimate goal of radiotherapy is yet within our reach: Using intense ultra-short infrared laser pulses we can now deposit a very large energy dose at unprecedented microscopic dose rates (up to 10(11) Gy/s) deep inside an adjustable, well-controlled macroscopic volume, without any dose deposit in front or behind the target volume. Our infrared laser pulses produce high density avalanches of low energy electrons via laser filamentation, a phenomenon that results in a spatial energy density and temporal dose rate that both exceed by orders of magnitude any values previously reported even for the most intense clinical radiotherapy systems. Moreover, we show that (i) the type of final damage and its mechanisms in aqueous media, at the molecular and biomolecular level, is comparable to that of conventional ionizing radiation, and (ii) at the tumor tissue level in an animal cancer model, the laser irradiation method shows clear therapeutic benefits. PMID:22927378

  4. 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.

  5. In vitro biotransformation rates in fish liver S9: effect of dosing techniques.

    PubMed

    Lee, Yung-Shan; Lee, Danny H Y; Delafoulhouze, Maximilien; Otton, S Victoria; Moore, Margo M; Kennedy, Chris J; Gobas, Frank A P C

    2014-08-01

    In vitro biotransformation assays are currently being explored to improve estimates of bioconcentration factors of potentially bioaccumulative organic chemicals in fish. The present study compares thin-film and solvent-delivery dosing techniques as well as single versus multiple chemical dosing for measuring biotransformation rates of selected polycyclic aromatic hydrocarbons in rainbow trout (Oncorhynchus mykiss) liver S9. The findings show that biotransformation rates of very hydrophobic substances can be accurately measured in thin-film sorbent-dosing assays from concentration-time profiles in the incubation medium but not from those in the sorbent phase because of low chemical film-to-incubation-medium mass-transfer rates at the incubation temperature of 13.5 °C required for trout liver assays. Biotransformation rates determined by thin-film dosing were greater than those determined by solvent-delivery dosing for chrysene (octanol-water partition coefficient [KOW ] =10(5.60) ) and benzo[a]pyrene (KOW  =10(6.04) ), whereas there were no statistical differences in pyrene (KOW  =10(5.18) ) biotransformation rates between the 2 methods. In sorbent delivery-based assays, simultaneous multiple-chemical dosing produced biotransformation rates that were not statistically different from those measured in single-chemical dosing experiments for pyrene and benzo[a]pyrene but not for chrysene. In solvent-delivery experiments, multiple-chemical dosing produced biotransformation rates that were much smaller than those in single-chemical dosing experiments for all test chemicals. While thin-film sorbent-phase and solvent delivery-based dosing methods are both suitable methods for measuring biotransformation rates of substances of intermediate hydrophobicity, thin-film sorbent-phase dosing may be more suitable for superhydrophobic chemicals.

  6. A graphite calorimeter for absolute measurements of absorbed dose to water: application in medium-energy x-ray filtered beams.

    PubMed

    Pinto, M; Pimpinella, M; Quini, M; D'Arienzo, M; Astefanoaei, I; Loreti, S; Guerra, A S

    2016-02-21

    The Italian National Institute of Ionizing Radiation Metrology (ENEA-INMRI) has designed and built a graphite calorimeter that, in a water phantom, has allowed the determination of the absorbed dose to water in medium-energy x-rays with generating voltages from 180 to 250 kV. The new standard is a miniaturized three-bodies calorimeter, with a disc-shaped core of 21 mm diameter and 2 mm thickness weighing 1.134 g, sealed in a PMMA waterproof envelope with air-evacuated gaps. The measured absorbed dose to graphite is converted into absorbed dose to water by means of an energy-dependent conversion factor obtained from Monte Carlo simulations. Heat-transfer correction factors were determined by FEM calculations. At a source-to-detector distance of 100 cm, a depth in water of 2 g cm(-2), and at a dose rate of about 0.15 Gy min(-1), results of calorimetric measurements of absorbed dose to water, D(w), were compared to experimental determinations, D wK, obtained via an ionization chamber calibrated in terms of air kerma, according to established dosimetry protocols. The combined standard uncertainty of D(w) and D(wK) were estimated as 1.9% and 1.7%, respectively. The two absorbed dose to water determinations were in agreement within 1%, well below the stated measurement uncertainties. Advancements are in progress to extend the measurement capability of the new in-water-phantom graphite calorimeter to other filtered medium-energy x-ray qualities and to reduce the D(w) uncertainty to around 1%. The new calorimeter represents the first implementation of in-water-phantom graphite calorimetry in the kilovoltage range and, allowing independent determinations of D(w), it will contribute to establish a robust system of absorbed dose to water primary standards for medium-energy x-ray beams. PMID:26841127

  7. 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.

  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. Occurence and implications of radiation dose-rate effects for material aging studies

    NASA Astrophysics Data System (ADS)

    Gillen, Kenneth T.; Clough, Roger L.

    A number of commercial cable materials, including ethylene propylene rubber and crosslinked polyolefin insulations and chloroprene and chlorosulfonated polyethylene jackets have been radiation aged in air and nitrogen at radiation dose rates ranging from approximately 10 3 to 10 6{rad}/{hr}. Material degradation was followed using ultimate tensile properties (elongation and tensile strength), swelling measurements and infrared spectroscopy. The tensile results indicate that in air environments radiation dose rate effects are important for all four materials, with more mechanical damage occurring as the dose rate is lowered. These results are interpreted as coming from a competition between crosslinking and oxidative scission in which scission becomes more important as the dose rate is lowered. The swelling results offer direct evidence in support of this interpretation. In addition the infrared results show increased carbonyl content at lower dose rates, also indicative of increased oxidation. The conclusions of this study have important implications for the qualification of elastomeric materials for nuclear applications, since they clearly indicate that the mechanism of degradation is quite different (and the amount usually more severe) under low dose rate exposures compared to the mechanism occurring under the high dose rate exposures normally utilized for stimulating the natural aging.

  10. Variation of indoor radon concentration and ambient dose equivalent rate in different outdoor and indoor environments.

    PubMed

    Stojanovska, Zdenka; Boev, Blazo; Zunic, Zora S; Ivanova, Kremena; Ristova, Mimoza; Tsenova, Martina; Ajka, Sorsa; Janevik, Emilija; Taleski, Vaso; Bossew, Peter

    2016-05-01

    Subject of this study is an investigation of the variations of indoor radon concentration and ambient dose equivalent rate in outdoor and indoor environments of 40 dwellings, 31 elementary schools and five kindergartens. The buildings are located in three municipalities of two, geologically different, areas of the Republic of Macedonia. Indoor radon concentrations were measured by nuclear track detectors, deployed in the most occupied room of the building, between June 2013 and May 2014. During the deploying campaign, indoor and outdoor ambient dose equivalent rates were measured simultaneously at the same location. It appeared that the measured values varied from 22 to 990 Bq/m(3) for indoor radon concentrations, from 50 to 195 nSv/h for outdoor ambient dose equivalent rates, and from 38 to 184 nSv/h for indoor ambient dose equivalent rates. The geometric mean value of indoor to outdoor ambient dose equivalent rates was found to be 0.88, i.e. the outdoor ambient dose equivalent rates were on average higher than the indoor ambient dose equivalent rates. All measured can reasonably well be described by log-normal distributions. A detailed statistical analysis of factors which influence the measured quantities is reported. PMID:26943159

  11. Comparison of measured and calculated dose rates for the Castor HAW 20/28 CG.

    PubMed

    Ringleb, O; Kühl, H; Scheib, H; Rimpler, A

    2005-01-01

    In January 2003 neutron and gamma dose rate measurements at a CASTOR HAW 20/28 CG were performed by the Bundesamt für Strahlenschutz at Gorleben. First, commercial dose rate measurement devices were used, then spectral measurements with a Bonner sphere system were made to verify the results. Axial and circumferential dose rate profiles were measured near the cask surface and spectral measurements were performed for some locations. A shielding analysis of the cask was performed with the MCNP Monte Carlo Code with ENDF/B-VI cross section libraries. The cask was modelled 'as built', i.e. with its real inventory, dimensions and material densities and with the same configuration and position as in the storage facility. The average C/E-ratios are 1.3 for neutron dose rates and 1.4 for gamma dose rates. Both the measured and calculated dose rates show the same qualitative trends in the axial and circumferential direction. The spectral measurements show a variation in the spectra across the cask surface. This correlates with the variation found in the C/E-ratios. At cask midheight good agreement between the Bonner sphere system and the commercial device (LB 6411) is found with a 7% lower derived H*(10) dose rate from the Bonner sphere system. PMID:16604722

  12. Conventional High-Dose-Rate Brachytherapy With Concomitant Complementary IMRT Boost: A Novel Approach for Improving Cervical Tumor Dose Coverage

    SciTech Connect

    Duan, Jun; Kim, Robert Y. Elassal, Shaaban; Lin Huiyi; Shen Sui

    2008-07-01

    Purpose: To investigate the feasibility of combining conventional high-dose-rate (HDR) brachytherapy with a concomitant complementary intensity-modulated radiotherapy (IMRT) boost for improved target coverage in cervical cancers. Methods and Materials: Six patients with cervical cancer underwent conventional HDR (C-HDR) treatment. Computed tomography (CT) and magnetic resonance imaging (MRI) scans were acquired with a CT/MRI-compatible applicator in place. The clinical target volumes (CTVs), defined as the gross target volume with a 3-mm margin and the uterus, were delineated on the CT scans, along with the organs at risk (OARs). The IMRT plans were optimized to generate dose distributions complementing those of C-HDR to cover the CTV while maintaining low doses to the OARs (IMRT-HDR). For comparison, dwell-weight optimized HDR (O-HDR) plans were also generated to cover the CTV and spare the OARs. The three treatment techniques (C-HDR, O-HDR, and IMRT-HDR) were compared. The percentage of volume receiving 95% of the prescription dose (V{sub 95}) was used to evaluate dose coverage to the CTV, and the minimal doses in the 2.0-cm{sup 3} volume receiving the greatest dose were calculated to compare the doses to the OARs. Results: The C-HDR technique provided very poor CTV coverage in 5 cases (V{sub 95} <62%). Although O-HDR provided excellent gross tumor volume coverage (V{sub 95} {>=}96.9%), it resulted in unacceptably high doses to the OARs in all 6 cases and unsatisfactory coverage to the whole CTV in 3 cases. IMRT-HDR not only yielded substantially improved CTV coverage (average V{sub 95} = 95.3%), but also kept the doses to the bladder and rectum reasonably low. Conclusion: Compared with C-HDR and O-HDR, concomitant IMRT boost complementary to C-HDR not only provided excellent CTV coverage, but also maintained reasonably low doses to the OARs.

  13. Treatment Outcome of Medium-Dose-Rate Intracavitary Brachytherapy for Carcinoma of the Uterine Cervix: Comparison With Low-Dose-Rate Intracavitary Brachytherapy

    SciTech Connect

    Kaneyasu, Yuko; Kita, Midori; Okawa, Tomohiko; Maebayashi, Katsuya; Kohno, Mari; Sonoda, Tatsuo; Hirabayashi, Hisae; Nagata, Yasushi; Mitsuhashi, Norio

    2012-09-01

    Purpose: To evaluate and compare the efficacy of medium-dose-rate (MDR) and low-dose-rate (LDR) intracavitary brachytherapy (ICBT) for uterine cervical cancer. Methods and Materials: We evaluated 419 patients with squamous cell carcinoma of the cervix who were treated by radical radiotherapy with curative intent at Tokyo Women's Medical University from 1969 to 1999. LDR was used from 1969 to 1986, and MDR has been used since July 1987. When compared with LDR, fraction dose was decreased and fraction size was increased (1 or 2 fractions) for MDR to make the total dose of MDR equal to that of LDR. In general, the patients received a total dose of 60 to 70 Gy at Point A with external beam radiotherapy combined with brachytherapy according to the International Federation of Gynecology and Obstetrics stage. In the LDR group, 32 patients had Stage I disease, 81 had Stage II, 182 had Stage III, and 29 had Stage IVA; in the MDR group, 9 patients had Stage I disease, 19 had Stage II, 55 had Stage III, and 12 had Stage IVA. Results: The 5-year overall survival rates for Stages I, II, III, and IVA in the LDR group were 78%, 72%, 55%, and 34%, respectively. In the MDR group, the 5-year overall survival rates were 100%, 68%, 52%, and 42%, respectively. No significant statistical differences were seen between the two groups. The actuarial rates of late complications Grade 2 or greater at 5 years for the rectum, bladder, and small intestine in the LDR group were 11.1%, 5.8%, and 2.0%, respectively. The rates for the MDR group were 11.7%, 4.2%, and 2.6%, respectively, all of which were without statistical differences. Conclusion: These data suggest that MDR ICBT is effective, useful, and equally as good as LDR ICBT in daytime (about 5 hours) treatments of patients with cervical cancer.

  14. Evaluation of Enhanced Low Dose Rate Sensitivity in Discrete Bipolar Junction Transistors

    NASA Technical Reports Server (NTRS)

    Chen, Dakai; Ladbury Raymond; LaBel, Kenneth; Topper, Alyson; Ladbury, Raymond; Triggs, Brian; Kazmakites, Tony

    2012-01-01

    We evaluate the low dose rate sensitivity in several families of discrete bipolar transistors across device parameter, quality assurance level, and irradiation bias configuration. The 2N2222 showed the most significant low dose rate sensitivity, with low dose rate enhancement factor of 3.91 after 100 krad(Si). The 2N2907 also showed critical degradation levels. The devices irradiated at 10 mrad(Si)/s exceeded specifications after 40 and 50 krad(Si) for the 2N2222 and 2N2907 devices, respectively.

  15. DETECTORS AND EXPERIMENTAL METHODS: ELDRS and dose-rate dependence of vertical NPN transistor

    NASA Astrophysics Data System (ADS)

    Zheng, Yu-Zhan; Lu, Wu; Ren, Di-Yuan; Wang, Gai-Li; Yu, Xue-Feng; Guo, Qi

    2009-01-01

    The enhanced low-dose-rate sensitivity (ELDRS) and dose-rate dependence of vertical NPN transistors are investigated in this article. The results show that the vertical NPN transistors exhibit more degradation at low dose rate, and that this degradation is attributed to the increase on base current. The oxide trapped positive charge near the SiO2-Si interface and interface traps at the interface can contribute to the increase on base current and the two-stage hydrogen mechanism associated with space charge effect can well explain the experimental results.

  16. Methodology for estimating radiation dose rates to freshwater biota exposed to radionuclides in the environment

    SciTech Connect

    Blaylock, B.G.; Frank, M.L.; O`Neal, B.R.

    1993-08-01

    The purpose of this report is to present a methodology for evaluating the potential for aquatic biota to incur effects from exposure to chronic low-level radiation in the environment. Aquatic organisms inhabiting an environment contaminated with radioactivity receive external radiation from radionuclides in water, sediment, and from other biota such as vegetation. Aquatic organisms receive internal radiation from radionuclides ingested via food and water and, in some cases, from radionuclides absorbed through the skin and respiratory organs. Dose rate equations, which have been developed previously, are presented for estimating the radiation dose rate to representative aquatic organisms from alpha, beta, and gamma irradiation from external and internal sources. Tables containing parameter values for calculating radiation doses from selected alpha, beta, and gamma emitters are presented in the appendix to facilitate dose rate calculations. The risk of detrimental effects to aquatic biota from radiation exposure is evaluated by comparing the calculated radiation dose rate to biota to the U.S. Department of Energy`s (DOE`s) recommended dose rate limit of 0.4 mGy h{sup {minus}1} (1 rad d{sup {minus}1}). A dose rate no greater than 0.4 mGy h{sup {minus}1} to the most sensitive organisms should ensure the protection of populations of aquatic organisms. DOE`s recommended dose rate is based on a number of published reviews on the effects of radiation on aquatic organisms that are summarized in the National Council on Radiation Protection and Measurements Report No. 109 (NCRP 1991). DOE recommends that if the results of radiological models or dosimetric measurements indicate that a radiation dose rate of 0. 1 mGy h{sup {minus}1} will be exceeded, then a more detailed evaluation of the potential ecological consequences of radiation exposure to endemic populations should be conducted.

  17. Study of coolant activation and dose rates with flow rate and power perturbations in pool-type research reactors

    SciTech Connect

    Mirza, N.M.; Mirza, S.M.; Ahmad, N. )

    1991-12-01

    This paper reports on a computer code using the multigroup diffusion theory based LEOPARD and ODMUG programs that has been developed to calculate the activity in the coolant leaving the core of a pool-type research reactor. Using this code, the dose rates at various locations along the coolant path with varying coolant flow rate and reactor power perturbations are determined. A flow rate decrease from 1000 to 145 m{sup 3}/h is considered. The results indicate that a flow rate decrease leads to an increase in the coolant outlet temperature, which affects the neutron group constants and hence the group fluxes. The activity in the coolant leaving the core increases with flow rate decrease. However, at the inlet of the holdup tank, the total dose rate first increases, then passes through a maximum at {approximately} 500 m{sup 3}/h, and finally decreases with flow rate decrease. The activity at the outlet of the holdup tank is mainly due to {sup 24}Na and {sup 56}Mn, and it increases by {approximately} 2% when the flow rate decreases from 1000 to 145 m{sup 3}/h. In an accidental power rise at constant flow rate, the activity in the coolant increases, and the dose rates at all the points along the coolant path show a slight nonlinear rise as the reactor power density increases.

  18. Commissioning of a 3D image-based treatment planning system for high-dose-rate brachytherapy of cervical cancer.

    PubMed

    Kim, Yongbok; Modrick, Joseph M; Pennington, Edward C; Kim, Yusung

    2016-01-01

    The objective of this work is to present commissioning procedures to clinically implement a three-dimensional (3D), image-based, treatment-planning system (TPS) for high-dose-rate (HDR) brachytherapy (BT) for gynecological (GYN) cancer. The physical dimensions of the GYN applicators and their values in the virtual applicator library were varied by 0.4 mm of their nominal values. Reconstruction uncertainties of the titanium tandem and ovoids (T&O) were less than 0.4 mm on CT phantom studies and on average between 0.8-1.0 mm on MRI when compared with X-rays. In-house software, HDRCalculator, was developed to check HDR plan parameters such as independently verifying active tandem or cylinder probe length and ovoid or cylinder size, source calibration and treatment date, and differences between average Point A dose and prescription dose. Dose-volume histograms were validated using another independent TPS. Comprehensive procedures to commission volume optimization algorithms and process in 3D image-based planning were presented. For the difference between line and volume optimizations, the average absolute differences as a percentage were 1.4% for total reference air KERMA (TRAK) and 1.1% for Point A dose. Volume optimization consistency tests between versions resulted in average absolute differences in 0.2% for TRAK and 0.9 s (0.2%) for total treatment time. The data revealed that the optimizer should run for at least 1 min in order to avoid more than 0.6% dwell time changes. For clinical GYN T&O cases, three different volume optimization techniques (graphical optimization, pure inverse planning, and hybrid inverse optimization) were investigated by comparing them against a conventional Point A technique. End-to-end testing was performed using a T&O phantom to ensure no errors or inconsistencies occurred from imaging through to planning and delivery. The proposed commissioning procedures provide a clinically safe implementation technique for 3D image-based TPS for HDR

  19. Methodology for Estimating Radiation Dose Rates to Freshwater Biota Exposed to Radionuclides in the Environment

    SciTech Connect

    Blaylock, B.G.

    1993-01-01

    The purpose of this report is to present a methodology for evaluating the potential for aquatic biota to incur effects from exposure to chronic low-level radiation in the environment. Aquatic organisms inhabiting an environment contaminated with radioactivity receive external radiation from radionuclides in water, sediment, and from other biota such as vegetation. Aquatic organisms receive internal radiation from radionuclides ingested via food and water and, in some cases, from radionuclides absorbed through the skin and respiratory organs. Dose rate equations, which have been developed previously, are presented for estimating the radiation dose rate to representative aquatic organisms from alpha, beta, and gamma irradiation from external and internal sources. Tables containing parameter values for calculating radiation doses from selected alpha, beta, and gamma emitters are presented in the appendix to facilitate dose rate calculations. The risk of detrimental effects to aquatic biota from radiation exposure is evaluated by comparing the calculated radiation dose rate to biota to the U.S. Department of Energy's (DOE's) recommended dose rate limit of 0.4 mGy h{sup -1} (1 rad d{sup -1}). A dose rate no greater than 0.4 mGy h{sup -1} to the most sensitive organisms should ensure the protection of populations of aquatic organisms. DOE's recommended dose rate is based on a number of published reviews on the effects of radiation on aquatic organisms that are summarized in the National Council on Radiation Protection and Measurements Report No. 109 (NCRP 1991). The literature identifies the developing eggs and young of some species of teleost fish as the most radiosensitive organisms. DOE recommends that if the results of radiological models or dosimetric measurements indicate that a radiation dose rate of 0.1 mGy h{sup -1} will be exceeded, then a more detailed evaluation of the potential ecological consequences of radiation exposure to endemic populations should be

  20. GaAs detectors irradiated by electrons at different dose rates

    NASA Astrophysics Data System (ADS)

    Sagatova, A.; Zatko, B.; Sedlackova, K.; Pavlovic, M.; Fulop, M.; Bohacek, P.; Necas, V.

    2014-12-01

    The radiation hardness of Semi-Insulating (SI) GaAs detectors against high-energy electrons was investigated. The detectors were irradiated by 5 MeV electrons. The influence of two irradiation parameters, the total absorbed dose (up to 24 kGy) and the applied dose rate (20, 40 and 80 kGy/h), on their spectrometric properties was studied. An 241Am gamma-ray source was used to evaluate the spectrometric properties. The applied dose has negatively affected the detector CCE (Charge Collection Efficiency) and has influenced also the energy resolution. Nevertheless, a global increase of detection efficiency with the dose was observed. Three different dose rates used during irradiation did not affect the CCE, but in the range of doses from 4 to 16 kGy an influence of the applied dose rate upon two other parameters was observed. With higher dose rates, a steeper increase in the detection efficiency and significant worsening of energy resolution were achieved.

  1. Eliminating the dose-rate effect in a radiochromic silicone-based 3D dosimeter

    NASA Astrophysics Data System (ADS)

    Høye, E. M.; Balling, P.; Yates, E. S.; Muren, L. P.; Petersen, J. B. B.; Skyt, P. S.

    2015-07-01

    Comprehensive dose verification, such as 3D dosimetry, may be required for safe introduction and use of advanced treatment modalities in radiotherapy. A radiochromic silicone-based 3D dosimetry system has recently been suggested, though its clinical use has so far been limited by a considerable dose-rate dependency of the dose response. In this study we have investigated the dose-rate dependency with respect to the chemical composition of the dosimeter. We found that this dependency was reduced with increasing dye concentration, and the dose response was observed to be identical for dosimeters irradiated with 2 and 6 Gy min-1 at concentrations of 0.26% (w/w) dye and 1% (w/w) dye solvent. Furthermore, for the optimized dosimeter formulation, no dose-rate effect was observed due to the attenuation of the beam fluence with depth. However, the temporal stability of the dose response decreased with dye concentration; the response was reduced by (62  ±  1)% within approximately 20 h upon irradiation, at the optimal chemical composition and storage at room temperature. In conclusion, this study presents a chemical composition for a dose-rate independent silicone dosimeter which has considerably improved the clinical applicability of such dosimeters, but at the cost of a decreased stability.

  2. Effect of frequency of dosing of plant sterols on plasma cholesterol levels and synthesis rate

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective was to compare the effects of plant sterols (PS) consumed as a single dose (single) at breakfast or as three doses consumed with breakfast, lunch and dinner (divided) on plasma lipoprotien levels and cholesterol endogenous fractional synthesis rate (FSR). A randomized, placebo-controll...

  3. 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.

  4. 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. PMID:26808877

  5. 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.

  6. 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.

  7. New method of proportional counter feedback biasing for wide-range radiation dose-rate monitors

    SciTech Connect

    Kopp, M.K.; Gueerant, G.C.; Manning, F.W.; Valentine, K.H.

    1985-02-01

    A prototypic wide-range radiation dose-rate monitor for civil defense applications has been developed and tested. The specified dose-rate range (0 to 500 R/h) was displayed on a single readout scale by using feedback-controlled biasing of a proportional counter. This new method is based on controlling the avalanche multiplication factor (gas gain) of the counter by varying its bias voltage in response to its measured output current (i.e., detected dose rate). The counter output current varies between 0 and 1.5 nA in a quasilogarithmic response to dose rates between 0 and 500 R/h. The corresponding values of gas gain and bias voltage range from 1 to 300 and 200 to 1900 V respectively.

  8. New method of proportional counter feedback biasing for wide-range radiation dose-rate monitors

    SciTech Connect

    Kopp, M.K.; Valentine, K.H.; Guerrant, G.C.; Manning, F.W.

    1984-01-01

    A prototypic wide-range radiation dose-rate monitor for civil defense applications has been developed and tested. The specified dose-rate range (0 to 500 R/h) was displayed on a single readout scale by using feedback-controlled biasing of a proportional counter. This new method is based on controlling the avalanche multiplication factor (gas gain) of the counter by varying its bias voltage in response to its measured output current (i.e., detected dose rate). The counter output current varies between 0 and 1.5 nA in a quasi-logarithmic response to dose rates between 0 and 500 R/h. The corresponding values of gas gain and bias voltage range from 1 to 300 and 200 to 1900 V respectively.

  9. An Interactive Point Kernel Program For Photon Dose Rate Prediction of Cylindrical Source/Shield Arrangements.

    1990-10-26

    Version 00 The program ZYLIND is an interactive point kernel program for photon dose rate prediction of a homogeneous cylindrical source shielded by cylindrical (radial) or plane (axial) layered shields.

  10. Numerical calculation of relative dose rates from spherical 106Ru beta sources used in ophthalmic brachytherapy

    NASA Astrophysics Data System (ADS)

    de Paiva, Eduardo

    Concave beta sources of 106Ru/106Rh are used in radiotherapy to treat ophthalmic tumors. However, a problem that arises is the difficult determination of absorbed dose distributions around such sources mainly because of the small range of the electrons and the steep dose gradients. In this sense, numerical methods have been developed to calculate the dose distributions around the beta applicators. In this work a simple code in Fortran language is developed to estimate the dose rates along the central axis of 106Ru/106Rh curved plaques by numerical integration of the beta point source function and results are compared with other calculated data.

  11. External dose rate in Unirea salt mine, Slanic-Prahova, Romania.

    PubMed

    Margineanu, R M; Apostu, A M; Duliu, O G; Bercea, S; Gomoiu, C M; Cristache, C I

    2009-05-01

    The distribution of the external dose rate within the former Unirea salt mine, host of the Low-Level Background Laboratory was determined and compared with calculated values based on the experimentally determined content of natural radioactive elements in the mine walls. The average external dose rate was found to be 1.3+/-0.3 nSv h(-1), close to calculated one of 1.4+/-0.2 nSv h(-1). PMID:19231217

  12. Absolute Summ

    NASA Astrophysics Data System (ADS)

    Phillips, Alfred, Jr.

    Summ means the entirety of the multiverse. It seems clear, from the inflation theories of A. Guth and others, that the creation of many universes is plausible. We argue that Absolute cosmological ideas, not unlike those of I. Newton, may be consistent with dynamic multiverse creations. As suggested in W. Heisenberg's uncertainty principle, and with the Anthropic Principle defended by S. Hawking, et al., human consciousness, buttressed by findings of neuroscience, may have to be considered in our models. Predictability, as A. Einstein realized with Invariants and General Relativity, may be required for new ideas to be part of physics. We present here a two postulate model geared to an Absolute Summ. The seedbed of this work is part of Akhnaton's philosophy (see S. Freud, Moses and Monotheism). Most important, however, is that the structure of human consciousness, manifest in Kenya's Rift Valley 200,000 years ago as Homo sapiens, who were the culmination of the six million year co-creation process of Hominins and Nature in Africa, allows us to do the physics that we do. .

  13. Recombination of W19 + ions with electrons: Absolute rate coefficients from a storage-ring experiment and from theoretical calculations

    NASA Astrophysics Data System (ADS)

    Badnell, N. R.; Spruck, K.; Krantz, C.; Novotný, O.; Becker, A.; Bernhardt, D.; Grieser, M.; Hahn, M.; Repnow, R.; Savin, D. W.; Wolf, A.; Müller, A.; Schippers, S.

    2016-05-01

    Experimentally measured and theoretically calculated rate coefficients for the recombination of W19 +([Kr ] 4 d10 4 f9 ) ions with free electrons (forming W18 +) are presented. At low electron-ion collision energies, the merged-beam rate coefficient is dominated by strong, mutually overlapping, recombination resonances as already found previously for the neighboring charge-state ions W18 + and W20 +. In the temperature range where W19 + is expected to form in a collisionally ionized plasma, the experimentally derived recombination rate coefficient deviates by up to a factor of about 20 from the theoretical rate coefficient obtained from the Atomic Data and Analysis Structure database. The present calculations, which employ a Breit-Wigner redistributive partitioning of autoionizing widths for dielectronic recombination via multi-electron resonances, reproduce the experimental findings over the entire temperature range.

  14. Absolute rate of the reaction of Cl(p-2) with molecular hydrogen from 200 - 500 K

    NASA Technical Reports Server (NTRS)

    Whytock, D. A.; Lee, J. H.; Michael, J. V.; Payne, W. A.; Stief, L. J.

    1976-01-01

    Rate constants for the reaction of atomic chlorine with hydrogen are measured from 200 - 500 K using the flash photolysis-resonance fluorescence technique. The results are compared with previous work and are discussed with particular reference to the equilibrium constant for the reaction and to relative rate data for chlorine atom reactions. Theoretical calculations, using the BEBO method with tunneling, give excellent agreement with experiment.

  15. Absolute rate of the reaction of atomic hydrogen with ethylene from 198 to 320 K at high pressure

    NASA Technical Reports Server (NTRS)

    Lee, J. H.; Michael, J. V.; Payne, W. A.; Stief, L. J.

    1978-01-01

    The rate constant for the H+C2H4 reaction has been measured as a function of temperature. Experiments were performed with high pressures of Ar heat bath gas at seven temperatures from 198 to 320 K with the flash photolysis-resonance fluorescence (FP-RF) technique. Pressures were chosen so as to isolate the addition rate constant k1. The results are well represented by an Arrhenius expression. The results are compared with other studies and are theoretically discussed.

  16. Impact on ambient dose rate in metropolitan Tokyo from the Fukushima Daiichi Nuclear Power Plant accident.

    PubMed

    Inoue, Kazumasa; Tsuruoka, Hiroshi; Van Le, Tan; Arai, Moeko; Saito, Kyoko; Fukushi, Masahiro

    2016-07-01

    A car-borne survey was made in metropolitan Tokyo, Japan, in December 2014 to estimate external dose. This survey was conducted for all municipalities of Tokyo and the results were compared with measurements done in 2003. The ambient dose rate measured in the whole area of Tokyo in December 2014 was 60 nGy h(-1) (23-142 nGy h(-1)), which was 24% higher than the rate in 2003. Higher dose rates (>70 nGy h(-1)) were observed on the eastern and western ends of Tokyo; furthermore, the contribution ratio from artificial radionuclides ((134)Cs and (137)Cs) to ambient dose rate in eastern Tokyo was twice as high as that of western Tokyo. Based on the measured ambient dose rate, the effective dose rate after the accident was estimated to be 0.45 μSv h(-1) in Tokyo. This value was 22% higher than the value before the accident as of December 2014. PMID:27055250

  17. Investigation of natural effective gamma dose rates case study: Ardebil Province in Iran

    PubMed Central

    2012-01-01

    Gamma rays pose enough energy to induce chemical changes that may be biologically important for the normal functioning of body cells. The external exposure of human beings to natural environmental gamma radiation normally exceeds that from all man-made sources combined. In this research natural background gamma dose rates and corresponding annual effective doses were determined for selected cities of Ardebil province. Outdoor gamma dose rates were measured using an Ion Chamber Survey Meter in 105 locations in selected districts. Average absorbed doses for Ardebil, Sar-Ein, Germy, Neer, Shourabil Recreational Lake, and Kosar were determined as 265, 219, 344, 233, 352, and 358 nSv/h, respectively. Although dose rates recorded for Germi and Kosar are comparable with some areas with high natural radiation background, however, the dose rates in other districts are well below the levels reported for such locations. Average annual effective dose due to indoor and outdoor gamma radiation for Ardebil province was estimated as 1.73 (1.35–2.39) mSv, which is on average 2 times higher than the world population weighted average. PMID:23369115

  18. On-site gamma dose rates at the Andreeva Bay shore technical base, northwest Russia.

    PubMed

    Reistad, O; Dowdall, M; Standring, W J F; Selnaes, Ø G; Hustveit, S; Steinhusen, F; Sørlie, A

    2008-07-01

    The spent nuclear fuel (SNF) and radioactive waste (RAW) storage facility at Andreeva Bay shore technical base (STB) is one of the largest and most hazardous nuclear legacy sites in northwest Russia. Originally commissioned in the 1960s the facility now stores large amounts of SNF and RAW associated with the Russian Northern Fleet of nuclear powered submarines. The objective of the present study was to map ambient gamma dose rates throughout the facility, in particular at a number of specific sites where SNF and RAW are stored. The data presented here are taken from a Norwegian-Russian collaboration enabling the first publication in the scientific literature of the complete survey of on-site dose rates. Results indicate that elevated gamma dose rates are found primarily at discrete sites within the facility; maximum dose rates of up to 1000 microSv/h close to the ground (0.1m) and up to 3000 microSv/h at 1m above ground were recorded, higher doses at the 1m height being indicative primarily of the presence of contaminated equipment as opposed to ground contamination. Highest dose rates were measured at sites located in the immediate vicinity of buildings used for storing SNF and sites associated with storage of solid and liquid radioactive wastes. Elevated dose rates were also observed near the former channel of a small brook that became heavily contaminated as a result of radioactive leaks from the SNF storage at Building 5 starting in 1982. Isolated patches of elevated dose rates were also observed throughout the STB. A second paper detailing the radioactive soil contamination at the site is published in this issue of Journal of Environmental Radioactivity.

  19. On-site gamma dose rates at the Andreeva Bay shore technical base, northwest Russia.

    PubMed

    Reistad, O; Dowdall, M; Standring, W J F; Selnaes, Ø G; Hustveit, S; Steinhusen, F; Sørlie, A

    2008-07-01

    The spent nuclear fuel (SNF) and radioactive waste (RAW) storage facility at Andreeva Bay shore technical base (STB) is one of the largest and most hazardous nuclear legacy sites in northwest Russia. Originally commissioned in the 1960s the facility now stores large amounts of SNF and RAW associated with the Russian Northern Fleet of nuclear powered submarines. The objective of the present study was to map ambient gamma dose rates throughout the facility, in particular at a number of specific sites where SNF and RAW are stored. The data presented here are taken from a Norwegian-Russian collaboration enabling the first publication in the scientific literature of the complete survey of on-site dose rates. Results indicate that elevated gamma dose rates are found primarily at discrete sites within the facility; maximum dose rates of up to 1000 microSv/h close to the ground (0.1m) and up to 3000 microSv/h at 1m above ground were recorded, higher doses at the 1m height being indicative primarily of the presence of contaminated equipment as opposed to ground contamination. Highest dose rates were measured at sites located in the immediate vicinity of buildings used for storing SNF and sites associated with storage of solid and liquid radioactive wastes. Elevated dose rates were also observed near the former channel of a small brook that became heavily contaminated as a result of radioactive leaks from the SNF storage at Building 5 starting in 1982. Isolated patches of elevated dose rates were also observed throughout the STB. A second paper detailing the radioactive soil contamination at the site is published in this issue of Journal of Environmental Radioactivity. PMID:18243437

  20. A radiobiological model for the relative biological effectiveness of high-dose-rate 252Cf brachytherapy.

    PubMed

    Rivard, Mark J; Melhus, Christopher S; Zinkin, Heather D; Stapleford, Liza J; Evans, Krista E; Wazer, David E; Odlozilíková, Anna

    2005-09-01

    While there is significant clinical experience using both low- and high-dose-rate 252Cf brachytherapy, there are minimal data regarding values for the neutron relative biological effectiveness (RBE) with both modalities. The aim of this research was to derive a radiobiological model for 252Cf neutron RBE and to compare these results with neutron RBE values used clinically in Russia. The linear-quadratic (LQ) model was used as the basis to characterize cell survival after irradiation, with identical cell killing rates (S(N) = S(gamma)) between 252Cf neutrons and photons used for derivation of RBE. Using this equality, a relationship among neutron dose and LQ radiobiological parameter (i.e., alpha(N), beta(N), alpha(gamma), beta(gamma)) was obtained without the need to specify the photon dose. These results were used to derive the 252Cf neutron RBE, which was then compared with Russian neutron RBE values. The 252Cf neutron RBE was determined after incorporating the LQ radiobiological parameters obtained from cell survival studies with fast neutrons and teletherapy photons. For single-fraction high-dose-rate neutron doses of 0.5, 1.0, 1.5 and 2.0 Gy, the total biologically equivalent doses were 1.8, 3.4, 4.7 and 6.0 RBE Gy with 252Cf neutron RBE values of 3.2, 2.9, 2.7 and 2.5, respectively. Using clinical data for late-responding reactions from 252Cf, Russian investigators created an empirical model that predicted high-dose-rate 252Cf neutron RBE values ranging from 3.6 to 2.9 for similar doses and fractionation schemes and observed that 252Cf neutron RBE increases with the number of treatment fractions. Using these relationships, our results were in general concordance with high-dose-rate 252Cf RBE values obtained from Russian clinical experience.

  1. The influence of dose, dose-rate and particle fragmentation on cataract induction by energetic iron ions

    NASA Technical Reports Server (NTRS)

    Medvedovsky, C.; Worgul, B. V.; Huang, Y.; Brenner, D. J.; Tao, F.; Miller, J.; Zeitlin, C.; Ainsworth, E. J.

    1994-01-01

    Because activities in space necessarily involve chronic exposure to a heterogeneous charged particle radiation field it is important to assess the influence of dose-rate and the possible modulating role of heavy particle fragmentation on biological systems. Using the well-studied cataract model, mice were exposed to plateau 600 MeV/amu Fe-56 ions either as acute or fractionated exposures at total doses of 5-504 cGy. Additional groups of mice received 20, 360 and 504 cGy behind 50 mm of polyethylene, which simulates body shielding. The reference radiation consisted of Co-60 gamma radiation. The animals were examined by slit lamp biomicroscopy over their three year life spans. In accordance with our previous observations with heavy particles, the cataractogenic potential of the 600 MeV/amu Fe-56 ions was greater than for low-Linear Energy Transfer (LET) radiation and increased with decreasing dose relative to gamma rays. Fractionation of a given dose of Fe-56 ions did not reduce the cataractogenicity of the radiation compared to the acute regimen. Fragmentation of the beam in the polyethylene did not alter the cataractotoxicity of the ions, either when administered singly or in fractions.

  2. An Absorbed-Dose/Dose-Rate Dependence for the Alanine-EPR Dosimetry System and Its Implications in High-Dose Ionizing Radiation Metrology

    PubMed Central

    Desrosiers, M. F.; Puhl, J. M.; Cooper, S. L.

    2008-01-01

    NIST developed the alanine dosimetry system in the early 1990s to replace radiochromic dye film dosimeters. Later in the decade the alanine system was firmly established as a transfer service for high-dose radiation dosimetry and an integral part of the internal calibration scheme supporting these services. Over the course of the last decade, routine monitoring of the system revealed a small but significant observation that, after examination, led to the characterization of a previously unknown absorbed-dose-dependent, dose-rate effect for the alanine system. Though the potential impact of this effect is anticipated to be extremely limited for NIST’s customer-based transfer dosimetry service, much greater implications may be realized for international measurement comparisons between National Measurement Institutes. PMID:27096113

  3. Short-term and Long-term Variations of Dose Rate measured by MSL/RAD

    NASA Astrophysics Data System (ADS)

    Guo, Jingnan; Zeitlin, Cary; Rafkin, Scot; Boettcher, Stephan; Reitz, Guenther; Koehler, Jan; Ehresmann, Bent; Martin, Cesar; Burmeister, Soenke; Posner, Arik; Wimmer-Schweingruber, Robert; Hassler, Donald M.; Brinza, David; Boehm, Henning Eckart; Lohf, Henning; Appel, Jan

    The Radiation Assessment Detector (RAD), onboard Mars Science Laboratory’s (MSL) rover Curiosity, measures the spectra of both energetic charged and neutral particles along with radiation dose rate at the surface of Mars. Several effects have been observed for the first time to influence the Galactic Cosmic Ray (GCR)-driven particle radiation on the surface: [a] short-term diurnal variations of the Martian atmospheric pressure caused by daily thermal tides [Rafkin 2014]; [b] long-term seasonal pressure changes in the Martian atmosphere; and [c] the modulation of the primary GCR fluxes by the heliospheric magnetic field, which correlates with long-term solar activities and heliospheric rotation. These concurrent factors affect the dose rate variations measured by RAD on the Martian surface. RAD also recorded the dose rate during the 253-day cruise phase of MSL from the Earth to Mars. The variations of the GCR-induced dose rates during quiet time period without the direct detection of Solar Particle Events (SPE) were solely driven by the changes of heliospheric conditions (i.e. [c]). The RAD cruise and surface dose measurements, along with the surface pressure data and the solar modulation factor, are analysed in order to understand how the long-term influences ([b] and [c]) individually correlate with the measured dose rates.

  4. Effect of Radiocesium Transfer on Ambient Dose Rate in Forest Environment

    NASA Astrophysics Data System (ADS)

    Kato, Hiroaki; Onda, Yuichi; Loffredo, Nicolas; Hisadome, Keigo; Kawamori, Ayumi

    2014-05-01

    We investigated the transfer of canopy-intercepted radiocesium to the forest floor following the Fukushima Daiichi nuclear power plant accident. The cesium-137 (Cs-137) contents of throughfall, stemflow, and litterfall were monitored in two coniferous stands (plantation of Japanese cedar) and a deciduous broad-leaved forest stand (beech with red pine). We also measured an ambient dose rate at different height in the forest by using a survey meter (TCS-172B, Hitachi-Aloka Medical, LTD.) and a portable Ge gamma-ray detector (Detective-DX-100T, Ortec, Ametek, Inc.). In decreasing order of total Cs-137 deposition from the canopy to forest floor were the mature cedar stand, the young cedar stand, and the broad-leaved forest. The ambient dose rate in forest exhibited height dependency and its vertical distribution varied by forest type and stand age. The ambient dose rate showed an exponential decrease with time for all the forest sites, however the decreasing trend differed depending on the height of dose measurement and forest type. The ambient dose rates at the canopy (approx. 10 m-) decreased earlier than physical attenuation of radiocesium, whereas those at the forest floor varied among three forest stands. These data suggested that an ambient dose rate in forest environment can be variable in spatially and temporally reflecting the transfer of radiocesium from canopy to forest floor.

  5. Effect of repeated oral therapeutic doses of methylphenidate on food intake and growth rate in rats.

    PubMed

    Alam, Nausheen; Najam, Rahila

    2015-01-01

    Central nervous system stimulants are known to produce anorexia. Previous data suggest that methylphenidate can have variable effects on caloric intake and growth rate. A dose-response study was performed to monitor caloric intake, liquid intake and growth rate in rats following repeated administration of human oral therapeutic doses 2 mg/kg/day, 5mg/kg/day and 8mg/kg/day of methylphenidate. We found that food intake and water intake, increased in all weeks and at all doses used in the study. Growth rate increased more at higher dose (8mg/kg/day) and at low dose (2mg/kg/day) of methylphenidate in 1(st) and 2(nd) week whereas more decreased by the above doses in 3(rd) week, suggesting that food stimulation leads to initial increase in growth rate but long term administration of methylphenidate attenuate growth rate that is not due to modulation of appetite but may be due to anxiety and increased activity produce by stimulants. A possible role of DA, 5HT receptors in modulation of appetite and anxiety is discussed.

  6. Dose rate effects in the radiation damage of the plastic scintillators of the CMS hadron endcap calorimeter

    NASA Astrophysics Data System (ADS)

    Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Litomin, A.; Mossolov, V.; Shumeiko, N.; Van De Klundert, M.; Van Haevermaet, H.; Van Mechelen, P.; Van Spilbeeck, A.; Alves, G. A.; Aldá Júnior, W. L.; Hensel, C.; Carvalho, W.; Chinellato, J.; De Oliveira Martins, C.; Matos Figueiredo, D.; Mora Herrera, C.; Nogima, H.; Prado Da Silva, W. L.; Tonelli Manganote, E. J.; Vilela Pereira, A.; Finger, M.; Finger, M., Jr.; Jain, S.; Khurana, R.; Adamov, G.; Tsamalaidze, Z.; Behrens, U.; Borras, K.; Campbell, A.; Costanza, F.; Gunnellini, P.; Lobanov, A.; Melzer-Pellmann, I.-A.; Muhl, C.; Roland, B.; Sahin, M.; Saxena, P.; Hegde, V.; Kothekar, K.; Pandey, S.; Sharma, S.; Beri, S. B.; Bhawandeep, B.; Chawla, R.; Kalsi, A.; Kaur, A.; Kaur, M.; Walia, G.; Bhattacharya, S.; Ghosh, S.; Nandan, S.; Purohit, A.; Sharan, M.; Banerjee, S.; Bhattacharya, S.; Bhowmik, S.; Chatterjee, S.; Das, P.; Dewanjee, R. K.; Jain, S.; Kumar, S.; Maity, M.; Majumder, G.; Mandakini, P.; Patil, M.; Sarkar, T.; Saikh, A.; Sezen, S.; Juodagalvis, A.; Afanasiev, S.; Bunin, P.; Ershov, Y.; Golutvin, I.; Malakhov, A.; Moisenz, P.; Smirnov, V.; Zarubin, A.; Chadeeva, M.; Chistov, R.; Danilov, M.; Popova, E.; Rusinov, V.; Andreev, Yu.; Dermenev, A.; Karneyeu, A.; Krasnikov, N.; Tlisov, D.; Toropin, A.; Epshteyn, V.; Gavrilov, V.; Lychkovskaya, N.; Popov, V.; Pozdnyakov, I.; Safronov, G.; Toms, M.; Zhokin, A.; Flacher, H.; Baskakov, A.; Belyaev, A.; Boos, E.; Dubinin, M.; Dudko, L.; Ershov, A.; Gribushin, A.; Kaminskiy, A.; Klyukhin, V.; Kodolova, O.; Lokhtin, I.; Miagkov, I.; Obraztsov, S.; Petrushanko, S.; Savrin, V.; Snigirev, A.; Andreev, V.; Azarkin, M.; Dremin, I.; Kirakosyan, M.; Leonidov, A.; Terkulov, A.; Bitioukov, S.; Elumakhov, D.; Kalinin, A.; Krychkine, V.; Mandrik, P.; Petrov, V.; Ryutin, R.; Sobol, A.; Troshin, S.; Volkov, A.; Adiguzel, A.; Bakirci, N.; Cerci, S.; Damarseckin, S.; Demiroglu, Z. S.; Dozen, C.; Dumanoglu, I.; Eskut, E.; Girgis, S.; Gokbulut, G.; Guler, Y.; Hos, I.; Kangal, E. E.; Kara, O.; Kayis Topaksu, A.; Kiminsu, U.; Oglakci, M.; Onengut, G.; Ozdemir, K.; Ozturk, S.; Polatoz, A.; Sunar Cerci, D.; Tali, B.; Topakli, H.; Turkcapar, S.; Zorbakir, I. S.; Zorbilmez, C.; Bilin, B.; Isildak, B.; Karapinar, G.; Murat Guler, A.; Ocalan, K.; Yalvac, M.; Zeyrek, M.; Gülmez, E.; Kaya, M.; Kaya, O.; Yetkin, E. A.; Yetkin, T.; Cankocak, K.; Sen, S.; Boyarintsev, A.; Grynyov, B.; Levchuk, L.; Popov, V.; Sorokin, P.; Borzou, A.; Call, K.; Dittmann, J.; Hatakeyama, K.; Liu, H.; Pastika, N.; Charaf, O.; Cooper, S. I.; Henderson, C.; Rumerio, P.; West, C.; Arcaro, D.; Gastler, D.; Hazen, E.; Rohlf, J.; Sulak, L.; Wu, S.; Zou, D.; Hakala, J.; Heintz, U.; Kwok, K. H. M.; Laird, E.; Landsberg, G.; Mao, Z.; Gary, J. W.; Ghiasi Shirazi, S. M.; Lacroix, F.; Long, O. R.; Wei, H.; Bhandari, R.; Heller, R.; Stuart, D.; Yoo, J. H.; Apresyan, A.; Chen, Y.; Duarte, J.; Spiropulu, M.; Winn, D.; Abdullin, S.; Banerjee, S.; Chlebana, F.; Freeman, J.; Green, D.; Hare, D.; Hirschauer, J.; Joshi, U.; Lincoln, D.; Los, S.; Pedro, K.; Spalding, W. J.; Strobbe, N.; Tkaczyk, S.; Whitbeck, A.; Linn, S.; Markowitz, P.; Martinez, G.; Bertoldi, M.; Hagopian, S.; Hagopian, V.; Kolberg, T.; Baarmand, M. M.; Noonan, D.; Roy, T.; Yumiceva, F.; Bilki, B.; Clarida, W.; Debbins, P.; Dilsiz, K.; Durgut, S.; Gandrajula, R. P.; Haytmyradov, M.; Khristenko, V.; Merlo, J.-P.; Mermerkaya, H.; Mestvirishvili, A.; Miller, M.; Moeller, A.; Nachtman, J.; Ogul, H.; Onel, Y.; Ozok, F.; Penzo, A.; Schmidt, I.; Snyder, C.; Southwick, D.; Tiras, E.; Yi, K.; Al-bataineh, A.; Bowen, J.; Castle, J.; McBrayer, W.; Murray, M.; Wang, Q.; Kaadze, K.; Maravin, Y.; Mohammadi, A.; Saini, L. K.; Baden, A.; Belloni, A.; Eno, S. C.; Ferraioli, C.; Grassi, T.; Hadley, N. J.; Jeng, G.-Y.; Kellogg, R. G.; Kunkle, J.; Mignerey, A.; Ricci-Tam, F.; Shin, Y. H.; Skuja, A.; Tonjes, M. B.; Yang, Z. S.; Apyan, A.; Bierwagen, K.; Brandt, S.; Klute, M.; Niu, X.; Chatterjee, R. M.; Evans, A.; Frahm, E.; Kubota, Y.; Lesko, Z.; Mans, J.; Ruckstuhl, N.; Heering, A.; Karmgard, D. J.; Musienko, Y.; Ruchti, R.; Wayne, M.; Benaglia, A. D.; Medvedeva, T.; Mei, K.; Tully, C.; Bodek, A.; de Barbaro, P.; Galanti, M.; Garcia-Bellido, A.; Khukhunaishvili, A.; Lo, K. H.; Vishnevskiy, D.; Zielinski, M.; Agapitos, A.; Chou, J. P.; Hughes, E.; Saka, H.; Sheffield, D.; Akchurin, N.; Damgov, J.; De Guio, F.; Dudero, P. R.; Faulkner, J.; Gurpinar, E.; Kunori, S.; Lamichhane, K.; Lee, S. W.; Libeiro, T.; Undleeb, S.; Volobouev, I.; Wang, Z.; Goadhouse, S.; Hirosky, R.; Wang, Y.; CMS-HCAL collaboration

    2016-10-01

    We present measurements of the reduction of light output by plastic scintillators irradiated in the CMS detector during the 8 TeV run of the Large Hadron Collider and show that they indicate a strong dose rate effect. The damage for a given dose is larger for lower dose rate exposures. The results agree with previous measurements of dose rate effects, but are stronger due to the very low dose rates probed. We show that the scaling with dose rate is consistent with that expected from diffusion effects.

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

    DOE PAGES

    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 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

  8. 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.

  9. 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

  10. Absolute rate constant of the reaction OH + H2O2 yields HO2 + H2O from 245 to 423 K

    NASA Technical Reports Server (NTRS)

    Keyser, L. F.

    1980-01-01

    The absolute rate constant of the reaction between the hydroxyl radical and hydrogen peroxide was measured by using the discharge-flow resonance fluorescence technique at total pressure between 1 and 4 torr. At 298 K the result is (1.64 + or - 0.32) x 10 to the -12th cu cm/molecule s. The observed rate constant is independent of pressure, surface-to-volume ratio, the addition of vibrational quenchers, and the source of OH. The temperature dependence has also been determined between 245 and 423 K; the resulting Arrhenius expression is k cu cm/molecule s is equal to (2.51 + or - 0.6) x 10 to the -12th exp(-126 + or - 76/T).

  11. Absolute rate of the reaction of O/3-P/ with hydrogen sulfide over the temperature range 263 to 495 K

    NASA Technical Reports Server (NTRS)

    Whytock, D. A.; Timmons, R. B.; Lee, J. H.; Michael, J. V.; Payne, W. A.; Stief, L. J.

    1976-01-01

    The technique of flash photolysis coupled with time resolved detection of O via resonance fluorescence has been used to obtain rate constants for the reaction of O(3-P) with H2S at temperatures from 263 to 495 K and at pressures in the range 10-400 torr. Under conditions where secondary reactions are avoided, the measured rate constants for the primary step obey the Arrhenius equation k = (7.24 plus or minus 1.07) x 10 to the -12th exp(-3300 plus or minus 100/1.987 T) cu cm/molecules/s. Experiments with D2S show that the reaction exhibits a primary isotope effect, in support of a hydrogen abstraction mechanism.

  12. Thiyl radical reaction with thymine: absolute rate constant for hydrogen abstraction and comparison to benzylic C-H bonds.

    PubMed

    Nauser, Thomas; Schöneich, Christian

    2003-09-01

    Free radical damage of DNA is a well-known process affecting biological tissue under conditions of oxidative stress. Thiols can repair DNA-derived radicals. However, the product thiyl radicals may also cause biological damage. To obtain quantitative information on the potential reactivity with DNA components, we measured the rate constant for hydrogen abstraction by cysteamine thiyl radicals from thymine C5-CH(3), k = (1.2 +/- 0.8) x 10(4) M(-1) s(-1), and thymidine-5'-monophosphate, k = (0.9 +/- 0.6) x 10(4) M(-1) s(-1). Hence, the hydrogen abstraction from C5-CH(3) occurs with rate constants similar to the hydrogen abstraction from the carbohydrate moieties. Especially at low oxygen concentration such as that found in skeletal muscle, such hydrogen abstraction processes by thiyl radicals may well compete against other dioxygen-dependent reactions. The rate constants for hydrogen abstraction at thymine C5-CH(3) were compared to those with benzylic substrates, toluenesulfonic acid, and benzyl alcohol.

  13. Kinetics of reaction of peroxynitrite with selenium- and sulfur-containing compounds: Absolute rate constants and assessment of biological significance.

    PubMed

    Storkey, Corin; Pattison, David I; Ignasiak, Marta T; Schiesser, Carl H; Davies, Michael J

    2015-12-01

    Peroxynitrite (the physiological mixture of ONOOH and its anion, ONOO(-)) is a powerful biologically-relevant oxidant capable of oxidizing and damaging a range of important targets including sulfides, thiols, lipids, proteins, carbohydrates and nucleic acids. Excessive production of peroxynitrite is associated with several human pathologies including cardiovascular disease, ischemic-reperfusion injury, circulatory shock, inflammation and neurodegeneration. This study demonstrates that low-molecular-mass selenols (RSeH), selenides (RSeR') and to a lesser extent diselenides (RSeSeR') react with peroxynitrite with high rate constants. Low molecular mass selenols react particularly rapidly with peroxynitrite, with second order rate constants k2 in the range 5.1 × 10(5)-1.9 × 10(6)M(-1)s(-1), and 250-830 fold faster than the corresponding thiols (RSH) and many other endogenous biological targets. Reactions of peroxynitrite with selenides, including selenosugars are approximately 15-fold faster than their sulfur homologs with k2 approximately 2.5 × 10(3)M(-1)s(-1). The rate constants for diselenides and sulfides were slower with k2 0.72-1.3 × 10(3)M(-1)s(-1) and approximately 2.1 × 10(2)M(-1)s(-1) respectively. These studies demonstrate that both endogenous and exogenous selenium-containing compounds may modulate peroxynitrite-mediated damage at sites of acute and chronic inflammation, with this being of particular relevance at extracellular sites where the thiol pool is limited.

  14. Radiation Dose Predicts for Biochemical Control in Intermediate-Risk Prostate Cancer Patients Treated With Low-Dose-Rate Brachytherapy

    SciTech Connect

    Ho, Alice Y.; Burri, Ryan J.; Cesaretti, Jamie A.; Stone, Nelson N.; Stock, Richard G.

    2009-09-01

    Purpose: To evaluate the influence of patient- and treatment-related factors on freedom from biochemical failure (FFbF) in patients with intermediate-risk prostate cancer. Methods and Materials: From a prospectively collected database of 2250 men treated at Mount Sinai Hospital from 1990 to 2004 with low-dose-rate brachytherapy for prostate cancer, 558 men with either one or more intermediate-risk features (prostate-specific antigen [PSA] level 10-20 ng/mL, Gleason score 7, or Stage T2b) were identified who had a minimum follow-up of 24 months and postimplant CT-based dosimetric analysis. Biologically effective dose (BED) values were calculated to compare doses from different isotopes and treatment regimens. Patients were treated with brachytherapy with or without hormone therapy and/or external-beam radiotherapy. Patient- and treatment-related factors were analyzed with respect to FFbF. The median follow-up was 60 months (range, 24-167 months). Biochemical failure was defined according to the Phoenix definition. Univariate analyses were used to determine whether any variable was predictive of FFbF. A two-sided p value of <0.05 was considered significant. Results: Overall, the actuarial FFbF at 10 years was 86%. Dose (BED <150 Gy{sub 2} vs. {>=}150 Gy{sub 2}) was the only significant predictor of FFbF (p < 0.001). None of the other variables (PSA, external-beam radiotherapy, Gleason score, treatment type, hormones, stage, and number of risk factors) was found to be a statistically significant predictor of 10-year FFbF. Conclusions: Radiation dose is an important predictor of FFbF in intermediate-risk prostate cancer. Treatment should continue to be individualized according to presenting disease characteristics until results from Radiation Therapy Oncology Group trial 0232 become available.

  15. Early effects comparison of X-rays delivered at high-dose-rate pulses by a plasma focus device and at low dose rate on human tumour cells.

    PubMed

    Virelli, A; Zironi, I; Pasi, F; Ceccolini, E; Nano, R; Facoetti, A; Gavoçi, E; Fiore, M R; Rocchi, F; Mostacci, D; Cucchi, G; Castellani, G; Sumini, M; Orecchia, R

    2015-09-01

    A comparative study has been performed on the effects of high-dose-rate (DR) X-ray beams produced by a plasma focus device (PFMA-3), to exploit its potential medical applications (e.g. radiotherapy), and low-DR X-ray beams produced by a conventional source (XRT). Experiments have been performed at 0.5 and 2 Gy doses on a human glioblastoma cell line (T98G). Cell proliferation rate and potassium outward currents (IK) have been investigated by time lapse imaging and patch clamp recordings. The results showed that PFMA-3 irradiation has a greater capability to reduce the proliferation rate activity with respect to XRT, while it does not affect IK of T98G cells at any of the dose levels tested. XRT irradiation significantly reduces the mean IK amplitude of T98G cells only at 0.5 Gy. This work confirms that the DR, and therefore the source of radiation, is crucial for the planning and optimisation of radiotherapy applications. PMID:25883300

  16. Early effects comparison of X-rays delivered at high-dose-rate pulses by a plasma focus device and at low dose rate on human tumour cells.

    PubMed

    Virelli, A; Zironi, I; Pasi, F; Ceccolini, E; Nano, R; Facoetti, A; Gavoçi, E; Fiore, M R; Rocchi, F; Mostacci, D; Cucchi, G; Castellani, G; Sumini, M; Orecchia, R

    2015-09-01

    A comparative study has been performed on the effects of high-dose-rate (DR) X-ray beams produced by a plasma focus device (PFMA-3), to exploit its potential medical applications (e.g. radiotherapy), and low-DR X-ray beams produced by a conventional source (XRT). Experiments have been performed at 0.5 and 2 Gy doses on a human glioblastoma cell line (T98G). Cell proliferation rate and potassium outward currents (IK) have been investigated by time lapse imaging and patch clamp recordings. The results showed that PFMA-3 irradiation has a greater capability to reduce the proliferation rate activity with respect to XRT, while it does not affect IK of T98G cells at any of the dose levels tested. XRT irradiation significantly reduces the mean IK amplitude of T98G cells only at 0.5 Gy. This work confirms that the DR, and therefore the source of radiation, is crucial for the planning and optimisation of radiotherapy applications.

  17. Radiobiological effects of altering dose rate in filter-free photon beams

    NASA Astrophysics Data System (ADS)

    Karan, T.; Moiseenko, V.; Gill, B.; Horwood, R.; Kyle, A.; Minchinton, A. I.

    2013-02-01

    To validate that altering radiotherapy dose rate through either changing pulse repetition frequency or instantaneous dose rate does not have an effect on cell survival, two human carcinoma and a hamster lung cell line were irradiated with various beam settings. Varian TrueBeam linac with a flattening filter free mode of operation was used for all experiments. The results obtained indicate that either method of changing dose rate has no effect on cell survival in the three cell lines studied. Filtered and filter free modes were also compared in treatments with protracted dose delivery which significantly increases overall treatment time. Cell survival indicated no difference between filter and filter free beam delivery in any of the protraction schemes. An increase in survival was seen in both modes upon protracting dose delivery to 15, 30 or 60 min rather than delivering acutely. Further, analysis of induced DNA double-strand breaks via the γH2AX assay showed no difference between filtered and unfiltered beams. The following study suggests that increasing dose rate is an acceptable manner of decreasing radiotherapy treatment time that does not have any detrimental effects on in vitro cell eradication.

  18. Effect of monomer dosing rate in the preparation of mesoporous polystyrene nanoparticles by semicontinuous heterophase polymerization.

    PubMed

    Sosa, Dalia Y; Guillén, Lourdes; Saade, Hened; Mendizábal, Eduardo; Puig, Jorge E; López, Raúl G

    2014-12-23

    The semicontinuous heterophase polymerization of styrene in the presence of cross-linking and porogen agents was carried out. Latexes with close to 20% solid content, which contained mesoporous nanoparticles with 28 nm in average diameters, up to 0.5 cm3/g in porosity and 6-8 nm in pore diameters were obtained. By varying the monomer dosing rate over the micellar solution, an unexpected direct dependence of instantaneous conversion on the monomer dosing rate was found. This was ascribed to the higher average number of radicals per particle attained in the polymerization at the higher dosing rate, which in turn would arise from the higher gel percentage in the polymer. It is believed that the cross-linked chains prevent encounters between radicals, delaying the bimolecular termination reactions and allowing the existence of more than one radical inside the particles, which in turn increases the propagation rate.

  19. Hydroxyl-radical-induced degradative oxidation of beta-lactam antibiotics in water: absolute rate constant measurements.

    PubMed

    Dail, Michelle K; Mezyk, Stephen P

    2010-08-19

    The beta-lactam antibiotics are some of the most prevalent pharmaceutical contaminants currently being detected in aquatic environments. Because the presence of any trace level of antibiotic in water may adversely affect aquatic ecosystems and contribute to the production of antibiotic-resistant bacteria, active removal by additional water treatments, such as using advanced oxidation and reduction processes (AO/RPs), may be required. However, to ensure that any AOP treatment process occurs efficiently and quantitatively, a full understanding of the kinetics and mechanisms of all of the chemical reactions involved under the conditions of use is necessary. In this study, we report on our kinetic measurements for the hydroxyl-radical-induced oxidation of 11 beta-lactam antibiotics obtained using electron pulse radiolysis techniques. For the 5-member ring species, an average reaction rate constant of (7.9 +/- 0.8) x 10(9) M(-1) s(-1) was obtained, slightly faster than for the analogous 6-member ring containing antibiotics, (6.6 +/- 1.2) x 10(9) M(-1) s(-1). The consistency of these rate constants for each group infers a common reaction mechanism, consisting of the partitioning of the hydroxyl radical between addition to peripheral aromatic rings and reaction with the central double-ring core of these antibiotics.

  20. Absolute rate constants for O + NO + M /= He, Ne, Ar, Kr/ yields NO2 + M from 217-500 K

    NASA Technical Reports Server (NTRS)

    Michael, J. V.; Payne, W. A.; Whytock, D. A.

    1976-01-01

    Rate constants for the reaction O + NO + M yields NO2 + M have been obtained at temperatures from 217-500 K in four different rare gases by a method combining flash photolysis with time resolved detection of O(3-P) by resonance fluorescence. The measured rate constants in Arrhenius form are (10.8 plus or minus 1.2) x 10 to the -33rd exp(1040 plus or minus 60/1.987 T) for helium; (9.01 plus or minus 1.16) x 10 to the -33rd exp(1180 plus or minus 70/1.987 T) for argon; (9.33 plus or minus 1.10) x 10 to the -33rd exp(1030 plus or minus 60/1.987 T) for neon; and (9.52 plus or minus 1.10) x 10 to the -33rd exp(1140 plus or minus 70/1.987 T) for krypton in units of cm to the 6th/sq molecule/s.

  1. 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.

  2. Per-beam, planar IMRT QA passing rates do not predict clinically relevant patient dose errors

    SciTech Connect

    Nelms, Benjamin E.; Zhen Heming; Tome, Wolfgang A.

    2011-02-15

    Purpose: The purpose of this work is to determine the statistical correlation between per-beam, planar IMRT QA passing rates and several clinically relevant, anatomy-based dose errors for per-patient IMRT QA. The intent is to assess the predictive power of a common conventional IMRT QA performance metric, the Gamma passing rate per beam. Methods: Ninety-six unique data sets were created by inducing four types of dose errors in 24 clinical head and neck IMRT plans, each planned with 6 MV Varian 120-leaf MLC linear accelerators using a commercial treatment planning system and step-and-shoot delivery. The error-free beams/plans were used as ''simulated measurements'' (for generating the IMRT QA dose planes and the anatomy dose metrics) to compare to the corresponding data calculated by the error-induced plans. The degree of the induced errors was tuned to mimic IMRT QA passing rates that are commonly achieved using conventional methods. Results: Analysis of clinical metrics (parotid mean doses, spinal cord max and D1cc, CTV D95, and larynx mean) vs IMRT QA Gamma analysis (3%/3 mm, 2/2, 1/1) showed that in all cases, there were only weak to moderate correlations (range of Pearson's r-values: -0.295 to 0.653). Moreover, the moderate correlations actually had positive Pearson's r-values (i.e., clinically relevant metric differences increased with increasing IMRT QA passing rate), indicating that some of the largest anatomy-based dose differences occurred in the cases of high IMRT QA passing rates, which may be called ''false negatives.'' The results also show numerous instances of false positives or cases where low IMRT QA passing rates do not imply large errors in anatomy dose metrics. In none of the cases was there correlation consistent with high predictive power of planar IMRT passing rates, i.e., in none of the cases did high IMRT QA Gamma passing rates predict low errors in anatomy dose metrics or vice versa. Conclusions: There is a lack of correlation between

  3. Effect of dose rate and oxygen on radiation crosslinking of silica filled fluorosilicone rubber

    NASA Astrophysics Data System (ADS)

    Aliev, Roustam

    1999-09-01

    Fluorosilicone (polymethyltrifluoropropylsiloxane) rubber containing silica filler was irradiated with γ-rays and accelerated electrons in air, argon and vacuum. Doses up to 0.5 MGy and dose rates of 1.4 and 10 3 Gy/s were used. The absorbed dose distribution across the rubber thickness during electron irradiation was determined. Oxidation, swelling in ethyl acetate and mechanical properties of this rubber depended on the conditions of irradiation that testified to different effectiveness of the rubber radiation crosslinking under these conditions. Effects of dose rate, diffusion of oxygen into rubber during irradiation, local heating and the oxygen desorption from the filler particles during the electron irradiation are considered for explanation of these differences.

  4. Measurement of radon/thoron exhalation rates and gamma-ray dose rate in granite areas in Japan.

    PubMed

    Prasad, G; Ishikawa, T; Hosoda, M; Sahoo, S K; Kavasi, N; Sorimachi, A; Tokonami, S; Uchida, S

    2012-11-01

    Radon and thoron exhalation rates and gamma-ray dose rate in different places in Hiroshima Prefecture were measured. Exhalation rates were measured using an accumulation chamber method. The radon exhalation rate was found to vary from 3 to 37 mBq m(-2) s(-1), while the thoron exhalation rate ranged from 40 to 3330 mBq m(-2) s(-1). The highest radon exhalation rate (37 mBq m(-2) s(-1)) and gamma-ray dose rate (92 nGy h(-1)) were found in the same city (Kure City). In Kure City, indoor radon and thoron concentrations were previously measured at nine selected houses using a radon-thoron discriminative detector (Raduet). The indoor radon concentrations varied from 16 to 78 Bq m(-3), which was higher than the average value in Japan (15.5 Bq m(-3)). The indoor thoron concentration ranged from ND (not detected: below a detection limit of approximately 10 Bq m(-3)) to 314 Bq m(-3). The results suggest that radon exhalation rate from the ground is an influential factor for indoor radon concentration.

  5. Dose Rate Analysis Capability for Actual Spent Fuel Transportation Cask Contents

    SciTech Connect

    Radulescu, Georgeta; Lefebvre, Robert A; Peplow, Douglas E.; Williams, Mark L; Scaglione, John M

    2014-01-01

    The approved contents for a U.S. Nuclear Regulatory Commission (NRC) licensed spent nuclear fuel casks are typically based on bounding used nuclear fuel (UNF) characteristics. However, the contents of the UNF canisters currently in storage at independent spent fuel storage installations are considerably heterogeneous in terms of fuel assembly burnup, initial enrichment, decay time, cladding integrity, etc. Used Nuclear Fuel Storage, Transportation & Disposal Analysis Resource and Data System (UNF ST&DARDS) is an integrated data and analysis system that facilitates automated cask-specific safety analyses based on actual characteristics of the as-loaded UNF. The UNF-ST&DARDS analysis capabilities have been recently expanded to include dose rate analysis of as-loaded transportation packages. Realistic dose rate values based on actual canister contents may be used in place of bounding dose rate values to support development of repackaging operations procedures, evaluation of radiation-related transportation risks, and communication with stakeholders. This paper describes the UNF-ST&DARDS dose rate analysis methodology based on actual UNF canister contents and presents sample dose rate calculation results.

  6. The accuracy of dose-rate-regulated tracking: a parametric study

    NASA Astrophysics Data System (ADS)

    Han-Oh, S.; Yi, B.; Berman, B. L.; Lerma, F.; Yu, C.

    2010-02-01

    Dose-rate-regulated tracking (DRRT) is a novel tumor-tracking technique based on a preprogrammed multileaf-collimator (MLC) sequence and dose-rate modulation. We have performed a parametric study on how limitations of the DRRT system and breathing irregularities affect the tracking error and the duty cycle of DRRT. The time delay and the allowed dose-rate increment (continuous-, discrete-increment or beam switching) were used as two parameters for the DRRT system limitation. The breathing irregularity was quantified in terms of three variables, namely, breathing period variation, variation of peak-to-peak amplitude and baseline drift. DRRT treatments were simulated using 2126 breathing cycles obtained from 24 lung-cancer patients. Tracking errors and duty cycles from all 24 patients were combined to evaluate their dependence on each parameter or variable. The tracking error and the duty cycle show a modest difference among the three dose-rate-increment cases. Time delay, breathing peak-to-peak variation and baseline drift are the main factors affecting tracking error. The duty cycle is affected mostly by the allowed dose-rate increment, peak-to-peak variation and baseline drift.

  7. Gross Gamma Dose Rate Measurements for TRIGA Spent Nuclear Fuel Burnup Validation

    SciTech Connect

    Winston, Philip Lon; Sterbentz, James William

    2001-04-01

    Gross gamma-ray dose rates from six spent TRIGA fuel elements were measured and compared to calculated values as a means to validate the reported element burnups. A newly installed and functional gamma-ray detection subsystem of the In-Cell Examination System was used to perform the measurements and is described in some detail. The analytical methodology used to calculate the corresponding dose rates is presented along with the calculated values. Comparison of the measured and calculated dose rates for the TRIGA fuel elements indicates good agreement (less than a factor of 2 difference). The intent of the subsystem is to measure the gross gamma dose rate and correlate the measurement to a calculated dose rate based on the element s known burnup and other pertinent spent fuel information. Although validation of the TRIGA elements’ burnup is of primary concern in this paper, the measurement and calculational techniques can be used to either validate an element’s reported burnup or provide a burnup estimate for an element with an unknown burnup.

  8. Salvage high-dose-rate interstitial brachytherapy for locally recurrent rectal cancer*

    PubMed Central

    Pellizzon, Antônio Cássio Assis

    2016-01-01

    For tumors of the lower third of the rectum, the only safe surgical procedure is abdominal-perineal resection. High-dose-rate interstitial brachytherapy is a promising treatment for local recurrence of previously irradiated lower rectal cancer, due to the extremely high concentrated dose delivered to the tumor and the sparing of normal tissue, when compared with a course of external beam radiation therapy. PMID:27403021

  9. Postoperative High-Dose-Rate Brachytherapy in the Prevention of Keloids

    SciTech Connect

    Veen, Ronald E. Kal, Henk B.

    2007-11-15

    Background: The aim of this study is to show the efficiency of keloidectomy and postoperative interstitial high-dose-rate (HDR) brachytherapy in the prevention of keloids. Methods and Materials: Between 1998 and 2004, 35 patients with 54 keloids were treated postoperatively with HDR brachytherapy. The first HDR dose was applied within 6 hours after surgery, and two additional HDR doses were administered on the next day with a six-hour interval. The majority of patients received 6 Gy as the first dose postsurgery and two fractions of 4 Gy (38 keloids) on the next day. Seven keloids were treated postoperatively with three fractions of 6 Gy. The biologically effective dose (BED), derived from the linear quadratic concept, was applied to calculate the BED for the various radiation regimens. The keloid recurrence rates at specific BED values were compared with those derived for other fractionation schemes in the literature. Results: Four recurrences/nonsatisfactory results out of nine treated keloids were observed after treatments with 1 x 4 Gy + 2 x 3 Gy. Only one recurrence out of 38 was found after 1 x 6 Gy + 2 x 4 Gy and none after 3 x 6 Gy. Better cosmetic results were found at the higher-dose schemes. Conclusion: The results of this study prove the effectiveness of HDR brachytherapy after keloidectomy provided that the total HDR dose is sufficient. Currently our scheme is 3 x 6 Gy.

  10. Dosimetric impact of source-positioning uncertainty in high-dose-rate balloon brachytherapy of breast cancer

    PubMed Central

    2015-01-01

    Purpose To evaluate the dosimetric impact of source-positioning uncertainty in high-dose-rate (HDR) balloon brachytherapy of breast cancer. Material and methods For 49 HDR balloon patients, each dwell position of catheter(s) was manually shifted distally (+) and proximally (–) with a magnitude from 1 to 4 mm. Total 392 plans were retrospectively generated and compared to corresponding clinical plans using 7 dosimetric parameters: dose (D95) to 95% of planning target volume for evaluation (PTV_EVAL), and volume covered by 100% and 90% of the prescribed dose (PD) (V100 and V90); skin and rib maximum point dose (Dmax); normal breast tissue volume receiving 150% and 200% of PD (V150 and V200). Results PTV_EVAL dosimetry deteriorated with larger average/maximum reduction (from ± 1 mm to ± 4 mm) for larger source position uncertainty (p value < 0.0001): from 1.0%/2.5%, 3.3%/5.9%, 6.3%/10.0% to 9.8%/14.5% for D95; from 1.0%/2.6%, 3.1%/5.7%, 5.8%/8.9% to 8.7%/12.3% for V100; from 0.2%/1.5%, 1.0%/4.0%, 2.7%/6.8% to 5.1%/10.3% for V90. ≥ ± 3 mm shift reduced average D95 to < 95% and average V100 to < 90%. While skin and rib Dmax change was case-specific, its absolute change (∣Δ(Value)∣) showed that larger shift and high dose group had larger variation compared to smaller and lower dose group (p value < 0.0001), respectively. Normal breast tissue V150 variation was case-specific and small. Average ∣Δ(V150)∣ was 0.2 cc for the largest shift (± 4 mm) with maximum < 1.7 cc. V200 was increased with higher elevation for larger shift: from 6.4 cc/9.8 cc, 7.0 cc/10.1 cc, 8.0 cc/11.3 cc to 9.2 cc/ 13.0 cc. Conclusions The tolerance of ± 2 mm recommended by AAPM TG 56 is clinically acceptable in most clinical cases. However, special attention should be paid to a case where both skin and rib are located proximally to balloon, and the orientation of balloon catheter(s) is vertical to these critical structures. In this case, sufficient dosimetric planning margins are

  11. Optically based quantification of absolute cerebral metabolic rate of oxygen (CMRO2) with high spatial resolution in rodents

    NASA Astrophysics Data System (ADS)

    Yaseen, Mohammad A.; Srinivasan, Vivek J.; Sakadžić, Sava; Vinogradov, Sergei A.; Boas, David A.

    2010-02-01

    Measuring oxygen delivery in brain tissue is important for identifying the pathophysiological changes associated with brain injury and various diseases such as cancer, stroke, and Alzheimer's disease. We have developed a multi-modal imaging system for minimally invasive measurement of cerebral oxygenation and blood flow in small animals with high spatial resolution. The system allows for simultaneous measurement of blood flow using Fourier-domain optical coherence tomography, and oxygen partial pressure (pO2) using either confocal or multiphoton phosphorescence lifetime imaging with exogenous porphyrin-based dyes sensitive to dissolved oxygen. Here we present the changes in pO2 and blood flow in superficial cortical vessels of Sprague Dawley rats in response to conditions such as hypoxia, hyperoxia, and functional stimulation. pO2 measurements display considerable heterogeneity over distances that cannot be resolved with more widely used oxygen-monitoring techniques such as BOLD-fMRI. Large increases in blood flow are observed in response to functional stimulation and hypoxia. Our system allows for quantification of cerebral metabolic rate of oxygen (CMRO2) with high spatial resolution, providing a better understanding of metabolic dynamics during functional stimulation and under various neuropathologies. Ultimately, better insight into the underlying mechanisms of neuropathologies will facilitate the development of improved therapeutic strategies to minimize damage to brain tissue.

  12. Pressure dependence of the absolute rate constant for the reaction Cl + C2H2 from 210-361 K

    NASA Technical Reports Server (NTRS)

    Brunning, J.; Stief, L. J.

    1985-01-01

    In recent years, considerable attention has been given to the role of chlorine compounds in the catalytic destruction of stratospheric ozone. However, while some reactions have been studied extensively, the kinetic data for the reaction of Cl with C2H2 is sparse with only three known determinations of the rate constant k3. The reactions involved are Cl + C2H2 yields reversibly ClC2H2(asterisk) (3a) and ClC2H2(asterisk) + M yields ClC2H2 + M (3b). In the present study, flash photolysis coupled with chlorine atomic resonance fluorescence have been employed to determine the pressure and temperature dependence of k3 with the third body M = Ar. Room temperature values are also reported for M = N2. The pressure dependence observed in the experiments confirms the expectation that the reaction involves addition of Cl to the unsaturated C2H2 molecule followed by collisional stabilization of the resulting adduct radical.

  13. The MapCHECK Measurement Uncertainty function and its effect on planar dose pass rates.

    PubMed

    Bailey, Daniel W; Spaans, Jason D; Kumaraswamy, Lalith K; Podgorsak, Matthew B

    2016-03-08

    Our study aimed to quantify the effect of the Measurement Uncertainty function on planar dosimetry pass rates, as measured and analyzed with the Sun Nuclear Corporation MapCHECK 2 array and its associated software. This optional function is toggled in the program preferences of the software (though turned on by default upon installation), and automatically increases the dose difference tolerance defined by the user for each planar dose comparison. Dose planes from 109 static-gantry IMRT fields and 40 VMAT arcs, of varying modulation complexity, were measured at 5 cm water-equivalent depth in the MapCHECK 2 diode array, and respective calculated dose planes were exported from a commercial treatment planning system. Planar dose comparison pass rates were calculated within the Sun Nuclear Corporation analytic software using a number of calculation parameters, including Measurement Uncertainty on and off. By varying the percent difference (%Diff) criterion for similar analyses performed with Measurement Uncertainty turned off, an effective %Diff criterion was defined for each field/arc corresponding to the pass rate achieved with Measurement Uncertainty turned on. On average, the Measurement Uncertainty function increases the user-defined %Diff criterion by 0.8%-1.1% for 3%/3 mm analysis, depending on plan type and calculation technique (corresponding to an average change in pass rate of 1.0%-3.5%, and a maximum change of 8.7%). At the 2%/2 mm level, the Measurement Uncertainty function increases the user-defined %Diff criterion by 0.7%-1.2% on average, again depending on plan type and calculation technique (corresponding to an average change in pass rate of 3.5%-8.1%, and a maximum change of 14.2%). The largest increases in pass rate due to the Measurement Uncertainty function are generally seen with poorly matched planar dose comparisons, while the function has a notably smaller effect as pass rates approach 100%. The Measurement Uncertainty function, then, may

  14. Chromosomal Aberrations in DNA Repair Defective Cell Lines: Comparisons of Dose Rate and Radiation Quality

    NASA Technical Reports Server (NTRS)

    George, K. A.; Hada, M.; Patel, Z.; Huff, J.; Pluth, J. M.; Cucinotta, F. A.

    2009-01-01

    Chromosome aberration yields were assessed in DNA double-strand break repair (DSB) deficient cells after acute doses of gamma-rays or high-LET iron nuclei, or low dose-rate (0.018 Gy/hr) gamma-rays. We studied several cell lines including fibroblasts deficient in ATM (product of the gene that is mutated in ataxia telangiectasia patients) or NBS (product of the gene mutated in the Nijmegen breakage syndrome), and gliomablastoma cells that are proficient or lacking in DNA-dependent protein kinase, DNA-PK activity. Chromosomes were analyzed using the fluorescence in-situ hybridization (FISH) chromosome painting method in cells at the first division post-irradiation and chromosome aberrations were identified as either simple exchanges (translocations and dicentrics) or complex exchanges (involving >2 breaks in 2 or more chromosomes). Gamma radiation induced higher yields of both simple and complex exchanges in the DSB repair defective cells than in the normal cells. The quadratic dose-response terms for both chromosome exchange types were significantly higher for the ATM and NBS defective lines than for normal fibroblasts. However, the linear dose-response term was significantly higher only for simple exchanges in the NBS cells. Large increases in the quadratic dose response terms indicate the important roles of ATM and NBS in chromatin modifications that facilitate correct DSB repair and minimize aberration formation. Differences in the response of AT and NBS deficient cells at lower doses suggests important questions about the applicability of observations of radiation sensitivity at high dose to low dose exposures. For all iron nuclei irradiated cells, regression models preferred purely linear and quadratic dose responses for simple and complex exchanges, respectively. All the DNA repair defective cell lines had lower Relative biological effectiveness (RBE) values than normal cells, the lowest being for the DNA-PK-deficient cells, which was near unity. To further

  15. Preliminary survey of outdoor gamma dose rates in Lesvos Island (Greece).

    PubMed

    Petalas, Anastasios B; Vogiannis, Efstratios; Nikolopoulos, Dimitrios; Halvadakis, Constantinos P

    2005-01-01

    This study reports the first attempt to record the radioactive background due to gamma radiation in Lesvos Island (Greece). The study reports the results from 335 outdoor total gamma effective dose rate measurements conducted using GPS navigation and a Geiger-Muller detector (Bicron, Micro Sievert) on the whole surface of the island together with a digital map produced by appropriate mapping GIS programme. The study also reports the measurements of outdoor gamma dose rates due to the 238U, 232Th and 40K radionuclides as estimated via in situ gamma-ray spectrometry measurements performed at 26 sites using a 3 x 3 inch NaI (thallium activated) portable detector. The results from the outdoor total gamma effective dose rates range between 0.0023 and 0.28 microSv h(-1). The highest outdoor total gamma effective dose rates (0.013-0.28 microSv h(-1)) were detected in the northeastern part of the island and the intermediate rates (0.066-0.13 microSv h(-1)) in the central region. The outdoor gamma dose rates due to 238U, 232Th and 40K radionuclides range between 1.7 +/- 0.8 and 154 +/- 7 nGy h(-1) with an average of 86 +/- 6 nGy h(-1). The average contribution of each of the examined radionuclides (238U, 232Th and 40K) to the total gamma dose rate was found to be equal to 12 +/- 4% for 238U, 58 +/- 6% for 232Th and 29 +/- 7% for 40K, respectively. PMID:15728423

  16. Dose Rate Calibration of a Commercial Beta-Particle Irradiator Used In Archeological and Geological Dating

    SciTech Connect

    Bernal, S.M.

    2004-10-31

    The 801E Multiple Sample Irradiator, manufactured by Daybreak Nuclear Systems, is capable of exposing up to 30 samples to beta radiation by placing each sample one by one directly beneath a heavily shielded ceramic Sr-90/Y-90 source and opening a specially designed shutter. Daybreak Nuclear Systems does not provide the {sup 90}Sr/{sup 90}Y dose rate to the sample because of variations of up to 20% in the nominal activity of the beta sources (separately manufactured by AEA Technology). Thus it is left to the end user to determine. Here aluminum oxide doped with carbon (Al{sub 2}O{sub 3}:C), in the form of Landauer's Luxel{trademark}, was irradiated to different known doses using a calibrated {sup 90}Sr/{sup 90}Y beta particle irradiator, and the OSL signal monitored after each irradiation to generate a calibration curve. Comparison of the OSL Signal from the unknown 801E Irradiator dose with the calibration curve enabled the dose and therefore dose rate to be determined. The timing accuracy of the 801E Irradiator was also evaluated and found to be +/- 0.5 seconds. The dose rate of the beta source was found to be 0.147 +/- 0.007 Gy/s.

  17. Efficacy of a Low Dose of Estrogen on Antioxidant Defenses and Heart Rate Variability

    PubMed Central

    Casali, Karina Rabello; Baraldi, Dhãniel; Conzatti, Adriana; Araújo, Alex Sander da Rosa; Khaper, Neelam; Llesuy, Susana; Rigatto, Katya; Belló-Klein, Adriane

    2014-01-01

    This study tested whether a low dose (40% less than the pharmacological dose of 17-β estradiol) would be as effective as the pharmacological dose to improve cardiovascular parameters and decrease cardiac oxidative stress. Female Wistar rats (n = 9/group) were divided in three groups: (1) ovariectomized (Ovx), (2) ovariectomized animals treated for 21 days with low dose (LE; 0.2 mg), and (3) high dose (HE; 0.5 mg) 17-β estradiol subcutaneously. Hemodynamic assessment and spectral analysis for evaluation of autonomic nervous system regulation were performed. Myocardial superoxide dismutase (SOD) and catalase (CAT) activities, redox ratio (GSH/GSSG), total radical-trapping antioxidant potential (TRAP), hydrogen peroxide, and superoxide anion concentrations were measured. HE and LE groups exhibited an improvement in hemodynamic function and heart rate variability. These changes were associated with an increase in the TRAP, GSH/GSSG, SOD, and CAT. A decrease in hydrogen peroxide and superoxide anion was also observed in the treated estrogen groups as compared to the Ovx group. Our results indicate that a low dose of estrogen is just as effective as a high dose into promoting cardiovascular function and reducing oxidative stress, thereby supporting the approach of using low dose of estrogen in clinical settings to minimize the risks associated with estrogen therapy. PMID:24738017

  18. Iron Oxide Nanoparticle Agglomeration Influences Dose-Rates and Modulates Oxidative Stress Mediated Dose-Response Profiles In Vitro

    SciTech Connect

    Sharma, Gaurav; Kodali, Vamsi K.; Gaffrey, Matthew J.; Wang, Wei; Minard, Kevin R.; Karin, Norman J.; Teeguarden, Justin G.; Thrall, Brian D.

    2013-07-31

    Spontaneous agglomeration of engineered nanoparticles (ENPs) is a common problem in cell culture media which can confound interpretation of in vitro nanotoxicity studies. The authors created stable agglomerates of iron oxide nanoparticles (IONPs) in conventional culture medium, which varied in hydrodynamic size (276 nm-1.5 μm) but were composed of identical primary particles with similar surface potentials and protein coatings. Studies using C10 lung epithelial cells show that the dose rate effects of agglomeration can be substantial, varying by over an order of magnitude difference in cellular dose in some cases. Quantification by magnetic particle detection showed that small agglomerates of carboxylated IONPs induced greater cytotoxicity and redox-regulated gene expression when compared with large agglomerates on an equivalent total cellular IONP mass dose basis, whereas agglomerates of amine-modified IONPs failed to induce cytotoxicity or redox-regulated gene expression despite delivery of similar cellular doses. Dosimetry modelling and experimental measurements reveal that on a delivered surface area basis, large and small agglomerates of carboxylated IONPs have similar inherent potency for the generation of ROS, induction of stress-related genes and eventual cytotoxicity. The results suggest that reactive moieties on the agglomerate surface are more efficient in catalysing cellular ROS production than molecules buried within the agglomerate core. Because of the dynamic, size and density-dependent nature of ENP delivery to cells in vitro, the biological consequences of agglomeration are not discernible from static measures of exposure concentration (μg/ml) alone, highlighting the central importance of integrated physical characterisation and quantitative dosimetry for in vitro studies. The combined experimental and computational approach provides a quantitative framework for evaluating relationships between the biocompatibility of nanoparticles and their

  19. Isodose mapping of terrestrial gamma radiation dose rate of Selangor state, Kuala Lumpur and Putrajaya, Malaysia.

    PubMed

    Sanusi, M S M; Ramli, A T; Gabdo, H T; Garba, N N; Heryanshah, A; Wagiran, H; Said, M N

    2014-09-01

    A terrestrial gamma radiation survey for the state of Selangor, Kuala Lumpur and Putrajaya was conducted to obtain baseline data for environmental radiological health practices. Based on soil type, geological background and information from airborne survey maps, 95 survey points statistically representing the study area were determined. The measured doses varied according to geological background and soil types. They ranged from 17 nGy h(-1) to 500 nGy h(-1). The mean terrestrial gamma dose rate in air above the ground was 182 ± 81 nGy h(-1). This is two times higher than the average dose rate of terrestrial gamma radiation in Malaysia which is 92 nGy h(-1) (UNSCEAR 2000). An isodose map was produced to represent exposure rate from natural sources of terrestrial gamma radiation.

  20. Image-Guided Stereotactic Radiosurgery Using a Specially Designed High-Dose-Rate Linac

    SciTech Connect

    Bayouth, John E. . E-mail: john-bayouth@uiowa.edu; Kaiser, Heather S.; Smith, Mark C.; Pennington, Edward C.; Anderson, Kathleen M. C.; Ryken, Timothy C.; Buatti, John M.

    2007-07-01

    Stereotactic radiosurgery and image-guided radiotherapy (IGRT) place enhanced demands on treatment delivery machines. In this study, we describe a high-dose-rate output accelerator as a part of our stereotactic IGRT delivery system. The linac is a Siemens Oncor without a flattening filter, and enables dose rates to reach 1000 monitor units (MUs) per minute. Even at this high-dose-rate, the linac dosimetry system remains robust; constancy, linearity, and beam energy remain within 1% for 3 to 1000 MU. Dose profiles for larger field sizes are not flat, but they are radially symmetric and, as such, able to be modeled by a treatment planning system. Target localization is performed via optical guidance utilizing a 3-dimensional (3D) ultrasound probe coupled to an array of 4 infrared light-emitting diodes. These diodes are identified by a fixed infrared camera system that determines diode position and, by extension, all objects imaged in the room coordinate system. This system provides sub-millimeter localization accuracy for cranial applications and better than 1.5 mm for extracranial applications. Because stereotactic IGRT can require significantly longer times for treatment delivery, the advantages of the high-dose-rate design and its direct impact on IGRT are discussed.

  1. 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.

  2. 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).

  3. 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).

  4. 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.

  5. 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

  6. [Measurement of the Dose Rate Using Dosimeters in Interventional Radiology and Its Difficulty].

    PubMed

    Yoshida, Hidenori; Takahashi, Chiharu; Narita, Nobuhiro; Mizusawa, Yasuhiko; Sekiya, Masaru; Ohkubo, Masaki

    2016-01-01

    In equipment used for interventional radiology (IVR), automatic exposure control (AEC) is incorporated to obtain the X-ray output suitable for the treatment of targeted lesions. For the AEC, users select a region as the signal sensing region (measuring field, MF) in the flat panel detector; MFs with various sizes and shapes were pre-defined and prepared in the system. The aim of this study was to examine the change of measured dose rate with the selection of MFs, the type of dosimeters (the ionization chamber dosimeter and the semiconductor dosimeter), and the dosimeter placement relative to the direction of X-ray tube (from cathode to anode). The IVR equipment was Allura Xper FD20/10 (Philips Medical Systems), and six kinds of built-in MFs were used. It was found that dose rate measured by the ionization chamber dosimeter showed a variation of -2 mGy/min with the MFs and the ionization chamber dosimeter placement. The dose rate measured by the semiconductor dosimeter showed more variation than the ionization chamber dosimeter. The change of dose rate with the dosimeter placement would be caused by the MF overlapping the dosimeter which would affect the AEC (the X-ray output). Also, the change of dose rate with the dosimeter placement was considered to be related to the heel effect of the X-ray beam. When performing dose rate measurements, we should notice that the selection of MFs, the type of dosimeters, and the dosimeter placement would affect the measured values. PMID:26796935

  7. Moving from gamma passing rates to patient DVH-based QA metrics in pretreatment dose QA

    SciTech Connect

    Zhen, Heming; Nelms, Benjamin E.; Tome, Wolfgang A.

    2011-10-15

    Purpose: The purpose of this work is to explore the usefulness of the gamma passing rate metric for per-patient, pretreatment dose QA and to validate a novel patient-dose/DVH-based method and its accuracy and correlation. Specifically, correlations between: (1) gamma passing rates for three 3D dosimeter detector geometries vs clinically relevant patient DVH-based metrics; (2) Gamma passing rates of whole patient dose grids vs DVH-based metrics, (3) gamma passing rates filtered by region of interest (ROI) vs DVH-based metrics, and (4) the capability of a novel software algorithm that estimates corrected patient Dose-DVH based on conventional phan-tom QA data are analyzed. Methods: Ninety six unique ''imperfect'' step-and-shoot IMRT plans were generated by applying four different types of errors on 24 clinical Head/Neck patients. The 3D patient doses as well as the dose to a cylindrical QA phantom were then recalculated using an error-free beam model to serve as a simulated measurement for comparison. Resulting deviations to the planned vs simulated measured DVH-based metrics were generated, as were gamma passing rates for a variety of difference/distance criteria covering: dose-in-phantom comparisons and dose-in-patient comparisons, with the in-patient results calculated both over the whole grid and per-ROI volume. Finally, patient dose and DVH were predicted using the conventional per-beam planar data as input into a commercial ''planned dose perturbation'' (PDP) algorithm, and the results of these predicted DVH-based metrics were compared to the known values. Results: A range of weak to moderate correlations were found between clinically relevant patient DVH metrics (CTV-D95, parotid D{sub mean}, spinal cord D1cc, and larynx D{sub mean}) and both 3D detector and 3D patient gamma passing rate (3%/3 mm, 2%/2 mm) for dose-in-phantom along with dose-in-patient for both whole patient volume and filtered per-ROI. There was considerable scatter in the gamma passing rate

  8. Validation of a new control system for Elekta accelerators facilitating continuously variable dose rate

    SciTech Connect

    Bertelsen, Anders; Lorenzen, Ebbe L.; Brink, Carsten

    2011-08-15

    Purpose: Elekta accelerators controlled by the current clinically used accelerator control system, Desktop 7.01 (D7), uses binned variable dose rate (BVDR) for volumetric modulated arc therapy (VMAT). The next version of the treatment control system (Integrity) supports continuously variable dose rate (CVDR) as well as BVDR. Using CVDR opposed to BVDR for VMAT has the potential of reducing the treatment time but may lead to lower dosimetric accuracy due to faster moving accelerator parts. Using D7 and a test version of Integrity, differences in ability to control the accelerator, treatment efficiency, and dosimetric accuracy between the two systems were investigated. Methods: Single parameter tests were designed to expose differences in the way the two systems control the movements of the accelerator. In these tests, either the jaws, multi leaf collimators (MLCs), or gantry moved at constant speed while the dose rate was changed in discrete steps. The positional errors of the moving component and dose rate were recorded using the control systems with a sampling frequency of 4 Hz. The clinical applicability of Integrity was tested using 15 clinically used VMAT plans (5 prostate, 5 H and N, and 5 lung) generated by the SmartArc algorithm in PINNACLE. The treatment time was measured from beam-on to beam-off and the accuracy of the dose delivery was assessed by comparing DELTA4 measurements and PINNACLE calculated doses using gamma evaluation. Results: The single parameter tests showed that Integrity had an improved feedback between gantry motion and dose rate at the slight expense of MLC control compared to D7. The single parameter test did not reveal any significant differences in the control of either jaws or backup jaws between the two systems. These differences in gantry and MLC control together with the use of CVDR gives a smoother Integrity VMAT delivery compared to D7 with less abrupt changes in accelerator motion. Gamma evaluation (2% of 2 Gy and 2 mm) of the

  9. ITER Generic Diagnostic Upper Port Plug Nuclear Heating and Personnel Dose Rate Assesment

    SciTech Connect

    Russell E. Feder and Mahmoud Z. Youssef

    2009-01-28

    Neutronics analysis to find nuclear heating rates and personnel dose rates were conducted in support of the integration of diagnostics in to the ITER Upper Port Plugs. Simplified shielding models of the Visible-Infrared diagnostic and of a large aperture diagnostic were incorporated in to the ITER global CAD model. Results for these systems are representative of typical designs with maximum shielding and a small aperture (Vis-IR) and minimal shielding with a large aperture. The neutronics discrete-ordinates code ATTILA® and SEVERIAN® (the ATTILA parallel processing version) was used. Material properties and the 500 MW D-T volume source were taken from the ITER “Brand Model” MCNP benchmark model. A biased quadrature set equivelant to Sn=32 and a scattering degree of Pn=3 were used along with a 46-neutron and 21-gamma FENDL energy subgrouping. Total nuclear heating (neutron plug gamma heating) in the upper port plugs ranged between 380 and 350 kW for the Vis-IR and Large Aperture cases. The Large Aperture model exhibited lower total heating but much higher peak volumetric heating on the upper port plug structure. Personnel dose rates are calculated in a three step process involving a neutron-only transport calculation, the generation of activation volume sources at pre-defined time steps and finally gamma transport analyses are run for selected time steps. ANSI-ANS 6.1.1 1977 Flux-to-Dose conversion factors were used. Dose rates were evaluated for 1 full year of 500 MW DT operation which is comprised of 3000 1800-second pulses. After one year the machine is shut down for maintenance and personnel are permitted to access the diagnostic interspace after 2-weeks if dose rates are below 100 μSv/hr. Dose rates in the Visible-IR diagnostic model after one day of shutdown were 130 μSv/hr but fell below the limit to 90 μSv/hr 2-weeks later. The Large Aperture style shielding model exhibited higher and more persistent dose rates. After 1-day the dose rate was 230

  10. Dose-rate and irradiation temperature dependence of BJT SPICE model rad-parameters

    SciTech Connect

    Montagner, X.; Briand, R.; Fouillat, P.; Touboul, A.; Schrimpf, R.D.; Galloway, K.F.; Calvet, M.C.; Calvel, P.

    1998-06-01

    A method to predict low dose rate degradation of bipolar transistors using high dose-rate, high temperature irradiation is evaluated, based on an analysis of four new rad-parameters that are introduced in the BJT SPICE model. This improved BJT model describes the radiation-induced excess base current with great accuracy. The low-level values of the rad-parameters are good tools for evaluating the proposed high-temperature test method because of their high sensitivity to radiation-induced degradation.

  11. 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.

  12. LET and dose rate effect on radiation-induced copolymerization in physical gel

    NASA Astrophysics Data System (ADS)

    Nakagawa, Seiko; Taguchi, Mitsumasa; Kimura, Atsushi; Nagasawa, Naotsugu; Hiroki, Akihiro

    2014-09-01

    N2-saturated 2-propanol solutions containing styrene and maleimide were gelled by the addition of hydroxypropylcellulose and irradiated by proton, He and C-ion beams. The trend in the dose rate and LET effects on the yield and molecular weight distribution of the polymer produced in the gel was almost the same in the solution. On the contrary, the dose rate effect in the gel was higher than that in the solution. This effect was accelerated for irradiations by proton as well as heavier ion with a higher LET value.

  13. ANALYSIS OF DOSE RATES DURING REPLACEMENT OF MANIPULATORS IN THE FFTF INTERIM EXAMINATION & MAINTENANCE (IEM) CELL

    SciTech Connect

    NELSON, J.V.

    2002-01-23

    Replacement of a master-slave manipulator in the Interim Examination and Maintenance Cell at the Fast Flux Test Facility was carried out in August 2001. This operation created a 178-mm opening in the thick concrete wall of the hot cell. To aid in radiological work planning, dose rates outside the penetration in the wall were predicted using MCNP{trademark} photon transport calculations. The predicted dose rate was 7.7 mrem/h, which was reasonably close to the value of 10.4 mrem/h inferred from measurements.

  14. Emesis as a Screening Diagnostic for Low Dose Rate (LDR) Total Body Radiation Exposure.

    PubMed

    Camarata, Andrew S; Switchenko, Jeffrey M; Demidenko, Eugene; Flood, Ann B; Swartz, Harold M; Ali, Arif N

    2016-04-01

    Current radiation disaster manuals list the time-to-emesis (TE) as the key triage indicator of radiation dose. The data used to support TE recommendations were derived primarily from nearly instantaneous, high dose-rate exposures as part of variable condition accident databases. To date, there has not been a systematic differentiation between triage dose estimates associated with high and low dose rate (LDR) exposures, even though it is likely that after a nuclear detonation or radiologic disaster, many surviving casualties would have received a significant portion of their total exposure from fallout (LDR exposure) rather than from the initial nuclear detonation or criticality event (high dose rate exposure). This commentary discusses the issues surrounding the use of emesis as a screening diagnostic for radiation dose after LDR exposure. As part of this discussion, previously published clinical data on emesis after LDR total body irradiation (TBI) is statistically re-analyzed as an illustration of the complexity of the issue and confounding factors. This previously published data includes 107 patients who underwent TBI up to 10.5 Gy in a single fraction delivered over several hours at 0.02 to 0.04 Gy min. Estimates based on these data for the sensitivity of emesis as a screening diagnostic for the low dose rate radiation exposure range from 57.1% to 76.6%, and the estimates for specificity range from 87.5% to 99.4%. Though the original data contain multiple confounding factors, the evidence regarding sensitivity suggests that emesis appears to be quite poor as a medical screening diagnostic for LDR exposures. PMID:26910032

  15. Development and characterization of a novel variable low-dose rate irradiator for in vivo mouse studies

    PubMed Central

    Olipitz, Werner; Hembrador, Sheena; Davidson, Matthew; Yanch, Jacquelyn C.; Engelward, Bevin P.

    2011-01-01

    Radiation exposure of humans generally results in low doses delivered at low dose-rate. Our limited knowledge of the biological effects of low dose radiation is mainly based on data from the atomic bomb long-term survivor study (LSS) cohort. However, the total doses and dose-rates in the LSS cohort are still higher than most environmental and occupational exposures in humans. Importantly, the dose-rate is a critical determinant of health risks stemming from radiation exposure. Understanding the shape of the dose-rate response curve for different biological outcomes is thus crucial for projecting the biological hazard from radiation in different environmental and man-made conditions. A significant barrier to performing low dose-rate studies is the difficulty in creating radiation source configurations compatible with long-term cellular or animal experiments. In this study the design and characterization of a large area, 125I-based irradiator is described. The irradiator allows continuous long-term exposure of mice at variable dose-rates and can be sited in standard animal care facilities. The dose-rate is determined by the level of 125I activity added to a large NaOH filled, rectangular phantom. The desired dose rate is maintained at essentially constant levels by weekly additions of 125I to compensate for decay. Dosimetry results for long-term animal irradiation at targeted dose rates of 0.00021 and 0.0021 cGy min−1 are presented. PMID:20386202

  16. Poster — Thur Eve — 27: Flattening Filter Free VMAT Quality Assurance: Dose Rate Considerations for Detector Response

    SciTech Connect

    Viel, Francis; Duzenli, Cheryl; Camborde, Marie-Laure; Strgar, Vincent; Horwood, Ron; Atwal, Parmveer; Gete, Ermias; Karan, Tania

    2014-08-15

    Introduction: Radiation detector responses can be affected by dose rate. Due to higher dose per pulse and wider range of mu rates in FFF beams, detector responses should be characterized prior to implementation of QA protocols for FFF beams. During VMAT delivery, the MU rate may also vary dramatically within a treatment fraction. This study looks at the dose per pulse variation throughout a 3D volume for typical VMAT plans and the response characteristics for a variety of detectors, and makes recommendations on the design of QA protocols for FFF VMAT QA. Materials and Methods: Linac log file data and a simplified dose calculation algorithm are used to calculate dose per pulse for a variety of clinical VMAT plans, on a voxel by voxel basis, as a function of time in a cylindrical phantom. Diode and ion chamber array responses are characterized over the relevant range of dose per pulse and dose rate. Results: Dose per pulse ranges from <0.1 mGy/pulse to 1.5 mGy/pulse in a typical VMAT treatment delivery using the 10XFFF beam. Diode detector arrays demonstrate increased sensitivity to dose (+./− 3%) with increasing dose per pulse over this range. Ion chamber arrays demonstrate decreased sensitivity to dose (+/− 1%) with increasing dose rate over this range. Conclusions: QA protocols should be designed taking into consideration inherent changes in detector sensitivity with dose rate. Neglecting to account for changes in detector response with dose per pulse can lead to skewed QA results.

  17. Ruthenium-106 brachytherapy for thick uveal melanoma: reappraisal of apex and base dose radiation and dose rate

    PubMed Central

    Jaberi, Ramin; Sedaghat, Ahad; Azma, Zohreh; Nojomi, Marzieh; Falavarjani, Khalil Ghasemi; Nazari, Hossein

    2016-01-01

    Purpose To evaluate the outcomes of ruthenium-106 (106Ru) brachytherapy in terms of radiation parameters in patients with thick uveal melanomas. Material and methods Medical records of 51 patients with thick (thickness ≥ 7 mm and < 11 mm) uveal melanoma treated with 106Ru brachytherapy during a ten-year period were reviewed. Radiation parameters, tumor regression, best corrected visual acuity (BCVA), and treatment-related complications were assessed. Results Fifty one eyes of 51 consecutive patients including 25 men and 26 women with a mean age of 50.5 ± 15.2 years were enrolled. Patients were followed for 36.1 ± 26.5 months (mean ± SD). Mean radiation dose to tumor apex and to sclera were 71 (± 19.2) Gy and 1269 (± 168.2) Gy. Radiation dose rates to tumor apex and to sclera were 0.37 (± 0.14) Gy/h and 6.44 (± 1.50) Gy/h. Globe preservation was achieved in 82.4%. Preoperative mean tumor thickness of 8.1 (± 0.9) mm decreased to 4.5 (± 1.6) mm, 3.4 (± 1.4) mm, and 3.0 (± 1.46) mm at 12, 24, and 48 months after brachytherapy (p = 0.03). Four eyes that did not show regression after 6 months of brachytherapy were enucleated. Secondary enucleation was performed in 5 eyes because of tumor recurrence or neovascular glaucoma. Tumor recurrence was evident in 6 (11.8%) patients. Mean Log MAR (magnification requirement) visual acuity declined from 0.75 (± 0.63) to 0.94 (± 0.5) (p = 0.04). Best corrected visual acuity of 20/200 or worse was recorded in 37% of the patients at the time of diagnosis and 61.7% of the patients at last exam (p = 0.04). Non-proliferative and proliferative radiation-induced retinopathy was observed in 20 and 7 eyes. Conclusions Thick uveal melanomas are amenable to 106Ru brachytherapy with less than recommended apex radiation dose and dose rates. PMID:26985199

  18. Indoor terrestrial gamma dose rate mapping in France: a case study using two different geostatistical models.

    PubMed

    Warnery, E; Ielsch, G; Lajaunie, C; Cale, E; Wackernagel, H; Debayle, C; Guillevic, J

    2015-01-01

    Terrestrial gamma dose rates show important spatial variations in France. Previous studies resulted in maps of arithmetic means of indoor terrestrial gamma dose rates by "departement" (French district). However, numerous areas could not be characterized due to the lack of data. The aim of our work was to obtain more precise estimates of the spatial variability of indoor terrestrial gamma dose rates in France by using a more recent and complete data base and geostatistics. The study was based on the exploitation of 97,595 measurements results distributed in 17,404 locations covering all of France. Measurements were done by the Institute for Radioprotection and Nuclear Safety (IRSN) using RPL (Radio Photo Luminescent) dosimeters, exposed during several months between years 2011 and 2012 in French dentist surgeries and veterinary clinics. The data used came from dosimeters which were not exposed to anthropic sources. After removing the cosmic rays contribution in order to study only the telluric gamma radiation, it was decided to work with the arithmetic means of the time-series measurements, weighted by the time-exposure of the dosimeters, for each location. The values varied between 13 and 349 nSv/h, with an arithmetic mean of 76 nSv/h. The observed statistical distribution of the gamma dose rates was skewed to the right. Firstly, ordinary kriging was performed in order to predict the gamma dose rate on cells of 1*1 km(2), all over the domain. The second step of the study was to use an auxiliary variable in estimates. The IRSN achieved in 2010 a classification of the French geological formations, characterizing their uranium potential on the bases of geology and local measurement results of rocks uranium content. This information is georeferenced in a map at the scale 1:1,000,000. The geological uranium potential (GUP) was classified in 5 qualitative categories. As telluric gamma rays mostly come from the progenies of the (238)Uranium series present in rocks, this

  19. Solar particle dose rate buildup and distribution in critical body organs

    NASA Technical Reports Server (NTRS)

    Atwell, William; Weyland, Mark D.; Simonsen, Lisa C.

    1993-01-01

    Human body organs have varying degrees of radiosensitivity as evidenced by radioepidemiologic tables. The major critical organs for both the male and female that have been identified include the lung, thyroid, stomach, and breast (female). Using computerized anatomical models of the 50th percentile United States Air Force male and female, we present the self-shielding effects of these various body organs and how the shielding effects change as the location (dose point) in the body varies. Several major solar proton events from previous solar cycles and several events from the current 22nd solar cycle have been analyzed. The solar particle event rise time, peak intensity, and decay time vary considerably from event to event. Absorbed dose and dose equivalent rate calculations and organ risk assessment data are presented for each critical body organ. These data are compared with the current NASA astronaut dose limits as recommended by the National Council on Radiation Protection and Measurements.

  20. Dosimetry in steep dose-rate gradient radiation fields: A challenge in clinical applications

    SciTech Connect

    Massillon-JL, G.

    2010-12-07

    The fundamental goal of radiotherapy is to reduce the damage to normal tissue and optimize the dose to the tumor with an associated high probability of cure. Because of this, an accurate and precise knowledge of the radiation dose distribution delivered around the tumor volume during radiotherapy treatments such as stereotactic radiosurgery, intensity modulated radiotherapy or brachytherapy with low-energy X-ray and beta particle sources is of great importance. However, in each of these radiation fields, there exists a steep dose-rate gradient which makes it very difficult to perform accurate dose measurements. In this work, the physics phenomena involved in the energy absorption for each of these situations are discussed, and a brief revision of what the Medical Physics community is doing is presented.

  1. Dosimetry in steep dose-rate gradient radiation fields: A challenge in clinical applications

    NASA Astrophysics Data System (ADS)

    Massillon-JL, G.

    2010-12-01

    The fundamental goal of radiotherapy is to reduce the damage to normal tissue and optimize the dose to the tumor with an associated high probability of cure. Because of this, an accurate and precise knowledge of the radiation dose distribution delivered around the tumor volume during radiotherapy treatments such as stereotactic radiosurgery, intensity modulated radiotherapy or brachytherapy with low-energy X-ray and beta particle sources is of great importance. However, in each of these radiation fields, there exists a steep dose-rate gradient which makes it very difficult to perform accurate dose measurements. In this work, the physics phenomena involved in the energy absorption for each of these situations are discussed, and a brief revision of what the Medical Physics community is doing is presented.

  2. Dose rate measurements from radiopharmaceuticals: implications for nuclear medicine staff and for children with radioactive parents.

    PubMed

    Greaves, C D; Tindale, W B

    1999-02-01

    Following the introduction of a number of radiopharmaceuticals, we assessed the dose received by staff working in the nuclear medicine department and also by children who may be in close contact with a radioactive parent. We measured departure dose rates (microSv.h-1) at distances of 0.1, 0.5 and 1.0 m from the skin surface at the level of the thyroid, chest and bladder of patients undergoing the following nuclear medicine procedures: MUGA scans using 99Tcm-labelled red blood cells, myocardial perfusion scans using 99Tcm-labelled radiopharmaceuticals, lymphoscintigraphy using colloidal 99Tcm (Re) sulphide, bone scans using 99Tcm-labelled oxidronate, 111In-octreotide scans, 111In-labelled leukocyte studies and cardiac reinjection studies using 201Tl. The maximum dose rates at 0.1 m were those from MUGA studies (167.3 microSv.h-1) and myocardial perfusion studies (one-day protocol = 391.7 microSv.h-1, two-day protocol = 121.8 microSv.h-1). The implications of these dose rates on both technical and nursing staff are assessed. Also, the dose received by an infant in close contact with a parent following a nuclear medicine investigation was estimated.

  3. Feasibility study of volumetric modulated arc therapy with constant dose rate for endometrial cancer

    SciTech Connect

    Yang, Ruijie; Wang, Junjie; Xu, Feng; Li, Hua; Zhang, Xile

    2013-10-01

    To investigate the feasibility, efficiency, and delivery accuracy of volumetric modulated arc therapy with constant dose rate (VMAT-CDR) for whole-pelvic radiotherapy (WPRT) of endometrial cancer. The nine-field intensity-modulated radiotherapy (IMRT), VMAT with variable dose-rate (VMAT-VDR), and VMAT-CDR plans were created for 9 patients with endometrial cancer undergoing WPRT. The dose distribution of planning target volume (PTV), organs at risk (OARs), and normal tissue (NT) were compared. The monitor units (MUs) and treatment delivery time were also evaluated. For each VMAT-CDR plan, a dry run was performed to assess the dosimetric accuracy with MatriXX from IBA. Compared with IMRT, the VMAT-CDR plans delivered a slightly greater V{sub 20} of the bowel, bladder, pelvis bone, and NT, but significantly decreased the dose to the high-dose region of the rectum and pelvis bone. The MUs decreased from 1105 with IMRT to 628 with VMAT-CDR. The delivery time also decreased from 9.5 to 3.2 minutes. The average gamma pass rate was 95.6% at the 3%/3 mm criteria with MatriXX pretreatment verification for 9 patients. VMAT-CDR can achieve comparable plan quality with significant shorter delivery time and smaller number of MUs compared with IMRT for patients with endometrial cancer undergoing WPRT. It can be accurately delivered and be an alternative to IMRT on the linear accelerator without VDR capability.

  4. Global Evaluation of Prompt Dose Rates in ITER Using Hybrid Monte Carlo/Deterministic Techniques

    SciTech Connect

    Ibrahim, A.; Sawan, M.; Mosher, Scott W; Evans, Thomas M; Peplow, Douglas E.; Wilson, P.; Wagner, John C

    2011-01-01

    The hybrid Monte Carlo (MC)/deterministic techniques - Consistent Adjoint Driven Importance Sampling (CADIS) and Forward Weighted CADIS (FW-CADIS) - enable the full 3-D modeling of very large and complicated geometries. The ability of performing global MC calculations for nuclear parameters throughout the entire ITER reactor was demonstrated. The 2 m biological shield (bioshield) reduces the total prompt operational dose by six orders of magnitude. The divertor cryo-pump port results in a peaking factor of 120 in the prompt operational dose rate behind the bioshield by a factor of 47. The peak values of the prompt dose rates at the back surface of the bioshield were 240 uSv/hr and 94 uSv/hr corresponding to the regions behind the divertor cryo-pump port and the equatorial port, respectively.

  5. Dosimetric evaluation of two treatment planning systems for high dose rate brachytherapy applications.

    PubMed

    Shwetha, Bondel; Ravikumar, Manickam; Supe, Sanjay S; Sathiyan, Saminathan; Lokesh, Vishwanath; Keshava, Subbarao L

    2012-01-01

    Various treatment planning systems are used to design plans for the treatment of cervical cancer using high-dose-rate brachytherapy. The purpose of this study was to make a dosimetric comparison of the 2 treatment planning systems from Varian medical systems, namely ABACUS and BrachyVision. The dose distribution of Ir-192 source generated with a single dwell position was compared using ABACUS (version 3.1) and BrachyVision (version 6.5) planning systems. Ten patients with intracavitary applications were planned on both systems using orthogonal radiographs. Doses were calculated at the prescription points (point A, right and left) and reference points RU, LU, RM, LM, bladder, and rectum. For single dwell position, little difference was observed in the doses to points along the perpendicular bisector. The mean difference between ABACUS and BrachyVision for these points was 1.88%. The mean difference in the dose calculated toward the distal end of the cable by ABACUS and BrachyVision was 3.78%, whereas along the proximal end the difference was 19.82%. For the patient case there was approximately 2% difference between ABACUS and BrachyVision planning for dose to the prescription points. The dose difference for the reference points ranged from 0.4-1.5%. For bladder and rectum, the differences were 5.2% and 13.5%, respectively. The dose difference between the rectum points was statistically significant. There is considerable difference between the dose calculations performed by the 2 treatment planning systems. It is seen that these discrepancies are caused by the differences in the calculation methodology adopted by the 2 systems.

  6. Total dose effect on soft error rate for dynamic metal-oxide-semiconductor memory cells

    NASA Technical Reports Server (NTRS)

    Benumof, Reuben

    1989-01-01

    A simple model for the soft error rate for dynamic metal-oxide-semiconductor random access memories due to normal galactic radiation was devised and then used to calculate the rate of decrease of the single-event-upset rate with total radiation dose. The computation shows that the decrease in the soft error rate is less than 10 percent per day if the shielding is 0.5 g/sq cm and the spacecraft is in a geosynchronous orbit. The decrease is considerably less in a polar orbiting device.

  7. Cisplatin dose rate as a risk factor for nephrotoxicity in children.

    PubMed Central

    Skinner, R.; Pearson, A. D.; English, M. W.; Price, L.; Wyllie, R. A.; Coulthard, M. G.; Craft, A. W.

    1998-01-01

    The purpose of the study was to evaluate the incidence, risk factors and changes in severity with time of cisplatin nephrotoxicity in children. A total of 35 children underwent measurement of glomerular filtration rate (GFR) and tubular function after completion of cisplatin chemotherapy. No child received ifosfamide. A clinically relevant 'nephrotoxicity score' was derived from GFR and serum magnesium. Follow-up studies were performed in 16 children at 1 year and in 15 at 2 years after cisplatin. Considerable interpatient variability in nephrotoxicity was observed. Treatment was modified in three patients because of nephrotoxicity. GFR was low in 18 out of 31 patients. Proximal nephron toxicity caused hypomagnesaemia in ten patients and hypocalcaemia in five patients. Elevated urinary N-acetylglucosaminidase excretion was seen in 22 out of 30 children, indicating subclinical tubular toxicity. Nephrotoxicity was less severe in children who received cisplatin courses at a dose rate of 40 mg m(-2) day(-1) than in those who received higher dose rates (P < 0.005), but there was no correlation with total dose received. Follow-up studies revealed partial recovery of GFR (P < 0.05). Glomerular and proximal nephron toxicity are common in children treated with cisplatin, and more severe at higher dose rates. Despite partial recovery of GFR, the long-term outcome of nephrotoxicity remains unknown and careful monitoring of chronic toxicity is necessary. PMID:9635848

  8. Absorbed dose rates in tissue from prompt gamma emissions from near-thermal neutron absorption

    DOE PAGES

    Schwahn, Scott O.

    2015-10-01

    Prompt gamma emission data from the International Atomic Energy Agency s Prompt Gamma-ray Neutron Activation Analysis database are analyzed to determine the absorbed dose rates in tissue to be expected when natural elements are exposed in a near-thermal neutron environment.

  9. Autoradiography-based, three-dimensional calculation of dose rate for murine, human-tumor xenografts.

    PubMed

    Koral, K F; Kwok, C S; Yang, F E; Brown, R S; Sisson, J C; Wahl, R L

    1993-11-01

    A Fast Fourier Transform method for calculating the three-dimensional dose rate distribution for murine, human-tumor xenografts is outlined. The required input includes evenly-spaced activity slices which span the tumor. Numerical values in these slices are determined by quantitative 125I autoradiography. For the absorbed dose-rate calculation, we assume the activity from both 131I- and 90Y-labeled radiopharmaceuticals would be distributed as is measured with the 125I label. Two example cases are presented: an ovarian-carcinoma xenograft with an IgG 2ak monoclonal antibody and a neuroblastoma xenograft with meta-iodobenzylguanidine (MIBG). Considering all the volume elements in a tumor, we show, by comparison of histograms and also relative standard deviations, that the measured 125I activity and the calculated 131I dose-rate distributions, are similarly non-uniform and that they are more non-uniform than the calculated 90Y dose-rate distribution. However, the maximum-to-minimum ratio, another measure of non-uniformity, decreases by roughly an order of magnitude from one distribution to the next in the order given above. PMID:8298569

  10. Saran-Chloropel plastic suit worker dose rates from airborne tritium exposure - first exposure hour

    SciTech Connect

    Edwards, T.

    1993-04-20

    Radiological Engineering was requested to develop Tritium Stay Time Chart dose rates for the 9 mil Saran-Chloropel (CPE) plastic suit for a period of one hour or less. Assumptions utilized in previous calculations were revised to better address the first hour of exposure in the suit for emergency situations.

  11. Dose rate and beam profile measurement of proton beam using a flat panel detector

    NASA Astrophysics Data System (ADS)

    Park, Jeong-Min

    2015-10-01

    A 20-MeV or 100-MeV proton beam is provided to users for their proton beam irradiation experiments at KOrea Multi-Purpose Accelerator Complex. Radiochromic film (Gafchromic / HDV2) has been used to measure the dose rate and the profile of an incident proton beam during irradiation experiments. However, such measurements using radiochromic film have some inconveniences because an additional scanning process of is required to quantify the film's image. Therefore, we tried to measure the dose rate and beam profile by using a flat panel detector (FPD), which was developed for X-ray radiography as a substitute for radiochromic film because the FPD can measure the beam profile and the dose rate directly through a digitized image with a high spatial resolution. In this work, we investigated the feasibility of using a FPD as a substitute for radiochromic film. The preliminary results for the beam profile and the dose rate measured by using the flat panel detector are reported in the paper.

  12. Correlation-study about the ambient dose rate and the weather conditions

    NASA Astrophysics Data System (ADS)

    Furuya, Masato; Hatano, Yuko; Aoyama, Tomoo; Igarashi, Yasuhito; Kita, Kazuyuki; Ishizuka, Masahide

    2016-04-01

    The long-term radiation risks are believed to be heavily affected by the resuspension process. We therefore focus on the surface-atmosphere exchange process of released radioactive materials in this study. Radioactive materials were deposited on the soil and float in the air, and such complicated process are influenced by the weather conditions deeply. We need to reveal the correlation between the weather conditions and the ambient dose rate. In this study, we study the correlation between the weather conditions and the ambient dose rate with the correction of the decrease due to the radioactive decay. We found that there is a negative correlation between the ambient dose rate and the soil water content by the correlation coefficient. Using this result, we reconstruct the ambient dose rate from the weather conditions by the multiple regression analysis and found that the reconstructed data agree with the observation very well. Using Kalman filter, which can be sequentially updates the state estimate, we obtained such a good agreement.

  13. A geochemical assessment of terrestrial gamma-ray absorbed dose rates.

    PubMed

    Wollenberg, H A; Smith, A R

    1990-02-01

    A survey of the geochemical literature and unpublished data has resulted in the classification of the concentrations of the naturally occurring radioelements U, Th, and K by their associated rock types. A data base of over 2500 entries has been compiled, permitting calculation of terrestrial gamma-ray absorbed dose rates. The general lithology of terrains may be distinguished by their radioelement ratios, relative abundances, and total gamma radioactivities. The gamma-ray absorbed dose rates in air above igneous rocks generally vary with their silica contents, and with the exception of shale, sedimentary rocks have lower K:U and K:Th ratios than most igneous rocks. The appreciable difference between the overall mean terrestrial gamma-ray dose rate for rock of the continental surface (approximately 7 X 10(-8) Gy h-1) and the mean dose rate from field measurements over soil (approximately 5 X 10(-8) Gy h-1) is explained by the substantial differences between radioelement concentrations of soil and rock, differences that may vary markedly with rock type.

  14. Monitoring performance of the cameras under the high dose-rate gamma ray environments.

    PubMed

    Cho, Jai Wan; Choi, Young Soo; Jeong, Kyung Min

    2014-05-01

    CCD/CMOS cameras, loaded on a robot system, are generally used as the eye of the robot and monitoring unit. A major problem that arises when dealing with images provided by CCD/CMOS cameras under severe accident situations of a nuclear power plant is the presence of speckles owing to the high dose-rate gamma irradiation fields. To use a CCD/CMOS camera as a monitoring unit in a high radiation area, the legibility of the camera image in such intense gamma-radiation fields should therefore be defined. In this paper, the authors describe the monitoring index as a figure of merit of the camera's legibleness under a high dose-rate gamma ray irradiation environment. From a low dose-rate (10 Gy h) to a high dose-rate (200 Gy h) level, the legible performances of the cameras owing to the speckles are evaluated. The numbers of speckles generated by gamma ray irradiation in the camera image are calculated by an image processing technique. The legibility of the sensor indicator (thermo/hygrometer) owing to the number of speckles is also presented. PMID:24667385

  15. Bladder–Rectum Spacer Balloon in High-Dose-Rate Brachytherapy in Cervix Carcinoma

    SciTech Connect

    Rai, Bhavana; Patel, Firuza D.; Chakraborty, Santam; Sharma, Suresh C.; Kapoor, Rakesh; Aprem, Abi Santhosh

    2013-04-01

    Purpose: To compare bladder and rectum doses with the use of a bladder–rectum spacer balloon (BRSB) versus standard gauze packing in the same patient receiving 2 high-dose-rate intracavitary brachytherapy fractions. Methods and Materials: This was a randomized study to compare the reduction in bladder and rectum doses with the use of a BRSB compared with standard gauze packing in patients with carcinoma of the cervix being treated with high-dose-rate intracavitary brachytherapy. The patients were randomized between 2 arms. In arm A, vaginal packing was done with standard gauze packing in the first application, and BRSB was used in the second application. Arm B was the reverse of arm A. The International Commission for Radiation Units and Measurement (ICRU) point doses and doses to 0.1-cm{sup 3}, 1-cm{sup 3}, 2-cm{sup 3}, 5-cm{sup 3}, and 10-cm{sup 3} volumes of bladder and rectum were compared. The patients were also subjectively assessed for the ease of application and the time taken for application. Statistical analysis was done using the paired t test. Results: A total of 43 patients were enrolled; however, 3 patients had to be excluded because the BRSB could not be inserted owing to unfavorable local anatomy. Thus 40 patients (80 plans) were evaluated. The application was difficult in 3 patients with BRSB, and in 2 patients with BRSB the application time was prolonged. There was no significant difference in bladder doses to 0.1 cm{sup 3}, 1 cm{sup 3}, 2 cm{sup 3}, 5 cm{sup 3}, and 10 cm{sup 3} and ICRU bladder point. Statistically significant dose reductions to 0.1-cm{sup 3}, 1-cm{sup 3}, and 2-cm{sup 3} volumes for rectum were observed with the BRSB. No significant differences in 5-cm{sup 3} and 10-cm{sup 3} volumes and ICRU rectum point were observed. Conclusion: A statistically significant dose reduction was observed for small high-dose volumes in rectum with the BRSB. The doses to bladder were comparable for BRSB and gauze packing. Transparent balloons of

  16. Dose dependent effect of GnRH analogue on pregnancy rate of repeat breeder crossbred cows.

    PubMed

    Kharche, S D; Srivastava, S K

    2007-05-01

    The aim of this study was to investigate the effect of treating repeat breeder dairy crossbred cows with different doses of GnRH analogue through i.m. at the time of artificial insemination, on pregnancy rates from their first service after treatment and overall pregnancy rates. One hundred and thirty seven crossbred dairy cows with a history of repeat breeding and eligible after 6-8 infertile services but clinically free of diseases were selected for the study. The animals were randomly divided into three groups. Group 1 (n = 55) cows were treated intramuscularly with each 20 microg Buserelin-acetate (Receptal, Hoechst Roussel Vet GmbH) at the time of artificial insemination. Group 2 (n = 40) cows were treated intramuscularly with each 10 microg Buserelin-acetate at the time of artificial insemination. Group 3 (n = 42) cows were treated intramuscularly with saline as control at the time of artificial insemination. The first service pregnancy rates in Groups 1-3 were 45, 25 and 17%, respectively. Similarly, the overall conception rates in Groups 1-3 were 87, 58 and 48%, respectively. The results indicated that the pregnancy rate in crossbred cows could be improved by the GnRH treatment. The higher dose of GnRH significantly increased (P < 0.05) the first service as well as overall pregnancy rate in a dose dependent manner in repeat breeder crossbred cow bred previously 6-8 times unsuccessfully. PMID:16787717

  17. Dose rate estimation of the Tohoku hynobiid salamander, Hynobius lichenatus, in Fukushima.

    PubMed

    Fuma, Shoichi; Ihara, Sadao; Kawaguchi, Isao; Ishikawa, Takahiro; Watanabe, Yoshito; Kubota, Yoshihisa; Sato, Youji; Takahashi, Hiroyuki; Aono, Tatsuo; Ishii, Nobuyoshi; Soeda, Haruhi; Matsui, Kumi; Une, Yumi; Minamiya, Yukio; Yoshida, Satoshi

    2015-05-01

    The radiological risks to the Tohoku hynobiid salamanders (class Amphibia), Hynobius lichenatus due to the Fukushima Dai-ichi Nuclear Power Plant accident were assessed in Fukushima Prefecture, including evacuation areas. Aquatic egg clutches (n = 1 for each sampling date and site; n = 4 in total), overwintering larvae (n = 1-5 for each sampling date and site; n = 17 in total), and terrestrial juveniles or adults (n = 1 or 3 for each sampling date and site; n = 12 in total) of H. lichenatus were collected from the end of April 2011 to April 2013. Environmental media such as litter (n = 1-5 for each sampling date and site; n = 30 in total), soil (n = 1-8 for each sampling date and site; n = 31 in total), water (n = 1 for each sampling date and site; n = 17 in total), and sediment (n = 1 for each sampling date and site; n = 17 in total) were also collected. Activity concentrations of (134)Cs + (137)Cs were 1.9-2800, 0.13-320, and 0.51-220 kBq (dry kg) (-1) in the litter, soil, and sediment samples, respectively, and were 0.31-220 and <0.29-40 kBq (wet kg)(-1) in the adult and larval salamanders, respectively. External and internal absorbed dose rates to H. lichenatus were calculated from these activity concentration data, using the ERICA Assessment Tool methodology. External dose rates were also measured in situ with glass dosimeters. There was agreement within a factor of 2 between the calculated and measured external dose rates. In the most severely contaminated habitat of this salamander, a northern part of Abukuma Mountains, the highest total dose rates were estimated to be 50 and 15 μGy h(-1) for the adults and overwintering larvae, respectively. Growth and survival of H. lichenatus was not affected at a dose rate of up to 490 μGy h(-1) in the previous laboratory chronic gamma-irradiation experiment, and thus growth and survival of this salamander would not be affected, even in the most severely contaminated habitat in Fukushima Prefecture. However, further

  18. Gamma radiation measurements and dose rates in commercially-used natural tiling rocks (granites).

    PubMed

    Tzortzis, Michalis; Tsertos, Haralabos; Christofides, Stelios; Christodoulides, George

    2003-01-01

    The gamma radiation in samples of a variety of natural tiling rocks (granites) imported in Cyprus for use in the building industry was measured, employing high-resolution gamma-ray spectroscopy. The rock samples were pulverised, sealed in 1-l plastic Marinelli beakers, and measured in the laboratory with an accumulating time between 10 and 14 h each. From the measured gamma-ray spectra, activity concentrations were determined for (232)Th (range from 1 to 906 Bq kg(-1)), (238)U (from 1 to 588 Bq kg(-1)) and (40)K (from 50 to 1606 Bq kg(-1)). The total absorbed dose rates in air calculated from the concentrations of the three radionuclides ranged from 7 to 1209 nGy h(-1) for full utilization of the materials, from 4 to 605 nGy h(-1) for half utilization and from 2 to 302 nGy h(-1) for one quarter utilization. The total effective dose rates per person indoors were determined to be between 0.02 and 2.97 mSv y(-1) for half utilization of the materials. Applying dose criteria recently recommended by the EU for superficial materials, 25 of the samples meet the exemption dose limit of 0.3 mSv y(-1), two of them meet the upper dose limit of 1 mSv y(-1) and only one clearly exceeds this limit.

  19. A full-dimensional model of ozone forming reaction: the absolute value of the recombination rate coefficient, its pressure and temperature dependencies.

    PubMed

    Teplukhin, Alexander; Babikov, Dmitri

    2016-07-28

    Rigorous calculations of scattering resonances in ozone are carried out for a broad range of rotational excitations. The accurate potential energy surface of Dawes is adopted, and a new efficient method for calculations of ro-vibrational energies, wave functions and resonance lifetimes is employed (which uses hyper-spherical coordinates, the sequential diagonalization/truncation approach, grid optimization and complex absorbing potential). A detailed analysis is carried out to characterize distributions of resonance energies and lifetimes, their rotational/vibrational content and their positions with respect to the centrifugal barrier. Emphasis is on the contribution of these resonances to the recombination process that forms ozone. It is found that major contributions come from localized resonances at energies near the top of the barrier. Delocalized resonances at higher energies should also be taken into account, while very narrow resonances at low energies (trapped far behind the centrifugal barrier) should be treated as bound states. The absolute value of the recombination rate coefficient, its pressure and temperature dependencies are obtained using the energy-transfer model developed in the earlier work. Good agreement with experimental data is obtained if one follows the suggestion of Troe, who argued that the energy transfer mechanism of recombination is responsible only for 55% of the recombination rate (with the remaining 45% coming from the competing chaperon mechanism). PMID:27364351

  20. A full-dimensional model of ozone forming reaction: the absolute value of the recombination rate coefficient, its pressure and temperature dependencies.

    PubMed

    Teplukhin, Alexander; Babikov, Dmitri

    2016-07-28

    Rigorous calculations of scattering resonances in ozone are carried out for a broad range of rotational excitations. The accurate potential energy surface of Dawes is adopted, and a new efficient method for calculations of ro-vibrational energies, wave functions and resonance lifetimes is employed (which uses hyper-spherical coordinates, the sequential diagonalization/truncation approach, grid optimization and complex absorbing potential). A detailed analysis is carried out to characterize distributions of resonance energies and lifetimes, their rotational/vibrational content and their positions with respect to the centrifugal barrier. Emphasis is on the contribution of these resonances to the recombination process that forms ozone. It is found that major contributions come from localized resonances at energies near the top of the barrier. Delocalized resonances at higher energies should also be taken into account, while very narrow resonances at low energies (trapped far behind the centrifugal barrier) should be treated as bound states. The absolute value of the recombination rate coefficient, its pressure and temperature dependencies are obtained using the energy-transfer model developed in the earlier work. Good agreement with experimental data is obtained if one follows the suggestion of Troe, who argued that the energy transfer mechanism of recombination is responsible only for 55% of the recombination rate (with the remaining 45% coming from the competing chaperon mechanism).

  1. Measuring the absolute disintegration rate of a radioactive gas with a moveable endplate discharge counter (MEP) and theoretical calculation of wall effect

    SciTech Connect

    Jaffey, A.H.; Gray, J.; Bentley, W.C.; Lerner, J.L.

    1987-09-01

    A precision built moveable endplate Geiger-Mueller counter was used to measure the absolute disintegration rate of a beta-emitting radioactive gas. A Geiger-Mueller counter used for measuring gaseous radioactivity has <100% counting efficiency owing to two factors: (1) ''end effect,'' due to decreased and distorted fields at the ends where wire-insulator joints are placed, and (2) ''wall effect,'' due to non-ionization by beta particles emitted near to and heading into the wall. The end effect was evaluated by making one end of the counter movable and measuring counting rates at a number of endplate positions. Much of the wall effect was calculated theoretically, based on known data for primary ionization of electrons as a function of energy and gas composition. Corrections were then made for the ''shakeoff'' effect in beta decay and for backscattering of electrons from the counter wall. Measurements and calculations were made for a sample of /sup 85/Kr (beta energy, 0.67 MeV). The wall effect calculation is readily extendable to other beta energies.

  2. Low dose radiation hypersensitivity and clustered DNA damages in human fibroblasts exposed to low dose and dose rate protons or 137CS y-rays

    SciTech Connect

    Bennett P. V.; Bennett, P.V.; Keszenman, D.J.; Johnson, A.M.; Sutherland, B.M.; Wilson, P.F.

    2013-05-14

    Effective radioprotection for human space travelers hinges upon understanding the individual properties of charged particles. A significant fraction of particle radiation astronauts will encounter in space exploratory missions will come from high energy protons in galactic cosmic radiation (GCR) and/or possible exposures to lower energy proton flux from solar particle events (SPEs). These potential exposures present major concerns for NASA and others, in planning and executing long term space exploratory missions. We recently reported cell survival and transformation (acquisition of anchorage-independent growth in soft agar) frequencies in apparently normal NFF-28 primary human fibroblasts exposed to 0-30 cGy of 50MeV, 100MeV (SPE-like), or 1000 MeV (GCR-like) monoenergetic protons. These were modeled after 1989 SPE energies at an SPE-like low dose-rate (LDR) of 1.65 cGy/min or high dose rate (HDR) of 33.3 cGy/min delivered at the NASA Space Radiation Laboratory (NSRL) at BNL.

  3. Real-time tracking of respiratory-induced tumor motion by dose-rate regulation

    NASA Astrophysics Data System (ADS)

    Han-Oh, Yeonju Sarah

    We have developed a novel real-time tumor-tracking technology, called Dose-Rate-Regulated Tracking (DRRT), to compensate for tumor motion caused by breathing. Unlike other previously proposed tumor-tracking methods, this new method uses a preprogrammed dynamic multileaf collimator (MLC) sequence in combination with real-time dose-rate control. This new scheme circumvents the technical challenge in MLC-based tumor tracking, that is to control the MLC motion in real time, based on real-time detected tumor motion. The preprogrammed MLC sequence describes the movement of the tumor, as a function of breathing phase, amplitude, or tidal volume. The irregularity of tumor motion during treatment is handled by real-time regulation of the dose rate, which effectively speeds up or slows down the delivery of radiation as needed. This method is based on the fact that all of the parameters in dynamic radiation delivery, including MLC motion, are enslaved to the cumulative dose, which, in turn, can be accelerated or decelerated by varying the dose rate. Because commercially available MLC systems do not allow the MLC delivery sequence to be modified in real time based on the patient's breathing signal, previously proposed tumor-tracking techniques using a MLC cannot be readily implemented in the clinic today. By using a preprogrammed MLC sequence to handle the required motion, the task for real-time control is greatly simplified. We have developed and tested the pre- programmed MLC sequence and the dose-rate regulation algorithm using lung-cancer patients breathing signals. It has been shown that DRRT can track the tumor with an accuracy of less than 2 mm for a latency of the DRRT system of less than 0.35 s. We also have evaluated the usefulness of guided breathing for DRRT. Since DRRT by its very nature can compensate for breathing-period changes, guided breathing was shown to be unnecessary for real-time tracking when using DRRT. Finally, DRRT uses the existing dose-rate control

  4. Benchmarking of Monte Carlo based shutdown dose rate calculations for applications to JET.

    PubMed

    Petrizzi, L; Batistoni, P; Fischer, U; Loughlin, M; Pereslavtsev, P; Villari, R

    2005-01-01

    The calculation of dose rates after shutdown is an important issue for operating nuclear reactors. A validated computational tool is needed for reliable dose rate calculations. In fusion reactors neutrons induce high levels of radioactivity and presumably high doses. The complex geometries of the devices require the use of sophisticated geometry modelling and computational tools for transport calculations. Simple rule of thumb laws do not always apply well. Two computational procedures have been developed recently and applied to fusion machines. Comparisons between the two methods showed some inherent discrepancies when applied to calculation for the ITER while good agreement was found for a 14 MeV point source neutron benchmark experiment. Further benchmarks were considered necessary to investigate in more detail the reasons for the different results in different cases. In this frame the application to the Joint European Torus JET machine has been considered as a useful benchmark exercise. In a first calculational benchmark with a representative D-T irradiation history of JET the two methods differed by no more than 25%. In another, more realistic benchmark exercise, which is the subject of this paper, the real irradiation history of D-T and D-D campaigns conducted at JET in 1997-98 were used to calculate the shut-down doses at different locations, irradiation and decay times. Experimental dose data recorded at JET for the same conditions offer the possibility to check the prediction capability of the calculations and thus show the applicability (and the constraints) of the procedures and data to the rather complex shutdown dose rate analysis of real fusion devices. Calculation results obtained by the two methods are reported below, comparison with experimental results give discrepancies ranging between 2 and 10. The reasons of that can be ascribed to the high uncertainty on the experimental data and the unsatisfactory JET model used in the calculation. A new

  5. Acute tolerance to rate-decreasing effects of single doses of ethanol.

    PubMed

    Ginsburg, Brett C; Martinez, Gerardo; Friesenhahn, Gregory; Javors, Martin; Lamb, R J

    2008-06-01

    Acute tolerance occurs when behavioral impairment is greater at a given blood ethanol concentration (BAC) on the ascending versus descending limb of the BAC-time curve following administration of a single dose of ethanol, however studies utilizing learned behaviors have not been widely reported. We assessed acute tolerance to single doses of ethanol in five Lewis rats responding under a fixed-ratio (FR8) schedule of food presentation. Response rates for food during 1-min components (ending 2, 4, 11, 18, 33, and 57 min after ethanol administration) were determined, and BAC was measured immediately after each component using a rat breathalyzer. Ethanol (0.4, 0.6, 0.8, and 1.2 g/kg, i.p.) produced dose-related decreases in responding for food that tended to recover over time for all but the highest dose tested. Similarly, dose-related increases in BAC were also observed. Using either an analysis that expressed impairment per unit BAC on the ascending limb versus the descending limb (by assessing the area under the curve (AUC) for behavior and BAC on each limb), the slope of the function that relates the behavioral effect to BAC (each expressed as percent maximum effect), or a variant of the Mellanby method (hysteresis), acute tolerance was observed following a dose of 0.4 g/kg ethanol. Though behavior appeared to recover on the descending limb following higher doses (especially 0.6 and 0.8 g/kg), acute tolerance to these doses was not present. PMID:18328511

  6. In vivo real-time dosimetric verification in high dose rate prostate brachytherapy

    SciTech Connect

    Seymour, Erin L.; Downes, Simon J.; Fogarty, Gerald B.; Izard, Michael A.; Metcalfe, Peter

    2011-08-15

    Purpose: To evaluate the performance of a diode array in the routine verification of planned dose to points inside the rectum from prostate high dose rate (HDR) brachytherapy using a real-time planning system. Methods: A dosimetric study involving 28 patients was undertaken where measured doses received during treatment were compared to those calculated by the treatment planning system (TPS). After the ultrasound imaging required for treatment planning had been recorded, the ultrasound probe was replaced with a geometric replica that contained an 8 mm diameter cylindrical cavity in which a PTW diode array type 9112 was placed. The replica probe was then positioned inside the rectum with the individual diode positions determined using fluoroscopy. Dose was then recorded during the patients' treatment and compared to associated coordinates in the planning system. Results: Factors influencing diode response and experimental uncertainty were initially investigated to estimate the overall uncertainty involved in dose measurements, which was determined to be {+-}10%. Data was acquired for 28 patients' first fractions, 11 patients' second fractions, and 13 patients' third fractions with collection dependent upon circumstances. Deviations between the diode measurements and predicted values ranged from -42% to +35% with 71% of measurements experiencing less than a 10% deviation from the predicted values. If the {+-}10% measurement uncertainty was combined with a tolerated dose discrepancy of {+-}10% then over 95% of the diode results exhibited agreement with the calculated data to within {+-}20%. It must also be noted that when large dose discrepancies were apparent they did not necessarily occur for all five diodes in the one measurement. Conclusions: This technique provided a method that could be utilized to detect gross errors in dose delivery of a real-time prostate HDR plan. Limitations in the detection system used must be well understood if meaningful results are to

  7. Extensive antibiotic prescription rate among hospitalized patients in Uganda: but with frequent missed-dose days

    PubMed Central

    Kiguba, Ronald; Karamagi, Charles; Bird, Sheila M.

    2016-01-01

    Objectives To describe the patterns of systemic antibiotic use and missed-dose days and detail the prescription, dispensing and administration of frequently used hospital-initiated antibiotics among Ugandan inpatients. Methods This was a prospective cohort of consented adult inpatients admitted on the medical and gynaecological wards of the 1790 bed Mulago National Referral Hospital. Results Overall, 79% (603/762; 95% CI: 76%–82%) of inpatients received at least one antibiotic during hospitalization while 39% (300/762; 95% CI: 36%–43%) had used at least one antibiotic in the 4 weeks pre-admission; 1985 antibiotic DDDs, half administered parenterally, were consumed in 3741 inpatient-days. Two-fifths of inpatients who received at least one of the five frequently used hospital-initiated antibiotics (ceftriaxone, metronidazole, ciprofloxacin, amoxicillin and azithromycin) missed at least one antibiotic dose-day (44%, 243/558). The per-day risk of missed antibiotic administration was greatest on day 1: ceftriaxone (36%, 143/398), metronidazole (27%, 67/245), ciprofloxacin (34%, 39/114) and all inpatients who missed at least one dose-day of prescribed amoxicillin and azithromycin. Most patients received fewer doses than were prescribed: ceftriaxone (74%, 273/371), ciprofloxacin (90%, 94/105) and metronidazole (97%, 222/230). Of prescribed doses, only 62% of ceftriaxone doses (1178/1895), 35% of ciprofloxacin doses (396/1130) and 27% of metronidazole doses (1043/3862) were administered. Seven percent (13/188) of patients on intravenous metronidazole and 6% (5/87) on intravenous ciprofloxacin switched to oral route. Conclusions High rates of antibiotic use both pre-admission and during hospitalization were observed, with low parenteral/oral switch of hospital-initiated antibiotics. Underadministration of prescribed antibiotics was common, especially on the day of prescription, risking loss of efficacy and antibiotic resistance. PMID:26945712

  8. Islet Oxygen Consumption Rate (OCR) Dose Predicts Insulin Independence in Clinical Islet Autotransplantation

    PubMed Central

    Papas, Klearchos K.; Bellin, Melena D.; Sutherland, David E. R.; Suszynski, Thomas M.; Kitzmann, Jennifer P.; Avgoustiniatos, Efstathios S.; Gruessner, Angelika C.; Mueller, Kathryn R.; Beilman, Gregory J.; Balamurugan, Appakalai N.; Loganathan, Gopalakrishnan; Colton, Clark K.; Koulmanda, Maria; Weir, Gordon C.; Wilhelm, Josh J.; Qian, Dajun; Niland, Joyce C.; Hering, Bernhard J.

    2015-01-01

    Background Reliable in vitro islet quality assessment assays that can be performed routinely, prospectively, and are able to predict clinical transplant outcomes are needed. In this paper we present data on the utility of an assay based on cellular oxygen consumption rate (OCR) in predicting clinical islet autotransplant (IAT) insulin independence (II). IAT is an attractive model for evaluating characterization assays regarding their utility in predicting II due to an absence of confounding factors such as immune rejection and immunosuppressant toxicity. Methods Membrane integrity staining (FDA/PI), OCR normalized to DNA (OCR/DNA), islet equivalent (IE) and OCR (viable IE) normalized to recipient body weight (IE dose and OCR dose), and OCR/DNA normalized to islet size index (ISI) were used to characterize autoislet preparations (n = 35). Correlation between pre-IAT islet product characteristics and II was determined using receiver operating characteristic analysis. Results Preparations that resulted in II had significantly higher OCR dose and IE dose (p<0.001). These islet characterization methods were highly correlated with II at 6–12 months post-IAT (area-under-the-curve (AUC) = 0.94 for IE dose and 0.96 for OCR dose). FDA/PI (AUC = 0.49) and OCR/DNA (AUC = 0.58) did not correlate with II. OCR/DNA/ISI may have some utility in predicting outcome (AUC = 0.72). Conclusions Commonly used assays to determine whether a clinical islet preparation is of high quality prior to transplantation are greatly lacking in sensitivity and specificity. While IE dose is highly predictive, it does not take into account islet cell quality. OCR dose, which takes into consideration both islet cell quality and quantity, may enable a more accurate and prospective evaluation of clinical islet preparations. PMID:26258815

  9. In vitro RABiT measurement of dose rate effects on radiation induction of micronuclei in human peripheral blood lymphocytes.

    PubMed

    Bertucci, Antonella; Smilenov, Lubomir B; Turner, Helen C; Amundson, Sally A; Brenner, David J

    2016-03-01

    Developing new methods for radiation biodosimetry has been identified as a high-priority need in case of a radiological accident or nuclear terrorist attacks. A large-scale radiological incident would result in an immediate critical need to assess the radiation doses received by thousands of individuals. Casualties will be exposed to different doses and dose rates due to their geographical position and sheltering conditions, and dose rate is one of the principal factors that determine the biological consequences of a given absorbed dose. In these scenarios, high-throughput platforms are required to identify the biological dose in a large number of exposed individuals for clinical monitoring and medical treatment. The Rapid Automated Biodosimetry Tool (RABiT) is designed to be completely automated from the input of blood sample into the machine to the output of a dose estimate. The primary goal of this paper was to quantify the dose rate effects for RABiT-measured micronuclei in vitro in human lymphocytes. Blood samples from healthy volunteers were exposed in vitro to different doses of X-rays to acute and protracted doses over a period up to 24 h. The acute dose was delivered at ~1.03 Gy/min and the low dose rate exposure at ~0.31 Gy/min. The results showed that the yield of micronuclei decreases with decreasing dose rate starting at 2 Gy, whereas response was indistinguishable from that of acute exposure in the low dose region, up to 0.5 Gy. The results showed a linear-quadratic dose-response relationship for the occurrence of micronuclei for the acute exposure and a linear dose-response relationship for the low dose rate exposure. PMID:26791381

  10. In vitro RABiT measurement of dose rate effects on radiation induction of micronuclei in human peripheral blood lymphocytes

    PubMed Central

    Bertucci, Antonella; Smilenov, Lubomir B.; Turner, Helen C.; Amundson, Sally A.; Brenner, David J.

    2016-01-01

    Developing new methods for radiation biodosimetry has been identified as a high priority need in case of a radiological accident or nuclear terrorist attacks. A large-scale radiological incident would result in an immediate critical need to assess the radiation doses received by thousands of individuals. Casualties will be exposed to different doses and dose-rates due to their geographical position and sheltering conditions, and dose-rate is one of the principal factors that determine the biological consequences of a given absorbed dose. In these scenarios high-throughput platforms are required to identify the biological dose in a large number of exposed individuals for clinical monitoring and medical treatment. The RABiT (Rapid Automated Biodosimetry Tool) is designed to be completely automated from the input of blood sample into the machine to the output of a dose estimate. The primary goal of this paper was to quantify the dose-rate effects for RABiT-measured micronuclei in vitro in human lymphocytes. Blood samples from healthy volunteers were exposed in vitro to different doses of X-rays to acute and protracted doses over a period up to 24 hours. The acute dose (ADR) was delivered at ∼1.03Gy/min and the low dose rate (LDR) exposure at ∼0.31Gy/min. The results showed that the yield of micronuclei decreases with decreasing dose-rate starting at 2Gy, whereas response was indistinguishable from that of acute exposure in the low dose region, up to 0.5Gy. The results showed a linear-quadratic dose-response relationship for the occurrence of micronuclei for the acute exposure and a linear dose-response relationship for the low dose-rate exposure. PMID:26791381

  11. The estimation of absorbed dose rates for non-human biota : an extended inter-comparison.

    SciTech Connect

    Batlle, J. V. I.; Beaugelin-Seiller, K.; Beresford, N. A.; Copplestone, D.; Horyna, J.; Hosseini, A.; Johansen, M.; Kamboj, S.; Keum, D.-K.; Kurosawa, N.; Newsome, L.; Olyslaegers, G.; Vandenhove, H.; Ryufuku, S.; Lynch, S. V.; Wood, M. D.; Yu, C.

    2011-05-01

    An exercise to compare 10 approaches for the calculation of unweighted whole-body absorbed dose rates was conducted for 74 radionuclides and five of the ICRP's Reference Animals and Plants, or RAPs (duck, frog, flatfish egg, rat and elongated earthworm), selected for this exercise to cover a range of body sizes, dimensions and exposure scenarios. Results were analysed using a non-parametric method requiring no specific hypotheses about the statistical distribution of data. The obtained unweighted absorbed dose rates for internal exposure compare well between the different approaches, with 70% of the results falling within a range of variation of {+-}20%. The variation is greater for external exposure, although 90% of the estimates are within an order of magnitude of one another. There are some discernible patterns where specific models over- or under-predicted. These are explained based on the methodological differences including number of daughter products included in the calculation of dose rate for a parent nuclide; source-target geometry; databases for discrete energy and yield of radionuclides; rounding errors in integration algorithms; and intrinsic differences in calculation methods. For certain radionuclides, these factors combine to generate systematic variations between approaches. Overall, the technique chosen to interpret the data enabled methodological differences in dosimetry calculations to be quantified and compared, allowing the identification of common issues between different approaches and providing greater assurance on the fundamental dose conversion coefficient approaches used in available models for assessing radiological effects to biota.

  12. The estimation of absorbed dose rates for non-human biota: an extended intercomparison.

    PubMed

    Vives i Batlle, J; Beaugelin-Seiller, K; Beresford, N A; Copplestone, D; Horyna, J; Hosseini, A; Johansen, M; Kamboj, S; Keum, D-K; Kurosawa, N; Newsome, L; Olyslaegers, G; Vandenhove, H; Ryufuku, S; Vives Lynch, S; Wood, M D; Yu, C

    2011-05-01

    An exercise to compare 10 approaches for the calculation of unweighted whole-body absorbed dose rates was conducted for 74 radionuclides and five of the ICRP's Reference Animals and Plants, or RAPs (duck, frog, flatfish egg, rat and elongated earthworm), selected for this exercise to cover a range of body sizes, dimensions and exposure scenarios. Results were analysed using a non-parametric method requiring no specific hypotheses about the statistical distribution of data. The obtained unweighted absorbed dose rates for internal exposure compare well between the different approaches, with 70% of the results falling within a range of variation of ±20%. The variation is greater for external exposure, although 90% of the estimates are within an order of magnitude of one another. There are some discernible patterns where specific models over- or under-predicted. These are explained based on the methodological differences including number of daughter products included in the calculation of dose rate for a parent nuclide; source-target geometry; databases for discrete energy and yield of radionuclides; rounding errors in integration algorithms; and intrinsic differences in calculation methods. For certain radionuclides, these factors combine to generate systematic variations between approaches. Overall, the technique chosen to interpret the data enabled methodological differences in dosimetry calculations to be quantified and compared, allowing the identification of common issues between different approaches and providing greater assurance on the fundamental dose conversion coefficient approaches used in available models for assessing radiological effects to biota. PMID:21113609

  13. The time variation of dose rate artificially increased by the Fukushima nuclear crisis

    PubMed Central

    Hosoda, Masahiro; Tokonami, Shinji; Sorimachi, Atsuyuki; Monzen, Satoru; Osanai, Minoru; Yamada, Masatoshi; Kashiwakura, Ikuo; Akiba, Suminori

    2011-01-01

    A car-borne survey for dose rate in air was carried out in March and April 2011 along an expressway passing northwest of the Fukushima Dai-ichi Nuclear Power Station which released radionuclides starting after the Great East Japan Earthquake on March 11, 2011, and in an area closer to the Fukushima NPS which is known to have been strongly affected. Dose rates along the expressway, i.e. relatively far from the power station were higher after than before March 11, in some places by several orders of magnitude, implying that there were some additional releases from Fukushima NPS. The maximum dose rate in air within the high level contamination area was 36 μGy h−1, and the estimated maximum cumulative external dose for evacuees who came from Namie Town to evacuation sites (e.g. Fukushima, Koriyama and Nihonmatsu Cities) was 68 mSv. The evacuation is justified from the viewpoint of radiation protection. PMID:22355606

  14. The effects of low dose rate irradiation and thermal aging on reactor structural alloys

    NASA Astrophysics Data System (ADS)

    Allen, T. R.; Trybus, C. L.; Cole, J. I.

    As part of the EBR-II reactor materials surveillance program, test samples of fifteen different alloys were placed into EBR-II in 1965. The surveillance (SURV) program was intended to determine property changes in reactor structural materials caused by irradiation and thermal aging. In this work, the effect of low dose rate (approximately 2 × 10 -8 dpa/s) irradiation at 380-410°C and long term thermal aging at 371°C on the properties of 20% cold worked 304 stainless steel, 420 stainless steel, Inconel X750, 304/308 stainless weld material, and 17-4 PH steel are evaluated. Doses of up to 6.8 dpa and thermal aging to 2994 days did not significantly affect the density of these alloys. The strength of 304 SS, X750, 17-4 PH, and 304/308 weld material increased with irradiation. In contrast, the strength of 420 stainless steel decreased with irradiation. Irradiation decreased the impact energy in both Inconel X750 and 17-4 PH steel. Thermal aging decreased the impact energy in 17-4 PH steel and increased the impact energy in Inconel X750. Tensile property comparisons of 304 SURV samples with 304 samples irradiated in EBR-II at a higher dose rate show that the higher dose rate samples had greater increases in strength and greater losses in ductility.

  15. Total-body irradiation and cataract incidence: A randomized comparison of two instantaneous dose rates

    SciTech Connect

    Ozsahin, M.; Belkacemi, Y.; Pene, F.; Dominique, C.; Schwartz, L.H.; Uzal, C.; Lefkopoulos, D.; Gindrey-Vie, B.; Vitu-Loas, L.; Touboul, E. )

    1994-01-15

    To assess the influence of instantaneous total-body irradiation dose rate in hematological malignancies, the authors randomized 157 patients according to different instantaneous dose rates. Patients have undergone a total-body irradiation before bone-marrow transplantation according to two different techniques: Either in one fraction (1000 cGy given to the midplane at the level of L4, and 800 cGy to the lungs) or in six fractions (1200 cGy over 3 consecutive days to the midplane at the level of L4, and 900 cGy to the lungs). Patients were randomized according to two instantaneous dose rates, called LOW and HIGH, in single-dose (6 vs. 15 cGy/min) and fractionated (3 vs. 6 cGy/min) TBI groups; there were 77 cases for the LOW and 80 for the HIGH groups, with 57 patients receiving single-dose (28 LOW, 29 HIGH) and 100 patients receiving fractionated total-body irradiation (49 LOW, 51 HIGH). As of July 1992, 16 of 157 patients developed cataracts after 17 to 46 months, with an estimated incidence of 23% at 5 years. Four of 77 patients in the LOW group, 12 of 80 patients in the HIGH group developed cataracts, with 5-year estimated incidences of 12% and 34%, respectively. Ten of 57 patients in the single-dose group, and 6 of 100 patients in the fractionated group developed cataracts, with 5-year estimated incidences of 39% and 13%, respectively. When the subgroups were considered, in the single-dose group, 3 of 28 LOW patients, and 7 of 29 HIGH patients developed cataracts, with 5-year estimated incidences of 24% and 53%, respectively; in the fractionated group, 1 of 49 LOW patients, and 5 of 51 HIGH patients developed cataracts, with 5-year estimated incidences of 4% and 22%, respectively. There was no statistically significant difference in terms of 5-year estimated cataract incidence between the patients receiving steroids and those not. The instantaneous dose rate was the only independent factor influencing the cataractogenesis. 18 refs., 5 figs., 1 tab.

  16. 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.

  17. Absolute rate constant and O(3P) yield for the O(1D)+N2O reaction in the temperature range 227 K to 719 K

    NASA Astrophysics Data System (ADS)

    Vranckx, S.; Peeters, J.; Carl, S. A.

    2008-10-01

    The absolute rate constant for the reaction that is the major source of stratospheric NOx, O(1D)+N2O → products, has been determined in the temperature range 227 K to 719 K, and, in the temperature range 248 K to 600 K, the fraction of the reaction that yields O(3P). Both the rate constants and product yields were determined using a recently-developed chemiluminescence technique for monitoring O(1D) that allows for higher precision determinations for both rate constants, and, particularly, O(3P) yields, than do other methods. We found the rate constant, kR1, to be essentially independent of temperature between 400 K and 227 K, having a value of (1.37±0.11)×10-10 cm3 s-1, and for temperatures greater than 450 K a marked decrease in rate constant was observed, with a rate constant of only (0.94±0.11)×10-10 cm3 s-1 at 719 K. The rate constants determined over the 227 K 400 K range show very low scatter and are significantly greater, by 20% at room temperature and 15% at 227 K, than the current recommended values. The fraction of O(3P) produced in this reaction was determined to be 0.002±0.002 at 250 K rising steadily to 0.010±0.004 at 600 K, thus the channel producing O(3P) can be entirely neglected in atmospheric kinetic modeling calculations. A further result of this study is an expression of the relative quantum yields as a function of temperature for the chemiluminescence reactions (kCL1)C2H + O(1D) → CH(A) + CO and (kCL2)C2H + O(3P) → CH(A) + CO, both followed by CH(A) → CH(X) + hν, as kCL1(T)/kCL2(T)=(32.8T-3050)/(6.29T+398).

  18. SU-E-J-93: Parametrisation of Dose to the Mucosa of the Anterior Rectal Wall in Transrectal Ultrasound Guided High-Dose-Rate Brachytherapy of the Prostate

    SciTech Connect

    Aitkenhead, A; Hamlett, L; Wood, D; Choudhury, A

    2014-06-01

    Purpose: In high-dose-rate (HDR) brachytherapy of the prostate, radiation is delivered from a number of radioactive sources which are inserted via catheter into the target volume. The rectal mucosa also receives dose during the treatment, which may lead to late toxicity effects. To allow possible links between rectal dose and toxicity to be investigated, suitable methods of parametrising the rectal dose are needed. Methods: During treatment of a series of 95 patients, anatomy and catheter locations were monitored by transrectal ultrasound, and target volume positions were contoured on the ultrasound scan by the therapist. The anterior rectal mucosal wall was identified by contouring the transrectal ultrasound balloon within the ultrasound scan. Source positions and dwell times, along with the dose delivered to the patient were computed using the Oncentra Prostate treatment planning system (TPS). Data for the series of patients were exported from the TPS in Dicom format, and a series of parametrisation methods were developed in a Matlab environment to assess the rectal dose. Results: Contours of the anterior rectal mucosa were voxelised within Matlab to allow the dose to the rectal mucosa to be analysed directly from the 3D dose grid. Dose parametrisations based on dose-surface (DSH) and dose-line (DLH) histograms were obtained. Both lateral and longitudinal extents of the mucosal dose were parametrised using dose-line histograms in the relevant directions. Conclusion: We have developed a series of dose parametrisations for quantifying the dose to the rectal mucosa during HDR prostate brachytherapy which are suitable for future studies investigating potential associations between mucosal dose and late toxicity effects. The geometry of the transrectal probe standardises the rectal anatomy, making this treatment technique particularly suited to studies of this nature.

  19. Analysis of high–dose rate brachytherapy dose distribution resemblance in CyberKnife hypofractionated treatment plans of localized prostate cancer

    SciTech Connect

    Sudahar, H.; Kurup, P.G.G.; Murali, V.; Mahadev, P.; Velmurugan, J.

    2013-01-01

    The present study is to analyze the CyberKnife hypofractionated dose distribution of localized prostate cancer in terms of high–dose rate (HDR) brachytherapy equivalent doses to assess the degree of HDR brachytherapy resemblance of CyberKnife dose distribution. Thirteen randomly selected localized prostate cancer cases treated using CyberKnife with a dose regimen of 36.25 Gy in 5 fractions were considered. HDR equivalent doses were calculated for 30 Gy in 3 fractions of HDR brachytherapy regimen. The D{sub 5%} of the target in the CyberKnife hypofractionation was 41.57 ± 2.41 Gy. The corresponding HDR fractionation (3 fractions) equivalent dose was 32.81 ± 1.86 Gy. The mean HDR fractionation equivalent dose, D{sub 98%}, was 27.93 ± 0.84 Gy. The V{sub 100%} of the prostate target was 95.57% ± 3.47%. The V{sub 100%} of the bladder and the rectum were 717.16 and 79.6 mm{sup 3}, respectively. Analysis of the HDR equivalent dose of CyberKnife dose distribution indicates a comparable resemblance to HDR dose distribution in the peripheral target doses (D{sub 98%} to D{sub 80%}) reported in the literature. However, there is a substantial difference observed in the core high-dose regions especially in D{sub 10%} and D{sub 5%}. The dose fall-off within the OAR is also superior in reported HDR dose distribution than the HDR equivalent doses of CyberKnife.

  20. Simulated Microgravity and Low-Dose/Low-Dose-Rate Radiation Induces Oxidative Damage in the Mouse Brain.

    PubMed

    Mao, Xiao Wen; Nishiyama, Nina C; Pecaut, Michael J; Campbell-Beachler, Mary; Gifford, Peter; Haynes, Kristine E; Becronis, Caroline; Gridley, Daila S

    2016-06-01

    Microgravity and radiation are stressors unique to the spaceflight environment that can have an impact on the central nervous system (CNS). These stressors could potentially lead to significant health risks to astronauts, both acutely during the course of a mission or chronically, leading to long-term, post-mission decrements in quality of life. The CNS is sensitive to oxidative injury due to high concentrations of oxidizable, unsaturated lipids and low levels of antioxidant defenses. The purpose of this study was to evaluate oxidative damage in the brain cortex and hippocampus in a ground-based model for spaceflight, which includes prolonged unloading and low-dose radiation. Whole-body low-dose/low-dose-rate (LDR) gamma radiation using (57)Co plates (0.04 Gy at 0.01 cGy/h) was delivered to 6 months old, mature, female C57BL/6 mice (n = 4-6/group) to simulate the radiation component. Anti-orthostatic tail suspension was used to model the unloading, fluid shift and physiological stress aspects of the microgravity component. Mice were hindlimb suspended and/or irradiated for 21 days. Brains were isolated 7 days or 9 months after irradiation and hindlimb unloading (HLU) for characterization of oxidative stress markers and microvessel changes. The level of 4-hydroxynonenal (4-HNE) protein, an oxidative specific marker for lipid peroxidation, was significantly elevated in the cortex and hippocampus after LDR + HLU compared to controls (P < 0.05). The combination group also had the highest level of nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2) expression compared to controls (P < 0.05). There was a significant decrease in superoxide dismutase (SOD) expression in the animals that received HLU only or combined LDR + HLU compared to control (P < 0.05). In addition, 9 months after LDR and HLU exposure, microvessel densities were the lowest in the combination group, compared to age-matched controls in the cortex (P < 0.05). Our data provide the first evidence

  1. The role of dose rate in radiation cancer risk: evaluating the effect of dose rate at the molecular, cellular and tissue levels using key events in critical pathways following exposure to low LET radiation

    PubMed Central

    Brooks, Antone L.; Hoel, David G.; Preston, R. Julian

    2016-01-01

    Abstract Purpose: This review evaluates the role of dose rate on cell and molecular responses. It focuses on the influence of dose rate on key events in critical pathways in the development of cancer. This approach is similar to that used by the U.S. EPA and others to evaluate risk from chemicals. It provides a mechanistic method to account for the influence of the dose rate from low-LET radiation, especially in the low-dose region on cancer risk assessment. Molecular, cellular, and tissues changes are observed in many key events and change as a function of dose rate. The magnitude and direction of change can be used to help establish an appropriate dose rate effectiveness factor (DREF). Conclusions: Extensive data on key events suggest that exposure to low dose-rates are less effective in producing changes than high dose rates. Most of these data at the molecular and cellular level support a large (2–30) DREF. In addition, some evidence suggests that doses delivered at a low dose rate decrease damage to levels below that observed in the controls. However, there are some data human and mechanistic data that support a dose-rate effectiveness factor of 1. In summary, a review of the available molecular, cellular and tissue data indicates that not only is dose rate an important variable in understanding radiation risk but it also supports the selection of a DREF greater than one as currently recommended by ICRP (2007) and BEIR VII (NRC/NAS 2006). PMID:27266588

  2. Absolute rate constant and O(3P) yield for the O(1D)+N2O reaction in the temperature range 227 K to 719 K

    NASA Astrophysics Data System (ADS)

    Vranckx, S.; Peeters, J.; Carl, S. A.

    2008-05-01

    We have determined, in the temperature range 227 K to 719 K, the absolute rate constant for the reaction O(1D)+N2O → products and, in the temperature range 248 K to 600 K, the fraction of the reaction that yields O(3P). Both the rate constants and product yields were determined using a recently-developed chemiluminescence technique for monitoring O(1D) that allows for higher precision determinations for both rate constants, and, particularly, O(3P) yields, than do other methods. We found the rate constant, kR1, to be essentially independent of temperature between 400 K and 227 K, having a value of (1.37±0.09)×10-10 cm3 s-1. For temperatures greater than 450 K a marked decrease in value was observed, with a rate constant of only (0.94±0.11)×10-10 cm3 s-1 at 719 K. The rate constants determined over the 227 K-400 K range show very low scatter and are significantly greater, by 20% at room temperature and by 15% at 227 K, than the current recommended values. The fraction of O(3P) produced in this reaction was determined to be 0.002±0.002 at 250 K rising steadily to 0.010±0.004 at 600 K, thus the channel producing O(3P) can be entirely neglected in atmospheric kinetic modeling calculations. A further result of this study is an expression of the relative quantum yields as a function of temperature for the chemiluminescence reactions (kCL1) C2H+O(1D) → CH(A)+CO and (kCL2) C2H+O(3P) → CH(A)+CO, both followed by CH(A) → CH(X)+hν, as kCL1(T)/kCL2(T)=(32.8T-3050)/(6.29T+398).

  3. Dose rate effect on micronuclei induction in human blood lymphocytes exposed to single pulse and multiple pulses of electrons.

    PubMed

    Acharya, Santhosh; Bhat, N N; Joseph, Praveen; Sanjeev, Ganesh; Sreedevi, B; Narayana, Y

    2011-05-01

    The effects of single pulses and multiple pulses of 7 MV electrons on micronuclei (MN) induction in cytokinesis-blocked human peripheral blood lymphocytes (PBLs) were investigated over a wide range of dose rates per pulse (instantaneous dose rate). PBLs were exposed to graded doses of 2, 3, 4, 6, and 8 Gy of single electron pulses of varying pulse widths at different dose rates per pulse, ranging from 1 × 10(6) Gy s(-1) to 3.2 × 10(8) Gy s(-1). Different dose rates per pulse were achieved by changing the dose per electron pulse by adjusting the beam current and pulse width. MN yields per unit absorbed dose after irradiation with single electron pulses were compared with those of multiple pulses of electrons. A significant decrease in the MN yield with increasing dose rates per pulse was observed, when dose was delivered by a single electron pulse. However, no reduction in the MN yield was observed when dose was delivered by multiple pulses of electrons. The decrease in the yield at high dose rates per pulse suggests possible radical recombination, which leads to decreased biological damage. Cellular response to the presence of very large numbers of chromosomal breaks may also alter the damage.

  4. Evaluation of continuous low dose rate versus acute single high dose rate radiation combined with oncolytic viral therapy for prostate cancer

    PubMed Central

    LIU, CHUNYAN; ZHANG, YONGGANG; LIU, MINZHI MAGGIE; ZHOU, HAOMING; CHOWDHURY, WASIM H.; LUPOLD, SHAWN E.; DEWEESE, TED L.; RODRIGUEZ, RONALD

    2011-01-01

    Purpose Conditionally Replicative Adenovirus (CRAd) has been previously demonstrated to augment the activity of radiation, resulting in synergy of cell kill. However, previous models combining radiation with CRAd have not focused on the methods of radiation delivery. Materials and methods We model the combination of a novel prostate-specific CRAd, Ad5 PSE/PBN E1A-AR (Ad5: adenovirus 5; PSE: prostate-specific enhancer; PBN: rat probasin promoter; E1A: early region 1A; AR: androgen receptor), with radiation delivered both acutely and continuously, in an effort to better mimic the potential clinical modes of prostate cancer radiotherapy. Results We demonstrate that pre-treatment of cells with acute single high dose rate (HDR) radiation 24 hours prior to viral infection results in significantly enhanced viral replication and virus-mediated cell death. In addition, this combination causes increased level of γ-H2AX (Phosphorylated histone protein H2AX on serine 139), a marker of double-stranded DNA damage and an indirect measure of nuclear fragmentation. In contrast, continuous low dose rate (LDR) radiation immediately following infection of the same CRAd results in no enhancement of viral replication, and only additive effects in virus-mediated cell death. Conclusions These data provide the first direct assessment of the real-time impact of radiation on viral replication and the first comparison of the effect of radiation delivery on the efficacy of CRAd virotherapy. Our data demonstrate substantial differences in CRAd efficacy based on the mode of radiation delivery. PMID:20201650

  5. In vivo measurements for high dose rate brachytherapy with optically stimulated luminescent dosimeters

    SciTech Connect

    Sharma, Renu; Jursinic, Paul A.

    2013-07-15

    Purpose: To show the feasibility of clinical implementation of OSLDs for high dose-rate (HDR) in vivo dosimetry for gynecological and breast patients. To discuss how the OSLDs were characterized for an Ir-192 source, taking into account low gamma energy and high dose gradients. To describe differences caused by the dose calculation formalism of treatment planning systems.Methods: OSLD irradiations were made using the GammaMedplus iX Ir-192 HDR, Varian Medical Systems, Milpitas, CA. BrachyVision versions 8.9 and 10.0, Varian Medical Systems, Milpitas, CA, were used for calculations. Version 8.9 used the TG-43 algorithm and version 10.0 used the Acuros algorithm. The OSLDs (InLight Nanodots) were characterized for Ir-192. Various phantoms were created to assess calculated and measured doses and the angular dependence and self-absorption of the Nanodots. Following successful phantom measurements, patient measurements for gynecological patients and breast cancer patients were made and compared to calculated doses.Results: The OSLD sensitivity to Ir-192 compared to 6 MV is between 1.10 and 1.25, is unique to each detector, and changes with accumulated dose. The measured doses were compared to those predicted by the treatment planning system and found to be in agreement for the gynecological patients to within measurement uncertainty. The range of differences between the measured and Acuros calculated doses was -10%-14%. For the breast patients, there was a discrepancy of -4.4% to +6.5% between the measured and calculated doses at the skin surface when the Acuros algorithm was used. These differences were within experimental uncertainty due to (random) error in the location of the detector with respect to the treatment catheter.Conclusions: OSLDs can be successfully used for HDR in vivo dosimetry. However, for the measurements to be meaningful one must account for the angular dependence, volume-averaging, and the greater sensitivity to Ir-192 gamma rays than to 6 MV x

  6. Computation of dose rate at flight altitudes during ground level enhancements no. 69, 70 and 71

    NASA Astrophysics Data System (ADS)

    Mishev, A. L.; Adibpour, F.; Usoskin, I. G.; Felsberger, E.

    2015-01-01

    A new numerical model of estimating and monitoring the exposure of personnel due to secondary cosmic radiation onboard aircraft, in accordance with radiation safety standards as well as European and national regulations, has been developed. The model aims to calculate the effective dose at flight altitude (39,000 ft) due to secondary cosmic radiation of galactic and solar origin. In addition, the model allows the estimation of ambient dose equivalent at typical commercial airline altitudes in order to provide comparison with reference data. The basics, structure and function of the model are described. The model is based on a straightforward full Monte Carlo simulation of the cosmic ray induced atmospheric cascade. The cascade simulation is performed with the PLANETOCOSMICS code. The flux of secondary particles, namely neutrons, protons, gammas, electrons, positrons, muons and charged pions is calculated. A subsequent conversion of the particle fluence into the effective dose or ambient dose equivalent is performed as well as a comparison with reference data. An application of the model is demonstrated, using a computation of the effective dose rate at flight altitude during the ground level enhancements of 20 January 2005, 13 December 2006 and 17 May 2012.

  7. Assessment of ambient gamma dose rate around a prospective uranium mining area of South India - A comparative study of dose by direct methods and soil radioactivity measurements

    NASA Astrophysics Data System (ADS)

    Karunakara, N.; Yashodhara, I.; Sudeep Kumara, K.; Tripathi, R. M.; Menon, S. N.; Kadam, S.; Chougaonkar, M. P.

    Indoor and outdoor gamma dose rates were evaluated around a prospective uranium mining region - Gogi, South India through (i) direct measurements using a GM based gamma dose survey meter, (ii) integrated measurement days using CaSO4:Dy based thermo luminescent dosimeters (TLDs), and (iii) analyses of 273 soil samples for 226Ra, 232Th, and 40K activity concentration using HPGe gamma spectrometry. The geometric mean values of indoor and outdoor gamma dose rates were 104 nGy h-1 and 97 nGy h-1, respectively with an indoor to outdoor dose ratio of 1.09. The gamma dose rates and activity concentrations of 226Ra, 232Th, and 40K varied significantly within a small area due to the highly localized mineralization of the elements. Correlation study showed that the dose estimated from the soil radioactivity is better correlated with that measured directly using the portable survey meter, when compared to that obtained from TLDs. This study showed that in a region having localized mineralization in situ measurements using dose survey meter provide better representative values of gamma dose rates.

  8. Incorporating dose-rate effects in Markov radiation cell survival models.

    PubMed

    Sachs, R K; Hlatky, L; Hahnfeldt, P; Chen, P L

    1990-11-01

    Markov models for the survival of cells subjected to ionizing radiation take stochastic fluctuations into account more systematically than do non-Markov counterparts. Albright's Markov RMR (repair-misrepair) model (Radiat. Res. 118, 1-20, 1989) and Curtis's Markov LPL (lethal-potentially lethal) model [in Quantitative Mathematical Models in Radiation Biology (J. Kiefer, Ed.), pp. 127-146. Springer, New York, 1989], which assume acute irradiation, are here generalized to finite dose rates. Instead of treating irradiation as an instantaneous event we introduce an irradiation period T and analyze processes during the interval T as well as afterward. Albright's RMR transition matrix is used throughout for computing the time development of repair and misrepair. During irradiation an additional matrix is added to describe the evolving radiation damage. Albright's and Curtis's Markov models are recovered as limiting cases by taking T----0 with total dose fixed; the opposite limit, of low dose rates, is also analyzed. Deviations from Poisson behavior in the statistical distributions of lesions are calculated. Other continuous-time Markov chain models ("compartmental models") are discussed briefly, for example, models which incorporate cell proliferation and saturable repair models. It is found that for low dose rates the Markov RMR and LPL models give lower survivals compared to the original non-Markov versions. For acute irradiation and high doses, the Markov models predict higher survivals. In general, theoretical extrapolations which neglect some random fluctuations have a systematic bias toward overoptimism when damage to irradiated tumors is compared with damage to surrounding tissues. PMID:2247602

  9. Effects of radiation types and dose rates on selected cable-insulating materials

    NASA Astrophysics Data System (ADS)

    Hanisch, F.; Maier, P.; Okada, S.; Schönbacher, H.

    A series of radiation tests have been carried out on halogen-free cable-insulating and cable-sheathing materials comprising commercial LDPE, EPR, EVA and SIR compounds. samples were irradiated at five different radiation sources, e.g. a nuclear reactor, fuel elements, a 60Co source, and in the stray radiation field of high-energy proton and electron accelerators at CERN and DESY. The integrated doses were within 50-5000 kGy and the dose rates within 10 mGy/s-70 Gy/s. Tensile tests and gel-fraction measurements were carried out. The results confirm that LDPEs are very sensitive to long-term ageing effects, and that important errors exceeding an order of magnitude can be made when assessing radiation damage by accelerated tests. On the other hand, well-stabilized LDPEs and the cross-linked rubber compounds do not show large dose-rate effects for the values given above. Furthermore, the interpretation of the elongation-at-break data and their relation to gel-fraction measurements show that radiation damage is related to the total absorbed dose irrespective of the different radiation types used in this experiment.

  10. Car-borne survey of natural background gamma dose rate in Çanakkale region, Turkey.

    PubMed

    Turhan, S; Arıkan, I H; Oğuz, F; Özdemir, T; Yücel, B; Varinlioğlu, A; Köse, A

    2012-01-01

    Natural background gamma radiation was measured along roads in the environs of Çanakkale region by using a car-borne spectrometer system with a plastic gamma radiation detector. In addition, activity concentrations of ²³⁸U, ²²⁶Ra, ²³²Th and ⁴⁰K in soil samples from the Çanakkale region were determined by using a gamma spectrometer with an HPGe detector. A total of 92,856 data of the background gamma dose rate were collected for the Çanakkale region. The background gamma dose rate of the Çanakkale region was mapped using ArcGIS software, applying the geostatistical inverse distance-weighted method. The average and population-weighted average of the gamma dose are 55.4 and 40.6 nGy h⁻¹, respectively. The corresponding average annual effective dose to the public ranged from 26.6 to 96.8 µSv. PMID:21362693

  11. IUdR polymers for combined continuous low-dose rate and high-dose rate sensitization of experimental human malignant gliomas.

    PubMed

    Yuan, X; Dillehay, L E; Williams, J R; Shastri, V R; Williams, J A

    2001-04-20

    Local polymeric delivery enhances IUdR radiosensitization of human malignant gliomas (MG). The combined low-dose rate (LDR) (0.03 Gy/h) and fractionated high-dose rate (HDR) treatments result in cures of experimental MGs. To enhance efficacy, we combined polymeric IUdR delivery, LDR, and HDR for treatments of both subcutaneous and intracranial MGs. In vitro: Cells (U251 MG) were trypsinized and replated in triplicate 1 day prior to LDR irradiation in media either without (control) or with 10 microM IUdR. After 72 hr, LDR irradiation cells were acutely irradiated (1.1 Gy/min) with increasing (0, 1.25, 2.5, 5.0, or 10 Gy) single doses. Implantable IUdR polymers [(poly(bis(p-carboxyphenoxy)-propane) (PCPP): sebaic acid (PCPP:SA), 20:80] (50% loading; 10 mg) were synthesized. In vivo: For flank vs. intracranial tumors, mice had 6 x 10(6) subcutaneous vs. 2 x 10(5) intracranial cells. For intracranial or subcutaneous MGs, mice had intratumoral blank (empty) vs. IUdR polymer treatments. One day after implantation, mice had immediate external LDR (3 cGy/h x 3 days total body irradiation) or HDR (2 Gy BID x 4 days to tumor site) or concurrent treatments. For the in vitro IUdR treatments, LDR resulted in a striking increase in cell-killing when combined with HDR. For the in vivo LDR treatments of flank tumors, the growth delay was greater for the IUdR vs. blank polymer treatments. For the combined LDR and HDR, the IUdR treatments resulted in a dramatic decrease in tumor volumes. On day 60 the log V/V0 were -1.7 +/- 0.22 for combined LDR + HDR + IUdR polymer (P < 0.05 vs. combined LDR + HDR + blank polymer). Survival for the intracranial controls was 22.9 +/- 1.2 days. For the blank polymer + LDR vs. blank polymer + LDR + HDR treatments, survival was 25.3 +/- 1.7 (P = NS) vs. 48.1 +/- 3.5 days (P < 0.05). For IUdR polymer + LDR treatment survival was 27.3 +/- 2.3 days (P = NS). The most striking improvement in survival followed the IUdR polymer + LDR + HDR treatment: 66

  12. A METHODOLOGY FOR DETERMINING THE DOSE RATE FOR BOUNDING MASS LIMITS IN A 9977 PACKAGING

    SciTech Connect

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

    2012-05-24

    The Small Gram Quantity (SGQ) concept is based on the understanding that the hazards associated with the shipment of a radioactive material are directly proportional to its mass. This study describes a methodology that estimates the acceptable masses for several neutron and gamma emitting isotopes that can be shipped in a 9977 Package compliant with the Title 10 of the Code of Federal Regulations, Part 71 (10CFR71) external radiation level limits. 10CFR71.33 states that a shipping application identifies the radioactive and fissile materials at their maximum quantity and provides an evaluation demonstrating compliance with the external radiation standards. Since rather small amounts of some isotopes emit sufficiently strong radiation to produce a large external dose rate, quantifying of the dose rate for a proposed content is a challenging issue for the SGQ approach. It is essential to quantify external radiation levels from several common gamma and neutron sources that can be safely placed in a specific packaging, to ensure compliance with federal regulations. A methodology was established for determining the dose rate for bounding mass limits for a set of isotopes in the Model 9977 Shipping Package. Calculations were performed to estimate external radiation levels using the MCNP radiation transport code to develop a set of response multipliers (Green's functions) for 'dose per source particle' for each neutron and photon spectral group. The source spectrum from one gram of each isotope was folded with the response multipliers to generate the dose rate per gram of each isotope in the 9977 shipping package and its associated shielded containers. The maximum amount of a single isotope that could be shipped within the regulatory limits for dose rate at the surface was determined. For a package containing a mixture of isotopes, the acceptability for shipment can be determined by a sum of fractions approach. Furthermore, the results of this analysis can be easily

  13. Characteristics and verification of a car-borne survey system for dose rates in air: KURAMA-II.

    PubMed

    Tsuda, S; Yoshida, T; Tsutsumi, M; Saito, K

    2015-01-01

    The car-borne survey system KURAMA-II, developed by the Kyoto University Research Reactor Institute, has been used for air dose rate mapping after the Fukushima Dai-ichi Nuclear Power Plant accident. KURAMA-II consists of a CsI(Tl) scintillation detector, a GPS device, and a control device for data processing. The dose rates monitored by KURAMA-II are based on the G(E) function (spectrum-dose conversion operator), which can precisely calculate dose rates from measured pulse-height distribution even if the energy spectrum changes significantly. The characteristics of KURAMA-II have been investigated with particular consideration to the reliability of the calculated G(E) function, dose rate dependence, statistical fluctuation, angular dependence, and energy dependence. The results indicate that 100 units of KURAMA-II systems have acceptable quality for mass monitoring of dose rates in the environment.

  14. Influence of clouds on the cosmic radiation dose rate on aircraft.

    PubMed

    Pazianotto, Maurício T; Federico, Claudio A; Cortés-Giraldo, Miguel A; Pinto, Marcos Luiz de A; Gonçalez, Odair L; Quesada, José Manuel M; Carlson, Brett V; Palomo, Francisco R

    2014-10-01

    Flight missions were made in Brazilian territory in 2009 and 2011 with the aim of measuring the cosmic radiation dose rate incident on aircraft in the South Atlantic Magnetic Anomaly and to compare it with Monte Carlo simulations. During one of these flights, small fluctuations were observed in the vicinity of the aircraft with formation of Cumulonimbus clouds. Motivated by these observations, in this work, the authors investigated the relationship between the presence of clouds and the neutron flux and dose rate incident on aircraft using computational simulation. The Monte Carlo simulations were made using the MCNPX and Geant4 codes, considering the incident proton flux at the top of the atmosphere and its propagation and neutron production through several vertically arranged slabs, which were modelled according to the ISO specifications. PMID:24925902

  15. Dose Rate Calculations for the 2-MCO/2-DHLW Waste Package

    SciTech Connect

    G. Radulescu

    2000-10-03

    The objective of this calculation is to determine the dose rates on the external surfaces of the waste package (WP) containing two Hanford defense high-level waste (DHLW) glass canisters and two Hanford multi-canister overpacks (MCO). Each MCO is loaded with the N Reactor spent nuclear fuel (SNF). The information provided by the sketches attached to this calculation is that of the potential design for the WP type considered in this calculation. The scope of this calculation is limited to reporting dose rates averaged over segments of the WP radial and axial surfaces and of surfaces 1 m and 2 m from the WP. The results of this calculation will be used to assess the shielding performance of the 2-MC012-DHLW WP engineering design.

  16. Influence of clouds on the cosmic radiation dose rate on aircraft.

    PubMed

    Pazianotto, Maurício T; Federico, Claudio A; Cortés-Giraldo, Miguel A; Pinto, Marcos Luiz de A; Gonçalez, Odair L; Quesada, José Manuel M; Carlson, Brett V; Palomo, Francisco R

    2014-10-01

    Flight missions were made in Brazilian territory in 2009 and 2011 with the aim of measuring the cosmic radiation dose rate incident on aircraft in the South Atlantic Magnetic Anomaly and to compare it with Monte Carlo simulations. During one of these flights, small fluctuations were observed in the vicinity of the aircraft with formation of Cumulonimbus clouds. Motivated by these observations, in this work, the authors investigated the relationship between the presence of clouds and the neutron flux and dose rate incident on aircraft using computational simulation. The Monte Carlo simulations were made using the MCNPX and Geant4 codes, considering the incident proton flux at the top of the atmosphere and its propagation and neutron production through several vertically arranged slabs, which were modelled according to the ISO specifications.

  17. Improved aseptic technique can reduce variable contamination rates of ward-prepared parenteral doses.

    PubMed

    Austin, P; Elia, M

    2013-02-01

    Aseptic techniques are required to manipulate central venous lines and prepare intravenous doses. This study aimed to examine whether different aseptic techniques affect the contamination rates of intravenous doses prepared on hospital wards. Syringes of tryptic soy broth test media prepared by one pharmacy operator and five nurses were assessed for contamination. The pharmacy operator achieved lower contamination than the nurses (0.0% vs 6.9%; Fisher's exact test, P < 0.001). Contamination differed significantly between nurses (∼2-17% of syringes; binary logistic regression, P = 0.018). In conclusion, appropriate training and experience in aseptic techniques should be embedded into routine clinical practice to reduce contamination rates.

  18. Open-source hardware and software and web application for gamma dose rate network operation.

    PubMed

    Luff, R; Zähringer, M; Harms, W; Bleher, M; Prommer, B; Stöhlker, U

    2014-08-01

    The German Federal Office for Radiation Protection operates a network of about 1800 gamma dose rate stations as a part of the national emergency preparedness plan. Each of the six network centres is capable of operating the network alone. Most of the used hardware and software have been developed in-house under open-source license. Short development cycles and close cooperation between developers and users ensure robustness, transparency and fast maintenance procedures, thus avoiding unnecessary complex solutions. This also reduces the overall costs of the network operation. An easy-to-expand web interface has been developed to make the complete system available to other interested network operators in order to increase cooperation between different countries. The interface is also regularly in use for education during scholarships of trainees supported, e.g. by the 'International Atomic Energy Agency' to operate a local area dose rate monitoring test network.

  19. Lymphoid cell kinetics under continuous low dose-rate gamma irradiation: A comparison study

    NASA Technical Reports Server (NTRS)

    Foster, B. R.

    1975-01-01

    A comparison study was conducted of the effects of continuous low dose-rate gamma irradiation on cell population kinetics of lymphoid tissue (white pulp) of the mouse spleen with findings as they relate to the mouse thymus. Experimental techniques employed included autoradiography and specific labeling with tritiated thymidine (TdR-(h-3)). The problem studied involved the mechanism of cell proliferation of lymphoid tissue of the mouse spleen and thymus under the stress of continuous irradiation at a dose rate of 10 roentgens (R) per day for 105 days (15 weeks). The aim was to determine whether or not a steady state or near-steady state of cell population could be established for this period of time, and what compensatory mechanisms of cell population were involved.

  20. Dose rate dependence of the speciation of neptunium in irradiated solutions of nitric acid

    SciTech Connect

    Precek, M.; Paulenova, A.; Mincher, B.J.; Mezyk, S.P.

    2013-07-01

    The effects of radiation on the redox speciation of neptunium are of interest due to their impact on the performance of separation of neptunium from highly radioactive solutions of dissolved used nuclear fuel. In this study, the influence of dose rate change from 0.4 kGy/h to 6 kGy/h was examined during irradiation of solutions of initially hexavalent 2.0-2.5 mM neptunium in nitric acid of two different concentrations (0.5 and 1 M). Results indicate that the immediate radiolytic steady-state concentration of neptunium(V) were depressed and its initial radiolytic yield was up to 2-times lower (in 1 M HNO{sub 3} solutions)during irradiations with the higher dose rate. The finding is explained on the basis of the enhancement of the role of oxidizing radicals during the radiolytic process. (authors)

  1. Mathematical Modeling of Radiocesium Migration and Air Dose Rate Changes in Eastern Fukushima Prefecture

    NASA Astrophysics Data System (ADS)

    Kitamura, A.; Sakuma, K.; Kurikami, H.; Malins, A.; Okumura, M.; Itakura, M.; Yamada, S.; Machida, M.

    2015-12-01

    Radioactive cesium that was deposited over Fukushima Prefecture after the accident at the Fukushima Daiichi nuclear power plant station is one of the major concerns regarding health physics today. Its migration is primarily by soil erosion and sediment transport within surface water during times of heavy rainfall and flooding. In order to predict the future distribution of radioactive cesium and resulting air dose rate at any location in Fukushima, we have integrated a number of mathematical models covering different time and spatial scales. In this presentation we report our overall scheme of prediction starting from sediment and radioactive cesium movement and resulting long term air dose rate changes. Specifically, we present simulation results of sediment movement and radioactive cesium migration using semi-empirical and physics based watershed models, and that of sediment and radioactive cesium behavior in a dam reservoir using one and two dimensional river simulation models. The model's results are compared with ongoing field monitoring.

  2. Terrestrial gamma radiation dose rate in Ryukyu Islands, subtropical region of Japan.

    PubMed

    Furukawa, M; Kina, S; Shiroma, M; Shiroma, Y; Masuda, N; Motomura, D; Hiraoka, H; Fujioka, S; Kawakami, T; Yasuda, Y; Arakawa, K; Fukahori, K; Jyunicho, M; Ishikawa, S; Ohomoto, T; Shingaki, R; Akata, N; Zhuo, W; Tokonami, S

    2015-11-01

    In order to explain the distribution of natural radiation level in the Asia, in situ measurements of dose rate in air due to terrestrial gamma radiation have been conducted in a total of 21 islands that belong to Ryukyu Islands (Ryukyu Archipelago), subtropical rejoin of southwest Japan. Car-borne surveys have also been carried out in Okinawa-jima, the biggest island of the archipelago. Based on the results for these measurements, arithmetic mean, the maximum and the minimum of the dose rates at 1 m in height from the unpaved soil ground in the archipelago were estimated to be 47, 165 and 8 nGy h(-1), respectively. A comparative study of car-borne data obtained prior to and subsequent to the 2011 Fukushima nuclear accident, as for Okinawa-jima, indicated that the nuclear accident has no impact on the environmental radiation at the present time. PMID:26065703

  3. Factors affecting quality for beta dose rate measurements using ISO 6980 series I reference sources

    SciTech Connect

    Burns, R.E. Jr.; O`Brien, J.M. Jr.

    1993-12-31

    Atlan-Tech, Inc. has performed several calibrations of ISO 6980 Series 1 reference beta sources over the past two to three years. There were many problems encountered in attempting to compare the results of these calibrations with those from other laboratories, indicating the need for more standardization in the methodology employed for the measurement of the absorbed dose rate from ISO 6980 Series 1 reference beta sources. This document describes some of the problems encountered in attempting to intercompare results of beta dose-rate measurements. It proposes some solutions in an attempt to open a dialogue among facilities using reference beta standards for the purpose of promoting better measurement quality assurance through data intercomparison.

  4. Dose-rate and the reciprocity law: TL response of Ge-doped SiO 2 optical fibers at therapeutic radiation doses

    NASA Astrophysics Data System (ADS)

    Abdul Rahman, A. T.; Nisbet, A.; Bradley, D. A.

    2011-10-01

    An investigation has been made on commercially available Ge-doped SiO 2 optical fibers as a novel thermoluminescence system for radiotherapy dosimetry. This dosimeter has previously been shown by the group to provide sensitive dosimetry over a wide range of electron and photon dose, suitable for the needs of radiotherapy. In addition the optical fiber offers small physical size (125 μm diameter) and hence high spatial resolution. The reciprocity between thermoluminescence (TL) yield of Ge-doped SiO 2 optical fibers and dose has been investigated for fixed radiation dose for a range of photon and electron dose rates. For electron beams of nominal energies in the range of 9-20 MeV, we have investigated the TL response of these fibers for dose rates between 100 and 1000 cGy min -1. For photon beams of nominal energies in the range of 6-15 MV, we have used dose rates of 100-600 cGy min -1. Reproducibility and fading at fixed absorbed dose (3 Gy) and dose rate for the optical fibers were also investigated. At fixed dose rates, the TL optical fibers were found to produce a flat TL yield within 4% (1σ) and 3% (1σ) for electron and photon beams, respectively. The optical fibers demonstrated good reproducibility (±1.5%), low residual signal for a readout temperature of 300 ºC and negligible fading. A weak dependence on dose-rate has been observed in the range of 3.4-3.9% for electrons (with an associated uncertainty of 4%) and 2.4-2.9% for photons (with an associated uncertainty of <4%). For electron and photon energies we note a consistent trend towards lower response in the TL yield of between 3.4-3.9% and 2.4-2.7%, respectively, at the higher dose rates in comparison with the response at lower dose rates. In addition we note an appreciable systematic energy dependence for both electron and photon beams. It is important to take such factors into account for providing precise and accurate radiotherapy dosimetry. It is also apparent that the optical fibers can be re

  5. Physical mechanisms contributing to enhanced bipolar gain degradation at low dose rates

    SciTech Connect

    Fleetwood, D.M.; Reber, R.A. Jr.; Winokur, P.S. ); Kosier, S.L.; Schrimpf, R.D.; Wei, A. . ECE Dept.); Nowlin, R.N. ); DeLaus, M. ); Combs, W.E. ); Pease, R.L. )

    1994-12-01

    The authors have performed capacitance-voltage (C-V) and thermally-stimulated-current (TSC) measurements on non-radiation-hard MOS capacitors simulating screen oxides of modern bipolar technologies. For 0-V irradiation of [approximately]25 C, the net trapped-positive-charge density (N[sub ox]) inferred from midgap C-V shifts is [approximately]25--40% greater for low-dose-rate (< 10 rad(SiO[sub 2])/s) than for high-dose-rate (> 100 rad(SiO[sub 2])/s) exposure. Device modeling shows that such a difference in screen-oxide N[sub ox] is enough to account for the enhanced low-rate gain degradation often observed in bipolar devices, due to the [approximately] exp(N[sub ox][sup 2]) dependence of the excess base current. At the higher rates, TSC measurements reveal a [approximately]10% decrease in trapped-hole density over low rates. Also, at high rates, up to [approximately]2.5-times as many trapped holes are compensated by electrons in border traps than at low rates for these devices and irradiation conditions. Both the reduction in trapped-hole density and increased charge compensation reduce the high-rate midgap shift. A physical model is developed which suggests that both effects are caused by time-dependent space charge in the bulk of these soft oxides associated with slowly transporting and/or metastably trapped holes (e.g., in E[delta][prime] centers). On the basis of this model, bipolar transistors and screen-oxide capacitors were irradiated at 60 C at 200 rad(SiO[sub 2])/s in a successful effort to match low-rate damage. these surprising results provide insight into enhanced low-rate bipolar gain degradation and suggest potentially promising new approaches to bipolar and BiCMOS hardness assurance for space applications.

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

    PubMed

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

    2015-10-13

    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

  7. 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

  8. Dose Rate Calucaltion for the DHL W/DOE SNF Codisposal Waste Package

    SciTech Connect

    G. Radulescu

    2000-02-12

    The purpose of this calculation is to determine the surface dose rates of the short codisposal waste package (WP) of defense high-level waste (DHLW) and TRIGA (Training, Research, Isotopes, General Atomics) spent nuclear fuel (SNF). The WP contains the TRIGA SNF, in a standardized 18-in. DOE (U.S. Department of Energy) SNF canister, and five 3-m-long Savannah River Site (SRS) DHLW pour glass canisters, which surround the DOE SNF canister.

  9. Radioactivity and gamma-dose rates observed at the Morungaba granites, Southeastern Brazil.

    PubMed

    Lucas, Fabio de Oliveira; Ribeiro, Fernando Brenha

    2013-07-01

    A ground gamma-ray survey was conducted over part of a large granitic body located near the city of Campinas, eastern São Paulo State, Brazil. The dominant rock types are K-feldspar porphyries-rich granites, porphyritic biotite and hornblend-bearing granites, fine to medium-grained monzogranites and medium to gross grained, biotite and muscovite-bearing monzogranites. The radioactive element distribution reflects local geology, in part re-worked by weathering, and the most radioactive rocks are the K-feldspar-rich granites. The rate of the absorbed dose by the air reflects the integrated effects of the radioactive elements distribution. Most of the observed values vary between 67 and 130 nGy h(-1) and with localised spots with the absorbed dose rate values up to 193 nGy h(-1) and low values of ∼25 nGy h(-1). The mean air absorbed dose rate for the studied area is 77 nGy h(-1).

  10. Statistical approaches to forecast gamma dose rates by using measurements from the atmosphere.

    PubMed

    Jeong, Hyo-Joon; Hwang, Won-Tae; Kim, Eun-Han; Han, Moon-Hee

    2008-01-01

    In this paper, the results obtained by inter-comparing several statistical techniques for estimating gamma dose rates, such as an exponential moving average model, a seasonal exponential smoothing model and an artificial neural networks model, are reported. Seven years of gamma dose rates data measured in Daejeon City, Korea, were divided into two parts to develop the models and validate the effectiveness of the generated predictions by the techniques mentioned above. Artificial neural networks model shows the best forecasting capability among the three statistical models. The reason why the artificial neural networks model provides a superior prediction to the other models would be its ability for a non-linear approximation. To replace the gamma dose rates when missing data for an environmental monitoring system occurs, the moving average model and the seasonal exponential smoothing model can be better because they are faster and easier for applicability than the artificial neural networks model. These kinds of statistical approaches will be helpful for a real-time control of radio emissions or for an environmental quality assessment.

  11. Radiation Dose-Rate Effects on Gene Expression in a Mouse Biodosimetry Model

    PubMed Central

    Paul, Sunirmal; Smilenov, Lubomir B.; Elliston, Carl D.; Amundson, Sally A.

    2015-01-01

    In the event of a nuclear accident or radiological terrorist attack, there will be a pressing need for biodosimetry to triage a large, potentially exposed population and to assign individuals to appropriate treatment. Exposures from fallout are likely, resulting in protracted dose delivery that would, in turn, impact the extent of injury. Biodosimetry approaches that can distinguish such low-dose-rate (LDR) exposures from acute exposures have not yet been developed. In this study, we used the C57BL/6 mouse model in an initial investigation of the impact of low-dose-rate delivery on the transcriptomic response in blood. While a large number of the same genes responded to LDR and acute radiation exposures, for many genes the magnitude of response was lower after LDR exposures. Some genes, however, were differentially expressed (P < 0.001, false discovery rate < 5%) in mice exposed to LDR compared with mice exposed to acute radiation. We identified a set of 164 genes that correctly classified 97% of the samples in this experiment as exposed to acute or LDR radiation using a support vector machine algorithm. Gene expression is a promising approach to radiation biodosimetry, enhanced greatly by this first demonstration of its potential for distinguishing between acute and LDR exposures. Further development of this aspect of radiation biodosimetry, either as part of a complete gene expression biodosimetry test or as an adjunct to other methods, could provide vital triage information in a mass radiological casualty event. PMID:26114327

  12. Gamma radiation and dose rate investigations on the Adriatic islands of magmatic origin.

    PubMed

    Petrinec, Branko; Franić, Zdenko; Leder, Nenad; Tsabaris, Christos; Bituh, Tomislav; Marović, Gordana

    2010-06-01

    Natural radioactivity of Middle-Adriatic Sea islands and islets was measured. Gamma spectrometric measurements, both in situ and in laboratory, as well as radon measurements in the seawater were performed. Activity concentrations and the associated dose rates due to naturally occurring (232)Th, (238)U and (40)K radioisotopes were determined. Dose rates calculated from in situ gamma spectrometry are in correlation with dose rates calculated from activity concentrations measured in collected samples of pebbles and rocks. In situ gamma ray spectrometry in the seawater has been performed, showing activity concentration of 220 and 240 Bq m(-3) for (214)Bi and (214)Pb, respectively due to the presence of magmatic rocks in the seabed. The radium equivalent activity varied from 13 to 53 Bq kg(-1). These values are lower than the limit values, indicating that the radiation hazard is not significant. The highest mean activity concentrations of naturally occurring radionuclides in rock samples collected were found on the islands of magmatic origin. PMID:20085897

  13. Dose-rate distribution of {sup 32}P-glass microspheres for intra-arterial brachytherapy

    SciTech Connect

    Guimaraes, Carla C.; Moralles, Mauricio; Sene, Frank F.; Martinelli, Jose R.

    2010-02-15

    Purpose: The intra-arterial administration of radioactive glass microspheres is an alternative therapy option for treating primary hepatocellular carcinoma, the main cause of liver cancer death, and metastatic liver cancer, another important kind of cancer induced in the liver. The technique involves the administration of radioactive microspheres in the hepatic artery, which are trapped preferentially in the tumor. Methods: In this work the GEANT4 toolkit was used to calculate the radial dose-rate distributions in water from {sup 32}P-loaded glass microspheres and also from {sup 90}Y-loaded glass microspheres. To validate the toolkit for this application, the authors compared the dose-rate distribution of {sup 32}P and {sup 90}Y point sources in water with data from the International Commission on Radiation Units and Measurements report 72. Results: Tables of radial dose-rate distributions are provided for practical use in brachytherapy planning with these microspheres. Conclusions: The simulations with the microspheres show that the shape of the beta ray energy spectra with respect to the {sup 32}P and {sup 90}Y sources is significantly modified by the glass matrix.

  14. Benchmarking of MCNP for calculating dose rates at an interim storage facility for nuclear waste.

    PubMed

    Heuel-Fabianek, Burkhard; Hille, Ralf

    2005-01-01

    During the operation of research facilities at Research Centre Jülich, Germany, nuclear waste is stored in drums and other vessels in an interim storage building on-site, which has a concrete shielding at the side walls. Owing to the lack of a well-defined source, measured gamma spectra were unfolded to determine the photon flux on the surface of the containers. The dose rate simulation, including the effects of skyshine, using the Monte Carlo transport code MCNP is compared with the measured dosimetric data at some locations in the vicinity of the interim storage building. The MCNP data for direct radiation confirm the data calculated using a point-kernel method. However, a comparison of the modelled dose rates for direct radiation and skyshine with the measured data demonstrate the need for a more precise definition of the source. Both the measured and the modelled dose rates verified the fact that the legal limits (<1 mSv a(-1)) are met in the area outside the perimeter fence of the storage building to which members of the public have access. Using container surface data (gamma spectra) to define the source may be a useful tool for practical calculations and additionally for benchmarking of computer codes if the discussed critical aspects with respect to the source can be addressed adequately. PMID:16381760

  15. High dose rate endorectal brachytherapy as a neoadjuvant treatment for patients with resectable rectal cancer.

    PubMed

    Vuong, T; Devic, S; Podgorsak, E

    2007-11-01

    In the era of total mesorectal surgery, the issue of radiation toxicity is raised. A novel endocavitary brachytherapy technique was tested as a neoadjuvant treatment for patients with resectable rectal cancer. The objectives of the study were to evaluate the treatment-related toxicity and effects on local recurrence. A dose of 26 Gy was prescribed to the gross tumour volume and intramesorectal deposits seen on magnetic resonance imaging and given over four daily treatments, using the high dose rate delivery system followed by surgery 6-8 weeks later. The study included 93 T3, four T4 and three T2 tumours. Acute proctitis of grade 2 was observed in all patients, but one required transfusion. At a median follow-up time of 60 months, the 5-year actual local recurrence rate was 5%, disease-free survival was 65%, and overall survival was 70%. High dose rate endorectal brachytherapy seems to prevent local recurrence and has a favourable toxicity pattern compared with external beam radiotherapy. PMID:17714925

  16. Remote Sensing of Radiation Dose Rate by a Robot for Outdoor Usage

    NASA Astrophysics Data System (ADS)

    Kobayashi, T.; Doi, K.; Kanematsu, H.; Utsumi, Y.; Hashimoto, R.; Takashina, T.

    2013-04-01

    In the present paper, the design and prototyping of a telemetry system, in which GPS, camera, and scintillation counter were mounted on a crawler type traveling vehicle, were conducted for targeting outdoor usage such as school playground. As a result, the crawler type traveling vehicle can be operated smoothly in the school grounds of brick and asphalt. The results were as follows: (1) It was confirmed that the crawler type traveling vehicle can be operated smoothly in the school grounds of brick and asphalt (running speed: 17[m/min]). (2) It was confirmed that the location information captured by GPS is visible on the Google map, and that the incorporation of video information is also possible to play. (3)A radiation dose rate of 0.09[μSv / h] was obtained in the ground. The value is less than the 1/40 ([3.8μSv / h]) allowable radiation dose rate for children in Fukushima Prefecture.(4)As a further work, modifying to program traveling, the measurement of the distribution of the radiation dose rate in a school of Fukushima Prefecture, and class delivery on radiation measurement will be carried out.

  17. Impact of small MU/segment and dose rate on delivery accuracy of volumetric-modulated arc therapy (VMAT).

    PubMed

    Huang, Long; Zhuang, Tingliang; Mastroianni, Anthony; Djemil, Toufik; Cui, Taoran; Xia, Ping

    2016-05-08

    Volumetric-modulated arc therapy (VMAT) plans may require more control points (or segments) than some of fixed-beam IMRT plans that are created with a limited number of segments. Increasing number of control points in a VMAT plan for a given prescription dose could create a large portion of the total number of segments with small number monitor units (MUs) per segment. The purpose of this study is to investigate the impact of the small number MU/segment on the delivery accuracy of VMAT delivered with various dose rates. Ten patient datasets were planned for hippocampus sparing for whole brain irradiation. For each dataset, two VMAT plans were created with maximum dose rates of 600 MU/min (the maximum field size of 21 × 40 cm2) and 1000 MU/min (the maximum field size of 15 × 15 cm2) for a daily dose of 3 Gy. Without reoptimization, the daily dose of these plans was purposely reduced to 1.5 Gy and 1.0 Gy while keeping the same total dose. Using the two dose rates and three different daily doses, six VMAT plans for each dataset were delivered to a physical phantom to investigate how the changes of dose rate and daily doses impact on delivery accuracy. Using the gamma index, we directly compared the delivered planar dose profiles with the reduced daily doses (1.5 Gy and 1.0 Gy) to the delivered planar dose at 3 Gy daily dose, delivered at dose rate of 600 MU/min and 1000 MU/min, respectively. The average numbers of segments with MU/segment ≤ 1 were 35 ± 8, 87 ± 6 for VMAT-600 1.5 Gy, VMAT-600 1 Gy plans, and 30 ± 7 and 42 ± 6 for VMAT-1000 1.5 Gy and VMAT-1000 1 Gy plans, respectively. When delivered at 600 MU/min dose rate, the average gamma index passing rates (1%/1 mm criteria) of comparing delivered 1.5 Gy VMAT planar dose profiles to 3.0 Gy VMAT delivered planar dose profiles was 98.28% ± 1.66%, and the average gamma index passing rate of comparing delivered 1.0 Gy VMAT planar dose to 3.0 Gy VMAT delivered planar dose was 83.75% ± 4.86%. If using 2%/2mm

  18. Effect of Remediation Parameters on in-Air Ambient Dose Equivalent Rates When Remediating Open Sites with Radiocesium-contaminated Soil.

    PubMed

    Malins, Alex; Kurikami, Hiroshi; Kitamura, Akihiro; Machida, Masahiko

    2016-10-01

    Calculations are reported for ambient dose equivalent rates [H˙*(10)] at 1 m height above the ground surface before and after remediating radiocesium-contaminated soil at wide and open sites. The results establish how the change in H˙*(10) upon remediation depends on the initial depth distribution of radiocesium within the ground, on the size of the remediated area, and on the mass per unit area of remediated soil. The remediation strategies considered were topsoil removal (with and without recovering with a clean soil layer), interchanging a topsoil layer with a subsoil layer, and in situ mixing of the topsoil. The results show the ratio of the radiocesium components of H˙*(10) post-remediation relative to their initial values (residual dose factors). It is possible to use the residual dose factors to gauge absolute changes in H˙*(10) upon remediation. The dependency of the residual dose factors on the number of years elapsed after fallout deposition is analyzed when remediation parameters remain fixed and radiocesium undergoes typical downward migration within the soil column. PMID:27575348

  19. Effect of Remediation Parameters on in-Air Ambient Dose Equivalent Rates When Remediating Open Sites with Radiocesium-contaminated Soil.

    PubMed

    Malins, Alex; Kurikami, Hiroshi; Kitamura, Akihiro; Machida, Masahiko

    2016-10-01

    Calculations are reported for ambient dose equivalent rates [H˙*(10)] at 1 m height above the ground surface before and after remediating radiocesium-contaminated soil at wide and open sites. The results establish how the change in H˙*(10) upon remediation depends on the initial depth distribution of radiocesium within the ground, on the size of the remediated area, and on the mass per unit area of remediated soil. The remediation strategies considered were topsoil removal (with and without recovering with a clean soil layer), interchanging a topsoil layer with a subsoil layer, and in situ mixing of the topsoil. The results show the ratio of the radiocesium components of H˙*(10) post-remediation relative to their initial values (residual dose factors). It is possible to use the residual dose factors to gauge absolute changes in H˙*(10) upon remediation. The dependency of the residual dose factors on the number of years elapsed after fallout deposition is analyzed when remediation parameters remain fixed and radiocesium undergoes typical downward migration within the soil column.

  20. Application of the dose rate spectroscopy to the dose-to-curie conversion method using a NaI(Tl) detector

    NASA Astrophysics Data System (ADS)

    JI, Young-Yong; Chung, Kun Ho; Kim, Chang-Jong; kang, Mun Ja; Park, Sang Tae

    2015-01-01

    Dose rate spectroscopy is a very useful method to directly calculate the individual dose rate from the converted energy spectrum for the dose rate using the G-factor which is related to the used detector response function. A DTC conversion method for the estimation of the radioactivity based on the measured dose rate from the radioactive materials can then be modified into a simple equation using the dose rate spectroscopy. In order to make the method validation of the modified DTC conversion method, experimental verifications using a 3″φx3″ NaI(Tl) detector were conducted at the simple geometry of the point source located onto a detector and more complex geometries which mean the assay of the simulated radioactive material. In addition, the linearity about the results from the modified DTC conversion method was also estimated by increasing the distance between source positions and a detector to confirm the method validation in the energy, dose rate, and distance range of the gamma nuclides.

  1. Absolute rate coefficients over extended temperature ranges and mechanisms of the CF(X(2)Pi) reactions with F(2), Cl(2) and O(2).

    PubMed

    Vetters, B; Dils, B; Nguyen, T L; Vereecken, L; Carl, S A; Peeters, J

    2009-06-01

    The absolute rate coefficients of the reactions of the carbyne-radical CF(X(2)Pi, nu = 0) with O(2), F(2) and Cl(2) have been measured over extended temperature ranges, using pulsed-laser photodissociation-laser-induced fluorescence (PLP-LIF) techniques. The CF(X(2)Pi) radicals were generated by KrF excimer laser 2-photon photolysis of CF(2)Br(2) at 248 nm and the real-time exponential decays of CF(X(2)Pi, nu = 0) at varying coreactant concentrations, in large excess, were monitored by LIF (A(2)Sigma(+), nu' = 1 <-- X(2)Pi, nu'' = 0 transition). The experimental bimolecular rate coefficients of the CF(X(2)Pi) reactions with F(2) and Cl(2) can be described by simple Arrhenius expressions: k(F2)(295-408 K) = (1.5 +/- 0.2) x 10(-11) exp[-(370 +/- 40)K/T] cm(3) molecule(-1) s(-1); and k(Cl2)(295-392 K) = (6.1 +/- 2.1) x 10(-12) exp[+(280 +/- 120)K/T]. The k(F2)(T) and k(Cl2)(T) results can be rationalized in terms of direct halogen-atom abstraction reactions in which the radical character of CF dominates; a quantum chemical CBS-Q//BHandHLYP/6-311G(d,p) study confirms that the ground state reactants CF(X(2)Pi) + F(2)(X(1)Sigma) connect directly with the ground-state products CF(2)(X(1)A(1)) + F((2)P) via a nearly barrierless F-atom abstraction route. The rate coefficient of CF(X(2)Pi) + O(2) can be represented by a two-term Arrhenius expression: k(O2)(258-780 K) = 1.1 x 10(-11) exp(-850 K/T) + 2.3 x 10(-13) exp(500 K/T), with a standard deviation of 5%. The first term dominates at higher temperatures T and the second at lower T where a negative temperature dependence is observed (<290 K). Quantum chemical computations at the CBS-QB3 and CCSD(T)/aug-cc-pVDZ levels of theory show that the k(O2)(T) behaviour is consistent with a change of the dominant rate-determining mechanism from a carbyne-type insertion into the O-O bond at high T to a radical-radical combination at low T.

  2. Operational specification and forecasting advances for Dst, LEO thermospheric densities, and aviation radiation dose and dose rate

    NASA Astrophysics Data System (ADS)

    Tobiska, W.; Knipp, D. J.; Burke, W. J.; Bouwer, D.; Bailey, J. J.; Hagan, M. P.; Didkovsky, L. V.; Garrett, H. B.; Bowman, B. R.; Gannon, J. L.; Atwell, W.; Blake, J. B.; Crain, W.; Rice, D.; Schunk, R. W.; Fulgham, J.; Bell, D.; Gersey, B.; Wilkins, R.; Fuschino, R.; Flynn, C.; Cecil, K.; Mertens, C. J.; Xu, X.; Crowley, G.; Reynolds, A.; Azeem, S. I.; Wiley, S.; Holland, M.; Malone, K.

    2013-12-01

    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 space environment domains that are affected by space weather, the magnetosphere, thermosphere, and even troposphere are key regions that are affected. Space Environment Technologies (SET) has developed and is producing innovative space weather applications. Key operational systems for providing timely information about the effects of space weather on these domains are SET's Magnetosphere Alert and Prediction System (MAPS), LEO Alert and Prediction System (LAPS), and Automated Radiation Measurements for Aviation Safety (ARMAS) system. MAPS provides a forecast Dst index out to 6 days through the data-driven, redundant data stream Anemomilos algorithm. Anemomilos uses observational proxies for the magnitude, location, and velocity of solar ejecta events. This forecast index is used by satellite operations to characterize upcoming geomagnetic storms, for example. LAPS is the SET fully redundant operational system providing recent history, current epoch, and forecast solar and geomagnetic indices for use in operational versions of the JB2008 thermospheric density model. The thermospheric densities produced by that system, driven by the LAPS data, are forecast to 72-hours to provide the global mass densities for satellite operators. ARMAS is a project that has successfully demonstrated the operation of a micro dosimeter on aircraft to capture the real-time radiation environment due to Galactic Cosmic Rays and Solar Energetic Particles. The dose and dose-rates are captured on aircraft, downlinked in real-time via the Iridium satellites, processed on the ground, incorporated into the most recent NAIRAS global radiation climatology data runs, and made available to end users via the web and smart phone apps. ARMAS provides the 'weather' of the radiation environment to improve air-crew and passenger safety

  3. Operational specification and forecasting advances for Dst, LEO thermospheric densities, and aviation radiation dose and dose rate

    NASA Astrophysics Data System (ADS)

    Tobiska, W. Kent

    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 space environment domains that are affected by space weather, the magnetosphere, thermosphere, and even troposphere are key regions that are affected. Space Environment Technologies (SET) has developed and is producing innovative space weather applications. Key operational systems for providing timely information about the effects of space weather on these domains are SET’s Magnetosphere Alert and Prediction System (MAPS), LEO Alert and Prediction System (LAPS), and Automated Radiation Measurements for Aviation Safety (ARMAS) system. MAPS provides a forecast Dst index out to 6 days through the data-driven, redundant data stream Anemomilos algorithm. Anemomilos uses observational proxies for the magnitude, location, and velocity of solar ejecta events. This forecast index is used by satellite operations to characterize upcoming geomagnetic storms, for example. In addition, an ENLIL/Rice Dst prediction out to several days has also been developed and will be described. LAPS is the SET fully redundant operational system providing recent history, current epoch, and forecast solar and geomagnetic indices for use in operational versions of the JB2008 thermospheric density model. The thermospheric densities produced by that system, driven by the LAPS data, are forecast to 72-hours to provide the global mass densities for satellite operators. ARMAS is a project that has successfully demonstrated the operation of a micro dosimeter on aircraft to capture the real-time radiation environment due to Galactic Cosmic Rays and Solar Energetic Particles. The dose and dose-rates are captured on aircraft, downlinked in real-time via the Iridium satellites, processed on the ground, incorporated into the most recent NAIRAS global radiation climatology data runs, and made available to end users via the web and

  4. Vertical distribution of radiation dose rates in the water of a brackish lake in Aomori Prefecture, Japan.

    PubMed

    Ohtsuka, Yoshihito; Iyogi, Takashi; Ueda, Shinji; Hisamatsu, Shun'ichi

    2015-11-01

    Seasonal radiation dose rates were measured with glass dosemeters housed in watertight cases at various depths in the water of Lake Obuchi, a brackish lake in Aomori Prefecture, Japan, during fiscal years 2011-2013 to assess the background external radiation dose to aquatic biota in the lake. The mean radiation dose in the surface water of the lake was found to be 27 nGy h(-1), which is almost the same as the absorption dose rate due to cosmic ray reported in the literature. Radiation dose rates decreased exponentially with water depth down to a depth of 1 m above the bottom sediment. In the water near the sediment, the dose rate increased with depth owing to the emission of γ-rays from natural radionuclides in the sediment.

  5. Global radiation damage at 300 and 260 K with dose rates approaching 1 MGy s−1

    PubMed Central

    Warkentin, Matthew; Badeau, Ryan; Hopkins, Jesse B.; Mulichak, Anne M.; Keefe, Lisa J.; Thorne, Robert E.

    2012-01-01

    Global radiation damage to 19 thaumatin crystals has been measured using dose rates from 3 to 680 kGy s−1. At room temperature damage per unit dose appears to be roughly independent of dose rate, suggesting that the timescales for important damage processes are less than ∼1 s. However, at T = 260 K approximately half of the global damage manifested at dose rates of ∼10 kGy s−1 can be outrun by collecting data at 680 kGy s−1. Appreciable sample-to-sample variability in global radiation sensitivity at fixed dose rate is observed. This variability cannot be accounted for by errors in dose calculation, crystal slippage or the size of the data sets in the assay. PMID:22281741

  6. Global radiation damage at 300 and 260 K with dose rates approaching 1 MGy s[superscript -1

    SciTech Connect

    Warkentin, Matthew; Badeau, Ryan; Hopkins, Jesse B.; Mulichak, Anne M.; Keefe, Lisa J.; Thorne, Robert E.

    2012-02-27

    Global radiation damage to 19 thaumatin crystals has been measured using dose rates from 3 to 680 kGy s{sup -1}. At room temperature damage per unit dose appears to be roughly independent of dose rate, suggesting that the timescales for important damage processes are less than {approx}1 s. However, at T = 260 K approximately half of the global damage manifested at dose rates of {approx}10 kGy s{sup -1} can be outrun by collecting data at 680 kGy s{sup -1}. Appreciable sample-to-sample variability in global radiation sensitivity at fixed dose rate is observed. This variability cannot be accounted for by errors in dose calculation, crystal slippage or the size of the data sets in the assay.

  7. Global radiation damage at 300 and 260 K with dose rates approaching 1 MGy s{sup −1}

    SciTech Connect

    Warkentin, Matthew; Badeau, Ryan; Hopkins, Jesse B.; Mulichak, Anne M.; Keefe, Lisa J.; Thorne, Robert E.

    2012-02-01

    Approximately half of global radiation damage to thaumatin crystals can be outrun at 260 K if data are collected in less than 1 s. Global radiation damage to 19 thaumatin crystals has been measured using dose rates from 3 to 680 kGy s{sup −1}. At room temperature damage per unit dose appears to be roughly independent of dose rate, suggesting that the timescales for important damage processes are less than ∼1 s. However, at T = 260 K approximately half of the global damage manifested at dose rates of ∼10 kGy s{sup −1} can be outrun by collecting data at 680 kGy s{sup −1}. Appreciable sample-to-sample variability in global radiation sensitivity at fixed dose rate is observed. This variability cannot be accounted for by errors in dose calculation, crystal slippage or the size of the data sets in the assay.

  8. Analysis of Potassium in Bricks--Determining the Dose Rate from {sup 40}K for Thermoluminescence Dating

    SciTech Connect

    Musilek, Ladislav; Polach, Tomas; Trojek, Tomas

    2008-08-07

    Thermoluminescence (TL) dating is based on accumulating the natural radiation dose in the material of a dated artefact (brick, pottery, etc.), and comparing the dose accumulated during the lifetime of the object with the dose rate within the sample collected for TL measurement. Determining the dose rate from natural radionuclides in materials is one of the most important and most difficult parts of the technique. The most important radionuclides present are usually nuclides of the uranium and thorium decay series and {sup 40}K. An analysis of the total potassium concentration enables us to determine the {sup 40}K content effectively, and from this it is possible to calculate the dose rate originating from this radiation source. X-ray fluorescence (XRF) analysis can be used to determine the potassium concentration in bricks rapidly and efficiently. The procedure for analysing potassium, examples of results of dose rate calculation and possible sources of error are described here.

  9. Automatic optimisation of gamma dose rate sensor networks: The DETECT Optimisation Tool

    NASA Astrophysics Data System (ADS)

    Helle, K. B.; Müller, T. O.; Astrup, P.; Dyve, J. E.

    2014-05-01

    Fast delivery of comprehensive information on the radiological situation is essential for decision-making in nuclear emergencies. Most national radiological agencies in Europe employ gamma dose rate sensor networks to monitor radioactive pollution of the atmosphere. Sensor locations were often chosen using regular grids or according to administrative constraints. Nowadays, however, the choice can be based on more realistic risk assessment, as it is possible to simulate potential radioactive plumes. To support sensor planning, we developed the DETECT Optimisation Tool (DOT) within the scope of the EU FP 7 project DETECT. It evaluates the gamma dose rates that a proposed set of sensors might measure in an emergency and uses this information to optimise the sensor locations. The gamma dose rates are taken from a comprehensive library of simulations of atmospheric radioactive plumes from 64 source locations. These simulations cover the whole European Union, so the DOT allows evaluation and optimisation of sensor networks for all EU countries, as well as evaluation of fencing sensors around possible sources. Users can choose from seven cost functions to evaluate the capability of a given monitoring network for early detection of radioactive plumes or for the creation of dose maps. The DOT is implemented as a stand-alone easy-to-use JAVA-based application with a graphical user interface and an R backend. Users can run evaluations and optimisations, and display, store and download the results. The DOT runs on a server and can be accessed via common web browsers; it can also be installed locally.

  10. Terrestrial gamma radiation dose rates (TGRD) from surface soil in Negeri Sembilan, Malaysia

    NASA Astrophysics Data System (ADS)

    Norbani, Nor Eliana; Abdullah Salim, Nazaratul Ashifa; Saat, Ahmad; Hamzah, Zaini; Ramli, Ahmad Termizi; Wan Idris, Wan Mohd Rizlan; Jaafar, Mohd Zuli; Bradley, David A.; Abdul Rahman, Ahmad Taufek

    2014-11-01

    Baseline data on background radiation levels allows for future assessment of possible changes in natural radionuclide concentrations, either as a result of geological processes or radioactive contamination. We have measured terrestrial gamma radiation dose-rates (TGRD) from surface soils throughout accessible areas in the Peninsular Malaysia state of Negeri Sembilan (NS). Dose rate measurements were carried out using a NaI (TI) scintillation survey meter, encompassing 1708 locations, covering about 73% of the 6645 km2 of the land area in NS. This has allowed development of a TGRD contour map, plotted using WinSurf software. The range of measured TGRD was from 71±3 nGy/h up to 1000±11 nGy/h. The greatest measured TGRD was obtained in an area covered by soil types originating from igneous rock of granitic formations, while the least value of TGRD was observed in an area covered by limestone composed of calcite mineral, mostly found near river and coastal areas. Mean values of TGRD across the seven districts of NS ranged from 244±7 nGy/h to 458±13 nGy/h, the global mean being 330±8 nGy/h compared to a mean value of 92 nGy/h and 59 nGy/h for Malaysia and the world, respectively. The average annual dose from such terrestrial gamma radiation dose-rates to an individual residing in NS, assuming a tropical rural setting, is estimated to be 0.96 mSv per year.

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

    PubMed

    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. These

  12. 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

  13. Determination of the Absorbed Dose Rate to Water for the 18-mm Helmet of a Gamma Knife

    SciTech Connect

    Chung, Hyun-Tai; Park, Youngho; Hyun, Sangil; Choi, Yongsoo; Kim, Gi Hong; Kim, Dong Gyu; Chun, Kook Jin

    2011-04-01

    Purpose: To measure the absorbed dose rate to water of {sup 60}Co gamma rays of a Gamma Knife Model C using water-filled phantoms (WFP). Methods and Materials: Spherical WFP with an equivalent water depth of 5, 7, 8, and 9 cm were constructed. The dose rates at the center of an 18-mm helmet were measured in an 8-cm WFP (WFP-3) and two plastic phantoms. Two independent measurement systems were used: one was calibrated to an air kerma (Set I) and the other was calibrated to the absorbed dose to water (Set II). The dose rates of WFP-3 and the plastic phantoms were converted to dose rates for an 8-cm water depth using the attenuation coefficient and the equivalent water depths. Results: The dose rate measured at the center of WFP-3 using Set II was 2.2% and 1.0% higher than dose rates measured at the center of the two plastic phantoms. The measured effective attenuation coefficient of Gamma Knife photon beam in WFPs was 0.0621 cm{sup -1}. After attenuation correction, the difference between the dose rate at an 8-cm water depth measured in WFP-3 and dose rates in the plastic phantoms was smaller than the uncertainty of the measurements. Conclusions: Systematic errors related to the characteristics of the phantom materials in the dose rate measurement of a Gamma Knife need to be corrected for. Correction of the dose rate using an equivalent water depth and attenuation provided results that were more consistent.

  14. Combined methodology for estimating dose rates and health effects from exposure to radioactive pollutants

    SciTech Connect

    Dunning, D.E. Jr.; Leggett, R.W.; Yalcintas, M.G.

    1980-12-01

    The work described in the report is basically a synthesis of two previously existing computer codes: INREM II, developed at the Oak Ridge National Laboratory (ORNL); and CAIRD, developed by the Environmental Protection Agency (EPA). The INREM II code uses contemporary dosimetric methods to estimate doses to specified reference organs due to inhalation or ingestion of a radionuclide. The CAIRD code employs actuarial life tables to account for competing risks in estimating numbers of health effects resulting from exposure of a cohort to some incremental risk. The combined computer code, referred to as RADRISK, estimates numbers of health effects in a hypothetical cohort of 100,000 persons due to continuous lifetime inhalation or ingestion of a radionuclide. Also briefly discussed in this report is a method of estimating numbers of health effects in a hypothetical cohort due to continuous lifetime exposure to external radiation. This method employs the CAIRD methodology together with dose conversion factors generated by the computer code DOSFACTER, developed at ORNL; these dose conversion factors are used to estimate dose rates to persons due to radionuclides in the air or on the ground surface. The combination of the life table and dosimetric guidelines for the release of radioactive pollutants to the atmosphere, as required by the Clean Air Act Amendments of 1977.

  15. PACKAGING CERTIFICATION PROGRAM METHODOLOGY FOR DETERMINING DOSE RATES FOR SMALL GRAM QUANTITIES IN SHIPPING PACKAGINGS

    SciTech Connect

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

    2012-05-09

    The Small Gram Quantity (SGQ) concept is based on the understanding that small amounts of hazardous materials, in this case radioactive materials (RAM), are significantly less hazardous than large amounts of the same materials. This paper describes a methodology designed to estimate an SGQ for several neutron and gamma emitting isotopes that can be shipped in a package compliant with 10 CFR Part 71 external radiation level limits regulations. These regulations require packaging for the shipment of radioactive materials, under both normal and accident conditions, to perform the essential functions of material containment, subcriticality, and maintain external radiation levels within the specified limits. By placing the contents in a helium leak-tight containment vessel, and limiting the mass to ensure subcriticality, the first two essential functions are readily met. Some isotopes emit sufficiently strong photon radiation that small amounts of material can yield a large dose rate outside the package. Quantifying the dose rate for a proposed content is a challenging issue for the SGQ approach. It is essential to quantify external radiation levels from several common gamma and neutron sources that can be safely placed in a specific packaging, to ensure compliance with federal regulations. The Packaging Certification Program (PCP) Methodology for Determining Dose Rate for Small Gram Quantities in Shipping Packagings provides bounding shielding calculations that define mass limits compliant with 10 CFR 71.47 for a set of proposed SGQ isotopes. The approach is based on energy superposition with dose response calculated for a set of spectral groups for a baseline physical packaging configuration. The methodology includes using the MCNP radiation transport code to evaluate a family of neutron and photon spectral groups using the 9977 shipping package and its associated shielded containers as the base case. This results in a set of multipliers for 'dose per particle' for

  16. On the use of pulsed reduced dose rate for improvement of the therapeutic ratio

    NASA Astrophysics Data System (ADS)

    Rasmussen, Karl H., V.

    This work demonstrates three related aspects of the efficacy, delivery, and verification of pulsed reduced dose rate radiotherapy (PRDR). PRDR is a method of irradiation designed to minimize radiation-related toxicities in patients undergoing reirradiation for loco-regional reoccurrence of glioblastoma. PRDR uses 0.2GyX10fx daily doses delivered over a 30-minute time span. Under PRDR treatments, a subset of patients have had an unexpectedly positive response to treatment. It was a primary goal of this project to determine if low-dose hyper-radiosensitivity was a contributor to the increased radio-response from these patients. This was done through the use of human T98G glioma and HT29 colorectal cells, and V79.379-A Chinese hamster fibroblasts with drug inhibition of the p53 and PI3K pathways. Radiation was delivered with a medical linear accelerator in either 2Gy acute doses or through PRDR. Methods used to analyze the effect of these techniques included clonogenic assay, flow cytometry, and western blots. Comparison of survival ratios demonstrated no decrease in efficacy for either the standard T98G or HT29 cell lines when using PRDR as compared to an acute dose. T98G with PI3K inhibition and V79.397-A cells demonstrated a decreased efficacy of treatment using PRDR relative to an acute dose. These results suggest an equivalency in tumor treatment with a possible improvement in normal tissue toxicities for the PRDR method. An additional method of delivering PRDR through the use of Tomotherapy was proposed and demonstrated to be accurate. Tomotherapy planning forces the short leaf open times for individual MLC projections from low dose fractionation closed, resulting in an undeliverable plan due to the loss of a large number of usable projections. Application of a virtual grid with directional blocking allows for the output from useable segments to be above this threshold, resulting in a deliverable treatment plan. Finally, analysis was performed on a proposed QA

  17. A Phase I/II Trial of Intensity Modulated Radiation (IMRT) Dose Escalation With Concurrent Fixed-dose Rate Gemcitabine (FDR-G) in Patients With Unresectable Pancreatic Cancer

    SciTech Connect

    Ben-Josef, Edgar; Schipper, Mathew; Francis, Isaac R.; Hadley, Scott; Ten-Haken, Randall; Lawrence, Theodore; Normolle, Daniel; Simeone, Diane M.; Sonnenday, Christopher; Abrams, Ross; Leslie, William; Khan, Gazala; Zalupski, Mark M.

    2012-12-01

    Purpose: Local failure in unresectable pancreatic cancer may contribute to death. We hypothesized that intensification of local therapy would improve local control and survival. The objectives were to determine the maximum tolerated radiation dose delivered by intensity modulated radiation with fixed-dose rate gemcitabine (FDR-G), freedom from local progression (FFLP), and overall survival (OS). Methods and Materials: Eligibility included pathologic confirmation of adenocarcinoma, radiographically unresectable, performance status of 0-2, absolute neutrophil count of {>=}1500/mm{sup 3}, platelets {>=}100,000/mm{sup 3}, creatinine <2 mg/dL, bilirubin <3 mg/dL, and alanine aminotransferase/aspartate aminotransferase {<=}2.5 Multiplication-Sign upper limit of normal. FDR-G (1000 mg/m{sup 2}/100 min intravenously) was given on days -22 and -15, 1, 8, 22, and 29. Intensity modulated radiation started on day 1. Dose levels were escalated from 50-60 Gy in 25 fractions. Dose-limiting toxicity was defined as gastrointestinal toxicity grade (G) {>=}3, neutropenic fever, or deterioration in performance status to {>=}3 between day 1 and 126. Dose level was assigned using TITE-CRM (Time-to-Event Continual Reassessment Method) with the target dose-limiting toxicity (DLT) rate set to 0.25. Results: Fifty patients were accrued. DLTs were observed in 11 patients: G3/4 anorexia, nausea, vomiting, and/or dehydration (7); duodenal bleed (3); duodenal perforation (1). The recommended dose is 55 Gy, producing a probability of DLT of 0.24. The 2-year FFLP is 59% (95% confidence interval [CI]: 32-79). Median and 2-year overall survival are 14.8 months (95% CI: 12.6-22.2) and 30% (95% CI 17-45). Twelve patients underwent resection (10 R0, 2 R1) and survived a median of 32 months. Conclusions: High-dose radiation therapy with concurrent FDR-G can be delivered safely. The encouraging efficacy data suggest that outcome may be improved in unresectable patients through intensification of local

  18. Radiation Leukemogenesis: Applying Basic Science of Epidemiological Estimates of Low Dose Risks and Dose-Rate Effects

    SciTech Connect

    Hoel, D. G.

    1998-11-01

    The next stage of work has been to examine more closely the A-bomb leukemia data which provides the underpinnings of the risk estimation of CML in the above mentioned manuscript. The paper by Hoel and Li (Health Physics 75:241-50) shows how the linear-quadratic model has basic non-linearities at the low dose region for the leukemias including CML. Pierce et. al., (Radiation Research 123:275-84) have developed distributions for the uncertainty in the estimated exposures of the A-bomb cohort. Kellerer, et. al., (Radiation and Environmental Biophysics 36:73-83) has further considered possible errors in the estimated neutron values and with changing RBE values with dose and has hypothesized that the tumor response due to gamma may not be linear. We have incorporated his neutron model and have constricted new A-bomb doses based on his model adjustments. The Hoel and Li dose response analysis has also been applied using the Kellerer neutron dose adjustments for the leukemias. Finally, both Pierce's dose uncertainties and Kellerer neutron adjustments are combined as well as the varying RBE with dose as suggested by Rossi and Zaider and used for leukemia dose-response analysis. First the results of Hoel and Li showing a significantly improved fit of the linear-quadratic dose response by the inclusion of a threshold (i.e. low-dose nonlinearity) persisted. This work has been complete for both solid tumor as well as leukemia for both mortality as well as incidence data. The results are given in the manuscript described below which has been submitted to Health Physics.

  19. Reversible intramolecular hydrogen transfer between cysteine thiyl radicals and glycine and alanine in model peptides: absolute rate constants derived from pulse radiolysis and laser flash photolysis

    PubMed Central

    Nauser, Thomas; Casi, Giulio; Koppenol, Willem H.; Schöneich, Christian

    2008-01-01

    The intramolecular reaction of cysteine thiyl radicals with peptide and protein αC-H bonds represents a potential mechanism for irreversible protein oxidation. Here, we have measured absolute rate constants for these reversible hydrogen transfer reactions by means of pulse radiolysis and laser flash photolysis of model peptides. For N-Ac-CysGly6 and N-Ac-CysGly2AspGly3, Cys thiyl radicals abstract hydrogen atoms from Gly with kf = (1.0-1.1)×105 s-1, generating carbon-centered radicals, while the reverse reaction proceeds with kr = (8.0-8.9)×105 s-1. The forward reaction shows a normal kinetic isotope effect of kH/kD = 6.9, while the reverse reaction shows a significantly higher normal kinetic isotope effect of 17.6, suggesting a contribution of tunneling. For N-Ac-CysAla2AspAla3, cysteine thiyl radicals abstract hydrogen atoms from Ala with kf =(0.9-1.0)×104 s-1, while the reverse reaction proceeds with kr = 1.0×105 s-1. The order of reactivity, Gly > Ala, is in accord with previous studies on intermolecular reactions of thiyl radicals with these amino acids. The fact that kf < kr suggests some secondary structure of the model peptides, which prevents the adoption of extended conformations, for which calculations of homolytic bond dissociation energies would have predicted kf > kr. Despite kf < kr, model calculations show that intramolecular hydrogen abstraction by Cys thiyl radicals can lead to significant oxidation of other amino acids in the presence of physiologic oxygen concentrations. PMID:18973367

  20. Natural radioactivity and associated dose rates in soil samples from Kalpakkam, South India.

    PubMed

    Sowmya, M; Senthilkumar, B; Seshan, B R R; Hariharan, G; Purvaja, R; Ramkumar, S; Ramesh, R

    2010-10-01

    The activity concentration of naturally occurring radioactive elements such as 226Ra, 232Th and 40K were measured for 46 soil samples collected in the vicinity of the Madras atomic power station, Kalpakkam, South India using gamma-ray spectroscopy. The average activity concentration of 226Ra, 232Th and 40K in soil samples were found to be 22.6 ± 12.6, 92.8 ± 44.3 and 434.1 ± 131.1 Bq kg(-1), respectively. The activity concentration of natural radionuclides is higher than the world average except for (226)Ra. The external absorbed gamma dose rates due to 226Ra, 232Th and 40K are observed to be 74.6 ± 30.8 nGy h(-1) with a corresponding annual effective dose of 91.5 ± 37.8 µSv y(-1), which are also above the world average. The values of radium equivalent activity and external hazard index are less than the world average. Whereas, the values of the radioactivity level index (I(γ)) and the total gamma dose rate were found to be above the required criterion. PMID:20522563

  1. Teaching Absolute Value Meaningfully

    ERIC Educational Resources Information Center

    Wade, Angela

    2012-01-01

    What is the meaning of absolute value? And why do teachers teach students how to solve absolute value equations? Absolute value is a concept introduced in first-year algebra and then reinforced in later courses. Various authors have suggested instructional methods for teaching absolute value to high school students (Wei 2005; Stallings-Roberts…

  2. Mutation induction by different dose rates of gamma rays in radiation-sensitive mutants of mouse leukemia cells

    SciTech Connect

    Furuno-Fukushi, I.; Matsudaira, H. )

    1989-11-01

    Induction of cell killing and mutation to 6-thioguanine resistance was examined in a radiation-sensitive mutant strain LX830 of mouse leukemia cells following gamma irradiation at dose rates of 30 Gy/h (acute), 20 cGy/h (low dose rate), and 6.2 mGy/h (very low dose rate). LX830 cells were hypersensitive to killing by acute gamma rays. A slight but significant increase was observed in cell survival with decreasing dose rate down to 6.2 mGy/h, where the survival leveled off above certain total doses. The cells were also hypersensitive to mutation induction compared to the wild type. The mutation frequency increased linearly with increasing dose for all dose rates. No significant difference was observed in the frequency of induced mutations versus total dose at the three different dose rates so that the mutation frequency in LX830 cells at 6.2 mGy/h was not significantly different from that for moderate or acute irradiation.

  3. Assessment of indoor absorbed gamma dose rate from natural radionuclides in concrete by the method of build-up factors.

    PubMed

    Manić, Vesna; Nikezic, Dragoslav; Krstic, Dragana; Manić, Goran

    2014-12-01

    The specific absorbed gamma dose rates, originating from natural radionuclides in concrete, were calculated at different positions of a detection point inside the standard room, as well as inside an example room. The specific absorbed dose rates corresponding to a wall with arbitrary dimensions and thickness were also evaluated, and appropriate fitting functions were developed, enabling dose rate calculation for most realistic rooms. In order to make calculation simpler, the expressions fitting the exposure build-up factors for whole (238)U and (232)Th radionuclide series and (40)K were derived in this work, as well as the specific absorbed dose rates from a point source in concrete. Calculated values of the specific absorbed dose rates at the centre point of the standard room for (238)U, (232)Th and (40)K are in the ranges of previously obtained data.

  4. External gamma-ray dose rate and radon concentration in indoor environments covered with Brazilian granites.

    PubMed

    Anjos, R M; Juri Ayub, J; Cid, A S; Cardoso, R; Lacerda, T

    2011-11-01

    Health hazard from natural radioactivity in Brazilian granites, covering the walls and floor in a typical dwelling room, was assessed by indirect methods to predict external gamma-ray dose rates and radon concentrations. The gamma-ray dose rate was estimated by a Monte Carlo simulation method and validated by in-situ measurements with a NaI spectrometer. Activity concentrations of (232)Th, (226)Ra, and (40)K in an extensive selection of Brazilian commercial granite samples measured by using gamma-ray spectrometry were found to be 4.5-450 Bq kg(-1), 4.9-160 Bq kg(-1) and 190-2029 Bq kg(-1), respectively. The maximum external gamma-ray dose rate from floor and walls covered with the Brazilian granites in the typical dwelling room (5.0 m × 4.0 m area, 2.8 m height) was found to be 120 nGy h(-1), which is comparable with the average worldwide exposure to external terrestrial radiation of 80 nGy h(-1) due to natural sources, proposed by United Nations Scientific Committee on the Effects of Atomic Radiation. Radon concentrations in the room were also estimated by a simple mass balance equation and exhalation rates calculated from the measured values of (226)Ra concentrations and the material properties. The results showed that the radon concentration in the room ventilated adequately (0.5 h(-1)) will be lower than 100 Bq m(-3), value recommended as a reference level by the World Health Organization.

  5. External gamma-ray dose rate and radon concentration in indoor environments covered with Brazilian granites.

    PubMed

    Anjos, R M; Juri Ayub, J; Cid, A S; Cardoso, R; Lacerda, T

    2011-11-01

    Health hazard from natural radioactivity in Brazilian granites, covering the walls and floor in a typical dwelling room, was assessed by indirect methods to predict external gamma-ray dose rates and radon concentrations. The gamma-ray dose rate was estimated by a Monte Carlo simulation method and validated by in-situ measurements with a NaI spectrometer. Activity concentrations of (232)Th, (226)Ra, and (40)K in an extensive selection of Brazilian commercial granite samples measured by using gamma-ray spectrometry were found to be 4.5-450 Bq kg(-1), 4.9-160 Bq kg(-1) and 190-2029 Bq kg(-1), respectively. The maximum external gamma-ray dose rate from floor and walls covered with the Brazilian granites in the typical dwelling room (5.0 m × 4.0 m area, 2.8 m height) was found to be 120 nGy h(-1), which is comparable with the average worldwide exposure to external terrestrial radiation of 80 nGy h(-1) due to natural sources, proposed by United Nations Scientific Committee on the Effects of Atomic Radiation. Radon concentrations in the room were also estimated by a simple mass balance equation and exhalation rates calculated from the measured values of (226)Ra concentrations and the material properties. The results showed that the radon concentration in the room ventilated adequately (0.5 h(-1)) will be lower than 100 Bq m(-3), value recommended as a reference level by the World Health Organization. PMID:21729819

  6. Neutron and gamma-ray dose-rates from the Little Boy replica

    SciTech Connect

    Plassmann, E.A.; Pederson, R.A.

    1984-01-01

    We report dose-rate information obtained at many locations in the near vicinity of, and at distances out to 0.64 km from, the Little Boy replica while it was operated as a critical assembly. The measurements were made with modified conventional dosimetry instruments that used an Anderson-Braun detector for neutrons and a Geiger-Mueller tube for gamma rays with suitable electronic modules to count particle-induced pulses. Thermoluminescent dosimetry methods provide corroborative data. Our analysis gives estimates of both neutron and gamma-ray relaxation lengths in air for comparison with earlier calculations. We also show the neutron-to-gamma-ray dose ratio as a function of distance from the replica. Current experiments and further data analysis will refine these results. 7 references, 8 figures.

  7. [Genetic changes in yeast cells Saccharomyces irradiated by fast neutrons with different dose rate].

    PubMed

    Malinova, I V; Tsyb, T S; Komarova, E V

    2009-01-01

    No neutron dose rate effects in the wide range of 10(-3) Gy/s to 10(6) Gy/s were observed in yeast diploid cells for induction of mitotic segregation and crossing-over. The RBE values for these effects were determined as doses ratio (Dgamma/D(n)) at maximum effects. The RBE were 2.2-1.9 for neutrons of the reactor BR-10 (E = = 0.85 MeV) and the pulse reactor BARS-6 (E = 1.44 MeV). The RBE values for genetic effects were 1.0 at the equal survival level for neutrons and gamma-rays 60Co.

  8. Impact of Dose Rate Effects and Damage Engineering on Device Performance

    SciTech Connect

    Shim, Kyuha; Guo, Baonian; Liu, Jinning; Erokhin, Yuri; Hwang, Yeonsang; Lee, Yongseung; An, Jungsoo; Ryu, Seonho; Hahn, Seungho; Cho, Changjune; Hur, Namhae

    2006-11-13

    Traditional implant conditions during source/drain formation process, such as dopant, dose, energy and incident angle have been known as key parameters determining device electrical characteristics. As devices scale down, instant dose rate of BF2 ion implantation, however, should be considered as an important factor to control buried channel PMOS characteristics since fluorine and boron diffusion behavior can be varied depending on implant damage and results in change of effective channel length. Ribbon beam single wafer high current implanters enable ion beam density to be modulated. By changing beam size with same beam current during source/drain implantation, PMOS electrical characteristics of 70nm Flash memory have been investigated. With achieved results, device matching to spot beam batch ion implanter has been demonstrated.

  9. Impact of Dose on Local Failure Rates After Image-Guided Reirradiation of Recurrent Paraspinal Metastases

    SciTech Connect

    Damast, Shari; Wright, Jean; Bilsky, Mark; Hsu, Meier; Zhang Zhigang; Lovelock, Michael; Cox, Brett; Zatcky, Joan; Yamada, Yoshiya

    2011-11-01

    Purpose: To examine the impact of dose on local failure (LF) rates in the re-treatment of recurrent paraspinal metastases with image-guided intensity-modulated radiotherapy (IG-IMRT). Methods and Materials: The records of patients with in-field recurrence after previous spine radiation (median dose, 30 Gy) who received salvage IG-IMRT with either five 4-Gy (20-Gy group, n = 42) or five 6-Gy (30-Gy group, n = 55) daily fractions between January 2003 and August 2008 were reviewed. Institutional practice was 20 Gy before April 2006, when it changed to 30 Gy. A total of 47 cases (48%) were treated adjuvantly, after surgery to decompress epidural disease. LF after IG-IMRT was defined radiographically. Results: The median follow-up was 12.1 months (range, 0.2-63.6 months). The 1-year cumulative incidences of LF after 20 Gy and 30 Gy IG-IMRT were 45% and 26%, respectively (p = 0.04). Of all treatment characteristics examined (20-Gy vs. 30-Gy dose group, dose to 95% of the planned and gross target volume, tumor size, histology, receipt of surgery, and interval between first and second radiation), only dose group had a significant impact on actuarial LF incidence (p = 0.04; unadjusted HR, 0.51; 95% CI, 0.27-0.96). There was no incidence of myelopathy. Conclusions: A significant decrease in LF after IG-IMRT with five 6-Gy fractions compared with five 4-Gy fractions was observed without increased risk of myelopathy. Until prospective data comparing stereotactic hypofractionated and single-fraction regimens become available, when reirradiating recurrent paraspinal metastases with IG-IMRT, administration of five 6-Gy daily fractions is reasonable.

  10. Dose rate estimates and spatial interpolation maps of outdoor gamma dose rate with geostatistical methods; A case study from Artvin, Turkey.

    PubMed

    Yeşilkanat, Cafer Mert; Kobya, Yaşar; Taşkin, Halim; Çevik, Uğur

    2015-12-01

    In this study, compliance of geostatistical estimation methods is compared to ensure investigation and imaging natural Fon radiation using the minimum number of data. Artvin province, which has a quite hilly terrain and wide variety of soil and located in the north-east of Turkey, is selected as the study area. Outdoor gamma dose rate (OGDR), which is an important determinant of environmental radioactivity level, is measured in 204 stations. Spatial structure of OGDR is determined by anisotropic, isotropic and residual variograms. Ordinary kriging (OK) and universal kriging (UK) interpolation estimations were calculated with the help of model parameters obtained from these variograms. In OK, although calculations are made based on positions of points where samples are taken, in the UK technique, general soil groups and altitude values directly affecting OGDR are included in the calculations. When two methods are evaluated based on their performances, it has been determined that UK model (r = 0.88, p < 0.001) gives quite better results than OK model (r = 0.64, p < 0.001). In addition, as a result of the maps created at the end of the study, it was illustrated that local changes are better reflected by UK method compared to OK method and its error variance is found to be lower.

  11. High-dose-rate (HDR) brachytherapy for the treatment of benign obstructive endobronchial granulation tissue

    SciTech Connect

    Madu, Chika N. . E-mail: chikam@xrt.upenn.edu; Machuzak, Michael S.; Sterman, Daniel H.; Musani, Ali; Ahya, Vivek; McDonough, James; Metz, James M.

    2006-12-01

    Background: Severe airway obstruction can occur in the setting of benign granulation tissue forming at bronchial anastomotic sites after lung transplantation in up to 20% of patients. Many of these benign lesions respond to stent placement, laser ablation, or balloon bronchoplasty. However, in certain cases, proliferation of granulation tissue may persist despite all therapeutic attempts. This study describes a series of refractory patients treated with high-dose-rate (HDR) brachytherapy for benign proliferation of granulation tissue, causing airway compromise. Methods and Materials: Between April 2002 and June 2005, 5 patients with significant airway compromise from recurrent granulation tissue were treated with HDR brachytherapy. All patients had previously failed to maintain a patent airway despite multiple bronchoscopic interventions. Treatment was delivered using an HDR brachytherapy afterloader with {sup 192}Ir. Dose prescription was to a depth of 1 cm. All patients were treated weekly, with total doses ranging from 10 Gy to 21 Gy in two to three fractions. Results: The median follow-up was 12 months. All patients experienced a reduction in therapeutic bronchoscopic procedures after HDR brachytherapy compared with the pretreatment period. With the exception of possible radiation-induced bronchitis in 1 patient, there were no other treatment related complications. At the time of this report, 2 patients have died and the other 3 are alive with marked symptomatic improvement and reduced bronchoscopic procedures. Conclusion: High-dose-rate brachytherapy is an effective treatment for benign proliferation of granulation tissue causing airway obstruction. The early response to therapy is encouraging and further follow-up is necessary to determine long-term durability and late effects.

  12. 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.

  13. 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.

  14. Thermal stability of PVC formulations gamma irradiated at different dose rates

    NASA Astrophysics Data System (ADS)

    Castañeda-Facio, A.; Benavides, R.; Martínez-Pardo, M. E.

    2014-04-01

    Polyvinyl chloride (PVC) formulated with two different stabilizer systems (Ca/Zn stearates and dibasic lead phthalate) irradiated at 75 kGy at two different dose rates were studied in order to evaluate their effect in thermal stability. Samples were degraded in a TGA instrument at different heating rates and the activation energy (Ea) to dehydrochlorination was calculated using the Arrhenius method in accordance with ASTM E 1641-07. TGA evaluations show that temperature for HCl evolution is higher when increasing heating rate, as well as higher resistance to degradation, for irradiated lead formulations; however, after activation energies calculation the irradiated Ca/Zn formulations are more stable. The controversial results are due to the low initial stability of lead additives in PVC.

  15. Reirradiation of Large-Volume Recurrent Glioma With Pulsed Reduced-Dose-Rate Radiotherapy

    SciTech Connect

    Adkison, Jarrod B.; Tome, Wolfgang; Seo, Songwon; Richards, Gregory M.; Robins, H. Ian; Rassmussen, Karl; Welsh, James S.; Mahler, Peter A.; Howard, Steven P.

    2011-03-01

    Purpose: Pulsed reduced-dose-rate radiotherapy (PRDR) is a reirradiation technique that reduces the effective dose rate and increases the treatment time, allowing sublethal damage repair during irradiation. Patients and Methods: A total of 103 patients with recurrent glioma underwent reirradiation using PRDR (86 considered to have Grade 4 at PRDR). PRDR was delivered using a series of 0.2-Gy pulses at 3-min intervals, creating an apparent dose rate of 0.0667 Gy/min to a median dose of 50 Gy (range, 20-60) delivered in 1.8-2.0-Gy fractions. The mean treatment volume was 403.5 {+-} 189.4 cm{sup 3} according to T{sub 2}-weighted magnetic resonance imaging and a 2-cm margin. Results: For the initial or upgraded Grade 4 cohort (n = 86), the median interval from the first irradiation to PRDR was 14 months. Patients undergoing PRDR within 14 months of the first irradiation (n = 43) had a median survival of 21 weeks. Those treated {>=}14 months after radiotherapy had a median survival of 28 weeks (n = 43; p = 0.004 and HR = 1.82 with a 95% CI ranging from 1.25 to 3.10). These data compared favorably to historical data sets, because only 16% of the patients were treated at first relapse (with 46% treated at the second relapse, 32% at the third or fourth relapse, and 4% at the fourth or fifth relapse). The median survival since diagnosis and retreatment was 6.3 years and 11.4 months for low-grade, 4.1 years and 5.6 months for Grade 3, and 1.6 years and 5.1 months for Grade 4 tumors, respectively, according to the initial histologic findings. Multivariate analysis revealed age at the initial diagnosis, initial low-grade disease, and Karnofsky performance score of {>=}80 to be significant predictors of survival after initiation of PRDR. Conclusion: PRDR allowed for safe retreatment of larger volumes to high doses with palliative benefit.

  16. High-dose-rate interstitial brachytherapy for liver metastases: first study from India

    PubMed Central

    Thulkar, Sanjay; Sharma, Seema; Gandhi, Ajeet Kumar; Haresh, Kunhi Parambath; Gupta, Subhash; Rath, Goura Kisor; Julka, Pramod Kumar

    2013-01-01

    Purpose To study the safety and efficacy of high-dose-rate interstitial brachytherapy (HDRIBT) in patients with liver metastases (LM). Material and methods Between 2009 and 2011, 10 patients with 12 metastatic lesions in the liver were enrolled in this prospective trial. All patients had either refused surgery or found ineligible for surgery due to various factors. Under CT guidance, 16 gauze blind end stainless steel or rigid plastic brachytherapy needle was inserted in the center of lesion through the percutaneous route. Generally, a single interstitial brachytherapy (IBT) needle for lesions up to 3 cm and multiple needles for lesions more than 3 cm in diameter were inserted. Treatment was delivered with a single high-dose-rate (HDR) dose of 20 Gy prescribed to the target. The needles were removed immediately after the treatment. The endpoints of study were acute complications and local control of the disease. Results The median size of the lesion was 3.8 cm (2.7-7.0 cm). The average time for the entire IBT procedure was 65 minutes (50-105 minutes). Median follow up was 9 months (3-17 months). None of the patients had fatal complications. Minor complications like pain, nausea/vomiting, and asymptomatic pleural effusion were observed in 3, 2 and 1 patients, respectively. Local control rate at 12 months was 75%. The 1-year local progression free survival (LPFS) was 33%. Conclusion Although limited by small sample size, the results of our first study from India suggest that HDRIBT is a safe and effective non surgical option for LM. PMID:23878550

  17. Radioactivity measurements and dose rate calculations using ERICA tool in the terrestrial environment of Greece.

    PubMed

    Sotiropoulou, Maria; Florou, Heleny; Manolopoulou, Metaxia

    2016-06-01

    In the present study, the radioactivity levels to which terrestrial non-human biota were exposed are examined. Organisms (grass and herbivore mammals) and abiotic components (soil) were collected during the period of 2010 to 2014 from grasslands where sheep and goats were free-range grazing. Natural background radionuclides ((226)Ra, (228)Ra, (228)Th) and artificial radionuclides ((137)Cs, (134)Cs, (131)I) were detected in the collected samples using gamma spectrometry. The actual measured activity concentrations and site-specific data of the studied organisms were imported in ERICA Assessment Tool (version 1.2.0) in order to provide an insight of the radiological dose rates. The highest activity concentrations were detected in samples collected from Lesvos island and the lowest in samples collected from Attiki and Etoloakarnania prefectures. The highest contribution to the total dose rate was clearly derived from the internal exposure and is closely related to the exposure to alpha emitters of natural background ((226)Ra and (228)Th). The Fukushima-derived traces of (137)Cs, (134)Cs, and (131)I, along with the residual (137)Cs, resulted in quite low contribution to the total dose rate. The obtained results may strengthen the adaptation of software tools to a wider range of ecosystems and may be proved useful in further research regarding the possible impact of protracted low level ionizing radiation on non-human biota. This kind of studies may contribute to the effective incorporation of dosimetry tools in the development of integrated environmental and radiological impact assessment policies.

  18. Radiation dose rates in Space Shuttle as a function of atmospheric density.

    PubMed

    Badhwar, G D

    1999-06-01

    Current models of the inner trapped belt describe the radiation environment at times of solar minimum and solar maximum, respectively. These two models were constructed using data acquired prior to 1970 during a small solar cycle, and no valid model for the past two high solar cycles exists. There is a clear need to accurately predict the radiation exposure of astronauts at all times between the solar minimum and solar maximum, not only on the short duration Space Shuttle flights, but on the longer term stay onboard the Mir orbital station and the planned International Space Station (ISS). An analysis of the trapped absorbed dose rate, D, at six fixed locations in the habitable volume of the Shuttle shows a power law relationship, D=A rho-n, where rho is the atmospheric density, rho. The index, n, is weakly dependent on the shielding, decreasing as the average shielding increases. A better representation is provided by D=A tan-1 [(Xi-Xi c)/(Xi c-Xi m)], where Xi=ln(rho), and A, Xi c, and Xi m are constants. Xi c is related to the atmospheric density near the altitude of atmospheric cutoff. These relationships hold over nearly four decades of density variation and throughout the solar cycle. This then provides a method of calculating absorbed dose rate at anytime in the solar cycle. These empirically derived relations were used to predict the dose rates for eleven Space Shuttle flights carried out since January 1997. The predictions are in excellent agreement with measured values. This method reduces the uncertainties of a factor of about 2 for the AP-8 MIN/MAX models to less than 30%.

  19. Radioactivity measurements and dose rate calculations using ERICA tool in the terrestrial environment of Greece.

    PubMed

    Sotiropoulou, Maria; Florou, Heleny; Manolopoulou, Metaxia

    2016-06-01

    In the present study, the radioactivity levels to which terrestrial non-human biota were exposed are examined. Organisms (grass and herbivore mammals) and abiotic components (soil) were collected during the period of 2010 to 2014 from grasslands where sheep and goats were free-range grazing. Natural background radionuclides ((226)Ra, (228)Ra, (228)Th) and artificial radionuclides ((137)Cs, (134)Cs, (131)I) were detected in the collected samples using gamma spectrometry. The actual measured activity concentrations and site-specific data of the studied organisms were imported in ERICA Assessment Tool (version 1.2.0) in order to provide an insight of the radiological dose rates. The highest activity concentrations were detected in samples collected from Lesvos island and the lowest in samples collected from Attiki and Etoloakarnania prefectures. The highest contribution to the total dose rate was clearly derived from the internal exposure and is closely related to the exposure to alpha emitters of natural background ((226)Ra and (228)Th). The Fukushima-derived traces of (137)Cs, (134)Cs, and (131)I, along with the residual (137)Cs, resulted in quite low contribution to the total dose rate. The obtained results may strengthen the adaptation of software tools to a wider range of ecosystems and may be proved useful in further research regarding the possible impact of protracted low level ionizing radiation on non-human biota. This kind of studies may contribute to the effective incorporation of dosimetry tools in the development of integrated environmental and radiological impact assessment policies. PMID:26897581

  20. Effect of ionizing dose rate on the radioresistance of some food pathogenic bacteria.

    PubMed

    Dion, P; Charbonneau, R; Thibault, C

    1994-05-01

    Food pathogenic bacteria including Listeria monocytogenes (1A1 and ATCC 19111), Staphylococcus aureus (GD13 and ATCC 13565), Escherichia coli O157:H7 (ATCC 35150), Salmonella typhimurium, Yersinia enterocolitica, Vibrio parahaemolyticus, and Campylobacter jejuni were exposed to various rates of ionizing radiation (0.78, 2.6, and 22 kGy/h) emitted by three different 60Co irradiators. D10 values (D10 is the radiation dose required to eliminate 90% of a bacterial population (one logarithmic cycle reduction)) were calculated for the various strains and growth conditions tested. A covariance analysis of these results revealed that the dose rates studied had no significant influence on the radiosensitivity of these bacteria. At all dose rates, the bacteria were more radiosensitive when irradiated in a saline solution (0.85% NaCl) than in a chicken breast meat suspension. The growth phase of the bacterial population had a variable influence on its radioresistance. For L. monocytogenes 1A1, Staphylococcus aureus ATCC 13565, E. coli O157:H7, Y. enterocolitica, and V. parahaemolyticus, radioresistance was not significantly different in the exponential and stationary phases. Populations of L. monocytogenes ATCC 19111 and Staphylococcus aureus GD13 were significantly more resistant in the stationary phase (D10 = 0.23 and 0.12 kGy, respectively) than in the exponential phase (D10 = 0.17 and 0.09 kGy, respectively). Among the pathogenic bacteria investigated in this study, the most radioresistant was L. monocytogenes (D10 = 0.16-0.38 kGy, Gram-positive bacilli) and the most radiosensitive was V. parahaemolyticus (D10 = 0.03-0.04 kGy, halophilic Gram-negative bacilli). PMID:8069779

  1. Differences in rates of decrease of environmental radiation dose rates by ground surface property in Fukushima City after the Fukushima Daiichi nuclear power plant accident.

    PubMed

    Kakamu, Takeyasu; Kanda, Hideyuki; Tsuji, Masayoshi; Kobayashi, Daisuke; Miyake, Masao; Hayakawa, Takehito; Katsuda, Shin-ichiro; Mori, Yayoi; Okouchi, Toshiyasu; Hazama, Akihiro; Fukushima, Tetsuhito

    2013-01-01

    After the Great East Japan Earthquake on 11 March 2011, the environmental radiation dose in Fukushima City increased. On 11 April, 1 mo after the earthquake, the environmental radiation dose rate at various surfaces in the same area differed greatly by surface property. Environmental radiation measurements continue in order to determine the estimated time to 50% reduction in environmental radiation dose rates by surface property in order to make suggestions for decontamination in Fukushima. The measurements were carried out from 11 April to 11 November 2011. Forty-eight (48) measurement points were selected, including four kinds of ground surface properties: grass (13), soil (5), artificial turf (7), and asphalt (23). Environmental radiation dose rate was measured at heights of 100 cm above the ground surface. Time to 50% reduction of environmental radiation dose rates was estimated for each ground surface property. Radiation dose rates on 11 November had decreased significantly compared with those on 11 April for all surface properties. Artificial turf showed the longest time to 50% reduction (544.32 d, standard error: 96.86), and soil showed the shortest (213.20 d, standard error: 35.88). The authors found the environmental radiation dose rate on artificial materials to have a longer 50% reduction time than that on natural materials. These results contribute to determining an order of priority for decontamination after nuclear disasters.

  2. The effects of heating rate on the dose response characteristics of TLD-200, TLD-300 and TLD-400

    NASA Astrophysics Data System (ADS)

    Kafadar, V. Emir; Necmeddin Yazici, A.; Güler Yildirim, R.

    2009-10-01

    In the given study; the effects of heating rates on the dose response characteristics of CaF 2:Dy (TLD-200), CaF 2:Tm (TLD-300) and CaF 2:Mn (TLD-400) crystals have been investigated using the dose dependence curve and dose response function f( D). It was observed from the dose response functions that the linearity and behaviour of the TL glow peaks of TLD-200 and TLD-400 are affected, but the TLD-300 is not affected from the heating rate.

  3. Operation logic and functionality of automatic dose rate and image quality control of conventional fluoroscopy

    SciTech Connect

    Lin, Pei-Jan Paul

    2009-05-15

    New generation of fluoroscopic imaging systems is equipped with spectral shaping filters complemented with sophisticated automatic dose rate and image quality control logic called ''fluoroscopy curve'' or ''trajectory''. Such fluoroscopy curves were implemented first on cardiovascular angiographic imaging systems and are now available on conventional fluoroscopy equipment. This study aims to investigate the control logic operations under the fluoroscopy mode and acquisition mode (equivalent to the legacy spot filming) of a conventional fluoroscopy system typically installed for upper-lower gastrointestinal examinations, interventional endoscopy laboratories, gastrointestinal laboratory, and pain clinics.

  4. Desensitization Using Bortezomib and High-dose Immunoglobulin Increases Rate of Deceased Donor Kidney Transplantation

    PubMed Central

    Jeong, Jong Cheol; Jambaldorj, Enkthuya; Kwon, Hyuk Yong; Kim, Myung-Gyu; Im, Hye Jin; Jeon, Hee Jung; In, Ji Won; Han, Miyeun; Koo, Tai Yeon; Chung, Junho; Song, Eun Young; Ahn, Curie; Yang, Jaeseok

    2016-01-01

    Abstract Combination therapy of intravenous immunoglobulin (IVIG) and rituximab showed a good transplant rate in highly sensitized wait-listed patients for deceased donor kidney transplantation (DDKT), but carried the risk of antibody-mediated rejection. The authors investigated the impact of a new combination therapy of bortezomib, IVIG, and rituximab on transplantation rate. This study was a prospective, open-labeled clinical trial. The desensitization regimen consisted of 2 doses of IVIG (2 g/kg), a single dose of rituximab (375 mg/m2), and 4 doses of bortezomib (1.3 mg/m2). The transplant rate was analyzed. Anti-Human leukocyte antigen (HLA) DRB antibodies were determined by a Luminex solid-phase bead assay at baseline and after 2, 3, and 6 months in the desensitized patients. There were 19 highly sensitized patients who received desensitization and 17 patients in the control group. Baseline values of class I and II panel reactive antibody (%, peak mean fluorescence intensity) were 83 ± 16.0 (14952 ± 5820) and 63 ± 36.0 (10321 ± 7421), respectively. Deceased donor kidney transplantation was successfully performed in 8 patients (42.1%) in the desensitization group versus 4 (23.5%) in the control group. Multivariate time-varying covariate Cox regression analysis showed that desensitization increased the probability of DDKT (hazard ratio, 46.895; 95% confidence interval, 3.468–634.132; P = 0.004). Desensitization decreased mean fluorescence intensity values of class I panel reactive antibody by 15.5% (20.8%) at 2 months. In addition, a liberal mismatch strategy in post hoc analysis increased the benefit of desensitization in donor-specific antibody reduction. Desensitization was well tolerated, and acute rejection occurred only in the control group. In conclusion, a desensitization protocol using bortezomib, high-dose IVIG, and rituximab increased the DDKT rate in highly sensitized, wait-listed patients. PMID:26844479

  5. Desensitization Using Bortezomib and High-dose Immunoglobulin Increases Rate of Deceased Donor Kidney Transplantation.

    PubMed

    Jeong, Jong Cheol; Jambaldorj, Enkthuya; Kwon, Hyuk Yong; Kim, Myung-Gyu; Im, Hye Jin; Jeon, Hee Jung; In, Ji Won; Han, Miyeun; Koo, Tai Yeon; Chung, Junho; Song, Eun Young; Ahn, Curie; Yang, Jaeseok

    2016-02-01

    Combination therapy of intravenous immunoglobulin (IVIG) and rituximab showed a good transplant rate in highly sensitized wait-listed patients for deceased donor kidney transplantation (DDKT), but carried the risk of antibody-mediated rejection. The authors investigated the impact of a new combination therapy of bortezomib, IVIG, and rituximab on transplantation rate.This study was a prospective, open-labeled clinical trial. The desensitization regimen consisted of 2 doses of IVIG (2  g/kg), a single dose of rituximab (375  mg/m), and 4 doses of bortezomib (1.3  mg/m). The transplant rate was analyzed. Anti-Human leukocyte antigen (HLA) DRB antibodies were determined by a Luminex solid-phase bead assay at baseline and after 2, 3, and 6 months in the desensitized patients.There were 19 highly sensitized patients who received desensitization and 17 patients in the control group. Baseline values of class I and II panel reactive antibody (%, peak mean fluorescence intensity) were 83  ±  16.0 (14952  ±  5820) and 63  ±  36.0 (10321  ±  7421), respectively. Deceased donor kidney transplantation was successfully performed in 8 patients (42.1%) in the desensitization group versus 4 (23.5%) in the control group. Multivariate time-varying covariate Cox regression analysis showed that desensitization increased the probability of DDKT (hazard ratio, 46.895; 95% confidence interval, 3.468-634.132; P = 0.004). Desensitization decreased mean fluorescence intensity values of class I panel reactive antibody by 15.5% (20.8%) at 2 months. In addition, a liberal mismatch strategy in post hoc analysis increased the benefit of desensitization in donor-specific antibody reduction. Desensitization was well tolerated, and acute rejection occurred only in the control group.In conclusion, a desensitization protocol using bortezomib, high-dose IVIG, and rituximab increased the DDKT rate in highly sensitized, wait-listed patients.

  6. High-Dose-Rate Intraoperative Radiation Therapy for Recurrent Head-and-Neck Cancer

    SciTech Connect

    Perry, David J.; Chan, Kelvin; Wolden, Suzanne; Zelefsky, Michael J.; Chiu, Johnny; Cohen, Gilad; Zaider, Marco; Kraus, Dennis; Shah, Jatin; Lee, Nancy

    2010-03-15

    Purpose: To report the use of high-dose-rate intraoperative radiation therapy (HDR-IORT) for recurrent head-and-neck cancer (HNC) at a single institution. Methods and Materials: Between July 1998 and February 2007, 34 patients with recurrent HNC received 38 HDR-IORT treatments using a Harrison-Anderson-Mick applicator with Iridium-192. A single fraction (median, 15 Gy; range, 10-20 Gy) was delivered intraoperatively after surgical resection to the region considered at risk for close or positive margins. In all patients, the target region was previously treated with external beam radiation therapy (median dose, 63 Gy; range, 24-74 Gy). The 1- and 2-year estimates for in-field local progression-free survival (LPFS), locoregional progression-free survival (LRPFS), distant metastases-free survival (DMFS), and overall survival (OS) were calculated. Results: With a median follow-up for surviving patients of 23 months (range, 6-54 months), 8 patients (24%) are alive and without evidence of disease. The 1- and 2-year LPFS rates are 66% and 56%, respectively, with 13 (34%) in-field recurrences. The 1- and 2-year DMFS rates are 81% and 62%, respectively, with 10 patients (29%) developing distant failure. The 1- and 2-year OS rates are 73% and 55%, respectively, with a median time to OS of 24 months. Severe complications included cellulitis (5 patients), fistula or wound complications (3 patients), osteoradionecrosis (1 patient), and radiation-induced trigeminal neuralgia (1 patient). Conclusions: HDR-IORT has shown encouraging local control outcomes in patients with recurrent HNC with acceptable rates of treatment-related morbidity. Longer follow-up with a larger cohort of patients is needed to fully assess the benefit of this procedure.

  7. PCP METHODOLOGY FOR DETERMINING DOSE RATES FOR SMALL GRAM QUANTITIES IN SHIPPING PACKAGINGS

    SciTech Connect

    Nathan, S.

    2011-08-23

    The Small Gram Quantity (SGQ) concept is based on the understanding that small amounts of hazardous materials, in this case radioactive materials, are significantly less hazardous than large amounts of the same materials. This study describes a methodology designed to estimate an SGQ for several neutron and gamma emitting isotopes that can be shipped in a package compliant with 10 CFR Part 71 external radiation level limits regulations. These regulations require packaging for the shipment of radioactive materials perform, under both normal and accident conditions, the essential functions of material containment, subcriticality, and maintain external radiation levels within regulatory limits. 10 CFR 71.33(b)(1)(2)&(3) state radioactive and fissile materials must be identified and their maximum quantity, chemical and physical forms be included in an application. Furthermore, the U.S. Federal Regulations require application contain an evaluation demonstrating the package (i.e., the packaging and its contents) satisfies the external radiation standards for all packages (10 CFR 71.31(2), 71.35(a), & 71.47). By placing the contents in a He leak-tight containment vessel, and limiting the mass to ensure subcriticality, the first two essential functions are readily met. Some isotopes emit sufficiently strong photon radiation that small amounts of material can yield a large external dose rate. Quantifying of the dose rate for a proposed content is a challenging issue for the SGQ approach. It is essential to quantify external radiation levels from several common gamma and neutron sources that can be safely placed in a specific packaging, to ensure compliance with federal regulations. The Packaging Certification Program (PCP) Methodology for Determining Dose Rate for Small Gram Quantities in Shipping Packagings described in this report provides bounding mass limits for a set of proposed SGQ isotopes. Methodology calculations were performed to estimate external radiation levels

  8. Monte Carlo dosimetric study of the Flexisource Co-60 high dose rate source

    PubMed Central

    Granero, Domingo; Perez-Calatayud, Jose; Ballester, Facundo

    2012-01-01

    Purpose Recently, a new HDR 60Co brachytherapy source, Flexisource Co-60, has been developed (Nucletron B.V. Veenendaal, The Netherlands). This study aims to obtain dosimetric data for this source for its use in clinical practice as required by AAPM and ESTRO. Material and methods Two Monte Carlo radiation transport codes were used: Penelope2008 and GEANT4. The source was centrally-positioned in a 100 cm radius water phantom. Absorbed dose and collisional kerma were obtained using 0.01 cm (close) and 0.1 cm (far) sized voxels to provide high-resolution dosimetry near (far from) the source. Dose rate distributions obtained with the two Monte Carlo codes were compared. Results and Discussion Simulations performed with those two radiation transport codes showed an agreement typically within 0.2% for r > 0.8 cm and up to 2% closer to the source. Detailed results of dose distributions are being made available. Conclusions Dosimetric data are provided for the new Flexisource Co-60 source. These data are meant to be used in treatment planning systems in clinical practice. PMID:23346138

  9. Novel Use of the Contura for High Dose Rate Cranial Brachytherapy

    SciTech Connect

    Scanderbeg, Daniel J.; Alksne, John F.; Lawson, Joshua D.; Murphy, Kevin T.

    2011-01-01

    A popular choice for treatment of recurrent gliomas was cranial brachytherapy using the GliaSite Radiation Therapy System. However, this device was taken off the market in late 2008, thus leaving a treatment void. This case study presents our experience treating a cranial lesion for the first time using a Contura multilumen, high-dose-rate (HDR) brachytherapy balloon applicator. The patient was a 47-year-old male who was diagnosed with a recurrent right frontal anaplastic oligodendroglioma. Previous radiosurgery made him a good candidate for brachytherapy. An intracavitary HDR balloon brachytherapy device (Contura) was placed in the resection cavity and treated with a single fraction of 20 Gy. The implant, treatment, and removal of the device were all completed without incident. Dosimetry of the device was excellent because the dose conformed very well to the target. V90, V100, V150, and V200 were 98.9%, 95.7%, 27.2, and 8.8 cc, respectively. This patient was treated successfully using the Contura multilumen balloon. Contura was originally designed for deployment in a postlumpectomy breast for treatment by accelerated partial breast irradiation. Being an intracavitary balloon device, its similarity to the GliaSite system makes it a viable replacement candidate. Multiple lumens in the device also make it possible to shape the dose delivered to the target, something not possible before with the GliaSite applicator.

  10. Validation of absolute axial neutron flux distribution calculations with MCNP with 197Au(n,γ)198Au reaction rate distribution measurements at the JSI TRIGA Mark II reactor.

    PubMed

    Radulović, Vladimir; Štancar, Žiga; Snoj, Luka; Trkov, Andrej

    2014-02-01

    The calculation of axial neutron flux distributions with the MCNP code at the JSI TRIGA Mark II reactor has been validated with experimental measurements of the (197)Au(n,γ)(198)Au reaction rate. The calculated absolute reaction rate values, scaled according to the reactor power and corrected for the flux redistribution effect, are in good agreement with the experimental results. The effect of different cross-section libraries on the calculations has been investigated and shown to be minor. PMID:24316530

  11. Analgesia dose prescribing and estimated glomerular filtration rate decline: a general practice database linkage cohort study

    PubMed Central

    Nderitu, Paul; Doos, Lucy; Strauss, Vicky Y; Lambie, Mark; Davies, Simon J; Kadam, Umesh T

    2014-01-01

    Objective We aimed to quantify the short-term effect of non-steroidal anti-inflammatory drugs (NSAIDs), aspirin and paracetamol analgesia dose prescribing on estimated glomerular filtration rate (eGFR) decline in the general practice population. Design A population-based longitudinal clinical data linkage cohort study. Setting Two large general practices in North Staffordshire, UK. Participants Patients aged 40 years and over with ≥2 eGFR measurements spaced ≥90 days apart between 1 January 2009 and 31 December 2010 were selected. Exposure Using WHO Defined Daily Dose standardised cumulative analgesia prescribing, patients were categorised into non-user, normal and high-dose groups. Outcome measure The primary outcome was defined as a >5 mL/min/1.73 m2/year eGFR decrease between the first and last eGFR. Logistic regression analyses were used to estimate risk, adjusting for sociodemographics, comorbidity, baseline chronic kidney disease (CKD) status, renin-angiotensin-system inhibitors and other analgesia prescribing. Results There were 4145 patients (mean age 66 years, 55% female) with an analgesia prescribing prevalence of 17.2% for NSAIDs, 39% for aspirin and 22% for paracetamol and stage 3–5 CKD prevalence was 16.1% (n=667). Normal or high-dose NSAID and paracetamol prescribing was not significantly associated with eGFR decline. High-dose aspirin prescribing was associated with a reduced risk of eGFR decline in patients with a baseline (first) eGFR ≥60 mL/min/1.73 m2; OR=0.52 (95% CI 0.35 to 0.77). Conclusions NSAID, aspirin and paracetamol prescribing over 2 years did not significantly affect eGFR decline with a reduced risk of eGFR decline in high-dose aspirin users with well-preserved renal function. However, the long-term effects of analgesia use on eGFR decline remain to be determined. PMID:25138808

  12. 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.

  13. Application of airborne gamma spectrometric survey data to estimating terrestrial gamma-ray dose rates: an example in California.

    PubMed

    Wollenberg, H A; Revzan, K L; Smith, A R

    1994-01-01

    We examined the applicability of radioelement data from the National Aerial Radiometric Reconnaissance, an element of the National Uranium Resource Evaluation, to estimate terrestrial gamma-ray absorbed dose rates, by comparing dose rates calculated from aeroradiometric surveys of uranium, thorium, and potassium concentrations with dose rates calculated from a radiogeologic data base and the distribution of lithologies in California. Gamma-ray dose rates increase generally from north to south following lithological trends, with low values of 25-30 nGy h-1 in the northernmost 1 x 2 degrees quadrangles between 41 and 42 degrees N to high values of 75-100 nGy h-1 in southeastern California. Lithologic-based estimates of mean dose rates in the quadrangles generally match those from aeroradiometric data, with statewide means of 63 and 60 nGy h-1, respectively. These are intermediate between a population-weighted global average of 51 nGy h-1 reported in 1982 by UNSCEAR and a weighted continental average of 70 nGy h-1, based on the global distribution of rock types. The concurrence of lithologically and aeroradiometrically determined dose rates in California, with its varied geology and topography encompassing settings representative of the continents, indicates that the National Aerial Radiometric Reconnaissance data are applicable to estimates of terrestrial absorbed dose rates from natural gamma emitters.

  14. 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.

  15. Catchment-scale distribution of radiocesium air dose rate in a mountainous deciduous forest and its relation to topography.

    PubMed

    Atarashi-Andoh, Mariko; Koarashi, Jun; Takeuchi, Erina; Tsuduki, Katsunori; Nishimura, Syusaku; Matsunaga, Takeshi

    2015-09-01

    A large number of air dose rate measurements were collected by walking through a mountainous area with a small gamma-ray survey system, KURAMA-II. The data were used to map the air dose rate of a mountainous deciduous forest that received radiocesium from the Fukushima Dai-ichi Nuclear Power Plant accident. Measurements were conducted in a small stream catchment (0.6 km(2) in area) in August and September 2013, and the relationship between air dose rates and the mountainous topography was examined. Air dose rates increased with elevation, indicating that more radiocesium was deposited on ridges, and suggesting that it had remained there for 2.5 y with no significant downslope migration by soil erosion or water drainage. Orientation in relation to the dominant winds when the radioactive plume flowed to the catchment also strongly affected the air dose rates. Based on our continuous measurements using the KURAMA-II, we describe the variation in air dose rates in a mountainous forest area and suggest that it is important to consider topography when determining sampling points and resolution to assess the spatial variability of dose rates and contaminant deposition.

  16. An automated optimization tool for high-dose-rate (HDR) prostate brachytherapy with divergent needle pattern.

    PubMed

    Borot de Battisti, M; Maenhout, M; Denis de Senneville, B; Hautvast, G; Binnekamp, D; Lagendijk, J J W; van Vulpen, M; Moerland, M A

    2015-10-01

    Focal high-dose-rate (HDR) for prostate cancer has gained increasing interest as an alternative to whole gland therapy as it may contribute to the reduction of treatment related toxicity. For focal treatment, optimal needle guidance and placement is warranted. This can be achieved under MR guidance. However, MR-guided needle placement is currently not possible due to space restrictions in the closed MR bore. To overcome this problem, a MR-compatible, single-divergent needle-implant robotic device is under development at the University Medical Centre, Utrecht: placed between the legs of the patient inside the MR bore, this robot will tap the needle in a divergent pattern from a single rotation point into the tissue. This rotation point is just beneath the perineal skin to have access to the focal prostate tumor lesion. Currently, there is no treatment planning system commercially available which allows optimization of the dose distribution with such needle arrangement. The aim of this work is to develop an automatic inverse dose planning optimization tool for focal HDR prostate brachytherapy with needle insertions in a divergent configuration. A complete optimizer workflow is proposed which includes the determination of (1) the position of the center of rotation, (2) the needle angulations and (3) the dwell times. Unlike most currently used optimizers, no prior selection or adjustment of input parameters such as minimum or maximum dose or weight coefficients for treatment region and organs at risk is required. To test this optimizer, a planning study was performed on ten patients (treatment volumes ranged from 8.5 cm(3)to 23.3 cm(3)) by using 2-14 needle insertions. The total computation time of the optimizer workflow was below 20 min and a clinically acceptable plan was reached on average using only four needle insertions. PMID:26378657

  17. An automated optimization tool for high-dose-rate (HDR) prostate brachytherapy with divergent needle pattern

    NASA Astrophysics Data System (ADS)

    Borot de Battisti, M.; Maenhout, M.; de Senneville, B. Denis; Hautvast, G.; Binnekamp, D.; Lagendijk, J. J. W.; van Vulpen, M.; Moerland, M. A.

    2015-10-01

    Focal high-dose-rate (HDR) for prostate cancer has gained increasing interest as an alternative to whole gland therapy as it may contribute to the reduction of treatment related toxicity. For focal treatment, optimal needle guidance and placement is warranted. This can be achieved under MR guidance. However, MR-guided needle placement is currently not possible due to space restrictions in the closed MR bore. To overcome this problem, a MR-compatible, single-divergent needle-implant robotic device is under development at the University Medical Centre, Utrecht: placed between the legs of the patient inside the MR bore, this robot will tap the needle in a divergent pattern from a single rotation point into the tissue. This rotation point is just beneath the perineal skin to have access to the focal prostate tumor lesion. Currently, there is no treatment planning system commercially available which allows optimization of the dose distribution with such needle arrangement. The aim of this work is to develop an automatic inverse dose planning optimization tool for focal HDR prostate brachytherapy with needle insertions in a divergent configuration. A complete optimizer workflow is proposed which includes the determination of (1) the position of the center of rotation, (2) the needle angulations and (3) the dwell times. Unlike most currently used optimizers, no prior selection or adjustment of input parameters such as minimum or maximum dose or weight coefficients for treatment region and organs at risk is required. To test this optimizer, a planning study was performed on ten patients (treatment volumes ranged from 8.5 cm3to 23.3 cm3) by using 2-14 needle insertions. The total computation time of the optimizer workflow was below 20 min and a clinically acceptable plan was reached on average using only four needle insertions.

  18. Quality Control of High-Dose-Rate Brachytherapy: Treatment Delivery Analysis Using Statistical Process Control

    SciTech Connect

    Able, Charles M.; Bright, Megan; Frizzell, Bart

    2013-03-01

    Purpose: Statistical process control (SPC) is a quality control method used to ensure that a process is well controlled and operates with little variation. This study determined whether SPC was a viable technique for evaluating the proper operation of a high-dose-rate (HDR) brachytherapy treatment delivery system. Methods and Materials: A surrogate prostate patient was developed using Vyse ordnance gelatin. A total of 10 metal oxide semiconductor field-effect transistors (MOSFETs) were placed from prostate base to apex. Computed tomography guidance was used to accurately position the first detector in each train at the base. The plan consisted of 12 needles with 129 dwell positions delivering a prescribed peripheral dose of 200 cGy. Sixteen accurate treatment trials were delivered as planned. Subsequently, a number of treatments were delivered with errors introduced, including wrong patient, wrong source calibration, wrong connection sequence, single needle displaced inferiorly 5 mm, and entire implant displaced 2 mm and 4 mm inferiorly. Two process behavior charts (PBC), an individual and a moving range chart, were developed for each dosimeter location. Results: There were 4 false positives resulting from 160 measurements from 16 accurately delivered treatments. For the inaccurately delivered treatments, the PBC indicated that measurements made at the periphery and apex (regions of high-dose gradient) were much more sensitive to treatment delivery errors. All errors introduced were correctly identified by either the individual or the moving range PBC in the apex region. Measurements at the urethra and base were less sensitive to errors. Conclusions: SPC is a viable method for assessing the quality of HDR treatment delivery. Further development is necessary to determine the most effective dose sampling, to ensure reproducible evaluation of treatment delivery accuracy.

  19. High dose rates obtained outside ISS in June 2015 during SEP event.

    PubMed

    Dachev, T P; Tomov, B T; Matviichuk, Yu N; Dimitrov, Pl G; Bankov, N G

    2016-06-01

    The R3DR2 instrument performed measurements in the European Space Agency (ESA) EXPOSE-R2 platform outside the Russian "Zvezda" module of the International Space Station (ISS) in the period 24 October 2014-11 January 2016. It is the Liulin-type deposited energy spectrometer (DES) (Dachev et al., 2015a). Took place in November 2014, this was the first attempt to monitor a small solar energetic particle (SEP) event outside ISS using the Liulin-type DES (Dachev et al., 2015d). In this study, we describe the dosimetric characteristics of the largest SEP event, observed on 22 June 2015 with the R3DR2 instrument outside ISS. The main finding of this study is that SEP protons with a minimum energy of approximately 7MeV at the surface of the R3DR2 detector produced high dose rates, reaching >5000µGyh(-1), while the inner radiation belt maximum dose was at the level of 2200µGyh(-1). If a virtual external vehicle activity (EVA) was performed in the same period of the SEP maximum on 22 June 2015, the doses obtained in the skin of cosmonauts/astronauts can reach 2.84mGy after 6.5h, which is similar to the average absorbed dose inside ISS for 15days (Reitz et al., 2005). A comparison with other extreme events measured with Liulin-type instruments shows that SEPs similar to that observed on 22 June 2015 could be one of the most dangerous events for the cosmonauts/astronauts involved in EVA. PMID:27345205

  20. High dose rates obtained outside ISS in June 2015 during SEP event

    NASA Astrophysics Data System (ADS)

    Dachev, T. P.; Tomov, B. T.; Matviichuk, Yu. N.; Dimitrov, Pl. G.; Bankov, N. G.

    2016-06-01

    The R3DR2 instrument performed measurements in the European Space Agency (ESA) EXPOSE-R2 platform outside the Russian "Zvezda" module of the International Space Station (ISS) in the period 24 October 2014-11 January 2016. It is the Liulin-type deposited energy spectrometer (DES) (Dachev et al., 2015a). Took place in November 2014, this was the first attempt to monitor a small solar energetic particle (SEP) event outside ISS using the Liulin-type DES (Dachev et al., 2015d). In this study, we describe the dosimetric characteristics of the largest SEP event, observed on 22 June 2015 with the R3DR2 instrument outside ISS. The main finding of this study is that SEP protons with a minimum energy of approximately 7 MeV at the surface of the R3DR2 detector produced high dose rates, reaching >5000 μGy h-1, while the inner radiation belt maximum dose was at the level of 2200 μGy h-1. If a virtual external vehicle activity (EVA) was performed in the same period of the SEP maximum on 22 June 2015, the doses obtained in the skin of cosmonauts/astronauts can reach 2.84 mGy after 6.5 h, which is similar to the average absorbed dose inside ISS for 15 days (Reitz et al., 2005). A comparison with other extreme events measured with Liulin-type instruments shows that SEPs similar to that observed on 22 June 2015 could be one of the most dangerous events for the cosmonauts/astronauts involved in EVA.

  1. Radiation dose rates now and in the future for residents neighboring restricted areas of the Fukushima Daiichi Nuclear Power Plant.

    PubMed

    Harada, Kouji H; Niisoe, Tamon; Imanaka, Mie; Takahashi, Tomoyuki; Amako, Katsumi; Fujii, Yukiko; Kanameishi, Masatoshi; Ohse, Kenji; Nakai, Yasumichi; Nishikawa, Tamami; Saito, Yuuichi; Sakamoto, Hiroko; Ueyama, Keiko; Hisaki, Kumiko; Ohara, Eiji; Inoue, Tokiko; Yamamoto, Kanako; Matsuoka, Yukiyo; Ohata, Hitomi; Toshima, Kazue; Okada, Ayumi; Sato, Hitomi; Kuwamori, Toyomi; Tani, Hiroko; Suzuki, Reiko; Kashikura, Mai; Nezu, Michiko; Miyachi, Yoko; Arai, Fusako; Kuwamori, Masanori; Harada, Sumiko; Ohmori, Akira; Ishikawa, Hirohiko; Koizumi, Akio

    2014-03-11

    Radiation dose rates were evaluated in three areas neighboring a restricted area within a 20- to 50-km radius of the Fukushima Daiichi Nuclear Power Plant in August-September 2012 and projected to 2022 and 2062. Study participants wore personal dosimeters measuring external dose equivalents, almost entirely from deposited radionuclides (groundshine). External dose rate equivalents owing to the accident averaged 1.03, 2.75, and 1.66 mSv/y in the village of Kawauchi, the Tamano area of Soma, and the Haramachi area of Minamisoma, respectively. Internal dose rates estimated from dietary intake of radiocesium averaged 0.0058, 0.019, and 0.0088 mSv/y in Kawauchi, Tamano, and Haramachi, respectively. Dose rates from inhalation of resuspended radiocesium were lower than 0.001 mSv/y. In 2012, the average annual doses from radiocesium were close to the average background radiation exposure (2 mSv/y) in Japan. Accounting only for the physical decay of radiocesium, mean annual dose rates in 2022 were estimated as 0.31, 0.87, and 0.53 mSv/y in Kawauchi, Tamano, and Haramachi, respectively. The simple and conservative estimates are comparable with variations in the background dose, and unlikely to exceed the ordinary permissible dose rate (1 mSv/y) for the majority of the Fukushima population. Health risk assessment indicates that post-2012 doses will increase lifetime solid cancer, leukemia, and breast cancer incidences by 1.06%, 0.03% and 0.28% respectively, in Tamano. This assessment was derived from short-term observation with uncertainties and did not evaluate the first-year dose and radioiodine exposure. Nevertheless, this estimate provides perspective on the long-term radiation exposure levels in the three regions.

  2. Radiation dose rates now and in the future for residents neighboring restricted areas of the Fukushima Daiichi Nuclear Power Plant

    PubMed Central

    Harada, Kouji H.; Niisoe, Tamon; Imanaka, Mie; Takahashi, Tomoyuki; Amako, Katsumi; Fujii, Yukiko; Kanameishi, Masatoshi; Ohse, Kenji; Nakai, Yasumichi; Nishikawa, Tamami; Saito, Yuuichi; Sakamoto, Hiroko; Ueyama, Keiko; Hisaki, Kumiko; Ohara, Eiji; Inoue, Tokiko; Yamamoto, Kanako; Matsuoka, Yukiyo; Ohata, Hitomi; Toshima, Kazue; Okada, Ayumi; Sato, Hitomi; Kuwamori, Toyomi; Tani, Hiroko; Suzuki, Reiko; Kashikura, Mai; Nezu, Michiko; Miyachi, Yoko; Arai, Fusako; Kuwamori, Masanori; Harada, Sumiko; Ohmori, Akira; Ishikawa, Hirohiko; Koizumi, Akio

    2014-01-01

    Radiation dose rates were evaluated in three areas neighboring a restricted area within a 20- to 50-km radius of the Fukushima Daiichi Nuclear Power Plant in August–September 2012 and projected to 2022 and 2062. Study participants wore personal dosimeters measuring external dose equivalents, almost entirely from deposited radionuclides (groundshine). External dose rate equivalents owing to the accident averaged 1.03, 2.75, and 1.66 mSv/y in the village of Kawauchi, the Tamano area of Soma, and the Haramachi area of Minamisoma, respectively. Internal dose rates estimated from dietary intake of radiocesium averaged 0.0058, 0.019, and 0.0088 mSv/y in Kawauchi, Tamano, and Haramachi, respectively. Dose rates from inhalation of resuspended radiocesium were lower than 0.001 mSv/y. In 2012, the average annual doses from radiocesium were close to the average background radiation exposure (2 mSv/y) in Japan. Accounting only for the physical decay of radiocesium, mean annual dose rates in 2022 were estimated as 0.31, 0.87, and 0.53 mSv/y in Kawauchi, Tamano, and Haramachi, respectively. The simple and conservative estimates are comparable with variations in the background dose, and unlikely to exceed the ordinary permissible dose rate (1 mSv/y) for the majority of the Fukushima population. Health risk assessment indicates that post-2012 doses will increase lifetime solid cancer, leukemia, and breast cancer incidences by 1.06%, 0.03% and 0.28% respectively, in Tamano. This assessment was derived from short-term observation with uncertainties and did not evaluate the first-year dose and radioiodine exposure. Nevertheless, this estimate provides perspective on the long-term radiation exposure levels in the three regions. PMID:24567380

  3. Radiation dose rates now and in the future for residents neighboring restricted areas of the Fukushima Daiichi Nuclear Power Plant.

    PubMed

    Harada, Kouji H; Niisoe, Tamon; Imanaka, Mie; Takahashi, Tomoyuki; Amako, Katsumi; Fujii, Yukiko; Kanameishi, Masatoshi; Ohse, Kenji; Nakai, Yasumichi; Nishikawa, Tamami; Saito, Yuuichi; Sakamoto, Hiroko; Ueyama, Keiko; Hisaki, Kumiko; Ohara, Eiji; Inoue, Tokiko; Yamamoto, Kanako; Matsuoka, Yukiyo; Ohata, Hitomi; Toshima, Kazue; Okada, Ayumi; Sato, Hitomi; Kuwamori, Toyomi; Tani, Hiroko; Suzuki, Reiko; Kashikura, Mai; Nezu, Michiko; Miyachi, Yoko; Arai, Fusako; Kuwamori, Masanori; Harada, Sumiko; Ohmori, Akira; Ishikawa, Hirohiko; Koizumi, Akio

    2014-03-11

    Radiation dose rates were evaluated in three areas neighboring a restricted area within a 20- to 50-km radius of the Fukushima Daiichi Nuclear Power Plant in August-September 2012 and projected to 2022 and 2062. Study participants wore personal dosimeters measuring external dose equivalents, almost entirely from deposited radionuclides (groundshine). External dose rate equivalents owing to the accident averaged 1.03, 2.75, and 1.66 mSv/y in the village of Kawauchi, the Tamano area of Soma, and the Haramachi area of Minamisoma, respectively. Internal dose rates estimated from dietary intake of radiocesium averaged 0.0058, 0.019, and 0.0088 mSv/y in Kawauchi, Tamano, and Haramachi, respectively. Dose rates from inhalation of resuspended radiocesium were lower than 0.001 mSv/y. In 2012, the average annual doses from radiocesium were close to the average background radiation exposure (2 mSv/y) in Japan. Accounting only for the physical decay of radiocesium, mean annual dose rates in 2022 were estimated as 0.31, 0.87, and 0.53 mSv/y in Kawauchi, Tamano, and Haramachi, respectively. The simple and conservative estimates are comparable with variations in the background dose, and unlikely to exceed the ordinary permissible dose rate (1 mSv/y) for the majority of the Fukushima population. Health risk assessment indicates that post-2012 doses will increase lifetime solid cancer, leukemia, and breast cancer incidences by 1.06%, 0.03% and 0.28% respectively, in Tamano. This assessment was derived from short-term observation with uncertainties and did not evaluate the first-year dose and radioiodine exposure. Nevertheless, this estimate provides perspective on the long-term radiation exposure levels in the three regions. PMID:24567380

  4. Salvage high-dose-rate (HDR) brachytherapy for recurrent head-and-neck cancer

    SciTech Connect

    Hepel, Jaroslaw T.; Syed, A.M. Nisar . E-mail: bvigil@memnet.org; Puthawala, Ajmel; Sharma, Anil; Frankel, Paul

    2005-08-01

    Background: A significant portion of head-and-neck cancer patients will develop persistent or recurrent disease after definitive treatment. Radiation therapy is often used as definitive therapy or as an adjunct to surgery. Recurrent cancer of the head and neck in the previously irradiated field is, thus, a common occurrence and poses a therapeutic challenge. Some studies have evaluated low-dose-rate (LDR) brachytherapy as a therapeutic option, including a large case series with long-term follow-up by our own institution. High-dose-rate (HDR) brachytherapy offers therapeutic advantages over LDR brachytherapy. This study evaluates the local control and outcomes of patients with previously irradiated recurrent head-and-neck cancer treated with HDR interstitial brachytherapy. Methods and Materials: Between 1997 and 2002, 30 patients who received prior radiation therapy for primary tumors of the head and neck were treated for biopsy-proven recurrent disease. All patients received previous radiation as definitive therapy alone or as adjunct to surgery. All patients were inoperable, refused surgery, or had gross residual disease after salvage surgery for their recurrent disease. Thirty-six sites on the 30 patients were implanted by application of high-dose-rate interstitial brachytherapy techniques with mean tumor dose of 34 Gy (18-48 Gy) in twice daily fractions of 300 to 400cGy per fraction. Results: At a minimum follow-up of 12 months, local tumor control was achieved in 69% of implanted sites. Disease-specific survival at 1 and 2 years was 54% and 45%, respectively. Overall survival at 1 and 2 years was 56% and 37%, respectively. Grade 3/4 late complications occurred in 16% of the patients. No fatal complications occurred. Conclusion: HDR brachytherapy can play an important role in the salvage treatment of previously irradiated recurrent head-and-neck cancer. This study shows that comparable results are obtained by HDR brachytherapy with fewer late complications than

  5. Modelling the dynamics of ambient dose rates induced by radiocaesium in the Fukushima terrestrial environment.

    PubMed

    Gonze, Marc-André; Mourlon, Christophe; Calmon, Philippe; Manach, Erwan; Debayle, Christophe; Baccou, Jean

    2016-09-01

    Since the Fukushima accident, Japanese scientists have been intensively monitoring ambient radiations in the highly contaminated territories situated within 80 km of the nuclear site. The surveys that were conducted through mainly carborne, airborne and in situ gamma-ray measurement devices, enabled to efficiently characterize the spatial distribution and temporal evolution of air dose rates induced by Caesium-134 and Caesium-137 in the terrestrial systems. These measurements revealed that radiation levels decreased at rates greater than expected from physical decay in 2011-2012 (up to a factor of 2), and dependent on the type of environment (i.e. urban, agricultural or forest). Unlike carborne measurements that may have been strongly influenced by the depuration of road surfaces, no obvious reason can be invoked for airborne measurements, especially above forests that are known to efficiently retain and recycle radiocaesium. The purpose of our research project is to develop a comprehensive understanding of the data acquired by Japanese, and identify the environmental mechanisms or factors that may explain such decays. The methodology relies on the use of a process-based and spatially-distributed dynamic model that predicts radiocaesium transfer and associated air dose rates inside/above a terrestrial environment (e.g., forests, croplands, meadows, bare soils and urban areas). Despite the lack of site-specific data, our numerical study predicts decrease rates that are globally consistent with both aerial and in situ observations. The simulation at a flying altitude of 200 m indicated that ambient radiation levels decreased over the first 12 months by about 45% over dense urban areas, 15% above evergreen coniferous forests and between 2 and 12% above agricultural lands, owing to environmental processes that are identified and discussed. In particular, we demonstrate that the decrease over evergreen coniferous regions might be due the combined effects of canopy

  6. Modelling the dynamics of ambient dose rates induced by radiocaesium in the Fukushima terrestrial environment.

    PubMed

    Gonze, Marc-André; Mourlon, Christophe; Calmon, Philippe; Manach, Erwan; Debayle, Christophe; Baccou, Jean

    2016-09-01

    Since the Fukushima accident, Japanese scientists have been intensively monitoring ambient radiations in the highly contaminated territories situated within 80 km of the nuclear site. The surveys that were conducted through mainly carborne, airborne and in situ gamma-ray measurement devices, enabled to efficiently characterize the spatial distribution and temporal evolution of air dose rates induced by Caesium-134 and Caesium-137 in the terrestrial systems. These measurements revealed that radiation levels decreased at rates greater than expected from physical decay in 2011-2012 (up to a factor of 2), and dependent on the type of environment (i.e. urban, agricultural or forest). Unlike carborne measurements that may have been strongly influenced by the depuration of road surfaces, no obvious reason can be invoked for airborne measurements, especially above forests that are known to efficiently retain and recycle radiocaesium. The purpose of our research project is to develop a comprehensive understanding of the data acquired by Japanese, and identify the environmental mechanisms or factors that may explain such decays. The methodology relies on the use of a process-based and spatially-distributed dynamic model that predicts radiocaesium transfer and associated air dose rates inside/above a terrestrial environment (e.g., forests, croplands, meadows, bare soils and urban areas). Despite the lack of site-specific data, our numerical study predicts decrease rates that are globally consistent with both aerial and in situ observations. The simulation at a flying altitude of 200 m indicated that ambient radiation levels decreased over the first 12 months by about 45% over dense urban areas, 15% above evergreen coniferous forests and between 2 and 12% above agricultural lands, owing to environmental processes that are identified and discussed. In particular, we demonstrate that the decrease over evergreen coniferous regions might be due the combined effects of canopy

  7. High-Dose-Rate Endobronchial Brachytherapy for Recurrent Airway Obstruction From Hyperplastic Granulation Tissue

    SciTech Connect

    Tendulkar, Rahul D. Fleming, Peter A.; Reddy, Chandana A.; Gildea, Thomas R.; Machuzak, Michael; Mehta, Atul C.

    2008-03-01

    Purpose: Benign endobronchial granulation tissue causes airway obstruction in up to 20% of patients after lung transplantation or stent placement. High-dose-rate endobronchial brachytherapy (HDR-EB) has been successful in some cases refractory to standard bronchoscopic interventions. Methods and Materials: Between September 2004 and May 2005, 8 patients with refractory benign airway obstruction were treated with HDR-EB, using one to two fractions of Ir-192 prescribed to 7.1 Gy at a radius of 1 cm. Charts were retrospectively reviewed to evaluate subjective clinical response, forced expiratory volume in 1 second (FEV{sub 1}), and frequency of therapeutic bronchoscopies over 6-month periods before and after HDR-EB. Results: The median follow-up was 14.6 months, and median survival was 10.5 months. The mean number of bronchoscopic interventions improved from 3.1 procedures in the 6-month pretreatment period to 1.8 after HDR-EB. Mean FEV{sub 1} improved from 36% predicted to 46% predicted. Six patients had a good-to-excellent subjective early response, but only one maintained this response beyond 6 months, and this was the only patient treated with HDR-EB within 24 h from the most recent bronchoscopic intervention. Five patients have expired from causes related to their chronic pulmonary disease, including one from hemoptysis resulting from a bronchoarterial fistula. Conclusion: High-dose-rate-EB may be an effective treatment for select patients with refractory hyperplastic granulation tissue causing recurrent airway stenosis. Performing HDR-EB within 24-48 h after excision of obstructive granulation tissue could further improve outcomes. Careful patient selection is important to maximize therapeutic benefit and minimize toxicity. The optimal patient population, dose, and timing of HDR-EB should be investigated prospectively.

  8. Safety management of nuclear medicine personnel with visualisation of air dose rate.

    PubMed

    Kawase, S; Ohno, K; Nakamoto, Y; Miyatake, H

    2015-07-01

    Many people are anxious about radiation exposure for the reason that radiation cannot be seen. With the aim of devising a way for medical personnel to perform their medical duties without worry about radiation exposure, we attempted safety management using a system that displays the air dose of radiation in real time. Measurements were made in a lung ventilation scintigraphy examination room with the use of Xe-133. An SCI-type RI detector from Hamamatsu Photonics, which displays the air dose rate in real time, was used for the measurements. These radiation measurements were continued from the start to finish of the examination. The measurements were made in two locations, on the patient inhalation tube side and on the opposite side. Measurements were made on the patient tube side in 24 tests and on the opposite side in 12 tests. The maximum air dose rate was 3.7 ± 2.1 μSv/h on the patient tube side and 1.1 ± 0.5 μSv/h on the opposite side. Thus, the level on the opposite side was about 1/5 that of the tube side. To accurately perform lung ventilation scintigraphy, a medical worker needs to observe the patient's breathing status up close. Because of this, some medical workers are worried about radiation exposure during tests. The simplest way to reduce exposure would be to maintain a distance from the examination tube that is the source of radiation. The measurements in this study were made to encourage medical workers' recognition of this fact. Displaying specific numbers not only serves as basic data for managing staff operations, but is also thought to reassure workers through visualization.

  9. High Dose-Rate Intracavitary Brachytherapy for Cervical Carcinomas With Lower Vaginal Infiltration

    SciTech Connect

    Kazumoto, Tomoko Kato, Shingo; Tabushi, Katsuyoshi; Kutsutani-Nakamura, Yuzuru; Mizuno, Hideyuki; Takahashi, Michiko; Shiromizu, Kenji; Saito, Yoshihiro

    2007-11-15

    Purpose: This report presents the clinical applications of an automated treatment-planning program of high-dose-rate intracavitary brachytherapy (HDR-ICBT) for advanced uterine cervical cancer infiltrating the parametrium and the lower vagina. Methods and Materials: We adopted HDR-ICBT under optimized dose distribution for 22 cervical cancer patients with tumor infiltration of the lower half of the vagina. All patients had squamous cell carcinoma with International Federation of Gynecology and Obstetrics clinical stages IIB-IVA. After whole pelvic external beam irradiation with a median dose of 30.6 Gy, a conventional ICBT was applied as 'pear-shaped' isodose curve. Then 3-4 more sessions per week of this new method of ICBT were performed. With a simple determination of the treatment volume, the cervix-parametrium, and the lower vagina were covered automatically and simultaneously by this program, that was designated as 'utero-vaginal brachytherapy'. The mean follow-up period was 87.4 months (range, 51.8-147.9 months). Results: Isodose curve for this program was 'galaxy-shaped'. Five-year local-progression-free survival and overall survival rates were 90.7% and 81.8%, respectively. Among those patients with late complications higher than Grade 2 Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer morbidity score, only one (4.5%) developed severe proctitis. Conclusions: Because of the favorable treatment outcomes, this treatment-planning program with a simplified target-volume based dosimetry was proposed for cervical cancer with lower vaginal infiltration.

  10. Measurement uncertainty analysis of low-dose-rate prostate seed brachytherapy: post-implant dosimetry.

    PubMed

    Gregory, Kent J; Pattison, John E; Bibbo, Giovanni

    2015-03-01

    The minimal dose covering 90 % of the prostate volume--D 90--is arguably the most important dosimetric parameter in low-dose-rate prostate seed brachytherapy. In this study an analysis of the measurement uncertainties in D 90 from low-dose-rate prostate seed brachytherapy was conducted for two common treatment procedures with two different post-implant dosimetry methods. The analysis was undertaken in order to determine the magnitude of D 90 uncertainty, how the magnitude of the uncertainty varied when D 90 was calculated using different dosimetry methods, and which factors were the major contributors to the uncertainty. The analysis considered the prostate as being homogeneous and tissue equivalent and made use of published data, as well as original data collected specifically for this analysis, and was performed according to the Guide to the expression of uncertainty in measurement (GUM). It was found that when prostate imaging and seed implantation were conducted in two separate sessions using only CT images for post-implant analysis, the expanded uncertainty in D 90 values were about 25 % at the 95 % confidence interval. When prostate imaging and seed implantation were conducted during a single session using CT and ultrasound images for post-implant analysis, the expanded uncertainty in D 90 values were about 33 %. Methods for reducing these uncertainty levels are discussed. It was found that variations in contouring the target tissue made the largest contribution to D 90 uncertainty, while the uncertainty in seed source strength made only a small contribution. It is important that clinicians appreciate the overall magnitude of D 90 uncertainty and understand the factors that affect it so that clinical decisions are soundly based, and resources are appropriately allocated.

  11. Influence of electron dose rate on electron counting images recorded with the K2 camera.

    PubMed

    Li, Xueming; Zheng, Shawn Q; Egami, Kiyoshi; Agard, David A; Cheng, Yifan

    2013-11-01

    A recent technological breakthrough in electron cryomicroscopy (cryoEM) is the development of direct electron detection cameras for data acquisition. By bypassing the traditional phosphor scintillator and fiber optic coupling, these cameras have greatly enhanced sensitivity and detective quantum efficiency (DQE). Of the three currently available commercial cameras, the Gatan K2 Summit was designed specifically for counting individual electron events. Counting further enhances the DQE, allows for practical doubling of detector resolution and eliminates noise arising from the variable deposition of energy by each primary electron. While counting has many advantages, undercounting of electrons happens when more than one electron strikes the same area of the detector within the analog readout period (coincidence loss), which influences image quality. In this work, we characterized the K2 Summit in electron counting mode, and studied the relationship of dose rate and coincidence loss and its influence on the quality of counted images. We found that coincidence loss reduces low frequency amplitudes but has no significant influence on the signal-to-noise ratio of the recorded image. It also has little influence on high frequency signals. Images of frozen hydrated archaeal 20S proteasome (~700 kDa, D7 symmetry) recorded at the optimal dose rate retained both high-resolution signal and low-resolution contrast and enabled calculating a 3.6 Å three-dimensional reconstruction from only 10,000 particles.

  12. Influence of electron dose rate on electron counting images recorded with the K2 camera.

    PubMed

    Li, Xueming; Zheng, Shawn Q; Egami, Kiyoshi; Agard, David A; Cheng, Yifan

    2013-11-01

    A recent technological breakthrough in electron cryomicroscopy (cryoEM) is the development of direct electron detection cameras for data acquisition. By bypassing the traditional phosphor scintillator and fiber optic coupling, these cameras have greatly enhanced sensitivity and detective quantum efficiency (DQE). Of the three currently available commercial cameras, the Gatan K2 Summit was designed specifically for counting individual electron events. Counting further enhances the DQE, allows for practical doubling of detector resolution and eliminates noise arising from the variable deposition of energy by each primary electron. While counting has many advantages, undercounting of electrons happens when more than one electron strikes the same area of the detector within the analog readout period (coincidence loss), which influences image quality. In this work, we characterized the K2 Summit in electron counting mode, and studied the relationship of dose rate and coincidence loss and its influence on the quality of counted images. We found that coincidence loss reduces low frequency amplitudes but has no significant influence on the signal-to-noise ratio of the recorded image. It also has little influence on high frequency signals. Images of frozen hydrated archaeal 20S proteasome (~700 kDa, D7 symmetry) recorded at the optimal dose rate retained both high-resolution signal and low-resolution contrast and enabled calculating a 3.6 Å three-dimensional reconstruction from only 10,000 particles. PMID:23968652

  13. 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.

  14. A Comprehensive Analysis of Cardiac Dose in Balloon-Based High-Dose-Rate Brachytherapy for Left-Sided Breast Cancer

    SciTech Connect

    Valakh, Vladimir; Kim, Yongbok; Werts, E. Day; Trombetta, Mark G.

    2012-04-01

    Purpose: To investigate radiation dose to the heart in 60 patients with left-sided breast cancer who were treated with balloon-based high-dose-rate brachytherapy using MammoSite or Contura applicators. Methods and Materials: We studied 60 consecutive women with breast cancer who were treated with 34 Gy in 10 twice-daily fractions using MammoSite (n = 37) or Contura (n = 23) applicators. The whole heart and the left and right ventricles were retrospectively delineated, and dose-volume histograms were analyzed. Multiple dosimetrics were reported, such as mean dose (D{sub mean}); relative volume receiving 1.7, 5, 10, and 20 Gy (V1.7, V5, V10, and V20, respectively); dose to 1 cc (D{sub 1cc}); and maximum point dose (D{sub max}). Biologic metrics, biologically effective dose and generalized equivalent uniform dose were computed. The impact of lumpectomy cavity location on cardiac dose was investigated. Results: The average {+-} standard deviation of D{sub mean} was 2.45 {+-} 0.94 Gy (range, 0.56-4.68) and 3.29 {+-} 1.28 Gy (range, 0.77-6.35) for the heart and the ventricles, respectively. The average whole heart V5 and V10 values were 10.2% and 1.3%, respectively, and the heart D{sub max} was >20 Gy in 7 of 60 (11.7%) patients and >25 Gy in 3 of 60 (5%) patients. No cardiac tissue received {>=}30 Gy. The V1.7, V5, V10, V20, and D{sub mean} values were all higher for the ventricles than for the whole heart. For balloons located in the upper inner quadrant of the breast, the average whole heart D{sub mean} was highest. The D{sub mean}, biologically effective dose, and generalized equivalent uniform dose values for heart and ventricles decreased with increasing minimal distance from the surface of the balloon. Conclusions: On the basis of these comprehensive cardiac dosimetric data, we recommend that cardiac dose be routinely reported and kept as low as possible in balloon-based high-dose-rate brachytherapy treatment planning for patients with left-sided breast cancer so

  15. Association between absolute volumes of lung spared from low-dose irradiation and radiation-induced lung injury after intensity-modulated radiotherapy in lung cancer: a retrospective analysis

    PubMed Central

    Chen, Jinmei; Hong, Jinsheng; Zou, Xi; Lv, Wenlong; Guo, Feibao; Hong, Hualan; Zhang, Weijian

    2015-01-01

    The aim of this study was to investigate the association between absolute volumes of lung spared from low-dose irradiation and radiation-induced lung injury (RILI) after intensity-modulated radiotherapy (IMRT) for lung cancer. The normal lung relative volumes receiving greater than 5, 10, 20 and 30 Gy (V5–30) mean lung dose (MLD), and absolute volumes spared from greater than 5, 10, 20 and 30 Gy (AVS5–30) for the bilateral and ipsilateral lungs of 83 patients were recorded. Any association of clinical factors and dose–volume parameters with Grade ≥2 RILI was analyzed. The median follow-up was 12.3 months; 18 (21.7%) cases of Grade 2 RILI, seven (8.4%) of Grade 3 and two (2.4%) of Grade 4 were observed. Univariate analysis revealed the located lobe of the primary tumor. V5, V10, V20, MLD of the ipsilateral lung, V5, V10, V20, V30 and MLD of the bilateral lung, and AVS5 and AVS10 of the ipsilateral lung were associated with Grade ≥2 RILI (P < 0.05). Multivariate analysis indicated AVS5 of the ipsilateral lung was prognostic for Grade ≥2 RILI (P = 0.010, OR = 0.272, 95% CI: 0.102–0.729). Receiver operating characteristic curves indicated Grade ≥2 RILI could be predicted using AVS5 of the ipsilateral lung (area under curve, 0.668; cutoff value, 564.9 cm3; sensitivity, 60.7%; specificity, 70.4%). The incidence of Grade ≥2 RILI was significantly lower with AVS5 of the ipsilateral lung ≥564.9 cm3 than with AVS5 < 564.9 cm3 (P = 0.008). Low-dose irradiation relative volumes and MLD of the bilateral or ipsilateral lung were associated with Grade ≥2 RILI, and AVS5 of the ipsilateral lung was prognostic for Grade ≥2 RILI for lung cancer after IMRT. PMID:26454068

  16. Development of a high precision dosimetry system for the measurement of surface dose rate distribution for eye applicators

    SciTech Connect

    Eichmann, Marion; Fluehs, Dirk; Spaan, Bernhard

    2009-10-15

    Purpose: The therapeutic outcome of the therapy with ophthalmic applicators is highly dependent on the application of a sufficient dose to the tumor, whereas the dose applied to the surrounding tissue needs to be minimized. The goal for the newly developed apparatus described in this work is the determination of the individual applicator surface dose rate distribution with a high spatial resolution and a high precision in dose rate with respect to time and budget constraints especially important for clinical procedures. Inhomogeneities of the dose rate distribution can be detected and taken into consideration for the treatment planning. Methods: In order to achieve this, a dose rate profile as well as a surface profile of the applicator are measured and correlated with each other. An instrumental setup has been developed consisting of a plastic scintillator detector system and a newly designed apparatus for guiding the detector across the applicator surface at a constant small distance. It performs an angular movement of detector and applicator with high precision. Results: The measurements of surface dose rate distributions discussed in this work demonstrate the successful operation of the measuring setup. Measuring the surface dose rate distribution with a small distance between applicator and detector and with a high density of measuring points results in a complete and gapless coverage of the applicator surface, being capable of distinguishing small sized spots with high activities. The dosimetrical accuracy of the measurements and its analysis is sufficient (uncertainty in the dose rate in terms of absorbed dose to water is <7%), especially when taking the surgical techniques in positioning of the applicator on the eyeball into account. Conclusions: The method developed so far allows a fully automated quality assurance of eye applicators even under clinical conditions. These measurements provide the basis for future calculation of a full 3D dose rate

  17. Dose rate effects on array CCDs exposed by Co-60 γ rays induce saturation output degradation and annealing tests

    SciTech Connect

    Wang, Zujun Chen, Wei; He, Baoping; Yao, Zhibin; Xiao, Zhigang; Sheng, Jiangkun; Liu, Minbo

    2015-10-15

    The experimental tests of dose rate and annealing effects on array charge-coupled devices (CCDs) are presented. The saturation output voltage (V{sub S}) versus the total dose at the dose rates of 0.01, 0.1, 1.0, 10.0 and 50 rad(Si)/s are compared. Annealing tests are performed to eliminate the time-dependent effects. The V{sub S} degradation levels depend on the dose rates. The V{sub S} degradation mechanism induced by dose rate and annealing effects is analyzed. The V{sub S} at 20 krad(Si) with the dose rate of 0.03 rad(Si)/s are supplemented to assure the degradation curves between the dose rates of 0.1 and 0.01 rad(Si)/s. The CCDs are divided into two groups, with one group biased and the other unbiased during {sup 60}Co γ radiation. The V{sub S} degradation levels of the biased CCDs during radiation are more severe than that of the unbiased CCDs.

  18. TLD skin dose measurements and acute and late effects after lumpectomy and high-dose-rate brachytherapy only for early breast cancer

    SciTech Connect

    Perera, Francisco . E-mail: francisco.perera@lrcc.on.ca; Chisela, Frank; Stitt, Larry; Engel, Jay; Venkatesan, Varagur

    2005-08-01

    Purpose: This report examines the relationships between measured skin doses and the acute and late skin and soft tissue changes in a pilot study of lumpectomy and high-dose-rate brachytherapy only for breast cancer. Methods and Materials: Thirty-seven of 39 women enrolled in this pilot study of high-dose-rate brachytherapy (37.2 Gy in 10 fractions b.i.d.) each had thermoluminescent dosimetry (TLD) at 5 points on the skin of the breast overlying the implant volume. Skin changes at TLD dose points and fibrosis at the lumpectomy site were documented every 6 to 12 months posttreatment using a standardized physician-rated cosmesis questionnaire. The relationships between TLD dose and acute skin reaction, pigmentation, or telangiectasia at 5 years were analyzed using the GEE algorithm and the GENMOD procedure in the SAS statistical package. Fisher's exact test was used to determine whether there were any significant associations between acute skin reaction and late pigmentation or telangiectasia or between the volumes encompassed by various isodoses and fibrosis or fat necrosis. Results: The median TLD dose per fraction (185 dose points) multiplied by 10 was 9.2 Gy. In all 37 patients, acute skin reaction Grade 1 or higher was observed at 5.9% (6 of 102) of dose points receiving 10 Gy or less vs. 44.6% (37 of 83) of dose points receiving more than 10 Gy (p < 0.0001). In 25 patients at 60 months, 1.5% telangiectasia was seen at dose points receiving 10 Gy or less (1 of 69) vs. 18% (10 of 56) telangiectasia at dose points receiving more than 10 Gy (p 0.004). Grade 1 or more pigmentation developed at 1.5% (1 of 69) of dose points receiving less than 10 Gy vs. 25% (14 of 56) of dose points receiving more than 10 Gy (p < 0.001). A Grade 1 or more acute skin reaction was also significantly associated with development of Grade 1 or more pigmentation or telangiectasia at 60 months. This association was most significant for acute reaction and telangiectasia directly over the

  19. Effect of radiocesium transfer on ambient dose rate in forest environments affected by the Fukushima Nuclear Power Plant accident

    NASA Astrophysics Data System (ADS)

    Kato, H.

    2015-12-01

    We investigated the transfer of canopy-intercepted radiocesium to the forest floor during 3 years following the Fukushima Daiichi Nuclear Power Plant accident. The cesium-137 (Cs-137) contents in throughfall, stemflow, and litterfall were monitored in two coniferous stands (plantation of Japanese cedar) and a deciduous broad-leaved forest stand (Japanese oak with red pine). We also measured the ambient dose rate (ADR) at different heights in the forest using a survey meter and a portable Ge gamma-ray detector. Total Cs-137 deposition flux from the canopy to forest floor for the mature cedar, young cedar, and the mixed broad-leaved stands were 166 kBq/m2, 174 kBq/m2, and 60 kBq/m2, respectively. These values correspond to 38%, 40% and 13% of total atmospheric input after the accident. The ambient dose rate in forest exhibited height dependency and its vertical distribution varied with forest type and stand age. The ambient dose rate showed an exponential decrease with time for all the forest sites, however the decreasing trend differed depending on the height of dose measurement and forest type. The ambient dose rate at the canopy (approx. 10 m-height) decreased faster than that expected from physical decay of the two radiocesium isotopes, whereas those at the forest floor varied between the three forest stands. The radiocesium deposition via throughfall seemed to increase ambient dose rate during the first 200 days after the accident, however there was no clear relationship between litterfall and ambient dose rate since 400 days after the accident. These data suggested that the ambient dose rate in forest environment varied both spatially and temporally reflecting the transfer of radiocesium from canopy to forest floor. However, further monitoring investigation and analysis are required to determine the effect of litterfall on long-term trend of ambient dose rate in forest environments.

  20. Eosinophil count - absolute

    MedlinePlus

    Eosinophils; Absolute eosinophil count ... the white blood cell count to give the absolute eosinophil count. ... than 500 cells per microliter (cells/mcL). Normal value ranges may vary slightly among different laboratories. Talk ...