The susceptibility of TaO x-based memristors to high dose rate ionizing radiation and total ionizing dose

DOE PAGES

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

2014-11-11

This paper investigates the effects of high dose rate ionizing radiation and total ionizing dose (TID) on tantalum oxide (TaO x) memristors. Transient data were obtained during the pulsed exposures for dose rates ranging from approximately 5.0 ×10 7 rad(Si)/s to 4.7 ×10 8 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 ×10 8 rad(Si)/s. This is the first dose rate study on any type ofmore » memristive memory technology. In addition to assessing the tolerance of TaO x 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

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.

Comparative performance analysis for computer aided lung nodule detection and segmentation on ultra-low-dose vs. standard-dose CT

NASA Astrophysics Data System (ADS)

Wiemker, Rafael; Rogalla, Patrik; Opfer, Roland; Ekin, Ahmet; Romano, Valentina; Bülow, Thomas

2006-03-01

The performance of computer aided lung nodule detection (CAD) and computer aided nodule volumetry is compared between standard-dose (70-100 mAs) and ultra-low-dose CT images (5-10 mAs). A direct quantitative performance comparison was possible, since for each patient both an ultra-low-dose and a standard-dose CT scan were acquired within the same examination session. The data sets were recorded with a multi-slice CT scanner at the Charite university hospital Berlin with 1 mm slice thickness. Our computer aided nodule detection and segmentation algorithms were deployed on both ultra-low-dose and standard-dose CT data without any dose-specific fine-tuning or preprocessing. As a reference standard 292 nodules from 20 patients were visually identified, each nodule both in ultra-low-dose and standard-dose data sets. The CAD performance was analyzed by virtue of multiple FROC curves for different lower thresholds of the nodule diameter. For nodules with a volume-equivalent diameter equal or larger than 4 mm (149 nodules pairs), we observed a detection rate of 88% at a median false positive rate of 2 per patient in standard-dose images, and 86% detection rate in ultra-low-dose images, also at 2 FPs per patient. Including even smaller nodules equal or larger than 2 mm (272 nodules pairs), we observed a detection rate of 86% in standard-dose images, and 84% detection rate in ultra-low-dose images, both at a rate of 5 FPs per patient. Moreover, we observed a correlation of 94% between the volume-equivalent nodule diameter as automatically measured on ultra-low-dose versus on standard-dose images, indicating that ultra-low-dose CT is also feasible for growth-rate assessment in follow-up examinations. The comparable performance of lung nodule CAD in ultra-low-dose and standard-dose images is of particular interest with respect to lung cancer screening of asymptomatic patients.

AREA RADIATION MONITOR

DOEpatents

Manning, F.W.; Groothuis, S.E.; Lykins, J.H.; Papke, D.M.

1962-06-12

S>An improved area radiation dose monitor is designed which is adapted to compensate continuously for background radiation below a threshold dose rate and to give warning when the dose integral of the dose rate of an above-threshold radiation excursion exceeds a selected value. This is accomplished by providing means for continuously charging an ionization chamber. The chamber provides a first current proportional to the incident radiation dose rate. Means are provided for generating a second current including means for nulling out the first current with the second current at all values of the first current corresponding to dose rates below a selected threshold dose rate value. The second current has a maximum value corresponding to that of the first current at the threshold dose rate. The excess of the first current over the second current, which occurs above the threshold, is integrated and an alarm is given at a selected integrated value of the excess corresponding to a selected radiation dose. (AEC)

[Brachytherapy for head and neck cancers].

PubMed

Peiffert, D; Coche-Dequéant, B; Lapeyre, M; Renard, S

2018-05-29

The main indications of the brachytherapy of head and neck cancers are the limited tumours of the lip, the nose, the oral cavity and the oropharynx. Nasopharynx tumours are nowadays treated by intensity-modulated radiotherapy. This technique can be exclusive, associated with external radiotherapy or postoperative. It can also be a salvage treatment for the second primaries in previously irradiated areas. If the low dose rate brachytherapy rules remain the reference, the pulse dose rate technique allows the prescription of the dose rate and the optimisation of the dose distribution. Results of high dose rate brachytherapy are now published. This paper reports the recommendations of the Gec-ESTRO, published in 2017, and takes into account the data of the historical low dose rate series, and is upgraded with the pulsed-dose rate and high dose rate series. Copyright © 2018. Published by Elsevier SAS.

Acute changes in the central nervous system of monkeys exposed to protons.

NASA Technical Reports Server (NTRS)

Haymaker, W.; Ibrahim, M. Z. M.; Miquel, J.; Call, N.; Noden, P.; Ashley, W.; Ballinger, E. R.; Ghidoni, J.; Lindsay, I. R.; Behar, A. J.

1972-01-01

Study of the changes occurring in simian brain exposed to protons of varied energy, given in wide dose and dose-rate ranges. Results show that inflammatory reaction and glycogen accumulation in astrocytes occurred practically in all animals. Cerebral cortical necrosis, granule cell pyknosis, and inflammatory reaction occurred at doses far lower than effective for high-energy gamma radiation given other series of monkeys at comparable dose rates. Metallic impregnation, carried out in virtually all the animals tested, revealed a wide variation in glial response even at equal doses and dose rates in the same proton energy series. Proton energy effect, dose effect, dose-time effect, and dose-rate effect were evident in the various morphological categories investigated, but inconsistencies were encountered.

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.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Viel, Francis; Duzenli, Cheryl; British Columbia Cancer Agency, Department of Medical Physics, Vancouver Centre

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 andmore » 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.« less

Recommended de minimis radiation dose rates for Canada. Report No. INFO-0355

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1990-01-01

A de minimis dose or dose rate as used in this report represents a level of risk which is generally accepted as being of no significance to an individual, or in the case of a population, of no significance to society. The report describes the risk of biological effects from radiation; radiation from natural and man-made sources; normal incidences of cancer and genetic defects; initiatives by other agencies in the U.S., the U.K. and internationally; the importance of collective dose and dose rate; assigning values to the de minimis dose rates; and application of the de minimis dose rates.

Comparison in vivo Study of Genotoxic Action of High- Versus Very Low Dose-Rate γ-Irradiation

PubMed Central

Osipov, A. N.; Klokov, D. Y.; Elakov, A. L.; Rozanova, O. M.; Zaichkina, S. I.; Aptikaeva, G. F.; Akhmadieva, A. Kh.

2004-01-01

The aim of the present study was to compare genotoxicity induced by high- versus very low dose-rate exposure of mice to γ-radiation within a dose range of 5 to 61 cGy using the single-cell gel electrophoresis (comet) assay and the micronucleus test. CBA/lac male mice were irradiated at a dose rate of 28.2 Gy/h (high dose rate) or 0.07 mGy/h (very low dose rate). The comet assay study on spleen lymphocytes showed that very low dose-rate irradiation resulted in a statistically significant increase in nucleoid relaxation (DNA breaks), starting from a dose of 20 cGy. Further prolongation of exposure time and, hence, increase of a total dose did not, however, lead to further increase in the extent of nucleoid relaxation. Doses of 20 and 61 cGy were equal in inducing DNA breaks in mouse spleen lymphocytes as assayed by the comet assay. Of note, the level of DNA damage by 20–61 cGy doses of chronic irradiation (0.07 mGy/h) was similar to that an induced by an acute (28.2 Gy/h) dose of 14 cGy. The bone marrow micronucleus test revealed that an increase in polychromatic erythrocytes with micronuclei over a background level was induced by very low-level γ-irradiation with a dose of 61 cGy only, with the extent of the cytogenetic effect being similar to that of 10 cGy high-dose-rate exposure. In summary, presented results support the hypothesis of the nonlinear threshold nature of mutagenic action of chronic low dose-rate irradiation. PMID:19330145

Micronucleus induction in Vicia faba roots. Part 1. Absence of dose-rate, fractionation, and oxygen effect at low doses of low LET radiations.

PubMed

Marshall, I; Bianchi, M

1983-08-01

Micronucleus indication in Vicia faba roots has been evaluated after irradiation with 60Co gamma-rays. The dependence of the damage on dose, dose rate, fractionation, and oxygen has been studied. The best fit to the experimental data in the dose region between 7 and 190 cGy is represented, for single-dose exposures, by a linear + quadratic relationship. In the low-dose region, between 7 and 20 cGy, where the linear dose dependence is dominant, no dose-rate, fractionation, or oxygen effect could be observed. These effects were, however, present in the high-dose region, where the quadratic dependence is dominant.

The threshold vs LNT showdown: Dose rate findings exposed flaws in the LNT model part 1. The Russell-Muller debate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Calabrese, Edward J., E-mail: edwardc@schoolph.uma

This paper assesses the discovery of the dose-rate effect in radiation genetics and how it challenged fundamental tenets of the linear non-threshold (LNT) dose response model, including the assumptions that all mutational damage is cumulative and irreversible and that the dose-response is linear at low doses. Newly uncovered historical information also describes how a key 1964 report by the International Commission for Radiological Protection (ICRP) addressed the effects of dose rate in the assessment of genetic risk. This unique story involves assessments by two leading radiation geneticists, Hermann J. Muller and William L. Russell, who independently argued that the report'smore » Genetic Summary Section on dose rate was incorrect while simultaneously offering vastly different views as to what the report's summary should have contained. This paper reveals occurrences of scientific disagreements, how conflicts were resolved, which view(s) prevailed and why. During this process the Nobel Laureate, Muller, provided incorrect information to the ICRP in what appears to have been an attempt to manipulate the decision-making process and to prevent the dose-rate concept from being adopted into risk assessment practices. - Highlights: • The discovery of radiation dose rate challenged the scientific basis of LNT. • Radiation dose rate occurred in males and females. • The dose rate concept supported a threshold dose-response for radiation.« less

LDR brachytherapy: can low dose rate hypersensitivity from the "inverse" dose rate effect cause excessive cell killing to peripherial connective tissues and organs?

PubMed

Leonard, B E; Lucas, A C

2009-02-01

Examined here are the possible effects of the "inverse" dose rate effect (IDRE) on low dose rate (LDR) brachytherapy. The hyper-radiosensitivity and induced radioresistance (HRS/IRR) effect benefits cell killing in radiotherapy, and IDRE and HRS/IRR seem to be generated from the same radioprotective mechanisms. We have computed the IDRE excess cell killing experienced in LDR brachytherapy using permanent seed implants. We conclude, firstly, that IDRE is a dose rate-dependent manifestation of HRS/IRR. Secondly, the presence of HRS/IRR or IDRE in a cell species or tissue must be determined by direct dose-response measurements. Thirdly, a reasonable estimate is that 50-80% of human adjoining connective and organ tissues experience IDRE from permanent implanted LDR brachytherapy. If IDRE occurs for tissues at point A for cervical cancer, the excess cell killing will be about a factor of 3.5-4.0 if the initial dose rate is 50-70 cGy h(-1). It is greater for adjacent tissues at lower dose rates and higher for lower initial dose rates at point A. Finally, higher post-treatment complications are observed in LDR brachytherapy, often for unknown reasons. Some of these are probably a result of IDRE excess cell killing. Measurements of IDRE need be performed for connective and adjacent organ tissues, i.e. bladder, rectum, urinary tract and small bowels. The measured dose rate-dependent dose responses should extended to <10 cGy h(-1) and involve multiple patients to detect patient variability. Results may suggest a preference for high dose rate brachytherapy or LDR brachytherapy without permanent retention of the implant seeds (hence the dose rates in peripheral tissues and organs remain above IDRE thresholds).

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.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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) tomore » be used for area monitoring and instrument calibrations. These quantities are used in ICRP-60 and ICRP-74. This report deals only with the changes in the ambient dose equivalent and ambient dose rate equivalent for neutrons as a result of the implementation of the revised 10 CFR 835. In the report, the terms neutron dose and neutron dose rate will be used for convenience for ambient neutron dose and ambient neutron dose rate unless otherwise stated. This report provides a qualitative and quantitative estimate of how much the neutron dose rates at LLNL will change with the implementation of the revised 10 CFR 835. Neutron spectra and dose rates from selected locations at the LLNL were measured with a high resolution spectroscopic neutron dose rate system (ROSPEC) as well as with a standard neutron rem meter (a.k.a., a remball). The spectra obtained at these locations compare well with the spectra from the Radiation Calibration Laboratory's (RCL) bare californium source that is currently used to calibrate neutron dose rate instruments. The measurements obtained from the high resolution neutron spectrometer and dose meter ROSPEC and the NRD dose meter compare within the range of {+-}25%. When the new radiation weighting factors are adopted with the implementation of the revised 10 CFR 835, the measured dose rates will increase by up to 22%. The health physicists should consider this increase for any areas that have dose rates near a posting limit, such as near the 100 mrem/hr for a high radiation area, as this increase in measured dose rate may result in some changes to postings and consequent radiological controls.« less

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.

Study of the dose rate effect of 180 nm nMOSFETs

NASA Astrophysics Data System (ADS)

He, Bao-Ping; Yao, Zhi-Bin; Sheng, Jiang-Kun; Wang, Zu-Jun; Huang, Shao-Yan; Liu, Min-Bo; Xiao, Zhi-Gang

2015-01-01

Radiation induced offstate leakage in the shallow trench isolation regions of SIMC 0.18 μm nMOSFETs is studied as a function of dose rate. A “true” dose rate effect (TDRE) is observed. Increased damage is observed at low dose rate (LDR) than at high dose rate (HDR) when annealing is taken into account. A new method of simulating radiation induced degradation in shallow trench isolation (STI) is presented. A comparison of radiation induced offstate leakage current in test nMOSFETs between total dose irradiation experiments and simulation results exhibits excellent agreement. The investigation results imply that the enhancement of the leakage current may be worse for the dose rate encountered in the environment of space.

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.

Impact of the Amount of Liquid Intake on the Dose Rate of Patients Treated with Radioiodine.

PubMed

Haghighatafshar, Mahdi; Banani, Aida; Zeinali-Rafsanjani, Banafsheh; Etemadi, Zahra; Ghaedian, Tahereh

2018-01-01

Despite therapeutic effects of radioiodine in patients with differentiated thyroid cancer, there are some disadvantages due to harmful radiation to other tissues. According to the current guidelines, patients are recommended to drink lots of water and frequent voiding to reduce the amount of 131 I in the body. This study was designed to assess the impact of the amount of liquid intake on reduction of the measured dose rate of radioiodine-treated patients. A total of 42 patients with differentiated thyroid cancer without metastasis who had undergone total thyroidectomy and had been treated with radioiodine were selected. The patients were divided into two groups according to the amount of their fluid intake which was measured during the first 48 h after 131 I administration. In all patients, the dose rate was measured immediately and 48 h after iodine administration. Each group included 21 patients. Dose rate ratio (the ratio of the second dose rate to the first dose rate) and dose rate difference ratio (the ratio of the difference between the two measured dose rates to the first dose rate) were calculated for each patient. Despite the significant difference in the amount of the liquid drunk, no statistically significant difference was seen between the different groups in parameters of dose-rate ratio and dose-rate difference ratio. Higher fluid intake (>60 ml/h in our study) alone would not effectively reduce the patient's radiation dose rate at least not more than a well-hydrated state. It seems that other interfering factors in the thyroidectomized patients may also have some impacts on this physiologic process.

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.

An accurate derivation of the air dose-rate and the deposition concentration distribution by aerial monitoring in a low level contaminated area

NASA Astrophysics Data System (ADS)

Nishizawa, Yukiyasu; Sugita, Takeshi; Sanada, Yukihisa; Torii, Tatsuo

2015-04-01

Since 2011, MEXT (Ministry of Education, Culture, Sports, Science and Technology, Japan) have been conducting aerial monitoring to investigate the distribution of radioactive cesium dispersed into the atmosphere after the accident at the Fukushima Dai-ichi Nuclear Power Plant (FDNPP), Tokyo Electric Power Company. Distribution maps of the air dose-rate at 1 m above the ground and the radioactive cesium deposition concentration on the ground are prepared using spectrum obtained by aerial monitoring. The radioactive cesium deposition is derived from its dose rate, which is calculated by excluding the dose rate of the background radiation due to natural radionuclides from the air dose-rate at 1 m above the ground. The first step of the current method of calculating the dose rate due to natural radionuclides is calculate the ratio of the total count rate of areas where no radioactive cesium is detected and the count rate of regions with energy levels of 1,400 keV or higher (BG-Index). Next, calculate the air dose rate of radioactive cesium by multiplying the BG-Index and the integrated count rate of 1,400 keV or higher for the area where the radioactive cesium is distributed. In high dose-rate areas, however, the count rate of the 1,365-keV peak of Cs-134, though small, is included in the integrated count rate of 1,400 keV or higher, which could cause an overestimation of the air dose rate of natural radionuclides. We developed a method for accurately evaluating the distribution maps of natural air dose-rate by excluding the effect of radioactive cesium, even in contaminated areas, and obtained the accurate air dose-rate map attributed the radioactive cesium deposition on the ground. Furthermore, the natural dose-rate distribution throughout Japan has been obtained by this method.

Total dose bias dependency and ELDRS effects in bipolar linear devices

NASA Technical Reports Server (NTRS)

Yui, C. C.; McClure, S. S.; Rex, B. G.; Lehman, J. M.; Minto, T. D.; Wiedeman, M.

2002-01-01

Total dose tests of several bipolar linear devices show sensitivity to both dose rate and bias during exposure. All devices exhibited Enhanced Low Dose Rate Sensitivity (ELDRS). An accelerated ELDRS test method for three different devices demonstrate results similar to tests at low dose rate. Behavior and critical parameters from these tests are compared and discussed.

Dose and dose rate extrapolation factors for malignant and non-malignant health endpoints after exposure to gamma and neutron radiation.

PubMed

Tran, Van; Little, Mark P

2017-11-01

Murine experiments were conducted at the JANUS reactor in Argonne National Laboratory from 1970 to 1992 to study the effect of acute and protracted radiation dose from gamma rays and fission neutron whole body exposure. The present study reports the reanalysis of the JANUS data on 36,718 mice, of which 16,973 mice were irradiated with neutrons, 13,638 were irradiated with gamma rays, and 6107 were controls. Mice were mostly Mus musculus, but one experiment used Peromyscus leucopus. For both types of radiation exposure, a Cox proportional hazards model was used, using age as timescale, and stratifying on sex and experiment. The optimal model was one with linear and quadratic terms in cumulative lagged dose, with adjustments to both linear and quadratic dose terms for low-dose rate irradiation (<5 mGy/h) and with adjustments to the dose for age at exposure and sex. After gamma ray exposure there is significant non-linearity (generally with upward curvature) for all tumours, lymphoreticular, respiratory, connective tissue and gastrointestinal tumours, also for all non-tumour, other non-tumour, non-malignant pulmonary and non-malignant renal diseases (p < 0.001). Associated with this the low-dose extrapolation factor, measuring the overestimation in low-dose risk resulting from linear extrapolation is significantly elevated for lymphoreticular tumours 1.16 (95% CI 1.06, 1.31), elevated also for a number of non-malignant endpoints, specifically all non-tumour diseases, 1.63 (95% CI 1.43, 2.00), non-malignant pulmonary disease, 1.70 (95% CI 1.17, 2.76) and other non-tumour diseases, 1.47 (95% CI 1.29, 1.82). However, for a rather larger group of malignant endpoints the low-dose extrapolation factor is significantly less than 1 (implying downward curvature), with central estimates generally ranging from 0.2 to 0.8, in particular for tumours of the respiratory system, vasculature, ovary, kidney/urinary bladder and testis. For neutron exposure most endpoints, malignant and non-malignant, show downward curvature in the dose response, and for most endpoints this is statistically significant (p < 0.05). Associated with this, the low-dose extrapolation factor associated with neutron exposure is generally statistically significantly less than 1 for most malignant and non-malignant endpoints, with central estimates mostly in the range 0.1-0.9. In contrast to the situation at higher dose rates, there are statistically non-significant decreases of risk per unit dose at gamma dose rates of less than or equal to 5 mGy/h for most malignant endpoints, and generally non-significant increases in risk per unit dose at gamma dose rates ≤5 mGy/h for most non-malignant endpoints. Associated with this, the dose-rate extrapolation factor, the ratio of high dose-rate to low dose-rate (≤5 mGy/h) gamma dose response slopes, for many tumour sites is in the range 1.2-2.3, albeit not statistically significantly elevated from 1, while for most non-malignant endpoints the gamma dose-rate extrapolation factor is less than 1, with most estimates in the range 0.2-0.8. After neutron exposure there are non-significant indications of lower risk per unit dose at dose rates ≤5 mGy/h compared to higher dose rates for most malignant endpoints, and for all tumours (p = 0.001), and respiratory tumours (p = 0.007) this reduction is conventionally statistically significant; for most non-malignant outcomes risks per unit dose non-significantly increase at lower dose rates. Associated with this, the neutron dose-rate extrapolation factor is less than 1 for most malignant and non-malignant endpoints, in many cases statistically significantly so, with central estimates mostly in the range 0.0-0.2.

Estimation of ambient dose equivalent distribution in the 18F-FDG administration room using Monte Carlo simulation.

PubMed

Nagamine, Shuji; Fujibuchi, Toshioh; Umezu, Yoshiyuki; Himuro, Kazuhiko; Awamoto, Shinichi; Tsutsui, Yuji; Nakamura, Yasuhiko

2017-03-01

In this study, we estimated the ambient dose equivalent rate (hereafter "dose rate") in the fluoro-2-deoxy-D-glucose (FDG) administration room in our hospital using Monte Carlo simulations, and examined the appropriate medical-personnel locations and a shielding method to reduce the dose rate during FDG injection using a lead glass shield. The line source was assumed to be the FDG feed tube and the patient a cube source. The dose rate distribution was calculated with a composite source that combines the line and cube sources. The dose rate distribution was also calculated when a lead glass shield was placed in the rear section of the lead-acrylic shield. The dose rate behind the automatic administration device decreased by 87 % with respect to that behind the lead-acrylic shield. Upon positioning a 2.8-cm-thick lead glass shield, the dose rate behind the lead-acrylic shield decreased by 67 %.

Comparison of Monoenergetic Photon Organ Dose Rate Coefficients for the Female Stylized and Voxel Phantoms Submerged in Air

DOE PAGES

Hiller, Mauritius; Dewji, Shaheen Azim

2017-02-16

Dose rate coefficients computed using the International Commission on Radiological Protection (ICRP) reference adult female voxel phantom were compared with values computed using the Oak Ridge National Laboratory (ORNL) adult female stylized phantom in an air submersion exposure geometry. This is a continuation of previous work comparing monoenergetic organ dose rate coefficients for the male adult phantoms. With both the male and female data computed, effective dose rate as defined by ICRP Publication 103 was compared for both phantoms. Organ dose rate coefficients for the female phantom and ratios of organ dose rates for the voxel and stylized phantoms aremore » provided in the energy range from 30 to 5 MeV. Analysis of the contribution of the organs to effective dose is also provided. Lastly, comparison of effective dose rates between the voxel and stylized phantoms was within 8% at 100 keV and is <5% between 200 and 5000 keV.« less

Comparison of Monoenergetic Photon Organ Dose Rate Coefficients for the Female Stylized and Voxel Phantoms Submerged in Air

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hiller, Mauritius; Dewji, Shaheen Azim

Dose rate coefficients computed using the International Commission on Radiological Protection (ICRP) reference adult female voxel phantom were compared with values computed using the Oak Ridge National Laboratory (ORNL) adult female stylized phantom in an air submersion exposure geometry. This is a continuation of previous work comparing monoenergetic organ dose rate coefficients for the male adult phantoms. With both the male and female data computed, effective dose rate as defined by ICRP Publication 103 was compared for both phantoms. Organ dose rate coefficients for the female phantom and ratios of organ dose rates for the voxel and stylized phantoms aremore » provided in the energy range from 30 to 5 MeV. Analysis of the contribution of the organs to effective dose is also provided. Lastly, comparison of effective dose rates between the voxel and stylized phantoms was within 8% at 100 keV and is <5% between 200 and 5000 keV.« less

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.

The estimation of galactic cosmic ray penetration and dose rates

NASA Technical Reports Server (NTRS)

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

1972-01-01

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

WE-FG-BRA-05: Potential Clinical Benefit of LINAC Flattening-Filter-Free (FFF) Mode - Improvement of Treatment Therapeutic Ratio

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, S; Department of Biomedical Engineering, University of North Carolina- Chapel Hill/ North Carolina State University, Chapel Hill, North Carolina; Lineberger Clinical Cancer Center, University of North Carolina, Chapel Hill, NC

Purpose: Ultrahigh dose-rate radiation at >40Gy/s has demonstrated astonishing normal-tissue sparing and tumor control in recent preclinical naive and tumor-bearing rodent studies when compared to the same radiation dose at a conventional dose-rate. The working mechanism of this fascinating dose-rate effect is currently under investigation. The aims of this work include investigating 1) whether LINAC FFF mode radiation at approximately 1Gy/s also has an improved therapeutic ratio compared to the same radiation dose at the conventional dose-rate of 0.05Gy/s, and 2) the dose-rate effect’s potential working mechanism by studying the expression of the P53 gene, linked to tumor suppression andmore » cell regulation after radiation damage. Methods: We used mouse model C57BL/6J, the same as that used in the ultrahigh dose-rate studies, and exposed them to total body irradiation (TBI) using the Elekta Versa accelerator 10MV photons. Mice (N=20) were given a total dose of 12Gy in both the high dose-rate group (n=10) using the FFF-mode and the conventional dose-rate group (n=10) using the conventional does rate mode. The FFF-mode treatment setup consisted of a 15cm×15cm field size setting at 53.2cm SSD while the conventional-mode set-up consisted of a 10cm×10cm field size at 100SSD. Post-radiation, animals were monitored daily for survival analysis and signs of moribundity requiring euthanasia. In addition, mouse spleens were harvested for P53 analysis at different time points. Results: For 12Gy TBI, the 1.3Gy/s FFF-mode high dose-rate produced a statistically significant (p=0.02) improvement in mouse survival compared to the 0.05Gy/s conventional dose-rate. An initial P53 study at the time of death time-point indicates that high dose-rate radiation induced a stronger expression of P53 than conventional dose-rate radiation. Conclusion: Our pilot study indicates that the FFF-mode high dose-rate radiation, which has been used largely to improve clinical throughput, may provide the added clinical benefit of improving treatment therapeutic ratio. Animal Studies were performed within the LCCC Animal Studies Core Facility at the University of North Carolina at Chapel Hill. The LCCC Animal Studies Core is supported in part by an NCI Center Core Support Grant (CA16086) to the UNC Lineberger Comprehensive Cancer Center.« less

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.

Daily radionuclide ingestion and internal radiation doses in Aomori prefecture, Japan.

PubMed

Ohtsuka, Yoshihito; Kakiuchi, Hideki; Akata, Naofumi; Takaku, Yuichi; Hisamatsu, Shun'ichi

2013-10-01

To assess internal annual dose in the general public in Aomori Prefecture, Japan, 80 duplicate cooked diet samples, equivalent to the food consumed over a 400-d period by one person, were collected from 100 volunteers in Aomori City and the village of Rokkasho during 2006–2010 and were analyzed for 11 radionuclides. To obtain average rates of ingestion of radionuclides, the volunteers were selected from among office, fisheries, agricultural, and livestock farm workers. Committed effective doses from ingestion of the diet over a 1-y period were calculated from the analytical results and from International Commission on Radiological Protection dose coefficients; for 40K, an internal effective dose rate from the literature was used. Fisheries workers had significantly higher combined internal annual dose than the other workers, possibly because of high rates of ingestion of marine products known to have high 210Po concentrations. The average internal dose rate, weighted by the numbers of households in each worker group in Aomori Prefecture, was estimated at 0.47 mSv y-1. Polonium-210 contributed 49% of this value. The sum of committed effective dose rates for 210Po, 210Pb, 228Ra, and 14C and the effective dose rate of 40K accounted for approximately 99% of the average internal dose rate.

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. © 2014 SETAC.

Development of a high precision dosimetry system for the measurement of surface dose rate distribution for eye applicators.

PubMed

Eichmann, Marion; Flühs, Dirk; Spaan, Bernhard

2009-10-01

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. 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. 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. 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 distribution, which then can be used as input for a refined clinical treatment planning system. The improved dose rate measurements will facilitate a clinical study, which could correlate the therapeutic outcome of a brachytherapy treatment with an applicator and its individual dose rate distribution.

Development of a high precision dosimetry system for the measurement of surface dose rate distribution for eye applicators

DOE Office of Scientific and Technical Information (OSTI.GOV)

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: Inmore » 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 distribution, which then can be used as input for a refined clinical treatment planning system. The improved dose rate measurements will facilitate a clinical study, which could correlate the therapeutic outcome of a brachytherapy treatment with an applicator and its individual dose rate distribution.« less

Characterization and prediction of monomer-based dose rate effects in electron-beam polymerization

NASA Astrophysics Data System (ADS)

Schissel, Sage M.; Lapin, Stephen C.; Jessop, Julie L. P.

2017-12-01

Properties of some materials produced by electron-beam (EB) induced polymerization appear dependent upon the rate at which the initiating dose was delivered. However, the magnitude of these dose rate effects (DREs) can vary greatly with different monomer formulations, suggesting DREs are dependent on chemical structure. The relationship among dose, dose rate, conversion, and the glass transition temperature (Tg) of the cured material was explored for an acrylate monomer series. A strong correlation was determined between the DRE magnitude and monomer size, and this correlation may be attributed to chain transfer. Using the Tg shift caused by changes in dose, a preliminary predictive relationship was developed to estimate the magnitude of the Tg DRE, enabling scale-up of process variables for polymers prone to dose rate effects.

Dose escalation using conformal high-dose-rate brachytherapy improves outcome in unfavorable prostate cancer.

PubMed

Martinez, Alvaro A; Gustafson, Gary; Gonzalez, José; Armour, Elwood; Mitchell, Chris; Edmundson, Gregory; Spencer, William; Stromberg, Jannifer; Huang, Raywin; Vicini, Frank

2002-06-01

To overcome radioresistance for patients with unfavorable prostate cancer, a prospective trial of pelvic external beam irradiation (EBRT) interdigitated with dose-escalating conformal high-dose-rate (HDR) prostate brachytherapy was performed. Between November 1991 and August 2000, 207 patients were treated with 46 Gy pelvic EBRT and increasing HDR brachytherapy boost doses (5.50-11.5 Gy/fraction) during 5 weeks. The eligibility criteria were pretreatment prostate-specific antigen level >or=10.0 ng/mL, Gleason score >or=7, or clinical Stage T2b or higher. Patients were divided into 2 dose levels, low-dose biologically effective dose <93 Gy (58 patients) and high-dose biologically effective dose >93 Gy (149 patients). No patient received hormones. We used the American Society for Therapeutic Radiology and Oncology definition for biochemical failure. The median age was 69 years. The mean follow-up for the group was 4.4 years, and for the low and high-dose levels, it was 7.0 and 3.4 years, respectively. The actuarial 5-year biochemical control rate was 74%, and the overall, cause-specific, and disease-free survival rate was 92%, 98%, and 68%, respectively. The 5-year biochemical control rate for the low-dose group was 52%; the rate for the high-dose group was 87% (p <0.001). Improvement occurred in the cause-specific survival in favor of the brachytherapy high-dose level (p = 0.014). On multivariate analysis, a low-dose level, higher Gleason score, and higher nadir value were associated with increased biochemical failure. The Radiation Therapy Oncology Group Grade 3 gastrointestinal/genitourinary complications ranged from 0.5% to 9%. The actuarial 5-year impotency rate was 51%. Pelvic EBRT interdigitated with transrectal ultrasound-guided real-time conformal HDR prostate brachytherapy boost is both a precise dose delivery system and a very effective treatment for unfavorable prostate cancer. We demonstrated an incremental beneficial effect on biochemical control and cause-specific survival with higher doses. These results, coupled with the low risk of complications, the advantage of not being radioactive after implantation, and the real-time interactive planning, define a new standard for treatment.

β-blocker dosage and outcomes after acute coronary syndrome.

PubMed

Allen, Jason E; Knight, Stacey; McCubrey, Raymond O; Bair, Tami; Muhlestein, Joseph Brent; Goldberger, Jeffrey J; Anderson, Jeffrey L

2017-02-01

Although β-blockers increase survival in acute coronary syndrome (ACS) patients, the doses used in trials were higher than doses used in practice, and recent data do not support an advantage of higher doses. We hypothesized that rates of major adverse cardiac events (MACE), all-cause death, myocardial infarction, and stroke are equivalent for patients on low-dose and high-dose β-blocker. Patients admitted to Intermountain Healthcare with ACS and diagnosed with ≥70% coronary stenosis between 1994 and 2013 were studied (N = 7,834). We classified low dose as ≤25% and high dose as ≥50% of an equivalent daily dose of 200 mg of metoprolol. Multivariate analyses were used to test association between low-dose versus high-dose β-blocker dosage and MACE at 0-6 months and 6-24 months. A total of 5,287 ACS subjects were discharged on β-blockers (87% low dose, 12% high dose, and 1% intermediate dose). The 6-month MACE outcomes rates for the β-blocker dosage (low versus high) were not equivalent (P = .18) (hazard ratio [HR] = 0.76; 95% CI, 0.52-1.10). However, subjects on low-dose β-blocker therapy did have a significantly decreased risk of myocardial infarction for 0-6 months (HR = 0.53; 95% CI, 0.33-0.86). The rates of MACE events during the 6-24 months after presentation with ACS were equivalent for the 2 doses (P = .009; HR = 1.03 [95% CI, 0.70-1.50]). In ACS patients, rates of MACE for high-dose and low-dose β-blocker doses are similar. These findings question the importance of achieving a high dose of β-blocker in ACS patients and highlight the need for further investigation of this clinical question. Copyright © 2016 Elsevier Inc. All rights reserved.

Maximum dose rate is a determinant of hypothyroidism after 131I therapy of Graves' disease but the total thyroid absorbed dose is not.

PubMed

Krohn, Thomas; Hänscheid, Heribert; Müller, Berthold; Behrendt, Florian F; Heinzel, Alexander; Mottaghy, Felix M; Verburg, Frederik A

2014-11-01

The determinants of successful (131)I therapy of Graves' disease (GD) are unclear. To relate dosimetry parameters to outcome of therapy to identify significant determinants eu- and/or hypothyroidism after (131)I therapy in patients with GD. A retrospective study in which 206 Patients with GD treated in University Hospital between November 1999 and January 2011. All received (131)I therapy aiming at a total absorbed dose to the thyroid of 250 Gy based on pre-therapeutic dosimetry. Post-therapy dosimetric thyroid measurements were performed twice daily until discharge. From these measurements, thyroid (131)I half-life, the total thyroid absorbed dose, and the maximum dose rate after (131)I administration were calculated. In all, 48.5% of patients were hypothyroid and 28.6% of patients were euthyroid after (131)I therapy. In univariate analysis, nonhyperthyroid and hyperthyroid patients only differed by sex. A lower thyroid mass, a higher activity per gram thyroid tissue, a shorter effective thyroidal (131)I half-life, and a higher maximum dose rate, but not the total thyroid absorbed dose, were significantly associated with hypothyroidism. In multivariate analysis, the maximum dose rate remained the only significant determinant of hypothyroidism (P < .001). Maximum dose rates of 2.2 Gy/h and higher were associated with a 100% hypothyroidism rate. Not the total thyroid absorbed dose, but the maximum dose rate is a determinant of successfully achieving hypothyroidism in Graves' disease. Dosimetric concepts aiming at a specific total thyroid absorbed dose will therefore require reconsideration if our data are confirmed prospectively.

Commentary 2 to Cox and Little: radiation-induced oncogenic transformation: the interplay between dose, dose protraction, and radiation quality

NASA Technical Reports Server (NTRS)

Brenner, D. J.; Hall, E. J.

1992-01-01

There is now a substantial body of evidence for end points such as oncogenic transformation in vitro, and carcinogenesis and life shortening in vivo, suggesting that dose protraction leads to an increase in effectiveness relative to a single, acute exposure--at least for radiations of medium linear energy transfer (LET) such as neutrons. Table I contains a summary of the pertinent data from studies in which the effect is seen. [table: see text] This phenomenon has come to be known as the "inverse dose rate effect," because it is in marked contrast to the situation at low LET, where protraction in delivery of a dose of radiation, either by fractionation or low dose rate, results in a decreased biological effect; additionally, at medium and high LET, for radiobiological end points such as clonogenic survival, the biological effectiveness is independent of protraction. The quantity and quality of the published reports on the "inverse dose rate effect" leaves little doubt that the effect is real, but the available evidence indicates that the magnitude of the effect is due to a complex interplay between dose, dose rate, and radiation quality. Here, we first summarize the available data on the inverse dose rate effect and suggest that it follows a consistent pattern in regard to dose, dose rate, and radiation quality; second, we describe a model that predicts these features; and, finally, we describe the significance of the effect for radiation protection.

Radiation-Induced Carcinogenesis: Mechanistically Based Differences between Gamma-Rays and Neutrons, and Interactions with DMBA

PubMed Central

Shuryak, Igor; Brenner, David J.; Ullrich, Robert L.

2011-01-01

Different types of ionizing radiation produce different dependences of cancer risk on radiation dose/dose rate. Sparsely ionizing radiation (e.g. γ-rays) generally produces linear or upwardly curving dose responses at low doses, and the risk decreases when the dose rate is reduced (direct dose rate effect). Densely ionizing radiation (e.g. neutrons) often produces downwardly curving dose responses, where the risk initially grows with dose, but eventually stabilizes or decreases. When the dose rate is reduced, the risk increases (inverse dose rate effect). These qualitative differences suggest qualitative differences in carcinogenesis mechanisms. We hypothesize that the dominant mechanism for induction of many solid cancers by sparsely ionizing radiation is initiation of stem cells to a pre-malignant state, but for densely ionizing radiation the dominant mechanism is radiation-bystander-effect mediated promotion of already pre-malignant cell clone growth. Here we present a mathematical model based on these assumptions and test it using data on the incidence of dysplastic growths and tumors in the mammary glands of mice exposed to high or low dose rates of γ-rays and neutrons, either with or without pre-treatment with the chemical carcinogen 7,12-dimethylbenz-alpha-anthracene (DMBA). The model provides a mechanistic and quantitative explanation which is consistent with the data and may provide useful insight into human carcinogenesis. PMID:22194850

Interstitial pneumonitis following bone marrow transplantation after low dose rate total body irradiation.

PubMed

Barrett, A; Depledge, M H; Powles, R L

1983-07-01

Idiopathic and infective interstitial pneumonitis (IPn) is a common complication after bone marrow transplantation (BMT) in many centers and carries a high mortality. We report here a series of 107 patients with acute leukemia grafted at the Royal Marsden Hospital in which only 11 (10.3%) developed IPn and only 5 died (5%). Only one case of idiopathic IPn was seen. Factors which may account for this low incidence are discussed. Sixty of 107 patients were transplanted in first remission of acute myeloid leukemia (AML) and were therefore in good general condition. Lung radiation doses were carefully monitored and doses of 10.5 Gy were not exceeded except in a group of 16 patients in whom a study of escalating doses of TBI (up to 13 Gy) was undertaken. The dose rate used for total body irradiation (TBI) was lower than that used in other centers and as demonstrated elsewhere by ourselves and others, reduction of dose rate to less than 0.05 Gy/min may be expected to lead to substantial reduction in lung damage. Threshold doses of approximately 8 Gy for IPn have been reported, but within the dose range of 8 to 10.5 Gy we suggest that dose rate may significantly affect the incidence. Data so far available suggest a true improvement in therapeutic ratio for low dose rate single fraction TBI compared with high dose rate.

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.

Integrated molecular analysis indicates undetectable change in DNA damage in mice after continuous irradiation at ~ 400-fold natural background radiation.

PubMed

Olipitz, Werner; Wiktor-Brown, Dominika; Shuga, Joe; Pang, Bo; McFaline, Jose; Lonkar, Pallavi; Thomas, Aline; Mutamba, James T; Greenberger, Joel S; Samson, Leona D; Dedon, Peter C; Yanch, Jacquelyn C; Engelward, Bevin P

2012-08-01

In the event of a nuclear accident, people are exposed to elevated levels of continuous low dose-rate radiation. Nevertheless, most of the literature describes the biological effects of acute radiation. DNA damage and mutations are well established for their carcinogenic effects. We assessed several key markers of DNA damage and DNA damage responses in mice exposed to low dose-rate radiation to reveal potential genotoxic effects associated with low dose-rate radiation. We studied low dose-rate radiation using a variable low dose-rate irradiator consisting of flood phantoms filled with 125Iodine-containing buffer. Mice were exposed to 0.0002 cGy/min (~ 400-fold background radiation) continuously over 5 weeks. We assessed base lesions, micronuclei, homologous recombination (HR; using fluorescent yellow direct repeat mice), and transcript levels for several radiation-sensitive genes. We did not observe any changes in the levels of the DNA nucleobase damage products hypoxanthine, 8-oxo-7,8-dihydroguanine, 1,N6-ethenoadenine, or 3,N4-ethenocytosine above background levels under low dose-rate conditions. The micronucleus assay revealed no evidence that low dose-rate radiation induced DNA fragmentation, and there was no evidence of double strand break-induced HR. Furthermore, low dose-rate radiation did not induce Cdkn1a, Gadd45a, Mdm2, Atm, or Dbd2. Importantly, the same total dose, when delivered acutely, induced micronuclei and transcriptional responses. These results demonstrate in an in vivo animal model that lowering the dose-rate suppresses the potentially deleterious impact of radiation and calls attention to the need for a deeper understanding of the biological impact of low dose-rate radiation.

[Dose rate-dependent cellular and molecular effects of ionizing radiation].

PubMed

Przybyszewski, Waldemar M; Wideł, Maria; Szurko, Agnieszka; Maniakowski, Zbigniew

2008-09-11

The aim of radiation therapy is to kill tumor cells while minimizing damage to normal cells. The ultimate effect of radiation can be apoptotic or necrotic cell death as well as cytogenetic damage resulting in genetic instability and/or cell death. The destructive effects of radiation arise from direct and indirect ionization events leading to peroxidation of macromolecules, especially those present in lipid-rich membrane structures as well as chromatin lipids. Lipid peroxidative end-products may damage DNA and proteins. A characteristic feature of radiation-induced peroxidation is an inverse dose-rate effect (IDRE), defined as an increase in the degree of oxidation(at constant absorbed dose) accompanying a lower dose rate. On the other hand, a low dose rate can lead to the accumulation of cells in G2, the radiosensitive phase of the cell cycle since cell cycle control points are not sensitive to low dose rates. Radiation dose rate may potentially be the main factor improving radiotherapy efficacy as well as affecting the intensity of normal tissue and whole-body side effects. A better understanding of dose rate-dependent biological effects may lead to improved therapeutic intervention and limit normal tissue reaction. The study reviews basic biological effects that depend on the dose rate of ionizing radiation.

Dose rate effects on array CCDs exposed by Co-60 γ rays induce saturation output degradation and annealing tests

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Zujun, E-mail: wangzujun@nint.ac.cn; Chen, Wei; He, Baoping

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 andmore » 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.« less

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. Copyright © 2014 Elsevier Ltd. All rights reserved.

Immediate effects of 33 to 180 rad/min (60)Co exposure on performance and blood pressure in monkeys. Topical report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruner, A.

1976-09-01

Four groups of monkeys received 1000 rads (60)Co at 33, 50, 75, or 180 rad/min wholebody irradiation while performing a delayed matching-to-sample task. Systematic dose rate effects were observed on performance and blood pressure within the initial 20 min postirradiation. The incidence and severity of performance decrement (PD) increased with higher dose rate. The appearance of postirradiation hypotension was systematically delayed and its rate of fall prolonged as dose rate was lower. The hypotension likewise appeared less deep with lower dose rate exposure. Based on the calculated cumulative dose absorbed at the time of symptom appearance two coactive thresholds weremore » proposed to exist: a total dose threshold of approximately 300 rads (midbody measurement), and a dose rate threshold of about 25 rad/min.« less

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

PubMed

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

2017-03-01

The purpose of this work was to establish an empirical model of the ion recombination in the Advanced Markus ionization chamber for measurements in high dose rate/dose-per-pulse electron beams. In addition, we compared the observed ion recombination to calculations using the standard Boag two-voltage-analysis method, the more general theoretical Boag models, and the semiempirical general equation presented by Burns and McEwen. Two independent methods were used to investigate the ion recombination: (a) Varying the grid tension of the linear accelerator (linac) gun (controls the linac output) and measuring the relative effect the grid tension has on the chamber response at different source-to-surface distances (SSD). (b) Performing simultaneous dose measurements and comparing the dose-response, in beams with varying dose rate/dose-per-pulse, with the chamber together with dose rate/dose-per-pulse independent Gafchromic™ EBT3 film. Three individual Advanced Markus chambers were used for the measurements with both methods. All measurements were performed in electron beams with varying mean dose rate, dose rate within pulse, and dose-per-pulse (10 -2  ≤ mean dose rate ≤ 10 3 Gy/s, 10 2  ≤ mean dose rate within pulse ≤ 10 7  Gy/s, 10 -4  ≤ dose-per-pulse ≤ 10 1  Gy), which was achieved by independently varying the linac gun grid tension, and the SSD. The results demonstrate how the ion collection efficiency of the chamber decreased as the dose-per-pulse increased, and that the ion recombination was dependent on the dose-per-pulse rather than the dose rate, a behavior predicted by Boag theory. The general theoretical Boag models agreed well with the data over the entire investigated dose-per-pulse range, but only for a low polarizing chamber voltage (50 V). However, the two-voltage-analysis method and the Burns & McEwen equation only agreed with the data at low dose-per-pulse values (≤ 10 -2 and ≤ 10 -1  Gy, respectively). An empirical model of the ion recombination in the chamber was found by fitting a logistic function to the data. The ion collection efficiency of the Advanced Markus ionization chamber decreases for measurements in electron beams with increasingly higher dose-per-pulse. However, this chamber is still functional for dose measurements in beams with dose-per-pulse values up toward and above 10 Gy, if the ion recombination is taken into account. Our results show that existing models give a less-than-accurate description of the observed ion recombination. This motivates the use of the presented empirical model for measurements with the Advanced Markus chamber in high dose-per-pulse electron beams, as it enables accurate absorbed dose measurements (uncertainty estimation: 2.8-4.0%, k = 1). The model depends on the dose-per-pulse in the beam, and it is also influenced by the polarizing chamber voltage, with increasing ion recombination with a lowering of the voltage. © 2017 American Association of Physicists in Medicine.

Rates of Change in Naturalistic Psychotherapy: Contrasting Dose-Effect and Good-Enough Level Models of Change

ERIC Educational Resources Information Center

Baldwin, Scott A.; Berkeljon, Arjan; Atkins, David C.; Olsen, Joseph A.; Nielsen, Stevan L.

2009-01-01

Most research on the dose-effect model of change has combined data across patients who vary in their total dose of treatment and has implicitly assumed that the rate of change during therapy is constant across doses. In contrast, the good-enough level model predicts that rate of change will be related to total dose of therapy. In this study, the…

Radiation protocols determine acute graft-versus-host disease incidence after allogeneic bone marrow transplantation in murine models.

PubMed

Schwarte, Sebastian; Bremer, Michael; Fruehauf, Joerg; Sorge, Yanina; Skubich, Susanne; Hoffmann, Matthias W

2007-09-01

Effects of radiation sources used for total body irradiation (TBI) on Graft-versus-Host Disease (GvHD) induction were examined. In a T cell receptor (TCR) transgenic mouse model, single fraction TBI was performed with different radiation devices ((60)Cobalt; (137)Cesium; 6 MV linear accelerator), dose rates (0.85; 1.5; 2.9; 5 Gy/min) and total doses before allogeneic bone marrow transplantation (BMT). Recipients were observed for 120 days. Different tissues were examined histologically. Acute GvHD was induced by a dose rate of 0.85 Gy/min ((60)Cobalt) and a total dose of 9 Gy and injection of 5 x 10(5) lymph node cells plus 5 x 10(6) bone marrow cells. Similar results were obtained using 6 MV linear accelerator- (linac-) photons with a dose rate of 1.5 Gy/min and 0.85 Gy/min, a total dose of 9.5 Gy and injection of same cell numbers. TBI with (137)Cesium (dose rate: 2.5 Gy/min) did not lead reproducibly to lethal acute GvHD. Experimental TBI in murine models may induce different immunological responses, depending on total energy, total single dose and dose rate. GvHD might also be induced by TBI with low dose rates.

Different dose rate-dependent responses of human melanoma cells and fibroblasts to low dose fast neutrons.

PubMed

Dionet, Claude; Müller-Barthélémy, Melanie; Marceau, Geoffroy; Denis, Jean-Marc; Averbeck, Dietrich; Gueulette, John; Sapin, Vincent; Pereira, Bruno; Tchirkov, Andrei; Chautard, Emmanuel; Verrelle, Pierre

2016-09-01

To analyze the dose rate influence in hyper-radiosensitivity (HRS) of human melanoma cells to very low doses of fast neutrons and to compare to the behaviour of normal human skin fibroblasts. We explored different neutron dose rates as well as possible implication of DNA double-strand breaks (DSB), apoptosis, and energy-provider adenosine-triphosphate (ATP) levels during HRS. HRS in melanoma cells appears only at a very low dose rate (VLDR), while a high dose rate (HDR) induces an initial cell-radioresistance (ICRR). HRS does not seem to be due either to DSB or to apoptosis. Both phenomena (HRS and ICRR) appear to be related to ATP availability for triggering cell repair. Fibroblast survival after neutron irradiation is also dose rate-dependent but without HRS. Melanoma cells or fibroblasts exert their own survival behaviour at very low doses of neutrons, suggesting that in some cases there is a differential between cancer and normal cells radiation responses. Only the survival of fibroblasts at HDR fits the linear no-threshold model. This new insight into human cell responses to very low doses of neutrons, concerns natural radiations, surroundings of accelerators, proton-therapy devices, flights at high altitude. Furthermore, ATP inhibitors could increase HRS during high-linear energy transfer (high-LET) irradiation.

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.

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

NASA Astrophysics Data System (ADS)

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

2017-05-01

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

Measurement of ambient dose equivalent rates by walk survey around Fukushima Dai-ichi Nuclear Power Plant using KURAMA-II until 2016.

PubMed

Andoh, Masaki; Yamamoto, Hideaki; Kanno, Takashi; Saito, Kimiaki

2018-05-17

Ambient dose equivalent rates in various environments related to human lives were measured by walk surveys using the KURAMA-II systems from 2013 to 2016 within an 80-km radius of the Fukushima Dai-ichi Nuclear Power Plant. The dose rate of the locations where the walk survey was performed decreased to about 38% of its initial value in the 42 months from June 2013 to the December 2016, which was beyond that attributable to the physical decay of radiocaesium. The ecological half-life of the slow decreasing component was evaluated to be 4.1 ± 0.2 y. The air dose rates decreased depending on the level of the evacuation areas, and the decrease in the dose rates was slightly larger in populated areas where humans are active. The dose rates as measured by walk surveys exhibited a good correlation with those by car-borne surveys, suggesting that car-borne survey data are reflecting the air dose rates in living environments surrounding roads. The comparison of walk survey data with car-borne survey data indicated that the air dose rate varies largely even within a 100 m square area, and the variation is enhanced by human activities. The dose rates measured by the walk surveys were estimated to be medial of those along roads and those of undisturbed flat ground, and they were found to be decreasing quickly compared with the air dose rate from the flat ground fixed-point measurements. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

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.

Object Kinetic Monte Carlo Simulations of Radiation Damage In Bulk Tungsten

NASA Astrophysics Data System (ADS)

Nandipati, Giridhar; Setyawan, Wahyu; Heinisch, Howard; Roche, Kenneth; Kurtz, Richard; Wirth, Brian

2015-11-01

Results are presented for the evolution of radiation damage in bulk tungsten investigated using the object KMC simulation tool, KSOME, as a function of dose, dose rate and primary knock-on atom (PKA) energies in the range of 10 to 100 keV, at temperatures of 300, 1025 and 2050 K. At 300 K, the number density of vacancies changes minimally with dose rate while the number density of vacancy clusters slightly decreases with dose rate indicating that larger clusters are formed at higher dose rates. Although the average vacancy cluster size increases slightly, the vast majority exists as mono-vacancies. At 1025 K void lattice formation was observed at all dose rates for cascades below 60 keV and at lower dose rates for higher PKA energies. After the appearance of initial features of the void lattice, vacancy cluster density increased minimally while the average vacancy cluster size increases rapidly with dose. At 2050 K, no accumulation of defects was observed over a broad range of dose rates for all PKA energies studied in this work. Further comparisons of results of irradiation simulations at various dose rates and PKA spectra, representative of the High Flux Isotope Reactor and future fusion relevant irradiation facilities will be discussed. The U.S. Department of Energy, Office of Fusion Energy Sciences (FES) and Office of Advanced Scientific Computing Research (ASCR) has supported this study through the SciDAC-3 program.

Some cosmic radiation dose measurements aboard flights connecting Zagreb Airport.

PubMed

Vuković, B; Radolić, V; Lisjak, I; Vekić, B; Poje, M; Planinić, J

2008-02-01

When primary particles from space, mainly protons, enter the atmosphere, they produce interactions with air nuclei, and cosmic-ray showers are induced. The radiation field at aircraft altitude is complex, with different types of particles, mainly photons, electrons, positrons and neutrons, with a large energy range. The non-neutron component of cosmic radiation dose aboard A320 and ATR40 aircraft was measured with TLD-100 (LiF:Mg,Ti) detectors and the Mini 6100 semiconductor dosimeter; the neutron dose was measured with the neutron dosimeter consisted of LR-115 track detector and boron foil BN-1 or 10B converter. The estimated occupational effective dose for the aircraft crew (A320) working 500 h per year was 1.64 mSv. Another experiment was performed at the flights Zagreb-Paris-Buenos Aires and reversely, when one measured non-neutron cosmic radiation dose; for 26.7 h of flight, the MINI 6100 dosimeter gave an average dose rate of 2.3 microSv/h and the TLD dosimeter registered the dose equivalent of 75 microSv or the average dose rate of 2.7 microSv/h; the neutron dosimeter gave the dose rate of 2.4 microSv/h. In the same month, February 2005, a traveling to Japan (24-h-flight: Zagreb-Frankfurt-Tokyo and reversely) and the TLD-100 measurement showed the average dose rate of 2.4microSv/h; the neutron dosimeter gave the dose rate of 2.5 microSv/h. Comparing dose rates of the non-neutron component (low LET) and the neutron one (high LET) of the radiation field at the aircraft flight level, we could conclude that the neutron component carried about 50% of the total dose, that was near other known data.

Organ Dose-Rate Calculations for Small Mammals at Maralinga, the Nevada Test Site, Hanford and Fukushima: A Comparison of Ellipsoidal and Voxelized Dosimetric Methodologies.

PubMed

Caffrey, Emily A; Johansen, Mathew P; Higley, Kathryn A

2015-10-01

Radiological dosimetry for nonhuman biota typically relies on calculations that utilize the Monte Carlo simulations of simple, ellipsoidal geometries with internal radioactivity distributed homogeneously throughout. In this manner it is quick and easy to estimate whole-body dose rates to biota. Voxel models are detailed anatomical phantoms that were first used for calculating radiation dose to humans, which are now being extended to nonhuman biota dose calculations. However, if simple ellipsoidal models provide conservative dose-rate estimates, then the additional labor involved in creating voxel models may be unnecessary for most scenarios. Here we show that the ellipsoidal method provides conservative estimates of organ dose rates to small mammals. Organ dose rates were calculated for environmental source terms from Maralinga, the Nevada Test Site, Hanford and Fukushima using both the ellipsoidal and voxel techniques, and in all cases the ellipsoidal method yielded more conservative dose rates by factors of 1.2-1.4 for photons and 5.3 for beta particles. Dose rates for alpha-emitting radionuclides are identical for each method as full energy absorption in source tissue is assumed. The voxel procedure includes contributions to dose from organ-to-organ irradiation (shown here to comprise 2-50% of total dose from photons and 0-93% of total dose from beta particles) that is not specifically quantified in the ellipsoidal approach. Overall, the voxel models provide robust dosimetry for the nonhuman mammals considered in this study, and though the level of detail is likely extraneous to demonstrating regulatory compliance today, voxel models may nevertheless be advantageous in resolving ongoing questions regarding the effects of ionizing radiation on wildlife.

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

The Impact of Dose Rate on the Accuracy of Step-and-Shoot Intensity-modulated Radiation Therapy Quality Assurance Using Varian 2300CD.

PubMed

Njeh, Christopher F; Salmon, Howard W; Schiller, Claire

2017-01-01

Intensity-modulated radiation therapy (IMRT) delivery using "step-and-shoot" technique on Varian C-Series linear accelerator (linac) is influenced by the communication frequency between the multileaf collimator and linac controllers. Hence, the dose delivery accuracy is affected by the dose rate. Our aim was to quantify the impact of using two dose rates on plan quality assurance (QA). Twenty IMRT patients were selected for this study. The plan QA was measured at two different dose rates. A gamma analysis was performed, and the degree of plan modulation on the QA pass rate was also evaluated in terms of average monitor unit per segment (MU/segment) and the total number of segments. The mean percentage gamma pass rate of 94.9% and 93.5% for 300 MU/min and 600 MU/min dose rate, respectively, was observed. There was a significant ( P = 0.001) decrease in percentage gamma pass rate when the dose rate was increased from 300 MU/min to 600 MU/min. There was a weak, but significant association between the percentage pass rate at both dose rate and total number of segments. The total number of MU was significantly correlated to the total number of segments ( r = 0.59). We found a positive correlation between the percentage pass rate and mean MU/segment, r = 0.52 and r = 0.57 for 300 MU/min and 600 MU/min, respectively. IMRT delivery using step-and-shoot technique on Varian 2300CD is impacted by the dose rate and the total amount of segments.

Concomitant use of FSH and low-dose recombinant hCG during the late follicular phase versus conventional controlled ovarian stimulation for intracytoplasmic sperm injection cycles.

PubMed

Iaconelli, Carla Andrade Rebello; Setti, Amanda Souza; Braga, Daniela Paes Almeida Ferreira; Maldonado, Luiz Guilherme Louzada; Iaconelli, Assumpto; Borges, Edson; Aoki, Tsutomu

2017-12-01

The objective of this study was to investigate the effects of low-dose hCG supplementation on ICSI outcomes and controlled ovarian stimulation (COS) cost. Three hundred and thirty patients undergoing ICSI were split into groups according to the COS protocol: (i) control group (n = 178), including patients undergoing conventional COS treatment; and (ii) low-dose hCG group (n = 152), including patients undergoing COS with low-dose hCG supplementation. Lower mean total doses of FSH administered and higher mean oestradiol level and mature oocyte rates were observed in the low-dose hCG group. A significantly higher fertilization rate, high-quality embryo rate and blastocyst formation rate were observed in the low-dose hCG group as compared to the control group. The miscarriage rate was significantly higher in the control group compared to the low-dose hCG group. A significantly lower incidence of OHSS was observed in the low-dose hCG group. There was also a significantly lower gonadotropin cost in the low-dose hCG group as compared to the control group ($1235.0 ± 239.0×$1763.0 ± 405.3, p < 0.001). The concomitant use of low-dose hCG and FSH results in a lower abortion rate and increased number of mature oocytes retrieved, as well as improved oocyte quality, embryo quality and blastocyst formation and reduced FSH requirements.

Dedicated high dose rate 192Ir brachytherapy radiation fields for in vitro cell exposures at variable source-target cell distances: killing of mammalian cells depends on temporal dose rate fluctuation

NASA Astrophysics Data System (ADS)

Veigel, Cornelia; Hartmann, Günther H.; Fritz, Peter; Debus, Jürgen; Weber, Klaus-Josef

2017-02-01

Afterloading brachytherapy is conducted by the stepwise movement of a radioactive source through surgically implanted applicator tubes where at predefined dwell positions calculated dwell times optimize spatial dose delivery with respect to a planned dose level. The temporal exposure pattern exhibits drastic fluctuations in dose rate at a given coordinate and within a single treatment session because of the discontinuous and repeated source movement into the target volume. This could potentially affect biological response. Therefore, mammalian cells were exposed as monolayers to a high dose rate 192Ir source by utilizing a dedicated irradiation device where the distance between a planar array of radioactive source positions and the plane of the cell monolayer could be varied from 2.5 mm to 40 mm, thus varying dose rate pattern for any chosen total dose. The Gammamed IIi afterloading system equipped with a nominal 370 GBq (10 Ci) 192-Ir source was used to irradiate V79 Chinese hamster lung fibroblasts from both confluent and from exponential growth phase with dose up to 12 Gy (at room temperature, total exposure not exceeding 1 h). For comparison, V79 cells were also exposed to 6 MV x-rays from a clinical linear accelerator (dose rate of 2.5 Gy min-1). As biological endpoint, cell survival was determined by standard colony forming assay. Dose measurements were conducted with a diamond detector (sensitive area 7.3 mm2), calibrated by means of 60Co radiation. Additionally, dose delivery was simulated by Monte Carlo calculations using the EGSnrc code system. The calculated secondary electron fluence spectra at the cell location did not indicate a significant change of radiation quality (i.e. higher linear energy transfer) at the lower distances. Clonogenic cell survival curves obtained after brachytherapy exhibited an altered biological response compared to x-rays which was characterized by a significant reduction of the survival curve shoulder when dose rate fluctuations were high. Therefore, also for the time scale of the present investigation, cellular effects of radiation are not invariant to the temporal pattern in dose rate. We propose that with high dose rate variation the cells activate less efficiently their DNA damage response than after continuous irradiation.

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

PubMed

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

2012-05-01

The use of laser accelerators in radiation therapy can perhaps increase the low number of proton and ion therapy facilities in some years due to the low investment costs and small size. The laser-based acceleration technology leads to a very high peak dose rate of about 10(11) Gy∕s. A first dosimetric task is the evaluation of dose rate dependence of clinical dosimeters and other detectors. 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. The dosimeters are dose rate independent up to 4●10(9) Gy∕s within 2% (OSL and TLD) and up to 15●10(9) Gy∕s within 5% (EBT films). The diamond detectors show strong dose rate dependence. TLD, OSL dosimeters, and EBT films are suitable for pulsed beams with a very high pulse dose rate like laser accelerated particle beams.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karsch, L.; Beyreuther, E.; Burris-Mog, T.

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 numbermore » 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.« less

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.

Genetic susceptibility: radiation effects relevant to space travel.

PubMed

Peng, Yuanlin; Nagasawa, Hatsumi; Warner, Christy; Bedford, Joel S

2012-11-01

Genetic variation in the capacity to repair radiation damage is an important factor influencing both cellular and tissue radiosensitivity variation among individuals as well as dose rate effects associated with such damage. This paper consists of two parts. The first part reviews some of the available data relating to genetic components governing such variability among individuals in susceptibility to radiation damage relevant for radiation protection and discusses the possibility and extent to which these may also apply for space radiations. The second part focuses on the importance of dose rate effects and genetic-based variations that influence them. Very few dose rate effect studies have been carried out for the kinds of radiations encountered in space. The authors present here new data on the production of chromosomal aberrations in noncycling low passage human ATM+/+ or ATM+/- cells following irradiations with protons (50 MeV or 1 GeV), 1 GeV(-1) n iron ions and gamma rays, where doses were delivered at a high dose rate of 700 mGy(-1) min, or a lower dose rate of 5 mGy min(-1). Dose responses were essentially linear over the dose ranges tested and not significantly different for the two cell strains. Values of the dose rate effectiveness factor (DREF) were expressed as the ratio of the slopes of the dose-response curves for the high versus the lower (5 mGy min(-1)) dose rate exposures. The authors refer to this as the DREF5. For the gamma ray standard, DREF5 values of approximately two were observed. Similar dose rate effects were seen for both energies of protons (DREF5 ≈ 2.2 in both cases). For 1 GeV(-1) n iron ions [linear energy transfer (LET) ≈ 150 keV μ(-1)], the DREF5 was not 1 as might have been expected on the basis of LET alone but was approximately 1.3. From these results and conditions, the authors estimate that the relative biological effectiveness for 1 GeV(-1) n iron ions for high and low dose rates, respectively, were about 10 and 15 rather than around 20 for low dose rates, as has been assumed by most recommendations from radiation protection organizations for charged particles of this LET. The authors suggest that similar studies using appropriate animal models of carcinogenesis would be valuable.

Effects of gamma irradiation dose-rate on sterile male Aedesaegypti

NASA Astrophysics Data System (ADS)

Ernawan, Beni; Tambunan, Usman Sumo Friend; Sugoro, Irawan; Sasmita, Hadian Iman

2017-06-01

Aedesaegypti is the most important vector for dengue, yellow fever and Zika viruses. Considering its medical importance, vector population control program utilizing radiation-based sterile insect technique (SIT) is one of the potential methods for preventing and limiting the dispersal of these viruses. The present study was undertaken to evaluate the dose-rates effects of γ-sterilization on quality parameters of sterile males. Males Ae.aegypti at the pupal stage were sterilized by applying 70 Gyγ-rays in varies dose-rates, i.e. 0 (control), 300, 600, 900, 1200 and 1500Gy/h utilizing panoramic irradiator. Adult males that emerged from the pupal stage were assessed for their quality parameters, which are the percentage of emergence, longevity, sterility and mating competitiveness. The results herein indicate that there was no major effect of dose-rate on the percentage of emergence, the data showedthat there were no differences between irradiated males compared with control. Generally, the longevity of irradiated males was lower compared to control. The data also demonstrated that longevity was significantly increased at the dose-rate from 300 to 900Gy/h, then decreased at the dose-rate 900 to 1500 Gy/h. Sterility of irradiated maleswas significantly different compared to control, while there was no significantly different at dose rate 300 to 1500 Gy/h. Mating competitiveness of irradiated males was increased at the dose rate from 300 to 1200 Gy/h, then the value was decreased significantly at the dose rate 1500 Gy/h. The dose-rate effects of γ-sterilization were discussed in the context genetic vector control, in particular, the SIT. The results give information and contribute to better understanding towards γ-sterilization optimization and quality parameters of sterile male Ae. aegypti on SIT methods.

Clinical outcomes and cost minimization with an alternative dosing regimen for meropenem in a community hospital.

PubMed

Patel, Gita Wasan; Duquaine, Susan M; McKinnon, Peggy S

2007-12-01

To compare outcomes and cost for the traditional United States Food and Drug Administration-approved dosing regimen for meropenem versus an alternative dosing regimen providing similar pharmacodynamic exposure with a lower total daily dose. Retrospective cohort study with a cost-minimization analysis. A 417-bed, privately owned community hospital. One hundred patients who received meropenem 1 g every 8 or 12 hours (traditional dosing regimen) between January 1 and September 30, 2004 (historical controls), and 192 patients who received meropenem 500 mg every 6 or 8 hours (alternative dosing regimen) between October 1, 2004, and September 30, 2005. Demographic and clinical data were collected for all patients. Cost-minimization analysis was performed by using the drug acquisition cost for meropenem. Demographics, sources of infection, distributions of organisms, and Charlson Comorbidity Index scores were similar between patients in the traditionally and alternatively dosed groups. Concomitant therapy, duration of therapy, success rates, lengths of stay, and in-hospital mortality rates were also similar between groups. Median time to the resolution of symptoms was 3 days for traditional dosing and 1.5 days for alternative dosing (p<0.0001). A logistic regression model including the dosing strategy showed that only polymicrobial infections and sepsis were associated with increased failure rates. The median cost for antibiotics was $439.05/patient for traditional dosing and $234.08/patient for alternative dosing (p<0.0001). An alternative dosing regimen for meropenem with a lower total daily dose yielded patient outcomes, including success rates and duration of therapy, equivalent to those of the traditional dosing regimen. Alternative dosing decreased total drug exposure, costs for antibiotics, and time to the resolution of infections.

Assessment of dose rate to terrestrial biota in the area around coal fired power plant applying ERICA tool and RESRAD BIOTA code.

PubMed

Ćujić, Mirjana; Dragović, Snežana

2018-08-01

This paper presents the environmental radiation risk assessment based on two software program approaches ERICA Tool (version 1.2) and RESRAD BIOTA (version 1.5) to estimate dose rates to terrestrial biota in the area around the largest coal fired power plant in Serbia. For dose rate assessment software's default reference animals and plants and the best estimated values of activity concentrations of 238 U, 234 U, 234 Th, 232 Th, 230 Th, 226 Ra, 210 Pb, 210 Po, 137 Cs in soil were used. Both approaches revealed the highest contribution to the internal dose rate due to 226 Ra and 210 Po, while 137 Cs contributed the most to the external dose rate. In the investigated area total dose rate to biota derived using ERICA Tool ranged from 0.3 to 14.4 μGy h -1 . The natural radionuclides exhibited significantly higher contribution to the total dose rate than the artificial one. In the investigated area, only dose rate for lichens and bryophytes exceeded ERICA Tool screening value of total dose rate of 10 μGy h -1 suggested as confident that environmental risks are negligible. The assessed total dose rates for reference animals and plants using RESRAD BIOTA were found to be 7 and 3 μGy h -1 , respectively. In RESRAD BIOTA - Level 3, 10 species (Lumbricus terrestris, Rana lessonae, Sciurus vulgaris, Anas platyrhynchos, Lepus europaeus, Vulpes vulpes, Capreolus capreolus, Suss crofa, Quercu srobur, Tilia spp.) representative for the study area were modeled. Among them the highest total dose rate (4.5 μGy h -1 ) was obtained for large mammals. Differences in the predicted dose rates to biota using the two software programs are the consequence of the difference in the values of transfer parameters used to calculate activity concentrations in biota. Doses of ionizing radiation estimated in this study will not exhibit deterministic effects at the population level. Thus, the obtained results indicate no significant radiation impact of coal fired power plant operation on terrestrial biota. This paper confirms the use ERICA Tool and RESRAD BIOTA softwares as flexible and effective means of radiation impact assessment. Copyright © 2017 Elsevier Ltd. All rights reserved.

MAGIC with formaldehyde applied to dosimetry of HDR brachytherapy source

NASA Astrophysics Data System (ADS)

Marques; T; Fernandes; J; Barbi; G; Nicolucci; P; Baffa; O

2009-05-01

The use of polymer gel dosimeters in brachytherapy can allow the determination of three-dimensional dose distributions in large volumes and with high spatial resolution if an adequate calibration process is performed. One of the major issues in these experiments is the polymer gel response dependence on dose rate when high dose rate sources are used and the doses in the vicinity of the sources are to be determinated. In this study, the response of a modified MAGIC polymer gel with formaldehyde around an Iridium-192 HDR brachytherapy source is presented. Experimental results obtained with this polymer gel were compared with ionization chamber measurements and with Monte Carlo simulation with PENELOPE. A maximum difference of 3.10% was found between gel dose measurements and Monte Carlo simulation at a radial distance of 18 mm from the source. The results obtained show that the gel's response is strongly influenced by dose rate and that a different calibration should be used for the vicinity of the source and for regions of lower dose rates. The results obtained in this study show that, provided the proper calibration is performed, MAGIC with formaldehyde can be successfully used to accurate determinate dose distributions form high dose rate brachytherapy sources.

Higher dose rate Gamma Knife radiosurgery may provide earlier and longer-lasting pain relief for patients with trigeminal neuralgia.

PubMed

Lee, John Y K; Sandhu, Sukhmeet; Miller, Denise; Solberg, Timothy; Dorsey, Jay F; Alonso-Basanta, Michelle

2015-10-01

Gamma Knife radiosurgery (GKRS) utilizes cobalt-60 as its radiation source, and thus dose rate varies as the fixed source decays over its half-life of approximately 5.26 years. This natural decay results in increasing treatment times when delivering the same cumulative dose. It is also possible, however, that the biological effective dose may change based on this dose rate even if the total dose is kept constant. Because patients are generally treated in a uniform manner, radiosurgery for trigeminal neuralgia (TN) represents a clinical model whereby biological efficacy can be tested. The authors hypothesized that higher dose rates would result in earlier and more complete pain relief but only if measured with a sensitive pain assessment tool. One hundred thirty-three patients were treated with the Gamma Knife Model 4C unit at a single center by a single neurosurgeon during a single cobalt life cycle from January 2006 to May 2012. All patients were treated with 80 Gy with a single 4-mm isocenter without blocking. Using an output factor of 0.87, dose rates ranged from 1.28 to 2.95 Gy/min. The Brief Pain Inventory (BPI)-Facial was administered before the procedure and at the first follow-up office visit 1 month from the procedure (mean 1.3 months). Phone calls were made to evaluate patients after their procedures as part of a retrospective study. Univariate and multivariate linear regression was performed on several independent variables, including sex, age in deciles, diagnosis, follow-up duration, prior surgery, and dose rate. In the short-term analysis (mean 1.3 months), patients' self-reported pain intensity at its worst was significantly correlated with dose rate on multivariate analysis (p = 0.028). Similarly, patients' self-reported interference with activities of daily living was closely correlated with dose rate on multivariate analysis (p = 0.067). A 1 Gy/min decrease in dose rate resulted in a 17% decrease in pain intensity at its worst and a 22% decrease in pain interference with activities of daily living. In longer-term follow-up (mean 1.9 years), GKRS with higher dose rates (> 2.0 Gy/min; p = 0.007) and older age in deciles (p = 0.012) were associated with a lower likelihood of recurrence of pain. Prior studies investigating the role of dose rate in Gamma Knife radiosurgical ablation for TN have not used validated outcome tools to measure pain preoperatively. Consequently, differences in pain outcomes have been difficult to measure. By administering pain scales both preoperatively as well as postoperatively, the authors have identified statistically significant differences in pain intensity and pain interference with activities of daily living when comparing higher versus lower dose rates. Radiosurgery with a higher dose rate results in more pain relief at the early follow-up evaluation, and it may result in a lower recurrence rate at later follow-up.

Detailed Distribution Map of Absorbed Dose Rate in Air in Tokatsu Area of Chiba Prefecture, Japan, Constructed by Car-Borne Survey 4 Years after the Fukushima Daiichi Nuclear Power Plant Accident.

PubMed

Inoue, Kazumasa; Arai, Moeko; Fujisawa, Makoto; Saito, Kyouko; Fukushi, Masahiro

2017-01-01

A car-borne survey was carried out in the northwestern, or Tokatsu, area of Chiba Prefecture, Japan, to make a detailed distribution map of absorbed dose rate in air four years after the Fukushima Daiichi Nuclear Power Plant accident. This area was chosen because it was the most heavily radionuclide contaminated part of Chiba Prefecture and it neighbors metropolitan Tokyo. Measurements were performed using a 3-in × 3-in NaI(Tl) scintillation spectrometer in June 2015. The survey route covered the whole Tokatsu area which includes six cities. A heterogeneous distribution of absorbed dose rate in air was observed on the dose distribution map. Especially, higher absorbed dose rates in air exceeding 80 nGy h-1 were observed along national roads constructed using high porosity asphalt, whereas lower absorbed dose rates in air were observed along local roads constructed using low porosity asphalt. The difference between these asphalt types resulted in a heterogeneous dose distribution in the Tokatsu area. The mean of the contribution ratio of artificial radionuclides to absorbed dose rate in air measured 4 years after the accident was 29% (9-50%) in the Tokatsu area. The maximum absorbed dose rate in air, 201 nGy h-1 was observed at Kashiwa City. Radiocesium was deposited in the upper 1 cm surface layer of the high porosity asphalt which was collected in Kashiwa City and the environmental half-life of the absorbed dose rate in air was estimated to be 1.7 years.

Measurements of air dose rates in and around houses in the Fukushima Prefecture in Japan after the Fukushima accident.

PubMed

Matsuda, Norihiro; Mikami, Satoshi; Sato, Tetsuro; Saito, Kimiaki

2017-01-01

Measurements of air dose rates for 192 houses in a less contaminated area (<0.5 μSv h -1 ) of the Fukushima Prefecture in Japan were conducted in both living rooms and/or bedrooms using optically stimulated luminescence (OSL) dosimeters and around the houses via a man-borne survey at intervals of several meters. The relation of the two air dose rates (inside and outside) for each house, including the background from natural radionuclides, was divided into several categories, determined by construction materials (light and heavy) and floor number, with the dose reduction factors being expressed as the ratio of the dose inside to that outside the house. For wooden and lightweight steel houses (classed as light), the dose rates inside and outside the houses showed a positive correlation and linear regression with a slope-intercept form due to the natural background, although the degree of correlation was not very high. The regression coefficient, i.e., the average dose reduction factor, was 0.38 on the first floor and 0.49 on the second floor. It was found that the contribution of natural radiation cannot be neglected when we consider dose reduction factors in less contaminated areas. The reductions in indoor dose rates are observed because a patch of ground under each house is not contaminated (this is the so-called uncontaminated effect) since the shielding capability of light construction materials is typically low. For reinforced steel-framed concrete houses (classed as heavy), the dose rates inside the houses did not show a correlation with those outside the houses due to the substantial shielding capability of these materials. The average indoor dose rates were slightly higher than the arithmetic mean value of the outdoor dose rates from the natural background because concrete acts as a source of natural radionuclides. The characteristics of the uncontaminated effect were clarified through Monte Carlo simulations. It was found that there is a great variation in air dose rates even within one house, depending on the height of the area and its closeness to the outside boundary. Measurements of outdoor dose rates required consideration of local variations depending on the environment surrounding each house. The representative value was obtained from detailed distributions of air dose rates around the house, as measured by a man-borne survey. Therefore, it is imperative to recognize that dose reduction factors fluctuate in response to various factors such as the size and shape of a house, construction materials acting as a shield and as sources, position (including height) within a room, floor number, total number of floors, and surrounding environment. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

SEMICONDUCTOR PHYSICS Dose-rate dependence of optically stimulated luminescence signal

NASA Astrophysics Data System (ADS)

Pingqiang, Wei; Zhaoyang, Chen; Yanwei, Fan; Yurun, Sun; Yun, Zhao

2010-10-01

Optically stimulated luminescence (OSL) is the luminescence emitted from a semiconductor during its exposure to light. The OSL intensity is a function of the total dose absorbed by the sample. The dose-rate dependence of the OSL signal of the semiconductor CaS doped Ce and Sm was studied by numerical simulation and experiments. Based on a one-trap/one-center model, the whole OSL process was represented by a series of differential equations. The dose-rate properties of the materials were acquired theoretically by solving the equations. Good coherence was achieved between numerical simulation and experiments, both of which showed that the OSL signal was independent of dose rate. This result validates that when using OSL as a dosimetry technique, the dose-rate effect can be neglected.

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

PubMed

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

2015-03-01

The biological risks associated with low-dose-rate (LDR) radiation exposures are not yet well defined. To assess the risk related to DNA damage, we compared the yields of two established biodosimetry end points, γ-H2AX and micronuclei (MNi), in peripheral mouse blood lymphocytes after prolonged in vivo exposure to LDR X rays (0.31 cGy/min) vs. acute high-dose-rate (HDR) exposure (1.03 Gy/min). C57BL/6 mice were total-body irradiated with 320 kVP X rays with doses of 0, 1.1, 2.2 and 4.45 Gy. Residual levels of total γ-H2AX fluorescence in lymphocytes isolated 24 h after the start of irradiation were assessed using indirect immunofluorescence methods. The terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay was used to determine apoptotic cell frequency in lymphocytes sampled at 24 h. Curve fitting analysis suggested that the dose response for γ-H2AX yields after acute exposures could be described by a linear dependence. In contrast, a linear-quadratic dose-response shape was more appropriate for LDR exposure (perhaps reflecting differences in repair time after different LDR doses). Dose-rate sparing effects (P < 0.05) were observed at doses ≤2.2 Gy, such that the acute dose γ-H2AX and TUNEL-positive cell yields were significantly larger than the equivalent LDR yields. At the 4.45 Gy dose there was no difference in γ-H2AX expression between the two dose rates, whereas there was a two- to threefold increase in apoptosis in the LDR samples compared to the equivalent 4.45 Gy acute dose. Micronuclei yields were measured at 24 h and 7 days using the in vitro cytokinesis-blocked micronucleus (CBMN) assay. The results showed that MNi yields increased up to 2.2 Gy with no further increase at 4.45 Gy and with no detectable dose-rate effect across the dose range 24 h or 7 days post exposure. In conclusion, the γ-H2AX biomarker showed higher sensitivity to measure dose-rate effects after low-dose LDR X rays compared to MNi formation; however, confounding factors such as variable repair times post exposure, increased cell killing and cell cycle block likely contributed to the yields of MNi with accumulating doses of ionizing radiation.

Passive dosimetry aboard the Mir Orbital Station: internal measurements.

PubMed

Benton, E R; Benton, E V; Frank, A L

2002-10-01

Passive radiation dosimeters were exposed aboard the Mir Orbital Station over a substantial portion of the solar cycle in order to measure the change in dose and dose equivalent rates as a function of time. During solar minimum, simultaneous measurements of the radiation environment throughout the habitable volume of the Mir were made using passive dosimeters in order to investigate the effect of localized shielding on dose and dose equivalent. The passive dosimeters consisted of a combination of thermoluminescent detectors to measure absorbed dose and CR-39 PNTDs to measure the linear energy transfer (LET) spectrum from charged particles of LET infinity H2O > or = 5 keV/micrometers. Results from the two detector types were then combined to yield mean total dose rate, mean dose equivalent rate, and average quality factor. Contrary to expectations, both dose and dose equivalent rates measured during May-October 1991 near solar maximum were higher than similar measurements carried out in 1996-1997 during solar minimum. The elevated dose and dose equivalent rates measured in 1991 were probably due to a combination of intense solar activity, including a large solar particle event on 9 June 1991, and the temporary trapped radiation belt created in the slot region by the solar particle event and ensuing magnetic storm of 24 March 1991. During solar minimum, mean dose and dose equivalent rates were found to vary by factors of 1.55 and 1.37, respectively, between different locations through the interior of Mir. More heavily shielded locations tended to yield lower total dose and dose equivalent rates, but higher average quality factor than did more lightly shielding locations. However, other factors such as changes in the immediate shielding environment surrounding a given detector location, changes in the orientation of the Mir relative to its velocity vector, and changes in the altitude of the station also contributed to the variation. Proton and neutron-induced target fragment secondaries, not primary galactic cosmic rays, were found to dominate the LET spectrum above 100 keV/micrometers. This indicates that in low earth orbit, trapped protons in the South Atlantic Anomaly are responsible for the major fraction of the total dose equivalent. c2002 Elsevier Science Ltd. All rights reserved.

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

Uveal Melanoma Treated With Iodine-125 Episcleral Plaque: An Analysis of Dose on Disease Control and Visual Outcomes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perez, Bradford A.; Mettu, Pradeep; Vajzovic, Lejla

2014-05-01

Purpose: To investigate, in the treatment of uveal melanomas, how tumor control, radiation toxicity, and visual outcomes are affected by the radiation dose at the tumor apex. Methods and Materials: A retrospective review was performed to evaluate patients treated for uveal melanoma with {sup 125}I plaques between 1988 and 2010. Radiation dose is reported as dose to tumor apex and dose to 5 mm. Primary endpoints included time to local failure, distant failure, and death. Secondary endpoints included eye preservation, visual acuity, and radiation-related complications. Univariate and multivariate analyses were performed to determine associations between radiation dose and the endpointmore » variables. Results: One hundred ninety patients with sufficient data to evaluate the endpoints were included. The 5-year local control rate was 91%. The 5-year distant metastases rate was 10%. The 5-year overall survival rate was 84%. There were no differences in outcome (local control, distant metastases, overall survival) when dose was stratified by apex dose quartile (<69 Gy, 69-81 Gy, 81-89 Gy, >89 Gy). However, increasing apex dose and dose to 5-mm depth were correlated with greater visual acuity loss (P=.02, P=.0006), worse final visual acuity (P=.02, P<.0001), and radiation complications (P<.0001, P=.0009). In addition, enucleation rates were worse with increasing quartiles of dose to 5 mm (P=.0001). Conclusions: Doses at least as low as 69 Gy prescribed to the tumor apex achieve rates of local control, distant metastasis–free survival, and overall survival that are similar to radiation doses of 85 Gy to the tumor apex, but with improved visual outcomes.« less

Radiation Hormesis: Historical Perspective and Implications for Low-Dose Cancer Risk Assessment

PubMed Central

Vaiserman, Alexander M.

2010-01-01

Current guidelines for limiting exposure of humans to ionizing radiation are based on the linear-no-threshold (LNT) hypothesis for radiation carcinogenesis under which cancer risk increases linearly as the radiation dose increases. With the LNT model even a very small dose could cause cancer and the model is used in establishing guidelines for limiting radiation exposure of humans. A slope change at low doses and dose rates is implemented using an empirical dose and dose rate effectiveness factor (DDREF). This imposes usually unacknowledged nonlinearity but not a threshold in the dose-response curve for cancer induction. In contrast, with the hormetic model, low doses of radiation reduce the cancer incidence while it is elevated after high doses. Based on a review of epidemiological and other data for exposure to low radiation doses and dose rates, it was found that the LNT model fails badly. Cancer risk after ordinarily encountered radiation exposure (medical X-rays, natural background radiation, etc.) is much lower than projections based on the LNT model and is often less than the risk for spontaneous cancer (a hormetic response). Understanding the mechanistic basis for hormetic responses will provide new insights about both risks and benefits from low-dose radiation exposure. PMID:20585444

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

PubMed

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

2018-01-01

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

The Effects of ELDRS at Ultra-Low Dose Rates

NASA Technical Reports Server (NTRS)

Chen, Dakai; Forney, James; Carts, Martin; Phan, Anthony; Cox, Stephen; Kruckmeyer, Kirby; Burns, Sam; Albarian, Rafi; Holcombe, Bruce; Little, Bradley;

Comparative analysis of dose rates in bricks determined by neutron activation analysis, alpha counting and X-ray fluorescence analysis for the thermoluminescence fine grain dating method

NASA Astrophysics Data System (ADS)

Bártová, H.; Kučera, J.; Musílek, L.; Trojek, T.

2014-11-01

In order to evaluate the age from the equivalent dose and to obtain an optimized and efficient procedure for thermoluminescence (TL) dating, it is necessary to obtain the values of both the internal and the external dose rates from dated samples and from their environment. The measurements described and compared in this paper refer to bricks from historic buildings and a fine-grain dating method. The external doses are therefore negligible, if the samples are taken from a sufficient depth in the wall. However, both the alpha dose rate and the beta and gamma dose rates must be taken into account in the internal dose. The internal dose rate to fine-grain samples is caused by the concentrations of natural radionuclides 238U, 235U, 232Th and members of their decay chains, and by 40K concentrations. Various methods can be used for determining trace concentrations of these natural radionuclides and their contributions to the dose rate. The dose rate fraction from 238U and 232Th can be calculated, e.g., from the alpha count rate, or from the concentrations of 238U and 232Th, measured by neutron activation analysis (NAA). The dose rate fraction from 40K can be calculated from the concentration of potassium measured, e.g., by X-ray fluorescence analysis (XRF) or by NAA. Alpha counting and XRF are relatively simple and are accessible for an ordinary laboratory. NAA can be considered as a more accurate method, but it is more demanding regarding time and costs, since it needs a nuclear reactor as a neutron source. A comparison of these methods allows us to decide whether the time- and cost-saving simpler techniques introduce uncertainty that is still acceptable.

Assessment of doses to game animals in Finland.

PubMed

Vetikko, Virve; Kostiainen, Eila

2013-11-01

A study was carried out to assess the dose rates to game animals in Finland affected by the radioactive caesium deposition that occurred after the accident at the Chernobyl nuclear power plant in Ukraine in 1986. The aim of this assessment was to obtain new information on the dose rates to mammals and birds under Finnish conditions. Dose rates were calculated using the ERICA Assessment Tool developed within the EC 6th Framework Programme. The input data consisted of measured activity concentrations of (137)Cs and (134)Cs in soil and lake water samples and in flesh samples of selected animal species obtained for environmental monitoring. The study sites were located in the municipality of Lammi, Southern Finland, where the average (137)Cs deposition was 46.5 kBq m(-2) (1 October 1987). The study sites represented the areas receiving the highest deposition in Finland after the Chernobyl accident. The selected species included moose (Alces alces), arctic hare (Lepus timidus) and several bird species: black grouse (Tetrao tetrix), hazel hen (Bonasia bonasia), mallard (Anas platurhynchos), goldeneye (Bucephala clangula) and teal (Anas crecca). For moose, dose rates were calculated for the years 1986-1990 and for the 2000s. For all other species, maximal measured activity concentrations were used. The results showed that the dose rates to these species did not exceed the default screening level of 10 μGy h(-1) used as a protection criterion. The highest total dose rate (internal and external summed), 3.7 μGy h(-1), was observed for the arctic hare in 1986. Although the dose rate of 3.7 μGy h(-1) cannot be considered negligible given the uncertainties involved in predicting the dose rates, the possible harmful effects related to this dose rate are too small to be assessed based on current knowledge on the biological effects of low doses in mammals. Copyright © 2013 Elsevier Ltd. All rights reserved.

Determination of spatial dose distribution in UCC treatments with LDR brachytherapy using Monte Carlo methods.

PubMed

Benites-Rengifo, Jorge Luis; Vega-Carrillo, Hector Rene

2018-05-19

Using Monte Carlos methods, with the MCNP5 code, a gynecological phantom and a vaginal cylinder were modeled. The spatial distribution of absorbed dose rates in Uterine Cervical Cancer treatment through low dose rate brachytherapy was determined. A liquid water gynecology computational phantom, including a vaginal cylinder applicator made of Lucite, was designed. The applicator has a linear array of four radioactive sources of Cesium 137. Around the vaginal cylinder, 13 water spherical cells of 0.5 cm-diameter were modeled to calculate absorbed dose emulating the procedure made by the treatment planning system. The gamma-ray fluence distribution was estimated, as well as the absorbed doses resulting approximately symmetrical for cells located at upper and lower of vaginal cylinder. Obtained results allow the use of the radioactive decay law to determine dose rate for Uterine Cervical Cancer using low dose rate brachytherapy. Copyright © 2018 Elsevier Ltd. All rights reserved.

Low-energy electron effects on tensile modulus and infrared transmission properties of a polypyromellitimide film

NASA Technical Reports Server (NTRS)

Ferl, J. E.; Long, E. R., Jr.

1981-01-01

Infrared (IR) spectroscopy and tensile modulus testing were used to evaluate the importance of experimental procedure on changes in properties of pyromellitic dianhydride-p,p prime-oxydianiline film exposed to electron radiation. The radiation exposures were accelerated, approximate equivalents to the total dose expected for a 30 year mission in geosynchronous Earth orbit. The change in the tensile modulus depends more on the dose rate and the time interval between exposure and testing than on total dose. The IR data vary with both total dose and dose rate. A threshold dose rate exists below which reversible radiation effects on the IR spectra occur. Above the threshold dose rate, irreversible effects occur with the appearance of a new band. Post-irradiation and in situ IR absorption bands are significantly different. It is suggested that the electron radiation induced metastable, excites molecular states.

The correlation between elongation at break and thermal decomposition of aged EPDM cable polymer

NASA Astrophysics Data System (ADS)

Šarac, T.; Devaux, J.; Quiévy, N.; Gusarov, A.; Konstantinović, M. J.

2017-03-01

The effect of simultaneous thermal and gamma irradiation ageing on the mechanical and physicochemical properties of industrial EPDM was investigated. Accelerated ageing, covering a wide range of dose rates, doses and temperatures, was preformed in stagnant air on EPDM polymer samples extracted from the cables in use in the Belgian nuclear power plants. The mechanical properties, ultimate tensile stress and elongation at break, are found to exhibit the strong dependence on the dose, ageing temperature and dose rate. The thermal decomposition of aged polymer is observed to be the dose dependent when thermogravimetry test is performed under air atmosphere. No dose dependence is observed when thermal decomposition is performed under nitrogen atmosphere. The thermal decomposition rates are found to fully mimic the reduction of elongation at break for all dose rates and ageing temperatures. This effect is argued to be the result of thermal and radiation mediated oxidation degradation process.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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, andmore » 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.« less

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 in improving the accuracy and tractability of dose and shielding calculations for nuclear medicine facility design.

A less stressful alternative to oral gavage for pharmacological and toxicological studies in mice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walker, Mary K., E-mail: mwalker@salud.unm.edu; Boberg, Jason R.; Walsh, Mary T.

Oral gavage dosing can induce stress and potentially confound experimental measurements, particularly when blood pressure and heart rate are endpoints of interest. Thus, we developed a pill formulation that mice would voluntarily consume and tested the hypothesis that pill dosing would be significantly less stressful than oral gavage. C57Bl/6 male mice were singly housed and on four consecutive days were exposed to an individual walking into the room (week 1, control), a pill being placed into the cage (week 2), and a dose of water via oral gavage (week 3). Blood pressure and heart rate were recorded by radiotelemetry continuouslymore » for 5 h after treatment, and feces collected 6–10 h after treatment for analysis of corticosterone metabolites. Both pill and gavage dosing significantly increased mean arterial pressure (MAP) during the first hour, compared to control. However, the increase in MAP was significantly greater after gavage and remained elevated up to 5 h, while MAP returned to normal within 2 h after a pill. Neither pill nor gavage dosing significantly increased heart rate during the first hour, compared to control; however, pill dosing significantly reduced heart rate while gavage significantly increased heart rate 2–5 h post dosing. MAP and heart rate did not differ 24 h after dosing. Lastly, only gavage dosing significantly increased fecal corticosterone metabolites, indicating a systemic stress response via activation of the hypothalamic–pituitary–adrenal axis. These data demonstrated that this pill dosing method of mice is significantly less stressful than oral gavage. -- Highlights: ► Developed a novel oral dosing method using a pill that mice will readily consume. ► Assessed stress by blood pressure, heart rate, and fecal corticosterone metabolites. ► Demonstrated that pill dosing is significantly less stressful than oral gavage.« less

SU-F-T-266: Dynalogs Based Evaluation of Different Dose Rate IMRT Using DVH and Gamma Index

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahmed, S; Ahmed, S; Ahmed, F

2016-06-15

Purpose: This work investigates the impact of low and high dose rate on IMRT through Dynalogs by evaluating Gamma Index and Dose Volume Histogram. Methods: The Eclipse™ treatment planning software was used to generate plans on prostate and head and neck sites. A range of dose rates 300 MU/min and 600 MU/min were applied to each plan in order to investigate their effect on the beam ON time, efficiency and accuracy. Each plan had distinct monitor units per fraction, delivery time, mean dose rate and leaf speed. The DVH data was used in the assessment of the conformity and planmore » quality.The treatments were delivered on Varian™ Clinac 2100C accelerator equipped with 120 leaf millennium MLC. Dynalogs of each plan were analyzed by MATLAB™ program. Fluence measurements were performed using the Sun Nuclear™ 2D diode array and results were assessed, based on Gamma analysis of dose fluence maps, beam delivery statistics and Dynalogs data. Results: Minor differences found by adjusted R-squared analysis of DVH’s for all the plans with different dose rates. It has been also found that more and larger fields have greater time reduction at high dose rate and there was a sharp decrease in number of control points observed in dynalog files by switching dose rate from 300 MU/min to 600 MU/min. Gamma Analysis of all plans passes the confidence limit of ≥95% with greater number of passing points in 300 MU/min dose rate plans. Conclusion: The dynalog files are compatible tool for software based IMRT QA. It can work perfectly parallel to measurement based QA setup and stand-by procedure for pre and post delivery of treatment plan.« less

Detailed Distribution Map of Absorbed Dose Rate in Air in Tokatsu Area of Chiba Prefecture, Japan, Constructed by Car-Borne Survey 4 Years after the Fukushima Daiichi Nuclear Power Plant Accident

PubMed Central

Inoue, Kazumasa; Arai, Moeko; Fujisawa, Makoto; Saito, Kyouko; Fukushi, Masahiro

2017-01-01

A car-borne survey was carried out in the northwestern, or Tokatsu, area of Chiba Prefecture, Japan, to make a detailed distribution map of absorbed dose rate in air four years after the Fukushima Daiichi Nuclear Power Plant accident. This area was chosen because it was the most heavily radionuclide contaminated part of Chiba Prefecture and it neighbors metropolitan Tokyo. Measurements were performed using a 3-in × 3-in NaI(Tl) scintillation spectrometer in June 2015. The survey route covered the whole Tokatsu area which includes six cities. A heterogeneous distribution of absorbed dose rate in air was observed on the dose distribution map. Especially, higher absorbed dose rates in air exceeding 80 nGy h-1 were observed along national roads constructed using high porosity asphalt, whereas lower absorbed dose rates in air were observed along local roads constructed using low porosity asphalt. The difference between these asphalt types resulted in a heterogeneous dose distribution in the Tokatsu area. The mean of the contribution ratio of artificial radionuclides to absorbed dose rate in air measured 4 years after the accident was 29% (9–50%) in the Tokatsu area. The maximum absorbed dose rate in air, 201 nGy h-1 was observed at Kashiwa City. Radiocesium was deposited in the upper 1 cm surface layer of the high porosity asphalt which was collected in Kashiwa City and the environmental half-life of the absorbed dose rate in air was estimated to be 1.7 years. PMID:28129382

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kurnaz, Asli; Kuecuekoemeroglu, B.; Okumusoglu, N. T.

In this study, it was determined environmental gamma radiation dose rate for some counties of Trabzon-Turkey. A detailed ambient gamma dose measurement has been performed in the seven counties of Trabzon, using a portable environmental survey meter (NaI detector, INSPECTOR 1000). The measurements were performed indoor and outdoor of buildings and also at each spot, a reading was taken at 1 m above ground level. The dose rates varied from 42.69 nGy/h and 140.91 nGy/h for indoor gamma dose and 27.84 nGy/h and 121.80 nGy/h for outdoor gamma dose . Average indoor and outdoor gamma dose rates were ascertained tomore » be 71.05 nGy/h and 60.20 nGy/h, respectively. The annual effective doses were calculated from indoor and outdoor gamma doses to be 348.56 muSv/y and 73.83 muSv/y, respectively.« less

Effects of breast-air and breast-lung interfaces on the dose rate at the planning target volume of a MammoSite catheter for Yb-169 and Ir-192 HDR sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cazeca, Mario J.; Medich, David C.; Munro, John J. III

2010-08-15

Purpose: To study the effects of the breast-air and breast-lung interfaces on the absorbed dose within the planning target volume (PTV) of a MammoSite balloon dose delivery system as well as the effect of contrast material on the dose rate in the PTV. Methods: The Monte Carlo MCNP5 code was used to simulate dose rate in the PTV of a 2 cm radius MammoSite balloon dose delivery system. The simulations were carried out using an average female chest phantom (AFCP) and a semi-infinite water phantom for both Yb-169 and Ir-192 high dose rate sources for brachytherapy application. Gastrografin was introducedmore » at varying concentrations to study the effect of contrast material on the dose rate in the PTV. Results: The effect of the density of the materials surrounding the MammoSite balloon containing 0% contrast material on the calculated dose rate at different radial distances in the PTV was demonstrated. Within the PTV, the ratio of the calculated dose rate for the AFCP and the semi-infinite water phantom for the point closest to the breast-air interface (90 deg.) is less than that for the point closest to the breast-lung interface (270 deg.) by 11.4% and 4% for the HDR sources of Yb-169 and Ir-192, respectively. When contrast material was introduced into the 2 cm radius MammoSite balloon at varying concentrations, (5%, 10%, 15%, and 20%), the dose rate in the AFCP at 3.0 cm radial distance at 90 deg. was decreased by as much as 14.8% and 6.2% for Yb-169 and Ir-192, respectively, when compared to that of the semi-infinite water phantom with contrast concentrations of 5%, 10%, 15%, and 20%, respectively. Conclusions: Commercially available software used to calculate dose rate in the PTV of a MammoSite balloon needs to account for patient anatomy and density of surrounding materials in the dosimetry analyses in order to avoid patient underdose.« less

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.

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. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Optimizing bevacizumab dosing in glioblastoma: less is more.

PubMed

Ajlan, Abdulrazag; Thomas, Piia; Albakr, Abdulrahman; Nagpal, Seema; Recht, Lawrence

2017-10-01

Compared to traditional chemotherapies, where dose limiting toxicities represent the maximum possible dose, monoclonal antibody therapies are used at doses well below maximum tolerated dose. However, there has been little effort to ascertain whether there is a submaximal dose at which the efficacy/complication ratio is maximized. Thus, despite the general practice of using Bevacizumab (BEV) at dosages of 10 mg/kg every other week for glioma patients, there has not been much prior work examining whether the relatively high complication rates reported with this agent can be decreased by lowering the dose without impairing efficacy. We assessed charts from 80 patients who received BEV for glioblastoma to survey the incidence of complications relative to BEV dose. All patients were treated with standard upfront chemoradiation. The toxicity was graded based on the NCI CTCAE, version 4.03. The rate of BEV serious related adverse events was 12.5% (n = 10/80). There were no serious adverse events (≥grade 3) when the administered dose was (<3 mg/kg/week), compared to a 21% incidence in those who received higher doses (≥3 mg/kg/week) (P < 0.01). Importantly, the three patient deaths attributable to BEV administration occurred in patients receiving higher doses. Patients who received lower doses also had a better survival rate, although this did not reach statistical significance [median OS 39 for low dose group vs. 17.3 for high dose group (P = 0.07)]. Lower rates of serious BEV related toxicities are noted when lower dosages are used without diminishing positive clinical impact. Further work aimed at optimizing BEV dosage is justified.

Gafchromic EBT-XD film: Dosimetry characterization in high-dose, volumetric-modulated arc therapy.

PubMed

Miura, Hideharu; Ozawa, Shuichi; Hosono, Fumika; Sumida, Naoki; Okazue, Toshiya; Yamada, Kiyoshi; Nagata, Yasushi

2016-11-08

Radiochromic films are important tools for assessing complex dose distributions. Gafchromic EBT-XD films have been designed for optimal performance in the 40-4,000 cGy dose range. We investigated the dosimetric characteristics of these films, including their dose-response, postexposure density growth, and dependence on scanner orientation, beam energy, and dose rate with applications to high-dose volumetric-modulated arc therapy (VMAT) verification. A 10 MV beam from a TrueBeam STx linear accelerator was used to irradiate the films with doses in the 0-4,000 cGy range. Postexposure coloration was analyzed at postirradiation times ranging from several minutes to 48 h. The films were also irradiated with 6 MV (dose rate (DR): 600 MU/min), 6 MV flattening filter-free (FFF) (DR: 1,400 MU/ min), and 10 MV FFF (DR: 2,400 MU/min) beams to determine the energy and dose-rate dependence. For clinical examinations, we compared the dose distribu-tion measured with EBT-XD films and calculated by the planning system for four VMAT cases. The red channel of the EBT-XD film exhibited a wider dynamic range than the green and blue channels. Scanner orientation yielded a variation of ~ 3% in the net optical density (OD). The difference between the film front and back scan orientations was negligible, with variation of ~ 1.3% in the net OD. The net OD increased sharply within the first 6 hrs after irradiation and gradually afterwards. No significant difference was observed for the beam energy and dose rate, with a variation of ~ 1.5% in the net OD. The gamma passing rates (at 3%, 3 mm) between the film- measured and treatment planning system (TPS)-calculated dose distributions under a high dose VMAT plan in the absolute dose mode were more than 98.9%. © 2016 The Authors.

SU-E-T-13: Comparison of Dose Rates with and without Gold Backing of USC #9 Radioactive Eye Plaque Using MCNP5.

PubMed

Aryal, P; Molloy, J

2012-06-01

To show the effect of gold backing on dose rates for the USC #9 radioactive eye plaque. An I125 source (IsoAid model IAI-125A) and gold backing was modeled using MCNP5 Monte Carlo code. A single iodine seed was simulated with and without gold backing. Dose rates were calculated in two orthogonal planes. Dose calculation points were structured in two orthogonal planes that bisect the center of the source. A 2×2 cm matrix of spherical points of radius 0.2 mm was created in a water phantom of 10 cm radius. 0.2 billion particle histories were tracked. Dose differences with and without the gold backing were analyzed using Matlab. The gold backing produced a 3% increase in the dose rate near the source surface (<1mm) relative to that without the backing. This was presumably caused by fluorescent photons from the gold. At distances between 1 and 2 cm, the gold backing reduced the dose rate by up to 12%, which we attribute to a lack of scatter resulting from the attenuation from the gold. Dose differences were most pronounced in the radial direction near the source center but off axis. The dose decreased by 25%, 65% and 81% at 1, 2, and 3 mm off axis at a distance of 1 mm from the source surface. These effects were less pronounced in the perpendicular dimension near the source tip, where maximum dose decreases of 2% were noted. I 125 sources embedded directly into gold troughs display dose differences of 2 - 90%, relative to doses without the gold backing. This is relevant for certain types of plaques used in treatment of ocular melanoma. Large dose reductions can be observed and may have implications for scleral dose reduction. © 2012 American Association of Physicists in Medicine.

[Application of half-dose depot long-acting triptorelin in postoperative adjuvant therapy for endometriosis].

PubMed

Liu, Xia; Zhang, Hong-xia; Wang, Li-ping; Fu, Wei-ping

2013-01-15

To evaluate the efficacy and adverse effects of half-dose depot long-acting triptorelin in the therapy of endometriosis. The efficacy and adverse effects of routine-dose or half-dose triptorelin in postoperative endometriosis patients were prospectively observed. A total of 186 postoperative patients with moderate or severe endometriosis received an intramuscular injection of triptorelin every 28 days for 6 times. They were randomly divided into 3 groups, i.e. half-dose group (n = 99): 1.875 mg each time; "draw-back" group (n = 52): 3.75 mg first time, then 1.875 mg each time; and routine-dose group (n = 35): 3.75 mg each time. Amenorrhea was effectively induced in all patients after the second injection. There was no significant difference in the rate of serum E2 level at Day 28 of every injection below the upper limit of "estrogen threshold (110 - 146 pmol/L)" not stimulating ectopic endometrium proliferation among half-dose group, "draw-back" group and routine-dose group (99% vs 100% and 99.0%, P > 0.05), the percentage of E2 < 37 pmol/L in E2 < 110 pmol/L in half-dose group was significantly lower than that in "draw-back" and routine-dose groups after 2-5(th) injection (69% vs 79% and 85%, P < 0.01), but there was no significant difference after first half-dose and routine-dose injection (71% vs 73%, P > 0.05). No significant difference existed in the rate of pelvic pain relief during the first returning menstruation and the recurrence rate of endometriosis within 1 year postoperation among three groups (both P > 0.05). However, the incidences of menopausal syndrome and severe menopausal syndrome in half-dose group were significantly lower than those in "draw-back" and routine-dose groups (both P < 0.01). And the incompletion rate of six-time drug for severe menopause syndrome was also significantly lower (P < 0.05) while the completion rate of six-time drug use in half-dose group was significantly higher (P < 0.05). As a postoperative adjuvant, half-dose depot triptorelin therapy is efficacious for endometriosis. It reduces menopausal syndrome and treatment cost and enhances patient compliance.

Long-Segment Fusion for Adult Spinal Deformity Correction Using Low-Dose Recombinant Human Bone Morphogenetic Protein-2: A Retrospective Review of Fusion Rates.

PubMed

Schmitt, Paul J; Kelleher, John P; Ailon, Tamir; Heller, Joshua E; Kasliwal, Manish K; Shaffrey, Christopher I; Smith, Justin S

2016-08-01

Although use of very high-dose recombinant human bone morphogenetic protein-2 (rhBMP-2) has been reported to markedly improve fusion rates in adult spinal deformity (ASD) surgery, most centers use much lower doses due to cost constraints. How effective these lower doses are for fusion enhancement remains unclear. To assess fusion rates using relatively low-dose rhBMP-2 for ASD surgery. This was a retrospective review of consecutive ASD patients that underwent thoracic to sacral fusion. Patients that achieved 2-year follow-up were analyzed. Impact of patient and surgical factors on fusion rate was assessed, and fusion rates were compared with historical cohorts. Of 219 patients, 172 (78.5%) achieved 2-year follow-up and were analyzed. Using an average rhBMP-2 dose of 3.1 mg/level (average total dose = 35.9 mg/case), the 2-year fusion rate was 73.8%. Cancellous allograft, local autograft, and very limited iliac crest bone graft (<20 mL, obtained during iliac bolt placement) were also used. On multivariate analysis, female sex was associated with a higher fusion rate, whereas age, comorbidity score, deformity type, and 3-column osteotomy were not. There were no complications directly attributable to rhBMP-2. Fusion rates for ASD using low-dose rhBMP-2 were comparable to those reported for iliac crest bone graft but lower than for high-dose rhBMP-2. Importantly, there were substantial differences between patients in the present series and those in the historical comparison groups that could not be fully adjusted for based on available data. Prospective evaluation of rhBMP-2 dosing for ASD surgery is warranted to define the most appropriate dose that balances benefits, risks, and costs. ASD, adult spinal deformityICBG, iliac crest bone graftOR, odds ratiorhBMP-2, recombinant human bone morphogenetic protein-2RR, risk ratioTCO, 3-column osteotomy.

The Schwarzschild effect of the dosimetry film Kodak EDR 2.

PubMed

Djouguela, A; Kollhoff, R; Rubach, A; Harder, D; Poppe, B

2005-11-07

The magnitude of the Schwarzschild effect or failure of the reciprocity law has been experimentally investigated for the dosimetry film EDR 2 from Kodak. When the dose rate applied to achieve a given dose was reduced by a factor of 12, the net optical density was reduced by up to 5%. The clinical importance of this effect is negligible as long as the films are calibrated at a value of the dose rate approximately representative of the dose rates occurring in the target volume, but in target regions of strongly reduced dose rate the Schwarzschild effect should be allowed for by a correction of the net optical density.

Radiation Parameters of High Dose Rate Iridium -192 Sources

NASA Astrophysics Data System (ADS)

Podgorsak, Matthew B.

A lack of physical data for high dose rate (HDR) Ir-192 sources has necessitated the use of basic radiation parameters measured with low dose rate (LDR) Ir-192 seeds and ribbons in HDR dosimetry calculations. A rigorous examination of the radiation parameters of several HDR Ir-192 sources has shown that this extension of physical data from LDR to HDR Ir-192 may be inaccurate. Uncertainty in any of the basic radiation parameters used in dosimetry calculations compromises the accuracy of the calculated dose distribution and the subsequent dose delivery. Dose errors of up to 0.3%, 6%, and 2% can result from the use of currently accepted values for the half-life, exposure rate constant, and dose buildup effect, respectively. Since an accuracy of 5% in the delivered dose is essential to prevent severe complications or tumor regrowth, the use of basic physical constants with uncertainties approaching 6% is unacceptable. A systematic evaluation of the pertinent radiation parameters contributes to a reduction in the overall uncertainty in HDR Ir-192 dose delivery. Moreover, the results of the studies described in this thesis contribute significantly to the establishment of standardized numerical values to be used in HDR Ir-192 dosimetry calculations.

Incidence of Hypoglycemia in Patients With Low eGFR Treated With Insulin and Dextrose for Hyperkalemia.

PubMed

Pierce, Dwayne A; Russell, Greg; Pirkle, James L

2015-12-01

Hyperkalemia is a potentially life-threatening condition that is common in kidney disease patients. Insulin is used to treat hyperkalemia, but may cause hypoglycemia, especially in kidney disease when insulin may be metabolized more slowly. We compared the rates of hypoglycemia in patients with low estimated glomerular filtration rate (eGFR) using high versus low doses of insulin for hyperkalemia to determine if lower doses of insulin would decrease the incidence of hypoglycemia. This was a retrospective study of hospitalized patients receiving intravenous insulin for hyperkalemia during a 6-month period. Patients with low eGFR were analyzed based on how much insulin they received: high dose (10 units, n = 78) versus low dose (5 units, n = 71). Postdose nadir blood glucose values were examined for up to 8 hours after the dose. The percentage of hypoglycemia (blood glucose ≤70 mg/dl) and a subset of severe hypoglycemia (blood glucose <50 mg/dl) were then reported for each dose group. A total of 149 doses were identified in patients with low eGFR. The rates of hypoglycemia were 16.7% and 19.7% (P = 0.79), respectively, among high-dose (n = 78) and low-dose (n = 71) groups. Rates of severe hypoglycemia were 8.9% and 7.0%, respectively (P = 0.90). More than 28% of hypoglycemic episodes with high doses occurred after 4 hours (median = 2.5 hours) compared with 14.3% with low doses (median = 2.38 hours). There was no difference in the rate of hypoglycemia or severe hypoglycemia between high or low doses of insulin in patients with low eGFR. We recommend monitoring up to 6 hours after insulin use in hyperkalemia. © The Author(s) 2015.

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 an improved understanding of the effects of dose and dose rate will aid single-particle cryo-electron microscopists to have better control of the outcome of their experiments.

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 combined with an improved understanding of the effects of dose and dose rate will aid single-particle cryo-electron microscopists to have better control of the outcome of their experiments. PMID:21525648

[Do poor-responder patients benefit from increasing the daily gonadotropin dose from 300 to 450 IU during controlled ovarian hyperstimulation for IVF?].

PubMed

Haas, Jigal; Zilberberg, Eran; Kedem, Alon; Dar, Shir; Orvieto, Raoul

2015-02-01

We aim to evaluate the IVF-ET outcome in patients receiving a high daily dose (300 IU) of gonadotropins during controlled ovarian hyperstimulation (COH) for IVF and to assess the role of increasing the daily dose to 450 IU on improving outcome. All consecutive women admitted to our IVF unit during an 11 year period who underwent COH consisting of daily gonadotropin dose of 300 IU were included in the study. The ovarian stimulation characteristics, number of oocytes retrieved, number of embryo transferred and pregnancy rate were assessed. We also evaluated the subsequent cycle, using daily gonadotropin doses of 450 IU, among those patients who did not conceive using the 300 IU daily gonadotropin dose. Nine hundred and forty-nine consecutive IVF cycles were evaluated. Patients who conceived using the daily gonadotropin dose of 300 IU (n = 133, 14% pregnancy rate) had significantly longer stimulation, yielded higher numbers of oocytes retrieved, fertilization rate and number of embryos transferred, compared to those who did not conceive. Moreover, while comparing IVF cycles using daily gonadotropin doses of 300 IU to 450 IU (n = 117), no in-between group differences were observed, except for significantly higher yields of oocytes retrieved. Moreover, cycles using daily gonadotropin doses of 450 IU resulted in a 7.7 live-birth rate. In poor responders undergoing COH with a daily gonadotropin dose of 300 IU, increasing the dose to 450 IU resulted in significantly higher oocyte yields and a reasonable live birth rate.

Absolute x-ray dosimetry on a synchrotron medical beam line with a graphite calorimeter.

PubMed

Harty, P D; Lye, J E; Ramanathan, G; Butler, D J; Hall, C J; Stevenson, A W; Johnston, P N

2014-05-01

The absolute dose rate of the Imaging and Medical Beamline (IMBL) on the Australian Synchrotron was measured with a graphite calorimeter. The calorimetry results were compared to measurements from the existing free-air chamber, to provide a robust determination of the absolute dose in the synchrotron beam and provide confidence in the first implementation of a graphite calorimeter on a synchrotron medical beam line. The graphite calorimeter has a core which rises in temperature when irradiated by the beam. A collimated x-ray beam from the synchrotron with well-defined edges was used to partially irradiate the core. Two filtration sets were used, one corresponding to an average beam energy of about 80 keV, with dose rate about 50 Gy/s, and the second filtration set corresponding to average beam energy of 90 keV, with dose rate about 20 Gy/s. The temperature rise from this beam was measured by a calibrated thermistor embedded in the core which was then converted to absorbed dose to graphite by multiplying the rise in temperature by the specific heat capacity for graphite and the ratio of cross-sectional areas of the core and beam. Conversion of the measured absorbed dose to graphite to absorbed dose to water was achieved using Monte Carlo calculations with the EGSnrc code. The air kerma measurements from the free-air chamber were converted to absorbed dose to water using the AAPM TG-61 protocol. Absolute measurements of the IMBL dose rate were made using the graphite calorimeter and compared to measurements with the free-air chamber. The measurements were at three different depths in graphite and two different filtrations. The calorimetry measurements at depths in graphite show agreement within 1% with free-air chamber measurements, when converted to absorbed dose to water. The calorimetry at the surface and free-air chamber results show agreement of order 3% when converted to absorbed dose to water. The combined standard uncertainty is 3.9%. The good agreement of the graphite calorimeter and free-air chamber results indicates that both devices are performing as expected. Further investigations at higher dose rates than 50 Gy/s are planned. At higher dose rates, recombination effects for the free-air chamber are much higher and expected to lead to much larger uncertainties. Since the graphite calorimeter does not have problems associated with dose rate, it is an appropriate primary standard detector for the synchrotron IMBL x rays and is the more accurate dosimeter for the higher dose rates expected in radiotherapy applications.

Analysis and evaluation for consumer goods containing NORM in Korea.

PubMed

Jang, Mee; Chung, Kun Ho; Lim, Jong Myoung; Ji, Young Yong; Kim, Chang Jong; Kang, Mun Ja

2017-08-01

We analyzed the consumer goods containing NORM by ICP-MS and evaluated the external dose. To evaluate the external dose, we assumed the small room model as irradiation scenario and calculated the specific effective dose rate using MCNPX code. The external doses for twenty goods are less than 1 mSv considering the specific effective dose rates and usage quantities. However, some of them have relatively high dose and the activity concentration limits are necessary as a screening tool. Copyright © 2017 Elsevier Ltd. All rights reserved.

Nanocluster irradiation evolution in Fe-9%Cr ODS and ferritic-martensitic alloys

NASA Astrophysics Data System (ADS)

Swenson, M. J.; Wharry, J. P.

2017-12-01

The objective of this study is to evaluate the influence of dose rate and cascade morphology on nanocluster evolution in a model Fe-9%Cr oxide dispersion strengthened steel and the commercial ferritic/martensitic (F/M) alloys HCM12A and HT9. We present a large, systematic data set spanning the three alloys, three irradiating particle types, four orders of magnitude in dose rate, and doses ranging 1-100 displacements per atom over 400-500 °C. Nanoclusters are characterized using atom probe tomography. ODS oxide nanoclusters experience partial dissolution after irradiation due to inverse Ostwald ripening, while F/M nanoclusters undergo Ostwald ripening. Damage cascade morphology is indicative of nanocluster number density evolution. Finally, the effects of dose rate on nanocluster morphology provide evidence for a temperature dilation theory, which purports that a negative temperature shift is necessary for higher dose rate irradiations to emulate nanocluster evolution in lower dose rate irradiations.

Remanent dose rates around the collimators of the LHC beam cleaning insertions.

PubMed

Brugger, M; Roesler, S

2005-01-01

The LHC will require an extremely powerful and unprecedented collimation system. As approximately 30% of the LHC beam is lost in the cleaning insertions, these will become some of the most radioactive locations around the entire LHC ring. Thus, remanent dose rates to be expected during later repair or maintenance interventions must be considered in the design phase itself. As a consequence, the beam cleaning insertions form a unique test bed for a recently developed approach to calculate remanent dose rates. A set of simulations, different in complexity, is used in order to evaluate methods for the estimation of remanent dose rates. The scope, as well as the restrictions, of the omega-factor method are shown and compared with the explicit simulation approach. The latter is then used to calculate remanent dose rates in the beam cleaning insertions. Furthermore, a detailed example for maintenance dose planning is given.

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

PubMed

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

2017-02-01

The aim of this study was to assess the suitability of Gafchromic EBT3 films for reference dose measurements in the beam of a prototype high dose-per-pulse linear accelerator (linac), capable of delivering electron beams with a mean dose-rate (Ḋ m ) ranging from 0.07 to 3000 Gy/s and a dose-rate in pulse (Ḋ p ) of up to 8 × 10 6 Gy/s. To do this, we evaluated the overall uncertainties in EBT3 film dosimetry as well as the energy and dose-rate dependence of their response. Our dosimetric system was composed of EBT3 Gafchromic films in combination with a flatbed scanner and was calibrated against an ionization chamber traceable to primary standard. All sources of uncertainties in EBT3 dosimetry were carefully analyzed using irradiations at a clinical radiotherapy linac. Energy dependence was investigated with the same machine by acquiring and comparing calibration curves for three different beam energies (4, 8 and 12 MeV), for doses between 0.25 and 30 Gy. Ḋ m dependence was studied at the clinical linac by changing the pulse repetition frequency (f) of the beam in order to vary Ḋ m between 0.55 and 4.40 Gy/min, while Ḋ p dependence was probed at the prototype machine for Ḋ p ranging from 7 × 10 3 to 8 × 10 6 Gy/s. Ḋ p dependence was first determined by studying the correlation between the dose measured by films and the charge of electrons measured at the exit of the machine by an induction torus. Furthermore, we compared doses from the films to independently calibrated thermo-luminescent dosimeters (TLD) that have been reported as being dose-rate independent up to such high dose-rates. We report that uncertainty below 4% (k = 2) can be achieved in the dose range between 3 and 17 Gy. Results also demonstrated that EBT3 films did not display any detectable energy dependence for electron beam energies between 4 and 12 MeV. No Ḋ m dependence was found either. In addition, we obtained excellent consistency between films and TLDs over the entire Ḋ p range attainable at the prototype linac confirming the absence of any dose-rate dependence within the investigated range (7 × 10 3 to 8 × 10 6 Gy/s). This aspect was further corroborated by the linear relationship between the dose-per-pulse (D p ) measured by films and the charge per pulse (C p ) measured at the prototype linac exit. Our study shows that the use of EBT3 Gafchromic films can be extended to reference dosimetry in pulsed electron beams with a very high dose rate. The measurement results are associated with an overall uncertainty below 4% (k = 2) and are dose-rate and energy independent. © 2016 American Association of Physicists in Medicine.

Optimal mapping of terrestrial gamma dose rates using geological parent material and aerogeophysical survey data.

PubMed

Rawlins, B G; Scheib, C; Tyler, A N; Beamish, D

2012-12-01

Regulatory authorities need ways to estimate natural terrestrial gamma radiation dose rates (nGy h⁻¹) across the landscape accurately, to assess its potential deleterious health effects. The primary method for estimating outdoor dose rate is to use an in situ detector supported 1 m above the ground, but such measurements are costly and cannot capture the landscape-scale variation in dose rates which are associated with changes in soil and parent material mineralogy. We investigate the potential for improving estimates of terrestrial gamma dose rates across Northern Ireland (13,542 km²) using measurements from 168 sites and two sources of ancillary data: (i) a map based on a simplified classification of soil parent material, and (ii) dose estimates from a national-scale, airborne radiometric survey. We used the linear mixed modelling framework in which the two ancillary variables were included in separate models as fixed effects, plus a correlation structure which captures the spatially correlated variance component. We used a cross-validation procedure to determine the magnitude of the prediction errors for the different models. We removed a random subset of 10 terrestrial measurements and formed the model from the remainder (n = 158), and then used the model to predict values at the other 10 sites. We repeated this procedure 50 times. The measurements of terrestrial dose vary between 1 and 103 (nGy h⁻¹). The median absolute model prediction errors (nGy h⁻¹) for the three models declined in the following order: no ancillary data (10.8) > simple geological classification (8.3) > airborne radiometric dose (5.4) as a single fixed effect. Estimates of airborne radiometric gamma dose rate can significantly improve the spatial prediction of terrestrial dose rate.

Absorbed doses of lungs from radon retained in airway lumens of mice and rats.

PubMed

Sakoda, Akihiro; Ishimori, Yuu; Yamaoka, Kiyonori; Kataoka, Takahiro; Mitsunobu, Fumihiro

2013-08-01

This paper provides absorbed doses arising from radon gas in air retained in lung airway lumens. Because radon gas exposure experiments often use small animals, the calculation was performed for mice and rats. For reference, the corresponding computations were also done for humans. Assuming that radon concentration in airway lumens is the same as that in the environment, its progeny's production in and clearance from airways were simulated. Absorbed dose rates were obtained for three lung regions and the whole lung, considering that secretory and basal cells are sensitive to radiation. The results showed that absorbed dose rates for all lung regions and whole lung generally increase from mice to rats to humans. For example, the dose rates for the whole lung were 25.4 in mice, 41.7 in rats, and 59.9 pGy (Bq m⁻³)⁻¹ h⁻¹ in humans. Furthermore, these values were also compared with lung dose rates from two other types of exposures, that is, due to inhalation of radon or its progeny, which were already reported. It was confirmed that the direct inhalation of radon progeny in the natural environment, which is known as a cause of lung cancer, results in the highest dose rates for all species. Based on the present calculations, absorbed dose rates of the whole lung from radon gas were lower by a factor of about 550 (mice), 200 (rats), or 70 (humans) than those from radon progeny inhalation. The calculated dose rate values are comparatively small. Nevertheless, the present study is considered to contribute to our understanding of doses from inhalation of radon and its progeny.

Organ and effective dose rate coefficients for submersion exposure in occupational settings

DOE PAGES

Veinot, K. G.; Y-12 National Security Complex, Oak Ridge, TN; Dewji, S. A.; ...

2017-08-24

External dose coefficients for environmental exposure scenarios are often computed using assumption on infinite or semi-infinite radiation sources. For example, in the case of a person standing on contaminated ground, the source is assumed to be distributed at a given depth (or between various depths) and extending outwards to an essentially infinite distance. In the case of exposure to contaminated air, the person is modeled as standing within a cloud of infinite, or semi-infinite, source distribution. However, these scenarios do not mimic common workplace environments where scatter off walls and ceilings may significantly alter the energy spectrum and dose coefficients.more » In this study, dose rate coefficients were calculated using the International Commission on Radiological Protection (ICRP) reference voxel phantoms positioned in rooms of three sizes representing an office, laboratory, and warehouse. For each room size calculations using the reference phantoms were performed for photons, electrons, and positrons as the source particles to derive mono-energetic dose rate coefficients. Since the voxel phantoms lack the resolution to perform dose calculations at the sensitive depth for the skin, a mathematical phantom was developed and calculations were performed in each room size with the three source particle types. Coefficients for the noble gas radionuclides of ICRP Publication 107 (e.g., Ne, Ar, Kr, Xe, and Rn) were generated by folding the corresponding photon, electron, and positron emissions over the mono-energetic dose rate coefficients. Finally, results indicate that the smaller room sizes have a significant impact on the dose rate per unit air concentration compared to the semi-infinite cloud case. For example, for Kr-85 the warehouse dose rate coefficient is 7% higher than the office dose rate coefficient while it is 71% higher for Xe-133.« less

Organ and effective dose rate coefficients for submersion exposure in occupational settings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Veinot, K. G.; Y-12 National Security Complex, Oak Ridge, TN; Dewji, S. A.

External dose coefficients for environmental exposure scenarios are often computed using assumption on infinite or semi-infinite radiation sources. For example, in the case of a person standing on contaminated ground, the source is assumed to be distributed at a given depth (or between various depths) and extending outwards to an essentially infinite distance. In the case of exposure to contaminated air, the person is modeled as standing within a cloud of infinite, or semi-infinite, source distribution. However, these scenarios do not mimic common workplace environments where scatter off walls and ceilings may significantly alter the energy spectrum and dose coefficients.more » In this study, dose rate coefficients were calculated using the International Commission on Radiological Protection (ICRP) reference voxel phantoms positioned in rooms of three sizes representing an office, laboratory, and warehouse. For each room size calculations using the reference phantoms were performed for photons, electrons, and positrons as the source particles to derive mono-energetic dose rate coefficients. Since the voxel phantoms lack the resolution to perform dose calculations at the sensitive depth for the skin, a mathematical phantom was developed and calculations were performed in each room size with the three source particle types. Coefficients for the noble gas radionuclides of ICRP Publication 107 (e.g., Ne, Ar, Kr, Xe, and Rn) were generated by folding the corresponding photon, electron, and positron emissions over the mono-energetic dose rate coefficients. Finally, results indicate that the smaller room sizes have a significant impact on the dose rate per unit air concentration compared to the semi-infinite cloud case. For example, for Kr-85 the warehouse dose rate coefficient is 7% higher than the office dose rate coefficient while it is 71% higher for Xe-133.« less

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.

Efficacy and Safety of Escalation of Adalimumab Therapy to Weekly Dosing in Pediatric Patients with Crohn's Disease.

PubMed

Dubinsky, Marla C; Rosh, Joel; Faubion, William A; Kierkus, Jaroslaw; Ruemmele, Frank; Hyams, Jeffrey S; Eichner, Samantha; Li, Yao; Huang, Bidan; Mostafa, Nael M; Lazar, Andreas; Thakkar, Roopal B

2016-04-01

The efficacy of adalimumab in inducing and maintaining remission in children with moderately to severely active Crohn's disease was shown in the IMAgINE 1 trial (NCT00409682). As per protocol, nonresponders or patients experiencing flare(s) on every other week (EOW) maintenance dosing could escalate to weekly dosing; we aimed to determine the therapeutic benefits of weekly dose escalation in this subpopulation. Week 52 remission and response rates were assessed in patients who escalated to weekly dosing from their previous EOW schedule, which was according to randomized treatment dose (higher dose [HD] adalimumab [≥40 kg, 40 mg EOW; <40 kg, 20 mg EOW] or lower dose [LD; ≥40 kg, 20 mg EOW; <40 kg, 10 mg EOW]). Adverse events were reported for patients remaining on EOW dosing and patients receiving weekly dosing. Escalation to weekly dosing occurred in 48/95 (50.5%) patients randomized to LD and 35/93 (37.6%) patients randomized to HD adalimumab (P = 0.076). Week 52 remission and response rates were 18.8% and 47.9% for patients receiving LD adalimumab weekly and 31.4% and 57.1% for patients receiving HD adalimumab weekly, respectively (LD versus HD, P = 0.19 for remission; P = 0.41 for response). Adverse event rates were similar for patients receiving EOW and weekly adalimumab. Weekly adalimumab dosing was clinically beneficial for children with Crohn's disease who experienced nonresponse or flare on EOW dosing. No increased safety risks were observed with weekly dosing.

Surface effects on the radiation response of nanoporous Au foams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fu, E. G.; Caro, M.; Wang, Y. Q.

2012-11-05

We report on an experimental and simulation campaign aimed at exploring the radiation response of nanoporous Au (np-Au) foams. We find different defect accumulation behavior by varying radiation dose-rate in ion-irradiated np-Au foams. Stacking fault tetrahedra are formed when np-Au foams are irradiated at high dose-rate, but they do not seem to be formed in np-Au at low dose-rate irradiation. A model is proposed to explain the dose-rate dependent defect accumulation based on these results.

Estimation of low-level neutron dose-equivalent rate by using extrapolation method for a curie level Am-Be neutron source.

PubMed

Li, Gang; Xu, Jiayun; Zhang, Jie

2015-01-01

Neutron radiation protection is an important research area because of the strong radiation biological effect of neutron field. The radiation dose of neutron is closely related to the neutron energy, and the connected relationship is a complex function of energy. For the low-level neutron radiation field (e.g. the Am-Be source), the commonly used commercial neutron dosimeter cannot always reflect the low-level dose rate, which is restricted by its own sensitivity limit and measuring range. In this paper, the intensity distribution of neutron field caused by a curie level Am-Be neutron source was investigated by measuring the count rates obtained through a 3 He proportional counter at different locations around the source. The results indicate that the count rates outside of the source room are negligible compared with the count rates measured in the source room. In the source room, 3 He proportional counter and neutron dosimeter were used to measure the count rates and dose rates respectively at different distances to the source. The results indicate that both the count rates and dose rates decrease exponentially with the increasing distance, and the dose rates measured by a commercial dosimeter are in good agreement with the results calculated by the Geant4 simulation within the inherent errors recommended by ICRP and IEC. Further studies presented in this paper indicate that the low-level neutron dose equivalent rates in the source room increase exponentially with the increasing low-energy neutron count rates when the source is lifted from the shield with different radiation intensities. Based on this relationship as well as the count rates measured at larger distance to the source, the dose rates can be calculated approximately by the extrapolation method. This principle can be used to estimate the low level neutron dose values in the source room which cannot be measured directly by a commercial dosimeter. Copyright © 2014 Elsevier Ltd. All rights reserved.

Dose-rate effect of ultrashort electron beam radiation on DNA damage and repair in vitro.

PubMed

Babayan, Nelly; Hovhannisyan, Galina; Grigoryan, Bagrat; Grigoryan, Ruzanna; Sarkisyan, Natalia; Tsakanova, Gohar; Haroutiunian, Samvel; Aroutiounian, Rouben

2017-11-01

Laser-generated electron beams are distinguished from conventional accelerated particles by ultrashort beam pulses in the femtoseconds to picoseconds duration range, and their application may elucidate primary radiobiological effects. The aim of the present study was to determine the dose-rate effect of laser-generated ultrashort pulses of 4 MeV electron beam radiation on DNA damage and repair in human cells. The dose rate was increased via changing the pulse repetition frequency, without increasing the electron energy. The human chronic myeloid leukemia K-562 cell line was used to estimate the DNA damage and repair after irradiation, via the comet assay. A distribution analysis of the DNA damage was performed. The same mean level of initial DNA damages was observed at low (3.6 Gy/min) and high (36 Gy/min) dose-rate irradiation. In the case of low-dose-rate irradiation, the detected DNA damages were completely repairable, whereas the high-dose-rate irradiation demonstrated a lower level of reparability. The distribution analysis of initial DNA damages after high-dose-rate irradiation revealed a shift towards higher amounts of damage and a broadening in distribution. Thus, increasing the dose rate via changing the pulse frequency of ultrafast electrons leads to an increase in the complexity of DNA damages, with a consequent decrease in their reparability. Since the application of an ultrashort pulsed electron beam permits us to describe the primary radiobiological effects, it can be assumed that the observed dose-rate effect on DNA damage/repair is mainly caused by primary lesions appearing at the moment of irradiation. © The Author 2017. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

Quintupling Inhaled Glucocorticoids to Prevent Childhood Asthma Exacerbations.

PubMed

Jackson, Daniel J; Bacharier, Leonard B; Mauger, David T; Boehmer, Susan; Beigelman, Avraham; Chmiel, James F; Fitzpatrick, Anne M; Gaffin, Jonathan M; Morgan, Wayne J; Peters, Stephen P; Phipatanakul, Wanda; Sheehan, William J; Cabana, Michael D; Holguin, Fernando; Martinez, Fernando D; Pongracic, Jacqueline A; Baxi, Sachin N; Benson, Mindy; Blake, Kathryn; Covar, Ronina; Gentile, Deborah A; Israel, Elliot; Krishnan, Jerry A; Kumar, Harsha V; Lang, Jason E; Lazarus, Stephen C; Lima, John J; Long, Dayna; Ly, Ngoc; Marbin, Jyothi; Moy, James N; Myers, Ross E; Olin, J Tod; Raissy, Hengameh H; Robison, Rachel G; Ross, Kristie; Sorkness, Christine A; Lemanske, Robert F

2018-03-08

Asthma exacerbations occur frequently despite the regular use of asthma-controller therapies, such as inhaled glucocorticoids. Clinicians commonly increase the doses of inhaled glucocorticoids at early signs of loss of asthma control. However, data on the safety and efficacy of this strategy in children are limited. We studied 254 children, 5 to 11 years of age, who had mild-to-moderate persistent asthma and had had at least one asthma exacerbation treated with systemic glucocorticoids in the previous year. Children were treated for 48 weeks with maintenance low-dose inhaled glucocorticoids (fluticasone propionate at a dose of 44 μg per inhalation, two inhalations twice daily) and were randomly assigned to either continue the same dose (low-dose group) or use a quintupled dose (high-dose group; fluticasone at a dose of 220 μg per inhalation, two inhalations twice daily) for 7 days at the early signs of loss of asthma control ("yellow zone"). Treatment was provided in a double-blind fashion. The primary outcome was the rate of severe asthma exacerbations treated with systemic glucocorticoids. The rate of severe asthma exacerbations treated with systemic glucocorticoids did not differ significantly between groups (0.48 exacerbations per year in the high-dose group and 0.37 exacerbations per year in the low-dose group; relative rate, 1.3; 95% confidence interval, 0.8 to 2.1; P=0.30). The time to the first exacerbation, the rate of treatment failure, symptom scores, and albuterol use during yellow-zone episodes did not differ significantly between groups. The total glucocorticoid exposure was 16% higher in the high-dose group than in the low-dose group. The difference in linear growth between the high-dose group and the low-dose group was -0.23 cm per year (P=0.06). In children with mild-to-moderate persistent asthma treated with daily inhaled glucocorticoids, quintupling the dose at the early signs of loss of asthma control did not reduce the rate of severe asthma exacerbations or improve other asthma outcomes and may be associated with diminished linear growth. (Funded by the National Heart, Lung, and Blood Institute; STICS ClinicalTrials.gov number, NCT02066129 .).

Design and characterization of a new high-dose-rate brachytherapy Valencia applicator for larger skin lesions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Candela-Juan, C., E-mail: ccanjuan@gmail.com; Niatsetski, Y.; Laarse, R. van der

Purpose: The aims of this study were (i) to design a new high-dose-rate (HDR) brachytherapy applicator for treating surface lesions with planning target volumes larger than 3 cm in diameter and up to 5 cm in size, using the microSelectron-HDR or Flexitron afterloader (Elekta Brachytherapy) with a {sup 192}Ir source; (ii) to calculate by means of the Monte Carlo (MC) method the dose distribution for the new applicator when it is placed against a water phantom; and (iii) to validate experimentally the dose distributions in water. Methods: The PENELOPE2008 MC code was used to optimize dwell positions and dwell times.more » Next, the dose distribution in a water phantom and the leakage dose distribution around the applicator were calculated. Finally, MC data were validated experimentally for a {sup 192}Ir mHDR-v2 source by measuring (i) dose distributions with radiochromic EBT3 films (ISP); (ii) percentage depth–dose (PDD) curve with the parallel-plate ionization chamber Advanced Markus (PTW); and (iii) absolute dose rate with EBT3 films and the PinPoint T31016 (PTW) ionization chamber. Results: The new applicator is made of tungsten alloy (Densimet) and consists of a set of interchangeable collimators. Three catheters are used to allocate the source at prefixed dwell positions with preset weights to produce a homogenous dose distribution at the typical prescription depth of 3 mm in water. The same plan is used for all available collimators. PDD, absolute dose rate per unit of air kerma strength, and off-axis profiles in a cylindrical water phantom are reported. These data can be used for treatment planning. Leakage around the applicator was also scored. The dose distributions, PDD, and absolute dose rate calculated agree within experimental uncertainties with the doses measured: differences of MC data with chamber measurements are up to 0.8% and with radiochromic films are up to 3.5%. Conclusions: The new applicator and the dosimetric data provided here will be a valuable tool in clinical practice, making treatment of large skin lesions simpler, faster, and safer. Also the dose to surrounding healthy tissues is minimal.« less

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.

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.

Dose-rate effects of Co60 irradiation on performance and physiology in monkeys. Topical report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruner, A.; Bogo, V.; Henderson, E.A.

1975-07-30

One thousand rad /sup 60/Co was administered to 12 monkeys at 75 rad/min and to 8 monkeys at 50 rad/min while they performed a delayed match-to-sample, shock avoidance task. Only four at 75 rad/min and two at 50 rad/min showed early performance decrement and/or early transient incapacitation (PD-ETI), in contrast to 13 of 16 previously studied monkeys who showed PD-ETI with an average dose rate of 180 rad/min. A dose-rate effect was concluded. When these three groups were compared with an untrained group exposed to a 4000-rad gamma-neutron pulse, all showed similar degrees of hypotension postirradiation. But the onset ofmore » hypotension was delayed and its rate of fall prolonged as dose rate decreased. Tentative interpretation was that radiation thresholds for the induction of PD-ETI exist for cumulative dose (+ or - 300 rad, midbody) and dose rate (+ or - 30 rad/min). (GRA)« less

Dosimetric characterizations of GZP6 60Co high dose rate brachytherapy sources: application of superimposition method

PubMed Central

Bahreyni Toossi, Mohammad Taghi; Ghorbani, Mahdi; Mowlavi, Ali Asghar; Meigooni, Ali Soleimani

2012-01-01

Background Dosimetric characteristics of a high dose rate (HDR) GZP6 Co-60 brachytherapy source have been evaluated following American Association of Physicists in MedicineTask Group 43U1 (AAPM TG-43U1) recommendations for their clinical applications. Materials and methods MCNP-4C and MCNPX Monte Carlo codes were utilized to calculate dose rate constant, two dimensional (2D) dose distribution, radial dose function and 2D anisotropy function of the source. These parameters of this source are compared with the available data for Ralstron 60Co and microSelectron192Ir sources. Besides, a superimposition method was developed to extend the obtained results for the GZP6 source No. 3 to other GZP6 sources. Results The simulated value for dose rate constant for GZP6 source was 1.104±0.03 cGyh-1U-1. The graphical and tabulated radial dose function and 2D anisotropy function of this source are presented here. The results of these investigations show that the dosimetric parameters of GZP6 source are comparable to those for the Ralstron source. While dose rate constant for the two 60Co sources are similar to that for the microSelectron192Ir source, there are differences between radial dose function and anisotropy functions. Radial dose function of the 192Ir source is less steep than both 60Co source models. In addition, the 60Co sources are showing more isotropic dose distribution than the 192Ir source. Conclusions The superimposition method is applicable to produce dose distributions for other source arrangements from the dose distribution of a single source. The calculated dosimetric quantities of this new source can be introduced as input data to the GZP6 treatment planning system (TPS) and to validate the performance of the TPS. PMID:23077455

Radiological environment within an NPP after a severe nuclear accident

NASA Astrophysics Data System (ADS)

Andgren, Karin; Fritioff, Karin; Buhr, Anna Maria Blixt; Huutoniemi, Tommi

2017-09-01

The radiological environment following a severe nuclear accident can be visualised on building layouts. The direct radiation in an area (or room) can be visualized on the layout by a colouring scheme depending on the dose rate level (for example orange for high gamma dose rate level and purple for an intermediate gamma dose rate level). Following the Fukushima accident, a need for update of these layouts has been identified at the Swedish nuclear power plant of Forsmark. Shielding calculations for areas where access is desired for severe accident management have been performed. Many different sources of radiation together with different types of shielding material contribute to the dose that would be received by a person entering the area. External radiation from radioactivity within e.g. pipes and components is considered and also external radiation from radioactivity in the air (originating from diffuse leakage of the containment atmosphere). Results are presented as dose rates for relevant dose points together with a method for estimating the dose rate levels for each of the rooms of the reactor building.

The effects of perphenazine on self-administration behavior.

PubMed

Johanson, C E; Kandel, D A; Bonese, K

1976-04-01

In Experiment 1.6 rhesus monkeys prepared with intravenous catheters responded on a fixed-ratio 10 schedule for either an injection of 0.2 mg/kg of cocaine or 0.5 mg/kg of pentobarbital during a daily 3 hr session. The substitution of saline or various doses of perphenazine resulted in very low rates of responding. These results indicate that perphenazine is not a positive reinforcer. Pretreating animals maintained on 0.1 mg/kg or 0.2 mg/kg of cocaine with perphenazine resulted in increases in rate of self-administration at some doses and a decrease in rate at higher doses. The dose of perphenazine which resulted in the maximal increase in cocaine self-administration was directly related to the dose of cocaine maintaining responding. Pretreating animals maintained on 0.5 mg/kg of pentobarbital with perphenazine had no effect at doses which increased cocaine self-administration but decreased rate of pentobarbital self-administration at higher doses. These results indicate that perphenazine is capable of antagonizing some of the effects of cocaine.

[Evaluation of an Experimental Production Wireless Dose Monitoring System for Radiation Exposure Management of Medical Staff].

PubMed

Fujibuchi, Toshioh; Murazaki, Hiroo; Kuramoto, Taku; Umedzu, Yoshiyuki; Ishigaki, Yung

2015-08-01

Because of the more advanced and more complex procedures in interventional radiology, longer treatment times have become necessary. Therefore, it is important to determine the exposure doses received by operators and patients. The aim of our study was to evaluate an experimental production wireless dose monitoring system for pulse radiation in diagnostic X-ray. The energy, dose rate, and pulse fluoroscopy dependence were evaluated as the basic characteristics of this system for diagnostic X-ray using a fully digital fluoroscopy system. The error of 1 cm dose equivalent rate was less than 15% from 35.1 keV to 43.2 keV with energy correction using metal filter. It was possible to accurately measure the dose rate dependence of this system, which was highly linear until 100 μSv/h. This system showed a constant response to the pulse fluoroscopy. This system will become useful wireless dosimeter for the individual exposure management by improving the high dose rate and the energy characteristics.

The rate of decay of fresh fission products from a nuclear reactor

NASA Astrophysics Data System (ADS)

Dolan, David J.

Determining the rate of decay of fresh fission products from a nuclear reactor is complex because of the number of isotopes involved, different types of decay, half-lives of the isotopes, and some isotopes decay into other radioactive isotopes. Traditionally, a simplified rule of 7s and 10s is used to determine the dose rate from nuclear weapons and can be to estimate the dose rate from fresh fission products of a nuclear reactor. An experiment was designed to determine the dose rate with respect to time from fresh fission products of a nuclear reactor. The experiment exposed 0.5 grams of unenriched Uranium to a fast and thermal neutron flux from a TRIGA Research Reactor (Lakewood, CO) for ten minutes. The dose rate from the fission products was measured by four Mirion DMC 2000XB electronic personal dosimeters over a period of six days. The resulting dose rate following a rule of 10s: the dose rate of fresh fission products from a nuclear reactor decreases by a factor of 10 for every 10 units of time.

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

PubMed Central

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

2018-01-01

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

Effects of virus dose and extrinsic incubation temperature on vector competence of Culex nigripalpus (Diptera: Culicidae) for St. Louis encephalitis virus.

PubMed

Richards, Stephanie L; Anderson, Sheri L; Lord, Cynthia C; Tabachnick, Walter J

2012-11-01

Culex nigripalpus Theobald is a primary vector of St. Louis encephalitis virus in the southeastern United States. Cx. nigripalpus females were fed blood containing a low (4.0 +/- 0.01 log10 plaque-forming unit equivalents (PFUeq) /ml) or high (4.7 +/- 0.1 log10 PFUeq/ml) St. Louis encephalitis virus dose and maintained at extrinsic incubation temperatures (EIT) of 25 or 28 degrees C for 12 d. Vector competence was measured via quantitative real-time reverse transcriptase polymerase chain reaction to estimate PFUeq using rates of infection, dissemination, and transmission. There were no differences in infection rates between the two EITs at either dose. The low dose had higher infection rates at both EITs. Dissemination rates were significantly higher at 28 degrees C compared with 25 degrees C at both doses. Virus transmission was observed (<7%) only at 28 degrees C for both doses. The virus titer in body tissues was greater at 28 degrees C compared with 25 degrees C at both doses. The difference between the EITs was greater at the low dose, resulting in a higher titer for the low dose than the high dose at 28 degrees C. Virus titers in leg tissues were greater in mosquitoes fed the high versus low dose, but were not influenced by EIT. Further investigations using a variety of environmental and biological factors would be useful in exploring the complexity of vector competence.

Effects of Virus Dose and Extrinsic Incubation Temperature on Vector Competence of Culex nigripalpus (Diptera: Culicidae) for St. Louis Encephalitis Virus

PubMed Central

RICHARDS, STEPHANIE L.; ANDERSON, SHERI L.; LORD, CYNTHIA C.; TABACHNICK, WALTER J.

2013-01-01

Culex nigripalpus Theobald is a primary vector of St. Louis encephalitis virus in the southeastern United States. Cx. nigripalpus females were fed blood containing a low (4.0 ± 0.01 log10 plaque-forming unit equivalents (PFUeq)/ml) or high (4.7 ± 0.1 log10 PFUeq/ml) St. Louis encephalitis virus dose and maintained at extrinsic incubation temperatures (EIT) of 25 or 28°C for 12 d. Vector competence was measured via quantitative real-time reverse transcriptase polymerase chain reaction to estimate PFUeq using rates of infection, dissemination, and transmission. There were no differences in infection rates between the two EITs at either dose. The low dose had higher infection rates at both EITs. Dissemination rates were significantly higher at 28°C compared with 25°C at both doses. Virus transmission was observed (<7%) only at 28°C for both doses. The virus titer in body tissues was greater at 28°C compared with 25°C at both doses. The difference between the EITs was greater at the low dose, resulting in a higher titer for the low dose than the high dose at 28°C. Virus titers in leg tissues were greater in mosquitoes fed the high versus low dose, but were not influenced by EIT. Further investigations using a variety of environmental and biological factors would be useful in exploring the complexity of vector competence. PMID:23270182

Continuous Exposure to Low-Dose-Rate Gamma Irradiation Reduces Airway Inflammation in Ovalbumin-Induced Asthma.

PubMed

Kim, Joong Sun; Son, Yeonghoon; Bae, Min Ji; Lee, Seung Sook; Park, Sun Hoo; Lee, Hae June; Lee, Soong In; Lee, Chang Geun; Kim, Sung Dae; Jo, Wol Soon; Kim, Sung Ho; Shin, In Sik

2015-01-01

Although safe doses of radiation have been determined, concerns about the harmful effects of low-dose radiation persist. In particular, to date, few studies have investigated the correlation between low-dose radiation and disease development. Asthma is a common chronic inflammatory airway disease that is recognized as a major public health problem. In this study, we evaluated the effects of low-dose-rate chronic irradiation on allergic asthma in a murine model. Mice were sensitized and airway-challenged with ovalbumin (OVA) and were exposed to continuous low-dose-rate irradiation (0.554 or 1.818 mGy/h) for 24 days after initial sensitization. The effects of chronic radiation on proinflammatory cytokines and the activity of matrix metalloproteinase-9 (MMP-9) were investigated. Exposure to low-dose-rate chronic irradiation significantly decreased the number of inflammatory cells, methylcholine responsiveness (PenH value), and the levels of OVA-specific immunoglobulin E, interleukin (IL)-4, and IL-5. Furthermore, airway inflammation and the mucus production in lung tissue were attenuated and elevated MMP-9 expression and activity induced by OVA challenge were significantly suppressed. These results indicate that low-dose-rate chronic irradiation suppresses allergic asthma induced by OVA challenge and does not exert any adverse effects on asthma development. Our findings can potentially provide toxicological guidance for the safe use of radiation and relieve the general anxiety about exposure to low-dose radiation.

Toward an organ based dose prescription method for the improved accuracy of murine dose in orthovoltage x-ray irradiators.

PubMed

Belley, Matthew D; Wang, Chu; Nguyen, Giao; Gunasingha, Rathnayaka; Chao, Nelson J; Chen, Benny J; Dewhirst, Mark W; Yoshizumi, Terry T

2014-03-01

Accurate dosimetry is essential when irradiating mice to ensure that functional and molecular endpoints are well understood for the radiation dose delivered. Conventional methods of prescribing dose in mice involve the use of a single dose rate measurement and assume a uniform average dose throughout all organs of the entire mouse. Here, the authors report the individual average organ dose values for the irradiation of a 12, 23, and 33 g mouse on a 320 kVp x-ray irradiator and calculate the resulting error from using conventional dose prescription methods. Organ doses were simulated in the Geant4 application for tomographic emission toolkit using the MOBY mouse whole-body phantom. Dosimetry was performed for three beams utilizing filters A (1.65 mm Al), B (2.0 mm Al), and C (0.1 mm Cu + 2.5 mm Al), respectively. In addition, simulated x-ray spectra were validated with physical half-value layer measurements. Average doses in soft-tissue organs were found to vary by as much as 23%-32% depending on the filter. Compared to filters A and B, filter C provided the hardest beam and had the lowest variation in soft-tissue average organ doses across all mouse sizes, with a difference of 23% for the median mouse size of 23 g. This work suggests a new dose prescription method in small animal dosimetry: it presents a departure from the conventional approach of assigninga single dose value for irradiation of mice to a more comprehensive approach of characterizing individual organ doses to minimize the error and uncertainty. In human radiation therapy, clinical treatment planning establishes the target dose as well as the dose distribution, however, this has generally not been done in small animal research. These results suggest that organ dose errors will be minimized by calibrating the dose rates for all filters, and using different dose rates for different organs.

Toward an organ based dose prescription method for the improved accuracy of murine dose in orthovoltage x-ray irradiators

PubMed Central

Belley, Matthew D.; Wang, Chu; Nguyen, Giao; Gunasingha, Rathnayaka; Chao, Nelson J.; Chen, Benny J.; Dewhirst, Mark W.; Yoshizumi, Terry T.

2014-01-01

Purpose: Accurate dosimetry is essential when irradiating mice to ensure that functional and molecular endpoints are well understood for the radiation dose delivered. Conventional methods of prescribing dose in mice involve the use of a single dose rate measurement and assume a uniform average dose throughout all organs of the entire mouse. Here, the authors report the individual average organ dose values for the irradiation of a 12, 23, and 33 g mouse on a 320 kVp x-ray irradiator and calculate the resulting error from using conventional dose prescription methods. Methods: Organ doses were simulated in the Geant4 application for tomographic emission toolkit using the MOBY mouse whole-body phantom. Dosimetry was performed for three beams utilizing filters A (1.65 mm Al), B (2.0 mm Al), and C (0.1 mm Cu + 2.5 mm Al), respectively. In addition, simulated x-ray spectra were validated with physical half-value layer measurements. Results: Average doses in soft-tissue organs were found to vary by as much as 23%–32% depending on the filter. Compared to filters A and B, filter C provided the hardest beam and had the lowest variation in soft-tissue average organ doses across all mouse sizes, with a difference of 23% for the median mouse size of 23 g. Conclusions: This work suggests a new dose prescription method in small animal dosimetry: it presents a departure from the conventional approach of assigning a single dose value for irradiation of mice to a more comprehensive approach of characterizing individual organ doses to minimize the error and uncertainty. In human radiation therapy, clinical treatment planning establishes the target dose as well as the dose distribution, however, this has generally not been done in small animal research. These results suggest that organ dose errors will be minimized by calibrating the dose rates for all filters, and using different dose rates for different organs. PMID:24593746

Toward an organ based dose prescription method for the improved accuracy of murine dose in orthovoltage x-ray irradiators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belley, Matthew D.; Wang, Chu; Nguyen, Giao

2014-03-15

Purpose: Accurate dosimetry is essential when irradiating mice to ensure that functional and molecular endpoints are well understood for the radiation dose delivered. Conventional methods of prescribing dose in mice involve the use of a single dose rate measurement and assume a uniform average dose throughout all organs of the entire mouse. Here, the authors report the individual average organ dose values for the irradiation of a 12, 23, and 33 g mouse on a 320 kVp x-ray irradiator and calculate the resulting error from using conventional dose prescription methods. Methods: Organ doses were simulated in the Geant4 application formore » tomographic emission toolkit using the MOBY mouse whole-body phantom. Dosimetry was performed for three beams utilizing filters A (1.65 mm Al), B (2.0 mm Al), and C (0.1 mm Cu + 2.5 mm Al), respectively. In addition, simulated x-ray spectra were validated with physical half-value layer measurements. Results: Average doses in soft-tissue organs were found to vary by as much as 23%–32% depending on the filter. Compared to filters A and B, filter C provided the hardest beam and had the lowest variation in soft-tissue average organ doses across all mouse sizes, with a difference of 23% for the median mouse size of 23 g. Conclusions: This work suggests a new dose prescription method in small animal dosimetry: it presents a departure from the conventional approach of assigninga single dose value for irradiation of mice to a more comprehensive approach of characterizing individual organ doses to minimize the error and uncertainty. In human radiation therapy, clinical treatment planning establishes the target dose as well as the dose distribution, however, this has generally not been done in small animal research. These results suggest that organ dose errors will be minimized by calibrating the dose rates for all filters, and using different dose rates for different organs.« less

Cocaine self-administration under variable-dose schedules in squirrel monkeys.

PubMed

Panlilio, Leigh V; Thorndike, Eric B; Schindler, Charles W

2006-06-01

Squirrel monkeys self-administered cocaine under a variable-dose schedule, with the dose varied from injection to injection. As in earlier studies with rats, post-injection pauses varied as a monotonic function of dose, allowing a cocaine dose-effect curve to be obtained during each session. These curves were shifted by pretreatment with dopamine antagonists, demonstrating that this procedure may provide an efficient means of evaluating treatments that affect drug self-administration. However, drug intake eventually became "dysregulated" after extensive training (100-300 sessions), with relatively short pauses following all doses. Dose-sensitivity was restored by adding a 60-s timeout period after each injection, suggesting that dysregulation occurred because the monkeys developed a tendency to self-administer another injection before the previous injection had been adequately distributed. Finally, when the response requirement under the variable-dose schedule was increased from 1 to 10, both the post-injection pause and the rate of responding following the pause ("run rates") were found to vary with dose. The dose-dependency of run rates suggests that post-injection pauses reflect not only motivational factors, such as satiety, but also the direct effects of cocaine on leverpressing.

Use of radiation protraction to escalate biologically effective dose to the treatment target

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuperman, V. Y.; Spradlin, G. S.; Department of Mathematics, Embry-Riddle University, Daytona Beach, Florida 32114

2011-12-15

Purpose: The aim of this study is to evaluate how simultaneously increasing fraction time and dose per fraction affect biologically effective dose for the target (BED{sub tar}) while biologically effective dose for the normal tissue (BED{sub nt}) is fixed. Methods: In this investigation, BED{sub tar} and BED{sub nt} were studied by assuming mono-exponential repair of sublethal damage with tissue dependent repair half-time. Results: Our results demonstrate that under certain conditions simultaneously increasing fraction time and dose per fraction result in increased BED{sub tar} while BED{sub nt} is fixed. The dependence of biologically effective dose on fraction time is influenced bymore » the dose rate. In this investigation we analytically determined time-varying dose rate R-tilde which minimizes BED. Changes in BED with fraction time were compared for constant dose rate and for R-tilde. Conclusions: A number of recent experimental and theoretical studies have demonstrated that slow delivery of radiation (known as radiation protraction) leads to reduced therapeutic effect because of increased repair of sublethal damage. In contrast, our analysis shows that under certain conditions simultaneously increasing fraction time and dose per fraction are radiobiologically advantageous.« less

Detection of IMRT delivery errors based on a simple constancy check of transit dose by using an EPID

NASA Astrophysics Data System (ADS)

Baek, Tae Seong; Chung, Eun Ji; Son, Jaeman; Yoon, Myonggeun

2015-11-01

Beam delivery errors during intensity modulated radiotherapy (IMRT) were detected based on a simple constancy check of the transit dose by using an electronic portal imaging device (EPID). Twenty-one IMRT plans were selected from various treatment sites, and the transit doses during treatment were measured by using an EPID. Transit doses were measured 11 times for each course of treatment, and the constancy check was based on gamma index (3%/3 mm) comparisons between a reference dose map (the first measured transit dose) and test dose maps (the following ten measured dose maps). In a simulation using an anthropomorphic phantom, the average passing rate of the tested transit dose was 100% for three representative treatment sites (head & neck, chest, and pelvis), indicating that IMRT was highly constant for normal beam delivery. The average passing rate of the transit dose for 1224 IMRT fields from 21 actual patients was 97.6% ± 2.5%, with the lower rate possibly being due to inaccuracies of patient positioning or anatomic changes. An EPIDbased simple constancy check may provide information about IMRT beam delivery errors during treatment.

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

DOE PAGES

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

2015-04-30

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

Radiation dose rate affects the radiosensitization of MCF-7 and HeLa cell lines to X-rays induced by dextran-coated iron oxide nanoparticles.

PubMed

Khoshgard, Karim; Kiani, Parvaneh; Haghparast, Abbas; Hosseinzadeh, Leila; Eivazi, Mohammad Taghi

2017-08-01

The aim of radiotherapy is to deliver lethal damage to cancerous tissue while preserving adjacent normal tissues. Radiation absorbed dose of the tumoral cells can increase when high atomic nanoparticles are present in them during irradiation. Also, the dose rate is an important aspect in radiation effects that determines the biological results of a given dose. This in vitro study investigated the dose-rate effect on the induced radiosensitivity by dextran-coated iron oxide in cancer cells. HeLa and MCF-7 cells were cultured in vitro and incubated with different concentrations of dextran-coated iron oxide nanoparticles. They were then irradiated with 6 MV photons at dose rates of 43, 185 and 370 cGy/min. The MTT test was used to obtain the cells' survival after 48 h of irradiations. Incubating the cells with the nanoparticles at concentrations of 10, 40 and 80 μg/ml showed no significant cytotoxicity effect. Dextran-coated iron oxide nanoparticles showed more radiosensitivity effect by increasing the dose rate and nanoparticles concentration. Radiosensitization enhancement factors of MCF-7 and HeLa cells at a dose-rate of 370 cGy/min and nanoparticles' concentration of 80 μg/ml were 1.21 ± 0.06 and 1.19 ± 0.04, respectively. Increasing the dose rate of 6 MV photons irradiation in MCF-7 and HeLa cells increases the radiosensitization induced by the dextran-coated iron nanoparticles in these cells.

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.

Assessment of the point-source method for estimating dose rates to members of the public from exposure to patients with 131I thyroid treatment

DOE PAGES

Dewji, Shaheen Azim; Bellamy, Michael B.; Hertel, Nolan E.; ...

2015-09-01

The U.S. Nuclear Regulatory Commission (USNRC) initiated a contract with Oak Ridge National Laboratory (ORNL) to calculate radiation dose rates to members of the public that may result from exposure to patients recently administered iodine-131 ( 131I) as part of medical therapy. The main purpose was to compare dose rate estimates based on a point source and target with values derived from more realistic simulations that considered the time-dependent distribution of 131I in the patient and attenuation of emitted photons by the patient’s tissues. The external dose rate estimates were derived using Monte Carlo methods and two representations of themore » Phantom with Movable Arms and Legs, previously developed by ORNL and the USNRC, to model the patient and a nearby member of the public. Dose rates to tissues and effective dose rates were calculated for distances ranging from 10 to 300 cm between the phantoms and compared to estimates based on the point-source method, as well as to results of previous studies that estimated exposure from 131I patients. The point-source method overestimates dose rates to members of the public in very close proximity to an 131I patient but is a broadly accurate method of dose rate estimation at separation distances of 300 cm or more at times closer to administration.« less

Characterizing regional-scale temporal evolution of air dose rates after the Fukushima Daiichi Nuclear Power Plant accident.

PubMed

Wainwright, Haruko M; Seki, Akiyuki; Mikami, Satoshi; Saito, Kimiaki

2018-09-01

In this study, we quantify the temporal changes of air dose rates in the regional scale around the Fukushima Dai-ichi Nuclear Power Plant in Japan, and predict the spatial distribution of air dose rates in the future. We first apply the Bayesian geostatistical method developed by Wainwright et al. (2017) to integrate multiscale datasets including ground-based walk and car surveys, and airborne surveys, all of which have different scales, resolutions, spatial coverage, and accuracy. This method is based on geostatistics to represent spatial heterogeneous structures, and also on Bayesian hierarchical models to integrate multiscale, multi-type datasets in a consistent manner. We apply this method to the datasets from three years: 2014 to 2016. The temporal changes among the three integrated maps enables us to characterize the spatiotemporal dynamics of radiation air dose rates. The data-driven ecological decay model is then coupled with the integrated map to predict future dose rates. Results show that the air dose rates are decreasing consistently across the region. While slower in the forested region, the decrease is particularly significant in the town area. The decontamination has contributed to significant reduction of air dose rates. By 2026, the air dose rates will continue to decrease, and the area above 3.8 μSv/h will be almost fully contained within the non-residential forested zone. Copyright © 2018 Elsevier Ltd. All rights reserved.

AREA MONITORING OF AMBIENT DOSE RATES IN PARTS OF SOUTH-WESTERN NIGERIA USING A GPS-INTEGRATED RADIATION SURVEY METER.

PubMed

Okeyode, I C; Rabiu, J A; Alatise, O O; Makinde, V; Akinboro, F G; Al-Azmi, D; Mustapha, A O

2017-04-01

A radiation monitoring system comprising a Geiger-Muller counter connected to a smart phone via Bluetooth was used for a dose rate survey in some parts of south-western Nigeria. The smart phone has the Geographical Positioning System, which provides the navigation information and saves it along with the dose rate data. A large number of data points was obtained that shows the dose rate distribution within the region. The results show that the ambient dose rates in the region range from 60 to 520 nSv -1 and showed a bias that is attributable to the influence of geology on the ambient radiation dose in the region. The geology influence was demonstrated by superimposing the dose rate plot and the geological map of the area. The potential applications of the device in determining baseline information and in area monitoring, e.g. for lost or abandoned sources, radioactive materials stockpiles, etc., were discussed in the article, particularly against the background of Nigeria's plan to develop its nuclear power program. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Outcome of stroke patients receiving different doses of recombinant tissue plasminogen activator.

PubMed

Ong, Cheung-Ter; Wong, Yi-Sin; Wu, Chi-Shun; Su, Yu-Hsiang

2017-01-01

Intravenous recombinant tissue plasminogen activator (tPA) at a dose of 0.9 mg/kg body weight is associated with a high hemorrhagic transformation (HT) rate. Low-dose tPA (0.6 mg/kg) may have a lower hemorrhage rate but the mortality and disability rates at 90 days cannot be confirmed as non-inferior to standard-dose tPA. Whether the doses 0.7 and 0.8 mg/kg have better efficacy and safety needs further investigation. Therefore, this study is to compare the efficacy and safety of each dose of tPA (0.6, 0.7, 0.8, and 0.9 mg/kg body weight) and to investigate the factors affecting early neurological improvement (ENI) and early neurological deterioration (END). For this observational study, data were obtained from 274 patients who received tPA thrombolytic therapy in Chia-Yi Christian Hospital stroke unit. The tPA dose was given at the discretion of each physician. The definition of ENI was a >8 point improvement (compared with baseline) at 24 h following thrombolytic therapy or an improvement in the National Institutes of Health Stroke Score (NIHSS) to 0 or 1 toward the end of tPA infusion. The definition of END was a >4 point increase in NIHSS (compared with baseline) within 24 h of tPA infusion. The primary objective was to investigate whether 0.7 and 0.8 mg/kg of tPA have higher ENI rate, lower END rate, and better outcome at 6 months. Poor outcome was defined as having a modified Rankin Scale of 3 to 6 (range, 0 [no symptoms] to 6 [death]). The secondary objective was to investigate whether low-dose tPA has a lower risk of intracerebral HT than that with standard-dose tPA. We also investigated the factors affecting ENI, END, HT, and 6-month outcome. A total of 274 patients were included during the study period, of whom 260 were followed up for >6 months. There was a trend for the HT rate to increase as the dose increased ( P =0.02). The symptomatic HT rate was not significantly different among the low-dose and standard-dose groups. The ENI and END ( P =0.52) were not significantly different among the four dosage groups. The clinical functional outcome at 6 months after stroke onset was poorer in the standard-dose group ( P =0.02). Stroke severity ( P <0.01), stroke type ( P =0.03), and diabetes mellitus ( P =0.04) affected the functional outcome at 6 months. Among the 274 patients receiving tPA thrombolytic therapy, the HT rate increased as dose increased. The symptomatic HT, ENI and END rates were not significantly different among the low-dose (0.6, 0.7, and 0.8 mg/kg) and standard-dose groups. Stroke severity (NIHSS >12), stroke type (cardioembolism and large artery atherosclerosis) and diabetes mellitus were associated with poor outcome at 6 months.

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

PubMed

Hamada, Nobuyuki

2017-10-01

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

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.

Lifetimes and spatio-temporal response of protein crystals in intense X-ray microbeams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warkentin, Matthew A.; Atakisi, Hakan; Hopkins, Jesse B.

Serial synchrotron-based crystallography using intense microfocused X-ray beams, fast-framing detectors and protein microcrystals held at 300 K promises to expand the range of accessible structural targets and to increase overall structure-pipeline throughputs. To explore the nature and consequences of X-ray radiation damage under microbeam illumination, the time-, dose- and temperature-dependent evolution of crystal diffraction have been measured with maximum dose rates of 50 MGy s −1 . At all temperatures and dose rates, the integrated diffraction intensity for a fixed crystal orientation shows non-exponential decays with dose. Non-exponential decays are a consequence of non-uniform illumination and the resulting spatial evolution of diffracted intensitymore » within the illuminated crystal volume. To quantify radiation-damage lifetimes and the damage state of diffracting crystal regions, a revised diffraction-weighted dose (DWD) is defined and it is shown that for Gaussian beams the DWD becomes nearly independent of actual dose at large doses. An apparent delayed onset of radiation damage seen in some intensity–dose curves is in fact a consequence of damage. Intensity fluctuations at high dose rates may arise from the impulsive release of gaseous damage products. Accounting for these effects, data collection at the highest dose rates increases crystal radiation lifetimes near 300 K (but not at 100 K) by a factor of ∼1.5–2 compared with those observed at conventional dose rates. Improved quantification and modeling of the complex spatio-temporal evolution of protein microcrystal diffraction in intense microbeams will enable more efficient data collection, and will be essential in improving the accuracy of structure factors and structural models.« less

Lifetimes and spatio-temporal response of protein crystals in intense X-ray microbeams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warkentin, Matthew A.; Atakisi, Hakan; Hopkins, Jesse B.

Serial synchrotron-based crystallography using intense microfocused X-ray beams, fast-framing detectors and protein microcrystals held at 300 K promises to expand the range of accessible structural targets and to increase overall structure-pipeline throughputs. To explore the nature and consequences of X-ray radiation damage under microbeam illumination, the time-, dose- and temperature-dependent evolution of crystal diffraction have been measured with maximum dose rates of 50 MGy s –1. At all temperatures and dose rates, the integrated diffraction intensity for a fixed crystal orientation shows non-exponential decays with dose. Non-exponential decays are a consequence of non-uniform illumination and the resulting spatial evolution ofmore » diffracted intensity within the illuminated crystal volume. To quantify radiation-damage lifetimes and the damage state of diffracting crystal regions, a revised diffraction-weighted dose (DWD) is defined and it is shown that for Gaussian beams the DWD becomes nearly independent of actual dose at large doses. An apparent delayed onset of radiation damage seen in some intensity–dose curves is in fact a consequence of damage. Intensity fluctuations at high dose rates may arise from the impulsive release of gaseous damage products. Accounting for these effects, data collection at the highest dose rates increases crystal radiation lifetimes near 300 K (but not at 100 K) by a factor of ~1.5–2 compared with those observed at conventional dose rates. As a result, improved quantification and modeling of the complex spatio-temporal evolution of protein microcrystal diffraction in intense microbeams will enable more efficient data collection, and will be essential in improving the accuracy of structure factors and structural models.« less

Lifetimes and spatio-temporal response of protein crystals in intense X-ray microbeams

DOE PAGES

Warkentin, Matthew A.; Atakisi, Hakan; Hopkins, Jesse B.; ...

2017-10-13

Serial synchrotron-based crystallography using intense microfocused X-ray beams, fast-framing detectors and protein microcrystals held at 300 K promises to expand the range of accessible structural targets and to increase overall structure-pipeline throughputs. To explore the nature and consequences of X-ray radiation damage under microbeam illumination, the time-, dose- and temperature-dependent evolution of crystal diffraction have been measured with maximum dose rates of 50 MGy s –1. At all temperatures and dose rates, the integrated diffraction intensity for a fixed crystal orientation shows non-exponential decays with dose. Non-exponential decays are a consequence of non-uniform illumination and the resulting spatial evolution ofmore » diffracted intensity within the illuminated crystal volume. To quantify radiation-damage lifetimes and the damage state of diffracting crystal regions, a revised diffraction-weighted dose (DWD) is defined and it is shown that for Gaussian beams the DWD becomes nearly independent of actual dose at large doses. An apparent delayed onset of radiation damage seen in some intensity–dose curves is in fact a consequence of damage. Intensity fluctuations at high dose rates may arise from the impulsive release of gaseous damage products. Accounting for these effects, data collection at the highest dose rates increases crystal radiation lifetimes near 300 K (but not at 100 K) by a factor of ~1.5–2 compared with those observed at conventional dose rates. As a result, improved quantification and modeling of the complex spatio-temporal evolution of protein microcrystal diffraction in intense microbeams will enable more efficient data collection, and will be essential in improving the accuracy of structure factors and structural models.« less

Lifetimes and spatio-temporal response of protein crystals in intense X-ray microbeams

DOE PAGES

Warkentin, Matthew A.; Atakisi, Hakan; Hopkins, Jesse B.; ...

2017-10-13

Serial synchrotron-based crystallography using intense microfocused X-ray beams, fast-framing detectors and protein microcrystals held at 300 K promises to expand the range of accessible structural targets and to increase overall structure-pipeline throughputs. To explore the nature and consequences of X-ray radiation damage under microbeam illumination, the time-, dose- and temperature-dependent evolution of crystal diffraction have been measured with maximum dose rates of 50 MGy s −1 . At all temperatures and dose rates, the integrated diffraction intensity for a fixed crystal orientation shows non-exponential decays with dose. Non-exponential decays are a consequence of non-uniform illumination and the resulting spatial evolution of diffracted intensitymore » within the illuminated crystal volume. To quantify radiation-damage lifetimes and the damage state of diffracting crystal regions, a revised diffraction-weighted dose (DWD) is defined and it is shown that for Gaussian beams the DWD becomes nearly independent of actual dose at large doses. An apparent delayed onset of radiation damage seen in some intensity–dose curves is in fact a consequence of damage. Intensity fluctuations at high dose rates may arise from the impulsive release of gaseous damage products. Accounting for these effects, data collection at the highest dose rates increases crystal radiation lifetimes near 300 K (but not at 100 K) by a factor of ∼1.5–2 compared with those observed at conventional dose rates. Improved quantification and modeling of the complex spatio-temporal evolution of protein microcrystal diffraction in intense microbeams will enable more efficient data collection, and will be essential in improving the accuracy of structure factors and structural models.« less

Real-time dosimetry in radiotherapy using tailored optical fibers

NASA Astrophysics Data System (ADS)

Rahman, A. K. M. Mizanur; Zubair, H. T.; Begum, Mahfuza; Abdul-Rashid, H. A.; Yusoff, Z.; Omar, Nasr Y. M.; Ung, N. M.; Mat-Sharif, K. A.; Bradley, D. A.

2016-05-01

Real-time dosimetry plays an important role for accurate patient-dose measurement during radiotherapy. A tiny piece of laboratory fabricated Ge-doped optical fiber has been investigated as a radioluminescence (RL) sensor for real-time dosimetry over the dose range from 1 Gy to 8 Gy under 6 MV photon beam by LINAC. Fiber-coupled software-based RL prototype system was used to assess essential dosimetric characteristics including dose response linearity, dose rate dependency, sensitivity, repeatability and output dependence on field sizes. The consistency level of RL photon counts versus dose rate was also compared with that of standard Al2O3:C chips. Sensitivity of Ge-doped fiber were found to be sufficiently sensitive for practical use and also provided linear dose responses for various dose rates from 100 cGy/min to 600 cGy/min using both 6 MV photon and 6 MeV electron beams. SEM-EDX analysis was performed to identify Ge-dopant concentration level within the optical fiber RL material. Accumulated doses were also estimated using simple integral technique and the error was found to be around less than 1% under dissimilar dose rates or repeat measurements. The evaluation of the Ge-doped optical fiber based RL dosimeter system indicates its potential in medical dosimetry.

Room model based Monte Carlo simulation study of the relationship between the airborne dose rate and the surface-deposited radon progeny.

PubMed

Sun, Kainan; Field, R William; Steck, Daniel J

2010-01-01

The quantitative relationships between radon gas concentration, the surface-deposited activities of various radon progeny, the airborne radon progeny dose rate, and various residential environmental factors were investigated through a Monte Carlo simulation study based on the extended Jacobi room model. Airborne dose rates were calculated from the unattached and attached potential alpha-energy concentrations (PAECs) using two dosimetric models. Surface-deposited (218)Po and (214)Po were significantly correlated with radon concentration, PAECs, and airborne dose rate (p-values <0.0001) in both non-smoking and smoking environments. However, in non-smoking environments, the deposited radon progeny were not highly correlated to the attached PAEC. In multiple linear regression analysis, natural logarithm transformation was performed for airborne dose rate as a dependent variable, as well as for radon and deposited (218)Po and (214)Po as predictors. In non-smoking environments, after adjusting for the effect of radon, deposited (214)Po was a significant positive predictor for one dose model (RR 1.46, 95% CI 1.27-1.67), while deposited (218)Po was a negative predictor for the other dose model (RR 0.90, 95% CI 0.83-0.98). In smoking environments, after adjusting for radon and room size, deposited (218)Po was a significant positive predictor for one dose model (RR 1.10, 95% CI 1.02-1.19), while a significant negative predictor for the other model (RR 0.90, 95% CI 0.85-0.95). After adjusting for radon and deposited (218)Po, significant increases of 1.14 (95% CI 1.03-1.27) and 1.13 (95% CI 1.05-1.22) in the mean dose rates were found for large room sizes relative to small room sizes in the different dose models.

Spiromax, a New Dry Powder Inhaler: Dose Consistency under Simulated Real-World Conditions.

PubMed

Canonica, Giorgio Walter; Arp, Jan; Keegstra, Johan René; Chrystyn, Henry

2015-10-01

Spiromax(®) is a novel dry powder inhaler for patients with asthma or chronic obstructive pulmonary disease (COPD). The studies presented here provide further data on attributes (in vitro dosing consistency with budesonide-formoterol (DuoResp) Spiromax; flow rates through empty versions of the Spiromax and Turbuhaler inhaler) of importance to patients with asthma or COPD. Dose-delivery studies were performed using low-, middle-, and high-strength DuoResp Spiromax. Dose consistency was assessed over inhaler life. Total emitted doses (TEDs) were measured at various flow rates, after exposure to high and low temperature or humidity, at different inhaler orientations, and after dropping the inhaler. The criterion for evaluating dose uniformity was whether mean TEDs were within the product specification limits. In separate studies, flow rates were measured after training, using the patient information leaflets, and again after enhanced training as part of a randomized, open-label, cross-over study. Mean values for both budesonide and formoterol were within 85%-115% of the label claim for each strength of DuoResp Spiromax for initial dose uniformity and for the other investigated conditions (temperature, humidity, orientation, dropping, knocking), with the exception of approximately an 80% increase in first dose after dropping the inhaler (subsequent doses not affected). In the flow rate patient study, two patients' inhalations with Spiromax and six with Turbuhaler were <30 L/min. The majority of asthma patients [91% (Spiromax) versus 82% (Turbuhaler)] achieved the preferred flow rate of >60 L/min. DuoResp Spiromax consistently meets dose uniformity criteria, under controlled laboratory conditions and with variations intended to mimic real-world use. Following enhanced training, all patients in the flow study were able to achieve the minimal inspiratory flow rate of >30 L/min, which is required for effective treatment.

The evaluation the magnitude radiation exposure dose rate in digital radiography room design

NASA Astrophysics Data System (ADS)

Dwiyanto, Agung; Setia Budi, Wahyu; Hardiman, Gagoek

2017-12-01

This study discusses the dose rate in digital radiography room, buit according to meet the provisions of KEMENKES No.1014 / Menkes / SK / XI / 2008 and Regulation of BAPETEN No. 8 / 2011. The provisions primary concern of radiation safety, not comfort, by considering the space design. There are five aspects to consider in designing the space: functionality, comfort, security, movement activities and aesthetics. However provisions only met three aspects of the design, which are a function, security and movement activity. Therefore, it is necessary to evaluate digital radiography room in terms of its ability to control external radiation exposure to be safe and comfortable The dose rate is measured by the range of primary and secondary radiation in the observation points by using Surveymeter. All data are obtained by the preliminary survey prior to the study. Furthermore, the review of digital radiography room is done based on architectural design theory. The dose rate for recommended improvement room is recalculated using the same method as the actual room with the help of computer modeling. The result of dose rate calculation at the inner and outer part of digital radiography observation room shows that in-room dose for a week at each measuring point exceeds the allowable dose limit both for staff and public. During a week of observation, the outdoor dose at some measuring points exceeds the dose limit set by the KEMENKES No.1014 / Menkes / SK / XI / 2008 and Regulation BEPETEN No 8/2011. Meanwhile, the result of dose rate calculation in the inner and outer part of the improved digital radiography room can meet the applicable regulations better.

A study on dosimetric properties of electronic portal imaging device and its use as a quality assurance tool in Volumetric Modulated Arc Therapy

PubMed Central

Sukumar, Prabakar; Padmanaban, Sriram; Jeevanandam, Prakash; Syam Kumar, S.A.; Nagarajan, Vivekanandan

2011-01-01

Aim In this study, the dosimetric properties of the electronic portal imaging device were examined and the quality assurance testing of Volumetric Modulated Arc Therapy was performed. Background RapidArc involves the variable dose rate, leaf speed and the gantry rotation. The imager was studied for the effects like dose, dose rate, field size, leaf speed and sag during gantry rotation. Materials and methods A Varian RapidArc machine equipped with 120 multileaf collimator and amorphous silicon detector was used for the study. The characteristics that are variable in RapidArc treatment were studied for the portal imager. The accuracy of a dynamic multileaf collimator position at different gantry angles and during gantry rotation was examined using the picket fence test. The control of the dose rate and gantry speed was verified using a test field irradiating seven strips of the same dose with different dose rate and gantry speeds. The control over leaf speed during arc was verified by irradiating four strips of different leaf speeds with the same dose in each strip. To verify the results, the RapidArc test procedure was compared with the X-Omat film and verified for a period of 6 weeks using EPID. Results The effect of gantry rotation on leaf accuracy was minimal. The dose in segments showed good agreement with mean deviation of 0.8% for dose rate control and 1.09% for leaf speed control over different gantry speeds. Conclusion The results provided a precise control of gantry speed, dose rate and leaf speeds during RapidArc delivery and were consistent over 6 weeks. PMID:24376989

Impact of a phenytoin loading dose program in the emergency department.

PubMed

Brancaccio, Adam; Giuliano, Christopher; McNorton, Kelly; Delgado, George

2014-11-01

The use of a combined physician-and pharmacist-directed phenytoin loading dose program in an emergency department (ED) was evaluated. This single-center, observational, preimplementation-postimplementation study evaluated adult patients who received a phenytoin loading dose in the ED. The primary outcome compared the proportion of optimal phenytoin loading doses in the preimplementation and postimplementation groups. The postimplementation group was further stratified into pharmacist- and prescriber-dosing groups. Other outcomes evaluated included the numbers of appropriate serum phenytoin concentrations measured, adverse drug reactions (ADRs), and recurrence of seizures within 24 hours of loading dose administration in the preimplementation and postimplementation groups. There was no difference in the proportion of optimal phenytoin loading doses between the preimplementation and postimplementation groups (50% versus 62%, respectively; p=0.19). When stratified by individual groups, the rate of optimal phenytoin loading doses increased by 64% in the postimplementation pharmacist group (50% versus 82%, p=0.007), while the rate in the prescriber-dosing group remained relatively unchanged (50% versus 49%, p=0.91). The number of appropriate serum phenytoin concentrations significantly improved in the postimplementation versus preimplementation group (65% versus 40%, p=0.025). Rates of ADRs and recurrence of seizures did not differ across the study groups. No change in the percentage of optimal phenytoin loading doses in the ED was observed after implementation of a combined pharmacist- and physician- dosing program. When stratified into pharmacist or prescriber dosing, the pharmacist-led dosing program significantly improved the proportion of patients who received optimal phenytoin loading doses. Copyright © 2014 by the American Society of Health-System Pharmacists, Inc. All rights reserved.

Space radiation absorbed dose distribution in a human phantom

NASA Technical Reports Server (NTRS)

Badhwar, G. D.; Atwell, W.; Badavi, F. F.; Yang, T. C.; Cleghorn, T. F.

2002-01-01

The radiation risk to astronauts has always been based on measurements using passive thermoluminescent dosimeters (TLDs). The skin dose is converted to dose equivalent using an average radiation quality factor based on model calculations. The radiological risk estimates, however, are based on organ and tissue doses. This paper describes results from the first space flight (STS-91, 51.65 degrees inclination and approximately 380 km altitude) of a fully instrumented Alderson Rando phantom torso (with head) to relate the skin dose to organ doses. Spatial distributions of absorbed dose in 34 1-inch-thick sections measured using TLDs are described. There is about a 30% change in dose as one moves from the front to the back of the phantom body. Small active dosimeters were developed specifically to provide time-resolved measurements of absorbed dose rates and quality factors at five organ locations (brain, thyroid, heart/lung, stomach and colon) inside the phantom. Using these dosimeters, it was possible to separate the trapped-proton and the galactic cosmic radiation components of the doses. A tissue-equivalent proportional counter (TEPC) and a charged-particle directional spectrometer (CPDS) were flown next to the phantom torso to provide data on the incident internal radiation environment. Accurate models of the shielding distributions at the site of the TEPC, the CPDS and a scalable Computerized Anatomical Male (CAM) model of the phantom torso were developed. These measurements provided a comprehensive data set to map the dose distribution inside a human phantom, and to assess the accuracy and validity of radiation transport models throughout the human body. The results show that for the conditions in the International Space Station (ISS) orbit during periods near the solar minimum, the ratio of the blood-forming organ dose rate to the skin absorbed dose rate is about 80%, and the ratio of the dose equivalents is almost one. The results show that the GCR model dose-rate predictions are 20% lower than the observations. Assuming that the trapped-belt models lead to a correct orbit-averaged energy spectrum, the measurements of dose rates inside the phantom cannot be fully understood. Passive measurements using 6Li- and 7Li-based detectors on the astronauts and inside the brain and thyroid of the phantom show the presence of a significant contribution due to thermal neutrons, an area requiring additional study.

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.

Microfluidic Thrombosis under Multiple Shear Rates and Antiplatelet Therapy Doses

PubMed Central

Ku, David N.; Forest, Craig R.

2014-01-01

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

Determination of the uncertainties in radiation doses from ingestion of strontium-90

NASA Astrophysics Data System (ADS)

Apostoaei, Andrei Iulian

Quantification of the uncertainties in the internal dosimetry is important because it can impact the outcome of dose reconstruction, risk assessment or epidemiological studies. This research focused on determination of the uncertainties in the dose factors from a single ingestion of 90Sr by adults, and analyzed the changes with age and the effect of gender. The uncertainties in the estimated dose factors are a factor of 6 for the bone surface, 5 for the red bone marrow, 2.5 for bladder and stomach, 2.2 for the small intestine, 2.1 for the upper large intestine and 2.7 for the lower large intestine. For the rest of the organs the uncertainty is a factor of 3. Only four parameters of the biokinetic model showed an age-dependency within the adult age group: the fractional transfers of strontium from plasma to cortical and trabecular bone, and the removal rates from the cortical and trabecular bone, respectively. When age-dependent biokinetic parameters were used, the estimated dose-factors are very close to the dose factors obtained using age-independent kinetics (within 40%). Thus, the dose factors based on age-independent parameters should suffice for most practical purposes. The dose factors and the associated uncertainties were also calculated as a function of age-at-exposure and attained age. These age dependent curves can be used for estimating doses from continuous intakes, or doses delivered over a limited portion of time. In addition to the committed dose, an expected dose is also estimated in this work. The expected dose is calculated using the dose rate weighted by the probability of surviving up to the age when the dose-rate is delivered. For exposure at young ages the expected dose and the committed dose are similar, but the committed dose decreases to zero when exposure occurs close to age 70, while the expected dose has elevated values pass age 70. No gender differences were found for bone surface, for red bone marrow, and the large intestine. The doses to the soft tissues for females are larger by 20% than the doses for males, because of the differences in the whole-body mass between males and females.

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

PubMed

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.

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.

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.

Dose rate evaluation of workers on the operation floor in Fukushima-Daiichi Unit 3

NASA Astrophysics Data System (ADS)

Matsushita, Kaoru; Kurosawa, Masahiko; Shirai, Keisuke; Matsuoka, Ippei; Mukaida, Naoki

2017-09-01

At Fukushima Daiichi Nuclear Power Plant Unit 3, installation of a fuel handling machine is planned to support the removal of spent fuel. The dose rates at the workplace were calculated based on the source distribution measured using a collimator in order to confirm that the dose rates on the operation floor were within a manageable range. It was confirmed that the accuracy of the source distribution was C/M = 1.0-2.4. These dose rates were then used to plan the work on the operation floor.

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.

Laser-based irradiation apparatus and method to measure the functional dose-rate response of semiconductor devices

DOEpatents

Horn, Kevin M [Albuquerque, NM

2008-05-20

A broad-beam laser irradiation apparatus can measure the parametric or functional response of a semiconductor device to exposure to dose-rate equivalent infrared laser light. Comparisons of dose-rate response from before, during, and after accelerated aging of a device, or from periodic sampling of devices from fielded operational systems can determine if aging has affected the device's overall functionality. The dependence of these changes on equivalent dose-rate pulse intensity and/or duration can be measured with the apparatus. The synchronized introduction of external electrical transients into the device under test can be used to simulate the electrical effects of the surrounding circuitry's response to a radiation exposure while exposing the device to dose-rate equivalent infrared laser light.

A New Approach for the Determination of Dose Rate and Radioactivity for Detected Gamma Nuclides Using an Environmental Radiation Monitor Based on an NaI(Tl) Detector.

PubMed

Ji, Young-Yong; Kim, Chang-Jong; Lim, Kyo-Sun; Lee, Wanno; Chang, Hyon-Sock; Chung, Kun Ho

2017-10-01

To expand the application of dose rate spectroscopy to the environment, the method using an environmental radiation monitor (ERM) based on a 3' × 3' NaI(Tl) detector was used to perform real-time monitoring of the dose rate and radioactivity for detected gamma nuclides in the ground around an ERM. Full-energy absorption peaks in the energy spectrum for dose rate were first identified to calculate the individual dose rates of Bi, Ac, Tl, and K distributed in the ground through interference correction because of the finite energy resolution of the NaI(Tl) detector used in an ERM. The radioactivity of the four natural radionuclides was then calculated from the in situ calibration factor-that is, the dose rate per unit curie-of the used ERM for the geometry of the ground in infinite half-space, which was theoretically estimated by Monte Carlo simulation. By an intercomparison using a portable HPGe and samples taken from the ground around an ERM, this method to calculate the dose rate and radioactivity of four nuclides using an ERM was experimentally verified and finally applied to remotely monitor them in real-time in the area in which the ERM had been installed.

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 cells and misrejoined breaks increased in both cell lines. The present study suggests that AT cells begin to rejoin breaks when a certain number of breaks are accumulated and an increased number of exchanges were observed in G0 AT cells, which is similar situation after high-dose-rate irradiation.

EFFECTS OF REACTOR RADIATION ON THE ELECTRICAL PROPERTIES OF ELECTRONIC COMPONENTS. PART II. VACUUM TUBES, TRANSISTORS AND TRANSFORMERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miglicco, P.S.; Spears, A.B.; Howell, D.B.

1957-11-22

Several types of vacuum tubes, transistors and transformers were irradiated with the Convair-Fort Worth Ground Test Reactor. The components were subjected to five different fluxes ranging from 10/sup 6/ to 10/sup 10/n/sub F// cm/sup 2/-sec and 10/sup 8/ to 10/sup 12/ gamma /cm/sup 2/-sec. The total integrated flux received was 10/sup 14/n/sub F//cm/sup 2/ and 10/sup 16/ gamma / cm/sup 2/. An attempt was made to separate radiation damage as a function of dose rate from radiation damage as a function of dose. The components were irradiated first at several low dose rates so that dose rate effects could bemore » studied while the accumulated dose was small, and then at a high dose rate to obtain the desired dose. However, because of the long time required to complete a data gathering cycle, the accumulated dose hindered the separation of dose rate and dose effects. Thus, in the report, the damage to the components is reported as a function of integrated flux. For reference, the integrated flux accumulated at each power level is given. The transformers exhibited the greatest resistance to irradiation. Every important parameter of the transistors deteriorated in the radiation field. Postirradiation tests at room temperature showed no significant recovery in the transistor's characteristics. The plate current of 65% of the tubes tested increased during irradiation. This effect, based on postirradiation tests, is considered permanent. (auth)« less

Testing Moderating Detection Systems with {sup 252}Cf-Based Reference Neutron Fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hertel, Nolan E.; Sweezy, Jeremy; Sauber, Jeremiah S.

Calibration measurements were carried out on a probe designed to measure ambient dose equivalent in accordance with ICRP Pub 60 recommendations. It consists of a cylindrical {sup 3}He proportional counter surrounded by a 25-cm-diameter spherical polyethylene moderator. Its neutron response is optimized for dose rate measurements of neutrons between thermal energies and 20 MeV. The instrument was used to measure the dose rate in four separate neutron fields: unmoderated {sup 252}Cf, D{sub 2}O-moderated {sup 252}Cf, polyethylene-moderated {sup 252}Cf, and WEP neutron howitzer with {sup 252}Cf at its center. Dose equivalent measurements were performed at source-detector centerline distances from 50 tomore » 200 cm. The ratio of air-scatter- and room-return-corrected ambient dose equivalent rates to ambient dose equivalent rates calculated with the code MCNP are tabulated.« less

Mapping of cosmic radiation dose in Croatia.

PubMed

Poje, M; Vuković, B; Radolić, V; Miklavčić, I; Faj, D; Varga Pajtler, M; Planinić, J

2012-01-01

The Earth is continually bombarded by high-energy particles coming from the outer space and the sun. These particles, termed cosmic radiation, interact with nuclei of atmospheric constituents and decrease in intensity with depth in the atmosphere. Measurements of photon and gamma radiation, performed with a Radiameter at 1 m above the ground, indicated dose rates of 50-100 nSv/h. The neutron dose rate was measured with the CR-39 track etch detector calibrated by the CERN-EU high-energy Reference Field (CERF) facility. Correlation between neutron dose rates and altitudes at 36 sites was examined in order to obtain a significant positive correlation coefficient; the resulting linear regression enabled estimation of a neutron dose at particular altitude. The measured neutron dose rate in Osijek (altitude of 89 m, latitude of 45.31° N) was 110 nSv/h. Copyright © 2011 Elsevier Ltd. All rights reserved.

Biphasic and monophasic repair: comparative implications for biologically equivalent dose calculations in pulsed dose rate brachytherapy of cervical carcinoma

PubMed Central

Millar, W T; Davidson, S E

2013-01-01

Objective: To consider the implications of the use of biphasic rather than monophasic repair in calculations of biologically-equivalent doses for pulsed-dose-rate brachytherapy of cervix carcinoma. Methods: Calculations are presented of pulsed-dose-rate (PDR) doses equivalent to former low-dose-rate (LDR) doses, using biphasic vs monophasic repair kinetics, both for cervical carcinoma and for the organ at risk (OAR), namely the rectum. The linear-quadratic modelling calculations included effects due to varying the dose per PDR cycle, the dose reduction factor for the OAR compared with Point A, the repair kinetics and the source strength. Results: When using the recommended 1 Gy per hourly PDR cycle, different LDR-equivalent PDR rectal doses were calculated depending on the choice of monophasic or biphasic repair kinetics pertaining to the rodent central nervous and skin systems. These differences virtually disappeared when the dose per hourly cycle was increased to 1.7 Gy. This made the LDR-equivalent PDR doses more robust and independent of the choice of repair kinetics and α/β ratios as a consequence of the described concept of extended equivalence. Conclusion: The use of biphasic and monophasic repair kinetics for optimised modelling of the effects on the OAR in PDR brachytherapy suggests that an optimised PDR protocol with the dose per hourly cycle nearest to 1.7 Gy could be used. Hence, the durations of the new PDR treatments would be similar to those of the former LDR treatments and not longer as currently prescribed. Advances in knowledge: Modelling calculations indicate that equivalent PDR protocols can be developed which are less dependent on the different α/β ratios and monophasic/biphasic kinetics usually attributed to normal and tumour tissues for treatment of cervical carcinoma. PMID:23934965

Effects of Epoetin Alfa Titration Practices, Implemented After Changes to Product Labeling, on Hemoglobin Levels, Transfusion Use, and Hospitalization Rates.

PubMed

Molony, Julia T; Monda, Keri L; Li, Suying; Beaubrun, Anne C; Gilbertson, David T; Bradbury, Brian D; Collins, Allan J

2016-08-01

Little is known about epoetin alfa (EPO) dosing at dialysis centers after implementation of the US Medicare prospective payment system and revision of the EPO label in 2011. Retrospective cohort study. Approximately 412,000 adult hemodialysis patients with Medicare Parts A and B as primary payer in 2009 to 2012 to describe EPO dosing and hemoglobin patterns; of these, about 70,000 patients clustered in about 1,300 dialysis facilities to evaluate facility-level EPO titration practices and patient-level outcomes in 2012. Facility EPO titration practices when hemoglobin levels were <10 and >11g/dL (grouped treatment variable) determined from monthly EPO dosing and hemoglobin level patterns. Patient mean hemoglobin levels, red blood cell transfusion rates, and all-cause and cause-specific hospitalization rates using a facility-based analysis. Monthly EPO dose and hemoglobin level, red blood cell transfusion rates, and all-cause and cause-specific hospitalization rates. Monthly EPO doses declined across all hemoglobin levels, with the greatest decline in patients with hemoglobin levels < 10g/dL (July-October 2011). In 2012, nine distinct facility titration practices were identified. Across groups, mean hemoglobin levels differed slightly (10.5-10.8g/dL) but within-patient hemoglobin standard deviations were similar (∼0.68g/dL). Patients at facilities implementing greater dose reductions and smaller dose escalations had lower hemoglobin levels and higher transfusion rates. In contrast, patients at facilities that implemented greater dose escalations (and large or small dose reductions) had higher hemoglobin levels and lower transfusion rates. There were no clinically meaningful differences in all-cause or cause-specific hospitalization events across groups. Possibly incomplete claims data; excluded small facilities and those without consistent titration patterns; hemoglobin levels reported monthly; inferred facility practice from observed dosing. Following prospective payment system implementation and labeling revisions, EPO doses declined significantly. Under the new label, facility EPO titration practices were associated with mean hemoglobin levels (but not standard deviations) and transfusion use, but not hospitalization rates. Copyright © 2016 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

Correlation of radiation dose and heart rate in dual-source computed tomography coronary angiography.

PubMed

Laspas, Fotios; Tsantioti, Dimitra; Roussakis, Arkadios; Kritikos, Nikolaos; Efthimiadou, Roxani; Kehagias, Dimitrios; Andreou, John

2011-04-01

Computed tomography coronary angiography (CTCA) has been widely used since the introduction of 64-slice scanners and dual-source CT technology, but the relatively high radiation dose remains a major concern. To evaluate the relationship between radiation exposure and heart rate (HR), in dual-source CTCA. Data from 218 CTCA examinations, performed with a dual-source 64-slices scanner, were statistically evaluated. Effective radiation dose, expressed in mSv, was calculated as the product of the dose-length product (DLP) times a conversion coefficient for the chest (mSv = DLPx0.017). Heart rate range and mean heart rate, expressed in beats per minute (bpm) of each individual during CTCA, were also provided by the system. Statistical analysis of effective dose and heart rate data was performed by using Pearson correlation coefficient and two-sample t-test. Mean HR and effective dose were found to have a borderline positive relationship. Individuals with a mean HR >65 bpm observed to receive a statistically significant higher effective dose as compared to those with a mean HR ≤65 bpm. Moreover, a strong correlation between effective dose and variability of HR of more than 20 bpm was observed. Dual-source CT scanners are considered to have the capability to provide diagnostic examinations even with high HR and arrhythmias. However, it is desirable to keep the mean heart rate below 65 bpm and heart rate fluctuation less than 20 bpm in order to reduce the radiation exposure.

Treatment of Pneumocystis pneumonia with intermediate-dose and step-down to low-dose trimethoprim-sulfamethoxazole: lessons from an observational cohort study.

PubMed

Creemers-Schild, Dina; Kroon, Frank P; Kuijper, Ed J; de Boer, Mark G J

2016-06-01

The recommended treatment of Pneumocystis jirovecii pneumonia (PCP) is high-dose trimethoprim-sulfamethoxazole (TMP-SMX) in an equivalent of TMP 15-20 mg/kg/day and SMX 75-100 mg/kg/day for 2 or 3 weeks. High rates of adverse events are reported with this dose, which raises the question if lower doses are possible. All adult patients diagnosed with PCP in various immune dysfunctions and treated with TMP-SMX between January 1, 2003 and July 1, 2013 in a tertiary university hospital were included. Per institutional protocol, patients initiated treatment on intermediate-dose TMP-SMX (TMP 10-15 mg/kg/day) and could be stepped down to low-dose TMP-SMX (TMP 4-6 mg/kg/day) during treatment. Clinical variables at presentation, relapse rate and mortality rates were compared between intermediate- and step-down treatment groups by uni- and multivariate analyses. A total of 104 patients were included. Twenty-four patients (23 %) were switched to low-dose TMP-SMX after a median of 4.5 days (IQR 2.8-7.0 days). One relapse (4 %) occurred in the step-down group versus none in the intermediate-dose group. The overall 30-day mortality was 13 %. There was 1 death in the step-down group (4 %) compared to 13 deaths (16 %) in the intermediate-dose group. We observed high cure rates of PCP by treatment with intermediate-dose TMP-SMX. In addition, a step-down strategy to low-dose TMP-SMX during treatment in selected patients appears to be safe and does not compromise the outcome of treatment.

Dosimetric characterization of the (60)Co BEBIG Co0.A86 high dose rate brachytherapy source using PENELOPE.

PubMed

Guerrero, Rafael; Almansa, Julio F; Torres, Javier; Lallena, Antonio M

2014-12-01

(60)Co sources are being used as an alternative to (192)Ir sources in high dose rate brachytherapy treatments. In a recent document from AAPM and ESTRO, a consensus dataset for the (60)Co BEBIG (model Co0.A86) high dose rate source was prepared by using results taken from different publications due to discrepancies observed among them. The aim of the present work is to provide a new calculation of the dosimetric characteristics of that (60)Co source according to the recommendations of the AAPM and ESTRO report. Radial dose function, anisotropy function, air-kerma strength, dose rate constant and absorbed dose rate in water have been calculated and compared to the results of previous works. Simulations using the two different geometries considered by other authors have been carried out and the effect of the cable density and length has been studied. Copyright © 2014 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

The Effect of Compliance on the Impact of Mass Drug Administration for Elimination of Lymphatic Filariasis in Egypt

PubMed Central

El-Setouhy, Maged; Abd Elaziz, Khaled M.; Helmy, Hanan; Farid, Hoda A.; Kamal, Hussein A.; Ramzy, Reda M. R.; Shannon, William D.; Weil, Gary J.

2008-01-01

We studied effects of compliance on the impact of mass drug administration (MDA) with diethylcarbamazine and albendazole for lymphatic filariasis (LF) in an Egyptian village. Baseline microfilaremia (mf) and filarial antigenemia rates were 11.5% and 19.0%, respectively. The MDA compliance rates were excellent (> 85%). However, individual compliance was highly variable; 7.4% of those surveyed after five rounds of MDA denied having ever taken the medications and 52.4% reported that they had taken all five doses. The mf and antigenemia rates were 0.2% and 2.7% in those who reported five doses of MDA and 8.3% and 13.8% in those who reported zero doses. There was no significant difference in residual infection rates among those who had taken two or more doses. These results underscore the importance of compliance for LF elimination programs based on MDA and suggest that two ingested doses of MDA are as effective as five doses for reducing filariasis infection rates. PMID:18165524

Effective dose rate coefficients for exposure to contaminated soil

DOE PAGES

Veinot, Kenneth G.; Eckerman, Keith F.; Bellamy, Michael B.; ...

2017-05-10

The Oak Ridge National Laboratory Center for Radiation Protection Knowledge has undertaken calculations related to various environmental exposure scenarios. A previous paper reported the results for submersion in radioactive air and immersion in water using age-specific mathematical phantoms. This paper presents age-specific effective dose rate coefficients derived using stylized mathematical phantoms for exposure to contaminated soils. Dose rate coefficients for photon, electron, and positrons of discrete energies were calculated and folded with emissions of 1252 radionuclides addressed in ICRP Publication 107 to determine equivalent and effective dose rate coefficients. The MCNP6 radiation transport code was used for organ dose ratemore » calculations for photons and the contribution of electrons to skin dose rate was derived using point-kernels. Bremsstrahlung and annihilation photons of positron emission were evaluated as discrete photons. As a result, the coefficients calculated in this work compare favorably to those reported in the US Federal Guidance Report 12 as well as by other authors who employed voxel phantoms for similar exposure scenarios.« less

Effective dose rate coefficients for exposure to contaminated soil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Veinot, Kenneth G.; Eckerman, Keith F.; Bellamy, Michael B.

The Oak Ridge National Laboratory Center for Radiation Protection Knowledge has undertaken calculations related to various environmental exposure scenarios. A previous paper reported the results for submersion in radioactive air and immersion in water using age-specific mathematical phantoms. This paper presents age-specific effective dose rate coefficients derived using stylized mathematical phantoms for exposure to contaminated soils. Dose rate coefficients for photon, electron, and positrons of discrete energies were calculated and folded with emissions of 1252 radionuclides addressed in ICRP Publication 107 to determine equivalent and effective dose rate coefficients. The MCNP6 radiation transport code was used for organ dose ratemore » calculations for photons and the contribution of electrons to skin dose rate was derived using point-kernels. Bremsstrahlung and annihilation photons of positron emission were evaluated as discrete photons. As a result, the coefficients calculated in this work compare favorably to those reported in the US Federal Guidance Report 12 as well as by other authors who employed voxel phantoms for similar exposure scenarios.« less

Lifetime Effective Dose Assessment Based on Background Outdoor Gamma Exposure in Chihuahua City, Mexico

PubMed Central

Luevano-Gurrola, Sergio; Perez-Tapia, Angelica; Pinedo-Alvarez, Carmelo; Carrillo-Flores, Jorge; Montero-Cabrera, Maria Elena; Renteria-Villalobos, Marusia

2015-01-01

Determining ionizing radiation in a geographic area serves to assess its effects on a population’s health. The aim of this study was to evaluate the spatial distribution of the background environmental outdoor gamma dose rates in Chihuahua City. This study also estimated the annual effective dose and the lifetime cancer risks of the population of this city. To determine the outdoor gamma dose rate in air, the annual effective dose and the lifetime cancer risk, 48 sampling points were randomly selected in Chihuahua City. Outdoor gamma dose rate measurements were carried out by using a Geiger-Müller counter. Outdoor gamma dose rates ranged from 113 to 310 nGy·h−1. At the same sites, 48 soil samples were taken to obtain the activity concentrations of 226Ra, 232Th and 40K and to calculate their terrestrial gamma dose rates. Radioisotope activity concentrations were determined by gamma spectrometry. Calculated gamma dose rates ranged from 56 to 193 nGy·h−1. Results indicated that the lifetime effective dose of the inhabitants of Chihuahua City is on average 19.8 mSv, resulting in a lifetime cancer risk of 0.001. In addition, the mean of the activity concentrations in soil were 52, 73 and 1097 Bq·kg−1, for 226Ra, 232Th and 40K, respectively. From the analysis, the spatial distribution of 232Th, 226Ra and 40K is to the north, to the north-center and to the south of city, respectively. In conclusion, the natural background gamma dose received by the inhabitants of Chihuahua City is high and mainly due to the geological characteristics of the zone. From the radiological point of view, this kind of study allows us to identify the importance of manmade environments, which are often highly variable and difficult to characterize. PMID:26437425

Lifetime Effective Dose Assessment Based on Background Outdoor Gamma Exposure in Chihuahua City, Mexico.

PubMed

Luevano-Gurrola, Sergio; Perez-Tapia, Angelica; Pinedo-Alvarez, Carmelo; Carrillo-Flores, Jorge; Montero-Cabrera, Maria Elena; Renteria-Villalobos, Marusia

2015-09-30

Determining ionizing radiation in a geographic area serves to assess its effects on a population's health. The aim of this study was to evaluate the spatial distribution of the background environmental outdoor gamma dose rates in Chihuahua City. This study also estimated the annual effective dose and the lifetime cancer risks of the population of this city. To determine the outdoor gamma dose rate in air, the annual effective dose and the lifetime cancer risk, 48 sampling points were randomly selected in Chihuahua City. Outdoor gamma dose rate measurements were carried out by using a Geiger-Müller counter. Outdoor gamma dose rates ranged from 113 to 310 nGy·h(-1). At the same sites, 48 soil samples were taken to obtain the activity concentrations of (226)Ra, (232)Th and (40)K and to calculate their terrestrial gamma dose rates. Radioisotope activity concentrations were determined by gamma spectrometry. Calculated gamma dose rates ranged from 56 to 193 nGy·h(-1). Results indicated that the lifetime effective dose of the inhabitants of Chihuahua City is on average 19.8 mSv, resulting in a lifetime cancer risk of 0.001. In addition, the mean of the activity concentrations in soil were 52, 73 and 1097 Bq·kg(-1), for (226)Ra, (232)Th and (40)K, respectively. From the analysis, the spatial distribution of (232)Th, (226)Ra and (40)K is to the north, to the north-center and to the south of city, respectively. In conclusion, the natural background gamma dose received by the inhabitants of Chihuahua City is high and mainly due to the geological characteristics of the zone. From the radiological point of view, this kind of study allows us to identify the importance of manmade environments, which are often highly variable and difficult to characterize.

VMAT testing for an Elekta accelerator

PubMed Central

Sweeney, Larry E.; Marshall, Edward I.; Mahendra, Saikanth

2012-01-01

Volumetric‐modulated arc therapy (VMAT) has been shown to be able to deliver plans equivalent to intensity‐modulated radiation therapy (IMRT) in a fraction of the treatment time. This improvement is important for patient immobilization/ localization compliance due to comfort and treatment duration, as well as patient throughput. Previous authors have suggested commissioning methods for this modality. Here, we extend the methods reported for the Varian RapidArc system (which tested individual system components) to the Elekta linear accelerator, using custom files built using the Elekta iComCAT software. We also extend the method reported for VMAT commissioning of the Elekta accelerator by verifying maximum values of parameters (gantry speed, multileaf collimator (MLC) speed, and backup jaw speed), investigating: 1) beam profiles as a function of dose rate during an arc, 2) over/under dosing due to MLC reversals, and 3) over/under dosing at changing dose rate junctions. Equations for construction of the iComCAT files are given. Results indicate that the beam profile for lower dose rates varies less than 3% from that of the maximum dose rate, with no difference during an arc. The gantry, MLC, and backup jaw maximum speed are internally consistent. The monitor unit chamber is stable over the MUs and gantry movement conditions expected. MLC movement and position during VMAT delivery are within IMRT tolerances. Dose rate, gantry speed, and MLC speed are accurately controlled. Over/under dosing at junctions of MLC reversals or dose rate changes are within clinical acceptability. PACS numbers: 87.55.de, 87.55.Qr, 87.56.bd PMID:22402389

Impact of weight-based ribavirin with peginterferon alfa-2b in African Americans with hepatitis C virus genotype 1.

PubMed

Jacobson, Ira M; Brown, Robert S; McCone, Jonathan; Black, Martin; Albert, Clive; Dragutsky, Michael S; Siddiqui, Firdous A; Hargrave, Thomas; Kwo, Paul Y; Lambiase, Louis; Galler, Greg W; Araya, Victor; Freilich, Bradley; Harvey, Joann; Griffel, Louis H; Brass, Clifford A

2007-10-01

WIN-R (Weight-based dosing of pegINterferon alfa-2b and Ribavirin) was a multicenter, randomized, open-label, investigator-initiated trial involving 236 community and academic sites in the United States, comparing response to pegylated interferon (PEG-IFN) alfa-2b plus a flat or weight-based dose of ribavirin (RBV) in treatment-naive patients with chronic hepatitis C and compensated liver disease. Patients were randomized to receive PEG-IFN alfa-2b at 1.5 microg/kg/week plus flat-dose (800 mg/day) or weight-based-dose RBV (800 mg/day for weight <65 kg, 1000 mg/day for 65-85 kg, 1200 mg/day for >85-105 kg, or 1400 mg/day for >105-<125 kg). Sustained virologic response (SVR; undetectable [<125 IU/mL] hepatitis C virus [HCV] RNA at end of follow-up) in patients > or =65 kg was the primary end point. Low SVR rates have been reported among African American individuals, in whom there is a preponderance of HCV genotype 1. This subanalysis of WIN-R was conducted to evaluate the efficacy of weight-based dosing among African American individuals with genotype 1 infection enrolled in the trial. Of 362 African American patients in the primary efficacy analysis, 188 received RBV flat dosing and 174 received weight-based dosing. SVR rates were higher (21% versus 10%; P = 0.0006) and relapse rates were lower (22% versus 30%) in the weight-based-dose group than in the flat-dose group. Safety and rates of drug discontinuation were similar between the 2 groups. Weight-based dosing of RBV is more effective than flat dosing in combination with PEG-IFN alfa-2b in African American individuals with HCV genotype 1. Even with weight-based dosing, response rates in African American individuals are lower than reported in other ethnic groups.

SU-F-T-68: Characterizes of Microdetectors in Electron Beam Dosimetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Das, I; Andersen, A; Akino, Y

Purpose: Electron beam dosimetry requires high resolution data due to finite range that can be accomplished with small volume detectors. The small-field used in advance technologies in photon beam has created a market for microdetectors, however characteristics are significantly variable in photon beams and relatively unknown in electron beam that is investigated in this study. Methods: Among nearly 2 dozen microdetectors that have been investigated in small fields of photon beam, two popular detectors (microDiamond 60019 (PTW)) and W1 plastic scintillator detector (Standard Imaging)) that are tissue equivalent and have very small sensitive volume are selected. Electron beams from Varianmore » linear accelerators were used to investigate dose linearity dose rate dependence, energy dependence, depth dose and profiles in a reference condition in a water phantom. For W1 that has its own Supermax electrometer point by point measurements were performed. For microDiamond, a PTW-scanning tank was used for both scanning and point dose measurements. Results: W1 detector showed excellent dose linearity (r{sup 2} =1.0) from 5–500 MU either with variation of dose rate or beam energy. Similar findings were also observed for microdiamond with r{sup 2}=1.0. Percent variations in dose/MU for W1 and microDiamond were 0.2–1.1% and 0.4–1.2%, respectively among dose rate and beam energy. This variation was random for microDiamond, whereas it decreased with beam energy and dose rate for W1. The depth dose and profiles were within ±1 mm for both detectors. Both detectors did not show any energy dependence in electron beams. Conclusion: Both microDiamond and W1 detectors provided superior characteristics of beam parameters in electron beam including dose, dose rate linearity and energy independence. Both can be used in electron beam except W1 require point by point measurements and microdiamond requires 1500 MU for initial quenching.« less

Gafchromic EBT‐XD film: Dosimetry characterization in high‐dose, volumetric‐modulated arc therapy

PubMed Central

Ozawa, Shuichi; Hosono, Fumika; Sumida, Naoki; Okazue, Toshiya; Yamada, Kiyoshi; Nagata, Yasushi

2016-01-01

Radiochromic films are important tools for assessing complex dose distributions. Gafchromic EBT‐XD films have been designed for optimal performance in the 40–4,000 cGy dose range. We investigated the dosimetric characteristics of these films, including their dose‐response, postexposure density growth, and dependence on scanner orientation, beam energy, and dose rate with applications to high‐dose volumetric‐modulated arc therapy (VMAT) verification. A 10 MV beam from a TrueBeam STx linear accelerator was used to irradiate the films with doses in the 0–4,000 cGy range. Postexposure coloration was analyzed at postirradiation times ranging from several minutes to 48 h. The films were also irradiated with 6 MV (dose rate (DR): 600 MU/min), 6 MV flattening filter‐free (FFF) (DR: 1,400 MU/ min), and 10 MV FFF (DR: 2,400 MU/min) beams to determine the energy and dose‐rate dependence. For clinical examinations, we compared the dose distribution measured with EBT‐XD films and calculated by the planning system for four VMAT cases. The red channel of the EBT‐XD film exhibited a wider dynamic range than the green and blue channels. Scanner orientation yielded a variation of ∼3% in the net optical density (OD). The difference between the film front and back scan orientations was negligible, with variation of ∼1.3% in the net OD. The net OD increased sharply within the first 6 hrs after irradiation and gradually afterwards. No significant difference was observed for the beam energy and dose rate, with a variation of ∼1.5% in the net OD. The gamma passing rates (at 3%, 3 mm) between the film‐ measured and treatment planning system (TPS)‐calculated dose distributions under a high dose VMAT plan in the absolute dose mode were more than 98.9%. PACS number(s): 87.56 Fc PMID:27929504

Optically Stimulated Luminescent Dosimetry for High Dose Rate Brachytherapy

PubMed Central

Tien, Christopher Jason; Ebeling, Robert; Hiatt, Jessica R.; Curran, Bruce; Sternick, Edward

2012-01-01

Purpose: The objective was to determine whether optically stimulated luminescent dosimeters (OSLDs) were appropriate for in vivo measurements in high dose rate brachytherapy. In order to make this distinction, three dosimetric characteristics were tested: dose linearity, dose rate dependence, and angular dependence. The Landauer nanoDot™ OSLDs were chosen due to their popularity and their availability commercially. Methods: To test the dose linearity, each OSLD was placed at a constant location and the dwell time was varied. Next, in order to test the dose rate dependence, each OSLD was placed at different OLSD-to-source distances and the dwell time was held constant. A curved geometry was created using a circular Accuboost® applicator in order to test angular dependence. Results: The OSLD response remained linear for high doses and was independent of dose rate. For doses up to 600 cGy, the linear coefficient of determination was 0.9988 with a response of 725 counts per cGy. The angular dependence was significant only in “edge-on” scenarios. Conclusion: OSLDs are conveniently read out using commercially available readers. OSLDs can be re-read and serve as a permanent record for clinical records or be annealed using conventional fluorescent light. Lastly, OSLDs are produced commercially for $5 each. Due to these convenient features, in conjunction with the dosimetric performance, OSLDs should be considered a clinically feasible and attractive tool for in vivo HDR brachytherapy measurements. PMID:22888476

Four-dimensional dose distributions of step-and-shoot IMRT delivered with real-time tumor tracking for patients with irregular breathing: Constant dose rate vs dose rate regulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang Xiaocheng; Han-Oh, Sarah; Gui Minzhi

2012-09-15

Purpose: Dose-rate-regulated tracking (DRRT) is a tumor tracking strategy that programs the MLC to track the tumor under regular breathing and adapts to breathing irregularities during delivery using dose rate regulation. Constant-dose-rate tracking (CDRT) is a strategy that dynamically repositions the beam to account for intrafractional 3D target motion according to real-time information of target location obtained from an independent position monitoring system. The purpose of this study is to illustrate the differences in the effectiveness and delivery accuracy between these two tracking methods in the presence of breathing irregularities. Methods: Step-and-shoot IMRT plans optimized at a reference phase weremore » extended to remaining phases to generate 10-phased 4D-IMRT plans using segment aperture morphing (SAM) algorithm, where both tumor displacement and deformation were considered. A SAM-based 4D plan has been demonstrated to provide better plan quality than plans not considering target deformation. However, delivering such a plan requires preprogramming of the MLC aperture sequence. Deliveries of the 4D plans using DRRT and CDRT tracking approaches were simulated assuming the breathing period is either shorter or longer than the planning day, for 4 IMRT cases: two lung and two pancreatic cases with maximum GTV centroid motion greater than 1 cm were selected. In DRRT, dose rate was regulated to speed up or slow down delivery as needed such that each planned segment is delivered at the planned breathing phase. In CDRT, MLC is separately controlled to follow the tumor motion, but dose rate was kept constant. In addition to breathing period change, effect of breathing amplitude variation on target and critical tissue dose distribution is also evaluated. Results: Delivery of preprogrammed 4D plans by the CDRT method resulted in an average of 5% increase in target dose and noticeable increase in organs at risk (OAR) dose when patient breathing is either 10% faster or slower than the planning day. In contrast, DRRT method showed less than 1% reduction in target dose and no noticeable change in OAR dose under the same breathing period irregularities. When {+-}20% variation of target motion amplitude was present as breathing irregularity, the two delivery methods show compatible plan quality if the dose distribution of CDRT delivery is renormalized. Conclusions: Delivery of 4D-IMRT treatment plans, stemmed from 3D step-and-shoot IMRT and preprogrammed using SAM algorithm, is simulated for two dynamic MLC-based real-time tumor tracking strategies: with and without dose-rate regulation. Comparison of cumulative dose distribution indicates that the preprogrammed 4D plan is more accurately and efficiently conformed using the DRRT strategy, as it compensates the interplay between patient breathing irregularity and tracking delivery without compromising the segment-weight modulation.« less

Dose-related difference in progression rates of cytomegalovirus retinopathy during foscarnet maintenance therapy. AIDS Clinical Trials Group Protocol 915 Team.

PubMed

Holland, G N; Levinson, R D; Jacobson, M A

1995-05-01

A previous dose-ranging study of foscarnet maintenance therapy for cytomegalovirus retinopathy showed a positive relationship between dose and survival but could not confirm a relationship between dose and time to first progression. This retrospective analysis of data from that study was undertaken to determine whether there was a relationship between dose and progression rates, which reflects the amount of retina destroyed when progression occurs. Patients were randomly given one of two foscarnet maintenance therapy doses (90 mg/kg of body weight/day [FOS-90 group] or 120 mg/kg of body weight/day [FOS-120 group] after induction therapy. Using baseline and follow-up photographs and pre-established definitions and methodology in a masked analysis, posterior progression rates and foveal proximity rates for individual lesions, selected by prospectively defined criteria, were calculated in each patient. Rates were compared between groups. The following median rates were greater for the FOS-90 group (N = 8) than for the FOS-120 group (N = 10): greatest maximum rate at which lesions enlarged in a posterior direction (43.5 vs 12.5 microns/day; P = .002); posterior progression rate for lesions closest to the fovea (42.8 vs 5.5 microns/day; P = .010); and maximum foveal proximity rate for either eye (32.3 vs 3.4 microns/day; P = .031). Patients receiving higher doses of foscarnet have slower rates of progression and therefore less retinal tissue damage during maintenance therapy. A foscarnet maintenance therapy dose of 120 mg/kg of body weight/day instead of 90 mg/kg of body weight/day may help to preserve vision in patients with cytomegalovirus retinopathy.

Image perception by expert readers as a function of patient skin entrance dose levels in digital radiography

NASA Astrophysics Data System (ADS)

Lehnert, T.; Korkusuz, H.; Khan, F.; Vogl, T. J.; Mack, M. G.

2008-03-01

In this study, image quality was based on required clinical criteria, in order to investigate to what degree entrance dose could be lowered and what kind of added filtration can be used without impinging on radiologist confidence levels in diagnosing. Images were taken of extremities from a cadaver using stepwise decreasing dose levels and variation of added filtration (no filtration, aluminum, aluminum/copper) under digital projection radiography (Kodak DirectView DR7500). The starting point dose level for all body parts imaged was the current x-ray technique. Two experienced and two resident radiologists were presented the images in a blinded fashion and rated each with an image quality score from 1 to 9 indicated very satisfied and 1 as very unsatisfied indicating loss of diagnostic value. The readers were not aware of which dose level and added filtration corresponded to which image. Dose levels considered were 100%, 75%, 50% and 25% of the normal and customary x-ray techniques used for the particular body part and projection. Images were reviewed on a clinical diagnostic workstation with no time limits imposed. Readers were also able to change the image presentation by adjusting the window width and level. Without added filtration image quality mean score was rated with 6.3 (dose level 100%), 6.2 (dose level 75%), 5.3 (dose level 50%) and with 4.4 (dose level 25%). An added aluminum filtration induced an image quality mean score of 6.3 (dose level 100%), 6.0 (dose level 75%), 5.1 (dose level 50%) and of 4.2 (dose level 25%). Using aluminum/copper filtration image quality mean score was rated with 6.0 (dose level 100%), 6.1 (dose level 75%), 5.0 (dose level 50%) and with 3.8 (dose level 25%). Regardless of the added filtration a differentiation between dose levels 100% and 75% was possible in 38.9%, between dose levels 75% and 50% in 66.7%, and between dose levels 50% and 25% in 70.0% of the cases. It is possible, in the case of extremities, to lower entrance doses up to 75 % of the normal value, a reduction of 25% in dose, under simultaneous use of added aluminum or aluminum/copper filtration, without comprising the diagnostic value required.

Development of Safety Assessment Code for Decommissioning of Nuclear Facilities

NASA Astrophysics Data System (ADS)

Shimada, Taro; Ohshima, Soichiro; Sukegawa, Takenori

A safety assessment code, DecDose, for decommissioning of nuclear facilities has been developed, based on the experiences of the decommissioning project of Japan Power Demonstration Reactor (JPDR) at Japan Atomic Energy Research Institute (currently JAEA). DecDose evaluates the annual exposure dose of the public and workers according to the progress of decommissioning, and also evaluates the public dose at accidental situations including fire and explosion. As for the public, both the internal and the external doses are calculated by considering inhalation, ingestion, direct radiation from radioactive aerosols and radioactive depositions, and skyshine radiation from waste containers. For external dose for workers, the dose rate from contaminated components and structures to be dismantled is calculated. Internal dose for workers is calculated by considering dismantling conditions, e.g. cutting speed, cutting length of the components and exhaust velocity. Estimation models for dose rate and staying time were verified by comparison with the actual external dose of workers which were acquired during JPDR decommissioning project. DecDose code is expected to contribute the safety assessment for decommissioning of nuclear facilities.

Dose estimation for astronauts using dose conversion coefficients calculated with the PHITS code and the ICRP/ICRU adult reference computational phantoms.

PubMed

Sato, Tatsuhiko; Endo, Akira; Sihver, Lembit; Niita, Koji

2011-03-01

Absorbed-dose and dose-equivalent rates for astronauts were estimated by multiplying fluence-to-dose conversion coefficients in the units of Gy.cm(2) and Sv.cm(2), respectively, and cosmic-ray fluxes around spacecrafts in the unit of cm(-2) s(-1). The dose conversion coefficients employed in the calculation were evaluated using the general-purpose particle and heavy ion transport code system PHITS coupled to the male and female adult reference computational phantoms, which were released as a common ICRP/ICRU publication. The cosmic-ray fluxes inside and near to spacecrafts were also calculated by PHITS, using simplified geometries. The accuracy of the obtained absorbed-dose and dose-equivalent rates was verified by various experimental data measured both inside and outside spacecrafts. The calculations quantitatively show that the effective doses for astronauts are significantly greater than their corresponding effective dose equivalents, because of the numerical incompatibility between the radiation quality factors and the radiation weighting factors. These results demonstrate the usefulness of dose conversion coefficients in space dosimetry. © Springer-Verlag 2010

Radiation dose reduction efficiency of buildings after the accident at the Fukushima Daiichi Nuclear Power Station.

PubMed

Monzen, Satoru; Hosoda, Masahiro; Osanai, Minoru; Tokonami, Shinji

2014-01-01

Numerous radionuclides were released from the Fukushima Daiichi Nuclear Power Station (F1-NPS) in Japan following the magnitude 9.0 earthquake and tsunami on March 11, 2011. Local residents have been eager to calculate their individual radiation exposure. Thus, absorbed dose rates in the indoor and outdoor air at evacuation sites in the Fukushima Prefecture were measured using a gamma-ray measuring devices, and individual radiation exposure was calculated by assessing the radiation dose reduction efficiency (defined as the ratio of absorbed dose rate in the indoor air to the absorbed dose rate in the outdoor air) of wood, aluminum, and reinforced concrete buildings. Between March 2011 and July 2011, dose reduction efficiencies of wood, aluminum, and reinforced concrete buildings were 0.55 ± 0.04, 0.15 ± 0.02, and 0.19 ± 0.04, respectively. The reduction efficiency of wood structures was 1.4 times higher than that reported by the International Atomic Energy Agency. The efficiency of reinforced concrete was similar to previously reported values, whereas that of aluminum structures has not been previously reported. Dose reduction efficiency increased in proportion to the distance from F1-NPS at 8 of the 18 evacuation sites. Time variations did not reflect dose reduction efficiencies at evacuation sites although absorbed dose rates in the outdoor air decreased. These data suggest that dose reduction efficiency depends on structure types, levels of contamination, and evacuee behaviors at evacuation sites.

Intravenous Nicotine Self-Administration in Smokers: Dose-Response Function and Sex Differences.

PubMed

Jensen, Kevin P; DeVito, Elise E; Valentine, Gerald; Gueorguieva, Ralitza; Sofuoglu, Mehmet

2016-07-01

Sex differences in the sensitivity to nicotine may influence vulnerability to tobacco dependence. The goal of this study was to investigate the dose-response function for the reinforcing and subjective effects of intravenous nicotine in male and female smokers. Tobacco-dependent subjects (12 male and 14 female) participated in four experimental sessions in which they received sample infusions of saline and nicotine (0.1, 0.2, 0.3, or 0.4 mg doses) in a randomized double-blind crossover design. During each session, subjects first received the sample infusions, and heart rate (HR), blood pressure, and subjective stimulatory, pleasurable and aversive responses were monitored. Immediately following the sample infusions, subjects self-administered either nicotine or saline in six double-blind forced-choice trials. A sex by dose interaction was observed in the nicotine choice paradigm. Nicotine self-administration rate was negatively correlated with nicotine dose in males (males displayed choice preference for low doses of nicotine over high doses of nicotine), but no significant relationship between dose and choice preference was evident in females. Relative to placebo, sample doses of nicotine increased heart rate and blood pressure, and induced stimulatory, pleasurable, and aversive subjective effects. Diastolic blood pressure increased dose dependently in males, but not in females. These findings, which demonstrate sex differences in nicotine self-administration for doses that are near to the reinforcement threshold, suggest that male and female smokers may respond differently to the changes in nicotine doses available for self-administration.

Staff Radiation Doses in a Real-Time Display Inside the Angiography Room

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sanchez, Roberto, E-mail: rmsanchez.hcsc@salud.madrid.org; Vano, E.; Fernandez, J. M.

MethodsThe evaluation of a new occupational Dose Aware System (DAS) showing staff radiation doses in real time has been carried out in several angiography rooms in our hospital. The system uses electronic solid-state detectors with high-capacity memory storage. Every second, it archives the dose and dose rate measured and is wirelessly linked to a base-station screen mounted close to the diagnostic monitors. An easy transfer of the values to a data sheet permits further analysis of the scatter dose profile measured during the procedure, compares it with patient doses, and seeks to find the most effective actions to reduce operatormore » exposure to radiation.ResultsThe cumulative occupational doses measured per procedure (shoulder-over lead apron) ranged from 0.6 to 350 {mu}Sv when the ceiling-suspended screen was used, and DSA (Digital Subtraction Acquisition) runs were acquired while the personnel left the angiography room. When the suspended screen was not used and radiologists remained inside the angiography room during DSA acquisitions, the dose rates registered at the operator's position reached up to 1-5 mSv/h during fluoroscopy and 12-235 mSv/h during DSA acquisitions. In such case, the cumulative scatter dose could be more than 3 mSv per procedure.ConclusionReal-time display of doses to staff members warns interventionists whenever the scatter dose rates are too high or the radiation protection tools are not being properly used, providing an opportunity to improve personal protection accordingly.« less

Measurements of environmental terrestrial gamma radiation dose rate in three mountainous locations in the western region of Saudi Arabia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Al-Ghorabie, Fayez H.H.

2005-06-01

This paper describes measurements of external gamma radiation dose rate from terrestrial gamma-rays 1 m above the ground in three different mountainous locations in the western region of the Kingdom of Saudi Arabia. These locations are At-Taif city, Al-Hada village, and Ash-Shafa village. CaSO{sub 4}:Dy (TLD-900) thermoluminescent dosimeters were used for the detection of terrestrial gamma radiation at 40 different places in the three locations. The values of terrestrial gamma radiation dose rate measured ranged between 14 and 279 nGy h{sup -1} for the time interval from June 2001 to June 2002. The measured dose rate varied with the seasonmore » of the year. The average gamma radiation dose rates were 468, 541, and 781 {mu}Gy y{sup -1} for At-Taif city, Al-Hada village, and Ash-Shafa village, respectively. The corresponding average absorbed doses to the population of the three locations were 328, 379, and 547 {mu}Sv y{sup -1}, respectively. The quality factor of 0.7 Sv Gy{sup -1} was applied in the calculations of the absorbed dose to humans.« less

Cost comparison of unit dose and traditional drug distribution in a long-term-care facility.

PubMed

Lepinski, P W; Thielke, T S; Collins, D M; Hanson, A

1986-11-01

Unit dose and traditional drug distribution systems were compared in a 352-bed long-term-care facility by analyzing nursing time, medication-error rate, medication costs, and waste. Time spent by nurses in preparing, administering, charting, and other tasks associated with medications was measured with a stop-watch on four different nursing units during six-week periods before and after the nursing home began using unit dose drug distribution. Medication-error rate before and after implementation of the unit dose system was determined by patient profile audits and medication inventories. Medication costs consisted of patient billing costs (acquisition cost plus fee) and cost of medications destroyed. The unit dose system required a projected 1507.2 hours less nursing time per year. Mean medication-error rates were 8.53% and 0.97% for the traditional and unit dose systems, respectively. Potential annual savings because of decreased medication waste with the unit dose system were $2238.72. The net increase in cost for the unit dose system was estimated at $615.05 per year, or approximately $1.75 per patient. The unit dose system appears safer and more time-efficient than the traditional system, although its costs are higher.

Development of a high sensitivity pinhole type gamma camera using semiconductors for low dose rate fields

NASA Astrophysics Data System (ADS)

Ueno, Yuichiro; Takahashi, Isao; Ishitsu, Takafumi; Tadokoro, Takahiro; Okada, Koichi; Nagumo, Yasushi; Fujishima, Yasutake; Yoshida, Akira; Umegaki, Kikuo

2018-06-01

We developed a pinhole type gamma camera, using a compact detector module of a pixelated CdTe semiconductor, which has suitable sensitivity and quantitative accuracy for low dose rate fields. In order to improve the sensitivity of the pinhole type semiconductor gamma camera, we adopted three methods: a signal processing method to set the discriminating level lower, a high sensitivity pinhole collimator and a smoothing image filter that improves the efficiency of the source identification. We tested basic performances of the developed gamma camera and carefully examined effects of the three methods. From the sensitivity test, we found that the effective sensitivity was about 21 times higher than that of the gamma camera for high dose rate fields which we had previously developed. We confirmed that the gamma camera had sufficient sensitivity and high quantitative accuracy; for example, a weak hot spot (0.9 μSv/h) around a tree root could be detected within 45 min in a low dose rate field test, and errors of measured dose rates with point sources were less than 7% in a dose rate accuracy test.

Nuclear mass inventory, photon dose rate and thermal decay heat of spent research reactor fuel assemblies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pond, R.B.; Matos, J.E.

1996-05-01

As part of the Department of Energy`s spent nuclear fuel acceptance criteria, the mass of uranium and transuranic elements in spent research reactor fuel must be specified. These data are, however, not always known or readily determined. It is the purpose of this report to provide estimates of these data for some of the more common research reactor fuel assembly types. The specific types considered here are MTR, TRIGA and DIDO fuel assemblies. The degree of physical protection given to spent fuel assemblies is largely dependent upon the photon dose rate of the spent fuel material. These data also, aremore » not always known or readily determined. Because of a self-protecting dose rate level of radiation (dose rate greater than 100 ren-x/h at I m in air), it is important to know the dose rate of spent fuel assemblies at all time. Estimates of the photon dose rate for spent MTR, TRIGA and DIDO-type fuel assemblies are given in this report.« less

``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).

DOSE CONTROLLER FOR AGUACLARA WATER TREATMENT PLANTS

EPA Science Inventory

The expected results include a proven design for a gravity powered dose controller that works for calcium hypochlorite or aluminum sulfate solutions. The dose controller will be coupled with plant flow rate measuring systems that have compatible relationships between flow rate...

Dose-rate effect was observed in T98G glioma cells following BNCT.

PubMed

Kinashi, Yuko; Okumura, Kakuji; Kubota, Yoshihisa; Kitajima, Erika; Okayasu, Ryuichi; Ono, Koji; Takahashi, Sentaro

2014-06-01

It is generally said that low LET radiation produce high dose-rate effect, on the other hand, no significant dose rate effect is observed in high LET radiation. Although high LET radiations are produced in BNCT, little is known about dose-rate effect of BNCT. T98G cells, which were tumor cells, were irradiated by neutron mixed beam with BPA. As normal tissue derived cells, Chinese hamster ovary (CHO-K1) cells and DNA double strand breaks (DNA-DSBs) repair deficient cells, xrs5 cells were irradiated by the neutrons (not including BPA). To DNA-DSBs analysis, T98G cells were stained immunochemically with 53BP1 antibody. The number of DNA-DSBs was determined by counting 53BP1 foci. There was no dose-rate effect in xrs5 cells. D0 difference between 4cGy/min and 20cGy/min irradiation were 0.5 and 5.9 at the neutron and gamma-ray irradiation for CHO-K1, and 0.3 at the neutron for T98G cells. D0 difference between 20cGy/min and 80cGy/min irradiation for T98G cells were 1.2 and 0.6 at neutron irradiation plus BPA and gamma-ray. The differences between neutron irradiations at the dose rate in T98G cells were supported by not only the cell viability but also 53BP1 foci assay at 24h following irradiation to monitor DNA-DSBs. Dose-rate effect of BNCT when T98G cells include 20ppm BPA was greater than that of gamma-ray irradiation. Moreover, Dose-rate effect of the neutron beam when CHO-K1 cells did not include BPA was less than that of gamma-ray irradiation These present results may suggest the importance of dose-rate effect for more efficient BNCT and the side effect reduction. © 2013 Published by Elsevier Ltd.

Nuclear Radiation Degradation Study on HD Camera Based on CMOS Image Sensor at Different Dose Rates.

PubMed

Wang, Congzheng; Hu, Song; Gao, Chunming; Feng, Chang

2018-02-08

In this work, we irradiated a high-definition (HD) industrial camera based on a commercial-off-the-shelf (COTS) CMOS image sensor (CIS) with Cobalt-60 gamma-rays. All components of the camera under test were fabricated without radiation hardening, except for the lens. The irradiation experiments of the HD camera under biased conditions were carried out at 1.0, 10.0, 20.0, 50.0 and 100.0 Gy/h. During the experiment, we found that the tested camera showed a remarkable degradation after irradiation and differed in the dose rates. With the increase of dose rate, the same target images become brighter. Under the same dose rate, the radiation effect in bright area is lower than that in dark area. Under different dose rates, the higher the dose rate is, the worse the radiation effect will be in both bright and dark areas. And the standard deviations of bright and dark areas become greater. Furthermore, through the progressive degradation analysis of the captured image, experimental results demonstrate that the attenuation of signal to noise ratio (SNR) versus radiation time is not obvious at the same dose rate, and the degradation is more and more serious with increasing dose rate. Additionally, the decrease rate of SNR at 20.0, 50.0 and 100.0 Gy/h is far greater than that at 1.0 and 10.0 Gy/h. Even so, we confirm that the HD industrial camera is still working at 10.0 Gy/h during the 8 h of measurements, with a moderate decrease of the SNR (5 dB). The work is valuable and can provide suggestion for camera users in the radiation field.

Nuclear Radiation Degradation Study on HD Camera Based on CMOS Image Sensor at Different Dose Rates

PubMed Central

Wang, Congzheng; Hu, Song; Gao, Chunming; Feng, Chang

2018-01-01

In this work, we irradiated a high-definition (HD) industrial camera based on a commercial-off-the-shelf (COTS) CMOS image sensor (CIS) with Cobalt-60 gamma-rays. All components of the camera under test were fabricated without radiation hardening, except for the lens. The irradiation experiments of the HD camera under biased conditions were carried out at 1.0, 10.0, 20.0, 50.0 and 100.0 Gy/h. During the experiment, we found that the tested camera showed a remarkable degradation after irradiation and differed in the dose rates. With the increase of dose rate, the same target images become brighter. Under the same dose rate, the radiation effect in bright area is lower than that in dark area. Under different dose rates, the higher the dose rate is, the worse the radiation effect will be in both bright and dark areas. And the standard deviations of bright and dark areas become greater. Furthermore, through the progressive degradation analysis of the captured image, experimental results demonstrate that the attenuation of signal to noise ratio (SNR) versus radiation time is not obvious at the same dose rate, and the degradation is more and more serious with increasing dose rate. Additionally, the decrease rate of SNR at 20.0, 50.0 and 100.0 Gy/h is far greater than that at 1.0 and 10.0 Gy/h. Even so, we confirm that the HD industrial camera is still working at 10.0 Gy/h during the 8 h of measurements, with a moderate decrease of the SNR (5 dB). The work is valuable and can provide suggestion for camera users in the radiation field. PMID:29419782

Predicting cancer rates in astronauts from animal carcinogenesis studies and cellular markers

NASA Technical Reports Server (NTRS)

Williams, J. R.; Zhang, Y.; Zhou, H.; Osman, M.; Cha, D.; Kavet, R.; Cuccinotta, F.; Dicello, J. F.; Dillehay, L. E.

1999-01-01

The radiation space environment includes particles such as protons and multiple species of heavy ions, with much of the exposure to these radiations occurring at extremely low average dose-rates. Limitations in databases needed to predict cancer hazards in human beings from such radiations are significant and currently do not provide confidence that such predictions are acceptably precise or accurate. In this article, we outline the need for animal carcinogenesis data based on a more sophisticated understanding of the dose-response relationship for induction of cancer and correlative cellular endpoints by representative space radiations. We stress the need for a model that can interrelate human and animal carcinogenesis data with cellular mechanisms. Using a broad model for dose-response patterns which we term the "subalpha-alpha-omega (SAO) model", we explore examples in the literature for radiation-induced cancer and for radiation-induced cellular events to illustrate the need for data that define the dose-response patterns more precisely over specific dose ranges, with special attention to low dose, low dose-rate exposure. We present data for multiple endpoints in cells, which vary in their radiosensitivity, that also support the proposed model. We have measured induction of complex chromosome aberrations in multiple cell types by two space radiations, Fe-ions and protons, and compared these to photons delivered at high dose-rate or low dose-rate. Our data demonstrate that at least three factors modulate the relative efficacy of Fe-ions compared to photons: (i) intrinsic radiosensitivity of irradiated cells; (ii) dose-rate; and (iii) another unspecified effect perhaps related to reparability of DNA lesions. These factors can produce respectively up to at least 7-, 6- and 3-fold variability. These data demonstrate the need to understand better the role of intrinsic radiosensitivity and dose-rate effects in mammalian cell response to ionizing radiation. Such understanding is critical in extrapolating databases between cellular response, animal carcinogenesis and human carcinogenesis, and we suggest that the SAO model is a useful tool for such extrapolation.

SU-F-T-12: Monte Carlo Dosimetry of the 60Co Bebig High Dose Rate Source for Brachytherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campos, L T; Almeida, C E V de

Purpose: The purpose of this work is to obtain the dosimetry parameters in accordance with the AAPM TG-43U1 formalism with Monte Carlo calculations regarding the BEBIG 60Co high-dose-rate brachytherapy. The geometric design and material details of the source was provided by the manufacturer and was used to define the Monte Carlo geometry. Methods: The dosimetry studies included the calculation of the air kerma strength Sk, collision kerma in water along the transverse axis with an unbounded phantom, dose rate constant and radial dose function. The Monte Carlo code system that was used was EGSnrc with a new cavity code, whichmore » is a part of EGS++ that allows calculating the radial dose function around the source. The XCOM photon cross-section library was used. Variance reduction techniques were used to speed up the calculation and to considerably reduce the computer time. To obtain the dose rate distributions of the source in an unbounded liquid water phantom, the source was immersed at the center of a cube phantom of 100 cm3. Results: The obtained dose rate constant for the BEBIG 60Co source was 1.108±0.001 cGyh-1U-1, which is consistent with the values in the literature. The radial dose functions were compared with the values of the consensus data set in the literature, and they are consistent with the published data for this energy range. Conclusion: The dose rate constant is consistent with the results of Granero et al. and Selvam and Bhola within 1%. Dose rate data are compared to GEANT4 and DORZnrc Monte Carlo code. However, the radial dose function is different by up to 10% for the points that are notably near the source on the transversal axis because of the high-energy photons from 60Co, which causes an electronic disequilibrium at the interface between the source capsule and the liquid water for distances up to 1 cm.« less

Febrile Neutropenia Rates According to Body Mass Index and Dose Capping in Women Receiving Chemotherapy for Early Breast Cancer.

PubMed

Lote, H; Sharp, A; Redana, S; Papadimitraki, E; Capelan, M; Ring, A

2016-09-01

Studies suggest worse outcomes in obese women with breast cancer than in non-obese women. One potential reason may be that oncologists 'dose cap' adjuvant chemotherapy in obese patients in order to avoid excessive toxicity. Reductions from standard dosing may compromise survival outcomes in the curative setting. Here we describe the body mass index (BMI) distribution of patients in a non-trial population, the frequency with which oncologists dose cap and its effect on febrile neutropenia chemotherapy toxicity. In this non-randomised study, electronic patient records retrospectively identified patients with early breast cancer who initiated neoadjuvant or adjuvant chemotherapy at the Royal Marsden Hospital between 1 January and 31 December 2013. Baseline data included age, BMI, performance status, tumour characteristics, granulocyte colony-stimulating factor and comorbidities. Chemotherapy doses, rates of dose capping across BMI groups and rates of febrile neutropenia were reported. In total, 325 patients were eligible: 79 (24.5%) were obese (BMI ≥ 30), 109 (33.5%) were overweight (BMI ≥25 - <30) and 137 (42%) were normal bodyweight (BMI < 25). Sixteen patients (20.5%) in the obese group received dose-capped chemotherapy. Overall, 62 patients (19%) had an episode of febrile neutropenia. Obese patients receiving uncapped chemotherapy did not experience a significant difference in febrile neutropenia rates when compared with overweight or normal bodyweight groups (P = 0.5798). The febrile neutropenia rate in obese patients receiving capped chemotherapy was 6.5%, compared with 24% in obese patients receiving uncapped chemotherapy (P = 0.1216). In a non-trial population of obese patients, dose capping is frequently used. Obese patients receiving uncapped chemotherapy do not experience increased febrile neutropenia rates when compared with uncapped overweight or normal bodyweight patients. Furthermore, dose capping was associated with a trend towards lower rates of febrile neutropenia than in other groups and may indicate relative under-dosing of chemotherapy. This supports international guidelines that state that obese patients should not be dose capped. Copyright © 2016 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

Novel Radiobiological Gamma Index for Evaluation of 3-Dimensional Predicted Dose Distribution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sumida, Iori, E-mail: sumida@radonc.med.osaka-u.ac.jp; Yamaguchi, Hajime; Kizaki, Hisao

2015-07-15

Purpose: To propose a gamma index-based dose evaluation index that integrates the radiobiological parameters of tumor control (TCP) and normal tissue complication probabilities (NTCP). Methods and Materials: Fifteen prostate and head and neck (H&N) cancer patients received intensity modulated radiation therapy. Before treatment, patient-specific quality assurance was conducted via beam-by-beam analysis, and beam-specific dose error distributions were generated. The predicted 3-dimensional (3D) dose distribution was calculated by back-projection of relative dose error distribution per beam. A 3D gamma analysis of different organs (prostate: clinical [CTV] and planned target volumes [PTV], rectum, bladder, femoral heads; H&N: gross tumor volume [GTV], CTV,more » spinal cord, brain stem, both parotids) was performed using predicted and planned dose distributions under 2%/2 mm tolerance and physical gamma passing rate was calculated. TCP and NTCP values were calculated for voxels with physical gamma indices (PGI) >1. We propose a new radiobiological gamma index (RGI) to quantify the radiobiological effects of TCP and NTCP and calculate radiobiological gamma passing rates. Results: The mean RGI gamma passing rates for prostate cases were significantly different compared with those of PGI (P<.03–.001). The mean RGI gamma passing rates for H&N cases (except for GTV) were significantly different compared with those of PGI (P<.001). Differences in gamma passing rates between PGI and RGI were due to dose differences between the planned and predicted dose distributions. Radiobiological gamma distribution was visualized to identify areas where the dose was radiobiologically important. Conclusions: RGI was proposed to integrate radiobiological effects into PGI. This index would assist physicians and medical physicists not only in physical evaluations of treatment delivery accuracy, but also in clinical evaluations of predicted dose distribution.« less

“Hallucinations” Following Acute Cannabis Dosing: A Case Report and Comparison to Other Hallucinogenic Drugs

PubMed Central

Barrett, Frederick S.; Schlienz, Nicolas J.; Lembeck, Natalie; Waqas, Muhammad; Vandrey, Ryan

2018-01-01

Abstract Introduction: Cannabis has been historically classified as a hallucinogen. However, subjective cannabis effects do not typically include hallucinogen-like effects. Empirical reports of hallucinogen-like effects produced by cannabis in controlled settings, particularly among healthy research volunteers, are rare and have mostly occurred after administration of purified Δ-9 tetrahydrocannabinol (THC) rather than whole plant cannabis. Methods: The case of a healthy 30-year-old male who experienced auditory and visual hallucinations in a controlled laboratory study after inhaling vaporized cannabis that contained 25 mg THC (case dose) is presented. Ratings on the Hallucinogen Rating Scale (HRS) following the case dose are compared with HRS ratings obtained from the participant after other doses of cannabis and with archival HRS data from laboratory studies involving acute doses of cannabis, psilocybin, dextromethorphan (DXM), and salvinorin A. Results: Scores on the Volition subscale of the HRS were greater for the case dose than for the maximum dose administered in any other comparison study. Scores on the Intensity and Perception subscales were greater for the case dose than for the maximum dose of cannabis, psilocybin, or salvinorin A. Scores on the Somaesthesia subscale were greater for the case dose than for the maximum dose of DXM, salvinorin A, or cannabis. Scores on the Affect and Cognition subscales for the case dose were significantly lower than for the maximum doses of psilocybin and DXM. Conclusion: Acute cannabis exposure in a healthy adult male resulted in self-reported hallucinations that rated high in magnitude on several subscales of the HRS. However, the hallucinatory experience in this case was qualitatively different than that typically experienced by participants receiving classic and atypical hallucinogens, suggesting that the hallucinatory effects of cannabis may have a unique pharmacological mechanism of action. This type of adverse event needs to be considered in the clinical use of cannabis. PMID:29682608

Caffeine induces a second wave of apoptosis after low dose-rate gamma radiation of HL-60 cells.

PubMed

Vávrová, Jirina; Mareková-Rezácová, Martina; Vokurková, Doris; Szkanderová, Sylva; Psutka, Jan

2003-10-01

Most cell lines that lack functional p53 protein are arrested in the G(2) phase of the cell cycle due to DNA damage. It was previously found that the human promyelocyte leukemia cells HL-60 (TP53 negative) that had been exposed to ionizing radiation at doses up to 10 Gy were arrested in the G(2) phase for a period of 24 h. The radioresistance of HL-60 cells that were exposed to low dose-rate gamma irradiation of 3.9 mGy/min, which resulted in a pronounced accumulation of the cells in the G(2) phase during the exposure period, increased compared with the radioresistance of cells that were exposed to a high dose-rate gamma irradiation of 0.6 Gy/min. The D(0) value (i.e. the radiation dose leading to 37% cell survival) for low dose-rate radiation was 3.7 Gy and for high dose-rate radiation 2.2 Gy. In this study, prevention of G(2) phase arrest by caffeine (2 mM) and irradiation of cells with low dose-rate irradiation in all phases of the cell cycle proved to cause radiosensitization (D(0)=2.2 Gy). The irradiation in the presence of caffeine resulted in a second wave of apoptosis on days 5-7 post-irradiation. Caffeine-induced apoptosis occurring later than day 7 post-irradiation is postulated to be a result of unscheduled DNA replication and cell cycle progress.

Effects of Solar Particle Event Proton Radiation on Parameters Related to Ferret Emesis

PubMed Central

Sanzari, J. K.; Wan, X. S.; Krigsfeld, G. S.; King, G. L.; Miller, A.; Mick, R.; Gridley, D. S.; Wroe, A. J.; Rightnar, S.; Dolney, D.; Kennedy, A. R.

2013-01-01

The effectiveness of simulated solar particle event (SPE) proton radiation to induce retching and vomiting was evaluated in the ferret experimental animal model. The endpoints measured in the study included: (1) the fraction of animals that retched or vomited, (2) the number of retches or vomits observed, (3) the latency period before the first retch or vomit and (4) the duration between the first and last retching or vomiting events. The results demonstrated that γ ray and proton irradiation delivered at a high dose rate of 0.5 Gy/min induced dose-dependent changes in the endpoints related to retching and vomiting. The minimum radiation doses required to induce statistically significant changes in retching- and vomiting-related endpoints were 0.75 and 1.0 Gy, respectively, and the relative biological effectiveness (RBE) of proton radiation at the high dose rate did not significantly differ from 1. Similar but less consistent and smaller changes in the retching- and vomiting-related endpoints were observed for groups irradiated with γ rays and protons delivered at a low dose rate of 0.5 Gy/h. Since this low dose rate is similar to a radiation dose rate expected during a SPE, these results suggest that the risk of SPE radiation-induced vomiting is low and may reach statistical significance only when the radiation dose reaches 1 Gy or higher. PMID:23883319

Dose responses for adaption to low doses of (60)Co gamma rays and (3)H beta particles in normal human fibroblasts.

PubMed

Broome, E J; Brown, D L; Mitchel, R E J

2002-08-01

The dose response for adaption to radiation at low doses was compared in normal human fibroblasts (AG1522) exposed to either (60)Co gamma rays or (3)H beta particles. Cells were grown in culture to confluence and exposed at either 37 degrees C or 0 degrees C to (3)H beta-particle or (60)Co gamma-ray adapting doses ranging from 0.1 mGy to 500 mGy. These cells, and unexposed control cells, were allowed to adapt during a fixed 3-h, 37 degrees C incubation prior to a 4-Gy challenge dose of (60)Co gamma rays. Adaption was assessed by measuring micronucleus frequency in cytokinesis-blocked, binucleate cells. No adaption was detected in cells exposed to (60)Co gamma radiation at 37 degrees C after a dose of 0.1 mGy given at a low dose rate or to 500 mGy given at a high dose rate. However, low-dose-rate exposure (1-3 mGy/min) to any dose between 1 and 500 mGy from either radiation, delivered at either temperature, caused cells to adapt and reduced the micronucleus frequency that resulted from the subsequent 4-Gy exposure. Within this dose range, the magnitude of the reduction was the same, regardless of the dose or radiation type. These results demonstrate that doses as low as (on average) about one track per cell (1 mGy) produce the same maximum adaptive response as do doses that deposit many tracks per cell, and that the two radiations were not different in this regard. Exposure at a temperature where metabolic processes, including DNA repair, were inactive (0 degrees C) did not alter the result, indicating that the adaptive response is not sensitive to changes in the accumulation of DNA damage within this range. The results also show that the RBE for low doses of tritium beta-particle radiation is 1, using adaption as the end point.

Mathematical optimization of high dose-rate brachytherapy—derivation of a linear penalty model from a dose-volume model

NASA Astrophysics Data System (ADS)

Morén, B.; Larsson, T.; Carlsson Tedgren, Å.

2018-03-01

High dose-rate brachytherapy is a method for cancer treatment where the radiation source is placed within the body, inside or close to a tumour. For dose planning, mathematical optimization techniques are being used in practice and the most common approach is to use a linear model which penalizes deviations from specified dose limits for the tumour and for nearby organs. This linear penalty model is easy to solve, but its weakness lies in the poor correlation of its objective value and the dose-volume objectives that are used clinically to evaluate dose distributions. Furthermore, the model contains parameters that have no clear clinical interpretation. Another approach for dose planning is to solve mixed-integer optimization models with explicit dose-volume constraints which include parameters that directly correspond to dose-volume objectives, and which are therefore tangible. The two mentioned models take the overall goals for dose planning into account in fundamentally different ways. We show that there is, however, a mathematical relationship between them by deriving a linear penalty model from a dose-volume model. This relationship has not been established before and improves the understanding of the linear penalty model. In particular, the parameters of the linear penalty model can be interpreted as dual variables in the dose-volume model.

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.

Dose-rate plays a significant role in synchrotron radiation X-ray-induced damage of rodent testes.

PubMed

Chen, Heyu; Wang, Ban; Wang, Caixia; Cao, Wei; Zhang, Jie; Ma, Yingxin; Hong, Yunyi; Fu, Shen; Wu, Fan; Ying, Weihai

2016-01-01

Synchrotron radiation (SR) X-ray has significant potential for applications in medical imaging and cancer treatment. However, the mechanisms underlying SR X-ray-induced tissue damage remain unclear. Previous studies on regular X-ray-induced tissue damage have suggested that dose-rate could affect radiation damage. Because SR X-ray has exceedingly high dose-rate compared to regular X-ray, it remains to be determined if dose-rate may affect SR X-ray-induced tissue damage. We used rodent testes as a model to investigate the role of dose-rate in SR X-ray-induced tissue damage. One day after SR X-ray irradiation, we determined the effects of the irradiation of the same dosage at two different dose-rates, 0.11 Gy/s and 1.1 Gy/s, on TUNEL signals, caspase-3 activation and DNA double-strand breaks (DSBs) of the testes. Compared to those produced by the irradiation at 0.11 Gy/s, irradiation at 1.1 Gy/s produced higher levels of DSBs, TUNEL signals, and caspase-3 activation in the testes. Our study has provided the first evidence suggesting that dose-rate could be a significant factor in SR X-ray-induced tissue damage, which may establish a valuable base for utilizing this factor to manipulate the tissue damage in SR X-ray-based medical applications.

Dose-rate plays a significant role in synchrotron radiation X-ray-induced damage of rodent testes

PubMed Central

Chen, Heyu; Wang, Ban; Wang, Caixia; Cao, Wei; Zhang, Jie; Ma, Yingxin; Hong, Yunyi; Fu, Shen; Wu, Fan; Ying, Weihai

2016-01-01

Synchrotron radiation (SR) X-ray has significant potential for applications in medical imaging and cancer treatment. However, the mechanisms underlying SR X-ray-induced tissue damage remain unclear. Previous studies on regular X-ray-induced tissue damage have suggested that dose-rate could affect radiation damage. Because SR X-ray has exceedingly high dose-rate compared to regular X-ray, it remains to be determined if dose-rate may affect SR X-ray-induced tissue damage. We used rodent testes as a model to investigate the role of dose-rate in SR X-ray-induced tissue damage. One day after SR X-ray irradiation, we determined the effects of the irradiation of the same dosage at two different dose-rates, 0.11 Gy/s and 1.1 Gy/s, on TUNEL signals, caspase-3 activation and DNA double-strand breaks (DSBs) of the testes. Compared to those produced by the irradiation at 0.11 Gy/s, irradiation at 1.1 Gy/s produced higher levels of DSBs, TUNEL signals, and caspase-3 activation in the testes. Our study has provided the first evidence suggesting that dose-rate could be a significant factor in SR X-ray-induced tissue damage, which may establish a valuable base for utilizing this factor to manipulate the tissue damage in SR X-ray-based medical applications. PMID:28078052

The use of ionisation chambers for dose rate measurements at industrial irradiation plants

NASA Astrophysics Data System (ADS)

Sephton, J. P.; Sharpe, P. H. G.; Chu, R. D. H.

2002-03-01

The use of ionisation chambers to measure dose rate at industrial irradiation plants has been studied as part of a wider project on real time dosimetry. The characteristics required of such a chamber are discussed. These include the ability to withstand operation at high cumulative doses (up to 5 MGy) and dose rates of up to about 150 kGy h -1. Other desirable features are water equivalence and immunity to environmental conditions such as temperature, pressure and humidity. A number of chambers have been assessed experimentally and a suitable chamber selected. The dosimetric characteristics of the chosen chamber have been assessed by comparison with absorbed dose measurements made using chemical dosimeters.

Gamma Radiation Doses In Sweden

NASA Astrophysics Data System (ADS)

Almgren, Sara; Barregârd, Lars; Isaksson, Mats

2008-08-01

Gamma dose rate measurements were performed in one urban and one rural area using thermoluminescence dosimeters (TLD) worn by 46 participants and placed in their dwellings. The personal effective dose rates were 0.096±0.019(1 SD) and 0.092±0.016(1 SD)μSv/h in the urban and rural area, respectively. The corresponding dose rates in the dwellings were 0.11±0.042(1 SD) and 0.091±0.026(1 SD)μSv/h. However, the differences between the areas were not significant. The values were higher in buildings made of concrete than of wood and higher in apartments than in detached houses. Also, 222Rn measurements were performed in each dwelling, which showed no correlation with the gamma dose rates in the dwellings.

Characterization of the radiation environment at the UNLV accelerator facility during operation of the Varian M6 linac

NASA Astrophysics Data System (ADS)

Hodges, M.; Barzilov, A.; Chen, Y.; Lowe, D.

2016-10-01

The bremsstrahlung photon flux from the UNLV particle accelerator (Varian M6 model) was determined using MCNP5 code for 3 MeV and 6 MeV incident electrons. Human biological equivalent dose rates due to accelerator operation were evaluated using the photon flux with the flux-to-dose conversion factors. Dose rates were computed for the accelerator facility for M6 linac use under different operating conditions. The results showed that the use of collimators and linac internal shielding significantly reduced the dose rates throughout the facility. It was shown that the walls of the facility, in addition to the earthen berm enveloping the building, provide equivalent shielding to reduce dose rates outside to below the 2 mrem/h limit.

Immunogenicity and safety of 1 vs 2 doses of quadrivalent meningococcal conjugate vaccine in youth infected with human immunodeficiency virus.

PubMed

Lujan-Zilbermann, Jorge; Warshaw, Meredith G; Williams, Paige L; Spector, Stephen A; Decker, Michael D; Abzug, Mark J; Heckman, Barb; Manzella, Adam; Kabat, Bill; Jean-Philippe, Patrick; Nachman, Sharon; Siberry, George K

2012-10-01

To compare the immunogenicity of 1 vs 2 doses of meningococcal polysaccharide conjugate vaccine (MCV4) in youth infected with human immunodeficiency virus (HIV). P1065 was a phase I/II immunogenicity and safety trial of MCV4 in 324 youth infected with HIV performed at 27 sites of the International Maternal Pediatric Adolescent AIDS Clinical Trials Group network in the US. At entry subjects received 1 dose of MCV4. At 24 weeks, those with screening cluster of differentiation 4 (CD4)% ≥ 15 were randomized to receive a second dose or not, and all with screening CD4% <15 received a second dose. Immunogenicity was evaluated as the proportion of subjects with a ≥ 4-fold rise from entry in serum bactericidal antibody against each meningococcal serogroup (SG) at weeks 28 and 72. Logistic regression models adjusting for HIV disease severity were used to evaluate the effect of 1 vs 2 MCV4 doses among those with screening CD4% ≥ 15. Subjects randomized to receive 2 vs 1 MCV4 dose had significantly higher response rates to all SGs at week 28 and to all except Neisseria meningitidis SG Y at week 72, with adjusted ORs of 2.5-5.6. In 31 subjects with screening CD4% <15 who received 2 MCV4 doses, response rates ranged from 22%-55% at week 28 and 6%-28% at week 72. In youth infected with HIV with a CD4% ≥ 15, a second dose of MCV4 given 6 months after the initial dose significantly improves response rates at 28 and 72 weeks. Subjects with CD4% <15 at entry had lower response rates despite 2 doses of MCV4. Copyright © 2012 Mosby, Inc. All rights reserved.

Chromosome translocations in T. scripta: the dose-rate effect and in vivo lymphocyte radiation response.

PubMed

Ulsh, B A; Whicker, F W; Congdon, J D; Bedford, J S; Hinton, T G

2001-01-01

Using a whole-chromosome FISH painting probe we previously developed for chromosome 1 of the yellow-bellied slider turtle (Trachemys scripta), we investigated the dose-rate effect for radiation-induced symmetrical translocations in T. scripta fibroblasts and lymphocytes. The dose rate below which no reduction in effect per unit dose is observed with further dose protraction was approximately 23 cGy h(-1). We estimated the whole-genome spontaneous background level of complete, apparently simple symmetrical translocations in T. scripta lymphocytes to be approximately 1.20 x 10(-3)/cell projected from aberrations occurring in chromosome 1. Similar spontaneous background levels reported for humans are some 6- to 25-fold higher, ranging from about 6 x 10(-3) to 3.4 x 10(-2) per cell. This relatively low background level for turtles would be a significant advantage for resolution of effects at low doses and dose rates. We also chronically irradiated turtles over a range of doses from 0-8 Gy delivered at approximately 5.5 cGy h(-1) and constructed a lymphocyte dose-response curve for complete, apparently simple symmetrical translocations suitable for use with animals chronically exposed to radiation in contaminated environments. The best-fitting calibration curve (not constrained through the zero dose estimate) was of the form Y(as) = c + aD + bD(2), where Y(as) was the number of apparently simple symmetrical translocations per cell, D was the dose (Gy), a = (0.0058 +/- 0.0009), b = (-0.00033 +/- 0.00011), and c = (0.0015 +/- 0.0013). With additional whole-chromosome probes to improve sensitivity, environmental biodosimetry using stable chromosome translocations could provide a practical and genetically relevant measurement end point for ecological risk assessments and biomonitoring programs.

Inverse Planning Approach for 3-D MRI-Based Pulse-Dose Rate Intracavitary Brachytherapy in Cervix Cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chajon, Enrique; Dumas, Isabelle; Touleimat, Mahmoud B.Sc.

2007-11-01

Purpose: The purpose of this study was to evaluate the inverse planning simulated annealing (IPSA) software for the optimization of dose distribution in patients with cervix carcinoma treated with MRI-based pulsed-dose rate intracavitary brachytherapy. Methods and Materials: Thirty patients treated with a technique using a customized vaginal mold were selected. Dose-volume parameters obtained using the IPSA method were compared with the classic manual optimization method (MOM). Target volumes and organs at risk were delineated according to the Gynecological Brachytherapy Group/European Society for Therapeutic Radiology and Oncology recommendations. Because the pulsed dose rate program was based on clinical experience with lowmore » dose rate, dwell time values were required to be as homogeneous as possible. To achieve this goal, different modifications of the IPSA program were applied. Results: The first dose distribution calculated by the IPSA algorithm proposed a heterogeneous distribution of dwell time positions. The mean D90, D100, and V100 calculated with both methods did not differ significantly when the constraints were applied. For the bladder, doses calculated at the ICRU reference point derived from the MOM differed significantly from the doses calculated by the IPSA method (mean, 58.4 vs. 55 Gy respectively; p = 0.0001). For the rectum, the doses calculated at the ICRU reference point were also significantly lower with the IPSA method. Conclusions: The inverse planning method provided fast and automatic solutions for the optimization of dose distribution. However, the straightforward use of IPSA generated significant heterogeneity in dwell time values. Caution is therefore recommended in the use of inverse optimization tools with clinical relevance study of new dosimetric rules.« less

Monte Carlo calculation of the neutron dose to a fetus at commercial flight altitudes

NASA Astrophysics Data System (ADS)

Alves, M. C.; Galeano, D. C.; Santos, W. S.; Hunt, John G.; d'Errico, Francesco; Souza, S. O.; de Carvalho Júnior, A. B.

2017-11-01

Aircrew members are exposed to primary cosmic rays as well as to secondary radiations from the interaction of cosmic rays with the atmosphere and with the aircraft. The radiation field at flight altitudes comprises neutrons, protons, electrons, positrons, photons, muons and pions. Generally, 50% of the effective dose to airplane passengers is due to neutrons. Care must be taken especially with pregnant aircrew members and frequent fliers so that the equivalent dose to the fetus will not exceed prescribed limits during pregnancy (1 mSv according to ICRP, and 5 mSv according to NCRP). Therefore, it is necessary to evaluate the equivalent dose to a fetus in the maternal womb. Up to now, the equivalent dose rate to a fetus at commercial flight altitudes was obtained using stylized pregnant-female phantom models. The aim of this study was calculating neutron fluence to dose conversion coefficients for a fetus of six months of gestation age using a new, realistic pregnant-female mesh-phantom. The equivalent dose rate to a fetus during an intercontinental flight was also calculated by folding our conversion coefficients with published spectral neutron flux data. The calculated equivalent dose rate to the fetus was 2.35 μSv.h-1, that is 1.5 times higher than equivalent dose rates reported in the literature. The neutron fluence to dose conversion coefficients for the fetus calculated in this study were 2.7, 3.1 and 3.9 times higher than those from previous studies using fetus models of 3, 6 and 9 months of gestation age, respectively. The differences between our study and data from the literature highlight the importance of using more realistic anthropomorphic phantoms to estimate doses to a fetus in pregnant aircrew members.

Three-dimensional dosimetric considerations from different point A definitions in cervical cancer low-dose-rate brachytherapy

PubMed Central

Chen, Ting; Kim, Leonard H.; Nelson, Carl; Gabel, Molly; Narra, Venkat; Haffty, Bruce; Yue, Ning J.

2013-01-01

Purpose To investigate the dosimetric difference due to the different point A definitions in cervical cancer low-dose-rate (LDR) intracavitary brachytherapy. Material and methods Twenty CT-based LDR brachytherapy plans of 11 cervical patients were retrospectively reviewed. Two plans with point As following the modified Manchester system which defines point A being 2 cm superior to the cervical os along the tandem and 2 cm lateral (Aos), and the American Brachytherapy Society (ABS) guideline definition in which the point A is 2 cm superior to the vaginal fornices instead of os (Aovoid) were generated. Using the same source strength, two plans prescribed the same dose to Aos and Aovoid. Dosimetric differences between plans including point A dose rate, treatment volume encompassed by the prescription isodose line (TV), and dose rate of 2 cc of the rectum and bladder to the prescription dose were measured. Results On average Aovoid was 8.9 mm superior to Aos along the tandem direction with a standard deviation of 5.4 mm. With the same source strength and arrangement, Aos dose rate was 19% higher than Aovoid dose rate. The average TV(Aovoid) was 118.0 cc, which was 30% more than the average TV(Aos) of 93.0 cc. D2cc/D(Aprescribe) increased from 51% to 60% for rectum, and increased from 89% and 106% for bladder, if the prescription point changed from Aos to Aovoid. Conclusions Different point A definitions lead to significant dose differences. Careful consideration should be given when changing practice from one point A definition to another, to ensure dosimetric and clinical equivalency from the previous clinical experiences. PMID:24474971

Prediction of obliteration after gamma knife surgery for cerebral arteriovenous malformations.

PubMed

Karlsson, B; Lindquist, C; Steiner, L

1997-03-01

To define the factors of importance for the obliteration of cerebral arteriovenous malformations (AVMs), thus making a prediction of the probability for obliteration possible. In 945 AVMs of a series of 1319 patients treated with the gamma knife during 1970 to 1990, the relationship between patient, AVMs, and treatment parameters on the one hand and the obliteration of the nidus on the other was analyzed. The obliteration rate increased both with increased minimum (lowest periphery) and average dose and decreased with increased AVM volume. The minimum dose to the AVMs was the decisive dose factor for the treatment result. The higher the minimum dose, the higher the chance for total obliteration. The curve illustrating this relation increased logarithmically to a value of 87%. A higher average dose shortened the latency to AVM obliteration. For the obliterated cases, the larger the malformation, the lower the minimum dose used. This prompted us to relate the obliteration rate to the product minimum dose (AVM volume)1/3 (K index). The obliteration rate increased linearly with the K index up to a value of approximately 27, and for higher K values, the obliteration rate had a constant value of approximately 80%. For the group of 273 cases treated with a minimum dose of at least 25 Gy, the obliteration rate at the study end point (defined as 2-yr latency) was 80% (95% confidence interval = 75-85%). If obliterations that occurred beyond the end point are included, the obliteration rate increased to 85% (81-89%). The probability of obliteration of AVMs after gamma knife surgery is related both to the lowest dose to the AVMs and the AVM volume, and it can be predicted using the K index.

Individualized Radiation Dose Escalation Based on the Decrease in Tumor FDG Uptake and Normal Tissue Constraints Improve Survival in Patients With Esophageal Carcinoma.

PubMed

Ma, Jinbo; Wang, Zhaoyang; Wang, Chengde; Chen, Ercheng; Dong, Yaozong; Song, Yipeng; Wang, Wei; You, Dong; Jiang, Wei; Zang, Rukun

2017-02-01

To determine whether individualized radiation dose escalation after planned chemoradiation based on the decrease in tumor and normal tissue constraints can improve survival in patients with esophageal carcinoma. From August 2005 to December 2010, 112 patients with squamous esophageal carcinoma were treated with radical concurrent chemoradiation. Patients received positron emission tomography-computer tomography scan twice, before radiation and after radiation dose of 50.4 Gy. All patients were noncomplete metabolic response groups according to the Response Evaluation Criteria in solid tumors. Only 52 patients with noncomplete metabolic response received individualized dose escalation based on tumor and normal tissue constraints. Survival and treatment failure were observed and analyzed using SPSS (13.0). The rate of complete metabolic response for patients with noncomplete metabolic response after dose escalation reached 17.3% (9 of 52). The 2-year overall survival rates for patients with noncomplete metabolic response in the conventional and dose-escalation groups were 20.5% and 42.8%, respectively( P = .001). The 2-year local control rates for patients were 35.7% and 76.2%, respectively ( P = .002). When patients were classified into partial metabolic response and no metabolic response, 2-year overall survival rates for patients with partial metabolic response were significantly different in conventional and dose-escalation groups (33.8% vs 78.4%; P = .000). The 2-year overall survival rates for patients with no metabolic response in two groups (8.6% vs 15.1%) did not significantly differ ( P = .917). Individualized radiation dose escalation has the potential to improve survival in patients with esophageal carcinoma according to increased rate of complete metabolic response. However, further trials are needed to confirm this and to identify patients who may benefit from dose escalation.

Dose estimation and dating of pottery from Turkey

NASA Astrophysics Data System (ADS)

Altay Atlıhan, M.; Şahiner, Eren; Soykal Alanyalı, Feriştah

2012-06-01

The luminescence method is a widely used technique for environmental dosimetry and dating archaeological, geological materials. In this study, equivalent dose (ED) and annual dose rate (AD) of an archaeological sample were measured. The age of the material was calculated by means of equivalent dose divided by the annual dose rate. The archaeological sample was taken from Antalya, Turkey. Samples were prepared by the fine grain technique and equivalent dose was found using multiple-aliquot-additive-dose (MAAD) and single aliquot regeneration (SAR) techniques. Also the short shine normalization-MAAD and long shine normalization-MAAD were applied and the results of the methods were compared with each other. The optimal preheat temperature was found to be 200 °C for 10 min. The annual doses of concentrations of the major radioactive isotopes were determined using a high-purity germanium detector and a low-level alpha counter. The age of the sample was found to be 510±40 years.

EFFECTS OF WEST NILE VIRUS DOSE AND EXTRINSIC INCUBATION TEMPERATURE ON TEMPORAL PROGRESSION OF VECTOR COMPETENCE IN CULEX PIPIENS QUINQUEFASCIATUS

PubMed Central

ANDERSON, SHERI L.; RICHARDS, STEPHANIE L.; TABACHNICK, WALTER J.; SMARTT, CHELSEA T.

2010-01-01

Culex pipiens quinquefasciatus were fed blood containing either 7.0 ± 0.1 logs plaque-forming units (pfu)/ml (high dose) or 5.9 ± 0.1 logs pfu/ml (low dose) of West Nile virus and held at extrinsic incubation temperatures (EIT) of 28°C or 25°C. Approximately 20 mosquitoes per dose were collected after incubation periods (IP) of 4, 6, 8, and 12 days postinfection (dpi). Infection rates were influenced by EIT and virus dose but not by IP. Body titer was significantly higher for mosquitoes fed the high dose and held at 28°C at the later IPs (6, 8, and 12 dpi). However, leg titer was significantly higher for mosquitoes at the later IPs but did not differ between EITs or doses. Because infection rates varied with EIT and dose, there is likely a midgut infection barrier influenced by these factors that is not influenced by IP. Dissemination rates were influenced by all 3 factors consistent with the presence of a midgut escape barrier. Dissemination rate, body titer, and leg titer were dependent on IP, indicating the need to investigate multiple time points in vector competence studies to elucidate critical events in infection and dissemination. PMID:20402358

Effects of West Nile virus dose and extrinsic incubation temperature on temporal progression of vector competence in Culex pipiens quinquefasciatus.

PubMed

Anderson, Sheri L; Richards, Stephanie L; Tabachnick, Walter J; Smartt, Chelsea T

2010-03-01

Culex pipiens quinquefasciatus were fed blood containing either 7.0 +/- 0.1 logs plaque-forming units (pfu)/ml (high dose) or 5.9 +/- 0.1 logs pfu/ml (low dose) of West Nile virus and held at extrinsic incubation temperatures (EIT) of 28 degrees C or 25 degrees C. Approximately 20 mosquitoes per dose were collected after incubation periods (IP) of 4, 6, 8, and 12 days postinfection (dpi). Infection rates were influenced by EIT and virus dose but not by IP. Body titer was significantly higher for mosquitoes fed the high dose and held at 28 degrees C at the later IPs (6, 8, and 12 dpi). However, leg titer was significantly higher for mosquitoes at the later IPs but did not differ between EITs or doses. Because infection rates varied with EIT and dose, there is likely a midgut infection barrier influenced by these factors that is not influenced by IP. Dissemination rates were influenced by all 3 factors consistent with the presence of a midgut escape barrier. Dissemination rate, body titer, and leg titer were dependent on IP, indicating the need to investigate multiple time points in vector competence studies to elucidate critical events in infection and dissemination.

Estimation of Effective Dose from External Exposure in The Six Prefectures adjacent to Fukushima Prefecture

NASA Astrophysics Data System (ADS)

Miyatake, Hirokazu; Yoshizawa, Nobuaki; Hirakawa, Sachiko; Murakami, Kana; Takizawa, Mari; Kawai, Masaki; Sato, Osamu; Takagi, Shunji; Suzuki, Gen

2017-09-01

The Fukushima Daiichi Nuclear Power Plant accident caused a release of radionuclides. Radionuclides were deposited on the ground not only in Fukushima prefecture but also in nearby prefectures. Since the accident, measurement of radiation in environment such as air dose rate and deposition density of radionuclides has been performed by many organizations and universities. In particular, Japan Atomic Energy Agency (JAEA) has been performing observations of air dose rate using a car-borne survey system continuously and over wide areas. In our study, using the data measured by JAEA, we estimated effective dose from external exposure in the six prefectures adjacent to Fukushima prefecture. Since car-borne survey was started a few months later after the accident, measured air dose rate in this method is mainly contributed by 137Cs and 134Cs whose half-lives are relatively long. Therefore, based on air dose rate of 137Cs and 134Cs and the ratio of deposition density of short-half-life nuclides to that of 137Cs and 134Cs, we also estimated effective dose contributed from not only 137Cs and 134Cs but also other short-half-life nuclides. We compared the effective dose estimated by the method above with that of UNSCEAR and measured data using personal dosimeters in some areas.

Multi-scale simulation of radiation damage accumulation and subsequent hardening in neutron-irradiated α-Fe

DOE PAGES

Dunn, Aaron; Dingreville, Remi; Capolungo, Laurent

2015-11-27

A hierarchical methodology is introduced to predict the effects of radiation damage and irradiation conditions on the yield stress and internal stress heterogeneity developments in polycrystalline α-Fe. Simulations of defect accumulation under displacement cascade damage conditions are performed using spatially resolved stochastic cluster dynamics. The resulting void and dislocation loop concentrations and average sizes are then input into a crystal plasticity formulation that accounts for the change in critical resolved shear stress due to the presence of radiation induced defects. The simulated polycrystalline tensile tests show a good match to experimental hardening data over a wide range of irradiation doses.more » With this capability, stress heterogeneity development and the effect of dose rate on hardening is investigated. The model predicts increased hardening at higher dose rates for low total doses. By contrast, at doses above 10 –2 dpa when cascade overlap becomes significant, the model does not predict significantly different hardening for different dose rates. In conclusion, the development of such a model enables simulation of radiation damage accumulation and associated hardening without relying on experimental data as an input under a wide range of irradiation conditions such as dose, dose rate, and temperature.« less

Mumps Postexposure Prophylaxis with a Third Dose of Measles-Mumps-Rubella Vaccine, Orange County, New York, USA

PubMed Central

Lawler, Jacqueline; Curns, Aaron T.; Brandeburg, Christina; Wallace, Gregory S.

2013-01-01

Although the measles-mumps-rubella (MMR) vaccine is not recommended for mumps postexposure prophylaxis (PEP), data on its effectiveness are limited. During the 2009–2010 mumps outbreak in the northeastern United States, we assessed effectiveness of PEP with a third dose of MMR vaccine among contacts in Orthodox Jewish households who were given a third dose within 5 days of mumps onset in the household’s index patient. We compared mumps attack rates between persons who received a third MMR dose during the first incubation period after onset in the index patient and 2-dose vaccinated persons who had not. Twenty-eight (11.7%) of 239 eligible household members received a third MMR dose as PEP. Mumps attack rates were 0% among third-dose recipients versus 5.2% among 2-dose recipients without PEP (p = 0.57). Although a third MMR dose administered as PEP did not have a significant effect, it may offer some benefits in specific outbreak contexts. PMID:23965729

SU-F-T-322: A Comparison of Two Si Detectors for in Vivo Dosimetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Talarico, O; Krylova, T; Lebedenko, I

Purpose: To compare two types of semiconductor detectors for in vivo dosimetry by their dependence from various parameters in different conditions. Methods: QED yellow (Sun Nuclear) and EDP (Scanditronix) Si detectors were radiated by a Varian Clinac 2300 ix with 6 and 18 MV energies. 10 cm thickness water equivalent phantom consisted of 30×30 cm{sup 2} squared plates was used for experiments. Dose dependencies for different beam angles (0 – 180°), field size (3–40 cm), dose (50 – 300 MU), and dose rates (50 – 300 MU/min) were obtained and calibrated with Standard Farmer chamber (PTW). Results: Reproducibility, linearity, dosemore » rate, angular dependence, and field size dependence were obtained for QED and EDP. They show no dose-rate dependence in available clinical dose rate range (100–600 MU/min). Both diodes have linear dependence with increasing the dose. Therefore even in case of high radiation therapy (including total body irradiation) it is not necessary to apply an additional correction during in vivo dosimetry. The diodes have different behavior for angular and field size dependencies. QED diode showed that dose value is stable for beam angles from 0 to 60°, for 60–180° correction factor has to be applied for each beam angle during in vivo measurements. For EDP diode dose value is sensitive to beam angle in whole range of angles. Conclusion: The study shows that QED diode is more suitable for in vivo dosimetry due to dose value independence from incident beam angle in the range 0–60°. There is no need in correction factors for increasing of dose and dose rate for both diodes. The next step will be to carry out measurements in non-standard conditions of total body irradiation. After this modeling of these experiments with Monte Carlo simulation for comparison calculated and obtained data is planned.« less

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

PubMed Central

2013-01-01

Purpose Permanent low-dose-rate (LDR-BT) and temporary high-dose-rate (HDR-BT) brachytherapy are competitive techniques for clinically localized prostate radiotherapy. Although a randomized trial will likely never to be conducted comparing these two forms of brachytherapy, a comparative analysis proves useful in understanding some of their intrinsic differences, several of which could be exploited to improve outcomes. The aim of this paper is to look for possible similarities and differences between both brachytherapy modalities. Indications and contraindications for monotherapy and for brachytherapy as a boost to external beam radiation therapy (EBRT) are presented. It is suggested that each of these techniques has attributes that advocates for one or the other. First, they represent the extreme ends of the spectrum with respect to dose rate and fractionation, and therefore have inherently different radiobiological properties. Low-dose-rate brachytherapy has the great advantage of being practically a one-time procedure, and enjoys a long-term follow-up database supporting its excellent outcomes and low morbidity. Low-dose-rate brachytherapy has been a gold standard for prostate brachytherapy in low risk patients since many years. On the other hand, HDR is a fairly invasive procedure requiring several sessions associated with a brief hospital stay. Although lacking in significant long-term data, it possesses the technical advantage of control over its postimplant dosimetry (by modulating the source dwell time and position), which is absent in LDR brachytherapy. This important difference in dosimetric control allows HDR doses to be escalated safely, a flexibility that does not exist for LDR brachytherapy. Conclusions Radiobiological models support the current clinical evidence for equivalent outcomes in localized prostate cancer with either LDR or HDR brachytherapy, using current dose regimens. At present, all available clinical data regarding these two techniques suggests that they are equally effective, stage for stage, in providing high tumor control rates. PMID:23634153

Effect of the gamma radiation dose rate on psychrotrophic bacteria, thiobarbituric acid reactive substances, and sensory characteristics of mechanically deboned chicken meat.

PubMed

Brito, Poliana P; Azevedo, Heliana; Cipolli, Kátia M V A B; Fukuma, Henrique T; Mourão, Gerson B; Roque, Cláudio V; Miya, Norma T; Pereira, José L

2011-03-01

Frozen samples of mechanically deboned chicken meat (MDCM) with skin were irradiated with gamma radiation doses of 0.0 kGy (control) and 3 kGy at 2 different radiation dose rates: 0.32 kGy/h (3 kGy) and 4.04 kGy/h (3 kGy). Batches of irradiated and control samples were evaluated during 11 d of refrigerated (2 ± 1 °C) storage for the following parameters: total psychrotrophic bacteria count, thiobarbituric acid reactive substances (TBARS), evaluation of objective color (L*, a*, and b*) and a sensory evaluation (irradiated odor, oxidized odor, pink and brown colors). No statistical difference (P > 0.05) was found amongst the TBARS values obtained for the MDCM samples irradiated with dose rates of 0.32 and 4.04 kGy/h. There was a significant increase (P < 0.05) in the psychrotrophic bacterial count as from the 7th day of refrigerated storage, for the MDCM samples irradiated at the dose rate of 4.04 kGy/h. With respect to the attribute of oxidized odor, the samples irradiated with a dose rate of 0.32 kGy/h showed a stronger intensity and were significantly different (P < 0.05) from the sample irradiated with a dose rate of 4.04 kGy/h on days 0 and 2 of refrigerated storage. Irradiation with a dose rate of 4.04 kGy/h (3 kGy) was shown to be the best condition for the processing of MDCM according to the evaluation of all the variables, under the conditions of this study. Practical Application:  The results obtained for the application of different dose rates of ionizing radiation to mechanically deboned chicken meat will provide the food industry with information concerning the definition of the best processing conditions to maximize the sensory and food quality.

Validating dose rate calibration of radiotherapy photon beams through IAEA/WHO postal audit dosimetry service.

PubMed

Jangda, Abdul Qadir; Hussein, Sherali

2012-05-01

In external beam radiation therapy (EBRT), the quality assurance (QA) of the radiation beam is crucial to the accurate delivery of the prescribed dose to the patient. One of the dosimetric parameters that require monitoring is the beam output, specified as the dose rate on the central axis under reference conditions. The aim of this project was to validate dose rate calibration of megavoltage photon beams using the International Atomic Energy Agency (IAEA)/World Health Organisation (WHO) postal audit dosimetry service. Three photon beams were audited: a 6 MV beam from the low-energy linac and 6 and 18 MV beams from a dual high-energy linac. The agreement between our stated doses and the IAEA results was within 1% for the two 6 MV beams and within 2% for the 18 MV beam. The IAEA/WHO postal audit dosimetry service provides an independent verification of dose rate calibration protocol by an international facility.

The Efficacy of Single-Dose versus Double-Dose Praziquantel Treatments on Schistosoma mansoni Infections: Its Implication on Undernutrition and Anaemia among Primary Schoolchildren in Two On-Shore Communities, Northwestern Tanzania

PubMed Central

Buza, Joram; Mpolya, Emmanuel A.; Angelo, Teckla; Kinung'hi, Safari M.

2017-01-01

Administering more than one treatment may increase Praziquantel cure and egg reduction rates, thereby hastening achievement of schistosomiasis transmission control. A total of 431 S. mansoni-infected schoolchildren were randomized to receive either a single or repeated 40 mg/kg Praziquantel dose. Heights, weights, and haemoglobin levels were determined using a stadiometer, weighing scale, and HemoCue, respectively. At 8 weeks, cure rate was higher on repeated dose (93.10%) compared to single dose (68.68%) (p < 0.001). The egg reduction rate was higher on repeated dose (97.54%) compared to single dose (87.27%) (p = 0.0062). Geometric mean egg intensity was lower among those on repeated dose (1.30 epg) compared to single dose (3.18 epg) (p = 0.036) but not at 5 (p > 0.05) and 8 (p > 0.05) months with no difference in reinfection rate. No difference in the prevalence of stunting was observed between the two treatment regimens (p > 0.05) at 8 months, but there was an increase in the prevalence of wasting among those on repeated dose (p < 0.001). There was an increase in the mean haemoglobin levels at 8 months with no difference between the two arms (p > 0.05). To achieve reduction of transmission intensity and disease control in highly endemic areas, repeated treatments alone may not be sufficient. This trial was registered with PACTR201601001416338. PMID:29094048

Defining success in clinical trials--profiling pregabalin, the newest AED.

PubMed

Ryvlin, P

2005-11-01

The efficacy and safety of pregabalin as adjunctive therapy for patients with partial epilepsy with or without secondary generalization has been established by four randomized, 12-week, double-blind, placebo-controlled trials (n = 1396) and four long-term open-label studies (n = 1480). Patients in the three fixed-dose trials were >/=12 years of age, had >/=6 partial seizures and no 4-week seizure-free period during the 8-week baseline period. Seventy-three per cent of patients were taking >/=2 concomitant antiepileptic drugs. Responder rates across the effective doses (150-600 mg/day) ranged from 14% to 51% and demonstrated a significant dose-response relationship. The most common adverse events were central nervous system related, generally mild or moderate, transient, and tended to be dose related. The fourth placebo-controlled trial compared a fixed dose of pregabalin 600 mg/day with a flexible-dose regimen (150-600 mg/day). Responder rates were greater for both the fixed dose (45.3%, P < 0.001) and flexible dose (31.3%, P < 0.001) when compared with placebo (11.0%). Compared with the fixed-dose group, the flexible-dose patients had a lower incidence of adverse events and study discontinuations. In long-term open-label trials, the efficacy of pregabalin was maintained with respect to 50% responder rates suggesting no obvious tolerance developing over 2 years. Seizure-free rates were 8.9% and 5.8% for the last 6 months and 1 year of pregabalin treatment, respectively. Long-term open-label pregabalin treatment was well tolerated.

Efficacy of a radiation absorbing shield in reducing dose to the interventionalist during peripheral endovascular procedures: a single centre pilot study.

PubMed

Power, S; Mirza, M; Thakorlal, A; Ganai, B; Gavagan, L D; Given, M F; Lee, M J

2015-06-01

This prospective pilot study was undertaken to evaluate the feasibility and effectiveness of using a radiation absorbing shield to reduce operator dose from scatter during lower limb endovascular procedures. A commercially available bismuth shield system (RADPAD) was used. Sixty consecutive patients undergoing lower limb angioplasty were included. Thirty procedures were performed without the RADPAD (control group) and thirty with the RADPAD (study group). Two separate methods were used to measure dose to a single operator. Thermoluminescent dosimeter (TLD) badges were used to measure hand, eye, and unshielded body dose. A direct dosimeter with digital readout was also used to measure eye and unshielded body dose. To allow for variation between control and study groups, dose per unit time was calculated. TLD results demonstrated a significant reduction in median body dose per unit time for the study group compared with controls (p = 0.001), corresponding to a mean dose reduction rate of 65 %. Median eye and hand dose per unit time were also reduced in the study group compared with control group, however, this was not statistically significant (p = 0.081 for eye, p = 0.628 for hand). Direct dosimeter readings also showed statistically significant reduction in median unshielded body dose rate for the study group compared with controls (p = 0.037). Eye dose rate was reduced for the study group but this was not statistically significant (p = 0.142). Initial results are encouraging. Use of the shield resulted in a statistically significant reduction in unshielded dose to the operator's body. Measured dose to the eye and hand of operator were also reduced but did not reach statistical significance in this pilot study.

Intermittent Drug Dosing Intervals Guided by the Operational Multiple Dosing Half Lives for Predictable Plasma Accumulation and Fluctuation

PubMed Central

Grover, Anita; Benet, Leslie Z.

2013-01-01

Intermittent drug dosing intervals are usually initially guided by the terminal pharmacokinetic half life and are dependent on drug formulation. For chronic multiple dosing and for extended release dosage forms, the terminal half life often does not predict the plasma drug accumulation or fluctuation observed. We define and advance applications for the operational multiple dosing half lives for drug accumulation and fluctuation after multiple oral dosing at steady-state. Using Monte Carlo simulation, our results predict a way to maximize the operational multiple dosing half lives relative to the terminal half life by using a first-order absorption rate constant close to the terminal elimination rate constant in the design of extended release dosage forms. In this way, drugs that may be eliminated early in the development pipeline due to a relatively short half life can be formulated to be dosed at intervals three times the terminal half life, maximizing compliance, while maintaining tight plasma concentration accumulation and fluctuation ranges. We also present situations in which the operational multiple dosing half lives will be especially relevant in the determination of dosing intervals, including for drugs that follow a direct PKPD model and have a narrow therapeutic index, as the rate of concentration decrease after chronic multiple dosing (that is not the terminal half life) can be determined via simulation. These principles are illustrated with case studies on valproic acid, diazepam, and anti-hypertensives. PMID:21499748

High dose-per-pulse electron beam dosimetry: Commissioning of the Oriatron eRT6 prototype linear accelerator for preclinical use.

PubMed

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

2018-02-01

The Oriatron eRT6 is an experimental high dose-per-pulse linear accelerator (linac) which was designed to deliver an electron beam with variable dose-rates, ranging from a few Gy/min up to hundreds of Gy/s. It was built to study the radiobiological effects of high dose-per-pulse/dose-rate electron beam irradiation, in the context of preclinical and cognitive studies. In this work, we report on the commissioning and beam monitoring of the Oriatron eRT6 prototype linac. The beam was characterized in different steps. The output stability was studied by performing repeated measurements over a period of 20 months. The relative output variations caused by changing beam parameters, such as the temporal electron pulse width, the pulse repetition frequency and the pulse amplitude were also analyzed. Finally, depth dose curves and field sizes were measured for two different beam settings, resulting in one beam with a conventional radiotherapy dose-rate and one with a much higher dose-rate. Measurements were performed with Gafchromic EBT3 films and with a PTW Advanced Markus ionization chamber. In addition, we developed a beam current monitoring system based on the signals from an induction torus positioned at the beam exit of the waveguide and from a graphite beam collimator. The stability of the output over repeated measurements was found to be good, with a standard deviation smaller than 1%. However, non-negligible day-to-day variations of the beam output were observed. Those output variations showed different trends depending on the dose-rate. The analysis of the relative output variation as a function of various beam parameters showed that in a given configuration, the dose-rate could be reliably varied over three orders of magnitude. Interdependence effects on the output variation between the parameters were also observed. The beam energy and field size were found to be slightly dose-rate-dependent and suitable mainly for small animal irradiation. The beam monitoring system was able to measure in a reproducible way the total charge of electrons that exit the machine, as long as the electron pulse amplitude remains above a given threshold. Furthermore, we were able to relate the charge measured with the monitoring system to the absorbed dose in a solid water phantom. The Oriatron eRT6 was successfully commissioned for preclinical use and is currently in full operation, with studies being performed on the radiobiological effects of high dose-per-pulse irradiation. © 2017 American Association of Physicists in Medicine.

Very low dose gamma irradiation stimulates gaseous exchange and carboxylation efficiency, but inhibits vascular sap flow in groundnut (Arachis hypogaea L.).

PubMed

Ahuja, Sumedha; Singh, Bhupinder; Gupta, Vijay Kumar; Singhal, R K; Venu Babu, P

2014-02-01

An experiment was carried out to determine the effect of low dose gamma radiation on germination, plant growth, nitrogen and carbon fixation and carbon flow and release characteristics of groundnut. Dry seeds of groundnut variety Trombay groundnut 37A (TG 37A), a radio mutant type developed by Bhabha Atomic Research Centre (BARC), Mumbai, India, were subjected to the pre-sowing treatment of gamma radiation within low to high dose physiological range, i.e., 0.0, 0.0082, 0.0164. 0.0328, 0.0656, 0.1312, 5, 25, 100, 500 Gray (Gy) from a cobalt source ((60)Co). Observations were recorded for the radiation effect on percentage germination, vigour, gas exchange attributes such as photosynthetic rate, stomatal conductance and transpiration rate, chlorophyll content, root exudation in terms of (14)C release, vascular sap flow rate and activities of rate defining carbon and nitrogen assimilating enzymes such as ribulose-1,5-bisphosphate carboxylase (rubisco) and nitrate reductase (NR). Seed germination was increased by 10-25% at the lower doses up to 5 Gy while the improvement in plant vigour in the same dose range was much higher (22-84%) than the unirradiated control. For radiation exposure above 5 Gy, a dose-dependent decline in germination and plant vigour was measured. No significant effect was observed on the photosynthesis at radiation exposure below 5 Gy but above 5 Gy dose there was a decline in the photosynthetic rate. Stomatal conductance and transpiration rate, however, were only inhibited at a high dose of 500 Gy. Leaf rubisco activity and NR activities remained unaffected at all the investigated doses of gamma irradiation. Mean root exudation and sap flow rate of the irradiated plants, irrespective of the dose, was reduced over the unirradiated control more so in a dose-dependent manner. Results indicated that a very low dose of gamma radiation, in centigray to gray range, did not pose any threat and in fact stimulated metabolic functions in such a way to aid growth and development of groundnut plants. It further showed that the radiation threshold for the gas exchange traits and rubisco activity, which ultimately determine the plant health and yield, were higher than compared to the other metabolic attributes and were well beyond 500 Gy and that the dose range above 500 Gy should be targeted to measure lethal effects of radiation on carbon assimilation attributes in leguminous crops, in general, and groundnut in particular.

OBJECT KINETIC MONTE CARLO SIMULATIONS OF RADIATION DAMAGE IN TUNGSTEN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nandipati, Giridhar; Setyawan, Wahyu; Heinisch, Howard L.

2015-04-16

We used our recently developed lattice-based object kinetic Monte Carlo code; KSOME [1] to carryout simulations of radiation damage in bulk tungsten at temperatures of 300, and 2050 K for various dose rates. Displacement cascades generated from molecular dynamics (MD) simulations for PKA energies at 60, 75 and 100 keV provided residual point defect distributions. It was found that the number density of vacancies in the simulation box does not change with dose rate while the number density of vacancy clusters slightly decreases with dose rate indicating that bigger clusters are formed at larger dose rates. At 300 K, althoughmore » the average vacancy cluster size increases slightly, the vast majority of vacancies exist as mono-vacancies. At 2050 K no accumulation of defects was observed during irradiation over a wide range of dose rates for all PKA energies studied in this work.« less

Do fungi need to be included within environmental radiation protection assessment models?

PubMed

Guillén, J; Baeza, A; Beresford, N A; Wood, M D

2017-09-01

Fungi are used as biomonitors of forest ecosystems, having comparatively high uptakes of anthropogenic and naturally occurring radionuclides. However, whilst they are known to accumulate radionuclides they are not typically considered in radiological assessment tools for environmental (non-human biota) assessment. In this paper the total dose rate to fungi is estimated using the ERICA Tool, assuming different fruiting body geometries, a single ellipsoid and more complex geometries considering the different components of the fruit body and their differing radionuclide contents based upon measurement data. Anthropogenic and naturally occurring radionuclide concentrations from the Mediterranean ecosystem (Spain) were used in this assessment. The total estimated weighted dose rate was in the range 0.31-3.4 μGy/h (5 th -95 th percentile), similar to natural exposure rates reported for other wild groups. The total estimated dose was dominated by internal exposure, especially from 226 Ra and 210 Po. Differences in dose rate between complex geometries and a simple ellipsoid model were negligible. Therefore, the simple ellipsoid model is recommended to assess dose rates to fungal fruiting bodies. Fungal mycelium was also modelled assuming a long filament. Using these geometries, assessments for fungal fruiting bodies and mycelium under different scenarios (post-accident, planned release and existing exposure) were conducted, each being based on available monitoring data. The estimated total dose rate in each case was below the ERICA screening benchmark dose, except for the example post-accident existing exposure scenario (the Chernobyl Exclusion Zone) for which a dose rate in excess of 35 μGy/h was estimated for the fruiting body. Estimated mycelium dose rate in this post-accident existing exposure scenario was close to the 400 μGy/h benchmark for plants, although fungi are generally considered to be less radiosensitive than plants. Further research on appropriate mycelium geometries and their radionuclide content is required. Based on the assessments presented in this paper, there is no need to recommend that fungi should be added to the existing assessment tools and frameworks; if required some tools allow a geometry representing fungi to be created and used within a dose assessment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Spiromax, a New Dry Powder Inhaler: Dose Consistency under Simulated Real-World Conditions

PubMed Central

Canonica, Giorgio Walter; Arp, Jan; Keegstra, Johan René

2015-01-01

Abstract Background: Spiromax® is a novel dry powder inhaler for patients with asthma or chronic obstructive pulmonary disease (COPD). The studies presented here provide further data on attributes (in vitro dosing consistency with budesonide–formoterol (DuoResp) Spiromax; flow rates through empty versions of the Spiromax and Turbuhaler inhaler) of importance to patients with asthma or COPD. Methods: Dose-delivery studies were performed using low-, middle-, and high-strength DuoResp Spiromax. Dose consistency was assessed over inhaler life. Total emitted doses (TEDs) were measured at various flow rates, after exposure to high and low temperature or humidity, at different inhaler orientations, and after dropping the inhaler. The criterion for evaluating dose uniformity was whether mean TEDs were within the product specification limits. In separate studies, flow rates were measured after training, using the patient information leaflets, and again after enhanced training as part of a randomized, open-label, cross-over study. Results: Mean values for both budesonide and formoterol were within 85%–115% of the label claim for each strength of DuoResp Spiromax for initial dose uniformity and for the other investigated conditions (temperature, humidity, orientation, dropping, knocking), with the exception of approximately an 80% increase in first dose after dropping the inhaler (subsequent doses not affected). In the flow rate patient study, two patients' inhalations with Spiromax and six with Turbuhaler were <30 L/min. The majority of asthma patients [91% (Spiromax) versus 82% (Turbuhaler)] achieved the preferred flow rate of >60 L/min. Conclusions: DuoResp Spiromax consistently meets dose uniformity criteria, under controlled laboratory conditions and with variations intended to mimic real-world use. Following enhanced training, all patients in the flow study were able to achieve the minimal inspiratory flow rate of >30 L/min, which is required for effective treatment. PMID:26352860

SU-F-T-669: Commissioning of An Electronic Brachytherapy System for Targeted Mouse Irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Culberson, W; Micka, J; Carchman, E

Purpose: The aim of this study was to commission the Xoft Axxent™ electronic brachytherapy (eBT) source and 10 mm diameter surface applicator with NIST traceability for targeted irradiations of mouse anal carcinomas. Methods: The Xoft Axxent™ electronic brachytherapy (eBT) and 10 mm diameter surface applicator was chosen by the collaborating physician as a radiation delivery mechanism for mouse anal carcinomas. The target dose was 2 Gy at a depth of 3 mm in tissue to be delivered in a single fraction. To implement an accurate and reliable irradiation plan, the system was commissioned by first determining the eBT source outputmore » and corresponding dose rate at a depth of 3 mm in tissue. This was determined through parallel-plate ion chamber measurements and published conversion factors. Well-type ionization chamber measurements were used to determine a transfer coefficient, which correlates the measured dose rate at 3 mm to the NIST-traceable quantity, air-kerma rate at 50 cm in air, for eBT sources. By correlating these two quantities, daily monitoring in the well chamber becomes an accurate and efficient quality assurance technique. Once the dose-rate was determined, a treatment recipe was developed and confirmed with chamber measurements to deliver the requested dose. Radiochromic film was used to verify the dose distribution across the field. Results: Dose rates at 3 mm depth in tissue were determined for two different Xoft Axxent™ sources and correlated with NIST-traceable well-type ionization chamber measurements. Unique transfer coefficients were determined for each source and the treatment recipe was validated by measurements. Film profiles showed a uniform dose distribution across the field. Conclusion: A Xoft Axxent™ eBT system was successfully commissioned for use in the irradiation of mouse rectal tumors. Dose rates in tissue were determined as well as other pertinent parameters to ensure accurate delivery of dose to the target region.« less

X-Ray-Induced Chromosome Aberrations in Mouse Dictyate Oocytes. II. Fractionation and Dose Rate Effects

PubMed Central

Brewen, J. G.; Payne, H. S.; Adler, I. D.

1977-01-01

Split-dose experiments were done on maturing dictyate oocytes to determine if the magnitude of the first dose influenced the "rejoining time" of radiation-induced chromosomal lesions. A total dose of 400r was split into various combinations with varying fractionation intervals. The data derived from analyzing interchanges indicate that there is no difference in the rejoining time whether the first dose was 100, 200, or 300r. It thus appears that the radiation dose in the ranges studied does not significantly alter the rate of repair of the chromosomal lesions. This conclusion is contrary to that which has been propounded to explain the nonlinear dose curves obtained for specific locus mutations. Chronic 60Co γ-ray exposures were given to female mice over an 8-day period. The exposures were delivered during the period of peak sensitivity, i.e., 8–16 days prior to ovulation. The doses given were 117, 240, 348, and 483r. The aberration yields observed were dramatically lower than for comparable doses of acute X rays even when the RBE of γ rays compared with X rays is taken into account. The large drop in yields at the low dose rates is interpreted as resulting from a large two-track component in the acute curve, and as being independent of effects on repair systems. PMID:604163

Dose Calculations for [131I] Meta-Iodobenzylguanidine-Induced Bystander Effects

PubMed Central

Gow, M. D.; Seymour, C. B.; Boyd, M.; Mairs, R. J.; Prestiwch, W. V.; Mothersill, C. E.

2014-01-01

Targeted radiotherapy is a potentially useful treatment for some cancers and may be potentiated by bystander effects. However, without estimation of absorbed dose, it is difficult to compare the effects with conventional external radiation treatment. Methods: Using the Vynckier – Wambersie dose point kernel, a model for dose rate evaluation was created allowing for calculation of absorbed dose values to two cell lines transfected with the noradrenaline transporter (NAT) gene and treated with [131I]MIBG. Results: The mean doses required to decrease surviving fractions of UVW/NAT and EJ138/NAT cells, which received medium from [131I]MIBG-treated cells, to 25 – 30% were 1.6 and 1.7 Gy respectively. The maximum mean dose rates achieved during [131I]MIBG treatment were 0.09 – 0.75 Gy/h for UVW/NAT and 0.07 – 0.78 Gy/h for EJ138/NAT. These were significantly lower than the external beam gamma radiation dose rate of 15 Gy/h. In the case of control lines which were incapable of [131I]MIBG uptake the mean absorbed doses following radiopharmaceutical were 0.03 – 0.23 Gy for UVW and 0.03 – 0.32 Gy for EJ138. Conclusion: [131I]MIBG treatment for ICCM production elicited a bystander dose-response profile similar to that generated by external beam gamma irradiation but with significantly greater cell death. PMID:24659931

Low-dose vs standard-dose unfractionated heparin for percutaneous coronary intervention in acute coronary syndromes treated with fondaparinux: the FUTURA/OASIS-8 randomized trial.

PubMed

Steg, Philippe Gabriel; Jolly, Sanjit S; Mehta, Shamir R; Afzal, Rizwan; Xavier, Denis; Rupprecht, Hans-Jurgen; López-Sendón, Jose L; Budaj, Andrzej; Diaz, Rafael; Avezum, Alvaro; Widimsky, Petr; Rao, Sunil V; Chrolavicius, Susan; Meeks, Brandi; Joyner, Campbell; Pogue, Janice; Yusuf, Salim

2010-09-22

The optimal unfractionated heparin regimen for percutaneous coronary intervention (PCI) in patients with non-ST-segment elevation acute coronary syndromes treated with fondaparinux is uncertain. To compare the safety of 2 unfractionated heparin regimens during PCI in high-risk patients with non-ST-segment elevation acute coronary syndromes initially treated with fondaparinux. Double-blind randomized parallel-group trial in 179 hospitals in 18 countries involving 2026 patients undergoing PCI within 72 hours, nested within a cohort of 3235 high-risk patients with non-ST-segment elevation acute coronary syndromes initially treated with fondaparinux enrolled from February 2009 to March 2010. Patients received intravenously either low-dose unfractionated heparin, 50 U/kg, regardless of use of glycoprotein IIb/IIIa (GpIIb-IIIa) inhibitors or standard-dose unfractionated heparin, 85 U/kg (60 U/kg with GpIIb-IIIa inhibitors), adjusted by blinded activated clotting time (ACT). Composite of major bleeding, minor bleeding, or major vascular access-site complications up to 48 hours after PCI. Key secondary outcomes include composite of major bleeding at 48 hours with death, myocardial infarction, or target vessel revascularization within day 30. The primary outcome occurred in 4.7% of those in the low-dose group vs 5.8% in the standard-dose group (odds ratio [OR], 0.80; 95% confidence interval [CI], 0.54-1.19; P = .27). The rates of major bleeding were not different but the rates of minor bleeding were lower with 0.7% in the low-dose group vs 1.7% in the standard-dose group (OR, 0.40; 95% CI, 0.16-0.97; P = .04). For the key secondary outcome, the rates for low-dose group were 5.8% vs 3.9% in the standard-dose group (OR, 1.51; 95% CI, 1.00-2.28; P = .05) and for death, myocardial infarction, or target vessel revascularization it was 4.5% for the low-dose group vs 2.9% for the standard-dose group (OR, 1.58; 95% CI, 0.98-2.53; P = .06). Catheter thrombus rates were very low (0.5% in the low-dose group and 0.1% in the standard-dose group, P = .15). Low-dose compared with standard-dose unfractionated heparin did not reduce major peri-PCI bleeding and vascular access-site complications. clinicaltrials.gov Identifier: NCT00790907.

THE DEPRESSANT EFFECT OF CONTINUOUS COBALT-60 RADIATION ON THE SECONDARY TETANUS ANTITOXIN RESPONSE IN MICE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stoner, R.D.; Hale, W.M.

1958-05-01

The radiosensitivity of the secondary tetanus antitoxin response in mice was demonstrated after rather low doses of continuous gamma -radiation given at a dose rate of 4 rep/hr. Accumulated doses of 48 to 288 rep depressed antitoxin formation. Comparable doses of acute gamma radiation did not depress antitoxin production. Acute doses of 350 to 650 rep sharply depressed the secondary antibody response, however. Extended periods of continuous gamma -radiation from 10 to 28 days to accumulated doses of 960 to 2688 rep markedly depressed the secondary antibody response. An accumulated dose of 2688 rep was needed to depress antitoxin formationmore » to the level observed after an acute dose of 650 rep. When the secondary stimulus of fluid tetanus toxoid was given prior to 10 days of continuous exposure to an accumulated dose of 860 rep, the secondary antibody respense was not depressed. Irradiated mice recovered the ability to produce a normal secondary antitoxin response during the second week after an accumulated dose of 1248 rep. The secondary antitoxin response was depressed in mice given long-continued gamma -radiation at a dose rate of 1 rep/hr. (auth)« less

Impact of high- versus low-dose neuromuscular blocking agent administration on unplanned 30-day readmission rates in retroperitoneal laparoscopic surgery.

PubMed

Boon, Martijn; Martini, Chris; Yang, H Keri; Sen, Shuvayu S; Bevers, Rob; Warlé, Michiel; Aarts, Leon; Niesters, Marieke; Dahan, Albert

2018-01-01

Recent data shows that a neuromuscular block (NMB) induced by administration of high doses of rocuronium improves surgical conditions in certain procedures. However, there are limited data on the effect such practices on postoperative outcomes. We performed a retrospective analysis to compare unplanned 30-day readmissions in patients that received high-dose versus low-dose rocuronium administration during general anesthesia for laparoscopic retroperitoneal surgery. This retrospective cohort study was performed in the Netherlands in an academic hospital where routine high-dose rocuronium NMB has been practiced since July 2015. Charts of patients receiving anesthesia between January 2014 and December 2016 were searched for surgical cases receiving high-dose rocuronium and matched with respect to procedure, age, sex and ASA classification to patients receiving low-dose rocuronium. The primary post-operative outcome was unplanned 30-day readmission rate. There were 130 patients in each cohort. Patients in the high- and low-dose rocuronium cohorts received 217 ± 49 versus 37 ± 5 mg rocuronium, respectively. In the high-dose rocuronium group neuromuscular activity was consistently monitored; matched patients were unreliably monitored. All patients receiving high-dose rocuronium were reversed with sugammadex, while just 33% of matched patients were reversed with sugammadex and 20% with neostigmine; the remaining patients were not reversed. Unplanned 30-day readmission rate was significantly lower in the high-dose compared to the low-dose rocuronium cohort (3.8% vs. 12.7%; p = 0.03; odds ratio = 0.33, 95% C.I. 0.12-0.95). This small retrospective study demonstrates a lower incidence of unplanned readmissions within 30-days following laparoscopic retroperitoneal surgery with high-dose relaxant anesthesia and sugammadex reversal in comparison to low-dose relaxant anesthesia. Further prospective studies are needed in larger samples to corroborate our findings and additionally assess the pharmacoeconomics of high-dose relaxant anesthesia taking into account the benefits (reduced readmissions) and harm (cost of relaxants and reversal agents) of such practice.

Dose-response characteristics of an amorphous silicon EPID.

PubMed

Winkler, Peter; Hefner, Alfred; Georg, Dietmar

2005-10-01

Electronic portal imaging devices (EPIDs) were originally developed for the purpose of patient setup verification. Nowadays, they are increasingly used as dosimeters (e.g., for IMRT verification and linac-specific QA). A prerequisite for any clinical dosimetric application is a detailed understanding of the detector's dose-response behavior. The aim of this study is to investigate the dosimetric properties of an amorphous silicon EPID (Elekta IVIEWGT) with respect to three photon beam qualities: 6, 10, and 25 MV. The EPID showed an excellent temporal stability on short term as well as on long term scales. The stability throughout the day was strongly influenced by warming up, which took several hours and affected EPID response by 2.5%. Ghosting effects increased the sensitivity of the EPID. They became more pronounced with decreasing time intervals between two exposures as well as with increasing dose. Due to ghosting, changes in pixel sensitivity amounted up to 16% (locally) for the 25 MV photon beam. It was observed that the response characteristics of our EPID depended on dose as well as on dose rate. Doubling the dose rate increased the EPID sensitivity by 1.5%. This behavior was successfully attributed to a dose per frame effect, i.e., a nonlinear relationship between the EPID signal and the dose which was delivered to the panel between two successive readouts. The sensitivity was found to vary up to 10% in the range of 1 to 1000 monitor units. This variation was governed by two independent effects. For low doses, the EPID signal was reduced due to the linac's changing dose rate during startup. Furthermore, the detector reading was influenced by intrabeam variations of EPID sensitivity, namely, an increase of detector response during uniform exposure. For the beam qualities which were used, the response characteristics of the EPID did not depend on energy. Differences in relative dose-response curves resulted from energy dependent temporal output characteristics of the accelerator. If ghosting is prevented from affecting the results and all dose-response effects are properly corrected for, the EPID signal becomes independent of dose rate, dose, and exposure time.

Hemopoietic Response to Low Dose-Rates of Ionizing Radiation Shows Stem Cell Tolerance and Adaptation

PubMed Central

Fliedner, Theodor M.; Graessle, Dieter H.; Meineke, Viktor; Feinendegen, Ludwig E.

2012-01-01

Chronic exposure of mammals to low dose-rates of ionizing radiation affects proliferating cell systems as a function of both dose-rate and the total dose accumulated. The lower the dose-rate the higher needs to be the total dose for a deterministic effect, i.e., tissue reaction to appear. Stem cells provide for proliferating, maturing and functional cells. Stem cells usually are particularly radiosensitive and damage to them may propagate to cause failure of functional cells. The paper revisits 1) medical histories with emphasis on the hemopoietic system of the victims of ten accidental chronic radiation exposures, 2) published hematological findings of long-term chronically gamma-irradiated rodents, and 3) such findings in dogs chronically exposed in large life-span studies. The data are consistent with the hypothesis that hemopoietic stem and early progenitor cells have the capacity to tolerate and adapt to being repetitively hit by energy deposition events. The data are compatible with the “injured stem cell hypothesis”, stating that radiation–injured stem cells, depending on dose-rate, may continue to deliver clones of functional cells that maintain homeostasis of hemopoiesis throughout life. Further studies perhaps on separated hemopoietic stem cells may unravel the molecular-biology mechanisms causing radiation tolerance and adaptation. PMID:23304110

LM193 Dual Differential Comparator Total Ionizing Dose Test Report

NASA Technical Reports Server (NTRS)

Topper, Alyson; Forney, James; Campola, Michael

2017-01-01

The purpose of this test was to characterize the flight lot of Texas Instruments' LM193 (flight part number is 5962-9452601Q2A) for total dose response. This test served as the radiation lot acceptance test (RLAT) for the lot date code (LDC) tested. Low dose rate (LDR) irradiations were performed in this test so that the device susceptibility to enhanced low dose rate sensitivity (ELDRS) was determined.

Suitability of point kernel dose calculation techniques in brachytherapy treatment planning

PubMed Central

Lakshminarayanan, Thilagam; Subbaiah, K. V.; Thayalan, K.; Kannan, S. E.

2010-01-01

Brachytherapy treatment planning system (TPS) is necessary to estimate the dose to target volume and organ at risk (OAR). TPS is always recommended to account for the effect of tissue, applicator and shielding material heterogeneities exist in applicators. However, most brachytherapy TPS software packages estimate the absorbed dose at a point, taking care of only the contributions of individual sources and the source distribution, neglecting the dose perturbations arising from the applicator design and construction. There are some degrees of uncertainties in dose rate estimations under realistic clinical conditions. In this regard, an attempt is made to explore the suitability of point kernels for brachytherapy dose rate calculations and develop new interactive brachytherapy package, named as BrachyTPS, to suit the clinical conditions. BrachyTPS is an interactive point kernel code package developed to perform independent dose rate calculations by taking into account the effect of these heterogeneities, using two regions build up factors, proposed by Kalos. The primary aim of this study is to validate the developed point kernel code package integrated with treatment planning computational systems against the Monte Carlo (MC) results. In the present work, three brachytherapy applicators commonly used in the treatment of uterine cervical carcinoma, namely (i) Board of Radiation Isotope and Technology (BRIT) low dose rate (LDR) applicator and (ii) Fletcher Green type LDR applicator (iii) Fletcher Williamson high dose rate (HDR) applicator, are studied to test the accuracy of the software. Dose rates computed using the developed code are compared with the relevant results of the MC simulations. Further, attempts are also made to study the dose rate distribution around the commercially available shielded vaginal applicator set (Nucletron). The percentage deviations of BrachyTPS computed dose rate values from the MC results are observed to be within plus/minus 5.5% for BRIT LDR applicator, found to vary from 2.6 to 5.1% for Fletcher green type LDR applicator and are up to −4.7% for Fletcher-Williamson HDR applicator. The isodose distribution plots also show good agreements with the results of previous literatures. The isodose distributions around the shielded vaginal cylinder computed using BrachyTPS code show better agreement (less than two per cent deviation) with MC results in the unshielded region compared to shielded region, where the deviations are observed up to five per cent. The present study implies that the accurate and fast validation of complicated treatment planning calculations is possible with the point kernel code package. PMID:20589118

Brachytherapy optimization using radiobiological-based planning for high dose rate and permanent implants for prostate cancer treatment

NASA Astrophysics Data System (ADS)

Seeley, Kaelyn; Cunha, J. Adam; Hong, Tae Min

2017-01-01

We discuss an improvement in brachytherapy--a prostate cancer treatment method that directly places radioactive seeds inside target cancerous regions--by optimizing the current standard for delivering dose. Currently, the seeds' spatiotemporal placement is determined by optimizing the dose based on a set of physical, user-defined constraints. One particular approach is the ``inverse planning'' algorithms that allow for tightly fit isodose lines around the target volumes in order to reduce dose to the patient's organs at risk. However, these dose distributions are typically computed assuming the same biological response to radiation for different types of tissues. In our work, we consider radiobiological parameters to account for the differences in the individual sensitivities and responses to radiation for tissues surrounding the target. Among the benefits are a more accurate toxicity rate and more coverage to target regions for planning high-dose-rate treatments as well as permanent implants.

Assessing doses to terrestrial wildlife at a radioactive waste disposal site: inter-comparison of modelling approaches.

PubMed

Johansen, M P; Barnett, C L; Beresford, N A; Brown, J E; Černe, M; Howard, B J; Kamboj, S; Keum, D-K; Smodiš, B; Twining, J R; Vandenhove, H; Vives i Batlle, J; Wood, M D; Yu, C

2012-06-15

Radiological doses to terrestrial wildlife were examined in this model inter-comparison study that emphasised factors causing variability in dose estimation. The study participants used varying modelling approaches and information sources to estimate dose rates and tissue concentrations for a range of biota types exposed to soil contamination at a shallow radionuclide waste burial site in Australia. Results indicated that the dominant factor causing variation in dose rate estimates (up to three orders of magnitude on mean total dose rates) was the soil-to-organism transfer of radionuclides that included variation in transfer parameter values as well as transfer calculation methods. Additional variation was associated with other modelling factors including: how participants conceptualised and modelled the exposure configurations (two orders of magnitude); which progeny to include with the parent radionuclide (typically less than one order of magnitude); and dose calculation parameters, including radiation weighting factors and dose conversion coefficients (typically less than one order of magnitude). Probabilistic approaches to model parameterisation were used to encompass and describe variable model parameters and outcomes. The study confirms the need for continued evaluation of the underlying mechanisms governing soil-to-organism transfer of radionuclides to improve estimation of dose rates to terrestrial wildlife. The exposure pathways and configurations available in most current codes are limited when considering instances where organisms access subsurface contamination through rooting, burrowing, or using different localised waste areas as part of their habitual routines. Crown Copyright © 2012. Published by Elsevier B.V. All rights reserved.

Impact of concomitant dexamethasone dosing schedule on bortezomib-induced peripheral neuropathy in multiple myeloma.

PubMed

Kumar, Shaji K; Laubach, Jacob P; Giove, Thomas J; Quick, Maureen; Neuwirth, Rachel; Yung, Godwin; Rajkumar, S Vincent; Richardson, Paul G

2017-09-01

Peripheral neuropathy (PN) is the most troublesome adverse event associated with the proteasome inhibitor bortezomib. Studies suggest an inflammatory aetiology for bortezomib-induced PN (BiPN) and it has been hypothesized that reducing inflammation with concomitant dexamethasone may reduce BiPN incidence and/or severity. We retrospectively analysed PN rates from 32 studies (2697 patients with previously untreated multiple myeloma) incorporating bortezomib and differing dexamethasone schedules: partnered dosing (days of and after bortezomib), weekly dosing, and other dosing schedules (e.g. days 1-4, 8-11). Pooled overall PN rates were 45·5%, 63·9%, and 47·5%, respectively, with 5·3%, 11·0%, and 9·6% grade ≥3. Adjusting for potential confounders (age, gender, presence of thalidomide, bortezomib treatment duration), PN rates in patients on partnered dosing schedules appeared lower than in patients on weekly or other dosing schedules. Analyses conducted using patient-level data suggest that cumulative dexamethasone dose, a potential confounding factor, is unlikely to have influenced the analyses. Findings were similar in a separate pooled analysis excluding data from regimens incorporating thalidomide, when pooled overall PN rates were 50·1%, 63·9%, and 48·3%, respectively, with 4·2%, 11·0%, and 8·6% grade ≥3. These findings suggest that partnered dexamethasone dosing may result in less severe BiPN compared with alternative dexamethasone dosing schedules. © 2017 John Wiley & Sons Ltd.

Comparison of the effective dose rate to aircrew members using hybrid computational phantoms in standing and sitting postures.

PubMed

Alves, M C; Galeano, D C; Santos, W S; Lee, Choonsik; Bolch, Wesley E; Hunt, John G; da Silva, A X; Carvalho, A B

2016-12-01

Aircraft crew members are occupationally exposed to considerable levels of cosmic radiation at flight altitudes. Since aircrew (pilots and passengers) are in the sitting posture for most of the time during flight, and up to now there has been no data on the effective dose rate calculated for aircrew dosimetry in flight altitude using a sitting phantom, we therefore calculated the effective dose rate using a phantom in the sitting and standing postures in order to compare the influence of the posture on the radiation protection of aircrew members. We found that although the better description of the posture in which the aircrews are exposed, the results of the effective dose rate calculated with the phantom in the sitting posture were very similar to the results of the phantom in the standing posture. In fact we observed only a 1% difference. These findings indicate the adequacy of the use of dose conversion coefficients for the phantom in the standing posture in aircrew dosimetry. We also validated our results comparing the effective dose rate obtained using the standing phantom with values reported in the literature. It was observed that the results presented in this study are in good agreement with other authors (the differences are below 30%) who have measured and calculated effective dose rates using different phantoms.

Dose-rate-dependent damage of cerium dioxide in the scanning transmission electron microscope.

PubMed

Johnston-Peck, Aaron C; DuChene, Joseph S; Roberts, Alan D; Wei, Wei David; Herzing, Andrew A

2016-11-01

Beam damage caused by energetic electrons in the transmission electron microscope is a fundamental constraint limiting the collection of artifact-free information. Through understanding the influence of the electron beam, experimental routines may be adjusted to improve the data collection process. Investigations of CeO 2 indicate that there is not a critical dose required for the accumulation of electron beam damage. Instead, measurements using annular dark field scanning transmission electron microscopy and electron energy loss spectroscopy demonstrate that the onset of measurable damage occurs when a critical dose rate is exceeded. The mechanism behind this phenomenon is that oxygen vacancies created by exposure to a 300keV electron beam are actively annihilated as the sample re-oxidizes in the microscope environment. As a result, only when the rate of vacancy creation exceeds the recovery rate will beam damage begin to accumulate. This observation suggests that dose-intensive experiments can be accomplished without disrupting the native structure of the sample when executed using dose rates below the appropriate threshold. Furthermore, the presence of an encapsulating carbonaceous layer inhibits processes that cause beam damage, markedly increasing the dose rate threshold for the accumulation of damage. Published by Elsevier B.V.

Dose-rate-dependent damage of cerium dioxide in the scanning transmission electron microscope

PubMed Central

Johnston-Peck, Aaron C.; DuChene, Joseph S.; Roberts, Alan D.; Wei, Wei David; Herzing, Andrew A.

2016-01-01

Beam damage caused by energetic electrons in the transmission electron microscope is a fundamental constraint limiting the collection of artifact-free information. Through understanding the influence of the electron beam, experimental routines may be adjusted to improve the data collection process. Investigations of CeO2 indicate that there is not a critical dose required for the accumulation of electron beam damage. Instead, measurements using annular dark field scanning transmission electron microscopy and electron energy loss spectroscopy demonstrate that the onset of measurable damage occurs when a critical dose rate is exceeded. The mechanism behind this phenomenon is that oxygen vacancies created by exposure to a 300 keV electron beam are actively annihilated as the sample re-oxidizes in the microscope environment. As a result, only when the rate of vacancy creation exceeds the recovery rate will beam damage begin to accumulate. This observation suggests that dose-intensive experiments can be accomplished without disrupting the native structure of the sample when executed using dose rates below the appropriate threshold. Furthermore, the presence of an encapsulating carbonaceous layer inhibits processes that cause beam damage, markedly increasing the dose rate threshold for the accumulation of damage. PMID:27469265

MODELING THE VARIATIONS OF DOSE RATE MEASURED BY RAD DURING THE FIRST MSL MARTIAN YEAR: 2012–2014

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Jingnan; Wimmer-Schweingruber, Robert F.; Heber, Bernd

2015-09-01

The Radiation Assessment Detector (RAD), on board Mars Science Laboratory’s (MSL) rover Curiosity, measures the energy spectra of both energetic charged and neutral particles along with the radiation dose rate at the surface of Mars. With these first-ever measurements on the Martian surface, RAD observed several effects influencing the galactic cosmic-ray (GCR) induced surface radiation dose concurrently: (a) short-term diurnal variations of the Martian atmospheric pressure caused by daily thermal tides, (b) long-term seasonal pressure changes in the Martian atmosphere, and (c) the modulation of the primary GCR flux by the heliospheric magnetic field, which correlates with long-term solar activitymore » and the rotation of the Sun. The RAD surface dose measurements, along with the surface pressure data and the solar modulation factor, are analyzed and fitted to empirical models that quantitatively demonstrate how the long-term influences ((b) and (c)) are related to the measured dose rates. Correspondingly, we can estimate dose rate and dose equivalents under different solar modulations and different atmospheric conditions, thus allowing empirical predictions of the Martian surface radiation environment.« less

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

PubMed Central

Sanders, Charles L.

2012-01-01

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

AN ESTIMATION OF THE EXPOSURE OF THE POPULATION OF ISRAEL TO NATURAL SOURCES OF IONIZING RADIATION.

PubMed

Epstein, L; Koch, J; Riemer, T; Haquin, G; Orion, I

2017-11-01

The radiation dose to the population of Israel due to exposure to natural sources of ionizing radiation was assessed. The main contributor to the dose is radon that accounts for 60% of the exposure to natural sources. The dose due to radon inhalation was assessed by combining the results of a radon survey in single-family houses with the results of a survey in apartments in multi-storey buildings. The average annual dose due to radon inhalation was found to be 1.2 mSv. The dose rate due to exposure to cosmic radiation was assessed using a code that calculates the dose rate at different heights above sea level, taking into account the solar cycle. The annual dose was calculated based on the fraction of time spent indoors and the attenuation provided by buildings and was found to be 0.2 mSv. The annual dose due to external exposure to the terrestrial radionuclides was similarly assessed. The indoor dose rate was calculated using a model that takes into account the concentrations of the natural radionuclides in building materials, the density and the thickness of the walls. The dose rate outdoors was calculated based on the concentrations of the natural radionuclides in different geological units in Israel as measured in an aerial survey and measurements above ground. The annual dose was found to be 0.2 mSv. Doses due to internal exposure other than exposure to radon were also calculated and were found to be 0.4 mSv. The overall annual exposure of the population of Israel to natural sources of ionizing radiation is therefore 2 mSv and ranges between 1.7 and 2.7 mSv. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Identifying the most successful dose (MSD) in dose-finding studies in cancer.

PubMed

Zohar, Sarah; O'Quigley, John

2006-01-01

For a dose finding study in cancer, the most successful dose (MSD), among a group of available doses, is that dose at which the overall success rate is the highest. This rate is the product of the rate of seeing non-toxicities together with the rate of tumor response. A successful dose finding trial in this context is one where we manage to identify the MSD in an efficient manner. In practice we may also need to consider algorithms for identifying the MSD which can incorporate certain restrictions, the most common restriction maintaining the estimated toxicity rate alone below some maximum rate. In this case the MSD may correspond to a different level than that for the unconstrained MSD and, in providing a final recommendation, it is important to underline that it is subject to the given constraint. We work with the approach described in O'Quigley et al. [Biometrics 2001; 57(4):1018-1029]. The focus of that work was dose finding in HIV where both information on toxicity and efficacy were almost immediately available. Recent cancer studies are beginning to fall under this same heading where, as before, toxicity can be quickly evaluated and, in addition, we can rely on biological markers or other measures of tumor response. Mindful of the particular context of cancer, our purpose here is to consider the methodology developed by O'Quigley et al. and its practical implementation. We also carry out a study on the doubly under-parameterized model, developed by O'Quigley et al. but not

Radiological characterization of the pressure vessel internals of the BNL High Flux Beam Reactor.

PubMed

Holden, Norman E; Reciniello, Richard N; Hu, Jih-Perng

2004-08-01

In preparation for the eventual decommissioning of the High Flux Beam Reactor after the permanent removal of its fuel elements from the Brookhaven National Laboratory, measurements and calculations of the decay gamma-ray dose-rate were performed in the reactor pressure vessel and on vessel internal structures such as the upper and lower thermal shields, the Transition Plate, and the Control Rod blades. Measurements of gamma-ray dose rates were made using Red Perspex polymethyl methacrylate high-dose film, a Radcal "peanut" ion chamber, and Eberline's RO-7 high-range ion chamber. As a comparison, the Monte Carlo MCNP code and MicroShield code were used to model the gamma-ray transport and dose buildup. The gamma-ray dose rate at 8 cm above the center of the Transition Plate was measured to be 160 Gy h (using an RO-7) and 88 Gy h at 8 cm above and about 5 cm lateral to the Transition Plate (using Red Perspex film). This compares with a calculated dose rate of 172 Gy h using Micro-Shield. The gamma-ray dose rate was 16.2 Gy h measured at 76 cm from the reactor core (using the "peanut" ion chamber) and 16.3 Gy h at 87 cm from the core (using Red Perspex film). The similarity of dose rates measured with different instruments indicates that using different methods and instruments is acceptable if the measurement (and calculation) parameters are well defined. Different measurement techniques may be necessary due to constraints such as size restrictions.

Dactinomycin and Vincristine Toxicity in the Treatment of Childhood Cancer: A Retrospective Study from the Children’s Oncology Group

PubMed Central

Langholz, Bryan; Skolnik, Jeffrey M.; Barrett, Jeffrey S.; Renbarger, Jamie; Seibel, Nita L.; Zajicek, Anne; Arndt, Carola A.S.

2011-01-01

Background Dactinomycin (AMD) and vincristine (VCR) have been used for the treatment of childhood cancer over the past 40 years but evidence-based dosing guidance is lacking. Methods Patient AMD and VCR dose and drug-related adverse event (AE) information from four rhabdomyosarcoma (RMS) and two Wilms tumor (WT) studies were assembled. Statistical modeling was used to account for differences in AE data collection across studies, develop rate models for grade 3/4 CTCAE v3 hepatic- (AMD) and neuro- (AMD) toxicity, assess variation in toxicity rates over age and other factors, and predict toxicity risk under current dosing guidelines. Results For the same dose/body size, AMD toxicity rates were higher in patients <1 year than older patients and VCR toxicity rates increased with age. The statistical model provided estimates for AMD and VCR toxicity risk under current dosing schedules and indicated that patients of smaller body size were at lower risk of VCR toxicity than larger patients of the same age. The rate of AMD toxicity was highest early in treatment and was lower in patients who tolerated initial AMD without toxicity. Conclusion The observed decrease in AMD toxicity rate with cumulative dose may indicate sensitivity in a subgroup of patients while the observed increase in VCR toxicity risk with age may indicate changing sensitivity to VCR. Current dosing practices result in a fairly uniform toxicity profile within age group. However, PK/PD studies should be done to provide further provide further information on best dosing guidelines. PMID:21671362

Simulation-Based Evaluation of Dose-Titration Algorithms for Rapid-Acting Insulin in Subjects with Type 2 Diabetes Mellitus Inadequately Controlled on Basal Insulin and Oral Antihyperglycemic Medications.

PubMed

Ma, Xiaosu; Chien, Jenny Y; Johnson, Jennal; Malone, James; Sinha, Vikram

2017-08-01

The purpose of this prospective, model-based simulation approach was to evaluate the impact of various rapid-acting mealtime insulin dose-titration algorithms on glycemic control (hemoglobin A1c [HbA1c]). Seven stepwise, glucose-driven insulin dose-titration algorithms were evaluated with a model-based simulation approach by using insulin lispro. Pre-meal blood glucose readings were used to adjust insulin lispro doses. Two control dosing algorithms were included for comparison: no insulin lispro (basal insulin+metformin only) or insulin lispro with fixed doses without titration. Of the seven dosing algorithms assessed, daily adjustment of insulin lispro dose, when glucose targets were met at pre-breakfast, pre-lunch, and pre-dinner, sequentially, demonstrated greater HbA1c reduction at 24 weeks, compared with the other dosing algorithms. Hypoglycemic rates were comparable among the dosing algorithms except for higher rates with the insulin lispro fixed-dose scenario (no titration), as expected. The inferior HbA1c response for the "basal plus metformin only" arm supports the additional glycemic benefit with prandial insulin lispro. Our model-based simulations support a simplified dosing algorithm that does not include carbohydrate counting, but that includes glucose targets for daily dose adjustment to maintain glycemic control with a low risk of hypoglycemia.

The New Radiobiology: Returning to Our Roots

PubMed Central

Ulsh, Brant A.

2012-01-01

In 2005, two expert advisory bodies examined the evidence on the effects of low doses of ionizing radiation. The U.S. National Research Council concluded that current scientific evidence is consistent with the linear no-threshold dose-response relationship (NRCNA 2005) while the French National Academies of Science and Medicine concluded the opposite (Aurengo et al. 2005). These contradictory conclusions may stem in part from an emphasis on epidemiological data (a “top down” approach) versus an emphasis on biological mechanisms (a “bottom up” approach). In this paper, the strengths and limitations of the top down and bottom up approaches are discussed, and proposals for strengthening and reconciling them are suggested. The past seven years since these two reports were published have yielded increasing evidence of nonlinear responses of biological systems to low radiation doses delivered at low dose-rates. This growing body of evidence is casting ever more doubt on the extrapolation of risks observed at high doses and dose-rates to estimate risks associated with typical environmental and occupational exposures. This paper compares current evidence on low dose, low dose-rate effects against objective criteria of causation. Finally, some questions for a post-LNT world are posed. PMID:23304107

Prescription order risk factors for pediatric dosing alerts.

PubMed

Stultz, J S; Porter, K; Nahata, M C

2015-02-01

To determine dosing alert rates based on prescription order characteristics and identify prescription order risk factors for the occurrence of dosing alerts. A retrospective analysis of inpatient medication orders and dosing alerts occurring during October 2011 and January, April, and July 2012 at a pediatric institution. Prescription orders and alerts were categorized by: medication class, patient age, route of administration, and month of the year. There were 228,259 orders during the studied period, with 11,072 alerted orders (4.9%). The most frequently alerted medication class was the non-analgesic central nervous system agent class (14% of alerts). Age, route, medication class, and month all independently affected dosing alert rates. The alert rate was highest for immunosuppressive agents (54%), neonates (6.7%), and orders for rectal administration (9.5%). The alert rate was higher in adult patients receiving their care at a pediatric institution (5.7%) compared to children (4.7%), but after multivariate analysis, pediatric orders had higher odds for an alert (OR 1.1, 95% CI 1.05-1.16). Mercaptopurine had the highest alert rate when categorized by active ingredient (73.9%). Albuterol 2.5mg/mL continuous aerosol and heparin 1000 units in 0.9% sodium chloride injection solution were the unique medications with the highest alert rates (100.0% and 97.7%, respectively). Certain types of prescription orders have a higher risk for causing dosing alerts than others. Patient age, medication class, route of administration, and the month of year can affect dosing alert rates. Design and customization efforts should focus on these medications and prescription order characteristics that increase the risk for dosing alerts. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Evaluation of ambient dose equivalent rates influenced by vertical and horizontal distribution of radioactive cesium in soil in Fukushima Prefecture.

PubMed

Malins, Alex; Kurikami, Hiroshi; Nakama, Shigeo; Saito, Tatsuo; Okumura, Masahiko; Machida, Masahiko; Kitamura, Akihiro

2016-01-01

The air dose rate in an environment contaminated with (134)Cs and (137)Cs depends on the amount, depth profile and horizontal distribution of these contaminants within the ground. This paper introduces and verifies a tool that models these variables and calculates ambient dose equivalent rates at 1 m above the ground. Good correlation is found between predicted dose rates and dose rates measured with survey meters in Fukushima Prefecture in areas contaminated with radiocesium from the Fukushima Dai-ichi Nuclear Power Plant accident. This finding is insensitive to the choice for modeling the activity depth distribution in the ground using activity measurements of collected soil layers, or by using exponential and hyperbolic secant fits to the measurement data. Better predictions are obtained by modeling the horizontal distribution of radioactive cesium across an area if multiple soil samples are available, as opposed to assuming a spatially homogeneous contamination distribution. Reductions seen in air dose rates above flat, undisturbed fields in Fukushima Prefecture are consistent with decrement by radioactive decay and downward migration of cesium into soil. Analysis of remediation strategies for farmland soils confirmed that topsoil removal and interchanging a topsoil layer with a subsoil layer result in similar reductions in the air dose rate. These two strategies are more effective than reverse tillage to invert and mix the topsoil. Copyright © 2015 Elsevier Ltd. All rights reserved.

Measurement of air dose rates over a wide area around the Fukushima Dai-ichi Nuclear Power Plant through a series of car-borne surveys.

PubMed

Andoh, Masaki; Nakahara, Yukio; Tsuda, Shuichi; Yoshida, Tadayoshi; Matsuda, Norihiro; Takahashi, Fumiaki; Mikami, Satoshi; Kinouchi, Nobuyuki; Sato, Tetsuro; Tanigaki, Minoru; Takamiya, Koichi; Sato, Nobuhiro; Okumura, Ryo; Uchihori, Yukio; Saito, Kimiaki

2015-01-01

A series of car-borne surveys using the Kyoto University RAdiation MApping (KURAMA) and KURAMA-II survey systems has been conducted over a wide area in eastern Japan since June 2011 to evaluate the distribution of air dose rates around the Fukushima Dai-ichi Nuclear Power Plant and to evaluate the time-dependent trend of decrease in air dose rates. An automated data processing system for the KURAMA-II system was established, which enabled rapid analysis of large amounts of data obtained using about 100 KURAMA-II units. The initial data used for evaluating the migration status of radioactive cesium were obtained in the first survey, followed by other car-borne surveys conducted over more extensive and wider measurement ranges. By comparing the measured air dose rates obtained in each survey (until December 2012), the decreasing trend of air dose rates measured through car-borne surveys was found to be more pronounced than those expected on the basis of the physical decay of radioactive cesium and of the air dose rates measured using NaI (Tl) survey meters in the areas surrounding the roadways. In addition, it was found that the extent of decrease in air dose rates depended on land use, wherein it decreased faster for land used as building sites than for forested areas. Copyright © 2014 Elsevier Ltd. All rights reserved.

Measuring in vitro biotransformation rates of super hydrophobic chemicals in rat liver s9 fractions using thin-film sorbent-phase dosing.

PubMed

Lee, Yung-Shan; Otton, S Victoria; Campbell, David A; Moore, Margo M; Kennedy, Chris J; Gobas, Frank A P C

2012-01-03

Methods for rapid and cost-effective assessment of the biotransformation potential of very hydrophobic and potentially bioaccumulative chemicals in mammals are urgently needed for the ongoing global evaluation of the environmental behavior of commercial chemicals. We developed and tested a novel solvent-free, thin-film sorbent-phase in vitro dosing system to measure the in vitro biotransformation rates of very hydrophobic chemicals in male Sprague-Dawley rat liver S9 homogenates and compared the rates to those measured by conventional solvent-delivery dosing. The thin-film sorbent-phase dosing system using ethylene vinyl acetate coated vials was developed to eliminate the incomplete dissolution of very hydrophobic substances in largely aqueous liver homogenates, to determine biotransformation rates at low substrate concentrations, to measure the unbound fraction of substrate in solution, and to simplify chemical analysis by avoiding the difficult extraction of test chemicals from complex biological matrices. Biotransformation rates using sorbent-phase dosing were 2-fold greater than those measured using solvent-delivery dosing. Unbound concentrations of very hydrophobic test chemicals were found to decline with increasing S9 and protein concentrations, causing measured biotransformation rates to be independent of S9 or protein concentrations. The results emphasize the importance of specifying both protein content and unbound substrate fraction in the measurement and reporting of in vitro biotransformation rates of very hydrophobic substances, which can be achieved in a thin-film sorbent-phase dosing system.

Lemna minor plants chronically exposed to ionising radiation: RNA-seq analysis indicates a dose rate dependent shift from acclimation to survival strategies.

PubMed

Van Hoeck, Arne; Horemans, Nele; Nauts, Robin; Van Hees, May; Vandenhove, Hildegarde; Blust, Ronny

2017-04-01

Ecotoxicological research provides knowledge on ionising radiation-induced responses in different plant species. However, the sparse data currently available are mainly extracted from acute exposure treatments. To provide a better understanding of environmental exposure scenarios, the response to stress in plants must be followed in more natural relevant chronic conditions. We previously showed morphological and biochemical responses in Lemna minor plants continuously exposed for 7days in a dose-rate dependent manner. In this study responses on molecular (gene expression) and physiological (photosynthetic) level are evaluated in L. minor plants exposed to ionising radiation. To enable this, we examined the gene expression profiles of irradiated L. minor plants by using an RNA-seq approach. The gene expression data reveal indications that L. minor plants exposed at lower dose rates, can tolerate the exposure by triggering acclimation responses. In contrast, at the highest dose rate tested, a high number of genes related to antioxidative defense systems, DNA repair and cell cycle were differentially expressed suggesting that only high dose rates of ionising radiation drive L. minor plants into survival strategies. Notably, the photosynthetic process seems to be unaffected in L. minor plants among the tested dose rates. This study, supported by our earlier work, clearly indicates that plants shift from acclimation responses towards survival responses at increasing dose rates of ionising radiation. Copyright © 2017 Elsevier B.V. All rights reserved.

Circulating Cytokine/Chemokine Concentrations Respond to Ionizing Radiation Doses but not Radiation Dose Rates: Granulocyte-Colony Stimulating Factor and Interleukin-18.

PubMed

Kiang, Juliann G; Smith, Joan T; Hegge, Sara R; Ossetrova, Natalia I

2018-06-01

Exposure to ionizing radiation is a crucial life-threatening factor in nuclear and radiological incidents. It is known that ionizing radiation affects cytokine/chemokine concentrations in the blood of B6D2F1 mice. It is not clear whether radiation dose rates would vary the physiological response. Therefore, in this study we utilized data from two experiments using B6D2F1 female mice exposed to six different dose rates ranging from low to high rates. In one experiment, mice received a total dose of 8 Gy (LD 0/30 ) of 60 Co gamma radiation at four dose rates: 0.04, 0.15, 0.30 and 0.47 Gy/min. Blood samples from mice were collected at 24 and 48 h postirradiation for cytokine/chemokine measurements, including interleukin (IL)-1β, IL-6, IL-10, keratinocyte cytokine (KC), IL-12p70, IL-15, IL-17A, IL-18, granulocyte-colony stimulating factor (G-CSF), granulocyte macrophage (GM)-CSF, macrophage (M)-CSF, monokine induced by gamma interferon (MIG), tumor necrosis factor (TNF)-α, fibroblast growth factor (FGF)-basic, vascular endothelial growth factor (VEGF) and platelet-derived growth factor basic (PDGF-bb). At 24 h after ionizing irradiation at dose rate of 0.04 Gy/min, significant increases were observed only in G-CSF and M-CSF ( P < 0.05). At 0.15 Gy/min, IL-10, IL-17A, G-CSF and GM-CSF concentrations were increased. At 0.3 Gy/min, IL-15, IL-18, G-CSF, GM-CSF, M-CSF, MCP-1, MIP-2, MIG, FGF-basic, VEGF and PDGF-bb were significantly elevated ( P < 0.05). At 0.47 Gy/min, IL-6, KC, IL-10, MCP-1, G-CSF, GM-CSF and M-CSF were significantly increased. At 48 h postirradiation, all cytokines/chemokines except MCP-1 returned to or were below their baselines, suggesting these increases are transient at LD 0/30 irradiation. Of note, there is a limitation on day 2 because cytokines/chemokines are either at or below their baselines. Other parameters such as fms-like tyrosine kinase receptor-3 ligand (Flt-3 ligand) concentrations and lymphocyte counts, which have proven to be unaffected by radiation dose rates, can be used instead for assessing the radiation dose. However, in a separate radiation dose and time-course experiment, increases in IL-18 and G-CSF depended on the radiation doses but showed no significant differences between 0.58 and 1.94 Gy/min ( P > 0.05) at 3 and 6 Gy but not 12 Gy. G-CSF continued to increase up to day 7, whereas IL-18 increased on day 4 and remained above baseline level on day 7. Therefore, time after irradiation at different doses should be taken into consideration. To our knowledge, these results are the first to suggest that ionizing radiation, even at a very low-dose-rate (0.04 Gy/min), induces circulating G-CSF increases but not others for selected time points; radiation-induced increases in IL-18 at radiation dose rates between 0.15 and 1.94 Gy/min are also not in a radiation dose-rate-dependent manner. C-CSF, lymphocyte counts and circulating Flt-3 ligand should be explored further as possible biomarkers of radiation exposure at early time points. IL-18 is also worthy of further study as a potential biomarker at later time points.

Comparison of 2D and 3D Imaging and Treatment Planning for Postoperative Vaginal Apex High-Dose Rate Brachytherapy for Endometrial Cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Russo, James K.; Armeson, Kent E.; Richardson, Susan, E-mail: srichardson@radonc.wustl.edu

2012-05-01

Purpose: To evaluate bladder and rectal doses using two-dimensional (2D) and 3D treatment planning for vaginal cuff high-dose rate (HDR) in endometrial cancer. Methods and Materials: Ninety-one consecutive patients treated between 2000 and 2007 were evaluated. Seventy-one and 20 patients underwent 2D and 3D planning, respectively. Each patient received six fractions prescribed at 0.5 cm to the superior 3 cm of the vagina. International Commission on Radiation Units and Measurements (ICRU) doses were calculated for 2D patients. Maximum and 2-cc doses were calculated for 3D patients. Organ doses were normalized to prescription dose. Results: Bladder maximum doses were 178% ofmore » ICRU doses (p < 0.0001). Two-cubic centimeter doses were no different than ICRU doses (p = 0.22). Two-cubic centimeter doses were 59% of maximum doses (p < 0.0001). Rectal maximum doses were 137% of ICRU doses (p < 0.0001). Two-cubic centimeter doses were 87% of ICRU doses (p < 0.0001). Two-cubic centimeter doses were 64% of maximum doses (p < 0.0001). Using the first 1, 2, 3, 4 or 5 fractions, we predicted the final bladder dose to within 10% for 44%, 59%, 83%, 82%, and 89% of patients by using the ICRU dose, and for 45%, 55%, 80%, 85%, and 85% of patients by using the maximum dose, and for 37%, 68%, 79%, 79%, and 84% of patients by using the 2-cc dose. Using the first 1, 2, 3, 4 or 5 fractions, we predicted the final rectal dose to within 10% for 100%, 100%, 100%, 100%, and 100% of patients by using the ICRU dose, and for 60%, 65%, 70%, 75%, and 75% of patients by using the maximum dose, and for 68%, 95%, 84%, 84%, and 84% of patients by using the 2-cc dose. Conclusions: Doses to organs at risk vary depending on the calculation method. In some cases, final dose accuracy appears to plateau after the third fraction, indicating that simulation and planning may not be necessary in all fractions. A clinically relevant level of accuracy should be determined and further research conducted to address this issue.« less

Immunogenicity to poliovirus type 2 following two doses of fractional intradermal inactivated poliovirus vaccine: A novel dose sparing immunization schedule.

PubMed

Anand, Abhijeet; Molodecky, Natalie A; Pallansch, Mark A; Sutter, Roland W

2017-05-19

The polio eradication endgame strategic plan calls for the sequential removal of Sabin poliovirus serotypes from the trivalent oral poliovirus vaccine (tOPV), starting with type 2, and the introduction of ≥1 dose of inactivated poliovirus vaccine (IPV), to maintain an immunity base against poliovirus type 2. The global removal of oral poliovirus type 2 was successfully implemented in May 2016. However, IPV supply constraints has prevented introduction in 21 countries and led to complete stock-out in >20 countries. We conducted a literature review and contacted corresponding authors of recent studies with fractional-dose IPV (fIPV), one-fifth of intramuscular dose administered intradermally, to conduct additional type 2 immunogenicity analyses of two fIPV doses compared with one full-dose IPV. Four studies were identified that assessed immunogenicity of two fIPV doses compared to one full-dose IPV. Two fractional doses are more immunogenic than 1 full-dose, with type 2 seroconversion rates improving between absolute 19-42% (median: 37%, p<0.001) and relative increase of 53-125% (median: 82%), and antibody titer to type 2 increasing by 2-32-fold (median: 10-fold). Early age of administration and shorter intervals between doses were associated with lower immunogenicity. Overall, two fIPV doses are more immunogenic than a single full-dose, associated with significantly increased seroconversion rates and antibody titers. Two fIPV doses together use two-fifth of the vaccine compared to one full-dose IPV. In response to the current IPV shortage, a schedule of two fIPV doses at ages 6 and 14weekshas been endorsed by technical oversight committees and has been introduced in some affected countries. Copyright © 2017. Published by Elsevier Ltd.

Impact of Number of Human Papillomavirus Vaccine Doses on Genital Warts Diagnoses Among a National Cohort of U.S. Adolescents.

PubMed

Perkins, Rebecca B; Lin, Mengyun; Wallington, Sherrie F; Hanchate, Amresh

2017-06-01

The impact of fewer than 3 doses of human papillomavirus (HPV) vaccine on genital warts is uncertain. Using the Truven Health Analytics Marketscan administrative database, we compared rates of genital warts among women receiving 0, 1, 2, or 3 doses of HPV vaccine. Females aged 9 to 18 years on January 1, 2007, who were continuously enrolled in the database through December 31, 2013, were included. Patients were assigned an HPV dose state (0, 1, 2, or 3) based on the last recorded dose. The exposure period began on January 1, 2007, or the date of the final HPV dose, and lasted until the first diagnosis of genital warts or December 31, 2013. Multivariable Poisson regression was performed to determine the risk of genital warts associated with vaccine doses. Among 387,906 subjects, mean age and exposure period were 14.73 and 5.64 years, respectively. The proportions of doses received were: 52.1%, 7.8%, 9.4%, and 30.7% for 0, 1, 2, and 3 doses, respectively. The rate of genital warts was 1.97/1000 person-years. Receipt of 0 or 1 dose was associated with more genital warts than 3 doses. The effectiveness of 2 doses following current Centers for Disease Control and Prevention guidelines was similar to 3 doses. The risk of genital warts rose with age. Prevention of genital warts is higher with completion of 3 vaccine doses than with 1 dose, though 2-dose recommendations appear to provide similar protection. Prospective effectiveness studies of recommended 2-dose schedules against clinical endpoints including persistent infection, genital warts, and cervical dysplasia are necessary to ensure long-term protection of vaccinated cohorts.

Conditioning of the 4 Curies Radium-226 Sealed Radiation Source in Thailand

DOE Office of Scientific and Technical Information (OSTI.GOV)

Punnachaiya, M.; Sawangsri, T.; Wanabongse, P.

This paper describes the conditioning of the 4 curies Radium-226 (Ra-226) sealed radiation source using as a teletherapy unit for cancer treatment in Thailand. The conditioning was under the International Atomic Energy Agency (IAEA) supervision and budgetary supports, comprised of 6 operational steps: the surface dose rate and actual dimension of radium unit measurements, the appropriate lead shielding design with IAEA approval, confirmation of radioactive contamination before conditioning (smear test and radon gas leakage test), transfer of radium source unit into the designed shielding, confirmation of radioactive contamination and dose rate measurement after conditioning, and transportation of Ra-226 conditioning wastemore » package to OAP interim waste storage. The Ra-226 unit was taken out of OAP temporary waste storage for the surface dose rate and the actual dimension measurements behind the 12 inches thick heavy concrete shielding. The maximum measured surface dose rate was 70 R/hr. The special lead container was designed according to its surface dose rate along the source unit which the maximum permissible dose limit for surface dose rate of waste package after conditioning at 2 mSv/hr was applied. The IAEA approved container had total weight of 2.4 ton. After the confirmation of radioactive contamination, Ra-226 source unit was transferred and loaded in the designed lead shielding within 2 minutes. The results of smear test before and after conditioning including radon gas leakage test revealed that there was no radioactive contamination. After conditioning, the surface dose rate measured on the top, bottom were 15,10 mR/hr and varied from 6 - 50 mR/hr around lead container. The Ra-226 conditioning waste package was safely transported to store in OAP interim waste storage. Total working time including the time consumed for radon gas leakage test was 3.5 hours. The total radiation dose received by 16 operators, were ranged from 1 - 69.84 {mu}Sv and the operational team completed the conditioning safely within the effective dose limit for occupational exposure of 50 mSv/year (200 {mu}Sv/day). (authors)« less

Characteristics and Dose Levels for Spent Reactor Fuels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coates, Cameron W

2007-01-01

Current guidance considers highly radioactive special nuclear materials to be those materials that, unshielded, emit a radiation dose [rate] measured at 1 m which exceeds 100 rem/h. Smaller, less massive fuel assemblies from research reactors can present a challenge from the point of view of self protection because of their size (lower dose, easier to handle) and the desirability of higher enrichments; however, a follow-on study to cross-compare dose trends of research reactors and power reactors was deemed useful to confirm/verify these trends. This paper summarizes the characteristics and dose levels of spent reactor fuels for both research reactors andmore » power reactors and extends previous studies aimed at quantifying expected dose rates from research reactor fuels worldwide.« less

The radiological exposure of man from radioactivity in the Baltic Sea.

PubMed

Nielsen, S P; Bengtson, P; Bojanowsky, R; Hagel, P; Herrmann, J; Ilus, E; Jakobson, E; Motiejunas, S; Panteleev, Y; Skujina, A; Suplinska, M

1999-09-30

A radiological assessment has been carried out considering discharges of radioactivity to the Baltic Sea marine environment since 1950. The sources of radioactivity that have been evaluated are atmospheric nuclear-weapons fallout, fallout from the Chernobyl accident in 1986, discharges of radionuclides from Sellafield and La Hague transported into the Baltic Sea, and discharges of radionuclides from nuclear installations located in the Baltic Sea area. Dose rates from man-made radioactivity to individual members of the public (critical groups) have been calculated based on annual intake of seafood and beach occupancy time. The dose rates to individuals from the regions of the Bothnian Sea and Gulf of Finland are predicted to be larger than from any other area in the Baltic Sea due to the pattern of Chernobyl fallout. The dose rates are predicted to have peaked in 1986 at a value of 0.2 mSv year-1. Collective committed doses to members of the public have been calculated based on fishery statistics and predicted concentrations of radionuclides in biota and coastal sediments. The total collective dose from man-made radioactivity in the Baltic Sea is estimated at 2600 manSv, of which approximately two-thirds originate from Chernobyl fallout, approximately one-quarter from atmospheric nuclear-weapons fallout, approximately 8% from European reprocessing facilities, and approximately 0.04% from nuclear installations bordering the Baltic Sea area. An assessment of small-scale dumping of low-level radioactive waste in the Baltic Sea in the 1960s by Sweden and the Soviet Union has showed that doses to man from these activities are negligible. Dose rates and doses from natural radioactivity dominate except for the year 1986 where dose rates to individuals from Chernobyl fallout in some regions of the Baltic Sea approached those from natural radioactivity.

Depth dependence of absorbed dose, dose equivalent and linear energy transfer spectra of galactic and trapped particles in polyethylene and comparison with calculations of models

NASA Technical Reports Server (NTRS)

Badhwar, G. D.; Cucinotta, F. A.; Wilson, J. W. (Principal Investigator)

1998-01-01

A matched set of five tissue-equivalent proportional counters (TEPCs), embedded at the centers of 0 (bare), 3, 5, 8 and 12-inch-diameter polyethylene spheres, were flown on the Shuttle flight STS-81 (inclination 51.65 degrees, altitude approximately 400 km). The data obtained were separated into contributions from trapped protons and galactic cosmic radiation (GCR). From the measured linear energy transfer (LET) spectra, the absorbed dose and dose-equivalent rates were calculated. The results were compared to calculations made with the radiation transport model HZETRN/NUCFRG2, using the GCR free-space spectra, orbit-averaged geomagnetic transmission function and Shuttle shielding distributions. The comparison shows that the model fits the dose rates to a root mean square (rms) error of 5%, and dose-equivalent rates to an rms error of 10%. Fairly good agreement between the LET spectra was found; however, differences are seen at both low and high LET. These differences can be understood as due to the combined effects of chord-length variation and detector response function. These results rule out a number of radiation transport/nuclear fragmentation models. Similar comparisons of trapped-proton dose rates were made between calculations made with the proton transport model BRYNTRN using the AP-8 MIN trapped-proton model and Shuttle shielding distributions. The predictions of absorbed dose and dose-equivalent rates are fairly good. However, the prediction of the LET spectra below approximately 30 keV/microm shows the need to improve the AP-8 model. These results have strong implications for shielding requirements for an interplanetary manned mission.

Radiation measurements and doses at SST altitudes

NASA Technical Reports Server (NTRS)

Foelsche, T.

1972-01-01

Radiation components and dose equivalents due to galactic and solar cosmic rays in the high atmosphere, especially at SST altitudes, are presented. The dose equivalent rate for the flight personnel flying 500 hours per year in cruise altitudes of 60,000-65,000 feet (18-19.5 km) in high magnetic latitudes is about 0.75-1.0 rem per year averaged over the solar cycle, or about 15-20 percent of the maximum permissible dose rate.

Single Dose Versus 3 Doses of Intramuscular Benzathine Penicillin for Early Syphilis in HIV: A Randomized Clinical Trial.

PubMed

Andrade, Roberto; Rodriguez-Barradas, Maria C; Yasukawa, Kosuke; Villarreal, Erick; Ross, Michael; Serpa, Jose A

2017-03-15

Patients coinfected with syphilis and human immunodeficiency virus (HIV) may have a slower decrease in rapid plasma reagin (RPR) titers. Currently a single dose of 2.4 million units of intramuscular benzathine penicillin G (BPG) is recommended for the treatment of early syphilis. Some observational studies have suggested that this regimen may lead to high failure rates in coinfected patients. We conducted an open-label randomized clinical trial to compare the efficacy of single-dose and 3-dose regimens of BPG for the treatment of early syphilis in HIV-infected individuals. RPR titers were monitored every 3 months. Treatment success was defined as a decrease in RPR titers of ≥2 dilutions (4-fold) during a 12-month follow-up period. Sixty-four patients were included. In the intention-to-treat analysis, treatment success rates were 80% (28 of 35 subjects) and 93% (27 of 29 subjects) in the single-dose and 3-dose regimens, respectively (absolute difference, 13% [95% confidence interval {CI}, -5% to 30%; P = .17). In the per-protocol analysis, success rates were 93% (27 of 29) and 100% in the single-dose and 3-dose regimens, respectively (absolute difference, 7% [95% CI, -7% to 22%]; P = .49). CD4 T-cell count, RPR titer and syphilis stage did not affect treatment results. When compared with a single dose of BPG, a 3-dose regimen did not improve syphilis serological outcomes. Our results support the Centers for Disease Control and Prevention recommendation of a single dose of BPG in HIV-infected patients with early syphilis. NCT02611765. © The Author 2017. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail journals.permissions@oup.com.

External dose-rate conversion factors of radionuclides for air submersion, ground surface contamination and water immersion based on the new ICRP dosimetric setting.

PubMed

Yoo, Song Jae; Jang, Han-Ki; Lee, Jai-Ki; Noh, Siwan; Cho, Gyuseong

2013-01-01

For the assessment of external doses due to contaminated environment, the dose-rate conversion factors (DCFs) prescribed in Federal Guidance Report 12 (FGR 12) and FGR 13 have been widely used. Recently, there were significant changes in dosimetric models and parameters, which include the use of the Reference Male and Female Phantoms and the revised tissue weighting factors, as well as the updated decay data of radionuclides. In this study, the DCFs for effective and equivalent doses were calculated for three exposure settings: skyshine, groundshine and water immersion. Doses to the Reference Phantoms were calculated by Monte Carlo simulations with the MCNPX 2.7.0 radiation transport code for 26 mono-energy photons between 0.01 and 10 MeV. The transport calculations were performed for the source volume within the cut-off distances practically contributing to the dose rates, which were determined by a simplified calculation model. For small tissues for which the reduction of variances are difficult, the equivalent dose ratios to a larger tissue (with lower statistical errors) nearby were employed to make the calculation efficient. Empirical response functions relating photon energies, and the organ equivalent doses or the effective doses were then derived by the use of cubic-spline fitting of the resulting doses for 26 energy points. The DCFs for all radionuclides considered important were evaluated by combining the photon emission data of the radionuclide and the empirical response functions. Finally, contributions of accompanied beta particles to the skin equivalent doses and the effective doses were calculated separately and added to the DCFs. For radionuclides considered in this study, the new DCFs for the three exposure settings were within ±10 % when compared with DCFs in FGR 13.

External dose-rate conversion factors of radionuclides for air submersion, ground surface contamination and water immersion based on the new ICRP dosimetric setting

PubMed Central

Yoo, Song Jae; Jang, Han-Ki; Lee, Jai-Ki; Noh, Siwan; Cho, Gyuseong

2013-01-01

For the assessment of external doses due to contaminated environment, the dose-rate conversion factors (DCFs) prescribed in Federal Guidance Report 12 (FGR 12) and FGR 13 have been widely used. Recently, there were significant changes in dosimetric models and parameters, which include the use of the Reference Male and Female Phantoms and the revised tissue weighting factors, as well as the updated decay data of radionuclides. In this study, the DCFs for effective and equivalent doses were calculated for three exposure settings: skyshine, groundshine and water immersion. Doses to the Reference Phantoms were calculated by Monte Carlo simulations with the MCNPX 2.7.0 radiation transport code for 26 mono-energy photons between 0.01 and 10 MeV. The transport calculations were performed for the source volume within the cut-off distances practically contributing to the dose rates, which were determined by a simplified calculation model. For small tissues for which the reduction of variances are difficult, the equivalent dose ratios to a larger tissue (with lower statistical errors) nearby were employed to make the calculation efficient. Empirical response functions relating photon energies, and the organ equivalent doses or the effective doses were then derived by the use of cubic-spline fitting of the resulting doses for 26 energy points. The DCFs for all radionuclides considered important were evaluated by combining the photon emission data of the radionuclide and the empirical response functions. Finally, contributions of accompanied beta particles to the skin equivalent doses and the effective doses were calculated separately and added to the DCFs. For radionuclides considered in this study, the new DCFs for the three exposure settings were within ±10 % when compared with DCFs in FGR 13. PMID:23542764

Evaluation of the dosimetric properties of a synthetic single crystal diamond detector in high energy clinical proton beams.

PubMed

Mandapaka, A K; Ghebremedhin, A; Patyal, B; Marinelli, Marco; Prestopino, G; Verona, C; Verona-Rinati, G

2013-12-01

To investigate the dosimetric properties of a synthetic single crystal diamond Schottky diode for accurate relative dose measurements in large and small field high-energy clinical proton beams. The dosimetric properties of a synthetic single crystal diamond detector were assessed by comparison with a reference Markus parallel plate ionization chamber, an Exradin A16 microionization chamber, and Exradin T1a ion chamber. The diamond detector was operated at zero bias voltage at all times. Comparative dose distribution measurements were performed by means of Fractional depth dose curves and lateral beam profiles in clinical proton beams of energies 155 and 250 MeV for a 14 cm square cerrobend aperture and 126 MeV for 3, 2, and 1 cm diameter circular brass collimators. ICRU Report No. 78 recommended beam parameters were used to compare fractional depth dose curves and beam profiles obtained using the diamond detector and the reference ionization chamber. Warm-up∕stability of the detector response and linearity with dose were evaluated in a 250 MeV proton beam and dose rate dependence was evaluated in a 126 MeV proton beam. Stem effect and the azimuthal angle dependence of the diode response were also evaluated. A maximum deviation in diamond detector signal from the average reading of less than 0.5% was found during the warm-up irradiation procedure. The detector response showed a good linear behavior as a function of dose with observed deviations below 0.5% over a dose range from 50 to 500 cGy. The detector response was dose rate independent, with deviations below 0.5% in the investigated dose rates ranging from 85 to 300 cGy∕min. Stem effect and azimuthal angle dependence of the diode signal were within 0.5%. Fractional depth dose curves and lateral beam profiles obtained with the diamond detector were in good agreement with those measured using reference dosimeters. The observed dosimetric properties of the synthetic single crystal diamond detector indicate that its behavior is proton energy independent and dose rate independent in the investigated energy and dose rate range and it is suitable for accurate relative dosimetric measurements in large as well as in small field high energy clinical proton beams.

SU-E-T-188: Film Dosimetry Verification of Monte Carlo Generated Electron Treatment Plans

DOE Office of Scientific and Technical Information (OSTI.GOV)

Enright, S; Asprinio, A; Lu, L

2014-06-01

Purpose: The purpose of this study was to compare dose distributions from film measurements to Monte Carlo generated electron treatment plans. Irradiation with electrons offers the advantages of dose uniformity in the target volume and of minimizing the dose to deeper healthy tissue. Using the Monte Carlo algorithm will improve dose accuracy in regions with heterogeneities and irregular surfaces. Methods: Dose distributions from GafChromic{sup ™} EBT3 films were compared to dose distributions from the Electron Monte Carlo algorithm in the Eclipse{sup ™} radiotherapy treatment planning system. These measurements were obtained for 6MeV, 9MeV and 12MeV electrons at two depths. Allmore » phantoms studied were imported into Eclipse by CT scan. A 1 cm thick solid water template with holes for bonelike and lung-like plugs was used. Different configurations were used with the different plugs inserted into the holes. Configurations with solid-water plugs stacked on top of one another were also used to create an irregular surface. Results: The dose distributions measured from the film agreed with those from the Electron Monte Carlo treatment plan. Accuracy of Electron Monte Carlo algorithm was also compared to that of Pencil Beam. Dose distributions from Monte Carlo had much higher pass rates than distributions from Pencil Beam when compared to the film. The pass rate for Monte Carlo was in the 80%–99% range, where the pass rate for Pencil Beam was as low as 10.76%. Conclusion: The dose distribution from Monte Carlo agreed with the measured dose from the film. When compared to the Pencil Beam algorithm, pass rates for Monte Carlo were much higher. Monte Carlo should be used over Pencil Beam for regions with heterogeneities and irregular surfaces.« less

Characterizing low dose and dose rate effects in rodent and human neural stem cells exposed to proton and gamma irradiation.

PubMed

Tseng, Bertrand P; Lan, Mary L; Tran, Katherine K; Acharya, Munjal M; Giedzinski, Erich; Limoli, Charles L

2013-01-01

Past work has shown that exposure to gamma rays and protons elicit a persistent oxidative stress in rodent and human neural stem cells (hNSCs). We have now adapted these studies to more realistic exposure scenarios in space, using lower doses and dose rates of these radiation modalities, to further elucidate the role of radiation-induced oxidative stress in these cells. Rodent neural stem and precursor cells grown as neurospheres and human neural stem cells grown as monolayers were subjected to acute and multi-dosing paradigms at differing dose rates and analyzed for changes in reactive oxygen species (ROS), reactive nitrogen species (RNS), nitric oxide and superoxide for 2 days after irradiation. While acute exposures led to significant changes in both cell types, hNSCs in particular, exhibited marked and significant elevations in radiation-induced oxidative stress. Elevated oxidative stress was more significant in hNSCs as opposed to their rodent counterparts, and hNSCs were significantly more sensitive to low dose exposures in terms of survival. Combinations of protons and γ-rays delivered as lower priming or higher challenge doses elicited radioadaptive changes that were associated with improved survival, but in general, only under conditions where the levels of reactive species were suppressed compared to cells irradiated acutely. Protective radioadaptive effects on survival were eliminated in the presence of the antioxidant N-acetylcysteine, suggesting further that radiation-induced oxidative stress could activate pro-survival signaling pathways that were sensitive to redox state. Data corroborates much of our past work and shows that low dose and dose rate exposures elicit significant changes in oxidative stress that have functional consequences on survival.

Doses of external exposure in Jordan house due to gamma-emitting natural radionuclides in building materials.

PubMed

Al-Jundi, J; Ulanovsky, A; Pröhl, G

2009-10-01

The use of building materials containing naturally occurring radionuclides as (40)K, (232)Th, and (238)U and their progeny results in external exposures of the residents of such buildings. In the present study, indoor dose rates for a typical Jordan concrete room are calculated using Monte Carlo method. Uniform chemical composition of the walls, floor and ceiling as well as uniform mass concentrations of the radionuclides in walls, floor and ceiling are assumed. Using activity concentrations of natural radionuclides typical for the Jordan houses and assuming them to be in secular equilibrium with their progeny, the maximum annual effective doses are estimated to be 0.16, 0.12 and 0.22 mSv a(-1) for (40)K, (232)Th- and (238)U-series, respectively. In a total, the maximum annual effective indoor dose due to external gamma-radiation is 0.50 mSv a(-1). Additionally, organ dose coefficients are calculated for all organs considered in ICRP Publication 74. Breast, skin and eye lenses have the maximum equivalent dose rate values due to indoor exposures caused by the natural radionuclides, while equivalent dose rates for uterus, colon (LLI) and small intestine are found to be the smallest. More specifically, organ dose rates (nSv a(-1)per Bq kg(-1)) vary from 0.044 to 0.060 for (40)K, from 0.44 to 0.60 for radionuclides from (238)U-series and from 0.60 to 0.81 for radionuclides from (232)Th-series. The obtained organ and effective dose conversion coefficients can be conveniently used in practical dose assessment tasks for the rooms of similar geometry and varying activity concentrations and local-specific occupancy factors.

Measurement of soil contamination by radionuclides due to the Fukushima Dai-ichi Nuclear Power Plant accident and associated estimated cumulative external dose estimation.

PubMed

Endo, S; Kimura, S; Takatsuji, T; Nanasawa, K; Imanaka, T; Shizuma, K

2012-09-01

Soil sampling was carried out at an early stage of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. Samples were taken from areas around FDNPP, at four locations northwest of FDNPP, at four schools and in four cities, including Fukushima City. Radioactive contaminants in soil samples were identified and measured by using a Ge detector and included (129 m)Te, (129)Te, (131)I, (132)Te, (132)I, (134)Cs, (136)Cs, (137)Cs, (140)Ba and (140)La. The highest soil depositions were measured to the northwest of FDNPP. From this soil deposition data, variations in dose rates over time and the cumulative external doses at the locations for 3 months and 1y after deposition were estimated. At locations northwest of FDNPP, the external dose rate at 3 months after deposition was 4.8-98 μSv/h and the cumulative dose for 1 y was 51 to 1.0 × 10(3)mSv; the highest values were at Futaba Yamada. At the four schools, which were used as evacuation shelters, and in the four urban cities, the external dose rate at 3 months after deposition ranged from 0.03 to 3.8μSv/h and the cumulative doses for 1 y ranged from 3 to 40 mSv. The cumulative dose at Fukushima Niihama Park was estimated as the highest in the four cities. The estimated external dose rates and cumulative doses show that careful countermeasures and remediation will be needed as a result of the accident, and detailed measurements of radionuclide deposition densities in soil will be important input data to conduct these activities. Copyright © 2011 Elsevier Ltd. All rights reserved.

Biological effective dose for comparison and combination of external beam and low-dose rate interstitial brachytherapy prostate cancer treatment plans

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jani, Ashesh B.; Hand, Christopher M.; Lujan, Anthony E.

2004-03-31

We report a methodology for comparing and combining dose information from external beam radiotherapy (EBRT) and interstitial brachytherapy (IB) components of prostate cancer treatment using the biological effective dose (BED). On a prototype early-stage prostate cancer patient treated with EBRT and low-dose rate I-125 brachytherapy, a 3-dimensional dose distribution was calculated for each of the EBRT and IB portions of treatment. For each component of treatment, the BED was calculated on a point-by-point basis to produce a BED distribution. These individual BED distributions could then be summed for combined therapies. BED dose-volume histograms (DVHs) of the prostate, urethra, rectum, andmore » bladder were produced and compared for various combinations of EBRT and IB. Transformation to BED enabled computation of the relative contribution of each modality to the prostate dose, as the relative weighting of EBRT and IB was varied. The BED-DVHs of the prostate and urethra demonstrated dramatically increased inhomogeneity with the introduction of even a small component of IB. However, increasing the IB portion relative to the EBRT component resulted in lower dose to the surrounding normal structures, as evidenced by the BED-DVHs of the bladder and rectum. Conformal EBRT and low-dose rate IB conventional dose distributions were successfully transformed to the common 'language' of BED distributions for comparison and for merging prostate cancer radiation treatment plans. The results of this analysis can assist physicians in quantitatively determining the best combination and weighting of radiation treatment modalities for individual patients.« less

Bovine spongiform encephalopathy: the effect of oral exposure dose on attack rate and incubation period in cattle - an update.

PubMed

Konold, Timm; Arnold, Mark E; Austin, Anthony R; Cawthraw, Saira; Hawkins, Steve A C; Stack, Michael J; Simmons, Marion M; Sayers, A Robin; Dawson, Michael; Wilesmith, John W; Wells, Gerald A H

2012-12-05

To provide information on dose-response and aid in modelling the exposure dynamics of the BSE epidemic in the United Kingdom groups of cattle were exposed orally to a range of different doses of brainstem homogenate of known infectious titre from clinical cases of classical bovine spongiform encephalopathy (BSE). Interim data from this study was published in 2007. This communication documents additional BSE cases, which occurred subsequently, examines possible influence of the bovine prion protein gene on disease incidence and revises estimates of effective oral exposure. Following interim published results, two further cattle, one dosed with 100 mg and culled at 127 months post exposure and the other dosed with 10 mg and culled at 110 months post exposure, developed BSE. Both had a similar pathological phenotype to previous cases. Based on attack rate and incubation period distribution according to dose, the dose estimate at which 50% of confirmed cases would be clinically affected was revised to 0.15 g of the brain homogenate used in the experiment, with a 95% confidence interval of 0.03-0.79 g. Neither the full open reading frame nor the promoter region of the prion protein gene of dosed cattle appeared to influence susceptibility to BSE, but this may be due to the sample size. Oral exposure of cattle to a large range of doses of a BSE brainstem homogenate produced disease in all dose groups. The pathological presentation resembled natural disease. The attack rate and incubation period were dependent on the dose.

High Resolution Mesoscale Weather Data Improvement to Spatial Effects for Dose-Rate Contour Plot Predictions

DTIC Science & Technology

2007-03-01

time. This is a very powerful tool in determining fine spatial resolution , as boundary conditions are not only updated at every timestep, but the ...HIGH RESOLUTION MESOSCALE WEATHER DATA IMPROVEMENT TO SPATIAL EFFECTS FOR DOSE-RATE CONTOUR PLOT PREDICTIONS THESIS Christopher P...11 1 HIGH RESOLUTION MESOSCALE WEATHER DATA IMPROVEMENT TO SPATIAL EFFECTS FOR DOSE-RATE CONTOUR PLOT

Estimation of absorbed radiation dose rates in wild rodents inhabiting a site severely contaminated by the Fukushima Dai-ichi nuclear power plant accident.

PubMed

Kubota, Yoshihisa; Takahashi, Hiroyuki; Watanabe, Yoshito; Fuma, Shoichi; Kawaguchi, Isao; Aoki, Masanari; Kubota, Masahide; Furuhata, Yoshiaki; Shigemura, Yusaku; Yamada, Fumio; Ishikawa, Takahiro; Obara, Satoshi; Yoshida, Satoshi

2015-04-01

The dose rates of radiation absorbed by wild rodents inhabiting a site severely contaminated by the Fukushima Dai-ichi Nuclear Power Plant accident were estimated. The large Japanese field mouse (Apodemus speciosus), also called the wood mouse, was the major rodent species captured in the sampling area, although other species of rodents, such as small field mice (Apodemus argenteus) and Japanese grass voles (Microtus montebelli), were also collected. The external exposure of rodents calculated from the activity concentrations of radiocesium ((134)Cs and (137)Cs) in litter and soil samples using the ERICA (Environmental Risk from Ionizing Contaminants: Assessment and Management) tool under the assumption that radionuclides existed as the infinite plane isotropic source was almost the same as those measured directly with glass dosimeters embedded in rodent abdomens. Our findings suggest that the ERICA tool is useful for estimating external dose rates to small animals inhabiting forest floors; however, the estimated dose rates showed large standard deviations. This could be an indication of the inhomogeneous distribution of radionuclides in the sampled litter and soil. There was a 50-fold difference between minimum and maximum whole-body activity concentrations measured in rodents at the time of capture. The radionuclides retained in rodents after capture decreased exponentially over time. Regression equations indicated that the biological half-life of radiocesium after capture was 3.31 d. At the time of capture, the lowest activity concentration was measured in the lung and was approximately half of the highest concentration measured in the mixture of muscle and bone. The average internal absorbed dose rate was markedly smaller than the average external dose rate (<10% of the total absorbed dose rate). The average total absorbed dose rate to wild rodents inhabiting the sampling area was estimated to be approximately 52 μGy h(-1) (1.2 mGy d(-1)), even 3 years after the accident. This dose rate exceeds 0.1-1 mGy d(-1) derived consideration reference level for Reference rat proposed by the International Commission on Radiological Protection (ICRP). Copyright © 2015 Elsevier Ltd. All rights reserved.

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. Copyright © 2016 American Association of Medical Dosimetrists. Published by Elsevier Inc. All rights reserved.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Ruijie, E-mail: ruijyang@yahoo.com; Zhao, Nan; Liao, Anyan

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 5 mm. Rectum, bladder, urethra, and femoral heads were considered as organs at risk. A 78 Gy in 39 fractions were prescribed for PTV. For HDR andmore » LDR plans, the dose prescription was D{sub 90} of 34 Gy in 8.5 Gy per fraction, and 145 Gy 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 2 Gy per fraction, EQD{sub 2}) for comparison of 3 techniques. HDR and LDR significantly reduced the dose to rectum and bladder compared with VMAT. The D{sub mean} (EQD{sub 2}) of rectum decreased 22.36 Gy in HDR and 17.01 Gy in LDR from 30.24 Gy in VMAT, respectively. The D{sub mean} (EQD{sub 2}) of bladder decreased 6.91 Gy in HDR and 2.53 Gy in LDR from 13.46 Gy 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 (EQD{sub 2}) was 80.26, 70.23, and 104.91 Gy 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.« less

Dose mapping inside a gamma irradiator measured with doped silica fibre dosimetry and Monte Carlo simulation

NASA Astrophysics Data System (ADS)

Moradi, F.; Khandaker, M. U.; Mahdiraji, G. A.; Ung, N. M.; Bradley, D. A.

2017-11-01

In recent years doped silica fibre thermoluminescent dosimeters (TLD) have been demonstrated to have considerable potential for irradiation applications, benefitting from the available sensitivity, spatial resolution and dynamic dose range, with primary focus being on the needs of medical dosimetry. Present study concerns the dose distribution inside a cylindrically shaped gamma-ray irradiator cavity, with irradiator facilities such as the familiar 60Co versions being popularly used in industrial applications. Quality assurance of the radiation dose distribution inside the irradiation cell of such a device is of central importance in respect of the delivered dose to the irradiated material. Silica fibre TLD dose-rates obtained within a Gammacell-220 irradiator cavity show the existence of non-negligible dose distribution heterogeneity, by up to 20% and 26% in the radial and axial directions respectively, Monte Carlo simulations and available literature providing some support for present findings. In practice, it is evident that there is need to consider making corrections to nominal dose-rates in order to avoid the potential for under-dosing.

PARMA: PHITS-based Analytical Radiation Model in the Atmosphere--Verification of Its Accuracy in Estimating Cosmic Radiation Doses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sato, Tatsuhiko; Satoh, Daiki; Endo, Akira

Estimation of cosmic-ray spectra in the atmosphere has been an essential issue in the evaluation of the aircrew doses. We therefore developed an analytical model that can predict the terrestrial neutron, proton, He nucleus, muon, electron, positron and photon spectra at altitudes below 20 km, based on the Monte Carlo simulation results of cosmic-ray propagation in the atmosphere performed by the PHITS code. The model was designated PARMA. In order to examine the accuracy of PARMA in terms of the neutron dose estimation, we measured the neutron dose rates at the altitudes between 20 to 10400 m, using our developedmore » dose monitor DARWIN mounted on an aircraft. Excellent agreement was observed between the measured dose rates and the corresponding data calculated by PARMA coupled with the fluence-to-dose conversion coefficients, indicating the applicability of the model to be utilized in the route-dose calculation.« less

Extra dose due to extravehicular activity during the NASA4 mission measured by an on-board TLD system.

PubMed

Deme, S; Apathy, I; Hejja, I; Lang, E; Feher, I

1999-01-01

A microprocessor-controlled on-board TLD system, 'Pille'96', was used during the NASA4 (1997) mission to monitor the cosmic radiation dose inside the Mir Space Station and to measure the extra dose to two astronauts in the course of their extravehicular activity (EVA). For the EVA dose measurements, CaSO4:Dy bulb dosemeters were located in specially designed pockets of the ORLAN spacesuits. During an EVA lasting 6 h, the dose ratio inside and outside Mir was measured. During the EVA, Mir crossed the South Atlantic Anomaly (SAA) three times. Taking into account the influence of these three crossings the mean EVA/internal dose rate ratio was 3.2. Internal dose mapping using CaSO4:Dy dosemeters gave mean dose rates ranging from 9.3 to 18.3 microGy h-1 at locations where the shielding effect was not the same. Evaluation results of the high temperature region of LiF dosemeters are given to estimate the mean LET.

Comparative dosimetric characterization for different types of detectors in high-energy electron beams

NASA Astrophysics Data System (ADS)

Lee, Chang Yeol; Kim, Woo Chul; Kim, Hun Jeong; Huh, Hyun Do; Park, Seungwoo; Choi, Sang Hyoun; Kim, Kum Bae; Min, Chul Kee; Kim, Seong Hoon; Shin, Dong Oh

2017-02-01

The purpose of this study is to perform a comparison and on analysis of measured dose factor values by using various commercially available high-energy electron beam detectors to measure dose profiles and energy property data. By analyzing the high-energy electron beam data from each detector, we determined the optimal detector for measuring electron beams in clinical applications. The dose linearity, dose-rate dependence, percentage depth dose, and dose profile of each detector were measured to evaluate the dosimetry characteristics of high-energy electron beams. The dose profile and the energy characteristics of high-energy electron beams were found to be different when measured by different detectors. Through comparison with other detectors based on the analyzed data, the microdiamond detector was found to have outstanding dose linearity, a low dose-rate dependency, and a small effective volume. Thus, this detector has outstanding spatial resolution and is the optimal detector for measuring electron beams. Radiation therapy results can be improved and related medical accidents can be prevented by using the procedure developed in this research in clinical practice for all beam detectors when measuring the electron beam dose.

Measurement of the ambient gamma dose equivalent and kerma from the small 252Cf source at 1 meter and the small 60Co source at 2 meters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carl, W. F.

NASA Langley Research Center requested a measurement and determination of the ambient gamma dose equivalent rate and kerma at 100 cm from the 252Cf source and determination of the ambient gamma dose equivalent rate and kerma at 200 cm from the 60Co source for the Radiation Budget Instrument Experiment (Rad-X). An Exradin A6 ion chamber with Shonka air-equivalent plastic walls in combination with a Supermax electrometer were used to measure the exposure rate and free-in-air kerma rate of the two sources at the requested distances. The measured gamma exposure, kerma, and dose equivalent rates are tabulated.

Comparison of monoenergetic photon organ dose rate coefficients for stylized and voxel phantoms submerged in air

DOE PAGES

Bellamy, Michael B.; Hiller, Mauritius M.; Dewji, Shaheen A.; ...

2016-02-01

As part of a broader effort to calculate effective dose rate coefficients for external exposure to photons and electrons emitted by radionuclides distributed in air, soil or water, age-specific stylized phantoms have been employed to determine dose coefficients relating dose rate to organs and tissues in the body. In this article, dose rate coefficients computed using the International Commission on Radiological Protection reference adult male voxel phantom are compared with values computed using the Oak Ridge National Laboratory adult male stylized phantom in an air submersion exposure geometry. Monte Carlo calculations for both phantoms were performed for monoenergetic source photonsmore » in the range of 30 keV to 5 MeV. Furthermore, these calculations largely result in differences under 10 % for photon energies above 50 keV, and it can be expected that both models show comparable results for the environmental sources of radionuclides.« less

Comparison of monoenergetic photon organ dose rate coefficients for stylized and voxel phantoms submerged in air

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bellamy, Michael B.; Hiller, Mauritius M.; Dewji, Shaheen A.

As part of a broader effort to calculate effective dose rate coefficients for external exposure to photons and electrons emitted by radionuclides distributed in air, soil or water, age-specific stylized phantoms have been employed to determine dose coefficients relating dose rate to organs and tissues in the body. In this article, dose rate coefficients computed using the International Commission on Radiological Protection reference adult male voxel phantom are compared with values computed using the Oak Ridge National Laboratory adult male stylized phantom in an air submersion exposure geometry. Monte Carlo calculations for both phantoms were performed for monoenergetic source photonsmore » in the range of 30 keV to 5 MeV. Furthermore, these calculations largely result in differences under 10 % for photon energies above 50 keV, and it can be expected that both models show comparable results for the environmental sources of radionuclides.« less

SU-G-TeP3-02: Determination of Geometry-Specific Backscatter Factors for Radiobiology Studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Viscariello, N; Culberson, W; Lawless, M

2016-06-15

Purpose: Radiation biology research relies on an accurate radiation dose delivered to the biological target. Large field irradiations in a cabinet irradiator may use the AAPM TG-61 protocol. This relies on an air-kerma measurement and conversion to absorbed dose to water (Dw) on the surface of a water phantom using provided backscatter factors. Cell or small animal studies differ significantly from this reference geometry. This study aims to determine the impact of the lack of full scatter conditions in four representative geometries that may be used in radiobiology studies. Methods: MCNP6 was used to model the Dw on the surfacemore » of a full scatter phantom in a validated orthovoltage x-ray reference beam. Dw in a cylindrical mouse, 100 mm Petri dish, 6-well and 96-well cell culture dishes was simulated and compared to this full scatter geometry. A reference dose rate was measured using the TG-61 protocol in a cabinet irradiator. This nominal dose rate was used to irradiate TLDs in each phantom to a given dose. Doses were obtained based on TLDs calibrated in a NIST-traceable beam. Results: Compared to the full scattering conditions, the simulated dose to water in the representative geometries were found to be underestimated by 12-26%. The discrepancy was smallest with the cylindrical mouse geometry, which most closely approximates adequate lateral- and backscatter. TLDs irradiated in the mouse and petri dish phantoms using the TG-61 determined dose rate showed similarly lower values of Dw. When corrected for this discrepancy, they agreed with the predicted Dw within 5%. Conclusion: Using the TG-61 in-air protocol and given backscatter factors to determine a reference dose rate in a biological irradiator may not be appropriate given the difference in scattering conditions between irradiation and calibration. Without accounting for this, the dose rate is overestimated and is dependent on irradiation geometry.« less

MO-FG-BRA-05: Dosimetric and Radiobiological Validation of Respiratory Gating in Conventional and Hypofractionated Radiotherapy of the Lung: Effect of Dose, Dose Rate, Gating Window and Breathing Pattern

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cervino, L; Soultan, D; Pettersson, N

2016-06-15

Purpose: to evaluate the dosimetric and radiobiological consequences from having different gating windows, dose rates, and breathing patterns in gated VMAT lung radiotherapy. Methods: A novel 3D-printed moving phantom with central high and peripheral low tracer uptake regions was 4D FDG-PET/CT-scanned using ideal, patient-specific regular, and irregular breathing patterns. A scan of the stationary phantom was obtained as a reference. Target volumes corresponding to different uptake regions were delineated. Simultaneous integrated boost (SIB) 6 MV VMAT plans were produced for conventional and hypofractionated radiotherapy, using 30–70 and 100% cycle gating scenarios. Prescribed doses were 200 cGy with SIB to 240more » cGy to high uptake volume for conventional, and 800 with SIB to 900 cGy for hypofractionated plans. Dose rates of 600 MU/min (conventional and hypofractionated) and flattening filter free 1400 MU/min (hypofractionated) were used. Ion chamber measurements were performed to verify delivered doses. Vials with A549 cells placed in locations matching ion chamber measurements were irradiated using the same plans to measure clonogenic survival. Differences in survival for the different doses, dose rates, gating windows, and breathing patterns were analyzed. Results: Ion chamber measurements agreed within 3% of the planned dose, for all locations, breathing patterns and gating windows. Cell survival depended on dose alone, and not on gating window, breathing pattern, MU rate, or delivery time. The surviving fraction varied from approximately 40% at 2Gy to 1% for 9 Gy and was within statistical uncertainty relative to that observed for the stationary phantom. Conclusions: Use of gated VMAT in PET-driven SIB radiotherapy was validated using ion chamber measurements and cell survival assays for conventional and hypofractionated radiotherapy.« less

Dependence of pentobarbital kinetics upon the dose of the drug and its pharmacodynamic effects.

PubMed

Kozlowski, K H; Szaykowski, A; Danysz, A

1977-01-01

Pentobarbital (PB), at dose range of 20--50 mg/kg, displays in rabbits non-linear, dose-dependent kinetics. Pharmacokinetics parameters of drug elimination depend largely upon the dose, while the distribution phase is dose-independent. The rate of disappearance of PB from the central compartment (plasma) decreases with the increase of the dose. The analysis of pharmacodynamic parameters has shown that this dose-dependent retardation of PB elimination is probably caused by an impairment of metabolic processes, resulting from disturbance of the circulatory system. A close correlation has been found between the hypotensive effect of PB and the elimination constant, k13, and also between the hypotensive effect and beta.Vd(extrap), a coefficient proportional to the rate of metabolism of PB [23, 29]. The results indicate the necessity of considering the changes in the functional state of the organism, related to the action of a drug, in pharmacokinetic studies.

On the radiation induced degradation of NBR-EPDM rubbers

NASA Astrophysics Data System (ADS)

Chipara, M. D.; Grecu, V. V.; Chipara, M. I.; Ponta, C.; Reyes Romero, J.

1999-05-01

The modification of the elongation at break for NBR-EPDM rubbers subjected to gamma irradiation at various integral doses ranging from 10 to 200 kGy, at different dose rates (0.14, 0.47, 1, 3, 4.7 kGy/h) are reported. The presence of the dose rate effect is noticed.

NOTE: Investigating the potential of polymer gel dosimetry for interventional radiology: first results

NASA Astrophysics Data System (ADS)

Antoniou, P. E.; Bousbouras, P.; Sandaltzopoulos, R.; Kaldoudi, E.

2008-04-01

Complex interventional radiology (IR) procedures contribute an increasing percentage of the overall medical radiation exposure of the population making accurate dosimetry a challenge. Magnetic resonance (MR) based polymer gel dosimetry has been widely employed in complex dosimetric problems in radiotherapy. The aim of this note is to investigate the feasibility of normoxic gel dosimetry in IR. Dose response, energy dependence and dose rate dependence were investigated in irradiation set-ups relevant to IR for a particular normoxic gel, based on methacrylic acid (MAA) as the monomer and including tetrakis-hydroxy-methyl-phosphonium chloride (THPC) as antioxidant. The gel presents a linear dose response beyond a 25 cGy threshold. No significant energy dependence was observed in the useful range of interventional radiology (80-110 kVp). A linear correlation between the gel response and dose rate was observed in the range of dose rates relevant to IR (5-8 cGy min-1). These results demonstrate a reduction of gel sensitivity at very low dose rate levels. A possible explanation of this effect is suggested.

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.

Comparison of the uncertainties of several European low-dose calibration facilities

NASA Astrophysics Data System (ADS)

Dombrowski, H.; Cornejo Díaz, N. A.; Toni, M. P.; Mihelic, M.; Röttger, A.

2018-04-01

The typical uncertainty of a low-dose rate calibration of a detector, which is calibrated in a dedicated secondary national calibration laboratory, is investigated, including measurements in the photon field of metrology institutes. Calibrations at low ambient dose equivalent rates (at the level of the natural ambient radiation) are needed when environmental radiation monitors are to be characterised. The uncertainties of calibration measurements in conventional irradiation facilities above ground are compared with those obtained in a low-dose rate irradiation facility located deep underground. Four laboratories quantitatively evaluated the uncertainties of their calibration facilities, in particular for calibrations at low dose rates (250 nSv/h and 1 μSv/h). For the first time, typical uncertainties of European calibration facilities are documented in a comparison and the main sources of uncertainty are revealed. All sources of uncertainties are analysed, including the irradiation geometry, scattering, deviations of real spectra from standardised spectra, etc. As a fundamental metrological consequence, no instrument calibrated in such a facility can have a lower total uncertainty in subsequent measurements. For the first time, the need to perform calibrations at very low dose rates (< 100 nSv/h) deep underground is underpinned on the basis of quantitative data.

In vivo urethral dose measurements: a method to verify high dose rate prostate treatments.

PubMed

Brezovich, I A; Duan, J; Pareek, P N; Fiveash, J; Ezekiel, M

2000-10-01

Radiation doses delivered in high dose rate (HDR) brachytherapy are susceptible to many inaccuracies and errors, including imaging, planning and delivery. Consequently, the dose delivered to the patient may deviate substantially from the treatment plan. We investigated the feasibility of using TLD measurements in the urethra to estimate the discrepancy in treatments for prostate cancer. The dose response of the 1 mm diam, 6 mm long LiF rods that we used for the in vivo measurements was calibrated with the 192Ir HDR source, as well as a 60Co teletherapy unit. A train of 20 rods contained in a sterile plastic tube was inserted into the urethral (Foley) catheter for the duration of a treatment fraction, and the measured doses were compared to the treatment plan. Initial results from a total of seven treatments in four patients show good agreement between theory and experiment. Analysis of any one treatment showed agreement within 11.7% +/- 6.2% for the highest dose encountered in the central prostatic urethra, and within 10.4% +/- 4.4% for the mean dose. Taking the average over all seven treatments shows agreement within 1.7% for the maximum urethral dose, and within 1.5% for the mean urethral dose. Based on these initial findings it seems that planned prostate doses can be accurately reproduced in the clinic.

Dose uniformity of budesonide Easyhaler® under simulated real-life conditions and with low inspiration flow rates.

PubMed

Haikarainen, Jussi; Rytilä, Paula; Roos, Sirkku; Metsärinne, Sirpa; Happonen, Anita

2017-01-01

Budesonide Easyhaler® multidose dry powder inhaler is approved for the treatment of asthma. Objectives were to determine the delivered dose (DD) uniformity of budesonide Easyhaler® in simulated real-world conditions and with different inspiration flow rates (IFRs). Three dose delivery studies were performed using 100, 200, and 400 µg/dose strengths of budesonide. Dose uniformity was assessed during in-use periods of 4-6 months after exposure to high temperature (30°C) and humidity (60% relative humidity) and after dropping and vibration testing. The influence of various IFRs (31, 43, and 54 L/min) on the DD was also investigated. Acceptable dose uniformity was declared when mean DD were within 80-120% of expected dose; all data reported descriptively. DD was constant (range: 93-109% of expected dose) at all in-use periods and after exposure to high temperature and humidity for a duration of up to 6 months. DD post-dropping and -vibration were unaffected (range 98-105% of expected dose). Similarly, DD was constant and within 10% of expected dose across all IFRs. Results indicate that budesonide Easyhaler® delivers consistently accurate doses in various real-life conditions. Budesonide Easyhaler® can be expected to consistently deliver a uniform dose and improve asthma control regardless of high temperature and humidity or varying IFR.

Switching to aripiprazole in outpatients with schizophrenia experiencing insufficient efficacy and/or safety/tolerability issues with risperidone: a randomized, multicentre, open-label study.

PubMed

Ryckmans, V; Kahn, J P; Modell, S; Werner, C; McQuade, R D; Kerselaers, W; Lissens, J; Sanchez, R

2009-05-01

This study evaluated the safety/tolerability and effectiveness of aripiprazole titrated-dose versus fixed-dose switching strategies from risperidone in patients with schizophrenia experiencing insufficient efficacy and/or safety/tolerability issues. Patients were randomized to an aripiprazole titrated-dose (starting dose 5 mg/day) or fixed-dose (dose 15 mg/day) switching strategy with risperidone down-tapering. Primary endpoint was rate of discontinuation due to adverse events (AEs) during the 12-week study. Secondary endpoints included positive and negative syndrome scale (PANSS), clinical global impressions - improvement of illness scale (CGI-I), preference of medication (POM), subjective well-being under neuroleptics (SWN-K) and GEOPTE (Grupo Español para la Optimización del Tratamiento de la Esquizofrenia) scales. Rates of discontinuations due to AEs were similar between titrated-dose and fixed-dose strategies (3.5% vs. 5.0%; p=0.448). Improvements in mean PANSS total scores were similar between aripiprazole titrated-dose and fixed-dose strategies (-14.8 vs. -17.2; LOCF), as were mean CGI-I scores (2.9 vs. 2.8; p=0.425; LOCF) and SWN-K scores (+8.6 vs.+10.3; OC,+7.8 vs.+9.8; LOCF). Switching can be effectively and safely achieved through a titrated-dose or fixed-dose switching strategy for aripiprazole, with down-titration of risperidone.

Hard beta and gamma emissions of 124I. Impact on occupational dose in PET/CT.

PubMed

Kemerink, G J; Franssen, R; Visser, M G W; Urbach, C J A; Halders, S G E A; Frantzen, M J; Brans, B; Teule, G J J; Mottaghy, F M

2011-01-01

The hard beta and gamma radiation of 124I can cause high doses to PET/CT workers. In this study we tried to quantify this occupational exposure and to optimize radioprotection. Thin MCP-Ns thermoluminescent dosimeters suitable for measuring beta and gamma radiation were used for extremity dosimetry, active personal dosimeters for whole-body dosimetry. Extremity doses were determined during dispensing of 124I and oral administration of the activity to the patient, the body dose during all phases of the PET/CT procedure. In addition, dose rates of vials and syringes as used in clinical practice were measured. The procedure for dispensing 124I was optimized using newly developed shielding. Skin dose rates up to 100 mSv/min were measured when in contact with the manufacturer's vial containing 370 MBq of 124I. For an unshielded 5 ml syringe the positron skin dose was about seven times the gamma dose. Before optimization of the preparation of 124I, using an already reasonably safe technique, the highest mean skin dose caused by handling 370 MBq was 1.9 mSv (max. 4.4 mSv). After optimization the skin dose was below 0.2 mSv. The highly energetic positrons emitted by 124I can cause high skin doses if radioprotection is poor. Under optimized conditions occupational doses are acceptable. Education of workers is of paramount importance.

Three-Dimensional Radiobiologic Dosimetry: Application of Radiobiologic Modeling to Patient-Specific 3-Dimensional Imaging–Based Internal Dosimetry

PubMed Central

Prideaux, Andrew R.; Song, Hong; Hobbs, Robert F.; He, Bin; Frey, Eric C.; Ladenson, Paul W.; Wahl, Richard L.; Sgouros, George

2010-01-01

Phantom-based and patient-specific imaging-based dosimetry methodologies have traditionally yielded mean organ-absorbed doses or spatial dose distributions over tumors and normal organs. In this work, radiobiologic modeling is introduced to convert the spatial distribution of absorbed dose into biologically effective dose and equivalent uniform dose parameters. The methodology is illustrated using data from a thyroid cancer patient treated with radioiodine. Methods Three registered SPECT/CT scans were used to generate 3-dimensional images of radionuclide kinetics (clearance rate) and cumulated activity. The cumulated activity image and corresponding CT scan were provided as input into an EGSnrc-based Monte Carlo calculation: The cumulated activity image was used to define the distribution of decays, and an attenuation image derived from CT was used to define the corresponding spatial tissue density and composition distribution. The rate images were used to convert the spatial absorbed dose distribution to a biologically effective dose distribution, which was then used to estimate a single equivalent uniform dose for segmented volumes of interest. Equivalent uniform dose was also calculated from the absorbed dose distribution directly. Results We validate the method using simple models; compare the dose-volume histogram with a previously analyzed clinical case; and give the mean absorbed dose, mean biologically effective dose, and equivalent uniform dose for an illustrative case of a pediatric thyroid cancer patient with diffuse lung metastases. The mean absorbed dose, mean biologically effective dose, and equivalent uniform dose for the tumor were 57.7, 58.5, and 25.0 Gy, respectively. Corresponding values for normal lung tissue were 9.5, 9.8, and 8.3 Gy, respectively. Conclusion The analysis demonstrates the impact of radiobiologic modeling on response prediction. The 57% reduction in the equivalent dose value for the tumor reflects a high level of dose nonuniformity in the tumor and a corresponding reduced likelihood of achieving a tumor response. Such analyses are expected to be useful in treatment planning for radionuclide therapy. PMID:17504874

Model-based Iterative Reconstruction: Effect on Patient Radiation Dose and Image Quality in Pediatric Body CT

PubMed Central

Dillman, Jonathan R.; Goodsitt, Mitchell M.; Christodoulou, Emmanuel G.; Keshavarzi, Nahid; Strouse, Peter J.

2014-01-01

Purpose To retrospectively compare image quality and radiation dose between a reduced-dose computed tomographic (CT) protocol that uses model-based iterative reconstruction (MBIR) and a standard-dose CT protocol that uses 30% adaptive statistical iterative reconstruction (ASIR) with filtered back projection. Materials and Methods Institutional review board approval was obtained. Clinical CT images of the chest, abdomen, and pelvis obtained with a reduced-dose protocol were identified. Images were reconstructed with two algorithms: MBIR and 100% ASIR. All subjects had undergone standard-dose CT within the prior year, and the images were reconstructed with 30% ASIR. Reduced- and standard-dose images were evaluated objectively and subjectively. Reduced-dose images were evaluated for lesion detectability. Spatial resolution was assessed in a phantom. Radiation dose was estimated by using volumetric CT dose index (CTDIvol) and calculated size-specific dose estimates (SSDE). A combination of descriptive statistics, analysis of variance, and t tests was used for statistical analysis. Results In the 25 patients who underwent the reduced-dose protocol, mean decrease in CTDIvol was 46% (range, 19%–65%) and mean decrease in SSDE was 44% (range, 19%–64%). Reduced-dose MBIR images had less noise (P > .004). Spatial resolution was superior for reduced-dose MBIR images. Reduced-dose MBIR images were equivalent to standard-dose images for lungs and soft tissues (P > .05) but were inferior for bones (P = .004). Reduced-dose 100% ASIR images were inferior for soft tissues (P < .002), lungs (P < .001), and bones (P < .001). By using the same reduced-dose acquisition, lesion detectability was better (38% [32 of 84 rated lesions]) or the same (62% [52 of 84 rated lesions]) with MBIR as compared with 100% ASIR. Conclusion CT performed with a reduced-dose protocol and MBIR is feasible in the pediatric population, and it maintains diagnostic quality. © RSNA, 2013 Online supplemental material is available for this article. PMID:24091359

An evaluation of some pertinent parameters that influence the dosimetric performance of synthetic diamond detectors

NASA Astrophysics Data System (ADS)

Ade, N.; Nam, T. L.; Mhlanga, S. H.

2013-05-01

Although the near-tissue equivalence of diamond allows the direct measurement of dose for clinical applications without the need for energy-corrections, it is often cited that diamond detectors require pre-irradiation, a procedure necessary to stabilize the response or sensitivity of a diamond detector before dose measurements. In addition it has been pointed out that the relative dose measured with a diamond detector requires dose rate dependence correction and that the angular dependence of a detector could be due to its mechanical design or to the intrinsic angular sensitivity of the detection process. While the cause of instability of response has not been meticulously investigated, the issue of dose rate dependence correction is uncertain as some studies ignored it but reported good results. The aims of this study were therefore to investigate, in particular (1) the major cause of the unstable response of diamond detectors requiring pre-irradiation; (2) the influence of dose rate dependence correction in relative dose measurements; and (3) the angular dependence of the diamond detectors. The study was conducted with low-energy X-rays and electron therapy beams on HPHT and CVD synthesized diamonds. Ionization chambers were used for comparative measurements. Through systematic investigations, the major cause of the unstable response of diamond detectors requiring the recommended pre-irradiation step was isolated and attributed to the presence and effects of ambient light. The variation in detector's response between measurements in light and dark conditions could be as high as 63% for a CVD diamond. Dose rate dependence parameters (Δ values) of 0.950 and 1.035 were found for the HPHT and CVD diamond detectors, respectively. Without corrections based on dose rate dependence, the relative differences between depth-doses measured with the diamond detectors and a Markus chamber for exposures to 7 and 14 MeV electron beams were within 2.5%. A dose rate dependence correction using the Δ values obtained seemed to worsen the performance of the HPHT sample (up to about 3.3%) but it had a marginal effect on the performance of the CVD sample. In addition, the angular response of the CVD diamond detector was shown to be comparable with that of a cylindrical chamber. This study concludes that once the responses of the diamond detectors have been stabilised and they are properly shielded from ambient light, pre-irradiation prior to each measurement is not required. Also, the relative dose measured with the diamond detectors do not require dose rate dependence corrections as the required correction is only marginal and could have no dosimetric significance.

Effects of sublethal fenitrothion ingestion on cholinesterase inhibition, standard metabolism, thermal preference, and prey-capture ability in the Australian central bearded dragon (Pogona vitticeps, Agamidae).

PubMed

Bain, David; Buttemer, William A; Astheimer, Lee; Fildes, Karen; Hooper, Michael J

2004-01-01

The central bearded dragon (Pogona vitticeps) is a medium-sized lizard that is common in semiarid habitats in Australia and that potentially is at risk of fenitrothion exposure from use of the chemical in plague locust control. We examined the effects of single sublethal doses of this organophosphate (OP; low dose = 2.0 mg/kg; high dose = 20 mg/kg; control = vehicle alone) on lizard thermal preference, standard metabolic rate, and prey-capture ability. We also measured activities of plasma total cholinesterase (ChE) and acetylcholinesterase before and at 0, 2, 8, 24, 120, and 504 h after OP dosing. Predose plasma total ChE activity differed significantly between sexes and averaged 0.66 +/- 0.06 and 0.45 +/- 0.06 micromol/min/ml for males and females, respectively. Approximately 75% of total ChE activity was attributable to butyrylcholinesterase. Peak ChE inhibition reached 19% 2 h after OP ingestion in the low-dose group, and 68% 8 h after ingestion in high-dose animals. Neither OP doses significantly affected diurnal body temperature, standard metabolic rate, or feeding rate. Plasma total ChE levels remained substantially depressed up to 21 d after dosing in the high-dose group, making this species a useful long-term biomonitor of OP exposure in its habitat.

Modern dosimetric tools for 60Co irradiation at high containment laboratories

PubMed Central

Twardoski, Barri; Feldmann, Heinz; Bloom, Marshall E.; Ward, Joe

2011-01-01

Purpose To evaluate an innovative photo-fluorescent film as a routine dosimetric tool during 60Co irradiations at a high containment biological research laboratory, and to investigate whether manufacturer-provided chamber exposure rates can be used to accurately administer a prescribed dose to biological specimens. Materials and methods Photo-fluorescent, lithium fluoride film dosimeters and National Institutes of Standards and Technology (NIST) transfer dosimeters were co-located in a self-shielded 60Co irradiator and exposed to γ-radiation with doses ranging from 5–85 kGy. Film dose-response relationships were developed for varying temperatures simulating conditions present when irradiating infectious biological specimens. Dose measurement results from NIST transfer dosimeters were compared to doses predicted using manufacturer-provided irradiator chamber exposure rates. Results The film dosimeter exhibited a photo-fluorescent response signal that was consistent and nearly linear in relationship to γ-radiation exposure over a wide dose range. The dosimeter response also showed negligible effects from dose fractionization and humidity. Significant disparities existed between manufacturer-provided chamber exposure rates and actual doses administered. Conclusion This study demonstrates the merit of utilizing dosimetric tools to validate the process of exposing dangerous and exotic biological agents to γ-radiation at high containment laboratories. The film dosimeter used in this study can be utilized to eliminate potential for improperly administering γ-radiation doses. PMID:21961968

Rectal Bleeding After High-Dose-Rate Brachytherapy Combined With Hypofractionated External-Beam Radiotherapy for Localized Prostate Cancer: The Relationship Between Dose-Volume Histogram Parameters and the Occurrence Rate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Okamoto, Masahiko, E-mail: masaoka@showa.gunma-u.ac.jp; Ishikawa, Hitoshi; Ebara, Takeshi

2012-02-01

Purpose: To determine the predictive risk factors for Grade 2 or worse rectal bleeding after high-dose-rate brachytherapy (HDR-BT) combined with hypofractionated external-beam radiotherapy (EBRT) for prostate cancer using dose-volume histogram analysis. Methods and Materials: The records of 216 patients treated with HDR-BT combined with EBRT were analyzed. The treatment protocols for HDR-BT were 5 Gy Multiplication-Sign five times in 3 days or 7 Gy Multiplication-Sign three, 10.5 Gy Multiplication-Sign two, or 9 Gy Multiplication-Sign two in 2 days. The EBRT doses ranged from 45 to 51 Gy with a fractional dose of 3 Gy. Results: In 20 patients Grade 2more » or worse rectal bleeding developed, and the cumulative incidence rate was 9% at 5 years. By converting the HDR-BT and EBRT radiation doses into biologic effective doses (BED), the BED{sub 3} at rectal volumes of 5% and 10% in the patients who experienced bleeding were significantly higher than those in the remaining 196 patients. Univariate analysis showed that a higher rectal BED{sub 3-5%} and the use of fewer needles in brachytherapy were correlated with the incidence of bleeding, but BED{sub 3-5%} was found to be the only significant factor on multivariate analysis. Conclusions: The radiation dose delivered to small rectal lesions as 5% is important for predicting Grade 2 or worse rectal bleeding after HDR-BT combined with EBRT for prostate cancer.« less

γ irradiation with different dose rates induces different DNA damage responses in Petunia x hybrida cells.

PubMed

Donà, Mattia; Ventura, Lorenzo; Macovei, Anca; Confalonieri, Massimo; Savio, Monica; Giovannini, Annalisa; Carbonera, Daniela; Balestrazzi, Alma

2013-05-15

In plants, there is evidence that different dose rate exposures to gamma (γ) rays can cause different biological effects. The dynamics of DNA damage accumulation and molecular mechanisms that regulate recovery from radiation injury as a function of dose rate are poorly explored. To highlight dose-rate dependent differences in DNA damage, single cell gel electrophoresis was carried out on regenerating Petunia x hybrida leaf discs exposed to LDR (total dose 50 Gy, delivered at 0.33 Gy min(-1)) and HDR (total doses 50 and 100 Gy, delivered at 5.15 Gy min(-1)) γ-ray in the 0-24h time period after treatments. Significant fluctuations of double strand breaks and different repair capacities were observed between treatments in the 0-4h time period following irradiation. Dose-rate-dependent changes in the expression of the PhMT2 and PhAPX genes encoding a type 2 metallothionein and the cytosolic isoform of ascorbate peroxidase, respectively, were detected by Quantitative RealTime-Polymerase Chain Reaction. The PhMT2 and PhAPX genes were significantly up-regulated (3.0- and 0.7-fold) in response to HDR. The results are discussed in light of the potential practical applications of LDR-based treatments in mutation breeding. Copyright © 2013 Elsevier GmbH. All rights reserved.

The Evaluation of the 0.07 and 3 mm Dose Equivalent with a Portable Beta Spectrometer

NASA Astrophysics Data System (ADS)

Hoshi, Katsuya; Yoshida, Tadayoshi; Tsujimura, Norio; Okada, Kazuhiko

Beta spectra of various nuclide species were measured using a commercially available compact spectrometer. The shape of the spectra obtained via the spectrometer was almost similar to that of the theoretical spectra. The beta dose equivalent at any depth was obtained as a product of the measured pulse height spectra and the appropriate conversion coefficients of ICRP Publication 74. The dose rates evaluated from the spectra were comparable with the reference dose rates of standard beta calibration sources. In addition, we were able to determine the dose equivalents with a relative error of indication of 10% without the need for complicated correction.

Common Errors in the Calculation of Aircrew Doses from Cosmic Rays

NASA Astrophysics Data System (ADS)

O'Brien, Keran; Felsberger, Ernst; Kindl, Peter

2010-05-01

Radiation doses to air crew are calculated using flight codes. Flight codes integrate dose rates over the aircraft flight path, which were calculated by transport codes or obtained by measurements from take off at a specific airport to landing at another. The dose rates are stored in various ways, such as by latitude and longitude, or in terms of the geomagnetic vertical cutoff. The transport codes are generally quite satisfactory, but the treatment of the boundary conditions is frequently incorrect. Both the treatment of solar modulation and of the effect of the geomagnetic field are often defective, leading to the systematic overestimate of the crew doses.

Portable neutron spectrometer and dosimeter

DOEpatents

Waechter, D.A.; Erkkila, B.H.; Vasilik, D.G.

The disclosure relates to a battery operated neutron spectrometer/dosimeter utilizing a microprocessor, a built-in tissue equivalent LET neutron detector, and a 128-channel pulse height analyzer with integral liquid crystal display. The apparatus calculates doses and dose rates from neutrons incident on the detector and displays a spectrum of rad or rem as a function of keV per micron of equivalent tissue and also calculates and displays accumulated dose in millirads and millirem as well as neutron dose rates in millirads per hour and millirem per hour.

Accelerated Irradiations for High Dose Microstructures in Fast Reactor Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiao, Zhijie

The objective of this project is to determine the extent to which high dose rate, self-ion irradiation can be used as an accelerated irradiation tool to understand microstructure evolution at high doses and temperatures relevant to advanced fast reactors. We will accomplish the goal by evaluating phase stability and swelling of F-M alloys relevant to SFR systems at very high dose by combining experiment and modeling in an effort to obtain a quantitative description of the processes at high and low damage rates.

Portable neutron spectrometer and dosimeter

DOEpatents

Waechter, David A.; Erkkila, Bruce H.; Vasilik, Dennis G.

1985-01-01

The disclosure relates to a battery operated neutron spectrometer/dosimeter utilizing a microprocessor, a built-in tissue equivalent LET neutron detector, and a 128-channel pulse height analyzer with integral liquid crystal display. The apparatus calculates doses and dose rates from neutrons incident on the detector and displays a spectrum of rad or rem as a function of keV per micron of equivalent tissue and also calculates and displays accumulated dose in millirads and millirem as well as neutron dose rates in millirads per hour and millirem per hour.

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

NASA Technical Reports Server (NTRS)

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

2017-01-01

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

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

NASA Astrophysics Data System (ADS)

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

2012-05-01

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

Dose-Effect Relationship in Chemoradiotherapy for Locally Advanced Rectal Cancer: A Randomized Trial Comparing Two Radiation Doses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jakobsen, Anders, E-mail: anders.jakobsen@slb.regionsyddanmark.dk; University of Southern Denmark, Odense; Ploen, John

2012-11-15

Purpose: Locally advanced rectal cancer represents a major therapeutic challenge. Preoperative chemoradiation therapy is considered standard, but little is known about the dose-effect relationship. The present study represents a dose-escalation phase III trial comparing 2 doses of radiation. Methods and Materials: The inclusion criteria were resectable T3 and T4 tumors with a circumferential margin of {<=}5 mm on magnetic resonance imaging. The patients were randomized to receive 50.4 Gy in 28 fractions to the tumor and pelvic lymph nodes (arm A) or the same treatment supplemented with an endorectal boost given as high-dose-rate brachytherapy (10 Gy in 2 fractions; armmore » B). Concomitant chemotherapy, uftoral 300 mg/m{sup 2} and L-leucovorin 22.5 mg/d, was added to both arms on treatment days. The primary endpoint was complete pathologic remission. The secondary endpoints included tumor response and rate of complete resection (R0). Results: The study included 248 patients. No significant difference was found in toxicity or surgical complications between the 2 groups. Based on intention to treat, no significant difference was found in the complete pathologic remission rate between the 2 arms (18% and 18%). The rate of R0 resection was different in T3 tumors (90% and 99%; P=.03). The same applied to the rate of major response (tumor regression grade, 1+2), 29% and 44%, respectively (P=.04). Conclusions: This first randomized trial comparing 2 radiation doses indicated that the higher dose increased the rate of major response by 50% in T3 tumors. The endorectal boost is feasible, with no significant increase in toxicity or surgical complications.« less

Evaluation of the Environmental Gamma-ray Dose Rate by Skyshine Analysis During the Maintenance of an Activated TFC in ITER

NASA Astrophysics Data System (ADS)

Sato, S.; Takatsu, H.; Maki, K.; Yamada, K.; Mori, S.; Iida, H.; Santoro, R. T.

1997-09-01

Gamma-ray exposure dose rates at the ITER site boundary were estimated for the cases of removal of a failed activated Toroidal Field (TF) coil from the torus and removal of a failed activated TF coil together with a sector of the activated Vacuum Vessel (VV). Skyshine analyses were performed using the two-dimensional SN radiation transport code, DOT3.5. The exposure gamma-ray dose rates on the ground at the site boundary (presently assumed to be 1 km from the ITER building), were calculated to be 1.1 and 84 μSv/year for removal of the TF coil without and with a VV sector, respectively. The dose rate level for the latter case is close to the tentative radiation limit of 100 μSv/year so an additional ˜14 cm of concrete is required in the ITER building roof to satisfy the criterion for a safety factor often for the site boundary dose rate.

The threshold vs LNT showdown: Dose rate findings exposed flaws in the LNT model part 2. How a mistake led BEIR I to adopt LNT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Calabrese, Edward J., E-mail: edwardc@schoolph.uma

This paper reveals that nearly 25 years after the used Russell's dose-rate data to support the adoption of the linear-no-threshold (LNT) dose response model for genetic and cancer risk assessment, Russell acknowledged a significant under-reporting of the mutation rate of the historical control group. This error, which was unknown to BEIR I, had profound implications, leading it to incorrectly adopt the LNT model, which was a decision that profoundly changed the course of risk assessment for radiation and chemicals to the present. -- Highlights: • The BEAR I Genetics Panel made an error in denying dose rate for mutation. •more » The BEIR I Genetics Subcommittee attempted to correct this dose rate error. • The control group used for risk assessment by BEIR I is now known to be in error. • Correcting this error contradicts the LNT, supporting a threshold model.« less

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.

Characterization of a MOSkin detector for in vivo skin dose measurements during interventional radiology procedures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Safari, M. J.; Wong, J. H. D.; Ng, K. H., E-mail: ngkh@um.edu.my

2015-05-15

Purpose: The MOSkin is a MOSFET detector designed especially for skin dose measurements. This detector has been characterized for various factors affecting its response for megavoltage photon beams and has been used for patient dose measurements during radiotherapy procedures. However, the characteristics of this detector in kilovoltage photon beams and low dose ranges have not been studied. The purpose of this study was to characterize the MOSkin detector to determine its suitability for in vivo entrance skin dose measurements during interventional radiology procedures. Methods: The calibration and reproducibility of the MOSkin detector and its dependency on different radiation beam qualitiesmore » were carried out using RQR standard radiation qualities in free-in-air geometry. Studies of the other characterization parameters, such as the dose linearity and dependency on exposure angle, field size, frame rate, depth-dose, and source-to-surface distance (SSD), were carried out using a solid water phantom under a clinical x-ray unit. Results: The MOSkin detector showed good reproducibility (94%) and dose linearity (99%) for the dose range of 2 to 213 cGy. The sensitivity did not significantly change with the variation of SSD (±1%), field size (±1%), frame rate (±3%), or beam energy (±5%). The detector angular dependence was within ±5% over 360° and the dose recorded by the MOSkin detector in different depths of a solid water phantom was in good agreement with the Markus parallel plate ionization chamber to within ±3%. Conclusions: The MOSkin detector proved to be reliable when exposed to different field sizes, SSDs, depths in solid water, dose rates, frame rates, and radiation incident angles within a clinical x-ray beam. The MOSkin detector with water equivalent depth equal to 0.07 mm is a suitable detector for in vivo skin dosimetry during interventional radiology procedures.« less

Characterization of a MOSkin detector for in vivo skin dose measurements during interventional radiology procedures.

PubMed

Safari, M J; Wong, J H D; Ng, K H; Jong, W L; Cutajar, D L; Rosenfeld, A B

2015-05-01

The MOSkin is a MOSFET detector designed especially for skin dose measurements. This detector has been characterized for various factors affecting its response for megavoltage photon beams and has been used for patient dose measurements during radiotherapy procedures. However, the characteristics of this detector in kilovoltage photon beams and low dose ranges have not been studied. The purpose of this study was to characterize the MOSkin detector to determine its suitability for in vivo entrance skin dose measurements during interventional radiology procedures. The calibration and reproducibility of the MOSkin detector and its dependency on different radiation beam qualities were carried out using RQR standard radiation qualities in free-in-air geometry. Studies of the other characterization parameters, such as the dose linearity and dependency on exposure angle, field size, frame rate, depth-dose, and source-to-surface distance (SSD), were carried out using a solid water phantom under a clinical x-ray unit. The MOSkin detector showed good reproducibility (94%) and dose linearity (99%) for the dose range of 2 to 213 cGy. The sensitivity did not significantly change with the variation of SSD (± 1%), field size (± 1%), frame rate (± 3%), or beam energy (± 5%). The detector angular dependence was within ± 5% over 360° and the dose recorded by the MOSkin detector in different depths of a solid water phantom was in good agreement with the Markus parallel plate ionization chamber to within ± 3%. The MOSkin detector proved to be reliable when exposed to different field sizes, SSDs, depths in solid water, dose rates, frame rates, and radiation incident angles within a clinical x-ray beam. The MOSkin detector with water equivalent depth equal to 0.07 mm is a suitable detector for in vivo skin dosimetry during interventional radiology procedures.

Reactogenicity of tetanus, diphtheria, 5-component acellular pertussis vaccine administered as a sixth consecutive acellular pertussis vaccine dose to adolescents.

PubMed

Liese, Johannes G; Rieber, Nikolaus; Malzer, Thomas; Ocak, Marion; Johnson, David R; Decker, Michael D

2010-12-01

Safety of a sixth consecutive dose of acellular pertussis vaccine in adolescents was assessed in a 2-armed, randomized study. Adolescents who had received 5 doses of acellular pertussis vaccine combined with diphtheria and tetanus toxoids (6-dose group) received 1 dose of reduced 5-component acellular pertussis vaccine combined with tetanus toxoid and reduced diphtheria toxoid (Tdap). Adolescents who had received a primary series of 3 doses of whole-cell pertussis and 1 acellular or whole-cell pertussis booster received 1 dose of Tdap vaccine (5-dose group). Of 214 participants, 176 (82%) reported an injection-site reaction with pain (80%), erythema (22%), and swelling (19%) most frequently reported. A systemic reaction was reported by 169 of 214 (79%) with myalgia (66%), headache (42%), malaise (39%), and fever (9%) most frequently reported. The overall rate of solicited reactions was lower in the 6-dose group than in the 5-dose group (for injection-site reactions: 76.1% vs. 89.7%; for systemic reactions 72.6% vs. 86.6%). Significant differences were observed for injection-site pain, erythema, and for grade 1 or grade 2 increases in arm circumference. Fever, myalgia, and headache were reported at a significantly lower rate in the 6-dose group. Swelling >10 cm was observed in 5 patients (2%), 4 in the 5-dose group. Tdap vaccine was safe when given to adolescents who had received 5 prior doses of acellular pertussis vaccine.

Influence of dose rate on the induction of simple and complex chromosome exchanges by gamma rays.

PubMed

Loucas, Bradford D; Eberle, Richard; Bailey, Susan M; Cornforth, Michael N

2004-10-01

Single-color painting of whole chromosomes, or protocols in which only a few chromosomes are distinctively painted, will always fail to detect a proportion of complex exchanges because they frequently produce pseudosimple painting patterns that are indistinguishable from those produced by bona fide simple exchanges. When 24-color multi-fluor FISH (mFISH) was employed for the purpose of distinguishing (truly) simple from pseudosimple exchanges, it was confirmed that the acute low-LET radiation dose-response relationship for simple exchanges lacked significant upward curvature. This result has been interpreted to indicate that the formation of simple exchanges requires only one chromosome locus be damaged (e.g. broken) by radiation to initiate an exchange-not two, as classical cytogenetic theory maintains. Because a one-lesion mechanism implies single-track action, it follows that the production of simple exchanges should not be influenced by changes in dose rate. To examine this prediction, we irradiated noncycling primary human fibroblasts with graded doses of (137)Cs gamma rays at an acute dose rate of 1.10 Gy/min and compared, using mFISH, the yield of simple exchanges to that observed after exposure to the same radiation delivered at a chronic dose rate of 0.08 cGy/min. The shape of the dose response was found to be quasi-linear for both dose rates, but, counter to providing support for a one-lesion mechanism, the yield of simple aberrations was greatly reduced by protracted exposure. Although chronic doses were delivered at rates low enough to produce damage exclusively by single-track action, this did not altogether eliminate the formation of complex aberrations, an analysis of which leads to the conclusion that a single track of low-LET radiation is capable of inducing complex exchanges requiring up to four proximate breaks for their formation. For acute exposures, the ratio of simple reciprocal translocations to simple dicentrics was near unity.

The direct biologic effects of radioactive 125I seeds on pancreatic cancer cells PANC-1, at continuous low-dose rates.

PubMed

Wang, Jidong; Wang, Junjie; Liao, Anyan; Zhuang, Hongqing; Zhao, Yong

2009-08-01

The relative biologic effectiveness of model 6711 125I seeds (Ningbo Junan Pharmaceutical Technology Company,Ningbo, China) and their effects on growth, cell cycle, and apoptosis in human pancreatic cancer cell line PANC-1 were examined in the present study. PANC-1 cells were exposed to the absorbed doses of 1, 2, 4, 6, 8, and 10 Gyeither with 125I seeds (initial dose rate, 2.59 cGy=h) or with 60Co g-ray irradiation (dose rate, 221 cGy=min),respectively. Significantly greater numbers of apoptotic PANC-1 cells were detected following the continuouslow-dose-rate (CLDR) irradiation of 125I seeds, compared with cells irradiated with identical doses of 60Co g-ray. The D(0) for 60Co g-ray and 125I seed irradiation were 2.30 and 1.66, respectively. The survival fraction after 125Iseed irradiation was significantly lower than that of 60Co g-ray, with a relative biologic effectiveness of 1.39.PANC-1 cells were dose dependently arrested in the S-phase by 60Co g-rays and in the G2=M phase by 125I seeds,24 hour after irradiation. CLDR irradiation by 125I seeds was more effective in inducing cell apoptosis in PANC-1cells than acute high-dose-rate 60Co g irradiation. Interestingly, CLDR irradiation by 125I seeds can cause PANC-1cell-cycle arrest at the G2=M phase and induce apoptosis, which may be an important mechanism underlying 125Iseed-induced PANC-1 cell inhibition.

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.

SU-F-J-45: Sparing Normal Tissue with Ultra-High Dose Rate in Radiation Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Y

Purpose: To spare normal tissue by reducing the location uncertainty of a moving target, we proposed an ultra-high dose rate system and evaluated. Methods: High energy electrons generated with a linear accelerator were injected into a storage ring to be accumulated. The number of the electrons in the ring was determined based on the prescribed radiation dose. The dose was delivered within a millisecond, when an online imaging system found that the target was in the position that was consistent with that in a treatment plan. In such a short time period, the displacement of the target was negligible. Themore » margin added to the clinical target volume (CTV) could be reduced that was evaluated by comparing of volumes between CTV and ITV in 14 cases of lung stereotactic body radiation therapy (SBRT) treatments. A design of the ultra-high dose rate system was evaluated based clinical needs and the recent developments of low energy (a few MeV) electron storage ring. Results: This design of ultra-high dose rate system was feasible based on the techniques currently available. The reduction of a target volume was significant by reducing the margin that accounted the motion of the target. ∼50% volume reduction of the internal target volume (ITV) could be achieved in lung SBRT treatments. Conclusion: With this innovation of ultra-high dose rate system, the margin of target is able to be significantly reduced. It will reduce treatment time of gating and allow precisely specified gating window to improve the accuracy of dose delivering.« less

Comparison of Data on Mutation Frequencies of Mice Caused by Radiation with Low Dose Model

NASA Astrophysics Data System (ADS)

Manabe, Yuichiro; Bando, Masako

2013-09-01

We propose low dose (LD) model, the extension of LDM model which was proposed in the previous paper [Y. Manabe et al.: J. Phys. Soc. Jpn. 81 (2012) 104004] to estimate biological damage caused by irradiation. LD model takes account of cell death effect in addition to the proliferation, apoptosis, repair which were included in LDM model. As a typical example of estimation, we apply LD model to the experiment of mutation frequency on the responses induced by the exposure to low levels of ionizing radiation. The most famous and extensive experiments are those summarized by Russell and Kelly [Proc. Natl. Acad. Sci. U.S.A. 79 (1982) 539], which are known as ``mega-mouse project''. This provides us with important information of the frequencies of transmitted specific-locus mutations induced in mouse spermatogonia stem-cells. It is found that the numerical results of the mutation frequency of mice are in reasonable agreement with the experimental data: the LD model reproduces the total dose and dose rate dependence of data reasonably. In order to see such dose-rate dependence more explicitly, we introduce the dose-rate effectiveness factor (DREF). This represents a sort of dose rate dependent effect, which are to be competitive with proliferation effect of broken cells induced by irradiation.

Estimation of dose rates at the entrance surface for exposure scenarios of total body irradiation using MCNPX code

NASA Astrophysics Data System (ADS)

Cunha, J. S.; Cavalcante, F. R.; Souza, S. O.; Souza, D. N.; Santos, W. S.; Carvalho Júnior, A. B.

2017-11-01

One of the main criteria that must be held in Total Body Irradiation (TBI) is the uniformity of dose in the body. In TBI procedures the certification that the prescribed doses are absorbed in organs is made with dosimeters positioned on the patient skin. In this work, we modelled TBI scenarios in the MCNPX code to estimate the entrance dose rate in the skin for comparison and validation of simulations with experimental measurements from literature. Dose rates were estimated simulating an ionization chamber laterally positioned on thorax, abdomen, leg and thigh. Four exposure scenarios were simulated: ionization chamber (S1), TBI room (S2), and patient represented by hybrid phantom (S3) and water stylized phantom (S4) in sitting posture. The posture of the patient in experimental work was better represented by S4 compared with hybrid phantom, and this led to minimum and maximum percentage differences of 1.31% and 6.25% to experimental measurements for thorax and thigh regions, respectively. As for all simulations reported here the percentage differences in the estimated dose rates were less than 10%, we considered that the obtained results are consistent with experimental measurements and the modelled scenarios are suitable to estimate the absorbed dose in organs during TBI procedure.

Dose rate calculations around 192Ir brachytherapy sources using a Sievert integration model

NASA Astrophysics Data System (ADS)

Karaiskos, P.; Angelopoulos, A.; Baras, P.; Rozaki-Mavrouli, H.; Sandilos, P.; Vlachos, L.; Sakelliou, L.

2000-02-01

The classical Sievert integral method is a valuable tool for dose rate calculations around brachytherapy sources, combining simplicity with reasonable computational times. However, its accuracy in predicting dose rate anisotropy around 192 Ir brachytherapy sources has been repeatedly put into question. In this work, we used a primary and scatter separation technique to improve an existing modification of the Sievert integral (Williamson's isotropic scatter model) that determines dose rate anisotropy around commercially available 192 Ir brachytherapy sources. The proposed Sievert formalism provides increased accuracy while maintaining the simplicity and computational time efficiency of the Sievert integral method. To describe transmission within the materials encountered, the formalism makes use of narrow beam attenuation coefficients which can be directly and easily calculated from the initially emitted 192 Ir spectrum. The other numerical parameters required for its implementation, once calculated with the aid of our home-made Monte Carlo simulation code, can be used for any 192 Ir source design. Calculations of dose rate and anisotropy functions with the proposed Sievert expression, around commonly used 192 Ir high dose rate sources and other 192 Ir elongated source designs, are in good agreement with corresponding accurate Monte Carlo results which have been reported by our group and other authors.

In vivo TLD dose measurements in catheter-based high-dose-rate brachytherapy.

PubMed

Adlienė, Diana; Jakštas, Karolis; Urbonavičius, Benas Gabrielis

2015-07-01

Routine in vivo dosimetry is well established in external beam radiotherapy; however, it is restricted mainly to detection of gross errors in high-dose-rate (HDR) brachytherapy due to complicated measurements in the field of steep dose gradients in the vicinity of radioactive source and high uncertainties. The results of in vivo dose measurements using TLD 100 mini rods and TLD 'pin worms' in catheter-based HDR brachytherapy are provided in this paper alongside with their comparison with corresponding dose values obtained using calculation algorithm of the treatment planning system. Possibility to perform independent verification of treatment delivery in HDR brachytherapy using TLDs is discussed. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Time-resolved in vivo luminescence dosimetry for online error detection in pulsed dose-rate brachytherapy.

PubMed

Andersen, Claus E; Nielsen, Søren Kynde; Lindegaard, Jacob Christian; Tanderup, Kari

2009-11-01

The purpose of this study is to present and evaluate a dose-verification protocol for pulsed dose-rate (PDR) brachytherapy based on in vivo time-resolved (1 s time resolution) fiber-coupled luminescence dosimetry. Five cervix cancer patients undergoing PDR brachytherapy (Varian GammaMed Plus with 192Ir) were monitored. The treatments comprised from 10 to 50 pulses (1 pulse/h) delivered by intracavitary/interstitial applicators (tandem-ring systems and/or needles). For each patient, one or two dosimetry probes were placed directly in or close to the tumor region using stainless steel or titanium needles. Each dosimeter probe consisted of a small aluminum oxide crystal attached to an optical fiber cable (1 mm outer diameter) that could guide radioluminescence (RL) and optically stimulated luminescence (OSL) from the crystal to special readout instrumentation. Positioning uncertainty and hypothetical dose-delivery errors (interchanged guide tubes or applicator movements from +/-5 to +/-15 mm) were simulated in software in order to assess the ability of the system to detect errors. For three of the patients, the authors found no significant differences (P>0.01) for comparisons between in vivo measurements and calculated reference values at the level of dose per dwell position, dose per applicator, or total dose per pulse. The standard deviations of the dose per pulse were less than 3%, indicating a stable dose delivery and a highly stable geometry of applicators and dosimeter probes during the treatments. For the two other patients, the authors noted significant deviations for three individual pulses and for one dosimeter probe. These deviations could have been due to applicator movement during the treatment and one incorrectly positioned dosimeter probe, respectively. Computer simulations showed that the likelihood of detecting a pair of interchanged guide tubes increased by a factor of 10 or more for the considered patients when going from integrating to time-resolved dose verification. The likelihood of detecting a +/-15 mm displacement error increased by a factor of 1.5 or more. In vivo fiber-coupled RL/OSL dosimetry based on detectors placed in standard brachytherapy needles was demonstrated. The time-resolved dose-rate measurements were found to provide a good way to visualize the progression and stability of PDR brachytherapy dose delivery, and time-resolved dose-rate measurements provided an increased sensitivity for detection of dose-delivery errors compared with time-integrated dosimetry.

Comparison of the Efficacy and Safety of Oritavancin Front-Loaded Dosing Regimens to Daily Dosing: an Analysis of the SIMPLIFI Trial ▿

PubMed Central

Dunbar, Lala M.; Milata, Joe; McClure, Ty; Wasilewski, Margaret M.

2011-01-01

Oritavancin is a novel lipoglycopeptide with demonstrated effectiveness against complicated skin and skin structure infections (cSSSI) caused by Gram-positive pathogens, including those caused by methicillin-resistant Staphylococcus aureus (MRSA). The pharmacokinetic and pharmacodynamic profile of oritavancin is favorable for single or infrequent dosing. A phase 2, multicenter, randomized, double-blind, parallel, active-comparator study (ClinicalTrials.gov identifier, NCT00514527) of single and infrequent dosing of intravenous (i.v.) oritavancin for the treatment of cSSSI caused by Gram-positive pathogens (wound infections, major abscess, and cellulitis) was undertaken to evaluate the noninferiority of front-loaded dosing regimens compared to a daily-dosing regimen. A total of 302 patients ≥18 years of age were randomized equally to one of three oritavancin treatment groups, receiving either a daily dose (200 mg) administered for 3 to 7 days, a single dose (1,200 mg), or an infrequent dose (800-mg dose, with the option for an additional 400 mg on day 5). The primary efficacy was defined as a clinical response in clinically evaluable (CE) patients assessed at days 21 to 29 (test of cure [TOC]). The cure rates in the CE population were 72.4% (55/76) in the daily-dose group, 81.5% (66/81) in the 1,200-mg-single-dose group, and 77.5% (55/71) in the infrequent-dose group. In patients with MRSA at baseline, the cure rates were 78.3% (18/23), 73.0% (27/37), and 87.0% (20/23) in the daily-, 1,200-mg-single-, and infrequent-dose groups, respectively; however, the study was not powered to assess outcomes in the MRSA subpopulation, and given the heterogeneity of the types of infection and the small sample size, these do not suggest any true differences in efficacy rates for these pathogens. The frequencies of adverse events were similar among treatment groups. The results of this study show that single- and infrequent-dosing schedules of oritavancin were as efficacious as daily administration and had a similar safety profile in treating cSSSI caused by Gram-positive pathogens, including MRSA. PMID:21537018

Efficacy of a Radiation Absorbing Shield in Reducing Dose to the Interventionalist During Peripheral Endovascular Procedures: A Single Centre Pilot Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Power, S.; Mirza, M.; Thakorlal, A.

PurposeThis prospective pilot study was undertaken to evaluate the feasibility and effectiveness of using a radiation absorbing shield to reduce operator dose from scatter during lower limb endovascular procedures.Materials and MethodsA commercially available bismuth shield system (RADPAD) was used. Sixty consecutive patients undergoing lower limb angioplasty were included. Thirty procedures were performed without the RADPAD (control group) and thirty with the RADPAD (study group). Two separate methods were used to measure dose to a single operator. Thermoluminescent dosimeter (TLD) badges were used to measure hand, eye, and unshielded body dose. A direct dosimeter with digital readout was also used tomore » measure eye and unshielded body dose. To allow for variation between control and study groups, dose per unit time was calculated.ResultsTLD results demonstrated a significant reduction in median body dose per unit time for the study group compared with controls (p = 0.001), corresponding to a mean dose reduction rate of 65 %. Median eye and hand dose per unit time were also reduced in the study group compared with control group, however, this was not statistically significant (p = 0.081 for eye, p = 0.628 for hand). Direct dosimeter readings also showed statistically significant reduction in median unshielded body dose rate for the study group compared with controls (p = 0.037). Eye dose rate was reduced for the study group but this was not statistically significant (p = 0.142).ConclusionInitial results are encouraging. Use of the shield resulted in a statistically significant reduction in unshielded dose to the operator’s body. Measured dose to the eye and hand of operator were also reduced but did not reach statistical significance in this pilot study.« less

SU-E-J-274: Responses of Medulloblastoma Cells to Radiation Dosimetric Parameters in Intensity-Modulated Radiation Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, J; Molecular Imaging Program at Stanford, Stanford, CA; Bio-X Program, Stanford, CA

2015-06-15

Purpose: To evaluate radiation responses of the medulloblastoma cell line Daoy in intensity-modulated radiation therapy (IMRT), quantitative variations to variable radiation dosimetic parameters were tracked by bioluminescent images (BLIs). Methods: The luciferase and green fluorescent protein positive Daoy cells were cultured on dishes. The medulloblastoma cells irradiated to different dose rate, interval of fractionated doses, field margin and misalignment, and dose uniformity in IMRT were monitored using bioluminescent images. The cultured cells were placed into a dedicated acrylic phantom to deliver intensity-modulated fluences and calculate accurate predicted dose distribution. The radiation with dose rate from 0.5 Gy/min to 15 Gy/minmore » was irradiated by adjusting monitor unit per minute and source-to-surface distances. The intervals of fractionated dose delivery were changed considering the repair time of double strand breaks (DSB) revealed by straining of gamma-H2AX.The effect of non-uniform doses on the cells were visualized by registering dose distributions and BLIs. The viability according to dosimetric parameters was correlated with bioluminescent intensities for cross-check of radiation responses. Results: The DSB and cell responses due to the first fractionated dose delivery significantly affected final tumor control rather than other parameters. The missing tumor volumes due to the smaller field margin than the tumor periphery or field misalignment caused relapse of cell responses on BLIs. The dose rate and gradient had effect on initial responses but could not bring out the distinguishable killing effect on cancer cells. Conclusion: Visualized and quantified bioluminescent images were useful to correlate the dose distributions with spatial radiation effects on cells. This would derive the effective combination of dose delivery parameters and fractionation. Radiation responses in particular IMRT configuration could be reflected to image based-dose re-optimization.« less

Biological equivalence between LDR and PDR in cervical cancer: multifactor analysis using the linear-quadratic model.

PubMed

Couto, José Guilherme; Bravo, Isabel; Pirraco, Rui

2011-09-01

The purpose of this work was the biological comparison between Low Dose Rate (LDR) and Pulsed Dose Rate (PDR) in cervical cancer regarding the discontinuation of the afterloading system used for the LDR treatments at our Institution since December 2009. In the first phase we studied the influence of the pulse dose and the pulse time in the biological equivalence between LDR and PDR treatments using the Linear Quadratic Model (LQM). In the second phase, the equivalent dose in 2 Gy/fraction (EQD(2)) for the tumor, rectum and bladder in treatments performed with both techniques was evaluated and statistically compared. All evaluated patients had stage IIB cervical cancer and were treated with External Beam Radiotherapy (EBRT) plus two Brachytherapy (BT) applications. Data were collected from 48 patients (26 patients treated with LDR and 22 patients with PDR). In the analyses of the influence of PDR parameters in the biological equivalence between LDR and PDR treatments (Phase 1), it was calculated that if the pulse dose in PDR was kept equal to the LDR dose rate, a small the-rapeutic loss was expected. If the pulse dose was decreased, the therapeutic window became larger, but a correction in the prescribed dose was necessary. In PDR schemes with 1 hour interval between pulses, the pulse time did not influence significantly the equivalent dose. In the comparison between the groups treated with LDR and PDR (Phase 2) we concluded that they were not equivalent, because in the PDR group the total EQD(2) for the tumor, rectum and bladder was smaller than in the LDR group; the LQM estimated that a correction in the prescribed dose of 6% to 10% was ne-cessary to avoid therapeutic loss. A correction in the prescribed dose was necessary; this correction should be achieved by calculating the PDR dose equivalent to the desired LDR total dose.

Biological equivalence between LDR and PDR in cervical cancer: multifactor analysis using the linear-quadratic model

PubMed Central

Bravo, Isabel; Pirraco, Rui

2011-01-01

Purpose The purpose of this work was the biological comparison between Low Dose Rate (LDR) and Pulsed Dose Rate (PDR) in cervical cancer regarding the discontinuation of the afterloading system used for the LDR treatments at our Institution since December 2009. Material and methods In the first phase we studied the influence of the pulse dose and the pulse time in the biological equivalence between LDR and PDR treatments using the Linear Quadratic Model (LQM). In the second phase, the equivalent dose in 2 Gy/fraction (EQD2) for the tumor, rectum and bladder in treatments performed with both techniques was evaluated and statistically compared. All evaluated patients had stage IIB cervical cancer and were treated with External Beam Radiotherapy (EBRT) plus two Brachytherapy (BT) applications. Data were collected from 48 patients (26 patients treated with LDR and 22 patients with PDR). Results In the analyses of the influence of PDR parameters in the biological equivalence between LDR and PDR treatments (Phase 1), it was calculated that if the pulse dose in PDR was kept equal to the LDR dose rate, a small the-rapeutic loss was expected. If the pulse dose was decreased, the therapeutic window became larger, but a correction in the prescribed dose was necessary. In PDR schemes with 1 hour interval between pulses, the pulse time did not influence significantly the equivalent dose. In the comparison between the groups treated with LDR and PDR (Phase 2) we concluded that they were not equivalent, because in the PDR group the total EQD2 for the tumor, rectum and bladder was smaller than in the LDR group; the LQM estimated that a correction in the prescribed dose of 6% to 10% was ne-cessary to avoid therapeutic loss. Conclusions A correction in the prescribed dose was necessary; this correction should be achieved by calculating the PDR dose equivalent to the desired LDR total dose. PMID:23346123

Methodological variations and their effects on reported medication administration error rates.

PubMed

McLeod, Monsey Chan; Barber, Nick; Franklin, Bryony Dean

2013-04-01

Medication administration errors (MAEs) are a problem, yet methodological variation between studies presents a potential barrier to understanding how best to increase safety. Using the UK as a case-study, we systematically summarised methodological variations in MAE studies, and their effects on reported MAE rates. Nine healthcare databases were searched for quantitative observational MAE studies in UK hospitals. Methodological variations were analysed and meta-analysis of MAE rates performed using studies that used the same definitions. Odds ratios (OR) were calculated to compare MAE rates between intravenous (IV) and non-IV doses, and between paediatric and adult doses. We identified 16 unique studies reporting three MAE definitions, 44 MAE subcategories and four different denominators. Overall adult MAE rates were 5.6% of a total of 21 533 non-IV opportunities for error (OE) (95% CI 4.6% to 6.7%) and 35% of a total of 154 IV OEs (95% CI 2% to 68%). MAEs were five times more likely in IV than non-IV doses (pooled OR 5.1; 95% CI 3.5 to 7.5). Including timing errors of ±30 min increased the MAE rate from 27% to 69% of 320 IV doses in one study. Five studies were unclear as to whether the denominator included dose omissions; omissions accounted for 0%-13% of IV doses and 1.8%-5.1% of non-IV doses. Wide methodological variations exist even within one country, some with significant effects on reported MAE rates. We have made recommendations for future MAE studies; these may be applied both within and outside the UK.

Clinical application of a OneDose MOSFET for skin dose measurements during internal mammary chain irradiation with high dose rate brachytherapy in carcinoma of the breast.

PubMed

Kinhikar, Rajesh A; Sharma, Pramod K; Tambe, Chandrashekhar M; Mahantshetty, Umesh M; Sarin, Rajiv; Deshpande, Deepak D; Shrivastava, Shyam K

2006-07-21

In our earlier study, we experimentally evaluated the characteristics of a newly designed metal oxide semiconductor field effect transistor (MOSFET) OneDose in-vivo dosimetry system for Ir-192 (380 keV) energy and the results were compared with thermoluminescent dosimeters (TLDs). We have now extended the same study to the clinical application of this MOSFET as an in-vivo dosimetry system. The MOSFET was used during high dose rate brachytherapy (HDRBT) of internal mammary chain (IMC) irradiation for a carcinoma of the breast. The aim of this study was to measure the skin dose during IMC irradiation with a MOSFET and a TLD and compare it with the calculated dose with a treatment planning system (TPS). The skin dose was measured for ten patients. All the patients' treatment was planned on a PLATO treatment planning system. TLD measurements were performed to compare the accuracy of the measured results from the MOSFET. The mean doses measured with the MOSFET and the TLD were identical (0.5392 Gy, 15.85% of the prescribed dose). The mean dose was overestimated by the TPS and was 0.5923 Gy (17.42% of the prescribed dose). The TPS overestimated the skin dose by 9% as verified by the MOSFET and TLD. The MOSFET provides adequate in-vivo dosimetry for HDRBT. Immediate readout after irradiation, small size, permanent storage of dose and ease of use make the MOSFET a viable alternative for TLDs.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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);more » 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.« less

Polymer gel dosimeters for pretreatment radiotherapy verification using the three-dimensional gamma evaluation and pass rate maps.

PubMed

Hsieh, Ling-Ling; Shieh, Jiunn-I; Wei, Li-Ju; Wang, Yi-Chun; Cheng, Kai-Yuan; Shih, Cheng-Ting

2017-05-01

Polymer gel dosimeters (PGDs) have been widely studied for use in the pretreatment verification of clinical radiation therapy. However, the readability of PGDs in three-dimensional (3D) dosimetry remain unclear. In this study, the pretreatment verifications of clinical radiation therapy were performed using an N-isopropyl-acrylamide (NIPAM) PGD, and the results were used to evaluate the performance of the NIPAM PGD on 3D dose measurement. A gel phantom was used to measure the dose distribution of a clinical case of intensity-modulated radiation therapy. Magnetic resonance imaging scans were performed for dose readouts. The measured dose volumes were compared with the planned dose volume. The relative volume histograms showed that relative volumes with a negative percent dose difference decreased as time elapsed. Furthermore, the histograms revealed few changes after 24h postirradiation. For the 3%/3mm and 2%/2mm criteria, the pass rates of the 12- and 24-h dose volumes were higher than 95%, respectively. This study thus concludes that the pass rate map can be used to evaluate the dose-temporal readability of PGDs and that the NIPAM PGD can be used for clinical pretreatment verifications. Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Estimation of internal organ motion-induced variance in radiation dose in non-gated radiotherapy

NASA Astrophysics Data System (ADS)

Zhou, Sumin; Zhu, Xiaofeng; Zhang, Mutian; Zheng, Dandan; Lei, Yu; Li, Sicong; Bennion, Nathan; Verma, Vivek; Zhen, Weining; Enke, Charles

2016-12-01

In the delivery of non-gated radiotherapy (RT), owing to intra-fraction organ motion, a certain degree of RT dose uncertainty is present. Herein, we propose a novel mathematical algorithm to estimate the mean and variance of RT dose that is delivered without gating. These parameters are specific to individual internal organ motion, dependent on individual treatment plans, and relevant to the RT delivery process. This algorithm uses images from a patient’s 4D simulation study to model the actual patient internal organ motion during RT delivery. All necessary dose rate calculations are performed in fixed patient internal organ motion states. The analytical and deterministic formulae of mean and variance in dose from non-gated RT were derived directly via statistical averaging of the calculated dose rate over possible random internal organ motion initial phases, and did not require constructing relevant histograms. All results are expressed in dose rate Fourier transform coefficients for computational efficiency. Exact solutions are provided to simplified, yet still clinically relevant, cases. Results from a volumetric-modulated arc therapy (VMAT) patient case are also presented. The results obtained from our mathematical algorithm can aid clinical decisions by providing information regarding both mean and variance of radiation dose to non-gated patients prior to RT delivery.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Uehara, K; Ogata, T; Nakayama, M

2015-06-15

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

Prediction of terrestrial gamma dose rate based on geological formations and soil types in the Johor State, Malaysia.

PubMed

Saleh, Muneer Aziz; Ramli, Ahmad Termizi; bin Hamzah, Khaidzir; Alajerami, Yasser; Moharib, Mohammed; Saeed, Ismael

2015-10-01

This study aims to predict and estimate unmeasured terrestrial gamma dose rate (TGDR) using statistical analysis methods to derive a model from the actual measurement based on geological formation and soil type. The measurements of TGDR were conducted in the state of Johor with a total of 3873 measured points which covered all geological formations, soil types and districts. The measurements were taken 1 m above the soil surface using NaI [Ti] detector. The measured gamma dose rates ranged from 9 nGy h(-1) to 1237 nGy h(-1) with a mean value of 151 nGy h(-1). The data have been normalized to fit a normal distribution. Tests of significance were conducted among all geological formations and soil types, using the unbalanced one way ANOVA. The results indicated strong significant differences due to the different geological formations and soil types present in Johor State. Pearson Correlation was used to measure the relations between gamma dose rate based on geological formation and soil type (D(G,S)) with the gamma dose rate based on geological formation (D(G)) or soil type (D(s)). A very good correlation was found between D(G,S) and D(G) or D(G,S) and D(s). A total of 118 pairs of geological formations and soil types were used to derive the statistical contribution of geological formations and soil types to gamma dose rates. The contribution of the gamma dose rate from geological formation and soil type were found to be 0.594 and 0.399, respectively. The null hypotheses were accepted for 83% of examined data, therefore, the model could be used to predict gamma dose rates based on geological formation and soil type information. Copyright © 2015 Elsevier Ltd. All rights reserved.

ESTIMATION OF EFFECTIVE DOSE FROM EXTERNAL EXPOSURE DUE TO SHORT-LIVED NUCLIDES IN THE PREFECTURES SURROUNDING FUKUSHIMA.

PubMed

Miyatake, Hirokazu; Yoshizawa, Nobuaki; Suzuki, Gen

2018-05-11

The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident resulted in a release of radionuclides into the environment. Since the accident, measurements of radiation in the environment such as air dose rate and deposition density of radionuclides have been performed by various organizations and universities. In particular, Japan Atomic Energy Agency (JAEA) has been performing observations of air dose rate using a car-borne survey system continuously over widespread areas. Based on the data measured by JAEA, we estimated effective dose from external exposure in the prefectures surrounding Fukushima. Since car-borne survey started a few months after the accident, the main contribution to measured data comes from 137Cs and 134Cs whose half-lives are relatively long. Using air dose rate of 137Cs and 134Cs and the ratio of deposition density of short-lived nuclides to that of 137Cs and 134Cs, we also estimated contributions to the effective dose from other short-lived nuclides.

External dose assessment in the Ukraine following the Chernobyl accident

NASA Astrophysics Data System (ADS)

Frazier, Remi Jordan Lesartre

While the physiological effects of radiation exposure have been well characterized in general, it remains unclear what the relationship is between large-scale radiological events and psychosocial behavior outcomes in individuals or populations. To investigate this, the National Science Foundation funded a research project in 2008 at the University of Colorado in collaboration with Colorado State University to expand the knowledge of complex interactions between radiation exposure, perception of risk, and psychosocial behavior outcomes by modeling outcomes for a representative sample of the population of the Ukraine which had been exposed to radiocontaminant materials released by the reactor accident at Chernobyl on 26 April 1986. In service of this project, a methodology (based substantially on previously published models specific to the Chernobyl disaster and the Ukrainian population) was developed for daily cumulative effective external dose and dose rate assessment for individuals in the Ukraine for as a result of the Chernobyl disaster. A software platform was designed and produced to estimate effective external dose and dose rate for individuals based on their age, occupation, and location of residence on each day between 26 April 1986 and 31 December 2009. A methodology was developed to transform published 137Cs soil deposition contour maps from the Comprehensive Atlas of Caesium Deposition on Europe after the Chernobyl Accident into a geospatial database to access these data as a radiological source term. Cumulative effective external dose and dose rate were computed for each individual in a 703-member cohort of Ukrainians randomly selected to be representative of the population of the country as a whole. Error was estimated for the resulting individual dose and dose rate values with Monte Carlo simulations. Distributions of input parameters for the dose assessment methodology were compared to computed dose and dose rate estimates to determine which parameters were driving the computed results. The mean external effective dose for all individuals in the cohort due to exposure to radiocontamination from the Chernobyl accident between 26 April 1986 and 31 December 2009 was found to be 1.2 mSv; the geometric mean was 0.84 mSv with a geometric standard deviation of 2.1. The mean value is well below the mean external effective dose expected due to typical background radiation (which in the United States over this time period would be 12.0 mSv). Sensitivity analysis suggests that the greatest driver of the distribution of individual dose estimates is lack of specific information about the daily behavior of each individual, specifically the portion of time each individual spent indoors (and shielded from radionuclides deposited on the soil) versus outdoors (and unshielded).

Estimated dose rates to members of the public from external exposure to patients with 131I thyroid treatment

DOE PAGES

Dewji, S.; Bellamy, M.; Hertel, N.; ...

2015-03-25

The purpose of this study is to estimate dose rates that may result from exposure to patients who had been administered iodine-131 ( 131I) as part of medical therapy were calculated. These effective dose rate estimates were compared with simplified assumptions under United States Nuclear Regulatory Commission Regulatory Guide 8.39, which does not consider body tissue attenuation nor time-dependent redistribution and excretion of the administered 131I. Methods: Dose rates were estimated for members of the public potentially exposed to external irradiation from patients recently treated with 131I. Tissue attenuation and iodine biokinetics were considered in the patient in a largermore » comprehensive effort to improve external dose rate estimates. The external dose rate estimates are based on Monte Carlo simulations using the Phantom with Movable Arms and Legs (PIMAL), previously developed by Oak Ridge National Laboratory and the United States Nuclear Regulatory Commission. PIMAL was employed to model the relative positions of the 131I patient and members of the public in three exposure scenarios: (1) traveling on a bus in a total of six seated or standing permutations, (2) two nursing home cases where a caregiver is seated at 30 cm from the patient’s bedside and a nursing home resident seated 250 cm away from the patient in an adjacent bed, and (3) two hotel cases where the patient and a guest are in adjacent rooms with beds on opposite sides of the common wall, with the patient and guest both in bed and either seated back-to-back or lying head to head. The biokinetic model predictions of the retention and distribution of 131I in the patient assumed a single voiding of urinary bladder contents that occurred during the trip at 2, 4, or 8 h after 131I administration for the public transportation cases, continuous first-order voiding for the nursing home cases, and regular periodic voiding at 4, 8, or 12 h after administration for the hotel room cases. Organ specific activities of 131I in the thyroid, bladder, and combined remaining tissues were calculated as a function of time after administration. Exposures to members of the public were considered for 131I patients with normal thyroid uptake (peak thyroid uptake of ~27% of administered 131I), differentiated thyroid cancer (DTC, 5% uptake), and hyperthyroidism (80% uptake). Results: The scenario with the patient seated behind the member of the public yielded the highest dose rate estimate of seated public transportation exposure cases. The dose rate to the adjacent room guest was highest for the exposure scenario in which the hotel guest and patient are seated by a factor of ~4 for the normal and differentiated thyroid cancer uptake cases and by a factor of ~3 for the hyperthyroid case. Conclusions: It was determined that for all modeled cases, the DTC case yielded the lowest external dose rates, whereas the hyperthyroid case yielded the highest dose rates. In estimating external dose to members of the public from patients with 131I therapy, consideration must be given to (patient- and case-specific) administered 131I activities and duration of exposure for a more complete estimate. The method implemented here included a detailed calculation model, which provides a means to determine dose rate estimates for a range of scenarios. Finally, the method was demonstrated for variations of three scenarios, showing how dose rates are expected to vary with uptake, voiding pattern, and patient location.« less

Estimated dose rates to members of the public from external exposure to patients with 131I thyroid treatment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dewji, S.; Bellamy, M.; Hertel, N.

The purpose of this study is to estimate dose rates that may result from exposure to patients who had been administered iodine-131 ( 131I) as part of medical therapy were calculated. These effective dose rate estimates were compared with simplified assumptions under United States Nuclear Regulatory Commission Regulatory Guide 8.39, which does not consider body tissue attenuation nor time-dependent redistribution and excretion of the administered 131I. Methods: Dose rates were estimated for members of the public potentially exposed to external irradiation from patients recently treated with 131I. Tissue attenuation and iodine biokinetics were considered in the patient in a largermore » comprehensive effort to improve external dose rate estimates. The external dose rate estimates are based on Monte Carlo simulations using the Phantom with Movable Arms and Legs (PIMAL), previously developed by Oak Ridge National Laboratory and the United States Nuclear Regulatory Commission. PIMAL was employed to model the relative positions of the 131I patient and members of the public in three exposure scenarios: (1) traveling on a bus in a total of six seated or standing permutations, (2) two nursing home cases where a caregiver is seated at 30 cm from the patient’s bedside and a nursing home resident seated 250 cm away from the patient in an adjacent bed, and (3) two hotel cases where the patient and a guest are in adjacent rooms with beds on opposite sides of the common wall, with the patient and guest both in bed and either seated back-to-back or lying head to head. The biokinetic model predictions of the retention and distribution of 131I in the patient assumed a single voiding of urinary bladder contents that occurred during the trip at 2, 4, or 8 h after 131I administration for the public transportation cases, continuous first-order voiding for the nursing home cases, and regular periodic voiding at 4, 8, or 12 h after administration for the hotel room cases. Organ specific activities of 131I in the thyroid, bladder, and combined remaining tissues were calculated as a function of time after administration. Exposures to members of the public were considered for 131I patients with normal thyroid uptake (peak thyroid uptake of ~27% of administered 131I), differentiated thyroid cancer (DTC, 5% uptake), and hyperthyroidism (80% uptake). Results: The scenario with the patient seated behind the member of the public yielded the highest dose rate estimate of seated public transportation exposure cases. The dose rate to the adjacent room guest was highest for the exposure scenario in which the hotel guest and patient are seated by a factor of ~4 for the normal and differentiated thyroid cancer uptake cases and by a factor of ~3 for the hyperthyroid case. Conclusions: It was determined that for all modeled cases, the DTC case yielded the lowest external dose rates, whereas the hyperthyroid case yielded the highest dose rates. In estimating external dose to members of the public from patients with 131I therapy, consideration must be given to (patient- and case-specific) administered 131I activities and duration of exposure for a more complete estimate. The method implemented here included a detailed calculation model, which provides a means to determine dose rate estimates for a range of scenarios. Finally, the method was demonstrated for variations of three scenarios, showing how dose rates are expected to vary with uptake, voiding pattern, and patient location.« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aitkenhead, A; Hamlett, L; Wood, D

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 wasmore » 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.« less

High dose psilocybin is associated with positive subjective effects in healthy volunteers.

PubMed

Nicholas, Christopher R; Henriquez, Kelsey M; Gassman, Michele C; Cooper, Karen M; Muller, Daniel; Hetzel, Scott; Brown, Randall T; Cozzi, Nicholas V; Thomas, Chantelle; Hutson, Paul R

2018-06-01

The aim of the current study was to investigate the relationship between escalating higher doses of psilocybin and the potential psilocybin occasioned positive subjective effects. Healthy participants ( n=12) were given three escalating doses of oral psilocybin (0.3 mg/kg; 0.45 mg/kg; 0.6 mg/kg) or (18.8-36.6 mg; 27.1-54.0 mg; 36.3-59.2 mg) a minimum of four weeks apart in a supervised setting. Blood and urine samples, vital signs, and electrocardiograms were obtained. Subjective effects were assessed using the Mystical Experience Questionnaire and Persisting Effects Questionnaire. There was a significant linear dose-related response in Mystical Experience Questionnaire total score and the transcendence of time and space subscale, but not in the rate of a complete mystical experience. There was also a significant difference between dose 3 compared to dose 1 on the transcendence of time and space subscale, while no dose-related differences were found for Mystical Experience Questionnaire total scores or rate of a mystical experience. Persisting Effects Questionnaire positive composite scores 30 days after completion of the last dose were significantly higher than negative composite scores. Persisting Effects Questionnaire results revealed a moderate increase in sense of well-being or life satisfaction on average that was associated with the maximum Mystical Experience Questionnaire total score. Pharmacokinetic measures were associated with dose but not with Mystical Experience Questionnaire total scores or rate of a mystical experience. High doses of psilocybin elicited subjective effects at least as strong as the lower doses and resulted in positive persisting subjective effects 30 days after, indicating that a complete mystical experience was not a prerequisite for positive outcomes.

Application of computational models to estimate organ radiation dose in rainbow trout from uptake of molybdenum-99 with comparison to iodine-131.

PubMed

Martinez, N E; Johnson, T E; Pinder, J E

2016-01-01

This study compares three anatomical phantoms for rainbow trout (Oncorhynchus mykiss) for the purpose of estimating organ radiation dose and dose rates from molybdenum-99 ((99)Mo) uptake in the liver and GI tract. Model comparison and refinement is important to the process of determining accurate doses and dose rates to the whole body and the various organs. Accurate and consistent dosimetry is crucial to the determination of appropriate dose-effect relationships for use in environmental risk assessment. The computational phantoms considered are (1) a geometrically defined model employing anatomically relevant organ size and location, (2) voxel reconstruction of internal anatomy obtained from CT imaging, and (3) a new model utilizing NURBS surfaces to refine the model in (2). Dose Conversion Factors (DCFs) for whole body as well as selected organs of O. mykiss were computed using Monte Carlo modeling and combined with empirical models for predicting activity concentration to estimate dose rates and ultimately determine cumulative radiation dose (μGy) to selected organs after several half-lives of (99)Mo. The computational models provided similar results, especially for organs that were both the source and target of radiation (less than 30% difference between all models). Values in the empirical model as well as the 14 day cumulative organ doses determined from (99)Mo uptake are compared to similar models developed previously for (131)I. Finally, consideration is given to treating the GI tract as a solid organ compared to partitioning it into gut contents and GI wall, which resulted in an order of magnitude difference in estimated dose for most organs. Copyright © 2015 Elsevier Ltd. All rights reserved.

Human Papillomavirus Vaccine Effectiveness Against Incident Genital Warts Among Female Health-Plan Enrollees, United States.

PubMed

Hariri, Susan; Schuler, Megan S; Naleway, Allison L; Daley, Matthew F; Weinmann, Sheila; Crane, Bradley; Newcomer, Sophia R; Tolsma, Dennis; Markowitz, Lauri E

2018-02-01

We examined the effectiveness of human papillomavirus vaccination by dose number and spacing against incident genital warts in a cohort of 64,517 female health-plan enrollees in the United States during 2006-2012. Eligible recipients were classified into groups by regimen: 0, 1, 2 (<6 months apart), 2 (≥6 months apart), or 3 doses. They were followed until a genital wart diagnosis, loss to follow-up, or the end of study. Propensity score weights were used to balance baseline differences across groups. To account for latent genital warts before vaccination, we applied 6- and 12-month buffer periods from last and first vaccine dose, respectively. Incidence rates and hazard ratios were calculated using Poisson regression and Cox models. The propensity score-weighted incidence rate per 100,000 person-years was 762 among unvaccinated participants. Using 6- and 12-month buffer periods, respectively, incidence rates were 641 and 257 for 1 dose, 760 and 577 for the 2-dose (<6-month interval) regimen, 313 and 194 for the 2-dose (≥6-month interval) regimen, and 199 and 162 among 3-dose vaccinees; vaccine effectiveness was 68% and 76% for the 2-dose (≥6-month interval) regimen and 77% and 80% in 3-dose vaccinees compared with unvaccinated participants. Vaccine effectiveness was not significant among vaccinees receiving 1-dose and 2-dose (<6-month interval) regimens compared with unvaccinated participants. Our findings contribute to a better understanding of the real-world effectiveness of HPV vaccination. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health 2017. This work is written by (a) US Government employee(s) and is in the public domain in the US.

Dosimetric evaluation of high-dose-rate interstitial brachytherapy boost treatments for localized prostate cancer.

PubMed

Fröhlich, Georgina; Agoston, Péter; Lövey, József; Somogyi, András; Fodor, János; Polgár, Csaba; Major, Tibor

2010-07-01

To quantitatively evaluate the dose distributions of high-dose-rate (HDR) prostate implants regarding target coverage, dose homogeneity, and dose to organs at risk. Treatment plans of 174 implants were evaluated using cumulative dose-volume histograms (DVHs). The planning was based on transrectal ultrasound (US) imaging, and the prescribed dose (100%) was 10 Gy. The tolerance doses to rectum and urethra were 80% and 120%, respectively. Dose-volume parameters for target (V90, V100, V150, V200, D90, D(min)) and quality indices (DNR [dose nonuniformity ratio], DHI [dose homogeneity index], CI [coverage index], COIN [conformal index]) were calculated. Maximum dose in reference points of rectum (D(r)) and urethra (D(u)), dose to volume of 2 cm(3) of the rectum (D(2ccm)), and 0.1 cm(3) and 1% of the urethra (D(0.1ccm) and D1) were determined. Nonparametric correlation analysis was performed between these parameters. The median number of needles was 16, the mean prostate volume (V(p)) was 27.1 cm(3). The mean V90, V100, V150, and V200 were 99%, 97%, 39%, and 13%, respectively. The mean D90 was 109%, and the D(min) was 87%. The mean doses in rectum and urethra reference points were 75% and 119%, respectively. The mean volumetric doses were D(2ccm) = 49% for the rectum, D(0.1ccm) = 126%, and D1 = 140% for the urethra. The mean DNR was 0.37, while the DHI was 0.60. The mean COIN was 0.66. The Spearman rank order correlation coefficients for volume doses to rectum and urethra were R(D(r),D(2ccm)) = 0.69, R(D(u),D0.(1ccm)) = 0.64, R(D(u),D1) = 0.23. US-based treatment plans for HDR prostate implants based on the real positions of catheters provided acceptable dose distributions. In the majority of the cases, the doses to urethra and rectum were kept below the defined tolerance levels. For rectum, the dose in reference points correlated well with dose-volume parameters. For urethra dose characterization, the use of D1 volumetric parameter is recommended.

Evaluation of optimal parameters for using low-dose computed tomography to diagnose urolithiasis

NASA Astrophysics Data System (ADS)

Chen, Hui-Hsien; Yu, Cheng-Ching; Hsu, Fang-Yuh

2017-11-01

Urolithiasis is a common disease; patients suspected of suffering from urolithiasis will be examined by abdomen x-ray, Sono, Intraudio Videonous Urography (IVU) and Computed Tomography (CT). The detection rates for calculus in above examinations are respectively: 50-70% (x-ray), 50-60% (Sono), 70-90% (IVU) and 97% (CT). In addition, the effective doses are respectively: 0.63 mSv (x-ray), no radiation dose (Sono), 2.6 mSv (IVU) and 8-16 mSv (CT). Although CT has the highest detection rate for calculus, it also has the highest radiation dose. This research sought to lower the radiation dose by using CT scans with different dose conditions of standard dose (SD), 50% SD, 25% SD, and 15% SD to diagnose patients who suffer from urolithiasis and thus explore the feasibility of examining urolithiasis via CT with lower dose conditions. This research simulated the examination of patients with RANDO phantom, collocating PMMA slice phantom and pig's kidney. Fake calculuses made of five different materials of different sizes were put into the phantom and scanned individually. The results of the scanned images were given to two physicians who had many years of diagnostic experience to interpret the urolithiasis images. This study explored the different image qualities of CT with different dose conditions. In addition, this research used thermoluminescent dosimeters (TLD) to measure the radiation doses and compared the results with the dose values shown on the screen of the CT scanner to estimate the dose conversion factor (k). The research results showed that a low-dose CT was able to provide good image quality and thus have a lower radiation dose. Therefore, a low-dose CT is suggested the main examination method to diagnose patients with urolithiasis.

New image-processing and noise-reduction software reduces radiation dose during complex endovascular procedures.

PubMed

Kirkwood, Melissa L; Guild, Jeffrey B; Arbique, Gary M; Tsai, Shirling; Modrall, J Gregory; Anderson, Jon A; Rectenwald, John; Timaran, Carlos

2016-11-01

A new proprietary image-processing system known as AlluraClarity, developed by Philips Healthcare (Best, The Netherlands) for radiation-based interventional procedures, claims to lower radiation dose while preserving image quality using noise-reduction algorithms. This study determined whether the surgeon and patient radiation dose during complex endovascular procedures (CEPs) is decreased after the implementation of this new operating system. Radiation dose to operators, procedure type, reference air kerma, kerma area product, and patient body mass index were recorded during CEPs on two Philips Allura FD 20 fluoroscopy systems with and without Clarity. Operator dose during CEPs was measured using optically stimulable, luminescent nanoDot (Landauer Inc, Glenwood, Ill) detectors placed outside the lead apron at the left upper chest position. nanoDots were read using a microStar ii (Landauer Inc) medical dosimetry system. For the CEPs in the Clarity group, the radiation dose to surgeons was also measured by the DoseAware (Philips Healthcare) personal dosimetry system. Side-by-side measurements of DoseAware and nanoDots allowed for cross-calibration between systems. Operator effective dose was determined using a modified Niklason algorithm. To control for patient size and case complexity, the average fluoroscopy dose rate and the dose per radiographic frame were adjusted for body mass index differences and then compared between the groups with and without Clarity by procedure. Additional factors, for example, physician practice patterns, that may have affected operator dose were inferred by comparing the ratio of the operator dose to procedural kerma area product with and without Clarity. A one-sided Wilcoxon rank sum test was used to compare groups for radiation doses, reference air kermas, and operating practices for each procedure type. The analysis included 234 CEPs; 95 performed without Clarity and 139 with Clarity. Practice patterns of operators during procedures with and without Clarity were not significantly different. For all cases, procedure radiation dose to the patient and the primary and assistant operators were significantly decreased in the Clarity group by 60% compared with the non-Clarity group. By procedure type, fluorography dose rates decreased from 44% for fenestrated endovascular repair and up to 70% with lower extremity interventions. Fluoroscopy dose rates also significantly decreased, from about 37% to 47%, depending on procedure type. The AlluraClarity system reduces the patient and primary operator's radiation dose by more than half during CEPs. This feature appears to be an effective tool in lowering the radiation dose while maintaining image quality. Copyright © 2016 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.

Comparative analysis of radioecological monitoring dosimeters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sobolev, A.I.; Pol`skii, O.G.; Shanin, O.B.

1995-03-01

This paper describes comparative estimates of radiation doses measured by two types of thermoluminescence dosimeters and two types of background radiation radiometers. The dosimetry systems were tested by simultaneously recording background radiation and standard radiation sources at a radioactive waste storage facility. Statistical analysis of the measurement results is summarized. The maximum recorded exposure dose rate for the experiment was 19 microrads per hour. The DTK-2 dosimeter overestimated dose rates by 6 to 43% and the DTU-2 dosimeter underestimated dose rates by 7 to 21%. Both devices are recommended for radioecological monitoring in populated areas. 4 refs., 3 figs., 5more » tabs.« less

Rigorous-two-Steps scheme of TRIPOLI-4® Monte Carlo code validation for shutdown dose rate calculation

NASA Astrophysics Data System (ADS)

Jaboulay, Jean-Charles; Brun, Emeric; Hugot, François-Xavier; Huynh, Tan-Dat; Malouch, Fadhel; Mancusi, Davide; Tsilanizara, Aime

2017-09-01

After fission or fusion reactor shutdown the activated structure emits decay photons. For maintenance operations the radiation dose map must be established in the reactor building. Several calculation schemes have been developed to calculate the shutdown dose rate. These schemes are widely developed in fusion application and more precisely for the ITER tokamak. This paper presents the rigorous-two-steps scheme implemented at CEA. It is based on the TRIPOLI-4® Monte Carlo code and the inventory code MENDEL. The ITER shutdown dose rate benchmark has been carried out, results are in a good agreement with the other participant.

Shielding Requirements for Particle Bed Propulsion Systems.

DTIC Science & Technology

1991-06-01

Heating Rates Rates Rates [W/cc] [W/cc] [W/cc] Hydrogen 11.5 0.09 0.38 Carbon 48 2.2 8.3 Aluminum 80 3.6 14.5 Titanium 335 4.8 36 Stainless Steel 500...12.4 31 Stainless Steel 320 21.5 80 Dose [Rad] Dose [Rad] Dose [Rad] Silicon 4.9e+9 1.36e+5 3.6e 5 The plenum region for these measurements can be...Aluminum (TPA) 0.32 Titanium (TPA) 0.41 Stainless Steel (TPA) 2.3 Dose/Fluence [Rad] / [n/c. 2 ] _ Silicon (TPA/void) 2.4e+4/2.2e+13 The neutron fluence

The nonuniformity of antibody distribution in the kidney and its influence on dosimetry.

PubMed

Flynn, Aiden A; Pedley, R Barbara; Green, Alan J; Dearling, Jason L; El-Emir, Ethaar; Boxer, Geoffrey M; Boden, Robert; Begent, Richard H J

2003-02-01

The therapeutic efficacy of radiolabeled antibody fragments can be limited by nephrotoxicity, particularly when the kidney is the major route of extraction from the circulation. Conventional dose estimates in kidney assume uniform dose deposition, but we have shown increased antibody localization in the cortex after glomerular filtration. The purpose of this study was to measure the radioactivity in cortex relative to medulla for a range of antibodies and to assess the validity of the assumption of uniformity of dose deposition in the whole kidney and in the cortex for these antibodies with a range of radionuclides. Storage phosphor plate technology (radioluminography) was used to acquire images of the distributions of a range of antibodies of various sizes, labeled with 125I, in kidney sections. This allowed the calculation of the antibody concentration in the cortex relative to the medulla. Beta-particle point dose kernels were then used to generate the dose-rate distributions from 14C, 131I, 186Re, 32P and 90Y. The correlation between the actual dose-rate distribution and the corresponding distribution calculated assuming uniform antibody distribution throughout the kidney was used to test the validity of estimating dose by assuming uniformity in the kidney and in the cortex. There was a strong inverse relationship between the ratio of the radioactivity in the cortex relative to that in the medulla and the antibody size. The nonuniformity of dose deposition was greatest with the smallest antibody fragments but became more uniform as the range of the emissions from the radionuclide increased. Furthermore, there was a strong correlation between the actual dose-rate distribution and the distribution when assuming a uniform source in the kidney for intact antibodies along with medium- to long-range radionuclides, but there was no correlation for small antibody fragments with any radioisotope or for short-range radionuclides with any antibody. However, when the cortex was separated from the whole kidney, the correlation between the actual dose-rate distribution and the assumed dose-rate distribution, if the source was uniform, increased significantly. During radioimmunotherapy, the extent of nonuniformity of dose deposition in the kidney depends on the properties of the antibody and radionuclide. For dosimetry estimates, the cortex should be taken as a separate source region when the radiopharmaceutical is small enough to be filtered by the glomerulus.

Long-term effects of ionizing radiation after the Chernobyl accident: Possible contribution of historic dose.

PubMed

Omar-Nazir, Laila; Shi, Xiaopei; Moller, Anders; Mousseau, Timothy; Byun, Soohyun; Hancock, Samuel; Seymour, Colin; Mothersill, Carmel

2018-08-01

The impact of the Chernobyl NPP accident on the environment is documented to be greater than expected, with higher mutation rates than expected at the current, chronic low dose rate. In this paper we suggest that the historic acute exposure and resulting non-targeted effects (NTE) such as delayed mutations and genomic instability could account at least in part for currently measured mutation rates and provide an initial test of this concept. Data from Møller and Mousseau on the phenotypic mutation rates of Chernobyl birds 9-11 generations post the Chernobyl accident were used and the reconstructed dose response for mutations was compared with delayed reproductive death dose responses (as a measure of genomic instability) in cell cultures exposed to a similar range of doses. The dose to birds present during the Chernobyl NPP accident was reconstructed through the external pathway due to Cs-137 with an estimate of the uncertainty associated with such reconstruction. The percentage of Chernobyl birds several generations after the accident without mutations followed the general shape of the clonogenic survival percentage of the progeny of irradiated cells, and it plateaued at low doses. This is the expected result if NTE of radiation are involved. We suggest therefore, that NTE induced by the historic dose may play a role in generating mutations in progeny many generations following the initial disaster. Copyright © 2018 Elsevier Inc. All rights reserved.

Cosmic radiation dose in aircraft--a neutron track etch detector.

PubMed

Vuković, B; Radolić, V; Miklavcić, I; Poje, M; Varga, M; Planinić, J

2007-01-01

Cosmic radiation bombards us at high altitude by ionizing particles. The radiation environment is a complex mixture of charged particles of solar and galactic origin, as well as of secondary particles produced in interaction of the galactic cosmic particles with the nuclei of atmosphere of the Earth. The radiation field at aircraft altitude consists of different types of particles, mainly photons, electrons, positrons and neutrons, with a large energy range. The non-neutron component of cosmic radiation dose aboard ATR 42 and A 320 aircrafts (flight level of 8 and 11 km, respectively) was measured with TLD-100 (LiF:Mg,Ti) detectors and the Mini 6100 semiconductor dosimeter. The estimated occupational effective dose for the aircraft crew (A 320) working 500 h per year was 1.64 mSv. Other experiments, or dose rate measurements with the neutron dosimeter, consisting of LR-115 track detector and boron foil BN-1 or 10B converter, were performed on five intercontinental flights. Comparison of the dose rates of the non-neutron component (low LET) and the neutron one (high LET) of the radiation field at the aircraft flight level showed that the neutron component carried about 50% of the total dose. The dose rate measurements on the flights from the Middle Europe to the South and Middle America, then to Korea and Japan, showed that the flights over or near the equator region carried less dose rate; this was in accordance with the known geomagnetic latitude effect.

Feasibility of using two-dimensional array dosimeter for in vivo dose reconstruction via transit dosimetry.

PubMed

Chung, Heeteak; Li, Jonathan; Samant, Sanjiv

2011-04-08

Two-dimensional array dosimeters are commonly used to perform pretreatment quality assurance procedures, which makes them highly desirable for measuring transit fluences for in vivo dose reconstruction. The purpose of this study was to determine if an in vivo dose reconstruction via transit dosimetry using a 2D array dosimeter was possible. To test the accuracy of measuring transit dose distribution using a 2D array dosimeter, we evaluated it against the measurements made using ionization chamber and radiochromic film (RCF) profiles for various air gap distances (distance from the exit side of the solid water slabs to the detector distance; 0 cm, 30 cm, 40 cm, 50 cm, and 60 cm) and solid water slab thicknesses (10 cm and 20 cm). The backprojection dose reconstruction algorithm was described and evaluated. The agreement between the ionization chamber and RCF profiles for the transit dose distribution measurements ranged from -0.2% ~ 4.0% (average 1.79%). Using the backprojection dose reconstruction algorithm, we found that, of the six conformal fields, four had a 100% gamma index passing rate (3%/3 mm gamma index criteria), and two had gamma index passing rates of 99.4% and 99.6%. Of the five IMRT fields, three had a 100% gamma index passing rate, and two had gamma index passing rates of 99.6% and 98.8%. It was found that a 2D array dosimeter could be used for backprojection dose reconstruction for in vivo dosimetry.

Radiation environment on the Mir orbital station during solar minimum.

PubMed

Badhwar, G D; Atwell, W; Cash, B; Petrov, V M; Akatov YuA; Tchernykh, I V; Shurshakov, V A; Arkhangelsky, V A

1998-01-01

The Mir station has been in a 51.65 degrees inclination orbit since March 1986. In March 1995, the first US astronaut flew on the Mir-18 mission and returned on the Space Shuttle in July 1995. Since then three additional US astronauts have stayed on orbit for up to 6 months. Since the return of the first US astronaut, both the Spektr and Priroda modules have docked with Mir station, altering the mass shielding distribution. Radiation measurements, including the direct comparison of US and Russian absorbed dose rates in the Base Block of the Mir station, were made during the Mir-18 and -19 missions. There is a significant variation of dose rates across the core module; the six locations sampled showed a variation of a factor of nearly two. A tissue equivalent proportional counter (TEPC) measured a total absorbed dose rate of 300 microGy/day, roughly equally divided between the rate due to trapped protons from the South Atlantic Anomaly (SAA) and galactic cosmic radiation (GCR). This dose rate is about a factor of two lower than the rate measured by the thinly shielded (0.5 g cm-2 of Al) operational ion chamber (R-16), and about 3/2 of the rate of the more heavily shielded (3.5 g cm-2 of Al) ion chamber. This is due to the differences in the mass shielding properties at the location of these detectors. A comparison of integral linear energy transfer (LET) spectra measured by TEPC and plastic nuclear track detectors (PNTDs) deployed side by side are in remarkable agreement in the LET region of 15-1000 keV/micrometer, where the PNTDs are fully efficient. The average quality factor, using the ICRP-26 definition, was 2.6, which is higher than normally used. There is excellent agreement between the measured GCR dose rate and model calculations, but this is not true for trapped protons. The measured Mir-18 crew skin dose equivalent rate was 1133 microSv/day. Using the skin dose rate and anatomical models, we have estimated the blood-forming organ (BFO) dose rate and the maximum stay time in orbit for International Space Station crew members.

Radiation damage in room-temperature data acquisition with the PILATUS 6M pixel detector.

PubMed

Rajendran, Chitra; Dworkowski, Florian S N; Wang, Meitian; Schulze-Briese, Clemens

2011-05-01

The first study of room-temperature macromolecular crystallography data acquisition with a silicon pixel detector is presented, where the data are collected in continuous sample rotation mode, with millisecond read-out time and no read-out noise. Several successive datasets were collected sequentially from single test crystals of thaumatin and insulin. The dose rate ranged between ∼ 1320 Gy s(-1) and ∼ 8420 Gy s(-1) with corresponding frame rates between 1.565 Hz and 12.5 Hz. The data were analysed for global radiation damage. A previously unreported negative dose-rate effect is observed in the indicators of global radiation damage, which showed an approximately 75% decrease in D(1/2) at sixfold higher dose rate. The integrated intensity decreases in an exponential manner. Sample heating that could give rise to the enhanced radiation sensitivity at higher dose rate is investigated by collecting data between crystal temperatures of 298 K and 353 K. UV-Vis spectroscopy is used to demonstrate that disulfide radicals and trapped electrons do not accumulate at high dose rates in continuous data collection.

Exclusive low-dose-rate brachytherapy in 279 patients with T2N0 mobile tongue carcinoma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bourgier, Celine; Coche-Dequeant, Bernard; Fournier, Charles

2005-10-01

Purpose: To evaluate the therapeutic results obtained with {sup 192}Ir low-dose-rate interstitial brachytherapy in T2N0 mobile tongue carcinoma. Patients and Methods: Between December 1979 and January 1998, 279 patients with T2N0 mobile tongue carcinoma were treated by exclusive low-dose-rate brachytherapy, with or without neck dissection. {sup 192}Ir brachytherapy was performed according to the 'Paris system' with a median total dose of 60 Gy (median dose rate, 0.5 Gy/h). Results: Overall survival was 74.3% and 46.6% at 2 and 5 years. Local control was 79.1% at 2 years and regional control, respectively, 75.9% and 69.5% at 2 and 5 years (Kaplan-Meiermore » method). Systematic dissection revealed 44.6% occult node metastases, and histologic lymph node involvement was identified as the main significant factor for survival. Complication rate was 16.5% (Grade 3, 2.9%). Half of the patients presented previous and/or successive malignant tumor (ear-nose-throat, esophagus, or bronchus). Conclusion: Exclusive low-dose-rate brachytherapy is an effective treatment for T2 tongue carcinoma. Regional control and survival are excellent in patients undergoing systematic neck dissection, which is mandatory in our experience because of a high rate of occult lymph node metastases.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hall, Matthew D.; Schultheiss, Timothy E., E-mail: schultheiss@coh.org; Smith, David D.

Purpose/Objective(s): To perform a meta-regression on published data and to model the 5-year probability of cataract development after hematopoietic stem cell transplantation (HSCT) with and without total body irradiation (TBI). Methods and Materials: Eligible studies reporting cataract incidence after HSCT with TBI were identified by a PubMed search. Seventeen publications provided complete information on radiation dose schedule, fractionation, dose rate, and actuarial cataract incidence. Chemotherapy-only regimens were included as zero radiation dose regimens. Multivariate meta-regression with a weighted generalized linear model was used to model the 5-year cataract incidence and contributory factors. Results: Data from 1386 patients in 21 seriesmore » were included for analysis. TBI was administered to a total dose of 0 to 15.75 Gy with single or fractionated schedules with a dose rate of 0.04 to 0.16 Gy/min. Factors significantly associated with 5-year cataract incidence were dose, dose times dose per fraction (D•dpf), pediatric versus adult status, and the absence of an ophthalmologist as an author. Dose rate, graft versus host disease, steroid use, hyperfractionation, and number of fractions were not significant. Five-fold internal cross-validation showed a model validity of 83% ± 8%. Regression diagnostics showed no evidence of lack-of-fit and no patterns in the studentized residuals. The α/β ratio from the linear quadratic model, estimated as the ratio of the coefficients for dose and D•dpf, was 0.76 Gy (95% confidence interval [CI], 0.05-1.55). The odds ratio for pediatric patients was 2.8 (95% CI, 1.7-4.6) relative to adults. Conclusions: Dose, D•dpf, pediatric status, and regimented follow-up care by an ophthalmologist were predictive of 5-year cataract incidence after HSCT. The low α/β ratio indicates the importance of fractionation in reducing cataracts. Dose rate effects have been observed in single institution studies but not in the combined data analyzed here. Although data were limited to articles with 5-year actuarial estimates, the development of radiation-induced cataracts extends beyond this time.« less

Fractional dosing of yellow fever vaccine to extend supply: a modelling study.

PubMed

Wu, Joseph T; Peak, Corey M; Leung, Gabriel M; Lipsitch, Marc

2016-12-10

The ongoing yellow fever epidemic in Angola strains the global vaccine supply, prompting WHO to adopt dose sparing for its vaccination campaign in Kinshasa, Democratic Republic of the Congo, in July-August, 2016. Although a 5-fold fractional-dose vaccine is similar to standard-dose vaccine in safety and immunogenicity, efficacy is untested. There is an urgent need to ensure the robustness of fractional-dose vaccination by elucidation of the conditions under which dose fractionation would reduce transmission. We estimate the effective reproductive number for yellow fever in Angola using disease natural history and case report data. With simple mathematical models of yellow fever transmission, we calculate the infection attack rate (the proportion of population infected over the course of an epidemic) with various levels of transmissibility and 5-fold fractional-dose vaccine efficacy for two vaccination scenarios, ie, random vaccination in a hypothetical population that is completely susceptible, and the Kinshasa vaccination campaign in July-August, 2016, with different age cutoff for fractional-dose vaccines. We estimate the effective reproductive number early in the Angola outbreak was between 5·2 and 7·1. If vaccine action is all-or-nothing (ie, a proportion of vaccine recipients receive complete protection [VE] and the remainder receive no protection), n-fold fractionation can greatly reduce infection attack rate as long as VE exceeds 1/n. This benefit threshold becomes more stringent if vaccine action is leaky (ie, the susceptibility of each vaccine recipient is reduced by a factor that is equal to the vaccine efficacy). The age cutoff for fractional-dose vaccines chosen by WHO for the Kinshasa vaccination campaign (2 years) provides the largest reduction in infection attack rate if the efficacy of 5-fold fractional-dose vaccines exceeds 20%. Dose fractionation is an effective strategy for reduction of the infection attack rate that would be robust with a large margin for error in case fractional-dose VE is lower than expected. NIH-MIDAS, HMRF-Hong Kong. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effectiveness of a Third Dose of MMR Vaccine for Mumps Outbreak Control.

PubMed

Cardemil, Cristina V; Dahl, Rebecca M; James, Lisa; Wannemuehler, Kathleen; Gary, Howard E; Shah, Minesh; Marin, Mona; Riley, Jacob; Feikin, Daniel R; Patel, Manisha; Quinlisk, Patricia

2017-09-07

The effect of a third dose of the measles-mumps-rubella (MMR) vaccine in stemming a mumps outbreak is unknown. During an outbreak among vaccinated students at the University of Iowa, health officials implemented a widespread MMR vaccine campaign. We evaluated the effectiveness of a third dose for outbreak control and assessed for waning immunity. Of 20,496 university students who were enrolled during the 2015-2016 academic year, mumps was diagnosed in 259 students. We used Fisher's exact test to compare unadjusted attack rates according to dose status and years since receipt of the second MMR vaccine dose. We used multivariable time-dependent Cox regression models to evaluate vaccine effectiveness, according to dose status (three vs. two doses and two vs. no doses) after adjustment for the number of years since the second dose. Before the outbreak, 98.1% of the students had received at least two doses of MMR vaccine. During the outbreak, 4783 received a third dose. The attack rate was lower among the students who had received three doses than among those who had received two doses (6.7 vs. 14.5 cases per 1000 population, P<0.001). Students had more than nine times the risk of mumps if they had received the second MMR dose 13 years or more before the outbreak. At 28 days after vaccination, receipt of the third vaccine dose was associated with a 78.1% lower risk of mumps than receipt of a second dose (adjusted hazard ratio, 0.22; 95% confidence interval, 0.12 to 0.39). The vaccine effectiveness of two doses versus no doses was lower among students with more distant receipt of the second vaccine dose. Students who had received a third dose of MMR vaccine had a lower risk of mumps than did those who had received two doses, after adjustment for the number of years since the second dose. Students who had received a second dose of MMR vaccine 13 years or more before the outbreak had an increased risk of mumps. These findings suggest that the campaign to administer a third dose of MMR vaccine improved mumps outbreak control and that waning immunity probably contributed to propagation of the outbreak. (Funded by the Centers for Disease Control and Prevention.).

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.

Head-to-head comparison of H2-receptor antagonists and proton pump inhibitors in the treatment of erosive esophagitis: A meta-analysis

PubMed Central

Wang, Wei-Hong; Huang, Jia-Qing; Zheng, Ge-Fan; Xia, Harry Hua-Xiang; Wong, Wai-Man; Lam, Shiu-Kum; Wong, Benjamin Chun-Yu

2005-01-01

AIM: To systematically evaluate the efficacy of H2-receptor antagonists (H2RAs) and proton pump inhibitors in healing erosive esophagitis (EE). METHODS: A meta-analysis was performed. A literature search was conducted in PubMed, Medline, Embase, and Cochrane databases to include randomized controlled head-to-head comparative trials evaluating the efficacy of H2RAs or proton pump inhibitors in healing EE. Relative risk (RR) and 95% confidence interval (CI) were calculated under a random-effects model. RESULTS: RRs of cumulative healing rates for each comparison at 8 wk were: high dose vs standard dose H2RAs, 1.17 (95%CI, 1.02-1.33); standard dose proton pump inhibitors vs standard dose H2RAs, 1.59 (95%CI, 1.44-1.75); standard dose other proton pump inhibitors vs standard dose omeprazole, 1.06 (95%CI, 0.98-1.06). Proton pump inhibitors produced consistently greater healing rates than H2RAs of all doses across all grades of esophagitis, including patients refractory to H2RAs. Healing rates achieved with standard dose omeprazole were similar to those with other proton pump inhibitors in all grades of esophagitis. CONCLUSION: H2RAs are less effective for treating patients with erosive esophagitis, especially in those with severe forms of esophagitis. Standard dose proton pump inhibitors are significantly more effective than H2RAs in healing esophagitis of all grades. Proton pump inhibitors given at the recommended dose are equally effective for healing esophagitis. PMID:15996033

Long-term Seroprotection Rates Following Second Dose of Measles as MMR Vaccine at 15 months in Indian Children.

PubMed

Hansashree, P; Verma, Sanjay; Rawat, Amit; Sankhyan, Naveen; Bharti, Bhavneet

2018-05-15

To find out seropositivity rates at 4-6 and 9-12 years of age; among those who received one-dose measles at 9 months and one-dose MMR at 15 months of age. 80 healthy children (53 males) at 4-6 or 9-12 years of age, attending outpatient department for vaccination were enrolled. Antibody titers were estimated using commercially available quantitative-IgG ELISA kits. The seropositivity rates against measles, mumps, rubella were 80% (40/50), 86% (43/50), and 96% (48/50), respectively at 4-6 years, and 83.3% (25/30), 96.7% (29/30) and 96.7% (29/30), respectively at 9-12 years of age. Single dose of rubella vaccine seems to provide adequate long-term protection; however, measles vaccine requires more doses for similar protection.

Survival of Chinese Hamster Ovary Cells Following Ultrahigh Dose Rate Electron and Bremsstrahlung Radiation

DTIC Science & Technology

1990-04-01

and a stepped lead flattening filter. The electron energy used for these studies was 13 MeV. Dosimetry was performed by the Health Physics Division...VolI LJSAFSAPA-TR-90-4 AD-A222 722 SURVIVAL OF CHINESE HAMSTER OVARY CELLS FOLLOWING ULTRAHIGH DOSE RATE ELECTRON AND BREMISSTRAHLUNG RADIATION...Include Security ;a!. iatcn) Survival of Chinese Hamster Ovary Cells Following Ultrahigh Dose Rate Electron and Bremsstrahlung Radiation 12 PERSONAL

Observation of dose-rate dependence in a Fricke dosimeter irradiated at low dose rates with monoenergetic X-rays.

PubMed

O'Leary, Mel; Boscolo, Daria; Breslin, Nicole; Brown, Jeremy M C; Dolbnya, Igor P; Emerson, Chris; Figueira, Catarina; Fox, Oliver J L; Grimes, David Robert; Ivosev, Vladimir; Kleppe, Annette K; McCulloch, Aaron; Pape, Ian; Polin, Chris; Wardlow, Nathan; Currell, Fred J

2018-03-16

Absolute measurements of the radiolytic yield of Fe3+ in a ferrous sulphate dosimeter formulation (6 mM Fe2+), with a 20 keV x-ray monoenergetic beam, are reported. Dose-rate suppression of the radiolytic yield was observed at dose rates lower than and different in nature to those previously reported with x-rays. We present evidence that this effect is most likely to be due to recombination of free radicals radiolytically produced from water. The method used to make these measurements is also new and it provides radiolytic yields which are directly traceable to the SI standards system. The data presented provides new and exacting tests of radiation chemistry codes.

Safety, tolerability, pharmacokinetics and pharmacodynamics of single doses of empagliflozin, a sodium glucose cotransporter 2 (SGLT2) inhibitor, in healthy Japanese subjects.

PubMed

Sarashina, Akiko; Koiwai, Kazuki; Seman, Leo J; Yamamura, Norio; Taniguchi, Atsushi; Negishi, Takahiro; Sesoko, Shogo; Woerle, Hans J; Dugi, Klaus A

2013-01-01

This randomized, placebo-controlled within dose groups, double-blind, single rising dose study investigated the safety, tolerability, pharmacokinetics and pharmacodynamics of 1 mg to 100 mg doses of empagliflozin in 48 healthy Japanese male subjects. Empagliflozin was rapidly absorbed, reaching peak levels in 1.25 to 2.50 h; thereafter, plasma concentrations declined in a biphasic fashion, with mean terminal elimination half-life ranging from 7.76 to 11.7 h. Increase in empagliflozin exposure was proportional to dose. Oral clearance was dose independent and ranged from 140 to 172 mL/min. In the 24 h following 100 mg empagliflozin administration, the mean (%CV) amount of glucose excreted in urine was 74.3 (17.1) g. The amount and the maximum rate of glucose excreted via urine increased with dose of empagliflozin. Nine adverse events, all of mild intensity, were reported by 8 subjects (7 with empagliflozin and 1 with the placebo). No hypoglycemia was reported. In conclusion, 1 mg to 100 mg doses of empagliflozin had a good safety and tolerability profile in healthy Japanese male subjects. Exposure to empagliflozin was dose proportional. The amount and rate of urinary glucose excretion were higher with empagliflozin than with the placebo, and increased with empagliflozin dose.

Dose assessment of digital tomosynthesis in pediatric imaging

NASA Astrophysics Data System (ADS)

Gislason, Amber; Elbakri, Idris A.; Reed, Martin

2009-02-01

We investigated the potential for digital tomosynthesis (DT) to reduce pediatric x-ray dose while maintaining image quality. We utilized the DT feature (VolumeRadTM) on the GE DefiniumTM 8000 flat panel system installed in the Winnipeg Children's Hospital. Facial bones, cervical spine, thoracic spine, and knee of children aged 5, 10, and 15 years were represented by acrylic phantoms for DT dose measurements. Effective dose was estimated for DT and for corresponding digital radiography (DR) and computed tomography (CT) patient image sets. Anthropomorphic phantoms of selected body parts were imaged by DR, DT, and CT. Pediatric radiologists rated visualization of selected anatomic features in these images. Dose and image quality comparisons between DR, DT, and CT determined the usefulness of tomosynthesis for pediatric imaging. CT effective dose was highest; total DR effective dose was not always lowest - depending how many projections were in the DR image set. For the cervical spine, DT dose was close to and occasionally lower than DR dose. Expert radiologists rated visibility of the central facial complex in a skull phantom as better than DR and comparable to CT. Digital tomosynthesis has a significantly lower dose than CT. This study has demonstrated DT shows promise to replace CT for some facial bones and spinal diagnoses. Other clinical applications will be evaluated in the future.

Efficacy of prokinetics with a split-dose of polyethylene glycol in bowel preparation for morning colonoscopy: a randomized controlled trial.

PubMed

Kim, Hyoung Jun; Kim, Tae Oh; Shin, Bong Chul; Woo, Jae Gon; Seo, Eun Hee; Joo, Hee Rin; Heo, Nae-Yun; Park, Jongha; Park, Seung Ha; Yang, Sung Yeon; Moon, Young Soo; Shin, Jin-Yong; Lee, Nae Young

2012-01-01

Currently, a split-dose of polyethylene glycol (PEG) is the mainstay of bowel preparation due to its tolerability, bowel-cleansing action, and safety. However, bowel preparation with PEG is suboptimal because residual fluid reduces the polyp detection rate and requires a more thorough colon inspection. The aim of our study was to demonstrate the efficacy of a sufficient dose of prokinetics on bowel cleansing together with split-dose PEG. A prospective endoscopist-blinded study was conducted. Patients were randomly allocated to two groups: prokinetic with split-dose PEG or split-dose PEG alone. A prokinetic [100 mg itopride (Itomed)], was administered twice simultaneously with each split-dose of PEG. Bowel-cleansing efficacy was measured by endoscopists using the Ottawa scale and the segmental fluidity scale score. Each participant completed a bowel preparation survey. Mean scores from the Ottawa scale, segmental fluid scale, and rate of poor preparation were compared between both groups. Patients in the prokinetics with split-dose PEG group showed significantly lower total Ottawa and segmental fluid scores compared with patients in the split-dose of PEG alone group. A sufficient dose of prokinetics with a split-dose of PEG showed efficacy in bowel cleansing for morning colonoscopy, largely due to the reduction in colonic fluid. Copyright © 2012 S. Karger AG, Basel.

Commissioning dosimetry and in situ dose mapping of a semi-industrial Cobalt-60 gamma-irradiation facility using Fricke and Ceric-cerous dosimetry system and comparison with Monte Carlo simulation data

NASA Astrophysics Data System (ADS)

Mortuza, Md Firoz; Lepore, Luigi; Khedkar, Kalpana; Thangam, Saravanan; Nahar, Arifatun; Jamil, Hossen Mohammad; Bandi, Laxminarayan; Alam, Md Khorshed

2018-03-01

Characterization of a 90 kCi (3330 TBq), semi-industrial, cobalt-60 gamma irradiator was performed by commissioning dosimetry and in-situ dose mapping experiments with Ceric-cerous and Fricke dosimetry systems. Commissioning dosimetry was carried out to determine dose distribution pattern of absorbed dose in the irradiation cell and products. To determine maximum and minimum absorbed dose, overdose ratio and dwell time of the tote boxes, homogeneous dummy product (rice husk) with a bulk density of 0.13 g/cm3 were used in the box positions of irradiation chamber. The regions of minimum absorbed dose of the tote boxes were observed in the lower zones of middle plane and maximum absorbed doses were found in the middle position of front plane. Moreover, as a part of dose mapping, dose rates in the wall positions and some selective strategic positions were also measured to carry out multiple irradiation program simultaneously, especially for low dose research irradiation program. In most of the cases, Monte Carlo simulation data, using Monte Carlo N-Particle eXtended code version MCNPX 2.7., were found to be in congruence with experimental values obtained from Ceric-cerous and Fricke dosimetry; however, in close proximity positions from the source, the dose rate variation between chemical dosimetry and MCNP was higher than distant positions.

Digital radiography can reduce scoliosis x-ray exposure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kling, T.F. Jr.; Cohen, M.J.; Lindseth, R.E.

1990-09-01

Digital radiology is a new computerized system of acquiring x-rays in a digital (electronic) format. It possesses a greatly expanded dose response curve that allows a very broad range of x-ray dose to produce a diagnostic image. Potential advantages include significantly reduced radiation exposure without loss of image quality, acquisition of images of constant density irrespective of under or over exposure, and reduced repeat rates for unsatisfactory films. The authors prospectively studied 30 adolescents with scoliosis who had both conventional (full dose) and digital (full, one-half, or one-third dose) x-rays. They found digital made AP and lateral image with allmore » anatomic areas clearly depicted at full and one-half dose. Digital laterals were better at full dose and equal to conventional at one-half dose. Cobb angles were easily measured on all one-third dose AP and on 8 of 10 one-third dose digital laterals. Digital clearly depicted the Risser sign at one-half and one-third dose and the repeat rate was nil in this study, indicating digital compensates well for exposure errors. The study indicates that digital does allow radiation dose to be reduced by at least one-half in scoliosis patients and that it does have improved image quality with good contrast over a wide range of x-ray exposure.« less

A current and historical perspective on disparities in US childhood pneumococcal conjugate vaccine adherence and in rates of invasive pneumococcal disease: Considerations for the routinely-recommended, pediatric PCV dosing schedule in the United States

PubMed Central

McLaughlin, John M; Utt, Eric A; Hill, Nina M; Welch, Verna L; Power, Edward; Sylvester, Gregg C

2016-01-01

Previous research has suggested that reducing the US 4-dose PCV13 schedule to a 3-dose schedule may provide cost savings, despite more childhood pneumococcal disease. The study also stressed that dose reduction should be coupled with improved PCV adherence, however, US PCV uptake has leveled-off since 2008. An estimated 24–36% of US children aged 5–19 months are already receiving a reduced PCV schedule (i.e., missing ≥1 dose). This raises a practical concern that, under a reduced, 3-dose schedule, a similar proportion of children may receive ≤2 doses. It is also unknown if a reduced, 3-dose PCV schedule in the United States will afford the same disease protection as 3-dose schedules used elsewhere, given lower US PCV adherence. Finally, more assurance is needed that, under a reduced schedule, racial, socioeconomic, and geographic disparities in PCV adherence will not correspond with disproportionately higher rates of pneumococcal disease among poor or minority children. PMID:26376039

Quality control in interstitial brachytherapy of the breast using pulsed dose rate: treatment planning and dose delivery with an Ir-192 afterloading system.

PubMed

Mangold, C A; Rijnders, A; Georg, D; Van Limbergen, E; Pötter, R; Huyskens, D

2001-01-01

In the Radiotherapy Department of Leuven, about 20% of all breast cancer patients treated with breast conserving surgery and external radiotherapy receive an additional boost with pulsed dose rate (PDR) Ir-192 brachytherapy. An investigation was performed to assess the accuracy of the delivered PDR brachytherapy treatment. Secondly, the feasibility of in vivo measurements during PDR dose delivery was investigated. Two phantoms are manufactured to mimic a breast, one for thermoluminescent dosimetry (TLD) measurements, and one for dosimetry using radiochromic films. The TLD phantom allows measurements at 34 dose points in three planes including the basal dose points. The film phantom is designed in such a way that films can be positioned in a plane parallel and orthogonal to the needles. The dose distributions calculated with the TPS are in good agreement with both TLD and radiochromic film measurements (average deviations of point doses <+/-5%). However, close to the interface tissue-air the dose is overestimated by the TPS since it neglects the finite size of a breast and the associated lack of backscatter (average deviations of point doses -14%). Most deviations between measured and calculated doses, are in the order of magnitude of the uncertainty associated with the source strength specification, except for the point doses measured close to the skin. In vivo dosimetry during PDR brachytherapy treatment was found to be a valuable procedure to detect large errors, e.g. errors caused by an incorrect data transfer.

Physics-aspects of dose accuracy in high dose rate (HDR) brachytherapy: source dosimetry, treatment planning, equipment performance and in vivo verification techniques

PubMed Central

Bradley, David; Nisbet, Andrew

2012-01-01

This study provides a review of recent publications on the physics-aspects of dosimetric accuracy in high dose rate (HDR) brachytherapy. The discussion of accuracy is primarily concerned with uncertainties, but methods to improve dose conformation to the prescribed intended dose distribution are also noted. The main aim of the paper is to review current practical techniques and methods employed for HDR brachytherapy dosimetry. This includes work on the determination of dose rate fields around brachytherapy sources, the capability of treatment planning systems, the performance of treatment units and methods to verify dose delivery. This work highlights the determinants of accuracy in HDR dosimetry and treatment delivery and presents a selection of papers, focusing on articles from the last five years, to reflect active areas of research and development. Apart from Monte Carlo modelling of source dosimetry, there is no clear consensus on the optimum techniques to be used to assure dosimetric accuracy through all the processes involved in HDR brachytherapy treatment. With the exception of the ESTRO mailed dosimetry service, there is little dosimetric audit activity reported in the literature, when compared with external beam radiotherapy verification. PMID:23349649

Fast method for in-flight estimation of total dose from protons and electrons using RADE Minstrument on JUICE

NASA Astrophysics Data System (ADS)

Hajdas, Wojtek; Mrigakshi, Alankrita; Xiao, Hualin

2017-04-01

The primary concern of the ESA JUICE mission to Jupiter is the harsh particle radiation environment. Ionizing particles introduce radiation damage by total dose effects, displacement damages or single events effects. Therefore, both the total ionizing dose and the displacement damage equivalent fluence must be assessed to alert spacecraft and its payload as well as to quantify radiation levels for the entire mission lifetime. We present a concept and implementations steps for simplified method used to compute in flight a dose rate and total dose caused by protons. We also provide refinement of the method previously developed for electrons. The dose rates values are given for predefined active volumes located behind layers of materials with known thickness. Both methods are based on the electron and proton flux measurements provided by the Electron and Proton Detectors inside the Radiation Hard Electron Monitor (RADEM) located on-board of JUICE. The trade-off between method accuracy and programming limitations for in-flight computations are discussed. More comprehensive and precise dose rate computations based on detailed analysis of all stack detectors will be made during off-line data processing. It will utilize full spectral unfolding from all RADEM detector subsystems.

Physics-aspects of dose accuracy in high dose rate (HDR) brachytherapy: source dosimetry, treatment planning, equipment performance and in vivo verification techniques.

PubMed

Palmer, Antony; Bradley, David; Nisbet, Andrew

2012-06-01

This study provides a review of recent publications on the physics-aspects of dosimetric accuracy in high dose rate (HDR) brachytherapy. The discussion of accuracy is primarily concerned with uncertainties, but methods to improve dose conformation to the prescribed intended dose distribution are also noted. The main aim of the paper is to review current practical techniques and methods employed for HDR brachytherapy dosimetry. This includes work on the determination of dose rate fields around brachytherapy sources, the capability of treatment planning systems, the performance of treatment units and methods to verify dose delivery. This work highlights the determinants of accuracy in HDR dosimetry and treatment delivery and presents a selection of papers, focusing on articles from the last five years, to reflect active areas of research and development. Apart from Monte Carlo modelling of source dosimetry, there is no clear consensus on the optimum techniques to be used to assure dosimetric accuracy through all the processes involved in HDR brachytherapy treatment. With the exception of the ESTRO mailed dosimetry service, there is little dosimetric audit activity reported in the literature, when compared with external beam radiotherapy verification.

LET spectra measurements from the STS-35 CPDs

NASA Technical Reports Server (NTRS)

1995-01-01

Linear energy transfer (LET) spectra derived form automated track analysis system (ATAS) track parameter measurements for crew passive dosimeters (CPD's) flown with the astronauts on STS-35 are plotted. The spread between the seven individual spectra is typical of past manual measurements of sets of CPD's. This difference is probably due to the cumulative net shielding variations experienced by the CPD's as the astronauts carrying them went about their activities on the Space Shuttle. The STS-35 mission was launched on Dec. 2, 1990, at 28.5 degrees inclination and 352-km altitude. This is somewhat higher than the nominal 300-km flights and the orbit intersects more of the high intensity trapped proton region in the South Atlantic Anomaly (SAA). However, in comparison with APD spectra measured on earlier lower altitude missions (STS-26, -29, -30, -32), the flux spectra are all roughly comparable. This may be due to the fact that the STS-35 mission took place close to solar maximum (Feb. 1990), or perhaps to shielding differences. The corresponding dose and dose equivalent spectra for this mission are shown. The effect of statistical fluctuations at the higher LET values, where track densities are small, is very noticeable. This results in an increased spread within the dose rate and dose equivalent rate spectra, as compared to the flux spectra. The contribution to dose and dose equivalent per measured track is much greater in the high LET region and the differences, though numerically small, are heavily weighted in the integral spectra. The optimum measurement and characterization of the high LET tails of the spectra represent an important part of the research into plastic nuclear track detector (PNTD) response. The integral flux, dose rate, dose equivalent rate and mission dose equivalent for the seven astronauts are also given.

Expression of Genes Associated with DNA Damage Sensing in Human Fibroblasts Exposed to Low-dose-rate Gamma Rays

NASA Technical Reports Server (NTRS)

Zhang, Ye; Mehta, Satish; Hammond, Diane; Pierson, Duane; Jeevarajan, Antony; Cucinotta, Francis; Rohde, Larry; Wu, Honglu

2007-01-01

Understanding of the molecular response to low-dose and low-dose-rate radiation exposure is essential for the extrapolation of high-dose radiation risks to those at dose levels relevant to space and other environmental concerns. Most of the reported studies of gene expressions induced by low-dose or low-dose-rate radiation were carried out on exponentially growing cells. In the present study, we analyzed expressions of 84 genes associated with DNA damage sensing using real time PCR in human fibroblasts in mostly G1 phase of the cell cycle. The cells were exposed continuously to gamma rays at a dose rate of 0.8 cGy/hr for 1, 2, 6 or 24 hrs at 37 C throughout the exposure. The total RNA was isolated immediately after the exposure was terminated. Of the 84 genes, only a few showed significant changes of the expression level. Some of the genes (e.g. DDit3 and BTG2) were found to be up or down regulated only after a short period of exposure, while other genes (e.g. PRKDC) displayed a highest expression level at the 24 hr time point. The expression profiles for the exposed cells which had a smaller portion of G1 cells indicated more cell cycle signaling and DNA repair genes either up or down regulated. Interestingly, the panel of genes changed from radiation exposure in G1 cells is different from the panel in cells having less G1 arrest cells. The gene expression profile of the cells responding to low-dose-radiation insult apparently depends on the cell growth stage. The response pathway in G1 cells may differ from that in exponentially growing cells.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, C A; Clarke, S D; Pozzi, S A

Purpose: To develop an instrument for measuring neutron and photon dose rates from mixed fields with a single device. Methods: Stilbene organic scintillators can be used to detect fast neutrons and photons. Stilbene was used to measure emission from mixed particle sources californium-252 (Cf-252) and plutonium-beryllium (PuBe). Many source detector configurations were used, along with varying amounts of shielding. Collected spectra were analyzed using pulse shape discrimination software, to separate neutron and photon interactions. With a measured light output to energy relationship the pulse height spectrum was converted to energy deposited in the detector. Energy deposited was converted to dosemore » with a variety of standard dose factors, for comparison to current methods. For validation, all measurements and processing was repeated using an EJ-309 liquid scintillator detector. Dose rates were also measured in the same configuration with commercially available dose meters for further validation. Results: Measurements of dose rates will show agreement across all methods. Higher accuracy of pulse shape discrimination at lower energies with stilbene leads to more accurate measurement of neutron and photon deposited dose. In strong fields of mixed particles discrimination can be performed well at a very low energy threshold. This shows accurate dose measurements over a large range of incident particle energy. Conclusion: Stilbene shows promise as a material for dose rate measurements due to its strong ability for separating neutrons and photon pulses and agreement with current methods. A dual particle dose meter would simplify methods which are currently limited to the measurement of only one particle type. Future work will investigate the use of a silicon photomultiplier to reduce the size and required voltage of the assembly, for practical use as a handheld survey meter, room monitor, or phantom installation. Funding From the United States Department of Energy and the National Nuclear Security Administration.« less

Effect of Ion Flux (Dose Rate) in Source-Drain Extension Ion Implantation for 10-nm Node FinFET and Beyond on 300/450mm Platforms

NASA Astrophysics Data System (ADS)

Shen, Ming-Yi

The improvement of wafer equipment productivity has been a continuous effort of the semiconductor industry. Higher productivity implies lower product price, which economically drives more demand from the market. This is desired by the semiconductor manufacturing industry. By raising the ion beam current of the ion implanter for 300/450mm platforms, it is possible to increase the throughput of the ion implanter. The resulting dose rate can be comparable to the performance of conventional ion implanters or higher, depending on beam current and beam size. Thus, effects caused by higher dose rate must be investigated further. One of the major applications of ion implantation (I/I) is source-drain extension (SDE) I/I for the silicon FinFET device. This study investigated the dose rate effects on the material properties and device performance of the 10-nm node silicon FinFET. In order to gain better understanding of the dose rate effects, the dose rate study is based on Synopsys Technology CAD (TCAD) process and device simulations that are calibrated and validated using available structural silicon fin samples. We have successfully shown that the kinetic monte carlo (KMC) I/I simulation can precisely model both the silicon amorphization and the arsenic distribution in the fin by comparing the KMC simulation results with TEM images. The results of the KMC I/I simulation show that at high dose rate more activated arsenic dopants were in the source-drain extension (SDE) region. This finding matches with the increased silicon amorphization caused by the high dose-rate I/I, given that the arsenic atoms could be more easily activated by the solid phase epitaxial regrowth process. This increased silicon amorphization led to not only higher arsenic activation near the spacer edge, but also less arsenic atoms straggling into the channel. Hence, it is possible to improve the throughput of the ion implanter when the dopants are implanted at high dose rate if the same doping level with a lower wafer dose can be achieved. In addition, the leakage current might also be reduced due to less undesired dopants in the channel. However, the twin defects from the problematic Si{111} recrystallization is well-known to cause excessive leakage current to the FinFET. This drawback can offset the benefits of the high dose rate I/I mentioned above. This work produced the first attempt at simulating the electrical impact of twin defects on advanced-node (10 nm) FinFET device performance. It was found that the high dose-rate I/I causes more twin defects in the silicon fin, and the physical locations of these defects were close to the channel. The defects undesirably induced trap-assisted band-to-band tunneling near the drain, which increased the leakage current. This issue could be mitigated by using asymmetrical gate overlap/underlap design or thicker spacer for SDE I/I so that the twin defects are not located in the depletion region near the drain.

Effects of low-dose rate γ-irradiation combined with simulated microgravity on markers of oxidative stress, DNA methylation potential, and remodeling in the mouse heart.

PubMed

Seawright, John W; Samman, Yusra; Sridharan, Vijayalakshmi; Mao, Xiao Wen; Cao, Maohua; Singh, Preeti; Melnyk, Stepan; Koturbash, Igor; Nelson, Gregory A; Hauer-Jensen, Martin; Boerma, Marjan

2017-01-01

Space travel is associated with an exposure to low-dose rate ionizing radiation and the microgravity environment, both of which may lead to impairments in cardiac function. We used a mouse model to determine short- and long-term cardiac effects to simulated microgravity (hindlimb unloading; HU), continuous low-dose rate γ-irradiation, or a combination of HU and low-dose rate γ-irradiation. Cardiac tissue was obtained from female, C57BL/6J mice 7 days, 1 month, 4 months, and 9 months following the completion of a 21 day exposure to HU or a 21 day exposure to low-dose rate γ-irradiation (average dose rate of 0.01 cGy/h to a total of 0.04 Gy), or a 21 day simultaneous exposure to HU and low-dose rate γ-irradiation. Immunoblot analysis, rt-PCR, high-performance liquid chromatography, and histology were used to assess inflammatory cell infiltration, cardiac remodeling, oxidative stress, and the methylation potential of cardiac tissue in 3 to 6 animals per group. The combination of HU and γ-irradiation demonstrated the strongest increase in reduced to oxidized glutathione ratios 7 days and 1 month after treatment, but a difference was no longer apparent after 9 months. On the other hand, no significant changes in 4-hydroxynonenal adducts was seen in any of the groups, at the measured endpoints. While manganese superoxide dismutase protein levels decreased 9 months after low-dose γ-radiation, no changes were observed in expression of catalase or Nrf2, a transcription factor that determines the expression of several antioxidant enzymes, at the measured endpoints. Inflammatory marker, CD-2 protein content was significantly decreased in all groups 4 months after treatment. No significant differences were observed in α-smooth muscle cell actin protein content, collagen type III protein content or % total collagen. This study has provided the first and relatively broad analysis of small molecule and protein markers of oxidative stress, T-lymphocyte infiltration, and cardiac remodeling in response to HU with simultaneous exposure to low-dose rate γ-radiation. Results from the late observation time points suggest that the hearts had mostly recovered from these two experimental conditions. However, further research is needed with larger numbers of animals for a more robust statistical power to fully characterize the early and late effects of simulated microgravity combined with exposure to low-dose rate ionizing radiation on the heart.

Effects of low-dose rate γ-irradiation combined with simulated microgravity on markers of oxidative stress, DNA methylation potential, and remodeling in the mouse heart

PubMed Central

Samman, Yusra; Sridharan, Vijayalakshmi; Mao, Xiao Wen; Cao, Maohua; Singh, Preeti; Melnyk, Stepan; Koturbash, Igor; Nelson, Gregory A.; Hauer-Jensen, Martin; Boerma, Marjan

2017-01-01

Purpose Space travel is associated with an exposure to low-dose rate ionizing radiation and the microgravity environment, both of which may lead to impairments in cardiac function. We used a mouse model to determine short- and long-term cardiac effects to simulated microgravity (hindlimb unloading; HU), continuous low-dose rate γ-irradiation, or a combination of HU and low-dose rate γ-irradiation. Methods Cardiac tissue was obtained from female, C57BL/6J mice 7 days, 1 month, 4 months, and 9 months following the completion of a 21 day exposure to HU or a 21 day exposure to low-dose rate γ-irradiation (average dose rate of 0.01 cGy/h to a total of 0.04 Gy), or a 21 day simultaneous exposure to HU and low-dose rate γ-irradiation. Immunoblot analysis, rt-PCR, high-performance liquid chromatography, and histology were used to assess inflammatory cell infiltration, cardiac remodeling, oxidative stress, and the methylation potential of cardiac tissue in 3 to 6 animals per group. Results The combination of HU and γ-irradiation demonstrated the strongest increase in reduced to oxidized glutathione ratios 7 days and 1 month after treatment, but a difference was no longer apparent after 9 months. On the other hand, no significant changes in 4-hydroxynonenal adducts was seen in any of the groups, at the measured endpoints. While manganese superoxide dismutase protein levels decreased 9 months after low-dose γ-radiation, no changes were observed in expression of catalase or Nrf2, a transcription factor that determines the expression of several antioxidant enzymes, at the measured endpoints. Inflammatory marker, CD-2 protein content was significantly decreased in all groups 4 months after treatment. No significant differences were observed in α-smooth muscle cell actin protein content, collagen type III protein content or % total collagen. Conclusions This study has provided the first and relatively broad analysis of small molecule and protein markers of oxidative stress, T-lymphocyte infiltration, and cardiac remodeling in response to HU with simultaneous exposure to low-dose rate γ-radiation. Results from the late observation time points suggest that the hearts had mostly recovered from these two experimental conditions. However, further research is needed with larger numbers of animals for a more robust statistical power to fully characterize the early and late effects of simulated microgravity combined with exposure to low-dose rate ionizing radiation on the heart. PMID:28678877

Interstitial rotating shield brachytherapy for prostate cancer.

PubMed

Adams, Quentin E; Xu, Jinghzu; Breitbach, Elizabeth K; Li, Xing; Enger, Shirin A; Rockey, William R; Kim, Yusung; Wu, Xiaodong; Flynn, Ryan T

2014-05-01

To present a novel needle, catheter, and radiation source system for interstitial rotating shield brachytherapy (I-RSBT) of the prostate. I-RSBT is a promising technique for reducing urethra, rectum, and bladder dose relative to conventional interstitial high-dose-rate brachytherapy (HDR-BT). A wire-mounted 62 GBq(153)Gd source is proposed with an encapsulated diameter of 0.59 mm, active diameter of 0.44 mm, and active length of 10 mm. A concept model I-RSBT needle/catheter pair was constructed using concentric 50 and 75 μm thick nickel-titanium alloy (nitinol) tubes. The needle is 16-gauge (1.651 mm) in outer diameter and the catheter contains a 535 μm thick platinum shield. I-RSBT and conventional HDR-BT treatment plans for a prostate cancer patient were generated based on Monte Carlo dose calculations. In order to minimize urethral dose, urethral dose gradient volumes within 0-5 mm of the urethra surface were allowed to receive doses less than the prescribed dose of 100%. The platinum shield reduced the dose rate on the shielded side of the source at 1 cm off-axis to 6.4% of the dose rate on the unshielded side. For the case considered, for the same minimum dose to the hottest 98% of the clinical target volume (D(98%)), I-RSBT reduced urethral D(0.1cc) below that of conventional HDR-BT by 29%, 33%, 38%, and 44% for urethral dose gradient volumes within 0, 1, 3, and 5 mm of the urethra surface, respectively. Percentages are expressed relative to the prescription dose of 100%. For the case considered, for the same urethral dose gradient volumes, rectum D(1cc) was reduced by 7%, 6%, 6%, and 6%, respectively, and bladder D(1cc) was reduced by 4%, 5%, 5%, and 6%, respectively. Treatment time to deliver 20 Gy with I-RSBT was 154 min with ten 62 GBq (153)Gd sources. For the case considered, the proposed(153)Gd-based I-RSBT system has the potential to lower the urethral dose relative to HDR-BT by 29%-44% if the clinician allows a urethral dose gradient volume of 0-5 mm around the urethra to receive a dose below the prescription. A multisource approach is necessary in order to deliver the proposed (153)Gd-based I-RSBT technique in reasonable treatment times.

Prognostic implication of simultaneous anemia and lymphopenia during concurrent chemoradiotherapy in cervical squamous cell carcinoma.

PubMed

Cho, Oyeon; Chun, Mison; Oh, Young-Taek; Noh, O Kyu; Chang, Suk-Joon; Ryu, Hee-Sug; Lee, Eun Ju

2017-10-01

Radioresistance often leads to poor survival in concurrent chemoradiotherapy-treated cervical squamous cell carcinoma, and reliable biomarkers can improve prognosis. We compared the prognostic potential of hemoglobin, absolute neutrophil count, and absolute lymphocyte count with that of squamous cell carcinoma antigen in concurrent chemoradiotherapy-treated squamous cell carcinoma. We analyzed 152 patients with concurrent chemoradiotherapy and high-dose-rate intracavitary brachytherapy-treated cervical squamous cell carcinoma. Hemoglobin, absolute neutrophil count, absolute lymphocyte count, and squamous cell carcinoma antigen were quantitated and correlated with survival, using Cox regression, receiver operating characteristic curve analysis, and Kaplan-Meier plots. Both hemoglobin and absolute lymphocyte count in the second week of concurrent chemoradiotherapy (Hb2 and ALC2) and squamous cell carcinoma antigen in the third week of concurrent chemoradiotherapy (mid-squamous cell carcinoma antigen) correlated significantly with disease-specific survival and progression-free survival. The ratio of high-dose-rate intracavitary brachytherapy dose to total dose (high-dose-rate intracavitary brachytherapy ratio) correlated significantly with progression-free survival. Patients with both low Hb2 (≤11 g/dL) and ALC2 (≤639 cells/µL) showed a lower 5-year disease-specific survival rate than those with high Hb2 and/or ALC2, regardless of mid-squamous cell carcinoma antigen (mid-squamous cell carcinoma antigen: ≤4.7 ng/mL; 5-year disease-specific survival rate: 85.5% vs 94.6%, p = 0.0096, and mid-squamous cell carcinoma antigen: >4.7 ng/mL; 5-year disease-specific survival rate: 43.8% vs 66.7%, p = 0.192). When both Hb2 and ALC2 were low, the low high-dose-rate intracavitary brachytherapy ratio (≤0.43) subgroup displayed significantly lower 5-year disease-specific survival rate compared to the subgroup high high-dose-rate intracavitary brachytherapy ratio (>0.43) (62.5% vs 88.2%, p = 0.0067). Patients with both anemia and lymphopenia during concurrent chemoradiotherapy showed poor survival, independent of mid-squamous cell carcinoma antigen, and escalating high-dose-rate intracavitary brachytherapy ratio might improve survival.

The role of single-shot metronidazole in the prevention of Clostridium difficile infection following ileostomy reversal surgery.

PubMed

Fernandes, Roland; Robinson, Paul; Rangarajan, Karan; Scott, Sophie; Angco, Laura

2017-05-01

Symptomatic infection with Clostridium difficile is strongly linked to antibiotic use and rates are higher for colorectal surgery. In February 2015, trust policy for antibiotic prophylaxis of ileostomy reversal surgery was changed from three doses of metronidazole plus cefuroxime to single-dose metronidazole, in a bid to reduce rates of Clostridium difficile infection. A retrospective cohort study was conducted at a single, large hospital trust between February 2014 and February 2016, before and after change in antimicrobial policy. Theatre data, clinical notes and pathology results were all reviewed. Outcome data, patient age, gender, length of operation and hospital stay were extracted. One hundred three patients underwent ileostomy reversal surgery between February 2014 and February 2015. All received cefuroxime together with metronidazole at induction of anaesthesia followed by two further post-operative doses as operative prophylaxis. Ninety-six patients underwent ileostomy reversal surgery between February 2015 and February 2016. All received single-dose metronidazole at induction as prophylaxis. Post-operative diarrhoea was significantly reduced in patients given single-dose metronidazole compared with patients managed with multiple dose, dual antibiotic therapy (32 vs 12.5%, P 0.001). Rates of CDI were also significantly reduced in patients given single-dose metronidazole (6.8 vs 1%, P 0.038). Single-dose, pre-operative metronidazole is effective at reducing post-operative diarrhoea and CDI in ileostomy reversal surgery compared with multiple-dose cefuroxime plus metronidazole. Metronidazole may be effective as a prophylactic antibiotic against CDI in colonic surgery.

Determination of the gamma-ray skyshine dose contribution in a Loss Of Shielding accident

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dennis, M.L.; Weiner, R.F.; Osborn, D.M.

2007-07-01

The goal of this research is to determine the gamma-ray dose contribution from skyshine. In a transportation accident involving the loss of lead gamma shielding, first responders to the accident will be exposed to both direct gamma radiation streaming from the exposed spent nuclear fuel and atmospherically reflected gamma radiation. The reflected radiation is referred to as skyshine and should contribute minimally to the overall dose; however, when there is minimal shielding above the exposed source, skyshine at large distances from the source must be considered. The program SKYDOSE developed by Shultis and Faw evaluates the gamma-ray skyshine dose frommore » a point, isotropic, polyenergetic, gamma-photon source. Assuming an infinite black wall shielding all direct radiation, the model assumes a first responder is located at varying distances from the wall. Skyshine doses are calculated both through SKYDOSE's integral line-beam method and an approximate approach prescribed by the National Council of Radiation Protection and Measurements. Initial results from SKYDOSE indicate nearly equivalent dose rates from either direct or skyshine radiation at nine meters from the wall, which seemed unusual and not readily explained. NCRP methodology, however, yields skyshine dose rates which are drastically smaller than direct dose rates at the same distance. Further investigation using the program MicroSkyshine{sup R}, which allows a variety of source configurations, suggests skyshine contributes minimally to dose in a loss-of-shielding accident. (authors)« less

TU-G-204-09: The Effects of Reduced- Dose Lung Cancer Screening CT On Lung Nodule Detection Using a CAD Algorithm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Young, S; Lo, P; Kim, G

2015-06-15

Purpose: While Lung Cancer Screening CT is being performed at low doses, the purpose of this study was to investigate the effects of further reducing dose on the performance of a CAD nodule-detection algorithm. Methods: We selected 50 cases from our local database of National Lung Screening Trial (NLST) patients for which we had both the image series and the raw CT data from the original scans. All scans were acquired with fixed mAs (25 for standard-sized patients, 40 for large patients) on a 64-slice scanner (Sensation 64, Siemens Healthcare). All images were reconstructed with 1-mm slice thickness, B50 kernel.more » 10 of the cases had at least one nodule reported on the NLST reader forms. Based on a previously-published technique, we added noise to the raw data to simulate reduced-dose versions of each case at 50% and 25% of the original NLST dose (i.e. approximately 1.0 and 0.5 mGy CTDIvol). For each case at each dose level, the CAD detection algorithm was run and nodules greater than 4 mm in diameter were reported. These CAD results were compared to “truth”, defined as the approximate nodule centroids from the NLST reports. Subject-level mean sensitivities and false-positive rates were calculated for each dose level. Results: The mean sensitivities of the CAD algorithm were 35% at the original dose, 20% at 50% dose, and 42.5% at 25% dose. The false-positive rates, in decreasing-dose order, were 3.7, 2.9, and 10 per case. In certain cases, particularly in larger patients, there were severe photon-starvation artifacts, especially in the apical region due to the high-attenuating shoulders. Conclusion: The detection task was challenging for the CAD algorithm at all dose levels, including the original NLST dose. However, the false-positive rate at 25% dose approximately tripled, suggesting a loss of CAD robustness somewhere between 0.5 and 1.0 mGy. NCI grant U01 CA181156 (Quantitative Imaging Network); Tobacco Related Disease Research Project grant 22RT-0131.« less

Image processing techniques revealing the relationship between the field-measured ambient gamma dose equivalent rate and geological conditions at a granitic area, Velence Mountains, Hungary

NASA Astrophysics Data System (ADS)

Beltran Torres, Silvana; Petrik, Attila; Zsuzsanna Szabó, Katalin; Jordan, Gyozo; Szabó, Csaba

2017-04-01

In order to estimate the annual dose that the public receive from natural radioactivity, the identification of the potential risk areas is required which, in turn, necessitates understanding the relationship between the spatial distribution of natural radioactivity and the geogenic risk factors (e.g., rock types, dykes, faults, soil conditions, etc.). A detailed spatial analysis of ambient gamma dose equivalent rate was performed in the western side of Velence Mountains, the largest outcropped granitic area in Hungary. In order to assess the role of local geology in the spatial distribution of ambient gamma dose rates, field measurements were carried out at ground level at 300 sites along a 250 m x 250 m regular grid in a total surface of 14.7 km2. Digital image processing methods were applied to identify anomalies, heterogeneities and spatial patterns in the measured gamma dose rates, including local maxima and minima determination, digital cross sections, gradient magnitude and gradient direction, second derivative profile curvature, local variability, lineament density, 2D autocorrelation and directional variogram analyses. Statistical inference showed that different gamma dose rate levels are associated with the rock types (i.e., Carboniferous granite, Pleistocene colluvial, proluvial, deluvial sediments and talus, and Pannonian sand and pebble), with the highest level on the Carboniferous granite including outlying values. Moreover, digital image processing revealed that linear gamma dose rate spatial features are parallel to the SW-NE dyke system and possibly to the NW-SE main fractures. The results of this study underline the importance of understanding the role of geogenic risk factors influencing the ambient gamma dose rate received by public. The study also demonstrates the power of the image processing techniques for the identification of spatial pattern in field-measured geogenic radiation.

Biological X-ray irradiator characterization for use with small animals and cells.

PubMed

Bruno, A Colello; Mazaro, S J; Amaral, L L; Rego, E M; Oliveira, H F; Pavoni, J F

2017-03-02

This study presents the characterization of an X-ray irradiator through dosimetric tests, which confirms the actual dose rate that small animals and cells will be exposed to during radiobiological experiments. We evaluated the linearity, consistency, repeatability, and dose distribution in the positions in which the animals or cells are placed during irradiation. In addition, we evaluated the performance of the X-ray tube (voltage and tube operating current), the radiometric survey (leakage radiation) and safety devices. The irradiator default setting was established as 160 kV and 25 mA. Tests showed that the dose rate was linear overtime (R2=1) and remained stable for long (constant) and short (repeatability) intervals between readings. The mean dose rate inside the animal cages was 1.27±0.06 Gy/min with a uniform beam of 95.40% (above the minimum threshold guaranteed by the manufacturer). The mean dose rate inside the cell plates was 0.92±0.19 Gy/min. The dose rate dependence with tube voltage and current presented a quadratic and linear relationship, respectively. There was no observed mechanical failure during evaluation of the irradiator safety devices and the radiometric survey obtained a maximum ambient equivalent dose rate of 0.26 mSv/h, which exempts it from the radiological protection requirements of the International Atomic Energy Agency. The irradiator characterization enables us to perform radiobiological experiments, and assists or even replaces traditional therapy equipment (e.g., linear accelerators) for cells and small animal irradiation, especially in early research stages.

High doses of dextromethorphan, an NMDA antagonist, produce effects similar to classic hallucinogens

PubMed Central

Carter, Lawrence P.; Johnson, Matthew W.; Mintzer, Miriam Z.; Klinedinst, Margaret A.; Griffiths, Roland R.

2013-01-01

Rationale Although reports of dextromethorphan (DXM) abuse have increased recently, few studies have examined the effects of high doses of DXM. Objective This study in humans evaluated the effects of supratherapeutic doses of DXM and triazolam. Methods Single, acute, oral doses of DXM (100, 200, 300, 400, 500, 600, 700, 800 mg/70 kg), triazolam (0.25, 0.5 mg/70kg), and placebo were administered to twelve healthy volunteers with histories of hallucinogen use, under double-blind conditions, using an ascending dose run-up design. Subjective, behavioral, and physiological effects were assessed repeatedly after drug administration for 6 hours. Results Triazolam produced dose-related increases in subject-rated sedation, observer-rated sedation, and behavioral impairment. DXM produced a profile of dose-related physiological and subjective effects differing from triazolam. DXM effects included increases in blood pressure, heart rate, and emesis, increases in observer-rated effects typical of classic hallucinogens (e.g. distance from reality, visual effects with eyes open and closed, joy, anxiety), and participant ratings of stimulation (e.g. jittery, nervous), somatic effects (e.g. tingling, headache), perceptual changes, end-of-session drug liking, and mystical-type experience. After 400 mg/70kg DXM, 11 of 12 participants indicated on a pharmacological class questionnaire that they thought they had received a classic hallucinogen (e.g. psilocybin). Drug effects resolved without significant adverse effects by the end of the session. In a 1-month follow up volunteers attributed increased spirituality and positive changes in attitudes, moods, and behavior to the session experiences. Conclusions High doses of DXM produced effects distinct from triazolam and had characteristics that were similar to the classic hallucinogen psilocybin. PMID:22526529

Assessment of Volumetric-Modulated Arc Therapy for Constant and Variable Dose Rates

PubMed Central

De Ornelas-Couto, Mariluz; Mihaylov, Ivaylo; Dogan, Nesrin

2017-01-01

Purpose: The aim of this study is to compare the effects of dose rate on volumetric-modulated arc therapy plans to determine optimal dose rates for prostate and head and neck (HN) cases. Materials and Methods: Ten prostate and ten HN cases were retrospectively studied. For each case, seven plans were generated: one variable dose rate (VDR) and six constant dose rate (CDR) (100–600 monitor units [MUs]/min) plans. Prescription doses were: 80 Gy to planning target volume (PTV) for the prostate cases, and 70, 60, and 54 Gy to PTV1, PTV2, and PTV3, respectively, for HN cases. Plans were normalized to 95% of the PTV and PTV1, respectively, with the prescription dose. Plans were assessed using Dose-Volume-Histogram metrics, homogeneity index, conformity index, MUs, and delivery time. Results: For the prostate cases, significant differences were found for rectum D35 between VDR and all CDR plans, except CDR500. Furthermore, VDR was significantly different than CDR100 and 200 for bladder D50. Delivery time for all CDR plans and MUs for CDR400–600 were significantly higher when compared to VDR. HN cases showed significant differences between VDR and CDR100, 500 and 600 for D2 to the cord and brainstem. Significant differences were found for delivery time and MUs for all CDR plans, except CDR100 for number of MUs. Conclusion: The most significant differences were observed in delivery time and number of MUs. All-in-all, the best CDR for prostate cases was found to be 300 MUs/min and 200 or 300 MUs/min for HN cases. However, VDR plans are still the choice in terms of MU efficiency and plan quality. PMID:29296033

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

PubMed Central

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

2014-01-01

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

Evaluation of forest decontamination using radiometric measurements.

PubMed

Cresswell, Alan J; Kato, Hiroaki; Onda, Yuichi; Nanba, Kenji

2016-11-01

An experiment has been conducted to evaluate the additional dose reduction by clear felling contaminated forestry in Fukushima Prefecture, Japan, and using the timber to cover the areas with wood chips. A portable gamma spectrometry system, comprising a backpack containing a 3 × 3″ NaI(Tl) detector with digital spectrometer and GPS receiver, has been used to map dose rate and radionuclide activity concentrations before, after and at stages during this experiment. The data show the effect of the different stages of the experiment on dose rate at different locations around the site. The spectrometric data have allowed the assessment of the contributions of natural and anthropogenic radionuclides to the dose rate at different parts of the site before and after the experiment. This has clearly demonstrated the value of radiometric methods in evaluating remediation, and the effect of other environmental processes. The value of spectrometric methods which directly measure radionuclide concentrations has also been shown, especially through the identification of the contribution of natural and anthropogenic activity to the measured dose rate. The experiment has shown that clearing trees and applying wood chips can reduce dose rates by 10-15% beyond that achieved by just clearing the forest litter and natural redistribution of radiocaesium. Copyright © 2016 Elsevier Ltd. All rights reserved.

Fieldable computer system for determining gamma-ray pulse-height distributions, flux spectra, and dose rates from Little Boy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moss, C.E.; Lucas, M.C.; Tisinger, E.W.

1984-01-01

Our system consists of a LeCroy 3500 data acquisition system with a built-in CAMAC crate and eight bismuth-germanate detectors 7.62 cm in diameter and 7.62 cm long. Gamma-ray pulse-height distributions are acquired simultaneously for up to eight positions. The system was very carefully calibrated and characterized from 0.1 to 8.3 MeV using gamma-ray spectra from a variety of radioactive sources. By fitting the pulse-height distributions from the sources with a function containing 17 parameters, we determined theoretical repsonse functions. We use these response functions to unfold the distributions to obtain flux spectra. A flux-to-dose-rate conversion curve based on the workmore » of Dimbylow and Francis is then used to obtain dose rates. Direct use of measured spectra and flux-to-dose-rate curves to obtain dose rates avoids the errors that can arise from spectrum dependence in simple gamma-ray dosimeter instruments. We present some gamma-ray doses for the Little Boy assembly operated at low power. These results can be used to determine the exposures of the Hiroshima survivors and thus aid in the establishment of radation exposure limits for the nuclear industry.« less

Antibiotic Dosing in Continuous Renal Replacement Therapy.

PubMed

Shaw, Alexander R; Mueller, Bruce A

2017-07-01

Appropriate antibiotic dosing is critical to improve outcomes in critically ill patients with sepsis. The addition of continuous renal replacement therapy makes achieving appropriate antibiotic dosing more difficult. The lack of continuous renal replacement therapy standardization results in treatment variability between patients and may influence whether appropriate antibiotic exposure is achieved. The aim of this study was to determine if continuous renal replacement therapy effluent flow rate impacts attaining appropriate antibiotic concentrations when conventional continuous renal replacement therapy antibiotic doses were used. This study used Monte Carlo simulations to evaluate the effect of effluent flow rate variance on pharmacodynamic target attainment for cefepime, ceftazidime, levofloxacin, meropenem, piperacillin, and tazobactam. Published demographic and pharmacokinetic parameters for each antibiotic were used to develop a pharmacokinetic model. Monte Carlo simulations of 5000 patients were evaluated for each antibiotic dosing regimen at the extremes of Kidney Disease: Improving Global Outcomes guidelines recommended effluent flow rates (20 and 35 mL/kg/h). The probability of target attainment was calculated using antibiotic-specific pharmacodynamic targets assessed over the first 72 hours of therapy. Most conventional published antibiotic dosing recommendations, except for levofloxacin, reach acceptable probability of target attainment rates when effluent rates of 20 or 35 mL/kg/h are used. Copyright © 2017 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

INDOS: conversational computer codes to implement ICRP-10-10A models for estimation of internal radiation dose to man

DOE Office of Scientific and Technical Information (OSTI.GOV)

Killough, G.G.; Rohwer, P.S.

1974-03-01

INDOS1, INDOS2, and INDOS3 (the INDOS codes) are conversational FORTRAN IV programs, implemented for use in time-sharing mode on the ORNL PDP-10 System. These codes use ICRP10-10A models to estimate the radiation dose to an organ of the body of Reference Man resulting from the ingestion or inhalation of any one of various radionuclides. Two patterns of intake are simulated: intakes at discrete times and continuous intake at a constant rate. The IND0S codes provide tabular output of dose rate and dose vs time, graphical output of dose vs time, and punched-card output of organ burden and dose vs time.more » The models of internal dose calculation are discussed and instructions for the use of the INDOS codes are provided. The INDOS codes are available from the Radiation Shielding Information Center, Oak Ridge National Laboratory, P. O. Box X, Oak Ridge, Tennessee 37830. (auth)« less

Radiotherapy of soft tissue sarcomas in dogs.

PubMed

McChesney, S L; Withrow, S J; Gillette, E L; Powers, B E; Dewhirst, M W

1989-01-01

Megavoltage radiotherapy was administered to 42 dogs with soft tissue sarcoma. Acceptable local control of these aggressive tumors was achieved after one year of treatment. Control rates of 48 and 67% were obtained at doses of 45 and 50 gray (Gy), respectively. At 2 years, control rates decreased to 33% at the dose of 50 Gy. Serious complications developed in 4 of 42 dogs at doses of 40 to 50 Gy. The estimated dose with a 50% probability for causing serious complications was 54 Gy, given in 10 fractions. We believe that the large doses per fraction used in this study probably led to an increased probability for necrosis. Hemangiopericytomas seemed to be more responsive than fibrosarcomas. Only 2 of 11 recurrent tumors were controlled with surgery. Good local control was achieved with radiation alone for one year at doses with a low probability for serious complications; however, higher total radiation doses or combined modalities, such as surgery and radiation or radiation and hyperthermia, may be needed for longer-term control.

Developing a virtual reality application for training nuclear power plant operators: setting up a database containing dose rates in the refuelling plant.

PubMed

Ródenas, J; Zarza, I; Burgos, M C; Felipe, A; Sánchez-Mayoral, M L

2004-01-01

Operators in Nuclear Power Plants can receive high doses during refuelling operations. A training programme for simulating refuelling operations will be useful in reducing the doses received by workers as well as minimising operation time. With this goal in mind, a virtual reality application is developed within the framework of the CIPRES project. The application requires doses, both instantaneous and accumulated, to be displayed at all times during operator training. Therefore, it is necessary to set up a database containing dose rates at every point in the refuelling plant. This database is based on radiological protection surveillance data measured in the plant during refuelling operations. Some interpolation routines have been used to estimate doses through the refuelling plant. Different assumptions have been adopted in order to perform the interpolation and obtain consistent data. In this paper, the procedures developed to set up the dose database for the virtual reality application are presented and analysed.

Dose-Rate Effects in Breaking DNA Strands by Short Pulses of Extreme Ultraviolet Radiation.

PubMed

Vyšín, Luděk; Burian, Tomáš; Ukraintsev, Egor; Davídková, Marie; Grisham, Michael E; Heinbuch, Scott; Rocca, Jorge J; Juha, Libor

2018-05-01

In this study, we examined dose-rate effects on strand break formation in plasmid DNA induced by pulsed extreme ultraviolet (XUV) radiation. Dose delivered to the target molecule was controlled by attenuating the incident photon flux using aluminum filters as well as by changing the DNA/buffer-salt ratio in the irradiated sample. Irradiated samples were examined using agarose gel electrophoresis. Yields of single- and double-strand breaks (SSBs and DSBs) were determined as a function of the incident photon fluence. In addition, electrophoresis also revealed DNA cross-linking. Damaged DNA was inspected by means of atomic force microscopy (AFM). Both SSB and DSB yields decreased with dose rate increase. Quantum yields of SSBs at the highest photon fluence were comparable to yields of DSBs found after synchrotron irradiation. The average SSB/DSB ratio decreased only slightly at elevated dose rates. In conclusion, complex and/or clustered damages other than cross-links do not appear to be induced under the radiation conditions applied in this study.

Solar Variability and the Near-Earth Environment: Mining Enhanced Low Dose Rate Sensitivity Data From the Microelectronics and Photonics Test Bed Space Experiment

NASA Technical Reports Server (NTRS)

Turflinger, T.; Schmeichel, W.; Krieg, J.; Titus, J.; Campbell, A.; Reeves, M.; Marshall (P.); Hardage, Donna (Technical Monitor)

2004-01-01

This effort is a detailed analysis of existing microelectronics and photonics test bed satellite data from one experiment, the bipolar test board, looking to improve our understanding of the enhanced low dose rate sensitivity (ELDRS) phenomenon. Over the past several years, extensive total dose irradiations of bipolar devices have demonstrated that many of these devices exhibited ELDRS. In sensitive bipolar transistors, ELDRS produced enhanced degradation of base current, resulting in enhanced gain degradation at dose rates <0.1 rd(Si)/s compared to similar transistors irradiated at dose rates >1 rd(Si)/s. This Technical Publication provides updated information about the test devices, the in-flight experiment, and both flight-and ground-based observations. Flight data are presented for the past 5 yr of the mission. These data are compared to ground-based data taken on devices from the same date code lots. Information about temperature fluctuations, power shutdowns, and other variables encountered during the space flight are documented.

Verification of the radiometric map of the Czech Republic.

PubMed

Matolín, Milan

2017-01-01

The radiometric map of the Czech Republic is based on uniform regional airborne radiometric total count measurements (1957-1959) which covered 100% of the country. The airborne radiometric instrument was calibrated to a 226 Ra point source. The calibration facility for field gamma-ray spectrometers, established in the Czech Republic in 1975, significantly contributed to the subsequent radiometric data standardization. In the 1990's, the original analogue airborne radiometric data were digitized and using the method of back-calibration (IAEA, 2003) converted to dose rate. The map of terrestrial gamma radiation expressed in dose rate (nGy/h) was published on the scale 1:500,000 in 1995. Terrestrial radiation in the Czech Republic, formed by magmatic, sedimentary and metamorphic rocks of Proterozoic to Quaternary age, ranges mostly from 6 to 245 nGy/h, with a mean of 65.6 ± 19.0 nGy/h. The elevated terrestrial radiation in the Czech Republic, in comparison to the global dose rate average of 54 nGy/h, reflects an enhanced content of natural radioactive elements in the rocks. The 1995 published radiometric map of the Czech Republic was successively studied and verified by additional ground gamma-ray spectrometric measurements and by comparison to radiometric maps of Germany, Poland and Slovakia in border zones. A ground dose rate intercomparison measurement under participation of foreign and domestic professional institutions revealed mutual dose rate deviations about 20 nGy/h and more due to differing technical parameters of applied radiometric instruments. Studies and verification of the radiometric map of the Czech Republic illustrate the magnitude of current deviations in dose rate data. This gained experience can assist in harmonization of dose rate data on the European scale. Copyright © 2016 Elsevier Ltd. All rights reserved.

The role of temperature increase rate in combinational hyperthermia chemotherapy treatment

NASA Astrophysics Data System (ADS)

Tang, Yuan; McGoron, Anthony J.

2010-02-01

Hyperthermia in combination with chemotherapy has been widely used in cancer treatment. Our previous study has shown that rapid rate hyperthermia in combination with chemotherapy can synergistically kill cancer cells whereas a sub-additive effect was found when a slow rate hyperthermia was applied. In this study, we explored the basis of this difference. For this purpose, in vitro cell culture experiments with a uterine cancer cell line (MES-SA) and its multidrug resistant (MDR) variant MES-SA/Dx5 were conducted. P-glycoprotein (P-gp) expression, Caspase 3 activity, and heat shock protein 70 (HSP 70) expression following the two different modes of heating were measured. Doxorubicin (DOX) was used as the chemotherapy drug. Indocyanine green (ICG), which absorbs near infrared light at 808nm (ideal for tissue penetration), was chosen for achieving rapid rate hyperthermia. Slow rate hyperthermia was provided by a cell culture incubator. Two sets of thermal doses were delivered by either slow rate or rapid rate hyperthermia. HSP70 expression was highly elevated under low dose slow rate incubator hyperthermia while maintained at the baseline level under the other three treatments. Caspase3 level slightly increased after low dose slow rate incubator hyperthermia while necrotic cell death was found in the other three types of heat treatment. In conclusion, when given at the same thermal dose, slow rate hyperthermia is more likely to induce thermotolerance. Meanwhile, hyperthermia showed a dose dependent capability in reversing P-gp mediated MDR; when MDR is reversed, the combinational treatment induced extensive necrotic cell death. During this process, the rate of heating also played a very important role; necrosis was more dramatic in rapid rate hyperthermia than in slow rate hyperthermia even though they were given at the same dose.

Efficacy of Single-Dose and Triple-Dose Albendazole and Mebendazole against Soil-Transmitted Helminths and Taenia spp.: A Randomized Controlled Trial

PubMed Central

Steinmann, Peter; Utzinger, Jürg; Du, Zun-Wei; Jiang, Jin-Yong; Chen, Jia-Xu; Hattendorf, Jan; Zhou, Hui; Zhou, Xiao-Nong

2011-01-01

Background The control of soil-transmitted helminth (STH) infections currently relies on the large-scale administration of single-dose oral albendazole or mebendazole. However, these treatment regimens have limited efficacy against hookworm and Trichuris trichiura in terms of cure rates (CR), whereas fecal egg reduction rates (ERR) are generally high for all common STH species. We compared the efficacy of single-dose versus triple-dose treatment against hookworm and other STHs in a community-based randomized controlled trial in the People's Republic of China. Methodology/Principal findings The hookworm CR and fecal ERR were assessed in 314 individuals aged ≥5 years who submitted two stool samples before and 3–4 weeks after administration of single-dose oral albendazole (400 mg) or mebendazole (500 mg) or triple-dose albendazole (3×400 mg over 3 consecutive days) or mebendazole (3×500 mg over 3 consecutive days). Efficacy against T. trichiura, Ascaris lumbricoides, and Taenia spp. was also assessed. Albendazole cured significantly more hookworm infections than mebendazole in both treatment regimens (single dose: respective CRs 69% (95% confidence interval [CI]: 55–81%) and 29% (95% CI: 20–45%); triple dose: respective CRs 92% (95% CI: 81–98%) and 54% (95% CI: 46–71%)). ERRs followed the same pattern (single dose: 97% versus 84%; triple dose: 99.7% versus 96%). Triple-dose regimens outperformed single doses against T. trichiura; three doses of mebendazole – the most efficacious treatment tested – cured 71% (95% CI: 57–82%). Both single and triple doses of either drug were highly efficacious against A. lumbricoides (CR: 93–97%; ERR: all >99.9%). Triple dose regimens cured all Taenia spp. infections, whereas single dose applications cured only half of them. Conclusions/Significance Single-dose oral albendazole is more efficacious against hookworm than mebendazole. To achieve high CRs against both hookworm and T. trichiura, triple-dose regimens are warranted. Trial Registration www.controlled-trials.com ISRCTN47375023 PMID:21980373

SU-E-T-538: Evaluation of IMRT Dose Calculation Based on Pencil-Beam and AAA Algorithms.

PubMed

Yuan, Y; Duan, J; Popple, R; Brezovich, I

2012-06-01

To evaluate the accuracy of dose calculation for intensity modulated radiation therapy (IMRT) based on Pencil Beam (PB) and Analytical Anisotropic Algorithm (AAA) computation algorithms. IMRT plans of twelve patients with different treatment sites, including head/neck, lung and pelvis, were investigated. For each patient, dose calculation with PB and AAA algorithms using dose grid sizes of 0.5 mm, 0.25 mm, and 0.125 mm, were compared with composite-beam ion chamber and film measurements in patient specific QA. Discrepancies between the calculation and the measurement were evaluated by percentage error for ion chamber dose and γ〉l failure rate in gamma analysis (3%/3mm) for film dosimetry. For 9 patients, ion chamber dose calculated with AAA-algorithms is closer to ion chamber measurement than that calculated with PB algorithm with grid size of 2.5 mm, though all calculated ion chamber doses are within 3% of the measurements. For head/neck patients and other patients with large treatment volumes, γ〉l failure rate is significantly reduced (within 5%) with AAA-based treatment planning compared to generally more than 10% with PB-based treatment planning (grid size=2.5 mm). For lung and brain cancer patients with medium and small treatment volumes, γ〉l failure rates are typically within 5% for both AAA and PB-based treatment planning (grid size=2.5 mm). For both PB and AAA-based treatment planning, improvements of dose calculation accuracy with finer dose grids were observed in film dosimetry of 11 patients and in ion chamber measurements for 3 patients. AAA-based treatment planning provides more accurate dose calculation for head/neck patients and other patients with large treatment volumes. Compared with film dosimetry, a γ〉l failure rate within 5% can be achieved for AAA-based treatment planning. © 2012 American Association of Physicists in Medicine.

WE-EF-BRA-06: Feasibility of Spatially Modulated Proton Beams for Small Animal Research

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, E; Meyer, J

Purpose: To investigate the feasibility of proton minibeam radiotherapy (pMBRT) for small animal research. The motivation is to explore with protons the extraordinary normal tissue sparing effects to spatially modulated beams as observed on high flux synchrotron beam lines. We hypothesized that we can design a multi-slit collimator for our proton beam line to produce planar-parallel dose profiles with high modulation in the entrance region and homogenous dose coverage in the overlap of the Bragg peaks. Methods: The high dose rate 50 MeV research proton beamline at the University of Washington was modeled using the TOol for PArticle Simulation (TOPAS)more » Monte Carlo package. A brass collimator was implemented to generate proton minibeams. The collimator consists of an array of 2 cm long slits to cover an area of 2×2 cm{sup 2}. The slit widths (0.1–1 mm), center-to-center (ctc) distances (1–3 mm) and collimator thickness (1–7 cm) were varied to evaluate the effect on dose rate, the peak-to-valley dose ratios (PVDR) and the change of penumbra and peak width (FWHM) with depth. Results: The Bragg peak was at a depth of ∼21 mm. The penumbra and FWHM remained relatively constant to a depth of about 10–15 mm. The PVDR ranged from 1.6 to 26 and the dose rate dropped exponentially with collimator thickness. A uniform dose can be achieved at depth with slightly compromised PVDRs and dose rate. Conclusion: The technical realization of pMBRT is feasible. The simulations have shown that it is possible to obtain uniform dose at depth while modulation is maintained on the entrance side. While the simulated beam widths are larger than on synchrotron generated microbeams the dosimetric advantage could avoid having to interlace two microbeams to achieve uniform dose in the target. The next steps are to build a collimator and verify the simulations experimentally.« less

Fiber-Coupled, Time-Gated { {Al}}_{2}{ {O}}_{3} : { {C}} Radioluminescence Dosimetry Technique and Algorithm for Radiation Therapy With LINACs

NASA Astrophysics Data System (ADS)

Magne, Sylvain; Deloule, Sybelle; Ostrowsky, Aimé; Ferdinand, Pierre

2013-08-01

An original algorithm for real-time In Vivo Dosimetry (IVD) based on Radioluminescence (RL) of dosimetric-grade Al2O3:C crystals is described and demonstrated in reference conditions with 12-MV photon beams from a Saturne 43 linear accelerator (LINAC), simulating External Beam Radiation Therapy (EBRT) treatments. During the course of irradiation, a portion of electrons is trapped within the Al2O3:C crystal while another portion recombines and generates RL, recorded on-line using an optical fiber. The RL sensitivity is dose-dependent and increases in accordance with the concentration of trapped electrons. Once irradiation is completed, the Al2O3:C crystal is reset by laser light (reusable) and the resultant OSL (Optically Stimulated Luminescence) is also collected back by the remote RL-OSL reader and finally integrated to yield the absorbed dose. During irradiation, scintillation and Cerenkov lights generated within the optical fiber (“stem effect”) are removed by a time-discrimination method involving a discriminating unit and a fiber-coupled BGO scintillator placed in the irradiation room, next to the LINAC. The RL signals were then calibrated with respect to reference dose and dose rate data using an ionization chamber (IC). The algorithm relies upon the integral of the RL and provides the accumulated dose (useful to the medical physicist) at any time during irradiation, the dose rate being derived afterwards. It is tested with both step and arbitrary dose rate profiles, manually operated from the LINAC control desk. The doses measured by RL and OSL are both compared to reference doses and deviations are about ±2% and ±1% respectively, thus demonstrating the reliability of the algorithm for arbitrary profiles and wide range of dose rates. Although the calculation was done off-line, it is amenable to real-time processing during irradiation.

Increased Radioresistance to Lethal Doses of Gamma Rays in Mice and Rats after Exposure to Microwave Radiation Emitted by a GSM Mobile Phone Simulator

PubMed Central

Mortazavi, SMJ; Mosleh-Shirazi, MA; Tavassoli, AR; Taheri, M; Mehdizadeh, AR; Namazi, SAS; Jamali, A; Ghalandari, R; Bonyadi, S; Haghani, M; Shafie, M

2013-01-01

The aim of this study was to investigate the effect of pre-irradiation with microwaves on the induction of radioadaptive response. In the 1st phase of the study, 110 male mice were divided into 8 groups. The animals in these groups were exposed/sham-exposed to microwave, low dose rate gamma or both for 5 days. On day six, the animals were exposed to a lethal dose (LD). In the 2nd phase, 30 male rats were divided into 2 groups of 15 animals. The 1st group received microwave exposure. The 2nd group (controls) received the same LD but there was no treatment before the LD. On day 5, all animals were whole-body irradiated with the LD. Statistically significant differences between the survival rate of the mice only exposed to lethal dose of gamma radiation before irradiation with a lethal dose of gamma radiation with those of the animals pre-exposed to either microwave (p=0.02), low dose rate gamma (p=0.001) or both of these physical adapting doses (p=0.003) were observed. Likewise, a statistically significant difference between survival rates of the rats in control and test groups was observed. Altogether, these experiments showed that exposure to microwave radiation may induce a significant survival adaptive response. PMID:23930107

Effects of UVB radiation on grazing of two cladocerans from high-altitude Andean lakes

PubMed Central

Rejas, Danny

2017-01-01

Climate change and water extraction may result in increased exposition of the biota to ultraviolet-B radiation (UVB) in high-altitude Andean lakes. Although exposition to lethal doses in these lakes is unlikely, sub-lethal UVB doses may have strong impacts in key compartments such as zooplankton. Here, we aimed at determining the effect of sub-lethal UVB doses on filtration rates of two cladoceran species (Daphnia pulicaria and Ceriodaphnia dubia). We firstly estimated the Incipient Limiting Concentration (ILC) and the Gut Passage Time (GPT) for both species. Thereafter we exposed clones of each species to four increasing UVB doses (treatments): i) DUV-0 (Control), ii) DUV-1 (0.02 MJ m2), iii) DUV-2 (0.03 MJ m2) and iv) DUV-3 (0.15 MJ m2); and estimated their filtration rates using fluorescent micro-spheres. Our results suggest that increasing sub-lethal doses of UVB radiation may strongly disturb the structure and functioning of high-altitude Andean lakes. Filtration rates of D. pulicaria were not affected by the lowest dose applied (DUV-1), but decreased by 50% in treatments DUV-2 and DUV-3. Filtration rates for C. dubia were reduced by more than 80% in treatments DUV-1 and DUV-2 and 100% of mortality occurred at the highest UVB dose applied (DUV-3). PMID:28379975

Optically Stimulated Luminescence Analysis Method for High Dose Rate Using an Optical Fiber Type Dosimeter

NASA Astrophysics Data System (ADS)

Ueno, Katsunori; Tominaga, Kazuo; Tadokoro, Takahiro; Ishizawa, Koji; Takahashi, Yoshinori; Kuwabara, Hitoshi

2016-08-01

The investigation of air dose rates at locations in the Fukushima Dai-ichi Nuclear Power Station is necessary for safe removal of the molten nuclear fuel. The target performance for the investigation is to analyze a dose rate in the range of 10-3 Gy/h to 102 Gy/h with a measurement precision of ±4.0% full scale (F.S.) at a measurement interval of 60 s. In order to achieve this target, the authors proposed an optically stimulated luminescence (OSL) analysis method using prompt OSL for a wide dynamic range of dose rates; the OSL is generated using BaFBr:Eu with a fast decay time constant. The luminescence intensity by prompt OSL was formulated by the electron concentration of the trapping state during gamma ray and stimulation light irradiations. The prototype OSL monitor using BaFBr:Eu was manufactured for investigation of prompt OSL and evaluation of the measurement precision. The time dependence of the luminescence intensity by prompt OSL was analyzed by irradiating the OSL sensor in a 60Co irradiation facility. The measured dose rates were obtained in a prompt mode and an accumulating mode with a precision of ±3.3% F.S. for the dose rate range of 9.5 ×10-4 Gy/h to 1.2 ×102 Gy/h.

Terrestrial Gamma Radiation Dose Rate of West Sarawak

NASA Astrophysics Data System (ADS)

Izham, A.; Ramli, A. T.; Saridan Wan Hassan, W. M.; Idris, H. N.; Basri, N. A.

2017-10-01

A study of terrestrial gamma radiation (TGR) dose rate was conducted in west of Sarawak, covering Kuching, Samarahan, Serian, Sri Aman, and Betong divisions to construct a baseline TGR dose rate level data of the areas. The total area covered was 20,259.2 km2, where in-situ measurements of TGR dose rate were taken using NaI(Tl) scintillation detector Ludlum 19 micro R meter NaI(Tl) approximately 1 meter above ground level. Twenty-nine soil samples were taken across the 5 divisions covering 26 pairings of 9 geological formations and 7 soil types. A hyperpure Germanium detector was then used to find the samples' 238U, 232Th, and 40K radionuclides concentrations producing a correction factor Cf = 0.544. A total of239 measured data were corrected with Cf resulting in a mean Dm of 47 ± 1 nGy h-1, with a range between 5 nGy h-1 - 103 nGy h-1. A multiple regression analysis was conducted between geological means and soil types means against the corrected TGR dose rate Dm, generating Dg,s= 0.847Dg+ 0.637Ds- 22.313 prediction model with a normalized Beta equation of Dg,s= 0.605Dg+ 0.395Ds. The model has an 84.6% acceptance of Whitney- Mann test null hypothesis when tested against the corrected TGR dose rates.

Dose rate estimation around a 60Co gamma-ray irradiation source by means of 115mIn photoactivation.

PubMed

Murataka, Ayanori; Endo, Satoru; Kojima, Yasuaki; Shizuma, Kiyoshi

2010-01-01

Photoactivation of nuclear isomer (115m)In with a halflife of 4.48 h occurs by (60)Co gamma-ray irradiation. This is because the resonance gamma-ray absorption occurs at 1078 keV level for stable (115)In, and that energy gamma-rays are produced by Compton scattering of (60)Co primary gamma-rays. In this work, photoactivation of (115m)In was applied to estimate the dose rate distribution around a (60)Co irradiation source utilizing a standard dose rate taken by alanine dosimeter. The (115m)In photoactivation was measured at 10 to 160 cm from the (60)Co source. The derived dose rate distribution shows a good agreement with both alanine dosimeter data and Monte Carlo simulation. It is found that angular distribution of the dose rate along a circumference at radius 2.8 cm from the central axis shows +/- 10% periodical variation reflecting the radioactive strength of the source rods, but less periodic distribution at radius 10 and 20 cm. The (115m)In photoactivation along the vertical direction in the central irradiation port strongly depends on the height and radius as indicated by Monte Carlo simulation. It is demonstrated that (115m)In photoactivation is a convenient method to estimate the dose rate distribution around a (60)Co source.

The Study of External Dose Rate and Retained Body Activity of Patients Receiving 131I Therapy for Differentiated Thyroid Carcinoma

PubMed Central

Zhang, Haiying; Jiao, Ling; Cui, Songye; Wang, Liang; Tan, Jian; Zhang, Guizhi; He, Yajing; Ruan, Shuzhou; Fan, Saijun; Zhang, Wenyi

2014-01-01

Radiation safety is an integral part of targeted radionuclide therapy. The aim of this work was to study the external dose rate and retained body activity as functions of time in differentiated thyroid carcinoma patients receiving 131I therapy. Seventy patients were stratified into two groups: the ablation group (A) and the follow-up group (FU). The patients’ external dose rate was measured, and simultaneously, their retained body radiation activity was monitored at various time points. The equations of the external dose rate and the retained body activity, described as a function of hours post administration, were fitted. Additionally, the release time for patients was calculated. The reduction in activity in the group receiving a second or subsequent treatment was more rapid than the group receiving only the initial treatment. Most important, an expeditious method was established to indirectly evaluate the retained body activity of patients by measuring the external dose rate with a portable radiation survey meter. By this method, the calculated external dose rate limits are 19.2, 8.85, 5.08 and 2.32 μSv·h−1 at 1, 1.5, 2 and 3 m, respectively, according to a patient’s released threshold level of retained body activity <400 MBq. This study is beneficial for radiation safety decision-making. PMID:25337944

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harrison, F.L.; Rice, D.W. Jr.

The usefulness of sister chromatid exchange (SCE) induction as a measure of low-level radiation effect was examined in a benthic marine worm, Neanthes arenaceodentata. Larvae were exposed to /sup 60/Co radiation for 12 to 24 h at total doses ranging from 0.5 to 309 R and at dose rates from 0.04 to 13 R/h. Animals exposed at intermediate dose rates (0.5, 0.6, 1.25, 2.0, and 2.5 R/h) had SCE frequencies per chromosome about twice that of those receiving no radiation (controls), whereas those exposed at the higher dose rates (7.0 and 13 R/h) had SCE frequencies lower than the controls.more » Animals exposed at the lower dose rates (0.04 and 0.1 R/h) had lower SCE frequencies than those exposed at intermediate dose rates (and higher SCE frequencies than controls). The length of chromosome pair number one differed among metaphase spreads and was used as an index of chromosome condensation in a given metaphase. Because there is a possibility that chromosome morphology may affect the ability to resolve SCEs, morphology will be monitored in future studies. A preliminary experiment was performed to assess the effects of 2.2 and 11.5 R/h for 24 h on growth and development. Larvae observed at 6 and 17 d after irradiation did not have significantly different numbers of abnormal larvae or survival rates.« less

Blockade of hyperpolarizing currents produces a dose-dependent effect on heart rate.

PubMed

Ziyatdinova, N I; Giniatullin, R A; Svyatova, N V; Zefirov, T L

2001-03-01

Intravenous injection of ZD 7288, a new specific hyperpolarizing current blocker, dose-dependently reduces heart rate in adult rats. The autonomic nervous system modulates changes in heart rate caused by hyperpolarizing currents.

The effect of radiation on the anaerobic corrosion of steel

NASA Astrophysics Data System (ADS)

Smart, N. R.; Rance, A. P.; Werme, L. O.

2008-09-01

To ensure the safe encapsulation of spent nuclear fuel elements for geological disposal, SKB of Sweden are considering using a canister, which consists of an outer copper canister and a cast iron insert. Previous work has investigated the rate of gas generation due to the anaerobic corrosion of ferrous materials over a range of conditions. This paper examines the effect of radiation on the corrosion of steel in repository environments. Tests were carried out at two temperatures (30 °C and 50 °C), two dose rates (11 Gray h -1 and 300 Gray h -1) and in two different artificial groundwaters, for exposure periods of several months. Radiation was found to enhance the corrosion rate at both dose rates but the greatest enhancement occurred at the higher dose rate. The corrosion products were predominantly magnetite, with some indications of unidentified higher oxidation state corrosion products being formed at the higher dose rates.

Improved neutron activation prediction code system development

NASA Technical Reports Server (NTRS)

Saqui, R. M.

1971-01-01

Two integrated neutron activation prediction code systems have been developed by modifying and integrating existing computer programs to perform the necessary computations to determine neutron induced activation gamma ray doses and dose rates in complex geometries. Each of the two systems is comprised of three computational modules. The first program module computes the spatial and energy distribution of the neutron flux from an input source and prepares input data for the second program which performs the reaction rate, decay chain and activation gamma source calculations. A third module then accepts input prepared by the second program to compute the cumulative gamma doses and/or dose rates at specified detector locations in complex, three-dimensional geometries.

Evidence for formation of DNA repair centers and dose-response nonlinearity in human cells

PubMed Central

Neumaier, Teresa; Swenson, Joel; Pham, Christopher; Polyzos, Aris; Lo, Alvin T.; Yang, PoAn; Dyball, Jane; Asaithamby, Aroumougame; Chen, David J.; Bissell, Mina J.; Thalhammer, Stefan; Costes, Sylvain V.

2012-01-01

The concept of DNA “repair centers” and the meaning of radiation-induced foci (RIF) in human cells have remained controversial. RIFs are characterized by the local recruitment of DNA damage sensing proteins such as p53 binding protein (53BP1). Here, we provide strong evidence for the existence of repair centers. We used live imaging and mathematical fitting of RIF kinetics to show that RIF induction rate increases with increasing radiation dose, whereas the rate at which RIFs disappear decreases. We show that multiple DNA double-strand breaks (DSBs) 1 to 2 μm apart can rapidly cluster into repair centers. Correcting mathematically for the dose dependence of induction/resolution rates, we observe an absolute RIF yield that is surprisingly much smaller at higher doses: 15 RIF/Gy after 2 Gy exposure compared to approximately 64 RIF/Gy after 0.1 Gy. Cumulative RIF counts from time lapse of 53BP1-GFP in human breast cells confirmed these results. The standard model currently in use applies a linear scale, extrapolating cancer risk from high doses to low doses of ionizing radiation. However, our discovery of DSB clustering over such large distances casts considerable doubts on the general assumption that risk to ionizing radiation is proportional to dose, and instead provides a mechanism that could more accurately address risk dose dependency of ionizing radiation. PMID:22184222

The importance of applicator design for intraluminal brachytherapy of rectal cancer.

PubMed

Hansen, Johnny Witterseh; Jakobsen, Anders

2006-09-01

An important aspect of designing an applicator for radiation treatment of rectal cancer is the ability to minimize dose to the mucosa and noninvolved parts of the rectum wall. For this reason we investigated a construction of a flexible multichannel applicator with several channels placed along the periphery of a cylinder and a construction of a rigid cylinder with a central channel and interchangeable shields. Calculations of the dose gradient, dose homogeneity in the tumor, and shielding ability were performed for the two applicators in question. Furthermore, the influence on dose distribution around a flexible multichannel applicator from an unintended off-axis positioning of the source inside a bent channel was investigated by film measurements on a single bent catheter. Calculations showed that a single-channel applicator with interchangeable shields yields a higher degree of shielding and has a better dose homogeneity in the tumor volume than that of a multi-channel applicator. A single-channel applicator with interchangeable shields was manufactured, and the influence of different size of shield angle on dose rate in front of and behind the shields was measured. While dose rate in front of the shield and shielding ability are closely independent of the size of the shield angle when measured 1 cm from the applicator surface, dose rate in more distant volumes will to some extent be influenced by shield angle due to volume scatter conditions.

The importance of applicator design for intraluminal brachytherapy of rectal cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hansen, Johnny Witterseh; Jakobsen, Anders; Department of Oncology, Hospital of Vejle, DK-7100 Vejle

2006-09-15

An important aspect of designing an applicator for radiation treatment of rectal cancer is the ability to minimize dose to the mucosa and noninvolved parts of the rectum wall. For this reason we investigated a construction of a flexible multichannel applicator with several channels placed along the periphery of a cylinder and a construction of a rigid cylinder with a central channel and interchangeable shields. Calculations of the dose gradient, dose homogeneity in the tumor, and shielding ability were performed for the two applicators in question. Furthermore, the influence on dose distribution around a flexible multichannel applicator from an unintendedmore » off-axis positioning of the source inside a bent channel was investigated by film measurements on a single bent catheter. Calculations showed that a single-channel applicator with interchangeable shields yields a higher degree of shielding and has a better dose homogeneity in the tumor volume than that of a multichannel applicator. A single-channel applicator with interchangeable shields was manufactured, and the influence of different size of shield angle on dose rate in front of and behind the shields was measured. While dose rate in front of the shield and shielding ability are closely independent of the size of the shield angle when measured 1 cm from the applicator surface, dose rate in more distant volumes will to some extent be influenced by shield angle due to volume scatter conditions.« less

Reducing the dose of smallpox vaccine reduces vaccine-associated morbidity without reducing vaccination success rates or immune responses.

PubMed

Couch, Robert B; Winokur, Patricia; Edwards, Kathryn M; Black, Steven; Atmar, Robert L; Stapleton, Jack T; Kissner, Jennifer M; Shinefield, Henry; Denny, Thomas N; Bybel, Michael J; Newman, Frances K; Yan, Lihan

2007-03-15

When the decision was made to prepare for a deliberate release of smallpox, the United States had approximately 15 million doses of Wyeth Dryvax vaccine, which was known to induce significant morbidity when used undiluted; Sanofi Pasteur, Inc., later identified approximately 85 million additional doses in storage. Eleven vaccine-dose groups, each with 30 vaccinia-naive subjects, were given diluted Dryvax vaccine or 1 of 2 lots of Sanofi Pasteur smallpox vaccine and were evaluated for vaccination success rates, morbidity, and immune responses. Estimated doses of 10(6.6)-10(8.2) pfu of virus/mL induced major reactions (or "takes") in 93%-100% of subjects in each dose group. No differences in vaccination take rates, lesion size, erythema, and induration or in serum neutralizing-antibody response were detected between the groups. However, systemic reactogenicity and missed activities were significantly lower for the vaccine groups given doses of 10(6.6)-10(7.2) pfu/mL than for those given doses of 10(7.6)-10(8.2) pfu/mL. These findings support the use of a higher dilution of Wyeth Dryvax vaccine and Sanofi Pasteur smallpox vaccine, given that the resulting morbidity should be significantly lower without loss of vaccine effectiveness. A plan for use of higher dilutions would create an enormous stockpile of vaccine.

Success rates of single-dose methotrexate and additional dose requirements among women with first and previous ectopic pregnancies.

PubMed

Cirik, Derya Akdag; Kinay, Tugba; Keskin, Ugur; Ozden, Eda; Altay, Metin; Gelisen, Orhan

2016-04-01

To compare the success of the single-dose methotrexate regimen and the requirement for a second or third dose of methotrexate between women with their first ectopic pregnancy (EP) and those with previous EP. In a retrospective cohort study, data were analyzed from women treated for EP by single-dose methotrexate at a Turkish tertiary referral center between January 2010 and December 2013. Data were compared between women with at least one previous EP and those with their first EP. The success rate of the protocol in the first and previous EP groups was similar: 93.0% (320/344) and 87.3% (48/55), respectively. History of previous EP was not a predictor of treatment failure. However, the requirement for additional methotrexate doses was significantly higher in the previous EP group (16/48 [33.4%]) than in the first EP group (55/320 [17.2%]; P=0.03). Multivariate analysis showed that history of tubal surgery (P=0.006) and initial levels of the β-subunit of human chorionic gonadotropin (P=0.001) were significant predictors of treatment failure. Although the single-dose regimen had similar success rates in the previous EP and first EP groups, additional doses of methotrexate were more frequently required in the previous EP group. Copyright © 2015 International Federation of Gynecology and Obstetrics. Published by Elsevier Ireland Ltd. All rights reserved.

Effects of an injectable trace mineral supplement on first-service conception rate of dairy cows.

PubMed

Vanegas, J A; Reynolds, J; Atwill, E R

2004-11-01

A total of 825 dairy cows from a commercial dairy farm in central California were used to evaluate effects of one or 2 doses of an injectable trace mineral supplement containing 20 mg/mL of zinc, 20 mg/mL of manganese, 5 mg/mL of selenium, and 10 mg/mL of copper on first-service conception rate. Cows were randomly allocated into treatment or control group to either a single dose (experiment 1) or a double dose (experiment 2) of injected supplement. Allocation was based on days in lactation for experiment 1 and the length of gestation periods for experiment 2. In experiment 1, cows 38 to 45 d in lactation (n = 190) received a single dose of 5 mL of injected supplement. Similar cows were used as controls (n = 227). In experiment 2, cows and pregnant heifers received an initial injection of 5 mL of the mineral supplement from 2 to 3 wk precalving (n = 186). An equal dose was repeated 38 to 45 d in lactation. A similar group of cows and pregnant heifers served as controls for experiment 2 (n = 222). Health and reproductive events postcalving were recorded. In experiment 1, the odds of first-service conception were not significantly different for cows receiving a one-dose regimen of minerals compared with untreated control cows; conception rates were 26.8 and 27.5% for experiment 1 treatment and control groups, respectively. In experiment 1, the odds of first-service conception were significantly lower (odds ratio = 0.66) for cows and heifers given the 2-dose regimen of minerals compared with untreated controls; overall conception rates were 21.5 and 31.5% for experiment 2 treatment and control groups, respectively. In this intensively managed dairy herd, a single dose of injected trace minerals before breeding had no beneficial effects on first-service conception rate. However, dairy cows receiving a dose of trace minerals before calving and another dose before breeding had lower conception at first service.

Is high–dose rate RapidArc-based radiosurgery dosimetrically advantageous for the treatment of intracranial tumors?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Bo; Yang, Yong, E-mail: yangy2@upmc.edu; Li, Xiang

In linac-based stereotactic radiosurgery (SRS) and radiotherapy (SRT), circular cone(s) or conformal arc(s) are conventionally used to treat intracranial lesions. However, when the target is in close proximity to critical structures, it is frequently quite challenging to generate a quality plan using these techniques. In this study, we investigated the dosimetric characteristics of using high–dose rate RapidArc (RA) technique for radiosurgical treatment of intracranial lesions. A total of 10 intracranial SRS/SRT cases previously planned using dynamic conformal arc (DCA) or cone-based techniques have been included in this study. For each case, 3 treatment plans were generated: (1) a DCA planmore » with multiple noncoplanar arcs, (2) a high–dose rate RA plan with arcs oriented the same as DCA (multiple-arc RA), and 3) a high–dose rate RA plan with a single coplanar arc (single-arc RA). All treatment plans were generated under the same prescription and similar critical structure dose limits. Plan quality for different plans was evaluated by comparing various dosimetric parameters such as target coverage, conformity index (CI), homogeneity index (HI), critical structures, and normal brain tissue doses as well as beam delivery time. With similar critical structure sparing, high–dose rate RA plans can achieve much better target coverage, dose conformity, and dose homogeneity than the DCA plans can. Plan quality indices CI and HI, for the DCA, multiple-arc RA, and single-arc RA techniques, were measured as 1.67 ± 0.39, 1.32 ± 0.28, and 1.38 ± 0.30 and 1.24 ± 0.11, 1.10 ± 0.04, and 1.12 ± 0.07, respectively. Normal brain tissue dose (V{sub 12} {sub Gy}) was found to be similar for DCA and multiple-arc RA plans but much larger for the single-arc RA plans. Beam delivery was similar for DCA and multiple-arc RA plans but shorter with single-arc RA plans. Multiple-arc RA SRS/SRT can provide better treatment plans than conventional DCA plans, especially for complex cases.« less

A Detailed Dosimetric Analysis of Spinal Cord Tolerance in High-Dose Spine Radiosurgery.

PubMed

Katsoulakis, Evangelia; Jackson, Andrew; Cox, Brett; Lovelock, Michael; Yamada, Yoshiya

2017-11-01

Dose-volume tolerance of the spinal cord (SC) in spinal stereotactic radiosurgery (SRS) is difficult to define because radiation myelitis rates are low, and published reports document cases of myelopathy but do not account for the total number of patients treated at given dose-volume combinations who do not have myelitis. This study reports SC toxicity from single-fraction spinal SRS and presents a comprehensive atlas of the incidence of adverse events to examine dose-volume predictors. A prospective database of all patients undergoing single-fraction spinal SRS at our institution between 2004 and 2011 was reviewed. SC toxicity was defined by clinical myelitis with accompanying magnetic resonance imaging (MRI) signal changes that were not attributable to tumor progression. Dose-volume histogram (DVH) atlases were created for these endpoints. Rates of adverse events with 95% confidence limits and probabilities that rates of adverse events were <2% and <5% for myelitis were determined as functions of dose and absolute volume. Information about DVH and myelitis was available for 228 patients treated at 259 sites. The median follow-up time was 14.6 months (range, 0.1-138.3 months). The median prescribed dose to the planning treatment volume was 24 Gy (range, 18-24 Gy). There were 2 cases of radiation myelitis (rate r=0.7%) with accompanying MRI signal changes. Myelitis occurred in 2 patients, with Dmax >13.33 Gy, and minimum doses to the hottest 0.1, 0.2, 0.5, and 1 cc were >10.66, 10.9, and 8 Gy, respectively; however, both myelitis cases occurred below the 34th percentile for Dmax and there were 194 DVHs in total with Dmax >13.33 Gy. A median SC Dmax of 13.85 Gy is safe and supports that a Dmax limit of 14 Gy carries a low <1% rate of myelopathy. No dose-volume thresholds or relationships between SC dose and myelitis were apparent. This is the largest study examining dosimetric data and radiation-induced myelitis in de novo spine SRS. Copyright © 2017 Elsevier Inc. All rights reserved.

Accuracy of micro powder dosing via a vibratory sieve-chute system.

PubMed

Besenhard, M O; Faulhammer, E; Fathollahi, S; Reif, G; Calzolari, V; Biserni, S; Ferrari, A; Lawrence, S M; Llusa, M; Khinast, J G

2015-08-01

This paper describes a powder dosing system with a vibratory sieve mounted on a chute that doses particles into a capsule. Vertical vibration occurred with a broad range of frequencies and amplitudes. During dosing events, the fill weight was accurately recorded via a capacitance sensor, covering the capsules and making it possible to analyze filling characteristics, that is, the fill rates and their robustness. The range of frequencies and amplitudes was screened for settings that facilitated reasonable (no blocking, no spilling) fill rates for three lactose powders. The filling characteristics were studied within this operating space. The results reveal similar operating spaces for all investigated powders. The fill rate robustness varied distinctly in the operating space, which is of prime importance for selecting the settings for continuous feeding applications. In addition, we present accurate dosing studies utilizing the knowledge about the filling characteristics of each powder. Copyright © 2015 Elsevier B.V. All rights reserved.

A consistent two-mutation model of bone cancer for two data sets of radium-injected beagles.

PubMed

Bijwaard, H; Brugmans, M J P; Leenhouts, H P

2002-09-01

A two-mutation carcinogenesis model has been applied to model osteosarcoma incidence in two data sets of beagles injected with 226Ra. Taking age-specific retention into account, the following results have been obtained: (1) a consistent and well-fitting solution for all age and dose groups, (2) mutation rates that are linearly dependent on dose rate, with an exponential decrease for the second mutation at high dose rates, (3) a linear-quadratic dose-effect relationship, which indicates that care should be taken when extrapolating linearly, (4) highest cumulative incidences for injection at young adult age, and highest risks for injection doses of a few kBq kg(-1) at these ages, and (5) when scaled appropriately, the beagle model compares fairly well with a description for radium dial painters, suggesting that a consistent model description of bone cancer induction in beagles and humans may be possible.

Benzodiazepine sensitivity in normal human subjects.

PubMed

Hommer, D W; Matsuo, V; Wolkowitz, O; Chrousos, G; Greenblatt, D J; Weingartner, H; Paul, S M

1986-06-01

Increasing intravenous doses of diazepam or placebo were administered to ten healthy normal volunteers, and the changes in saccadic eye velocity, self-rated sedation and anxiety, and plasma cortisol and growth hormone concentrations were measured. Diazepam administration (4.4 to 140 micrograms/kg, cumulative dose) resulted in a dose-dependent decrease in saccadic eye velocity and plasma cortisol level as well as a dose-dependent increase in self-rated sedation and plasma growth hormone level. Self-rated anxiety was unaffected in these relatively nonanxious subjects. The diazepam-induced changes in saccadic eye velocity, sedation, and growth hormone and cortisol levels were highly correlated with each other and with increasing plasma diazepam concentration. These results are consistent with a benzodiazepine receptor-mediated action of diazepam. The highly quantifiable and dose-dependent decrease in saccadic eye velocity by benzodiazepines should make this a useful measure of benzodiazepine receptor sensitivity in humans.

Investigation of pulsed IMRT and VMAT for re-irradiation treatments: dosimetric and delivery feasibilities

NASA Astrophysics Data System (ADS)

Lin, Mu-Han; Price, Robert A., Jr.; Li, Jinsheng; Kang, Shengwei; Li, Jie; Ma, C.-M.

2013-11-01

Many tumor cells demonstrate hyperradiosensitivity at doses below ˜50 cGy. Together with the increased normal tissue repair under low dose rate, the pulsed low dose rate radiotherapy (PLDR), which separates a daily fractional dose of 200 cGy into 10 pulses with 3 min interval between pulses (˜20 cGy/pulse and effective dose rate 6.7 cGy min-1), potentially reduces late normal tissue toxicity while still providing significant tumor control for re-irradiation treatments. This work investigates the dosimetric and technical feasibilities of intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT)-based PLDR treatments using Varian Linacs. Twenty one cases (12 real re-irradiation cases) including treatment sites of pancreas, prostate, pelvis, lung, head-and-neck, and breast were recruited for this study. The lowest machine operation dose rate (100 MU min-1) was employed in the plan delivery. Ten-field step-and-shoot IMRT and dual-arc VMAT plans were generated using the Eclipse TPS with routine planning strategies. The dual-arc plans were delivered five times to achieve a 200 cGy daily dose (˜20 cGy arc-1). The resulting plan quality was evaluated according to the heterogeneity and conformity indexes (HI and CI) of the planning target volume (PTV). The dosimetric feasibility of retaining the hyperradiosensitivity for PLDR was assessed based on the minimum and maximum dose in the target volume from each pulse. The delivery accuracy of VMAT and IMRT at the 100 MU min-1 machine operation dose rate was verified using a 2D diode array and ion chamber measurements. The delivery reproducibility was further investigated by analyzing the Dynalog files of repeated deliveries. A comparable plan quality was achieved by the IMRT (CI 1.10-1.38 HI 1.04-1.10) and the VMAT (CI 1.08-1.26 HI 1.05-1.10) techniques. The minimum/maximum PTV dose per pulse is 7.9 ± 5.1 cGy/33.7 ± 6.9 cGy for the IMRT and 12.3 ± 4.1 cGy/29.2 ± 4.7 cGy for the VMAT. Six out of the 186 IMRT pulses (fields) were found to exceed 50 cGy maximum PTV dose per pulse while the maximum PTV dose per pulse was within 40 cGy for all the VMAT pulses (arcs). However, for VMAT plans, the dosimetric quality of the entire treatment plan was less superior for the breast cases and large irregular targets. The gamma passing rates for both techniques at the 100 MU min-1 dose rate were at least 94.1% (3%/3 mm) and the point dose measurements agreed with the planned values to within 2.2%. The average root mean square error of the leaf position was 0.93 ± 0.83 mm for IMRT and 0.53 ± 0.48 mm for VMAT based on the Dynalog file analysis. The RMS error of the leaf position was nearly identical for the repeated deliveries of the same plans. In general, both techniques are feasible for PLDR treatments. VMAT was more advantageous for PLDR with more uniform target dose per pulse, especially for centrally located tumors. However, for large, irregular and/or peripheral tumors, IMRT could produce more favorable PLDR plans. By taking the biological benefit of PLDR delivery and the dosimetric benefit of IMRT and VMAT, the proposed methods have a great potential for those previously-irradiated recurrent patients.

Dose properties of a laser accelerated electron beam and prospects for clinical application.

PubMed

Kainz, K K; Hogstrom, K R; Antolak, J A; Almond, P R; Bloch, C D; Chiu, C; Fomytskyi, M; Raischel, F; Downer, M; Tajima, T

2004-07-01

Laser wakefield acceleration (LWFA) technology has evolved to where it should be evaluated for its potential as a future competitor to existing technology that produces electron and x-ray beams. The purpose of the present work is to investigate the dosimetric properties of an electron beam that should be achievable using existing LWFA technology, and to document the necessary improvements to make radiotherapy application for LWFA viable. This paper first qualitatively reviews the fundamental principles of LWFA and describes a potential design for a 30 cm accelerator chamber containing a gas target. Electron beam energy spectra, upon which our dose calculations are based, were obtained from a uniform energy distribution and from two-dimensional particle-in-cell (2D PIC) simulations. The 2D PIC simulation parameters are consistent with those reported by a previous LWFA experiment. According to the 2D PIC simulations, only approximately 0.3% of the LWFA electrons are emitted with an energy greater than 1 MeV. We studied only the high-energy electrons to determine their potential for clinical electron beams of central energy from 9 to 21 MeV. Each electron beam was broadened and flattened by designing a dual scattering foil system to produce a uniform beam (103%>off-axis ratio>95%) over a 25 x 25 cm2 field. An energy window (deltaE) ranging from 0.5 to 6.5 MeV was selected to study central-axis depth dose, beam flatness, and dose rate. Dose was calculated in water at a 100 cm source-to-surface distance using the EGS/BEAM Monte Carlo algorithm. Calculations showed that the beam flatness was fairly insensitive to deltaE. However, since the falloff of the depth-dose curve (R10-R90) and the dose rate both increase with deltaE, a tradeoff between minimizing (R10-R90) and maximizing dose rate is implied. If deltaE is constrained so that R10-R90 is within 0.5 cm of its value for a monoenergetic beam, the maximum practical dose rate based on 2D PIC is approximately 0.1 Gy min(-1) for a 9 MeV beam and 0.03 Gy min(-1) for a 15 MeV beam. It was concluded that current LWFA technology should allow a table-top terawatt (T3) laser to produce therapeutic electron beams that have acceptable flatness, penetration, and falloff of depth dose; however, the dose rate is still 1%-3% of that which would be acceptable, especially for higher-energy electron beams. Further progress in laser technology, e.g., increasing the pulse repetition rate or number of high energy electrons generated per pulse, is necessary to give dose rates acceptable for electron beams. Future measurements confirming dosimetric calculations are required to substantiate our results. In addition to achieving adequate dose rate, significant engineering developments are needed for this technology to compete with current electron acceleration technology. Also, the functional benefits of LWFA electron beams require further study and evaluation.

Commissioning and quality assurance for VMAT delivery systems: An efficient time-resolved system using real-time EPID imaging.

PubMed

Zwan, Benjamin J; Barnes, Michael P; Hindmarsh, Jonathan; Lim, Seng B; Lovelock, Dale M; Fuangrod, Todsaporn; O'Connor, Daryl J; Keall, Paul J; Greer, Peter B

2017-08-01

An ideal commissioning and quality assurance (QA) program for Volumetric Modulated Arc Therapy (VMAT) delivery systems should assess the performance of each individual dynamic component as a function of gantry angle. Procedures within such a program should also be time-efficient, independent of the delivery system and be sensitive to all types of errors. The purpose of this work is to develop a system for automated time-resolved commissioning and QA of VMAT control systems which meets these criteria. The procedures developed within this work rely solely on images obtained, using an electronic portal imaging device (EPID) without the presence of a phantom. During the delivery of specially designed VMAT test plans, EPID frames were acquired at 9.5 Hz, using a frame grabber. The set of test plans was developed to individually assess the performance of the dose delivery and multileaf collimator (MLC) control systems under varying levels of delivery complexities. An in-house software tool was developed to automatically extract features from the EPID images and evaluate the following characteristics as a function of gantry angle: dose delivery accuracy, dose rate constancy, beam profile constancy, gantry speed constancy, dynamic MLC positioning accuracy, MLC speed and acceleration constancy, and synchronization between gantry angle, MLC positioning and dose rate. Machine log files were also acquired during each delivery and subsequently compared to information extracted from EPID image frames. The largest difference between measured and planned dose at any gantry angle was 0.8% which correlated with rapid changes in dose rate and gantry speed. For all other test plans, the dose delivered was within 0.25% of the planned dose for all gantry angles. Profile constancy was not found to vary with gantry angle for tests where gantry speed and dose rate were constant, however, for tests with varying dose rate and gantry speed, segments with lower dose rate and higher gantry speed exhibited less profile stability. MLC positional accuracy was not observed to be dependent on the degree of interdigitation. MLC speed was measured for each individual leaf and slower leaf speeds were shown to be compensated for by lower dose rates. The test procedures were found to be sensitive to 1 mm systematic MLC errors, 1 mm random MLC errors, 0.4 mm MLC gap errors and synchronization errors between the MLC, dose rate and gantry angle controls systems of 1°. In general, parameters measured by both EPID and log files agreed with the plan, however, a greater average departure from the plan was evidenced by the EPID measurements. QA test plans and analysis methods have been developed to assess the performance of each dynamic component of VMAT deliveries individually and as a function of gantry angle. This methodology relies solely on time-resolved EPID imaging without the presence of a phantom and has been shown to be sensitive to a range of delivery errors. The procedures developed in this work are both comprehensive and time-efficient and can be used for streamlined commissioning and QA of VMAT delivery systems. © 2017 American Association of Physicists in Medicine.

Cost-effectiveness of allopurinol and febuxostat for the management of gout.

PubMed

Jutkowitz, Eric; Choi, Hyon K; Pizzi, Laura T; Kuntz, Karen M

2014-11-04

Gout is the most common inflammatory arthritis in the United States. To evaluate the cost-effectiveness of urate-lowering treatment strategies for the management of gout. Markov model. Published literature and expert opinion. Patients for whom allopurinol or febuxostat is a suitable initial urate-lowering treatment. Lifetime. Health care payer. 5 urate-lowering treatment strategies were evaluated: no treatment; allopurinol- or febuxostat-only therapy; allopurinol-febuxostat sequential therapy; and febuxostat-allopurinol sequential therapy. Two dosing scenarios were investigated: fixed dose (80 mg of febuxostat daily, 0.80 success rate; 300 mg of allopurinol daily, 0.39 success rate) and dose escalation (≤120 mg of febuxostat daily, 0.82 success rate; ≤800 mg of allopurinol daily, 0.78 success rate). Discounted costs, discounted quality-adjusted life-years, and incremental cost-effectiveness ratios. In both dosing scenarios, allopurinol-only therapy was cost-saving. Dose-escalation allopurinol-febuxostat sequential therapy was more costly but more effective than dose-escalation allopurinol therapy, with an incremental cost-effectiveness ratio of $39 400 per quality-adjusted life-year. The relative rankings of treatments did not change. Our results were relatively sensitive to several potential variations of model assumptions; however, the cost-effectiveness ratios of dose escalation with allopurinol-febuxostat sequential therapy remained lower than the willingness-to-pay threshold of $109 000 per quality-adjusted life-year. Long-term outcome data for patients with gout, including medication adherence, are limited. Allopurinol single therapy is cost-saving compared with no treatment. Dose-escalation allopurinol-febuxostat sequential therapy is cost-effective compared with accepted willingness-to-pay thresholds. Agency for Healthcare Research and Quality.

Monte Carlo calculated TG-60 dosimetry parameters for the {beta}{sup -} emitter {sup 153}Sm brachytherapy source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sadeghi, Mahdi; Taghdiri, Fatemeh; Hamed Hosseini, S.

Purpose: The formalism recommended by Task Group 60 (TG-60) of the American Association of Physicists in Medicine (AAPM) is applicable for {beta} sources. Radioactive biocompatible and biodegradable {sup 153}Sm glass seed without encapsulation is a {beta}{sup -} emitter radionuclide with a short half-life and delivers a high dose rate to the tumor in the millimeter range. This study presents the results of Monte Carlo calculations of the dosimetric parameters for the {sup 153}Sm brachytherapy source. Methods: Version 5 of the (MCNP) Monte Carlo radiation transport code was used to calculate two-dimensional dose distributions around the source. The dosimetric parameters ofmore » AAPM TG-60 recommendations including the reference dose rate, the radial dose function, the anisotropy function, and the one-dimensional anisotropy function were obtained. Results: The dose rate value at the reference point was estimated to be 9.21{+-}0.6 cGy h{sup -1} {mu}Ci{sup -1}. Due to the low energy beta emitted from {sup 153}Sm sources, the dose fall-off profile is sharper than the other beta emitter sources. The calculated dosimetric parameters in this study are compared to several beta and photon emitting seeds. Conclusions: The results show the advantage of the {sup 153}Sm source in comparison with the other sources because of the rapid dose fall-off of beta ray and high dose rate at the short distances of the seed. The results would be helpful in the development of the radioactive implants using {sup 153}Sm seeds for the brachytherapy treatment.« less

An algorithm for treatment of patients with hypersensitivity reactions after vaccines.

PubMed

Wood, Robert A; Berger, Melvin; Dreskin, Stephen C; Setse, Rosanna; Engler, Renata J M; Dekker, Cornelia L; Halsey, Neal A

2008-09-01

Concerns about possible allergic reactions to immunizations are raised frequently by both patients/parents and primary care providers. Estimates of true allergic, or immediate hypersensitivity, reactions to routine vaccines range from 1 per 50000 doses for diphtheria-tetanus-pertussis to approximately 1 per 500000 to 1000000 doses for most other vaccines. In a large study from New Zealand, data were collected during a 5-year period on 15 marketed vaccines and revealed an estimated rate of 1 immediate hypersensitivity reaction per 450000 doses of vaccine administered. Another large study, conducted within the Vaccine Safety Datalink, described a range of reaction rates to >7.5 million doses. Depending on the study design and the time after the immunization event, reaction rates varied from 0.65 cases per million doses to 1.53 cases per million doses when additional allergy codes were included. For some vaccines, particularly when allergens such as gelatin are part of the formulation (eg, Japanese encephalitis), higher rates of serious allergic reactions may occur. Although these per-dose estimates suggest that true hypersensitivity reactions are quite rare, the large number of doses that are administered, especially for the commonly used vaccines, makes this a relatively common clinical problem. In this review, we present background information on vaccine hypersensitivity, followed by a detailed algorithm that provides a rational and organized approach for the evaluation and treatment of patients with suspected hypersensitivity. We then include 3 cases of suspected allergic reactions to vaccines that have been referred to the Clinical Immunization Safety Assessment network to demonstrate the practical application of the algorithm.

Feasibility of using two‐dimensional array dosimeter for in vivo dose reconstruction via transit dosimetry

PubMed Central

Li, Jonathan; Samant, Sanjiv

2011-01-01

Two‐dimensional array dosimeters are commonly used to perform pretreatment quality assurance procedures, which makes them highly desirable for measuring transit fluences for in vivo dose reconstruction. The purpose of this study was to determine if an in vivo dose reconstruction via transit dosimetry using a 2D array dosimeter was possible. To test the accuracy of measuring transit dose distribution using a 2D array dosimeter, we evaluated it against the measurements made using ionization chamber and radiochromic film (RCF) profiles for various air gap distances (distance from the exit side of the solid water slabs to the detector distance; 0 cm, 30 cm, 40 cm, 50 cm, and 60 cm) and solid water slab thicknesses (10 cm and 20 cm). The backprojection dose reconstruction algorithm was described and evaluated. The agreement between the ionization chamber and RCF profiles for the transit dose distribution measurements ranged from ‐0.2%~ 4.0% (average 1.79%). Using the backprojection dose reconstruction algorithm, we found that, of the six conformal fields, four had a 100% gamma index passing rate (3%/3 mm gamma index criteria), and two had gamma index passing rates of 99.4% and 99.6%. Of the five IMRT fields, three had a 100% gamma index passing rate, and two had gamma index passing rates of 99.6% and 98.8%. It was found that a 2D array dosimeter could be used for backprojection dose reconstruction for in vivo dosimetry. PACS number: 87.55.N‐

[Immune response to one booster dose of inactivated hepatitis A vaccine in college students].

PubMed

Liao, Z; Feng, X W; Liu, X E; Zhou, Y S; Wen, H R; Peng, S H; Zhang, Y X; Xu, B; Zhuang, H; Chen, H Y

2017-05-10

Objective: To evaluate the safety and immunogenicity of one booster dose of inactivated hepatitis A vaccine in young adults. Methods: The subjects were selected from participants in the clinical trial of immunogenicity of inactivated and attenuated live hepatitis A vaccine in young adults. Eligible subjects were those who had received one dose of inactivated or attenuated hepatitis A vaccine, could be contacted and were sero-negative before primary vaccination. All qualified subjects were immunized with one booster dose of inactivated hepatitis A vaccine. The blood samples were collected before booster dose vaccination and 28 days after the immunization. Anti-HAV antibody titer ≥20 mIU/ml was considered to be sero-protected against hepatitis A virus. Results: The GMCs in the inactivated HAV vaccine group and attenuated live vaccine group before booster dose vaccination were 70.80 mIU/ml and 50.12 mIU/ml, respectively, and the sero-protection rates were 94.7 % and 65.0 % , respectively. After the vaccination of the booster dose, the sero-protection rates in both groups were 100.0 % , and the GMCs were 2 816.09 mIU/ml and 2 654.55 mIU/ml, respectively. Conclusion: The GMCs and sero-protection rates of anti-HAV antibody in young adults declined after three years of the primary vaccination. However, the higher GMC and sero-protection rate were observed in the inactivated vaccine group than in the attenuated live vaccine group. Significant increases of GMC levels were observed in both groups after one booster dose vaccination.

Delivery confirmation of bolus electron conformal therapy combined with intensity modulated x-ray therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kavanaugh, James A.; Hogstrom, Kenneth R.; Fontenot, Jonas P.

2013-02-15

Purpose: The purpose of this study was to demonstrate that a bolus electron conformal therapy (ECT) dose plan and a mixed beam plan, composed of an intensity modulated x-ray therapy (IMXT) dose plan optimized on top of the bolus ECT plan, can be accurately delivered. Methods: Calculated dose distributions were compared with measured dose distributions for parotid and chest wall (CW) bolus ECT and mixed beam plans, each simulated in a cylindrical polystyrene phantom that allowed film dose measurements. Bolus ECT plans were created for both parotid and CW PTVs (planning target volumes) using 20 and 16 MeV beams, respectively,more » whose 90% dose surface conformed to the PTV. Mixed beam plans consisted of an IMXT dose plan optimized on top of the bolus ECT dose plan. The bolus ECT, IMXT, and mixed beam dose distributions were measured using radiographic films in five transverse and one sagittal planes for a total of 36 measurement conditions. Corrections for film dose response, effects of edge-on photon irradiation, and effects of irregular phantom optical properties on the Cerenkov component of the film signal resulted in high precision measurements. Data set consistency was verified by agreement of depth dose at the intersections of the sagittal plane with the five measured transverse planes. For these same depth doses, results for the mixed beam plan agreed with the sum of the individual depth doses for the bolus ECT and IMXT plans. The six mean measured planar dose distributions were compared with those calculated by the treatment planning system for all modalities. Dose agreement was assessed using the 4% dose difference and 0.2 cm distance to agreement. Results: For the combined high-dose region and low-dose region, pass rates for the parotid and CW plans were 98.7% and 96.2%, respectively, for the bolus ECT plans and 97.9% and 97.4%, respectively, for the mixed beam plans. For the high-dose gradient region, pass rates for the parotid and CW plans were 93.1% and 94.62%, respectively, for the bolus ECT plans and 89.2% and 95.1%, respectively, for the mixed beam plans. For all regions, pass rates for the parotid and CW plans were 98.8% and 97.3%, respectively, for the bolus ECT plans and 97.5% and 95.9%, respectively, for the mixed beam plans. For the IMXT component of the mixed beam plans, pass rates for the parotid and CW plans were 93.7% and 95.8%. Conclusions: Bolus ECT and mixed beam therapy dose delivery to the phantom were more accurate than IMXT delivery, adding confidence to the use of planning, fabrication, and delivery for bolus ECT tools either alone or as part of mixed beam therapy. The methodology reported in this work could serve as a basis for future standardization of the commissioning of bolus ECT or mixed beam therapy. When applying this technology to patients, it is recommended that an electron dose algorithm more accurate than the pencil beam algorithm, e.g., a Monte Carlo algorithm or analytical transport such as the pencil beam redefinition algorithm, be used for planning to ensure the desired accuracy.« less

A dual two dimensional electronic portal imaging device transit dosimetry model based on an empirical quadratic formalism

PubMed Central

Metwaly, M; Glegg, M; Baggarley, S P; Elliott, A

2015-01-01

Objective: This study describes a two dimensional electronic portal imaging device (EPID) transit dosimetry model that can predict either: (1) in-phantom exit dose, or (2) EPID transit dose, for treatment verification. Methods: The model was based on a quadratic equation that relates the reduction in intensity to the equivalent path length (EPL) of the attenuator. In this study, two sets of quadratic equation coefficients were derived from calibration dose planes measured with EPID and ionization chamber in water under reference conditions. With two sets of coefficients, EPL can be calculated from either EPID or treatment planning system (TPS) dose planes. Consequently, either the in-phantom exit dose or the EPID transit dose can be predicted from the EPL. The model was tested with two open, five wedge and seven sliding window prostate and head and neck intensity-modulated radiation therapy (IMRT) fields on phantoms. Results were analysed using absolute gamma analysis (3%/3 mm). Results: The open fields gamma pass rates were >96.8% for all comparisons. For wedge and IMRT fields, comparisons between predicted and TPS-computed in-phantom exit dose resulted in mean gamma pass rate of 97.4% (range, 92.3–100%). As for the comparisons between predicted and measured EPID transit dose, the mean gamma pass rate was 97.5% (range, 92.6–100%). Conclusion: An EPID transit dosimetry model that can predict in-phantom exit dose and EPID transit dose was described and proven to be valid. Advances in knowledge: The described model is practical, generic and flexible to encourage widespread implementation of EPID dosimetry for the improvement of patients' safety in radiotherapy. PMID:25969867

Efficacy of albendazole against nematode parasites isolated from a goat farm in Ethiopia: relationship between dose and efficacy in goats.

PubMed

Eguale, Tadesse; Chaka, Hassen; Gizaw, Daniel

2009-10-01

A suspected case of albendazole resistance in a goat farm of Hawassa University was examined using faecal egg count reduction test (FECRT), controlled anthelmintic efficacy test and egg hatch assay (EHA) to verify the development of resistance and/or the need for higher doses of the drug in goats than in sheep. The experiment was conducted in 12 sheep (2 groups: treatment versus control) and 24 goats (4 groups: 3 treatments versus control, n = 6; per group) following artificial infection with infective larvae of Haemonchus contortus and Oesophagostomum columbianum. The first group of sheep and goats were treated orally with albendazole at the dose rate of 3.8 mg/kg body weight (i.e. manufacturer's recommended dose for sheep) while the second group of sheep and the fourth group of goats were left untreated. The second and the third group of goats were treated with albendazole at 5.7 and 7.6 mg/kg respectively. The FECRT showed an efficacy of albendazole in goats to be 65.5, 81.4 and 84.1% at the dose rate of 3.8, 5.7 and 7.6 mg/kg body weight respectively while in sheep it was 62% at the dose rate of 3.8 mg/kg. Increasing the dose to 1.5 the sheep recommended dose induced minor improvement of efficacy in goats; however the efficacy was almost the same at 1.5 and twice the dose recommended for sheep. Worm counts at day 15 post-treatment revealed that H. contortus has developed resistance to albendazole. EHA results also supported these findings. On the other hand, O. columbianum was 100% susceptible at all dose levels tested.

Digital holographic interferometry: a novel optical calorimetry technique for radiation dosimetry.

PubMed

Cavan, Alicia; Meyer, Juergen

2014-02-01

To develop and demonstrate the proof-of-principle of a novel optical calorimetry method to determine radiation absorbed dose in a transparent medium. The calorimetric property of water is measured during irradiation by means of an interferometer, which detects temperature-induced changes in the refractive index that can be mathematically related to absorbed dose. The proposed method uses a technique called digital holographic interferometry (DHI), which comprises an optical laser interferometer setup and consecutive physical reconstruction of the recorded wave fronts by means of the Fresnel transform. This paper describes the conceptual framework and provides the mathematical basis for DHI dosimetry. Dose distributions from a high dose rate Brachytherapy source were measured by a prototype optical setup to demonstrate the feasibility of the approach. The developed DHI dosimeter successfully determined absorbed dose distributions in water in the region adjacent to a high dose rate Brachytherapy source. A temperature change of 0.0381 K across a distance of 6.8 mm near the source was measured, corresponding to a dose of 159.3 Gy. The standard deviation in a typical measurement set was ± 3.45 Gy (corresponding to an uncertainty in the temperature value of ± 8.3 × 10(-4) K). The relative dose fall off was in agreement with treatment planning system modeled data. First results with a prototype optical setup and a Brachytherapy source demonstrate the proof-of-principle of the approach. The prototype achieves high spatial resolution of approximately 3 × 10(-4) m. The general approach is fundamentally independent of the radiation type and energy. The sensitivity range determined indicates that the method is predominantly suitable for high dose rate applications. Further work is required to determine absolute dose in all three dimensions.

Long-term results of high-dose conformal radiotherapy for patients with medically inoperable T1-3N0 non-small-cell lung cancer: is low incidence of regional failure due to incidental nodal irradiation?

PubMed

Chen, Ming; Hayman, James A; Ten Haken, Randall K; Tatro, Daniel; Fernando, Shaneli; Kong, Feng-Ming

2006-01-01

To report the results of high-dose conformal irradiation and examine incidental nodal irradiation and nodal failure in patients with inoperable early-stage non-small-cell lung cancer (NSCLC). This analysis included patients with inoperable CT-staged T1-3N0M0 NSCLC treated on our prospective dose-escalation trial. Patients were treated with radiation alone (total dose, 63-102.9 Gy in 2.1-Gy daily fractions) with a three-dimensional conformal technique without intentional nodal irradiation. Bilateral highest mediastinal and upper/lower paratracheal, prevascular and retrotracheal, sub- and para-aortic, subcarinal, paraesophageal, and ipsilateral hilar regions were delineated individually. Nodal failure and doses of incidental irradiation were studied. The potential median follow-up was 104 months. For patients who completed protocol treatment, median survival was 31 months. The actuarial overall survival rate was 86%, 61%, 43%, and 21% and the cause-specific survival rate was 89%, 70%, 53%, and 35% at 1, 2, 3, and 5 years, respectively. Weight loss (p = 0.008) and radiation dose in Gy (p = 0.013) were significantly associated with overall survival. In only 22% and 13% of patients examined did ipsilateral hilar and paratracheal (and subaortic for left-sided tumor) nodal regions receive a dose of > or = 40 Gy, respectively. Less than 10% of all other nodal regions received a dose of > or = 40 Gy. No patients failed initially at nodal sites. Radiation dose is positively associated with overall survival in patients with medically inoperable T1-3N0 NSCLC, though long-term results remain poor. The nodal failure rate is low and does not seem to be due to high-dose incidental irradiation.

Calculations vs. measurements of remnant dose rates for SNS spent structures

NASA Astrophysics Data System (ADS)

Popova, I. I.; Gallmeier, F. X.; Trotter, S.; Dayton, M.

2018-06-01

Residual dose rate measurements were conducted on target vessel #13 and proton beam window #5 after extraction from their service locations. These measurements were used to verify calculation methods of radionuclide inventory assessment that are typically performed for nuclear waste characterization and transportation of these structures. Neutronics analyses for predicting residual dose rates were carried out using the transport code MCNPX and the transmutation code CINDER90. For transport analyses complex and rigorous geometry model of the structures and their surrounding are applied. The neutronics analyses were carried out using Bertini and CEM high energy physics models for simulating particles interaction. Obtained preliminary calculational results were analysed and compared to the measured dose rates and overall are showing good agreement with in 40% in average.

Benchmark studies of induced radioactivity produced in LHC materials, Part II: Remanent dose rates.

PubMed

Brugger, M; Khater, H; Mayer, S; Prinz, A; Roesler, S; Ulrici, L; Vincke, H

2005-01-01

A new method to estimate remanent dose rates, to be used with the Monte Carlo code FLUKA, was benchmarked against measurements from an experiment that was performed at the CERN-EU high-energy reference field facility. An extensive collection of samples of different materials were placed downstream of, and laterally to, a copper target, intercepting a positively charged mixed hadron beam with a momentum of 120 GeV c(-1). Emphasis was put on the reduction of uncertainties by taking measures such as careful monitoring of the irradiation parameters, using different instruments to measure dose rates, adopting detailed elemental analyses of the irradiated materials and making detailed simulations of the irradiation experiment. The measured and calculated dose rates are in good agreement.

Calculations vs. measurements of remnant dose rates for SNS spent structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Popova, Irina I.; Gallmeier, Franz X.; Trotter, Steven M.

Residual dose rate measurements were conducted on target vessel #13 and proton beam window #5 after extraction from their service locations. These measurements were used to verify calculation methods of radionuclide inventory assessment that are typically performed for nuclear waste characterization and transportation of these structures. Neutronics analyses for predicting residual dose rates were carried out using the transport code MCNPX and the transmutation code CINDER90. For transport analyses complex and rigorous geometry model of the structures and their surrounding are applied. The neutronics analyses were carried out using Bertini and CEM high energy physics models for simulating particles interaction.more » Obtained preliminary calculational results were analysed and compared to the measured dose rates and overall are showing good agreement with in 40% in average.« less

High resolution digital autoradiographic and dosimetric analysis of heterogeneous radioactivity distribution in xenografted prostate tumors.

PubMed

Timmermand, Oskar V; Nilsson, Jenny; Strand, Sven-Erik; Elgqvist, Jörgen

2016-12-01

The first main aim of this study was to illustrate the absorbed dose rate distribution from 177 Lu in sections of xenografted prostate cancer (PCa) tumors using high resolution digital autoradiography (DAR) and compare it with hypothetical identical radioactivity distributions of 90 Y or 7 MeV alpha-particles. Three dosimetry models based on either dose point kernels or Monte Carlo simulations were used and evaluated. The second and overlapping aim, was to perform DAR imaging and dosimetric analysis of the distribution of radioactivity, and hence the absorbed dose rate, in tumor sections at an early time point after injection during radioimmunotherapy using 177 Lu-h11B6, directed against the human kallikrein 2 antigen. Male immunodeficient BALB/c nude mice, aged 6-8 w, were inoculated by subcutaneous injection of ∼10 7 LNCaP cells in a 200 μl suspension of a 1:1 mixture of medium and Matrigel. The antibody h11B6 was conjugated with the chelator CHX-A″-DTPA after which conjugated h11B6 was mixed with 177 LuCl 3 . The incubation was performed at room temperature for 2 h, after which the labeling was terminated and the solution was purified on a NAP-5 column. About 20 MBq 177 Lu-h11B6 was injected intravenously in the tail vein. At approximately 10 h postinjection (hpi), the mice were sacrificed and one tumor was collected from each of the five animals and cryosectioned into 10 μm thick slices. The tumor slices were measured and imaged using the DAR MicroImager system and the M3Vision software. Then the absorbed dose rate was calculated using a dose point kernel generated with the Monte Carlo code gate v7.0. The DAR system produced high resolution images of the radioactivity distribution, close to the resolution of single PCa cells. The DAR images revealed a pronounced heterogeneous radioactivity distribution, i.e., count rate per area, in the tumors, indicated by the normalized intensity variations along cross sections as mean ± SD: 0.15 ± 0.15, 0.20 ± 0.18, 0.12 ± 0.17, 0.15 ± 0.16, and 0.23 ± 0.22, for each tumor section, respectively. The absorbed dose rate distribution for 177 Lu at the time of dissection 10 hpi showed a maximum value of 2.9 ± 0.4 Gy/h (mean ± SD), compared to 6.0 ± 0.9 and 159 ± 25 Gy/h for the hypothetical 90 Y and 7 MeV alpha-particle cases assuming the same count rate densities. Mean absorbed dose rate values were 0.13, 0.53, and 6.43 Gy/h for 177 Lu, 90 Y, and alpha-particles, respectively. The initial uptake of 177 Lu-h11B6 produces a high absorbed dose rate, which is important for a successful therapeutic outcome. The hypothetical 90 Y case indicates a less heterogeneous absorbed dose rate distribution and a higher mean absorbed dose rate compared to 177 Lu, although with a potentially increased irradiation of surrounding healthy tissue. The hypothetical alpha-particle case indicates the possibility of a higher maximum absorbed dose rate, although with a more heterogeneous absorbed dose rate distribution.

Initial experience of ArcCHECK and 3DVH software for RapidArc treatment plan verification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Infusino, Erminia; Mameli, Alessandra, E-mail: e.infusino@unicampus.it; Conti, Roberto

2014-10-01

The purpose of this study was to perform delivery quality assurance with ArcCHECK and 3DVH system (Sun Nuclear, FL) and to evaluate the suitability of this system for volumetric-modulated arc therapy (VMAT) (RapidArc [RA]) verification. This software calculates the delivered dose distributions in patients by perturbing the calculated dose using errors detected in fluence or planar dose measurements. The device is tested to correlate the gamma passing rate (%GP) and the composite dose predicted by 3DVH software. A total of 28 patients with prostate cancer who were treated with RA were analyzed. RA treatments were delivered to a diode arraymore » phantom (ArcCHECK), which was used to create a planned dose perturbation (PDP) file. The 3DVH analysis used the dose differences derived from comparing the measured dose with the treatment planning system (TPS)-calculated doses to perturb the initial TPS-calculated dose. The 3DVH then overlays the resultant dose on the patient's structures using the resultant “PDP” beams. Measured dose distributions were compared with the calculated ones using the gamma index (GI) method by applying the global (Van Dyk) normalization and acceptance criteria, i.e., 3%/3 mm. Paired differences tests were used to estimate statistical significance of the differences between the composite dose calculated using 3DVH and %GP. Also, statistical correlation by means of logistic regression analysis has been analyzed. Dose-volume histogram (DVH) analysis for patient plans revealed small differences between treatment plan calculations and 3DVH results for organ at risk (OAR), whereas planning target volume (PTV) of the measured plan was systematically higher than that predicted by the TPS. The t-test results between the planned and the estimated DVH values showed that mean values were incomparable (p < 0.05). The quality assurance (QA) gamma analysis 3%/3 mm showed that in all cases there were only weak-to-moderate correlations (Pearson r: 0.12 to 0.74). Moreover, clinically relevant differences increased with increasing QA passing rate, indicating that some of the largest dose differences occurred in the cases of high QA passing rates, which may be called “false negatives.” The clinical importance of any disagreement between the measured and the calculated dose is often difficult to interpret; however, beam errors (either in delivery or in TPS calculation) can affect the effectiveness of the patient dose. Further research is needed to determinate the role of a PDP-type algorithm to accurately estimate patient dose effect.« less

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 investigate the sensitivity differences for low and low high doses, we performed chronic low dose-rate irradiation, and have begun studies with ATM and Nibrin inhibitors and siRNA knockout of these proteins. Results support the conclusion that for the endpoint of simple chromosomal aberrations (translocation or dicentrics), the increased radiation sensitivity of AT cells found at high doses (>1 Gy) does not carry over to low doses or doserates, while NBS cells show increased sensitivity for both high and low dose exposures.

MO-F-CAMPUS-I-02: Occupational Conceptus Doses From Fluoroscopically-Guided Interventional Procedures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Damilakis, J; Perisinakis, K; Solomou, G

Purpose: The aim of this method was to provide dosimetric data on conceptus dose for the pregnant employee who participates in fluoroscopically-guided interventional procedures. Methods: Scattered air-kerma dose rates were obtained for 17 fluoroscopic projections involved in interventional procedures. These projections were simulated on an anthropomorphic phantom placed on the examination table supine. The operating theater was divided into two grids relative to the long table sides. Each grid consisted of 33 cells spaced 0.50 m apart. During the simulated exposures, at each cell, scatter air-kerma rate was measured at 110 cm from the floor i.e. at the height ofmore » the waist of the pregnant worker. Air-kerma rates were divided by the dose area product (DAP) rate of each exposure to obtain normalized data. For each projection, measurements were performed for 3 kVp and 3 filtration values i.e. for 9 different x-ray spectra. All measurements were performed by using a modern C-arm angiographic system (Siemens Axiom Artis, Siemens, Germany) and a radiation meter equipped with an ionization chamber. Results: The results consist of 153 iso-dose maps, which show the spatial distribution of DAP-normalized scattered air-kerma doses at the waist level of a pregnant worker. Conceptus dose estimation is possible using air-kerma to embryo/fetal dose conversion coefficients published in a previous study (J Cardiovasc Electrophysiol, Vol. 16, pp. 1–8, July 2005). Using these maps, occupationally exposed pregnant personnel may select a working position for a certain projection that keeps abdominal dose as low as reasonably achievable. Taking into consideration the regulatory conceptus dose limit for occupational exposure, determination of the maximum workload allowed for the pregnant personnel is also possible. Conclusion: Data produced in this work allow for the anticipation of conceptus dose and the determination of the maximum workload for a pregnant worker from any fluoroscopically-guided interventional procedure. This study was supported by the Greek Ministry of Education and Religious Affairs, General Secretariat for Research and Technology, Operational Program ‘Education and Lifelong Learning’, ARISTIA (Research project: CONCERT)« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, X

Purpose: To explore the real-time dose verification method in volumetric modulated arc radiotherapy (VMAT) with a 2D array ion chamber array. Methods: The 2D ion chamber array was fixed on the panel of electronic portal imaging device (EPID). Source-detector distance (SDD)was 140cm. 8mm RW3 solid water was added to the detector panel to achieve maximum readings.The patient plans for esophageal, prostate and liver cancers were selected to deliver on the cylindrical Cheese phantom 5 times in order to validate the reproducibility of doses. Real-time patient transit dose measurements were performed at each fraction. Dose distributions wereevaluated using gamma index criteriamore » of 3mm DTA and 3% dose difference referred to the firsttime Result. Results: The gamma index pass rate in the Cheese phantom were about 98%; The gamma index pass rate for esophageal, liver and prostate cancer patient were about 92%,94%, and 92%, respectively; Gamma pass rate for all single fraction were more than 90%. Conclusion: The 2D array is capable of monitoring the real time transit doses during VMAT delivery. It is helpful to improve the treatment accuracy.« less

Beta- and gamma-dose measurements of the Godiva IV critical assembly.

PubMed

Hankins, D E

1984-03-01

To aid in the re-evaluation of an exposure that occurred in 1963, information was required on the response of film badges to the beta- and gamma-ray doses from a critical assembly. Of particular interest was the beta spectra from the assembly. The techniques used and the results obtained in this study are of interest to health physicists at facilities where exposures to betas occur. The dose rates from the Los Alamos National Laboratory Godiva IV Critical Assembly were measured at numerous distances from the assembly four and 12 days following a burst. Information was obtained on the beta-particle spectra using absorption curve studies. The beta/gamma dose-rate ratio as a function of distance from the assembly was determined. Shielding provided by various metals, gloves and clothing was measured. The beta- and gamma-ray doses measured were compared with a film packet used in the past at the Nevada Test Site with two types of current TLD personnel badges. Measurements made with a commercial thin-window ion chamber instrument are compared with the dose rates obtained using other dosimeters.

Sol-gel derived copper-doped silica glass as a sensitive material for X-ray beam dosimetry

NASA Astrophysics Data System (ADS)

Capoen, Bruno; Hamzaoui, Hicham El; Bouazaoui, Mohamed; Ouerdane, Youcef; Boukenter, Aziz; Girard, Sylvain; Marcandella, Claude; Duhamel, Olivier

2016-01-01

The light emission from a sol-gel-derived Cu-doped silica glass was studied under 10 keV X-ray irradiation using a fibered setup. Both radioluminescence (RL) and optically stimulated luminescence (OSL) were analyzed at different high dose rates up to 50 Gy/s and for different exposure times, yielding accumulated doses up to 50 kGy (in SiO2). Even if a darkening effect appears at this dose level, the material remains X-sensitive after exposure to several kGy. At low dose rate, the scintillation mechanisms are similar to photoluminescence, involving the Cu+ ions electronic levels, contrary to the nonlinear domain (for dose rates higher than 30 Gy/s). This RL, as well as the OSL, could be exploited in their linear domain to measure doses as high as 3 kGy. A thorough study of the OSL signal has shown that it must be employed with caution in order to take the fading phenomenon and the response dependency on stimulation source intensity into consideration.

Acute Hematological Effects in Mice Exposed to the Expected Doses, Dose-rates, and Energies of Solar Particle Event-like Proton Radiation.

PubMed

Sanzari, Jenine K; Cengel, Keith A; Wan, X Steven; Rusek, Adam; Kennedy, Ann R

2014-07-01

NASA has funded several projects that have provided evidence for the radiation risk in space. One radiation concern arises from solar particle event (SPE) radiation, which is composed of energetic electrons, protons, alpha particles and heavier particles. SPEs are unpredictable and the accompanying SPE radiation can place astronauts at risk of blood cell death, contributing to a weakened immune system and increased susceptibility to infection. The doses, dose rates, and energies of the proton radiation expected to occur during a SPE have been simulated at the NASA Space Radiation Laboratory, Brookhaven National Laboratory, delivering total body doses to mice. Hematological values were evaluated at acute time points, up to 24 hrs. post-radiation exposure.

Acute hematological effects in mice exposed to the expected doses, dose-rates, and energies of solar particle event-like proton radiation

NASA Astrophysics Data System (ADS)

Sanzari, Jenine K.; Cengel, Keith A.; Steven Wan, X.; Rusek, Adam; Kennedy, Ann R.

2014-07-01

NASA has funded several projects that have provided evidence for the radiation risk in space. One radiation concern arises from solar particle event (SPE) radiation, which is composed of energetic electrons, protons, alpha particles and heavier particles. SPEs are unpredictable and the accompanying SPE radiation can place astronauts at risk of blood cell death, contributing to a weakened immune system and increased susceptibility to infection. The doses, dose rates, and energies of the proton radiation expected to occur during an SPE have been simulated at the NASA Space Radiation Laboratory, Brookhaven National Laboratory, delivering total body doses to mice. Hematological values were evaluated at acute time points, up to 24 hours post-radiation exposure.

Particle effects on ultraviolet disinfection of coliform bacteria in recycled water.

PubMed

Jolis, D; Lam, C; Pitt, P

2001-01-01

Pilot- and bench-scale coliform inactivation tests with UV irradiation were used to show how suspended solids remaining in filtered secondary effluent affect the efficiency of the UV disinfection process. Observed kinetic inactivation rates decreased with increasing suspended particle sizes of 7 microm or larger present in tertiary effluent. First-order inactivation rates estimated from collimated beam dose-response curves for discrete ranges of UV doses were substantially different, which should caution researchers not to compare inactivation data obtained with largely dissimilar UV doses or suspended particle distributions. A dose of approximately 800 J/m2 was identified as the minimum dose that will consistently meet the California wastewater reclamation coliform criterion when applied to in-line filtration effluent.

Comparison of Immunogenicity Between Inactivated and Live Attenuated Hepatitis A Vaccines Among Young Adults: A 3-Year Follow-up Study.

PubMed

Liu, Xue-en; Chen, Hai-ying; Liao, Zheng; Zhou, Yisheng; Wen, Hairong; Peng, Shihui; Liu, Yan; Li, Rui; Li, Jie; Zhuang, Hui

2015-10-15

A randomized clinical trial of hepatitis A vaccines (1 or 2 doses of inactivated vaccine [Healive] or 1 dose of live attenuated vaccine [Biovac]) was conducted among adults to evaluate seroprotection rates and geometric mean concentrations of antibody against hepatitis A virus for 36 months. High rates of seroprotection persisted for at least 36 months among adults who received 1 or 2 doses of inactivated hepatitis A vaccine but not among adults who received 1 dose of live attenuated hepatitis A vaccine. The long-term serial monitoring of immunogenicity induced by 1 dose of inactivated hepatitis A vaccine is needed to determine an effective alternative to a 2-dose schedule. NCT01865968. © The Author 2015. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Environmental radioactivity in the UK: the airborne geophysical view of dose rate estimates.

PubMed

Beamish, David

2014-12-01

This study considers UK airborne gamma-ray data obtained through a series of high spatial resolution, low altitude surveys over the past decade. The ground concentrations of the naturally occurring radionuclides Potassium, Thorium and Uranium are converted to air absorbed dose rates and these are used to assess terrestrial exposure levels from both natural and technologically enhanced sources. The high resolution airborne information is also assessed alongside existing knowledge from soil sampling and ground-based measurements of exposure levels. The surveys have sampled an extensive number of the UK lithological bedrock formations and the statistical information provides examples of low dose rate lithologies (the formations that characterise much of southern England) to the highest sustained values associated with granitic terrains. The maximum dose rates (e.g. >300 nGy h(-1)) encountered across the sampled granitic terrains are found to vary by a factor of 2. Excluding granitic terrains, the most spatially extensive dose rates (>50 nGy h(-1)) are found in association with the Mercia Mudstone Group (Triassic argillaceous mudstones) of eastern England. Geological associations between high dose rate and high radon values are also noted. Recent studies of the datasets have revealed the extent of source rock (i.e. bedrock) flux attenuation by soil moisture in conjunction with the density and porosity of the temperate latitude soils found in the UK. The presence or absence of soil cover (and associated presence or absence of attenuation) appears to account for a range of localised variations in the exposure levels encountered. The hypothesis is supported by a study of an extensive combined data set of dose rates obtained from soil sampling and by airborne geophysical survey. With no attenuation factors applied, except those intrinsic to the airborne estimates, a bias to high values of between 10 and 15 nGy h(-1) is observed in the soil data. A wide range of technologically enhanced, localised contributions to dose rate values are also apparent in the data sets. Two detailed examples are provided that reveal the detectability of site-scale environmental impacts due to former industrial activities and the high dose values (>500 nGy h(-1)) that are associated with former, small-scale Uranium mining operations. Copyright © 2014. Published by Elsevier Ltd.

Cost-effectiveness of hepatitis A vaccination in Indonesia.

PubMed

Suwantika, Auliya A; Beutels, Philippe; Postma, Maarten J

2014-01-01

This study aims to assess the cost-effectiveness of hepatitis A immunization in Indonesia, including an explicit comparison between one-dose and two-dose vaccines. An age-structured cohort model based on a decision tree was developed for the 2012 Indonesia birth cohort. Using the model, we made a comparison on the use of two-dose and one-dose vaccines. The model involved a 70-year time horizon with 1-month cycles for children less than 2 years old and annually thereafter. Monte Carlo simulations were used to examine the economic acceptability and affordability of the hepatitis A vaccination. Vaccination would save US$ 3,795,148 and US$ 2,892,920 from the societal perspective, for the two-dose and one-dose vaccine schedules, respectively, in the context of hepatitis A treatment. It also would save 8917 and 6614 discounted quality-adjusted-life-years (QALYs), respectively. With the vaccine price of US$ 3.21 per dose, the implementation of single dose vaccine would yield an incremental cost-effectiveness ratio (ICER) of US$ 4933 per QALY gained versus no vaccination, whereas the two-dose versus one-dose schedule would cost US$ 14 568 per QALY gained. Considering the 2012 gross-domestic-product (GDP) per capita in Indonesia of US$ 3557, the results indicate that hepatitis A vaccination would be a cost-effective intervention, both for the two-dose and one-dose vaccine schedules in isolation, but two-dose vaccination would no longer be cost-effective if one-dose vaccination is a feasible option. Vaccination would be 100% affordable at budgets of US$ 71,408 000 and US$ 37,690,000 for the implementation of the two-dose and one-dose vaccine schedules, respectively. The implementation of hepatitis A vaccination in Indonesia would be a cost-effective health intervention under the market vaccine price. Given the budget limitations, the use of a one-dose-vaccine schedule would be more realistic to be applied than a two-dose schedule. The vaccine price, mortality rate and discount rate were the most influential parameters impacting the ICERs.

Cost-effectiveness of hepatitis A vaccination in Indonesia

PubMed Central

Suwantika, Auliya A; Beutels, Philippe; Postma, Maarten J

2014-01-01

Objective This study aims to assess the cost-effectiveness of hepatitis A immunization in Indonesia, including an explicit comparison between one-dose and two-dose vaccines. Methods An age-structured cohort model based on a decision tree was developed for the 2012 Indonesia birth cohort. Using the model, we made a comparison on the use of two-dose and one-dose vaccines. The model involved a 70-year time horizon with 1-month cycles for children less than 2 years old and annually thereafter. Monte Carlo simulations were used to examine the economic acceptability and affordability of the hepatitis A vaccination. Results Vaccination would save US$ 3 795 148 and US$ 2 892 920 from the societal perspective, for the two-dose and one-dose vaccine schedules, respectively, in the context of hepatitis A treatment. It also would save 8917 and 6614 discounted quality-adjusted-life-years (QALYs), respectively. With the vaccine price of US$ 3.21 per dose, the implementation of single dose vaccine would yield an incremental cost-effectiveness ratio (ICER) of US$ 4933 per QALY gained versus no vaccination, whereas the two-dose versus one-dose schedule would cost US$ 14 568 per QALY gained. Considering the 2012 gross-domestic-product (GDP) per capita in Indonesia of US$ 3557, the results indicate that hepatitis A vaccination would be a cost-effective intervention, both for the two-dose and one-dose vaccine schedules in isolation, but two-dose vaccination would no longer be cost-effective if one-dose vaccination is a feasible option. Vaccination would be 100% affordable at budgets of US$ 71 408 000 and US$ 37 690 000 for the implementation of the two-dose and one-dose vaccine schedules, respectively. Conclusions The implementation of hepatitis A vaccination in Indonesia would be a cost-effective health intervention under the market vaccine price. Given the budget limitations, the use of a one-dose-vaccine schedule would be more realistic to be applied than a two-dose schedule. The vaccine price, mortality rate and discount rate were the most influential parameters impacting the ICERs. PMID:25424941

Comparison of filgrastim and pegfilgrastim to prevent neutropenia and maintain dose intensity of adjuvant chemotherapy in patients with breast cancer.

PubMed

Kourlaba, Georgia; Dimopoulos, Meletios A; Pectasides, Dimitrios; Skarlos, Dimosthenis V; Gogas, Helen; Pentheroudakis, George; Koutras, Angelos; Fountzilas, George; Maniadakis, Nikos

2015-07-01

The aim of this study was to compare the effectiveness of prophylactic single fixed dose of pegfilgrastim and daily administration of filgrastim on febrile neutropenia (FN), severe neutropenia, treatment delay, and dose reduction in patients with breast cancer receiving dose-dense adjuvant chemotherapy. A retrospective cohort study with 1058 breast cancer patients matched by age and chemotherapy was conducted. The primary endpoints were FN, severe (grade 3, 4) neutropenia, dose reduction (>10 % reduction of the dose planned), and treatment delay (dose given more than 2 days later). Eighteen episodes of FN (3.4%) in the filgrastim group and 23 (4.3%) in the pegfilgrastim group (p = 0.500) were recorded. More than half of the total episodes (27/41) occurred during the first 4 cycles of treatment. Patients who received filgrastim were almost three times more likely to experience a severe neutropenia episode and were significantly more likely to experience a dose reduction (18.5%) compared to those who received pegfilgrastim (10.8%) (p < 0.001). The percentage of patients, who received their planned dose on time, was significantly lower in patients receiving filgrastim (58%) compared to those receiving pegfilgrastim (72.4%, p < 0.001). No significant difference was detected on FN rate between daily administration of filgrastim and single administration of pegfilgrastim. However, patients receiving pegfilgrastim had a significantly lower rate of severe neutropenia, as well as dose reduction and treatment delay, thus, achieving a higher dose density.