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1

Volume computed tomography air kerma index and image quality evaluation in Brazil.  

UK PubMed Central (United Kingdom)

The aim of this study was to evaluate the image quality of 29 computed tomography (CT) scanners in Brazil and to perform estimations of patient dose and image quality of common CT examinations at these equipment. The volume CT air kerma indexes (C(VOL)) were estimated, using normalised weighted air kerma indexes, supplied by the ImPACT group. The image quality tests were performed using the phantom and accreditation protocol from the American College of Radiology (ACR). The C(VOL) values for head scans varied between 8.7 and 108 mGy. The Hi-res chest examinations presented C(VOL) values varying from 0.4 to 32 mGy. For abdominal scans, the estimated C(VOL) values varied between 4.1 and 94 mGy. This wide variation of air kerma between different centres is related to the scanner type and also to the scanning parameters. The results also showed that the image quality did not attend all ACR CT accreditation requirements.

Mecca FA; Andrade ME; Jakubiak RR; Khoury HJ; Dias SK; Miquelin CA; Nader A

2012-03-01

2

Volume computed tomography air kerma index and image quality evaluation in Brazil.  

Science.gov (United States)

The aim of this study was to evaluate the image quality of 29 computed tomography (CT) scanners in Brazil and to perform estimations of patient dose and image quality of common CT examinations at these equipment. The volume CT air kerma indexes (C(VOL)) were estimated, using normalised weighted air kerma indexes, supplied by the ImPACT group. The image quality tests were performed using the phantom and accreditation protocol from the American College of Radiology (ACR). The C(VOL) values for head scans varied between 8.7 and 108 mGy. The Hi-res chest examinations presented C(VOL) values varying from 0.4 to 32 mGy. For abdominal scans, the estimated C(VOL) values varied between 4.1 and 94 mGy. This wide variation of air kerma between different centres is related to the scanner type and also to the scanning parameters. The results also showed that the image quality did not attend all ACR CT accreditation requirements. PMID:21561947

Mecca, Fernando A; Andrade, Marcos E A; Jakubiak, Rosangela R; Khoury, Helen J; Dias, Simone K; Miquelin, Charlie A; Nader, Alejandro

2011-05-11

3

Image quality and volume computed tomography air kerma index (Cvol) evaluation in Recife  

International Nuclear Information System (INIS)

The Computed Tomography (CT) is an important diagnostic imaging method, widely used. However, in spite of all the advantages and technologic advances within the CT scanners, the tomographic procedures result in high absorbed doses to patients. The main objective of this work was to perform a dosimetric study of CT scanners located at Recife and to evaluate the image quality on CT examinations in these equipment. The volume CT air kerma index (CVOL) and air kerma length product (PKL,CT) were estimated. These values were calculated using normalized weighted air kerma indexes in CT standard dosimetry phantoms (nCW), supplied by ImPACT group for several CT scanners, and the scan parameters of routine head, routine chest and hi-resolution chest CT exams performed at 20 institutions. The irradiation parameters of 15 adult patients for each CT procedure were registered at six participating centres, at which the phantom from the American College of Radiology (ACR) CT accreditation protocol was used for the image quality measurements. For routine head exams, the CVOL values varied between 12 and 58 mGy (at the posterior fossa) and 15 to 58 mGy (at the cerebrum) and the PKL,CT, from 150 to 750 mGy·cm. The CVOL values for routine chest procedures varied from 3 to 26 mGy and the PKL,CT, between 120 and 460 mGy·cm. In relation to Hi-resolution chest exams, CVOL values were from 1.0 to 2.7 mGy and the PKL,CT values varied between 24 and 67 mGy·cm. The image quality evaluations results showed that almost all scanners presented at least one inadequacy. One of the equipment presented faults at 70% of the tests. With regard to the image noise, only two scanners presented acceptable results. From these results, it is possible to conclude that the volume CT air kerma index values are lower than the European reference levels. However, the image quality of these CT scanners does not attend the ACR requirements, suggesting the need to implement quality assurance programs at the evaluated institutions. (author)

2008-01-01

4

Inherent uncertainty of air kerma  

Science.gov (United States)

Air kerma is defined in air, the constituents and the amounts of which are determined experimentally with some uncertainties. The inherent uncertainty of air kerma in a photon beam stemming from the uncertainties of atomic weights and composition data in air was evaluated as a function of photon energy. The uncertainty was 1 part in 104 for photon beams with energies in the range 1 keV to 20 MeV.

Yi, Chul-Young

2013-04-01

5

Image quality and volume computed tomography air kerma index (C{sub vol}) evaluation in Recife; Avaliacao da qualidade de imagem e do indice volumetrico de Kerma ar em tomografia computadorizada (C{sub vol}) em Recife  

Energy Technology Data Exchange (ETDEWEB)

The Computed Tomography (CT) is an important diagnostic imaging method, widely used. However, in spite of all the advantages and technologic advances within the CT scanners, the tomographic procedures result in high absorbed doses to patients. The main objective of this work was to perform a dosimetric study of CT scanners located at Recife and to evaluate the image quality on CT examinations in these equipment. The volume CT air kerma index (C{sub VOL}) and air kerma length product (P{sub KL,CT}) were estimated. These values were calculated using normalized weighted air kerma indexes in CT standard dosimetry phantoms ({sub n}C{sub W}), supplied by ImPACT group for several CT scanners, and the scan parameters of routine head, routine chest and hi-resolution chest CT exams performed at 20 institutions. The irradiation parameters of 15 adult patients for each CT procedure were registered at six participating centres, at which the phantom from the American College of Radiology (ACR) CT accreditation protocol was used for the image quality measurements. For routine head exams, the C{sub VOL} values varied between 12 and 58 mGy (at the posterior fossa) and 15 to 58 mGy (at the cerebrum) and the P{sub KL,CT}, from 150 to 750 mGy{center_dot}cm. The C{sub VOL} values for routine chest procedures varied from 3 to 26 mGy and the P{sub KL,CT}, between 120 and 460 mGy{center_dot}cm. In relation to Hi-resolution chest exams, C{sub VOL} values were from 1.0 to 2.7 mGy and the P{sub KL,CT} values varied between 24 and 67 mGy{center_dot}cm. The image quality evaluations results showed that almost all scanners presented at least one inadequacy. One of the equipment presented faults at 70% of the tests. With regard to the image noise, only two scanners presented acceptable results. From these results, it is possible to conclude that the volume CT air kerma index values are lower than the European reference levels. However, the image quality of these CT scanners does not attend the ACR requirements, suggesting the need to implement quality assurance programs at the evaluated institutions. (author)

Andrade, Marcos Ely Almeida

2008-07-01

6

Air kerma rate constants for radionuclides  

International Nuclear Information System (INIS)

[en] Conversion to SI units requires that the exposure rate constant which was usually quoted in R . h-1 . mCi-1 . cm2 be replaced by the air kerma rate constant with units m2 . Gy . Bq-1s-1. The conversion factor is derived and air kerma rate constants for 30 radionuclides used in nuclear medicine and brachytherapy are listed. A table for calculation of air kerma rates for other radionuclides is also given. To calculate absorbed dose to tissue, the air kerma rate has to be multiplied by approximately 1.1. A dose equivalent rate constant is thus listed which allows direct calculation of dose equivalent rate to soft tissue without resorting to exposure rate constants tabulated in the special units R . m2 . mCi-1h-1 which should no longer be used. (orig.)

1988-01-01

7

Air kerma measurement for high energy gamma  

International Nuclear Information System (INIS)

[en] The authors present the measurement method and results for 6-9 MeV gamma radiation as well as brief light on reference radiation fields at this energy. Air kerma measurement is performed by spherical graphite cavity chambers whose collective volume is 3 and 50 cm3, respectively. Having discussed the parameters needed for air kerma evaluation and determined their values, final results are given with total uncertainty about 4.2%, which are consistent well with that determined by spectrum method within the uncertainties

1994-01-01

8

Evaluation of air kerma - air product in fluoroscopic procedures  

International Nuclear Information System (INIS)

[en] This paper presents the values of air kerma-area product obtained in fluoroscopic procedures performed in two teaching hospitals in Recife, Brazil. A total of 78 procedures from Oesophagus-Gastric-Duodenal (OGD) tract and Cystourethrography examination were studied. The air kerma- area product was determined using a transmission chamber associated to a Diamentor M2-PTW. The results obtained showed that the average values of the air kerma - area product, from the two institutions, range from 8.6 to 34 Gy/cm2 for OGD tract examination and between 5.9 to 25 Gy/cm2 for Cystourethrography examination. (author)

2002-01-01

9

New LNHB primary standard for 60Co air kerma  

Science.gov (United States)

As a single working chamber for a national air kerma standard was not considered safe and robust enough, a new set of six ionization chambers was devised to establish the French 60Co air kerma standard. Although every new ionization chamber was treated as much as possible in the same way (manufacturing, measurements of volumes, wall effect calculations, current corrections), a maximum discrepancy of 0.2% was observed between the final measurement results from each chamber. The final value of the air kerma rate in reference conditions was determined as the mean value of the measurement results from all six chambers. Among the different factors whose determination is necessary to calculate the air kerma rate, some are considered independent of or common to all the graphite-walled ionization chambers (example: mean energy expended by an electron to produce an ion pair in dry air), while others vary for each chamber (example: air cavity ionic collection volume). Considering that the uncertainties of the individual ionization chamber measurement results seem slightly underestimated, the uncertainty on the mean of the products of the six chamber-dependent factors was taken equal to the standard deviation of the sample composed of the products of the six chamber-dependent factors (0.078%). Compared with the previous standard, the air kerma rate of the 60Co photon beam would then increase by 0.09% and the air kerma rate uncertainty would drop from 0.38% to 0.31%.

Delaunay, F.; Donois, M.; Gouriou, J.; Leroy, E.; Ostrowsky, A.

2010-12-01

10

Determining air kerma from pixel values in digital mammography  

International Nuclear Information System (INIS)

The pixels in digital detectors used in x-ray imaging can be considered as small dose meters. In mammography, the image detector area is commonly only partly covered by tissue and the incident air kerma could be monitored by using pixel values from the detector elements in the unattenuated primary beam area. The measured air kerma could be used for patient dose estimation. The air kerma and radiation quality dependence of the response of pixel values within a large exposure range for two direct digital detector types was experimentally investigated for this purpose. Using these calibration results, air kerma was measured from clinical images and compared with tube output calculation. The differences between the two methods were typically below 2% and measurements based on pixel values can therefore be recommended.

2009-06-21

11

DEVELOPMENT OF A PHANTOM AND A METHODOLOGY FOR EVALUATION OF DEPTH KERMA AND KERMA INDEX FOR DENTAL CONE BEAM COMPUTED TOMOGRAPHY.  

UK PubMed Central (United Kingdom)

Basically, all modalities of diagnostic radiology require phantoms suitable for dosimetric evaluations. New technologies frequently arise unaccompanied of tools for dosimetric evaluations and quality control. In this study, a low-cost phantom and a consequent proposed methodology for dosimetric evaluations in cone beam computed tomography (CBCT) were presented. The developed phantom has typical dimensions of the human face, was built in polymethyl methacrylate and filled with water. Three devices with different technological concepts were evaluated and a proposed index, kerma index-height product (PKIH), was defined as an option to the use of air kerma-area product. The results of this study show relatively uniform kerma profiles for scanners with field of views (FOVs) of large diameters and non-uniform for FOVs of small diameters. With regard to the values obtained for the kerma indexes, much higher values were found for the equipment FOVs with small diameter compared with the values of the two other equipment that have larger diameters. The results indicate that (1) there is a need for special phantoms for use in CBCT, (2) the use of PKA in the evaluation of protocols on different equipment can lead to false interpretations and (3) the new index is a suitable alternative for the use of PKA in CBCT.

Batista WO; Navarro MV; Maia AF

2013-07-01

12

Air kerma intercomparison at 60Co by solid TL detectors  

International Nuclear Information System (INIS)

[en] Air kerma produced by 60Co gamma radiation from two laboratories were compared by irradiating dosemeters on the same day in Sao Paulo and in Helsinki. The thermoluminescent fading of the posted dosemeters was controlled by performing irradiations in the same laboratory 13 days before and 10 days after the irradiation of the reference group. The ratio of the air kerma values as determined from the irradiations in the two laboratories was 0.971 ± 0.016, at the 95% confidence level. The uncertainty caused by fading was shown to be negligible. The difference of about 3% in the air kerma values was thus clearly demonstrated by the TLD method. Systematic and random errors in TLD with solid detectors are discussed together with methods for their minimisation. (author)

1990-01-01

13

Corrections to air kerma rate measurements of 137Cs environmental sources for free space conditions  

International Nuclear Information System (INIS)

[en] Air kerma rate measurements between 2 m and 4 m from a set of 137Cs reference environmental sources (with both stainless steel and brass encapsulation) have been made at NPL using a calibrated Reuter-Stokes high pressure ionisation chamber. Monte Carlo techniques are used to calculate the air kerma rate components over a similar range of distances from these sources. The calculated air kerma values are compared with measurements and the deviation of the data from the inverse square law is investigated. Corrections to the measurement data are then derived to obtain the air kerma rate in free space at 2.5 m from each source. (author)

1996-01-01

14

Studies on the performance of diagnostic ionisation air Kerma meters in the United States  

International Nuclear Information System (INIS)

[en] The dependence of response of air-kerma meters on air-kerma rate and beam energy is investigated for meters used in the United States. The response of some meters is reduced considerably at the high kerma rates sometimes encountered in diagnostic examinations. The energy dependence of some meters leads to inaccurate measurements of the half-value layer in mammography. Performance characteristics of meters necessary to produce sufficiently accurate measurements are discussed

1992-01-01

15

Studies on the performance of diagnostic ionisation air kerma meters in the United States  

International Nuclear Information System (INIS)

[en] The dependence of response of air kerma meters on air kerma rate and beam energy is investigated for meters used in the United States. The response of some meters is reduced considerably at the high kerma rates sometimes encountered in diagnostic examinations. The energy dependence of some meters leads to inaccurate measurements of the half-value layer in mammography. Performance characteristics of meters necessary to produce sufficiently accurate measurements are discussed. (author)

1992-01-01

16

Studies on the performance of diagnostic ionisation air kerma meters in the United States  

Energy Technology Data Exchange (ETDEWEB)

The dependence of response of air kerma meters on air kerma rate and beam energy is investigated for meters used in the United States. The response of some meters is reduced considerably at the high kerma rates sometimes encountered in diagnostic examinations. The energy dependence of some meters leads to inaccurate measurements of the half-value layer in mammography. Performance characteristics of meters necessary to produce sufficiently accurate measurements are discussed. (author).

Wagner, L.K. (Texas Univ., Houston, TX (United States). Dept. of Radiology)

1992-01-01

17

Status of air kerma and absorbed dose standards in India  

International Nuclear Information System (INIS)

Full text: The Radiation Safety Systems Division of Bhabha Atomic Research Centre, India maintains Primary and Secondary Standards of various parameters of radiation measurements and provides calibration services to various users of radiation in the country. This is an apex laboratory in India and plays a pivotal role in ensuring accurate radiological measurements. The laboratory coordinates national intercomparisons of radiation measurements to maintain their uniformity and traceability and is linked through various programmes with the other International organizations such as Bureau Internationale des Poids et Mesures (BIPM) Paris, International Atomic Energy Agency (IAEA) Vienna, Asia Pacific Metrology Programme (APMP) Taiwan. It is the recognized Regional Secondary Standards Dosimetry Laboratory (SSDL) of IAEA/WHO (World Health Organisation). This paper brings out the status of various primary and secondary standards for radiological measurements maintained at BARC. 1. Primary Exposure/Air-kerma standard at Co-60 energy (therapy level): The primary standard for exposure/ air-kerma measurements maintained at BARC is a graphite cavity chamber of volume 4.362 cc with an internal diameter of 1.8 cm, internal height of 1.78 cm and wall thickness of 704.3mg/cm2. Correction factors for the difference between electron stopping powers, photon mass energy absorption coefficients of air and graphite wall, correction for recombination, radiation field non-uniformity, stem scatter and polarity effect are applied and the maximum overall uncertainty in the realisation of exposure/air-kerma is around ±1%. This standard has been intercompared with IAEA and BIPM through transfer standard and the agreement in the results are better than ±1%. An intercomparison under the APMP programme is to be held during May, 2002. 2. Primary Exposure/Air-kerma standard at protection and brachytherapy level: A set of three spherical graphite-walled cavity chambers of different air-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/m3. 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 ND,W are maintained. For air kerma at medium energy x-rays, chambers of the type Exradin A2, NE 2571, NE2577, Victoreen 415 B, Victoreen 415, Exradin A3 and NE 2581 are

2002-01-01

18

Corrections to Air Kerma Rate Measurements of (125)I Brachytherapy Sources to Free Space Conditions.  

Science.gov (United States)

Air kerma rate measurements have been made between 40 cm and 100 cm from one of a set of (125)I reference sources within the facilities of Amersham International plc. Monte Carlo techniques have been used to calculate the air kerma rate components over th...

D. R. Shipley S. Duane

1994-01-01

19

Routine measurement of gamma ray air kerma rate in the environment  

International Nuclear Information System (INIS)

[en] This Note, issued by Her Majesty's Inspectorate of Pollution, provides technical guidance on the routine measurement of gamma ray air kerma rate in the environment. It includes a protocol for the measurement, interpretation and reporting of environmental gamma ray air kerma rates and appendices reviewing existing techniques, instruments, calibration facilities and the physics of such measurements. (UK)

1995-01-01

20

Review of requirements for a primary standard of air kerma for 60Co and 137Cs ?-rays at protection level air kerma rates  

International Nuclear Information System (INIS)

[en] The three cavity chambers which comprise the primary standard of air kerma for 60Co and 137Cs ?-rays are reaching the end of their working life. A new primary standard suitable for use at protection level air kerma rates is proposed to replace them and the main parameters which must be addressed in the design are identified. Recommendations are made for further work needed to inform the design process. (author)

2000-01-01

 
 
 
 
21

Review of requirements for a primary standard of air kerma for {sup 60}Co and {sup 137}Cs {gamma}-rays at protection level air kerma rates  

Energy Technology Data Exchange (ETDEWEB)

The three cavity chambers which comprise the primary standard of air kerma for {sup 60}Co and {sup 137}Cs {gamma}-rays are reaching the end of their working life. A new primary standard suitable for use at protection level air kerma rates is proposed to replace them and the main parameters which must be addressed in the design are identified. Recommendations are made for further work needed to inform the design process. (author)

Angliss, R.; Moretti, C

2000-03-01

22

Influence of atmospheric rainfall to ? radiation Kerma rate in surface air  

International Nuclear Information System (INIS)

Objective: To investigate the influence rule of the atmospheric Rainfall to the ? radiation Kerma rate in surface air in order to revise the result of its measurement during rainfall. Methods: The influence factors of rainfall to the measurement of the ? radiation Kerma rate in air were analyzed and then the differential equation of the correlation factors was established theoretically, and by resolving the equation, the mathematical model Was obtained. The model was discussed through several practical examples. Results: The mathematical model was coincided with the tendency of curve about the measured data on the influence rule of rainfall to the ? radiation Kerma rate in surface air. Conclusion: By using the theoretical formula in this article which is established to explain the relationship between the rainfall and the ? radiation Kerma rate in surface air, the influence of rainfall to the ? radiation Kerma rate in surface air could be correctly revised. (authors)

2009-01-01

23

Computation of air kerma rate around an industrial radiography source  

International Nuclear Information System (INIS)

Use of Iridium-192 and Cobalt-60 sources in Industrial Radiography has recorded a steep rise in the last three decades in India. There are about 425 institutions in possession of 1100 radiography equipment's. Widespread use of these sources call for meticulous radiation safety programme in the use of these sources. A gamma radiography exposure device comprises of adequately shielded source holder assembly and accessories such as remote control cable and guide tube with suitable mechanism to facilitate radiation exposure in a safe manner for industrial radiography work. The source holder assembly is driven out of the shielded container through the guide tube by means of a suitable drive mechanism. Various built-in design safety features are incorporated in these devices to ensure safe operation and to avoid untoward incidents. In spite of effective regulatory control, accidents may take place. For example, an accident situation may arise due to decoupling of the source assembly which may lead to the source falling on the ground and consequent exposure of people around the source and also the personnel involved in source retrieval operations. A knowledge of the air kerma distribution around the source will be of use in estimating the doses to the concerned personnel. This paper discusses the air kerma distribution around and iridium-192 radiography source computed using Monte Carlo method

2001-01-01

24

Kerma-in air measurement and conversion coefficients to dose due to the environmental gamma radiation  

International Nuclear Information System (INIS)

This work aims to establish a calibration methodology for HPGe detectors calibration methodology, for in situ gamma measurements for air kerma due to environmental radiation exposure and to establish a procedure for the determination of dose applied to environmental gamma exposure based on the air kerma energy distribution and conversion coefficients from kerma to age-dependent dose. It was developed a methodology for characterization of HPGe detector by Monte Carlo calculation based on the EGS4 computer code. The calibration parameters were determined for detectors to be used in in situ gamma spectrometry to determine the air kerma. It has been calculated, also by Monte Carlo calculation, conversion coefficients from air kerma to effective dose and dose in organs and tissues to an exposure from a infinite plane source for several age groups. The ADAM code, developed for the simulation of an adult, was modified in order to accommodate the several anthropomorphic mathematical models with varying age and both sex. (author)

1999-01-01

25

Seasonal variation of air kerma rate in Sicily  

Energy Technology Data Exchange (ETDEWEB)

Thermoluminescence dosimetry has been used to measure air kerma in 29 sites in Sicily. Four three month measurement campaigns have been carried out in order to assess seasonal variations. Average annual values between 20 and 90 nGy h{sup -1}, after cosmic background subtraction, are reported. Average annual values are strongly dependent on site lithology, and we find that winter data are generally the highest, while spring and autumn rates are generally the lowest with very similar trends in any site. Summer values generally lay in between. Largest seasonal variations are found in sites along the southern coast of the island, probably because of stronger action of winds affecting radon, along with its progeny, concentrations at ground level.

Basile, S. [Dipartimento di Fisica e Tecnologie Relative, Universita degli Studi di Palermo, Viale delle Scienze, Edificio 18, I-90128, Palermo (Italy)], E-mail: basile@unipa.it; Brai, M.; Marrale, M. [Dipartimento di Fisica e Tecnologie Relative, Universita degli Studi di Palermo, Viale delle Scienze, Edificio 18, I-90128, Palermo (Italy); Rizzo, S. [Dipartimento di Ingegneria Nucleare, Universita degli Studi di Palermo, Viale delle Scienze, Edificio 6, I-90128, Palermo (Italy)

2008-07-15

26

Corrections to air kerma rate measurements of 125I brachytherapy sources to free space conditions  

International Nuclear Information System (INIS)

[en] Air kerma rate measurements have been made between 40 cm and 100 cm from one of a set of 125I reference sources within the facilities of Amersham International plc. Monte Carlo techniques have been used to calculate the air kerma rate components over the same range of distances from this source. After comparing the calculated data with measurements, the compliance of the data with the inverse square law was investigated, and corrections were derived to obtain the air kerma rate at 1 m in free space from each source. Simulations of the experimental setup with an isotropic monoenergetic point source close to the effective energy of 125I were found to reproduce the air kerma rate measurements reasonably accurately, and indicated that the contribution due to scattered photons was significant. The overall correction (which is defined as the product of individual corrections for chamber size effect, air attenuation and radiation scatter) required to the inverse square law to obtain the air kerma rate at 1 m in free space was found to be 0.981, 0.984 and 0.980, respectively, for air kerma rate measurements at 40 cm, 60 cm and 100 cm from the 125I reference source. The total uncertainty in these corrections was estimated to be 0.88% at the 1? level. (author)

1994-01-01

27

Corrections to air kerma rate measurements of {sup 125}I brachytherapy sources to free space conditions  

Energy Technology Data Exchange (ETDEWEB)

Air kerma rate measurements have been made between 40 cm and 100 cm from one of a set of {sup 125}I reference sources within the facilities of Amersham International plc. Monte Carlo techniques have been used to calculate the air kerma rate components over the same range of distances from this source. After comparing the calculated data with measurements, the compliance of the data with the inverse square law was investigated, and corrections were derived to obtain the air kerma rate at 1 m in free space from each source. Simulations of the experimental setup with an isotropic monoenergetic point source close to the effective energy of {sup 125}I were found to reproduce the air kerma rate measurements reasonably accurately, and indicated that the contribution due to scattered photons was significant. The overall correction (which is defined as the product of individual corrections for chamber size effect, air attenuation and radiation scatter) required to the inverse square law to obtain the air kerma rate at 1 m in free space was found to be 0.981, 0.984 and 0.980, respectively, for air kerma rate measurements at 40 cm, 60 cm and 100 cm from the {sup 125}I reference source. The total uncertainty in these corrections was estimated to be 0.88% at the 1{sigma} level. (author).

Shipley, D.R.; Duane, S.

1994-05-01

28

Calibration and features of air-kerma length product meters.  

UK PubMed Central (United Kingdom)

Pencil-type air-kerma length product meters are generally used for quality control and radiation exposure measurements in computed tomography. To ensure reliable results, these meters should be calibrated so that measurements are traceable to international standards. Suitable calibration procedures, together with the properties of these meters, were examined and compared with the international standards and recommendations. The calibration procedure and setup used in this study were slightly modified compared with international recommendations. The special collimator system was found to cause less scatter than similar setups in earlier studies. The energy dependence of the meter response was investigated for several types of meters with standard radiation qualities. With most tested meter types, the total variation due to energy dependence was <4 %, but some had strong energy dependence and the variation was up to 15 % or higher. This highlights the importance of a proper calibration. The response of one semiconductor meter type varied up to 8 % when rotating the meter around its axis; this should be taken into account when making calibrations with a static setup.

Merimaa K; Tapiovaara M; Kosunen A; Toroi P

2012-12-01

29

Calibration and features of air-kerma length product meters.  

Science.gov (United States)

Pencil-type air-kerma length product meters are generally used for quality control and radiation exposure measurements in computed tomography. To ensure reliable results, these meters should be calibrated so that measurements are traceable to international standards. Suitable calibration procedures, together with the properties of these meters, were examined and compared with the international standards and recommendations. The calibration procedure and setup used in this study were slightly modified compared with international recommendations. The special collimator system was found to cause less scatter than similar setups in earlier studies. The energy dependence of the meter response was investigated for several types of meters with standard radiation qualities. With most tested meter types, the total variation due to energy dependence was <4 %, but some had strong energy dependence and the variation was up to 15 % or higher. This highlights the importance of a proper calibration. The response of one semiconductor meter type varied up to 8 % when rotating the meter around its axis; this should be taken into account when making calibrations with a static setup. PMID:22539532

Merimaa, K; Tapiovaara, M; Kosunen, A; Toroi, P

2012-04-26

30

Factor kerma decrease for interactions X and gamma rays with air, water, polyethylene and plexiglass  

International Nuclear Information System (INIS)

KERMA decrease caused by secondary particle energy loss in air, water, polyethylene and plexiglass in 0.5 MeV to 10 MeV region of X and gamma-photons, is presented in this paper. The calculations of KERMA factor decrease are made for Compton, photo effects and pair production effects by incident X and gamma rays, in the mentioned energy interval. (author)

1997-01-01

31

The IPEM code of practice for determination of the reference air kerma rate for HDR 192Ir brachytherapy sources based on the NPL air kerma standard  

Science.gov (United States)

This paper contains the recommendations of the high dose rate (HDR) brachytherapy working party of the UK Institute of Physics and Engineering in Medicine (IPEM). The recommendations consist of a Code of Practice (COP) for the UK for measuring the reference air kerma rate (RAKR) of HDR 192Ir brachytherapy sources. In 2004, the National Physical Laboratory (NPL) commissioned a primary standard for the realization of RAKR of HDR 192Ir brachytherapy sources. This has meant that it is now possible to calibrate ionization chambers directly traceable to an air kerma standard using an 192Ir source (Sander and Nutbrown 2006 NPL Report DQL-RD 004 (Teddington: NPL) http://publications.npl.co.uk). In order to use the source specification in terms of either RAKR, \\dot K_R (ICRU 1985 ICRU Report No 38 (Washington, DC: ICRU); ICRU 1997 ICRU Report No 58 (Bethesda, MD: ICRU)), or air kerma strength, SK (Nath et al 1995 Med. Phys. 22 209-34), it has been necessary to develop algorithms that can calculate the dose at any point around brachytherapy sources within the patient tissues. The AAPM TG-43 protocol (Nath et al 1995 Med. Phys. 22 209-34) and the 2004 update TG-43U1 (Rivard et al 2004 Med. Phys. 31 633-74) have been developed more fully than any other protocol and are widely used in commercial treatment planning systems. Since the TG-43 formalism uses the quantity air kerma strength, whereas this COP uses RAKR, a unit conversion from RAKR to air kerma strength was included in the appendix to this COP. It is recommended that the measured RAKR determined with a calibrated well chamber traceable to the NPL 192Ir primary standard is used in the treatment planning system. The measurement uncertainty in the source calibration based on the system described in this COP has been reduced considerably compared to other methods based on interpolation techniques.

Bidmead, A. M.; Sander, T.; Locks, S. M.; Lee, C. D.; Aird, E. G. A.; Nutbrown, R. F.; Flynn, A.

2010-06-01

32

Realization of reference air-kerma rate for low-energy photon sources  

Energy Technology Data Exchange (ETDEWEB)

A large air-filled parallel-plate extrapolation chamber with thin graphite front and back electrodes is used as a primary standard measuring device for low-energy interstitial brachytherapy sources from which the unit of air-kerma strength or reference air-kerma rate can be derived. The chamber is suitable for low-energy photons with energies up to 40 keV. The underlying principle is that the air-kerma rate at a given point is proportional to the increment of ionization per increment of chamber volume at chamber depths greater than the range of secondary electrons originating from the electrode. The fundamentals for evaluating the extrapolation curves are presented as well as a detailed description of the present set-up of the P.T.B. large-volume extrapolation chamber (G.R.O.V.E.X.). Comparisons between the G.R.O.V.E.X. and other primary standards for air-kerma and reference air-kerma rate are presented. (authors)

Selbach, H.J.; Kramer, H.M. [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany); Culberson, W.S. [Wisconsin Univ., Medical Radiation Research Centre, Madison (United States)

2008-08-15

33

Realization of reference air-kerma rate for low-energy photon sources  

International Nuclear Information System (INIS)

A large air-filled parallel-plate extrapolation chamber with thin graphite front and back electrodes is used as a primary standard measuring device for low-energy interstitial brachytherapy sources from which the unit of air-kerma strength or reference air-kerma rate can be derived. The chamber is suitable for low-energy photons with energies up to 40 keV. The underlying principle is that the air-kerma rate at a given point is proportional to the increment of ionization per increment of chamber volume at chamber depths greater than the range of secondary electrons originating from the electrode. The fundamentals for evaluating the extrapolation curves are presented as well as a detailed description of the present set-up of the P.T.B. large-volume extrapolation chamber (G.R.O.V.E.X.). Comparisons between the G.R.O.V.E.X. and other primary standards for air-kerma and reference air-kerma rate are presented. (authors)

2008-01-01

34

Quality assurance of air kerma strength for Ir-192 high dose rate source  

Energy Technology Data Exchange (ETDEWEB)

AAPM TG43 report has recommended to measure air kerma strength with the strength of source. Main purpose of this study is to verify the accuracy of air kerma strength provided by manufacturer. Materials for this study were MAX-4001 Electrometer, HDR 1000 Plus of the corporation of standard imaging, and 6 french bronchial Applicator with 1000 mm. We measured ionization current in 10-90 mm range from the bottom of the central axis of chamber. The reference point of calibration displayed by the maximum ionization current in the ionization current curve was measured, and air kerma strength was computed from the maximum ionization current. We acquired 50 mm distance to correspond with the maximum ionization current in the ionization current curve. Its distance has perfectly fitted to the source reference point of calibration certificate of UW-ADCL. Air kerma strength computed value has measured about 0.5% more than calibration value provided by manufacturer. Air kerma strength of calibration certificate provided by manufacturer has acquired reliable results. This study shows that considering the move error of dwell position of source and the dead space length in well-type chamber is a good way to get an accurate result.

Kim, Jong Eon [Inje University, Kimhae (Korea, Republic of); Yoon, Chun Sil [Gyeongsang National University, Ginju (Korea, Republic of); Kim, Sung Hyun [Chonnam National University, Gwangju (Korea, Republic of)

2007-06-15

35

Attenuation effects on the kerma rates in air after cesium depositions on grasslands  

International Nuclear Information System (INIS)

[en] Since the reactor accident of Chernobyl, cesium depth profiles and nuclide-specific kerma rates in air have been determined for various grassland sites in south Bavaria and in Ukraine. The sites are described by soil characteristics, annual precipitation, distance from release point, mode of deposition, and activity per unit area. The effects of surface roughness and migration of cesium into the soil on the kerma rate in air over grasslands was determined by two methods. The kerma rates in air obtained by the evaluations of in situ gamma-ray spectrometry results and of measured activity distributions in the soil showed only negligible differences for the observation period of 6 years after deposition. for the sites in Ukraine the kerma rate in air per activity per unit area was found to be systematically 40% higher than in Bavaria. The results from Bavaria on the attenuation of the kerma rate and a data set, including experiences from the weapons test fallout, are analytically approximated as a function of time up to 25 years after deposition. (orig.)

1994-01-01

36

Air kerma and absorbed dose on the torso of a patient during a mammography study  

International Nuclear Information System (INIS)

Two dosimetric magnitudes, due to the dispersed radiation, have been determined during a mammography study. The magnitudes that were determined are the kerma at the entrance of the torso and the absorbed dose by the torso. This determination was made in a paraffin phantom and with thermoluminescent dosemeters. One of the important parameters in the radiological protection of a patient to which is practiced a mammography is the value of the media glandular dose. However, during the taking of the X-ray a radiation portion that impacts on the mammary gland it is dispersed toward the patient's torso. In this work thermoluminescent dosemeters of ZrO2 has been used to determine the kerma at the entrance of the torso like the absorbed dose. The dosemeters was placed on the surface of the torso phantom while to the mamma phantom was made the mammography. As mamma phantom was used glucose serum to 5%. Of the obtained results we find that 3% of the air kerma at the entrance of the mamma it corresponds at the air kerma that receives the torso and 3.2% of the media glandular dose it is the absorbed dose of the same one. Another important result is the percentage value of the air kerma on the entrance of the thyroid area during a mammography, due to the dispersed radiation, it is 4% of the kerma at the entrance of the mamma. The air kerma at the entrance of the thyroid is of 0.41 ±0.07 mGy, 10% of this value corresponds to the absorbed dose by the thyroid. Therefore, it is observed that the media glandular dose and the air kerma at the entrance of the mamma they influence on the dispersed radiation toward the torso. Also, the superior part of the torso has less attenuation capacity to the dispersed radiation that those located in the inferior part. Therefore, the thyroid receives the major quantity of air kerma at the entrance. (Author)

2009-01-01

37

Air kerma rate estimation by means of in-situ gamma spectrometry: A Bayesian approach  

International Nuclear Information System (INIS)

Full text: Bayesian inference is used to determine the Air Kerma Rate based on a set of in situ environmental gamma spectra measurements performed with a NaI(Tl) scintillation detector. A natural advantage of such approach is the possibility to quantify uncertainty not only in the Air Kerma Rate estimation but also for the gamma spectra which is unfolded within the procedure. The measurements were performed using a 3'' x 3'' NaI(Tl) scintillation detector. The response matrices of such detection system were calculated using a Monte Carlo code. For the calculations of the spectra as well as the Air Kerma Rate the WinBugs program was used. WinBugs is a dedicated software for Bayesian inference using Monte Carlo Markov chain methods (MCMC). The results of such calculations are shown and compared with other non-Bayesian approachs such as the Scofield-Gold iterative method and the Maximum Entropy Method

2008-01-01

38

Assessment of the linear reference air kerma rate of 192Ir wires  

International Nuclear Information System (INIS)

[en] In this study, a procedure to test the linear reference air kerma rate of 192Ir wires using a well-type chamber is described. The method is based on a special lead insert with a 1 cm acrylic aperture that provides a differential response of the well chamber. The wire is considered divided into 1 cm parts. Using an external positioning system it is possible to place every part of the wire at the aperture position in the lead insert allowing measurement of each 1 cm making up the length of the wire. By means of a set of equations that take into account the contribution of all parts of the wire, in all possible positions, the relative linear reference air kerma rate is obtained. The estimated uncertainties of this procedure are about 2 to 3%. So, a well chamber and the specific inserts allow the measurements of total and linear reference air kerma rate for 192Ir wires. (author)

2001-01-01

39

Characteristic analysis for dose area product meter and conversion to air kerma  

International Nuclear Information System (INIS)

[en] Among the basic characteristics of the dose area product meter, the following were examined: effect of the heel effect which derives from hardening, atmospheric correction coefficient, response of measuring plane of the DAP meter, target focus angle of an x-ray tube assembly of quality of radiation by the area dosimeter mounting, and conversion from the value of the area dosage of air kerma. In terms of tube voltage, the IEC standard is almost always observed, if the radiation field in the dosimeter's surface area is within 6 cm x 6 cm. Error was 17.6%, even if all factors were not considered, and even if the conversion to air kerma was possible. It was indicated that the conversion to air kerma in the patient was possible when the radiation field and measurement error in the dosimeter's surface were considered. (author)

2001-01-01

40

Second EUROMET comparison of air kerma rate and activity measurements of 192Ir brachytherapy wires  

International Nuclear Information System (INIS)

[en] At the occasion of the EUROMET Workshop on Ionising Radiation and Radioactivity at the NPL, it was decided to carry out a second intercomparison on air kerma rate (AKR) and activity measurements on 192Ir brachytherapy sources in the frame of EUROMET project no. 219. The intercomparison has shown that both air kerma rate measurements and activity measurements of 192Ir brachytherapy wires are not trivial. One of the drawbacks is the appreciable inhomogeneity of the wires. Disregarding some outliers, the spread of the AKR measurements was below 1.5%, while the variation in the activity measurements was very large, due to reasons which are not completely understood. (orig.)

1994-01-22

 
 
 
 
41

Air Kerma Rate estimation by means of in-situ gamma spectrometry: A Bayesian approach  

International Nuclear Information System (INIS)

Bayesian inference is used to determine the Air Kerma Rate based on in-situ gamma spectrum measurement performed with an NaI(Tl) scintillation detector. The procedure accounts for uncertainties in the measurement and in the mass energy transfer coefficients needed for the calculation. The WinBUGS program () was used. The results show that the relative uncertainties in the Air Kerma estimate are of about 1%, and that the choice of unfolding procedure may lead to an estimate systematic error of 3%.

2010-01-01

42

Calibration of Ionization Chambers for Measuring Air Kerma Integrated over Beam Area in Diagnostic Radiology  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The air kerma area product PKA is an important quantity used by hospital physicists in quality assurance and optimization processes in diagnostic radiology and is recommended by national authorities for setting of diagnostic reference levels. PKA can be measured using a transmission ionization chamb...

Larsson, Peter

43

Photon radiation and the air kerma rate constants of 152Eu and 154Eu radionuclides  

International Nuclear Information System (INIS)

[en] It is often required to estimate the kerma rate at a distance from the radionuclides sources emitted photon radiation such as, for instance, 152Eu and 154Eu which represents frequently used sources in many fields of science, technology and medicine. The factor relating activity and air kerma is the air kerma rate constant - ??. Analysis of accessible data on this quantity for mentioned radionuclides led us to the conclusion that discrepancies in reported calculated values exist because the radionuclides decay scheme and other nuclear spectroscopy data pertinent to these calculations were not well known. That is the reason we calculated these quantities on the basis of our methodology, nuclear spectroscopy data given by many authors and the latest data for the mass-energy transfer coefficients for air. In this way the air kerma rate constants are calculated to be 41,1 ± 0,6 aGy m2 s-1 Bq-1 for 152Eu and 44,1 ± 0,2 aGy m2 s-1 Bq-1 for 154Eu. Calculation was made for the unfiltered point source including emitted photon radiation with energies greater than 20 keV and yield per decay event higher than 0,05%. (author)

2000-01-01

44

Variation of the air kerma rate from natural radionuclides in the ground due to the change of source configurations  

International Nuclear Information System (INIS)

[en] It is well known that the source configuration is an essential factor to change the kerma rate in air from natural radionuclides in soil and artificial structures. For example, the kerma rate increases in tunnels or concrete buildings surrounded by source, while the kerma rate decreases on a water body like a river which does not contain radionuclides. However, the features of the change in kerma rate due to source configurations have not been thoroughly investigated. In this study, the kerma rates due to natural radionuclides were calculated using Monte Carlo simulation for different source configurations. The considered terrain was 1) spherical caves in the ground, 2) cylindrical tunnels in the ground, 3) slab-shaped hollows in the ground, 4) two pieces of semi-infinite plain ground which joints at divers angles, 5) rectangular cuts in the ground, and 6) parallel rivers. The natural radionuclides of the U-238 series, Th-232 series, and K-40 were assumed to distribute uniformly in the ground at some typical concentration ratios. The calculated kerma rates were normalized to the value for infinite plain ground geometry. The kerma rate changes according to the solid angle viewing the soil containing radionuclides. Generally, the kerma rate is proportional to the solid angle viewing the soil, but the normalized kerma rate never exceeds two even though the solid angle viewing source is 4p. One a river the kerma rate deceases as the position gets close to the middle, but the decreasing tendency is slower that the decrease of the solid angle viewing the source. Basically, the kerma rates at 1 m on the ground were calculated, but the tendency of change in kerma rate due to height was also discussed for some cases. (author)

2000-01-01

45

Variation of the air kerma rate from natural radionuclides in the ground due to the change of source configurations  

Energy Technology Data Exchange (ETDEWEB)

It is well known that the source configuration is an essential factor to change the kerma rate in air from natural radionuclides in soil and artificial structures. For example, the kerma rate increases in tunnels or concrete buildings surrounded by source, while the kerma rate decreases on a water body like a river which does not contain radionuclides. However, the features of the change in kerma rate due to source configurations have not been thoroughly investigated. In this study, the kerma rates due to natural radionuclides were calculated using Monte Carlo simulation for different source configurations. The considered terrain was 1) spherical caves in the ground, 2) cylindrical tunnels in the ground, 3) slab-shaped hollows in the ground, 4) two pieces of semi-infinite plain ground which joints at divers angles, 5) rectangular cuts in the ground, and 6) parallel rivers. The natural radionuclides of the U-238 series, Th-232 series, and K-40 were assumed to distribute uniformly in the ground at some typical concentration ratios. The calculated kerma rates were normalized to the value for infinite plain ground geometry. The kerma rate changes according to the solid angle viewing the soil containing radionuclides. Generally, the kerma rate is proportional to the solid angle viewing the soil, but the normalized kerma rate never exceeds two even though the solid angle viewing source is 4p. One a river the kerma rate deceases as the position gets close to the middle, but the decreasing tendency is slower that the decrease of the solid angle viewing the source. Basically, the kerma rates at 1 m on the ground were calculated, but the tendency of change in kerma rate due to height was also discussed for some cases. (author)

Saito, Kimiaki [Department of Heath Physics, Japan Atomic Energy Research Institute, Tokai, Ibaraki (Japan)

2000-05-01

46

A secondary air kerma strength standard for Yb-169 interstitial brachytherapy sources  

International Nuclear Information System (INIS)

[en] Ytterbium-169 (169Yb) is a promising new intermediate low-energy isotope for interstitial implantation. To date, no air kerma strength (SK) standard for this source exists that can serve as a sound foundation for comparing various dose measurements and theoretical calculations. We have solved this problem by adapting the free air measurement technique of Goetsch et al, originally developed for 192Ir. Using a 100 cm3 spherical ion chamber with NIST traceable external beam calibrations in a free air geometry, we have measured the air kerma strength of six different source batches (two type 6 batches, three type 8 batches, and one experimental high-intensity source). Room scatter corrections, derived from an empirical fit to the data (following Goetsch et al) and/or directly by Monte Carlo simulation, yielded identical results with a reproducibility of 1%. (author)

1995-01-01

47

Correction for departure from constant room scatter in the air-kerma strength standardization of a 137Cs brachytherapy source  

International Nuclear Information System (INIS)

[en] Air-kerma strength, Sk is the key quantity in the dosimetry protocol recommended for photon emitting brachytherapy sources. In the present study, values of air kerma rate per source content activity of 1 Bq were calculated at various source-to-detector distances (d = 10 to 100 cm), when the investigated source was assumed to be suspended in free space, dry air and room of various sizes

2002-01-01

48

? GONIO: an orientation detector and environmental ? air kerma ratemeter  

International Nuclear Information System (INIS)

The aim of the ?-gonio is to guide a vehicle in order to find out a lost gamma source or to determine a remote area contaminated by ?-emitting pieces following a nuclear accident. It is essentially made of an aluminium sphere (diameter: 10 cm) with 6 detectors located inside, 1 cm deep from the sphere surface. The detectors are placed on 3 orthogonal diameters. The detector counting rates are processed by a software set on a microprocessor giving by cycles the orientation of the ?-source in terms of azimuth and elevation angles, the kerma rate at the sphere centre and the effective energy of the ?-beam incident on the sphere. The physical and mathematical concepts used to develop the instrument are described.

1992-01-01

49

Standards of air kerma at the BEV for 137Cs ? rays  

International Nuclear Information System (INIS)

[en] At the BEV two cylindrical cavity ionisation chambers have been established as primary standards to measure air kerma for 137Cs ? rays. The design of both chambers is the same, the chambers only differ by the specifications of the graphite they are made from. The main volume of the cavity was determined by two independent methods, i.e. length measurement of the diameter and of the depth of the cavity and also by filling the cavity with water. The applied correction factors for air density, recombination losses, humidity, stem scattering, wall attenuation, wall scattering, mean origin of electrons, axial non-uniformity and radial non-uniformity are described. The air kerma rates measured by the two standards agree within 0.33%. (Author)

1996-01-01

50

Comparison of the standards of air kerma of the NCM Bulgaria and the BIPM for {sup 60}Co {gamma} rays  

Energy Technology Data Exchange (ETDEWEB)

A comparison of the standards of air kerma of the National Center of Metrology (NCM) and of the Bureau International des Poids et Mesures (BIPM) has been carried out in {sup 60}Co radiation. It shows that the ratio of the NCM and BIPM standards is 1.0117 with a relative standard uncertainty of 1.9 x 10{sup -3}. This is the first comparison of air kerma standards of the NCM with the BIPM. (authors)

Allisy-Roberts, P.J.; Burns, D.T. [Bureau International des Poids et Mesures (BIPM), 92 - Sevres (France); Kessler, C. [Centro Regional de Referencia para Dosimetria, Buenos Aries (Argentina); Ivanov, R.N. [National Center of Metrology, Sofia (Bulgaria)

2002-03-15

51

Determination of calibration factors in terms of air kerma and absorbed dose to water in the 60Co ? rays  

International Nuclear Information System (INIS)

The method of calibration of an instrument, as performed at the BIPM in the 60Co field in terms of air kerma or absorbed dose to water, is described in detail. The influence of various parameters which can affect the calibration factor is analyzed. The uncertainty is of order 0.3% and 0.5% for calibration factors in terms of air kerma and of absorbed dose to water, respectively. (author). 14 refs, 10 figs, 3 tabs

1993-01-01

52

Comparison of the standards for air kerma of the KRISS and the BIPM for 137Cs gamma radiation  

International Nuclear Information System (INIS)

A direct comparison of the standards for air kerma of the Korea Research Institute of Standards and Science (KRISS), Korea, and of the Bureau International des Poids et Mesures (BIPM) was carried out in the 137Cs radiation beam of the BIPM in August 2010. The result, expressed as a ratio of the KRISS and the BIPM standards for air kerma, is 0.9986 with a combined standard uncertainty of 2.2 * 10-3. (authors)

2010-01-01

53

Calculation of air kerma to average glandular tissue dose conversion factors for mammography  

International Nuclear Information System (INIS)

[en] Among the quantities used for dose specification in mammography the average absorbed dose in glandular tissue is most appropriate for risk assessments. Generally, average absorbed dose in glandular tissue is derived from measurement of air kerma free-in-air combined with conversion factors obtained from radiation transport calculations in mathematical breast models. Air kerma to glandular tissue dose conversion factors are published by various authors as a function of half-value layer (HVL) for simple breast phantoms. Calculations by different authors differ in radiation transport codes, photon interaction data, photon spectra, composition and thickness of superficial layer (representing skin and subcutaneous adipose tissue), presence of compression plate, and are not performed with the tissue compositions recommended by the ICRU. Protocols for dosimetry in mammography in different European countries (UK, Netherlands, Sweden) use results from different authors. To study the influence of the parameters indicated, air kerma to glandular tissue dose conversion factors, g, are calculated using the MCNP radiation transport code. Use of different spectra can cause differences in g values up to about 7%. The use of a compression plate results in a 4.5 ± 1.5% smaller g value for the same HVL. The use of MCPLIB cross sections results in 10% higher g values compared to the use of XCOM data. The influence of the backscatter material (composition and thickness) on the g value is marginal (

1993-10-01

54

Selection of an appropriate air kerma rate constant for 75Se sources.  

UK PubMed Central (United Kingdom)

Monte Carlo simulation techniques using a Monte Carlo N-Particle code (MCNP5) analyzed six Source Production & Equipment Co., Inc., Se industrial radiography sources to determine an appropriate air kerma rate constant for Se, factoring in source encapsulation and compared to a theoretical approximation. Based on this study, an air kerma rate constant was calculated to be 17.7 Gy cm h Ci (0.203 R m h Ci), which was found to be five times lower than values published in the 1992 Edition of the Radiological Health Handbook and Oak Ridge National Laboratory RISC-45. Simulations were also employed to determine the effects of self-attenuation with the SPEC sources, the relationship between photon transmission values, and the thickness of various shielding materials in reducing exposure rates from a (75)Se source.

H Currier B; Munro JJ 3rd; Medich DC

2013-05-01

55

Implications of new correction factors on primary air kerma standards in 60Co-beams  

International Nuclear Information System (INIS)

[en] Comparisons of primary standards for air kerma in 60Co-beams are re-analysed taking into account the recently developed formalism that defines uniquely the various correction factors and the development of analytic and Monte Carlo methods to quantify these corrections. After a brief historical review of air kerma comparisons and ion chamber calculations, the new corrections are applied in a re-analysis of previously published comparison data. An independent Monte Carlo verification of the analytic point-source non-uniformity correction factor is presented. The combination of new proposed correction factors imply that some national standards should increase by as much as 1% and that the global increase is of the order of 0.6%. (author)

1992-06-01

56

Selection of an appropriate air kerma rate constant for 75Se sources.  

Science.gov (United States)

Monte Carlo simulation techniques using a Monte Carlo N-Particle code (MCNP5) analyzed six Source Production & Equipment Co., Inc., Se industrial radiography sources to determine an appropriate air kerma rate constant for Se, factoring in source encapsulation and compared to a theoretical approximation. Based on this study, an air kerma rate constant was calculated to be 17.7 Gy cm h Ci (0.203 R m h Ci), which was found to be five times lower than values published in the 1992 Edition of the Radiological Health Handbook and Oak Ridge National Laboratory RISC-45. Simulations were also employed to determine the effects of self-attenuation with the SPEC sources, the relationship between photon transmission values, and the thickness of various shielding materials in reducing exposure rates from a (75)Se source. PMID:23532080

H Currier, Blake; Munro, John J; Medich, David C

2013-05-01

57

Experimental verification of the air kerma to absorbed dose conversion factor Cw,u  

International Nuclear Information System (INIS)

In a recently published code of practice for the dosimetry of high-energy photon beams, the absorbed dose to water is determined using an ionization chamber having an air kerma calibration factor and applying the air kerma to absorbed dose conversion factor Cw,u. The consistency of these Cw,u values has been determined for four commonly employed types of ionization chambers in photon beams with quality varying between 60Co gamma-rays and 25 MV X-rays. Using a graphite calorimeter, Cw,u has been determined for a graphite-walled ionization chamber (NE 2561) for the same qualities. The values of Cw,u determined with the calorimeter are within the experimental uncertainty equal to Cw,u values determined according to any of the recent dosimetry protocols. (Auth.).

1987-01-01

58

Kerma-in air measurement and conversion coefficients to dose due to the environmental gamma radiation; Medida de Kerma no ar e determinacao de coeficientes de conversao para dose devido a radiacao gama ambiental  

Energy Technology Data Exchange (ETDEWEB)

This work aims to establish a calibration methodology for HPGe detectors calibration methodology, for in situ gamma measurements for air kerma due to environmental radiation exposure and to establish a procedure for the determination of dose applied to environmental gamma exposure based on the air kerma energy distribution and conversion coefficients from kerma to age-dependent dose. It was developed a methodology for characterization of HPGe detector by Monte Carlo calculation based on the EGS4 computer code. The calibration parameters were determined for detectors to be used in in situ gamma spectrometry to determine the air kerma. It has been calculated, also by Monte Carlo calculation, conversion coefficients from air kerma to effective dose and dose in organs and tissues to an exposure from a infinite plane source for several age groups. The ADAM code, developed for the simulation of an adult, was modified in order to accommodate the several anthropomorphic mathematical models with varying age and both sex. (author)

Conti, Claudio de Carvalho

1999-07-01

59

Determination of the reference air kerma rate for 192Ir brachytherapy sources and the related uncertainty  

International Nuclear Information System (INIS)

Different methods exist to determine the air kerma calibration factor of an ionization chamber for the spectrum of a 192Ir high-dose-rate (HDR) or pulsed-dose-rate (PDR) source. An analysis of two methods to obtain such a calibration factor was performed: (i) the method recommended by [Goetsch et al., Med. Phys. 18, 462-467 (1991)] and (ii) the method employed by the Dutch national standards institute NMi [Petersen et al., Report S-EI-94.01 (NMi, Delft, The Netherlands, 1994)]. This analysis showed a systematic difference on the order of 1% in the determination of the strength of 192Ir HDR and PDR sources depending on the method used for determining the air kerma calibration factor. The definitive significance of the difference between these methods can only be addressed after performing an accurate analysis of the associated uncertainties. For an NE 2561 (or equivalent) ionization chamber and an in-air jig, a typical uncertainty budget of 0.94% was found with the NMi method. The largest contribution in the type-B uncertainty is the uncertainty in the air kerma calibration factor for isotope i, Nki, as determined by the primary or secondary standards laboratories. This uncertainty is dominated by the uncertainties in the physical constants for the average mass-energy absorption coefficient ratio and the stopping power ratios. This means that it is not foreseeable that the standards laboratories can decrease the uncertainty in the air kerma calibration factors for ionization chambers in the short term. When the results of the determination of the 192Ir reference air kerma rates in, e.g., different institutes are compared, the uncertainties in the physical constants are the same. To compare the applied techniques, the ratio of the results can be judged by leaving out the uncertainties due to these physical constants. In that case an uncertainty budget of 0.40% (coverage factor=2) should be taken into account. Due to the differences in approach between the method used by NMi and the method recommended by Goetsch et al., an extra type-B uncertainty of 0.9% (k=1) has to be taken into account when the method of Goetsch et al. is applied. Compared to the uncertainty of 1% (k=2) found for the air calibration of 192Ir, the difference of 0.9% found is significant.

2004-01-01

60

Air-over-ground calculations of the neutron, prompt, and secondary-gamma free-in-air tissue kerma from the Hiroshima and Nagasaki devices  

Energy Technology Data Exchange (ETDEWEB)

This paper reports preliminary results of the two-dimensional discrete-ordinate, calculations for the air-over-ground transport of radiation from the Hiroshima and Nagasaki weapon devices. It was found that the gamma-ray kerma dominated the total kerma for both environments.

Pace, J.V. III; Knight, J.R.; Bartine, D.E.

1982-01-01

 
 
 
 
61

New approach for establishing a primary standard of air kerma in a 60Co ? ray beam  

International Nuclear Information System (INIS)

[en] The determination of a primary standard of kerma in air is generally based on the use of an absolute cavity ionization chamber with graphite walls and filled with air. For laboratories in possession of primary standard graphite calorimeters, it appears possible to derive air kerma from absorbed dose in graphite by a transfer method. This derivation can be achieved using a transfer instrument, e.g. a small air filled cavity chamber, successively irradiated in the graphite phantom at the reference depth and in free air. The advantages of this method are the replacement of an absolute current measurement by a relative one, the replacement of the graphite to air stopping power ratio by the quotient of the stopping power ratio in free air by that in graphite, and the elimination of the effective volume of the chamber and of W, the mean energy expended per ion pair formed in air. In return, a correction factor for the perturbation of the particle fluence, due to the air cavity irradiated in the graphite phantom, must be applied. A critical analysis of the accuracies of both methods is made, the expected gains in metrological safety with the new method are pointed out and preliminary results are presented. (author). 11 refs, 1 tab

1994-01-01

62

Effect of pressure, temperature and humidity in air on photon fluence and air kerma values at low photon energies  

International Nuclear Information System (INIS)

An investigation into the effect of pressure, temperature and humidity in air on photon fluence at a typical mammography, low bremsstrahlung energy (25 kVp), has been carried out. Pressure values corrected for humidity at varying temperatures were employed to determine the density of moist air. Using the corrected moist air densities, the X-ray photon fluence remaining after air attenuation has been computed assuming an X-ray focal spot-detector distance of 65 cm. Bremsstrahlung spectral distributions and the effects of pressure, temperature and humidity on the photon fluence from molybdenum and tungsten targets are illustrated. Comparative results suggest that such effects could be significant and need to be considered when calculating exposure levels from low-energy photons. The investigation showed that air kerma values from an X-ray spectrum that has significant lower-energy components is likely to be more sensitive to changes in pressure, temperature and humidity than the air kerma from an X-ray spectrum with lower-energy components less pronounced. Non-negligible air kerma values are involved.

2003-01-01

63

Calculated neutron air kerma strength conversion factors for a generically encapsulated Cf-252 brachytherapy source  

International Nuclear Information System (INIS)

[en] The 252Cf neutron air kerma strength conversion factor (SKN/mCf) is a parameter needed to convert the radionuclide mass (?g) provided by Oak Ridge National Laboratory into neutron air kerma strength required by modern clinical brachytherapy dosimetry formalisms indicated by Task Group No. 43 of the American Association of Physicists in Medicine (AAPM). The impact of currently used or proposed encapsulating materials for 252Cf brachytherapy sources (Pt/Ir-10%, 316L stainless steel, nitinol, and Zircaloy-2) on SKN/mCf was calculated and results were fit to linear equations. Only for substantial encapsulation thicknesses, did SKN/mCf decrease, while the impact of source encapsulation composition is increasingly negligible as Z increases. These findings are explained on the basis of the non-relativistic kinematics governing the majority of 252Cf neutron interactions. Neutron kerma and energy spectra results calculated herein using MCNP were compared with results of Colvett et al. and Rivard et al

2002-01-01

64

Calculated neutron air kerma strength conversion factors for a generically encapsulated Cf-252 brachytherapy source  

CERN Multimedia

The sup 2 sup 5 sup 2 Cf neutron air kerma strength conversion factor (S sub K sub N /m sub C sub f) is a parameter needed to convert the radionuclide mass (mu g) provided by Oak Ridge National Laboratory into neutron air kerma strength required by modern clinical brachytherapy dosimetry formalisms indicated by Task Group No. 43 of the American Association of Physicists in Medicine (AAPM). The impact of currently used or proposed encapsulating materials for sup 2 sup 5 sup 2 Cf brachytherapy sources (Pt/Ir-10%, 316L stainless steel, nitinol, and Zircaloy-2) on S sub K sub N /m sub C sub f was calculated and results were fit to linear equations. Only for substantial encapsulation thicknesses, did S sub K sub N /m sub C sub f decrease, while the impact of source encapsulation composition is increasingly negligible as Z increases. These findings are explained on the basis of the non-relativistic kinematics governing the majority of sup 2 sup 5 sup 2 Cf neutron interactions. Neutron kerma and energy spectra resul...

Rivard, M J; D'Errico, F; Tsai, J S; Ulin, K; Engler, M J

2002-01-01

65

Effects of aluminum-copper alloy filtration on photon spectra, air kerma rate and image contrast  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese Este estudo avaliou a redução da taxa de kerma no ar, o espectro de energia dos raios X e alterações na qualidade da imagem radiográfica. Comparações com várias espessuras do filtro de liga de alumínio-cobre em três diferentes porcentagens foram feitas com o filtro de alumínio. Os experimentos foram feitos utilizando-se um aparelho de raios X odontológico convencional, obtendo radiografias com auxílio de um fantoma de segmento de mandíbula e de uma escala de (more) densidade confeccionada com alumínio laminado. Dependendo da espessura da filtração da liga de alumínio-cobre, o feixe de raios X pôde ser endurecido em relação ao filtro de alumínio. O uso do filtro de liga de alumínio-cobre resultou em 8,40% a 47,33% de redução da taxa média de kerma no ar e indicou contraste da imagem radiográfica sem alteração, quando comparado com a filtração de alumínio, mostrando que os filtros de liga de alumínio-cobre tornam-se alternativas aceitáveis em relação aos filtros de alumínio. Abstract in english This study evaluated the performance of aluminum-copper alloy filtration, without the original aluminum filter, for dental radiography in terms of x-ray energy spectrum, air kerma rate and image quality. Comparisons of various thicknesses of aluminum-copper alloy in three different percentages were made with aluminum filtration. Tests were conducted on an intra-oral dental x-ray machine and were made on mandible phantom and on step-wedge. Depending on the thickness of alu (more) minum-copper alloy filtration, the beam could be hardened and filtrated. The use of the aluminum-copper alloy filter resulted in reductions in air kerma rate from 8.40% to 47.33%, and indicated the same image contrast when compared to aluminum filtration. Aluminum-copper alloy filtration may be considered a good alternative to aluminum filtration.

Gonçalves, Andréa; Rollo, João Manuel Domingos de Almeida; Gonçalves, Marcelo; Haiter Neto, Francisco; Bóscolo, Frab Norberto

2004-12-01

66

In situ gamma-ray spectrometry in forests: determination of kerma rate in air from 137Cs  

International Nuclear Information System (INIS)

A method is presented to determine the kerma rate in air from 137Cs due to Chernobyl fallout in forests. In situ gamma-ray spectra from several forest sites in Russia, in the Ukraine and in Southern Germany are evaluated with the aim of deducing the ratio of primary and forward scattered photons for 137Cs. With this ratio and the results of Monte-Carlo simulations of photon transport the contribution of scattered photons to the total kerma is assessed successfully. Scattered photons contribute between 42% and 50% to the total kerma rate from radiocesium, which is less than according values for grassland areas. The contribution of radiocesium to the total kerma rate varies between 40% and 90%, whereas radiocesium stored in the forest biomass contributes only a few percent. The mean mass depth of radiocesium ranges from 2.6 to 6.4 g cm-2 in the forest soils.

2002-01-01

67

Air-kerma strength determination of a miniature x-ray source for brachytherapy applications  

Science.gov (United States)

A miniature x-ray source has been developed by Xoft Inc. for high dose-rate brachytherapy treatments. The source is contained in a 5.4 mm diameter water-cooling catheter. The source voltage can be adjusted from 40 kV to 50 kV and the beam current is adjustable up to 300 muA. Electrons are accelerated toward a tungsten-coated anode to produce a lightly-filtered bremsstrahlung photon spectrum. The sources were initially used for early-stage breast cancer treatment using a balloon applicator. More recently, Xoft Inc. has developed vaginal and surface applicators. The miniature x-ray sources have been characterized using a modification of the American Association of Physicists in Medicine Task Group No. 43 formalism normally used for radioactive brachytherapy sources. Primary measurements of air kerma were performed using free-air ionization chambers at the University of Wisconsin (UW) and the National Institute of Standards and Technology (NIST). The measurements at UW were used to calibrate a well-type ionization chamber for clinical verification of source strength. Accurate knowledge of the emitted photon spectrum was necessary to calculate the corrections required to determine air-kerma strength, defined in vacuo. Theoretical predictions of the photon spectrum were calculated using three separate Monte Carlo codes: MCNP5, EGSnrc, and PENELOPE. Each code used different implementations of the underlying radiological physics. Benchmark studies were performed to investigate these differences in detail. The most important variation among the codes was found to be the calculation of fluorescence photon production following electron-induced vacancies in the L shell of tungsten atoms. The low-energy tungsten L-shell fluorescence photons have little clinical significance at the treatment distance, but could have a large impact on air-kerma measurements. Calculated photon spectra were compared to spectra measured with high-purity germanium spectroscopy systems at both UW and NIST. The effects of escaped germanium fluorescence photons and Compton-scattered photons were taken into account for the UW measurements. The photon spectrum calculated using the PENELOPE Monte Carlo code had the best agreement with the spectrum measured at NIST. Corrections were applied to the free-air chamber measurements to arrive at an air-kerma strength determination for the miniature x-ray sources.

Davis, Stephen D.

68

Sensitivity/uncertainty analysis for free-in-air tissue kerma due to initial radiation at Hiroshima and Nagasaki  

International Nuclear Information System (INIS)

[en] Uncertainty estimates and cross correlations by range/survivor have been calculated for the Hiroshima and Nagasaki free-in-air (FIA) tissue kerma obtained from two-dimensional air/ground transport calculations. The uncertainties due to modeling parameter and basic nuclear transport data uncertainties were calculated for 700-, 1000-, and 1500-m ground ranges. Only the FIA tissue kerma due to initial radiation was treated in the analysis; the uncertainties associated with terrain and building shielding and phantom attenuation were not considered in this study. Uncertainties of --20% were obtained for the prompt neutron and secondary gamma kerma and 30% for the prompt gamma kerma at both cities. The uncertainties on the total prompt kerma at Hiroshima and Nagasaki are --18 and 15%, respectively. The estimated uncertainties vary only slightly by ground range and are fairly highly correlated. The total prompt kerma uncertainties are dominated by the secondary gamma uncertainties, which in turn are dominated by the modeling parameter uncertainties, particularly those associated with the weapon yield and radiation sources

1988-01-01

69

Proposed specification for a primary standard of air kerma for 60Co, 137Cs and 192Ir ?-ray sources  

International Nuclear Information System (INIS)

[en] The three cavity chambers, the mean response of which constitutes the primary standard of air kerma for 60Co and 137Cs ?-rays in the United Kingdom, have been in continuous, almost daily, use at the National Physical Laboratory (NPL) since 1956. These chambers were initially designed for use with 2 MV X-rays at therapy level air kerma rates. However since 1978 they have also been used for protection level air kerma rates, initially, with X-rays generated at 1 MV and 2 MV and more recently with 60Co and 137Cs ?-rays. They have been used for therapy level air kerma calibrations with 60Co ?-rays since 1997 following the demise of the NPL 2 MV Van de Graaff generator. This report describes the proposals for a new primary standard and the methods that will be used to give a better performance than the present standard when used with air kerma rates from as high as 1 Gy min-1 down to 10 mGy hr-1. The design will also seek to ensure that the standard will be capable of providing traceable calibration for 192Ir high dose rate brachytherapy sources. (author)

70

New approach for establishing a primary standard of Kerma in air, in a (sup 60)Co gamma ray beam.  

Science.gov (United States)

The determination of a primary standard of kerma in air is generally based on the use of an absolute cavity ionization chamber, with graphite wall and filled with air. For laboratories in possession of primary standard graphite calorimeters, it appears po...

B. Chauvenet F. Delaunay J. P. Simoen

1993-01-01

71

Avaliação do kerma no ar na superfície de entrada e da qualidade da imagem em radiografias de tórax Evaluation of entrance surface air kerma rate and clinical images quality in chest radiography  

Directory of Open Access Journals (Sweden)

Full Text Available OBJETIVO: Avaliar os fatores de técnica utilizados durante exames de tórax póstero-anterior em pacientes-padrão e correlacioná-los aos valores de kerma no ar na superfície de entrada e à qualidade das imagens clínicas. MATERIAIS E MÉTODOS: O estudo foi realizado em três hospitais do Rio de Janeiro, num total de cinco salas de raios X, com dez pacientes por sala. As imagens foram avaliadas pelos radiologistas dos serviços segundo o protocolo europeu. O kerma no ar na superfície de entrada foi estimado a partir da curva de rendimento do equipamento de raios X, que foi obtida utilizando câmara de ionização acoplada a um eletrômetro. Análise de variância foi realizada para verificar se a diferença entre os valores de kerma no ar na superfície de entrada é significativa. RESULTADOS: Os valores de kerma no ar na superfície de entrada variaram entre 0,05 e 0,26 mGy, com média 60% inferior ao nível de referência publicado na Portaria 453. Das imagens avaliadas, 98% atenderam acima de 65% dos critérios de qualidade. CONCLUSÃO: Para um padrão de qualidade da imagem, aceitável para o diagnóstico, verificou-se ampla variação do kerma no ar na superfície de entrada para pacientes-padrão. Isto demonstra a falta de padronização dos fatores de técnica e a existência de um potencial de redução do valor do kerma no ar na superfície de entrada.OBJECTIVE: To evaluate technical factors involved in posteroanterior chest radiography in standard patients, and correlating them with entrance surface air kerma rate and with the clinical images quality. MATERIALS AND METHODS: The present study was developed at three hospitals in Rio de Janeiro, Brazil, involving a total of five x-ray rooms, with ten patients per room. The images were evaluated by the radiologists of the institutions, in accordance with the European protocol. The estimation of surface entrance air kerma rate was based on the x-ray equipment output curve obtained with an ionization chamber coupled with an electrometer. Variance analysis was performed to evaluate the significance of the difference between entrance surface air kerma rates. RESULTS: Entrance surface air kerma rates ranged between 0.05 and 0.26 mGy, with a mean value 60% lower than the reference level established by the Order (Portaria) 453. Among the images evaluated, 98% fulfilled > 65% of the images quality criteria. CONCLUSION: For a standard image quality that is acceptable for diagnosis purposes, a significant variation was observed in the entrance surface air kerma rate for standard patients, demonstrating the lack of technical factors standardization and a potential for decreasing the entrance surface air kerma rate.

Angelo Bernardo Brasil de Souza; Simone Kodlulovich Dias; Fernando Mecca Augusto; Winston Andrade Marques

2009-01-01

72

Comparison of the standards for air kerma of the NIM and the BIPM for 60Co gamma radiation  

International Nuclear Information System (INIS)

A comparison of the standards for air kerma of the National Institute of Metrology of China and of the Bureau International des Poids et Mesures was carried out in 60Co gamma radiation at the BIPM in December 2001. The ratio of the NIM and the BIPM standards for air kerma is 0.9992, with a combined standard uncertainty of 0.0018. The degrees of equivalence between the NIM and the other participants in the ongoing key comparison BIPM.RI(I)-K1 have been calculated and the results are presented in the form of a matrix. A graphical presentation is also given. (authors)

2009-01-01

73

Air kerma rate calibration of small sources of 60Co, 137Cs, 226Ra and 192Ir  

International Nuclear Information System (INIS)

[en] The results presented indicate a level of agreement between NPL and Amersham source output measurements which is within the NPL measurement uncertainties alone. The 3% discrepancy reported earlier was not reproduced in this work which may reflect an improved performance of the secondary standard ionization chamber in its present form. These results provide assurance on source air kerma rate figures provided by the manufacturer and which are based on a traceability route to standards of activity. Alternatively the results could be used as a basis to change the traceability route to air kerma standards. (author)

1991-01-01

74

Comparison of the standards for air kerma of the NPL and the BIPM for 60Co ? rays  

International Nuclear Information System (INIS)

An indirect comparison of the standards for air kerma of the National Physical Laboratory (NPL), United Kingdom and of the Bureau International des Poids et Mesures (BIPM) was made in 60Co gamma radiation in September 2007. The comparison result, based on the calibration coefficients for two transfer chambers and expressed as a ratio of the NPL and the BIPM standards for air kerma, is 1.0011 (0.0038). The degrees of equivalence between the NPL and the other participants in the key comparison have been calculated and the results are presented in the form of a matrix. A graphical presentation is also given. (authors)

2010-01-01

75

Air kerma strength calibration of 0.6 cc Farmer chamber for 192Ir HDR source  

International Nuclear Information System (INIS)

[en] One of the methods adopted by hospitals for the calibration of the HDR 192Ir source, in terms of Air Kerma Strength (AKS) is to use 0.6cc chamber at short source to chamber distances for measuring the air kerma rate at the chamber position and then compute the AKS using the appropriate correction factors. However, the 0.6 cc Farmer type chambers purchased by the users for the calibration of the HDR 192Ir source, are not generally provided with an HDR 192Ir calibration factor. With the result, many hospitals that have purchased the Farmer type chamber for the calibration of 192Ir HDR sources, use the 60Co calibration factor for this purpose. The use of 60Co calibration factor for the 192Ir HDR source would unnecessarily increase the uncertainty of the measured AKS. Again, because of the low chamber sensitivity, hospitals often use, source to chamber distances as small as a few cm for calibrating the 192Ir HDR source. In the absence of a rigid source-chamber positioning system, this can lead to several percent errors in AKS determination. Also, hospitals often don't take into account corrections for the room scatter or the fluence non-uniformity across the chamber, which further increase the uncertainty of the measured AKS

2001-01-01

76

Correlation of radioactivity measurements, air kerma rates and geological features of Sicily  

Energy Technology Data Exchange (ETDEWEB)

Sicily, the largest Mediterranean island (with an extension of about 25000km{sup 2}), exhibits a very wide variety of lithologies, ranging from sedimentary to metamorphic and volcanic rocks. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) have been applied to air kerma values measured by thermoluminescent dosimetry in several sites and to data of radionuclide concentrations, geochemical and mineralogical features of rocks and soils sampled in 29 sites of Sicily to point out similarities among different lithologies. The study was devoted to find multiple correlations and allow a better classification of Sicilian lithotypes. Samples of rocks and soils have been analyzed by X-ray fluorescence (XRF), X-ray diffractometry (XRD), and gamma-ray spectrometry. Major element concentrations, mineralogical data, along with specific activities of {sup 40}K, {sup 238}U, and {sup 232}Th natural radionuclides, have been determined in several samples. Geochemical, mineralogical and petrographic features are in good agreement with radiometric data. A survey was also performed to measure air kerma in outdoor environment using thermoluminescent dosimeters. The measured values were compared with the predicted levels computed from the radioisotope concentrations present in rock and soil samples. Moreover, collected data can be used to evaluate the health impact of the natural radioactivity on the population.

Brai, M. [Dipartimento di Fisica e Tecnologie Relative and Unita INFM, Universita di Palermo, Viale delle Scienze, Edificio 18, 90128 Palermo (Italy)]. E-mail: mbrai@unipa.it; Bellia, S. [Dipartimento di Chimica e Fisica della Terra ed Applicazioni alle Georisorse e ai Rischi Naturali, Universita di Palermo, Via Archirafi 36, 90123 Palermo (Italy); Hauser, S. [Dipartimento di Chimica e Fisica della Terra ed Applicazioni alle Georisorse e ai Rischi Naturali, Universita di Palermo, Via Archirafi 36, 90123 Palermo (Italy); Puccio, P. [Dipartimento di Ingegneria Nucleare, Universita di Palermo, Viale delle Scienze, Edificio 6, 90128 Palermo (Italy); Rizzo, S. [Dipartimento di Ingegneria Nucleare, Universita di Palermo, Viale delle Scienze, Edificio 6, 90128 Palermo (Italy); Basile, S. [Dipartimento di Fisica e Tecnologie Relative and Unita INFM, Universita di Palermo, Viale delle Scienze, Edificio 18, 90128 Palermo (Italy); Marrale, M. [Dipartimento di Fisica e Tecnologie Relative and Unita INFM, Universita di Palermo, Viale delle Scienze, Edificio 18, 90128 Palermo (Italy)

2006-04-15

77

Correlation of radioactivity measurements, air kerma rates and geological features of Sicily  

International Nuclear Information System (INIS)

[en] Sicily, the largest Mediterranean island (with an extension of about 25000km2), exhibits a very wide variety of lithologies, ranging from sedimentary to metamorphic and volcanic rocks. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) have been applied to air kerma values measured by thermoluminescent dosimetry in several sites and to data of radionuclide concentrations, geochemical and mineralogical features of rocks and soils sampled in 29 sites of Sicily to point out similarities among different lithologies. The study was devoted to find multiple correlations and allow a better classification of Sicilian lithotypes. Samples of rocks and soils have been analyzed by X-ray fluorescence (XRF), X-ray diffractometry (XRD), and gamma-ray spectrometry. Major element concentrations, mineralogical data, along with specific activities of 40K, 238U, and 232Th natural radionuclides, have been determined in several samples. Geochemical, mineralogical and petrographic features are in good agreement with radiometric data. A survey was also performed to measure air kerma in outdoor environment using thermoluminescent dosimeters. The measured values were compared with the predicted levels computed from the radioisotope concentrations present in rock and soil samples. Moreover, collected data can be used to evaluate the health impact of the natural radioactivity on the population

2006-01-01

78

Ozone - Current Air Quality Index  

Science.gov (United States)

... more announcements Air Quality Basics Air Quality Index | Ozone | Particle Pollution | UV | Smoke from fires | What You ... International Kids Movies NAQ Conferences NOAA Older Adults Ozone Particle Pollution (PM2.5, PM10) List of Partners ...

79

Comparison of air kerma standards of the BNM-LPRI and BIPM for the gamma photons of the cesium 137  

International Nuclear Information System (INIS)

A comparison between the air kerma standards for 137Cs photons of the Laboratoire Primaire des Rayonnements Ionisants (BNM-LPRI) and the Bureau International des Poids et Mesures (BIPM) has been carried out in the 137Cs beam of BIPM. The observed differences are of about 0;2 %. The results are in good agreement, within their uncertainties. (authors).

1997-01-01

80

Air kerma transmission factors of scattered X-rays in the maze of a linac room for lead shield  

International Nuclear Information System (INIS)

Spectra of scattered X-rays in the maze of a Linac (X-ray energies of 4, 6, and 10 MV) room were estimated by means of the Monte Carlo simulation, and air kerma transmission factors of the X-rays scattered through a lead shield were evaluated based on those spectra. Spectra of scattered X-rays showed a maximum in the energy area below 200 keV. The higher the accelerated electron energy, also, the smaller the scattering angle that tended to spread to the higher energy area of the distribution of spectra. The air kerma transmission factor of 120 deg scattered X-rays of 4 MV X-rays obtained in this study was larger than the transmission factors of 124 deg scattered photons of 60Co gamma rays through a lead shield given in ICRP. The air kerma transmission factors of 120 deg scattered X-rays of 6 MV X-rays were smaller than the transmission factors of 90 deg scattered photons of 60Co gamma rays. The air kerma transmission factors of 120 deg scattered X-rays of 10 MV X-rays was slightly larger than transmission factors of 90 deg scattered photons of 60Co gamma rays. Therefore, in the case of a 4 MV X-ray Linac room, the calculation method given in the ''Manual of Practical Shield Calculation of Radiation Facilities (2000)'' causes underestimation of leakage doses. (authors)

2005-01-01

 
 
 
 
81

Theoretical and experimental studies of the influence of air kerma rate on threshold contrast in diagnostic fluoroscopy systems  

Energy Technology Data Exchange (ETDEWEB)

Experimental measurements of threshold contrast (Csub(T)) as a function of air kerma rate at the input plane of the image intensifier have been made for several diagnostic fluoroscopy units in clinical use. Threshold contrasts are determined by viewing a test object containing holes of fixed diameter and various depths under defined irradiation conditions. Kerma rate variations are effected by introducing aluminum sheets into the x-ray beam at fixed values of tube potential and current. At low kerma rates where quantum noise dominates, low tube potentials (60 kVsub(p)) usually yield lower values of Csub(T) than do higher potentials (100 kVsub(p)). At higher kerma rates the opposite is often true. A simple theoretical model for noise propagation in fluoroscopic imaging systems using models of diagnostic x-ray spectra lends qualitative support to the experimental findings. The often-quoted suggested upper limit of 100 ..mu..R s/sup -1/ (0.87 ..mu..Gy s/sup -1/) at the input phosphor would seem to be justified under the test conditions since little improvement in Csub(T) is usually observed at higher kerma rates. However, application to clinical practice would ideally require the use of more realistic phantom studies.

Harrison, R.M.; Day, M.J. (Newcastle upon Tyne Univ. (UK). Newcastle General Hospital)

1983-11-01

82

A conversion method of air kerma from the primary, scatter, and leakage radiations to effective dose for calculating x-ray shielding barriers in mammography  

International Nuclear Information System (INIS)

In this study, a new approach has been introduced for derivation of the effective dose from air kerma to calculate shielding requirements in mammography facilities. This new approach has been used to compute the conversion coefficients relating air kerma to the effective dose for the mammography reference beam series of the Netherlands Metrology Institute Van Swinden Laboratorium, National Institute of Standards and Technology, and International Atomic Energy Agency laboratories. The results show that, in all cases, the effective dose in mammography energy range is less than 25% of the incident air kerma for the primary and the scatter radiations and does not exceed 75% for the leakage radiation.

2005-01-01

83

Study and determination of the national dosimetric standards in terms of air kerma for X-rays radiation fields of low and medium-energies  

International Nuclear Information System (INIS)

Progress in radiation protection and radiotherapy, and the increased needs in terms of accuracy lead national metrology institutes to improve the standard. For ionizing radiation, the standard is defined by an absolute instrument used for air kerma rate measurement. The aim of the thesis is to establish standards, in terms of air kerma for X-rays beams of low and medium-energies. This work enables to complement the standard beam range of the Laboratoire National Henri Becquerel (LNHB). Two free-air chambers have been developed, WK06 for medium-energy and WK07 for low-energy. The air-kerma rate is corrected by several correction factors. Some are determined experimentally; and the others by using Monte Carlo simulations. The uncertainty budget of the air-kerma rate at one standard deviation has been established. These dosimetric standards were compared with those of counterparts' laboratories and are consistent in terms of degree of equivalence. (author)

2008-01-01

84

The ratios of effective dose to entrance skin dose to the air kerma for some medical sources  

International Nuclear Information System (INIS)

Results are presented for the ratios of the effective dose to skin entrance dose and to air kerma for broad beams of radiation expected to be encountered by medical workers. These workers are monitored by the Personal Radiation Monitoring Service (PRMS) using thermoluminescent dosimeters worn at the front of the body to provide estimates of the entrance skin dose. Factors are given for converting estimates of entrance skin dose to effective dose as defined by the International Commission on Radiological Protection (ICRP 1991) for beams incident on the body by one of three modes-from the front of the subject, from the back of the subject or by rotation around the subject. Additional tables are also given to calculate effective dose for these beams from a measurement of air kerma free-in-air

1998-01-01

85

The ratios of effective dose to entrance skin dose to the air kerma for some medical sources  

Energy Technology Data Exchange (ETDEWEB)

Results are presented for the ratios of the effective dose to skin entrance dose and to air kerma for broad beams of radiation expected to be encountered by medical workers. These workers are monitored by the Personal Radiation Monitoring Service (PRMS) using thermoluminescent dosimeters worn at the front of the body to provide estimates of the entrance skin dose. Factors are given for converting estimates of entrance skin dose to effective dose as defined by the International Commission on Radiological Protection (ICRP 1991) for beams incident on the body by one of three modes-from the front of the subject, from the back of the subject or by rotation around the subject. Additional tables are also given to calculate effective dose for these beams from a measurement of air kerma free-in-air 4 figs., 9 tabs.

Wise, K.N. [Australian Radiation Laboratory, Yallambie, VIC (Australia)

1998-03-01

86

Kerma rates in air several years after a 137Cs deposition  

International Nuclear Information System (INIS)

[en] A method to derive the kerma rate in air due to 137Cs from in situ gamma-ray spectra recorded in populated areas is introduced. The method is also applicable several years after the deposition. It is based on the peak-to-valley method in combination with the assumption that the effective 137Cs distribution in the ground can be described by a Lorentz function. The three parameters of the Lorentz function are derived from the 662 keV peak count rate, the count rate in the region of 620 keV to 650 keV, and an assumed correlation between the depth and the width of the maximum of the distribution. The method is applied to 95 in situ gamma-ray spectra recorded at nine sites in the period June 1986 to September 1995. The results indicate that location factors continue to decrease three years after the deposition. (orig.)[de] In diesem Beitrag wird eine Methode vorgestellt, die Kerma-Rate in Luft durch 137Cs in bewohnten Gebieten mittels in situ Gammaspektrometrie zu bestimmen. Diese Methode ist insbesondere einige Jahre nach der Deposition anwendbar. Sie beruht auf der Peak-to-Valley Methode sowie der Annahme, dass die effektive Tiefenverteilung von 137Cs im Boden durch eine Lorentz-Funktion beschrieben werden kann. Die drei Parameter der Lorentz-Funktion lassen sich aus der Zaehlrate des 662 keV-Peaks, der Zaehlrate im Bereich von 620 keV bis 650 keV und einer angenommenen Korrelation zwischen der Tiefe und der Breite des Maximums der Verteilung bestimmen. Die Methode wird auf 95 in situ Gammaspektren angewendet, die im Zeitraum von Juni 1986 bis September 1995 an neuen Messorten aufgenommen wurden. Die Ergebnisse lassen erkennen, dass die Umgebungsfaktoren auch spaeter als drei Jahre nach der Deposition weiterhin abnehmen. (orig.)

1997-01-01

87

Corrections to air kerma and exposure measured with free air ionisation chambers for charge of photoelectrons, Compton electrons and auger electrons  

International Nuclear Information System (INIS)

The signal charge from a free air ionisation chamber for the measurement of air kerma and exposure consists of not only the charge of ion pairs produced by secondary electrons (i.e. photoelectrons, Compton electrons and Auger electrons), but also the charge of the secondary electrons and single and multiple charged ions formed by the release of the secondary electrons. In the present work, correction factors for air kerma and exposure for the charge of the secondary electrons and ions were calculated for photons with energies in the range from 1 to 400 keV. The effects of an increase in the W value of air for low-energy electrons were also taken into consideration. It was found that the correction factors for air kerma and exposure have a maximum value near a photon energy of 30 keV; in the lower energy region, the correction factor for exposure monotonically decreases with a decrease in photon energy except for a small dip due to K-edge absorption by argon atoms in air. The values of the correction factors were found to be 0.9951 and 0.9892, respectively, for a spectrum with a mean energy of 7.5 keV, the reference X-ray spectrum with the lowest mean energy in ISO 4037-1. The air kerma correction is smaller than that for exposure, because for air kerma the signal due to the charge of secondary electrons and ions is partly compensated by the decrease in the number of ion pairs produced by the secondary electrons due to the increase of the W value of air for lower energy electrons. (authors)

2008-01-01

88

Survivor dosimetry. Part B. DS02 free-in-air neutron and gamma tissue kerma relative to DS86  

International Nuclear Information System (INIS)

The major determinant of the radiation dose to a survivor at a given location with respect to the hypocenter of a bomb detonation is the radiation field in the open at that location. Therefore, a change in free-in-air (FIA) kerma at any given distance from the bomb has a proportional effect on the doses of all survivors at that distance, if the shielding is not changed. The fluence-to-kerma coefficients used in the DS02 studies are discussed in Chapter 12, Part A, where one can see that the differences between the newer DS02 and older DS86 kerma coefficients for soft tissues of the body are quite small at the neutron and gamma-ray energies that are most important in the radiation dosimetry for the survivors. Thus, the differences in DS02 and DS86 FIA tissue kermas from neutrons and photons are due essentially to differences in the DS02 and DS86 source term and transport calculations discussed in Chapters 2 and 3. (J.P.N.)

89

Comparison of the standards of air kerma and absorbed dose of the BNM-LPRI and BIPM for 60 Cobalt gamma photons  

International Nuclear Information System (INIS)

[en] Comparisons between the standards of air kerma, absorbed dose to graphite and absorbed dose to water of the Laboratoire primaire des rayonnements ionisants (BNM-LPRI) and the Bureau international des poids et mesures (BIPM) have been carried out in the 60Co beam of BIPM. The observed differences are of about 0.3% for air kerma and 0.1% for absorbed doses. The results are in good agreement, within their uncertainties. (authors). 10 tabs., 15 refs

1995-01-01

90

Revised correction factor for the UK national primary standard for air kerma for 137Cs and 60Co gamma-rays  

International Nuclear Information System (INIS)

From 1 May 2009 the United Kingdom National Physical Laboratory (NPL) has changed its air kerma standards for Cs-137 and Co-60 ?-rays. Adoption of the new correction factors results in an increase in the NPL air kerma standard by ? 1% for both Cs-137 and Co-60 ?-rays. All NPL secondary standard calibrations issued after 1 May 2009 contain the revised correction factor. (authors)

2009-05-01

91

Uncertainty evaluation of the kerma in the air, related to the active volume in the ionization chamber of concentric cylinders, by Monte Carlo simulation  

International Nuclear Information System (INIS)

[en] To implant the primary standard of the magnitude kerma in the air for X-ray between 10 - 50 keV, the National Metrology Laboratory of Ionizing Radiations (LNMRI) must evaluate all the uncertainties of measurement related with Victtoren chamber. So, it was evaluated the uncertainty of the kerma in the air consequent of the inaccuracy in the active volume of the chamber using the calculation of Monte Carlo as a tool through the Penelope software

2009-01-01

92

Transmission ionization chambers for measurements of air collision kerma integrated over beam area. Factors limiting the accuracy of calibration  

International Nuclear Information System (INIS)

Kerma-area product meters (KAP meters) are frequently used in diagnostic radiology to measure the integral of air-collision kerma over an area A(?A Kc,air dA) perpendicular to the x-ray beam. In this work, a precise method for calibrating a KAP meter to measure ?A Kc,air dA is described and calibration factors determined for a broad range of tube potentials (40-200kV). The integral is determined using a large number of TL dosimeters spread over and outside the nominal field area defined as the area within 50% of maximum Kc,air. The method is compared to a simplified calibration method which approximates the integral by multiplying the kerma in the centre of the field by the nominal field area Anom. While the calibration factor using the precise method is independent of field area and distance from the source, that using the simplified method depends on both. This can be accounted for by field inhomogeneities caused by the heel effect, extrafocal radiation and scattered radiation from the KAP meter. The deviations between the calibration factors were as large as ±15% for collimator apertures of 5-100cm2 and distances from the source of 50 - 160 cm. The uncertainty in the calibration factor using the precise method was carefully evaluated and the expanded relative uncertainty estimated to be ±3% with a confidence level of 95%. (author)

1996-01-01

93

Characterization of the radiation quality of 60Co therapy units by the fraction of air kerma attributable to scattered photons  

International Nuclear Information System (INIS)

In this work we present a new parameter for characterizing the emitted photon spectra of 60Co radiotherapy units. It is intended to propose this parameter for the revised DIN standard 6809-1. In the previous DIN regulation, it had been sufficient to state the nature of the radioactive material within the source. However, scatter processes within the radioactive material as well as the source housing and the collimator system influence the shape of the photon spectrum, with a noticeable contribution in the low-energy portion. The fraction of the air kerma for a given distance from the source, position and beam size in air comprising all contributions by scattered photons up to an upper energy limit for the emitted spectrum from 60Co decay, will be proposed as a typical parameter. The new quantity, which is termed the 'fraction of air kerma attributable to scattered photons', PEScatter, has been calculated for E = 1.17 MeV and compared for four different Monte Carlo-simulated spectra of used 60Co devices. Not included in this new formalism is the air kerma contribution by scattered photons in between the two lines of the 60Co spectrum. A simple measurement procedure based on the signal ratio of two Farmer chamber detectors with different wall materials is discussed and its feasibility shown. (note)

2007-04-07

94

Monte Carlo simulations in CT for the study of the surface air kerma and energy imparted to phantoms of varying size and position  

Energy Technology Data Exchange (ETDEWEB)

A Monte Carlo computational model of CT has been developed and used to investigate the effect of various physical factors on the surface air kerma length product, the peak surface air kerma, the air kerma length product within a phantom and the energy imparted. The factors investigated were the bow-tie filter and the size, shape and position of a phantom which simulates the patient. The calculations show that the surface air kerma length product and the maximum surface air kerma are mainly dependent on phantom position and decrease along the vertical axis of the CT plane as the phantom surface moves away from the isocentre along this axis. As a result, measurements using standard body dosimetry phantoms may underestimate the skin dose for real patients. This result is specially important for CT fluoroscopic procedures: for an adult patient the peak skin dose can be 37% higher than that estimated with a standard measurement on the body AAPM (American Association of Physicists in Medicine) phantom. The results also show that the energy imparted to a phantom is mainly influenced by phantom size and is nearly independent of phantom position (within 3%) and shape (up to 5% variation). However, variations of up to 30% were found for the air kerma to regions within the AAPM body phantom when it is moved vertically. This highlights the importance of calculating doses to organs taking into account their size and position within the gantry.

Lucas, P Aviles [Physics Department, Royal Marsden Hospital, Fulham Road, London SW3 6JJ (United Kingdom); Dance, D R [Physics Department, Royal Marsden Hospital, Fulham Road, London SW3 6JJ (United Kingdom); Castellano, I A [Physics Department, Royal Marsden Hospital, Fulham Road, London SW3 6JJ (United Kingdom); Vano, E [Departamento de RadiologIa, Facultad de Medicina, Universidad Complutense de Madrid, Madrid 28040 (Spain)

2004-04-21

95

Comparison of the standards for air kerma of the BEV and the BIPM for {sup 137}Cs gamma radiation  

Energy Technology Data Exchange (ETDEWEB)

A direct comparison of the standards for air kerma of the Bundesamt fur Eich- und Vermessungswesen (BEV), Austria, and of the Bureau International des Poids et Mesures (BIPM) was carried out in the {sup 137}Cs radiation beam of the BIPM in March 2009. The result, expressed as ratios of the BEV and the BIPM standards for air kerma, is 1.0041 with a combined standard uncertainty of 3.1 * 10{sup -3}. The result of the earlier direct comparison in {sup 137}Csgamma rays, made in 1995, was 0.9961 (28); taking into account the changes made recently to both standards, the 1995 result becomes 1.0035 (24), in agreement with the present comparison result. The degrees of equivalence between the BEV and the other participants in the key comparison have been calculated and the results are presented in the form of a matrix. A graphical presentation is also given. (authors)

Kessler, C.; Allisy, P.J.; Burns, D.T. [Bureau International des Poids et Mesures (BIPM), 92 - Sevres (France); Steurer, A.; Tiefenboeck, W.; Gabris, F. [Bundesamt fur Eich- und Vermessungswesen, Vienna (Austria)

2010-02-15

96

Comparison of the standards for air kerma of the BEV and the BIPM for 137Cs gamma radiation  

International Nuclear Information System (INIS)

A direct comparison of the standards for air kerma of the Bundesamt fur Eich- und Vermessungswesen (BEV), Austria, and of the Bureau International des Poids et Mesures (BIPM) was carried out in the 137Cs radiation beam of the BIPM in March 2009. The result, expressed as ratios of the BEV and the BIPM standards for air kerma, is 1.0041 with a combined standard uncertainty of 3.1 * 10-3. The result of the earlier direct comparison in 137Cs? rays, made in 1995, was 0.9961 (28); taking into account the changes made recently to both standards, the 1995 result becomes 1.0035 (24), in agreement with the present comparison result. The degrees of equivalence between the BEV and the other participants in the key comparison have been calculated and the results are presented in the form of a matrix. A graphical presentation is also given. (authors)

2010-01-01

97

Comparison of the standards of air kerma of the LNE-LNHB and the BIPM for 60Co gamma radiation  

International Nuclear Information System (INIS)

A direct comparison of the standards for air kerma of the Laboratoire National de Metrologie et d'Essais - Laboratoire National Henri Becquerel (LNE-LNHB), France and of the Bureau International des Poids et Mesures (BIPM) was carried out in the 60Co radiation beam of the BIPM in December 2003. The results, expressed as ratios of the LNE-LNHB and the BIPM standards for air kerma, indicate a relative difference of 3.5 x 10-3 with a combined standard uncertainty of 2.7 x 10-3. The earlier direct comparison in 60Co ? rays, made in 1993, resulted in an agreement of the two standards within 2.5 x 10-3. (authors)

2006-01-01

98

Comparison of the standards for air kerma of the VNIIM and the BIPM for 137Cs gamma radiation  

Science.gov (United States)

An indirect comparison of the standards for air kerma of the D I Mendeleyev Institute for Metrology (VNIIM), Russian Federation, and of the Bureau International des Poids et Mesures (BIPM) was carried out in the 137Cs radiation beam of the BIPM in November 2009. The comparison result, based on the calibration coefficient for one transfer standard and expressed as a ratio of the VNIIM and the BIPM standards for air kerma, is 1.0013 with a combined standard uncertainty of 2.7 × 10-3. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI Section I, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Kessler, C.; Allisy-Roberts, P. J.; Oborin, A. V.; Villevalde, A. Y.

2011-01-01

99

Review of reconstruction of radiation incident air kerma by measurement of absorbed dose in tooth enamel with EPR.  

UK PubMed Central (United Kingdom)

Electron paramagnetic resonance dosimetry with tooth enamel has been proved to be a reliable method to determine retrospectively exposures from photon fields with minimal detectable doses of 100 mGy or lower, which is lower than achievable with cytogenetic dose reconstruction methods. For risk assessment or validating dosimetry systems for specific radiation incidents, the relevant dose from the incident has to be calculated from the total absorbed dose in enamel by subtracting additional dose contributions from the radionuclide content in teeth, natural external background radiation and medical exposures. For calculating organ doses or evaluating dosimetry systems the absorbed dose in enamel from a radiation incident has to be converted to air kerma using dose conversion factors depending on the photon energy spectrum and geometry of the exposure scenario. This paper outlines the approach to assess individual dose contributions to absorbed dose in enamel and calculate individual air kerma of a radiation incident from the absorbed dose in tooth enamel.

Wieser A

2012-03-01

100

Comparison of the standards of air kerma of the OMH and the BIPM for 60Co gamma radiation  

International Nuclear Information System (INIS)

A direct comparison between the standards for air kerma of the Orszagos Meresugyi Hivatal (OMH) and of the Bureau International des Poids et Mesures (BIPM) has been carried out in the 60Co radiation beams of the BIPM. The result, expressed as a ratio of the OMH and the BIPM standards for air kerma, indicates a relative difference of 10.9 x 10-3 with a combined standard uncertainty of 2.2 x 10-3. This new result agrees at the level of 0.4 x 10-3 with the earlier direct comparisons performed in 1986 and 1994, as modified in 2001 by the application of wall and axial non-uniformity correction factors, calculated for the OMH standards using the Monte Carlo method. (authors)

2006-01-01

 
 
 
 
101

Effect of bedside shielding on air-kerma rates around gynecologic intracavitary brachytherapy patients containing 226Ra or 137Cs  

International Nuclear Information System (INIS)

[en] An anthropomorphic phantom was implanted with 226Ra or 137Cs gynecologic intracavitary brachytherapy sources. Air-kerma rate measurements were taken at 10-cm increments along a horizontal plane from the side of the bed at 50 cm, 87 cm, and 136 cm heights above the floor. Five portable lead shields were placed at the head, at the foot and along one side of the bed and readings were taken again at the corresponding heights above, below and behind the shields. The readings were normalized to 100-mg Ra equivalence, and air-kerma rate curves were drawn allowing for the comparison of 226Ra and 137Cs with and without lead shields. The data demonstrated that the air-kerma rates for 137Cs were reduced more than those for 226Ra with the use of the portable lead shields. There was four times the transmission with 226Ra than with 137Cs. The optimal placement was with the lateral bedside shields proximal to the head and foot closest to the bed, with the middle shield overlapping in back. The shields at the head and foot should extend out and overlap the bedside shields. The level of the sources should be positioned near the bottom of the shields. This information will provide the medical health physicist with an estimate of air-kerma rates for both 226Ra and 137Cs with and without shielding for evaluating personnel exposures as well as the effectiveness of current shielding in relation to radiation protection requirements in adjacent rooms or hallways

1990-01-01

102

Comparison of the standards of air kerma of the LNMRI/IRD and the BIPM for 60Co ? rays  

International Nuclear Information System (INIS)

A third comparison of the standards for air kerma of Laboratorio Nacional de Metrologia das Radiacoes Ionizantes/Institute de Radioprotecao e Dosimetria (LNMRI/IRD), Rio de Janeiro, Brazil and of the Bureau International des Poids et Mesures (BIPM) has been carried out in 60Co radiation. The comparison result is 1.0007 and demonstrates that the LNMRI/IRD and BIPM standards agree closely, as was the case for the previous comparisons in 1986 and 1996. (authors)

2005-01-01

103

Avaliação do kerma no ar na superfície de entrada e da qualidade da imagem em radiografias de tórax/ Evaluation of entrance surface air kerma rate and clinical images quality in chest radiography  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese OBJETIVO: Avaliar os fatores de técnica utilizados durante exames de tórax póstero-anterior em pacientes-padrão e correlacioná-los aos valores de kerma no ar na superfície de entrada e à qualidade das imagens clínicas. MATERIAIS E MÉTODOS: O estudo foi realizado em três hospitais do Rio de Janeiro, num total de cinco salas de raios X, com dez pacientes por sala. As imagens foram avaliadas pelos radiologistas dos serviços segundo o protocolo europeu. O kerma no (more) ar na superfície de entrada foi estimado a partir da curva de rendimento do equipamento de raios X, que foi obtida utilizando câmara de ionização acoplada a um eletrômetro. Análise de variância foi realizada para verificar se a diferença entre os valores de kerma no ar na superfície de entrada é significativa. RESULTADOS: Os valores de kerma no ar na superfície de entrada variaram entre 0,05 e 0,26 mGy, com média 60% inferior ao nível de referência publicado na Portaria 453. Das imagens avaliadas, 98% atenderam acima de 65% dos critérios de qualidade. CONCLUSÃO: Para um padrão de qualidade da imagem, aceitável para o diagnóstico, verificou-se ampla variação do kerma no ar na superfície de entrada para pacientes-padrão. Isto demonstra a falta de padronização dos fatores de técnica e a existência de um potencial de redução do valor do kerma no ar na superfície de entrada. Abstract in english OBJECTIVE: To evaluate technical factors involved in posteroanterior chest radiography in standard patients, and correlating them with entrance surface air kerma rate and with the clinical images quality. MATERIALS AND METHODS: The present study was developed at three hospitals in Rio de Janeiro, Brazil, involving a total of five x-ray rooms, with ten patients per room. The images were evaluated by the radiologists of the institutions, in accordance with the European prot (more) ocol. The estimation of surface entrance air kerma rate was based on the x-ray equipment output curve obtained with an ionization chamber coupled with an electrometer. Variance analysis was performed to evaluate the significance of the difference between entrance surface air kerma rates. RESULTS: Entrance surface air kerma rates ranged between 0.05 and 0.26 mGy, with a mean value 60% lower than the reference level established by the Order (Portaria) 453. Among the images evaluated, 98% fulfilled > 65% of the images quality criteria. CONCLUSION: For a standard image quality that is acceptable for diagnosis purposes, a significant variation was observed in the entrance surface air kerma rate for standard patients, demonstrating the lack of technical factors standardization and a potential for decreasing the entrance surface air kerma rate.

Souza, Angelo Bernardo Brasil de; Dias, Simone Kodlulovich; Augusto, Fernando Mecca; Marques, Winston Andrade

2009-10-01

104

NaI(Tl) scintillator detectors stripping procedure for air kerma measurements of diagnostic X-ray beams  

Science.gov (United States)

Air kerma is an essential quantity for the calibration of national standards used in diagnostic radiology and the measurement of operating parameters used in radiation protection. Its measurement within the appropriate limits of accuracy, uncertainty and reproducibility is important for the characterization and control of the radiation field for the dosimetry of the patients submitted to diagnostic radiology and, also, for the assessment of the system which produces radiological images. Only the incident beam must be considered for the calculation of the air kerma. Therefore, for energy spectrum, counts apart the total energy deposition in the detector must be subtracted. It is necessary to establish a procedure to sort out the different contributions to the original spectrum and remove the counts representing scattered photons in the detector's materials, partial energy deposition due to the interactions in the detector active volume and, also, the escape peaks contributions. The main goal of this work is to present spectrum stripping procedure, using the MCNP Monte Carlo computer code, for NaI(Tl) scintillation detectors to calculate the air kerma due to an X-ray beam usually used in medical radiology. The comparison between the spectrum before stripping procedure against the reference value showed a discrepancy of more than 63%, while the comparison with the same spectrum after the stripping procedure showed a discrepancy of less than 0.2%.

Oliveira, L. S. R.; Conti, C. C.; Amorim, A. S.; Balthar, M. C. V.

2013-03-01

105

Direct calibration of a reference standard against the air kerma strength primary standard, at 192Ir HDR energy  

International Nuclear Information System (INIS)

[en] The primary standard of low air kerma rate sources or beams, maintained at the Radiological Standards Laboratory (RSL) of the Bhabha Atomic Research Centre (BARC), is a 60 cm3 spherical graphite ionization chamber. A 192Ir HDR source was standardized at the hospital site in units of air kerma strength (AKS) using this primary standard. A 400 cm3 bakelite chamber, functioning as a reference standard at the RSL for a long period, at low air kerma rates (compared to external beam dose rates), was calibrated against the primary standard. It was seen that the primary standard and the reference standard, both being of low Z, showed roughly the same scatter response and yielded the same calibration factor for the 400 cm3 reference chamber, with or without room scatter. However, any likelihood of change in the reference chamber calibration factor would necessitate the re-transport of the primary standard to the hospital site for re-calibration. Frequent transport of the primary standard can affect the long-term stability of the primary standard, due to its movement or other extraneous causes. The calibration of the reference standard against the primary standard at the RSL, for an industrial type 192Ir source maintained at the laboratory, showed excellent agreement with the hospital calibration, making it possible to check the reference chamber calibration at RSL itself. Further calibration procedures have been developed to offer traceable calibration of the hospital well ionization chambers. (author)

2002-01-01

106

Direct calibration of a reference standard against the air kerma strength primary standard, at {sup 192}Ir HDR energy  

Energy Technology Data Exchange (ETDEWEB)

The primary standard of low air kerma rate sources or beams, maintained at the Radiological Standards Laboratory (RSL) of the Bhabha Atomic Research Centre (BARC), is a 60 cm{sup 3} spherical graphite ionization chamber. A {sup 192}Ir HDR source was standardized at the hospital site in units of air kerma strength (AKS) using this primary standard. A 400 cm{sup 3} bakelite chamber, functioning as a reference standard at the RSL for a long period, at low air kerma rates (compared to external beam dose rates), was calibrated against the primary standard. It was seen that the primary standard and the reference standard, both being of low Z, showed roughly the same scatter response and yielded the same calibration factor for the 400 cm{sup 3} reference chamber, with or without room scatter. However, any likelihood of change in the reference chamber calibration factor would necessitate the re-transport of the primary standard to the hospital site for re-calibration. Frequent transport of the primary standard can affect the long-term stability of the primary standard, due to its movement or other extraneous causes. The calibration of the reference standard against the primary standard at the RSL, for an industrial type {sup 192}Ir source maintained at the laboratory, showed excellent agreement with the hospital calibration, making it possible to check the reference chamber calibration at RSL itself. Further calibration procedures have been developed to offer traceable calibration of the hospital well ionization chambers. (author)

Govinda Rajan, K.N. [Radiological Physics and Advisory Division, BARC, Mumbai (India)]. E-mail: grajanmpss@vsnl.com; Palani Selvam, T.; Bhatt, B.C. [Radiological Physics and Advisory Division, BARC, Mumbai (India); Vijayam, M.; Patki, V.S.; Vinatha [Radiation Safety Systems Division, BARC, Mumbai (India); Pendse, A. M.; Kannan, V. [Hinduja Hospital and Research Centre, Mumbai (India)

2002-04-01

107

A new approach for establishing a primary standard of Kerma in air, in a {sup 60}Co gamma ray beam  

Energy Technology Data Exchange (ETDEWEB)

The determination of a primary standard of kerma in air is generally based on the use of an absolute cavity ionization chamber, with graphite wall and filled with air. For laboratories in possession of primary standard graphite calorimeters, it appears possible to derive by a transfer method air kerma from absorbed dose in graphite. This derivation can be achieved using a transfer instrument, e.g. a small air-filled cavity chamber, successively irradiated in the graphite phantom at the reference depth and in free air. The advantages of this method are the replacement on an absolute current measurement by a relative one, the replacement of the graphite-to-air stopping power ratio by the quotient of that stopping power ratio in free air by that in graphite, the elimination of the effective volume of the chamber and of W, the mean energy expended per ion pair formed in air. In return, a correction factor for the perturbation of the particle fluence, due to the air cavity irradiated in the graphite phantom must be applied. A critical analysis of accuracies proper to both methods is made, the expected gains in metrological safety with the new method pointed out, and preliminary results are presented. (author).

Chauvenet, B.; Delaunay, F.; Simoen, J.P.

1993-12-01

108

A new approach for establishing a primary standard of Kerma in air, in a 60Co gamma ray beam  

International Nuclear Information System (INIS)

The determination of a primary standard of kerma in air is generally based on the use of an absolute cavity ionization chamber, with graphite wall and filled with air. For laboratories in possession of primary standard graphite calorimeters, it appears possible to derive by a transfer method air kerma from absorbed dose in graphite. This derivation can be achieved using a transfer instrument, e.g. a small air-filled cavity chamber, successively irradiated in the graphite phantom at the reference depth and in free air. The advantages of this method are the replacement on an absolute current measurement by a relative one, the replacement of the graphite-to-air stopping power ratio by the quotient of that stopping power ratio in free air by that in graphite, the elimination of the effective volume of the chamber and of W, the mean energy expended per ion pair formed in air. In return, a correction factor for the perturbation of the particle fluence, due to the air cavity irradiated in the graphite phantom must be applied. A critical analysis of accuracies proper to both methods is made, the expected gains in metrological safety with the new method pointed out, and preliminary results are presented. (author).

1993-01-01

109

Air kerma standardization for diagnostic radiology, and requirements proposal for calibration laboratories  

International Nuclear Information System (INIS)

The demand for calibration services and quality control in diagnostic radiology has grown in the country since the publication of the governmental regulation 453, issued by the Ministry of Health in 1998. At that time, to produce results facing the new legislation, many laboratories used different standards and radiation qualities, some of which could be inadequate. The international standards neither supplied consistent radiation qualities and standardization for the different types of equipment available. This situation changed with the publication of the new edition of the IEC 61267 standard, published in 2005. A metrology network was created, but it is not yet accredited by the accreditation organism of the country, INMETRO. The objective of this work was to implement the standardization of the air kerma for the un attenuated qualities (RQR) of IEC 61267, and to develop a requirement proposal for instruments calibration laboratories. Results of interlaboratory comparisons demonstrate that the quantity is standardized and internationally traceable. A laboratory requirement proposal was finalized and it shall be submitted to INMETRO to be used as auxiliary normative document in laboratory accreditation. (author)

2009-01-01

110

Verification of air-kerma strength of 125I seed for permanent prostate implants in Japan  

International Nuclear Information System (INIS)

[en] To assure the physical quality of brachytherapy, we investigated the difference between measured and manufacturer's stated source strengths in a single model SourceTech Medical (STM) 1251 125I seed. A well-type ionization chamber with a single-seed holder was used to measure the source strength of 2412 125I seeds before implant in 34 patients. The air-kerma strength was 0.450 U for all cases. The mean source strength for each patient was measured and compared with the manufacturer's stated value. The deviation from the measured value was compared with the tolerance range of the American Association of Physicists in Medicine (AAPM) TG-56 report's recommendation. The measured source strength was higher than the manufacturer's stated value, with a median difference of 1% (range, -2% to 5%). Sixteen of the totals of 2412 seeds (0.7%) were more than 5% different from the manufacturer's stated value. The median standard deviation (SD) from the mean value was 2.2% (range, 1.1% to 2.5%) for all patients. This is the first report of a single-seed assay performed for the model STM1251 125I seed. In this study the manufacturer's stated strength agreed well with the measured value. Nevertheless, the advisability of performing a single-seed assay at every institution should be considered, by referring to the appropriate regulations; for example, those used in the United States. (author)

2009-01-01

111

Calculation of conversion factors of kerma in air for environmental dose equivalent in radiotherapy  

International Nuclear Information System (INIS)

This work aims to estimate the average conversion factor of Kerma in air to H(10) using photon beams coming from clinic linear accelerators, transmitted through concrete walls of a radiotherapeutic treatment room. The transmitted photon spectra by both 1 meter and 2 meters concrete walls, in an area of 40 x 40 cm2, were calculated when the primary beam impart in an angle of 0o. The (secondary) photon beams transmitted respectively by 0,5 meter, 1,0 meter and 2,0 meter concrete walls, after they scattered by an angle of 90o in a cylindric phantom inside the room, were also determined. Generally, 50 millions of histories were computed for each simulation made for the primary beam. For the 90o spread, the number of histories was 100 millions. The computational code used on this work was the MCNP4B. The most common clinic accelerators used on radiotherapeutic treatments were used on this work CLINAC-4, CLINAC-6, CLINAC-18 and CLINAC-2500. From the spectra analysis obtained in this work, it was possible to dispose the conversion factor for realistic beams found in radiotherapeutic establishment. (author)

2000-01-01

112

Calculation of conversion factor of Kerma in the air for ambient dose equivalent in radiotherapy  

International Nuclear Information System (INIS)

This work aims to estimate the average conversion factor of Kerma in air to H * (10) using photon beams coming from clinic linear accelerators, transmitted through concrete walls of a radiotherapic treatment room. The transmitted photon spectra by both 1 meter and 2 meters concrete walls, in an area of 40 x 40 cm2, were calculated when the primary beam impart in an angle of 0 deg. The (secondary) photon beams transmitted respectively by 0,5 meter, 1,0 meter, 1,0 meter and 2,0 meter concrete walls, after they scattered by an angle of 90 deg in a cylindric phantom inside the room, were also determined. Generally, 50 millions of histories were computed for each simulation made for the primary beam. For the 90 deg spread, the number of histories was 100 millions. The computational code used on this work was the MCNP4B. The most common clinic accelerators used on radiotheraphic treatments were used on this work CLINAC-4, CLINAC-6, CLINAC-18 and CLINAC-2500. From the spectra analysis obtained in this work, it was possible to dispose the conversion factor for realistic beams found in radiotherapeutic establishment. (author)

2000-01-01

113

Cofrac interlaboratory comparison in air kerma and absorbed dose to water for 60Co photons  

International Nuclear Information System (INIS)

In 1996, the standard laboratories accredited in dosimetry by COFRAC have been for the first time made directly traceable to the national standard of absorbed dose to water for 60Co ?-rays. For this radiation, their traceability was formerly established only in air kerma. The aim of this interlaboratory comparison, organised in the frame of COFRAC, was to test the coherence of the calibrations carried out by these laboratories for both quantities. It consisted in comparing, for a radiotherapy type dosimeter, the calibration coefficients obtained by the participants in their own 60Co beams, to the values of BNM-LPRI. Results were in good agreement. Some problems arising from calibrations in absorbed dose to water, placing at the reference point the effective point of measurement of the ionization chamber instead of its centre, were pointed out. In that case, the differences in irradiation conditions during calibration and measurements (especially the source-to-detector distance) can result in errors of some tenths of percent. (authors)

1998-01-01

114

Study and determination of the national dosimetric standards in terms of air kerma for X-rays radiation fields of low and medium-energies; Etude et realisation des references dosimetriques nationales en termes de kerma dans l'air pour les faisceaux de rayons X de basses et moyennes energies  

Energy Technology Data Exchange (ETDEWEB)

Progress in radiation protection and radiotherapy, and the increased needs in terms of accuracy lead national metrology institutes to improve the standard. For ionizing radiation, the standard is defined by an absolute instrument used for air kerma rate measurement. The aim of the thesis is to establish standards, in terms of air kerma for X-rays beams of low and medium-energies. This work enables to complement the standard beam range of the Laboratoire National Henri Becquerel (LNHB). Two free-air chambers have been developed, WK06 for medium-energy and WK07 for low-energy. The air-kerma rate is corrected by several correction factors. Some are determined experimentally; and the others by using Monte Carlo simulations. The uncertainty budget of the air-kerma rate at one standard deviation has been established. These dosimetric standards were compared with those of counterparts' laboratories and are consistent in terms of degree of equivalence. (author)

Ksouri, W

2008-12-15

115

Influence of photon energy spectra from brachytherapy sources on Monte Carlo simulations of kerma and dose rates in water and air.  

UK PubMed Central (United Kingdom)

PURPOSE: For a given radionuclide, there are several photon spectrum choices available to dosimetry investigators for simulating the radiation emissions from brachytherapy sources. This study examines the dosimetric influence of selecting the spectra for 192Ir, 125I, and 103Pd on the final estimations of kerma and dose. METHODS: For 192Ir, 125I, and 103Pd, the authors considered from two to five published spectra. Spherical sources approximating common brachytherapy sources were assessed. Kerma and dose results from GEANT4, MCNP5, and PENELOPE-2008 were compared for water and air. The dosimetric influence of 192Ir, 125I, and 103Pd spectral choice was determined. RESULTS: For the spectra considered, there were no statistically significant differences between kerma or dose results based on Monte Carlo code choice when using the same spectrum. Water-kerma differences of about 2%, 2%, and 0.7% were observed due to spectrum choice for 192Ir, 125, and 103Pd, respectively (independent of radial distance), when accounting for photon yield per Bq. Similar differences were observed for air-kerma rate. However, their ratio (as used in the dose-rate constant) did not significantly change when the various photon spectra were selected because the differences compensated each other when dividing dose rate by air-kerma strength. CONCLUSIONS: Given the standardization of radionuclide data available from the National Nuclear Data Center (NNDC) and the rigorous infrastructure for performing and maintaining the data set evaluations, NNDC spectra are suggested for brachytherapy simulations in medical physics applications.

Rivard MJ; Granero D; Perez-Calatayud J; Ballester F

2010-02-01

116

Re-evaluation of the product of (W/e)air and the graphite to air stopping-power ratio for 60Co air kerma standards  

Science.gov (United States)

Experiments which determine the product of (W/e)air, the average energy deposited per coulomb of charge of one sign released by an electron coming to rest in dry air, and (\\bar{L}_\\Delta / \\rho )^C_a, the Spencer-Attix mean restricted mass collision stopping-power ratio for graphite to air, in a 60Co or 137Cs beam are reanalysed. Correction factors, e.g., to account for gaps about a calorimeter core or perturbations due to a cavity's presence, are calculated using the EGSnrc Monte Carlo code system and these generally decrease the value of (W/e)air(\\bar{L}_\\Delta / \\rho )^C_a for each experiment. Stopping-power ratios are calculated for different choices of density correction and average excitation energy (I-value) for graphite. To calculate an average value (W/e)air(\\bar{L}_{BIPM} / \\rho )^C_a for the BIPM air kerma standard, each experimental result is multiplied by the ratio (\\bar{L}_{BIPM} / \\rho )^C_a/(\\bar{L}_\\Delta / \\rho )^C_a. While individual values of (\\bar{L}_\\Delta / \\rho )^C_a are sensitive to the I-values and density corrections assumed, this ratio varies by less than 0.1% for different choices. Hence, the product (W/e)air(\\bar{L}_{BIPM} / \\rho )^C_a is relatively insensitive to these choices. The weighted mean of the updated data is (W/e)air(\\bar{L}_{BIPM} / \\rho )^C_a= 33.68 J C-1 ± 0.2%, suggesting that the accepted value of 33.97 J C-1 ± 0.1% is 0.8% too high. This has implications for primary 60Co air kerma standards worldwide and potentially for the choice of graphite I-value and density correction for the calculation of the graphite stopping power, as well as the value of (W/e)air.

Thomson, R. M.; Rogers, D. W. O.

2010-07-01

117

Re-evaluation of the product of (W/e)air and the graphite to air stopping-power ratio for 60Co air kerma standards.  

Science.gov (United States)

Experiments which determine the product of (W/e)air, the average energy deposited per coulomb of charge of one sign released by an electron coming to rest in dry air, and (LDelta/rho)Ca, the Spencer-Attix mean restricted mass collision stopping-power ratio for graphite to air, in a 60Co or 137Cs beam are reanalysed. Correction factors, e.g., to account for gaps about a calorimeter core or perturbations due to a cavity's presence, are calculated using the EGSnrc Monte Carlo code system and these generally decrease the value of (W/e)air(LDelta/rho)Ca for each experiment. Stopping-power ratios are calculated for different choices of density correction and average excitation energy (I-value) for graphite. To calculate an average value (W/e)air(LBIPM/rho)Ca for the BIPM air kerma standard, each experimental result is multiplied by the ratio (LBIPM/rho)Ca/(LDelta/Rho)Ca. While individual values of (LDelta/rho)Ca are sensitive to the I-values and density corrections assumed, this ratio varies by less than 0.1% for different choices. Hence, the product (W/e)air(LBIPM/rho)Ca is relatively insensitive to these choices. The weighted mean of the updated data is (W/e)air(LBIPM/rho)Ca=33.68 J C(-1)+/-0.2%, suggesting that the accepted value of 33.97 J C(-1)+/-0.1% is 0.8% too high. This has implications for primary 60Co air kerma standards worldwide and potentially for the choice of graphite I-value and density correction for the calculation of the graphite stopping power, as well as the value of (W/e)air. PMID:20526037

Thomson, R M; Rogers, D W O

2010-06-04

118

Re-evaluation of the product of (W/e)air and the graphite to air stopping-power ratio for 60Co air kerma standards.  

UK PubMed Central (United Kingdom)

Experiments which determine the product of (W/e)air, the average energy deposited per coulomb of charge of one sign released by an electron coming to rest in dry air, and (LDelta/rho)Ca, the Spencer-Attix mean restricted mass collision stopping-power ratio for graphite to air, in a 60Co or 137Cs beam are reanalysed. Correction factors, e.g., to account for gaps about a calorimeter core or perturbations due to a cavity's presence, are calculated using the EGSnrc Monte Carlo code system and these generally decrease the value of (W/e)air(LDelta/rho)Ca for each experiment. Stopping-power ratios are calculated for different choices of density correction and average excitation energy (I-value) for graphite. To calculate an average value (W/e)air(LBIPM/rho)Ca for the BIPM air kerma standard, each experimental result is multiplied by the ratio (LBIPM/rho)Ca/(LDelta/Rho)Ca. While individual values of (LDelta/rho)Ca are sensitive to the I-values and density corrections assumed, this ratio varies by less than 0.1% for different choices. Hence, the product (W/e)air(LBIPM/rho)Ca is relatively insensitive to these choices. The weighted mean of the updated data is (W/e)air(LBIPM/rho)Ca=33.68 J C(-1)+/-0.2%, suggesting that the accepted value of 33.97 J C(-1)+/-0.1% is 0.8% too high. This has implications for primary 60Co air kerma standards worldwide and potentially for the choice of graphite I-value and density correction for the calculation of the graphite stopping power, as well as the value of (W/e)air.

Thomson RM; Rogers DW

2010-07-01

119

Air kerma standardization for diagnostic radiology, and requirements proposal for calibration laboratories; Padronizacao da grandeza Kerma no ar para radiodiagnostico e proposta de requisitos para laboratorios de calibracao  

Energy Technology Data Exchange (ETDEWEB)

The demand for calibration services and quality control in diagnostic radiology has grown in the country since the publication of the governmental regulation 453, issued by the Ministry of Health in 1998. At that time, to produce results facing the new legislation, many laboratories used different standards and radiation qualities, some of which could be inadequate. The international standards neither supplied consistent radiation qualities and standardization for the different types of equipment available. This situation changed with the publication of the new edition of the IEC 61267 standard, published in 2005. A metrology network was created, but it is not yet accredited by the accreditation organism of the country, INMETRO. The objective of this work was to implement the standardization of the air kerma for the un attenuated qualities (RQR) of IEC 61267, and to develop a requirement proposal for instruments calibration laboratories. Results of interlaboratory comparisons demonstrate that the quantity is standardized and internationally traceable. A laboratory requirement proposal was finalized and it shall be submitted to INMETRO to be used as auxiliary normative document in laboratory accreditation. (author)

Ramos, Manoel Mattos Oliveira

2009-07-01

120

Experimental estimation of conversion factors between air kerma free-in-air and individual dose equivalent penetrating for 4-7 MeV photons  

International Nuclear Information System (INIS)

[en] The conversion factor for 4-7 MeV photons for conversion from the air kerma free-in-air to the ambient dose equivalent is 1.11-1.10 according to ICRP publication 51. For normal incidence the ambient dose equivalent corresponds to the directional dose equivalent at 10 mm depth in the ICRU sphere. The directional dose equivalent at 10 mm depth is considered as a good approximation of the individual dose equivalent, penetrating. Measurements with TL dosemeters on and in a PMMA slab phantom are compared with air kerma for 4-7 MeV photons. The measurements show that the conversion factor for 4-7 MeV photons for conversion from the air kerma free-in-air to the dose equivalent at 8 mm in a PMMA slab phantom is in the range 1.12-1.08. This is in good agreement with the conversion factors reported in ICRP publication 51. The tested personal dosemeters on the phantom under-respond by up to 6 per cent, relative to the directional dose equivalent at 10 mm depth, for normal incidence and up to 13% at 30o and 60o from normal incidence. This is mainly due to the fact that the dosemeters are not covered with enough build-up material. (author)

1993-01-01

 
 
 
 
121

Comparison of the standards of air kerma and absorbed dose of the BNM-LPRI and BIPM for {sup 60} Cobalt gamma photons; Comparaison des etalons de kerma dans l`air et de dose absorbee du BNM-LPRI et du BIPM pour les photons gamma du cobalt-60  

Energy Technology Data Exchange (ETDEWEB)

Comparisons between the standards of air kerma, absorbed dose to graphite and absorbed dose to water of the Laboratoire primaire des rayonnements ionisants (BNM-LPRI) and the Bureau international des poids et mesures (BIPM) have been carried out in the {sup 60}Co beam of BIPM. The observed differences are of about 0.3% for air kerma and 0.1% for absorbed doses. The results are in good agreement, within their uncertainties. (authors). 10 tabs., 15 refs.

Chauvenet, B.; Daures, J.; Delaunay, F.; Leroy, E.; Ostrowsky, A. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. des Applications et de la Metrologie des Rayonnements Ionisants; Perroche, A.M.; Boutillon, M. [Bureau International des Poids et Mesures (BIPM), 92 - Sevres (France)

1995-07-01

122

Conversion of Airborne Gamma ray Spectra to Ground Level Air Kerma Rates  

DEFF Research Database (Denmark)

A new method for relating airborne gamma-ray spectra to dose rates and kerma rates at ground level is presented. Dependent on flying altitude 50 m to 125 m the method gives correct results for gamma energies above 250 keV respective 350 keV. At lower energies the method underestimate the dose or kerma rates; by having a large fraction of the ground level gamma-rays at energies below 350 keV special care should be taken at an interpretation of the results.

Bargholz, Kim; Korsbech, Uffe C C

1997-01-01

123

Air kerma to Hp(3) conversion coefficients for a new cylinder phantom for photon reference radiation qualities.  

UK PubMed Central (United Kingdom)

The International Organization for Standardization (ISO) has issued a standard series on photon reference radiation qualities (ISO 4037). In this series, no conversion coefficients are contained for the quantity personal dose equivalent at a 3 mm depth, H(p)(3). In the past, for this quantity, a slab phantom was recommended as a calibration phantom; however, a cylinder phantom much better approximates the shape of a human head than a slab phantom. Therefore, in this work, the conversion coefficients from air kerma to H(p)(3) for the cylinder phantom are supplied for X- and gamma radiation qualities defined in ISO 4037.

Behrens R

2012-09-01

124

Air kerma to Hp(3) conversion coefficients for a new cylinder phantom for photon reference radiation qualities.  

Science.gov (United States)

The International Organization for Standardization (ISO) has issued a standard series on photon reference radiation qualities (ISO 4037). In this series, no conversion coefficients are contained for the quantity personal dose equivalent at a 3 mm depth, H(p)(3). In the past, for this quantity, a slab phantom was recommended as a calibration phantom; however, a cylinder phantom much better approximates the shape of a human head than a slab phantom. Therefore, in this work, the conversion coefficients from air kerma to H(p)(3) for the cylinder phantom are supplied for X- and gamma radiation qualities defined in ISO 4037. PMID:22434922

Behrens, R

2012-03-20

125

Comparison of the standards for air kerma of the ARPANSA and the BIPM for 60Co gamma radiation  

Science.gov (United States)

An indirect comparison of the standards for air kerma of the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA), Australia, and of the Bureau International des Poids et Mesures (BIPM) was carried out in the 60Co radiation beam of the BIPM in May 2010. The comparison result, based on the calibration coefficients for two transfer standards and expressed as a ratio of the ARPANSA and the BIPM standards for air kerma, is 1.0009 with a combined standard uncertainty of 3.1 × 10-3. The degrees of equivalence between the ARPANSA and the other participants in the key comparison have been calculated and the results are presented in the form of a matrix. A graphical presentation is also given. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI Section I, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Kessler, C.; Allisy-Roberts, P. J.; Lye, J.; Oliver, C.

2011-01-01

126

Comparison of the standards for air kerma of the NIST and the BIPM for 60Co gamma radiation  

Science.gov (United States)

An indirect comparison of the standards for air kerma of the National Institute of Standards and Technology (NIST), USA, and of the Bureau International des Poids et Mesures (BIPM) was carried out in the 60Co radiation beam of the BIPM in September 2011. The comparison result, based on the calibration coefficients for two transfer standards and expressed as a ratio of the NIST and the BIPM standards for air kerma, is 1.0039 with a combined standard uncertainty of 0.0034. The results are analysed and presented in terms of degrees of equivalence for entry in the BIPM key comparison database. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Kessler, C.; Allisy-Roberts, P. J.; Minniti, Ronaldo

2013-01-01

127

Comparison of the standards for air kerma of the VNIIM and the BIPM for 60Co gamma radiation  

Science.gov (United States)

An indirect comparison of the standards for air kerma of the D I Mendeleyev Institute for Metrology (VNIIM), Russian Federation, and of the Bureau International des Poids et Mesures (BIPM) was carried out in the 60Co radiation beam of the BIPM in November 2009. The comparison result, based on the calibration coefficient for a transfer standard and expressed as a ratio of the VNIIM and the BIPM standards for air kerma, is 1.0008 with a combined standard uncertainty of 1.8 × 10-3. The degrees of equivalence between the VNIIM and the other participants in this BIPM.RI(I)-K1 key comparison have been calculated and the results are presented in the form of a matrix. A graphical presentation is also given. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI Section I, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Kessler, C.; Allisy-Roberts, P. J.; Oborin, A. V.; Villevalde, A. Y.

2011-01-01

128

Comparison of air kerma standards for medium-energy x-radiation between the MKEH and the IAEA  

Science.gov (United States)

A comparison of the air kerma standards for medium-energy x-radiation was performed between the MKEH and the IAEA. Two reference class ionization chambers of the IAEA, traceable to the PTB with volumes 1000 cm3 and 100 cm3, and the ISO 4037 N-40, N-60, N-120 and N-300 standard beam qualities were selected for the comparison. The calibration coefficients, NK, were determined for both chambers at the MKEH in August 2011 and before and after this at the IAEA Dosimetry Laboratory. The comparison ratio of the calibration coefficients normalized to the previous comparison results of the PTB and MKEH primary air kerma standards was in the range from 0.989 to 0.994 for the beam qualities used. The relative expanded (k = 2) uncertainty for each of these ratios is around 2%. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by EURAMET, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Csete, István; Czap, Ladislav; Gomola, Igor

2012-01-01

129

Air kerma standard for calibration of well-type chambers in Brazil using 192Ir HDR sources and its traceability  

International Nuclear Information System (INIS)

In Brazil there are over 100 high dose rate (HDR) brachytherapy facilities using well-type chambers for the determination of the air kerma rate of 192Ir sources. This paper presents the methodology developed and extensively tested by the Laboratorio de Ciencias Radiologicas (LCR) and presently in use to calibrate those types of chambers. The system was initially used to calibrate six well-type chambers of brachytherapy services, and the maximum deviation of only 1.0% was observed between the calibration coefficients obtained and the ones in the calibration certificate provided by the UWADCL. In addition to its traceability to the Brazilian National Standards, the whole system was taken to University of Wisconsin Accredited Dosimetry Calibration Laboratory (UWADCL) for a direct comparison and the same formalism to calculate the air kerma was used. The comparison results between the two laboratories show an agreement of 0.9% for the calibration coefficients. Three Brazilian well-type chambers were calibrated at the UWADCL, and by LCR, in Brazil, using the developed system and a clinical HDR machine. The results of the calibration of three well chambers have shown an agreement better than 1.0%. Uncertainty analyses involving the measurements made both at the UWADCL and LCR laboratories are discussed.

2009-01-01

130

Evaluation of the air kerma rates values of x radiation systems used in calibration of measurement instruments in radiodiagnosis  

International Nuclear Information System (INIS)

In this work it was made the evaluation of the air kerma rates values obtained during the calibration of instruments used in diagnostic radiology measurements at the Calibration Laboratory of IPEN, as well as its variation according to the ambient conditions. This evaluation is part of the quality control programme of the reference instruments used in this type of calibration. The measurements carried out from August of 2003 to April of 2004 were analyzed for the Medicor X radiation system and from January to May of 2005 for the Seifert/Pantak X radiation system. Monitor chambers were added in the field in order to correct any possible variations in the electric beam that could cause an alteration in the primary beam for both X radiation systems. After the positioning of the monitor chambers a maximum decrease of 6.9 % for 90 kV in the primary beam was verified. After that the air kerma rates values presented a maximum variation of 8 %. The ambient conditions (temperature, pressure and humidity) control was made using appropriate calibrated instruments for each case. (author)

2005-09-02

131

A PROPOSED UNIFORM AIR POLLUTION INDEX  

Science.gov (United States)

A uniform air pollution index for the U.S. is proposed. The index was developed from ten criteria identified in a survey of all the air pollution indices currently in use in the U.S. and Canada. The proposed index, named the Pollutant Standards Index (PSI), was designed to overco...

132

Absorbed dose to water based dosimetry versus air kerma based dosimetry for high-energy photon beams: an experimental study  

International Nuclear Information System (INIS)

[en] In recent years, a change has been proposed from air kerma based reference dosimetry to absorbed dose based reference dosimetry for all radiotherapy beams of ionizing radiation. In this paper, a dosimetry study is presented in which absorbed dose based dosimetry using recently developed formalisms was compared with air kerma based dosimetry using older formalisms. Three ionization chambers of each of three different types were calibrated in terms of absorbed dose to water and air kerma and sent to five hospitals. There, reference dosimetry with all the chambers was performed in a total of eight high-energy clinical photon beams. The selected chamber types were the NE2571, the PTW-30004 and the Wellhoefer-FC65G (previously Wellhoefer-IC70). Having a graphite wall, they exhibit a stable volume and the presence of an aluminium electrode ensures the robustness of these chambers. The data were analysed with the most important recommendations for clinical dosimetry: IAEA TRS-398, AAPM TG-51, IAEA TRS-277, NCS report-2 (presently recommended in Belgium) and AAPM TG-21. The necessary conversion factors were taken from those protocols, or calculated using the data in the different protocols if data for a chamber type are lacking. Polarity corrections were within 0.1% for all chambers in all beams. Recombination corrections were consistent with theoretical predictions, did not vary within a chamber type and only slightly between different chamber types. The maximum chamber-to-chamber variations of the dose obtained with the different formalisms within the same chamber type were between 0.2% and 0.6% for the NE2571, between 0.2% and 0.6% for the PTW-30004 and 0.1% and 0.3% for the Wellhoefer-FC65G for the different beams. The absorbed dose results for the NE2571 and Wellhoefer-FC65G chambers were in good agreement for all beams and all formalisms. The PTW-30004 chambers gave a small but systematically higher result compared to the result for the NE2571 chambers (on the average 0.1% for IAEA TRS-277, 0.3% for NCS report-2 and AAPM TG-21 and 0.4% for IAEA TRS-398 and AAPM TG-51). Within the air kerma based protocols, the results obtained with the TG-21 protocol were 0.4-0.8% higher mainly due to the differences in the data used. Both absorbed dose to water based formalisms resulted in consistent values within 0.3%. The change from old to new formalisms is discussed together with the traceability of calibration factors obtained at the primary absorbed dose and air kerma standards in the reference beams (60Co). For the particular situation in Belgium (calibrations at the Laboratory for Standard Dosimetry of Ghent) the change amounts to 0.1-0.6%. This is similar to the magnitude of the change determined in other countries. (author)

2002-02-07

133

Calculation of factors to convert from air kerma to absorbed dose to water for medium energy photons  

International Nuclear Information System (INIS)

[en] The IPEMB code of practice for the determination of absorbed dose for X-rays below 300 kV generating potential is a dedicated dosimetry protocol for the determination of absorbed dose based on the air kerma evaluation method for medium energy X-rays. Three separate energy ranges are dealt with in the code of practice, however, this report is only attempting to reproduce the factors in one particular range (0.5 - 4.0 nun Cu HVL) for X-rays generated at 135 and 280 kV. These X-ray qualities are used in the NPL therapy level calibration service. This new method includes the use of an air kerma calibration factor, NK, for the ionisation chamber, and the ratio of the mass-energy absorption coefficients of water to air and factors that account for the change in the response of a NE2561 ionisation chamber between calibration in air and measurement in a water phantom, kch, instead of the old F factor. This report describes the work that was undertaken to reproduce the product of the ratio of the mass-energy absorption coefficients of water to air and the kch factors. The majority of this work was carried out using Monte Carlo techniques based on the EGS4 code system. The factors calculated in this report were found to agree with values quoted in the IPEMB code of practice to within 4.2%. The quoted uncertainty for this work is 1.4% and the uncertainties for the factors quoted in the EPEMB code of practice are 3%. Hence this is reasonable agreement. Possible discrepancies in the values may be due either to limitations in the EGS4 code system, simplifications made in the chamber geometry or on the reliance on experimental data which is not quite applicable to its' use in this work. (author)

2000-01-01

134

The performance of the INER improved free-air ionization chamber in the comparison of air kerma calibration coefficients for medium-energy X-rays  

International Nuclear Information System (INIS)

[en] This paper describes modifications to an original design, correction factors and uncertainty evaluations for an improved free-air ionization chamber constructed at the Institute of Nuclear Energy Research (INER, Taiwan). In addition, a comparison of secondary standard air kerma calibration coefficients for 100-250 kV medium-energy X-rays was performed to verify the experimental accuracy and measurement consistency of the improved chamber. The comparison results showed a satisfactory agreement in the measurements which were within the combined expanded uncertainties (k=2)

2005-01-01

135

The performance of the INER improved free-air ionization chamber in the comparison of air kerma calibration coefficients for medium-energy X-rays  

Energy Technology Data Exchange (ETDEWEB)

This paper describes modifications to an original design, correction factors and uncertainty evaluations for an improved free-air ionization chamber constructed at the Institute of Nuclear Energy Research (INER, Taiwan). In addition, a comparison of secondary standard air kerma calibration coefficients for 100-250 kV medium-energy X-rays was performed to verify the experimental accuracy and measurement consistency of the improved chamber. The comparison results showed a satisfactory agreement in the measurements which were within the combined expanded uncertainties (k=2)

Lee, J.-H. E-mail: jhlee@iner.gov.tw; Kotler, L.H.; Bueermann, Ludwig; Hwang, W.-S.; Chiu, J.-H.; Wang, C.-F

2005-01-01

136

Construction of a laboratory for the implantation of primary standardization of the magnitude kerma in the air for the X-ray beams used in mammography  

International Nuclear Information System (INIS)

Aiming to diminish the uncertainty in each phase of the metrological chain, and the uncertainty in dosimetry processed at the X-ray beam applied in the mammography, is necessary that the LNMRI/IRD to develop a reference primary standard for the absolute form to the magnitude kerma in the air

2009-01-01

137

Calculation of the correction factors for the primary standard of kerma in the air at the LNMRI-IRD, Rio de Janeiro, Brazil  

International Nuclear Information System (INIS)

[en] In order to determine the primary standardization in terms of kerma in the air, a graphite ionization chamber is used for calculation some correction factors. A program was elaborated, using the Monte Carlo Penelope for simulate the CC01-110 at the LNMRI/IRD, Rio de Janeiro, Brazil

2009-01-01

138

Re-establishment of the air kerma and ambient dose equivalent standards for the BIPM protection-level {sup 60}Co beam  

Energy Technology Data Exchange (ETDEWEB)

The air kerma and ambient dose equivalent standards for the protection-level {sup 60}Co beam have been re-established following the repositioning of the irradiator and modifications to the beam. Details concerning the standards and the new uncertainty budgets are described in this report with their implications for dosimetry comparisons and calibrations. (authors)

Kessler, C.; Roger, P

2005-07-15

139

Reference dosimetry at the Australian Synchrotron's imaging and medical beamline using free-air ionization chamber measurements and theoretical predictions of air kerma rate and half value layer.  

UK PubMed Central (United Kingdom)

PURPOSE: Novel, preclinical radiotherapy modalities are being developed at synchrotrons around the world, most notably stereotactic synchrotron radiation therapy and microbeam radiotherapy at the European Synchrotron Radiation Facility in Grenoble, France. The imaging and medical beamline (IMBL) at the Australian Synchrotron has recently become available for preclinical radiotherapy and imaging research with clinical trials, a distinct possibility in the coming years. The aim of this present study was to accurately characterize the synchrotron-generated x-ray beam for the purposes of air kerma-based absolute dosimetry. METHODS: The authors used a theoretical model of the energy spectrum from the wiggler source and validated this model by comparing the transmission through copper absorbers (0.1-3.0 mm) against real measurements conducted at the beamline. The authors used a low energy free air ionization chamber (LEFAC) from the Australian Radiation Protection and Nuclear Safety Agency and a commercially available free air chamber (ADC-105) for the measurements. The dimensions of these two chambers are different from one another requiring careful consideration of correction factors. RESULTS: Measured and calculated half value layer (HVL) and air kerma rates differed by less than 3% for the LEFAC when the ion chamber readings were corrected for electron energy loss and ion recombination. The agreement between measured and predicted air kerma rates was less satisfactory for the ADC-105 chamber, however. The LEFAC and ADC measurements produced a first half value layer of 0.405 ± 0.015 and 0.412 ± 0.016 mm Cu, respectively, compared to the theoretical prediction of 0.427 ± 0.012 mm Cu. The theoretical model based upon a spectrum calculator derived a mean beam energy of 61.4 keV with a first half value layer of approximately 30 mm in water. CONCLUSIONS: The authors showed in this study their ability to verify the predicted air kerma rate and x-ray attenuation curve on the IMBL using a simple experimental method, namely, HVL measurements. The HVL measurements strongly supports the x-ray beam spectrum, which in turn has a profound effect on x-ray dosimetry.

Crosbie JC; Rogers PA; Stevenson AW; Hall CJ; Lye JE; Nordström T; Midgley SM; Lewis RA

2013-06-01

140

Dosimetric characteristics, air-kerma strength calibration and verification of Monte Carlo simulation for a new ytterbium-169 brachytherapy source  

Energy Technology Data Exchange (ETDEWEB)

Ytterbium-169 ([sup 169]Yb) is a promising new isotope for brachytherapy with a half life of 32 days and an average photon energy of 93 KeV. It has an Ir-192-equivalent dose distribution in water but a much smaller half-value layer in lead (0.2 mm), affording improved radiation protection and customized shielding of dose-limiting anatomic structures. The goals of this study are to: (a) experimentally validate Monte Carlo photon transport dose-rate calculations for this energy range, (b) to develop a secondary air-kerma strength standard for [sup 169]Yb, and (c) to present essential treatment planning data including the transverse-axis dose-rate distribution and dose correction factors for a number of local shielding materials. Several interstitial [sup 169]Yb sources (type 6) and an experimental high dose-rate source were made available for this study. Monte Carlo photon-transport (MCPT) simulations, based upon validated geometric models of source structure, were used to calculate dose rates in water. To verify MCPT predictions, the transverse-axis dose distribution in homogeneous water medium was measured using a silicon-diode detector. For use in designing shielded applicators, heterogeneity correction factors (HCF) arising from small cylindrical heterogeneities of lead, aluminum, titanium, steel and air were measured in a water medium. Finally, to provide a sound experimental basis for comparing experimental and theoretical dose-rate distributions, the air-kerma strength of the sources was measured using a calibrated ion chamber. To eliminate the influence of measurement artifacts on the comparison of theory and measurement, simulated detector readings were compared directly to measured diode readings. The final data are presented in the format endorsed by the Interstitial Collaborative Working Group. 33 refs., 8 figs., 3 tabs.

Perera, H.; Williamson, J.F.; Li, Zuofeng; Mishra, V.; Meigooni, A.S. (Washington Univ. School of Medicine, St. Louis, MO (United States))

1994-03-01

 
 
 
 
141

Conversion coefficients from air kerma to personal dose equivalent Hp(3) fir eye-lens dosimetry  

International Nuclear Information System (INIS)

[en] This work has been performed within the frame of the European Union ORAMED project (Optimization of Radiation protection for Medical staff). The main goal of the project is to improve standards of protection for medical staff for procedure resulting in potentially high exposures and to develop methodologies for better assessing and for reducing exposures to medical staff. The Work Package WP2 is involved in the development of practical eye lens dosimetry in interventional radiology. This study is complementary of the part of the ENEA report concerning the calculations with the MCNP code of the conversion factors related to the operational quantity Hp(3). A set of energy and angular dependent conversion coefficients Hp(3)/Kair in the new proposed square cylindrical phantom of ICRU tissue, have been calculated with the Monte-Carlo code PENELOPE. The Hp(3) values have been determined in terms of absorbed dose, according to the definition of this quantity, and also with the kerma approximation as formerly reported in ICRU reports. At low photon energy, up to 1 MeV, the two sets of conversion coefficients are consistent. Nevertheless, the differences increase at higher energy. This is mainly due to the lack of electronic equilibrium, especially for small angle incidences. The values of the conversion coefficients obtained with the code MCNP published by ENEA, agree with the kerma approximation calculations with PENELOPE. They are coherent with previous calculations in phantoms different in shape. But above 1 MeV, differences between conversion coefficient values calculated with the absorbed dose and with kerma approximation are significantly increasing, especially at low incidence angles. At those energies the electron transport has to be simulated. (author)

2009-01-01

142

Uncertainty evaluation of the kerma in the air, related to the active volume in the ionization chamber of concentric cylinders, by Monte Carlo simulation; Avaliacao de incerteza no kerma no ar, em relacao ao volume ativo da camara de ionizacao de cilindros concentricos, por simulacao de Monte Carlo  

Energy Technology Data Exchange (ETDEWEB)

To implant the primary standard of the magnitude kerma in the air for X-ray between 10 - 50 keV, the National Metrology Laboratory of Ionizing Radiations (LNMRI) must evaluate all the uncertainties of measurement related with Victtoren chamber. So, it was evaluated the uncertainty of the kerma in the air consequent of the inaccuracy in the active volume of the chamber using the calculation of Monte Carlo as a tool through the Penelope software

Lo Bianco, A.S.; Oliveira, H.P.S.; Peixoto, J.G.P., E-mail: abianco@ird.gov.b [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil). Lab. Nacional de Metrologia das Radiacoes Ionizantes (LNMRI)

2009-07-01

143

Neutron fluence and kerma free in air in a fission beam  

International Nuclear Information System (INIS)

[en] The reactor-neutron-therapy facility of the Munich research reactor provides an intense beam of fission radiation with nearly equal intensities of the neutron and photon component, both having complex spectral structure in the energy region from 0.01 MeV up to 10 MeV. We determined the physical properties of the beam behind a 2.5 cm lead filter (RENT I) and of the unfiltered beam (RENT II) at a separation distance of 545 cm. Total neutron fluence rates (I: 1.31.108 s-1cm-2, II: 2.28.108 s-1cm-2) and the fission neutron fluence rate (I: 1.3% 0.1.108 s-1cm-2, II: 2.3% 0.2.108 s-1cm-2) were measured by means of the Mn-bath technique and threshold activation detectors, respectively. For the determination of the Kerma rates two pairs of neutron sensitive (t) and insensitive (u) chambers were employed. By means of measurements in the beam without and with additional thin filters of polyethylene the wall effects could be determined separately for the neutron and photon radiation components. This procedure offered the possibility to determine the chamber parameters for any mixed radiation field if the neutron sensitivity ksub(t) could be calculated for the involved fields. The kerma rates at 12kW thermal converter power were found to be for RENT I: Ksub(n) = 21.5 cGy/min and Ksub(g) = 6.4 cGy/min and for RENT II: Ksub(n) = 36.4 cGy/min and Ksub(g) = 32 cGy/min

1985-01-01

144

LNE-LNHB air-kerma and absorbed dose to water primary standards for low dose-rate 125I brachytherapy sources  

Science.gov (United States)

The devices and methods applied for the LNE-LNHB primary standards in terms of reference air-kerma and absorbed dose to water for low dose-rate brachytherapy sources are described. Both standards are based on ionometric measurements, using a circular-shaped free-in-air ionization chamber, and Monte Carlo calculated conversion factors. Results for an IBt Bebig 125I source are presented and used here to assess the dose-rate constant. Uncertainties of 1.5% and 1.6% (with k = 1) were found for the air-kerma rate and the absorbed dose to water rate estimated with the new primary standards. Good agreement was found between our values and the AAPM published dose-rate constants. Comparisons with other primary standards are in progress.

Aubineau-Lanièce, I.; Chauvenet, B.; Cutarella, D.; Gouriou, J.; Plagnard, J.; Aviles Lucas, P.

2012-10-01

145

LNE-LNHB air-kerma and absorbed dose to water primary standards for low dose-rate 125I brachytherapy sources  

International Nuclear Information System (INIS)

The devices and methods applied for the LNE-LNHB primary standards in terms of reference air-kerma and absorbed dose to water for low dose-rate brachytherapy sources are described. Both standards are based on ionimetric measurements, using a circular-shaped free-in-air ionization chamber, and Monte Carlo calculated conversion factors. Results for an IBt Bebig 125I source are presented and used here to assess the dose-rate constant. Uncertainties of 1.5% and 1.6% (with k = 1) were found for the air-kerma rate and the absorbed dose to water rate estimated with the new primary standards. Good agreement was found between our values and the AAPM published dose-rate constants. Comparisons with other primary standards are in progress. (authors)

2011-12-01

146

Determination of air-kerma strength for the 192Ir GammaMedplus iX pulsed-dose-rate brachytherapy source.  

UK PubMed Central (United Kingdom)

PURPOSE: Pulsed-dose-rate (PDR) brachytherapy was originally proposed to combine the therapeutic advantages of high-dose-rate (HDR) and low-dose-rate brachytherapy. Though uncommon in the United States, several facilities employ pulsed-dose-rate brachytherapy in Europe and Canada. Currently, there is no air-kerma strength standard for PDR brachytherapy (192)Ir sources traceable to the National Institute of Standards and Technology. Discrepancies in clinical measurements of the air-kerma strength of the PDR brachytherapy sources using HDR source-calibrated well chambers warrant further investigation. METHODS: In this research, the air-kerma strength for an (192)Ir PDR brachytherapy source was compared with the University of Wisconsin Accredited Dosimetry Calibration Laboratory transfer standard well chambers, the seven-distance technique [B. E. Rasmussen et al., "The air-kerma strength standard for 192Ir HDR sources," Med. Phys. 38, 6721-6729 (2011)], and the manufacturer's stated value. Radiochromic film and Monte Carlo techniques were also employed for comparison to the results of the measurements. RESULTS: While the measurements using the seven-distance technique were within + 0.44% from the manufacturer's determination, there was a + 3.10% difference between the transfer standard well chamber measurements and the manufacturer's stated value. Results showed that the PDR brachytherapy source has geometric and thus radiological qualities that exhibit behaviors similar to a point source model in contrast to a conventional line source model. CONCLUSIONS: The resulting effect of the pointlike characteristics of the PDR brachytherapy source likely account for the differences observed between well chamber and in-air measurements.

Riley AD; Pike TL; Micka JA; Fulkerson RK; DeWerd LA

2013-07-01

147

Key comparison BIPM.RI(I)-K1 of the air-kerma standards of the ININ, Mexico and the BIPM in 60Co gamma radiation  

Science.gov (United States)

A direct comparison of the standards for air kerma of the Instituto Nacional de Investigaciones Nucleares (ININ), Mexico, and of the Bureau International des Poids et Mesures (BIPM) was carried out in the 60Co radiation beam of the BIPM in 2012. The comparison result, evaluated as a ratio of the ININ and the BIPM standards for air kerma, is 1.0035 with a combined standard uncertainty of 2.1 × 10-3. The results are analysed and presented in terms of degrees of equivalence for entry in the BIPM key comparison database. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Kessler, C.; Alvarez Romero, J. T.; Tovar-Muñoz, V. M.

2013-01-01

148

Room scatter studies in the air kerma strength standardization of the Amersham CDCS-J-type 137Cs source: a Monte Carlo study  

International Nuclear Information System (INIS)

[en] Corrections for room scatter, [ksc(d, H)]RM, as a function of source-to-detector distance, d, and source-to-floor-height, H, and also departure from constant room scatter, ksl, have been computed for rooms of various sizes using Monte Carlo methods for air kerma strength standardization of the Amersham CDCS-J-type 137Cs brachytherapy source. These corrections will also be applicable to any type of 137Cs source that may be considered for standardization. It was found that, depending upon the relative position of the source with respect to the surrounding concrete scattering surfaces (side walls, floor and ceiling) and different set of d values, the assumption of constant room scatter overestimated the air kerma strength, Sk, by between 0.2% and 0.6%. (author)

2002-05-07

149

Determining the Photon Air Kerma Backscatter Factor Profiles for the ISO and ICRU Recommended Slab Phantoms: Comparison Between LiF Measurements and Monte Carlo Calculations  

International Nuclear Information System (INIS)

Following the ICRU and ISO documents concerned with the calibration of photon personal dosemeters on slab phantoms, the ENEA Institute for Radiation Protection performed a series of studies aimed at adopting suitable routine procedures. The reference ISO and ICRU slab phantoms for calibrating dosemeters in terms of Hp (10,?) and Hp (0.07,?) have therefore been acquired. A slab phantom should in principle allow the simultaneous calibration of several dosemeters for the whole body. On the other hand, besides the inhomogeneity of the incident beam, it has to be taken into account that the phantom itself is responsible for a spatial dependence of the air kerma backscatter factor along its front face, implying a limitation of the practical calibration area. The results of Monte Carlo homogeneity area calculations are summarised, and validated using ionisation chamber independent mapping, and of a series of TL measurements of the same air kerma backscatter factor profiles are described. (author)

1999-01-01

150

Comparisons of the standards for air kerma of the GUM and the BIPM for 60Co and 137Cs gamma radiation  

International Nuclear Information System (INIS)

Direct comparisons of the standards for air kerma of the Glowny Urzad Miar (GUM, Poland) and of the Bureau International des Poids et Mesures (BIPM) were carried out in the 60Co and 137Cs radiation beams of the BIPM in 2006. The results, expressed as ratios of the GUM and the BIPM standards for air kerma, are 1.0023 with a combined standard uncertainty of 2.4 * 10-3 in 60Co, and 0.9995 with a combined standard uncertainty of 2.9 * 10-3 in 137Cs. The result in 60Co agrees with the direct comparison carried out in 1996 when the new correction factors adopted by the GUM and the BIPM in 2007 and 2009 are applied for the present comparison. (authors)

2011-01-01

151

European comparison of Monte Carlo codes users on the uncertainty calculations of air kerma determined in front of a cesium-137 beam  

International Nuclear Information System (INIS)

Within the framework of the European project CONRAD (Coordinated Network for Radiation Dosimetry, contract FP6-12684) coordinated by EURADOS (European Radiation Dosimetry group), WP4 was devoted to numerical dosimetry under the title 'Uncertainty assessment in computational dosimetry: an intercomparison of approaches'. Within this activity, a working group sent a list of eight exercises, dealing with radiation transport of photons, neutrons, protons and electrons, to be solved by the international community. This paper presents exercise number 4, dealing with the calculation of air kerma for a 137Cs beam. This problem was aimed at estimating the components of the uncertainty on the air kerma which cannot be measured, namely those due to geometrical data such as the source location, the diameter of the collimator, the material density, etc. 12 institutes of 10 different countries took part in this work, showing the interest in this proposal. (authors)

2011-01-01

152

Comparisons of the standards for air kerma of the GUM and the BIPM for {sup 60}Co and {sup 137}Cs gamma radiation  

Energy Technology Data Exchange (ETDEWEB)

Direct comparisons of the standards for air kerma of the Glowny Urzad Miar (GUM, Poland) and of the Bureau International des Poids et Mesures (BIPM) were carried out in the {sup 60}Co and {sup 137}Cs radiation beams of the BIPM in 2006. The results, expressed as ratios of the GUM and the BIPM standards for air kerma, are 1.0023 with a combined standard uncertainty of 2.4 * 10{sup -3} in {sup 60}Co, and 0.9995 with a combined standard uncertainty of 2.9 * 10{sup -3} in {sup 137}Cs. The result in {sup 60}Co agrees with the direct comparison carried out in 1996 when the new correction factors adopted by the GUM and the BIPM in 2007 and 2009 are applied for the present comparison. (authors)

Allisy-Roberts, P.J.; Kessler, C.; Burns, D.T. [Bureau International des Poids et Mesures, F-92312 Sevres Cedex, (France); Derlacinski, M.; Kokocinski, J. [Glowny Urzad Miar, Miar, Elektoralna 2, Warsaw, (Poland)

2011-07-01

153

Effect of bedside shielding on air-kerma rates around gynecologic intracavitary brachytherapy patients containing sup 226 Ra or sup 137 Cs  

Energy Technology Data Exchange (ETDEWEB)

An anthropomorphic phantom was implanted with 226Ra or 137Cs gynecologic intracavitary brachytherapy sources. Air-kerma rate measurements were taken at 10-cm increments along a horizontal plane from the side of the bed at 50 cm, 87 cm, and 136 cm heights above the floor. Five portable lead shields were placed at the head, at the foot and along one side of the bed and readings were taken again at the corresponding heights above, below and behind the shields. The readings were normalized to 100-mg Ra equivalence, and air-kerma rate curves were drawn allowing for the comparison of 226Ra and 137Cs with and without lead shields. The data demonstrated that the air-kerma rates for 137Cs were reduced more than those for 226Ra with the use of the portable lead shields. There was four times the transmission with 226Ra than with 137Cs. The optimal placement was with the lateral bedside shields proximal to the head and foot closest to the bed, with the middle shield overlapping in back. The shields at the head and foot should extend out and overlap the bedside shields. The level of the sources should be positioned near the bottom of the shields. This information will provide the medical health physicist with an estimate of air-kerma rates for both 226Ra and 137Cs with and without shielding for evaluating personnel exposures as well as the effectiveness of current shielding in relation to radiation protection requirements in adjacent rooms or hallways.

Papin, P.J.; Ramsey, M.J.; LaFontaine, R.L.; LePage, R.P. (San Diego State Univ., CA (USA))

1990-04-01

154

Measuring instruments of the Physikalisch-Technische Bundesanstalt for realization of the units of the dosimetric quantities standard ion dose, photon-equivalent dose and air-kerma  

International Nuclear Information System (INIS)

[en] The realization of the units of the dosimetric quantities exposure, air-kerma and photon-equivalent dose is an important task of the Physikalisch-Technische Bundesanstalt. The report describes the measuring instruments and other technical equipment as well as the determination of the numerous corrections needed. All data and correction factors required for the realization of the units mentioned above are given in many diagrams and tables. (orig.)

1988-01-01

155

Kerma factors for neutron and photons with energies below 20 MeV  

International Nuclear Information System (INIS)

[en] A comprehensive set of kerma factors for neutrons and photons has been computed for the International Commission on Radiological Protection's (ICRP) standard man, ICRP soft tissue, ICRP red bone marrow, ICRP eye lens, H2O, dry air, Al, Si, 32S, Ar, and four thermoluminescent dosimeter materials. The energy range for neutrons is 10-9 to 20 MeV, divided into 175 energy groups. For photons, the energy range is 10-3 to 20 MeV, and kerma factors are calculated at 144 energy values. The kerma factors were computed using the neutron group-averaged and photon pointwise Evaluated Nuclear Data Library. Results are compared with those in other works where appropriate. The use of kerma factors to convert fluence to absorbed-dose index for ICRP tissue is discussed

1979-01-01

156

Calibration of a 7.6 cm x 7.6 cm (3 inch x 3 inch) Sodium Iodide Gamma Ray Spectrometer for Air Kerma Rate  

International Nuclear Information System (INIS)

[en] An experimental procedure is described for converting a gamma ray spectral measurement from a 7.6 cm x 7.6 cm (3 inch x 3 inch) sodium iodide (NaI) detector to air kerma rate. The calibration procedure involves measuring the energy deposited in the detector using 10 radioactive sources of known activity covering an energy range from 60 keV to 1836 keV. For each of the 10 sources, gamma ray spectra were measured with the source at different angles to the detector axis. The total energy deposited in the detector for the ten sources was confirmed by Monte Carlo calculations. The spectra measured at different angles were combined to produce a spectrum that would represent a homogeneous semi-infinite source of radiation. The resultant spectrum was then subdivided into 10 energy regions. Based on the known air kerma rates due to the sources, a calibration coefficient was calculated for each of the 10 energy regions. These calibration coefficients could then be used to convert the energy deposited in the 10 regions of an unknown spectrum to air kerma rate. The calibration procedure was confirmed by comparing the results from the detector with those from calibrated collimated beams of 137Cs and 60Co. A comparison of measurements using a calibrated pressurised ionisation chamber with those from a similar NaI spectrometer in Finland provided additional confirmation of the calibration procedure. (author)

2001-01-01

157

Monte Carlo aided room scatter studies in the primary air kerma strength standardization of a remote afterloading 192Ir HDR source  

International Nuclear Information System (INIS)

[en] Corrections for room scatter, [ksc(d, H)]RM, were derived using Monte Carlo methods for rooms of various sizes, including the brachytherapy treatment room, in which primary air kerma strength standardization of a remote afterloading microSelectron 192Ir HDR source was carried out, using a 60 cm3 spherical graphite ion chamber. It was observed that for a given source-to-floor height, H, the air kerma rate due to room scatter was found to be decreasing with increase in source-to-detector distance, d, whereas it is assumed to be constant in the experimental determination (multiple-distance method) of the air kerma strength (AKS). Irrespective of the room size considered in the present study and when H=100 cm, the assumption of 'constant room scatter' for d=50, 75 and 100 cm resulted in overestimation of the AKS by about 1%. However, when d was in the range 13-25 cm, it was only 0.20%. The room scatter correction for the shadow cone method was also computed and the result showed that no additional correction was required on account of forward scatter from the cone. Further, at larger d (50-100 cm), the number of low-energy photons (40-200 keV) relative to the total number of photons was found to be very significant, which may be useful to revisit the Spencer-Attix cavity theory. (author)

2001-01-01

158

Calibration of a 7.6 cm x 7.6 cm (3 inch x 3 inch) Sodium Iodide Gamma Ray Spectrometer for Air Kerma Rate  

Energy Technology Data Exchange (ETDEWEB)

An experimental procedure is described for converting a gamma ray spectral measurement from a 7.6 cm x 7.6 cm (3 inch x 3 inch) sodium iodide (NaI) detector to air kerma rate. The calibration procedure involves measuring the energy deposited in the detector using 10 radioactive sources of known activity covering an energy range from 60 keV to 1836 keV. For each of the 10 sources, gamma ray spectra were measured with the source at different angles to the detector axis. The total energy deposited in the detector for the ten sources was confirmed by Monte Carlo calculations. The spectra measured at different angles were combined to produce a spectrum that would represent a homogeneous semi-infinite source of radiation. The resultant spectrum was then subdivided into 10 energy regions. Based on the known air kerma rates due to the sources, a calibration coefficient was calculated for each of the 10 energy regions. These calibration coefficients could then be used to convert the energy deposited in the 10 regions of an unknown spectrum to air kerma rate. The calibration procedure was confirmed by comparing the results from the detector with those from calibrated collimated beams of {sup 137}Cs and {sup 60}Co. A comparison of measurements using a calibrated pressurised ionisation chamber with those from a similar NaI spectrometer in Finland provided additional confirmation of the calibration procedure. (author)

Grasty, R.L.; Walters, B.R.B.; Hovgaard, J.; LaMarre, J.R

2001-07-01

159

Energy imparted to the patient in diagnostic radiology: calculation of conversion factors for determining the energy imparted from measurements of the air collision kerma integrated over beam area  

International Nuclear Information System (INIS)

The energy imparted to the patient in diagnostic radiology, related to radiation risk in examinations of the trunk and head, can be deduced from a measurement of the air collision kerma (or exposure) of the incident primary photons integrated over beam area by using a thin, flat ionisation chamber covering the entire roentgen beam. Factors for converting the integral of the air collision kerma to energy imparted to the patient have been calculated using a Monte Carlo method. The patient is simulated by laterally infinite water slabs with thicknesses from 100-300 mm. Calculations are performed for monoenergetic photons (5-300 keV) and energy spectra commonly used in diagnostic radiology (40-130 kV acceleration potential differences and values of the half-value thickness of air collision kerma in aluminium from 0.9 to 9.9 mm). Correction factors which take into account the additional escape of scattered photons from the sides of a laterally finite water slab as a function of field size and focal distance are also given. (author).

1984-01-01

160

Cofrac interlaboratory comparison in air kerma and absorbed dose to water for {sup 60}Co photons; Comparaison Cofrac interlaboratoire de kerma dans l`air et de dose absorbee dans l`eau pour les photons du cobalt 60  

Energy Technology Data Exchange (ETDEWEB)

In 1996, the standard laboratories accredited in dosimetry by COFRAC have been for the first time made directly traceable to the national standard of absorbed dose to water for {sup 60}Co {gamma}-rays. For this radiation, their traceability was formerly established only in air kerma. The aim of this interlaboratory comparison, organised in the frame of COFRAC, was to test the coherence of the calibrations carried out by these laboratories for both quantities. It consisted in comparing, for a radiotherapy type dosimeter, the calibration coefficients obtained by the participants in their own {sup 60}Co beams, to the values of BNM-LPRI. Results were in good agreement. Some problems arising from calibrations in absorbed dose to water, placing at the reference point the effective point of measurement of the ionization chamber instead of its centre, were pointed out. In that case, the differences in irradiation conditions during calibration and measurements (especially the source-to-detector distance) can result in errors of some tenths of percent. (authors)

Chauvenet, B.; Ostrowsky, A.; Leroy, E. [CEA Saclay, 91 - Gif-sur-Yvette (France). Laboratoire primaire des rayonnements ionisants

1998-04-01

 
 
 
 
161

A study of the relationship between peak skin dose and cumulative air kerma in interventional neuroradiology and cardiology  

International Nuclear Information System (INIS)

A study of peak skin doses (PSDs) during neuroradiology and cardiology interventional procedures has been carried out using Gafchromic XR-RV2 film. Use of mosaics made from squares held in cling film has allowed doses to the head to be mapped successfully. The displayed cumulative air kerma (CAK) has been calibrated in terms of cumulative entrance surface dose (CESD) and results indicate that this can provide a reliable indicator of the PSD in neuroradiology. Results linking PSD to CESD for interventional cardiology were variable, but CAK is still considered to provide the best option for use as an indicator of potential radiation-induced effects. A CESD exceeding 3 Gy is considered a suitable action level for triggering follow-up of patients in neuroradiology and cardiology for possible skin effects. Application of dose action levels defined in this way would affect 8% of neurological embolisation procedures and 5% of cardiology ablation and multiple stent procedures at the hospitals where the investigations were carried out. A close relationship was observed between CESD and dose-area product (DAP) for particular types of procedure, and DAPs of 200-300 Gy cm2 could be used as trigger levels where CAK readings were not available. The DAP value would depend on the mean field size and would need to be determined for each application.

2010-12-01

162

Summary of the BIPM.RI(I)-K5 comparison for air kerma in 137Cs gamma radiation  

Science.gov (United States)

International comparisons of air kerma in 137Cs gamma radiation beams have been made at the Bureau International des Poids et Mesures (BIPM) since 1994. Twelve national metrology institutes have taken part, seven of which have repeated the comparison over the intervening years. The key comparison reference value (KCRV) is taken as the BIPM evaluation, each comparison result being the ratio of the national metrology institute (NMI) evaluation to that of the BIPM standard under the same reference conditions. The degrees of equivalence between each NMI and the KCRV and a graphical presentation are given using the most recent published result for eleven NMIs. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

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

2013-01-01

163

A study of the relationship between peak skin dose and cumulative air kerma in interventional neuroradiology and cardiology  

Energy Technology Data Exchange (ETDEWEB)

A study of peak skin doses (PSDs) during neuroradiology and cardiology interventional procedures has been carried out using Gafchromic XR-RV2 film. Use of mosaics made from squares held in cling film has allowed doses to the head to be mapped successfully. The displayed cumulative air kerma (CAK) has been calibrated in terms of cumulative entrance surface dose (CESD) and results indicate that this can provide a reliable indicator of the PSD in neuroradiology. Results linking PSD to CESD for interventional cardiology were variable, but CAK is still considered to provide the best option for use as an indicator of potential radiation-induced effects. A CESD exceeding 3 Gy is considered a suitable action level for triggering follow-up of patients in neuroradiology and cardiology for possible skin effects. Application of dose action levels defined in this way would affect 8% of neurological embolisation procedures and 5% of cardiology ablation and multiple stent procedures at the hospitals where the investigations were carried out. A close relationship was observed between CESD and dose-area product (DAP) for particular types of procedure, and DAPs of 200-300 Gy cm{sup 2} could be used as trigger levels where CAK readings were not available. The DAP value would depend on the mean field size and would need to be determined for each application.

Neil, S; Padgham, C; Martin, C J [Health Physics, Gartnavel Royal Hospital, Glasgow G12 0XH (United Kingdom)

2010-12-01

164

A conversion method of air-kerma from the primary, scatter and leakage radiations to ambient dose equivalent for calculating the mamography x-ray shielding barrier  

International Nuclear Information System (INIS)

The primary, scatter, and leakage doses(in Gy), which constitute the data base for calculating shielding requirements for x-ray facilities, are often converted to the equivalent dose (in sievert) by using a constant of conversion of 1.145Sv/Gy. This constant is used for diagnostic radiology as well as for mammography spectra, and is derived by considering an exposure of 1 R corresponds to an air kerma of 8.73 m Gy, which renders by tradition an equivalent dose of 10 mSv. However, this conversion does not take into account the energy dependence of the conversion coefficients relating air kerma to the equivalent dose as described in ICRU report. Moreover, current radiation protection standards propose the use of the quantity ambient dose equivalent in order to qualify the efficiently of given radiation shielding. Therefore, in this study, a new approach has been introduced for derivation ambient dose equivalent from air kerma to calculate shielding requirements in mammography facilities. This new approach has been used to compute the conversion coefficients relating air kerma to ambient dose equivalent for mammography reference beam series of the Netherlands Metrology Institute Van Swinden Laboratorium (NMi), National Institute of Standards and Technology (NIST), and International Atomic Energy Agency (AIEA) laboratories. The calculation has been performed by the means of two methods which show a maximum deviation less than 10%2 for the primary, scatter, and leakage radiations. The results show that the conversion coefficients vary from 0.242 Sv/ Gy to 0.692 Sv/Gy with an average value of 0.436 Sv/Gy for the primary and the scatter radiations, and form 0.156 Sv/Gy to 1.329 Sv/Gy with an average value of 0.98 Sv/Gy for the leakage radiation. Simpkin et al. using an empirical approach propose a conversion value of 0.50 Sv/Gy for the mammography x-ray spectra. This value approximately coincides with the average conversion value of 0.436 Sv/Gy obtained in this work for the primary radiation. Thus, the traditional conversion coefficient, assuming that the exposure of 1 R or the air kerma of 8.73 mGy corresponds to the equivalent dose of 10 mSv for any x-ray spectra, should be reconsidered.

2005-01-01

165

Air kerma to dose equivalent conversion coefficients for cylindrical phantoms irradiated by extended plane-parallel photon beams of oblique incidence relative to the cylinder main axis  

International Nuclear Information System (INIS)

[en] For the purposes of type testing extremity dosemeters, the conversion coefficients between the receptor-free air collision kerma and the collision kerma for 4-element ICRU tissue have been calculated at a depth of 0.07 mm in two right-angled circular phantoms made of 4-element ICRU tissue and irradiated by extended plane-parallel photon beams of oblique incidence relative to the cylinder's main axis. The calculations were performed by Monte Carlo simulation of the energy transport of monoenergetic photons through the phantoms as a function of energy and of the angle of incidence. The results for monoenergetic photons have also been used to derive the corresponding conversion coefficients for a variety of X ray beam qualities frequently employed in the procedure for calibrating and type testing personal radiation protection dosemeters. (author)

1995-01-01

166

A Multisite-Multipollutant Air Quality Index  

Science.gov (United States)

In this paper, starting from a multivariate spatio-temporal array, containing air pollution data collected for the main pollutants at different monitoring sites over a 1-year period, a new approach is proposed to get a Multipollutant-Multisite Air Quality Index (AQI) time series. A two steps aggregation, related to space and to pollutants, is considered. For the first aggregation (spatial synthesis) a PCA is performed on data array opportunely rearranged, while the index I2, proposed in Ruggieri and Plaia (2011), is used for the second aggregation (pollutant synthesis), obtaining the new index I2MS. Daily data of four air pollutants from the city of Palermo (Italy) are analyzed to test the performance of the new index. The index I2MS overcomes the main issues presented by other indices, many of which based on AQI computed by US EPA, considering the highest pollutant concentration adequately standardized. The comparison carried out shows that the index here proposed has a better performance than the synthesis by median-maximum (Bruno and Cocchi, 2002) and the synthesis by PCA along both space and pollutant dimensions, if the conjoint effect on air quality of the different pollutants has to be taken into account.

Plaia, A.; Di Salvo, F.; Ruggieri, M.; Agró, G.

2013-05-01

167

Angular dependence factors and air kerma to dose equivalent conversion coefficients for cylindrical phantoms irradiated by plane-parallel extended monoenergetic photon beams  

International Nuclear Information System (INIS)

[en] With the aid of the Monte Carlo method, conversion coefficients between the receptor-free air collision kerma and the collision kerma for 4-element ICRU tissue have been calculated at a depth of 0.007 g.cm-2 in circular cylinder phantoms irradiated by broad plane-parallel photon beams in a direction perpendicular to the cylinder main axis. The phantom material was ICRU tissue or PMMA: the phantom diameter 1.9 cm, 7.3 cm, or 30 cm; the phantom length 30 cm. The calculations were performed for monoenergetic photons in the energy range between 4 keV and 1.25 MeV. The conversion coefficients can be used in the field of extremity dosimetry to convert measured kerma or exposure values into personal dose equivalents; the results for the 7.3 cm diameter cylinder phantoms for the calibration of wrist or ankle dosemeters; those for the 1.9 cm diameter phantoms for the calibration of finger dosemeters. In addition to the conversion coefficients, their angular dependence factors in the middle plane of the phantoms perpendicular to the main axis were also studied. Such quantities for the ICRU tissue phantoms are necessary in the procedure for type testing extremity dosemeters on rod or pillar phantoms. (author)

1995-01-01

168

Proposed specification for a primary standard of air kerma for sup 6 sup 0 Co, sup 1 sup 3 sup 7 Cs and sup 1 sup 9 sup 2 Ir gamma-ray sources  

CERN Document Server

The three cavity chambers, the mean response of which constitutes the primary standard of air kerma for sup 6 sup 0 Co and sup 1 sup 3 sup 7 Cs gamma-rays in the United Kingdom, have been in continuous, almost daily, use at the National Physical Laboratory (NPL) since 1956. These chambers were initially designed for use with 2 MV X-rays at therapy level air kerma rates. However since 1978 they have also been used for protection level air kerma rates, initially, with X-rays generated at 1 MV and 2 MV and more recently with sup 6 sup 0 Co and sup 1 sup 3 sup 7 Cs gamma-rays. They have been used for therapy level air kerma calibrations with sup 6 sup 0 Co gamma-rays since 1997 following the demise of the NPL 2 MV Van de Graaff generator. This report describes the proposals for a new primary standard and the methods that will be used to give a better performance than the present standard when used with air kerma rates from as high as 1 Gy min sup - sup 1 down to 10 mGy hr sup - sup 1. The design will also seek to...

Angliss, R; Nutbrown, R

2001-01-01

169

Comparison of the air kerma standards of the IAEA and the BIPM in mammography x-rays  

Science.gov (United States)

The Dosimetry Laboratory of the International Atomic Energy Agency (IAEA), Seibersdorf, Austria, calibrates reference standards in mammography x-ray beams for IAEA/WHO SSDL Network members (more than 80 laboratories worldwide). As a signatory of the Mutual Recognition Arrangement (CIPM MRA), the IAEA laboratory maintains a Quality Management System (QMS) complying with ISO 17025 and requires updated 'supporting evidence' for its dosimetry calibration and measurement capabilities (CMC), first published in Appendix C of the CIPM MRA key comparison database in 2007. For this purpose, an indirect comparison has been made between the air kerma standards of the IAEA and the Bureau International des Poids et Mesures (BIPM) in the mammography x-ray range from 25 kV to 35 kV, using as transfer instruments two thin-window parallel-plate ionization chambers belonging to the IAEA. The IAEA and BIPM standards for mammography x-rays are shown to be in agreement within the standard uncertainty of the comparison of 5.5 parts in 103. This agreement can be used to support the calibration and measurements capabilities of the IAEA listed in Appendix C of the key comparison database. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Kessler, C.; Burns, D. T.; Czap, L.; Csete, I.; Gomola, I.

2013-01-01

170

Calculation of conversion coefficients for air kerma to ambient dose equivalent using transmitted spectra of megavoltage X-rays through concrete.  

Science.gov (United States)

With the fast advancement of technology, (60)Co teletherapy units are largely being replaced with medical linear accelerators. In most cases, the linear accelerator tends to be installed in the same room in which the (60)Co teletherapy unit was previously placed. If in-depth structural remodelling is out of the question, high-density concrete is usually used to improve shielding against primary, scatter and leakage radiation originating in the new equipment. This work presents a study based on Monte Carlo simulations of the transmission of some clinical photon spectra (from 6, 10, 15, 18 and 25 MV accelerators) through concrete, considering two different densities. Concrete walls with thickness ranging from 0.70 to 2.0 m were irradiated with 30 cm×30 cm primary beam spectra. The results show that the thickness of the barrier decreases up to ?65 % when barite (high-density concrete) is used instead of ordinary concrete. The average energies of primary and transmitted beam spectra were also calculated. In addition, conversion coef?cients from air kerma to ambient dose equivalent, H*(d)/K(air), and air kerma to effective dose, E/K(air), for photon spectra from the transmitted spectra were calculated and compared. The results suggest that the 10-mm depth is not the best choice to represent the effective dose. PMID:22683619

Cordeiro, T P V; Silva, A X

2012-06-07

171

Forecasting air pollution index in Hong Kong  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The Environmental Protection Department (EPD) of Hong Kong Government started the reporting of the Air Pollution Index (API) and its forecast in June 1995. API is calculated by comparing the concentrations of five pollutants, namely, nitrogen dioxide, sulphur dioxide, ozone, carbon monoxide, respira...

Yan, TL; Ng, CN

172

Key comparison BIPM.RI(I)-K7 of the air-kerma standards of the PTB, Germany and the BIPM in mammography x-rays  

International Nuclear Information System (INIS)

A first key comparison has been made between the air-kerma standards of the PTB and the BIPM in mammography x-ray beams. The results show the standards to be in agreement at the level of the combined standard uncertainty of 3.7 parts in 103. A comparison of the standards has also been made in simulated mammography x-ray beams. The standards agree at the level of the combined standard uncertainty of 3.5 parts in 103. The results are analysed and presented in terms of degrees of equivalence for entry in the BIPM key comparison database. (authors)

2011-01-01

173

Construction of a laboratory for the implantation of primary standardization of the magnitude kerma in the air for the X-ray beams used in mammography; Construcao de um laboratorio para a implantacao da padronizacao primaria da grandeza kerma no ar para os feixes de raios X empregados em mamografia  

Energy Technology Data Exchange (ETDEWEB)

Aiming to diminish the uncertainty in each phase of the metrological chain, and the uncertainty in dosimetry processed at the X-ray beam applied in the mammography, is necessary that the LNMRI/IRD to develop a reference primary standard for the absolute form to the magnitude kerma in the air

Cardozo, W.L.; Magalhes, L.A.A.M.F.; Peixoto, J.G.P., E-mail: wagnerlc@ird.gov.b [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil). Lab. Nacional de Metrologia das Radiacoes Ionizantes (LNMRI)

2009-07-01

174

Calculation of the correction factors for the primary standard of kerma in the air at the LNMRI-IRD, Rio de Janeiro, Brazil; Calculo de fatores de correcao para o padrao primario em kerma no ar do LNMRI-IRD, Rio de Janeiro, Brasil  

Energy Technology Data Exchange (ETDEWEB)

In order to determine the primary standardization in terms of kerma in the air, a graphite ionization chamber is used for calculation some correction factors. A program was elaborated, using the Monte Carlo Penelope for simulate the CC01-110 at the LNMRI/IRD, Rio de Janeiro, Brazil

Silva, Cosme Norival Mello da, E-mail: cosme@ird.gov.b [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil). Lab. Nacional de Metrologia das Radiacoes Ionizantes (LNMRI)

2009-07-01

175

Calibration of low activity 192Ir brachytherapy sources in terms of reference air kerma rate with large volume spherical ionization chambers  

International Nuclear Information System (INIS)

[en] An air kerma rate calibration method for low dose rate 192Ir brachytherapy sources was elaborated using three different large volume spherical ionization chambers (PTW LS-10, NE 2551, Exradin A6) in a collaborative series of experiments between the University of Ghent (UG) and the Netherlands Measurements Institute (NMI). To this end these chambers were calibrated for x-ray qualities in the energy range 35 keV to 305 keV and for 137Cs and 60Co gamma rays. The results of these measurements are used to derive mean weighted calibration factors for the photon radiation of 192Ir brachytherapy sources. Furthermore, the effect of the finite chamber size on the effective measuring point and the correction for the contribution of scattered radiation were studied. Measurements on the same sets of sources show that the ionization chambers and the methods used yield results for the reference air kerma rates of 192Ir sources which agree within 0.42%. (author)

1992-01-01

176

A method for evaluating air kerma and directional dose equivalent for currently available multi-element dosemeters in radiation protection dosimetry  

International Nuclear Information System (INIS)

[en] A method is outlined for estimating air kerma and directional dose equivalent from indications on multielement dosemeters having energy and angle response functions that are different for at least two of the dosemeter's radiation-sensitive elements. The method employs dosemeter calibrations relating response of each element and the corresponding indication ratio(s) to radiation energy and angle of radiation incidence. Indications are measured in the usual way on the elements of each dosemeter irradiated under unknown conditions, and the ratio is formed of the indications of any two elements known to have different response functions. Using the calibration curves, energy-angle pairs are found that correspond to these indication ratios, and are then used to determine the corresponding response values - of which there are, in general, several per energy-angle pair. Finally, the response values corresponding to any given energy-angle pair are averaged, and air kerma or directional dose equivalent is computed from average response and the measured indication(s). The method is illustrated for a dosemeter for which photon calibration data were available. (author)

1989-01-01

177

Comparisons of the standards for air kerma of the GUM and the BIPM for 60Co and 137Cs gamma radiation  

Science.gov (United States)

Direct comparisons of the standards for air kerma of the G?ówny Urz?d Miar (GUM, Poland) and of the Bureau International des Poids et Mesures (BIPM) were carried out in the 60Co and 137Cs radiation beams of the BIPM in 2006. The results, expressed as ratios of the GUM and the BIPM standards for air kerma, are 1.0023 with a combined standard uncertainty of 2.4 × 10-3 in 60Co, and 0.9995 with a combined standard uncertainty of 2.9 × 10-3 in 137Cs. The result in 60Co agrees with the direct comparison carried out in 1996 when the new correction factors adopted by the GUM and the BIPM in 2007 and 2009 are applied for the present comparison. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI Section I, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Allisy-Roberts, P. J.; Kessler, C.; Burns, D. T.; Derlaci?ski, M.; Kokoci?ski, J.

2011-01-01

178

Key comparison BIPM.RI(I)-K1 of the air-kerma standards of the LNE-LNHB, France and the BIPM in 60Co gamma radiation  

Science.gov (United States)

An indirect comparison of the standards for air kerma of the Laboratoire National de Métrologie et d'Essais-Laboratoire National Henri Becquerel (LNE-LNHB), France and of the Bureau International des Poids et Mesures (BIPM) was carried out in the 60Co radiation beam of the BIPM in April 2013. The comparison result, evaluated as a ratio of the LNE-LNHB and the BIPM standards for air kerma, is 0.9994 with a combined standard uncertainty of 1.8 × 10-3. The results are analysed and presented in terms of degrees of equivalence for entry in the BIPM key comparison database. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Kessler, C.; Burns, D. T.; Delaunay, F.; Donois, M.

2013-01-01

179

Key comparison BIPM.RI(I)-K1 of the air kerma standards of the NMIJ, Japan and the BIPM in 60Co gamma radiation  

Science.gov (United States)

A direct comparison of the standards for air kerma of the National Metrology Institute of Japan (NMIJ) and of the Bureau International des Poids et Mesures (BIPM) was carried out in the 60Co radiation beam of the BIPM in June 2012. The comparison result, expressed as a ratio of the NMIJ and the BIPM standards for air kerma, is 1.0012 with a combined standard uncertainty of 2.2 × 10-3. Taking into account the changes made to the BIPM standard, the result of the present comparison agrees within the uncertainties with the result of the earlier direct comparison carried out in 2001. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Kessler, C.; Saito, N.; Kurosawa, T.

2013-01-01

180

Estimation of mean-glandular dose from monitoring breast entrance skin air kerma using a high sensitivity metal oxide semiconductor field effect transistor (MOSFET) dosimeter system in mammography  

International Nuclear Information System (INIS)

[en] Estimation of mean-glandular dose (MGD) has been investigated in recent years due to the potential risks of radiation-induced carcinogenesis associated with the mammographic examination for diagnostic radiology. In this study, a new technique for immediate readout of breast entrance skin air kerma (BESAK) using high sensitivity MOSFET dosimeter after mammographic projection was introduced and a formula for the prediction of tube output with exposure records was developed. A series of appropriate conversion factors was applied to the MGD determination from the BESAK. The study results showed that signal response of the high sensitivity MOSFET exhibited excellent linearity within mammographic dose ranges, and that the energy dependence was less than 3% for each anode/filter combination at the tube potentials 25-30 kV. Good agreement was observed between the BESAK and the tube exposure output measurement for breasts thicker than 30 mm. In addition, the air kerma estimated from our prediction formula provided sufficient accuracy for thinner breasts. The average MGD from 120 Asian females was 1.5 mGy, comparable to other studies. Our results suggest that the high sensitivity MOSFET dosimeter system is a good candidate for immediately readout of BESAK after mammographic procedures

2002-01-01

 
 
 
 
181

Key comparison BIPM.RI(I)-K5 of the air kerma standards of the NMIJ, Japan and the BIPM in 137Cs gamma radiation  

Science.gov (United States)

A direct comparison of the standards for air kerma of the National Metrology Institute of Japan (NMIJ) and of the Bureau International des Poids et Mesures (BIPM) was carried out in the 137Cs radiation protection-level beam of the BIPM in June 2012. The comparison result, expressed as a ratio of the NMIJ and the BIPM standards for air kerma, is 0.9977 with a combined standard uncertainty of 2.6 × 10-3 Taking into account the changes made to the BIPM standard, the result of the present comparison agrees within the uncertainties with the result of the direct comparison carried out in 2001. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Kessler, C.; Saito, N.; Kurosawa, T.

2013-01-01

182

Air kerma standard for calibration of well-type chambers in Brazil using {sup 192}Ir HDR sources and its traceability  

Energy Technology Data Exchange (ETDEWEB)

In Brazil there are over 100 high dose rate (HDR) brachytherapy facilities using well-type chambers for the determination of the air kerma rate of {sup 192}Ir sources. This paper presents the methodology developed and extensively tested by the Laboratorio de Ciencias Radiologicas (LCR) and presently in use to calibrate those types of chambers. The system was initially used to calibrate six well-type chambers of brachytherapy services, and the maximum deviation of only 1.0% was observed between the calibration coefficients obtained and the ones in the calibration certificate provided by the UWADCL. In addition to its traceability to the Brazilian National Standards, the whole system was taken to University of Wisconsin Accredited Dosimetry Calibration Laboratory (UWADCL) for a direct comparison and the same formalism to calculate the air kerma was used. The comparison results between the two laboratories show an agreement of 0.9% for the calibration coefficients. Three Brazilian well-type chambers were calibrated at the UWADCL, and by LCR, in Brazil, using the developed system and a clinical HDR machine. The results of the calibration of three well chambers have shown an agreement better than 1.0%. Uncertainty analyses involving the measurements made both at the UWADCL and LCR laboratories are discussed.

Di Prinzio, Renato; Almeida, Carlos Eduardo de [Laboratorio de Ciencias Radiologicas-Universidade do Estado do Rio de Janeiro (LCR/UERJ), R. Sao Francisco Xavier, 524, Pavilhao Haroldo Lisboa da Cunha, Terreo, Sala 136-Maracana, CEP 20550-900-Rio de Janeiro/RJ-Rio de Janeiro, RJ (Brazil) and Instituto de Radioprotecao e Dosimetria-Comissao Nacional de Energia Nuclear (IRD/CNEN), Av. Salvador Allende, s/n, Jacarepagua-CE22780-160-Rio de Janeiro, RJ (Brazil); Laboratorio de Ciencias Radiologicas-Universidade do Estado do Rio de Janeiro (LCR/UERJ), R. Sao Francisco Xavier, 524, Pavilhao Haroldo Lisboa da Cunha, Terreo, Sala 136-Maracana, CEP 20550-900-Rio de Janeiro/RJ-Rio de Janeiro, RJ (Brazil)

2009-03-15

183

Comparisons of the standards for air kerma of the PTB and the BIPM for 60Co and 137Cs gamma radiation  

International Nuclear Information System (INIS)

Direct comparisons of the standards for air kerma of the Physikalisch-Technische Bundesanstalt (PTB, Germany) and of the Bureau International des Poids et Mesures (BIPM) were carried out in the 60Co and 137 Cs radiation beams of the BIPM in 2000. The results, expressed as ratios of the PTB and the BIPM standards for air kerma, indicate a relative difference in 60Co of 9.9 x 10-3 with a combined standard uncertainty of 1.8 x 10-3, and in 137Cs of 6.4 x 10-3 with a combined standard uncertainty of 2.8 x 10-3. The earlier comparisons in 60Co ? rays made in 1971 (direct) and 1989 (indirect) resulted in an agreement of the two standards within 2 x 10-3. The differences obtained now are due to the application of new correction factors for wall effects and point source non-uniformity of the beam, kwall and kpn, for the PTB standards, which were calculated using Monte Carlo methods. (authors)

2005-01-01

184

Comparisons of the standards for air kerma of the PTB and the BIPM for {sup 60}Co and {sup 137}Cs gamma radiation  

Energy Technology Data Exchange (ETDEWEB)

Direct comparisons of the standards for air kerma of the Physikalisch-Technische Bundesanstalt (PTB, Germany) and of the Bureau International des Poids et Mesures (BIPM) were carried out in the {sup 60}Co and {sup 137} Cs radiation beams of the BIPM in 2000. The results, expressed as ratios of the PTB and the BIPM standards for air kerma, indicate a relative difference in {sup 60}Co of 9.9 x 10{sup -3} with a combined standard uncertainty of 1.8 x 10{sup -3}, and in {sup 137}Cs of 6.4 x 10{sup -3} with a combined standard uncertainty of 2.8 x 10{sup -3}. The earlier comparisons in {sup 60}Co {gamma} rays made in 1971 (direct) and 1989 (indirect) resulted in an agreement of the two standards within 2 x 10{sup -3}. The differences obtained now are due to the application of new correction factors for wall effects and point source non-uniformity of the beam, k{sub wall} and k{sub pn}, for the PTB standards, which were calculated using Monte Carlo methods. (authors)

Allisy-Roberts, P.J.; Burns, D.T. [Bureau International des Poids et Mesures (BIPM), 92 - Sevres (France); Buermann, L.; Kramer, H.M. [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany)

2005-11-15

185

Calculation of conversion factor of Kerma in the air for ambient dose equivalent in radiotherapy; Calculo dos fatores de conversao de Kerma no ar para equivalente de dose ambiental em radioterapia  

Energy Technology Data Exchange (ETDEWEB)

This work aims to estimate the average conversion factor of Kerma in air to H {sup *} (10) using photon beams coming from clinic linear accelerators, transmitted through concrete walls of a radiotherapic treatment room. The transmitted photon spectra by both 1 meter and 2 meters concrete walls, in an area of 40 x 40 cm{sup 2}, were calculated when the primary beam impart in an angle of 0 deg. The (secondary) photon beams transmitted respectively by 0,5 meter, 1,0 meter, 1,0 meter and 2,0 meter concrete walls, after they scattered by an angle of 90 deg in a cylindric phantom inside the room, were also determined. Generally, 50 millions of histories were computed for each simulation made for the primary beam. For the 90 deg spread, the number of histories was 100 millions. The computational code used on this work was the MCNP4B. The most common clinic accelerators used on radiotheraphic treatments were used on this work CLINAC-4, CLINAC-6, CLINAC-18 and CLINAC-2500. From the spectra analysis obtained in this work, it was possible to dispose the conversion factor for realistic beams found in radiotherapeutic establishment. (author)

Lima, Marco Antonio Frota

2000-03-01

186

Investigation of photon spectra and contributions to air kerma rates in the environment near nuclear facilities using portable germanium gamma spectrometry  

International Nuclear Information System (INIS)

[en] Portable spectrometers based on NaI or Ge detectors are now important additions to the tools available for monitoring and assessment of radioactivity and radiation dose rates in the environment due to both natural and anthropogenic sources. The high resolution of the Ge detector is of particular use in rapidly identifying and assessing radionuclides of significance. Portable spectrometry is of importance in assessing deposited activity and contributions to air kerma rates, and the rapid availability of these results would be significant in the event of a nuclear emergency in addition to the more usual application of measuring concentrations of radionuclides in environmental samples. In the course of developing a portable germanium detector system, spectra were measured at a number of locations in the environment near nuclear establishments in the UK. These spectra are presented and analysed in this paper in terms of the radionuclide contributions and gamma air kerma rates. Particular features are highlighted. First, background contributions are characterised using an example spectrum measured at Lowestoft beach, where anthropogenic influences are low. By contrast, near the Magnox nuclear power station at Bradwell, Essex there are contributions to the spectra due to photons from 16N, 41Ar and 60Co. In the Ravenglass estuary near Sellafield, 137Cs features prominently, with smaller contributions due to other radionuclides discharged in liquid waste from Sellafield. In the Ribble estuary which is influenced by discharges from the Springfields fuel fabrication plant as well as from Sellafield, measurements were made on a houseboat at high and low tide; there was a significant difference in the contribution due to 137Cs from Sellafield. Upstream of the Springfields works, peaks in the spectrum were observed due to 234Th and 234mPa due to discharges from the site, as well as 137Cs from BNFL Sellafield. The paper highlights and comments on all these features. In addition, the spectra were analysed in terms of contributions to gamma air kerma rates and the components due to natural background. Dose rates to members of the public who may spend time at the relevant locations are well within the dose limit of 1 mSv per year recommended by the ICRP. The different contributions to dose rates are contrasted. By highlighting particular features, this study demonstrates the wide range of applications of portable Ge spectrometry in environmental situations. (author)

2000-01-01

187

Key comparison BIPM.RI(I)-K2 of the air-kerma standards of the NRC, Canada and the BIPM in low-energy x-rays  

Science.gov (United States)

A key comparison has been made between the air-kerma standards of the NRC and the BIPM in the low-energy x ray range. The results show the standards to be in agreement at the level of the combined standard uncertainty of 2.8 parts in 103. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI Section I, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Burns, D. T.; Kessler, C.; McCaffrey, J. P.

2011-01-01

188

Key comparison BIPM.RI(I)-K3 of the air-kerma standards of the NMIJ, Japan and the BIPM in medium-energy x-rays  

Science.gov (United States)

A key comparison has been made between the air-kerma standards of the NMIJ, Japan and the BIPM in the medium-energy x-ray range. The results show the standards to be in general agreement at the level of two standard uncertainties (6 parts in 103). A significant trend is evident in the results for the different radiation qualities and consistency with measurements made in 2001 for an APMP comparison is not as expected. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI Section I, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Burns, D. T.; Roger, P.; Saito, N.; Kurosawa, T.; Morishita, Y.

2011-01-01

189

Key comparison BIPM.RI(I)-K3 of the air-kerma standards of the GUM, Poland and the BIPM in medium-energy x-rays  

Science.gov (United States)

A key comparison has been made between the air-kerma standards of the GUM and the BIPM in the medium-energy x-ray range. The results show the standards to be in agreement at the level of the expanded uncertainty for the comparison of 5.6 parts in 103. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Burns, D. T.; Kessler, C.; Knyziak, A. B.

2013-01-01

190

Key comparison BIPM.RI(I)-K2 of the air-kerma standards of the NIST, USA and the BIPM in low-energy x-rays  

Science.gov (United States)

A key comparison has been made between the air-kerma standards of the NIST and the BIPM in the low-energy x-ray range. The results show the standards to be in general agreement at the level of the combined standard uncertainty for the comparison of 4.1 parts in 103, although the results for the different radiation qualities show variations that are larger than would be expected. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI Section I, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Burns, D. T.; Kessler, C.; Brien, M. O.

2012-01-01

191

Where should we measure the entrance air kerma rate during acceptance testing of the automatic dose control of a fluoroscopic system?  

Science.gov (United States)

In Japan, the entrance air kerma rate (EAKR) to a patient cannot exceed 50 mGy/min in conventional fluoroscopy. However, it is unclear where the EAKR should be measured. We obtained the tube potential and tube current as a function of polymethylmethacrylate (PMMA) thickness, and the EAKR at the interventional reference point (IRP) was measured from the trajectory. The EAKR at the point established by the U.S. Food and Drug Administration (FDA) was calculated from EAKR at the IRP. The EAKR at the IRP exceeded the limit at a PMMA thickness of 22-28 cm. However, the EAKR did not exceed the limit at the FDA point. If the EAKR to a patient is being verified to meet the recent Japanese ruling, the EAKR should be measured at the FDA point, and if the EAKR is being evaluated for determination of the skin dose, it should be monitored at the IRP. PMID:23413079

Fukuda, Atsushi; Miyati, Tosiaki; Matsubara, Kosuke

2013-02-15

192

Key comparison BIPM.RI(I)-K7 of the air-kerma standards of the NIST, USA and the BIPM in mammography x-rays  

Science.gov (United States)

A first key comparison has been made between the air-kerma standards of the NIST and the BIPM in mammography x-ray beams. The results show the standards to be in agreement at the level of the combined standard uncertainty of 3.2 parts in 103. The results are analysed and presented in terms of degrees of equivalence for entry in the BIPM key comparison database. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI Section I, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Kessler, C.; Burns, D. T.; O'Brien, M.

2011-01-01

193

Key comparison BIPM.RI(I)-K2 of the air-kerma standards of the GUM, Poland and the BIPM in low-energy x-rays  

Science.gov (United States)

A key comparison has been made between the air-kerma standards of the GUM and the BIPM in the low-energy x-ray range. The results show the standards to be in agreement to better than the expanded uncertainty (k = 2) for the comparison of 6.0 parts in 103. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI Section I, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Burns, D. T.; Roger, P.; Knyziak, A. B.

2012-01-01

194

Where should we measure the entrance air kerma rate during acceptance testing of the automatic dose control of a fluoroscopic system?  

UK PubMed Central (United Kingdom)

In Japan, the entrance air kerma rate (EAKR) to a patient cannot exceed 50 mGy/min in conventional fluoroscopy. However, it is unclear where the EAKR should be measured. We obtained the tube potential and tube current as a function of polymethylmethacrylate (PMMA) thickness, and the EAKR at the interventional reference point (IRP) was measured from the trajectory. The EAKR at the point established by the U.S. Food and Drug Administration (FDA) was calculated from EAKR at the IRP. The EAKR at the IRP exceeded the limit at a PMMA thickness of 22-28 cm. However, the EAKR did not exceed the limit at the FDA point. If the EAKR to a patient is being verified to meet the recent Japanese ruling, the EAKR should be measured at the FDA point, and if the EAKR is being evaluated for determination of the skin dose, it should be monitored at the IRP.

Fukuda A; Miyati T; Matsubara K

2013-07-01

195

Key comparison BIPM.RI(I)-K3 of the air-kerma standards of the MKEH, Hungary and the BIPM in medium-energy x-rays  

Science.gov (United States)

A key comparison has been made between the air-kerma standards of the MKEH, Hungary and the BIPM in the medium-energy x-ray range. The results show the standards to be in agreement within the standard uncertainty for the comparison of 3.4 parts in 103. No significant trend is observed in the results for the different radiation qualities. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI Section I, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Burns, D. T.; Csete, I.; Roger, P.

2011-01-01

196

Key comparison BIPM.RI(I)-K7 of the air-kerma standards of the VNIIM, Russian Federation and the BIPM in mammography x-rays  

Science.gov (United States)

A first key comparison has been made between the air-kerma standards of the VNIIM and the BIPM in mammography x-ray beams in the range from 25 kV to 35 kV, using two thin-window parallel-plate ionization chambers as transfer instruments. The results show the standards to be in agreement within the expanded uncertainty of 4.8 parts in 103. The results are also analysed and presented in terms of degrees of equivalence for entry in the BIPM key comparison database. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Kessler, C.; Burns, D. T.; Oborin, A. V.; Villevalde, A. Y.

2013-01-01

197

Key comparison BIPM.RI(I)-K2 of the air-kerma standards of the MKEH, Hungary and the BIPM in low-energy x-rays  

Science.gov (United States)

A key comparison has been made between the air-kerma standards of the MKEH, Hungary and the BIPM in the low-energy x-ray range. The results show the standards to be in agreement within the expanded uncertainty for the comparison of 4.1 parts in 103. No significant trend with radiation quality is observed. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI Section I, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Burns, D. T.; Kessler, C.; Roger, P.; Csete, I.

2012-01-01

198

Key comparison BIPM.RI(I)-K7 of the air-kerma standards of the NRC, Canada and the BIPM in mammography x-rays  

Science.gov (United States)

A first key comparison has been made between the air-kerma standards of the NRC and the BIPM in mammography x-ray beams. The results show the standards to be in agreement at the level of the combined standard uncertainty of 3.0 parts in 103. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI Section I, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Kessler, C.; Burns, D. T.; McCaffrey, J. P.

2011-01-01

199

Key comparison BIPM.RI(I)-K3 of the air-kerma standards of the ARPANSA, Australia and the BIPM in medium-energy x-rays  

Science.gov (United States)

A key comparison has been made between the air-kerma standards of the ARPANSA, Australia and the BIPM in the medium-energy x-ray range. The results show the standards to be in agreement within the expanded uncertainty for the comparison of 7.7 parts in 103. No significant trend is observed in the results for the different radiation qualities. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI Section I, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Burns, D. T.; Lye, J. E.; Roger, P.; Butler, D. J.

2012-01-01

200

Comparison of the NIST and BIPM air-kerma standards for measurements in the low-energy x-ray range  

International Nuclear Information System (INIS)

A direct comparison was made between the air-kerma standards used for the measurement of low-energy x rays at the National Institute of Standards and Technology (NIST) and the Bureau International des Poids et Mesures (BIPM). The comparison was carried out at the BIPM using the BIPM reference beam qualities in the range from 10kV to 100 kV. The results show the standards to be in agreement to around 0.5% at reference beam qualities up to 50kV and at 100 kV. The result at the 80kV beam quality is less favorable, with agreement at the 1% level

1999-01-01

 
 
 
 
201

Determination of the Kwall correction factor for a cylindrical ionization chamber to measure air-kerma in 60Co gamma beams  

International Nuclear Information System (INIS)

The factor Kwall to correct for photon attenuation and scatter in the wall of ionization chambers for 60Co air-kerma measurement has been traditionally determined by a procedure based on a linear extrapolation of the chamber current to zero wall thickness. Monte Carlo calculations by Rogers and Bielajew (1990 Phys. Med. Biol. 35 1065-78) provided evidence, mostly for chambers of cylindrical and spherical geometry, of appreciable deviations between the calculated values of Kwall and those obtained by the traditional extrapolation procedure. In the present work an experimental method other than the traditional extrapolation procedure was used to determine the Kwall factor. In this method the dependence of the ionization current in a cylindrical chamber was analysed as a function of an effective wall thickness in place of the physical (radial) wall thickness traditionally considered in this type of measurement. To this end the chamber wall was ideally divided into distinct regions and for each region an effective thickness to which the chamber current correlates was determined. A Monte Carlo calculation of attenuation and scatter effects in the different regions of the chamber wall was also made to compare calculation to measurement results. The Kwall values experimentally determined in this work agree within 0.2% with the Monte Carlo calculation. The agreement between these independent methods and the appreciable deviation (up to about 1%) between the results of both these methods and those obtained by the traditional extrapolation procedure support the conclusion that the two independent methods providing comparable results are correct and the traditional extrapolation procedure is likely to be wrong. The numerical results of the present study refer to a cylindrical cavity chamber like that adopted as the Italian national air-kerma standard at INMRI-ENEA (Italy). The method used in this study applies, however, to any other chamber of the same type. (author)

2002-07-21

202

Index to the AEC/ERDA/DOE Air Cleaning Conferences  

Energy Technology Data Exchange (ETDEWEB)

A comprehensive index to the papers in the second through sixteenth AEC/ERDA/DOE Nuclear Air Cleaning Conference is discussed. The index will be published in early 1981 and will be designated as Volume 3 of the proceeding of the sixteenth conference. The index has three parts, a straight numeric tabulation, an author index, and a key word in context (KWIC) index. (JGB)

Burchsted, C.A.

1980-01-01

203

KERMA ratios in pediatric CT dosimetry.  

UK PubMed Central (United Kingdom)

BACKGROUND: Patient organ doses may be estimated from CTDI values. More accurate estimates may be obtained by measuring KERMA (Kinetic Energy Released in Matter) in anthropomorphic phantoms and referencing these values to free-in-air X-ray intensity. OBJECTIVE: To measure KERMA ratios (R(K)) in pediatric phantoms at CT. MATERIALS & METHODS: CT scans produce an air KERMA K in a phantom and an air KERMA K(CT) at isocenter. KERMA ratios (R(K)) are defined as (K/K(CT)), measured using TLD chips in phantoms representing newborns to 10-year-olds. RESULTS: R(K) in the newborn is approximately constant. For the other phantoms, there is a peak R(K) value in the neck. The median R(K) values for the GE scanner at 120 kV were 0.92, 0.83, 0.77 and 0.76 for newborns, 1-year-olds, 5-year-olds and 10-year-olds, respectively. Organ R(K) values were 0.91?±?0.04, 0.84?±?0.07, 0.74?±?0.09 and 0.72?±?0.10 in newborns, 1-year-olds, 5-year-olds and 10-year-olds, respectively. At 120 kV, a Siemens Sensation 16 scanner had R(K) values 5% higher than those of the GE LightSpeed Ultra. CONCLUSION: KERMA ratios may be combined with air KERMA measurements at the isocenter to estimate organ doses in pediatric CT patients.

Huda W; Ogden KM; Lavallee RL; Roskopf ML; Scalzetti EM

2012-05-01

204

Control letters and uncertainties of the kerma patterns in air, dose absorbed in water and dose absorbed in air of the LSCD  

International Nuclear Information System (INIS)

With the purpose of characterizing the component of uncertainty of long term of the patron ionization chambers of the LSCD, for the magnitudes: speed of kerma in air ???, dose speed absorbed in water D??, and speed absorbed dose in air D??, it use the technique of letters of control l-MR/S. This statistical technique it estimates the component of uncertainty of short term by means of the deviation standard inside groups ?? and that of long term by means of the standard deviation among groups ??, being this it finishes an estimator of the stability of the patterns.The letters of control l-MR/S it construct for: i) ???, in radiation field of 60Co for patterns: primary CC01 series 131, secondary NE 2611 series 176, secondary PTW TN30031 series 578 and Third PTW W30001 series 365. ii) D?),en radiation field of 60Co for patterns: primary CC01 series 131, Secondary PTW TN30031 series 578 and tertiary PTW W30001 series 365. iii) I-MR/S with extrapolation chamber PTW primary pattern, measurement realizes in secondary patron fields of 90Sr-90Y. The expanded uncertainty U it is calculated of agreement with the Guide of the ISO/BIPM being observed the following thing: a. In some the cases ??, is the component of the U that more cone mensurations that allow to reduce the value of ??. For example with sizes of subgroup ?? 30 data, or with a number of subgroups ??. That which is achieved automating the mensuration processes. b.The component of the temperature is also one of those that but they contribute to the U, of there the necessity of: to recover the tracking for this magnitude of it influences and to increase the precision in the determinations of the temperature to diminish their influence in the U. c. The percentage difference of the magnitudes dosemeters carried out by it patterns are consistent with U certain. However, it is necessary to diminish the uncertainty in the physical factors different to ?? and ?? for the one case of the primary patterns; because these they should be those of smaller value of U. d. In the case of the secondary patterns and tertiary for the realization of the??? is necessary to determine the corrections explicitly for recombination and polarization; and to analyze their contribution in the U. e. It is necessary to recover the tracking for the mensurations of the humidity. f. It is recommended to continue the control mensurations for each pattern, taking its the least a measure every fifteen days, that it corresponds at two measured for month and 24 at the year. g. The operation of the air conditioned perturb the measumends not to use it, and alone to leave in balance the chamber with the air of the engine room. (Author)

2005-01-01

205

Comparison between absorbed dose to water standards established by water calorimetry at the LNE-LNHB and by application of international air-kerma based protocols for kilovoltage medium energy x-rays  

Science.gov (United States)

Nowadays, the absorbed dose to water for kilovoltage x-ray beams is determined from standards in terms of air-kerma by application of international dosimetry protocols. New standards in terms of absorbed dose to water has just been established for these beams at the LNE-LNHB, using water calorimetry, at a depth of 2 cm in water in accordance with protocols. The aim of this study is to compare these new standards in terms of absorbed dose to water, to the dose values calculated from the application of four international protocols based on air-kerma standards (IAEA TRS-277, AAPM TG-61, IPEMB and NCS-10). The acceleration potentials of the six beams studied are between 80 and 300 kV with half-value layers between 3.01 mm of aluminum and 3.40 mm of copper. A difference between the two methods smaller than 2.1% was reported. The standard uncertainty of water calorimetry being below 0.8%, and the one associated with the values from protocols being around 2.5%, the results are in good agreement. The calibration coefficients of some ionization chambers in terms of absorbed dose to water, established by application of calorimetry and air-kerma based dosimetry protocols, were also compared. The best agreement with the calibration coefficients established by water calorimetry was found for those established with the AAPM TG-61 protocol.

Perichon, N.; Rapp, B.; Denoziere, M.; Daures, J.; Ostrowsky, A.; Bordy, J.-M.

2013-05-01

206

Comparison between absorbed dose to water standards established by water calorimetry at the LNE-LNHB and by application of international air-kerma based protocols for kilovoltage medium energy x-rays.  

UK PubMed Central (United Kingdom)

Nowadays, the absorbed dose to water for kilovoltage x-ray beams is determined from standards in terms of air-kerma by application of international dosimetry protocols. New standards in terms of absorbed dose to water has just been established for these beams at the LNE-LNHB, using water calorimetry, at a depth of 2 cm in water in accordance with protocols. The aim of this study is to compare these new standards in terms of absorbed dose to water, to the dose values calculated from the application of four international protocols based on air-kerma standards (IAEA TRS-277, AAPM TG-61, IPEMB and NCS-10). The acceleration potentials of the six beams studied are between 80 and 300 kV with half-value layers between 3.01 mm of aluminum and 3.40 mm of copper. A difference between the two methods smaller than 2.1% was reported. The standard uncertainty of water calorimetry being below 0.8%, and the one associated with the values from protocols being around 2.5%, the results are in good agreement. The calibration coefficients of some ionization chambers in terms of absorbed dose to water, established by application of calorimetry and air-kerma based dosimetry protocols, were also compared. The best agreement with the calibration coefficients established by water calorimetry was found for those established with the AAPM TG-61 protocol.

Perichon N; Rapp B; Denoziere M; Daures J; Ostrowsky A; Bordy JM

2013-05-01

207

Estudo comparativo da qualidade da imagem e do kerma, de entrada e de saída, em simulador de tórax utilizando sistemas analógico e digitalizado CR de aquisição de imagens Comparative study of image quality and entrance and exit air kerma measurements on chest phantom utilizing analog and CR digital imaging systems  

Directory of Open Access Journals (Sweden)

Full Text Available OBJETIVO: O processo de migração de sistemas analógicos para digitalizados, para aplicações diagnósticas, requer cuidados específicos, a fim de manter a qualidade das imagens e minimizar a dose no paciente. Este trabalho tem como objetivo analisar e comparar a qualidade da imagem e o kerma num simulador não antropomórfico de tórax gerados por sistemas analógicos e digitalizados CR. MATERIAIS E MÉTODOS: Foram analisados a qualidade da imagem e o kerma, de entrada e saída, no simulador para dois equipamentos de raios X diferentes (Siemens e Emic), com diferentes sistemas de retificação de onda (12 pulsos e alta frequência). Ambos os sistemas (analógico e digitalizado) estavam sendo utilizados no mesmo local. Foram geradas imagens em filme e em image plates. RESULTADOS: Foi observado aumento na tensão e/ou na carga transportada pelo tubo de raios X quando houve a migração para o sistema CR, para manutenção das características diagnósticas da imagem. Isto resultou em aumento de kerma coletado. CONCLUSÃO: As maiores diferenças determinadas (aumento de dose e redução da qualidade da imagem) foram observadas no equipamento com retificação de onda de 12 pulsos e transdutor de imagem CR (image plates).OBJECTIVE: The process of migration from analog to digital imaging system requires specific attention to preserve images quality and minimizing the dose to the patients. The present study was aimed at analyzing and comparing images quality and entrance and exist air kerma measurements in a non-anthropomorphic chest phantom with analog and CR digital imaging systems. MATERIALS AND METHODS: Two different X-ray units (Siemens and Emic) with different wave rectification systems (12-pulse and high-frequency) were utilized in a single institution along the process of migration from analog to CR digital imaging system. Images were acquired on films and image plates. RESULTS: An increase on the X-ray tube peak voltage and/or load was observed in the migration from analog to CR digital system to preserve the diagnostic quality of the image. As a result, an increase in the air kerma rate was observed. CONCLUSION: The greatest differences (increase in dose and decrease in image quality) were observed with the 12-pulse wave rectification system with the CR image transducer (imaging plates).

Renata Matos da Luz; Gabriela Hoff

2010-01-01

208

Estudo comparativo da qualidade da imagem e do kerma, de entrada e de saída, em simulador de tórax utilizando sistemas analógico e digitalizado CR de aquisição de imagens/ Comparative study of image quality and entrance and exit air kerma measurements on chest phantom utilizing analog and CR digital imaging systems  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese OBJETIVO: O processo de migração de sistemas analógicos para digitalizados, para aplicações diagnósticas, requer cuidados específicos, a fim de manter a qualidade das imagens e minimizar a dose no paciente. Este trabalho tem como objetivo analisar e comparar a qualidade da imagem e o kerma num simulador não antropomórfico de tórax gerados por sistemas analógicos e digitalizados CR. MATERIAIS E MÉTODOS: Foram analisados a qualidade da imagem e o kerma, de entra (more) da e saída, no simulador para dois equipamentos de raios X diferentes (Siemens e Emic), com diferentes sistemas de retificação de onda (12 pulsos e alta frequência). Ambos os sistemas (analógico e digitalizado) estavam sendo utilizados no mesmo local. Foram geradas imagens em filme e em image plates. RESULTADOS: Foi observado aumento na tensão e/ou na carga transportada pelo tubo de raios X quando houve a migração para o sistema CR, para manutenção das características diagnósticas da imagem. Isto resultou em aumento de kerma coletado. CONCLUSÃO: As maiores diferenças determinadas (aumento de dose e redução da qualidade da imagem) foram observadas no equipamento com retificação de onda de 12 pulsos e transdutor de imagem CR (image plates). Abstract in english OBJECTIVE: The process of migration from analog to digital imaging system requires specific attention to preserve images quality and minimizing the dose to the patients. The present study was aimed at analyzing and comparing images quality and entrance and exist air kerma measurements in a non-anthropomorphic chest phantom with analog and CR digital imaging systems. MATERIALS AND METHODS: Two different X-ray units (Siemens and Emic) with different wave rectification syste (more) ms (12-pulse and high-frequency) were utilized in a single institution along the process of migration from analog to CR digital imaging system. Images were acquired on films and image plates. RESULTS: An increase on the X-ray tube peak voltage and/or load was observed in the migration from analog to CR digital system to preserve the diagnostic quality of the image. As a result, an increase in the air kerma rate was observed. CONCLUSION: The greatest differences (increase in dose and decrease in image quality) were observed with the 12-pulse wave rectification system with the CR image transducer (imaging plates).

Luz, Renata Matos da; Hoff, Gabriela

2010-02-01

209

Air kerma to HP(3) conversion coefficients for photons from 10 keV to 10 MeV, calculated in a cylindrical phantom.  

UK PubMed Central (United Kingdom)

In the framework of the ORAMED project (Optimization of RAdiation protection for MEDical staff), funded by the European Union Seventh Framework Programme, different studies were aimed at improving the quality of radiation protection in interventional radiology and nuclear medicine. The main results of the project were presented during a final workshop held in Barcelona in January 2011, the proceedings of which are available in the open literature. One of the ORAMED tasks was focused on the problem of eye-lens photon exposure of the medical staff, a topic that gained more importance especially after the ICRP decision to lower the limiting equivalent dose to 20 mSv per year. The present technical note has the scope, besides briefly summarising the physical reasons of the proposal and the practical implications, to provide, in tabular form, a set of air kerma to Hp(3) conversion coefficients based on the adoption of a theoretical cylindrical model that is well suited for reproduction of the mass and the shape of a human head.

Gualdrini G; Bordy JM; Daures J; Fantuzzi E; Ferrari P; Mariotti F; Vanhavere F

2013-05-01

210

Comparison of the air kerma standards for 137Cs and 60Co gamma-ray beams between the IAEA and the NIST  

Science.gov (United States)

A comparison of the air kerma standards for 137Cs and 60Co gamma-ray beams was performed between the NIST and the IAEA. Two reference class ionization chambers owned by the IAEA were used as part of this comparison and were calibrated at each facility. The calibration coefficients, NK, were determined for both chambers and in both gamma-ray beams. The measurements were performed at the IAEA and NIST facilities starting in the fall of 2009 and were completed in 2010. The comparison ratio of the calibration coefficients for each chamber, NK,IAEA/NK,NIST, between the IAEA and NIST was 0.999 and 0.997 for the 137Cs and 60Co gamma-ray beams respectively. The relative standard uncertainty for each of these ratios is 0.5%. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by SIM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Minniti, Ronaldo; Czap, Ladislav

2011-01-01

211

Comparison of air kerma measurements between the PTB and the IAEA for x-radiation qualities used in general diagnostic radiology and mammography  

Science.gov (United States)

A comparison of the air kerma standards for x-radiation qualities used in general diagnostic radiology and mammography, identified as EURAMET.RI(I)-S10 (EURAMET project #1221), was performed between the PTB and the IAEA. Two spherical and two parallel-plate reference-class ionization chambers of the IAEA and 12 beam qualities standardized in the IEC standard 61267:2005 plus 7 additional standard beam qualities established at both laboratories were selected for the comparison. The calibration coefficients were determined for the transfer chambers at the PTB in September 2012 and before and after this at the IAEA Dosimetry Laboratory. The results show the calibration coefficients of both laboratories to be in good agreement within the standard uncertainty of the comparison of about 0.47%. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by EURAMET, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Csete, István; Büermann, Ludwig; Gomola, Igor; Girzikowsky, Reinhard

2013-01-01

212

Air kerma to HP(3) conversion coefficients for photons from 10 keV to 10 MeV, calculated in a cylindrical phantom.  

Science.gov (United States)

In the framework of the ORAMED project (Optimization of RAdiation protection for MEDical staff), funded by the European Union Seventh Framework Programme, different studies were aimed at improving the quality of radiation protection in interventional radiology and nuclear medicine. The main results of the project were presented during a final workshop held in Barcelona in January 2011, the proceedings of which are available in the open literature. One of the ORAMED tasks was focused on the problem of eye-lens photon exposure of the medical staff, a topic that gained more importance especially after the ICRP decision to lower the limiting equivalent dose to 20 mSv per year. The present technical note has the scope, besides briefly summarising the physical reasons of the proposal and the practical implications, to provide, in tabular form, a set of air kerma to Hp(3) conversion coefficients based on the adoption of a theoretical cylindrical model that is well suited for reproduction of the mass and the shape of a human head. PMID:23097520

Gualdrini, G; Bordy, J M; Daures, J; Fantuzzi, E; Ferrari, P; Mariotti, F; Vanhavere, F

2012-10-24

213

Key comparison BIPM.RI(I)-K7 of the air-kerma standards of the PTB, Germany and the BIPM in mammography x-rays  

Science.gov (United States)

A first key comparison has been made between the air-kerma standards of the PTB and the BIPM in mammography x-ray beams. The results show the standards to be in agreement at the level of the combined standard uncertainty of 3.7 parts in 103. A comparison of the standards has also been made in simulated mammography x-ray beams. The standards agree at the level of the combined standard uncertainty of 3.5 parts in 103. The results are analysed and presented in terms of degrees of equivalence for entry in the BIPM key comparison database. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI Section I, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Kessler, C.; Burns, D. T.; Büermann, L.

2011-01-01

214

APMP/TCRI key comparison report of measurement of air kerma for medium-energy x-rays (APMP.RI(I)-K3)  

International Nuclear Information System (INIS)

[en] The APMP/TCRI Dosimetry Working Group performed the APMP.RI(I)-K3 key comparison of measurement of air kerma for medium-energy x-rays (100 kV to 250 kV) between 2000 and 2003. In total, 11 institutes took part in the comparison, among which 8 were APMP member laboratories. Two commercial cavity ionization chambers were used as transfer instruments and circulated among the participants. All the participants established the 100 kV, 135 kV, 180 kV and 250 kV x-ray beam qualities equivalent to those of the BIPM. The results showed that the maximum difference between the participants and the BIPM in the medium-energy x-ray range, evaluated using the comparison data of the linking laboratories ARPANSA and PTB, is less than 1.4%. The degrees of equivalence between the participants are presented and this comparison confirms the calibration capabilities of the participating laboratories. (authors)

215

APMP/TCRI key comparison report of measurement of air kerma for medium-energy x-rays (APMP.RI(I)-K3)  

Energy Technology Data Exchange (ETDEWEB)

The APMP/TCRI Dosimetry Working Group performed the APMP.RI(I)-K3 key comparison of measurement of air kerma for medium-energy x-rays (100 kV to 250 kV) between 2000 and 2003. In total, 11 institutes took part in the comparison, among which 8 were APMP member laboratories. Two commercial cavity ionization chambers were used as transfer instruments and circulated among the participants. All the participants established the 100 kV, 135 kV, 180 kV and 250 kV x-ray beam qualities equivalent to those of the BIPM. The results showed that the maximum difference between the participants and the BIPM in the medium-energy x-ray range, evaluated using the comparison data of the linking laboratories ARPANSA and PTB, is less than 1.4%. The degrees of equivalence between the participants are presented and this comparison confirms the calibration capabilities of the participating laboratories. (authors)

Lee, J.H.; Hwang, W.S. [Institute of Nuclear Energy Research, Longtan, Taiwan (China); Kotler, L.H.; Webb, D.V. [Australian Radiation Protection and Nuclear Safety Agency, Yallambie (Australia); Buermann, L. [Physikalisch Technische Bundesanstalt, Braunschweig (Germany); Burns, D.T. [Bureau International de Poids et Mesures, 92 - Sevres (France); Takeyeddin, M. [Atomic Energy Commission, Damascus (Syrian Arab Republic); Shaha, V.V. [Bhabha Atomic Research Centre, Mumbai (India); Srimanoroth, S. [Department of Medical Sciences, Nonthaburi (Thailand); Meghzifene, A. [International Atomic Energy Agency, Vienna (Austria); Hah, S.H.; Chun, K.J. [Korea Research Institute of Standards and Science, Yusong (Korea, Republic of); Kadni, T.B. [Malaysian Nuclear Agency, Kajang (Malaysia); Takata, N. [National Metrology Institute of Japan, Tsukuba (Japan); Msimang, Z. [National Metrology Institute of South Africa, Pretoria (South Africa)

2008-10-15

216

Comparison of mammography radiation dose values obtained from direct incident air kerma measurements with values from measured X-ray spectral data  

International Nuclear Information System (INIS)

The application of X-rays and ionising radiations for diagnostic radiology requires that the procedure is justified and optimised and that the exposure to the patient is kept as low as possible, without compromising image information. X-ray mammography is considered to be the most sensitive technique currently available for early detection of breast cancer. The magnitude of the absorbed radiation dose to the breast from mammography X-ray beams forms an important part of the quality control of the mammographic examination since it gives an indication of the performance of the mammographic imaging system as well as an estimated risk to the patient. In this work mean glandular dose (MGD) values were obtained at various tube potentials and tube loadings (TL) using direct measurements of the incident air kerma (ESAK) at the surface of a standard breast phantom and also from spectral measurements acquired with a solid-state detector. Comparisons of the MGD values thus derived are presented and the relationship between MGD, phantom thickness, image quality and tube operating parameters is discussed.

2005-01-01

217

Radiological investigations at the "Taiga" nuclear explosion site, part II: man-made ?-ray emitting radionuclides in the ground and the resultant kerma rate in air.  

UK PubMed Central (United Kingdom)

Samples of soil and epigeic lichens were collected from the "Taiga" peaceful nuclear explosion site (61.30°N 56.60°E, the Perm region, Russia) in 2009 and analyzed using high resolution ?-ray spectrometry. For soil samples obtained at six different plots, two products of fission ((137)Cs and (155)Eu), five products of neutron activation ((60)Co, (94)Nb, (152)Eu, (154)Eu, (207)Bi) and (241)Am have been identified and quantified. The maximal activity concentrations of (60)Co, (137)Cs, and (241)Am for the soils samples were measured as 1650, 7100, and 6800 Bq kg(-1) (d.w.), respectively. The deposit of (137)Cs for the top 20 cm of soil on the tested plots at the "Taiga" site ranged from 30 to 1020 kBq m(-2); the maximal value greatly (by almost 3 orders of magnitude) exceeded the regional background (from global fallout) level of 1.4 kBq m(-2). (137)Cs contributes approximately 57% of the total ground inventory of the man-made ?-ray emitters for the six plots tested at the "Taiga" site. The other major radionuclides -(241)Am and (60)Co, constitute around 40%. Such radionuclides as (60)Co, (137)Cs, (241)Am, and (207)Bi have also been determined for the epigeic lichens (genera Cladonia) that colonized certain areas at the ground lip produced by the "Taiga" explosion. Maximal activity concentrations (up to 80 Bq kg(-1) for (60)Co, 580 Bq kg(-1) for (137)Cs, 200 Bq kg(-1) for (241)Am, and 5 Bq kg(-1) for (207)Bi; all are given in terms of d.w.) have been detected for the lower dead section of the organisms. The air kerma rates associated with the anthropogenic sources of gamma radiation have been calculated using the data obtained from the laboratory analysis. For the six plots tested, the kerma rates ranged from 50 to 1200 nGy h(-1); on average, 51% of the dose can be attributed to (137)Cs and 45% to (60)Co. These estimates agree reasonably well with the results of the in situ measurements made during our field survey of the "Taiga" site in August 2009.

Ramzaev V; Repin V; Medvedev A; Khramtsov E; Timofeeva M; Yakovlev V

2012-07-01

218

Microionization chamber air-kerma calibration coefficients as a function of photon energy for x-ray spectra in the range of 20-250 kVp relative to 60Co.  

UK PubMed Central (United Kingdom)

PURPOSE: To investigate the applicability of a wide range of microionization chambers for reference dosimetry measurements in low- and medium-energy x-ray beams. METHODS: Measurements were performed with six cylindrical microchamber models, as well as one scanning chamber and two Farmer-type chambers for comparison purposes. Air-kerma calibration coefficients were determined at the University of Wisconsin Accredited Dosimetry Calibration Laboratory for each chamber for a range of low- and medium-energy x-ray beams (20-250 kVp), with effective energies ranging from 11.5 keV to 145 keV, and a (60)Co beam. A low-Z proof-of-concept microchamber was developed and calibrated with and without a high-Z silver epoxy on the collecting electrode. RESULTS: All chambers composed of low-Z materials (Z ? 13), including the Farmer-type chambers, the scanning chamber, and the PTW TN31014 and the proof-of-concept microchambers, exhibited air-kerma calibration coefficients with little dependence on the quality of the beam. These chambers typically exhibited variations in calibration coefficients of less than 3% with the beam quality, for medium energy beams. However, variations in air-kerma calibration coefficients of greater than 50% were measured over the range of medium-energy x-ray beams for each of the microchambers containing high-Z collecting electrodes (Z > 13). For these high-Z chambers, which include the Exradin A14SL and A16 chambers, the PTW TN31006 chamber, the IBA CC01 chamber, and the proof-of-concept chamber containing silver, the average variation in air-kerma calibration coefficients between any two calibration beams was nearly 25% over the entire range of beam qualities investigated. CONCLUSIONS: Due to the strong energy dependence observed with microchambers containing high-Z components, these chambers may not be suitable dosimeters for kilovoltage x-ray applications, as they do not meet the TG-61 requirements. It is recommended that only microchambers containing low-Z materials (Z ? 13) be considered for air-kerma calibrations for reference dosimetry in low- and medium-energy x-ray beams.

Snow JR; Micka JA; DeWerd LA

2013-04-01

219

Calibration of area-kerma meters  

International Nuclear Information System (INIS)

[en] Two large area, plane ionization chambers (monitors) were calibrated to measure the integral of air collision kerma over an area, ?Kc,air dA. Because of the field inhomogeneities determinations of ?Kc,air dA were derived according to its definition using an X ray film calibrated with 80 TL dosimeters. A simplified calibration method is frequently used which approximates ?Kc,air dA with the product of field area and kerma in the centre of the field. Simplified calibrations were performed for different field areas and distances from the focus. Deviations between the two methods were found to vary with both field area and distance from the focus. The main reasons for the deviations are different anode filtrations (heel effect) and the influence of off-focal radiation, which cause field inhomogeneities in Kc,air. The influence of off-focal radiation varies with distance from the focus. (author). 8 refs, 6 figs

1994-01-01

220

Direct reference air-kerma rate calibration of 192Ir for a thimble-type ionization chamber in a cylindrical solid phantom  

Science.gov (United States)

International and national reports strongly recommend experimental verification of the calibration of new HDR 192Ir sources prior to their clinical application for afterloading brachytherapy. To guarantee traceability, calibrated transfer standards are used, e.g. the recommended well-type ionization chambers (WIC) or certain detector-phantom arrangements (DPA) consisting of a thimble-type ionization chamber with a solid phantom. In Germany, direct calibrations for 192Ir were only provided for WICs. In June 2010, the PTB directly calibrated a DPA-transfer standard in the quantity reference air-kerma rate (RAKR) for 192Ir photons for the University Hospital Tübingen. This direct calibration provides the advantage that the comprehensive RAKR 192Ir calibration coefficient already takes all influence quantities into account—their correction factors are thus unified—except for the air-density correction k?. The DPA-transfer standard described above and a WIC used as a reference were compared for acceptance tests of three GammaMedplus HDR 192Ir afterloading sources. The measurement uncertainty of the WIC and of the DPA-transfer standard were ±2.6%(k = 2) and ±2.8%(k = 2) respectively. A strong correlation was found between these measurement results with a coefficient of determination of r2 = 0.9998. Determining the RAKR of an HDR 192Ir afterloading source is as simple with the DPA as it is with WIC. The direct 192Ir calibrated DPA-transfer standard can therefore be used alternatively in future with the same measurement uncertainty if no WIC is available.

Kaulich, Theodor W.; Quast, Ulrich; Bamberg, Michael; Selbach, Hans-Joachim

2012-10-01

 
 
 
 
221

The calculation of wall and non-uniformity correction factors for the BIPM air-kerma standard for 60Co using the Monte Carlo code PENELOPE  

International Nuclear Information System (INIS)

Traditionally, the correction factor kwall for attenuation and scatter in the walls of cavity ionization chamber primary standards has been evaluated experimentally using an extrapolation method. During the past decade, there have been a number of Monte Carlo calculations of kwall indicating that for certain ionization chamber types the extrapolation method may not be valid. In particular, values for kwall have been proposed that, if adopted by each laboratory concerned, would have a significant effect on the results of international comparisons of air-kerma primary standards. The calculations have also proposed new values for the axial component kan of the point-source uniformity correction. Central to the results of international comparisons is the BIPM air-kerma standard. Unlike most others, the BIPM standard is of the parallel-plate design for which the extrapolation method for evaluating kwall should be valid. The value in use at present is kwall=1.0026 (standard uncertainty 0.0008). Rogers and Treurniet calculated the value kwall=1.0014 for the BIPM standard, which is in moderate agreement with the value in use (no overall uncertainty was given). However, they also calculated kan=1.0024 (statistical uncertainty 0.0003) which is very different from the value kan=0.9964 (0.0007) in use at present for the BIPM standard. A new 60Co facility has recently been installed at the BIPM and the opportunity was taken to re-evaluate the correction factors for the BIPM standard in this new beam. Given that almost all of the Monte Carlo work to date has used the EGS Monte Carlo code, it was decided to use the code PENELOPE. The new source, container, head and collimating jaws were simulated in detail with more that fifty components being modelled, as shown. This model was used to create a phase-space file in the plane 90 cm from the source. The normalized distribution of photon number with energy is shown, where the various sources of scattered photons are identified. This phase-space file was used to calculate kwall for the BIPM standard using the technique of photon regeneration. At the point of each photon interaction in the chamber wall, a new photon is generated with the same energy and direction as the incoming photon. The deposition of energy in the air cavity by regenerated photons effectively corrects for attenuation in the wall. At the same time, any outgoing scattered photon is tagged so that a correction for the energy deposition due to scattered photons may be evaluated. The result of these calculations is kwall=1.0017 (statistical uncertainty 0.0001), which is in good agreement with previous results. The overall uncertainties remain to be evaluated. For the calculation of kan, a modified technique was used which makes use of the full phase-space information rather than assuming, as is usual, that the beam is well approximated by a point source. When using the same model for the BIPM standard as used previously, the result kan=1.0032 (statistical uncertainty 0.0005) agrees reasonably well with previous results (the small difference may be due to the use of a point source rather than the realistic angular distribution). However, there is evidence that these new values are an artefact of the method and model and that the true non-uniformity correction is much closer to unity. Before implementing any new kan value for the BIPM standard, a more detailed study will be undertaken to explain the large difference between the new and existing values

2002-01-01

222

Ferramenta computacional para avaliação de kerma no ar em aplicações de radioproteção em áreas de internação de pacientes: proposição de um método simples para avaliação experimental Computational toolkit for evaluating air kerma with the purpose of radiation protection of hospital inpatients: proposal of a simple experimental evaluation method  

Directory of Open Access Journals (Sweden)

Full Text Available OBJETIVO: Apresentar uma ferramenta de análise de dados que pode ser utilizada para proteção de pacientes e trabalhadores em áreas de uso de equipamentos móveis. MATERIAIS E MÉTODOS: Foi desenvolvida uma ferramenta, em planilha ativa Excel®, que utiliza medidas de exposição para gerar um banco de dados de fatores de forma e calcular o kerma no ar ao entorno de um leito. O banco de dados inicial foi coletado com três equipamentos móveis. Um espalhador não antropomórfico foi utilizado, sendo realizadas medidas de exposição em uma malha de (4,2 × 4,2) m², ao passo de 0,3 m. RESULTADOS: A ferramenta calcula o kerma no ar (associado à exposição de pacientes expostos e ao equivalente de dose ambiente) à radiação secundária. Para distâncias inferiores a 60,0 cm, valores acima do limite máximo de equivalente de dose ambiente definido para área livre (0,5 mSv/ano) foram verificados. Os dados coletados a 2,1 m foram sempre inferiores a 12% do referido limite. CONCLUSÃO: A ferramenta é capaz de auxiliar na proteção radiológica de pacientes e trabalhadores, quando associada à coleta de dados adequada, pois possibilita a determinação de áreas livres ao entorno de leitos em áreas onde equipamentos móveis geradores de radiação X são utilizados.OBJECTIVE: To present a data analysis toolkit that may be utilized with the purpose of radiation protection of hospital inpatients and workers in areas where mobile apparatuses are used. MATERIALS AND METHODS: An Excel® ActiveSheet was utilized to develop a computational toolkit with exposure measurements to generate a database of shape factors and to calculate the air kerma around hospital beds. The initial database included data collected with three mobile apparatuses. A non-anthropomorphic phantom was utilized and exposure measurements were performed on a (4.2 × 4.2) m² mesh-grid at 0.3 m steps. RESULTS: The toolkit calculates the air kerma (associated with patients' radiation exposure and with ambient equivalent dose) under secondary radiation. For distances lower than 60.0 cm, values above the maximum ambient equivalent dose threshold defined for radiation free areas (0.5 mSv/year) were verified. Data collected at 2.1 m have always presented values lower than 12% of that threshold. CONCLUSION: The toolkit can aid in the radiological protection of patients and workers, provided it is combined with appropriate data collection, since it allows the determination of radiation free areas around beds in rooms where mobile X-ray apparatuses are utilized.

Gabriela Hoff; José Rodrigo Mendes Andrade; Andréia Caroline Fischer da Silveira Fischer; Alexandre Bacelar

2012-01-01

223

The influence of micro location on the air freezing index  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper are exposed research results of air freezing index values occurring in area of Bosnia and Herzegovina. Theoretic probabilities of air freezing index occurrence are calculated, based on data of 26 meteorological stations, in order to determine its return periods of appearing (the probability of air freezing index appearance average once in period considered). To this purpose five the most frequent in praxis theoretic distribution functions are used: GAUSS, GALTON, LOG-PEARSON, PEARSON and GUMBEL. As the most appropriate function for all meteorogic stations the LOG-PEARSON was selected because it on the best way approximates values of calculated air freezing index. Regarding to influence of micro location on the value of air freezing index some independent parameters of location which are measurable (variables) and have supposed influence, are took in analysis. To this purpose the mathematic model of multi variant regression analysis was used and the regression equation of the associated influence of independent parameters was determined. Using this discovered equation designers of road pavement can for each micro-location cutted by the road line, calculate the air freezing index and check the pavement structure on the harmful freezing effects.

Mazi? Branko

2004-01-01

224

Hold your breath: A new index of air quality  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Environmental quality and climate change have long attracted attention in policy debates. Recently, air quality has emerged on the policy agenda. We calculate a new index of air quality using CO2 and SO2 emissions per capita as indicators and provide a ranking for 122 countries from 1985 to 2005. Th...

Buehn, Andreas; Farzanegan, Mohammad Reza

225

Relationship between kerma and treatment volume in intracavitary radiation therapy  

International Nuclear Information System (INIS)

[en] Data on 200 patients with carcinoma of the uterine cervix irradiated with afterloading brachytherapy using various high dose rate source configurations have been evaluated with respect to the total reference air kerma and the treatment volume as well as other volumes of interest. The experimental results showed good correlation between kerma and volume, and have also been discussed theoretically for the single-source, double-source and triple-source configurations. The possibility of using the demonstrated kerma-volume relationships for simple estimation of volumes enables us to select the appropriate treatment plan for the individual patient and to evaluate the results of the treatment. (orig.)

1990-01-01

226

Calculation of conversion factors of kerma in air to the ambient dose equivalent using monoenergetic photons beam in range of 0,01 MeV to 50 MeV  

International Nuclear Information System (INIS)

The International Commission on Radiological Protection, presented news conversion factor of kerma in air, Ka-r, to the ambient dose equivalent, H*(d), using monoenergetic photons beam in the range of 0.01 to 10 MeV. This work presents results for the same conversions factors mentioned above, but only to the monoenergetic photons beam to 50 MeV contributing this way for future works. The method used to obtain the results was the Monte Carlo code MCNP version 4(2). (author)

2002-01-01

227

Nuclear heating constant KERMA library  

International Nuclear Information System (INIS)

Based on evaluated nuclear data file JENDL-3, published in April 1990, we produced a nuclear group constant KERMA library for fusion nuclear group constant set FUSION-J3 instead of the KERMA library for GICX40. Neutron KERMA factors were calculated directly by considering the kinematics in collisions, called 'Direct Method'. In this method, uncertainties in calculated KERMA factors are expected to be reduced since subtraction between great numbers is not necessary as in the energy balance method. Gamma ray KERMA factors were calculated by the energy balance method. In case of gamma ray, there is no problem in calculating gamma ray KERMA by the energy balance method since gamma ray heating means energy deposition of kinetic energy in gamma ray. Produced KERMA library is applicable to fusion neutronics calculations. It is expected that highly accurate results will be obtained in nuclear heating calculations for fusion reactor designs. (author).

1991-01-01

228

The use of air quality index (AQI) in environmental management  

International Nuclear Information System (INIS)

[en] The air quality index (AQI) is considered a global air quality index in a particular moment or day and in a specific monitoring station. The AQI is to be interpreted as a guiding air quality index for the general public. Specialists should take into account other factors when studying the pollution levels. The behaviour of air pollution is studied by using the AQI in two monitoring points in Regla, where the main pollutants are measured: SO2, NO2 and total suspended particulates. It was founded that particulates and NO2 are the pollutants that contribute most to the air quality deterioration, which occurs with greater frequency-days in the categories Poor and Bad, and show an increase in the categories Terrible and Critical. The necessary recommendations for the reduction of air pollution are given. The use of this AQI for assessing air pollution in settlements is recommended as a good tool for environmental information and management. A visual scale is proposed to improve and facilitate the public's understanding

2006-01-01

229

Alberta's air quality index : facts at your fingertip  

International Nuclear Information System (INIS)

[en] Alberta Environment measures the airborne concentrations of carbon dioxide, fine particulate matter, nitrogen dioxide, ozone and sulphur dioxide on a continuous basis at air quality monitoring stations in Edmonton, Calgary, Red Deer and Beaverlodge. Every hour, the readings are converted to an Air Quality Index (AQI) number to report on Alberta's outdoor air quality as either good, fair, poor or very poor. The categories relate to guidelines under Alberta's Environmental Protection and Enhancement Act and reflect the maximum acceptable levels specified by the National Ambient Air Quality Objectives. Current air quality conditions are available to the public through Alberta Environment's web site or by phoning a toll free number. Both Edmonton and Calgary report good air quality at least 90 per cent of the time. Occasionally, air quality in the two cities may reach the fair category, but it is seldom poor. Fair, poor or very poor air quality occurs with strong temperature inversion and light winds. Under these conditions, air pollutants, usually from automobiles, are trapped in a layer of stagnant air. Fair and poor air quality can also be caused by summer heat when photochemical smog forms by chemical reactions with oxides of nitrogen and volatile hydrocarbons. 1 ref., 1 tab., 1 fig

2003-01-01

230

Final report on APMP.RI(I)-K1: APMP/TCRI key comparison report of measurement of air kerma for 60Co gamma-rays  

Science.gov (United States)

The APMP.RI(I)-K1 key comparison of the measurement standards of air kerma for 60Co gamma-rays was undertaken by the APMP/TCRI Dosimetry Working Group between 2004 and 2006, coordinated by the Korean Research Institute of Standards and Science (KRISS). In total, 10 institutes took part in the comparison, among which 7 were APMP member laboratories. Three Farmer-type commercial cavity chambers were used as transfer chambers and circulated among the participants. All the participants carried out their measurements according to the guidelines for the comparison established by the KRISS with the cooperation of the ARPANSA. For each transfer chamber, an NMI calibration coefficient was obtained and a ratio derived by dividing by the average result from the linking laboratories, ARPANSA and NMIJ. The APMP comparison reference value for each chamber was calculated as the mean of the NMI-determined calibration coefficients divided by the average result from the linking laboratories. The results showed that the maximum difference between the APMP linked ratio of a participating NMI and the APMP reference value was 1.76%. The measured ratios of the calibration coefficient RNMI, BIPM between the participating NMI and the BIPM via the link laboratories for the transfer chambers were obtained. The maximum expanded uncertainty of RNMI, BIPM for any participating laboratory was 2.0%. The degree of equivalence of each participating laboratory with respect to the key comparison reference value was also evaluated. The expanded uncertainty of the difference between the results ranged from 0.5% to 1.2%. The pair-wise degree of equivalence between each pair of laboratories was also obtained and the largest difference of the expanded uncertainty of the difference for any pair-wise degree of equivalence was within the expanded uncertainty of the measurement for the pair of laboratories. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Chun, K. J.; Butler, D. J.; Webb, D.; Mahant, A. K.; Meghzifene, A.; Lee, J. H.; Hah, S. H.; Kadni, T. B.; Zhang, Y.; Kurosawa, T.; Msimang, Z. L. M.; Caseria, E. S.

2013-01-01

231

Air pollution forecast in cities by an air pollution index highly correlated with meteorological variables  

International Nuclear Information System (INIS)

There are many different air pollution indexes which represent the global urban air pollution situation. The daily index studied here is also highly correlated with meteorological variables and this index is capable of identifying those variables that significantly affect the air pollution. The index is connected with attention levels of NO2, CO and O3 concentrations. The attention levels are fixed by a law proposed by the Italian Ministries of Health and Environment. The relation of that index with some meteorological variables is analysed by the linear multiple partial correlation statistical method. Florence, Milan and Vicence were selected to show the correlation among the air pollution index and the daily thermic excursion, the previous day's air pollution index and the wind speed. During the January-March period the correlation coefficient reaches 0.85 at Milan. The deterministic methods of forecasting air pollution concentrations show very high evaluation errors and are applied on limited areas around the observation stations, as opposed to the whole urban areas. The global air pollution, instead of the concentrations at specific observation stations, allows the evaluation of the level of the sanitary risk regarding the whole urban population. (Author)

2001-01-01

232

Developing a risk-based air quality health index  

Science.gov (United States)

We developed a risk-based, multi-pollutant air quality health index (AQHI) reporting system in Hong Kong, based on the Canadian approach. We performed time series studies to obtain the relative risks of hospital admissions for respiratory and cardiovascular diseases associated with four air pollutants: sulphur dioxide, nitrogen dioxide, ozone, and particulate matter with an aerodynamic diameter less than 10 ?m (PM10). We then calculated the sum of excess risks of the hospital admissions associated with these air pollutants. The cut-off points of the summed excess risk, for the issuance of different health warnings, were based on the concentrations of these pollutants recommended as short-term Air Quality Guidelines by the World Health Organization. The excess risks were adjusted downwards for young children and the elderly. Health risk was grouped into five categories and sub-divided into eleven bands, with equal increments in excess risk from band 1 up to band 10 (the 11th band is 'band 10+'). We developed health warning messages for the general public, including at-risk groups: young children, the elderly, and people with pre-existing cardiac or respiratory diseases. The new system addressed two major shortcomings of the current standard-based system; namely, the time lag between a sudden rise in air pollutant concentrations and the issue of a health warning, and the reliance on one dominant pollutant to calculate the index. Hence, the AQHI represents an improvement over Hong Kong's existing air pollution index.

Wong, Tze Wai; Tam, Wilson Wai San; Yu, Ignatius Tak Sun; Lau, Alexis Kai Hon; Pang, Sik Wing; Wong, Andromeda H. S.

2013-09-01

233

Air quality health index variation across British Columbia  

Energy Technology Data Exchange (ETDEWEB)

The new Air Quality Health Index (AQHI) is a tool aiming to present the health risks related to air pollution in Canada. This index can be used by individuals to help them reduce their health risk resulting from poor air quality. An assessment of the short term health risk induced by poor air quality is provided to Canadians through the AQHI. The AQHI is based on three factors: ambient concentrations of nitrogen dioxide, fine particulate matter and ozone, the local air quality information being presented on an hourly and daily basis and being calculated each hour for several locations across Canada. Pulmonary disorders and impacts on cardiac function are the more significant short term health risks. Longer term exposure to poor air quality is associated with increased rates of allergies and asthma, low birth weight, atherosclerosis, poorer lung development in children, lung cancer and ear infections. Information on the AQHI and on the variation across British Columbia of the health risk associated with this index are presented in this document. 19 refs., 5 tabs., 5 figs.

Hasselback, P. [Interior Health Authority, Kelowna, BC (Canada); Taylor, E. [British Columbia Ministry of Health Living and Sport, Vancouver, BC (Canada)

2010-09-15

234

Measurement of conversion coefficients between air Kerma and personal dose equivalent and backscatter factors for diagnostic X-ray beams; Determinacao experimental dos coeficientes de conversao de Kerma no ar para o equivalente de dose pessoal, Hp(d), e fatores de retroespalhamento em feixes de raios-x diagnostico  

Energy Technology Data Exchange (ETDEWEB)

Two sets of quantities are import in radiological protection: the protection and operational quantities. Both sets can be related to basic physical quantities such as kerma through conversion coefficients. For diagnostic x-ray beams the conversion coefficients and backscatter factors have not been determined yet, those parameters are need for calibrating dosimeters that will be used to determine the personal dose equivalent or the entrance skin dose. Conversion coefficients between air kerma and personal dose equivalent and backscatter factors were experimentally determined for the diagnostic x-ray qualities RQR and RQA recommended by the International Electrotechnical Commission (IEC). The air kerma in the phantom and the mean energy of the spectrum were measured for such purpose. Harshaw LiF-100H thermoluminescent dosemeters (TLD) were used for measurements after being calibrated against an 180 cm{sup 3} Radcal Corporation ionization chamber traceable to a reference laboratory. A 300 mm x 300 mm x 150 mm polymethylmethacrylate (PMMA) slab phantom was used for deep-dose measurements. Tl dosemeters were placed in the central axis of the x-ray beam at 5, 10, 15, 25 and 35 mm depth in the phantom upstream the beam direction Another required parameter for determining the conversion coefficients from was the mean energy of the x-ray spectrum. The spectroscopy of x-ray beams was done with a CdTe semiconductor detector that was calibrated with {sup 133} Ba, {sup 241} Am and {sup 57} Co radiation sources. Measurements of the x-ray spectra were carried out for all RQR and RQA IEC qualities. Corrections due to the detector intrinsic efficiency, total energy absorption, escape fraction of the characteristic x-rays, Compton effect and attenuation in the detector were done aiming an the accurate determination of the mean energy. Measured x-ray spectra were corrected with the stripping method by using these response functions. The typical combined standard uncertainties of conversion coefficients and backscatter factors were 12% and 6% respectively. (author)

Rosado, Paulo Henrique Goncalves

2008-07-01

235

Angular dependence factors and air kerma to dose equivalent conversion coefficients for 1.9 cm rod and 7.3 cm pillar phantoms irradiated by extended monodirectional X ray beams  

International Nuclear Information System (INIS)

[en] Based on radiation simulations for the transport of monoenergetic photons through right-angled circular cylinder phantoms, the conversion coefficients between receptor-free air collision kerma and the collision kerma for 4-element ICRU tissue has been investigated for extended plane-parallel X ray beams in two 1.9 cm rod phantoms and two 7.3 cm pillar phantoms 30 cm in length made of 4-element ICRU tissue or PMMA; the X ray beam direction was perpendicular to the phantoms' main axis. Two different types of quantities were calculated for each phantom, (i) the conversion coefficient at that point in the circular middle plane of the phantom perpendicular to its main axis which is localised at a depth of 0.007 g.cm-2 on the radius opposed to the beam direction and (ii) the angular dependence factor which describes the change of the conversion coefficient at the same point in the phantom after performing a rotation around the phantom's main axis. All these data, in particular those for the tissue phantoms, are of interest in the procedure for calibrating and type testing extremity dosemeters; the data on rod phantoms for finger dosemeters and those on pillar phantoms for wrist and ankle dosemeters. (author)

1995-01-01

236

Development of fuzzy air quality index using soft computing approach.  

UK PubMed Central (United Kingdom)

Proper assessment of air quality status in an atmosphere based on limited observations is an essential task for meeting the goals of environmental management. A number of classification methods are available for estimating the changing status of air quality. However, a discrepancy frequently arises from the quality criteria of air employed and vagueness or fuzziness embedded in the decision making output values. Owing to inherent imprecision, difficulties always exist in some conventional methodologies like air quality index when describing integrated air quality conditions with respect to various pollutants parameters and time of exposure. In recent years, the fuzzy logic-based methods have demonstrated to be appropriated to address uncertainty and subjectivity in environmental issues. In the present study, a methodology based on fuzzy inference systems (FIS) to assess air quality is proposed. This paper presents a comparative study to assess status of air quality using fuzzy logic technique and that of conventional technique. The findings clearly indicate that the FIS may successfully harmonize inherent discrepancies and interpret complex conditions.

Mandal T; Gorai AK; Pathak G

2012-10-01

237

Seasonal ARIMA for Forecasting Air Pollution Index: A Case Study  

Directory of Open Access Journals (Sweden)

Full Text Available Problem statement: Both developed and developing countries are the major reason that affects the world environment quality. In that case, without limit or warning, this pollution may affect human health, agricultural, forest species and ecosystems. Therefore, the aim of this study was to determine the monthly and seasonal variations of Air Pollution Index (API) at all monitoring stations in Johor. Approach: In this study, time series models will be discussed to analyze future air quality and used in modeling and forecasting monthly future air quality in Malaysia. A Box-Jenkins ARIMA approach was applied in order to analyze the API values in Johor. Results: In all this three stations, high values recorded at sekolah menengah pasir gudang dua (CA0001). This situation indicates that the most polluted area in Johor located in Pasir Gudang. This condition appears to be the reason that Pasir Gudang is the most developed area especially in industrial activities. Conclusion: Time series model used in forecasting is an important tool in monitoring and controlling the air quality condition. It is useful to take quick action before the situations worsen in the long run. In that case, better model performance is crucial to achieve good air quality forecasting. Moreover, the pollutants must in consideration in analysis air pollution data.

Muhammad H. Lee; Nur H.A. Rahman; Suhartono; Mohd T. Latif; Maria E. Nor; Nur A.B. Kamisan

2012-01-01

238

Key comparison BIPM.RI(I)-K2 of the air-kerma standards of the ENEA-INMRI, Italy and the BIPM in low-energy x-rays  

Science.gov (United States)

A key comparison has been made between the air-kerma standards of the ENEA-INMRI, Italy and the BIPM in the low-energy x-ray range. The results show the standards to be in agreement at the level of the standard uncertainty for the comparison of 1.9 parts in 103. No significant trend with radiation quality is observed. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI Section I, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Burns, D. T.; Kessler, C.; Roger, P.; Toni, M. P.; Pinto, M.; Bovi, M.; Cappadozzi, G.; Silvestri, C.

2011-01-01

239

Key comparison BIPM.RI(I)-K2 of the air-kerma standards of the VNIIM, Russian Federation and the BIPM in low-energy x-rays  

Science.gov (United States)

A key comparison has been made between the air-kerma standards of the VNIIM and the BIPM in the low-energy x-ray range. The results show the standards to be in agreement at the level of the combined standard uncertainty of 2.4 parts in 103, with evidence of a slight trend with radiation quality. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI Section I, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Burns, D. T.; Roger, P.; Villevalde, A. Y.; Oborin, A. V.

2012-01-01

240

Key comparison BIPM.RI(I)-K2 of the air-kerma standards of the LNE-LNHB, France and the BIPM in low-energy x-rays  

Science.gov (United States)

A key comparison has been made between the air-kerma standards of the LNE-LNHB, France and the BIPM in the low-energy x-ray range. The results show the standards to be in agreement at the level of the standard uncertainty of the comparison of 1.6 parts in 103, with no evidence of a trend in the results at different radiation qualities. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI Section I, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Burns, D. T.; Roger, P.; Denozière, M.; Leroy, E.

2011-01-01

 
 
 
 
241

Key comparison BIPM.RI(I)-K3 of the air-kerma standards of the VNIIM, Russian Federation and the BIPM in medium-energy x-rays  

Science.gov (United States)

A key comparison has been made between the air-kerma standards of the VNIIM and the BIPM in the medium-energy x-ray range. The results show the standards to be in agreement at the level of the stated standard uncertainty for the comparison of 1.8 parts in 103. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI Section I, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Burns, D. T.; Kessler, C.; Villevalde, A. Y.; Oborin, A. V.

2011-01-01

242

Comparison of factors given in ICRU Report 23 and IAEA TRS 277 for converting from exposure/air kerma to absorbed dose to water for medium energy X-rays  

International Nuclear Information System (INIS)

New values of the factors required to convert the reading of an ionization chamber calibrated in terms of air kerma (or exposure) to absorbed dose to water for medium energy X-rays were given in a Code of Practice published by the IAEA in 1987. These factors differ by a maximum of 12.5% at 0.15 mm Cu HVL from those given in ICRU Report 23. This paper discusses the difference between the ICRU and IAEA conversion factors and forms the basis of the recommendation of the IPSM low and medium energy X-ray dosimetry working party, that dosimetry in the U.K. should continue to be based on ICRU Report 23 and therefore on the current HPA Code of Practice. (author)

1991-01-01

243

Kinematic kerma factors  

International Nuclear Information System (INIS)

[en] The HEATR module of NJOY computes heat production by energy-balance (usually); that is, it assumes that the energy available for charged-particle emission and nuclear recoil can be obtained from the available energy (E + Q) minus the energy carried away by neutrons (E/sub n/) and the energy carried away by photons (anti E/sub ?/). If there are errors in either anti E/sub n/ or anti E /sub ?/, the local heating will be incorrect. In a large enough system, this heating error will be exactly compensated for by photon energy deposition, and the correct result for total heating will be obtained. However, in very small systems where most of the photons escape, the local heating can have very large errors resulting from a lack of energy conservation in the nuclear data evaluation. Accurate values for this local heating can be computed for some reactions by kinematics (radiative capture, elastic and inelastic neutron scattering). Reactions that emit charged particles are more difficult because the ENDF/B files do not contain the required particle spectra or angular distributions. Nevertheless, it is possible to establish an upper limit for the kinematic kerma factor by assuming that such reactions emit no photons. The HEATR module has been modified to add kinematic kerma factors computed in this way to the NJOY calculational path. This means that they are available for either multigroup or Monte Carlo processing

1985-01-01

244

Determination of Tehran air quality with emphasis on air quality index (AQI); 2008-2009  

Directory of Open Access Journals (Sweden)

Full Text Available Background and aimsIn recent years, because of excessive population growth, increasing of vehicles and developing of the industries, Tehran has been encountered with seriousenvironmental crisis, such as air pollution. So, for setting the control programs, air pollution monitoring and determination of Tehran air quality are necessaryMethodsIn the present study, Tehran air quality index (AQI) was calculated based on the five criteria pollutants levels (O levels in 1387 and with regarding to the national air quality standards for each pollutant categorized as good, moderate, unhealthy for sensitive groups, unhealthy and very unhealthy.Results The results of this research showed that in 2008-2009, with attention to United State environmental protection agency standards, in 43 days, air quality index was calculated lower than 100 and in the other 323 days, air quality index was higher than 100, that unhealthy for sensitive groups, very unhealthy and unhealthy was 40%, 27% and 21%, respectively. Also, in the summer, ozone and in the winter, carbon monoxide was determined as the pollutant responsible for the highest index value that is called the ''critical'' pollutant. The most polluted months with the average index of 204 and 214 were occurred in Tir (22 June to22 July) and Mordad (23 July to 22 August), respectively.Conclusioncomparison of the results of this study with others can be found that Tehran air quality did not improved and is in the very serious situation with regarding to public health, especially for sensitive groups. 3, PM10, SO2, NO2 and CO) through linear interpolation based on these

S. Golbaz; M. Farzadkia; M. Kermani

2010-01-01

245

Report on EUROMET.RI(I)-K1 and EUROMET.RI(I)-K4 (EUROMET project no. 813): Comparison of air kerma and absorbed dose to water measurements of 60Co radiation beams for radiotherapy  

International Nuclear Information System (INIS)

The results of an unprecedented international effort involving 26 countries are reported. The EUROMET.RI(I)-K1 and EUROMET.RI(I)-K4 key comparisons were conducted with the goal of supporting the relevant calibration and measurement capabilities (CMC) planned for publication by the participant laboratories. The measured quantities were the air kerma (Kair) and the absorbed dose to water (Dw) in 60Co radiotherapy beams. The comparison was conducted by the pilot laboratory MKEH (Hungary), in a star-shaped arrangement from January 2005 to December 2008. The calibration coefficients of four transfer ionization chambers were measured using two electrometers. The largest deviation between any two calibration coefficients for the four chambers in terms of air kerma and absorbed dose to water was 2.7% and 3.3% respectively. An analysis of the participant uncertainty budgets enabled the calculation of degrees of equivalence (DoE), in terms of the deviations of the results and their associated uncertainties. As a result of this EUROMET project 813 comparison, the BIPM key comparison database (KCDB) will include eleven new Kair and fourteen new Dw DoE values of European secondary standard dosimetry laboratories (SSDLs), and the KCDB will be updated with the new DoE values of the other participant laboratories. The pair-wise degrees of equivalence of participants were also calculated. In addition to assessing calibration techniques and uncertainty calculations of the participants, these comparisons enabled the experimental determinations of NDw/NKair ratios in the 60Co gamma radiation beam for the four radiotherapy transfer chambers. (authors)

2010-01-01

246

Índice integrado de calidad del aire para ciudades colombianas/ Integrated air quality index for Colombian cities  

Scientific Electronic Library Online (English)

Full Text Available Abstract in spanish En este trabajo se propone un índice que integra información sobre los dos contaminantes criterio de mayor incidencia sobre la salud humana en las ciudades colombianas, ozono (O3) y material particulado con diámetro menor a 10?m (PM10), utilizando lógica difusa. El índice se calcula para las normas de calidad del aire que rigen actualmente en Colombia, aunque su adaptación a otras reglamentaciones es sencilla. Abstract in english In this work an integrated index is proposed using fuzzy logic which incorporates information on the two criteria pollutants of highest incidence on human health in Colombian cities, ozone (O3) and particulate matter with diameter less than 10?m (PM10). The index is calculated for current Colombian air quality standards, although its adaptation to others is straightforward.

Jaramillo, Mauricio; González, Daniel Enrique; Núñez, María Eugenia; Portilla, Gloria

2009-06-01

247

Neutron KERMA factors of Human Tissues  

Directory of Open Access Journals (Sweden)

Full Text Available A program to calculate the neutron KERMA in human tissues has been developed. The program was developed in Mathcad and contains the neutron kerma factors of those elements that are present in different human tissues. Having the elemental composition of any human tissue the neutron kerma can be easily calculated. The program was tested using the elemental composition of tumor tissues such as sarcoma, melanoma, carcinoma and adenoid cystic. Neutron kerma for adipose and muscle tissue for normal adult was calculated. The results are in agreement with those published in literature. The neutron kerma for water was also calculated because in some dosimetric calculations water is used to describe normal and tumor tissues. From this comparison was found that at larger energies kerma factors are approximately the same, but energies less than 100 eV the differences are large.

Vega-Carrillo, H.R.; Manzanares-Acuña, E.; Barquero, R.; Gutierrez-Villanueva, J.L.; Martin-Martin, A.

2007-01-01

248

Experimental comparison among the laboratories accredited within the framework of the European Co-operation for Accreditation on the calibration of a radiation protection dosimeters in the terms of the quantity air Kerma  

International Nuclear Information System (INIS)

The European co-operation for Accreditation (EA) formalises the collaboration of the Accreditation Bodies of the Member States of the European Union and the European Free Trade Association covering all conformity assessment activities. This collaboration is based on a Memorandum of Understanding dated the 27 November 1997 and aims at developing and maintain Multilateral Agreements (MLAs) within EA and with non-members accreditation bodies. MLAs Signatories guarantee uniformity of accreditation by continuous and rigorous evaluation. Based on mutual confidence, the MLAs recognise the equivalence of the accreditation systems administered by EA Members and of certificates and reports issued by bodies accredited under these systems. A basic element of the program to establish and maintain mutual confidence among calibration services is the participation of the accredited laboratories in experimental interlaboratory comparisons (ILC) organised by EA members or other international organisations. The aim of these ILC is to verify the technical equivalence of calibration services within the EA. The ILC which it is dealt with in the present work was recently carried out over a period of two years, ending in May 2002. It interested the laboratories accredited in the ionising radiation field for calibration of dosimeters at radiation protection levels in terms of the quantity air kerma (Kair) due to 60Co and 137Cs gamma radiation. The ILC was planned by the EA expert group on Ionising radiation and radioactivity and approved by the EA General Assembly in December 1999 with the title Calibration of a Radiation Protection Dosimeter under the code IR3. The need of this comparison also resulted from an inquiry carried out in 1998 by the expert group among the different Accreditation Bodies members of EA and associated to EA. The organization of the ILC was carried out according to the EA rules by the Italian Accreditation Body in the ionising radiation field, the SIT-ENEA , in cooperation with the Italian National Metrology Institute in the ionising radiation field, the ENEA-INMRI, as the reference laboratory.

1997-11-27

249

In-patient to isocenter KERMA ratios in CT  

Energy Technology Data Exchange (ETDEWEB)

Purpose: To estimate in-patient KERMA for specific organs in computed tomography (CT) scanning using ratios to isocenter free-in-air KERMA obtained using a Rando phantom.Method: A CT scan of an anthropomorphic phantom results in an air KERMA K at a selected phantom location and air kerma K{sub CT} at the CT scanner isocenter when the scan is repeated in the absence of the phantom. The authors define the KERMA ratio (R{sub K}) as K/ K{sub CT}, which were experimentally determined in a Male Rando Phantom using lithium fluoride chips (TLD-100). R{sub K} values were obtained for a total of 400 individual point locations, as well as for 25 individual organs of interest in CT dosimetry. CT examinations of Rando were performed on a GE LightSpeed Ultra scanner operated at 80 kV, 120 kV, and 140 kV, as well as a Siemens Sensation 16 operated at 120 kV. Results: At 120 kV, median R{sub K} values for the GE and Siemens scanners were 0.60 and 0.64, respectively. The 10th percentile R{sub K} values ranged from 0.34 at 80 kV to 0.54 at 140 kV, and the 90th percentile R{sub K} values ranged from 0.64 at 80 kV to 0.78 at 140 kV. The average R{sub K} for the 25 Rando organs at 120 kV was 0.61 {+-} 0.08. Average R{sub K} values in the head, chest, and abdomen showed little variation. Relative to R{sub K} values in the head, chest, and abdomen obtained at 120 kV, R{sub K} values were about 12% lower in the pelvis and about 58% higher in the cervical spine region. Average R{sub K} values were about 6% higher on the Siemens Sensation 16 scanner than the GE LightSpeed Ultra. Reducing the x-ray tube voltage from 120 kV to 80 kV resulted in an average reduction in R{sub K} value of 34%, whereas increasing the x-ray tube voltage to 140 kV increased the average R{sub K} value by 9%. Conclusions: In-patient to isocenter relative KERMA values in Rando phantom can be used to estimate organ doses in similar sized adults undergoing CT examinations from easily measured air KERMA values at the isocenter (free in air). Conversion from in-patient air KERMA values to tissue dose would require the use of energy-appropriate conversion factors.

Huda, Walter; Ogden, Kent M.; Lavallee, Robert L.; Roskopf, Marsha L.; Scalzetti, Ernest M. [Department of Radiology and Radiological Science, Medical University of South Carolina (MUSC), 96 Jonathan Lucas Street (MSC 323), Charleston, South Carolina 29425-3230 (United States); Department of Radiology, SUNY Upstate Medical University, 750 E Adams Street, Syracuse, New York 13210 (United States)

2011-10-15

250

Proposal for an Environmental Ship Index. Air pollutants and CO2  

Energy Technology Data Exchange (ETDEWEB)

This report develops an environmental index for the air emissions of seagoing ships. The ports of Le Havre (France), Antwerp (Belgium), Rotterdam (Netherlands), Bremen and Hamburg (both Germany) want to develop a uniform Environmental Ship Index (ESI) that identifies ships that go beyond the current average technology in reducing air emissions. The index should be transparent, easy to determine and easy to verify. It should build on current legislation on air pollutant emissions. Therefore, the report reviews current legislation, existing indices in the maritime sector and in other modes of transport.

Den Boer, E.; Faber, J.; Nelissen, D.

2009-02-15

251

Theory of measurement of collision kerma in photon beams with an ionization chamber  

International Nuclear Information System (INIS)

[en] Despite the accepted limitation to the determination of exposure for photons of energies higher than a few MeV, it is shown that the collision kerma for a suitable material or the exposure is a measurable quantity which is useful to describe the high-energy photon field. These quantities are measured at a point in free space or inside a material different from air by using ionization chambers, which have small gas cavities, calibrated in terms of exposure, air kerma or absorbed dose in the cavity gas for photons of a specified quality. As for measurements of collision kerma in soft tissue, the correction factor for attenuation and scatter in the wall and buildup cap of the chamber when exposed in air to the calibration photons or user's beams may be experimentally determined if the chamber wall and buildup cap are of tissue-equivalent materials. (author)

1990-01-01

252

Secondary Charged Particle Spectra and Kerma Calculations.  

Science.gov (United States)

The calculation of kerma factors from known cross sections is not as simple as is often implied. The kerma factors are strongly influenced by the reaction mechanism assumed. An important example of this dependence on the reaction mechanism is the contribu...

J. J. Coyne H. M. Gerstenberg L. A. Hennen

1985-01-01

253

Air quality, monitoring and air quality index in the Helsinki metropolitan area, Finland  

Energy Technology Data Exchange (ETDEWEB)

Helsinki Metropolitan Area Council (YTV) is responsible for the air quality monitoring as well as the planning, research, education and information on air pollution control in the metropolitan area i.e. the cities of Helsinki, Espoo, Kauniainen, and Vantaa. Air quality is monitored in order to observe air quality, to monitor the effects of different sources to air quality, to evaluate the air pollution control measures and to inform the public of the air quality. The Air Pollution Control Act requires municipalities to be aware of the air quality within their territory

Aarnio, P.; Haemekoski, K.; Koskentalo, T.; Virtanen, T. [Helsinki Metropolitan Area Council, Helsinki (Finland). Environmental Office

1995-12-31

254

Secondary charged particle spectra and kerma calculations  

Energy Technology Data Exchange (ETDEWEB)

The calculation of kerma factors from known cross sections is not as simple as is often implied. The kerma factors are strongly influenced by the reaction mechanism assumed. An important example of this dependence on the reaction mechanism is the contribution of the /sup 12/C(n,n')3..cap alpha.. reaction to the total kerma in carbon. First, a short review will be given of the ENDF/B-V carbon cross sections which were used in the calculation of carbon kerma factors. Using the reaction channels implied in the ENDF/B-V evaluation, the contribution of various reactions to the total kerma factors in carbon will be given. A detailed analysis of the reaction mechanisms which could contribute to the (n,n')3..cap alpha.. reaction in carbon has been carried out. First their contribution to kerma, independent of cross section, will be calculated and then the initial spectra of alpha particles produced by the various reaction mechanisms will be given. A discussion of possible ways of experimentally distinguishing the reaction mechanisms will be made by comparing their different initial spectra and their variation in kerma with neutron energy. Finally, the event-size spectra for tissue-equivalent proportional counters will be presented, giving only the contributions from the (n,n')3..cap alpha.. reaction and its various possible reaction channels. 3 refs., 11 figs., 4 tabs.

Coyne, J.J.; Gerstenberg, H.M.; Hennen, L.A.

1985-09-16

255

Tsp and Pm10 Measurement and Description of Air Quality Index (Aqi) in the Ambient Air in Shariati Hospital District  

Directory of Open Access Journals (Sweden)

Full Text Available Apparently, breathing clean air is of significant importance to human beings and thus attention to what enters our body through inhalation is on the increase. Tehran’s air pollution has received considerable media coverage in recent years: Since particulate matter (TSP and PM10) is one of the important pollutants in this city, an attempt was made to study TSP and PM10 concentrations and to make a qualitative assessment of air using the Air Quality Index (AQI), with TSP and PM10 sampling both daily and on a monthly basis. Shariati Hospital district was selected as study area from 22 December 2001 to 20 April 2002. To determine the amount of TSP and PM10 according to EPA and WHO standards, 61 samples were taken for TSP and 61 samples for PM10 with High Volume Sampler. The results indicated that: •As for TSP and PM10, the period extending from 20 February to 20 March (Esfand) was the most heavily polluted one in this study. The cleanest spell was observed from 21 March to 20 April (Farvardin). •Saturdays and Mondays were the most polluted days of the week for TSP and PM10 and Fridays were the cleanest. •As for TSP, In 51 percent of the samples the Air Quality Index (AQI) was below 100 (AQI100). •In the case of PM10, in 75.5 percent of samples the Air Quality Index (AQI) was below 100 (AQI100).

M Kermani; K Naddafi; M Shariat; A.S Mesbah

2004-01-01

256

Status of JENDL KERMA/PKA file  

International Nuclear Information System (INIS)

[en] The JENDL KERMA/PKA file is one of the special purpose files of JENDL, giving the cross section data for neutron radiation damage studies. Two codes, PKAR and KERMA, have been developed to generate the file by processing the composite spectra of emitted neutron and charged particles with the effective single particle emission model. The calculated results for iron generally agree with those of the Monte Carlo method which is based on the exciton and evaporation models for PKA spectra and with those calculated by Howerton et al. for KERMA factors. Future scope of the file generation is also described. (author)

1992-01-01

257

Evaluation of reference kerma rate determination procedures applied to 192Ir sealed radionuclide sources by radiotherapy departments in the Czech Republic  

International Nuclear Information System (INIS)

Reference air kerma rates of 192Ir sealed high-dose rate sources determined by the National Radiation Protection Institute within independent audits of carried brachytherapy departments in the Czech Republic were compared with the data in the sealed radionuclide source certificates and status test reports. The reference air kerma rates were measured by the free in-air technique. Furthermore, the reference air kerma rate determination procedures applied during independent audits and during radiation source acceptance procedures and status tests are mutually compared. Particular attention is paid to the determination of the 192Ir calibration factor and to the use of correction factors. Recommendations are given for a correct determination of the reference air kerma rates. (orig.)

2011-01-01

258

Alberta's air quality index : facts at your fingertip  

Energy Technology Data Exchange (ETDEWEB)

Alberta Environment measures the airborne concentrations of carbon dioxide, fine particulate matter, nitrogen dioxide, ozone and sulphur dioxide on a continuous basis at air quality monitoring stations in Edmonton, Calgary, Red Deer and Beaverlodge. Every hour, the readings are converted to an Air Quality Index (AQI) number to report on Alberta's outdoor air quality as either good, fair, poor or very poor. The categories relate to guidelines under Alberta's Environmental Protection and Enhancement Act and reflect the maximum acceptable levels specified by the National Ambient Air Quality Objectives. Current air quality conditions are available to the public through Alberta Environment's web site or by phoning a toll free number. Both Edmonton and Calgary report good air quality at least 90 per cent of the time. Occasionally, air quality in the two cities may reach the fair category, but it is seldom poor. Fair, poor or very poor air quality occurs with strong temperature inversion and light winds. Under these conditions, air pollutants, usually from automobiles, are trapped in a layer of stagnant air. Fair and poor air quality can also be caused by summer heat when photochemical smog forms by chemical reactions with oxides of nitrogen and volatile hydrocarbons. 1 ref., 1 tab., 1 fig.

NONE

2003-06-01

259

Air pollution forecasting in Ankara, Turkey using air pollution index and its relation to assimilative capacity of the atmosphere.  

UK PubMed Central (United Kingdom)

Spatial and temporal variations in concentrations of CO, NO, NO(2), SO(2), and PM(10), measured between 1999 and 2000, at traffic-impacted and residential stations in Ankara were investigated. Air quality in residential areas was found to be influenced by traffic activities in the city. Pollutant ratios were proven to be reliable tracers to differentiate between different sources. Air pollution index (API) of the whole city was calculated to evaluate the level of air quality in Ankara. Multiple linear regression model was developed for forecasting API in Ankara. The correlation coefficients were found to be 0.79 and 0.63 for different time periods. The assimilative capacity of Ankara atmosphere was calculated in terms of ventilation coefficient (VC). The relation between API and VC was investigated and found that the air quality in Ankara was determined by meteorology rather than emissions.

Genc DD; Yesilyurt C; Tuncel G

2010-07-01

260

Arima and integrated arfima models for forecasting air pollution index in Shah Alam, Selangor  

International Nuclear Information System (INIS)

Air pollution is one of the major issues that has been affecting human health, agricultural crops, forest species and ecosystems. Since 1980, Malaysia has had a series of haze episodes and the worst ever was reported in 1997. As a result, the government has established the Malaysia Air Quality Guidelines, the Air Pollution Index (API) and Haze Action Plan, to improve the air quality. The API was introduced as an index system for classifying and reporting the ambient air quality in Malaysia. The API for a given period is calculated based on the sub-index value (sub-API) for all the five air pollutants, namely sulphur dioxide (SO2), nitrogen dioxide (NO2), ozone (O3), carbon monoxide (CO) and particulate matter below 10 micron size (PM10). The forecast of air pollution can be used for air pollution assessment and management. It can serve as information and warning to the public in cases of high air pollution levels and for policy management of many different chemical compounds. Hence, the objective of this project is to fit and illustrate the use of time series models in forecasting the API in Shah Alam, Selangor. The data used in this study consists of 70 monthly observations of API (from March 1998 to December 2003) published in the Annual Reports of the Department of Environment, Selangor. The time series models that were being considered were the Integrated Autoregressive Moving Average (ARIMA) and the Integrated Long Memory Model (ARFIMA) models. The lowest MAE, RMSE and MAPE values were used as the model selection criteria. Between these two models considered, the integrated ARFIMA model appears to be the better model as it has the lowest MAPE value. However, the actual value of May 2003 falls outside the 95% forecast interval, probably due to emissions from mobile sources (i.e., motor vehicles), industrial emissions, burning of solid wastes and forest fires. (author)

2008-01-01

 
 
 
 
261

Gamma Rays, Q-Values, and Kerma Factors.  

Science.gov (United States)

Formats have been proposed to allow the inclusion of evaluated neutron kerma factors in ENDF/B. The task of preparing evaluated kerma factors is analyzed in this report and is found to present numerous difficulties. Two alternative approaches to kerma-fac...

D. W. Muir

1976-01-01

262

An analysis of the annual and seasonal trends of air quality index of Delhi.  

UK PubMed Central (United Kingdom)

The Air Quality Index (AQI) is an index for reporting daily air quality. A study on the annual and seasonal variations of Air Quality Index over a period of 9 years (1996-2004) based on daily averaged concentration data of criteria air pollutants has been conducted for Delhi. An attempt has been made to quantify the changes in the AQI on annual and seasonal (winter, summer, monsoon and post monsoon) basis for 9 years. Measurements for the seven monitoring sites (Nizamuddin, Ashok Vihar, Shahzada Baug, Shahadara, Janakpuri, Sirifort and ITO) in Delhi were analysed and trends were also compared amongst these sites. Maximum Operator Function method was used to compute the Air Quality Index of the above areas and percentage variations in different severity class is discussed which provides in depth analysis of the trends. The best air quality was depicted by Shahzada Baug followed by Shahdara, both of these were classified as industrial areas indicating that policy measures relating to the industries in the city during past years have helped in improving the air quality. The air quality in other areas have improved slightly in the span of nine years but still remains critical indicating continued rigorous efforts in this direction. Increased traffic density seems to have resulted into the worst air quality at ITO in the city amongst all the monitoring stations. There is a shift for the worst AQI in the city from winter to summer season in a time span of these nine years. Change of season for worst AQI from Winter to Summer may also be likely due to increased photochemical reactions playing major role with change in the nature of emissions imposed due to different control measures such as CNG implementation, significant shift to LPG in domestic sector etc. calling for a detailed study, those which started after the year 2000. After the year 2000, there is a significant increase in the Nitrogen-dioxide (NO(2)) concentration at all stations. ITO which has shown continuous exponential increase in pollution levels has first time showed a declining AQI trend in the year 2004 and one of the contributing factors could have been the Delhi metro (initiated in 2002) passing through congested neighbouring areas causing traffic decongestion here. In general, the areas which are farthest from metro route viz., Siri-fort, Nizamuddin, Janakpuri etc. did not record declining AQI in 2003 onwards as happened with stations closer to Metro route such as Ashok Vihar and ITO. An attempt has been made to quantify the reasons that lead to the changes in the values of the AQI.

Mohan M; Kandya A

2007-08-01

263

An analysis of the annual and seasonal trends of air quality index of Delhi.  

Science.gov (United States)

The Air Quality Index (AQI) is an index for reporting daily air quality. A study on the annual and seasonal variations of Air Quality Index over a period of 9 years (1996-2004) based on daily averaged concentration data of criteria air pollutants has been conducted for Delhi. An attempt has been made to quantify the changes in the AQI on annual and seasonal (winter, summer, monsoon and post monsoon) basis for 9 years. Measurements for the seven monitoring sites (Nizamuddin, Ashok Vihar, Shahzada Baug, Shahadara, Janakpuri, Sirifort and ITO) in Delhi were analysed and trends were also compared amongst these sites. Maximum Operator Function method was used to compute the Air Quality Index of the above areas and percentage variations in different severity class is discussed which provides in depth analysis of the trends. The best air quality was depicted by Shahzada Baug followed by Shahdara, both of these were classified as industrial areas indicating that policy measures relating to the industries in the city during past years have helped in improving the air quality. The air quality in other areas have improved slightly in the span of nine years but still remains critical indicating continued rigorous efforts in this direction. Increased traffic density seems to have resulted into the worst air quality at ITO in the city amongst all the monitoring stations. There is a shift for the worst AQI in the city from winter to summer season in a time span of these nine years. Change of season for worst AQI from Winter to Summer may also be likely due to increased photochemical reactions playing major role with change in the nature of emissions imposed due to different control measures such as CNG implementation, significant shift to LPG in domestic sector etc. calling for a detailed study, those which started after the year 2000. After the year 2000, there is a significant increase in the Nitrogen-dioxide (NO(2)) concentration at all stations. ITO which has shown continuous exponential increase in pollution levels has first time showed a declining AQI trend in the year 2004 and one of the contributing factors could have been the Delhi metro (initiated in 2002) passing through congested neighbouring areas causing traffic decongestion here. In general, the areas which are farthest from metro route viz., Siri-fort, Nizamuddin, Janakpuri etc. did not record declining AQI in 2003 onwards as happened with stations closer to Metro route such as Ashok Vihar and ITO. An attempt has been made to quantify the reasons that lead to the changes in the values of the AQI. PMID:17242967

Mohan, Manju; Kandya, Anurag

2007-01-23

264

Application of normal and high-pressure ionisation chambers for the determination of A150 kerma components in a 19 MeV neutron field  

International Nuclear Information System (INIS)

[en] The twin-detector method was applied to determine the A150 plastic kerma components in a 19 MeV mixed neutron-photon field in free air. High-pressure ionisation chambers and thimble-type ionisation chambers at normal pressure were used. The spectral neutron fluence was measured to subtract the background neutrons and to evaluate the kerma factor for 19 MeV monoenergetic neutrons. The A150 plastic kerma factors derived from the various measurements agree well. They are higher than previously published experimental data, but about 7% lower than the value calculated by Caswell et al. (author)

1988-01-01

265

Trends of air pollution in Denmark - Normalised by a simple weather index model  

International Nuclear Information System (INIS)

This report is a part of the Traffic Pool projects on 'Traffic and Environments', 1995-99, financed by the Danish Ministry of Transport. The Traffic Pool projects included five different projects on 'Surveillance of the Air Quality', 'Atmospheric Modelling', 'Atmospheric Chemistry Modelling', 'Smog and ozone' and 'Greenhouse effects and Climate', [Rasmussen, 2000]. This work is a part of the project on 'Surveillance of the Air Quality' with the main objectives to make trend analysis of levels of air pollution from traffic in Denmark. Other participants were from the Road Directory mainly focusing on measurement of traffic and trend analysis of the air quality utilising a nordic model for the air pollution in street canyons called BLB (Beregningsmodel for Luftkvalitet i Byluftgader) [Vejdirektoratet 2000], National Environmental Research Institute (HERI) mainly focusing on. measurements of air pollution and trend analysis with the Operational Street Pollution Model (OSPM) [DMU 2000], and the Copenhagen Environmental Protection Agency mainly focusing on measurements. In this study a more simple statistical model has been developed for trend analysis of the air quality. The model is filtering out the influence of the variations from year to year in the meteorological conditions on the air pollution levels. The weather factors found most important are wind speed, wind direction and mixing height. Measurements of CO, NO and NO2 from three streets in Copenhagen have been used, these streets are Jagtvej, Bredgade and H. C. Andersen's Boulevard (HCAB). The years 1994-1996 were used for evaluation of the method and annual indexes of air pollution index dependent only on meteorological parameters, called WEATHIX, were calculated for the years 1990-1997 and used for normalisation of the observed air pollution trends. Meteorological data were taken from either the background stations at the H.C. Oersted - building situated close to one of the street stations or the synoptic station at Kastrup Airport just outside Copenhagen. The mixing height was calculated using a bulk Richardson method on vertical profiles provided by the Numerical Weather Prediction model DMI-HIRLAM (Danish Meteorological Institute - High Resolution Limited Area Model). The model in general gives a good explanation of variations from year to year in the air quality. (au)

2000-01-01

266

Air trapping on computed tomography images of healthy individuals: effects of respiration and body mass index  

Energy Technology Data Exchange (ETDEWEB)

Aim: To evaluate the relationships of changes in the lung area during respiration and of individual body mass index (BMI) to air trapping on expiratory computed tomography (CT) in young non-smoking adults of either gender. Methods: The volunteers were 10 women and 10 men (mean age 25.7 years) who were healthy lifelong non-smokers. We obtained both end-inspiratory and end-expiratory CT images at three levels: the upper, middle and lower lung. The ratio of cross-sectional lung area upon expiration to cross-sectional lung area upon inspiration (lung area ratio) was determined for each lung at each of the three levels. In cases showing air trapping, we calculated the percentage of area of air in relation to the total lung area in each section. BMI was calculated for each participant. Results: Air trapping was present in dependent areas of the lungs of 6 women and 5 men. The mean percentage of area of air trapped was statistically greater for men (9.8 {+-} 9.2%) than for women (4.9 {+-} 5.2%). The mean lung area ratio was 0.52 {+-} 0 14 among volunteers with air trapping (66 sections) and 0.69 {+-} 0.12 among those without air trapping (54 sections) (p < 0.001). At each lung level, the mean lung area ratio was greater in individuals with air trapping than in those without. Mean BMI was also greater in these people (p = 0.009). Conclusion: Change in the respiratory lung area and BMI contribute to development of air trapping.

Hashimoto, M.; Tate, E.; Watarai, J.; Sasaki, M

2006-10-15

267

ZZ KERMAL, Neutron and Gamma Kerma Library from ENDL and EGDL  

International Nuclear Information System (INIS)

[en] Description of program or function: 1 - Calculated Neutron Kerma Factors: - Format: TART Monte Carlo neutron transport code; - Number of groups: 175 neutron energy groups; - Nuclides: tissue, bone, muscle, standard man, plastic,nylon-6.6/6, Lucite, liquid muscle equivalent, water, acetylene, dry air, water-saturated air, carbon dioxide, Ethylene, Te gas with methane. - Origin: LLNL Evaluated Nuclear Data Library (ENDL). 2 - Calculated Photon kerma Factors: - Format: TART Monte Carlo neutron transport code; - Number of groups: 191 energy groups; - Nuclides: tissue, bone, muscle, standard man, plastic,nylon-6.6/6, Lucite, liquid muscle equivalent, water, acetylene, dry air, water-saturated air, carbon dioxide, Ethylene, Te gas with methane. - Origin: LLNL Evaluated Gamma-Ray Data Library (ENDL). These libraries contain neutron and gamma ray Kerma factors. KENDL, the neutron Kerma factors have been calculated from the LLNL Evaluated Nuclear Data Library (ENDL) data file. The results are for the 175 neutron energy groups used by the TART Monte Carlo neutron transport code for isotopes and elemental mixtures. They are tabulated for 15 composite materials and for the isotopes or elements in the ENDL file from Z=1 to Z=29. The incident neutron energies range from 1.882 x 1.0 E-5 to 20 MeV for the composite materials and from 1.307 x 1.0 E-9 to 20 MeV for the isotopes and elements. KEGDL, the gamma-ray KERMA factors calculated from the LLNL Evaluated Gamma-Ray Data Library (EGDL) file, are tabulated for the elements from Z=1 to Z=30 and for 15 composite materials. The KERMA factors are presented for 191 energy groups over the incident photon energy range from 100 eV to 100 MeV. The following composite materials are tabulated: tissue, bone, muscle, standard man, plastic, nylon-6.6/6, Lucite, liquid muscle equivalent, water, acetylene, dry air, water-saturated air, carbon dioxide, gas Te with methane

1996-01-01

268

Tolerance Levels of Roadside Trees to Air Pollutants Based on Relative Growth Rate and Air Pollution Tolerance Index  

Directory of Open Access Journals (Sweden)

Full Text Available Motor vehicles release carbon monoxide, nitrogen dioxide, sulphur dioxide, and particulate matters to the air as pollutants. Vegetation can absorb these pollutants through gas exchange processes. The objective of this study was to examine the combination of the relative growth rate (RGR) and physiological responses in determining tolerance levels of plant species to air pollutants. Physiological responses were calculated as air pollution tolerance index (APTI). Eight roadside tree species were placed at polluted (Jagorawi highway) and unpolluted (Sindangbarang field) area. Growth and physiological parameters of the trees were recorded, including plant height, leaf area, total ascorbate, total chlorophyll, leaf-extract pH, and relative water content. Scoring criteria for the combination of RGR and APTI method was given based on means of the two areas based on two-sample t test. Based on the total score of RGR and APTI, Lagerstroemia speciosa was categorized as a tolerant species; and Pterocarpus indicus, Delonix regia, Swietenia macrophylla were categorized as moderately tolerant species. Gmelina arborea, Cinnamomum burmanii, and Mimusops elengi were categorized as intermediate tolerant species. Lagerstroemia speciosa could be potentially used as roadside tree. The combination of RGR and APTI value was better to determinate tolerance level of plant to air pollutant than merely APTI method.

SULISTIJORINI; ZAINAL ALIM MAS’UD; NIZAR NASRULLAH; AHMAD BEY; SOEKISMAN TJITROSEMITO

2008-01-01

269

Tissue kerma vs distance relationships for initial nuclear radiation from the atomic bombs Hiroshima and Nagasaki  

International Nuclear Information System (INIS)

Initial nuclear radiation is comprised of prompt neutrons and prompt primary gamma rays from an exploding nuclear device, prompt secondary gamma rays produced by neutron interactions in the environment, and delayed neutrons and delayed fission-product gamma rays from the fireball formed after the nuclear device explodes. These various components must all be considered in establishing tissue kerma vs distance relationships which describe the decrease of initial nuclear radiation with distance in Hiroshima and Nagasaki. An interest in initial nuclear radiation at distances of as much as 2000 m from the hypocenter demands the use of discrete ordinates transport (DOT) techniques. The two-dimensional (2D) DOT-IV code developed at Oak Ridge National Laboratory (ORNL) was used to calculate the tissue kerma in an air-over-ground geometry from prompt neutrons and prompt primary gamma rays and from prompt secondary gamma rays produced in air and in soil. Data from the Los Alamos National Laboratory (LANL) were used as the source terms. The tissue kerma at ground level from delayed fission-product gamma rays and delayed neutrons, was investigated using the NUIDEA code developed by Science Applications, Inc., (SAI). This code incorporates very detailed models which can take into account such features as the immediate rise of the fireball, the rapid radioactive decay of fission-products in it, and the perturbation of the atmosphere by the explosion. Tissue kerma vs distance relationships obtained by summing results of these current state-of-the-art calculations will be discussed. Our results clearly show that the prompt secondary gamma rays and delayed fission-product gamma rays are the dominant components of the total tissue kerma from initial nuclear radiation of the atomic (or pure-fission) devices detonated over Hiroshima and Nagasaki. (author).

1983-01-01

270

Indexed  

CERN Multimedia

Jessica Hagy is a different kind of thinker. She has an astonishing talent for visualizing relationships, capturing in pictures what is difficult for most of us to express in words. At indexed.blogspot.com, she posts charts, graphs, and Venn diagrams drawn on index cards that reveal in a simple and intuitive way the large and small truths of modern life. Praised throughout the blogosphere as “brilliant,” “incredibly creative,” and “comic genius,” Jessica turns her incisive, deadpan sense of humor on everything from office politics to relationships to religion. With new material along with some of Jessica’s greatest hits, this utterly unique book will thrill readers who demand humor that makes them both laugh and think.

Hagy, Jessica

2008-01-01

271

Neutron and gamma kerma and spectrum measurements to 1.6 km from a neutron source  

International Nuclear Information System (INIS)

The Army Pulse Radiation Division at Aberdeen Proving Ground operates a neutron source which provides U235 fission neutrons and gamma rays in an air-over-ground geometry. Neutron and gamma tissue kerma and spectra have been measured out to a range of 1.6 km from the source. These data are used to validate various analytical radiation transport and shielding models, including those used in Hiroshima-Nagasaki dose reevaluation efforts. (author).

1983-01-01

272

The air quality health index and asthma morbidity: a population-based study.  

UK PubMed Central (United Kingdom)

BACKGROUND: Exposure to air pollution has been linked to the exacerbation of respiratory diseases. The Air Quality Health Index (AQHI), developed in Canada, is a new health risk scale for reporting air quality and advising risk reduction actions. OBJECTIVE: We used the AQHI to estimate the impact of air quality on asthma morbidity, adjusting for potential confounders. METHODS: Daily air pollutant measures were obtained from 14 regional monitoring stations in Ontario. Daily counts of asthma-attributed hospitalizations, emergency department (ED) visits, and outpatient visits were obtained from a provincial registry of 1.5 million patients with asthma. Poisson regression was used to estimate health services rate ratios (RRs) as a measure of association between the AQHI or individual pollutants and health services use. We adjusted for age, sex, season, year, and region of residence. RESULTS: The AQHI values were significantly associated with increased use of asthma health services on the same day and on the 2 following days, depending on the specific outcome assessed. A 1-unit increase in the AQHI was associated with a 5.6% increase in asthma outpatient visits (RR = 1.056; 95% CI: 1.053, 1.058) and a 2.1% increase in the rate of hospitalization (RR = 1.021; 95% CI: 1.014, 1.028) on the same day and with a 1.3% increase in the rate of ED visits (RR = 1.013; 95% CI: 1.010, 1.017) after a 2-day lag. CONCLUSIONS: The AQHI values were significantly associated with the use of asthma-related health services. Timely AQHI health risk advisories with integrated risk reduction messages may reduce morbidity associated with air pollution in patients with asthma.

To T; Shen S; Atenafu EG; Guan J; McLimont S; Stocks B; Licskai C

2013-01-01

273

Kerma associated with high energy neutrons  

International Nuclear Information System (INIS)

[en] The kerma for monoenergetic neutrons of nominal energies 27, 42 and 63 MeV was measured with commercial tissue-equivalent and carbon proportional counters. By operating the detectors in helix mode and exposing them to pulsed beams of quasi-monoenergetic neutrons, time-of-flight (TOF) techniques enabled the unambiguous identification of pulse height events associated with the neutron energies of interest. The microdosimetric spectra so obtained were used to derive gas-to-wall dose conversion factors for the TE gas filled carbon proportional counter. Subsequently the kerma ratios for carbon to A-150 plastic at the three nominal neutron energies were determined with the monoenergetic data. The results concur with other published data using different techniques. (Author)

1994-01-01

274

Active suppression of air refractive index fluctuation using a Fabry-Perot cavity and a piezoelectric volume actuator  

International Nuclear Information System (INIS)

Air refractive index fluctuation (?nair) is one of the largest uncertainty sources in precision interferometry systems that require a resolution of nanometer order or less. We introduce a method for the active suppression of ?nair inside a normal air-environment chamber using a Fabry-Perot cavity and a piezoelectric volume actuator. The temporal air refractive index (nair) at a local point is maintained constant with an expanded uncertainty of ?4.2x10-9 (k=2), a sufficiently low uncertainty for precise measurements unaffected by ?nair to be made inside a chamber.

2011-01-01

275

Investigation of Humidity Effect on the Air Refractive Index using an Optical Fiber Design  

Directory of Open Access Journals (Sweden)

Full Text Available In this study operation of an optical design based on the intensity modulation for the refractive index change has been described. The reported instrument measures the transmitted output power depending up on the medium refractive index in the light path of a fiber-to-fiber design. A liquid cell is located between the fibers in the light path and power variations for different cold and hot water levels in the cell are measured. By using a reference humidity meter the calibration curve representing the relative humidity (%RH) as a function of the transmitted output power is obtained. For the hot water with the final temperature of T = 32.7C the output power range of 255.0 -313.0 nW is measured for a relative humidity change of 32.76 -41.26%. A power variation of 58 nW is noted for the 8.5% RH variation which shows the high sensitivity for the reported sensor. For the light transmitted in dry air path the output power is 516.7 nW while for the water path such power is 784.6 nW. Thus, the reported device can check the presence of the water vapor, water, or any other transparent liquid in the gap between the two axially aligned fibers. Performance of the new system is satisfactory as a refractive index monitoring mean and for the water/water vapor sensing.

A. Mehrabani; H. Golnabi

2011-01-01

276

An international calibration of Kerma - Area Product meters for patient dose optimisation study  

International Nuclear Information System (INIS)

The results of international calibration of Kerma Area Product (KAP) meters for European SENTINEL survey on patient dose optimisation of cardiac and interventional radiology practice are presented. Twelve countries were involved in the study. An investigation was conduced on 25 KAP meters fitted to under-couch X-ray tubes; 13 KAP meters were installed on cardiac units and the remaining 12 on interventional ones. The simplified calibration method has been applied, consisting of KAP estimation by multiplying the air kerma at the centre of the X-ray field by the irradiated area. The obtained values of calibration factors range from 0.4 to 0.9 and from 0.4 to 0.8 for KAP meters installed on cardiac and interventional units, respectively. They account also for table and mattress attenuation. For air kerma assessment, measurements with thermoluminescent dosemeters have been applied and when possible compared against an additional reference dosemeter. As the result of the investigation, the importance of calibration of KAP meters in clinical conditions that include mattress and table attenuation has been recognised. (authors)

2008-01-01

277

Radioactive Aerosols as an Index of Air Pollution in the City of Thessaloniki, Greece  

International Nuclear Information System (INIS)

This study summarizes results of an investigation done in order to find out how the radioactive aerosols of 7Be could serve as indicators of air pollution conditions. Beryllium-7 is a cosmic-ray produced radionuclide with an important fraction of its production to take place in the upper troposphere. Once it is formed is rapidly associated with submicron aerosol particles and participates in the formation and growth of the accumulation mode aerosols, which is a major reservoir of pollutants in the atmosphere. In order to define any influence of AMAD of 7Be aerosols by air pollution conditions, the aerodynamic size distribution of 7Be aerosols was determined by collecting samples at different locations in the suburban area of the city of Thessaloniki, including rural areas, industrial areas, high elevations, marine environment and the airport area. The aerodynamic size distribution of 7Be aerosols in different locations was obtained by using Andersen 1-ACFM cascade impactors and the Activity Median Aerodynamic Diameter (AMAD) was determined. Some dependency of the AMADs on height has been observed, while in near marine environment the 7Be activity size distribution was dominant in the upper size range of aerosol particles. Low AMADs as low as 0.62 to 0.74 ?m of 7Be aerosols have been observed at locations characterized with relative low pollution, while it is concluded that in the activity size distribution of ambient aerosols, 7Be changes to larger particle sizes in the presence of pollutants, since low AMADs of 7Be aerosols have been observed at low polluted locations. Preliminary data of simultaneous measurements of 214Pb and 212Pb with gaseous air pollutants CO, NO, NOX, SO2 and total suspended particulate matter (TSP) show that radon decay products near the ground could be a useful index of air pollution potential conditions and transport processes in the boundary layer.

2010-01-21

278

The ambient air quality accounts for the Nova Scotia Genuine Progress Index  

International Nuclear Information System (INIS)

[en] The Nova Scotia Genuine Progress Index (GPI) is a measure of sustainable development which provides a complete and accurate picture of our well-being as a society. The GPI assigns explicit values to environmental quality, population health, livelihood security, equity, free time, and educational attainment. The Nova Scotia GPI includes 22 social, economic and environmental components, including ambient air quality. This report investigates Nova Scotia's ambient air concentrations and emissions of carbon monoxide (CO), total particulate matter (PM), sulphur dioxide (SO2), nitrogen oxides (NOx), and volatile organic compounds (VOC). The costs of damages caused by the these key air pollutants are also examined. Exposure to these pollutants results in negative impacts on human health, damage to materials, agricultural crops and changes in forest productivity. From 1979 to 1996, national ambient concentrations of each of these pollutants decreased significantly. However, the national average concentration of ground-level ozone increased by 34 per cent during the same time period. In Nova Scotia, concentrations of CO, PM and SO2 have declined dramatically since 1979, but the trends for NO2 and ground-level ozone do not show significant declines. On a per capita basis, SOx emissions from electric power generation in the province are more than 8 times the Canadian average. The province also had higher per capita emissions of CO, PM, SOx and VOCs than all reporting OECD countries. Electric power generation is the greatest source of fuel combustion emissions in the province, followed by industrial and transportation sources. This report also described some individual actions that can be taken to reduce air pollutant emissions. 174 refs., 37 tabs., 60 figs

2004-01-01

279

Effects of Age, Gender and Body Mass Index on Reaction to Air Condition  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract: This study investigated the effect of age, gender, and body mass index (BMI) on reaction to air condition. Forty eight undergraduates (21 males and 27 females) randomly selected from Imo State University, Owerri, Nigeria within the age range of 17-30 years participated in the study. 26 of them were of normal weight (BMI 24). They were exposed to an air conditioned room for two hours and then their reaction to cold measured using Response to Cold questionnaire. Employing t-test and ANOVA for data analyses, the results showed that body size, age, and gender had no statistically significant effect on reaction to cold condition while exposure to cold condition had a significant influence on both systolic and diastolic blood pressures of all participants. Key words: Body mass index; Air condition; Reaction; Blood pressure; Systolic blood pressure; Diastolic blood pressure; Cold Résumé: Cette étude a examiné l'effet de l'âge, du sexe et de l’indice de masse corporelle (IMC) sur la réaction des gens envers l’air climatisé. Quarante-huit étudiants de premier cycle (21 hommes et 27 femmes) sélectionnés au hasard dans l'Université de l’état d’Imo à Owerri au Nigeria dans une tranche d'âge de 17 ans à 30 ans ont participé à cette étude. 26 d'entre eux avaient un poids normal (IMC 24). Ils ont été exposés dans une salle climatisée pour deux heures, puis leur réaction au froid a été mesuré en utilisant le questionnaire de Réponse au froid. Après le t-test et une analyse de variance des données, les résultats ont montré que la taille corporelle, l'âge et le sexe n'avaient aucun d’effet statistiquement significatif sur la réaction à l'état froid, tandis que l'exposition à l'état froid avait une influence significative sur les pressions artérielles systoliques et diastoliques de tous les participants. Mots clés: Indice de masse corporelle; Climatisation; Iréaction; Pression artérielle; Pression artérielle systolique; Pression artérielle diastolique; Froid

Nkwam C. Uwaoma; Anthony Nkwocha

2011-01-01

280

Kerma Factors in Interaction of Neutrons with Boron Carbide.  

Science.gov (United States)

Heat generation in neutron interactions with boron carbide B/sup 10/; B/sup 11/ and /sup 12/C is calculated. Kerma-factors (kerma-kinetic energy released in materials) were calculated for neutron energies between 10/sup -4/ eV and 15 MeV. No major simplif...

I. M. Bondarenko

1986-01-01

 
 
 
 
281

Working with 150-MeV evaluations: NJOY and KERMA  

Energy Technology Data Exchange (ETDEWEB)

New evaluations of neutron and proton data to 150 MeV will allow the accurate determination of radiation heating for several important applications including accelerator technologies and radiation therapy. The NJOY Nuclear Data Processing System has been extended to convert these data into kerma factors for easy calculations of neutron heating. The results compare well with experimental kerma measurements.

MacFarlane, R.E.; Chadwick, M.B.

1997-08-01

282

Kerma factors in interaction of neutrons with boron carbide  

International Nuclear Information System (INIS)

Heat generation in neutron interactions with boron carbide B10; B11 and 12C is calculated. Kerma-factors (kerma-kinetic energy released in materials) were calculated for neutron energies between 10-4 eV and 15 MeV. No major simplifying assumptions are introduced, and the accuracy of the calculated kerma-factors depends only on availability and accuracy of the basic nuclear data. The ENDF/B-4 data and recent experimental information are used for the calculation of kerma-factors. Plots of these kerma-factors are presented in units of eVxb/atom and wtxsec/(cmxn) as a function of neutron energy.

1979-01-01

283

Assessment of air pollution tolerance index of some trees in Moradabad city, India.  

UK PubMed Central (United Kingdom)

To see the relative tolerance of the plant species, ten different plant species i.e. Ficus rumphii, Pongamia pinnata, Alstonia scholaris, Holoptelea integrifolia, Saraca indica, Pithecolobium dulcis, Cassia simea, Bauhinia variegata, Azadirachta indica and Grewelia robusta was taken from residential (SI), industrial (SII) and commercial (SIII) area of the city as this florais very much common to the Brass city and is planted on the roadside. The quality of air with respect to SPM, SO2 and NO2 has been also assessed on respective sites to see its effect on biochemical parameters of the leaves i.e. pH, total water content, chlorophyll and ascorbic acid and evaluate the (air pollution tolerance index (APTI) of various plants. It was concluded that Pongamia pinnata 15.8, Pithecolobium dulcis 34.8, Holoptelea integrifolia 55.8 and Saraca indica 52.0 have very high APTI value over control so these are considered as high tolerant tree species, Ficus rumphii 35.7, Azadirachta indica 30.5 and Grewelia robusta 34.3 have slightlymoreAPTI value over control so these are considered as moderately tolerant tree species and Alstonia scholaris 21.5, Cassia simea 6.09 and Bauhinia variegata 18.22 have lessAPTI value than control, so these are sensitive species respectively. One way ANOVA finds the obtained values to be highly significant (p < 0.001) at the industrial site. Thus present findings show that Brass and allied industries are the prominent sources responsible for the elevated level of air pollutants at the industrial site.

Tripathi A; Tiwari PB; Mahima; Singh D

2009-07-01

284

Kerma measurements in polyenergetic neutron fields  

International Nuclear Information System (INIS)

[en] Absorbed dose was measured as a function of neutron energy with a small spherical proportional counter (PC) irradiated in the pulsed-beam broad energy spectrum neutron fields of the Physikalisch-Technische Bundesanstalt (PTB) that were produced with the p + Be reaction and extended to 20 MeV neutron energy. Time-of-flight (TOF) discrimination methods augmented the traditional microdosimetric pulse height (PH) analysis and yielded absorbed dose as a function of lineal energy y and neutron TOF. Below 0.7 keV.?m-1 lineal energy, unfolding procedures greatly improve the time resolution, e.g. from 225 ns full width at half maximum (FWHM) to 65 ns FWHM at 1.2 keV.?m-1. The overall time resolution from unfolded TOF spectra is approximately 30 ns FWHM. The absorbed dose was normalised to neutron spectral fluence and, on the assumption that kerma is numerically equal to absorbed dose, yielded relative neutron-fluence-to-kerma conversion coefficients as a function of energy that are in good agreement with values from previous work. (author)

1997-01-01

285

Proceedings of the 20th DOE/NRC nuclear air cleaning conference: An index to the 1st--20th AEC/ERDA/DOE and DOE/NRC nuclear air cleaning conferences  

International Nuclear Information System (INIS)

This document contains a cumulative index to the first through twentieth AEC, ERDA, DOE, and DOE/NRC Nuclear Air Cleaning Conferences and incorporates corrections of errors appearing in prior intermediate indexes.

1989-01-01

286

Gamma rays, Q-values, and kerma factors  

International Nuclear Information System (INIS)

Formats have been proposed to allow the inclusion of evaluated neutron kerma factors in ENDF/B. The task of preparing evaluated kerma factors is analyzed in this report and is found to present numerous difficulties. Two alternative approaches to kerma-factor calculations are suggested, both of which require modifications of existing evaluations, notably through the inclusion of cross sections now missing for a number of neutron reactions, to allow postevaluation kerma-factor processing. The first approach requires neutron-induced charged-particle spectra, in addition to the missing reaction data. The second approach, which would not require the charged-particle spectra, would enforce energy conservation in the computed results

1976-01-01

287

Kerma-factor determination by charged-particle spectroscopy  

Energy Technology Data Exchange (ETDEWEB)

Neutron kerma factors can determined by measuring the cross sections, angular distributions and charged-particle emission spectra from (n,z) reactions where z stands for the light charged particles, namely protons, deuterons, tritons, {sup 3}He, or {alpha}-particles, and combining these data with information on the heavy nuclear recoils. This approach is compared with other approaches of determining kerma factors. Data are given near 14 MeV for materials from carbon to niobium.

Haight, R.C.

1994-07-01

288

Kerma-factor determination by charged-particle spectroscopy  

International Nuclear Information System (INIS)

Neutron kerma factors can determined by measuring the cross sections, angular distributions and charged-particle emission spectra from (n,z) reactions where z stands for the light charged particles, namely protons, deuterons, tritons, 3He, or ?-particles, and combining these data with information on the heavy nuclear recoils. This approach is compared with other approaches of determining kerma factors. Data are given near 14 MeV for materials from carbon to niobium

1994-01-01

289

X ray beam quality specification for kerma area product meters  

International Nuclear Information System (INIS)

Full text: The kerma area product (KAP) in a diagnostic X ray beam is usually measured with a plane parallel transmission ionization chamber. The response of KAP chambers depend significantly on the energy distribution of radiation, and KAP meters are commonly calibrated with a discrete set of radiation qualities. Appropriate specification of radiation quality is needed to allow interpolation between the measured calibration coefficients. This is especially evident when calibration coefficients for laboratory radiation qualities are converted to clinical qualities. Radiation quality of an X ray beam can be specified explicitly by the tube voltage and total filtration, together with anode angle and material. The half value layer (HVL) of the X ray beam is a generally used beam quality specifier and depends on all these parameters. When a high quality cavity ionization chamber is used properly, the response of the chamber depends on energy rather smoothly and the HVL can be used to specify radiation quality and to interpolate the calibration coefficients between radiation qualities. This is not the case with KAP chambers, however. The energy dependence of the response is affected by the materials and design of the KAP chamber. IEC standard for KAP meters sets a requirement of maximum overall uncertainty of 25% (2 SD) for the accuracy of KAP measurement, including the maximum deviation of ±8% arising from X ray tube voltage variation, in the range of 50 kV to 150 kV with a 2,5 mm aluminium filtration. No requirements for the response are stated in the standard for other filtrations. ICRU recommendations for diagnostic dosimetry state a maximum overall uncertainty of 7% (2 SD) for KAP measurements. This also emphasizes the need for accurate beam quality specification. In this work the energy dependence of KAP ionization chambers was investigated using a tungsten anode X ray tube (anode angle 20 deg.) with a set of standard and clinical radiation qualities. Tube voltages of 40 kV-150 kV and filtrations from 1,3 mm to 5 mm Al, and 4 mm Al with 0,1 mm and 0,2 mm Cu were used. The HVL values ranged from 1 mm to 9 mm Al. A diaphragm providing a strictly defined radiation field was designed and the KAP measurements were performed at 5 cm distance from the diaphragm. The reference value for the kerma area product was determined as the product of air kerma measured in the field centre and the area of the field at the same distance. For a KAP meter the calibration coefficient was determined as a quotient of the reference value by the measured KAP value. Calibration coefficients were expressed relative to different beam quality specifiers: HVL, tube voltage and filtration. For any individual KAP meter the variation of calibration coefficients was in the range of 20%-30% for the used beam qualities, yet the behaviour of the response relative to radiation quality was clearly different for KAP chambers of different design. For constant HVL values the variation of calibration coefficients ranged up to 10% among typical clinical radiation qualities used in this study, and thus the HVL alone cannot specify the radiation quality adequately. At least two beam quality specifiers need to be known to describe the response of a KAP meter. For a KAP meter, it is not possible to interpolate calibration coefficients between different X ray qualities relative to the HVL alone. Adequate and convenient specifiers in practice are the tube voltage and total filtration or, if one of these parameters is not known, the HVL instead of that. To allow the interpolations, measured calibration coefficients should cover the range of all clinically used radiation qualities. This work is part of the IAEA coordinated research project for testing the implementation of the IAEA Code of Practice on Dosimetry in X ray Diagnostic Radiology. (author)

2006-01-01

290

Measurement and calculation of fluence, spectra and tissue kerma at large distances from a fission source  

International Nuclear Information System (INIS)

An experimental program is underway at the Army Pulse Radiation Division reactor (APRDR) at Aberdeen Proving Ground, Maryland, to provide benchmark quality radiation transport data characterizing an air-over-ground environment. The data are used to evaluate analytical radiation transport models and provide validation for techniques used to measure radiation protection or shielding of various materiel. The APRDR is a bare critical assembly fueled with uranium ten weight percent molybdenum alloy. For this application the reactor is operated outdoors 14M above ground. Todate measurements have been made by both US and German scientists of neutron and gamma fluence, spectra, and kerma at ranges from 1 to 400 meters from the reactor.

1979-10-05

291

TE and TM guided modes in an air waveguide with negative-index-material cladding.  

UK PubMed Central (United Kingdom)

We numerically demonstrate that a planar waveguide in which the inner layer is a gas with refractive index n0 = 1, sandwiched between two identical semi-infinite layers of a negative index material, can support both transverse electric and transverse magnetic guided modes with low losses. Recent developments in the design of metamaterials with an effective negative index suggest that this waveguide could operate in the infrared region of the spectrum.

D'Aguanno G; Mattiucci N; Scalora M; Bloemer MJ

2005-04-01

292

Retrospective assessment of exposure to traffic air pollution using the ExTra index in the VESTA French epidemiological study.  

Science.gov (United States)

This study applies a traffic exhaust air dispersion model (the ExTra index) to 403 children enrolled in a French multicentric case-control study, the VESTA study (Five [V] Epidemiological Studies on Transport and Asthma). The ExTra index (previously validated by our team) was used to assess lifelong average traffic-related air pollutant (TAP) concentrations (nitrogen oxides) children in the study were exposed to in front of their living places. ExTra index took into account traffic density, topographical parameters (building height, road and pavement width), weather conditions (wind direction and strength) and background pollution levels. Topographical and traffic data were collected, using a specific questionnaire for each home, school or nursery address, attended by children. The assessment of time-weighted NOx levels in front of the children's living places highlighted significant disparities: mean ExTra index values and share attributable to proximity traffic were, respectively, 70+/-42 and 14+/-22 microg/m3 NOx equivalent NO2 for the 403 children in our study. Not only would this diversity not have been revealed using urban background pollution data provided by air quality networks, it would have resulted in 40% of the children being misclassified with regard to their TAP exposure by underestimating it in half of the cases and overestimating it in the other half. Such errors of classification, which are highly prejudicial in epidemiology, argue strongly for the use of an index such as the ExTra, which enables TAP exposure to be reconstructed within the framework of retrospective or prospective epidemiological studies. PMID:15942641

Reungoat, Patrice; Chiron, Mireille; Gauvin, Stéphanie; Zmirou-Navier, Denis; Momas, Isabelle

2005-11-01

293

MACK, Fluence to Kerma Generator from ENDF/B  

International Nuclear Information System (INIS)

1 - Nature of physical problem solved: The principal purpose of the program is in calculating pointwise neutron energy release parameters (fluence-to-kerma factors) at an arbitrary energy mesh from nuclear data in ENDF/B format (2). The kerma factors are of prime importance for calculating heating and dose rates in any nuclear system. The program processes all reactions significant to energy deposition. In addition, the program calculates energy group kerma factors and group cross sections by reactions (group constants not transfer matrices) averaged over an arbitrary input weighting function or any of the 'built-in' functions. When resonance data is available, the code calculates the contribution from the resolved and unresolved resonance parameters. The pointwise cross sections, pointwise kerma factors, energy group cross sections and energy group kerma factors can be printed, punched, and/or saved on tape for all reactions and the sum as selected by input. The pointwise kerma factors can be saved for later use (3) to generate group kerma factors for a different energy group structure or possibly for inclusion in the ENDF/B evaluation for the nuclide with the appropriate MT numbers in the 300's series (2). 2 - Method of solution: The expressions for the energy release per reaction are obtained from a solution of the kinematics of nuclear reactions. The anisotropy of elastic and inelastic scattering is considered. The contribution to energy deposition from radioactive decay of the residual nucleus can be added by reaction and is calculated using Fermi theory in the case of beta decay. In the resolved resonance region, MACK accepts either single or multi level Breit-Wigner parameters. Doppler broadening is performed at an arbitrary input temperature. The unresolved resonance treatment includes some shielding effects through a 1/sigma t weighting. The energy group kerma factors and cross sections are calculated by averaging the pointwise data over either a user supplied input spectrum or 'built-in' weighting functions. The program calculates the contribution to the energy release from all reactions and the accuracy of the kerma factor calculation is set only by the availability of the required nuclear data. 3 - Restrictions on the complexity of the problem: Because of the variable dimensioning technique used in the program, the principal restriction on the size of the problem is the availability of sufficient core storage. Problems with up to about 1500 energy points can be run in less than 65 k words of core storage. Core storage requirements are not affected by the number of reactions processed for the nuclides or the number of nuclides in the run. The code recognizes almost all of the multiplicity of data formats allowed by ENDF

1979-01-01

294

A CRITICAL REVIEW OF AIR POLLUTION INDEX SYSTEMS IN THE UNITED STATES AND CANADA  

Science.gov (United States)

An extensive survey was conducted of all the air pollution indices that are presently utilized or are available. The data were obtained from a literature review; from telephone discussions with personnel in State, local, and Provincial air pollution control agencies; and from mat...

295

Communicating air pollution-related health risks to the public: an application of the Air Quality Health Index in Shanghai, China.  

UK PubMed Central (United Kingdom)

The Air Quality Health Index (AQHI) was originally developed in Canada. However, little is known about its validity in communicating morbidity risks. We aimed to establish the AQHI in Shanghai, China, and to compare the associations of AQHI and existing Air Pollution Index (API) with daily mortality and morbidity. We constructed the AQHI as the sum of excess total mortality associated with individual air pollutants, and then adjusted it to an arbitrary scale (0-10), according to a time-series analysis of air pollution and mortality in Shanghai from 2001 to 2008. We examined the associations of AQHI with daily mortality and morbidity, and compared these associations with API from 2005 to 2008. The coefficients of short-term associations of total mortality with particulate matter with an aerodynamic diameter less than 10 ?m (PM(10)), PM(2.5) and nitrogen dioxide (NO(2)) were used in the establishment of AQHI. During 2005-2008, the AQHI showed linear non-threshold positive associations with daily mortality and morbidity. A unit increase of the PM(10)-AQHI was associated with a 0.90% [95% (confidence interval, CI), 0.43 to 1.37], 1.04% (95%CI, 0.04 to 2.04), 1.62% (95%CI, 0.39 to 2.85) and 0.51% (95%CI, 0.09 to 0.93) increase of current-day total mortality, hospital admissions, outpatient visits and emergency room visits, respectively. The PM(2.5)-AQHI showed quite similar effect estimates with the PM(10)-AQHI. In contrast, the associations for API were much weaker and generally statistically insignificant. The AQHI, compared with the existing API, provided a more effective tool to communicate the air pollution-related health risks to the public.

Chen R; Wang X; Meng X; Hua J; Zhou Z; Chen B; Kan H

2013-01-01

296

Evaluation of kerma in carbon and the carbon cross sections  

International Nuclear Information System (INIS)

[en] A preliminary simultaneous least squares fit to measurements of kerma in carbon, and carbon cross sections taken from the ENDF/B-V file was carried out. In the calculation the shapes of the total cross section and the various partial cross sections were rigid but their absolute values were allowed to float in the fit within the constraints of the ENDF/B-V uncertainties. The construction of the ENDF/B-V file imposed improbable shapes, particularly in the case of the (12)C(n,n'3(alpha)) reaction, which were incompatible with direct measurements of kerma and of the reaction cross sections. Consequently a new evaluation of the cross section data became necessary. Since the available time was limited the new evaluation concentrated particularly on those aspects of the ENDF/B-V carbon file which would have most impact on kerma calculations. Following the new evaluation of cross sections new tables of kerma factors were produced. Finally, the simultaneous least squares fit to measurements of kerma and the new cross section file was repeated

1992-01-01

297

HIgh energy neutron and proton kerma factors for different elements  

International Nuclear Information System (INIS)

[en] A generalisation of the kerma concept for uncharged particles, extending it to all ionising radiations, is proposed. In accordance with the new concept, the kerma factor of ionising particles, k, is considered as a sum of the nuclear, kn, and electromagnetic, ke, components, where ke for charged particles is equal to L?/?. The values of the nuclear component of kerma factor, kn, for neutrons and protons with energies 20-1000 MEV have been calculated for 25 elements from hydrogen to lead as well as for the ICRU muscle tissue. The cascade-exciton model of nuclear interactions was used in the calculations. The presented results of test calculations of the secondary charged particle spectra from reactions of nucleons with different nuclei demonstrate good agreement with experiment. The calculated data also agree well with the experimental values of high energy neutron kerma in light nuclei. The results obtained will remedy a shortage of information on high energy nucleon kerma and will find an application in different fields of radiation protection. (author)

1995-01-01

298

Evaluation of kerma in carbon and the carbon cross sections  

Energy Technology Data Exchange (ETDEWEB)

A preliminary simultaneous least squares fit to measurements of kerma in carbon, and carbon cross sections taken from the ENDF/B-V file was carried out. In the calculation the shapes of the total cross section and the various partial cross sections were rigid but their absolute values were allowed to float in the fit within the constraints of the ENDF/B-V uncertainties. The construction of the ENDF/B-V file imposed improbable shapes, particularly in the case of the (12)C(n,n'3(alpha)) reaction, which were incompatible with direct measurements of kerma and of the reaction cross sections. Consequently a new evaluation of the cross section data became necessary. Since the available time was limited the new evaluation concentrated particularly on those aspects of the ENDF/B-V carbon file which would have most impact on kerma calculations. Following the new evaluation of cross sections new tables of kerma factors were produced. Finally, the simultaneous least squares fit to measurements of kerma and the new cross section file was repeated.

Axton, E.J.

1992-02-01

299

HIgh energy neutron and proton kerma factors for different elements  

Energy Technology Data Exchange (ETDEWEB)

A generalisation of the kerma concept for uncharged particles, extending it to all ionising radiations, is proposed. In accordance with the new concept, the kerma factor of ionising particles, k, is considered as a sum of the nuclear, k{sub n}, and electromagnetic, k{sub e}, components, where k{sub e} for charged particles is equal to L{sub {infinity}}/{rho}. The values of the nuclear component of kerma factor, k{sub n}, for neutrons and protons with energies 20-1000 MEV have been calculated for 25 elements from hydrogen to lead as well as for the ICRU muscle tissue. The cascade-exciton model of nuclear interactions was used in the calculations. The presented results of test calculations of the secondary charged particle spectra from reactions of nucleons with different nuclei demonstrate good agreement with experiment. The calculated data also agree well with the experimental values of high energy neutron kerma in light nuclei. The results obtained will remedy a shortage of information on high energy nucleon kerma and will find an application in different fields of radiation protection. (author).

Savitskaya, E.N.; Sannikov, A.V. [Institut Fiziki Vysokikh Ehnergij, Protvino (Russian Federation)

1995-12-31

300

Differential displacement kerma cross sections for neutron interactions in Si and GaAs  

International Nuclear Information System (INIS)

[en] The cross-section processing code NJOY has been modified to calculate flux-averaged partially integrated differential displacement kerma cross sections, or displacement kerma matrix elements, for neutron interactions. These, and total displacement kerma cross sections, have been calculated using ENDF/B-V and ENDL-84 data files for Si, Ga and As. The displacement kerma matrices for Si and GaAs allow calculations of the distribution of displacement energy between displacement cascades

1990-01-01

 
 
 
 
301

Differential displacement kerma cross sections for neutron interactions in Si and GaAs  

Energy Technology Data Exchange (ETDEWEB)

The cross-section processing code NJOY has been modified to calculate flux-averaged partially integrated differential displacement kerma cross sections, or displacement kerma matrix elements, for neutron interactions. These, and total displacement kerma cross sections, have been calculated using ENDF/B-V and ENDL-84 data files for Si, Ga and As. The displacement kerma matrices for Si and GaAs allow calculations of the distribution of displacement energy between displacement cascades.

Ougouag, A.M.; Williams, J.G.; Danjaji, M.B.; Yang, S.Y. (Univ. of Illinois, Urbana-Champaign, IL (US)); Meason, J.L. (Nuclear Effects Lab., White Sands Missile Range, NM (US))

1990-12-01

302

Paediatric entrance doses from exposure index in computed radiography  

International Nuclear Information System (INIS)

Over the last two years we have evaluated paediatric patient doses in projection radiography derived from exposure level (EL) in computed radiography (CR) in a large university hospital. Entrance surface air kerma (ESAK) for 3501 paediatric examinations was calculated from the EL, which is a dose index parameter related to the light emitted by the phosphor-stimulable plate, archived in the Digital Imaging and Communications in Medicine (DICOM) header of the images and automatically transferred to a database using custom-built dedicated software. Typical mean thicknesses for several age bands of paediatric patients was estimated to calculate ESAK from the EL values, using results of experimental measurements with phantoms for the typical x-ray beam qualities used in paediatric examinations. Mean/median ESAK values (in ?Gy) for the age bands of

303

Measured Neutron Carbon Kerma Factors from 14.1 MeV to 18 MeV.  

Science.gov (United States)

For A-150 tissue-equivalent plastic, the total neutron kerma is dominated by the hydrogen kerma. Tissue kerma is inferred with reasonable accuracy by normalization to the kerma factor ratio between tissue and A-150 plastic. Because of the close match in t...

P. M. Deluca H. H. Barschall R. C. Haight J. C. McDonald

1984-01-01

304

The role of air pollution in the relationship between a heat stress index and human mortality in Toronto  

International Nuclear Information System (INIS)

In this study we considered confounding from air pollutants and chronological variables in the relation between humidex, a summer temperature and humidity index, and nonaccidental mortality, from 1980-1996 in Toronto, Canada. Changes in the risk of death by age group, gender, and combined cardiac-respiratory cause of death were estimated for both 1 deg. C and 50-95th percentile increases in humidex using a generalized additive linear model. With air pollution terms in the models, relative risk (RR) point estimates narrowly exceeded 1.0 for all groups. Humidex effects were most apparent for females (RR=1.006, 95% CI=1.004-1.008 per 1 deg. C humidex and RR=1.089, 95% CI=1.058-1.121 for 50th to 95th percentile humidex). When air pollution was omitted from the model, RR in the 50-95th percentile analysis increased less than 1.71% for all groups except females, for which RR decreased 1.42%. Differences in RR per 1 deg. C humidex were all less than 0.12%. Confidence intervals narrowed slightly for all groups investigated. Heat stress has a statistically significant, yet minimal impact on Toronto populations, and air pollution does appear to have a small, but consistent confounding effect on humidex effect estimates.

2003-01-01

305

Utilizing map pattern classification and surface weather typing to relate climate to the Air Quality Index in Cleveland, Ohio  

Science.gov (United States)

Employing both map pattern classification and weather typing, this study examines the role of climate in impacting air quality in Cleveland, Ohio from 1998 to 2007. This research creates a large-scale map pattern-classification of 500 mb geopotential heights that characterizes the broad scale flow of the atmosphere and the Spatial Synoptic Classification (SSC), which typifies the weather situation at the surface, where pollutants ultimately interact with the population. Surface weather types are found to have a greater impact on the Air Quality Index (AQI) than typical circulation patterns. Warm (cool) weather types and circulation patterns with a ridge (trough) consistently relate to poor (better) air quality in Cleveland. When weather types and circulation patterns are considered in tandem, these relationships are reinforced. Circulation patterns appear to have considerable influence on air quality in conjunction with moderate surface weather types, with impacts differing by the primary pollutant considered. Spike days of high AQIs (days with an AQI of at least 100) show similar results.

Lee, Cameron C.; Ballinger, Thomas J.; Domino, Natalia A.

2012-12-01

306

Kerma Factors for Use in 37-Group Neutron Spectrum Calculations.  

Science.gov (United States)

Neutron kerma factors have been regrouped from the format of the International Commission on Radiation Units and Measurements Report 26 (ICRU-26) to supplement those available in the 37-group format of the Oak Ridge Data Library Collection 31 (DLC-31). Li...

G. H. Zeman W. S. Bice

1983-01-01

307

Evaluation of Kerma in Carbon and the Carbon Cross Sections.  

Science.gov (United States)

A preliminary simultaneous least squares fit to measurements of kerma in carbon, and carbon cross sections taken from the ENDF/B-V file was carried out. In the calculation the shapes of the total cross section and the various partial cross sections were r...

E. J. Axton

1992-01-01

308

A measurement of kerma and absorbed dose in photon fields  

International Nuclear Information System (INIS)

Determination of the relation between the kerma(Kinetic Energy Released in Material) and the absorbed dose is one of the basic problems of dosimetry. Kerma and absorbed dose were measured for 6 MV X-ray from the high energy medical linear accelerator and 60Co gamma-ray. The experimental results showed that the absorbed dose in the transient equilibrium region practically coincide with the kerma in water and Al for 60Co. The maximum dose depths were 1.45 g/cm2 for 6 MV X-ray and 0.48 g/cm2 for 60Co gamma-ray. The ratios of the absorbed dose at maximum build-up to the collision kerma at the surface, (Katt), were 0.949 for 6 MV X-ray and 0.992 for 60Co gamma-ray. No difference was found between water and Al when the standard field size was used. This results show that the dependence of Katt on the material is very small. (Author).

1986-01-01

309

Displacement Kerma Cross Sections for Neutron Interactions in Molybdenum  

Energy Technology Data Exchange (ETDEWEB)

Modifications to the displacement kerma cross section methods employed in the NJOY99 nuclear data processing code are described. Calculations were performed with the modified code for molybdenum using ENDF-6 neutron interaction data. Results are presented for a range of plausible Ed values.

A. M. Ougouag; C. A. Wemple; C. D. Van Siclen

2004-04-01

310

Predicting plant uptake of organic chemicals from soil or air using octanol/water and octanol/air partition ratios and a molecular connectivity index  

Energy Technology Data Exchange (ETDEWEB)

A bioconcentration ratio (BCR) represents the ratio of the concentration of a chemical found in an exposed biological system, such as a plant or fish, to the concentration in the exposure medium (water, soil, or air). A comparison is made of the precision and accuracy of the molecular connectivity index (MCI) and the octanol/water partition coefficient (K{sub ow}) as predictors of BCRs from the soil matrix into above- or below-ground vegetation tissues. Calculated octanol/air partition coefficient (K{sub oa}) values are compared with calculated K{sub ow} and MCI values as predictors of measured air-to-plant BCRs. Based on a statistical evaluation of explained variance, residual error, and cross-validation, this evaluation reveals that the MCI provides higher precision, greater ease of use, and a more cost-effective method for predicting the potential bioconcentration of a chemical from soil into above-ground vegetation. Statistical analyses of the various methods reveal that both the K{sub ow} and MCI approaches have a similar level of precision for predicting BCRs from soil solution into roots and, among MCI, K{sub oa} and K{sub ow}; K{sub oa} is somewhat more precise and valid than MCI and K{sub ow} for estimating uptake, but all have limited accuracy as bioconcentration predictors. These latter results are derived mainly from the paucity of both reliable K{sub oa} values and measured air-to-plant BCRs and indicate a need for more experimental measurements from which more accurate models may be developed.

Dowdy, D.L. [Univ. of California, Davis, CA (United States). Dept. of Environmental Toxicology; McKone, T.E. [Univ. of California, Berkeley, CA (United States). School of Public Health

1997-12-01

311

Status of Obesity in Terms of Body Mass Index among Indian Air Force Personnel  

Directory of Open Access Journals (Sweden)

Full Text Available Introduction: This paper investigates the prevalence of obesity (BMI >30 kg/m2) among five geographical groups of Indian Air Force personnel of different age. Purpose of study: To observe the status of obesity among IAF and see whether there is age-wise and regional difference in obesity among the different geographical groups. Results: Gradual increase in mean BMI is seen as age of the population increases. There is an overall marked increase in BMI level among all the three age groups for all the other four zones. F-ratio test of normal range BMI does show significant difference among the zones. There is a statistically significant difference in normal BMI (18.5–24.9 wt/ht2) among all the age groups (F-ratio=11.561, p < 0.05). BMI correlated positively with age in the 20-25 age groups (r = 0.119, p= 0.000) and 26-30 age groups (r = 0.075, p= 0.009) respectively, but BMI did not show any statistically significant correlation with age in the 31-35 age group. Observations: A marked increase in overweight and pre-obese prevalence is seen both age and region wise in the IAF personnel if the Asian BMI cut off levels are applied

L. Robert Varte; D. Majumdar; Shweta Rawat; Inderjeet Singh

2011-01-01

312

Partial Kerma Factors for Neutron Scattering from ^16O^  

Science.gov (United States)

Success for the use of neutron for radiation therapy and other applications in radiological physics depends on the understanding of the interaction of neutron with elements in the tissue. Study of the mechanisms of energy deposition by neutron interaction with matter is very important to improve the understanding of the neutron dosimetry. Cross section data are the basic inputs for many types of calculations in radiation physics. One important quantity in some radiological applications of neutron is the kerma (kinetic energy released in material.) Differential elastic and inelastic neutron scattering from some elements of biological interests are available at energies 18 -- 26 MeV. Optical Model Potentials based on these measured cross sections may be used to calculate various quantities of interest for the neutron dosimetry at higher energies where cross section data may not be available. Kerma values for elastic and inelastic scattering of neutron from ^16O are obtained from differential cross sections.

Islam, Mohammed

2011-10-01

313

Evaluation and file making of PKA, KERMA and DPA data  

International Nuclear Information System (INIS)

[en] The formulas to calculate PKA spectrum, KERMA factor and DPA cross section are summarized as well as modeling effect on PKA spectrum. Enhancement of the higher energy neutron emission due to pre-equilibrium process hardens the spectrum of PKA recoiled by neutron but inversely the anisotropy of secondary neutron makes it softer. As a whole, pre-equilibrium process affects on softening the PKA spectrum and increases by a few ten percent DPA cross section due to inelastic scattering. For (n, 2n) reaction, significance of two particle emission is shown in case of the iron PKA spectrum. A scope of PKA and KERMA related data file is also presented. (author)

1991-01-01

314

Analysis of Kerma Area Product Measurements of Barium Enema Examinations  

International Nuclear Information System (INIS)

In Iceland guidance levels for patient radiation doses are expressed in terms of kerma area product (KAP) for complete examinations. Radiological departments' compliance with these guidance levels is based on the average value from kerma area product measurements on a sample of patients. Along with the measurements, supplementary data linked to the performance of the examination are recorded, and analysed for influence on the measurement results. Key parameters recorded are the number of film-screen radiographs, fluoroscopy KAP rate and time, applied tube potential and speed of film-screen system. By comparing the average values of these parameters with other radiological departments or with guidelines for radiographic procedures, the reasons for a deviation from the guidance level can be identified. (author)

1998-01-01

315

Experimental hydrogen kerma factors for incident neutron energies from 25 to 75 MeV  

International Nuclear Information System (INIS)

Hydrogen kerma factors and their uncertainties are deduced on an experimental basis, starting from our previously measured differential cross sections completed with available data from the literature, in the incident neutron energy range 25 to 75 MeV. The deduced experimental kerma factors are compared with theoretical predictions. A simple to use parametrization of the hydrogen kerma factor values in the incident neutron energy range 0.3 to 100 MeV is also proposed. (author)

1999-01-01

316

Fundamental relationships between linear energy transfer, absorbed dose, kerma, and exposure. Application to changes of mediums  

International Nuclear Information System (INIS)

[en] After briefly defining the quantities used in dosimetry and presenting them with a view to their simple adaptation to health physics problems, the authors establish simple mathematical relationships to express the absorbed dose, kerma and exposure in the case of electrons and photons, and also relationships between these various quantities considered in air. They then proceed to study the variations in these quantities at the interface between the air and the soft tissues of the organism and in depth in the tissues. They give the numerical values of the discontinuities liable to appear at the interface and the values obtained, relative to air, after electronic equilibrium is established in depth in the tissues. An example of application to dosimetry is also given in the case of an aluminium-walled ionization chamber. To conclude, the conditions to be fulfilled in order to make a direct measurement of the absorbed dose in the tissues are presented and discussed. (authors)[fr] Apres un bref rappel des definitions des grandeurs utilisees en dosimetrie et leur presentation en vue d'une adaptation simple aux problemes de radioprotection, les auteurs etablissent des relations mathematiques simples pour exprimer, dans le cas des electrons et des photons, la dose absorbee, le kerma et l'exposition ainsi que des relations entre ces diverses grandeurs considerees dans l'air. Les auteurs etudient ensuite les variations de ces grandeurs a l'interface de separation air-tissus mous de l'organisme et en profondeur dans les tissus. Ils donnent les valeurs numeriques des discontinuites susceptibles d'apparaitre a l'interface et les valeurs obtenues, relativement a l'air, apres etablissement de l'equilibre electronique en profondeur dans les tissus. Un exemple d'application a la dosimetrie est egalement donne dans le cas d'une chambre d'ionisation a paroi d'aluminium. En conclusion, les conditions a remplir en vue d'une mesure directe de la dose absorbee dans les tissus sont presentees et discutees. (auteurs)

1968-01-01

317

174?Reduction in Allergic Rhinitis Index by Decreasing Aero-Allergens and Malodor Causing Volatile Organic Compounds by Luna Air Purifiers Using Photo-Catalytic Oxidation (PCO) Technology.  

UK PubMed Central (United Kingdom)

BackgroundThe quality of the environment within buildings is a topic of major importance for public health. Breathing pure and clean air allows us to think more clearly, sleep more soundly, and stay healthier. Studies show that we receive 56% of our energy from the air we breathe, more than from water and food combined. On average we breathe 37 pounds of air a day. It has been established that the use of negative ions in a purification system is an effective means of eradicating aeroallergens in room air.MethodsThe wall-mount, Inducts and Mobile Sanifier air purification units of Luna are designed to sanitize air, to kill surface mold, bacteria, and viruses in areas up to 26,000 cubic feet. Samples were collected from the clinic rooms to analyze the VOC concentrations using the Luna air purifiers to detect the efficiency in reducing the VOCs in the indoor air. We analyzed the aroallergens and VOCs prevalent in the indoor air in the clinics at the Coulter Animal Hospital, Amarillo, Texas. The data were correlated to the inhalant allergy index before and after running air purifiers that use PCO technology.ResultsSamples from the clinic rooms to analyze the VOC concentrations using the Luna air purifiers to detect the efficiency in reducing the VOCs in the indoor air. The SKC Pocket Pump and thermal desorption tubes were used to obtain the samples from the indoor air. Pumps were set on 200 mL/min as air flow to estimate the concentration of Acetic acid, Isobutyric acid, Butyric acid, Isovaleric acid, Valeric acid, Hexanoic acid, Phenol, p-cresol, 4-ethyl, 2-amino, Indole, and Skatole. All desorption tube samples were analyzed using a Markes UNITY and Markes Ultra automated thermal desorber (ATD) and a Varian 3800/Saturn 2000 GC with a MS. Slides with double sticky tape were exposed to room air stained with 2% safranin and were observed using a BX-40 Olympus microscope with DP-70 and Image Pro Plus software.ConclusionsThe data were correlated with the aeroallergen index and the frequency of inhalant allergy cases that showed reduction in allergic rhinitis index on using air purifiers.

Ghosh N; Aguaiza C; Guzman A; Chudasama J; Bennert J; Das AB

2012-02-01

318

Improved models and results for evaluating neutron kerma factors  

International Nuclear Information System (INIS)

[en] The problem addressed in this thesis research is the accurate evaluation of neutron fluence-to-kerma (Kinetic Energy Released in Materials) factors from microscopic nuclear data. The algorithms developed for this purpose combine in a consistent manner the two basic methods for computing kerma factors, namely kinematics and direct energy balance. These algorithms are implemented in the code KAOS-V which was used as the main evaluation tool to construct the response function library KAOS/LIB-V. The library contains kerma factors and other nuclear response functions for 43 nonfissionable and 15 fissionable isotopes and elements. The chief source of data is the evaluated nuclear data files ENDF/B-V. Auxiliary nuclear data bases, e.g., the Japanese evaluated nuclear data library JENDL-2 were used as a source of isotopic cross sections when these data are not provided in ENDF/B-V files for a natural element. These are needed mainly to estimate average quantities such as effective Q-values for the natural element. This analysis of local energy disposition was instrumental in detecting and understanding energy-balance deficiencies and other problems in the ENDF/B-V data

1987-01-01

319

New evaluated kerma factor library from ENDF/B-V data  

International Nuclear Information System (INIS)

[en] The problem addressed in this paper is the accurate evaluation of neutron fluence-to-kerma (kinetic energy released in materials) factors from microscopic nuclear data. Accurate kerma factors are necessary for calculating the local heat generation in materials subject to neutron irradiation, such as shields and fusion reactor blankets. The new algorithms developed for this purpose combine in a consistent manner the two basic methods for computing kerma factors, namely, reaction kinematics and direct energy balance. These algorithms are implemented in the code KAOS-V (kerma and other stuff), which was used as the main evaluating tool to construct the nuclear response function library KAOS/LIB-V

1989-01-01

320

Kerma factors for use in 37-group neutron spectrum calculations. Technical report  

Energy Technology Data Exchange (ETDEWEB)

Neutron kerma factors have been regrouped from the format of the International Commission on Radiation Units and Measurements Report 26 (ICRU-26) to supplement those available in the 37-group format of the Oak Ridge Data Library Collection 31 (DLC-31). Lists of regrouped neutron kerma factors are presented for eight elements and for seven compounds and mixtures. For several elements, disagreements in excess of 15% were observed between those neutron kerma factors available in DLC-31 and the regrouped neutron kerma factors of ICRU-26.

Zeman, G.H.; Bice, W.S. Jr.

1983-12-01

 
 
 
 
321

Particulate Matter Concentrations and the Air Quality Index in the Central Part of Tehran City, Tehran, Iran  

Directory of Open Access Journals (Sweden)

Full Text Available Background and Aim: The association between particulate matter (PM) and cardiovascular diseases (CVD) was shown in the mid-1990 through several epidemiological studies. Increased hospital admissions of patients with cardiovascular and respiratory problems in days when, due to high concentrations of PM, air pollution is high, bears witness to this. In this study we measured concentrations of the PM fractions in the air in the central part of Tehran city, Tehran, Iran Methods and Materials: The concentrations of suspended particles (PM10, PM2.5 and PM1) were measured during February-June 2007 in two stations in central Tehran. Stations1 was in the Enghelab Square, a crowded part of the city with highly polluted air, where many educational institutes (e.g. Tehran University) are located, while station 2 was located near the Nasr Bridge, through which one of the most important highways (Martyr Chamran Highway) passes. The MP concentrations were measured once every 3 days, twice each day, once during the morning traffic rush hour (9-11 AM) and once during the afternoon traffic rush hour (4-6 PM), using a portable device, e.g., Environmental Dust Monitor Model GRIMM107.Results: One-way ANOVA tests showed significant differences (p<0.05) between PM concentration in the two stations. The daily mean concentrations of PM10, PM2.5 and PM1were, respectively, 77.67, 44.46 and 26.89 ?mm-3, in station 1, and 55.31, 28.15 and 19.12 ?mm-3, in station 2."nConclusion: The concentrations of PM10, PM2.5 and PM1 were lower in both stations than the respective USEPA 24-hour primary NAAQS standards, established in 1987 for PM10 and in 1999 for PM2.5. However, the proportions of the total samples with PM concentrations exceeding the new EPA standards established in 2006 were 67% and 25% in stations 1 and 2, respectively. The air quality index (AQI) was unhealthy in 32% and 10.5% of the samples in stations 1 and 2, respectively. In addition, PM2.5 was the indicator pollutant in 87% of the samples in station 1 and 82% of the samples in station 2.

M Leili; K Nadafi; R. Nabizadeh; M Yunesian; A R Mesdaghinia; Sh Nazmara

2009-01-01

322

Nuclear heating constant KERMA library. Nuclear heating constant library for fusion nuclear group constant set FUSION-J3.  

Science.gov (United States)

Based on evaluated nuclear data file JENDL-3, published in April 1990, we produced a nuclear group constant KERMA library for fusion nuclear group constant set FUSION-J3 instead of the KERMA library for GICX40. Neutron KERMA factors were calculated direct...

K. Maki Y. Seki H. Kawasaki K. Kosako

1991-01-01

323

The use of evaluated nuclear data libraries for the calculation of kerma factors  

International Nuclear Information System (INIS)

[en] A computational model is developed for calculating neutron kerma factors and total energy of protons from basic nuclear data for all neutron reaction types in any energy range. The evaluated nuclear data libraries are used for calculating the kerma factors. (author). 4 refs

1989-01-01

324

One-hour equivalent of a 24-hour average particulate matter standard and its potential application in the index of the quality of the air (IQUA) formulation  

Energy Technology Data Exchange (ETDEWEB)

The feasibility of incorporating a PM2.5 standard into the Alberta Index of the Quality of the Air (IQUA) was discussed. The IQUA is part of Alberta's air quality management system which provides a qualitative description of air quality based on hourly concentration of carbon monoxide, ozone, nitrogen oxides, sulfur dioxide and coefficient of haze (COH). If the new parameter of PM2.5 is to be added to these five major air quality parameters, the resulting cumulative exposure index (CUEX) should reflect relevant air quality guidelines and standards. These issues were addressed in a three-part analysis based on: (1) a one-hour equivalent of the 24-hour PM2.5 Canada Wide standard, (2) an assessment of hypothetical exposure, and (3) the potential application of a one-hour PM2.5 concentration in the IQUA. Daily maximum and daily average PM2.5 data from monitors found at two locations in Alberta were used to determine the relationship between one-hour and 24-hour average PM2.5 levels. The study showed that when the one-hour equivalent concentrations were used in the formulation of Alberta's IQUA, the percentage of time air quality was in the 'Good' category and decreased from 93.6 per cent to 90.5 per cent in 1998 at the Edmonton Northwest Station and from 99.5 per cent to 98.1 per cent in 1998 at the Calgary Central Station where 'fair' air quality was noted. It was also determined that PM2.5 concentrations can effectively indicate air quality during forest fires. When PM2.5 replaced COH in the IQUA, the number of 'poor' air quality hours increased from zero to 23 hours at both stations during smoke events. 10 refs., 10 tabs., 9 figs.

Fu, L.; Hunt, K.; Ayers, J. [Alberta Environment, AB (Canada). Science and Technology Branch; Myrick, B.; Aklilu, Y. [Alberta Environment, AB (Canada)

2000-07-01

325

Neutron kerma factor measurements near 15 MeV using microdosimetric techniques  

Energy Technology Data Exchange (ETDEWEB)

The neutron kerma factor is the initial kinetic energy imparted to charged particles per unit mass per unit neutron fluence. Accurate kerma factors can be calculated if particle cross section measurements are available for numerous emission angles, all particle species produced, and many neutron bombarding energies. Alternatively, kerma factors can be inferred from integral absorbed dose measurements under conditions satisfying transient charged particle equilibrium so that dose and kerma can be equated. This report summarizes such measurements using small, low pressure gas, spherical proportional counters exposed to 14-18 MeV neutrons. In this energy interval, the neutron kerma factor values are found to be systematically lower than calculated values based upon microscopic cross sections tabulated in ENDF/B-IV and -V.

Deluca, P.M. Jr.

1985-05-15

326

Relations between effective dose, effective dose equivalent, area-kerma product, and energy imparted in chest radiography  

International Nuclear Information System (INIS)

[en] To estimate both effective dose (E) and effective dose equivalent (HE) in PA chest radiography, measurements of the absorbed dose to different organs were performed with thermoluminescence dosemeters placed in a water-filled phantom with the geometry of a 70 kg adult. During the X-ray investigations of the phantom, measurements of the air kerma integrated over the beam area were performed to determine the energy imparted, ?. The ratios between E and ? for three different radiation qualities between 100 and 140 kVp were found to be between 13 and 15 mSv.J-1. The corresponding ratios between E and the area-kerma product varied between 1500 and 2800 mSv per mGy.m2. The ratio between HE and ? was found to be 17-18 mSv.J-1. With the X ray equipment used, mean value of E for 36 adult patients undergoing PA chest examination was 35 ± 10 ?Sv (1 SD) and the mean HE value 44 ± 11 ?Sv (1 SD). (author)

1993-01-01

327

The relative tissue kerma sensitivity of thermoluminescent materials to neutrons  

International Nuclear Information System (INIS)

This review is intended as the basis for establishing the response of thermoluminescent (TL) materials to neutrons. There are many factors which affect the relative tissue kerma sensitivity, K, including the TL material itself; the characteristics of the TL reader; the irradiation conditions; batch to batch variations; and environmental conditions such as temperature, humidity, UV light and irradiation history. Most of the data in the literature are produced under different conditions and so a true comparison is not valid. However, it has been possible to eliminate the kerma-dependent factors from k and so demonstrate that the efficiency of TL materials for detecting neutrons, etasub(n), relative to that for detecting 60Co gamma rays, etasub(s), is essentially constant for a given material for neutron energies from thermal to about 10 MeV. Above this energy, etasub(n)/etasub(s) increases significantly for some TL materials. The increase can be accounted for qualitatively by a reduction in LET at higher energies. There are large uncertainties in the data which could be reduced if they are produced under well defined conditions. The main objective of this review is to provide the neutron relative sensitivity for several TL materials which may be used for assessing the gamma ray dose in a mixed field. (author).

1986-01-01

328

A RADIATION EXPOSURE INDEX FOR CT.  

UK PubMed Central (United Kingdom)

The purpose of this study is to define an Exposure Index for CT (EICT) and to estimate the magnitude of the EICT for common clinical CT examinations. For a single-axial rotation of a CT X-ray tube that includes only rays that pass through the patient, the CT Exposure Index (EICT) is defined as the average Air Kerma that would be incident on an extended 360° detector array completely surrounding the patient. For an axial scan of a uniform cylindrical phantom, EICT can be approximated as T × [(CTDIair)/4] × [?°/360°] where T is the fractional transmission through the cylinder, CTDIair is the CT Dosimetry Index-determined 'free in air' at isocentre, and ?/2 is the fan beam angle that will completely irradiate a cylindrical phantom at isocentre. The value of CTDIair can be estimated from the weighted CTDI (CTDIw) for a given CT examination, and the angle ? depends on the irradiation geometry that can be obtained from the cylinder diameter (r) and the focus to isocentre distance (R). At a voltage of 120 kV, transmission through an adult head was ?2.6%, through an adult abdomen?0.4% and through a 5-y-old paediatric abdomen ?3%. Average ratios of CTDIair/CTDIw were 1.42±0.12 in 16-cm dosimetry phantom and 2.82±0.37 in 32-cm phantom. Values of ? ranged from 30.1° (R = 61 cm and r=8 cm) to 85.3° (R = 55 cm and r=20 cm). For an adult head CT examination, EICT was estimated to be?70 µGy at a CTDIvol of 75 mGy (16 cm), and for an adult abdominal CT examination, EICT was estimated to be?11 µGy at a CTDIvol of 25 mGy (32 cm). For an abdomen CT examination in a 5-y-old child, EICT was estimated to be ?21 µGy at a CTDIvol of 20 mGy (16 cm). The EICT is introduced that provides a quantitative measure of the amount of the radiation used to generate images in any CT examination and is analogous to the average image receptor Exposure Index recently proposed for use in projection imaging. The EICT metric provides operators with an objective index of the amount of the radiation used to create CT images and can be used to control quantum mottle in CT.

Huda W

2013-05-01

329

A RADIATION EXPOSURE INDEX FOR CT.  

Science.gov (United States)

The purpose of this study is to define an Exposure Index for CT (EICT) and to estimate the magnitude of the EICT for common clinical CT examinations. For a single-axial rotation of a CT X-ray tube that includes only rays that pass through the patient, the CT Exposure Index (EICT) is defined as the average Air Kerma that would be incident on an extended 360° detector array completely surrounding the patient. For an axial scan of a uniform cylindrical phantom, EICT can be approximated as T × [(CTDIair)/4] × [?°/360°] where T is the fractional transmission through the cylinder, CTDIair is the CT Dosimetry Index-determined 'free in air' at isocentre, and ?/2 is the fan beam angle that will completely irradiate a cylindrical phantom at isocentre. The value of CTDIair can be estimated from the weighted CTDI (CTDIw) for a given CT examination, and the angle ? depends on the irradiation geometry that can be obtained from the cylinder diameter (r) and the focus to isocentre distance (R). At a voltage of 120 kV, transmission through an adult head was ?2.6%, through an adult abdomen?0.4% and through a 5-y-old paediatric abdomen ?3%. Average ratios of CTDIair/CTDIw were 1.42±0.12 in 16-cm dosimetry phantom and 2.82±0.37 in 32-cm phantom. Values of ? ranged from 30.1° (R = 61 cm and r=8 cm) to 85.3° (R = 55 cm and r=20 cm). For an adult head CT examination, EICT was estimated to be?70 µGy at a CTDIvol of 75 mGy (16 cm), and for an adult abdominal CT examination, EICT was estimated to be?11 µGy at a CTDIvol of 25 mGy (32 cm). For an abdomen CT examination in a 5-y-old child, EICT was estimated to be ?21 µGy at a CTDIvol of 20 mGy (16 cm). The EICT is introduced that provides a quantitative measure of the amount of the radiation used to generate images in any CT examination and is analogous to the average image receptor Exposure Index recently proposed for use in projection imaging. The EICT metric provides operators with an objective index of the amount of the radiation used to create CT images and can be used to control quantum mottle in CT. PMID:23690648

Huda, Walter

2013-05-19

330

The ability of bispectral index to detect intra-operative wakefulness during isoflurane/air anaesthesia, compared with the isolated forearm technique.  

Science.gov (United States)

Clinical signs are unreliable for guiding anaesthetic administration and it is suggested that using the bispectral index can improve anaesthetic delivery. In the current study, isoflurane administration was guided to a bispectral index range of 55-60. Intra-operative responsiveness, as assessed by the isolated forearm technique, was compared with whether the bispectral index predicted/identified a patient's appropriate hand movements in response to commands. Thirty-four women underwent major gynaecological surgery with isoflurane/air and atracurium. Eleven women responded on 32 occasions with appropriate hand movements to commands given during surgery, of which the bispectral index detected 17 (sensitivity 53%). The bispectral index suggested consciousness 660 times in the absence of any movement responses (specificity 69%). The positive predictive value of the bispectral index was 3%. The median (IQR [range]) bispectral index value associated with an intra-operative response was significantly lower than that associated with eye opening after surgery: 60 (50-68 [36-83]) vs 77 (75-84 [59-90]), respectively (p = 2.25 × 10(-8)). Conversely, end-tidal isoflurane concentration was significantly higher at intra-operative response than at eye opening: 0.3 (0.3-0.4 [0.2-0.9]) vs 0.2 (0.1-0.2 [0.1-0.3]), respectively (p = 7.36 × 10(-8)). For patients who responded more than once during surgery, the bispectral index value associated with a response was not constant. No patient had recall for surgery or the taped commands, and only one could remember dreaming (a good dream). Titrating isoflurane to target a bispectral index range of 55-60 may result in an unacceptable number of patients who are conscious during surgery (albeit without recall). PMID:24047289

Russell, I F

2013-10-01

331

Kerma factors of elements and compounds for neutron energies below 30 MeV  

International Nuclear Information System (INIS)

Based on recently calculated tables of neutron kerma factors for 19 elements, kerma factors for 44 compounds have been calculated. The neutron energy range covered extends from 8 eV to 30 MeV. Because of the increased uncertainty in the nuclear data at the higher energies, care must be taken when the tables are applied above 15 MeV. The user must also be careful when applying these results to compounds at low neutron energies, because of the difficulties in associating kerma values with molecular materials at energies below approximately 30 eV. (author)

1982-01-01

332

Carbon Kerma factor for 18- and 20-MeV neutrons  

Energy Technology Data Exchange (ETDEWEB)

Earlier measurements of the kerma factor of carbon have been extended to neutron energies of 18 and 20 MeV. The measured values are lower than published values based on estimated microscopic cross sections.

DeLuca, P.M. Jr.; Barschell, H.H.; Burhoe, M.; Haight, R.C.

1986-10-01

333

Spectrum-averaged kerma factors for reactor dosimetry with paired ion chambers. Technical report  

Energy Technology Data Exchange (ETDEWEB)

Neutron and gamma spectrum-averaged kerma factors (SAKF's) were calculated for four reference spectra and 18 configurations of the AFRRI TRIGA reactor for materials of interest in dosimetry applications. Reactor gamma SAKF ratios for tissue to carbon and for tissue to magnesium (ion chamber wall materials) gave average values + or - 2 standard deviations of 1.13 + or - 1% and 1.09 + or - 3%, respectively. For some reactor configurations, the gamma SAKF ratios were as much as 7.6% different from corresponding values for cobalt-60 gamma rays. Reactor neutron SAKF ratios for ICRU (International Commission on Radiation Units and Measurements) muscle to ion chamber gas materials were as follows: TE (tissue-equivalent) gas, 0.983 + or - 0.5% for all configurations; carbon dioxide, 9.8 + 10%; and argon, 71 + or - 27%. At depth in a phantom, the neutron SAKF for ICRU muscle differed substantially from the free-in-air value for the same reactor configuration. This finding suggests the need for more thorough spectrum determinations in anatomical phantoms and for more sophisticated dosimetric tools to better quantitate the dose deposition process.

Ferlic, K.P.; Zeman, G.H.

1983-09-01

334

Kerma factors for neutrons with energies above 20 MeV  

International Nuclear Information System (INIS)

[en] A short review is presented concerning the calculation of kerma factors for neutrons with energies above 20 MeV. Using the program ALICE, the light particle spectra from neutron-induced reaction and kerma factors for C, N, O and tissue have been calculated. The spectra are also compared with experimental results by Romero et al. at 27.4, 39.7 and 60.7 MeV neutron energy. (author)

1989-01-01

335

Generation and comparison of KERMA and damage data of lead, iron and silicon  

International Nuclear Information System (INIS)

The KERMA and damage data of lead, iron and silicon were generated from ENDF/B-VI.8, JENDL-3.3 and JEFF-3. The KERMA by the elastic, inelastic and disapperance reactions were calculated, respectively. The damage data by neutron irradiation were also generated and tried to calculate DPA of the materials. The material damage is mainly made by absorption reaction at lower energy, elastic next and inelastic scattering reactions at higher energy.

2003-01-01

336

C/O Kerma coefficient ratio for 96 MeV neutrons deduced from microscopic measurements  

International Nuclear Information System (INIS)

Double-differential cross sections for neutron-induced light-ion production at 96 MeV have been measured for a variety of nuclei at The Svedberg Laboratory. Using the measured cross-section data, we deduce the Kerma coefficient from carbon and oxygen for p, d, t, 3He and ? particles. In order to get the total Kerma for C and O, we add GNASH calculation values where experimental data are not available and obtain a Kerma coefficient of 7.85 ± 0.63 fGy m2 for carbon and 7.09 ± 0.57 fGy m2 for oxygen. The C/O Kerma coefficient ratio then becomes 1.11 ± 0.11. In addition we determine the Kerma ratio between ICRU muscle and A-150, again adding calculations with the GNASH code where no experimental data are available, and obtain a value of 0.98 ± 0.05. While the Kerma coefficients for carbon and oxygen do not agree with the prediction in ICRU Report 63, the ratio values are in good agreement with existing predictions.

2010-01-01

337

Obtención de un índice de riesgo de erosión eólica y su aplicación en la provincia de Buenos Aires, Argentina Erosion risk index attainment and its application in the Buenos Aires province, Argentina  

Directory of Open Access Journals (Sweden)

Full Text Available En este trabajo se propone un índice climático para estimar el riesgo de ocurrencia de erosión eólica basado en las leyes físicas que cuantifican el efecto de la agresión del medio (turbulencia atmosférica) sobre la resistencia del sistema (textura del suelo). Este indicador es obtenido en función de observaciones meteorológicas estándar a partir de un modelo que incluye la alteración del perfil vertical del viento ocasionada por la presencia de partículas de suelo en el aire y es expresado en términos de la probabilidad de que la potencia del viento supere las condiciones umbrales para el comienzo del proceso. Si bien el índice fue obtenido para suelo seco y desnudo, la metodología permite avanzar hacia un modelo de evaluación de riesgo más general, si se determinan previamente los valores de velocidad de fricción umbral que corresponden a distintas condiciones que afectan la resistencia del suelo tales como la humedad del suelo, el contenido de materia orgánica, cobertura y uso de la tierra. Este modelo ha sido utilizado para evaluar la distribución espacial del riesgo de erosión eólica en la Provincia de Buenos Aires, Argentina.This paper proposes a climatic index to estimate the wind erosion risk based upon physical laws that quantify the effect of environment's aggression (atmospheric turbulence) on system resistance (soil texture). This index is obtained as a function of standard meteorological observations including the alteration of the wind profile produced by the presence of soil particles in the air and it is expressed in terms of the probability for the wind power to exceed the threshold conditions. Although this index was obtained for dry and bare soil, it may mean an advance towards a more general model for risk evaluation if other factors intervening in soil resistance, such as soil humidity, organic material content, land cover and use are included. This model has been used to evaluate the spatial distribution of the wind erosion risk in Buenos Aires Province, Argentina.

Susana Goldberg; Gabriel Weiss

2004-01-01

338

Kerma factor evaluation and its application in nuclear heating experiment analysis  

International Nuclear Information System (INIS)

[en] The accuracy of calculating 'kerma factor', which is the response function for nuclear heating is very important in many applications, particularly fusion systems. A computer code, called MAZE, has been developed primarily for evaluating neutron and gamma kerma factors based on an improved modeling and a capability to analyze basic data and evaluate consistency in preserving energy. Kinematics equations and energy conservation considerations are modeled in the code. The code has features that allow comparison and analysis among different methods of calculating the kerma factor and it provides users with data information needed to make user-oriented selections from two to three, often different, results. A kerma factor library, called MAZE-LIB, has been generated with MAZE for most of the materials of interest in fusion based on the most recent and accurate data available, FENDL library, which is the nuclear data library selected by ITER. The kerma factor library provided in this work is the result of an extensive analysis of nuclear data and careful selection from among often different results from the different calculational methods. It was shown that some data inconsistency problems in preserving the energy still exist in the FENDL library. Some problems with the widely used computer code NJOY were exposed during the process of the kerma factor evaluation, which is crucial at this stage of fusion research, since NJOY is the primary nuclear data processing code selected by ITER. Comparison with nuclear heating experimental data, derived from very recent integral experiments with 14 MeV neutrons and the analysis of the uncertainty in prediction have been carried out using the newly developed kerma factors. (orig.)

1997-01-01

339

Kerma factor evaluation and its application in nuclear heating experiment analysis  

Energy Technology Data Exchange (ETDEWEB)

The accuracy of calculating `kerma factor`, which is the response function for nuclear heating is very important in many applications, particularly fusion systems. A computer code, called MAZE, has been developed primarily for evaluating neutron and gamma kerma factors based on an improved modeling and a capability to analyze basic data and evaluate consistency in preserving energy. Kinematics equations and energy conservation considerations are modeled in the code. The code has features that allow comparison and analysis among different methods of calculating the kerma factor and it provides users with data information needed to make user-oriented selections from two to three, often different, results. A kerma factor library, called MAZE-LIB, has been generated with MAZE for most of the materials of interest in fusion based on the most recent and accurate data available, FENDL library, which is the nuclear data library selected by ITER. The kerma factor library provided in this work is the result of an extensive analysis of nuclear data and careful selection from among often different results from the different calculational methods. It was shown that some data inconsistency problems in preserving the energy still exist in the FENDL library. Some problems with the widely used computer code NJOY were exposed during the process of the kerma factor evaluation, which is crucial at this stage of fusion research, since NJOY is the primary nuclear data processing code selected by ITER. Comparison with nuclear heating experimental data, derived from very recent integral experiments with 14 MeV neutrons and the analysis of the uncertainty in prediction have been carried out using the newly developed kerma factors. (orig.)

Zhang Li; Abdou, M.A. [California Univ., Los Angeles, CA (United States)

1997-07-01

340

The energy balance of nuclear reaction and KERMA factors  

International Nuclear Information System (INIS)

The unified Hauser-Feshbach and exciton model has been established, with which the continuum and discrete states in both equilibrium and pre-equilibrium reaction processes can be described in a unified approach. Based on this model the UNF code system for calculating nuclear reaction data has been developed. Now it has been widely used for nuclear data calculations and for the analysis of the experimental data. In the UNF code system the reactions induced by neutron, changed particles and gamma ray are involved. The angular momentum conservation and parity conservation are taken into account in whole reaction processes. In view of the recoil effect, as to the multi-particle emissions processes has not been considered fully in other models, the energy spectra for all of kinds multi-particle emission mechanism are derived in this report with fully energy balance. By means of this formula the energies carried by the outgoing particles can be obtained exactly. The problems of kerma factor calculations are discussed

2001-01-01

 
 
 
 
341

Precision refractive index measurements of air, N2, O2, Ar, and CO2 with a frequency comb  

International Nuclear Information System (INIS)

We report precision measurements of the refractive indices of dry air, N2, O2, Ar, and CO2, performed by using a frequency comb as the light source in a Mach-Zehnder interferometer setup. Improved dispersion formulas for all gases are derived with a sensitivity level of 10-9. These results are valid for a wavelength range from 740 to 860 nm and are in good agreement with measurements from other groups.

2008-06-10

342

Direct determination of kerma for a d(48.5)+Be therapy beam  

Energy Technology Data Exchange (ETDEWEB)

An experimental determination of the neutron kerma ratio between muscle tissue and A-150 plastic was performed at the newly commissioned d(48.5)+Be therapy facility in Detroit. Low-pressure proportional counters with separate walls made from A-150 plastic, graphite, zirconium oxide and zirconium served to measure ionization yield spectra. The absorbed dose in the wall of each counter was determined and rendered the A-150 and carbon kerma directly, whilst that for oxygen was deduced from differences between the matched metal oxide and metal pair. This enabled the evaluation of an effective kerma ratio as a function of radiation field size and hydrogenous filtration. Although filtration was observed to harden the beam, the application of a single kerma ratio for the various irradiation conditions investigated was found to be appropriate. A neutron kerma ratio of 0.90{+-}0.03 was assessed for the Detroit facility, which is lower at the 1{sigma} level than the 0.95 currently recommended in the dosimetry protocol for high-energy neutron beams. (author)

Binns, P.J.; DeLuca, P.M. Jr. [University of Wisconsin, Madison, WI 53706 (United States); Maughan, R.L.; Kota, C. [Harper Hospital, Detroit, MI 48201 (United States)

1998-12-01

343

Energy and kerma dependence of the Czechoslovak dosimetric Si-diode  

International Nuclear Information System (INIS)

The dose-response relationships were studied the Czechoslovak long base silicon diode in a neutron field. Diodes were manufactured from an N type silicon monocrystal and were 1.2x1.8x1.8 mm3 in size; the response of such diodes is given by the change in voltage on the diode during the flow of a constant 25 mA forward current. The properties of the diode were studied in neutron fields from the following sources: 252Cf, U 120 M isochronous cyclotron, WWR-S research reactor, pulse reactors IBR-30 and IBR-2. The found variation of voltage changes with tissue kerma of neutrons were not linear and their shape depended on the energy spectrum of the neutrons, thus differing from one source to another. The variation could well be approximated by the function K/sub n/=a?U/sup b/ (K/sub n/ - tissue kerma, energy dependence of the diodes and the errors which may occur in the determination of kerma in an unknown neutron field. Within the kerma value range of 0.5 to 30 Gy the uncertainty of determining kerma is given by the factor 1.3+-1. (A.K.).

1985-01-01

344

Neutron kerma factors for magnesium and aluminium measured with low-pressure proportional counters  

Energy Technology Data Exchange (ETDEWEB)

Low-pressure proportional counters enable the simultaneous determination of neutron absorbed dose in the detector wall material and of ionisation yield spectra. In well defined neutron fields the kerma to fluence ratio (kerma factor) can be evaluated from the absorbed dose results. To date this type of investigation has been performed mainly with the compound tissue-equivalent material A-150 plastic. The determination of elemental kerma factors with the proportional counter method is applicable to those materials which enable the construction of electrically conductive chamber walls. In the present investigation, kerma factor measurements with aluminium- and magnesium-walled proportional counters were performed at neutron energies of 13.9, 15.0, 17.0 and 19.0 MeV. The gas-to-wall absorbed dose conversion factors were assessed making use of the measured ionisation yield spectra. Up to 17 MeV neutron energy the measured kerma factors are in good agreement with values calculated by Caswell et al and Dimbylow. At 19.0 MeV the measured results are significantly higher than those of Caswell et al but are in good agreement with those of Dimbylow.

Buehler, G.; Menzel, H.G.; Schuhmacher, H.; Dietze, G.; Guldbakke, S.

1986-06-01

345

Air  

International Nuclear Information System (INIS)

In recent years several regulations and standards for air quality and limits for air pollution were issued or are in preparation by the European Union, which have severe influence on the environmental monitoring and legislation in Austria. This chapter of the environmental control report of Austria gives an overview about the legal situation of air pollution control in the European Union and in specific the legal situation in Austria. It gives a comprehensive inventory of air pollution measurements for the whole area of Austria of total suspended particulates, ozone, volatile organic compounds, nitrogen oxides, sulfur dioxide, carbon monoxide, heavy metals, benzene, dioxin, polycyclic aromatic hydrocarbons and eutrophication. For each of these pollutants the measured emission values throughout Austria are given in tables and geographical charts, the environmental impact is discussed, statistical data and time series of the emission sources are given and legal regulations and measures for an effective environmental pollution control are discussed. In particular the impact of fossil-fuel power plants on the air pollution is analyzed. (a.n.)

2001-01-01

346

Calculated photon KERMA factors based on the LLNL EGDL [Evaluated Gamma-Ray Data Library] data file  

International Nuclear Information System (INIS)

[en] Photon (Gamma-Ray) KERMA factors calculated from the LLNL EGDL (Evaluated Gamma-Ray Data Library) file are tabulated for the elements from Z=1 to Z=30 and for 15 composite materials. The KERMA factors are presented for 191 energy groups over the incident photon energy range from 100 eV to 100 MeV. 3 refs

1986-01-01

347

Methodology for the generation of neutron kerma factors from JEF2 lithium-7 data  

International Nuclear Information System (INIS)

[en] The nuclear data processing code NJOY89 is designed to generate neutron kerma factors using double-differential charged-particle data from JEF-2 and ENDF/B-VI. No such data is given for 7Li and JEF-2, file 6 containing double-differential neutron distributions instead. An alternative approach, involving the multigroup neutron kerma code ENBAL2 and some pre-processing using NJOY89, is presented. At present, this is the only method of utilizing the double-differential neutron data for the generation of neutron kerma factors. An outline of the methodology involved is given, together with a description of errors discovered in NJOY89, and their solutions. (orig.)

1992-01-01

348

Kerma factors of oxygen, aluminium, and silicon for 15 to 20 MeV neutrons  

International Nuclear Information System (INIS)

[en] The previously reported measurements of the kerma factor of carbon have been extended to O, Al, and Si. Cylindrical proportional counters were constructed with walls of Zr, ZrO, Al, and Si. Charged particles produced in the walls deposited energy in the low pressure filling gas. The resulting microdosimetric spectra yielded kerma values. The kerma for O was obtained from the difference between spectra obtained with the ZrO and Zr counters. A similar counter constructed of A-150 tissue-equivalent plastic and an A-150 walled ionisation chamber served to determine the neutron fluence. 15 MeV neutrons were produced with the Lawrence Livermore National Laboratory Rotating Target Neutron Source. 17 to 19 MeV neutrons were obtained by bombarding a tritium gas target with deuterons from the University of Wisconsin electrostatic accelerator. (author)

1988-01-01

349

Effects of nuclear reaction mechanisms on high-energy neutron kerma factors for carbon  

International Nuclear Information System (INIS)

[en] Kerma factors are crucial in neutron radiotherapy to convert the output of an ionization chamber into a dose in tissue, allowing intercomparison between different facilities. The most recent major evaluation of neutron-carbon cross sections was made in 1978 for the latest version of the Evaluation Neutron Data File (ENDF/B-V). However considerable evidence has recently accrued to indicate that there may be major discrepancies in this evaluation at 14 MeV and above. As the sixth version of ENDF is several years away, and kerma factors are required immediately, it is timely to call attention to this issue. The kerma factor for carbon (kinetic energy released to charged particles per unit mass per unit fluence), requires knowledge not only of the integrated cross section, but also of the emitted charged-particle-energy spectra. Thus, detailed reaction mechanisms or, equivalently, complete secondary charged-particle spectra must be known

1986-01-01

350

Comparison of entry kerma in the skin with the variation of automatic exposure control in mammography  

International Nuclear Information System (INIS)

The purpose of this work was to analyze the entry kerma values in the skin in comparison with the automatic exposure control tests. To achieve that, 44 mammographies were evaluatecl in the city of Rio de Janeiro. The reference values adopted were taken from the current Brazilian legislation, 'Portaria no. 453/98 do Ministerio da Saude', where the reference entry kerma value in the skin corresponds to 10 mGy and the maximum variation accepted to the automatic exposure control test corresponds to 30 optic unities. It was observed that 46.7% of the analyzecl mammographies presented entry kerma values in the skin above the reference level established, whereas the automatic exposition control for these same mammographies was within the acceptability parameters. (author)

2009-01-01

351

Obtención de un índice de riesgo de erosión eólica y su aplicación en la provincia de Buenos Aires, Argentina/ Erosion risk index attainment and its application in the Buenos Aires province, Argentina  

Scientific Electronic Library Online (English)

Full Text Available Abstract in spanish En este trabajo se propone un índice climático para estimar el riesgo de ocurrencia de erosión eólica basado en las leyes físicas que cuantifican el efecto de la agresión del medio (turbulencia atmosférica) sobre la resistencia del sistema (textura del suelo). Este indicador es obtenido en función de observaciones meteorológicas estándar a partir de un modelo que incluye la alteración del perfil vertical del viento ocasionada por la presencia de partículas de (more) suelo en el aire y es expresado en términos de la probabilidad de que la potencia del viento supere las condiciones umbrales para el comienzo del proceso. Si bien el índice fue obtenido para suelo seco y desnudo, la metodología permite avanzar hacia un modelo de evaluación de riesgo más general, si se determinan previamente los valores de velocidad de fricción umbral que corresponden a distintas condiciones que afectan la resistencia del suelo tales como la humedad del suelo, el contenido de materia orgánica, cobertura y uso de la tierra. Este modelo ha sido utilizado para evaluar la distribución espacial del riesgo de erosión eólica en la Provincia de Buenos Aires, Argentina. Abstract in english This paper proposes a climatic index to estimate the wind erosion risk based upon physical laws that quantify the effect of environment's aggression (atmospheric turbulence) on system resistance (soil texture). This index is obtained as a function of standard meteorological observations including the alteration of the wind profile produced by the presence of soil particles in the air and it is expressed in terms of the probability for the wind power to exceed the threshol (more) d conditions. Although this index was obtained for dry and bare soil, it may mean an advance towards a more general model for risk evaluation if other factors intervening in soil resistance, such as soil humidity, organic material content, land cover and use are included. This model has been used to evaluate the spatial distribution of the wind erosion risk in Buenos Aires Province, Argentina.

Goldberg, Susana; Weiss, Gabriel

2004-12-01

352

Determination of kerma factors for A-150 plastic and carbon for neutron energies above 20 MeV  

International Nuclear Information System (INIS)

[en] Kerma factors for carbon and A-150 tissue-equivalent plastic were measured in nearly monoenergetic neutron beams with energies of 26 and 38 MeV, respectively. The kerma was measured with low-pressure propotional counters (PC) with walls made of graphite and A-150 plastic material. Corrections had to be made for significant fractions of low-energy neutrons which were present in the beams. The correction factors for kerma were determined from time-of-flight measurements using NE213 scintillation detectors and PCs. For the kerma factor weighted mean neutron energies of 26.3(29) and 37.8(25) MeV the kerma factors for carbon were determined to be 34.7(29) and 41.0(37) pGy cm2 and for A-150 plastic to be 75.2(51) and 78.4(53) pGy cm2. (orig.)

1992-01-01

353

Measurement of neutron kerma factors in C, O, and Si at 18, 23 and 25 MeV  

International Nuclear Information System (INIS)

[en] Carbon, oxygen, and silicon kerma factor values were measured at neutron energies of 18-25 MeV using microdosimetric techniques. Small spherical and cylindrical proportional counters served to measure neutron kerma, while detection of the activity induced in Teflon (C2F4)n samples by the 19F(n,2n)18F reaction determined the fast neutron fluence. Deuteron bombardment of a tritium gas target provided a monoenergetic neutron source plus a secondary flux of 0 to 6 MeV neutrons. At each energy, a liquid scintillator-based time-of-flight spectrometer measured the neutron spectrum. In order to correct our measurements for kerma contributed by off-energy neutrons, we combined the secondary neutron spectrum with tabulated energy-dependent kerma factors and subtracted the result from the total measured kerma. (author)

1992-01-01

354

Experimental kerma coefficients for carbon deduced from microscopic cross sections at 96 MeV incident neutron energy  

International Nuclear Information System (INIS)

The double-differential cross sections for (n, px), (n, dx), (n, tx), (n, 3Hex) and (n, ?x) reactions in carbon have been measured at 96 MeV incident neutron energy. The various charged particles (inclusive spectra) were identified using ?E-E techniques. From the experimental data, energy- and angle-differential as well as production cross sections were determined, and subsequently the partial and total kerma coefficients. The deduced partial and total kerma coefficients were compared to previous experimental results and theoretical calculations. The findings indicate that the deduced kerma coefficients for the hydrogen isotopes are in good agreement with those deduced from a previous measurement, and that the kerma coefficient values, in particular of the hydrogen isotopes, are systematically higher than values obtained from recent model calculations, which consequently resulted in a total kerma coefficient which is up to 30% higher than predicted by the calculations.

2004-10-07

355

Measurement of neutron kerma factors in C, O, and Si at 18, 23 and 25 MeV  

Energy Technology Data Exchange (ETDEWEB)

Carbon, oxygen, and silicon kerma factor values were measured at neutron energies of 18-25 MeV using microdosimetric techniques. Small spherical and cylindrical proportional counters served to measure neutron kerma, while detection of the activity induced in Teflon (C[sub 2]F[sub 4])[sub n] samples by the [sup 19]F(n,2n)[sup 18]F reaction determined the fast neutron fluence. Deuteron bombardment of a tritium gas target provided a monoenergetic neutron source plus a secondary flux of 0 to 6 MeV neutrons. At each energy, a liquid scintillator-based time-of-flight spectrometer measured the neutron spectrum. In order to correct our measurements for kerma contributed by off-energy neutrons, we combined the secondary neutron spectrum with tabulated energy-dependent kerma factors and subtracted the result from the total measured kerma. (author).

Hartmann, C.L.; DeLuca, P.M. Jr.; Pearson, D.W. (Wisconsin Univ., Madison, WI (United States). Dept. of Medical Physics)

1992-01-01

356

Atomic data required in accurate measurements of kerma for neutrons with low pressure proportional counters  

International Nuclear Information System (INIS)

[en] The accuracy achievable in neutron dosimetry for radiation therapy critically depends on the knowledge of the kerma factors for the tissue components and the detector materials. Gas filled cavity chambers allow to achieve relatively accurate measurements of kerma for the chamber wall material. Ionisation chambers and proportional counters measure with high precision the charge from ionisation produced in the gas by the charged particles released in neutron interactions with the wall and with the gas. However, the overall uncertainty of the kerma measurement depends on the quality of the basic physical data required in the application of the cavity chamber principles, in particular, W-values, stopping powers and stopping power ratios for the charged particles released and their energy dependence. The paper summarizes the experience gained in evaluating atomic data to be used in cavity chamber principles for neutron kerma measurements with tissue-equivalent and non hydrogenous proportional counters. Proportional counters with walls made of A-150 TE plastic, graphite, Al, Mg, Fe, Zr and ZrO have been used to measure neutron kerma factors by several groups. Different mixtures such as methane based TE gas, propane based TE gas or CO2 were used as counting gases. It is shown that the spectral information provided by the proportional counters can be used to assess quantities such as the gas-to-wall absorbed dose conversion factor. An attempt is made to assess the uncertainties in kerma measurements due to the uncertainties of basic atomic data. (author). 40 refs, 12 figs, 5 tabs

1989-01-01

357

Spatial variation of dose and kerma in a composite slab - an interface study  

International Nuclear Information System (INIS)

[en] This work investigates the spatial variation of kerma and dose, when 60Co, 4 MV and 6 MV conical photon beams are incident on composite slab in contact geometry. Discontinuities in both kerma and dose profiles have been observed at the interfaces. The influence of Bone+Marrow (BM) on dose and secondary-electron fluence, in the Fat-BM interface, have mainly been discussed in this work. It is seen that at the Fat-BM interface, the dose has been enhanced by about 3 %, at 0.25 mm in the backward direction, for all photon beams considered in the calculations. (author)

2001-01-01

358

Axial kerma and dose equivalent for neutrons in the ICRU-sphere  

International Nuclear Information System (INIS)

This report is compiled and published as a supplement to GSF-report S-880, 1982, 'Discrete Ordinates and SAM-CE Monte-Carlo calculations in the ICRU-sphere'. It contains the complete data set of calculated axial kerma and kerma equivalents in the ICRU-sphere for external irradiation with a parallel homogeneous beam of neutrons. The calculations have been performed by means of the Ssub(N)-transport programme DOT-2, distributed by RSIC-ORNL, Oak Ridge. The results were verified by those of Monte-Carlo calculations for several incident energies, demonstrating perfect agreement. (orig./HP).

1984-01-01

359

Air Pollution Quality Index (AQI) and Density of PM1, PM2.5 and PM10 in the Air of Qom  

Directory of Open Access Journals (Sweden)

Full Text Available Background and Objectives: Air pollution has broad social, economical, political and technical aspects. one of the major issues in this regard is taking measures to prevent its increase. Since suspended particles are among the standard pollutants, the present study was carried out with the aim of measuring the amounts of these particles.Methods: In the present study, the suspended particles ( PM1, PM2.5 and PM10) were measured at two sites in Qom city. For each of them, 60 samples were selected with the Enviro Check during five consecutive months during summer (2 months) and fall.Results: During sampling, PM10 in the period between October 22'th to November 22nd 2007 had the maximum amount with the mean of 117µg/m3 and in the period between September 22'th to October 22nd 2007 it had the minimum amount with the mean of 83µg/m3. PM2.5 in the period between November 22nd to December 22nd 2007 with the mean of 33µg/m3 had the maximum amount and in the period between July 22nd to October 22nd 2007 it had the minimum amount with the mean of 8µg/m3. Conclusion: Based on the findings of this study, the densities of suspended particles PM1, PM2.5 and PM10 were below the standard levels on most occasions. The amounts of AQI for them were normal and acceptable.

Azizifar M; Naddafi K; Mohammadian M; Safdari M; Khazaei M

2011-01-01

360

Air Pollution Quality Index (AQI) and Density of PM1, PM2.5 and PM10 in the Air of Qom  

Directory of Open Access Journals (Sweden)

Full Text Available Background and Objectives: Air pollution has broad social, economical, political and technical aspects. one of the major issues in this regard is taking measures to prevent its increase. Since suspended particles are among the standard pollutants, the present study was carried out with the aim of measuring the amounts of these particles. Methods: In the present study, the suspended particles ( PM1, PM2.5 and PM10) were measured at two sites in Qom city. For each of them, 60 samples were selected with the Enviro Check during five consecutive months during summer (2 months) and fall. Results: During sampling, PM10 in the period between October 22'th to November 22nd 2007 had the maximum amount with the mean of 117µg/m3 and in the period between September 22'th to October 22nd 2007 it had the minimum amount with the mean of 83µg/m3. PM2.5 in the period between November 22nd to December 22nd 2007 with the mean of 33µg/m3 had the maximum amount and in the period  between July 22nd to October 22nd 2007 it had the minimum amount with the mean of 8µg/m3.  Conclusion: Based on the findings of this study, the densities of suspended particles PM1, PM2.5 and PM10 were below the standard levels on most occasions. The amounts of AQI for them were normal and acceptable.

M Azizifar

2012-01-01

 
 
 
 
361

A Hybrid Method to Improve Forecasting Accuracy - An Introduction of a Day of the Week Index for Air Cargo Weight Data  

Directory of Open Access Journals (Sweden)

Full Text Available Air cargo loading weight forecasting is an important factor for managers in the aviation industry because revenue is dependent on the amount of weight loaded. In this paper, we propose a new method to improve forecasting accuracy and confirm them by the numerical example. Focusing that the equation of exponential smoothing method(ESM) is equivalent to (1,1) order ARMA model equation, a new method of estimation of smoothing constant in exponential smoothing method is proposed before by us which satisfies minimum variance of forecasting error. Generally, smoothing constant is selected arbitrarily. But in this paper, we utilize above stated theoretical solution. Firstly, we make estimation of ARMA model parameter and then estimate smoothing constants. Thus theoretical solution is derived in a simple way and it may be utilized in various fields. Combining the trend removing method with this method, we aim to improve forecasting accuracy. Furthermore, “a day of the week index” is newly introduced for the daily air cargo weight data and we have obtained good result. The effectiveness of this method should be examined in various cases.

Tatsuhiro Kuroda; Keiko Nagata; Kazuhiro Takeyasu

2012-01-01

362

Measurement of the tissue to A-150 tissue equivalent plastic kerma ratio at two p(66)Be neutron therapy facilities  

International Nuclear Information System (INIS)

[en] The ICRU tissue to A-150 tissue equivalent plastic kerma ratio is needed for neutron therapy dosimetry. The current ICRU protocol for neutron dosimetry recommends using a common conversion factor of 0.95 at all high-energy neutron therapy facilities. In an effort to determine facility specific ICRU tissue to A-150 plastic kerma ratios, an experimental approach was pursued. Four low pressure proportional counters that differed in wall materials (i.e. A-150, carbon, zirconium and zirconium-oxide) were used as dosimeters and integral kerma ratios were determined directly in the clinical beam. Measurements were performed at two p(66)Be facilities: iThemba LABS near Cape Town and Fermilab near Chicago. At the iThemba facility the clinical neutron beam is routinely filtered by a flattening and hardening filter combination. The influence of beam filtration on the kerma ratio was evaluated. Using two recent gas-to-wall dose conversion factor (rm,g value) evaluations a mean ICRU tissue to A-150 plastic kerma ratio of 0.93 ± 0.05 was determined for the clinical beam at iThemba LABS. The respective value for the Fermilab beam is 0.95 ± 0.05. The experimentally determined ICRU tissue to A-150 plastic kerma ratios for the two clinical beams are in agreement with theoretical evaluations. Beam filtration reduces the kerma ratio by 3 ± 2%

2003-05-21

363

Measured neutron carbon kerma factors from 14.1 MeV to 18 MeV  

International Nuclear Information System (INIS)

[en] For A-150 tissue-equivalent plastic, the total neutron kerma is dominated by the hydrogen kerma. Tissue kerma is inferred with reasonable accuracy by normalization to the kerma factor ratio between tissue and A-150 plastic. Because of the close match in the hydrogen abundance in these materials, the principal uncertainty is due to the kerma factors of carbon and oxygen. We have measured carbon kerma factor values of 0.183 +- 0.015 10-8 cGy cm2 and 0.210 +- 0.16 10-8 cGy cm2 at 14.1-MeV and 15-MeV neutron energy, respectively. A preliminary value of 0.297 +- 0.03 10-8 cGy cm2 has been determined at 17.9 MeV. A recent microscopic cross section measurement of the (n,n'3?) reaction in carbon at 14.1-MeV energy gives a kerma factor of 0.184 +- 0.019 108 cGy cm2 in agreement with the present result. 9 refs., 4 figs., 2 tabs

1984-01-01

364

Measurement of the tissue to A-150 tissue equivalent plastic kerma ratio at two p(66)Be neutron therapy facilities  

Energy Technology Data Exchange (ETDEWEB)

The ICRU tissue to A-150 tissue equivalent plastic kerma ratio is needed for neutron therapy dosimetry. The current ICRU protocol for neutron dosimetry recommends using a common conversion factor of 0.95 at all high-energy neutron therapy facilities. In an effort to determine facility specific ICRU tissue to A-150 plastic kerma ratios, an experimental approach was pursued. Four low pressure proportional counters that differed in wall materials (i.e. A-150, carbon, zirconium and zirconium-oxide) were used as dosimeters and integral kerma ratios were determined directly in the clinical beam. Measurements were performed at two p(66)Be facilities: iThemba LABS near Cape Town and Fermilab near Chicago. At the iThemba facility the clinical neutron beam is routinely filtered by a flattening and hardening filter combination. The influence of beam filtration on the kerma ratio was evaluated. Using two recent gas-to-wall dose conversion factor (r{sub m,g} value) evaluations a mean ICRU tissue to A-150 plastic kerma ratio of 0.93 {+-} 0.05 was determined for the clinical beam at iThemba LABS. The respective value for the Fermilab beam is 0.95 {+-} 0.05. The experimentally determined ICRU tissue to A-150 plastic kerma ratios for the two clinical beams are in agreement with theoretical evaluations. Beam filtration reduces the kerma ratio by 3 {+-} 2%.

Langen, K M [iThemba LABS, Somerset West 7129 (South Africa); Binns, P J [iThemba LABS, Somerset West 7129 (South Africa); Schreuder, A N [iThemba LABS, Somerset West 7129 (South Africa); Lennox, A J [Neutron Therapy Facility, Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States); Deluca, P M Jr. [Department of Medical Physics, University of Wisconsin, Madison, WI 53706 (United States)

2003-05-21

365

Status and evaluation methods of JENDL fusion file and JENDL PKA/KERMA file  

International Nuclear Information System (INIS)

[en] The status of evaluated nuclear data in the JENDL fusion file and PKA/KERMA file is presented. The JENDL fusion file was prepared in order to improve the quality of the JENDL-3.1 data especially on the double-differential cross sections (DDXs) of secondary neutrons and gamma-ray production cross sections, and to provide DDXs of secondary charged particles (p, d, t, 3He and ?-particle) for the calculation of PKA and KERMA factors. The JENDL fusion file contains evaluated data of 26 elements ranging from Li to Bi. The data in JENDL fusion file reproduce the measured data on neutron and charged-particle DDXs and also on gamma-ray production cross sections. Recoil spectra in PKA/KERMA file were calculated from secondary neutron and charged-particle DDXs contained in the fusion file with two-body reaction kinematics. The data in the JENDL fusion file and PKA/KERMA file were compiled in ENDF-6 format with an MF=6 option to store the DDX data. (orig.)

1997-01-01

366

A simple device for the measurement of kerma based on commercial PIN photo diodes  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The development of a dose reader for the measurement of the radiation dose from neutron and ionizing radiation is presented. The dose reader (kerma meter) is using as active element commercial PIN diodes with long base, which can provide a maximal dependence of the lifetime of minority carriers from...

Kushpil V.; Kushpil S.; Huna Z.

367

Monte Carlo evaluation of kerma at a point for photon transport problems  

International Nuclear Information System (INIS)

[en] Estimation of collision kerma at a geometric point arising from scattered photons is a potentially important application of Monte Carlo simulation, especially in the presence of steep flux gradients. We examine the usual method of extracting point-kerma estimates from randomly generated photon trajectories which consists of tallying the energy lost by photon collisions occurring in the vicinity of the point of interest. Several other methods derived from the equivalence of track length per unit volume and flux are evaluated as to accuracy and efficiency. Finally, a next-flight estimator is discussed in which the expected contribution of each simulated photon collision to kerma at the point of interest is calculated regardless of proximity of the collision to the point. All of these techniques are shown to involve a trade-off between statistical precision and spatial resolution: increasing the number of contributing collisions requires averaging kerma over a larger volume. Based upon both analytic models and realistic Monte Carlo simulations, use of next-flight and track-length estimators is shown to improve simulation efficiencies by factors of 2 to 20 compared to analog scoring. Practical guidelines as to choice of estimator and successful implementation are presented

1987-01-01

368

Review of the research and application of KERMA factor and DPA cross section  

International Nuclear Information System (INIS)

The data for recoil atom spectra, KERMA factor and displacement cross sections from neutron-induced reactions are calling increasing interest for applications to the study of radiation damage, calculation of heat generation in reactor, neutron therapy and biological research. PKA spectra sub-working group was recently established in Japanese Nuclear Data Committee as a part of developing JENDL Special Purpose Data Files. Current status of the data and various features of application of the KERMA-related problems were reviewed and discussed at the first meeting of the sub-working group. Present report is a compilation of the items presented at the meeting, covering a brief review of the existing research and the data, method of calculation, the KERMA factor data in neutron therapy, the deduction of KERMA factor of C-12 from neutron reaction measurement and analysis, the data base for radiation damage, the damage simulation calculation, and the method of storaging the evaluated data in ENDF/B-VI format. (author)

1991-01-01

369

Monte Carlo evaluation of kerma at a point for photon transport problems  

Energy Technology Data Exchange (ETDEWEB)

Estimation of collision kerma at a geometric point arising from scattered photons is a potentially important application of Monte Carlo simulation, especially in the presence of steep flux gradients. We examine the usual method of extracting point-kerma estimates from randomly generated photon trajectories which consists of tallying the energy lost by photon collisions occurring in the vicinity of the point of interest. Several other methods derived from the equivalence of track length per unit volume and flux are evaluated as to accuracy and efficiency. Finally, a next-flight estimator is discussed in which the expected contribution of each simulated photon collision to kerma at the point of interest is calculated regardless of proximity of the collision to the point. All of these techniques are shown to involve a trade-off between statistical precision and spatial resolution: increasing the number of contributing collisions requires averaging kerma over a larger volume. Based upon both analytic models and realistic Monte Carlo simulations, use of next-flight and track-length estimators is shown to improve simulation efficiencies by factors of 2 to 20 compared to analog scoring. Practical guidelines as to choice of estimator and successful implementation are presented.

Williamson, J.F.

1987-07-01

370

Transport-materials handling index  

Energy Technology Data Exchange (ETDEWEB)

The Transport-Materials Handling Index consists of Products and Services Index arranged alphabetically; Brand Names Index in alphabetical order; Company Index; Company Listings in alphabetical order through the following sections - road and rail; air cargo; sea transport; freight forwarding; storage and warehousing; customs agents; finance and insurance; truck service and supply; materials handling.

1988-01-01

371

Determination of kerma factors of A-150 plastic and carbon at neutron energies between 45 and 66 MeV  

International Nuclear Information System (INIS)

[en] Kerma factors of carbon and A-150 tissue-equivalent plastic have been measured in nearly monoenergetic neutron beams at energies between 45 and 66 MeV. The kerma was measured with low pressure proportional counters (PC), the walls consisting either of graphite or A-150 plastic material, and the neutron beam fluence was measured with a proton recoil telescope. The kerma factor corrections were determined from time-of-flight measurements with NE213 scintillation detectors and PCs. At neutron energies of (44.5±2.6) MeV and (66.0±3.0) MeV, the kerma factors were (40.9±4.1) pGy.cm2 and (49.5+ 8.7) pGy.cm2 for carbon and (80.4±6.3) pGy.cm2 and (80.1±8.2) pGy.cm2 for A-150 plastic. (author)

1992-01-01

372

A simple device for the measurement of kerma based on commercial PIN photo diodes  

Directory of Open Access Journals (Sweden)

Full Text Available The development of a dose reader for the measurement of the radiation dose from neutron and ionizing radiation is presented. The dose reader (kerma meter) is using as active element commercial PIN diodes with long base, which can provide a maximal dependence of the lifetime of minority carriers from the absorbed dose. We consider a simple theory of PIN diodes for the role of the kerma meter and discuss the idea for optimization of the calibration procedure. The characteristics of the dosimeter were measured for a few types of commercial diodes. The device can be useful for many practical tasks of control for radiation environments in the environment, nuclear physics and for industrial application.

Kushpil V.; Kushpil S.; Huna Z.

2012-01-01

373

A simple device for the measurement of kerma based on commercial PIN photo diodes  

Science.gov (United States)

The development of a dose reader for the measurement of the radiation dose from neutron and ionizing radiation is presented. The dose reader (kerma meter) is using as active element commercial PIN diodes with long base, which can provide a maximal dependence of the lifetime of minority carriers from the absorbed dose. We consider a simple theory of PIN diodes for the role of the kerma meter and discuss the idea for optimization of the calibration procedure. The characteristics of the dosimeter were measured for a few types of commercial diodes. The device can be useful for many practical tasks of control for radiation environments in the environment, nuclear physics and for industrial application.

Kushpil, V.; Kushpil, S.; Huna, Z.

2012-04-01

374

Calculated neutron KERMA factors based on the LLNL ENDL data file. Volume 27  

International Nuclear Information System (INIS)

[en] Neutron KERMA factors calculated from the LLNL ENDL data file are tabulated for 15 composite materials and for the isotopes or elements in the ENDL file from Z = 1 to Z = 29. The incident neutron energies range from 1.882 x 10-5 to 20. MeV for the composite materials and from 1.30 x 10-9 to 20. MeV for the isotopes and elements

1986-01-01

375

Calculated neutron KERMA factors based on the LLNL ENDL data file. Volume 27  

Energy Technology Data Exchange (ETDEWEB)

Neutron KERMA factors calculated from the LLNL ENDL data file are tabulated for 15 composite materials and for the isotopes or elements in the ENDL file from Z = 1 to Z = 29. The incident neutron energies range from 1.882 x 10/sup -5/ to 20. MeV for the composite materials and from 1.30 x 10/sup -9/ to 20. MeV for the isotopes and elements.

Howerton, R.J.

1986-01-01

376

21 CFR 1020.30 - Diagnostic x-ray systems and their major components.  

Science.gov (United States)

...on or after June 10, 2006. (G) Fluoroscopic air kerma display devices manufactured on or after June 10, 2006...instructions, such as a tabletop cassette holder. Air kerma means kerma in air (see definition of Kerma ). Air kerma...

2010-04-01

377

Studies on effective atomic number, electron density and kerma for some fatty acids and carbohydrates  

DEFF Research Database (Denmark)

The effective atomic number, Z(eff), the effective electron density, N-el, and kerma have been calculated for some fatty acids and carbohydrates for photon interaction in the extended energy range from 1 keV to 100 GeV using an accurate database of photon-interaction cross sections and the WinXCom program. The significant variation of Z(eff) and N-el is due to the variations in the dominance of different interaction processes in different energy regions. The maximum values of Z(eff) and N-el are found in the low-energy range, where photoelectric absorption is the main interaction process. The minimum values of Z(eff) and N-el are found at intermediate energies, typically 0.05 MeV kerma than fatty acids in the low-energy region, where photoelectric absorption dominates. In contrast, fatty acids have a larger kerma than carbohydrates in the MeV range, where Compton scattering is the main interaction process.

Manohara, S.R.; Hanagodimath, S.M.

2008-01-01

378

Cross section data and kerma coefficients at 95 MeV neutrons for medical applications  

International Nuclear Information System (INIS)

[en] Motivated by the need of data on neutron-induced reactions with biologically relevant materials, e.g., carbon and oxygen, we have constructed and installed the MEDLEY detector array at the neutron beam facility of the The Svedberg Laboratory in Uppsala. The central detection elements of MEDLEY are three-detector telescopes, consisting of two silicon detectors and a CsI crystal. To cover wide energy and angle ranges, we have mounted eight such telescopes at 20deg intervals. We have used ?E - ?E - E techniques to obtain good particle identification for protons, deuterons, tritons, 3He and ? particles over an energy range from a few MeV up to 100 MeV. To define the detector solid angle, plastic scintillators were employed to serve as active collimators. We have up to now measured double-differential cross sections of inclusive light-ion production induced by 95 MeV neutrons on carbon and oxygen. From these data production cross sections, as well as partial kerma coefficients, are being determined. We have found that especially the proton kerma coefficient for carbon is substantially larger than that of a recent evaluation, leading to a larger total kerma coefficient. The obtained data supports a trend observed for similar data at lower energies. (author)

2002-01-01

379

Absorbed dose and collision kerma relationship for high-energy photons  

International Nuclear Information System (INIS)

Historically, exposure has been used as an important quantity to specify x- or ?-ray beams. For any photon beam the energy fluence is proportional to the exposure. Exposure can be calculated and/or measured if the spectrum of the beam is known and charged particle equilibrium (CPE) exists. For low energy photons (up to approximately 1 MeV), due to the existence of CPE, absorbed dose (D) is equal to the collision kerma (K/sub c/). For megavoltage photons this equality is lost due to CPE failure, which also restricts the measurement of exposure. It is possible, though, to find a relationship between the absorbed dose and collision kerma when transient charged particle equilibrium (TCPE) exists. This basic idea was originally proposed by Roesch in 1958 and its refinement has been discussed by Attix in 1979 and 1983. The modified Roesch's formula that enables measuring exposure even for high-energy photons is given by D = ? K/sub c/ approx. = K/sub c/ (1 + ?' ), where ?' is the effective linear attenuation coefficient and is the mean distance the secondary electrons carry kinetic energy in the direction of the photon beam while depositing it as absorbed dose. The symbol ? is the quotient of the absorbed dose and the collision kerma. Calculations were also performed for several photon energies and materials, using the Roesch method, which does not include photon scattering effects. Comparisons of measured and calculated values of show reasonable agreement.

1984-01-01

380

Paediatric entrance doses from exposure index in computed radiography  

Energy Technology Data Exchange (ETDEWEB)

Over the last two years we have evaluated paediatric patient doses in projection radiography derived from exposure level (EL) in computed radiography (CR) in a large university hospital. Entrance surface air kerma (ESAK) for 3501 paediatric examinations was calculated from the EL, which is a dose index parameter related to the light emitted by the phosphor-stimulable plate, archived in the Digital Imaging and Communications in Medicine (DICOM) header of the images and automatically transferred to a database using custom-built dedicated software. Typical mean thicknesses for several age bands of paediatric patients was estimated to calculate ESAK from the EL values, using results of experimental measurements with phantoms for the typical x-ray beam qualities used in paediatric examinations. Mean/median ESAK values (in {mu}Gy) for the age bands of <1 year, 1-5 years, 6-10 years and 11-15 years have been obtained for chest without a bucky: 51/41, 57/34, 91/54 and 122/109; chest with a bucky (for only the last three age bands): 114/87, 129/105 and 219/170; abdomen: 119/91, 291/225, 756/600 and 1960/1508 and pelvis: 65/48, 455/314, 943/707 and 2261/1595. Sample sizes of clinical images used for the (indirect) measurements were 1724 for chest without a bucky, 799 for chest with a bucky, 337 for abdomen and 641 for pelvis. The methodology we describe could be applicable to other centres using CR as an imaging modality for paediatrics. Presently, this method is the only practical approach to automatically extract parameters contained in the DICOM header, for the calculation of patient dose values for the CR modality.

Vano, E; Martinez, D; Fernandez, J M; Ordiales, J M; Prieto, C; Floriano, A [Medical Physics Service, San Carlos University Hospital, 28040 Madrid (Spain); Ten, J I [Diagnostic Radiology Service, San Carlos University Hospital, 28040 Madrid (Spain)], E-mail: eliseo@med.ucm.es

2008-06-21

 
 
 
 
381

BIPM and COMECON comparisons of air kerma standards in X- and ?-radiation fields  

International Nuclear Information System (INIS)

[en] The results of comparisons undertaken by a regional metrology organization at several x- and ?-ray qualities are compared with those of BIPM international comparisons. The results are statistically coherent in most cases. (authors)

1999-01-01

382

A consistent set of neutron kerma coefficients from thermal to 150 MeV for biologically important materials  

International Nuclear Information System (INIS)

Neutron cross sections for nonelastic and elastic reactions on a range of elements have been evaluated for incident energies up to 150 MeV. These cross sections agree well with experimental cross section data for charged-particle production as well as neutron and photon production. Therefore they can be used to determine kerma coefficients for calculations of energy deposition by neutrons in matter. Methods used to evaluate the neutron cross sections above 20 MeV, using nuclear model calculations and experimental data, are described. Below 20 MeV, the evaluated cross sections from the ENDF/B-VI library are adopted. Comparisons are shown between the evaluated charged-particle production cross sections and measured data. Kerma coefficients are derived from the neutron cross sections, for major isotopes of H, C, N, O, Al, Si, P, Ca, Fe, Cu, W, Pb, and for ICRU-muscle, A-150 tissue-equivalent plastic, and other compounds important for treatment planning and dosimetry. Numerous comparisons are made between our kerma coefficients and experimental kerma coefficient data, to validate our results, and agreement is found to be good. An important quantity in neutron dosimetry is the kerma coefficient ratio of ICRU-muscle to A-150 plastic. When this ratio is calculated from our kerma coefficient data, and averaged over the neutron energy spectra for higher-energy clinical therapy beams [three p(68)+Be beams, and a d(48.5)+Be beam], a value of 0.94±0.03 is obtained. Kerma ratios for water to A-150 plastic, and carbon to oxygen, are also compared with measurements where available. copyright 1999 American Association of Physicists in Medicine

1999-01-01

383

Air Quality Guide for Ozone  

Science.gov (United States)

Local Air Quality Conditions Zip Code: State : National Summary Air Quality Guide for Ozone You may have seen the ... 08-001 March 2008 http://www.airnow.gov Air Quality Guide for Ozone Air Quality Index Protect ...

384

Comparison of entry kerma in the skin with the variation of automatic exposure control in mammography;Comparacao do kerma de entrada na pele com a variacao do controle automatico de exposicao em exames mamograficos  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this work was to analyze the entry kerma values in the skin in comparison with the automatic exposure control tests. To achieve that, 44 mammographies were evaluatecl in the city of Rio de Janeiro. The reference values adopted were taken from the current Brazilian legislation, 'Portaria no. 453/98 do Ministerio da Saude', where the reference entry kerma value in the skin corresponds to 10 mGy and the maximum variation accepted to the automatic exposure control test corresponds to 30 optic unities. It was observed that 46.7% of the analyzecl mammographies presented entry kerma values in the skin above the reference level established, whereas the automatic exposition control for these same mammographies was within the acceptability parameters. (author)

Macao Junior, J.L. [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil); Mecca, F.A. [Instituto Nacional de Cancer (INCa), Rio de Janeiro, RJ (Brazil); Gomes, B.C. [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

2009-07-01

385

Kerma factors for neutrons of 14 MeV to 60 MeV in elemental H, C, N and O  

Energy Technology Data Exchange (ETDEWEB)

Total kerma factors, and partial kerma factors for production of specified charged H and He particles and heavier recoils, have been computed using basic theoretical and experimental nuclear data for neutrons at energies between 14 MeV and 60 MeV in the main tissue elements and in ICRU muscle tissue. All the more recent computations of total kerma factors, along with those determined from direct experimental measurements of partial kerma factors, now form a reasonably consistent set of data enabling average total kerma factors with coefficients of better than 3% for hydrogen, 16% for carbon, 23% for nitrogen and 9% for oxygen to be recommended for application to medical dosimetry and radiation protection. Total kerma factors for ICRU muscle tissue have a precision of better than 2.5% over the neutron energy range considered. Although there is adequate precision for total kerma factors for soft tissue, nevertheless analysis of the partial kerma factors indicates that caution must be exercised in use of the information for quality specification, e.g. in microdose spectra, and that more detailed basic reaction data is required for fast neutrons.

Behrooz, M.A.; Watt, D.E. (Dundee Univ. (UK). Dept. of Medical Biophysics)

1981-01-01

386

Neutron kerma factors for H, C, N, O, and tissue in the energy range of 20 to 70 MeV  

International Nuclear Information System (INIS)

[en] Calculated kerma factors (kerma per unit fluence) in the energy range of 20 to 70 MeV based on nonelastic charged-particle-production cross-section data obtained from the intranuclear-cascade model of nuclear reactions are given for H, C, N, O, and tissue

1976-01-01

387

Indexing Books  

CERN Document Server

Since 1994, Nancy Mulvany's Indexing Books has been the gold standard for thousands of professional indexers, editors, and authors. This long-awaited second edition, expanded and completely updated, will be equally revered. Like its predecessor, this edition of Indexing Books offers comprehensive, reliable treatment of indexing principles and practices relevant to authors and indexers alike. In addition to practical advice, the book presents a big-picture perspective on the nature and purpose of indexes and their role in published works. New to this edition are discussions of "information

Mulvany, Nancy C

2005-01-01

388

Measurement of neutron kerma factors in C and O: neutron energy range of 20 MeV to 70 MeV  

International Nuclear Information System (INIS)

[en] Kerma factors for oxygen and carbon have been measured in nearly monoenergetic neutron beams of energies between 34 MeV and 66 MeV. The kerma was determined experimentally with low pressure proportional counters (PC) by measuring the absorbed doses to the gases. Recently calculated gas-to-wall absorbed dose conversion factors, rm,g, were used to deduce the doses in the PC wall materials. The kerma in oxygen was obtained from the difference of the kerma determined with ZrO2 and Zr walled PCs, that in carbon was determined with graphite-walled PCs. The neutron fluence were measured with a proton recoil telescope, the spectral fluences with an NE213 scintillation detector by applying pulse shape and time-of-flight techniques. The kerma factors of carbon from the present measurements were compared with values of previous works which were analysed anew using the improved rm,g values. (author)

1995-01-01

389

The variability in kerma output and radiation quality of medical diagnostic x-ray units  

International Nuclear Information System (INIS)

The use of diagnostic x-ray tubes results in an increased roughness of the anode surface. This effect of tube ageing increases the inherent filtration of the x-ray tube, hereby reducing kerma output and changing radiation quality. To study this effect, used rotating anodes were collected; the surface profiles and surface roughness of 8 focal tracks were determined. The surface profiles were then used to calculate x-ray spectra using a computer code. The results indicate that an increased roughness induces an additional filtration in the tungsten anode. The roughest surface (Ra=5.22 ?m) yields a mean additional absorber thickness in direction of the x-ray beam of about 18 ?m with a corresponding loss in kerma output of about 30 % at 70 kV. The effects on mean photon energy and HVL are rather small but highest around 70 kV and lowest at 140 kV. This is due to the K-edge in the attenuation coefficients of tungsten at 69.5 keV. To study the influence of tube ageing on beam quality with clinical x-ray units, kerma measurements were made for 19 samples as to determine attenuation curves. A fit method for the determination of total filtration including the effects of anode surface deterioration was devised. The thicknesses of the tungsten layers obtained using this method vary from 2.43 ?m to 11.89 ?m with an associated surface roughness Ra from 1.5 to 4.5 ?m corresponding very well to the thicknesses of the additional absorbing layers determined for rough anodes. A determination of additional filtration in terms of an equivalent aluminium filter gave thicknesses from 0.34 to 1.72 mm aluminium. The results showed that the effects of tube ageing on the x-rays could be described by an additional filtration of aluminium. (author)

2004-01-01

390

KAOS-V code: An evaluation tool for neutron kerma factors and other nuclear responses  

Energy Technology Data Exchange (ETDEWEB)

The accurate evaluation of neutron fluence-to-kerma factors from microscopic nuclear data is the subject of this report. The algorithms developed for this purpose combine in a consistent manner the two basic methods for computing kerma factors, namely kinematics and direct energy balance. These algorithms are implemented in the code KAOS-V which was used as the main evaluation tool to construct the response function library KAOS/LIB-V. KAOS-V uses data from the evaluated nuclear data files ENDF/B/V. Auxiliary nuclear data bases, e.g., the Japanese evaluated nuclear data library JENDL-2 can be used as a source of isotopic cross sections when these data are not provided in ENDF/B-V files for a natural element. These are needed mainly to estimate average quantities such as effective Q-values for the natural element. The code has the ability to compare the different results which aids in the choice of a consistent set of algorithms to evaluate kerma factors. Data in ENDF/B-IV and ENDF/B-V format can be processed. For resonance treatment, the code has the ability to access NJOY and NPTXS interface files in formatted or binary forms. No input instructions are necessary to run the code interactively. The user can simply respond to the interactive messages sent by the code if an INPUT file is absent. An INPUT file is automatically generated following an interactive run, and can be edited and used to rerun or produce different results. Grouped and point output data can be produced along with graphic representation. These features are instrumental in detecting and understanding energy balance deficiencies and other problems in the nuclear data files. 60 refs., 4 figs.

Farawila, Y.; Gohar, Y.; Maynard, C. (Georgia Inst. of Tech., Atlanta, GA (USA); Argonne National Lab., IL (USA); Wisconsin Univ., Madison, WI (USA). Dept. of Nuclear Engineering and Engineering Physics)

1989-09-01

391

Heat Index  

Science.gov (United States)

... Heat! Summer Weather Safety and Survival The Heat Index Your local weather experts at the National Weather ... hot weather "feels" to the body. The Heat Index is based on work by R.G. Steadman ...