WorldWideScience
 
 
1

Evaluation of the relation between breast glandular absorbed dose and radiographic quality in mammography  

International Nuclear Information System (INIS)

Breast is one of the main radiological sensitive organs, hence it is important to evaluate absorbed dose to this organ especially to the glandular parts. It is the aim of this study to measure mean glandular dose and image contrast in terms of different mammographic parameters. Materials and Methods: In this study two mammography machines located at Said-al Shohada (Giotto) and Shahid Behesti (GE) hospitals were used. According to the recommendations of ACR and MQSA, breast phantoms were constructed and used for this study. For dose evaluation TLD dosimetry method was used. The TLD dosimeters were of LiF type and the reader was a Solaro TLD reader. Results: To obtain a constant contrast when increasing kVp from 22 to 24, it was necessary to reduce mAs by 12 percent. The obtained relation between these two parameters is: contrast=0.2829D-0.2427. It was also found that there is a linear relationship between contrast and image quality. The relation between these two parameters is: Image quality = 28.117 Contrast + 20.134. Increasing kVp and hence decreasing mAs results a reduction to the glandular dose, especially in patients with large breast. Increasing kVp from 28 to 30 results in reduction of dose from 6.8 mGy to 5 mGy. Conclusions: It was found that there has been a linear relationship between contrast and image quality. It was also found that increasing kVp necessitate to reduce mAs for a constant contrast and hence reduction of glandular dose.

2

Media glandular dose in mammography  

International Nuclear Information System (INIS)

The objective of this work was to determine the media glandular dose of the patients group who most frequently are exposed at mammographic studies in the General Hospital of Zone No. 1 of IMSS in Zacatecas, later to compare this dose with the value that establishes the Mexican Official Standard and to know risk-benefit that a patient is exposed when it is realized studies of this nature. This with the purpose of to know if the patients who are realized this type of studies are exhibited to irradiations of unnecessary way. In order to obtain the media glandular dose, first it was choose the age group of feminine population that is predominant to this suffering. Of the classification of the age group it was determine the frequency of each thickness of mamma, and on the basis of the thickness of the compressed mamma the conditions were registered with it radiates the patient. When having the age and compressed mamma thickness of patient and the voltage, current, anode/filter that uses the mammography equipment for to radiate it was calculated the media glandular dose. The media glandular dose was calculated using two algorithms proposed in literature and thermoluminescent dosemeters. For the case of the thermoluminescent dosemeters were used two phantoms. In this study was detected that the limits, with that they radiate the patients who are exposed at mammographic studies it is by underneath of 3 mGy. Finally, it was detected that the Mexican Official Standard lacks of elements to offer radiological limits for the mammography area, because in this standard they are excluded the radiological limits for anode and filter of Mo/Rh and Rh/Rh. To know the dose applying these anodes and filters is of extreme importance because 85% of the population that is exposed to this studies type was radiated with anode and filter of Mo/Rh and Rh/Rh. (Author)

3

Mammographic glandular dose: Definition of ''tissue at highest risk''  

International Nuclear Information System (INIS)

In 1979, various authors published data on ''mean glandular dose.'' In their study, the glandular dose was averaged across the entire breast parenchyma. But most breast cancers occur in glandular tissues situated centrally and laterally, that is, about 1-2 cm below the skin entrance of the beam. The authors calculated the mean dosage to this ''tissue at highest risk,'' assuming compressed fat and skin thickness of 0.25 cm, and actual compressed breast thickness. The data shows a substantial increase in absorbed dose in this tissue at highest risk. The potential effect on mammographic planning, patient education, and dose risk calculations are discussed

4

Assessment of mean glandular dose in mammography  

International Nuclear Information System (INIS)

The routine assessment of patient dose in the National Health Service Breast Screening Programme is performed as part of the quality assurance protocol recommended by the Institute of Physical Sciences in Medicine. The mean glandular dose to a standard breast is deduced from measurement of the air kerma at the entrance surface of a 4 cm Perspex phantom by applying a series of conversion factors. The exposure factors for this measurement are those used clinically. The measured mean glandular dose is then compared with nationally accepted action levels. In some centres the assessment of mean glandular dose using Perspex is supplemented by patient dose surveys. The mean glandular dose to a series of patients attending a breast screening unit may be estimated from a knowledge of the exposure factors and compressed breast thickness, using a knowledge of the X-ray tube output. Measurements made on units in the Northern Region of England and in Scotland using both methods are presented. (author)

5

Monte Carlo calculation of normalized glandular dose in mammography  

International Nuclear Information System (INIS)

To get the dose evaluation in mammography be executed more easily, Monte Carlo simulation (EGS4-LSCAT) is utilized to calculate normalized glandular dose for mammographic x-ray spectra of wide ranges. Normalized glandular dose is just mean glandular dose, which is the most relevant indicator of risk in mammography, normalized to entrance surface dose. Clinically, entrance surface dose can be measured easily and mean glandular dose comes out after entrance surface dose being multiplied by normalized glandular dose. This study aims to establish a table of normalized glandular dose for different beam qualities (different half-value layers). (author)

6

Evaluation of depth dose and glandular dose for digital mammography  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this study is to evaluate the depth dose and mean glandular dose for the latest digital mammography. Depth doses were measured using GR-200F thin-film TLDs comprising LiF:Mg,Cu,P over three kinds of composition of mammographic phantom (glandular/fat: 30/70; 50/50; 70/30) under automatic exposure control by a digital mammographic unit (Novation DR, Siemens). Mean glandular doses were derived from entrance surface doses which were measured according to the Mammography Quality Control Manual of American College of Radiology. Two types of mean glandular dose calculation system were used and compared in this study. The depth dose could be established with thin-film TLDs and fitted by the model considered the primary and scatter radiation. The 50% depth dose falls at a depth of between 0.62 and 1.71 cm, which can represent the beam quality of X-ray spectra. The MGD calculated by Dance's method is 9-21% higher than that by Wu's method. Therefore, the difference should be considered by the Taiwan's regulation for Novation DR digital mammographic units.

Tsai, H.Y. [Department of Medical Imaging and Radiological Sciences, Chang Gung University, Taoyuan 333, Taiwan (China); Chong, N.S. [Department of Radiation Oncology, Far Eastern Memorial Hospital, Taipei 220, Taiwan (China); Ho, Y.J. [Department of Medical Imaging and Radiological Sciences, Chang Gung University, Taoyuan 333, Taiwan (China); Tyan, Y.S., E-mail: huiyutsai@gmail.co [Department of Medical Imaging and Radiological Sciences, Chung Shan Medical University, 110, Sec.1, Jianguo N Rd., Taichung 402, Taiwan (China); Department of Radiology, Chung Shan Medical University Hospital, Taichung 402, Taiwan (China)

2010-03-15

7

Monte Carlo simulation of average glandular dose and an investigation of influencing factors  

International Nuclear Information System (INIS)

This study aims to determine the average absorbed dose of radiation in glandular tissue during mammography and to investigate factors that influence the average glandular dose, particularly the local distribution of glandular tissue within the breast and breast skin thickness. An EGSnrc Monte Carlo code and associated codes were employed in the simulation. The breast voxel models used consist of a homogeneous and heterogeneous mixture of adipose and glandular tissues embedded in a skin layer. The percent depth dose and normalized average glandular dose coefficients for spectra of Mo-Mo target-filter combination were calculated. The results showed good agreement with the experimental results (percent depth dose) and literature values (normalized average glandular dose coefficients) when the breast model is homogeneous. Additional investigation of a heterogeneous breast phantom indicates that the local distribution of glandular tissue within the breast, as well as breast skin thickness, could affect the average glandular dose considerably more than that of a typical homogeneous breast model. This problem may be a concern in most practical situations of breast dosimetry when assessing the radiation risk to patients. (author)

8

Monte Carlo simulation of average glandular dose and an investigation of influencing factors.  

Science.gov (United States)

This study aims to determine the average absorbed dose of radiation in glandular tissue during mammography and to investigate factors that influence the average glandular dose, particularly the local distribution of glandular tissue within the breast and breast skin thickness. An EGSnrc Monte Carlo code and associated codes were employed in the simulation. The breast voxel models used consist of a homogeneous and heterogeneous mixture of adipose and glandular tissues embedded in a skin layer. The percent depth dose and normalized average glandular dose coefficients for spectra of Mo-Mo target-filter combination were calculated. The results showed good agreement with the experimental results (percent depth dose) and literature values (normalized average glandular dose coefficients) when the breast model is homogeneous. Additional investigation of a heterogeneous breast phantom indicates that the local distribution of glandular tissue within the breast, as well as breast skin thickness, could affect the average glandular dose considerably more than that of a typical homogeneous breast model. This problem may be a concern in most practical situations of breast dosimetry when assessing the radiation risk to patients. PMID:20523013

Nigapruke, Khatayut; Puwanich, Patana; Phaisangittisakul, Nakorn; Youngdee, Wiwat

2010-01-01

9

Spectral dependence of glandular tissue dose in screen-film mammography.  

Science.gov (United States)

The average glandular tissue dose in mammography is generally determined from published tables with knowledge of the breast entrance skin exposure, x-ray tube target material, beam quality (half-value layer [HVL]), breast thickness, and breast composition. Using a carefully designed and experimentally validated Monte Carlo simulation, the authors found that average glandular dose also depends on x-ray tube voltage and, to a lesser extent, on x-ray tube voltage waveform. For currently employed molybdenum target-molybdenum filter source assemblies, a difference in dose of 10% or more is possible in estimating the average glandular dose obtained with different x-ray tube voltages but with the same HVL. Presented are normalized average glandular tissue doses in units of radiation absorbed dose per unit entrance skin exposure for different tube voltages and tube voltage waveforms as well as for different breast thicknesses and compositions and beam filtrations. PMID:2006265

Wu, X; Barnes, G T; Tucker, D M

1991-04-01

10

Estimating mean glandular dose using proprietary mammography phantoms  

Energy Technology Data Exchange (ETDEWEB)

Screening mammography programs prescribe limits on the radiation dose to the glandular tissue of a compressed breast - the Mean Glandular Dose (MGD) - which may vary between 2 and 3 mGy for a 50% adipose and 50% glandular tissue compressed breast of 4.2 to 5.0 cm thickness. Commercially available breast phantoms offer a choice of equivalent tissue thicknesses and composition ranging typically from 30% adipose and 70% glandular tissue to 50% adipose and 50% glandular tissue. A number of these phantom were compared under clinical conditions and the MGD calculated for each using the factors developed by Wu et al. [Wu, X., Barnes, G.T. and Tucker, D.M. (1991) Spectral dependence of glandular tissue dose in screen film mammography, Radiology 179, 143-148].

Hartley, L.D.; Cobb, B.J.; Hutchinson, D.E

1999-01-01

11

Estimating mean glandular dose using proprietary mammography phantoms  

International Nuclear Information System (INIS)

Screening mammography programs prescribe limits on the radiation dose to the glandular tissue of a compressed breast - the Mean Glandular Dose (MGD) - which may vary between 2 and 3 mGy for a 50% adipose and 50% glandular tissue compressed breast of 4.2 to 5.0 cm thickness. Commercially available breast phantoms offer a choice of equivalent tissue thicknesses and composition ranging typically from 30% adipose and 70% glandular tissue to 50% adipose and 50% glandular tissue. A number of these phantom were compared under clinical conditions and the MGD calculated for each using the factors developed by Wu et al. [Wu, X., Barnes, G.T. and Tucker, D.M. (1991) Spectral dependence of glandular tissue dose in screen film mammography, Radiology 179, 143-148

12

Evaluation of subject contrast and normalized average glandular dose by semianalytical models  

International Nuclear Information System (INIS)

Full text: Mammography is the most effective and accurate method for early diagnostic of breast cancer. The performance of the mammographic system is evaluated with respect to the image quality (mainly contrast and noise) and the absorbed dose, which are usually determined by experimental and simulation (Monte Carlo) approaches. Nevertheless, these approaches are time demanding, and thus the development of analytical models to study these parameters in a fast and simple way would be worthwhile. In this work we show semianalytic models to determine the subject contrast and the normalized average glandular dose in mammography. The model used to determine the subject contrast takes into account the primary and scatter contribution of the transmitted radiation. This model also allows evaluating detection limits for masses and calcification. The normalized average glandular absorbed dose was estimated considering two simplified models, which allow predicting lower and upper limit values, and a more realist model, which includes the contribution of single and double scattered radiation. These models were used to study the dependence of the subject contrast and the absorbed dose on breast characteristics (thickness and composition), radiographic technique, target-filter combination and image receptor. The preliminary results of this work show that when the glandular content and breast thickness increase, the subject contrast and the normalized average glandular dose decreasenormalized average glandular dose decrease up to 90%, and 70%, respectively. Besides, it was verified that the subject contrast and the normalized average breast dose depend on the kVp and target-filter combination, varying up to 35% and 25%, respectively. The results were compared with previous works, showing discrepancies lower than 10%. Finally, on the basis of the results for subject contrast, were estimated a detection limit of up to 2mm for masses, considering a usual mammographic spectra (Mo/Mo - 28kVp) and a breast of 4 cm of thickness and normal composition (50% adipose: 50% glandular)

13

Average glandular dose in patients submitted to mammographic examinations  

International Nuclear Information System (INIS)

Doses in mammography should be maintained as low as possible without reducing the high image quality needed to the early detection of the breast cancer. As the breast is composed of tissues with very soft composition and densities, it increases the difficulty to detect small changes in the normal anatomical structures that may be associated with breast cancer. To achieve the standards of resolution and contrast for mammography, the quality and intensity of the x-ray beam, the breast positioning and compression, the film-screen system, and the film processing must be in optimal operational conditions. This study intended to evaluate the mean glandular dose of patients undergoing routine exams in one mammography unit. Patient image analyses were done by a radiologist doctor who took into account 10 evaluation criteria for each CC and MLO incidences. For estimating each patient glandular dose the radiographic technique parameters (kV and mA.s) and the thickness of the compressed breast were recorded. European image quality criteria were adopted by the radiologist doctor to accept the image for diagnostic purpose. For breast densities of 50% adipose and 50% glandular tissues the incident air-kerma was measured and the glandular dose calculated considering the x-ray output during the exam. In the study of 50 patients the mean glandular dose varied from 0.90 to 3.27 mGy with a mean value of 1.98 mGy for CC incidences. For MLO incidences the mean glandular doses ranged from nces the mean glandular doses ranged from 0.97 to 3.98 mGy and a mean value of 2.60 mGy. (author)

14

Glandularity and mean glandular dose determined for individual women at four regional breast cancer screening units in The Netherlands  

Energy Technology Data Exchange (ETDEWEB)

The nationwide breast cancer screening programme using mammography has been in full operation in The Netherlands since 1997. There is concern that the mean glandular doses due to mammography might be differing between different regions of the country due to differences in glandularity and compressed breast thickness. To investigate regional differences, glandularity, compressed breast thickness and mean glandular dose were determined for individual breasts during screening at mammography units at four locations in The Netherlands. Differences in glandularity were observed, which could be related qualitatively to differences in age of the participants at the different locations. Mean glandular dose depends on compressed breast thickness, glandularity and technical conditions of screening. The lowest average value of the mean glandular dose was found for the unit in Amsterdam. This is most likely due to the use of the Mo/Rh anode/filter combination at this unit, in addition to the Mo/Mo combination. At the other three units, almost exclusively the Mo/Mo anode/filter combination was used. Differences in mean glandular dose averaged per unit could be related mainly to differences in tube-current exposure-time product values. Consequently, it is concluded that differences in mean glandular dose at different units are marginal.

Zoetelief, J [Department of Radiation, Radionuclides and Reactors, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629 JB Delft (Netherlands); Veldkamp, W J H [Department of Radiology, Leiden University Medical Center, Albinusdreef 2, 2300 RC Leiden (Netherlands); Thijssen, M A O [National Expert and Training Centre for Breast Cancer Screening, Radboud University Nijmegen Medical Centre, Geert Grooteplein-Zuid 10, 6525 GA Nijmegen (Netherlands); Jansen, J T M [Department of Radiation, Radionuclides and Reactors, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629 JB Delft (Netherlands)

2006-04-07

15

Glandularity and mean glandular dose determined for individual women at four regional breast cancer screening units in The Netherlands  

Science.gov (United States)

The nationwide breast cancer screening programme using mammography has been in full operation in The Netherlands since 1997. There is concern that the mean glandular doses due to mammography might be differing between different regions of the country due to differences in glandularity and compressed breast thickness. To investigate regional differences, glandularity, compressed breast thickness and mean glandular dose were determined for individual breasts during screening at mammography units at four locations in The Netherlands. Differences in glandularity were observed, which could be related qualitatively to differences in age of the participants at the different locations. Mean glandular dose depends on compressed breast thickness, glandularity and technical conditions of screening. The lowest average value of the mean glandular dose was found for the unit in Amsterdam. This is most likely due to the use of the Mo/Rh anode/filter combination at this unit, in addition to the Mo/Mo combination. At the other three units, almost exclusively the Mo/Mo anode/filter combination was used. Differences in mean glandular dose averaged per unit could be related mainly to differences in tube-current exposure-time product values. Consequently, it is concluded that differences in mean glandular dose at different units are marginal.

Zoetelief, J.; Veldkamp, W. J. H.; Thijssen, M. A. O.; Jansen, J. T. M.

2006-04-01

16

Average glandular dose in patients submitted to mammography exams  

International Nuclear Information System (INIS)

Doses in mammography should be maintained as low as possible, however without reducing the standards of image quality necessary for an early detection of breast cancer. As the breast is composed of tissues with very soft composition and densities, detection of small changes in the normal anatomical structures that may be associated with breast cancer becomes more difficult. In order to achieve the standards of resolution and contrast for mammography, quality and intensity of the X- ray beam, breast positioning and compression, film-screen system, and the film processing must be in optimal operational conditions. This study aims at evaluating the average glandular dose in patients undergoing routine tests in a mammography unit in the city of Belo Horizonte. Patient image analysis was done by a radiologist who took into account 10 evaluation criteria for each CC and MLO incidences. The estimation of each patient's glandular dose and the radiographic technique parameters (kV and mA.s) as well as the thickness of the compressed breast were recorded. European image quality criteria were adopted by the radiologist in order to make the image acceptable for diagnostic purposes. For breast densities of 50%/50%, 70%/30%, 30%/70%, adipose and glandular tissues and the incident air-kerma were measured and the glandular dose calculated taking into account the X-ray output during the test. In the study carried out with 63 patients, the mean glandular dose varied from 30% incidence of CC to MLO. (author)

17

Average glandular dose in patients submitted to mammography exams  

Energy Technology Data Exchange (ETDEWEB)

Doses in mammography should be maintained as low as possible, however without reducing the standards of image quality necessary for an early detection of breast cancer. As the breast is composed of tissues with very soft composition and densities, detection of small changes in the normal anatomical structures that may be associated with breast cancer becomes more difficult. In order to achieve the standards of resolution and contrast for mammography, quality and intensity of the X- ray beam, breast positioning and compression, film-screen system, and the film processing must be in optimal operational conditions. This study aims at evaluating the average glandular dose in patients undergoing routine tests in a mammography unit in the city of Belo Horizonte. Patient image analysis was done by a radiologist who took into account 10 evaluation criteria for each CC and MLO incidences. The estimation of each patient's glandular dose and the radiographic technique parameters (kV and mA.s) as well as the thickness of the compressed breast were recorded. European image quality criteria were adopted by the radiologist in order to make the image acceptable for diagnostic purposes. For breast densities of 50%/50%, 70%/30%, 30%/70%, adipose and glandular tissues and the incident air-kerma were measured and the glandular dose calculated taking into account the X-ray output during the test. In the study carried out with 63 patients, the mean glandular dose varied from 30% incidence of CC to MLO. (author)

Gomes, Danielle S.; Barragan, Carolina V.M.; Costa, Katiane C.; Donato, Sabrina; Castro, William J.; Nogueira, Maria S., E-mail: dsg@cdtn.br, E-mail: kcc@cdtn.br, E-mail: sds@cdtn.br, E-mail: wjc@cdtn.br, E-mail: mnogue@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN), Belo Horizonte, MG (Brazil); Rezende, Adriana M.L. [Clinica Radiologica Davi Rezende, Belo Horizonte, MG (Brazil); Pinheiro, Luciana J.S. [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN), Belo Horizonte, MG (Brazil). Post-graduation in Sciences and Technology of Radiations, Minerals and Materials; Oliveira, Marcio A. de [Superintendencia Estadual de Vigilancia Sanitaria, Belo Horizonte, MG (Brazil)

2011-07-01

18

Radiopharmaceutical absorbed dose considerations  

International Nuclear Information System (INIS)

From the discussion in this chapter the reader may get the impression that absorbed dose calculations are primarily guesswork. Admittedly, assumptions must be made in some calculations when there are gaps in the available data. These calculations, however, represent an estimate of the true absorbed dose with reasonably sufficient accuracy to assure the physician and regulatory agencies that patients are not receiving excessively high absorbed radiation doses. The MIRD technique appears to be an acceptable method of dose calculations, with individual calculations being only as good as the input information. All possible situations have not been modeled, nor will they ever be, but absorbed dose estimation can continue to be of use with application of available data, some common sense, and a few reasonable assumptions

19

Parametrization of mammography normalized average glandular dose tables.  

Science.gov (United States)

Data from existing tables of normalized glandular doses in mammography were parametrized to determine analytical expressions that match tabulated results within known uncertainties. The parametrization was performed for three different target/filter combinations (molybdenum target-molybdenum filter, molybdenum target-rhodium filter, and rhodium target-rhodium filter) and three different breast compositions (100% adipose, 50% adipose-50% glandular, and 100% glandular). The analytical expressions provide the normalized glandular dose for any breast composition within stated ranges of tabulated input parameters (kVp, half-value layer, and breast thickness). The maximum difference between tabulated and parametrized data is 1.29%, which is smaller than the stated 2% uncertainty in tabulated dose data due to uncertainties in the x-ray spectra models used to generate the tables. Analytical expressions are easily coded to create custom functions that return the normalized glandular dose for the set of input parameters. Examples of implementation are presented in Microsoft Visual Basic for Applications (VBA). PMID:9127307

Sobol, W T; Wu, X

1997-04-01

20

Media glandular dose in mammography;Dosis glandular media en mamografia  

Energy Technology Data Exchange (ETDEWEB)

The objective of this work was to determine the media glandular dose of the patients group who most frequently are exposed at mammographic studies in the General Hospital of Zone No. 1 of IMSS in Zacatecas, later to compare this dose with the value that establishes the Mexican Official Standard and to know risk-benefit that a patient is exposed when it is realized studies of this nature. This with the purpose of to know if the patients who are realized this type of studies are exhibited to irradiations of unnecessary way. In order to obtain the media glandular dose, first it was choose the age group of feminine population that is predominant to this suffering. Of the classification of the age group it was determine the frequency of each thickness of mamma, and on the basis of the thickness of the compressed mamma the conditions were registered with it radiates the patient. When having the age and compressed mamma thickness of patient and the voltage, current, anode/filter that uses the mammography equipment for to radiate it was calculated the media glandular dose. The media glandular dose was calculated using two algorithms proposed in literature and thermoluminescent dosemeters. For the case of the thermoluminescent dosemeters were used two phantoms. In this study was detected that the limits, with that they radiate the patients who are exposed at mammographic studies it is by underneath of 3 mGy. Finally, it was detected that the Mexican Official Standard lacks of elements to offer radiological limits for the mammography area, because in this standard they are excluded the radiological limits for anode and filter of Mo/Rh and Rh/Rh. To know the dose applying these anodes and filters is of extreme importance because 85% of the population that is exposed to this studies type was radiated with anode and filter of Mo/Rh and Rh/Rh. (Author)

Duran M, H. A.; Hernandez O, M.; Pinedo S, A.; Guerra M, J. A.; Gonzalez G, R.; Salas L, M. A.; Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Calle Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Rivera M, T. [IPN, Centro de Investigacion en Ciencia Aplicada en Tecnologia Avanzada, Av. Legaria 694, 11500 Mexico D. F. (Mexico); Azorin N, J., E-mail: hduran20_1@hotmail.co [Universidad Autonoma Metropolitana, Unidad Iztapalapa, Av. San Rafael Atlixco 186, 09340 Mexico D. F. (Mexico)

2009-10-15

 
 
 
 
21

Mean glandular dose for different angles of the X-ray tube using different glandularity phantoms  

Science.gov (United States)

Digital breast tomosynthesis (DBT) is a three-dimensional radiographic technique that is beginning to be used as part of an imaging diagnostic program in some of Brazilian clinical practices. Studies are needed to evaluate the performance and to determine the radiation dose of patients that are undergoing this new procedure. The aim of this work is to present results of the mean glandular dose (DG) for different angles of the X-ray tube using a computed radiography (CR) mammography unit and different glandularity standard breast phantoms. DG values were derived from measurements of the incident air kerma (Ki) and tabulated conversion coefficients that are dependent on the half-value layer (HVL) of the X-ray spectrum. Irradiations were done in a 3000 Nova model Siemens MAMMOMAT mammography unit with the X-ray tube angle ranging from -30° to 30°. The protocol with 28 kV was used for Mo/Mo combination. The distance between focus and the 90×5-6 M model Radcal ionization chamber was 60.5 cm and the tube loading (PIt) used was 50 mA s. Exposures were done for DG determination using the semi-automatic exposure control mode and the 45 mm Computerized Imaging Reference Systems, Inc phantoms which approximately simulate a standard breast with glandularities of 0, 30, 50, 70 and 100%. DG values ranged from 1.3±0.1 to 7.6±0.7 mGy. The results are in according to the reference level of 3 mGy established by the International Basic Safety Standards (BSS115) to breast with 45 mm of thickness, 50% of glandularity and for the X-ray tube positioned in 0°. The results showed that DG increases with the glandularity and with the rotation of the X-ray tube. This work contributes to begin in Brazil the dosimetry in DBT equipments using different protocols and target/filter combinations.

Oliveira, B. B.; Nogueira, M. S.

2014-02-01

22

Average glandular dose in patients submitted to mammographic examinations  

International Nuclear Information System (INIS)

Doses in mammography should be maintained as low as possible without reducing the high image quality needed to the early detection of the breast cancer. As the breast is composed of tissues with very soft composition and densities, it increases the difficulty to detect small changes in the normal anatomical structures that may be associated with breast cancer. To achieve the standards of resolution and contrast for mammography, the quality and intensity of the X-ray beam, the breast positioning and compression, the film screen system, and the film processing must be in optimal operational conditions. This study intended to evaluate the mean glandular dose of patients undergoing routine exams in one mammography unit. Patient image analyses were done by a radiologist doctor who took into account 10 evaluation criteria for each CC and MLO incidences. For estimating each patient glandular dose the radiographic technique parameters (kV and mAs) and the thickness of the compressed breast were recorded. European image quality criteria were adopted by the radiologist doctor to accept the image for diagnostic purpose. For breast densities of 50% adipose and 50% glandular tissues the incident air-kerma was measured and the glandular dose calculated considering the x-ray output during the exam. In the study of 50 patients the mean glandular dose varied from 0.90 to 3.27 mGy with a mean value of 1.98 mGy for CC incidences. For MLO incidences the mean glandular doses ranged from 0.97 to 3.98 mGy and a mean value of 2.60 mGy. (author)

23

Evaluation of glandular dose in conventional and digital mammography systems  

International Nuclear Information System (INIS)

A survey was conducted to estimate the average glandular dose (Dg) for patients undergoing mammography and to report the distribution of incident air kerma (Ki), patient age, compressed breast thickness and glandular tissue content. From 1183 cranio caudal mammograms clinical data were collected and doses were measured. The survey data included mammograms from six mammography equipment: two screen/film units (SFM), two computed radiography units (CR) and two full-field digital (DR). Mean value for patient age and compressed breast thickness were 57 +-12 y and 5.4 +-1.4 cm, respectively. To investigate the importance of technical characteristics of three different mammography systems and breast glandularity, Ki and Dg were measured for individual breast of 392 patients from the original sample with compressed breast thickness in the range of 5.5 cm to 6.5 cm using tissue-equivalent phantoms of different glandularities manufactured in this study to mimic both the attenuation and the density of breast tissues. Mean Ki value was 10.0 +-3.6 mGy for SFM systems, 12.0 +-3.6 mGy for CR systems and 4.9 +-1.3 mGy for DR systems. Mean Dg value was 1.4 +-0.5 mGy for S/F systems, 1.7 +-0.5 mGy for CR systems and 0.9 +-0.2 mGy for D R systems. Statistical analysis for differences in mean values of Ki and Dg between mammography systems showed significant effect of their technical characteristics (p i and Dg, it was observed statistically significant differences between the group of patients with 0 to 50% glandularity and the group of patients with 50 to 100% glandularity. (author)

24

Average glandular dose in routine mammography screening using a Sectra Microdose Mammography unit  

International Nuclear Information System (INIS)

The Sectra MicroDose Mammography system is based on direct photon counting (with a solid-state detector), and a substantially lower dose to the breast than when using conventional system can be expected. In this work absorbed dose measurements have been performed for the first unit used in routine mammography screening (at the Hospitals of Helsingborg (Sweden)). Two European protocols on dosimetry in mammography have been followed. Measurement of half value layer (HVL) cannot be performed as prescribed, but this study has demonstrated than non-invasive measurements of HVL can be performed accurately with a sensitive and well collimated solid-state detector with simultaneous correction for the energy dependence. The average glandular dose for a 50 mm standard breast with 50% glandularity, simulated by 45 mm polymethylmethacrylate, was found to be 0.21 and 0.28 mGy in March and December 2004, respectively. These values are much lower than for any other mammography system on the market today. It has to be stressed that the measurement were made using the current clinical settings and that no systematic optimisation of the relationship between absorbed dose and diagnostic image quality has been performed within the present study. In order to further increase the accuracy of absorbed dose measurements for this unit, the existing dose protocols should be revised to account also for the tungsten/aluminium anode/filter combination, the multi-slit pre-collimator device and the occurrence of a dose profile in the scanning direction. (authors)

25

Mean glandular dose in a breast screening programme  

Energy Technology Data Exchange (ETDEWEB)

Breast density has an important role in early detection of breast cancer, because has been reported the strong association between breast density and invasive breast cancer risk. Mammography is the gold standard to early detection of breast cancer, despite of this require ionizing radiation that may increase radio-induced cancer risk. This maybe limited with a quality control programme of mammographic units, with the main goal of achieving high quality images with low radiation dose. International Atomic Energy Agency (IAEA) published in 2011 the {sup Q}uality assurance programme for digital mammography{sup ,} where glandular tissue quantity is an important parameter to compute mean glandular dose (MGD), which is necessary to reduce its associated risk. In this work we show the first results in our country applying this protocol and studying breast density in a small group. MGD complies with national and IAEA dose limits.

Galvan, H. A.; Perez-Badillo, M. P.; Villasenor, Y. [Instituto Nacional de Cancerologia, Av. San Fernando No. 22, Col Seccion XVI, Mexico, D. F., C. P. 14080 (Mexico)

2012-10-23

26

Mean glandular dose in a breast screening programme  

International Nuclear Information System (INIS)

Breast density has an important role in early detection of breast cancer, because has been reported the strong association between breast density and invasive breast cancer risk. Mammography is the gold standard to early detection of breast cancer, despite of this require ionizing radiation that may increase radio-induced cancer risk. This maybe limited with a quality control programme of mammographic units, with the main goal of achieving high quality images with low radiation dose. International Atomic Energy Agency (IAEA) published in 2011 the Quality assurance programme for digital mammography, where glandular tissue quantity is an important parameter to compute mean glandular dose (MGD), which is necessary to reduce its associated risk. In this work we show the first results in our country applying this protocol and studying breast density in a small group. MGD complies with national and IAEA dose limits.

27

Mean glandular dose in a breast screening programme  

Science.gov (United States)

Breast density has an important role in early detection of breast cancer, because has been reported the strong association between breast density and invasive breast cancer risk. Mammography is the gold standard to early detection of breast cancer, despite of this require ionizing radiation that may increase radio-induced cancer risk. This maybe limited with a quality control programme of mammographic units, with the main goal of achieving high quality images with low radiation dose. International Atomic Energy Agency (IAEA) published in 2011 the "Quality assurance programme for digital mammography", where glandular tissue quantity is an important parameter to compute mean glandular dose (MGD), which is necessary to reduce its associated risk. In this work we show the first results in our country applying this protocol and studying breast density in a small group. MGD complies with national and IAEA dose limits.

Galván, H. A.; Pérez-Badillo, M. P.; Villaseñor, Y.

2012-10-01

28

Development of an excel spreadsheet formean glandular dose in mammography  

International Nuclear Information System (INIS)

The purpose of this study was to develop an Excel spreadsheet to calculate mean glandular dose (Dg) in mammography using clinical exposure data. Dg can be calculated as the product of incident air kerma (Ka) and DgN (i.e., Dg=Ka x DgN). According to the method of Klein et al (Phys Med Biol 1997; 42: 651-671), Ka was measured at the entrance surface with an ionization dosimeter. Normalized glandular dose (DgN) coefficients, taking into account breast glandularity, were computed using Boone's method (Med Phys 2002; 29: 869-875). DgN coefficients can be calculated for any arbitrary X-ray spectrum. These calculation procedures were input into a Microsoft Excel spreadsheet. The resulting Excel spreadsheet is easy to use and is always applicable in the field of mammography. The exposure conditions concerning Dg in clinical practice were also investigated in 22 women. Four exposure conditions (target/filter combination and tube voltage) were automatically selected in this study. This investigation found that average Dg for each exposure was 1.9 mGy. Because it is recommended that quality control of radiation dose management in mammography is done using an American College of Radiology (ACR) phantom, information about patient dose is not obtained in many facilities. The present Excel spreadsheet was accordingly considered useful for optimization dingly considered useful for optimization of exposure conditions and explanation of mammography to patients. (author)

29

Mean glandular dose and equipment variability in screen-film mammography  

International Nuclear Information System (INIS)

Breast tissue is mainly composed of glandular tissue, adipose tissue and connective tissue. The inspection of 27 mammography facilities was conducted in a period of two years to evaluate the mean glandular dose of patients

30

The study of mean glandular dose in mammography in Yazd and the factors affecting it  

International Nuclear Information System (INIS)

The objective of this study was to determine the mean glandular dose resulting from mammography examinations in Yazd, southeastern Iran and to identify the factors affecting it. Patients and Methods: This survey was conducted during May to December 2005 to estimate the mean glandular dose for women undergoing mammography and to report the distribution of dose. compressed breast thickness, glandular tissue content, and mammography technique used. The clinical data were collected from 946 mammograms taken from 246 women who were referred to four mammography centers. The mammography instruments in these centers were four modern units with a molybdenum anode and either molybdenum or rhodium filter. The exposure conditions of each mammogram were recorded. The breast glandular content of each mammogram was estimated by a radiologist. The mean glandular dose was calculated based on measuring the normalized entrance skin dose in air. half value layer, kVp, mAs, breast thickness and glandular content. Half value layer, kVp and entrance skin dose were measured by a solid-state detector. The analytical method of Sobol et al. was used for calculation of mean glandular dose . Results: The mean±SD mean glandular dose per film was.2±0.6 mGy for cranio caudal and 1.63±O.9 mGy for mediolateral oblique views. The mean±SD mean glandular dose per woman was 5.5 3.1.mGy. A positive correlation was found between the beam Half value layer with mean glandular dose (r=O.38) and the breast thickness with mean glandular dose (r=O.5). Conclusion: The mean±SD mean glandular dose per film of 1.42±0.8 mGy in present study was lower than most of similar reports. However, the mean mean glandular dose per woman was higher than that in other studies

31

Monte Carlo simulation for correlation analysis of average glandular dose by breast thickness and glandular ratio in breast tissue.  

Science.gov (United States)

A glandular breast tissue is a radio-sensitive tissue. So during the evaluation of an X-ray mammography device, Average Glandular Dose (AGD) measurement is a very important part. In reality, it is difficult to measure AGD directly, Monte Carlo simulation was used to analyze the correlation between the AGD and breast thickness. As a result, AGDs calculated through the Monte Carlo simulation were 1.64, 1.41 and 0.88 mGy. The simulated AGDs mainly depend on the glandular ratio of the breast. With the increase of glandular breast tissue, absorption of low photon-energy increased so that the AGDs increased, too. In addition, the thicker the breast was, the more the AGD became. Consequently, this study will be used as basic data for establishing the diagnostic reference levels of mammography. PMID:24704647

Kim, Sang-Tae; Cho, Jung-Keun

2014-01-01

32

TLD measurements and Monte Carlo simulations for glandular dose and scatter fraction assessment in mammography: A comparative study  

International Nuclear Information System (INIS)

assessment of mean glandular dose and comparison with experimental data. ? Dose variation inside the breast from 12% to 230% of the mean glandular dose. ? Monte Carlo estimation of backscatter factor and dose scatter fraction.

33

Absorbed dose and dose reduction in mammography  

International Nuclear Information System (INIS)

First, absorbed dose at entrance surface was measured in routine mammography. Secondly, a possibility of dose reduction after introduction of Fuji computed radiography (FCR) system was examined. In a total of 350 mammographic studies including craniocaudal and medilateral projections, average thickness of compressed breast was less than 4 cm and most frequently recorded absorbed dose was 0.2-0.3 cGy (200-300 mrad). Minimum dose to obtain clinically acceptable mammograms in FCR system was estimated by comparing image quality of routine versus reduced dose studies. It was concluded that absorbed dose could be reduced to 1/4 of routine dose without creating significant drawback in diagnosis. (author)

34

Estimation of mean glandular dose for mammography of augmented breasts  

International Nuclear Information System (INIS)

The standard quantity used to relate breast surface exposure to radiation risk is the mean dose received by the radiation sensitive tissue contained within the female breast, the mean glandular dose (MGD). At present, little is known about the MGD received by women with breast implants as there is no technique available to facilitate its calculation. The present work has involved modification of the conventional method for MGD estimation to make it applicable to women with augmented breasts. The technique was used to calculate MGDs for a cohort of 80 women with breast implants, which were compared with similar data calculated for a total of 1258 non-augmented women. Little difference was found in median MGD at low compressed breast thickness. At high breast thickness, however, the MGDs received by women with augmented breasts were found to be considerably lower than those relating to their non-augmented counterparts. (author)

35

Estimation of mean glandular dose for mammography of augmented breasts  

Science.gov (United States)

The standard quantity used to relate breast surface exposure to radiation risk is the mean dose received by the radiation sensitive tissue contained within the female breast, the mean glandular dose (MGD). At present, little is known about the MGD received by women with breast implants as there is no technique available to facilitate its calculation. The present work has involved modification of the conventional method for MGD estimation to make it applicable to women with augmented breasts. The technique was used to calculate MGDs for a cohort of 80 women with breast implants, which were compared with similar data calculated for a total of 1258 non-augmented women. Little difference was found in median MGD at low compressed breast thickness. At high breast thickness, however, the MGDs received by women with augmented breasts were found to be considerably lower than those relating to their non-augmented counterparts.

Beckett, J. R.; Kotre, C. J.

2000-11-01

36

Estimation of mean glandular dose for mammography of augmented breasts  

Energy Technology Data Exchange (ETDEWEB)

The standard quantity used to relate breast surface exposure to radiation risk is the mean dose received by the radiation sensitive tissue contained within the female breast, the mean glandular dose (MGD). At present, little is known about the MGD received by women with breast implants as there is no technique available to facilitate its calculation. The present work has involved modification of the conventional method for MGD estimation to make it applicable to women with augmented breasts. The technique was used to calculate MGDs for a cohort of 80 women with breast implants, which were compared with similar data calculated for a total of 1258 non-augmented women. Little difference was found in median MGD at low compressed breast thickness. At high breast thickness, however, the MGDs received by women with augmented breasts were found to be considerably lower than those relating to their non-augmented counterparts. (author)

Beckett, J.R.; Kotre, C.J. [Regional Medical Physics Department, Newcastle General Hospital, Westgate Road, Newcastle upon Tyne NE4 6BE (United Kingdom)

2000-11-01

37

Calculation of mean glandular dose for mammography practice in Bangladesh  

International Nuclear Information System (INIS)

The incidence of breast cancer in the western world is worryingly high now. The prognosis is best if the disease is detected early, whilst the tumour is small and before it has spread, As a consequence breast-screening programmes based upon X-ray mammography have been instigated in many countries. In Bangladesh the frequency of diagnosis by mammography is increasing day by day. Some of the examinations are repeated due to the low image contrast. This causes increase in personal dose as well as population dose. The technicians working in this field are concerned with the image quality but not about the dose that they impart to the patient. The radiation dose to breast from ionizing radiation varies with the examination types and machine types used for diagnosis. It varies with the technical parameters (kVp, mAs, source to skin distance) used during mammography examination. Many works regarding this field have been done in different countries in the world. They have a regular radiation dose assessment program but in Bangladesh, hardly any work has been done in this field. On this plea, mainly, the present work has been undertaken. The aim of this work was to evaluate the mean glandular dose to breast

38

Estimating the glandular average dose in some mammography labs  

International Nuclear Information System (INIS)

Mammography is the safest method of detecting breast cancer but, at the same time, the most accurate radiological examination which implies getting high quality images and a minimum dose per breast. This type of examination requires a special equipment and technique for the following reasons: a similarity of X-rays attenuating factors in the breast structure, an undetectable difference between the soft tissue density of the normal breast and of the sick breast, the importance of detecting minute details such as micro-calcifications. The present study was carried out in five mammography laboratories, from which only one has partially implemented a programme of quality control. There were evaluated the phantom image, film contrast, background optical density, density difference, and radiation beam quality. Also, the entrance surface air kerma was measured. The glandular average dose was estimated for the standard breast using the conversion coefficients corresponding to the used target-filter combination, and the values were determined for the radiation beam quality. Compared to the reference lab, all the other four labs failed all the tests, obtaining unacceptable results both for the phantom image and for the contrast, for the background optical density and density difference. The average glandular doses estimated for the standard breast varied between 0.71 and 1.59 mSv, being in four out of the five hospitals, statistically significant (p<0.001), lower than those curignificant (p<0.001), lower than those currently accepted by international authorities (3 mSv). The increasing number of breast cancer, of the equipment types and of the frequency of this type of investigation renders necessary the implementation of quality checking programmes. Such simple quality control procedures will improve the chances of accurate diagnosis and reduce the probability of false negatives. This is particularly important for early detection and treatment of breast cancer which is the most frequent type of cancer among females. (authors)

39

Dependence of mean glandular dose on compression plate position  

International Nuclear Information System (INIS)

The aim of this study is to explore the influence of the compression plate position and type of dosimetry detector used while performing radiation output measurements for determination of incident air kerma (IAK) in mammography. The European protocol on dosimetry in mammography and the European protocol for the quality control of the physical and technical aspects of mammography screening do not specify the precise position of the compression plate. The Code of Practice for Dosimetry in diagnostic radiology (TRS 457) of the IAEA defines the place of the plate in contact with the dosimetry detector but only for phantom measurements. The last edition of the British protocol for Commissioning and routine testing of mammographic X-ray systems specifies the plate position at least 5 cm above the detector. All these protocols use the same values of the conversion coefficients for calculation of mean glandular dose (MGD) from IAK

40

Investigation of mean glandular dose in diagnostic mammography in China.  

Science.gov (United States)

A survey of 420 exposures of mammography was performed with the parameters recorded. Entrance skin air kerma (ESAK) was measured and the mean glandular dose (MGD) was calculated according to the Dance's formula. Correlation analysis showed that several factors could affect the MGD level. Mann-whitney test and Non-parametric ANOVA analyses were used to compare the MGD level grouped by view type and radiographic systems. No significant difference was found in MGD between the craniocaudal (CC) group and the mediolateral oblique (MLO) group. The MGD level was higher in the CR group than in the other two groups. MGD was positively correlated with the compressed breast thickness (CBT). MGD varied with the half value layer (HVL) and increased first then decreased. The mean MGD level in China is about 1.6 mGy and is lower than the guidance level in the International Basic Safety Standards (IBSS). PMID:24827723

Du, Xiang; Wang, Jin; Yang, Chun Yong; Zhou, Xian Feng; Chen, Wei; Cao, Xing Jiang; Zhou, Yuan Yuan; Le Yu, Ning

2014-05-01

 
 
 
 
41

Dosimetry in Mammography: Average Glandular Dose Based on Homogeneous Phantom  

Science.gov (United States)

The objective of this study was to demonstrate that a clinical dosimetry protocol that utilizes a dosimetric breast phantom series based on population anthropometric measurements can reliably predict the average glandular dose (AGD) imparted to the patient during a routine screening mammogram. AGD was calculated using entrance skin exposure and dose conversion factors based on fibroglandular content, compressed breast thickness, mammography unit parameters and modifying parameters for homogeneous phantom (phantom factor), compressed breast lateral dimensions (volume factor) and anatomical features (anatomical factor). The patient fibroglandular content was evaluated using a calibrated modified breast tissue equivalent homogeneous phantom series (BRTES-MOD) designed from anthropomorphic measurements of a screening mammography population and whose elemental composition was referenced to International Commission on Radiation Units and Measurements Report 44 and 46 tissues. The patient fibroglandular content, compressed breast thickness along with unit parameters and spectrum half-value layer were used to derive the currently used dose conversion factor (DgN). The study showed that the use of a homogeneous phantom, patient compressed breast lateral dimensions and patient anatomical features can affect AGD by as much as 12%, 3% and 1%, respectively. The protocol was found to be superior to existing methodologies. The clinical dosimetry protocol developed in this study can reliably predict the AGD imparted to an individual patient during a routine screening mammogram.

Benevides, Luis A.; Hintenlang, David E.

2011-05-01

42

Dosimetry in Mammography: Average Glandular Dose Based on Homogeneous Phantom  

International Nuclear Information System (INIS)

The objective of this study was to demonstrate that a clinical dosimetry protocol that utilizes a dosimetric breast phantom series based on population anthropometric measurements can reliably predict the average glandular dose (AGD) imparted to the patient during a routine screening mammogram. AGD was calculated using entrance skin exposure and dose conversion factors based on fibroglandular content, compressed breast thickness, mammography unit parameters and modifying parameters for homogeneous phantom (phantom factor), compressed breast lateral dimensions (volume factor) and anatomical features (anatomical factor). The patient fibroglandular content was evaluated using a calibrated modified breast tissue equivalent homogeneous phantom series (BRTES-MOD) designed from anthropomorphic measurements of a screening mammography population and whose elemental composition was referenced to International Commission on Radiation Units and Measurements Report 44 and 46 tissues. The patient fibroglandular content, compressed breast thickness along with unit parameters and spectrum half-value layer were used to derive the currently used dose conversion factor (DgN). The study showed that the use of a homogeneous phantom, patient compressed breast lateral dimensions and patient anatomical features can affect AGD by as much as 12%, 3% and 1%, respectively. The protocol was found to be superior to existing methodologies. The clinical dosimetry protocol developed in this study can reliably predict the AGD imparted to an individual patient during a routine screening mammogram.

43

Analysis of patient exposure dose for mammography. Estimation of average glandular dose in 1998 questionnaire  

International Nuclear Information System (INIS)

Recently, patient exposure dose for mammography are varied because of a great demand for mammography, which non-palpable lesion can be detected, diffusion of special X-ray equipment, progress of CR and enlightenment or study on mammography in Japanese society of radiological technology. Therefore, the newest patient exposure dose obtained from '98 questionnaire carried out to the whole country in Japan was investigated. Furthermore, the average glandular dose based on '98 was compared with that of '93. The average glandular dose can be calculated from the product of the breast entrance skin exposure and DgN (the average glandular dose per unit entrance skin exposure). The breast entrance skin dose was estimated from the dose of 782 institutions in '98, which was calculated from data measured at 51 institutions in Tokai and Hokuriku area. DgN was used published table of 50% adipose-50% glandular breast composition and 4.2 cm breast thickness corresponding to measured half-value layer (HVL) on each tube voltages. Then, patient exposure dose for mammography was estimated from exposure condition (tube voltage, mAs value) obtained '98 questionnaire. The dose in '98 estimated 1.422 mGy was reduced that compared with in '93 estimated 1.610 mGy. The dose of '98 without grid was reduced about 30% of '93. The dose of 98 with grid was not any reduced than the dose of '93. However, the number of institution of '98 with grid was about 2.8 times than '93. The patient exposure dose for mammography was reduced approximately 10% during 5 years. There are probability that mammography with grid for guidance level will be 1.5 mGy. (author)

44

Analysis of patient exposure dose for mammography: estimation of average glandular dose in 2007 questionnaire  

International Nuclear Information System (INIS)

Recently, the swift progress of digital mammography has resulted in variation in patient exposure doses during mammography in Japan. We therefore carried out a study in 2007 to determine the latest patient exposure dose by means of a nationwide questionnaire survey of Japan, and compared the average glandular dose with those of 1993, 1998, and 2001. The average glandular dose can be calculated from the product of the breast entrance skin exposure and DgN (the average glandular dose per unit entrance skin exposure). The 2007 breast entrance skin dose was estimated from doses at 434 institutions, calculated on the basis of tube voltages measured at 51 institutions in the Tokai and Hokuriku regions of Japan. The DgN was calculated by using a published table of 50% adipose-50% glandular breast composition and 4.2 cm breast thickness corresponding to the measured half-value layer (HVL) at each tube voltage. The patient exposure dose for mammography was then estimated from exposure conditions (tube voltage, mAs value) obtained from the 2007 questionnaire. The 2007 estimated dose of about 1.7 mGy had increased compared with 1.4 mGy in 1998 and 1.5 mGy in 2001, returning to a value close to that of 1.6 mGy in 1993. This is the result of the great popularity of digital mammography, in particular computed radiography (CR). Digital mammography is increasing, accounting for about 70% of all mammography in the current investigation in comparison with 28.3% in 2001, 24.0% in 1998 and 8.8% in 1993, when the first survey of patient exposure dose for mammography was carried out. The patient exposure dose during digital mammography, and for CR in particular, should therefore be reconsidered. (author)

45

A Quality Assurance programme in mammography and an evaluation of the mean glandular dose  

International Nuclear Information System (INIS)

The use of X-ray in medicine for diagnosis represents the largest man-made sources of public exposure to ionizing radiation. Therefore a reduction of medical exposure is desired without reduction of the diagnostic capability. Dose and image quality are essential component of a Quality Assurance (QA) programme in mammography where the characteristic of diagnostic signs, represented by microcalcifications and low contrast structures, and the radiosensitivity of the glandular tissue of the breast stress the need of QA programme. The paper describes QA procedures in mammography and reports the results obtained in more than 120 periodic tests, performed on 63 mammographic units of 41 centers. Moreover individual evaluation of entrance exposure are presented for 340 patients. The experimental data permits to evaluate the mean grandular absorbed dose in the single exams using different procedures based on Monte Carlo simulations. (author)

46

Average glandular dose and phantom image quality in mammography  

Energy Technology Data Exchange (ETDEWEB)

Doses in mammography should be maintained as low as possible without reducing the high image quality needed for early detection of the breast cancer. The breast is composed of tissues with very close composition and densities. It increases the difficulty to detect small changes in the normal anatomical structures which may be associated with breast cancer. To achieve the standards of definition and contrast for mammography, the quality and intensity of the X-ray beam, the breast positioning and compression, the film-screen system, and the film processing have to be in optimal operational conditions. This study sought to evaluate average glandular dose (AGD) and image quality on a standard phantom in 134 mammography units in the state of Minas Gerais, Brazil, between December 2004 and May 2006. AGDs were obtained by means of entrance kerma measured with TL LiF100 dosimeters on phantom surface. Phantom images were obtained with automatic exposure technique, fixed 28 kV and molybdenum anode-filter combination. The phantom used contained structures simulating tumoral masses, microcalcifications, fibers and low contrast areas. High-resolution metallic meshes to assess image definition and a stepwedge to measure image contrast index were also inserted in the phantom. The visualization of simulated structures, the mean optical density and the contrast index allowed to classify the phantom image quality in a seven-point scale. The results showed that 54.5% of the facilities did not achieve the minimum performance level for image quality. It is mainly due to insufficient film processing observed in 61.2% of the units. AGD varied from 0.41 to 2.73 mGy with a mean value of 1.32{+-}0.44 mGy. In all optimal quality phantom images, AGDs were in this range. Additionally, in 7.3% of the mammography units, the AGD constraint of 2 mGy was exceeded. One may conclude that dose level to patient and image quality are not in conformity to regulations in most of the facilities. This indicates that ongoing actions are needed to optimize image quality and radiation dose for early detection of the breast cancer.

Oliveira, M. [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN), Comissao Nacional de Energia Nuclear (CNEN), Rua Prof. Mario Werneck, s/n Cidade Universitaria-Pampulha, 30123-970 Belo Horizonte, MG (Brazil); Superintendencia Estadual de Vigilancia Sanitaria, Belo Horizonte, MG (Brazil); Nogueira, M.S. [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN), Comissao Nacional de Energia Nuclear (CNEN), Rua Prof. Mario Werneck, s/n Cidade Universitaria-Pampulha, 30123-970 Belo Horizonte, MG (Brazil)], E-mail: mnogue@cdtn.br; Guedes, E. [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN), Comissao Nacional de Energia Nuclear (CNEN), Rua Prof. Mario Werneck, s/n Cidade Universitaria-Pampulha, 30123-970 Belo Horizonte, MG (Brazil); Andrade, M.C. [Superintendencia Estadual de Vigilancia Sanitaria, Belo Horizonte, MG (Brazil); Peixoto, J.E. [Radiology Department, UFRJ, Av. Brig. Trompowisky, s/n Rio de Janeiro CEP 21941-590 (Brazil); Joana, G.S.; Castro, J.G. [Superintendencia Estadual de Vigilancia Sanitaria, Belo Horizonte, MG (Brazil)

2007-09-21

47

Average glandular dose and phantom image quality in mammography  

Science.gov (United States)

Doses in mammography should be maintained as low as possible without reducing the high image quality needed for early detection of the breast cancer. The breast is composed of tissues with very close composition and densities. It increases the difficulty to detect small changes in the normal anatomical structures which may be associated with breast cancer. To achieve the standards of definition and contrast for mammography, the quality and intensity of the X-ray beam, the breast positioning and compression, the film-screen system, and the film processing have to be in optimal operational conditions. This study sought to evaluate average glandular dose (AGD) and image quality on a standard phantom in 134 mammography units in the state of Minas Gerais, Brazil, between December 2004 and May 2006. AGDs were obtained by means of entrance kerma measured with TL LiF100 dosimeters on phantom surface. Phantom images were obtained with automatic exposure technique, fixed 28 kV and molybdenum anode-filter combination. The phantom used contained structures simulating tumoral masses, microcalcifications, fibers and low contrast areas. High-resolution metallic meshes to assess image definition and a stepwedge to measure image contrast index were also inserted in the phantom. The visualization of simulated structures, the mean optical density and the contrast index allowed to classify the phantom image quality in a seven-point scale. The results showed that 54.5% of the facilities did not achieve the minimum performance level for image quality. It is mainly due to insufficient film processing observed in 61.2% of the units. AGD varied from 0.41 to 2.73 mGy with a mean value of 1.32±0.44 mGy. In all optimal quality phantom images, AGDs were in this range. Additionally, in 7.3% of the mammography units, the AGD constraint of 2 mGy was exceeded. One may conclude that dose level to patient and image quality are not in conformity to regulations in most of the facilities. This indicates that ongoing actions are needed to optimize image quality and radiation dose for early detection of the breast cancer.

Oliveira, M.; Nogueira, M. S.; Guedes, E.; Andrade, M. C.; Peixoto, J. E.; Joana, G. S.; Castro, J. G.

2007-09-01

48

The Study of Mean Glandular Dose in Mammography in Yazd and the Factors Affecting It  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Backgrounds/Objective: The objective of this study was to determine the mean glandular dose (MGD) resulting from mammography examinations in Yazd, southeastern Iran and to identify the factors affecting it. Patients and Methods: This survey was conducted during May to December 2005 to estimate the MGD for women undergoing mammography and to report the distribution of dose, com-pressed breast thickness, glandular tissue content, and mammography technique used. The clinical data were collected ...

Bouzarjomehri, F.; Mostaar, A.; Ghasemi, A.; Ehramposh, M. H.; Khosravi, H.

2006-01-01

49

Additional factors for the estimation of mean glandular breast dose using the UK mammography dosimetry protocol  

International Nuclear Information System (INIS)

The UK and European protocols for mammographic dosimetry use conversion factors that relate incident air kerma to the mean glandular dose (MGD) within the breast. The conversion factors currently used were obtained by computer simulation of a model breast with a composition of 50% adipose and 50% glandular tissues by weight (50% glandularity). Relative conversion factors have been calculated which allow the extension of the protocols to breasts of varying glandularity and for a wider range of mammographic x-ray spectra. The data have also been extended to breasts of a compressed thickness of 11 cm. To facilitate the calculation of MGD in patient surveys, typical breast glandularities are tabulated for women in the age ranges 40-49 and 50-64 years, and for breasts in the thickness range 2-11 cm. In addition, tables of equivalent thickness of polymethyl methacrylate have been provided to allow the simulation for dosimetric purposes of typical breasts of various thicknesses. (author)

50

Additional factors for the estimation of mean glandular breast dose using the UK mammography dosimetry protocol  

Energy Technology Data Exchange (ETDEWEB)

The UK and European protocols for mammographic dosimetry use conversion factors that relate incident air kerma to the mean glandular dose (MGD) within the breast. The conversion factors currently used were obtained by computer simulation of a model breast with a composition of 50% adipose and 50% glandular tissues by weight (50% glandularity). Relative conversion factors have been calculated which allow the extension of the protocols to breasts of varying glandularity and for a wider range of mammographic x-ray spectra. The data have also been extended to breasts of a compressed thickness of 11 cm. To facilitate the calculation of MGD in patient surveys, typical breast glandularities are tabulated for women in the age ranges 40-49 and 50-64 years, and for breasts in the thickness range 2-11 cm. In addition, tables of equivalent thickness of polymethyl methacrylate have been provided to allow the simulation for dosimetric purposes of typical breasts of various thicknesses. (author)

Dance, D.R. [Physics Department, The Royal Marsden NHS Trust, London SW3 6JJ (United Kingdom). E-mail: d.dance at icr.ac.uk; Skinner, C.L. [Physics Department, The Royal Marsden NHS Trust, London SW3 6JJ (United Kingdom); Young, K.C. [National Coordinating Centre for the Physics of Mammography, Royal Surrey County Hospital, Guildford GU2 7XX (United Kingdom); Beckett, J.R.; Kotre, C.J. [Regional Medical Physics Department, Newcastle General Hospital, Newcastle-upon-Tyne NE4 6BE (United Kingdom)

2000-11-01

51

Additional factors for the estimation of mean glandular breast dose using the UK mammography dosimetry protocol  

Science.gov (United States)

The UK and European protocols for mammographic dosimetry use conversion factors that relate incident air kerma to the mean glandular dose (MGD) within the breast. The conversion factors currently used were obtained by computer simulation of a model breast with a composition of 50% adipose and 50% glandular tissues by weight (50% glandularity). Relative conversion factors have been calculated which allow the extension of the protocols to breasts of varying glandularity and for a wider range of mammographic x-ray spectra. The data have also been extended to breasts of a compressed thickness of 11 cm. To facilitate the calculation of MGD in patient surveys, typical breast glandularities are tabulated for women in the age ranges 40-49 and 50-64 years, and for breasts in the thickness range 2-11 cm. In addition, tables of equivalent thickness of polymethyl methacrylate have been provided to allow the simulation for dosimetric purposes of typical breasts of various thicknesses.

Dance, D. R.; Skinner, C. L.; Young, K. C.; Beckett, J. R.; Kotre, C. J.

2000-11-01

52

Normalized glandular dose (DgN) coefficients for flat-panel CT breast imaging  

Science.gov (United States)

The development of new digital mammography techniques such as dual-energy imaging, tomosynthesis and CT breast imaging will require investigation of optimal camera design parameters and optimal imaging acquisition parameters. In optimizing these acquisition protocols and imaging systems it is important to have knowledge of the radiation dose to the breast. This study presents a methodology for estimating the normalized glandular dose to the uncompressed breast using the geometry proposed for flat-panel CT breast imaging. The simulation uses the GEANT 3 Monte Carlo code to model x-ray transport and absorption within the breast phantom. The Monte Carlo software was validated for breast dosimetry by comparing results of the normalized glandular dose (DgN) values of the compressed breast to those reported in the literature. The normalized glandular dose was then estimated for a range of breast diameters from 10 cm to 18 cm using an uncompressed breast model with a homogeneous composition of adipose and glandular tissue, and for monoenergetic x-rays from 10 keV to 120 keV. These data were fit providing expressions for the normalized glandular dose. Using these expressions for the DgN coefficients and input variables such as the diameter, height and composition of the breast phantom, the mean glandular dose for any spectra can be estimated. A computer program to provide normalized glandular dose values has been made available online. In addition, figures displaying energy deposition maps are presented to better understand the spatial distribution of dose in CT breast imaging.

Thacker, Samta C.; Glick, Stephen J.

2004-12-01

53

Normalized glandular dose (DgN) coefficients for flat-panel CT breast imaging  

Energy Technology Data Exchange (ETDEWEB)

The development of new digital mammography techniques such as dual-energy imaging, tomosynthesis and CT breast imaging will require investigation of optimal camera design parameters and optimal imaging acquisition parameters. In optimizing these acquisition protocols and imaging systems it is important to have knowledge of the radiation dose to the breast. This study presents a methodology for estimating the normalized glandular dose to the uncompressed breast using the geometry proposed for flat-panel CT breast imaging. The simulation uses the GEANT 3 Monte Carlo code to model x-ray transport and absorption within the breast phantom. The Monte Carlo software was validated for breast dosimetry by comparing results of the normalized glandular dose (DgN) values of the compressed breast to those reported in the literature. The normalized glandular dose was then estimated for a range of breast diameters from 10 cm to 18 cm using an uncompressed breast model with a homogeneous composition of adipose and glandular tissue, and for monoenergetic x-rays from 10 keV to 120 keV. These data were fit providing expressions for the normalized glandular dose. Using these expressions for the DgN coefficients and input variables such as the diameter, height and composition of the breast phantom, the mean glandular dose for any spectra can be estimated. A computer program to provide normalized glandular dose values has been made available online. In addition, figures displaying energy deposition maps are presented to better understand the spatial distribution of dose in CT breast imaging.

Thacker, Samta C [Department of Radiology, University of Massachusetts, Medical School, Worcester, MA 01655 (United States); Glick, Stephen J [Department of Radiology, University of Massachusetts, Medical School, Worcester, MA 01655 (United States)

2004-12-21

54

Normalized glandular dose (DgN) coefficients for flat-panel CT breast imaging  

International Nuclear Information System (INIS)

The development of new digital mammography techniques such as dual-energy imaging, tomosynthesis and CT breast imaging will require investigation of optimal camera design parameters and optimal imaging acquisition parameters. In optimizing these acquisition protocols and imaging systems it is important to have knowledge of the radiation dose to the breast. This study presents a methodology for estimating the normalized glandular dose to the uncompressed breast using the geometry proposed for flat-panel CT breast imaging. The simulation uses the GEANT 3 Monte Carlo code to model x-ray transport and absorption within the breast phantom. The Monte Carlo software was validated for breast dosimetry by comparing results of the normalized glandular dose (DgN) values of the compressed breast to those reported in the literature. The normalized glandular dose was then estimated for a range of breast diameters from 10 cm to 18 cm using an uncompressed breast model with a homogeneous composition of adipose and glandular tissue, and for monoenergetic x-rays from 10 keV to 120 keV. These data were fit providing expressions for the normalized glandular dose. Using these expressions for the DgN coefficients and input variables such as the diameter, height and composition of the breast phantom, the mean glandular dose for any spectra can be estimated. A computer program to provide normalized glandular dose values has been made available online. In addition, figures displaying energy d. In addition, figures displaying energy deposition maps are presented to better understand the spatial distribution of dose in CT breast imaging

55

Computation of the glandular radiation dose in digital tomosynthesis of the breast.  

Science.gov (United States)

Tomosynthesis of the breast is currently a topic of intense interest as a logical next step in the evolution of digital mammography. This study reports on the computation of glandular radiation dose in digital tomosynthesis of the breast. Previously, glandular dose estimations in tomosynthesis have been performed using data from studies of radiation dose in conventional planar mammography. This study evaluates, using Monte Carlo methods, the normalized glandular dose (DgN) to the breast during a tomosynthesis study, and characterizes its dependence on breast size, tissue composition, and x-ray spectrum. The conditions during digital tomosynthesis imaging of the breast were simulated using a computer program based on the Geant4 toolkit. With the use of simulated breasts of varying size, thickness and tissue composition, the DgN to the breast tissue was computed for varying x-ray spectra and tomosynthesis projection angle. Tomosynthesis projections centered about both the cranio-caudal (CC) and medio-lateral oblique (MLO) views were simulated. For each projection angle, the ratio of the glandular dose for that projection to the glandular dose for the zero degree projection was computed. This ratio was denoted the relative glandular dose (RGD) coefficient, and its variation under different imaging parameters was analyzed. Within mammographic energies, the RGD was found to have a weak dependence on glandular fraction and x-ray spectrum for both views. A substantial dependence on breast size and thickness was found for the MLO view, and to a lesser extent for the CC view. Although RGD values deviate substantially from unity as a function of projection angle, the RGD averaged over all projections in a complete tomosynthesis study varies from 0.91 to 1.01. The RGD results were fit to mathematical functions and the resulting equations are provided. PMID:17278508

Sechopoulos, Ioannis; Suryanarayanan, Sankararaman; Vedantham, Srinivasan; D'Orsi, Carl; Karellas, Andrew

2007-01-01

56

Computation of the glandular radiation dose in digital tomosynthesis of the breast  

International Nuclear Information System (INIS)

Tomosynthesis of the breast is currently a topic of intense interest as a logical next step in the evolution of digital mammography. This study reports on the computation of glandular radiation dose in digital tomosynthesis of the breast. Previously, glandular dose estimations in tomosynthesis have been performed using data from studies of radiation dose in conventional planar mammography. This study evaluates, using Monte Carlo methods, the normalized glandular dose (DgN) to the breast during a tomosynthesis study, and characterizes its dependence on breast size, tissue composition, and x-ray spectrum. The conditions during digital tomosynthesis imaging of the breast were simulated using a computer program based on the Geant4 toolkit. With the use of simulated breasts of varying size, thickness and tissue composition, the DgN to the breast tissue was computed for varying x-ray spectra and tomosynthesis projection angle. Tomosynthesis projections centered about both the cranio-caudal (CC) and medio-lateral oblique (MLO) views were simulated. For each projection angle, the ratio of the glandular dose for that projection to the glandular dose for the zero degree projection was computed. This ratio was denoted the relative glandular dose (RGD) coefficient, and its variation under different imaging parameters was analyzed. Within mammographic energies, the RGD was found to have a weak dependence on glandular fraction and x-ray spectrum for both viewsfraction and x-ray spectrum for both views. A substantial dependence on breast size and thickness was found for the MLO view, and to a lesser extent for the CC view. Although RGD values deviate substantially from unity as a function of projection angle, the RGD averaged over all projections in a complete tomosynthesis study varies from 0.91 to 1.01. The RGD results were fit to mathematical functions and the resulting equations are provided

57

The effect of breast composition on absorbed dose and image contrast  

International Nuclear Information System (INIS)

We have studied the effect of breast composition on the average whole breast dose, average glandular dose, and image contrast in mammography, using both computational and experimental methods. Three glandular/adipose compositions were considered: 30/70, 50/50, and 70/30 by weight, for both 3- and 5-cm breast thickness. Absorbed dose was found to increase with greater glandular content and this increase is more pronounced for thick breasts and softer beams. For typical screen-film x-ray beams, the average dose to a highly glandular breast is nearly twice the dose to a highly adipose breast and the average glandular dose about 40% higher. Dose was reduced when higher energy beams were employed. The use of a grid increased the dose by a factor of 2.0 to 2.6. Finally, the measured image contrast decreases with increasing breast glandularity, to a greater extent in small breasts and when low energy beams were employed

58

An investigation into variations in the estimation of mean glandular dose in mammography  

International Nuclear Information System (INIS)

The regular assessment of breast dose is an important part of a quality control programme in mammography. It is common practice in the United Kingdom to deduce the mean glandular dose from an estimate of air kerma at the entrance surface of a standard breast phantom manufactured from Perspex (ICI, Darwin) of nominal thickness 40 mm. Factors are used to deduce the mean glandular dose from the entrance air kerma. The objectives of this study were to assess the impact of variations in technique on the assessment of mean glandular dose and the implications for comparative surveys. It was deduced that it is possible to achieve consistent dosimetry measurements, provided standard Perspex blocks are used and tube output is measured at a specific position. (Author)

59

The accuracy of retrospective dose estimation based on the mean glandular dose compressed breast thickness relationship  

International Nuclear Information System (INIS)

Assessment of breast radiation dose for mammographic examinations is important, and alternative dose measurement methods considering the expertise of the user have been proposed. Standard phantom measurements are easy to implement and useful for comparing doses between different mammographic systems, but they do not provide complete information about doses received by the patients. Determination of mean glandular dose (MGD) for patient breast is a well accepted dosimetric technique for mammography. However, for situations where dose measurements cannot be provided continuously in house, a previously created database relating the compressed breast thickness to MGD can be used for the estimation of breast doses retrospectively. The breast dose - thicknesses relationship is also useful for the presentation of screening results. Dose variations at each thickness should be minimum for the reliability of the results but high scattering of the data from the best fit are usually seen. Use of different beam qualities, variations on patient breast compositions at specific breast thickness, fluctuations of tube outputs, compression force uncertainties, and film processing conditions, problems in the performance of automatic exposure control (AEC) performance and in film/screen combinations could be the reasons for these uncertainties. The main objective of this paper is to investigate the effect of breast composition and beam quality to the MGD versus thickness relationship both for patient examinations and phantom experiments. All measurements were obtained with a GE Senographe DMR mammography unit. The frequently used anode - filter combinations for this system are Mo-Mo, Mo-Rh, Rh- Rh. Although manual selection of kVp and target-filter is possible, the Automatic Optimization Parameter (AOP) mode of the system, together with the automatic exposure control (AEC), provides automatic selection of target material, filter, tube potential (kV) and mAs. This feature of the system enables the operator to make a selection of one of the modes of contrast, standard or dose modes. Gradual reduction of the breast dose is carried out from contrast to dose mode. In order to establish a database for our mammography department the post exposure mAs, compressed breast thicknesses, tube potential, target-filter combination and AEC settings were recorded for each exposure of patient studies. A total of 105 patients have been included in this investigation. Two different exposure techniques were used for the CC view of each breast; one breast was examined with the standard mode of automatic selection of the system which was also the routine technique of the Department. A manual technique, considering the approximate glandularity content of the breast and its compressed thickness was used for the examination of the second breast. In order to have an initial idea regarding to the glandularity content of the breast before the exposure, we tried to make a best guess of breast glandularity through the evaluation of X ray film of the other breast that was already examined by the automatic technique or from the previous films of the patient. Based upon this decision criteria, patient breasts were divided into three groups according to their glandularity content. Breasts with the glandularities of more than 75% and lower than 25% were categorized as dense and fatty breasts, respectively. All the breasts with glandularities between 25%-75% were collected in the third group. Beam qualities to be used for the manual exposure technique were selected according to these ratios and compressed breast thickness; Mo-Mo combination with 27 and 28 kVs were used for breast thicknesses between 3-5 cm. In case of 5-7 cm thickness range, 28 kV with Mo-Mo and 26-28 kVs with Mo-Rh combinations were selected. The MGD was calculated according to a formula given by Dance. MGD versus compressed breast thickness relationship for the 105 patients examined with manual technique and different target/filter combinations for each glandularity group are presented in Table 1. Less d ata

60

An improved method for determining the mean glandular dose in mammography  

International Nuclear Information System (INIS)

In mammography, it is currently assumed that the mean dose to glandular tissue DG is relevant to characterize the risk of carcinogenesis. The mean glandular dose DG results from the measured air kerma Ka at the location of the entrance surface of the breast multiplied by the conversion factors g, which usually are calculated with the help of Monte-Carlo-Simulations and which are mostly given for a standard composition of tissue (50% glandular/50% adipose tissue). By means of the signals of the double-detector of the automatic-exposure-control of the mammographic device, it is possible to obtain information about the mean composition of the breast-tissue. The knowledge of this composition enables a better calculation of the mean glandular dose DG by using conversion factors that are adapted to the tissue. This method was applied to a total of 1020 women. The comparison with the evaluation by using the conventional method shows, on average, deviations in the mean glandular dose of 9%, in specific cases the differences can be as much as 35%. (orig.)

 
 
 
 
61

Evaluation of glandular dose in conventional and digital mammography systems; Avaliacao da dose glandular em sistemas de mamografia convencional e digital utilizando um fantoma dosimetrico  

Energy Technology Data Exchange (ETDEWEB)

A survey was conducted to estimate the average glandular dose (D{sub g}) for patients undergoing mammography and to report the distribution of incident air kerma (K{sub i}), patient age, compressed breast thickness and glandular tissue content. From 1183 cranio caudal mammograms clinical data were collected and doses were measured. The survey data included mammograms from six mammography equipment: two screen/film units (SFM), two computed radiography units (CR) and two full-field digital (DR). Mean value for patient age and compressed breast thickness were 57 +-12 y and 5.4 +-1.4 cm, respectively. To investigate the importance of technical characteristics of three different mammography systems and breast glandularity, K{sub i} and D{sub g} were measured for individual breast of 392 patients from the original sample with compressed breast thickness in the range of 5.5 cm to 6.5 cm using tissue-equivalent phantoms of different glandularities manufactured in this study to mimic both the attenuation and the density of breast tissues. Mean K{sub i} value was 10.0 +-3.6 mGy for SFM systems, 12.0 +-3.6 mGy for CR systems and 4.9 +-1.3 mGy for DR systems. Mean D{sub g} value was 1.4 +-0.5 mGy for S/F systems, 1.7 +-0.5 mGy for CR systems and 0.9 +-0.2 mGy for D R systems. Statistical analysis for differences in mean values of K{sub i} and D{sub g} between mammography systems showed significant effect of their technical characteristics (p < 0.05). In regard to the influence of glandular tissue content in K{sub i} and D{sub g}, it was observed statistically significant differences between the group of patients with 0 to 50% glandularity and the group of patients with 50 to 100% glandularity. (author)

Coutinho, Celia Maria Campos

2009-07-01

62

Evaluation of subject contrast and normalized average glandular dose by semi-analytical models  

International Nuclear Information System (INIS)

In this work, two semi-analytical models are described to evaluate the subject contrast of nodules and the normalized average glandular dose in mammography. Both models were used to study the influence of some parameters, such as breast characteristics (thickness and composition) and incident spectra (kVp and target-filter combination) on the subject contrast of a nodule and on the normalized average glandular dose. From the subject contrast results, detection limits of nodules were also determined. Our results are in good agreement with those reported by other authors, who had used Monte Carlo simulation, showing the robustness of our semi-analytical method.

63

Evaluation of subject contrast and normalized average glandular dose by semi-analytical models  

Energy Technology Data Exchange (ETDEWEB)

In this work, two semi-analytical models are described to evaluate the subject contrast of nodules and the normalized average glandular dose in mammography. Both models were used to study the influence of some parameters, such as breast characteristics (thickness and composition) and incident spectra (kVp and target-filter combination) on the subject contrast of a nodule and on the normalized average glandular dose. From the subject contrast results, detection limits of nodules were also determined. Our results are in good agreement with those reported by other authors, who had used Monte Carlo simulation, showing the robustness of our semi-analytical method.

Tomal, A. [Departamento de Fisica e Matematica, Faculdade de Filosofia, Ciencias e Letras de Ribeirao Preto, Universidade de Sao Paulo, Ribeirao Preto, SP (Brazil); Poletti, M.E. [Departamento de Fisica e Matematica, Faculdade de Filosofia, Ciencias e Letras de Ribeirao Preto, Universidade de Sao Paulo, Ribeirao Preto, SP (Brazil)], E-mail: poletti@ffclrp.usp.br; Caldas, L.V.E. [Instituto de Pesquisas Energeticas e Nucleares, Comissao Nacional de Energia Nuclear, Sao Paulo, SP (Brazil)

2010-04-15

64

Evaluation of subject contrast and normalized average glandular dose by semi-analytical models.  

Science.gov (United States)

In this work, two semi-analytical models are described to evaluate the subject contrast of nodules and the normalized average glandular dose in mammography. Both models were used to study the influence of some parameters, such as breast characteristics (thickness and composition) and incident spectra (kVp and target-filter combination) on the subject contrast of a nodule and on the normalized average glandular dose. From the subject contrast results, detection limits of nodules were also determined. Our results are in good agreement with those reported by other authors, who had used Monte Carlo simulation, showing the robustness of our semi-analytical method. PMID:19836251

Tomal, A; Poletti, M E; Caldas, L V E

2010-01-01

65

Estudo comparativo de dosimetria computacional entre modelos homogêneos e um modelo voxel em mamografia: uma discussão de aplicações em testes de constância e cálculo de dose glandular em pacientes Comparative study of computational dosimetry involving homogeneous phantoms and a voxel phantom in mammography: a discussion on applications in constancy tests and calculation of glandular dose in patients  

Directory of Open Access Journals (Sweden)

Full Text Available OBJETIVO: Comparar dados de dosimetria e fluência de fótons entre diferentes modelos de mama, discutindo as aplicações em testes de constância e estudos dosimétricos aplicados à mamografia. MATERIAIS E MÉTODOS: Foram simulados diferentes modelos homogêneos e um modelo antropomórfico de mama tipo voxel, sendo contabilizadas: a dose total absorvida no modelo, a dose absorvida pelo tecido glandular/material equivalente, e a dose absorvida e a fluência de fótons em diferentes profundidades dos modelos. Uma câmara de ionização simulada coletou o kerma de entrada na pele. As combinações alvo-filtro estudadas foram Mo-30Mo e Mo-25Rh, para diferentes potenciais aceleradores de 26 kVp até 34 kVp. RESULTADOS: A dose glandular normalizada, comparada ao modelo voxel, resultou em diferenças entre -15% até -21% para RMI, -10% para PhantomMama e 10% para os modelos Barts e Keithley. A variação dos valores da camada semirredutora entre modelos foi geralmente inferior a 10% para todos os volumes sensíveis. CONCLUSÃO: Para avaliar a dose glandular normalizada e a dose glandular, em mamas médias, recomenda-se o modelo de Dance. Os modelos homogêneos devem ser utilizados para realizar testes de constância em dosimetria, mas eles não são indicados para estimar a dosimetria em pacientes reaisOBJECTIVE: To compare data regarding dosimetry and photons fluence in different breast phantoms, discussing constancy tests and dosimetry applied to mammography. MATERIALS AND METHODS: Different homogeneous breast phantoms and one anthropomorphic voxel phantom were developed for collection of data regarding total absorbed dose in the phantom, absorbed dose in the glandular tissue material-equivalent, absorbed dose and photons fluence at different depths in the phantoms. A simulated ionization chamber collected the entrance skin kerma. Target-filter combinations (Mo-30Mo and Mo-25Rh were studied for different accelerating potentials of 26 kVp to 34 kVp. RESULTS: As compared with the voxel phantom, the normalized glandular dose resulted in differences from -15% to -21% for RMI, -10% for PhantomMama, and 10% for the Barts and Keithley models. The half-value layer variation was generally < 10% for all the sensitive volumes. CONCLUSION: The phantom proposed by Dance is recommended for evaluating the glandular dose and normalized glandular dose in a standard breast. Homogeneous phantoms should be utilized for constancy tests in dosimetry, but they are not appropriate for estimating dosimetry in actual patients

Vagner Ferreira Cassola

2010-12-01

66

Glandular radiation dose in tomosynthesis of the breast using tungsten targets.  

Science.gov (United States)

With the advent of new detector technology, digital tomosynthesis imaging of the breast has, in the past few years, become a technique intensely investigated as a replacement for planar mammography. As with all other x-ray-based imaging methods, radiation dose is of utmost concern in the development of this new imaging technology. For virtually all development and optimization studies, knowledge of the radiation dose involved in an imaging protocol is necessary. A previous study characterized the normalized glandular dose in tomosynthesis imaging and its variation with various breast and imaging system parameters. This characterization was performed with x-ray spectra generated by molybdenum and rhodium targets. In the recent past, many preliminary patient studies of tomosynthesis imaging have been reported in which the x-ray spectra were generated with x-ray tubes with tungsten targets. The differences in x-ray distribution among spectra from these target materials make the computation of new normalized glandular dose values for tungsten target spectra necessary. In this study we used previously obtained monochromatic normalized glandular dose results to obtain spectral results for twelve different tungsten target x-ray spectra. For each imaging condition, two separate values were computed: the normalized glandular dose for the zero degree projection angle (DgN0), and the ratio of the glandular dose for non-zero projection angles to the glandular dose for the zero degree projection (the relative glandular dose, RGD(alpha)). It was found that DgN0 is higher for tungsten target x-ray spectra when compared with DgN0 values for molybdenum and rhodium target spectra of both equivalent tube voltage and first half value layer. Therefore, the DgN0 for the twelve tungsten target x-ray spectra and different breast compositions and compressed breast thicknesses simulated are reported. The RGD(alpha) values for the tungsten spectra vary with the parameters studied in a similar manner to that found for the molybdenum and rhodium target spectra. The surface fit equations and the fit coefficients for RGD(alpha) included in the previous study were also found to be appropriate for the tungsten spectra. PMID:19020492

Sechopoulos, Ioannis; D'Orsi, Carl J

2008-01-01

67

Monte Carlo simulation of glandular dose in a dedicated breast CT system  

International Nuclear Information System (INIS)

A dedicated breast CT system (DBCT) is a new method for breast cancer detection proposed in recent years. In this paper, the glandular dose in the DBCT is simulated using the Monte Carlo method. The phantom shape is half ellipsoid, and a series of phantoms with different sizes, shapes and compositions were constructed. In order to optimize the spectra, monoenergy X-ray beams of 5-80 keV were used in simulation. The dose distribution of a breast phantom was studied: a higher energy beam generated more uniform distribution, and the outer parts got more dose than the inner parts. For polyenergetic spectra, four spectra of Al filters with different thicknesses were simulated, and the polyenergetic glandular dose was calculated as a spectral weighted combination of the monoenergetic dose. (authors)

68

Method for the evaluation of a average glandular dose in mammography  

International Nuclear Information System (INIS)

This paper concerns a method for accurate evaluation of average glandular dose (AGD) in mammography. At different energies, the interactions of photons with tissue are not uniform. Thus, optimal accuracy in the estimation of AGD is achievable when the evaluation is carried out using the normalized glandular dose values, g(x,E), that are determined for each (monoenergetic) x-ray photon energy, E, compressed breast thickness (CBT), x, breast glandular composition, and data on photon energy distribution of the exact x-ray beam used in breast imaging. A generalized model for the values of g(x,E) that is for any arbitrary CBT ranging from 2 to 9 cm (with values that are not whole numbers inclusive, say, 4.2 cm) was developed. Along with other dosimetry formulations, this was integrated into a computer software program, GDOSE.FOR, that was developed for the evaluation of AGD received from any x-ray tube/equipment (irrespective of target-filter combination) of up to 50 kVp. Results are presented which show that the implementation of GDOSE.FOR yields values of normalized glandular dose that are in good agreement with values obtained from methodologies reported earlier in the literature. With the availability of a portable device for real-time acquisition of spectra, the model and computer software reported in this work provide for the routine evaluation of AGD received by a specific woman of known age and CBT

69

Method for the evaluation of a average glandular dose in mammography.  

Science.gov (United States)

This paper concerns a method for accurate evaluation of average glandular dose (AGD) in mammography. At different energies, the interactions of photons with tissue are not uniform. Thus, optimal accuracy in the estimation of AGD is achievable when the evaluation is carried out using the normalized glandular dose values, g(x,E), that are determined for each (monoenergetic) x-ray photon energy, E, compressed breast thickness (CBT), x, breast glandular composition, and data on photon energy distribution of the exact x-ray beam used in breast imaging. A generalized model for the values of g(x,E) that is for any arbitrary CBT ranging from 2 to 9 cm (with values that are not whole numbers inclusive, say, 4.2 cm) was developed. Along with other dosimetry formulations, this was integrated into a computer software program, GDOSE. FOR, that was developed for the evaluation of AGD received from any x-ray tube/equipment (irrespective of target-filter combination) of up to 50 kVp. Results are presented which show that the implementation of GDOSE. FOR yields values of normalized glandular dose that are in good agreement with values obtained from methodologies reported earlier in the literature. With the availability of a portable device for real-time acquisition of spectra, the model and computer software reported in this work provide for the routine evaluation of AGD received by a specific woman of known age and CBT. PMID:16696493

Okunade, Akintunde Akangbe

2006-04-01

70

Evaluation of mean glandular dose and phantom image quality by JSRT mammographic quality control program  

Energy Technology Data Exchange (ETDEWEB)

We describe the results of dose measurements and image quality evaluation in mammography using a phantom for the ACR accreditation program. Screen-film images were obtained with the following systems: Min-R2000 screen and Min-R2000 film (Kodak), and UM Mammo Fine and UM-MA HC film (Fuji). CR images were obtained with the FCR7000 (Fuji). Compared with the Mo filter system, mean glandular dose with the Rh filter at 28 kV and 30 kV decreased 22% and 10%, respectively. However, at 32 kV and 34 kV, there was no significant difference between the dose with the Mo filter and that with the Rh filter. Area exposure product correlated well with entrance exposure dose and seemed to be useful for approximating glandular dose. Although the quality of images obtained with the Mo filter at 28 kV was acceptable, images obtained with the Min-R2000 system were superior to those obtained with the other two. According to the mammography quality assurance program established by JSRT, mean glandular dose could be calculated by measurement of the entrance exposure dose for a mammograghic phantom. (author)

Gotoh, Shinichi; Ohtsuka, Akiko; Oniki, Rika; Fukushima, Yoshiaki; Fukuda, Touru [Nagasaki Univ. (Japan). Hospital; Hattori, Akiko

1999-10-01

71

Evaluation of mean glandular dose and phantom image quality by JSRT mammographic quality control program  

International Nuclear Information System (INIS)

We describe the results of dose measurements and image quality evaluation in mammography using a phantom for the ACR accreditation program. Screen-film images were obtained with the following systems: Min-R2000 screen and Min-R2000 film (Kodak), and UM Mammo Fine and UM-MA HC film (Fuji). CR images were obtained with the FCR7000 (Fuji). Compared with the Mo filter system, mean glandular dose with the Rh filter at 28 kV and 30 kV decreased 22% and 10%, respectively. However, at 32 kV and 34 kV, there was no significant difference between the dose with the Mo filter and that with the Rh filter. Area exposure product correlated well with entrance exposure dose and seemed to be useful for approximating glandular dose. Although the quality of images obtained with the Mo filter at 28 kV was acceptable, images obtained with the Min-R2000 system were superior to those obtained with the other two. According to the mammography quality assurance program established by JSRT, mean glandular dose could be calculated by measurement of the entrance exposure dose for a mammograghic phantom. (author)

72

Average glandular dose and phantom image quality in mammography  

International Nuclear Information System (INIS)

ults showed that 54.5% of the facilities did not achieve the minimum performance level for image quality. It is mainly due to insufficient film processing observed in 61.2% of the units. AGD varied from 0.41 to 2.73 mGy with a mean value of 1.32±0.44 mGy. In all optimal quality phantom images, AGDs were in this range. Additionally, in 7.3% of the mammography units, the AGD constraint of 2 mGy was exceeded. One may conclude that dose level to patient and image quality are not in conformity to regulations in most of the facilities. This indicates that ongoing actions are needed to optimize image quality and radiation dose for early detection of the breast cancer

73

Determination of a method for calculating mean glandular dose in conventional mammography exams  

International Nuclear Information System (INIS)

We present the application of a numerical model to estimate the mean glandular dose for mammography.A General Electric mammography system, tube voltage of 20-35 kV with increments of 1 kV, tube current of 10-250 mAs, anode/filter combinations molybdenum/molybdenum was used. Over a period of two months, data from 162 scans with craniocaudal and mediolateral oblique projections in both breasts were recorded. The thickness of the compressed breast ranged from 2.5 to 6.5 cm. The mean glandular dose for each craniocaudal projection ranged from 0.4 to 0.7 mGy for a thickness of 2.5 cm and 1.9 to 2.8 mGy for a thickness of 6.5 cm. All average values of mean glandular dose estimated by cranio-caudal projection were found to be below the international reference dose value of 3 mGy recommended by the American College of Radiology

74

Average glandular dose with amorphous silicon full-field digital mammography - clinical results  

International Nuclear Information System (INIS)

Purpose: Determination of average glandular dose with a full-field digital mammography system using a flat-panel X-ray detector based on amorphous silicon technology for a large group of patients. Material and Methods: The patient group includes women who were examined in a 4-month period with the digital mammographic system Senographe 2000D. The number of women was 591 and the number of exposures was 1116; only cranio-caudal projections were considered. Various quantities, including entrance surface air kerma, tube loading, and compressed breast thickness, were determined during actual mammography. Average glandular dose was determined using conversion factors g for standard breast composition. Results: The mean average glandular dose was 1.51 mGy (0.66-4.05 mGy) for a single view. The mean compressed breast thickness was 55.7 mm. The mean age of patients was 55 years (34-81 years). Conclusion: The results demonstrate that full-field digital mammography with a flat-panel detector based on amorphous silicon needs about 25% less dose in comparison with conventional screen-film mammography. (orig.)

75

The effect of aluminium added filter on mean glandular dose using mammography machine in MINT Medical Physics Laboratory  

International Nuclear Information System (INIS)

The effect of various thickness of aluminium added filter on mean glandular dose in mammography is investigated for a standard breast phantom, 4.2 cm Perspex. A mammography machine in Medical Physics Laboratory MINT, Bennett Model DMF-150 is used to provide radiation in various kV range under clinical condition. The mean glandular dose on the phantom were measured based on technique recommended by AAPM protocol (1990) report no 29. The mean glandular dose was found reducing with increasing thickness of added filter. A more detail results of this study is presented in this paper. (Author)

76

Uncertainties involved in the estimation of mean glandular dose for women in the norwegian breast cancer screening program (NBCSP)  

International Nuclear Information System (INIS)

The aim of this study was to reflect on the estimation of the mean glandular dose for women in Norway aged 50-69 y. Estimation of mean glandular dose (MGD) has been conducted by applying the method of Dance et al. (1990, 2000, 2009). Uncertainties in the thickness of approximately ±10 mm adds uncertainties in the MGD of approximately ±10 %, and uncertainty in the glandularity of ±0 % will lead to an uncertainty in the MGD of ±4 %. However, the inherent uncertainty in the air kerma, given by the European protocol on dosimetry, will add an uncertainty of 12 %. The total uncertainty in the MGD is estimated to be ?20 %, taking into consideration uncertainties in compressed breast thickness (±10 %), the air kerma (12 %), change in HVL by 20.05 mm (29.0 %), uncertainty in the s-factor of ±2.1 % and changing the glandularity to an age-dependent glandularity distribution (18.4 %). (authors)

77

Absorbed radiation dose on LHC interconnects  

CERN Document Server

Here we present the results of our FLUKA simulations devoted to the evaluation of the peak dose absorbed by the busbar insulator in the LHC Interaction Region 7 interconnects. The peak dose absorbed by the cold magnet coils are also presented.

Versaci, R; Vlachoudis, V; CERN. Geneva. ATS Department

2011-01-01

78

Estudo comparativo de dosimetria computacional entre modelos homogêneos e um modelo voxel em mamografia: uma discussão de aplicações em testes de constância e cálculo de dose glandular em pacientes / Comparative study of computational dosimetry involving homogeneous phantoms and a voxel phantom in mammography: a discussion on applications in constancy tests and calculation of glandular dose in patients  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese OBJETIVO: Comparar dados de dosimetria e fluência de fótons entre diferentes modelos de mama, discutindo as aplicações em testes de constância e estudos dosimétricos aplicados à mamografia. MATERIAIS E MÉTODOS: Foram simulados diferentes modelos homogêneos e um modelo antropomórfico de mama tipo vox [...] el, sendo contabilizadas: a dose total absorvida no modelo, a dose absorvida pelo tecido glandular/material equivalente, e a dose absorvida e a fluência de fótons em diferentes profundidades dos modelos. Uma câmara de ionização simulada coletou o kerma de entrada na pele. As combinações alvo-filtro estudadas foram Mo-30Mo e Mo-25Rh, para diferentes potenciais aceleradores de 26 kVp até 34 kVp. RESULTADOS: A dose glandular normalizada, comparada ao modelo voxel, resultou em diferenças entre -15% até -21% para RMI, -10% para PhantomMama e 10% para os modelos Barts e Keithley. A variação dos valores da camada semirredutora entre modelos foi geralmente inferior a 10% para todos os volumes sensíveis. CONCLUSÃO: Para avaliar a dose glandular normalizada e a dose glandular, em mamas médias, recomenda-se o modelo de Dance. Os modelos homogêneos devem ser utilizados para realizar testes de constância em dosimetria, mas eles não são indicados para estimar a dosimetria em pacientes reais Abstract in english OBJECTIVE: To compare data regarding dosimetry and photons fluence in different breast phantoms, discussing constancy tests and dosimetry applied to mammography. MATERIALS AND METHODS: Different homogeneous breast phantoms and one anthropomorphic voxel phantom were developed for collection of data r [...] egarding total absorbed dose in the phantom, absorbed dose in the glandular tissue material-equivalent, absorbed dose and photons fluence at different depths in the phantoms. A simulated ionization chamber collected the entrance skin kerma. Target-filter combinations (Mo-30Mo and Mo-25Rh) were studied for different accelerating potentials of 26 kVp to 34 kVp. RESULTS: As compared with the voxel phantom, the normalized glandular dose resulted in differences from -15% to -21% for RMI, -10% for PhantomMama, and 10% for the Barts and Keithley models. The half-value layer variation was generally

Vagner Ferreira, Cassola; Gabriela, Hoff.

2010-12-01

79

The Study of Mean Glandular Dose in Mammography in Yazd and the Factors Affecting It  

Directory of Open Access Journals (Sweden)

Full Text Available Backgrounds/Objective: The objective of this study was to determine the mean glandular dose (MGD resulting from mammography examinations in Yazd, southeastern Iran and to identify the factors affecting it. Patients and Methods: This survey was conducted during May to December 2005 to estimate the MGD for women undergoing mammography and to report the distribution of dose, com-pressed breast thickness, glandular tissue content, and mammography technique used. The clinical data were collected from 946 mammograms taken from 246 women who were referred to four mammography centers. The mammography instruments in these centers were four modern units with a molybdenum anode and either molybdenum or rhodium filter. The exposure conditions of each mammogram were recorded. The breast glandular content of each mammogram was estimated by a radiologist. The MGD was calculated based on measuring the normalized entrance skin dose (ESD in air, Half Value Layer (HVL, kVp, mAs, breast thickness and glandular content. HVL, kVp and ESD were measured by a solid-state detector. The analytical method of Sobol et al. was used for calculation of MGD. Results: The mean±SD MGD per film was 1.2±0.6 mGy for craniocaudal and 1.63±0.9 mGy for mediolateral oblique views. The mean±SD MGD per woman was 5.57±3.1 mGy. A positive correlation was found between the beam HVL with MGD (r=0.38 and the breast thickness with MGD (r=0.5. Conclusion: The mean±SD MGD per film of 1.42±0.8 mGy in present study was lower than most of similar reports. However, the mean MGD per woman was higher than that in other studies.

F. Bouzarjomehri

2006-08-01

80

Nationwide survey of glandular tissue dose for establishment of breast cancer screening using mammography  

Energy Technology Data Exchange (ETDEWEB)

A nationwide survey was performed in an attempt to investigate the distribution of average glandular doses caused by mammography for breast cancer mass screening, and to utilize the data to determine the national guidance level for mammography. A phantom equivalent to a breast with a compressed thickness of 42 mm, and glass radio-photo luminescence dosimeters were sent to 104 institutions and facilities. The dosimeters were exposed using a method based on the protocols described in the Mammography Quality Control Manual. The returned dosimeters were then analyzed, and the beam qualities and the entrance surface exposure were determined. Using these values, the average glandular doses were estimated with an accuracy of {+-}8%. The doses ranged from 0.5 to 3.7 mGy. The mean dose and the standard deviation were 1.48 mGy and 0.52 mGy, respectively. In 91 facilities, the doses were less than 2 mGy. Regarding the technical factors for facilities which presented doses of 2 mGy or over, it seemed that the doses could be easily reduced to less than 2 mGy if the settings of the auto exposure controller (AEC), anti-scatter grid and/or the film-screen system were optimized. (author)

Katoh, Tsuguhisa; Matsumoto, Mitsuomi [Tokyo Metropolitan Univ. of Health Sciences (Japan); Higashida, Yoshiharu [and others

1999-06-01

 
 
 
 
81

Measurement of absorbed doses in computed tomography  

International Nuclear Information System (INIS)

Absorbed doses associated with CT scanning of the mandible- and maxillo-facial areas were examined using phantom studies. Conventional tomography and sialography were performed for comparison. Absorbed doses were smaller in CT scanning than conventional tomography of the maxillary sinus. In CT scanning of the submandibular gland and parotid gland, absorbed doses were far larger than in sialography. In scanning the maxillary sinus, the use of CT seems reasonable because of its ability to identify specific tissues using a mean CT number. For the submandibular gland and parotid gland, the use of CT should be carefully considered when combined with sialography. (Namekawa, K)

82

DETERMINACIÓN DE UN MÉTODO DE CALCULO DE DOSIS GLANDULAR PROMEDIO EN EXAMENES DE MAMOGRAFIA CONVENCIONAL / DETERMINATION OF A METHOD FOR CALCULATING MEAN GLANDULAR DOSE IN CONVENTIONAL MAMMOGRAPHY EXAMS  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: Spanish Abstract in spanish Presentamos la aplicación de un modelo numérico para estimarla dosis glandular promedio en mamografía. Hemos utilizado un mamógrafo General Electric, tensión del tubo: 20-35 kV con incrementos de 1 kV; carga del tubo: 10-250 mAs; combinación ánodo-filtro de Molibdeno-Molibdeno. Durante dos meses dat [...] os de 162 exploraciones con proyecciones cráneo-caudal y medio lateral oblicua en ambas mamas. El espesor de mama comprimida se encuentra en el rango de 2,5 a 6,5 cm. Los rangos de dosis glandular promedio, por cada proyección cráneo-caudal, se encuentran de 0,4 a 0,7 mGy para un espesor de 2,5 cm y de 1,9 a 2,8 mGy para un espesor de 6,5 cm. Los valores medios de dosis glandular promedio estimados por proyección cráneo-caudal, en su totalidad resultan por debajo del valor de referencia dado por el Colegio Americano de Radiología (3 mGy). Abstract in english We present the application of a numerical model to estimate the mean glandular dose for mammography. A General Electric mammography system, tube voltaje of 20-35 kV with increments of 1 kV, tube current of 10-250 mAs, anode/filter combinations molybdenum/molybdenum was used. Over a period of two mon [...] ths, data from 162scans with craniocaudal and mediolateral oblique projections in both breasts were recorded. The thickness of the compressed breast ranged from 2.5 to 6.5 cm. The mean glandular dose for each craniocaudal projection ranged from 0.4 to 0.7mGy for a thickness of2.5 cm and 1.9 to 2.8 mGy for a thickness of 6.5 cm. All average values of mean glandular dose estimated by cranio-caudal projection were found to be below the international reference dose value of3 mGy recommended by the American College of Radiology.

Oswaldo, Ramos N; Manuel, Villarreal U.

83

DETERMINACIÓN DE UN MÉTODO DE CALCULO DE DOSIS GLANDULAR PROMEDIO EN EXAMENES DE MAMOGRAFIA CONVENCIONAL DETERMINATION OF A METHOD FOR CALCULATING MEAN GLANDULAR DOSE IN CONVENTIONAL MAMMOGRAPHY EXAMS  

Directory of Open Access Journals (Sweden)

Full Text Available Presentamos la aplicación de un modelo numérico para estimarla dosis glandular promedio en mamografía. Hemos utilizado un mamógrafo General Electric, tensión del tubo: 20-35 kV con incrementos de 1 kV; carga del tubo: 10-250 mAs; combinación ánodo-filtro de Molibdeno-Molibdeno. Durante dos meses datos de 162 exploraciones con proyecciones cráneo-caudal y medio lateral oblicua en ambas mamas. El espesor de mama comprimida se encuentra en el rango de 2,5 a 6,5 cm. Los rangos de dosis glandular promedio, por cada proyección cráneo-caudal, se encuentran de 0,4 a 0,7 mGy para un espesor de 2,5 cm y de 1,9 a 2,8 mGy para un espesor de 6,5 cm. Los valores medios de dosis glandular promedio estimados por proyección cráneo-caudal, en su totalidad resultan por debajo del valor de referencia dado por el Colegio Americano de Radiología (3 mGy.We present the application of a numerical model to estimate the mean glandular dose for mammography. A General Electric mammography system, tube voltaje of 20-35 kV with increments of 1 kV, tube current of 10-250 mAs, anode/filter combinations molybdenum/molybdenum was used. Over a period of two months, data from 162scans with craniocaudal and mediolateral oblique projections in both breasts were recorded. The thickness of the compressed breast ranged from 2.5 to 6.5 cm. The mean glandular dose for each craniocaudal projection ranged from 0.4 to 0.7mGy for a thickness of2.5 cm and 1.9 to 2.8 mGy for a thickness of 6.5 cm. All average values of mean glandular dose estimated by cranio-caudal projection were found to be below the international reference dose value of3 mGy recommended by the American College of Radiology.

Oswaldo Ramos N

2009-01-01

84

Measurement of breast entrance exposure and mean glandular dose during screen-film mammography examination at our centre  

International Nuclear Information System (INIS)

Radiation based imaging modalities have been of great benefit to mankind due to their ability to help in diagnosis. Mammography is recognized as the most optimized imaging modality for early detection of breast cancer. However there has been a growing concern among the general public, as well as the scientific and medical communities regarding the ill effect of radiation exposure from diagnostic X-ray examination. Therefore increased attention has recently been directed towards radiation dose to the patient. Several years ago the radiation dose received during mammography was measured as the entrance dose to the skin of the breast. Now, it is presumed that it is the breast glandular tissue that is at risk for developing cancer in future therefore measurement of mean glandular dose (MGD) is the quantity recommended by ICRP and European Protocol for performance assessment of the system. With optimization technique and continued quality assurance programme the breast dose can be kept at lower levels without sacrificing diagnostic value. Our objective intends to evaluate the Breast Entrance Exposure (BEE) and Mean Glandular Dose (MGD) received by the patients during mammography examination. According to the Mammography Quality Standard Act (MQSA, 2002), USA, the average glandular dose to an average (4.2 cm compressed) breast must not exceed 3 mGy per view for film-screen image receptors. The European protocol specifies the average glandular dose for a 4.5 cm thick breast typically less than 2.0 mGy

85

Reconstruction of absorbed doses to fibroglandular tissue of the breast of women undergoing mammography (1960 to the present).  

Science.gov (United States)

The assessment of potential benefits versus harms from mammographic examinations as described in the controversial breast cancer screening recommendations of the U.S. Preventive Task Force included limited consideration of absorbed dose to the fibroglandular tissue of the breast (glandular tissue dose), the tissue at risk for breast cancer. Epidemiological studies on cancer risks associated with diagnostic radiological examinations often lack accurate information on glandular tissue dose, and there is a clear need for better estimates of these doses. Our objective was to develop a quantitative summary of glandular tissue doses from mammography by considering sources of variation over time in key parameters, including imaging protocols, X-ray target materials, voltage, filtration, incident air kerma, compressed breast thickness, and breast composition. We estimated the minimum, maximum and mean values for glandular tissue dose for populations of exposed women within 5-year periods from 1960 to the present, with the minimum to maximum range likely including 90% to 95% of the entirety of the dose range from mammography in North America and Europe. Glandular tissue dose from a single view in mammography is presently about 2 mGy, about one-sixth the dose in the 1960s. The ratio of our estimates of maximum to minimum glandular tissue doses for average-size breasts was about 100 in the 1960s compared to a ratio of about 5 in recent years. Findings from our analysis provide quantitative information on glandular tissue doses from mammographic examinations that can be used in epidemiological studies of breast cancer. PMID:21988547

Thierry-Chef, Isabelle; Simon, Steven L; Weinstock, Robert M; Kwon, Deukwoo; Linet, Martha S

2012-01-01

86

Monte Carlo generated conversion factors for the estimation of average glandular dose in contact and magnification mammography  

Energy Technology Data Exchange (ETDEWEB)

Magnification mammography is a special technique used in the cases where breast complaints are noted by a woman or when an abnormality is found in a screening mammogram. The carcinogenic risk in mammography is related to the dose deposited in the glandular tissue of the breast rather than the adipose, and average glandular dose (AGD) is the quantity taken into consideration during a mammographic examination. Direct measurement of the AGD is not feasible during clinical practice and thus, the incident air KERMA on the breast surface is used to estimate the glandular dose, with the help of proper conversion factors. Additional conversion factors adapted for magnification and tube voltage are calculated, using Monte Carlo simulation. The effect of magnification degree, tube voltage, various anode/filter material combinations and glandularity on AGD is also studied, considering partial breast irradiation. Results demonstrate that the estimation of AGD utilizing conversion factors depends on these parameters, while the omission of correction factors for magnification and tube voltage can lead to significant underestimation or overestimation of AGD. AGD was found to increase with filter material's k-absorption edge, anode material's k-emission edge, tube voltage and magnification. Decrease of the glandularity of the breast leads to higher AGD due to the increased penetrating ability of the photon beam in thick breasts with low glandularity.

Koutalonis, M [Department of Medical Physics, School of Medicine, University of Patras, 265 00 Patras (Greece); Delis, H [Department of Medical Physics, School of Medicine, University of Patras, 265 00 Patras (Greece); Spyrou, G [Department of Medical Physics, School of Medicine, University of Patras, 265 00 Patras (Greece); Costaridou, L [Department of Medical Physics, School of Medicine, University of Patras, 265 00 Patras (Greece); Tzanakos, G [Department of Physics, Div. Nucl. and Particle Physics, University of Athens, 157 71 Athens (Greece); Panayiotakis, G [Department of Medical Physics, School of Medicine, University of Patras, 265 00 Patras (Greece)

2006-11-07

87

[Investigation of quality control and average glandular dose and image quality in digital mammography in Hokkaido].  

Science.gov (United States)

A questionnaire survey about mammography in Hokkaido was mailed to 121 facilities from August to September 2009. We surveyed the conditions of digital mammography with regard to quality control (QC) and average glandular dose at 79 facilities in Hokkaido in 2009, and the results of the survey were compared with those of 2004. We found that digital mammography techniques were widely used across Hokkaido and that computed radiography (CR) systems were quite widespread, with 70% of facilities having them. The average glandular dose ranged from 1.04 to 2.3 mGy (mean: 1.73 mGy) for digital equipment. The results revealed several problems. Although the use of 1-, 2-, and 3-megapixel (MP) liquid crystal displays (LCDs) was not uncommon, 5-MP LCDs were used in most cases when reading digital mammograms. Facilities that have mammography equipment are unlikely to have quality control instruments for mammography. Although daily QC is performed in most facilities, further quality control for digital mammography should be developed, including that for monitors. In a second study, we evaluated the 1 Shot Phantom M Plus (1 Shot Phantom), which enables objective evaluation by providing for one physical measurement rather than a subjective visual analysis. The results indicated that the 1 Shot Phantom was very useful for digital mammography systems in daily QC testing because it enabled objectivity. PMID:21532248

Kurowarabi, Kunio; Abe, Hiroko; Horita, Hiroshi; Kaneta, Kazuyuki

2011-01-01

88

A study on the image quality of mammography and the average glandular dose  

Energy Technology Data Exchange (ETDEWEB)

We came to the following conclusion as the results of experiment on the image quality of mammography and the average glandular dose using 4 apparatuses at 3 hospital in Seoul. Whereas the measurement of half value layer showed no differences among the apparatuses, the measurement by an attenuation curve method showed some differences by 5.9%. There were 9.1% differences in the measurement by aluminum conversion method. The basic density of an automatic exposure control unit must be D = 1.40, but there was no automatic exposure unit adjusted precisely at any hospital. The unit at the B hospital exceeded the allowable limit by {+-} 0.15. In the photographing using an automatic exposure control unit and the management of an automatic film processor using a sensitometer, most automatic film processors were well kept. But in some cases the mean value of a fluctuation coefficient exceeded the allowable limit. There is a need for more cautious management. The image quality of breast phantom photography was affected by the screen/film system among the hospital. The average glandular dose at a breast of 4.2 cm thickness depended on the tube voltage, In the case of Mo/Mo, it was measured 0.26 {approx} 1.39 mGy less than ACR standard 3.0 mGy.

Lee, In Ja; Kim, Hak Sung [Dong Nam College, Suwon (Korea, Republic of); Kim, Sung Soo [Shin Gu College, Seongnam (Korea, Republic of); Huh, Joon [Institute of Radiological Technology Listem Co., Ltd., Seoul (Korea, Republic of)

2002-09-15

89

Mean glandular dose measurement on various breast phantom using mammography machine in MINT Medical Physics Laboratory  

International Nuclear Information System (INIS)

Until recently, mammography have been the primary means of detecting early breast cancer. Although there is a risk of radiation- induced carcinogenesis associated with the x-ray examination of the female breast, but this risk is small compared to its benefits with modern equipment and technique. Therefore, it is important to determine the dose of the tissue at risk from radiation exposure by measuring the mean glandular dose (MGD). This can help minimize the risk to the patient. This paper describe the MGD measurement done on various types and thickness of breast phantom using a Bennett mammography machine model DMF-150 in the Medical Physics laboratory at the Malaysian Institute for Nuclear Technology Research (MINT). Results of this study are discussed in this paper. (Author)

90

Mammography equipment performance, image quality and mean glandular dose in Malta  

International Nuclear Information System (INIS)

In this first Maltese national mammography survey, the effectiveness of direct digital (DR) mammography in breast cancer screening has been confirmed. Patient data were made available from three clinics out of the participating nine. A dose survey of mean glandular dose (MGD) calculated for 759 patients examined in the state-owned mammography facilities was performed. An MGD national diagnostic reference level was set at 1.87 mGy for patients with breast compression thicknesses (BCT) between 5.0 and 7.0 cm. This range was selected since patient data were retrieved from three clinics only and the results showed that other international BCT reference levels may be unsuitable for the Maltese population. In fact, the overall average BCT was 5.75±1.4 cm. The survey results have shown that the technical standard of mammographic equipment in the Malta National Breast Screening Programme is on a par with other countries, including its Western European counterparts. (authors)

91

Assessment of glandular dose and image quality in mammography using computerised radiography employing a polymethylmetacrilate breast simulator  

International Nuclear Information System (INIS)

In Brazil there are around 600 mammography equipment with CR system. Taking into account the quality of image is essential to evaluate the mean glandular dose so you can optimize the radiation protection of patients evaluated with this type of system. Therefore, this study aimed to determine the mean glandular dose and quality of image for the CR system of laboratory of radioprotection applied to mammography of the Centre of Development of Nuclear Technology (CDTN). For this, we evaluated the linearity of the detector’s response, contrast to noise ratio and signal to noise ratio, which, according to European protocol, showed results within acceptable limits. Next, evaluated the quality of image with the CDMAM Phantom and mean glandular dose to the detector Fluke Biomedical TNT 12000WD, where they presented, respectively, within the results expected by the manufacturer and the limits of acceptable and desirable by the European protocol. then, the CR system of CDTN is optimized.

92

Average glandular dose with amorphous silicon full-field digital mammography - clinical results  

Energy Technology Data Exchange (ETDEWEB)

Purpose: Determination of average glandular dose with a full-field digital mammography system using a flat-panel X-ray detector based on amorphous silicon technology for a large group of patients. Material and Methods: The patient group includes women who were examined in a 4-month period with the digital mammographic system Senographe 2000D. The number of women was 591 and the number of exposures was 1116; only cranio-caudal projections were considered. Various quantities, including entrance surface air kerma, tube loading, and compressed breast thickness, were determined during actual mammography. Average glandular dose was determined using conversion factors g for standard breast composition. Results: The mean average glandular dose was 1.51 mGy (0.66-4.05 mGy) for a single view. The mean compressed breast thickness was 55.7 mm. The mean age of patients was 55 years (34-81 years). Conclusion: The results demonstrate that full-field digital mammography with a flat-panel detector based on amorphous silicon needs about 25% less dose in comparison with conventional screen-film mammography. (orig.) [German] Ziel: Bestimmung der mittleren Parenchymdosis fuer ein grosses Patientenkollektiv bei der digitalen Vollfeldmammographie mit einem Flachdetektor auf der Basis von amorphem Silizium. Material und Methoden: Das Patientenkollektiv umfasste Frauen, die in einem Zeitraum von 4 Monaten mit dem digitalen Mammographiesystem Senographe 2000D untersucht wurden. Die Zahl der Frauen betrug 591, die Zahl der Aufnahmen 1116. Es wurden nur kranio-kaudale Projektionen beruecksichtigt. Waehrend jeder Aufnahme wurden verschiedene Kenngroessen, darunter die Einfalldosis, das mAs-Produkt und die Kompressionsschichtdicke ermittelt. Auf dieser Basis wurde die mittlere Parenchymdosis unter Verwendung tabellierter Konversionsfaktoren g fuer eine angenommene Standardzusammensetzung der Brust berechnet. Ergebnisse: Die durchschnittliche mittlere Parenchymdosis betrug 1,51 mGy (0,66-4,05 mGy) fuer eine Einzelaufnahme. Die mittlere Kompressionsschichtdicke lag bei 55,7 mm. Das mittlere Alter der Patientinnen war 55 Jahre (34-81 Jahre). Schlussfolgerung: Die Ergebnisse zeigen, dass die digitale Vollfeldmammographie mit einem Flachdetektor auf der Basis von amorphem Silizium im Vergleich zur konventionellen Film-Folien-Mamogrpahie ca. 25% weniger Dosis benoetigt. (orig.)

Hermann, K.P.; Obenauer, S.; Marten, K.; Kehbel, S.; Fischer, U.; Grabbe, E. [Dept. of Diagnostic Radiology, Georg-August-Univ. of Goettingen (Germany)

2002-06-01

93

Determination of average glandular dose with modern mammography units for two large groups of patients  

International Nuclear Information System (INIS)

influence of the actual breast composition causes variations of the order of about 15%. For group 1 and group 2, the mean values of average glandular dose (using g actors corrected for tissue composition) were 1.59 and 2.07 mGy respectively. The number of exposures per woman was on average 3.4 and 3.6 respectively. The mean value of compressed breast thickness was 55.9 and 50.8 m respectively. The mean age of group 1 was 53.6 years (for group 2 the age as not recorded). The fraction by mass of glandular tissue FGL decreases with increasing compressed breast thickness and age of patient (from 75% at 5 mm to 20% at 80 mm, and from 65% at 20 years to 30% at 75 years). For a medium-sized breast, i.e. a compressed breast thickness of 55 mm, FGL is about 35%, indicating that the standard mix (FGL 50%) might need some modification, particularly because of additional evidence from another investigation with similar results on FGL. (author)

94

QC of direct radiography and computed radiography mammography systems: Image quality and average glandular dose  

International Nuclear Information System (INIS)

Today, two technologies have emerged in digital mammography: direct radiology (DR) and computed radiology (CR). The introduction of these technologies leads to different measures and limitations in the quality control (QC) of these mammography systems. The objective of this work was to carry out QC tests on DR and CR mammography systems using the EUREF protocol about image quality and average glandular dose (AGD). These evaluations were made using the same test tools for both SIEMENS DR and CR mammography systems. Image quality was compared in terms of low contrast detectability, exposure time, and ghost factors. Exposure factors were selected clinically. Entrance surface air kerma (ESAK) was calculated from the measured output for PMMA thickness of 2, 3, 4, 5, 6, and 7 cm. The AGD was determined from ESAK and the measured half-value layer (HVL), and the respective conversion factors were obtained from the protocol. Test results indicated that DR mammography system selected a longer exposure time and a higher ghost image factor. CR mammography system yielded mean contrast-detail score higher than that of the DR system, for smaller details. The contrast-detail curves of both systems are shown. They indicate that the DR system has better low contrast detectability than the CR system, as seen from the contrast-detail curve that extends further to the left toward small detail. HVL of DR mammography system is higher than that of CR system. The entrance surface air kerma an system. The entrance surface air kerma and average glandular dose of both systems: direct radiography and computed radiography is shown. For both systems, AGD decreases as PMMA thickness increases; AGD for DR is higher. To conclude, both DR and CR mammography systems performed well within the stated values of the EUREF protocol. However, we found that the DR mammography system operated with higher beam quality that resulted in higher dose and better low contrast detectability. Therefore, DR should not be considered equal to CR mammography system

95

Determination of mean glandular dose on patients and phantom in X-ray mammography  

International Nuclear Information System (INIS)

The statistics of breast cancer rate in Bulgaria show a tendency towards increase of the morbidity from this disease. Last years campaigns against breast cancer are organized yearly. This leads to an increased number of screening and diagnostic mammograms that are made in the country. The dose associated with the examination is very low but not slightingly small. The glandular tissue in the breast is considered to be the most sensitive in relation to the radiation exposure. Several publications propose different methods, measurement set up or conversion coefficients for the calculation of the mean glandular dose (MGD) delivered to the breast during the X-ray examination. The question about the standardization of the measurement procedures arises since the differences in the results obtained using different methodologies may be quite big. The aim of this work is to develop a standard procedure for the measurement of MGD based on the recommendations mentioned in the European protocol on dosimetry in mammography, the European protocol for the quality control of the physical and technical aspects of mammography screening and the Code of practice: TRS 457 of the IAEA. Five contemporary film-screen mammography units were included in this study. Attention should be paid to the measurement set up. The reference point is chosen 6 cm from the chest wall edge laterally centered. If an ionization chamber is used for dose measurements the compression plate should be placed in close contact with it. If solid state detectors are used the compression plate should be put away from the detector and the output recalculated like if the plate is near the detector. The conversion coefficients for age dependence are not used in this study as not appropriate for the population included in it. PMMA measurements for the determination of diagnostic reference levels could be used but more correct results would be obtained with patient measurements

96

Preliminary Studies into the Determination of Mean Glandular Dose During Diagnostic Mammography Procedure in Ghana  

Directory of Open Access Journals (Sweden)

Full Text Available The objective of this project was to determine the mean glandular dose (MGD from Craniocaudal (CC and Mediolateral Oblique (MLO views to the breast during diagnostic mammography and the total dose per woman. The study was conducted at the Mammography Unit of Komfo Anokye Teaching Hospital and Peace and Love Hospital, Oduom. Data such as age, weight, height, bust size, compressed breast thickness, time of exposure, milli-ampere second (mAs, kilovoltage peak (KVp and half value layer (HVL were recorded from 440 films from 110 women. The MGD per film was 1.17± 0.02 mGy and 1.25±0.03 mGy for the craniocaudal (CC and mediolateral oblique (MLO views, respectively. The mean MGD per woman was 1.80±0.03mGy. The only factors that were found to affect MGD were mAs and the compressed breast thickness. No significant relationships were seen between MGD per woman with respect to ethnicity and educational background. The dose values obtained fall within the internationally acceptable dose range of 1-3 mGy. This suggests mammography x-ray generators at the two hospitals are capable of achieving acceptable dose levels for patient safety and this prompted us to rule out the fact that all other factors considered, they are not at risk of induced cancer from mammography.

Irene Nsiah-Akoto

2011-08-01

97

Evaluation of mean glandular dose in a full-field digital mammography unit in Tabriz (IR)  

International Nuclear Information System (INIS)

This study was aimed at evaluating the mean glandular dose (MGD) and affecting factors during mammography examinations by a full-field digital mammography unit. An extensive quality control program was performed to assure that the unit is properly working. Required information including compressed breast thickness (CBT), breast parenchymal pattern and technical factors used for imaging were recorded. An entrance skin exposure measurement was also performed using slabs of polymethylmethacrylate with 2-8 cm thickness. On the basis of recorded information and measured data, the MGD was estimated for 1145 mammography examinations obtained from 298 patients. Mean CBTs of 4.9 and 5.8 cm and MGDs of 2 and 2.4 mGy were observed for cranio-caudal and medio-lateral oblique views, respectively. Significant correlation was seen between MGD and CBT, breast parenchymal pattern and applied kVp and mAs. (authors)

98

Evaluation of mean glandular dose in a full-field digital mammography unit in Tabriz, Iran.  

Science.gov (United States)

This study was aimed at evaluating the mean glandular dose (MGD) and affecting factors during mammography examinations by a full-field digital mammography unit. An extensive quality control program was performed to assure that the unit is properly working. Required information including compressed breast thickness (CBT), breast parenchymal pattern and technical factors used for imaging were recorded. An entrance skin exposure measurement was also performed using slabs of polymethylmethacrylate with 2-8 cm thickness. On the basis of recorded information and measured data, the MGD was estimated for 1145 mammography examinations obtained from 298 patients. Mean CBTs of 4.9 and 5.8 cm and MGDs of 2 and 2.4 mGy were observed for craniocaudal and mediolateral oblique views, respectively. Significant correlation was seen between MGD and CBT, breast parenchymal pattern and applied kVp and mAs. PMID:20823039

Alizadeh Riabi, Hamed; Mehnati, Parinaz; Mesbahi, Asghar

2010-12-01

99

An investigation into the impact of anatomical variation upon mean glandular dose produced within a standard breast  

Energy Technology Data Exchange (ETDEWEB)

By using the EGS4 Monte Carlo computer program the normalised mean glandular dose (MGD) was calculated for a breast model that is intended to reflect the composition of an `average` breast. The reliability of the calculation was established by comparing the predictions with previously published values for a breast model. The breast model used was then altered in order to reflect the possible extremes in glandular distribution that could occur within a compressed breast. These results show that the MGD could vary by up to a factor of four depending upon where the majority of glandular tissue is located within the breast. The impact of this variation in MGD upon risk assessment within mammography is then discussed 29 refs., 5 tabs., 5 figs.

Wilkinson, L.E. [St. Vincent`s Hospital, Melbourne, VIC (Australia). Department of Medical Imaging; Heggie, J.C.P. [St. Vincent`s Hospital, Melbourne, VIC (Australia). Department of Medical Engineering and Physics; Johnston, P.N. [RMIT University, VIC (Australia). Department of Applied Physics

1999-06-01

100

An investigation into the impact of anatomical variation upon mean glandular dose produced within a standard breast  

International Nuclear Information System (INIS)

By using the EGS4 Monte Carlo computer program the normalised mean glandular dose (MGD) was calculated for a breast model that is intended to reflect the composition of an 'average' breast. The reliability of the calculation was established by comparing the predictions with previously published values for a breast model. The breast model used was then altered in order to reflect the possible extremes in glandular distribution that could occur within a compressed breast. These results show that the MGD could vary by up to a factor of four depending upon where the majority of glandular tissue is located within the breast. The impact of this variation in MGD upon risk assessment within mammography is then discussed

 
 
 
 
101

Mammography radiation dose: Initial results from Serbia based on mean glandular dose assessment for phantoms and patients  

International Nuclear Information System (INIS)

The primary objective of this study is to investigate the actual mammography dose levels in Serbia and establish a baseline dose database for the future screening programme. The mean glandular dose (MGD) was assessed for standard size breast substituted by 45 mm polymethyl methacrylate (PMMA) phantom and imaged under typical clinical conditions at 30 screen film mammography facilities. Average MGD was (1.9 ± 1.0) mGy, with a range of 0.12-5.2 mGy. These results were used for the calculation of the initial diagnostic reference levels in mammography in Serbia, which was set to 2.1 mGy for a standard breast. At some facilities, high doses were observed and the assessed MGD was supplemented by a patient dose survey. MGD was measured for 53 women having a diagnostic mammography in cranio-caudal (CC) and medio-lateral oblique (MLO) projections at the largest mammography facilities in Serbia. The parameters recorded were: age, compressed breast thickness, tube potential (in kV), tube loading (in mAs) and the MLO projection angle. The average MGD per image was 2.8 mGy for the CC projection and 4.3 mGy for the MLO projection. Dose to breast was compared with dose for PMMA phantoms of various sizes, assessed at the same facilities. The results have indicated that phantom dose values can assist in setting optimisation activities in mammography. Both phantom and patient dose values indicated unnecessary high doses in facilities with an extremely high mammography workload. For these facilities, urgent dose-reduction measures and follow-up actions were recommended. (authors)

102

Mammography radiation dose: initial results from Serbia based on mean glandular dose assessment for phantoms and patients.  

Science.gov (United States)

The primary objective of this study is to investigate the actual mammography dose levels in Serbia and establish a baseline dose database for the future screening programme. The mean glandular dose (MGD) was assessed for standard size breast substituted by 45 mm polymethyl methacrylate (PMMA) phantom and imaged under typical clinical conditions at 30 screen-film mammography facilities. Average MGD was (1.9 +/- 1.0) mGy, with a range of 0.12-5.2 mGy. These results were used for the calculation of the initial diagnostic reference levels in mammography in Serbia, which was set to 2.1 mGy for a standard breast. At some facilities, high doses were observed and the assessed MGD was supplemented by a patient dose survey. MGD was measured for 53 women having a diagnostic mammography in cranio-caudal (CC) and mediolateral oblique (MLO) projections at the largest mammography facilities in Serbia. The parameters recorded were: age, compressed breast thickness, tube potential (in kV), tube loading (in mAs) and the MLO projection angle. The average MGD per image was 2.8 mGy for the CC projection and 4.3 mGy for the MLO projection. Dose to breast was compared with dose for PMMA phantoms of various sizes, assessed at the same facilities. The results have indicated that phantom dose values can assist in setting optimisation activities in mammography. Both phantom and patient dose values indicated unnecessary high doses in facilities with an extremely high mammography workload. For these facilities, urgent dose-reduction measures and follow-up actions were recommended. PMID:20159918

Ciraj-Bjelac, Olivera; Beciric, Snezana; Arandjic, Danijela; Kosutic, Dusko; Kovacevic, Milojko

2010-06-01

103

Glandular dose and image quality control in mammography facilities with computerized radiography systems  

International Nuclear Information System (INIS)

Breast cancer is the most common cancer among women, and early detection is critical to its diagnosis and treatment. To date, the most effective method for early detection of breast cancer has been x-ray mammography for which the screen/film (SF) technique has been the gold standard. However, even though SF combinations have been improved and optimized over the years for breast imaging, there are some critical limitations, including a narrow exposure range, image artifacts, film processing problems, and inflexibility in image processing and film management. In recent years, digital mammography has been introduced in cancer screening programmes with the screen/film techniques gradually being phased out. Computed radiography (CR), also commonly known as photostimulable phosphor (PSP) imaging or storage phosphor, employs reusable imaging plates and associated hardware and software to acquire and to display digital projection radiographs. In this work, a protocol model was tested for performing image quality control and average glandular dose (AGD) evaluation in 19 institutions with computed radiography systems for mammography. The protocol was validated through tests at the Laboratorio de Radioprotecao Aplicada a Mamografia (LARAM) from the Centro de Desenvolvimento da Tecnologia Nuclear (CDTN). The image quality visual evaluation of CDMAM phantom showed that 53% of the facilities were able to produce images of excellent quality. Furthermore, the automated evaluation of image quality, using the analyze software cdcom.exe, showed that 57% of the images were considered to be of good quality. The detector linearity test showed that the CR response is very linear, where 95% of facilities evaluated were considered to be compliant. For the image noise was found that only 20% of facilities are in agreement with the parameters established for this test. The average glandular doses, which patients may be getting to perform an examination, were below the action levels recommended by the European Protocol for Quality Assurance in Mammography Screening in 70% of the facilities. However, if acceptable levels were considered, the situation becomes complicated because more than half of the facilities have obtained doses above these levels. Moreover, for 50 mm PMMA thickness standard, the AGD was 87 % higher than in screen/film systems. (author)

104

Real-time estimation system for mean glandular dose in mammography  

International Nuclear Information System (INIS)

The purpose of this study was to construct a system that calculates mean glandular dose (MGD) in mammography in real-time on the radiology information system (RIS) network. Measurement of the half-value layer (HVL) and exposure dose were measured according to the Japanese mammographic quality control manual. A parallel plate chamber (10X5-6M; soft X-rays only) was used for measurement. Exposure dose was measured from 26 to 32 kV. Effective energy (Eeff [keV]) could be determined from tube voltage (V [kV]) using the measure of the HVL according to the following equations: for the Mo/Mo combination, Eeff=0.1325V+11.80; for the Mo/Rh combination, Eeff=0.1435V+12.20; for the Rh/Rh combination, Eeff=0.1724V+11.29. Exposure output (XmAs [mR/mAs]), which can be determined from dosimetry per 1 mAs, becomes the following equation if effective energy is expressed as a variable: for the Mo/Mo combination, XmAs=2.1329 Eeff2-57.784 Eeff+392.71; for the Mo/Rh combination, XmAs=1.1919 Eeff2-31.924 Eeff+212.23; and for the Rh/Rh combination, XmAs=2.6929 Eeff2-82.831 Eeff+643.54. The MGD conversion factor (DgN [mGy/mR]) can be determined from effective energy using the American College of Radiology (ACR) protocol according to the following equation: for the Mo/Mo combination, DgN=(0.3962 Eeff-4.3178)·10-3; for the Mo/Rh combination, DgN=(0.3495 Eeff-3.5479)·10-3; and for the Rh/Rh combination, DgN=(0.4498 Eeff-5.0448)·10-3. However, in these cases, compression breast thickness (CBT) was 4.2 cm, and the ratio of adipose and glandular tissue was 50/50. MGD can be determined using mAs obtained from mammography, exposure output (XmAs), MGD conversion factor (DgN), and source-skin distance compensation factor (SSDcf) according to the following equation: MGD [mGy]=mAs·XmAs [mR/mAs]·DgN [mGy/mR]· SSDcf where SSDcf={64/(64-CBT [cm]){2. (author)

105

Patient investigation of average glandular dose and incident air kerma for digital mammography.  

Science.gov (United States)

Our aim in this study was to investigate the incident air kerma (IAK) and average glandular dose (AGD) for polymethylmethacrylate (PMMA) phantoms and patient breasts for each thickness by use of digital mammography units, and to determine the correlation between phantom and patient measurements. An additional aim was to calculate the numerical value of the diagnostic reference level (DRL) for digital mammography in Japan based on the AGD from patient measurements. Patient-based IAK and AGD values were calculated for 300 patients who underwent mammographic examinations at three institutions. On examination of a 40-mm PMMA phantom, the IAK and the AGD were 7.89 and 1.84 mGy, respectively. The mean patient breast thickness was 37.6 mm, and the mean IAK and the AGD calculated from actual patient data for breast thicknesses between 40 mm and 50 mm were 8.91 and 2.08 mGy, respectively. Approximately 20 % of the 300 patients had IAK >10 mGy. The distributions of patient-based IAK and AGD values were higher than the IAK and AGD values for the PMMA phantom. The patient dose with use of the PMMA phantom can be underestimated. The DRL was calculated from patient-based AGDs of the regular breast thickness as 2.0 mGy in Japan. PMID:24234736

Kawaguchi, Ai; Matsunaga, Yuta; Otsuka, Tomoko; Suzuki, Shoichi

2014-01-01

106

Mammography equipment performance, image quality and mean glandular dose in Malta.  

Science.gov (United States)

In this first Maltese national mammography survey, the effectiveness of direct digital (DR) mammography in breast cancer screening has been confirmed. Patient data were made available from three clinics out of the participating nine. A dose survey of mean glandular dose (MGD) calculated for 759 patients examined in the state-owned mammography facilities was performed. An MGD national diagnostic reference level was set at 1.87 mGy for patients with breast compression thicknesses (BCT) between 5.0 and 7.0 cm. This range was selected since patient data were retrieved from three clinics only and the results showed that other international BCT reference levels may be unsuitable for the Maltese population. In fact, the overall average BCT was 5.75 ± 1.4 cm. The survey results have shown that the technical standard of mammographic equipment in the Malta National Breast Screening Programme is on a par with other countries, including its Western European counterparts. PMID:23525916

Borg, M; Badr, I; Royle, G J

2013-09-01

107

Investigation of absorbed radiation dose in refraction-enhanced breast tomosynthesis by a Laue case analyser  

International Nuclear Information System (INIS)

An early diagnosis system for breast cancer using refraction-enhanced breast tomosynthesis is under development. Tomograms of breast specimens based on refraction-contrast were demonstrated using the simplest shift-and-add tomosynthesis algorithm. Raw projection image data of breast specimens for tomosynthesis were acquired for a total of 51 views over an angle of 50 deg., in increments of 1 deg., by rotating the object. The incident X ray was monochromatic synchrotron radiation with 20 keV. The purpose of this study was to estimate the absorbed dose of a new X-ray imaging method. As breast cancer almost always arises in glandular breast tissue, the average absorbed dose in such glandular tissue should be measured to estimate the radiation risk associated with mammography. The absorbed dose of the mammary gland due to monochromatic X rays was calculated by the Monte Carlo method, and the optimal X ray energy range for refraction-enhanced breast tomosynthesis was investigated through actual measurements. Compared with the conventional method, it was found to be below one-sixth per inspection. (authors)

108

Normalized mean glandular dose computation from mammography using GATE: a validation study  

Science.gov (United States)

Mean glandular dose (MGD) is the figure of merit to assess breast dose after a mammographic acquisition. The use of normalized MGD obtained from Monte Carlo computations with measured incident air kerma determines the MGD delivered to patients. The Geant4 Application for Tomographic Emission (GATE) toolkit is a modern Monte Carlo application specifically designed for medical imaging systems modelling. Although there is an increasing number of publications using GATE worldwide for a wide range of medical imaging and therapeutic applications, there is currently no means to obtain normalized MGD. In this work, the GATE toolkit is extended, through the development of two new modules, to provide normalized MGD information for compressed breast phantoms based on simple geometries. The normalized MGD values were validated against published work and provided results at half value layers lower than 0.3 and greater than 0.6 mmAl. In addition, the skin thickness and composition were considered. Normalized MGD was computed after substitution of the adipose layer surrounding the standard breast phantom with skin tissue and the relative difference is reported. Spectrum generation was facilitated by further development of previously published work by other authors. Validation of the new GATE extension showed good agreement with published data and can be used to assess breast dose from mammographic as well as more complex x-ray imaging techniques. Changing skin thickness and composition revealed substantial changes in normalized MGD specifically for compressed breast thickness different than 5 cm and a possible revision of the structure of the standard breast model may be necessary.

Myronakis, Marios E.; Zvelebil, Marketa; Darambara, Dimitra G.

2013-04-01

109

Normalized mean glandular dose computation from mammography using GATE: a validation study  

International Nuclear Information System (INIS)

Mean glandular dose (MGD) is the figure of merit to assess breast dose after a mammographic acquisition. The use of normalized MGD obtained from Monte Carlo computations with measured incident air kerma determines the MGD delivered to patients. The Geant4 Application for Tomographic Emission (GATE) toolkit is a modern Monte Carlo application specifically designed for medical imaging systems modelling. Although there is an increasing number of publications using GATE worldwide for a wide range of medical imaging and therapeutic applications, there is currently no means to obtain normalized MGD. In this work, the GATE toolkit is extended, through the development of two new modules, to provide normalized MGD information for compressed breast phantoms based on simple geometries. The normalized MGD values were validated against published work and provided results at half value layers lower than 0.3 and greater than 0.6 mmAl. In addition, the skin thickness and composition were considered. Normalized MGD was computed after substitution of the adipose layer surrounding the standard breast phantom with skin tissue and the relative difference is reported. Spectrum generation was facilitated by further development of previously published work by other authors. Validation of the new GATE extension showed good agreement with published data and can be used to assess breast dose from mammographic as well as more complex x-ray imaging techniques. Changing skin thickness and composition revealed substantial changes in normalized MGD specifically for compressed breast thickness different than 5 cm and a possible revision of the structure of the standard breast model may be necessary. (paper)

110

Comparison of anode/filter combinations in digital mammography with respect to the average glandular dose  

Energy Technology Data Exchange (ETDEWEB)

To investigate the average glandular dose (AGD) applied for clinical digital mammograms acquired with the anode/filter combinations molybdenum/molybdenum (Mo/Mo), molybdenum/rhodium (Mo/Rh), and tungsten/rhodium (W/Rh). Using the method of Dance, the AGD was evaluated from the exposure data of 4867 digital mammograms at two sites equipped with a full-field digital mammography (FFDM) system based on an amorphous selenium detector. 1793 images were acquired and analyzed with Mo/Mo, 643 with Mo/Rh, and 2431 with W/Rh. In the Mo/Mo cases the mean compressed breast thickness was 46 {+-} 10 mm with an average AGD of 2.29 {+-} 1.31 mGy. For the Mo/Rh cases with a mean compressed thickness of 64 {+-} 9 mm, we obtained 2.76 {+-} 1.31 mGy. The W/Rh cases with a mean compressed thickness of 52 {+-} 13 mm resulted in 1.26 {+-} 0.44 mGy. The image quality was assessed as normal and adequate for diagnostic purposes in all cases. (orig.)

Uhlenbrock, D.F. [Radiologie, Gemeinschaftspraxis fuer Radiologie und Nuklearmedizin (Germany); Mertelmeier, Thomas [Siemens AG Healthcare, Erlangen (Germany)

2009-03-15

111

Comparison of anode/filter combinations in digital mammography with respect to the average glandular dose  

International Nuclear Information System (INIS)

To investigate the average glandular dose (AGD) applied for clinical digital mammograms acquired with the anode/filter combinations molybdenum/molybdenum (Mo/Mo), molybdenum/rhodium (Mo/Rh), and tungsten/rhodium (W/Rh). Using the method of Dance, the AGD was evaluated from the exposure data of 4867 digital mammograms at two sites equipped with a full-field digital mammography (FFDM) system based on an amorphous selenium detector. 1793 images were acquired and analyzed with Mo/Mo, 643 with Mo/Rh, and 2431 with W/Rh. In the Mo/Mo cases the mean compressed breast thickness was 46 ± 10 mm with an average AGD of 2.29 ± 1.31 mGy. For the Mo/Rh cases with a mean compressed thickness of 64 ± 9 mm, we obtained 2.76 ± 1.31 mGy. The W/Rh cases with a mean compressed thickness of 52 ± 13 mm resulted in 1.26 ± 0.44 mGy. The image quality was assessed as normal and adequate for diagnostic purposes in all cases. (orig.)

112

TLD measurements and Monte Carlo simulations for glandular dose and scatter fraction assessment in mammography: A comparative study  

Energy Technology Data Exchange (ETDEWEB)

The main purpose of this study was to validate and compare Mean Glandular Dose (MGD) values obtained using Monte Carlo simulations with experimental values obtained from Entrance Surface Dose (ESD) and depth dose measurements performed in a Hospital mammography unit. ESD and depth dose were measured using ThermoLuminescent Dosimeters (TLDs), and a tissue equivalent mammography phantom recommended by the American College of Radiology (ACR). Measurements and Monte Carlo simulations were also compared with the MGD calculated using the Automatic Exposure Control (AEC) system of the mammographic unit. In the simulations the Doppler energy broadening effect was also taken into account. The simulated ESD are about 5%-10% higher than the measured ESD values. The deviation between the measured and simulated MGD values in the phantom is of about 15%. The MGD evaluated using the AEC system is smaller both with respect to the Monte Carlo simulation and experimental result by a factor of about 15% and 25% respectively. Moreover the BackScatter Factor (BSF) estimated by Monte Carlo simulations was used for the MGD calculation according to the Wu's method. Finally the inclusion of the energy broadening effect on MGD calculation produces negligible variations on the simulated results. - Highlights: > Depth dose measurements in breast phantom with TLD and an X-ray mammography system. > Entrance surface dose measurements with TLD. > Monte Carlo assessment of mean glandular dose and comparison with experimental data. > Dose variation inside the breast from 12% to 230% of the mean glandular dose. > Monte Carlo estimation of backscatter factor and dose scatter fraction.

Di Maria, S., E-mail: salvatore@itn.pt [Instituto Tecnologico e Nuclear, EN 10, 2686-953 Sacavem (Portugal); Barros, S.; Bento, J.; Teles, P.; Figueira, C.; Pereira, M.; Vaz, P. [Instituto Tecnologico e Nuclear, EN 10, 2686-953 Sacavem (Portugal); Paulo, G. [Escola Superior de Tecnologia da Saude de Coimbra, rua 5 de Outubro, 3046-854 Coimbra (Portugal)

2011-10-15

113

Results of a 2011 national questionnaire for investigation of mean glandular dose from mammography in Japan.  

Science.gov (United States)

Diagnostic reference levels (DRLs) for mammography have yet to be created in Japan. A national questionnaire investigation into radiographic conditions in Japan was carried out for the purpose of creating DRLs. Items investigated included the following: tube voltage; tube current; current-time product; source-image distance; craniocaudal view; automatic exposure control (AEC) settings; name of mammography unit; image receptor system (computed radiography (CR), flat panel detector (FPD), or film/screen (F/S)); and supported or unsupported monitor diagnosis (including monitor resolution). Estimation of the mean glandular dose (MGD) for mammography was performed and compared with previous investigations. The MGD was 1.58(0.48) mGy, which did not significantly differ from a 2007 investigation. In relation to image receptors, although no difference in average MGD values was observed between CR and FPD systems, F/S systems had a significantly decreased value compared to both CR and FPDs. Concerning digital systems (FPDs), the MGD value of the direct conversion system was significantly higher than the indirect conversion system. No significant difference in MGD value was evident concerning type of monitor diagnosis for either the CR or the FPD digital systems; however, hard copies were used more often in CR. No significant difference in the MGD value was found in relation to monitor resolution. This report suggests ways to lower the doses patients undergoing mammography receive in Japan, and serves as reference data for 4.2 cm compressed breast tissue of 50% composition DRLs. Furthermore, our findings suggest that further optimisation of FPD settings can promote a reduction in the MGD value. PMID:24334729

Asada, Y; Suzuki, S; Minami, K; Shirakawa, S

2014-03-01

114

Comparison of primary water absorbed dose standards  

International Nuclear Information System (INIS)

During the last two decades national laboratories have been developing primary standards of absorbed dose to water and calibration services for dosimeters based on these standards. A brief description is given of the primary standards of the Bureau international des poids et mesures (BIPM), the United States National Institute of Standards and Technology, the United Kingdom National Physical Laboratory, the National Research Council Canada and the German Physikalisch-Technische Bundesanstalt involved in recent comparisons at high energy photon radiation. As the standards are no longer transportable, ionization chambers and Fricke solution contained in ampoules are used as transfer instruments. At 60Co ? radiation all comparisons are linked to the BIPM international reference system. The agreement of all primary standards is well within the stated uncertainties, which is around half a per cent for each of these standards. At high energy X rays from linear accelerators a very satisfactory agreement was also found. The characterization of the radiation quality of the accelerator beams needs further investigation. This first 'snapshot' of the relation between various absorbed dose to water standards which are at different stages of development reveals a sound basis for the calibration of dosimeters to be used in clinical practice. (author). 38 refs, 2 figs, 5 tabs

115

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, ibsorbed 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)

116

Validation of mean glandular dose values provided by a digital breast tomosynthesis system in Brazil  

Energy Technology Data Exchange (ETDEWEB)

Digital breast tomosynthesis (DBT) is an emerging imaging modality that provides quasi-three-dimensional structural information of the breast and has strong promise to improve the differentiation of normal tissue and suspicious masses reducing the tissue overlaps. DBT images are reconstructed from a sequence of low-dose X-ray projections of the breast acquired at a small number of angles over a limited angular range. The Ho logic Selen ia Dimensions system is equipped with an amorphous Selenium (a-Se) detector layer of 250 ?m thickness and a 70 ?m pixel pitch. Studies are needed to determine the radiation dose of patients that are undergoing this emerging procedure to compare with the results obtained in DBT images. The mean glandular dose (D{sub G}) is the dosimetric quantity used in quality control of the mammographic systems. The aim of this work is to validate D{sub G} values for different breast thicknesses provided by a Ho logic Selen ia Dimensions system using a DBT mode in comparison with the same results obtained by a calibrated 90 X 5-6M-model Radcal ionization chamber. D{sub G} values were derived from the incident air kerma (K{sub i}) measurements and tabulated conversion coefficients that are dependent on the half value layer (HVL) of the X-ray spectrum. Voltage and tube loading values were recorded in irradiations using W/Al anode/filter combination, automatic exposure control mode and polymethyl methacrylate (PMMA) slabs which simulate different breast thicknesses. For K{sub i} measurements, the ionization chamber was positioned at 655 mm from the focus and the same radiographic technique values were selected with the manual mode. D{sub G} values for a complete procedure ranged from 0.9 ± 0.1 to 3.7 ± 0.4 mGy. The results for different breast thicknesses are in accordance with values obtained by DBT images and with acceptable levels established by the Commission of the European Communities (Cec) and the International Atomic Energy Agency (IAEA). This work contributes to determine the reliable radiation dose received by the patients and validate the values provided by this DBT system. (Author)

Beraldo O, B.; Paixao, L.; Donato da S, S. [Centro de Desenvolvimento da Tecnologia Nuclear / CNEN, Post-graduation in Sciences and Technology of Radiations Minerals and Materials, Pte. Antonio Carlos 6627, 31270-901 Belo Horizonte (Brazil); Araujo T, M. H. [Dr Maria Helena Araujo Teixeira Clinic, Guajajaras 40, 30180-100 Belo Horizonte (Brazil); Nogueira, M. S., E-mail: bbo@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear / CNEN, Pte. Antonio Carlos 6627, 31270-901 Belo Horizonte (Brazil)

2014-08-15

117

Validation of mean glandular dose values provided by a digital breast tomosynthesis system in Brazil  

International Nuclear Information System (INIS)

Digital breast tomosynthesis (DBT) is an emerging imaging modality that provides quasi-three-dimensional structural information of the breast and has strong promise to improve the differentiation of normal tissue and suspicious masses reducing the tissue overlaps. DBT images are reconstructed from a sequence of low-dose X-ray projections of the breast acquired at a small number of angles over a limited angular range. The Ho logic Selen ia Dimensions system is equipped with an amorphous Selenium (a-Se) detector layer of 250 ?m thickness and a 70 ?m pixel pitch. Studies are needed to determine the radiation dose of patients that are undergoing this emerging procedure to compare with the results obtained in DBT images. The mean glandular dose (DG) is the dosimetric quantity used in quality control of the mammographic systems. The aim of this work is to validate DG values for different breast thicknesses provided by a Ho logic Selen ia Dimensions system using a DBT mode in comparison with the same results obtained by a calibrated 90 X 5-6M-model Radcal ionization chamber. DG values were derived from the incident air kerma (Ki) measurements and tabulated conversion coefficients that are dependent on the half value layer (HVL) of the X-ray spectrum. Voltage and tube loading values were recorded in irradiations using W/Al anode/filter combination, automatic exposure control mode and polymethyl methacrylate (PMMA) slabs which simulate different breast thicknesses. For Ki measurements, the ionization chamber was positioned at 655 mm from the focus and the same radiographic technique values were selected with the manual mode. DG values for a complete procedure ranged from 0.9 ± 0.1 to 3.7 ± 0.4 mGy. The results for different breast thicknesses are in accordance with values obtained by DBT images and with acceptable levels established by the Commission of the European Communities (Cec) and the International Atomic Energy Agency (IAEA). This work contributes to determine the reliable radiation dose received by the patients and validate the values provided by this DBT system. (Author)

118

Neutron absorbed dose in a pacemaker CMOS  

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: English Abstract in spanish El espectro y la dosis absorbida, debida a neutrones, por un Semiconductor de Óxido Meta´lico Complementario ha sido estimada utilizando métodos Monte Carlo. Eventualmente, una persona con marcapasos se convierte en un paciente oncológico que debe ser tratado en un acelerador lineal. El marcapasos [...] contiene circuitos integrados como los CMOS que son sensibles a los campos de radiaci ón intensos y pulsados. El haz terapéutico de un LINAC operando a voltajes mayores a 7 MV está contaminado con fotoneutrones que pueden dañar el CMOS. En este trabajo se estimó el espectro de neutrones y la dosis absorbida por un CMOS; además, se calcularon los espectros de neutrones en dos detectores puntuales ubicados dentro de la sala. El espectro de neutrones en el CMOS tiene un pico entre 0.1 y 1 MeV y otro en la región de los térmicos, conectados mediante neutrones epitérmicos. Estas mismas características se observan en los otros detectores. La dosis absorbida por el CMOS es 1:522 x 10-17 Gy por cada neutrón emitido por el término fuente. Abstract in english The neutron spectrum and the absorbed dose in a Complementary Metal Oxide Semiconductor, has been estimated using Monte Carlo methods. Eventually a person with a pacemaker becomes an oncology patient that must be treated in a linear accelerator. Pacemaker has integrated circuits as CMOS that are sen [...] sitive to intense and pulsed radiation fields. Above 7 MV therapeutic beam is contaminated with photoneutrons that could damage the CMOS. Here, the neutron spectrum and the absorbed dose in a CMOS cell was calculated, also the spectra were calculated in two point-like detectors in the room. Neutron spectrum in the CMOS cell shows a small peak between 0.1 to 1 MeV and a larger peak in the thermal region, joined by epithermal neutrons, same features were observed in the point-like detectors. The absorbed dose in the CMOS was 1:522 x 10-17 Gy per neutron emitted by the source.

C.G., Borja-Hernández; K.A., Guzmán-García; C., Valero-Luna; A., Bañuelos-Frías; L., Paredes-Gutiérrez; V.M., Hernández-Dávila; H.R., Vega-Carrillo.

2012-06-01

119

Image quality, threshold contrast and mean glandular dose in CR mammography  

International Nuclear Information System (INIS)

In many countries, computed radiography (CR) systems represent the majority of equipment used in digital mammography. This study presents a method for optimizing image quality and dose in CR mammography of patients with breast thicknesses between 45 and 75 mm. Initially, clinical images of 67 patients (group 1) were analyzed by three experienced radiologists, reporting about anatomical structures, noise and contrast in low and high pixel value areas, and image sharpness and contrast. Exposure parameters (kV, mAs and target/filter combination) used in the examinations of these patients were reproduced to determine the contrast-to-noise ratio (CNR) and mean glandular dose (MGD). The parameters were also used to radiograph a CDMAM (version 3.4) phantom (Artinis Medical Systems, The Netherlands) for image threshold contrast evaluation. After that, different breast thicknesses were simulated with polymethylmethacrylate layers and various sets of exposure parameters were used in order to determine optimal radiographic parameters. For each simulated breast thickness, optimal beam quality was defined as giving a target CNR to reach the threshold contrast of CDMAM images for acceptable MGD. These results were used for adjustments in the automatic exposure control (AEC) by the maintenance team. Using optimized exposure parameters, clinical images of 63 patients (group 2) were evaluated as described above. Threshold contrast, CNR and MGD for such exposure parameters were also determined. Results showed that the proposed optimization method was effective for all breast thicknesses studied in phantoms. The best result was found for breasts of 75 mm. While in group 1 there was no detection of the 0.1 mm critical diameter detail with threshold contrast below 23%, after the optimization, detection occurred in 47.6% of the images. There was also an average MGD reduction of 7.5%. The clinical image quality criteria were attended in 91.7% for all breast thicknesses evaluated in both patient groups. Finally, this study also concluded that the use of the AEC of the x-ray unit based on the constant dose to the detector may bring some difficulties to CR systems to operate under optimal conditions. More studies must be performed, so that the compatibility between systems and optimization methodologies can be evaluated, as well as this optimization method. Most methods are developed for phantoms, so comparative studies including clinical images must be developed. (paper)

120

Image quality, threshold contrast and mean glandular dose in CR mammography  

Science.gov (United States)

In many countries, computed radiography (CR) systems represent the majority of equipment used in digital mammography. This study presents a method for optimizing image quality and dose in CR mammography of patients with breast thicknesses between 45 and 75 mm. Initially, clinical images of 67 patients (group 1) were analyzed by three experienced radiologists, reporting about anatomical structures, noise and contrast in low and high pixel value areas, and image sharpness and contrast. Exposure parameters (kV, mAs and target/filter combination) used in the examinations of these patients were reproduced to determine the contrast-to-noise ratio (CNR) and mean glandular dose (MGD). The parameters were also used to radiograph a CDMAM (version 3.4) phantom (Artinis Medical Systems, The Netherlands) for image threshold contrast evaluation. After that, different breast thicknesses were simulated with polymethylmethacrylate layers and various sets of exposure parameters were used in order to determine optimal radiographic parameters. For each simulated breast thickness, optimal beam quality was defined as giving a target CNR to reach the threshold contrast of CDMAM images for acceptable MGD. These results were used for adjustments in the automatic exposure control (AEC) by the maintenance team. Using optimized exposure parameters, clinical images of 63 patients (group 2) were evaluated as described above. Threshold contrast, CNR and MGD for such exposure parameters were also determined. Results showed that the proposed optimization method was effective for all breast thicknesses studied in phantoms. The best result was found for breasts of 75 mm. While in group 1 there was no detection of the 0.1 mm critical diameter detail with threshold contrast below 23%, after the optimization, detection occurred in 47.6% of the images. There was also an average MGD reduction of 7.5%. The clinical image quality criteria were attended in 91.7% for all breast thicknesses evaluated in both patient groups. Finally, this study also concluded that the use of the AEC of the x-ray unit based on the constant dose to the detector may bring some difficulties to CR systems to operate under optimal conditions. More studies must be performed, so that the compatibility between systems and optimization methodologies can be evaluated, as well as this optimization method. Most methods are developed for phantoms, so comparative studies including clinical images must be developed.

Jakubiak, R. R.; Gamba, H. R.; Neves, E. B.; Peixoto, J. E.

2013-09-01

 
 
 
 
121

Determination of absorbed dose in reactors  

International Nuclear Information System (INIS)

There are many areas in the use and operation of research reactors where the absorbed dose and the neutron fluence are required. These include work on the determination of the radiolytic stability of the coolant and moderator and on the determination of radiation damage in structural materials, and reactor experiments involving radiation chemistry and radiation biology. The requirements range from rough estimates of the total heating due to radiation to precise values specifying the contributions of gamma rays, thermal neutrons and fast neutrons. To meet all these requirements a variety of experimental measurements and calculations as well as a knowledge of reactor radiations and their interactions is necessary. Realizing the complexity and importance of this field, its development at widely separated laboratories and the need to bring the experts in this work together, the IAEA has convened three panel meetings. These were: 'In-pile dosimetry', held in July 1964 (published by the Agency as Technical Reports Series No. 46); 'Neutron fluence measurements', in October 1965; and 'In-pile dosimetry', in November 1966. The recommendations of these three panels led the Agency to form a Working Group on Reactor Radiation Measurements and to commission the writing of this book and a book on Neutron Fluence Measurements. The latter was published in May 1970 (Technical Reports Series No. 107). The material on neutron fluence and absorbed dose measurements is widely scattered in reports and reviews. It was considered that it was time for all relevant information to be evaluated and put together in the form of a practical guide that would be valuable both to experienced workers and beginners in the field

122

Estimation of mean glandular dose for breast tomosynthesis: factors for use with the UK, European and IAEA breast dosimetry protocols  

Science.gov (United States)

A formalism is proposed for the estimation of mean glandular dose for breast tomosynthesis, which is a simple extension of the UK, European and IAEA protocols for dosimetry in conventional projection mammography. The formalism introduces t-factors for the calculation of breast dose from a single projection and T-factors for a complete exposure series. Monte Carlo calculations of t-factors have been made for an imaging geometry with full-field irradiation of the breast for a wide range of x-ray spectra, breast sizes and glandularities. The t-factors show little dependence on breast glandularity and tables are provided as a function of projection angle and breast thickness, which may be used for all x-ray spectra simulated. The T-factors for this geometry depend upon the choice of projection angles and weights per projection, but various example calculations gave values in the range 0.93-1.00. T-factors are also provided for the Sectra tomosynthesis system, which employs a scanned narrow-beam imaging geometry. In this quite different configuration, the factor (denoted TS) shows an important dependence on breast thickness, varying between 0.98 and 0.76 for 20 and 110 mm thick breasts, respectively. Additional data are given to extend the current tabulations of g-, c- and s-factors used for dosimetry of conventional 2D mammography.

Dance, D. R.; Young, K. C.; van Engen, R. E.

2011-01-01

123

Estimation of mean glandular dose for breast tomosynthesis: factors for use with the UK, European and IAEA breast dosimetry protocols  

Energy Technology Data Exchange (ETDEWEB)

A formalism is proposed for the estimation of mean glandular dose for breast tomosynthesis, which is a simple extension of the UK, European and IAEA protocols for dosimetry in conventional projection mammography. The formalism introduces t-factors for the calculation of breast dose from a single projection and T-factors for a complete exposure series. Monte Carlo calculations of t-factors have been made for an imaging geometry with full-field irradiation of the breast for a wide range of x-ray spectra, breast sizes and glandularities. The t-factors show little dependence on breast glandularity and tables are provided as a function of projection angle and breast thickness, which may be used for all x-ray spectra simulated. The T-factors for this geometry depend upon the choice of projection angles and weights per projection, but various example calculations gave values in the range 0.93-1.00. T-factors are also provided for the Sectra tomosynthesis system, which employs a scanned narrow-beam imaging geometry. In this quite different configuration, the factor (denoted T{sub S}) shows an important dependence on breast thickness, varying between 0.98 and 0.76 for 20 and 110 mm thick breasts, respectively. Additional data are given to extend the current tabulations of g-, c- and s-factors used for dosimetry of conventional 2D mammography.

Dance, D R; Young, K C [NCCPM, Medical Physics Department, Royal Surrey County Hospital, Guildford GU2 7XX (United Kingdom); Van Engen, R E, E-mail: daviddance@nhs.net [National Training and Expert Centre for Breast Cancer Screening (LRCB), Radboud University Nijmegen Medical Centre, PO Box 6873, 6532 SZ Nijmegen (Netherlands)

2011-01-21

124

Estimation of mean glandular dose for breast tomosynthesis: factors for use with the UK, European and IAEA breast dosimetry protocols  

International Nuclear Information System (INIS)

A formalism is proposed for the estimation of mean glandular dose for breast tomosynthesis, which is a simple extension of the UK, European and IAEA protocols for dosimetry in conventional projection mammography. The formalism introduces t-factors for the calculation of breast dose from a single projection and T-factors for a complete exposure series. Monte Carlo calculations of t-factors have been made for an imaging geometry with full-field irradiation of the breast for a wide range of x-ray spectra, breast sizes and glandularities. The t-factors show little dependence on breast glandularity and tables are provided as a function of projection angle and breast thickness, which may be used for all x-ray spectra simulated. The T-factors for this geometry depend upon the choice of projection angles and weights per projection, but various example calculations gave values in the range 0.93-1.00. T-factors are also provided for the Sectra tomosynthesis system, which employs a scanned narrow-beam imaging geometry. In this quite different configuration, the factor (denoted TS) shows an important dependence on breast thickness, varying between 0.98 and 0.76 for 20 and 110 mm thick breasts, respectively. Additional data are given to extend the current tabulations of g-, c- and s-factors used for dosimetry of conventional 2D mammography.

125

Dose absorbed in adults and children thyroid due to the I123 using the dosimetry MIRD and Marinelli  

International Nuclear Information System (INIS)

Using the dosimetry MIRD, and representation Cristy-Eckerman in the thyroid gland and organs of their bio-kinetics when I123 (Iodine) is used, the study demonstrates that the absorbed dose by the gland of an adult, children, and newly born, is their auto-dose, independent of the compartments number of their bio-kinetics. The dosimetric contributions of the organs of their bio-kinetics are insignificant. Their results are not significantly different to those obtained by the formalism MARINELLI (auto-dose) when it uses a sphere like glandular representation. In consequence, the kinetic model corresponding to the glandular representation decreases to a compartment, where the gland can also be represented like a sphere. (Author)

126

Displacement corrections used in absorbed dose determination  

International Nuclear Information System (INIS)

When an (exposure) calibrated ionization chamber is used for the determination of absorbed dose from a photon beam, the reading of the instrument must be multiplied by a number of factors, one of which is an attenuation correction for phantom material displaced by the chamber. The magnitude of this correction must depend on the size and shape of the ionization chamber as well as the energy of the radiation beam. For cobalt-60 radiation, a single number, 0.985, has generally been used. Recent measurements, however, and ''first scatter'' calculations, of kerma suggest that a more appropriate value for a Farmer-type chamber used in a water phantom would be 0.975. Such a change is small but would be important when dose calculations based on ''in phantom'' measurements are compared to calculations that are based on in air measurements. Values for the attenuation factor for other beam energies have not been generally available. We have carried out ''first scatter'' calculations for a rather wide range of energies and spectra. Measurements in 60Co beams and in a high-energy (25 MV) photon beam support the calculations. A set of proposed displacement correction factors is presented

127

Cistitis glandular / Glandular cystitis  

Scientific Electronic Library Online (English)

Full Text Available SciELO Cuba | Language: Spanish Abstract in spanish Se presenta un caso de cistitis glandular, enfermedad rara, generalmente asintomática, que consiste en un desorden proliferativo de las glándulas que producen moco dentro de la mucosa y submucosa del epitelio urinario de la vejiga. La irritación crónica constituye el factor de riesgo de mayor import [...] ancia en su aparición. La evolución hacia la malignidad (adenocarcinoma) es excepcional y ocurre en caso de la persistencia del factor de predisposición. Para llegar a establecer el diagnóstico es necesario el examen clínico, radiológico e histológico. A este caso se le realizó ecografía vesical y se encontró tumoración pequeña de 3 cm en fondo vesical, que primeramente se le efectuó biopsia por cistoscopia y después se resecó totalmente. Confirmado el diagnóstico, el tratamiento fue esencialmente quirúrgico. La vigilancia anual por cistoscopia con biopsias de vejiga resulta necesaria en estos casos. La forma florida es mucho más rara e incapacitante pues precisa resección amplia de las lesiones. Abstract in english This is the case of glandular cystitis a uncommon disease generally asymptomatic consisted of a proliferative disorder of glands producing mucus within mucosa and submucosa of vesical urinary epithelium. Chronic irritation is the risk factor more significant in its appearance. Course to malignancy ( [...] adenocarcinoma) is exceptional and occur in case of persistence of the predisposition factor. To made diagnosis it is necessary the clinical, radiological and histological examination. This case undergoes a vesical echography noting a 3 cm small tumor in vesical fundus and a biopsy by cystoscopy after a total resection. Diagnosis was confirmed and treatment was essentially surgical. Annual surveillance by cystoscopy with vesical biopsies is necessary in these cases. The progressive way is rarer and incapacitant since a wide resection of lesions is essential.

Barbara Paula, Piñera; Yaimara, Hernández Puentes; Mercedes, Salinas Olivares; Myrna Inocencia, Moreno Miravalles; Midalys, Casa de Valle Castro; Ramón, Ramos Zayas.

2010-03-01

128

Cistitis glandular Glandular cystitis  

Directory of Open Access Journals (Sweden)

Full Text Available Se presenta un caso de cistitis glandular, enfermedad rara, generalmente asintomática, que consiste en un desorden proliferativo de las glándulas que producen moco dentro de la mucosa y submucosa del epitelio urinario de la vejiga. La irritación crónica constituye el factor de riesgo de mayor importancia en su aparición. La evolución hacia la malignidad (adenocarcinoma es excepcional y ocurre en caso de la persistencia del factor de predisposición. Para llegar a establecer el diagnóstico es necesario el examen clínico, radiológico e histológico. A este caso se le realizó ecografía vesical y se encontró tumoración pequeña de 3 cm en fondo vesical, que primeramente se le efectuó biopsia por cistoscopia y después se resecó totalmente. Confirmado el diagnóstico, el tratamiento fue esencialmente quirúrgico. La vigilancia anual por cistoscopia con biopsias de vejiga resulta necesaria en estos casos. La forma florida es mucho más rara e incapacitante pues precisa resección amplia de las lesiones.This is the case of glandular cystitis a uncommon disease generally asymptomatic consisted of a proliferative disorder of glands producing mucus within mucosa and submucosa of vesical urinary epithelium. Chronic irritation is the risk factor more significant in its appearance. Course to malignancy (adenocarcinoma is exceptional and occur in case of persistence of the predisposition factor. To made diagnosis it is necessary the clinical, radiological and histological examination. This case undergoes a vesical echography noting a 3 cm small tumor in vesical fundus and a biopsy by cystoscopy after a total resection. Diagnosis was confirmed and treatment was essentially surgical. Annual surveillance by cystoscopy with vesical biopsies is necessary in these cases. The progressive way is rarer and incapacitant since a wide resection of lesions is essential.

Barbara Paula Piñera

2010-03-01

129

Cistitis glandular / Glandular cystitis  

Scientific Electronic Library Online (English)

Full Text Available SciELO Cuba | Language: Spanish Abstract in spanish Se presenta un caso de cistitis glandular, enfermedad rara, generalmente asintomática, que consiste en un desorden proliferativo de las glándulas que producen moco dentro de la mucosa y submucosa del epitelio urinario de la vejiga. La irritación crónica constituye el factor de riesgo de mayor import [...] ancia en su aparición. La evolución hacia la malignidad (adenocarcinoma) es excepcional y ocurre en caso de la persistencia del factor de predisposición. Para llegar a establecer el diagnóstico es necesario el examen clínico, radiológico e histológico. A este caso se le realizó ecografía vesical y se encontró tumoración pequeña de 3 cm en fondo vesical, que primeramente se le efectuó biopsia por cistoscopia y después se resecó totalmente. Confirmado el diagnóstico, el tratamiento fue esencialmente quirúrgico. La vigilancia anual por cistoscopia con biopsias de vejiga resulta necesaria en estos casos. La forma florida es mucho más rara e incapacitante pues precisa resección amplia de las lesiones. Abstract in english This is the case of glandular cystitis a uncommon disease generally asymptomatic consisted of a proliferative disorder of glands producing mucus within mucosa and submucosa of vesical urinary epithelium. Chronic irritation is the risk factor more significant in its appearance. Course to malignancy ( [...] adenocarcinoma) is exceptional and occur in case of persistence of the predisposition factor. To made diagnosis it is necessary the clinical, radiological and histological examination. This case undergoes a vesical echography noting a 3 cm small tumor in vesical fundus and a biopsy by cystoscopy after a total resection. Diagnosis was confirmed and treatment was essentially surgical. Annual surveillance by cystoscopy with vesical biopsies is necessary in these cases. The progressive way is rarer and incapacitant since a wide resection of lesions is essential.

Barbara Paula, Piñera; Yaimara, Hernández Puentes; Mercedes, Salinas Olivares; Myrna Inocencia, Moreno Miravalles; Midalys, Casa de Valle Castro; Ramón, Ramos Zayas.

130

Determination of Absorbed Dose Using a Dosimetric Film  

International Nuclear Information System (INIS)

This paper presents the absorbed dose measurements by means of the irradiated dosimetric reference films. The dose distributions were made by MULTIDATA film densitometer using RTD-4 software, in INFLPR Linear Accelerator Department

131

Determination of Total Absorbed Dose Following Accidental and Chronic Exposure  

International Nuclear Information System (INIS)

The paper proposes methods and formulae for calculating the dose absorbed by the critical organs following accidental and chronic (external and internal) exposure. The doses absorbed by the critical organs upon external exposure are calculated on the basis of the following measurements of internal exposure doses: (1) Concentration of radioactive aerosols and period of time during which they enter the body; (2) Activity of the excreta; (3) Activity of the body. Finally, an example is given illustrating the summation of absorbed doses accruing from external and internal exposure. (author)

132

Optimal beam quality selection based on contrast-to-noise ratio and mean glandular dose in digital mammography  

International Nuclear Information System (INIS)

Full text: The performance of a digital mammography system (Siemens Mammomat Novation) using different target/filter combinations and tube voltage has been assessed. The objective of this study is to optimize beam quality selection based on contrast-to-noise ratio (CNR) and mean glandular dose (MOD). Three composition of breast were studied with composition of glandular/adipose of 30/70, SO/SO, and 70/30. CNR was measured using 2, 4 and 6 cm-thick simulated breast phantoms with an aluminium sheet of 0.1 mm thickness placed on top of the phantom. Three target/filter combinations, namely molybdenum/molybdenum (Mo/Mo), molybdenum/rh dium (Mo/Rh) and tungsten/rhodium (W/Rh) with various tube voltage and mAs were tested. MOD was measured for each exposure. For SO/SO breast composition, Mo/Rh combination with tube voltage 26 kYp is optimal for 2cm thick breast. W/Rh combination with tube voltage 27 and 28 kYp are optimal for 4 and 6 cm-thick breast, respectively. For both 30/70 and 70/30 breast composition, W/Rh combination is optimal with tube voltage 25, 26 and 27 kYp, respectively. From our study it was shown that there are potential of dose reduction up to 11 % for a set CNR of 3.0 by using beam quality other than that are

133

Forward-scattered radiation from the compression paddle should be considered in glandular dose estimations.  

Science.gov (United States)

From major protocols on dosimetry in mammography, there is no doubt that the incident air kerma should be evaluated without backscattered radiation to the dosemeter. However, forward-scattered radiation from the compression paddle is neglected. The aim of this work was to analyse the contribution of forward-scattered radiation for typical air kerma measurements. Measurements of forward-scatter were performed with a plane-parallel ionisation chamber on four mammography units. The forward-scatter contribution to the air kerma was 2-10 % and increased with the compression paddle thickness, but also with the half-value layer value. For incident air kerma in mammography, it can be as important to consider forward-scattered as backscattered radiation. If an ionisation chamber is used, the compression paddle should be in contact with the chamber; otherwise the air kerma and absorbed dose will be underestimated. If a dosemeter based on semiconductors with much less sensitivity to scattered radiation is used, it is suggested that a forward-scatter factor (FSF) is applied. Based on the results of this work, FSF = 1.06 will lead to a maximum error of ~4 %. PMID:21778158

Hemdal, Bengt

2011-09-01

134

Absorbed dose equations. The general solution of the absorbed dose equation and solutions under different kinds of radiation equilibrium  

International Nuclear Information System (INIS)

All practical calculations of absorbed dose rely on the assumption of one or another type of radiation equilibrium. The aim of this work is to analyze different kinds of radiation equilibrium conditions and to find the corresponding exact expressions for the absorbed dose. The concept of radiation equilibrium is more carefully analyzed than has been done previously. Moreover, the definition of the mass energy absorption coefficient for indirectly (uncharged) ionizing particles is critically analyzed. A new definition is proposed relevant to calculations of the absorbed dose in cases when charged particle equilibirum exists within a homogeneous medium due to the uniform liberation of charged particles by uncharged particles. (author)

135

Fast neutron radiation inactivation of Bacillus subtilis: Absorbed dose determination  

International Nuclear Information System (INIS)

In this paper, fast neutron inactivation effects of Bacillus subtilis were investigated with fission fast neutrons from CFBR-II reactor of INPC (Institute of Nuclear Physics and Chemistry) and mono-energetic neutrons from the Van de Graaff accelerator at Peking University. The method for determining the absorbed dose in the Bacillus subtilis suspension contained in test tubes is introduced. The absorbed dose, on account of its dependence on the volume and the form of confined state, was determined by combined experiments and Monte Carlo method. Using the calculation results of absorbed dose, the fast neutron inactivation effects on Bacillus subtilis were studied. The survival rates and absorbed dose curve was constructed. (authors)

136

Specification of absorbed dose for reporting a therapeutic irradiation  

International Nuclear Information System (INIS)

The problem of dose specification in external beam therapy with photons and electrons has been dealt with in ICRU Report 29 (1978). This problem arises from the fact that the absorbed dose distribution is usually not uniform in the target volume and that for the purpose of treatment reporting a nominal absorbed dose - which will be called target absorbed dose - has to be selected. When comparing the clinical results obtained between radiotherapy centres, the differences in the reported target absorbed doses which can be introduced by differences in the methods of dose specification often are much larger than the differences related to the dosimetric procedures themselves. This shows the importance of the problem. In this paper, some definitions of terms and concepts currently used in radiotherapy are first recalled: tumour volume, target volume, treatment volume, etc. These definitions have been proposed in ICRU Report 29 for photon and electron beams; they can be extended to any kind of irradiation. For external beam therapy with photons and electrons, the target absorbed dose is defined as the absorbed dose at selected point(s) (specification point(s)) having a meaningful relation to the target volume and/or the irradiation beams. Examples are discussed for typical cases. As far as interstitial and intracavitary therapy is concerned, the problem is more complex and no recommendations have so far been made by the ICRU Commission. A major difficulty arises from the sharp dose gradient as a function of the distance to the sources. The particular case of the treatment of cervix carcinoma is considered and some possible methods of specification are discussed: (1) the indication of the sources (in adequate units) and the duration of the application, (2) the absorbed doses at selected reference points (bladder, rectum, bony structures) and (3) the description of the tissue volume (height, width, thickness) encompassed by a given isodose surface (60Gy). (author)

137

Comportamento da dose glandular versus contraste do objeto em mamografia: determinação de formalismo semi-empírico para diferentes combinações alvo-filtro / Behavior of subject contrast versus glandular dose in mammography: determination of a semi-empirical formalism for different target-filter combinations  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese OBJETIVO: Verificar o efeito da mudança no contraste do objeto, tempo de exposição e dose de radiação quando diferentes espessuras de filtração de molibdênio (Mo) e ródio (Rh) são empregadas em mamógrafos. MATERIAIS E MÉTODOS: Realizaram-se medidas da exposição na entrada da pele com uma câmara de i [...] onização para diferentes espessuras para os filtros de Mo e Rh. Para determinar a dose glandular média foi utilizado simulador de BR12 (50% tecido adiposo e 50% tecido glandular) de diferentes espessuras (4 cm e 8 cm). Energias na faixa de 24 kVp a 34 kVp foram empregadas e filmes Kodak MinR 2000 foram utilizados. RESULTADOS: Os resultados evidenciaram dados de contraste do objeto, dose glandular e tempo de exposição para diferentes espessuras de filtros adicionais e diferentes tensões. Esses dados indicaram aumento nos valores de contraste do objeto e tempo de exposição, com o aumento da espessura dos filtros. A dose glandular apresentou comportamento com diferentes tendências para cada caso analisado. Equações foram definidas para possibilitar a estimativa do contraste do objeto, dose glandular e tempo de exposição para os casos estudados. CONCLUSÃO: Os resultados possibilitaram a estimativa de equações que auxiliam na verificação do comportamento do contraste do objeto e da dose glandular para simuladores com espessura de 4 cm e 8 cm e para os filtros de Rh e Mo. Dessa forma, torna-se possível estimar a figura de mérito (razão entre o contraste do objeto e a dose glandular), podendo auxiliar na análise da relação risco-benefício dos casos estudados. Abstract in english OBJECTIVE: Our purpose was to verify the effect of changes in subject contrast, exposure time and radiation dose when different thicknesses of molybdenum (Mo) and rhodium (Rh) filters are used in mammography equipments. MATERIALS AND METHODS: Entrance skin exposure measurements were performed with a [...] n ionization chamber for different thicknesses of Mo and Rh filters. Average glandular dose was determined with a BR12 simulator (50% fat tissue and 50% glandular tissue) of different thicknesses (4 cm and 8 cm). Energies in the range of 24 to 34 kVp and Kodak MinR 2000 films were used. RESULTS: Results have evidenced data on subject contrast data, glandular dose and exposure time for different thicknesses of additional filters and different kVp values. These data have indicated an increase both in values of subject contrast and exposure time when filters thickness is increased. The glandular dose has presented a different behavior tendency for each case analyzed. Equations were defined to allow us to estimate subject contrast, glandular dose and exposure time for the cases studied. CONCLUSION: The results have made possible to define equations to assist with the evaluation of subject contrast and glandular dose behavior in simulators with 4 cm and 8 cm thicknesses and for Rh and Mo additional filters. In this way, it is possible to estimate the figure of merit (subject contrast/glandular dose ratio) to assist in the risk-benefit analysis of the cases studied.

Gabriela, Hoff; Carlos Eduardo de, Almeida; Gary T., Barnes.

138

Comportamento da dose glandular versus contraste do objeto em mamografia: determinação de formalismo semi-empírico para diferentes combinações alvo-filtro / Behavior of subject contrast versus glandular dose in mammography: determination of a semi-empirical formalism for different target-filter combinations  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese OBJETIVO: Verificar o efeito da mudança no contraste do objeto, tempo de exposição e dose de radiação quando diferentes espessuras de filtração de molibdênio (Mo) e ródio (Rh) são empregadas em mamógrafos. MATERIAIS E MÉTODOS: Realizaram-se medidas da exposição na entrada da pele com uma câmara de i [...] onização para diferentes espessuras para os filtros de Mo e Rh. Para determinar a dose glandular média foi utilizado simulador de BR12 (50% tecido adiposo e 50% tecido glandular) de diferentes espessuras (4 cm e 8 cm). Energias na faixa de 24 kVp a 34 kVp foram empregadas e filmes Kodak MinR 2000 foram utilizados. RESULTADOS: Os resultados evidenciaram dados de contraste do objeto, dose glandular e tempo de exposição para diferentes espessuras de filtros adicionais e diferentes tensões. Esses dados indicaram aumento nos valores de contraste do objeto e tempo de exposição, com o aumento da espessura dos filtros. A dose glandular apresentou comportamento com diferentes tendências para cada caso analisado. Equações foram definidas para possibilitar a estimativa do contraste do objeto, dose glandular e tempo de exposição para os casos estudados. CONCLUSÃO: Os resultados possibilitaram a estimativa de equações que auxiliam na verificação do comportamento do contraste do objeto e da dose glandular para simuladores com espessura de 4 cm e 8 cm e para os filtros de Rh e Mo. Dessa forma, torna-se possível estimar a figura de mérito (razão entre o contraste do objeto e a dose glandular), podendo auxiliar na análise da relação risco-benefício dos casos estudados. Abstract in english OBJECTIVE: Our purpose was to verify the effect of changes in subject contrast, exposure time and radiation dose when different thicknesses of molybdenum (Mo) and rhodium (Rh) filters are used in mammography equipments. MATERIALS AND METHODS: Entrance skin exposure measurements were performed with a [...] n ionization chamber for different thicknesses of Mo and Rh filters. Average glandular dose was determined with a BR12 simulator (50% fat tissue and 50% glandular tissue) of different thicknesses (4 cm and 8 cm). Energies in the range of 24 to 34 kVp and Kodak MinR 2000 films were used. RESULTS: Results have evidenced data on subject contrast data, glandular dose and exposure time for different thicknesses of additional filters and different kVp values. These data have indicated an increase both in values of subject contrast and exposure time when filters thickness is increased. The glandular dose has presented a different behavior tendency for each case analyzed. Equations were defined to allow us to estimate subject contrast, glandular dose and exposure time for the cases studied. CONCLUSION: The results have made possible to define equations to assist with the evaluation of subject contrast and glandular dose behavior in simulators with 4 cm and 8 cm thicknesses and for Rh and Mo additional filters. In this way, it is possible to estimate the figure of merit (subject contrast/glandular dose ratio) to assist in the risk-benefit analysis of the cases studied.

Gabriela, Hoff; Carlos Eduardo de, Almeida; Gary T., Barnes.

2006-06-01

139

Comportamento da dose glandular versus contraste do objeto em mamografia: determinação de formalismo semi-empírico para diferentes combinações alvo-filtro Behavior of subject contrast versus glandular dose in mammography: determination of a semi-empirical formalism for different target-filter combinations  

Directory of Open Access Journals (Sweden)

Full Text Available OBJETIVO: Verificar o efeito da mudança no contraste do objeto, tempo de exposição e dose de radiação quando diferentes espessuras de filtração de molibdênio (Mo e ródio (Rh são empregadas em mamógrafos. MATERIAIS E MÉTODOS: Realizaram-se medidas da exposição na entrada da pele com uma câmara de ionização para diferentes espessuras para os filtros de Mo e Rh. Para determinar a dose glandular média foi utilizado simulador de BR12 (50% tecido adiposo e 50% tecido glandular de diferentes espessuras (4 cm e 8 cm. Energias na faixa de 24 kVp a 34 kVp foram empregadas e filmes Kodak MinR 2000 foram utilizados. RESULTADOS: Os resultados evidenciaram dados de contraste do objeto, dose glandular e tempo de exposição para diferentes espessuras de filtros adicionais e diferentes tensões. Esses dados indicaram aumento nos valores de contraste do objeto e tempo de exposição, com o aumento da espessura dos filtros. A dose glandular apresentou comportamento com diferentes tendências para cada caso analisado. Equações foram definidas para possibilitar a estimativa do contraste do objeto, dose glandular e tempo de exposição para os casos estudados. CONCLUSÃO: Os resultados possibilitaram a estimativa de equações que auxiliam na verificação do comportamento do contraste do objeto e da dose glandular para simuladores com espessura de 4 cm e 8 cm e para os filtros de Rh e Mo. Dessa forma, torna-se possível estimar a figura de mérito (razão entre o contraste do objeto e a dose glandular, podendo auxiliar na análise da relação risco-benefício dos casos estudados.OBJECTIVE: Our purpose was to verify the effect of changes in subject contrast, exposure time and radiation dose when different thicknesses of molybdenum (Mo and rhodium (Rh filters are used in mammography equipments. MATERIALS AND METHODS: Entrance skin exposure measurements were performed with an ionization chamber for different thicknesses of Mo and Rh filters. Average glandular dose was determined with a BR12 simulator (50% fat tissue and 50% glandular tissue of different thicknesses (4 cm and 8 cm. Energies in the range of 24 to 34 kVp and Kodak MinR 2000 films were used. RESULTS: Results have evidenced data on subject contrast data, glandular dose and exposure time for different thicknesses of additional filters and different kVp values. These data have indicated an increase both in values of subject contrast and exposure time when filters thickness is increased. The glandular dose has presented a different behavior tendency for each case analyzed. Equations were defined to allow us to estimate subject contrast, glandular dose and exposure time for the cases studied. CONCLUSION: The results have made possible to define equations to assist with the evaluation of subject contrast and glandular dose behavior in simulators with 4 cm and 8 cm thicknesses and for Rh and Mo additional filters. In this way, it is possible to estimate the figure of merit (subject contrast/glandular dose ratio to assist in the risk-benefit analysis of the cases studied.

Gabriela Hoff

2006-06-01

140

Normalized glandular dose (DgN) coefficients for arbitrary X-ray spectra in mammography: computer-fit values of Monte Carlo derived data.  

Science.gov (United States)

Normalized glandular dose (DgN) values have been reported by several investigators for specific spectra, however for unconventional or unanticipated x-ray spectra considered for use in mammography, practical methods are not available for DgN computation. In this study, the previously validated SIERRA Monte Carlo code was used to compute the normalized glandular dose coefficients for monoenergetic energies from 8 keV to 50 keV. The overall mammography geometry used was a 65 cm source to image distance, a 1.2 cm air gap between the breast and the detector, and breast thicknesses ranging from 2 to 9 cm. A 4 mm layer of skin was also modeled, and semicircular breast radii of 8.5 cm and 10.0 cm were studied. Breast compositions of 0% glandular, 50% glandular, and 100% glandular were evaluated. The Monte Carlo derived DgN results demonstrated coefficients of variation less than 0.3%. The monoenergetic DgN values, DgN(E), were computer fit using commercial software and the best fit equations are reported. All fits resulted in r2 values of 0.9999 or better. The computer fit equations, along with easy to use spectral modeling routines, are available electronically on the web. PMID:12033583

Boone, John M

2002-05-01

 
 
 
 
141

Normalized glandular dose (DgN) coefficients for arbitrary x-ray spectra in mammography: Computer-fit values of Monte Carlo derived data  

International Nuclear Information System (INIS)

Normalized glandular dose (DgN) values have been reported by several investigators for specific spectra, however for unconventional or unanticipated x-ray spectra considered for use in mammography, practical methods are not available for DgN computation. In this study, the previously validated SIERRA Monte Carlo code was used to compute the normalized glandular dose coefficients for monoenergetic energies from 8 keV to 50 keV. The overall mammography geometry used was a 65 cm source to image distance, a 1.2 cm air gap between the breast and the detector, and breast thicknesses ranging from 2 to 9 cm. A 4 mm layer of skin was also modeled, and semicircular breast radii of 8.5 cm and 10.0 cm were studied. Breast compositions of 0% glandular, 50% glandular, and 100% glandular were evaluated. The Monte Carlo derived DgN results demonstrated coefficients of variation less than 0.3%. The monoenergetic DgN values, DgN(E), were computer fit using commercial software and the best fit equations are reported. All fits resulted in r2 values of 0.9999 or better. The computer fit equations, along with easy to use spectral modeling routines, are available electronically on the web

142

Digital breast tomosynthesis and digital mammography: A comparison of figures of merit for various average glandular doses  

Science.gov (United States)

Previous studies on the application of tomosynthesis to breast imaging have demonstrated the potential of digital breast tomosynthesis (DBT). DBT can improve the specificity of digital mammography (DM) through improved marginal visibility of lesions and early breast cancer detection for women with dense breasts. To investigate possible improvements in the accuracy of lesion detection with DBT systems as compared to DM, we conducted a quantitative evaluation by using simulated lesions embedded in a breast phantom. A prototype DBT and dedicated DM system were used in this study. For the DBT system, the average glandular dose (AGD) was calculated using a formalism that was a simple extension of mammography dosimetry. The DBT and the DM images were acquired with average glandular doses (AGDs) ranging from 1 to 4 mGy. To analyze the results objectively, we calculated metrics for in-plane lesion visibility in the form of the contrast-to-noise ratio for the in-focus plane from the DBT reconstruction image and from the craniocaudal (CC) image from the DM system. The imaging performance of DBT was quantitatively compared with that of DM in terms of the figure of merit. Although the DM showed better results in terms of the contrast-to-noise ratio (CNR) of the mass due to the reduced overlapping of tissue and lesion, an increase in breast thickness of over 3 cm increased the CNR of the mass with the DBT system. For microcalcification detection, the DBT system showed significantly higher CNR than the DM system and gave better predictions of the microcalcification size. We compared the performances of the DM and the DBT systems for various AGDs and breast thicknesses. In conclusion, the results indicate that the DBT systems can play an important role in the detection of masses or microcalcifications without severe compression.

Kim, Ye-seul; Park, Hye-Suk; Park, SuJin; Kim, Hee-Joung; Choi, Jae-Gu; Choi, Young-Wook; Park, Jun-Ho; Lee, Jae-Jun

2013-05-01

143

Optimal beam quality selection based on contrast-to-noise ratio and mean glandular dose in digital mammography.  

Science.gov (United States)

The performance of a digital mammography system (Siemens Mammomat Novation) using different target/filter combinations and tube voltage has been assessed. The objective of this study is to optimize beam quality selection based on contrast-to-noise ratio (CNR) and mean glandular dose (MGD). Three composition of breast were studied with composition of glandular/adipose of 30/70, 50/50, and 70/30. CNR was measured using 2, 4 and 6 cm-thick simulated breast phantoms with an aluminium sheet of 0.1 mm thickness placed on top of the phantom. Three target/filter combinations, namely molybdenum/molybdenum (Mo/Mo), molybdenum/rhodium (Mo/Rh) and tungsten/rhodium (W/Rh) with various tube voltage and mAs were tested. MGD was measured for each exposure. For 50/50 breast composition, Mo/Rh combination with tube voltage 26 kVp is optimal for 2 cm-thick breast. W/Rh combination with tube voltage 27 and 28 kVp are optimal for 4 and 6 cm-thick breast, respectively. For both 30/70 and 70/30 breast composition, W/Rh combination is optimal with tube voltage 25, 26 and 27 kVp, respectively. From our study it was shown that there are potential of dose reduction up to 11% for a set CNR of 3.0 by using beam quality other than that are determined by AEC selection. Under the constraint of lowest MGD, for a particular breast composition, calcification detection is optimized by using a softer X-ray beam for thin breast and harder X-ray beam for thick breast. These experimental results also indicate that for breast with high fibroglandular tissues (70/30), the use of higher beam quality does not always increase calcification detection due to additional structured noise caused by the fibroglandular tissues itself. PMID:20938762

Aminah, M; Ng, K H; Abdullah, B J J; Jamal, N

2010-12-01

144

Direct MC conversion of absorbed dose to graphite to absorbed dose to water for 60Co radiation  

International Nuclear Information System (INIS)

The ARPANSA calibration service for 60Co gamma rays is based on a primary standard graphite calorimeter that measures absorbed dose to graphite. Measurements with the calorimeter are converted to the absorbed dose to water using the calculation of the ratio of the absorbed dose in the calorimeter to the absorbed dose in a water phantom. ARPANSA has recently changed the basis of this calculation from a photon fluence scaling method to a direct Monte Carlo (MC) calculation. The MC conversion uses an EGSnrc model of the cobalt source that has been validated against water tank and graphite phantom measurements, a step that is required to quantify uncertainties in the underlying interaction coefficients in the MC code. A comparison with the Bureau International des Poids et Mesures (BIPM) as part of the key comparison BIPM.RI(I)-K4 showed an agreement of 0.9973 (53). (authors)

145

Depth absorbed dose distributions for electrons  

International Nuclear Information System (INIS)

There is controversy over the comparative depth dose distributions produced by 10 MeV microtron and linear accelerator electron beams. The arguments produced by Brahme and Svensson in their rejection of silicon diode and LiF depth dose measurements (1976, Phys. Med. Biol., vol. 21, 304; 1978, Phys. Med. Biol., vol. 23, 788) have been shown to be insubstantial. These depth dose measurements in fact confirm that the two types of electron beam are not significantly different at 10 MeV. The significant differences originally reported by Brahme et al. on the basis of liquid ionisation chamber measurements (Brahme, A., Hulten, G., and Svensson, H., 1975, Phys. Med. Biol., vol. 20, 39), and the implied clinical advantage of the microtron, therefore both remain in doubt. (UK)

146

In vivo dosimetry for head and neck carcinoma: determination of target absorbed dose from entrance and exit absorbed dose measurements  

International Nuclear Information System (INIS)

The aims of this work were to measure the entrance and exit dose for patient treated for head and neck tumors. The target absorbed dose was determined from the exit and entrance dose measurement. Twenty patients were evaluated. The results were compared to the calculated values and the midline dose was determinate and compared with the prescribed dose. 80 entrance doses and 80 exit doses measurements were performed. The average difference from expected values was 1.93% for entrance dose (SD 1.92%) and -0.34% for exit dose (SD 4.1%). The target absorbed dose differed from prescribed dose values by 2.94% (1.97%) for the results using the Noel method and 3.34% (SD: 2.29%) with the Rizzotti method. The total uncertainty budget in the measurement of the absorbed entrance and exit dose with diode, including diode reading, correction factors and diode calibration coefficient, is determined as 3.02% (1 s). Simple in vivo dose measurements are an additional safeguard against major setup errors and calculation or transcription errors that were missed during pre-treatment chart check. (authors)

147

In vivo dosimetry for head and neck carcinoma: determination of target absorbed dose from entrance and exit absorbed dose measurements  

Energy Technology Data Exchange (ETDEWEB)

The aims of this work were to measure the entrance and exit dose for patient treated for head and neck tumors. The target absorbed dose was determined from the exit and entrance dose measurement. Twenty patients were evaluated. The results were compared to the calculated values and the midline dose was determinate and compared with the prescribed dose. 80 entrance doses and 80 exit doses measurements were performed. The average difference from expected values was 1.93% for entrance dose (SD 1.92%) and -0.34% for exit dose (SD 4.1%). The target absorbed dose differed from prescribed dose values by 2.94% (1.97%) for the results using the Noel method and 3.34% (SD: 2.29%) with the Rizzotti method. The total uncertainty budget in the measurement of the absorbed entrance and exit dose with diode, including diode reading, correction factors and diode calibration coefficient, is determined as 3.02% (1 s). Simple in vivo dose measurements are an additional safeguard against major setup errors and calculation or transcription errors that were missed during pre-treatment chart check. (authors)

Farhat, L.; Daoud, J. [Service de radiotherapie carcinologique, CHU Habib-Bourguiba, 3029 Sfax (Tunisia); Besbes, M. [Service de radiotherapie carcinologique, Institut Salah-Azaiz, Boulevard du 9-avril-Bab-Saadoun, 1006 Tunis (Tunisia); Bridier, A. [Service de radiophysique, Institut Gustave-Roussy, 39 rue Camille-Desmoulins, 94805 Villejuif Cedex (France)

2011-04-15

148

Evaluation of the absorbed dose in odontological computerized tomography  

International Nuclear Information System (INIS)

This paper evaluated the absorbed dose at the surface entry known as 'cone beam computed tomography' (CBCT) in odontological computerized tomography. Examination were simulated with CBCT for measurements of dose. A phantom were filled with water, becoming scatter object of radiation. Thermoluminescent dosemeters were positioned on points correspondent to eyes and salivary glands

149

Glandular dose and image quality control in mammography facilities with computerized radiography systems; Dose glandular e controle de qualidade da imagem em servicos de mamografia com sistema de radiografia computadorizada  

Energy Technology Data Exchange (ETDEWEB)

Breast cancer is the most common cancer among women, and early detection is critical to its diagnosis and treatment. To date, the most effective method for early detection of breast cancer has been x-ray mammography for which the screen/film (SF) technique has been the gold standard. However, even though SF combinations have been improved and optimized over the years for breast imaging, there are some critical limitations, including a narrow exposure range, image artifacts, film processing problems, and inflexibility in image processing and film management. In recent years, digital mammography has been introduced in cancer screening programmes with the screen/film techniques gradually being phased out. Computed radiography (CR), also commonly known as photostimulable phosphor (PSP) imaging or storage phosphor, employs reusable imaging plates and associated hardware and software to acquire and to display digital projection radiographs. In this work, a protocol model was tested for performing image quality control and average glandular dose (AGD) evaluation in 19 institutions with computed radiography systems for mammography. The protocol was validated through tests at the Laboratorio de Radioprotecao Aplicada a Mamografia (LARAM) from the Centro de Desenvolvimento da Tecnologia Nuclear (CDTN). The image quality visual evaluation of CDMAM phantom showed that 53% of the facilities were able to produce images of excellent quality. Furthermore, the automated evaluation of image quality, using the analyze software cdcom.exe, showed that 57% of the images were considered to be of good quality. The detector linearity test showed that the CR response is very linear, where 95% of facilities evaluated were considered to be compliant. For the image noise was found that only 20% of facilities are in agreement with the parameters established for this test. The average glandular doses, which patients may be getting to perform an examination, were below the action levels recommended by the European Protocol for Quality Assurance in Mammography Screening in 70% of the facilities. However, if acceptable levels were considered, the situation becomes complicated because more than half of the facilities have obtained doses above these levels. Moreover, for 50 mm PMMA thickness standard, the AGD was 87 % higher than in screen/film systems. (author)

Dantas, Marcelino Vicente de Almeida

2010-07-01

150

determining absorbed dose of people from Iran's background gamma radiation  

International Nuclear Information System (INIS)

1. Investigating the various procedures to measure outdoor radiation and determine the proper procedure, 2. determining the absorbed dose in different points of Iran by different procedures, 3. The annual outdoor exposure of Iranians from background gamma radiation related to life in outdoor and indoor residential houses, 4. Absorbed dose changes due to heights, 5. Drawing exposure map of Iran with emphasis on populated cities, 6. Determining the high natural exposure places, 7. Determining radioactivity of building materials and soil in order to estimate gamma's absorbed dose in residential buildings and comparing it with evaluated measures. These are the main aims of this thesis. The results obtained show that the indoor exposure of gamma is 9.6-20.5? R/h and outdoor exposure is 8-19.8? R/h. The mean values are 12.4, and 14.6 micro Roentgen. In addition, exposure ratio of indoor to outdoor of residential environment for constructed building was 1.17 and for wooden houses were 0.82. The investigation of absorbed dose for individual Iranians from gamma background radiation is 136.5 n Gy/h and annual effective dose for individuals is 1.195 m Sv. The measured absorbed dose for individual from radionuclides226 Ra, 232 Th and 40 K in building material and soil samples are 146.8 n Gy/h

151

Absorbed - dose measurements with plastic and dyed-plastic  

International Nuclear Information System (INIS)

In an effort to choose a suitable dosimeter for a medical sterilization plant, some commercial perspexes have been studied. Here we present results on the comparison between clear and brown perspex, both irradiated with gamma rays. The optical density increased linearly with the increase of absorbed dose in the range from 10 to 60 KGy for clear perspex. For the same dose range, linearity was also observed between the decrease in optical density and the increase in absorbed dose in brown perspex. The study includes an investigation of the effect of some parameters on the change in optical density during the storage period after irradiation

152

Determination of superficial absorbed dose based on experiment and theory  

International Nuclear Information System (INIS)

The methods determining the superficial absorbed dose distributions in a water phantom by experiments and available theories are reported. The distributions of beta dose were measured by an extrapolation ionization chamber at definite depths corresponding to some superficial organs and tissues such as the radiosensitive layer of the skin, cornea, sclera, anterior chamber and lens of eyeball. The ratios among superficial absorbed dose D(0.07) and average absorbed doses at the depths of 1,2,3,4,5 and 6 mm are also obtained with Cross's methods. They can be used for confining the deterministic effects of some superficial tissues and organs such as the skin and the components of eyeball for weakly penetrating radiations

153

Effect of backscatter factor on absorbed dose in radiotherapy  

International Nuclear Information System (INIS)

This paper is to study how the absorbed dose was affected by the organ backscatter caused in radiotherapy. With the change of radiation energy, back organ depth, different back organ material type, the backscatter factor (Bs) was determined by measuring absolute dose compared with 1 cm depth of back solid water. The actual absorbed dose was really affected by the back organ depth in radiotherapy. The Bs value increased with the increase of radiation energy, back organ depth. The absorbed dose to organ or tumor should be modified with the measured Bs based on the depth of back tissue of the tumor, back organ material type, radiation energy, so as to improve the effect of radiotherapy and to be able to protect normal tissue. (authors)

154

Absorbed Doses to Patients in Nuclear Medicine  

International Nuclear Information System (INIS)

The Swedish radiation protection authority, (SSI), has supported work on estimates of radiation doses to patients from nuclear medicine examinations since more than 20 years. A number of projects have been reported. The results are put together and published under the name 'Doskatalogen' which contains data on doses to different organs and tissues from radiopharmaceuticals used for diagnostics and research. This new report contains data on: 11C-labelled substances (realistic maximum model), amino acids labelled with 11C, 18F or 75Se, 99mTc-apcitide, 123I-labelled fatty acids (123I- BMIPP and 123I-IPPA) and revised models for previously reported 15O-labelled water, 99mTc-tetrofosmin (rest as well as exercise) and 201Tl-ion Data for almost 200 substances and radionuclides are included in the 'Doskatalogen' today. Since the year 2001 the 'Doskatalogen' is available on the authority's home page (www.ssi.se)

155

Phantoms for calculations of absorbed organ dose  

Energy Technology Data Exchange (ETDEWEB)

We have developed a computer code IDES (Internal Dose Estimation System). In this code, MIRD Transformation Method is used and photon simulation by Monte Carlo method is also possible. We have studied Japanese phantoms in two procedures, mathematical phantom and `symbol phantoms`. Our mathematical phantoms realize their height and body weights but does not hold some of organ weights, which were measured by TANAKA and KAWAMURA. The symbol phantom can solve this discrepancy and realize a realistic phantom, although it remains problems of authorization and normalization. Errors were estimated for internal dose calculations and it was pointed out that to use realistic organ weights and parameters of kinetics was important competitively to reduce uncertainty of the results. (author).

Takeshita, Hiroshi; Yamaguchi, Hiroshi; Hongo, Shozo [National Inst. of Radiological Sciences, Chiba (Japan); Iwai, Satoshi; Iwai, Kazuo

1994-03-01

156

An Investigation of Mean Glandular Dose from Routine Mammography in Urmia, Northwestern Iran and the Factors Affecting It  

Directory of Open Access Journals (Sweden)

Full Text Available The objective of this study was to determine the Mean Glandular Dose (MGD resulting from Craniocaudal (CC and Mediolateral oblique (MLO views in one breast and the total dose per woman in Urmia, northwestern Iran and to identify the factors affecting it. This study was conducted during 9 months to estimate the MGD for women undergoing mammography and to report the distribution of dose. The clinical data were collected from 460 mammograms taken from 230 women who were referred to radiology center of Imam Reza hospital in Urmia. The piranha system version 3.8A was used for determining the MGD in this work. The MGD values are based on measurements of ESAK (entrance surface air krema and HVL. Significant differences were found between MGD from CC and MLO views. The mean±SD MGD per film was 1.18±0.38 mGy for craniocaudal and 1.39±0.51 mGy for mediolateral oblique views, (p<0.001. The mean±SD MGD per woman was 2.57±0.44 mGy. The mean± SD MGD per film in present study were lower than most of similar reports. The dose values obtained fall within the internationally acceptable dose range of 1-3mGy. This suggests mammography x-ray generators in this part of the country are capable of achieving acceptable dose levels for patient safety. Therefore, with considering the all other factors, the establishment of screening mammography program is achievable.

Leili rahmatnezhad

2012-09-01

157

Review of calorimeter-based absorbed dose to water standards  

International Nuclear Information System (INIS)

The major techniques currently used at standards laboratories for the realization of the quantity absorbed-dose to water, can be grouped in three distinct classes: (1) ionization chamber-based absorbed-dose standards, (2) total absorption-based absorbed-dose standards, and (3) absorbed-dose calorimeter-based standards. Over the last two decades, however, water calorimeters have gained considerable interest and research has shown that estimated uncertainties using water calorimeter standards have become competitive with those associated with graphite calorimeter standards. In this paper, we review graphite calorimeter and water calorimeter-based absorbed dose to water standards. Although both techniques belong to the same class, the difference in details and approaches are so dramatic that each of the methods can be considered largely independent from the other. This review focuses on absorbed-dose calorimeter standards in high energy photon and electron beams. Graphite calorimeter-based standards Graphite calorimeters are multi-body systems where, using sensors (thermistors), the average temperature rise is measured in a central body or core that is thermally isolated from its surrounding bodies (jackets) by vacuum gaps. The system can be calibrated by dissipating a known amount of electrical energy in its bodies and measuring the corresponding temperature rise. There are three major modes of operation: (1) the quasi adiabatic mode, in which the core and the jacket temperature are raised at the same rate so as to minimize heat-loss from the core; (2) the heat-loss compensated mode, in which the heat-loss from the core is quantified by summing core and jacket signals and (3) the isothermal mode of operation, in which the heat-loss from the core is kept constant and such that its temperature drift is zero. Since graphite is an efficient conductor, the temperature variations from point to point within a body are usually ignored and the thermal behaviour of the system can be relatively easily modeled once the heat transfer coefficients between the different bodies as well as the specific heat capacities of the bodies have been determined. Determination of absorbed dose to graphite requires corrections for the effect of the gaps in the calorimeter. Absorbed dose to graphite needs to be converted into absorbed-dose to water and to this end scaling techniques or ionization chamber-based methods are being used. Although a frequently used calorimeter design at standards laboratories is that of Domen, different graphite calorimeter types have been constructed for different purposes. Estimates of typical relative (%) standard uncertainties in absorbed dose to graphite for high energy photon beams as achieved with state-of-the-art traditional graphite calorimetry are summarized. We conclude that typical standard uncertainties of absorbed dose to graphite at standards laboratories are of the order of 0.5%. The dose conversion procedure to derive absorbed dose to water from this may typically add an uncertainty of 0.3% to this figure. In contrast to water calorimetry, graphite calorimeters have been widely used for electron beam dosimetry. Areas of continued development are technical investigations into the accuracy of the electrical calibration and the development of portable systems that can be used directly in clinical beams. Water calorimeter-based standards Early water calorimeters tested at standards laboratories were small, stirred water calorimeters and were instrumental in understanding the radiation chemistry of water. In the beginning of the eighties however Domen showed that, as a result of the low thermal diffusivity of water, absorbed dose to water could be practically derived from the measured temperature rise at a point in continuous water. Water calorimetry relies on an accurate knowledge of the specific heat capacity of water under standard, constant-pressure conditions. The calibration of a water calorimeter involves a calibration of the sensors (thermistors) in terms of an absolute temperature difference rather tha

158

Neutron absorbed dose measurements in phantom from 252Cf source  

International Nuclear Information System (INIS)

The fluence and neutron absorbed dose distribution from a 252Cf source inside tissue equivalent phantom has been investigated. This has been done for three different source-phantom geometries: source at the centre of the phantom, source at the phantom surface as well as at 15 cm distance from the phantom surface. The results of fluence and absorbed dose measured with solid state nuclear track etching detectors were presented and compared with other experimental and calculated data. A distribution down to 0.06 cm depth and up to 40 cm has been obtained with reasonable accuracy as compared with others

159

Radiographic fallopian tube recanalization: Absorbed ovarian radiation dose  

Energy Technology Data Exchange (ETDEWEB)

Absorbed radiation dose to the ovaries during radiographic fallopian tube recanalization was estimated in 29 patients with use of thermoluminescent dosimeters placed in the vaginal fornix. With an average fluoroscopic time of 8.5 minutes {plus minus} 5.5 and an average of 14 {plus minus} 5 105-mm spot radiographs obtained, the average absorbed dose to the ovaries was 8.5 mGy {plus minus} 5.6 (0.85 rad {plus minus} 0.56). Technical guidelines for keeping patient radiation exposure to a minimum during this new interventional procedure are suggested.

Hedgpeth, P.L.; Thurmond, A.S.; Fry, R.; Schmidgall, J.R.; Roesch, J. (Department of Diagnostic Radiology, Oregon Health Sciences University, Portland (USA))

1991-07-01

160

Radiographic fallopian tube recanalization: Absorbed ovarian radiation dose  

International Nuclear Information System (INIS)

Absorbed radiation dose to the ovaries during radiographic fallopian tube recanalization was estimated in 29 patients with use of thermoluminescent dosimeters placed in the vaginal fornix. With an average fluoroscopic time of 8.5 minutes ± 5.5 and an average of 14 ± 5 105-mm spot radiographs obtained, the average absorbed dose to the ovaries was 8.5 mGy ± 5.6 (0.85 rad ± 0.56). Technical guidelines for keeping patient radiation exposure to a minimum during this new interventional procedure are suggested

 
 
 
 
161

Radiographic fallopian tube recanalization: absorbed ovarian radiation dose.  

Science.gov (United States)

Absorbed radiation dose to the ovaries during radiographic fallopian tube recanalization was estimated in 29 patients with use of thermoluminescent dosimeters placed in the vaginal fornix. With an average fluoroscopic time of 8.5 minutes +/- 5.5 and an average of 14 +/- 5 105-mm spot radiographs obtained, the average absorbed dose to the ovaries was 8.5 mGy +/- 5.6 (0.85 rad +/- 0.56). Technical guidelines for keeping patient radiation exposure to a minimum during this new interventional procedure are suggested. PMID:2052677

Hedgpeth, P L; Thurmond, A S; Fry, R; Schmidgall, J R; Rösch, J

1991-07-01

162

Determining absolute absorbed dose rates for electron beams  

International Nuclear Information System (INIS)

The practice describes the measurement of fluence rates of electron beams with energies from 5 to 50 MeV. The measurement technique employs a series of scattering plates, collimators, and a Faraday cup. Procedures for calculating absolute absorbed dose rates in thin slabs of silicon from the measured fluence rates are given. Although the practice may be used for other applications, the specific area of interest is radiation-hardness testing of electronic devices. The practice is applicable to absorbed dose rates of 105 Gy(Si)/s[107 rad(Si)/s] or greater and to beam pulse lengths from 0.1 ?s to several microseconds

163

Can the average glandular dose in routine digital mammography screening be reduced? A pilot study using revised image quality criteria  

International Nuclear Information System (INIS)

There is a need for tools that in a simple way can be used for the evaluation of image quality related to clinical requirements in mammography. The aim of this work was to adjust the present European image quality criteria to be relevant also for digital mammography images, and to use as simple and as few criteria as possible. A pilot evaluation of the new set of criteria was made with mammograms of 28 women from a General Electric Senographe 2000D full-field digital mammography system. One breast was exposed using the standard automatic exposure mode, the other using about half of that absorbed dose. Three experienced radiologists evaluated the images using visual grading analysis technique. The results indicate that the new quality criteria can be used for the evaluation of image quality related to clinical requirements in digital mammography in a simple way. The results also suggest that absorbed doses for the mammography system used may be substantially reduced. (authors)

164

Determination of absorbed dose for mantle field with extended FSD  

International Nuclear Information System (INIS)

Determination of absorbed dose for Mantle Field technique by conventional method and direct dosimetry is studied and compared in this paper. Mantle field is used for supradiaphragmatic disease. The target volume for a mantle field includes the occipital, submental, submandibular, anterior and posterior cervical and supraclavicular nodes. In addition it covers the infraclavicular, axillary, medial-pectoral, paratracheal and mediastinal lymph nodes

165

Absorbed Doses to Patients in Nuclear Medicine; Doskatalogen foer nukleaermedicin  

Energy Technology Data Exchange (ETDEWEB)

The work with a Swedish catalogue of radiation absorbed doses to patients undergoing nuclear medicine investigations has continued. After the previous report in 1999, biokinetic data and dose estimates (mean absorbed dose to various organs and tissues and effective dose) have been produced for a number of substances: {sup 11}C- acetate, {sup 11}C- methionine, {sup 18}F-DOPA, whole antibody labelled with either {sup 99m}Tc, {sup 111}In, {sup 123}I or {sup 131}I, fragment of antibody, F(ab'){sub 2} labelled with either {sup 99m}Tc, {sup 111}In, {sup 123}I or {sup 131}I and fragment of antibody, Fab' labelled with either {sup 99m}Tc, {sup 111}In, {sup 123}I or {sup 131}I. The absorbed dose estimates for these substances have been made from published biokinetic information. For other substances of interest, e.g. {sup 14}C-urea (children age 3-6 years), {sup 14}C-glycocholic acid, {sup 14}C-xylose and {sup 14}C-triolein, sufficient literature data have not been available. Therefore, a large number of measurements on patients and volunteers have been carried out, in order to determine the biokinetics and dosimetry for these substances. Samples of breast milk from 50 mothers, who had been subject to nuclear medicine investigations, have been collected at various times after administration of the radiopharmaceutical to the mother. The activity concentration in the breast milk samples has been measured. The absorbed dose to various organs and tissues and the effective dose to the child who ingests the milk have been determined for 17 different radiopharmaceuticals. Based on these results revised recommendations for interruption of breast-feeding after nuclear medicine investigations are suggested.

Leide-Svegborn, Sigrid; Mattsson, Soeren; Nosslin, Bertil [Universitetssjukhuset MAS, Malmoe (Sweden). Avd. foer radiofysik; Johansson, Lennart [Norrlands Universitetssjukhus, Umeaa (Sweden). Avd. foer radiofysik

2004-09-01

166

Determination of doses absorbed by female patients in grid mammography  

International Nuclear Information System (INIS)

This study is intended to present data for optimizing absorbed dose and image quality in grid mammography by comparing data obtained with phantoms with those obtained under clinical conditions with patients, using three different film-screen systems. The Kodak system with NMB film and Min-R screen is characterized by relatively low radiation dose and good detail sharpness. For patients with big breasts, the dose can be reduced to 1/5 of the dose applied by the conventional system. This effect is less significant for patients with small breasts. If in the case of dense mammal tissue and unclear findings the film-screen system NDT 70/MR 50 is used, the dose may double and may relatively often even come up to four times the dose determined with phantoms. The imaging quality, however, is far better than that of all other systems, even smallest calcifications up to 100 ?m are detected with good sharpness. (orig./WU)

167

Study of absorbed dose distribution to high energy electron beams  

International Nuclear Information System (INIS)

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

168

Bone marrow and thyroid absorbed doses from mammography  

International Nuclear Information System (INIS)

Breast dose from mammography has been estimated by various investigators, because of the established effectiveness of mammography in early screening for breast cancer and the relatively high sensitivity of the breast to radiation carcinogenesis. Nevertheless, to our knowledge, there is no available information in the literature about absorbed doses from mammography to organs other than the breast. The absorbed doses to the red bone marrow in the sternum and to the thyroid, due to scattered radiation from mammographic examinations, have been measured using a Plexiglas upper-body phantom and thermoluminescent dosemeters. Their dependence on several parameters has also been examined. It is necessary to emphasize that this work is still in progress. (author)

169

Calculation of absorbed dose distributions from dynamic wedges  

Energy Technology Data Exchange (ETDEWEB)

In radiotherapy with photon beams, the use of dynamic wedges, which are obtained by the movement of one of the jaws, offers an increasing flexibility relative to the traditional use of metal wedges. But it is a disadvantage for the measurement of absorbed dose distributions, because the absorbed dose at each measurement point can only be obtained after a complete movement of the jaw. Consequently, for radiotherapy planning, an algorithm should be available that does not require measurements for any specific dynamically wedged beam, but is based on only a modest number of measurements. In this paper, an algorithm for the calculation of the dose distribution from dynamic wedges is described. This algorithm uses the convolution of pencil beam kernels with a non-uniform field function. These pencil beam kernels are derived from empirical dataresulting from measurements of the open beam only. (author)

Storchi, Pascal; Woudstra, Evert; Verlinde, Philip [Dr Daniel den Hoed Cancer Center, Groene Hilledijk 301, PO Box 5201, 3008 AE Rotterdam (Netherlands); Johansson, Karl-Axel; Samuelsson, Anna [Sahlgrenska University Hospital, 413 45 Goetenborg (Sweden)

1998-06-01

170

Absorbed dose optimization in the microplanar beam radiotherapy  

International Nuclear Information System (INIS)

Full text: Recent advances in synchrotron generated X-ray beams with high fluence rate, small divergence and sharply defined microbeam margins permit investigation of the application of an array of closely spaced, parallel or converging microbeams for radiotherapy. The proposed technique takes advantage of the repair mechanism hypothesis of capillary endothelial cells between alternate microbeam zones, which regenerates the lethally irradiated capillaries. Unlike a pencil beam, more accurate dose calculation, beam width and spacing are essential to minimise radiation damage to normal tissue cells outside the target. The absorbed dose between microbeam zones should be kept below the threshold for irreversible radiation damage. Thus the peak-to-valley ratio for the dose distribution should be optimized. The absorbed dose profile depends on the energy of the incident beam and the composition and density of the medium. Using Monte Carlo computations, the radial absorbed dose of single 24 x 24 ?m2 cross-section X-ray beams of different energies in a tissue/lung/tissue phantom was investigated. The results indicated that at 100 keV, closely spaced square cross-sectional microbeams can be applied to the lung. A bundle of parallel 24 ?m-wide planar microbeams spaced at 200 ?m intervals provides much more irradiation coverage of tissue than is provided by a bundle of parallel, square cross-sectional microbeam, although the former is associated with much smaller Peak (maximum absorbed dose on the beam axis) -to-Valley ( minimum interbeam absorbed dose ) ratios than the latter. In this study the lateral and depth dose of single and multiple microplanar beams with beam dimensions of width 24 ?m and 48 ?m and height 2-20 cm with energy of 100 keV in a tissue/lung/tissue phantom are investigated. The EGS4 Monte Carlo code is used to calculate dose profiles at different depths and bundles of beams (2 x 2 cm2 to 20 x 20 cm2 square cross section) with a 150 ?m 200 ?m and 300 ?m beam spacing. The peak-to-valley ratios are compared at different depths, bundles, heights, widths and beam spacing to determine the optimum parameters for irradiation

171

Absorbed dose evaluation by SISCODES code, kerma and fluence deviations  

Energy Technology Data Exchange (ETDEWEB)

Radiotherapy is a common treatment of cancer. Radiotherapy exposes the patient to a radiation field, producing ionization, and absorbed dose. A precise dose calculation and the ability to execute the irradiation on the patient are necessary in order to avoid serious injuries on the surrounding health tissue, thus, the maximum acceptable absorbed dose error from the prescribed and applied is about 5%. The doses on radiotherapy are usually calculated by superimposition experimental dose profile, namely PDP, which is experimentally measured in a water simulator. Moreover, the radiation interaction with human body tissues depends on the chemical composition and the tissue density, which means the anthropomorphism and anthropometric of the human being. This paper evaluates the deviation of calculated value of kerma, induced by human body heterogeneities. To do this job two thorax voxel models created on SISCODES (one filled with various tissues other filled with water) were applied. The result of simulations permits two different comparisons. One is the ratio between tissues kermas and water kerma. Another is the ratio between human phantom fluence, where exists radiation scatter and reflection, and water phantom fluence. The reconstructed pictures of studied regions showing the calculated ratios, and graphs of the ratios versus energy of each tissue are shown. The dose ratio deviations obtained are, in some situations, larger than the acceptable 5% point out serious miscalculation of doses for some spatial regions on the human body. (author)

Trindade, Bruno M.; Campos, Tarcisio P.R. de [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Programa de Pos-Graduacao em Ciencias e Tecnicas Nucleares]. E-mail: bmtrindade@yahoo.com; campos@nuclear.ufmg.br

2007-07-01

172

Absorbed doses due to mammography in various Dutch hospitals  

International Nuclear Information System (INIS)

Because of the relatively high incidence of mammary cancer in The Netherlands (5000 new cases per 7 million women per year), it is presently being considered to implement screening programs for breast cancer. In this connection, it is of interest to determine the absolute dose and dose distributions in functional mammography installations. The mammography procedures in twelve hospitals have been compared with respect to the dose and the dose distribution in an acrylic plastic phantom (10.2 x 10.2 x 4.9 cm3) simulating the breast. Dose determinations were made at 4.95, 24.5 and 44.05 mm depth with a Baldwin-Farmer ionisation chamber (BFIC) connected to a Keithley 616 digital electrometer and with thermoluminescent dosimeters (TLD). The measurements were made under conditions similar to those in routine mammography using the automatic phototimers. The doses received per mammoradiograph as derived from the ionisation chamber differed greatly among the different hospitals: between 2 and 21 mGy for the entrance dose, 0.1 and 0.3 mGy for the exit dose and 0.8 and 4 mGy for the mean tissue dose. The mean absorbed dose in the breast per investigation varies from 2 to 9 mGy. (Auth.)

173

Electron absorbed dose measurements in LINACs by thermoluminescent dosimeters.  

Science.gov (United States)

In this work, electron absorbed doses measurements in radiation therapy (RT) were obtained. Radiation measurements were made using thermoluminescent dosimeters of calcium sulfate doped with dysprosium (CaSO4:Dy) and zirconium oxide (ZrO2). TL response calibration was obtained by irradiating TLDs and a Farmer cylindrical ionization chamber PTW 30013 at the same time. Each TL material showed a typical glow curve according to each material. Both calcium sulfate doped with dysprosium and zirconium oxide exhibited better light intensity to high energy electron beam compared with lithium fluoride. TL response as a function of absorbed dose was analyzed. TL response as a function of high energy electron beam was also studied. PMID:24060149

Cortés, J Rodríguez; Romero, R Alvarez; Nieto, J Azorín; Montalvo, T Rivera

2014-01-01

174

Sensors of absorbed dose of ionizing radiation based on mosfet  

Directory of Open Access Journals (Sweden)

Full Text Available The requirements to technology and design of p-channel and n-channel MOS transistors with a thick oxide layer designed for use in the capacity of integral dosimeters of absorbed dose of ionizing radiation are defined. The technology of radiation-sensitive MOS transistors with a thick oxide in the p-channel and n-channel version is created.

Perevertaylo V. L.

2010-10-01

175

Primary standards of absorbed dose for electron beams  

International Nuclear Information System (INIS)

The development of primary standards of absorbed dose for electron beams has lagged somewhat the development of photon beam standards. However, this has not limited the diversity of designs, or the range of applications. This review describes the state-of-the-art in electron beam standards as practised today in a number of primary standards laboratories and research institutions around the world. The devices detailed cover electron energies from 80 keV to 25 MeV and doses from 1 Gy to tens of kilo-gray, although the focus of the majority of research is on dosimetry for radiation therapy. (authors)

176

Absorbed Dose Distribution in a Pulse Radiolysis Optical Cell  

DEFF Research Database (Denmark)

When a liquid solution in an optical cell is irradiated by an intense pulsed electron beam, it may be important in the chemical analysis of the solution to know the distribution of energy deposited throughout the cell. For the present work, absorbed dose distributions were measured by thin radiochromic dye film dosimeters placed at various depths in a quartz glass pulse radiolysis cell. The cell was irradiated with 30 ns pulses from a field-emission electron accelerator having a broad spectrum with a maximum energy of ?MeV. The measured three-dimensional dose distributions showed sharp gradients in dose at the largest penetration depths in the cell and at the extreme lateral edges of the cell interior near the optical windows. This method of measurement was convenient because of the high spatial resolution capability of the detector and the linearity and absence of dose-rate dependence of its response.

Miller, Arne

1975-01-01

177

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

International Nuclear Information System (INIS)

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

178

The radiologist and angiographic procedures. Absorbed radiation dose.  

Science.gov (United States)

The radiation dose absorbed by the angiographer during angiographic procedures is of vital importance to the radiologist. Nevertheless, most articles on the subject are incomplete, and few measure gonadal dose. In this study, three TLDs were used for each of the following sites: radiologist's eyes, thyroid, gonads with and without shielding apron, and hands. The average dose during carotid angiograms was 2.6, 4.1, 0.4, 4.7, and 7.1 mrads to the eyes, thyroid, gonads with and without .5 mm of lead shielding, and hands, respectively. Average dose during abdominal and peripheral vascular angiographic procedures was 5.2, 7.5, 1.2, 8.5, and 39.9 mrads to the eyes, thyroid, gonads with and without shielding, and hands, respectively. A literature review demonstrates a significant reduction in radiation dose to the angiographer after the advent of automated injectors. Our measured doses for carotid angiography are compatible with contemporary reported values. There was poor correlation with fluoroscopy time and measured dose to the angiographer. PMID:3679765

Tryhus, M; Mettler, F A; Kelsey, C

1987-09-01

179

Absorbed dose by thyroid in case of nuclear accidents  

International Nuclear Information System (INIS)

Radioisotopes of iodine are produced in abundance in nuclear fission reactions, and great amounts of radioiodine may be released into the environment in case of a nuclear reactor accident. Thyroid gland is among the most radiosensitive organs due to its capacity to concentrate iodine. The aim of this work was to evaluate the importance of contributions of internally deposited iodines (131I, 132I, 133I, 134I and 135I) to the dose absorbed to thyroid follicle and to the whole organ, after internal contamination by those isotopes. For internal dose calculation, the code of particles transport MCNP4C was employed. The results showed that, in case of nuclear accidents, the contribution of short-lived iodines for total dose is about 45% for thyroid of newborn and about 40% for thyroid of adult. Thus, these contributions should not be neglected in a prospective evaluation of risks associated to internal contamination by radioactive iodine. (author)

180

[Can hand radiation absorbed dose from radiosynomicronvectomy be high?].  

Science.gov (United States)

Preparing and injecting radiopharmaceuticals containing beta emitting radionuclides, for radiosynovectomy (RS), implies the risk of exceeding the upper limit of skin and hand radiation absorbed dose, of 500 mSv/year to both technologists, who prepare and to doctors, who inject these radiopharmacuticals. A high number of RS treatments per day lack of effective radiation protection devices and skin contamination, increase the skin radiation absorbed dose. Pronounced dosimetric and radiation protection data for radionuclides used for RS, like yttrium-90, erbium-169, rhenium-186, dysprosium-165 and holmium-166, indicate the risk and the rationale for minimizing skin radiation doses to the hands of technologists and to doctors. Hands and skin radiation exposure is mainly due to direct beta radiation from yttrium-90 containing syringes. However skin contamination, may increase this dose independently of the radionuclide used for RS. Using a syringe shield with 5 mm perspex and holding the syringe by forceps, especially for the fixation of the needle to the syringe, beta radiation exposure to the finger tips may be reduced effectively. The use of radiation-resistant gloves reduces beta radiation dose to the skin only slightly, but offers a much better protection than Latex gloves for radioactive contamination. In this article we report measurements performed by us, underlining aspects of the most effective syringe shielding applied for RS. For reducing hands beta radiation exposure during RS the following are proposed: a) To use radiation protection devices, like manipulators and perspex syringe shields and b) Special training of the personnel for the proper handling of doses and for the removal of possible contamination from beta-emitting radionuclides and c) To use beta radiation personal ring dosimeters. PMID:17160165

Markou, Pavlos

2006-01-01

 
 
 
 
181

Estimation of absorbed organ doses and effective dose based on body mass index in digital radiography  

International Nuclear Information System (INIS)

With the introduction of digital radiography, patients undergoing radiographic procedures are subject to being overexposed to radiation. Therefore, it is necessary to estimate the absorbed organ dose and the effective dose, which are significant for patient health, along with body type. During chest radiographic examinations conducted in 899 patients for screening, the absorbed dose of the 13 major organs, the average whole-body dose, and two effective doses weighted by factors published in ICRP 60 and ICRP 103 were calculated on the basis of patient information such as height, weight and examination condition, including kilovolt potential, focus-skin distance and entrance surface dose (ESD), using a PC-based Monte Carlo program simulation. It was found that dose per unit ESD had a tendency to decrease with body mass index (BMI). In particular, the absorbed dose for most organs was larger at high voltages (140 kVp) than at low voltages (120 kVp, 100 kVp). In addition, the effective dose which was based on ICRP 60 and ICRP 103 also represented the same tendency in respect of BMI and tube voltage. (authors)

182

Use of a new breast phantom for dosimetric determination of incident air kerma and mean glandular dose in digital mammography system  

Energy Technology Data Exchange (ETDEWEB)

Mammography aims to achieve a high image quality associated with a dose in the patient as low as feasible. Values of average glandular dose, D{sub G}, can be obtained by means of two dosimetric methods: one based on the measurement of incident air kerma, K{sub i}, associated with tables of conversion factors that depend on the half value layer, the thickness and the glandular composition of the breast. And the one that makes the measure directly to thermoluminescent dosimeters, TLDs, placed in a new dosimetric phantom. Thus, this study aims to determine the incident air kerma (K{sub i}) and average glandular dose (D{sub G}) applied on patients in a digital mammography system (DR) using the phantom dosimetric developed. Another objective is to compare the results with the values of D{sub G} determined from K{sub i} and also with the values of K{sub i} and D{sub G} indicated in the examination of each patient by the digital mammography unit. The result of the average values measured in 77 patients with compressed breast thickness within the range of 5.5 cm and 6.5 cm, shows that the K{sub i} values ranged around 7.9% between the methods of action. The result of the values of D{sub G} ranged around 14.7% between the two methods of action. It is observed that the estimate of D{sub G} by the software is higher than the values measured with the dosimetric phantom. (author)

Coutinho, Celia M.C.; Almeida, Claudio D. de, E-mail: celia@ird.gov.b, E-mail: claudio@ird.gov.b [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil); Peixoto, Joao E., E-mail: joao.e.peixoto@uol.com.b [Instituto Nacional de Cancer (INCa/RJ), Rio de Janeiro, RJ (Brazil); Lopes, Ricardo T., E-mail: ricardo@lin.ufrj.b [Coordenacao dos Programas de Pos-graduacao de Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Nuclear

2009-07-01

183

The measurement of absorbed dose and dose-equivalent levels for in vivo neutron activation analysis  

International Nuclear Information System (INIS)

A dual-chamber dosimetric method together with microdosimetric measurements have been employed to characterise the mixed neutron-? radiation field of a d-T neutron activation facility. Central axis and patient axis air kerma levels are reported together with patient midline dose levels determined from phantom measurements. The ?-ray fraction of the total absorbed dose determined by the dual-chamber and microdosimetric method were found to be in agreement, within the estimated uncertainty limits. The free air measurements indicate a uniform kerma profile across the patient couch with a midpoint kerma rate of about 0.2 mGy min-1 and a ?-ray fraction of 14%. Phantom measurements yielded a patient midline total absorbed rate of about half this value and a ?-ray fraction of 27%. A mean neutron quality factor of 9.3 derived from microdosimetric measurements was assigned to the neutron absorbed dose. (author)

184

Calculation and measurements of absorbed dose in total body irradiation  

International Nuclear Information System (INIS)

A method which is simple, reliable, and rapid to use in clinical routine for basic dose calculation in total body irradiation (TBI) has ben tested with 8 MV X-rays. The dosimetry follows, as far as possible, national and international recommendations for conventional radiotherapy. The dose rate at different locations and depths is calculated from the absorbed dose rate at dose maximum for a phantom size of 30x30x30 cm in the TBI field (dD/dtc), an inverse square law factor (SAD2/SPD2), the tissue-maximum ratio (TMR), an equivalent phantom and patient size correction factor (A), a factor for lack of back-scattering material (B), an off-axis output correction factor (O), and a factor that corrects for off-axis variations in effective photon beam energy and for oblique beam penetration of the patient (R). The collimator opening is constant for all patient sizes. It is shown that TMR, A, B and R can be measured in conventional geometry in ordinary phantoms but at an extended distance, while dD/dtc, O and SAD2/SPD2 must be measured in TBI geometry. Tests in Humanoid phantoms showed an agreement in measured and planned AP/2 doses of 2% or better. If the calculation method is used for lower photon energies or in other TBI geometires it may be necessary to correct for the elliptical shape of the patient and for back-scattered radiation from the walls or floor. (orig.)

185

Which factors affect on Estimation of absorbed dose and effective dose?  

Directory of Open Access Journals (Sweden)

Full Text Available Introduction: Assessment of radiation dose is an important task in radiation protection dosimetry whereas absorbed and effective dose measurements directly in body organs are impossible. So Monte Carlo simulations is necessary to estimate radiation dose. The method of dose calculation, the body model and the computational code can be mentioned as three main factors that have an affect on dosimetric quantities. The aim of this study is the determination of the above factors influence on the absorbed dose and effective dose evaluation. For this purpose different comparisons between the mathematical and the voxel phantoms were done. Methods: ORNL modified adult phantom is the mathematical phantom which is described by Cristy and Eckerman in 1987. This phantom is utilized for calculation of the absorbed dose. The effective dose is calculated according to the manner which is introduced in the ICRP reported 60 and 103. Results: All of the doses Evaluation have an uncertainty less than 0.5%. MCNPX code and ORNL modified adult phantom are applied for the dose assessment in the energy range 10-9 - 20 MeV, under AP, PA, RLAT, LLAT, ROT and ISo irradiation conditions. The results are then normalized to the unit of neutron fluence. The calculated absorbed dose was compared with ICRP74 data in 9 organs and with Bozkurt et al data in 18 organs. The effective dose was calculated for whole body. Then these data were compared with results of a mathematical phantom and some voxel models in different irradiation geometries. Conclusion: Although the absorbed dose results of ORNL show fewer differences with ICRP data than Bozkurt et al data, one can deduce neither complete agreement nor disparity between the ORNL data and the other two data sets. Totally 73% of the ORNL data in comparison with MIRD data and 48% of data in comparison with VIP_MAN results have difference less than 15%. Comparison of the ORNL effective dose with some male and female voxel phantoms (TARA, HANAKO, GSF, VIP_MAN and an analytical model (MIRD show that the changing of body model and computational code have few influence (less than 15% on the effective dose results. But changing of wR and wT parameters have a significant effect on the results so that the largest discrepancies are about 100% on some data

Keyhandokht Karimi Shahri

2010-10-01

186

Computerized manual for the evaluation of radiation absorbed dose from mammary glands during mammography  

International Nuclear Information System (INIS)

The computerized transletion of ''Handbook of glandular tissue doses in mammography'' (HHS publication FDA 85-8239) is presented. It is registered on floppy disk and suitable for use in MS DOS on IBM personal computer, Olivetti or compatible. The manual collects data published by many autors and suggests a method to estimate the dose released to the glandular tissue (considered at risk for breast cancer) in the most commonly used conditions for mammography. Basied translation manual, the program helds an algorhythm developed by the authors, which allows the dose to the glandular tissue to be evaluated, given the following data: 1)projection: craniocaudal or mediolateral; 2)compression level:firm or moderate; 3)breast size: small, medium or large; 4)breast composition: percentage of glandular tissue content (by weight); X-ray beam quality: HVL mm Al. The algorhythm is obtained from a bidimensional fit of the original data and is based on the terms contained in the manual. The program flow is guided by menus that make the procedure suitable for unexperienced operators too, both for consulting and printing and for computing program

187

Referent 3D solid tumour model and absorbed dose calculations at cellular level in radionuclide therapy  

International Nuclear Information System (INIS)

adii. Absorbed doses of cells and spatial distributions of the absorbed doses in the referent 3D solid tumour were calculated for radionuclides I-131 and Y-90. Dose scintigram or voxel presentation of absorbed dose distributions showed higher homogeneity for Y-90 than for I-131. A differential dose volume histogram, or spectrum, of the relative absorbed dose of cells, was much closer to the average absorbed dose of the tumour for Y-90 than I-131. An accumulated dose volume histogram showed that most tumour cells received a lower dose than average, or prescribed, tumour absorbed dose. Those discrepancies between conventional and cellular approach show that dosimetry on the cellular level is necessary for a better selection of the radionuclide and optimal calculation of administered activity in the radionuclide therapy. (author)

188

Absorbed dose determination in photon fields using the tandem method  

International Nuclear Information System (INIS)

The purpose of this work is to develop an alternative method to determine the absorbed dose and effective energy of photons with unknown spectral distributions. It includes a 'tandem' system that consists of two thermoluminescent dosemeters with different energetic dependence. LiF: Mg, Ti, CaF2: Dy thermoluminescent dosemeters and a Harshaw 3500 reading system are employed. Dosemeters are characterized with 90Sr-90Y, calibrated with the energy of 60Co and irradiated with seven different qualities of x-ray beams, suggested by ANSI No. 13 and ISO 4037. The answers of each type of dosemeter are adjusted to a function that depends on the effective energy of photons. The adjustment is carried out by means of the Rosenbrock minimization algorithm. The mathematical model used for this function includes five parameters and has a gauss and a straight line. Results show that the analytical functions reproduce the experimental data of the answers, with a margin of error of less than 5%. The reason of the answers of the CaF2: Dy and LiF: Mg, Ti, according to the energy of the radiation, allows us to establish the effective energy of photons and the absorbed dose, with a margin of error of less than 10% and 20% respectively

189

Absorbed dose in the presence of contrast agents during pediatric cardiac catheterization  

International Nuclear Information System (INIS)

Administration of x-ray contrast agents during heart catheterization examination increases the absorbed radiation dose in tissue. To estimate the dose absorbed by the blood of children undergoing diagnostic heart catheterization and angiocardiography, a number of measurements and calculations were conducted including entrance and exit exposures to the patient. A dose enhancement factor and a mean absorbed dose to the patient's blood were calculated. For eight pediatric patients monitored, absorbed doses to the blood ranged between 3 and 12 rad. These values were two to three times greater than the expected dose without administration of a contrast agent

190

Absorbed dose measurements of insulating material for TRISTAN magnets by IR spectrometry  

International Nuclear Information System (INIS)

Absorbed dose measurements of the insulating material for 29GeV TRISTAN Main-Ring magnets were carried out with the Infrared spectrometry. From the fact that carbonyl radical is induced in epoxy resin by irradiation, infrared absorbance in the range of 1705-1720 cm-1 due to carbonyl radicals was applied to the estimations of the absorbed dose of the epoxy resin. Relationship between absorbance of carbonyl band and absorbed dose was investigated exposing the epoxy resin in two irradiation fields, TRISTAN MR and irradiation facility of 3kCi 60Co source. From this work, it was found that IR absorbance method could be applied to the absorbed dose measurements from 103 to 107 Gy and that absorbed doses obtained from 31 specimens of epoxy resin shaved from coils of TRISTAN MR magnets had a distribution extending from 2.6 x 103 to 1.07 x 107 Gy, mostly order of 104 to 105 Gy. (author)

191

Determination of the Absorbed Doses in Shanks of Interventional Radiologists  

International Nuclear Information System (INIS)

Complicated procedures of interventional radiology require usually a much longer investigation time, comparing to the conventional radiography. Moreover, interventional radiology procedures require the presence of the medical staff next to the patient in order to perform the procedure. This results in higher risk for health professionals. Even though these persons reasonably keep away from the primary X ray beam, they are under the effects of scatter radiation due to the interaction of the primary beam with the patient. The protection aprons, thyroid protectors and shielding glasses are used in order to minimize the doses for the staff, but lower parts of legs remain usually unprotected and the absorbed doses in shanks are not recorded. The paper presents the measured values of the absorbed dose in lower extremities of medical staff, involved in the procedures of interventional radiology, completed with the measurements of air kerma under the patient table. Measurements were performed in one of big hospitals in Warsaw during all the procedures performed in six weeks. Majority of the procedures constituted angioplasty or angioplasty with vascular stenting, uterine fibroid embolization and cholangiography. In the angioplasty procedure, imaging techniques are used to guide a balloon-tipped catheter into an artery and advance it to where the vessel is narrow or blocked. The balloon is then inflated to open the vessel, deflated and removed. In vascular stenting, which is often performed with angioplasty, a small wire mesh tube (a stent) is permanently placed in the newly opened artery to help it remain open. In a uterine fibroid embolization procedure, the image guidance is used in order to place an embolic agent (synthetic material) inside one or more of the blood vessels that supply the fibroid tumors with blood. As a result, these vessels become occluded, or closed off, and the fibroid tissue shrinks. Percutaneous transhepatic cholangiography is a way of examining the bile duct system in the liver. During the exam, a thin needle is inserted through the skin (percutaneous) and through the liver (transhepatic) into a bile duct. Then dye is injected, and the bile duct system is outlined on x-rays. Our measurements consist of three parts: Measurements of kerma in air, under the patient table, in dependence on the dose rate and the distance from the X-ray tube, along the table; Measurements of kerma in air under the table during real interventions and comparison with the DAP values; measurements of the individual doses in shanks of medical personnel, using TLD dosemeters

192

Influence of radioactive contaminants on absorbed dose estimates for radiopharmaceuticals  

International Nuclear Information System (INIS)

Several popular radiopharmaceutical products contain low levels of radioactive contaminants. These contaminants increase the radiation absorbed dose to the patient without any increased benefit and, in some cases, with a decrease in image quality. The importance of a contaminant to the radiation dosimetry picture is a function of (1) the contaminant level, (2) the physical half-life of the contaminant, (3) the organ uptake and the biological half-time of the contaminant in the various body systems, and (4) the decay mode, energy, etc. of the contaminant. The general influence of these parameters is discussed in this paper; families of curves are included that reflect the changing importance of contaminant dosimetry with respect to the primary radionuclide as a function of these variables. Several specific examples are also given of currently used radiopharmaceutical products which can contain radioactive contaminants (I-123, In-111, Tl-201, Ir-191m, Rb-82, Au-195m). 7 refs., 8 figs., 4 tabs

193

Absorbed dose determination with plane-parallel chambers.  

Science.gov (United States)

According to IAEA TRS 398 recommendations the determination of absorbed dose with plane-parallel ionisation chambers calibrated in terms of N(K,Q0) can be done using N(D,W,Q0) = (M(Q0)(free air)/M(Q0)(surface)) N(K,Q0)B[(mu(en)/rho)(W,air)](free air) P(Q0). This equation takes into account only the scattering from the stem of the soft ionisation chamber, not the total scattering published in the scientific literature. That makes it difficult to perform dosimetry with field sizes different from those used in the standardisation laboratory to calibrate the chamber. This paper describes a method to calculate D(W,Q0) by using either N(K,Q0) or N(D,W,Q0) for different radiation field sizes. PMID:14690331

Austerlitz, C

2003-01-01

194

Absorbed dose determination with plane-parallel chambers  

International Nuclear Information System (INIS)

According to IAEA TRS 398 recommendations the determination of absorbed dose with plane-parallel ionisation chambers calibrated in terms of NK,Q0 can be done using ND,W,Q0 (MQ0freeair/MQ0surface) NK,Q0[(?en/rho)w,air]Q0freeairP. This equation takes into account only the scattering from the stem of the soft ionisation chamber, not the total scattering published in the scientific literature. That makes it difficult to perform dosimetry with field sizes different from those used in the standardisation laboratory to calibrate the chamber. This paper describes a method to calculate DW,Q0 by using either NK,Q0 or ND,W,Q0 for different radiation field sizes. (author)

195

Dose absorbed in adults and children thyroid due to the I{sup 123} using the dosimetry MIRD and Marinelli; Dosis absorbida en tiroides de adultos y ninos debido al I{sup 123} utilizando las dosimetrias MIRD y Marinelli  

Energy Technology Data Exchange (ETDEWEB)

Using the dosimetry MIRD, and representation Cristy-Eckerman in the thyroid gland and organs of their bio-kinetics when I{sup 123} (Iodine) is used, the study demonstrates that the absorbed dose by the gland of an adult, children, and newly born, is their auto-dose, independent of the compartments number of their bio-kinetics. The dosimetric contributions of the organs of their bio-kinetics are insignificant. Their results are not significantly different to those obtained by the formalism MARINELLI (auto-dose) when it uses a sphere like glandular representation. In consequence, the kinetic model corresponding to the glandular representation decreases to a compartment, where the gland can also be represented like a sphere. (Author)

Vasquez, M.; Castillo, C.; Cabrera, C.; Sarachaga, R.; Castaneda, J. [Universidad Nacional de Trujillo, Av. Juan Pablo II s/n, Ciudad Universitaria, Trujillo (Peru); Diaz, E., E-mail: marvva@hotmail.com [Universidade Federal do Rio Grande do Sul, Av. Paulo Gamma 110, Bairro Farropilhas, Porto Alegre, RS 90040-060 (Brazil)

2014-08-15

196

Scaling neutron absorbed dose distributions from one medium to another  

Energy Technology Data Exchange (ETDEWEB)

Central axis depth dose (CADD) and off-axis absorbed dose ratio (OAR) measurements were made in water, muscle and whole skeletal bone TE-solutions, mineral oil and glycerin with a clinical neutron therapy beam. These measurements show that, for a given neutron beam quality and field size, there is a universal CADD distribution at infinity if the depth in the phantom is expressed in terms of appropriate scaling lengths. These are essentially the kerma-weighted neutron mean free paths in the media. The method used in ICRU No. 26 to scale the CADD by the ratio of the densities is shown to give incorrect results. the OAR's measured in different media at depths proportional to the respective mean free paths were also found to be independent of the media to a good approximation. It is recommended that relative CADD and OAR measurements be performed in water because of its universality and convenience. A table of calculated scaling lengths is given for various neutron energy spectra and for various tissues and materials of practical importance in neutron dosimetry.

Awschalom, M.; Rosenberg, I.; Ten Haken, R.K.

1982-11-01

197

Concentration factors and absorbed doses of Sr-90 and Cs-137 in the Sava river fishes  

International Nuclear Information System (INIS)

The concentration factors and the absorbed doses for Sr-90 and Cs-137 in certain species of fish from the Sava river have been determined. Knowing the concentration factor for fish/water relation and the absorbed doses for fishes provides the possibility of determining the doses of radiation in the water-fish-human being system. (author)

198

Measurement of absorbed dose received by people subjected to chest X-rays  

International Nuclear Information System (INIS)

A first set of measurements of the absorbed dose received by people subjected to chest X-rays was undertaken with a view to comparing the values obtained by radiophotographic and standard methods respectively. Since the radiophotographic absorbed dose values appeared too high the different working parameters were reviewed; the new measurements have shown a gain of a factor 10 on the absorbed dose received by a 'standard' 70-kg man, the quality of image remaining acceptable

199

The realization of the unit of absorbed dose at the Austrian dosimetry laboratory Seibersdorf  

International Nuclear Information System (INIS)

The absorbed dose primary standard of the BEV is a graphite calorimeter. Two methods are employed for the conversion of absorbed dose to graphite into absorbed dose to water: calculation on the one hand and the use of an ionization chamber in combination with cavity theory on the other hand. The two methods are described, details of experimental work are given and results of international comparisons are presented. (author)

200

'In vivo' average glandular dose evaluation: One-to-one comparison between digital breast tomosynthesis and full-field digital mammography  

International Nuclear Information System (INIS)

We analysed 300 patients X rayed with digital breast tomosynthesis (DBT), full-field digital mammography (FFDM) and 'COMBO' (single view both in FFDM and DBT in a single breast compression)-Hologic Selenia Dimension-W/Rh-Ag- Al: three different anode-filter combinations-automatic exposure control modalities. Examination parameter data collection (EPDC) and 'in vivo' dosimetry using metal oxide semiconductor field effect transistor (MOSFET) were utilised to determine and compare entrance skin air kerma (ESAK) and average glandular dose (AGD) from a radioprotection viewpoint in the DBT and COMBO modalities. MOSFET has been tested to be introduced in clinical routine. EPDC of DBT underlines increase in ESAK and AGD compared with FFDM (p 15 %. DBT increases ESAK and AGD, due to the 3D acquisition modality. MOSFET may be considered in DBT as a routine check. (authors)

 
 
 
 
201

Scaling neutron absorbed dose distributions from one medium to another  

International Nuclear Information System (INIS)

Central axis depth dose (CADD) and off-axis absorbed dose ratio (OAR) measurements were made in water, muscle and whole skeletal bone tissue-equivalent (TE) solutions, mineral oil, and glycerin with a clinical neutron therapy beam. These measurements show that, for a given neutron beam quality and field size, there is a universal CADD distribution at infinity if the depth in the phantom is expressed in terms of appropriate scaling lengths. These are essentially the kerma-weighted neutron mean free paths in the media. The method used in ICRU Report No. 26 to scale the CADD by the ratio of the densities is shown to give incorrect results. The OARs measured in different media at depths proportional to the respective mean free paths were also found to be independent of the media to a good approximation. Therefore, neutron beam CADDs and OARs may be measured in either TE solution (USA practice) or water (European practice), and having determined the respective scaling lengths, all measurements may be scaled from one medium to any other. It is recommended that for general treatment planning purposes, scaling be made to TE muscle with a density of 1.04 g cm-3, since this value represents muscle and other soft tissues better than TE solution of density 1.07 g cm-3. For such a transformation, relative measurements made in water are found to require very small corrections. Hence, it is further recommended that relative CADD and OAR measurements be performetive CADD and OAR measurements be performed in water because of its universality and convenience. Finally, a table of calculated scaling lengths is given for various neutron energy spectra and for various tissues and materials of practical importance in neutron dosimetry

202

Dose conversion for the BIPM graphite calorimeter standard for absorbed dose to water  

International Nuclear Information System (INIS)

The existing standard for absorbed dose to water in 60Co gamma radiation at the BIPM is a parallel-plate cavity ionization chamber. The present paper describes a new standard for use in 60Co and in accelerator photon beams based on a graphite calorimeter. The realization of the standard can be divided into three major stages: a measurement of the specific heat capacity of the graphite used for the calorimeter construction; the design and construction of the graphite calorimeter itself; the conversion from the mean graphite absorbed dose to the calorimeter core, Dc, to the absorbed dose to water at the reference point in a water phantom, Dw. The dose conversion makes use of the Monte Carlo code PENELOPE and experimental measurements using a transfer ionization chamber tailored to the specific needs of the dose conversion. Results and uncertainties. Results for Cw,c will be presented for the reference 60Co beam at the BIPM. In the context of a programme of key comparisons of Dw standards for high-energy photon beams, the new standard was transported to the accelerators of the NRC in June 2009 and the PTB in March 2010, and is scheduled to be used at the NIST in September 2010. Results will be presented for these beams, evaluated using phase-space information supplied by each laboratory. A detailed analysis has addressed uncertainties associated with simulated geometries, radiation transport meculated geometries, radiation transport mechanics, interaction coefficients and phase-space spectra. The results suggest a standard uncertainty for Cw,c below 0.25 %. Additionally, in connection with the comparison at the NRC, calculations of Cw,c for the BIPM standard were made by the NRC using the EGSnrc code. Agreement between the BIPM and NRC calculations at the 0.2 % level strongly supports the uncertainty analysis and the view that the symmetry of the method results in a low sensitivity to the details of the Monte Carlo calculations

203

Absorbed dose determination with plane-parallel chambers  

Energy Technology Data Exchange (ETDEWEB)

According to IAEA TRS 398 recommendations the determination of absorbed dose with plane-parallel ionisation chambers calibrated in terms of N{sub K},Q{sub 0} can be done using N{sub D},W,Q{sub 0} (M{sub Q0}{sup freeair}/M{sub Q0}{sup surface}) N{sub K,}Q{sub 0}[({mu}{sub en}/rho)w,{sub air}]{sub Q0}{sup freeair}P. This equation takes into account only the scattering from the stem of the soft ionisation chamber, not the total scattering published in the scientific literature. That makes it difficult to perform dosimetry with field sizes different from those used in the standardisation laboratory to calibrate the chamber. This paper describes a method to calculate D{sub W,Q0} by using either N{sub K,Q0} or N{sub D,W,Q0} for different radiation field sizes. (author)

Austerlitz, C

2003-07-01

204

Absorbed dose determination in photon fields using the tandem method  

CERN Document Server

The purpose of this work is to develop an alternative method to determine the absorbed dose and effective energy of photons with unknown spectral distributions. It includes a 'tandem' system that consists of two thermoluminescent dosemeters with different energetic dependence. LiF: Mg, Ti, CaF sub 2 : Dy thermoluminescent dosemeters and a Harshaw 3500 reading system are employed. Dosemeters are characterized with sup 9 sup 0 Sr- sup 9 sup 0 Y, calibrated with the energy of sup 6 sup 0 Co and irradiated with seven different qualities of x-ray beams, suggested by ANSI No. 13 and ISO 4037. The answers of each type of dosemeter are adjusted to a function that depends on the effective energy of photons. The adjustment is carried out by means of the Rosenbrock minimization algorithm. The mathematical model used for this function includes five parameters and has a gauss and a straight line. Results show that the analytical functions reproduce the experimental data of the answers, with a margin of error of less than ...

Marques-Pachas, J F

1999-01-01

205

Calibration procedure for thermoluminescent dosemeters in water absorbed doses for Iridium-192 high dose rate sources  

International Nuclear Information System (INIS)

Thermoluminescent dosimeters are used in brachytherapy services quality assurance programs, with the aim of guaranteeing the correct radiation dose supplied to cancer patients, as well as with the purpose of evaluating new clinical procedures. This work describes a methodology for thermoluminescent dosimeters calibration in terms of absorbed dose to water for 192Ir high dose rate sources. The reference dose used is measured with an ionization chamber previously calibrated for 192Ir energy quality, applying the methodology proposed by Toelli. This methodology aims to standardizing the procedure, in a similar form to that used for external radiotherapy. The work evolves the adaptation of the TRS-277 Code of the International Atomic Energy Agency, for small and big cavities, through the introduction for non-uniform experimental factor, for the absorbed dose in the neighborhood of small brachytherapy sources. In order to simulate a water medium around the source during the experimental work, an acrylic phantom was used. It guarantees the reproducibility of the ionization chamber and the thermoluminescent dosimeter's location in relation to the radiation source. The values obtained with the ionization chamber and the thermoluminescent dosimeters, exposed to a 192Ir high dose rate source, were compared and correction factors for different source-detector distances were determined for the thermoluminescent dosimeters. A numeric function was generated relating the correction factors and the source-detector distance. These correction factors are in fact the thermoluminescent dosimeter calibration factors for the 192Ir source considered. As a possible application of this calibration methodology for thermoluminescent dosimeters, a practical range of source-detector distances is proposed for quality control of 192Ir high dose rate sources. (author)

206

Radiochromic Plastic Films for Accurate Measurement of Radiation Absorbed Dose and Dose Distributions  

DEFF Research Database (Denmark)

Thin radiochromic dye films are useful for measuring large radiation absorbed doses (105–108 rads) and for high-resolution imaging of dose patterns produced by penetrating radiation beams passing through non-homogeneous media. Certain types of amino-substituted triarylmethane cyanides dissolved in polymeric solutions can be cast into flexible free-standing thin films of uniform thickness and reproducible response to ultraviolet and ionizing radiation. The increase in optical density versus energy deposited by radiation is linear over a wide range of doses and is for practical purposes independent of dose rate (1–1014 rad s?1). Upon irradiation of the film, the profile of the radiation field is registered as a permanent colored image of the dose distribution. Unlike most other types of dyed plastic dose meters, the optical density produced by irradiation is in most cases stable for periods of at least one year. Methods have been developed for casting various types of thin radiochromic plastic films and combinations of plastics (cellulose acetate, polyvinyl butyral, polyvinyl acetate, polyvinyl pyrrolidone and polyvinyl chloride) having radiation absorption characteristics corresponding to those of many polymeric systems in industrial radiation processing. The result is that errors due to energy dependence of response of the radiation sensor are effectively reduced, since the spectral sensitivity of the dose meter matches that of the polymer of interest, over a wide range of photon and electron energies (0.01–10 MeV).

Miller, Arne; Pedersen, Walther Batsberg

1977-01-01

207

Blood compounds irradiation process: assessment of absorbed dose using Fricke and Thermoluminescent dosimetric systems  

Energy Technology Data Exchange (ETDEWEB)

The assessment of gamma absorbed doses in irradiation facilities allows the quality assurance and control of the irradiation process. The liability of dose measurements is assign to the metrological procedures adopted including the uncertainty evaluation. Fricke and TLD 800 dosimetric systems were used to measure absorbed dose in the blood compounds using the methodology presented in this paper. The measured absorbed doses were used for evaluating the effectiveness of the irradiation procedure and the gamma dose absorption inside the irradiation room of a gamma irradiation facility. The radiation eliminates the functional and proliferative capacities of donor T-lymphocytes, preventing Transfusion associated graft-versus-host disease (TA-GVHD), a possible complication of blood transfusions. The results show the applicability of such dosimetric systems in quality assurance programs, assessment of absorbed doses in blood compounds and dose uniformity assign to the blood compounds irradiation process by dose measurements in a range between 25 Gy and 100 Gy. (author)

Soares, Gabriela de Amorim; Squair, Peterson Lima; Pinto, Fausto Carvalho; Belo, Luiz Claudio Meira; Grossi, Pablo Andrade [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN-CNEN/MG), Belo Horizonte, MG (Brazil)], e-mail: gas@cdtn.br, e-mail: pls@cdtn.br, e-mail: fcp@cdtn.br, e-mail: lcmb@cdtn.br, e-mail: pabloag@cdtn.br

2009-07-01

208

X-ray absorbed doses evaluation on patients under radiological studies  

International Nuclear Information System (INIS)

The skin absorbed doses were evaluated on patient submitted to the following x-ray exams : chest, facial sinus, lumbar spine. Thermoluminescent dosimetry was used and a variety of irradiation techniques performed. The results shown considerable differences on the absorbed dose for the various alternative technical conditions

209

Uncertainty analysis for absorbed dose from a brain receptor imaging agent  

Energy Technology Data Exchange (ETDEWEB)

Absorbed dose estimates are known to contain uncertainties. A recent literature search indicates that prior to this study no rigorous investigation of uncertainty associated with absorbed dose has been undertaken. A method of uncertainty analysis for absorbed dose calculations has been developed and implemented for the brain receptor imaging agent {sup 123}I-IPT. The two major sources of uncertainty considered were the uncertainty associated with the determination of residence time and that associated with the determination of the S values. There are many sources of uncertainty in the determination of the S values, but only the inter-patient organ mass variation was considered in this work. The absorbed dose uncertainties were determined for lung, liver, heart and brain. Ninety-five percent confidence intervals of the organ absorbed dose distributions for each patient and for a seven-patient population group were determined by the ``Latin Hypercube Sampling`` method. For an individual patient, the upper bound of the 95% confidence interval of the absorbed dose was found to be about 2.5 times larger than the estimated mean absorbed dose. For the seven-patient population the upper bound of the 95% confidence interval of the absorbed dose distribution was around 45% more than the estimated population mean. For example, the 95% confidence interval of the population liver dose distribution was found to be between 1.49E+0.7 Gy/MBq and 4.65E+07 Gy/MBq with a mean of 2.52E+07 Gy/MBq. This study concluded that patients in a population receiving {sup 123}I-IPT could receive absorbed doses as much as twice as large as the standard estimated absorbed dose due to these uncertainties.

Aydogan, B.; Miller, L.F. [Univ. of Tennessee, Knoxville, TN (United States). Nuclear Engineering Dept.; Sparks, R.B. [Oak Ridge Inst. for Science and Education, TN (United States); Stubbs, J.B. [Radiation Dosimetry Systems of Oak Ridge, Inc., Knoxville, TN (United States)

1999-01-01

210

[Absorbed doses and hematological shifts in dogs inhaling submicron 239Pu dioxide].  

Science.gov (United States)

In dogs breathing submicron 239Pu dioxide, the absorbed doses were determined in 12 organs and tissues where the radionuclide was deposited; the integral doses to a whole body were also determined by the sum of the exposed organs. The relationship of the hematologic changes not only with the doses for "critical" tissues but also with the integral dose was studied. PMID:3615815

Kalmykova, Z I; Oslina, I V; Buldakov, L A; Kharunzhin, V V; Sokolova, S N

1987-01-01

211

SADDE (Scaled Absorbed Dose Distribution Evaluator): A code to generate input for VARSKIN  

International Nuclear Information System (INIS)

The VARSKIN computer code has been limited to the isotopes for which the scaled absorbed dose distributions were provided by the Medical Internal Radiation Dose (MIRD) Committee or to data that could be interpolated from isotopes that had similar spectra. This document describes the methodology to calculate the scaled absorbed dose distribution data for any isotope (including emissions by the daughter isotopes) and its implementation by a computer code called SADDE (Scaled Absorbed Dose Distribution Evaluator). The SADDE source code is provided along with input examples and verification calculations. 10 refs., 4 figs

212

Determination of absorbed dose to the lens of eye from external sources  

International Nuclear Information System (INIS)

The methods of determining absorbed dose distributions in human eyeball by means of the experiments and available theories have been reported. A water phantom was built up. The distributions of beta dose were measured by an extrapolation ionization chamber at some depths corresponding to components of human eyeball such as cornea, sclera, anterior chamber and the lens of eye. The ratios among superficial absorbed dose (at 0.07 mm) and average absorbed doses at the depths 1,2,3 mm are obtained. They can be used for confining the deterministic effects of superficial tissues and organs such as the lens of eye for weakly penetrating radiations

213

Assessment of out-of-field absorbed dose and equivalent dose in proton fields  

Energy Technology Data Exchange (ETDEWEB)

Purpose: In proton therapy, as in other forms of radiation therapy, scattered and secondary particles produce undesired dose outside the target volume that may increase the risk of radiation-induced secondary cancer and interact with electronic devices in the treatment room. The authors implement a Monte Carlo model of this dose deposited outside passively scattered fields and compare it to measurements, determine the out-of-field equivalent dose, and estimate the change in the dose if the same target volumes were treated with an active beam scanning technique. Methods: Measurements are done with a thimble ionization chamber and the Wellhofer MatriXX detector inside a Lucite phantom with field configurations based on the treatment of prostate cancer and medulloblastoma. The authors use a GEANT4 Monte Carlo simulation, demonstrated to agree well with measurements inside the primary field, to simulate fields delivered in the measurements. The partial contributions to the dose are separated in the simulation by particle type and origin. Results: The agreement between experiment and simulation in the out-of-field absorbed dose is within 30% at 10-20 cm from the field edge and 90% of the data agrees within 2 standard deviations. In passive scattering, the neutron contribution to the total dose dominates in the region downstream of the Bragg peak (65%-80% due to internally produced neutrons) and inside the phantom at distances more than 10-15 cm from the field edge. The equivalent doses using 10 for the neutron weighting factor at the entrance to the phantom and at 20 cm from the field edge are 2.2 and 2.6 mSv/Gy for the prostate cancer and cranial medulloblastoma fields, respectively. The equivalent dose at 15-20 cm from the field edge decreases with depth in passive scattering and increases with depth in active scanning. Therefore, active scanning has smaller out-of-field equivalent dose by factors of 30-45 in the entrance region and this factor decreases with depth. Conclusions: The dose deposited immediately downstream of the primary field, in these cases, is dominated by internally produced neutrons; therefore, scattered and scanned fields may have similar risk of second cancer in this region. The authors confirm that there is a reduction in the out-of-field dose in active scanning but the effect decreases with depth. GEANT4 is suitable for simulating the dose deposited outside the primary field. The agreement with measurements is comparable to or better than the agreement reported for other implementations of Monte Carlo models. Depending on the position, the absorbed dose outside the primary field is dominated by contributions from primary protons that may or may not have scattered in the brass collimating devices. This is noteworthy as the quality factor of the low LET protons is well known and the relative dose risk in this region can thus be assessed accurately.

Clasie, Ben; Wroe, Andrew; Kooy, Hanne; Depauw, Nicolas; Flanz, Jay; Paganetti, Harald; Rosenfeld, Anatoly [Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114 (United States); Department of Radiation Medicine, Loma Linda University Medical Center, Loma Linda, California 92354 (United States) and Centre for Medical Radiation Physics, University of Wollongong, Wollongong, New South Wales, 2522 (Australia); Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114 (United States); Centre for Medical Radiation Physics, University of Wollongong, Wollongong, New South Wales, 2522 (Australia)

2010-01-15

214

Determination of absorbed x-ray dose and dose distribution in layers during radiostimulation of plant tissues  

International Nuclear Information System (INIS)

The influence of the material composition of irradiated medium and of the spectral distribution of irradiation on absorbed doses in plant tissues were investigated using x-radiation with maximum energy of 200 keV. It was shown that the ratios of absorbed doses in tissue layers achieved the value of 5-6 which may lead to obscuring the stimulation response reactions. Mean dose/medium dose quotient and dose inhomogeneity quotient were introduced. Finally, it is stated that knowledge of the spectra of the radiation source and of the elemental composition of the irradiated medium is essential for the determination of quantitative relations. (author)

215

Monte Carlo simulation of absorbed dose in quartz from beta rays  

International Nuclear Information System (INIS)

The absorbed dose in quartz samples irradiated by ? rays in TL or OSL dating protocol was simulated using the EGSnrc /DOSRZnrc code. Effects of thickness and grain size of the quartz samples on the absorbed dose were evaluated with the samples of ?0.97 cm x (10-500) ?m, in grain size of 60-300 ?m. The results show that the absorbed dose in quartz is relative to the sample thickness, and the maximum difference of the relative dose can be up to 10%. The absorbed dose is relative to the grain size, too. The relative dose increases with decreasing grain size, and the maximum difference can be up to 19%. These factors should be considered in the dating. (authors)

216

Conversion of ionization measurements to radiation absorbed dose in non-water density material.  

Science.gov (United States)

The radiation absorbed dose to non-water equivalent materials of interest in radiotherapy is the dose to lung and the dose to bone. The measurement and calculation of dose to the lung has been of great interest and much effort has gone into the development of accurate lung dose calculation methods. The radiation absorbed dose to the bone is usually not calculated and most absorbed dose calculations have been done without correcting for the presence of bone. For the lower megavoltage photon beams this may be appropriate, however, as the energy of the photon beam increases, the region of electronic disequilibrium becomes larger and pair production which depends on the atomic number of the material becomes significant. Therefore the bone will produce greater perturbations of the dose distribution. The dose to lung-equivalent material is uniquely obtained from ionization measurements. However, in bone-equivalent materials two different calculations of absorbed dose are possible: the absorbed dose to soft tissue plastic (polystyrene) within bone-equivalent material and the dose to the bone-equivalent material itself. Both can be calculated from ionization measurements in phantoms. These two calculations result in significantly different doses in a heterogeneous phantom composed of polystyrene and aluminium (a bone substitute). The dose to a thin slab of polystyrene in aluminium is much higher than the dose to the aluminium itself at the same depth in the aluminium. Monte Carlo calculations confirm that the calculation of dose to polystyrene in aluminium can be accurately carried out using existing dosimetry protocols. However, the conversion of ionization measurements to absorbed dose to high atomic number materials cannot be accurately carried out with existing protocols and appropriate conversion factors need to be determined. PMID:1438563

el-Khatib, E; Connors, S

1992-11-01

217

Mean glandular dose estimation using MCNPX for a digital breast tomosynthesis system with tungsten/aluminum and tungsten/aluminum+silver x-ray anode-filter combinations  

International Nuclear Information System (INIS)

Breast cancer screening with x-ray mammography, using one or two projection images of the breast, is an indispensible tool in the early detection of breast cancer in women. Digital breast tomosynthesis (DBT) is a 3D imaging technique that promises higher sensitivity and specificity in breast cancer screening at a similar radiation dose to conventional two-view screening mammography. In DBT a 3D volume is reconstructed with anisotropic voxels from a limited number of x-ray projection images acquired over a limited angle. Although the benefit of early cancer detection through screening mammography outweighs the potential risks associated with radiation, the radiation dosage to women in terms of mean glandular dose (MGD) is carefully monitored. This work studies the MGD arising from a prototype DBT system under various parameters. Two anode/filter combinations (W/Al and W/Al+Ag) were investigated; the tube potential ranges from 20 to 50 kVp; and the breast size varied between 4 and 10 cm chest wall-to-nipple distance and between 3 and 7 cm compressed breast thickness. The dosimetric effect of breast positioning with respect to the imaging detector was also reviewed. It was found that the position of the breast can affect the MGD by as much as 5% to 13% depending on the breast size.

218

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  

Energy Technology Data Exchange (ETDEWEB)

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.

Dong, S.L.; Chu, T.C.; Lee, J.S.; Lan, G.Y.; Wu, T.H.; Yeh, Y.H.; Hwang, J.J. E-mail: jjhwang@ym.edu.tw

2002-12-01

219

Mean glandular dose estimation using MCNPX for a digital breast tomosynthesis system with tungsten/aluminum and tungsten/aluminum+silver x-ray anode-filter combinations  

Energy Technology Data Exchange (ETDEWEB)

Breast cancer screening with x-ray mammography, using one or two projection images of the breast, is an indispensible tool in the early detection of breast cancer in women. Digital breast tomosynthesis (DBT) is a 3D imaging technique that promises higher sensitivity and specificity in breast cancer screening at a similar radiation dose to conventional two-view screening mammography. In DBT a 3D volume is reconstructed with anisotropic voxels from a limited number of x-ray projection images acquired over a limited angle. Although the benefit of early cancer detection through screening mammography outweighs the potential risks associated with radiation, the radiation dosage to women in terms of mean glandular dose (MGD) is carefully monitored. This work studies the MGD arising from a prototype DBT system under various parameters. Two anode/filter combinations (W/Al and W/Al+Ag) were investigated; the tube potential ranges from 20 to 50 kVp; and the breast size varied between 4 and 10 cm chest wall-to-nipple distance and between 3 and 7 cm compressed breast thickness. The dosimetric effect of breast positioning with respect to the imaging detector was also reviewed. It was found that the position of the breast can affect the MGD by as much as 5% to 13% depending on the breast size.

Ma, Andy K. W.; Darambara, Dimitra G.; Stewart, Alexander; Gunn, Spencer; Bullard, Edward [Joint Department of Physics, Institute of Cancer Research and The Royal Marsden Hospital, Fulham Road, London SW3 6JJ (United Kingdom); Dexela Ltd., 1 Water Lane, Camden Town, London NW1 8NZ (United Kingdom)

2008-12-15

220

A comparison of mean glandular dose diagnostic reference levels within the all-digital Irish National Breast Screening Programme and the Irish Symptomatic Breast Services.  

Science.gov (United States)

Data on image quality, compression and radiation dose were collected from symptomatic breast units within the Republic of Ireland. Quantitative and qualitative data were analysed using SPSS. Recommendations of mean glandular dose (MGD) diagnostic reference levels were made at various levels for film-screen and full field digital mammography units to match levels published worldwide. MGDs received by symptomatic breast patients within Ireland are higher than those received in the all-digital Irish Breast Screening service; 55-65 mm breast: 1.75 mGy (screening) vs. 2.4 mGy (symptomatic) at the 95th percentile; various reasons are proposed for the differences. MGDs achieved in the screening service may be lower because of the exacting requirements for radiographer training, characteristics of the patients and equipment quality assurance levels. More precise imaging guidelines, standards and training of symptomatic radiographers performing mammography are suggested to remediate MGDs delivered to the breasts of Irish women attending the symptomatic breast services. PMID:22740646

O'Leary, Desiree; Rainford, Louise

2013-03-01

 
 
 
 
221

Mean glandular dose estimation using MCNPX for a digital breast tomosynthesis system with tungsten/aluminum and tungsten/aluminum+silver x-ray anode-filter combinations.  

Science.gov (United States)

Breast cancer screening with x-ray mammography, using one or two projection images of the breast, is an indispensible tool in the early detection of breast cancer in women. Digital breast tomosynthesis (DBT) is a 3D imaging technique that promises higher sensitivity and specificity in breast cancer screening at a similar radiation dose to conventional two-view screening mammography. In DBT a 3D volume is reconstructed with anisotropic voxels from a limited number of x-ray projection images acquired over a limited angle. Although the benefit of early cancer detection through screening mammography outweighs the potential risks associated with radiation, the radiation dosage to women in terms of mean glandular dose (MGD) is carefully monitored. This work studies the MGD arising from a prototype DBT system under various parameters. Two anode/filter combinations (W/Al and W/Al+Ag) were investigated; the tube potential ranges from 20 to 50 kVp; and the breast size varied between 4 and 10 cm chest wall-to-nipple distance and between 3 and 7 cm compressed breast thickness. The dosimetric effect of breast positioning with respect to the imaging detector was also reviewed. It was found that the position of the breast can affect the MGD by as much as 5% to 13% depending on the breast size. PMID:19175087

Ma, Andy K W; Darambara, Dimitra G; Stewart, Alexander; Gunn, Spencer; Bullard, Edward

2008-12-01

222

Absorbed doses on patients undergoing tomographic exams for pre-surgery planning of dental implants  

International Nuclear Information System (INIS)

The thermoluminescent (TL) dosimetry was used to measure entrance skin absorbed doses at anatomical points close to critical organs of patients undergoing tomographic techniques as part of a pre-surgery planning for dental implants. The dosimetric procedure was applied in 19 patients, and absorbed doses could be measured with a combined uncertainty down to 14%. Results showed that patient doses may be increased by a factor of 20 in the helical computed tomography compared to panoramic and spiral conventional tomographic exams

223

Variation of absorbed doses onboard of ISS Russian Service Module as measured with passive detectors  

International Nuclear Information System (INIS)

Cosmic radiation represents possible risk for the astronauts. For estimation of the radiation onboard the spacecraft in space flights, it is necessary to obtain the data on dose distribution in real space flight conditions. This contribution deals with the study of absorbed dose and dose equivalent due to space radiation in different compartments of the International Space Station (ISS) using passive detectors. Luminescent detectors (LD) and CR-39 plastic nuclear track detectors (PNTD) were exposed onboard of Russian Service Module on ISS from August 2004 to October 2005 (425 days); they were placed at SPD boxes and positioned at 6 various locations inside the Russian Service Module. LD were used to measure absorbed doses, particularly from low-LET particles and photons, PNTDs were used to measure the spectra of linear energy transfer (LET), absorbed dose, and dose equivalents from particles with LET?H2O >5 keV/?m. Results from both types of detectors (LD and PNTD) were then combined together to obtain total values of absorbed doses and dose equivalents. Distribution of absorbed doses and dose equivalents measured with passive detectors, as well as LET spectra of registered particle fluxes, are presented as the function of position of SPD boxes (shielding thickness). Also the influence of position of detectors inside the SPD boxes (top and bottom wall) will be discussed. The dose characteristics depend on the location inside the Service Module; their variation has been observed to be up to factor of almost 2.

224

Absorbed dose ratio factor of Al2O3 in 6 MV radiotherapeutic beams  

International Nuclear Information System (INIS)

The EGSnrc Monte Carlo codes of BEAMnrc, DOSXYZnrc and DOSRZnrc were used to simulate absorbed dose of an Al2O3 dosimeter and absorbed dose of the equivalent water volume in corresponding position irradiated by radiotherapeutic Varian 600C 6 MV beams and Mohan 6 MV spectrum in a water phantom. The absorbed dose ratio factor fmd was calculated, and dosimetry characteristics of the Al2O3 dosimeter were discussed.Simulations were done for a cylindrical geometry dosimeter (?4 mm x 1 mm) and the dosimeter was at the centre of the water phantom at different depths of 0.5-8.0 cm. The results reveal that the absorbed dose of the Al2O3 dosimeter is less than that of the equivalent water. The absorbed dose ratio factor is dependent on the dosimeter depth in the phantom. In the buildup region the absorbed dose ratio factor fmd is sensitive to the depth of the dosimeter. Over the buildup region fmd is insensitive to the depth.This allows the use of averaged absorbed dose ratio factor without introducing discrepancies more than 1.0%. (authors)

225

Estimation and minimization of fetal absorbed dose: data from common radiographic examinations  

International Nuclear Information System (INIS)

A simple method of estimating fetal absorbed dose from common abdominal and pelvic radiographic examinations is presented. The method uses experimentally determined normalized depth dose curves (rad/Roentgen exposure free-in-air) and sonographic localization of the fetus. The method is useful for estimating fetal absorbed dose when a pregnant woman inadvertently undergoes a radiographic examination. However, its primary value is in minimizing fetal dose when a woman, known to be pregnant, must undergo a radiographic examination. Selection of proper projection and deliberate adjustment of bladder volume can result in significant fetal dose reduction particularly in the critical first trimester

226

Estimation and minimization of fetal absorbed dose: data from common radiographic examinations  

Energy Technology Data Exchange (ETDEWEB)

A simple method of estimating fetal absorbed dose from common abdominal and pelvic radiographic examinations is presented. The method uses experimentally determined normalized depth dose curves (rad/Roentgen exposure free-in-air) and sonographic localization of the fetus. The method is useful for estimating fetal absorbed dose when a pregnant woman inadvertently undergoes a radiographic examination. However, its primary value is in minimizing fetal dose when a woman, known to be pregnant, must undergo a radiographic examination. Selection of proper projection and deliberate adjustment of bladder volume can result in significant fetal dose reduction particularly in the critical first trimester.

Ragozzino, M.W. (Mayo Medical School, Rochester, MN); Gray, J.E.; Burke, T.M.

1981-10-01

227

Estimation and minimization of fetal absorbed dose: data from common radiographic examinations  

Energy Technology Data Exchange (ETDEWEB)

A simple method of estimating fetal absorbed dose from common abdominal and pelvic radiographic examinations is presented. The method uses experimentally determined normalized depth dose curves (rad/Roentgen exposure free-in-air) and sonographic localization of the fetus. The method is useful for estimating fetal absorbed dose when a pregnant woman inadvertently undergoes a radiographic examination. However, its primary value is in minimizing fetal dose when a woman, known to be pregnant, must undergo a radiographic examination. Selection of proper projection and deliberate adjustment of bladder volume can result in significant fetal dose reduction particularly in the critical first trimester.

Ragozzino, M.W.; Gray, J.E.; Burke, T.M.; Van Lysel, M.S.

1981-01-01

228

A Survey On Mean Glandular Dose From Full-Field Digital Mammography Systems, Operate Using Mo/ Mo And W/Rh Target/ Filter Combinations  

International Nuclear Information System (INIS)

We had conducted a survey on Mean Glandular Dose (MGD) from Full-Field Digital Mammography systems (FFDM) operate using Molybdenum/ Molybdenum (Mo/ Mo) and Tungsten/ Rhodium (W/ Rh) target/ filter combinations. A survey was carried out at two randomly selected mammography centres in Malaysia, namely National Cancer Society and International Islamic University of Malaysia. The first centre operates using a W/ Rh, while the second centre operates using an Mo/ Mo target/ filter combinations. On the basis of recorded information, data on mammographic views, MGD, age and Compressed Breast Thickness (CBT) were recorded for 100 patients, for each mammographic centre respectively. The MGD data were analyzed for variation with age group, with 5 years increment. The MGD data were also analyzed for variation with CBT, with 5 mm increment. We found that for both CC and MLO views, FFDM systems operated using Mo/ Mo and W/ Rh target/ filter combinations present the same trend on MGD. The average MGD decreases as age increases. While average MGD increases with the increasing of CBT. However, FFDM system operates using Mo/ Mo gives higher MGD as compared with FFDM system operates using W/ Rh. (author)

229

Application of European protocol in the evaluation of contrast-to-noise ratio and mean glandular dose for two digital mammography systems  

International Nuclear Information System (INIS)

The performance of two digital mammography systems, Agfa CR75 and CRMM3 computed radiography (CR) and IMS Giotto MD direct digital radiography (DR), was assessed by applying a method recommended in the European protocol for quality control in mammography screening. The contrast-to-noise ratio (CNR) and mean glandular dose (MGD) values were measured and contrast detail (CD) analysis was performed. The CNRs for system CR were 21.9, 12.9, 9.5, 8.8, 7.4, 5.5 and 4.4 for 2, 3, 4, 4.5, 5, 6 and 7-cm polymethylmethacrylate (PMMA) thickness, respectively. The respective CNRs for system DR were 10.4, 8.8, 6.3, 7.3, 7.2, 6.4 and 6.54. For the same phantom thickness sequence, the MGDs were 0.7, 1.1, 1.3, 1.6, 1.9, 2.5 and 3.4 mGy for system CR, whereas they were 0.7, 1.2, 1.1, 1.3, 1.8, 3.5 and 3.9 mGy for system DR. The CNR and MGD results satisfactorily correlate with CD analysis results. The MGD values compare well with the values recommended in the European protocol. Despite being simple, CNR and MGD can provide an effective system for performance assessment and constancy checks for related optimisations. (authors)

230

'In vivo' average glandular dose evaluation: one-to-one comparison between digital breast tomosynthesis and full-field digital mammography.  

Science.gov (United States)

We analysed 300 patients X rayed with digital breast tomosynthesis (DBT), full-field digital mammography (FFDM) and 'COMBO' (single view both in FFDM and DBT in a single breast compression)-Hologic Selenia Dimension-W/Rh-Ag-Al: three different anode-filter combinations-automatic exposure control modalities. Examination parameter data collection (EPDC) and 'in vivo' dosimetry using metal oxide semiconductor field effect transistor (MOSFET) were utilised to determine and compare entrance skin air kerma (ESAK) and average glandular dose (AGD) from a radioprotection viewpoint in the DBT and COMBO modalities. MOSFET has been tested to be introduced in clinical routine. EPDC of DBT underlines increase in ESAK and AGD compared with FFDM (p mean percentage increase was 34 % (+17 %) in ESAK and 46 % (+16 %) in AGD. In the COMBO modality, the mean percentage increase in ESAK was 162 % (+41 %) and in AGD was 202 % (+61 %). Differences between MOSFET measurement and calculated values were 15 %. DBT increases ESAK and AGD, due to the 3D acquisition modality. MOSFET may be considered in DBT as a routine check. PMID:23734057

Cavagnetto, Francesca; Taccini, Gianni; Rosasco, Raffaella; Bampi, Rossana; Calabrese, Massimo; Tagliafico, Alberto

2013-11-01

231

Absorbed dose evaluations in retrospective dosimetry: Methodological developments using quartz  

DEFF Research Database (Denmark)

Dose evaluation procedures based on luminescence techniques were applied to 50 quartz samples extracted from bricks that had been obtained from populated or partly populated settlements in Russia and Ukraine downwind of the Chernobyl NPP. Determinations of accrued dose in the range similar to 30-300 mGy were obtained using TL (210 degreesC TL and pre-dose) and OSL (single and multiple aliquot) procedures. Overall, good inter-laboratory concordance of dose evaluations was achieved, with a variance (1 sigma) of similar to+/-10 mGy for the samples examined. (C) 2000 Elsevier Science Ltd. All rights reserved.

BØtter-Jensen, L.

2000-01-01

232

Development of methodology for assessment of absorbed dose and stopping power for low energy conversion electrons  

International Nuclear Information System (INIS)

The evaluation of absorbed dose in the case of external and internal contamination due to radionuclides is sometimes hard, because of the difficulties in the assessment of the absorbed dose caused by electrons with energy less than 100 KeV in mucous membrane. In this work, a methodology for assessment of absorbed dose and stopping power in VYNS (co-polymer of polivinyl chloride - acetate) absorbers, for the 62.5 KeV and 84-88 KeV energy 109 Cd conversion electrons, working with a 4 ? proportional pressurized detector, is presented. In order to assure the reproducibility of measurement conditions, one of the detector halves has been used to obtain a spectrum of a thin 109 Cd source, without absorber. The other half of the detector was used in concomitance to obtain spectra with different thicknesses if absorber. The absorbed energy was obtained subtracting each spectrum with absorber from the spectrum without absorber, which were stored in a microcomputer connected to signal processing systems by ACE type interface. The VYNS weight and thickness were evaluated using common radionuclide metrology procedures. As VYNS has characteristics similar to a tissue equivalent material, the results obtained are consistent with dosimetric concepts and have a good agreement with those of the literature. (author)

233

Measurement of absorbed dose-rate in skin for low-level beta-rays  

International Nuclear Information System (INIS)

A new type of beta-ray absorbed dose-rate meter is described which evaluates absorbed dose in skin at a depth of 7 mg/cm2 from the dose rate on the surface of a contaminated sandy beach. Based on the response energy spectra measured for various point and surface sources of radionuclides with different beta-ray energy spectra, such as 90Y, 204Tl, and 137Cs, the discrimination level and the window width were determined so that the instrument response may be best correlated with the absorbed dose-rate. The measured and calculated dose rates for the actual sample of beach sands were compared. With this instrument the dose rate of about 1 ?rad/hr surface contamination can be measured by 90 minutes counting. (H.K.)

234

Determining of the neutron absorbed doses in fast neutron fields at the RB reactor  

International Nuclear Information System (INIS)

A number of experimental devices for obtaining fast neutron fields at the R-B reactor is created. Absorbed neutron doses in these fields are computed. Calculated and experimental values of neutron flux densities are compared. (author)

235

Absorbed dose in mice prostate: Comparison of experimental measurements and Monte-Carlo simulations  

International Nuclear Information System (INIS)

The main purpose of our study is to set up a reproducible irradiation protocol in which the absorbed dose delivered to the prostate is well known and constant. The X-ray unit used for experimental irradiation is the Faxitron CP-160 (nominal X-ray tube voltage: 160 kV). Two kinds of approaches are considered. First, an experimental measurement of the absorbed dose delivered to the prostate of a mouse. Absorbed dose measurements were performed by the use of Lif:Mg,Ti thermoluminescent dosimeters (TLD) with a sensitive range between 50 ?Gy and 500 Gy. Secondly, absorbed dose calculation via Monte-Carlo modelling of radiation transport and energy deposition

236

Estimation of terrestrial air-absorbed dose rate from the data of regional geochemistry database  

International Nuclear Information System (INIS)

This paper presents an estimation of air-absorbed dose rate from the data of K2O, U and Th content from Chinese regional geochemical database. A total of 421 group original data of combined samples in Zhongshan City (ZSC), Guangdong Province and south China were extracted from the national geochemical database. Estimated average value of air-absorbed dose rate is 139.4 nGy h-1 in the granite area and 73.7 nGy h-1 in the sedimentary area. The level of air-absorbed dose rate is closely related with the surface lithology. Estimated mean air-absorbed dose rate approximates to the measured average value by a portable plastic scintillator dosemeter in Zhuhai City were bordered with ZSC. The results show that the pre-evaluation of ionizing radiation level using regional geochemical data is feasible. (author)

237

Comparison of theoretical and experimental values of TRS 398 absorbed dose to water  

Digital Repository Infrastructure Vision for European Research (DRIVER)

OBJECTIVES: In this study, experimentally and theoretically determined absorbed dose to water calibration factors were compared. We used 6 MV photon and 12 MeV electron energies to compare experimentally and theoretically determined beam quality dependence factors. METHODS:Measurements were made at SSD=100 cm distance (LINAC), 10x10 cm standard field size and reference depth. Five different cylindrical and three parallel plate chambers were used. RESULTS: For absorbed dose to water calibratio...

Acar, Hilal

2008-01-01

238

Genetic effects induced by neutrons in Drosophila melanogaster I. Determination of absorbed dose  

International Nuclear Information System (INIS)

A method to obtain the absorbed dose in Drosophila melanogaster irradiated in the thermal column facility of the Triga Mark III Reactor has been developed. The method is based on the measurements of neutron activation of gold foils produced by neutron capture to obtain the neutron fluxes. These fluxes, combined with the calculations of kinetic energy released per unit mass, enables one to obtain the absorbed doses in Drosophila melanogaster

239

Evaluation of the absorbed dose in odontological computerized tomography; Avaliacao da dose absorvida em tomografia computadorizada odontologica  

Energy Technology Data Exchange (ETDEWEB)

This paper evaluated the absorbed dose at the surface entry known as 'cone beam computed tomography' (CBCT) in odontological computerized tomography. Examination were simulated with CBCT for measurements of dose. A phantom were filled with water, becoming scatter object of radiation. Thermoluminescent dosemeters were positioned on points correspondent to eyes and salivary glands

Legnani, Adriano; Schelin, Hugo R.; Rocha, Anna Silvia P.S. da, E-mail: schelin@utfpr.edu.b, E-mail: anna@utfpr.edu.b [Universidade Tecnologica Federal do Parana (UTFPR), Curitiba, PR (Brazil); Khoury, Helen J., E-mail: khoury@ufpe.b [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil)

2011-10-26

240

Biological indicators for radiation absorbed dose: a review  

International Nuclear Information System (INIS)

Biological dosimetry has an important role to play in assessing the cumulative radiation exposure of persons working with radiation and also in estimating the true dose received during accidents involving external and internal exposure. Various biodosimetric methods have been tried to estimate radiation dose for the above purposes. Biodosimetric methods include cytogenetic, immunological and mutational assays. Each technique has certain advantages and disadvantages. We present here a review of each technique, the actual method used for detection of dose, the sensitivity of detection and its use in long term studies. (author)

 
 
 
 
241

Control of absorbed dose in radiotherapy with 60 Co units  

International Nuclear Information System (INIS)

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

242

The absorbed dose in femur exposed to diagnostic radiography  

International Nuclear Information System (INIS)

A femur phantom made of wax and a real human bone was used to study the dose during radiographical procedures. The depth dose inside the phantom was determined using DOSXYZnrc, a Monte Carlo simulation software. The results were verified with measurements using TLD-100H. It was found that for 2.5 mm aluminium filtered 84-kVp X-rays, the radiation dose in the bone reached 57 % higher than the surface dose, i.e. 3.23 mGy as opposed to 2.06 mGy at the surface. The use of real bone introduces variations in the bone density in the DOSXYZnrc model, resulting in a lower attenuation effect than expected from solid bone tissues. (authors)

243

Absorbed dose from 14C xylose and 14C mannose  

International Nuclear Information System (INIS)

Tissue distribution and excretion studies have been performed in rats and mice for up to 1 week after oral administration of 14C xylose and 14C mannose. The effective dose-equivalent is calculated to be 15 ?Sv/MBq for xylose and 120 ?Sv/MBq for mannose. Since there was no clearance of mannose during the period of the study, the effective dose-equivalent for mannose is almost entirely dependent upon the assumptions made about expected lifetime exposure. (author)

244

Absorbed neutron dose measurement on nuclear moisture density gauge operators using thermoluminescence dosimeters (TLD)  

International Nuclear Information System (INIS)

Moisture density gauges (MDG) are widely used in monitoring soil and pavement properties but emit gamma and neutron radiation that could pose a health hazard. Neutron dose absorbed received by the personnel from using an MDG was determined using neutron thermoluminescence dosimeter (TLD). Result shows neutron dose levels received were comparable with gamma dose that could exceed the safe dose limits for radiation workers. It was also shown that radiation backscattering differs with dry and moist media. (author)

245

Absorbed radiation doses due to chronic ingestion of cesium-137 or strontium-90 by mice  

International Nuclear Information System (INIS)

The knowledge of the absorbed radiation dose is essential in order to interpret the results of animal experiments with chronic ingestion of radionuclides by rodents. In order to evaluate this absorbed dose, we applied the dose conversion factors proposed by ICRP publication 108 to mouse chronic ingestion experiments with 20 kBq.L-1 137Cs- or 90Sr-contaminated water. The results indicated that whole-body absorbed doses were 9 mGy and 10 mGy by the end of 20 weeks of 137Cs or 90Sr ingestion, respectively. These results of dose calculations were compared with results obtained with a more refined method using published organ-specific absorbed fractions of energy. There was good agreement between the two methods, indicating that, despite the simple hypotheses used to apply the ICRP 108 dose conversion factors to our mouse model, this method allows one to calculate in a simple and reliable way the absorbed radiation dose received by the rodents during long-term experiments on chronic ingestion of radionuclides. (authors)

246

Assessment of absorbed dose rate in air over plowed arable lands in Sinnar State, central Sudan  

International Nuclear Information System (INIS)

The absorbed gamma-dose rate in air at a height of 1 m above ground level was calculated from activity concentrations of gamma-emitting radionuclides in arable soil samples collected from eight locations within Sinnar State using the published Dose Rate Conversion Factors. Measurements were carried out using high-resolution gamma-spectrometry. On average, the activity concentrations obtained were 38 ± 8 (232Th), 17 ± 2 (226Ra), 174 ± 19 (40K) and 0.9 ± 0.2 Bq kg-1 for the fallout radionuclide 137Cs. The average value obtained here for 232Th is slightly higher than the corresponding world-average. The calculated absorbed dose rate in air at a height of 1 m for all sampled locations ranges from 31 to 47 nGy h-1 with an average value of 39 ± 7 nGy h-1 which is characteristic of normal background radiation areas. The corresponding annual effective dose was 47.8 ± 6 ?Sv y-1. The major contribution to the total absorbed dose rate comes from 232Th, which amounts to 61%. Recalculation of the absorbed dose rate-based gamma-energies of individual nuclides from uranium and thorium decay series and 40K showed that the greater part of the absorbed dose from the uranium series is due to 214Bi, whereas for the 232Th series it is equally attributed to 228Ac and 208Tl. (authors)

247

Influence of unit voxel size of cumulated radioactivity distribution on 3D absorbed dose estimates  

International Nuclear Information System (INIS)

In radiotherapy due to administration of radionuclides, accurate estimates of three-dimensional (3D) absorbed dose distributions of target regions can be performed using a 3D dose matrix convolution method which has already been developed based on a voxel based calculation algorithm by the authors. The purpose of this study is to elucidate the influence of unit voxel sizes of cumulated radioactivity distributions of beta-emitting radionuclides on 3D absorbed dose estimates. Computer simulations were performed using cubic phantoms (24 x 24 x 24 mm, 32 x 32 x 32 mm, and 48 x 48 x 48 mm) and the MIRD thyroid phantom as the target regions assumed distributed uniformly for various beta-emitting radionuclides (32P, 90Y, 131I, 186Re, and 188Re). The maximum, mean and minimum absorbed doses for their phantoms comprised of various unit voxel sizes (1 x 1 x 1 mm, 4 x 4 x 4 mm, and 8 x 8 x 8 mm) were estimated using the 3D dose matrix convolution method developed. In the cases of the 3D cumulated radioactivity distributions of the target regions comprised of various unit voxel sizes were identical with one another, the maximum and mean absorbed doses for the target volumes were independent of the unit voxel sizes. However, as the unit voxel sizes were increased, the minimum absorbed doses were overestimated. (author)

248

Plastic film materials for dosimetry of very large absorbed doses  

DEFF Research Database (Denmark)

Most plastic films have limited response ranges for dosimetry because of radiation-induced brittleness, degradation, or saturation of the signal used for analysis (e.g. spectrophotometry) at high doses. There are, however, a few types of thin plastic films showing linearity of response even up to doses as high as 2 × 106 Gy (200 Mrad) without severe loss of mechanical properties. Among many candidate film types tested, those showing such resistance to radiation damage and continued response at such high doses are polyethylene terephthalate, high-density polyethylene, dyed polyvinylchloride, polystyrene, dyed and undyed polyhalostyrenes, dyed aromatic polyamides, and polyvinylidene fluoride. Although most of these systems have fairly stable absorption spectra after irradiation, tests of dependence on dose rate and on temperature during irradiation show that only polystyrene and some of the polyhalostyrenes have essentially rate-independent and moderately temperature-dependent responses to such large doses of ionizing radiation. While radiation-induced optical absorption in the ultraviolet for polystyrene is unstable following irradiation, thus leading to an intrinsic low-intensity rate dependence, the dyed polychlorostyrenes show essentially the same response to radiation-processing gamma-ray fields and to very high-intensity electron beams, and a relatively stable absorption spectrum at wavelengths for dosimetry analysis in the visible spectral region of ?430 nm.

Miller, Arne

1985-01-01

249

Absorbed dose by crystalline in middle ear tomography  

International Nuclear Information System (INIS)

Measurements of the incident dose on the eye have been taken during the tomographic examinations of the middle ear. These measurements have been effectuated without any protection of the eye, and with a Pb-diagram protection, thickness 2mm. The tomograph which has been used is an Italian one (Eurostrator-Zuder, Genoa) provided with complex radiation movements (circular, spiral) and which gives technical results such as the Polytom (generally used for these researches) but which has a focus-film distance of 1m instead of 1.40m. The average incident dose on the crystalline lens is high (11.7R); the use of the Pb-diaphragm reduces the dose considerably (0.65R) without any significant imperfections on the radiological image

250

Absorbed dose in polymers during a positron annihilation experiment  

International Nuclear Information System (INIS)

A positron annihilation lifetime (PAL) technique has been recognized as being a useful method to study the characteristics of polymers. However, radiation effects due to positrons used as a probe have been raised as being a problem, since positrons emitted from 22Na have sufficient energy to induce radiation damage in polymers. In this study, the radiation dose induced by positrons emitted from 22Na was estimated for such polymers like polyethylenes and polypropylenes using the EGS4 code. The radiation damage during PAL measurements is also discussed. It has been shown that the calculated dose is consistent with that estimated from an empirical equation of the mass-attenuation coefficient. (author)

251

Absorbed dose measurement on disprin tablets by ESR technique  

International Nuclear Information System (INIS)

In this investigation an attempt has been made to measure the dose from free radicals induced in medicine tables by ESR. About 60mg of powdered irradiated Disprin tablets (acetyl salicylic acid 72% calcium carbonate 21% anhydrous citric acid 7%) was loaded into quartz tube and free radical density was measured using Bruker ESP-300 spectrometer. A linear response of dose with peak to peak height was obtained in the range of 1Gy to 700Gy at g=1.9975. (author). 5 refs., 1 fig

252

Specification of absorbed dose to water using model-based dose calculation algorithms for treatment planning in brachytherapy  

Science.gov (United States)

Model-based dose calculation algorithms (MBDCAs), recently introduced in treatment planning systems (TPS) for brachytherapy, calculate tissue absorbed doses. In the TPS framework, doses have hereto been reported as dose to water and water may still be preferred as a dose specification medium. Dose to tissue medium Dmed then needs to be converted into dose to water in tissue Dw,med. Methods to calculate absorbed dose to differently sized water compartments/cavities inside tissue, infinitesimal (used for definition of absorbed dose), small, large or intermediate, are reviewed. Burlin theory is applied to estimate photon energies at which cavity sizes in the range 1 nm-10 mm can be considered small or large. Photon and electron energy spectra are calculated at 1 cm distance from the central axis in cylindrical phantoms of bone, muscle and adipose tissue for 20, 50, 300 keV photons and photons from 125I, 169Yb and 192Ir sources; ratios of mass-collision-stopping powers and mass energy absorption coefficients are calculated as applicable to convert Dmed into Dw,med for small and large cavities. Results show that 1-10 nm sized cavities are small at all investigated photon energies; 100 µm cavities are large only at photon energies Free radicals from DNA bound water of nanometre dimensions contribute to DNA damage and cell killing and may be the most important water compartment in cells implying use of ratios of mass-collision-stopping powers for converting Dmed into Dw,med.

Carlsson Tedgren, Åsa; Alm Carlsson, Gudrun

2013-04-01

253

MIRD Dose Estimate Report No. 20: Radiation Absorbed-Dose Estimates for 111In- and 90Y-Ibritumomab Tiuxetan  

International Nuclear Information System (INIS)

Absorbed dose calculations provide a scientific basis for evaluating the biological effects associated with administered radiopharmaceuticals. In cancer therapy, radiation dosimetry also supports treatment planning, dose-response analyses, predictions of therapy effectiveness, and completeness of patient medical records. In this study, we evaluated the organ radiation absorbed doses resulting from intravenously administered 111In- and 90Y-Ibritumomab Tiuxetan (Zevalin). Methods: Ten patients (six male, four female) with non-Hodgkin's lymphoma, cared for at three different medical centers, were administered tracer 111In-Ibritumomab Tiuxetan and were assessed using planar scintillation camera imaging at five time points, blood clearance measurements, and CT-organ volumetrics, to determine patient-specific organ biokinetics and dosimetry. Explicit attenuation correction based on transmission scan or transmission measurements provided the fraction of 111In administered activity in seven major organs, the whole body, and remainder tissues over time through complete decay. Activity-time curves were constructed, and radiation doses were calculated using MIRD methods and implementing software (OLINDA-EXM). Results: Mean radiation absorbed doses in 10 cancer patients for 111In- and for 90-Y-Ibritumomab Tiuxetan are reported for 24 organs and the whole body. Biological uptake and retention data are given for seven major source organs, remainder tissues, and the whole body. Median absorbed dose values calculated by this method were compared to previously published dosimetry for Zevalin and the product package insert. Conclusions: Careful dosimetry techniques provide useful information on absorbed dose from administered radiopharmaceuticals in patients. The importance of patient-specific dosimetry emerges in high-dose radioimmunotherapy when the objective of treatment planning is to achieve disease cures safely by limiting radiation doses to any critical normal organ to a maximum tolerable value.

254

Evaluation of the distribution of absorbed dose in child phantoms exposed to diagnostic medical x rays  

International Nuclear Information System (INIS)

The purpose of the study was to determine, by theoretical calculation and experimental measurement, the absorbed dose distributions in two heterogeneous phantoms representing one-year- and five-year-old children from typical radiographic examinations for those ages. Theoretical work included the modification of an existing internal dose code which used Monte Carlo methods to determine doses within the Snyder-Fisher mathematical phantom. A Ge(Li) detector and a pinhole collimator were used to measure x-ray spectra which served as input (i.e., the source routine) to the modified Monte Carlo codes which were used to calculate organ doses in children. Experimental work included the fabrication of child phantoms to match the existing mathematical models. These phantoms were constructed of molded lucite shells filled with differing materials to simulate lung, skeletal, and soft-tissue regions. The skeleton regions of phantoms offered the opportunity to perform meaningful measurements of absorbed dose to bone marrow and bone. Thirteen to fourteen sites in various bones of the skeleton were chosen for placement of TLDs. These sites represented important regions in which active bone marrow is located. Sixteen typical radiographic examinations were performed representing common pediatric diagnostic procedures. The calculated and measured tissue-air values were compared for a number of organs. For most organs, the results of the calculated absorbed doses agreed with the measureded absorbed doses agreed with the measured absorbed doses within twice the coefficient of variation of the calculated value. The absorbed dose to specific organs for several selected radiological examinations are given for one-year-old, five-year-old, and adult phantoms. For selected radiological exposures, the risk factors of leukemia, thyroid cancer, and genetic death are estimated for one-year- and five-year-old children

255

Evaluation of scatter-to-primary ratio, grid performance and normalized average glandular dose in mammography by Monte Carlo simulation including interference and energy broadening effects  

International Nuclear Information System (INIS)

In this work, a computational code for the study of imaging systems and dosimetry in conventional and digital mammography through Monte Carlo simulations is described. The developed code includes interference and Doppler energy broadening for simulation of elastic and inelastic photon scattering, respectively. The code estimates the contribution of scattered radiation to image quality through the spatial distribution of the scatter-to-primary ratio (S/P). It allows the inclusion of different designs of anti-scatter grids (linear or cellular), for evaluation of contrast improvement factor (CIF), Bucky factor (BF) and signal difference-to-noise ratio improvement factor (SIF). It also allows the computation of the normalized average glandular dose, D-bar g,N. These quantities were studied for different breast thicknesses and compositions, anode/filter combinations and tube potentials. Results showed that the S/P increases linearly with breast thickness, varying slightly with breast composition or the spectrum used. Evaluation of grid performance showed that the cellular grid provides the highest CIF with smaller BF. The SIF was also greater for the cellular grid, although both grids showed SIF g,N showed that it increases with the half-value layer (HVL) of the spectrum, decreases considerably with breast thickness and has a small dependence on the anode/filter combination. Inclusion of interference effects of ion. Inclusion of interference effects of breast tissues affected the values of S/P obtained with the grid up to 25%, while the energy broadening effect produced smaller variations on the evaluated quantities.

256

Evaluation of scatter-to-primary ratio, grid performance and normalized average glandular dose in mammography by Monte Carlo simulation including interference and energy broadening effects  

Science.gov (United States)

In this work, a computational code for the study of imaging systems and dosimetry in conventional and digital mammography through Monte Carlo simulations is described. The developed code includes interference and Doppler energy broadening for simulation of elastic and inelastic photon scattering, respectively. The code estimates the contribution of scattered radiation to image quality through the spatial distribution of the scatter-to-primary ratio (S/P). It allows the inclusion of different designs of anti-scatter grids (linear or cellular), for evaluation of contrast improvement factor (CIF), Bucky factor (BF) and signal difference-to-noise ratio improvement factor (SIF). It also allows the computation of the normalized average glandular dose, \\bar{D}_{g,N} . These quantities were studied for different breast thicknesses and compositions, anode/filter combinations and tube potentials. Results showed that the S/P increases linearly with breast thickness, varying slightly with breast composition or the spectrum used. Evaluation of grid performance showed that the cellular grid provides the highest CIF with smaller BF. The SIF was also greater for the cellular grid, although both grids showed SIF < 1 for thin breasts. Results for \\bar{D}_{g,N} showed that it increases with the half-value layer (HVL) of the spectrum, decreases considerably with breast thickness and has a small dependence on the anode/filter combination. Inclusion of interference effects of breast tissues affected the values of S/P obtained with the grid up to 25%, while the energy broadening effect produced smaller variations on the evaluated quantities.

Cunha, D. M.; Tomal, A.; Poletti, M. E.

2010-08-01

257

Radiation absorbed dose estimate for rubidium-82 determined from in vivo measurements in human subjects  

International Nuclear Information System (INIS)

Radiation absorbed doses from rubidium-82 injected intravenously were determined in two young men, aged 23 and 27, using a dynamic conjugate counting technique to provide data for the net organ integrated time-activity curves in five organs: kidneys, lungs, liver, heart, and testes. This technique utilized a tungsten collimated Anger camera and the accuracy was validated in a prestwood phantom. The data for each organ were compared with conjugate count rates of a reference Ge-68/Ga-68 standard which had been calibrated against the Rb-82 injected. The effects of attenuation in the body were eliminated. The MIRD method was used to calculate the organ self absorbed doses and the total organ absorbed doses. The mean total absorbed doses were as follows (mrads/mCi injected): kidneys 30.9, heart walls 7.5, lungs 6.0, liver 3.0, testes 2.0 (one subject only), red marrow 1.3, remainder of body 1.3 and, extrapolating to women, ovaries 1.2. This absorbed dose to the kidney is significantly less than the pessimistic estimate of 59.4 mrads/mCi, made assuming instantaneous uptake and complete extraction of activity with no excretion by the kidneys, which receive 20% of the cardiac output. Further, in a 68 year old man the renal self absorbed dose was approximately 40% less than the mean renal self absorbed dose of the younger men. This decrease is probably related to the decline in renal blood flow which occurs with advancing age but other factors may also contribute to the observed difference. 14 references, 4 figures, 2 tables

258

Distributions of absorbed dose from ?--meson beams calculated from a new Monte Carlo program  

International Nuclear Information System (INIS)

We describe the structure and the physical input data of a new Monte Carlo program for calculations of the absorbed dose which is transferred by negatively charged pions to tissue equivalent phantoms. The program is based mainly on experimentally determined input data. Contributions to absorbed dose from nuclear reactions of pions in flight and from nuclear fragmentation following the absorption of stopped pions were studied in detail. The resulting dose distributions are presented for cases of narrow as well as extended parallel beams of ?--mesons with an initial average momentum of 170 MeV/c. (orig.)

259

Norwegian system for implementing the IAEA code of practice based on absorbed dose to water  

International Nuclear Information System (INIS)

In 2001 the Nordic secondary standards dosimetry laboratories (SSDLs) recommended the use of absorbed dose to water as the quantity for the calibration standard and code of practice in radiotherapy.The code of practice adopted was IAEA Technical Reports Series No. 398. The Norwegian system for implementation includes the 60Co calibration of SSDL and hospital dosimeters in terms of absorbed dose to water at the Norwegian SSDL and on-site visits to every clinic teaching the new code and performing dose measurements. Comparisons of the Norwegian Radiation Protection Authority 60Co absorbed dose to water calibration at the Finnish SSDL with the French primary standards dosimetry laboratory showed agreement within 0.4%.The on-site visit measuring system compared with the Finnish on-site equipment agreed within 0.6%.The on-site visits were welcomed, and demonstrated the need for external dosimetry audits to improve the local implementation of the code of practice. (author)

260

Determination of superficial absorbed dose from external exposure of weakly penetrating radiations  

International Nuclear Information System (INIS)

The methods of determining the superficial absorbed dose distributions in a water phantom by means of the experiments and available theories are reported. The distributions of beta dose are measured by an extrapolation ionization chamber at definite depths corresponding to some superficial organs and tissues such as the radiosensitive layer of the skin, cornea, sclera, anterior chamber and lens of eyeball. The ratios among superficial absorbed dose D(0.07) and average absorbed doses at the depths 1,2,3,4,5 and 6 mm are also obtained with Cross's methods. They can be used for counting the deterministic effects of some superficial tissues and organs such as the skin and the components of eyeball for weakly penetrating radiations

 
 
 
 
261

Measurement of the absorbed dose received by patients undergoing lung X-ray examination  

International Nuclear Information System (INIS)

The present work concentrates on the radioprotection aspect in the use of a Siemens triomat type X-ray generator for lung radiography. A first set of measurements of the absorbed dose received by patients undergoing lung X-ray examinations was used to compare the values observed during radiographic operations and when standard plates are obtained. The absorbed dose received for the radiophotographs seemed too high, so the various working parameters were reviewed; the new measurements carried out showed a factor 10 gain on the absorbed dose for a 'standard' 70 kg man, the quality of the image remaining acceptable. This report gives the results of all the measurements performed. The doses received with standard plates remain the lowest. Experience acquired at the time of these measurements brings out the absolute necessity for a periodic check on the accuracy of the parameters displayed on the X-ray generator control panels

262

Measurement of absorbed dose from radionuclide solutions mixed intimately with the FBX dosimeter  

International Nuclear Information System (INIS)

Chemical dosimeters are used widely for accurate measurement of large radiation doses due to external beam irradiation from radioisotope sources and from particle accelerators. Their use for measurement of absorbed doses from radioactive solutions mixed in the dosimeter solution was reported as early as 1952, but the large activities needed to produce suitable absorbance values in the relatively insensitive dosimeters of that time discouraged further work. The results of an investigation into the suitability of the ferrous sulfate-benzoic acid-xylenol orange (FBX) dosimeter for measurement of small absorbed doses caused by radionuclide solutions dissolved in the dosimeter solution is reported. The FBX dosimeter exhibited a linear dose response as a function of activity for two common radiopharmaceuticals, technetium-99m sodium pertechnetate and iodine-131 sodium iodide

263

Absorbed doses in tissue-equivalent spheres above radioactive sources in soil.  

Science.gov (United States)

Doses due to external exposure of terrestrial biota are assessed using differential air kerma from radioactive sources in soil and energy-dependent 'absorbed dose-per-air kerma' conversion factors computed for spherical tissue-equivalent bodies. The presented approach allows computing average whole body absorbed dose for terrestrial organisms with body masses from 1 mg to 1,000 kg located at heights from 10 cm to 500 m above ground. Radioactive sources in soil emitting photons with energies from 10 keV to 10 MeV have been considered. Interpolation of the computed quantities over source energy, body mass, and height above ground results in plausible estimates of whole body average absorbed doses for non-human terrestrial biota from gamma-radiation emitted by any radionuclides in contaminated terrain. PMID:25129621

Ulanovsky, Alexander

2014-11-01

264

Standard method of test for absorbed gamma and electron radiation dose with the ferrous sulfate--cupric sulfate dosimeter  

International Nuclear Information System (INIS)

Preparation and use of ferrous sulfate-cupric sulfate dosimeters for measuring absorbed ? and electron radiation are described. The dosimeter is suitable for accurate measurement of the absorbed dose in water irradiated with x or ? rays or high-energy electrons. The change in absorbance at 3050A of the irradiated solution of ferrous sulfate-cupric sulfate is measured in a temperature-controlled spectrophotometer. The absorbed dose in rads in the solution is proportional to the change in the absorbance. The method is accurate for absorbed doses in the range from 2 x 105 to 8 x 105 rads

265

Patient absorbed dose and radiation risk in nuclear medicine  

International Nuclear Information System (INIS)

Since the introduction of technetium-99m labelled radiopharmaceuticals used as imaging agents in the nuclear medicine departments of Australian hospitals, patients have voiced concern about the effect of having radioactive materials injected into their bodies. The danger of X-ray exposure is widely known and well accepted, as is exposure to ultrasound, computed tomography scans and other imaging techniques. However, radioactivity is an unknown, and fear of the unknown can occasionally lead to patients refusing to undergo a nuclear medicine procedure. The authors emphasised that the radiation dose to a patient from a typical procedure would depend on the patient's medical history and treatment; the average dose being approximately 50 times the exposure received from the natural environmental background radiation. Furthermore, over an extended period the body can repair most minor damage caused by radiation, just as the body can repair the damage caused by sunburn resulting from too much exposure to sunlight. The risk of genetic effects as a result of a medical radiation dose is than very small

266

Glandular hypospadias repair.  

Science.gov (United States)

Glandular hypospadias represents approximately 15% of the hypospadias variants seen. This article will examine common surgical approaches applicable to the child with glandular hypospadias. Hypospadias repairs discussed in this article will include urethromeatoplasty, MAGPI, the GAP procedure, MIV glans plasty, urethral advancement procedure, and parameatal based flap variants, including the Mathieu and Barcat procedures. Because these anomalies are cosmetically less aberrant than more proximal variants, only those surgical techniques which assure a normal-appearing penis should be undertaken. PMID:12371221

Zaontz, Mark R; Dean, Gregory E

2002-05-01

267

Radiation absorbed dose measurement after I-131 metaiodobenzylguanidine treatment in a patient with pheochromycytoma  

International Nuclear Information System (INIS)

The measurement of radiation absorbed dose is useful to predict the response after I-131 labeled metaiodobenzylguanidine (MIBG) therapy and determine therapy dose in patients with unresectable or malignant pheochromocytoma. We estimated the absorbed dose in tumor tissue after high dose I-131 MIBG in a patient with pheochromocytoma using a gamma camera and Medical Internal Radiation Dose (MIRD) formula. A 64-year old female patient with pheochromocytoma who had multiple metastases of mediastinum, right kidney and periaortic lymph nodes, received 74 GBq (200 mCi) of K-131 MIBG. We obtained anterior and posterior images at 0.5, 16, 24, 64 and 145 hours after treatment. Two standard sources of 37 and 74 MBq of I-131 were imaged simulatanously. Cummulated I-131 MIBG uptake in tumor tissue was calculated after the correction of background activity, attenuation, system sensitivity and count loss at a high count rate. The calculated absorbed radiation dose was 32-63 Gy/ 74 GBq, which was lower than the known dose for tumor remission (150-200 Gy). Follow-up studies at 1 month showed minimally reduced tumor size on computed tomography, and mildly reduced I-131 MIBG uptake. We estimated radiation absorbed dose after therapeutic I-131 MIBG using a gamma camera and MIRD formula, which can be peformed in a clinical nuclear medicine laboratory. Our results suggest that the measurement of radiation absorbed dose in I-131 MIBG therapy is feasible as a routine clinical practice that can guide further treatment plan. The accuracy of dose measurement and correlation with clinical outcome should be evaluated further

268

Calculation of absorbed doses in an organ using the MIRD method  

International Nuclear Information System (INIS)

For the application of radiopharmaceuticals in nuclear diagnostics, it is necessary to know the absorbed dose the patient is subjected to. An accurate estimation is very important if one wants to weigh the risks against the profits of the examination. In this report, the MIRD (Medical Internal Radiation Dose) method is described so as to calculate the absorbed dose in some organ. In doing so, the author distinguishes source organs in which nuclides are doped and target organs the dose of which is calculated. The target organ can be irradiated from one or more source organs. After a description of the dosimetric model, the way the results of dose calculations have been presented is dealt with. Intermediate results are cast in tables from which observed doses are easy to derive. As an instance of the MIRD method, a full calculation is figured out. (Auth.)

269

Evaluation of the distribution of absorbed dose in child phantoms exposed to diagnostic medical x rays  

International Nuclear Information System (INIS)

The purpose of this study was to determine, by theoretical calculation and experimental measurement, the absorbed dose distributions in two heterogeneous phantoms representing one-year- and five-year-old children from typical radiographic examinations for those ages. Theoretical work included the modification of an existing internal dose code which uses Monte Carlo methods to determine doses within the Snyder-Fisher mathematical phantom. A Ge(Li) detector and a pinhole collimator were used to measure x-ray spectra which served as input to the modified Monte Carlo codes which were used to calculate organ doses in children. The calculated and measured tissue-air values were compared for a number of organs. For most organs, the results of the calculated absorbed doses agreed with the measured absorbed doses within twice the coefficient of variation of the calculated value. The absorbed dose to specific organs for several selected radiological examinations are given for one-year-old, five-year-old, and adult phantoms

270

Measurement of absorbed dose with a bone-equivalent extrapolation chamber  

International Nuclear Information System (INIS)

raphite electrodes do not affect the dose measurement in the Solid Water trade mark sign PEEC but decrease the cavity dose by up to 5% in the bone-equivalent PEEC even for very thin graphite electrodes (<0.0025 cm). In conjunction with appropriate correction factors determined with Monte Carlo techniques, the uncalibrated hybrid PEEC can be used for measuring absorbed dose in bone material to within 2% for high-energy photon and electron beams

271

Analysis of contrast and absorbed doses in mammography  

International Nuclear Information System (INIS)

One of the great causes of mortality between women in the world is the breast cancer. The mammograms are the method most efficient to detect some cases of cancer of breast before this to be clinically concrete. The quality of a picture system must be determined by the ability to detect tissue soft masses, cyst or tumors, but also calcifications. This detection is directly connected with the contrast obtained in these pictures. This work has for objective to develop a method for the analysis of this contrast in mammograms verifying the doses referred to these mammograms and comparing them with national and international levels of reference. (author)

272

National absorbed dose to water references for radiotherapy medium energy X-rays by water calorimetry  

International Nuclear Information System (INIS)

LNE-LNHB current references for medium energy X-rays are established in terms of air kerma. Absorbed dose to water, which is the quantity of interest for radiotherapy, is obtained by transfer dosimetric techniques following a methodology described in international protocols. The aim of the thesis is to establish standards in terms of absorbed dose to water in the reference protocol conditions by water calorimetry. The basic principle of water calorimetry is to measure the absorbed dose from the rise in temperature of water under irradiation. A calorimeter was developed to perform measurements at a 2 cm depth in water according to IAEA TRS-398 protocol for medium energy x-rays. Absorbed dose rates to water measured by calorimetry were compared to the values established using protocols based on references in terms of air kerma. A difference lower than 2.1% was reported. Standard uncertainty of water calorimetry being 0.8%, the one associated to the values from protocols being around 3.0%, results are consistent considering the uncertainties. Thanks to these new standards, it will be possible to use IAEA TRS-398 protocol to determine absorbed dose to water: a significant reduction of uncertainties is obtained (divided by 3 by comparison with the application of the IAEA TRS-277 protocol). Currently, none of the counterparts' laboratories own such an instrument allowing direct determination of standards in the reference conditions recommended by the international radiotherapy protocols. (author)

273

Absorbed Doses to Embryo from Intravenous Urography at Selected Radiological Departments in Slovakia  

International Nuclear Information System (INIS)

Actual legislation used in radiological protection requires quality assurance program for decreasing radiation load of patients from radiological examinations. The information about irradiation of pregnant women is very important, because the embryo is more radiosensitive as adult organism. On the basis of absence of unified calculations or measurements of absorbed doses to embryo from various radiological examinations in Slovakia we present in this study the values of absorbed doses to embryo from intravenous urography at selected radiological departments in Slovakia. Absorbed doses to embryo were obtained by measurement and calculation using the simulation of irradiation of pregnant woman by intravenous urography. The results of our study indicate, that absorbed doses to embryo were at various radiological departments considerably different, depending on type of X-ray machine and different settings of technical parameters of X-ray machine. In accordance with worldwide trend it is necessary to decrease radiation load of patients as low as possible level. Differences in radiation load between radiological departments indicate, that it is necessary to continue in solving of this problem and perform measurements and calculations of absorbed doses to embryo at different types of X-ray machines and at different examinations, where the embryo is in direct beam of X-ray. (author)

274

Review and status of absorbed dose standardization at therapy-level  

International Nuclear Information System (INIS)

A review of dosimetry protocols is presented considering the improvement of the physical basic data and the trends of Primary Standard Dosimetry Laboratories towards implementing calibrations in terms of absorbed dose to water, showing the status of dosimetry since the implementation of the IAEA Code of Practice in 1987. Absorbed dose to water is the quantity of main interest in radiation therapy, since this quantity relates closely to the biological effects of radiation. Following this concept several standards laboratories have developed calorimeter as primary standard for absorbed dose to water in 60 Co and in accelerator beams. At the present moment, IAEA presented the final draft of new International Code of Practice based on standards of absorbed dose to water which will be implemented in Brazil gradually, making the transition from the existing Code of Practice (IAEA 1987) in the country. At National Laboratory for Metrology of Ionizing Radiation, where the possibility of having and accelerator is remote, the approach used is to provide users with a calibration factor in terms of absorbed dose to water for the ionization chamber at the reference quality 60 Co and theoretically derived quality correction factors for that chamber type which must be applied for other beam qualities. (author)

275

Monte Carlo simulations of absorbed dose in a mouse phantom from 18-fluorine compounds  

International Nuclear Information System (INIS)

The purpose of this study was to calculate internal absorbed dose distribution in mice from preclinical small animal PET imaging procedures with fluorine-18 labeled compounds (18FDG, 18FLT, and fluoride ion). The GATE Monte Carlo software and a realistic, voxel-based mouse phantom that included a subcutaneous tumor were used to perform simulations. Discretized time-activity curves obtained from dynamic in vivo studies with each of the compounds were used to set the activity concentration in the simulations. For 18FDG, a realistic range of uptake ratios was considered for the heart and tumor. For each simulated time frame, the biodistribution of the radionuclide in the phantom was considered constant, and a sufficient number of decays were simulated to achieve low statistical uncertainty. Absorbed dose, which was scaled to take into account radioactive decay, integration with time, and changes in biological distribution was reported in mGy per MBq of administered activity for several organs and uptake scenarios. The mean absorbed dose ranged from a few mGy/MBq to hundreds of mGy/MBq. Major organs receive an absorbed dose in a range for which biological effects have been reported. The effects on a given investigation are hard to predict; however, investigators should be aware of potential perturbations especially when the studied organ receives high absorbed dose and when longitudinal imaging protocols are considered

276

Theoretical study of the influence of a heterogeneous activity distribution on intratumoral absorbed dose distribution  

International Nuclear Information System (INIS)

Radioimmunotherapy of hematopoeitic cancers and micrometastases has been shown to have significant therapeutic benefit. The treatment of solid tumors with radionuclide therapy has been less successful. Previous investigations of intratumoral activity distribution and studies on intratumoral drug delivery suggest that a probable reason for the disappointing results in solid tumor treatment is nonuniform intratumoral distribution coupled with restricted intratumoral drug penetrance, thus inhibiting antineoplastic agents from reaching the tumor's center. This paper describes a nonuniform intratumoral activity distribution identified by limited radiolabeled tracer diffusion from tumor surface to tumor center. This activity was simulated using techniques that allowed the absorbed dose distributions to be estimated using different intratumoral diffusion capabilities and calculated for tumors of varying diameters. The influences of these absorbed dose distributions on solid tumor radionuclide therapy are also discussed. The absorbed dose distribution was calculated using the dose point kernel method that provided for the application of a three-dimensional (3D) convolution between a dose rate kernel function and an activity distribution function. These functions were incorporated into 3D matrices with voxels measuring 0.10x0.10x0.10 mm3. At this point fast Fourier transform (FFT) and multiplication in frequency domain followed by inverse FFT (iFFT) were used to effwed by inverse FFT (iFFT) were used to effect this phase of the dose calculation process. The absorbed dose distribution for tumors of 1, 3, 5, 10, and 15 mm in diameter were studied. Using the therapeutic radionuclides of 131I, 186Re, 188Re, and 90Y, the total average dose, center dose, and surface dose for each of the different tumor diameters were reported. The absorbed dose in the nearby normal tissue was also evaluated. When the tumor diameters exceed 15 mm, a much lower tumor center dose is delivered compared with tumors between 3 and 5 mm in diameter. Based on these findings, the use of higher ?-energy radionuclides, such as 188Re and 90Y is more effective in delivering a higher absorbed dose to the tumor center at tumor diameters around 10 mm

277

A study on absorbed dose in the breast tissue using geant4 simulation for mammography  

Energy Technology Data Exchange (ETDEWEB)

As the breast cancer rate is increasing fast in Korean women, people pay more attention to mammography and number of mammography have been increasing dramatically over the last few years. Mammography is the only means to diagnose breast cancer early, but harms caused by radiation exposure shouldn't be overlooked. Therefore, it is important to calculate the radiation dose being absorbed into the breast tissue during the process of mammography for a protective measure against radiation exposure. Because it is impossible to directly measure the radiation dose being absorbed into the human body, statistical calculation methods are commonly used, and most of them are supposed to simulate the interaction between radiation and matter by describing the human body internal structure with anthropomorphic phantoms. However, a simulation using Geant4 Code of Monte Carlo Method, which is well-known as most accurate in calculating the absorbed dose inside the human body, helps calculate exact dose by recreating the anatomical human body structure as it is through the DICOM file of CT. To calculate the absorbed dose in the breast tissue, therefore, this study carried out a simulation using Geant4 Code, and by using the DICOM converted file provided by Geant4, this study changed the human body structure expressed on the CT image data into geometry needed for this simulation. Besides, this study attempted to verify if the dose calculation of Geant4 interlocking with the DICOM file is useful, by comparing the calculated dose provided by this simulation and the measured dose provided by the PTW ion chamber. As a result, under the condition of 28kVp/190mAs, the Difference(%) between the measured dose and the calculated dose was found to be 0.08 %{approx}0.33 %, and at 28 kVp/70 mAs, the Difference(%) of dose was 0.01 %{approx}0.16 %, both of which showed results within 2%, the effective difference range. Therefore, this study found out that calculation of the absorbed dose using Geant4 Simulation is useful in measuring the absorbed dose in the breast tissue for mammography.

Lee, Sang Ho; Han, Sang Hyun [Seonam Univ., Namwon (Korea, Republic of); Lee, Jong Seok [Dept. of Radiological Wonkwang Health Science Univ., Iksan (Korea, Republic of)

2012-12-15

278

Absorbed dose calibration for high energy X rays: A new service for secondary standard dosimetry laboratories?  

International Nuclear Information System (INIS)

A calibration service for high energy X rays used in radiotherapy was introduced by the United Kingdom National Physical Laboratory (NPL) in 1988. A secondary standard dosimeter (type NE 2560 electrometer and type NE 2561 ionization chamber) was calibrated at the NPL in terms of absorbed dose to water for different X ray qualities. This dosimeter is used to calibrate the output of therapeutic X ray beams. Calibration factors, expressed in terms of absorbed dose to water, have been determined using the direct calibration factor obtained from the NPL and dosimetry protocols. The results obtained indicate that the values of the two calibration factors are in good agreement. However, the absorbed dose to water calibration factor obtained by using the NPL factor has a lower measurement uncertainty (2%) than the one determined from dosimetry protocols (over 3%). (author). 8 refs, 2 figs

279

Experimental basis for absorbed-dose calculations in medical uses of radionuclides  

International Nuclear Information System (INIS)

This report reviews the status of the methods used to estimate the radiation absorbed does to humans from internally deposited radionuclides with the emphasis on medical applications. The emphasis is placed on comparing the results of direct measurements with calculations based on mathematical models used to estimate the parameters that enter into dose calculations. The history of internal radiation dosimetry is reviewed and the physical parameters and transport calculations of dosimetry are discussed. Also discussed are the techniques used to measure the activity distributions in humans, and the factors which should be considered in making in-vivo absorbed dose measurements. Comparisons of measured and calculated absorbed dose values in phantom animals and humans are made. A formalism is included that can be used to quantify the radioactivity in irregular geometric shapes using an external measurement technique. 197 references, 6 figures, 4 tables

280

The Standard DIN 6800: Procedures for absorbed dose determination in radiology by the ionization method  

International Nuclear Information System (INIS)

In the Federal Republic of Germany, the Physikalisch-Technische Bundesanstalt (PTB) as the national Primary Standard Dosimetry Laboratory has developed primary standards of absorbed dose to water. Thus it is possible to calibrate therapy level dosimeters directly in a water phantom to indicate absorbed dose in gray. The Standard Committee on Radiology (Normenausschuss Radiologie) in the Federal Republic of Germany decided that in the field of dosimetry for radiation therapy, exposure should be replaced only by absorbed dose to water in a water phantom. A working group has been established to revise the Standard DIN 6800 'Dosismessverfahren in der radiologischen Technik -Ionisationsdosimetrie' accordingly. In this new concept one quantity is used exclusively from the primary standard to the user's instrument. A draft of the revised standard will soon be available. (author). 17 refs, 3 tabs

 
 
 
 
281

The effect of latex maturity on the absorbed dose for preparing RVNRL of optimum tensile strength  

International Nuclear Information System (INIS)

This paper present the results of the studies on the effects of using latex of different maturity periods, between 0 to 15 weeks on gamma irradiation dose require to prepare RVNRL of optimum tensile strength. Absorbed dose to prepare RVNRL of optimum tensile strength, molecular weight between cross-links and cross-link density were found to be influenced by the maturity of the latex used in the studies. With respect to optimum tensile strength and absorbed dose, latex of about six weeks maturity was found most suitable and economical for radiation vulcanization process. Using latex either with or without added secondary preservative the optimum tensile strength was determined at an absorbed of 8 kGy. However, the optimum tensile strength of RVNRL prepared from latex contained added secondary preservative was found to be higher than the optimum tensile strength of RVNRL prepared from latex without secondary preservative

282

The estimation of absorbed doses received by a victim of a Chinese radiation accident  

International Nuclear Information System (INIS)

The aim of this work was to estimate absorbed doses received by a victim of the radiation accident with a 60Co source in Henan province, China. With a Monte Carlo stochastic simulation method, an estimation method for doses to the radiation accident victim was made. It utilised a mathematical model of adult man and a relative applied computer program was developed. By means of the simulated conditions of the accident, the absorbed doses to the victim's main organ and total body doses were estimated. The results estimated by our Monte Carlo method are close to those of experimental simulation measurement of the accident. With its convenience and rapidity, this method will be valuable for radiation dose reconstruction for victims in radiation accidents. (author)

283

Dose absorbed by technologists in positron emission tomography procedures with FDG  

Energy Technology Data Exchange (ETDEWEB)

The objective of this work was to evaluate radiation doses delivered to technologists engaged in different tasks involving positron emission tomography (PET) studies with FDG (fluorodeoxyglucose). This investigation was performed in two French nuclear medicine departments, which presented significant differences in their arrangements and radiation safety conditions. Both centers administered about 300 MBq per PET/CT study, although only one of them is a dedicated clinical PET center. Dose equivalent Hp(10) and skin dose Hp(0.07) were measured using Siemens electronic personnel dosimeters. For assessment dose absorbed by hands during drawing up of tracer and injection into the patient, a Polimaster wristwatch gamma dosimeter was employed. Absorbed dose and the time spent during each investigated task were recorded for a total of 180 whole-body PET studies. In this report, the methodology employed, the results and their radioprotection issues are presented as well as discussed. (author)

Amaral, Ademir [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Dept. de Energia Nuclear. Grupo de Estudos em Radioprotecao e Radioecologia (GERAR)]. E-mail: ajamaral@oi.com.br; Itie, Christian [Institut de Radioprotection et de Surete Nucleaire (IRSN), Fontenay-aux-Roses (France). Lab. of External Dosimetry Studies and Researches; Bok, Bernard [Centre Tep Paris-Nord Roger Perez, Sarcelles (France)

2007-09-15

284

Estimation of absorbed dose in the covering skin of human melanoma treated by neutron capture therapy  

International Nuclear Information System (INIS)

A patient with malignant melanoma was treated by thermal neutron capture therapy using 10B-paraboronophenylalanine. The compound was injected subcutaneously into ten locations in the tumor-surrounding skin, and the patient was then irradiated with thermal neutrons from the Musashi Reactor at reactor power of 100 KW and neutron flux of 1.2 X 10(9) n/cm2/s. Total absorbed dose to the skin was 11.7-12.5 Gy in the radiation field. The dose equivalents of these doses were estimated as 21.5 and 24.4 Sv, respectively. Early skin reaction after irradiation was checked from day 1 to day 60. The maximum and mean skin scores were 2.0 and 1.5, respectively, and the therapy was safely completed as far as skin reaction was concerned. Some factors influencing the absorbed dose and dose equivalent to the skin are discussed

285

Absorbed Dose in the Uterus of a Three Months Pregnant Woman Due to 131I  

International Nuclear Information System (INIS)

The use of 131I is widely used in diagnostic and treatment of patients. If the patient is pregnant the 131I presence in the thyroid it becomes a source of constant exposition to other organs and the fetus. In this study the absorbed dose in the uterus of a 3 months pregnant woman with 131I in her thyroid gland has been calculated. The dose was determined using Monte Carlo methods in which a detailed model of the woman has been developed. The dose was also calculated using a simple procedure that was refined including the photons' attenuation in the woman organs and body. To verify these results an experiment was carried out using a neck phantom with 131I. Comparing the results it was found that the simple calculation tend to overestimate the absorbed dose, by doing the corrections due to body and organs photon attenuation the dose is 0.14 times the Monte Carlo estimation

286

Use of human phantom to assess the internal thoracic organs absorbed dose from external gamma irradiation  

International Nuclear Information System (INIS)

This study presents the scatter radiological exposure of patients organs and tissues while irradiated in teletherapy. Measurements of scattered gamma radiation has been carried out during planned irradiation sessions of patients and similar experimental irradiation of human-like phantom. Comparison of the external absorbed doses (inlet and exit) between patients treated by teletherapy using cobalt-60 and phantom using the same source revealed symmetry of doses. Insertion of TLDs in positions equivalent to internal organs of the thoracic cage in the phantom reflect the absorbed doses to that organ. The results revealed that the most affected organ is the chest wall in the left side (81% of the original dose). The least affected part is the postero-lateral location of the chest wall in the right side (0.4% of the original dose)

287

Measuring the absorbed dose in critical organs during low rate dose brachytherapy with 137 Cs using thermoluminescent dosemeters  

International Nuclear Information System (INIS)

Intracavitary Brachytherapy is one of the most used methods for the treatment of the cervical-uterine cancer. This treatment consists in the insertion of low rate dose 137Cs sources into the patient. The most used system for the treatment dose planning is that of Manchester. This planning is based on sources, which are considered fixed during the treatment. However, the experience has shown that, during the treatment, the sources could be displaced from its initial position, changing the dose from that previously prescribed. For this reason, it is necessary to make measurements of the absorbed dose to the surrounding organs (mainly bladder and rectum). This paper presents the results of measuring the absorbed dose using home-made LiF: Mg, Cu, P + Ptfe thermoluminescent dosimeters (TLD). Measurements were carried out in-vivo during 20 minutes at the beginning and at the end of the treatments. Results showed that the absorbed dose to the critical organs vary significantly due to the movement of the patient during the treatment. (Author)

288

Determination of maximum/minimum ratio of absorbed dose of dried figs  

International Nuclear Information System (INIS)

In the framework of an FAO/IAEA project, the ECB dosimeter and STERIN-125 and STERIN-300 dosimeters have been used for dose measurement in the dried figs packs. They were irradiated in our Gamma Irradiation Plant and were given 6 kGy dose. It was observed that all Sterin label dose indicators became very dark after a 6 kGy dose and the absorbance could not be measured with UV spectrophotometer. Therefore these label dose indicators were separately irradiated between 10-700 Gy doses by gamma rays to establish the dose sensitive curve of these indicators. After the irradiation of ECB dosimeter which is located in dried fig packs, we found the Dose Uniformity Ratio as 1.4 according to bulk density of 0.62 gr/cc. (author)

289

Neutron absorbed dose rate with 252 Cf sources for medical applications  

Directory of Open Access Journals (Sweden)

Full Text Available The 252 Cf brachytherapy reduces the effect caused by the tumor hypoxia in photon radiotherapy and chemotherapy. The AAPM TG-43 modified formalism was used for the calculation of the fast neutron absorbed dose rate of 252 Cf brachytherapy sources for normal tissues and malignant tumors. Three models of HDR 252 Cf sources; AT, VariSource and ?Selectron were simulated using spherical geometry, Watt fission spectrum and the MCNPX code. The results show that small variations in the elemental composition between the normal tissues and malignant tumors, produce variations in the reference fast neutron absorbed dose rate up to 14%.

L. Paredes

2010-01-01

290

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

Energy Technology Data Exchange (ETDEWEB)

The arrangements for the maintenance of the Australian standards for {sup 60}Co are described in detail. The primary standards are a graphite cavity chamber for exposure/air kerma and a graphite calorimeter for absorbed dose. These secondary standards are described and their responses in corresponding {sup 90}Sr reference sources are reported. Accurate ratios between the Australian Radiation Laboratory (ARL) and Australian Nuclear Science and Technology (ANSTO) {sup 90}Sr reference sources are derived for use in future calibrations. The value of 28.8 years for the half-life of {sup 90}Sr is confirmed. The usefulness of {sup 90}Sr reference source measurements in quality assurance is discussed. The charge sensitivity and linearity of the ANSTO electrometers are reported by two different methods and are compared with previous results. Calibration factors for all the secondary standard ionization chambers are given, in terms of exposure, air kerma and absorbed dose to water. Calibration factors are also given for most of the chambers in terms of absorbed dose to graphite. The methods of deriving the calibration factors are explained in detail, including all the corrections applied to both the primary and secondary standard measurements. Three alternative methods of deriving the absorbed dose to water calibration factors are compared. The reported calibration factors are compared with previous results. Changes in the Australian units of exposure, air kerma and absorbed dose to graphite and water are derived from changes in the corresponding calibration factors. The Australian units of exposure and air kerma have not changed significantly since 1990. The Australian unit of absorbed dose to graphite is now 1.1 % smaller than in 1993 and 1.3 % smaller than in 1990. The Australian unit of absorbed dose to water is now 1.4 % smaller than in 1993, but is only 0.9 % smaller than in 1990. Comparisons of the Australian standards of exposure/air kerma and absorbed dose with those of the Bureau International des Poids et Mesures (BIPM) were performed in 1997 and show that the Australian units fall within the range of those of other countries. (authors) 31refs., 19 tabs., 8 figs.

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

1998-05-01

291

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

International Nuclear Information System (INIS)

The arrangements for the maintenance of the Australian standards for 60Co are described in detail. The primary standards are a graphite cavity chamber for exposure/air kerma and a graphite calorimeter for absorbed dose. These secondary standards are described and their responses in corresponding 90Sr reference sources are reported. Accurate ratios between the Australian Radiation Laboratory (ARL) and Australian Nuclear Science and Technology (ANSTO) 90Sr reference sources are derived for use in future calibrations. The value of 28.8 years for the half-life of 90Sr is confirmed. The usefulness of 90Sr reference source measurements in quality assurance is discussed. The charge sensitivity and linearity of the ANSTO electrometers are reported by two different methods and are compared with previous results. Calibration factors for all the secondary standard ionization chambers are given, in terms of exposure, air kerma and absorbed dose to water. Calibration factors are also given for most of the chambers in terms of absorbed dose to graphite. The methods of deriving the calibration factors are explained in detail, including all the corrections applied to both the primary and secondary standard measurements. Three alternative methods of deriving the absorbed dose to water calibration factors are compared. The reported calibration factors are compared with previous results. Changes in the Australian units of exposure, air kerma and absorbed dose to graphite and water are derived from changes in the corresponding calibration factors. The Australian units of exposure and air kerma have not changed significantly since 1990. The Australian unit of absorbed dose to graphite is now 1.1 % smaller than in 1993 and 1.3 % smaller than in 1990. The Australian unit of absorbed dose to water is now 1.4 % smaller than in 1993, but is only 0.9 % smaller than in 1990. Comparisons of the Australian standards of exposure/air kerma and absorbed dose with those of the Bureau International des Poids et Mesures (BIPM) were performed in 1997 and show that the Australian units fall within the range of those of other countries. (authors)

292

Absorbed dose to water secondary standard for brachytherapy sources in Austria  

International Nuclear Information System (INIS)

Full text: In a frame of a joint research project within the European Association of National Metrology Institutes (EURAMET e.V.) ''T2.J06, Increasing cancer treatment efficacy using 3D brachytherapy'' aiming to establish across the Europe a more accurate metrological basis for the dosimetry of radioactive sources used in the clinic for Brachytherapy (BT) treatment. It leads to the necessity to create suitable metrology chain for traceability of absorbed dose measurements of BT radiation sources to absorbed dose to water primary and secondary standards. The absorbed dose to water, Dw, is the quantity of interest for dosimetry in radiotherapy - but no absorbed-dose-to-water primary standards are so far available for dosimetry of BT sources and following secondary standards are also not used. Currently, the procedures to determine from the existing standards the absorbed dose imparted to the patient are affected by an uncertainty that could reduce the cure rate. A significant fraction of this uncertainty is due to a lack of metrology. During first three years of the project run it was created one of the first primary standards of absorbed dose to water, Dw quantity at the PTB Germany - the water calorimeter. BEV Austria as the national metrology institute has developed its absorbed dose to water secondary standard on a base of well type ionizing chamber and the current measuring system with made measuring software to optimize measuring process and to minimize possible subject mistake. All needed metrology characteristics of the standard were stated by measurements, Monte-Carlo simulation calculation has been done as well. First Dw quantity calibration for BT source 192Ir was realized at the PTB primary laboratory this spring and the BEV secondary standard is now able to serve to hospitals with the calibration of their measuring instruments. Details of the BEV Dw quantity secondary standard will be described as well as the result of the calibration. Second output of the project in Austria is the development and construction of the measuring system for scanning of in the practice used BT sources to measure their real distribution of the absorbed dose to water in short distances of about 1,5 cm from the source axis. The aim is check them for homogeneity and isotropy. Measuring system based on the set of five IBA Dosimetry CC08 ionizing chambers placed inside the water phantom and moved around the source axis as well as some real measurements results will be presented and discussed. Finally the third problem solution - how to effectively check outputs of the therapy planning systems by measurements - will be presented. As an effective tool was IBA 2D Detector Matrix used and results of measurements will be discussed

293

Model of the absorbed dose on a small sphere into a gamma irradiation field  

International Nuclear Information System (INIS)

Several models of the absorbed dose calculated as the energy deposited by the secondary electrons on a small volume sphere are presented. The calculations use the Compton scattering of a uniform photon beam in water, the photon attenuation and the electron stopping power are included. The sphere total absorbed dose is due to the stopping of the electrons generated in three regions: into the sphere volume, ahead and behind the sphere volume. Calculations are performed for spheres of different radius and placed at various depth of the vacuum - water interface. (author)

294

Average fetal depth in utero: data for estimation of fetal absorbed radiation dose  

Energy Technology Data Exchange (ETDEWEB)

To estimate fetal absorbed dose from radiographic examinations, the depth from the anterior maternal surface to the midline of the fetal skull and abdomen was measured by ultrasound in 97 pregnant women. The relationships between fetal depth, fetal presentation, and maternal parameters of height, weight, anteroposterior (AP) thickness, gestational age, placental location, and bladder volume were analyzed. Maternal AP thickness (MAP) can be estimated from gestational age, maternal height, and maternal weight. Fetal midskull and abdominal depths were nearly equal. Fetal depth normalized to MAP was independent or nearly independent of maternal parameters and fetal presentation. These data enable a reasonable estimation of absorbed dose to fetal brain, abdomen, and whole body.

Ragozzino, M.W.; Breckle, R.; Hill, L.M.; Gray, J.E.

1986-02-01

295

Optical fibre temperature sensor technology and potential application in absorbed dose calorimetry  

International Nuclear Information System (INIS)

Optical fibre based sensors are proposed as a potential alternative to the thermistors traditionally used as temperature sensors in absorbed dose calorimetry. The development of optical fibre temperature sensor technology over the last ten years is reviewed. The potential resolution of various optical techniques is assessed with particular reference to the requirements of absorbed dose calorimetry. Attention is drawn to other issues which would require investigation before the development of practical optical fibre sensors for this purpose could occur. 192 refs., 5 tabs., 4 figs

296

Average fetal depth in utero: data for estimation of fetal absorbed radiation dose  

International Nuclear Information System (INIS)

To estimate fetal absorbed dose from radiographic examinations, the depth from the anterior maternal surface to the midline of the fetal skull and abdomen was measured by ultrasound in 97 pregnant women. The relationships between fetal depth, fetal presentation, and maternal parameters of height, weight, anteroposterior (AP) thickness, gestational age, placental location, and bladder volume were analyzed. Maternal AP thickness (MAP) can be estimated from gestational age, maternal height, and maternal weight. Fetal midskull and abdominal depths were nearly equal. Fetal depth normalized to MAP was independent or nearly independent of maternal parameters and fetal presentation. These data enable a reasonable estimation of absorbed dose to fetal brain, abdomen, and whole body

297

Comparison of absorbed radiation doses in barium and air enema reduction of intussusception: a phantom study  

International Nuclear Information System (INIS)

Objective. We assessed the relative radiation load in patients undergoing hydrostatic and pneumatic reduction of childhood intussusception. Materials and methods. In a phantom study we simulated two situations occurring during reduction of intussusception. The absorbed radiation dose was measured at several positions in the phantom using either barium sulphate (BaSO4) or air in the simulated reduction, combined with either automatic exposure control (AEC) or constant exposure rate (CER) at fluoroscopy. From these values the mean absorbed dose was calculated for different depth compartments within the phantom. Results. In the barium study the mean absorbed dose averaged over the total irradiated volume was 14-23 % lower when CER was used instead of AEC; in the air study the dose was 35-43 % lower when AEC was used instead of CER. The combination of air and AEC provided the lowest mean absorbed dose in the tissue. The barium enema created a low-radiation zone, which might be utilized for protecting radiation sensitive tissue. Conclusion. The use of BaSO4 or air in reduction of intussusception requires the proper combination with CER and AEC, respectively, to minimize the radiation load to the patient; the lowest radiation load is obtained by using air and AEC. (orig.). With 1 fig., 3 tabs

298

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

Science.gov (United States)

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

Benedetto, Anthony Richard

299

Determination of absorbed dose in the experimental animal irradiated on the Leksell gamma knife  

International Nuclear Information System (INIS)

The purpose of this study was to evaluate and quantify inaccuracy of Leksell GammaPlan relative and absolute dose calculations for the experimental animal and to determine necessary corrections that must be applied. Both TLD and semiconductor detectors appeared to be suitable for measurement of absorbed dose in the rat brain irradiated on the Leksell gamma knife. Both detectors, due to their size, measured mean doses, nay doses to maximum. The Leksell GammaPlan treatment planning system can be employed for the calculation of absorbed doses even in such an extreme condition like irradiation of experimental animals. However, in our concrete case, it was necessary to apply correction factor of 1.0779 for the absolute absorbed dose to obtain reliable results. Comparison of dose profiles in all three axis calculated by the treatment planning system and measured ones by polymer gel dosimeter showed acceptable agreement. Results presented in this study are strictly related to the Leksell GammaPlan treatment planning system and the special fixation device developed in Na Homolce Hospital. (authors)

300

Evaluation of the measurement uncertainty of absorbed dose for ECB dosimetry system at IRASM  

International Nuclear Information System (INIS)

Full text: ECB dosimetric system is used for evaluating absorbed dose in the gamma irradiated product at irradiation facility IRASM. In order to use it in process validation and in process control for radiation treatment of products, the calculation of the uncertainty associated with the dose measurement is required. In this paper, the identification of specific sources of uncertainty and the evaluation of their contributions to the combined standard uncertainty of measured absorbed dose are presented, using analysis of variance ANOVA. The dose range was determined using one-way ANOVA with equal group sizes, the uncertainty components associated with the variability in readout oscillometric equipment and with the dosimeter-to-dosimeter scatter for (10. . . 50) kGy. The uncertainty due to polynomial fit to actual dosimetry calibration data was evaluated by using the 95 % confidence interval about the fit. The combined relative uncertainty for the dosimetric system is dose dependent. For the specific dose range, the relative combined standard uncertainty of the calibrated system varies from 2.0 % (Dx=30.0 kGy) to 3.3 % (Dx=10.0 kGy), and the combined relative uncertainty of measured absorbed dose value Dx, from 2.2 % (Dx=30.0 kGy) to 3.4 % (Dx=10.0 kGy). (author)

 
 
 
 
301

Improved estimates of the radiation absorbed dose to the urinary bladder wall  

Science.gov (United States)

Specific absorbed fractions (SAFs) have been calculated as a function of the content in the urinary bladder in order to allow more realistic calculations of the absorbed dose to the bladder wall. The SAFs were calculated using the urinary bladder anatomy from the ICRP male and female adult reference computational phantoms. The urinary bladder and its content were approximated by a sphere with a wall of constant mass, where the thickness of the wall depended on the amount of urine in the bladder. SAFs were calculated for males and females with 17 different urinary bladder volumes from 10 to 800 mL, using the Monte Carlo computer program MCNP5, at 25 energies of mono-energetic photons and electrons ranging from 10 KeV to 10 MeV. The decay was assumed to be homogeneously distributed in the urinary bladder content and the urinary bladder wall, and the mean absorbed dose to the urinary bladder wall was calculated. The Monte Carlo simulations were validated against measurements made with thermoluminescent dosimeters. The SAFs obtained for a urine volume of 200 mL were compared to the values calculated for the urinary bladder wall using the adult reference computational phantoms. The mean absorbed dose to the urinary wall from 18F-FDG was found to be 77 µGy/MBq formales and 86 µGy/MBq for females, while for 99mTc-DTPA the mean absorbed doses were 80 µGy/MBq for males and 86 µGy/MBq for females. Compared to calculations using a constant value of the SAF from the adult reference computational phantoms, the mean absorbed doses to the bladder wall were 60% higher for 18F-FDG and 30% higher for 99mTc-DTPA using the new SAFs.

Andersson, Martin; Minarik, David; Johansson, Lennart; Mattsson, Sören; Leide-Svegborn, Sigrid

2014-05-01

302

Computational modelling of cellular effects post-irradiation with low- and high-LET particles and different absorbed doses  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The use of computational methods to improve the understanding of biological responses to various types of radiation is an approach, where multiple parameters can be modelled and a variety of data is generated. This study compares cellular effects modelled for low absorbed doses against high absorbed doses. The authors hypothesized that low and high absorbed doses would contribute to cell killing via different mechanisms, potentially impacting on targeted tumour radiotherapy outcomes. Cellular...

Tavares, Adriana Alexandre S.; Tavares, Joa?o Manuel R. S.

2013-01-01

303

Depth distribution of absorbed dose on the external surface of Cosmos 1887 biosatellite  

Science.gov (United States)

Significant absorbed dose levels exceeding 1.0 Gy day(exp -1) have been measured on the external surface of the Cosmos 1887 biosatellite as functions of depth in stacks of thin thermoluminescent detectors (TLD's) made in U.S.S.R. and U.S.A. The dose was found to decrease rapidly with increasing absorber thickness, thereby indicating the presence of intensive fluxes of low-energy particles. Comparison between the U.S.S.R. and U.S.A. results and calculations based on the Vette Model environment are in satisfactory agreement. The major contribution to the dose under thin shielding thickness is shown to be from electrons. The fraction of the dose due to protons and heavier charged particles increases with shielding thickness.

Watts, J. W., Jr.; Parnell, T. A.; Akatov, Yu. A.; Dudkin, V. E.; Kovalev, E. E.; Benton, E. V.; Frank, A. L.

1995-01-01

304

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

305

Estimation of eye absorbed doses in head & neck radiotherapy practices using thermoluminescent detectors  

Directory of Open Access Journals (Sweden)

Full Text Available  Determination of eye absorbed dose during head & neck radiotherapy is essential to estimate the risk of cataract. Dose measurements were made in 20 head & neck cancer patients undergoing 60Co radiotherapy using LiF(MCP thermoluminescent dosimeters. Head & neck cancer radiotherapy was delivered by fields using SAD & SSD techniques. For each patient, 3 TLD chips were placed on each eye. Head & neck dose was about 700-6000 cGy in 8-28 equal fractions. The range of eye dose is estimated to be (3.49-639.1 mGy with a mean of maximum dose (98.114 mGy, which is about 3 % of head & neck dose. Maximum eye dose was observed for distsnces of about 3 cm from edge of the field to eye.

Gh Bagheri

2011-09-01

306

Radiation-induced color centers in LiF for dosimetry at high absorbed dose rates  

International Nuclear Information System (INIS)

Color centers formed by irradiation of optically clear crystals of pure LiF may be analyzed spectrophotometrically for dosimetry in the absorbed dose range from 102 to 107 Gy. Routine monitoring of intense electron beams is an important application. Both 6LiF and 7LiF forms are commercially available, and when used with filters as albedo dosimeters in pairs, they provide discrimination of neutron and gamma-ray doses. (orig.)

307

Radiation-Induced Color Centers in LiF for Dosimetry at High Absorbed Dose Rates  

DEFF Research Database (Denmark)

Color centers formed by irradiation of optically clear crystals of pure LiF may be analyzed spectrophotometrically for dosimetry in the absorbed dose range from 102 to 107 Gy. Routine monitoring of intense electron beams is an important application. Both 6LiF and 7LiF forms are commercially available, and when used with filters as albedo dosimeters in pairs, they provide discrimination of neutron and gamma-ray doses.

Miller, Arne

1980-01-01

308

Generalized approach to absorbed dose calculations for dynamic tumor and organ masses  

International Nuclear Information System (INIS)

Tumor absorbed dose calculations in radionuclide therapy are presently based on the assumption of static tumor mass. This work examines the effect of dynamic tumor mass (growth and/or shrinkage) on the absorbed dose. Tumor mass kinetic characteristics were modeled with the Gompertz equation to simulate tumor growth and an additional exponential term to accommodate tumor shrinkage that may result as a consequence of therapy. Correction factors, defined as the ratio of the absorbed dose, which was calculated by considering tumor mass dynamics, to the absorbed dose, which was calculated by assuming static mass, are presented for 1- and 100-g tumors with different tumor mass kinetics. The dependence of the correction factor on the effective half-life Te of the radioactivity in the tumor and the tumor shrinkage half-time Ts was examined. The correction factors for the 1-g tumor were > 1 for short Ts and Te. In contrast, the correction factor was less than 1 for long Ts (> 9 days). The dose correction factors for the 100-g tumor were > 1 for all Ts and Te. Finally, the dosimetric method for dynamic masses is illustrated with experimental data on Chinese hamster V79 multicellular spheroids that were treated with 3H. Correction factors as high as about 10 are likely when Te and Ts are short. As Ts increases beyond 20 days, the importance of dynamic mass diminishes because most of the activity decays before the mass changes appreciably. In some cases, mass dynamics should be taken into account when the absorbed dose to tumors is estimated. 15 refs., 6 figs., 1 tab

309

Absorbed dose dependence of the connection factors for ionization chamber cable irradiation effects  

International Nuclear Information System (INIS)

A simple method was developed to be suggested to hospital physicists to evaluate the irradiation effects on cables and connectors during large radiation fields dosimetry with ionization chambers and to determine correction factors for the used system or geometry. This method was based on the absorbed dose rate dependence of the correction factor. (author)

310

Comparison of the NPL and PTB absorbed dose rate standards for beta radiation at protection levels  

International Nuclear Information System (INIS)

Both the National Physical Laboratory (NPL) and the Physikalisch-Technische Bundesanstalt (PTB) operate primary standard ionization chambers for the measurement of protection-level absorbed dose rates for beta radiation. Both standards are intended to measure or derive the absorbed dose rate to tissue, at a specified depth below the skin surface, from a source of beta radiation. A report has been submitted which describes the NPL primary standard, its construction, operation and performance; it also presents the results of a comparison of the NPL and PTB primary standards carried out at each laboratory using its standard to measure the absorbed dose rates from a number of NPL secondary standard sources of the radionuclides Sr + Y-90, Tl-204 and Pm-147. The agreement between NPL and PTB for Sr + Y-90 is very good, for Tl-204 is good and for Pm-147 is satisfactory. For Pm-147 the agreement between the absorbed dose rates to both air and tissue at the tissue surface is well within the claimed uncertainties but at a depth in tissue the agreement is about the same as the claimed uncertainties. (U.K.)

311

Exposure distribution, absorbed doses, and energy imparted for panoramic radiography using Orthopantomograph model OP 5  

International Nuclear Information System (INIS)

The absorbed doses and energy imparted for the Orthopantomograph model OP 5 using two different collimators (0.9-1.3 X 33 mm2 and 0.6-0.9 X 39.5 mm2, respectively) were examined at 70 and 75 kV. The absorbed doses were estimated by thermoluminescence dosimetry in a sectioned phantom and by the energy imparted from measurements of areal exposure using a plane parallel transmission ionization chamber. The exposure distribution was surveyed on radiographic film. The anterior part of the parotid glands received the highest absorbed doses (2.4-3.2 mGy) when the wider collimator was used, with a decrease of two to three times when the narrower collimator was used. Other areas received absorbed doses of about 1.0 to 1.5 mGy or below. An increase of the kV from 70 to 75 had a minor influence. The energy imparted for the wider collimator was 0.6-0.8 and for the narrower collimator, 0.4-0.6 mJ

312

Aquatic ecosystems of the Chernobyl NPP exclusion zone: dynamics of contamination, radiation absorbed doses, radiation effects  

International Nuclear Information System (INIS)

The results of radioactive contamination dynamics in the main components of aquatic ecosystems and absorbed dose rate for hydrobionts within the Chernobyl accident exclusion zone has been analysed. Some cytogenetic and haematological effects of long-term irradiation on aquatic organisms as well as damage of higher aquatic plants by parasitic fungi and gall-producing arthropods have been considered. (authors)

313

Simulation of absorbed dose in human blood with MCNP 4C code  

International Nuclear Information System (INIS)

Biological dosimetry, based on the analysis of solid stained dicentric chromosomes, has been used since the mid 1960s. The intervening years have seen great improvements bringing the technique to a point where dicentric analysis has become a routine component of the radiological protection programs of many countries. Experience of its application in thousands of cases of actual or suspected overexposures has proved the worth of the method. The aberrations scored in the lymphocytes are interpreted in terms of absorbed dose by reference to a dose response calibration curve. This curve will have been produced by exposure of blood in vitro to doses of the appropriate quality of radiation. The doses given to the specimens should be traceable via a physical instrument such as an ionization chamber, to a primary or secondary standard. An alternative to obtain the information about absorbed dose in a specific blood volume is through the Monte Carlo method. The use of such technique is worldwide when physical measurements are inconvenient or impossible, and particularly useful for the solution of complex problems that cannot be modeled by codes that use deterministic methods. It is applied to particle systems as neutrons and electrons, as well as photons or still in mixed systems. Due to difficulties that involve the use of neutrons, this technique has shown extreme importance for preliminary research and experimental arrangements with neutron sources. In this study, the main objective was to simulate the dose absorbed by a blood sample in an experimental arrangement through the irradiation with sources of 241AmBe. It was used the code Monte Carlo N-Particle version 4C (MCNP 4C) whose data had been processed parallel in a computational structure in a cluster. This method allowed estimating the absorbed dose in a specific blood volume, making possible the experimental setup arrangement. (author)

314

The METAS absorbed dose to water calibration service for high energy photon and electron beam radiotherapy  

International Nuclear Information System (INIS)

Full text: The Swiss Federal Office of Metrology and Accreditation (METAS) provides an absorbed dose to water calibration service for reference dosimeters using 60Co ? radiation, ten X-ray beam qualities between TPR20,10=0.639 and 0.802 and ten electron beam qualities between R50=1.75 gcm-2 and 8.54 gcm-2. A 22 MeV microtron accelerator with a conventional treatment head is used as radiation source for the high energy photon and electron beams. The treatment head produces clinical beams. The METAS absorbed dose calibration service for high energy photons is based on a primary standard sealed water calorimeter of the Domen type, that is used to calibrate several METAS transfer standards of type NE2611A and NE2571A in terms of absorbed dose to water in the energy range from 60Co to TPR20,10 = 0.802. User reference dosimeters are compared with the transfer standards to give calibration factors in absorbed dose to water with an uncertainty of 1.0% for 60Co ? radiation and 1.4% for higher energies (coverage factor k=2). The calibration service was launched in 1997. The calibration factors measured by METAS have been compared with those derived from the Code of Practice of the International Atomic Energy Agency using the calculated kQ factors listed in table 14. The comparison showed a maximum difference of 0.8% for the NE25611A and NE 2571A chambers. At 60Co ? radiation the METAS primary standard of absorbed dose to water was bilaterally compared with the primary standards of the Bureau International des Poids et Mesures BIPM (Sevres) as well as of the National Research Council NRC (Canada). In either case the standards were in agreement within the comparison uncertainties. The METAS absorbed dose calibration service for high energy electron beams is based on a primary standard chemical dosimeter. A monoenergetic electron beam of precisely known particle energy and beam charge is totally absorbed in Fricke solution (ferrous ammonium sulphate) of a given mass. This experiment is similar to the one described by Feist, but extended to an energy range from 5.3 MeV to 22.4 MeV, allowing to determine the energy dependence of the response of the Fricke dosimeter. The absorbed dose to Fricke solution is determined using the particle energy, the total beam charge and the mass of the solution. The absorbed dose to Fricke solution is converted to an absorbed dose to water applying a general conversion factor taken from Ma et al. The thus calibrated Fricke solution is then used to calibrate several METAS plane-parallel transfer ionisation chambers of type NACP-02 in the mentioned energy range. The user dosimeters are finally compared to the METAS transfer standards following the procedures described in IAEA Technical Reports Series No. 398. It is anticipated that the overall uncertainty in the calibration factor of a user dosimeter will be around 2% (coverage factor k=2). (author)

315

Absorbed 18F-FDG Dose to the Fetus During Early Pregnancy  

International Nuclear Information System (INIS)

We describe a rare case of a woman who underwent 18F-FDG PET/CT during early pregnancy (fetus age, 10 wk). The fetal absorbed dose was calculated by taking into account the 18F-FDG fetal self-dose, photon dose coming from the maternal tissues, and CT dose received by both mother and fetus. Methods: The patient (weight, 71 kg) had received 296 MBq of 18F-FDG. Imaging started at 1 h, with unenhanced CT acquisition, followed by PET acquisition. From the standardized uptake value measured in fetal tissues, we calculated the total number of disintegrations per unit of injected activity. Monte Carlo analysis was then used to derive the fetal 18F-FDG self-dose, including positrons and self-absorbed photons. Photon dose from maternal tissues and CT dose were added to obtain the final dose. Results: The maximum standardized uptake value in fetal tissues was 4.5. Monte Carlo simulation showed that the fetal self-dose was 3.0 * 10-2 mGy/MBq (2.7 * 10-2 mGy/MBq from positrons and 0.3 * 10-2 mGy/MBq from photons). The estimated photon dose to the fetus from maternal tissues was 1.04*10-2 mGy/MBq. Accordingly, the specific 18F-FDG dose to the fetus was about 4.0 *10-2 mGy/MBq (11.8 mGy in this patient). The CT scan added a further 10 mGy. Conclusion: The dose to the fetus during early pregnancy can be as high as 4.0*10-2 mGy/MBq of 18F-FDG. Current dosimetric standards in early pregnancy may need to be revised. (authors)

316

The METAS absorbed dose to water calibration service for high energy photon and electron beam radiotherapy  

International Nuclear Information System (INIS)

The Swiss Federal Office of Metrology and Accreditation (METAS) provides an absorbed dose to water calibration service for reference dosimeters. The calibration service uses 60Co gamma radiation, ten high energy photon beam qualities between TPR20,10 = 0.639 and 0.802 and ten electron beam qualities between R50 = 1.75 g/cm2 and 8.54 g/cm2. The METAS absorbed dose calibration service for high energy photons is based on a primary standard sealed water calorimeter used to calibrate several METAS NE 2611A and NE 2571A type ionization chamber working standards in terms of absorbed dose to water in the energy range of 60Co to TPR20,10 = 0.802. The users' reference dosimeters are compared with the working standards to give calibration factors in absorbed dose to water with an uncertainty of 1.0% for 60Co radiation and 1.4% for higher energies (coverage factor k = 2). The calibration service was launched in 1997. The calibration factors measured by METAS have been compared with those derived from the IAEA Technical Reports Series No. 398 (TRS 398) code of practice and from Recommendations No. 4 of the Swiss Society of Radiobiology and Medical Physics (SSRMP). The comparisons showed a maximum difference of 1.2% for the NE 2561A and NE 2571A chambers. At 60Co gamma radiation the METAS primary standard of absorbed dose to water was bilaterally compared with the primary standards oflly compared with the primary standards of the Bureau international des poids et mesures.The standards were in agreement within the comparison uncertainties. The METAS absorbed dose calibration service for high energy electron beams is based on a primary standard chemical dosimeter. A monoenergetic electron beam of known particle energy and beam charge is totally absorbed in Fricke solution. The experiment was carried out in the energy range of 5.3 MeV to 22.4 MeV, which allows the determination of the response of the Fricke dosimeter. Finally, the users' dosimeters are compared with the METAS working standards. The overall uncertainty in the calibration factor of a user's dosimeter is 2% (coverage factor k = 2). The calibration factors measured by METAS have been compared with those derived from TRS 398 and from Recommendations No. 4 of the SSRMP. The comparison showed a maximum difference of 1.2% and 2.5%, respectively, for the NACP-02 chamber. (author)

317

Skin Absorbed Doses from Full Mouth Standard Intraoral Radiography in Bisecting Angle and Paralleling techniques  

Energy Technology Data Exchange (ETDEWEB)

This study was performed to measure the skin absorbed doses from full mouth standard intraoral radiography(14 exposures) in bisecting angle and paralleling techniques. Thermoluminescent dosimeters were used in a phantom. Circular tube collimator (60 mm in diameter, 20 cm in length) and rectangular collimator (35 mm X 44 mm, 40 cm in length) were set for bisecting angle and paralleling techniques respectively. All measurement sites were classified into 8 groups according to distance from each point of central rays. The results were as follows: 1. The skin absorbed doses from the paralleling technique were significantly decreased than those from the bisecting technique in both points at central ray and points away from central ray. The percentage rats of decrease were greater at points away from central ray than those at central ray. 2. The skin absorbed doses at the lens of eye, parotid gland, submandibular gland and thyroid region were significantly decreased in paralleling technique, but those of the midline of palate remained similar in both techniques. 3. The highest doses were measured at the site 20 mm above the point of central ray for the mandibular premolars in bisecting angle technique and at the point of central ray for the mandibular premolars in paralleling techniques. The lowest doses were measured at the thyroid region in both techniques.

Nah, Kyung Soo; Kim, Ae Ji [Dept. of Oral Radiology, College of Dentistry, Pusan National University, Pusan (Korea, Republic of); Doh, Shi Hong [Dept. of Applied physics . National Fisheries University of Pusan Department of Radiotherapy, Pusan (Korea, Republic of); Kim, Hyun Ja [Dept. of Oral Radiology, Baptist Hospital, Pusan (Korea, Republic of); Yoo, Meong Jin [Dept. of Radiology, College of Dentistry, Pusan National University, Pusan (Korea, Republic of)

1990-08-15

318

Skin Absorbed Doses from Full Mouth Standard Intraoral Radiography in Bisecting Angle and Paralleling techniques  

International Nuclear Information System (INIS)

This study was performed to measure the skin absorbed doses from full mouth standard intraoral radiography(14 exposures) in bisecting angle and paralleling techniques. Thermoluminescent dosimeters were used in a phantom. Circular tube collimator (60 mm in diameter, 20 cm in length) and rectangular collimator (35 mm X 44 mm, 40 cm in length) were set for bisecting angle and paralleling techniques respectively. All measurement sites were classified into 8 groups according to distance from each point of central rays. The results were as follows: 1. The skin absorbed doses from the paralleling technique were significantly decreased than those from the bisecting technique in both points at central ray and points away from central ray. The percentage rats of decrease were greater at points away from central ray than those at central ray. 2. The skin absorbed doses at the lens of eye, parotid gland, submandibular gland and thyroid region were significantly decreased in paralleling technique, but those of the midline of palate remained similar in both techniques. 3. The highest doses were measured at the site 20 mm above the point of central ray for the mandibular premolars in bisecting angle technique and at the point of central ray for the mandibular premolars in paralleling techniques. The lowest doses were measured at the thyroid region in both techniques.

319

evaluation of the products yields-absorbed dose relationship for benzene -carbon tetrachloride gamma irradiated system  

International Nuclear Information System (INIS)

gas chromatographic peak areas of the major products yields of ?- irradiated carbon tetrachloride - benzene system (chlorobenzene: PhCl, hexachloroethane: C2Cl6, trichloromethyl benzene: CCl3Ph, biphenyl: Ph2) was found to be linearly dependent on absorbed radiation dose from 0 kGy to 236 kGy. the linearity of the curves were evaluated according to regression coefficients (R2), and were found to be 0.9873, 09865,0.9735 and 0.9815 for PhCl, C2Cl6, CCl3Ph, and Ph2 respectively. statistical analysis of GC peak area measurements such as standard deviation, standard error, 95 %, 99 % confidences and % relative standard deviation (RSD) were calculated for each product. the uncertainty associated with products peaks areas as a response of the adsorbed dose was expressed in the term of coefficient of variation (CV %) . reproducibility of the readings at different absorbed doses as well as reliability was discussed. precision was also evaluated, according to CV % values of each product model. moreover, the knowledge of G-value of chlorobenzene in ?-irradiated carbon tetrachloride - benzene system, presents this model as a good candidate for the direct measurement of absorbed dose within the studied dose range.

320

Calculation of ?-ray absorbed dose rate for 131I applied to the inflorescence of Tradescantia  

International Nuclear Information System (INIS)

Effects of 131I applied to the inflorescence on the induction of somatic mutations in Tradescantia stamen hairs were previously investigated, and the doubling dose (activity) was estimated to be 4 nCi. In the present paper, the absorbed dose rate in stamen hairs of Tradescantia for ? rays from the applied 131I was calculated. The doubling dose for the 131I (4 nCi) applied to the inflorescence was estimated to be higher than 0.3 rad (assuming uniform distribution of 131I on the surface of the buds and assuming that the shape of the buds was a sphere) and lower than 1.0 rad

 
 
 
 
321

Absorbed doses received by infants subjected to panoramic dental and cephalic radiographs  

International Nuclear Information System (INIS)

The IAEA Report No. 115 recommends that each country or region can establish levels of absorbed doses for each radiographic technique employed in diagnostic. assuming the extended and expensive of this purpose, we have been to begin in a first step with the dentistry area, in order to estimate the dose levels received at crystalline and thyroid level in infants that go to an important public institution in our country to realize panoramic and cephalic radiographs. This work will serve to justify and impel a quality assurance program in Venezuela on the dentistry area which includes aspects such as training for the medical lap referring the justification of the radiological practice, optimization of X-ray units to produce an adequate image quality that delivers to patient an absorbed dose as much lower as reasonably it can be reached without diagnostic detriment. (Author)

322

Calculation of absorbed dose of anchorage-dependent cells from internal beta-rays irradiation  

International Nuclear Information System (INIS)

Objective: To elicit the formula of internal dosimetry in anchorage-dependent cells by beta-emitting radionuclides from uniformly distributed volume sources. Methods: By means of the definition of absorbed dose and the MIRD (Medical International Radiation Dose) scheme the formula of internal dosimetry was reasonably deduced. Firstly, studying the systems of suspension culture cells. Then, taking account of the speciality of the systems of the anchorage-dependent cells and the directions of irradiation, the absorbed dose of anchorage -dependent cells was calculated by the accumulated radioactivity, beta-ray energy, and the volume of the cultured systems. Results: The formula of internal dosimetry of suspension culture cells and anchorage-dependent cells were achieved. At the same time, the formula of internal dosimetry of suspension culture cells was compared with that of MIRD and was confirmed accurate. Conclusion: The formula of internal dosimetry is concise, reliable and accurate

323

Biological dosimetry for the reconstruction of doses absorbed during accidents in radiotherapy  

International Nuclear Information System (INIS)

Medical radiation represents by far the largest man-made source of radiation exposure. The recent accident in a radiotherapy unit in Bialystok, Poland, clearly showed the necessity to develop biological methods allowing a reconstruction of the absorbed dose in case of an accidental exposure. We are currently analysing the frequencies of micronuclei in lymphocytes of patients undergoing radiotherapy of tumors localized in different parts of the body. The aim of the studies in the setting up to appropriate calibration curves with the help of which a dose absorbed during an accident could be estimated. In addition, the applicability of such calibration curves for quality assurance of teleradiotherapy will be considered. In order to calculate the expected frequencies of aberrations and micronuclei in lymphocytes of patients undergoing teleradiotherapy a mathematical model was developed. The modeled dose-response curves agree well with the majority of published experimental results and will serve as a basis for ongoing studies. (author)

324

High-energy electron-beam absorbed-dose computation for shaped fields  

International Nuclear Information System (INIS)

The high-energy electron beams produced by the medical linear accelerator or betatron are widely used for treatment of cancers. The determination of the electron-beam absorbed dose distribution in tissue, with sufficient accuracy, is a complex problem in computational methods that need to be confirmed with measured doses. The electron treatment fields are often shaped in various forms from a standard beam applicator using secondary blocking to fit the treatment area or volume. Shaping a field within the limit of practical range of the electron beam energy (a) changes the absorbed dose distribution within the irradiated volume, (b) shifts the d/sub max/ (the point of maximum absorbed dose), and also (c) alters the output factor (ratio of the output for a shaped field to the output for a reference field). In this study, an investigation of the validity of electron-beam absorbed dose computational methods using (a) a strip-beam summation method and (b) a narrow-beam summation method for shaped fields was performed. The results indicate that the finite length strip-beam model is the most accurate to predict the d/sub max/-shift, output factor variation and also the depth dose as well as isodose distributions for shaped fields. The important finding in this study was that the d/sub max/-shift is strongly dependent upon the smallest dimension of the shaped field as long as the other dimension is larger than the practical range. This study also shows that the output factor v study also shows that the output factor variation can be predicted within a 5% accuracy compared to the measured value. A complete isodose distribution can be produced without a direct measurement

325

Fetus absorbed dose evaluation in head and neck radiotherapy procedures of pregnant patients  

International Nuclear Information System (INIS)

Each year a considerable amount of pregnant women needs to be submitted to radiotherapeutic procedures to combat malignant tumors. Radiation therapy is often a treatment of choice for these patients. It is possible to use shielding and beam positioning such that the potential dose to the fetus can be minimized. In this work the head and neck cancer treatment of a pregnant patient was experimentally simulated. The patient was simulated by an anthropomorphic Alderson phantom and the absorbed dose to the fetus was evaluated using micro-rod TLD-100 detectors in two conditions, namely protecting the patients abdomen with a 7 cm lead layer and using no abdomen shielding. The aim of this experiment was to evaluate the efficiency of the abdomen protection in reducing the fetus absorbed dose. Irradiations were performed with a Trilogy linear accelerator using x-rays of 6 MV. A total dose of 50 Gy to the target volume was delivered. The fetus doses evaluated with and without the lead shielding were, respectively, 0.52±0.039 and (0.88±0.052) c Gy, corresponding to a dose reduction of 59%. The dose (0.52±0.039) c Gy is within the zone of biological tolerance for the fetus. (Author)

326

Fetus absorbed dose evaluation in head and neck radiotherapy procedures of pregnant patients  

Energy Technology Data Exchange (ETDEWEB)

Each year a considerable amount of pregnant women needs to be submitted to radiotherapeutic procedures to combat malignant tumors. Radiation therapy is often a treatment of choice for these patients. It is possible to use shielding and beam positioning such that the potential dose to the fetus can be minimized. In this work the head and neck cancer treatment of a pregnant patient was experimentally simulated. The patient was simulated by an anthropomorphic Alderson phantom and the absorbed dose to the fetus was evaluated using micro-rod TLD-100 detectors in two conditions, namely protecting the patients abdomen with a 7 cm lead layer and using no abdomen shielding. The aim of this experiment was to evaluate the efficiency of the abdomen protection in reducing the fetus absorbed dose. Irradiations were performed with a Trilogy linear accelerator using x-rays of 6 MV. A total dose of 50 Gy to the target volume was delivered. The fetus doses evaluated with and without the lead shielding were, respectively, 0.52±0.039 and (0.88±0.052) c Gy, corresponding to a dose reduction of 59%. The dose (0.52±0.039) c Gy is within the zone of biological tolerance for the fetus. (Author)

Camargo da C, E.; Ribeiro da R, L. A.; Santos B, D. V., E-mail: etieli@ird.gov.br [Instituto de Radioprotecao e Dosimetria / CNEN, Av. Salvador Allende s/n, Barra de Tijuca, 22783-127 Rio de Janeiro (Brazil)

2014-08-15

327

3D calculation of absorbed dose for 131I-targeted radiotherapy: A Monte Carlo study  

International Nuclear Information System (INIS)

Various methods, such as those developed by the Medical Internal Radiation Dosimetry (MIRD) Committee of the Society of Nuclear Medicine or employing dose point kernels, have been applied to the radiation dosimetry of 131I radionuclide therapy. However, studies have not shown a strong relationship between tumour absorbed dose and its overall therapeutic response, probably due in part to inaccuracies in activity and dose estimation. In the current study, the GATE Monte Carlo computer code was used to facilitate voxel-level radiation dosimetry for organ activities measured in an. 131I-treated thyroid cancer patient. This approach allows incorporation of the size, shape and composition of organs (in the current study, in the Zubal anthropomorphic phantom) and intra-organ and intra-tumour inhomogeneities in the activity distributions. The total activities of the tumours and their heterogeneous distributions were measured from the SPECT images to calculate the dose maps. For investigating the effect of activity distribution on dose distribution, a hypothetical homogeneous distribution of the same total activity was considered in the tumours. It was observed that the tumour mean absorbed dose rates per unit cumulated activity were 0.65 E-5 and 0.61 E-5 mGY MBq-1 s-1 for the uniform and non-uniform distributions in the tumour, respectively, which do not differ considerably. However, the dose-volume histograms (DVH) show that the tue-volume histograms (DVH) show that the tumour non-uniform activity distribution decreases the absorbed dose to portions of the tumour volume. In such a case, it can be misleading to quote the mean or maximum absorbed dose, because overall response is likely limited by the tumour volume that receives low (i.e. non-cytocidal) doses. Three-dimensional radiation dosimetry, and calculation of tumour DVHs, may lead to the derivation of clinically reliable dose-response relationships and therefore may ultimately improve treatment planning as well as response assessment for radionuclide therapy. All rights reserved. (authors)

328

Dose absorbed by technologists in positron emission tomography procedures with FDG  

Directory of Open Access Journals (Sweden)

Full Text Available The objective of this work was to evaluate radiation doses delivered to technologists engaged in different tasks involving positron emission tomography (PET studies with FDG (fluorodeoxyglucose. This investigation was performed in two French nuclear medicine departments, which presented significant differences in their arrangements and radiation safety conditions. Both centers administered about 300 MBq per PET/CT study, although only one of them is a dedicated clinical PET center. Dose equivalent Hp(10 and skin dose Hp(0.07 were measured using Siemens electronic personnel dosimeters. For assessment dose absorbed by hands during drawing up of tracer and injection into the patient, a Polimaster wristwatch gamma dosimeter was employed. Absorbed dose and the time spent during each investigated task were recorded for a total of 180 whole-body PET studies. In this report, the methodology employed, the results and their radioprotection issues are presented as well as discussed.O objetivo deste trabalho foi o de avaliar doses absorvidas por profissionais de saúde em diferentes tarefas relacionadas à tomografia por emissão de pósitrons com [18F]-FDG (fluordesoxiglicose. Esta pesquisa foi realizada em dois centros de medicina nuclear na França, os quais apresentavam diferenças significativas em sua organização e radioproteção. Esses centros aplicavam aproximadamente 300 MBq por exame PET/CT, embora apenas um deles correspondesse a um serviço de medicina nuclear dedicado a exames por PET. A dose equivalente (Hp(10 e a dose na pele Hp(0,07 foram medidas usando dosímetros eletrônicos (Siemens. Para avaliação da dose nas mãos do tecnologista durante a preparação do radiofármaco e durante injeção no paciente, um dosímetro tipo relógio de pulso (Polimaster foi empregado. A dose absorvida e o tempo empregado durante cada tarefa foram registrados para um total de 180 exames de corpo inteiro através da PET. Neste trabalho, a metodologia empregada, os resultados e suas conseqüências na dose absorvida para o profissional de saúde são apresentados e discutidos.

Ademir Amaral

2007-09-01

329

Optimization of technique factors for a silicon diode array full-field digital mammography system and comparison to screen-film mammography with matched average glandular dose  

International Nuclear Information System (INIS)

Contrast-detail experiments were performed to optimize technique factors for the detection of low-contrast lesions using a silicon diode array full-field digital mammography (FFDM) system under the conditions of a matched average glandular dose (AGD) for different techniques. Optimization was performed for compressed breast thickness from 2 to 8 cm. FFDM results were compared to screen-film mammography (SFM) at each breast thickness. Four contrast-detail (CD) images were acquired on a SFM unit with optimal techniques at 2, 4, 6, and 8 cm breast thicknesses. The AGD for each breast thickness was calculated based on half-value layer (HVL) and entrance exposure measurements on the SFM unit. A computer algorithm was developed and used to determine FFDM beam current (mAs) that matched AGD between FFDM and SFM at each thickness, while varying target, filter, and peak kilovoltage (kVp) across the full range available for the FFDM unit. CD images were then acquired on FFDM for kVp values from 23-35 for a molybdenum-molybdenum (Mo-Mo), 23-40 for a molybdenum-rhodium (Mo-Rh), and 25-49 for a rhodium-rhodium (Rh-Rh) target-filter under the constraint of matching the AGD from screen-film for each breast thickness (2, 4, 6, and 8 cm). CD images were scored independently for SFM and each FFDM technique by six readers. CD scores were analyzed to assess trends as a function of target-filter and kVp and were compared to SFM at each breast thickness. For 2 cm thick breasts, optimal FFDkness. For 2 cm thick breasts, optimal FFDM CD scores occurred at the lowest possible kVp setting for each target-filter, with significant decreases in FFDM CD scores as kVp was increased under the constraint of matched AGD. For 2 cm breasts, optimal FFDM CD scores were not significantly different from SFM CD scores. For 4-8 cm breasts, optimum FFDM CD scores were superior to SFM CD scores. For 4 cm breasts, FFDM CD scores decreased as kVp increased for each target-filter combination. For 6 cm breasts, CD scores decreased slightly as kVp increased for Mo-Mo, but did not change significantly as a function of kVp for either Mo-Rh or Rh-Rh. For 8 cm breasts, Rh/Rh FFDM CD scores were superior to other target-filter combinations and increased significantly as kVp increased. These results indicate that low-contrast lesion detection was optimized for FFDM by using a softer x-ray beam for thin breasts and a harder x-ray beam for thick breasts, when AGD was kept constant for a given breast thickness. Under this constraint, optimum low-contrast lesion detection with FFDM was superior to that for SFM for all but the thinnest breasts

330

Radiation absorbed doses from iron-52, iron-55, and iron-59 used to study ferrokinetics  

Energy Technology Data Exchange (ETDEWEB)

Biological data obtained principally with Fe-59 citrate are used with physical data to calculate radiation absorbed doses for ionic or weak chelate forms of Fe-52, Fe-55, and Fe-59, administered by intravenous injection. Doses are calculated for normal subjects, primary hemochromatosis (also called idiopathic or hereditary hemochromatosis), pernicious anemia in relapse, iron-deficiency anemia, and polycythemia vera. The Fe-52 doses include the dose from the Mn-52m daughter generated after injection of Fe-52. Special attention has been given to the dose to the spleen, which has a relatively high concentration of RBCs and therefore of radioiron, and which varies significantly in size in both health and disease.

Robertson, J.S.; Price, R.R.; Budinger, T.F.; Fairbanks, V.F.; Pollycove, M.

1983-04-01

331

Radiation absorbed doses from iron-52, iron-55, and iron-59 used to study ferrokinetics  

International Nuclear Information System (INIS)

Biological data obtained principally with Fe-59 citrate are used with physical data to calculate radiation absorbed doses for ionic or weak chelate forms of Fe-52, Fe-55, and Fe-59, administered by intravenous injection. Doses are calculated for normal subjects, primary hemochromatosis (also called idiopathic or hereditary hemochromatosis), pernicious anemia in relapse, iron-deficiency anemia, and polycythemia vera. The Fe-52 doses include the dose from the Mn-52m daughter generated after injection of Fe-52. Special attention has been given to the dose to the spleen, which has a relatively high concentration of RBCs and therefore of radioiron, and which varies significantly in size in both health and disease

332

Microdosimetric measurements for neutron-absorbed dose determination during proton therapy  

International Nuclear Information System (INIS)

This work presents microdosimetric measurements performed at the Midwest Proton Radiotherapy Inst. in Bloomington, Indiana, USA. The measurements were done simulating clinical setups with a water phantom and for a variety of stopping targets. The water phantom was irradiated by a proton spread out Bragg peak (SOBP) and by a proton pencil beam. Stopping target measurements were performed only for the pencil beam. The targets used were made of polyethylene, brass and lead. The objective of this work was to determine the neutron-absorbed dose for a passive and active proton therapy delivery, and for the interactions of the proton beam with materials typically in the beam line of a proton therapy treatment nozzle. Neutron doses were found to be higher at 45 deg. and 90 deg. from the beam direction for the SOBP configuration by a factor of 1.1 and 1.3, respectively, compared with the pencil beam. Meanwhile, the pencil beam configuration produced neutron-absorbed doses 2.2 times higher at 0 deg. than the SOBP. For stopping targets, lead was found to dominate the neutron-absorbed dose for most angles due to a large production of low-energy neutrons emitted isotropically. (authors)

333

Comparison of cone beam CT and conventional CT in absorbed and effective dose  

International Nuclear Information System (INIS)

This study provides comparative measurements of absorbed and effective doses for newly developed cone beam computed tomography (CT) in comparison with these doses for conventional CT. Thermoluminescent dosimeter rods (TLD rod: GR-200, Thermo Fisher Scientific Inc., Waltham, MA, USA) were placed at 25 sites throughout the layers of Male ART Head and Neck Phantom (Radiology Support Devices Inc., Long Beach, USA) for dosimetry. Implagraphy, DCT Pro (Vatech Co., Hwasung, Korea) units, SCT-6800TXL (Shimadzu Corp., Kyoto, Japan), and Cranex 3+ (Soredex Orion Corp., Helsinki, Finland) were used for radiation exposures. Absorption doses were measured with Harshaw 3500TLD reader (Thermo Fisher Scientific Inc., Waltham, MA, USA). Radiation weighted doses and effective doses were measured and calculated by 2005 ICRP tissue weighting factors. Absorbed doses in Rt. submandibular gland were 110.57 mGy for SCT 6800TXL (Implant), 24.56 mGy for SCT 6800TXL (3D), 22.39 mGy for Implagraphy3, 7.19 mGy for DCT Pro, 5.96 mGy for Implagraphy1, 0.70 mGy for Cranex 3+. Effective doses (E2005draft) were 2.551 mSv for SCT 6800TXL (Implant), 1.272 mSv for SCT 6800TXL (3D), 0.598 mSv for Implagraphy3, 0.428 mSv for DCT Pro and 0.146 mSv for Implagraphy1. These are 108.6, 54.1, 25.5, 18.2 and 6.2 times greater than panoramic examination (Cranex 3+) doses (0.023 mSv). Cone beam CT machines recently developed in Korea, showed lower effective doses than conventional CT. Cone beam CT provides a lower ntional CT. Cone beam CT provides a lower dose and cost motive to conventional CT, promising to revolutionize the practice of oral and maxillofacial radiology.

334

Calculation of doses absorbed by samples irradiated in epithermal neutron spectra  

International Nuclear Information System (INIS)

A methodology has been recently developed for evaluation of doses absorbed by samples irradiated in research reactors, in which the partial doses due to thermal neutrons, epithermal neutrons, fast neutrons and gamma radiation are individually quantified. In this methodology the calculation of the dose due to epithermal neutrons assumes that the neutron spectrum in the irradiation device has a 1/E variation over the 0.5 eV to 0.1 MeV range. Although this hypothesis is in general satisfactory there may be specific experimental situations in which it is necessary to describe the spectrum as varying with 1/E 1+?, in which ? takes into account significant deviations relatively to the 1/E variation. In the present work we present a simple formulation for evaluation of doses absorbed by samples in spectra with a 1/E 1+?, based on average elementary kerma factors, calculated for different ? values in the -0.1 to 0.2 range. We conclude that, for most multi-element samples the dose rate is a decreasing function of ?. To evaluate the doses it is necessary to know only their elementary composition and the epithermal neutron flux in the irradiation position. This formulation is valid for irradiation devices located in the neighbourhood of the reactor core, where the spectrum varies usually with 1/E 1+?. Taking into account that experiments can also be done in irradiation devices in which the spectrum does not vary in this way, e.g., in the extremity of irradiation tubes for BNCT, we present graphics with the variation of the elementary kerma factors as function of the neutron energy, in the 0.5 eV - 10 MeV range. It is thus possible to estimate the doses absorbed by multi-element samples, both for epithermal neutrons as well as for an eventual fast neutron contamination

335

External Auditing on Absorbed Dose Using a Solid Water Phantom for Domestic Radiotherapy Facilities  

International Nuclear Information System (INIS)

We report the results of an external audit on the absorbed dose of radiotherapy beams independently performed by third parties. For this effort, we developed a method to measure the absorbed dose to water in an easy and convenient setup of solid water phantom. In 2008, 12 radiotherapy centers voluntarily participated in the external auditing program and 47 beams of X-ray and electron were independently calibrated by the third party's American Association of Physicists in Medicine (AAPM) task group (TG)-51 protocol. Even though the AAPM TG-51 protocol recommended the use of water, water as a phantom has a few disadvantages, especially in a busy clinic. Instead, we used solid water phantom due to its reproducibility and convenience in terms of setup and transport. Dose conversion factors between solid water and water were determined for photon and electron beams of various energies by using a scaling method and experimental measurements. Most of the beams (74%) were within ±2% of the deviation from the third party's protocol. However, two of 20 X-ray beams and three of 27 electron beams were out of the tolerance (±3%), including two beams with a >10% deviation. X-ray beams of higher than 6 MV had no conversion factors, while a 6 MV absorbed dose to a solid water phantom was 0.4% less than the dose to water. The electron dose conversion factors between the solid water phantom and water were determined: The higher the electron energy, the less is the conversion factor. rgy, the less is the conversion factor. The total uncertainty of the TG-51 protocol measurement using a solid water phantom was determined to be ±1.5%. The developed method was successfully applied for the external auditing program, which could be evolved into a credential program of multi-institutional clinical trials. This dosimetry saved time for measuring doses as well as decreased the uncertainty of measurement possibly resulting from the reference setup in water.

336

Determination of the Absorbed Dose and the Average LET of Space Radiation in Dependence of Shielding Conditions  

International Nuclear Information System (INIS)

The HRT method, developed for determination of absorbed dose and average LET of mixed radiation fields in space, was applied during several space missions on space station MIR, space shuttles and satellites. The method utilises the changes of peak height ratios in the glow curves in dependence on the linear energy transfer LET. Due to the small size of the dosemeters the evaluation of the variation of absorbed dose and average LET in dependence on the position of the dosemeters inside the space station is possible. The dose and LET distribution was determined during the experiment ADLET where dosemeters were exposed in two positions with different shielding conditions and during two following experiments (MIR-95, MIR-96) using six positions inside the space station. The results were compared with the shielding conditions of the positions. Calculations of the absorbed dose were carried out for comparison. Results have shown that the average LET increases with increasing absorbing thickness while the absorbed dose decreases. (author)

337

Radiation absorbed dose estimates for positron emission tomography (PET): 38K, 81Rb, 82Rb, and 130Cs  

International Nuclear Information System (INIS)

Radiation absorbed dose estimates were made for 38K, 81Rb, 82Rb, and 130Cs, potential radionuclides for myocardial and brain studies with positron emission tomography (PET). Biodistribution data for 42K, 86Rb, and 137Cs in rats were used, together with the most recent radiation absorbed dose computational techniques and data. Renal radiation absorbed doses for 38K, 81Rb, 83Rb, and 130Cs were estimated to be 56, 120, 19, and 150 mrad, respectively, per mCi administered. Corresponding radiation absorbed doses in the heart were 42, 54, 13, and 68 mrad/mCi. Radiation absorbed doses in the brain of 1.3, 3.5, 0.25, and 3.7 mrad/mCi were estimated for these four radionuclides

338

Total body irradiation with 6MVX-rays. Absorbed dose distribution in a humanoid phantom  

International Nuclear Information System (INIS)

Dose distribution in a humanoid phantom irradiated with total body irradiation of long SAD techniques by 6MV x-rays are discussed. Absorbed dose are measured by x-ray films or TLDs set in slice of the phntom. Uniformity of dose distribution is compared among the results of irradiations by anterior-posterior opposing two beams, lateral opposing two beams, and these combination (four beams). In the cases of lateral opposing two beams irradiation, irradiation is done with and without water boluses at head and neck region. In the case of four beams (anterior-posterior and bilateral), the uniformity is best among the three irradiation techniques, and the uniformity is within ±10%. In the case of anterior posterior opposing two beams irradiation, the uniformity is rather good, but exceeds ±10%. Lateral opposing two beam irradiation results the worst uniformity. But an application of boluses shows improvent of uniformity of midline of a humanoid phantom. In thoracicregion, as lung is irradiated over high absorbed dose, lung compensator is sufficiently nesessary for dose homogeneous and dose reduction. (author)

339

The therapeutic effects and absorbed dose of I-131 MIBG in patients with malignant pheochromocytoma  

International Nuclear Information System (INIS)

High selective tumor uptake and retention of I-131 MIBG (MIBG) is known as a prerequisite for successful treatment of pheochromocytoma. We evaluated the relationship of absorbed dose of MIBG in tumor and therapeutic effects in twelve selected patients gained over a period of more than 5 years. All patients were diagnosed as malignant adrenal or extra-adrenal pheochromocytoma clinically. The metastases were identified in 10 patients on tracer dose images prior to therapy. Except for 4 patients, all others were symptomatic and had raised hormones indicative of tumor hyper-secretion at the time of enrolment. The number of doses of MIBG ranged from 1 to 3 times with 3.7 GBq per course and a cumulative activity from 3.7 to 11.1 GBq. The estimation of the therapeutic MIBG absorbed dose was performed on the basis of measurement after a therapy by using SPECT on day 1,3,and 5. The absorbed dose was calculated from MIRD data. None of the patients had a complete remission to I-131 MIBG therapy. In one patient, died with DIC 4 months after therapy. Of the 11 patients evaluated, a partial remission (PR) and stable disease was observed in one case individually. A dramatic improvement of the symptoms was noticed in this PR patient and maintained well condition now, 12.0 years after initial MIBG therapy. The cumulated absorbed dose with 11.1 GBq of MIBG calculated in lung and lymph node metastases was exceeded over 150Gy. MIBG uptake in each tumor was thought to be homogeneous. The other nine patients, however, showed little effects, and five were died with disease in 2.6 to 4.1 years after therapy. MIBG therapy is an effective palliative treatment for malignant pheochromocytoma, although a complete tumor response rate is low. It is sufficient in the therapy of these difficult tumors that response of tumors is partial remission or the tumor arrest. Criteria of patient selection with therapeutic modalities should be estimated including the absorbed dose and also the distribution of MIBG within the tumors

340

A new approach for standardizing absorbed dose from beta radioactive wires used for intravascular brachytherapy  

International Nuclear Information System (INIS)

n the next step a water solid material will be used for RIC's body. The inner electrode of a RIC chamber was adjusted in such way to obtain the equivalent depth in water close to 2 mm, which is the recommended reference point. The depth doses in water and in PMMA for 32P and 90Y radioactive line sources were calculated by MC method. The equivalent depth in water for a given depth in PMMA was derived from these calculations. The ND factor for the RIC's model has been derived from calibration in 60CO beam at SSDL (traceable to a national standard). The ND,w values for 60Co and 32P (90Y) derived from ND are seen together with the relevant interaction coefficients. As can be seen, the values of the ND,w for PMMA (and water) for 60C and 32P (90Y) sources differ only by 1%. This creates a very comfortable situation that the absorbed dose to water calibration factor for beta radioactive sources is within 1% equal to calibration factor for 60C. Absorbed dose rate at 2 mm depth in water from 32P source (Guidant certified, traceable to NIST standard) was estimated based on the measurements by presented method and compared with the certified value. The Guidant certificate estimates the uncertainty of absorbed dose rate to be ? 16%. The ratio of the measured to certified dose rate is equal to 0.91. The total uncertainty of the estimated dose rate in water with presented approach is actually evaluated. One of the advantages of the new method (over the up to date in use) is very good geometrical reproducibility - source - detector which in turn gives the excellent reproducibility of the dose readings. The described method is equally acceptable for standardisation of absorbed dose from 192lr sources used for brachytherapy. In conclusions: the proposed method opens a new way for improving the quality of cardiovascular brachytherapy procedures with respect to dose estimation

 
 
 
 
341

Studies of absorbed dose determinations and spatial dose distributions for high energy proton beams  

International Nuclear Information System (INIS)

Absolute dose determinations were made with three types of ionization chamber and a Faraday cup. Methane based tissue equivalent (TE) gas, nitrogen, carbon dioxide, air were used as an ionizing gas with flow rate of 10 ml per minute. Measurements were made at the entrance position of unmodulated beams and for a beam of a spread out Bragg peak at a depth of 17.3 mm in water. For both positions, the mean value of dose determined by the ionization chambers was 0.993 +- 0.014 cGy for which the value of TE gas was taken as unity. The agreement between the doses estimated by the ionization chambers and the Faraday cup was within 5%. Total uncertainty estimated in the ionization chamber and the Faraday cup determinations is 6 and 4%, respectively. Common sources of error in calculating the dose from ionization chamber measurements are depend on the factors of ion recombination, W value, and mass stopping power ratio. These factors were studied by both experimentally and theoretically. The observed values for the factors show a good agreement to the predicted one. Proton beam dosimetry intercomparison between Japan and the United States was held. Good agreement was obtained with standard deviation of 1.6%. The value of the TE calorimeter is close to the mean value of all. In the proton spot scanning system, lateral dose distributions at any depth for one spot beam can be simulated by the Gaussian distribution. From the Gaussian distributions and the central axis depth doses fbutions and the central axis depth doses for one spot beam, it is easy to calculate isodose distributions in the desired field by superposition of dose distribution for one spot beam. Calculated and observed isodose curves were agreed within 1 mm at any dose levels. (J.P.N.)

342

Development of an absorbed dose calorimeter for use in IMRT and small field external beam radiotherapy  

International Nuclear Information System (INIS)

A calorimeter is in development for the absolute measurement of absorbed dose in small fields and complex fields such as those used to deliver intensity modulated radiation therapy. The probe consists of a spherical graphite core surrounded by and separated from a spherical graphite jacket, enclosed in water-equivalent plastic envelope. A spherical geometry was chosen to give approximately isotropic response and sensitivity to dose gradients. Temperature sensing and electrical heating are provided via small thermistors embedded in the graphite, and the temperatures of each component are actively controlled at a set value. Energy absorbed from radiation is measured by substitution, using the electrical heaters. The basic measurement is one of absorbed dose rate rather than absorbed dose. The device is calibrated in terms of absorbed dose to water under standard reference conditions and corrections to its response, in smaller and irregular non-reference fields, are calculated using EGSnrc Monte Carlo and Comsol MultiPhysics to perform finite element analysis of the heat transfer equation. Linearity of the heat equation plays a critical role in analysing measurement uncertainty and the limits on calorimeter performance. In measurements on the central axis of a small field, volume averaging effects make the correction for beam non-uniformity become dominant when the field size is comparable to the core diameter which, in the initial prototype, is 5 mm. The jacket diameter is 7 mm. Absorbed dose in the target volume of an IMRT treatment is measured as a time integral of dose rate, summed over the component fields in a multi-field plan, or integrated over the whole arc in an arc therapy treatment. Although the IMRT planned dose is uniform over the target volume, the instantaneous dose rate (i.e. the dose within a component field, or the dose rate during the arc delivery) is spatially non-uniform. Such variations in dose rate drive heat transfers within the calorimeter whose magnitude is inversely proportional to the time constant of heat exchange between core and jacket. So in this case, calorimeter performance is limited by the time taken to complete the delivery of each field or the whole arc. The non water- equivalent components, including gaps, perturb the radiation field being measured, and Monte Carlo simulation of the interactions in the calorimeter is required to evaluate this perturbation. The fluence perturbation correction, and its uncertainty, decreases with core diameter. However this increases the surface to volume ratio of the core, and decreases the time constant associated with heat transfer between core and jacket. In an IMRT treatment there is evidence that volume averaging effects tend to cancel provided the sensitive volume of the detector is entirely contained within the planned target volume. In a calorimetric measurement, this may indicate that the limit on core size could be relaxed so that the core is only contained within the target volume. However the non water-equivalence of the core creates a significant fluence perturbation if the core is too large. Results will be presented from measurements with the initial prototype calorimeter, with perturbation corrections evaluated using EGSnrc Monte Carlo and heat transfer corrections calculated using finite element analysis of the heat transfer equation using COMSOL

343

Measurement of absorbed dose by 7-GeV bremsstrahlung in a PMMA phantom  

CERN Document Server

High-energy electron storage rings generate energetic bremsstrahlung photons through radiative interaction of the particle beam with the residual gas molecules and other components inside the storage ring. At synchrotron radiation facilities, where beamlines are channeled out of the storage ring, a continuous bremsstrahlung spectrum, with a maximum energy of the stored particle beam, will be present. At the advanced photon source (APS), where the stored beam energy is 7 GeV, bremsstrahlung generated in the straight sections of the insertion device beamlines, which are a total of 15.38 m in length, can be significant. The contribution from each bremsstrahlung interaction adds up to produce a narrow mono-directional bremsstrahlung beam that comes down through the insertion device beamlines. The resulting absorbed dose distributions by this radiation in a 300 mmx300 mmx300 mm tissue substitute cube phantom were measured with LiF:Mg,Ti (TLD-700) thermoluminescent dosemeters. The normalized absorbed dose, in a cro...

Job, P K; Semones, E

1999-01-01

344

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

International Nuclear Information System (INIS)

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)

345

Absorbed dose assessment in particle-beam irradiated metal-oxide and metal-nonmetal memristors  

Directory of Open Access Journals (Sweden)

Full Text Available Absorbed dose was estimated after Monte Carlo simulation of proton and ion beam irradiation on metal-oxide and metal-nonmetal memristors. A memristive device comprises two electrodes, each of a nanoscale width, and a double-layer active region disposed between and in electrical contact with electrodes. Following materials were considered for the active region: titanium dioxide, zirconium dioxide, hafnium dioxide, strontium titanium trioxide and galium nitride. Obtained results show that significant amount of oxygen ion - oxygen and nonmetal ion - nonmetal vacancy pairs is to be generated. The loss of such vacancies from the device is believed to deteriorate the device performance over time. Estimated absorbed dose values in the memristor for different constituting materials are of the same order of magnitude because of the close values of treshold displacement energies for the investigated materials.

Kneževi? Ivan D.

2012-01-01

346

Determination of radiation dose absorbed by natural objects and human being  

International Nuclear Information System (INIS)

New method, based on autoradiography, to determine ? radiation dose absorbed by a natural object (tree) is presented. This report presents outcomes of its studying, as well as the dose values absorbed by a human being and obtained by means of electron-paramagnetic-resonance (EPR) dosimetry methods.The tree rings allow determining D within concrete years. For example, total D for poplar tree (age of 1955-1995) growing in Urda village of West Kazakstan Region was 2,2±0,8 rad, including 1,1±0,4 rad on account of nuclear explosions at 'Kapustin Yar' test site, 0,7±0,2 rad - at Lobnor test site and 0,3±0,1 rad - after Chernobyl accident. This report presents information on D for different regions of Kazakstan

347

Potassium dithionate EPR dosimetry for determination of absorbed dose and LET distributions in different radiation qualities  

International Nuclear Information System (INIS)

With an increasing interest in using protons and light ions for radiation therapy there is a need for possibilities to simultaneously determine both absorbed dose (D) and linear energy transfer, LET, (L?). Potassium dithionate (K2S2O6) tablets were irradiated in a conventional 6 MV linear accelerator photon beam and a N7+ beam (E = 33.5 MeV/u) respectively. The EPR spectrum of irradiated potassium dithionate is a narrow doublet consisting of two signals, R1 and R2, with different microwave power saturation properties. On the basis of identification in related substances by EPR and ENDOR, these two signals are assigned to two non-equivalent SO3- - radicals. Our experiments showed that the ratios of these two lines (R1/R2) were clearly connected to beam LET. Irrespective of the mechanistic details this investigation suggests a new method for measurement of absorbed dose and beam LET by using potassium dithionate EPR dosimetry.

348

The design of a calorimetric standard of ionising radiation absorbed dose  

International Nuclear Information System (INIS)

The design of a calorimetric working standard of ionising radiation absorbed dose is discussed. A brief history of the appropriate quantities and units of measurement is given. Detailed design considerations follow a summary of the relevant literature. The methods to be used to relate results to national standards of measurement are indicated, including the need for various correction factors. A status report is given on the construction and testing program

349

Axial distribution of absorbed doses in fast neutron field at the RB reactor  

International Nuclear Information System (INIS)

The coupled fast thermal system CFTS at the RB reactor is created for obtaining fast neutron fields. The axial distribution of fast neutron flux density in its second configuration (CFTS-2) is measured. The axial distribution of absorbed doses is computed on the basis of mentioned experimental results. At the end these experimental and computed results are given. 6 refs., 3 figs., 1 tab. (Author)

350

Analyse of the international recommendations on the calculation of absorbed dose in the biota  

International Nuclear Information System (INIS)

This paper evaluates the recommendations of ICRP which has as objective the environmental radioprotection. It was analysed the recommendations 26, 60, 91, 103 and 108 of the ICRP. The ICRP-103 defined the concept of animal and plant of reference (APR) to be used in the RAP based on the calculation of absorbed dose based on APR concept. This last view allows to build a legal framework of environmental protection with a etic, moral and scientific visualization, more defensible than the anthropomorphic concept

351

Measurement of absorbed dose rate of gamma radiation for lead compounds  

Science.gov (United States)

An attempt has been made to estimate the absorbed dose rate using both theoretical and measured mass energy attenuation coefficient of gamma for the lead compounds such as PbNO 3, PbCl 2, PbO 2 and PbO using various gamma sources such as 22Na (511, 1274), 137Cs (661.6), 54Mn (835) and 60Co (1173, 1332 keV).

Rudraswamy, B.; Dhananjaya, N.; Manjunatha, H. C.

2010-07-01

352

Distribution of absorbed dose in human eye simulated by SRNA-2KG computer code  

International Nuclear Information System (INIS)

Rapidly increasing performances of personal computers and development of codes for proton transport based on Monte Carlo methods will allow, very soon, the introduction of the computer planning proton therapy as a normal activity in regular hospital procedures. A description of SRNA code used for such applications and results of calculated distributions of proton-absorbed dose in human eye are given in this paper. (author)

353

General properties of radiochromic dye film used for the measurement of electron absorbed dose  

International Nuclear Information System (INIS)

Some general properties of the radiochromic pararosaniline cyanide (PR-CN) dye polyvinyl butyral (PVB)-based film for the measurement of absorbed dose of electron beams are reported. The optical absorption spectrum, the changes in optical densities as a function of film thickness, the distribution of background optical densities, reproducibility, stability, the time of establishing complete response and effects of environmental factors on the background optical density as well as the responses after irradiations have been experimentally in vestigated

354

Measurement of absorbed doses in a homogeneous ? rays fields with an extrapolation chamber  

International Nuclear Information System (INIS)

The main characteristics of a variable cavity ionization chamber are described. Using the ionization current of the detector irradiated in homogeneous ? rays fields, the tissue absorbed dose is determined. The corrective factors required to compute this quantity are analysed. Finally, international recommandations (ISO standards) relating to ? rays reference fields are given, with the characteristics of ? sources required for the energy response study of radiation protection instruments

355

Distribution of Absorbed Doses to the Important Organs of Head and Neck Region in Panoramic Radiography  

International Nuclear Information System (INIS)

p to 75 kVp and 1.9 times when kilovoltage changes from 75 kVp to 85 kVp at internal anatomic sites. According to increase of kilovoltage, the radiation absorbed doses were increased 1.3 times when kilovoltage changes from 65 kVp to 75 kVp and 1.6 times when kilovoltage changes from 75 kVp to 85 kVp at skin surfaces.

356

Simulations of absorbed dose on the phantom surface of MATROSHKA-R experiment at the ISS  

Science.gov (United States)

The health risks associated with exposure to various components of space radiation are of great concern when planning manned long-term interplanetary missions, such as future missions to Mars. Since it is not possible to measure the radiation environment inside of human organs in deep space, simulations based on radiation transport/interaction codes coupled to phantoms of tissue equivalent materials are used. However, the calculated results depend on the models used in the codes, and it is therefore necessary to verify their validity by comparison with measured data. The goal of this paper is to compare absorbed doses obtained in the MATROSHKA-R experiment performed at the International Space Station (ISS) with simulations performed with the three-dimensional Monte Carlo Particle and Heavy-Ion Transport code System (PHITS). The absorbed dose was measured using passive detectors (packages of thermoluminescent and plastic nuclear track detectors) placed on the surface of the spherical tissue equivalent phantom MATROSHKA-R, which was exposed aboard the ISS in the Service Zvezda Module from December 2005 to September 2006. The data calculated by PHITS assuming an ISS shielding of 3 g/cm2 and 5 g/cm2 aluminum mass thickness were in good agreement with the measurements. Using a simplified geometrical model of the ISS, the influence of variations in altitude and wall mass thickness of the ISS on the calculated absorbed dose was estimated. The uncertainties of the calculated data are also discussed; the relative expanded uncertainty of absorbed dose in phantom was estimated to be 44% at a 95% confidence level.

Kolísková (Mrázová), Z.; Sihver, L.; Ambrožová, I.; Sato, T.; Spurný, F.; Shurshakov, V. A.

2012-01-01

357

Measurement of absorbed dose rate of gamma radiation for lead compounds  

Energy Technology Data Exchange (ETDEWEB)

An attempt has been made to estimate the absorbed dose rate using both theoretical and measured mass energy attenuation coefficient of gamma for the lead compounds such as PbNO{sub 3}, PbCl{sub 2}, PbO{sub 2} and PbO using various gamma sources such as {sup 22}Na (511, 1274), {sup 137}Cs (661.6), {sup 54}Mn (835) and {sup 60}Co (1173, 1332 keV).

Rudraswamy, B., E-mail: rbasavanna2002@yahoo.co [Department of Physics, Bangalore University, Bangalore 560 056, Karnataka (India); Dhananjaya, N., E-mail: dhanu.siri@yahoo.co.i [Department of Physics, Bangalore University, Bangalore 560 056, Karnataka (India); Manjunatha, H.C. [Department of Physics, Bangalore University, Bangalore 560 056, Karnataka (India)

2010-07-21

358

Retrospective evaluation of absorbed doses in polluted landscapes of the Middlerussian height  

International Nuclear Information System (INIS)

Retrospective analysis of absorbed dose at low-grade level of contamination of the area by fission-produced radionuclides of the ChNPP was conducted. The mathematical model of gamma field was developed where form, sizes, power of raditing matter, radioisotope composition and gamma spectrum feature were taken into consideration. Leading role of the solid effluence in primary radionuclide migration on contaminated areas was revealed

359

Patient absorbed dose in coronary angiography determined by the flat panel digital detector X-ray system  

International Nuclear Information System (INIS)

The INNOVA 2000, an all-digital cardiovascular X-ray system with flat panel detector, is equipped with a monitoring function that makes it possible to track a patient's absorbed dose by displaying the real-time presumed absorbed dose. We verified this dose monitoring system and evaluated how it is affected by various parameters. We also compared the INNOVA 2000 to a conventional machine, the Advantx LC. The average absorbed dose of the INNOVA 2000 was 1,066 mGy, while that of the Adnantx LC was calculated to be 2,028 mGy. Dose reduction with the INNOVA 2000 was 76% at Low mode and 52% even at Normal mode. The INNOVA provides an advantage in lowering absorbed dose, even considering that it has a rectangular image intensifier (I.I.) versus the Advantx LC's round I.I. This comparison was made by cine and digital angiography. (author)

360

Absorbed dose by thyroid in case of nuclear accidents; Dose absorvida pela tireoide em casos de acidentes nucleares  

Energy Technology Data Exchange (ETDEWEB)

Radioisotopes of iodine are produced in abundance in nuclear fission reactions, and great amounts of radioiodine may be released into the environment in case of a nuclear reactor accident. Thyroid gland is among the most radiosensitive organs due to its capacity to concentrate iodine. The aim of this work was to evaluate the importance of contributions of internally deposited iodines ({sup 131}I, {sup 132}I, {sup 133}I, {sup 134}I and {sup 135}I) to the dose absorbed to thyroid follicle and to the whole organ, after internal contamination by those isotopes. For internal dose calculation, the code of particles transport MCNP4C was employed. The results showed that, in case of nuclear accidents, the contribution of short-lived iodines for total dose is about 45% for thyroid of newborn and about 40% for thyroid of adult. Thus, these contributions should not be neglected in a prospective evaluation of risks associated to internal contamination by radioactive iodine. (author)

Campos, Laelia; Attie, Marcia Regina Pereira [Universidade Federal de Sergipe (UFS), Sao Cristovao, SE (Brazil). Dept. de Fisica; Lima, Fernando Roberto de Andrade, E-mail: falima@cnen.gov.b [Centro Regional de Ciencias Nucleares do Nordeste (CRCN-NE/CNEN-PE), Recife, PE (Brazil); Amaral, Ademir [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Dept. de Energia Nuclear

2011-07-01

 
 
 
 
361

The Australian Commonwealth standard of measurement for absorbed radiation dose. Part 1  

International Nuclear Information System (INIS)

As an agent for the Commonwealth Scientific and Industrial Research Organisation, the Australian Nuclear Science and Technology Organisation is responsible for maintenance of the Australian Commonwealth standard of absorbed dose. This standard of measurement has application in radiation therapy dosimetry, which is required for the treatment of cancer patients. This report is the first in a series of reports documenting the absorbed dose standard for photon beams in the range from 1 to 25 MeV. The Urquhart graphite micro-calorimeters, which is used for the determination of absorbed dose under high energy photon beams, has been now placed under computer control. Accordingly, a complete upgrade of the calorimeter systems was performed to allow operation in the hospital. In this report, control and monitoring techniques have been described, with an assessment of the performance achieved being given for 6 and 18 MeV bremsstrahlung beams. Random errors have been reduced to near negligible proportions, while systematic errors have b