CURRENT STATUS OF INDIVIDUAL DOSIMETRIC MONITORING IN UKRAINE.

PubMed

Chumak, V; Deniachenko, N; Makarovska, O; Mihailescu, L-C; Prykhodko, A; Voloskyi, V; Vanhavere, F

2016-09-01

About 50 000 workers are being occupationally exposed to radiation in Ukraine. Individual dosimetric monitoring (IDM) is provided by 77 dosimetry services and laboratories of very different scale with a number of monitored workers ranging from several persons to ∼9000. In the present work, the current status of personal dosimetry in Ukraine was studied. The First National Intercomparison (FNI) of the IDM labs was accompanied by a survey of the laboratory operation in terms of coverage, types of dosimetry provided, instrumentation and methodologies used, metrological support, data recording, etc. Totally, 34 laboratories responded to the FNI call, and 18 services with 19 different personal dosimetry systems took part in the intercomparison exercise providing 24 dosimeters each for blind irradiation to photons of 6 different qualities (ISO N-series X-rays, S-Cs and S-Co sources) in a dose range of 5-60 mSv. Performance of the dosimetry labs was evaluated according to ISO 14146 criteria of matching trumpet curves with H0 = 0.2 mSv. The test revealed that 8 of the 19 systems meet ISO 14146 criteria in full, 5 other labs show marginal performance and 6 laboratories demonstrated catastrophic quality of dosimetric results. Altogether, 18 participating labs provide dosimetric monitoring to 37 477 workers (about three-fourths of all occupationally exposed workers), usually on monthly (nuclear industry) or quarterly (rest of applications) basis. Of this number, 20 664 persons (55 %) receive completely adequate individual monitoring, and the number of personnel receiving IDM of inadequate quality counts 3054 persons. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Calorimetry of electron beams and the calibration of dosimeters at high doses

NASA Astrophysics Data System (ADS)

Humphreys, J. C.; McLaughlin, W. L.

Graphite or metal calorimeters are used to make absolute dosimetric measurements of high-energy electron beams. These calibrated beams are then used to calibrate several types of dosimeters for high-dose applications such as medical-product sterilization, polymer modification, food processing, or electronic-device hardness testing. The electron beams are produced either as continuous high-power beams at approximately 4.5 MeV by d.c. type accelerators or in the energy range of approximately 8 to 50 MeV using pulsed microwave linear accelerators (linacs). The continuous beams are generally magnetically scanned to produce a broad, uniform radiation environment for the processing of materials of extended lateral dimensions. The higher-energy pulsed beams may also be scanned for processing applications or may be used in an unscanned, tightly-focused mode to produce maximum absorbed dose rates such as may be required for electronic-device radiation hardness testing. The calorimeters are used over an absorbed dose range of 10 2 to 10 4 Gy. Intercomparison studies are reported between National Institute of Standards and Technology (NIST) and UK National Physical Laboratory (NPL) graphite disk calorimeters at high doses, using the NPL 10-MeV linac, and agreement was found within 1.5%. It was also shown that the electron-beam responses of radiochromic film dosimeters and alanine pellet dosimeters can be accurately calibrated by comparison with calorimeter readings.

Design and results of the ice sheet model initialisation experiments initMIP-Greenland: an ISMIP6 intercomparison

NASA Astrophysics Data System (ADS)

Goelzer, Heiko; Nowicki, Sophie; Edwards, Tamsin; Beckley, Matthew; Abe-Ouchi, Ayako; Aschwanden, Andy; Calov, Reinhard; Gagliardini, Olivier; Gillet-Chaulet, Fabien; Golledge, Nicholas R.; Gregory, Jonathan; Greve, Ralf; Humbert, Angelika; Huybrechts, Philippe; Kennedy, Joseph H.; Larour, Eric; Lipscomb, William H.; Le clec'h, Sébastien; Lee, Victoria; Morlighem, Mathieu; Pattyn, Frank; Payne, Antony J.; Rodehacke, Christian; Rückamp, Martin; Saito, Fuyuki; Schlegel, Nicole; Seroussi, Helene; Shepherd, Andrew; Sun, Sainan; van de Wal, Roderik; Ziemen, Florian A.

2018-04-01

Earlier large-scale Greenland ice sheet sea-level projections (e.g. those run during the ice2sea and SeaRISE initiatives) have shown that ice sheet initial conditions have a large effect on the projections and give rise to important uncertainties. The goal of this initMIP-Greenland intercomparison exercise is to compare, evaluate, and improve the initialisation techniques used in the ice sheet modelling community and to estimate the associated uncertainties in modelled mass changes. initMIP-Greenland is the first in a series of ice sheet model intercomparison activities within ISMIP6 (the Ice Sheet Model Intercomparison Project for CMIP6), which is the primary activity within the Coupled Model Intercomparison Project Phase 6 (CMIP6) focusing on the ice sheets. Two experiments for the large-scale Greenland ice sheet have been designed to allow intercomparison between participating models of (1) the initial present-day state of the ice sheet and (2) the response in two idealised forward experiments. The forward experiments serve to evaluate the initialisation in terms of model drift (forward run without additional forcing) and in response to a large perturbation (prescribed surface mass balance anomaly); they should not be interpreted as sea-level projections. We present and discuss results that highlight the diversity of data sets, boundary conditions, and initialisation techniques used in the community to generate initial states of the Greenland ice sheet. We find good agreement across the ensemble for the dynamic response to surface mass balance changes in areas where the simulated ice sheets overlap but differences arising from the initial size of the ice sheet. The model drift in the control experiment is reduced for models that participated in earlier intercomparison exercises.

Design and results of the ice sheet model initialisation experiments initMIP-Greenland: an ISMIP6 intercomparison

DOE PAGES

Goelzer, Heiko; Nowicki, Sophie; Edwards, Tamsin; ...

2018-04-19

Earlier large-scale Greenland ice sheet sea-level projections (e.g. those run during the ice2sea and SeaRISE initiatives) have shown that ice sheet initial conditions have a large effect on the projections and give rise to important uncertainties. Here, the goal of this initMIP-Greenland intercomparison exercise is to compare, evaluate, and improve the initialisation techniques used in the ice sheet modelling community and to estimate the associated uncertainties in modelled mass changes. initMIP-Greenland is the first in a series of ice sheet model intercomparison activities within ISMIP6 (the Ice Sheet Model Intercomparison Project for CMIP6), which is the primary activity within themore » Coupled Model Intercomparison Project Phase 6 (CMIP6) focusing on the ice sheets. Two experiments for the large-scale Greenland ice sheet have been designed to allow intercomparison between participating models of (1) the initial present-day state of the ice sheet and (2) the response in two idealised forward experiments. The forward experiments serve to evaluate the initialisation in terms of model drift (forward run without additional forcing) and in response to a large perturbation (prescribed surface mass balance anomaly); they should not be interpreted as sea-level projections. We present and discuss results that highlight the diversity of data sets, boundary conditions, and initialisation techniques used in the community to generate initial states of the Greenland ice sheet. We find good agreement across the ensemble for the dynamic response to surface mass balance changes in areas where the simulated ice sheets overlap but differences arising from the initial size of the ice sheet. The model drift in the control experiment is reduced for models that participated in earlier intercomparison exercises.« less

Design and results of the ice sheet model initialisation experiments initMIP-Greenland: an ISMIP6 intercomparison

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

Goelzer, Heiko; Nowicki, Sophie; Edwards, Tamsin

Earlier large-scale Greenland ice sheet sea-level projections (e.g. those run during the ice2sea and SeaRISE initiatives) have shown that ice sheet initial conditions have a large effect on the projections and give rise to important uncertainties. Here, the goal of this initMIP-Greenland intercomparison exercise is to compare, evaluate, and improve the initialisation techniques used in the ice sheet modelling community and to estimate the associated uncertainties in modelled mass changes. initMIP-Greenland is the first in a series of ice sheet model intercomparison activities within ISMIP6 (the Ice Sheet Model Intercomparison Project for CMIP6), which is the primary activity within themore » Coupled Model Intercomparison Project Phase 6 (CMIP6) focusing on the ice sheets. Two experiments for the large-scale Greenland ice sheet have been designed to allow intercomparison between participating models of (1) the initial present-day state of the ice sheet and (2) the response in two idealised forward experiments. The forward experiments serve to evaluate the initialisation in terms of model drift (forward run without additional forcing) and in response to a large perturbation (prescribed surface mass balance anomaly); they should not be interpreted as sea-level projections. We present and discuss results that highlight the diversity of data sets, boundary conditions, and initialisation techniques used in the community to generate initial states of the Greenland ice sheet. We find good agreement across the ensemble for the dynamic response to surface mass balance changes in areas where the simulated ice sheets overlap but differences arising from the initial size of the ice sheet. The model drift in the control experiment is reduced for models that participated in earlier intercomparison exercises.« less

Long History of IAM Comparisons

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

Smith, Steven J.; Clarke, Leon E.; Edmonds, James A.

2015-04-23

Correspondence to editor: We agree with the editors that the assumptions behind models of all types, including integrated assessment models (IAMs), should be as transparent as possible. The editors were in error, however, when they implied that the IAM community is just “now emulating the efforts of climate researchers by instigating their own model inter-comparison projects (MIPs).” In fact, model comparisons for integrated assessment and climate models followed a remarkably similar trajectory. Early General Circulation Model (GCM) comparison efforts, evolved to the first Atmospheric Model Inter-comparison Project (AMIP), which was initiated in the early 1990s. Atmospheric models evolved to coupledmore » atmosphere-ocean models (AOGCMs) and results from the first Coupled Model Inter-Comparison Project (CMIP1) become available about a decade later. Results of first energy model comparison exercise, conducted under the auspices of the Stanford Energy Modeling Forum, were published in 1977. A summary of the first comparison focused on climate change was published in 1993. As energy models were coupled to simple economic and climate models to form IAMs, the first comparison exercise for IAMs (EMF-14) was initiated in 1994, and IAM comparison exercises have been on-going since this time.« less

Intercomparison of analytical methods for arsenic speciation in human urine.

PubMed

Crecelius, E; Yager, J

1997-06-01

An intercomparison exercise was conducted for the quantification of arsenic species in spiked human urine. The primary objective of the exercise was to determine the variance among laboratories in the analysis of arsenic species such as inorganic As (As+3 and As+5), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA). Laboratories that participated had previous experience with arsenic speciation analysis. The results of this interlaboratory comparison are encouraging. There is relatively good agreement on the concentrations of these arsenic species in urine at concentrations that are relevant to research on the metabolism of arsenic in humans and other mammals. Both the accuracy and precision are relatively poor for arsenic concentrations of less than about 5 micrograms/l.

ACIX: Atmospheric Correction Inter-comparison Exercise

NASA Astrophysics Data System (ADS)

Doxani, Georgia; Gascon, Ferran; Vermote, Éric; Roger, Jean-Claude

2017-04-01

The free and open data access policy to Sentinel-2 (S-2) and Landsat-8 (L-8) satellite imagery has stimulated the development of atmospheric correction (AC) processors for generating Bottom-of-Atmosphere (BOA) products. Several entities have started to generate (or plan to generate in the short term) BOA reflectance products at global scale for S-2 and L-8 missions. To this end, the European Space Agency (ESA) and NASA are organizing an exercise on AC processors inter-comparison. The results of the exercise are expected to point out the strengths and weaknesses, as well as communalities and discrepancies of various AC processors, in order to suggest and define ways for their further improvement. In particular, 13 atmospheric processors from five different countries participate in ACIX with the aim to inter-compare their performance when applied to L-8 and S-2 data. A protocol describing the inter-comparison process and the test dataset, which is based on the AERONET sites, will be presented. The protocol has been defined according to what was agreed among the participants during the 1st ACIX workshop held in June 2016. It includes the comparison of aerosol optical thickness and water vapour products of the processors with the AERONET measurements. Moreover, concerning the surface reflectances, the protocol describes the inter-comparison among the processors, as well as the comparison with the MODIS surface reflectance and with a reference surface reflectance product. Such a reference product will be obtained using the AERONET characterization of the aerosol (size distribution and refractive indices) and an accurate radiative transfer code. The inter-comparison outcomes will be presented and discussed among the participants in the 2nd ACIX workshop, which will be held on 11-12 April 2017 (ESRIN/ESA). The proposed presentation is an opportunity for the user community to be informed for the first time about the ACIX results and conclusions.

Design of the MISMIP+, ISOMIP+, and MISOMIP ice-sheet, ocean, and coupled ice sheet-ocean intercomparison projects

NASA Astrophysics Data System (ADS)

Asay-Davis, Xylar; Cornford, Stephen; Martin, Daniel; Gudmundsson, Hilmar; Holland, David; Holland, Denise

2015-04-01

The MISMIP and MISMIP3D marine ice sheet model intercomparison exercises have become popular benchmarks, and several modeling groups have used them to show how their models compare to both analytical results and other models. Similarly, the ISOMIP (Ice Shelf-Ocean Model Intercomparison Project) experiments have acted as a proving ground for ocean models with sub-ice-shelf cavities.As coupled ice sheet-ocean models become available, an updated set of benchmark experiments is needed. To this end, we propose sequel experiments, MISMIP+ and ISOMIP+, with an end goal of coupling the two in a third intercomparison exercise, MISOMIP (the Marine Ice Sheet-Ocean Model Intercomparison Project). Like MISMIP3D, the MISMIP+ experiments take place in an idealized, three-dimensional setting and compare full 3D (Stokes) and reduced, hydrostatic models. Unlike the earlier exercises, the primary focus will be the response of models to sub-shelf melting. The chosen configuration features an ice shelf that experiences substantial lateral shear and buttresses the upstream ice, and so is well suited to melting experiments. Differences between the steady states of each model are minor compared to the response to melt-rate perturbations, reflecting typical real-world applications where parameters are chosen so that the initial states of all models tend to match observations. The three ISOMIP+ experiments have been designed to to make use of the same bedrock topography as MISMIP+ and using ice-shelf geometries from MISMIP+ results produced by the BISICLES ice-sheet model. The first two experiments use static ice-shelf geometries to simulate the evolution of ocean dynamics and resulting melt rates to a quasi-steady state when far-field forcing changes in either from cold to warm or from warm to cold states. The third experiment prescribes 200 years of dynamic ice-shelf geometry (with both retreating and advancing ice) based on a BISICLES simulation along with similar flips between warm and cold states in the far-field ocean forcing. The MISOMIP experiment combines the MISMIP+ experiments with the third ISOMIP+ experiment. Changes in far-field ocean forcing lead to a rapid (over ~1-2 years) increase in sub-ice-shelf melting, which is allowed to drive ice-shelf retreat for ~100 years. Then, the far-field forcing is switched to a cold state, leading to a rapid decrease in melting and a subsequent advance over ~100 years. To illustrate, we present results from BISICLES and POP2x experiments for each of the three intercomparison exercises.

PFLOTRAN-RepoTREND Source Term Comparison Summary.

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

Frederick, Jennifer M.

Code inter-comparison studies are useful exercises to verify and benchmark independently developed software to ensure proper function, especially when the software is used to model high-consequence systems which cannot be physically tested in a fully representative environment. This summary describes the results of the first portion of the code inter-comparison between PFLOTRAN and RepoTREND, which compares the radionuclide source term used in a typical performance assessment.

Intercomparison of analytical methods for arsenic speciation in human urine.

PubMed Central

Crecelius, E; Yager, J

1997-01-01

An intercomparison exercise was conducted for the quantification of arsenic species in spiked human urine. The primary objective of the exercise was to determine the variance among laboratories in the analysis of arsenic species such as inorganic As (As+3 and As+5), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA). Laboratories that participated had previous experience with arsenic speciation analysis. The results of this interlaboratory comparison are encouraging. There is relatively good agreement on the concentrations of these arsenic species in urine at concentrations that are relevant to research on the metabolism of arsenic in humans and other mammals. Both the accuracy and precision are relatively poor for arsenic concentrations of less than about 5 micrograms/l. PMID:9288500

Progress in high-dose radiation dosimetry. Final report

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

Ettinger, K.V.; Nam, J.W.; McLaughlin, W.L.

1981-01-01

The last decade has witnessed a deluge of new high-dose dosimetry techniques and expended applications of methods developed earlier. Many of the principal systems are calibrated by means of calorimetry, although production of heat is not always the final radiation effect of interest. Requirements for a stable and reliable transfer dose meters have led to further developments of several important high-dose systems: thermoluminescent materials, radiochromic dyes, ceric-cerous solutions analyzed by high-frequency oscillometry. A number of other prospective dosimeters are also treated in this review. In addition, an IAEA program of high-dose intercomparison and standardization for industrial radiation processing is described.

Progress in high-dose radiation dosimetry. Final report

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

Ettinger, K.V.; Nam, J.W.; McLaughlin, W.L.

1981-01-01

The last decade has witnessed a deluge of new high-dose dosimetry techniques and expended applications of methods developed earlier. Many of the principal systems are calibrated by means of calorimetry, although production of heat is not always the final radiation effect of interest. Requirements for a stable and reliable transfer dose meters have led to further developments of several important high-dose systems: thermoluminescent materials, radiochromic dyes, ceric-cerous solutions analyzed by high-frequency oscillometry. A number of other prospective dosimeters also treated in this review. In addition, an IAEA programme of high-dose intercomparison and standardization for industrial radiation processing is described.

Atmospheric Correction Inter-comparison Exercise (ACIX)

NASA Astrophysics Data System (ADS)

Vermote, E.; Doxani, G.; Gascon, F.; Roger, J. C.; Skakun, S.

2017-12-01

The free and open data access policy to Landsat-8 (L-8) and Sentinel-2 (S-2) satellite imagery has encouraged the development of atmospheric correction (AC) approaches for generating Bottom-of-Atmosphere (BOA) products. Several entities have started to generate (or plan to generate in the short term) BOA reflectance products at global scale for L-8 and S-2 missions. To this end, the European Space Agency (ESA) and National Aeronautics and Space Administration (NASA) have initiated an exercise on the inter-comparison of the available AC processors. The results of the exercise are expected to point out the strengths and weaknesses, as well as communalities and discrepancies of various AC processors, in order to suggest and define ways for their further improvement. In particular, 11 atmospheric processors from five different countries participate in ACIX with the aim to inter-compare their performance when applied to L-8 and S-2 data. All the processors should be operational without requiring parametrization when applied on different areas. A protocol describing in details the inter-comparison metrics and the test dataset based on the AERONET sites has been agreed unanimously during the 1st ACIX workshop in June 2016. In particular, a basic and an advanced run of each of the processor were requested in the frame of ACIX, with the aim to draw robust and reliable conclusions on the processors' performance. The protocol also describes the comparison metrics of the aerosol optical thickness and water vapour products of the processors with the corresponding AERONET measurements. Moreover, concerning the surface reflectances, the inter-comparison among the processors is defined, as well as the comparison with the MODIS surface reflectance and with a reference surface reflectance product. Such a reference product will be obtained using the AERONET characterization of the aerosol (size distribution and refractive indices) and an accurate radiative transfer code. The inter-comparison outcomes were presented and discussed among the ACIX participants in the 2nd ACIX workshop, which was held on 11-12 April 2017 (ESRIN/ESA) and a detailed report was compiled. The proposed presentation is an opportunity for the user community to be informed about the ACIX results and conclusions.

Intercomparison of methods for coincidence summing corrections in gamma-ray spectrometry--part II (volume sources).

PubMed

Lépy, M-C; Altzitzoglou, T; Anagnostakis, M J; Capogni, M; Ceccatelli, A; De Felice, P; Djurasevic, M; Dryak, P; Fazio, A; Ferreux, L; Giampaoli, A; Han, J B; Hurtado, S; Kandic, A; Kanisch, G; Karfopoulos, K L; Klemola, S; Kovar, P; Laubenstein, M; Lee, J H; Lee, J M; Lee, K B; Pierre, S; Carvalhal, G; Sima, O; Tao, Chau Van; Thanh, Tran Thien; Vidmar, T; Vukanac, I; Yang, M J

2012-09-01

The second part of an intercomparison of the coincidence summing correction methods is presented. This exercise concerned three volume sources, filled with liquid radioactive solution. The same experimental spectra, decay scheme and photon emission intensities were used by all the participants. The results were expressed as coincidence summing corrective factors for several energies of (152)Eu and (134)Cs, and different source-to-detector distances. They are presented and discussed. Copyright © 2012 Elsevier Ltd. All rights reserved.

ISMIP6 - initMIP: Greenland ice sheet model initialisation experiments

NASA Astrophysics Data System (ADS)

Goelzer, Heiko; Nowicki, Sophie; Payne, Tony; Larour, Eric; Abe Ouchi, Ayako; Gregory, Jonathan; Lipscomb, William; Seroussi, Helene; Shepherd, Andrew; Edwards, Tamsin

2016-04-01

Earlier large-scale Greenland ice sheet sea-level projections e.g. those run during ice2sea and SeaRISE initiatives have shown that ice sheet initialisation can have a large effect on the projections and gives rise to important uncertainties. This intercomparison exercise (initMIP) aims at comparing, evaluating and improving the initialization techniques used in the ice sheet modeling community and to estimate the associated uncertainties. It is the first in a series of ice sheet model intercomparison activities within ISMIP6 (Ice Sheet Model Intercomparison Project for CMIP6). The experiments are conceived for the large-scale Greenland ice sheet and are designed to allow intercomparison between participating models of 1) the initial present-day state of the ice sheet and 2) the response in two schematic forward experiments. The latter experiments serve to evaluate the initialisation in terms of model drift (forward run without any forcing) and response to a large perturbation (prescribed surface mass balance anomaly). We present and discuss first results of the intercomparison and highlight important uncertainties with respect to projections of the Greenland ice sheet sea-level contribution.

Results of the Greenland Ice Sheet Model Initialisation Experiments ISMIP6 - initMIP-Greenland

NASA Astrophysics Data System (ADS)

Goelzer, H.; Nowicki, S.; Edwards, T.; Beckley, M.; Abe-Ouchi, A.; Aschwanden, A.; Calov, R.; Gagliardini, O.; Gillet-chaulet, F.; Golledge, N. R.; Gregory, J. M.; Greve, R.; Humbert, A.; Huybrechts, P.; Larour, E. Y.; Lipscomb, W. H.; Le ´h, S.; Lee, V.; Kennedy, J. H.; Pattyn, F.; Payne, A. J.; Rodehacke, C. B.; Rückamp, M.; Saito, F.; Schlegel, N.; Seroussi, H. L.; Shepherd, A.; Sun, S.; Vandewal, R.; Ziemen, F. A.

2016-12-01

Earlier large-scale Greenland ice sheet sea-level projections e.g. those run during ice2sea and SeaRISE initiatives have shown that ice sheet initialisation can have a large effect on the projections and gives rise to important uncertainties. The goal of this intercomparison exercise (initMIP-Greenland) is to compare, evaluate and improve the initialization techniques used in the ice sheet modeling community and to estimate the associated uncertainties. It is the first in a series of ice sheet model intercomparison activities within ISMIP6 (Ice Sheet Model Intercomparison Project for CMIP6). Two experiments for the large-scale Greenland ice sheet have been designed to allow intercomparison between participating models of 1) the initial present-day state of the ice sheet and 2) the response in two schematic forward experiments. The forward experiments serve to evaluate the initialisation in terms of model drift (forward run without any forcing) and response to a large perturbation (prescribed surface mass balance anomaly). We present and discuss final results of the intercomparison and highlight important uncertainties with respect to projections of the Greenland ice sheet sea-level contribution.

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

Heinrichs, Dave; Beller, Tim; Burch, Jennifer

This document is the Final Design (CED-2) Report for IER-148, “International Inter-comparison Exercise for Nuclear Accident Dosimetry at the DAF Using Godiva-IV.” The report describes the structure of the exercise consisting of three irradiations; identifies the participating laboratories and their points of contact; provides the details of all dosimetry elements and their placement in proximity to Godiva-IV on support stands or phantoms ; and lists the counting and spectroscopy equipment each laboratory will utilize in the Mercury NAD Lab. The exercise is tentatively scheduled for one week in August 2015.

Evaluation of Dosimetry Check software for IMRT patient-specific quality assurance.

PubMed

Narayanasamy, Ganesh; Zalman, Travis; Ha, Chul S; Papanikolaou, Niko; Stathakis, Sotirios

2015-05-08

The purpose of this study is to evaluate the use of the Dosimetry Check system for patient-specific IMRT QA. Typical QA methods measure the dose in an array dosimeter surrounded by homogenous medium for which the treatment plan has been recomputed. With the Dosimetry Check system, fluence measurements acquired on a portal dosimeter is applied to the patient's CT scans. Instead of making dose comparisons in a plane, Dosimetry Check system produces isodose lines and dose-volume histograms based on the planning CT images. By exporting the dose distribution from the treatment planning system into the Dosimetry Check system, one is able to make a direct comparison between the calculated dose and the planned dose. The versatility of the software is evaluated with respect to the two IMRT techniques - step and shoot and volumetric arc therapy. The system analyzed measurements made using EPID, PTW seven29, and IBA MatriXX, and an intercomparison study was performed. Plans from patients previously treated at our institution with treated anatomical site on brain, head & neck, liver, lung, and prostate were analyzed using Dosimetry Check system for any anatomical site dependence. We have recommendations and possible precautions that may be necessary to ensure proper QA with the Dosimetry Check system.

Estimation of absorbed dose in clinical radiotherapy linear accelerator beams: Effect of ion chamber calibration and long-term stability

PubMed Central

Ravichandran, Ramamoorthy; Binukumar, Johnson Pichy; Davis, Cheriyathmanjiyil Antony

2013-01-01

The measured dose in water at reference point in phantom is a primary parameter for planning the treatment monitor units (MU); both in conventional and intensity modulated/image guided treatments. Traceability of dose accuracy therefore still depends mainly on the calibration factor of the ion chamber/dosimeter provided by the accredited Secondary Standard Dosimetry Laboratories (SSDLs), under International Atomic Energy Agency (IAEA) network of laboratories. The data related to Nd,water calibrations, thermoluminescent dosimetry (TLD) postal dose validation, inter-comparison of different dosimeter/electrometers, and validity of Nd,water calibrations obtained from different calibration laboratories were analyzed to find out the extent of accuracy achievable. Nd,w factors in Gray/Coulomb calibrated at IBA, GmBH, Germany showed a mean variation of about 0.2% increase per year in three Farmer chambers, in three subsequent calibrations. Another ion chamber calibrated in different accredited laboratory (PTW, Germany) showed consistent Nd,w for 9 years period. The Strontium-90 beta check source response indicated long-term stability of the ion chambers within 1% for three chambers. Results of IAEA postal TL “dose intercomparison” for three photon beams, 6 MV (two) and 15 MV (one), agreed well within our reported doses, with mean deviation of 0.03% (SD 0.87%) (n = 9). All the chamber/electrometer calibrated by a single SSDL realized absorbed doses in water within 0.13% standard deviations. However, about 1-2% differences in absorbed dose estimates observed when dosimeters calibrated from different calibration laboratories are compared in solid phantoms. Our data therefore imply that the dosimetry level maintained for clinical use of linear accelerator photon beams are within recommended levels of accuracy, and uncertainties are within reported values. PMID:24672156

Invited Article: Radon and thoron intercomparison experiments for integrated monitors at NIRS, Japan

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

Janik, M., E-mail: mirek@fml.nirs.go.jp; Ishikawa, T.; Omori, Y.

Inhalation of radon ({sup 222}Rn) and its short-lived decay products and of products of the thoron ({sup 220}Rn) series accounts for more than half of the effective dose from natural radiation sources. At this time, many countries have begun large-scale radon and thoron surveys and many different measurement methods and instruments are used in these studies. Consequently, it is necessary to improve and standardize technical methods of measurements and to verify quality assurance by intercomparisons between laboratories. Four international intercomparisons for passive integrating radon and thoron monitors were conducted at the NIRS (National Institute of Radiological Sciences, Japan). Radon exercisesmore » were carried out in the 24.4 m{sup 3} inner volume walk-in radon chamber that has systems to control radon concentration, temperature, and humidity. Moreover, the NIRS thoron chamber with a 150 dm{sup 3} inner volume was utilized to provide three thoron intercomparisons. At present, the NIRS is the only laboratory world-wide that has carried out periodic thoron intercomparison of passive monitors. Fifty laboratories from 26 countries participated in the radon intercomparison, using six types of detectors (charcoal, CR-39, LR 115, polycarbonate film, electret plate, and silicon photodiode). Eighteen laboratories from 12 countries participated in the thoron intercomparisons, using two etch-track types (CR-39 and polycarbonate) detectors. The tests were made under one to three different exposures to radon and thoron. The data presented in this paper indicated that the performance quality of laboratories for radon measurement has been gradually increasing. Results of thoron exercises showed that the quality for thoron measurements still needs further development and additional studies are needed to improve its measuring methods. The present paper provides a summary of all radon and thoron international intercomparisons done at NIRS from 2007 to date and it describes the present status on radon and thoron passive, one-time cycle monitors.« less

The ENEA criticality accident dosimetry system: a contribution to the 2002 international intercomparison at the SILENE reactor.

PubMed

Gualdrini, G; Bedogni, R; Fantuzzi, E; Mariotti, F

2004-01-01

The present paper summarises the activity carried out at the ENEA Radiation Protection Institute for updating the methodologies employed for the evaluation of the neutron and photon dose to the exposed workers in case of a criticality accident, in the framework of the 'International Intercomparison of Criticality Accident Dosimetry Systems' (Silène reactor, IRSN-CEA-Valduc June 2002). The evaluation of the neutron spectra and the neutron dosimetric quantities relies on activation detectors and on unfolding algorithms. Thermoluminescent detectors are employed for the gamma dose measurement. The work is aimed at accurately characterising the measurement system and, at the same time, testing the algorithms. Useful spectral information were included, based on Monte Carlo simulations, to take into account the potential accident scenarios of practical interest. All along this exercise intercomparison a particular attention was devoted to the 'traceability' of all the experimental and computational parameters and therefore, aimed at an easy treatment by the user.

On the feasibility of utilizing active personal dosimeters worn on the chest to estimate occupational eye lens dose in x-ray angiography.

PubMed

Omar, Artur; Marteinsdottir, Maria; Kadesjö, Nils; Fransson, Annette

2015-06-01

The International Commission on Radiological Protection (ICRP) has recommended that the occupational dose limit to the eye lens be substantially reduced. To ensure compliance with these recommendations, monitoring of the occupational eye lens dose is essential in certain hospital work environments. For assessment of the eye lens dose it is recommended to use a supplementary dosimeter placed at a position adjacent to the eye(s). Wearing a dosimeter at eye level can, however, be impractical and distributing and managing additional dosimeters over long periods of time is cumbersome and costly for large clinical sites. An attractive alternative is to utilize active personal dosimeters (APDs), which are routinely used by clinical staff for real-time monitoring of the personal dose equivalent rate (H(p)(10)). In this work, a formalism for the determination of eye lens dose from the response of such APD's worn on the chest is proposed and evaluated. The evaluation is based on both phantom and clinical measurements performed in an x-ray angiography suite for interventional cardiology. The main results show that the eye lens dose to the primary operator and to the assisting clinical staff can be conservatively estimated from the APD response as D(eye)(conductor) = 2.0 APD chest and D(eye)(assisting) = 1.0 APD chest, respectively. However, care should be exercised for particularly short assisting staff and if radiation protection shields are misused. These concerns can be greatly mitigated if the clinical staff are provided with adequate radiation protection training.

NOAA National Status and Trends Program Twelfth Round Intercomparison Exercise Results for Trace Metals in Marine Sediments and Biological Tissues. National Status and Trends Program for marine environmental quality: Technical memo

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

Willie, S.

1998-11-01

The report summarizes the results of the Twelfth Round Intercomparison for Trace Metals in Marine Sediments and Biological Tissues under the directive of the NOAA National Status and Trends Program. A total of forty-four participants were included in the exercise, including NOAA, USEPA, state, Austrailian, Canadian, Mexican and Argentinean laboratories. Two samples were sent by NRC to each participant, a marine sediment collected on the east coast of Canada and a freeze-dried mussel tissue. Laboratories were also asked to analyze two certified reference materials (CRMs) MESS-2 and CRM 2976. The elements to be determined were Al, Cr, Fe, Ni, Cu,more » Zn, As, Se, Ag, Cd, Sn, Hg, and Pb for both matrices, plus Be, Si, Mn, Sb, and Tl for the sediments. An accepted mean and confidence interval was calculated for each analyte in the two unknown samples, laboratory biases were identified and an overall rating of superior, good, fair or others were assigned to each laboratory.« less

Intercomparison of Operational Ocean Forecasting Systems in the framework of GODAE

NASA Astrophysics Data System (ADS)

Hernandez, F.

2009-04-01

One of the main benefits of the GODAE 10-year activity is the implementation of ocean forecasting systems in several countries. In 2008, several systems are operated routinely, at global or basin scale. Among them, the BLUElink (Australia), HYCOM (USA), MOVE/MRI.COM (Japan), Mercator (France), FOAM (United Kingdom), TOPAZ (Norway) and C-NOOFS (Canada) systems offered to demonstrate their operational feasibility by performing an intercomparison exercise during a three months period (February to April 2008). The objectives were: a) to show that operational ocean forecasting systems are operated routinely in different countries, and that they can interact; b) to perform in a similar way a scientific validation aimed to assess the quality of the ocean estimates, the performance, and forecasting capabilities of each system; and c) to learn from this intercomparison exercise to increase inter-operability and collaboration in real time. The intercomparison relies on the assessment strategy developed for the EU MERSEA project, where diagnostics over the global ocean have been revisited by the GODAE contributors. This approach, based on metrics, allow for each system: a) to verify if ocean estimates are consistent with the current general knowledge of the dynamics; and b) to evaluate the accuracy of delivered products, compared to space and in-situ observations. Using the same diagnostics also allows one to intercompare the results from each system consistently. Water masses and general circulation description by the different systems are consistent with WOA05 Levitus climatology. The large scale dynamics (tropical, subtropical and subpolar gyres ) are also correctly reproduced. At short scales, benefit of high resolution systems can be evidenced on the turbulent eddy field, in particular when compared to eddy kinetic energy deduced from satellite altimetry of drifter observations. Comparisons to high resolution SST products show some discrepancies on ocean surface representation, either due to model and forcing fields errors, or assimilation scheme efficiency. Comparisons to sea-ice satellite products also evidence discrepancies linked to model, forcing and assimilation strategies of each forecasting system. Key words: Intercomparison, ocean analysis, operational oceanography, system assessment, metrics, validation GODAE Intercomparison Team: L. Bertino (NERSC/Norway), G. Brassington (BMRC/Australia), E. Chassignet (FSU/USA), J. Cummings (NRL/USA), F. Davidson (DFO/Canda), M. Drévillon (CERFACS/France), P. Hacker (IPRC/USA), M. Kamachi (MRI/Japan), J.-M. Lellouche (CERFACS/France), K. A. Lisæter (NERSC/Norway), R. Mahdon (UKMO/UK), M. Martin (UKMO/UK), A. Ratsimandresy (DFO/Canada), and C. Regnier (Mercator Ocean/France)

Satellite Derived Volcanic Ash Product Inter-Comparison in Support to SCOPE-Nowcasting

NASA Astrophysics Data System (ADS)

Siddans, Richard; Thomas, Gareth; Pavolonis, Mike; Bojinski, Stephan

2016-04-01

In support of aeronautical meteorological services, WMO organized a satellite-based volcanic ash retrieval algorithm inter-comparison activity, to improve the consistency of quantitative volcanic ash products from satellites, under the Sustained, Coordinated Processing of Environmental Satellite Data for Nowcasting (SCOPEe Nowcasting) initiative (http:/ jwww.wmo.int/pagesjprogjsatjscopee nowcasting_en.php). The aims of the intercomparison were as follows: 1. Select cases (Sarychev Peak 2009, Eyjafyallajökull 2010, Grimsvötn 2011, Puyehue-Cordón Caulle 2011, Kirishimayama 2011, Kelut 2014), and quantify the differences between satellite-derived volcanic ash cloud properties derived from different techniques and sensors; 2. Establish a basic validation protocol for satellite-derived volcanic ash cloud properties; 3. Document the strengths and weaknesses of different remote sensing approaches as a function of satellite sensor; 4. Standardize the units and quality flags associated with volcanic cloud geophysical parameters; 5. Provide recommendations to Volcanic Ash Advisory Centers (VAACs) and other users on how to best to utilize quantitative satellite products in operations; 6. Create a "road map" for future volcanic ash related scientific developments and inter-comparison/validation activities that can also be applied to SO2 clouds and emergent volcanic clouds. Volcanic ash satellite remote sensing experts from operational and research organizations were encouraged to participate in the inter-comparison activity, to establish the plans for the inter-comparison and to submit data sets. RAL was contracted by EUMETSAT to perform a systematic inter-comparison of all submitted datasets and results were reported at the WMO International Volcanic Ash Inter-comparison Meeting to held on 29 June - 2 July 2015 in Madison, WI, USA (http:/ /cimss.ssec.wisc.edujmeetings/vol_ash14). 26 different data sets were submitted, from a range of passive imagers and spectrometers and these were inter-compared against each other and against validation data such as CALIPSO lidar, ground-based lidar and aircraft observations. Results of the comparison exercise will be presented together with the conclusions and recommendations arising from the activity.

Thermoluminescence dosimetry and its applications in medicine--Part 2: History and applications.

PubMed

Kron, T

1995-03-01

Thermoluminescence dosimetry (TLD) has been available for dosimetry of ionising radiation for nearly 100 years. The variety of materials and their different physical forms allow the determination of different radiation qualities over a wide range of absorbed dose. This makes TL dosimeters useful in radiation protection where dose levels of microGy are monitored as well as in radiotherapy where doses up to several Gray are to be measured. The major advantages of TL detectors are their small physical size and that no cables or auxiliary equipment is required during the dose assessment. Therefore TLD is a good method for point dose measurements in phantoms as well as for in vivo dosimetry on patients during radiotherapy treatment. As an integrative dosimetric technique, it can be applied to personal dosimetry and it lends itself to the determination of dose distributions due to multiple or moving radiation sources (e.g. conformal and dynamic radiotherapy, computed tomography). In addition, TL dosimeters are easy to transport, and they can be mailed. This makes them well suited for intercomparison of doses delivered in different institutions. The present article aims at describing the various applications TLD has found in medicine by taking into consideration the physics and practice of TLD measurements which have been discussed in the first part of this review (Australas. Phys. Eng. Sci. Med. 17: 175-199, 1994).

The role of simulation chambers in the development of spectroscopic techniques: campaigns at EUPHORE

NASA Astrophysics Data System (ADS)

Ródenas, Milagros; Muñoz, Amalia; Euphore Team

2016-04-01

Simulation chambers represent a very useful tool for the study of chemical reactions and their products, but also to characterize instruments. The development of spectroscopic techniques throughout the last decades has benefited from tests and intercomparison exercises carried out in chambers. In fact, instruments can be exposed to various controlled atmospheric scenarios that account for different environmental conditions, eliminating the uncertainties associated to fluctuations of the air mass, which must be taken into account when extrapolating results to the real conditions. Hence, a given instrument can be characterized by assessing its precision, accuracy, detection limits, time response and potential interferences in the presence of other chemical compounds, aerosols, etc. This implies that the instrument can be calibrated and validated, which allows to enhance the features of the instrument. Moreover, chambers are also the scenario of intercomparison trials, permitting multiple instruments to sample from the same well-mixed air mass simultaneously. An overview of different campaigns to characterize and/or intercompare spectroscopic techniques that have taken place in simulation chambers will be given; in particular, those carried out at EUPHORE (two twin domes, 200 m3 each, Spain), where various intercomparison exercises have been deployed under the frame of European projects (e.g. TOXIC, FIONA, PSOA campaigns supported by EUROCHAMP-II). With the common aim of measuring given compounds (e.g. HONO, NO2, OH, glyoxal, m-glyoxal, etc), an important number of spectroscopic instruments and institutions have been involved in chamber experiments, having the chance to intercompare among them and also with other non-spectroscopic systems (e.g. monitors, cromatographs, etc) or model simulations.

An Overview of Measurement Comparisons from the INTEX-B/MILAGRO Airborne Field Campaign

NASA Technical Reports Server (NTRS)

Kleb, Mary M.; Chen, Gao; Crawford, James H.; Flocke, Frank M.; Brown, Clyde C.

2011-01-01

As part of the NASA's INTEX-B mission, the NASA DC-8 and NSF C-130 conducted three wing-tip to wing-tip comparison flights. The intercomparison flights sampled a variety of atmospheric conditions (polluted urban, non-polluted, marine boundary layer, clean and polluted free troposphere). These comparisons form a basis to establish data consistency, but also should also be viewed as a continuation of efforts aiming to better understand and reduce measurement differences as identified in earlier field intercomparison exercises. This paper provides a comprehensive overview of 140 intercomparisons of data collected as well as a record of the measurement consistency demonstrated during INTEX-B. It is the primary goal to provide necessary information for the future research to determine if the observations from different INTEX-B platforms/instrument are consistent within the PI reported uncertainties and used in integrated analysis. This paper may also contribute to the formulation strategy for future instrument developments. For interpretation and most effective use of these results, the reader is strongly urged to consult with the instrument principle investigator.

Results of the Greenland ice sheet model initialisation experiments: ISMIP6 - initMIP-Greenland

NASA Astrophysics Data System (ADS)

Goelzer, Heiko; Nowicki, Sophie; Edwards, Tamsin; Beckley, Matthew

2017-04-01

Ice sheet model initialisation has a large effect on projected future sea-level contributions and gives rise to important uncertainties. The goal of this intercomparison exercise for the continental-scale Greenland ice sheet is therefore to compare, evaluate and improve the initialisation techniques used in the ice sheet modelling community. The initMIP-Greenland project is the first in a series of ice sheet model intercomparison activities within ISMIP6 (Ice Sheet Model Intercomparison Project for CMIP6). The experimental set-up has been designed to allow comparison of the initial present-day state of the Greenland ice sheet between participating models and against observations. Furthermore, the initial states are tested with two schematic forward experiments to evaluate the initialisation in terms of model drift (forward run without any forcing) and response to a large perturbation (prescribed surface mass balance anomaly). We present and discuss results that highlight the wide diversity of data sets, boundary conditions and initialisation techniques used in the community to generate initial states of the Greenland ice sheet.

RENEB intercomparisons applying the conventional Dicentric Chromosome Assay (DCA).

PubMed

Oestreicher, Ursula; Samaga, Daniel; Ainsbury, Elizabeth; Antunes, Ana Catarina; Baeyens, Ans; Barrios, Leonardo; Beinke, Christina; Beukes, Philip; Blakely, William F; Cucu, Alexandra; De Amicis, Andrea; Depuydt, Julie; De Sanctis, Stefania; Di Giorgio, Marina; Dobos, Katalin; Dominguez, Inmaculada; Duy, Pham Ngoc; Espinoza, Marco E; Flegal, Farrah N; Figel, Markus; Garcia, Omar; Monteiro Gil, Octávia; Gregoire, Eric; Guerrero-Carbajal, C; Güçlü, İnci; Hadjidekova, Valeria; Hande, Prakash; Kulka, Ulrike; Lemon, Jennifer; Lindholm, Carita; Lista, Florigio; Lumniczky, Katalin; Martinez-Lopez, Wilner; Maznyk, Nataliya; Meschini, Roberta; M'kacher, Radia; Montoro, Alegria; Moquet, Jayne; Moreno, Mercedes; Noditi, Mihaela; Pajic, Jelena; Radl, Analía; Ricoul, Michelle; Romm, Horst; Roy, Laurence; Sabatier, Laure; Sebastià, Natividad; Slabbert, Jacobus; Sommer, Sylwester; Stuck Oliveira, Monica; Subramanian, Uma; Suto, Yumiko; Que, Tran; Testa, Antonella; Terzoudi, Georgia; Vral, Anne; Wilkins, Ruth; Yanti, LusiYanti; Zafiropoulos, Demetre; Wojcik, Andrzej

2017-01-01

Two quality controlled inter-laboratory exercises were organized within the EU project 'Realizing the European Network of Biodosimetry (RENEB)' to further optimize the dicentric chromosome assay (DCA) and to identify needs for training and harmonization activities within the RENEB network. The general study design included blood shipment, sample processing, analysis of chromosome aberrations and radiation dose assessment. After manual scoring of dicentric chromosomes in different cell numbers dose estimations and corresponding 95% confidence intervals were submitted by the participants. The shipment of blood samples to the partners in the European Community (EU) were performed successfully. Outside the EU unacceptable delays occurred. The results of the dose estimation demonstrate a very successful classification of the blood samples in medically relevant groups. In comparison to the 1st exercise the 2nd intercomparison showed an improvement in the accuracy of dose estimations especially for the high dose point. In case of a large-scale radiological incident, the pooling of ressources by networks can enhance the rapid classification of individuals in medically relevant treatment groups based on the DCA. The performance of the RENEB network as a whole has clearly benefited from harmonization processes and specific training activities for the network partners.

Lawrence Livermore National Laboratory and Sandia National Laboratory Nuclear Accident Dosimetry Support of IER 252 and the Dose Characterization of the Flattop Reactor at the DAF

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

Hickman, D. P.; Jeffers, K. L.; Radev, R. P.

In support of IER 252 “Characterization of the Flattop Reactor at the NCERC”, LLNL performed ROSPEC measurements of the neutron spectrum and deployed 129 Personnel Nuclear Accident Dosimeters (PNAD) to establish the need for height corrections and verification of neutron spectrum evaluation of the fluences and dose. A very limited number of heights (typically only one or two heights) can be measured using neutron spectrometers, therefore it was important to determine if any height correction would be needed in future intercomparisons and studies. Specific measurement positions around the Flatttop reactor are provided in Figure 1. Table 1 provides run andmore » position information for LLNL measurements. The LLNL ROSPEC (R2) was used for run numbers 1 – 7, and vi. PNADs were positioned on trees during run numbers 9, 11, and 13.« less

Preparation and Current Situation of Proton-ICCHIBAN-2 Experiment

NASA Astrophysics Data System (ADS)

Uchihori, Yukio; Yasuda, Nakahiro; Kitamura, H.; Kodaira, S.; Benton, Eric; Hajek, Michael; Berger, Thomas; Jadrnickova, Iva; Ploc, Ondrej

The ICCHIBAN (Inter Comparison for Cosmicrays with Heavy Ion Beams at NIRS) working group has organized and performed various ICCHIBAN runs for active and passive radiation detectors at HIMAC, NIRS, Japan, Loma Linda and Brookhaven, USA and CERN, Switzer-land since the start of the ICCHIBAN project in the year 2002. One of the main focus points of this project is to understand the response of the applied detector systems (either active or passive) for personal and area dosimetry in space environment to a simulated sub-set of the space radiation environment, focusing on the heavy ion response. This is of special importance for the further intercomparison of space radiation data gathered by various international in-stitutes and universities for space radiation experiments as MATROSHKA, DOSIS, DOBIES, BRADOS, MATROSHKA-R etc. The ICCHIBAN experiments have created a big database of response data, especially for all the different passive radiation detectors and detector materials (Thermoluminescence (TLD) and Optical Luminescence (OSL)) over the last 7 years, resulting in a better understanding of how and why we still have differences in the measurement results from common space experiments -as the Space ICCHIBAN 2 experiment. One of the reasons why for the differences in the TLD/OSL results is the lack of intercomparison and response data for low LET particles up to around 10 keV/m, especially protons. Due to the fact, that the main contribution to absorbed dose in low earth orbit is due to protons, the ICCHIBAN working group has started the set-up of a Proton ICCHIBAN intercomparison experiment at NIRS. The Proton ICCHIBAN run has been performed at the cyclotron at NIRS, Chiba in February 2010. 15 institutes from 12 countries sent or brought their dosimeters and exposed them to 40 and 70 MeV proton beams with the same doses and exposure conditions. In this paper, the experiment procedures and current situation of the intercomparision experiments will be shown.

An international marine-atmospheric {sup 222}Rn measurement intercomparison in Bermuda. Part 2: Results for the participating laboratories

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

Colle, R.; Unterweger, M.P.; Hutchinson, J.M.R.

1996-01-01

As part of an international measurement intercomparison of instruments used to measure atmospheric {sup 222}Rn, four participating laboratories made nearly simultaneous measurements of {sup 222}Rn activity concentration in commonly sampled, ambient air over approximately a 2 week period, and three of these four laboratories participated in the measurement comparison of 14 introduced samples with known, but undisclosed (blind) {sup 222}Rn activity concentration. The exercise was conducted in Bermuda in October 1991. The {sup 222}Rn activity concentrations in ambient Bermudian air over the course of the intercomparison ranged from a few hundredths of a Bq {center_dot} m{sup {minus}3} to about 2more » Bq {center_dot} m{sup {minus}3}, while the standardized sample additions covered a range from approximately 2.5 Bq {center_dot} m{sup {minus}3} to 35 Bq {center_dot} m{sup {minus}3}. The overall uncertainty in the latter concentrations was in the general range of 10%, approximating a 3 standard deviation uncertainty interval. The results of the intercomparison indicated that two of the laboratories were within very good agreement with the standard additions, and almost within expected statistical variations. These same two laboratories, however, at lower ambient concentrations, exhibited a systematic difference with an averaged offset of roughly 0.3 Bq {center_dot} m{sup {minus}3}. The third laboratory participating in the measurement of standardized sample additions was systematically low by about 65% to 70%, with respect to the standard addition which was also confirmed in their ambient air concentration measurements. The fourth laboratory, participating in only the ambient measurement part of the intercomparison, was also systematically low by at least 40% with respect to the first two laboratories.« less

Intercomparison measurements with energy deposition spectrometer Liulin and TEPC Hawk at HIMAC, and related calculations with PHITS

NASA Astrophysics Data System (ADS)

Ploc, Ondrej; Uchihori, Yukio; Kitamura, H.; Kodaira, S.; Dachev, Tsvetan; Spurny, Frantisek; Jadrnickova, Iva; Mrazova, Zlata; Kubancak, Jan

Liulin type detectors are recently used in a wide range of cosmic radiation measurements, e.g. at alpine observatories, onboard aircrafts and spacecrafts. They provide energy deposition spectra up to 21 MeV, higher energy deposition events are stored in the last (overflow) channel. Their main advantages are portability (about the same size as a pack of cigarettes) and ability to record spectra as a function of time, so they can be used as personal dosimeters. Their well-known limitations are: (i) the fact that they are not tissue equivalent, (ii) they can be used as LET spectrometer only under specific conditions (e.g. broad parallel beam), and (iii) that the energy deposition event from particles of LETH20¿35 keV/µm is stored in the overflow bin only so the spectral information is missing. Tissue equivalent proportional counter (TEPC) Hawk has no of these limitations but on the other hand, it cannot be used as personal dosimeter because of its big size (cylinder of 16 cm diameter and 34 cm long). An important fraction of dose equivalent onboard spacecrafts is caused by heavy ions. This contribution presents results from intercomparison measurements with Liulin and Hawk at Heavy Ion Medical Accelerator in Chiba (HIMAC) and cyclotron beams, and related calculations with PHITS (Particle and Heavy-ion Transport code System). Following particles/ions and energies were used: protons 70 MeV, He 150 MeV, Ne 400 MeV, C 135 MeV, C 290 MeV, and Fe 500 MeV. Calculations of LET spectra by PHITS were performed for both, Liulin and Hawk. In case of Liulin, the dose equivalent was calculated using simulations in which several tissue equivalent materials were used as active volume instead of the silicon diode. Dose equivalents calculated in such way was compared with that measured with Hawk. LET spectra measured with Liulin and Hawk were compared for each ion at several points behind binary filters along the Brag curve. Good agreement was observed for some configurations; for the other configurations, the difference was reasonably described (e.g. thickness of stainless steel of TEPC wall and size of Hawk's active volume).

Models and Measurements Intercomparison 2

NASA Technical Reports Server (NTRS)

Park, Jae H. (Editor); Ko, Malcolm K. W. (Editor); Jackman, Charles H. (Editor); Plumb, R. Alan (Editor); Kaye, Jack A. (Editor); Sage, Karen H. (Editor)

1999-01-01

Models and Measurement Intercomparison II (MM II) summarizes the intercomparison of results from model simulations and observations of stratospheric species. Representatives from twenty-three modeling groups using twenty-nine models participated in these MM II exercises between 1996 and 1999. Twelve of the models were two- dimensional zonal-mean models while seventeen were three-dimensional models. This was an international effort as seven were from outside the United States. Six transport experiments and five chemistry experiments were designed for various models. Models participating in the transport experiments performed simulations of chemically inert tracers providing diagnostics for transport. The chemistry experiments involved simulating the distributions of chemically active trace cases including ozone. The model run conditions for dynamics and chemistry were prescribed in order to minimize the factors that caused differences in the models. The report includes a critical review of the results by the participants and a discussion of the causes of differences between modeled and measured results as well as between results from different models, A sizable effort went into preparation of the database of the observations. This included a new climatology for ozone. The report should help in evaluating the results from various predictive models for assessing humankind perturbations of the stratosphere.

The Second Cabauw Intercomparison of Nitrogen Dioxide Measuring Instruments (CINDI-2)

NASA Astrophysics Data System (ADS)

Van Roozendael, M.; Hendrick, F.; Apituley, A.; Kreher, K.; Friess, U.; Richter, A.; Wagner, T.; Fehr, T.

2017-12-01

For the validation of space borne UV-Vis observations of air quality gases, ground based remote-sensing instruments using the MAXDOAS technique are an excellent choice, since they rely on similar retrieval techniques as the observations from orbit. Over the last decade, MAXDOAS instruments of various designs (including PANDORA systems) have been deployed worldwide forming the basis for a global ground based reference network suitable for the validation of future satellite sensors, such as TROPOMI/Sentinel-5 precursor, GEMS, TEMPO, and Sentinel 4 and 5. To ensure proper traceability of these observations, assess their accuracy and progress towards harmonized data acquisition and delivery, a thorough intercomparison campaign known as the Second Cabauw Intercomparison of Nitrogen Dioxide Measuring Instruments (CINDI-2) was held in Cabauw, The Netherlands during the month of September 2016. About 35 MAXDOAS instruments operated by 25 different groups were deployed, together with systems providing key ancillary in-situ measurements of NO2 and aerosol optical properties, as well as vertical profiles of NO2 by lidar and sonde and vertical profiles of aerosol optical properties by Raman lidar. We provide an overview of the main outcome of the campaign, which included a formal semi-blind slant column intercomparison and a number of additional exercises aiming at assessing the potential of the MAXDOAS technique for retrieving vertically-resolved information on NO2, aerosol, HCHO, O3 and a few other more challenging species such as HONO and glyoxal.

FIRST EURADOS INTERCOMPARISON EXERCISE OF EYE LENS DOSEMETERS FOR MEDICAL APPLICATIONS.

PubMed

Clairand, I; Ginjaume, M; Vanhavere, F; Carinou, E; Daures, J; Denoziere, M; Silva, E H; Roig, M; Principi, S; Van Rycheghem, L

2016-09-01

In the context of the decrease in the eye lens dose limit for occupational exposure to 20 mSv per year stated by the recent revision of the European Basic Safety Standards Directive 2013/59/EURATOM, the European Radiation Dosimetry Group (EURADOS) has organised in 2014, for the first time, an intercomparison exercise for eye lens dosemeters. The main objective was to assess the capabilities of the passive eye lens dosemeters currently in use in Europe for occupational monitoring in medical fields. A total of 20 European individual monitoring services from 15 different countries have participated. The dosemeters provided by the participants were all composed of thermoluminescent detectors, of various types and designs. The irradiations were carried out with several photon fields chosen to cover the energy and angle ranges encountered in medical workplace. Participants were asked to report the doses in terms of Hp(3) using their routine protocol. The results provided by each participant were compared with the reference delivered doses. All the results were anonymously analysed. Results are globally satisfactory since, among the 20 participants, 17 were able to provide 90 % of their response in accordance with the ISO 14146 standard requirements. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Trends in ice sheet mass balance, 1992 to 2017

NASA Astrophysics Data System (ADS)

Shepherd, A.; Ivins, E. R.; Smith, B.; Velicogna, I.; Whitehouse, P. L.; Rignot, E. J.; van den Broeke, M. R.; Briggs, K.; Hogg, A.; Krinner, G.; Joughin, I. R.; Nowicki, S.; Payne, A. J.; Scambos, T.; Schlegel, N.; Moyano, G.; Konrad, H.

2017-12-01

The Ice Sheet Mass Balance Inter-Comparison Exercise (IMBIE) is a community effort, jointly supported by ESA and NASA, that aims to provide a consensus estimate of ice sheet mass balance from satellite gravimetry, altimetry and mass budget assessments, on an annual basis. The project has five experiment groups, one for each of the satellite techniques and two others to analyse surface mass balance (SMB) and glacial isostatic adjustment (GIA). The basic premise for the exercise is that individual ice sheet mass balance datasets are generated by project participants using common spatial and temporal domains to allow meaningful inter-comparison, and this controlled comparison in turn supports aggregation of the individual datasets over their full period. Participation is open to the full community, and the quality and consistency of submissions is regulated through a series of data standards and documentation requirements. The second phase of IMBIE commenced in 2015, with participant data submitted in 2016 and a combined estimate due for public release in 2017. Data from 48 participant groups were submitted to one of the three satellite mass balance technique groups or to the ancillary dataset groups. The individual mass balance estimates and ancillary datasets have been compared and combined within the respective groups. Following this, estimates of ice sheet mass balance derived from the individual techniques were then compared and combined. The result is single estimates of ice sheet mass balance for Greenland, East Antarctica, West Antarctica, and the Antarctic Peninsula. The participants, methodology and results of the exercise will be presented in this paper.

International Intercomparison Exercise for Nuclear Accident Dosimetry at the DAF Using GODIVA-IV

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

Hickman, David; Hudson, Becka

The Nuclear Criticality Safety Program operated under the direction of Dr. Jerry McKamy completed the first NNSA Nuclear Accident Dosimetry exercise on May 27, 2016. Participants in the exercise were from Lawrence Livermore National Laboratory (LLNL), Los Alamos National Laboratory (LANL), Sandia National Laboratory (SNL), Savanah River Site (SRS), Pacific Northwest National Laboratory (PNNL), US Navy, the Atomic Weapons Establishment (United Kingdom) under the auspices of JOWOG 30, and the Institute for Radiological Protection and Nuclear Safety (France) by special invitation and NCSP memorandum of understanding. This exercise was the culmination of a series of Integral Experiment Requests (IER) thatmore » included the establishment of the Nuclear Criticality Experimental Research Center, (NCERC) the startup of the Godiva Reactor (IER-194), the establishment of a the Nuclear Accident Dosimetry Laboratory (NAD LAB) in Mercury, NV, and the determination of reference dosimetry values for the mixed neutron and photon radiation field of Godiva within NCERC.« less

A quality assurance program for clinical PDT

NASA Astrophysics Data System (ADS)

Dimofte, Andreea; Finlay, Jarod; Ong, Yi Hong; Zhu, Timothy C.

2018-02-01

Successful outcome of Photodynamic therapy (PDT) depends on accurate delivery of prescribed light dose. A quality assurance program is necessary to ensure that light dosimetry is correctly measured. We have instituted a QA program that include examination of long term calibration uncertainty of isotropic detectors for light fluence rate, power meter head intercomparison for laser power, stability of the light-emitting diode (LED) light source integrating sphere as a light fluence standard, laser output and calibration of in-vivo reflective fluorescence and absorption spectrometers. We examined the long term calibration uncertainty of isotropic detector sensitivity, defined as fluence rate per voltage. We calibrate the detector using the known calibrated light fluence rate of the LED light source built into an internally baffled 4" integrating sphere. LED light sources were examined using a 1mm diameter isotropic detector calibrated in a collimated beam. Wavelengths varying from 632nm to 690nm were used. The internal LED method gives an overall calibration accuracy of +/- 4%. Intercomparison among power meters was performed to determine the consistency of laser power and light fluence rate measured among different power meters. Power and fluence readings were measured and compared among detectors. A comparison of power and fluence reading among several power heads shows long term consistency for power and light fluence rate calibration to within 3% regardless of wavelength. The standard LED light source is used to calibrate the transmission difference between different channels for the diffuse reflective absorption and fluorescence contact probe as well as isotropic detectors used in PDT dose dosimeter.

SU-E-T-506: Intercomparison Study On Small Field Output Factor Measurements

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

Talamonti, C; Casati, M; Compagnucci, A

2015-06-15

Purpose In radiotherapy, uncertainties due to small field measurements (SFM) introduce systematic errors to the treatment process and the development of new dosimeters for quality assurance programs is a challenge. In this work we analyze the behavior of seven detectors measuring output factors of 6MV photon beam. Methods The dosimeters employed are: a single cristal diamond detector (SCCD) developed at the University of Rome Tor Vergata, a silicon diode developed within the project MAESTRO, a IBA Razor silicon diode, A1SL and A26 Exradin ion chambers, an EBT3 Gafchromic film and the Exradin W1 Scintillator.Diamond sensitive volume is a cylinder 2.2mmmore » in diameter and 1μm thick. MAESTRO diode is 2×2mm2 active area. Razor sensitive volume is a cylinder 0.6 mm in diameter and 0.02 mm thick. A16 and A1Sl have a collecting volume of 0,015cc and 0,053cc. The W1 is an optical fiber with an active volume of 0.002cc. All measurements were performed in a water phantom, with detector positioned at the isocenter (SSD=90cm, d=10cm), MAESTRO diode being sandwiched in solid water to obtain an equivalent experimental setup. Results These measurements are challenging due to the absence of charged particle equilibrium conditions, detector size and positioning problems. They are in good agreement among each other, especially GAF, Razor, W1 and SCDD. Maximum deviations reported are related to the field 0.8×0.8cm2 for MAESTRO and chambers data with respect to EBT3: around 15% (A1SLvsEBT3), 16% (MAESTROvsEBT3). Razor and W1 show a deviation around 3% with respect to SCDD. Conclusion In this work measurements made with a variety of detectors are compared. These study show the possibility to choose different detectors for SFM and that smaller ion chambers are still not competitive with solid state detectors. Silicon, diamond and optical fiber dosimeters show a similar behavior with minor discrepancies for the smallest field.« less

The InterFrost benchmark of Thermo-Hydraulic codes for cold regions hydrology - first inter-comparison phase results

NASA Astrophysics Data System (ADS)

Grenier, Christophe; Rühaak, Wolfram

2016-04-01

Climate change impacts in permafrost regions have received considerable attention recently due to the pronounced warming trends experienced in recent decades and which have been projected into the future. Large portions of these permafrost regions are characterized by surface water bodies (lakes, rivers) that interact with the surrounding permafrost often generating taliks (unfrozen zones) within the permafrost that allow for hydrologic interactions between the surface water bodies and underlying aquifers and thus influence the hydrologic response of a landscape to climate change. Recent field studies and modeling exercises indicate that a fully coupled 2D or 3D Thermo-Hydraulic (TH) approach is required to understand and model past and future evolution such units (Kurylyk et al. 2014). However, there is presently a paucity of 3D numerical studies of permafrost thaw and associated hydrological changes, which can be partly attributed to the difficulty in verifying multi-dimensional results produced by numerical models. A benchmark exercise was initialized at the end of 2014. Participants convened from USA, Canada, Europe, representing 13 simulation codes. The benchmark exercises consist of several test cases inspired by existing literature (e.g. McKenzie et al., 2007) as well as new ones (Kurylyk et al. 2014; Grenier et al. in prep.; Rühaak et al. 2015). They range from simpler, purely thermal 1D cases to more complex, coupled 2D TH cases (benchmarks TH1, TH2, and TH3). Some experimental cases conducted in a cold room complement the validation approach. A web site hosted by LSCE (Laboratoire des Sciences du Climat et de l'Environnement) is an interaction platform for the participants and hosts the test case databases at the following address: https://wiki.lsce.ipsl.fr/interfrost. The results of the first stage of the benchmark exercise will be presented. We will mainly focus on the inter-comparison of participant results for the coupled cases TH2 & TH3. Both cases are essentially theoretical but include the full complexity of the coupled non-linear set of equations (heat transfer with conduction, advection, phase change and Darcian flow). The complete set of inter-comparison results shows that the participating codes all produce simulations which are quantitatively similar and correspond to physical intuition. From a quantitative perspective, they agree well over the whole set of performance measures. The differences among the simulation results will be discussed in more depth throughout the test cases especially for the identification of the threshold times for each system as these exhibited the least agreement. However, the results suggest that in spite of the difficulties associated with the resolution of the set of TH equations (coupled and non-linear structure with phase change providing steep slopes), the developed codes provide robust results with a qualitatively reasonable representation of the processes and offer a quantitatively realistic basis. Further perspectives of the exercise will also be presented.

Intercomparison of active, passive and continuous instruments for radon and radon progeny measurements in the EML chamber and test facility

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

Scarpitta, S.C.; Tu, K.W.; Fisenne, I.M.

1996-10-01

Results are presented from the Fifth Intercomparison of Active, Passive and Continuous Instruments for Radon and Radon Progeny Measurements conducted in the EML radon exposure and test facility in May 1996. In total, thirty-four government, private and academic facilities participated in the exercise with over 170 passive and electronic devices exposed in the EML test chamber. During the first week of the exercise, passive and continuous measuring devices were exposed (usually in quadruplicate) to about 1,280 Bq m{sup {minus}3} {sup 222}Rn for 1--7 days. Radon progeny measurements were made during the second week of the exercise. The results indicate thatmore » all of the tested devices that measure radon gas performed well and fulfill their intended purpose. The grand mean (GM) ratio of the participants` reported values to the EML values, for all four radon device categories, was 0.99 {plus_minus} 0.08. Eighty-five percent of all the radon measuring devices that were exposed in the EML radon test chamber were within {plus_minus}1 standard deviation (SD) of the EML reference values. For the most part, radon progeny measurements were also quite good as compared to the EML values. The GM ratio for the 10 continuous PAEC instruments was 0.90 {plus_minus} 0.12 with 75% of the devices within 1 SD of the EML reference values. Most of the continuous and integrating electronic instruments used for measuring the PAEC underestimated the EML values by about 10--15% probably because the concentration of particles onto which the radon progeny were attached was low (1,200--3,800 particles cm{sup {minus}3}). The equilibrium factor at that particle concentration level was 0.10--0.22.« less

Intercomparison of two comparative reactivity method instruments inf the Mediterranean basin during summer 2013

NASA Astrophysics Data System (ADS)

Zannoni, N.; Dusanter, S.; Gros, V.; Sarda Esteve, R.; Michoud, V.; Sinha, V.; Locoge, N.; Bonsang, B.

2015-09-01

The hydroxyl radical (OH) plays a key role in the atmosphere, as it initiates most of the oxidation processes of volatile organic compounds (VOCs), and can ultimately lead to the formation of ozone and secondary organic aerosols (SOAs). There are still uncertainties associated with the OH budget assessed using current models of atmospheric chemistry and direct measurements of OH sources and sinks have proved to be valuable tools to improve our understanding of the OH chemistry. The total first order loss rate of OH, or total OH reactivity, can be directly measured using three different methods, such as the following: total OH loss rate measurement, laser-induced pump and probe technique and comparative reactivity method. Observations of total OH reactivity are usually coupled to individual measurements of reactive compounds in the gas phase, which are used to calculate the OH reactivity. Studies using the three methods have highlighted that a significant fraction of OH reactivity is often not explained by individually measured reactive compounds and could be associated to unmeasured or unknown chemical species. Therefore accurate and reproducible measurements of OH reactivity are required. The comparative reactivity method (CRM) has demonstrated to be an advantageous technique with an extensive range of applications, and for this reason it has been adopted by several research groups since its development. However, this method also requires careful corrections to derive ambient OH reactivity. Herein we present an intercomparison exercise of two CRM instruments, CRM-LSCE (Laboratoire des Sciences du Climat et de l'Environnement) and CRM-MD (Mines Douai), conducted during July 2013 at the Mediterranean site of Ersa, Cape Corsica, France. The intercomparison exercise included tests to assess the corrections needed by the two instruments to process the raw data sets as well as OH reactivity observations. The observation was divided in three parts: 2 days of plant emissions (8-9 July), 2 days of ambient measurements (10-11 July) and 2 days (12-13 July) of plant emissions. We discuss in detail the experimental approach adopted and how the data sets were processed for both instruments. Corrections required for the two instruments lead to higher values of reactivity in ambient air; overall 20 % increase for CRM-MD and 49 % for CRM-LSCE compared to the raw data. We show that ambient OH reactivity measured by the two instruments agrees very well (correlation described by a linear least squares fit with a slope of 1 and R2 of 0.75). This study highlights that ambient measurements of OH reactivity with differently configured CRM instruments yield consistent results in a low NOx (NO + NO2), terpene rich environment, despite differential corrections relevant to each instrument. Conducting more intercomparison exercises, involving more CRM instruments operated under different ambient and instrumental settings will help in assessing the variability induced due to instrument-specific corrections further.

Dosimetry audits and intercomparisons in radiotherapy: A Malaysian profile

NASA Astrophysics Data System (ADS)

M. Noor, Noramaliza; Nisbet, A.; Hussein, M.; Chu S, Sarene; Kadni, T.; Abdullah, N.; Bradley, D. A.

2017-11-01

Quality audits and intercomparisons are important in ensuring control of processes in any system of endeavour. Present interest is in control of dosimetry in teletherapy, there being a need to assess the extent to which there is consistent radiation dose delivery to the patient. In this study we review significant factors that impact upon radiotherapy dosimetry, focusing upon the example situation of radiotherapy delivery in Malaysia, examining existing literature in support of such efforts. A number of recommendations are made to provide for increased quality assurance and control. In addition to this study, the first level of intercomparison audit i.e. measuring beam output under reference conditions at eight selected Malaysian radiotherapy centres is checked; use being made of 9 μm core diameter Ge-doped silica fibres (Ge-9 μm). The results of Malaysian Secondary Standard Dosimetry Laboratory (SSDL) participation in the IAEA/WHO TLD postal dose audit services during the period between 2011 and 2015 will also been discussed. In conclusion, following review of the development of dosimetry audits and the conduct of one such exercise in Malaysia, it is apparent that regular periodic radiotherapy audits and intercomparison programmes should be strongly supported and implemented worldwide. The programmes to-date demonstrate these to be a good indicator of errors and of consistency between centres. A total of ei+ght beams have been checked in eight Malaysian radiotherapy centres. One out of the eight beams checked produced an unacceptable deviation; this was found to be due to unfamiliarity with the irradiation procedures. Prior to a repeat measurement, the mean ratio of measured to quoted dose was found to be 0.99 with standard deviation of 3%. Subsequent to the repeat measurement, the mean distribution was 1.00, and the standard deviation was 1.3%.

Characterisation of a reference site for quantifying uncertainties related to soil sampling.

PubMed

Barbizzi, Sabrina; de Zorzi, Paolo; Belli, Maria; Pati, Alessandra; Sansone, Umberto; Stellato, Luisa; Barbina, Maria; Deluisa, Andrea; Menegon, Sandro; Coletti, Valter

2004-01-01

The paper reports a methodology adopted to face problems related to quality assurance in soil sampling. The SOILSAMP project, funded by the Environmental Protection Agency of Italy (APAT), is aimed at (i) establishing protocols for soil sampling in different environments; (ii) assessing uncertainties associated with different soil sampling methods in order to select the "fit-for-purpose" method; (iii) qualifying, in term of trace elements spatial variability, a reference site for national and international inter-comparison exercises. Preliminary results and considerations are illustrated.

Intercomparison of HONO Measurements Made Using Wet-Chemical (NITROMAC) and Spectroscopic (IBBCEAS & LP/FAGE) Techniques

NASA Astrophysics Data System (ADS)

Dusanter, S.; Lew, M.; Bottorff, B.; Bechara, J.; Mielke, L. H.; Berke, A.; Raff, J. D.; Stevens, P. S.; Afif, C.

2013-12-01

A good understanding of the oxidative capacity of the atmosphere is important to tackle fundamental issues related to climate change and air quality. The hydroxyl radical (OH) is the dominant oxidant in the daytime troposphere and an accurate description of its sources in atmospheric models is of utmost importance. Recent field studies indicate higher-than-expected concentrations of HONO during the daytime, suggesting that the photolysis of HONO may be an important underestimated source of OH. Understanding the tropospheric HONO budget requires confidence in analytical instrumentation capable of selectively measuring HONO. In this presentation, we discuss an intercomparison study of HONO measurements performed during summer 2013 at the edge of a hardwood forest in Southern Indiana. This exercise involved a wet chemical technique (NITROMAC), an Incoherent Broad-Band Cavity Enhanced Absorption Spectroscopy instrument (IBBCEAS), and a Laser-Photofragmentation/Fluorescence Assay by Gas Expansion instrument (LP/FAGE). The agreement observed between the three techniques will be discussed for both ambient measurements and cross calibration experiments.

Validation of 131I ecological transfer models and thyroid dose assessments using Chernobyl fallout data from the Plavsk district, Russia

PubMed Central

Zvonova, I.; Krajewski, P.; Berkovsky, V.; Ammann, M.; Duffa, C.; Filistovic, V.; Homma, T.; Kanyar, B.; Nedveckaite, T.; Simon, S.L.; Vlasov, O.; Webbe-Wood, D.

2009-01-01

Within the project “Environmental Modelling for Radiation Safety” (EMRAS) organized by the IAEA in 2003 experimental data of 131I measurements following the Chernobyl accident in the Plavsk district of Tula region, Russia were used to validate the calculations of some radioecological transfer models. Nine models participated in the inter-comparison. Levels of 137Cs soil contamination in all the settlements and 131I/137Cs isotopic ratios in the depositions in some locations were used as the main input information. 370 measurements of 131I content in thyroid of townspeople and villagers, and 90 measurements of 131I concentration in milk were used for validation of the model predictions. A remarkable improvement in models performance comparing with previous inter-comparison exercise was demonstrated. Predictions of the various models were within a factor of three relative to the observations, discrepancies between the estimates of average doses to thyroid produced by most participant not exceeded a factor of ten. PMID:19783331

Bilateral Comparison of Mercury and Gallium Fixed-Point Cells Using Standard Platinum Resistance Thermometer

NASA Astrophysics Data System (ADS)

Bojkovski, J.; Veliki, T.; Zvizdić, D.; Drnovšek, J.

2011-08-01

The objective of project EURAMET 1127 (Bilateral comparison of triple point of mercury and melting point of gallium) in the field of thermometry is to compare realization of a triple point of mercury (-38.8344 °C) and melting point of gallium (29.7646 °C) between the Slovenian national laboratory MIRS/UL-FE/LMK and the Croatian national laboratory HMI/FSB-LPM using a long-stem 25 Ω standard platinum resistance thermometer (SPRT). MIRS/UL/FE-LMK participated in a number of intercomparisons on the level of EURAMET. On the other hand, the HMI/LPM-FSB laboratory recently acquired new fixed-point cells which had to be evaluated in the process of intercomparisons. A quartz-sheathed SPRT has been selected and calibrated at HMI/LPM-FSB at the triple point of mercury, the melting point of gallium, and the water triple point. A second set of measurements was made at MIRS/UL/FE-LMK. After its return, the SPRT was again recalibrated at HMI/LPM-FSB. In the comparison, the W value of the SPRT has been used. Results of the bilateral intercomparison confirmed that the new gallium cell of the HMI/LPM-FSB has a value that is within uncertainty limits of both laboratories that participated in the exercise, while the mercury cell experienced problems. After further research, a small leakage in the mercury fixed-point cell has been found.

Investigation and Implementation of Commercially Available Optically Stimulated Luminescence Dosimeters for Use in Fixed Nuclear Accident Dosimeter Systems.

PubMed

Georgeson, David L; Christiansen, Byron H

2018-06-01

Idaho National Laboratory transitioned from an external dosimetry system reliant on thermoluminescent dosimeters to one that uses optically stimulated luminescence dosimeters in 2010. This change not only affected the dosimeters worn by personnel, but those found in the nuclear-accident dosimeters used across Idaho National Laboratory. The elimination of on-site use and processing of thermoluminescent dosimeters impacted Idaho National Laboratory's ability to process nuclear-accident dosimeters in a timely manner. This change in processes drove Idaho National Laboratory to develop an alternative method for fixed nuclear-accident dosimeter gamma-dose analyses. This new method was driven by the need to establish a simple, cost-effective, and rapid-turnaround alternative to the thermoluminescent-dosimeter-based fixed nuclear-accident dosimeter system. An adaptation of existing technologies proved to be the most efficient path to this end. The purpose of this article is to delineate the technical basis for replacing the thermoluminescent dosimeter contained within the Idaho National Laboratory fixed nuclear-accident dosimeter system with optically stimulated luminescence-based Landauer, Inc., nanoDot dosimeters.

Radiation dosimeters

DOEpatents

Hoelsher, James W.; Hegland, Joel E.; Braunlich, Peter F.; Tetzlaff, Wolfgang

1992-01-01

Radiation dosimeters and dosimeter badges. The dosimeter badges include first and second parts which are connected to join using a securement to produce a sealed area in which at least one dosimeter is held and protected. The badge parts are separated to expose the dosimeters to a stimulating laser beam used to read dose exposure information therefrom. The badge is constructed to allow automated disassembly and reassembly in a uniquely fitting relationship. An electronic memory is included to provide calibration and identification information used during reading of the dosimeter. Dosimeter mounts which reduce thermal heating requirements are shown. Dosimeter constructions and production methods using thin substrates and phosphor binder-layers applied thereto are also taught.

Composite material dosimeters

DOEpatents

Miller, Steven D.

1996-01-01

The present invention is a composite material containing a mix of dosimeter material powder and a polymer powder wherein the polymer is transparent to the photon emission of the dosimeter material powder. By mixing dosimeter material powder with polymer powder, less dosimeter material is needed compared to a monolithic dosimeter material chip. Interrogation is done with excitation by visible light.

WE-D-17A-05: Measurement of Stray Radiation Within An Active Scanning Proton Therapy Facility: EURADOS WG9 Intercomparison Exercise of Active Dosimetry Systems

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

Farah, J; Trompier, F; Stolarczyk, L

2014-06-15

Purpose: Intercomparison of active dosemeters in the measurement of stray radiation at the Trento active-scanning proton therapy facility. Methods: EURADOS WG9 carried out a large intercomparison exercise to test different dosemeters while measuring secondary neutrons within a 230 MeV scanned proton therapy facility. Detectors included two Bonner Sphere Spectrometers (BSS), three tissue equivalent proportional counters (TEPCHawk) and six rem-counters (Wendi II, Berthold, RadEye, a regular and an extended-range Anderson and Braun NM2B counters). Measurements of neutron ambient dose equivalents, H*(10), were done at several positions inside (8 positions) and outside (3 positions) the treatment room while irradiating a water tankmore » phantom with a 10 × 10 × 10 cc field. Results: A generally good agreement on H*(10) values was observed for the tested detectors. At distance of 2.25 m and angles 45°, 90° and 180° with respect to the beam axis, BSS and proportional counters agreed within 30%. Higher differences (up to 60%) were observed at the closest and farthest distances, i.e. at positions where detectors sensitivity, energy, fluence and angular response are highly dependent on neutron spectra (flux and energy). The highest neutron H*(10) value, ∼60 microSv/Gy, was measured at 1.15 m along the beam axis. H*(10) decreased significantly with the distance from the isocenter dropping to 1.1 microSv/Gy at 4.25 m and 90° from beam axis, ∼2 nanoSv/Gy at the entrance of the maze, 0.2 nanoSv/Gy at the door outside the room and below detection limit in the gantry control room and at an adjacent room. These values remain considerately lower than those of passively scattered proton beams. BSS and Hawk unfolded spectra provide valuable inputs when studying the response of each detector. Conclusion: TEPCs and BSS enable accurate measurements of stray neutrons while other rem-meters also give satisfactory results but require further improvements to reduce uncertainties.« less

Dosimetry in dentistry.

PubMed

Asha, M L; Chatterjee, Ingita; Patil, Preeti; Naveen, S

2015-01-01

The purpose of this paper was to review various dosimeters used in dentistry and the cumulative results of various studies done with various dosimeters. Several relevant PubMed indexed articles from 1999 to 2013 were electronically searched by typing "dosimeters", "dosimeters in dentistry", "properties of dosimeters", "thermoluminescent and optically stimulated dosimeters", "recent advancements in dosimetry in dentistry." The searches were limited to articles in English to prepare a concise review on dental dosimetry. Titles and abstracts were screened, and articles that fulfilled the criteria of use of dosimeters in dental applications were selected for a full-text reading. Article was divided into four groups: (1) Biological effects of radiation, (2) properties of dosimeters, (3) types of dosimeters and (4) results of various studies using different dosimeters. The present review on dosimetry based on various studies done with dosimeters revealed that, with the advent of radiographic technique the effective dose delivered is low. Therefore, selection of radiological technique plays an important role in dental dose delivery.

SOLID-STATE DOSIMETERS BASED ON OPTICAL THEORY (in Hungarian)

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

Patko, J.

1962-01-01

A comparison is made of applications of various dosimeters based on solid materials, and their comparative merits are described. Characteristics of the following types of dosimeters effective at various radiation intensities are discussed: condensation chambers for measurements over the range 10/sup -4/-10/ sup 2/ rad, film dosimeters 10/sup -1/-10/sup 5/ rad, thermoluminescent types 10/ sup -3/ - 10/sup 4/ rad, photoluminescent dosimeters 10/sup 1/-- 10/sup 4/ rad, crystal types 10/sup 1/- 10/sup 4/ rad, glass dosimeters 10/sup 3/- 10/sup 7/ rad, synthetic material types 10/sup 5/- 10/sup 9/ rad, and luminescent degradation dosimeters 10/sup 5/-10/sup 8/ rad. Special attention ismore » given to the thermoluminescent dosimeter, which utilizes Mn-activated Ca phosphate. This dosimeter utilizes a glass ampulla instead of a glass vacuum tube and polarography is used to determine the luminescence curve. Simple evaluation equipment is being developed to be used with this dosimeter. Such thermoluminescent dosimeters are generally small in size. Its high sensitivity makes it applicable to low intensity radiation aad after calibration it can again be utilized. Manganese-activated Ca phosphate dosimeters do not show any fading of response in the first hour after use. Use of solid dosimeters, for high- energy measurements« less

[Measurement of the air kerma using dosimeters embedded in an acrylic phantom in interventional radiology.].

PubMed

Kawabe, Atsushi; Shibuya, Koichi; Takeda, Yoshihiro

2006-01-01

Interventional radiology procedure guidelines and a measurement manual (IVR guidelines) have been published for the maintenance of interventional equipment with an objective of avoiding serious radiation-induced skin injuries. In the IVR guidelines, the positioning of a dosimeter at the interventional reference point is determined, whereas placement of a phantom is not specified. Therefore, the phantom is placed at any convenient location between the dosimeter and image intensifier. The space around the dosimeter reduces detection of scattered radiation. In this study, dosimeters (consisting of a parallel plate ionization chamber, glass dosimeter and OSL dosimeter) were embedded in the phantom surface to detected scattered radiation accurately. As a result, when dosimeters were embedded in the phantom surface, the air kerma was increased compared with that when dosimeters were placed on the phantom. This suggested that embedded dosimeters were able to detect scattered radiation from the phantom.

Development and evaluation of polycrystalline cadmium telluride dosimeters for accurate quality assurance in radiation therapy

NASA Astrophysics Data System (ADS)

Oh, K.; Han, M.; Kim, K.; Heo, Y.; Moon, C.; Park, S.; Nam, S.

2016-02-01

For quality assurance in radiation therapy, several types of dosimeters are used such as ionization chambers, radiographic films, thermo-luminescent dosimeter (TLD), and semiconductor dosimeters. Among them, semiconductor dosimeters are particularly useful for in vivo dosimeters or high dose gradient area such as the penumbra region because they are more sensitive and smaller in size compared to typical dosimeters. In this study, we developed and evaluated Cadmium Telluride (CdTe) dosimeters, one of the most promising semiconductor dosimeters due to their high quantum efficiency and charge collection efficiency. Such CdTe dosimeters include single crystal form and polycrystalline form depending upon the fabrication process. Both types of CdTe dosimeters are commercially available, but only the polycrystalline form is suitable for radiation dosimeters, since it is less affected by volumetric effect and energy dependence. To develop and evaluate polycrystalline CdTe dosimeters, polycrystalline CdTe films were prepared by thermal evaporation. After that, CdTeO3 layer, thin oxide layer, was deposited on top of the CdTe film by RF sputtering to improve charge carrier transport properties and to reduce leakage current. Also, the CdTeO3 layer which acts as a passivation layer help the dosimeter to reduce their sensitivity changes with repeated use due to radiation damage. Finally, the top and bottom electrodes, In/Ti and Pt, were used to have Schottky contact. Subsequently, the electrical properties under high energy photon beams from linear accelerator (LINAC), such as response coincidence, dose linearity, dose rate dependence, reproducibility, and percentage depth dose, were measured to evaluate polycrystalline CdTe dosimeters. In addition, we compared the experimental data of the dosimeter fabricated in this study with those of the silicon diode dosimeter and Thimble ionization chamber which widely used in routine dosimetry system and dose measurements for radiation therapy.

Fundamentals of Polymer Gel Dosimeters

NASA Astrophysics Data System (ADS)

McAuley, Kim B.

2006-12-01

The recent literature on polymer gel dosimetry contains application papers and basic experimental studies involving polymethacrylic-acid-based and polyacrylamide-based gel dosimeters. The basic studies assess the relative merits of these two most commonly used dosimeters, and explore the effects of tetrakis hydroxymethyl phosphonium chloride (THPC) antioxidant on dosimeter performance. Polymer gel dosimeters that contain THPC or other oxygen scavengers are called normoxic dosimeters, because they can be prepared under normal atmospheric conditions, rather than in a glove box that excludes oxygen. In this review, an effort is made to explain some of the underlying chemical phenomena that affect dosimeter performance using THPC, and that lead to differences in behaviour between dosimeters made using the two types of monomer systems. Progress on the development of new more effective and less toxic dosimeters is also reported.

Development and characterization of a three-dimensional radiochromic film stack dosimeter for megavoltage photon beam dosimetry.

PubMed

McCaw, Travis J; Micka, John A; DeWerd, Larry A

2014-05-01

Three-dimensional (3D) dosimeters are particularly useful for verifying the commissioning of treatment planning and delivery systems, especially with the ever-increasing implementation of complex and conformal radiotherapy techniques such as volumetric modulated arc therapy. However, currently available 3D dosimeters require extensive experience to prepare and analyze, and are subject to large measurement uncertainties. This work aims to provide a more readily implementable 3D dosimeter with the development and characterization of a radiochromic film stack dosimeter for megavoltage photon beam dosimetry. A film stack dosimeter was developed using Gafchromic(®) EBT2 films. The dosimeter consists of 22 films separated by 1 mm-thick spacers. A Virtual Water™ phantom was created that maintains the radial film alignment within a maximum uncertainty of 0.3 mm. The film stack dosimeter was characterized using simulations and measurements of 6 MV fields. The absorbed-dose energy dependence and orientation dependence of the film stack dosimeter were investigated using Monte Carlo simulations. The water equivalence of the dosimeter was determined by comparing percentage-depth-dose (PDD) profiles measured with the film stack dosimeter and simulated using Monte Carlo methods. Film stack dosimeter measurements were verified with thermoluminescent dosimeter (TLD) microcube measurements. The film stack dosimeter was also used to verify the delivery of an intensity-modulated radiation therapy (IMRT) procedure. The absorbed-dose energy response of EBT2 film differs less than 1.5% between the calibration and film stack dosimeter geometries for a 6 MV spectrum. Over a series of beam angles ranging from normal incidence to parallel incidence, the overall variation in the response of the film stack dosimeter is within a range of 2.5%. Relative to the response to a normally incident beam, the film stack dosimeter exhibits a 1% under-response when the beam axis is parallel to the film planes. Measured and simulated PDD profiles agree within a root-mean-square difference of 1.3%. In-field film stack dosimeter and TLD measurements agree within 5%, and measurements in the field penumbra agree within 0.5 mm. Film stack dosimeter and TLD measurements have expanded (k = 2) overall measurement uncertainties of 6.2% and 5.8%, respectively. Film stack dosimeter measurements of an IMRT dose distribution have 98% agreement with the treatment planning system dose calculation, using gamma criteria of 3% and 2 mm. The film stack dosimeter is capable of high-resolution, low-uncertainty 3D dose measurements, and can be readily incorporated into an existing film dosimetry program.

AN INTERLABORATORY COMPARISON ON THE DETERMINATION OF 241Am, 244Cm AND 252Cf IN URINE.

PubMed

Gerstmann, Udo C; Taubner, Kerstin; Hartmann, Martina

2016-09-01

An intercomparison exercise on the determination of (241)Am, (244)Cm and (252)Cf in urine was performed. Since it was designed with regard to emergency preparedness, the detection limit for each nuclide was set to 0.1 Bq per 24-h urine sample. Most of the participating laboratories were established bioassay laboratories. However, some laboratories that routinely determine (241)Am only in environmental samples were also invited in order to explore their potential for emergency bioassay analysis. Another aspect of the intercomparison was to investigate the performance of all laboratories concerning the chemical yields of the (243)Am tracer in comparison with (244)Cm and (252)Cf. In summary, both types of laboratories showed good results. There was a negative bias for the results of (244)Cm and (252)Cf, which can be explained by slightly different radiochemical behaviours of americium, curium and californium and which is in agreement with results reported in the literature. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Emergency radiobioassay preparedness exercises through the NIST radiochemistry intercomparison program.

PubMed

Nour, Svetlana; LaRosa, Jerry; Inn, Kenneth G W

2011-08-01

The present challenge for the international emergency radiobioassay community is to analyze contaminated samples rapidly while maintaining high quality results. The National Institute of Standards and Technology (NIST) runs a radiobioassay measurement traceability testing program to evaluate the radioanalytical capabilities of participating laboratories. The NIST Radiochemistry Intercomparison Program (NRIP) started more than 10 years ago, and emergency performance testing was added to the program seven years ago. Radiobioassay turnaround times under the NRIP program for routine production and under emergency response scenarios are 60 d and 8 h, respectively. Because measurement accuracy and sample turnaround time are very critical in a radiological emergency, response laboratories' analytical systems are best evaluated and improved through traceable Performance Testing (PT) programs. The NRIP provides participant laboratories with metrology tools to evaluate their performance and to improve it. The program motivates the laboratories to optimize their methodologies and minimize the turnaround time of their results. Likewise, NIST has to make adjustments and periodical changes in the bioassay test samples in order to challenge the participating laboratories continually. With practice, radioanalytical measurements turnaround time can be reduced to 3-4 h.

Feasibility Study on Applying Radiophotoluminescent Glass Dosimeters for CyberKnife SRS Dose Verification

PubMed Central

Hsu, Shih-Ming; Hung, Chao-Hsiung; Liao, Yi-Jen; Fu, Hsiao-Mei; Tsai, Jo-Ting

2017-01-01

CyberKnife is one of multiple modalities for stereotactic radiosurgery (SRS). Due to the nature of CyberKnife and the characteristics of SRS, dose evaluation of the CyberKnife procedure is critical. A radiophotoluminescent glass dosimeter was used to verify the dose accuracy for the CyberKnife procedure and validate a viable dose verification system for CyberKnife treatment. A radiophotoluminescent glass dosimeter, thermoluminescent dosimeter, and Kodak EDR2 film were used to measure the lateral dose profile and percent depth dose of CyberKnife. A Monte Carlo simulation for dose verification was performed using BEAMnrc to verify the measured results. This study also used a radiophotoluminescent glass dosimeter coupled with an anthropomorphic phantom to evaluate the accuracy of the dose given by CyberKnife. Measurements from the radiophotoluminescent glass dosimeter were compared with the results of a thermoluminescent dosimeter and EDR2 film, and the differences found were less than 5%. The radiophotoluminescent glass dosimeter has some advantages in terms of dose measurements over CyberKnife, such as repeatability, stability, and small effective size. These advantages make radiophotoluminescent glass dosimeters a potential candidate dosimeter for the CyberKnife procedure. This study concludes that radiophotoluminescent glass dosimeters are a promising and reliable dosimeter for CyberKnife dose verification with clinically acceptable accuracy within 5%. PMID:28046056

Intercomparison of active and passive instruments for radon and radon progeny in North America

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

George, A.C.; Tu, Keng-Wu; Knutson, E.O.

1995-02-01

An intercomparison exercise for radon and radon progeny instruments and methods was held at the Environmental Measurements Laboratory (EML) from April 22--May 2, 1994. The exercise was conducted in the new EML radon test and calibration facility in which conditions of exposure are very well controlled. The detection systems of the intercompared instruments consisted of. (1) pulse ionization chambers, (2) electret ionization chambers, (3) scintillation detectors, (4) alpha particle spectrometers with silicon diodes, surface barrier or diffused junction detectors, (5) registration of nuclear tracks in solid-state materials, and (6) activated carbon collectors counted by gamma-ray spectrometry or by alpha- andmore » beta-liquid scintillation counting. 23 private firms, government laboratories and universities participated with a 165 passive integrating devices consisting of: Activated carbon collectors, nuclear alpha track detectors and electret ionization chambers, and 11 active and passive continuous radon monitors. Five portable integrating and continuous instruments were intercompared for radon progeny. Forty grab samples for radon progeny were taken by five groups that participated in person to test and evaluate their primary instruments and methods that measure individual radon progeny and the potential alpha energy concentration (PAEC) in indoor air. Results indicate that more than 80% of the measurements for radon performed with a variety of instruments, are within {plus_minus}10% of actual value. The majority of the instruments that measure individual radon progeny and the PAEC gave results that are in good agreement with the EML reference value. Radon progeny measurements made with continuous and integrating instruments are satisfactory with room for improvement.« less

Response of personal noise dosimeters to continuous and impulse-like signals

NASA Astrophysics Data System (ADS)

Evans, D. J.; Flynn, D. R.; Nedzelnitsky, V.; Burnett, E. D.

1991-06-01

A study of the capabilities of noise dosimeters to measure personal exposure to time varying and impulse-like noises was carried out. Ten commercial noise dosimeters were obtained. A laboratory reference noise dosimeter was constructed to provide a demonstrably accurate basis with which to compare the commercial noise dosimeters. Each commercial dosimeter, when ordered from the manufacturer, was specified to have a threshold A-weighted sound level of 80 dB, a criterion sound level of 90 dB, and an exchange rate of 5 dB and/or 3 dB. The performance of the commercial dosimeters was compared with theory and with results obtained from the reference dosimeter. Except in a few isolated cases, the commercial dosimeters were in general agreement with the performance specification of the appropriate American National Standard and with the Occupational Safety and Health Administration (OSHA) regulations.

Development of Eye Dosimeter Using Additive Manufacturing Techniques to Monitor Occupational Eye Lens Exposures to Interventional Radiologists

NASA Astrophysics Data System (ADS)

Choi, JungHwan

In this project, an eye dosimeter was designed for monitoring occupational lens of the eye exposures targeted to interventional radiologists who are often indirectly exposed to scattered radiation from the patient while performing image-guided procedures. The dosimeter was designed with a computer-aided design software to facilitate additive manufacturing techniques to make the dosimeter. The dosimeter consisted of three separate components that are attached to the hinges and the bridge of the occupational worker's protective eyewear. The produced dosimeter was radiologically calibrated to measure the lens dose on an anthropomorphic phantom of the human head. To supplement the physical design, an algorithm was written that prompts the user to input the element responses of the dosimeter, then estimates the average angle, energy, and resulting lens dose of the exposure by comparing the input with the data acquired during the dosimeter calibration procedure. The performance of the calibrated dosimeter (and the algorithm) was evaluated according to guidelines of the American National Standards Institute, and the dosimeter demonstrated a performance that was in compliance with the standard's performance criteria which suggests that the design of the eye dosimeter is feasible.

Development and characterization of a three-dimensional radiochromic film stack dosimeter for megavoltage photon beam dosimetry

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

McCaw, Travis J., E-mail: mccaw@wisc.edu; Micka, John A.; DeWerd, Larry A.

Purpose: Three-dimensional (3D) dosimeters are particularly useful for verifying the commissioning of treatment planning and delivery systems, especially with the ever-increasing implementation of complex and conformal radiotherapy techniques such as volumetric modulated arc therapy. However, currently available 3D dosimeters require extensive experience to prepare and analyze, and are subject to large measurement uncertainties. This work aims to provide a more readily implementable 3D dosimeter with the development and characterization of a radiochromic film stack dosimeter for megavoltage photon beam dosimetry. Methods: A film stack dosimeter was developed using Gafchromic{sup ®} EBT2 films. The dosimeter consists of 22 films separated bymore » 1 mm-thick spacers. A Virtual Water™ phantom was created that maintains the radial film alignment within a maximum uncertainty of 0.3 mm. The film stack dosimeter was characterized using simulations and measurements of 6 MV fields. The absorbed-dose energy dependence and orientation dependence of the film stack dosimeter were investigated using Monte Carlo simulations. The water equivalence of the dosimeter was determined by comparing percentage-depth-dose (PDD) profiles measured with the film stack dosimeter and simulated using Monte Carlo methods. Film stack dosimeter measurements were verified with thermoluminescent dosimeter (TLD) microcube measurements. The film stack dosimeter was also used to verify the delivery of an intensity-modulated radiation therapy (IMRT) procedure. Results: The absorbed-dose energy response of EBT2 film differs less than 1.5% between the calibration and film stack dosimeter geometries for a 6 MV spectrum. Over a series of beam angles ranging from normal incidence to parallel incidence, the overall variation in the response of the film stack dosimeter is within a range of 2.5%. Relative to the response to a normally incident beam, the film stack dosimeter exhibits a 1% under-response when the beam axis is parallel to the film planes. Measured and simulated PDD profiles agree within a root-mean-square difference of 1.3%. In-field film stack dosimeter and TLD measurements agree within 5%, and measurements in the field penumbra agree within 0.5 mm. Film stack dosimeter and TLD measurements have expanded (k = 2) overall measurement uncertainties of 6.2% and 5.8%, respectively. Film stack dosimeter measurements of an IMRT dose distribution have 98% agreement with the treatment planning system dose calculation, using gamma criteria of 3% and 2 mm. Conclusions: The film stack dosimeter is capable of high-resolution, low-uncertainty 3D dose measurements, and can be readily incorporated into an existing film dosimetry program.« less

Electron microscopy and computed microtomography studies of in vivo implanted mini-TL dosimeters.

PubMed

Strand, S E; Strandh, M; Spanne, P

1993-01-01

The need for direct methods of measuring the absorbed dose in vivo increases for systemic radiation therapy, and in more sophisticated methodologies developed for radioimmunotherapy. One method suggested is the use of mini-thermoluminescent dosimeters (TLD). Recent reports indicate a marked loss of signal when the dosimeters are used in vivo. We investigated the exterior surface of the dosimeters with scanning electron microscopy and the interior dosimeter volume with computed microtomography. The results show that the dosimeters initially have crystals uniformly embedded in the teflon matrix, with some of them directly exposed to the environment. After incubation in gel, holes appear in the dosimeter matrix where the crystals should have been. The computed microtomographic images show that crystals remain in the interior of the matrix, producing the remaining signal. We conclude that these dosimeters should be very carefully handled, and for practical use of mini-TLDs in vivo the dosimeters should be calibrated in equivalent milieus. An alternative solution to the problem of decreased TL efficiency, would be to coat the dosimeters with a thin layer, of Teflon, or other suitable material.

Deficiencies of active electronic radiation protection dosimeters in pulsed fields.

PubMed

Ankerhold, U; Hupe, O; Ambrosi, P

2009-07-01

Nowadays nearly all radiation fields used for X-ray diagnostics are pulsed. These fields are characterised by a high dose rate during the pulse and a short pulse duration in the range of a few milliseconds. The use of active electronic dosimeters has increased in the past few years, but these types of dosimeters might possibly not measure reliably in pulsed radiation fields. Not only personal dosimeters but also area dosimeters that are used mainly for dose rate measurements are concerned. These cannot be substituted by using passive dosimeter types. The characteristics of active electronic dosimeters determined in a continuous radiation field cannot be transferred to those in pulsed fields. Some provisional measurements with typical electronic dosimeters in pulsed radiation fields are presented to reveal this basic problem.

NOAA national status and trends program eleventh round intercomparison exercise results for trace metals in marine sediments and biological tissues. National status and trends program for marine environmental quality: Technical memo

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

Willie, S.

1997-12-01

A total of thirty-nine participants were included in the exercise, including OAA, USEPA, state, Australian, Canadian, Mexican and Argentinean laboratories. Two samples were sent by NRC to each participant, and contaminated marine sediment from Esquimalt harbor in British Columbia and a freeze-dried oyster tissue. Laboratories were also asked to analyze two certified reference materials (CRMs) MESS-2 and CRM 2976. The elements to be determined were Al, Cr, Fe, Ni, Cu, Zn, As, Se, Ag, Cd, Sn, Hg and Pb for both matrices, plus Be, Si, Mn, Sb and Tl for the sediments. An accepted mean and confidence interval was calculatedmore » for each analyte in the two unknown samples, laboratory biases were identified and an overall rating of superior, good, fair or others were assigned to each laboratory.« less

Assessing doses to interventional radiologists using a personal dosimeter worn over a protective apron.

PubMed

Stranden, E; Widmark, A; Sekse, T

2008-05-01

Interventional radiologists receive significant radiation doses, and it is important to have simple methods for routine monitoring of their exposure. To evaluate the usefulness of a dosimeter worn outside the protective apron for assessments of dose to interventional radiologists. Assessments of effective dose versus dose to dosimeters worn outside the protective apron were achieved by phantom measurements. Doses outside and under the apron were assessed by phantom measurements and measurements on eight radiologists wearing two routine dosimeters for a 2-month period during ordinary working conditions. Finger doses for the same radiologists were recorded using thermoluminescent dosimeters (TLD; DXT-RAD Extremity dosimeters). Typical values for the ratio between effective dose and dosimeter dose were found to be about 0.02 when the radiologist used a thyroid shield and about 0.03 without. The ratio between the dose to the dosimeter under and outside a protective apron was found to be less than 0.04. There was very good correlation between finger dose and dosimeter dose. A personal dosimeter worn outside a protective apron is a good screening device for dose to the eyes and fingers as well as for effective dose, even though the effective dose is grossly overestimated. Relatively high dose to the fingers and eyes remains undetected by a dosimeter worn under the apron.

Intercomparison of different operational oceanographic forecast products in the CMEMS IBI area

NASA Astrophysics Data System (ADS)

Lorente, Pablo; Sotillo, Marcos G.; Dabrowski, Tomasz; Amo-Baladrón, Arancha; Aznar, Roland; De Pascual, Alvaro; Levier, Bruno; Bowyer, Peter; Cossarini, Gianpiero; Salon, Stefano; Tonani, Marina; Alvarez-Fanjul, Enrique

2017-04-01

The development of skill assessment software packages and dedicated web applications is a relatively novel theme in operational oceanography. Within the CMEMS IBI-MFC, the quality of IBI (Iberia-Biscay-Ireland) forecast products is assessed by means of NARVAL (North Atlantic Regional VALidation) web-based tool. The validation of IBI against independent in situ and remote-sensing measurements is routinely conducted to evaluate model's veracity and prognostic capabilities. Noticeable efforts are in progress to define meaningful skill scores and statistical metrics to quantitatively assess the quality and reliability of the IBI model solution. Likewise, the IBI-MFC compares the IBI forecast products with other model solutions by setting up specific intercomparison exercises on overlapping areas at diverse timescales. In this context, NARVAL web tool already includes a specific module to evaluate strengths and weaknesses of IBI versus other CMEMS operational ocean forecasting systems (OOFSs). In particular, the IBI physical ocean solution is compared against the CMEMS MED and NWS OOFSs. These CMEMS regional services delivered for the Mediterranean and the North West Shelves include data assimilation schemes in their respective operational chains and generate analogous ocean forecast products to the IBI ones. A number of physical parameters (i.e. sea surface temperature, salinity and current velocities) are evaluated through NARVAL on a daily basis in the overlapping areas existing between these three regional systems. NARVAL is currently being updated in order to extend this intercomparison of ocean model parameters to the biogeochemical solutions provided by the aforementioned OOFSs. More specifically, the simulated chlorophyll concentration is evaluated over several subregions of particular concern by using as benchmark the CMEMS satellite-derived observational products. In addition to this IBI comparison against other regional CMEMS products on overlapping areas, a specific intercomparison between the CMEMS GLOBAL solution and the IBI (regional application dynamically embedded in the former) is conducted in order to check its consistency and ability to outperform the parent model solution. Particular emphasis is placed on the comparison of time-series at specified locations (class-2 metrics). The standardized validation methodology presented here is particularly useful and could encompass the intercomparison of the regional application (IBI) and other nested higher resolution models at coastal/shelf scales to quantify the added value of downscaling in local downstream approaches.

Characterization of a Fiber Optic Coupled Dosimeter for Clinical Electron Beam Dosimetry

DTIC Science & Technology

2010-04-29

2010 2. REPORT TYPE 3. DATES COVERED 00-00-2010 to 00-00-2010 4. TITLE AND SUBTITLE Characterization of a Fiber Optic Coupled Dosimeter for...Fiber Optic Coupled Dosimeter for Clinical Electron Beam Dosimetry. Abstract approved: Camille J. Lodwick Fiber-optic-coupled dosimeters ...Rights Reserved CHARACTERIZATION OF A FIBER OPTIC COUPLED DOSIMETER FOR CLINICAL ELECTRON

Summary Report for the Environmental Protection Agency MERL/FRMAC Mission Alignment Exercise held at the Environmental Protection Agency Facility on June 24-26 2014

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

Allen, Mark B.; Shanks, Sonoya Toyoko; Fournier, Sean Donovan

From June 24th thru June 26th 2014, members of the Federal Radiological Monitoring and Assessment Center (FRMAC), FRMAC Fly Away Laboratory, and the Environmental Protection Agency (EPA) participated in a joint nuclear incident emergency response/round robin exercise at the EPA facility in Las Vegas, Nevada. The purpose of this exercise was to strengthen the interoperability relationship between the FRMAC Fly Away Laboratory (FAL) and the EPA Mobile Environmental Radiation Laboratory (MERL) stationed in Las Vegas, Nevada. The exercise was designed to allow for immediate delivery of pre-staged, spiked samples to the EPA MERL and the FAL for sample preparation andmore » radiological analysis. Upon completion of laboratory analysis, data was reviewed and submitted back to the FRMAC via an electronic data deliverable (EDD). In order to conduct a laboratory inter-comparison study, samples were then traded between the two laboratories and re-counted. As part of the exercise, an evaluation was conducted to identify gaps and potential areas for improvements for FRMAC, FAL and EPA operations. Additionally, noteworthy practices and potential future areas of interoperability opportunities between the FRMAC, FAL and EPA were acknowledged. The exercise also provided a unique opportunity for FRMAC personnel to observe EPA sample receipt and sample preparation processes and to gain familiarity with the MERL laboratory instrumentation and radiation detection capabilities. The areas for potential improvements and interoperability from this exercise will be critical for developing a more efficient, integrated response for future interactions between the FRMAC and EPA MERL assets.« less

Feasibility Study of Glass Dosimeter for In Vivo Measurement: Dosimetric Characterization and Clinical Application in Proton Beams

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

Rah, Jeong-Eun; Oh, Do Hoon; Kim, Jong Won

Purpose: To evaluate the suitability of the GD-301 glass dosimeter for in vivo dose verification in proton therapy. Methods and Materials: The glass dosimeter was analyzed for its dosimetrics characteristic in proton beam. Dosimeters were calibrated in a water phantom using a stairlike holder specially designed for this study. To determine the accuracy of the glass dosimeter in proton dose measurements, we compared the glass dosimeter and thermoluminescent dosimeter (TLD) dose measurements using a cylindrical phantom. We investigated the feasibility of the glass dosimeter for the measurement of dose distributions near the superficial region for proton therapy plans with amore » varying separation between the target volume and the surface of 6 patients. Results and Discussion: Uniformity was within 1.5%. The dose-response has good linearity. Dose-rate, fading, and energy dependence were found to be within 3%. The beam profile measured using the glass dosimeter was in good agreement with the profile obtained from the ionization chamber. Depth-dose distributions in nonmodulated and modulated proton beams obtained with the glass dosimeter were estimated to be within 3%, which was lower than those with the ionization chamber. In the phantom study, the difference of isocenter dose between the delivery dose calculated by the treatment planning system and that measured by the glass dosimeter was within 5%. With in vivo dosimetry, the calculated surface doses overestimated measurements by 4%-16% using glass dosimeter and TLD. Conclusion: It is recommended that bolus be added for these clinical cases. We also believe that the glass dosimeter has considerable potential for use with in vivo patient proton dosimetry.« less

Feasibility study of glass dosimeter for in vivo measurement: dosimetric characterization and clinical application in proton beams.

PubMed

Rah, Jeong-Eun; Oh, Do Hoon; Kim, Jong Won; Kim, Dae-Hyun; Suh, Tae-Suk; Ji, Young Hoon; Shin, Dongho; Lee, Se Byeong; Kim, Dae Yong; Park, Sung Yong

2012-10-01

To evaluate the suitability of the GD-301 glass dosimeter for in vivo dose verification in proton therapy. The glass dosimeter was analyzed for its dosimetrics characteristic in proton beam. Dosimeters were calibrated in a water phantom using a stairlike holder specially designed for this study. To determine the accuracy of the glass dosimeter in proton dose measurements, we compared the glass dosimeter and thermoluminescent dosimeter (TLD) dose measurements using a cylindrical phantom. We investigated the feasibility of the glass dosimeter for the measurement of dose distributions near the superficial region for proton therapy plans with a varying separation between the target volume and the surface of 6 patients. Uniformity was within 1.5%. The dose-response has good linearity. Dose-rate, fading, and energy dependence were found to be within 3%. The beam profile measured using the glass dosimeter was in good agreement with the profile obtained from the ionization chamber. Depth-dose distributions in nonmodulated and modulated proton beams obtained with the glass dosimeter were estimated to be within 3%, which was lower than those with the ionization chamber. In the phantom study, the difference of isocenter dose between the delivery dose calculated by the treatment planning system and that measured by the glass dosimeter was within 5%. With in vivo dosimetry, the calculated surface doses overestimated measurements by 4%-16% using glass dosimeter and TLD. It is recommended that bolus be added for these clinical cases. We also believe that the glass dosimeter has considerable potential for use with in vivo patient proton dosimetry. Copyright © 2012 Elsevier Inc. All rights reserved.

Deconnable self-reading pocket dosimeter containment with self-contained light

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

Stevens, R.L.; Arnold, G.N.; McBride, R.G.

1996-10-22

A container for a self-reading pocket dosimeter includes a transparent tube for receiving the self-reading pocket dosimeter, a light source mounted at one end of the transparent tube, and an eyepiece mounted on an opposite end of the transparent tube for viewing a read-out of the self-reading pocket dosimeter. The container may further include an activation device for selectively supplying power to the light source. The container both protects the dosimeter from being contaminated and provides a light source for viewing the dosimeter. 4 figs.

Deconnable self-reading pocket dosimeter containment with self-contained light

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

Stevens, R.L.; Arnold, G.N.; McBride, R.G.

1995-12-31

A container for a self-reading pocket dosimeter includes a transparent tube for receiving the self-reading pocket dosimeter, a light source mounted at one end of the transparent tube, and an eyepiece mounted on an opposite end of the transparent tube for viewing a read-out of the self-reading pocket dosimeter. The container may further include an activation device for selectively supplying power to the light source. The container both protects the dosimeter from being contaminated and provides a light source for viewing the dosimeter.

Deconnable self-reading pocket dosimeter containment with self-contained light

DOEpatents

Stevens, Robyn L.; Arnold, Greg N.; McBride, Ryan G.

1996-01-01

A container for a self-reading pocket dosimeter includes a transparent tube for receiving the self-reading pocket dosimeter, a light source mounted at one end of the transparent tube, and an eyepiece mounted on an opposite end of the transparent tube for viewing a read-out of the self-reading pocket dosimeter. The container may further include an activation device for selectively supplying power to the light source. The container both protects the dosimeter from being contaminated and provides a light source for viewing the dosimeter.

Subglacial Hydrology Model Intercomparison Project (SHMIP)

NASA Astrophysics Data System (ADS)

Werder, Mauro A.; de Fleurian, Basile; Creyts, Timothy T.; Damsgaard, Anders; Delaney, Ian; Dow, Christine F.; Gagliardini, Olivier; Hoffman, Matthew J.; Seguinot, Julien; Sommers, Aleah; Irarrazaval Bustos, Inigo; Downs, Jakob

2017-04-01

The SHMIP project is the first intercomparison project of subglacial drainage models (http://shmip.bitbucket.org). Its synthetic test suites and evaluation were designed such that any subglacial hydrology model producing effective pressure can participate. In contrast to ice deformation, the physical processes of subglacial hydrology (which in turn impacts basal sliding of glaciers) are poorly known. A further complication is that different glacial and geological settings can lead to different drainage physics. The aim of the project is therefore to qualitatively compare the outputs of the participating models for a wide range of water forcings and glacier geometries. This will allow to put existing studies, which use different drainage models, into context and will allow new studies to select the most suitable model for the problem at hand. We present the results from the just completed intercomparison exercise. Twelve models participated: eight 2D and four 1D models; nine include both an efficient and inefficient system, the other three one of the systems; all but two models use R-channels as efficient system, and/or a linked-cavity like inefficient system, one exception uses porous layers with different characteristic for each of the systems, the other exception is based on canals. The main variable used for the comparison is effective pressure, as that is a direct proxy for basal sliding of glaciers. The models produce large differences in the effective pressure fields, in particular for higher water input scenarios. This shows that the selection of a subglacial drainage model will likely impact the conclusions of a study significantly.

The Agricultural Model Intercomparison and Improvement Project (AgMIP): Progress and Preliminary Results

NASA Astrophysics Data System (ADS)

Rosenzweig, C.

2011-12-01

The Agricultural Model Intercomparison and Improvement Project (AgMIP) is a distributed climate-scenario simulation exercise for historical model intercomparison and future climate change conditions with participation of multiple crop and agricultural trade modeling groups around the world. The goals of AgMIP are to improve substantially the characterization of risk of hunger and world food security due to climate change and to enhance adaptation capacity in both developing and developed countries. Recent progress and the current status of AgMIP will be presented, highlighting three areas of activity: preliminary results from crop pilot studies, outcomes from regional workshops, and emerging scientific challenges. AgMIP crop modeling efforts are being led by pilot studies, which have been established for wheat, maize, rice, and sugarcane. These crop-specific initiatives have proven instrumental in testing and contributing to AgMIP protocols, as well as creating preliminary results for aggregation and input to agricultural trade models. Regional workshops are being held to encourage collaborations and set research activities in motion for key agricultural areas. The first of these workshops was hosted by Embrapa and UNICAMP and held in Campinas, Brazil. Outcomes from this meeting have informed crop modeling research activities within South America, AgMIP protocols, and future regional workshops. Several scientific challenges have emerged and are currently being addressed by AgMIP researchers. Areas of particular interest include geospatial weather generation, ensemble methods for climate scenarios and crop models, spatial aggregation of field-scale yields to regional and global production, and characterization of future changes in climate variability.

Dosimetric characteristics of PASSAG as a new polymer gel dosimeter with negligible toxicity

NASA Astrophysics Data System (ADS)

Farhood, Bagher; Abtahi, Seyed Mohammad Mahdi; Geraily, Ghazale; Ghorbani, Mehdi; Mahdavi, Seied Rabi; Zahmatkesh, Mohammad Hasan

2018-06-01

Despite many advantages of polymer gel dosimeters, their clinical use is only not realized now. Toxicity of polymer gel dosimeters can be considered as one of their main limitations for use in routine clinical applications. In the current study, a new polymer gel dosimeter is introduced with negligible toxicity. For this purpose, 2-Acrylamido-2-Methy-1-PropaneSulfonic acid (AMPS) sodium salt monomer was replaced instead of acrylamide monomer used in PAGAT gel dosimeter by using %6 T and %50 C to the gel formula and the new formulation is called PASSAG (Poly AMPS Sodium Salt and Gelatin) polymer gel dosimeter. The irradiation of gel dosimeters was carried out using a Co-60 therapy machine. MRI technique was used to quantify the dose responses of the PASSAG gel dosimeter. Then, the MRI responses (R2) of the gel dosimeter was analyzed at different dose values, post-irradiation times, and scanning temperatures. The results showed that the new gel formulation has a negligible toxicity and it is also eco-friendly. In addition, carcinogenicity and genetic toxicity tests are negative for the monomer used in PASSAG. The radiological properties of PASSAG gel dosimeter showed that this substance can be considered as a soft tissue/water equivalent material. Furthermore, dosimetric evaluation of the new polymer gel dosimeter revealed an excellent linear R2-dose response in the evaluated dose range (0-15 Gy). The R2-dose sensitivity and dose resolution of PASSAG gel dosimeter were 0.081 s-1Gy-1 (in 0-15 Gy dose range) and 1 Gy (in 0-10 Gy dose range), respectively. Moreover, it was shown that the R2-dose sensitivity and dose resolution of the new gel dosimeter improves over time after irradiation. It was also found that the R2 response of the PASSAG gel dosimeter has less dependency to the 18, 20, and 24 °C scanning temperature in comparison to that of room temperature (22 °C).

TH-CD-201-11: Optimizing the Response and Cost of a DNA Double-Strand Break Dosimeter

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

Obeidat, M; Cline, K; Stathakis, S

Purpose: A DNA double-strand break (DSB) dosimeter was developed to measure the biological effect of radiation. The goal here is to refine the fabrication method of this dosimeter to reproducibly create a low coefficient of variation (CoV) and reduce the cost for the dosimeter. Methods: Our dosimeter consists of 4 kilo-base pair DNA strands (labeled on one end with biotin and on the other with fluorescein) attached to streptavidin magnetic beads. The final step of the DNA dosimeter fabrication is to suspend these attached beads in phosphate-buffered saline (PBS). The amount of PBS used to suspend the attached beads andmore » the relative volume of the DNA strands to the beads both affect the CoV and dosimeter cost. We diluted the beads attached with DNA in different volumes of PBS (100, 200, and 400 µL) to create different concentrations of the DNA dosimeter. Then we irradiated these dosimeters (50 µL samples) in a water-equivalent plastic phantom at 25 and 50 Gy (three samples per dose) and calculated the CoV for each dosimeter concentration. Also, we used different masses of DNA strands (1, 2, 8, 16, 24, and 32 µg) to attach to the same volume of magnetic beads (100 µL) to explore how this affects the cost of the dosimeter. Results: The lowest CoV was produced for the highest concentration of dosimeter (100 µL of PBS), which created CoV of 2.0 and 1.0% for 25 and 50 Gy, respectively. We found that the lowest production cost for the dosimeter occurs by attaching 16 µg of DNA strands with 100 µL of beads. Conclusion: : We optimized the fabrication of the DNA dosimeter to produce low CoV and cost, but we still need to explore ways to further improve the dosimeter for use at lower doses. This work was supported in part by Yarmouk University (Irbid, Jordan) and CPRIT (RP140105)« less

NOTE: Cell-phone interference with pocket dosimeters

NASA Astrophysics Data System (ADS)

Djajaputra, David; Nehru, Ramasamy; Bruch, Philip M.; Ayyangar, Komanduri M.; Raman, Natarajan V.; Enke, Charles A.

2005-05-01

Accurate reporting of personal dose is required by regulation for hospital personnel that work with radioactive material. Pocket dosimeters are commonly used for monitoring this personal dose. We show that operating a cell phone in the vicinity of a pocket dosimeter can introduce large and erroneous readings of the dosimeter. This note reports a systematic study of this electromagnetic interference. We found that simple practical measures are enough to mitigate this problem, such as increasing the distance between the cell phone and the dosimeter or shielding the dosimeter, while maintaining its sensitivity to ionizing radiation, by placing it inside a common anti-static bag.

Description of ARCAL XXXIV Project: Repair and Calibration of Electrometers and Ionization Chambers Used in Radiotherapy

NASA Astrophysics Data System (ADS)

Cruz-Estrada, P.; Ramírez-Jiménez, F. J.; Villaverde-Lozano, A.

2003-09-01

The technological tools for the diagnosis of diseases and treatment of cancer are based mostly on the use of ionizing radiations. This situation worries to the International Atomic Energy Agency (IAEA), which has implemented programs of technical cooperation for the protection of the human health. One of these programs is running in Latin America under the ARCAL project (Regional Agreement of Cooperation for the Promotion of the Nuclear Science and Technology in Latin America and the Caribbean). One objective of the ARCAL XXXIV project is the establishment of three Regional Centres for the repair, maintenance and electrical calibration of clinical dosimeters, in Mexico we have one of these centres. Some other objectives of the project are: the generation of calibration procedures, the release of training courses in the region, the establishment of an inter-comparison network for the region in the control of standards of calibration with electrometers and the design of low current sources that simulates the ionization chamber and can serve as field standards for each of the participant countries. A description of the results of the project is presented in this work.

SU-E-T-139: Feasibility Study of Glass Dosimeter for in Vivo Measurement: Dosimetric Characterization and Clinical Application in Proton Beams.

PubMed

Lah, J; Kim, D; Park, S

2012-06-01

To evaluate the suitability of the GD-301 glass dosimeter for use in in vivo dose verification in proton therapy. The glass dosimeter was analyzed for its dosimetric characteristic in proton beam. Dosimeters were calibrated in a water phantom using a stair-like holder specially designed for this study. To determine the accuracy of the glass dosimeter in proton dose measurements, we compared the glass dosimeter and TLD dose measurements of plan delivery using a cylindrical phantom. We investigated the feasibility of the glass dosimeter for the measurement of dose distributions near the superficial region for proton therapy plans with a varying separation between the target volume and the surface of 6 patients. Uniformity was within 1.5%. The dose-response has a good linear. Dose-rate, fading, and energy dependence were found to be within 3%. The beam profile measured using the glass dosimeter was in good agreement with the profile obtained from the ionization chamber. Depth-dose distributions in non-modulated and modulated proton beams obtained with the glass dosimeter were estimated to be within 3%, which was lower than those with the ionization chamber. In the phantom study, the difference of isocenter dose between the delivery dose calculated by the Eclipse and that of the measured by the glass dosimeter was within 5%. In vivo dosimetry of patients, given the results of the glass dosimeter and TLD measurements, calculated doses on the surface of the patient are typically overestimated between 4% and 16%. As such, it is recommended that bolus be added for these clinical cases. We also believe that the glass dosimeter has considerable potential to be used for in vivo patient proton dosimetry. © 2012 American Association of Physicists in Medicine.

The importance of serum serotonin levels in the measurement of radiation-induced bystander cell death in HaCaT cells.

PubMed

Lyng, Fiona M; Desplanques, Maxime; Jella, Kishore Kumar; Garcia, Amaya; McClean, Brendan

2012-10-01

The aim of this study was to investigate the importance of serum serotonin levels in the measurement of bystander cell death. The study was undertaken as part of an intercomparison exercise involving seven European laboratories funded under the European Union Sixth Framework Programme (FP6) Non-Targeted Effects (NOTE) integrated project. Three batches of foetal bovine serum were tested; serum with high and low serotonin content from the intercomparison exercise as well as serum from the home laboratory. Three sets of human keratinocytes (HaCaT cell line) were cultured in DMEM:F12 medium supplemented with serum with high or low serotonin content or serum from the home laboratory and both donor and recipient HaCaT cells were plated. The donor HaCaT cells were irradiated (0.5 Gy) using a cobalt 60 teletherapy unit, the medium was harvested 1 hour post irradiation and transferred to the recipient HaCaT cells. Bystander induced cell death was measured by the clonogenic survival assay and the Alamar blue viability assay. A significant reduction in cell survival, as measured by the clonogenic assay, and in cell viability, as measured by the Alamar blue assay, was observed in the recipient HaCaT cells treated with medium from irradiated cells compared to the cells treated with medium from unirradiated cells. No significant difference was found between the three batches of serum. The data suggest that in our cell system and with our endpoints (clonogenic assay and Alamar blue assay), serum serotonin levels do not play a role in bystander-induced cell death.

Results of the eruptive column model inter-comparison study

USGS Publications Warehouse

Costa, Antonio; Suzuki, Yujiro; Cerminara, M.; Devenish, Ben J.; Esposti Ongaro, T.; Herzog, Michael; Van Eaton, Alexa; Denby, L.C.; Bursik, Marcus; de' Michieli Vitturi, Mattia; Engwell, S.; Neri, Augusto; Barsotti, Sara; Folch, Arnau; Macedonio, Giovanni; Girault, F.; Carazzo, G.; Tait, S.; Kaminski, E.; Mastin, Larry G.; Woodhouse, Mark J.; Phillips, Jeremy C.; Hogg, Andrew J.; Degruyter, Wim; Bonadonna, Costanza

2016-01-01

This study compares and evaluates one-dimensional (1D) and three-dimensional (3D) numerical models of volcanic eruption columns in a set of different inter-comparison exercises. The exercises were designed as a blind test in which a set of common input parameters was given for two reference eruptions, representing a strong and a weak eruption column under different meteorological conditions. Comparing the results of the different models allows us to evaluate their capabilities and target areas for future improvement. Despite their different formulations, the 1D and 3D models provide reasonably consistent predictions of some of the key global descriptors of the volcanic plumes. Variability in plume height, estimated from the standard deviation of model predictions, is within ~ 20% for the weak plume and ~ 10% for the strong plume. Predictions of neutral buoyancy level are also in reasonably good agreement among the different models, with a standard deviation ranging from 9 to 19% (the latter for the weak plume in a windy atmosphere). Overall, these discrepancies are in the range of observational uncertainty of column height. However, there are important differences amongst models in terms of local properties along the plume axis, particularly for the strong plume. Our analysis suggests that the simplified treatment of entrainment in 1D models is adequate to resolve the general behaviour of the weak plume. However, it is inadequate to capture complex features of the strong plume, such as large vortices, partial column collapse, or gravitational fountaining that strongly enhance entrainment in the lower atmosphere. We conclude that there is a need to more accurately quantify entrainment rates, improve the representation of plume radius, and incorporate the effects of column instability in future versions of 1D volcanic plume models.

Sensitivity of grounding line dynamics to basal conditions

NASA Astrophysics Data System (ADS)

Gagliardini, O.; Brondex, J.; Chauveau, G.; Gillet-chaulet, F.; Durand, G.

2017-12-01

In the context of a warming climate, the dynamical contribution of Antarctica to future sea level rise is still tainted by high uncertainties. Among the processes entering these uncertainties is the link between basal hydrology, friction and grounding line dynamics. Recent works have shown how sensitive is the response of the grounding line retreat to the choice of the form of the friction law. Indeed, starting from the same initial state, grounding line retreat rates can range over almost two orders of magnitude depending on the friction law formulation.Here, we use a phenomenological law that depends on the water pressure and allows a continuous transition from a Weertman-type friction at low water pressure to a Coulomb-type friction at high water pressure. This friction law depends on two main parameters that control the Weertman and Coulomb regimes. The range of values for these two parameters is only weakly physically constrained, and it can be shown that, for a given basal shear stress, different couples of parameters can conduct to the same sliding velocity. In addition, we show that close to the grounding line where basal water pressure is high, determining these two parameters might conduct to an ill-posed inverse problem with no solution.The aim of this presentation is to discuss a methodology to guide the choice of the two friction parameters and explore the sensitivity of the grounding line dynamics to this initial choice. We present results obtained both on a synthetic configuration used by the Marine Ice Sheet Model Intercomparison exercise and for the Amundsen sea sector using the experiments proposed by InitMIP-Antarctica, the first exercise in a series of ISMIP6 ice-sheet model intercomparison activities.

Measuring pacemaker dose: a clinical perspective.

PubMed

Studenski, Matthew T; Xiao, Ying; Harrison, Amy S

2012-01-01

Recently in our clinic, we have seen an increased number of patients presenting with pacemakers and defibrillators. Precautions are taken to develop a treatment plan that minimizes the dose to the pacemaker because of the adverse effects of radiation on the electronics. Here we analyze different dosimeters to determine which is the most accurate in measuring pacemaker or defibrillator dose while at the same time not requiring a significant investment in time to maintain an efficient workflow in the clinic. The dosimeters analyzed here were ion chambers, diodes, metal-oxide-semiconductor field effect transistor (MOSFETs), and optically stimulated luminescence (OSL) dosimeters. A simple phantom was used to quantify the angular and energy dependence of each dosimeter. Next, 8 patients plans were delivered to a Rando phantom with all the dosimeters located where the pacemaker would be, and the measurements were compared with the predicted dose. A cone beam computed tomography (CBCT) image was obtained to determine the dosimeter response in the kilovoltage energy range. In terms of the angular and energy dependence of the dosimeters, the ion chamber and diode were the most stable. For the clinical cases, all the dosimeters match relatively well with the predicted dose, although the ideal dosimeter to use is case dependent. The dosimeters, especially the MOSFETS, tend to be less accurate for the plans, with many lateral beams. Because of their efficiency, we recommend using a MOSFET or a diode to measure the dose. If a discrepancy is observed between the measured and expected dose (especially when the pacemaker to field edge is <10 cm), we recommend analyzing the treatment plan to see whether there are many lateral beams. Follow-up with another dosimeter rather than repeating multiple times with the same type of dosimeter. All dosimeters should be placed after the CBCT has been acquired. Copyright © 2012 American Association of Medical Dosimetrists. Published by Elsevier Inc. All rights reserved.

Measuring pacemaker dose: A clinical perspective

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

Studenski, Matthew T., E-mail: matthew.studenski@jeffersonhospital.org; Xiao Ying; Harrison, Amy S.

2012-07-01

Recently in our clinic, we have seen an increased number of patients presenting with pacemakers and defibrillators. Precautions are taken to develop a treatment plan that minimizes the dose to the pacemaker because of the adverse effects of radiation on the electronics. Here we analyze different dosimeters to determine which is the most accurate in measuring pacemaker or defibrillator dose while at the same time not requiring a significant investment in time to maintain an efficient workflow in the clinic. The dosimeters analyzed here were ion chambers, diodes, metal-oxide-semiconductor field effect transistor (MOSFETs), and optically stimulated luminescence (OSL) dosimeters. Amore » simple phantom was used to quantify the angular and energy dependence of each dosimeter. Next, 8 patients plans were delivered to a Rando phantom with all the dosimeters located where the pacemaker would be, and the measurements were compared with the predicted dose. A cone beam computed tomography (CBCT) image was obtained to determine the dosimeter response in the kilovoltage energy range. In terms of the angular and energy dependence of the dosimeters, the ion chamber and diode were the most stable. For the clinical cases, all the dosimeters match relatively well with the predicted dose, although the ideal dosimeter to use is case dependent. The dosimeters, especially the MOSFETS, tend to be less accurate for the plans, with many lateral beams. Because of their efficiency, we recommend using a MOSFET or a diode to measure the dose. If a discrepancy is observed between the measured and expected dose (especially when the pacemaker to field edge is <10 cm), we recommend analyzing the treatment plan to see whether there are many lateral beams. Follow-up with another dosimeter rather than repeating multiple times with the same type of dosimeter. All dosimeters should be placed after the CBCT has been acquired.« less

Sacramento Regional Response Guide to Radiation Emergencies

DTIC Science & Technology

2006-09-01

emergency operations. Additionally, the utilization of thermo luminescence dosimeters ( TLD ) may be beneficial to track long term exposure for...a radiation area. Stakeholder agency emergency response equipment have been issued electronic dosimeters The purpose of the radiation dosimeter is...Incident.............................................................................84 2. Detection/ Dosimeter Equipment

TH-AB-BRA-11: Using 3D Dosimeters for the Investigation of the Electron Return Effect (ERE) in MR-Guided Radiation Therapy: A Feasibility Study

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

Choi, G; Lee, H; Alqathami, M

Purpose: To demonstrate the capability of 3D radiochromic PRESAGE and Fricke-type dosimeters to measure the influence of magnetic fields on dose distribution, including the electron return effect (ERE), for MR-guided radiation therapy applications. Methods: Short cylindrical 3D dosimeters with PRESAGE and Fricke-type formulations were created in-house prior to irradiations in a 1.5T/7MV MR-linac. Each dosimeter was prepared with a concentric cylindrical air cavity with diameters of 1.5 cm and 2.5 cm, and the diameters of the dosimeters were 7.2 cm and 8.8 cm for PRESAGE and Fricke-type respectively. The dosimeters were irradiated within the bore of the MR-linac with themore » flat face of the dosimeters perpendicular to the magnetic field. Dosimeters were irradiated to approximately 9 Gy and 29 Gy to the center of dosimeters with a 15×15 cm{sup 2} field. The PRESAGE dosimeter was scanned using an optical-CT 2 hours post-irradiation; the Fricke-type dosimeter was immediately imaged with the MR component of the MR-linac post-irradiation. Results: Axial slices of the dose distributions show a clear demonstration of the dose enhancement due to the ERE above the cavity and the region of reduced dose below the cavity. The regions of increased and reduced dose are rotated with respect to the radiation beam axis due to the average directional change of the electrons. Measurements from line profiles show the dose enhanced up to ∼0.5 cm around the cavity by up to a factor of 1.3 and 1.4 for PRESAGE and Fricke-type dosimeters respectively. Conclusion: PRESAGE and Fricke-type dosimeters are able to qualitatively measure the ERE with good agreement with previously published simulation and 2D dosimetry demonstrations of the ERE. Further investigation of these 3D dosimeters as promising candidates for quality assurance of MR-guided radiation therapy systems is encouraged to assess changes in response and measurement accuracy due to the magnetic field.« less

Comprehensive Angular Response Study of LLNL Panasonic Dosimeter Configurations and Artificial Intelligence Algorithm

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

Stone, D. K.

In April of 2016, the Lawrence Livermore National Laboratory External Dosimetry Program underwent a Department of Energy Laboratory Accreditation Program (DOELAP) on-site assessment. The assessment reported a concern that the study performed in 2013 Angular Dependence Study Panasonic UD-802 and UD-810 Dosimeters LLNL Artificial Intelligence Algorithm was incomplete. Only the responses at ±60° and 0° were evaluated and independent data from dosimeters was not used to evaluate the algorithm. Additionally, other configurations of LLNL dosimeters were not considered in this study. This includes nuclear accident dosimeters (NAD) which are placed in the wells surrounding the TLD in the dosimeter holder.

Measurement of Absorbed Dose from Radionuclide Solutions Mixed Intimately with the Fbx Dosimeter.

NASA Astrophysics Data System (ADS)

Benedetto, Anthony Richard

Chemical dosimeters are used widely for accurate measurement of large radiation doses due to external beam irradiation from radioisotope sources and from particle accelerators. Their use for measurement of absorbed doses from radioactive solutions mixed in the dosimeter solution was reported as early as 1952, but the large activities needed to produce suitable absorbance values in the relatively insensitive dosimeters of that time discouraged further work. This manuscript reports the results of an investigation into the suitability of the ferrous sulfate-benzoic acid -xylenol orange (FBX) dosimeter for measurement of small absorbed doses caused by radionuclide solutions dissolved in the dosimeter solution. The FBX dosimeter exhibited a linear dose response as a function of activity for two common radiopharmaceuticals, technetium-99m sodium pertechnetate and iodine-131 sodium iodide. Conditions under which the FBX dosimeter may be used with radionuclide solutions were studied and were found to be amenable to routine use by laboratories possessing relatively unsophisticated instrumentation. It appears likely that any radionuclide could be studied using this dosimeter. Finally, potential applications and future research work are suggested, including measurement of absorbed dose from radiopharmaceuticals using realistic human-like phantoms to assess the risk from clinical nuclear medicine studies.

Integration of new biological and physical retrospective dosimetry methods into EU emergency response plans - joint RENEB and EURADOS inter-laboratory comparisons.

PubMed

Ainsbury, Elizabeth; Badie, Christophe; Barnard, Stephen; Manning, Grainne; Moquet, Jayne; Abend, Michael; Antunes, Ana Catarina; Barrios, Lleonard; Bassinet, Celine; Beinke, Christina; Bortolin, Emanuela; Bossin, Lily; Bricknell, Clare; Brzoska, Kamil; Buraczewska, Iwona; Castaño, Carlos Huertas; Čemusová, Zina; Christiansson, Maria; Cordero, Santiago Mateos; Cosler, Guillaume; Monaca, Sara Della; Desangles, François; Discher, Michael; Dominguez, Inmaculada; Doucha-Senf, Sven; Eakins, Jon; Fattibene, Paola; Filippi, Silvia; Frenzel, Monika; Georgieva, Dimka; Gregoire, Eric; Guogyte, Kamile; Hadjidekova, Valeria; Hadjiiska, Ljubomira; Hristova, Rositsa; Karakosta, Maria; Kis, Enikő; Kriehuber, Ralf; Lee, Jungil; Lloyd, David; Lumniczky, Katalin; Lyng, Fiona; Macaeva, Ellina; Majewski, Matthaeus; Vanda Martins, S; McKeever, Stephen W S; Meade, Aidan; Medipally, Dinesh; Meschini, Roberta; M'kacher, Radhia; Gil, Octávia Monteiro; Montero, Alegria; Moreno, Mercedes; Noditi, Mihaela; Oestreicher, Ursula; Oskamp, Dominik; Palitti, Fabrizio; Palma, Valentina; Pantelias, Gabriel; Pateux, Jerome; Patrono, Clarice; Pepe, Gaetano; Port, Matthias; Prieto, María Jesús; Quattrini, Maria Cristina; Quintens, Roel; Ricoul, Michelle; Roy, Laurence; Sabatier, Laure; Sebastià, Natividad; Sholom, Sergey; Sommer, Sylwester; Staynova, Albena; Strunz, Sonja; Terzoudi, Georgia; Testa, Antonella; Trompier, Francois; Valente, Marco; Hoey, Olivier Van; Veronese, Ivan; Wojcik, Andrzej; Woda, Clemens

2017-01-01

RENEB, 'Realising the European Network of Biodosimetry and Physical Retrospective Dosimetry,' is a network for research and emergency response mutual assistance in biodosimetry within the EU. Within this extremely active network, a number of new dosimetry methods have recently been proposed or developed. There is a requirement to test and/or validate these candidate techniques and inter-comparison exercises are a well-established method for such validation. The authors present details of inter-comparisons of four such new methods: dicentric chromosome analysis including telomere and centromere staining; the gene expression assay carried out in whole blood; Raman spectroscopy on blood lymphocytes, and detection of radiation-induced thermoluminescent signals in glass screens taken from mobile phones. In general the results show good agreement between the laboratories and methods within the expected levels of uncertainty, and thus demonstrate that there is a lot of potential for each of the candidate techniques. Further work is required before the new methods can be included within the suite of reliable dosimetry methods for use by RENEB partners and others in routine and emergency response scenarios.

EURADOS intercomparison on emergency radiobioassay.

PubMed

Li, Chunsheng; Battisti, Paolo; Berard, Philippe; Cazoulat, Alain; Cuellar, Antonio; Cruz-Suarez, Rodolfo; Dai, Xiongxin; Giardina, Isabella; Hammond, Derek; Hernandez, Carolina; Kiser, Stephen; Ko, Raymond; Kramer-Tremblay, Sheila; Lecompte, Yannick; Navarro, Eva; Navas, Cristina; Sadi, Baki; Sierra, Inmaculada; Verrezen, Freddy; Lopez, Maria A

2015-12-01

Nine laboratories participated in an intercomparison exercise organised by the European Radiation Dosimetry Group (EURADOS) for emergency radiobioassay involving four high-risk radionuclides ((239)Pu, (241)Am, (90)Sr and (226)Ra). Diverse methods of analysis were used by the participating laboratories for the in vitro determination of each of the four radionuclides in urine samples. Almost all the methods used are sensitive enough to meet the requirements for emergency radiobioassay derived for this project in reference to the Clinical Decision Guide introduced by the NCRP. Results from most of the methods meet the requirements of ISO 28218 on accuracy in terms of relative bias and relative precision. However, some technical gaps have been identified. For example, some laboratories do not have the ability to assay samples containing (226)Ra, and sample turnaround time would be expected to be much shorter than that reported by many laboratories, as timely results for internal contamination and early decisions on medical intervention are highly desired. Participating laboratories are expected to learn from each other on the methods used to improve the interoperability among these laboratories. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Uranium adsorption on weathered schist - Intercomparison of modeling approaches

USGS Publications Warehouse

Payne, T.E.; Davis, J.A.; Ochs, M.; Olin, M.; Tweed, C.J.

2004-01-01

Experimental data for uranium adsorption on a complex weathered rock were simulated by twelve modelling teams from eight countries using surface complexation (SC) models. This intercomparison was part of an international project to evaluate the present capabilities and limitations of SC models in representing sorption by geologic materials. The models were assessed in terms of their predictive ability, data requirements, number of optimised parameters, ability to simulate diverse chemical conditions and transferability to other substrates. A particular aim was to compare the generalised composite (GC) and component additivity (CA) approaches for modelling sorption by complex substrates. Both types of SC models showed a promising capability to simulate sorption data obtained across a range of chemical conditions. However, the models incorporated a wide variety of assumptions, particularly in terms of input parameters such as site densities and surface site types. Furthermore, the methods used to extrapolate the model simulations to different weathered rock samples collected at the same field site tended to be unsatisfactory. The outcome of this modelling exercise provides an overview of the present status of adsorption modelling in the context of radionuclide migration as practised in a number of countries worldwide.

Water equivalence of NIPAM based polymer gel dosimeters with enhanced sensitivity for x-ray CT

NASA Astrophysics Data System (ADS)

Gorjiara, Tina; Hill, Robin; Bosi, Stephen; Kuncic, Zdenka; Baldock, Clive

2013-10-01

Two new formulations of N-isopropylacrylamide (NIPAM) based three dimensional (3D) gel dosimeters have recently been developed with improved sensitivity to x-ray CT readout, one without any co-solvent and the other one with isopropanol co-solvent. The water equivalence of the NIPAM gel dosimeters was investigated using different methods to calculate their radiological properties including: density, electron density, number of electrons per grams, effective atomic number, photon interaction probabilities, mass attenuation and energy absorption coefficients, electron collisional, radiative and total mass stopping powers and electron mass scattering power. Monte Carlo modelling was also used to compare the dose response of these gel dosimeters with water for kilovoltage and megavoltage x-ray beams and for megavoltage electron beams. We found that the density and electron density of the co-solvent free gel dosimeter are more water equivalent with less than a 2.6% difference compared to a 5.7% difference for the isopropanol gel dosimeter. Both the co-solvent free and isopropanol solvent gel dosimeters have lower effective atomic numbers than water, differing by 2.2% and 6.5%, respectively. As a result, their photoelectric absorption interaction probabilities are up to 6% and 19% different from water, respectively. Compton scattering and pair production interaction probabilities of NIPAM gel with isopropanol differ by up to 10% from water while for the co-solvent free gel, the differences are 3%. Mass attenuation and energy absorption coefficients of the co-solvent free gel dosimeter and the isopropanol gel dosimeter are up to 7% and 19% lower than water, respectively. Collisional and total mass stopping powers of both gel dosimeters differ by less than 2% from those of water. The dose response of the co-solvent free gel dosimeter is water equivalent (with <1% discrepancy) for dosimetry of x-rays with energies <100 keV while the discrepancy increases (up to 5%) for the isopropanol gel dosimeter over the same energy range. For x-ray beams over the energy range 180 keV-18 MV, both gel dosimeters have less than 2% discrepancy with water. For megavoltage electron beams, the dose differences with water reach 7% and 14% for the co-solvent free gel dosimeter and the isopropanol gel dosimeter, respectively. Our results demonstrate that for x-ray beam dosimetry with photon energies higher than 100 keV and megavoltage electron beams, correction factors are needed for both NIPAM gels to be used as water equivalent dosimeters.

Polymer gel dosimeters with reduced toxicity: a preliminary investigation of the NMR and optical dose response using different monomers

NASA Astrophysics Data System (ADS)

Senden, R. J.; DeJean, P.; McAuley, K. B.; Schreiner, L. J.

2006-07-01

In this work, three new polymer gel dosimeter recipes were investigated that may be more suitable for widespread applications than polyacrylamide gel dosimeters, since the extremely toxic acrylamide has been replaced with the less harmful monomers N-isopropylacrylamide (NIPAM), diacetone acrylamide and N-vinylformamide. The new gel dosimeters studied contained gelatin (5 wt%), monomer (3 wt%), N,N'-methylene-bis-acrylamide crosslinker (3 wt%) and tetrakis (hydroxymethyl) phosphonium chloride antioxidant (10 mM). The NMR response (R2) of the dosimeters was analysed for conditions of varying dose, dose rate, time post-irradiation, and temperature during irradiation and scanning. It was shown that the dose-response behaviour of the NIPAM/Bis gel dosimeter is comparable to that of normoxic polyacrylamide gel (PAGAT) in terms of high dose-sensitivity and low dependence on dose rate and irradiation temperature, within the ranges considered. The dose-response (R2) of NIPAM/Bis appears to be linear over a greater dose range than the PAGAT gel dosimeter. The effects of time post-irradiation (temporal instability) and temperature during NMR scanning on the R2 response were more significant for NIPAM/Bis dosimeters. Diacetone acrylamide and N-vinylformamide gel dosimeters possessed considerably lower dose-sensitivities. The optical dose-response, measured in terms of the attenuation coefficient for each polymer gel dosimeter, showed potential for the use of optical imaging techniques in future studies.

Personal noise dosimeters: accuracy and reliability in varied settings.

PubMed

Cook-Cunningham, Sheri Lynn

2014-01-01

This study investigated the accuracy, reliability, and characteristics of three brands of personal noise dosimeters (N = 7 units) in both pink noise (PN) environments and natural environments (NEs) through the acquisition of decibel readings, Leq readings and noise doses. Acquisition periods included repeated PN conditions, choir room rehearsals and participant (N = 3) Leq and noise dosages procured during a day in the life of a music student. Among primary results: (a) All dosimeters exhibited very strong positive correlations for PN measurements across all instruments; (b) all dosimeters were within the recommended American National Standard Institute (ANSI) SI.25-1991 standard of ±2 dB (A) of a reference measurement; and (c) all dosimeters were within the recommended ANSI SI.25-1991 standard of ±2 dB (A) when compared with each other. Results were discussed in terms of using personal noise dosimeters within hearing conservation and research contexts and recommendations for future research. Personal noise dosimeters were studied within the contexts of PN environments and NEs (choral classroom and the day in the life of collegiate music students). This quantitative study was a non-experimental correlation design. Three brands of personal noise dosimeters (Cirrus doseBadge, Quest Edge Eg5 and Etymotic ER200D) were tested in two environments, a PN setting and a natural setting. There were two conditions within each environment. In the PN environment condition one, each dosimeter was tested individually in comparison with two reference measuring devices (Ivie and Easera) while PN was generated by a Whites Instrument PN Tube. In condition two, the PN procedures were replicated for longer periods while all dosimeters measured the sound levels simultaneously. In the NE condition one, all dosimeters were placed side by side on a music stand and recorded sound levels of choir rehearsals over a 7-h rehearsal period. In NE, condition two noise levels were measured during a day in the life of college music students. Three participants each wore two types of dosimeters for an 8-h period during a normal school day. Descriptive statistical analyzes including means, standard deviation and Pearson product-moment correlation. The primary finding is that the dosimeters in this study recorded results within ±2 dB of either a reference measurement or within dosimeters in all four conditions examined. All dosimeters studied measured steady noise source accurately and consistently, with strong positive correlations across all instruments. Measurements acquired during choral rehearsals indicated a maximum of 1.5 dB difference across dosimeters. The Etymotic research personal noise dosimeters (ER200D) could provide individuals and schools of music with a relatively inexpensive tool to monitor sound doses. Findings from this study suggest that the three brands of dosimeters tested will provide reliable Leq levels and hearing dosages in both PN and natural settings.

Energy dependence measurement of small-type optically stimulated luminescence (OSL) dosimeter by means of characteristic X-rays induced with general diagnostic X-ray equipment.

PubMed

Takegami, Kazuki; Hayashi, Hiroaki; Okino, Hiroki; Kimoto, Natsumi; Maehata, Itsumi; Kanazawa, Yuki; Okazaki, Tohru; Hashizume, Takuya; Kobayashi, Ikuo

2016-01-01

For X-ray inspections by way of general X-ray equipment, it is important to measure an entrance-skin dose. Recently, a small optically stimulated luminescence (OSL) dosimeter was made commercially available by Landauer, Inc. The dosimeter does not interfere with the medical images; therefore, it is expected to be a convenient detector for measuring personal exposure doses. In an actual clinical situation, it is assumed that X-rays of different energies will be detected by a dosimeter. For evaluation of the exposure dose measured by a dosimeter, it is necessary to know the energy dependence of the dosimeter. Our aim in this study was to measure the energy dependence of the OSL dosimeter experimentally in the diagnostic X-ray region. Metal samples weighing several grams were irradiated and, in this way, characteristic X-rays having energies ranging from 8 to 85 keV were generated. Using these mono-energetic X-rays, the dosimeter was irradiated. Simultaneously, the fluence of the X-rays was determined with a CdTe detector. The energy-dependent efficiency of the dosimeter was derived from the measured value of the dosimeter and the fluence. Moreover, the energy-dependent efficiency was calculated by Monte-Carlo simulation. The efficiency obtained in the experiment was in good agreement with that of the simulation. In conclusion, our proposed method, in which characteristic X-rays are used, is valuable for measurement of the energy dependence of a small OSL dosimeter in the diagnostic X-ray region.

Electronic gating circuit and ultraviolet laser excitation permit improved dosimeter sensitivity

NASA Technical Reports Server (NTRS)

Eggenberger, D.; King, D.; Longnecker, A.; Schutt, D.

1968-01-01

Standard dosimeter reader, modified by adding an electronic gating circuit to trigger the intensity level photomultiplier, increases readout sensitivity of photoluminescent dosimeter systems. The gating circuit is controlled by a second photomultiplier which senses a short ultraviolet pulse from a laser used to excite the dosimeter.

Low-cost solar array project: Four absolute cavity radiometer (pyrheliometer) intercomparisons at New River, Arizona: Radiometer standards

NASA Technical Reports Server (NTRS)

Estey, R. S.; Seaman, C. H.

1981-01-01

Four detailed intercomparisons were made for a number of models of cavity-type self-calibrating radiometers (pyrheliometers). Each intercomparison consisted of simultaneous readings of pyrheliometers at 30-second intervals in runs of 10 minutes, with at least 15 runs per intercomparison. Twenty-seven instruments were in at least one intercomparison, and five were in all four. Summarized results and all raw data are provided from the intercomparisons.

Pocket radiation dosimeter: dosimeter charger assembly

DOEpatents

Manning, F.W.

1982-03-17

This invention is a novel pocket-type radiation dosimeter comprising an electrometric radiation dosimeter and a charging circuit therefor. The instrument is especially designed to be amenable to mass production, to have a long shelf life, and to be compact, lightweight, and usable by the layman. The dosimeter proper may be of conventional design. The charging circuit includes a shake-type electrostatic generator, a voltage doubler for integrating generator output voltages of one polarity, and a switch operated by an external permanent magnet.

Pocket radiation dosimeter--dosimeter charger assembly

DOEpatents

Manning, Frank W.

1984-01-01

This invention is a novel pocket-type radiation dosimeter comprising an electrometric radiation dosimeter and a charging circuit therefor. The instrument is especially designed to be amenable to mass production, to have a long shelf life, and to be compact, lightweight, and usable by the layman. The dosimeter proper may be of conventional design. The charging circuit includes a shake-type electrostatic generator, a voltage doubler for integrating generator output voltages of one polarity, and a switch operated by an external permanent magnet.

Surface dose measurement for helical tomotherapy.

PubMed

Snir, Jonatan A; Mosalaei, Homeira; Jordan, Kevin; Yartsev, Slav

2011-06-01

To compare the surface dose measurements made by different dosimeters for the helical tomotherapy (HT) plan in the case of the target close to the surface. Surface dose measurements in different points for the HT plan to deliver 2 Gy to the planning target volume (PTV) at 5 mm below the surface of the cylindrical phantom were performed by radiochromic films, single use metal oxide semiconductor field-effect transistor (MOSFET) dosimeters, silicon IVD QED diode, and optically stimulated luminescence (OSL) dosimeters. The measured doses by all dosimeters were within 12 +/- 8% difference of each other. Radiochromic films, EBT, and EBT2, provide high spatial resolution, although it is difficult to get accurate measurements of dose. Both the OSL and QED measured similar dose to that of the MOSFET detectors. The QED dosimeter is promising as a reusable on-line wireless dosimeter, while the OSL dosimeters are easier to use, require minimum setup time and are very precise.

Dosimeter and method for using the same

DOEpatents

Warner, Benjamin P.; Johns, Deidre M.

2003-06-24

A very sensitive dosimeter that detects ionizing radiation is described. The dosimeter includes a breakable sealed container. A solution of a reducing agent is inside the container. The dosimeter has an air-tight dosimeter body with a transparent portion and an opaque portion. The transparent portion includes a transparent chamber that holds the breakable container with the reducing agent. The opaque portion includes an opaque chamber that holds an emulsion of silver salt (AgX) selected from silver chloride, silver bromide, silver iodide, and combinations of them. A passageway in the dosimeter provides fluid communication between the transparent chamber and the opaque chamber. The dosimeter may also include a chemical pH indicator in the breakable container that provides a detectable color change to the solution for a pH of about 3-10. The invention also includes a method of detecting ionizing radiation that involves producing the dosimeter, breaking the breakable container, allowing the solution to flow through the passageway and contact the emulsion, detecting any color change in the solution and using the color change to determine a radiation dosage.

The responses of three kinds of passive dosimeters to secondary cosmic rays in the lower atmosphere.

PubMed

Yang, Zhen; Chen, Bo; Zhuo, Weihai; Fan, Dunhuang; Zhao, Chao; Zhang, Yu

2015-12-01

For accurate measurements of the secondary cosmic rays by using passive dosimeters, the relative responses of the thermoluminescence dosimeter (TLD), optically stimulated luminescence (OSL) dosimeter, and radiophotoluminescent glass dosimeter (RPLGD) were studied. The cosmic-ray shower generator was used to simulate the secondary cosmic rays at the sea level. Monte Carlo simulations were performed to calculate the air kerma and absorbed doses in each kind of dosimeter. The results showed that compared with their responses to gamma rays of (137)Cs, the relative responses of the TLD, OSL, and RPLGD were 0.786, 0.707, and 0.735 to the hard component of cosmic rays, respectively, and the values were 0.904, 0.838, and 0.857 to the soft component of cosmic rays, respectively. To verify the simulations results, an in situ measurement with the three kinds of dosimeters was performed at the same place. The results indicated that the secondary cosmic rays monitored with the three kinds of dosimeters were well consistent with each other provided their relative responses were taken into account.

The responses of three kinds of passive dosimeters to secondary cosmic rays in the lower atmosphere

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

Yang, Zhen; Chen, Bo, E-mail: bochenfys@fudan.edu.cn; Zhuo, Weihai

For accurate measurements of the secondary cosmic rays by using passive dosimeters, the relative responses of the thermoluminescence dosimeter (TLD), optically stimulated luminescence (OSL) dosimeter, and radiophotoluminescent glass dosimeter (RPLGD) were studied. The cosmic-ray shower generator was used to simulate the secondary cosmic rays at the sea level. Monte Carlo simulations were performed to calculate the air kerma and absorbed doses in each kind of dosimeter. The results showed that compared with their responses to gamma rays of {sup 137}Cs, the relative responses of the TLD, OSL, and RPLGD were 0.786, 0.707, and 0.735 to the hard component of cosmicmore » rays, respectively, and the values were 0.904, 0.838, and 0.857 to the soft component of cosmic rays, respectively. To verify the simulations results, an in situ measurement with the three kinds of dosimeters was performed at the same place. The results indicated that the secondary cosmic rays monitored with the three kinds of dosimeters were well consistent with each other provided their relative responses were taken into account.« less

The responses of three kinds of passive dosimeters to secondary cosmic rays in the lower atmosphere

NASA Astrophysics Data System (ADS)

Yang, Zhen; Chen, Bo; Zhuo, Weihai; Fan, Dunhuang; Zhao, Chao; Zhang, Yu

2015-12-01

For accurate measurements of the secondary cosmic rays by using passive dosimeters, the relative responses of the thermoluminescence dosimeter (TLD), optically stimulated luminescence (OSL) dosimeter, and radiophotoluminescent glass dosimeter (RPLGD) were studied. The cosmic-ray shower generator was used to simulate the secondary cosmic rays at the sea level. Monte Carlo simulations were performed to calculate the air kerma and absorbed doses in each kind of dosimeter. The results showed that compared with their responses to gamma rays of 137Cs, the relative responses of the TLD, OSL, and RPLGD were 0.786, 0.707, and 0.735 to the hard component of cosmic rays, respectively, and the values were 0.904, 0.838, and 0.857 to the soft component of cosmic rays, respectively. To verify the simulations results, an in situ measurement with the three kinds of dosimeters was performed at the same place. The results indicated that the secondary cosmic rays monitored with the three kinds of dosimeters were well consistent with each other provided their relative responses were taken into account.

Anisn-Dort Neutron-Gamma Flux Intercomparison Exercise for a Simple Testing Model

NASA Astrophysics Data System (ADS)

Boehmer, B.; Konheiser, J.; Borodkin, G.; Brodkin, E.; Egorov, A.; Kozhevnikov, A.; Zaritsky, S.; Manturov, G.; Voloschenko, A.

2003-06-01

The ability of transport codes ANISN, DORT, ROZ-6, MCNP and TRAMO, as well as nuclear data libraries BUGLE-96, ABBN-93, VITAMIN-B6 and ENDF/B-6 to deliver consistent gamma and neutron flux results was tested in the calculation of a one-dimensional cylindrical model consisting of a homogeneous core and an outer zone with a single material. Model variants with H2O, Fe, Cr and Ni in the outer zones were investigated. The results are compared with MCNP-ENDF/B-6 results. Discrepancies are discussed. The specified test model is proposed as a computational benchmark for testing calculation codes and data libraries.

Entrance surface dose measurements using a small OSL dosimeter with a computed tomography scanner having 320 rows of detectors.

PubMed

Takegami, Kazuki; Hayashi, Hiroaki; Yamada, Kenji; Mihara, Yoshiki; Kimoto, Natsumi; Kanazawa, Yuki; Higashino, Kousaku; Yamashita, Kazuta; Hayashi, Fumio; Okazaki, Tohru; Hashizume, Takuya; Kobayashi, Ikuo

2017-03-01

Entrance surface dose (ESD) measurements are important in X-ray computed tomography (CT) for examination, but in clinical settings it is difficult to measure ESDs because of a lack of suitable dosimeters. We focus on the capability of a small optically stimulated luminescence (OSL) dosimeter. The aim of this study is to propose a practical method for using an OSL dosimeter to measure the ESD when performing a CT examination. The small OSL dosimeter has an outer width of 10 mm; it is assumed that a partial dose may be measured because the slice thickness and helical pitch can be set to various values. To verify our method, we used a CT scanner having 320 rows of detectors and checked the consistencies of the ESDs measured using OSL dosimeters by comparing them with those measured using Gafchromic™ films. The films were calibrated using an ionization chamber on the basis of half-value layer estimation. On the other hand, the OSL dosimeter was appropriately calibrated using a practical calibration curve previously proposed by our group. The ESDs measured using the OSL dosimeters were in good agreement with the reference ESDs from the Gafchromic™ films. Using these data, we also estimated the uncertainty of ESDs measured with small OSL dosimeters. We concluded that a small OSL dosimeter can be considered suitable for measuring the ESD with an uncertainty of 30 % during CT examinations in which pitch factors below 1.000 are applied.

Composite Resin Dosimeters: A New Concept and Design for a Fibrous Color Dosimeter.

PubMed

Kinashi, Kenji; Iwata, Takato; Tsuchida, Hayato; Sakai, Wataru; Tsutsumi, Naoto

2018-04-11

Polystyrene (PS)-based composite microfibers combined with a photochromic spiropyran dye, 1,3,3-trimethylindolino-6'-nitrobenzopyrylospiran (6-nitro BIPS), and a photostimulable phosphor, europium-doped barium fluorochloride (BaFCl:Eu 2+ ), were developed for the detection of X-ray exposure doses on the order of approximately 1 Gy. To produce the PS-based composite microfibers, we employed a forcespinning method that embeds a high concentration of phosphor in PS in a safe, inexpensive, and simple procedure. On the basis of the optimization of the forcespinning process, fibrous color dosimeters with a high radiation dose sensitivity of 1.2-4.4 Gy were fabricated. The color of the dosimeters was found to transition from white to blue in response to X-ray exposure. The optimized fibrous color dosimeter, made from a solution having a PS/6-nitro BIPS/BaFCl:Eu 2+ /C 2 Cl 4 ratio of 7.0/0.21/28.0/28.0 (wt %) and produced with a 290 mm distance between the needle and collectors, a 0.34 mm 23 G needle nozzle, and a spinneret rotational rate of 3000 rpm, exhibited sensitivity to a dose as low as 1.2 Gy. To realize practical applications, we manufactured the optimized fibrous color dosimeter into a clothlike color dosimeter. The clothlike color dosimeter was mounted on a stuffed bear, and its coloring behavior was demonstrated upon X-ray exposure. After exposure with X-ray, a blue colored and shaped in the form of the letter "[Formula: see text]" clearly appeared on the surface of the clothlike color dosimeter. The proposed fibrous color dosimeters having excellent workability will be an unprecedented dosimetry and contributed to all industries utilizing radiation dosimeters. This new fibrous "composite resin dosimeter" should be able to replace traditional, wearable, and individual radiation dose monitoring devices, such as film badges.

SU-D-213-07: Initial Characterization of a Gel Patch Dosimeter for in Vivo Dosimetry

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

Matrosic, C; Culberson, W; Rosen, B

Purpose: In vivo dosimetry, despite being the most direct method for monitoring the dose delivered during radiation therapy and being recommended by several national and international organizations (AAPM, ICRU, NACP), is underutilized in the clinic due to issues associated with dose sensitivity, feasibility, and cost. Given the increasing complexity of radiation therapy modern treatments, there is a compelling need for a robust, affordable in vivo dosimetry option. In this work we present the initial characterization of a novel gel patch in vivo dosimeter. Methods: DEFGEL (6%T) was used to make 1-cm thick small cylindrical patch dosimeters. The optical density ofmore » each dosimeter was read before and after irradiation by an in-house laser densitometer. The dosimeters were irradiated using a Varian Clinac EX linac. Three separate batches of gel patches were used to create dose response curves and evaluate repeatability. The development time of the dosimeter was also evaluated. Results: The dose response of the dosimeter was found to be linear from a range of approximately 1-Gy to 20-Gy, which is a larger window of linearity compared to other in vivo dosimeters. At doses below 1-Gy, the cumulative uncertainties were on the order of the measured data. When compared, the three batches demonstrated repeatability from 1-Gy to approximately 13-Gy, with some variation at higher doses. For doses of >8-Gy, the dosimeter reached full optical density after 4-hours, whereas low doses developed within an hour. Conclusion: Initial results indicate that the gel patch dosimeter is a reliable and simple way to measure a large range of doses, including high doses such as those delivered during hypofractionated treatments (e.g. SBRT or MR-guided radiotherapy). The simple fabrication method for the dosimeter and the use of a laser densitometer would allow for the dosimeter to used and read in-house, cheaply and easily.« less

Characteristics of optically stimulated luminescence dosimeters in the spread-out Bragg peak region of clinical proton beams

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

Kerns, James R.; Kry, Stephen F.; Sahoo, Narayan

Purpose: Optically stimulated luminescent detectors (OSLDs) have a number of advantages in radiation dosimetry making them excellent dosimeters for quality assurance and patient dose verification. Although the dosimeters have been investigated in several modalities, relatively little work has been done in examining the dosimeters for use in clinical proton beams. This study examined a number of characteristics of the response of the dosimeters in the spread-out Bragg peak (SOBP) region of clinical proton beams. Methods: Optically stimulated luminescence (OSL) dosimeters from Landauer, Inc., specifically the nanoDot dosimeter, were investigated. These dosimeters were placed in a special phantom with a recessmore » to fit the dosimeters without an air gap. Beams with nominal energies of 160, 200, and 250 MeV were used in the passively-scattered proton beam at the MD Anderson Cancer Center Proton Therapy Center. Dosimetric properties including linearity, field size dependence, energy dependence, residual signal as a function of cumulative dose, and postirradiation fading were investigated by taking measurements at the center of SOBPs. Results: The dosimeters showed 1% supralinearity at 200 cGy and 5% supralinearity at 1000 cGy. No noticeable field size dependence of the detector was found for field sizes from 2 x 2 cm{sup 2} to 18 x 18 cm{sup 2}. Residual signal as a function of cumulative dose showed a small increase for measurements up to 1000 cGy. Readout signal depletion of the dosimeters after consecutive readings showed a slightly larger depletion in protons for doses up to 500 cGy but not by a clinically significant amount. Within the center of various SOBP widths and proton energies the variation in response was less than 2%. An average beam quality factor of 1.089 with experimental standard deviation of 0.007 was determined and applied to the data such that the results were within 1.2% of ion chamber data. Conclusions: The nanoDot OSL dosimeter characteristics were studied in the SOBP region of clinical proton beams. To achieve accurate dosimetric readings, corrections to the dosimeter response were applied. Corrections tended to be minimal or broadly consistent. The nanoDot OSLD was found to be an acceptable dosimeter for measurement in the SOBP region for a range of clinical proton beams.« less

Characteristics of optically stimulated luminescence dosimeters in the spread-out Bragg peak region of clinical proton beams.

PubMed

Kerns, James R; Kry, Stephen F; Sahoo, Narayan

2012-04-01

Optically stimulated luminescent detectors (OSLDs) have a number of advantages in radiation dosimetry making them excellent dosimeters for quality assurance and patient dose verification. Although the dosimeters have been investigated in several modalities, relatively little work has been done in examining the dosimeters for use in clinical proton beams. This study examined a number of characteristics of the response of the dosimeters in the spread-out Bragg peak (SOBP) region of clinical proton beams. Optically stimulated luminescence (OSL) dosimeters from Landauer, Inc., specifically the nanoDot dosimeter, were investigated. These dosimeters were placed in a special phantom with a recess to fit the dosimeters without an air gap. Beams with nominal energies of 160, 200, and 250 MeV were used in the passively-scattered proton beam at the MD Anderson Cancer Center Proton Therapy Center. Dosimetric properties including linearity, field size dependence, energy dependence, residual signal as a function of cumulative dose, and postirradiation fading were investigated by taking measurements at the center of SOBPs. The dosimeters showed 1% supralinearity at 200 cGy and 5% supralinearity at 1000 cGy. No noticeable field size dependence of the detector was found for field sizes from 2 × 2 cm(2) to 18 × 18 cm(2). Residual signal as a function of cumulative dose showed a small increase for measurements up to 1000 cGy. Readout signal depletion of the dosimeters after consecutive readings showed a slightly larger depletion in protons for doses up to 500 cGy but not by a clinically significant amount. Within the center of various SOBP widths and proton energies the variation in response was less than 2%. An average beam quality factor of 1.089 with experimental standard deviation of 0.007 was determined and applied to the data such that the results were within 1.2% of ion chamber data. The nanoDot OSL dosimeter characteristics were studied in the SOBP region of clinical proton beams. To achieve accurate dosimetric readings, corrections to the dosimeter response were applied. Corrections tended to be minimal or broadly consistent. The nanoDot OSLD was found to be an acceptable dosimeter for measurement in the SOBP region for a range of clinical proton beams.

Comparative study of nuclear magnetic resonance and UV-visible spectroscopy dose-response of polymer gel based on N-(Isobutoxymethyl) acrylamide

NASA Astrophysics Data System (ADS)

Lotfy, S.; Basfar, A. A.; Moftah, B.; Al-Moussa, A. A.

2017-12-01

A comparative study of nuclear magnetic resonance and UV-visible spectroscopy of dose-response for polymer gel dosimeters was performed. Dosimeters were prepared using N-(Isobutoxymethyl) acrylamide (NIBMA) as a new monomer via radiation induced polymerization for use in radiotherapy planning. The prepared dosimeters were irradiated with doses up to 30 Gy at a constant dose rate of 600 MU/min. Using a medical linear accelerator at irradiation energies of 6, 10 and 18 MV photon beam. The nuclear magnetic resonance (NMR), via spin-spin relaxation rate (R2) for water proton surrounding the polymer formulation and UV-Visible spectroscopy, via the optical absorbance measurements of irradiated dosimeters at selected wavelengths of 500 nm, was used to investigate the dose response of NIBMAGAT gel dosimeters. Scavenge of oxygen was done using tetrakis (hydroxymethyl) phosphonium chloride (THPC). The THPC optimum concentration in the dosimeters formulations were 5 and 10 mM for the NMR and optical absorbance measurements respectively. The quantitative investigation of the dosimeters components reveals the selective formulations based on 4% w/w gelatin, 1% w/w NIBMA, 3% w/w BisAAm, 5 or 10 mM THPC and 17% w/w glycerol which significantly increase the dosimeters dose response. The prepared dosimeters were found to be dose rate and photon beam irradiation energy independent. The stability study shows no change in the relaxation rate or in the optical absorbance of the gel dosimeters up to 8 days post-irradiation. The prepared polymer gel dosimeters at the energies of 6, 10 and 18 MV photon beam irradiation in the range of 1-30 Gy have the linearity of the dose response function in the case of R2 is better than in the case of absorbance measurements; correlation coefficient (r2) equals 0.995 and 0.991, respectively. Dose sensitivity, R2 of NIBMAGAT dosimeters (0.0775 s-1 Gy-1). The absorption band intensity increases linearly with a dose sensitivity of 0.016 cm-1 Gy-1. The detection limit of the present dosimeter analyzed by R2 and absorbance measurements is 1 Gy and 2 Gy respectively. The overall uncertainty measurements of dose approve that by using the absorbance measurements the gel is not useful as a dosimeter like as R2 measurements. It could be a new composition of dosimeters successfully utilized for MRI (Magnetic Resonance Imaging) for radiotherapy treatment planning.

2014 ICHLNRRA intercomparison of radon/thoron gas and radon short-lived decay products measuring instruments in the NRPI Prague.

PubMed

Jílek, K; Timková, J

2015-06-01

During the Eighth International Conference on High Levels of Natural Radiation and Radon Areas held in autumn 2014 at Prague, the third intercomparison of radon/thoron gas and radon short-lived decay products measurement instruments was organised by and held at the Natural Radiation Division of the National Radiation Protection Institute (NRPI; SÚRO v.v.i.) in Prague. The intercomparison was newly focussed also on continuous monitors with active sampling adapters capable to distinguish radon/thoron gas in their mix field.The results of radon gas measurements carried out in the big NRPI radon chamber indicated very well an average deviation of up to 5 % from the reference NRPI value for 80 % of all the exposed instruments. The results of equilibrium equivalent concentration continuous monitors indicated an average deviation of up to 5 % from the reference NRPI value for 40 % of all the exposed instruments and their ~8-10 % shift compared with the NRPI. The results of investigated ambient conditions upon response of exposed continuous monitors indicated influence of aerosol changes upon response of radon monitors with an active air sampling adapters through the filter, only. The exposures of both radon/thoron gas discriminative continuous monitors and passive detectors have been indicated inconsistent results: on one hand, their excellent agreement up to several per cent for both the gases, and on the other hand, systematic unsatisfactory differences up to 40 %. Additional radon/thoron exercises are recommended to improve both the instruments themselves and quality of their operators. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Recommendations for diagnosing effective radiative forcing from climate models for CMIP6

DOE PAGES

Forster, Piers M.; Richardson, Thomas; Maycock, Amanda C.; ...

2016-10-27

The usefulness of previous Coupled Model Intercomparison Project (CMIP) exercises has been hampered by a lack of radiative forcing information. This has made it difficult to understand reasons for differences between model responses. Effective radiative forcing (ERF) is easier to diagnose than traditional radiative forcing in global climate models (GCMs) and is more representative of the eventual temperature response. Here we examine the different methods of computing ERF in two GCMs. We find that ERF computed from a fixed sea surface temperature (SST) method (ERF_fSST) has much more certainty than regression based methods. Thirty year integrations are sufficient to reducemore » the 5–95% confidence interval in global ERF_fSST to 0.1Wm ~2. For 2xCO2 ERF, 30 year integrations are needed to ensure that the signal is larger than the local confidence interval over more than 90% of the globe. Within the ERF_fSST method there are various options for prescribing SSTs and sea ice. We explore these and find that ERF is only weakly dependent on the methodological choices. Prescribing the monthly averaged seasonally varying model’s preindustrial climatology is recommended for its smaller random error and easier implementation. As part of CMIP6, the Radiative Forcing Model Intercomparison Project (RFMIP) asks models to conduct 30 year ERF_fSST experiments using the model’s own preindustrial climatology of SST and sea ice. The Aerosol and Chemistry Model Intercomparison Project (AerChemMIP) will also mainly use this approach. Lastly, we propose this as a standard method for diagnosing ERF and recommend that it be used across the climate modeling community to aid future comparisons.« less

Recommendations for diagnosing effective radiative forcing from climate models for CMIP6

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

Forster, Piers M.; Richardson, Thomas; Maycock, Amanda C.

The usefulness of previous Coupled Model Intercomparison Project (CMIP) exercises has been hampered by a lack of radiative forcing information. This has made it difficult to understand reasons for differences between model responses. Effective radiative forcing (ERF) is easier to diagnose than traditional radiative forcing in global climate models (GCMs) and is more representative of the eventual temperature response. Here we examine the different methods of computing ERF in two GCMs. We find that ERF computed from a fixed sea surface temperature (SST) method (ERF_fSST) has much more certainty than regression based methods. Thirty year integrations are sufficient to reducemore » the 5–95% confidence interval in global ERF_fSST to 0.1Wm ~2. For 2xCO2 ERF, 30 year integrations are needed to ensure that the signal is larger than the local confidence interval over more than 90% of the globe. Within the ERF_fSST method there are various options for prescribing SSTs and sea ice. We explore these and find that ERF is only weakly dependent on the methodological choices. Prescribing the monthly averaged seasonally varying model’s preindustrial climatology is recommended for its smaller random error and easier implementation. As part of CMIP6, the Radiative Forcing Model Intercomparison Project (RFMIP) asks models to conduct 30 year ERF_fSST experiments using the model’s own preindustrial climatology of SST and sea ice. The Aerosol and Chemistry Model Intercomparison Project (AerChemMIP) will also mainly use this approach. Lastly, we propose this as a standard method for diagnosing ERF and recommend that it be used across the climate modeling community to aid future comparisons.« less

Recommendations for diagnosing effective radiative forcing from climate models for CMIP6

NASA Astrophysics Data System (ADS)

Smith, C. J.; Forster, P.; Richardson, T.; Myhre, G.; Pincus, R.

2016-12-01

The usefulness of previous Coupled Model Intercomparison Project (CMIP) exercises has been hampered by a lack of radiative forcing information. This has made it difficult to understand reasons for differences between model responses. Effective radiative forcing (ERF) is easier to diagnose than traditional radiative forcing in global climate models (GCMs) and is more representative of the ultimate climate response. Here we examine the different methods of computing ERF in two GCMs. We find that ERF computed from a fixed sea-surface temperature (SST) method (ERF_fSST) has much more certainty than regression-based methods. Thirty-year integrations are sufficient to reduce the standard error in global ERF to 0.05 Wm-2. For 2xCO2 ERF, 30 year integrations are needed to ensure that the signal is larger than the standard error over more than 90% of the globe. Within the ERF_fSST method there are various options for prescribing SSTs and sea-ice. We explore these and find that ERF is only weakly dependent on the methodological choices. Prescribing the monthly-averaged seasonally varying model's preindustrial climatology is recommended for its smaller random error and easier implementation. As part of CMIP6, the Radiative Forcing Model Intercomparison Project (RFMIP) asks models to conduct 30-year ERF_fSST experiments using the model's own preindustrial climatology of SST and sea-ice. The Aerosol and Chemistry Model intercomparison Project (AerChemMIP) will also mainly use this approach. We propose this as a standard method for diagnosing ERF in models and recommend that it be used across the climate modeling community to aid future comparisons.

Recommendations for diagnosing effective radiative forcing from climate models for CMIP6

NASA Astrophysics Data System (ADS)

Forster, Piers M.; Richardson, Thomas; Maycock, Amanda C.; Smith, Christopher J.; Samset, Bjorn H.; Myhre, Gunnar; Andrews, Timothy; Pincus, Robert; Schulz, Michael

2016-10-01

The usefulness of previous Coupled Model Intercomparison Project (CMIP) exercises has been hampered by a lack of radiative forcing information. This has made it difficult to understand reasons for differences between model responses. Effective radiative forcing (ERF) is easier to diagnose than traditional radiative forcing in global climate models (GCMs) and is more representative of the eventual temperature response. Here we examine the different methods of computing ERF in two GCMs. We find that ERF computed from a fixed sea surface temperature (SST) method (ERF_fSST) has much more certainty than regression based methods. Thirty year integrations are sufficient to reduce the 5-95% confidence interval in global ERF_fSST to 0.1 W m-2. For 2xCO2 ERF, 30 year integrations are needed to ensure that the signal is larger than the local confidence interval over more than 90% of the globe. Within the ERF_fSST method there are various options for prescribing SSTs and sea ice. We explore these and find that ERF is only weakly dependent on the methodological choices. Prescribing the monthly averaged seasonally varying model's preindustrial climatology is recommended for its smaller random error and easier implementation. As part of CMIP6, the Radiative Forcing Model Intercomparison Project (RFMIP) asks models to conduct 30 year ERF_fSST experiments using the model's own preindustrial climatology of SST and sea ice. The Aerosol and Chemistry Model Intercomparison Project (AerChemMIP) will also mainly use this approach. We propose this as a standard method for diagnosing ERF and recommend that it be used across the climate modeling community to aid future comparisons.

GAMMA AND X-RAY DOSIMETER AND DOSIMETRIC METHOD

DOEpatents

Taplin, G.V.; Douglas, C.H.; Sigoloff, S.C.

1958-08-19

An improvement in colorimetric gamma and x-ray dosimeter systems and a self-contained. hand carried dostmeter of the afore-mentioned type ts described. A novel point of the invention ltes in the addition of specific quantities of certain normalizing agents to the two phase chlorinated hydro-carbon-aqueous dyc colortmetric dosimeter to eliminate the after reaction and thereby extend the utility of such systein. The structure of the two phase colorimetric dosimeter tubes and the carrying case for the tubes of the portable dosimeter are unique features.

An NMR relaxometry and gravimetric study of gelatin-free aqueous polyacrylamide dosimeters

NASA Astrophysics Data System (ADS)

Babic, Steven; Schreiner, L. John

2006-09-01

In conformal radiation therapy, a high dose of radiation is given to a target volume to increase the probability of cure, and care is taken to minimize the dose to surrounding healthy tissue. The techniques used to achieve this are very complicated and the precise verification of the resulting three-dimensional (3D) dose distribution is required. Polyacrylamide gelatin (PAG) dosimeters with magnetic resonance imaging and optical computed tomography scanning provide the required 3D dosimetry with high spatial resolution. Many basic studies have characterized these chemical dosimeters that polymerize under irradiation. However, the investigation of the fundamental properties of the radiation-induced polymerization in PAG dosimeters is complicated by the presence of the background gelatin matrix. In this work, a gelatin-free model system for the study of the basic radiation-induced polymerization in PAG dosimeters has been developed. Experiments were performed on gelatin-free dosimeters, named aqueous polyacrylamide (APA) dosimeters, containing equal amounts of acrylamide and N,N'-methylene-bisacrylamide. The APA dosimeters were prepared with four different total monomer concentrations (2, 4, 6 and 8% by weight). Nuclear magnetic resonance (NMR) spin-spin and spin-lattice proton relaxation measurements at 20 MHz, and gravimetric analyses performed on all four dosimeters, show a continuous degree of polymerization over the dose range of 0-25 Gy. The developed NMR model explains the relationship observed between the relaxation data and the amount of crosslinked polymer formed at each dose. This model can be extended with gelatin relaxation data to provide a fundamental understanding of radiation-induced polymerization in the conventional PAG dosimeters.

Technical Note: Improving proton stopping power ratio determination for a deformable silicone-based 3D dosimeter using dual energy CT

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

Taasti, Vicki Trier, E-mail: victaa@rm.dk; Høye, Ellen Marie; Hansen, David Christoffer

Purpose: The aim of this study was to investigate whether the stopping power ratio (SPR) of a deformable, silicone-based 3D dosimeter could be determined more accurately using dual energy (DE) CT compared to using conventional methods based on single energy (SE) CT. The use of SECT combined with the stoichiometric calibration method was therefore compared to DECT-based determination. Methods: The SPR of the dosimeter was estimated based on its Hounsfield units (HUs) in both a SECT image and a DECT image set. The stoichiometric calibration method was used for converting the HU in the SECT image to a SPR valuemore » for the dosimeter while two published SPR calibration methods for dual energy were applied on the DECT images. Finally, the SPR of the dosimeter was measured in a 60 MeV proton by quantifying the range difference with and without the dosimeter in the beam path. Results: The SPR determined from SECT and the stoichiometric method was 1.10, compared to 1.01 with both DECT calibration methods. The measured SPR for the dosimeter material was 0.97. Conclusions: The SPR of the dosimeter was overestimated by 13% using the stoichiometric method and by 3% when using DECT. If the stoichiometric method should be applied for the dosimeter, the HU of the dosimeter must be manually changed in the treatment planning system in order to give a correct SPR estimate. Using a wrong SPR value will cause differences between the calculated and the delivered treatment plans.« less

An NMR relaxometry and gravimetric study of gelatin-free aqueous polyacrylamide dosimeters.

PubMed

Babic, Steven; Schreiner, L John

2006-09-07

In conformal radiation therapy, a high dose of radiation is given to a target volume to increase the probability of cure, and care is taken to minimize the dose to surrounding healthy tissue. The techniques used to achieve this are very complicated and the precise verification of the resulting three-dimensional (3D) dose distribution is required. Polyacrylamide gelatin (PAG) dosimeters with magnetic resonance imaging and optical computed tomography scanning provide the required 3D dosimetry with high spatial resolution. Many basic studies have characterized these chemical dosimeters that polymerize under irradiation. However, the investigation of the fundamental properties of the radiation-induced polymerization in PAG dosimeters is complicated by the presence of the background gelatin matrix. In this work, a gelatin-free model system for the study of the basic radiation-induced polymerization in PAG dosimeters has been developed. Experiments were performed on gelatin-free dosimeters, named aqueous polyacrylamide (APA) dosimeters, containing equal amounts of acrylamide and N,N'-methylene-bisacrylamide. The APA dosimeters were prepared with four different total monomer concentrations (2, 4, 6 and 8% by weight). Nuclear magnetic resonance (NMR) spin-spin and spin-lattice proton relaxation measurements at 20 MHz, and gravimetric analyses performed on all four dosimeters, show a continuous degree of polymerization over the dose range of 0-25 Gy. The developed NMR model explains the relationship observed between the relaxation data and the amount of crosslinked polymer formed at each dose. This model can be extended with gelatin relaxation data to provide a fundamental understanding of radiation-induced polymerization in the conventional PAG dosimeters.

Development of a wavelength-separated type scintillator with optical fiber (SOF) dosimeter to compensate for the Cerenkov radiation effect

PubMed Central

Ishikawa, Masayori; Nagase, Naomi; Matsuura, Taeko; Hiratsuka, Junichi; Suzuki, Ryusuke; Miyamoto, Naoki; Sutherland, Kenneth Lee; Fujita, Katsuhisa; Shirato, Hiroki

2015-01-01

Abstract The scintillator with optical fiber (SOF) dosimeter consists of a miniature scintillator mounted on the tip of an optical fiber. The scintillator of the current SOF dosimeter is a 1-mm diameter hemisphere. For a scintillation dosimeter coupled with an optical fiber, measurement accuracy is influenced by signals due to Cerenkov radiation in the optical fiber. We have implemented a spectral filtering technique for compensating for the Cerenkov radiation effect specifically for our plastic scintillator-based dosimeter, using a wavelength-separated counting method. A dichroic mirror was used for separating input light signals. Individual signal counting was performed for high- and low-wavelength light signals. To confirm the accuracy, measurements with various amounts of Cerenkov radiation were performed by changing the incident direction while keeping the Ir-192 source-to-dosimeter distance constant, resulting in a fluctuation of <5%. Optical fiber bending was also addressed; no bending effect was observed for our wavelength-separated SOF dosimeter. PMID:25618136

In situ ion-beam-induced luminescence analysis for evaluating a micrometer-scale radio-photoluminescence glass dosimeter

NASA Astrophysics Data System (ADS)

Kawabata, Shunsuke; Kada, Wataru; Parajuli, Raj Kumar; Matsubara, Yoshinori; Sakai, Makoto; Miura, Kenta; Satoh, Takahiro; Koka, Masashi; Yamada, Naoto; Kamiya, Tomihiro; Hanaizumi, Osamu

2016-06-01

Micrometer-scale responses of radio-photoluminescence (RPL) glass dosimeters to focused ionized particle radiation were evaluated by combining ion-beam-induced luminescence (IBIL) and proton beam writing (PBW) using a 3 MeV focused proton microbeam. RPL phosphate glass dosimeters doped with ionic Ag or Cu activators at concentrations of 0.2 and 0.1% were fabricated, and their scintillation intensities were evaluated by IBIL spectroscopy under a PBW micropatterning condition. Compared with the Ag-doped dosimeter, the Cu-doped dosimeter was more tolerant of the radiation, while the peak intensity of its luminescence was lower, under the precise dose control of the proton microprobe. Proton-irradiated areas were successfully recorded using these dosimeters and their RPL centers were visualized under 375 nm ultraviolet light. The reproduction of the irradiated region by post-RPL imaging suggests that precise estimation of irradiation dose using microdosimeters can be accomplished by optimizing RPL glass dosimeters for various proton microprobe applications in organic material analysis and in micrometer-scale material modifications.

Water equivalency evaluation of PRESAGE® dosimeters for dosimetry of Cs-137 and Ir-192 brachytherapy sources

NASA Astrophysics Data System (ADS)

Gorjiara, Tina; Hill, Robin; Kuncic, Zdenka; Baldock, Clive

2010-11-01

A major challenge in brachytherapy dosimetry is the measurement of steep dose gradients. This can be achieved with a high spatial resolution three dimensional (3D) dosimeter. PRESAGE® is a polyurethane based dosimeter which is suitable for 3D dosimetry. Since an ideal dosimeter is radiologically water equivalent, we have investigated the relative dose response of three different PRESAGE® formulations, two with a lower chloride and bromide content than original one, for Cs-137 and Ir-192 brachytherapy sources. Doses were calculated using the EGSnrc Monte Carlo package. Our results indicate that PRESAGE® dosimeters are suitable for relative dose measurement of Cs-137 and Ir-192 brachytherapy sources and the lower halogen content PRESAGE® dosimeters are more water equivalent than the original formulation.

Laser readable thermoluminescent radiation dosimeters and methods for producing thereof

DOEpatents

Braunlich, Peter F.; Tetzlaff, Wolfgang

1989-01-01

Thin layer thermoluminescent radiation dosimeters for use in laser readable dosimetry systems, and methods of fabricating such thin layer dosimeters. The thin layer thermoluminescent radiation dosimeters include a thin substrate made from glass or other inorganic materials capable of withstanding high temperatures and high heating rates. A thin layer of a thermoluminescent phoshphor material is heat bonded to the substrate using an inorganic binder such as glass. The dosimeters can be mounted in frames and cases for ease in handling. Methods of the invention include mixing a suitable phosphor composition and binder, both being in particulate or granular form. The mixture is then deposited onto a substrate such as by using mask printing techniques. The dosimeters are thereafter heated to fuse and bond the binder and phosphor to the substrate.

Indoor and Outdoor Spectroradiometer Intercomparison for Spectral Irradiance Measurement

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

Habte, A.; Andreas, A.; Ottoson, L.

2014-05-01

This report details the global spectral irradiance intercomparison using spectroradiometers that was organized by the National Renewable Energy Laboratory's Solar Radiation Research Laboratory. The intercomparison was performed both indoors and outdoors on September 17, 2013. Five laboratories participated in the intercomparison using 10 spectroradiometers, and a coordinated measurement setup and a common platform were employed to compare spectral irradiances under both indoor and outdoor conditions. The intercomparison aimed to understand the performance of the different spectroradiometers and to share knowledge in making spectral irradiance measurements. This intercomparison was the first of its kind in the United States.

Fast-neutron solid-state dosimeter

DOEpatents

Kecker, K.H.; Haywood, F.F.; Perdue, P.T.; Thorngate, J.H.

1975-07-22

This patent relates to an improved fast-neutron solid-state dosimeter that does not require separation of materials before it can be read out, that utilizes materials that do not melt or otherwise degrade at about 300$sup 0$C readout temperature, that provides a more efficient dosimeter, and that can be reused. The dosimeters are fabricated by intimately mixing a TL material, such as CaSO$sub 4$:Dy, with a powdered polyphenyl, such as p-sexiphenyl, and hot- pressing the mixture to form pellets, followed by out-gassing in a vacuum furnace at 150$sup 0$C prior to first use dosimeters. (auth)

Photon Dosimetry by Luminescence Methods

ERIC Educational Resources Information Center

Raeside, D. E.

1973-01-01

Discusses the fundamentals of two personnel dosimeters: the lithium fluoride thermoluminescent dosimeter and the silver-activated phosphate glass radiophotoluminescent dosimeter, and indicates the usefulness of this presentation for both teachers and students. (CC)

TU-E-TOUR-I-00: Exhibit Hall Guided Tours-Dosimters for QC in Diagnostic Imaging (Tuesday)

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

NONE

Tour Leader: Xia Jiang, Ohio State University, Columbus, OH Tour Guides: Xia Jiang, Ohio State University, Columbus, OH Kevin Little, The University of Chicago, Chicago, IL Christina Sammet, Lurie Children’s Hospital of Chicago, Chicago, IL Participating Vendors: IBA PTW - New York Radcal Corporation RTI Electronics, Inc. Exhibit Hall Guided Tours is a new program launching this year at the Annual Meeting. The Guided Tours are designed to enhance the interaction between meeting attendees and exhibitors. This year’s Imaging Guided Tours are organized around the theme of dosimeters for quality control in diagnostic imaging. Tours will begin with an introductionmore » and background given by Dr. Xia Jiang, the Tour Leader. The introduction will cover the types and properties of different radiation dosimeters used for quality assurance in clinical radiology. Attendees will then break into smaller groups, each lead by an AAPM-member Tour Guide. The tour groups will visit the exhibit booths of vendors who provide appropriate dosimeters, and a vendor representative will give a presentation to the group about their particular product(s). The vendor representatives as well as the Tour Guides will be available to answer questions. Outline: Types and properties of radiation detectors and dosimeters Ionization chamber dosimeters Solid state dosimeters Dosimeter calibration: Primary and secondary standards dosimetry laboratories Instruments for measuring tube voltage and exposure time Vendor presentations will likely cover features and innovations of different dosimeter systems, as well as their practical use. Learning Objectives: Understand the types and properties of different instrumentations used for quality control in diagnostic imaging. Understand the process of dosimeter calibration. Gain familiarity with the latest commercial dosimeter systems from different vendors.« less

WE-C-TOUR-I-00: Exhibit Hall Guided Tours-Dosimters for QC in Diagnostic Imaging (Wednesday)

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

NONE

Tour Leader: Xia Jiang, Ohio State University, Columbus, OH Tour Guides: Xia Jiang, Ohio State University, Columbus, OH Kevin Little, The University of Chicago, Chicago, IL Adrien Sanchez, University of Chicago, Chicago, IL Participating Vendors: IBA PTW - New York Radcal Corporation RTI Electronics, Inc. Exhibit Hall Guided Tours is a new program launching this year at the Annual Meeting. The Guided Tours are designed to enhance the interaction between meeting attendees and exhibitors. This year’s Imaging Guided Tours are organized around the theme of dosimeters for quality control in diagnostic imaging. Tours will begin with an introduction and backgroundmore » given by Dr. Xia Jiang, the Tour Leader. The introduction will cover the types and properties of different radiation dosimeters used for quality assurance in clinical radiology. Attendees will then break into smaller groups, each lead by an AAPM-member Tour Guide. The tour groups will visit the exhibit booths of vendors who provide appropriate dosimeters, and a vendor representative will give a presentation to the group about their particular product(s). The vendor representatives as well as the Tour Guides will be available to answer questions. Outline: Types and properties of radiation detectors and dosimeters Ionization chamber dosimeters Solid state dosimeters Dosimeter calibration: Primary and secondary standards dosimetry laboratories Instruments for measuring tube voltage and exposure time Vendor presentations will likely cover features and innovations of different dosimeter systems, as well as their practical use. Learning Objectives: Understand the types and properties of different instrumentations used for quality control in diagnostic imaging. Understand the process of dosimeter calibration. Gain familiarity with the latest commercial dosimeter systems from different vendors.« less

WE-C-TOUR-I-01: Dosimters for QC in Diagnostic Imaging

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

Jiang, X.

Tour Leader: Xia Jiang, Ohio State University, Columbus, OH Tour Guides: Xia Jiang, Ohio State University, Columbus, OH Kevin Little, The University of Chicago, Chicago, IL Adrien Sanchez, University of Chicago, Chicago, IL Participating Vendors: IBA PTW - New York Radcal Corporation RTI Electronics, Inc. Exhibit Hall Guided Tours is a new program launching this year at the Annual Meeting. The Guided Tours are designed to enhance the interaction between meeting attendees and exhibitors. This year’s Imaging Guided Tours are organized around the theme of dosimeters for quality control in diagnostic imaging. Tours will begin with an introduction and backgroundmore » given by Dr. Xia Jiang, the Tour Leader. The introduction will cover the types and properties of different radiation dosimeters used for quality assurance in clinical radiology. Attendees will then break into smaller groups, each lead by an AAPM-member Tour Guide. The tour groups will visit the exhibit booths of vendors who provide appropriate dosimeters, and a vendor representative will give a presentation to the group about their particular product(s). The vendor representatives as well as the Tour Guides will be available to answer questions. Outline: Types and properties of radiation detectors and dosimeters Ionization chamber dosimeters Solid state dosimeters Dosimeter calibration: Primary and secondary standards dosimetry laboratories Instruments for measuring tube voltage and exposure time Vendor presentations will likely cover features and innovations of different dosimeter systems, as well as their practical use. Learning Objectives: Understand the types and properties of different instrumentations used for quality control in diagnostic imaging. Understand the process of dosimeter calibration. Gain familiarity with the latest commercial dosimeter systems from different vendors.« less

TH-CD-BRA-04: Effect of a Strong Magnetic Field On TLDs, OSLDs, and Gafchromic Films Using An Electromagnet

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

Wang, J; Rubinstein, A; Ohrt, J

Purpose: To study the effect of strong magnetic field on three types of dosimeters using an electromagnet inside a Linac vault. Materials and Methods: Three types of dosimeters, thermoluminescent Dosimeters (TLDs), optically stimulated luminescent Dosimeters (OSLDs), and EBT3 Film were used to measure radiation dose response inside an electromagnet that could produce a strong magnetic field (B>1.5 T). The dosimeters were placed inside a plastic phantom between the two poles of the magnet, at approximately 3 meters from the iso-center of an Elekta Versa HD Linac. The B field was calibrated with a Gauss meter (Model: GM-2, AlphaLab Inc). Themore » dosimeters received ∼2 Gy with and without the presence of the 1.5 T magnetic field. The EBT3 films were scanned 24 hours before and 24 hours after irradiation. The TLD dosimeters were read 1 week after irradiation. The OSLDs were read two weeks after irradiation. The ratios of signals of dosimeters irradiated with the B field to the signals without the B field were calculated. Two experiments have been conducted so far. Results: The ratios (averaged over two experiments) of dosimeter signals with vs without B field were 0.994 for films, 0.994 for OSLDs, and 1.002 for TLDs. The statistical uncertainty was ∼3%. Conclusions: The three types of dosimeters (film, TLD, OSLD) seem not affected by the presence of a magnetic field (B=1.5 T) with the uncertainty of ∼3%. They may be suitable for QA purposes in a strong B field up to 1.5 T. More measurements will be conducted for reproducibility testing. We acknowledge research support from Elekta AB.« less

Laser readable thermoluminescent radiation dosimeters and methods for producing thereof

DOEpatents

Braunlich, P.F.; Tetzlaff, W.

1989-04-25

Thin layer thermoluminescent radiation dosimeters for use in laser readable dosimetry systems, and methods of fabricating such thin layer dosimeters are disclosed. The thin layer thermoluminescent radiation dosimeters include a thin substrate made from glass or other inorganic materials capable of withstanding high temperatures and high heating rates. A thin layer of a thermoluminescent phosphor material is heat bonded to the substrate using an inorganic binder such as glass. The dosimeters can be mounted in frames and cases for ease in handling. Methods of the invention include mixing a suitable phosphor composition and binder, both being in particulate or granular form. The mixture is then deposited onto a substrate such as by using mask printing techniques. The dosimeters are thereafter heated to fuse and bond the binder and phosphor to the substrate. 34 figs.

Development of a Dosimeter System for Unsymmetrical Dimethylhydrazine, Monomethylhydrazine and Hydrazine

DTIC Science & Technology

1994-06-27

the amount of dilution air . Conditioned house- compressed air was used as the diluent. The conditioning procedure consisted of passing the house air ...unsymmetrical dlmethylhydrazine (UDMI-) in air has been developed. The dosimeter consists of a replaceable dosimeter card and a reusable...Department of Defense and NASA require air monitoring for hydrazines in areas where they are handled and/or stored. A real-time dosimeter using vanillin

Guide to U.S. Atmospheric Nuclear Weapon Effects Data

DTIC Science & Technology

1993-12-01

biological warfare agents, and radiation dosimeters . XRD- 163 identifies the test location of each 4-6 biological sample. Reports containing the results...along with position of the animals at the time of the detonation. Vycor Glass Gamma Ray Dosimeters XRD-176 A rugged new dosimeter capable of measuring...gamma doses on animals exposed to high levels of radiation was employed during Able. Dosimeter readings, locations, and animal condition are reported

Measurement of relative depth-dose distribution in radiochromic film dosimeters irradiated with 43-70 keV electron beam for industrial application

NASA Astrophysics Data System (ADS)

Matsui, Shinjiro; Hattori, Takeaki; Nonaka, Takashi; Watanabe, Yuki; Morita, Ippei; Kondo, Junichi; Ishikawa, Masayoshi; Mori, Yoshitaka

2018-05-01

The relative dose in a layer, which is thinner than the thickness of the dosimeter is evaluated using simulated depth-dose distributions, and the measured responses of dosimeters with acceleration voltages from 43 to 70 kV, via ultra-low-energy electron beam (ULEB) irradiation. By stacking thin film dosimeters, we confirmed that the simulated depth-dose distributions coincided with the measured depth-dose curve within the measurement uncertainty (k = 2). Using the measurement dose of the 47 μm dosimeter and the simulated depth-dose distribution, the dose of 11 μm dosimeters in the surface was evaluated within the measurement uncertainty (k = 2). We also verified the effectiveness of this method for a thinner layer by changing the acceleration voltage of the irradiation source. We evaluated the relative dose for an adjusted depth of energy deposition from 4.4 μm to 22.8 μm. As a result, this method was found to be effective for a thickness, which is less than the thickness of the dosimeter. When irradiation conditions are well known with accuracy, using the confirmed relative depth-dose distributions across any dosimeter thickness range, a dose evaluation, in several μm steps will possibly improve the design of industrial ULEB processes.

[Accuracy Check of Monte Carlo Simulation in Particle Therapy Using Gel Dosimeters].

PubMed

Furuta, Takuya

2017-01-01

Gel dosimeters are a three-dimensional imaging tool for dose distribution induced by radiations. They can be used for accuracy check of Monte Carlo simulation in particle therapy. An application was reviewed in this article. An inhomogeneous biological sample placing a gel dosimeter behind it was irradiated by carbon beam. The recorded dose distribution in the gel dosimeter reflected the inhomogeneity of the biological sample. Monte Carlo simulation was conducted by reconstructing the biological sample from its CT image. The accuracy of the particle transport by Monte Carlo simulation was checked by comparing the dose distribution in the gel dosimeter between simulation and experiment.

Design of Interrogation Protocols for Radiation Dose Measurements Using Optically-Stimulated Luminescent Dosimeters.

PubMed

Abraham, Sara A; Kearfott, Kimberlee J; Jawad, Ali H; Boria, Andrew J; Buth, Tobias J; Dawson, Alexander S; Eng, Sheldon C; Frank, Samuel J; Green, Crystal A; Jacobs, Mitchell L; Liu, Kevin; Miklos, Joseph A; Nguyen, Hien; Rafique, Muhammad; Rucinski, Blake D; Smith, Travis; Tan, Yanliang

2017-03-01

Optically-stimulated luminescent dosimeters are capable of being interrogated multiple times post-irradiation. Each interrogation removes a fraction of the signal stored within the optically-stimulated luminescent dosimeter. This signal loss must be corrected to avoid systematic errors in estimating the average signal of a series of optically-stimulated luminescent dosimeter interrogations and requires a minimum number of consecutive readings to determine an average signal that is within a desired accuracy of the true signal with a desired statistical confidence. This paper establishes a technical basis for determining the required number of readings for a particular application of these dosimeters when using certain OSL dosimetry systems.

Development of a wavelength-separated type scintillator with optical fiber (SOF) dosimeter to compensate for the Cerenkov radiation effect.

PubMed

Ishikawa, Masayori; Nagase, Naomi; Matsuura, Taeko; Hiratsuka, Junichi; Suzuki, Ryusuke; Miyamoto, Naoki; Sutherland, Kenneth Lee; Fujita, Katsuhisa; Shirato, Hiroki

2015-03-01

The scintillator with optical fiber (SOF) dosimeter consists of a miniature scintillator mounted on the tip of an optical fiber. The scintillator of the current SOF dosimeter is a 1-mm diameter hemisphere. For a scintillation dosimeter coupled with an optical fiber, measurement accuracy is influenced by signals due to Cerenkov radiation in the optical fiber. We have implemented a spectral filtering technique for compensating for the Cerenkov radiation effect specifically for our plastic scintillator-based dosimeter, using a wavelength-separated counting method. A dichroic mirror was used for separating input light signals. Individual signal counting was performed for high- and low-wavelength light signals. To confirm the accuracy, measurements with various amounts of Cerenkov radiation were performed by changing the incident direction while keeping the Ir-192 source-to-dosimeter distance constant, resulting in a fluctuation of <5%. Optical fiber bending was also addressed; no bending effect was observed for our wavelength-separated SOF dosimeter. © The Author 2015. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

Topical Review: Polymer gel dosimetry

PubMed Central

Baldock, C; De Deene, Y; Doran, S; Ibbott, G; Jirasek, A; Lepage, M; McAuley, K B; Oldham, M; Schreiner, L J

2010-01-01

Polymer gel dosimeters are fabricated from radiation sensitive chemicals which, upon irradiation, polymerize as a function of the absorbed radiation dose. These gel dosimeters, with the capacity to uniquely record the radiation dose distribution in three-dimensions (3D), have specific advantages when compared to one-dimensional dosimeters, such as ion chambers, and two-dimensional dosimeters, such as film. These advantages are particularly significant in dosimetry situations where steep dose gradients exist such as in intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery. Polymer gel dosimeters also have specific advantages for brachytherapy dosimetry. Potential dosimetry applications include those for low-energy x-rays, high-linear energy transfer (LET) and proton therapy, radionuclide and boron capture neutron therapy dosimetries. These 3D dosimeters are radiologically soft-tissue equivalent with properties that may be modified depending on the application. The 3D radiation dose distribution in polymer gel dosimeters may be imaged using magnetic resonance imaging (MRI), optical-computerized tomography (optical-CT), x-ray CT or ultrasound. The fundamental science underpinning polymer gel dosimetry is reviewed along with the various evaluation techniques. Clinical dosimetry applications of polymer gel dosimetry are also presented. PMID:20150687

Clinical application of the OneDose™ Patient Dosimetry System for total body irradiation

NASA Astrophysics Data System (ADS)

Best, S.; Ralston, A.; Suchowerska, N.

2005-12-01

The OneDose™ Patient Dosimetry System (Sicel Technologies) is a new dosimeter based on metal oxide semiconductor field-effect transistor technology and designed for the in vivo measurement of patient dose during radiotherapy. In vivo dosimetry for total body irradiation (TBI) is challenging due to the extended treatment distance, low dose rates and beam spoilers. Phantom results confirm the suitability of the dosimeter for TBI in terms of inherent build-up, post-irradiation fading, accuracy, reproducibility, linearity and temperature dependence. Directional dependence is significant and should be taken into account. The OneDose™ dosimeters were also trialed in vivo for two TBI patients and the dose measured compared to conventional dosimeter measurements using an ionization chamber and thermoluminescent dosimeters (TLD), with agreement to within 2.2% and 3.9%, respectively. Phantom and patient results confirm that the OneDose™ patient dosimetry system is a practical and convenient alternative to TLDs for TBI in vivo dosimetry. For increased confidence in results with this dosimeter, we recommend that two dosimeters be used for each site of interest.

Clinical application of the OneDose Patient Dosimetry System for total body irradiation.

PubMed

Best, S; Ralston, A; Suchowerska, N

2005-12-21

The OneDose Patient Dosimetry System (Sicel Technologies) is a new dosimeter based on metal oxide semiconductor field-effect transistor technology and designed for the in vivo measurement of patient dose during radiotherapy. In vivo dosimetry for total body irradiation (TBI) is challenging due to the extended treatment distance, low dose rates and beam spoilers. Phantom results confirm the suitability of the dosimeter for TBI in terms of inherent build-up, post-irradiation fading, accuracy, reproducibility, linearity and temperature dependence. Directional dependence is significant and should be taken into account. The OneDose dosimeters were also trialed in vivo for two TBI patients and the dose measured compared to conventional dosimeter measurements using an ionization chamber and thermoluminescent dosimeters (TLD), with agreement to within 2.2% and 3.9%, respectively. Phantom and patient results confirm that the OneDose patient dosimetry system is a practical and convenient alternative to TLDs for TBI in vivo dosimetry. For increased confidence in results with this dosimeter, we recommend that two dosimeters be used for each site of interest.

Optically stimulated luminescence in vivo dosimetry for radiotherapy: physical characterization and clinical measurements in (60)Co beams.

PubMed

Mrčela, I; Bokulić, T; Izewska, J; Budanec, M; Fröbe, A; Kusić, Z

2011-09-21

A commercial optically stimulated luminescence (OSL) dosimetry system was investigated for in vivo dosimetry in radiation therapy. Dosimetric characteristics of InLight dot dosimeters and a microStar reader (Landauer Inc.) were tested in (60)Co beams. The reading uncertainty of a single dosimeter was 0.6%. The reproducibility of a set of dosimeters after a single irradiation was 1.6%, while in repeated irradiations of the same dosimeters it was found to be 3.5%. When OSL dosimeters were optically bleached between exposures, the reproducibility of repeated measurements improved to 1.0%. Dosimeters were calibrated for the entrance dose measurements and a full set of correction factors was determined. A pilot patient study that followed phantom validation testing included more than 100 measured fields with a mean relative difference of the measured entrance dose from the expected dose of 0.8% and the standard deviation of 2.5%. In conclusion, these results demonstrate that OSL dot dosimeters represent a valid alternative to already established in vivo dosimetry systems.

The thermoluminescence study of epoxy based LiF:Mg,Cu,P dosimeters

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

Rahangdale, S. R., E-mail: sachin.rahangdale1@gmail.com; Palikundwar, U. A.; Moharil, S. V.

The LiF:Mg,Cu,P phosphor is the most investigated phosphor in radiation dosimetry. Results on thermoluminescence of the epoxy based LiF:Mg,Cu,P dosimeters irradiated with gamma radiations are presented and compared with results of LiF:Mg,Cu,P powder. The glow curve structure of both LiF powder and dosimeter are same and only difference is found in the glow curve peak temperature. The LiF dosimeters were made from the 5012A and 5012B epoxy. The dosimeters had a mass of about 18 mg, 5.0 mm diameter and 0.5 mm thickness. The sensitivity variation of the dosimeters for exposure to {sup 60}Co gamma rays at different angles of incidence of themore » radiation is found to be within 4%. Its minimum detectable dose is about 3020 µGy. The epoxy based dosimeters withstand different environment and it can be used with general TL reader without need of any special design due to its small size and plane surface.« less

Optically stimulated luminescence in vivo dosimetry for radiotherapy: physical characterization and clinical measurements in 60Co beams

NASA Astrophysics Data System (ADS)

Mrčela, I.; Bokulić, T.; Izewska, J.; Budanec, M.; Fröbe, A.; Kusić, Z.

2011-09-01

A commercial optically stimulated luminescence (OSL) dosimetry system was investigated for in vivo dosimetry in radiation therapy. Dosimetric characteristics of InLight dot dosimeters and a microStar reader (Landauer Inc.) were tested in 60Co beams. The reading uncertainty of a single dosimeter was 0.6%. The reproducibility of a set of dosimeters after a single irradiation was 1.6%, while in repeated irradiations of the same dosimeters it was found to be 3.5%. When OSL dosimeters were optically bleached between exposures, the reproducibility of repeated measurements improved to 1.0%. Dosimeters were calibrated for the entrance dose measurements and a full set of correction factors was determined. A pilot patient study that followed phantom validation testing included more than 100 measured fields with a mean relative difference of the measured entrance dose from the expected dose of 0.8% and the standard deviation of 2.5%. In conclusion, these results demonstrate that OSL dot dosimeters represent a valid alternative to already established in vivo dosimetry systems.

Agricultural model intercomparison and improvement project: Overview of model intercomparisons

USDA-ARS?s Scientific Manuscript database

Improvement of crop simulation models to better estimate growth and yield is one of the objectives of the Agricultural Model Intercomparison and Improvement Project (AgMIP). The overall goal of AgMIP is to provide an assessment of crop model through rigorous intercomparisons and evaluate future clim...

Pistol-shaped dosimeter charger

DOEpatents

Maples, R.A.

A pistol-shaped charger assembly clamps a cylindrical radiation dosimeter against one edge thereof. A triggerlike lever on the handgrip of the assembly is manually pivoted to actuate a piezoelectric current generator held in the handgrip and thereby charge the dosimeter.

Pistol-shaped dosimeter charger

DOEpatents

Maples, Robert A.

1985-01-01

A pistol-shaped charger assembly clamps a cylindrical radiation dosimeter against one edge thereof. A triggerlike lever on the handgrip of the assembly is manually pivoted to actuate a piezoelectric current generator held in the handgrip and thereby charge the dosimeter.

Wristwatch dosimeter

DOEpatents

Wolf, Michael A.; Waechter, David A.; Umbarger, C. John

1986-01-01

The disclosure is directed to a wristwatch dosimeter utilizing a CdTe detector, a microprocessor and an audio and/or visual alarm. The dosimeter is entirely housable with a conventional digital watch case having an additional aperture enabling the detector to receive radiation.

A new radiochromic dosimeter film

NASA Astrophysics Data System (ADS)

Sidney, L. N.; Lynch, D. C.; Willet, P. S.

By employing acid-sensitive leuco dyes in a chlorine-containing polymer matrix, a new radiochromic dosimeter film has been developed for gamma, electron beam, and ultraviolet radiation. These dosimeter films undergo a color change from colorless to royal blue, red fuchsia, or black, depending on dye selection, and have been characterized using a visible spectrophotometer over an absorbed dose range of 1 to 100 kGy. The primary features of the film are improved color stability before and after irradiation, whether stored in the dark or under artificial lights, and improved moisture resistance. The effects of absorbed dose, dose rate, and storage conditions on dosimeter performance are discussed. The dosimeter material may be produced as a free film or coated onto a transparent substrate and optionally backed with adhesive. Potential applications for these materials include gamma sterilization indicator films for food and medical products, electron beam dosimeters, and in-line radiation monitors for electron beam and ultraviolet processing.

Feasibility of smartphone diaries and personal dosimeters to quantitatively study exposure to ultraviolet radiation in a small national sample.

PubMed

Køster, Brian; Søndergaard, Jens; Nielsen, Jesper B; Allen, Martin; Bjerregaard, Mette; Olsen, Anja; Bentzen, Joan

2015-09-01

In 2007, a national skin cancer prevention campaign was launched to reduce the UV exposure of the Danish population. To improve campaign evaluation a questionnaire validation using UV-dosimeters was initiated. To show the feasibility of dosimeters for national representative studies and of smartphones as a data collection tool. Participants were sent a dosimeter which they wore for 7 days, received a short diary questionnaire by text message each day and subsequently a longer questionnaire. Correlation between responses from questionnaire, smartphone diaries and dosimeters were examined. This study shows a 99.5% return rate (n = 205) of the dosimeters by ordinary mail and high response-rates for a smartphone questionnaire dairy. Correlation coefficients for outdoor-time reported through smartphones and dosimeters as average by week 0.62 (0.39-0.77), P < 0.001 (n = 40). Correlation coefficient for outdoor time estimated by questionnaire and dosimeters were 0.42 (0.11-0.64), P = 0.008. The subjective perception of the weather was the only covariate significantly influencing questionnaire estimates of actual outdoor exposure. We showed that dosimeter studies are feasible in national settings and that smartphones are a useful tool for monitoring and collecting UV behavior data. We found diary data reported on a daily basis through smartphones more strongly associated with actual outdoor time than questionnaire data. Our results demonstrate tools and possible considerations for executing a UV behavior questionnaire validation. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Characterization of a commercially-available, optically-stimulated luminescent dosimetry system for use in computed tomography.

PubMed

Lavoie, Lindsey; Ghita, Monica; Brateman, Libby; Arreola, Manuel

2011-09-01

Optically-stimulated luminescent (OSL) nanoDot dosimeters, commercially available from Landauer, Inc. (Glenwood, IL), were assessed for use in computed tomography (CT) for erasure and reusability, linearity and reproducibility of response, and angular and energy response in different scattering conditions. Following overnight exposure to fluorescent room light, the residual signal on the dosimeters was 2%. The response of the dosimeters to identical exposures was consistent, and reported doses were within 4% of each other. The dosimeters responded linearly with dose up to 1 Gy. The dosimeter response to the CT beams decreased with increased tube voltage, showing up to a -16% difference when compared to a 0.6-cm(3) NIST-traceable calibrated ionization chamber for a 135 kVp CT beam. The largest range in percent difference in dosimeter response to scatter at central and peripheral positions inside CTDI phantoms was 14% at 80 kVp CT tube voltage, when compared to the ionization chamber. The dosimeters responded uniformly to x-ray tube angle over the ranges of increments of 0° to 75° and 105° to 180° when exposed in air, and from 0° to 360° when exposed inside a CTDI phantom. While energy and scatter correction factors should be applied to dosimeter readings for the purpose of determining absolute doses, these corrections are straightforward but depend on the accuracy of the ionization chamber used for cross-calibration. The linearity and angular responses, combined with the ability to reuse the dosimeters, make this OSL system an excellent choice for clinical CT dose measurements.

Performance of KCl:Eu2+ storage phosphor dosimeters for low dose measurements

PubMed Central

Li, H. Harold; Hansel, Rachael; Knutson, Nels; Yang, Deshan

2013-01-01

Recent research has demonstrated that europium doped potassium chloride (KCl:Eu2+) storage phosphor material has the potential to become the physical foundation of a novel and reusable dosimetry system using either film-like devices or devices similar to thermoluminescent dosimeter (TLD) chips. The purposes of this work are to quantify the performance of KCl:Eu2+ prototype dosimeters for low dose measurements and to demonstrate how it can be incorporated into clinical application for in vivo peripheral dose measurements. Pellet-style KCl:Eu2+ dosimeters, 6 mm in diameter, and 1 mm thick, were fabricated in-house for this study. The dosimeters were read using a laboratory photostimulated luminescence detection system. KCl:Eu2+ prototype storage phosphor dosimeter was capable of measuring a dose-to-water as low as 0.01 cGy from a 6 MV photon beam with a signal-to-noise ratio greater than 6. A pre-readout thermal annealing procedure enabled the dosimeter to be read within an hour post irradiation. After receiving large accumulated doses (~10 kGy), the dosimeters retained linear response in the low dose region with only a 20 percent loss of sensitivity comparing to a fresh sample (zero Gy history). The energy-dependence encountered during low dose peripheral measurements could be accounted for via a single point outside-field calibration per each beam quality. With further development the KCl:Eu2+− based dosimeter could become a versatile and durable dosimetry tool with large dynamic range (sub-cGy to 100 Gy). PMID:23735856

Wrist-watch dosimeter

DOEpatents

Wolf, M.A.; Waechter, D.A.; Umbarger, C.J.

1982-04-16

The disclosure is directed to a wristwatch dosimeter utilizing a CdTe detector, a microprocessor and an audio and/or visual alarm. The dosimeter is entirely housable within a conventional digital watch case having an additional aperture enabling the detector to receive radiation.

Wristwatch dosimeter

DOEpatents

Wolf, M.A.; Waechter, D.A.; Umbarger, C.J.

1986-08-26

The disclosure is directed to a wristwatch dosimeter utilizing a CdTe detector, a microprocessor and an audio and/or visual alarm. The dosimeter is entirely housable with a conventional digital watch case having an additional aperture enabling the detector to receive radiation. 10 figs.

SU-E-T-296: Dosimetric Analysis of Small Animal Image-Guided Irradiator Using High Resolution Optical CT Imaging of 3D Dosimeters

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

Na, Y; Qian, X; Wuu, C

Purpose: To verify the dosimetric characteristics of a small animal image-guided irradiator using a high-resolution of optical CT imaging of 3D dosimeters. Methods: PRESAEGE 3D dosimeters were used to determine dosimetric characteristics of a small animal image-guided irradiator and compared with EBT2 films. Cylindrical PRESAGE dosimeters with 7cm height and 6cm diameter were placed along the central axis of the beam. The films were positioned between 6×6cm{sup 2} cubed plastic water phantoms perpendicular to the beam direction with multiple depths. PRESAGE dosimeters and EBT2 films were then irradiated with the irradiator beams at 220kVp and 13mA. Each of irradiated PRESAGEmore » dosimeters named PA1, PA2, PB1, and PB2, was independently scanned using a high-resolution single laser beam optical CT scanner. The transverse images were reconstructed with a 0.1mm high-resolution pixel. A commercial Epson Expression 10000XL flatbed scanner was used for readout of irradiated EBT2 films at a 0.4mm pixel resolution. PDD curves and beam profiles were measured for the irradiated PRESAGE dosimeters and EBT2 films. Results: The PDD agreements between the irradiated PRESAGE dosimeter PA1, PA2, PB1, PB2 and the EB2 films were 1.7, 2.3, 1.9, and 1.9% for the multiple depths at 1, 5, 10, 15, 20, 30, 40 and 50mm, respectively. The FWHM measurements for each PRESAEGE dosimeter and film agreed with 0.5, 1.1, 0.4, and 1.7%, respectively, at 30mm depth. Both PDD and FWHM measurements for the PRESAGE dosimeters and the films agreed overall within 2%. The 20%–80% penumbral widths of each PRESAGE dosimeter and the film at a given depth were respectively found to be 0.97, 0.91, 0.79, 0.88, and 0.37mm. Conclusion: Dosimetric characteristics of a small animal image-guided irradiator have been demonstrated with the measurements of PRESAGE dosimeter and EB2 film. With the high resolution and accuracy obtained from this 3D dosimetry system, precise targeting small animal irradiation can be achieved.« less

The Development of a Beta-Gamma Personnel Dosimeter

NASA Astrophysics Data System (ADS)

Tsakeres, Frank Steven

The assessment of absorbed dose in mixed beta and gamma radiation fields is an extremely complex task. For many years, the assessment of the absorbed dose to tissue from the weakly penetrating components of a radiation field (i.e., beta particles, electrons) has been largely ignored. Beta radiation fields are encountered routinely in a nuclear facility and may represent the major radiation component under certain accident or emergency conditions. Many attempts have been made to develop an accurate mixed field personnel dosimeter. However, all of these dosimeters have exhibited numerous response problems which have limited their usefulness for personnel dose assessment. Consequently, the determination of the absorbed dose at the epidermal depth (i.e., 7 mg/cm('2)) has been difficult to measure accurately. The objective of this research project was to design, build, and test a sensitive and accurate personnel dosimeter for mixed field applications. The selection of the various dosimeter elements were determined by evaluating several types of phosphors, filters, and backscatter materials. After evaluating the various response characteristics of the badge components, a prototype dosimeter, the CHEMM (CaF(,2):Dy Highly Efficient Multiple Element Multiple Filter) personnel dosimeter, was developed and tested at Georgia Tech, Emory University and the National Bureau of Standards. This dosimeter was comprised of four large CaF(,2):Dy (TLD-200) TLD's and a standard LiF (TLD-100) chip. The weakly penetrating and penetrating components of a radiation field were separated using a series of TLD/filter combinations and a new dose assessment algorithm. The large TLD-200 chips, along with a series of tissue-equivalent filters, were used to determine the absorbed dose due to the weakly penetrating radiation while a LiF/filter combination was used to measure the penetrating component. In addition, a new backscatter material was included in the badge design to better simulate a tissue-equivalent response. The CHEMM personnel dosimeter performance tests were conducted to simulate actual mixed radiation field environments. This dosimeter provided a high degree of sensitivity with accuracies well within the ANSI recommended performance standards for personnel dosimeters. In addition, it was concluded that the CHEMM dosimetry system provided a practical dosimeter alternative with a higher dose assessment accuracy and measurement sensitivity than the personnel dosimetry systems presently used in the nuclear power industry.

SU-G-JeP2-04: Comparison Between Fricke-Type 3D Radiochromic Dosimeters for Real-Time Dose Distribution Measurements in MR-Guided Radiation Therapy

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

Lee, H; Alqathami, M; Wang, J

Purpose: To assess MR signal contrast for different ferrous ion compounds used in Fricke-type gel dosimeters for real-time dose measurements for MR-guided radiation therapy applications. Methods: Fricke-type gel dosimeters were prepared in 4% w/w gelatin prior to irradiation in an integrated 1.5 T MRI and 7 MV linear accelerator system (MR-Linac). 4 different ferrous ion (Fe2?) compounds (referred to as A, B, C, and D) were investigated for this study. Dosimeter D consisted of ferrous ammonium sulfate (FAS), which is conventionally used for Fricke dosimeters. Approximately half of each cylindrical dosimeter (45 mm diameter, 80 mm length) was irradiated tomore » ∼17 Gy. MR imaging during irradiation was performed with the MR-Linac using a balanced-FFE sequence of TR/TE = 5/2.4 ms. An approximate uncertainty of 5% in our dose delivery was anticipated since the MR-Linac had not yet been fully commissioned. Results: The signal intensities (SI) increased between the un-irradiated and irradiated regions by approximately 8.6%, 4.4%, 3.2%, and 4.3% after delivery of ∼2.8 Gy for dosimeters A, B, C, and D, respectively. After delivery of ∼17 Gy, the SI had increased by 24.4%, 21.0%, 3.1%, and 22.2% compared to the un-irradiated regions. The increase in SI with respect to dose was linear for dosimeters A, B, and D with slopes of 0.0164, 0.0251, and 0.0236 Gy{sup −1} (R{sup 2} = 0.92, 0.97, and 0.96), respectively. Visually, dosimeter A had the greatest optical contrast from yellow to purple in the irradiated region. Conclusion: This study demonstrated the feasibility of using Fricke-type dosimeters for real-time dose measurements with the greatest optical and MR contrast for dosimeter A. We also demonstrated the need to investigate Fe{sup 2+} compounds beyond the conventionally utilized FAS compound in order to improve the MR signal contrast in 3D dosimeters used for MR-guided radiation therapy. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship Program under Grant No. LH- 102SPS.« less

Investigations of interference between electromagnetic transponders and wireless MOSFET dosimeters: a phantom study.

PubMed

Su, Zhong; Zhang, Lisha; Ramakrishnan, V; Hagan, Michael; Anscher, Mitchell

2011-05-01

To evaluate both the Calypso Systems' (Calypso Medical Technologies, Inc., Seattle, WA) localization accuracy in the presence of wireless metal-oxide-semiconductor field-effect transistor (MOSFET) dosimeters of dose verification system (DVS, Sicel Technologies, Inc., Morrisville, NC) and the dosimeters' reading accuracy in the presence of wireless electromagnetic transponders inside a phantom. A custom-made, solid-water phantom was fabricated with space for transponders and dosimeters. Two inserts were machined with positioning grooves precisely matching the dimensions of the transponders and dosimeters and were arranged in orthogonal and parallel orientations, respectively. To test the transponder localization accuracy with/without presence of dosimeters (hypothesis 1), multivariate analyses were performed on transponder-derived localization data with and without dosimeters at each preset distance to detect statistically significant localization differences between the control and test sets. To test dosimeter dose-reading accuracy with/without presence of transponders (hypothesis 2), an approach of alternating the transponder presence in seven identical fraction dose (100 cGy) deliveries and measurements was implemented. Two-way analysis of variance was performed to examine statistically significant dose-reading differences between the two groups and the different fractions. A relative-dose analysis method was also used to evaluate transponder impact on dose-reading accuracy after dose-fading effect was removed by a second-order polynomial fit. Multivariate analysis indicated that hypothesis 1 was false; there was a statistically significant difference between the localization data from the control and test sets. However, the upper and lower bounds of the 95% confidence intervals of the localized positional differences between the control and test sets were less than 0.1 mm, which was significantly smaller than the minimum clinical localization resolution of 0.5 mm. For hypothesis 2, analysis of variance indicated that there was no statistically significant difference between the dosimeter readings with and without the presence of transponders. Both orthogonal and parallel configurations had difference of polynomial-fit dose to measured dose values within 1.75%. The phantom study indicated that the Calypso System's localization accuracy was not affected clinically due to the presence of DVS wireless MOSFET dosimeters and the dosimeter-measured doses were not affected by the presence of transponders. Thus, the same patients could be implanted with both transponders and dosimeters to benefit from improved accuracy of radiotherapy treatments offered by conjunctional use of the two systems.

Temporal dosimeter and method

DOEpatents

Warner, Benjamin P.; Lopez, Thomas A.

2003-09-30

The invention includes a temporal dosimeter. One dosimeter embodiment includes a housing that is opaque to visible light but transparent to ionizing radiation. The dosimeter also includes a sensor for recording dosages of ionizing radiation, a drive mechanism, a power source, and rotatable shields that work together to produce a compound aperture to unveil different portions of the sensor at different times to ionizing radiation. Another dosimeter embodiment includes a housing, a sensor, a shield with an aperture portion, and a linear actuator drive mechanism coupled to the sensor for moving the sensor past the aperture portion. The sensor turns as it moves past the aperture, tracing a timeline record of exposure to ionizing radiation along a helical path on the sensor.

Floating Gate CMOS Dosimeter With Frequency Output

NASA Astrophysics Data System (ADS)

Garcia-Moreno, E.; Isern, E.; Roca, M.; Picos, R.; Font, J.; Cesari, J.; Pineda, A.

2012-04-01

This paper presents a gamma radiation dosimeter based on a floating gate sensor. The sensor is coupled with a signal processing circuitry, which furnishes a square wave output signal, the frequency of which depends on the total dose. Like any other floating gate dosimeter, it exhibits zero bias operation and reprogramming capabilities. The dosimeter has been designed in a standard 0.6 m CMOS technology. The whole dosimeter occupies a silicon area of 450 m250 m. The initial sensitivity to a radiation dose is Hz/rad, and to temperature and supply voltage is kHz/°C and 0.067 kHz/mV, respectively. The lowest detectable dose is less than 1 rad.

Unfolding neutron spectra from simulated response of thermoluminescence dosimeters inside a polyethylene sphere using GRNN neural network

NASA Astrophysics Data System (ADS)

Lotfalizadeh, F.; Faghihi, R.; Bahadorzadeh, B.; Sina, S.

2017-07-01

Neutron spectrometry using a single-sphere containing dosimeters has been developed recently, as an effective replacement for Bonner sphere spectrometry. The aim of this study is unfolding the neutron energy spectra using GRNN artificial neural network, from the response of thermoluminescence dosimeters, TLDs, located inside a polyethylene sphere. The spectrometer was simulated using MCNP5. TLD-600 and TLD-700 dosimeters were simulated at different positions in all directions. Then the GRNN was used for neutron spectra prediction, using the TLDs' readings. Comparison of spectra predicted by the network with the real spectra, show that the single-sphere dosimeter is an effective instrument in unfolding neutron spectra.

Noise dosimetry for tactical environments.

PubMed

Smalt, Christopher J; Lacirignola, Joe; Davis, Shakti K; Calamia, Paul T; Collins, Paula P

2017-06-01

Noise exposure and the subsequent hearing loss are well documented aspects of military life. Numerous studies have indicated high rates of noise-induced hearing injury (NIHI) in active-duty service men and women, and recent statistics from the U.S. Department of Veterans Affairs indicate a population of veterans with hearing loss that is growing at an increasing rate. In an effort to minimize hearing loss, the U.S. Department of Defense (DoD) updated its Hearing Conservation Program in 2010, and also has recently revised the DoD Design Criteria Standard Noise Limits (MIL-STD-1474E) which defines allowable noise levels in the design of all military acquisitions including weapons and vehicles. Even with such mandates, it remains a challenge to accurately quantify the noise exposure experienced by a Warfighter over the course of a mission or training exercise, or even in a standard work day. Noise dosimeters are intended for exactly this purpose, but variations in device placement (e.g., free-field, on-body, in/near-ear), hardware (e.g., microphone, analog-to-digital converter), measurement time (e.g., work day, 24-h), and dose metric calculations (e.g., time-weighted energy, peak levels, Auditory Risk Units), as well as noise types (e.g., continuous, intermittent, impulsive) can cause exposure measurements to be incomplete, inaccurate, or inappropriate for a given situation. This paper describes the design of a noise dosimeter capable of acquiring exposure data across tactical environments. Two generations of prototypes have been built at MIT Lincoln Laboratory with funding from the U.S. Army, Navy, and Marine Corps. Details related to hardware, signal processing, and testing efforts are provided, along with example tactical military noise data and lessons learned from early fieldings. Finally, we discuss the continued need to prioritize personalized dosimetry in order to improve models that predict or characterize the risk of auditory damage, to integrate dosimeters with hearing-protection devices, and to inform strategies and metrics for reducing NIHI. Copyright © 2016 Elsevier B.V. All rights reserved.

MO-AB-BRA-04: Radiation Measurements with a DNA Double-Strand-Break Dosimeter

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

Obeidat, M; Cline, K; Stathakis, S

Purpose: Many types of dosimeters are used to measure radiation, but none of them directly measures the biological effect of this dose. The purpose here is to create a dosimeter that can measure the probability of double-strand breaks (DSB) for DNA, which is directly related to the biological effect of radiation. Methods: The dosimeter has DNA strands, which are labeled on one end with biotin and on the other with fluorescein. The biotin attaches these strands to magnetic beads. We suspended the DNA dosimeter in phosphate-buffered saline (PBS) as it matches the internal environment of the body. We placed smallmore » volumes (50µL) of the DNA dosimeter into tubes and irradiated these samples in a water-equivalent plastic phantom with several doses (three samples per dose). After irradiating the samples, a magnet was placed against the tubes. The fluorescein attached to broken DNA strands was extracted (called the supernatant) and placed into a different tube. The fluorescein on the unbroken strands remained attached to the beads in the tube and was re-suspended with 50µL of PBS. A fluorescence reader was used to measure the fluorescence for both the re-suspended beads and supernatant. To prove that we are measuring DSB, we tested dosimeter response with two different lengths of attached DNA strands (1 and 4 kilo-base pair). Results: The probability of DSB at the dose levels of 5, 10, 25, and 50 Gy were 0.05, 0.08, 0.12, and 0.19, respectively, while the coefficients of variation were 0.14, 0.07, 0.02, and 0.01, respectively. The 4 kilo-base-pair dosimeter produced 5.3 times the response of the 1 kilo-base-pair dosimeter. Conclusion: The DNA dosimeter yields a measurable response to dose that scales with the DNA strand length. The goal now is to refine the dosimeter fabrication to reproducibly create a low coefficient of variation for the lower doses. This work was supported in part by Yarmouk University (Irbid, Jordan) and CPRIT (RP140105)« less

SU-E-T-171: Characterization of the New Xoft Axxent Electronic Brachytherapy Source Using PRESAGE Dosimeters

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

Steinmann, A; Followill, D; Ibbott, G

Purpose: To characterize the Xoft Axxent electronic brachytherapy source using PRESAGE™ dosimeters to obtain independent confirmation of TG-43U1 dosimetry values from previous studies and ascertain its reproducibility in HDR brachytherapy. Methods: PRESAGE™ dosimeters are solid, polyurethane-based dosimeters doped with radiochromic leucodyes that produce a linear optical-density response when exposed to radiation. Eight 1-kg dosimeters were scanned prior to irradiation on an optical-CT scanner to eliminate background signal and any optical imperfections from each dosimeter. To quantify potential imaging artifacts due to oversaturated responses in the immediate range of the source, half of the eight dosimeters were cast with a smallermore » channel diameter of 5.4 mm, and the other half were cast with a larger channel diameter of 15mm. During irradiation, the catheters were placed in the center of each channel. Catheters fit the 5.4mm diameters channels whereas polyurethane plugs were inserted into the larger channels to create a sturdy, immobile catheter which allowed uniform dose distributions. Two dosimeters of each 5.4mm and 15mm were irradiated at either 1517.3 cGy or 2017.5 cGy. Post-irradiation scans were performed within 48 hours of irradiation. A 3D reconstruction based on subtraction of these two images and the relative dose measurements were made using in-house software. Results: Comparing measured radial dose rates with previous results revealed smaller percent errors when PRESAGE™ irradiations were at lower maximum dose. The dosimeters showed small deviations in radial dose function, g{sub p} (r), from previous studies. Among the dosimeters irradiated at 1517.3 cGy, the g{sub p}(r) compared to previous studies fluctuated from 0.0043 to 0.3922. This suggests small fluctuations can drastically change radial dose calculations. Conclusion: The subtraction of pre-irradiation and post-irradiation scans of PRESAGE™ dosimeters using an optical-CT scanner shows promising results in determining 3D dosimetry for Xoft Axxent devices; however, further research is recommended. NIH Grant#: 5-U24-CA081647-13; ROI Grant#: 5R01CA100835.« less

SU-E-T-753: Three-Dimensional Dose Distributions of Incident Proton Particle in the Polymer Gel Dosimeter and the Radiochromic Gel Dosimeter: A Simulation Study with MCNP Code

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

Park, M; Kim, G; Ji, Y

Purpose: The purpose of this study is to estimate the three-dimensional dose distributions in the polymer and the radiochromic gel dosimeter, and to identify the detectability of both gel dosimeters by comparing with the water phantom in case of irradiating the proton particles. Methods: The normoxic polymer gel and the LCV micelle radiochromic gel were used in this study. The densities of polymer and the radiochromic gel dosimeter were 1.024 and 1.005 g/cm{sup 3}, respectively. The dose distributions of protons in the polymer and radiochromic gel were simulated using Monte Carlo radiation transport code (MCNPX, Los Alamos National Laboratory). Themore » shape of phantom irradiated by proton particles was a hexahedron with the dimension of 12.4 × 12.4 × 15.0 cm{sup 3}. The energies of proton beam were 50, 80, and 140 MeV energies were directed to top of the surface of phantom. The cross-sectional view of proton dose distribution in both gel dosimeters was estimated with the water phantom and evaluated by the gamma evaluation method. In addition, the absorbed dose(Gy) was also calculated for evaluating the proton detectability. Results: The evaluation results show that dose distributions in both gel dosimeters at intermediated section and Bragg-peak region are similar with that of the water phantom. At entrance section, however, inconsistencies of dose distribution are represented, compared with water. The relative absorbed doses in radiochromic and polymer gel dosimeter were represented to be 0.47 % and 2.26 % difference, respectively. These results show that the radiochromic gel dosimeter was better matched than the water phantom in the absorbed dose evaluation. Conclusion: The polymer and the radiochromic gel dosimeter show similar characteristics in dose distributions for the proton beams at intermediate section and Bragg-peak region. Moreover the calculated absorbed dose in both gel dosimeters represents similar tendency by comparing with that in water phantom.« less

Investigations into the feasibility of optical-CT 3D dosimetry with minimal use of refractively matched fluids

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

Chisholm, Kelsey; Miles, Devin; Rankine, Leith

Purpose: In optical-CT, the use of a refractively matched polyurethane solid-tank in place of a fluid bath has the potential to greatly increase practical convenience, reduce cost, and possibly improve the efficacy of flood corrections. This work investigates the feasibility of solid-tank optical-CT imaging for 3D dosimetry through computer simulation. Methods: A MATLAB ray-tracing simulation platform, ScanSim, was used to model a parallel-source telecentric optical-CT imaging system through a polyurethane solid-tank containing a central cylindrical hollow into which PRESAGE radiochromic dosimeters can be placed. A small amount of fluid fills the 1–5 mm gap between the dosimeter and the wallsmore » of the tank. The use of the solid-tank reduces the required amount of fluid by approximately 97%. To characterize the efficacy of solid-tank, optical-CT scanning simulations investigated sensitivity to refractive index (RI) mismatches between dosimeter, solid-tank, and fluid, for a variety of dosimeter (RI = 1.5–1.47) and fluid (RI = 1.55–1.0) combinations. Efficacy was evaluated through the usable radius (r{sub u}) metric, defined as the fraction of the radius of the dosimeter where measured dose is predicted to be within 2% of the ground truth entered into the simulation. Additional simulations examined the effect of increasing gap size (1–5 mm) between the dosimeter and solid-tank well. The effects of changing the lens tolerance (0.5°–5.0°) were also investigated. Results: As the RI mismatch between the dosimeter and solid-tank increased from 0 to 0.02, the usable radius decreased from 97.6% to 50.2%. The optimal fluid RI decreased nonlinearly from 1.5 to 1.34 as the mismatch increased and was up to 9% lower than the tank. Media mismatches between the dosimeter and solid-tank also exacerbate the effects of changing the gap size, with no easily quantifiable relationship with usable radius. Generally, the optimal fluid RI value increases as gap size increases and is closely matched to the dosimeter at large gap sizes (>3 mm). Increasing the telecentric lens tolerance increases the usable radius for all refractive media combinations and improves the maximum usable radius of mismatched media to that of perfectly matched media for tolerances >5.0°. The maximum usable radius can be improved up to a factor of 2 when lens tolerances are small (<1.0°). Conclusions: Dry solid-tank optical-CT imaging in a telecentric system is feasible if the dosimeter RI is a close match with the solid-tank (<0.01 difference), providing accurate dose measurements within ±2% of true dose to over 80% of the dosimeter volume. In order to achieve accurate measurements over 96% of the dosimeter volume (representing out to 2 mm from the dosimeter edge), the dosimeter-tank RI mismatch must be less than 0.005. Optimal results occur when the RI of the dosimeter and tank is the same, in which case the fluid will have the same RI. If mismatches between the tank and dosimeter RI occur, the RI of the matching fluid needs to be fine tuned to achieve the highest usable radius.« less

Investigations into the feasibility of optical-CT 3D dosimetry with minimal use of refractively matched fluids.

PubMed

Chisholm, Kelsey; Miles, Devin; Rankine, Leith; Oldham, Mark

2015-05-01

In optical-CT, the use of a refractively matched polyurethane solid-tank in place of a fluid bath has the potential to greatly increase practical convenience, reduce cost, and possibly improve the efficacy of flood corrections. This work investigates the feasibility of solid-tank optical-CT imaging for 3D dosimetry through computer simulation. A matlab ray-tracing simulation platform, ScanSim, was used to model a parallel-source telecentric optical-CT imaging system through a polyurethane solid-tank containing a central cylindrical hollow into which PRESAGE radiochromic dosimeters can be placed. A small amount of fluid fills the 1-5 mm gap between the dosimeter and the walls of the tank. The use of the solid-tank reduces the required amount of fluid by approximately 97%. To characterize the efficacy of solid-tank, optical-CT scanning simulations investigated sensitivity to refractive index (RI) mismatches between dosimeter, solid-tank, and fluid, for a variety of dosimeter (RI = 1.5-1.47) and fluid (RI = 1.55-1.0) combinations. Efficacy was evaluated through the usable radius (ru) metric, defined as the fraction of the radius of the dosimeter where measured dose is predicted to be within 2% of the ground truth entered into the simulation. Additional simulations examined the effect of increasing gap size (1-5 mm) between the dosimeter and solid-tank well. The effects of changing the lens tolerance (0.5°-5.0°) were also investigated. As the RI mismatch between the dosimeter and solid-tank increased from 0 to 0.02, the usable radius decreased from 97.6% to 50.2%. The optimal fluid RI decreased nonlinearly from 1.5 to 1.34 as the mismatch increased and was up to 9% lower than the tank. Media mismatches between the dosimeter and solid-tank also exacerbate the effects of changing the gap size, with no easily quantifiable relationship with usable radius. Generally, the optimal fluid RI value increases as gap size increases and is closely matched to the dosimeter at large gap sizes (> 3 mm). Increasing the telecentric lens tolerance increases the usable radius for all refractive media combinations and improves the maximum usable radius of mismatched media to that of perfectly matched media for tolerances > 5.0°. The maximum usable radius can be improved up to a factor of 2 when lens tolerances are small (< 1.0°). Dry solid-tank optical-CT imaging in a telecentric system is feasible if the dosimeter RI is a close match with the solid-tank (< 0.01 difference), providing accurate dose measurements within ± 2% of true dose to over 80% of the dosimeter volume. In order to achieve accurate measurements over 96% of the dosimeter volume (representing out to 2 mm from the dosimeter edge), the dosimeter-tank RI mismatch must be less than 0.005. Optimal results occur when the RI of the dosimeter and tank is the same, in which case the fluid will have the same RI. If mismatches between the tank and dosimeter RI occur, the RI of the matching fluid needs to be fine tuned to achieve the highest usable radius.

Dosimetry for Small Fields in Stereotactic Radiosurgery Using Gafchromic MD-V2-55 Film, TLD-100 and Alanine Dosimeters

PubMed Central

Massillon-JL, Guerda; Cueva-Prócel, Diego; Díaz-Aguirre, Porfirio; Rodríguez-Ponce, Miguel; Herrera-Martínez, Flor

2013-01-01

This work investigated the suitability of passive dosimeters for reference dosimetry in small fields with acceptable accuracy. Absorbed dose to water rate was determined in nine small radiation fields with diameters between 4 and 35 mm in a Leksell Gamma Knife (LGK) and a modified linear accelerator (linac) for stereotactic radiosurgery treatments. Measurements were made using Gafchromic film (MD-V2-55), alanine and thermoluminescent (TLD-100) dosimeters and compared with conventional dosimetry systems. Detectors were calibrated in terms of absorbed dose to water in 60Co gamma-ray and 6 MV x-ray reference (10×10 cm2) fields using an ionization chamber calibrated at a standards laboratory. Absorbed dose to water rate computed with MD-V2-55 was higher than that obtained with the others dosimeters, possibly due to a smaller volume averaging effect. Ratio between the dose-rates determined with each dosimeter and those obtained with the film was evaluated for both treatment modalities. For the LGK, the ratio decreased as the dosimeter size increased and remained constant for collimator diameters larger than 8 mm. The same behaviour was observed for the linac and the ratio increased with field size, independent of the dosimeter used. These behaviours could be explained as an averaging volume effect due to dose gradient and lack of electronic equilibrium. Evaluation of the output factors for the LGK collimators indicated that, even when agreement was observed between Monte Carlo simulation and measurements with different dosimeters, this does not warrant that the absorbed dose to water rate in the field was properly known and thus, investigation of the reference dosimetry should be an important issue. These results indicated that alanine dosimeter provides a high degree of accuracy but cannot be used in fields smaller than 20 mm diameter. Gafchromic film can be considered as a suitable methodology for reference dosimetry. TLD dosimeters are not appropriate in fields smaller than 10 mm diameters. PMID:23671677

SU-E-T-749: Thorough Calibration of MOSFET Dosimeters

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

Plenkovich, D; Thomas, J

Purpose: To improve the accuracy of the MOSFET calibration procedure by performing the measurement several times and calculating the average value of the calibration factor for various photon and electron energies. Methods: The output of three photon and six electron beams of Varian Trilogy linear accelerator SN 5878 was calibrated. Five reinforced standard sensitivity MOSFET dosimeters were placed in the calibration jig and connected to the Reader Module. As the backscatter material was used 7 cm of Virtual Water. The MOSFET dosimeters were covered with 1.5 cm thick bolus for the regular and SRS 6 MV beams, 3 cm bolusmore » for 15 MV beam, 1.5 cm bolus for 6 MeV electron beam, and 2 cm bolus for the electron energies of 9, 12, 15, 18, and 22 MeV. The dosimeters were exposed to 100 MU, and the calibration factor was determined using the mobileMOSFET software. To improve the accuracy of calibration, this procedure was repeated ten times and the calibration factors were averaged. Results: As the number of calibrations was increasing the variability of calibration factors of different dosimeters was decreasing. After ten calibrations, the calibration factors for all five dosimeters were within 1% of one another for all energies, except 6 MV SRS photons and 6 MeV electrons, for which the variability was 2%. Conclusions: The described process results in calibration factors which are almost independent of modality or energy. Once calibrated, the dosimeters may be used for in-vivo dosimetry or for daily verification of the beam output. Measurement of the radiation dose under bolus and scatter to the eye are examples of frequent use of calibrated MOSFET dosimeters. The calibration factor determined for full build-up is used under these circumstances. To the best of our knowledge, such thorough procedure for calibrating MOSFET dosimeters has not been reported previously. Best Medical Canada provided MOSFET dosimeters for this project.« less

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

Qian, X; Wuu, C; Admovics, J

Purpose: A 3-D radiochromic plastic dosimeter has been used to cross-test the isocentricity of a high resolution image-guided small animal microirradiation platform. In this platform, the mouse stage rotating for cone beam CT imaging is perpendicular to the gantry rotation for sub-millimeter radiation delivery. A 3-D dosimeter can be used to verify both imaging and irradiation coordinates. Methods: A 3-D dosimeter and optical CT scanner were used in this study. In the platform, both mouse stage and gantry can rotate 360° with rotation axis perpendicular to each other. Isocentricity and coincidence of mouse stage and gantry rotations were evaluated usingmore » star patterns. A 3-D dosimeter was placed on mouse stage with center at platform isocenter approximately. For CBCT isocentricity, with gantry moved to 90°, the mouse stage rotated horizontally while the x-ray was delivered to the dosimeter at certain angles. For irradiation isocentricity, the gantry rotated 360° to deliver beams to the dosimeter at certain angles for star patterns. The uncertainties and agreement of both CBCT and irradiation isocenters can be determined from the star patterns. Both procedures were repeated 3 times using 3 dosimeters to determine short-term reproducibility. Finally, dosimeters were scanned using optical CT scanner to obtain the results. Results: The gantry isocentricity is 0.9 ± 0.1 mm and mouse stage rotation isocentricity is about 0.91 ± 0.11 mm. Agreement between the measured isocenters of irradiation and imaging coordinates was determined. The short-term reproducibility test yielded 0.5 ± 0.1 mm between the imaging isocenter and the irradiation isocenter, with a maximum displacement of 0.7 ± 0.1 mm. Conclusion: The 3-D dosimeter can be very useful in precise verification of targeting for a small animal irradiation research. In addition, a single 3-D dosimeter can provide information in both geometric and dosimetric uncertainty, which is crucial for translational studies.« less

Passive radon/thoron personal dosimeter using an electrostatic collector and a diffused-junction detector

NASA Astrophysics Data System (ADS)

Bigu, J.; Raz, R.

1985-01-01

A solid-state alpha dosimeter has been designed and tested suitable for personal and environmental radon/thoron monitoring. The dosimeter basically consists of an electrostatic collector and an alpha-particle counting system with spectroscopy capabilities. The sensitive volume (˜20 cm3) of the electrostatic collector consists of a cylindrically shaped metal wire screen and a diffused-junction silicon alpha-detector covered with a thin aluminized Mylar sheet. A dc voltage (˜500 V) is applied between the wire screen and the Mylar sheet, with the latter held at negative potential relative to the former. Data can be retrieved during or after sampling by means of a microcomputer (Epson HX20) via a RS-232 communication interface unit. The dosimeter has been calibrated in a large (26 m3) radon/thoron test facility. A linear relationship was found between the dosimeter's alpha-count and both radon gas concentration and radon daughter working level. The dosimeter is mounted on top of an ordinary miner's cap lamp battery and is ideally suited for personal monitoring in underground uranium mines and other working areas. The dosimeter presented here is a considerably improved version of an earlier prototype.

Applicability of Glass Dosimeters for In-vivo Dosimetry in Brachytherapy

NASA Astrophysics Data System (ADS)

Moon, Sun Young; Son, Jaeman; Yoon, Myonggeun; Jeang, EunHee; Lim, Young Kyung; Chung, Weon Kyu; Kim, Dong Wook

2018-06-01

During brachytherapy, confirming the dose delivered is very important in order to prevent radiation-associated side effects. Therefore, we aimed to confirm the accuracy of dose delivery near the source by inserting glass dosimeters within the applicator. We created an alternative pelvic phantom with the same shape and internal structures as the usual patient. In addition, we created a tandem for insertion of the glass dosimeters and measured the dose near the source by inserting the glass dosimeters into the tandem and evaluating the accuracy of the dwell position and time through the dose near the source. Errors between the values obtained from the five glass dosimeters and the values from the treatment planning system were -6.27, -2.1, -4.18, 6.31, and -0.39%, respectively. The mean error was 3.85%. This value was acceptable considering that the error of the glass dosimeter itself is approximately 3%. Even though a complement of the applicator and the error calibration is required in order to apply this technique clinically, we believe that radiation accidents and overdoses can be prevented through in-vivo dosimetry using a glass dosimeter for brachytherapy.

Feasibility study of glass dosimeter postal dosimetry audit of high-energy radiotherapy photon beams.

PubMed

Mizuno, Hideyuki; Kanai, Tatsuaki; Kusano, Yohsuke; Ko, Susumu; Ono, Mari; Fukumura, Akifumi; Abe, Kyoko; Nishizawa, Kanae; Shimbo, Munefumi; Sakata, Suoh; Ishikura, Satoshi; Ikeda, Hiroshi

2008-02-01

The characteristics of a glass dosimeter were investigated for its potential use as a tool for postal dose audits. Reproducibility, energy dependence, field size and depth dependence were compared to those of a thermoluminescence dosimeter (TLD), which has been the major tool for postal dose audits worldwide. A glass dosimeter, GD-302M (Asahi Techno Glass Co.) and a TLD, TLD-100 chip (Harshaw Co.) were irradiated with gamma-rays from a (60)Co unit and X-rays from a medical linear accelerator (4, 6, 10 and 20 MV). The dosimetric characteristics of the glass dosimeter were almost equivalent to those of the TLD, in terms of utility for dosimetry under the reference condition, which is a 10 x 10 cm(2) field and 10 cm depth. Because of its reduced fading, compared to the TLD, and easy quality control with the ID number, the glass dosimeter proved to be a suitable tool for postal dose audits. Then, we conducted postal dose surveys of over 100 facilities and got good agreement, with a standard deviation of about 1.3%. Based on this study, postal dose audits throughout Japan will be carried out using a glass dosimeter.

Dosimeter for monitoring vapors and aerosols of organic compounds

DOEpatents

Vo-Dinh, Tuan

1987-01-01

A dosimeter is provided for collecting and detecting vapors and aerosols of organic compounds. The dosimeter comprises a lightweight, passive device that can be conveniently worn by a person as a badge or placed at a stationary location. The dosimeter includes a sample collector comprising a porous web treated with a chemical for inducing molecular displacement and enhancing phosphorescence. Compounds are collected onto the web by molecular diffusion. The web also serves as the sample medium for detecting the compounds by a room temperature phosphorescence technique.

Photoluminescence and Optically Stimulated Luminescence Studies of LiAlO2 and LiGaO2 Crystals

DTIC Science & Technology

2015-03-26

tests from the past. In terms of personal dosimetry, OSL dosimeters could potentially replace ther- moluminescence dosimeters (TLDs) which are widely...used by individuals conducting research and maintaining nuclear weapons ( OSL dosimeters are a promising alterna- tive to TLDs because they do not...because they contain lithium, unlike Al2O3:C, the most commonly used OSL dosimeter [2]. The large neutron 1 cross section of lithium-6 makes enriched

NASA Crew Personal Active Dosimeters (CPADs): Leveraging Novel Terrestrial Personal Radiation Monitoring Capabilities for Space Exploration

NASA Technical Reports Server (NTRS)

Leitgab, Martin; Semones, Edward; Lee, Kerry

2016-01-01

The NASA Space Radiation Analysis Group (SRAG) is developing novel Crew Personal Active Dosimeters (CAPDs) for upcoming crewed space exploration missions and beyond. To reduce the resource footprint of the project a COTS dosimeter base is used for the development of CPADs. This base was identified from evaluations of existing COTS personal dosimeters against the concept of operations of future crewed missions and tests against detection requirements for radiation characteristic of the space environment. CPADs exploit operations efficiencies from novel features for space flight personal dosimeters such as real-time dose feedback, and autonomous measuring and data transmission capabilities. Preliminary CPAD design, results of radiation testing and aspects of operational integration will be presented.

Characterization of Thymol blue Radiochromic dosimeters for high dose applications

NASA Astrophysics Data System (ADS)

Aldweri, Feras M.; Abuzayed, Manar H.; Al-Ajaleen, Musab S.; Rabaeh, Khalid A.

2018-03-01

Thymol blue (TB) solutions and Thymol blue Polyvinyl Alcohol (TB-PVA) films have been introduced as Radiochromic dosimeter for high dose applications. The dosimeters were irradiated with gamma ray (60Co source) from 5 to 30 kGy for film, and from 0.150 kGy to 4 kGy for solution. The optical density of unirradiated and irradiated TB solution as well as TB-PVA film dosimeters were studied in terms of absorbance at 434 nm using UV/VIS spectrophotometer. The effects of scan temperature, light pre-gamma irradiation, dose rate, relative humidity and stability of the absorbance of solutions and films after irradiation were investigated. We found the dose sensitivity of TB solution and TB-PVA film dosimeters increases significantly with increases of the absorbed dose as well as with the increases of TB dye concentrations. The useful dose range of developed TB solutions and TB-PVA films dosimeters is in the range 0.125-1 kGy and of 5-20 kGy, respectively.

Characterization of ferrous-methylthymol blue-polyvinyl alcohol gel dosimeters using nuclear magnetic resonance and optical techniques

NASA Astrophysics Data System (ADS)

Rabaeh, Khalid A.; Eyadeh, Molham M.; Hailat, Tariq F.; Aldweri, Feras M.; Alheet, Samer M.; Eid, Rania M.

2018-07-01

A new composition of Ferrous sulphate-Metheylthymol blue (MTB)-Polyvinyl alcohol (PVA) dosimeter is introduced in this work and evaluated using nuclear magnetic resonance (NMR) and absorbance spectrophotometry techniques. The Fricke-MTB-PVA dosimeters were irradiated using a medical linear accelerator in a cubic water phantom. The dose response of the dosimeters was investigated using NMR in terms of spin-spin relaxation rate (R2), and ultraviolet and visible regions (UV-Vis) spectrophotometry in terms of absorbance. The dosimeter presents a linear dose response for doses up to 20 Gy with UV-Vis and 40 Gy with NMR method. The sample with 0.1 mM MTB, 5% PVA by weight showed highest dose sensitivity for both techniques. The Fricke-MTB-PVA dosimeter developed in this work has a significant advance over the Fricke-MTB-gelatin system: the NMR sensitivity was remarkably improved; the auto-oxidation rate was seven times lower, and no significant dose rate or photon energy effects were observed.

Evaluation of film and thermoluminescent dosimetry of high-energy electron beams in heterogeneous phantoms.

PubMed

el-Khatib, E; Antolak, J; Scrimger, J

1992-01-01

Film and thermoluminescent dosimetry (TLD) are investigated in heterogeneous phantoms irradiated by high-energy electron beams. Both film and TLD are practical dosimeters for multiple and moving beam radiotherapy. The accuracy and precision of these dosimeters for radiation dose measurements in homogeneous water-equivalent phantoms has been discussed in the literature. However, film and TLD are often used for dose measurements in heterogeneous phantoms. In those situations perturbations are produced which are related to the density and atomic number of the phantom material and the physical size and orientation of the dosimeter. In our experiments the relative dose measurements in homogeneous phantoms were the same regardless of dosimeter or dosimeter orientation. However, significant differences were observed between the dose measurements within the inhomogeneity. These differences were influenced by the type and orientation of the dosimeter in addition to the properties of the heterogeneity. These differences could be reproduced with Monte Carlo calculations and modeling of the experimental conditions.

Water-equivalent fiber radiation dosimeter with two scintillating materials

PubMed Central

Qin, Zhuang; Hu, Yaosheng; Ma, Yu; Lin, Wei; Luo, Xianping; Zhao, Wenhui; Sun, Weimin; Zhang, Daxin; Chen, Ziyin; Wang, Boran; Lewis, Elfed

2016-01-01

An inorganic scintillating material plastic optical fiber (POF) dosimeter for measuring ionizing radiation during radiotherapy applications is reported. It is necessary that an ideal dosimeter exhibits many desirable qualities, including water equivalence, energy independence, reproducibility, dose linearity. There has been much recent research concerning inorganic dosimeters. However, little reference has been made to date of the depth-dose characteristics of dosimeter materials. In the case of inorganic scintillating materials, they are predominantly non water-equivalent, with their effective atomic weight (Zeff) being typically much greater than that of water. This has been a barrier in preventing inorganic scintillating material dosimeter from being used in actual clinical applications. In this paper, we propose a parallel-paired fiber light guide structure to solve this problem. Two different inorganic scintillating materials are embedded separately in the parallel-paired fiber. It is shown that the information of water depth and absorbed dose at the point of measurement can be extracted by utilizing their different depth-dose properties. PMID:28018715

Characteristics of a normoxic polymethacrylic acid gel dosimeter for a 72-MeV proton beam

NASA Astrophysics Data System (ADS)

Bong, Jihye; Shin, Dongho; Kwon, Soo-Il

2014-01-01

The characteristics of a normoxic polymethacrylic acid gel dosimeter for a 72-MeV proton beam were evaluated. A polymer gel dosimeter was synthesized using gelatin, methacrylic acid, hydroquinone, tetrakis(hydroxymethyl) phosphonium chloride, and highly purified distilled water. The dosimeter was manufactured by placement in a polyethylene (PE) container. Irradiated dosimeters were analyzed to determine the transverse relaxation time (T2) using a 1.5-T MRI. A calibration curve was obtained as a function of the absorbed dose. A Bragg curve made by irradiating the gel with mono-energy was compared with the results for a parallel plate ionization chamber. The spread-out Bragg peak (SOBP) range and distal dose fall-off (DDF) were comparatively analyzed by comparing the irradiated gel with a spread-out Bragg peak against with the ion chamber. Lastly, the gel's usefulness as a dosimeter for therapeutic radiation quality assurance was evaluated by obtaining its practical field size, flatness, and symmetry, through comparison of the profiles of the gel and ion chamber.

Analysis of uni and bi-parental markers in mixture samples: Lessons from the 22nd GHEP-ISFG Intercomparison Exercise.

PubMed

Toscanini, U; Gusmão, L; Álava Narváez, M C; Álvarez, J C; Baldassarri, L; Barbaro, A; Berardi, G; Betancor Hernández, E; Camargo, M; Carreras-Carbonell, J; Castro, J; Costa, S C; Coufalova, P; Domínguez, V; Fagundes de Carvalho, E; Ferreira, S T G; Furfuro, S; García, O; Goios, A; González, R; de la Vega, A González; Gorostiza, A; Hernández, A; Jiménez Moreno, S; Lareu, M V; León Almagro, A; Marino, M; Martínez, G; Miozzo, M C; Modesti, N M; Onofri, V; Pagano, S; Pardo Arias, B; Pedrosa, S; Penacino, G A; Pontes, M L; Porto, M J; Puente-Prieto, J; Pérez, R Ramírez; Ribeiro, T; Rodríguez Cardozo, B; Rodríguez Lesmes, Y M; Sala, A; Santiago, B; Saragoni, V G; Serrano, A; Streitenberger, E R; Torres Morales, M A; Vannelli Rey, S A; Velázquez Miranda, M; Whittle, M R; Fernández, K; Salas, A

2016-11-01

Since 1992, the Spanish and Portuguese-Speaking Working Group of the ISFG (GHEP-ISFG) has been organizing annual Intercomparison Exercises (IEs) coordinated by the Quality Service at the National Institute of Toxicology and Forensic Sciences (INTCF) from Madrid, aiming to provide proficiency tests for forensic DNA laboratories. Each annual exercise comprises a Basic (recently accredited under ISO/IEC 17043: 2010) and an Advanced Level, both including a kinship and a forensic module. Here, we show the results for both autosomal and sex-chromosomal STRs, and for mitochondrial DNA (mtDNA) in two samples included in the forensic modules, namely a mixture 2:1 (v/v) saliva/blood (M4) and a mixture 4:1 (v/v) saliva/semen (M8) out of the five items provided in the 2014 GHEP-ISFG IE. Discrepancies, other than typos or nomenclature errors (over the total allele calls), represented 6.5% (M4) and 4.7% (M8) for autosomal STRs, 15.4% (M4) and 7.8% (M8) for X-STRs, and 1.2% (M4) and 0.0% (M8) for Y-STRs. Drop-out and drop-in alleles were the main cause of errors, with laboratories using different criteria regarding inclusion of minor peaks and stutter bands. Commonly used commercial kits yielded different results for a micro-variant detected at locus D12S391. In addition, the analysis of electropherograms revealed that the proportions of the contributors detected in the mixtures varied among the participants. In regards to mtDNA analysis, besides important discrepancies in reporting heteroplasmies, there was no agreement for the results of sample M4. Thus, while some laboratories documented a single control region haplotype, a few reported unexpected profiles (suggesting contamination problems). For M8, most laboratories detected only the haplotype corresponding to the saliva. Although the GHEP-ISFG has already a large experience in IEs, the present multi-centric study revealed challenges that still exist related to DNA mixtures interpretation. Overall, the results emphasize the need for further research and training actions in order to improve the analysis of mixtures among the forensic practitioners. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Sensitivity tests to define the source apportionment performance criteria in the DeltaSA tool

NASA Astrophysics Data System (ADS)

Pernigotti, Denise; Belis, Claudio A.

2017-04-01

Identification and quantification of the contribution of emission sources to a given area is a key task for the design of abatement strategies. Moreover, European member states are obliged to report this kind of information for zones where the pollution levels exceed the limit values. At present, little is known about the performance and uncertainty of the variety of methodologies used for source apportionment and the comparability between the results of studies using different approaches. The source apportionment Delta (SA Delta) is a tool developed by the EC-JRC to support the particulate matter source apportionment modellers in the identification of sources (for factor analysis studies) and/or in the measure of their performance. The source identification is performed by the tool measuring the proximity of any user chemical profile to preloaded repository data (SPECIATE and SPECIEUROPE). The model performances criteria are based on standard statistical indexes calculated by comparing participants' source contribute estimates and their time series with preloaded references data. Those preloaded data refer to previous European SA intercomparison exercises: the first with real world data (22 participants), the second with synthetic data (25 participants) and the last with real world data which was also extended to Chemical Transport Models (38 receptor models and 4 CTMs). The references used for the model performances are 'true' (predefined by JRC) for the synthetic while they are calculated as ensemble average of the participants' results in real world intercomparisons. The candidates used for each source ensemble reference calculation were selected among participants results based on a number of consistency checks plus the similarity between their chemical profiles to the repository measured data. The estimation of the ensemble reference uncertainty is crucial in order to evaluate the users' performances against it. For this reason a sensitivity analysis on different methods to estimate the ensemble references' uncertainties was performed re-analyzing the synthetic intercomparison dataset, the only one where 'true' reference and ensemble reference contributions were both present. The Delta SA is now available on-line and will be presented, with a critical discussion of the sensitivity analysis on the ensemble reference uncertainty. In particular the grade of among participants mutual agreement on the presence of a certain source should be taken into account. Moreover also the importance of the synthetic intercomparisons in order to catch receptor models common biases will be stressed.

Determining the applicability of the Landauer nanoDot as a general public dosimeter in a research imaging facility.

PubMed

Charlton, Michael A; Thoreson, Kelly F; Cerecero, Jennifer A

2012-11-01

The Research Imaging Institute (RII) building at the University of Texas Health Science Center at San Antonio (UTHSCSA) houses two cyclotron particle accelerators, positron emission tomography (PET) machines, and a fluoroscopic unit. As part of the radiation protection program (RPP) and meeting the standard for achieving ALARA (as low as reasonably achievable), it is essential to minimize the ionizing radiation exposure to the general public through the use of controlled areas and area dose monitoring. Currently, thirty-four whole body Luxel+ dosimeters, manufactured by Landauer, are being used in various locations within the RII to monitor dose to the general public. The intent of this research was to determine if the nanoDot, a single point dosimeter, can be used as a general public dosimeter in a diagnostic facility. This was tested by first verifying characteristics of the nanoDot dosimeter including dose linearity, dose rate dependence, angular dependence, and energy dependence. Then, the response of the nanoDot dosimeter to the Luxel+ dosimeter when placed in a continuous, low dose environment was investigated. Finally, the nanoDot was checked for appropriate response in an acute, high dose environment. Based on the results, the current recommendation is that the nanoDot should not replace the Luxel+ dosimeter without further work to determine the energy spectra in the RII building and without considering the limitation of the microStar reader, portable on-site OSL reader, at doses below 0.1 mGy (10 mrad).

Light scattering in optical CT scanning of Presage dosimeters

NASA Astrophysics Data System (ADS)

Xu, Y.; Adamovics, J.; Cheeseborough, J. C.; Chao, K. S.; Wuu, C. S.

2010-11-01

The intensity of the scattered light from the Presage dosimeters was measured using a Thorlabs PM100D optical power meter (Thorlabs Inc, Newton, NJ) with an optical sensor of 1 mm diameter sensitive area. Five Presage dosimeters were made as cylinders of 15.2 cm, 10 cm, 4 cm diameters and irradiated with 6 MV photons using a Varian Clinac 2100EX. Each dosimeter was put into the scanning tank of an OCTOPUS" optical CT scanner (MGS Research Inc, Madison, CT) filled with a refractive index matching liquid. A laser diode was positioned at one side of the water tank to generate a stationary laser beam of 0.8 mm width. On the other side of the tank, an in-house manufactured positioning system was used to move the optical sensor in the direction perpendicular to the outgoing laser beam from the dosimeters at an increment of 1 mm. The amount of scattered photons was found to be more than 1% of the primary light signal within 2 mm from the laser beam but decreases sharply with increasing off-axis distance. The intensity of the scattered light increases with increasing light attenuations and/or absorptions in the dosimeters. The scattered light at the same off-axis distance was weaker for dosimeters of larger diameters and for larger detector-to-dosimeter distances. Methods for minimizing the effect of the light scattering in different types of optical CT scanners are discussed.

FACTORS AFFECTING THE USE OF CAF2:MN THERMOLUMINESCENT DOSIMETERS FOR LOW-LEVEL ENVIRONMENTAL RADIATION MONITORING

EPA Science Inventory

An investigation was made of factors affecting the use of commercially-produced CaF2:Mn thermoluminescent dosimeters for low level environmental radiation monitoring. Calibration factors and self-dosing rates were quantified for 150 thermoluminescent dosimeters. Laboratory studie...

The InterFrost benchmark of Thermo-Hydraulic codes for cold regions hydrology - first inter-comparison results

NASA Astrophysics Data System (ADS)

Grenier, Christophe; Roux, Nicolas; Anbergen, Hauke; Collier, Nathaniel; Costard, Francois; Ferrry, Michel; Frampton, Andrew; Frederick, Jennifer; Holmen, Johan; Jost, Anne; Kokh, Samuel; Kurylyk, Barret; McKenzie, Jeffrey; Molson, John; Orgogozo, Laurent; Rivière, Agnès; Rühaak, Wolfram; Selroos, Jan-Olof; Therrien, René; Vidstrand, Patrik

2015-04-01

The impacts of climate change in boreal regions has received considerable attention recently due to the warming trends that have been experienced in recent decades and are expected to intensify in the future. Large portions of these regions, corresponding to permafrost areas, are covered by water bodies (lakes, rivers) that interact with the surrounding permafrost. For example, the thermal state of the surrounding soil influences the energy and water budget of the surface water bodies. Also, these water bodies generate taliks (unfrozen zones below) that disturb the thermal regimes of permafrost and may play a key role in the context of climate change. Recent field studies and modeling exercises indicate that a fully coupled 2D or 3D Thermo-Hydraulic (TH) approach is required to understand and model the past and future evolution of landscapes, rivers, lakes and associated groundwater systems in a changing climate. However, there is presently a paucity of 3D numerical studies of permafrost thaw and associated hydrological changes, and the lack of study can be partly attributed to the difficulty in verifying multi-dimensional results produced by numerical models. Numerical approaches can only be validated against analytical solutions for a purely thermic 1D equation with phase change (e.g. Neumann, Lunardini). When it comes to the coupled TH system (coupling two highly non-linear equations), the only possible approach is to compare the results from different codes to provided test cases and/or to have controlled experiments for validation. Such inter-code comparisons can propel discussions to try to improve code performances. A benchmark exercise was initialized in 2014 with a kick-off meeting in Paris in November. Participants from USA, Canada, Germany, Sweden and France convened, representing altogether 13 simulation codes. The benchmark exercises consist of several test cases inspired by existing literature (e.g. McKenzie et al., 2007) as well as new ones. They range from simpler, purely thermal cases (benchmark T1) to more complex, coupled 2D TH cases (benchmarks TH1, TH2, and TH3). Some experimental cases conducted in cold room complement the validation approach. A web site hosted by LSCE (Laboratoire des Sciences du Climat et de l'Environnement) is an interaction platform for the participants and hosts the test cases database at the following address: https://wiki.lsce.ipsl.fr/interfrost. The results of the first stage of the benchmark exercise will be presented. We will mainly focus on the inter-comparison of participant results for the coupled cases (TH1, TH2 & TH3). Further perspectives of the exercise will also be presented. Extensions to more complex physical conditions (e.g. unsaturated conditions and geometrical deformations) are contemplated. In addition, 1D vertical cases of interest to the Climate Modeling community will be proposed. Keywords: Permafrost; Numerical modeling; River-soil interaction; Arctic systems; soil freeze-thaw

Evaluation of a Colorimetric Personal Dosimeter for Nitrogen Oxide.

ERIC Educational Resources Information Center

Diamond, Philip

A personal colorimetric dosimeter for nitrogen dioxide was developed. Tests were performed to determine the response of these strips to various concentrations of NO2. The dosimeter strips were satisfactory for approximate determinations of total exposure (concentration + time) of nitrogen dioxide. The total exposure was calculated in terms of time…

10 CFR 34.89 - Location of documents and records.

Code of Federal Regulations, 2010 CFR

2010-01-01

... problems identified in daily checks of equipment as required by § 34.73(a); (5) Records of alarm system and... as pocket dosimeter and/or electronic personal dosimeters readings as required by § 34.83; (7... calibrations of alarm ratemeters and operability checks of pocket dosimeters and/or electronic personal...

10 CFR 34.89 - Location of documents and records.

Code of Federal Regulations, 2011 CFR

2011-01-01

... problems identified in daily checks of equipment as required by § 34.73(a); (5) Records of alarm system and... as pocket dosimeter and/or electronic personal dosimeters readings as required by § 34.83; (7... calibrations of alarm ratemeters and operability checks of pocket dosimeters and/or electronic personal...

Dosimeter for monitoring vapors and aerosols of organic compounds

DOEpatents

Vo-Dinh, T.

1987-07-14

A dosimeter is provided for collecting and detecting vapors and aerosols of organic compounds. The dosimeter comprises a lightweight, passive device that can be conveniently worn by a person as a badge or placed at a stationary location. The dosimeter includes a sample collector comprising a porous web treated with a chemical for inducing molecular displacement and enhancing phosphorescence. Compounds are collected onto the web by molecular diffusion. The web also serves as the sample medium for detecting the compounds by a room temperature phosphorescence technique. 7 figs.

Measurement of a 200 MeV proton beam using a polyurethane dosimeter

NASA Astrophysics Data System (ADS)

Heard, Malcolm; Adamovics, John; Ibbott, Geoffrey

2006-12-01

PRESAGETM (Heuris Pharma LLC, Skillman, NJ) is a three-dimensional polyurethane dosimeter containing a leuco dye that generates a color change when irradiated. The dosimeter is solid and does not require a container to maintain its shape. The dosimeter is transparent before irradiation and the maximum absorbance of the leuco dye occurs at 633 nm which is compatible with the OCT-OPUSTM laser CT scanner (MGS Research, Inc., Madison, CT). The purpose of this study was to investigate the response of PRESAGETM to proton beam radiotherapy.

[Fabrication of annealing equipment for optically stimulated luminescence (OSL) dosimeter].

PubMed

Nakagawa, Kohei; Hayashi, Hiroaki; Okino, Hiroki; Takegami, Kazuki; Okazaki, Tohru; Kobayashi, Ikuo

2014-10-01

The optically stimulated luminescence (OSL) dosimeter is a useful detector for measuring absorbed doses of X-rays. A small-type OSL dosimeter, "nanoDot", has recently been developed by Landauer, Inc., who also manufacture "microStar" reading equipment. However, additional annealing equipment is needed if the nanoDot OSL dosimeter is used repeatedly. The aim of this study was to fabricate suitable annealing equipment using commonly available products. Our device positions four fluorescent light tubes in a close configuration. The heat from the fluorescent light tubes is dissipated using fans. Experiments using diagnostic X-ray equipment were carried out to evaluate the capability of our annealing equipment. The results indicated that our equipment can fully anneal the nanoDot OSL dosimeter with annealing times of approximately 20 hours.

Method and apparatus for reading free falling dosimeter punchcodes

DOEpatents

Langsted, James M.

1992-12-22

A punchcode reader is provided for reading data encoded in a punchcode hole array on a dosimeter. The dosimeter falls through a passage in the reader containing photosensor detectors disposed along the passage which provide output signals to a microprocessor. The signals are processed to determine the orientation of the dosimeter in the reader, the location and state of punchcode holes in a two row array thereby decoding the encoded data. Multiple rate of fall calculations are made, and if appropriate matching of the punchcode array is not obtained in three tries, an error signal is outputted to the operator. The punchcode reader also provides for storage of data from multiple dosimeters passed through the reader, and for the output of decoded data to an external display or a computer for further processing.

Angular dependence of the MOSFET dosimeter and its impact on in vivo surface dose measurement in breast cancer treatment.

PubMed

Qin, S; Chen, T; Wang, L; Tu, Y; Yue, N; Zhou, J

2014-08-01

The focus of this study is the angular dependence of two types of Metal Oxide Semiconductor Field Effect Transistor (MOSFET) dosimeters (MOSFET20 and OneDose/OneDosePlus) when used for surface dose measurements. External beam radiationat different gantry angles were delivered to a cubic solid water phantom with a MOSFET placed on the top surface at CAX. The long axis of the MOSFET was oriented along the gantry axis of rotation, with the dosimeter (bubble side) facing the radiation source. MOSFET-measured surface doses were compared against calibrated radiochromic film readings. It was found that both types of MOSFET dosimeters exhibited larger than previously reported angular dependence when measuring surface dose in beams at large oblique angles. For the MOSFET20 dosimeter the measured surface dose deviation against film readings was as high as 17% when the incident angle was 72 degrees to the norm of the phantom surface. It is concluded that some MOSFET dosimeters may have a strong angular dependence when placed on the surface of water-equivalent material, even though they may have an isotropic angular response when surrounded by uniform medium. Extra on-surface calibration maybe necessary before using MOSFET dosimeters for skin dose measurement in tangential fields.

Experimental evaluation of a MOSFET dosimeter for proton dose measurements.

PubMed

Kohno, Ryosuke; Nishio, Teiji; Miyagishi, Tomoko; Hirano, Eriko; Hotta, Kenji; Kawashima, Mitsuhiko; Ogino, Takashi

2006-12-07

The metal oxide semiconductor field-effect transistor (MOSFET) dosimeter has been widely studied for use as a dosimeter for patient dose verification. The major advantage of this detector is its size, which acts as a point dosimeter, and also its ease of use. The commercially available TN502RD MOSFET dosimeter manufactured by Thomson and Nielsen has never been used for proton dosimetry. Therefore we used the MOSFET dosimeter for the first time in proton dose measurements. In this study, the MOSFET dosimeter was irradiated with 190 MeV therapeutic proton beams. We experimentally evaluated dose reproducibility, linearity, fading effect, beam intensity dependence and angular dependence for the proton beam. Furthermore, the Bragg curve and spread-out Bragg peak were also measured and the linear-energy transfer (LET) dependence of the MOSFET response was investigated. Many characteristics of the MOSFET response for proton beams were the same as those for photon beams reported in previous papers. However, the angular MOSFET responses at 45, 90, 135, 225, 270 and 315 degrees for proton beams were over-responses of about 15%, and moreover the MOSFET response depended strongly on the LET of the proton beam. This study showed that the angular dependence and LET dependence of the MOSFET response must be considered very carefully for quantitative proton dose evaluations.

SU-F-BRF-13: Investigating the Feasibility of Accurate Dose Measurement in a Deforming Radiochromic Dosimeter

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

Juang, T; Adamovics, J; Oldham, M

Purpose: Presage-Def, a deformable radiochromic 3D dosimeter, has been previously shown to have potential for validating deformable image registration algorithms. This work extends this effort to investigate the feasibility of using Presage-Def to validate dose-accumulation algorithms in deforming structures. Methods: Two cylindrical Presage-Def dosimeters (8cm diameter, 4.5cm length) were irradiated in a water-bath with a simple 4-field box treatment. Isocentric dose was 20Gy. One dosimeter served as control (no deformation) while the other was laterally compressed during irradiation by 21%. Both dosimeters were imaged before and after irradiation with a fast (∼10 minutes for 1mm isotropic resolution), broad beam, highmore » resolution optical-CT scanner. Measured dose distributions were compared to corresponding distributions calculated by a commissioned Eclipse planning system. Accuracy in the control was evaluated with 3D gamma (3%/3mm). The dose distribution calculated for the compressed dosimeter in the irradiation geometry cannot be directly compared via profiles or 3D gamma to the measured distribution, which deforms with release from compression. Thus, accuracy under deformation was determined by comparing integral dose within the high dose region of the deformed dosimeter distribution versus calculated dose. Dose profiles were used to study temporal stability of measured dose distributions. Results: Good dose agreement was demonstrated in the control with a 3D gamma passing rate of 96.6%. For the dosimeter irradiated under compression, the measured integral dose in the high dose region (518.0Gy*cm3) was within 6% of the Eclipse-calculated integral dose (549.4Gy*cm3). Elevated signal was noted on the dosimeter edge in the direction of compression. Change in dosimeter signal over 1.5 hours was ≤2.7%, and the relative dose distribution remained stable over this period of time. Conclusion: Presage-Def is promising as a 3D dosimeter capable of accurately measuring dose in a deforming structure, and warrants further study to quantify comprehensive accuracy at different levels of deformation. This work was supported by NIH R01CA100835. John Adamovics is the president of Heuris Inc., which commercializes PRESAGE.« less

SU-F-T-159: Monte Carlo Simulation Studies of Three-Dimensional Dose Distribution for Polymer Gel Dosimeter and Radiochromic Gel Dosimeter in a Proton Beam

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

Park, M; Kim, G; Jung, H

Purpose: The purpose of this simulation study is to evaluate the proton detectability of gel dosimeters, and estimate the three-dimensional dose distribution of protons in the radiochromic gel and polymer gel dosimeter compared with the dose distribution in water. Methods: The commercial composition ratios of normoxic polymer gel and LCV micelle radiochromic gel were included in this simulation study. The densities of polymer and radiochromic gel were 1.024 and 1.005 g/cm3, respectively. The 50, 80 and 140 MeV proton beam energies were selected. The dose distributions of protons in the polymer and radiochromic gel were simulated using Monte Carlo radiationmore » transport code (MCNPX 2.7.0, Los Alamos Laboratory). The water equivalent depth profiles and the dose distributions of two gel dosimeters were compared for the water. Results: In case of irradiating 50, 80 and 140 MeV proton beam to water phantom, the reference Bragg-peak depths are represented at 2.22, 5.18 and 13.98 cm, respectively. The difference in the water equivalent depth is represented to about 0.17 and 0.37 cm in the radiochromic gel and polymer gel dosimeter, respectively. The proton absorbed doses in the radiochromic gel dosimeter are calculated to 2.41, 3.92 and 6.90 Gy with increment of incident proton energies. In the polymer gel dosimeter, the absorbed doses are calculated to 2.37, 3.85 and 6.78 Gy with increment of incident proton energies. The relative absorbed dose in radiochromic gel (about 0.47 %) is similar to that of water than the relative absorbed dose of polymer gel (about 2.26 %). In evaluating the proton dose distribution, we found that the dose distribution of both gel dosimeters matched that of water in most cases. Conclusion: As the dosimetry device, the radiochromic gel dosimeter has the potential particle detectability and is feasible to use for quality assurance of proton beam therapy beam.« less

Early development and characterization of a DNA-based radiation dosimeter

NASA Astrophysics Data System (ADS)

Avarmaa, Kirsten A.

It is the priority of first responders to minimize damage to persons and infrastructure in the case of a nuclear emergency due to an accident or deliberate terrorist attack -- if this emergency includes a radioactive hazard, first responders require a simple-to-use, accurate and complete dosimeter for radiation protection purposes in order to minimize the health risk to these individuals and the general population at large. This work consists of the early evaluation of the design and performance of a biologically relevant dosimeter which uses DNA material that can respond to the radiation of any particle type. The construct consists of fluorescently tagged strands of DNA. The signalling components of this dosimeter are also investigated for their sensitivity to radiation damage and light exposure. The dual-labelled dosimeter that is evaluated in this work gave a measurable response to gamma radiation at dose levels of 10 Gy for the given detector design and experimental setup. Further testing outside of this work confirmed this finding and indicated a working range of 100 mGy to 10 Gy using a custom-built fluorimeter as part of a larger CRTI initiative. Characterization of the chromatic components of the dosimeter showed that photobleaching is not expected to have an effect on dosimeter performance, but that radiation can damage the non-DNA signalling components at higher dose levels, although this damage is minimal at lower doses over the expected operating ranges. This work therefore describes the early steps in the quantification of the behaviour of the DNA dosimeter as a potential biologically-based device to measure radiation dose.

Marine anthropogenic radiotracers in the Southern Hemisphere: New sampling and analytical strategies

NASA Astrophysics Data System (ADS)

Levy, I.; Povinec, P. P.; Aoyama, M.; Hirose, K.; Sanchez-Cabeza, J. A.; Comanducci, J.-F.; Gastaud, J.; Eriksson, M.; Hamajima, Y.; Kim, C. S.; Komura, K.; Osvath, I.; Roos, P.; Yim, S. A.

2011-04-01

The Japan Agency for Marine Earth Science and Technology conducted in 2003-2004 the Blue Earth Global Expedition (BEAGLE2003) around the Southern Hemisphere Oceans, which was a rare opportunity to collect many seawater samples for anthropogenic radionuclide studies. We describe here sampling and analytical methodologies based on radiochemical separations of Cs and Pu from seawater, as well as radiometric and mass spectrometry measurements. Several laboratories took part in radionuclide analyses using different techniques. The intercomparison exercises and analyses of certified reference materials showed a reasonable agreement between the participating laboratories. The obtained data on the distribution of 137Cs and plutonium isotopes in seawater represent the most comprehensive results available for the Southern Hemisphere Oceans.

A soil sampling reference site: the challenge in defining reference material for sampling.

PubMed

de Zorzi, Paolo; Barbizzi, Sabrina; Belli, Maria; Fajgelj, Ales; Jacimovic, Radojko; Jeran, Zvonka; Sansone, Umberto; van der Perk, Marcel

2008-11-01

In the frame of the international SOILSAMP project, funded and coordinated by the Italian Environmental Protection Agency, an agricultural area was established as a reference site suitable for performing soil sampling inter-comparison exercises. The reference site was characterized for trace element content in soil, in terms of the spatial and temporal variability of their mass fraction. Considering that the behaviour of long-lived radionuclides in soil can be expected to be similar to that of some stable trace elements and that the distribution of these trace elements in soil can simulate the distribution of radionuclides, the reference site characterised in term of trace elements, can be also used to compare the soil sampling strategies developed for radionuclide investigations.

The Agriculture Model Intercomparison and Improvement Project (AgMIP) (Invited)

NASA Astrophysics Data System (ADS)

Rosenzweig, C.

2010-12-01

The Agricultural Model Intercomparison and Improvement Project (AgMIP) is a distributed climate-scenario simulation exercise for historical model intercomparison and future climate change conditions with participation of multiple crop and world agricultural trade modeling groups around the world. The goals of AgMIP are to improve substantially the characterization of risk of hunger and world food security due to climate change and to enhance adaptation capacity in both developing and developed countries. Historical period results will spur model improvement and interaction among major modeling groups, while future period results will lead directly to tests of adaptation and mitigation strategies across a range of scales. AgMIP will consist of a multi-scale impact assessment utilizing the latest methods for climate and agricultural scenario generation. Scenarios and modeling protocols will be distributed on the web, and multi-model results will be collated and analyzed to ensure the widest possible coverage of agricultural crops and regions. AgMIP will place regional changes in agricultural production in a global context that reflects new trading opportunities, imbalances, and shortages in world markets resulting from climate change and other driving forces for food supply. Such projections are essential inputs from the Vulnerability, Impacts, and Adaptation (VIA) research community to the Intergovernmental Panel on Climate Change Fifth Assessment (AR5), now underway, and the UN Framework Convention on Climate Change. They will set the context for local-scale vulnerability and adaptation studies, supply test scenarios for national-scale development of trade policy instruments, provide critical information on changing supply and demand for water resources, and elucidate interactive effects of climate change and land use change. AgMIP will not only provide crucially-needed new global estimates of how climate change will affect food supply and hunger in the agricultural regions of the world, but it will also build the capabilities of developing countries to estimate how climate change will affect their supply and demand for food.

Reliability of an x-ray system for calibrating and testing personal radiation dosimeters

NASA Astrophysics Data System (ADS)

Guimarães, M. C.; Silva, C. R. E.; Rosado, P. H. G.; Cunha, P. G.; Da Silva, T. A.

2018-03-01

Metrology laboratories are expected to maintain standardized radiation beams and traceable standard dosimeters to provide reliable calibrations or testing of detectors. Results of the characterization of an x-ray system for performing calibration and testing of radiation dosimeters used for individual monitoring are shown in this work.

Ceric and ferrous dosimeters show precision for 50-5000 rad range

NASA Technical Reports Server (NTRS)

Frigerio, N. A.; Henry, V. D.

1968-01-01

Ammonium thiocyanate, added to the usual ferrous sulfate dosimeter solution, yielded a very stable, precise and temperature-independent system eight times as sensitive as the classical Fricke system in the 50 to 5000 rad range. The ceric dosimeters, promising for use in mixed radiation fields, respond nearly independently of LET.

Evaluation of discrepancies between thermoluminescent dosimeter and direct-reading dosimeter results

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

Shaw, K.R.

1993-07-01

Currently at Oak Ridge National Laboratory (ORNL), the responses of thermoluminescent dosimeters (TLDs) and direct-reading dosimeters (DRDs) are not officially compared or the discrepancies investigated. However, both may soon be required due to the new US Department of Energy (DOE) Radiological Control Manual. In the past, unofficial comparisons of the two dosimeters have led to discrepancies of up to 200%. This work was conducted to determine the reasons behind such discrepancies. For tests conducted with the TLDs, the reported dose was most often lower than the delivered dose, while DRDs most often responded higher than the delivered dose. Trends weremore » identified in personnel DRD readings, and ft was concluded that more training and more control of the DRDs could improve their response. TLD responses have already begun to be improved; a new background subtraction method was implemented in April 1993, and a new dose algorithm is being considered. It was concluded that the DOE Radiological Control Manual requirements are reasonable for identifying discrepancies between dosimeter types, and more stringent administrative limits might even be considered.« less

Three-dimensional radiation dosimetry based on optically-stimulated luminescence

NASA Astrophysics Data System (ADS)

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

2017-05-01

A new approach to three-dimensional (3D) dosimetry based on optically-stimulated luminescence (OSL) is presented. By embedding OSL-active particles into a transparent silicone matrix (PDMS), the well-established dosimetric properties of an OSL material are exploited in a 3D-OSL dosimeter. By investigating prototype dosimeters in standard cuvettes in combination with small test samples for OSL readers, it is shown that a sufficient transparency of the 3D-OSL material can be combined with an OSL response giving an estimated >10.000 detected photons in 1 second per 1mm3 voxel of the dosimeter at a dose of 1 Gy. The dose distribution in the 3D-OSL dosimeters can be directly read out optically without the need for subsequent reconstruction by computational inversion algorithms. The dosimeters carry the advantages known from personal-dosimetry use of OSL: the dose distribution following irradiation can be stored with minimal fading for extended periods of time, and dosimeters are reusable as they can be reset, e.g. by an intense (bleaching) light field.

Enhancement of Dose Response and Nuclear Magnetic Resonance Image of PAGAT Polymer Gel Dosimeter by Adding Silver Nanoparticles

PubMed Central

Sabbaghizadeh, Rahim; Shamsudin, Roslinda; Deyhimihaghighi, Najmeh; Sedghi, Arman

2017-01-01

In the present study, the normoxic polyacrylamide gelatin and tetrakis hydroxy methyl phosphoniun chloride (PAGAT) polymer gel dosimeters were synthesized with and without the presence of silver (Ag) nanoparticles. The amount of Ag nanoparticles varied from 1 to 3 ml with concentration 3.14 g/l, thus forming two types of PAGAT polymer gel dosimeters before irradiating them with 6 to 25 Gy produced by 1.25-MeV 60Co gamma rays. In this range, the predominant gamma ray interaction with matter is by Compton scattering effect, as the photoelectric absorption effect diminishes. MRI was employed when evaluating the polymerization of the dosimeters and the gray scale of the MRI film was determined via an optical densitometer. Subsequent analyses of optical densities revealed that the extent of polymerization increased with the increase in the absorbed dose, while the increase of penetration depth within the dosimeters has a reverse effect. Moreover, a significant increase in the optical density-dose response (11.82%) was noted for dosimeters containing 2 ml Ag nanoparticles. PMID:28060829

A diffusion-free and linear-energy-transfer-independent nanocomposite Fricke gel dosimeter

NASA Astrophysics Data System (ADS)

Maeyama, T.; Fukunishi, N.; Ishikawa, K. L.; Furuta, T.; Fukasaku, K.; Takagi, S.; Noda, S.; Himeno, R.; Fukuda, S.

2014-03-01

We report a new magnetic-resonance-imaging (MRI) based nanocomposite Fricke gel (NC-FG) dosimeter system, which is free from two main drawbacks of conventional Fricke gel dosimeters, namely, the diffusion of the radiation products and the linear-energy-transfer (LET) dependence of the radiation sensitivity when used for ion beams. The NC-FG dosimeter was prepared by incorporating 1% (w/w) clay nanoparticles into deaerated Fricke gel. We have dosimetrically characterized the NC-FG by using MRI measurements after irradiation with a monoenergetic 290 MeV/nucleon carbon beam. No diffusion of the radiation products was observed during nine days after the irradiation. Moreover, its response faithfully reproduced the depth-dose distribution measured by an ionization chamber, which indicates the absence of the LET dependence. Also, the NC-FG dosimeter exhibited a good linearity up to 800 Gy.

Method and apparatus for reading free falling dosimeter punchcodes

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

Langsted, J.M.

1992-12-22

A punchcode reader is provided for reading data encoded in a punchcode hole array on a dosimeter. The dosimeter falls through a passage in the reader containing photosensor detectors disposed along the passage which provide output signals to a microprocessor. The signals are processed to determine the orientation of the dosimeter in the reader, the location and state of punchcode holes in a two row array thereby decoding the encoded data. Multiple rate of fall calculations are made, and if appropriate matching of the punchcode array is not obtained in three tries, an error signal is output to the operator.more » The punchcode reader also provides for storage of data from multiple dosimeters passed through the reader, and for the output of decoded data to an external display or a computer for further processing. 8 figs.« less

Method and apparatus for reading free falling dosimeter punchcodes

DOEpatents

Langsted, J.M.

1992-12-22

A punchcode reader is provided for reading data encoded in a punchcode hole array on a dosimeter. The dosimeter falls through a passage in the reader containing photosensor detectors disposed along the passage which provide output signals to a microprocessor. The signals are processed to determine the orientation of the dosimeter in the reader, the location and state of punchcode holes in a two row array thereby decoding the encoded data. Multiple rate of fall calculations are made, and if appropriate matching of the punchcode array is not obtained in three tries, an error signal is output to the operator. The punchcode reader also provides for storage of data from multiple dosimeters passed through the reader, and for the output of decoded data to an external display or a computer for further processing. 8 figs.

Effects of elevated temperatures during interruption of irradiation on Harwell Red 4034 PMMA and Kodak Biomax alanine film dosimetry systems

NASA Astrophysics Data System (ADS)

Sidereas, P.; Patil, D. S.; Garcia, R.; Tracy, R. P.; Holzman, J. M.

2007-11-01

In the industrial setting it is not uncommon for a process interruption to occur during irradiation. In this event, dosimeters may be exposed to prolonged periods of elevated temperature without exposure to ionizing radiation. Once the process is restarted, the same dosimeters are exposed to ionizing radiation in order to achieve target dose. The goal of this experiment was to simulate a process interruption within limits and quantify the effects of a combination of factors (heat, time, and fractionation) on dosimeter response. We present an in-depth experimental study on the response of dosimeters that have been irradiated, stored for a fixed period of time at several temperatures, and then re-irradiated. This study was performed using Harwell Red 4034 polymethylmethacrylate (PMMA) and Kodak BioMax alanine film dosimeters.

Radiation dose enhancement of gold nanoparticle on different polymer gel dosimeters

NASA Astrophysics Data System (ADS)

Jabaseelan Samuel, E. James; Srinivasan, K.; Poopathi, V.

2017-05-01

In this work, we evaluated the dose enhancement produced by gold nanoparticle on ten different polymer gel dosimeters with a concentration of 7mgAu /g over a wide photon energy range of 15KeV to 20MeV and the results were compared with Soft tissue ICRU-44 produced. Our result showed that maximum DEF was observed at 40KeV, while it was almost negligible at higher energy range. Dose enhancement produced by AuNP on the gel dosimeter medium was varied compared to the reference ICRU-44 tissue, it was ± <1% for PAGAT, NIPAM, nPAG and ± <5% for PABIG, VIPAR, HEAG, BANG1, nMAG & ± <10% for MAGIC, ABAGIC gel dosimeters. Hence, we conclude that choosing the proper gel dosimeter is essential in dose enhancement study.

Monte-Carlo based assessment of MAGIC, MAGICAUG, PAGATUG and PAGATAUG polymer gel dosimeters for ovaries and uterus organ dosimetry in brachytherapy, nuclear medicine and Tele-therapy.

PubMed

Adinehvand, Karim; Rahatabad, Fereidoun Nowshiravan

2018-06-01

Calculation of 3D dose distribution during radiotherapy and nuclear medicine helps us for better treatment of sensitive organs such as ovaries and uterus. In this research, we investigate two groups of normoxic dosimeters based on meta-acrylic acid (MAGIC and MAGICAUG) and polyacrylamide (PAGATUG and PAGATAUG) for brachytherapy, nuclear medicine and Tele-therapy in their sensitive and critical role as organ dosimeters. These polymer gel dosimeters are compared with soft tissue while irradiated by different energy photons in therapeutic applications. This comparison has been simulated by Monte-Carlo based MCNPX code. ORNL phantom-Female has been used to model the critical organs of kidneys, ovaries and uterus. Right kidney is proposed to be the source of irradiation and another two organs are exposed to this irradiation. Effective atomic numbers of soft tissue, MAGIC, MAGICAUG, PAGATUG and PAGATAUG are 6.86, 7.07, 6.95, 7.28, and 7.07 respectively. Results show the polymer gel dosimeters are comparable to soft tissue for using in nuclear medicine and Tele-therapy. Differences between gel dosimeters and soft tissue are defined as the dose responses. This difference is less than 4.1%, 22.6% and 71.9% for Tele-therapy, nuclear medicine and brachytherapy respectively. The results approved that gel dosimeters are the best choice for ovaries and uterus in nuclear medicine and Tele-therapy respectively. Due to the slight difference between the effective atomic numbers of these polymer gel dosimeters and soft tissue, these polymer gels are not suitable for brachytherapy since the dependence of photon interaction to atomic number, for low energy brachytherapy, had been so effective. Also this dependence to atomic number, decrease for photoelectric and increase for Compton. Therefore polymer gel dosimeters are not a good alternative to soft tissue replacement in brachytherapy. Copyright © 2018 Elsevier B.V. All rights reserved.

WE-D-17A-02: Evaluation of a Two-Dimensional Optical Dosimeter On Measuring Lateral Profiles of Proton Pencil Beams

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

Hsi, W; Lee, T; Schultz, T

Purpose: To evaluate the accuracy of a two-dimensional optical dosimeter on measuring lateral profiles for spots and scanned fields of proton pencil beams. Methods: A digital camera with a color image senor was utilized to image proton-induced scintillations on Gadolinium-oxysulfide phosphor reflected by a stainless-steel mirror. Intensities of three colors were summed for each pixel with proper spatial-resolution calibration. To benchmark this dosimeter, the field size and penumbra for 100mm square fields of singleenergy pencil-scan protons were measured and compared between this optical dosimeter and an ionization-chamber profiler. Sigma widths of proton spots in air were measured and compared betweenmore » this dosimeter and a commercial optical dosimeter. Clinical proton beams with ranges between 80 mm and 300 mm at CDH proton center were used for this benchmark. Results: Pixel resolutions vary 1.5% between two perpendicular axes. For a pencil-scan field with 302 mm range, measured field sizes and penumbras between two detection systems agreed to 0.5 mm and 0.3 mm, respectively. Sigma widths agree to 0.3 mm between two optical dosimeters for a proton spot with 158 mm range; having widths of 5.76 mm and 5.92 mm for X and Y axes, respectively. Similar agreements were obtained for others beam ranges. This dosimeter was successfully utilizing on mapping the shapes and sizes of proton spots at the technical acceptance of McLaren proton therapy system. Snow-flake spots seen on images indicated the image sensor having pixels damaged by radiations. Minor variations in intensity between different colors were observed. Conclusions: The accuracy of our dosimeter was in good agreement with other established devices in measuring lateral profiles of pencil-scan fields and proton spots. A precise docking mechanism for camera was designed to keep aligned optical path while replacing damaged image senor. Causes for minor variations between emitted color lights will be investigated.« less

Characterization of MOSFET dosimeters for low-dose measurements in maxillofacial anthropomorphic phantoms.

PubMed

Koivisto, Juha H; Wolff, Jan E; Kiljunen, Timo; Schulze, Dirk; Kortesniemi, Mika

2015-07-08

The aims of this study were to characterize reinforced metal-oxide-semiconductor field-effect transistor (MOSFET) dosimeters to assess the measurement uncertainty, single exposure low-dose limit with acceptable accuracy, and the number of exposures required to attain the corresponding limit of the thermoluminescent dosimeters (TLD). The second aim was to characterize MOSFET dosimeter sensitivities for two dental photon energy ranges, dose dependency, dose rate dependency, and accumulated dose dependency. A further aim was to compare the performance of MOSFETs with those of TLDs in an anthropomorphic phantom head using a dentomaxillofacial CBCT device. The uncertainty was assessed by exposing 20 MOSFETs and a Barracuda MPD reference dosimeter. The MOSFET dosimeter sensitivities were evaluated for two photon energy ranges (50-90 kVp) using a constant dose and polymethylmethacrylate backscatter material. MOSFET and TLD comparative point-dose measurements were performed on an anthropomorphic phantom that was exposed with a clinical CBCT protocol. The MOSFET single exposure low dose limit (25% uncertainty, k = 2) was 1.69 mGy. An averaging of eight MOSFET exposures was required to attain the corresponding TLD (0.3 mGy) low-dose limit. The sensitivity was 3.09 ± 0.13 mV/mGy independently of the photon energy used. The MOSFET dosimeters did not present dose or dose rate sensitivity but, however, presented a 1% decrease of sensitivity per 1000 mV for accumulated threshold voltages between 8300 mV and 17500 mV. The point doses in an anthropomorphic phantom ranged for MOSFETs between 0.24 mGy and 2.29 mGy and for TLDs between 0.25 and 2.09 mGy, respectively. The mean difference was -8%. The MOSFET dosimeters presented statistically insignificant energy dependency. By averaging multiple exposures, the MOSFET dosimeters can achieve a TLD-comparable low-dose limit and constitute a feasible method for diagnostic dosimetry using anthropomorphic phantoms. However, for single in vivo measurements (<1.7 mGy) the sensitivity is too low.

European Community Respiratory Health Survey calibration project of dosimeter driving pressures.

PubMed

Ward, R J; Ward, C; Johns, D P; Skoric, B; Abramson, M; Walters, E H

2002-02-01

Two potential sources of systematic variation in output from Mefar dosimeters, the system used in the European Community Respiratory Health Survey (ECRHS) study have been evaluated: individual nebulizer characteristics and dosimeter driving pressure. Output variation from 366 new nebulizers produced in two batches for the second ECRHS were evaluated, using a solute tracer method, at a fixed driving pressure. The relationship between dosimeter driving pressure was then characterized and between-centre variation in dosimeter driving pressure was evaluated in an Internet-based survey. A systematic difference between nebulizers manufactured in the two batches was identified. Batch one had a mean+/-SD output of 7.0+/-0.8 mg x s(-1) and batch two, 6.3+/-0.7 mg x s(-1) (p<0.005). There was a wide range of driving pressures generated by Mefar dosimeters as set, ranging between 70-245 kPa, with most outside the quoted manufacturer's specification of 180+/-5%. Nebulizer output was confirmed as linearly related to dosimeter driving pressure (coefficient of determination (R2)=0.99, output=0.0377 x driving pressure-0.4151). The range in driving pressures observed was estimated as consistent with a variation of about one doubling in the provocative dose causing a 20% fall in forced expiratory volume in one second. Systematic variation has been identified that constitutes potentially significant confounders for between-centre comparisons of airway responsiveness in the European Community Respiratory Health Survey, with the dosimeter driving pressure representing the most serious issue. This work confirms the need for appropriate quality control of both nebulizer output and dosimeter driving pressure, in laboratories undertaking field measurements of airway responsiveness. In particular, appropriate data on driving pressures need to be collected and factored into between-centre comparisons. Comprehensive collection of such data to optimize quality control is practicable and has been instigated by the organizing committee for the European Community Respiratory Health Survey II.

TH-CD-201-08: Flexible Dosimeter Bands for Whole-Body Dosimetry

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

Kim, T; Fahimian, B; Pratx, G

Purpose: The two commonly used radiotherapy techniques are total body irradiation (TBI) and the total skin irradiation (TSI). In order to ensure the accuracy of the prescription beams, the dose received throughout the entire body must be checked using dosimetry. However, the available number of data points is limited as the dosimeters are manually placed on the patient. We developed a flexible and wearable dosimeter that can collect 1D continuous dose information around the peripheral of the patients’ body, including areas obscured from the beam path. Methods: The flexible dosimeter bands are fabricated by embedding storage phosphor powders in amore » thin layer of non-toxic silicone based elastomer (PDMS). An additional elastomer layer is formed on top of the phosphor layer to provide additional mechanical support for the dosimeter. Once the curing process is complete, the dosimeter is cut into multiple bands and rolled into spools prior to use. Results: The dose responses are tested using a preclinical cabinet X-ray system, where the readout is performed with a storage phosphor reader. Results show that the dose calibration factor is ∼1400 (A.U./Gy) from the beam center. Also, 1-D dose distribution experiment was performed in water phantoms, where preliminary results demonstrate that the dose in water is indeed attenuated compared to in air. Conclusion: Dose response and high-resolution 1-D dosimetry is demonstrated using the flexible dosimeters. By providing a detailed spatial description of the beam dose profile, we expect that the dosimeter bands may aid in enhancing the current existing modality in dosimetry. Since the dosimeter is flexible (can retract back to its original length), they can be comfortably worn around the patient. Potentially, multiple 1-D dose information can be stitched together and extrapolated to provide a coarse 3-D image of the dose distribution. This work was supported by funding from the Cutaneous Lymphoma Foundation under the CLARIONS grant.« less

A history of radiation detection instrumentation.

PubMed

Frame, Paul W

2004-08-01

A review is presented of the history of radiation detection instrumentation. Specific radiation detection systems that are discussed include the human senses, photography, calorimetry, color dosimetry, ion chambers, electrometers, electroscopes, proportional counters, Geiger Mueller counters, scalers and rate meters, barium platinocyanide, scintillation counters, semiconductor detectors, radiophotoluminescent dosimeters, thermoluminescent dosimeters, optically stimulated luminescent dosimeters, direct ion storage, electrets, cloud chambers, bubble chambers, and bubble dosimeters. Given the broad scope of this review, the coverage is limited to a few key events in the development of a given detection system and some relevant operating principles. The occasional anecdote is included for interest.

A history of radiation detection instrumentation.

PubMed

Frame, Paul W

2005-06-01

A review is presented of the history of radiation detection instrumentation. Specific radiation detection systems that are discussed include the human senses, photography, calorimetry, color dosimetry, ion chambers, electrometers, electroscopes, proportional counters, Geiger Mueller counters, scalers and rate meters, barium platinocyanide, scintillation counters, semiconductor detectors, radiophotoluminescent dosimeters, thermoluminescent dosimeters, optically stimulated luminescent dosimeters, direct ion storage, electrets, cloud chambers, bubble chambers, and bubble dosimeters. Given the broad scope of this review, the coverage is limited to a few key events in the development of a given detection system and some relevant operating principles. The occasional anecdote is included for interest.

Polymer gel dosimeter with AQUAJOINT® as hydrogel matrix

NASA Astrophysics Data System (ADS)

Maeyama, Takuya; Ishida, Yasuhiro; Kudo, Yoshihiro; Fukasaku, Kazuaki; Ishikawa, Kenichi L.; Fukunishi, Nobuhisa

2018-05-01

We report a polymer gel dosimeter based on a new gel matrix (AQUAJOINT®) that is a thermo-irreversible hydrogel formed by mixing two types of water-based liquids at room temperature. Normoxic N-vinylpyrrolidone-based polymer gels were prepared with AQUAJOINT® instead of gelatin. This AQUAJOINT®-based gel dosimeter exhibits a 2.5-fold increase in sensitivity over a gelatin-based gel dosimeter and a linear dose-response in the dose range of 0-8 Gy. This gel has heat resistance in a jar and controlled gel properties such as viscoelastic and mechanical characters, which may be useful for deformable polymer gel dosimetry.

A comprehensive evaluation of the PRESAGE/optical-CT 3D dosimetry system

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

Sakhalkar, H. S.; Adamovics, J.; Ibbott, G.

2009-01-15

This work presents extensive investigations to evaluate the robustness (intradosimeter consistency and temporal stability of response), reproducibility, precision, and accuracy of a relatively new 3D dosimetry system comprising a leuco-dye doped plastic 3D dosimeter (PRESAGE) and a commercial optical-CT scanner (OCTOPUS 5x scanner from MGS Research, Inc). Four identical PRESAGE 3D dosimeters were created such that they were compatible with the Radiologic Physics Center (RPC) head-and-neck (H and N) IMRT credentialing phantom. Each dosimeter was irradiated with a rotationally symmetric arrangement of nine identical small fields (1x3 cm{sup 2}) impinging on the flat circular face of the dosimeter. A repetitiousmore » sequence of three dose levels (4, 2.88, and 1.28 Gy) was delivered. The rotationally symmetric treatment resulted in a dose distribution with high spatial variation in axial planes but only gradual variation with depth along the long axis of the dosimeter. The significance of this treatment was that it facilitated accurate film dosimetry in the axial plane, for independent verification. Also, it enabled rigorous evaluation of robustness, reproducibility and accuracy of response, at the three dose levels. The OCTOPUS 5x commercial scanner was used for dose readout from the dosimeters at daily time intervals. The use of improved optics and acquisition technique yielded substantially improved noise characteristics (reduced to {approx}2%) than has been achieved previously. Intradosimeter uniformity of radiochromic response was evaluated by calculating a 3D gamma comparison between each dosimeter and axially rotated copies of the same dosimeter. This convenient technique exploits the rotational symmetry of the distribution. All points in the gamma comparison passed a 2% difference, 1 mm distance-to-agreement criteria indicating excellent intradosimeter uniformity even at low dose levels. Postirradiation, the dosimeters were all found to exhibit a slight increase in opaqueness with time. However, the relative dose distribution was found to be extremely stable up to 90 h postirradiation indicating excellent temporal stability. Excellent interdosimeter reproducibility was also observed between the four dosimeters. Gamma comparison maps between each dosimeter and the average distribution of all four dosimeters showed full agreement at the 2% difference, 2 mm distance-to-agreement level. Dose readout from the 3D dosimetry system was found to agree better with independent film measurement than with treatment planning system calculations in penumbral regions and was generally accurate to within 2% dose difference and 2 mm distance-to-agreement. In conclusion, these studies demonstrate excellent precision, accuracy, robustness, and reproducibility of the PRESAGE/optical-CT system for relative 3D dosimetry and support its potential integration with the RPC H and N credentialing phantom for IMRT verification.« less

Small-Field Measurements of 3D Polymer Gel Dosimeters through Optical Computed Tomography.

PubMed

Shih, Tian-Yu; Wu, Jay; Shih, Cheng-Ting; Lee, Yao-Ting; Wu, Shin-Hua; Yao, Chun-Hsu; Hsieh, Bor-Tsung

2016-01-01

With advances in therapeutic instruments and techniques, three-dimensional dose delivery has been widely used in radiotherapy. The verification of dose distribution in a small field becomes critical because of the obvious dose gradient within the field. The study investigates the dose distributions of various field sizes by using NIPAM polymer gel dosimeter. The dosimeter consists of 5% gelatin, 5% monomers, 3% cross linkers, and 5 mM THPC. After irradiation, a 24 to 96 hour delay was applied, and the gel dosimeters were read by a cone beam optical computed tomography (optical CT) scanner. The dose distributions measured by the NIPAM gel dosimeter were compared to the outputs of the treatment planning system using gamma evaluation. For the criteria of 3%/3 mm, the pass rates for 5 × 5, 3 × 3, 2 × 2, 1 × 1, and 0.5 × 0.5 cm2 were as high as 91.7%, 90.7%, 88.2%, 74.8%, and 37.3%, respectively. For the criteria of 5%/5 mm, the gamma pass rates of the 5 × 5, 3 × 3, and 2 × 2 cm2 fields were over 99%. The NIPAM gel dosimeter provides high chemical stability. With cone-beam optical CT readouts, the NIPAM polymer gel dosimeter has potential for clinical dose verification of small-field irradiation.

The role of inter-comparisons in radiocarbon quality assurance

NASA Astrophysics Data System (ADS)

Scott, Marian; Cook, Gordon; Naysmith, Philip

2016-04-01

Radiocarbon dating is used widely in many geochronology projects as a basis for the creation and testing of chronological constructs. Radiocarbon measurements are by their nature complex and the degree of sample pre-treatment varies considerably depending on the material. Within the UK and Europe, there are a number of well-established laboratories and increasingly, scientists are not just commissioning new dates, but also using statistical modelling of assemblages of dates, perhaps measured in different laboratories, to provide formal date estimates for their investigations. The issue of comparability of measurements (and thus bias, accuracy and precision of measurement) from the diverse laboratories is one which has been the focus of some attention both within the 14C community and the wider user communities for some time. As a result of this but also as part of laboratory benchmarking and quality assurance, the 14C community has undertaken a wide-scale, far-reaching and evolving programme of inter-comparisons, to the benefit of laboratories and users alike. This paper presents the results from the most recent exercise SIRI. The objectives of SIRI included, through choice of material, to contribute to the discussion concerning laboratory offsets and error multipliers in the context of IntCal (the International Calibration Programme) and to gain a better understanding of differences in background derived from a range of infinite age material types.

QA /QC of European NOx measurements by round robin and side by side experiment at the Meteorological Observatory Hohenpeissenberg in the framework of ACTRIS

NASA Astrophysics Data System (ADS)

Gilge, Stefan; Plass-Dülmer, Christian; Weyrauch, Dietmar; Rohrer, Franz

2013-04-01

The European ACTRIS (Aerosols, Clouds, and Trace gases Research InfraStructure Network) project, Work Package 4, aims at harmonization and improvement of the measurement of volatile organic carbon and nitrogen oxides. Central tools to assess and compare the performance of European NOx monitoring stations and labs within ACTRIS are a round robin experiment (2012) and side-by-side intercomparisons (Nov 2012). While the first checked the used laboratories' scales versus a common scale, the latter investigated weather same samples are identically and artefact-free analyzed by collocated instruments. The ACTRIS-NOx-side-by-side intercomparison was realised by instruments sampling from a common manifold which was fed by zero gas, synthetic air mixtures, ambient air, and spiked ambient air. Thus, the side-by-side experiments enabled a full characterization of the detection limit, the linear range, the span, and of potential artefacts due to interfering species for each of the contributing instruments. Generally, CLD type NOx instruments were used in the comparisons supplemented by four new optical techniques, comprising LIF and cavity enhanced techniques. In the round robin exercise, some 20 monitoring sites participated, and 14 instruments were running side-by-side in the one week Nov comparison. The results of both experiments will be presented and discussed with respect to the data quality objectives of GAW and ACTRIS.

Technical Note: Intercomparison of formaldehyde measurements at the atmosphere simulation chamber SAPHIR

NASA Astrophysics Data System (ADS)

Wisthaler, A.; Apel, E. C.; Bossmeyer, J.; Hansel, A.; Junkermann, W.; Koppmann, R.; Meier, R.; Müller, K.; Solomon, S. J.; Steinbrecher, R.; Tillmann, R.; Brauers, T.

2008-04-01

The atmosphere simulation chamber SAPHIR at the Research Centre Jülich was used to test the suitability of state-of-the-art analytical instruments for the measurement of gas-phase formaldehyde (HCHO) in air. Five analyzers based on four different sensing principles were deployed: a differential optical absorption spectrometer (DOAS), cartridges for 2,4-dinitrophenylhydrazine (DNPH) derivatization followed by off-line high pressure liquid chromatography (HPLC) analysis, two different types of commercially available wet chemical sensors based on Hantzsch fluorimetry, and a proton-transfer-reaction mass spectrometer (PTR-MS). A new optimized mode of operation was used for the PTR-MS instrument which significantly enhanced its performance for online HCHO detection at low absolute humidities. The instruments were challenged with typical ambient levels of HCHO ranging from zero to several ppb. Synthetic air of high purity and particulate-filtered ambient air were used as sample matrices in the atmosphere simulation chamber onto which HCHO was spiked under varying levels of humidity and ozone. Measurements were compared to mixing ratios calculated from the chamber volume and the known amount of HCHO injected into the chamber; measurements were also compared between the different instruments. The formal and blind intercomparison exercise was conducted under the control of an independent referee. A number of analytical problems associated with the experimental set-up and with individual instruments were identified, the overall agreement between the methods was fair.

RAMI4PILPS: An intercomparison of formulations for the partitioning of solar radiation in land surface models

NASA Astrophysics Data System (ADS)

Widlowski, J.-L.; Pinty, B.; Clerici, M.; Dai, Y.; de Kauwe, M.; De Ridder, K.; Kallel, A.; Kobayashi, H.; Lavergne, T.; Ni-Meister, W.; Olchev, A.; Quaife, T.; Wang, S.; Yang, W.; Yang, Y.; Yuan, H.

2011-06-01

Remotely sensed, multiannual data sets of shortwave radiative surface fluxes are now available for assimilation into land surface schemes (LSSs) of climate and/or numerical weather prediction models. The RAMI4PILPS suite of virtual experiments assesses the accuracy and consistency of the radiative transfer formulations that provide the magnitudes of absorbed, reflected, and transmitted shortwave radiative fluxes in LSSs. RAMI4PILPS evaluates models under perfectly controlled experimental conditions in order to eliminate uncertainties arising from an incomplete or erroneous knowledge of the structural, spectral and illumination related canopy characteristics typical for model comparison with in situ observations. More specifically, the shortwave radiation is separated into a visible and near-infrared spectral region, and the quality of the simulated radiative fluxes is evaluated by direct comparison with a 3-D Monte Carlo reference model identified during the third phase of the Radiation transfer Model Intercomparison (RAMI) exercise. The RAMI4PILPS setup thus allows to focus in particular on the numerical accuracy of shortwave radiative transfer formulations and to pinpoint to areas where future model improvements should concentrate. The impact of increasing degrees of structural and spectral subgrid variability on the simulated fluxes is documented and the relevance of any thus emerging biases with respect to gross primary production estimates and shortwave radiative forcings due to snow and fire events are investigated.

INTERCOMPARISON OF OPTICAL REMOTE SENSING SYSTEMS FOR ROADSIDE MEASUREMENTS

EPA Science Inventory

The presentation describes results of an intercomparison of three optical remote sensing systems for measurements of nitric oxide emitted from passenger cars and light-duty trucks. The intercomparison included a standards comparison to establish comparability of standards, follo...

Adaptive error detection for HDR/PDR brachytherapy: Guidance for decision making during real-time in vivo point dosimetry

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

Kertzscher, Gustavo, E-mail: guke@dtu.dk; Andersen, Claus E., E-mail: clan@dtu.dk; Tanderup, Kari, E-mail: karitand@rm.dk

Purpose: This study presents an adaptive error detection algorithm (AEDA) for real-timein vivo point dosimetry during high dose rate (HDR) or pulsed dose rate (PDR) brachytherapy (BT) where the error identification, in contrast to existing approaches, does not depend on an a priori reconstruction of the dosimeter position. Instead, the treatment is judged based on dose rate comparisons between measurements and calculations of the most viable dosimeter position provided by the AEDA in a data driven approach. As a result, the AEDA compensates for false error cases related to systematic effects of the dosimeter position reconstruction. Given its nearly exclusivemore » dependence on stable dosimeter positioning, the AEDA allows for a substantially simplified and time efficient real-time in vivo BT dosimetry implementation. Methods: In the event of a measured potential treatment error, the AEDA proposes the most viable dosimeter position out of alternatives to the original reconstruction by means of a data driven matching procedure between dose rate distributions. If measured dose rates do not differ significantly from the most viable alternative, the initial error indication may be attributed to a mispositioned or misreconstructed dosimeter (false error). However, if the error declaration persists, no viable dosimeter position can be found to explain the error, hence the discrepancy is more likely to originate from a misplaced or misreconstructed source applicator or from erroneously connected source guide tubes (true error). Results: The AEDA applied on twoin vivo dosimetry implementations for pulsed dose rate BT demonstrated that the AEDA correctly described effects responsible for initial error indications. The AEDA was able to correctly identify the major part of all permutations of simulated guide tube swap errors and simulated shifts of individual needles from the original reconstruction. Unidentified errors corresponded to scenarios where the dosimeter position was sufficiently symmetric with respect to error and no-error source position constellations. The AEDA was able to correctly identify all false errors represented by mispositioned dosimeters contrary to an error detection algorithm relying on the original reconstruction. Conclusions: The study demonstrates that the AEDA error identification during HDR/PDR BT relies on a stable dosimeter position rather than on an accurate dosimeter reconstruction, and the AEDA’s capacity to distinguish between true and false error scenarios. The study further shows that the AEDA can offer guidance in decision making in the event of potential errors detected with real-timein vivo point dosimetry.« less

Sensitivity and variability of Presage dosimeter formulations in sheet form with application to SBRT and SRS QA

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

Dumas, Michael, E-mail: mdumas1127@gmail.com; Rakowski, Joseph T.

Purpose: To measure sensitivity and stability of the Presage dosimeter in sheet form for various chemical concentrations over a range of clinical photon energies and examine its use for stereotactic body radiation therapy (SBRT) and stereotactic radiosurgery (SRS) QA. Methods: Presage polymer dosimeters were formulated to investigate and optimize their sensitivity and stability. The dosimeter is composed of clear polyurethane base, leucomalachite green (LMG) reporting dye, and bromoform radical initiator in 0.9–1.0 mm thick sheets. The chemicals are mixed together for 2 min, cast in an aluminum mold, and left to cure at 60 psi for a minimum of twomore » days. Dosimeter response was characterized at energies Co-60, 6 MV, 10 MV flattening-filter free, 15 MV, 50 kVp (mean 19.2 keV), and Ir-192. The dosimeters were scanned by a Microtek Scanmaker i800 at 300 dpi, 2{sup 16} bit depth per color channel. Red component images were analyzed with ImageJ and RIT. SBRT QA was done with gamma analysis tolerances of 2% and 2 mm DTA. Results: The sensitivity of the Presage dosimeter increased with increasing concentration of bromoform. Addition of tin catalyst decreased curing time and had negligible effect on sensitivity. LMG concentration should be at least as high as the bromoform, with ideal concentration being 2% wt. Gamma Knife SRS QA measurements of relative output and profile widths were within 2% of manufacturer’s values validated at commissioning, except the 4 mm collimator relative output which was within 3%. The gamma pass rate of Presage with SBRT was 73.7%, compared to 93.1% for EBT2 Gafchromic film. Conclusions: The Presage dosimeter in sheet form was capable of detecting radiation over all tested photon energies and chemical concentrations. The best sensitivity and photostability of the dosimeter were achieved with 2.5% wt. LMG and 8.2% wt. bromoform. Scanner used should not emit any UV radiation as it will expose the dosimeter, as with the Epson 10000 XL scanner. Presage dosimeter in this form was sensitive enough for use in SRS and SBRT QA. The lower gamma pass rate for Presage compared to Gafchromic film can be attributed to the simple equipment used in the fabrication process, which limited the dosimeter’s sensitivity uniformity by agglomeration of air bubbles in the material, nonuniform concentration of chemicals throughout the material, and thickness variations. This demands improvements in mixing tools and molds.« less

Investigations of interference between electromagnetic transponders and wireless MOSFET dosimeters: A phantom study

PubMed Central

Su, Zhong; Zhang, Lisha; Ramakrishnan, V.; Hagan, Michael; Anscher, Mitchell

2011-01-01

Purpose: To evaluate both the Calypso Systems’ (Calypso Medical Technologies, Inc., Seattle, WA) localization accuracy in the presence of wireless metal–oxide–semiconductor field-effect transistor (MOSFET) dosimeters of dose verification system (DVS, Sicel Technologies, Inc., Morrisville, NC) and the dosimeters’ reading accuracy in the presence of wireless electromagnetic transponders inside a phantom.Methods: A custom-made, solid-water phantom was fabricated with space for transponders and dosimeters. Two inserts were machined with positioning grooves precisely matching the dimensions of the transponders and dosimeters and were arranged in orthogonal and parallel orientations, respectively. To test the transponder localization accuracy with∕without presence of dosimeters (hypothesis 1), multivariate analyses were performed on transponder-derived localization data with and without dosimeters at each preset distance to detect statistically significant localization differences between the control and test sets. To test dosimeter dose-reading accuracy with∕without presence of transponders (hypothesis 2), an approach of alternating the transponder presence in seven identical fraction dose (100 cGy) deliveries and measurements was implemented. Two-way analysis of variance was performed to examine statistically significant dose-reading differences between the two groups and the different fractions. A relative-dose analysis method was also used to evaluate transponder impact on dose-reading accuracy after dose-fading effect was removed by a second-order polynomial fit.Results: Multivariate analysis indicated that hypothesis 1 was false; there was a statistically significant difference between the localization data from the control and test sets. However, the upper and lower bounds of the 95% confidence intervals of the localized positional differences between the control and test sets were less than 0.1 mm, which was significantly smaller than the minimum clinical localization resolution of 0.5 mm. For hypothesis 2, analysis of variance indicated that there was no statistically significant difference between the dosimeter readings with and without the presence of transponders. Both orthogonal and parallel configurations had difference of polynomial-fit dose to measured dose values within 1.75%.Conclusions: The phantom study indicated that the Calypso System’s localization accuracy was not affected clinically due to the presence of DVS wireless MOSFET dosimeters and the dosimeter-measured doses were not affected by the presence of transponders. Thus, the same patients could be implanted with both transponders and dosimeters to benefit from improved accuracy of radiotherapy treatments offered by conjunctional use of the two systems. PMID:21776780

Residual Optically Stimulated Luminescent (OSL) Signals For Al2O3: C and a Readout System With Reproducible Partial Signal Clearance.

PubMed

Abraham, Sara A; Kearfott, Kimberlee J

2018-06-15

Optically stimulated luminescent dosimeters are devices that, when stimulated with light, emit light in proportion to the integrated ionizing radiation dose. The stimulation of optically stimulated luminescent material results in the loss of a small fraction of signal stored within the dosimetric traps. Previous studies have investigated the signal loss due to readout stimulation and the optical annealing of optically stimulated luminescent dosimeters. This study builds on former research by examining the behavior of optically stimulated luminescent signals after annealing, exploring the functionality of a previously developed signal loss model, and comparing uncertainties for dosimeters reused with or without annealing. For a completely annealed dosimeter, the minimum signal level was 56 ± 8 counts, and readings followed a Gaussian distribution. For dosimeters above this signal level, the fractional signal loss due to the reading process has a linear relationship with the calculated signal. At low signal levels (below 20,000 counts) in this optically stimulated luminescent dosimeter system, calculated signal percent errors increase significantly but otherwise are on average 0.72 ± 0.27%, 0.40 ± 0.19%, 0.33 ± 0.12%, and 0.24 ± 0.07% for 30, 75, 150, and 300 readings, respectively. Theoretical calculations of uncertainties showed that annealing before reusing dosimeters allows for dose errors below 1% with as few as 30 readings. Reusing dosimeters multiple times increases the dose errors especially with low numbers of readouts, so theoretically around 300 readings would be necessary to achieve errors around 1% or below in most scenarios. Note that these dose errors do not include the error associated with the signal-to-dose conversion factor.

SU-F-T-17: A Feasibility Study for the Transit Dosimetry with a Glass Dosimeter in Brachytherapy

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

Moon, S; Yoon, M; Chung, W

Purpose: Confirming the dose delivered to a patient is important to make sure the treatment quality and safety of the radiotherapy. Measuring a transit dose of the patient during the radiotherapy could be an interesting way to confirm the patient dose. In this study, we evaluated the feasibility of the transit dosimetry with a glass dosimeter in brachytherapy. Methods: We made a phantom that inserted the glass dosimeters and placed under patient lying on a couch for cervix cancer brachytherapy. The 18 glass dosimeters were placed in the phantom arranged 6 per row. A point putting 1cm vertically from themore » source was prescribed as 500.00 cGy. Solid phantoms of 0, 2, 4, 6, 8, 10 cm were placed between the source and the glass dosimeter. The transit dose was measured each thickness using the glass dosimeters and compared with a treatment planning system (TPS). Results: When the transit dose was smaller than 10 cGy, the average of the differences between measured values and calculated values by TPS was 0.50 cGy and the standard deviation was 0.69 cGy. If the transit dose was smaller than 100 cGy, the average of the error was 1.67 ± 4.01 cGy. The error to a point near the prescription point was −14.02 cGy per 500.00 cGy of the prescription dose. Conclusion: The distances from the sources to skin of the patient generally are within 10 cm for cervix cancer cases in brachytherapy. The results of this preliminary study showed the probability of the glass dosimeter as the transit dosimeter in brachytherapy.« less

Estimation of identification limit for a small-type OSL dosimeter on the medical images by measurement of X-ray spectra.

PubMed

Takegami, Kazuki; Hayashi, Hiroaki; Okino, Hiroki; Kimoto, Natsumi; Maehata, Itsumi; Kanazawa, Yuki; Okazaki, Tohru; Hashizume, Takuya; Kobayashi, Ikuo

2016-07-01

Our aim in this study is to derive an identification limit on a dosimeter for not disturbing a medical image when patients wear a small-type optically stimulated luminescence (OSL) dosimeter on their bodies during X-ray diagnostic imaging. For evaluation of the detection limit based on an analysis of X-ray spectra, we propose a new quantitative identification method. We performed experiments for which we used diagnostic X-ray equipment, a soft-tissue-equivalent phantom (1-20 cm), and a CdTe X-ray spectrometer assuming one pixel of the X-ray imaging detector. Then, with the following two experimental settings, corresponding X-ray spectra were measured with 40-120 kVp and 0.5-1000 mAs at a source-to-detector distance of 100 cm: (1) X-rays penetrating a soft-tissue-equivalent phantom with the OSL dosimeter attached directly on the phantom, and (2) X-rays penetrating only the soft-tissue-equivalent phantom. Next, the energy fluence and errors in the fluence were calculated from the spectra. When the energy fluence with errors concerning these two experimental conditions was estimated to be indistinctive, we defined the condition as the OSL dosimeter not being identified on the X-ray image. Based on our analysis, we determined the identification limit of the dosimeter. We then compared our results with those for the general irradiation conditions used in clinics. We found that the OSL dosimeter could not be identified under the irradiation conditions of abdominal and chest radiography, namely, one can apply the OSL dosimeter to measurement of the exposure dose in the irradiation field of X-rays without disturbing medical images.

Study of a non-diffusing radiochromic gel dosimeter for 3D radiation dose imaging

NASA Astrophysics Data System (ADS)

Marsden, Craig Michael

2000-12-01

This thesis investigates the potential of a new radiation gel dosimeter, based on nitro-blue tetrazolium (NBTZ) suspended in a gelatin mold. Unlike all Fricke based gel dosimeters this dosimeter does not suffer from diffusive loss of image stability. Images are obtained by an optical tomography method. Nitro blue tetrazolium is a common biological indicator that when irradiated in an aqueous medium undergoes reduction to a highly colored formazan, which has an absorbance maximum at 525nm. Tetrazolium is water soluble while the formazan product is insoluble. The formazan product sticks to the gelatin matrix and the dose image is maintained for three months. Methods to maximize the sensitivity of the system were evaluated. It was found that a chemical detergent, Triton X-100, in combination with sodium formate, increased the dosimeter sensitivity significantly. An initial G-value of formazan production for a dosimeter composed of 1mM NBTZ, gelatin, and water was on the order of 0.2. The addition of Triton and formate produced a G-value in excess of 5.0. The effects of NBTZ, triton, formate, and gel concentration were all investigated. All the gels provided linear dose vs. absorbance plots for doses from 0 to >100 Gy. It was determined that gel concentration had minimal if any effect on sensitivity. Sensitivity increased slightly with increasing NBTZ concentration. Triton and formate individually and together provided moderate to large increases in dosimeter sensitivity. The dosimeter described in this work can provide stable 3D radiation dose images for all modalities of radiation therapy equipment. Methods to increase sensitivity are developed and discussed.

Antioxidant effect of green tea on polymer gel dosimeter

NASA Astrophysics Data System (ADS)

Samuel, E. J. J.; Sathiyaraj, P.; Deena, T.; Kumar, D. S.

2015-01-01

Extract from Green Tea (GTE) acts as an antioxidant in acrylamide based polymer gel dosimeter. In this work, PAGAT gel was used for investigation of antioxidant effect of GTE.PAGAT was called PAGTEG (Polyacrylamide green tea extract gel dosimeter) after adding GTE. Free radicals in water cause pre polymerization of polymer gel before irradiation. Polyphenols from GTE are highly effective to absorb the free radicals in water. THPC is used as an antioxidant in polymer gel dosimeter but here we were replaced it by GTE and investigated its effect by spectrophotometer. GTE added PAGAT samples response was lower compared to THPC added sample. To increase the sensitivity of the PAGTEG, sugar was added. This study confirmed that THPC was a good antioxidant for polymer gel dosimeter. However, GTE also can be used as an antioxidant in polymer gel if use less quantity (GTE) and add sugar as sensitivity enhancer.

Validation of an Innovative Satellite-Based UV Dosimeter

NASA Astrophysics Data System (ADS)

Morelli, Marco; Masini, Andrea; Simeone, Emilio; Khazova, Marina

2016-08-01

We present an innovative satellite-based UV (ultraviolet) radiation dosimeter with a mobile app interface that has been validated by exploiting both ground-based measurements and an in-vivo assessment of the erythemal effects on some volunteers having a controlled exposure to solar radiation.Both validations showed that the satellite-based UV dosimeter has a good accuracy and reliability needed for health-related applications.The app with this satellite-based UV dosimeter also includes other related functionalities such as the provision of safe sun exposure time updated in real-time and end exposure visual/sound alert. This app will be launched on the global market by siHealth Ltd in May 2016 under the name of "HappySun" and available both for Android and for iOS devices (more info on http://www.happysun.co.uk).Extensive R&D activities are on-going for further improvement of the satellite-based UV dosimeter's accuracy.

PRESAGE® as a solid 3-D radiation dosimeter: A review article

NASA Astrophysics Data System (ADS)

Khezerloo, Davood; Nedaie, Hassan Ali; Takavar, Abbas; Zirak, Alireza; Farhood, Bagher; Movahedinejhad, Hadi; Banaee, Nooshin; Ahmadalidokht, Isa; Knuap, Courtney

2017-12-01

Radiation oncology has been rapidly improved by the application of new equipment and techniques. With the advent of new complex and precise radiotherapy techniques such as intensity modulated radiotherapy, stereotactic radiosurgery, and volumetric modulated arc therapy, the demand for an accurate and feasible three-dimensional (3-D) dosimetry system has increased. The most important features of a 3-D dosimeter, apart from being precise, accurate and reproducible, include also its low cost, feasibility, and availability. In 2004 a new generation of solid plastic dosimeters which demonstrate a radiochromic response to ionizing radiation was introduced. PRESAGE® plastic dosimeter lacks the limitations of previous Ferric and polymer plastic 3-D dosimeters such as diffusion, sensitivity to oxygen, fabrication problems, scanning and read out challenges. In this decade, a large number of efforts have been carried out to enhance PRESAGE® structure and scanning methods. This article attempts to review and reflect on the results of these investigations.

Citizen's dosimeter

DOEpatents

Klemic, Gladys [Naperville, IL; Bailey, Paul [Chicago, IL; Breheny, Cecilia [Yonkers, NY

2008-09-02

The present invention relates to a citizen's dosimeter. More specifically, the invention relates to a small, portable, personal dosimetry device designed to be used in the wake of a event involving a Radiological Dispersal Device (RDD), Improvised Nuclear Device (IND), or other event resulting in the contamination of large area with radioactive material or where on site personal dosimetry is required. The card sized dosimeter generally comprises: a lower card layer, the lower card body having an inner and outer side; a upper card layer, the layer card having an inner and outer side; an optically stimulated luminescent material (OSLM), wherein the OSLM is sandwiched between the inner side of the lower card layer and the inner side of the upper card layer during dosimeter radiation recording, a shutter means for exposing at least one side of the OSLM for dosimeter readout; and an energy compensation filter attached to the outer sides of the lower and upper card layers.

Determination of the depth dose distribution of proton beam using PRESAGE TM dosimeter

NASA Astrophysics Data System (ADS)

Zhao, L.; Das, I. J.; Zhao, Q.; Thomas, A.; Adamovics, J.; Oldman, M.

2010-11-01

PRESAGETM dosimeter dosimeter has been proved useful for 3D dosimetry in conventional photon therapy and IMRT [1-5]. Our objective is to examine the use of PRESAGETM dosimeter for verification of depth dose distribution in proton beam therapy. Three PRESAGETM samples were irradiated with a 79 MeV un-modulated proton beam. Percent depth dose profile measured from the PRESAGETM dosimeter is compared with data obtained in a water phantom using a parallel plate Advanced Markus chamber. The Bragg-peak position determined from the PRESAGETM is within 2 mm compared to measurements in water. PRESAGETM shows a highly linear response to proton dose. However, PRESAGETM also reveals an underdosage around the Bragg peak position due to LET effects. Depth scaling factor and quenching correction factor need further investigation. Our initial result shows that PRESAGETM has promising dosimetric characteristics that could be suitable for proton beam dosimetry.

A design solution to increasing the sensitivity of pMOS dosimeters: The stacked RADFET approach

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

Kelleher, A.; Lane, W.; Adams, L.

1995-02-01

pMOS Radiation Sensitive Field Effect Transistors (RADFET`S) have applications as integrating dosimeters in laboratories and medicine to measure the amount of radiation dose absorbed. The suitability of these dosimeters to a certain application depends on the sensitivity of the RADFET being used. To date, this sensitivity is limited to the sensitivity of the gate oxide to radiation. The aim of this paper is to introduce a new design approach which will allow greater sensitivities to be achieved than is currently possible. An additional attractive feature of this design approach is that the sensitivity of the dosimeter may be changed dependingmore » on the total dose which is to be measured; essentially a dosimeter with auto-scaling may be achieved. This study introduces this autoscaling concept along with presenting the optimum RADFET device requirements which are necessary for this new design approach.« less

Optical computed tomography in PRESAGE® three-dimensional dosimetry: Challenges and prospective.

PubMed

Khezerloo, Davood; Nedaie, Hassan Ali; Farhood, Bagher; Zirak, Alireza; Takavar, Abbas; Banaee, Nooshin; Ahmadalidokht, Isa; Kron, Tomas

2017-01-01

With the advent of new complex but precise radiotherapy techniques, the demands for an accurate, feasible three-dimensional (3D) dosimetry system have been increased. A 3D dosimeter system generally should not only have accurate and precise results but should also feasible, inexpensive, and time consuming. Recently, one of the new candidates for 3D dosimetry is optical computed tomography (CT) with a radiochromic dosimeter such as PRESAGE®. Several generations of optical CT have been developed since the 90s. At the same time, a large attempt has been also done to introduce the robust dosimeters that compatible with optical CT scanners. In 2004, PRESAGE® dosimeter as a new radiochromic solid plastic dosimeters was introduced. In this decade, a large number of efforts have been carried out to enhance optical scanning methods. This article attempts to review and reflect on the results of these investigations.

Dosimetry of Al2O3 optically stimulated luminescent dosimeter at high energy photons and electrons

NASA Astrophysics Data System (ADS)

Yusof, M. F. Mohd; Joohari, N. A.; Abdullah, R.; Shukor, N. S. Abd; Kadir, A. B. Abd; Isa, N. Mohd

2018-01-01

The linearity of Al2O3 OSL dosimeters (OSLD) were evaluated for dosimetry works in clinical photons and electrons. The measurements were made at a reference depth of Zref according to IAEA TRS 398:2000 codes of practice at 6 and 10 MV photons and 6 and 9 MeV electrons. The measured dose was compared to the thermoluminescence dosimeters (TLD) and ionization chamber commonly used for dosimetry works for higher energy photons and electrons. The results showed that the measured dose in OSL dosimeters were in good agreement with the reported by the ionization chamber in both high energy photons and electrons. A reproducibility test also reported excellent consistency of readings with the OSL at similar energy levels. The overall results confirmed the suitability of OSL dosimeters for dosimetry works involving high energy photons and electrons in radiotherapy.

Polymer gel dosimeter based on itaconic acid.

PubMed

Mattea, Facundo; Chacón, David; Vedelago, José; Valente, Mauro; Strumia, Miriam C

2015-11-01

A new polymeric dosimeter based on itaconic acid and N, N'-methylenebisacrylamide was studied. The preparation method, compositions of monomer and crosslinking agent and the presence of oxygen in the dosimetric system were analyzed. The resulting materials were irradiated with an X-ray tube at 158cGy/min, 226cGymin and 298cGy/min with doses up to 1000Gy. The dosimeters presented a linear response in the dose range 75-1000Gy, sensitivities of 0.037 1/Gyat 298cGy/min and an increase in the sensitivity with lower dose rates. One of the most relevant outcomes in this study was obtaining different monomer to crosslinker inclusion in the formed gel for the dosimeters where oxygen was purged during the preparation method. This effect has not been reported in other typical dosimeters and could be attributed to the large differences in the reactivity among these species. Copyright © 2015 Elsevier Ltd. All rights reserved.

Compton effect thermally activated depolarization dosimeter

DOEpatents

Moran, Paul R.

1978-01-01

A dosimetry technique for high-energy gamma radiation or X-radiation employs the Compton effect in conjunction with radiation-induced thermally activated depolarization phenomena. A dielectric material is disposed between two electrodes which are electrically short circuited to produce a dosimeter which is then exposed to the gamma or X radiation. The gamma or X-radiation impinging on the dosimeter interacts with the dielectric material directly or with the metal composing the electrode to produce Compton electrons which are emitted preferentially in the direction in which the radiation was traveling. A portion of these electrons becomes trapped in the dielectric material, consequently inducing a stable electrical polarization in the dielectric material. Subsequent heating of the exposed dosimeter to the point of onset of ionic conductivity with the electrodes still shorted through an ammeter causes the dielectric material to depolarize, and the depolarization signal so emitted can be measured and is proportional to the dose of radiation received by the dosimeter.

Field test to intercompare carbon monoxide, nitric oxide and hydroxyl instrumentation at Wallops Island, Virginia

NASA Technical Reports Server (NTRS)

Gregory, Gerald L.; Beck, Sherwin M.; Bendura, Richard J.

1987-01-01

Documentation of the first of three instrument intercomparisons conducted as part of NASA Global Tropospheric Experiment/Chemical Instrumentation Test and Evaluation (GTE/CITE-1) is given. This ground-based intercomparison was conducted during July 1983 at NASA Wallops Flight Facility. Instruments intercompared included one laser system and three grab-sample approaches for CO; two chemiluminescent systems and one laser-induced fluorescent (LIF) technique for NO; and two different LIF systems and a radiochemical tracer technique for OH. The major objectives of this intercomparison was to intercompare ambient measurements of CO, NO, and OH at a common site by using techniques of fundamentally different detection principles and to identify any major biases among the techniques prior to intercomparison on an aircraft platform. Included in the report are comprehensive discussions of workshop requirements, philosophies, and operations as well as intercomparison analyses and results. In addition, the large body of nonintercomparison data incorporated into the workshop measurements is summarized. The report is an important source document for those interested in conducting similar large and complex intercomparison tests as well as those interested in using the data base for purposes other than instrument intercomparison.

RESULTS FROM THE NORTH AMERICAN MERCURY MODEL INTER-COMPARISON STUDY (NAMMIS)

EPA Science Inventory

A North American Mercury Model Intercomparison Study (NAMMIS) has been conducted to build upon the findings from previous mercury model intercomparison in Europe. In the absence of mercury measurement networks sufficient for model evaluation, model developers continue to rely on...

Combating WMD Journal. Issue 2

DTIC Science & Technology

2008-03-01

can be conducted utilizing passive detectors such as thermoluminescent dosime- ters (TLDs) or optically stimulated luminescent ( OSL ) dosimeters ...reasonable estimate of the dose. The challenge in high-energy bremsstrahlung fields is that current (standard) dosimeters do not provide for CPE...above a few MeV. CPE can be obtained by placing tissue- equivalent material (such as a build- up cap) around the dosimeter . This Dosimetry Needs

Study of EPR/ESR Dosimetry in Fingernails as a Method for Assessing Dose of Victims of Radiological Accidents/Incidents

DTIC Science & Technology

2008-06-17

dosimeters . .............................................................................................. 117 Figure 4-2. Flow chart illustrating...alanine, various sugars, quartz in rocks and sulfates, as EPR dosimeters [15]. Alternatively, radiation-induced EPR signals have been detected using...the medical response to radiological accidents, as a method for estimating radiation dose without the use of physical dosimeters and using exposed

Adaptation of a Pocket PC for Use as a Wearable Voice Dosimeter

ERIC Educational Resources Information Center

Popolo, Peter S.; Svec, Jan G.; Titze, Ingo R.

2005-01-01

This article deals with the adaptation of a commercially available Pocket PC for use as a voice dosimeter, a wearable device that measures the vocal dose of teachers or other individuals on the job, at home, and elsewhere during the course of an entire day. An engineering approach for designing a voice dosimeter is described, and design data are…

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

Fiber-type dosimeter with improved illuminator

DOEpatents

Fox, Richard J.

1987-01-01

A single-piece, molded plastic, Cassigrainian-type condenser arrangement is incorporated in a tubular-shaped personal pocket dosimeter of the type which combines an ionization chamber with an optically-read fiber electrometer to provide improved illumination of the electrometer fiber. The condenser routes incoming light from one end of the dosimeter tubular housing around a central axis charging pin assembly and focuses the light at low angles to the axis so that it falls within the acceptance angle of the electrometer fiber objective lens viewed through an eyepiece lens disposed in the opposite end of the dosimeter. This results in improved fiber illumination and fiber image contrast.

Dose estimation of eye lens for interventional procedures in diagnosis

NASA Astrophysics Data System (ADS)

Liu, Yu-Rong; Huang, Chia-Yu; Hsu, Ching-Han; Hsu, Fang-Yuh

2017-11-01

The International Commission on Radiological Protection (ICRP) recommended that the equivalent dose limit for the lens of the eye be decreased from 150 mSv/y (ICRP, 2007) to 20 mSv/y averaged over five years (ICRP, 2011). How to accurately measure the eye-lens dose has, therefore, been an issue of interest recently. Interventional radiologists are at a higher risk of radiation-induced eye injury, such as cataracts, than all other occupational radiation workers. The main objective of this study is to investigate the relationship between the doses to the eye lenses of interventional radiologists measured by different commercial eye-lens dosimeters. This study measured a reference eye-lens dose, which involved placing thermoluminescent dosimeter (TLD) chips at the surface of the eye of the Rando Phantom, and the TLD chips were covered by a 3-mm-thick tissue-equivalent bolus. Commercial eye-lens dosimeters, such as a headband dosimeter and standard personnel dose badges, were placed at the positions recommended by the manufacturers. The results show that the personnel dose badge is not an appropriate dosimeter for evaluating eye-lens dose. Dose deviations for different dosimeters are discussed and presented in this study.

Optically stimulated Al2O3:C luminescence dosimeters for teletherapy: Hp(10) performance evaluation.

PubMed

Hashim, S; Musa, Y; Ghoshal, S K; Ahmad, N E; Hashim, I H; Yusop, M; Bradley, D A; Kadir, A B A

2018-05-01

The performance of optically stimulated luminescence dosimeters (OSLDs, Al 2 O 3 :C) was evaluated in terms of the operational quantity of H P (10) in Co-60 external beam teletherapy unit. The reproducibility, signal depletion, and dose linearity of each dosimeter was investigated. For ten repeated readouts, each dosimeter exposed to 50mSv was found to be reproducible below 1.9 ± 3% from the mean value, indicating good reader stability. Meanwhile, an average signal reduction of 0.5% per readout was found. The dose response revealed a good linearity within the dose range of 5-50mSv having nearly perfect regression line with R 2 equals 0.9992. The accuracy of the measured doses were evaluated in terms of operational quantity H P (10), wherein the trumpet curve method was used respecting the 1990 International Commission on Radiological Protection (ICRP) standard. The accuracy of the overall measurements from all dosimeters was discerned to be within the trumpet curve and devoid of outlier. It is established that the achieved OSL Al 2 O 3 :C dosimeters are greatly reliable for equivalent dose assessment. Copyright © 2018 Elsevier Ltd. All rights reserved.

Cerium nanoparticle effect on sensitivity of Fricke gel dosimeter: Initial investigation

NASA Astrophysics Data System (ADS)

Ebenezer Suman Babu, S.; Peace Balasingh, S. Timothy; Benedicta Pearlin, R.; Rabi Raja Singh, I.; Ravindran, B. Paul

2017-05-01

Fricke gel dosimeters (FXGs) have been the preferred dosimeters because of its ease in preparation and water and tissue equivalency. Visible changes happen three dimensionally in the dosimeter as the ferrous (Fe2+) ions change into ferric (Fe3+) ions upon irradiation and the measure of this change can be correlated to the dose absorbed. Nanoparticles are promising entities that can improve the sensitivity of the gel dosimeter. Cerium Oxide nanoparticle was investigated for possible enhancement of absorbed dose in the FXG. Various concentrations of the nanoparticle based gel dosimeters were prepared and irradiated for a clinical dose range of 0-3 Gy in a telegamma unit. The optimal concentration of 0.1 mM nanoparticle incorporated in the FXG enhances the radiation sensitivity of the unmodified FXG taken as reference without modifying the background absorbance prior to irradiation. The gel recipe consisted of 5% (wt) gelatin, 50 mM Sulphuric acid, 0.05 mM Xylenol Orange, 0.5 mM Ferrous Ammonium Sulphate and 0.1 mM Cerium (IV) Oxide nanoparticle (< 25 nm particle size) and triple distilled water. The FXGs with nanoparticle showed linear dose response in the dose range tested.

FlexyDos3D: a deformable anthropomorphic 3D radiation dosimeter: radiation properties

NASA Astrophysics Data System (ADS)

De Deene, Y.; Skyt, P. S.; Hil, R.; Booth, J. T.

2015-02-01

Three dimensional radiation dosimetry has received growing interest with the implementation of highly conformal radiotherapy treatments. The radiotherapy community faces new challenges with the commissioning of image guided and image gated radiotherapy treatments (IGRT) and deformable image registration software. A new three dimensional anthropomorphically shaped flexible dosimeter, further called ‘FlexyDos3D’, has been constructed and a new fast optical scanning method has been implemented that enables scanning of irregular shaped dosimeters. The FlexyDos3D phantom can be actuated and deformed during the actual treatment. FlexyDos3D offers the additional advantage that it is easy to fabricate, is non-toxic and can be molded in an arbitrary shape with high geometrical precision. The dosimeter formulation has been optimized in terms of dose sensitivity. The influence of the casting material and oxygen concentration has also been investigated. The radiophysical properties of this new dosimeter are discussed including stability, spatial integrity, temperature dependence of the dosimeter during radiation, readout and storage, dose rate dependence and tissue equivalence. The first authors Y De Deene and P S Skyt made an equivalent contribution to the experimental work presented in this paper.

TH-C-19A-05: Evaluation of a New Reusable 3D Dosimeter

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

Juang, T; Adamovics, J; Oldham, M

Purpose: PRESAGE is a radiochromic plastic which has demonstrated strong potential for high resolution single-use 3D dosimetry. This study evaluates a new PRESAGE formulation (Presage-RU) in which the radiochromic response is reversible (the dosimeter optically clears after irradiation), enabling the potential for reusability. Methods: Presage-RU dose response and optical-clearing rates were evaluated in both small volume dosimeters (1×1×4.5cm) and a larger cylindrical dosimeter (8cm diameter, 4.5cm length). All dosimeters were allowed to fully optically clear in dark, room temperature conditions between irradiations. Dose response was determined by irradiating small volume samples from 0–8.0Gy and measuring change in optical density. Themore » cylindrical dosimeter was irradiated with a simple 4-field box plan (parallel opposed pairs of 4cm×4cm AP-PA beams and 2cm×4cm lateral beams) to 20Gy. High resolution 3D dosimetry was achieved utilizing optical-CT readout. Readings were tracked up to 14 days to characterize optical clearing. Results: Initial irradiation yielded a response of 0.0119△OD/(Gy*cm) while two subsequent reirradiations yielded a lower but consistent response of 0.0087△OD/(Gy*cm). Strong linearity of dose response was observed for all irradiations. In the large cylindrical dosimeter, the integral dose within the high dose region exhibited an exponential decay in signal over time (halflife= 23.9 hours), with the dosimeter effectively cleared (0.04% of the initial signal) after 10 days. Subsequent irradiation resulted in 19.5% lower initial signal but demonstrated that the exponential clearing rate remained consistent. Results of additional subsequent irradiations will also be presented. Conclusion: This work introduces a new re-usable radiochromic dosimeter (Presage-RU) compatible with high resolution (sub-millimeter) 3D dosimetry. Sensitivity of the initial radiation was observed to be slightly higher than subsequent irradiations, but the clearing time remained constant, indicating the dosimeter can be re-used after 10 days. Presage-RU has potential to dramatically improve cost-effectiveness and thereby lower the barrier for implementing comprehensive, high resolution 3D dosimetry. John Adamovics is the president of Heuris Inc., which commercializes PRESAGE.« less

Accuracy of tretyakov precipitation gauge: Result of wmo intercomparison

USGS Publications Warehouse

Yang, Daqing; Goodison, Barry E.; Metcalfe, John R.; Golubev, Valentin S.; Elomaa, Esko; Gunther, Thilo; Bates, Roy; Pangburn, Timothy; Hanson, Clayton L.; Emerson, Douglas G.; Copaciu, Voilete; Milkovic, Janja

1995-01-01

The Tretyakov non-recording precipitation gauge has been used historically as the official precipitation measurement instrument in the Russian (formerly the USSR) climatic and hydrological station network and in a number of other European countries. From 1986 to 1993, the accuracy and performance of this gauge were evaluated during the WMO Solid Precipitation Measurement Intercomparison at 11 stations in Canada, the USA, Russia, Germany, Finland, Romania and Croatia. The double fence intercomparison reference (DFIR) was the reference standard used at all the Intercomparison stations in the Intercomparison. The Intercomparison data collected at the different sites are compatible with respect to the catch ratio (measured/DFIR) for the same gauge, when compared using mean wind speed at the height of the gauge orifice during the observation period.The Intercomparison data for the Tretyakov gauge were compiled from measurements made at these WMO intercomparison sites. These data represent a variety of climates, terrains and exposures. The effects of environmental factors, such as wind speed, wind direction, type of precipitation and temperature, on gauge catch ratios were investigated. Wind speed was found to be the most important factor determining the gauge catch and air temperature had a secondary effect when precipitation was classified into snow, mixed and rain. The results of the analysis of gauge catch ratio versus wind speed and temperature on a daily time step are presented for various types of precipitation. Independent checks of the correction equations against the DFIR have been conducted at those Intercomparison stations and a good agreement (difference less than 10%) has been obtained. The use of such adjustment procedures should significantly improve the accuracy and homogeneity of gauge-measured precipitation data over large regions of the former USSR and central Europe.

Operational overview of NASA GTE/CITE 1 airborne instrument intercomparisons - Carbon monoxide, nitric oxide, and hydroxyl instrumentation. [Global Tropospheric Experiment/Chemical Instrumentation Test and Evaluation

NASA Technical Reports Server (NTRS)

Beck, Sherwin M.; Bendura, Richard J.; Mcdougal, David S.; Hoell, James M., Jr.; Gregory, Gerald L.; Sachse, Glen W.; Hill, Gerald F.; Curfman, Howard J., Jr.; Torres, Arnold L.; Condon, Estelle P.

1987-01-01

An overview of the airborne intercomparisons of CO, NO, and OH instrumentation is presented in this first paper of the series on the NASA Global Tropospheric Experiment/Chemical Instrumentation Test and Evaluation (GTE/CITE 1). This paper provides the reader with background information about several important characteristics of the project. These include the overall objectives and approach, the measurements taken, the intercomparison protocol, aircraft platform, profiles of each aircraft flight, and the participants. A synopsis of the overall results of the CO, NO, and OH instrument intercomparisons is also included. Companion papers discuss the detailed results of the CO and NO intercomparison tests as well as pertinent scientific findings.

The agricultural model intercomparison and improvement project (AgMIP): Protocols and pilot studies

USDA-ARS?s Scientific Manuscript database

The Agricultural Model Intercomparison and Improvement Project (AgMIP) is a distributed climate-scenario simulation research activity for historical period model intercomparison and future climate change conditions with participation of multiple crop and agricultural economic model groups around the...

Surface-enhanced Raman scattering (SERS) dosimeter and probe

DOEpatents

Vo-Dinh, Tuan

1995-01-01

A dosimeter and probe for measuring exposure to chemical and biological compounds is disclosed. The dosimeter or probe includes a collector which may be analyzed by surface-enhanced Raman spectroscopy. The collector comprises a surface-enhanced Raman scattering-active material having a coating applied thereto to improve the adsorption properties of the collector. The collector may also be used in automated sequential devises, in probe array devices.

Proceedings: TRIAGE of Irradiated Personnel, 25-27 September 1996

DTIC Science & Technology

1998-03-01

thermoluminescent dosimeter project group (PG-29) has recommended grani- (TLD) systems accredited by the National Volun- setron as the deployable...individual phylactic antiemetic medications and regimens dosimeter system currently fielded is the high-range were evaluated prior to adoption of...granisetron. photoluminescent AN/PDR-75. This system con- sists of the ruggedized DT-236 wristband dosimeter Two drugs exceeded the criteria (shown below

Characterization of MOSFET dosimeters for low‐dose measurements in maxillofacial anthropomorphic phantoms

PubMed Central

Wolff, Jan E.; Kiljunen, Timo; Schulze, Dirk; Kortesniemi, Mika

2015-01-01

The aims of this study were to characterize reinforced metal‐oxide‐semiconductor field‐effect transistor (MOSFET) dosimeters to assess the measurement uncertainty, single exposure low‐dose limit with acceptable accuracy, and the number of exposures required to attain the corresponding limit of the thermoluminescent dosimeters (TLD). The second aim was to characterize MOSFET dosimeter sensitivities for two dental photon energy ranges, dose dependency, dose rate dependency, and accumulated dose dependency. A further aim was to compare the performance of MOSFETs with those of TLDs in an anthropomorphic phantom head using a dentomaxillofacial CBCT device. The uncertainty was assessed by exposing 20 MOSFETs and a Barracuda MPD reference dosimeter. The MOSFET dosimeter sensitivities were evaluated for two photon energy ranges (50–90 kVp) using a constant dose and polymethylmethacrylate backscatter material. MOSFET and TLD comparative point‐dose measurements were performed on an anthropomorphic phantom that was exposed with a clinical CBCT protocol. The MOSFET single exposure low dose limit (25% uncertainty, k=2) was 1.69 mGy. An averaging of eight MOSFET exposures was required to attain the corresponding TLD (0.3 mGy) low‐dose limit. The sensitivity was 3.09±0.13 mV/mGy independently of the photon energy used. The MOSFET dosimeters did not present dose or dose rate sensitivity but, however, presented a 1% decrease of sensitivity per 1000 mV for accumulated threshold voltages between 8300 mV and 17500 mV. The point doses in an anthropomorphic phantom ranged for MOSFETs between 0.24 mGy and 2.29 mGy and for TLDs between 0.25 and 2.09 mGy, respectively. The mean difference was −8%. The MOSFET dosimeters presented statistically insignificant energy dependency. By averaging multiple exposures, the MOSFET dosimeters can achieve a TLD‐comparable low‐dose limit and constitute a feasible method for diagnostic dosimetry using anthropomorphic phantoms. However, for single in vivo measurements (<1.7 mGy) the sensitivity is too low. PACS number: 87.50.wj PMID:26219008

Environmental dosimeter of the thermoluminescent type

DOEpatents

Eichner, F.N.; Kocher, L.F.

1974-01-29

A dosimeter for accurately monitoring normally low-energy radiation including a thermoluminescent CaF phosphor enclosed within a tantalum capsule is described. The tantalum acts as a filter to weaken the measured dose due to photons having energies below about 0.2 MeV. Tantalum end caps are maintained on the capsule body by a polyolefin sheath formed from heat-contractable tubing. After exposing the dosimeter to environmental radiation, it is placed in a shielded chamber for about 24 h and subsequently annealed at about 80 deg C to release radiation energy accumulated in low-temperature traps. The dosimeter is then disassembled and the phosphors photometrically read at temperatures about 50 deg C to determine the absorbed radiation dose. (Official Gazette)

Dose control in electron beam processing: Comparison of results from a graphite charge collector, routine dosimeters and the ISS alanine-based dosimeter

NASA Astrophysics Data System (ADS)

Fuochi, P. G.; Onori, S.; Casali, F.; Chirco, P.

1993-10-01

A 12 MeV linear accelerator is currently used for electron beam processing of power semiconductor devices for lifetime control and, on an experimental basis, for food irradiation, sludge treatment etc. In order to control the irradiation process a simple, quick and reliable method for a direct evaluation of dose and fluence in a broad electron beam has been developed. This paper presents the results obtained using a "charge collector" which measures the charge absorbed in a graphite target exposed in air. Calibration of the system with super-Fricke dosimeter and comparison of absorbed dose results obtained with plastic dosimeters and alanine pellets are discussed.

Investigating the accuracy of microstereotactic-body-radiotherapy utilizing anatomically accurate 3D printed rodent-morphic dosimeters.

PubMed

Bache, Steven T; Juang, Titania; Belley, Matthew D; Koontz, Bridget F; Adamovics, John; Yoshizumi, Terry T; Kirsch, David G; Oldham, Mark

2015-02-01

Sophisticated small animal irradiators, incorporating cone-beam-CT image-guidance, have recently been developed which enable exploration of the efficacy of advanced radiation treatments in the preclinical setting. Microstereotactic-body-radiation-therapy (microSBRT) is one technique of interest, utilizing field sizes in the range of 1-15 mm. Verification of the accuracy of microSBRT treatment delivery is challenging due to the lack of available methods to comprehensively measure dose distributions in representative phantoms with sufficiently high spatial resolution and in 3 dimensions (3D). This work introduces a potential solution in the form of anatomically accurate rodent-morphic 3D dosimeters compatible with ultrahigh resolution (0.3 mm(3)) optical computed tomography (optical-CT) dose read-out. Rodent-morphic dosimeters were produced by 3D-printing molds of rodent anatomy directly from contours defined on x-ray CT data sets of rats and mice, and using these molds to create tissue-equivalent radiochromic 3D dosimeters from Presage. Anatomically accurate spines were incorporated into some dosimeters, by first 3D printing the spine mold, then forming a high-Z bone equivalent spine insert. This spine insert was then set inside the tissue equivalent body mold. The high-Z spinal insert enabled representative cone-beam CT IGRT targeting. On irradiation, a linear radiochromic change in optical-density occurs in the dosimeter, which is proportional to absorbed dose, and was read out using optical-CT in high-resolution (0.5 mm isotropic voxels). Optical-CT data were converted to absolute dose in two ways: (i) using a calibration curve derived from other Presage dosimeters from the same batch, and (ii) by independent measurement of calibrated dose at a point using a novel detector comprised of a yttrium oxide based nanocrystalline scintillator, with a submillimeter active length. A microSBRT spinal treatment was delivered consisting of a 180° continuous arc at 225 kVp with a 20 × 10 mm field size. Dose response was evaluated using both the Presage/optical-CT 3D dosimetry system described above, and independent verification in select planes using EBT2 radiochromic film placed inside rodent-morphic dosimeters that had been sectioned in half. Rodent-morphic 3D dosimeters were successfully produced from Presage radiochromic material by utilizing 3D printed molds of rat CT contours. The dosimeters were found to be compatible with optical-CT dose readout in high-resolution 3D (0.5 mm isotropic voxels) with minimal artifacts or noise. Cone-beam CT image guidance was possible with these dosimeters due to sufficient contrast between high-Z spinal inserts and tissue equivalent Presage material (CNR ∼10 on CBCT images). Dose at isocenter measured with optical-CT was found to agree with nanoscintillator measurement to within 2.8%. Maximum dose in line profiles taken through Presage and film dose slices agreed within 3%, with FWHM measurements through each profile found to agree within 2%. This work demonstrates the feasibility of using 3D printing technology to make anatomically accurate Presage rodent-morphic dosimeters incorporating spinal-mimicking inserts. High quality optical-CT 3D dosimetry is feasible on these dosimeters, despite the irregular surfaces and implanted inserts. The ability to measure dose distributions in anatomically accurate phantoms represents a powerful useful additional verification tool for preclinical microSBRT.

Investigating the accuracy of microstereotactic-body-radiotherapy utilizing anatomically accurate 3D printed rodent-morphic dosimeters

PubMed Central

Bache, Steven T.; Juang, Titania; Belley, Matthew D.; Koontz, Bridget F.; Adamovics, John; Yoshizumi, Terry T.; Kirsch, David G.; Oldham, Mark

2015-01-01

Purpose: Sophisticated small animal irradiators, incorporating cone-beam-CT image-guidance, have recently been developed which enable exploration of the efficacy of advanced radiation treatments in the preclinical setting. Microstereotactic-body-radiation-therapy (microSBRT) is one technique of interest, utilizing field sizes in the range of 1–15 mm. Verification of the accuracy of microSBRT treatment delivery is challenging due to the lack of available methods to comprehensively measure dose distributions in representative phantoms with sufficiently high spatial resolution and in 3 dimensions (3D). This work introduces a potential solution in the form of anatomically accurate rodent-morphic 3D dosimeters compatible with ultrahigh resolution (0.3 mm3) optical computed tomography (optical-CT) dose read-out. Methods: Rodent-morphic dosimeters were produced by 3D-printing molds of rodent anatomy directly from contours defined on x-ray CT data sets of rats and mice, and using these molds to create tissue-equivalent radiochromic 3D dosimeters from Presage. Anatomically accurate spines were incorporated into some dosimeters, by first 3D printing the spine mold, then forming a high-Z bone equivalent spine insert. This spine insert was then set inside the tissue equivalent body mold. The high-Z spinal insert enabled representative cone-beam CT IGRT targeting. On irradiation, a linear radiochromic change in optical-density occurs in the dosimeter, which is proportional to absorbed dose, and was read out using optical-CT in high-resolution (0.5 mm isotropic voxels). Optical-CT data were converted to absolute dose in two ways: (i) using a calibration curve derived from other Presage dosimeters from the same batch, and (ii) by independent measurement of calibrated dose at a point using a novel detector comprised of a yttrium oxide based nanocrystalline scintillator, with a submillimeter active length. A microSBRT spinal treatment was delivered consisting of a 180° continuous arc at 225 kVp with a 20 × 10 mm field size. Dose response was evaluated using both the Presage/optical-CT 3D dosimetry system described above, and independent verification in select planes using EBT2 radiochromic film placed inside rodent-morphic dosimeters that had been sectioned in half. Results: Rodent-morphic 3D dosimeters were successfully produced from Presage radiochromic material by utilizing 3D printed molds of rat CT contours. The dosimeters were found to be compatible with optical-CT dose readout in high-resolution 3D (0.5 mm isotropic voxels) with minimal artifacts or noise. Cone-beam CT image guidance was possible with these dosimeters due to sufficient contrast between high-Z spinal inserts and tissue equivalent Presage material (CNR ∼10 on CBCT images). Dose at isocenter measured with optical-CT was found to agree with nanoscintillator measurement to within 2.8%. Maximum dose in line profiles taken through Presage and film dose slices agreed within 3%, with FWHM measurements through each profile found to agree within 2%. Conclusions: This work demonstrates the feasibility of using 3D printing technology to make anatomically accurate Presage rodent-morphic dosimeters incorporating spinal-mimicking inserts. High quality optical-CT 3D dosimetry is feasible on these dosimeters, despite the irregular surfaces and implanted inserts. The ability to measure dose distributions in anatomically accurate phantoms represents a powerful useful additional verification tool for preclinical microSBRT. PMID:25652497

Investigating the accuracy of microstereotactic-body-radiotherapy utilizing anatomically accurate 3D printed rodent-morphic dosimeters

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

Bache, Steven T.; Juang, Titania; Belley, Matthew D.

Purpose: Sophisticated small animal irradiators, incorporating cone-beam-CT image-guidance, have recently been developed which enable exploration of the efficacy of advanced radiation treatments in the preclinical setting. Microstereotactic-body-radiation-therapy (microSBRT) is one technique of interest, utilizing field sizes in the range of 1–15 mm. Verification of the accuracy of microSBRT treatment delivery is challenging due to the lack of available methods to comprehensively measure dose distributions in representative phantoms with sufficiently high spatial resolution and in 3 dimensions (3D). This work introduces a potential solution in the form of anatomically accurate rodent-morphic 3D dosimeters compatible with ultrahigh resolution (0.3 mm{sup 3}) opticalmore » computed tomography (optical-CT) dose read-out. Methods: Rodent-morphic dosimeters were produced by 3D-printing molds of rodent anatomy directly from contours defined on x-ray CT data sets of rats and mice, and using these molds to create tissue-equivalent radiochromic 3D dosimeters from Presage. Anatomically accurate spines were incorporated into some dosimeters, by first 3D printing the spine mold, then forming a high-Z bone equivalent spine insert. This spine insert was then set inside the tissue equivalent body mold. The high-Z spinal insert enabled representative cone-beam CT IGRT targeting. On irradiation, a linear radiochromic change in optical-density occurs in the dosimeter, which is proportional to absorbed dose, and was read out using optical-CT in high-resolution (0.5 mm isotropic voxels). Optical-CT data were converted to absolute dose in two ways: (i) using a calibration curve derived from other Presage dosimeters from the same batch, and (ii) by independent measurement of calibrated dose at a point using a novel detector comprised of a yttrium oxide based nanocrystalline scintillator, with a submillimeter active length. A microSBRT spinal treatment was delivered consisting of a 180° continuous arc at 225 kVp with a 20 × 10 mm field size. Dose response was evaluated using both the Presage/optical-CT 3D dosimetry system described above, and independent verification in select planes using EBT2 radiochromic film placed inside rodent-morphic dosimeters that had been sectioned in half. Results: Rodent-morphic 3D dosimeters were successfully produced from Presage radiochromic material by utilizing 3D printed molds of rat CT contours. The dosimeters were found to be compatible with optical-CT dose readout in high-resolution 3D (0.5 mm isotropic voxels) with minimal artifacts or noise. Cone-beam CT image guidance was possible with these dosimeters due to sufficient contrast between high-Z spinal inserts and tissue equivalent Presage material (CNR ∼10 on CBCT images). Dose at isocenter measured with optical-CT was found to agree with nanoscintillator measurement to within 2.8%. Maximum dose in line profiles taken through Presage and film dose slices agreed within 3%, with FWHM measurements through each profile found to agree within 2%. Conclusions: This work demonstrates the feasibility of using 3D printing technology to make anatomically accurate Presage rodent-morphic dosimeters incorporating spinal-mimicking inserts. High quality optical-CT 3D dosimetry is feasible on these dosimeters, despite the irregular surfaces and implanted inserts. The ability to measure dose distributions in anatomically accurate phantoms represents a powerful useful additional verification tool for preclinical microSBRT.« less

Comparison and applicability analysis of models for estimating radiological dose rates of freshwater biota

NASA Astrophysics Data System (ADS)

Zhang, Xiaofeng; Yang, Zongzhen; Qin, Chunli

2018-01-01

A number of inter-comparisons of non-human biota radiation assessment models have been fulfilled by international researchers and organizations. This paper describes the radiological impact to reference biota in Chinese inland nuclear power plant scenario, by using RESRAD-Biota, ERICA and R&D 128. The estimation results are ranging from 6.1×10-3μGy/h to 6.17×10-2μGy/h, mainly contributed by 134Cs and 137Cs, obviously below recommended limits and thus prove the biota in reservoir can be adequately protected from effluent discharge. By comparing models characteristics and performances in exercise, we conclude the ERICA tool reveals more applicability in Chinese nuclear sites and propose several suggestions to establish native framework for non-human biota assessment.

Feasibility of reading LiF thermoluminescent dosimeters by electron spin resonance

NASA Astrophysics Data System (ADS)

Breen, S. L.; Battista, J. J.

1999-08-01

Lithium fluoride is a commonly used solid state dosimeter. During irradiation, electrons and holes become trapped in crystal imperfections; thermoluminescence dosimetry measures their thermally induced recombination. Electron paramagnetic resonance (EPR) spectroscopy can be used to measure the resonant absorption of microwaves by the unpaired electrons trapped in LiF. In an effort to extend the use of LiF dosimeters to smaller sizes and to the harsh environments encountered in internal dosimetry, EPR was evaluated as an alternative technique to read the radiation dose delivered to TLD-100 dosimeters. TLD-100 rods were irradiated with a 60Co source to doses of 10 Gy to 100 Gy. A radiation-induced signal (with a g-value of 2.002) could be detected only at liquid nitrogen temperatures at doses above 20 Gy. The EPR spectrum of irradiated LiF contains three components, one of which correlates positively with dose. However, the low sensitivity of the technique, and difficulty in interpreting the EPR spectrum from polycrystalline dosimeters, preclude its use as a dosimetry technique.

Observations on personnel dosimetry for radiotherapy personnel operating high-energy LINACs.

PubMed

Glasgow, G P; Eichling, J; Yoder, R C

1986-06-01

A series of measurements were conducted to determine the cause of a sudden increase in personnel radiation exposures. One objective of the measurements was to determine if the increases were related to changing from film dosimeters exchanged monthly to TLD-100 dosimeters exchanged quarterly. While small increases were observed in the dose equivalents of most employees, the dose equivalents of personnel operating medical electron linear accelerators with energies greater than 20 MV doubled coincidentally with the change in the personnel dosimeter program. The measurements indicated a small thermal neutron radiation component around the accelerators operated by these personnel. This component caused the doses measured with the TLD-100 dosimeters to be overstated. Therefore, the increase in these personnel dose equivalents was not due to changes in work habits or radiation environments. Either film or TLD-700 dosimeters would be suitable for personnel monitoring around high-energy linear accelerators. The final choice would depend on economics and personal preference.

Feasibility of reading LiF thermoluminescent dosimeters by electron spin resonance.

PubMed

Breen, S L; Battista, J J

1999-08-01

Lithium fluoride is a commonly used solid state dosimeter. During irradiation, electrons and holes become trapped in crystal imperfections; thermoluminescence dosimetry measures their thermally induced recombination. Electron paramagnetic resonance (EPR) spectroscopy can be used to measure the resonant absorption of microwaves by the unpaired electrons trapped in LiF. In an effort to extend the use of LiF dosimeters to smaller sizes and to the harsh environments encountered in internal dosimetry, EPR was evaluated as an alternative technique to read the radiation dose delivered to TLD-100 dosimeters. TLD-100 rods were irradiated with a 60Co source to doses of 10 Gy to 100 Gy. A radiation-induced signal (with a g-value of 2.002) could be detected only at liquid nitrogen temperatures at doses above 20 Gy. The EPR spectrum of irradiated LiF contains three components, one of which correlates positively with dose. However, the low sensitivity of the technique, and difficulty in interpreting the EPR spectrum from polycrystalline dosimeters, preclude its use as a dosimetry technique.

Improvements in opti-chromic dosimeters for radiation processing

NASA Astrophysics Data System (ADS)

Humpherys, K. C.; Kantz, A. D.

"Opti-Chromic" dosimeters consisting of radiachromic dye in flourinated polymer tubing have been introduced as a dosimetry system in the range from 10 1 to 5 × 10 4 Gy. Batches of "Opti-Chromic" dosimeters have been produced to evaluate performance under large scale industrial conditions. A systematic study was undertaken to determine the effect of various dosimeter parameters on radiation sensitivity, shelf life, and response characteristics at the higher absorbed doses. These parameters were (A) Type of flourinated polymer tubing; (B) Organic solvent used to activate the radiachromic dye; (C) Concentration of radiachromic dye; (D) Additives to provide proper viscosity, color stability, and high-dose response. Prototype batches were produced and experimental dosimeters exposed to a range of absorbed doses and the response measured as a function of shelf life and dose. The results of the study are presented, and an improved formulation recommended for application to Food Processing. Other formulations may be of value in specific requirements of sensitivity or temperature.

Portable battery-free charger for radiation dosimeters

DOEpatents

Manning, Frank W.

1984-01-01

This invention is a novel portable charger for dosimeters of the electrometer type. The charger does not require batteries or piezoelectric crystals and is of rugged construction. In a preferred embodiment, the charge includes a housing which carries means for mounting a dosimeter to be charged. The housing also includes contact means for impressing a charging voltage across the mounted dosimeter. Also, the housing carries a trigger for operating a charging system mounted in the housing. The charging system includes a magnetic loop including a permanent magnet for establishing a magnetic field through the loop. A segment of the loop is coupled to the trigger for movement thereby to positions opening and closing the loop. A coil inductively coupled with the loop generates coil-generated voltage pulses when the trigger is operated to open and close the loop. The charging system includes an electrical circuit for impressing voltage pulses from the coil across a capacitor for integrating the pulses and applying the resulting integrated voltage across the above-mentioned contact means for charging the dosimeter.

Thin thermoluminescent dosimeter and method of making same

DOEpatents

Simons, Gale G.; DeBey, Timothy M.

1987-01-01

An improved thermoluminescent ionizing radiation dosimeter of solid, extremely thin construction for more accurate low energy beta dosimetry is provided, along with a method of fabricating the dosimeter. In preferred forms, the dosimeter is a composite including a backing support (which may be tissue equivalent) and a self-sustaining body of solid thermoluminescent material such as LiF having a thickness of less than about 0.25 millimeters and a volume of at least about 0.0125 mm.sup.3. In preferred fabrication procedures, an initially thick (e.g., 0.89 millimeters) TLD body is wet sanded using 600 grit or less sandpaper to a thickness of less than about 0.25 millimeters, followed by adhesively attaching the sanded body to an appropriate backing. The sanding procedure permits routine production of extremely thin (about 0.05 millimeters) TLD bodies, and moreover serves to significantly reduce non-radiation-induced thermoluminescence. The composite dosimeters are rugged in use and can be subjected to annealing temperatures for increased accuracy.

Digital Mammography Breast Dosimetry Using Copper-Doped Lithium Fluoride (LiF:MCP) Thermoluminescent Dosimeters (TLDs)

DTIC Science & Technology

2003-06-18

Mammography Breast Dosimetry Using Copper-Doped Lithium Fluoride (LiF:MCP) Thermoluminescent Dosimeters ( TLDs ) 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c...34Digital Mammography Breast Dosimetry Using Copper- Doped Lithium Fluoride (LiF:MCP) Thermoluminescent Dosimeters ( TLDs )" Author: LT John J. Tomon...Title of Thesis: " Digital Mammography Breast Dosimetry Using Copper-Doped Lithium Fluoride (LiF:MCP) Thermoluminescent

Surface-enhanced Raman scattering (SERS) dosimeter and probe

DOEpatents

Vo-Dinh, T.

1995-03-21

A dosimeter and probe for measuring exposure to chemical and biological compounds is disclosed. The dosimeter or probe includes a collector which may be analyzed by surface-enhanced Raman spectroscopy. The collector comprises a surface-enhanced Raman scattering-active material having a coating applied thereto to improve the adsorption properties of the collector. The collector may also be used in automated sequential devices, in probe array devices. 10 figures.

1997 NRL Review

DTIC Science & Technology

1997-04-01

are subsequently read out using a low- doped Glasses power, solid-state diode laser. Figure 4 shows a schematic of the OSL dosimeter . The 807-nm A.L...Huston, S, Rychnovsky, and B.L. Justus (near infrared) diode laser light stimulates blue OSL Optical Sciences Division emission from the dosimeter , and...The sensitivity of the hole pairs become trapped and may persist until prototype OSL dosimeter exceeds that of the stimulated to luminesce by the

Length of stain dosimeter

NASA Astrophysics Data System (ADS)

Lueck, Dale E.

1994-04-01

Payload customers for the Space Shuttle have recently expressed concerns about the possibility of their payloads at an adjacent pad being contaminated by plume effluents from a shuttle at an active pad as they await launch on an inactive pad. As part of a study to satisfy such concerns a ring of inexpensive dosimeters was deployed around the active pad at the inter-pad distance. However, following a launch, dosimeters cannot be read for several hours after the exposure. As a consequence factors such as different substrates, solvent systems, and possible volatilization of HCl from the badges were studied. This observation led to the length of stain (LOS) dosimeters of this invention. Commercial passive LOS dosimeters are sensitive only to the extent of being capable of sensing 2 ppm to 20 ppm if the exposure is 8 hours. To map and quantitate the HCl generated by Shuttle launches, and in the atmosphere within a radius of 1.5 miles from the active pad, a sensitivity of 2 ppm HCl in the atmospheric gases on an exposure of 5 minutes is required. A passive length of stain dosimeter has been developed having a sensitivity rendering it capable of detecting a gas in a concentration as low as 2 ppm on an exposure of five minutes.

Length of stain dosimeter

NASA Technical Reports Server (NTRS)

Lueck, Dale E. (Inventor)

1994-01-01

Payload customers for the Space Shuttle have recently expressed concerns about the possibility of their payloads at an adjacent pad being contaminated by plume effluents from a shuttle at an active pad as they await launch on an inactive pad. As part of a study to satisfy such concerns a ring of inexpensive dosimeters was deployed around the active pad at the inter-pad distance. However, following a launch, dosimeters cannot be read for several hours after the exposure. As a consequence factors such as different substrates, solvent systems, and possible volatilization of HCl from the badges were studied. This observation led to the length of stain (LOS) dosimeters of this invention. Commercial passive LOS dosimeters are sensitive only to the extent of being capable of sensing 2 ppm to 20 ppm if the exposure is 8 hours. To map and quantitate the HCl generated by Shuttle launches, and in the atmosphere within a radius of 1.5 miles from the active pad, a sensitivity of 2 ppm HCl in the atmospheric gases on an exposure of 5 minutes is required. A passive length of stain dosimeter has been developed having a sensitivity rendering it capable of detecting a gas in a concentration as low as 2 ppm on an exposure of five minutes.

A critical assessment of two types of personal UV dosimeters.

PubMed

Seckmeyer, Gunther; Klingebiel, Marcus; Riechelmann, Stefan; Lohse, Insa; McKenzie, Richard L; Liley, J Ben; Allen, Martin W; Siani, Anna-Maria; Casale, Giuseppe R

2012-01-01

Doses of erythemally weighted irradiances derived from polysulphone (PS) and electronic ultraviolet (EUV) dosimeters have been compared with measurements obtained using a reference spectroradiometer. PS dosimeters showed mean absolute deviations of 26% with a maximum deviation of 44%, the calibrated EUV dosimeters showed mean absolute deviations of 15% (maximum 33%) around noon during several test days in the northern hemisphere autumn. In the case of EUV dosimeters, measurements with various cut-off filters showed that part of the deviation from the CIE erythema action spectrum was due to a small, but significant sensitivity to visible radiation that varies between devices and which may be avoided by careful preselection. Usually the method of calibrating UV sensors by direct comparison to a reference instrument leads to reliable results. However, in some circumstances the quality of measurements made with simple sensors may be over-estimated. In the extreme case, a simple pyranometer can be used as a UV instrument, providing acceptable results for cloudless skies, but very poor results under cloudy conditions. It is concluded that while UV dosimeters are useful for their design purpose, namely to estimate personal UV exposures, they should not be regarded as an inexpensive replacement for meteorological grade instruments. © 2011 Wiley Periodicals, Inc. Photochemistry and Photobiology © 2011 The American Society of Photobiology.

Assessment of radiation exposure in dental cone-beam computerized tomography with the use of metal-oxide semiconductor field-effect transistor (MOSFET) dosimeters and Monte Carlo simulations.

PubMed

Koivisto, J; Kiljunen, T; Tapiovaara, M; Wolff, J; Kortesniemi, M

2012-09-01

The aims of this study were to assess the organ and effective dose (International Commission on Radiological Protection (ICRP) 103) resulting from dental cone-beam computerized tomography (CBCT) imaging using a novel metal-oxide semiconductor field-effect transistor (MOSFET) dosimeter device, and to assess the reliability of the MOSFET measurements by comparing the results with Monte Carlo PCXMC simulations. Organ dose measurements were performed using 20 MOSFET dosimeters that were embedded in the 8 most radiosensitive organs in the maxillofacial and neck area. The dose-area product (DAP) values attained from CBCT scans were used for PCXMC simulations. The acquired MOSFET doses were then compared with the Monte Carlo simulations. The effective dose measurements using MOSFET dosimeters yielded, using 0.5-cm steps, a value of 153 μSv and the PCXMC simulations resulted in a value of 136 μSv. The MOSFET dosimeters placed in a head phantom gave results similar to Monte Carlo simulations. Minor vertical changes in the positioning of the phantom had a substantial affect on the overall effective dose. Therefore, the MOSFET dosimeters constitute a feasible method for dose assessment of CBCT units in the maxillofacial region. Copyright © 2012 Elsevier Inc. All rights reserved.

Angular dependence of the nanoDot OSL dosimeter.

PubMed

Kerns, James R; Kry, Stephen F; Sahoo, Narayan; Followill, David S; Ibbott, Geoffrey S

2011-07-01

Optically stimulated luminescent detectors (OSLDs) are quickly gaining popularity as passive dosimeters, with applications in medicine for linac output calibration verification, brachytherapy source verification, treatment plan quality assurance, and clinical dose measurements. With such wide applications, these dosimeters must be characterized for numerous factors affecting their response. The most abundant commercial OSLD is the InLight/OSL system from Landauer, Inc. The purpose of this study was to examine the angular dependence of the nanoDot dosimeter, which is part of the InLight system. Relative dosimeter response data were taken at several angles in 6 and 18 MV photon beams, as well as a clinical proton beam. These measurements were done within a phantom at a depth beyond the build-up region. To verify the observed angular dependence, additional measurements were conducted as well as Monte Carlo simulations in MCNPX. When irradiated with the incident photon beams parallel to the plane of the dosimeter, the nanoDot response was 4% lower at 6 MV and 3% lower at 18 MV than the response when irradiated with the incident beam normal to the plane of the dosimeter. Monte Carlo simulations at 6 MV showed similar results to the experimental values. Examination of the results in Monte Carlo suggests the cause as partial volume irradiation. In a clinical proton beam, no angular dependence was found. A nontrivial angular response of this OSLD was observed in photon beams. This factor may need to be accounted for when evaluating doses from photon beams incident from a variety of directions.

Angular dependence of the nanoDot OSL dosimeter

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

Kerns, James R.; Kry, Stephen F.; Sahoo, Narayan

Purpose: Optically stimulated luminescent detectors (OSLDs) are quickly gaining popularity as passive dosimeters, with applications in medicine for linac output calibration verification, brachytherapy source verification, treatment plan quality assurance, and clinical dose measurements. With such wide applications, these dosimeters must be characterized for numerous factors affecting their response. The most abundant commercial OSLD is the InLight/OSL system from Landauer, Inc. The purpose of this study was to examine the angular dependence of the nanoDot dosimeter, which is part of the InLight system. Methods: Relative dosimeter response data were taken at several angles in 6 and 18 MV photon beams, asmore » well as a clinical proton beam. These measurements were done within a phantom at a depth beyond the build-up region. To verify the observed angular dependence, additional measurements were conducted as well as Monte Carlo simulations in MCNPX. Results: When irradiated with the incident photon beams parallel to the plane of the dosimeter, the nanoDot response was 4% lower at 6 MV and 3% lower at 18 MV than the response when irradiated with the incident beam normal to the plane of the dosimeter. Monte Carlo simulations at 6 MV showed similar results to the experimental values. Examination of the results in Monte Carlo suggests the cause as partial volume irradiation. In a clinical proton beam, no angular dependence was found. Conclusions: A nontrivial angular response of this OSLD was observed in photon beams. This factor may need to be accounted for when evaluating doses from photon beams incident from a variety of directions.« less

Angular dependence of the nanoDot OSL dosimeter

PubMed Central

Kerns, James R.; Kry, Stephen F.; Sahoo, Narayan; Followill, David S.; Ibbott, Geoffrey S.

2011-01-01

Purpose: Optically stimulated luminescent detectors (OSLDs) are quickly gaining popularity as passive dosimeters, with applications in medicine for linac output calibration verification, brachytherapy source verification, treatment plan quality assurance, and clinical dose measurements. With such wide applications, these dosimeters must be characterized for numerous factors affecting their response. The most abundant commercial OSLD is the InLight∕OSL system from Landauer, Inc. The purpose of this study was to examine the angular dependence of the nanoDot dosimeter, which is part of the InLight system.Methods: Relative dosimeter response data were taken at several angles in 6 and 18 MV photon beams, as well as a clinical proton beam. These measurements were done within a phantom at a depth beyond the build-up region. To verify the observed angular dependence, additional measurements were conducted as well as Monte Carlo simulations in MCNPX.Results: When irradiated with the incident photon beams parallel to the plane of the dosimeter, the nanoDot response was 4% lower at 6 MV and 3% lower at 18 MV than the response when irradiated with the incident beam normal to the plane of the dosimeter. Monte Carlo simulations at 6 MV showed similar results to the experimental values. Examination of the results in Monte Carlo suggests the cause as partial volume irradiation. In a clinical proton beam, no angular dependence was found.Conclusions: A nontrivial angular response of this OSLD was observed in photon beams. This factor may need to be accounted for when evaluating doses from photon beams incident from a variety of directions. PMID:21858992

Direct and pulsed current annealing of p-MOSFET based dosimeter: the "MOSkin".

PubMed

Alshaikh, Sami; Carolan, Martin; Petasecca, Marco; Lerch, Michael; Metcalfe, Peter; Rosenfeld, Anatoly

2014-06-01

Contemporary radiation therapy (RT) is complicated and requires sophisticated real-time quality assurance (QA). While 3D real-time dosimetry is most preferable in RT, it is currently not fully realised. A small, easy to use and inexpensive point dosimeter with real-time and in vivo capabilities is an option for routine QA. Such a dosimeter is essential for skin, in vivo or interface dosimetry in phantoms for treatment plan verification. The metal-oxide-semiconductor-field-effect-transistor (MOSFET) detector is one of the best choices for these purposes, however, the MOSFETs sensitivity and its signal stability degrade after essential irradiation which limits its lifespan. The accumulation of positive charge on the gate oxide and the creation of interface traps near the silicon-silicon dioxide layer is the primary physical phenomena responsible for this degradation. The aim of this study is to investigate MOSFET dosimeter recovery using two proposed annealing techniques: direct current (DC) and pulsed current (PC), both based on hot charged carrier injection into the gate oxide of the p-MOSFET dosimeter. The investigated MOSFETs were reused multiple times using an irradiation-annealing cycle. The effect of the current-annealing parameters was investigated for the dosimetric characteristics of the recovered MOSFET dosimeters such as linearity, sensitivity and initial threshold voltage. Both annealing techniques demonstrated excellent results in terms of maintaining a stable response, linearity and sensitivity of the MOSFET dosimeter. However, PC annealing is more preferable than DC annealing as it offers better dose response linearity of the reused MOSFET and has a very short annealing time.

Method for correcting for isotope burn-in effects in fission neutron dosimeters

DOEpatents

Gold, Raymond; McElroy, William N.

1988-01-01

A method is described for correcting for effect of isotope burn-in in fission neutron dosimeters. Two quantities are measured in order to quantify the "burn-in" contribution, namely P.sub.Z',A', the amount of (Z', A') isotope that is burned-in, and F.sub.Z', A', the fissions per unit volume produced in the (Z', A') isotope. To measure P.sub.Z', A', two solid state track recorder fission deposits are prepared from the very same material that comprises the fission neutron dosimeter, and the mass and mass density are measured. One of these deposits is exposed along with the fission neutron dosimeter, whereas the second deposit is subsequently used for observation of background. P.sub.Z', A' is then determined by conducting a second irradiation, wherein both the irradiated and unirradiated fission deposits are used in solid state track recorder dosimeters for observation of the absolute number of fissions per unit volume. The difference between the latter determines P.sub.Z', A' since the thermal neutron cross section is known. F.sub.Z', A' is obtained by using a fission neutron dosimeter for this specific isotope, which is exposed along with the original threshold fission neutron dosimeter to experience the same neutron flux-time history at the same location. In order to determine the fissions per unit volume produced in the isotope (Z', A') as it ingrows during the irradiation, B.sub.Z', A', from these observations, the neutron field must generally be either time independent or a separable function of time t and neutron energy E.

The Internet's role in a biodosimetric response to a radiation mass casualty event.

PubMed

Sugarman, S L; Livingston, G K; Stricklin, D L; Abbott, M G; Wilkins, R C; Romm, H; Oestreicher, U; Yoshida, M A; Miura, T; Moquet, J E; Di Giorgio, M; Ferrarotto, C; Gross, G A; Christiansen, M E; Hart, C L; Christensen, D M

2014-05-01

Response to a large-scale radiological incident could require timely medical interventions to minimize radiation casualties. Proper medical care requires knowing the victim's radiation dose. When physical dosimetry is absent, radiation-specific chromosome aberration analysis can serve to estimate the absorbed dose in order to assist physicians in the medical management of radiation injuries. A mock exercise scenario was presented to six participating biodosimetry laboratories as one individual acutely exposed to Co under conditions suggesting whole-body exposure. The individual was not wearing a dosimeter and within 2-3 h of the incident began vomiting. The individual also had other medical symptoms indicating likelihood of a significant dose. Physicians managing the patient requested a dose estimate in order to develop a treatment plan. Participating laboratories in North and South America, Europe, and Asia were asked to evaluate more than 800 electronic images of metaphase cells from the patient to determine the dicentric yield and calculate a dose estimate with 95% confidence limits. All participants were blind to the physical dose until after submitting their estimates based on the dicentric chromosome assay (DCA). The exercise was successful since the mean biological dose estimate was 1.89 Gy whereas the actual physical dose was 2 Gy. This is well within the requirements for guidance of medical management. The exercise demonstrated that the most labor-intensive step in the entire process (visual evaluation of images) can be accelerated by taking advantage of world-wide expertise available on the Internet.

Hand and body radiation exposure with the use of mini C-arm fluoroscopy.

PubMed

Tuohy, Christopher J; Weikert, Douglas R; Watson, Jeffry T; Lee, Donald H

2011-04-01

To determine whole body and hand radiation exposure to the hand surgeon wearing a lead apron during routine intraoperative use of the mini C-arm fluoroscope. Four surgeons (3 hand attending surgeons and 1 hand fellow) monitored their radiation exposure for a total of 200 consecutive cases (50 cases per surgeon) requiring mini C-arm fluoroscopy. Each surgeon measured radiation exposure with a badge dosimeter placed on the outside breast pocket of the lead apron (external whole body exposure), a second badge dosimeter under the lead apron (shielded whole body exposure), and a ring dosimeter (hand exposure). Completed records were noted in 198 cases, with an average fluoroscopy time of 133.52 seconds and average cumulative dose of 19,260 rem-cm(2) per case. The total measured radiation exposures for the (1) external whole body exposure dosimeters were 16 mrem (for shallow depth), 7 mrem (for eye depth), and less than 1 mrem (for deep depth); (2) shielded whole body badge dosimeters recorded less than 1 mrem; and (3) ring dosimeters totaled 170 mrem. The total radial exposure for 4 ring dosimeters that had registered a threshold of 30 mrem or more of radiation exposure was 170 mrem at the skin level, for an average of 42.5 mrem per dosimeter ring or 6.3 mrem per case. This study of whole body and hand radiation exposure from the mini C-arm includes the largest number of surgical cases in the published literature. The measured whole body and hand radiation exposure received by the hand surgeon from the mini C-arm represents a minimal risk of radiation, based on the current National Council on Radiation Protection and Management standards of annual dose limits (5,000 mrem per year for whole body and 50,000 mrem per year to the extremities). Copyright © 2011 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.

SU-E-I-06: Measurement of Skin Dose from Dental Cone-Beam CT Scans.

PubMed

Akyalcin, S; English, J; Abramovitch, K; Rong, J

2012-06-01

To directly measure skin dose using point-dosimeters from dental cone-beam CT (CBCT) scans. To compare the results among three different dental CBCT scanners and compare the CBCT results with those from a conventional panoramic and cephalomic dental imaging system. A head anthropomorphic phantom was used with nanoDOT dosimeters attached to specified anatomic landmarks of selected radiosensitive tissues of interest. To ensure reliable measurement results, three dosimeters were used for each location. The phantom was scanned under various modes of operation and scan protocols for typical dental exams on three dental CBCT systems plus a conventional dental imaging system. The Landauer OSL nanoDOT dosimeters were calibrated under the same imaging condition as the head phantom scan protocols, and specifically for each of the imaging systems. Using nanoDOT dosimeters, skin doses at several positions on the surface of an adult head anthropomorphic phantom were measured for clinical dental imaging. The measured skin doses ranged from 0.04 to 4.62mGy depending on dosimeter positions and imaging systems. The highest dose location was at the parotid surface for all three CBCT scanners. The surface doses to the locations of the eyes were ∼4.0mGy, well below the 500mGy threshold for possibly causing cataract development. The results depend on x-ray tube output (kVp and mAs) and also are sensitive to SFOV. Comparing to the conventional dental imaging system operated in panoramic and cephalometric modes, doses from all three CBCT systems were at least an order of magnitude higher. No image artifact was caused by presence of nanoDOT dosimeters in the head phantom images. Direct measurements of skin dose using nanoDOT dosimeters provided accurate skin dose values without any image artifacts. The results of skin dose measurements serve as dose references in guiding future dose optimization efforts in dental CBCT imaging. © 2012 American Association of Physicists in Medicine.

SU-G-BRB-08: Investigation On the Magnetic Field Effect On TLDs, OSLDs, and Gafchromic Films Using An MR-Linac

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

Wen, Z; Wang, J; O’Brien, D

Purpose: To investigate whether a strong magnetic field (B=1.5 T) can affect dose responses of thermoluminescent dosimeters (TLDs), optically stimulated luminescence dosimeters (OSLDs) and Gafchromic films using an MR-Linac (Elekta) before and after the magnet was ramped down from 1.5 T to 0 T. Methods: Three types of dosimeters (TLDs, OSLDs, EBT3 films) were divided into two groups. Group 1 was first irradiated in a phantom of Solid Water slabs (Standard Imaging) inside a B=1.5 T field with a 7 MV beam from an MR-Linac system. The radiation output at the location of the dosimeters (isocenter at 10 cm depth)more » was measured using an ion chamber (NE2571, Phoenix Dosimetry). Three doses (150, 300, 600 MU, corresponding to 1.18, 2.36, and 4.74 Gy) were delivered to the dosimeters. A week later the MR magnet was ramped down to zero field and dosimeters in Group 2 were irradiated with the same MUs. Dosimeters of each type were read out during the same session (about 4 weeks post irradiation in the B field, and 3 weeks with no B field). The ratios of signals between Group 1 and Group 2 were calculated. Results: Radiation output measured with the chamber was within 1% before and after ramping down the MR magnet. For TLDs, the ratio of signals with B field to signals without B field averaged over three dose levels was 1.003±0.016; for OSLDs, the ratio was 0.994±0.022; for films, the ratios of two batches (different manufacturing dates) were 0.997 and 0.985. Conclusion: Dose responses of all three dosimeters seem not affected by the presence of a 1.5 T magnetic field within uncertainty of ∼2%. More measurements will be conducted to test reproducibility. We acknowledge research support from Elekta AB.« less

SU-E-I-60: Validation of An Optically Stimulated Luminescent (OSL) Dosimeter for Use in Output Exposure Control Verification of Mammography Imaging Systems.

PubMed

Ranger, R; Butler, P; Yahnke, C; Valentino, D

2012-06-01

To develop and validate an Optically Stimulated Luminescent (OSL) dosimeter for exposure control verification of x-ray projection mammography imaging systems. The active detection element of the dosimeter is a strip of OSL material 3.0 mm wide, 0.13 mm thick and 30.0 mm long with an overlying aluminum step wedge with thicknesses of 0, 0.2, 0.4 and 0.6 mm Al, encapsulated in a light-tight plastic enclosure with outer dimensions of 10.0 mm wide, 5.4 mm thick, and 54.0 mm long. The dosimeter is used in conjunction with a breast phantom for the purpose of estimating the half-value layer (HVL), entrance surface exposure (ESE), and average glandular dose (AGD) in conventional projection mammography. ESE and HVL were computed based on analysis of exposure profiles obtained from exposed strip dosimeters. The AGD was estimated by multiplying the ESE by the appropriate exposure to dose conversion factor for the thickness and % glandular tissue fraction represented by the phantom and target-filter combination employed. The accuracy and reproducibility of the ESE, HVL and AGD estimates obtained using the dosimeter positioned on the surface of the ACR phantom at the chest wall edge, was evaluated using mammography systems utilizing different imaging receptor technology, i.e. screen-film (SF), computed radiography (CR) and direct radiography (DR) and compared against results obtained using a calibrated ion chamber fitted with a mammography probe. ESE, AGD and HVL results obtained using the OSL mammography QA dosimeter agreed with results obtained using an ion chamber to within 5-10%, depending on the target-filter combination used. Repeat readings were highly consistent with a coefficient of variation = 5%. The OSL mammography QA dosimeter has been shown to effectively estimate ESE, HVL and AGD, demonstrating its usefulness for secondary monitoring of output exposure of mammography imaging systems. © 2012 American Association of Physicists in Medicine.

SU-E-T-368: Effect of a Strong Magnetic Field On Select Radiation Dosimeters

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

Mathis, M; Wen, Z; Tailor, R

Purpose: To determine the effect of a strong magnetic field on TLD-100, OSLD (Al{sub 2}O{sub 2}:C), and PRESAGE dosimetry devices. This study will help to determine which types of dosimeters can be used for quality assurance and in-vivo dosimetry measurements in a magnetic resonance imaginglinear accelerator (MRI-linac) system. Methods: The dosimeters were separated into two categories which were either exposed or not exposed to a strong magnetic field. In each category a set of dosimeters was irradiated with 0, 2, or 6 Gy. To expose the dosimeters to a magnetic field the samples in that category were place in amore » Bruker small animal magnetic resonance scanner at a field strength slightly greater than 2.5 T for at least 1 hour preirradiation and at least 1 hour post-irradiation. Irradiations were performed with a 6 MV x-ray beam from a Varian TrueBeam linac with 10×10 cm{sup 2} field at a 600 MU/min dose rate. The samples that received no radiation dose were used as control detectors. Results: The readouts of the dosimeters which were not exposed to a strong magnetic field were compared with the measurements of the dosimetry devices which were exposed to a magnetic field. No significant differences (less than 2% difference) in the performance of TLD, OSLD, or PRESAGE dosimeters due to exposure to a strong magnetic field were observed. Conclusion: Exposure to a strong magnetic field before and after irradiation does not appear to change the dosimetric properties of TLD, OSLD, or PRESAGE which indicates that these dosimeters have potential for use in quality assurance and in-vivo dosimetry in a MRI-linac. We plan to further test the effect of magnetic fields on these devices by irradiating them in the presence of a magnetic fields similar to those produced by a MRI-linac system. Elekta-MD Anderson Cancer Center Research Agreement.« less

Proficiency Tests for Environmental Radioactivity Measurement Organized by an Accredited Laboratory

NASA Astrophysics Data System (ADS)

Aubert, Cédric; Osmond, Mélanie

2008-08-01

For 40 years, STEME (Environmental Sample Processing and Metrology Department) organized international proficiency testing (PT) exercises formerly for WHO (World Health Organization) and EC (European Community) and currently for ASN (French Nuclear Safety Authority). Five PT exercises are organized each year for the measurement of radionuclides (alpha, beta and gamma) in different matrixes (water, soil, biological and air samples) at environmental levels. ASN can deliver a French ministerial agreement to participate on environmental radioactivity measurements French network for laboratories asking it [1]. Since 2006, November, STEME is the first French entity obtaining a COFRAC (French Committee of Accreditation) accreditation as "Interlaboratory Comparisons" for the organization of proficiency tests for environmental radioactivity measurement according to standard International Standard Organization (ISO) 17025 and guide ISO 43-1. STEME has in charge to find, as far as possible, real sample or to create, by radionuclide adding, an adapted sample. STEME realizes the sampling, the samples preparation and the dispatching. STEME is also accredited according to Standard 17025 for radioactivity measurements in environmental samples and determines homogeneity, stability and reference values. After the reception of participating laboratories results, STEME executes statistical treatments in order to verify the normal distribution, to eliminate outliers and to evaluate laboratories performance. Laboratories participate with several objectives, to obtain French agreement, to prove the quality of their analytical performance in regards to standard 17025 or to validate new methods or latest developments. For 2 years, in addition to usual PT exercises, new PT about alpha or beta measurement in air filters, radioactive iodine in carbon cartridges or measurement of environmental dosimeters are organized. These PT exercises help laboratories to improve radioactive measurements and to rectify old mistakes. The PT exercises organized by STEME are becoming essential for French and some European laboratories working in radioactive measurements. The STEME organization, in respect of accreditation references, is presented.

Proficiency Tests for Environmental Radioactivity Measurement Organized by an Accredited Laboratory

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

Aubert, Cedric; Osmond, Melanie

2008-08-14

For 40 years, STEME (Environmental Sample Processing and Metrology Department) organized international proficiency testing (PT) exercises formerly for WHO (World Health Organization) and EC (European Community) and currently for ASN (French Nuclear Safety Authority). Five PT exercises are organized each year for the measurement of radionuclides (alpha, beta and gamma) in different matrixes (water, soil, biological and air samples) at environmental levels. ASN can deliver a French ministerial agreement to participate on environmental radioactivity measurements French network for laboratories asking it. Since 2006, November, STEME is the first French entity obtaining a COFRAC (French Committee of Accreditation) accreditation as 'Interlaboratorymore » Comparisons' for the organization of proficiency tests for environmental radioactivity measurement according to standard International Standard Organization (ISO) 17025 and guide ISO 43-1. STEME has in charge to find, as far as possible, real sample or to create, by radionuclide adding, an adapted sample. STEME realizes the sampling, the samples preparation and the dispatching. STEME is also accredited according to Standard 17025 for radioactivity measurements in environmental samples and determines homogeneity, stability and reference values. After the reception of participating laboratories results, STEME executes statistical treatments in order to verify the normal distribution, to eliminate outliers and to evaluate laboratories performance.Laboratories participate with several objectives, to obtain French agreement, to prove the quality of their analytical performance in regards to standard 17025 or to validate new methods or latest developments. For 2 years, in addition to usual PT exercises, new PT about alpha or beta measurement in air filters, radioactive iodine in carbon cartridges or measurement of environmental dosimeters are organized. These PT exercises help laboratories to improve radioactive measurements and to rectify old mistakes. The PT exercises organized by STEME are becoming essential for French and some European laboratories working in radioactive measurements.The STEME organization, in respect of accreditation references, is presented.« less

On the climate policy implications of substitutability and flexibility in the economy: An in-depth integrated assessment model diagnostic

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

Craxton, Melanie; Merrick, James; Makridis, Christos

This paper conducts an in-depth model diagnostic exercise for two parameters, 1) the elasticity of substitution between the capital/labour aggregate and the energy aggregate in the Integrated Assessment Model (IAM) MERGE's production function and 2) the rate at which new technologies can be deployed within the energy system. We show that in a more complementary world the model's ability to adjust the carbon intensity of its energy sector is more important whereas in a more substitutable world the ability to expand carbon free technologies is of lesser relative importance. The uncertainty in the literature surrounding the elasticity of substitution parameter,more » its interaction with the mechanisms of technical change, and the associated danger of grounding forward-looking analyses in historically based parameters lend support to the importance of such a diagnostic exercise. Building on work from model intercomparison studies, we investigate whether a given model's choice of strategy is primarily a function of the choice of its parameter values or its structure. As a result, a deeper understanding of what drives model behaviour is beneficial to both modellers and the policymakers who utilise their insights and output.« less

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

Baglan, N.; Kim, S.B.; Cossonnet, C.

Organically bound tritium (OBT) has become of increased interest within the last decade, with a focus on its behaviour and also its analysis, which are important to assess tritium distribution in the environment. In contrast, there are no certified reference materials and no standard analytical method through the international organization related to OBT. In order to resolve this issue, an OBT international working group was created in May 2012. Over 20 labs from around the world participated and submitted their results for the first intercomparison exercise results on potato (Sep 2013). The samples, specially-prepared potatoes, were provided in March 2013more » to each participant. Technical information and results from this first exercise are discussed here for all the labs which have realised the five replicates necessary to allow a reliable statistical treatment. The results are encouraging as the increased number of participating labs did not degrade the observed dispersion of the results for a similar activity level. Therefore, the results do not seem to depend on the analytical procedure used. From this work an optimised procedure can start to be developed to deal with OBT analysis and will guide subsequent planned OBT trials by the international group.« less

What are the Starting Points? Evaluating Base-Year Assumptions in the Asian Modeling Exercise

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

Chaturvedi, Vaibhav; Waldhoff, Stephanie; Clarke, Leon E.

2012-12-01

A common feature of model inter-comparison efforts is that the base year numbers for important parameters such as population and GDP can differ substantially across models. This paper explores the sources and implications of this variation in Asian countries across the models participating in the Asian Modeling Exercise (AME). Because the models do not all have a common base year, each team was required to provide data for 2005 for comparison purposes. This paper compares the year 2005 information for different models, noting the degree of variation in important parameters, including population, GDP, primary energy, electricity, and CO2 emissions. Itmore » then explores the difference in these key parameters across different sources of base-year information. The analysis confirms that the sources provide different values for many key parameters. This variation across data sources and additional reasons why models might provide different base-year numbers, including differences in regional definitions, differences in model base year, and differences in GDP transformation methodologies, are then discussed in the context of the AME scenarios. Finally, the paper explores the implications of base-year variation on long-term model results.« less

On the climate policy implications of substitutability and flexibility in the economy: An in-depth integrated assessment model diagnostic

DOE PAGES

Craxton, Melanie; Merrick, James; Makridis, Christos; ...

2017-07-12

This paper conducts an in-depth model diagnostic exercise for two parameters, 1) the elasticity of substitution between the capital/labour aggregate and the energy aggregate in the Integrated Assessment Model (IAM) MERGE's production function and 2) the rate at which new technologies can be deployed within the energy system. We show that in a more complementary world the model's ability to adjust the carbon intensity of its energy sector is more important whereas in a more substitutable world the ability to expand carbon free technologies is of lesser relative importance. The uncertainty in the literature surrounding the elasticity of substitution parameter,more » its interaction with the mechanisms of technical change, and the associated danger of grounding forward-looking analyses in historically based parameters lend support to the importance of such a diagnostic exercise. Building on work from model intercomparison studies, we investigate whether a given model's choice of strategy is primarily a function of the choice of its parameter values or its structure. As a result, a deeper understanding of what drives model behaviour is beneficial to both modellers and the policymakers who utilise their insights and output.« less

AFRRI (Armed Forces Radiobiology Research Institute) Reports, January-March 1985

DTIC Science & Technology

1985-01-01

monkey and human gastric functions Address osl i ,194 Arorlett: July~ (1, 1118. (6). .). and thle drug dosage was close to that ustid inAi~oattno...ionization chambers this requires the use of the two- * dosimeter method. One of the chambers is constructed of A-150 tissue- equivalent (TE) plastic, and...out excessively high flow rates. A photon energy-compensated Geiger- * Muller (GM) dosimeter is often used as the second dosimeter . However

Technology Assessment and Roadmap for the Emergency Radiation Dose Assessment Program (ERDAP)

DTIC Science & Technology

2005-06-01

l2O3:C OSL dosimeters . Overall design is based on similar systems described earlier by Justus et al. (1999) and Huston et al. (2001). Similar apparatus...Radioisotope Contamination 4. Pre-Positioned Physical Dosimeters C. Assessment of Emerging Dosimetry Technologies 1. Biological Measurements 2. Physico...architectures for radiation dose assessment tools. • Focus initial studies on defining the role of pre-positioned dosimeters , optimizing the size and

[Polymer Gel Dosimeter].

PubMed

Hayashi, Shin-Ichiro

2017-01-01

With rapid advances being made in radiotherapy treatment, three-dimensional (3D) dose measurement techniques of great precision are required more than ever before. It is expected that 3D polymer gel dosimeters will satisfy clinical needs for an effective detector that can measure the complex 3D dose distributions. Polymer gel dosimeters are devices that utilize the radiation-induced polymerization reactions of vinyl monomers in a gel to store information about radiation dose. The 3D absorbed dose distribution can be deduced from the resulting polymer distribution using several imaging modalities, such as MRI, X-ray and optical CTs. In this article, the fundamental characteristics of polymer gel dosimeter are reviewed and some challenging keys are also suggested for the widely spread in clinical use.

Comprehensive Australasian multicentre dosimetric intercomparison: issues, logistics and recommendations.

PubMed

Ebert, M A; Harrison, K M; Cornes, D; Howlett, S J; Joseph, D J; Kron, T; Hamilton, C S; Denham, J W

2009-02-01

The present paper describes the logistics of the 2004-2008 Australasian Level III Dosimetry Intercomparison. Dosimetric intercomparisons (or 'audits') can be used in radiotherapy to evaluate the accuracy and quality of radiation delivery. An intercomparison was undertaken in New Zealand and Australia to evaluate the feasibility and logistics of ongoing dosimetric intercomparisons that evaluate all steps in the radiotherapy treatment process, known as a 'Level III' intercomparison. The study commenced in 2002 with the establishment of a study team, definition of the study protocol, acquisition of appropriate equipment and recruitment of participating radiotherapy centres. Measurements were undertaken between October 2004 and March 2008, and included collation of data on time, costs and logistics of the study. Forty independent Australian and New Zealand radiotherapy centres agreed to participate. Measurement visits were made to 37 of these centres. Data is presented on the costs of the study and the level of support required. The study involved the participation of 16 staff at the study centre who invested over 4000 hours in the study, and of over 200 professionals at participating centres. Recommendations are provided for future phantom-based intercomparisons. It is hoped that the present paper will be of benefit to any centres or groups contemplating similar activities by identifying the processes involved in establishing the study, the potential hazards and pitfalls, and expected resource requirements.

Intercomparison of OH and OH reactivity measurements in a high isoprene and low NO environment during the Southern Oxidant and Aerosol Study (SOAS)

NASA Astrophysics Data System (ADS)

Sanchez, Dianne; Jeong, Daun; Seco, Roger; Wrangham, Ian; Park, Jeong-Hoo; Brune, William H.; Koss, Abigail; Gilman, Jessica; de Gouw, Joost; Misztal, Pawel; Goldstein, Allen; Baumann, Karsten; Wennberg, Paul O.; Keutsch, Frank N.; Guenther, Alex; Kim, Saewung

2018-02-01

We intercompare OH and OH reactivity datasets from two different techniques, chemical ionization mass spectrometry (CIMS) and laser-induced fluorescence (LIF) in a high isoprene and low NO environment in a southeastern US forest during the Southern Oxidant and Aerosol Study (SOAS). An LIF instrument measured OH and OH reactivity at the top of a tower, a CIMS instrument measured OH at the top of the tower, and a CIMS based comparative reactivity method (CRM-CIMS) instrument deployed at the base of the tower measured OH reactivity. Averaged diel variations of OH and OH reactivity from these datasets agree within analytical uncertainty and correlations of LIF versus CIMS for OH and OH reactivity have slopes of 0.65 and 0.97, respectively. However, there are systematic differences between the measurement datasets. The CRM-CIMS measurements of OH reactivity were ∼16% lower than those by the LIF technique in the late afternoon. We speculate that it is caused by losses in the sampling line down to the CRM-CIMS instrument. On the other hand, we could not come up with a reasonable explanation for the difference in the LIF and CIMS OH datasets for early morning and late afternoon when OH is below 1 × 106 molecules cm-3. Nonetheless, results of this intercomparison exercise strengthen previous publications from the field site on OH concentrations and atmospheric reactivity.

Characterization and implementation of OSL dosimeters for use in evaluating the efficacy of organ-based tube current modulation for CT scans of the face and orbits

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

Marsh, R. M.; Silosky, M., E-mail: michael.silosky@ucdenver.edu

Purpose: The purpose of this work was to characterize commercially available optically stimulated luminescent (OSL) dosimeters for general clinical applications and apply the results to the development of a method to evaluate the efficacy of a vendor-specific organ-based tube current modulation application for both phantom and clinical computed tomography (CT) scans of the face and orbits. Methods: This study consisted of three components: (1) thorough characterization of the dosimeters for CT scans in phantom, including evaluations of depletion, fading, angular dependence, and conversion from counts to absorbed dose; (2) evaluation of the efficacy of using plastic glasses to position themore » dosimeters over the eyes in both phantom and clinical studies; and (3) preliminary dosimetry measurements made using organ-based tube current modulation in computed tomography dose index (CTDI) and anthropomorphic phantom studies. Results: (1) Depletion effects were found to have a linear relationship with the output of the OSL dosimeters (R{sup 2} = 0.96). Fading was found to affect dosimeter readings during the first two hours following exposure but had no effect during the remaining 60-h period observed. No significant angular dependence was observed for the exposure conditions used in this study (with p-values ranging from 0.9 to 0.26 for all t-tests). Dosimeter counts varied linearly with absorbed dose when measured in the center and 12 o’clock positions of the CTDI phantoms. These linear models of counts versus absorbed dose had overlapping 95% confidence intervals for the intercepts but not for the slopes. (2) When dosimeters were positioned using safety glasses, there was no adverse effect on image quality, and there was no statistically significant difference between this placement and placement of the dosimeters directly on the eyes of the phantom (p = 0.24). (3) When using organ-based tube current modulation, the dose to the lens of the eye was reduced between 19% and 43%, depending on the scan protocol used and the positioning of the phantom. Furthermore, the amount of dose reduction was significantly affected by the vertical position of the phantom, with the largest reduction in dose seen when the phantom was centered in the gantry. Conclusions: (1) An appropriate correction factor, specific to CT scanning, was developed to account for depletion and fading characteristics of the dosimeters. Additionally, an equation to convert dosimeter counts to absorbed dose was established. (2) The use of plastic safety glasses was validated as an appropriate positioning device when measuring dose to the lens of the eye. (3) The use of organ-based tube current modulation can reduce dose to the lens of the eye during CT scanning. The amount of dose reduction, however, is largely influenced by the positioning of the anatomy in the gantry.« less

Characterization and implementation of OSL dosimeters for use in evaluating the efficacy of organ-based tube current modulation for CT scans of the face and orbits.

PubMed

Marsh, R M; Silosky, M

2015-04-01

The purpose of this work was to characterize commercially available optically stimulated luminescent (OSL) dosimeters for general clinical applications and apply the results to the development of a method to evaluate the efficacy of a vendor-specific organ-based tube current modulation application for both phantom and clinical computed tomography (CT) scans of the face and orbits. This study consisted of three components: (1) thorough characterization of the dosimeters for CT scans in phantom, including evaluations of depletion, fading, angular dependence, and conversion from counts to absorbed dose; (2) evaluation of the efficacy of using plastic glasses to position the dosimeters over the eyes in both phantom and clinical studies; and (3) preliminary dosimetry measurements made using organ-based tube current modulation in computed tomography dose index (CTDI) and anthropomorphic phantom studies. (1) Depletion effects were found to have a linear relationship with the output of the OSL dosimeters (R(2) = 0.96). Fading was found to affect dosimeter readings during the first two hours following exposure but had no effect during the remaining 60-h period observed. No significant angular dependence was observed for the exposure conditions used in this study (with p-values ranging from 0.9 to 0.26 for all t-tests). Dosimeter counts varied linearly with absorbed dose when measured in the center and 12 o'clock positions of the CTDI phantoms. These linear models of counts versus absorbed dose had overlapping 95% confidence intervals for the intercepts but not for the slopes. (2) When dosimeters were positioned using safety glasses, there was no adverse effect on image quality, and there was no statistically significant difference between this placement and placement of the dosimeters directly on the eyes of the phantom (p = 0.24). (3) When using organ-based tube current modulation, the dose to the lens of the eye was reduced between 19% and 43%, depending on the scan protocol used and the positioning of the phantom. Furthermore, the amount of dose reduction was significantly affected by the vertical position of the phantom, with the largest reduction in dose seen when the phantom was centered in the gantry. (1) An appropriate correction factor, specific to CT scanning, was developed to account for depletion and fading characteristics of the dosimeters. Additionally, an equation to convert dosimeter counts to absorbed dose was established. (2) The use of plastic safety glasses was validated as an appropriate positioning device when measuring dose to the lens of the eye. (3) The use of organ-based tube current modulation can reduce dose to the lens of the eye during CT scanning. The amount of dose reduction, however, is largely influenced by the positioning of the anatomy in the gantry.

Anisotropic mesh adaptation for marine ice-sheet modelling

NASA Astrophysics Data System (ADS)

Gillet-Chaulet, Fabien; Tavard, Laure; Merino, Nacho; Peyaud, Vincent; Brondex, Julien; Durand, Gael; Gagliardini, Olivier

2017-04-01

Improving forecasts of ice-sheets contribution to sea-level rise requires, amongst others, to correctly model the dynamics of the grounding line (GL), i.e. the line where the ice detaches from its underlying bed and goes afloat on the ocean. Many numerical studies, including the intercomparison exercises MISMIP and MISMIP3D, have shown that grid refinement in the GL vicinity is a key component to obtain reliable results. Improving model accuracy while maintaining the computational cost affordable has then been an important target for the development of marine icesheet models. Adaptive mesh refinement (AMR) is a method where the accuracy of the solution is controlled by spatially adapting the mesh size. It has become popular in models using the finite element method as they naturally deal with unstructured meshes, but block-structured AMR has also been successfully applied to model GL dynamics. The main difficulty with AMR is to find efficient and reliable estimators of the numerical error to control the mesh size. Here, we use the estimator proposed by Frey and Alauzet (2015). Based on the interpolation error, it has been found effective in practice to control the numerical error, and has some flexibility, such as its ability to combine metrics for different variables, that makes it attractive. Routines to compute the anisotropic metric defining the mesh size have been implemented in the finite element ice flow model Elmer/Ice (Gagliardini et al., 2013). The mesh adaptation is performed using the freely available library MMG (Dapogny et al., 2014) called from Elmer/Ice. Using a setup based on the inter-comparison exercise MISMIP+ (Asay-Davis et al., 2016), we study the accuracy of the solution when the mesh is adapted using various variables (ice thickness, velocity, basal drag, …). We show that combining these variables allows to reduce the number of mesh nodes by more than one order of magnitude, for the same numerical accuracy, when compared to uniform mesh refinement. For transient solutions where the GL is moving, we have implemented an algorithm where the computation is reiterated allowing to anticipate the GL displacement and to adapt the mesh to the transient solution. We discuss the performance and robustness of this algorithm.

The Ice Sheet Mass Balance Inter-comparison Exercise

NASA Astrophysics Data System (ADS)

Shepherd, A.; Ivins, E. R.

2015-12-01

Fluctuations in the mass of ice stored in Antarctica and Greenland are of considerable societal importance. The Ice Sheet Mass Balance Inter-Comparison Exercise (IMBIE) is a joint-initiative of ESA and NASA aimed at producing a single estimate of the global sea level contribution to polar ice sheet losses. Within IMBIE, estimates of ice sheet mass balance are developed from a variety of satellite geodetic techniques using a common spatial and temporal reference frame and a common appreciation of the contributions due to external signals. The project brings together the laboratories and space agencies that have been instrumental in developing independent estimates of ice sheet mass balance to date. In its first phase, IMBIE involved 27 science teams, and delivered a first community assessment of ice sheet mass imbalance to replace 40 individual estimates. The project established that (i) there is good agreement between the three main satellite-based techniques for estimating ice sheet mass balance, (ii) combining satellite data sets leads to significant improvement in certainty, (iii) the polar ice sheets contributed 11 ± 4 mm to global sea levels between 1992 and 2012, and (iv) that combined ice losses from Antarctica and Greenland have increased over time, rising from 10% of the global trend in the early 1990's to 30% in the late 2000's. Demand for an updated assessment has grown, and there are now new satellite missions, new geophysical corrections, new techniques, and new teams producing data. The period of overlap between independent satellite techniques has increased from 5 to 12 years, and the full period of satellite data over which an assessment can be performed has increased from 19 to 40 years. It is also clear that multiple satellite techniques are required to confidently separate mass changes associated with snowfall and ice dynamical imbalance - information that is of critical importance for climate modelling. This presentation outlines the approach for the second phase of IMBIE, including the project organisation, the work programme and schedule, the main science goals, and its current status, and reviews the recent and historical contributions that the Antarctic and Greenland ice sheets have made to global sea level rise.

The Assessment of Atmospheric Correction Processors for MERIS Based on In-Situ Measurements-Updates in OC-CCI Round Robin

NASA Astrophysics Data System (ADS)

Muller, Dagmar; Krasemann, Hajo; Zuhilke, Marco; Doerffer, Roland; Brockmann, Carsten; Steinmetz, Francois; Valente, Andre; Brotas, Vanda; Grant, kMicheal G.; Sathyendranath, Shubha; Melin, Frederic; Franz, Bryan A.; Mazeran, Constant; Regner, Peter

2016-08-01

The Ocean Colour Climate Change Initiative (OC- CCI) provides a long-term time series of ocean colour data and investigates the detectable climate impact. A reliable and stable atmospheric correction (AC) procedure is the basis for ocean colour products of the necessary high quality.The selection of atmospheric correction processors is repeated regularly based on a round robin exercise, at the latest when a revised production and release of the OC-CCI merged product is scheduled. Most of the AC processors are under constant development and changes are implemented to improve the quality of satellite-derived retrievals of remote sensing reflectances. The changes between versions of the inter-comparison are not restricted to the implementation of AC processors. There are activities to improve the quality flagging for some processors, and the system vicarious calibration for AC algorithms in their sensor specific behaviour are widely studied. Each inter-comparison starts with an updated in-situ database, as more spectra are included in order to broaden the temporal and spatial range of satellite match-ups. While the OC-CCI's focus has laid on case-1 waters in the past, it has expanded to the retrieval of case-2 products now. In light of this goal, new bidirectional correction procedures (normalisation) for the remote sensing spectra have been introduced. As in-situ measurements are not always available at the satellite sensor specific central wave- lengths, a band-shift algorithm has to be applied to the dataset.In order to guarantee an objective selection from a set of four atmospheric correction processors, the common validation strategy of comparisons between in-situ and satellite-derived water leaving reflectance spectra, is aided by a ranking system. In principal, the statistical parameters are transformed into relative scores, which evaluate the relationship of quality dependent on the algorithms under study. The sensitivity of these scores to the selected database has been assessed by a bootstrapping exercise, which allows identification of the uncertainty in the scoring results.A comparison of round robin results for the OC-CCI version 2 and the current version 3 is presented and some major changes are highlighted.

Solar UV exposure among outdoor workers in Denmark measured with personal UV-B dosimeters: technical and practical feasibility.

PubMed

Grandahl, Kasper; Mortensen, Ole Steen; Sherman, David Zim; Køster, Brian; Lund, Paul-Anker; Ibler, Kristina Sophie; Eriksen, Paul

2017-10-10

Exposure to solar ultraviolet radiation is a well-known cause of skin cancer. This is problematic for outdoor workers. In Denmark alone, occupational skin cancer poses a significant health and safety risk for around 400,000 outdoor workers. Objective measures of solar ultraviolet radiation exposure are needed to help resolve this problem. This can be done using personal ultraviolet radiation dosimeters. We consider technical and practical feasibility of measuring individual solar ultraviolet exposure at work and leisure in professions with different á priori temporal high-level outdoor worktime, using aluminium gallium nitride (AlGaN) photodiode detector based personal UV-B dosimeters. Essential technical specifications including the spectral and angular responsivity of the dosimeters are described and pre-campaign dosimeter calibration applicability is verified. The scale and conduct of dosimeter deployment and campaign in-field measurements including failures and shortcomings affecting overall data collection are presented. Nationwide measurements for more than three hundred and fifty workers from several different professions were collected in the summer of 2016. On average, each worker's exposure was measured for a 2-week period, which included both work and leisure. Data samples of exposure at work during a Midsummer day show differences across professions. A construction worker received high-level occupational UV exposure most of the working day, except during lunch hour, accumulating to 5.1 SED. A postal service worker was exposed intermittently around noon and in the afternoon, preceded by no exposure forenoon when packing mail, accumulating to 1.6 SED. A crane fitter was exposed only during lunch hour, accumulating to 0.7 SED. These findings are in line with our specialist knowledge as occupational physicians. Large-scale use of personal UV-B dosimeters for measurement of solar ultraviolet radiation exposure at work and leisure in Denmark is indeed feasible from a technical and practical viewpoint. Samples of exposure data shown support the presumption that the Danish campaign UV-B dosimeter measurement dataset can be used to sum and compare exposure between groups of professions with reliable results to be used in future analysis with clinical as well as epidemiological/questionnaire data. This was despite some dosimeter failures and shortcomings.

Initial Characterization of a Gel Patch Dosimeter for In Vivo Dosimetry

PubMed Central

Matrosic, C; Culberson, W; Rosen, B; Madsen, E; Frank, G; Bednarz, B

2016-01-01

In vivo dosimetry is a greatly underutilized tool for patient safety in clinical external beam radiotherapy treatments, despite being recommended by several national and international organizations (AAPM, ICRU, IAEA, NACP). The reasons for this underutilization mostly relate to the feasibility and cost of in vivo dosimetry methods. Due to the increase in the number of beam angles and dose per fraction in modern treatments, there is a compelling need for a novel dosimeter that is robust and affordable while able to operate properly in these complex conditions. This work presents a gel patch dosimeter as a novel method of in vivo dosimetry. DEFGEL, a 6%T normoxic polyacrylamide gel, was injected into 1-cm thick acrylic molds to create 1-cm thick small cylindrical patch dosimeters. To evaluate the change in optical density due to radiation induced polymerization, dosimeters were scanned before and after irradiation using an in-house developed laser densitometer. The dose-responses of three separate batches of gel were evaluated and compared to check for linearity and repeatability. The response development time was evaluated to ensure that the patch dosimeter could be high throughput. Additionally, the potential of this system to be used as an in vivo dosimeter was tested with a clinically relevant end-to-end in vivo phantom test. All irradiations were performed with a Varian Clinac 21EX at the University of Wisconsin Medical Radiation Research Center (UWMRRC). The dose response of all three batches of gel was found to be linear within the range of 2–20 Gy. At doses below 0.5 Gy the statistical uncertainties were prohibitively large to make quantitative assessments of the results. The three batches demonstrated good repeatability in the range of 2 Gy to up to 10 Gy, with only slight variations in response at higher doses. For low doses the dosimeter fully developed within an hour while at higher doses they fully developed within four hours. During the in vivo phantom test the predicted patch absorbed dose was 4.23 Gy while the readout dose was evaluated to be 4.37 Gy, which corresponds to a 3.2% discrepancy. The dosimeter and densitometer pairing shows promise as an in vivo dosimetry system, especially for hypofractionated or MRI-guided radiotherapy treatments where higher doses are prescribed. PMID:27088207

Initial characterization of a gel patch dosimeter for in vivo dosimetry

NASA Astrophysics Data System (ADS)

Matrosic, C.; Culberson, W.; Rosen, B.; Madsen, E.; Frank, G.; Bednarz, B.

2016-05-01

In vivo dosimetry is a greatly underutilized tool for patient safety in clinical external beam radiotherapy treatments, despite being recommended by several national and international organizations (AAPM, ICRU, IAEA, NACP). The reasons for this underutilization mostly relate to the feasibility and cost of in vivo dosimetry methods. Due to the increase in the number of beam angles and dose per fraction in modern treatments, there is a compelling need for a novel dosimeter that is robust and affordable while able to operate properly in these complex conditions. This work presents a gel patch dosimeter as a novel method of in vivo dosimetry. DEFGEL, a 6% T normoxic polyacrylamide gel, was injected into 1 cm thick acrylic molds to create 1 cm thick small cylindrical patch dosimeters. To evaluate the change in optical density due to radiation induced polymerization, dosimeters were scanned before and after irradiation using an in-house developed laser densitometer. The dose-responses of three separate batches of gel were evaluated and compared to check for linearity and repeatability. The response development time was evaluated to ensure that the patch dosimeter could be high throughput. Additionally, the potential of this system to be used as an in vivo dosimeter was tested with a clinically relevant end-to-end in vivo phantom test. All irradiations were performed with a Varian Clinac 21EX at the University of Wisconsin Medical Radiation Research Center (UWMRRC). The dose-response of all three batches of gel was found to be linear within the range of 2-20 Gy. At doses below 0.5 Gy the statistical uncertainties were prohibitively large to make quantitative assessments of the results. The three batches demonstrated good repeatability in the range of 2 Gy to up to 10 Gy, with only slight variations in response at higher doses. For low doses the dosimeter fully developed within an hour while at higher doses they fully developed within four hours. During the in vivo phantom test the predicted patch absorbed dose was 4.23 Gy while the readout dose was evaluated to be 4.37 Gy, which corresponds to a 3.2% discrepancy. The dosimeter and densitometer pairing shows promise as an in vivo dosimetry system, especially for hypofractionated or MRI-guided radiotherapy treatments where higher doses are prescribed.

SU-E-T-353: Effects of Time and Temperature On a Potential Reusable 3D Dosimeter

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

Juang, T; Miles, D; Crockett, E

Purpose: Preliminary studies of a novel, optically-clearing PRESAGE 3D dosimeter formulation (Presage-RU) demonstrated potential reusability. This study investigates the effects of time and temperature on the accuracy and reusability of Presage-RU, and reports on progress toward developing a reusable 3D dosimeter. Methods: Presage-RU was cast as small volume samples (1×1×4.5cm). The effect of dose response sensitivity with reirradiation and time was evaluated by irradiating samples from 0–10Gy, measuring change in optical density (ΔOD), clearing at room temperature (RT) (5–7 days to fully clear), and then repeating for a total of 5 irradiations. Effects of heating on clearing rate were investigatedmore » by irradiating samples to 8Gy, then tracking measurements with samples held at RT, 35°C, and 45°C. Two cylindrical dosimeters (11cm diameter, 9.5cm length) were evaluated for dosimetric accuracy when stored at RT and −3°C prior to irradiation. Plans delivered were 2 overlapping AP fields (RT) and VMAT (-3°C). Results: Heating the dosimeters reduced the clearing half-life from 16.3h at RT to 5.8h (35°C) and 5.1h (45°C), but also increased background ΔOD by 1.7x (35°C) and 2.3x (45°C). Reductions in dose response were more closely linked to age than reirradiation, and storage at RT showed pronounced desensitization from dosimeter edges. These results suggest desensitization from oxygen diffusion. It should be noted that atmospheric diffusion into the dosimeter is not seen in standard, single-use PRESAGE, and is likely caused by differences in the Presage-RU polyurethane matrix. The dosimeter kept in cold storage, however, showed no evidence of desensitization and exhibited accuracy on par with standard PRESAGE with a 3%/3mm 3D gamma passing rate of 98.1%. Conclusions: Presage-RU is sensitive to storage temperatures and time, both of which affect oxygen diffusion and subsequent desensitization. Development shows promising progress with further formulation optimization as the next step toward achieving a successful reusable 3D dosimeter. This work was supported by NIH R01CA100835. John Adamovics is the president of Heuris Inc., which commercializes PRESAGE.« less

Radiation Measured with Different Dosimeters for ISS-Expedition 18-19/ULF2 on Board International Space Station during Solar Minimum

NASA Technical Reports Server (NTRS)

Zhou, Dazhuang; Gaza, R.; Roed, Y.; Semones, E.; Lee, K.; Steenburgh, R.; Johnson, S.; Flanders, J.; Zapp, N.

2010-01-01

Radiation field of particles in low Earth orbit (LEO) is mainly composed of galactic cosmic rays (GCR), solar energetic particles and particles in SAA (South Atlantic Anomaly). GCR are modulated by solar activity, at the period of solar minimum activity, GCR intensity is at maximum and the main contributor for space radiation is GCR. At present for space radiation measurements conducted by JSC (Johnson Space Center) SRAG (Space Radiation Analysis Group), the preferred active dosimeter sensitive to all LET (Linear Energy Transfer) is the tissue equivalent proportional counter (TEPC); the preferred passive dosimeters are thermoluminescence dosimeters (TLDs) and optically stimulated luminescence dosimeters (OSLDs) sensitive to low LET as well as CR-39 plastic nuclear track detectors (PNTDs) sensitive to high LET. For the method using passive dosimeters, radiation quantities for all LET can be obtained by combining radiation results measured with TLDs/OSLDs and CR-39 PNTDs. TEPC, TLDs/OSLDs and CR-39 detectors were used to measure the radiation field for the ISS (International Space Station) - Expedition 18-19/ULF2 space mission which was conducted from 15 November 2008 to 31 July 2009 - near the period of the recent solar minimum activity. LET spectra (differential and integral fluence, absorbed dose and dose equivalent) and radiation quantities were measured for positions TEPC, TESS (Temporary Sleeping Station, inside the polyethylene lined sleep station), SM-P 327 and 442 (Service Module - Panel 327 and 442). This paper presents radiation LET spectra measured with TEPC and CR-39 PNTDs and radiation dose measured with TLDs/OSLDs as well as the radiation quantities combined from results measured with passive dosimeters.

SU-E-T-274: Does Atmospheric Oxygen Affect the PRESAGE Dosimeter?

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

Alqathami, M; Ibbott, G; Blencowe, A

Purpose: To experimentally determine the influence of atmospheric oxygen on the efficiency of the PRESAGE dosimeter and its reporting system. Methods: Batches of the reporting system – a mixture of chloroform and leuchomalachite green dye – and PRESAGE were prepared in aerobic and anaerobic conditions. For anaerobic batches, samples were deoxygenated by bubbling nitrogen through the dosimeter precursors or reporting system for 10 min. The dosimeters and reporting systems were prepared in spectrophotometric cuvettes and glass vials, respectively, and were irradiated with 6 MV photons to various radiation doses using a clinical linear accelerator. Changes in optical density of themore » dosimeters and reporting system before and after irradiation were measured using a spectrophotometer. In addition, the concentrations of dissolved oxygen were measured using a dissolved oxygen meter. Results: The experiments revealed that oxygen has little influence on the characteristics of PRESAGE, with the radical initiator oxidizing the leucomalachite green even in the presence of oxygen. However, deoxygenation of the reporting system leads to an increase in sensitivity to radiation dose by ∼ 30% when compared to the non-deoxygenated system. A slight improvement in sensitivity (∼ 5%) was also achieved by deoxygenating the PRESAGE precursor prior to casting. Measurement of the dissolved oxygen revealed low levels (0.4 ppm) in the polyurethane precursor used to fabricate the dosimeters, as compared to water (8.6 ppm). In addition, deoxygenation had no effect on the retention of the post-response absorption value of the PRESAGE dosimeter. Conclusion: The results suggest that the presence of oxygen does not inhibit the radiochromic properties of the PRESAGE system. In addition, there were no observed changes in the dose linearity, absorption spectrum and post-response photofading characteristics of the PRESAGE under the conditions investigated.« less

The development of remote wireless radiation dose monitoring system

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

Lee, Jin-woo; Chonbuk National University, Jeonjoo-Si; Jeong, Kyu-hwan

Internet of things (IoT) technology has recently shown a large flow of IT trends in human life. In particular, our lives are now becoming integrated with a lot of items around the 'smart-phone' with IoT, including Bluetooth, Near Field Communication (NFC), Beacons, WiFi, and Global Positioning System (GPS). Our project focuses on the interconnection of radiation dosimetry and IoT technology. The radiation workers at a nuclear facility should hold personal dosimeters such as a Thermo-Luminescence Dosimeter (TLD), an Optically Stimulated Luminescence Dosimeter (OSL), pocket ionization chamber dosimeters, an Electronic Personal Dosimeter (EPD), or an alarm dosimeter on their body. Somemore » of them have functions that generate audible or visible alarms to radiation workers in a real working area. However, such devices used in radiation fields these days have no functions for communicating with other areas or the responsible personnel in real time. In particular, when conducting a particular task in a high dose area, or a number of repair works within a radiation field, radiation dose monitoring is important for the health of the workers and the work efficiency. Our project aims at the development of a remote wireless radiation dose monitoring system (RWRD) that can be used to monitor the radiation dose in a nuclear facility for radiation workers and a radiation protection program In this project, a radiation dosimeter is the detection device for personal radiation dose, a smart phone is the mobile wireless communication tool, and, Beacon is the wireless starter for the detection, communication, and position of the worker using BLE (Bluetooth Low Energy). In this report, we report the design of the RWRD and a demonstration case in a real radiation field. (authors)« less

An Efficient, Affordable Optically Stimulated Luminescent (OSL) Annealer.

PubMed

Abraham, Sara A; Frank, Samuel J; Kearfott, Kimberlee J

2017-07-01

Optically stimulated luminescent (OSL) dosimeters are devices used for measuring doses of ionizing radiation. Signal is stored within an OSL material so that when stimulated with light, light of a specific wavelength is emitted in proportion to the integrated ionizing radiation dose. Each interrogation of the material results in the loss of a small fraction of signal, thus allowing multiple interrogations leading to more accurate measurements of dose. In order to reuse a dosimeter, the residual signals from prior doses must be taken into account and subtracted from current readings, adding uncertainty to any future measurements. To reduce these errors when they become large, it is desirable to completely clear the stored signal or anneal the dosimeter. Traditionally, heating the material has accomplished this. In a commercially available dosimeter badge system, the OSL material Al2O3:C is incorporated into a plastic slide that would melt at the necessary high temperatures, which can reach 900 °C, required for annealing. Fortunately, due to the material's high sensitivity to light, OSLs can be optically annealed instead. In order to do this, an affordable OSL dosimeter annealer was designed with inexpensive, exchangeable blue, green, and white high intensity light-emitting diodes (LEDs). Several dosimeters were repeatedly annealed for recorded intervals and then read out. A single dosimeter was partially annealed through repeated interrogations with the LED array from a commercial reader. The signal loss due to the exposure to each light was analyzed to determine the practicality and efficiency of each color. The rate and extent of signal loss was dependent not only on the spectrum of annealing light but on the initial signal levels as well. These findings suggest that blue LEDs are the most promising for effective and rapid clearing of the OSL material Al2O3:C.

Fiber-optic dosimeters for radiation therapy

NASA Astrophysics Data System (ADS)

Li, Enbang; Archer, James

2017-10-01

According to the figures provided by the World Health Organization, cancer is a leading cause of death worldwide, accounting for 8.8 million deaths in 2015. Radiation therapy, which uses x-rays to destroy or injure cancer cells, has become one of the most important modalities to treat the primary cancer or advanced cancer. The newly developed microbeam radiation therapy (MRT), which uses highly collimated, quasi-parallel arrays of x-ray microbeams (typically 50 μm wide and separated by 400 μm) produced by synchrotron sources, represents a new paradigm in radiotherapy and has shown great promise in pre-clinical studies on different animal models. Measurements of the absorbed dose distribution of microbeams are vitally important for clinical acceptance of MRT and for developing quality assurance systems for MRT, hence are a challenging and important task for radiation dosimetry. On the other hand, during the traditional LINAC based radiotherapy and breast cancer brachytherapy, skin dose measurements and treatment planning also require a high spatial resolution, tissue equivalent, on-line dosimeter that is both economical and highly reliable. Such a dosimeter currently does not exist and remains a challenge in the development of radiation dosimetry. High resolution, water equivalent, optical and passive x-ray dosimeters have been developed and constructed by using plastic scintillators and optical fibers. The dosimeters have peak edge-on spatial resolutions ranging from 50 to 500 microns in one dimension, with a 10 micron resolution dosimeter under development. The developed fiber-optic dosimeters have been test with both LINAC and synchrotron x-ray beams. This work demonstrates that water-equivalent and high spatial resolution radiation detection can be achieved with scintillators and optical fiber systems. Among other advantages, the developed fiber-optic probes are also passive, energy independent, and radiation hard.

Selection and use of TLDS for high precision NERVA shielding measurements

NASA Technical Reports Server (NTRS)

Woodsum, H. C.

1972-01-01

An experimental evaluation of thermoluminescent dosimeters was performed in order to select high precision dosimeters for a study whose purpose is to measure gamma streaming through the coolant passages of a simulated flight type internal NERVA reactor shield. Based on this study, the CaF2 chip TLDs are the most reproducible dosimeters with reproducibility generally within a few percent, but none of the TLDs tested met the reproducibility criterion of plus or minus 2%.

Measurement of dose given by Co-60 in radiotherapy with TLD-500

NASA Astrophysics Data System (ADS)

Tanır, Güneş; Cengiz, Ferhat; Hicabi Bölükdemir, M.

2012-04-01

The uses of dosimeters based on optically stimulated luminescence technique have become widespread in clinical applications. In the present study, the dose values given by Cobalt-60 radiotherapy machine were measured with optically stimulated luminescence (OSL) technique using TLD-500 and compared with those of commonly used ionization chamber dosimeter system. The percentage depth dose (DD%) values and graphs were formed. OSL system with TLD-500 can be reliably used as medical and personal dosimeter.

Dosimeter incorporating radiophotoluminescent detectors for thermal neutrons and γ-rays in n-γ fields

NASA Astrophysics Data System (ADS)

Salem, Y. O.; Nachab, A.; Roy, C.; Nourreddine, A.

2016-10-01

We have developed a dosimeter associating different neutron converters with two radiophotoluminescent detectors to measure thermal neutrons and γ-rays in a mixed n-γ field. Tests show that the H∗(10) and Hp(10) responses to thermal neutrons and γ-rays are linear with detection limits lower than 0.4 mSv. The angular dependence of the dosimeter response is satisfactory and the influence of a phantom on the results is examined.

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

High-precision dosimetry for radiotherapy using the optically stimulated luminescence technique and thin Al2O3:C dosimeters.

PubMed

Yukihara, E G; Yoshimura, E M; Lindstrom, T D; Ahmad, S; Taylor, K K; Mardirossian, G

2005-12-07

The potential of using the optically stimulated luminescence (OSL) technique with aluminium oxide (Al(2)O(3):C) dosimeters for a precise and accurate estimation of absorbed doses delivered by high-energy photon beams was investigated. This study demonstrates the high reproducibility of the OSL measurements and presents a preliminary determination of the depth-dose curve in water for a 6 MV photon beam from a linear accelerator. The uncertainty of a single OSL measurement, estimated from the variance of a large sample of dosimeters irradiated with the same dose, was 0.7%. In the depth-dose curve obtained using the OSL technique, the difference between the measured and expected doses was < or =0.7% for depths between 1.5 and 10 cm, and 1.1% for a depth of 15 cm. The readout procedure includes a normalization of the response of the dosimeter with respect to a reference dose in order to eliminate variations in the dosimeter mass, dosimeter sensitivity, and the reader's sensitivity. This may be relevant for quality assurance programmes, since it simplifies the requirements in terms of personnel training to achieve the precision and accuracy necessary for radiotherapy applications. We concluded that the OSL technique has the potential to be reliably incorporated in quality assurance programmes and dose verification.

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

Development of Solid Ceramic Dosimeters for the Time-Integrative Passive Sampling of Volatile Organic Compounds in Waters.

PubMed

Bonifacio, Riza Gabriela; Nam, Go-Un; Eom, In-Yong; Hong, Yong-Seok

2017-11-07

Time-integrative passive sampling of volatile organic compounds (VOCs) in water can now be accomplished using a solid ceramic dosimeter. A nonporous ceramic, which excludes the permeation of water, allowing only gas-phase diffusion of VOCs into the resin inside the dosimeter, effectively captured the VOCs. The mass accumulation of 11 VOCs linearly increased with time over a wide range of aqueous-phase concentrations (16.9 to 1100 μg L -1 ), and the linearity was dependent upon the Henry's constant (H). The average diffusivity of the VOCs in the solid ceramic was 1.46 × 10 -10 m 2 s -1 at 25 °C, which was 4 orders of magnitude lower than that in air (8.09 × 10 -6 m 2 s -1 ). This value was 60% greater than that in the water-permeable porous ceramic (0.92 × 10 -10 m 2 s -1 ), suggesting that its mass accumulation could be more effective than that of porous ceramic dosimeters. The mass accumulation of the VOCs in the solid ceramic dosimeter increased in the presence of salt (≥0.1 M) and with increasing temperature (4 to 40 °C) but varied only slightly with dissolved organic matter concentration. The solid ceramic dosimeter was suitable for the field testing and measurement of time-weighted average concentrations of VOC-contaminated waters.

LOW-COST PERSONNEL DOSIMETER.

DTIC Science & Technology

specification was achieved by simplifying and improving the basic Bendix dosimeter design, using plastics for component parts, minimizing direct labor, and making the instrument suitable for automated processing and assembly. (Author)

Performance improvement of pentacosa-diynoic acid label dosimeter for radiation processing technology

NASA Astrophysics Data System (ADS)

Abdel-Fattah, A. A.; Soliman, Y. S.

2017-12-01

A radiation sensitive material, 10,12-pentacosa-diynoic acid (PCDA), was incorporated into polyvinyl butyral (PVB) films to develop indicators/dosimeters for blood and food irradiation. The present study aims to improve the dosimetric performance of these previously prepared dosimeters and to extend their shelf life by the combination of a radical scavenger, propyl gallate (PG), and a UV absorber, tinuvin-p (TP). The X-ray diffraction (XRD) patterns of the dosimeters were analysed and their dosimetric characteristics were investigated by specular reflectance in the visible spectrum range of 400-700 nm. Upon irradiation, the films turn blue exhibiting two main bands around 670 and 620 nm. Their dose-response functions were fitted by a double exponential growth, 5 parameters, equation. Irradiation temperature influences the dosimeter response at 670 nm without causing thermochromic transition up to 50 °C in poly-PCDA. The useful dose range is 5-4000 Gy depending on the wavelengths of analysis and PCDA content in the films. The overall uncertainty of dose measurement is less than 6% at 2σ.

Intercomparison of hydrologic processes in global climate models

NASA Technical Reports Server (NTRS)

Lau, W. K.-M.; Sud, Y. C.; Kim, J.-H.

1995-01-01

In this report, we address the intercomparison of precipitation (P), evaporation (E), and surface hydrologic forcing (P-E) for 23 Atmospheric Model Intercomparison Project (AMIP) general circulation models (GCM's) including relevant observations, over a variety of spatial and temporal scales. The intercomparison includes global and hemispheric means, latitudinal profiles, selected area means for the tropics and extratropics, ocean and land, respectively. In addition, we have computed anomaly pattern correlations among models and observations for different seasons, harmonic analysis for annual and semiannual cycles, and rain-rate frequency distribution. We also compare the joint influence of temperature and precipitation on local climate using the Koeppen climate classification scheme.

Evaluation of a LiF:Mg,Ti thermoluminescent ring dosimeter according to the IEC 62387:2012 Standards

NASA Astrophysics Data System (ADS)

Oliveira, Edyelle L. B.; de Barros, Vinícius S. M.; Asfora, Viviane K.; Khoury, Helen J.

2018-03-01

This work shows results of type testing of a ring radiation dosimeter system under IEC 62387:2012. The personal dosimeter investigated in this work consists of a commercial one element plastic ring which contains an LiF:Mg,Ti thermoluminescent pellet. By applying requirements for statistical fluctuations and linearity, a minimum measurable dose in Hp(0.07) was established. Energy and angular dependence aided in determining energy correction factors and fading requirements were used to select the most appropriate preheat scheme. Type testing of passive radiation monitors was performed in the Radiation Metrology Laboratory (LMRI-DEN/UFPE) of the Federal University of Pernambuco and is a major step in Brazil for the independent evaluation of these dosimeters, currently not available in the country.

Airborne sulfur trace species intercomparison campaign: Sulfur dioxide, dimethylsulfide, hydrogen sulfide, carbon disulfide, and carbonyl sulfide

NASA Technical Reports Server (NTRS)

Gregory, Gerald L.; Hoell, James M., Jr.; Davis, Douglas D.

1991-01-01

Results from an airborne intercomparison of techniques to measure tropospheric levels of sulfur trace gases are presented. The intercomparison was part of the NASA Global Tropospheric Experiment (GTE) and was conducted during the summer of 1989. The intercomparisons were conducted on the Wallops Electra aircraft during flights from Wallops Island, Virginia, and Natal, Brazil. Sulfur measurements intercompared included sulfur dioxide (SO2), dimethylsulfide (DMS), hydrogen sulfide (H2S), carbon disulfide (CS2), and carbonyl sulfide (OCS). Measurement techniques ranged from filter collection systems with post-flight analyses to mass spectrometer and gas chromatograph systems employing various methods for measuring and identifying the sulfur gases during flight. Sampling schedules for the techniques ranged from integrated collections over periods as long as 50 minutes to one- to three-minute samples every ten or fifteen minutes. Several of the techniques provided measurements of more than one sulfur gas. Instruments employing different detection principles were involved in each of the sulfur intercomparisons. Also included in the intercomparison measurement scenario were a host of supporting measurements (i.e., ozone, nitrogen oxides, carbon monoxide, total sulfur, aerosols, etc.) for purposes of: (1) interpreting results (i.e., correlation of any noted instrument disagreement with the chemical composition of the measurement environment); and (2) providing supporting chemical data to meet CITE-3 science objectives of studying ozone/sulfur photochemistry, diurnal cycles, etc. The results of the intercomparison study are briefly discussed.

Results from Preliminary Checks on AmBe Neutron Source Number 71

DTIC Science & Technology

2011-02-01

radiation and additional lead shielding was used to shield against gamma radiation emissions. Electronic dosimeters , the MGP DMC2000GN and Thermo EPD...DMC2000GN (S/N: 007395) and EPD-N2 (S/N: 07106323) electronic dosimeters were employed as these both are able to measure and record gamma and neutron...the AN/VDR-2 gamma radiation meter and Meridian Model 5085 neutron meter to confirm this and electronic dosimeters would be worn by personnel to

The Demonstration and Science Experiments (DSX): A Fundamental Science Research Mission Advancing Technologies that Enable MEO Spaceflight

DTIC Science & Technology

2006-01-01

dosimeters aboard the TSX5 and DSP satellites in LEO and GEO, respectively. Figure 13. Space weather data from TSX5 and DSP The Space Weather...capabilities are described in detail in the following sub- sections. 3.2.1 Compact Environment Anomaly Sensor (CEASE) Composed of two dosimeters , two...for DSX is that CEASE will capture and downlink the full dose spectra from each dosimeter , whereas prior versions only captured six reduced data

Personnel Radiation Exposure Associated With X-Rays Emanating from U.S. Coast Guard LORAN High Voltage Vacuum Tube Transmitter Units

DTIC Science & Technology

2011-07-01

dosimeter program. Unfortunately, this limited personnel monitoring program did not address the case of an individual who may have performed...and forearms; feet and ankles 18 ¾ Skin of whole body 7 ½ The USCG does maintain a small radiation personnel dosimeter monitoring program for x...ray technicians at USCG medical clinics (USCG, 2006). This medical clinic dosimeter program reflects a civilian standard of practice, where the x-ray

Overview of the AFRL’s Demonstration and Science Experiments (DSX) Program

DTIC Science & Technology

2006-09-01

most of the space weather data to-date has been accumulated in the LEO and GEO regimes, as illustrated in Figure 11 with data from dosimeters aboard...Composed of two dosimeters , two particle telescopes and a Single Event Effect detector, CEASE has the capability to monitor a broad range of space...panel of the payload module. One change for DSX is that CEASE will capture and downlink the full dose spectra from each dosimeter , whereas prior

Dose-equivalent neutron dosimeter

DOEpatents

Griffith, R.V.; Hankins, D.E.; Tomasino, L.; Gomaa, M.A.M.

1981-01-07

A neutron dosimeter is disclosed which provides a single measurement indicating the amount of potential biological damage resulting from the neutron exposure of the wearer, for a wide range of neutron energies. The dosimeter includes a detecting sheet of track etch detecting material such as a carbonate plastic, for detecting higher energy neutrons, and a radiator layer contaning conversion material such as /sup 6/Li and /sup 10/B lying adjacent to the detecting sheet for converting moderate energy neutrons to alpha particles that produce tracks in the adjacent detecting sheet.

Environmental Monitoring Instrumentation and Monitoring Techniques for Space Shuttle Launches.

DTIC Science & Technology

1983-07-01

Monitoring Instrumentation 32 1. Chemiluminescence HCl 32 2. Passive Dosimeter 34 3. Piezoelectric Quartz Crystal Microbalance 34 iJ ,- r, T , .{ , , : , Z...Sensing for STS Launohes 44 IV. SUISIAiR AND CONCLUSIONS 45 V. IBCOIMXIONS 47 References 49 Appendix A - Dosimeter Tube Monitoring Results 52 B - TenaxR...Monitoring Results 6 3 Summary of GBOMET HCI Data for the Launches of STS-i through 8 STS-5 at KSC 4 Dosimeter Tube Inlet Configuration Comparison 14 5 pH

Uncertainties in Coastal Ocean Color Products: Impacts of Spatial Sampling

NASA Technical Reports Server (NTRS)

Pahlevan, Nima; Sarkar, Sudipta; Franz, Bryan A.

2016-01-01

With increasing demands for ocean color (OC) products with improved accuracy and well characterized, per-retrieval uncertainty budgets, it is vital to decompose overall estimated errors into their primary components. Amongst various contributing elements (e.g., instrument calibration, atmospheric correction, inversion algorithms) in the uncertainty of an OC observation, less attention has been paid to uncertainties associated with spatial sampling. In this paper, we simulate MODIS (aboard both Aqua and Terra) and VIIRS OC products using 30 m resolution OC products derived from the Operational Land Imager (OLI) aboard Landsat-8, to examine impacts of spatial sampling on both cross-sensor product intercomparisons and in-situ validations of R(sub rs) products in coastal waters. Various OLI OC products representing different productivity levels and in-water spatial features were scanned for one full orbital-repeat cycle of each ocean color satellite. While some view-angle dependent differences in simulated Aqua-MODIS and VIIRS were observed, the average uncertainties (absolute) in product intercomparisons (due to differences in spatial sampling) at regional scales are found to be 1.8%, 1.9%, 2.4%, 4.3%, 2.7%, 1.8%, and 4% for the R(sub rs)(443), R(sub rs)(482), R(sub rs)(561), R(sub rs)(655), Chla, K(sub d)(482), and b(sub bp)(655) products, respectively. It is also found that, depending on in-water spatial variability and the sensor's footprint size, the errors for an in-situ validation station in coastal areas can reach as high as +/- 18%. We conclude that a) expected biases induced by the spatial sampling in product intercomparisons are mitigated when products are averaged over at least 7 km × 7 km areas, b) VIIRS observations, with improved consistency in cross-track spatial sampling, yield more precise calibration/validation statistics than that of MODIS, and c) use of a single pixel centered on in-situ coastal stations provides an optimal sampling size for validation efforts. These findings will have implications for enhancing our understanding of uncertainties in ocean color retrievals and for planning of future ocean color missions and the associated calibration/validation exercises.

Effects of refractive index mismatch in optical CT imaging of polymer gel dosimeters.

PubMed

Manjappa, Rakesh; Makki S, Sharath; Kumar, Rajesh; Kanhirodan, Rajan

2015-02-01

Proposing an image reconstruction technique, algebraic reconstruction technique-refraction correction (ART-rc). The proposed method takes care of refractive index mismatches present in gel dosimeter scanner at the boundary, and also corrects for the interior ray refraction. Polymer gel dosimeters with high dose regions have higher refractive index and optical density compared to the background medium, these changes in refractive index at high dose results in interior ray bending. The inclusion of the effects of refraction is an important step in reconstruction of optical density in gel dosimeters. The proposed ray tracing algorithm models the interior multiple refraction at the inhomogeneities. Jacob's ray tracing algorithm has been modified to calculate the pathlengths of the ray that traverses through the higher dose regions. The algorithm computes the length of the ray in each pixel along its path and is used as the weight matrix. Algebraic reconstruction technique and pixel based reconstruction algorithms are used for solving the reconstruction problem. The proposed method is tested with numerical phantoms for various noise levels. The experimental dosimetric results are also presented. The results show that the proposed scheme ART-rc is able to reconstruct optical density inside the dosimeter better than the results obtained using filtered backprojection and conventional algebraic reconstruction approaches. The quantitative improvement using ART-rc is evaluated using gamma-index. The refraction errors due to regions of different refractive indices are discussed. The effects of modeling of interior refraction in the dose region are presented. The errors propagated due to multiple refraction effects have been modeled and the improvements in reconstruction using proposed model is presented. The refractive index of the dosimeter has a mismatch with the surrounding medium (for dry air or water scanning). The algorithm reconstructs the dose profiles by estimating refractive indices of multiple inhomogeneities having different refractive indices and optical densities embedded in the dosimeter. This is achieved by tracking the path of the ray that traverses through the dosimeter. Extensive simulation studies have been carried out and results are found to be matching that of experimental results.

Characterization of MOSFET dosimeter angular dependence in three rotational axes measured free-in-air and in soft-tissue equivalent material.

PubMed

Koivisto, Juha; Kiljunen, Timo; Wolff, Jan; Kortesniemi, Mika

2013-09-01

When performing dose measurements on an X-ray device with multiple angles of irradiation, it is necessary to take the angular dependence of metal-oxide-semiconductor field-effect transistor (MOSFET) dosimeters into account. The objective of this study was to investigate the angular sensitivity dependence of MOSFET dosimeters in three rotational axes measured free-in-air and in soft-tissue equivalent material using dental photon energy. Free-in-air dose measurements were performed with three MOSFET dosimeters attached to a carbon fibre holder. Soft tissue measurements were performed with three MOSFET dosimeters placed in a polymethylmethacrylate (PMMA) phantom. All measurements were made in the isocenter of a dental cone-beam computed tomography (CBCT) scanner using 5º angular increments in the three rotational axes: axial, normal-to-axial and tangent-to-axial. The measurements were referenced to a RADCAL 1015 dosimeter. The angular sensitivity free-in-air (1 SD) was 3.7 ± 0.5 mV/mGy for axial, 3.8 ± 0.6 mV/mGy for normal-to-axial and 3.6 ± 0.6 mV/mGy for tangent-to-axial rotation. The angular sensitivity in the PMMA phantom was 3.1 ± 0.1 mV/mGy for axial, 3.3 ± 0.2 mV/mGy for normal-to-axial and 3.4 ± 0.2 mV/mGy for tangent-to-axial rotation. The angular sensitivity variations are considerably smaller in PMMA due to the smoothing effect of the scattered radiation. The largest decreases from the isotropic response were observed free-in-air at 90° (distal tip) and 270° (wire base) in the normal-to-axial and tangent-to-axial rotations, respectively. MOSFET dosimeters provide us with a versatile dosimetric method for dental radiology. However, due to the observed variation in angular sensitivity, MOSFET dosimeters should always be calibrated in the actual clinical settings for the beam geometry and angular range of the CBCT exposure.

Characterization of MOSFET dosimeter angular dependence in three rotational axes measured free-in-air and in soft-tissue equivalent material

PubMed Central

Koivisto, Juha; Kiljunen, Timo; Wolff, Jan; Kortesniemi, Mika

2013-01-01

When performing dose measurements on an X-ray device with multiple angles of irradiation, it is necessary to take the angular dependence of metal-oxide-semiconductor field-effect transistor (MOSFET) dosimeters into account. The objective of this study was to investigate the angular sensitivity dependence of MOSFET dosimeters in three rotational axes measured free-in-air and in soft-tissue equivalent material using dental photon energy. Free-in-air dose measurements were performed with three MOSFET dosimeters attached to a carbon fibre holder. Soft tissue measurements were performed with three MOSFET dosimeters placed in a polymethylmethacrylate (PMMA) phantom. All measurements were made in the isocenter of a dental cone-beam computed tomography (CBCT) scanner using 5º angular increments in the three rotational axes: axial, normal-to-axial and tangent-to-axial. The measurements were referenced to a RADCAL 1015 dosimeter. The angular sensitivity free-in-air (1 SD) was 3.7 ± 0.5 mV/mGy for axial, 3.8 ± 0.6 mV/mGy for normal-to-axial and 3.6 ± 0.6 mV/mGy for tangent-to-axial rotation. The angular sensitivity in the PMMA phantom was 3.1 ± 0.1 mV/mGy for axial, 3.3 ± 0.2 mV/mGy for normal-to-axial and 3.4 ± 0.2 mV/mGy for tangent-to-axial rotation. The angular sensitivity variations are considerably smaller in PMMA due to the smoothing effect of the scattered radiation. The largest decreases from the isotropic response were observed free-in-air at 90° (distal tip) and 270° (wire base) in the normal-to-axial and tangent-to-axial rotations, respectively. MOSFET dosimeters provide us with a versatile dosimetric method for dental radiology. However, due to the observed variation in angular sensitivity, MOSFET dosimeters should always be calibrated in the actual clinical settings for the beam geometry and angular range of the CBCT exposure. PMID:23520268

Effects of refractive index mismatch in optical CT imaging of polymer gel dosimeters

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

Manjappa, Rakesh; Makki S, Sharath; Kanhirodan, Rajan, E-mail: rajan@physics.iisc.ernet.in

2015-02-15

Purpose: Proposing an image reconstruction technique, algebraic reconstruction technique-refraction correction (ART-rc). The proposed method takes care of refractive index mismatches present in gel dosimeter scanner at the boundary, and also corrects for the interior ray refraction. Polymer gel dosimeters with high dose regions have higher refractive index and optical density compared to the background medium, these changes in refractive index at high dose results in interior ray bending. Methods: The inclusion of the effects of refraction is an important step in reconstruction of optical density in gel dosimeters. The proposed ray tracing algorithm models the interior multiple refraction at themore » inhomogeneities. Jacob’s ray tracing algorithm has been modified to calculate the pathlengths of the ray that traverses through the higher dose regions. The algorithm computes the length of the ray in each pixel along its path and is used as the weight matrix. Algebraic reconstruction technique and pixel based reconstruction algorithms are used for solving the reconstruction problem. The proposed method is tested with numerical phantoms for various noise levels. The experimental dosimetric results are also presented. Results: The results show that the proposed scheme ART-rc is able to reconstruct optical density inside the dosimeter better than the results obtained using filtered backprojection and conventional algebraic reconstruction approaches. The quantitative improvement using ART-rc is evaluated using gamma-index. The refraction errors due to regions of different refractive indices are discussed. The effects of modeling of interior refraction in the dose region are presented. Conclusions: The errors propagated due to multiple refraction effects have been modeled and the improvements in reconstruction using proposed model is presented. The refractive index of the dosimeter has a mismatch with the surrounding medium (for dry air or water scanning). The algorithm reconstructs the dose profiles by estimating refractive indices of multiple inhomogeneities having different refractive indices and optical densities embedded in the dosimeter. This is achieved by tracking the path of the ray that traverses through the dosimeter. Extensive simulation studies have been carried out and results are found to be matching that of experimental results.« less

Modelling oil plumes from subsurface spills.

PubMed

Lardner, Robin; Zodiatis, George

2017-11-15

An oil plume model to simulate the behavior of oil from spills located at any given depth below the sea surface is presented, following major modifications to a plume model developed earlier by Malačič (2001) and drawing on ideas in a paper by Yapa and Zheng (1997). The paper presents improvements in those models and numerical testing of the various parameters in the plume model. The plume model described in this paper is one of the numerous modules of the well-established MEDSLIK oil spill model. The deep blowout scenario of the MEDEXPOL 2013 oil spill modelling exercise, organized by REMPEC, has been applied using the improved oil plume module of the MEDSLIK model and inter-comparison with results having the oil spill source at the sea surface are discussed. Copyright © 2017 Elsevier Ltd. All rights reserved.

ULTRASONIC NEUTRON DOSIMETER

DOEpatents

Truell, R.; de Klerk, J.; Levy, P.W.

1960-02-23

A neutron dosimeter is described which utilizes ultrasonic waves in the megacycle region for determination of the extent of neutron damage in a borosilicate glass through ultrasonic wave velocity and attenuation measurements before and after damage.

System for use with solid state dosimeter

DOEpatents

Miller, Steven D.; McDonald, Joseph C.; Eichner, Fred N.; Tomeraasen, Paul L.

1990-01-01

The present invention constitutes a system for determining the amounts of ionizing radiation to which dosimeters using thermoluminescent materials have been exposed. In accordance with this system, the thermoluminescent materials which comprise the dosimeters are first cooled by contact with a cryogenic substance such as liquified nitrogen. The thermoluminescent materials are then optically stimulated by exposure to ultraviolet light. Thereafter, the amounts of visible light emitted by the thermoluminescent materials are detected and counted as the materials are allowed to warm up to room temperature. The amounts of luminescence exhibited by the materials are related to radiation exposure and provide a sensitive measure of radiation dosage. It has been discovered that the above procedure is most effective when heavily doped thermoluminescent materials are used and that the procedure allows many useful plastic materials to now be employed in dosimeter constructions.

System for use with solid state dosimeter

DOEpatents

Miller, S.D.; McDonald, J.C.; Eichner, F.N.; Tomeraasen, P.L.

1990-09-04

The present invention constitutes a system for determining the amounts of ionizing radiation to which dosimeters using thermoluminescent materials have been exposed. In accordance with this system, the thermoluminescent materials which comprise the dosimeters are first cooled by contact with a cryogenic substance such as liquefied nitrogen. The thermoluminescent materials are then optically stimulated by exposure to ultraviolet light. Thereafter, the amounts of visible light emitted by the thermoluminescent materials are detected and counted as the materials are allowed to warm up to room temperature. The amounts of luminescence exhibited by the materials are related to radiation exposure and provide a sensitive measure of radiation dosage. It has been discovered that the above procedure is most effective when heavily doped thermoluminescent materials are used and that the procedure allows many useful plastic materials to now be employed in dosimeter constructions. 3 figs.

Development and evaluation of multi-energy PbO dosimeter for quality assurance of image-guide radiation therapy devices

NASA Astrophysics Data System (ADS)

Kim, Kyo-Tae; Heo, Ye-Ji; Han, Moo-Jae; Oh, Kyung-Min; Lee, Young-Kyu; Kim, Shin-Wook; Park, Sung-Kwang

2017-04-01

In radiation therapy, accurate radiotherapy treatment plan (RTP) reproduction is necessary to optimize the clinical results. Thus, attempts have recently been made to ensure high RTP reproducibility using image-guide radiation therapy (IGRT) technology. However, the clinical use of digital X-ray equipment requires extended quality assurance (QA) for those devices, since the IGRT device quality determines the precision of intensity-modulated radiation therapy. The study described in this paper was focused on developing a multi-energy PbO dosimeter for IGRT device QA. The Schottky-type polycrystalline PbO dosimeter with a Au/PbO/ITO structure was evaluated by comparing its response coincidence, dose linearity, measurement reproducibility, linear attenuation coefficient, and percent depth dose with those of Si diode and standard ionization chamber dosimeters.

The study of N-isopropylacrylamide gel dosimeter doped iodinated contrast agents

NASA Astrophysics Data System (ADS)

Chang, Y. J.; Hsieh, L. L.; Liu, M. H.; Liu, J. S.; Hsieh, B. T.

2013-06-01

Low toxicity of N-isopropylacrylamide (NIPAM) dosimeter was doped with clinical iodinated contrast medium agents(Iobitridol (Xenetix® 350) and organically bound iodine (Conray® 60) as radiation sensitizers; The suitable gel dosimeter preparation formula in this research was 5 w/w% gelatin, 5 w/w% N-isopropylacrylamide, 3 w/w% N,N-methylene-bis-acrylamide, and 5 mM Tetrakis phosphonium chloride. The spiral CT was irradiator, and 120 kVp was the operating tube voltage. The maximum radiation dose was 0.6 Gy, and optical CT was the gel measurement device used. The results showed SERs with the addition of radiosensitizers were 10.70 (Xenetix® 350) and 9.67 (Conray® 60), respectively. Thus, the polymerized gel dosimeter could be used in the efficacy evaluation of low-energy and low-radiation dose.

Redox-Phen solution: A water equivalent dosimeter for UVA, UVB and X-rays radiation

NASA Astrophysics Data System (ADS)

Marini, A.; Ciribolla, C.; Lazzeri, L.; d'Errico, F.

2018-06-01

Polysulphone films are the only type of UV passive dosimeters that are widely adopted for research and personal monitoring. Even though many studies concentrated on the development and characterization of these films, they still present some shortcomings. The more important limitations of them are that they can measure only UVB radiations and that they change color at 330 nm, requiring special equipment to read them. To overcome these limitations we developed an aqueous dosimeter that is sensitive to UVA, UVB and X-rays named Redox-Phen solution. This dosimeter is inexpensive and water equivalent, being made of more than 99 wt% of water. It changes color in the visible region upon irradiation, thus it can be measured via simple optical method, and an evaluation of the exposition can be made also by naked eyes.

Estimation of the influence of radical effect in the proton beams using a combined approach with physical data and gel data

NASA Astrophysics Data System (ADS)

Haneda, K.

2016-04-01

The purpose of this study was to estimate an impact on radical effect in the proton beams using a combined approach with physical data and gel data. The study used two dosimeters: ionization chambers and polymer gel dosimeters. Polymer gel dosimeters have specific advantages when compared to other dosimeters. They can measure chemical reaction and they are at the same time a phantom that can map in three dimensions continuously and easily. First, a depth-dose curve for a 210 MeV proton beam measured using an ionization chamber and a gel dosimeter. Second, the spatial distribution of the physical dose was calculated by Monte Carlo code system PHITS: To verify of the accuracy of Monte Carlo calculation, and the calculation results were compared with experimental data of the ionization chamber. Last, to evaluate of the rate of the radical effect against the physical dose. The simulation results were compared with the measured depth-dose distribution and showed good agreement. The spatial distribution of a gel dose with threshold LET value of proton beam was calculated by the same simulation code. Then, the relative distribution of the radical effect was calculated from the physical dose and gel dose. The relative distribution of the radical effect was calculated at each depth as the quotient of relative dose obtained using physical and gel dose. The agreement between the relative distributions of the gel dosimeter and Radical effect was good at the proton beams.

Personnel neutron dosimetry using electrochemically etched CR-39 foils

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

Hankins, D.E.; Homann, S.; Westermark, J.

1986-09-17

A personnel neutron dosimetry system has been developed based on the electrochemical etching of CR-39 plastic at elevated temperatures. The doses obtained using this dosimeter system are more accurate than those obtained using other dosimetry systems, especially when varied neutron spectra are encountered. This Cr-39 dosimetry system does not have the severe energy dependence that exists with albedo neutron dosimeters or the fading and reading problems encountered with NTA film. The dosimetry system employs an electrochemical etch procedure that be used to process large numbers of Cr-39 dosimeters. The etch procedure is suitable for operations where the number of personnelmore » requires that many CR-39 dosimeters be processed. Experience shows that one full-time technician can etch and evaluate 2000 foils per month. The energy response to neutrons is fairly flat from about 80 keV to 3.5 MeV, but drops by about a factor of three in the 13 to 16 MeV range. The sensitivity of the dosimetry system is about 7 tracks/cm/sup 2//mrem, with a background equivalent to about 8 mrem for new CR-39 foils. The limit of sensitivity is approximately 10 mrem. The dosimeter has a significant variation in directional dependence, dropping to about 20% at 90/sup 0/. This dosimeter has been used for personnel neutron dosimetry at the Lawrence Livermore National Laboratory for more tha 18 months. 6 refs., 23 figs., 2 tabs.« less

Alternative chitosan-based EPR dosimeter applicable for a relatively wide range of gamma radiation doses

NASA Astrophysics Data System (ADS)

Piroonpan, Thananchai; Katemake, Pichayada; Panritdam, Eagkapong; Pasanphan, Wanvimol

2017-12-01

Chitosan biopolymer is proposed as an alternative EPR dosimeter. Its ability to be EPR dosimeter was studied in comparison with the conventional alanine, sugars (i.e., glucose and sucrose), formate derivatives (i.e., lithium (Li), magnesium (Mg), and calcium (Ca) formate). Ethylene vinyl acetate (EVA) and paraffin were used as binder for the preparation of composite EPR dosimeter. Dose responses of all materials were investigated in a wide dose range of radiation doses, i.e., low-level (0-1 kGy), medium-level (1-10 kGy) and high-level (10-100 kGy). The EPR dosimeter properties were studied under different parameters, i.e., microwave power, materials contents, absorbed doses, storage conditions and post-irradiation effects. Li-formate showed a simple EPR spectrum and exhibited superior radiation response for low-dose range; whereas chitosan and sucrose exhibited linear dose response in all studied dose ranges. The EPR signals of chitosan exhibited similar stability as glucose, Li-formate and alanine at ambient temperature after irradiation as long as a year. All EPR signals of the studied materials were affected post-irradiation temperature and humidity after gamma irradiation. The EPR signal of chitosan exhibited long-term stability and it was not sensitive to high storage temperatures and humidity values after irradiation. Chitosan has a good merit as the alternative bio-based material for a stable EPR dosimeter in a wide range of radiation-absorbed doses.

a Thermally Desorbable Miniature Passive Dosimeter for Organic Vapors

NASA Astrophysics Data System (ADS)

Gonzalez, Jesus Antonio

A thermally desorbable miniature passive dosimeter (MPD) for organic vapors has been developed in conformity with theoretical and practical aspects of passive dosimeter design. The device was optimized for low sample loadings resulting from short-term and/or low concentration level exposure. This was accomplished by the use of thermal desorption rather than solvent elution, which provided the GC method with significantly higher sensitivity. Laboratory evaluation of this device for factors critical to the performance of passive dosimeters using benzene as the test vapor included: desorption efficiency (97.2%), capacity (1400 ppm-min), sensitivity (7ng/sample or 0.06 ppmv for 15 minutes sampling) accuracy and precision, concentration level, environmental conditions (i.e., air face velocity, relative humidity) and sample stability during short (15 minutes) and long periods of time (15 days). This device has demonstrated that its overall accuracy meets NIOSH and OSHA requirements for a sampling and analytical method for the exposure concentration range of 0.1 to 50 ppm (v/v) and 15 minutes exposures. It was demonstrated that the MPD operates in accordance with theoretically predicted performance and should be adequate for short-term and/or low concentration exposure monitoring of organic vapors in the workplace. In addition a dynamic vapor exposure evaluation system for passive dosimeters have been validated using benzene as the test vapor. The system is capable of generating well defined short-square wave concentration profiles suitable for the evaluation of passive dosimeters for ceiling exposure monitoring.

Dose verification to cochlea during gamma knife radiosurgery of acoustic schwannoma using MOSFET dosimeter.

PubMed

Sharma, Sunil D; Kumar, Rajesh; Akhilesh, Philomina; Pendse, Anil M; Deshpande, Sudesh; Misra, Basant K

2012-01-01

Dose verification to cochlea using metal oxide semiconductor field effect transistor (MOSFET) dosimeter using a specially designed multi slice head and neck phantom during the treatment of acoustic schwannoma by Gamma Knife radiosurgery unit. A multi slice polystyrene head phantom was designed and fabricated for measurement of dose to cochlea during the treatment of the acoustic schwannoma. The phantom has provision to position the MOSFET dosimeters at the desired location precisely. MOSFET dosimeters of 0.2 mm x 0.2 mm x 0.5 μm were used to measure the dose to the cochlea. CT scans of the phantom with MOSFETs in situ were taken along with Leksell frame. The treatment plans of five patients treated earlier for acoustic schwannoma were transferred to the phantom. Dose and coordinates of maximum dose point inside the cochlea were derived. The phantom along with the MOSFET dosimeters was irradiated to deliver the planned treatment and dose received by cochlea were measured. The treatment planning system (TPS) estimated and measured dose to the cochlea were in the range of 7.4 - 8.4 Gy and 7.1 - 8 Gy, respectively. The maximum variation between TPS calculated and measured dose to cochlea was 5%. The measured dose values were found in good agreement with the dose values calculated using the TPS. The MOSFET dosimeter can be a suitable choice for routine dose verification in the Gamma Knife radiosurgery.

Pliocene Model Intercomparison Project (PlioMIP): Experimental Design and Boundary Conditions (Experiment 2)

NASA Technical Reports Server (NTRS)

Haywood, A. M.; Dowsett, H. J.; Robinson, M. M.; Stoll, D. K.; Dolan, A. M.; Lunt, D. J.; Otto-Bliesner, B.; Chandler, M. A.

2011-01-01

The Palaeoclimate Modelling Intercomparison Project has expanded to include a model intercomparison for the mid-Pliocene warm period (3.29 to 2.97 million yr ago). This project is referred to as PlioMIP (the Pliocene Model Intercomparison Project). Two experiments have been agreed upon and together compose the initial phase of PlioMIP. The first (Experiment 1) is being performed with atmosphere only climate models. The second (Experiment 2) utilizes fully coupled ocean-atmosphere climate models. Following on from the publication of the experimental design and boundary conditions for Experiment 1 in Geoscientific Model Development, this paper provides the necessary description of differences and/or additions to the experimental design for Experiment 2.

Pliocene Model Intercomparison Project (PlioMIP): experimental design and boundary conditions (Experiment 2)

USGS Publications Warehouse

Haywood, A.M.; Dowsett, H.J.; Robinson, M.M.; Stoll, D.K.; Dolan, A.M.; Lunt, D.J.; Otto-Bliesner, B.; Chandler, M.A.

2011-01-01

The Palaeoclimate Modelling Intercomparison Project has expanded to include a model intercomparison for the mid-Pliocene warm period (3.29 to 2.97 million yr ago). This project is referred to as PlioMIP (the Pliocene Model Intercomparison Project). Two experiments have been agreed upon and together compose the initial phase of PlioMIP. The first (Experiment 1) is being performed with atmosphere-only climate models. The second (Experiment 2) utilises fully coupled ocean-atmosphere climate models. Following on from the publication of the experimental design and boundary conditions for Experiment 1 in Geoscientific Model Development, this paper provides the necessary description of differences and/or additions to the experimental design for Experiment 2.

Manufacture and calibration of optical supersmooth roughness artifacts for intercomparisons

NASA Astrophysics Data System (ADS)

Ringel, Gabriele A.; Kratz, Frank; Schmitt, Dirk-Roger; Mangelsdorf, Juergen; Creuzet, Francois; Garratt, John D.

1995-09-01

Intercomparison roughness measurements have been carried out on supersmooth artifacts fabricated from BK7, fused silica, and Zerodur. The surface parameters were determined using the optical heterodyne profiler Z5500 (Zygo), a special prototype of the mechanical profiler Nanostep (Rank Taylor Hobson), and an Atomic Force Microscope (Park Scientific Instruments) with an improved acquisition technique. The intercomparison was performed after the range of collected spatial wavelengths for each instrument was adjusted using digital filtering techniques. It is demonstrated for different roughness ranges that the applied superpolishing techniques yield supersmooth artifacts which can be used for more intercomparisons. More than 100 samples were investigated. Criteria were developed to select artifacts from the sample stock.

Hair dosimetry following neutron irradiation.

PubMed

Lebaron-Jacobs, L; Gaillard-Lecanu, E; Briot, F; Distinguin, S; Boisson, P; Exmelin, L; Racine, Y; Berard, P; Flüry-Herard, A; Miele, A; Fottorino, R

2007-05-01

Use of hair as a biological dosimeter of neutron exposure was proposed a few years ago. To date, the (32)S(n,p)(32)P reaction in hair with a threshold of 2.5 MeV is the best choice to determine the fast neutron dose using body activation. This information is essential with regards to the heterogeneity of the neutron transfer to the organism. This is a very important parameter for individual dose reconstruction from the surface to the deeper tissues. This evaluation is essential to the adapted management of irradiated victims by specialized medical staff. Comparison exercises between clinical biochemistry laboratories from French sites (the CEA and COGEMA) and from the IRSN were carried out to validate the measurement of (32)P activity in hair and to improve the techniques used to perform this examination. Hair was placed on a phantom and was irradiated at different doses in the SILENE reactor (Valduc, France). Different parameters were tested: variation of hair type, minimum weight of hair sample, hair wash before measurement, delivery period of results, and different irradiation configurations. The results obtained in these comparison exercises by the different laboratories showed an excellent correlation. This allowed the assessment of a dose-activity relationship and confirmed the feasibility and the interest of (32)P measurement in hair following fast neutron irradiation.

Fully 3D refraction correction dosimetry system.

PubMed

Manjappa, Rakesh; Makki, S Sharath; Kumar, Rajesh; Vasu, Ram Mohan; Kanhirodan, Rajan

2016-02-21

The irradiation of selective regions in a polymer gel dosimeter results in an increase in optical density and refractive index (RI) at those regions. An optical tomography-based dosimeter depends on rayline path through the dosimeter to estimate and reconstruct the dose distribution. The refraction of light passing through a dose region results in artefacts in the reconstructed images. These refraction errors are dependant on the scanning geometry and collection optics. We developed a fully 3D image reconstruction algorithm, algebraic reconstruction technique-refraction correction (ART-rc) that corrects for the refractive index mismatches present in a gel dosimeter scanner not only at the boundary, but also for any rayline refraction due to multiple dose regions inside the dosimeter. In this study, simulation and experimental studies have been carried out to reconstruct a 3D dose volume using 2D CCD measurements taken for various views. The study also focuses on the effectiveness of using different refractive-index matching media surrounding the gel dosimeter. Since the optical density is assumed to be low for a dosimeter, the filtered backprojection is routinely used for reconstruction. We carry out the reconstructions using conventional algebraic reconstruction (ART) and refractive index corrected ART (ART-rc) algorithms. The reconstructions based on FDK algorithm for cone-beam tomography has also been carried out for comparison. Line scanners and point detectors, are used to obtain reconstructions plane by plane. The rays passing through dose region with a RI mismatch does not reach the detector in the same plane depending on the angle of incidence and RI. In the fully 3D scanning setup using 2D array detectors, light rays that undergo refraction are still collected and hence can still be accounted for in the reconstruction algorithm. It is found that, for the central region of the dosimeter, the usable radius using ART-rc algorithm with water as RI matched medium is 71.8%, an increase of 6.4% compared to that achieved using conventional ART algorithm. Smaller diameter dosimeters are scanned with dry air scanning by using a wide-angle lens that collects refracted light. The images reconstructed using cone beam geometry is seen to deteriorate in some planes as those regions are not scanned. Refraction correction is important and needs to be taken in to consideration to achieve quantitatively accurate dose reconstructions. Refraction modeling is crucial in array based scanners as it is not possible to identify refracted rays in the sinogram space.

Monte Carlo Assessments of Absorbed Doses to the Hands of Radiopharmaceutical Workers Due to Photon Emitters

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

Ilas, Dan; Eckerman, Keith F; Karagiannis, Harriet

This paper describes the characterization of radiation doses to the hands of nuclear medicine technicians resulting from the handling of radiopharmaceuticals. Radiation monitoring using ring dosimeters indicates that finger dosimeters that are used to show compliance with applicable regulations may overestimate or underestimate radiation doses to the skin depending on the nature of the particular procedure and the radionuclide being handled. To better understand the parameters governing the absorbed dose distributions, a detailed model of the hands was created and used in Monte Carlo simulations of selected nuclear medicine procedures. Simulations of realistic configurations typical for workers handling radiopharmaceuticals weremore » performedfor a range of energies of the source photons. The lack of charged-particle equilibrium necessitated full photon-electron coupled transport calculations. The results show that the dose to different regions of the fingers can differ substantially from dosimeter readings when dosimeters are located at the base of the finger. We tried to identify consistent patterns that relate the actual dose to the dosimeter readings. These patterns depend on the specific work conditions and can be used to better assess the absorbed dose to different regions of the exposed skin.« less

Dose Assessments to the Hands of Radiopharmaceutical Workers

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

Ilas, Dan; Eckerman, Keith F; Sherbini, Sami

This paper describes the characterization of radiation doses to the hands of nuclear medicine technicians resulting from the handling of radiopharmaceuticals. Radiation monitoring using ring dosimeters indicates that finger dosimeters may overestimate or underestimate the radiation doses to the skin that are used to show compliance with applicable regulations depending on the nature of the particular procedure and the radioisotope being handled. To better understand the parameters governing the absorbed dose distributions, a detailed model of the hands was created and used in Monte Carlo simulations of selected nuclear medicine procedures. Simulations on realistic configurations typical for workers handling radiopharmaceuticalsmore » were performed for a range of energies of the source photons. The lack of charged-particle equilibrium necessitated full photon-electron coupled transport calculations. The results show that the dose to different regions of the fingers can differ substantially from the dosimeters' readings when the dosimeters are located at the base of the finger. We tried to identify consistent patterns that relate the actual dose to the dosimeter readings. These patterns depend on the specific work conditions and can be used to better assess the absorbed dose to different regions of the exposed skin.« less

Prevention of Transfusion-Associated Graft-versus-Host Disease by Irradiation: Technical Aspect of a New Ferrous Sulphate Dosimetric System

PubMed Central

Del Lama, Lucas Sacchini; de Góes, Evamberto Garcia; Petchevist, Paulo César Dias; Moretto, Edson Lara; Borges, José Carlos; Covas, Dimas Tadeu; de Almeida, Adelaide

2013-01-01

Irradiation of whole blood and blood components before transfusion is currently the only accepted method to prevent Transfusion-Associated Graft-Versus-Host-Disease (TA-GVHD). However, choosing the appropriate technique to determine the dosimetric parameters associated with blood irradiation remains an issue. We propose a dosimetric system based on the standard Fricke Xylenol Gel (FXG) dosimeter and an appropriate phantom. The modified dosimeter was previously calibrated using a 60Co teletherapy unit and its validation was accomplished with a 137Cs blood irradiator. An ionization chamber, standard FXG, radiochromic film and thermoluminescent dosimeters (TLDs) were used as reference dosimeters to determine the dose response and dose rate of the 60Co unit. The dose distributions in a blood irradiator were determined with the modified FXG, the radiochromic film, and measurements by TLD dosimeters. A linear response for absorbed doses up to 54 Gy was obtained with our system. Additionally, the dose rate uncertainties carried out with gel dosimetry were lower than 5% and differences lower than 4% were noted when the absorbed dose responses were compared with ionization chamber, film and TLDs. PMID:23762345

Dose algorithm for EXTRAD 4100S extremity dosimeter for use at Sandia National Laboratories.

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

Potter, Charles Augustus

An updated algorithm for the EXTRAD 4100S extremity dosimeter has been derived. This algorithm optimizes the binning of dosimeter element ratios and uses a quadratic function to determine the response factors for low response ratios. This results in lower systematic bias across all test categories and eliminates the need for the 'red strap' algorithm that was used for high energy beta/gamma emitting radionuclides. The Radiation Protection Dosimetry Program (RPDP) at Sandia National Laboratories uses the Thermo Fisher EXTRAD 4100S extremity dosimeter, shown in Fig 1.1 to determine shallow dose to the extremities of potentially exposed individuals. This dosimeter consists ofmore » two LiF TLD elements or 'chipstrates', one of TLD-700 ({sup 7}Li) and one of TLD-100 (natural Li) separated by a tin filter. Following readout and background subtraction, the ratio of the responses of the two elements is determined defining the penetrability of the incident radiation. While this penetrability approximates the incident energy of the radiation, X-rays and beta particles exist in energy distributions that make determination of dose conversion factors less straightforward in their determination.« less

Investigation of vacuum pumping on the dose response of the MAGAS normoxic polymer gel dosimeter.

PubMed

Venning, A J; Mather, M L; Baldock, C

2005-06-01

The effect of vacuum pumping on the dose response of the MAGAS polymer gel dosimeter has been investigated. A delay of several days post-manufacture before irradiation was previously necessary due to the slow oxygen scavenging of ascorbic acid. The MAGAS polymer gel dosimeter was vacuum pumped before gelation to remove dissolved oxygen. The MAGAS polymer gel dosimeter was poured into glass screw-top vials, which were irradiated at various times, post-manufacture to a range of doses. Magnetic resonance imaging techniques were used to determine the R2-dose response and R2-dose sensitivity of the MAGAS polymer gel. The results were compared with a control batch of MAGAS polymer gel that was not vacuum pumped. It was shown that vacuum pumping on the MAGAS polymer gel solution immediately prior to sealing in glass screw-top vials initially increases the R2-dose response and R2-dose sensitivity of the dosimeter. An increase in the R2-dose response and R2-dose sensitivity was observed with increasing time between manufacture and irradiation. Over the range of post-manufacture irradiation times investigated, the greatest R2-dose response and R2-dose sensitivity occurred at 96 hours.

Chemical Dosimeter Tube With Coaxial Sensing Rod

NASA Technical Reports Server (NTRS)

Lueck, Dale E.

1993-01-01

Improved length-of-stain (LOS) chemical dosimeter indicates total dose of chemical vapor in air. Made with rods and tubes of various diameters to obtain various sensitivities and dynamic ranges. Sensitivity larger and dose range smaller when more room for diffusion in gap between tube and rod. Offers greater resistance to changing of color of exposed dye back to color of unexposed condition, greater sensitivity, and higher degree of repeatability. Developed to measure doses of gaseous HCI, dosimeter modified by use of other dyes to indicate doses of other chemical vapors.

Descriptive Summaries of the Research Development Test & Evaluation. Army Appropriation Fiscal Year 1984. Supporting Data Fiscal Year 1984 Budget Estimate Submitted to Congress--February 1983. Volume II.

DTIC Science & Technology

1983-02-01

of reprogranming action to support procurement of the reader, CP-69, associated with the Individual dosimeter , DT-238. The funding decrease of $23,700...meter has been adapted for Army use, and the Air For- i is participating in the tactical dosimeter program. An installation fallout monitor and alarm...system, the AN/GDQ3. was developed Jointly with the C.~nadian Department of Defense Production. and the DT-236 Individual dosimeter Is being developed

Performance of optically stimulated luminescence Al₂O₃ dosimeter for low doses of diagnostic energy X-rays.

PubMed

Lim, Chang Seon; Lee, Sang Bock; Jin, Gye Hwan

2011-10-01

Personal dosimeters measure the radiation dose from exposure to hazardous sources outside the body. The present manuscript evaluates the performance of a commercially available optically stimulated luminescence (OSL) Al₂O₃ dosimeter using diagnostic energy X-rays. The OSL system satisfies the ANSI N13.11-2001 performance criteria for low dose diagnostic energy X-rays. Non-uniformity of sensitivity, dose linearity, X-ray energy response, and angular performance are all within the criteria of IEC-62387-1(2007). Copyright © 2011 Elsevier Ltd. All rights reserved.

SU-E-I-09: Application of LiF:Mg,Cu (TLD-100H) Dosimeters for in Diagnostic Radiology

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

Sina, S; Zeinali, B; Karimipourfard, M

Purpose: Accurate dosimetery is very essential in diagnostic radiology. The goal of this study is to verify the application of LiF:Mg,Cu,P (TLD100H) in obtaining the Entrance skin dose (ESD) of patients undergoing diagnostic radiology. The results of dosimetry performed by TLD-100H, were compared with those obtained by TLD100, which is a common dosimeter in diagnostic radiology. Methods: In this study the ESD values were measured using two types of Thermoluminescence dosimeters (TLD-100, and TLD-100H) for 16 patients undergoing diagnostic radiology (lumbar spine imaging). The ESD values were also obtained by putting the two types of TLDs at the surface ofmore » Rando phantom for different imaging techniques and different views (AP, and lateral). The TLD chips were annealed with a standard procedure, and the ECC values for each TLD was obtained by exposing the chips to equal amount of radiation. Each time three TLD chips were covered by thin dark plastic covers, and were put at the surface of the phantom or the patient. The average reading of the three chips was used for obtaining the dose. Results: The results show a close agreement between the dose measuered by the two dosimeters.According to the results of this study, the TLD-100H dosimeters have higher sensitivities (i.e.signal(nc)/dose) than TLD-100.The ESD values varied between 2.71 mGy and 26.29 mGy with the average of 11.89 mGy for TLD-100, and between 2.55 mGy and 27.41 mGy with the average of 12.32 mGy for measurements. Conclusion: The TLD-100H dosimeters are suggested as effective dosimeters for dosimetry in low dose fields because of their higher sensitivities.« less

SU-D-213-06: Dosimetry of Modulated Electron Radiation Therapy Using Fricke Gel Dosimeter

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

Gawad, M Abdel; Elgohary, M; Hassaan, M

Purpose: Modulated electron radiation therapy (MERT) has been proposed as an effective modality for treatment of superficial targets. MERT utilizes multiple beams of different energies which are intensity modulated to deliver optimized dose distribution. Energy independent dosimeters are thus needed for quantitative evaluations of MERT dose distributions and measurements of absolute doses delivered to patients. Thus in the current work we study the feasibility of Fricke gel dosimeters in MERT dosimetry. Methods: Batches of radiation sensitive Fricke gel is fabricated and poured into polymethyl methacrylate cuvettes. The samples were irradiated in solid water phantom and a thick layer of bolusmore » was used as a buildup. A spectrophotometer system was used for measuring the color changes (the absorbance) before and after irradiation and then we calculate net absorbance. We constructed calibration curves to relate the measured absorbance in terms of absorbed dose for all available electron energies. Dosimetric measurements were performed for mixed electron beam delivery and we also performed measurement for segmented field delivery with the dosimeter placed at the junction of two adjacent electron beams of different energies. Dose measured by our gel dosimetry is compared to that calculation from our precise treatment planning system. We also initiated a Monte Carlo study to evaluate the water equivalence of our dosimeters. MCBEAM and MCSIM codes were used for treatment head simulation and phantom dose calculation. PDDs and profiles were calculated for electron beams incident on a phantom designed with 1cm slab of Fricke gel. Results: The calibration curves showed no observed energy dependence with all studied electron beam energies. Good agreement was obtained between dose calculated and that obtained by gel dosimetry. Monte Carlo results illustrated the tissue equivalency of our Gel dosimeters. Conclusion: Fricke Gel dosimeters represent a good option for the dosimetric quality assurance prior to MERT application.« less

SU-E-T-643: Pure Alanine Dosimeter for Verification Dosimetry in IMRT

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

Al-Karmi, Anan M.; Zraiqat, Fadi

Purpose: The objective of this study was evaluation of accuracy of pure alanine dosimeters measuring intensity-modulated radiation therapy (IMRT) dose distributions in a thorax phantom. Methods: Alanine dosimeters were prepared in the form of 110 mg pure L-α-alanine powder filled into clear tissue-equivalent polymethylmethacrylate (PMMA) plastic tubes with the dimensions 25 mm length, 3 mm inner diameter, and 1 mm wall thickness. A dose-response calibration curve was established for the alanine by placing the dosimeters at 1.5 cm depth in a 30×30×30 cm{sup 3} solid water phantom and then irradiating on a linac with 6 MV photon beam at 10×10more » cm{sup 2} field size to doses ranging from 1 to 5 Gy. Electron paramagnetic resonance (EPR) spectroscopy was used to determine the absorbed dose in alanine. An IMRT treatment plan was designed for a commercial heterogeneous CIRS thorax phantom and the dose values were calculated at three different points located in tissue, lung, and bone equivalent materials. A set of dose measurements was carried out to compare measured and calculated dose values by placing the alanine dosimeters at those selected locations inside the thorax phantom and delivering the IMRT to the phantom. Results: The alanine dose measurements and the IMRT plan dose calculations were found to be in agreement within ±2%. Specifically, the deviations were −0.5%, 1.3%, and −1.7% for tissue, lung, and bone; respectively. The slightly large deviations observed for lung and bone may be attributed to tissue inhomogeneity, steep dose gradients in these regions, and uncontrollable changes in spectrometer conditions. Conclusion: The results described herein confirmed that pure alanine dosimeter was suitable for in-phantom dosimetry of IMRT beams because of its high sensitivity and acceptable accuracy. This makes the dosimeter a promising option for quality control of the therapeutic beams, complementing the commonly used ionization chambers, TLDs, and films.« less

SU-F-T-304: Complex Multi-PTV Treatment Evaluation Using a Remotely Processed 3D Gel Dosimeter

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

Hoisak, J; Dragojevic, I; Sutlief, S

Purpose: A new 3D gel dosimeter (ClearView™, Modus Medical Systems) was investigated for use as a QA tool for stereotactic radiosurgery (SRS) plans exhibiting high dose gradients and spatially separated treatment targets. The unique feature of this gel dosimeter is the remote processing service provided by Modus Medical Systems. Methods: The gel dosimeters were filled in either 10 cm diameter or 15 cm diameter clear plastic jars. The jars were then shipped in ice-cooled containers to our department for irradiation. Clinical SRS plans for treatment of multiple metastases and plans with simulated concave structures were applied to a CT scanmore » of the gel dosimeter. The gel was irradiated in treatment position using modulated arcs and then returned in the cooled container for processing. The 3D gel dose was compared to the DICOM-RT dose from the treatment plan to assess dosimetric and geometric agreement. Results: There was no discernible difference between the planned and measured dose for dose gradients as high as 10%/mm, which was the highest gradient we evaluated. Geometric agreement for distant metastases separated by 6 cm was within 1.5 mm. Among three identically irradiated gels using a plan intended for nine metastases, the 3%/3mm gamma passing rate was 84.5% with a range of 14.7%, measured over the entire volume of the dosimeter. Regions of larger gamma values correlated with geometric offsets between the planned and measured data. Conclusion: The gel dosimeter exhibits the dosimetric and geometric characteristics necessary for 3D evaluation of treatment plan deliverability. The range of observed gamma passing rates suggests a high sensitivity to geometric registration. With proper management of geometric registration between planned and measured data, this service should enable a radiation oncology department to use 3D dosimetry in end-to-end testing or patient plan delivery QA without the expense of an in-house processing system.« less

TU-F-BRE-08: Significant Variations in Measured Small Cone Output Factor for FFF Beams

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

Sudhyadhom, A; Ma, L; Kirby, N

2014-06-15

Purpose: To evaluate the measurement accuracy of several dosimeters for small cone output factors in two SRS/SBRT dedicated systems with Flattening Filter Free (FFF) beams: a Varian TrueBeam STx (TB) and an Accuray CyberKnife VSI (CK). Output factors (OFs) were measured for both machines and for CK, compared against a Monte Carlo model. Methods: Dose measurements were taken using three different FFF beams (TB 6XFFF, TB 10XFFF, and CK 6XFFF). Three commonly used types of dosimeters were examined in this work: a micro-ion chamber (Exradin A16), two shielded diodes (PTW TN60008 and PTW TN60017), and radiochromic film (Gafchromic EBT2). Measuredmore » OFs from these dosimeters were compared with each other and OFs measured with an Exradin W1 scintillator. Monte Carlo determined correction factors for the CK beam for the micro-ion chamber and diodes were applied to the respective OF measurements and compared against scintillator measured OFs corrected for volume averaging. Results: OFs measured for the smallest fields using the micro-ion chamber, diodes, scintillator, and film varied substantially (with up to a 16% difference between dosimeters). Micro-ion chamber and film OF measurements were up to 9% and 10%, respectively, lower than scintillator measurements for the smallest fields. OF measurements by diode were up to 6% greater than scintillator measurements for the smallest fields. With correction factors, the micro-ion chamber and diode measured OFs showed good agreement with scintillator measured OFs for the CK 6XFFF beam (within 3% and 1.5%, respectively). Conclusion: Uncorrected small field OFs vary significantly with dosimeter. The accuracy of scintillator measurements for small field OFs may be greater than the other dosimeters studied in this work (when uncorrected). Measurements involving EBT2 film may Result in lower accuracy for smaller fields (less than 10mm). Care should be taken in the choice of the dosimeter used for small field OF measurements.« less

SU-F-T-477: Investigation of DEFGEL Dosimetry Using MRI

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

Matrosic, C; McMillan, A; Bednarz, B

Purpose: The DEFGEL dosimeter/phantom allows for the measurement of 3D dose distributions while maintaining tissue equivalence and deformability. Although DEFGEL is traditionally read out with optical CT, the use of MRI would permit the measurement of 3D dose distributions in optically interfering configurations, like while embedded in a phantom. To the knowledge of the authors, this work is the first investigation that uses MRI to measure dose distributions in DEFGEL dosimeters. Methods: The DEFGEL (6%T) formula was used to create 1 cm thick, 4.5 cm diameter cylindrical dosimeters. The dosimeters were irradiated using a Varian Clinac 21EX linac. The MRImore » based transverse relaxation rate (R2) of the gel was measured in a central slice of the dosimeter with a Spin-Echo (SE) pulse sequence on a 3T GE SIGNA PET/MR scanner. The R2 values were fit to a monoexponential dose response equation using in-house software (MATLAB). Results: The data was well fit using a monoexponential fit for R2 as a function of absorbed dose (R{sup 2} = 0.9997). The fitting parameters of the monoexponential fit resulted in a 0.1229 Gy{sub −1}s{sub −1} slope. The data also resulted in an average standard deviation of 1.8% for the R2 values within the evaluated ROI. Conclusion: The close fit for the dose response curve shows that a DEFGEL based dosimeter can be paired with a SE MRI acquisition. The Type A uncertainty of the MRI method shows adequate precision, while the slope of the fit curve is large enough that R2 differences between different gel doses are distinguishable. These results suggest that the gel could potentially be used in configurations where an optical readout is not viable, such as measurements with the gel dosimeter positioned inside larger or optically opaque phantoms. This work is partially funded by NIH grant R01CA190298.« less

Radiation dosimeter utilizing the thermoluminescence of lithium fluoride.

PubMed

CAMERON, J R; DANIELS, F; JOHNSON, N; KENNEY, G

1961-08-04

A dosimeter, with little wavelength dependence and large useful energy range for electromagnetic radiation, which is simple to use and read, has been developed. It appears to have applications in personnel monitoring as well as radiation research.

Characterisation of TruView™: a new 3-D reusable radiochromic MethylThymolBlue based gel dosimeter for ionising radiations

NASA Astrophysics Data System (ADS)

Colnot, J.; Huet, C.; Clairand, I.

2017-05-01

TruView™ is a new water-equivalent reusable Fricke gel dosimeter based on MethylThymolBlue reactive dye. Details of the characterisation of the TruView™ MTB gel dosimeter by spectrophotometric measurements and of its reading with the Optical-CT Scanner Vista™ are described. In this study, the different parameters influencing TruView™ dose response have been studied and its performances have been compared to chamber and diodes measurements. This gel presents a linear response with dose up to 20 Gy, independent in the investigated range of photon beam energy and dose rate and also a good intra-batch uniformity. Ions diffusion into the matrix homogenizes the gel after a week, losing dosimetric information but allowing a new irradiation to be performed. However, auto-oxidation happens before and after irradiation, degrading the dosimeter response and stability. Storage and reading conditions affect the response as well.

RADIATION DOSIMETER

DOEpatents

Balkwell, W.R. Jr.; Adams, G.D. Jr.

1960-05-10

An improvement was made in the determination of amounts of ionizing radiation, particularly low-energy beta particles of less than 1000 rad total dose by means of fluid-phase dosimeter employing a stabilized-- sensitized ferrous-ferric colorimetric system in a sulphuric acid medium. The improvement in the dosimeter consists of adding to the ferrous-ferric system in concentrations of 10/sub -2/ to 10/sup -4/M an organic compound having one or more carboxylic or equivalent groups, such compounds being capable of chelating or complexing the iron ions in the solution. Suitable sensitizing and stabilizing agents are benzoic, phthalic, salicylic, malonic, lactic, maleic, oxalic, citric, succinic, phenolic tartaric, acetic, and adipic acid, as well as other compounds which are added to the solution alone or in certain combinations. As in conventional fluid-phase dosimeters, the absorbed dosage is correlated with a corresponding change in optical density at particular wavelengths of the solution.

Printable UV personal dosimeter: sensitivity as a function of DoD parameters and number of layers of a functional photonic ink

NASA Astrophysics Data System (ADS)

Sousa, Felipe L. N.; Mojica-Sánchez, Lizeth C.; Gavazza, Sávia; Florencio, Lourdinha; Vaz, Elaine C. R.; Santa-Cruz, Petrus A.

2016-04-01

This work presents ‘intelligent papers’ obtained by functional inks printed on cellulose-sheets by DoD inkjet technology and their performance as a photonic device for UV-radiation dosimetry. The dosimeter operation is based on the photodegradation of the active part of a photonic ink, btfa (4,4,4-trifluoro-1-phenyl-1,3-butanedione) ligands in Eu(III) complex, as a function of the UV dose (Jcm-2), and the one-way device is read by the luminescence quenching of (5D0 → 7F2) Eu3+ transition after UV exposure of the printed paper. The printed dosimeter presented an exponential behavior, measured here up to 10 Jcm-2 for UV-A, UV-B and UV-C, and it was shown that the number of jetted layers could fit the dosimeter sensitivity.

Validation and in vivo assessment of an innovative satellite-based solar UV dosimeter for a mobile app dedicated to skin health.

PubMed

Morelli, M; Masini, A; Simeone, E; Khazova, M

2016-08-31

We present an innovative satellite-based solar UV (ultraviolet) radiation dosimeter with a mobile app interface that has been validated by exploiting both ground-based measurements and an in vivo assessment of the erythemal effects on some volunteers having controlled exposure to solar radiation. The app with this satellite-based UV dosimeter also includes other related functionalities such as the provision of safe sun exposure time updated in real-time and end exposure visual/sound alert. Both validations showed that the system has a good accuracy and reliability needed for health-related applications. This app will be launched on the market by siHealth Ltd in May 2016 under the name of "HappySun" and is available for both Android and iOS devices (more info on ). Extensive R&D activities are on-going for the further improvement of the satellite-based UV dosimeter's accuracy.

Monitoring of environmental UV radiation by biological dosimeters

NASA Astrophysics Data System (ADS)

Rontó, Gy.; Bérces, A.; Gróf, P.; Fekete, A.; Kerékgyártó, T.; Gáspár, S.; Stick, C.

As a consequence of the stratospheric ozone layer depletion biological systems can be damaged due to increased UV-B radiation. The aim of biological dosimetry is to establish a quantitative basis for the risk assessment of the biosphere. DNA is the most important target molecule of biological systems having special sensitivity against short wavelength components of the environmental radiation. Biological dosimeters are usually simple organisms, or components of them, modeling the cellular DNA. Phage T7 and polycrystalline uracil biological dosimeters have been developed and used in our laboratory for monitoring the environmental radiation in different radiation conditions (from the polar to equatorial regions). Comparisons with Robertson-Berger (RB) meter data, as well as with model calculation data weighted by the corresponding spectral sensitivities of the dosimeters are presented. Suggestion is given how to determine the trend of the increase in the biological risk due to ozone depletion.

Pliocene Model Intercomparison (PlioMIP) Phase 2: Scientific Objectives and Experimental Design

NASA Technical Reports Server (NTRS)

Haywood, A. M.; Dowsett, H. J.; Dolan, A. M.; Rowley, D.; Abe-Ouchi, A.; Otto-Bliesner, B.; Chandler, M. A.; Hunter, S. J.; Lunt, D. J.; Pound, M.;

Section 9.1 new dosimeters. New dosimetry systems

NASA Astrophysics Data System (ADS)

McLaughlin, William L.

During the past two years there have been significant advances in several forms of radiation measurement systems for radiation processing, covering dose ranges of 1-10 6 Gy. Calorimeters as reference standards for both ionizing photon and electron fields have become well-established. In addition to the older ceric-cerous dosimetry solution analyzed potentiometrically, new liquid-phase dosimeters include those analyzed by spectrophotometry, e.g., improved forms of acidic aqueous solutions of K-Ag dichromate and organic radiochromic dye solutions. It has recently been demonstrated that by using certain refined sugars, e.g., D-(-) ribose, optical rotation response in aqueous solutions can be enhanced for dosimetry at doses > 10 4 Gy. There has been expanded development, use, and formulation (rods, tablets, and thin films) of the amino acid, alanine, as a solid-phase dosimeter analyzed by either ESR spectrometry or by glutamine or alanine spectrophotometry of complexes with ferric ion in the presence of a sulfonphthalein dye (xylenol orange). New commercial types of radiochromic plastic dosimeters, e.g., GafChromic TM, Riso B3 TM, GAMMACHROME YR TM, Radix TM, and Gammex TM, have been introduced and applied in practice. Improvements and broader use of optical waveguide dosimeters, e.g., Opti-Chromic TM, have also been reported, especially in food irradiation applications. Several novel dyed plastic dosimeters are available in large quantities and they lose color due to irradiation. An example is a dyed cellulosic thin film (ATC type DY-42 TM) which can be measured spectrophotometrically or densitometrically up to doses as high as 10 6 Gy.

Electron paramagnetic resonance (EPR) dosimetry using lithium formate in radiotherapy: comparison with thermoluminescence (TL) dosimetry using lithium fluoride rods.

PubMed

Vestad, Tor Arne; Malinen, Eirik; Olsen, Dag Rune; Hole, Eli Olaug; Sagstuen, Einar

2004-10-21

Solid-state radiation dosimetry by electron paramagnetic resonance (EPR) spectroscopy and thermoluminescence (TL) was utilized for the determination of absorbed doses in the range of 0.5-2.5 Gy. The dosimeter materials used were lithium formate and lithium fluoride (TLD-100 rods) for EPR dosimetry and TL dosimetry, respectively. 60Co gamma-rays and 4, 6, 10 and 15 MV x-rays were employed. The main objectives were to compare the variation in dosimeter reading of the respective dosimetry systems and to determine the photon energy dependence of the two dosimeter materials. The EPR dosimeter sensitivity was constant over the dose range in question, while the TL sensitivity increased by more than 5% from 0.5 to 2.5 Gy, thus displaying a supralinear dose response. The average relative standard deviation in the dosimeter reading per dose was 3.0% and 1.2% for the EPR and TL procedures, respectively. For EPR dosimeters, the relative standard deviation declined significantly from 4.3% to 1.1% over the dose range in question. The dose-to-water energy response for the megavoltage x-ray beams relative to 60Co gamma-rays was in the range of 0.990-0.979 and 0.984-0.962 for lithium formate and lithium fluoride, respectively. The results show that EPR dosimetry with lithium formate provides dose estimates with a precision comparable to that of TL dosimetry (using lithium fluoride) for doses above 2 Gy, and that lithium formate is slightly less dependent on megavoltage photon beam energy than lithium fluoride.

Electron paramagnetic resonance (EPR) dosimetry using lithium formate in radiotherapy: comparison with thermoluminescence (TL) dosimetry using lithium fluoride rods

NASA Astrophysics Data System (ADS)

Vestad, Tor Arne; Malinen, Eirik; Rune Olsen, Dag; Olaug Hole, Eli; Sagstuen, Einar

2004-10-01

Solid-state radiation dosimetry by electron paramagnetic resonance (EPR) spectroscopy and thermoluminescence (TL) was utilized for the determination of absorbed doses in the range of 0.5-2.5 Gy. The dosimeter materials used were lithium formate and lithium fluoride (TLD-100 rods) for EPR dosimetry and TL dosimetry, respectively. 60Co ggr-rays and 4, 6, 10 and 15 MV x-rays were employed. The main objectives were to compare the variation in dosimeter reading of the respective dosimetry systems and to determine the photon energy dependence of the two dosimeter materials. The EPR dosimeter sensitivity was constant over the dose range in question, while the TL sensitivity increased by more than 5% from 0.5 to 2.5 Gy, thus displaying a supralinear dose response. The average relative standard deviation in the dosimeter reading per dose was 3.0% and 1.2% for the EPR and TL procedures, respectively. For EPR dosimeters, the relative standard deviation declined significantly from 4.3% to 1.1% over the dose range in question. The dose-to-water energy response for the megavoltage x-ray beams relative to 60Co ggr-rays was in the range of 0.990-0.979 and 0.984-0.962 for lithium formate and lithium fluoride, respectively. The results show that EPR dosimetry with lithium formate provides dose estimates with a precision comparable to that of TL dosimetry (using lithium fluoride) for doses above 2 Gy, and that lithium formate is slightly less dependent on megavoltage photon beam energy than lithium fluoride.

Practical calibration curve of small-type optically stimulated luminescence (OSL) dosimeter for evaluation of entrance skin dose in the diagnostic X-ray region.

PubMed

Takegami, Kazuki; Hayashi, Hiroaki; Okino, Hiroki; Kimoto, Natsumi; Maehata, Itsumi; Kanazawa, Yuki; Okazaki, Tohru; Kobayashi, Ikuo

2015-07-01

For X-ray diagnosis, the proper management of the entrance skin dose (ESD) is important. Recently, a small-type optically stimulated luminescence dosimeter (nanoDot OSL dosimeter) was made commercially available by Landauer, and it is hoped that it will be used for ESD measurements in clinical settings. Our objectives in the present study were to propose a method for calibrating the ESD measured with the nanoDot OSL dosimeter and to evaluate its accuracy. The reference ESD is assumed to be based on an air kerma with consideration of a well-known back scatter factor. We examined the characteristics of the nanoDot OSL dosimeter using two experimental conditions: a free air irradiation to derive the air kerma, and a phantom experiment to determine the ESD. For evaluation of the ability to measure the ESD, a calibration curve for the nanoDot OSL dosimeter was determined in which the air kerma and/or the ESD measured with an ionization chamber were used as references. As a result, we found that the calibration curve for the air kerma was determined with an accuracy of 5 %. Furthermore, the calibration curve was applied to the ESD estimation. The accuracy of the ESD obtained was estimated to be 15 %. The origin of these uncertainties was examined based on published papers and Monte-Carlo simulation. Most of the uncertainties were caused by the systematic uncertainty of the reading system and the differences in efficiency corresponding to different X-ray energies.

Feasibility of dose enhancement assessment: Preliminary results by means of Gd-infused polymer gel dosimeter and Monte Carlo study.

PubMed

Santibáñez, M; Guillen, Y; Chacón, D; Figueroa, R G; Valente, M

2018-04-11

This work reports the experimental development of an integral Gd-infused dosimeter suitable for Gd dose enhancement assessment along with Monte Carlo simulations applied to determine the dose enhancement by radioactive and X-ray sources of interest in conventional and electronic brachytherapy. In this context, capability to elaborate a stable and reliable Gd-infused dosimeter was the first goal aimed at direct and accurate measurements of dose enhancement due to Gd presence. Dose-response was characterized for standard and Gd-infused PAGAT polymer gel dosimeters by means of optical transmission/absorbance. The developed Gd-infused PAGAT dosimeters demonstrated to be stable presenting similar dose-response as standard PAGAT within a linear trend up to 13 Gy along with good post-irradiation readout stability verified at 24 and 48 h. Additionally, dose enhancement was evaluated for Gd-infused PAGAT dosimeters by means of Monte Carlo (PENELOPE) simulations considering scenarios for isotopic and X-ray generator sources. The obtained results demonstrated the feasibility of obtaining a maximum enhancement around of (14 ± 1)% for 192 Ir source and an average enhancement of (70 ± 13)% for 241 Am. However, dose enhancement up to (267 ± 18)% may be achieved if suitable filtering is added to the 241 Am source. On the other hand, optimized X-ray spectra may attain dose enhancements up to (253 ± 22) %, which constitutes a promising future alternative for replacing radioactive sources by implementing electronic brachytherapy achieving high dose levels. Copyright © 2018. Published by Elsevier Ltd.

Comparative study on skin dose measurement using MOSFET and TLD for pediatric patients with acute lymphatic leukemia.

PubMed

Al-Mohammed, Huda I; Mahyoub, Fareed H; Moftah, Belal A

2010-07-01

The object of this study was to compare the difference of skin dose measured in patients with acute lymphatic leukemia (ALL) treated with total body irradiation (TBI) using metal oxide semiconductor field-effect transistors (mobile MOSFET dose verification system (TN-RD-70-W) and thermoluminescent dosimeters (TLD-100 chips, Harshaw/ Bicron, OH, USA). Because TLD has been the most-commonly used technique in the skin dose measurement of TBI, the aim of the present study is to prove the benefit of using the mobile MOSFET (metal oxide semiconductor field effect transistor) dosimeter, for entrance dose measurements during the total body irradiation (TBI) over thermoluminescent dosimeters (TLD). The measurements involved 10 pediatric patients ages between 3 and 14 years. Thermoluminescent dosimeters and MOSFET dosimetry were performed at 9 different anatomic sites on each patient. The present results show there is a variation between skin dose measured with MOSFET and TLD in all patients, and for every anatomic site selected, there is no significant difference in the dose delivered using MOSFET as compared to the prescribed dose. However, there is a significant difference for every anatomic site using TLD compared with either the prescribed dose or MOSFET. The results indicate that the dosimeter measurements using the MOSFET gave precise measurements of prescribed dose. However, TLD measurement showed significant increased skin dose of cGy as compared to either prescribed dose or MOSFET group. MOSFET dosimeters provide superior dose accuracy for skin dose measurement in TBI as compared with TLD.

Beam profiles measured with thermoluminescent dosimeters

NASA Technical Reports Server (NTRS)

Lucks, H.; Marcowitz, S. M.; Wheeler, R. W.

1969-01-01

Beam profilometer, using thermoluminescent dosimeters, gives a quantitative and qualitative representation of the focus of an external protron beam of a synchrotron. The total number of particles in the beam, particle distribution, and the shape of the beam are determined.

Practical new method of measuring thermal-neutron fluence

NASA Technical Reports Server (NTRS)

Siebold, J. R.; Warman, E. A.

1967-01-01

Thermoluminescence dosimeter technique measures thermal-neutron fluence by encapsulating lithium flouride phosphor powder and exposing it to a neutron environment. The capsule is heated in a dosimeter reader, which results in light emission proportional to the neutron fluence.

Impacts of parameterized orographic drag on the Northern Hemisphere winter circulation

PubMed Central

Bechtold, Peter; Beljaars, Anton; Bozzo, Alessio; Pithan, Felix; Shepherd, Theodore G.; Zadra, Ayrton

2016-01-01

Abstract A recent intercomparison exercise proposed by the Working Group for Numerical Experimentation (WGNE) revealed that the parameterized, or unresolved, surface stress in weather forecast models is highly model‐dependent, especially over orography. Models of comparable resolution differ over land by as much as 20% in zonal mean total subgrid surface stress (τtot). The way τtot is partitioned between the different parameterizations is also model‐dependent. In this study, we simulated in a particular model an increase in τtot comparable with the spread found in the WGNE intercomparison. This increase was simulated in two ways, namely by increasing independently the contributions to τtot of the turbulent orographic form drag scheme (TOFD) and of the orographic low‐level blocking scheme (BLOCK). Increasing the parameterized orographic drag leads to significant changes in surface pressure, zonal wind and temperature in the Northern Hemisphere during winter both in 10 day weather forecasts and in seasonal integrations. However, the magnitude of these changes in circulation strongly depends on which scheme is modified. In 10 day forecasts, stronger changes are found when the TOFD stress is increased, while on seasonal time scales the effects are of comparable magnitude, although different in detail. At these time scales, the BLOCK scheme affects the lower stratosphere winds through changes in the resolved planetary waves which are associated with surface impacts, while the TOFD effects are mostly limited to the lower troposphere. The partitioning of τtot between the two schemes appears to play an important role at all time scales. PMID:27668040

Impacts of parameterized orographic drag on the Northern Hemisphere winter circulation

NASA Astrophysics Data System (ADS)

Sandu, Irina; Bechtold, Peter; Beljaars, Anton; Bozzo, Alessio; Pithan, Felix; Shepherd, Theodore G.; Zadra, Ayrton

2016-03-01

A recent intercomparison exercise proposed by the Working Group for Numerical Experimentation (WGNE) revealed that the parameterized, or unresolved, surface stress in weather forecast models is highly model-dependent, especially over orography. Models of comparable resolution differ over land by as much as 20% in zonal mean total subgrid surface stress (τtot). The way τtot is partitioned between the different parameterizations is also model-dependent. In this study, we simulated in a particular model an increase in τtot comparable with the spread found in the WGNE intercomparison. This increase was simulated in two ways, namely by increasing independently the contributions to τtot of the turbulent orographic form drag scheme (TOFD) and of the orographic low-level blocking scheme (BLOCK). Increasing the parameterized orographic drag leads to significant changes in surface pressure, zonal wind and temperature in the Northern Hemisphere during winter both in 10 day weather forecasts and in seasonal integrations. However, the magnitude of these changes in circulation strongly depends on which scheme is modified. In 10 day forecasts, stronger changes are found when the TOFD stress is increased, while on seasonal time scales the effects are of comparable magnitude, although different in detail. At these time scales, the BLOCK scheme affects the lower stratosphere winds through changes in the resolved planetary waves which are associated with surface impacts, while the TOFD effects are mostly limited to the lower troposphere. The partitioning of τtot between the two schemes appears to play an important role at all time scales.

Intercomparison of three microwave/infrared high resolution line-by-line radiative transfer codes

NASA Astrophysics Data System (ADS)

Schreier, F.; Garcia, S. Gimeno; Milz, M.; Kottayil, A.; Höpfner, M.; von Clarmann, T.; Stiller, G.

2013-05-01

An intercomparison of three line-by-line (lbl) codes developed independently for atmospheric sounding - ARTS, GARLIC, and KOPRA - has been performed for a thermal infrared nadir sounding application assuming a HIRS-like (High resolution Infrared Radiation Sounder) setup. Radiances for the HIRS infrared channels and a set of 42 atmospheric profiles from the "Garand dataset" have been computed. Results of this intercomparison and a discussion of reasons of the observed differences are presented.

Radiation dosimetry with fiber Bragg gratings

NASA Astrophysics Data System (ADS)

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

2014-05-01

The measurement and monitoring of radiation dose delivered in patient tissues is a critical aspect in radiation therapy. Various dosimeters have proven effective in measuring radiations at low doses. However, there is a growing demand for new dosimeters based on small, non-invasive and high resolution devices. Here we report on a miniature dosimeter based on an optical fiber cavity. We demonstrate an ultimate detection limit of 160 mGy with an effective interaction region of 6 x 10-4 mm3. Due to its reliability, compactness and biomedical dose level sensitivity, our system shows itself suitable for applications in radiation therapy dosimetry.

Applicability of Topaz Composites to Electron Dosimetry

NASA Astrophysics Data System (ADS)

Bomfim, K. S.; Souza, D. N.

2010-11-01

Thermoluminescent dosimetric topaz properties have been investigated and the results have shown that this mineral presents characteristics of a good dosimeter mainly in doses evaluation in radiotherapy with photons beams in radiotherapy. Typical applications of thermoluminescent dosimeters in radiotherapy are: in vivo dosimetry on patients (either as a routine quality assurance procedure or for dose monitoring in special cases); verification of treatment techniques; dosimetry audits; and comparisons among hospitals. The mean aim of this work was to evaluate the efficiency of topaz-Teflon pellets as thermoluminescent dosimeters in high-energy electron beams used to radiotherapy. Topaz-Teflon pellets were used as TLD.

Evaluation of the response to xenon-133 radiations by thermoluminescent dosimeters used during the accident at Three Mile Island.

PubMed

Riley, R J; Zanzonico, P B; Masterson, M E; St Germain, J M; Laughlin, J S

1982-03-01

An evaluation is presented of the accuracy and sensitivity of three types of TLD's used during the accident at the Three Mile Island Nuclear Station. This evaluation indicated that, due to the method of calibration, all the dosimeters over-responded to 133Xe radiations. The response ranged from slightly above unity to almost two. Exposures of the TLD's were of two types, namely, the characteristic X-rays either were or were not filtered from the beam. The angular sensitivity of the dosimeters is also reported.

X-ray microbeam measurements with a high resolution scintillator fibre-optic dosimeter.

PubMed

Archer, James; Li, Enbang; Petasecca, Marco; Dipuglia, Andrew; Cameron, Matthew; Stevenson, Andrew; Hall, Chris; Hausermann, Daniel; Rosenfeld, Anatoly; Lerch, Michael

2017-09-29

Synchrotron microbeam radiation therapy is a novel external beam therapy under investigation, that uses highly brilliant synchrotron x-rays in microbeams 50 μm width, with separation of 400 μm, as implemented here. Due to the fine spatial fractionation dosimetry of these beams is a challenging and complicated problem. In this proof-of-concept work, we present a fibre optic dosimeter that uses plastic scintillator as the radiation conversion material. We claim an ideal one-dimensional resolution of 50 μm. Using plastic scintillator and fibre optic makes this dosimeter water-equivalent, a very desirable dosimetric property. The dosimeter was tested at the Australian Synchrotron, on the Imaging and Medical Beam-Line. The individual microbeams were able to be resolved and the peak-to-valley dose ratio and the full width at half maximum of the microbeams was measured. These results are compared to a semiconductor strip detector of the same spatial resolution. A percent depth dose was measured and compared to data acquired by an ionisation chamber. The results presented demonstrate significant steps towards the development of an optical dosimeter with the potential to be applied in quality assurance of microbeam radiation therapy, which is vital if clinical trials are to be performed on human patients.

Characterization of OSL dosimeters for use in dose assessment in Computed Tomography procedures.

PubMed

Giansante, Louise; Santos, Josilene C; Umisedo, Nancy K; Terini, Ricardo A; Costa, Paulo R

2018-03-01

This study describes the characterization of an Al 2 O 3 :C OSLD (Landauer's Luxel™ tape) for dose evaluation in Computed Tomography. The irradiations were conducted using both a constant potential X-ray equipment and a 64-slice clinical CT scanner, and the readouts were performed using a Risø TL/OSL reader. The following aspects were studied: batch homogeneity, energy response, linearity of dose response, reproducibility, reusability, and effect of uncertainties with the normalization of OSL signals per their response to beta radiation. A group of 330 dosimeters from the 452 irradiated with the same dose presented OSL signals within the interval of 4.7% from the average. The dosimeters presented energy-dependent response in good agreement with results found in the literature. The air kerma response of the OSL signal showed a linear trend for both the constant potential X-ray device and the clinical CT scanner, with differences in their slopes of approximately 10%. Reproducibility, reusability, and effect of beta normalization were analyzed by separating 72 dosimeters in 3 groups. The results obtained in this study together with those of previous works indicate that this type of dosimeter is adequate for dose evaluation in CT clinical applications. Copyright © 2018 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

[Measurement of scatter radiation on MDCT equipment using an OSL dosimeter].

PubMed

Tomita, Hironobu; Morozumi, Kunihiko

2004-11-01

The recent introduction of multi-detector row computed tomography (MDCT) has made it possible to scan the entire abdomen within approximately 10 sec in procedures such as interventional radiology computed tomography (IVRCT), which are associated with operator exposure. Therefore, anxious patients and patients who are not able to remain still can be examined with an assistant. In the present study, radiation exposure to the assistant was estimated, and the distribution of scattered radiation near the gantry was measured using an optically stimulated luminescence (OSL) dosimeter. Simultaneous measurements were obtained using a direction storage (DIS) dosimeter for reference. The maximum value of 1.47 mSv per examination was obtained at the point closest to the gantry's center (50 cm from the center at a height of 150 cm above the floor) . In addition, scattered radiation decreased as the measurement point was moved further from the gantry's center, falling below the limit of detection (0.1 mSv or less) at 200 cm and at the sides of the gantry. OSL dosimeters are also employed as personal dosimeters, permitting reliable values to be obtained easily. They were found to be an effective tool for the measurement of scattered radiation, as in the present study, helping to provide better understanding of the distribution of scattered radiation within the CT room.

Effect of the Scattering Radiation in Air and Two Type of Slap Phantom between PMMA and the ISO Water Phantom for Personal Dosimeters Calibration

NASA Astrophysics Data System (ADS)

Kamwang, N.; Rungseesumran, T.; Saengchantr, D.; Monthonwattana, S.; Pungkun, V.

2017-06-01

The calibration of personal dosimeter to determine the quantities of the personal dose equivalent, Hp(d), is required to be placed on a suitable phantom in order to provide a reasonable approximation to the radiation backscattering properties as equivalent as part of body. The dosimeter which is worn on the trunk usually calibrated with slap phantom which recommended in ICRU 47 with dimension of 30 cm (w) x 30 cm (h) x 15 cm (t) PMMA slab phantom to achieve uniformity in calibration procedures, on the other hand the International Organization for Standardization (ISO), ISO 4037-3, proposed the ISO water slap phantom, with PMMA walls, same dimension but different wall thickness (front wall 2.5 mm and other side wall 10 mm thick) and fill with water. However, some laboratories are still calibrating a personal dosimeter in air in term of ambient dose equivalent, H*(d). This research study the effect of the scattering radiation in two type of those slap phantoms and in air, to calibrate two type of OSL (XA and LA) and electronic personal dosimeters. The X-ray and Cs-137 radiation field with the energy range from 33 to 662 keV were used. The results of this study will be discussed.

Study of L-aspartic acid for its possible use as a dosimeter in the interval of 3.4-20 kGy at different irradiation temperatures

NASA Astrophysics Data System (ADS)

Meléndez-López, Adriana; Negrón-Mendoza, Alicia; Gómez-Vidales, Virginia; Uribe, Roberto M.; Ramos-Bernal, Sergio

2014-11-01

Certain commercial applications of radiation processing increase the efficiency of chemical reactions at low temperatures to decrease the free radicals in the bulk material and avoid the synergistic effects of heat. Such applications have motivated the search for a reliable, low-temperature dosimeter for use under the conditions of the irradiation process. For this purpose, polycrystalline samples of L-aspartic acid (2-aminobutanedioic acid) were irradiated with gamma rays at low temperatures and doses in the kiloGray range (3.4-64 kGy). The potential use of the aspartic acid system as a chemical dosimeter is based on the formation of stable free radicals when the amino acid is exposed to ionizing radiation. These radicals can be studied and quantified using electron spin resonance (ESR). The response curves at different temperatures show that the intensity of the ESR spectra (the five characteristic lines) depends on the dose received. The response of the dosimeter increases with increasing temperature, and this relationship is linear up to 20 kGy at 298 K. The decay characteristics show that the change in the ESR signal over time is low and reproducible. In addition, the L-aspartic acid dosimeter is easy to handle and has low cost.

Feasibility of CBCT dosimetry for IMRT using a normoxic polymethacrylic-acid gel dosimeter

NASA Astrophysics Data System (ADS)

Bong, Ji Hye; Kwon, Soo-Il; Kim, Kum Bae; Kim, Mi Suk; Jung, Hai Jo; Ji, Young Hoon; Ko, In Ok; Park, Ji Ae; Kim, Kyeong Min

2013-09-01

The purpose of this study is to evaluate the availability of cone-beam computed tomography(CBCT) for gel dosimetry. The absorbed dose was analyzed by using intensity-modulated radiation therapy(IMRT) to irradiate several tumor shapes with a calculated dose and several tumor acquiring images with CBCT in order to verify the possibility of reading a dose on the polymer gel dosimeter by means of the CBCT image. The results were compared with those obtained using magnetic resonance imaging(MRI) and CT. The linear correlation coefficients at doses less than 10 Gy for the polymer gel dosimeter were 0.967, 0.933 and 0.985 for MRI, CT and CBCT, respectively. The dose profile was symmetric on the basis of the vertical axis in a circular shape, and the uniformity was 2.50% for the MRI and 8.73% for both the CT and the CBCT. In addition, the gradient in the MR image of the gel dosimeter irradiated in an H shape was 109.88 while the gradients of the CT and the CBCT were 71.95 and 14.62, respectively. Based on better image quality, the present study showed that CBCT dosimetry for IMRT could be restrictively performed using a normoxic polymethacrylic-acid gel dosimeter.

An intercomparison of nitric oxide measurement techniques

NASA Technical Reports Server (NTRS)

Hoell, J. M., Jr.; Gregory, G. L.; Mcdougal, D. S.; Carroll, M. A.; Mcfarland, M.; Ridley, B. A.; Davis, D. D.; Bradshaw, J.; Rodgers, M. O.; Torres, A. L.

1985-01-01

Results from an intercomparison of techniques to measure tropospheric levels of nitric oxide (NO) are discussed. The intercomparison was part of the National Aeronautics and Space Administration's Global Tropospheric Experiment and was conducted at Wallops Island, VA, in July 1983. Instruments intercompared included a laser-induced fluorescence system and two chemiluminescence instruments. The intercomparisons were performed with ambient air at NO mixing ratios ranging from 10 to 60 pptv and NO-enriched ambient air at mixing ratios from 20 to 170 pptv. All instruments sampled from a common manifold. The techniques exhibited a high degree of correlation among themselves and with changes in the NO mixing ratio. Agreement among the three techniques was placed at approximately + or - 30 percent. Within this level of agreement, no artifacts or species interferences were identified.

ISMIP6: Ice Sheet Model Intercomparison Project for CMIP6

NASA Technical Reports Server (NTRS)

Nowicki, S.

2015-01-01

ISMIP6 (Ice Sheet Model Intercomparison Project for CMIP6) targets the Cryosphere in a Changing Climate and the Future Sea Level Grand Challenges of the WCRP (World Climate Research Program). Primary goal is to provide future sea level contribution from the Greenland and Antarctic ice sheets, along with associated uncertainty. Secondary goal is to investigate feedback due to dynamic ice sheet models. Experiment design uses and augment the existing CMIP6 (Coupled Model Intercomparison Project Phase 6) DECK (Diagnosis, Evaluation, and Characterization of Klima) experiments. Additonal MIP (Model Intercomparison Project)- specific experiments will be designed for ISM (Ice Sheet Model). Effort builds on the Ice2sea, SeaRISE (Sea-level Response to Ice Sheet Evolution) and COMBINE (Comprehensive Modelling of the Earth System for Better Climate Prediction and Projection) efforts.

Assessment of the uncertainties in the Radiological Protection Institute of Ireland (RPII) radon measurements service.

PubMed

Hanley, O; Gutiérrez-Villanueva, J L; Currivan, L; Pollard, D

2008-10-01

The RPII radon (Rn) laboratory holds accreditation for the International Standard ISO/IEC 17025. A requirement of this standard is an estimate of the uncertainty of measurement. This work shows two approaches to estimate the uncertainty. The bottom-up approach involved identifying the components that were found to contribute to the uncertainty. Estimates were made for each of these components, which were combined to give a combined uncertainty of 13.5% at a Rn concentration of approximately 2500 Bq m(-3) at the 68% confidence level. By applying a coverage factor of k=2, the expanded uncertainty is +/-27% at the 95% confidence level. The top-down approach used information previously gathered from intercomparison exercises to estimate the uncertainty. This investigation found an expanded uncertainty of +/-22% at approximately 95% confidence level. This is good agreement for such independent estimates.

Sources of Variability in Chlorophyll Analysis by Fluorometry and High-Performance Liquid Chromatography in a SIMBIOS Inter-Calibration Exercise

NASA Technical Reports Server (NTRS)

VanHeukelem, Laurie; Thomas, Crystal S.; Gilbert, Patricia M.; Fargion, Giulietta S. (Editor); McClain, Charles R. (Editor)

2002-01-01

The purpose of this technical report is to provide current documentation of the Sensor Intercomparison and Merger for Biological and Interdisciplinary Oceanic Studies (SIMBIOS) Project activities, NASA Research Announcement (NRA) research status, satellite data processing, data product validation, and field calibration. This documentation is necessary to ensure that critical information is related to the scientific community and NASA management. This critical information includes the technical difficulties and challenges of validating and combining ocean color data from an array of independent satellite systems to form consistent and accurate global bio-optical time series products. This technical report is not meant as a substitute for scientific literature. Instead, it will provide a ready and responsive vehicle for the multitude of technical reports issued by an operational project. This particular document focus on the variability in chlorophyll pigment measurements resulting from differences in methodologies and laboratories conducting the pigment analysis.

Coupling Processes Between Atmospheric Chemistry and Climate

NASA Technical Reports Server (NTRS)

Ko, Malcolm K. W.; Weisenstein, Debra; Rodriguez, Jose; Danilin, Michael; Scott, Courtney; Shia, Run-Lie; Eluszkiewicz, Junusz; Sze, Nien-Dak

1999-01-01

This is the final report. The overall objective of this project is to improve the understanding of coupling processes among atmospheric chemistry, aerosol and climate, all important for quantitative assessments of global change. Among our priority are changes in ozone and stratospheric sulfate aerosol, with emphasis on how ozone in the lower stratosphere would respond to natural or anthropogenic changes. The work emphasizes two important aspects: (1) AER's continued participation in preparation of, and providing scientific input for, various scientific reports connected with assessment of stratospheric ozone and climate. These include participation in various model intercomparison exercises as well as preparation of national and international reports. and (2) Continued development of the AER three-wave interactive model to address how the transport circulation will change as ozone and the thermal properties of the atmosphere change, and assess how these new findings will affect our confidence in the ozone assessment results.

A comprehensive study of radon levels and associated radiation doses in Himalayan groundwater

NASA Astrophysics Data System (ADS)

Prasad, Mukesh; Kumar, G. Anil; Sahoo, B. K.; Ramola, R. C.

2018-03-01

The concentration of radon in groundwater is mainly governed by the radium content in the rocks of the aquifer. The internal exposure to high levels of radon in water is directly associated with the radiological risk to members of public. In this work, radon concentrations were measured in groundwater of Garhwal Himalaya, India, using scintillation detector-based RnDuo and silicon detector-based RAD7 monitors. An inter-comparison exercise was carried out between RnDuo and RAD7 techniques for a few samples to validate the results. The radiation doses associated with the exposure to radon in water were estimated from measured values of activity concentrations. An attempt has been made to see the effect of geology, geohydrology and different types of sources on radon levels in Himalayan groundwater. The experimental techniques and results obtained are discussed in detail.

Raman LIDAR for UHECR experiments: an overview of the L'Aquila (Italy) lidar station experience for the retrieval of quality-assured data

NASA Astrophysics Data System (ADS)

Iarlori, Marco; Rizi, Vincenzo; D'Amico, Giuseppe; Freudenthaler, Volker; Wandinger, Ulla; Grillo, Aurelio

L'Aquila (Italy) lidar station is part of the EARLINET (European Aerosol Research Lidar Network) since its beginning in the 2000. In the EARLINET community great efforts are devoted to the quality-assurance of the aerosol optical properties inserted in the database. To this end, each lidar station performed intercomparisons with reference instruments, a series of internal hardware checks in order to assess the quality of their instruments and exercises to test the algorithms used to retrieve the aerosol optical parameters. In this paper we give an overview of our experience within EARLINET qualityassurance (QA) program, which was adopted for the Raman lidar (RL) operated in the AUGER Observatory. This program could be systematically adopted for the lidar systems needed for the current and upcoming UHECR experiments, like CTA (Cherenkov Telescope Array).

Dose evaluation of an NIPAM polymer gel dosimeter using gamma index

NASA Astrophysics Data System (ADS)

Chang, Yuan-Jen; Lin, Jing-Quan; Hsieh, Bor-Tsung; Yao, Chun-Hsu; Chen, Chin-Hsing

2014-11-01

An N-isopropylacrylamide (NIPAM) polymer gel dosimeter has great potential in clinical applications. However, its three-dimensional dose distribution must be assessed. In this work, a quantitative evaluation of dose distributions was performed to evaluate the NIPAM polymer gel dosimeter using gamma analysis. A cylindrical acrylic phantom filled with NIPAM gel measuring 10 cm (diameter) by 10 cm (height) by 3 mm (thickness) was irradiated by a 4×4 cm2 square light field. The irradiated gel phantom was scanned using an optical computed tomography (optical CT) scanner (OCTOPUS™, MGS Research, Inc., Madison, CT, USA) at 1 mm resolution. The projection data were transferred to an image reconstruction program, which was written using MATLAB (The MathWorks, Natick, MA, USA). The program reconstructed the image of the optical density distribution using the algorithm of a filter back-projection. Three batches of replicated gel phantoms were independently measured. The average uncertainty of the measurements was less than 1%. The gel was found to have a high degree of spatial uniformity throughout the dosimeter and good temporal stability. A comparison of the line profiles of the treatment planning system and of the data measured by optical CT showed that the dose was overestimated in the penumbra region because of two factors. The first is light scattering due to changes in the refractive index at the edge of the irradiated field. The second is the edge enhancement caused by free radical diffusion. However, the effect of edge enhancement on the NIPAM gel dosimeter is not as significant as that on the BANG gel dosimeter. Moreover, the dose uncertainty is affected by the inaccuracy of the gel container positioning process. To reduce the uncertainty of 3D dose distribution, improvements in the gel container holder must be developed.

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.

An optically stimulated luminescence dosimeter for measuring patient exposure from imaging guidance procedures.

PubMed

Ding, George X; Malcolm, Arnold W

2013-09-07

There is a growing interest in patient exposure resulting from an x-ray imaging procedure used in image-guided radiation therapy. This study explores a feasibility to use a commercially available optically stimulated luminescence (OSL) dosimeter, nanoDot, for estimating imaging radiation exposure to patients. The kilovoltage x-ray sources used for kV-cone-beam CT (CBCT) imaging acquisition procedures were from a Varian on-board imager (OBI) image system. An ionization chamber was used to determine the energy response of nanoDot dosimeters. The chamber calibration factors for x-ray beam quality specified by half-value layer were obtained from an Accredited Dosimetry Calibration Laboratory. The Monte Carlo calculated dose distributions were used to validate the dose distributions measured by using the nanoDot dosimeters in phantom and in vivo. The range of the energy correction factors for the nanoDot as a function of photon energy and bow-tie filters was found to be 0.88-1.13 for different kVp and bow-tie filters. Measurement uncertainties of nanoDot were approximately 2-4% after applying the energy correction factors. The tests of nanoDot placed on a RANDO phantom and on patient's skin showed consistent results. The nanoDot is suitable dosimeter for in vivo dosimetry due to its small size and manageable energy dependence. The dosimeter placed on a patient's skin has potential to serve as an experimental method to monitor and to estimate patient exposure resulting from a kilovoltage x-ray imaging procedure. Due to its large variation in energy response, nanoDot is not suitable to measure radiation doses resulting from mixed beams of megavoltage therapeutic and kilovoltage imaging radiations.

An optically stimulated luminescence dosimeter for measuring patient exposure from imaging guidance procedures

NASA Astrophysics Data System (ADS)

Ding, George X.; Malcolm, Arnold W.

2013-09-01

There is a growing interest in patient exposure resulting from an x-ray imaging procedure used in image-guided radiation therapy. This study explores a feasibility to use a commercially available optically stimulated luminescence (OSL) dosimeter, nanoDot, for estimating imaging radiation exposure to patients. The kilovoltage x-ray sources used for kV-cone-beam CT (CBCT) imaging acquisition procedures were from a Varian on-board imager (OBI) image system. An ionization chamber was used to determine the energy response of nanoDot dosimeters. The chamber calibration factors for x-ray beam quality specified by half-value layer were obtained from an Accredited Dosimetry Calibration Laboratory. The Monte Carlo calculated dose distributions were used to validate the dose distributions measured by using the nanoDot dosimeters in phantom and in vivo. The range of the energy correction factors for the nanoDot as a function of photon energy and bow-tie filters was found to be 0.88-1.13 for different kVp and bow-tie filters. Measurement uncertainties of nanoDot were approximately 2-4% after applying the energy correction factors. The tests of nanoDot placed on a RANDO phantom and on patient's skin showed consistent results. The nanoDot is suitable dosimeter for in vivo dosimetry due to its small size and manageable energy dependence. The dosimeter placed on a patient's skin has potential to serve as an experimental method to monitor and to estimate patient exposure resulting from a kilovoltage x-ray imaging procedure. Due to its large variation in energy response, nanoDot is not suitable to measure radiation doses resulting from mixed beams of megavoltage therapeutic and kilovoltage imaging radiations.

Development of a high efficiency personal/environmental radon dosimeter using polycarbonate detectors.

PubMed

Taheri, M; Jafarizadeh, M; Baradaran, S; Zainali, Gh

2006-12-01

Passive radon dosimeters, based on alpha particle etched track detectors, are widely used for the assessment of radon exposure. These methods are often applied in radon dosimetry for long periods of time. In this research work, we have developed a highly efficient method of personal/environmental radon dosimetry that is based upon the detection of alpha particles from radon daughters, (218)Po and (214)Po, using a polycarbonate detector (PC). The radon daughters are collected on the filter surface by passing a fixed flow of air through it and the PC detector, placed at a specified distance from the filter, is simultaneously exposed to alpha particles. After exposure, the latent tracks on the detector are made to appear by means of an electrochemical etching process; these are proportional to the radon dose. The air flow rate and the detector-filter distance are the major factors that can affect the performance of the dosimeter. The results obtained in our experimental investigations have shown that a distance of 1.5 cm between the detector and the filter, an absorber layer of Al with a thickness of 12 microm and an air flow rate of 4 l min(-1) offer the best design parameters for a high efficiency radon dosimeter. Then, the designed dosimeter was calibrated against different values of radon exposures and the obtained sensitivity was found to be 2.1 (tracks cm(-2)) (kBq h m(-3))(-1). The most important advantages of this method are that it is reliable, fast and convenient when used for radon dose assessment. In this paper, the optimized parameters of the dosimeter structure and its calibration procedure are presented and discussed.

Measurement of Entrance Surface Dose on an Anthropomorphic Thorax Phantom Using a Miniature Fiber-Optic Dosimeter

PubMed Central

Yoo, Wook Jae; Shin, Sang Hun; Jeon, Dayeong; Hong, Seunghan; Sim, Hyeok In; Kim, Seon Geun; Jang, Kyoung Won; Cho, Seunghyun; Youn, Won Sik; Lee, Bongsoo

2014-01-01

A miniature fiber-optic dosimeter (FOD) system was fabricated using a plastic scintillating fiber, a plastic optical fiber, and a multi-pixel photon counter to measure real-time entrance surface dose (ESD) during radiation diagnosis. Under varying exposure parameters of a digital radiography (DR) system, we measured the scintillating light related to the ESD using the sensing probe of the FOD, which was placed at the center of the beam field on an anthropomorphic thorax phantom. Also, we obtained DR images using a flat panel detector of the DR system to evaluate the effects of the dosimeter on image artifacts during posteroanterior (PA) chest radiography. From the experimental results, the scintillation output signals of the FOD were similar to the ESDs including backscatter simultaneously obtained using a semiconductor dosimeter. We demonstrated that the proposed miniature FOD can be used to measure real-time ESDs with minimization of DR image artifacts in the X-ray energy range of diagnostic radiology. PMID:24694678

Measurement of entrance surface dose on an anthropomorphic thorax phantom using a miniature fiber-optic dosimeter.

PubMed

Yoo, Wook Jae; Shin, Sang Hun; Jeon, Dayeong; Hong, Seunghan; Sim, Hyeok In; Kim, Seon Geun; Jang, Kyoung Won; Cho, Seunghyun; Youn, Won Sik; Lee, Bongsoo

2014-04-01

A miniature fiber-optic dosimeter (FOD) system was fabricated using a plastic scintillating fiber, a plastic optical fiber, and a multi-pixel photon counter to measure real-time entrance surface dose (ESD) during radiation diagnosis. Under varying exposure parameters of a digital radiography (DR) system, we measured the scintillating light related to the ESD using the sensing probe of the FOD, which was placed at the center of the beam field on an anthropomorphic thorax phantom. Also, we obtained DR images using a flat panel detector of the DR system to evaluate the effects of the dosimeter on image artifacts during posteroanterior (PA) chest radiography. From the experimental results, the scintillation output signals of the FOD were similar to the ESDs including backscatter simultaneously obtained using a semiconductor dosimeter. We demonstrated that the proposed miniature FOD can be used to measure real-time ESDs with minimization of DR image artifacts in the X-ray energy range of diagnostic radiology.

Characterization and application of two kinds of ESR dosimeters

NASA Astrophysics Data System (ADS)

Marchioni, Eric; Pabst, Jean-Yves; Kuntz, Florent

2002-09-01

Many previous papers described the use of low-concentration alanine pellets, powder or films for industrial high-dose application, but very few authors presented applications of such dosimeters to the low-dose range used for wastewater, flowers or radiotherapy treatment. The present paper describes the large-scale manufacturing process of high-concentration alanine pellets used for radiotherapy dose control in some French hospitals. The fading process due to sunlight exposure has been evaluated by means of direct UV light irradiation. The major disadvantage of alanine is its strong solubility in water (the pellets are completely dissolved when immersed for 10 min in pure water). The use of barium sulphate, not soluble in water, made it possible to carry out dosimetric measurements even when the dosimeter is completely immersed in water or stored after irradiation in high humidity levels. The paper presents manufacturing process of barium sulphate pellets, their dosimetric characteristics and one application of this dosimeter for the control of the absorbed doses during wastewater treatments.

Food irradiation dosimetry by opti-chromic technique

NASA Astrophysics Data System (ADS)

Zhan-Jun, Liu; Radak, B. B.; McLaughlin, W. L.

The measurement of gamma-radiation quantities, e.g., absorbed dose in materials such as water, plastics, foodstuffs, is a convenient means of quality assurance in radiation processing. A new dosimetry system, called the "Opti-Chromic" dosimeter, is commercially available in large batches for use as a routine measurement system in the absorbed dose range 10 to 2x10 4 Gy. This dose range covers most food irradiation applications. A statistical evaluation was made of the reproducibility of this dosimeter for measuring doses appropriate for the disinfestation and shelf-life extension of many foods, namely 10 to 2x10 3 Gy. In addition, the small dosimeters were used to map absorbed dose distributions in boxes of foods having four different bulk densities (grapefruit, lemons, peanuts, and wheat bran). It is demonstrated that the dosimeters are rugged and stable enough to be used over a wide temperature and humidity range, and, in fact, can be placed in such environments as the inside of citrus fruits without adverse effects on their ability to give satisfactory dose assessment.

Method for preparing dosimeter for measuring skin dose

DOEpatents

Jones, Donald E.; Parker, DeRay; Boren, Paul R.

1982-01-01

A personnel dosimeter includes a plurality of compartments containing thermoluminescent dosimeter phosphors for registering radiation dose absorbed in the wearer's sensitive skin layer and for registering more deeply penetrating radiation. Two of the phosphor compartments communicate with thin windows of different thicknesses to obtain a ratio of shallowly penetrating radiation, e.g. beta. A third phosphor is disposed within a compartment communicating with a window of substantially greater thickness than the windows of the first two compartments for estimating the more deeply penetrating radiation dose. By selecting certain phosphors that are insensitive to neutrons and by loading the holder material with neutron-absorbing elements, energetic neutron dose can be estimated separately from other radiation dose. This invention also involves a method of injection molding of dosimeter holders with thin windows of consistent thickness at the corresponding compartments of different holders. This is achieved through use of a die insert having the thin window of precision thickness in place prior to the injection molding step.

Dosimeter for measuring skin dose and more deeply penetrating radiation

DOEpatents

Jones, Donald E.; Parker, DeRay; Boren, Paul R.

1981-01-01

A personnel dosimeter includes a plurality of compartments containing thermoluminescent dosimeter phosphors for registering radiation dose absorbed in the wearer's sensitive skin layer and for registering more deeply penetrating radiation. Two of the phosphor compartments communicate with thin windows of different thicknesses to obtain a ratio of shallowly penetrating radiation, e.g. beta. A third phosphor is disposed within a compartment communicating with a window of substantially greater thickness than the windows of the first two compartments for estimating the more deeply penetrating radiation dose. By selecting certain phosphors that are insensitive to neutrons and by loading the holder material with netruon-absorbing elements, energetic neutron dose can be estimated separately from other radiation dose. This invention also involves a method of injection molding of dosimeter holders with thin windows of consistent thickness at the corresponding compartments of different holders. This is achieved through use of a die insert having the thin window of precision thickness in place prior to the injection molding step.

Radiotherapy fiber dosimeter probes based on silver-only coated hollow glass waveguides

NASA Astrophysics Data System (ADS)

Darafsheh, Arash; Melzer, Jeffrey E.; Harrington, James A.; Kassaee, Alireza; Finlay, Jarod C.

2018-01-01

Manifestation of Čerenkov radiation as a contaminating signal is a significant issue in radiation therapy dose measurement by fiber-coupled scintillator dosimeters. To enhance the scintillation signal transmission while minimizing Čerenkov radiation contamination, we designed a fiber probe using a silver-only coated hollow waveguide (HWG). The HWG with scintillator inserted in its tip, embedded in tissue-mimicking phantoms, was irradiated with clinical electron and photon beams generated by a medical linear accelerator. Optical spectra of the irradiated tip were taken using a fiber spectrometer, and the signal was deconvolved with a linear fitting algorithm. The resultant decomposed spectra of the scintillator with and without Čerenkov correction were in agreement with measurements performed by a standard electron diode and ion chamber for electron and photon beam dosimetry, respectively, indicating the minimal effect of Čerenkov contamination in the HWG-based dosimeter. Furthermore, compared with a silver/dielectric-coated HWG fiber dosimeter design, we observed higher signal transmission in the design based on the use of silver-only HWG.

MMAB Sea Ice Forecast Page

Science.gov Websites

verification statistics Grumbine, R. W., Virtual Floe Ice Drift Forecast Model Intercomparison, Weather and Forecasting, 13, 886-890, 1998. MMAB Note: Virtual Floe Ice Drift Forecast Model Intercomparison 1996 pdf ~47

Development of an Automated Reader for Analysis and Storage of Personnel Dosimeter Badge Data

NASA Technical Reports Server (NTRS)

Meneghelli, B. J.; Hodge, T. R.; Robinson, L. J.; Lueck, D. E.

1997-01-01

The collection and archiving of data from personnel dosimeters has become increasingly important in light of the lowered threshold limit values (TLV) for hydrazine (HZ), monomethylhydrazine (MMH), and unsymmetrical dimethylhydrazine (UDMH). The American Conference of Government Industrial Hygienists (ACGIH) lowered the TLV from 100 parts per billion (ppb) to 10 ppb and has caused increased concern over long term exposures of personnel to trace levels of these hypergols and other potentially harmful chemicals. An automated system of reading the exposure levels of personnel dosimeters and storing exposure data for subsequent evaluation has been developed. The reading of personnel dosimeter badges for exposure lo potentially harmful vapor concentrations of hydrazines or other chemicals is performed visually by comparing the color developed by the badge with a calibrated color comparator. The result obtained using visual comparisons of the developed badge color with the comparator may vary widely from user to user. The automated badge reader takes the variability out of the dosimeter reading by accurately comparing the reflectance obtained from a colored spot on the badge with a reading on the same spot prior to any exposure to chemical vapors. The observed difference between the reflectance values is used as part of a calculation of the dose value for the badge based on a stored calibration curve. The badge reader also stores bar-code data unique to each badge, as well as bar-code information on the user, as part of the permanent badge record. The start and stop exposure times for each badge are recorded and can be used as part of the calculated concentration, in ppm, for each badge logged during a recording period. The badge reader is equipped with a number of badge holders, each of which is unique to a specific type of personnel dosimeter badge. This gives the reader maximum flexibility to allow for the reading of several different types of badges. Test results of the badge reader for several different types of personnel dosimeter badges are presented within the body of this paper.

Development of an Automated Reader for Analysis and Storage of Personnel Dosimeter Badge Data

NASA Technical Reports Server (NTRS)

Meneghelli, B. J.; Hodge, T. R.; Robinson, L. J.; Lueck, D. E.

1997-01-01

The collection and archiving of data from personnel dosimeters has become increasingly important in light of the lowered Threshold Limit Values (TLV) for HydraZine (HZ), MonoMethylHydrazine (MMH), and Unsymmetrical DiMethylHydrazine (UDMH). The American Conference of Government Industrial Hygienists (ACGIH) lowered the TLV from 100 parts per billion (ppb) to IO ppb and has caused increased concern over long term exposures of personnel to trace levels of these hypergols and other potentially harmful chemicals. An automated system of reading the exposure levels of personnel dosimeters and storing exposure data for subsequent evaluation has been developed. The reading of personnel dosimeter badges for exposure to potentially harmful vapor concentrations of hydrazines or other chemicals is performed visually by comparing the color developed by the badge with a calibrated color comparator. The result obtained using visual comparisons of the developed badge color with the comparator may vary widely from user to user. The automated badge reader takes the variability out of the dosimeter reading by accurately comparing the reflectance obtained from a colored spot on the badge with a reading on the same spot prior to any exposure to chemical vapors. The observed difference between the reflectance values is used as part of a calculation of the dose value for the badge based on a stored calibration curve. The badge reader also stores bar-code data unique to each badge, as well as bar-code information on the user, as part of the permanent badge record. The start and stop exposure times for each badge are recorded and can be used as part of the calculated concentration, in ppm, for each badge logged during a recording period. The badge reader is equipped with a number of badge holders, each of which is unique to a specific type of personnel dosimeter badge. This gives the reader maximum flexibility to allow for the reading of several different types of badges. Test results of the badge reader for several different types of personnel dosimeter badges are presented within the body of this paper.

SU-E-T-105: Development of 3D Dose Verification System for Volumetric Modulated Arc Therapy Using Improved Polyacrylamide-Based Gel Dosimeter

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

Ono, K; Fujimoto, S; Akagi, Y

2014-06-01

Purpose: The aim of this dosimetric study was to develop 3D dose verification system for volumetric modulated arc therapy (VMAT) using polyacrylamide-based gel (PAGAT) dosimeter improved the sensitivity by magnesium chloride (MgCl{sub 2}). Methods: PAGAT gel containing MgCl{sub 2} as a sensitizer was prepared in this study. Methacrylic-acid-based gel (MAGAT) was also prepared to compare the dosimetric characteristics with PAGAT gel. The cylindrical glass vials (4 cm diameter, 12 cm length) filled with each polymer gel were irradiated with 6 MV photon beam using Novalis Tx linear accelerator (Varian/BrainLAB). The irradiated polymer gel dosimeters were scanned with Signa 1.5 Tmore » MRI system (GE), and dose calibration curves were obtained using T{sub 2} relaxation rate (R{sub 2} = 1/T{sub 2}). Dose rate (100-600 MU min{sup −1}) and fractionation (1-8 fractions) were varied. In addition, a cubic acrylic phantom (10 × 10 × 10 cm{sup 3}) filled with improved PAGAT gel inserted into the IMRT phantom (IBA) was irradiated with VMAT (RapidArc). C-shape structure was used for the VMAT planning by the Varian Eclipse treatment planning system (TPS). The dose comparison of TPS and measurements with the polymer gel dosimeter was accomplished by the gamma index analysis, overlaying the dose profiles for a set of data on selected planes using in-house developed software. Results: Dose rate and fractionation dependence of improved PAGAT gel were smaller than MAGAT gel. A high similarity was found by overlaying the dose profiles measured with improved PAGAT gel dosimeter and the TPS dose, and the mean pass rate of the gamma index analysis using 3%/3 mm criteria was achieved 90% on orthogonal planes for VMAT using improved PAGAT gel dosimeter. Conclusion: In-house developed 3D dose verification system using improved polyacrylamide-based gel dosimeter had a potential as an effective tool for VMAT QA.« less

Errors introduced by dose scaling for relative dosimetry

PubMed Central

Watanabe, Yoichi; Hayashi, Naoki

2012-01-01

Some dosimeters require a relationship between detector signal and delivered dose. The relationship (characteristic curve or calibration equation) usually depends on the environment under which the dosimeters are manufactured or stored. To compensate for the difference in radiation response among different batches of dosimeters, the measured dose can be scaled by normalizing the measured dose to a specific dose. Such a procedure, often called “relative dosimetry”, allows us to skip the time‐consuming production of a calibration curve for each irradiation. In this study, the magnitudes of errors due to the dose scaling procedure were evaluated by using the characteristic curves of BANG3 polymer gel dosimeter, radiographic EDR2 films, and GAFCHROMIC EBT2 films. Several sets of calibration data were obtained for each type of dosimeters, and a calibration equation of one set of data was used to estimate doses of the other dosimeters from different batches. The scaled doses were then compared with expected doses, which were obtained by using the true calibration equation specific to each batch. In general, the magnitude of errors increased with increasing deviation of the dose scaling factor from unity. Also, the errors strongly depended on the difference in the shape of the true and reference calibration curves. For example, for the BANG3 polymer gel, of which the characteristic curve can be approximated with a linear equation, the error for a batch requiring a dose scaling factor of 0.87 was larger than the errors for other batches requiring smaller magnitudes of dose scaling, or scaling factors of 0.93 or 1.02. The characteristic curves of EDR2 and EBT2 films required nonlinear equations. With those dosimeters, errors larger than 5% were commonly observed in the dose ranges of below 50% and above 150% of the normalization dose. In conclusion, the dose scaling for relative dosimetry introduces large errors in the measured doses when a large dose scaling is applied, and this procedure should be applied with special care. PACS numbers: 87.56.Da, 06.20.Dk, 06.20.fb PMID:22955658

Initial Results from the Radiation Dosimetry Experiment (RaD-X) Balloon Flight Mission

NASA Technical Reports Server (NTRS)

Mertens, Christopher J.

2015-01-01

The NASA Radiation Dosimetry Experiment (RaD-X) high-altitude balloon mission was successfully launched from Fort Sumner, New Mexico USA on 25 September, 2015. Over 15 hours of science data were obtained from four dosimeters at altitudes above about 25 km. The four dosimeters flown on the RaD-X science payload are a Hawk version 3.0 Tissue Equivalent Proportional Counter (TEPC) manufactured by Far West Technologies, a Liulin dosimeter-spectrometer produced by the Solar Research and Technology Institute, Bulgarian Academy of Sciences, a total ionizing dose detector manufactured by Teledyne Microelectronic Technologies, and the RaySure detector provided by the University of Surrey.

Transferability of ASTM/NIST alanine-polyethylene recipe at ISS. American Society for Testing and Materials/National Institute for Standards and Technology. Istituto Superiore de Sanita

PubMed

De Angelis C; Fattibene; Onori; Petetti; Bartolotta; Sansone Santamaria A

2000-05-01

Alanine-polyethylene solid state dosimeters were prepared at Istituto Superiore di Sanita (ISS) following the recipe proposed by National Institute of Standards and Technology (NIST) with the goal of testing its transferability. Dosimeters were prepared using 95% alanine and 5% polyethylene, by weight. They are rugged and of increased sensitivity, repeatability and reproducibility as respect to the ISS alanine-paraffin pellets. Reproducibility of about 1% was obtained at 10 Gy and at 3 Gy if one single pellet or a stack of five dosimeters were used, respectively.

Thermoluminescence dosimeter

DOEpatents

Zendle, R.

1983-11-03

A thermoluminescence dosimeter having a very small rate of decline of sensitivity during subsequent uses after heating is disclosed. The dosimeter includes a detector crystal and a glass enclosure in which the detector crystal is located. The glass enclosure is air tight and is filled with a super dry inert fill gas. The inert fill gas is nonreactive with the detector crystal when the detector crystal is heated to thermoluminescence. The fill gas is selected from the group consisting of air, nitrogen, and argon, suitable admixed with 5 to 25 percent helium. The detector crystal consists essentially of calcium fluoride. The fill gas is preferably contained at a subatmospheric pressure in the glass enclosure.

Linearity and reproducibility response of Fricke dosimetry for low energy X-Ray beam

NASA Astrophysics Data System (ADS)

Mantuano, A.; de Amorim, G. J.; David, M. G.; Rosado, P. H. G.; Salata, C.; Magalhães, L. A. G.; deAlmeida, C. E.

2018-03-01

The Fricke dosimeter is the most used, liquid chemical dosimeter. It has been shown to be a feasible option for the absorbed dose standard. The present work aims to determinate a dose-response curve of Fricke solution using different doses and reproducibility test comparing the calculated dose to Fricke solution and Ionizing Chamber. Tests were performed using an X-ray irradiator for biological research at Radiological Science Laboratory (LCR/UERJ). The results showed a linear response to different doses of type A uncertainties from 0.08 to 1.2%. Reproducibility test showed type A uncertainties of 0.16% to the dosimeter.

Thermoluminescence dosimeter

DOEpatents

Zendle, Robert

1985-01-01

A thermoluminescence dosimeter having a very small rate of decline of sensitivity during subsequent uses after heating is disclosed. The dosimeter includes a detector crystal and a glass enclosure in which the detector crystal is located. The glass enclosure is air tight and is filled with a super dry inert fill gas. The inert fill gas is nonreactive with the detector crystal when the detector crystal is heated to thermoluminescence. The fill gas is selected from the group consisting of air, nitrogen, and argon, suitable admixed with 5 to 25 percent helium. The detector crystal consists essentially of calcium fluoride. The fill gas is preferably contained at a subatmospheric pressure in the glass enclosure.

Building a statistical emulator for prediction of crop yield response to climate change: a global gridded panel data set approach

NASA Astrophysics Data System (ADS)

Mistry, Malcolm; De Cian, Enrica; Wing, Ian Sue

2015-04-01

There is widespread concern that trends and variability in weather induced by climate change will detrimentally affect global agricultural productivity and food supplies. Reliable quantification of the risks of negative impacts at regional and global scales is a critical research need, which has so far been met by forcing state-of-the-art global gridded crop models with outputs of global climate model (GCM) simulations in exercises such as the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP)-Fastrack. Notwithstanding such progress, it remains challenging to use these simulation-based projections to assess agricultural risk because their gridded fields of crop yields are fundamentally denominated as discrete combinations of warming scenarios, GCMs and crop models, and not as model-specific or model-averaged yield response functions of meteorological shifts, which may have their own independent probability of occurrence. By contrast, the empirical climate economics literature has adeptly represented agricultural responses to meteorological variables as reduced-form statistical response surfaces which identify the crop productivity impacts of additional exposure to different intervals of temperature and precipitation [cf Schlenker and Roberts, 2009]. This raises several important questions: (1) what do the equivalent reduced-form statistical response surfaces look like for crop model outputs, (2) do they exhibit systematic variation over space (e.g., crop suitability zones) or across crop models with different characteristics, (3) how do they compare to estimates based on historical observations, and (4) what are the implications for the characterization of climate risks? We address these questions by estimating statistical yield response functions for four major crops (maize, rice, wheat and soybeans) over the historical period (1971-2004) as well as future climate change scenarios (2005-2099) using ISIMIP-Fastrack data for five GCMs and seven crop models under rain-fed and irrigated management regimes. Our approach, which is patterned after Lobell and Burke [2010], is a novel application of cross-section/time-series statistical techniques from the climate economics literature to large, high-dimension, multi-model datasets, and holds considerable promise as a diagnostic methodology to elucidate uncertainties in the processes simulated by crop models, and to support the development of climate impact intercomparison exercises.

42 CFR 82.14 - What types of information could be used in dose reconstructions?

Code of Federal Regulations, 2011 CFR

2011-10-01

...) External dosimetry data, including external dosimeter readings (film badge, TLD, neutron dosimeters); and, (2) Pocket ionization chamber data. (c) Internal dosimetry data, including: (1) Urinalysis results; (2) Fecal sample results; (3) In Vivo measurement results; (4) Incident investigation reports; (5...

42 CFR 82.14 - What types of information could be used in dose reconstructions?

Code of Federal Regulations, 2012 CFR

2012-10-01

...) External dosimetry data, including external dosimeter readings (film badge, TLD, neutron dosimeters); and, (2) Pocket ionization chamber data. (c) Internal dosimetry data, including: (1) Urinalysis results; (2) Fecal sample results; (3) In Vivo measurement results; (4) Incident investigation reports; (5...

42 CFR 82.14 - What types of information could be used in dose reconstructions?

Code of Federal Regulations, 2010 CFR

2010-10-01

...) External dosimetry data, including external dosimeter readings (film badge, TLD, neutron dosimeters); and, (2) Pocket ionization chamber data. (c) Internal dosimetry data, including: (1) Urinalysis results; (2) Fecal sample results; (3) In Vivo measurement results; (4) Incident investigation reports; (5...

42 CFR 82.14 - What types of information could be used in dose reconstructions?

Code of Federal Regulations, 2014 CFR

2014-10-01

...) External dosimetry data, including external dosimeter readings (film badge, TLD, neutron dosimeters); and, (2) Pocket ionization chamber data. (c) Internal dosimetry data, including: (1) Urinalysis results; (2) Fecal sample results; (3) In Vivo measurement results; (4) Incident investigation reports; (5...

42 CFR 82.14 - What types of information could be used in dose reconstructions?

Code of Federal Regulations, 2013 CFR

2013-10-01

...) External dosimetry data, including external dosimeter readings (film badge, TLD, neutron dosimeters); and, (2) Pocket ionization chamber data. (c) Internal dosimetry data, including: (1) Urinalysis results; (2) Fecal sample results; (3) In Vivo measurement results; (4) Incident investigation reports; (5...

Measurements of SNAC2 area dosimeters placed in different configurations around the PROSPERO reactor and comparison with TRIPOLI-4 calculations

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

Rousseau, G.; Chambru, L.; Authier, N.

2015-07-01

In the context of criticality accident alarm system tests, several experiments were carried out in 2013 on the PROSPERO reactor to study the response to neutron and gamma of different devices and dosimeters, particularly on the SNAC2 dosimeter. This article presents the results of this criticality dosimeter in different configurations, and compares the experimental measurements with the results of calculation performed with the TRIPOLI-4 Monte-Carlo Neutral Particles transport code. PROSPERO is a metallic critical assembly managed by the Criticality, Neutron Science and Measurement Department located at the French CEA Research Center of Valduc. The core, surrounded by a reflector ofmore » depleted uranium, is composed of 2 horizontal cylindrical blocks made of a highly enriched uranium alloy which can be placed in contact, and of 4 depleted uranium control rods which allow the reactor to be driven. This reactor, placed in a cell 10 m x 8 m x 6 m high, with 1.4-meter-thick concrete walls, is used as a fast neutron spectrum source and is operated at stable power level in delayed critical state, which can vary from 3 mW to 3 kW. PROSPERO is extensively used for electronic hardening or to study the effect of the neutrons on various materials. The SNAC2 criticality dosimeter is a zone dosimeter allowing the off line measurement of criticality accident neutron doses. This dosimeter consists of the pile up of seven activation foils embedded into a 23 mm diameter x 21 mm height cadmium container. The activation measurement of each foil, using a gamma spectroscopy technique, gives information about the neutron reaction rates. The SNAC2 software allows the spectrum unfolding from these values, taking into account the hypothesis of a particular spectrum shape, in three components: a Maxwell spectrum component for the thermal range, a 1/E component for the epithermal range, and a Watt spectrum component for the high energy range. Moreover, from the neutron spectrum, the SNAC software can calculate the neutron fluence integrated by the dosimeter and the neutron dose. During the 3 weeks measurement campaign many radioprotection devices were used. To modify the spectrum seen by these devices, several shields of various thicknesses made of concrete or polyethylene, with or without cadmium covers, were placed in the PROSPERO cell. These devices allow the study of criticality accident spectra in several environments: from metal to pseudo liquid. The fluxes measured by the SNAC2 devices were compared with TRIPOLI-4 calculations. (authors)« less

Characterization of a new dosimeter for the development of a position-sensitive detector of radioactive sources in industrial NDT equipment

NASA Astrophysics Data System (ADS)

Kim, K. T.; Kim, J. H.; Han, M. J.; Heo, Y. J.; Park, S. K.

2018-02-01

Imaging technology based on gamma-ray sources has been extensively used in non-destructive testing (NDT) to detect any possible internal defects in products without changing their shapes or functions. However, such technology has been subject to increasingly stricter regulations, and an international radiation-safety management system has been recently established. Consequently, radiation source location in NDT systems has become an essential process, given that it can prevent radiation accidents. In this study, we focused on developing a monitoring system that can detect, in real time, the position of a radioactive source in the source guide tube of a projector. We fabricated a lead iodide (PbI2) dosimeter based on the particle-in-binder method, which has a high production yield and facilitates thickness and shape adjustment. Using a gamma-ray source, we then tested the reproducibility, linearity of the dosimeter response, and the dosimeter's percentage interval distance (PID). It was found that the fabricated PbI2 dosimeter yields highly accurate, reproducible, and linear dose measurements. The PID analysis—conducted to investigate the possibility of developing a monitoring system based on the proposed dosimeter—indicated that the valid detection distance was approximately 11.3 cm. The results of this study are expected to contribute to the development of an easily usable radiation monitoring system capable of significantly reducing the risk of radiation accidents.

Evaluation and comparison of absorbed dose for electron beams by LiF and diamond dosimeters

NASA Astrophysics Data System (ADS)

Mosia, G. J.; Chamberlain, A. C.

2007-09-01

The absorbed dose response of LiF and diamond thermoluminescent dosimeters (TLDs), calibrated in 60Co γ-rays, has been determined using the MCNP4B Monte Carlo code system in mono-energetic megavoltage electron beams from 5 to 20 MeV. Evaluation of the dose responses was done against the dose responses of published works by other investigators. Dose responses of both dosimeters were compared to establish if any relation exists between them. The dosimeters were irradiated in a water phantom with the centre of their top surfaces (0.32×0.32 cm 2), placed at dmax perpendicular to the radiation beam on the central axis. For LiF TLD, dose responses ranged from 0.945±0.017 to 0.997±0.011. For the diamond TLD, the dose response ranged from 0.940±0.017 to 1.018±0.011. To correct for dose responses by both dosimeters, energy correction factors were generated from dose response results of both TLDs. For LiF TLD, these correction factors ranged from 1.003 up to 1.058 and for diamond TLD the factors ranged from 0.982 up to 1.064. The results show that diamond TLDs can be used in the place of the well-established LiF TLDs and that Monte Carlo code systems can be used in dose determinations for radiotherapy treatment planning.

Does the lead apron and collar always reduce radiation dose?

PubMed

Nortje, C J; Harris, A M; Lackovic, K P; Wood, R E

2001-11-01

The possibility that personal lead shielding devices can increase absorption of radiation has not been entertained. The purpose of the present investigation specifically was to determine whether pituitary dose might be increased when a leaded apron and thyroid collar are used. Thermoluminescent dosimeters (TLDs) were used to measure absorbed dose. They were calibrated at the kVp used in the clinical situation and a calibration curve relating light output to dose was generated. Lithium fluoride TLD discs were placed in the pituitary gland region of a Rando-Alderson female human phantom. The equivalent of 100 transpharyngeal exposures were delivered. The resultant light output from recovered dosimeters was converted to a uGy value using the calibration curve. The experiment was repeated using a 0.25 mm lead equivalent collar and apron fitted to the phantom in the customary manner. The entire process was repeated in order to have 30 dosimeters for the unshielded and 30 dosimeters for the shielded conditions. A further 30 dosimeters were sham irradiated and served as controls. A statistical comparison between unshielded and shielded conditions was performed. When the leaded apron and thyroid collar were used the absorbed dose to the pituitary gland was increased significantly (P < 0.05). Following this a second group, using a different dosimetry system and a male phantom repeated the experiment. In both cases, the shielded phantom received significantly higher dose to the pituitary region than the unshielded.

Investigation of the response characteristics of OSL albedo neutron dosimeters in a 241AmBe reference neutron field

NASA Astrophysics Data System (ADS)

Liamsuwan, T.; Wonglee, S.; Channuie, J.; Esoa, J.; Monthonwattana, S.

2017-06-01

The objective of this work was to systematically investigate the response characteristics of optically stimulated luminescence Albedo neutron (OSLN) dosimeters to ensure reliable personal dosimetry service provided by Thailand Institute of Nuclear Technology (TINT). Several batches of InLight® OSLN dosimeters were irradiated in a reference neutron field generated by the in-house 241AmBe neutron irradiator. The OSL signals were typically measured 24 hours after irradiation using the InLight® Auto 200 Reader. Based on known values of delivered neutron dose equivalent, the reading correction factor to be used by the reader was evaluated. Subsequently, batch homogeneity, dose linearity, lower limit of detection and fading of the OSLN dosimeters were examined. Batch homogeneity was evaluated to be 0.12 ± 0.05. The neutron dose response exhibited a linear relationship (R2=0.9974) within the detectable neutron dose equivalent range under test (0.4-3 mSv). For this neutron field, the lower limit of detection was between 0.2 and 0.4 mSv. Over different post-irradiation storage times of up to 180 days, the readings fluctuated within ±5%. Personal dosimetry based on the investigated OSLN dosimeter is considered to be reliable under similar neutron exposure conditions, i.e. similar neutron energy spectra and dose equivalent values.

A comparative evaluation of luminescence detectors: RPL-GD-301, TLD-100 and OSL-AL2O3:C, using Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Benali, A.-H.; Medkour Ishak-Boushaki, G.; Nourreddine, A.-M.; Allab, M.; Papadimitroulas, P.

2017-07-01

The luminescent dosimeters are widely used in clinical practice, for the monitoring of patient dose in external radiation therapy. Three of the most common dosimeter categories are the thermoluminescence (TLDs), the radiophotoluminescence (RPLs) and the optically stimulated luminescence (OSLs), with similar physical processes on their properties. The aim of the present study is to compare and evaluate the dosimetric properties of three specific luminescent detectors namely: a) RPL glass dosimeter, commercially known as GD-301, b) lithium fluoride TLD-100 (LiF:Mg,Ti) and c) carbon-doped aluminum oxide (Al2O3:C). For this purpose, Monte Carlo simulations were applied, using the MCNP5 code to estimate the responses of these dosimeters in terms of absorbed dose, output factor, the angular and energy dependence. In the present study, we found that the differences between the output factors were less than ± 4.2% for all detector materials RPLGD, TLD and OSLD. The variations in sensitivity for angles up to ± 80 degrees from the central axis of the beam were approximately 0.5%, 0.8% and 1.5% for the TLD-100, GD-301 and Al2O3:C, respectively. The energy dependence of the RPL and OSL dosimeters are stated as less than a 2.2%, and within 5.8% for TLD.

Analysis of measurement deviations for the patient-specific quality assurance using intensity-modulated spot-scanning particle beams

NASA Astrophysics Data System (ADS)

Li, Yongqiang; Hsi, Wen C.

2017-04-01

To analyze measurement deviations of patient-specific quality assurance (QA) using intensity-modulated spot-scanning particle beams, a commercial radiation dosimeter using 24 pinpoint ionization chambers was utilized. Before the clinical trial, validations of the radiation dosimeter and treatment planning system were conducted. During the clinical trial 165 measurements were performed on 36 enrolled patients. Two or three fields of particle beam were used for each patient. Measurements were typically performed with the dosimeter placed at special regions of dose distribution along depth and lateral profiles. In order to investigate the dosimeter accuracy, repeated measurements with uniform dose irradiations were also carried out. A two-step approach was proposed to analyze 24 sampling points over a 3D treatment volume. The mean value and the standard deviation of each measurement did not exceed 5% for all measurements performed on patients with various diseases. According to the defined intervention thresholds of mean deviation and the distance-to-agreement concept with a Gamma index analysis using criteria of 3.0% and 2 mm, a decision could be made regarding whether the dose distribution was acceptable for the patient. Based measurement results, deviation analysis was carried out. In this study, the dosimeter was used for dose verification and provided a safety guard to assure precise dose delivery of highly modulated particle therapy. Patient-specific QA will be investigated in future clinical operations.

Radiant energy dosimeter for field use

Treesearch

A. Broido; A.W. McMasters

1967-01-01

Thermal radiation measurements in Project Flambeau fires involved a limited number of conventional radiometers located outside the fire periphery. A simple, cheap, easily-fabricated, light-weight, self-contained, rugged dosimeter was desired to withstand a hot fire environment, including a specific energy input of 5,000 cal cm -2, and to record...

Feasibility study of a photoconductor based dosimeter for quality assurance in radiotherapy

NASA Astrophysics Data System (ADS)

Lee, Y. K.; Kim, S. W.; Kim, J. N.; Kang, Y. N.; Kim, J. Y.; Lee, D. S.; Kim, K. T.; Han, M. J.; Ahn, K. J.; Park, S. K.

2017-09-01

With the recent market entries of new types of linear accelerators (LINACs) with a multi leaf collimator (MLC) mounted on them, high-precision radiosurgery applying a LINAC to measure high-dose radiation on the target region has been gaining popularity. Systematic and accurate quality assurance (QA) is of vital important for high-precision radiosurgery because of its increased risk of side effects including life-threatening ones such as overexposure of healthy tissues to high-dose radiation beams concentrated on small areas. Therefore, accurate dose and dose-distribution measurements are crucial in the treatment procedure. The accurate measurement of the properties of beams concentrated on small areas requires high-precision dosimeters capable of high-resolution output and dose mapping as well as accurate dosimetry in penumbra regions. In general, the properties of beams concentrated on small areas are measured using thermos luminescent dosimeters (TLD), diode detectors, ion chambers, diamond detectors, or films, and many papers have presented the advantages and disadvantages of each of these detectors for dosimetry. In this study, a solid-state photoconductor dosimeter was developed, and its clinical usability was tested by comparing its relative dosimetric performance with that of a conventional ion chamber. As materials best-suited for radiation dosimeters, four candidates namely lead (II) iodide (PbI2), lead (II) oxide (PbO), mercury (II) iodide (HgI2), and HgI2/ titanium dioxide (TiO2) composite, the performances of which were proved in previous studies, were used. The electrical properties of each candidate material were examined using the sedimentation method, one of the particle-in-binder (PIB) methods, and unit-cell-type prototypes were fabricated. The unit-cell samples thus prepared were cut into specimens of area 1 × 1 cm2 with 400-μ m thickness. The electrical properties of each sample, such as sensitivity, dark current, output current, rising time, falling time, and response delay, were then measured, in addition to the consistency, reproducibility and linearity of each unit-cell. According to the measurement results, HgI2/TiO2 composite outperformed the other candidate materials. A radiation dosimeter with a chamber-type structure was fabricated in this study using a LINAC under accelerating voltages of 6, and 15 MV and compared with a commercial ion chamber. Percent depth dose (PDD) and beam profile were measured on a water phantom at a fixed area of 10 × 10 cm2 by using the fabricated chamber-type dosimeter, and the values were compared with those measured by a commercial ion chamber. Additionally, a homogeneous phantom was fabricated, and the exposure doses of the center points were measured according to a real treatment plan, followed by a comparison of the measured values as relative values. In this paper, we report that the manufactured dosimeter shows similar characteristics in terms of PDD and beam profile and results for the conventional ion chamber. Based on these results, it is demonstrated that the HgI2/TiO2-based dosimeter complies with radiotherapy QA requirements, namely Superior detection characteristics, consistency, dose linearity, reproducibility. Thus, we expect the HgI2/TiO2-based dosimeter to be used commercially in the future.

Assessing agricultural risks of climate change in the 21st century in a global gridded crop model intercomparison

PubMed Central

Rosenzweig, Cynthia; Elliott, Joshua; Deryng, Delphine; Ruane, Alex C.; Müller, Christoph; Arneth, Almut; Boote, Kenneth J.; Folberth, Christian; Glotter, Michael; Khabarov, Nikolay; Neumann, Kathleen; Piontek, Franziska; Pugh, Thomas A. M.; Schmid, Erwin; Stehfest, Elke; Yang, Hong; Jones, James W.

2014-01-01

Here we present the results from an intercomparison of multiple global gridded crop models (GGCMs) within the framework of the Agricultural Model Intercomparison and Improvement Project and the Inter-Sectoral Impacts Model Intercomparison Project. Results indicate strong negative effects of climate change, especially at higher levels of warming and at low latitudes; models that include explicit nitrogen stress project more severe impacts. Across seven GGCMs, five global climate models, and four representative concentration pathways, model agreement on direction of yield changes is found in many major agricultural regions at both low and high latitudes; however, reducing uncertainty in sign of response in mid-latitude regions remains a challenge. Uncertainties related to the representation of carbon dioxide, nitrogen, and high temperature effects demonstrated here show that further research is urgently needed to better understand effects of climate change on agricultural production and to devise targeted adaptation strategies. PMID:24344314

Assessing Agricultural Risks of Climate Change in the 21st Century in a Global Gridded Crop Model Intercomparison

NASA Technical Reports Server (NTRS)

Rosenzweig, Cynthia E.; Elliott, Joshua; Deryng, Delphine; Ruane, Alex C.; Mueller, Christoph; Arneth, Almut; Boote, Kenneth J.; Folberth, Christian; Glotter, Michael; Khabarov, Nikolay

2014-01-01

Here we present the results from an intercomparison of multiple global gridded crop models (GGCMs) within the framework of the Agricultural Model Intercomparison and Improvement Project and the Inter-Sectoral Impacts Model Intercomparison Project. Results indicate strong negative effects of climate change, especially at higher levels of warming and at low latitudes; models that include explicit nitrogen stress project more severe impacts. Across seven GGCMs, five global climate models, and four representative concentration pathways, model agreement on direction of yield changes is found in many major agricultural regions at both low and high latitudes; however, reducing uncertainty in sign of response in mid-latitude regions remains a challenge. Uncertainties related to the representation of carbon dioxide, nitrogen, and high temperature effects demonstrated here show that further research is urgently needed to better understand effects of climate change on agricultural production and to devise targeted adaptation strategies.

Measurement of low‐energy backscatter factors using GAFCHROMIC film and OSLDs

PubMed Central

Elson, Howard R.; Lamba, Michael A. S.

2012-01-01

Some of the lowest voltages used in radiotherapy are termed Grenz and superficial X‐rays of ~ 20 and ~ 100 kVp, respectively. Dosimetrically, the surface doses from these beams are calculated with the use of a free in‐air air kerma measurement combined with a backscatter factor and the appropriate ratio of mass energy absorption coefficients from the measurement material to water. Alternative tools to the standard ion chamber for measuring the BSF are GAFCHROMIC EBT2 film and optically stimulated luminescent dosimeter (OSLD) crystals made from Al2O3. The scope of this project included making three different backscatter measurements with an Xstrahl‐D3100 X‐ray unit on the Grenz ray and superficial settings. These measurements were with OSLDs, GAFCHROMIC EBT2 film, and a PTW ionization chamber. The varied measurement methods allowed for intercomparison to determine the accuracy of the results. The ion chamber measurement was the least accurate, as expected from previous experimental findings. GAFCHROMIC EBT2 film proved to be a useful tool which gave reasonable results, and Landauer OSLDs showed good results for smaller field sizes and an increasing overresponse with larger fields. The specific backscatter factors for this machine demonstrated values about 5% higher than the universal values suggested by the AAPM and IPEMB codes of practice for the 100 kVp setting. The 20 kvp measured data from both techniques showed general agreement with those found in the BJR Supplement No. 10, indicating that this unit's Grenz ray spectrum is similar to those used in previous experimental work. PACS number: 87.53.Bn PMID:23149776

Study of the absorption spectra of Fricke Xylenol Orange gel dosimeters

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

Gambarini, Grazia; Artuso, Emanuele; Liosi, Giulia Maria

2015-07-01

A systematic study of the absorption spectra of Fricke Xylenol Orange gel dosimeters has been performed, in the wavelength range from 300 nm to 700 nm. The spectrum of Xylenol Orange (without ferrous sulphate solution) has been achieved, in order to subtract its contribution from the absorption spectra of the irradiated Fricke Xylenol Orange gel dosimeters. The absorbance due to ferric ions chelated by Xylenol Orange has been studied for various irradiation doses. Two absorbance peaks are visible, mainly at low doses: the first peak increases with the dose more slowly than the second one. This effect can explain themore » apparent threshold dose that was frequently evidenced. (authors)« less

Vitamin D Investigation

NASA Technical Reports Server (NTRS)

1986-01-01

The solar dosimeter, a spinoff from NASA solar cell technology, measures the amount of solar radiation to which its wearer is exposed. It was used in a University of Cincinnati Medical Center investigation into the effect of sunlight exposure on maintaining vitamin D status in infants. The infants were exposed to sunlight and records were kept by mothers. Each baby wore a solar dosimeter. The two circular "eyes" in the instrument are silicon photovoltaic detectors which collect solar energy, convert it to electric signals and transmit the charge to E-cells that record the charge by plating silver ions onto an electrode. The time required to plate the silver measures the radiation received. The University found the solar dosimeter to be very effective.

The AgMIP Coordinated Global and Regional Assessments (CGRA) of Climate Change Impacts on Agriculture and Food Security

NASA Technical Reports Server (NTRS)

Ruane, Alex; Rosenzweig, Cynthia; Elliott, Joshua; Antle, John

2015-01-01

The Agricultural Model Intercomparison and Improvement Project (AgMIP) has been working since 2010 to construct a protocol-based framework enabling regional assessments (led by regional experts and modelers) that can provide consistent inputs to global economic and integrated assessment models. These global models can then relay important global-level information that drive regional decision-making and outcomes throughout an interconnected agricultural system. AgMIPs community of nearly 800 climate, crop, livestock, economics, and IT experts has improved the state-of-the-art through model intercomparisons, validation exercises, regional integrated assessments, and the launch of AgMIP programs on all six arable continents. AgMIP is now launching Coordinated Global and Regional Assessments (CGRA) of climate change impacts on agriculture and food security to link global and regional crop and economic models using a protocol-based framework. The CGRA protocols are being developed to utilize historical observations, climate projections, and RCPsSSPs from CMIP5 (and potentially CMIP6), and will examine stakeholder-driven agricultural development and adaptation scenarios to provide cutting-edge assessments of climate changes impact on agriculture and food security. These protocols will build on the foundation of established protocols from AgMIPs 30+ activities, and will emphasize the use of multiple models, scenarios, and scales to enable an accurate assessment of related uncertainties. The CGRA is also designed to provide the outputs necessary to feed into integrated assessment models (IAMs), nutrition and food security assessments, nitrogen and carbon cycle models, and additional impact-sector assessments (e.g., water resources, land-use, biomes, urban areas). This presentation will describe the current status of CGRA planning and initial prototype experiments to demonstrate key aspects of the protocols before wider implementation ahead of the IPCC Sixth Assessment Report.

EARLINET Single Calculus Chain - technical - Part 1: Pre-processing of raw lidar data

NASA Astrophysics Data System (ADS)

D'Amico, Giuseppe; Amodeo, Aldo; Mattis, Ina; Freudenthaler, Volker; Pappalardo, Gelsomina

2016-02-01

In this paper we describe an automatic tool for the pre-processing of aerosol lidar data called ELPP (EARLINET Lidar Pre-Processor). It is one of two calculus modules of the EARLINET Single Calculus Chain (SCC), the automatic tool for the analysis of EARLINET data. ELPP is an open source module that executes instrumental corrections and data handling of the raw lidar signals, making the lidar data ready to be processed by the optical retrieval algorithms. According to the specific lidar configuration, ELPP automatically performs dead-time correction, atmospheric and electronic background subtraction, gluing of lidar signals, and trigger-delay correction. Moreover, the signal-to-noise ratio of the pre-processed signals can be improved by means of configurable time integration of the raw signals and/or spatial smoothing. ELPP delivers the statistical uncertainties of the final products by means of error propagation or Monte Carlo simulations. During the development of ELPP, particular attention has been payed to make the tool flexible enough to handle all lidar configurations currently used within the EARLINET community. Moreover, it has been designed in a modular way to allow an easy extension to lidar configurations not yet implemented. The primary goal of ELPP is to enable the application of quality-assured procedures in the lidar data analysis starting from the raw lidar data. This provides the added value of full traceability of each delivered lidar product. Several tests have been performed to check the proper functioning of ELPP. The whole SCC has been tested with the same synthetic data sets, which were used for the EARLINET algorithm inter-comparison exercise. ELPP has been successfully employed for the automatic near-real-time pre-processing of the raw lidar data measured during several EARLINET inter-comparison campaigns as well as during intense field campaigns.

The AgMIP Coordinated Global and Regional Assessments (CGRA) of Climate Change Impacts on Agriculture and Food Security

NASA Astrophysics Data System (ADS)

Ruane, A. C.; Rosenzweig, C.; Antle, J. M.; Elliott, J. W.

2015-12-01

The Agricultural Model Intercomparison and Improvement Project (AgMIP) has been working since 2010 to construct a protocol-based framework enabling regional assessments (led by regional experts and modelers) that can provide consistent inputs to global economic and integrated assessment models. These global models can then relay important global-level information that drive regional decision-making and outcomes throughout an interconnected agricultural system. AgMIP's community of nearly 800 climate, crop, livestock, economics, and IT experts has improved the state-of-the-art through model intercomparisons, validation exercises, regional integrated assessments, and the launch of AgMIP programs on all six arable continents. AgMIP is now launching Coordinated Global and Regional Assessments (CGRA) of climate change impacts on agriculture and food security to link global and regional crop and economic models using a protocol-based framework. The CGRA protocols are being developed to utilize historical observations, climate projections, and RCPs/SSPs from CMIP5 (and potentially CMIP6), and will examine stakeholder-driven agricultural development and adaptation scenarios to provide cutting-edge assessments of climate change's impact on agriculture and food security. These protocols will build on the foundation of established protocols from AgMIP's 30+ activities, and will emphasize the use of multiple models, scenarios, and scales to enable an accurate assessment of related uncertainties. The CGRA is also designed to provide the outputs necessary to feed into integrated assessment models (IAMs), nutrition and food security assessments, nitrogen and carbon cycle models, and additional impact-sector assessments (e.g., water resources, land-use, biomes, urban areas). This presentation will describe the current status of CGRA planning and initial prototype experiments to demonstrate key aspects of the protocols before wider implementation ahead of the IPCC Sixth Assessment Report.

Inconsistent Strategies to Spin up Models in CMIP5: Implications for Ocean Biogeochemical Model Performance Assessment

NASA Technical Reports Server (NTRS)

Seferian, Roland; Gehlen, Marion; Bopp, Laurent; Resplandy, Laure; Orr, James C.; Marti, Olivier; Dunne, John P.; Christian, James R.; Doney, Scott C.; Ilyina, Tatiana;

Generating Vegetation Leaf Area Index Earth System Data Record from Multiple Sensors. Part 2; Implementation, Analysis and Validation

NASA Technical Reports Server (NTRS)

Ganguly, Sangram; Samanta, Arindam; Schull, Mitchell A.; Shabanov, Nikolay V.; Milesi, Cristina; Nemani, Ramajrushna R,; Knyazikhin, Yuri; Myneni, Ranga B.

2008-01-01

The evaluation of a new global monthly leaf area index (LAI) data set for the period July 1981 to December 2006 derived from AVHRR Normalized Difference Vegetation Index (NDVI) data is described. The physically based algorithm is detailed in the first of the two part series. Here, the implementation, production and evaluation of the data set are described. The data set is evaluated both by direct comparisons to ground data and indirectly through inter-comparisons with similar data sets. This indirect validation showed satisfactory agreement with existing LAI products, importantly MODIS, at a range of spatial scales, and significant correlations with key climate variables in areas where temperature and precipitation limit plant growth. The data set successfully reproduced well-documented spatio-temporal trends and inter-annual variations in vegetation activity in the northern latitudes and semi-arid tropics. Comparison with plot scale field measurements over homogeneous vegetation patches indicated a 7% underestimation when all major vegetation types are taken into account. The error in mean values obtained from distributions of AVHRR LAI and high-resolution field LAI maps for different biomes is within 0.5 LAI for six out of the ten selected sites. These validation exercises though limited by the amount of field data, and thus less than comprehensive, indicated satisfactory agreement between the LAI product and field measurements. Overall, the intercomparison with short-term LAI data sets, evaluation of long term trends with known variations in climate variables, and validation with field measurements together build confidence in the utility of this new 26 year LAI record for long term vegetation monitoring and modeling studies.

Pen Ink as an Ultraviolet Dosimeter

ERIC Educational Resources Information Center

Downs, Nathan; Turner, Joanna; Parisi, Alfio; Spence, Jenny

2008-01-01

A technique for using highlighter ink as an ultraviolet dosimeter has been developed for use by secondary school students. The technique requires the students to measure the percentage of colour fading in ink drawn onto strips of paper that have been exposed to sunlight, which can be calibrated to measurements of the ultraviolet irradiance using…

Passive, Low Cost Neutron Detectors for Neutron Diagnostics at the National Ignition Facility

DTIC Science & Technology

2013-03-01

Facility PTFE Polytetrafluoroethylene TLD Thermoluminescent Dosimeter α Conversion Coefficient (Conversion...because they required a large investment in automated track counting equipment. Thermoluminescent dosimeters ( TLDs ) remained as a viable option. They...necessary to predict radiation damage to measurement electronics . Due to programmatic and facility limitations, traditional neutron measurement

Feasibility of a semiconductor dosimeter to monitor skin dose in interventional radiology.

PubMed

Meyer, P; Regal, R; Jung, M; Siffert, P; Mertz, L; Constantinesco, A

2001-10-01

The design and preliminary test results of a semiconductor silicon dosimeter are presented in this article. Use of this dosimeter is foreseen for real-time skin dose control in interventional radiology. The strong energy dependence of this kind of radiation detector is well overcome by filtering the silicon diode. Here, the optimal filter features have been calculated by numerical Monte Carlo simulations. A prototype has been built and tested in a radiological facility. The first experimental results show a good match between the filtered semiconductor diode response and an ionization chamber response, within 2% fluctuation in a 2.2 to 4.1 mm Al half-value layer (HVL) energy range. Moreover, the semiconductor sensor response is linear from 0.02 Gy/min to at least 6.5 Gy/min, covering the whole dose rate range found in interventional radiology. The results show that a semiconductor dosimeter could be used to monitor skin dose during the majority of procedures using x-rays below 150 keV. The use of this device may assist in avoiding radiation-induced skin injuries and lower radiation levels during interventional procedures.

Thermoluminescent dosimetry in electron beams: energy dependence.

PubMed

Robar, V; Zankowski, C; Olivares Pla, M; Podgorsak, E B

1996-05-01

The response of thermoluminescent dosimeters to electron irradiations depends on the radiation dose, mean electron energy at the position of the dosimeter in phantom, and the size of the dosimeter. In this paper the semi-empirical expression proposed by Holt et al. [Phys. Med. Biol. 20, 559-570 (1975)] is combined with the calculated electron dose fraction to determine the thermoluminescent dosimetry (TLD) response as a function of the mean electron energy and the dosimeter size. The electron and photon dose fractions, defined as the relative contributions of electrons and bremsstrahlung photons to the total dose for a clinical electron beam, are calculated with Monte Carlo techniques using EGS4. Agreement between the calculated and measured TLD response is very good. We show that the considerable reduction in TLD response per unit dose at low electron energies, i.e., at large depths in phantom, is offset by an ever-increasing relative contribution of bremsstrahlung photons to the total dose of clinical electron beams. This renders the TLD sufficiently reliable for dose measurements over the entire electron depth dose distribution despite the dependence of the TLD response on electron beam energy.

Development of a personal dosimetry system based on optically stimulated luminescence of alpha-Al2O3:C for mixed radiation fields.

PubMed

Lee, S Y; Lee, K J

2001-04-01

To develop a personal optically stimulated luminescence (OSL) dosimetry system for mixed radiation fields using alpha-Al2O3:C, a discriminating badge filter system was designed by taking advantage of its optically stimulable properties and energy dependencies. This was done by designing a multi-element badge system for powder layered alpha-Al2O3:C material and an optical reader system based on high-intensity blue light-emitting diode (LED). The design of the multielement OSL dosimeter badge system developed allows the measurement of a personal dose equivalent value Hp(d) in mixed radiation fields of beta and gamma. Dosimetric properties of the personal OSL dosimeter badge system investigated here were the dose response, energy response and multi-readability. Based on the computational simulations and experiments of the proposed dosimeter design, it was demonstrated that a multi-element dosimeter system with an OSL technology based on alpha-Al2O3:C is suitable to obtain personal dose equivalent information in mixed radiation fields.

PM 2.5 ORGANIC SPECIATION INTERCOMPARISON RESULTS

EPA Science Inventory

This abstract describes a poster on results to a laboratory intercomparison of organic aerosol speciation analysis to be presented at the 2006 International Aerosol Conference sponsored by the American Association for Aerosol Research in St. Paul, Minnesota on September 10-15. T...

Total ozone measurement: Intercomparison of prototype New Zealand filter instrument and Dobson spectrophotometer

NASA Technical Reports Server (NTRS)

Basher, R. E.

1978-01-01

A five month intercomparison showed that the total ozone amounts of a prototype narrowband interference filter instrument were 7% less than those of a Dobson instrument for an ozone range of 0.300 to 0.500 atm cm and for airmasses less than two. The 7% bias was within the intercomparison calibration uncertainty. An airmass dependence in the Dobson instrument made the bias relationship airmass-dependent but the filter instrument's ozone values were generally constant to 2% up to an airmass of four. Long term drift in the bias was negligible.

The Inter-Sectoral Impact Model Intercomparison Project (ISI–MIP): Project framework

PubMed Central

Warszawski, Lila; Frieler, Katja; Huber, Veronika; Piontek, Franziska; Serdeczny, Olivia; Schewe, Jacob

2014-01-01

The Inter-Sectoral Impact Model Intercomparison Project offers a framework to compare climate impact projections in different sectors and at different scales. Consistent climate and socio-economic input data provide the basis for a cross-sectoral integration of impact projections. The project is designed to enable quantitative synthesis of climate change impacts at different levels of global warming. This report briefly outlines the objectives and framework of the first, fast-tracked phase of Inter-Sectoral Impact Model Intercomparison Project, based on global impact models, and provides an overview of the participating models, input data, and scenario set-up. PMID:24344316

Fabrication and characterization of optical super-smooth surfaces

NASA Astrophysics Data System (ADS)

Schmitt, Dirk-Roger; Kratz, Frank; Ringel, Gabriele A.; Mangelsdorf, Juergen; Creuzet, Francois; Garratt, John D.

1995-08-01

Intercomparison roughness measurements have been carried out at supersmooth artefacts fabricated from BK7, fused silica, and Zerodur. The surface parameters were determined using a special prototype of the mechanical profiler Nanostep (Rank Taylor Hobson), the Optical Heterodyne Profiler Z5500 (Zygo), and an Atomic Force Microscope (Park Scientific) with an improved acquisition technique. The intercomparison was performed after the range of collected spatial wavelength for each instrument was adjusted using digital filtering techniques. It is demonstrated for different roughness ranges that are applied superpolishing techniques yield supersmooth artefacts which can be used for more intercomparisons.

Water vapour inter-comparison effort in the framework of the hydrological cycle in the mediterranean experiment - special observation period (hymex-sop1)

NASA Astrophysics Data System (ADS)

Summa, Donato; Di Girolamo, Paolo; Flamant, Cyrille; De Rosa, Benedetto; Cacciani, Marco; Stelitano, Dario

2018-04-01

Accurate measurements of the vertical profiles of water vapour are of paramount importance for most key areas of atmospheric sciences. A comprehensive inter-comparison between different remote sensing and in-situ sensors has been carried out in the frame work of the first Special Observing Period of the Hydrological cycle in the Mediterranean Experiment for the purpose of obtaining accurate error estimates for these sensors. The inter-comparison involves a ground-based Raman lidar (BASIL), an airborne DIAL (LEANDRE2), a microwave radiometer, radiosondes and aircraft in-situ sensors.

Evaluation of the annual Canadian biodosimetry network intercomparisons

PubMed Central

Wilkins, Ruth C.; Beaton-Green, Lindsay A.; Lachapelle, Sylvie; Kutzner, Barbara C.; Ferrarotto, Catherine; Chauhan, Vinita; Marro, Leonora; Livingston, Gordon K.; Boulay Greene, Hillary; Flegal, Farrah N.

2015-01-01

Abstract Purpose: To evaluate the importance of annual intercomparisons for maintaining the capacity and capabilities of a well-established biodosimetry network in conjunction with assessing efficient and effective analysis methods for emergency response. Materials and methods: Annual intercomparisons were conducted between laboratories in the Canadian National Biological Dosimetry Response Plan. Intercomparisons were performed over a six-year period and comprised of the shipment of 10–12 irradiated, blinded blood samples for analysis by each of the participating laboratories. Dose estimates were determined by each laboratory using the dicentric chromosome assay (conventional and QuickScan scoring) and where possible the cytokinesis block micronucleus (CBMN) assay. Dose estimates were returned to the lead laboratory for evaluation and comparison. Results: Individual laboratories performed comparably from year to year with only slight fluctuations in performance. Dose estimates using the dicentric chromosome assay were accurate about 80% of the time and the QuickScan method for scoring the dicentric chromosome assay was proven to reduce the time of analysis without having a significant effect on the dose estimates. Although analysis with the CBMN assay was comparable to QuickScan scoring with respect to speed, the accuracy of the dose estimates was greatly reduced. Conclusions: Annual intercomparisons are necessary to maintain a network of laboratories for emergency response biodosimetry as they evoke confidence in their capabilities. PMID:25670072

Dissolution and subsequent re-crystallization as zeroing mechanism, thermal properties and component resolved dose response of salt (NaCl) for retrospective dosimetry.

PubMed

Polymeris, George S; Kitis, George; Kiyak, Nafiye G; Sfamba, Ioanna; Subedi, Bhagawan; Pagonis, Vasilis

2011-09-01

In the present study we report dosimetric properties of iodized salt aiming at using it as an accidental luminescent dosimeter. It was found that the very good sensitivity of its main dosimetric peak is strongly affected by thermal treatments. This is also the case for OSL emission. The sensitivity loss due to heating implies that caution should be exercised while applying single aliquot protocols for dose evaluation. The sequence of dissolution and subsequent re-crystallization was established to be an extremely effective zeroing mechanism for the TL signal. The linearity in the dose response was also monitored in the case of dissolved and subsequently re-crystallized salt. In the case of naturally occurring salt, zeroing of the TL signal due to dissolution as well as the linearity of dose response up to doses as large as 100 Gy were found to be very promising features for dating applications. Copyright © 2011 Elsevier Ltd. All rights reserved.

Activation of Dosimeters Used in qa of Medical Linear Accelerators

NASA Astrophysics Data System (ADS)

Polaczek-Grelik, Kinga; Nowacka, Magdalena; Raczkowski, Maciej

2017-09-01

This paper presents the first results of a project intended to investigate γ-radiation activity induced in dosimeters used in clinical practice during routine quality assurance of high-energy photon beams emitted by electron linear accelerators. Two aspects of the activation via photonuclear reactions (X, n) of therapeutic beam and subsequent capture of secondary neutrons (n,γ) are under considerations: the influence of activation on intrinsic background of the dosimeters and exposure of dosimetrists who operate this equipment. The activation of several types of ionization chambers as well as the silicon diodes was studied after long-time exposure (10 000 MUs) of the 15 MV photon beam (Elekta Synergy). Photon fluxes obtained from spectra of γ-rays registered by HPGe spectrometer were subsequently converted to equivalent doses using appropriate coefficients. The main contribution to the induced activity comes from the neutron capture process on Al, Mn and Cu, therefore it decays quite fast with the half-lives of the order of 15 minutes. Nevertheless, the activation of chlorine was also observed. The estimated equivalent doses to skin and eye lens were in the range 0.19 - 0.62 μSv/min. However, no influence on intrinsic background signal of all studied dosimeters was observed. The preliminary results indicate that induced radioactivity of dosimeters is strongly influenced by therapeutic beam quality and neutron source strength of particular linac. This dependence will be studied deeper in order to quantify it more precisely.

How do monomeric components of a polymer gel dosimeter respond to ionising radiation: A steady-state radiolysis towards preparation of a 3D polymer gel dosimeter

NASA Astrophysics Data System (ADS)

Kozicki, Marek

2011-12-01

Ionising radiation-induced reactions of aqueous single monomer solutions and mixtures of poly(ethylene glycol) diacrylate (PEGDA) and N, N'-methylenebisacrylamide (Bis) in a steady-state condition are presented below and above gelation doses in order to highlight reactions in irradiated 3D polymer gel dosimeters, which are assigned for radiotherapy dosimetry. Both monomers are shown to undergo radical polymerisation and cross-linking, which result in the measured increase in molecular weight and radius of gyration of the formed polydisperse polymer coils. The formation of nanogels was also observed for Bis solutions at a low concentration. In the case of PEGDA-Bis mixtures, co-polymerisation is suggested as well. At a sufficiently high radiation dose, the formation of a polymer network was observed for both monomers and their mixture. For this reason a sol-gel analysis for PEGDA and Bis was performed gravimetrically and a proposition of an alternative to this method employing a nuclear magnetic resonance technique is made. The two monomers were used for preparation of 3D polymer gel dosimeters having the acronyms PABIG and PABIG nx. The latter is presented for the first time in this work and is a type of the formerly established PABIG polymer gel dosimeter. The elementary characteristics of the new composition are presented, underlining the ease of its preparation, low dose threshold, and slightly increased sensitivity but lower quasi-linear range of dose response in comparison to PABIG.

Dosimetry of gamma chamber blood irradiator using PAGAT gel dosimeter and Monte Carlo simulations

PubMed Central

Mohammadyari, Parvin; Zehtabian, Mehdi; Sina, Sedigheh; Tavasoli, Ali Reza

2014-01-01

Currently, the use of blood irradiation for inactivating pathogenic microbes in infected blood products and preventing graft‐versus‐host disease (GVHD) in immune suppressed patients is greater than ever before. In these systems, dose distribution and uniformity are two important concepts that should be checked. In this study, dosimetry of the gamma chamber blood irradiator model Gammacell 3000 Elan was performed by several dosimeter methods including thermoluminescence dosimeters (TLD), PAGAT gel dosimetry, and Monte Carlo simulations using MCNP4C code. The gel dosimeter was put inside a glass phantom and the TL dosimeters were placed on its surface, and the phantom was then irradiated for 5 min and 27 sec. The dose values at each point inside the vials were obtained from the magnetic resonance imaging of the phantom. For Monte Carlo simulations, all components of the irradiator were simulated and the dose values in a fine cubical lattice were calculated using tally F6. This study shows that PAGAT gel dosimetry results are in close agreement with the results of TL dosimetry, Monte Carlo simulations, and the results given by the vendor, and the percentage difference between the different methods is less than 4% at different points inside the phantom. According to the results obtained in this study, PAGAT gel dosimetry is a reliable method for dosimetry of the blood irradiator. The major advantage of this kind of dosimetry is that it is capable of 3D dose calculation. PACS number: 87.53.Bn PMID:24423829

A phantom study on bladder and rectum dose measurements in brachytherapy of cervix cancer using FBX aqueous chemical dosimeter.

PubMed

Bansal, Anil K; Semwal, Manoj K; Arora, Deepak; Sharma, D N; Julka, P K; Rath, G K

2013-06-01

The ferrous sulphate-benzoic acid-xylenol orange (FBX) chemical dosimeter, due to its aqueous form can measure average volume doses and hence may overcome the limitations of point dosimetry. The present study was undertaken to validate the use of FBX dosimeter for rectum and bladder dose measurement during intracavitary brachytherapy (ICBT) and transperineal interstitial brachytherapy (TIB). We filled cylindrical polypropylene tubes (PT) and Foley balloons (FB) with FBX solution and used them as substitutes for rectum and bladder dose measurements respectively. A water phantom was fabricated with provision to place the Fletcher-type ICBT and MUPIT template applicators, and FBX filled PT and FB within the phantom. The phantom was then CT scanned for treatment planning and subsequent irradiation. Our results show that the average difference between DVH derived dose value and FBX measured dose is 3.5% (PT) and 13.7% (FB) for ICBT, and 9% (PT) and 9.9% (FB) for TIB. We believe that the FBX system should be able to provide accuracy and precision sufficient for routine quality assurance purposes. The advantage of the FBX system is its water equivalent composition, average volume dose measuring capability, and energy and temperature independent response as compared to TLD or semiconductor dosimeters. However, detailed studies will be needed with regards to its safety before actual in-vivo dose measurements are possible with the FBX dosimeter. Copyright © 2012 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

[BeO-OSL detectors for dose measurements in cell cultures].

PubMed

Andreeff, M; Sommer, D; Freudenberg, R; Reichelt, U; Henniger, J; Kotzerke, J

2009-01-01

The absorbed dose is an important parameter in experiments involving irradiation of cells in vitro with unsealed radionuclides. Typically, this is estimated with a model calculation, although the results thus obtained cannot be verified. Generally used real-time measurement methods are not applicable in this setting. A new detector material with in vitro suitability is the subject of this work. Optically-stimulated luminescence (OSL) dosimeters based on beryllium oxide (BeO) were used for dose measurement in cell cultures exposed to unsealed radionuclides. Their qualitative properties (e. g. energy-dependent count rate sensitivity, fading, contamination by radioactive liquids) were determined and compared to the results of a Monte Carlo simulation (using AMOS software). OSL dosimeters were tested in common cell culture setups with a known geometry. Dose reproducibility of the OSL dosimeters was +/-1.5%. Fading at room temperature was 0.07% per day. Dose loss (optically-stimulated deletion) under ambient lighting conditions was 0.5% per minute. The Monte Carlo simulation for the relative sensitivity at different beta energies provided corresponding results to those obtained with the OSL dosimeters. Dose profile measurements using a 6 well plate and 14 ml PP tube showed that the geometry of the cell culture vessel has a marked influence on dose distribution with 188Re. A new dosimeter system was calibrated with beta-emitters of different energy. It turned out as suitable for measuring dose in liquids. The dose profile measurements obtained are suitably precise to be used as a check against theoretical dose calculations.

Type testing of the Siemens Plessey electronic personal dosemeter.

PubMed

Hirning, C R; Yuen, P S

1995-07-01

This paper presents the results of a laboratory assessment of the performance of a new type of personal dosimeter, the Electronic Personal Dosemeter made by Siemens Plessey Controls Limited. Twenty pre-production dosimeters and a reader were purchased by Ontario Hydro for the assessment. Tests were performed on radiological performance, including reproducibility, accuracy, linearity, detection threshold, energy response, angular response, neutron response, and response time. There were also tests on the effects of a variety of environmental factors, such as temperature, humidity, pulsed magnetic and electric fields, low- and high-frequency electromagnetic fields, light exposure, drop impact, vibration, and splashing. Other characteristics that were tested were alarm volume, clip force, and battery life. The test results were compared with the relevant requirements of three standards: an Ontario Hydro standard for personal alarming dosimeters, an International Electrotechnical Commission draft standard for direct reading personal dose monitors, and an International Electrotechnical Commission standard for thermoluminescence dosimetry systems for personal monitoring. In general, the performance of the Electronic Personal Dosemeter was found to be quite acceptable: it met most of the relevant requirements of the three standards. However, the following deficiencies were found: slow response time; sensitivity to high-frequency electromagnetic fields; poor resistance to dropping; and an alarm that was not loud enough. In addition, the response of the electronic personal dosimeter to low-energy beta rays may be too low for some applications. Problems were experienced with the reliability of operation of the pre-production dosimeters used in these tests.

Studies on new neutron-sensitive dosimeters using an optically stimulated luminescence technique

NASA Astrophysics Data System (ADS)

Kulkarni, M. S.; Luszik-Bhadra, M.; Behrens, R.; Muthe, K. P.; Rawat, N. S.; Gupta, S. K.; Sharma, D. N.

2011-07-01

The neutron response of detectors prepared using α-Al 2O 3:C phosphor developed using a melt processing technique and mixed with neutron converters was studied in monoenergetic neutron fields. The detector pellets were arranged in two different pairs: α-Al 2O 3:C + 6LiF/α-Al 2O 3:C + 7LiF and α-Al 2O 3:C + high-density polyethylene/α-Al 2O 3:C + Teflon, for neutron dosimetry using albedo and recoil proton techniques. The optically stimulated luminescence response of the Al 2O 3:C + 6,7LiF dosimeter to radiation from a 252Cf source was 0.21, in terms of personal dose equivalent Hp(10) and relative to radiation from a 137Cs source. This was comparable to results obtained with similar detectors prepared using commercially available α-Al 2O 3:C phosphor. The Hp(10) response of the α-Al 2O 3:C + 6,7LiF dosimeters was found to decrease by more than two orders of magnitude with increasing neutron energy, as expected for albedo dosimeters. The response of the α-Al 2O 3:C + high-density polyethylene/α-Al 2O 3:C + Teflon dosimeters was small, of the order of 1% to 2% in terms of Hp(10) and relative to radiation from a 137Cs source, for neutron energies greater than 1 MeV.

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.