Consequences of Secondary Calibrations on Divergence Time Estimates.

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John J Schenk

Full Text Available Secondary calibrations (calibrations based on the results of previous molecular dating studies are commonly applied in divergence time analyses in groups that lack fossil data; however, the consequences of applying secondary calibrations in a relaxed-clock approach are not fully understood. I tested whether applying the posterior estimate from a primary study as a prior distribution in a secondary study results in consistent age and uncertainty estimates. I compared age estimates from simulations with 100 randomly replicated secondary trees. On average, the 95% credible intervals of node ages for secondary estimates were significantly younger and narrower than primary estimates. The primary and secondary age estimates were significantly different in 97% of the replicates after Bonferroni corrections. Greater error in magnitude was associated with deeper than shallower nodes, but the opposite was found when standardized by median node age, and a significant positive relationship was determined between the number of tips/age of secondary trees and the total amount of error. When two secondary calibrated nodes were analyzed, estimates remained significantly different, and although the minimum and median estimates were associated with less error, maximum age estimates and credible interval widths had greater error. The shape of the prior also influenced error, in which applying a normal, rather than uniform, prior distribution resulted in greater error. Secondary calibrations, in summary, lead to a false impression of precision and the distribution of age estimates shift away from those that would be inferred by the primary analysis. These results suggest that secondary calibrations should not be applied as the only source of calibration in divergence time analyses that test time-dependent hypotheses until the additional error associated with secondary calibrations is more properly modeled to take into account increased uncertainty in age estimates.

Calibration and intercomparison methods of dose calibrators used in nuclear medicine facilities

International Nuclear Information System (INIS)

Costa, Alessandro Martins da

1999-01-01

Dose calibrators are used in most of the nuclear medicine facilities to determine the amount of radioactivity administered to a patient in a particular investigation or therapeutic procedure. It is therefore of vital importance that the equipment used presents good performance and is regular;y calibrated at a authorized laboratory. This occurs of adequate quality assurance procedures are carried out. Such quality control tests should be performed daily, other biannually or yearly, testing, for example, its accuracy and precision, the reproducibility and response linearity. In this work a commercial dose calibrator was calibrated with solution of radionuclides used in nuclear medicine. Simple instrument tests, such as response linearity and the response variation of the source volume increase at a constant source activity concentration, were performed. This instrument can now be used as a working standard for calibration of other dose calibrators/ An intercomparison procedure was proposed as a method of quality control of dose calibrators used in nuclear medicine facilities. (author)

Accuracy determination of dose calibrators in Nuclear Medicine Centers using Tl-201

International Nuclear Information System (INIS)

Sattari, A.; Feizi, H.; Ghafoori, M.

2008-01-01

Full text: Correct administrated activity of radiopharmaceuticals is an important factor to ensure that administrated radiopharmaceutical is accurately measured and to avoid unnecessary exposure to patients. In this article, nuclear medicine group and Secondary Standard Dosimetry Laboratory (SSDL), has introduced a comparison study with 201 Tl to check the accuracy of dose calibrators in some nuclear medicine centers. First, the dose calibrator in cyclotron department was calibrated by SSDL using 133 Ba, 57 Co, 137 Cs and standard Europium sources. Then, 2ml produced 201 Tl solution containing 16±0.1 mCi was accurately sub-divided into a series of 10 ml Schott vials and delivered to 12 nuclear medicine centers that have been participated in this study. Participants were requested to assay their Schott vials in their dose calibrators at the same time and report the result on the especial sheet. Difference between the activities values reported by participants (A p ) with assayed activity on cyclotron department (Ac), defined as error value. In comparison of A c with A p , 10 centers (83%) has positive and 2 others (17%) has negative error. The range of positive error 2.6% -17.9% and range of negative error 5%-8.5%, by the average of 8.67 and %SD = 7.39 have been calculated. In conclusion, although nuclear medicine centers do calibration on their dose calibrators but establishment a regular audit system seems to be necessary. (author)

Secondary radiation dose during high-energy total body irradiation

Energy Technology Data Exchange (ETDEWEB)

Janiszewska, M.; Raczkowski, M. [Lower Silesian Oncology Center, Medical Physics Department, Wroclaw (Poland); Polaczek-Grelik, K. [University of Silesia, Medical Physics Department, Katowice (Poland); Szafron, B.; Konefal, A.; Zipper, W. [University of Silesia, Department of Nuclear Physics and Its Applications, Katowice (Poland)

2014-05-15

The goal of this work was to assess the additional dose from secondary neutrons and γ-rays generated during total body irradiation (TBI) using a medical linac X-ray beam. Nuclear reactions that occur in the accelerator construction during emission of high-energy beams in teleradiotherapy are the source of secondary radiation. Induced activity is dependent on the half-lives of the generated radionuclides, whereas neutron flux accompanies the treatment process only. The TBI procedure using a 18 MV beam (Clinac 2100) was considered. Lateral and anterior-posterior/posterior-anterior fractions were investigated during delivery of 2 Gy of therapeutic dose. Neutron and photon flux densities were measured using neutron activation analysis (NAA) and semiconductor spectrometry. The secondary dose was estimated applying the fluence-to-dose conversion coefficients. The main contribution to the secondary dose is associated with fast neutrons. The main sources of γ-radiation are the following: {sup 56}Mn in the stainless steel and {sup 187}W of the collimation system as well as positron emitters, activated via (n,γ) and (γ,n) processes, respectively. In addition to 12 Gy of therapeutic dose, the patient could receive 57.43 mSv in the studied conditions, including 4.63 μSv from activated radionuclides. Neutron dose is mainly influenced by the time of beam emission. However, it is moderated by long source-surface distances (SSD) and application of plexiglass plates covering the patient body during treatment. Secondary radiation gives the whole body a dose, which should be taken into consideration especially when one fraction of irradiation does not cover the whole body at once. (orig.) [German] Die zusaetzliche Dosis durch sekundaere Neutronen- und γ-Strahlung waehrend der Ganzkoerperbestrahlung mit Roentgenstrahlung aus medizinischen Linearbeschleunigern wurde abgeschaetzt. Bei der Emission hochenergetischer Strahlen zur Teletherapie finden hauptsaechlich im Beschleuniger

Dosimetry through the Secondary Laboratory of Dosimetric Calibration of Mexico

International Nuclear Information System (INIS)

Tovar M, V.M.; Alvarez R, J.T.; Medina O, V.P.; Vergara M, F.; Anaya M, R.; Cejudo A, J.; Salinas L, B.

2004-01-01

In the beginnings of the sixty years an urgent necessity is presented mainly in the developing countries, of improving in important form the accuracy in the dosimetry of external faces in therapy of radiations (radiotherapy centers), mainly in the calibration of c linical dosemeters . In 1976 the International Atomic Energy Agency, (IAEA), and the World Health Organization, (WHO), they carried out a mutual agreement with regard to the establishment and operation of a net of Secondary Patron Laboratories of Dosimetry, (LSCD). The necessity to establish measure patterns in the field of the dosimetry of the ionizing radiations, is necessary, to have an accuracy but high in the dosimetry of the radiation beams in therapy which is highly dependent of the dose given to the tumor of those patient with cancer. Similar levels of accuracy are required in protection measures to the radiation with an acceptable smaller accuracy, however, when the personal dosemeters are used to determine the doses received by the individuals under work conditions, such mensurations in therapy of radiations and radiological protection will have traceability through a chain of comparisons to primary or national patterns. The traceability is necessary to assure the accuracy and acceptability of the dosimetric measures, as well as, the legal and economic implications. The traceability is also necessary in the dosimetry of high dose like in the sterilization of different products. The main function of the LSCD is to provide a service in metrology of ionizing radiations, maintaining the secondary or national patterns, which have a traceability to the International System of measures, which is based for if same in the comparison of patterns in the Primary Laboratories of Dosimetry (LPD) under the auspice of the International Office of Weights and Measure (BIPM). The secondary and national patterns in the LSCD constitute in Mexico, the national patterns of the magnitudes in the dosimetry of the

Exploitation of secondary standard for calibration in units of Dw,1cm and assessment of several HDR brachytherapy planning systems

International Nuclear Information System (INIS)

Gabris, F.; Zeman, J.; Valenta, J.; Gabris, F.; Selbach, H.J.

2012-01-01

A secondary standard of the BEV, calibrated at the PTB in terms of D w,1c m, was used for calibration of the well-type chamber-based measuring systems used in clinics. In addition to the calibration, we tried to employ it for assessment of treatment planning systems (TPS) used for each particular after-loader. The dose to water at 1 cm distance from the source position was calculated by the TPS, using reference data from the source producer certificate. The values were compared directly with the dose measured at the same distance from the source. The comparison has been carried out for GammaMed Plus and MicroSelectron HDR sources. Differences of secondary standard measurements and TPS calculations were lower than ±5%, which is below the achievable uncertainty of both dose measurement and dose determination by the TPS. Nevertheless, it is higher than generally accepted in the case of external beam radiotherapy. Additional direct measurements in terms of D w,1c m may improve the safety and reliability of patient treatment. (authors)

Performance standard for dose Calibrator

CERN Document Server

Darmawati, S

2002-01-01

Dose calibrator is an instrument used in hospitals to determine the activity of radionuclide for nuclear medicine purposes. International Electrotechnical Commission (IEC) has published IEC 1303:1994 standard that can be used as guidance to test the performance of the instrument. This paper briefly describes content of the document,as well as explains the assessment that had been carried out to test the instrument accuracy in Indonesia through intercomparison measurement.Its is suggested that hospitals acquire a medical physicist to perform the test for its dose calibrator. The need for performance standard in the form of Indonesia Standard is also touched.

Absorbed dose calibration factors for parallel-plate chambers in high energy photon beams

International Nuclear Information System (INIS)

McEwen, M.R.; Duane, S.; Thomas, R.A.S.

2002-01-01

An investigation was carried out into the performance of parallel-plate chambers in 60 Co and MV photon beams. The aim was to derive calibration factors, investigate chamber-to-chamber variability and provide much-needed information on the use of parallel-plate chambers in high-energy X-ray beams. A set of NE2561/NE2611 reference chambers, calibrated against the primary standard graphite calorimeter is used for the dissemination of absorbed dose to water. The parallel-plate chambers were calibrated by comparison with the NPL reference chambers in a water phantom. Two types of parallel-plate chamber were investigated - the NACP -02 and Roos and measurements were made at 60 C0 and 6 linac photon energies (6-19 MV). Calibration factors were derived together with polarity corrections. The standard uncertainty in the calibration of a chamber in terms of absorbed dose to water is estimated to be ±0.75%. The results of the polarity measurements were somewhat confusing. One would expect the correction to be small and previous measurements in electron beams have indicated that there is little variation between chambers of these types. However, some chambers gave unexpectedly large polarity corrections, up to 0.8%. By contrast the measured polarity correction for a NE2611 chamber was less than 0.13% at all energies. The reason for these large polarity corrections is not clear, but experimental error and linac variations have been ruled out. By combining the calibration data for the different chambers it was possible to obtain experimental k Q factors for the two chamber types. It would appear from the data that the variations between chambers of the same type are random and one can therefore define a generic curve for each chamber type. These are presented in Figure 1, together with equivalent data for two cylindrical chamber types - NE2561/NE2611 and NE2571. As can be seen, there is a clear difference between the curves for the cylindrical chambers and those for the

The role of the Secondary Laboratory of Dosimetric calibration in the implementation of the dosimetric magnitudes with radiological protection aims

International Nuclear Information System (INIS)

Perez Medina O, V.; Alvarez R, J.T.; Tovar M, V.M.

2006-01-01

It is very well-known the paper of the net of secondary laboratories of dosimetric calibration of the OAS in the dissemination of the traceability of the dosimetric magnitudes: kerma in air and absorbed dose in water, to the radiotherapy departments, given the high accuracy and precision that require the radiotherapy treatments. However the LSCD has other important areas at least for the development, implementation and evaluation of dosimetric magnitudes denominated operative magnitudes with ends of radiological protection: environmental equivalent dose H*(10), directional equivalent dose H'(0.07) and personal equivalent dose Hp. In the case of radiological protection the LSCD-ININ has been implementing the infrastructure to give service of personal dosimetry for photons and beta particles in terms of the operative magnitudes. For photons: X and gamma rays, it account with a secondary pattern camera PTW T34035 gauged in H * and Hp in the primary laboratory of Germany PTB. For the case of beta radiation its account with an extrapolation camera PTW 23392 with a secondary pattern kit of sources of the type I, gauged in terms of H'(0.07) in the PTB. (Author)

Spectral calibration of EBT3 and HD-V2 radiochromic film response at high dose using 20 MeV proton beams

Science.gov (United States)

Feng, Yiwei; Tiedje, Henry F.; Gagnon, Katherine; Fedosejevs, Robert

2018-04-01

Radiochromic film is used extensively in many medical, industrial, and scientific applications. In particular, the film is used in analysis of proton generation and in high intensity laser-plasma experiments where very high dose levels can be obtained. The present study reports calibration of the dose response of Gafchromic EBT3 and HD-V2 radiochromic films up to high exposure densities. A 2D scanning confocal densitometer system is employed to carry out accurate optical density measurements up to optical density 5 on the exposed films at the peak spectral absorption wavelengths. Various wavelengths from 400 to 740 nm are also scanned to extend the practical dose range of such films by measuring the response at wavelengths removed from the peak response wavelengths. Calibration curves for the optical density versus exposure dose are determined and can be used for quantitative evaluation of measured doses based on the measured optical densities. It was found that blue and UV wavelengths allowed the largest dynamic range though at some trade-off with overall accuracy.

High dose rate 192Ir calibration: Indonesia experiences

International Nuclear Information System (INIS)

Nasukha; Tjiptanto, D.; Darmasyah, R.; Kurniawan, B.

2002-01-01

Indonesia with a population of more than 200 Million people which spread on about 5000 islands, up to now only has 23 radiotherapy centers and some not active anymore. As mention by Parkin et al that Cervix/Utery and breast cancer are the most estimated numbers of new cases of cancers in women for developing countries, stomach and lung cancers in men. Indonesia as a developing country is likely similar to other developing countries on numbers of new cases of cancers in women. But quite different in men, in Indonesia the most common cancers are nasopharynx and thyroid cancers. The use of lr-192 sources in high dose-rate (HDR) remotely afterloaded brachytherapy treatments have greatly increased in recent years and variety of such sources are commercially available. Nine radiotherapy centers in Indonesia installed Nucletron microSelectron HDR remote afterloader. Based on the data of CiptoMangunkusurno Hospital, Jakarta that the most common cancers are the cervix, breast, nasopharynx and thyroid cancers which of percentage are about 31%, 25 %, 13%, and 6 % respectively. It means that the use of HDR 192 Ir brachytherapy has to be an effective tool in the treatments. Two methods have been studied and applied to calibrate HDR 192 Ir brachytherapy in Indonesia, especially for Nucletron microSelectron HDR 192 lr remote afterloader brachytherapy. Calibration of HDR 192 Ir brachytherapy source has been done by Cavity lonization Chamber and with Well Type lonization Chamber. First, 0.6 cc of NE Farmer type dosimeter that was calibrated to 60 Co and 250 kV of x-rays in air kerma was used in this experiment. Position of measurement (detector and source) at the center of the room and about 1 meter from the floor. Eight variation of distances from 10 cm to 40 cms have been carried out measurement as recommended by IAEA-TECDOC-1079. Correction have been given for scatters, non-uniformity, and attenuation. To solve the problem of scatter correction factor was used Matlab programming

Measurement of extrapolation curves for the secondary pattern of beta radiation Nr. 86 calibrated in rapidity of absorbed dose for tissue equivalent by the Physikalisch Technische Bundesanstalt

International Nuclear Information System (INIS)

Alvarez R, J.T.

1988-10-01

The following report has as objective to present the obtained results of measuring - with a camera of extrapolation of variable electrodes (CE) - the dose speed absorbed in equivalent fabric given by the group of sources of the secondary pattern of radiation Beta Nr. 86, (PSB), and to compare this results with those presented by the calibration certificates that accompany the PSB extended by the primary laboratory Physikalisch Technische Bundesanstalt, (PTB), of the R.F.A. as well as the uncertainties associated to the measure process. (Author)

Standard Test Method for Calibration of Non-Concentrator Photovoltaic Secondary Reference Cells

CERN Document Server

American Society for Testing and Materials. Philadelphia

2010-01-01

1.1 This test method covers calibration and characterization of secondary terrestrial photovoltaic reference cells to a desired reference spectral irradiance distribution. The recommended physical requirements for these reference cells are described in Specification E1040. Reference cells are principally used in the determination of the electrical performance of a photovoltaic device. 1.2 Secondary reference cells are calibrated indoors using simulated sunlight or outdoors in natural sunlight by reference to a primary reference cell previously calibrated to the same desired reference spectral irradiance distribution. 1.3 Secondary reference cells calibrated according to this test method will have the same radiometric traceability as the of the primary reference cell used for the calibration. Therefore, if the primary reference cell is traceable to the World Radiometric Reference (WRR, see Test Method E816), the resulting secondary reference cell will also be traceable to the WRR. 1.4 This test method appli...

Validation of a densimeter calibration procedure for a secondary calibration laboratory

International Nuclear Information System (INIS)

Alpizar Herrera, Juan Carlos

2014-01-01

A survey was conducted to quantify the need for calibration of a density measurement instrument at the research units at the Sede Rodrigo Facio of the Universidad de Costa Rica. A calibration procedure was documented for the instrument that presented the highest demand in the survey by the calibration service. A study of INTE-ISO/IEC 17025: 2005 and specifically in section 5.4 of this standard was done, to document the procedure for calibrating densimeters. Densimeter calibration procedures and standards were sought from different national and international sources. The method of hydrostatic weighing or Cuckow method was the basis of the defined procedure. Documenting the calibration procedure and creating other documents was performed for data acquisition log, intermediate calculation log and calibration certificate copy. A veracity test was performed using as reference laboratory a laboratory of calibration secondary national as part of the validation process of the documented procedure. The results of the E_n statistic of 0.41; 0.34 and 0.46 for the calibration points 90%, 50% and 10% were obtained for the densimeter scale respectively. A reproducibility analysis of the method was performed with satisfactory results. Different suppliers were contacted to estimate the economic costs of the equipment and materials, needed to develop the documented method of densimeter calibration. The acquisition of an analytical balance was recommended, instead of a precision scale, in order to improve the results obtained with the documented method [es

Status of radiation dosimetry in Germany using ionization chamber calibrated in terms of absorbed dose to water

International Nuclear Information System (INIS)

Hohlfeld, Klaus; Roos, Martin

1995-01-01

In 1984 the PTB as PSDL and the DIN Standard Committee on Radiology (NAR) in close co-operation decided that in Germany the measured absorbed dose to water in a water phantom should replace exposure in the dosimetry for radiation therapy. The PTB has established primary standards of water absorbed dose in the whole range of photon and electron radiation, and international comparisons at the BIPM and with other PSDLs proved agreement within 0.5%. Secondary standards are calibrated in a water phantom under reference conditions in a Co-60 gamma radiation beam at the PTB. Thus, the calibration factor in terms of water absorbed dose, N W , is transferred to the manufacturers of dosimeters, the German Calibration Service and the dosimetry laboratories of the verification authorities. The Verification Law subjects each ionization dosimeter used in the treatment of patients with external photon radiation beams under a type-test at PTB and under a verification procedure, where the calibration factor, N W , must be shown to be within given limits. The absorbed dose determination at the users' level follows the foralism prescribed in the Standard DIN 6800-2 (1995) 'Procedures for Absorbed Dose Determination in Radiology by the Ionization Method'. The concept of this DIN Standard uses exclusively one quantity from the primary standard to the user's instrument eliminating uncertainties and sources of mistakes associated with the conversion of a calibration factor. The concept is simple and clear and covers the whole range of photon and electron radiation. As a means of quality assurance in basic dosimetry the PTB runs a calibration service, up to now on a voluntary basis, which allows the user to compare his dosimetry system against PTB standards using mailed Fricke ampoules, with water absorbed dose as measured and used

Secondary intracranial meningiomas after high-dose cranial irradiation: report of five cases and review of the literature

International Nuclear Information System (INIS)

Strojan, Primoz; Popovic, Mara; Jereb, Berta

2000-01-01

Purpose: To review cases of secondary intracranial meningiomas following high-dose cranial irradiation (≥ 10 Gy) identified in Slovenia between 1968 and 1998, to determine their histological profile and to review the literature on this topic. Methods and Materials: Personal files of patients treated for secondary intracranial meningioma during a 31-year period were reviewed. In cases which met the criteria for radiation-induced tumors, steroid hormone receptor and Ki-67 status were analyzed. For the literature review, computerized database systems and reference lists from respective publications were used. Results: Five patients (2 females, 3 males), 3-11 years old at the time of cranial irradiation, developed secondary meningioma after a latency period of 9.5-31.5 years. Three patients had multiple tumors and 2 developed recurrent disease. Of 9 histologically examined tumors, 5 were graded as benign and 4 as atypical meningiomas, with Ki-67 proliferative index 3.2 ± 3.6 and 10 ± 6, respectively. The ratio between positive and negative meningiomas regarding immunostaining for progesterone and estrogen receptors was eight-to-one and six-to-three, respectively. Cumulative actuarial risk of secondary meningioma in a cohort of 445 children 16 years or younger treated with high-dose cranial irradiation between 1968 and 1990 in Slovenia at 10, 20, and 25 years was 0.53%, 1.2%, and 8.18%, respectively. Out of 126 cases of radiation-induced meningiomas reported, 57% were females and 43% were males, with mean age at presentation 33 ± 17.3 years. The majority (68%) of patients was irradiated during childhood. The latency period was significantly shorter in those who aged 5 years or less at the time of cranial irradiation (p = 0.04), and in those with atypical/anaplastic tumor (p = 0.01). Correlation between radiation dose and latency period could not be found. Conclusion: Secondary meningiomas following high-dose cranial irradiation are characterized by younger age at

Analysis of uncertainties in the measurements of absorbed dose to water in a secondary standard dosimetry laboratory (SSDL) 60Cobalt

International Nuclear Information System (INIS)

Silva, Cosme Norival Mello da; Rosado, Paulo Henrique Goncalves

2011-01-01

The National Metrology Laboratory of Ionizing Radiation (LNMRI) is the laboratory designated by INMETRO in the field of Metrology of ionizing radiation and is a Secondary Standard Dosimetry Laboratory (SSDL). One of its guidelines is to maintain and disseminate LNMRI absorbed dose in water used as a national standard dosimetry in radiotherapy. For this pattern is metrologically acceptable accuracy and uncertainties should be assessed over time. The objective of this study is to analyze the uncertainties involved in determining the absorbed dose rate in water and standard uncertainty of absorbed dose calibration in water from a clinical dosimeter. The largest sources of uncertainty in determining the rate of absorbed dose in water are due to: calibration coefficient of the calibration certificate supplied by the BIPM, electrometer calibration, camber stability over time, variation of pressure and humidity, strong dependence and non-uniformity of the field. The expanded uncertainty is 0.94% for k = 2. For the calibration standard uncertainty of absorbed dose in water of a dosimeter in a clinical a major source of uncertainty is due to the absorbed dose rate in water (0.94%). The value of expanded uncertainty of calibrating a clinical dosimeter is 1.2% for k = 2. (author)

Syringe calibration factors and volume correction factors for the NPL secondary standard radionuclide calibrator

CERN Document Server

Tyler, D K

2002-01-01

The activity assay of a radiopharmaceutical administration to a patient is normally achieved via the use of a radionuclide calibrator. Because of the different geometries and elemental compositions between plastic syringes and glass vials, the calibration factors for syringes may well be significantly different from those for the glass containers. The magnitude of these differences depends on the energies of the emitted photons. For some radionuclides variations have been observed of 70 %, it is therefore important to recalibrate for syringes or use syringe calibration factors. Calibration factors and volume correction factors have been derived for the NPL secondary standard radionuclide calibrator, for a variety of commonly used syringes and needles, for the most commonly used medical radionuclide.

Dose calibrator user and quality control guide

International Nuclear Information System (INIS)

Blanchis, Philippe; Amiot, Marie-Noelle; Moune, Muriel; Bellanger, Anne-Christine; Chauvenet, Bruno; Verdeau, Eric; Gardin, Isabelle; Martineau, Antoine; Ricard, Marcel; Caselles, Olivier; Guilhem, Marie-Therese; Hapdey, Sebastien; Lisbona, Albert; Bonnot-Lours, Sophie; Dumont, Agnes; Lemercier, Valerie; Rizzo-Padoin, Nathalie

2006-06-01

This document is a practical guide for the use and control of dose calibrators which are instruments used for radioactivity measurements. After a recall of the calibrator operation principle, the authors describe all the operations performed on this apparatus all along its lifetime: controls to be performed for device acceptance, aspects to be addressed during installation, controls to be performed before any use, daily controls, more detailed controls, and operations to be performed for maintenance, in case of dysfunctions or for re-calibration

Calibration and intercomparison methods of dose calibrators used in nuclear medicine facilities; Metodos de calibracao e de intercomparacao de calibradores de dose utilizados em servicos de medicina nuclear

Energy Technology Data Exchange (ETDEWEB)

Costa, Alessandro Martins da

1999-07-01

Dose calibrators are used in most of the nuclear medicine facilities to determine the amount of radioactivity administered to a patient in a particular investigation or therapeutic procedure. It is therefore of vital importance that the equipment used presents good performance and is regular;y calibrated at a authorized laboratory. This occurs of adequate quality assurance procedures are carried out. Such quality control tests should be performed daily, other biannually or yearly, testing, for example, its accuracy and precision, the reproducibility and response linearity. In this work a commercial dose calibrator was calibrated with solution of radionuclides used in nuclear medicine. Simple instrument tests, such as response linearity and the response variation of the source volume increase at a constant source activity concentration, were performed. This instrument can now be used as a working standard for calibration of other dose calibrators/ An intercomparison procedure was proposed as a method of quality control of dose calibrators used in nuclear medicine facilities. (author)

A self-calibrating ionisation chamber for the precise intensity calibration of high-energy heavy-ion beam monitors

International Nuclear Information System (INIS)

Junghans, A.

1996-01-01

The intensity of a 136 Xe(600 A MeV) beam has been determined by simultaneously measuring the particle rate and the corresponding ionisation current with an ionisation chamber. The ionisation current of this self-calibrating device was compared at higher intensities with the current of a secondary-electron monitor and a calibration of the secondary-electron current was achieved with a precision of 2%. This method can be applied to all high-energy heavy-ion beams. (orig.)

On the absorbed dose determination method in high energy electrons beams

International Nuclear Information System (INIS)

Scarlat, F.; Scarisoreanu, A.; Oane, M.; Mitru, E.; Avadanei, C.

2008-01-01

The absorbed dose determination method in water for electron beams with energies in the range from 1 MeV to 50 MeV is presented herein. The dosimetry equipment for measurements is composed of an UNIDOS.PTW electrometer and different ionization chambers calibrated in air kerma in a Co 60 beam. Starting from the code of practice for high energy electron beams, this paper describes the method adopted by the secondary standard dosimetry laboratory (SSDL) in NILPRP - Bucharest

On the absorbed dose determination method in high energy photon beams

International Nuclear Information System (INIS)

Scarlat, F.; Scarisoreanu, A.; Oane, M.; Mitru, E.; Avadanei, C.

2008-01-01

The absorbed dose determination method in water, based on standards of air kerma or exposure in high energy photon beams generated by electron with energies in the range of 1 MeV to 50 MeV is presented herein. The method is based on IAEA-398, AAPM TG-51, DIN 6800-2, IAEA-381, IAEA-277 and NACP-80 recommendations. The dosimetry equipment is composed of UNIDOS T 10005 electrometer and different ionization chambers calibrated in air kerma method in a Co 60 beam. Starting from the general formalism showed in IAEA-381, the determination of absorbed dose in water, under reference conditions in high energy photon beams, is given. This method was adopted for the secondary standard dosimetry laboratory (SSDL) in NILPRP-Bucharest

Simplified method for creating a density-absorbed dose calibration curve for the low dose range from Gafchromic EBT3 film

Directory of Open Access Journals (Sweden)

Tatsuhiro Gotanda

2016-01-01

Full Text Available Radiochromic film dosimeters have a disadvantage in comparison with an ionization chamber in that the dosimetry process is time-consuming for creating a density-absorbed dose calibration curve. The purpose of this study was the development of a simplified method of creating a density-absorbed dose calibration curve from radiochromic film within a short time. This simplified method was performed using Gafchromic EBT3 film with a low energy dependence and step-shaped Al filter. The simplified method was compared with the standard method. The density-absorbed dose calibration curves created using the simplified and standard methods exhibited approximately similar straight lines, and the gradients of the density-absorbed dose calibration curves were −32.336 and −33.746, respectively. The simplified method can obtain calibration curves within a much shorter time compared to the standard method. It is considered that the simplified method for EBT3 film offers a more time-efficient means of determining the density-absorbed dose calibration curve within a low absorbed dose range such as the diagnostic range.

Quality control for dose calibrators

International Nuclear Information System (INIS)

Mendes, L.C.G.

1984-01-01

Nuclear medicine laboratories are required to assay samples of radioactivity to be administered to patients. Almost universally, these assays are accomplished by use of a well ionization chamber isotope calibrator. The Instituto de Radioprotecao e Dosimetria (Institute for Radiological Protection and Dosimetry) of the Comissao Nacional de Energia Nuclear (National Commission for Nuclear Energy) is carrying out a National Quality Control Programme in Nuclear Medicine, supported by the International Atomic Energy Agency. The assessment of the current needs and practices of quality control in the entire country of Brazil includes Dose Calibrators and Scintillation Cameras, but this manual is restricted to the former. Quality Control Procedures for these Instruments are described in this document together with specific recommendations and assessment of its accuracy. (author)

Present status of calibration system and implementation of the new ICRU operational quantities in China

International Nuclear Information System (INIS)

Zhang Qingli

1995-01-01

Accompanying the wide use of ionizing radiation, general public have gradually become aware of the detriments of ionizing radiation. The adequate calibration standards, calibration facilities and calibration techniques, and the proper use of radiation-measuring instruments are the key steps of the measurements. In China, national standards are maintained by the National Institute of Metrology. The secondary standards including standard reference radiation sources, standard reference instruments and calibration phantoms in the Secondary Standard Dose Laboratory (SSDL) and other main calibration services are calibrated directly and periodically with the national (primary) standards. ICRU dose equivalent standards are established, and the calibration procedures being followed are consistent with the suggestions of International Standard Organization. γ ray and X-ray calibration facilities are explained. Since the issue of ICRU Report 39, ambient dose equivalent and directional dose equivalent for area monitoring and individual dose equivalent, penetrating and superficial, have been introduced. The concepts of quality assurance in radiation monitoring have been introduced. (K.I.)

Calibration of the NPL secondary standard radionuclide calibrator for the new 10R Schott, Type 1+ vials

International Nuclear Information System (INIS)

Baker, M.

2005-01-01

For many years, P6 vials have been used for the distribution of a wide range of diagnostic and therapeutic radioactive solutions. The activity measurements were performed in this geometry and, in time, the UK calibration system for nuclear medicine was based on this container as a standard. However, one major supplier of radiopharmaceuticals has replaced the P6 vial with the 10R Type 1+ Schott vial. As the dimensions of the new vial are different from those of the P6 vial and the responses of radionuclide calibrators are known to be container dependent, the need for re-calibration became apparent. Preliminary measurements made on some typical radionuclide calibrators for 125 I solution indicated a difference in response of about 10% between the two vials. The master ionisation chamber of the NPL secondary standard radionuclide calibrator has been re-calibrated and new calibration factors and volume correction factors for 10R Schott vials have been derived for the relevant medical radionuclides. The standard holder was also modified to accommodate the new larger vial. The complete list of factors and the method used to determine them is presented in this paper. The availability of these new factors will improve the quality of activity measurements in nuclear medicine, as calibration services can now be provided by NPL for the new container. These factors can also be employed for all commercial NPL secondary standard radionuclide calibrators (now known as the NPL-CRC and previously as the 671 or ISOCAL IV)

Calibration setting numbers for dose calibrators for the PET isotopes "5"2Mn, "6"4Cu, "7"6Br, "8"6Y, "8"9Zr, "1"2"4I

International Nuclear Information System (INIS)

Wooten, A. Lake; Lewis, Benjamin C.; Szatkowski, Daniel J.; Sultan, Deborah H.; Abdin, Kinda I.; Voller, Thomas F.; Liu, Yongjian; Lapi, Suzanne E.

2016-01-01

For PET radionuclides, the radioactivity of a sample can be conveniently measured by a dose calibrator. These devices depend on a “calibration setting number”, but many recommended settings from manuals were interpolated based on standard sources of other radionuclide(s). We conducted HPGe gamma-ray spectroscopy, resulting in a reference for determining settings in two types of vessels containing one of several PET radionuclides. Our results reiterate the notion that in-house, experimental calibrations are recommended for different radionuclides and vessels. - Highlights: • Dose calibrators measure radioactivity by ionization of gas from emitted radiation. • Accuracy of dose calibrators depends on “calibration setting numbers” for isotopes. • Many manufacturer settings are interpolated from emissions of other radionuclides. • As a high-precision reference, HPGe gamma-ray spectroscopy was conducted. • New calibrations were found for PET isotopes "5"2Mn, "6"4Cu, "7"6Br, "8"6Y, "8"9Zr, and "1"2"4I.

Poster — Thur Eve — 42: Radiochromic film calibration for low-energy seed brachytherapy dose measurement

Energy Technology Data Exchange (ETDEWEB)

Morrison, H; Menon, G; Sloboda, R [Department of Medical Physics, Cross Cancer Institute, Edmonton, Alberta T6G 1Z2 (Canada); Department of Oncology, University of Alberta, Edmonton, Alberta T6G 2R3 (Canada)

2014-08-15

The purpose of this study was to investigate the accuracy of radiochromic film calibration procedures used in external beam radiotherapy when applied to I-125 brachytherapy sources delivering higher doses, and to determine any necessary modifications to achieve similar accuracy in absolute dose measurements. GafChromic EBT3 film was used to measure radiation doses upwards of 35 Gy from 6 MV, 75 kVp and (∼28 keV) I-125 photon sources. A custom phantom was used for the I-125 irradiations to obtain a larger film area with nearly constant dose to reduce the effects of film heterogeneities on the optical density (OD) measurements. RGB transmission images were obtained with an Epson 10000XL flatbed scanner, and calibration curves relating OD and dose using a rational function were determined for each colour channel and at each energy using a non-linear least square minimization method. Differences found between the 6 MV calibration curve and those for the lower energy sources are large enough that 6 MV beams should not be used to calibrate film for low-energy sources. However, differences between the 75 kVp and I-125 calibration curves were quite small; indicating that 75 kVp is a good choice. Compared with I-125 irradiation, this gives the advantages of lower type B uncertainties and markedly reduced irradiation time. To obtain high accuracy calibration for the dose range up to 35 Gy, two-segment piece-wise fitting was required. This yielded absolute dose measurement accuracy above 1 Gy of ∼2% for 75 kVp and ∼5% for I-125 seed exposures.

Proposal of a postal system for Ir-192 sources calibration used in high dose rate brachytherapy with LiF:Mn:Ti thermoluminescent dosemeters

International Nuclear Information System (INIS)

Vieira, W.S.; Borges, J.C.; Almeida, C.E.V.

1998-01-01

A proposal in order to improve the brachytherapy quality control and to allow postal intercomparison of Ir-192 sources used in high dose rate brachytherapy has been presented. The LiF: Mn: Ti (TLD 100) detector has been selected for such purpose. The experimental array and the TLDs irradiation and calibration techniques, at the treatment units, have been specified in the light of more recent methodology of Ir-192 calibration sources. (Author)

Calibration and quality control for personnel dose meter

International Nuclear Information System (INIS)

Wu Rongtao; Zhang Dianqin

1999-01-01

Calibration and quality control are the important aspects to assure thermoluminescence dose measurement compliance with the technical standards. The author discussed some problems to implement technical standards and regulations

Measurement of beta emitting radionuclides in dose calibrators routinely used in nuclear medicine departments

International Nuclear Information System (INIS)

Tastan, S.; Soylu, A.; Kucuk, O.; Ibis, E.

2004-01-01

Full text: Radionuclides for diagnostics purposes like Tc-99m, Tl-201, Ga-67 and In-111 are measured by using ionization type of dose calibrators. Therapeutic radionuclides, which emit both beta and gamma rays are detected by the same type of dose calibrators. Other therapeutic products like Y-90, P-32 and Sr-89 are pure beta emitters and they are gaining wider utility because various new therapy radiopharmaceuticals are being developed. The type of container material, like glass or plastic, may seriously affect radioactivity measurement due to attenuation, Since it is crucial to give the exact amount of radioactivity to the patient for therapy purposes, dedicated dose calibrators are specially manufactured for the measurement of these radionuclides. But these measuring systems are not widely available in nuclear medicine centers where therapy is applied to the patient. It is a known fact that dose calibrators routinely used in nuclear medicine departments can be calibrated for vials and syringes using standard sources of the same radioisotope. The method of calibration of Y-90 measurement for two ionization chamber dose calibrators available in the institute will be summarized in this presentation

Measurement of beta emitting radionuclides in dose calibrators routinely used in nuclear medicine departments

International Nuclear Information System (INIS)

Tastan, S.; Soylu, A.; Kucuk, O.; Ibis, E.

2004-01-01

Radionuclides for diagnostics purposes like Tc-99m, Tl-201, Ga-67 and In-111 are measured by using ionization type of dose calibrators. Therapeutic radionuclides, which emit both beta and gamma rays are detected by the same type of dose calibrators. Other therapeutic products like Y-90, P-32 and Sr-89 are pure beta emitters and they are gaining wider utility because various new therapy radiopharmaceuticals are being developed. The type of container material, like glass or plastic, may seriously affect radioactivity measurement due to attenuation, Since it is crucial to give the exact amount of radioactivity to the patient for therapy purposes, dedicated dose calibrators are specially manufactured for the measurement of these radionuclides. But these measuring systems are not widely available in nuclear medicine centers where therapy is applied to the patient. It is a known fact that dose calibrators routinely used in nuclear medicine departments can be calibrated for vials and syringes using standard sources of the same radioisotope. The method of calibration of Y-90 measurement for two ionization chamber dose calibrators available in the institute will be summarized in this presentation. (author)

Absolute dose calibration of an X-ray system and dead time investigations of photon-counting techniques

CERN Document Server

Carpentieri, C; Ludwig, J; Ashfaq, A; Fiederle, M

2002-01-01

High precision concerning the dose calibration of X-ray sources is required when counting and integrating methods are compared. The dose calibration for a dental X-ray tube was executed with special dose calibration equipment (dosimeter) as function of exposure time and rate. Results were compared with a benchmark spectrum and agree within +-1.5%. Dead time investigations with the Medipix1 photon-counting chip (PCC) have been performed by rate variations. Two different types of dead time, paralysable and non-paralysable will be discussed. The dead time depends on settings of the front-end electronics and is a function of signal height, which might lead to systematic defects of systems. Dead time losses in excess of 30% have been found for the PCC at 200 kHz absorbed photons per pixel.

Development of a correction factor for Xe-133 vials for use with a dose calibrator

International Nuclear Information System (INIS)

Gels, G.L.; Piltingsrud, H.V.

1982-01-01

Manufacturers of dose calibrators who give calibration settings for various radionuclies sometimes do not specify the type of radionuclide container the calibration is for. The container, moreover, may not be of the same type as those a user might purchase. When these factors are not considered, the activity administered to the patient may be significantly different from that intended. An experiment is described in which calibration factors are determined for measurement of Xe-133 activity in vials in a dose calibrator. This was accomplished by transferring the Xe-133 from the commercial vials to standard NBS calibration ampules. Based on ten such transfers, the resulting correction factor for the dose calibrator was 1.22

External dose distributions of exposure to natural uranium slab for calibration of beta absorbed dose

International Nuclear Information System (INIS)

Chen Lishu

1987-01-01

The depth dose distributions and uniformity of beta radiation fields from a natural uranium slab in equilibration were measured using a tissue equivalent extrapolation chamber and film dosimeter. The advantages for calibration of enviromental dose instument or survey meter and personal dosimeter, for routine monitoring in terms of directional dose equivalent and superficial individual dose equivalent were summarized. Finally, the values measured agree well with that of theoretical calculation

External dose distributions of exposure to natural uranium slab for calibration of beta absorbed dose

Energy Technology Data Exchange (ETDEWEB)

Lishu, Chen

1987-05-01

The depth dose distributions and uniformity of beta radiation fields from a natural uranium slab in equilibration were measured using a tissue equivalent extrapolation chamber and film dosimeter. The advantages for calibration of enviromental dose instument or survey meter and personal dosimeter, for routine monitoring in terms of directional dose equivalent and superficial individual dose equivalent were summarized. Finally, the values measured agree well with that of theoretical calculation.

On the calibration of radiotherapy dosemeters in Australia

International Nuclear Information System (INIS)

Huntley, R.; Kotler, L.; Webb, D.

2000-01-01

Full text: Dosemeters for external beam radiotherapy are calibrated in Australia by ARPANSA, against the national primary standards of exposure and absorbed dose. The primary standards are free air chambers for exposure at low and medium energy X-rays, a graphite cavity chamber for exposure at 60 Co, and a graphite calorimeter for absorbed dose at 60 Co and high energy (MV) X -rays. Radiotherapy dosemeters are calibrated against these standards using a well documented formalism to provide calibration factors suitable for use with dosimetry protocols. A dosemeter usually comprises an ionization chamber connected to an independent electrometer. These are calibrated separately if possible. A combined calibration factor is reported together with the electrometer calibration factor (sensitivity). The dosimetry protocol used in radiotherapy centres in Australia and New Zealand is currently the simplified version of the IAEA TRS277 protocol, published by the New Zealand NRL and recommended by the ACPSEM. This protocol requires the use of an exposure or air kerma calibration factor at 60 Co (Nx or Nk) to evaluate the absorbed dose to air calibration factor N D . The chamber is then placed in a water phantom with its centre displaced from the reference point by p eff . ARPANSA can also supply calibration factors in absorbed dose to water (N D,w ), as required as input to the new IAEA CoP. If an absorbed dose to water calibration factor is used by the radiotherapy centre, the chamber should be placed with its centre at the reference point in the water phantom. ARPANSA has for some years coordinated the participation of Australian radiotherapy centres in the IAEA TLD Quality Audit service. Note that this service does not represent a calibration and should not be referred to as such. The only calibration is that provided by ARPANSA for a reference dosemeter at each radiotherapy centre. As soon as the ANSTO SSDL is operational, calibrations of reference dosemeters will also be

High dose gamma-ray standard

International Nuclear Information System (INIS)

Macrin, R.; Moraru, R.

1999-01-01

The high gamma-ray doses produced in a gamma irradiator are used, mainly, for radiation processing, i.e. sterilization of medical products, processing of food, modifications of polymers, irradiation of electronic devices, a.s.o. The used absorbed doses depend on the application and cover the range 10 Gy to 100 MGy. The regulations in our country require that the response of the dosimetry systems, used for the irradiation of food and medical products, be calibrated and traceable to the national standards. In order to be sure that the products receive the desired absorbed dose, appropriate dosimetric measurements must be performed, including the calibration of the dosemeters and their traceability to the national standards. The high dose gamma-ray measurements are predominantly based on the use of reference radiochemical dosemeters. Among them the ferrous sulfate can be used as reference dosemeter for low doses (up to 400 Gy) but due to its characteristics it deserves to be considered a standard dosemeter and to be used for transferring the conventional absorbed dose to other chemical dosemeters used for absorbed doses up to 100 MGy. The study of the ferrous sulfate dosemeter consisted in preparing many batches of solution by different operators in quality assurance conditions and in determining for all batches the linearity, the relative intrinsic error, the repeatability and the reproducibility. The principal results are the following: the linear regression coefficient: 0.999, the relative intrinsic error: max.6 %, the repeatability (for P* = 95 %): max.3 %, the reproducibility (P* = 95%): max.5 %. (authors)

Progress in high-dose radiation dosimetry

International Nuclear Information System (INIS)

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

1981-01-01

The last decade has witnessed a deluge of new high-dose dosimetry techniques and expanded 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. Reference systems also include a number of chemical dose meters: ferrous sulphate, ferrous-cupric sulphate, and ceric sulphate acidic aqueous solutions. Requirements for stable and reliable transfer dose meters have led to further developments of several important high-dose systems: amino acids and saccharides analysed by ESR or lyoluminescence, thermoluminescent materials, radiochromic dyes and plastics, ceric-cerous solutions analysed by potentiometry, and ethanol-chlorobenzene solutions analysed by high-frequency oscillometry. A number of other prospective dose meters are also treated in this review. In addition, an IAEA programme of high-dose standardization and intercomparison for industrial radiation processing is described. (author)

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

International Nuclear Information System (INIS)

Jangda, A.Q.; Hussein, S.

2012-01-01

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

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

Science.gov (United States)

Jangda, Abdul Qadir; Hussein, Sherali

2012-05-01

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

Inherent calibration of microdosemeters for dose distributions in lineal energy

Energy Technology Data Exchange (ETDEWEB)

Crossman, J.S.P.; Watt, D.E. [Saint Andrews Univ. (United Kingdom). Dept. of Physics and Astronomy

1994-12-31

A method, utilising the inherent electron event spectra, is described for the absolute calibration of microdosemeters in the presence of a photon field. The method, which avoids the problems and uncertainties present in conventional calibration techniques, involves simple extrapolation of the dose distribution in lineal energy associated with `exact stopper` electrons. Validation of the method is made using the published experimental distributions of Rossi, of Kliauga, and of Dvorak and by direct theoretical calculation of the components of the microdose distributions for gamma rays. Further experimental data from a cylindrical TEPC in a photon field generated by an external source of {sup 137}Cs are obtained for comparison. A `universal` calibration curve for the dose-weighted lineal energy as a function of the simulated mean diameter of the microdosemeter, is presented for use in practical applications. (author).

Inherent calibration of microdosemeters for dose distributions in lineal energy

International Nuclear Information System (INIS)

Crossman, J.S.P.; Watt, D.E.

1994-01-01

A method, utilising the inherent electron event spectra, is described for the absolute calibration of microdosemeters in the presence of a photon field. The method, which avoids the problems and uncertainties present in conventional calibration techniques, involves simple extrapolation of the dose distribution in lineal energy associated with 'exact stopper' electrons. Validation of the method is made using the published experimental distributions of Rossi, of Kliauga, and of Dvorak and by direct theoretical calculation of the components of the microdose distributions for gamma rays. Further experimental data from a cylindrical TEPC in a photon field generated by an external source of 137 Cs are obtained for comparison. A 'universal' calibration curve for the dose-weighted lineal energy as a function of the simulated mean diameter of the microdosemeter, is presented for use in practical applications. (author)

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

International Nuclear Information System (INIS)

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

2009-01-01

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

Effective dose calculation in CT using high sensitivity TLDs

International Nuclear Information System (INIS)

Brady, Z.; Johnston, P.N.

2010-01-01

Full text: To determine the effective dose for common paediatric CT examinations using thermoluminescence dosimetry (TLD) mea surements. High sensitivity TLD chips (LiF:Mg,Cu,P, TLD-IOOH, Thermo Fisher Scientific, Waltham, MA) were calibrated on a linac at an energy of 6 MY. A calibration was also performed on a superricial X-ray unit at a kilovoltage energy to validate the megavoltage cali bration for the purpose of measuring doses in the diagnostic energy range. The dose variation across large organs was assessed and a methodology for TLD placement in a 10 year old anthropomorphic phantom developed. Effective dose was calculated from the TLD measured absorbed doses for typical CT examinations after correcting for the TLD energy response and taking into account differences in the mass energy absorption coefficients for different tissues and organs. Results Using new tissue weighting factors recommended in ICRP Publication 103, the effective dose for a CT brain examination on a 10 year old was 1.6 millisieverts (mSv), 4.9 mSv for a CT chest exa ination and 4.7 mSv for a CT abdomen/pelvis examination. These values are lower for the CT brain examination, higher for the CT chest examination and approximately the same for the CT abdomen/ pelvis examination when compared with effective doses calculated using ICRP Publication 60 tissue weighting factors. Conclusions High sensitivity TLDs calibrated with a radiotherapy linac are useful for measuring dose in the diagnostic energy range and overcome limitations of output reproducibility and uniformity asso ciated with traditional TLD calibration on CT scanners or beam quality matched diagnostic X-ray units.

Development of the 60Co gamma-ray standard field for therapy-level dosimeter calibration in terms of absorbed dose to water (ND,W)

International Nuclear Information System (INIS)

Fukumura, Akifumi; Mizuno, Hideyuki; Fukahori, Mai; Sakata, Suoh

2013-01-01

A primary standard for the absorbed dose rate to water in a 60 Co gamma-ray field was established at National Metrology Institute of Japan (NMIJ) in fiscal year 2011. Then, a 60 Co gamma-ray standard field for therapy-level dosimeter calibration in terms of absorbed dose to water was developed at National Institute of Radiological Sciences (NIRS) as a secondary standard dosimetry laboratory (SSDL). The results of an International Atomic Energy Agency (IAEA)/World Health Organization (WHO) TLD SSDL audit demonstrated that there was good agreement between NIRS stated absorbed dose to water and IAEA measurements. The IAEA guide based on the International Organization for Standardization (ISO) standard was used to estimate the relative expanded uncertainty of the calibration factor for a therapy-level Farmer type ionization chamber in terms of absorbed dose to water (N D,W ) with the new field. The uncertainty of N D,W was estimated to be 1.1% (k=2), which corresponds to approximately one third of the value determined in the existing air kerma field. The dissemination of traceability of the calibration factor determined in the new field is expected to diminish the uncertainty of dose delivered to patients significantly. (author)

Numerical design and testing of a sound source for secondary calibration of microphones using the Boundary Element Method

DEFF Research Database (Denmark)

Cutanda Henriquez, Vicente; Juhl, Peter Møller; Barrera Figueroa, Salvador

2009-01-01

Secondary calibration of microphones in free field is performed by placing the microphone under calibration in an anechoic chamber with a sound source, and exposing it to a controlled sound field. A calibrated microphone is also measured as a reference. While the two measurements are usually made...... apart to avoid acoustic interaction. As a part of the project Euromet-792, aiming to investigate and improve methods for secondary free-field calibration of microphones, a sound source suitable for simultaneous secondary free-field calibration has been designed using the Boundary Element Method...... of the Danish Fundamental Metrology Institute (DFM). The design and verification of the source are presented in this communication....

Secondary standards laboratories for ionizing radiation calibrations: the national laboratory interests

International Nuclear Information System (INIS)

Roberson, P.L.; Campbell, G.W.

1984-11-01

The national laboratories are probable candidates to serve as secondary standards laboratories for the federal sector. Representatives of the major Department of Energy laboratories were polled concerning attitudes toward a secondary laboratory structure. Generally, the need for secondary laboratories was recognized and the development of such a program was encouraged. The secondary laboratories should be reviewed and inspected by the National Bureau of Standards. They should offer all of the essential, and preferably additional, calibration services in the field of radiological health protection. The selection of secondary laboratories should be based on economic and geographic criteria and/or be voluntary. 1 ref., 2 tabs

Comparison of CT number calibration techniques for CBCT-based dose calculation

International Nuclear Information System (INIS)

Dunlop, Alex; McQuaid, Dualta; Nill, Simeon; Hansen, Vibeke N.; Oelfke, Uwe; Murray, Julia; Bhide, Shreerang; Harrington, Kevin; Poludniowski, Gavin; Nutting, Christopher; Newbold, Kate

2015-01-01

The aim of this work was to compare and validate various computed tomography (CT) number calibration techniques with respect to cone beam CT (CBCT) dose calculation accuracy. CBCT dose calculation accuracy was assessed for pelvic, lung, and head and neck (H and N) treatment sites for two approaches: (1) physics-based scatter correction methods (CBCT r ); (2) density override approaches including assigning water density to the entire CBCT (W), assignment of either water or bone density (WB), and assignment of either water or lung density (WL). Methods for CBCT density assignment within a commercially available treatment planning system (RS auto ), where CBCT voxels are binned into six density levels, were assessed and validated. Dose-difference maps and dose-volume statistics were used to compare the CBCT dose distributions with the ground truth of a planning CT acquired the same day as the CBCT. For pelvic cases, all CTN calibration methods resulted in average dose-volume deviations below 1.5 %. RS auto provided larger than average errors for pelvic treatments for patients with large amounts of adipose tissue. For H and N cases, all CTN calibration methods resulted in average dose-volume differences below 1.0 % with CBCT r (0.5 %) and RS auto (0.6 %) performing best. For lung cases, WL and RS auto methods generated dose distributions most similar to the ground truth. The RS auto density override approach is an attractive option for CTN adjustments for a variety of anatomical sites. RS auto methods were validated, resulting in dose calculations that were consistent with those calculated on diagnostic-quality CT images, for CBCT images acquired of the lung, for patients receiving pelvic RT in cases without excess adipose tissue, and for H and N cases. (orig.) [de

Validation of dose-response calibration curve for X-Ray field of CRCN-NE/CNEN: preliminary results

Energy Technology Data Exchange (ETDEWEB)

Silva, Laís Melo; Mendonç, Julyanne Conceição de Goes; Andrade, Aida Mayra Guedes de; Hwang, Suy F.; Mendes, Mariana Esposito; Lima, Fabiana F., E-mail: falima@cnen.gov.br, E-mail: mendes_sb@hotmail.com [Centro Regional de Ciências Nucleares, (CRCN-NE/CNEN-PE), Recife, PE (Brazil); Melo, Ana Maria M.A., E-mail: july_cgm@yahoo.com.br [Universidade Federal de Pernambuco (UFPE), Vitória de Santo Antão, PE (Brazil). Centro Acadêmico de Vitória

2017-07-01

It is very important in accident investigations that accurate estimating of absorbed dose takes place, so that it contributes to medical decisions and overall assessment of long-term health consequences. Analysis of chromosome aberrations is the most developed method for biological monitoring, and frequencies of dicentric chromosomes are related to absorbed dose of human peripheral blood lymphocytes using calibration curves. International Atomic Energy Agency (IAEA) recommends that each biodosimetry laboratory sets its own calibration curves, given that there are intrinsic differences in protocols and dose interpretations when using calibration curves produced in other laboratories, which could add further uncertainties to dose estimations. The Laboratory for Biological Dosimetry CRCN-NE recently completed dose-response calibration curves for X ray field. Curves of chromosomes dicentrics and dicentrics plus rings were made using Dose Estimate. This study aimed to validate the calibration curves dose-response for X ray with three irradiated samples. Blood was obtained by venipuncture from healthy volunteer and three samples were irradiated by x-rays of 250 kVp with different absorbed doses (0,5Gy, 1Gy and 2Gy). The irradiation was performed at the CRCN-NE/CNEN Metrology Service with PANTAK X-ray equipment, model HF 320. The frequency of dicentric and centric rings chromosomes were determined in 500 metaphases per sample after cultivation of lymphocytes, and staining with Giemsa 5%. Results showed that the estimated absorbed doses are included in the confidence interval of 95% of real absorbed dose. These Dose-response calibration curves (dicentrics and dicentrics plus rings) seems valid, therefore other tests will be done with different volunteers. (author)

Validation of dose-response calibration curve for X-Ray field of CRCN-NE/CNEN: preliminary results

International Nuclear Information System (INIS)

Silva, Laís Melo; Mendonç, Julyanne Conceição de Goes; Andrade, Aida Mayra Guedes de; Hwang, Suy F.; Mendes, Mariana Esposito; Lima, Fabiana F.; Melo, Ana Maria M.A.

2017-01-01

It is very important in accident investigations that accurate estimating of absorbed dose takes place, so that it contributes to medical decisions and overall assessment of long-term health consequences. Analysis of chromosome aberrations is the most developed method for biological monitoring, and frequencies of dicentric chromosomes are related to absorbed dose of human peripheral blood lymphocytes using calibration curves. International Atomic Energy Agency (IAEA) recommends that each biodosimetry laboratory sets its own calibration curves, given that there are intrinsic differences in protocols and dose interpretations when using calibration curves produced in other laboratories, which could add further uncertainties to dose estimations. The Laboratory for Biological Dosimetry CRCN-NE recently completed dose-response calibration curves for X ray field. Curves of chromosomes dicentrics and dicentrics plus rings were made using Dose Estimate. This study aimed to validate the calibration curves dose-response for X ray with three irradiated samples. Blood was obtained by venipuncture from healthy volunteer and three samples were irradiated by x-rays of 250 kVp with different absorbed doses (0,5Gy, 1Gy and 2Gy). The irradiation was performed at the CRCN-NE/CNEN Metrology Service with PANTAK X-ray equipment, model HF 320. The frequency of dicentric and centric rings chromosomes were determined in 500 metaphases per sample after cultivation of lymphocytes, and staining with Giemsa 5%. Results showed that the estimated absorbed doses are included in the confidence interval of 95% of real absorbed dose. These Dose-response calibration curves (dicentrics and dicentrics plus rings) seems valid, therefore other tests will be done with different volunteers. (author)

A recommendation for revised dose calibrator measurement procedures for 89Zr and 124I.

Directory of Open Access Journals (Sweden)

Bradley J Beattie

Full Text Available Because of their chemical properties and multiday half lives, iodine-124 and zirconium-89 are being used in a growing number of PET imaging studies. Some aspects of their quantitation, however, still need attention. For (89Zr the PET images should, in principle, be as quantitatively accurate as similarly reconstructed 18F measurements. We found, however, that images of a 20 cm well calibration phantom containing (89Zr underestimated the activity by approximately 10% relative to a dose calibrator measurement (Capintec CRC-15R using a published calibration setting number of 465. PET images of (124I, in contrast, are complicated by the contribution of decays in cascade that add spurious coincident events to the PET data. When these cascade coincidences are properly accounted for, quantitatively accurate images should be possible. We found, however, that even with this correction we still encountered what appeared to be a large variability in the accuracy of the PET images when compared to dose calibrator measurements made using the calibration setting number, 570, recommended by Capintec. We derive new calibration setting numbers for (89Zr and (124I based on their 511 keV photon peaks as measured on an HPGe detector. The peaks were calibrated relative to an 18F standard, the activity level of which was precisely measured in a dose calibrator under well-defined measurement conditions. When measuring (89Zr on a Capintec CRC-15R we propose the use of calibration setting number 517. And for (124I, we recommend the use of a copper filter surrounding the sample and the use of calibration setting number 494. The new dose calibrator measurement procedures we propose will result in more consistent and accurate radioactivity measurements of (89Zr and (124I. These and other positron emitting radionuclides can be accurately calibrated relative to 18F based on measurements of their 511 keV peaks and knowledge of their relative positron abundances.

Estimation of personal dose based on the dependent calibration of personal dosimeters in interventional radiology

International Nuclear Information System (INIS)

Mori, Hiroshige; Koshida, Kichiro; Ichikawa, Katsuhiro

2007-01-01

The purpose of present study is, in interventional radiology (IVR), to elucidate the differences between each personal dosimeter, and the dependences and calibrations of area or personal dose by measurement with electronic dosimeters in particular. We compare space dose rate distributions measured by an ionization survey meter with the value measured by personal dosimeter: an optically stimulated luminescence, two fluoroglass, and two electronic dosimeters. Furthermore, with electronic dosimeters, we first measured dose rate, energy, and directional dependences. Secondly, we calibrated the dose rate measured by electronic dosimeters with the results, and estimated these methods with coefficient of determination and Akaike's Information Criterion (AIC). The results, especially in electronic dosimeters, revealed that the dose rate measured fell by energy and directional dependences. In terms of methods of calibration, the method is sufficient for energy dependence, but not for directional dependence, because of the lack of stable calibration. This improvement poses a question for the future. The study suggested that these dependences of the personal dosimeter must be considered when area or personal dose is estimated in IVR. (author)

Some methods for calibration and beta radiation dosimetry

International Nuclear Information System (INIS)

Caldas, Linda V. Ehlin

1980-01-01

The calibration of beta radiation was studied from the point of view of primary and secondary standardization, using extrapolation chambers and examining several effects. The properties of a commercial ionization chamber were investigated, and the possibility of its use in calibration and dosimetry of 90 Sr- 90 Y beta radiation was demonstrated . A secondary standard calibration facility was developed and the results obtained with this facility were compared with those obtained from a primary system directly or indirectly. Nearly energy independent response was obtained in.the range 60 keV to 0,8 MeV with this secondary standard. Two solid state techniques namely thermoluminescence (TL) and thermally stimulated exoelectron emission (TSEE) were also used for beta dosimetry. Various characteristics like reproducibility, response with dose,energy dependence, etc. were studied for the materials: LiF, CaF 2 ,Li 2 B 4 O 7 , Be O, CaSO 4 and Al 2 O 3 . TL detectors of thickness 0,9 mm underestimate the dose 60 μm thick CaSO 4 :Tm embedded on a thin aluminium plate gave energy independent response behind skin layers of 7 mg/cm 2 . Mixed field of beta, X and gamma radiation was analysed using this detector. Quartz based Be O and graphite based alpha beta-Al 2 O 3 were found to be good beta radiation detectors when the TSEE technique is used. Energy independent CaSO 4 :Tm TL dosimeters were used in international comparison for dose measurements and the results obtained were in agreement with the actual given doses within 10%. The TL detectors were also used for dose rate measurements from glazed painted tiles used in construction industry and a 85 Kr source used in textile and metal industries. Results obtained in the later case were Q compared with those using the secondary standard facility. (author)

Experiences of calibration in photon beams for the personal dose equivalent

International Nuclear Information System (INIS)

Lindborg, L.; Gullberg, O.

1994-01-01

The calibration quantity shall, according to ICRU, be the personal dose equivalent, H p (d), in a phantom having the composition of the ICRU tissue and the same shape and size as the recommended PMMA calibration phantom, 30 x 30 x 15 cm 3 . There exist differences in backscattering between PMMA and tissue that for certain photon energies could be of importance. This could either be treated as a systematic uncertainty or be incorporated in the definition. However, monoenergetic beams seldom appear in reality and the difference in backscatter is not thought to be important. The calibration quantity for photons was chosen as the absorbed dose to ICRU tissue (times a quality factor 1) at 10 mm depth in a tissue-equivalent slab phantom. In Sweden 13 different services run personal dosimetry. Their initial hesitation about the change of quantity disappeared after testing their photon energy responses. It was found that most TLD systems were measuring the new quantity better than the old one and that the film systems needed only minor corrections. Most TLD systems now report 5% larger dose equivalents for the same irradiation in a photon beam from a 137 Cs source. (author)

Total skin high-dose-rate electron therapy dosimetry using TG-51

International Nuclear Information System (INIS)

Gossman, Michael S.; Sharma, Subhash C.

2004-01-01

An approach to dosimetry for total skin electron therapy (TSET) is discussed using the currently accepted TG-51 high-energy calibration protocol. The methodology incorporates water phantom data for absolute calibration and plastic phantom data for efficient reference dosimetry. The scheme is simplified to include the high-dose-rate mode conversion and provides support for its use, as it becomes more available on newer linear accelerators. Using a 6-field, modified Stanford technique, one may follow the process for accurate determination of absorbed dose

SU-E-T-470: Importance of HU-Mass Density Calibration Technique in Proton Pencil Beam Dose Calculation

Energy Technology Data Exchange (ETDEWEB)

Penfold, S; Miller, A [University of Adelaide, Adelaide, SA (Australia)

2015-06-15

Purpose: Stoichiometric calibration of Hounsfield Units (HUs) for conversion to proton relative stopping powers (RStPs) is vital for accurate dose calculation in proton therapy. However proton dose distributions are not only dependent on RStP, but also on relative scattering power (RScP) of patient tissues. RScP is approximated from material density but a stoichiometric calibration of HU-density tables is commonly neglected. The purpose of this work was to quantify the difference in calculated dose of a commercial TPS when using HU-density tables based on tissue substitute materials and stoichiometric calibrated ICRU tissues. Methods: Two HU-density calibration tables were generated based on scans of the CIRS electron density phantom. The first table was based directly on measured HU and manufacturer quoted density of tissue substitute materials. The second was based on the same CT scan of the CIRS phantom followed by a stoichiometric calibration of ICRU44 tissue materials. The research version of Pinnacle{sup 3} proton therapy was used to compute dose in a patient CT data set utilizing both HU-density tables. Results: The two HU-density tables showed significant differences for bone tissues; the difference increasing with increasing HU. Differences in density calibration table translated to a difference in calculated RScP of −2.5% for ICRU skeletal muscle and 9.2% for ICRU femur. Dose-volume histogram analysis of a parallel opposed proton therapy prostate plan showed that the difference in calculated dose was negligible when using the two different HU-density calibration tables. Conclusion: The impact of HU-density calibration technique on proton therapy dose calculation was assessed. While differences were found in the calculated RScP of bony tissues, the difference in dose distribution for realistic treatment scenarios was found to be insignificant.

Dose Calibration of the ISS-RAD Fast Neutron Detector

Science.gov (United States)

Zeitlin, C.

2015-01-01

The ISS-RAD instrument has been fabricated by Southwest Research Institute and delivered to NASA for flight to the ISS in late 2015 or early 2016. ISS-RAD is essentially two instruments that share a common interface to ISS. The two instruments are the Charged Particle Detector (CPD), which is very similar to the MSL-RAD detector on Mars, and the Fast Neutron Detector (FND), which is a boron-loaded plastic scintillator with readout optimized for the 0.5 to 10 MeV energy range. As the FND is completely new, it has been necessary to develop methodology to allow it to be used to measure the neutron dose and dose equivalent. This talk will focus on the methods developed and their implementation using calibration data obtained in quasi-monoenergetic (QMN) neutron fields at the PTB facility in Braunschweig, Germany. The QMN data allow us to determine an approximate response function, from which we estimate dose and dose equivalent contributions per detected neutron as a function of the pulse height. We refer to these as the "pSv per count" curves for dose equivalent and the "pGy per count" curves for dose. The FND is required to provide a dose equivalent measurement with an accuracy of ?10% of the known value in a calibrated AmBe field. Four variants of the analysis method were developed, corresponding to two different approximations of the pSv per count curve, and two different implementations, one for real-time analysis onboard ISS and one for ground analysis. We will show that the preferred method, when applied in either real-time or ground analysis, yields good accuracy for the AmBe field. We find that the real-time algorithm is more susceptible to chance-coincidence background than is the algorithm used in ground analysis, so that the best estimates will come from the latter.

Calibration of reference KAP-meters at SSDL and cross calibration of clinical KAP-meters

International Nuclear Information System (INIS)

Hetland, Per O.; Friberg, Eva G.; Oevreboe, Kirsti M.; Bjerke, Hans H.

2009-01-01

In the summer of 2007 the secondary standard dosimetry laboratory (SSDL) in Norway established a calibration service for reference air-kerma product meter (KAP-meter). The air-kerma area product, PKA, is a dosimetric quantity that can be directly related to the patient dose and used for risk assessment associated with different x-ray examinations. The calibration of reference KAP-meters at the SSDL gives important information on parameters influencing the calibration factor for different types of KAP-meters. The use of reference KAP-meters calibrated at the SSDL is an easy and reliable way to calibrate or verify the PKA indicated by the x-ray equipment out in the clinics. Material and methods. Twelve KAP-meters were calibrated at the SSDL by use of the substitution method at five diagnostic radiation qualities (RQRs). Results. The calibration factors varied from 0.94 to 1.18. The energy response of the individual KAP-meters varied by a total of 20% between the different RQRs and the typical chamber transmission factors ranged from 0.78 to 0.91. Discussion. It is important to use a calibrated reference KAP-meter and a harmonised calibration method in the PKA calibration in hospitals. The obtained uncertainty in the PKA readings is comparable with other calibration methods if the information in the calibration certificate is correct used, corrections are made and proper positioning of the KAP-chamber is performed. This will ensure a reliable estimate of the patient dose and a proper optimisation of conventional x-ray examinations and interventional procedures

Development of a quality assurance program for ionizing radiation secondary calibration laboratories

Energy Technology Data Exchange (ETDEWEB)

Heaton, H.T. II; Taylor, A.R. Jr. [Center for Devices and Radiological Health, Rockville, MD (United States)

1993-12-31

For calibration laboratories, routine calibrations of instruments meeting stated accuracy goals are important. One method of achieving the accuracy goals is to establish and follow a quality assurance program designed to monitor all aspects of the calibration program and to provide the appropriate feedback mechanism if adjustments are needed. In the United States there are a number of organizations with laboratory accreditation programs. All existing accreditation programs require that the laboratory implement a quality assurance program with essentially the same elements in all of these programs. Collectively, these elements have been designated as a Measurement Quality Assurance (MQA) program. This paper will briefly discuss the interrelationship of the elements of an MQA program. Using the Center for Devices and Radiological Health (CDRH) X-ray Calibration Laboratory (XCL) as an example, it will focus on setting up a quality control program for the equipment in a Secondary Calibration Laboratory.

Development of a quality assurance program for ionizing radiation secondary calibration laboratories

International Nuclear Information System (INIS)

Heaton, H.T. II; Taylor, A.R. Jr.

1993-01-01

For calibration laboratories, routine calibrations of instruments meeting stated accuracy goals are important. One method of achieving the accuracy goals is to establish and follow a quality assurance program designed to monitor all aspects of the calibration program and to provide the appropriate feedback mechanism if adjustments are needed. In the United States there are a number of organizations with laboratory accreditation programs. All existing accreditation programs require that the laboratory implement a quality assurance program with essentially the same elements in all of these programs. Collectively, these elements have been designated as a Measurement Quality Assurance (MQA) program. This paper will briefly discuss the interrelationship of the elements of an MQA program. Using the Center for Devices and Radiological Health (CDRH) X-ray Calibration Laboratory (XCL) as an example, it will focus on setting up a quality control program for the equipment in a Secondary Calibration Laboratory

Dosimetry through the Secondary Laboratory of Dosimetric Calibration of Mexico; Dosimetria a traves del Laboratorio Secundario de Calibracion Dosimetrica de Mexico

Energy Technology Data Exchange (ETDEWEB)

Tovar M, V.M.; Alvarez R, J.T.; Medina O, V.P.; Vergara M, F.; Anaya M, R.; Cejudo A, J.; Salinas L, B. [ININ, A.P. 18-1027, 11801 Mexico D.F. (Mexico)

2004-07-01

In the beginnings of the sixty years an urgent necessity is presented mainly in the developing countries, of improving in important form the accuracy in the dosimetry of external faces in therapy of radiations (radiotherapy centers), mainly in the calibration of ''clinical dosemeters''. In 1976 the International Atomic Energy Agency, (IAEA), and the World Health Organization, (WHO), they carried out a mutual agreement with regard to the establishment and operation of a net of Secondary Patron Laboratories of Dosimetry, (LSCD). The necessity to establish measure patterns in the field of the dosimetry of the ionizing radiations, is necessary, to have an accuracy but high in the dosimetry of the radiation beams in therapy which is highly dependent of the dose given to the tumor of those patient with cancer. Similar levels of accuracy are required in protection measures to the radiation with an acceptable smaller accuracy, however, when the personal dosemeters are used to determine the doses received by the individuals under work conditions, such mensurations in therapy of radiations and radiological protection will have traceability through a chain of comparisons to primary or national patterns. The traceability is necessary to assure the accuracy and acceptability of the dosimetric measures, as well as, the legal and economic implications. The traceability is also necessary in the dosimetry of high dose like in the sterilization of different products. The main function of the LSCD is to provide a service in metrology of ionizing radiations, maintaining the secondary or national patterns, which have a traceability to the International System of measures, which is based for if same in the comparison of patterns in the Primary Laboratories of Dosimetry (LPD) under the auspice of the International Office of Weights and Measure (BIPM). The secondary and national patterns in the LSCD constitute in Mexico, the national patterns of the magnitudes in the

Intercomparison of the air kerma and absorbed dose to water therapy calibrations provided by NRPA and CPRH SSDLs

International Nuclear Information System (INIS)

Morales, J.A.; Campa, R.; Bjerke, H.; Jensen, H.

2001-01-01

The primary goal of any calibration laboratory is to routinely provide calibration services of the highest accuracy. To this end, the laboratory should be equipped with measuring standards of the highest metrological quality traceable to the international measuring system, should establish the appropriate calibration conditions and implement good measuring and working practices. In the case of the Secondary Standard Dosimetry Laboratory (SSDL) members of the IAEA/WHO Network of SSDLs, a great deal of the service quality relies on the appropriate laboratory design and implementation of the recommended calibration practices. Different approaches have been used by SSDLs to guarantee the traceability of the reference standard to the international measurement system. These include calibration of their standards at the IAEA Dosimetry Laboratory, direct calibration at a primary standards laboratory or at a national calibration laboratory. The stability of reference and working standards is usually checked by means of radioactive check source measurements. The most comprehensive way that a laboratory could test its overall measurement competence is by taking part in comparisons with other laboratories of the same or higher metrological level. Regular efforts have been done at the regional scale by organizing such intercomparison exercises where the evaluation of the accuracy of secondary standards or the validation of new calibration methods has been the main objectives. Perhaps, the most important contribution to the assessment of SSDLs quality has been the periodical external measurement audit provided by the IAEA during the last years. Mos of these efforts have, however, only been focused on in-air and recently in-water calibration at the 60 Co radiation quality. An intercomparison of the therapy calibration services available at the SSDLs of the Norwegian Radiation Protection Authority (NRPA) and of the Center for Radiation Protection and Hygiene (CPHR) was organized

Comparing Hp(3) evaluated from the conversion coefficients from air kerma to personal dose equivalent for eye lens dosimetry calibrated on a new cylindrical PMMA phantom

Science.gov (United States)

Esor, J.; Sudchai, W.; Monthonwattana, S.; Pungkun, V.; Intang, A.

2017-06-01

Based on a new occupational dose limit recommended by ICRP (2011), the annual dose limit for the lens of the eye for workers should be reduced from 150 mSv/y to 20 mSv/y averaged over 5 consecutive years in which no single year exceeding 50 mSv. This new dose limit directly affects radiologists and cardiologists whose work involves high radiation exposure over 20 mSv/y. Eye lens dosimetry (Hp(3)) has become increasingly important and should be evaluated directly based on dosimeters that are worn closely to the eye. Normally, Hp(3) dose algorithm was carried out by the combination of Hp(0.07) and Hp(10) values while dosimeters were calibrated on slab PMMA phantom. Recently, there were three reports from European Union that have shown the conversion coefficients from air kerma to Hp(3). These conversion coefficients carried out by ORAMED, PTB and CEA Saclay projects were performed by using a new cylindrical head phantom. In this study, various delivered doses were calculated using those three conversion coefficients while nanoDot, small OSL dosimeters, were used for Hp(3) measurement. These calibrations were performed with a standard X-ray generator at Secondary Standard Dosimetry Laboratory (SSDL). Delivered doses (Hp(3)) using those three conversion coefficients were compared with Hp(3) from nanoDot measurements. The results showed that percentage differences between delivered doses evaluated from the conversion coefficient of each project and Hp(3) doses evaluated from the nanoDots were found to be not exceeding -11.48 %, -8.85 % and -8.85 % for ORAMED, PTB and CEA Saclay project, respectively.

Evaluation of Some Dose Calibration for Measuring of 99mTc

International Nuclear Information System (INIS)

Nazaroh; Erni-Juita; Hermawan-Candra

2001-01-01

99m Tc is a prime radionuclide in nuclear medicine because of worthwhile in many diagnoses. According to ALARA concept, the lowest risk should be considered in the use of radioactive materials especially for health. Center for development of Radioisotopes and Radiopharmacy-BATAN, Serpong, serves several nuclear medicine departments supplying all their 99m Tc radiopharmaceuticals on a daily basis. It was observed that there was very poor consistency between the assays as determined by P3KRBin and those determined in the various nuclear medicine, using Dose-Calibrator. Investigation has been done to correct measurements result of 99m Tc using several Dose-Calibrators in some hospitals in Java island and the correction factors were vary from 0.91 to 1.16. The same survey done by researcher in Canada using a mock 99m Tc ( 57 Co) and 99m Tc and the correction factors were between 0.74 and 1. Investigation of influences of various environmental conditions on the Calibrator function was also carried out. Influences factors obtained from the survey were vary from 1 to 1.19. (author)

Accuracy, reproducibility, and uncertainty analysis of thyroid-probe-based activity measurements for determination of dose calibrator settings.

Science.gov (United States)

Esquinas, Pedro L; Tanguay, Jesse; Gonzalez, Marjorie; Vuckovic, Milan; Rodríguez-Rodríguez, Cristina; Häfeli, Urs O; Celler, Anna

2016-12-01

, 188 Re, 131 I, and 57 Co samples to high purity Ge (HPGe) γ-ray spectroscopy measurements. The experimental 188 Re dial settings determined with the TP were 76.5 ± 4.8 and 646 ± 43 for Atomlab 100plus and Capintec CRC-55tR, respectively. In the case of Atomlab 100plus, the TP-based dial settings improved the accuracy of 188 Re activity measurements (confirmed by HPGe measurements) as compared to manufacturer-recommended settings. For Capintec CRC-55tR, the TP-based settings were in agreement with previous results [B. E. Zimmerman et al., J. Nucl. Med. 40, 1508-1516 (1999)] which demonstrated that manufacturer-recommended settings overestimate 188 Re activity by more than 20%. The largest source of uncertainty in the experimentally determined dial settings was due to the application of a geometry correction factor, followed by the uncertainty of the scatter-corrected photopeak counts and the uncertainty of the TP efficiency calibration experiment. When using the most intense photopeak of the sample's emissions, the TP method yielded accurate (within 5% errors) and reproducible (COV = 2%) measurements of sample's activity. The relative uncertainties associated with such measurements ranged from 6% to 8% (expanded uncertainty at 95% confidence interval, k = 2). Accurate determination/verification of dose calibrator dial settings can be performed using a thyroid-probe in the nuclear medicine department.

Calibration and consistency of results of an ionization-chamber secondary standard measuring system for activity

International Nuclear Information System (INIS)

Schrader, Heinrich

2000-01-01

Calibration in terms of activity of the ionization-chamber secondary standard measuring systems at the PTB is described. The measurement results of a Centronic IG12/A20, a Vinten ISOCAL IV and a radionuclide calibrator chamber for nuclear medicine applications are discussed, their energy-dependent efficiency curves established and the consistency checked using recently evaluated radionuclide decay data. Criteria for evaluating and transferring calibration factors (or efficiencies) are given

Feasibility study for the development of a Dose Calibrator with a well ionization chamber

International Nuclear Information System (INIS)

Arista Romeu, E. J.

2015-01-01

Dose calibrators are intended for the metrological assurance of medical diagnostic studies in which radiopharmaceuticals are used. It is the final link in the national system of standards to ensure quality control and the radiation safety of the dose administered to patients while using these nuclear techniques. The wide utilization of radiopharmaceuticals in our country in several modules of nuclear medicine and other laboratories where radio-isotopic preparations are used, as well as the existence of the National Center of Isotopes to produce them determine the necessity of national production of dose calibration equipment. In this paper, it is presented the result of a feasibility study to develop a dose calibrator with a well-type ionization chamber for nuclear medicine services of the National Health System with gamma camera. It is specifically intended to contribute to monitor and control the activity of the prepared samples to be administered to patients under studies with gamma cameras to ensure compliance with the current requirements of quality and radiation safety. (Author)

Automation of the Calibration of Reference Dosimeters Used in Radiotherapy

International Nuclear Information System (INIS)

Romero Acosta, A.; Gutierrez Lores, S.

2013-01-01

Traceability, accuracy and consistency of radiation measurements are essential in radiation dosimetry, particularly in radiotherapy, where the outcome of treatments is highly dependent on the radiation dose delivered to patients. The role of Secondary Standard Dosimetry Laboratories (SSDLs) is crucial in providing traceable calibrations to hospitals, since these laboratories disseminate calibrations at specific radiation qualities appropriate to the use of radiation measuring instruments. These laboratories follow IAEA/WHO guidelines for calibration procedures, often being current and charge measurements described in these guidelines a tedious task. However, these measurements are usually done using modern electrometers which are equipped with a RS-232 interface that allows instrument control from a PC. This paper presents the design and employment of an automated system aimed to the measurements of the radiotherapy dosimeters calibration process for Cobalt-60 gamma rays. A software was developed using Lab View, in order to achieve the acquisition of the charge values measured, calculation of the calibration coefficient and issue of a calibration certificate. A primary data report file is filled and stored in the PC's hard disk. By using this software tool, a better control over the calibration process is achieved, it reduces the need for human intervention and it also reduces the exposure of the laboratory staff. The automated system has been used for the calibration of reference dosimeters used in radiotherapy at the Cuban Secondary Standard Dosimetry Laboratory of the Center for Radiation Protection and Hygiene (Author)

Calibration of radiation protection area monitoring instruments in Sudan

International Nuclear Information System (INIS)

Suliman, I.I.; Youssif, B.E.; Beineen, A.A.; Hassan, M.

2010-01-01

This article presents results of measurements for the calibration of radiation protection area monitoring instruments carried out during the period 2006-2008 at Secondary Standard Dosimetry Laboratory of Sudan. The work performed included quality assurance measurements, measurements for the dosimeter calibrations and uncertainty analysis. Calibrations were performed using 137 Cs gamma ray sources produced by OB 85 and OB 34/1 gamma calibrators producing air kerma rate that ranged from 10 μGy/h to 50 mGy/h. Area monitoring instruments were calibrated in terms of ambient dose equivalent, H*(10) derived using air kerma to ambient dose equivalent conversion coefficients. Results are presented for 78 area monitoring instruments representing most commonly used types in Sudan. Radioactive check source measurements for the reference chamber showed deviation within 1% limit. The accuracy in the beam output measurements was within 5% internationally considered as acceptable. The results highlighted the importance of radiation protection calibrations. Regulations are further need to ensure safety aspect really meet the required international standards.

Secondary calibration laboratory for ionizing radiation laboratory accreitation program National Institute of Standards and Technology National Voluntary Laboratory Accreditation Program

Energy Technology Data Exchange (ETDEWEB)

Martin, P.R.

1993-12-31

This paper presents an overview of the procedures and requirements for accreditation under the Secondary Calibration Laboratory for Ionizing Radiation Program (SCLIR LAP). The requirements for a quality system, proficiency testing and the onsite assessment are discussed. The purpose of the accreditation program is to establish a network of secondary calibration laboratories that can provide calibrations traceable to the primary national standards.

Secondary calibration laboratory for ionizing radiation laboratory accreitation program National Institute of Standards and Technology National Voluntary Laboratory Accreditation Program

International Nuclear Information System (INIS)

Martin, P.R.

1993-01-01

This paper presents an overview of the procedures and requirements for accreditation under the Secondary Calibration Laboratory for Ionizing Radiation Program (SCLIR LAP). The requirements for a quality system, proficiency testing and the onsite assessment are discussed. The purpose of the accreditation program is to establish a network of secondary calibration laboratories that can provide calibrations traceable to the primary national standards

Dose calibrator linearity test: {sup 99m}Tc versus {sup 18}F radioisotopes

Energy Technology Data Exchange (ETDEWEB)

Willegaignon, Jose; Coura-Filho, George Barberio; Garcez, Alexandre Teles, E-mail: willegaignon@hotmail.com [Instituto do Cancer do Estado de Sao Paulo Octavio Frias de Oliveira (ICESP), Sao Paulo, SP (Brazil); Sapienza, Marcelo Tatit; Buchpiguel, Carlos Alberto [Universidade de Sao Paulo (FM/USP), Sao Paulo, SP (Brazil). Fac. de Medicina; Alves, Carlos Eduardo Gonzalez Ribeiro; Cardona, Marissa Anabel Rivera; Gutterres, Ricardo Fraga [Comissao Nacional de Energia Nuclear (CNEN), Rio de Janeiro, RJ (Brazil)

2015-01-15

Objective: the present study was aimed at evaluating the viability of replacing {sup 18}F with {sup 99m}Tc in dose calibrator linearity testing. Materials and methods: the test was performed with sources of {sup 99m}Tc (62 GBq) and {sup 18}F (12 GBq) whose activities were measured up to values lower than 1 MBq. Ratios and deviations between experimental and theoretical {sup 99m}Tc and {sup 18}F sources activities were calculated and subsequently compared. Results: mean deviations between experimental and theoretical {sup 99m}Tc and {sup 18}F sources activities were 0.56 (± 1.79)% and 0.92 (± 1.19)%, respectively. The mean ratio between activities indicated by the device for the {sup 99m}Tc source as measured with the equipment precalibrated to measure {sup 99m}Tc and {sup 18}F was 3.42 (± 0.06), and for the {sup 18}F source this ratio was 3.39 (± 0.05), values considered constant over the measurement time. Conclusion: the results of the linearity test using {sup 99m}Tc were compatible with those obtained with the {sup 18}F source, indicating the viability of utilizing both radioisotopes in dose calibrator linearity testing. Such information in association with the high potential of radiation exposure and costs involved in {sup 18}F acquisition suggest {sup 99m}Tc as the element of choice to perform dose calibrator linearity tests in centers that use {sup 18}F, without any detriment to the procedure as well as to the quality of the nuclear medicine service. (author)

The efficacy of low and high dose (99m)Tc-MIBI protocols for intraoperative identification of hyperplastic parathyroid glands in secondary hyperparathyroidism.

Science.gov (United States)

Gencoglu, Esra Arzu; Aktas, Ayse

2014-01-01

The aim of this study was to compare the efficacy of low- and high-dose (99m)Tc-MIBI protocols for intraoperative identification of hyperplastic parathyroid glands via gamma probe in secondary hyperparathyroidism. This retrospective study was conducted using a prospective database of 59 patients who had undergone radioguided subtotal parathyroidectomy between 2004-2012. The patients were studied in 2 groups. Group 1 (n=31) received 37 MBq (99m)Tc-MIBI intravenously in the surgical room approximately 10 min before the beginning of the intervention and surgery was performed under gamma probe guidance. Group 2 (n=28) received 555 MBq (99m)Tc- MIBI intravenously 2h before surgery, which was also performed under gamma probe guidance. Intraoperative gamma probe findings, laboratory findings, and histopathological findings were evaluated together. Using acceptance of the histopathological findings as gold standard, sensitivity and specificity of intraoperative gamma probe for identifying hyperplastic parathyroid glands was 98% and 100%, respectively, in both groups. In the light of these findings, it is concluded that the low-dose (99m)Tc-MIBI protocol might be preferable for intraoperative identification of hyperplastic parathyroid glands in secondary hyperparathyroidism patients because it was observed to be as effective as the high-dose (99m)Tc-MIBI protocol. Furthermore, the low-dose protocol does not have the disadvantages that are associated with the high-dose protocol. Copyright © 2014 Elsevier España, S.L. and SEMNIM. All rights reserved.

Secondary neutron doses received by patients of different ages during intracranial proton therapy treatments

International Nuclear Information System (INIS)

Sayah, R.

2012-01-01

Proton therapy is an advanced radiation therapy technique that allows delivering high doses to the tumor while saving the healthy surrounding tissues due to the protons' ballistic properties. However, secondary particles, especially neutrons, are created during protons' nuclear reactions in the beam-line and the treatment room components, as well as inside the patient. Those secondary neutrons lead to unwanted dose deposition to the healthy tissues located at distance from the target, which may increase the secondary cancer risks to the patients, especially the pediatric ones. The aim of this work was to calculate the neutron secondary doses received by patients of different ages treated at the Institut Curie-centre de Protontherapie d'Orsay (ICPO) for intracranial tumors, using a 178 MeV proton beam. The treatments are undertaken at the new ICPO room equipped with an IBA gantry. The treatment room and the beam-line components, as well as the proton source were modeled using the Monte Carlo code MCNPX. The obtained model was then validated by a series of comparisons between model calculations and experimental measurements. The comparisons concerned: a) depth and lateral proton dose distributions in a water phantom, b) neutron spectrometry at one position in the treatment room, c) ambient dose equivalents at different positions in the treatment room and d) secondary absorbed doses inside a physical anthropomorphic phantom. A general good agreement was found between calculations and measurements, thus our model was considered as validated. The University of Florida hybrid voxelized phantoms of different ages were introduced into the MCNPX validated model, and secondary neutron doses were calculated to many of these phantoms' organs. The calculated doses were found to decrease as the organ's distance to the treatment field increases and as the patient's age increases. The secondary doses received by a one year-old patient may be two times higher than the doses

Calibration of a radiation survey meter using Cs-137 gamma source

International Nuclear Information System (INIS)

Khalid, R. O.

2005-07-01

The survey instrument smartIon was calibrated at the Secondary Standard Dosimetry Laboratory, Sudan Atomic Energy Commission, in terms of kerma, free in air using Cs-137 gamma radiation. All the calibrations were performed using the reference instrument spherical ionization chamber LS-01. This reference instrument has been calibrated at the International Atomic Energy Agency, Vienna for x-rays, 137 Cs and 60 Co gamma radiation. The air kerma calibration factors for the instrument were determined as the ratio of the dose rates obtained with the reference standard chamber LS-01 and the dose rates of the instrument under calibration. The uncertainties for the survey meter smartIon and another survey meter RADOS were obtained and the results compared with the uncertainty for the reference standard chamber. Also, the values of dose rates were obtained for various angles of the incident beam, by changing the angle by which the radiation was incident on the sensitive point of the instrument.(Author)

Calibration of ARI QC ionisation chambers using the Australian secondary standards for activity

International Nuclear Information System (INIS)

Mo, L.; Van Der Gaast, H.A.; Alexiev, D.; Butcher, K.S.A.; Davies, J.

1999-01-01

The Secondary Standard Activity Laboratory (SSAL) in ANSTO routinely provides standardised radioactive sources, traceable activity measurements and custom source preparation services to customers. The most important activity carried out is the calibration of ionisation chambers located in the Quality Control (QC) section of Australian Radioisotopes (ARI). This ensures that their activity measurements are traceable to the Australian primary methods of standardisation. ARI QC ionisation chambers are calibrated for 99m Tc, 67 Ga, 131 I, 201 Tl and 153 Sm. The SSAL has a TPA ionisation chamber, which has been directly calibrated against a primary standard for a variety of radioactive nuclides. Calibration factors for this chamber were determined specifically for the actual volumes (5ml for 99m Tc, 131 I, 2ml for 67 Ga, 201 Tl and 3 ml for 153 Sm) and types of vial (Wheaton) which are routinely used at ARI. These calibration factors can be used to accurately measure the activity of samples prepared by ARI. The samples can subsequently be used to calibrate the QC ionisation chambers. QC ionisation chambers are re-calibrated biannually

Collimation system for a laboratory of primary and secondary ionizing radiation calibration

International Nuclear Information System (INIS)

Oliveira, S.R.; David, M.G.

2003-01-01

This work is part of a cooperation plan between the LNMRI/IRD and the LCR/UERJ, for the a primary calibration at the IRD and a secondary laboratory at the LCR, both calibrated for mammographic beams which will be part a Calibration National Network. For the mounting of the primary laboratory, the first step was to install two additional collimators in order to guarantee that the beam area over the ionization chamber to satisfy the calibration international standards. So, the collimators were constructed obeying the geometric rules, the first being of conic format and the second of the cylindrical format, therefore avoiding the effects of the scattering radiation on the edges. By using this collimation system it was possible to verify the uniformity of the radiation field incident the ionization chamber to be over 98% of the total area, guaranteeing better precision of the measurement

Preliminary assessment of the operating performance and calibration of rectilinear scanners and dose calibrators in Rio de Janeiro - Brazil

International Nuclear Information System (INIS)

Mendes, L.; Wegst, A.

1983-01-01

Thirty rectilinear scanners and ten dose calibrators were tested for a variety of operating conditions. The test for rectilinear scanners were based on image quality obtained with phantoms of the brain, liver (Williams phantom) and thyroid. The parameters investigated specifically for rectilinear scanners included those under direct control of the operator, such as proper setting of the focal distance, the velocity, the photopeak calibration, contrast correct collimator, line spacing, and background count. (E.G.) [pt

Optical calibration and test of the VLT Deformable Secondary Mirror

Science.gov (United States)

Briguglio, Runa; Xompero, Marco; Riccardi, Armando; Andrighettoni, Mario; Pescoller, Dietrich; Biasi, Roberto; Gallieni, Daniele; Vernet, Elise; Kolb, Johann; Arsenault, Robin; Madec, Pierre-Yves

2013-12-01

The Deformable Secondary Mirror (DSM) for the VLT (ESO) represents the state-of-art of the large-format deformable mirror technology with its 1170 voice-coil actuators and its internal metrology based on actuator co-located capacitive sensors to control the shape of the 1.12m-diameter 2mm-thick convex shell. The present paper reports the results of the optical characterization of the mirror unit with the ASSIST facility located at ESO-Garching and executed in a collaborative effort by ESO, INAF-Osservatorio Astrofisico di Arcetri and the DSM manufacturing companies (Microgate s.r.l. and A.D.S. International s.r.l.). The main purposes of the tests are the optical characterization of the shell flattening residuals, the corresponding calibration of flattening commands, the optical calibration of the capacitive sensors and the optical calibration of the mirror influence functions. The results are used for the optical acceptance of the DSM and to allow the next test phase coupling the DSM with the wave-front sensor modules of the new Adaptive Optics Facility (AOF) of ESO.

Calibration of neutrons monitors with moderators and application in the calibration factors of albedo dosemeters

International Nuclear Information System (INIS)

Schuch, L.A.

1978-11-01

The calibration factors and the reproducibility of an Albedo Dosimeter designed for personal neutron monitoring were determined. These factor were obtained simulating the dosimeter reading and the equivalent dose in the locality by a convenient combination of responses of the Bonner Sphere Spectrometer. The results obtained in the simulation were verified experimentally for different spectra employing the Am-Be, bare 252 Cf source and 253 Cf source with graphite sields of varying thickness. Different standards were used in the procedures necessary for the determination of the calibration factors. An Am-Be neutron source, standardized by the activation of a manganese sulphate bath was used as a primary standard. As a secondary standard, for the measurement of the neutron fluence, a De Pangher Long Counter was used and the scattering effects were determined using the shadow cone method. The other monitors such as the Rem-Counter and the Bonner Sphere Spectrometer were also calibrated with reference to the secondary standard with a view to comparing the results obtained with those furnished by the Albedo Dosimeter. (Author) [pt

A hardware-software system for the automation of verification and calibration of oil metering units secondary equipment

Science.gov (United States)

Boyarnikov, A. V.; Boyarnikova, L. V.; Kozhushko, A. A.; Sekachev, A. F.

2017-08-01

In the article the process of verification (calibration) of oil metering units secondary equipment is considered. The purpose of the work is to increase the reliability and reduce the complexity of this process by developing a software and hardware system that provides automated verification and calibration. The hardware part of this complex carries out the commutation of the measuring channels of the verified controller and the reference channels of the calibrator in accordance with the introduced algorithm. The developed software allows controlling the commutation of channels, setting values on the calibrator, reading the measured data from the controller, calculating errors and compiling protocols. This system can be used for checking the controllers of the secondary equipment of the oil metering units in the automatic verification mode (with the open communication protocol) or in the semi-automatic verification mode (without it). The peculiar feature of the approach used is the development of a universal signal switch operating under software control, which can be configured for various verification methods (calibration), which allows to cover the entire range of controllers of metering units secondary equipment. The use of automatic verification with the help of a hardware and software system allows to shorten the verification time by 5-10 times and to increase the reliability of measurements, excluding the influence of the human factor.

Measuring conditions used for the calibration of ionization chambers at the BIPM

International Nuclear Information System (INIS)

Allisy-Roberts, P.J.; Burs, D.T.; Kessler, C.

2004-12-01

Information is presented on the experimental conditions used at the BIPM in the x- and γ-radiation beams for the calibration of secondary standards in terms of air kerma, absorbed dose in water and ambient dose equivalent, together with the uncertainties involved in the determination of these dosimetric quantities. (authors)

Comparing calibration methods of electron beams using plane-parallel chambers with absorbed-dose to water based protocols

International Nuclear Information System (INIS)

Stewart, K.J.; Seuntjens, J.P.

2002-01-01

Recent absorbed-dose-based protocols allow for two methods of calibrating electron beams using plane-parallel chambers, one using the N D,w Co for a plane-parallel chamber, and the other relying on cross-calibration of the plane-parallel chamber in a high-energy electron beam against a cylindrical chamber which has an N D,w Co factor. The second method is recommended as it avoids problems associated with the P wall correction factors at 60 Co for plane-parallel chambers which are used in the determination of the beam quality conversion factors. In this article we investigate the consistency of these two methods for the PTW Roos, Scanditronics NACP02, and PTW Markus chambers. We processed our data using both the AAPM TG-51 and the IAEA TRS-398 protocols. Wall correction factors in 60 Co beams and absorbed-dose beam quality conversion factors for 20 MeV electrons were derived for these chambers by cross-calibration against a cylindrical ionization chamber. Systematic differences of up to 1.6% were found between our values of P wall and those from the Monte Carlo calculations underlying AAPM TG-51, and up to 0.6% when comparing with the IAEA TRS-398 protocol. The differences in P wall translate directly into differences in the beam quality conversion factors in the respective protocols. The relatively large spread in the experimental data of P wall , and consequently the absorbed-dose beam quality conversion factor, confirms the importance of the cross-calibration technique when using plane-parallel chambers for calibrating clinical electron beams. We confirmed that for well-guarded plane-parallel chambers, the fluence perturbation correction factor at d max is not significantly different from the value at d ref . For the PTW Markus chamber the variation in the latter factor is consistent with published fits relating it to average energy at depth

Secondary clarifier hybrid model calibration in full scale pulp and paper activated sludge wastewater treatment

Energy Technology Data Exchange (ETDEWEB)

Sreckovic, G.; Hall, E.R. [British Columbia Univ., Dept. of Civil Engineering, Vancouver, BC (Canada); Thibault, J. [Laval Univ., Dept. of Chemical Engineering, Ste-Foy, PQ (Canada); Savic, D. [Exeter Univ., School of Engineering, Exeter (United Kingdom)

1999-05-01

The issue of proper model calibration techniques applied to mechanistic mathematical models relating to activated sludge systems was discussed. Such calibrations are complex because of the non-linearity and multi-model objective functions of the process. This paper presents a hybrid model which was developed using two techniques to model and calibrate secondary clarifier parts of an activated sludge system. Genetic algorithms were used to successfully calibrate the settler mechanistic model, and neural networks were used to reduce the error between the mechanistic model output and real world data. Results of the modelling study show that the long term response of a one-dimensional settler mechanistic model calibrated by genetic algorithms and compared to full scale plant data can be improved by coupling the calibrated mechanistic model to as black-box model, such as a neural network. 11 refs., 2 figs.

Assessment of doses due to secondary neutrons received by patient treated by proton therapy

International Nuclear Information System (INIS)

Sayah, R.; Martinetti, F.; Donadille, L.; Clairand, I.; Delacroix, S.; De Oliveira, A.; Herault, J.

2010-01-01

Proton therapy is a specific technique of radiotherapy which aims at destroying cancerous cells by irradiating them with a proton beam. Nuclear reactions in the device and in the patient himself induce secondary radiations involving mainly neutrons which contribute to an additional dose for the patient. The author reports a study aimed at the assessment of these doses due to secondary neutrons in the case of ophthalmological and intra-cranial treatments. He presents a Monte Carlo simulation of the room and of the apparatus, reports the experimental validation of the model (dose deposited by protons in a water phantom, ambient dose equivalent due to neutrons in the treatment room, absorbed dose due to secondary particles in an anthropomorphic phantom), and the assessment with a mathematical phantom of doses dues to secondary neutrons received by organs during an ophthalmological treatment. He finally evokes current works of calculation of doses due to secondary neutrons in the case of intra-cranial treatments

Radioactivity measurement of 18F in 16 ml vials for calibration of radionuclide calibrators

International Nuclear Information System (INIS)

Wurdiyanto, Gatot; Marsoem, Pujadi; Candra, Hermawan; Wijono, Paidi

2012-01-01

Fluorine-18 is obtained through the reaction 18 O(p, n) 18 F using a cyclotron that is situated in a hospital in Jakarta. Standardization of the 18 F solution is performed by gamma spectrometry using calibration sources of 152 Eu, 60 Co and 137 Cs that have traceability to the International System of units (SI). The activities in the 16 ml vials that were used for calibrating the radionuclide calibrators were between 1 and 2 GBq, with expanded uncertainties of 3.8%. The expanded uncertainty, at a coverage factor of k=2, on the derived calibration factor for the radionuclide calibrator was 6.6%. - Highlights: ► PTKMR–BATAN as a NMI of Indonesia is required to have procedures to calibrate the radionuclide calibrators. ► Standardizations were carried out on a solution of [ 18 F]FDG using gamma spectrometry. ► The volume of 18 F solutions used was 16 ml because this is the volume often used in hospitals. ► The Secondary Standard ionization chamber is a CRC-7BT Capintec radionuclide calibrator. ► A dial setting for 16 ml of [ 18 F]FDG solution in a vial is 443 for the Capintec dose calibrator.

Radiation processing and high-dose dosimetry at ANSTO

International Nuclear Information System (INIS)

Gant, G.J.; Saunders, M.; Banos, C.; Mo, L.; Davies, J.; Evans, O.

2001-01-01

The Radiation Technology group at ANSTO is part of the Physics Division and provides services and advice in the areas of gamma irradiation and high-dose dosimetry. ANSTO's irradiation facilities are designed for maximum dose uniformity and provide a precision irradiation service unique in Australia. Radiation Technology makes and sells reference and transfer standard dosimeters which are purchased by users and suppliers of commercial irradiation services in Australia and the Asia-Pacific region. A calibration service is also provided for dosimeters purchased from other suppliers

Poster - 53: Improving inter-linac DMLC IMRT dose precision by fine tuning of MLC leaf calibration

International Nuclear Information System (INIS)

Nakonechny, Keith; Tran, Muoi; Sasaki, David; Beck, James; Poirier, Yannick; Malkoske, Kyle

2016-01-01

Purpose: To develop a method to improve the inter-linac precision of DMLC IMRT dosimetry. Methods: The distance between opposing MLC leaf banks (“gap size”) can be finely tuned on Varian linacs. The dosimetric effect due to small deviations from the nominal gap size (“gap error”) was studied by introducing known errors for several DMLC sliding gap sizes, and for clinical plans based on the TG119 test cases. The plans were delivered on a single Varian linac and the relationship between gap error and the corresponding change in dose was measured. The plans were also delivered on eight Varian 2100 series linacs (at two institutions) in order to quantify the inter-linac variation in dose before and after fine tuning the MLC calibration. Results: The measured dose differences for each field agreed well with the predictions of LoSasso et al. Using the default MLC calibration, the variation in the physical MLC gap size was determined to be less than 0.4 mm between all linacs studied. The dose difference between the linacs with the largest and smallest physical gap was up to 5.4% (spinal cord region of the head and neck TG119 test case). This difference was reduced to 2.5% after fine tuning the MLC gap calibration. Conclusions: The inter-linac dose precision for DMLC IMRT on Varian linacs can be improved using a simple modification of the MLC calibration procedure that involves fine adjustment of the nominal gap size.

Poster - 53: Improving inter-linac DMLC IMRT dose precision by fine tuning of MLC leaf calibration

Energy Technology Data Exchange (ETDEWEB)

Nakonechny, Keith; Tran, Muoi; Sasaki, David; Beck, James; Poirier, Yannick; Malkoske, Kyle [Simcoe-Muskoka Regional Cancer Centre (Canada)

2016-08-15

Purpose: To develop a method to improve the inter-linac precision of DMLC IMRT dosimetry. Methods: The distance between opposing MLC leaf banks (“gap size”) can be finely tuned on Varian linacs. The dosimetric effect due to small deviations from the nominal gap size (“gap error”) was studied by introducing known errors for several DMLC sliding gap sizes, and for clinical plans based on the TG119 test cases. The plans were delivered on a single Varian linac and the relationship between gap error and the corresponding change in dose was measured. The plans were also delivered on eight Varian 2100 series linacs (at two institutions) in order to quantify the inter-linac variation in dose before and after fine tuning the MLC calibration. Results: The measured dose differences for each field agreed well with the predictions of LoSasso et al. Using the default MLC calibration, the variation in the physical MLC gap size was determined to be less than 0.4 mm between all linacs studied. The dose difference between the linacs with the largest and smallest physical gap was up to 5.4% (spinal cord region of the head and neck TG119 test case). This difference was reduced to 2.5% after fine tuning the MLC gap calibration. Conclusions: The inter-linac dose precision for DMLC IMRT on Varian linacs can be improved using a simple modification of the MLC calibration procedure that involves fine adjustment of the nominal gap size.

The 1997 determination of the Australian standards of exposure and absorbed dose at 60Co

International Nuclear Information System (INIS)

Huntley, R.B.; Boas, J.F.; Van der Gaast, H.

1998-05-01

The arrangements for the maintenance of the Australian standards for 60 Co are described in detail. The primary standards are a graphite cavity chamber for exposure/air kerma and a graphite calorimeter for absorbed dose. These secondary standards are described and their responses in corresponding 90 Sr reference sources are reported. Accurate ratios between the Australian Radiation Laboratory (ARL) and Australian Nuclear Science and Technology (ANSTO) 90 Sr reference sources are derived for use in future calibrations. The value of 28.8 years for the half-life of 90 Sr is confirmed. The usefulness of 90 Sr reference source measurements in quality assurance is discussed. The charge sensitivity and linearity of the ANSTO electrometers are reported by two different methods and are compared with previous results. Calibration factors for all the secondary standard ionization chambers are given, in terms of exposure, air kerma and absorbed dose to water. Calibration factors are also given for most of the chambers in terms of absorbed dose to graphite. The methods of deriving the calibration factors are explained in detail, including all the corrections applied to both the primary and secondary standard measurements. Three alternative methods of deriving the absorbed dose to water calibration factors are compared. The reported calibration factors are compared with previous results. Changes in the Australian units of exposure, air kerma and absorbed dose to graphite and water are derived from changes in the corresponding calibration factors. The Australian units of exposure and air kerma have not changed significantly since 1990. The Australian unit of absorbed dose to graphite is now 1.1 % smaller than in 1993 and 1.3 % smaller than in 1990. The Australian unit of absorbed dose to water is now 1.4 % smaller than in 1993, but is only 0.9 % smaller than in 1990. Comparisons of the Australian standards of exposure/air kerma and absorbed dose with those of the Bureau

Audits in high dose rate brachytherapy in Brazil

International Nuclear Information System (INIS)

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

2002-01-01

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

Applichation of the sulphate ceric dosimetric in the high doses range

International Nuclear Information System (INIS)

Prieto Miranda, F.

1991-01-01

The ceric-cerous dosimetric system is one of the system more employed in the high dose dosimetry. The spectrophotometric procedure to measure the ceric-concentration is an usual analityc method to determine the absorbed dose. On the other hand, due at increase employ of the irradiation process control. In this paper is realized the ceric-cerous dosimetric calibration in the dose range of 0,6 - 5 kGy and the application in the irradiation process control to differents absorbed dose values

Ten years of a National Service of Dosimetric calibration at radiation protection

International Nuclear Information System (INIS)

Morales, J.A.; Jova, L.; Hernandez, E.; Campa, R.; Walwyn, G.

1996-01-01

Since 1986, the CPHR has offered a national service of calibration of dosimetric instruments at levels of radiation protection. The history of such a service is the chronology of efforts to reduce the uncertainties of the calibration process, expand the ranges of useful dose rates, and enhance the radiological safety when using the sources. The crowning of those efforts is the complement and start-up of the secondary la laboratory of dosimetric calibration (SLDC), which is currently a member of the IAEA/WHO. SLDC international network. As a result of this service, 256 instruments have been calibration and 867 personal dosimeters film badges and TLD and 72 environmental TLD dosimeters have been irradiated at known doses. The service rendered has benefited 62 national institutions which are users of ionizing radiations

Monte Carlo simulation of secondary neutron dose for scanning proton therapy using FLUKA.

Directory of Open Access Journals (Sweden)

Chaeyeong Lee

Full Text Available Proton therapy is a rapidly progressing field for cancer treatment. Globally, many proton therapy facilities are being commissioned or under construction. Secondary neutrons are an important issue during the commissioning process of a proton therapy facility. The purpose of this study is to model and validate scanning nozzles of proton therapy at Samsung Medical Center (SMC by Monte Carlo simulation for beam commissioning. After the commissioning, a secondary neutron ambient dose from proton scanning nozzle (Gantry 1 was simulated and measured. This simulation was performed to evaluate beam properties such as percent depth dose curve, Bragg peak, and distal fall-off, so that they could be verified with measured data. Using the validated beam nozzle, the secondary neutron ambient dose was simulated and then compared with the measured ambient dose from Gantry 1. We calculated secondary neutron dose at several different points. We demonstrated the validity modeling a proton scanning nozzle system to evaluate various parameters using FLUKA. The measured secondary neutron ambient dose showed a similar tendency with the simulation result. This work will increase the knowledge necessary for the development of radiation safety technology in medical particle accelerators.

Calibration of photon and beta ray sources used in brachytherapy. Guidelines on standardized procedures at Secondary Standards Dosimetry Laboratories

International Nuclear Information System (INIS)

2004-03-01

It has generally been recognized that international harmonization in radiotherapy dosimetry is essential. Consequently, the IAEA has given much effort to this, for example by publishing a number of reports in the Technical Reports Series (TRS) for external beam dosimetry, most notably TRS-277 and more recently TRS-398. Both of these reports describe in detail the steps to be taken for absorbed dose determination in water and they are often referred to as 'dosimetry protocols'. Similar to TRS-277, it is expected that TRS-398 will be adopted or used as a model by a large number of countries as their national protocol. In 1996, the IAEA established a calibration service for low dose rate (LDR) 137 Cs brachytherapy sources, which is the most widely used source for treatment of gynecological cancer. To further enhance harmonization in brachytherapy dosimetry, the IAEA published in 1999 IAEA-TECDOC-1079 entitled 'Calibration of Brachytherapy Sources. Guidelines on Standardized Procedures for the Calibration of Brachytherapy Sources at Secondary Standard Dosimetry Laboratories (SSDLs) and Hospitals'. The report was well received and was distributed in a large number of copies to the members of the IAEA/WHO network of SSDLs and to medical physicists working with brachytherapy. The present report is an update of the aforementioned TECDOC. Whereas TECDOC-1079 described methods for calibrating brachytherapy sources with photon energies at or above those of 192 Ir, the current report has a wider scope in that it deals with standardization of calibration of all the most commonly used brachytherapy sources, including both photon and beta emitting sources. The latter sources have been in use for a few decades already, but their calibration methods have been unclear. Methods are also described for calibrating sources used in the rapidly growing field of cardiovascular angioplasty. In this application, irradiation of the vessel wall is done in an attempt to prevent restenosis after

SU-F-T-492: The Impact of Water Temperature On Absolute Dose Calibration

Energy Technology Data Exchange (ETDEWEB)

Islam, N [State University of New York at Buffalo, Buffalo, NY (United States); Podgorsak, M [State University of New York at Buffalo, Buffalo, NY (United States); Roswell Park Cancer Institute, Buffalo, NY (United States)

2016-06-15

Purpose: The Task Group 51 (TG 51) protocol prescribes that dose calibration of photon beams be done by irradiating an ionization chamber in a water tank at pre-defined depths. Methodologies are provided to account for variations in measurement conditions by applying correction factors. However, the protocol does not completely account for the impact of water temperature. It is well established that water temperature will influence the density of air in the ion chamber collecting volume. Water temperature, however, will also influence the size of the collecting volume via thermal expansion of the cavity wall and the density of the water in the tank. In this work the overall effect of water temperature on absolute dosimetry has been investigated. Methods: Dose measurements were made using a Farmer-type ion chamber for 6 and 23 MV photon beams with water temperatures ranging from 10 to 40°C. A reference ion chamber was used to account for fluctuations in beam output between successive measurements. Results: For the same beam output, the dose determined using TG 51 was dependent on the temperature of the water in the tank. A linear regression of the data suggests that the dependence is statistically significant with p-values of the slope equal to 0.003 and 0.01 for 6 and 23 MV beams, respectively. For a 10 degree increase in water phantom temperature, the absolute dose determined with TG 51 increased by 0.27% and 0.31% for 6 and 23 MV beams, respectively. Conclusion: There is a measurable effect of water temperature on absolute dose calibration. To account for this effect, a reference temperature can be defined and a correction factor applied to account for deviations from this reference temperature during beam calibration. Such a factor is expected to be of similar magnitude to most of the existing TG 51 correction factors.

SU-F-T-492: The Impact of Water Temperature On Absolute Dose Calibration

International Nuclear Information System (INIS)

Islam, N; Podgorsak, M

2016-01-01

Purpose: The Task Group 51 (TG 51) protocol prescribes that dose calibration of photon beams be done by irradiating an ionization chamber in a water tank at pre-defined depths. Methodologies are provided to account for variations in measurement conditions by applying correction factors. However, the protocol does not completely account for the impact of water temperature. It is well established that water temperature will influence the density of air in the ion chamber collecting volume. Water temperature, however, will also influence the size of the collecting volume via thermal expansion of the cavity wall and the density of the water in the tank. In this work the overall effect of water temperature on absolute dosimetry has been investigated. Methods: Dose measurements were made using a Farmer-type ion chamber for 6 and 23 MV photon beams with water temperatures ranging from 10 to 40°C. A reference ion chamber was used to account for fluctuations in beam output between successive measurements. Results: For the same beam output, the dose determined using TG 51 was dependent on the temperature of the water in the tank. A linear regression of the data suggests that the dependence is statistically significant with p-values of the slope equal to 0.003 and 0.01 for 6 and 23 MV beams, respectively. For a 10 degree increase in water phantom temperature, the absolute dose determined with TG 51 increased by 0.27% and 0.31% for 6 and 23 MV beams, respectively. Conclusion: There is a measurable effect of water temperature on absolute dose calibration. To account for this effect, a reference temperature can be defined and a correction factor applied to account for deviations from this reference temperature during beam calibration. Such a factor is expected to be of similar magnitude to most of the existing TG 51 correction factors.

Secondary calibration laboratory for dosimetry in levels of therapy at the University of Santiago

International Nuclear Information System (INIS)

Gomez Rodriguez, F.; Gonzalez Castano, D. M.; Pazos Alvarez, A.

2011-01-01

A basic inherent benefits provided by the existence of a traceability chain radiation in any application, add the legal requirement for hospitals as pointed to by the RO. 1566/1998, which sets quality standards in radiotherapy. The decree attributed to hospital specialists radio physics in article 10 the responsibility for determining the acceptance and initial reference state of radiation generating equipment for therapeutic purposes, and the establishment and implementation of quality control programs associated and technical and physical aspects of radiation dosimetry. Different international organizations such as ICRU and IAEA recommendations on maintaining the accuracy of the dose delivered to patients in general, should be placed at least 5% considering the whole chain irradiation. In order to achieve this purpose it is necessary to establish programs of quality control and calibration dosimetric regular basis. The protocol of the IAEA TRS398 recommended dose calibration in water because it is a quantity of interest closest to clinical use and allows a relative uncertainty in the calibration environment reduced to 1%.. (Author)

Biological dosimetry of ionizing radiation: Evaluation of the dose with cytogenetic methodologies by the construction of calibration curves

Science.gov (United States)

Zafiropoulos, Demetre; Facco, E.; Sarchiapone, Lucia

2016-09-01

In case of a radiation accident, it is well known that in the absence of physical dosimetry biological dosimetry based on cytogenetic methods is a unique tool to estimate individual absorbed dose. Moreover, even when physical dosimetry indicates an overexposure, scoring chromosome aberrations (dicentrics and rings) in human peripheral blood lymphocytes (PBLs) at metaphase is presently the most widely used method to confirm dose assessment. The analysis of dicentrics and rings in PBLs after Giemsa staining of metaphase cells is considered the most valid assay for radiation injury. This work shows that applying the fluorescence in situ hybridization (FISH) technique, using telomeric/centromeric peptide nucleic acid (PNA) probes in metaphase chromosomes for radiation dosimetry, could become a fast scoring, reliable and precise method for biological dosimetry after accidental radiation exposures. In both in vitro methods described above, lymphocyte stimulation is needed, and this limits the application in radiation emergency medicine where speed is considered to be a high priority. Using premature chromosome condensation (PCC), irradiated human PBLs (non-stimulated) were fused with mitotic CHO cells, and the yield of excess PCC fragments in Giemsa stained cells was scored. To score dicentrics and rings under PCC conditions, the necessary centromere and telomere detection of the chromosomes was obtained using FISH and specific PNA probes. Of course, a prerequisite for dose assessment in all cases is a dose-effect calibration curve. This work illustrates the various methods used; dose response calibration curves, with 95% confidence limits used to estimate dose uncertainties, have been constructed for conventional metaphase analysis and FISH. We also compare the dose-response curve constructed after scoring of dicentrics and rings using PCC combined with FISH and PNA probes. Also reported are dose response curves showing scored dicentrics and rings per cell, combining

measurement of high dose radiation using yellow perspex dosimeter

International Nuclear Information System (INIS)

Thamrin, M Thoyib; Sofyan, Hasnel

1996-01-01

Measurement of high dose radiation using yellow perspex dosemeter has been carried out. Dose range used was between 0.1 to 3.0 kGy. Measurement of dose rate against Fricke dosemeter as a standard dose meter From the irradiation of Fricke dosemeter with time variation of 3,6,9,12,15 and 18 minute, it was obtained average dose rate of 955.57 Gy/hour, linear equation of dose was Y= 2.333+15.776 X with its correlation factor r = 0.9999. Measurement result using yellow perspex show that correlation between net optical density and radiation dose was not linear with its equation was ODc exp. [Bo + In(dose).Bi] Value of Bo = -0.215 and Bi=0.5020. From the experiment it was suggested that routine dosimeter (yellow perspex) should be calibrated formerly against standard dosemeters

Determination of the secondary electron equilibrium using an extrapolation chamber

International Nuclear Information System (INIS)

Marshall, E.T.; Vaziri, K.; Krueger, F.P.; Cossairt, J.D.

1996-09-01

To ensure that the external personnel dosimetry program conducted by U. S. Department of Energy (DOE) contractors is of the highest quality, the DOE established the Department of Energy Laboratory Accreditation Program or DOELAP. The contractor's dosimetry program is assessed against the criteria set forth for dosimeter performance and the associated quality assurance and calibration programs. Although personnel dosimeters are not processed or calibrated by Fermilab, a proactive quality assurance program is in place to ensure accurate monitoring. This program includes quarterly blind testing of the dosimeters used by personnel. During the on-site assessment conducted of Fermilab's external dosimetry program during May 1994, an observation with regard to equipment maintenance and calibration was made: ''calibration personnel should probably review the electron secondary equilibrium needs at various irradiation distances from the 137 Cs irradiation systems'' The majority of the secondary electrons are generated through interactions of the beam with the collimator. Secondary electrons increase the low energy component of the radiation field, increasing the shallow doses measured. For dosimetric purposes, this increase needs to be defined so appropriate corrections to calculations or modifications to the facility can be made. Prompted by this observation, a study was designed to investigate the electron secondary equilibrium in the facility used for the blind testing by determining the dose equivalent as a function of depth in a tissue-equivalent medium. This presentation summarizes the methodology utilized and results of the investigation

Calculation of primary and secondary dose in proton therapy of brain tumors using Monte Carlo method

International Nuclear Information System (INIS)

Moghbel Esfahani, F.; Alamatsaz, M.; Karimian, A.

2012-01-01

High-energy beams of protons offer significant advantages for the treatment of deep-seated local tumors. Their physical depth-dose distribution in tissue is characterized by a small entrance dose and a distinct maximum - Bragg peak - near the end of range with a sharp falloff at the distal edge. Therefore, research must be done to investigate the possible negative and positive effects of using proton therapy as a treatment modality. In proton therapy, protons do account for the vast majority of dose. However, when protons travel through matter, secondary particles are created by the interactions of protons and matter en route to and within the patient. It is believed that secondary dose can lead to secondary cancer, especially in pediatric cases. Therefore, the focus of this work is determining both primary and secondary dose. Dose calculations were performed by MCNPX in tumoral and healthy parts of brain. The brain tumor has a 10 mm diameter and is located 16 cm under the skin surface. The brain was simulated by a cylindrical water phantom with the dimensions of 19 x 19cm 2 (length x diameter), with 0.5 cm thickness of plexiglass (C 4 H 6 O 2 ). Then beam characteristics were investigated to ensure the accuracy of the model. Simulations were initially validated with against packages such as SRIM/TRIM. Dose calculations were performed using different configurations to evaluate depth-dose profiles and dose 2D distributions.The results of the simulation show that the best proton energy interval, to cover completely the brain tumor, is from 152 to 154 MeV. (authors)

Precision and accuracy control of dose calibrator: CAPINTEC CRC 12 in laboratory for radiopharmacy of Nuclear Medicine Institute of Sucre, Bolivia

International Nuclear Information System (INIS)

Huanca Sardinas, E; Castro Sacci, O; Torrez Cabero, M; Vasquez Ibanez, M.R; Zambrana Zelada, AJ.

2013-01-01

The dose calibrator is one of the indispensable tools in radiopharmacy laboratories of a nuclear medicine department also is mandated to provide accurate readings. A very high doses produce unnecessary radiation exposure to the patient or a very low dose, prolong the acquisition time of the studies affecting the quality of the image. In the present work we did a retrospective analysis of the results of quality checks performed at precision accuracy of the Gauge CRC12 CAPINTEC dose calibrator over a period of 16 years, using sealed certified sources with low power, medium and high: Ba 133 , Cs 137 , Co 60 and Co 57 . The results showed that the lowest standard deviation value was 0.17 for Ba133, relative to Co 57 of 2.97 in the control of accuracy. Accuracy over control values were also lower standard deviation for Ba 133 1.00, relative to Co 57 10.06. Being stated that the CRC12 CAPINTEC activimeter reliability is acceptable during the reporting period and under the conditions indicated. Therefore, we continue to make these quality control procedures and the professional must feel confident that the measurements obtained with it are reliable

Evaluation of secondary dose and cancer risk for out-of-field organ in esophageal cancer IMRT in a chinese hospital using atom phantom measurements

International Nuclear Information System (INIS)

Qi, Yaping; He, Lijuan; Liu, Yuanyuan; Liu, Hongdong; Huo, Wanli; Chen, Zhi; Wang, Zhi; Xu, X. George

2017-01-01

There have been few studies on the secondary cancer after radiation treatment in Chinese hospitals. This study has measured out-of-field absorbed organ doses from intensity-modulated radiation therapy (IMRT) radiotherapy for esophageal cancer in a Chinese hospital and evaluated the risks of secondary cancer. The dose measurements were based on the thermoluminescence dosemeter (TLD) and the ATOM phantom, which represents an adult male. Over 100 TLD chips were placed in 35 different organ sites and one group of the same TLDs was set as background contrast. All TLDs were calibrated against the same Linac accelerator performing an IMRT plan for esophageal cancer. The measured doses were used to calculate the secondary cancer risks according to biological effects of ionizing radiation (BEIR) VII methodology. The baseline risks and survival data were based on relevant statistics for the Chinese population. It is found that the out-of-field organ doses depended greatly on the distance between organ sites and the target isocenter. The organ doses decreased exponentially as the distance from the target isocenter increased, and, for distances <15 cm, the organ doses fell off more rapidly and almost decreased by 99.55%. When compared with the calculation results by the Pinnacle treatment planning system (TPS), most of the out-of-field organ doses were underestimated in the TPS and the percentage of underestimation reached 100% for distant organs such as the bladder, prostate and testis. These trends are due to a known fact that out-of-field organs received secondary radiation resulted from patients and collimator scattering as well as leakage in the gantry head. The higher lifetime attribute risks (LARs) per 100 000 population were in the lower esophagus (186) and lungs (93.2) near the target. But all LARs of considered organs were found to be less than the baseline cancer risks. Results in this article can help to provide a database about the effect of radiotherapy

Calibration of Kodak EDR2 film for patient skin dose assessment in cardiac catheterization procedures.

Science.gov (United States)

Morrell, Rachel E; Rogers, Andy

2004-12-21

Kodak EDR2 film has been calibrated across the range of exposure conditions encountered in our cardiac catheterization laboratory. Its dose-response function has been successfully modelled, up to the saturation point of 1 Gy. The most important factor affecting film sensitivity is the use of beam filtration. Spectral filtration and kVp together account for a variation in dose per optical density of -10% to +25%, at 160 mGy. The use of a dynamic wedge filter may cause doses to be underestimated by up to 6%. The film is relatively insensitive to variations in batch, field size, exposure rate, time to processing and day-to-day fluctuations in processor performance. Overall uncertainty in the calibration is estimated to be -20% to +40%, at 160 mGy. However, the uncertainty increases at higher doses, as the curve saturates. Artefacts were seen on a number of films, due to faults in the light-proofing of the film packets.

IAEA/WHO TLD postal dose audit service and high precision measurements for radiotherapy level dosimetry

International Nuclear Information System (INIS)

Izewska, J.; Bera, P.; Vatnitsky, S.

2002-01-01

Since 1969 the International Atomic Energy Agency, together with the World Health Organization, has performed postal TLD audits to verify calibration of radiotherapy beams in developing countries. The TLD programme also monitors activities of Secondary Standard Dosimetry Laboratories (SSDLs). The programme has checked approximately 4000 clinical beams in over 1100 hospitals, and in many instances significant errors have been detected in the beam calibration. Subsequent follow-up actions help to resolve the discrepancies, thus preventing further mistreatment of patients. The audits for SSDLs check the implementation of the dosimetry protocol in order to assure proper dissemination of dosimetry standards to the end-users. The TLD audit results for SSDLs show good consistency in the basic dosimetry worldwide. New TLD procedures and equipment have recently been introduced by the IAEA that include a modified TLD calibration methodology and computerised tools for automation of dose calculation from TLD readings. (author)

Measurements of the personal dose equivalent

International Nuclear Information System (INIS)

Scarlat, F.; Scarisoreanu, A.; Badita, E.; Oane, M.; Mitru, E.

2008-01-01

Full text: The paper presents the results of measurements related to the personal dose equivalent in the rooms adjacent to NILPRP 7 MeV linear accelerator, by means of the secondary standard chamber T34035 Hp(10). The chamber was calibrated by PTB at S- 137 Cs (E av = 661.6 keV, T 1/2 11050 days) and has N H = 3.17x10 6 Sv/C calibration factor for the personal dose equivalent, Hp(10), at a depth of 10 mm in climatic reference conditions. The measurements were made for the two operation mode of the 7 MeV linac: electrons and bremsstrahlung

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

Science.gov (United States)

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

2017-02-01

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

Improving calibration accuracy in gel dosimetry

International Nuclear Information System (INIS)

Oldham, M.; McJury, M.; Webb, S.; Baustert, I.B.; Leach, M.O.

1998-01-01

A new method of calibrating gel dosimeters (applicable to both Fricke and polyacrylamide gels) is presented which has intrinsically higher accuracy than current methods, and requires less gel. Two test-tubes of gel (inner diameter 2.5 cm, length 20 cm) are irradiated separately with a 10x10cm 2 field end-on in a water bath, such that the characteristic depth-dose curve is recorded in the gel. The calibration is then determined by fitting the depth-dose measured in water, against the measured change in relaxivity with depth in the gel. Increased accuracy is achieved in this simple depth-dose geometry by averaging the relaxivity at each depth. A large number of calibration data points, each with relatively high accuracy, are obtained. Calibration data over the full range of dose (1.6-10 Gy) is obtained by irradiating one test-tube to 10 Gy at dose maximum (D max ), and the other to 4.5 Gy at D max . The new calibration method is compared with a 'standard method' where five identical test-tubes of gel were irradiated to different known doses between 2 and 10 Gy. The percentage uncertainties in the slope and intercept of the calibration fit are found to be lower with the new method by a factor of about 4 and 10 respectively, when compared with the standard method and with published values. The gel was found to respond linearly within the error bars up to doses of 7 Gy, with a slope of 0.233±0.001 s -1 Gy -1 and an intercept of 1.106±0.005 Gy. For higher doses, nonlinear behaviour was observed. (author)

Standardization of irradiation values at the Radiation Calibration Laboratory

International Nuclear Information System (INIS)

Pham Van Dung; Hoang Van Nguyen; Phan Van Toan; Phan Dinh Sinh; Tran Thi Tuyet; Do Thi Phuong

2007-01-01

The objective of the theme is to determine dose rates around radiation facilities and sources in the NRI Radiation Calibration Laboratory. By improving equipment, calibrating a main dosemeter and carrying out experiments, the theme team received the following results: 1. The controller of a X-rays generator PY(-200 was improved. It permits to increase accuracy of radiation dose calibration up to 2-4 times; 2. The FAMER DOSEMETER 2570/1B with the ionization chamber NE 2575 C of the NRI Radiation Calibration Laboratory was calibrated at SSDL (Hanoi); 3. Dose rates at 4 positions around a high activity Co-60 source were determined; 4. Dose rates at 3 positions around a low activity Co-60 source were determined; 5. Dose rates at 3 positions around a low activity Cs-137 source were determined; 6. Dose rate at 1 position of a X-rays beam (Eaverage = 48 keV) was determined; 7. Dose rate at 1 position of a X-rays beam (Eaverage = 65 keV) was determined. (author)

Calibration of Photon Sources for Brachytherapy

Science.gov (United States)

Rijnders, Alex

Source calibration has to be considered an essential part of the quality assurance program in a brachytherapy department. Not only it will ensure that the source strength value used for dose calculation agrees within some predetermined limits to the value stated on the source certificate, but also it will ensure traceability to international standards. At present calibration is most often still given in terms of reference air kerma rate, although calibration in terms of absorbed dose to water would be closer to the users interest. It can be expected that in a near future several standard laboratories will be able to offer this latter service, and dosimetry protocols will have to be adapted in this way. In-air measurement using ionization chambers (e.g. a Baldwin—Farmer ionization chamber for 192Ir high dose rate HDR or pulsed dose rate PDR sources) is still considered the method of choice for high energy source calibration, but because of their ease of use and reliability well type chambers are becoming more popular and are nowadays often recommended as the standard equipment. For low energy sources well type chambers are in practice the only equipment available for calibration. Care should be taken that the chamber is calibrated at the standard laboratory for the same source type and model as used in the clinic, and using the same measurement conditions and setup. Several standard laboratories have difficulties to provide these calibration facilities, especially for the low energy seed sources (125I and 103Pd). Should a user not be able to obtain properly calibrated equipment to verify the brachytherapy sources used in his department, then at least for sources that are replaced on a regular basis, a consistency check program should be set up to ensure a minimal level of quality control before these sources are used for patient treatment.

Guidelines on calibration of neutron measuring devices

International Nuclear Information System (INIS)

Burger, G.

1988-01-01

The International Atomic Energy Agency and the World Health Organization have agreed to establish an IAEA/WHO Network of Secondary Standard Dosimetry Laboratories (SSDLs) in order to improve accuracy in applied radiation dosimetry throughout the world. These SSDLs must be equipped with, and maintain, secondary standard instruments, which have been calibrated against primary standards, and must be nominated by their governments for membership of the network. The majority of the existing SSDLs were established primarily to work with photon radiation (X-rays and gamma rays). Neutron sources are, however, increasingly being applied in industrial processes, research, nuclear power development and radiation biology and medicine. Thus, it is desirable that the SSDLs in countries using neutron sources on a regular basis should also fulfil the minimum requirements to calibrate neutron measuring devices. It is the primary purpose of this handbook to provide guidance on calibration of instruments for radiation protection. A calibration laboratory should also be in a position to calibrate instrumentation being used for the measurement of kerma and absorbed dose and their corresponding rates. This calibration is generally done with photons. In addition, since each neutron field is usually contaminated by photons produced in the source or by scatter in the surrounding media, neutron protection instrumentation has to be tested with respect to its intrinsic photon response. The laboratory will therefore need to possess equipment for photon calibration. This publication deals primarily with methods of applying radioactive neutron sources for calibration of instrumentation, and gives an indication of the space, manpower and facilities needed to fulfil the minimum requirements of a calibration laboratory for neutron work. It is intended to serve as a guide for centres about to start on neutron dosimetry standardization and calibration. 94 refs, 8 figs, 12 tabs

The 1997 determination of the Australian standards of exposure and absorbed dose at {sup 60}Co

Energy Technology Data Exchange (ETDEWEB)

Huntley, R.B.; Boas, J.F. [Australian Radiation Laboratory, Yallambie, VIC (Australia); Van der Gaast, H. [Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW (Australia)

1998-05-01

The arrangements for the maintenance of the Australian standards for {sup 60}Co are described in detail. The primary standards are a graphite cavity chamber for exposure/air kerma and a graphite calorimeter for absorbed dose. These secondary standards are described and their responses in corresponding {sup 90}Sr reference sources are reported. Accurate ratios between the Australian Radiation Laboratory (ARL) and Australian Nuclear Science and Technology (ANSTO) {sup 90}Sr reference sources are derived for use in future calibrations. The value of 28.8 years for the half-life of {sup 90}Sr is confirmed. The usefulness of {sup 90}Sr reference source measurements in quality assurance is discussed. The charge sensitivity and linearity of the ANSTO electrometers are reported by two different methods and are compared with previous results. Calibration factors for all the secondary standard ionization chambers are given, in terms of exposure, air kerma and absorbed dose to water. Calibration factors are also given for most of the chambers in terms of absorbed dose to graphite. The methods of deriving the calibration factors are explained in detail, including all the corrections applied to both the primary and secondary standard measurements. Three alternative methods of deriving the absorbed dose to water calibration factors are compared. The reported calibration factors are compared with previous results. Changes in the Australian units of exposure, air kerma and absorbed dose to graphite and water are derived from changes in the corresponding calibration factors. The Australian units of exposure and air kerma have not changed significantly since 1990. The Australian unit of absorbed dose to graphite is now 1.1 % smaller than in 1993 and 1.3 % smaller than in 1990. The Australian unit of absorbed dose to water is now 1.4 % smaller than in 1993, but is only 0.9 % smaller than in 1990. Comparisons of the Australian standards of exposure/air kerma and absorbed dose with

Standardization of high-dose measurement of electron and gamma ray absorbed doses and dose rates

International Nuclear Information System (INIS)

McLaughlin, W.L.

1985-01-01

Intense electron beams and gamma radiation fields are used for sterilizing medical devices, treating municipal wastes, processing industrial goods, controlling parasites and pathogens, and extending the shelf-life of foods. Quality control of such radiation processes depends largely on maintaining measurement quality assurance through sound dosimetry procedures in the research leading to each process, in the commissioning of that process, and in the routine dose monitoring practices. This affords documentation as to whether satisfactory dose uniformity is maintained throughout the product and throughout the process. Therefore, dosimetry at high doses and dose rates must in many radiation processes be standardized carefully, so that 'dosimetry release' of a product is verified. This standardization is initiated through preliminary dosimetry intercomparison studies such as those sponsored recently by the IAEA. This is followed by establishing periodic exercises in traceability to national or international standards of absorbed dose and dose rate. Traceability is achieved by careful selection of dosimetry methods and proven reference dosimeters capable of giving sufficiently accurate and precise 'transfer' dose assessments: (1) they must be calibrated or have well-established radiation-yield indices; (2) their radiation response characteristics must be reproducible and cover the dose range of interest; (3) they must withstand the rigours of back-and-forth mailing between a central standardizing laboratory and radiation processing facilities, without excessive errors arising due to instabilities, dosimeter batch non-uniformities, and environmental and handling stresses. (author)

High-dose dosimetry using electron spin resonance (ESR) spectroscopy

International Nuclear Information System (INIS)

Kojima, Takuji; Tanaka, Ryuichi

1992-01-01

An electron spin resonance (ESR) dosimeter capable of measuring large doses of radiation in radiotherapy and radiation processing is outlined. In particular, an alanine/ESR dosimeter is discussed, focusing on the development of elements, the development of the ESR dosimetric system, the application of alanine/ESR dosimeter, and basic researches. Rod elements for gamma radiation and x radiation and film elements for electron beams are described in detail. The following recent applications of the alanine/ESR dosimeter are introduced: using as a transfer dosimeter, applying to various types of radiation, diagnosing the deterioration of radiological materials and equipments, and applying to ESR imaging. The future subjects to be solved in the alanine/ESR dosimetric system are referred to as follows: (1) improvement of highly accurate elements suitable for the measurement of various types of radiation, (2) establishment of sensitive calibration method of the ESR equipment itself, and (3) calibration and standardization of radiation doses. (K.N.) 65 refs

Procedures for calibration of brachytherapy sources

International Nuclear Information System (INIS)

Alfonso Laguardia, R.; Alonso Samper, J.L.; Morales Lopez, J.L.; Saez Nunez, D.G.

1997-01-01

Brachytherapy source strength verification is a responsibility of the user of these source, in fact of the Medical Physicists in charge of this issue in a Radiotherapy Service. The calibration procedures in the users conditions are shown. Specifics methods for source strength determination are recommended, both for High Dose Rate (HDR) sources with Remote Afterloading equipment and for Low Dose Rate sources. The The results of the calibration of HDR Remote After loaders are indicated

Experiences on the implementation of a postal auditing service to know teletherapy doses using Cobalt 60 attained by the Secondary laboratory for dosimetric calibration from CPHR

International Nuclear Information System (INIS)

Campa, R.; Morales, J.A.; Molina, D.; Dominguez, L.

1998-01-01

This paper analyzes experiences gained by LSCD from CPHR on the implementation and validation of a postal auditing system. The system checks doses absorbed by water for teletherapy equipment using Cobalt 60. The verification was made with Chinese DTL type JR 1152F (microbars) introduced in capsules developed and employed by IAEA in the postal auditing service for doses IAEA/WHO. The analysis includes the creation of groups of detectors based on their individual sensibility. They have a dispersion range that was almost 2%. Here irradiation was applied to a water dummy. Other tests employed were that for thermal treatment and calibration. Besides one auditing the effectiveness of the postal technique in two facilities using Cobalt 60. The methodology implemented helps to determine doses absorbed in reference conditions with a lower global uncertainty (k=2) (3.2%)

Computational tools for the construction of calibration curves for use in dose calculations in radiotherapy treatment planning

International Nuclear Information System (INIS)

Oliveira, Alex C.H.; Vieira, Jose W.; Escola Politecnica de Pernambuco , Recife, PE

2011-01-01

The realization of tissue inhomogeneity corrections in image-based treatment planning improves the accuracy of radiation dose calculations for patients undergoing external-beam radiotherapy. Before the tissue inhomogeneity correction can be applied, the relationship between the computed tomography (CT) numbers and density must be established. This relationship is typically established by a calibration curve empirically obtained from CT images of a phantom that has several inserts of tissue-equivalent materials, covering a wide range of densities. This calibration curve is scanner-dependent and allows the conversion of CT numbers in densities for use in dose calculations. This paper describes the implementation of computational tools necessary to construct calibration curves. These tools are used for reading and displaying of CT images in DICOM format, determination of the mean CT numbers (and their standard deviations) of each tissue-equivalent material and construction of calibration curves by fits with bilinear equations. All these tools have been implemented in the Microsoft Visual Studio 2010 in C≠ programming language. (author)

Changes in deviation of absorbed dose to water among users by chamber calibration shift.

Science.gov (United States)

Katayose, Tetsurou; Saitoh, Hidetoshi; Igari, Mitsunobu; Chang, Weishan; Hashimoto, Shimpei; Morioka, Mie

2017-07-01

The JSMP01 dosimetry protocol had adopted the provisional 60 Co calibration coefficient [Formula: see text], namely, the product of exposure calibration coefficient N C and conversion coefficient k D,X . After that, the absorbed dose to water D w  standard was established, and the JSMP12 protocol adopted the [Formula: see text] calibration. In this study, the influence of the calibration shift on the measurement of D w among users was analyzed. The intercomparison of the D w using an ionization chamber was annually performed by visiting related hospitals. Intercomparison results before and after the calibration shift were analyzed, the deviation of D w among users was re-evaluated, and the cause of deviation was estimated. As a result, the stability of LINAC, calibration of the thermometer and barometer, and collection method of ion recombination were confirmed. The statistical significance of standard deviation of D w was not observed, but that of difference of D w among users was observed between N C and [Formula: see text] calibration. Uncertainty due to chamber-to-chamber variation was reduced by the calibration shift, consequently reducing the uncertainty among users regarding D w . The result also pointed out uncertainty might be reduced by accurate and detailed instructions on the setup of an ionization chamber.

Comparison of CT number calibration techniques for CBCT-based dose calculation

Energy Technology Data Exchange (ETDEWEB)

Dunlop, Alex [The Royal Marsden NHS Foundation Trust, Joint Department of Physics, Institute of Cancer Research, London (United Kingdom); The Royal Marsden Hospital, Sutton, Surrey, Downs Road (United Kingdom); McQuaid, Dualta; Nill, Simeon; Hansen, Vibeke N.; Oelfke, Uwe [The Royal Marsden NHS Foundation Trust, Joint Department of Physics, Institute of Cancer Research, London (United Kingdom); Murray, Julia; Bhide, Shreerang; Harrington, Kevin [The Royal Marsden Hospital, Sutton, Surrey, Downs Road (United Kingdom); The Institute of Cancer Research, London (United Kingdom); Poludniowski, Gavin [Karolinska University Hospital, Department of Medical Physics, Stockholm (Sweden); Nutting, Christopher [The Institute of Cancer Research, London (United Kingdom); Newbold, Kate [The Royal Marsden Hospital, Sutton, Surrey, Downs Road (United Kingdom)

2015-12-15

The aim of this work was to compare and validate various computed tomography (CT) number calibration techniques with respect to cone beam CT (CBCT) dose calculation accuracy. CBCT dose calculation accuracy was assessed for pelvic, lung, and head and neck (H and N) treatment sites for two approaches: (1) physics-based scatter correction methods (CBCT{sub r}); (2) density override approaches including assigning water density to the entire CBCT (W), assignment of either water or bone density (WB), and assignment of either water or lung density (WL). Methods for CBCT density assignment within a commercially available treatment planning system (RS{sub auto}), where CBCT voxels are binned into six density levels, were assessed and validated. Dose-difference maps and dose-volume statistics were used to compare the CBCT dose distributions with the ground truth of a planning CT acquired the same day as the CBCT. For pelvic cases, all CTN calibration methods resulted in average dose-volume deviations below 1.5 %. RS{sub auto} provided larger than average errors for pelvic treatments for patients with large amounts of adipose tissue. For H and N cases, all CTN calibration methods resulted in average dose-volume differences below 1.0 % with CBCT{sub r} (0.5 %) and RS{sub auto} (0.6 %) performing best. For lung cases, WL and RS{sub auto} methods generated dose distributions most similar to the ground truth. The RS{sub auto} density override approach is an attractive option for CTN adjustments for a variety of anatomical sites. RS{sub auto} methods were validated, resulting in dose calculations that were consistent with those calculated on diagnostic-quality CT images, for CBCT images acquired of the lung, for patients receiving pelvic RT in cases without excess adipose tissue, and for H and N cases. (orig.) [German] Ziel dieser Arbeit ist der Vergleich und die Validierung mehrerer CT-Kalibrierungsmethoden zur Dosisberechnung auf der Grundlage von Kegelstrahlcomputertomographie

Postal auditing methodology used to find out the performance of high rate brachytherapy equipment

International Nuclear Information System (INIS)

Morales, J.A.; Campa, R.

1998-01-01

This work describes results from a methodology implemented at the Secondary Laboratory for Dosimetric Calibration at CPHR used to check the brachytherapy performance at high doses rate using Cesium 137 or cobalt 60 sources

Comparison of two methods of therapy level calibration at 60Co gamma beams

International Nuclear Information System (INIS)

Bjerke, H.; Jaervinen, H.; Grimbergen, T.W.M.; Grindborg, J.E.; Chauvenet, B.; Czap, L.; Ennow, K.; Moretti, C.; Rocha, P.

1998-01-01

The accuracy and traceability of the calibration of radiotherapy dosimeters is of great concern to those involved in the delivery of radiotherapy. It has been proposed that calibration should be carried out directly in terms of absorbed dose to water, instead of using the conventional and widely applied quantity of air kerma. In this study, the faithfulness in disseminating standards of both air kerma and absorbed dose to water were evaluated, through comparison of both types of calibration for three types of commonly used radiotherapy dosimeters at 60 Co gamma beams at a few secondary and primary standard dosimetry laboratories (SSDLs and PSDLs). A supplementary aim was to demonstrate the impact which the change in the method of calibration would have on clinical dose measurements at the reference point. Within the estimated uncertainties, both the air kerma and absorbed dose to water calibration factors obtained at different laboratories were regarded as consistent. As might be expected, between the SSDLs traceable to the same PSDL the observed differences were smaller (less than 0.5%) than between PSDLs or SSDLs traceable to different PSDLs (up to 1.5%). This can mainly be attributed to the reported differences between the primary standards. The calibration factors obtained by the two methods differed by up to about 1.5% depending on the primary standards involved and on the parameters of calculation used for 60 Co gamma radiation. It is concluded that this discrepancy should be settled before the new method of calibration at 60 Co gamma beams in terms of absorbed dose to water is taken into routine use. (author)

Comparison of two methods of therapy level calibration at 60Co gamma beams

International Nuclear Information System (INIS)

Bjerke, H; Jaervinen, H; Grimbergen, T W M; Grindborg, J-E; Chauvenet, B; Czap, L; Ennow, K; Moretti, C; Rocha, P

1998-01-01

The accuracy and traceability of the calibration of radiotherapy dosimeters is of great concern to those involved in the delivery of radiotherapy. It has been proposed that calibration should be carried out directly in terms of absorbed dose to water, instead of using the conventional and widely applied quantity of air kerma. In this study, the faithfulness in disseminating standards of both air kerma and absorbed dose to water were evaluated, through comparison of both types of calibration for three types of commonly used radiotherapy dosimeters at 60 Co gamma beams at a few secondary and primary standard dosimetry laboratories (SSDLs and PSDLs). A supplementary aim was to demonstrate the impact which the change in the method of calibration would have on clinical dose measurements at the reference point. Within the estimated uncertainties, both the air kerma and absorbed dose to water calibration factors obtained at different laboratories were regarded as consistent. As might be expected, between the SSDLs traceable to the same PSDL the observed differences were smaller (less than 0.5%) than between PSDLs or SSDLs traceable to different PSDLs (up to 1.5%). This can mainly be attributed to the reported differences between the primary standards. The calibration factors obtained by the two methods differed by up to about 1.5% depending on the primary standards involved and on the parameters of calculation used for 60 Co gamma radiation. It is concluded that this discrepancy should be settled before the new method of calibration at 60 Co gamma beams in terms of absorbed dose to water is taken into routine use

Dose equivalent distributions in the AAEC total body nitrogen facility

International Nuclear Information System (INIS)

Allen, B.J.; Bailey, G.M.; McGregor, B.J.

1985-01-01

The incident neutron dose equivalent in the AAEC total body nitrogen facility is measured by a calibrated remmeter. Dose equivalent rates and distributions are calculated by Monte Carlo techniques which take account of the secondary neutron flux from the collimator. Experiment and calculation are found to be in satisfactory agreement. The effective dose equivalent per exposure is determined by weighting organ doses, and the potential detriment per exposure is calculated from ICRP risk factors

Calibration of well-type ionization chambers

International Nuclear Information System (INIS)

Alves, C.F.E.; Leite, S.P.; Pires, E.J.; Magalhaes, L.A.G.; David, M.G.; Almeida, C.E. de

2015-01-01

This paper presents the methodology developed by the Laboratorio de Ciencias Radiologicas and presently in use for determining of the calibration coefficient for well-type chambers used in the dosimetry of 192 Ir high dose rate sources. Uncertainty analysis involving the calibration procedure are discussed. (author)

Calibration factor or calibration coefficient?

International Nuclear Information System (INIS)

Meghzifene, A.; Shortt, K.R.

2002-01-01

Full text: The IAEA/WHO network of SSDLs was set up in order to establish links between SSDL members and the international measurement system. At the end of 2001, there were 73 network members in 63 Member States. The SSDL network members provide calibration services to end-users at the national or regional level. The results of the calibrations are summarized in a document called calibration report or calibration certificate. The IAEA has been using the term calibration certificate and will continue using the same terminology. The most important information in a calibration certificate is a list of calibration factors and their related uncertainties that apply to the calibrated instrument for the well-defined irradiation and ambient conditions. The IAEA has recently decided to change the term calibration factor to calibration coefficient, to be fully in line with ISO [ISO 31-0], which recommends the use of the term coefficient when it links two quantities A and B (equation 1) that have different dimensions. The term factor should only be used for k when it is used to link the terms A and B that have the same dimensions A=k.B. However, in a typical calibration, an ion chamber is calibrated in terms of a physical quantity such as air kerma, dose to water, ambient dose equivalent, etc. If the chamber is calibrated together with its electrometer, then the calibration refers to the physical quantity to be measured per electrometer unit reading. In this case, the terms referred have different dimensions. The adoption by the Agency of the term coefficient to express the results of calibrations is consistent with the 'International vocabulary of basic and general terms in metrology' prepared jointly by the BIPM, IEC, ISO, OIML and other organizations. The BIPM has changed from factor to coefficient. The authors believe that this is more than just a matter of semantics and recommend that the SSDL network members adopt this change in terminology. (author)

Physics and quality assurance for high dose rate brachytherapy

International Nuclear Information System (INIS)

Anderson, Lowell L.

1995-01-01

Purpose: To review the physical aspects of high dose rate (HDR) brachytherapy, including commissioning and quality assurance, source calibration and dose distribution measurements, and treatment planning methods. Following the introduction of afterloading in brachytherapy, development efforts to make it 'remote' culminated in 1964 with the near-simultaneous appearance of remote afterloaders in five major medical centers. Four of these machines were 'high dose rate', three employing 60Co and one (the GammaMed) using a single, cable-mounted 192Ir source. Stepping-motor source control was added to the GammaMed in 1974, making it the precursor of modern remote afterloaders, which are now suitable for interstitial as well as intracavitary brachytherapy by virtue of small source-diameter and indexer-accessed multiple channels. Because the 192Ir sources currently used in HDR remote afterloaders are supplied at a nominal air-kerma strength of 11.4 cGy cm2 s-1 (10 Ci), are not collimated in clinical use, and emit a significant fraction (15%) of photons at energies greater than 600 keV, shielding and facility design must be undertaken as carefully and thoroughly as for external beam installations. Licensing requirements of regulatory agencies must be met with respect both to maximum permissible dose limits and to the existence and functionality of safety devices (door interlocks, radiation monitors, etc.). Commissioning and quality assurance procedures that must be documented for HDR remote afterloading relate to (1) machine, applicator, guide-tube, and facility functionality checks, (2) source calibration, (3) emergency response readiness, (4) planning software evaluation, and (5) independent checks of clinical dose calculations. Source calibration checks must be performed locally, either by in-air measurement of air kerma strength or with a well ionization chamber calibrated (by an accredited standards laboratory) against an in-air measurement of air kerma strength for the

Calibration for radiation protection survey meter SSM1

International Nuclear Information System (INIS)

Jin Hua.

1992-03-01

The calibration functions for the Radiation Protection Survey Meter SSM1 built-in Geiger Mueller measuring tubes of the type ZP 1201 (low dose rate tube) and ZP 1313 (high dose rate tube) are given in the present study. Six dose rate points are proposed as the calibration points of covering the range from 500 nSv/h up to 5 Sv/h. The difference between the true dose rate and the values calculated with the method in this paper for No. 382 SSM1 is less than ±2%. (author)

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

International Nuclear Information System (INIS)

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

2014-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

Chu, A; Ahmad, M; Chen, Z; Nath, R [Yale New Haven Hospital/School of Medicine Yale University, New Haven, CT (United States); Feng, W [New York Presbyterian Hospital, Tenafly, NJ (United States)

2014-06-01

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

Estimate of neutron secondary doses received by patients in proton therapy: cases of ophthalmologic treatments

International Nuclear Information System (INIS)

Martinetti, F.

2009-12-01

This research thesis aims at assessing doses due to secondary neutrons and received by the organs of a patient which are located outside of the treatment field. The study focused on ophthalmological treatments performed at the Orsay proton therapy centre. A 75 eV beam line model has first been developed with the MCNPX Monte Carlo code. Several experimental validations of this model have been performed: proton dose distribution in a water phantom, ambient equivalent dose due to secondary neutrons and neutron spectra in the treatment room, and doses deposited by secondary neutrons in an anthropomorphous phantom. Simulations and measurements are in correct agreement. Then, a numeric assessment of secondary doses received by the patient's organs has been performed by using a MIRD-type mathematical phantom. These doses have been computed for several organs: the non-treated eye, the brain, the thyroid, and other parts of the body situated either in the front part of the body (the one directly exposed to neutrons generated in the treatment line) or deeper and further from the treatment field

Calibration of photon and beta ray sources used in brachytherapy. Guidelines on standardized procedures at Secondary Standards Dosimetry Laboratories (SSDLs) and hospitals

International Nuclear Information System (INIS)

2002-03-01

It has generally been recognized that international harmonization in radiotherapy dosimetry is essential. Consequently, the IAEA has given much effort to this, for example by publishing a number of reports in the Technical Reports Series (TRS) for external beam dosimetry, most notably TRS-277 and more recently TRS-398. Both of these reports describe in detail the steps to be taken for absorbed dose determination in water and they are often referred to as 'dosimetry protocols'. Similar to TRS-277, it is expected that TRS-398 will be adopted or used as a model by a large number of countries as their national protocol. In 1996, the IAEA established a calibration service for low dose rate (LDR) 137 Cs brachytherapy sources, which is the most widely used source for treatment of gynecological cancer. To further enhance harmonization in brachytherapy dosimetry, the IAEA published in 1999 IAEA-TECDOC-1079 entitled 'Calibration of Brachytherapy Sources. Guidelines on Standardized Procedures for the Calibration of Brachytherapy Sources at Secondary Standard Dosimetry Laboratories (SSDLs) and Hospitals'. The report was well received and was distributed in a large number of copies to the members of the IAEA/WHO network of SSDLs and to medical physicists working with brachytherapy. The present report is an update of the aforementioned TECDOC. Whereas TECDOC-1079 described methods for calibrating brachytherapy sources with photon energies at or above those of 192 Ir, the current report has a wider scope in that it deals with standardization of calibration of all the most commonly used brachytherapy sources, including both photon and beta emitting sources. The latter sources have been in use for a few decades already, but their calibration methods have been unclear. Methods are also described for calibrating sources used in the rapidly growing field of cardiovascular angioplasty. In this application, irradiation of the vessel wall is done in an attempt to prevent restenosis after

Performance of dichromate dosimetry systems in calibration and dose intercomparison

International Nuclear Information System (INIS)

Bof, E.S.; Smolko, E.

1999-01-01

This report presents the results of the High Dose Dosimetry Laboratory of Argentina during ten years of international intercomparisons for high dose with the International Dose Assurance Service (IDAS) of the IAEA, using the standard high dose dichromate dosimetry system, and the results of a high dose intercomparison regional exercise in which our Laboratory acted as a reference laboratory, using the standard high dose and low dose dichromate dosimetry system. (author)

System for determining absorbed dose and its distribution for high-energy electron radiation

International Nuclear Information System (INIS)

Hegewald, H.; Wulff, W.

1977-01-01

Taking into account the polarization effect, the dose determination for high-energy electron radiation from particle accelerators depends on the knowledge of the energy dependence of the mass stopping power. Results obtained with thermoluminescent dosemeters agree with theoretical values. For absorbed dose measurements the primary energy of electron radiation has been determined by nuclear photoreactions, and the calculation of the absorbed dose from charge measurements by means of the mass stopping power is described. Thus the calibration of ionization chambers for high-energy electron radiation by absolute measurements with the Faraday cage and chemical dosemeters has become possible. (author)

High Gain Antenna Calibration on Three Spacecraft

Science.gov (United States)

Hashmall, Joseph A.

2011-01-01

This paper describes the alignment calibration of spacecraft High Gain Antennas (HGAs) for three missions. For two of the missions (the Lunar Reconnaissance Orbiter and the Solar Dynamics Observatory) the calibration was performed on orbit. For the third mission (the Global Precipitation Measurement core satellite) ground simulation of the calibration was performed in a calibration feasibility study. These three satellites provide a range of calibration situations-Lunar orbit transmitting to a ground antenna for LRO, geosynchronous orbit transmitting to a ground antenna fer SDO, and low Earth orbit transmitting to TDRS satellites for GPM The calibration results depend strongly on the quality and quantity of calibration data. With insufficient data the calibration Junction may give erroneous solutions. Manual intervention in the calibration allowed reliable parameters to be generated for all three missions.

Dose rate range extension of the calibration of dosemeters at LNMRI, Rio de Janeiro, Brazil

International Nuclear Information System (INIS)

Cabral, T.S.; Carlos, M.T.; Ramos, M.M.O.

2009-01-01

The present work has an objective the implantation of a experimental arrange for application of essays of instrument calibration for measurement of low dose rate, which measure rate less than 10 μSv/h

Secondary standard dosimetry laboratory at INFLPR

Energy Technology Data Exchange (ETDEWEB)

Scarlat, F.; Minea, R.; Scarisoreanu, A.; Badita, E.; Sima, E.; Dumitrascu, M.; Stancu, E.; Vancea, C., E-mail: scarlat.f@gmail.com [National Institute for Laser, Plasma and Radiation Physics - INFLPR, Bucharest (Romania)

2011-07-01

National Institute for Laser, Plasma and Radiation Physics (INFLPR) has constructed a High Energy Secondary Standard Dosimetry Laboratory SSDL-STARDOOR - for performing dosimetric calibrations according to ISO IEC SR/EN 17025:2005 standards. This is outfitted with UNIDOS Secondary Standard Dosimeter from PTW (Freiburg Physikalisch-Technische Werksttaten) calibrated at the PTB-Braunschweig (German Federal Institute of Physics and Metrology). A radiation beam of the quality of Q used by our laboratory as calibration source are provided by INFLPR 7 MeV electron beam linear accelerator mounted in our facility. (author)

Cross-Calibration of Secondary Electron Multiplier in Noble Gas Analysis

Science.gov (United States)

Santato, Alessandro; Hamilton, Doug; Deerberg, Michael; Wijbrans, Jan; Kuiper, Klaudia; Bouman, Claudia

2015-04-01

The latest generation of multi-collector noble gas mass spectrometers has decisively improved the precision in isotopic ratio analysis [1, 2] and helped the scientific community to address new questions [3]. Measuring numerous isotopes simultaneously has two significant advantages: firstly, any fluctuations in signal intensity have no effect on the isotope ratio and secondly, the analysis time is reduced. This particular point becomes very important in static vacuum mass spectrometry where during the analysis, the signal intensity decays and at the same time the background increases. However, when multi-collector analysis is utilized, it is necessary to pay special attention to the cross calibration of the detectors. This is a key point in order to have accurate and reproducible isotopic ratios. In isotope ratio mass spectrometry, with regard to the type of detector (i.e. Faraday or Secondary Electron Multiplier, SEM), analytical technique (TIMS, MC-ICP-MS or IRMS) and isotope system of interest, several techniques are currently applied to cross-calibrate the detectors. Specifically, the gain of the Faraday cups is generally stable and only the associated amplifier must be calibrated. For example, on the Thermo Scientific instrument control systems, the 1011 and 1012 ohm amplifiers can easily be calibrated through a fully software controlled procedure by inputting a constant electric signal to each amplifier sequentially [4]. On the other hand, the yield of the SEMs can drift up to 0.2% / hour and other techniques such as peak hopping, standard-sample bracketing and multi-dynamic measurement must be used. Peak hopping allows the detectors to be calibrated by measuring an ion beam of constant intensity across the detectors whereas standard-sample bracketing corrects the drift of the detectors through the analysis of a reference standard of a known isotopic ratio. If at least one isotopic pair of the sample is known, multi-dynamic measurement can be used; in this

Establishment of 60Co dose calibration curve using fluorescent in situ hybridization assay technique: Result of preliminary study

International Nuclear Information System (INIS)

Rahimah Abdul Rahim; Noriah Jamal; Noraisyah Mohd Yusof; Juliana Mahamad Napiah; Nelly Bo Nai Lee

2010-01-01

This study aims at establishing an in-vitro 60 Co dose calibration curve using Fluorescent In-Situ Hybridization assay technique for the Malaysian National Bio dosimetry Laboratory. Blood samples collected from a female healthy donor were irradiated with several doses of 60 Co radiation. Following culturing of lymphocytes, microscopic slides are prepared, denatured and hybridized. The frequencies of translocation are estimated in the metaphases. A calibration curve was then generated using a regression technique. It shows a good fit to a linear-quadratic model. The results of this study might be useful in estimating absorbed dose for the individual exposed to ionizing radiation retrospectively. This information may be useful as a guide for medical treatment for the assessment of possible health consequences. (author)

Evaluating secondary neutron doses of a refined shielded design for a medical cyclotron using the TLD approach

International Nuclear Information System (INIS)

Lin, Jye-Bin; Tseng, Hsien-Chun; Liu, Wen-Shan; Lin, Ding-Bang; Hsieh, Teng-San; Chen, Chien-Yi

2013-01-01

An increasing number of cyclotrons at medical centers in Taiwan have been installed to generate radiopharmaceutical products. An operating cyclotron generates immense amounts of secondary neutrons from reactions such the 18 O(p, n) 18 F, used in the production of FDG. This intense radiation can be hazardous to public health, particularly to medical personnel. To increase the yield of 18 F-FDG from 4200 GBq in 2005 to 48,600 GBq in 2011, Chung Shan Medical University Hospital (CSMUH) has prolonged irradiation time without changing the target or target current to meet requirements regarding the production 18 F. The CSMUH has redesigned the CTI Radioisotope Delivery System shield. The lack of data for a possible secondary neutron doses has increased due to newly designed cyclotron rooms. This work aims to evaluate secondary neutron doses at a CTI cyclotron center using a thermoluminescent dosimeter (TLD-600). Two-dimensional neutron doses were mapped and indicated that neutron doses were high as neutrons leaked through self-shielded blocks and through the L-shaped concrete shield in vault rooms. These neutron doses varied markedly among locations close to the H 2 18 O target. The Monte Carlo simulation and minimum detectable dose are also discussed and demonstrated the reliability of using the TLD-600 approach. Findings can be adopted by medical centers to identify radioactive hot spots and develop radiation protection. - Highlights: • Neutron doses were verified using TLD approach. • Neutron doses were increased at cyclotron centers. • Revised L-shaped shield suppresses effectively the neutrons. • Neutron dose can be attenuated to 1.13×10 6 %

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

International Nuclear Information System (INIS)

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

2015-01-01

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

Proposal of a postal system for Ir-192 sources calibration used in high dose rate brachytherapy with LiF:Mn:Ti thermoluminescent dosemeters; Proposta de um sistema postal para a calibracao de fontes de {sup 192} Ir, utilizadas em braquiterapia de alta taxa de dose, com dosimetros termoluminescentes de LiF: Mn: Ti

Energy Technology Data Exchange (ETDEWEB)

Vieira, W.S.; Borges, J.C.; Almeida, C.E.V. [Instituto de Radioprotecao e Dosimetria. CNEN Caixa Postal 37750, 22780-160, Rio de Janeiro (Brazil)

1998-12-31

A proposal in order to improve the brachytherapy quality control and to allow postal intercomparison of Ir-192 sources used in high dose rate brachytherapy has been presented. The LiF: Mn: Ti (TLD 100) detector has been selected for such purpose. The experimental array and the TLDs irradiation and calibration techniques, at the treatment units, have been specified in the light of more recent methodology of Ir-192 calibration sources. (Author)

Determination of air kerma standard of high dose rate 192Ir brachytherapy source

International Nuclear Information System (INIS)

Pires, E.J.; Alves, C.F.E.; Leite, S.P.; Magalhaes, L.A.G.; David, M.G.; Almeida, C.E. de

2015-01-01

This paper presents the methodology developed by the Laboratorio de Ciencias Radiologicas and presently in use for determining of the air kerma standard of 192 Ir high dose rate sources to calibrate well-type chambers. Uncertainty analysis involving the measurements procedure are presented. (author)

Experiences of a secondary laboratory of dosimetric calibration from the radiation protection and hygiene center CPHR in its first year of work and the procedures for quality assessment used in the calibration and quality control service

International Nuclear Information System (INIS)

Morales, J.A.; Campa, R.; Jova Sed, L.

1996-01-01

Experiences of a secondary laboratory of dosimetric calibration from the Radiation Protection and Hygiene Center (CPHR) in first year of work and the procedures for quality assessment used in the calibration and quality control service of radiotherapeutic equipment. For the yield calibration of the calibrated sources an ionometric method was used using ionizing chambers coupled to electrometers. Those determination were based on dosimetric American Association of Physicists in Medicine (AAPM)

MRI dosimetry using an echo-quotient technique for high dose rate brachytherapy

International Nuclear Information System (INIS)

Ansbacher, W.

1996-01-01

MRI gel dosimetry is a relatively new technique that has many advantages over conventional methods, and is particularly suited to High Dose Rate (HDR) Brachytherapy. The dosimeter has high spatial resolution and a water-equivalent response over a wide range of photon energies. Because it is an integrating dosimeter, it allows for efficient mapping of the dynamically-produced distributions from an HDR source. As an example of this technique, the dose response, which is calibrated in terms of the change in spin-spin relaxation time, has been used to investigate the anisotropy of an HDR source. (author). 1 fig

International comparison of calibration standards for exposure and absorbed dose

International Nuclear Information System (INIS)

Horakova, I.; Wagner, R.

1990-01-01

A comparison was performed of the primary calibration standards for 60 Co gamma radiation dose from Czechoslovakia (UDZ CSAV, Prague), Austria (OEFZS/BEV Seibersdorf) and Hungary (OMH Budapest) using ND 1005 (absolute measurement) and V-415 (by means of N x ) graphite ionization chambers. BEV achieved agreement better than 0.1%, OMH 0.35%. Good agreement was also achieved for the values of exposure obtained in absolute values and those obtained via N x , this for the ND 1005/8105 chamber. The first ever international comparison involving Czechoslovakia was also performed of the unit of absorbed gamma radiation in a water and/or graphite phantom. The participants included Czechoslovakia (UDZ CSAV Prague), the USSR (VNIIFTRI Moscow) and Austria (OEFZS/BEV Seibersdorf). In all measurements, the agreement was better than 1%, which, in view of the differences in methodologies (VNIIFTRI, BEV: calorimetry, UDZ, UVVVR: ionometry) and the overall inaccuracies in determining the absorbed dose values, is a good result. (author)

Calibrating page sized Gafchromic EBT3 films

International Nuclear Information System (INIS)

Crijns, W.; Maes, F.; Heide, U. A. van der; Van den Heuvel, F.

2013-01-01

Purpose: The purpose is the development of a novel calibration method for dosimetry with Gafchromic EBT3 films. The method should be applicable for pretreatment verification of volumetric modulated arc, and intensity modulated radiotherapy. Because the exposed area on film can be large for such treatments, lateral scan errors must be taken into account. The correction for the lateral scan effect is obtained from the calibration data itself. Methods: In this work, the film measurements were modeled using their relative scan values (Transmittance, T). Inside the transmittance domain a linear combination and a parabolic lateral scan correction described the observed transmittance values. The linear combination model, combined a monomer transmittance state (T 0 ) and a polymer transmittance state (T ∞ ) of the film. The dose domain was associated with the observed effects in the transmittance domain through a rational calibration function. On the calibration film only simple static fields were applied and page sized films were used for calibration and measurements (treatment verification). Four different calibration setups were considered and compared with respect to dose estimation accuracy. The first (I) used a calibration table from 32 regions of interest (ROIs) spread on 4 calibration films, the second (II) used 16 ROIs spread on 2 calibration films, the third (III), and fourth (IV) used 8 ROIs spread on a single calibration film. The calibration tables of the setups I, II, and IV contained eight dose levels delivered to different positions on the films, while for setup III only four dose levels were applied. Validation was performed by irradiating film strips with known doses at two different time points over the course of a week. Accuracy of the dose response and the lateral effect correction was estimated using the dose difference and the root mean squared error (RMSE), respectively. Results: A calibration based on two films was the optimal balance between

Effects of secondary interactions on the dose calculation in treatments with Boron Neutron Capture Therapy (BNCT)

International Nuclear Information System (INIS)

Monteiro, E.

2004-01-01

The aimed of this work consists of evaluating the influence of the secondary contributions of dose (thermal neutrons dose, epithermal neutrons dose, fast neutrons dose and photon dose) in treatment planning with BNCT. MCNP4B Code was used to calculate RBE-Gy doses through the irradiation of the modified Snyder head head phantom.A reduction of the therapeutical gain of monoenergetic neutron beans was observed in non invasive treatments, provoked for the predominance of the fast neutron dose component in the skin, showing that the secondary contributions of dose can contribute more in the direction to raise the dose in the fabric healthy that in the tumor, thus reducing the treatment efficiency. (author)

Dosemeter calibration in X-ray and in cobalt-60

International Nuclear Information System (INIS)

Silva, T.A. da

1988-01-01

Some tests about quality security for clinical dosemeter calibration in secondary standard dosimetry laboratory are described. The tests in gama calibration system, in X-ray calibration, in secondary standard dosimeter, in the dosemeter that will be calibrated, during the calibration and after the calibration are shown. (C.G.C.) [pt

Measurement of absorbed doses near interfaces, and dose mapping using gas chromic dosimetry media. Vol. 2

Energy Technology Data Exchange (ETDEWEB)

Abdel-Rehim, F; Said, F I.A.; Abdel-Fattah, A A [National Centre for Radiation Research and Technology, Atomic Energy Athority, P.O.Box 29 Nasr City, Cairo (Egypt)

1996-03-01

Gas chromic dosimetry media is a thin-coated film which has advantages for high-dose radiation dosimetry, and produces high-resolution radiation image for gamma radiation. Therefore, these films were calibrated for the dose range 0.1-50 kGy in terms of increase in absorbance at 600 nm, 400 nm; increase in the area of the absorption spectra in the ranges 395-405 nm and 320-450 nm wave length as a function of absorbed dose in water. The calibrated films were used for measurement of absorbed doses close to metal interface, and dose mapping of the radiation field inside product box during a run for sterilizing surgical gloves at the mega-gamma irradiation facility.7 figs.

Estimation dose of secondary neutrons in proton therapy

International Nuclear Information System (INIS)

Urban, T.

2014-01-01

Most of proton therapy centers for cancer treatment are still based on the passive scattering, in some of them there is system of the active scanning installed as well. The aim of this study is to compare secondary neutron doses in and around target volumes in proton therapy for both treatment techniques and for different energies and profile of incident proton beam. The proton induced neutrons have been simulated in the very simple geometry of tissue equivalent phantom (imitate the patient) and scattering and scanning nozzle, respectively. In simulations of the scattering nozzle, different types of scattering filters and brass collimators have been used as well. 3D map of neutron doses in and around the chosen/potential target volume in the phantom/patient have been evaluated and compared in the context of the dose deposited in the target volume. Finally, the simulation results have been compared with published data. (author)

Physics and quality assurance for brachytherapy - Part I: High dose rates

International Nuclear Information System (INIS)

Anderson, Lowell L.

1997-01-01

Purpose: To review the physical aspects of high dose rate (HDR) brachytherapy, including commissioning and quality assurance, source calibration and dose distribution measurements, and treatment planning methods. Following the introduction of afterloading in brachytherapy, development efforts to make it 'remote' culminated in 1964 with the near-simultaneous appearance of remote afterloaders in five major medical centers. Four of these machines were 'high dose rate', three employing 60Co and one (the GammaMed) using a single, cable-mounted 192Ir source. Stepping-motor source control was added to the GammaMed in 1974, making it the precursor of modern remote afterloaders, which are now suitable for interstitial, well as intracavitary brachytherapy by virtue of small source-diameter and indexer-accessed multiple channels. Because the 192Ir sources currently used in HDR remote afterloaders are supplied at a nominal air-kerma strength of 11.4 cGy cm2 s-1 (10 Ci), are not collimated in clinical use, and emit a significant fraction (15%) of photons at energies greater than 600 keV, shielding and facility design must be undertaken as carefully and thoroughly as for external beam installations. Licensing requirements of regulatory agencies must be met with respect both to maximum permissible dose limits and to the existence and functionality of safety devices (door interlocks, radiation monitors, etc.). Commissioning and quality assurance procedures that must be documented for HDR remote afterloading relate to (1) machine, applicator, guide-tube, and facility functionality checks, (2) source calibration, (3) emergency response readiness, (4) planning software evaluation, and (5) independent checks of clinical dose calculations. Source calibration checks must be performed locally, either by in-air measurement of air kerma strength or with a well ionization chamber calibrated (by an accredited standards laboratory) against an in-air measurement of air kerma strength for the

Measurement of extrapolation curves for the secondary pattern of beta radiation Nr. 86 calibrated in rapidity of absorbed dose for tissue equivalent by the Physikalisch Technische Bundesanstalt; Medicion de curvas de extrapolacion para el patron secundario de radiacion beta Nr. 86 calibrado en rapidez de dosis absorbida para tejido equivalente por el Physikalisch Technische Bundesanstalt

Energy Technology Data Exchange (ETDEWEB)

Alvarez R, J.T

1988-10-15

The following report has as objective to present the obtained results of measuring - with a camera of extrapolation of variable electrodes (CE) - the dose speed absorbed in equivalent fabric given by the group of sources of the secondary pattern of radiation Beta Nr. 86, (PSB), and to compare this results with those presented by the calibration certificates that accompany the PSB extended by the primary laboratory Physikalisch Technische Bundesanstalt, (PTB), of the R.F.A. as well as the uncertainties associated to the measure process. (Author)

Automation of dosimeters calibration for radiotherapy in secondary dosimetric calibration laboratory of the CPHR

International Nuclear Information System (INIS)

Acosta, Andy L. Romero; Lores, Stefan Gutierrez

2013-01-01

This paper presents the design and implementation of an automated system for measurements in the calibration of reference radiation dosimeters. It was made a software application that performs the acquisition of the measured values of electric charge, calculated calibration coefficient and automates the calibration certificate issuance. These values are stored in a log file on a PC. The use of the application improves control over the calibration process, helps to humanize the work and reduces personnel exposure. The tool developed has been applied to the calibration of dosimeters radiation patterns in the LSCD of the Centro de Proteccion e Higiene de las Radiaciones, Cuba

Quality assurance regime for the fabrication and calibration of ambient dose rate measuring instruments with proportional counters

International Nuclear Information System (INIS)

Schloesser, H.

1997-01-01

The proportional detectors FHZ 600A and FHZ 601A serve as examples to illustrate the quality assurance regime applied in fabrication and operation of the detector. Calibration is done by a licensed establishment connected to the standard 137 Cs calibration source at PTB. In addition to the basic calibration, the intrinsic selfdosing effect of the device and its response to cosmic radiation are known and can be taken into account in interpretations of measured results. The individual calibration of the intelligent probes of type FHZ 601A achieves a yet better measuring accuracy at higher dose rates, as compared to the basic calibration and performance of the FHZ 600A probes, as was shown by a type approval test. The paper also shows that control measurements and ''intelligent'' measuring systems with integrated checking routines improve the measuring reliability. (orig./CB) [de

Calibration of ratemeters used for gamma radiation detection

International Nuclear Information System (INIS)

Hantanirina, P.A.

2017-01-01

The Secondary Standard Dosimetry Laboratory (SSDL) of INSTN-Madagascar is in charge of the calibration of every dosimetry measurement instrument in hospitals and companies using radioactive sources in Madagascar. It has a secondary standard delivered and calibrated by a Primary Standard Laboratory in Dosimetry (PSLD). This standard is used to compare its reference values with those displayed on the instruments to be calibrated. During our training period, three (3) ratemeters were calibrated, the Graetz X5DE, the Graetz X5C and the Identifinder 2. We have determined the calibration factor for every ratemeter by doing calculation with the reference value. By using the three surveymeters for direct radiations measurements, it has been found that the difference between the displayed values and the real values for every ratemeter does not exceed the tolerance limit which is 20 %. Then we can conclude that these ratemeters are still in good condition of functioning. Concerning the calibration factor curve N_k with the K_a_i_r , we can observe that for the Graetz X5C ratemeter, this curve is almost constant. As well as for the linearity, it is still the Graetz X5C ratemeter which is linear almost integrally for the measured and calculated dose rate values. So we can say that this ratemeter is the most recommended for the radiations measurements.This work which has been carried within the framework of collaboration between the section PNAE (Physique Nucléaire Appliquée et Environnement) of the University of Antananarivo and INSTN-Madagascar has been a good and rewarding experience which allowed us to put into practice all knowledges acquired during our years of studies. [fr

Estimated of associated uncertainties of the linearity test of dose calibrators

International Nuclear Information System (INIS)

Sousa, Carlos H.S.; Peixoto, Jose G.P.

2013-01-01

Activimeters determine the activity of radioactive samples and them are validated by performance tests. This research determined the expanded uncertainties associated to the linearity test. Were used three dose calibrators and three sources of 99 Tc m for testing using recommended protocol by the IAEA, which considered the decay of radioactive samples. The expanded uncertainties evaluated were not correlated with each other and their analysis considered a rectangular probability distribution. The results are also presented in graphical form by the function of normalized activity measured in terms of conventional true value. (author)

Variable transformation of calibration equations for radiation dosimetry

International Nuclear Information System (INIS)

Watanabe, Yoichi

2005-01-01

For radiation dosimetry, dosimetric equipment must be calibrated by using known doses. The calibration is done to determine an equation that relates the absorbed dose to a physically measurable quantity. Since the calibration equation is accompanied by unavoidable uncertainties, the doses estimated with such equations suffer from inherent uncertainties. We presented mathematical formulation of the calibration when the calibration relation is either linear or nonlinear. We also derived equations for the uncertainty of the estimated dose as a function of the uncertainties of the parameters in the equations and the measured physical quantity. We showed that a dosimeter with a linear calibration equation with zero dose-offset enables us to perform relative dosimetry without calibration data. Furthermore, a linear equation justifies useful data manipulations such as rescaling the dose and changing the dose-offset for comparing dose distributions. Considering that some dosimeters exhibit linear response with a large dose-offset or often nonlinear response, we proposed variable transformations of the measured physical quantity, namely, linear- and log-transformation methods. The proposed methods were tested with Kodak X-Omat V radiographic film and BANG (registered) polymer gel dosimeter. We demonstrated that the variable transformation methods could lead to linear equations with zero dose-offset and could reduce the uncertainty of the estimated dose

Jaws calibration method to get a homogeneous distribution of dose in the junction of hemi fields

International Nuclear Information System (INIS)

Cenizo de Castro, E.; Garcia Pareja, S.; Moreno Saiz, C.; Hernandez Rodriguez, R.; Bodineau Gil, C.; Martin-Viera Cueto, J. A.

2011-01-01

Hemi fields treatments are widely used in radiotherapy. Because the tolerance established for the positioning of each jaw is 1 mm, may be cases of overlap or separation of up to 2 mm. This implies heterogeneity of doses up to 40% in the joint area. This paper presents an accurate method of calibration of the jaws so as to obtain homogeneous dose distributions when using this type of treatment. (Author)

Calibrating page sized Gafchromic EBT3 films

Energy Technology Data Exchange (ETDEWEB)

Crijns, W.; Maes, F.; Heide, U. A. van der; Van den Heuvel, F. [Department of Radiation Oncology, University Hospitals Leuven, Herestraat 49, 3000 Leuven (Belgium); Department ESAT/PSI-Medical Image Computing, Medical Imaging Research Center, KU Leuven, Herestraat 49, 3000 Leuven (Belgium); Department of Radiation Oncology, The Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Plesmanlaan 121, 1066 CX Amsterdam (Netherlands); Department of Radiation Oncology, University Hospitals Leuven, Herestraat 49, 3000 Leuven (Belgium)

2013-01-15

Purpose: The purpose is the development of a novel calibration method for dosimetry with Gafchromic EBT3 films. The method should be applicable for pretreatment verification of volumetric modulated arc, and intensity modulated radiotherapy. Because the exposed area on film can be large for such treatments, lateral scan errors must be taken into account. The correction for the lateral scan effect is obtained from the calibration data itself. Methods: In this work, the film measurements were modeled using their relative scan values (Transmittance, T). Inside the transmittance domain a linear combination and a parabolic lateral scan correction described the observed transmittance values. The linear combination model, combined a monomer transmittance state (T{sub 0}) and a polymer transmittance state (T{sub {infinity}}) of the film. The dose domain was associated with the observed effects in the transmittance domain through a rational calibration function. On the calibration film only simple static fields were applied and page sized films were used for calibration and measurements (treatment verification). Four different calibration setups were considered and compared with respect to dose estimation accuracy. The first (I) used a calibration table from 32 regions of interest (ROIs) spread on 4 calibration films, the second (II) used 16 ROIs spread on 2 calibration films, the third (III), and fourth (IV) used 8 ROIs spread on a single calibration film. The calibration tables of the setups I, II, and IV contained eight dose levels delivered to different positions on the films, while for setup III only four dose levels were applied. Validation was performed by irradiating film strips with known doses at two different time points over the course of a week. Accuracy of the dose response and the lateral effect correction was estimated using the dose difference and the root mean squared error (RMSE), respectively. Results: A calibration based on two films was the optimal

A program on quality assurance and dose calibration for radiation therapy units in Venezuela

International Nuclear Information System (INIS)

Padilla, M.C. de; Carrizales, L.; Diaz, J.; Gutt, F.; Cozman, A.

1996-01-01

The results of a five year program (1988-90-91-92-93) on quality assurance and dose calibration for 12 Cobalt-60 units from public hospitals, which represents 30% of total radiation therapy units in Venezuela, are presented. The remarkable improvement in the general performance of these units can be seen in the IAEA/WHO Postal TLD Intercomparison results which gave 100% within ± 5% in 1990 and 1992, while 63% in 1990 and 44% in 1992, with errors up to 37% were obtained for the participants not included in the program. The difference between the two groups lead the government to decrete through the Gaceta Oficial de la Republica de Venezuela, Resolution G-1397 on March 3, 1993, the quality assurance and dose calibration programs shall be established for all radiation therapy installations in Venezuela. The project for the standards was developed by the SSDL physicists and it was already approbated by the Health Ministry. It is expected that the Norms will enter into effect by the end of 1994. (author). 14 refs, 1 fig., 3 tabs

A program on quality assurance and dose calibration for radiation therapy units in Venezuela

Energy Technology Data Exchange (ETDEWEB)

Padilla, M.C. de; Carrizales, L; Diaz, J; Gutt, F; Cozman, A [Instituto Venezolano de Investigaciones Cientificas, Caracas (Venezuela). Lab. de Calibracion Dosimetrica

1996-08-01

The results of a five year program (1988-90-91-92-93) on quality assurance and dose calibration for 12 Cobalt-60 units from public hospitals, which represents 30% of total radiation therapy units in Venezuela, are presented. The remarkable improvement in the general performance of these units can be seen in the IAEA/WHO Postal TLD Intercomparison results which gave 100% within {+-} 5% in 1990 and 1992, while 63% in 1990 and 44% in 1992, with errors up to 37% were obtained for the participants not included in the program. The difference between the two groups lead the government to decrete through the Gaceta Oficial de la Republica de Venezuela, Resolution G-1397 on March 3, 1993, the quality assurance and dose calibration programs shall be established for all radiation therapy installations in Venezuela. The project for the standards was developed by the SSDL physicists and it was already approbated by the Health Ministry. It is expected that the Norms will enter into effect by the end of 1994. (author). 14 refs, 1 fig., 3 tabs.

Quality control tests in dose calibrators used in research laboratories of IPEN

International Nuclear Information System (INIS)

Kuahara, Lilian T.; Junior, Amaury C.R.; Martins, Elaine W.; Dias, Carla R.; Correa, Eduardo de L.; Potiens, Maria da Penha A.

2013-01-01

The aim of this study was to do the intercomparison between two dose calibrators used in research laboratories at IPEN-CNEN / SP, one being the Capinted NPL-CRC, of the Laboratorio de Calibracao de Instrumentos (LCI) do IPEN, and the other Capintec CRC-15R of the Centro de Radiofarmacia (CR). The standard sources used for carrying out the comparing tests between the two laboratories were 57 Co, 133 Ba and the 13 7 C s

The measurement of exposure rate and absorbed dose for photons of 6 to 7 MeV

International Nuclear Information System (INIS)

Birchall, I.

1978-01-01

Using the 16 N source at the Universities Reactor Centre, which provides a source of high energy photons of 6 and 7 MeV, experiments have been carried out to provide a calibration point for secondary standard and general survey instruments. The source was designed primarily for shielding experiments and suffers from a number of disadvantages if precise dose or exposure data are required. In particular the exposure rate is low, the source is physically large and the energy spectrum is contaminated with lower energy photons. A summary of the basic techniques is given because of the inherent difficulties in dose measurements particularly for high energy photons. (author)

Collateral patient doses in the Varian 21iX radiotherapy Linac

International Nuclear Information System (INIS)

Barquero, R.; Castillo, A. del

2008-01-01

Full text: The radiotherapy aim is to irradiate the patient tumor cells while the doses in healthy tissue remains as low as possible. Nevertheless, when high photon energy accelerators are used, collateral undesired photon and neutron doses are always implied during the treatments and became more important with the new accelerators and techniques as IMRT. To assess secondary cancer risk outside the treatment volume as a long-term medical consequence of treatments, the total doses received by each patient outside the primary field during his treatment must be estimated. To achieve this purpose photon and neutron dose equivalents Hp(10) and H*(10) has been measured in a new Varian 21iX with maximum photon energy of 15 MV placed recently in our radiotherapy department. Three devices: 1) a neutron dose rate meter BERTHOLD LB 4111 calibrated recently in the German PTB laboratory, 2) a calibrated environmental pressurized photon ionization chamber (IC) VICTOREEN 450-PI n/s 1020, and 3) a calibrated personal electronic photon dosimeter GAMMACOM 4200M, were placed above the treatment couch outside the primary field while the Varian 21iX reference test were done. In particular the photon and neutron doses in the couch were measured while a water phantom was irradiated during automatic beam data acquisition for a 15 MV beam. A complete set of measurements changing field size are made. These 15 MV results are compared with data measured previously by thermoluminescence and bubble dosimeters in the same facility for an Elekta Precise and a Siemens KDS both with maximum photon energy of 18 MV. From this the benefits in the patient collateral doses of decreasing the maximum treatment photon energy are discussed. The patient doses obtained in the Varian 21iX had values that go from 80 to 800 uSv per treatment Gray. As the Varian 21iX therapy Linac is operated in pulsed mode with short pulse length the discussion of the results includes: 1. The correction of dead time in the GM

Determination of absorbed dose calibration factors for therapy level electron beam ionization chambers.

Science.gov (United States)

McEwen, M R; Williams, A J; DuSautoy, A R

2001-03-01

Over several years the National Physical Laboratory (NPL) has been developing an absorbed dose calibration service for electron beam radiotherapy. To test this service, a number of trial calibrations of therapy level electron beam ionization chambers have been carried out during the last 3 years. These trials involved 17 UK radiotherapy centres supplying a total of 46 chambers of the NACP, Markus, Roos and Farmer types. Calibration factors were derived from the primary standard calorimeter at seven energies in the range 4 to 19 MeV with an estimated uncertainty of +/-1.5% at the 95% confidence level. Investigations were also carried out into chamber perturbation, polarity effects, ion recombination and repeatability of the calibration process. The instruments were returned to the radiotherapy centres for measurements to be carried out comparing the NPL direct calibration with the 1996 IPEMB air kerma based Code of Practice. It was found that, in general, all chambers of a particular type showed the same energy response. However, it was found that polarity and recombination corrections were quite variable for Markus chambers-differences in the polarity correction of up to 1% were seen. Perturbation corrections were obtained and were found to agree well with the standard data used in the IPEMB Code. The results of the comparison between the NPL calibration and IPEMB Code show agreement between the two methods at the +/-1% level for the NACP and Farmer chambers, but there is a significant difference for the Markus chambers of around 2%. This difference between chamber types is most likely to be due to the design of the Markus chamber.

TU-AB-BRC-12: Optimized Parallel MonteCarlo Dose Calculations for Secondary MU Checks

Energy Technology Data Exchange (ETDEWEB)

French, S; Nazareth, D [Roswell Park Cancer Institute, Buffalo, NY (United States); Bellor, M [Lockheed Martin, Manassas, VA (United States)

2016-06-15

Purpose: Secondary MU checks are an important tool used during a physics review of a treatment plan. Commercial software packages offer varying degrees of theoretical dose calculation accuracy, depending on the modality involved. Dose calculations of VMAT plans are especially prone to error due to the large approximations involved. Monte Carlo (MC) methods are not commonly used due to their long run times. We investigated two methods to increase the computational efficiency of MC dose simulations with the BEAMnrc code. Distributed computing resources, along with optimized code compilation, will allow for accurate and efficient VMAT dose calculations. Methods: The BEAMnrc package was installed on a high performance computing cluster accessible to our clinic. MATLAB and PYTHON scripts were developed to convert a clinical VMAT DICOM plan into BEAMnrc input files. The BEAMnrc installation was optimized by running the VMAT simulations through profiling tools which indicated the behavior of the constituent routines in the code, e.g. the bremsstrahlung splitting routine, and the specified random number generator. This information aided in determining the most efficient compiling parallel configuration for the specific CPU’s available on our cluster, resulting in the fastest VMAT simulation times. Our method was evaluated with calculations involving 10{sup 8} – 10{sup 9} particle histories which are sufficient to verify patient dose using VMAT. Results: Parallelization allowed the calculation of patient dose on the order of 10 – 15 hours with 100 parallel jobs. Due to the compiler optimization process, further speed increases of 23% were achieved when compared with the open-source compiler BEAMnrc packages. Conclusion: Analysis of the BEAMnrc code allowed us to optimize the compiler configuration for VMAT dose calculations. In future work, the optimized MC code, in conjunction with the parallel processing capabilities of BEAMnrc, will be applied to provide accurate

Evaluation of secondary exposure doses to transportation and medical personnel in the radiation emergency medicine

International Nuclear Information System (INIS)

Kato, Hideki; Suzuki, Shoichi; Koga, Sukehiko; Mukoyama, Takashi; Tomatsu, Hirotaka; Suzuki, Yusuke

2009-01-01

Radionuclide contamination is one of the accidents that might occur while carrying out a periodical inspection of nuclear power stations during normal reactor operation. When such an accident occurs, rescue and medical personnel, involved in transporting and treating affected workers run the risk of exposure to secondary radiation. In this study, the ambient dose equivalent rate at a certain distance from the surface of the human body contaminated with typical radioactive corrosion products was calculated. Further, the relationships among the adhesion area, contamination density, and secondary exposure dose were clarified. The secondary exposure dose and permissible working hours in a radiation emergency medicine were estimated by presenting these relationships in the form of a chart and by specifying the contamination levels. (author)

Low dose versus high dose anti-snake venom therapy in the treatment of haematotoxic snake bite in South India.

Science.gov (United States)

Joseph, Imanto M; Kuriakose, Cijoy K; Dev, Anand Vimal; Philip, George A

2017-10-01

Most of the studies on the appropriate dose of anti-snake venom (ASV) are from tertiary hospitals and the guidelines are unclear. Our observational study compared the outcomes of two prevalent treatment regimes for haematotoxic snake bite in a secondary care hospital in South India. The time to normalisation of whole blood clotting time, mortality and complications were not different between the groups. The average dose of ASV required in the low and high dose groups were 106 mL and 246 mL, respectively. Consequently, patients who received low dose ASV incurred approximately 50% less expense. Urticarial rashes were also significantly fewer in the low dose group.

Calibration procedures for mammography dosemeters in Poland

International Nuclear Information System (INIS)

Gwiazdowska, B.; Ulkowski, P.; Tolwinski, J.; Bulski, W.

2002-01-01

Breast cancer is the most frequent tumour in women and the effectiveness of the treatment depends dramatically on the early detection of the disease. That is the reason why in Poland the mammography control examinations are strongly supported by the Centre of Oncology. In Poland there are over 400 mammography units which account for about 300,000 examinations per year. An investigation performed by the Medical Physics Department of the Centre of Oncology in Warsaw at about 100 mammography facilities proved that in most cases the doses absorbed by the patients could be reduced without decrease of image quality. This is one of the reasons why the Polish Secondary Standard Dosimetry Laboratory (SSDL) dealing mainly with calibration of radiotherapy dosemeters is extending its activities and therefore new facilities and equipment adapted for calibration of mammographic dosemeters have been installed. The mammography dosimetry calibration equipment is permanently installed in the same laboratory room where the radiotherapy dosemeters are calibrated. A base of a mammography unit no longer in clinical use, together with its movable system has been adapted to handle ionization chamber holders. An X-ray tube with a 50 kV high frequency generator was also installed. The tube, a Varian type OEG-50-2, (designed for laboratory applications) with molybdenum anode of an anode angle 23,7 deg. and with a large focus, effective size approximately 5 mm 2 , has an inherent filtration of 0,25 mm beryllium. It is installed in a housing with 2mm lead shielding; a cone shaped beam is formed by a system of three collimators

Usefulness assessment of secondary shield for the lens exposure dose reduction during radiation treatment of peripheral orbit

International Nuclear Information System (INIS)

Kwak, Yong Kuk; Hong, Sun Gi; Ha, Min Yong; Park, Jang Pil; Yoo, Sook Hyun; Cho, Woong

2015-01-01

This study presents the usefulness assessment of secondary shield for the lens exposure dose reduction during radiation treatment of peripheral orbit. We accomplished IMRT treatment plan similar with a real one through the computed treatment planning system after CT simulation using human phantom. For the secondary shield, we used Pb plate (thickness 3mm, diameter 25mm) and 3 mm tungsten eye-shield block. And we compared lens dose using OSLD between on TPS and on simulation. Also, we irradiated 200 MU(6 MV, SPD(Source to Phantom Distance)=100 cm, F·S 5×5 cm)on a 5 cm acrylic phantom using the secondary shielding material of same condition, 3 mm Pb and tungsten eye-shield block. And we carried out the same experiment using 8 cm Pb block to limit effect of leakage and transmitted radiation out of irradiation field. We attached OSLD with a 1cm away from the field at the side of phantom and applied a 3mm bolus equivalent to the thickness of eyelid. Using human phantom, the Lens dose on IMRT treatment plan is 315.9 cGy and the real measurement value is 216.7 cGy. And after secondary shield using 3mm Pb plate and tungsten eye-shield block, each lens dose is 234.3, 224.1 cGy. The result of a experiment using acrylic phantom, each value is 5.24, 5.42 and 5.39 cGy in case of no block, 3mm Pb plate and tungsten eye-shield block. Applying O.S.B out of the field, each value is 1.79, 2.00 and 2.02 cGy in case of no block, 3 mm Pb plate and tungsten eye-shield block. When secondary shielding material is used to protect critical organ while irradiating photon, high atomic number material (like metal) that is near by critical organ can be cause of dose increase according to treatment region and beam direction because head leakage and collimator and MLC transmitted radiation are exist even if it's out of the field. The attempt of secondary shield for the decrease of exposure dose was meaningful, but untested attempt can have a reverse effect. So, a preliminary inspection

Characterization of TLD-100 in powders for dosimetric quality control of 192 Ir sources used in brachytherapy of high dose rate

International Nuclear Information System (INIS)

Loaiza C, S.P.

2007-01-01

The Secondary Standard Dosimetric at the National Institute of Nuclear Research (ININ) calibrated a lot of powdered TLD-100 (LiF:Mg,Ti) in terms of absorbed dose to water D w for the energy of: 60 Co, 137C s, X rays of 250 and 50 kVp. Later on, it is carried out an interpolation of the calibration for the energy of the 192 Ir. This calibration is part of a dosimetric quality control program, to solve the problems of traceability for the measurements carried out by the users of 192 Ir sources employed in the treatments of High Dose Rate Brachytherapy (HDR) at the Mexican Republic. The calibrations of the radiation beams are made with the following protocols: IAEA TRS-398 for the 60 Co for D w , using a secondary standard ionization chamber PTW N30013 calibrated in D w by the National Research Council (NRC, Canada). AAPM TG-43 for D w in terms of the strength kerma Sk, calibrating this last one quantity for the 137 Cs radioactive source, with a well chamber HDR 1000 PLUS traceable to the University of Wisconsin (US). AAPM TG-61 for X ray of 250 and 50 kVp for D w start to Ka using field standard a Farmer chamber PTW 30001 traceable to K for the Central Laboratory of Electric Industries (CLEI, France). The calibration curves (CC) they built for the response of the powder TLD: R TLD vs D w : For the energy of 60 Co, 137 Cs, X rays of 250 and 50 kVp. Fitting them with the least square method weighed by means of a polynomial of second grade that corrects the supra linearity of the response. iii. Each one of the curves was validated with a test by lack of fitting and for the Anderson Darling normality test, using the software MINITAB in both cases. iv. The sensibility factor (F s ) for each energy corresponds to the slope of the CC, v. The F s for the two 192 Ir sources used are interpolated: one for a Micro Selectron source and the other one a Vari Source source. Finally, a couple of capsules were sent to two hospitals that have the HDR Brachytherapy with sources of 192

Quality control of radiopharmaceutical dose calibrators in nuclear medicine unit

International Nuclear Information System (INIS)

Oliveira, C.F.M.; Lucindo Junior, C.R.; Lopes Filho, F.J.

2015-01-01

As part of the program to ensure quality in nuclear medicine unit, in addition to diagnostic procedures, are evaluated activity meters, which is intended to measure the aliquot of radiation of radionuclides and / or radiopharmaceuticals that are administered to patients undergoing diagnostic investigation and / or therapeutic treatment. The good operating condition of dose calibrators is essential to ensure efficiency, safety and reliability of the measurements, once the lack of accuracy in the responses of these equipments can cause significant errors in the activity administered to the patient and may result in poor quality images resulting in the repetition of examis and interference in the successful treatment of the patient. This study aims to, considering the need for constant evaluation of the functioning of the activity meters and the fact that this issue be part the responsibilities of the professional of radiology, perform quality control testing of these instruments in relation to the most recent norm of National Commission of nuclear Energy (CNEN-NN 3:05) in Brazil, that is also in according to the international standards and reference values established during acceptance testing of these instruments in a nuclear medicine service. For this, was made a review of specific literature and the use of barium, cobalt and cesium to the tests in a nuclear medicine service of the state of Pernambuco in Brazil. The obtained results of the specific tests utilized to verify the correct working of the dose calibrators show coherency with the resolutions of the CNEN-NN 3:05 and are also in agreement with the international standards to that the measurement of activities be made with accurate results and thereby contribute to the proper functioning of nuclear medicine service. (authors)

Characterization of different qualities in X-rays, for instruments calibration in radiological protection

International Nuclear Information System (INIS)

Cejudo A, J.; Tovar M, V. M.; Vergara M, F.

2010-09-01

In the Secondary Laboratory of Dosimetric Calibration in Mexico was realized the qualities characterization of the series X-rays RQR reported in the International Code of Practices in Dosimetry and Diagnostic Radiology No. 457, using attenuator filters of high purity aluminum and ionizing radiation equipment of inherent filtration of 4 mm Be with and emergent X-radiation beam of 40 grades. For the attenuation was used a geometric arrangement with three beam limiters and a monitor camera prepared on the established form in the mentioned technical report, and a spherical ionization chamber with collection volume of 3.6 cm 3 , aligning its geometric center with the focus of X-rays tube to get that the incident radiation direction will be perpendicular to the ionization chamber. From the perspective of the radiological protection is important to know the X-radiation quality for the application dedicated to the instruments calibration and can to give to these the traceability to a reference laboratory, this way the quality combination and reference chamber can give as a result a procedure for the evaluation of the entrance in surface dose to estimate the dose orientate levels, specified in the basic standards of safety. (Author)

Neutron dose measurements of Varian and Elekta linacs by TLD600 and TLD700 dosimeters and comparison with MCNP calculations.

Science.gov (United States)

Nedaie, Hassan Ali; Darestani, Hoda; Banaee, Nooshin; Shagholi, Negin; Mohammadi, Kheirollah; Shahvar, Arjang; Bayat, Esmaeel

2014-01-01

High-energy linacs produce secondary particles such as neutrons (photoneutron production). The neutrons have the important role during treatment with high energy photons in terms of protection and dose escalation. In this work, neutron dose equivalents of 18 MV Varian and Elekta accelerators are measured by thermoluminescent dosimeter (TLD) 600 and TLD700 detectors and compared with the Monte Carlo calculations. For neutron and photon dose discrimination, first TLDs were calibrated separately by gamma and neutron doses. Gamma calibration was carried out in two procedures; by standard 60Co source and by 18 MV linac photon beam. For neutron calibration by (241)Am-Be source, irradiations were performed in several different time intervals. The Varian and Elekta linac heads and the phantom were simulated by the MCNPX code (v. 2.5). Neutron dose equivalent was calculated in the central axis, on the phantom surface and depths of 1, 2, 3.3, 4, 5, and 6 cm. The maximum photoneutron dose equivalents which calculated by the MCNPX code were 7.06 and 2.37 mSv.Gy(-1) for Varian and Elekta accelerators, respectively, in comparison with 50 and 44 mSv.Gy(-1) achieved by TLDs. All the results showed more photoneutron production in Varian accelerator compared to Elekta. According to the results, it seems that TLD600 and TLD700 pairs are not suitable dosimeters for neutron dosimetry inside the linac field due to high photon flux, while MCNPX code is an appropriate alternative for studying photoneutron production.

Dose intercomparison studies for standardization of high-dose dosimetry in Viet Nam

International Nuclear Information System (INIS)

Mai Hoang Hoa; Duong Nguyen Dinh; Kojima, T.

1999-01-01

The Irradiation Center of the Vietnam Atomic Energy Commission (IC-VAEC) is planning to establish a traceability system for high-dose dosimetry and to provide high-dose standards as a secondary standard dosimetry laboratory (SSDL) level in Vietnam. For countries which do not have a standard dosimetry laboratory, the participation in the International Dose Assurance Service (IDAS) operated by the International Atomic Energy Agency (IAEA) is the most common means to verify own dosimetry performance with a certain uncertainty. This is, however, only one-direction dose intercomparison with evaluation by IAEA including unknown parameter at participant laboratories. The SSDL level laboratory should have traceability as well as compatibility, ability to evaluate uncertainties of its own dosimetry performance by itself In the present paper, we reviewed our dosimetry performance through two-way dose intercomparison studies and self-evaluation of uncertainty in our dosimetry procedure. The performance of silver dichromate dosimeter as reference transfer dosimeter in IC-VAEC was studied through two-way blind dose intercomparison experiments between the IC-VAEC and JAERI. As another channel of dose intercomparison with IAEA, alanine dosimeters issued by IDAS were simultaneously irradiated with the IC-VAEC dichromate dosimeters at IC-VAEC and analyzed by IAEA. Dose intercomparison between IC-VAEC and JAERI results into a good agreement (better than ±2.5%), and IDAS results also show similar agreement within ±3.0%. The uncertainty was self-estimated on the basis of the JAERI alanine dosimetry, and a preliminary value of about 1.86% at a 68% confidence level is established. The results from these intercomparisons and our estimation of the uncertainty are consistent. We hope that our experience is valuable to other countries which do not have dosimetry standard laboratories and/or are planning to establish them. (author)

Development of dose calibrators Tandem systems and establishment of beta dosimetry in nuclear medicine

International Nuclear Information System (INIS)

Cecatti, Sonia Garcia Pereira

2004-01-01

A quality control program at Nuclear Medicine Services includes the checking of all equipment used for diagnostics and treatment, and the individual monitoring of the workers occupationally exposed to ionizing radiations. In this work the main quality control tests were performed with three dose calibrators using standard radiation sources of 57 Co, 133 Ba, 137 Cs and 60 Co. Tandem systems of dose calibrators were established and characterized using four cylindrical absorbers of different materials for an additional quality control test in Nuclear Medicine. The main utility of this new test is the possibility of impurity detection in radiopharmaceuticals, when the ratio of the measurements with different absorbers is different from that obtained at the laboratory in ideal conditions. The dosimetric characteristics of three types of CaS0 4 :Dy + Teflon pellets were studied for an appropriate choice of the material to be used for individual monitoring of workers. The thermoluminescent detectors were irradiated using beta sources of 90 Sr+ 90 Y, 204 TI, 147 Pm, 153 Sm and 32 P. A wrist badge for beta individual monitoring was developed for workers that handle beta radiopharmaceuticals in Nuclear Medicine Services. (author)

Calibration procedures of area monitors in terms of the Ambient Dose Equivalent H*(10), for gamma, x-ray radiation fields

International Nuclear Information System (INIS)

Dieguez Davila, L.E.

1998-01-01

In the present thesis procedures for calibrating portable survey meters in terms of the new ICRU quantities H*(10) ambient dose equivalent are discussed. Also the remendations of International Comission on Radiation Protection in their report ICRP 60 that inludes the operational magnitudes that the International Comission of Radiation Units proposed for calibrating area monitors

Advances in absorbed dose measurement standards at the australian radiation laboratory

International Nuclear Information System (INIS)

Boas, J.F.; Hargrave, N.J.; Huntley, R.B.; Kotler, L.H.; Webb, D.V.; Wise, K.N.

1996-01-01

The applications of ionising radiation in the medical and industrial fields require both an accurate knowledge of the amount of ionising radiation absorbed by the medium in question and the capability of relating this to National and International standards. The most useful measure of the amount of radiation is the absorbed dose which is defined as the energy absorbed per unit mass. For radiotherapy, the reference medium is water, even though the measurement of the absorbed dose to water is not straightforward. Two methods are commonly used to provide calibrations in absorbed dose to water. The first is the calibration of the chamber in terms of exposure in a Cobalt-60 beam, followed by the conversion by a protocol into dose to water in this and higher energy beams. The other route is via the use of a graphite calorimeter as a primary standard device, where the conversion from absorbed dose to graphite to absorbed dose in water is performed either by theoretical means making use of cavity ionisation theory, or by experiment where the graphite calorimeter and secondary standard ionisation chamber are placed at scaled distances from the source of the radiation beam (known as the Dose-Ratio method). Extensive measurements have been made at Cobalt-60 at ARL using both the exposure and absorbed dose to graphite routes. Agreement between the ARL measurements and those based on standards maintained by ANSTO and NPL is within ± 0.3%. Absorbed dose measurements have also been performed at ARL with photon beams of nominal energy 16 and 19 MeV obtained from the ARL linac. The validity of the protocols at high photon energies, the validity of the methods used to convert from absorbed dose in graphite to absorbed dose in water and the validity of the indices used to specify the beams are discussed. Brief mention will also be made of the establishment of a calibration facility for neutron monitors at ARL and of progress in the development of ERP dosimetry

Advances in absorbed dose measurement standards at the australian radiation laboratory

Energy Technology Data Exchange (ETDEWEB)

Boas, J.F.; Hargrave, N.J.; Huntley, R.B.; Kotler, L.H.; Webb, D.V.; Wise, K.N. [Australian Radiation Laboratory, Yallambie, VIC (Australia)

1996-12-31

The applications of ionising radiation in the medical and industrial fields require both an accurate knowledge of the amount of ionising radiation absorbed by the medium in question and the capability of relating this to National and International standards. The most useful measure of the amount of radiation is the absorbed dose which is defined as the energy absorbed per unit mass. For radiotherapy, the reference medium is water, even though the measurement of the absorbed dose to water is not straightforward. Two methods are commonly used to provide calibrations in absorbed dose to water. The first is the calibration of the chamber in terms of exposure in a Cobalt-60 beam, followed by the conversion by a protocol into dose to water in this and higher energy beams. The other route is via the use of a graphite calorimeter as a primary standard device, where the conversion from absorbed dose to graphite to absorbed dose in water is performed either by theoretical means making use of cavity ionisation theory, or by experiment where the graphite calorimeter and secondary standard ionisation chamber are placed at scaled distances from the source of the radiation beam (known as the Dose-Ratio method). Extensive measurements have been made at Cobalt-60 at ARL using both the exposure and absorbed dose to graphite routes. Agreement between the ARL measurements and those based on standards maintained by ANSTO and NPL is within {+-} 0.3%. Absorbed dose measurements have also been performed at ARL with photon beams of nominal energy 16 and 19 MeV obtained from the ARL linac. The validity of the protocols at high photon energies, the validity of the methods used to convert from absorbed dose in graphite to absorbed dose in water and the validity of the indices used to specify the beams are discussed. Brief mention will also be made of the establishment of a calibration facility for neutron monitors at ARL and of progress in the development of ERP dosimetry.

Fourth IRMF comparison of calibrations of portable gamma-ray dose- rate monitors 2001-2002 Ionising radiation

CERN Document Server

Lewis, V E

2002-01-01

The Ionising Radiations Metrology Forum (IRMF) organised a fourth comparison of calibrations of gamma-ray dose-rate monitors in which fifteen establishments in the UK participated. The exercise involved the circulation of three gamma-ray monitors for calibration in the fields produced using sup 1 sup 3 sup 7 Cs, sup 2 sup 4 sup 1 Am and sup 6 sup 0 Co. The instruments used were an Electra with MC 20 probe, a Mini-Instruments Mini-rad 1000 and a Siemens electronic personal dosemeter Mk 2 (EPD). The responses relative to 'true' dose equivalent rate were calculated by the individual participants and submitted to the for analysis along with details of the facilities and fields employed. Details of the estimated uncertainties were also reported. The results are compared and demonstrate generally satisfactory agreement between the participating establishments. However, the participants' treatment of uncertainties needs improvement and demonstrates a need for guidance in this area.

Characterization of thermal neutron fields for calibration of neutron monitors in accordance with great equivalent dose environment H⁎(10)

International Nuclear Information System (INIS)

Silva, Larissa P. S. da; Silva, Felipe S.; Fonseca, Evaldo S.; Patrao, Karla C.S.; Pereira, Walsan W.

2017-01-01

The Laboratório Brasileiro de Nêutrons do Instituto de Radioproteção e Dosimetria (IRD/CNEN) has developed and built a thermal neutron flux facility to provide neutron fluence for dosimeters (Astuto, 2014). This fluency is obtained by four 16 Ci sources 241 AmBe (α, n) positioned around the channel positioned in the center of the Thermal Flow Unit (UFT). The UFT was built with blocks of paraffin with graphite addition and graphite blocks of high purity to obtain a central field with a homogeneous thermal neutron fluence for calibration purposes with the following measurements: 1.2 x 1.2 x 1.2 m 3 . The objective of this work is to characterize several points, in the thermal energy range, in terms of the equivalent ambient dose quantity H⁎(10) for calibration and irradiation of monitors neutrons

Control of absorbed dose in radiotherapy with 60 Co units

International Nuclear Information System (INIS)

Penchev, V.; Constantinov, B.; Buchakliev, Z.

2000-01-01

A Network for External Quality Audit has been developed and established in Bulgaria by the Secondary Standard Dosimetry Laboratory (SSDL) - Sofia. The results prove the usefulness of the TL Postal Dose programme in helping Bulgarian radiotherapy departments improve and maintain the consistency of patient doses in clinically acceptable level. The participation of the SSDL-Sofia in the IAEA Quality Audit Programme confirms the quite satisfactory accuracy of the therapy level dose measurements and determination achieved. The role of the SSDL is critical in providing traceable calibration to hospitals

Measurement of high dose rates of 60Co by gamma activation of115In and 111Cd foils

International Nuclear Information System (INIS)

Haddad, Kh; Qattan, M.; Taleb, A.

2009-12-01

The high gamma dose rate measurement technique using nuclear reaction (γ,(γ ' ') was introduced in this work. This technique is cheap, easy, reliable, and independent of chemical and physical factors, which affect other techniques. The response to the absorbed dose in this technique is linear and can be used for high dose. Cd and In foils were irradiated using 60 Co source and the resulted isomer activities were measured using gamma spectrometer. These foils were calibrated to be used as dosemeter and its results were compared with conventional one. The dose distribution in the irradiation field was determined using In foils. (authors)

High-precision efficiency calibration of a high-purity co-axial germanium detector

Energy Technology Data Exchange (ETDEWEB)

Blank, B., E-mail: blank@cenbg.in2p3.fr [Centre d' Etudes Nucléaires de Bordeaux Gradignan, UMR 5797, CNRS/IN2P3, Université de Bordeaux, Chemin du Solarium, BP 120, 33175 Gradignan Cedex (France); Souin, J.; Ascher, P.; Audirac, L.; Canchel, G.; Gerbaux, M.; Grévy, S.; Giovinazzo, J.; Guérin, H.; Nieto, T. Kurtukian; Matea, I. [Centre d' Etudes Nucléaires de Bordeaux Gradignan, UMR 5797, CNRS/IN2P3, Université de Bordeaux, Chemin du Solarium, BP 120, 33175 Gradignan Cedex (France); Bouzomita, H.; Delahaye, P.; Grinyer, G.F.; Thomas, J.C. [Grand Accélérateur National d' Ions Lourds, CEA/DSM, CNRS/IN2P3, Bvd Henri Becquerel, BP 55027, F-14076 CAEN Cedex 5 (France)

2015-03-11

A high-purity co-axial germanium detector has been calibrated in efficiency to a precision of about 0.15% over a wide energy range. High-precision scans of the detector crystal and γ-ray source measurements have been compared to Monte-Carlo simulations to adjust the dimensions of a detector model. For this purpose, standard calibration sources and short-lived online sources have been used. The resulting efficiency calibration reaches the precision needed e.g. for branching ratio measurements of super-allowed β decays for tests of the weak-interaction standard model.

Metabolomics by Proton High-Resolution Magic-Angle-Spinning Nuclear Magnetic Resonance of Tomato Plants Treated with Two Secondary Metabolites Isolated from Trichoderma.

Science.gov (United States)

Mazzei, Pierluigi; Vinale, Francesco; Woo, Sheridan Lois; Pascale, Alberto; Lorito, Matteo; Piccolo, Alessandro

2016-05-11

Trichoderma fungi release 6-pentyl-2H-pyran-2-one (1) and harzianic acid (2) secondary metabolites to improve plant growth and health protection. We isolated metabolites 1 and 2 from Trichoderma strains, whose different concentrations were used to treat seeds of Solanum lycopersicum. The metabolic profile in the resulting 15 day old tomato leaves was studied by high-resolution magic-angle-spinning nuclear magnetic resonance (HRMAS NMR) spectroscopy directly on the whole samples without any preliminary extraction. Principal component analysis (PCA) of HRMAS NMR showed significantly enhanced acetylcholine and γ-aminobutyric acid (GABA) content accompanied by variable amount of amino acids in samples treated with both Trichoderma secondary metabolites. Seed germination rates, seedling fresh weight, and the metabolome of tomato leaves were also dependent upon doses of metabolites 1 and 2 treatments. HRMAS NMR spectroscopy was proven to represent a rapid and reliable technique for evaluating specific changes in the metabolome of plant leaves and calibrating the best concentration of bioactive compounds required to stimulate plant growth.

parameters affecting the calibration uniformity and traceability of gamma measuring devices

International Nuclear Information System (INIS)

Youssef, S.K.; Henaish, B.A.

1985-01-01

One of the problems which usually defeats the dosimetric evaluations performed by the health and safety experts is the absence of the reproducibility and accuracy of the used measuring devices systems. Furthermore, the traceability of the dose evaluation done by the users themselves are not achieved. Also the uniformity and homogeneity between the various users dosimeters and that available at specified central organization are not maintained. The present manuscript is scoping to deal with such various problems such as: a) dosimeter accuracy, b) traceability of the various users dosimeters and measuring devices. This paper also suggests a programme for the minimum facilities which are required for operating a central calibration laboratory. the responsibility of that central calibration lab., beside the linking chain between the different users and that calibration lab. are stated and discussed in detail. Furthermore, the authors experiences gained in operating the secondary standards calibration laboratory are also reviewed. 2 fig

Electro-optical equivalent calibration technology for high-energy laser energy meters

Energy Technology Data Exchange (ETDEWEB)

Wei, Ji Feng, E-mail: wjfcom2000@163.com [State Key Laboratory of Precision Measurement Technology and Instrument, Tsinghua University, Beijing 100084 (China); Institute of Applied Electronics, China Academy of Engineering Physics, Mianyang 621900 (China); Graduate School of China Academy of Engineering Physics, Beijing 100088 (China); Key Laboratory of Laser Science and Technology, China Academy of Engineering Physics, Mianyang 621900 (China); Chang, Yan; Zhang, Kai; Hu, Xiao Yang; Zhang, Wei [Institute of Applied Electronics, China Academy of Engineering Physics, Mianyang 621900 (China); Key Laboratory of Laser Science and Technology, China Academy of Engineering Physics, Mianyang 621900 (China); Sun, Li Qun [State Key Laboratory of Precision Measurement Technology and Instrument, Tsinghua University, Beijing 100084 (China)

2016-04-15

Electro-optical equivalent calibration with high calibration power and high equivalence is particularly well-suited to the calibration of high-energy laser energy meters. A large amount of energy is reserved during this process, however, which continues to radiate after power-off. This study measured the radiation efficiency of a halogen tungsten lamp during power-on and after power-off in order to calculate the total energy irradiated by a lamp until the high-energy laser energy meter reaches thermal equilibrium. A calibration system was designed based on the measurement results, and the calibration equivalence of the system was analyzed in detail. Results show that measurement precision is significantly affected by the absorption factor of the absorption chamber and by heat loss in the energy meter. Calibration precision is successfully improved by enhancing the equivalent power and reducing power-on time. The electro-optical equivalent calibration system, measurement uncertainty of which was evaluated as 2.4% (k = 2), was used to calibrate a graphite-cone-absorption-cavity absolute energy meter, yielding a calibration coefficient of 1.009 and measurement uncertainty of 3.5% (k = 2). A water-absorption-type high-energy laser energy meter with measurement uncertainty of 4.8% (k = 2) was considered the reference standard, and compared to the energy meter calibrated in this study, yielded a correction factor of 0.995 (standard deviation of 1.4%).

Systematic Calibration for Ultra-High Accuracy Inertial Measurement Units

Directory of Open Access Journals (Sweden)

Qingzhong Cai

2016-06-01

Full Text Available An inertial navigation system (INS has been widely used in challenging GPS environments. With the rapid development of modern physics, an atomic gyroscope will come into use in the near future with a predicted accuracy of 5 × 10−6°/h or better. However, existing calibration methods and devices can not satisfy the accuracy requirements of future ultra-high accuracy inertial sensors. In this paper, an improved calibration model is established by introducing gyro g-sensitivity errors, accelerometer cross-coupling errors and lever arm errors. A systematic calibration method is proposed based on a 51-state Kalman filter and smoother. Simulation results show that the proposed calibration method can realize the estimation of all the parameters using a common dual-axis turntable. Laboratory and sailing tests prove that the position accuracy in a five-day inertial navigation can be improved about 8% by the proposed calibration method. The accuracy can be improved at least 20% when the position accuracy of the atomic gyro INS can reach a level of 0.1 nautical miles/5 d. Compared with the existing calibration methods, the proposed method, with more error sources and high order small error parameters calibrated for ultra-high accuracy inertial measurement units (IMUs using common turntables, has a great application potential in future atomic gyro INSs.

Secondary leukemia associated with a conventional dose of etoposide: review of serial germ cell tumor protocols.

Science.gov (United States)

Nichols, C R; Breeden, E S; Loehrer, P J; Williams, S D; Einhorn, L H

1993-01-06

Case reports have suggested that treatment with high-dose etoposide can result in development of a unique secondary leukemia. This study was designed to estimate the risk of developing leukemia for patients receiving conventional doses of etoposide along with cisplatin and bleomycin. We reviewed the records at Indiana University of all untreated patients entering clinical trials using etoposide at conventional doses (cumulative dose, 2000 mg/m2 or less) for germ cell cancer between 1982 and 1991. The records of all patients who received a chemotherapy regimen containing etoposide, ifosfamide, or cisplatin after failing to respond to primary chemotherapy were also reviewed. Between 1982 and 1991, 538 patients entered serial clinical trials with planned cumulative etoposide doses of 1500-2000 mg/m2 in combination with cisplatin plus either ifosfamide or bleomycin. Of these 538 patients, 348 received an etoposide combination as initial chemotherapy and 190 received etoposide as part of salvage treatment. To date, 315 patients are alive, with median follow-up of 4.9 years, and 337 patients have had follow-up beyond 2 years. Two patients (0.37%) developed leukemia. One developed acute undifferentiated leukemia with a t(4;11) (q21;q23) cytogenetic abnormality 2.0 years after starting etoposide-based therapy, and one developed acute myelomonoblastic leukemia with no chromosome abnormalities 2.3 years after beginning chemotherapy. During this period, several hundred patients were treated with etoposide-based chemotherapy and did not enter clinical trials. Three of these patients are known to have developed hematologic abnormalities, including one patient with acute monoblastic leukemia with a t(11;19)(q13;p13) abnormality. Secondary leukemia after treatment with a conventional dose of etoposide does occur, but the low incidence does not alter the risk-to-benefit ratio of etoposide-based chemotherapy in germ cell cancer. The reports of leukemia associated with high doses of

The use of a secondary standard x-ray exposure meter to calibrate a field instrument for use in output measurements

International Nuclear Information System (INIS)

1974-11-01

It is stated that the recommended procedures have been closely correlated with ICRU Report 23 (1973), 'Measurements of absorbed dose in a phantom irradiated by a single beam of X- or gamma-rays'. The present report is contained in sections entitled: introduction; equipment and outline of procedures; calibration and use of field instrument in a phantom; calibration and use of the field instrument in air; local reference instrument; summary of recommended procedures. Appendices are entitled: the Perspex Intercomparison Phantom; the implications of applying an in-air calibration factor to readings made in a water phantom. (U.K.)

Evaluation of secondary electron filter for removing contaminant electrons from high-energy 6 MV x-ray beam

International Nuclear Information System (INIS)

Kumagai, Kozo

1988-01-01

When using high energy X-rays, the dose increases at the skin surface and build-up region of beam contamination of secondary electrons coming out from the inner surface of the lineac head. At our radiotherapy department, many cases of external otitis from severe skin reactions, particularly resulting from whole brain irradiation of primary and metastatic brain tumors with a 6 MV X-ray lineac, have been encountered. An investigation was made of the physical aspects of a 6 MV X-ray beam using three electron filters, lead lucite, lead glass and lucite to remove secondary electrons. Transparent materials for filters should be preferable for locating the light field. The following results were obtained: 1) For removing secondary electrons, a lead lucite filter was found best. 2) The lead lucite filter proved most effective for removing secondary electrons from the area of treatment. It reduced the dose of irradiation to the skin surface and build-up region, and furthermore improved the depth dose relative to that without filters. 3) From a clinical standpoint, skin reactions such as external otitis remarkably decreased using a lead lucite filter. 4) It thus appears necessary to use a high energy X-ray with newly designed filters to reduce beam contamination of secondary electrons. (author)

Performance evaluation of commercial radionuclide calibrators in Indonesian hospitals

International Nuclear Information System (INIS)

Candra, Hermawan; Marsoem, Pujadi; Wurdiyanto, Gatot

2012-01-01

Dose calibrator is one of the supporting equipments in the field of nuclear medicine. At the hospitals, dose calibrator is used for activity measurement of radiopharmaceutical before it is administered to patients. Comparison of activity measurements of 131 I and 99m Tc with dose calibrators was organized in Indonesia during 2007–2010 with the the aim of obtaining information dose calibrator performance in the hospitals. Seven Indonesian hospitals participated in this comparison. The measurement results were evaluated using the E n criteria. The result presented in this paper facilitated the evaluation of dose calibrator performance at several hospitals. - Highlights: ► National comparisons of 131 I and 99m Tc radionuclides in Indonesian hospitals. ► Standardization using a Centronic IG11/A20 4πγ Ionization Chamber and participants using commercial radionuclide calibrators. ► Performance radionuclide calibrator in nuclear medicine in Indonesia. ► Measurement of activity of 99m Tc and 131 I was found satisfactory.

SU-E-T-762: Toward Volume-Based Independent Dose Verification as Secondary Check

International Nuclear Information System (INIS)

Tachibana, H; Tachibana, R

2015-01-01

Purpose: Lung SBRT plan has been shifted to volume prescription technique. However, point dose agreement is still verified using independent dose verification at the secondary check. The volume dose verification is more affected by inhomogeneous correction rather than point dose verification currently used as the check. A feasibility study for volume dose verification was conducted in lung SBRT plan. Methods: Six SBRT plans were collected in our institute. Two dose distributions with / without inhomogeneous correction were generated using Adaptive Convolve (AC) in Pinnacle3. Simple MU Analysis (SMU, Triangle Product, Ishikawa, JP) was used as the independent dose verification software program, in which a modified Clarkson-based algorithm was implemented and radiological path length was computed using CT images independently to the treatment planning system. The agreement in point dose and mean dose between the AC with / without the correction and the SMU were assessed. Results: In the point dose evaluation for the center of the GTV, the difference shows the systematic shift (4.5% ± 1.9 %) in comparison of the AC with the inhomogeneous correction, on the other hands, there was good agreement of 0.2 ± 0.9% between the SMU and the AC without the correction. In the volume evaluation, there were significant differences in mean dose for not only PTV (14.2 ± 5.1 %) but also GTV (8.0 ± 5.1 %) compared to the AC with the correction. Without the correction, the SMU showed good agreement for GTV (1.5 ± 0.9%) as well as PTV (0.9% ± 1.0%). Conclusion: The volume evaluation for secondary check may be possible in homogenous region. However, the volume including the inhomogeneous media would make larger discrepancy. Dose calculation algorithm for independent verification needs to be modified to take into account the inhomogeneous correction

Dose calibrators quality controls in Switzerland: six years of experience

International Nuclear Information System (INIS)

Bochud, F.; Spring, Ph.; Baechler, S.; Twerenbold, D.; Linder, R.; Leibundgut, F.

2006-01-01

In Switzerland, the legal use of open radioactive sources in nuclear medicine and the general requirements for quality controls are defined in a federal ordinance. The metrological traceability is guaranteed through a directive of the Swiss metrological office (M.E.T.A.S.) that requires each instrument to be monitored at least once a year through either a verification or an intercomparison. The verification is performed onsite by an accredited laboratory with a set of three gamma sources (Co-57, Cs-137 and Co-60) and - if applicable - a beta source (Sr-90/Y- 90). The intercomparison is made through conventional mail. A source of I-131 or Tc- 99 m is measured both in the nuclear medicine department and in an accredited laboratory. The maximum tolerated error is 10% for gamma sources and 20% for beta sources. This methodology guarantees that the instruments have a correct response for most of the energy range used in practice. Not all nuclides are systematically probed and manufacturers are ultimately responsible for the calibration factors. The precision of the measurements performed in Switzerland is satisfactory with only about 6% of the measurements out of the tolerances. This monitoring also allowed us to improve the skills of the personnel and update the park of instruments by getting rid of dose calibrators displaying old units. (authors)

Dose calibrators quality controls in Switzerland: six years of experience

Energy Technology Data Exchange (ETDEWEB)

Bochud, F.; Spring, Ph.; Baechler, S. [Institut Universitaire de Radiophysique Appliquee, Lausanne (Switzerland); Twerenbold, D. [METAS, Lindenweg 50, Bern-Wabern (Switzerland); Linder, R. [Bundesamt fur Gesundheit, Abteilung Strahlenschutz, Bern (Switzerland); Leibundgut, F. [Raditec radiation and technology, Schoftland (Switzerland)

2006-07-01

In Switzerland, the legal use of open radioactive sources in nuclear medicine and the general requirements for quality controls are defined in a federal ordinance. The metrological traceability is guaranteed through a directive of the Swiss metrological office (M.E.T.A.S.) that requires each instrument to be monitored at least once a year through either a verification or an intercomparison. The verification is performed onsite by an accredited laboratory with a set of three gamma sources (Co-57, Cs-137 and Co-60) and - if applicable - a beta source (Sr-90/Y- 90). The intercomparison is made through conventional mail. A source of I-131 or Tc- 99 m is measured both in the nuclear medicine department and in an accredited laboratory. The maximum tolerated error is 10% for gamma sources and 20% for beta sources. This methodology guarantees that the instruments have a correct response for most of the energy range used in practice. Not all nuclides are systematically probed and manufacturers are ultimately responsible for the calibration factors. The precision of the measurements performed in Switzerland is satisfactory with only about 6% of the measurements out of the tolerances. This monitoring also allowed us to improve the skills of the personnel and update the park of instruments by getting rid of dose calibrators displaying old units. (authors)

Calibration of GafChromic EBT3 for absorbed dose measurements in 5 MeV proton beam and 60Co γ-rays

International Nuclear Information System (INIS)

Vadrucci, M.; Ronsivalle, C.; Marracino, F.; Montereali, R. M.; Picardi, L.; Piccinini, M.; Vincenti, M. A.; Esposito, G.; De Angelis, C.; Cherubini, R.; Pimpinella, M.

2015-01-01

Purpose: To study EBT3 GafChromic film in low-energy protons, and for comparison purposes, in a reference 60 Co beam in order to use it as a calibrated dosimetry system in the proton irradiation facility under construction within the framework of the Oncological Therapy with Protons (TOP)-Intensity Modulated Proton Linear Accelerator for RadioTherapy (IMPLART) Project at ENEA-Frascati, Italy. Methods: EBT3 film samples were irradiated at the Istituto Nazionale di Fisica Nucleare—Laboratori Nazionali di Legnaro, Italy, with a 5 MeV proton beam generated by a 7 MV Van de Graaff CN accelerator. The nominal dose rates used were 2.1 Gy/min and 40 Gy/min. The delivered dose was determined by measuring the particle fluence and the energy spectrum in air with silicon surface barrier detector monitors. A preliminary study of the EBT3 film beam quality dependence in low-energy protons was conducted by passively degrading the beam energy. EBT3 films were also irradiated at ENEA-National Institute of Ionizing Radiation Metrology with gamma radiation produced by a 60 Co source characterized by an absorbed dose to water rate of 0.26 Gy/min as measured by a calibrated Farmer type ionization chamber. EBT3 film calibration curves were determined by means of a set of 40 film pieces irradiated to various doses ranging from 0.5 Gy to 30 Gy absorbed dose to water. An EPSON Expression 11000XL color scanner in transmission mode was used for film analysis. Scanner response stability, intrafilm uniformity, and interfilm reproducibility were verified. Optical absorption spectra measurements were performed on unirradiated and irradiated EBT3 films to choose the most sensitive color channel to the dose range used. Results: EBT3 GafChromic films show an under response up to about 33% for low-energy protons with respect to 60 Co gamma radiation, which is consistent with the linear energy transfer dependence already observed with higher energy protons, and a negligible dose-rate dependence in

Measurement uncertainty. A practical guide for Secondary Standards Dosimetry Laboratories

International Nuclear Information System (INIS)

2008-05-01

The need for international traceability for radiation dose measurements has been understood since the early nineteen-sixties. The benefits of high dosimetric accuracy were recognized, particularly in radiotherapy, where the outcome of treatments is dependent on the radiation dose delivered to patients. When considering radiation protection dosimetry, the uncertainty may be greater than for therapy, but proper traceability of the measurements is no less important. To ensure harmonization and consistency in radiation measurements, the International Atomic Energy Agency (IAEA) and the World Health Organization (WHO) created a Network of Secondary Standards Dosimetry Laboratories (SSDLs) in 1976. An SSDL is a laboratory that has been designated by the competent national authorities to undertake the duty of providing the necessary link in the traceability chain of radiation dosimetry to the international measurement system (SI, for Systeme International) for radiation metrology users. The role of the SSDLs is crucial in providing traceable calibrations; they disseminate calibrations at specific radiation qualities appropriate for the use of radiation measuring instruments. Historically, although the first SSDLs were established mainly to provide radiotherapy level calibrations, the scope of their work has expanded over the years. Today, many SSDLs provide traceability for radiation protection measurements and diagnostic radiology in addition to radiotherapy. Some SSDLs, with the appropriate facilities and expertise, also conduct quality audits of the clinical use of the calibrated dosimeters - for example, by providing postal dosimeters for dose comparisons for medical institutions or on-site dosimetry audits with an ion chamber and other appropriate equipment. The requirements for traceable and reliable calibrations are becoming more important. For example, for international trade where radiation products are manufactured within strict quality control systems, it is

Effects of Different Containers on Radioactivity Measurements using a Dose Calibrator with Special Reference to 111In and 123I.

Science.gov (United States)

Inoue, Yusuke; Abe, Yutaka; Kikuchi, Kei; Miyatake, Hiroki; Watanabe, Atsushi

2017-01-01

Low-energy characteristic x-rays emitted by 111 In and 123 I sources are easily absorbed by the containers of the sources, affecting radioactivity measurements using a dose calibrator. We examined the effects of different containers on the estimated activities. The radioactivities of 111 In, 123 I, 201 Tl, and 99m Tc were measured in containers frequently employed in clinical practice in Japan. The 111 In measurements were performed in the vials A and B of the 111 In-pentetreotide preparation kit and in the plastic syringe. The activities of 123 I-metaiodobenzylguanidine and 201 Tl chloride were measured in the prefilled glass syringes and plastic syringes. The milking vial, vial A, vial B, and plastic syringe were used to assay 99m Tc. For 111 In and 123 I, measurements were performed with and without a copper filter. The filter was inserted into the well of the dose calibrator to absorb low-energy x-rays. The relative estimate was defined as the ratio of the activity estimated with the dose calibrator to the standard activity. The estimated activities varied greatly depending on the container when 111 In and 123 I sources were assayed without the copper filter. The relative estimates of 111 In were 0.908, 1.072, and 1.373 in the vial A, vial B, and plastic syringe, respectively. The relative estimates of 123 I were 1.052 and 1.352 in the glass syringe and plastic syringe, respectively. Use of the copper filter eliminated the container-dependence in 111 In and 123 I measurements. Container-dependence was demonstrated in neither 201 Tl nor 99m Tc measurements. The activities of 111 In and 123 I estimated with a dose calibrator differ greatly among the containers. Accurate estimation may be attained using the container-specific correction factor or using the copper filter.

Evaluation of Gafchromic EBT-XD film, with comparison to EBT3 film, and application in high dose radiotherapy verification

Science.gov (United States)

Palmer, Antony L.; Dimitriadis, Alexis; Nisbet, Andrew; Clark, Catharine H.

2015-11-01

There is renewed interest in film dosimetry for the verification of dose delivery of complex treatments, particularly small fields, compared to treatment planning system calculations. A new radiochromic film, Gafchromic EBT-XD, is available for high-dose treatment verification and we present the first published evaluation of its use. We evaluate the new film for MV photon dosimetry, including calibration curves, performance with single- and triple-channel dosimetry, and comparison to existing EBT3 film. In the verification of a typical 25 Gy stereotactic radiotherapy (SRS) treatment, compared to TPS planned dose distribution, excellent agreement was seen with EBT-XD using triple-channel dosimetry, in isodose overlay, maximum 1.0 mm difference over 200-2400 cGy, and gamma evaluation, mean passing rate 97% at 3% locally-normalised, 1.5 mm criteria. In comparison to EBT3, EBT-XD gave improved evaluation results for the SRS-plan, had improved calibration curve gradients at high doses, and had reduced lateral scanner effect. The dimensions of the two films are identical. The optical density of EBT-XD is lower than EBT3 for the same dose. The effective atomic number for both may be considered water-equivalent in MV radiotherapy. We have validated the use of EBT-XD for high-dose, small-field radiotherapy, for routine QC and a forthcoming multi-centre SRS dosimetry intercomparison.

Evaluation of Gafchromic EBT-XD film, with comparison to EBT3 film, and application in high dose radiotherapy verification

International Nuclear Information System (INIS)

Palmer, Antony L; Dimitriadis, Alexis; Nisbet, Andrew; Clark, Catharine H

2015-01-01

There is renewed interest in film dosimetry for the verification of dose delivery of complex treatments, particularly small fields, compared to treatment planning system calculations. A new radiochromic film, Gafchromic EBT-XD, is available for high-dose treatment verification and we present the first published evaluation of its use. We evaluate the new film for MV photon dosimetry, including calibration curves, performance with single- and triple-channel dosimetry, and comparison to existing EBT3 film. In the verification of a typical 25 Gy stereotactic radiotherapy (SRS) treatment, compared to TPS planned dose distribution, excellent agreement was seen with EBT-XD using triple-channel dosimetry, in isodose overlay, maximum 1.0 mm difference over 200–2400 cGy, and gamma evaluation, mean passing rate 97% at 3% locally-normalised, 1.5 mm criteria. In comparison to EBT3, EBT-XD gave improved evaluation results for the SRS-plan, had improved calibration curve gradients at high doses, and had reduced lateral scanner effect. The dimensions of the two films are identical. The optical density of EBT-XD is lower than EBT3 for the same dose. The effective atomic number for both may be considered water-equivalent in MV radiotherapy. We have validated the use of EBT-XD for high-dose, small-field radiotherapy, for routine QC and a forthcoming multi-centre SRS dosimetry intercomparison. (paper)

Monte Carlo dose calibration in CT scanner

International Nuclear Information System (INIS)

Yadav, Poonam; Ramasubramanian, V.; Subbaiah, K.V.; Thayalan, K.

2008-01-01

Computed Tomography (CT) scanner is a high radiation imaging modality compared to radiography. The dose from a CT examination can vary greatly depending on the particular CT scanner used, the area of the body examined, and the operating parameters of the scan. CT is a major contributor to collective effective dose in diagnostic radiology. Apart from the clinical benefits, the widespread use of multislice scanner is increasing radiation level to patient in comparison with conventional CT scanner. So, it becomes necessary to increase awareness about the CT scanner. (author)

Calibration of nuclear medicine gamma counters

International Nuclear Information System (INIS)

Orlic, M.; Spasic-Jokic, V.; Jovanovic, M.; Vranjes, S. . E-mail address of corresponding author: morlic@vin.bg.ac.yu; Orlic, M.)

2005-01-01

In this paper the practical problem of nuclear medicine gamma counters calibration has been solved by using dose calibrators CRC-15R with standard error ±5%. The samples from technetium generators have been measured both by dose calibrators CRC-15R and gamma counter ICN Gamma 3.33 taking into account decay correction. Only the linear part of the curve has practical meaning. The advantage of this procedure satisfies the requirements from international standards: the calibration of sources used for medical exposure be traceable to a standard dosimetry laboratory and radiopharmaceuticals for nuclear medicine procedures be calibrated in terms of activity of the radiopharmaceutical to be administered. (author)

CERN Radiation Protection (RP) calibration facilities

CERN Document Server

AUTHOR|(CDS)2082069; Macián-Juan, Rafael

Radiation protection calibration facilities are essential to ensure the correct operation of radiation protection instrumentation. Calibrations are performed in specific radiation fields according to the type of instrument to be calibrated: neutrons, photons, X-rays, beta and alpha particles. Some of the instruments are also tested in mixed radiation fields as often encountered close to high-energy particle accelerators. Moreover, calibration facilities are of great importance to evaluate the performance of prototype detectors; testing and measuring the response of a prototype detector to well-known and -characterized radiation fields contributes to improving and optimizing its design and capabilities. The CERN Radiation Protection group is in charge of performing the regular calibrations of all CERN radiation protection devices; these include operational and passive dosimeters, neutron and photon survey-meters, and fixed radiation detectors to monitor the ambient dose equivalent, H*(10), inside CERN accelera...

A real-time in vivo dosimetric verification method for high-dose rate intracavitary brachytherapy of nasopharyngeal carcinoma

Energy Technology Data Exchange (ETDEWEB)

Qi Zhenyu; Deng Xiaowu; Cao Xinping; Huang Shaomin; Lerch, Michael; Rosenfeld, Anatoly [State Key Laboratory of Oncology in South China, Sun Yat-sen University Cancer Center, Guangzhou 510060 (China) and Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW 2522 (Australia); State Key Laboratory of Oncology in South China, Sun Yat-sen University Cancer Center, Guangzhou 510060 (China); Centre for Medical Radiation Physics, University of Wollongong, Wollongong, NSW 2522 (Australia)

2012-11-15

Purpose: A real-time in vivo dosimetric verification method using metal-oxide-semiconductor field effect transistor (MOSFET) dosimeters has been developed for patient dosimetry in high-dose rate (HDR) intracavitary brachytherapy of nasopharyngeal carcinoma (NPC). Methods: The necessary calibration and correction factors for MOSFET measurements in {sup 192}Iridium source were determined in a water phantom. With the detector placed inside a custom-made nasopharyngeal applicator, the actual dose delivered to the tumor was measured in vivo and compared to the calculated values using a commercial brachytherapy planning system. Results: Five MOSFETs were independently calibrated with the HDR source, yielding calibration factors of 0.48 {+-} 0.007 cGy/mV. The maximum sensitivity variation was no more than 7% in the clinically relevant distance range of 1-5 cm from the source. A total of 70 in vivo measurements in 11 NPC patients demonstrated good agreement with the treatment planning. The mean differences between the planned and the actually delivered dose within a single treatment fraction were -0.1%{+-} 3.8% and -0.1%{+-} 3.7%, respectively, for right and left side assessments. The maximum dose deviation was less than 8.5%. Conclusions: In vivo measurement using the real-time MOSFET dosimetry system is possible to evaluate the actual dose to the tumor received by the patient during a treatment fraction and thus can offer another line of security to detect and prevent large errors.

The Effects of Halo Assembly Bias on Self-Calibration in Galaxy Cluster Surveys

Energy Technology Data Exchange (ETDEWEB)

Wu, Hao-Yi; Rozo, Eduardo; Wechsler, Risa H.

2008-08-07

Self-calibration techniques for analyzing galaxy cluster counts utilize the abundance and the clustering amplitude of dark matter halos. These properties simultaneously constrain cosmological parameters and the cluster observable-mass relation. It was recently discovered that the clustering amplitude of halos depends not only on the halo mass, but also on various secondary variables, such as the halo formation time and the concentration; these dependences are collectively termed 'assembly bias'. Applying modified Fisher matrix formalism, we explore whether these secondary variables have a significant impact on the study of dark energy properties using the self-calibration technique in current (SDSS) and the near future (DES, SPT, and LSST) cluster surveys. The impact of the secondary dependence is determined by (1) the scatter in the observable-mass relation and (2) the correlation between observable and secondary variables. We find that for optical surveys, the secondary dependence does not significantly influence an SDSS-like survey; however, it may affect a DES-like survey (given the high scatter currently expected from optical clusters) and an LSST-like survey (even for low scatter values and low correlations). For an SZ survey such as SPT, the impact of secondary dependence is insignificant if the scatter is 20% or lower but can be enhanced by the potential high scatter values introduced by a highly-correlated background. Accurate modeling of the assembly bias is necessary for cluster self-calibration in the era of precision cosmology.

Improving the quality control program for patient dose calibrator according to IEC 60580

International Nuclear Information System (INIS)

Costa, Nathalia Almeida; Potiens, Maria da Penha Albuquerque

2013-01-01

The objective of this work was to improve the program quality control of this equipment based on the International Standard IEC 60580 - Medical electrical equipment - Dose area product meters . The initial program was established following the recommendations of IEC 61674 quoting dosimeters with ionization chambers and / or semiconductor detectors used in diagnostic X-ray image, however, the IEC 60580 is referred specifically to gauges and KAP (kerma-area product) presents additional tests. Tests included: intrinsic relative error, repeatability, scanning resolution, settling time, restarting, float values, response time and spatial uniformity of response. As a rule, all measurements are within the range characteristic of equipment performance. Thus, the PDC (Patient Dose Calibrator) again shows a device with excellent functionality and reliability in characterization tests carried out to quality control as( for the test in clinical PKA meters

Calibration of gamma cameras for the evaluation of accidental intakes of high-energy photon emitting radionuclides by humans based on urine samples

Energy Technology Data Exchange (ETDEWEB)

Degenhardt, A.L.; Lucena, E.A.; Reis, A.A. dos; Souza, W.O.; Dantas, A.L.A.; Dantas, B.M., E-mail: bmdantas@ird.gov.br [Instituto de Radioproteção e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil). Div. de Dosimetria

2017-07-01

The prompt response to emergency situations involving suspicion of intakes of radionuclides requires the use of simple and rapid methods of internal monitoring of the exposed individuals. The use of gamma cameras to estimate intakes and committed doses was investigated by the Centers for Disease Control and Preventions (CDC) of the USA in 2010.The present study aims to develop a calibration protocol for gamma cameras to be applied on internal monitoring based on urine samples to evaluate the incorporation of high-energy photon emitting radionuclides in emergency situations. A gamma camera available in a public hospital located in the city of Rio de Janeiro was calibrated using a standard liquid source of {sup 152}Eu supplied by the LNMRI of the IRD.'Efficiency vs Energy' curves at 10 and 30 cm were obtained. Calibration factors, Minimum Detectable Activities and Minimum Detectable Effective Doses of the gamma camera were calculated for {sup 137}Cs and {sup 60}Co. The gamma camera evaluated in this work presents enough sensitivity to detect activities of such radionuclides at dose levels suitable to assess suspected accidental intakes. (author)

Comparative dosimetric study in the estimation of the dose rate of the Transelektro LGI-01 irradiator

International Nuclear Information System (INIS)

Carrasco A, H.; Urena N, F.F.

2004-01-01

The 60 Co TRANSELEKTRO, model LGI-0 1, Hungarian, is similar to the Canadian Gamma cell. The evaluation of the dose ratio in the geometric center of the exposition chamber of the LGI-0 1 is presented in this paper. In order to do this two types of dosimeters were used: the alanine, and the L8-C 1 red acrylic (Canadian). Three dosimeters of each type were irradiated at 1, 2, 3, 4, 5, 6, 7 and 8 h. The respective intensities and absorbencies were measured and used to determine the proper absorbed doses and the dose ratio. The results obtained with both dosimeters were compared with the ratio dose that was reported by the Secondary Laboratory of Dosimetric Calibration of the Metrology Department of the ININ, which used a ionization chamber for the calibration of the LGI-0 1. The alanine dosemeter showed a ± 1.3% dispersion while with the acrylic dosemeter the dispersion was of ± 3.2%, with respect to the value reported by the authorized Calibration Laboratory. This paper was also used to update the calibration table of the L8-C1 red acrylic. (Author)

Calibration of farmer dosemeters

International Nuclear Information System (INIS)

Ahmad, S.S.; Anwar, K.; Arshed, W.; Mubarak, M.A.; Orfi, S.D.

1984-08-01

The Farmer Dosemeters of Atomic Energy Medical Centre (AEMC) Jamshoro were calibrated in the Secondary Standard Dosimetry Laboratory (SSDL) at PINSTECH, using the NPL Secondary Standard Therapy level X-ray exposure meter. The results are presented in this report. (authors)

Measurement with total scatter calibrate factor at different depths in the calculation of prescription dose

International Nuclear Information System (INIS)

Li Lijun; Zhu Haijun; Zhang Xinzhong; Li Feizhou; Song Hongyu

2004-01-01

Objective: To evaluate the method of measurement of total scatter calibrate factor (Sc, p). Methods: To measure the Sc, p at different depths on central axis of 6MV, 15MV photon beams through different ways. Results: It was found that the measured data of Sc, p changed with the different depths to a range of 1% - 7%. Using the direct method, the Sc, p measured depth should be the same as the depth in dose normalization point of the prescription dose. If the Sc, p (fsz, d) was measured at the other depths, it could be obtained indirectly by the calculation formula. Conclusions: The Sc, p in the prescription dose can be obtained either by the direct measure method or the indirect calculation formula. But emphasis should be laid on the proper measure depth. (authors)

Verification of the plan dosimetry for high dose rate brachytherapy using metal-oxide-semiconductor field effect transistor detectors

International Nuclear Information System (INIS)

Qi Zhenyu; Deng Xiaowu; Huang Shaomin; Lu Jie; Lerch, Michael; Cutajar, Dean; Rosenfeld, Anatoly

2007-01-01

The feasibility of a recently designed metal-oxide-semiconductor field effect transistor (MOSFET) dosimetry system for dose verification of high dose rate (HDR) brachytherapy treatment planning was investigated. MOSFET detectors were calibrated with a 0.6 cm 3 NE-2571 Farmer-type ionization chamber in water. Key characteristics of the MOSFET detectors, such as the energy dependence, that will affect phantom measurements with HDR 192 Ir sources were measured. The MOSFET detector was then applied to verify the dosimetric accuracy of HDR brachytherapy treatments in a custom-made water phantom. Three MOSFET detectors were calibrated independently, with the calibration factors ranging from 0.187 to 0.215 cGy/mV. A distance dependent energy response was observed, significant within 2 cm from the source. The new MOSFET detector has a good reproducibility ( 2 =1). It was observed that the MOSFET detectors had a linear response to dose until the threshold voltage reached approximately 24 V for 192 Ir source measurements. Further comparison of phantom measurements using MOSFET detectors with dose calculations by a commercial treatment planning system for computed tomography-based brachytherapy treatment plans showed that the mean relative deviation was 2.2±0.2% for dose points 1 cm away from the source and 2.0±0.1% for dose points located 2 cm away. The percentage deviations between the measured doses and the planned doses were below 5% for all the measurements. The MOSFET detector, with its advantages of small physical size and ease of use, is a reliable tool for quality assurance of HDR brachytherapy. The phantom verification method described here is universal and can be applied to other HDR brachytherapy treatments

Use of Low-dose Aspirin as Secondary Prevention of Atherosclerotic Cardiovascular Disease Among US Adults (From the National Health Interview Survey, 2012)

Science.gov (United States)

Fang, Jing; George, Mary G.; Gindi, Renee M.; Hong, Yuling; Yang, Quanhe; Ayala, Carma; Ward, Brian W.; Loustalot, Fleetwood

2015-01-01

Current guidelines recommend that adults with atherosclerotic cardiovascular disease take low-dose aspirin or other antiplatelet medications as secondary prevention of recurrent cardiovascular events. Yet, no national level assessment of low-dose aspirin use for secondary prevention of cardiovascular disease has been reported among a community-based population. Using data from the 2012 National Health Interview Survey, we assessed low-dose aspirin use among those with atherosclerotic cardiovascular disease. We estimated the prevalence ratios of low-dose aspirin use, adjusting for sociodemographic status, health insurance, and cardiovascular risk factors. Among those with atherosclerotic cardiovascular disease (n=3,068), 76% had been instructed to take aspirin, and 88% of those were following this advice. Of those not advised, 11% took aspirin on this own. Overall, 70% were taking aspirin (including those who followed their health care provider's advice and those who were not advised but took aspirin on their own). Logistic regression models showed that women, non-Hispanic blacks and Hispanics, those aged 40–64 years, with a high school education or with some college, or with fewer cardiovascular disease risk factors were less likely to take aspirin than men, non-Hispanic whites, those aged ≥65 years, with a college education or higher, or with all four selected cardiovascular disease risk factors, respectively. Additional analyses conducted among those with coronary heart disease only (n=2,007) showed similar patterns. In conclusion, use of low-dose aspirin for secondary prevention was 70%, with high reported adherence to health care providers' advice to take low-dose aspirin (88%), and significant variability within subgroups. PMID:25670639

Automatic Calibration of High Density Electric Muscle Stimulation

DEFF Research Database (Denmark)

Knibbe, Jarrod; Strohmeier, Paul; Boring, Sebastian

2017-01-01

. (2) EMS requires time consuming, expert calibration -- confining these interaction techniques to the lab. EMS arrays have been shown to increase stimulation resolution, but as calibration complexity increases exponentially as more electrodes are used, we require heuristics or automated procedures......Electric muscle stimulation (EMS) can enable mobile force feedback, support pedestrian navigation, or confer object affordances. To date, however, EMS is limited by two interlinked problems. (1) EMS is low resolution -- achieving only coarse movements and constraining opportunities for exploration...... for successful calibration. We explore the feasibility of using electromyography (EMG) to auto-calibrate high density EMS arrays. We determine regions of muscle activity during human-performed gestures, to inform stimulation patterns for EMS-performed gestures. We report on a study which shows that auto...

The calibration procedures in the Studsvik standardized personnel dosimetry system

International Nuclear Information System (INIS)

Widell, C.O.

1978-01-01

Every large nuclear installation in Sweden reads its own personnel TLDs. In order to supervise this decentralized reading of dose meters, the TLD readers are connected by telephone lines to a central computer for dose registration. This computer is used both for registering the personnel doses and for checking the TLD readers. This checking is performed by the use of pre-irradiated calibration dose meters which are always used when a batch of personnel dose meters are read. The pre-irradiated dose meters are either irradiated using 137 Cs to various doses up to 100mSv(10000mrem) or using a 90 Sr source in a reference dose irradiator to a dose equal to 3mSv(300mrem) from a 137 Cs source. The results from the reading of the pre-irradiated dose meters are processed by the computer and a calibration factor is calculated. The calibration factor is automatically used to calculate the doses to the personnel TLD's. However, if the calibration factor deviates by more than 10% from the previously used factor, this fact is shown to the operator - who then has to decide what calibration factor is going to be used. This calibration and supervisory procedure together with the safety interlocks in the TLD readers has resulted in a very reliable and accurate dosimetry system. (author)

High-efficiency detector of secondary and backscattered electrons for low-dose imaging in the ESEM.

Science.gov (United States)

Neděla, Vilém; Tihlaříková, Eva; Runštuk, Jiří; Hudec, Jiří

2018-01-01

A new Combined System for high-efficiency detection of Secondary and Backscattered Electrons (CSSBE) in the ESEM consists of three detectors: an ionisation SE detector, an improved scintillation BSE detector, and a new Ionisation Secondary Electron Detector with an electrostatic Separator (ISEDS). The ISEDS optimizes conditions for electron-gas ionisation phenomena in the ESEM to achieve a strongly amplified signal from the secondary electrons with a minimal contribution from backscattered and beam electrons. For this purpose, it is originally equipped with an electrostatic separator, which focuses signal electrons towards a detection electrode and controls the concentration of positive ions above the sample. The working principle of the ISEDS is explained by simulations of signal electron trajectories in gas using the EOD program with our Monte Carlo module. The ability to detect the signal electrons in a selected range of energies is described with Geant4 Monte Carlo simulations of electron-solid interactions and proven by experimental results. High-efficiency detection of the ISEDS is demonstrated by imaging a low atomic number sample under a reduced beam energy of 5 keV, very low beam currents of up to 0.2 pA, and gas pressure of hundreds of Pa. Copyright © 2017 Elsevier B.V. All rights reserved.

Response of the 'patient dose calibrator' chamber for incident positions and sizes of X-ray fields

International Nuclear Information System (INIS)

Oliveira, Cassio M.; Abrantes, Marcos Eugenio S.; Ferreira, Flavia C. Bastos; Lacerda, Marco A. de Souza; Alonso, Thessa C.; Silva, Teogenes A. da; Oliveira, Paulo Marcio C.

2009-01-01

The evaluation of patient doses is an important tool for optimizing radiodiagnostic medical procedures with conventional X-ray equipment and for improving the quality of the radiographic image. The Patient Dose Calibrator (PDC) chamber is a dosimetric instrument that is used in the evaluation of the air kerma-area product (P KA ) quantity aiming the reduction of patient doses. The objective this work was to study the P KA variation caused by different field incident positions and sizes of the X-ray beam on the PDC chamber. Results showed that the PDC chamber has repeatability lower than 0.6%, beam position dependence of 3% and linearity response within ± 6%; these characteristics are to be taken into account during evaluation of the radiological protection conditions of conventional x-ray equipment. (author)

Gearbox Reliability Collaborative High-Speed Shaft Calibration

Energy Technology Data Exchange (ETDEWEB)

Keller, J.; McNiff, B.

2014-09-01

Instrumentation has been added to the high-speed shaft, pinion, and tapered roller bearing pair of the Gearbox Reliability Collaborative gearbox to measure loads and temperatures. The new shaft bending moment and torque instrumentation was calibrated and the purpose of this document is to describe this calibration process and results, such that the raw shaft bending and torque signals can be converted to the proper engineering units and coordinate system reference for comparison to design loads and simulation model predictions.

Analysis of uncertainties in the IAEA/WHO TLD postal dose audit system

Energy Technology Data Exchange (ETDEWEB)

Izewska, J. [Department of Nuclear Sciences and Applications, International Atomic Energy Agency, Wagramer Strasse 5, Vienna (Austria)], E-mail: j.izewska@iaea.org; Hultqvist, M. [Department of Medical Radiation Physics, Karolinska Institute, Stockholm University, Stockholm (Sweden); Bera, P. [Department of Nuclear Sciences and Applications, International Atomic Energy Agency, Wagramer Strasse 5, Vienna (Austria)

2008-02-15

The International Atomic Energy Agency (IAEA) and the World Health Organisation (WHO) operate the IAEA/WHO TLD postal dose audit programme. Thermoluminescence dosimeters (TLDs) are used as transfer devices in this programme. In the present work the uncertainties in the dose determination from TLD measurements have been evaluated. The analysis of uncertainties comprises uncertainties in the calibration coefficient of the TLD system and uncertainties in factors correcting for dose response non-linearity, fading of TL signal, energy response and influence of TLD holder. The individual uncertainties have been combined to estimate the total uncertainty in the dose evaluated from TLD measurements. The combined relative standard uncertainty in the dose determined from TLD measurements has been estimated to be 1.2% for irradiations with Co-60 {gamma}-rays and 1.6% for irradiations with high-energy X-rays. Results from irradiations by the Bureau international des poids et mesures (BIPM), Primary Standard Dosimetry Laboratories (PSDLs) and Secondary Standards Dosimetry Laboratories (SSDLs) compare favourably with the estimated uncertainties, whereas TLD results of radiotherapy centres show higher standard deviations than those derived theoretically.

Use of national metrological references of dose absorbed in water and application of the IAEA TRS nr 398 dosimetry protocol to high energy photon beams. BNM-LNHB-LCIE-SFPM working group

International Nuclear Information System (INIS)

Chauvenet, B.; Delaunay, F.; Dolo, J.M.; Le Roy, G.; Bridier, A.; Francois, P.; Sabattier, R.

2003-01-01

Metrological references of dose absorbed in water for high energy photon beams used in radiotherapy have been elaborated during the past years by national calibration laboratories, and these new references are the basis of recent dosimetry protocols. However, the passage from metrological references of air kerma to dose absorbed in water, as well as the practical application of new calibration opportunities for dosemeters in high energy X ray beams requires a specific attention to maintain the consistency of dose measurement references over the hospital site. In this respect, this guide aims at the application of these metrological references. It proposes recommendations for the application of metrological references in terms of dose absorbed in water on the hospital site with reference to their determination conditions and to the implementation of the new IAEA dosimetry protocol (TRS nr 398). Thus, this guide proposes an overview of metrological references in French calibration laboratories, presents calibration methods (air kerma in a cobalt 60 gamma photon beam, dose absorbed in water) and a comparison with the IAEA TRS 277 dosimetry protocol. It addresses various practical aspects, and discusses uncertainties

Studies on the dose distribution and treatment technique of high energy electron beams

International Nuclear Information System (INIS)

Lee, D.H.; Chu, S.S.

1978-01-01

Some important properties of high energy electron beams from the linear accelerator, LMR-13, installed in the Yonsei Cancer Center were studied. The results of experimental studies on the problems associated with the 8, 10, and 12 MeV electron beam therapy were as followings; The ionization type dosemeters calibrated by 90 Sr standard source were suitable to the measurements of the outputs and the obsorbed doses in accuracy point of view, and dose measurements using ionization chambers were difficult when measuring doses in small field size and the regions of rapid fall off. The electron energies were measured precisely with an energy spectrometer, and the practical electron energy was calculated within 5% error in the maximum range of the high energy electron beam in water. The correcting factors of perturbated dose distributions owing to radiation field, energy, and materials of the treatment cone were checked and described systematically and thus the variation of dose distributions due to the non-homogeneities of tissues and slopping skin surfaces were completely compensated. The electron beams were adequately diffused using the scatterers, and minimized the bremsstrahlung, irradiation field size, and materials of scatterers. Thus, the therapeutic capacity with the limited electron energy could be extended by improving the dose distributions. (author)

Imaging dose in breast radiotherapy: does breast size affect the dose to the organs at risk and the risk of secondary cancer to the contralateral breast?

International Nuclear Information System (INIS)

Batumalai, Vikneswary; Quinn, Alexandra; Jameson, Michael; Delaney, Geoff; Holloway, Lois

2015-01-01

Correct target positioning is crucial for accurate dose delivery in breast radiotherapy resulting in utilisation of daily imaging. However, the radiation dose from daily imaging is associated with increased probability of secondary induced cancer. The aim of this study was to quantify doses associated with three imaging modalities and investigate the correlation of dose and varying breast size in breast radiotherapy. Planning computed tomography (CT) data sets of 30 breast cancer patients were utilised to simulate the dose received by various organs from a megavoltage computed tomography (MV-CT), megavoltage electronic portal image (MV-EPI) and megavoltage cone-beam computed tomography (MV-CBCT). The mean dose to organs adjacent to the target volume (contralateral breast, lungs, spinal cord and heart) were analysed. Pearson correlation analysis was performed to determine the relationship between imaging dose and primary breast volume and the lifetime attributable risk (LAR) of induced secondary cancer was calculated for the contralateral breast. The highest contralateral breast mean dose was from the MV-CBCT (1.79 Gy), followed by MV-EPI (0.22 Gy) and MV-CT (0.11 Gy). A similar trend was found for all organs at risk (OAR) analysed. The primary breast volume inversely correlated with the contralateral breast dose for all three imaging modalities. As the primary breast volume increases, the likelihood of a patient developing a radiation-induced secondary cancer to the contralateral breast decreases. MV-CBCT showed a stronger relationship between breast size and LAR of developing a radiation-induced contralateral breast cancer in comparison with the MV-CT and MV-EPI. For breast patients, imaging dose to OAR depends on imaging modality and treated breast size. When considering the use of imaging during breast radiotherapy, the patient's breast size and contralateral breast dose should be taken into account

IAEA/SSDL intercomparison of calibration factors for therapy level ionization chambers

International Nuclear Information System (INIS)

Lu Jilong; Cheng Jinsheng; Guo Zhaohui; Li Kaibao

2005-01-01

Objective: By participating in IAEA-SSDL intercomparison, a dose to water calibration factor was introduced in order to check the measuring accuracy of 60 Co radiotherapy dose level standard and ensure the reliability and consistency of our calibration. Methods: The authors carried out both air kerma and absorbed dose to water calibrations against 60 Co γ-rays for one of our field class ionization chambers, and sent the results together with the chamber to IAEA dosimetry laboratory for calibration, then IAEA calibrated it and gave the deviation of the intercomparison. Results: The deviation of our air kerma calibration factors is -0.5%, and the deviation of our absorbed dose to water calibration factors is 0.4%. Conclusion: The deviation of calibration factors between IAEA and SSDL should be no more than ±1.5%. Therefore, the result of this intercomparison is considered satisfactory. (authors)

New routes of preparation of polyaniline films and dosimetric characterization for high-doses gamma radiation

International Nuclear Information System (INIS)

Pacheco, Ana Paula Lima

2003-08-01

This work presents a new conducting polymeric material based on polyaniline thin films that will be used in the confection of dosimetric devices. On preparation of the films a homogeneous and viscous solution of poly (acrylic acid) and MnO 2 is deposited on PMMA surface, which after dried, is immersed in an acid aniline solution. The films formed present low resistivity (6.10 2 Ωm), good mechanical resistance and adherence on the electrodes. The films were characterized by infrared spectroscopy, conductivity measurements and manganese elemental analyses. The resistance variations show linear correlation (r 2 = 0,9928) with gamma irradiation dose in the range of 1000 to 6000 Gy, with medium error less than 5% and sensitivity response. The dosimetric devices present as advantage real time measurements, low cost, use in calibration of industrial radioactive sources. Moreover, this composite could in future replace Fricke dosimeter and its applications. A calibration curve is showed for PANI dosimeter, here proposed, to use at high gamma doses. (author)

Accuracy of Dose Calibrators for 68Ga PET Imaging: Unexpected Findings in a Multicenter Clinical Pretrial Assessment.

Science.gov (United States)

Bailey, Dale L; Hofman, Michael S; Forwood, Nicholas J; O'Keefe, Graeme J; Scott, Andrew M; van Wyngaardt, Winifred M; Howe, Bonnie; Kovacev, Olga; Francis, Roslyn J

2018-04-01

We report the discovery of a systematic miscalibration during the work-up process for site validation of a multicenter clinical PET imaging trial using 68 Ga, which manifested as a consistent and reproducible underestimation in the quantitative accuracy (assessed by SUV) of a range of PET systems from different manufacturers at several different facilities around Australia. Methods: Sites were asked to follow a strict preparation protocol to create a radioactive phantom with 68 Ga to be imaged using a standard clinical protocol before commencing imaging in the trial. All sites had routinely used 68 Ga for clinical PET imaging for many years. The reconstructed image data were transferred to an imaging core laboratory for analysis, along with information about ancillary equipment such as the radionuclide dose calibrator. Fourteen PET systems were assessed from 10 nuclear medicine facilities in Australia, with the aim for each PET system being to produce images within 5% of the true SUV. Results: At initial testing, 10 of the 14 PET systems underestimated the SUV by 15% on average (range, 13%-23%). Multiple PET systems at one site, from two different manufacturers, were all similarly affected, suggesting a common cause. We eventually identified an incorrect factory-shipped dose calibrator setting from a single manufacturer as being the cause. The calibrator setting for 68 Ga was subsequently adjusted by the users so that the reconstructed images produced accurate values. Conclusion: PET imaging involves a chain of measurements and calibrations to produce accurate quantitative performance. Testing of the entire chain is simple, however, and should form part of any quality assurance program or prequalifying site assessment before commencing a quantitative imaging trial or clinical imaging. © 2018 by the Society of Nuclear Medicine and Molecular Imaging.

Experimental comparison between total calibration factors and components calibration factors of reference dosemeters used in secondary standard laboratory dosemeters

International Nuclear Information System (INIS)

Silva, T.A. da.

1981-06-01

A quantitative comparison of component calibration factors with the corresponding overall calibration factor was used to evaluate the adopted component calibration procedure in regard to parasitic elements. Judgement of significance is based upon the experimental uncertainty of a well established procedure for determination of the overall calibration factor. The experimental results obtained for different ionization chambers and different electrometers demonstrate that for one type of electrometer the parasitic elements have no influence on its sensitivity considering the experimental uncertainty of the calibration procedures. In this case the adopted procedure for determination of component calibration factors is considered to be equivalent to the procedure of determination of the overall calibration factor and thus might be used as a strong quality control measure in routine calibration. (Author) [pt

Secondary standard dosimetry laboratory at the Ruder Boskovic Institute, Zagreb, Croatia

International Nuclear Information System (INIS)

Vekic, B.; Ban, R.; Saveta, M.

2006-01-01

The Secondary Standard Dosimetry Laboratory at the Ruder Boskovic Institute, Zagreb, Croatia, was installed during the several last years. The installation of this Laboratory was strongly supported by the International Atomic Energy Agency (IAEA) through the Technical Cooperation Project (C.R.O. 1/004/; Establishing Calibration Services). Inside the country this Technical Cooperation Project was supported by the State Office for Standardization and Metrology, State Office for Radiation Protection and the Ministry of Health of the Republic of Croatia. The Secondary Standard Dosimetry Laboratory at the Ruder Boskovic Institute, Zagreb, Croatia was installed in two calibration rooms. The both of these calibration rooms are 9.6 meters long and 6 meters wide. In the both of these calibration rooms the proper air conditioning was installed. The walls of the both calibration rooms are thick enough (1 meter of concrete) and the entrance doors are protected by Pb to protect any radiation hazard in control rooms, in neighbouring rooms and in environment. In the first calibration room, placed in the basement, two sealed sources share the same calibration bench (produced by Hopewell Designs, Inc., USA) between them which is 6 meters long. On one side is Co -60 source of the 30 TBq activity (December 2004) for the calibration of radiotherapy ionizing chambers and the other equipment in the field of high dose rate range. On the other side is irradiation unit consists of 2 sealed sources for radiation protection purposes: (1) Cs-137 source, activity of 740 MBq (February 2004) and (2) Co- 60 source, activity of 185 MBq (February 2004). For this second source three attenuators are provided that give a nominal attenuation of *10, *100 and *1000. In the second calibration room placed just above the first one the X -ray unit (gift from P.T.B., Germany, I.S.O.V.O.L.T. 420, 40 -300 kV, 1-20 mA) is placed. In front of this are: (1.) Aperture Wheel Assembly designed to modify the beam

Severe encephalopathy after high-dose chemotherapy with autologous stem cell support for brain tumours

NARCIS (Netherlands)

van den Berkmortel, F.; Gidding, C.; de Kanter, M.; Punt, C. J. A.

2006-01-01

Recurrent medulloblastoma carries a poor prognosis. Long-term survival has been obtained with high-dose chemotherapy with autologous stem cell transplantation and secondary irradiation. A 21-year-old woman with recurrent medulloblastoma after previous chemotherapy and radiotherapy is presented. The

Implementation of ISO guide 25 in a medical dosimetry secondary standards calibration laboratory

International Nuclear Information System (INIS)

DeWerd, L.A.

1995-01-01

Currently, there is a great deal of discussion among industry and government agencies about ISO 9000 accreditation. U.S. manufacturers with ISO 9000 accreditation are regarded more favorably by European countries. The principles behind the ISO 9000 accreditation are based on the Total Quality Management (TQM) principles that are being implemented in many U.S. industries. This paper will deal only with the calibration issue. There is a difference in the areas covered by ISO 9000 and ISO Guide 25 documents. ISO 9000, in particular ISO 9001 - ISO 9003, cover the open-quotes calibrationclose quotes of inspection, measuring and test equipment. This equipment is basically used for open-quotes factory calibrationsclose quotes to determine that equipment is performing within manufacturer specifications. ISO Guide 25 is specifically for open-quotes calibration and testing laboratories,close quotes generally laboratories that have painstaking procedures to reduce uncertainties and establish high accuracy of the transfer of calibration. The experience of the University of Wisconsin Accredited Dosimetry Calibration Laboratory in conforming to ISO Guide 25 will be outlined. The entire laboratory staff must become familiar with the process and an individual with direct authority must become the one to maintain the quality of equipment and calibrations in the role of open-quotes quality-assurance manager.close quotes

Field calibration of a TLD albedo dosemeter in the high-energy neutron field of CERF

International Nuclear Information System (INIS)

Haninger, T.; Kleinau, P.; Haninger, S.

2017-01-01

The new albedo dosemeter-type AWST-TL-GD 04 has been calibrated in the CERF neutron field (CERN-EU high-energy Reference Field). This type of albedo dosemeter is based on thermoluminescent detectors (TLDs) and used by the individual monitoring service of the Helmholtz Zentrum Muenchen (AWST) since 2015 for monitoring persons, who are exposed occupationally against photon and neutron radiation. The motivation for this experiment was to gain a field specific neutron correction factor N n for workplaces at high-energy particle accelerators. N n is a dimensionless factor relative to a basic detector calibration with 137 Cs and is used to calculate the personal neutron dose in terms of H p (10) from the neutron albedo signal. The results show that the sensitivity of the albedo dosemeter for this specific neutron field is not significantly lower as for fast neutrons of a radionuclide source like 252 Cf. The neutron correction factor varies between 0.73 and 1.16 with a midrange value of 0.94. The albedo dosemeter is therefore appropriate to monitor persons, which are exposed at high-energy particle accelerators. (authors)

Calibration of high resolution digital camera based on different photogrammetric methods

International Nuclear Information System (INIS)

Hamid, N F A; Ahmad, A

2014-01-01

This paper presents method of calibrating high-resolution digital camera based on different configuration which comprised of stereo and convergent. Both methods are performed in the laboratory and in the field calibration. Laboratory calibration is based on a 3D test field where a calibration plate of dimension 0.4 m × 0.4 m with grid of targets at different height is used. For field calibration, it uses the same concept of 3D test field which comprised of 81 target points located on a flat ground and the dimension is 9 m × 9 m. In this study, a non-metric high resolution digital camera called Canon Power Shot SX230 HS was calibrated in the laboratory and in the field using different configuration for data acquisition. The aim of the calibration is to investigate the behavior of the internal digital camera whether all the digital camera parameters such as focal length, principal point and other parameters remain the same or vice-versa. In the laboratory, a scale bar is placed in the test field for scaling the image and approximate coordinates were used for calibration process. Similar method is utilized in the field calibration. For both test fields, the digital images were acquired within short period using stereo and convergent configuration. For field calibration, aerial digital images were acquired using unmanned aerial vehicle (UAV) system. All the images were processed using photogrammetric calibration software. Different calibration results were obtained for both laboratory and field calibrations. The accuracy of the results is evaluated based on standard deviation. In general, for photogrammetric applications and other applications the digital camera must be calibrated for obtaining accurate measurement or results. The best method of calibration depends on the type of applications. Finally, for most applications the digital camera is calibrated on site, hence, field calibration is the best method of calibration and could be employed for obtaining accurate

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

International Nuclear Information System (INIS)

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

2014-08-01

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

Solid ferrous ammonium sulfate as a dosimeter at low temperatures and high doses

International Nuclear Information System (INIS)

Juarez-calderon, J.M.; Ramos B, S.; Negron M, A.

2006-01-01

This paper presents the results obtained from a study of the radiation induced oxidation of crystalline ferrous ammonium sulfate with gamma rays at 295 K, 263 K and 77 K and doses from 0 to 300 kGy. The radiation induced decomposition of ferrous ammonium sulfate has been studied by the dissolution of the irradiated salt in 0,8 N sulfuric acid. The main product is ferric ion (Fe 3+ ) and its molar concentration was determined spectrophotometrically in the UV region at 304 nm. The optical density values showed a linear dependence with dose, indicating that the data obtained might be used to create a calibrating curve. Color in irradiated salt changes from blue to green, yellow and orange according to the absorbed dose. The accuracy and the reproducibility of the system were tested. In addition, some other characteristics make possible the use of this system as a dosimeter, similar to Fricke chemical dosimeter, for studies and works at low temperatures and high doses. (authors)

Solid ferrous ammonium sulfate as a dosimeter at low temperatures and high doses

Energy Technology Data Exchange (ETDEWEB)

Juarez-calderon, J.M.; Ramos B, S.; Negron M, A. [Mexico Univ. Nacional Autonoma, Instituto de Ciencias Nucleares (Mexico)

2006-07-01

This paper presents the results obtained from a study of the radiation induced oxidation of crystalline ferrous ammonium sulfate with gamma rays at 295 K, 263 K and 77 K and doses from 0 to 300 kGy. The radiation induced decomposition of ferrous ammonium sulfate has been studied by the dissolution of the irradiated salt in 0,8 N sulfuric acid. The main product is ferric ion (Fe{sup 3+}) and its molar concentration was determined spectrophotometrically in the UV region at 304 nm. The optical density values showed a linear dependence with dose, indicating that the data obtained might be used to create a calibrating curve. Color in irradiated salt changes from blue to green, yellow and orange according to the absorbed dose. The accuracy and the reproducibility of the system were tested. In addition, some other characteristics make possible the use of this system as a dosimeter, similar to Fricke chemical dosimeter, for studies and works at low temperatures and high doses. (authors)

Off-axis dose equivalent due to secondary neutrons from uniform scanning proton beams during proton radiotherapy

Science.gov (United States)

Islam, M. R.; Collums, T. L.; Zheng, Y.; Monson, J.; Benton, E. R.

2013-11-01

The production of secondary neutrons is an undesirable byproduct of proton therapy and it is important to quantify the contribution from secondary neutrons to patient dose received outside the treatment volume. The purpose of this study is to investigate the off-axis dose equivalent from secondary neutrons experimentally using CR-39 plastic nuclear track detectors (PNTD) at ProCure Proton Therapy Center, Oklahoma City, OK. In this experiment, we placed several layers of CR-39 PNTD laterally outside the treatment volume inside a phantom and in air at various depths and angles with respect to the primary beam axis. Three different proton beams with max energies of 78, 162 and 226 MeV and 4 cm modulation width, a 5 cm diameter brass aperture, and a small snout located 38 cm from isocenter were used for the entire experiment. Monte Carlo simulations were also performed based on the experimental setup using a simplified snout configuration and the FLUKA Monte Carlo radiation transport code. The measured ratio of secondary neutron dose equivalent to therapeutic primary proton dose (H/D) ranged from 0.3 ± 0.08 mSv Gy-1 for 78 MeV proton beam to 37.4 ± 2.42 mSv Gy-1 for 226 MeV proton beam. Both experiment and simulation showed a similar decreasing trend in dose equivalent with distance to the central axis and the magnitude varied by a factor of about 2 in most locations. H/D was found to increase as the energy of the primary proton beam increased and higher H/D was observed at 135° compared to 45° and 90°. The overall higher H/D in air indicates the predominance of external neutrons produced in the nozzle rather than inside the body.

Off-axis dose equivalent due to secondary neutrons from uniform scanning proton beams during proton radiotherapy

International Nuclear Information System (INIS)

Islam, M R; Collums, T L; Monson, J; Benton, E R; Zheng, Y

2013-01-01

The production of secondary neutrons is an undesirable byproduct of proton therapy and it is important to quantify the contribution from secondary neutrons to patient dose received outside the treatment volume. The purpose of this study is to investigate the off-axis dose equivalent from secondary neutrons experimentally using CR-39 plastic nuclear track detectors (PNTD) at ProCure Proton Therapy Center, Oklahoma City, OK. In this experiment, we placed several layers of CR-39 PNTD laterally outside the treatment volume inside a phantom and in air at various depths and angles with respect to the primary beam axis. Three different proton beams with max energies of 78, 162 and 226 MeV and 4 cm modulation width, a 5 cm diameter brass aperture, and a small snout located 38 cm from isocenter were used for the entire experiment. Monte Carlo simulations were also performed based on the experimental setup using a simplified snout configuration and the FLUKA Monte Carlo radiation transport code. The measured ratio of secondary neutron dose equivalent to therapeutic primary proton dose (H/D) ranged from 0.3 ± 0.08 mSv Gy −1  for 78 MeV proton beam to 37.4 ± 2.42 mSv Gy −1  for 226 MeV proton beam. Both experiment and simulation showed a similar decreasing trend in dose equivalent with distance to the central axis and the magnitude varied by a factor of about 2 in most locations. H/D was found to increase as the energy of the primary proton beam increased and higher H/D was observed at 135° compared to 45° and 90°. The overall higher H/D in air indicates the predominance of external neutrons produced in the nozzle rather than inside the body. (paper)

Optimization of SPECT calibration for quantification of images applied to dosimetry with iodine-131

International Nuclear Information System (INIS)

Carvalho, Samira Marques de

2018-01-01

SPECT systems calibration plays an essential role in the accuracy of the quantification of images. In this work, in its first stage, an optimized SPECT calibration method was proposed for 131 I studies, considering the partial volume effect (PVE) and the position of the calibration source. In the second stage, the study aimed to investigate the impact of count density and reconstruction parameters on the determination of the calibration factor and the quantification of the image in dosimetry studies, considering the reality of clinical practice in Brazil. In the final step, the study aimed evaluating the influence of several factors in the calibration for absorbed dose calculation using Monte Carlo simulations (MC) GATE code. Calibration was performed by determining a calibration curve (sensitivity versus volume) obtained by applying different thresholds. Then, the calibration factors were determined with an exponential function adjustment. Images were performed with high and low counts densities for several source positions within the simulator. To validate the calibration method, the calibration factors were used for absolute quantification of the total reference activities. The images were reconstructed adopting two approaches of different parameters, usually used in patient images. The methodology developed for the calibration of the tomographic system was easier and faster to implement than other procedures suggested to improve the accuracy of the results. The study also revealed the influence of the location of the calibration source, demonstrating better precision in the absolute quantification considering the location of the target region during the calibration of the system. The study applied in the Brazilian thyroid protocol suggests the revision of the calibration of the SPECT system, including different positions for the reference source, besides acquisitions considering the Signal to Noise Ratio (SNR) of the images. Finally, the doses obtained with the

A comparison of protocols for external beam radiotherapy beam calibrations

International Nuclear Information System (INIS)

Saeed Al-Ahbabi, Salma; Bradley, D.A.; Beyomi, M.; Alkatib, Z.; Adhaheri, S.; Darmaki, M.; Nisbet, A.

2012-01-01

A number of codes of practice (CoP) for electron and photon radiotherapy beam dosimetry are currently in use. Comparison is made of the more widely used of these, specifically those of the International Atomic Energy Agency (IAEA TRS-398), the American Association of Physicists in Medicine (AAPM TG-51) and the Institute of Physics and Engineering in Medicine (IPEM 2003). All are based on calibration of ionization chambers in terms of absorbed dose to water, each seeking to reduce uncertainty in delivered dose, providing an even stronger system of primary standards than previous air-kerma based approaches. They also provide a firm, traceable and straight-forward formalism. Included in making dose assessments for the three CoP are calibration coefficients for a range of beam quality indices. Measurements have been performed using clinical photon and electron beams, the absorbed dose to water being obtained following the recommendations given by each code. Electron beam comparisons have been carried out using measurements for electron beams of nominal energies 6, 9, 12, 16 and 20 MeV. Comparisons were also carried out for photon beams of nominal energies 6 and 18 MV. For photon beams use was made of NE2571 cylindrical graphite walled ionization chambers, cross-calibrated against an NE2611 Secondary Standard; for electron beams, PTW Markus and NACP-02 plane-parallel chambers were used. Irradiations were made using Varian 600C/2100C linacs, supported by water tanks and Virtual Water™ phantoms. The absorbed doses for photon and electron beams obtained following these CoP are all in good agreement, with deviations of less than 2%. A number of studies have been carried out by different groups in different countries to examine the consistency of dosimetry codes of practice or protocols. The aim of these studies is to confirm that the goal of those codes is met, namely uniformity in establishment of dosimetry of all radiation beam types used in cancer therapy in the world

Antiproton Radiotherapy Peripheral Dose from Secondary Neutrons produced in the Annihilation of Antiprotons in the Target

CERN Document Server

Fahimian, Benjamin P; Keyes, Roy; Bassler, Niels; Iwamoto, Keisuke S; Zankl, Maria; Holzscheiter, Michael H

2009-01-01

The AD-4/ACE collaboration studies the biological effects of antiprotons with respect to a possible use of antiprotons in cancer therapy. In vitro experiments performed by the collaboration have shown an enhanced biological effectiveness for antiprotons relative to protons. One concern is the normal tissue dose resulting from secondary neutrons produced in the annihilation of antiprotons on the nucleons of the target atoms. Here we present the first organ specific Monte Carlo calculations of normal tissue equivalent neutron dose in antiproton therapy through the use of a segmented CT-based human phantom. The MCNPX Monte Carlo code was employed to quantify the peripheral dose for a cylindrical spread out Bragg peak representing a treatment volume of 1 cm diameter and 1 cm length in the frontal lobe of a segmented whole-body phantom of a 38 year old male. The secondary neutron organ dose was tallied as a function of energy and organ.

Integral Dose and Radiation-Induced Secondary Malignancies: Comparison between Stereotactic Body Radiation Therapy and Three-Dimensional Conformal Radiotherapy

Directory of Open Access Journals (Sweden)

Stefano G. Masciullo

2012-11-01

Full Text Available The aim of the present paper is to compare the integral dose received by non-tumor tissue (NTID in stereotactic body radiation therapy (SBRT with modified LINAC with that received by three-dimensional conformal radiotherapy (3D-CRT, estimating possible correlations between NTID and radiation-induced secondary malignancy risk. Eight patients with intrathoracic lesions were treated with SBRT, 23 Gy × 1 fraction. All patients were then replanned for 3D-CRT, maintaining the same target coverage and applying a dose scheme of 2 Gy × 32 fractions. The dose equivalence between the different treatment modalities was achieved assuming α/β = 10Gy for tumor tissue and imposing the same biological effective dose (BED on the target (BED = 76Gy10. Total NTIDs for both techniques was calculated considering α/β = 3Gy for healthy tissue. Excess absolute cancer risk (EAR was calculated for various organs using a mechanistic model that includes fractionation effects. A paired two-tailed Student t-test was performed to determine statistically significant differences between the data (p ≤ 0.05. Our study indicates that despite the fact that for all patients integral dose is higher for SBRT treatments than 3D-CRT (p = 0.002, secondary cancer risk associated to SBRT patients is significantly smaller than that calculated for 3D-CRT (p = 0.001. This suggests that integral dose is not a good estimator for quantifying cancer induction. Indeed, for the model and parameters used, hypofractionated radiotherapy has the potential for secondary cancer reduction. The development of reliable secondary cancer risk models seems to be a key issue in fractionated radiotherapy. Further assessments of integral doses received with 3D-CRT and other special techniques are also strongly encouraged.

Efficacy of low-dose cinacalcet on alternate days for the treatment of secondary hyperparathyroidism in hemodialysis patients: a single-center study

Directory of Open Access Journals (Sweden)

Gojaseni P

2017-02-01

Full Text Available Pongsathorn Gojaseni, Dolnapa Pattarathitinan, Anutra Chittinandana Division of Nephrology, Department of Medicine, Bhumibol Adulyadej Hospital, Directorate of Medical Services, Royal Thai Air Force, Bangkok, Thailand Introduction: Cinacalcet is effective in reducing serum parathyroid hormone (PTH in patients with secondary hyperparathyroidism (HPT. This study focused on testing whether a prescription of low-dose cinacalcet on alternate days could be an option for treatment of secondary HPT.Materials and methods: A retrospective clinical study was conducted on chronic maintenance hemodialysis patients. Patients with secondary HPT who received cinacalcet at a starting dose of 25 mg on alternate days were reviewed (low-dose group. Patients who were being treated with a standard dose of cinacalcet in the same period of time were selected as the control group. The primary outcome was difference in the percentage of patients achieving >30% reduction of intact parathyroid hormone (iPTH levels at 16 weeks. The changes of serum iPTH and other biochemical data were also tested.Results: A total of 30 patients (16 low doses and 14 controls took part in the study. Baseline iPTH levels in the low-dose and control group were 1,065.9±477.7 and 1,214.1±497.6 pg/mL, respectively (p=0.413. The analysis showed that the percentage of patients who achieved the primary outcome showed little or no difference (33.3% in the low-dose group compared with 38.5% in the control group, p=1.0. Serum iPTH reduction during 16 weeks of study period in the low-dose and control group was 253.5±316.1 and 243.4±561.3 pg/mL, respectively (p=0.957. There was no difference in the adverse events between both groups.Conclusion: Among patients with secondary HPT, initial treatment with cinacalcet 25 mg on alternate days can decrease serum PTH levels. The role of low-dose cinacalcet in secondary HPT should be further determined in large-scale, randomized controlled trials. Keywords

NVLAP activities at Department of Defense calibration laboratories

Energy Technology Data Exchange (ETDEWEB)

Schaeffer, D.M. [Defense Nuclear Agency, Alexandria, VA (United States)

1993-12-31

There are 367 active radiological instrument calibration laboratories within the U.S. Department of Defense (DoD). Each of the four services in DoD manages, operates, and certifies the technical proficiency and competency of those laboratories under their cognizance. Each service has designated secondary calibration laboratories to trace all calibration source standards to the National Institute of Standards and Technology. Individual service radiological calibration programs and capabilities, present and future, are described, as well as the measurement quality assurance (MQA) processes for their traceability. National Voluntary Laboratory Accreditation Program (NVLAP) programs for dosimetry systems are briefly summarized. Planned NVLAP accreditation of secondary laboratories is discussed in the context of current technical challenges and future efforts.

NVLAP activities at Department of Defense calibration laboratories

International Nuclear Information System (INIS)

Schaeffer, D.M.

1993-01-01

There are 367 active radiological instrument calibration laboratories within the U.S. Department of Defense (DoD). Each of the four services in DoD manages, operates, and certifies the technical proficiency and competency of those laboratories under their cognizance. Each service has designated secondary calibration laboratories to trace all calibration source standards to the National Institute of Standards and Technology. Individual service radiological calibration programs and capabilities, present and future, are described, as well as the measurement quality assurance (MQA) processes for their traceability. National Voluntary Laboratory Accreditation Program (NVLAP) programs for dosimetry systems are briefly summarized. Planned NVLAP accreditation of secondary laboratories is discussed in the context of current technical challenges and future efforts

Reference beta radiations for calibrating dosemeters and dose ratemeters and for determining their response as a function of beta radiation energy. 1. ed.

International Nuclear Information System (INIS)

1984-01-01

This International Standard specifies the requirements for reference beta radiations produced by radionuclide sources to be used for the calibration of protection level dosemeters and dose ratemeters, and for the determination of their response as a function of beta energy. It gives the characteristics of radionuclides which have been used to produce reference beta radiations, gives examples of suitable source constructions and describes methods for the measurement of the residual maximum beta energy and the absorbed dose rate at a depth of 7 mg·cm -2 in a semi-infinite tissue-equivalent medium. The energy range involved lies between 66 keV and 3.6 MeV and the absorbed dose rates are in the range from about 10 μGy·h -1 (1 mrad·h -1 ) to at least 10 Gy·h -1 (10 3 rad·h -1 ). This International Standard proposes two series of beta reference radiations from which the radiation necessary for determining the characteristics (calibration and energy response) of an instrument shall be selected. Series 1 reference radiations are produced by radionuclide sources used with beam flattening filters designed to give uniform dose rates over a large area at a specific distance. The proposed sources of 90 Sr+ 90 Y, 204 TI and 147 Pm produce maximum dose rates of approximately 5mGy·h -1 (0.5 rad·h -1 ). Series 2 reference radiations are produced without the use of beam flattening filters which allows a range of source-to-calibration plane distances to be used. Close to the sources only relatively small areas of uniform dose rate are produced but this Series has the advantage of extending the energy and dose rate ranges beyond those of Series 1. The radionuclides used are those of Series 1 with the addition of the radionuclides 14 C and 106 Ru+ 106 Rh; these sources produce dose rates of up to 10 Gy·h -1 (10 3 rad·h -1 )

Dose-response calibration curves of {sup 137}Cs gamma rays for dicentric chromosome aberrations in human lymphocytes

Energy Technology Data Exchange (ETDEWEB)

Jo, Wol Soon; Oh, Su Jung; Jeong, Soo Kyun; Yang, Kwang Mo [Dept. of Research center, Dong Nam Institute of Radiological and Medical Sciences, Busan (Korea, Republic of); Jeong, Min Ho [Dept. of Microbiology, Dong A University College of Medicine, Busan (Korea, Republic of)

2012-11-15

Recently, the increased threat of radiologically industrial accident such as radiation nondestructive inspection or destruction of nuclear accident by natural disaster such as Fukushima accident requires a greater capacity for cytogenetic biodosimetry, which is critical for clinical triage of potentially thousands of radiation-exposed individuals. Dicentric chromosome aberration analysis is the conventional means of assessing radiation exposure. Dose–response calibration curves for {sup 13}'7Cs gamma rays have been established for unstable chromosome aberrations in human peripheral blood lymphocytes in many laboratories of international biodosimetry network. In this study, therefore, we established dose– response calibration curves of our laboratory for {sup 137}Cs gamma raysaccording to the IAEA protocols for conducting the dicentric chromosome assay We established in vitro dose–response calibration curves for dicentric chromosome aberrations in human lymphocytes for{sup 13}'7Cs gamma rays in the 0 to 5 Gy range, using the maximum likelihood linear-quadratic model, Y = c+αD+βD2. The estimated coefficients of the fitted curves were within the 95% confidence intervals (CIs) and the curve fitting of dose–effect relationship data indicated a good fit to the linear-quadratic model. Hence, meaningful dose estimation from unknown sample can be determined accurately by using our laboratory’s calibration curve according to standard protocol.

Status of air kerma and absorbed dose standards in India

International Nuclear Information System (INIS)

Vijayam, M.; Ramanathan, G.; Patki, V.S.; Soman, A.T.; Shigwan, J.B.; Vinatha, S.P.; Jadhavgaonkar, P.S.; Kadam, V.D.; Shaha, V.V.; Abani, M.C.

2002-01-01

-volumes are maintained as primary standards for protection level and brachytherapy measurements of Ir-192, Cs-137 and Co-60 sources. These chambers are made of high purity reactor-grade graphite of density 1700 kg/m 3 . The three chambers have different wall thickness, the external diameters of all the chambers being equal. A reference standard in the form of a re-entrant chamber developed at BARC, calibrated against this primary standard was intercompared with a reference standard from M.D Anderson Centre, Houston, U.S.A and the results showed a good agreement. Recently one of the chambers was used for the Cs-137 intercomparison with IAEA and showed an agreement of better than ± 1%. 3. Primary Standard for X-rays - the free air chamber (FAC): This facility is utilized in conjunction with a Philips RT-250 X-ray machine for calibrating secondary standard dosemeters at different X-ray qualities in the 75 to 250 kV range. The total uncertainty in the realization of air kerma is around ±1% using the free air chamber. Accuracy of calibration of the secondary standards is estimated to be better than ±2%. The FAC has been intercompared via transferable transfer standards with FACs at BIPM (1971), BNM (France) RCL (Canada) and Kriss (Korea), which showed good agreement within ±1% after necessary correction for the spectral differences in X-ray beams. BARC is just now taking part in intercomparisons of X-ray air kerma calibration factors organised by Institute of Nuclear Energy Research (INER), Taiwan under Asia Pacific Metrology Programme. In addition to the above-mentioned primary standards, the SSDL is also maintaining the following secondary standards. For air kerma measurements at Co-60 gamma energy, ionisation chambers of Exradin A3, NE2571, NE2577 and Victoreen 415 types are calibrated and maintained. For Co-60 radiation dose to water measurements, NE 2571 and NE 2577 chambers calibrated at BIPM in terms of N D,W are maintained. For air kerma at medium energy x

Dose equivalent near the bone-soft tissue interface from nuclear fragments produced by high-energy protons

Science.gov (United States)

Shavers, M. R.; Poston, J. W.; Cucinotta, F. A.; Wilson, J. W.

1996-01-01

During manned space missions, high-energy nucleons of cosmic and solar origin collide with atomic nuclei of the human body and produce a broad linear energy transfer spectrum of secondary particles, called target fragments. These nuclear fragments are often more biologically harmful than the direct ionization of the incident nucleon. That these secondary particles increase tissue absorbed dose in regions adjacent to the bone-soft tissue interface was demonstrated in a previous publication. To assess radiological risks to tissue near the bone-soft tissue interface, a computer transport model for nuclear fragments produced by high energy nucleons was used in this study to calculate integral linear energy transfer spectra and dose equivalents resulting from nuclear collisions of 1-GeV protons transversing bone and red bone marrow. In terms of dose equivalent averaged over trabecular bone marrow, target fragments emitted from interactions in both tissues are predicted to be at least as important as the direct ionization of the primary protons-twice as important, if recently recommended radiation weighting factors and "worst-case" geometry are used. The use of conventional dosimetry (absorbed dose weighted by aa linear energy transfer-dependent quality factor) as an appropriate framework for predicting risk from low fluences of high-linear energy transfer target fragments is discussed.

Calibration of personnel monitors by exposure to gamma radiation with energies up to 9 MeV

International Nuclear Information System (INIS)

Leao, J.L.B.; Cunha, P.G. da; Diz, R.; Oberhofer, M.

Occupational exposure with photons of high energy (higher than those from 60 Co) might occur from nuclear reactors and accelerators. Radiation monitors for absorbed dose determination, however, often do not have a wall thickness sufficient to establish electronical equilibrium in that energy range. Using calibration factors determined for lower energies (calibration factors for 60 Co radiation) might cause a significant underestimation of the soft tissue absorbed dose. The calibration factor of the personnel monitors of the Eberline Instrument Co.based on TL dosimeters of LiF is reported. This monitor was calibrated with 9 MeV photons produced by thermal neutrons capture in a Nitarget, at an absorbed dose rate of 125 rads/h at the C.E.N. in France. The results are compared with the corresponding calibration factors for different energies up to 60 Co radiation determined in the IRD (Instituto de Radioprotecao e Dosimetria Rio de Janeiro). (Author) [pt

Very High Radiation Detector for the LHC BLM System Based on Secondary Electron Emission

CERN Document Server

Dehning, B; Holzer, EB; Kramer, D

2007-01-01

Beam Loss Monitoring (BLM) system plays a vital role in the active protection of the LHC accelerators elements. It should provide the number of particles lost from the primary hadron beam by measuring the radiation field induced by their interaction with matter surrounding the beam pipe. The LHC BLM system will use ionization chambers as standard detectors but in the areas where very high dose rates are expected, the Secondary Emission Monitor (SEM) chambers will be employed because of their high linearity, low sensitivity and fast response. The SEM needs a high vacuum for proper operation and has to be functional for up to 20 years, therefore all the components were designed according to the UHV requirements and a getter pump was included. The SEM electrodes are made of Ti because of its Secondary Emission Yield (SEY) stability. The sensitivity of the SEM was modeled in Geant4 via the Photo-Absorption Ionization module together with custom parameterization of the very low energy secondary electron production...

Shielding calculations for neutron calibration bunker using Monte Carlo code MCNP-4C

International Nuclear Information System (INIS)

Suman, H.; Kharita, M. H.; Yousef, S.

2008-02-01

In this work, the dose arising from an Am-Be source of 10 8 neutron/sec strength located inside the newly constructed neutron calibration bunker in the National Radiation Metrology Laboratories, was calculated using MCNP-4C code. It was found that the shielding of the neutron calibration bunker is sufficient. As the calculated dose is not expected to exceed in inhabited areas 0.183 μSv/hr, which is 10 times smaller than the regulatory dose constraints. Hence, it can be concluded that the calibration bunker can house - from the external exposure point of view - an Am-Be neutron source of 10 9 neutron/sec strength. It turned out that the neutron dose from the source is few times greater than the photon dose. The sky shine was found to contribute significantly to the total dose. This contribution was estimated to be 60% of the neutron dose and 10% of the photon dose. The systematic uncertainties due to various factors have been assessed and was found to be between 4 and 10% due to concrete density variations; 15% due to the dose estimation method; 4 -10% due to weather variations (temperature and moisture). The calculated dose was highly sensitive to the changes in source spectra. The uncertainty due to the use of two different neutron spectra is about 70%.(author)

143 GHz BRIGHTNESS MEASUREMENTS OF URANUS, NEPTUNE, AND OTHER SECONDARY CALIBRATORS WITH BOLOCAM BETWEEN 2003 AND 2010

International Nuclear Information System (INIS)

Sayers, J.; Czakon, N. G.; Golwala, S. R.

2012-01-01

Bolocam began collecting science data in 2003 as the long-wavelength imaging camera at the Caltech Submillimeter Observatory. The planets, along with a handful of secondary calibrators, have been used to determine the flux calibration for all of the data collected with Bolocam. Uranus and Neptune stand out as the only two planets that are bright enough to be seen with high signal-to-noise in short integrations without saturating the standard Bolocam readout electronics. By analyzing all of the 143 GHz observations made with Bolocam between 2003 and 2010, we find that the brightness ratio of Uranus to Neptune is 1.027 ± 0.006, with no evidence for any variations over that period. Including previously published results at ≅ 150 GHz, we find a brightness ratio of 1.029 ± 0.006 with no evidence for time variability over the period 1983-2010. Additionally, we find no evidence for time variability in the brightness ratio of either Uranus or Neptune to the ultracompact H II region G34.3 or the protostellar source NGC 2071IR. Using recently published Wilkinson Microwave Anisotropy Probe results we constrain the absolute 143 GHz brightness of both Uranus and Neptune to ≅ 3%. Finally, we present ≅ 3% absolute 143 GHz peak flux density values for the ultracompact H II regions G34.3 and K3-50A and the protostellar source NGC 2071IR.

Gamma dosimetry of high doses

International Nuclear Information System (INIS)

Martinez C, T.; Galvan G, A.; Canizal, G.

1991-01-01

The gamma dosimetry of high doses is problematic in almost all the classic dosemeters either based on the thermoluminescence, electric, chemical properties, etc., because they are saturated to very high dose and they are no longer useful. This work carries out an investigation in the interval of high doses. The solid system of heptahydrate ferrous sulfate, can be used as solid dosemeter of routine for high doses of radiation. The proposed method is simple, cheap and it doesn't require sophisticated spectrophotometers or spectrometers but expensive and not common in some laboratories

Dimethylamine as a Replacement for Ammonia Dosing in the Secondary Circuit of an Advanced Gas-Cooled Reactor (AGR) Power Station

International Nuclear Information System (INIS)

Armstrong, C.; Mitchell, M.; Bull, A.; Quirk, G.P.; Rudge, A.

2012-09-01

Increasing flow resistance observed over recent years within the helical once-through boilers in the four Advanced Gas-Cooled Reactors (AGRs) at Hartlepool and Heysham 1 Power stations have reduced boiler performance, resulting in reductions in feedwater flow, steam temperatures, power output and the need to carry out periodic chemical cleaning. The root cause is believed to be the development of magnetite deposits with high flow impedance in the 9%Cr evaporator section of the boiler tubing. To prevent continued increases in boiler flow resistance, dimethylamine is being trialled, in one of the four affected units, as a replacement to the conventional ammonia dosing. Dimethylamine increases the pH at temperature around the secondary circuit and, based on full scale boiler rig simulations, is expected to reduce iron transport and prevent flow resistance increases within the evaporator section of the boiler. The dimethylamine plant trial commenced in January 2011 and is ongoing. The feedwater concentration of dimethylamine has been increased progressively towards a final target value of 900 μg kg -1 and its effect on iron transport and boiler pressure loss is being closely monitored. The high steam temperatures (>500 deg. C) of the secondary circuit lead to some decomposition of dimethylamine, which is being carefully monitored at various locations around the circuit. The decomposition products identified with dimethylamine dosing include ammonia, methylamine, formic acid, carbon dioxide and, as yet, unidentified neutral organic species. The effect of dimethylamine dosing on iron transport, boiler pressure drops and its decomposition behaviour around the secondary circuit during the plant trial will be presented in this paper. (authors)

Fast film dosimetry calibration method for IMRT treatment plan verification

International Nuclear Information System (INIS)

Schwob, N.; Wygoda, A.

2004-01-01

Intensity-Modulated Radiation Therapy (IMRT) treatments are delivered dynamically and as so, require routinely performed verification measurements [1]. Radiographic film dosimetry is a well-adapted method for integral measurements of dynamic treatments fields, with some drawbacks related to the known problems of dose calibration of films. Classically, several films are exposed to increasing doses, and a Net Optical Density (N.O.D) vs. dose sensitometric curve (S.C.) is generated. In order to speed up the process, some authors have developed a method based on the irradiation of a single film with a non-uniform pattern of O.D., delivered with a dynamic MLC. However, this curve still needs to be calibrated to dose by the means of measurements in a water phantom. It is recommended to make a new calibration for every series of measurements, in order to avoid the processing quality dependence of the film response. These frequent measurements are very time consuming. We developed a simple method for quick dose calibration of films, including a check of the accuracy of the calibration curve obtained

Thermocouple calibration facility for 2900 deg C high temperature and its applications

International Nuclear Information System (INIS)

Chen Daolong

1991-01-01

The construction and the performance characteristic of a 2900 deg C high temperature thermocouple calibration facility are described. The calibration error analysis is made. The test results of the calibration characteristics of high temperature thermocouples Mo/Nb, W-3Re/W-25Re, and W-1Mo/W-25Mo are given. The test result of temperature dependent resistivity of BeO made by this facility is given

How to calibrate Grenz-beams in clinical practice?

Energy Technology Data Exchange (ETDEWEB)

Schaeken, B [Algemeen Ziekenhius Middelheim, Antwerp (Belgium); Bressers, E [Virga jesse Ziekenhius, Hasselt (Belgium)

1995-12-01

In recent years, considerable efforts have been spent improving the precision and consistency in the whole process of calibration of high energy photon and electron beams (national protocols, primary calibration facilities ....). The reading in air of 5 different ionisation chambers (NE2532, NE2536, NE2571, PTWM23342, Markus) in an X-ray beam (RT50, HVL=0.35 mm Al) has been compared. Ali NE chambers were provided with a calibration factor Nk, the PTW chamber was directly calibrated in dose water ND,W. The polarisation and recombination effects were measured. In our reference field (ssd=4cm, field diameter 40 mm), the readings in air for the dedicated plan parallel chambers deviated by not more than 8%. The measurements with the NE2571 chamber did not correspond very well with the other measurements. For the equipment in our hospital, the dose rate in air for the reference field was measured from 1971 on and found to be very stable: 17.36 Gy/min (0.48) (1sd). An attempt was made to measure the BSF for the field defining cones used in clinical practice using a Markus plane parallel chamber, but the resulting BSF did not correspond to those reported in BJR/suppl. 17. Special attention has been be paid to the calibration of beams with field size comparable to the dimension of the chamber window- chamber body.

Calibration of GafChromic XR-RV3 radiochromic film for skin dose measurement using standardized x-ray spectra and a commercial flatbed scanner

International Nuclear Information System (INIS)

McCabe, Bradley P.; Speidel, Michael A.; Pike, Tina L.; Van Lysel, Michael S.

2011-01-01

Purpose: In this study, newly formulated XR-RV3 GafChromic film was calibrated with National Institute of Standards and Technology (NIST) traceability for measurement of patient skin dose during fluoroscopically guided interventional procedures. Methods: The film was calibrated free-in-air to air kerma levels between 15 and 1100 cGy using four moderately filtered x-ray beam qualities (60, 80, 100, and 120 kVp). The calibration films were scanned with a commercial flatbed document scanner. Film reflective density-to-air kerma calibration curves were constructed for each beam quality, with both the orange and white sides facing the x-ray source. A method to correct for nonuniformity in scanner response (up to 25% depending on position) was developed to enable dose measurement with large films. The response of XR-RV3 film under patient backscattering conditions was examined using on-phantom film exposures and Monte Carlo simulations. Results: The response of XR-RV3 film to a given air kerma depended on kVp and film orientation. For a 200 cGy air kerma exposure with the orange side of the film facing the source, the film response increased by 20% from 60 to 120 kVp. At 500 cGy, the increase was 12%. When 500 cGy exposures were performed with the white side facing the x-ray source, the film response increased by 4.0% (60 kVp) to 9.9% (120 kVp) compared to the orange-facing orientation. On-phantom film measurements and Monte Carlo simulations show that using a NIST-traceable free-in-air calibration curve to determine air kerma in the presence of backscatter results in an error from 2% up to 8% depending on beam quality. The combined uncertainty in the air kerma measurement from the calibration curves and scanner nonuniformity correction was ±7.1% (95% C.I.). The film showed notable stability. Calibrations of film and scanner separated by 1 yr differed by 1.0%. Conclusions: XR-RV3 radiochromic film response to a given air kerma shows dependence on beam quality and film

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

Energy Technology Data Exchange (ETDEWEB)

Chibani, Omar, E-mail: omar.chibani@fccc.edu; C-M Ma, Charlie [Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111 (United States)

2014-05-15

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

Early Angiographic Resolution of Cerebral Vasospasm with High Dose Intravenous Milrinone Therapy

Directory of Open Access Journals (Sweden)

F. A. Zeiler

2015-01-01

Full Text Available Background. Treatment of symptomatic delayed cerebral ischemia (DCI after subarachnoid hemorrhage (SAH is difficult. Recent studies suggest intravenous (IV high dose milrinone as a potential therapy. The timing to angiographic response with this is unclear. Methods. We reviewed the chart of one patient admitted for SAH who developed symptomatic DCI and was treated with high dose IV milrinone. Results. A 66-year-old female was admitted with a Hunt and Hess clinical grade 4, World Federation of Neurological Surgeons (WFNS clinical grade 4, and SAH secondary to a left anterior choroidal artery aneurysm which was clipped. After bleed day 6, the patient developed symptomatic DCI. We planned for angioplasty of the proximal segments. We administered high dose IV milrinone bolus followed by continuous infusion which led to clinical improvement prior to angiography. The angiogram performed 1.5 hours after milrinone administration displayed resolution of the CT angiogram and MRI based cerebral vasospasm such that further intra-arterial therapy was aborted. She completed 6 days of continuous IV milrinone therapy, was transferred to the ward, and subsequently rehabilitated. Conclusions. High dose IV milrinone therapy for symptomatic DCI after SAH can lead to rapid neurological improvement with dramatic early angiographic improvement of cerebral vasospasm.

Calibration of instrument and personnel monitoring in radiological protection

International Nuclear Information System (INIS)

Abdul Aziz Mohamad Ramli; Wan Saffiey Wan Abdullah

1987-01-01

It is difficult to choose radioprotection equipments that are not too expensive and suit the purpose. Some of the dosimetric characteristics of good dosemeters outlined by ISO 4071-1978 (E) namely scale linearity, energy dependence, radiation quality dependence and angular dependence for some of the commercially available dosemeters are discussed. The calibration procedures practised at the National Secondary Standard Dosimetry Laboratory (SSDL), of the Nuclear Energy Unit (NEU) is also explained. The radiological equipments for personnel monitoring such as film badge and TLD are widely used to estimate the radiation dose delivered to the whole or partial body of a personnel. Both of the personnel monitoring procedures have been established at the NEU. The objective, use and maintenance of the devices are also discussed in detail. The evaluation of the monthly dose received by a personnel from various establishments in the country are also presented. (author). 17 figs

High-Dose Versus Low-Dose Pitavastatin in Japanese Patients With Stable Coronary Artery Disease (REAL-CAD): A Randomized Superiority Trial.

Science.gov (United States)

Taguchi, Isao; Iimuro, Satoshi; Iwata, Hiroshi; Takashima, Hiroaki; Abe, Mitsuru; Amiya, Eisuke; Ogawa, Takanori; Ozaki, Yukio; Sakuma, Ichiro; Nakagawa, Yoshihisa; Hibi, Kiyoshi; Hiro, Takafumi; Fukumoto, Yoshihiro; Hokimoto, Seiji; Miyauchi, Katsumi; Yamazaki, Tsutomu; Ito, Hiroshi; Otsuji, Yutaka; Kimura, Kazuo; Takahashi, Jun; Hirayama, Atsushi; Yokoi, Hiroyoshi; Kitagawa, Kazuo; Urabe, Takao; Okada, Yasushi; Terayama, Yasuo; Toyoda, Kazunori; Nagao, Takehiko; Matsumoto, Masayasu; Ohashi, Yasuo; Kaneko, Tetsuji; Fujita, Retsu; Ohtsu, Hiroshi; Ogawa, Hisao; Daida, Hiroyuki; Shimokawa, Hiroaki; Saito, Yasushi; Kimura, Takeshi; Inoue, Teruo; Matsuzaki, Masunori; Nagai, Ryozo

2018-05-08

Current guidelines call for high-intensity statin therapy in patients with cardiovascular disease on the basis of several previous "more versus less statins" trials. However, no clear evidence for more versus less statins has been established in an Asian population. In this prospective, multicenter, randomized, open-label, blinded end point study, 13 054 Japanese patients with stable coronary artery disease who achieved low-density lipoprotein cholesterol (LDL-C) fashion to high-dose (pitavastatin 4 mg/d; n=6526) or low-dose (pitavastatin 1 mg/d; n=6528) statin therapy. The primary end point was a composite of cardiovascular death, nonfatal myocardial infarction, nonfatal ischemic stroke, or unstable angina requiring emergency hospitalization. The secondary composite end point was a composite of the primary end point and clinically indicated coronary revascularization excluding target-lesion revascularization at sites of prior percutaneous coronary intervention. The mean age of the study population was 68 years, and 83% were male. The mean LDL-C level before enrollment was 93 mg/dL with 91% of patients taking statins. The baseline LDL-C level after the run-in period on pitavastatin 1 mg/d was 87.7 and 88.1 mg/dL in the high-dose and low-dose groups, respectively. During the entire course of follow-up, LDL-C in the high-dose group was lower by 14.7 mg/dL than in the low-dose group ( P Japanese patients with stable coronary artery disease. URL: https://www.clinicaltrials.gov. Unique identifier: NCT01042730. © 2018 The Authors.

Calibration Curves for Biological Dosimetry by Fluorescence In situ Hybridisation

International Nuclear Information System (INIS)

Stonati, L.; Durante, M.; Gensabella, G.; Gialanella, G.; Grossi, G.F.; Pugliese, M.; Scampoli, P.; Sgura, A.; Testa, A.; Tanzarella, C.

2001-01-01

Dose-response curves were measured for the induction of chromosomal aberrations in peripheral blood lymphocytes after acute exposure in vitro to 60 Co γ rays. Blood was obtained from four different healthy donors, and chromosomes were either observed at metaphase, following colcemid accumulation, or prematurely condensed by calyculin A. Cells were analysed in three different Italian laboratories. Chromosomes 1, 2, and 4 were painted, and simple-type interchanges between painted and non-painted chromosomes were scored in cells exposed in the dose range 0.1-3.0 Gy. The chemical-induced premature chromosome condensation method was also used combined with chromosome painting (chromosome 4 only) to determine calibration curves for high dose exposures (up to 20 Gy X rays). Calibration curves described in this paper will be used in our laboratories for biological dosimetry by fluorescence in situ hybridisation. (author)

Absorbed-dose beam quality conversion factors for cylindrical chambers in high energy photon beams.

Science.gov (United States)

Seuntjens, J P; Ross, C K; Shortt, K R; Rogers, D W

2000-12-01

Recent working groups of the AAPM [Almond et al., Med. Phys. 26, 1847 (1999)] and the IAEA (Andreo et al., Draft V.7 of "An International Code of Practice for Dosimetry based on Standards of Absorbed Dose to Water," IAEA, 2000) have described guidelines to base reference dosimetry of high energy photon beams on absorbed dose to water standards. In these protocols use is made of the absorbed-dose beam quality conversion factor, kQ which scales an absorbed-dose calibration factor at the reference quality 60Co to a quality Q, and which is calculated based on state-of-the-art ion chamber theory and data. In this paper we present the measurement and analysis of beam quality conversion factors kQ for cylindrical chambers in high-energy photon beams. At least three chambers of six different types were calibrated against the Canadian primary standard for absorbed dose based on a sealed water calorimeter at 60Co [TPR10(20)=0.572, %dd(10)x=58.4], 10 MV [TPR10(20)=0.682, %dd(10)x=69.6), 20 MV (TPR10(20)=0.758, %dd(10)x= 80.5] and 30 MV [TPR10(20) = 0.794, %dd(10)x= 88.4]. The uncertainty on the calorimetric determination of kQ for a single chamber is typically 0.36% and the overall 1sigma uncertainty on a set of chambers of the same type is typically 0.45%. The maximum deviation between a measured kQ and the TG-51 protocol value is 0.8%. The overall rms deviation between measurement and the TG-51 values, based on 20 chambers at the three energies, is 0.41%. When the effect of a 1 mm PMMA waterproofing sleeve is taken into account in the calculations, the maximum deviation is 1.1% and the overall rms deviation between measurement and calculation 0.48%. When the beam is specified using TPR10(20), and measurements are compared with kQ values calculated using the version of TG-21 with corrected formalism and data, differences are up to 1.6% when no sleeve corrections are taken into account. For the NE2571 and the NE2611A chamber types, for which the most literature data are

High intensity line source for x-ray spectrometer calibration

International Nuclear Information System (INIS)

Thoe, R.S.

1986-06-01

A high intensity electron-impact x-ray source using a one-dimensional Pierce lens has been built for the purpose of calibrating a bent crystal x-ray spectrometer. This source focuses up to 100 mA of 20-keV electrons to a line on a liquid-cooled anode. The line (which can serve as a virtual slit for the spectrometer) measures approximately 800 μ x 2 cm. The source is portable and therefore adaptable to numerous types of spectrometer applications. One particular application, the calibration of a high resolution (r = 10 4 ) time-resolved cyrstal spectrometer, will be discussed in detail

High Accuracy Transistor Compact Model Calibrations

Energy Technology Data Exchange (ETDEWEB)

Hembree, Charles E. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Mar, Alan [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Robertson, Perry J. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)

2015-09-01

Typically, transistors are modeled by the application of calibrated nominal and range models. These models consists of differing parameter values that describe the location and the upper and lower limits of a distribution of some transistor characteristic such as current capacity. Correspond- ingly, when using this approach, high degrees of accuracy of the transistor models are not expected since the set of models is a surrogate for a statistical description of the devices. The use of these types of models describes expected performances considering the extremes of process or transistor deviations. In contrast, circuits that have very stringent accuracy requirements require modeling techniques with higher accuracy. Since these accurate models have low error in transistor descriptions, these models can be used to describe part to part variations as well as an accurate description of a single circuit instance. Thus, models that meet these stipulations also enable the calculation of quantifi- cation of margins with respect to a functional threshold and uncertainties in these margins. Given this need, new model high accuracy calibration techniques for bipolar junction transis- tors have been developed and are described in this report.

Share of erythema dose of solar radiation in high mountains

International Nuclear Information System (INIS)

Blumthaler, M.; Ambach, W.

1987-01-01

The erythema dose was measured using a Robertson-Berger Sunburn Meter. The spectral sensitivity of the detector is adapted to an erythema action spectrum with the optical center at about 300 nm. The erythema dose is expressed in the biologically relevant Sunburn Units (SU). The Robertson-Berger Sunburn Meter has been recommended by the WMO for global monitoring of solar UV-B erythema dose. UV-A radiation was measured with a UV-radiometer. The spectral sensitivity of the detector has a flat maximum at 345 nm and a half band width of +- 25 nm. Global radiation was measured using a pyranometer. All detectors were placed horizontally and calibrated several times. Readings were taken in intervals of one minute

Design and development of semi-automatic radiation test and calibration facility

International Nuclear Information System (INIS)

Yadav, Ashok Kumar; Chouhan, V.K.; Narayan, Pradeep

2008-01-01

Semi-automatic gamma radiation test and calibration facility have been designed, developed and commissioned at Defence Laboratory Jodhpur (DLJ). The facility comprises of medium and high dose rate range setup using 30 Ci Cobalt-60 source, in a portable remotely operated Techops camera and a 15000 Ci 60 Co source in a Tele-therapy machine. The radiation instruments can be positioned at any desired position using a computer controlled positioner having three translational and one rotational motion. User friendly software helps in positioning the Device Under Test (DUT) at any desired dose rate or distance and acquire the data automatically. The servo and stepper motor controlled positioner helps in achieving the required precision and accuracy for the radiation calibration of the instruments. This paper describes the semi-automatic radiation test and calibration facility commissioned at DLJ. (author)

An assessment of the secondary neutron dose in the passive scattering proton beam facility of the national cancer center

Energy Technology Data Exchange (ETDEWEB)

Han, Sang Eun [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of); Cho, Gyuseong [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Lee, Se Byeong [Proton Therapy Center, National Cancer Center, Goyang (Korea, Republic of)

2017-06-15

The purpose of this study is to assess the additional neutron effective dose during passive scattering proton therapy. Monte Carlo code (Monte Carlo N-Particle 6) simulation was conducted based on a precise modeling of the National Cancer Center's proton therapy facility. A three-dimensional neutron effective dose profile of the interior of the treatment room was acquired via a computer simulation of the 217.8-MeV proton beam. Measurements were taken with a 3He neutron detector to support the simulation results, which were lower than the simulation results by 16% on average. The secondary photon dose was about 0.8% of the neutron dose. The dominant neutron source was deduced based on flux calculation. The secondary neutron effective dose per proton absorbed dose ranged from 4.942 ± 0.031 mSv/Gy at the end of the field to 0.324 ± 0.006 mSv/Gy at 150 cm in axial distance.

Estimated of associated uncertainties of the linearity test of dose calibrators; Estimativa das incertezas associadas ao teste de linearidade de calibradores de dose

Energy Technology Data Exchange (ETDEWEB)

Sousa, Carlos H.S.; Peixoto, Jose G.P., E-mail: chenrique@ird.gov.br [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), RIo de Janeiro, RJ (Brazil)

2013-07-01

Activimeters determine the activity of radioactive samples and them are validated by performance tests. This research determined the expanded uncertainties associated to the linearity test. Were used three dose calibrators and three sources of {sup 99}Tc{sup m} for testing using recommended protocol by the IAEA, which considered the decay of radioactive samples. The expanded uncertainties evaluated were not correlated with each other and their analysis considered a rectangular probability distribution. The results are also presented in graphical form by the function of normalized activity measured in terms of conventional true value. (author)

Calibration of solid state nuclear track detectors at high energy ion beams for cosmic radiation measurements: HAMLET results

International Nuclear Information System (INIS)

Szabó, J.; Pálfalvi, J.K.

2012-01-01

The MATROSHKA experiments and the related HAMLET project funded by the European Commission aimed to study the dose burden of the crew working on the International Space Station (ISS). During these experiments a human phantom equipped with several thousands of radiation detectors was exposed to cosmic rays inside and outside the ISS. Besides the measurements realized in Earth orbit, the HAMLET project included also a ground-based program of calibration and intercomparison of the different detectors applied by the participating groups using high-energy ion beams. The Space Dosimetry Group of the Centre for Energy Research (formerly Atomic Energy Research Institute) participated in these experiments with passive solid state nuclear track detectors (SSNTDs). The paper presents the results of the calibration experiments performed in the years 2008–2011 at the Heavy Ion Medical Accelerator (HIMAC) of the National Institute of Radiological Sciences (NIRS), Chiba, Japan. The data obtained serve as update and improvement for the previous calibration curves which are necessary for the evaluation of the SSNTDs exposed in unknown space radiation fields.

Calibration of solid state nuclear track detectors at high energy ion beams for cosmic radiation measurements: HAMLET results

Energy Technology Data Exchange (ETDEWEB)

Szabo, J., E-mail: julianna.szabo@energia.mta.hu [Hungarian Academy of Sciences, Centre for Energy Research, Konkoly Thege Miklos ut 29-33, 1525 Budapest 114, P.O. Box 49 (Hungary); Palfalvi, J.K. [Hungarian Academy of Sciences, Centre for Energy Research, Konkoly Thege Miklos ut 29-33, 1525 Budapest 114, P.O. Box 49 (Hungary)

2012-12-01

The MATROSHKA experiments and the related HAMLET project funded by the European Commission aimed to study the dose burden of the crew working on the International Space Station (ISS). During these experiments a human phantom equipped with several thousands of radiation detectors was exposed to cosmic rays inside and outside the ISS. Besides the measurements realized in Earth orbit, the HAMLET project included also a ground-based program of calibration and intercomparison of the different detectors applied by the participating groups using high-energy ion beams. The Space Dosimetry Group of the Centre for Energy Research (formerly Atomic Energy Research Institute) participated in these experiments with passive solid state nuclear track detectors (SSNTDs). The paper presents the results of the calibration experiments performed in the years 2008-2011 at the Heavy Ion Medical Accelerator (HIMAC) of the National Institute of Radiological Sciences (NIRS), Chiba, Japan. The data obtained serve as update and improvement for the previous calibration curves which are necessary for the evaluation of the SSNTDs exposed in unknown space radiation fields.

IAEA workshop/seminar on calibration procedures in dosimetry, Quito, 6-24 October 1986

International Nuclear Information System (INIS)

1987-01-01

The International Atomic Energy Agency in co-operation with the Ecuadorian Atomic Energy Commission organized a workshop and seminar on calibration procedures in dosimetry at the SSDL Quito, 6 to 24 October 1986. All calibration laboratories in the Latin American region were invited to participate. The purpose of the workshop were calibration exercises with therapy-level and protection-level secondary standards at various calibration qualities, discussions on progress made in the different SSDLs in the region and delivering lectures on pertinent subjects. A total of 15 Secondary Standards (10 therapy-level and 5 protection-level) were brought along by the participants and 35 calibration comparisons were performed with those having a valid calibration factor. Thirty-three determinations of calibration factors were performed for secondary standards not having had a calibration before. Twelve different calibration qualities were available (Cobalt-60 and X-rays) and Agency's Secondary Standards traceable to BIPM were the reference standards. The participants were divided into two working groups, each one week and each group into two sub-groups. Both irradiation bunkers were used simultaneously. The one houses the teletherapy Cobalt-60 unit and the protection-level Cobalt-60 irradiator, the other one the constant potential X-ray machine with maximum generating potential of 320 KV and suitable for both therapy-level as well as protection-level calibrations. Due to the heavy workload and limited time available some nightshifts were required to accomplish the requested calibration comparisons

Calibration of clinical dosemeters in the IAEA water phantom

International Nuclear Information System (INIS)

Caldas, L.V.E.; Albuquerque, M.P.P.

1994-01-01

The procedures recommended by the IAEA Code of Practice were applied at the Calibration Laboratory of Sao Paulo in order to provide in the future the clinical dosemeters users with absorbed dose to water calibration factors for Cobalt 60 radiation beams. In this work the clinical dosemeters were calibrated free in air and in water, and the results were compared, using conversion factors. The several tested clinical dosemeters of different manufacturers and models belong to the laboratory and to hospitals. For the measurements in water the IAEA cubic water phantom was used. The dosemeters were all calibrated free in air in terms of air kerma, and the calibration factors in terms of absorbed dose to water were obtained through conversion factors. the same dosemeters were also calibrated into the water phantom. Good agreement was found between the two methods, the differences were always less than 0.5%. The data obtained during this work show that when the dosemeters are used only in Cobalt 60 radiation and the users apply in the hospital routine work the IAEA Code of Practice, the calibration can be performed directly in the water phantom. This procedure provides the useful calibration factors in terms of absorbed dose to water

A comparison of Australian and Canadian calibration coefficients for air kerma and absorbed dose to water for 60Co gamma radiation.

Science.gov (United States)

Shortt, K R; Huntley, R B; Kotler, L H; Boas, J F; Webb, D V

2006-06-01

Australian and Canadian calibration coefficients for air kerma and absorbed dose to water for 60Co gamma radiation have been compared using transfer standard ionization chambers of types NE 2561 and NE 2611A. Whilst the primary standards of air kerma are similar, both being thick-walled graphite cavity chambers but employing different methods to evaluate the Awall correction, the primary standards of absorbed dose to water are quite different. The Australian standard is based on measurements made with a graphite calorimeter, whereas the Canadian standard uses a sealed water calorimeter. The comparison result, expressed as a ratio of calibration coefficients R=N(ARPANSA)/N(NRC), is 1.0006 with a combined standard uncertainty of 0.35% for the air kerma standards and 1.0052 with a combined standard uncertainty of 0.47% for the absorbed dose to water standards. This demonstrates the agreement of the Australian and Canadian radiation dosimetry standards. The results are also consistent with independent comparisons of each laboratory with the BIPM reference standards. A 'trilateral' analysis confirms the present determination of the relationship between the standards, within the 0.09% random component of the combined standard uncertainty for the three comparisons.

Development and calibration of a portable detection device for in vivo measurement of high-energy photon emitters incorporated by humans

International Nuclear Information System (INIS)

Soares, A.B.; Arbach, M.N.; Lucena, E.A.; Dantas, A.L.A.; Dantas, B.M.

2017-01-01

This work presents the evaluation of the applicability and sensitivity of a portable detection device specially designed for in vivo measurement of high-energy photon emitters in the human body. The calibration was performed at the In-Vivo Monitoring Laboratory of the IRD. The equipment consists of a lead-collimated NaI (Tl) 3″ x 3″ scintillation detector assembled on a tripod. The detector and its compact associated electronics are connected via USB cable to a portable PC. Spectrum acquisition and analysis is controlled by specific commercially available software. The calibration was performed using a standard liquid source of 152 Eu contained in 3 L polyethylene bottles. The evaluation of the system is based on the estimation of the minimum committed effective doses associated to the minimum detectable activities, calculated using current biokinetic and dosimetric models available in the literature. The dose detection limits for selected radionuclides of interest in an emergency scenario have shown to be far below 1 mSv allowing the system to be useful in accident situations. (author)

Development and calibration of a portable detection device for in vivo measurement of high-energy photon emitters incorporated by humans

Energy Technology Data Exchange (ETDEWEB)

Soares, A.B.; Arbach, M.N.; Lucena, E.A.; Dantas, A.L.A.; Dantas, B.M., E-mail: alexandrebaso@globo.com [Instituto de Radioproteção e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil). Lab. de Monitoração Interna

2017-07-01

This work presents the evaluation of the applicability and sensitivity of a portable detection device specially designed for in vivo measurement of high-energy photon emitters in the human body. The calibration was performed at the In-Vivo Monitoring Laboratory of the IRD. The equipment consists of a lead-collimated NaI (Tl) 3″ x 3″ scintillation detector assembled on a tripod. The detector and its compact associated electronics are connected via USB cable to a portable PC. Spectrum acquisition and analysis is controlled by specific commercially available software. The calibration was performed using a standard liquid source of {sup 152}Eu contained in 3 L polyethylene bottles. The evaluation of the system is based on the estimation of the minimum committed effective doses associated to the minimum detectable activities, calculated using current biokinetic and dosimetric models available in the literature. The dose detection limits for selected radionuclides of interest in an emergency scenario have shown to be far below 1 mSv allowing the system to be useful in accident situations. (author)

Is the dose equivalent index a quantity to be measured

International Nuclear Information System (INIS)

Wagner, S.R.

1980-01-01

ICRP introduced the concept of Effective Dose Equivalent H(sub)E and fixed the basic limits of radiation exposure in terms of H(sub)I. As H(sub)E cannot be measured, ICRP stated that with external exposure to penetrating radiation the limitation of the Dose Equivalent Index H(sub)I would afford at least as good a level of protection. However, difficulties arise in measuring H(sub)I and in calibrating instruments in terms of H(sub)I, since the height and location of the dose equivalent maximum in the sphere which is the phantom used in the definition of H(sub)I, depend on the energy and the angular distribution of the incident radiation. That is, H(sub)I is not an additive quantity relative to the partial H(sub)I(sub)i-values of the different energy and angular components. Hence, 1) the distribution of dose equivalent in the sphere must be measured in full for a determination of H(sub)I, and 2) it is not possible to calibrate an instrument which does not exhibit the scattering and absorption properties of the sphere, consistently for arbitrary radiation fields in terms of H(sub)I. Thus the calibration in an unidirectional beam would infer an uncertainty which may amount to a factor of up to 4. This would hardly be tolerable as a base for radiation protection provisions. An alternative is to introduce operational quantities which are additive, e.g. 1) the sum of maxima of the dose equivalent distributions in the sphere produced by different radiation components, and 2) the mean dose equivalent in the sphere. Their relation to H(sub)E for different types of radiation and consequences on secondary limits are discussed. (H.K.)

Calibration of thermoluminiscent materials

International Nuclear Information System (INIS)

Bos, A.J.J.

1989-07-01

In this report the relation between exposure and absorbed radiation dose in various materials is represented, on the base of recent data. With the help of this a calibration procedure for thermoluminescent materials, adapted to the IRI radiation standard is still the exposure in rontgen. In switching to the air kerma standard the calibration procedure will have to be adapted. (author). 6 refs.; 4 tabs

LET calibration for CR-39 detectors in different oxygen environments

International Nuclear Information System (INIS)

Zhou, D.; Semones, E.; Weyland, M.; Benton, E.R.

2007-01-01

High LET (linear energy transfer) radiation is the main contributor to the radiation field in low Earth orbit (LEO) in terms of dose equivalent. CR-39 plastic nuclear track detectors (PNTDs) can measure the LET spectrum and charge spectrum for the complicated radiation field in space. Previous research indicated that the sensitivity of CR-39 is different for CR-39 PNTDs working in different oxygen environments. LET calibration for CR-39 detectors in different oxygen environments is needed. Almost all the previous LET calibration work was carried out for CR-39 detectors in good-oxygen condition, LET calibration work for CR-39 in poor-oxygen condition has not been conducted until our work. Systematic LET calibrations were carried out by JSC-SRAG (Space Radiation Analysis Group) for CR-39 detectors working in different oxygen environments and abundant results of LET calibrations were obtained. This paper introduces the method for CR-39 LET calibration, presents and discusses the calibration results and some applications

Characterisation of a protection level Am-241 calibration source

Science.gov (United States)

Bass, G. A.; Rossiter, M. J.; Williams, T. T.

1992-11-01

The various measurements involved in the commissioning process of an Am-241 radioactive source and transport mechanisms to be used for protection level calibration work are detailed. The source and its handling mechanisms are described and measurements to characterize the resultant gamma ray beam are described. For the beam measurements, the inverse square law is investigated and beam uniformity is assessed. A trial calibration of ionization chambers is described. The Am-241 irradiation facility is concluded to be suitable for calibrating secondary standards as part of the calibration service offered for protection level instruments. The umbra part of beam is acceptably uniform for a range of chambers and the measurements obtained were predictable and consistent. This quality will be added to the range of qualities offered as part of the protection level secondary standard calibration service.

Feasibility study of radiophotoluminescent glass rod dosimeter postal dose intercomparison for high energy photon beam

International Nuclear Information System (INIS)

Rah, Jeong-Eun; Kim, Siyong; Cheong, Kwang-Ho; Lee, Jeong-Woo; Chung, Jin-Beom; Shin, Dong-Oh; Suh, Tae-Suk

2009-01-01

A radiophotoluminescent glass rod dosimeter (GRD) system has recently become commercially available. In this study we evaluated whether the GRD would be suitable for external dosimetric audit program in radiotherapy. For this purpose, we introduced a methodology of the absorbed dose determination with the GRD by establishing calibration coefficient and various correction factors (non-linearity dose response, fading, energy dependence and angular dependence). A feasibility test of the GRD postal dose intercomparison was also performed for eight high photon beams by considering four radiotherapy centers in Korea. In the accuracy evaluation of the GRD dosimetry established in this study, we obtained within 1.5% agreements with the ionization chamber dosimetry for the 60 Co beam. It was also observed that, in the feasibility study, all the relative deviations were smaller than 3%. Based on these results, we believe that the new GRD system has considerable potential to be used for a postal dose audit program

Optical System Error Analysis and Calibration Method of High-Accuracy Star Trackers

Directory of Open Access Journals (Sweden)

Zheng You

2013-04-01

Full Text Available The star tracker is a high-accuracy attitude measurement device widely used in spacecraft. Its performance depends largely on the precision of the optical system parameters. Therefore, the analysis of the optical system parameter errors and a precise calibration model are crucial to the accuracy of the star tracker. Research in this field is relatively lacking a systematic and universal analysis up to now. This paper proposes in detail an approach for the synthetic error analysis of the star tracker, without the complicated theoretical derivation. This approach can determine the error propagation relationship of the star tracker, and can build intuitively and systematically an error model. The analysis results can be used as a foundation and a guide for the optical design, calibration, and compensation of the star tracker. A calibration experiment is designed and conducted. Excellent calibration results are achieved based on the calibration model. To summarize, the error analysis approach and the calibration method are proved to be adequate and precise, and could provide an important guarantee for the design, manufacture, and measurement of high-accuracy star trackers.

Optical system error analysis and calibration method of high-accuracy star trackers.

Science.gov (United States)

Sun, Ting; Xing, Fei; You, Zheng

2013-04-08

The star tracker is a high-accuracy attitude measurement device widely used in spacecraft. Its performance depends largely on the precision of the optical system parameters. Therefore, the analysis of the optical system parameter errors and a precise calibration model are crucial to the accuracy of the star tracker. Research in this field is relatively lacking a systematic and universal analysis up to now. This paper proposes in detail an approach for the synthetic error analysis of the star tracker, without the complicated theoretical derivation. This approach can determine the error propagation relationship of the star tracker, and can build intuitively and systematically an error model. The analysis results can be used as a foundation and a guide for the optical design, calibration, and compensation of the star tracker. A calibration experiment is designed and conducted. Excellent calibration results are achieved based on the calibration model. To summarize, the error analysis approach and the calibration method are proved to be adequate and precise, and could provide an important guarantee for the design, manufacture, and measurement of high-accuracy star trackers.

Brachytherapy source calibration, reviews, and consistency of 192Ir high-dose rate afterloading sources supplied over the period of 10 years: a retrospective analysis

International Nuclear Information System (INIS)

Nagappan, Balasubramanian; Kumar, Yogesh; Patel, Narayan P.; Dhull, Anil Kumar; Kaushal, Vivek

2015-01-01

Measurement and verification of strength of monomodal high-dose rate (mHDR) 192 Ir source supplied by the vendor is a major part of quality assurance program. Reference air kerma rate (RAKR) or air kerma strength (AKS) is the recommended quantity to specify the strength of gamma emitting brachytherapy sources. Physicist in our institution performed the source calibration as soon as each 192 Ir new source was loaded on the mHDR afterloading machine. The AKS accurately measured using a physikalisch technische werkstatten (PTW) re-entrant chamber-electrometer system in a scatter-free geometry was used to compute the air kerma rate (AKR) at one-meter distance in the air. To ensure accurate dose delivery to brachytherapy patients, measured AKS or RAKR should be entered correctly in both HDR treatment console station (TCS) as well as treatment planning system (TPS) associated with it. The clinical outcome mainly depends not only on the accuracy of the source strength measurement in the hospital but also on the correct source strength entered into both TCS and TPS software. A retrospective study on 22 mHDR V2 sources supplied by the vendor for the period of 10 years was taken up to access the accuracy of source strength supplied to the Radiotherapy department. The results are analyzed and reported. The accuracy in measured RAKR of all 22 sources supplied by vendor was well within the tolerance limits set by the national regulatory body and international recommendations. The deviations observed between measured RAKR versus manufacturer's quoted RAKR were in the range from -1.71% to +1.15%. In conclusion, the measured RAKR have good agreement with vendor quoted RAKR values. (author)

Calibration of radiation monitors at nuclear power plants

International Nuclear Information System (INIS)

Boudreau, L.; Miller, A.D.; Naughton, M.D.

1994-03-01

This work was performed to provide guidance to the utilities in the primary and secondary calibration of the radiation monitoring systems (RMS) installed in nuclear power plants. These systems are installed in nuclear power plants to monitor ongoing processes, identify changing radiation fields, predict and limit personnel radiation exposures and measure and control discharge of radioactive materials to the environment. RMS are checked and calibrated on a continuing basis to ensure their precision and accuracy. This report discusses various approaches towards primary and secondary calibrations of the RMS equipment in light of accepted practices at typical power plants and recent interpretations of regulatory guidance. Detailed calibration techniques and overall system responses, trends, and practices are discussed. Industry, utility, and regulatory sources were contacted to create an overall consensus of the most reasonable approaches to optimizing the performance of this equipment

Radiotherapy Dosimetry Protocols For High Energy Photons And Electrons

International Nuclear Information System (INIS)

Thwaites, D.I.

1999-01-01

One vital requirement in radiotherapy is to ensure as closely as possible consistency in determination of dose between different centers and at different times, both within a given country and internationally, because the comparison and transfer of clinical experience and the evaluation of clinical trials is dependent on common statements of dose delivered. In addition at each loon] centre it is vital that the absorbed dose calibration of each beam is carried out to exacting and consistent standards, as this is the fundamental measurement upon which the quality of all treatments on that machine depend throughout its clinical lifetime. The systems in place to ensure consistency in dosimetry differ in the details from country to country, but all depend on the same basic considerations: - the use of ion chambers of similar design and similar construction materials, - traceable calibrations of these chambers to an accredited primary or secondary standard dosimetry laboratory (SSDL) in terms of some agreed relevant dosimetric quantity, - dose statements in terms of absorbed dose to a common material, water, - the application of an appropriate recommended national or international dosimetry protocol (or code of practice) which ensures commonality in the method of use of the calibrated ion chamber, the radiotherapy treatment beam calibration conditions and any data required to convert the ion chamber reading to absorbed dose to water, and - strict quality control on each step in this process

Measurement of secondary cosmic radiation and calculation of associated dose conversion coefficients for humans

International Nuclear Information System (INIS)

Simmer, Gregor

2012-01-01

Due to secondary cosmic radiation (SCR), pilots and flight attendants receive elevated effective doses at flight altitudes. For this reason, since 2003 aircrew members are considered as occupationally exposed, in Germany. This work deals with the calculation of dose conversion coefficients (DCC) for protons, neutrons, electrons, positrons, photons and myons, which are crucial for estimation of effective dose from SCR. For the first time, calculations were performed combining Geant4 - a Monte Carlo code developed at CERN - with the voxel phantoms for the reference female and male published in 2008 by ICRP and ICRU. Furthermore, measurements of neutron fluence spectra - which contribute the major part to the effective dose of SCR - were carried out at the Environmental Research Station Schneefernerhaus (UFS) located at 2650 m above sea level nearby the Zugspitze mountain, Germany. These measured neutron spectra, and additionally available calculated spectra, were then folded with the DCC calculated in this work, and effective dose rates for different heights were calculated.

A simultaneous electron energy and dosimeter calibration method for an electron beam irradiator

International Nuclear Information System (INIS)

Tanaka, R.; Sunaga, H.; Kojima, T.

1991-01-01

In radiation processing using electron accelerators, the reproducibility of absorbed dose in the product depends not only on the variation of beam current and conveyor speed, but also on variations of other accelerator parameters. This requires routine monitoring of the beam current and the scan width, and also requires periodical calibration of routine dosimeters usually in the shape of film, electron energy, and other radiation field parameters. The electron energy calibration is important especially for food processing. The dose calibration method using partial absorption calorimeters provides only information about absorbed dose. Measurement of average electron current density provides basic information about the radiation field formed by the beam scanning and scattering at the beam window, though it does not allow direct dose calibration. The total absorption calorimeter with a thick absorber allows dose and dosimeter calibration, if the depth profile of relative dose in a reference absorber is given experimentally. It also allows accurate calibration of the average electron energy at the surface of the calorimeter core, if electron fluence received by the calorimeter is measured at the same time. This means that both electron energy and dosimeters can be simultaneously calibrated by irradiation of a combined system including the calorimeter, the detector of the electron current density meter, and a thick reference absorber for depth profile measurement of relative dose. We have developed a simple and multifunctional system using the combined calibration method for 5 MeV electron beams. The paper describes a simultaneous calibration method for electron energy and film dosimeters, and describes the electron current density meter, the total absorption calorimeter, and the characteristics of this method. (author). 13 refs, 7 figs, 3 tabs

The absolute radiometric calibration of the advanced very high resolution radiometer

Science.gov (United States)

Slater, P. N.; Teillet, P. M.; Ding, Y.

1988-01-01

An increasing number of remote sensing investigations require radiometrically calibrated imagery from NOAA Advanced Very High Resolution Radiation (AVHRR) sensors. Although a prelaunch calibration is done for these sensors, there is no capability for monitoring any changes in the in-flight absolute calibration for the visible and near infrared spectral channels. Hence, the possibility of using the reflectance-based method developed at White Sands for in-orbit calibration of LANDSAT Thematic Mapper (TM) and SPOT Haute Resolution Visible (HVR) data to calibrate the AVHRR sensor was investigated. Three diffrent approaches were considered: Method 1 - ground and atmospheric measurements and reference to another calibrated satellite sensor; Method 2 - ground and atmospheric measurements with no reference to another sensor; and Method 3 - no ground and atmospheric measurements but reference to another satellite sensor. The purpose is to describe an investigation on the use of Method 2 to calibrate NOAA-9 AVHRR channels 1 and 2 with the help of ground and atmospheric measurements at Rogers (dry) Lake, Edwards Air Force Base (EAFB) in the Mojave desert of California.

The absolute radiometric calibration of the advanced very high resolution radiometer

Science.gov (United States)

Slater, P. N.; Teillet, P. M.; Ding, Y.

1988-10-01

An increasing number of remote sensing investigations require radiometrically calibrated imagery from NOAA Advanced Very High Resolution Radiation (AVHRR) sensors. Although a prelaunch calibration is done for these sensors, there is no capability for monitoring any changes in the in-flight absolute calibration for the visible and near infrared spectral channels. Hence, the possibility of using the reflectance-based method developed at White Sands for in-orbit calibration of LANDSAT Thematic Mapper (TM) and SPOT Haute Resolution Visible (HVR) data to calibrate the AVHRR sensor was investigated. Three diffrent approaches were considered: Method 1 - ground and atmospheric measurements and reference to another calibrated satellite sensor; Method 2 - ground and atmospheric measurements with no reference to another sensor; and Method 3 - no ground and atmospheric measurements but reference to another satellite sensor. The purpose is to describe an investigation on the use of Method 2 to calibrate NOAA-9 AVHRR channels 1 and 2 with the help of ground and atmospheric measurements at Rogers (dry) Lake, Edwards Air Force Base (EAFB) in the Mojave desert of California.

Spectral correction factors for conventional neutron dose meters used in high-energy neutron environments improved and extended results based on a complete survey of all neutron spectra in IAEA-TRS-403

International Nuclear Information System (INIS)

Oparaji, U.; Tsai, Y. H.; Liu, Y. C.; Lee, K. W.; Patelli, E.; Sheu, R. J.

2017-01-01

This paper presents improved and extended results of our previous study on corrections for conventional neutron dose meters used in environments with high-energy neutrons (E n > 10 MeV). Conventional moderated-type neutron dose meters tend to underestimate the dose contribution of high-energy neutrons because of the opposite trends of dose conversion coefficients and detection efficiencies as the neutron energy increases. A practical correction scheme was proposed based on analysis of hundreds of neutron spectra in the IAEA-TRS-403 report. By comparing 252 Cf-calibrated dose responses with reference values derived from fluence-to-dose conversion coefficients, this study provides recommendations for neutron field characterization and the corresponding dose correction factors. Further sensitivity studies confirm the appropriateness of the proposed scheme and indicate that (1) the spectral correction factors are nearly independent of the selection of three commonly used calibration sources: 252 Cf, 241 Am-Be and 239 Pu-Be; (2) the derived correction factors for Bonner spheres of various sizes (6''-9'') are similar in trend and (3) practical high-energy neutron indexes based on measurements can be established to facilitate the application of these correction factors in workplaces. (authors)

Biological dose estimation for accidental supra-high dose gamma-ray exposure

International Nuclear Information System (INIS)

Chen, Y.; Yan, X.K.; Du, J.; Wang, Z.D.; Zhang, X.Q.; Zeng, F.G.; Zhou, P.K.

2011-01-01

To correctly estimate the biological dose of victims accidentally exposed to a very high dose of 60 Co gamma-ray, a new dose-effect curve of chromosomal dicentrics/multicentrics and rings in the supra-high dose range was established. Peripheral blood from two healthy men was irradiated in vitro with doses of 60 Co gamma-rays ranging from 6 to 22 Gy at a dose rate of 2.0 Gy/min. Lymphocytes were concentrated, cultured and harvested at 52 h, 68 h and 72 h. The numbers of dic + r were counted. The dose-effect curves were established and validated using comparisons with doses from the Tokai-mura accident and were then applied to two victims of supra-high dose exposure accident. The results indicated that there were no significant differences in chromosome aberration frequency among the different culture times from 52 h to 72 h. The 6-22 Gy dose-effect curve was fitted to a linear quadratic model Y = -2.269 + 0.776D - 7.868 x l0 -3 D 2 . Using this mathematic model, the dose estimates were similar to data from Tokai-mura which were estimated by PCC ring. Whole body average doses of 9.7 Gy and 18.1 Gy for two victims in the Jining accident were satisfactorily given. We established and successfully applied a new dose-effect curve of chromosomal dicentrics plus ring (dic + r) after 6-22 Gy γ-irradiation from a supra-high dose 60 Co gamma-ray accident.

Calibration of Single High Purity Germanium Detector for Whole Body Counter

International Nuclear Information System (INIS)

Taha, T.M.; Morsi, T.M.

2009-01-01

A new Accuscan II single germanium detector for whole body counter was installed in NRC (Egypt). The current paper concerned on calibration of single high purity germanium detector for whole body counter. Physical parameters affecting on performance of whole body counter such as linearity, minimum detectable activity and source detector distance, SDD were investigated. Counting efficiencies for the detector have been investigated in rear wall, fixed diagnostic position in air. Counting efficiencies for organ compartments such as thyroid, lung, upper and lower gastrointestinal tract have been investigated using transfer phantom in fixed diagnostic and screening positions respectively. The organ compartment efficiencies in screening geometry were higher than that value of diagnostic geometry by a factor of three. The committed dose equivalents of I-131 in thyroid were ranged from 0.073 ± 0.004 to 1.73±0.09 mSv and in lung was 0.02±0.001 mSv

Intercomparison of calibration procedures of high dose rate 192 Ir sources in Brazil and a proposal of a new methodology

International Nuclear Information System (INIS)

Marechal, M.H.; Almeida, C.E. de

1998-01-01

The objective of this paper is to report the results of an intercomparison of the calibration procedures for 192 Ir sources presently in use in Brazil and to proposal a calibration procedure to derive the N k for a Farmer type ionization chamber for 192 Ir energy by interpolating from a 60 Co gamma-rays and 250 kV x-rays calibration factors. the intercomparison results were all within ± 3.0 % except one case where 4.6 % was observed and latter identified as a problem with N-k value for X-rays. The method proposed by the present work make possible the improvement of the metrological coherence among the calibration laboratories and their users once the N k values could then provided by any of the members of SSDL network. (Author)

Laboratory implantation for well type ionization chambers calibration

International Nuclear Information System (INIS)

Vianello, E.A.; Dias, D.J.; Almeida, C.E. de

1998-01-01

The Radiological Science Laboratory is implanting a service for calibration of well type chambers by IAEA training program. The kerma rate in the air (mu Gy/h) of the linear Cs-137 reference source CDCS-J4 have been determined using a well type chamber Standard Imaging HDR-1000 model, which have been calibrated at Secondary Standard Laboratory Calibration of IAEA, whereas two HDR-1000 Plus chambers were calibrated too, following the same standards. The results were compared with Wisconsin University calibration certification and has demonstrated that well type ionization chamber calibration can be used in brachytherapy for several kinds of radionuclides. (Author)

Calibration models for high enthalpy calorimetric probes.

Science.gov (United States)

Kannel, A

1978-07-01

The accuracy of gas-aspirated liquid-cooled calorimetric probes used for measuring the enthalpy of high-temperature gas streams is studied. The error in the differential temperature measurements caused by internal and external heat transfer interactions is considered and quantified by mathematical models. The analysis suggests calibration methods for the evaluation of dimensionless heat transfer parameters in the models, which then can give a more accurate value for the enthalpy of the sample. Calibration models for four types of calorimeters are applied to results from the literature and from our own experiments: a circular slit calorimeter developed by the author, single-cooling jacket probe, double-cooling jacket probe, and split-flow cooling jacket probe. The results show that the models are useful for describing and correcting the temperature measurements.

Direct megavoltage photon calibration service in Australia

International Nuclear Information System (INIS)

Butler, D.J.; Ramanthan, G.; Oliver, C.; Cole, A.; Harty, P.D.; Wright, T.; Webb, D.V.; Lye, J.; Followill, D.S.

2014-01-01

The Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) maintains the Australian primary standard of absorbed dose. Until recently, the standard was used to calibrate ionisation chambers only in 60 Co gamma rays. These chambers are then used by radiotherapy clinics to determine linac output, using a correction factor (k Q ) to take into account the different spectra of 60 Co and the linac. Over the period 2010–2013, ARPANSA adapted the primary standard to work in megavoltage linac beams, and has developed a calibration service at three photon beams (6, 10 and 18 MV) from an Elekta Synergy linac. We describe the details of the new calibration service, the method validation and the use of the new calibration factors with the International Atomic Energy Agency’s TRS-398 dosimetry Code of Practice. The expected changes in absorbed dose measurements in the clinic when shifting from 60 Co to the direct calibration are determined. For a Farmer chamber (model 2571), the measured chamber calibration coefficient is expected to be reduced by 0.4, 1.0 and 1.1 % respectively for these three beams when compared to the factor derived from 60 Co. These results are in overall agreement with international absorbed dose standards and calculations by Muir and Rogers in 2010 of k Q factors using Monte Carlo techniques. The reasons for and against moving to the new service are discussed in the light of the requirements of clinical dosimetry.

Investigation of Workplace-like Calibration Fields via a Deuterium-Tritium (D-T) Neutron Generator.

Science.gov (United States)

Mozhayev, Andrey V; Piper, Roman K; Rathbone, Bruce A; McDonald, Joseph C

2017-04-01

Radiation survey meters and personal dosimeters are typically calibrated in reference neutron fields based on conventional radionuclide sources, such as americium-beryllium (Am-Be) or californium-252 (Cf), either unmodified or heavy-water moderated. However, these calibration neutron fields differ significantly from the workplace fields in which most of these survey meters and dosimeters are being used. Although some detectors are designed to yield an approximately dose-equivalent response over a particular neutron energy range, the response of other detectors is highly dependent upon neutron energy. This, in turn, can result in significant over- or underestimation of the intensity of neutron radiation and/or personal dose equivalent determined in the work environment. The use of simulated workplace neutron calibration fields that more closely match those present at the workplace could improve the accuracy of worker, and workplace, neutron dose assessment. This work provides an overview of the neutron fields found around nuclear power reactors and interim spent fuel storage installations based on available data. The feasibility of producing workplace-like calibration fields in an existing calibration facility has been investigated via Monte Carlo simulations. Several moderating assembly configurations, paired with a neutron generator using the deuterium tritium (D-T) fusion reaction, were explored.

Calibration results using highly aberrated images for aligning the JWST instruments to the telescope

Science.gov (United States)

Smith, Koby Z.; Acton, D. Scott; Gallagher, Ben B.; Knight, J. Scott; Dean, Bruce H.; Jurling, Alden S.; Zielinski, Thomas P.

2016-07-01

mostly of 3rd-order astigmatism and coma. This is because the elliptical tertiary mirror of the AOS is used off of its ideal foci locations without the compensating wavefront effects of the JWST primary and secondary mirrors. Therefore, the PSFs created are highly asymmetric with relatively complex structure and the centroid and encircled energy analyses traditionally used to locate images are not sufficient for ensuring the AOS to ISIM alignment. A novel approach combining phase retrieval and spatial metrology was developed to both locate the images with respect to the AOS and provide calibration information for eventual AOS to ISIM alignment verification. During final JWST OTE and ISIM (OTIS) testing, only a single thru-focus image will be collected by the instruments. Therefore, tools and processes were developed to perform single-image phase retrieval on these highly aberrated images such that any single image of the ASPA source can provide calibrated knowledge of the instruments' position relative to the AOS. This paper discusses the results of the methodology, hardware, and calibration performed to ensure that the AOS and ISIM are aligned within their respective tolerances at JWST OTIS testing.

The ENEA calibration service for ionising radiations

International Nuclear Information System (INIS)

Monteventi, F.; Sermenghi, I.

1999-01-01

The report describes all the facilities available at the the service of the ENEA Calibration Service for Ionising Radiations at Bologna (Italy). It gives a detailed description of all equipments qualified for photon fields metrology including the secondary standards and the calibration procedures performed for radiation monitoring devices and dosemeters [it

Site-specific calibration of the Hanford personnel neutron dosimeter

International Nuclear Information System (INIS)

Endres, A.W.; Brackenbush, L.W.; Baumgartner, W.V.; Rathbone, B.A.

1994-10-01

A new personnel dosimetry system, employing a standard Hanford thermoluminescent dosimeter (TLD) and a combination dosimeter with both CR-39 nuclear track and TLD-albedo elements, is being implemented at Hanford. Measurements were made in workplace environments in order to verify the accuracy of the system and establish site-specific factors to account for the differences in dosimeter response between the workplace and calibration laboratory. Neutron measurements were performed using sources at Hanford's Plutonium Finishing Plant under high-scatter conditions to calibrate the new neutron dosimeter design to site-specific neutron spectra. The dosimeter was also calibrated using bare and moderated 252 Cf sources under low-scatter conditions available in the Hanford Calibration Laboratory. Dose equivalent rates in the workplace were calculated from spectrometer measurements using tissue equivalent proportional counter (TEPC) and multisphere spectrometers. The accuracy of the spectrometers was verified by measurements on neutron sources with calibrations directly traceable to the National Institute of Standards and Technology (NIST)

Tritium β-radiation induction of chromosomal damage: a calibration curve for low dose, low dose rate exposures of human cells to tritiated water

International Nuclear Information System (INIS)

Morrison, D.P.; Gale, K.L.; Lucas, J.N.

1997-01-01

Radiation exposures from tritium contribute to the occupational radiation exposures associated with CANDU reactors. Tritiated water is of particular interest since it is readily taken up by human cells and its elimination from the body, and, consequently, the radiation exposure of the cells, is spread over a period of days. Occupational exposures to tritiated water result in what are effectively chronic β-radiation exposures. The doses and dose rates ordinarily used in the definition of cellular responses to radiation in vitro, for use in biological dosimetry (the assessment of radiation exposures based on the observed levels of changes in the cells of exposed individuals), are usually much higher than for most occupational exposures and involve radiations other than tritium β-rays. As a result, their use in assessing the effects from tritiated water exposures may not be appropriate. We describe here an in vitro calibration curve for chronic tritium β-radiation induction of reciprocal chromosomal translocations in humn peripheral blood lymphocytes (PBLs) for use in biodosimetry. (author)

Physical requirements for measurement of radiation dose and their relationship to personnel dose meter design and use

International Nuclear Information System (INIS)

Chabot, G.E. Jr.; Jimenez, M.A.; Skrable, K.W.

1978-01-01

This paper stems from the concerns of the authors with both the design of current personnel dose meters and the interpretation of dose information from them in light of the actual physical requirements to measure dose. These concerns have been reinforced and extended following a comparative study of the responses of particular TLD and film systems and as the result of a recent national survey on personnel dosimetry conducted by the authors. Among the major points discussed are the systems available for penetrating and shallow dose assessment, dose meter calibration, the measurement and interpretation of skin dose, and the deficiencies of neutron albedo dose meters for routine personnel use. Calibration considerations address the questions of whether or not a phantom should be used and the difference in interpretation of responses with and without a phantom; the relationship between calculated and measured doses; and electronic equilibrium considerations in the measurement of photon doses. Matters of importance in relation to skin dose measurement include techniques in use to interpret skin dose from dose meter response; the appropriateness of evaluation of the surface dose to the live skin layer versus the average dose to the live skin layer and the limitations and requirements on dose meter design with respect to the dose being evaluated; and the significance of dose meter response in relationship to currently used beta calibration standards. Regarding the use of TLD albedo type neutron dose meters currently available, considerations are extended to the strong energy spectral dependence of the dose meter response and the possibility of making significant over or underestimations of neutron dose equivalent, depending on the calibration techniques used and the spectral quality encountered. (author)

Optimization of shadow cone length and mass for determination the amount of scattered radiation dose in the calibration laboratory of Am/Be neutron source

International Nuclear Information System (INIS)

Raisali, G.; Hamidi, S.; Hallajfard, E.; Shahvar, A.; Hajiloo, N.

2007-01-01

The shadow cone technique is one of the methods which is used for determining the contribution of scattered particles on the response of neutron detectors. This technique is used for neutron field calibration in Agriculture, Medicine and Industry Research School. In this investigation, we have designed and constructed an optimized shadow cone. According to the calculated neutron dose equivalent attenuation factors, a cone with 20 cm of iron and 30 cm of polyethylene has been found as optimum. For this cone, the neutron dose equivalent attenuation factor for 241 Am/Be neutron source, is 0.00035 for which the contribution of scattered neutrons in Agriculture, Medicine and Industry Research School neutron calibration laboratory according to the calculation and measurement results, can be evaluated with less than 0.5% of error

Optimized dose distribution of a high dose rate vaginal cylinder

International Nuclear Information System (INIS)

Li Zuofeng; Liu, Chihray; Palta, Jatinder R.

1998-01-01

Purpose: To present a comparison of optimized dose distributions for a set of high-dose-rate (HDR) vaginal cylinders calculated by a commercial treatment-planning system with benchmark calculations using Monte-Carlo-calculated dosimetry data. Methods and Materials: Optimized dose distributions using both an isotropic and an anisotropic dose calculation model were obtained for a set of HDR vaginal cylinders. Mathematical optimization techniques available in the computer treatment-planning system were used to calculate dwell times and positions. These dose distributions were compared with benchmark calculations with TG43 formalism and using Monte-Carlo-calculated data. The same dwell times and positions were used for a quantitative comparison of dose calculated with three dose models. Results: The isotropic dose calculation model can result in discrepancies as high as 50%. The anisotropic dose calculation model compared better with benchmark calculations. The differences were more significant at the apex of the vaginal cylinder, which is typically used as the prescription point. Conclusion: Dose calculation models available in a computer treatment-planning system must be evaluated carefully to ensure their correct application. It should also be noted that when optimized dose distribution at a distance from the cylinder surface is calculated using an accurate dose calculation model, the vaginal mucosa dose becomes significantly higher, and therefore should be carefully monitored

Radiation doses to patients in haemodynamic procedures

International Nuclear Information System (INIS)

Canadillas-Perdomo, B.; Catalan-Acosta, A.; Hernandez-Armas, J.; Perez-Martin, C.; Armas-Trujillo, D. de

2001-01-01

Interventional radio-cardiology gives high doses to patients due to high values of fluoroscopy times and large series of radiographic images. The main objective of the present work is the determination of de dose-area product (DAP) in patients of three different types of cardiology procedures with X-rays. The effective doses were estimated trough the organ doses values measured with thermoluminescent dosimeters (TLDs-100), suitable calibrated, placed in a phantom type Rando which was submitted to the same radiological conditions corresponding to the procedures made on patients. The values for the effective doses in the procedures CAD Seldinger was 6.20 mSv on average and 1.85mSv for pacemaker implants. (author)

Radiation doses to patients in haemodynamic procedures

Energy Technology Data Exchange (ETDEWEB)

Canadillas-Perdomo, B; Catalan-Acosta, A; Hernandez-Armas, J [Servicio de Fisica Medica, Hospital Universitario de Canarias, La Laguna, Tenerife (Spain); Perez-Martin, C [Servicio de Ingenieria Biomedica, Hospital Universitario de Canarias, La Laguna, Tenerife (Spain); Armas-Trujillo, D de [Servicio de Cardiologia, Hospital Universitario de Canarias, La Laguna, Tenerife (Spain)

2001-03-01

Interventional radio-cardiology gives high doses to patients due to high values of fluoroscopy times and large series of radiographic images. The main objective of the present work is the determination of de dose-area product (DAP) in patients of three different types of cardiology procedures with X-rays. The effective doses were estimated trough the organ doses values measured with thermoluminescent dosimeters (TLDs-100), suitable calibrated, placed in a phantom type Rando which was submitted to the same radiological conditions corresponding to the procedures made on patients. The values for the effective doses in the procedures CAD Seldinger was 6.20 mSv on average and 1.85mSv for pacemaker implants. (author)

High-dose versus low-dose local anaesthetic for transversus abdominis plane block post-Caesarean delivery analgesia: a meta-analysis.

Science.gov (United States)

Ng, S C; Habib, A S; Sodha, S; Carvalho, B; Sultan, P

2018-02-01

The optimal local-anaesthetic (LA) dose for transversus-abdominis-plane (TAP) block is unclear. In this meta-analysis, we aimed to determine whether TAP blocks for Caesarean delivery (CD) with low-dose (LD) LA demonstrated non-inferiority in terms of analgesic efficacy, compared with high-dose (HD) LA. A literature search was performed for randomised controlled trials examining the analgesic efficacy of TAP blocks vs control after CD. The different dosing used in these studies was classified as HD or LD (bupivacaine equivalents >50 or ≤50 mg per block side, respectively). The pooled results of each dose group vs control were indirectly compared using the Q test. The primary outcome was 24 h opioid consumption. Secondary outcomes included 6 and 24 h postoperative pain scores, time to first analgesia, 6 h opioid consumption, opioid-related side-effects, and maternal satisfaction. Fourteen studies consisting of 770 women (389 TAP and 381 control) were included. Compared with controls, the 24 h opioid consumption (milligram morphine equivalents) was lower in HD [mean difference (MD) 95% confidence interval (CI) -22.41 (-38.56, -6.26); P=0.007; I 2 =93%] and LD [MD 95% CI -16.29 (-29.74, -2.84); P=0.02; I 2 =98%] TAP groups. However, no differences were demonstrated between the HD and LD groups (P=0.57). There were also no differences between the HD and LD groups for the 6 h opioid consumption, time to first analgesia, 6 and 24 h pain scores, postoperative nausea and vomiting, pruritus, and maternal satisfaction. Low-dose TAP blocks for Caesarean delivery provide analgesia and opioid-sparing effects comparable with the high-dose blocks. This suggests that lower doses can be used to reduce local anaesthetic toxicity risk without compromising the analgesic efficacy. Copyright © 2017 British Journal of Anaesthesia. Published by Elsevier Ltd. All rights reserved.

Dose calibrations of itensifying screens and neutral density filters for use on pulsed x-ray sources

International Nuclear Information System (INIS)

Gersten, M.; Rauch, J.E.; Shannon, J.

1983-01-01

We calibrated three intensifying screens: Kodak Lanex Regular, Kodak X-Omatic Regular, and Kodak X-Omatic Fine, with relative speeds of 400, 100, and 15 for exposures to a 85 keV bremsstrahling spectrum when used in conjunction with Ortho G film. We also calibrated three neutral density filters: 0.6, 1, and 2 OD. When the screens are used in conjunction with the neutral density filters, 12 configurations can be obtained, with a total dynamic range of 2700. The film/screen/filter pack calibrations were performed in support of the bremsstrahlung experiments on Maxwell Laboratories BLACKJACK 5' pulse generator; the film/screen/filter packs are used to record pinhole photographs, one of the major diagnostics in the program. Because of reciprocity failure associated with the exposure of photographic film by visible light, an intense pulsed X-ray source was needed for the calibration. We used Maxwell Laboratories modular bremsstrahlung source, MBS. In the mode used (mean electron energy 213 + or - 6 keV, peak diode voltage 264 + or - 8 keV, and peak diode current 368 + or - 24 kA), a source strength of 47 + or - 2 J was obtained in a 30 + or - 1.2 ns FWHM pulse. In this mode, 41 + or - 4 percent of the fluence was above 67 keV. In this experiment, the machine operating parameters were held constant and the flux on the film/screen/filter pack was varied between 1.5 x 10 -3 - 5.6 x 10 -8 J/cm 2 . This was achieved by varying the distance between the film/screen/filter pack and the source and-by aperturing the source. The fil/screen/filter pack used for the calibration had three horizontal strips of screen pairs, overlayed with three vertical strips of neutral density filter pairs. One vertical section was left unfiltered. In this configuration 12 exposures are obtained simulatenously. The dose was measured with four TLD's placed inside the film/screen/filter pack at four corners

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

Science.gov (United States)

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

2012-09-18

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

High-accuracy self-calibration method for dual-axis rotation-modulating RLG-INS

Science.gov (United States)

Wei, Guo; Gao, Chunfeng; Wang, Qi; Wang, Qun; Long, Xingwu

2017-05-01

Inertial navigation system has been the core component of both military and civil navigation systems. Dual-axis rotation modulation can completely eliminate the inertial elements constant errors of the three axes to improve the system accuracy. But the error caused by the misalignment angles and the scale factor error cannot be eliminated through dual-axis rotation modulation. And discrete calibration method cannot fulfill requirements of high-accurate calibration of the mechanically dithered ring laser gyroscope navigation system with shock absorbers. This paper has analyzed the effect of calibration error during one modulated period and presented a new systematic self-calibration method for dual-axis rotation-modulating RLG-INS. Procedure for self-calibration of dual-axis rotation-modulating RLG-INS has been designed. The results of self-calibration simulation experiment proved that: this scheme can estimate all the errors in the calibration error model, the calibration precision of the inertial sensors scale factor error is less than 1ppm and the misalignment is less than 5″. These results have validated the systematic self-calibration method and proved its importance for accuracy improvement of dual -axis rotation inertial navigation system with mechanically dithered ring laser gyroscope.

IAEA/ WHO TLD postal dose intercomparison results in Bangladesh

International Nuclear Information System (INIS)

Mollah, A.S.; Bhuiyan, N.U.; Rahman, S.

2001-01-01

Full text: For the accurate delivery of prescribed dose to the patients, high precision and accuracy in radiation dosimetry is required. The hospital/medical physicist is responsible for the accurate delivery of whole planned radiation doses to the patients prescribed by the radio therapist. The proper delivery of radiation doses depends upon the accurate output measurements of doses from the therapy machines. In Bangladesh, only six 60 Co units and five deep therapy machines are in use. Some more are expected to be installed soon. Still in 2001, none of the Government radiotherapy centers in Bangladesh was properly equipped with medical physicists as well as radiotherapy dosimetry equipment. Bangladesh Atomic Energy Commission (BAEC) is responsible for radiation safety in Bangladesh and BAEC has assigned Secondary Standard Dosimetry Laboratory (SSDL) of Bangladesh for providing dosimetry calibration to all radiotherapy centers in Bangladesh. The output measurements of therapy machines are performed once in a year by SSDL and the results are compared by participating in the annual TLD postal dose intercomparison program organized by IAEA/WHO SSDL Network. The absorbed dose to water is determined using IAEA dosimetry protocol (TRS 277 and 381) and water phantom of size 30 x 30 x 30 cm 3 , The measurements of SSDL are traceable to NPL of UK. The accuracy achieved in SSDL, Bangladesh has been found better than ± 3.5%, which is within the prescribed limit of dosimetry standard of IAEA. The methodology of output dose measurements in different radiotherapy centers in Bangladesh is described along with the IAEA/WHO intercomparison results

Dose rate range extension of the calibration of dosemeters at LNMRI, Rio de Janeiro, Brazil; Expansao da faixa de taxas de dose para a calibracao de instrumentos de medir radiacao no LNMRI, Rio de Janeiro, Brasil

Energy Technology Data Exchange (ETDEWEB)

Cabral, T.S.; Carlos, M.T.; Ramos, M.M.O., E-mail: tschirn@ird.gov.b, E-mail: marcia@ird.gov.b, E-mail: mmoramos@ird.gov.b [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

2009-07-01

The present work has an objective the implantation of a experimental arrange for application of essays of instrument calibration for measurement of low dose rate, which measure rate less than 10 {mu}Sv/h

Monte Carlo simulations of the secondary neutron ambient and effective dose equivalent rates from surface to suborbital altitudes and low Earth orbit.

Science.gov (United States)

El-Jaby, Samy; Richardson, Richard B

2015-07-01

Occupational exposures from ionizing radiation are currently regulated for airline travel (Earth orbit (∼300-400 km). Aircrew typically receive between 1 and 6 mSv of occupational dose annually, while aboard the International Space Station, the area radiation dose equivalent measured over just 168 days was 106 mSv at solar minimum conditions. It is anticipated that space tourism vehicles will reach suborbital altitudes of approximately 100 km and, therefore, the annual occupational dose to flight crew during repeated transits is expected to fall somewhere between those observed for aircrew and astronauts. Unfortunately, measurements of the radiation environment at the high altitudes reached by suborbital vehicles are sparse, and modelling efforts have been similarly limited. In this paper, preliminary MCNPX radiation transport code simulations are developed of the secondary neutron flux profile in air from surface altitudes up to low Earth orbit at solar minimum conditions and excluding the effects of spacecraft shielding. These secondary neutrons are produced by galactic cosmic radiation interacting with Earth's atmosphere and are among the sources of radiation that can pose a health risk. Associated estimates of the operational neutron ambient dose equivalent, used for radiation protection purposes, and the neutron effective dose equivalent that is typically used for estimates of stochastic health risks, are provided in air. Simulations show that the neutron radiation dose rates received at suborbital altitudes are comparable to those experienced by aircrew flying at 7 to 14 km. We also show that the total neutron dose rate tails off beyond the Pfotzer maximum on ascension from surface up to low Earth orbit. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

The use of potassium dichromate for ultra high dose up to 120 kGy measurements in industrial irradiation process

International Nuclear Information System (INIS)

Conceicao, Cirilo C.S.

2009-01-01

The purpose of this work is the study of radiation-induced reduction of the Potassium Dichromate dosimeter in perchloric acid using modification in the composition of Dichromate dosimeter proposed by Sharpe (NPL, October 1982) to extend dose limit up to 120 kGy. This modification can allow measuring dose in process of irradiation of gem and cork directly, in these processes that the absorbed doses are very high. The dosimeter study reached linear response between 10 to 120 kGy. This dosimeter was traceable to the international metrology system, using Gammacell calibrated by Fricke reference dosimeter. The evaluation of the doses was done by spectrophotometric method. Compared to the costs using PMMA (perpex dosimeters), the use of dichromate dosimeters can reduce up to 70% of the dosimetry costs in Brazil. (author)

Terms and definitions in the field of radiological technique. Dose quantities and units

International Nuclear Information System (INIS)

1985-12-01

The standard gives the terms and definitions of concepts, dose quantities and units. The radiation field condition 'secondary electron equilibrium', which forms part of the definition of standard ion dose, is given more precisely. The term 'free in air' is used in its original meaning, i.e. characterization of measuring conditions excluding avoidable stray radiation, which deviates from DIN 6814, part 3/06.72. Dosemeters for measurement of standard ion dose of air kerma are calibrated 'free in air', but this calibration condition is not part of the quantity definition. The quantities standard ion dose or air kerma therefore can also be measured in any other material. The qunatitative relationships between standard ion dose and the quantities 'exposure' and air kerma, as given in the ICRU publication 33 'Quantities and Units' (1980), are explained. The standard introduces the SI units Gray (for energy dose), Sievert (for dose equivalent), and Becquerel (for the activity of a radioactive substance). As the change to the SI units conceals the approximated equality of the numerical values of the standrd ion dose of photon radiation in roentgen, of the energy dose for soft tissue in rad, and of the dose equivalent in rem, new definitions are given in accordance with ICRU 33 for the quantities specified dose rate, dose rate constant, and area exposure product. These definitions use the terms 'energy dose' and 'kerma'. The dose concepts applied in the field of radiation protection, especially ambient dose and individual dose, are defined as dose equivalents in compliance with the Radiation Protection Ordinance. The relevant sections present information on the conversion of standard ion dose values to the corresponding values of kerma, energy dose, or dose equivalent. (orig./HP) [de

Calibration curves for biological dosimetry

International Nuclear Information System (INIS)

Guerrero C, C.; Brena V, M. . E-mail cgc@nuclear.inin.mx

2004-01-01

The generated information by the investigations in different laboratories of the world, included the ININ, in which settles down that certain class of chromosomal leisure it increases in function of the dose and radiation type, has given by result the obtaining of calibrated curves that are applied in the well-known technique as biological dosimetry. In this work is presented a summary of the work made in the laboratory that includes the calibrated curves for gamma radiation of 60 Cobalt and X rays of 250 k Vp, examples of presumed exposure to ionizing radiation, resolved by means of aberration analysis and the corresponding dose estimate through the equations of the respective curves and finally a comparison among the dose calculations in those people affected by the accident of Ciudad Juarez, carried out by the group of Oak Ridge, USA and those obtained in this laboratory. (Author)

Immediate needs for MQA testing at state secondary calibration laboratories

Energy Technology Data Exchange (ETDEWEB)

Cline, R. [Radiation Instrument Calibration Laboratory, Springfield, IL (United States)

1993-12-31

The Calibration Laboratory attempts to provide services that satisfy the needs and requests for a variety of customers. New needs and requests have resulted in calibration of instrumentation outside the original laboratory designs. These tasks require several changes at the laboratory and a need for new support services, especially measurement quality assurance (MQA). The MQA tests are gamma (Cs-137) below 0.5 mrem (5{mu}Sv) per hour and x-ray kVp. Modification to the current gamma (Cs-137) MQA test is recommended because lower intensity fields are commonly measured.

Immediate needs for MQA testing at state secondary calibration laboratories

International Nuclear Information System (INIS)

Cline, R.

1993-01-01

The Calibration Laboratory attempts to provide services that satisfy the needs and requests for a variety of customers. New needs and requests have resulted in calibration of instrumentation outside the original laboratory designs. These tasks require several changes at the laboratory and a need for new support services, especially measurement quality assurance (MQA). The MQA tests are gamma (Cs-137) below 0.5 mrem (5μSv) per hour and x-ray kVp. Modification to the current gamma (Cs-137) MQA test is recommended because lower intensity fields are commonly measured

Precision High-Voltage DC Dividers and Their Calibration

Czech Academy of Sciences Publication Activity Database

Dragounová, Naděžda

2005-01-01

Roč. 54, č. 5 (2005), s. 1911-1915 ISSN 0018-9456 R&D Projects: GA AV ČR KSK1048102; GA ČR GA202/03/0889 Keywords : calibration * dc voltage * high voltage (HV) Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 0.665, year: 2005

Optimization of protection and calibration of the moisture-density gages troxler

International Nuclear Information System (INIS)

RAKOTONDRAVANONA, J.E.

2011-01-01

The purpose of this work is the implementation of the principle of optimization of the protection and calibration of moisture-density gages TROXLER. The main objectives are the application of radiation protection and the feasibility of a calibration laboratory design. The calibration of density and moisture may confirm the calibration of moisture-density gages TROXLER. The calibration of density consists of the assembly of measurements on three calibration blocks (magnesium, aluminium and magnesium/aluminium) built in the TRACKER. The value of density uncertainty is ±32 Kg.m -3 . The calibration of moisture is carried out on two calibration blocks (magnesium and magnesium/polyethylene)The value of moisture uncertainty is ±16 Kg.m -3 . The design of the laboratory returns to the dose limitation. The laboratory is designed mainly wall out of ordinary concrete, a good attenuator of the gamma radiations and neutron. For the design, the value of term source gamma is 25.77±0.20μSv.h -1 and the value of term source neutron is 7.88±0.35μSv.h -1 are used for the thickness of the walls. The importance of the design makes it possible to attenuate to the maximum doses and rates dose until the total absorption of the radiations. [fr

Intracranial meningiomas after high-dose irradiation

International Nuclear Information System (INIS)

Soffer, D.; Gomori, J.M.; Siegal, T.; Shalit, M.N.

1989-01-01

Three patients who presented with intracranial meningiomas 12, 15, and 20 years, respectively, after therapeutic high-dose irradiation of a primary brain tumor are described. Analysis of these cases and similar documented cases suggests that meningiomas after high-dose irradiation constitute a recognizable entity. Patients with such tumors received radiation therapy at a young age (mean age, 9.4 years). After a latent period of 2 to 47 years (mean, 19.8 years) they developed meningiomas at the site of irradiation, at a much younger age than patients with ''spontaneous'' meningiomas. Similar to the situation with meningiomas after low-dose irradiation, a relatively high proportion of meningiomas induced by high-dose irradiation tend to be malignant and biologically aggressive. A very young age at the time of irradiation seems to predispose to the induction of malignant meningiomas, rather than benign tumors. These unusual features provide indirect evidence that high-dose radiation may play a role in the pathogenesis of meningiomas.41 references

High-dose radiation-induced meningioma following prophylactic cranial irradiation for acute lymphoblastic leukaemia

International Nuclear Information System (INIS)

Matsuda, Ryosuke; Nikaido, Yuji; Yamada, Tomonori; Mishima, Hideaki; Tamaki, Ryo

2005-01-01

A 12 year-old girl was treated with prophylactic cranial irradiation for acute lymphoblastic leukaemia (ALL). At the age of 39, she was admitted to our hospital for status epilepticus. Computed tomography demonstrated two, enhancing bilateral sided intracranial tumors. After surgery, this patient presented meningiomas which histologically, were of the meningothelial type. The high cure rate in childhood ALL, attributable to aggressive chemotherapy and prophylactic cranial irradiation, is capable of inducing secondary brain tumor. Twelve cases of high-dose radiation-induced meningioma following ALL are also reviewed. (author)

High-dose radiation-induced meningioma following prophylactic cranial irradiation for acute lymphoblastic leukaemia

Energy Technology Data Exchange (ETDEWEB)

Matsuda, Ryosuke; Nikaido, Yuji; Yamada, Tomonori; Mishima, Hideaki; Tamaki, Ryo [National Hospital Organization Osaka Minami Medical Center, Kawachinagano (Japan)

2005-03-01

A 12 year-old girl was treated with prophylactic cranial irradiation for acute lymphoblastic leukaemia (ALL). At the age of 39, she was admitted to our hospital for status epilepticus. Computed tomography demonstrated two, enhancing bilateral sided intracranial tumors. After surgery, this patient presented meningiomas which histologically, were of the meningothelial type. The high cure rate in childhood ALL, attributable to aggressive chemotherapy and prophylactic cranial irradiation, is capable of inducing secondary brain tumor. Twelve cases of high-dose radiation-induced meningioma following ALL are also reviewed. (author)

Calibration of photographic dosemeters to evaluate the personal equivalent dose, Hp (10), irradiated by different radiation qualities and angles of incidence

International Nuclear Information System (INIS)

Santoro, Christiana; Antonio Filho, Joao

2013-01-01

To use radiation detectors, should periodically perform tests and calibrations on instruments in order to verify its good functionality. One way to ascertain the quality of the instrument is to conduct a study of the angular dependence of the response of the radiation detectors. The photographic dosimetry has been used widely to quantify the radiation doses and to estimate levels of doses received by workers involved with X-and gamma radiation. Photographic dosimeters are used because provide wide range of exposure and good accuracy. One of the sources of error have been introduced by different irradiation geometries between calibration and measurement in radiation fields used in x-ray and gamma ray sources, therefore, there is a need for an evaluation of the sensitivity of dosimeters with variation of the angle of the incident beam. In this study were tested 190 photographic dosemeters in the Metrology Laboratory of the Centro Regional de Ciencias Nucleares do Nordeste (CRCN-NE) using the phantom H p (10), where the dosimeters are evaluated on the basis of the new operational magnitude for individual monitoring, the equivalent personal dose, H p (10). Angular dependence of these radiation detectors was studied in X radiation fields (in the range of 45 keV energy to 164 keV) and gamma radiation ( 137 Cs-662 keV e 60 Co - 1250 keV)

High-dose erythropoietin in patients with progressive multiple sclerosis

DEFF Research Database (Denmark)

Schreiber, Karen; Magyari, Melinda; Sellebjerg, Finn

2017-01-01

BACKGROUND: Erythropoietin (EPO) is a part of an endogenous neuroprotective system in the brain and may address pathophysiological mechanisms in progressive multiple sclerosis (MS). OBJECTIVE: To evaluate a treatment effect of EPO on progressive MS. METHODS: This was a single-center, randomized......, double-blind, placebo-controlled phase 2 trial, in which 52 patients with secondary or primary progressive MS were allocated to treatment with recombinant EPO (48,000 IU) or placebo, administered intravenously 17 times during 24 weeks. Patients had an Expanded Disability Status Score (EDSS) from 4 to 6......: This study provides class II evidence that treatment with high-dose EPO is not an effective treatment in patients with moderately advanced progressive MS....

Characterization of High Dose Mn, Fe, and Ni implantation into p-GaN

CERN Document Server

Pearton, S J; Thaler, G; Abernathy, C R; Theodoropoulou, N; Hebard, A F; Chu, S N G; Wilson, R G; Zavada, J M; Polyakov, A Y; Osinsky, A V; Norris, P E; Chow, P P; Wowchack, A M; Hove, J M V; Park, Y D

2002-01-01

The magnetization of p-GaN or p-AlGaN/GaN superlattices was measured after implantation with high doses (3-5x10 sup 1 sup 6 cm sup - sup 2) of Mn, Fe, or Ni and subsequent annealing at 700-1000 deg. C. The samples showed ferromagnetic contributions below temperatures ranging from 190-250 K for Mn to 45-185 K for Ni and 80-250 K for Fe. The use of superlattices to enhance the hole concentration did not produce any change in ferromagnetic ordering temperature. No secondary phase formation was observed by x-ray diffraction, transmission electron microscopy, or selected area diffraction pattern analysis for the doses we employed.

On the determination of the water energy dose for X-rays produced with high voltages up to 100 kV

International Nuclear Information System (INIS)

Engelke, B.A.; Grosswendt, B.

1989-01-01

For X-rays produced with high-tensions up to 100 kV the absorbed dose to water in water can be determined by measuring the exposure or air kerma and by means of the calibration factor of the dosemeter for these quantities and a conversion factor and a correction factor. For this procedure it is necessary that the exposure or air kerma measured and the correction factor are referred to the same diameter of the X-ray beam and the same measuring distance as used for the determination of the calibration factor. If they do not agree, an additional correction factor for the influence of this discrepancy in the measuring geometry is needed. The paper gives the values of this correction factor. Furthermore, it informs on new values of the backscattering factor in water and of the correction k a→w required for the determination of the absorbed dose to water in water. (orig.) [de

Planck 2015 results. VIII. High Frequency Instrument data processing: Calibration and maps

CERN Document Server

Adam, R.; Aghanim, N.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Banday, A.J.; Barreiro, R.B.; Bartolo, N.; Battaner, E.; Benabed, K.; Benoît, A.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bertincourt, B.; Bielewicz, P.; Bock, J.J.; Bonavera, L.; Bond, J.R.; Borrill, J.; Bouchet, F.R.; Boulanger, F.; Bucher, M.; Burigana, C.; Calabrese, E.; Cardoso, J.-F.; Catalano, A.; Challinor, A.; Chamballu, A.; Chiang, H.C.; Christensen, P.R.; Clements, D.L.; Colombi, S.; Colombo, L.P.L.; Combet, C.; Couchot, F.; Coulais, A.; Crill, B.P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R.D.; Davis, R.J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J.-M.; Désert, F.-X.; Diego, J.M.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Ducout, A.; Dupac, X.; Efstathiou, G.; Elsner, F.; Enßlin, T.A.; Eriksen, H.K.; Falgarone, E.; Fergusson, J.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A.A.; Franceschi, E.; Frejsel, A.; Galeotta, S.; Galli, S.; Ganga, K.; Ghosh, T.; Giard, M.; Giraud-Héraud, Y.; Gjerløw, E.; González-Nuevo, J.; Górski, K.M.; Gratton, S.; Gruppuso, A.; Gudmundsson, J.E.; Hansen, F.K.; Hanson, D.; Harrison, D.L.; Henrot-Versillé, S.; Herranz, D.; Hildebrandt, S.R.; Hivon, E.; Hobson, M.; Holmes, W.A.; Hornstrup, A.; Hovest, W.; Huffenberger, K.M.; Hurier, G.; Jaffe, A.H.; Jaffe, T.R.; Jones, W.C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T.S.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C.R.; Le Jeune, M.; Leahy, J.P.; Lellouch, E.; Leonardi, R.; Lesgourgues, J.; Levrier, F.; Liguori, M.; Lilje, P.B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P.M.; Macías-Pérez, J.F.; Maggio, G.; Maino, D.; Mandolesi, N.; Mangilli, A.; Maris, M.; Martin, P.G.; Martínez-González, E.; Masi, S.; Matarrese, S.; McGehee, P.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Moreno, R.; Morgante, G.; Mortlock, D.; Moss, A.; Mottet, S.; Munshi, D.; Murphy, J.A.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C.B.; Nørgaard-Nielsen, H.U.; Noviello, F.; Novikov, D.; Novikov, I.; Oxborrow, C.A.; Paci, F.; Pagano, L.; Pajot, F.; Paoletti, D.; Pasian, F.; Patanchon, G.; Pearson, T.J.; Perdereau, O.; Perotto, L.; Perrotta, F.; Pettorino, V.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Pratt, G.W.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Rachen, J.P.; Reinecke, M.; Remazeilles, M.; Renault, C.; Renzi, A.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rossetti, M.; Roudier, G.; Rusholme, B.; Sandri, M.; Santos, D.; Sauvé, A.; Savelainen, M.; Savini, G.; Scott, D.; Seiffert, M.D.; Shellard, E.P.S.; Spencer, L.D.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J.A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tucci, M.; Tuovinen, J.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vibert, L.; Vielva, P.; Villa, F.; Wade, L.A.; Wandelt, B.D.; Watson, R.; Wehus, I.K.; Yvon, D.; Zacchei, A.

2016-01-01

This paper describes the processing applied to the Planck High Frequency Instrument (HFI) cleaned, time-ordered information to produce photometrically calibrated maps in temperature and (for the first time) in polarization. The data from the 2.5 year full mission include almost five independent full-sky surveys. HFI observes the sky over a broad range of frequencies, from 100 to 857 GHz. To get the best accuracy on the calibration over such a large range, two different photometric calibration schemes have been used. The 545 and 857 GHz data are calibrated using models of planetary atmospheric emission. The lower frequencies (from 100 to 353 GHz) are calibrated using the time-variable cosmological microwave background dipole which we call the orbital dipole. This source of calibration only depends on the satellite velocity with respect to the solar system and permits an independent measurement of the amplitude of the CMB solar dipole (3364.5 +/- 0.8 \\mu K) which is 1\\sigma\\ higher than the WMAP measurement wit...

A method for the calibration of concave 90Sr+90Y ophthalmic applicators

International Nuclear Information System (INIS)

Soares, C.G.

1992-01-01

At the Amersham Laboratory (Amersham, UK) absorbed-dose rate in tissue at a depth of 7 mg cm -2 from curved ophthalmic applicators is measured with calibrated scintillator probes (Amersham International 1979, Sinclair and Trott 1956). The probes are approximately 3 mm in diameter, 0.5 mm thick and are covered with 7 mg cm -2 of aluminium. They are calibrated using standard sources whose dose rate has been determined using an extrapolation chamber equipped with a 3 mm diameter collecting electrode. Crucial to this technique is the availability of well calibrated sources of nearly the same geometry and dose rate as the source to be calibrated. A technique is presented here which yields accurate measurement of the surface absorbed-dose rate in a very simple and straightforward fashion. (author)

Characterization of different qualities in X-rays, for instruments calibration in radiological protection; Caracterizacion de diferentes calidades en rayos X, para calibracion de instrumentos en proteccion radiologica

Energy Technology Data Exchange (ETDEWEB)

Cejudo A, J.; Tovar M, V. M.; Vergara M, F., E-mail: jesus.cejudo@inin.gob.m [ININ, Departamento de Metrologia de Radiaciones Ionizantes, Laboratorio Secundario de Calibracion Dosimetrica, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico)

2010-09-15

In the Secondary Laboratory of Dosimetric Calibration in Mexico was realized the qualities characterization of the series X-rays RQR reported in the International Code of Practices in Dosimetry and Diagnostic Radiology No. 457, using attenuator filters of high purity aluminum and ionizing radiation equipment of inherent filtration of 4 mm Be with and emergent X-radiation beam of 40 grades. For the attenuation was used a geometric arrangement with three beam limiters and a monitor camera prepared on the established form in the mentioned technical report, and a spherical ionization chamber with collection volume of 3.6 cm{sup 3}, aligning its geometric center with the focus of X-rays tube to get that the incident radiation direction will be perpendicular to the ionization chamber. From the perspective of the radiological protection is important to know the X-radiation quality for the application dedicated to the instruments calibration and can to give to these the traceability to a reference laboratory, this way the quality combination and reference chamber can give as a result a procedure for the evaluation of the entrance in surface dose to estimate the dose orientate levels, specified in the basic standards of safety. (Author)

High-dose irradiation of food

International Nuclear Information System (INIS)

Diehl, J.F.

1999-01-01

Studies performed on behalf of the International Project on Food Irradiation in the period from 1971 until 1980 resulted in the concluding statement that ''.the irradiation of any food commodity up to an overall average dose of 10 kGy presents no toxicological hazard; hence, toxicological testing of foods so treated is no longer required.'' Since then, licenses for food irradiation have been restricted to this maximum dose in any country applying this technology. Further testing programmes have been carried out investigating the wholesomeness or hazards of high-dose irradiation, but there has been little demand so far by the food industry for licensing of high-dose irradiation, as there is only a small range of products whose irradiation at higher doses offers advantages for given, intended use. These include eg. spices, dried herbs, meat products in flexible pouch packagings for astronauts, or patients with immune deficiencies. (orig./CB) [de

Automated Calibration of Dosimeters for Diagnostic Radiology

International Nuclear Information System (INIS)

Romero Acosta, A.; Gutierrez Lores, S.

2015-01-01

Calibration of dosimeters for diagnostic radiology includes current and charge measurements, which are often repetitive. However, these measurements are usually done using modern electrometers, which are equipped with an RS-232 interface that enables instrument control from a computer. This paper presents an automated system aimed to the measurements for the calibration of dosimeters used in diagnostic radiology. A software application was developed, in order to achieve the acquisition of the electric charge readings, measured values of the monitor chamber, calculation of the calibration coefficient and issue of a calibration certificate. A primary data record file is filled and stored in the computer hard disk. The calibration method used was calibration by substitution. With this system, a better control over the calibration process is achieved and the need for human intervention is reduced. the automated system will be used in the calibration of dosimeters for diagnostic radiology at the Cuban Secondary Standard Dosimetry Laboratory of the Center for Radiation Protection and Hygiene. (Author)

Characterization of responses and comparison of calibration factor for commercial MOSFET detectors.

Science.gov (United States)

Bharanidharan, Ganesan; Manigandan, Durai; Devan, Krishnamurthy; Subramani, Vellaiyan; Gopishankar, Natanasabapathi; Ganesh, Tharmar; Joshi, Rakeshchander; Rath, Gourakishore; Velmurugan, Jagadeesan; Aruna, Prakasarao; Ganesan, Singaravelu

2005-01-01

A commercial metal oxide silicon field effect transistor (MOSFET) dosimeter of model TN502-RD has been characterized for its linearity, reproducibility, field size dependency, dose rate dependency, and angular dependency for Cobalt-60 (60Co), 6-MV, and 15-MV beam energies. The performance of the MOSFET clearly shows that it is highly reproducible, independent of field size and dose rate. Furthermore, MOSFET has a very high degree of linearity, with r-value>0.9 for all 3 energies. The calibration factor for 2 similar MOSFET detectors of model TN502-RD were also estimated and compared for all 3 energies. The calibration factor between the 2 similar MOSFET detectors shows a variation of about 1.8% for 60Co and 15 MV, and for 6 MV it shows variation of about 2.5%, indicating that calibration should be done whenever a new MOSFET is used. However, the detector shows considerable angular dependency of about 8.8% variation. This may be due to the variation in radiation sensitivity between flat and bubble sides of the MOSFET, and indicates that positional care must be taken while using MOSFET for stereotactic radiosurgery and stereotactic radiotherapy dosimetric applications.

''Low dose'' and/or ''high dose'' in radiation protection: A need to setting criteria for dose classification

International Nuclear Information System (INIS)

Sohrabi, M.

1997-01-01

The ''low dose'' and/or ''high dose'' of ionizing radiation are common terms widely used in radiation applications, radiation protection and radiobiology, and natural radiation environment. Reading the title, the papers of this interesting and highly important conference and the related literature, one can simply raise the question; ''What are the levels and/or criteria for defining a low dose or a high dose of ionizing radiation?''. This is due to the fact that the criteria for these terms and for dose levels between these two extreme quantities have not yet been set, so that the terms relatively lower doses or higher doses are usually applied. Therefore, setting criteria for classification of radiation doses in the above mentioned areas seems a vital need. The author while realizing the existing problems to achieve this important task, has made efforts in this paper to justify this need and has proposed some criteria, in particular for the classification of natural radiation areas, based on a system of dose limitation. (author)

High accuracy wavelength calibration for a scanning visible spectrometer

Energy Technology Data Exchange (ETDEWEB)

Scotti, Filippo; Bell, Ronald E. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

2010-10-15

Spectroscopic applications for plasma velocity measurements often require wavelength accuracies {<=}0.2 A. An automated calibration, which is stable over time and environmental conditions without the need to recalibrate after each grating movement, was developed for a scanning spectrometer to achieve high wavelength accuracy over the visible spectrum. This method fits all relevant spectrometer parameters using multiple calibration spectra. With a stepping-motor controlled sine drive, an accuracy of {approx}0.25 A has been demonstrated. With the addition of a high resolution (0.075 arc sec) optical encoder on the grating stage, greater precision ({approx}0.005 A) is possible, allowing absolute velocity measurements within {approx}0.3 km/s. This level of precision requires monitoring of atmospheric temperature and pressure and of grating bulk temperature to correct for changes in the refractive index of air and the groove density, respectively.

Study of absorbed dose distribution to high energy electron beams

International Nuclear Information System (INIS)

Cecatti, E.R.

1983-01-01

The depth absorbed dose distribution by electron beams was studied. The influence of the beam energy, the energy spread, field size and design characteristics of the accelerator was relieved. Three accelerators with different scattering and collimation systems were studied leading todifferent depth dose distributions. A theoretical model was constructed in order to explain the increase in the depth dose in the build-up region with the increase of the energy. The model utilizes a three-dimensional formalism based on the Fermi-Eyges multiple scattering theory, with the introduction of modifications that takes into account the criation of secondary electrons. (Author) [pt

Collection of radiation resistant characteristics reports for instruments and materials in high dose rate environment

International Nuclear Information System (INIS)

Kusano, Joichi

2008-03-01

This document presents the collected official reports of radiation irradiation study for the candidate materials to be used in high dose rate environment as J-PARC facility. The effect of radiation damage by loss-beam or secondary particle beam of the accelerators influences the performance and the reliability of various instruments. The knowledge on the radiation resistivity of the materials is important to estimate the life of the equipments, the maintenance interval and dose evaluation for the personnel at the maintenance period. The radiation damage consists with mechanical property, electrical property and gas-evolution property. (author)

Calibration method of radiation monitoring system at TQNPC

International Nuclear Information System (INIS)

Liu Zhengshan; Zhang Qingli; Liu Jinjin; Miao Yuxing; Geng Lixin; Zhuang Yun; Dong Jianfeng; He Change

2009-04-01

The calibration methods and calibration device for standard monitor of radioactive particulate, iodine, noble gas and so on are not yet set up at home. On consideration of the present situation of the radiation monitoring system at the Third Qinshan Nuclear Power Co. Ltd., we have studied the calibration method of these radiation monitoring instruments used for measuring the waste liquid, particulate, iodine and noble gas produced during the operation of nuclear reactor. Through the check against these instruments during the No. 202 and No. 103 overhaul, we got initially the method of the calibration and obtained the transfer coefficient of calibration when secondary solid sources are used for calibration. Through the testing and calibration, the credibility of the radiation monitoring system is enhanced. And at the same time, the problems existing in the calibration are discussed. (authors)

Secondary standard dosimetry laboratory Saraykoy Nuclear Research and Training Center Ankara, Turkey

International Nuclear Information System (INIS)

Okruhlica, P.

2014-01-01

Turkish Saraykoy Nuclear Research and Training Center (SANA) was founded in 2005. In 2014 the company PTW Freiburg in cooperation with VF Cerna Hora started the construction of a comprehensive national metrology laboratories of ionizing radiation 'Secondary Standard Dosimetry Laboratory' (SSDL). The laboratory will be located in the area of 'Saraykoy Nuclear Research and Training Center' in Ankara in Turkey. SSDL will be equipped with metrology departments for calibration and measurement of standard required quantities of metrology of ionizing radiation: - Neutron workplace; Gamma workplace (low-energy X-ray, gamma Standard Cs-137 and high dose rate, Co-60); - Beta workplace; - Control system of metrology laboratories and irradiation VF DARS; - Radiation monitoring system VF RMS; - Camera and security system; - Measuring instruments (ionization chambers, electrometers, monitors for environmental measurements ...) with the appropriate phantoms and other systems.

Neither high-dose nor low-dose brachytherapy increases flap morbidity in salvage treatment of recurrent head and neck cancer

Directory of Open Access Journals (Sweden)

Peter W. Henderson

2016-08-01

Full Text Available Purpose: While brachytherapy is often used concurrently with flap reconstruction following surgical ablation for head and neck cancer, it remains unclear whether it increases morbidity in the particularly high risk subset of patients undergoing salvage treatment for recurrent head and neck cancer (RH&NC. Material and methods : A retrospective chart review was undertaken that evaluated patients with RH&NC who underwent flap coverage after surgical re-resection and concomitant brachytherapy. The primary endpoint was flap viability, and the secondary endpoints were flap and recipient site complications. Results : In the 23 subjects included in series, flap viability and skin graft take was 100%. Overall recipient site complication rate was 34.8%, high-dose radiation (HDR group 50%, and low-dose radiation (LDR group 29.4%. There was no statistically significant difference between these groups. Conclusions : In patients who undergo flap reconstruction and immediate postoperative radiotherapy following salvage procedures for RH&NC, flap coverage of defects in combination with brachytherapy remains a safe and effective means of providing stable soft tissue coverage.

Automatic camera to laser calibration for high accuracy mobile mapping systems using INS

Science.gov (United States)

Goeman, Werner; Douterloigne, Koen; Gautama, Sidharta

2013-09-01

A mobile mapping system (MMS) is a mobile multi-sensor platform developed by the geoinformation community to support the acquisition of huge amounts of geodata in the form of georeferenced high resolution images and dense laser clouds. Since data fusion and data integration techniques are increasingly able to combine the complementary strengths of different sensor types, the external calibration of a camera to a laser scanner is a common pre-requisite on today's mobile platforms. The methods of calibration, nevertheless, are often relatively poorly documented, are almost always time-consuming, demand expert knowledge and often require a carefully constructed calibration environment. A new methodology is studied and explored to provide a high quality external calibration for a pinhole camera to a laser scanner which is automatic, easy to perform, robust and foolproof. The method presented here, uses a portable, standard ranging pole which needs to be positioned on a known ground control point. For calibration, a well studied absolute orientation problem needs to be solved. In many cases, the camera and laser sensor are calibrated in relation to the INS system. Therefore, the transformation from camera to laser contains the cumulated error of each sensor in relation to the INS. Here, the calibration of the camera is performed in relation to the laser frame using the time synchronization between the sensors for data association. In this study, the use of the inertial relative movement will be explored to collect more useful calibration data. This results in a better intersensor calibration allowing better coloring of the clouds and a more accurate depth mask for images, especially on the edges of objects in the scene.

Diamond detector in absorbed dose measurements in high-energy linear accelerator photon and electron beams.

Science.gov (United States)

Ravichandran, Ramamoorthy; Binukumar, John Pichy; Al Amri, Iqbal; Davis, Cheriyathmanjiyil Antony

2016-03-08

Diamond detectors (DD) are preferred in small field dosimetry of radiation beams because of small dose profile penumbras, better spatial resolution, and tissue-equivalent properties. We investigated a commercially available 'microdiamond' detector in realizing absorbed dose from first principles. A microdiamond detector, type TM 60019 with tandem electrometer is used to measure absorbed doses in water, nylon, and PMMA phantoms. With sensitive volume 0.004 mm3, radius 1.1mm, thickness 1 x10(-3) mm, the nominal response is 1 nC/Gy. It is assumed that the diamond detector could collect total electric charge (nC) developed during irradiation at 0 V bias. We found that dose rate effect is less than 0.7% for changing dose rate by 500 MU/min. The reproducibility in obtaining readings with diamond detector is found to be ± 0.17% (1 SD) (n = 11). The measured absorbed doses for 6 MV and 15 MV photons arrived at using mass energy absorption coefficients and stop-ping power ratios compared well with Nd, water calibrated ion chamber measured absorbed doses within 3% in water, PMMA, and nylon media. The calibration factor obtained for diamond detector confirmed response variation is due to sensitivity due to difference in manufacturing process. For electron beams, we had to apply ratio of electron densities of water to carbon. Our results qualify diamond dosimeter as a transfer standard, based on long-term stability and reproducibility. Based on micro-dimensions, we recommend these detectors for pretreatment dose verifications in small field irradiations like stereotactic treatments with image guidance.

Absorbed dose determination in external beam radiotherapy. An international code of practice for dosimetry based on standards of absorbed dose to water

International Nuclear Information System (INIS)

2000-01-01

The International Atomic Energy Agency published in 1987 an International Code of Practice entitled 'Absorbed Dose Determination in Photon and Electron Beams' (IAEA Technical Reports Series No. 277 (TRS-277)), recommending procedures to obtain the absorbed dose in water from measurements made with an ionization chamber in external beam radiotherapy. A second edition of TRS-277 was published in 1997 updating the dosimetry of photon beams, mainly kilovoltage X rays. Another International Code of Practice for radiotherapy dosimetry entitled 'The Use of Plane-Parallel Ionization Chambers in High Energy Electron and Photon Beams' (IAEA Technical Reports Series No. 381 (TRS-381)) was published in 1997 to further update TRS-277 and complement it with respect to the area of parallel-plate ionization chambers. Both codes have proven extremely valuable for users involved in the dosimetry of the radiation beams used in radiotherapy. In TRS-277 the calibration of the ionization chambers was based on primary standards of air kerma; this procedure was also used in TRS-381, but the new trend of calibrating ionization chambers directly in a water phantom in terms of absorbed dose to water was introduced. The development of primary standards of absorbed dose to water for high energy photon and electron beams, and improvements in radiation dosimetry concepts, offer the possibility of reducing the uncertainty in the dosimetry of radiotherapy beams. The dosimetry of kilovoltage X rays, as well as that of proton and heavy ion beams, interest in which has grown considerably in recent years, can also be based on these standards. Thus a coherent dosimetry system based on standards of absorbed dose to water is possible for practically all radiotherapy beams. Many Primary Standard Dosimetry Laboratories (PSDLs) already provide calibrations in terms of absorbed dose to water at the radiation quality of 60 Co gamma rays. Some laboratories have extended calibrations to high energy photon and

Study of the indirect calibration of clinical air kerma-area meters

International Nuclear Information System (INIS)

Almeida Junior, Jose N.; Terini, Ricardo A.; Herdade, Silvio B.

2011-01-01

Kerma-area product (P KA ) is a quantity which is independent of the distance to the X-ray tube focal spot and that can be used to assess the effective dose in patients. Clinical P KA meters are usually calibrated on-site by measuring the air kerma with an ion chamber and evaluating the irradiated area by means of a radiographic image. This work presents a preliminary metrological evaluation of the calibration of a device marketed recently (PDC, Patient Dose Calibrator, Radcal), designed for calibrating clinical P KA meters. Results are also shown of applying the PDC to the cross calibration of a clinical P KA meter from a radiology equipment. Results confirm a lower energy dependence of the PDC relative to the tested clinical meter. (author)

Measurement of irradiation doses secondary to bedside radiographs in a medical intensive care unit

Energy Technology Data Exchange (ETDEWEB)

Boles, J M; Boussert, F; Manens, J P; Le Cam, B; Bellet, M; Garre, M

1987-01-01

The authors prospectively studied the radiation doses to radio-sensitive organs secondary to bedside radiographs in intensive care patients and in a control phantom. Dosimeters were taped on different organs during each bedside X-ray. The mean radiation doses, expressed in 10(-5) Gy (m-rad), for an ''average patient'' who was hospitalized 9 days and had 6 chest X-rays were respectively: 292 to the sternal bone marrow; 239 to the thyroid gland; 3 to the testes; 1 to the ovaries; 605 to the eye for 2 maxillary sinus X-rays. No diffused irradiation was measured during a 2-month period in the intensive care unit nor on dosimeters worn by four nurses.

Dose-reduction techniques for high-dose worker groups in nuclear power plants

International Nuclear Information System (INIS)

Khan, T.A.; Baum, J.W.; Dionne, B.J.

1991-03-01

This report summarizes the main findings of a study of the extent of radiation dose received by special work groups in the nuclear power industry. Work groups which chronically get large doses were investigated, using information provided by the industry. The tasks that give high doses to these work groups were examined and techniques described that were found to be particularly successful in reducing dose. Quantitative information on the extent of radiation doses to various work groups shows that significant numbers of workers in several critical groups receive doses greater than 1 and even 2 rem per year, particularly contract personnel and workers at BWR-type plants. The number of radiation workers whose lifetime dose is greater than their age is much less. Although the techniques presented would go some way in reducing dose, it is likely that a sizeable reduction to the high-dose work groups may require development of new dose-reduction techniques as well as major changes in procedures. 10 refs., 26 tabs

Quality control of secondary standards and calibration systems, therapy level, of National Laboratory of Metrology from Ionizing Radiations (LNMRI)

International Nuclear Information System (INIS)

Cecatti, E.R.; Freitas, L.C. de

1992-01-01

The results of quality control program of secondary standards, therapy level, and the calibration system of clinical dosemeters were analysed from 1984, when a change in the laboratory installation occurred and new standards were obtained. The national and the international intercomparisons were emphasised. The results for graphite wall chambers were compared, observing a maximum variation of about 0,6%. In the case of Delrin (TK01) wall chambers, the maximum variation was 1,7%. The results of post intercomparisons with thermoluminescent dosemeters have presented derivations lesser than 1%, securing the standards consistence at LNMRI with the international metrological system. (C.G.C.)

PLEIADES ABSOLUTE CALIBRATION : INFLIGHT CALIBRATION SITES AND METHODOLOGY

Directory of Open Access Journals (Sweden)

S. Lachérade

2012-07-01

Full Text Available In-flight calibration of space sensors once in orbit is a decisive step to be able to fulfil the mission objectives. This article presents the methods of the in-flight absolute calibration processed during the commissioning phase. Four In-flight calibration methods are used: absolute calibration, cross-calibration with reference sensors such as PARASOL or MERIS, multi-temporal monitoring and inter-bands calibration. These algorithms are based on acquisitions over natural targets such as African deserts, Antarctic sites, La Crau (Automatic calibration station and Oceans (Calibration over molecular scattering or also new extra-terrestrial sites such as the Moon and selected stars. After an overview of the instrument and a description of the calibration sites, it is pointed out how each method is able to address one or several aspects of the calibration. We focus on how these methods complete each other in their operational use, and how they help building a coherent set of information that addresses all aspects of in-orbit calibration. Finally, we present the perspectives that the high level of agility of PLEIADES offers for the improvement of its calibration and a better characterization of the calibration sites.

Performance of thermoluminescent materials for high dose dosimetry

International Nuclear Information System (INIS)

Texeira, Maria I.; Cecatti, Sonia G.P.; Caldas, Linda V.E.

2008-01-01

Cases involving high-doses of ionizing radiation are becoming increasingly common.The objective of this work was to characterize thermoluminescent materials for the dosimetry of workers exposed to high doses. Samples of TLD-200, TLD-400 and TLD-800 pellets from Thermo Electron Corporation were studied in gamma high-doses. Dose-response curves were obtained for doses between 100 mGy and 100 Gy. The reproducibility, the lower detection limits and dose-response curves were obtained for all three materials. The different kinds of detectors show usefulness for dosimetry of workers exposed accidentally to high doses. (author)

A fundamental parameter-based calibration model for an intrinsic germanium X-ray fluorescence spectrometer

International Nuclear Information System (INIS)

Christensen, L.H.; Pind, N.

1982-01-01

A matrix-independent fundamental parameter-based calibration model for an energy-dispersive X-ray fluorescence spectrometer has been developed. This model, which is part of a fundamental parameter approach quantification method, accounts for both the excitation and detection probability. For each secondary target a number of relative calibration constants are calculated on the basis of knowledge of the irradiation geometry, the detector specifications, and tabulated fundamental physical parameters. The absolute calibration of the spectrometer is performed by measuring one pure element standard per secondary target. For sample systems where all elements can be analyzed by means of the same secondary target the absolute calibration constant can be determined during the iterative solution of the basic equation. Calculated and experimentally determined relative calibration constants agree to within 5-10% of each other and so do the results obtained from the analysis of an NBS certified alloy using the two sets of constants. (orig.)

SSDL newsletter. No. 45[Secondary Standard Dosimetry Laboratories

Energy Technology Data Exchange (ETDEWEB)

NONE

2001-07-01

The first article of this issue of the SSDL Newsletter is about intercomparison of air kerma and absorbed dose to water calibration factors between the SSDLs of Norway and Cuba. The intercomparison covered Co-60 gamma rays (for air kerma and absorbed dose to water) and x-ray beams (air kerma at medium and low energy). The results are presented in this article. The Secretariat of the IAEA/WHO SSDL Network encourages this type of exercise between the SSDLs as it reinforces confidence in the measurement system. The IAEA also provides intercomparison services to its Network members, using ionization chambers. Although the service is presently limited to Co-60 gamma rays, it will soon be expanded to cover x-ray beams. For this purpose, a consultants' meeting will be held soon in Vienna to advise the IAEA on the methodology to be adopted. The second article is a report by the SSDL of Iran on the design, construction and calibration of plane parallel ionization chambers. This article presents the design characteristics of the chambers and the results of their calibration as well as dose determination of electron beams by air kerma based and absorbed dose to water based dosimetry procedures using these chambers. The third article is a report of a Nordic dosimetry meeting (Oslo, 19 January 2001) on the implementation of the new international Code of Practice based on absorbed dose to water standards (TRS-398). This report summarizes the main discussions and conclusions of the meeting. The editor wishes to draw the attention of the readers to the recommendations adopted in section 3 of the report. In addition, the Secretariat of the Network would appreciate receiving reports or minutes of meetings organized by SSDLs and hospitals on the implementation of TRS-398. The last article is a report of a consultants' meeting, held at the IAEA Headquarters in May 2001, on the calibration of well type ionization chambers for High Dose Rate {sup 192}Ir quality. The conclusions and

The response of different types of TL lithium fluoride detectors to high-energy mixed radiation fields

Energy Technology Data Exchange (ETDEWEB)

Obryk, B. [Institute of Nuclear Physics PAN (IFJ), ul. Radzikowskiego 152, 31-342 Krakow (Poland)], E-mail: barbara.obryk@ifj.edu.pl; Bilski, P.; Budzanowski, M. [Institute of Nuclear Physics PAN (IFJ), ul. Radzikowskiego 152, 31-342 Krakow (Poland); Fuerstner, M. [CERN - European Organization for Nuclear Research, 1211 Geneva 23 (Switzerland); Ilgner, C. [CERN - European Organization for Nuclear Research, 1211 Geneva 23 (Switzerland) and University of Dortmund, Dortmund (Germany); Jaquenod, F. [Ecole d' Ingenieurs de Geneve, Geneva (Switzerland); Olko, P.; Puchalska, M. [Institute of Nuclear Physics PAN (IFJ), ul. Radzikowskiego 152, 31-342 Krakow (Poland); Vincke, H. [CERN - European Organization for Nuclear Research, 1211 Geneva 23 (Switzerland)

2008-02-15

Thermoluminescent (TL) dosimeters are routinely used to monitor absorbed doses in many kinds of radiation fields which contain photons, electrons and neutrons. However, TLDs are mainly calibrated to photon sources. We studied the response of TLDs to complex secondary fields arising during the operation of high-energy accelerators (e.g. the Large Hadron Collider (LHC) at CERN). The experiments were conducted at the CERN-EU high-energy reference field facility (CERF). Six different LiF-based TLDs (MTS-N, MTS-7, MTS-6, MCP-N, MCP-7, MCP-6) were exposed to various secondary CERF's fields (both for high and low doses), by placing them at various positions: at the target and concrete top and side positions. For the experiment at the target the corresponding Monte Carlo calculations were also carried out using the FLUKA transport code and compared with experimental results. In addition, alanine dosimeters were used as an independent reference. The results show that TLDs are well suited for monitoring radiation fields around the LHC. Nevertheless, further investigations are required, some of which are in progress.

The impact of low-dose aspirin on preterm birth: secondary analysis of a randomized controlled trial.

Science.gov (United States)

Allshouse, A A; Jessel, R H; Heyborne, K D

2016-06-01

The objective of this study is to determine whether low-dose aspirin (LDA) reduced the rate of preterm birth (PTB) in a cohort of women at high risk for preeclampsia. Secondary analysis of the Maternal-Fetal Medicine Units High-Risk Aspirin trial. Preterm births were categorized by phenotype: indicated, spontaneous or due to preterm premature rupture of membranes (PPROMs). Of 1789 randomized women, 30.5% delivered before 37 weeks (18.5% indicated, 5.8% spontaneous and 6.2% following preterm PPROMs). Among women randomized to LDA, we observed a trend favoring fewer PTBs due to spontaneous preterm labor and preterm PPROMs, odds ratio (OR: 0.826 (0.620, 1.099)); the incidence of indicated PTBs appeared unchanged, OR: 0.999 (0.787, 1.268). Although not reaching significance, we observed an effect size similar to other studies of both low- and high-risk women. These results support findings from other studies assessing LDA as a PTB prevention strategy.

Comparative dosimetric study in the estimation of the dose rate of the Transelektro LGI-01 irradiator; Estudio dosimetrico comparativo en la estimacion de la razon de dosis del irradiador Transelektro LGI-01

Energy Technology Data Exchange (ETDEWEB)

Carrasco A, H.; Urena N, F.F. [ININ, A.P. 18-1027, 11801 Mexico D.F. (Mexico)

2004-07-01

The {sup 60} Co TRANSELEKTRO, model LGI-0 1, Hungarian, is similar to the Canadian Gamma cell. The evaluation of the dose ratio in the geometric center of the exposition chamber of the LGI-0 1 is presented in this paper. In order to do this two types of dosimeters were used: the alanine, and the L8-C 1 red acrylic (Canadian). Three dosimeters of each type were irradiated at 1, 2, 3, 4, 5, 6, 7 and 8 h. The respective intensities and absorbencies were measured and used to determine the proper absorbed doses and the dose ratio. The results obtained with both dosimeters were compared with the ratio dose that was reported by the Secondary Laboratory of Dosimetric Calibration of the Metrology Department of the ININ, which used a ionization chamber for the calibration of the LGI-0 1. The alanine dosemeter showed a {+-} 1.3% dispersion while with the acrylic dosemeter the dispersion was of {+-} 3.2%, with respect to the value reported by the authorized Calibration Laboratory. This paper was also used to update the calibration table of the L8-C1 red acrylic. (Author)

Calibration of thin-film dosimeters irradiated with 80-120 kev electrons

DEFF Research Database (Denmark)

Helt-Hansen, J.; Miller, A.; McEwen, M.

2004-01-01

A method for calibration of thin-film dosimeters irradiated with 80-120keV electrons has been developed. The method is based on measurement of dose with a totally absorbing graphite calorimeter, and conversion of dose in the graphite calorimeter to dose in the film dosimeter by Monte Carlo calcul......V electron irradiation. The two calibrations were found to be equal within the estimated uncertainties of +/-10% at 1 s.d. (C) 2004 Elsevier Ltd. All rights reserved....

Assessment of organ dose reduction and secondary cancer risk associated with the use of proton beam therapy and intensity modulated radiation therapy in treatment of neuroblastomas

International Nuclear Information System (INIS)

Fuji, Hiroshi; Harada, Hideyuki; Asakura, Hirofumi; Nishimura, Tetsuo; Schneider, Uwe; Ishida, Yuji; Konno, Masahiro; Yamashita, Haruo; Kase, Yuki; Murayama, Shigeyuki; Onoe, Tsuyoshi; Ogawa, Hirofumi

2013-01-01

To compare proton beam therapy (PBT) and intensity-modulated radiation therapy (IMRT) with conformal radiation therapy (CRT) in terms of their organ doses and ability to cause secondary cancer in normal organs. Five patients (median age, 4 years; range, 2–11 years) who underwent PBT for retroperitoneal neuroblastoma were selected for treatment planning simulation. Four patients had stage 4 tumors and one had stage 2A tumor, according to the International Neuroblastoma Staging System. Two patients received 36 Gy, two received 21.6 Gy, and one received 41.4 Gy of radiation. The volume structures of these patients were used for simulations of CRT and IMRT treatment. Dose–volume analyses of liver, stomach, colon, small intestine, pancreas, and bone were performed for the simulations. Secondary cancer risks in these organs were calculated using the organ equivalent dose (OED) model, which took into account the rates of cell killing, repopulation, and the neutron dose from the treatment machine. In all evaluated organs, the mean dose in PBT was 20–80% of that in CRT. IMRT also showed lower mean doses than CRT for two organs (20% and 65%), but higher mean doses for the other four organs (110–120%). The risk of secondary cancer in PBT was 24–83% of that in CRT for five organs, but 121% of that in CRT for pancreas. The risk of secondary cancer in IMRT was equal to or higher than CRT for four organs (range 100–124%). Low radiation doses in normal organs are more frequently observed in PBT than in IMRT. Assessments of secondary cancer risk showed that PBT reduces the risk of secondary cancer in most organs, whereas IMRT is associated with a higher risk than CRT

Update of the Picker C9 irradiator control system of the gamma II room of the secondary laboratory of dosimetric calibration

International Nuclear Information System (INIS)

Simon S, L. E.

2016-01-01

The Picker C9 irradiator is responsible for the calibration of different radiological equipment and the control system that maintains it in operation is designed in the graphical programming software LabVIEW (Laboratory Virtual Instrumentation Engineering Workbench), being its major advantages: the different types of communication, easy interconnection with other software and the recognition of different hardware devices, among others. Operation of the irradiator control system is performed with the NI-Usb-6008 (DAQ) data acquisition module of the National Instruments Company. The purpose of this work is to update the routines that make the Picker C9 control system of the gamma II room of the secondary laboratory of dosimetric calibration, using the graphic programming software LabVIEW, as well as to configure the new acquisition hardware of data that is implemented to control the Picker C9 irradiator system and ensure its operation. (Author)