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FORTRAN Code for Glandular Dose Calculation in Mammography Using Sobol-Wu Parameters  

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Full Text Available Background: Accurate computation of the radiation dose to the breast is essential to mammography. Various the thicknesses of breast, the composition of the breast tissue and other variables affect the optimal breast dose. Furthermore, the glandular fraction, which refers to the composition of the breasts, as partitioned between radiation-sensitive glandular tissue and the adipose tissue, also has an effect on this calculation. Fatty or fibrous breasts would have a lower value for the glandular fraction than dense breasts. Breast tissue composed of half glandular and half adipose tissue would have a glandular fraction in between that of fatty and dense breasts. Therefore, the use of a computational code for average glandular dose calculation in mammography is a more effective means of estimating the dose of radiation, and is accurate and fast. Methods: In the present work, the Sobol-Wu beam quality parameters are used to write a FORTRAN code for glandular dose calculation in molybdenum anode-molybdenum filter (Mo-Mo, molybdenum anode-rhodium filter (Mo-Rh and rhodium anode-rhodium filter (Rh-Rh target-filter combinations in mammograms. The input parameters of code are: tube voltage in kV, half-value layer (HVL of the incident x-ray spectrum in mm, breast thickness in cm (d, and glandular tissue fraction (g. Results: The average glandular dose (AGD variation against the voltage of the mammogram X-ray tube for d = 4 cm, HVL = 0.34 mm Al and g=0.5 for the three filter-target combinations, as well as its variation against the glandular fraction of breast tissue for kV=25, HVL=0.34, and d=4 cm has been calculated. The results related to the average glandular absorbed dose variation against HVL for kV = 28, d=4 cm and g= 0.6 are also presented. The results of this code are in good agreement with those previously reported in the literature. Conclusion: The code developed in this study calculates the glandular dose quickly, and it is complete and accurate. Furthermore, it is user friendly and useful for dose optimizing in mammography imaging.

Mowlavi A A

2007-07-01

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

International Nuclear Information System (INIS)

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. - Highlights: ? Glandularity phantoms and a computed radiography mammography unit were used. ? Results were calculated from the incident air kerma and conversion coefficients. ? They are in according to the reference level established to a standard breast. ? Mean glandular dose increases with the glandularity and X-ray tube rotation. ? This work contributes to begin in Brazil the dosimetry in tomosynthesis

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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)

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Average glandular dose in patients submitted to mammography exams  

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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

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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)

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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)

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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

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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

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Average glandular dose in digital mammography and breast tomosynthesis  

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Purpose: To determine the average glandular dose (AGD) in digital full-field mammography (2 D imaging mode) and in breast tomosynthesis (3 D imaging mode). Materials and Methods: Using the method described by Boone, the AGD was calculated from the exposure parameters of 2247 conventional 2 D mammograms and 984 mammograms in 3 D imaging mode of 641 patients examined with the digital mammographic system Hologic Selenia Dimensions. The breast glandular tissue content was estimated by the Hologic R2 Quantra automated volumetric breast density measurement tool for each patient from right craniocaudal (RCC) and left craniocaudal (LCC) images in 2 D imaging mode. Results: The mean compressed breast thickness (CBT) was 52.7 mm for craniocaudal (CC) and 56.0 mm for mediolateral oblique (MLO) views. The mean percentage of breast glandular tissue content was 18.0 % and 17.4 % for RCC and LCC projections, respectively. The mean AGD values in 2 D imaging mode per exposure for the standard breast were 1.57 mGy and 1.66 mGy, while the mean AGD values after correction for real breast composition were 1.82 mGy and 1.94 mGy for CC and MLO views, respectively. The mean AGD values in 3 D imaging mode per exposure for the standard breast were 2.19 mGy and 2.29 mGy, while the mean AGD values after correction for the real breast composition were 2.53 mGy and 2.63 mGy for CC and MLO views, respectively. No significant relationship was found between the AGD and CBT in 2 D imaging mode and a good correlation coefficient of 0.98 in 3 D imaging mode. Conclusion: In this study the mean calculated AGD per exposure in 3 D imaging mode was on average 34 % higher than for 2 D imaging mode for patients examined with the same CBT.

Olgar, T. [Ankara Univ. (Turkey). Dept. of Engineering Physics; Universitaetsklinikum Leipzig AoeR (Germany). Klinik und Poliklinik fuer Diagnostische und Interventionelle Radiologie; Kahn, T.; Gosch, D. [Universitaetsklinikum Leipzig AoeR (Germany). Klinik und Poliklinik fuer Diagnostische und Interventionelle Radiologie

2012-10-15

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Average glandular dose in digital mammography and breast tomosynthesis  

International Nuclear Information System (INIS)

Purpose: To determine the average glandular dose (AGD) in digital full-field mammography (2 D imaging mode) and in breast tomosynthesis (3 D imaging mode). Materials and Methods: Using the method described by Boone, the AGD was calculated from the exposure parameters of 2247 conventional 2 D mammograms and 984 mammograms in 3 D imaging mode of 641 patients examined with the digital mammographic system Hologic Selenia Dimensions. The breast glandular tissue content was estimated by the Hologic R2 Quantra automated volumetric breast density measurement tool for each patient from right craniocaudal (RCC) and left craniocaudal (LCC) images in 2 D imaging mode. Results: The mean compressed breast thickness (CBT) was 52.7 mm for craniocaudal (CC) and 56.0 mm for mediolateral oblique (MLO) views. The mean percentage of breast glandular tissue content was 18.0 % and 17.4 % for RCC and LCC projections, respectively. The mean AGD values in 2 D imaging mode per exposure for the standard breast were 1.57 mGy and 1.66 mGy, while the mean AGD values after correction for real breast composition were 1.82 mGy and 1.94 mGy for CC and MLO views, respectively. The mean AGD values in 3 D imaging mode per exposure for the standard breast were 2.19 mGy and 2.29 mGy, while the mean AGD values after correction for the real breast composition were 2.53 mGy and 2.63 mGy for CC and MLO views, respectively. No significant relationship was found between the AGD and CBT in 2 D imaging mode and a ghe AGD and CBT in 2 D imaging mode and a good correlation coefficient of 0.98 in 3 D imaging mode. Conclusion: In this study the mean calculated AGD per exposure in 3 D imaging mode was on average 34 % higher than for 2 D imaging mode for patients examined with the same CBT.

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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

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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 etry protocol developed in this study can reliably predict the AGD imparted to an individual patient during a routine screening mammogram.

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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)

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Average glandular dose and phantom image quality in mammography  

International Nuclear Information System (INIS)

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 dults 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

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FORTRAN Code for Glandular Dose Calculation in Mammography Using Sobol-Wu Parameters  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Background: Accurate computation of the radiation dose to the breast is essential to mammography. Various the thicknesses of breast, the composition of the breast tissue and other variables affect the optimal breast dose. Furthermore, the glandular fraction, which refers to the composition of the breasts, as partitioned between radiation-sensitive glandular tissue and the adipose tissue, also has an effect on this calculation. Fatty or fibrous breasts would have a lower value for the glandula...

Mowlavi A A

2007-01-01

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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)

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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 boththe 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 g

18

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.

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

Science.gov (United States)

Studies are needed to determine the radiation dose of patients that are undergoing Digital breast tomosynthesis (DBT) procedures. Mean glandular dose (DG) values were derived from the incident air kerma (Ki) measurements and tabulated conversion coefficients. Ki values were obtained through an ionization chamber positioned in a Hologic Selenia Dimensions system using appropriate exposure parameters. This work contributes to determine the reliable radiation dose received by the patients and compare DG values provided by this DBT system images. PMID:25457188

Beraldo Oliveira, Bruno; Paixão, Lucas; Donato da Silva, Sabrina; Teixeira, Maria Helena Araújo; Nogueira, Maria do Socorro

2014-11-11

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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)...

Irene Nsiah-Akoto; Aba Bentil Andam; Kt, Eric Adisson; Ama Jaben Forson

2011-01-01

 
 
 
 
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MONTE CARLO SIMULATION FOR THE ESTIMATION OF THE GLANDULAR BREAST DOSE FOR A DIGITAL BREAST TOMOSYNTHESIS SYSTEM.  

Science.gov (United States)

Digital breast tomosynthesis (DBT) is a screening and diagnostic modality that acquires images of the breast at multiple angles during a short scan. The Selenia Dimensions (Hologic, Bedford, Mass) DBT system can perform both full-field digital mammography and DBT. The system acquires 15 projections over a 15° angular range (from -7.5° to +7.5°). An important factor in determining the optimal imaging technique for breast tomosynthesis is the radiation dose. In breast imaging, the radiation dose of concern is that deposited in the glandular tissue of the breast because this is the tissue that has a risk of developing cancer. The concept of the normalised mean glandular dose (DgN) has been introduced as the metric for the dose in breast imaging. The DgN is difficult to measure. The Monte Carlo techniques offer an alternative method for a realistic estimation of the radiation dose. The purpose of this work was to use the Monte Carlo code MCNPX technique to generate monoenergetic glandular dose data for estimating the breast tissue dose in tomosynthesis for arbitrary spectra as well as to observe the deposited radiation dose by projection on the glandular portion of the breast in a Selenia Dimensions DBT system. A Monte Carlo simulation of the system was developed to compute the DgN in a craniocaudal view. Monoenergetic X-ray beams from 10 to 49 keV in 1-keV increments were used. The simulation utilised the assumption of a homogeneous breast composition and three compositions (0 % glandular, 50 % glandular and 100 % glandular). The glandular and adipose tissue compositions were specified according ICRU Report 44. A skin layer of 4 mm was assumed to encapsulate the breast on all surfaces. The breast size was varied using the chest wall-to-nipple distance (CND) and compressed breast thickness (t). In this work, the authors assumed a CND of 5 cm and the thicknesses ranged from 2 to 8 cm, in steps of 2 cm. The fractional energy absorption increases (up to 44.35 % between 0 % glandular and 100 % glandular) with the increase in the glandular fraction due to changing the composition and increasing the density. Low-energy photon absorption occurred in the first tissue layer. The DgN decreases with increasing the compressed breast thickness. The graphs show that between 15 and 30 keV provides the greatest contribution to the dose and that the glandular dose is almost constant as a function of the projection angle. The results may be useful for optimising tomosynthesis procedures and evaluating the dose distribution in the projections in a craniocaudal view. PMID:25480841

Rodrigues, Leonardo; Magalhaes, Luis Alexandre Goncalves; Braz, Delson

2014-12-01

22

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)

23

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

24

Absorbed dose by a CMOS in radiotherapy  

International Nuclear Information System (INIS)

Absorbed dose by a complementary metal oxide semiconductor (CMOS) circuit as part of a pacemaker, has been estimated using Monte Carlo calculations. For a cancer patient who is a pacemaker carrier, scattered radiation could damage pacemaker CMOS circuits affecting patient's health. Absorbed dose in CMOS circuit due to scattered photons is too small and therefore is not the cause of failures in pacemakers, but neutron calculations shown an absorbed dose that could cause damage in CMOS due to neutron-hydrogen interactions. (Author)

25

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

26

The MIRD method of estimating absorbed dose  

International Nuclear Information System (INIS)

The estimate of absorbed radiation dose from internal emitters provides the information required to assess the radiation risk associated with the administration of radiopharmaceuticals for medical applications. The MIRD (Medical Internal Radiation Dose) system of dose calculation provides a systematic approach to combining the biologic distribution data and clearance data of radiopharmaceuticals and the physical properties of radionuclides to obtain dose estimates. This tutorial presents a review of the MIRD schema, the derivation of the equations used to calculate absorbed dose, and shows how the MIRD schema can be applied to estimate dose from radiopharmaceuticals used in nuclear medicine

27

Absorbed dose by a CMOS in radiotherapy  

Energy Technology Data Exchange (ETDEWEB)

Absorbed dose by a complementary metal oxide semiconductor (CMOS) circuit as part of a pacemaker, has been estimated using Monte Carlo calculations. For a cancer patient who is a pacemaker carrier, scattered radiation could damage pacemaker CMOS circuits affecting patient's health. Absorbed dose in CMOS circuit due to scattered photons is too small and therefore is not the cause of failures in pacemakers, but neutron calculations shown an absorbed dose that could cause damage in CMOS due to neutron-hydrogen interactions. (Author)

Borja H, C. G.; Valero L, C. Y.; Guzman G, K. A.; Banuelos F, A.; Hernandez D, V. M.; Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Calle Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Paredes G, L. C., E-mail: candy_borja@hotmail.com [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico)

2011-10-15

28

Determination of absorbed dose in water  

International Nuclear Information System (INIS)

This report describes the experimental work carried out for the determination of absorbed dose in water in the energy of X-rays generated at potentials of 100 kV to 250 kV. Two small cavity ionization chambers were used for this experiment. The results of these measurements were compared with the results obtained by using NPL Secondary Standard Therapy level X-ray exposure meter. The related problems of converting an exposure quantity into absorbed dose in water an absorbed dose in water have also been discussed. (Orig./A.B.)

29

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

International Nuclear Information System (INIS)

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. (author)

30

Acceptance of the EU regulations on mean doses of glandular on women's during mammographic examination in the Czech Republic  

International Nuclear Information System (INIS)

Diagnostic reference levels (further DRU) are on indications for medical irradiation regulation. DRU = 3 mGy per pictures and standard breast thickness 45 mm was used for cc projection during mammographic examination in the Czech Republic. However the examinations in EU country indicated that the mean glandular dose for standard breast thickness 45 mm was reduced to a Dg =2 mGy per picture. At the same time there was a change of standard breast thickness from 45 mm to 53 mm, new standard for glandular dose was set up to Dg = 2.5 mGy. The aim is to estimate, whether glandular dose measured during examinations in cz fulfil recommended levels for particular PMMA equivalent thickness as stated above. (authors)

31

A ?-ray absorbed dose rate meter, (1)  

International Nuclear Information System (INIS)

A measuring method and dose rate meter for ?-ray absorbed dose independent of the ?-ray maximum energy have been developed. To obtain constant dose sensitivity (counting rate per absorbed dose rate), a thin plastic scintillator is used as the detector, and the pulses selected by a single channel analyzer (SCA) are counted. The desirable pulse height distribution in obtaining a constant dose sensitivity is obtained with 2 mm thick scintillator. The lower level of discrimination and the window width of the SCA are chosen according to the epidermal thickness of tissue exposed to ?-rays. The dose sensitivity of the absorbed dose rate meter is constant at 50 cps/(mrad/hr) +-15% for ?-rays with maximum energy 0.4 -- 3.5 MeV (epidermal thickness 7 mg/cm2) and 0.3 -- 3.5 MeV (epidermal thickness 40 mg/cm2). The absorbed dose rate is given by multiplying the counting rate by a constant factor 2.0 x 10-2 (mrad/hr)/cps. The lower limit of dose rate measurement is 1.7 x 10-2 mrad/hr (7 mg/cm2) and 9.4 x 10-3 mrad/hr (40 mg/cm2). (auth.)

32

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

International Nuclear Information System (INIS)

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 glandularityularity

33

On the definition of absorbed dose  

Science.gov (United States)

Purpose: The quantity absorbed dose is used extensively in all areas concerning the interaction of ionizing radiation with biological organisms, as well as with matter in general. The most recent and authoritative definition of absorbed dose is given by the International Commission on Radiation Units and Measurements (ICRU) in ICRU Report 85. However, that definition is incomplete. The purpose of the present work is to give a rigorous definition of absorbed dose. Methods: Absorbed dose is defined in terms of the random variable specific energy imparted. A random variable is a mathematical function, and it cannot be defined without specifying its domain of definition which is a probability space. This is not done in report 85 by the ICRU, mentioned above. Results: In the present work a definition of a suitable probability space is given, so that a rigorous definition of absorbed dose is possible. This necessarily includes the specification of the experiment which the probability space describes. In this case this is an irradiation, which is specified by the initial particles released and by the material objects which can interact with the radiation. Some consequences are discussed. Specific energy imparted is defined for a volume, and the definition of absorbed dose as a point function involves the specific energy imparted for a small mass contained in a volume surrounding the point. A possible more precise definition of this volume is suggested and discussed. Conclusions: The importance of absorbed dose motivates a proper definition, and one is given in the present work. No rigorous definition has been presented before.

Grusell, Erik

2015-02-01

34

Neutron absorbed dose in a pacemaker CMOS  

Energy Technology Data Exchange (ETDEWEB)

The neutron spectrum and the absorbed dose in a Complementary Metal Oxide Semiconductor (CMOS), 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 sensitive 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{sup -17} Gy per neutron emitted by the source. (Author)

Borja H, C. G.; Guzman G, K. A.; Valero L, C.; Banuelos F, A.; Hernandez D, V. M.; Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Paredes G, L., E-mail: fermineutron@yahoo.com [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico)

2012-06-15

35

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

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

2010-01-01

36

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 thtremely high mammography workload. For these facilities, urgent dose-reduction measures and follow-up actions were recommended. (authors)

37

6.3. Determination of absorbed dose  

International Nuclear Information System (INIS)

The principles are given of the selection of tissue-equivalent materials and a survey is given of the properties of most frequently used tissue equivalent materials for photon radiation and electrons. The principles and methods are given for the determination of absorbed doses. Calorimetry, chemical dosimetry, the use of ionization chambers and their calibration are discussed. (J.P.)

38

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)

39

Absorbed Doses to Patients in Nuclear Medicine  

International Nuclear Information System (INIS)

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: 11C- acetate, 11C- methionine, 18F-DOPA, whole antibody labelled with either 99mTc, 111In, 123I or 131I, fragment of antibody, F(ab')2 labelled with either 99mTc, 111In, 123I or 131I and fragment of antibody, Fab' labelled with either 99mTc, 111In, 123I or 131I. The absorbed dose estimates for these substances have been made from published biokinetic information. For other substances of interest, e.g. 14C-urea (children age 3-6 years), 14C-glycocholic acid, 14C-xylose and 14C-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

40

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. PMID:23475310

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

2013-04-01

 
 
 
 
41

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

42

A polystyrene absorbed-dose-rate calorimeter  

International Nuclear Information System (INIS)

A simple portable calorimeter was constructed by embedding a calibrated thermistor on the axis of a polystyrene rod. This instrument was positioned on the axis of a cylindrical array of 60Co rods. The duration of the measurements was ?70 s. Absorbed dose rates of ?70 Gy/min were measured to a daily precision of several tenths of a percent standard deviation. The results are in good agreement with earlier measurements made with a graphite calorimeter. An absorbed dose of 620 kGy resulted in no detectable change in thermistor sensitivity. The specific heat capacity of the polystyrene presumably increased ?0.0024%/kGy. The use of a chart recorder was not necessary. (orig.)

43

High energy absorbed dose project at ARL  

International Nuclear Information System (INIS)

In Australia, the calibration of radiotherapy beams from linear accelerators is referenced to an air kerma calibration at 60Co and the extension to higher energies is made by means of a common, well accepted protocol. For nominal beam energies above 4-6 MV, another approach is to establish standards of absorbed dose directly and compare instruments with a standard at the relevant quality. This approach is becoming more widespread as higher energy therapy beams are increasingly being used

44

Mammography quality control program in Tokai University Hospital. The measurement of half value layer and average glandular dose  

International Nuclear Information System (INIS)

In late years, if importance of mammography rises with increase of, cancer of the breast and introduces mammography into, cancer of the breast examination, I reach it. Several many inspection items are nominated for quality control of mammography. Reduction of quantity of being affected by exposure dose is made in those as an important item. This is because I may give excessive exposure dose so that mammography uses soft X-ray. I add some references consideration about the measurement of; half value layer and Average Glandular Dose in these studies and report it. (author)

45

Radiologist and angiographic procedures. Absorbed radiation dose  

International Nuclear Information System (INIS)

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

46

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

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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)

48

Neutron absorbed dose in a pacemaker CMOS  

International Nuclear Information System (INIS)

The absorbed dose due to neutrons by a Complementary Metal Oxide Semiconductor (CMOS) has been estimated using Monte Carlo methods. Eventually a person with a pacemaker becomes a patient that must be treated by radiotherapy with a linear accelerator; the pacemaker has integrated circuits as CMOS that are sensitive to intense and pulsed radiation fields. When the Linac is working in Bremsstrahlung mode an undesirable neutron field is produced due to photoneutron reactions; these neutrons could damage the CMOS putting the patient at risk during the radiotherapy treatment. In order to estimate the neutron dose in the CMOS a Monte Carlo calculation was carried out where a full radiotherapy vault room was modeled with a W-made spherical shell in whose center was located the source term of photoneutrons produced by a Linac head operating in Bremsstrahlung mode at 18 MV. In the calculations a phantom made of tissue equivalent was modeled while a beam of photoneutrons was applied on the phantom prostatic region using a field of 10 x 10 cm2. During simulation neutrons were isotropically transported from the Linac head to the phantom chest, here a 1 ? x 1 cm2 cylinder made of polystyrene was modeled as the CMOS, where the neutron spectrum and the absorbed dose were estimated. Main damages to CMOS are by protons produced during neutron collisions protective cover made of H-rich materials, here the neutron spectrum that reach the CMOS was calculated showinghat reach the CMOS was calculated showing a small peak around 0.1 MeV and a larger peak in the thermal region, both connected through epithermal neutrons. (Author)

49

Neutron absorbed dose in a pacemaker CMOS  

Energy Technology Data Exchange (ETDEWEB)

The absorbed dose due to neutrons by a Complementary Metal Oxide Semiconductor (CMOS) has been estimated using Monte Carlo methods. Eventually a person with a pacemaker becomes a patient that must be treated by radiotherapy with a linear accelerator; the pacemaker has integrated circuits as CMOS that are sensitive to intense and pulsed radiation fields. When the Linac is working in Bremsstrahlung mode an undesirable neutron field is produced due to photoneutron reactions; these neutrons could damage the CMOS putting the patient at risk during the radiotherapy treatment. In order to estimate the neutron dose in the CMOS a Monte Carlo calculation was carried out where a full radiotherapy vault room was modeled with a W-made spherical shell in whose center was located the source term of photoneutrons produced by a Linac head operating in Bremsstrahlung mode at 18 MV. In the calculations a phantom made of tissue equivalent was modeled while a beam of photoneutrons was applied on the phantom prostatic region using a field of 10 x 10 cm{sup 2}. During simulation neutrons were isotropically transported from the Linac head to the phantom chest, here a 1 {theta} x 1 cm{sup 2} cylinder made of polystyrene was modeled as the CMOS, where the neutron spectrum and the absorbed dose were estimated. Main damages to CMOS are by protons produced during neutron collisions protective cover made of H-rich materials, here the neutron spectrum that reach the CMOS was calculated showing a small peak around 0.1 MeV and a larger peak in the thermal region, both connected through epithermal neutrons. (Author)

Borja H, C. G.; Guzman G, K. A.; Valero L, C. Y.; Banuelos F, A.; Hernandez D, V. M.; Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Calle Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Paredes G, L., E-mail: candy_borja@hotmail.com [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico)

2011-11-15

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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

51

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

52

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

53

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

54

Influence of anode and filter material on image quality and glandular dose for screen-film mammography  

International Nuclear Information System (INIS)

The influence of anode and filter materials on the performance (image quality and dose) of a mammography system is investigated. The image quality is evaluated with the image quality index method. A computer simulation has been developed to calculate the physical parameters of the image quality index (contrast, resolution and noise) as well as the mean glandular dose. The experimental conclusions are confirmed: the use of a tungsten anode with a rhodium filter allows a dose reduction without a significant degradation of image quality. The computer program can also be used to simulate the influence of factors which are difficult to combine in practice, e.g. various anode and filter materials, monoenergetic x-rays, etc. (author)

55

The BIPM Graphite Calorimeter Standard for Absorbed Dose to Water  

International Nuclear Information System (INIS)

The BIPM has constructed a graphite calorimeter for use as a primary standard for absorbed dose. It is employed to measure absorbed dose to water in the BIPM 60Co reference beam and in accelerator photon beams. It is currently in use for a series of international comparisons of absorbed dose to water in the accelerator photon beams of national metrology institutes. The paper describes the BIPM calorimeter and presents some recent results. (author)

56

Absorbed dose calculation at cellular level in radionuclide therapy  

International Nuclear Information System (INIS)

An accurate calculation of the absorbed dose at cellular level in radionuclide therapy lead to optimisation of administered activity and best clinical response. This work describe the method of calculations absorbed dose of cells and voxels for referent 3D solid tumor model. The FOTELP code based on a Monte Carlo simulations of the photon and electron transport was used on referent 3D solid tumor model and spatial distribution of absorbed doses and differential and cumulated dose volume histograms (DVHs) were generated for radionuclide Cu-67, I-131, Sm- 153, Y-90, Re-188. The referent 3D solid tumor model was defined as sphera filled with cells, which were defined as spheras with radii and cells density. Labeling of cells is defined with intracellular to extracellular radionuclide concentration and labelled cells density. Spatial distribution of the absorbed dose is given as dose scintigraphy for tumor slices. The DVHs were generated as percentage of tumor' cells in function of relative absorbed dose, which was defined as cells absorbed dose divided with average tumor absorbed dose. DVHs for high energy beta emitters like Re-188 and Y-90 are very close to average tumor absorbed dose, but for low energy beta emiters like Cu-67, I-131 and Sm-153, spectras shows that lot of the cells got much lower doses then is average tumor absorbed dose. With spatial distribution of absorbed doses and DVHs it is possible select best radionuclide and calculate optimal administered actide and calculate optimal administered activity for specific tumor and radiopharmaceutic, and on that way find best plan in radionuclide therapy. (authors)

57

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

International Nuclear Information System (INIS)

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 %. (authors)

58

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

59

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

60

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)

Full text: Measurement of the absorbed dose in a target volume is widely considered to be an important tool for quality assurance in external radiotherapy. The aims of this work were to measure the entrance and exit doses for patients treated for head and neck tumors. The target absorbed dose was determined from the exit and entrance dose measurement Twenty patients were evaluated. Initially, measurements with commercial diodes were performed on a polystyrene phantom in order to calibrate diodes in terms of entrance and exit doses; and to determine appropriate correction factors. The results were compared to the calculated values, and the midline dose was determinate and compared with the prescribed dose. 100 entrance dose and 100 exit dose measurements were performed. The average difference from expected values was 1,2 % for entrance dose (SD 2,9%) and 0,5 % for exit dose (SD 5,3%). The target absorbed dose differed from prescribed dose values by 2.5% (2.8 %) for the results using the Noel method and 3 % (SD:3.2 %) 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 % (1 SD). Simple in vivo dose measurements are an additional safeguard against major setup errors and calculation or transcription errors that can be missed during pre-treatment chart check

 
 
 
 
61

Dosimetric evaluation of carbon fiber tabletop on absorbed doses  

International Nuclear Information System (INIS)

Objective: To evaluate the dosimetric effect of carbon fiber tabletop on the patient doses in radiotherapy. Methods: The transmission factors of couch and inserts were measured in air and solid water phantom using 0.6 cm3 ion chamber and PTW 2D ion chamber array for 6 MV, 10 MV and 18 MV X-ray, respectively. Absorbed doses at depth of maximum dose, 5 cm and 10 cm in solid water were measured with the 2D ion chamber array. Absorbed doses fluctuations with different gantry angles and air gaps between phantom and couch were also measured. Results: The posterior field measurement showed that the reductions of absorbed doses at the depth maximum dose, 5 cm and 10 cm were within 5%. The ratios of the absorbed doses with to without couch increased with the oblique incident angles and varied slightly with the air gap at depth of 5 cm. The transmission factors of inserts were less than those of couch owing to its thinner thickness. Conclusion: The carbon-fiber tabletop affects the absorbed doses and dose distributions of the target, and this effect changes with the gantry angle and air gap. Special considerations should be taken during treatment planning. (authors)

62

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)

63

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)

64

Use of absorbers for optimizing surface dose in megavoltage radiotherapy  

International Nuclear Information System (INIS)

The surface dose in megavoltage X-ray therapy can be modified using two different techniques: either varying the thickness of an absorber positioned directly on the surface of the patient or varying the distance to the surface of an absorber with constant thickness. Surface dose as a function of distance and absorber thickness has been measured at 4 MV and 8 MV X-rays. Both methods yield sufficiently and well defined dose-enhancements at the surface of the patient as desired clinically. The variation of the absorber-surface distance however has been proved to be the more simple and practicable method, offering the additional advantage of no contacting the patients skin. (orig.)

65

Absorbed doses to patients from angioradiology  

International Nuclear Information System (INIS)

The aim of study was to know patients doses exposes when three different procedures of angioradiology were carried out. The explorations considered were drainage biliary, varicocele embolization and dacriocistography made in the Radiodiagnostic Service at the University Hospital of Canary Islands, Tenerife (Spain). In total 14 patients were studied. The measurements were made using large area transmission ionisation chamber which gives the values of Dose Area Product (DAP). In addition, thermoluminescent dosimeters type TLD-100 were used in anthropomorphic phantom in order to obtain values of organ doses when the phantom was submitted to the same procedures rather than the actual patients. Furthermore, the Effdose program was used to estimate the effective doses in the procedures conditions. The values for DAP were in the range of 70-300 for drainage biliary, 43-180 for varicocele embolization and 1.4-9 for dacriocistography. The organ doses measured with TLD-100 were higher than the corresponding values estimated by Effdose program. The results for varicocele embolization were higher than other published data. In the case of drainage biliary procedure, the values were closed to other published results. It was not possible to find data for dacriocistography from other authors. (author)

66

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)

67

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

68

Towards a dosimetry system based on absorbed dose standards  

International Nuclear Information System (INIS)

A review is given of the rationale for establishing primary standards of absorbed dose in accelerator photon beams and the progress at the National Research Council Canada (NRC) towards establishing these standards. Attention is drawn to the primary standards of air kerma in 60Co beams. Current clinical dosimetry based on air kerma standards has many problems, from intellectual obscurity, to practical complexity, to problems with the standards themselves which are subject to possible common errors. In contrast, clinical photon beam dosimetry based on absorbed dose standards is intellectually clear, simple in practice and founded on a very robust system of absorbed dose standards which are in the final stages of development. With these observations in mind, the AAPM TG-51, which is charged with producing a new or revised clinical dosimetry protocol, is investigating the feasibility of a protocol based on absorbed dose calibration factors. The German protocol is already using this approach. On the basis of present understanding, changing to an absorbed dose based system will not significantly change the dose determined in careful clinical dosimetry, but because it is so much simpler to use and understand, it is bound to improve clinical practice. 32 refs, 6 figs

69

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

70

Measurement of absorbed dose and proposed radiation exposure level  

International Nuclear Information System (INIS)

Absorbed dose was measured in clinical X-ray examinations using thermoluminescence dosimeter (TLD). Moreover, we distributed the levels of radiation exposure into 3 classes. The presumed dose of the internal organs, e.g., uterus dose, was computed to depth doses with a surface dose. This information provides a prediction of the influence of radiation, and the examination can be performed with the informed consent of the patient. Moreover, we examined the distribution of the level of absorbed dose. We proposed two kinds of radiation exposure level, one to the fetus in a pregnant woman and a general level of radiation exposure that is not applied to pregnant women. The levels were as follows: 0.5 mGy and 100 mGy were considered the boundaries for fetal radiation exposure in a pregnant woman, and 200 mGy and 3 Gy were considered the boundaries for the general level of radiation exposure (excluding pregnant women). (author)

71

Measurement of absorbed dose and proposed radiation exposure level  

Energy Technology Data Exchange (ETDEWEB)

Absorbed dose was measured in clinical X-ray examinations using thermoluminescence dosimeter (TLD). Moreover, we distributed the levels of radiation exposure into 3 classes. The presumed dose of the internal organs, e.g., uterus dose, was computed to depth doses with a surface dose. This information provides a prediction of the influence of radiation, and the examination can be performed with the informed consent of the patient. Moreover, we examined the distribution of the level of absorbed dose. We proposed two kinds of radiation exposure level, one to the fetus in a pregnant woman and a general level of radiation exposure that is not applied to pregnant women. The levels were as follows: 0.5 mGy and 100 mGy were considered the boundaries for fetal radiation exposure in a pregnant woman, and 200 mGy and 3 Gy were considered the boundaries for the general level of radiation exposure (excluding pregnant women). (author)

Hasegawa, Takayuki; Koizumi, Masayuki; Furukawa, Tomo [Tokai Univ., Isehara, Kanagawa (Japan). Hospital

2003-03-01

72

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)

73

Thyroid radiation absorbed dose from diagnostic procedures in US population  

Energy Technology Data Exchange (ETDEWEB)

According to a 1981 survey of thyroid imaging methods in the United States, radionuclide thyroid scans and uptake studies increased 250%-300% between 1966 and 1981, while the US population increased only 17%. Collective absorbed dose decreased from 18 x 10/sup 6/ rad (18 x 10/sup 4/ Gy) in 1966 to 13.9 x 10/sup 6/ rad (13.9 x 10/sup 4/ Gy) in 1981. The decrease was due to the use of iodine 123 and technetium 99m pertechnetate rather than iodine 131 and also to fewer free-standing thyroid uptake studies. Even with reduced usage, I-131 still accounted for 93% of the collective absorbed dose in 1981. If I-131 were eliminated from diagnostic procedures, the annual absorbed dose would decrease to 1.4 x 10/sup 6/ rad (1.4 x 10/sup 4/ Gy). The number of radiation-induced cancer cases would also be reduced.

Rosenberg, R.D.; Mettler, F.A. Jr.; Moseley, R.D. Jr.; Parker, T.; Williams, A.G.; Christie, J.H.; Kelsey, C.A.

1985-07-01

74

Time improvement of photoelectric effect calculation for absorbed dose estimation  

International Nuclear Information System (INIS)

Ionizing radiation therapy is a very useful tool in cancer treatment. It is very important to determine absorbed dose in human tissue to accomplish an effective treatment. A mathematical model based on affected areas is the most suitable tool to estimate the absorbed dose. Lately, Monte Carlo based techniques have become the most reliable, but they are time expensive. Absorbed dose calculating programs using different strategies have to choose between estimation quality and calculating time. This paper describes an optimized method for the photoelectron polar angle calculation in photoelectric effect, which is significant to estimate deposited energy in human tissue. In the case studies, time cost reduction nearly reached 86%, meaning that the time needed to do the calculation is approximately 1/7 th of the non optimized approach. This has been done keeping precision invariant

75

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

International Nuclear Information System (INIS)

Mammography aims to achieve a high image quality associated with a dose in the patient as low as feasible. Values of average glandular dose, DG, can be obtained by means of two dosimetric methods: one based on the measurement of incident air kerma, Ki, 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 (Ki) and average glandular dose (DG) 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 DG determined from Ki and also with the values of Ki and DG 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 Ki values ranged around 7.9% between the methods of action. The result of the values of DG ranged around 14.7% between the two methods of action. It is observed that the estimate of DG by the software is higher than the values measured with the dosimetric phantom. (author)

76

Nonintracranial absorbed doses during leksell gamma knife stereotactic treatment  

International Nuclear Information System (INIS)

Nearly 30 000 patients have been treated with the use of the Leksell Gamma Knife (LGK) since 1968. Although many dosimetric aspects related to the target volume or surrounding brain tissue have been addressed, a little attention has been focused upon doses to nonintracranial sites, especially to the most radiosensitive organs with a potential risk of radiation sequelae or secondary induced carcinogenesis. This study was concentrated on measurements of absorbed doses to the eyes, thyroid, breast, abdomen, gonads, knee and ankle received during the LGK treatment using thermoluminiscent dosimetry (TLD). TLD in-vivo measurements have been performed on 51 patients. The measured absorbed doses to organs and sites of interest were 0,223 ± 0,168 Gy for the eyes, 0,081 ± 0,050 Gy for the thyroid, 0,049 ± 0,033 Gy for the breast, 0,024 ± 0,018 Gy for the abdomen, 0,012 ± 0,008 Gy for the gonads, 0,003 ± 0,002 Gy for the knee, 0,002 ± 0,002 Gy for the ankle. The doses to nonintracranial organs and sites received during LGK radiosurgery treatment mainly depend on the total maximum target dose and the number of shots used for the treatment. These doses are generally low, the maximum dose receive eyes (? 0,7% of maximum target dose) and the doses to other body organs are exponentially decreasing with the increasing distance from isocentre of the LGK radiation unit

77

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

78

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

79

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)

80

Space radiation absorbed dose distribution in a human phantom  

Science.gov (United States)

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

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

2002-01-01

 
 
 
 
81

The absorbed dose to blood from blood-borne activity  

Science.gov (United States)

The radiation absorbed dose to blood and organs from activity in the blood is relevant for nuclear medicine dosimetry and for research in biodosimetry. The present study provides coefficients for the average absorbed dose rates to the blood from blood-borne activity for radionuclides frequently used in targeted radiotherapy and in PET diagnostics. The results were deduced from published data for vessel radius-dependent dose rate coefficients and reasonable assumptions on the blood-volume distribution as a function of the vessel radius. Different parts of the circulatory system were analyzed separately. Vessel size information for heart chambers, aorta, vena cava, pulmonary artery, and capillaries was taken from published results of morphometric measurements. The remaining blood not contained in the mentioned vessels was assumed to reside in fractal-like vascular trees, the smallest branches of which are the arterioles or venules. The applied vessel size distribution is consistent with recommendations of the ICRP on the blood-volume distribution in the human. The resulting average absorbed dose rates to the blood per nuclear disintegration per milliliter (ml) of blood are (in 10?11?Gy·s?1·Bq?1·ml) Y-90: 5.58, I-131: 2.49, Lu-177: 1.72, Sm-153: 2.97, Tc-99m: 0.366, C-11: 4.56, F-18: 3.61, Ga-68: 5.94, I-124: 2.55. Photon radiation contributes 1.1–1.2·10?11?Gy·s?1·Bq?1·ml to the total dose rate for positron emitters but significantly less for the other nuclides. Blood self-absorption of the energy emitted by ß-particles in the whole blood ranges from 37% for Y-90 to 80% for Tc-99m. The correspondent values in vascular trees, which are important for the absorbed dose to organs, range from 30% for Y-90 to 82% for Tc-99m.

Hänscheid, H.; Fernández, M.; Lassmann, M.

2015-01-01

82

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

83

Radiation absorbed doses at radiographic examination of third molars  

International Nuclear Information System (INIS)

The radiation absorbed doses to critical organs, i.e. the thyroid and salivary glands and the gonadal region, were measured at radiographic examination of third molars. A tissue equivalent phantom was used together with ionization chamber detectors and TLDs. The greatest thyroid dose, 35 ?Gy, came from a mandibular disto-oblique projection with the circular tube collimator and Ultra-Speed film. The doses in different parts of the parotid gland from the disto-oblique mandibular projection with Ultra-Speed film ranged between 2.65 and 0.052 mGy. the corresponding doses in the submandibular gland were 1.74 mGy beneath the mandible and 0.458 mGy in the fovea. A rectangular tube collimator reduced the doses by approximately 50 %. The Ekta-Speed film requirted approximately 40 % lower exposure than the Ultra-Speed film. A horizontal radiation shield reduced the thyroid doses by between 12 and 46 % and the gonadal doses by between 50 and 95 %. The reduction effect from the shield was relatively greater when using the larger aperture of the tube collimator. Combinations of leaded aprons and soft leaded collars reduced the thyroid doses between 15 and 42 % and the gonadal doses by two orders of magnitude. (Authors)

84

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

85

Some comments on the concept of absorbed dose  

International Nuclear Information System (INIS)

The main physical quantity for the evaluation of the induced effects by radiation ionizing is absorbed dose. ICRU report 51 defines this concept as quantity d? divided by dm, where d? is the mean energy imparted by radiation ionizing to matter of mass dm. However, nothing is said about the average operation concerning the stochastic energy imparted ?. Nevertheless, because considers the sum of all changes of rest mass of the involved nuclei and elementary particles in all interactions which occur within the mass (i.e. nuclear reactions and transformations of elementary particles), the average operation can not be done with an equilibrium statistical operator, rather, this has to be defined with a non-equilibrium statistical operator, therefore, absorbed dose is a function dependent on time. Furthermore, we present a discussion to clarify the equilibrium radiation and charged particle equilibrium within the context of thermodynamic equilibrium. (Author)

86

Some comments on the concept of absorbed dose  

Energy Technology Data Exchange (ETDEWEB)

The main physical quantity for the evaluation of the induced effects by radiation ionizing is absorbed dose. ICRU report 51 defines this concept as quantity d{epsilon} divided by dm, where d{epsilon} is the mean energy imparted by radiation ionizing to matter of mass dm. However, nothing is said about the average operation concerning the stochastic energy imparted {epsilon}. Nevertheless, because considers the sum of all changes of rest mass of the involved nuclei and elementary particles in all interactions which occur within the mass (i.e. nuclear reactions and transformations of elementary particles), the average operation can not be done with an equilibrium statistical operator, rather, this has to be defined with a non-equilibrium statistical operator, therefore, absorbed dose is a function dependent on time. Furthermore, we present a discussion to clarify the equilibrium radiation and charged particle equilibrium within the context of thermodynamic equilibrium. (Author)

Alvarez R, J.T. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico)

1998-12-15

87

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

88

Calibration of ionization chambers and determination of the absorbed doses  

International Nuclear Information System (INIS)

In order to further improve the accuracy of dosimetric measurements in radiation therapy, the IAEA and WHO supported the establishment of Secondary Standard Dosimetry Laboratory (SSDLs). These SSDLs bridge the gap between the primary measurement standards and the user of ionizing radiation by providing the latter with calibrations against the SSDLs' secondary standards and by giving technical advice and assistance. However, a properly calibrated dosimeter is just necessary first condition for the determination of the dose. It has been demonstrated that the success or failure of radiation treatment depends on the absorbed dose delivered to the tumour and that this should not vary by more than a few per cent from described values.

89

Use of osseoequivalent mixtures to measure absorbed doses  

International Nuclear Information System (INIS)

The use of osseoequivalent mixtures composed of thermoluminophore LiF holds out promise in radiotherapy for the dosimetry of compact bone tissue. The distribution of absorbed doses in the vertebral column, and thyroid has been compared for two methods of irradiation of thyroid cancer patients using a Rokus-M unit. A shaped anterior cervical-thoracic field was used and irradiation procedure was performed from two postero-lateral fields at an angle of 120 deg to the saggital plane. The second method is preferable as in this case the absorped dose for bone tissue of vertebrae is less and the decrease of the dose along the vertebrae longitudinal axis is strongly expressed. Measured dose values in osseous tissue were higher than those calculated according to the atlas of the isodose fields by 10-70% probably because of the contribution of scattered radiation. This fact should be taken into consideration particularly when the bone is a critical system

90

Specific absorbed fractions and S-factors for calculating absorbed dose to embryo and fetus  

International Nuclear Information System (INIS)

The variation of specific absorbed fractions from maternal tissues to embryo/fetus is investigated for four different target masses and geometries. S-factors are calculated for selected radionuclides assumed to be distributed uniformly in fetal tissues represented by spheres from 1 mg to 4 kg. As an example, the dose to fetal tissues for iodine-131 and iron-59 is estimated based on human biokinetic data for various stages of pregnancy. 24 references, 4 tables

91

Abdominal Pediatric Cancer Surveillance using Serial CT: Evaluation of Organ Absorbed Dose and Effective Dose  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Computed tomography (CT) is used extensively in cancer diagnosis, staging, evaluation of response to treatment, and in active surveillance for cancer reoccurrence. A review of CT technology is provided, at a level of detail appropriate for a busy clinician to review. The basis of x-ray CT dosimetry is also discussed, and concepts of absorbed dose and effective dose are distinguished. Absorbed dose is a physical quantity (measured in milliGray) equal to the x-ray energy deposited in a mass of ...

Lam, Diana; Wootton-gorges, Sandra L.; Mcgahan, John P.; Stern, Robin; Boone, John M.

2011-01-01

92

Concept of radiation dose. Pt.1. Is the absorbed dose a well-defined quantity  

International Nuclear Information System (INIS)

Radiation dosimetry is a common basis to all sciences treating with effects of ionizing radiation on matter. Radiation dose is introduced as the measure of causes of radiation effects. The absorbed dose being used as the most fundamental quantity in the current system of radiation dosimetry, it is worth while to check rigidity of its concept and adequacy of its definition from various points of view. In this presentation it is shown that the concept of the absorbed dose contains ambiguity related to its physical entities, and the definition given by ICRU contains deficiencies related to the emerging radiant energies, Rout, and to changes in the rest energies, ?Q. It is also pointed out that the dosimetric quantities, including the absorb dose, are generally not independent of time, and their values are not uniquely determined unless the elapsed time after irradiation is assigned

93

Reduction of absorbed doses in radiography of the facial skeleton  

International Nuclear Information System (INIS)

Radiation absorbed doses from radiography of the paranasal sinuses and the facial skeleton were measured with thermoluminescent dosimeters (TLD) on a phantom head using high-sensitivity screens in an Orbix stand. The entrance doses to the skin of the head ranged from 0.31 to 2.9 mGy per exposure. The absorbed dose from a full series of sinus exposures averaged 0.33 mGy for the oral mucous membrane, 0.33 mGy for the maxillary sinus mucous membrane, 0.11 mGy for the parotid gland, 0.15 mGy for the submandibular gland, 0.61 mGy for the eye lens, and 0.75 mGy for the thyroid gland region. A leaded soft collar adapted to the thyroid region reduced the thyroid doses by more than one order of magnitude, but also reduced the image field. The mean energy imparted from a full series of paranasal sinus projections was 4.8 mJ and from a total series of the facial skeleton, 7.9 mJ

94

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)

95

Absorbed dose measurements of high energy photon beams  

International Nuclear Information System (INIS)

Accurate dose measurement of high energy photon beams is important in radiotherapy. Measurement of absorbed dose to water through ionization chamber is the most commonly used method for routine dose evaluation. The International Code of Practice, recommended by International Atomic Energy Agency is one of the widely used code for this purpose. Salient features of this code are given, with special reference to Bhabha Atomic Research Centre (BARC) make dosimeter, having a tufnol walled ion chamber. The recent observations made during the testing of this code at different laboratories are discussed. The status of dosimetry in India at primary, secondary and user levels is given. The results of TLD intercomparisons with various radiotherapy centres in the country are discussed. (author). 15 refs., 2 figs., 6 tabs

96

[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

97

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)

98

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)

99

Estimation of absorbed doses in the body using a transit dose chamber  

International Nuclear Information System (INIS)

The purpose of this study was to estimate absorbed doses in the body by measuring transit doses with a new model of diode dose chamber. Tissue phantom ratios obtained by this model were in good agreement with calculated values. The use of this new model for transit dose measurement offers the following advantages: (1) the technical procedure is simple, (2) doses can be monitored during irradiation, (3) several sites are simultaneously displayed, (4) few errors that are induced by output changes from a linear accelerator occur, and (5) feedback to the linear accelerator is possible by controlling doses in each site using a computer. However, it remains to be confirmed whether the estimated doses agree with the actual doses. (Namekawa, K.)

100

Estimation of mean glandular dose for contrast enhanced digital mammography: factors for use with the UK, European and IAEA breast dosimetry protocols.  

Science.gov (United States)

The UK, European and IAEA protocols for breast dosimetry in mammography use tabulations of conversion factors, which relate measurements of incident air kerma to the mean glandular dose to the breast. To supplement the existing tabulations, a Monte Carlo computer program has been used to calculate conversion factors for the high-energy spectra used for contrast enhanced digital mammography. The calculations were made for the x-ray spectra from a tungsten target (tube voltage range 40-50 kV) filtered by 0.28, 0.30 and 0.32 mm of copper, and from molybdenum and rhodium targets (tube voltage range 40-49 kV), each filtered by 0.30 mm of copper. The g-factors for all of these spectra were plotted for each breast thickness as a function of half value layer (HVL) and were found to lie on smooth curves within 0.3%. These reflect the fact that the characteristic x-rays present in the spectra from molybdenum and rhodium are heavily filtered and all the spectra are essentially Bremsstrahlung. As a consequence, the s-factor previously used in the dosimetry protocols to adjust for different target/filter combinations can be taken as unity for all of the spectra considered. Tables of g-factors and c-factors are provided for breast thicknesses in the range 20-110 mm and HVLs in the range 2.4-3.6 mm of aluminium. The tables of c-factors are given for breast glandularities in the range 0.1%-100% and for typical glandularities for women in the age bands 40-49 and 50-64 attending the UK national breast screening programme. PMID:24699200

Dance, D R; Young, K C

2014-05-01

 
 
 
 
101

Estimation of mean glandular dose for contrast enhanced digital mammography: factors for use with the UK, European and IAEA breast dosimetry protocols  

Science.gov (United States)

The UK, European and IAEA protocols for breast dosimetry in mammography use tabulations of conversion factors, which relate measurements of incident air kerma to the mean glandular dose to the breast. To supplement the existing tabulations, a Monte Carlo computer program has been used to calculate conversion factors for the high-energy spectra used for contrast enhanced digital mammography. The calculations were made for the x-ray spectra from a tungsten target (tube voltage range 40-50 kV) filtered by 0.28, 0.30 and 0.32 mm of copper, and from molybdenum and rhodium targets (tube voltage range 40-49 kV), each filtered by 0.30 mm of copper. The g-factors for all of these spectra were plotted for each breast thickness as a function of half value layer (HVL) and were found to lie on smooth curves within 0.3%. These reflect the fact that the characteristic x-rays present in the spectra from molybdenum and rhodium are heavily filtered and all the spectra are essentially Bremsstrahlung. As a consequence, the s-factor previously used in the dosimetry protocols to adjust for different target/filter combinations can be taken as unity for all of the spectra considered. Tables of g-factors and c-factors are provided for breast thicknesses in the range 20-110 mm and HVLs in the range 2.4-3.6 mm of aluminium. The tables of c-factors are given for breast glandularities in the range 0.1%-100% and for typical glandularities for women in the age bands 40-49 and 50-64 attending the UK national breast screening programme.

Dance, D. R.; Young, K. C.

2014-05-01

102

''Nonisolated-sensor'' solid polystyrene absorbed dose measurements  

International Nuclear Information System (INIS)

A ''nonisolated-sensor'' solid polystyrene calorimeter was constructed to test the role of thermal diffusion in limiting the length of irradiation time during which temperature measurements with nonisolated sensors could be made sufficiently free of drift for determining dose with radiation fields such as gamma rays, x rays, and high-energy electrons. From measured ratios of dose at 5.0 and 0.5 cm in polystyrene and comparisons to dose measurements with a polystyrene parallel-plate (pancake) ion chamber, it was shown that thermal diffusion is sufficiently small in polystyrene to permit accurate measurements for irradiation periods of less than 20 min. Comparison of the absorbed dose measurements and depth dose ratios with pancake ion chambers and calorimeter showed, that within the precision and accuracy of the two measuring systems, there is close agreement. The nonisolated-sensor solid polystyrene calorimeter has the interesting features of (i) simplicity of construction, (ii) simplicity of operation without vacuum or feedback for temperature control, (iii) capability of simultaneous measurements at several depths and off-axis positions, (iv) the very small thermal defect correction with polystyrene, and (v) operation with the calorimeter in any orientation

103

Nonisolated-sensor solid polystyrene absorbed dose measurements  

International Nuclear Information System (INIS)

A nonisolated-sensor solid polystyrene calorimeter was constructed to test the role of thermal diffusion in limiting the length of irradiation time during which temperature measurements with nonisolated sensors could be made sufficiently free of drift for determining dose with radiation fields such as gamma rays, x rays, and high-energy electrons. From measured ratios of dose at 5.0 and 0.5 cm in polystyrene and comparisons to dose measurements with a polystyrene parallel-plate (pancake) ion chamber, it was shown that thermal diffusion is sufficiently small in polystyrene to permit accurate measurements for irradiation periods of less than 20 min. Comparison of the absorbed dose measurements and depth dose ratios with pancake ion chambers and calorimeter showed, that within the precision and accuracy of the two measuring systems, there is close agreement. The nonisolated-sensor solid polystyrene calorimeter has the interesting features of (i) simplicity of construction, (ii) simplicity of operation without vacuum or feedback for temperature control, (iii) capability of simultaneous measurements at several depths and off-axis positions, (iv) the very small thermal defect correction with polystyrene, and (v) operation with the calorimeter in any orientation

104

Transfer of the absorbed dose unit by ferrous sulphate dosemeter  

International Nuclear Information System (INIS)

To establish a coherent system of metrological references it is necessary in particular to define and employ transfer methods so that the knowledge can be reflected with minimum loss. In the field of ionizing radiation dosimetry it was necessary after the roentgen which is the unit of exposure, to develop transfer methods for the rad, absorbed dose unit. Without excluding other possibilities the method adopted is based on the use of the ferrous sulphate dosimeter, for standardized dosimetric conditions (geometry, medium) and in the users'own beams. The metrological characteristics of the ferrous sulphate dosimeter, were studied beforehand, especially the conservation of data in time and the yield G as a function of energy. The method proposed leads to the water-absorbed dose calibration of the user's dosimeter in his own beam, for X or ? photons of energies between about 0.5 and 1.5 MeV; for higher-energy photons and for 10 to 35 MeV electrons the same procedure is applicable as long as certain conventions (measurement depths and yield G of the transfer dosimeter) are adopted temporarily

105

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

106

The absorbed dose and the effective dose of panoramic temporo mandibular joint radiography  

International Nuclear Information System (INIS)

This study measured the radiation doses absorbed by the patient during Panoramic temporo mandibular joint radiography (Panoramic TMJ), Schullers method and Orbitoramus projection. The dose of the frontal view in Panoramic TMJ was compared to that with Orbitoramus projection and the lateral view in Panoramic TMJ was compared to that with Schuellers method. We measured the doses received by various organs and calculated the effective doses using the guidelines of the International Commission on Radiological Protection in Publication 103. Organ absorbed doses were measured using an anthropomorphic phantom, loaded with thermoluminescent dosimeters (TLD), located at 160 sensitive sites. The dose shows the sum value of irradiation on both the right and left sides. In addition, we set a few different exposure field sizes. The effective dose for a frontal view in Panoramic TMJ was 11 ?Sv, and that for the lateral view was 14 ?Sv. The lens of the Orbitoramus projection was 40 times higher than the frontal view in Panoramic TMJ. Although the effective dose of the lateral view in Panoramic TMJ was 3 times higher than that of the small exposure field (10 x 10 cm on film) in Schueller's method, it was the same as that of a mid-sized exposure field. When the exposure field in the inferior 1/3 was reduced during panoramic TMJ, the effective doses could be decreased. Therefore we recommend that the size of the exposure field in Panoramic TMJ be decreased. (author)be decreased. (author)

107

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

108

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

109

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

110

'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 breasts thicker than 30 mm; otherwise, the errors are >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

111

'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)

112

Absorbed dose to water: Standards and traceability for radiation oncology  

International Nuclear Information System (INIS)

Although the need for appropriate quantities and units for ionizing radiation has existed since shortly after discovery of X-rays, the quantities and units in general use today were not completely formalized until about 15 years ago. The development of appropriate national and international standards have also been ongoing. For many years the quantity, exposure, measured in units of roentgen was the national standard and they were also the quantity and units in which radiotherapy was described. With the introduction of megavoltage X-ray and electron-beam equipment and the adoption of the quantity open-quotes absorbed-doseclose quotes measured in units of rad (or gray) different approaches to calibrating these beams were needed. This was especially the case since the national standard in terms of exposure at a maximum photon energy for 60Co gamma rays was only available. Since the late 1960s various machine calibration protocols have been published. These protocols have to accommodate changes in modality, energy, quantities and units between the national standard and the user. Because of this, a new definition of traceability is proposed to accommodate the present system. By recording all intercomparisons and parameters used, an auditable calibration chain can be maintained. Even with the introduction of calibration protocols based upon national absorbed dose standards, the proposed traceability definition will still be needed be needed

113

Calibration of film dosimeters by means of absorbed dose calorimeters  

International Nuclear Information System (INIS)

Methods of graduating film dosimeters by means of calorimeters of absorbed doses, are considered. Graduating of film dosimeters at the energies of accelerated electrons from 4 to 10 MeV can be carried out by means of quasiadiabatic calorimeter of local absorption, the absorber thickness of which should not exceed 5-10% of Rsub(e) value, where Rsub(e) - free electron path of the given energy. In this case film is located inside the calorimeter. For graduating films with thickness not less than (0.1-0.2)Rsub(e) it is suggested to use calorimeter of full absorption; then the graduated dosimeters are located in front of the calorimeter. Graduation of films at small energies of electrons is exercised by means of a package of films, approximately Rsub(e) thick. A design of quasiadiabatic calorimeter, intended for graduating dosimeters within the energy range of electron beam from 4 to 10 MeV, is considered. The quasiadiabatic calorimeter is a thin graphite tablet with heater and thermocouple, surrounded by foam plastic thermostating case. Electricity quantity, accumulated during the radiation field pass, is measured in the case of using the quasiadiabatic calorimeter for film graduating. The results of graduating film dosimeters, obtained using film package with Rsub(e) thickness, are presented. The obtained results coincide within 5% limits with the data known beforehand

114

Absorbed dose reconstruction using modern methods of biological dosimetry  

International Nuclear Information System (INIS)

The performed examination was estimate opportunities for use two modern biological dosimetric methods cytogenetic (G-banding) and electron spin resonance of enamel in 22 residents of Sarzhal village. The increased frequency of chromosome aberration has been revealed (1.6±0.2 for 100 cells) in lymphocytes and prevalence of complicated structural infractions in aberration spectrum - dicentric chromosomes, centric rings that are unstable markers of ionizing impact, that were revealed in 80 % of examined objects, the total frequency was 0.3 for 100 cells, while for control group the frequency was 0.02 for 100 metaphases. It was performed the electron spine resonance of enamel. It was studied cytogenetic parameter-dependence due to absorbed dose that was reconstructed in accordance with spin resonance of enamel. l(author)

115

Implementation of an absorbed dose postal QA programme for radiosurgery  

International Nuclear Information System (INIS)

Radiosurgery is becoming a well accepted method for the treatment of small intra cranial benign lesions and neoplasic tumours. It can be delivered using multiple sources of 60Co gamma rays (i.e. Gamma knife) or using high energy photons, typically 6 MV, produced by clinical linear accelerators. The main objective of this work was to develop, test, and implement a Postal System of Quality Assurance of the absorbed dose applicable specifically to radiosurgery. Due to the specificity of the radiation field including the steep dose gradients, several measuring systems were necessary in order to guarantee the required dose accuracy. The ionization chamber (0,125 cm3/ PTW-Model 31010), thermoluminescent mini dosimeters (TLD), film, and mini Alanina dosimeters were selected. The dosimeters were calibrated against a PTW ionization dosimeter previously calibrated at the PTW secondary standards. The postal evaluation system consist of a main cylindrical acrylic phantom, with 16 cm of length and 21 cm of diameter, and four smaller cylindrical (C1-C4) inserts with 10 cm of length and 7 cm of diameter with the following specific characteristics: - C1 contains a small air volume with 2 cm of diameter that simulates the target with 3 air micro spheres with a diameter of 3 mm; - C2 contains five cylindrical rods where the mini TLDs with 2 mm of diameter and 0,5 mm of length were inserted and placed 5, 15, and 35 mm froe inserted and placed 5, 15, and 35 mm from the centre; - C3 contains five cylindrical rods where the alanine dosimeters with 1 mm of diameter and 2 mm of length were inserted at distances similar to those of the TLDs; - C4 contains an oncology film (X Omat-V) placed inside. In addition, a set of forms for data register and written procedures were sent to the participating institutions. A total dose of 25 Gy is requested to be delivered at the target. The overall management procedure is described, and the three main phases of the procedure are as follows: 1) An evaluation was made of the coordinate system of CT images as defined in the center of the target as well as at the micro spheres in the treatment planning system for later comparison with the reference coordinates. For this evaluation the four participating institutions agreed within 0,3%; 2) The positioning accuracy of a 2 cm diameter beam was studied by placing small steel balls in the C1 insert in order to produce a set of images for the phantom position at 0 and 90 degrees. The agreement was within 0,7mm; 3) Accuracy of the treatment planning system was evaluated by comparing the calculated values and the measured values with TLDs, Alanine and Film all placed at the centre of the cylinders C2, C3 and C4. The required doses were 10 Gy for the TLDs, 25 Gy for alanine, and 1,2 Gy for film. The results obtained showed an agreement better than 1,26% for the dose at the mid-target position, 1,51% at 5mm away from the mid target, 2.9% at 15mm away from the central point at the target, 2.9% at 35mm away from central point, and finally 0.48% for the total absorbed dose. The overall results of the participating institutions are within the recommended tolerance levels and the metrological coherence of this project encourages its recommendation to be used as part of a QA of the radiosurgery procedures

116

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)

117

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 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

118

The effects of the capture gamma-ray spectra on the absorbed dose  

International Nuclear Information System (INIS)

The effect upon the absorbed dose of the differences in capture gamma-ray yields due to thermal neutron capture has been examined using the yield data of aluminum and iron in POPOP4 library. The absorbed doses normalized to energy deposition of the emitted capture gamma rays agree well within accuracy of absorbed dose measurements. Important criteria for selecting the capture gamma-ray yield data are the total energy release and the average energy of the emitted capture gamma rays. (auth.)

119

A tool for estimating organ absorbed doses, effective dose and risk for common CT examinations  

International Nuclear Information System (INIS)

Full text: A software tool has been developed for estimating the effective dose and the associated risk cancer incidence and mortality from routine CT procedures. This tool has been developed to allow for quick and easy use and to be independent of the CT scanner model being used. The tool estimates the organ absorbed doses and effective dose using the concept of normalised organ dose coefficients. These coefficients have been derived from the same Monte Carlo data sets that are utilised in the popular ImPACT CT dosimetry spreadsheet. The risk of cancer incidence and cancer mortality from radiation exposure has been from derived using age and sex dependent data that has been published using data that has been published in BEIR VII report. (author)

120

Evaluation of patient absorbed dose management system in percutaneous coronary intervention  

International Nuclear Information System (INIS)

The angiography equipment Infinix Celeve of Toshiba Corp. is a system that estimates patient absorbed dose at the skin by using a dose area product meter. This system performs incidence area compensation, which corresponds to the changes of image intensifier (I.I.) size, focus image distance (FID), and focus table distance (FTD). We evaluated the clinical usefulness of patient entrance skin dose management by the dose area product meter of Celeve by verifying the effects of various clinical parameters on absorbed dose. We determined compensation according to the various angles usually used by clinicians, and estimated the absorbed peak dose at the skin. By using the angle compensation of the C arm, the displayed values on the dose area product meter of Celeve could be used for skin doses as they were. The skin absorbed dose was 3.0 Gy or more in 33 of the 332 examples. (author)

 
 
 
 
121

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)

122

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

123

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).

McLaughlin, W. L.; Miller, Arne

1977-01-01

124

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

125

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

126

Advances in absorbed dose measurement standards at the australian radiation laboratory  

International Nuclear Information System (INIS)

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

127

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.

128

Radiation absorbed dose estimates to the embryo from some nuclear medicine procedures  

International Nuclear Information System (INIS)

Using the specific absorbed fractions reported by Smith and Warner, the radiation doses absorbed by the embryo in early pregnancy were calculated for various radiopharmaceuticals used in the diagnostic procedures of nuclear medicine. Radiopharmaceuticals are considered which are excreted predominantly through urine and cause the doses to the embryo to be 40%-90% higher than gonad doses. Also discussed are large differences of doses reported by various authors to the embryo by sup(99m)Tc-pertechnetate. (orig.)

129

Absorbed and effective dose in direct and indirect digital panoramic radiography  

Energy Technology Data Exchange (ETDEWEB)

We evaluated the absorbed doses to the organs and calculated the effective doses when using the digital panoramic radiography. The absorbed dose averages in major organs of oral and maxillofacial region were measured using the Dental head phantom (CIRS Co., USA), nLi2B4O7 TLD chip and UD-716AGL dosimeter (Matsushita Electric Industrial Co., JPN) when performing indirect and direct digital panoramic radiography. Effective doses were calculated from correspond to ICRP 2007 recommendations for two panoramic radiography. The absorbed dose average on indirect and direct digital panoramic radiography was highest in parotid glands as measured 1259.6 mGy and 680.7 mGy respectively. Absorbed dose average in another organs were high in order of esophagus, submandibular gland, tongue and thyroid gland on both types of digital panoramic radiography. The absorbed dose average was higher on indirect type than direct one (p?0.05). The effective dose was higher on indirect type than direct one as measured 13.28 mSv and 8.70 mSv respectively. The absorbed doses in salivary gland and oral mucosa were high. However, thyroid gland also demands the attention on radiography due to high tissue weighting factor in spite of the low absorbed dose.

Lee, Gun Sun; Kim, Jin Soo; Kim, Jae Duk [Department of Oral and Maxilloficial Radiology School of Dentistry, Oral Biology Research Institute, Chosun University, Gwangju (Korea, Republic of)

2010-03-15

130

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

131

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

132

Reusability of CaF2:Mn TLDS photon irradiations at high absorbed-dose levels  

International Nuclear Information System (INIS)

The effects of high absorbed dose on the reusability of CaF2:Mn thermoluminescence dosimeters (TLDs) are investigated to determine a recommended upper limit on absorbed dose for TLDs that are to be reused. This investigation examines degradation in the uniformity of response and changes in sensitivity of a batch of TLDs when exposed to gamma-radiation doses ranging from 1 Gy to 1000 Gy, and confirms earlier work suggesting that CaF2:Mn TLDs should not be reused in applications where cumulative absorbed doses are likely to exceed 100 Gy

133

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

134

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

135

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

International Nuclear Information System (INIS)

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. (author)

136

Mathematical modeling correlated to MIRD for absorbed dose calculation from animal biodistribution data  

International Nuclear Information System (INIS)

The purpose of this study was to develop a mathematic model to estimate the absorbed dose for normal and tumor tissues using biodistribution data of 177 Lu-DOTA-TATE in HRS1 tumor-bearing rats. The model presented interactions between physical, chemical, and biological parameters, enabling the tool to calculate the dose absorbed by each investigated organ, and suggested a potential extrapolation of the results to calculate 177 Lu-DOTA-TATE therapy doses. (authors)

137

Isoeffective dose: a concept for biological weighting of absorbed dose in proton and heavier-ion therapies  

CERN Document Server

When reporting radiation therapy procedures, International Commission on Radiation Units and Measurements (ICRU) recommends specifying absorbed dose at/in all clinically relevant points and/or volumes. In addition, treatment conditions should be reported as completely as possible in order to allow full understanding and interpretation of the treatment prescription. However, the clinical outcome does not only depend on absorbed dose but also on a number of other factors such as dose per fraction, overall treatment time and radiation quality radiation biology effectiveness (RBE). Therefore, weighting factors have to be applied when different types of treatments are to be compared or to be combined. This had led to the concept of `isoeffective absorbed dose', introduced by ICRU and International Atomic Energy Agency (IAEA). The isoeffective dose D(IsoE) is the dose of a treatment carried out under reference conditions producing the same clinical effects on the target volume as those of the actual treatment. It i...

Wambersie, A; Menzel, H G; Gahbauer, R; DeLuca, P M; Hendry, J H; Jones, D T L

2011-01-01

138

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)

139

Comparison of IAEA absorbed dose protocols TRS 277 and TRS 398 for different photon energies  

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Full Text Available OBJECTIVES: In this study, calculation of absorbed doses according to three different IAEA protocols for Co-60, 6 MV, 25 MV photon energies are compared. METHODS: Absorbed dose measurements are made at SSD=SAD distance, 10x10 cm field size and referance depth. Photon energies are measured with five different cylindirical chambers. Polarity and recombination effects are measured for all ionization chambers and energies. RESULTS: After the measurements, calculations are made according to two different protocols and absorbe dose calculated according to TRS 398 protocol is maximum 0.32% bigger than TRS 277’s dose for Co-60, and 0.57% bigger for 6 MV and 1.53% bigger for 25 MV. CONCLUSION: As a result, TRS 398 protocol enables us to calculate much more accurate absorbe dose.

Hilal ACAR

2006-01-01

140

Determination of water absorbed dose in a carbon ion beam using thimble ionization chambers  

International Nuclear Information System (INIS)

The method to measure absorbed dose to water in a field of carbon ions as applied for the heavy ion therapy project at the Heavy Ion Research Laboratory in Darmstadt (GSI), Germany, is described in detail. Thimble ionization chambers with a water absorbed calibration factor are applied. The dose obtained with this method was compared with that obtained at the heavy ion therapy facility HIMAC at the National Institute of Radiological Sciences in Chiba, Japan, using the Japanese code of practice. The agreement found was better than 1%. The combined uncertainty of the determination of absorbed dose to water was estimated to amount to 5%. (author)

 
 
 
 
141

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.

142

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)

143

Palladium-109 and holmium-166 potential radionuclides for synoviotherapy - radiation absorbed dose calculations  

International Nuclear Information System (INIS)

Palladium-109 and holmium-166 are radionuclides with nuclear, physical and chemical characteristics appropriate for therapeutic purposes. Radiation absorbed doses are calculated and compared with currently used radionuclides in synoviotherapy. (author)

144

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)

145

Absorbed dose determination for interstitial 125I boost therapy  

International Nuclear Information System (INIS)

Iodine-125 implants are being used to boost external beam treatments of unresectable pancreas and lung tumors. Calculations of the 125I activity required to achieve a specific average peripheral dose are presented as a function of the average tumor dimension for spherical, ellipsoidal, and cylindrical implants. Both uniform and random seed spacings are investigated. The results indicate that the average peripheral dose is relatively insensitive to the seed distribution as well as to the seed activity. The average tumor dose is typically 20% greater than the average peripheral dose

146

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.

Bailiff, I.K.; BØtter-Jensen, L.

2000-01-01

147

Patient absorbed doses in digital grey-scale fluorography  

International Nuclear Information System (INIS)

This article describes a preliminary comparison between the levels of patient dose used in digital grey-scale fluorography (DGF) and screen-film radiography. Patient doses were measured in three common radiographic examinations, postero-anterior chest, antero-posterior lumbar spine and lateral lumbo-sacral junction, using thermoluminescent dose-meters and an anthropomorphic phantom. Within the limitations of the image quality currently available in DGF, the findings indicate that digital radiography with the large-field X-ray image intensifier promises significant savings in patient dose compared with conventional radiography. (author)

148

Absorbed dose simulations in near-surface regions using high dose rate Iridium-192 sources applied for brachytherapy  

International Nuclear Information System (INIS)

Brachytherapy treatment with Iridium-192 high dose rate (HDR) sources is widely used for various tumours and it could be developed in many anatomic regions. Iridium-192 sources are inserted inside or close to the region that will be treated. Usually, the treatment is performed in prostate, gynaecological, lung, breast and oral cavity regions for a better clinical dose coverage compared with other techniques, such as, high energy photons and Cobalt-60 machines. This work will evaluate absorbed dose distributions in near-surface regions around Ir-192 HDR sources. Near-surface dose measurements are a complex task, due to the contribution of beta particles in the near-surface regions. These dose distributions should be useful for non-tumour treatments, such as keloids, and other non-intracavitary technique. For the absorbed dose distribution simulations the Monte Carlo code PENELOPE with the general code penEasy was used. Ir-192 source geometry and a Polymethylmethacrylate (PMMA) tube, for beta particles shield were modelled to yield the percentage depth dose (PDD) on a cubic water phantom. Absorbed dose simulations were realized at the central axis to yield the Ir-192 dose fall-off along central axis. The results showed that more than 99.2% of the absorbed doses (relative to the surface) are deposited in 5 cm depth but with slower rate at higher distances. Near-surface treatments with Ir-192 HDR sources yields achievable measurements and with proper clinical technique and accessories should apply as an alternative for treatment of lesions where only beta sources were used. - Highlights: ? A PMMA (polymethylmethacrylate) tube was used to surround the HDR Ir-192 to shield the beta particles. ? 99.2% of the absorbed doses (relative to the surface) are deposited in 5 cm depth. ? Near-surface treatments with Ir-192 HDR sources yields achievable measurements

149

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

150

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

151

Absorbed doses due to synchrotron radiation in the tunnel of the storage ring PETRA  

International Nuclear Information System (INIS)

Absorbed doses due to synchrotron radiation were measured in the accelerator tunnel of the high-energy electron-positron storage ring PETRA, at beam energies between 17 and 22.8 GeV. For energies between 17 and 30 GeV calculations were performed using the Monte Carlo code EGS. An agreement with the measured values was obtained within a factor of 2. In addition, the absorbed doses in a straight part of the accelerator tunnel were studied. (orig.)

152

Ionometric determination of absorbed dose to water for cobalt-60 gamma rays  

International Nuclear Information System (INIS)

An ionometric method has been used for the determination of absorbed dose to water for 60Co ? rays. Reliable estimation of the perturbation correction, which accounts for the presence of the chamber inside the water phantom, allows an accurate determination of absorbed dose. Details of the experimental work are given together with the theoretical background necessary for evaluation of the perturbation correction. The results are discussed by comparing them with those obtained by other methods. (author)

153

Determination of Absorbed and Annual Effective Doses around Birnin Gwari Artisanal Goldmine, Kaduna State, Nigeria  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This study presents result of outdoor absorbed dose rate and estimated annual effective dose rate from the naturally occurring radionuclides 238U, 232Th and 40K around BirninGwari artisanal goldmine using Instrumental Neutron Activation Analysis (INAA). The results showed that the mean absorbed dose rate is 96.52 nGy/h with a standard deviation of 33.3 nGy/h and the standard error of 9.62 nGy/h the range falls between 26.67-123.85 nGy/h. The mean effective dose rate was estimated to be 0.675 ...

Zakari, Y. I.; Nasiru, R.; Abdullahi, M. A.

2013-01-01

154

High absorbed dose (104 to 108 Gy) gamma dosimeters based on organic conductors  

International Nuclear Information System (INIS)

Organic conductors are promising candidates for gamma dosimetry in the range of 104 to 108Gy. Their electrical resistance increases with the absorbed dose, and this variation can be predicted theoretically over a large dose range. One of these conductors called (TMTSF)(DMTCNQ) has been tested in the industrial gamma irradiator of reactor Osiris at a temperature of 500C. The resolution of this absorbed-dose integrator was shown to be better than 104Gy for a maximum integrated dose of several 107Gy. The measurement of this dosimeter in situ during irradiation permits accurate monitoring and control of the industrial irradiation plant for a period of several months

155

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

 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...

Gh Bagheri; Sakhaee, M.; Vahabi-moghaddam, M.

2011-01-01

156

Absorbed-dose specification in nuclear medicine. ICRU Report 67  

International Nuclear Information System (INIS)

A number of factors have led to a reappraisal of dose specification for nuclear medicine. These include 1) an appreciation of non-uniformities in the distribution of radioactivity in the body, at all levels, for even the most common diagnostic and therapeutic agents 2) an increasing need to deal with the complexities of varying dose rates 3) the imperative to provide individual rather than standardised dose estimates as targeted radionuclide therapy becomes more sophisticated, and 4) improvements in technology. This report deals first with biological considerations that inform the rational use of radionuclide dosimetry. Radiobiological factors in the selection of radionuclides and tumour and normal tissue dose-responses are discussed. Then, the MIRD approach to nuclear medical dosimetry is described, a robust method that has proven its clinical utility. Following on is an elaboration of non-uniform distributions of radioactivity and of varying dose rates. Lastly, the report deals with techniques and procedures for measuring time-variant activity distributions, image fusion, patient-specific dose computations, small-scale dosimetry, and the comparison of calculated and measured doses. (author)

157

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)

158

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

159

Eye lens dosimetry for interventional procedures – Relation between the absorbed dose to the lens and dose at measurement positions  

International Nuclear Information System (INIS)

This study investigated the relationship between the absorbed dose to the lens of the eye and the absorbed dose at different measurement positions near the eye of interventional radiologists. It also visualised the dose distribution inside the head, both when protective eyewear were used and without such protection. The best position for an eye lens dosimeter was found to be at the side of the head nearest to the radiation source, close to the eye. Positioning the dosimeter at the eyebrow could lead to an underestimation of the lens dose of as much as 45%. The measured dose distribution showed that the absorbed dose to the eye lenses was high compared to the other parts of the head, which stresses the importance of wearing protective eyewear. However, many models of eyewear were found to be deficient as the radiation could slip through at several places, e.g. at the cheek. The relationship between the absorbed dose to the lens and the kerma-area-product (PKA) delivered to the patient was also studied.

160

Difference in radiation absorbed dose according to the panoramic radiographic machines  

Energy Technology Data Exchange (ETDEWEB)

The primary objective of this study was to estimate the radiation absorbed doses in certain critical organs in the head and neck region with an Orthopos plus, a Panelipse, and a Panex-E machines. The second objective was to compare the absorbed doses between 5 inch by 12 inch and 6 inch by 12 inch image field for the Orthopos plus. Rando phantom and LiF TLD chips were used for dosimetry. The absorbed doses were measured at the thyroid gland, the submandibular gland, the parotid gland, the mouth floor, the maxillary sinus, the brain, the mandibular body, the mandibular ramus, the 2nd cervical spine and the skin over TMJ area. The highest absorbed dose value was recorded at the mandibular ramus for the Orthopos plus with narrow image field. Higher absorbed dose values were recorded at the parotid gland, the mouth floor, the submandibular gland, and the 2nd cervical spine. The doses in the parotid gland were 597 microGy and 529 microGy with Orthopos plus, 638 microGy with Panelipse, and 1094 microGy with Panex-E. Corresponding figures for the mandibular ramus were 2363 microGy and 1220 microGy, 248 microGy, and 118 microGy. The absorbed doses to the thyroid gland, the maxillary sinus, the brain, and the skin over TMJ were very low. Higher exposure values were recorded for the Orthopos plus than Panelipse and Panex-E. There was no significant differences of the absorbed doses according to the image field size.

Choi, Soon Chul [Dept. of Oral and Maxillofacial Radiology and Dental Research Institute College of Dentistry, Seoul National University, Seoul (Korea, Republic of)

2000-03-15

 
 
 
 
161

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.

McLaughlin, W.L.; Miller, Arne

1985-01-01

162

measurement of absorbed dose in mix-dp phantom irradiated by x and gamma rays  

International Nuclear Information System (INIS)

It has been done of x-rays dan gamma rays absorbed dose measurement of mix-dp phantom of 70 kVp.90kvp and 110 kvp x rays kxo-12 medical exposure and cobalt-60 gamma (50 ci) by UD-170A BeO-TLD. Ionization chamber 12 cc NIRS-R2 as reference dosemeter, which was calibrated on primer dosemeter. In X-rays energy used, it was done of absorbed dose measurement on Mix-Dp phantom surface and depth (d= 10cm) beam field area 10 x 10 cm, focus distance (FSD), s=80 cm dose measurement of 90 kvp X-rays on Mix-Dp phantom surface, depth and scattering (d=15 cm) beam field area 12 x 12 cm, focus distance (FSD),s=79 cm and measurement of absorbed dose Co-60 gamma: 5 R, 10R, 20 R, 30R, 40R and 50R by dose rate 0.434 R/min. It was shown that in clinical, effective energy range of X-rays relative lower than dose range Co-60 gamma. BeO-TLD characteristic on energy dependence is low based on TI sensitivity ± 1.3 for energy below 100 keV. Relation between absorbed dose and TL response to 90 kVp X-rays shown that rperm=0.990, r ber=0.995 and r sact=0.962. In measurement of Co-60 gamma absorbed dose by BeO-TLD shown TI sensitivity decrease ± 0.900. The result still needed corrections to achieve optimum measurement of absorbed dose X-rays and gamma by UD-170A BeO-TLD, which were performed optimum fading time and anealling temperature

163

Radiation environments and absorbed dose estimations on manned space missions  

Science.gov (United States)

The dose and dose-equivalent estimates that astronauts might be expected to receive in space were assessed for the development of new radiation protection guidelines, considering several space mission scenarios. These scenarios included a 90-day LEO mission at 450 km altitude with orbital inclinations appropriate for NASA's Space Station (28.5, 57, and 90 deg), a 15-day sortie to GEO, and a 90-day lunar mission. All the missions contemplated would present space travelers with dose equivalents between 5 and 10 rem to the blood-forming organs, assuming no encounter with a large solar particle event; a large particle event could add considerable exposure for all scenarios except for the one at 28.5 orbital inclination. Adequate shielding must be included to guard against the radiation produced by such events.

Curtis, S. B.; Atwell, W.; Beever, R.; Hardy, A.

1986-01-01

164

Estimation of absorbed dose in medical diagnostics with use of radioisotope and X-rays  

International Nuclear Information System (INIS)

In this work we estimate the absorbed dose of the patients undergoing medical examination with use of the radioisotope Tc-99m and X-rays. The discussion has been presented for several examples of complementary diagnostics methods such as kidneys (renoscintigraphy, urography), bones (scintigraphy, spine X-ray examination) and breast (mammoscintigraphy, mammography). The medical internal dose (MIRD) has been evaluated. (author)

165

Dose of radiation absorbed by the gonads during diagnostic radiological investigations  

International Nuclear Information System (INIS)

In the work the authors report the results of measurements of the doses absorbed by the gonads of patients subjected to different radiological investigations. It was found that the gonads of the patients received the highest doses during radiological investigations of abdominal organs, particularly during urography, rectal contrast enemas, hysterosalpingography. (author)

166

Estimation of target absorbed dose by in-vivo measure for cavum and larynx cancer  

International Nuclear Information System (INIS)

The goal of radiotherapy is to deliver the prescribed dose with a relative standard deviation in tumour control probability less than 5%, in order to control the disease while minimising complication to normal tissues. In this study, the absorbed dose delivered to the target volume by using transmission curves established for a cobalt unit is determined

167

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

168

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)

169

Absorbed dose simulations in near-surface regions using high dose rate Iridium-192 sources applied for brachytherapy  

Science.gov (United States)

Brachytherapy treatment with Iridium-192 high dose rate (HDR) sources is widely used for various tumours and it could be developed in many anatomic regions. Iridium-192 sources are inserted inside or close to the region that will be treated. Usually, the treatment is performed in prostate, gynaecological, lung, breast and oral cavity regions for a better clinical dose coverage compared with other techniques, such as, high energy photons and Cobalt-60 machines. This work will evaluate absorbed dose distributions in near-surface regions around Ir-192 HDR sources. Near-surface dose measurements are a complex task, due to the contribution of beta particles in the near-surface regions. These dose distributions should be useful for non-tumour treatments, such as keloids, and other non-intracavitary technique. For the absorbed dose distribution simulations the Monte Carlo code PENELOPE with the general code penEasy was used. Ir-192 source geometry and a Polymethylmethacrylate (PMMA) tube, for beta particles shield were modelled to yield the percentage depth dose (PDD) on a cubic water phantom. Absorbed dose simulations were realized at the central axis to yield the Ir-192 dose fall-off along central axis. The results showed that more than 99.2% of the absorbed doses (relative to the surface) are deposited in 5 cm depth but with slower rate at higher distances. Near-surface treatments with Ir-192 HDR sources yields achievable measurements and with proper clinical technique and accessories should apply as an alternative for treatment of lesions where only beta sources were used.

Moura, E. S.; Zeituni, C. A.; Sakuraba, R. K.; Gonçalves, V. D.; Cruz, J. C.; Júnior, D. K.; Souza, C. D.; Rostelato, M. E. C. M.

2014-02-01

170

Evaluation of the dose absorbed by the thyroid of patients undergoing treatment of Graves disease  

International Nuclear Information System (INIS)

The radioiodine is used as complementary treatment of thyroid cancer and as first choice for the treatment of Graves' disease, being efficient, safe and easy administration, but without there is a protocol defined. This work was evaluated the thyroid absorbed dose from its mass and maximum uptake of I-131 obtained in the examination of diagnostic radiology of radiotherapeutic patients undergoing treatment of Graves' disease. Based on the results, it is observed that the thyroid absorbed dose, as much in terms of mass as the maximum uptake of I-131 for different values of administered activity, varies significantly. The analysis of these parameters is an excellent indicator for the pre-define quantity of radionuclide that is administered to the patient in terms of the radiation dose required to achieve an efficient therapeutic treatment. Moreover, it was observed that the thyroid absorbed dose depends on the degree of pathology of the disease, its mass and of the maximum uptake of I-131. (author)

171

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

172

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.)

173

Determination of the absorbed dose and dose-distribution in water for low- and medium-energetic photons  

International Nuclear Information System (INIS)

The methods to determine the absorbed dose to water for low and medium energy photons were studied. Large differences between the results of these methods exists. So, a research proposition has been made to explain these differences. The goal of this research will be the development of a method to determine the absorbed dose below approximately 400 keV with an ionization chamber calibrated at 60Co gamma radiation. To explain the differences between the set of methods, some causes were proposed, like the influence of the ionisation chamber on the measurement in water. Also, some methods to determine the factors are proposed. (author). 29 refs

174

Three dimensional measurements of absorbed dose in BNCT by Fricke-gel imaging  

International Nuclear Information System (INIS)

A method has been studied for absorbed dose imaging and profiling in a phantom exposed to thermal or epithermal neutron fields, also discriminating between various contributions to the absorbed dose. The proposed technique is based on optical imaging of FriXy-gel phantoms, which are proper tissue-equivalent phantoms acting as continuous dosimeters. Convenient modifications in phantom composition allow, from differential measurements, the discrimination of various contributions to the absorbed dose. The dosimetry technique is based on a chemical dosimeter incorporated in a tissue-equivalent gel (Agarose). The chemical dosimeter is a ferrous sulphate solution (which is the main component of the standard Fricke dosimeter) added with a metal ion indicator (Xylenol Orange). The absorbed dose is measured by analysing the variation of gel optical absorption in the visible spectrum, imaged by means of a CCD camera provided with a suitable filter. The technique validity has been tested by irradiating and analysing phantoms in the thermal facility of the fast research reactor TAPIRO (ENEA, Casaccia, Italy). In a cylindrical phantom simulating a head, we have imaged the therapy dose from thermal neutron reactions with 10B and the dose in healthy tissue not containing boron. In tissue without boron, we have discriminated between the two main contributions to the absorbed dose, which comes from the 1H(n,?)2H and 14N(n,p)14C reactions. The comparison with the results of other experimental techniques and of simulations reveals that the technique is very promising. A method for the discrimination of fast neutron contribution to the absorbed dose, still in an experimental stage, is proposed too. (author)

175

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

Energy Technology Data Exchange (ETDEWEB)

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.

Chen, W. L.; Poston, J. W.; Warner, G. G.

1978-04-01

176

Entrance absorbed dose measurements in clinical telecobalt beams  

International Nuclear Information System (INIS)

As the telecobalt machines are made with different collimator designs, knowledge of the build-up profile and effect of different intervening materials in the beam is necessary. In this study, the build-up dose measurements were performed in different telecobalt machines using a PTW parallel plate chamber. Results from the study showed that the surface dose drastically increases with the presence of lucite tray in the path of the beam at short SSD. However, the effect is not significant at longer SSDs. Also, any conventional long SSD machine when used for short SSD treatment will result in clinically adverse skin reactions. The introduction of a 2.8 mm lead plate improves the beam characteristics at short SSD with clearance of 10 cm to surface level. The result has relevance in the design of suggested short SSD telecobalt machine in India for the treatment of head and neck cancers. (author)

177

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)

178

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)

179

The absorbed doses from each exposure program of the Orthopos panoramic machine  

Energy Technology Data Exchange (ETDEWEB)

The objective of this study was to estimate the radiation absorbed doses in certain critical organs in the head and neck region with 16 imaging programs available on the Orthopos panoramic machine. A Rando phantom and LiF TLD chips were used for dosimetry. The absorbed doses were measured at the thyroid gland, the submandibular gland, the parotid gland, the mouth floor, the maxillary sinus, the brain, the mandibular body, the mandibular ramus, the 2nd cervical spine and the skin over TMJ area. The overall absorbed doses with imaging programs available on the Orthopos panoramic machine were much less than that of standard program (program 1) except program 8, 11, and 16. Generally, the absorbed doses to the bone marrow of the mandibular ramus and the parotid gland were high, but the absorbed doses to the bone marrow in the mandibular body, brain, maxillary sinus, and, especially, the thyroid gland were very low. The modified imaging programs available on the Orthopos panoramic can be effectively used in aspect of radiation protection.

Choi, Soon Chul; Lee, Sul Mi [Seoul National Univ. College of Dentistry, Seoul (Korea, Republic of)

2001-12-15

180

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

International Nuclear Information System (INIS)

The purpose of this study was to estimate the distribution of absorbed doses of each important organs of head and neck region in panoramic radiography. Radiation dosimetry at internal anatomic sites and skin surfaces of phantom (RT-210 Humanoid Head and Neck Section R) was performed with lithium fluoride (TLD-100R) thermoluminescent dosimeters according to change of kilovoltage (65 kVp, 75 kVp and 85 kVp) with 4 miliamperage and 20 second exposure time. The results obtained were as follows; Radiation absorbed doses of internal anatomic sites were presented the highest does of 1.04 mGy, 1.065 mGy and 2.09 mGy in nasopharynx, relatively high doses of 0.525 mGy, 0.59 mGy and 1.108 mGy in deep lobe of parotid gland, 0.481 mGy, 0.68 mGy and 1.191 mGy in submandibular gland. But there were comparatively low doses of 0.172 mGy and 0.128 mGy in eyes and thyroid gland that absorbed dose was estimated at 85kVp. Radiation absorbed doses of skin surfaces were presented the highest doses of 1.263 mGy, 1.538 mGy and 2.952 mGy in back side of first cervical vertebra and relatively high doses of 0.267 mGy, 0.401 mGy and 0.481 mGy in parotid gland. But there were comparatively low doses of 0.057 mGy, 0.068 mGy and 0.081 mGy in philtrum and 0.059 mGy in middle portion of chin that absorbed dose was estimated at 85 kVp. According to increase of kilovoltage, the radiation absorbed doses were increased 1.1 times when kilovoltage changes from 65 kVp to 75 kVp and 1.9 times when kilovoltagep 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.

 
 
 
 
181

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

International Nuclear Information System (INIS)

The Norwegian Radiation Protection Authority (NRPA) SSDL recommended in 2000 the use of absorbed dose to water as the quality for calibration and code of practice in radiotherapy. The absorbed dose to water standard traceable to BIPM was established in Norway in 1995. The international code of practice, IAEA TRS 398 was under preparation. As a part of the implementation of the new dosimetry system the SSDL went to radiotherapy departments in Norway in 2001. The aim of the visit was to: Prepare and support the users in the implementation of TRS 398 by teaching, discussions and measurements on-site; Gain experience for NRPA in the practical implementation of TRS 398 and perform comparisons between TRS 277 and TRS 398 for different beam qualities; Report experience from implementation of TRS 398 to IAEA. The NRPA 30x30x30 cm3 water phantom is equal to the BIPM calibration phantom. This was used for the photon measurements in 16 different beams. NRPA used three chambers: NE 2571, NE 2611 and PR06C for the photon measurements. As a quality control the set-up was compared with the Finnish site-visit equipment at University Hospital of Helsinki, and the measured absorbed dose to water agreed within 0.6%. The Finnish SSDL calibrated the Norwegian chambers and the absorbed dose to water calibration factors given by the two SSDLs for the three chambers agreed within 0.3%. The local clinical dosimetry in Norway was based on TRS 277. For the site-visit the absorbed dose to water was determined by NRPA using own equipment including the three chambers and the hospitals reference chamber. The hospital determined the dose the same evening using their local equipment. For the 16 photon beams the deviations between the two absorbed dose to water determinations for TRS 277 were in the range -1,7% to +4.0%. The uncertainty in the measurements was 1% (k=1). The deviation was explained in local implementation of TRS 277, the use of plastic phantoms, no resent calibration of thermometers, barometers and electrometers. A new roundtrip was done for electron beams. The aim of this visit was to cross-calibrate the hospital plan-parallel chambers in a high energy electron beam and measure absorbed dose to water in different high energy electron beams. The measurements were performed in the local water tank for beam data measurements. The absorbed dose was this time compared to the treatment units monitor calibration. Results from absorbed dose to water measurements for high energy electron beams showed that compared to TRS 398 the electron beams was off in the range -2,3 to + 4,6%. The uncertainty of the electron measurements was 1.5 % (k=1). The absorbed dose to water calculated from the former air kerma 60Co standard is at the Norwegian SSDL 0.5% lower than absorbed dose to water 60Co standard. From calculation one can see that the CoP TRS 277 give 0.5% to 1.0% higher dose than CoP TRS 398 in high energy photon beams depending on beam quality. For electrons this deviation is in the range - 0.3% to + 0.1%. The air kerma standard and TRS 277 CoP give in Norway 1.0 % to 1.5 % too high doses for high energy photons, while the dose change for electron beams is smaller than the uncertainty. On site measurements show higher deviations because of local implementation of a code of practice. The medical physicists welcomed the visit and requested more visits. This research was done in cooperation with IAEA, Agreement No. 11627

182

Do Only Small Uremic Toxins, Chromophores, Contribute to the Online Dialysis Dose Monitoring by UV Absorbance?  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The aim of this work was to evaluate the contributions of the main chromophores to the total UV absorbance of the spent dialysate and to assess removal dynamics of these solutes during optical on-line dialysis dose monitoring. High performance chromatography was used to separate and quantify UV-absorbing solutes in the spent dialysate sampled at the start and at the end of dialysis sessions. Chromatograms were monitored at 210, 254 and 280 nm routinely and full absorption spectra were registe...

Fredrik Uhlin; Ivo Fridolin; Jürgen Arund; Risto Tanner

2012-01-01

183

Absorbed Doses to Patients in Nuclear Medicine; Doskatalogen foer nukleaermedicin  

Energy Technology Data Exchange (ETDEWEB)

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: {sup 11}C-labelled substances (realistic maximum model), amino acids labelled with {sup 11}C, {sup 18}F or {sup 75}Se, {sup 99m}Tc-apcitide, {sup 123}I-labelled fatty acids ({sup 123}I- BMIPP and {sup 123}I-IPPA) and revised models for previously reported {sup 15}O-labelled water, {sup 99m}Tc-tetrofosmin (rest as well as exercise) and {sup 201}Tl-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)

Leide-Svegborn, Sigrid; Mattsson, Soeren; Johansson, Lennart; Fernlund, Per; Nosslin, Bertil

2007-04-15

184

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

International Nuclear Information System (INIS)

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 eant4 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 %?0.33 %, and at 28 kVp/70 mAs, the Difference(%) of dose was 0.01 %?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

185

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

Science.gov (United States)

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.

Vega-Carrillo, Héctor René; Manzanares-Acuña, Eduardo; Hernández-Dávila, Víctor Martín; Arcos-Pichardo, Areli; Barquero, Raquel; Iñiguez, M. Pilar

2006-09-01

186

Comparison of absorbed dose in bone substitute material and water using ionization measurements  

International Nuclear Information System (INIS)

Absorbed dose in a liquid substitute for bone has been compared with absorbed dose in water for 9-, 12-, and 15-MeV electron beams using ionization chamber measurements. The ionization readings were converted to dose using collisional mass stopping power ratios. The collisional mass stopping powers for the liquid substitute of bone were calculated using the Monte Carlo Code PEGS4. The results of our study show that there is an increase in dose in the liquid bone substitute compared to water at shallow depths. The maximum increase in dose was 5%, 4%, and 2% at depths of 1.2, 1.5, and 2.0 cm, respectively, for 9-, 12-, and 15-MeV electrons. The density of the liquid bone substitute was 1360 kg/m3 and the effective atomic number was 11

187

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

188

Comparision between the IAEA's protocols (TRS-277 and TRS-398) for absorbed dose determination  

International Nuclear Information System (INIS)

The aim of this study is to compare between two IAEA's Protocols [IAEA-TRS-277 (1987) and IAEA-TRS-398 (2000)] for Absorbed Dose Determination. Five types (5 Chamber) of commonly used cylindrical ionization chambers (Farmer type, 0.6 cc) were used to check the difference in absorbed dose to water determination for Co-60 beams under reference condition. TLD dosimeter was also used for inter-comparison with IAEA's SSDL. The mean values of the measured absorbed dose were found to be similar in both cases and the relative error D (TRS-398)/D (TRS-277) is found to be approximately less than 0.5% for all chambers used in this study.(authors)

189

On the Influence of Patient Posture on Organ and Tissue Absorbed Doses Caused by Radiodiagnostic Examinations  

International Nuclear Information System (INIS)

Virtual human phantoms, frequently used for organ and tissue absorbed dose assessment in radiology, normally represent the human body either in standing or in supine posture. This raises the question as to whether it matters dosimetrically if the postures of the patient and of the phantom do not match. This study uses the recently developed FASH2sta (Female Adult meSH) and FASH2sup phantoms which represent female adult persons in standing and supine posture. The effect of the posture on organ and tissue absorbed doses will be studied using the EGSnrc Monte Carlo code for simulating abdominal radiographs and special attention will be directed to the influence of body mass on the results. For the exposure conditions considered here, posture-dependent absorbed dose differences by up to a factor of two were found. (author)

190

Contribution to the determination of a standard of absorbed dose in water for cobalt 60 photons  

International Nuclear Information System (INIS)

A new standard, expressed in terms of absorbed dose at a depth of 5g/cm2 in a water phantom irradiated by cobalt 60 gamma photons, is determined. The procedure developed is based on a transfer method using two dosimetric techniques: Fricke dosimetry and ionometry (0.6 cm3 NE 2571 radiotherapy ionization chamber). Their calibration is performed with the primary calibration standard of absorbed dose: the graphite calorimeter. The relative discrepancy between the values of absorbed dose in water determined by the chemical dosimeter and the ionization chamber is equal to 1%. The ionization chamber has been also calibrated near the Cobalt 60 reference beam characterized in terms of air kerma

191

Extension of the Commonwealth standard of absorbed dose from cobalt-60 energy to 25 MV  

International Nuclear Information System (INIS)

With the introduction of high energy linear accelerators in hospitals, there is a need for direct measurement of absorbed dose for energies to 25 MV for photons and 20 MeV electrons. The present Australian standard for absorbed dose at cobalt-60 energy is a graphite micro-calorimeter maintained at the AAEC Lucas Heights Research Laboratories. A thorough theoretical analysis of calorimeter operation suggests that computer control and monitoring techniques are appropriate. Solution of Newton's law of cooling for a four-body calorimeter allows development of a computer simulation model. Different temperature control algorithms may then be run and assessed using this model. In particular, the application of a simple differencer is examined. Successful implementation of the calorimeter for energies up to 25 MV could lead to the introduction of an Australian absorbed dose protocol based on calorimetry, therby reducing the uncertainties associated with exposure-based protocols

192

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

193

Comparison of absorbed dose to air calibration factors for a parallel plate ionization chamber  

International Nuclear Information System (INIS)

Objective: the objective of this study was to compare the absorbed dose to air calibration factors determined in gamma (60Co) and electron beams.Objective: an irradiator with a 60Co source and a Varian, Clinac 2100C linear accelerator with photon and electron beams were utilized. One thimble-type and three parallel-plate ionization chambers were tested. Results: The measurement systems were submitted to preliminary tests (response stability and leakage current), with quite good results. The absorbed dose to air calibration factors were determined using four measurement systems and two types of phantoms. Results were obtained in compliance with the international recommendations.Conclusion: absorbed dose to air calibration factors obtained for parallel plate ionization chambers, determined in 60Co beams, at maximum, are 1.2% higher than the values obtained in high energy electron beams. (author)

194

Comparison of absorbed dose to air calibration factors for a parallel plate ionization chamber  

Energy Technology Data Exchange (ETDEWEB)

Objective: the objective of this study was to compare the absorbed dose to air calibration factors determined in gamma ({sup 60}Co) and electron beams.Objective: an irradiator with a {sup 60}Co source and a Varian, Clinac 2100C linear accelerator with photon and electron beams were utilized. One thimble-type and three parallel-plate ionization chambers were tested. Results: The measurement systems were submitted to preliminary tests (response stability and leakage current), with quite good results. The absorbed dose to air calibration factors were determined using four measurement systems and two types of phantoms. Results were obtained in compliance with the international recommendations.Conclusion: absorbed dose to air calibration factors obtained for parallel plate ionization chambers, determined in {sup 60}Co beams, at maximum, are 1.2% higher than the values obtained in high energy electron beams. (author)

Bulla, Roseli T.; Caldas, Linda V.E. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN), Sao Paulo, SP (Brazil)]. E-mail: lcaldas@ipen.br; rtbulla@ig.com.br

2006-05-15

195

Comparison of absorbed dose determinations between water and polystyrene-water calorimeters  

International Nuclear Information System (INIS)

The absorbed dose in water determined by a water calorimeter was compared with that determined by a polystyrene-water calorimeter. An ionisation chamber was also used in the absorbed dose determinations. The beams that were used were cobalt-60 gamma rays, and 10 and 25 MV x-ray photons. A nominal 18 MeV electron beam was also included in the study. Results indicate that the absorbed dose measured by the water calorimeter using once-deionised water is 1.4 to 3.6% higher than that by the polystyrene-water calorimeter, indicating an average of 2.5% exothermicity of water. This finding is similar to that in the literature. (author)

196

The accuracy of absorbed dose estimates in tumours determined by Quantitative SPECT: A Monte Carlo study  

Energy Technology Data Exchange (ETDEWEB)

Background. Dosimetry in radionuclide therapy estimates delivered absorbed doses to tumours and ensures that absorbed dose levels to normal organs are below tolerance levels. One procedure is to determine time-activity curves in volumes-of-interests from which the absorbed dose is estimated using SPECT with appropriate corrections for attenuation, scatter and collimator response. From corrected SPECT images the absorbed energy can be calculated by (a) assuming kinetic energy deposited in the same voxel where particles were emitted, (b) convolve with point-dose kernels or (c) use full Monte Carlo (MC) methods. A question arises which dosimetry method is optimal given the limitations in reconstruction- and quantification procedures. Methods. Dosimetry methods (a) and (c) were evaluated by comparing dose-rate volume histograms (DrVHs) from simulated SPECT of 111In, 177Lu, 131I and Bremsstrahlung from 90Y to match true dose rate images. The study used a voxel-based phantom with different tumours in the liver. SPECT reconstruction was made using an iterative OSEM method and MC dosimetry was performed using a charged-particle EGS4 program that also was used to determined true absorbed dose rate distributions for the same phantom geometry but without camera limitations. Results. The DrVHs obtained from SPECT differed from true DrVH mainly due to limited spatial resolution. MC dosimetry had a marginal effect because the SPECT spatial resolution is in the same order as the energy distribution caused by the electron track ranges. For 131I, full MC dosimetry made a difference due to the additional contribution from high-energy photons. SPECT-based DrVHs differ significantly from true DrVHs unless the tumours are considerable larger than the spatial resolution. Conclusion. It is important to understand limitations in quantitative SPECT images and the reasons for apparent heterogeneities since these have an impact on dose-volume histograms. A MC-based dosimetry calculation from SPECT images is not always warranted

Ljungberg, Michael; Sjoegreen-Gleisner, Katarina (Dept. of Medical Radiation Physics, Clinical Sciences, Lund Univ., Lund (Sweden)), e-mail: michael.ljungberg@med.lu.se

2011-08-15

197

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)

198

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

199

Absorbed dose determination in high energy photon beams using new IAEA TRS - 398 Code of Practice  

International Nuclear Information System (INIS)

The absorbed dose calibration of 6 and 10 MV X-ray beams from Varian Clinac 1800 at King Chulalongkorn Memorial Hospital Bangkok, Thailand were performed using cylindrical chamber 0.6 cc NE2571 Serial No. 1633 with graphite wall and Delrin build up cap and lonex Dosemaster NE 2590 Serial No. 223. The absorbed dose determination followed the IAEA code of practice TRS-277. The new IAEA code of practice TRS-398 have been studied to compare the result with the IAEA TRS-277

200

Absorbed-dose calibration of ionization chambers in a Co-60 gamma-ray beam  

Science.gov (United States)

Calibrations were provided for customer-owned ionization chambers so that they may be used to determine absorbed dose to water in Co-60 gamma-ray beams. The calibrations are based on calorimetric measurement of absorbed dose to graphite in a graphite phantom. Transformation of the calibrations to a water phantom is made with a specially-designed graphite ionization chamber, and requires knowledge of photon mass attenuation coefficients and the perturbation of the graphite chamber in the water medium. The determination of these quantities is described in detail, along with the operational techniques normally used to transfer the calibration to customer-owned chambers.

Pruitt, John S.

1990-10-01

 
 
 
 
201

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)

202

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

203

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

204

Absorbed dose profiles for radionuclides of frequent use in radiation synovectomy.  

Science.gov (United States)

Absorbed dose profiles are presented for radionuclides of frequent or potential use in radiation synovectomy, an intraarticular technique aimed at treating rheumatoid arthritis through direct and highly selective irradiation of inflamed synovium. The radionuclides investigated were 198Au, 165Dy, 32P, 186Re, 90Y, and 166Ho. These profiles reveal the absorbed dose imparted per unit activity of injected radionuclide (Gy/mCi) as a function of penetration distance (mm) to major components of the arthritic synovial joint. Their usefulness is twofold: they can be employed to select the radionuclide best suited to achieving the proper depth of penetration in tissue (approximating the thickness of the inflamed synovium) and to determine, a priori, the necessary dose of radioactivity (delivering an absorbed dose sufficient to effectively treat all the diseased tissue). The extent of radiation of other synovial joint components, such as bone and articular cartilage, and how the advancing rheumatoid arthritis can be expected to alter the extent and pattern of absorbed dose penetration in the joint are also discussed. PMID:1747137

Johnson, L S; Yanch, J C

1991-12-01

205

Absorbed doses of radiation after an intravenous injection of N-13 ammonia in man: concise communication  

International Nuclear Information System (INIS)

Using body distribution data with the MIRD tables and equations, the radiation dose delivered by an i.v. injection of N-13 ammonia has been calculated for several human organs. The liver and the urinary bladder wall receive 0.017 and 0.051 rad/mCi injected respectively; the latter can be reduced by early post-injection voiding. The brain-to-brain absorbed dose is 0.016 rad/mCi injected. The absorbed doses for the whole body, the red marrow, the ovaries, and the testes are, respectively, 0.0055, 0.0054, 0.0098, and 0.0010 rad/mCi injected. Severe liver disease is associated with a reduction in the fraction of the injected N-13 that is excreted in the urine, and thus causes a reduction in the absorbed dose to the urinary bladder wall from the bladder contents. Hepatomegaly increases the fraction of the N-13 ammonia trapped by the liver, and complicates calculation of the absorbed dose of radiation. These data should facilitate the evaluation of the risk from radiation absorption following i.v. injections of N-13 ammonia in humans

206

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)

207

Absorbed dose distribution at a large scale gamma irradiator - a data analysis  

International Nuclear Information System (INIS)

Laboratory experiments on the sand samples separated from sludge have been carried out to study their uncertainty associated with dose response and calibration. The uniformity of absorbed dose in a batch of sludge in a large-scale liquid sludge gamma irradiator has been examined by using sand samples separated from sludge as an in-situ dosimeter. Statistical analysis of the data, by applying ANOVA test, has been used to evaluate uniformity of dose. The re-circulation time for irradiation of sewage sludge to a dose of 3 kGy for its disinfection has been optimized using the data obtained. (author)

208

Computational Modeling of Cellular Effects Post-Irradiation with Low- and High-Let Particles and Different Absorbed Doses  

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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.

2012-01-01

209

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

210

Absorbed doses by the thyroid follicles due to the short half-lives isotope  

International Nuclear Information System (INIS)

The aim of this work is to evaluate the contributions of internally deposited short-lived iodines to the dose absorbed by thyroid's follicle, in the case of nuclear accidents . Dose calculation was carried out, at follicular level, for 131 I and short-lived iodines (132I, 133I, 134I and 135I), using the code MCNP4C. The thyroid's follicles were modeled as spheres, with different diameters (between 40 to 240 ?m), having the same density as for soft tissue (? = 1.04 g.cm-3). The results showed that the contribution of short-lived iodines for total dose is about 72%. The results reported in this work pointed out that, in case of nuclear accidents, the contributions of the short-lived iodines to the total dose absorbed by thyroid, at follicular level, cannot be neglected in a prospective evaluation of risks associated to internal contamination by radioactive iodine.(author)

211

Methods to verify absorbed dose of irradiated orange containers and evaluation of dosimeters  

International Nuclear Information System (INIS)

The research on dose distribution on irradiated food containers and evaluation of several methods to verify absorbed dose were carried out. The minimum absorbed dose of treated five orange containers was in the top of the highest or in the bottom of lowest container in a commercial 60Co facility. Dmax/Dmin in this study was 1.45. The density of orange containers was 0.391 g/cm3. The evaluation of dosimeters showed that the PMMA-YL and clear PMMA dosimeters have line relationship with dose response, and the word NOT in STERIN-125 and STERIN-300 indicators were covered completely at the dosage of 125 and 300 Gy, respectively

212

Monte Carlo simulation of conversion of absorbed dose in different medium for gamma-ray  

International Nuclear Information System (INIS)

The EGSnrc Monte Carlo Code was used to calculate the converting factor of absorbed dose to water to absorbed dose to silicon. The factor is useful in the study of irradiation effects in semiconductor devices. The irradiation source, water and silicon phantom were simulated by EGSnrc code. The electron equilibrium thickness were calculated for water and silicon irradiated by 60Co gamma-ray. The factor was calculated in two ways, one is average of energy fluence of photon, the other is ratio of dose. The results showed that the factor from tow ways agreed with the result from the national standard GB/T 15447-2008. This calculating methed can be used to determinate the dose conversion of two medium that they have very different atomic number. (authors)

213

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

Science.gov (United States)

Color centers formed by irradiation of optically clear crystals of pure LiF may be analyzed spectrophotometrically for dosimetry in the absorbed dose range from 10 2 to 10 7 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.

McLaughlin, William L.; Miller, Arne; Ellis, Stuart C.; Lucas, Arthur C.; Kapsar, Barbara M.

1980-09-01

214

27012 dosemeter metrological certifying in units of X-ray absorbed doses  

International Nuclear Information System (INIS)

For metrological certification of the 27012 clinical dosemeter methods are suggested for the exposure dose determination by absorbed doses in water in the 9-30 keV effective energy range. Ionizing chamber incorporated in a dosemeter is certified using a tissue-equivalent phantom. The confidence limit for the basic error of dosemeters certified according to these methods is not over than 8%, the confidence level being 0.95

215

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

216

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)

217

Measurement of absorbed dose in TMJ tomography utilizing rotational panoramic radiography  

International Nuclear Information System (INIS)

The absorbed doses in SCANORA were measured with thermoluminescence dosimeters (CaF2) at various determination sites and in the temporomandibular joint of a Rando female phantom. The pituitary gland, eye lenses, parotid glands, submandibular glands, sublingual glands, thyroid glands, chest (mammary glands), ovaries, testis and surface of the skin at the temporomandibular joint were the sites for the measurement. Measurement results of 4-3 SCANORA were 48276.3?Gy the highest, for the mandible joint skin side and next, 4176.0?Gy for the pituitary gland, 1900.8?Gy for the parotid gland and 560.3?Gy for the submandibular gland. Measurement results of 2-2 SCANORA were 82510.8?Gy the highest, for the mandible joint skin side and next, 9048.0?Gy for the pituitary gland, 3062.4?Gy for the parotid gland and 849.1?Gy for the submandibular gland. The absorbed doses of 2-2 SCANORA were higher than the absorbed doses of 4-3 SCANORA by 1.5-1.8 times at all sites. Absorbed doses when taking x-ray tomographs of the temporomandibular joint by SCANORA indicated a considerably high value compared with those by orthopantomography and simple radiography. (K.H.)

218

Monte Carlo simulation of trabecular bone remodeling and absorbed dose coefficients for tritium and 14C  

International Nuclear Information System (INIS)

A Monte Carlo simulation of multiple trabecular bone cavities in adult bone was developed and the absorbed radiation dose factors evaluated for 3H and 14C. The model was developed to assess the dose from radionuclide uptake in quiescent bone, but also the effects of temporal changes in bone turnover by incorporating bone-modelling units (BMU). Absorbed dose fractions were calculated for target regions that include the endosteal layer where radiation-sensitive stem cells in bone marrow are considered to reside preferentially. There were large differences in the absorbed fractions for two types of bone surface, quiescent and forming. Tritium in quiescent bone results in a dose to the endosteum about 20 times that for the same activity in forming bone surface irradiating osteoblasts. When the quiescent bone surface source was extended from an infinitely thin layer to a more realistic 1 mm thick, the tritium absorbed fractions for endosteum and red marrow targets fell by more than 2-fold. (authors)

219

Realization of the unit of absorbed dose of fast neutrons for tissue  

International Nuclear Information System (INIS)

The behaviour of spherical gas flow ionization chambers for neutron dosimetry in mixed neutron-gamma-fields with neutron energies of about 4 and 14 MeV is described. The determination of the absorbed dose and of various correction factors is discussed. The uncertainty of the measuring result is between 6 and 8% at an confidence level of 95%. (author)

220

Acquisition of quantitative biologic data in humans for radiation absorbed dose estimates  

International Nuclear Information System (INIS)

Guidelines are presented for the collection in humans of quantitative in vivo biokinetic data suitable for the estimation of radiation absorbed doses. Technique and instrumentation are discussed. Internal checks built into the procedures are described which assure accountability for 100 percent of the radioactivity

 
 
 
 
221

Isoeffective dose: a concept for biological weighting of absorbed dose in proton and heavier-ion therapies.  

Science.gov (United States)

When reporting radiation therapy procedures, International Commission on Radiation Units and Measurements (ICRU) recommends specifying absorbed dose at/in all clinically relevant points and/or volumes. In addition, treatment conditions should be reported as completely as possible in order to allow full understanding and interpretation of the treatment prescription. However, the clinical outcome does not only depend on absorbed dose but also on a number of other factors such as dose per fraction, overall treatment time and radiation quality radiation biology effectiveness (RBE). Therefore, weighting factors have to be applied when different types of treatments are to be compared or to be combined. This had led to the concept of 'isoeffective absorbed dose', introduced by ICRU and International Atomic Energy Agency (IAEA). The isoeffective dose D(IsoE) is the dose of a treatment carried out under reference conditions producing the same clinical effects on the target volume as those of the actual treatment. It is the product of the total absorbed dose (in gray) used and a weighting factor W(IsoE) (dimensionless): D(IsoE)=D×W(IsoE). In fractionated photon-beam therapy, the dose per fraction and the overall treatment time (in days) are the two main parameters that the radiation oncologist has the freedom to adjust. The weighting factor for an alteration of the dose per fraction is commonly evaluated using the linear-quadratic (?/?) model. For therapy with protons and heavier ions, radiation quality has to be taken into account. A 'generic proton RBE' of 1.1 for clinical applications is recommended in a joint ICRU-IAEA Report [ICRU (International Commission on Radiation Units and Measurements) and IAEA (International Atomic Energy Agency). Prescribing, recording and reporting proton-beam therapy. ICRU Report 78, jointly with the IAEA, JICRU, 7(2) Oxford University Press (2007)]. For heavier ions (e.g. carbon ions), the situation is more complex as the RBE values vary markedly with particle type, energy and depth in tissue. PMID:21138926

Wambersie, A; Menzel, H G; Andreo, P; DeLuca, P M; Gahbauer, R; Hendry, J H; Jones, D T L

2011-02-01

222

Determination of the absorbed radiation dose in urograms according to equipment technical characteristics and quality control results  

International Nuclear Information System (INIS)

The radiation dose absorbed by the patient on the skin during urograms was determined using thermoluminescent dosimeters (Ca SO4:Dy). The measure dose values were compared to the results of the radiological equipment quality control program. Consequently, an equation to calculate the absorbed dose was proposed as a function of the dose rate associated with the X-rays output (m C/kg.m As). This allows calculation of the absorbed dose in urograms in any radiological center provided that operational conditions are known through the quality control program and the applied technique is compared to the one used in this study. (author)

223

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)

224

Primordial radionuclides in soil and their contributions to absorbed dose rate in air  

International Nuclear Information System (INIS)

The predominant primordial radionuclides in soil which give rise to terrestrial radiation (external irradiation) were analyzed by gamma spectrometry. 40K has the highest average activity mass concentration, i.e. 212 Bq kg-1. 238U and 232Th concentrations are much lower and are only 14 and 16 Bq kg-1 respectively. Based on conversion factors given in the UNSCEAR Report (1988), the absorbed dose rates in air at one meter above the ground surface per unit activity mass concentration of primordial radionuclides were calculated. The average per caput absorbed dose rate in air received by Filipinos due to terrestrial radiation is 23 nGy h-1. The relative contribution of 232Th series to the total absorbed dose rate is highest, followed closely by 40K. The contribution of 238U series is only about one-half that of the 232Th series. Based on the results obtained, the terrestrial component of the average per caput exposure dose rate due to natural radiation sources is 2.64 ?R h-1 or roughly 3 ?R h-1. This leads to an annual average effective dose equivalent to 202 ?Sv. (Author). 5 annexes; 4 figs.; 3 tabs.; 6 refs

225

Electron paramagnetic resonance measurements of absorbed dose in teeth from citizens of Ozyorsk.  

Science.gov (United States)

In 1945, within the frame of the Uranium Project for the production of nuclear weapons, the Mayak nuclear facilities were constructed at the Lake Irtyash in the Southern Urals, Russia. The nuclear workers of the Mayak Production Association (MPA), who lived in the city of Ozyorsk, are the focus of epidemiological studies for the assessment of health risks due to protracted exposure to ionising radiation. Electron paramagnetic resonance measurements of absorbed dose in tooth enamel have already been used in the past, in an effort to validate occupational external doses that were evaluated in the Mayak Worker Dosimetry System. In the present study, 229 teeth of Ozyorsk citizens not employed at MPA were investigated for the assessment of external background exposure in Ozyorsk. The annually absorbed dose in tooth enamel from natural background radiation was estimated to be (0.7 ± 0.3) mGy. For citizens living in Ozyorsk during the time of routine noble gas releases of the MPA, which peaked in 1953, the average excess absorbed dose in enamel above natural background was (36 ± 29) mGy, which is consistent with the gamma dose obtained by model calculations. In addition, there were indications of possible accidental gaseous MPA releases that affected the population of Ozyorsk, during the early and late MPA operation periods, before 1951 and after 1960. PMID:24604722

Wieser, A; Vasilenko, E; Aladova, E; Fattibene, P; Semiochkina, N; Smetanin, M

2014-05-01

226

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)

227

Absorbed gamma and electron radiation dose with the ferrous sulfate-cupric sulfate dosimeter  

International Nuclear Information System (INIS)

Ferrous-cupric sulfate dosimetry is used for accurate measurement of the absorbed dose in water irradiated with x- or gamma-rays or high-energy electrons. It is based on the process of oxidation of ferrous to ferric ions by ionizing radiation. The method is most accurate for absorbed doses in the range from 2 x 105 to 8 x 105 rads, using spectrophotometric measurement of the ferric ion concentration. It can be used to measure doses as low as 6 x 104 rads with decreased accuracy. The method covers preparation and use of the dosimeter and includes a discussion of interferences, apparatus, reagents, calibration and standardization procedure, dosimetry procedure, calculation, precision, and accuracy

228

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)

229

Uneven surface absorbed dose distribution in electron-accelerator irradiation of rubber items  

International Nuclear Information System (INIS)

Electron accelerators for industrial use are equipped with scanning devices, where the scan frequency or linear velocity along the window may vary. In a flow technology, where the items are transported to the irradiation zone at a set rate, the speed of an item may be comparable with the scan speed, so there is substantial nonuniformity in the absorbed dose, which adversely affects the quality. We have examined the dose nonuniformity for long rubber items during vulcanization by means of LUE-8-5RV and ELV-2 accelerators. The absorbed dose is calculated for an elementary part along which the irradiation is uniform on the assumption that current density distribution in the unswept beam is uniform as a result of scattering in the foil

230

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

231

Measurement of absorbed radiation doses during whole body irradiation for bone marrow transplants using thermoluminescent dosimeters  

International Nuclear Information System (INIS)

The objective was to evaluate the precision of the absorbed radiation doses in bone marrow transplant therapy during whole body irradiation. Two-hundred CaSO4:Dy + teflon tablets were calibrated in air and in 'phantom'. These tablets were randomly selected and divided in groups of five in the patients' body. The dosimetric readings were obtained using a Harshaw 4000A reader. Nine patients had their entire bodies irradiated in parallel and opposite laterals in a cobalt-60 Alcion II model, with a dose rate of 0.80 Gy/min at 80.5 cm, {(10 ? 10) cm2 field. The dosimetry of this unit was performed using a Victoreen 500 dosimeter. For the determination of the mean dose at each point evaluated, the individual values of the tablets calibrated in air or 'phantom' were used, resulting in a build up of 2 mm to superficialize the dose at a distance of 300 cm. In 70% of the patients a variation of less than 5% in the dose was obtained. In 30% of the patients this variation was less than 10%, when values obtained were compared to the values calculated at each point. A mean absorption of 14% was seen in the head, and an increase of 2% of the administered dose was seen in the lungs. In patients with latero-lateral distance greater than 35 cm the variation between the calculated doses and the measured doses reached 30% of the desired dose, without the use of compensation filters. The measured values of the absorbed doses at the various anatomic points compared toat the various anatomic points compared to the desired doses (theoretic) presented a tolerance of ± 10%, considering the existent anatomical differences and when using the individual calibration factors of the tablets. (author)

232

Radiation absorbed dose to the bladder from 2-FDG and other radiopharmaceuticals  

International Nuclear Information System (INIS)

The radiation absorbed dose to the bladder, especially for rapidly excreted materials such as 2-fluorodeoxyglucose (2-FDG) and Tc-99m DTPA, depends on the concentration of activity in the urine so that the dilution of the excreted activity by urine already in the bladder becomes a critical factor. The current MIRD calculation takes no cognizance of this since it assumes a constant 200 ml bladder volume. The published Monte Carlo calculations of dose from penetrating radiation for varying bladder volumes in an ellipsoidal bladder, differ little except at small volumes, from simpler classical dose calculations assuming a spherical model. The actual shape of the bladder, however, differs radically from either model at small volumes. The radiation absorbed dose rate from nonpenetrating radiation, more or less independent of bladder shape, is proportional to the concentration of activity, and contributes, in the case of beta emitters, the major fraction of the radiation dose. In the present study, the published urinary excretion of 2-FDG was used to calculate the bladder concentration of activity at various urine production rates, residual fractions, and initial bladder volumes. The dose rates from penetrating and nonpenetrating radiation to the surface of the bladder mucosa were calculated using the spherical model. The estimated dose starting with an nearly empty bladder, ?1 rad/mCi injected, was 3 to 4 times greater than when starting with a volume of 300 to 400 ml. The optimal strategy for minimizing the absorbed dose requires a large initial bladder volume and high urine production rate. For 2-FDG, the optimal first void time was found to be at about 1 hr after injection with a urine production rate of 75 ml/hr and 400 cc initial volume, giving about 250 mrad/mCi

233

Absorbed dose evaluation of thyroid during nasopharynx and breast carcinoma irradiation by in vivo dosimetry  

International Nuclear Information System (INIS)

Aims. - The thyroid dysfunction after radiotherapy has led to evaluate the dose received by thyroid during nasopharynx and breast carcinoma irradiation. This evaluation was facilitated by in vivo dosimetry. The aims of this work were to evaluate the thyroid dose and to compare released dose at the reference point in the two localizations. Patients and methods. - A total of 30 patients were evaluated: 18 patients with nasopharynx carcinoma and 12 patients with breast carcinoma were included in the final analysis. In the first group, the total thyroid but the isthmus was irradiated. On the other hand, in the second group, only one thyroid lobe was included into the target volume. All patients have been treated by gamma rays of cobalt 60 and the thyroid absorbed dose was measured by semiconductor dosimeters (Scanditronix DPD6). These dosimeters were calibrated in the same geometric conditions of the irradiation. Results. - The measured absorbed dose of the thyroid parenchyma was equal to the calculated absorbed dose at the target that has being specified at a depth of -3 em. Under the block, the isthmus received 5.1 ± 0.9 Gy (9.9 ± 1.8%) in nasopharynx carcinoma irradiation. However, in breast carcinoma irradiation, the distal thyroid lobe and the isthmus received 2.9 ± 0.7 Gy (6.55 ± 1.56%) and 3.69 ± 0.77 (8.39 ± 1.76%),i respectively. Conclusion. - This study shows that the thyroid received a dose equal to the prescribed dose in both nasopharynx and breast cancein both nasopharynx and breast cancer, patients. It is recommended to. follow the function of the thyroid gland in these patients. (authors)

234

Absorbed doses for internal radiotherapy from 22 beta-emitting radionuclides: beta dosimetry of small spheres.  

Science.gov (United States)

We calculated the mean absorbed fractions, specific absorbed fractions and mean doses per unit of cumulated activity in source spheres 10 microm-2 cm in radius for 22 beta-emitting radionuclides potentially useful in radioimmunotherapy. We considered two models of radionuclide distribution, either uniform at the surface of the source or throughout its volume. For each model, we calculated both the absorbed fractions in the spherical segments composing the source and the mean absorbed fractions. For surface distribution, we calculated the mean dose per unit of cumulated activity for a concentric sphere with a small radius (5 microm) in order to determine the minimal dose delivered to the target. Calculations were performed using point kernels for monoenergetic emissions and then integrated into the beta spectra of the different emitters (32p, 33p, 47Sc, 67Cu, 77As, 90Y, 105Rh, 109Pd, 111Ag, 121Sn, 131I, 142Pr, 143Pr, 149Pm, 153Sm, 159Gd, 166Ho, 177Lu, 186Re, 188Re, 194Ir and 199Au). Monoenergetic emissions were taken into account. Results are reported in the form of tables to facilitate use during dosimetric studies for radioimmunotherapy. An application is presented showing the potential utility of associating emitters with different energies in order to sterilize a range of tumour targets of variable size. PMID:15551573

Bardiès, M; Chatal, J F

1994-06-01

235

Absorbed doses for internal radiotherapy from 22 beta-emitting radionuclides: beta dosimetry of small spheres  

International Nuclear Information System (INIS)

We calculated the mean absorbed fractions, specific absorbed fractions and mean doses per unit of cumulated activity in source spheres 10 ?m-2 cm in radius for 22 beta-emitting radionuclides potentially useful in radioimmunotherapy. We considered two models of radionuclide distribution, either uniform at the surface of the source or throughout its volume. For each model, we calculated both the absorbed fractions in the spherical segments composing the source and the mean absorbed fractions. For surface distribution, we calculated the mean dose per unit of cumulated activity for a concentric sphere with a small radius (5 ?m) in order to determine the minimal dose delivered to the target. Calculations were performed using point kernels for monoenergetic emissions and then integrated into the beta spectra of the different emitters (32P, 33P, 47Sc, 67Cu, 77As, 90Y, 105Rh, 109Pd, 111Ag, 121Sn, 131I, 142Pr, 143Pr, 149Pm, 153Sm, 159Gd, 166Ho, 177Lu, 186Re, 188Re, 194Ir and 199Au). Monoenergetic emissions were taken into account. (author)

236

Graves' disease radioiodine-therapy: Choosing target absorbed doses for therapy planning  

Energy Technology Data Exchange (ETDEWEB)

Purpose: The precise determination of organ mass (m{sub th}) and total number of disintegrations within the thyroid gland (A{sup ~}) are essential for thyroid absorbed-dose calculations for radioiodine therapy. Nevertheless, these parameters may vary according to the method employed for their estimation, thus introducing uncertainty in the estimated thyroid absorbed dose and in any dose–response relationship derived using such estimates. In consideration of these points, thyroid absorbed doses for Graves’ disease (GD) treatment planning were calculated using different approaches to estimating the m{sub th} and the A{sup ~}. Methods: Fifty patients were included in the study. Thyroid{sup 131}I uptake measurements were performed at 2, 6, 24, 48, 96, and 220 h postadministration of a tracer activity in order to estimate the effective half-time (T{sub eff}) of {sup 131}I in the thyroid; the thyroid cumulated activity was then estimated using the T{sub eff} thus determined or, alternatively, calculated by numeric integration of the measured time-activity data. Thyroid mass was estimated by ultrasonography (USG) and scintigraphy (SCTG). Absorbed doses were calculated with the OLINDA/EXM software. The relationships between thyroid absorbed dose and therapy response were evaluated at 3 months and 1 year after therapy. Results: The average ratio (±1 standard deviation) betweenm{sub th} estimated by SCTG and USG was 1.74 (±0.64) and that between A{sup ~} obtained by T{sub eff} and the integration of measured activity in the gland was 1.71 (±0.14). These differences affect the calculated absorbed dose. Overall, therapeutic success, corresponding to induction of durable hypothyroidism or euthyroidism, was achieved in 72% of all patients at 3 months and in 90% at 1 year. A therapeutic success rate of at least 95% was found in the group of patients receiving doses of 200 Gy (p = 0.0483) and 330?Gy (p = 0.0131) when m{sub th} was measured by either USG or SCTG and A{sup ~} was determined by the integration of measured {sup 131}I activity in the thyroid gland and based on T{sub eff}, respectively. No statistically significant relationship was found between therapeutic response and patients’ age, administered {sup 131}I activity (MBq), 24-h thyroid {sup 131}I uptake (%) or T{sub eff} (p ? 0.064); nonetheless, a good relationship was found between the therapeutic response and m{sub th} (p ? 0.035). Conclusions: According to the results of this study, the most effective thyroid absorbed dose to be targeted in GD therapy should not be based on a fixed dose but rather should be individualized based on the patient'sm{sub th} and A{sup ~}. To achieve a therapeutic success (i.e., durable euthyroidism or hypothyroidism) rate of at least 95%, a thyroid absorbed dose of 200 or 330?Gy is required depending on the methodology used for estimating m{sub th} and A{sup ~}.

Willegaignon, J., E-mail: j.willegaignon@gmail.com; Sapienza, M. T.; Coura-Filho, G. B.; Buchpiguel, C. A. [Cancer Institute of São Paulo State (ICESP), Clinical Hospital, School of Medicine, University of São Paulo, São Paulo 01246-000 (Brazil); Nuclear Medicine Service, Department of Radiology, School of Medicine, University of São Paulo, Sao Paulo 01246-000 (Brazil); Watanabe, T. [Nuclear Medicine Service, Department of Radiology, School of Medicine, University of São Paulo, São Paulo 01246-000 (Brazil); Traino, A. C. [Unit of Medical Physics, Azienda Ospedaliero-Universitaria Pisana, Pisa 56126 (Italy)

2014-01-15

237

X-ray absorbed doses evaluation on patients under radiological studies; Avaliacao das doses de radiacao X recebidas por pacientes em estudos radiologicos  

Energy Technology Data Exchange (ETDEWEB)

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

Medeiros, Regina Bitelli; Daros, Kellen A.C. [Universidade Federal de Sao Paulo, SP (Brazil). Escola Paulista de Medicina. Dept. de Diagnostico por Imagem

1996-12-31

238

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

239

The accuracy of absorbed dose estimates in tumours determined by Quantitative SPECT: A Monte Carlo study  

International Nuclear Information System (INIS)

Background. Dosimetry in radionuclide therapy estimates delivered absorbed doses to tumours and ensures that absorbed dose levels to normal organs are below tolerance levels. One procedure is to determine time-activity curves in volumes-of-interests from which the absorbed dose is estimated using SPECT with appropriate corrections for attenuation, scatter and collimator response. From corrected SPECT images the absorbed energy can be calculated by (a) assuming kinetic energy deposited in the same voxel where particles were emitted, (b) convolve with point-dose kernels or (c) use full Monte Carlo (MC) methods. A question arises which dosimetry method is optimal given the limitations in reconstruction- and quantification procedures. Methods. Dosimetry methods (a) and (c) were evaluated by comparing dose-rate volume histograms (DrVHs) from simulated SPECT of 111In, 177Lu, 131I and Bremsstrahlung from 90Y to match true dose rate images. The study used a voxel-based phantom with different tumours in the liver. SPECT reconstruction was made using an iterative OSEM method and MC dosimetry was performed using a charged-particle EGS4 program that also was used to determined true absorbed dose rate distributions for the same phantom geometry but without camera limitations. Results. The DrVHs obtained from SPECT differed from true DrVH mainly due to limited spatial resolution. MC dosimetry had a marginal effect because the SPECT spatiaa marginal effect because the SPECT spatial resolution is in the same order as the energy distribution caused by the electron track ranges. For 131I, full MC dosimetry made a difference due to the additional contribution from high-energy photons. SPECT-based DrVHs differ significantly from true DrVHs unless the tumours are considerable larger than the spatial resolution. Conclusion. It is important to understand limitations in quantitative SPECT images and the reasons for apparent heterogeneities since these have an impact on dose-volume histograms. A MC-based dosimetry calculation from SPECT images is not always warranted

240

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

Energy Technology Data Exchange (ETDEWEB)

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 dose and cost motive to conventional CT, promising to revolutionize the practice of oral and maxillofacial radiology.

Kim, Sang Yeon; Han, Jin Woo; Park, In Woo [Department of Oral and Maxillofacial Radiology, College of Dentistry, Kangnung National University and Reseach Institute of Oral Science, Gangneung (Korea, Republic of)

2008-03-15

 
 
 
 
241

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.

242

Intercomparison programme of absorbed dose measurement for 60Co teletherapy units in Turkey  

International Nuclear Information System (INIS)

During the period 1989-1992, three TLD postal dose intercomparisons were performed on a number of 60Co teletherapy units in Turkey. The method followed was based on the original IAEA/WHO programme using mailed LiF powder TLDs. The participants were asked to expose capsules filled with LiF to an absorbed dose of 2.0. Gy at a depth of 5 cm in water. The irradiated capsules were measured and evaluated by the Secondary Standard Dosimetry Laboratory (SSDL) at the Cekmece Nuclear Research and Training Centre. The first intercomparison was executed in 1989 as a pilot study involving 12 radiotherapy centres. This intercomparison showed that 9 radiotherapy centres had deviations of less than ±5% in the absorbed dose. Three institutions applied an absorbed dose with deviations exceeding the ±5% limit. The results were also compared with those from the ionometric method. The second and third intercomparisons were performed in 1991 and 1992, respectively, and 17 institutions participated in each comparison. The second intercomparison gave deviations varying between -16.0% and +0.8%, with 14 institutions having deviations within ±5%. The third intercomparison showed deviations exceeding ±5% for six 60Co units. Evaluation of the data sheets demonstrated that some of these units were not controlled by qualified hospital physicists. The studies conducted during the period 1989-1992 show the necessity of an intercomparison programme to provide an accuracy of n programme to provide an accuracy of better than ±5% in radiotherapy. Thus the intercomparison programmes performed by the SSDL have helped to evaluate the accuracy of the clinical delivery of absorbed dose. (author). 5 refs, 4 tabs

243

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

244

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.

245

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 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

246

Evaluation and comparison of absorbed dose for electron beams by LiF and diamond dosimeters  

International Nuclear Information System (INIS)

The absorbed dose response of LiF and diamond thermoluminescent dosimeters (TLDs), calibrated in 60Co ?-rays, has been determined using the MCNP4B Monte Carlo code system in mono-energetic megavoltage electron beams from 5 to 20 MeV. Evaluation of the dose responses was done against the dose responses of published works by other investigators. Dose responses of both dosimeters were compared to establish if any relation exists between them. The dosimeters were irradiated in a water phantom with the centre of their top surfaces (0.32x0.32 cm2), placed at dmax perpendicular to the radiation beam on the central axis. For LiF TLD, dose responses ranged from 0.945±0.017 to 0.997±0.011. For the diamond TLD, the dose response ranged from 0.940±0.017 to 1.018±0.011. To correct for dose responses by both dosimeters, energy correction factors were generated from dose response results of both TLDs. For LiF TLD, these correction factors ranged from 1.003 up to 1.058 and for diamond TLD the factors ranged from 0.982 up to 1.064. The results show that diamond TLDs can be used in the place of the well-established LiF TLDs and that Monte Carlo code systems can be used in dose determinations for radiotherapy treatment planning

247

Evaluation and comparison of absorbed dose for electron beams by LiF and diamond dosimeters  

Energy Technology Data Exchange (ETDEWEB)

The absorbed dose response of LiF and diamond thermoluminescent dosimeters (TLDs), calibrated in {sup 60}Co {gamma}-rays, has been determined using the MCNP4B Monte Carlo code system in mono-energetic megavoltage electron beams from 5 to 20 MeV. Evaluation of the dose responses was done against the dose responses of published works by other investigators. Dose responses of both dosimeters were compared to establish if any relation exists between them. The dosimeters were irradiated in a water phantom with the centre of their top surfaces (0.32x0.32 cm{sup 2}), placed at d{sub max} perpendicular to the radiation beam on the central axis. For LiF TLD, dose responses ranged from 0.945{+-}0.017 to 0.997{+-}0.011. For the diamond TLD, the dose response ranged from 0.940{+-}0.017 to 1.018{+-}0.011. To correct for dose responses by both dosimeters, energy correction factors were generated from dose response results of both TLDs. For LiF TLD, these correction factors ranged from 1.003 up to 1.058 and for diamond TLD the factors ranged from 0.982 up to 1.064. The results show that diamond TLDs can be used in the place of the well-established LiF TLDs and that Monte Carlo code systems can be used in dose determinations for radiotherapy treatment planning.

Mosia, G.J. [University of Limpopo, Medunsa Campus, Department of Medical Physics, PO MEDUNSA 0204 (South Africa)], E-mail: gmosia@ul.ac.za; Chamberlain, A.C. [University of Limpopo, Medunsa Campus, Department of Medical Physics, PO MEDUNSA 0204 (South Africa)

2007-09-21

248

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 diameteral 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

249

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)

250

The influence of the patient's posture on organ and tissue absorbed doses caused by radiodiagnostic examinations  

International Nuclear Information System (INIS)

Due to the gravitational force, organ positions and subcutaneous fat distribution change when a standing person lies down on her/his back, which is called 'supine posture'. Both postures, standing and supine, are very common in X-ray diagnosis, however, phantoms used for the simulation of patients for organ and tissue absorbed dose assessments normally represent humans either in standing or in supine posture. Consequently, the exposure scenario simulated sometimes does not match the real X-ray examination with respect to the patient's posture. Using standing and supine versions of mesh-based female and male adult phantoms, this study investigates the 'posture-effect' on organ and tissue absorbed doses for radiographs of the pelvis and the lumbar spine in order to find out if the errors from simulating the false posture are significant. (author)

251

Implementation of absorbed dose standardization at therapy-level in Brazil  

International Nuclear Information System (INIS)

At the present moment, IAEA presented the final document of the 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 Nuclear and Energy Research Institute (IPEN/CNEN/SP) and at National Laboratory for Metrology of Ionizing Radiation (IRD/CNEN/RJ), where the possibility of having an 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)

252

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

253

Energy backscattering of electron beams and absorbed dose in thin layer  

International Nuclear Information System (INIS)

Recent research development in this laboratory concerning radiation effects on the thin layer specimens of organic polymers and p-n junction of semiconductors requires the accurate evaluation of backscattered energy which is especially important for low energy electrons below 1.0 MeV and gives rise to errors of up to some 60 % depending on the materials of backing substrates. The present report describes the past studies on backscattering phenomena on backing substances of various elements and summarizes the experimental results of the measurements of the dose rate absorbed by the thin layer substance on backing substances of various elements as numerical tables which allow convenient determination of dose absorbed by the thin layer specimens on the backing substances. (author)

254

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

255

Determination of absorbed dose in electron beams using parallel-plane ionization chambers  

International Nuclear Information System (INIS)

Objective: The objective of this paper was to establish a procedure for the determination of calibration factors and absorbed doses in electron beams. Materials And Methods: An irradiator with a 60 Co source and a linear accelerator Varian, Clinac 2100C, with photon and electron beams, were utilized. Thimble type and parallel-plane ionization chambers were tested. Results: The measurement systems showed very good results in the preliminary tests (response stability and leakage current). The ionization chambers used for electron beam dosimetry were calibrated using four different methods. For the determination of absorbed dose, three methodologies recommended by the International Atomic Energy Agency were applied. Concordant results were obtained in almost all cases. Conclusion: The majority of the ionization chambers tested showed good results according to the established international limits. (author)

256

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

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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

257

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

258

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

259

Absorbed Dose and Collision Kerma Relationship for High-Energy Photons  

Science.gov (United States)

Historically, exposure has been used as an important quantity to specify X- or (gamma)- ray beams. For any photon beam the energy fluence is proportional to the exposure. Exposure can be calculated and/or measured if the spectrum of the beam is known and charged particle equilibrium (CPE) exists. For low energy photons (up to approximately 1 MeV), due to the existence of CPE, absorbed dose (D) is equal to the collision kerma (K(,c)). For megavoltage photons this equality is lost due to CPE failure, which also restricts the measurement of exposure. It is possible, though, to find a relationship between the absorbed dose and collision kerma when transient charged particle equilibrium (TCPE) exists. This basic idea was originally proposed by Roesch in 1958 and its refinement has been discussed by Attix in 1979 and 1983. The modified Roesch's formula which enables us to measure exposure even for high-energy photons is given by D = (beta) K(,c) (TURNEQ) K(,c) (1 + (mu)' ) where (mu)' is the effective linear attenuation coefficient and is the mean distance the secondary electrons carry kinetic energy in the direction of the photon beam while depositing it as absorbed dose. The symbol (beta) is the quotient of the absorbed dose and the collision kerma. The importance of Roesch's formula has been recognized and used implicitly in the recent dosimetry protocol of the AAPM (Task Group 21). However, the value used in the protocol is based on theoretical calculations which do not include photon scattering. As a result of the present effort the parameters (mu)' and have been determined experimentally, for the first time. The dependence of (beta) on several factors has been studied and (beta) has been obtained including the effects of scattering. Calculations were also performed for several photon energies and materials, using the Roesch method, which does not include photon scattering effects. Comparisons of measured and calculated values of show reasonable agreement.

Sibata, Claudio Hissao

260

Absorbed dose determination in water in medium energy x-ray beam  

International Nuclear Information System (INIS)

Absorbed dose determination in water phantom in medium energy X-ray beam, according to IAEA recommendations is given. This method is applied on Radiotherapy department of Military Academy Hospital in Belgrade. Reference points of measurements are on depth of 5 cm and 2 cm as it recommended in ref. Experimental results are shown in aim to introduce new dosimetric concept based on air kerma calibration factor recommended for application in our radiotherapy centers (author)

 
 
 
 
261

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Kneževi? Ivan D.; Zdjelarevi? Nevena S.; Obrenovi? Marija D.; Vujisi? Miloš Lj.

2012-01-01

262

Absorbed doses and energy imparted from radiographic examination of velopharyngeal function during speech  

International Nuclear Information System (INIS)

Absorbed doses of radiation were measured by thermoluminescent dosimeters (TLDs) using a skull phantom during simulated cinefluorographic and videofluorographic examination of velopharyngeal function in frontal and lateral projections. Dosages to the thyroid gland, the parotid gland, the pituitary gland, and ocular lens were measured. Radiation dosage was found to be approximately 10 times less for videofluoroscopy when compared with that of cinefluoroscopy. In addition, precautionary measures were found to reduce further the exposure of radiation-sensitive tissues. Head fixation and shielding resulted in dose reduction for both video- and cinefluoroscopy. Pulsing exposure for cinefluoroscopy also reduced the dosage

263

Calculation of absorbed doses in sphere volumes around the Mammosite using the Monte Carlo simulation code MCNPX  

International Nuclear Information System (INIS)

The objective of this study is to investigate the changes observed in the absorbed doses in mammary gland tissue when irradiated with a equipment of high dose rate known as Mammosite and introducing material resources contrary to the tissue that constitutes the mammary gland. The modeling study is performed with the code MCNPX, 2005 version, the equipment and the mammary gland and calculating the absorbed doses in tissue when introduced small volumes of air or calcium in the system. (Author)

264

Method for Fast CT/SPECT-Based 3D Monte Carlo Absorbed Dose Computations in Internal Emitter Therapy  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The DPM (Dose Planning Method) Monte Carlo electron and photon transport program, designed for fast computation of radiation absorbed dose in external beam radiotherapy, has been adapted to the calculation of absorbed dose in patient-specific internal emitter therapy. Because both its photon and electron transport mechanics algorithms have been optimized for fast computation in 3D voxelized geometries (in particular, those derived from CT scans), DPM is perfectly suited for performing patient...

Wilderman, S. J.; Dewaraja, Y. K.

2007-01-01

265

Absorbed Dose Calculations Using Mesh-based Human Phantoms And Monte Carlo Methods  

Science.gov (United States)

Health risks attributable to the exposure to ionizing radiation are considered to be a function of the absorbed or equivalent dose to radiosensitive organs and tissues. However, as human tissue cannot express itself in terms of equivalent dose, exposure models have to be used to determine the distribution of equivalent dose throughout the human body. An exposure model, be it physical or computational, consists of a representation of the human body, called phantom, plus a method for transporting ionizing radiation through the phantom and measuring or calculating the equivalent dose to organ and tissues of interest. The FASH2 (Female Adult meSH) and the MASH2 (Male Adult meSH) computational phantoms have been developed at the University of Pernambuco in Recife/Brazil based on polygon mesh surfaces using open source software tools and anatomical atlases. Representing standing adults, FASH2 and MASH2 have organ and tissue masses, body height and body mass adjusted to the anatomical data published by the International Commission on Radiological Protection for the reference male and female adult. For the purposes of absorbed dose calculations the phantoms have been coupled to the EGSnrc Monte Carlo code, which can transport photons, electrons and positrons through arbitrary media. This paper reviews the development of the FASH2 and the MASH2 phantoms and presents dosimetric applications for X-ray diagnosis and for prostate brachytherapy.

Kramer, Richard

2011-08-01

266

Quantification of micronuclei in blood lymphocytes of patients exposed to gamma radiation for dose absorbed assessment  

International Nuclear Information System (INIS)

Dose assessment in an important step to evaluate biological effects as a result of individual exposure to ionizing radiation. The use of cytogenetic dosimetry based on the quantification of micronuclei in lymphocytes is very important to complement physical dosimetry, since the measurement of absorbed dose cannot be always performed. In this research, the quantification of micronuclei was carried out in order to evaluate absorbed dose as a result of radiotherapy with 60Co, using peripheral blood samples from 5 patients with cervical uterine cancer. For this purpose, an aliquot of whole blood from the individual patients was added in culture medium RPMI 1640 supplemented with fetal calf serum and phytohaemagglutinin. The culture was incubated for 44 hours. Henceforth, cytochalasin B was added to block the dividing lymphocytes in cytokinesis. The culture was returned to the incubator for further of 28 hours. Thus, cells were harvested, processed and analyzed. Values obtained considering micronuclei frequency after pelvis irradiation with absorption of 0,08 Gy and 1,8 Gy were, respectively, 0,0021 and 0,052. These results are in agreement with some recent researches that provided some standard values related to micronuclei frequency induced by gamma radiation exposure in different exposed areas for the human body. The results presented in this report emphasizes biological dosimetry as an important tool for dose assessment of either total or partial-body exposure to ionizing radiation, mainly in retrospective dose investigation. (author)

267

Investigation of magnevist pharmacokinetics for calculation of absorbed dose at neutron-capture therapy  

International Nuclear Information System (INIS)

Full text: The neutron-capture therapy with use of gadolinium-containing pharmacological preparations is one of perspective and not enough investigated directions of application of neutron irradiation in medicine. At definition of the absorbed dose of neutron-capture therapy one of important questions is definition of concentration gadolinium and pharmacokinetics in irradiated tumour. In the given study has been investigated pharmacokinetics of gadolinium-containing preparation 'Magnevist' at intratumoral injection in inoculated tumours of sarcoma C180 at mice. For 'Magnevist' detection its property of radioopacity has been used. In experiments to mice with inoculated tumours C180 the various doses of 'Magnevist' (0.1, 0.2, 0.3 and 0.4 ml) were injected into tumour centre. X-ray images were made before 'Magnevist' injection (control) and after preparation injection every 5 minutes within one hour. It has been shown that at dose 0.1 ml 'Magnevist' eliminated from tumour within 10 minutes. At higher doses of preparation more slow elimination of 'Magnevist' from injection site was observed. Obtained results allow with sufficient accuracy to calculate the time of presence of optimum concentration of 'Magnevist' in tumour at intratumoral injection. It in turn gives the chance to calculate precisely the absorbed dose at irradiation by beam of epi-thermal neutrons. (author)

268

Determination of Absorbed and Annual Effective Doses around Birnin Gwari Artisanal Goldmine, Kaduna State, Nigeria  

Directory of Open Access Journals (Sweden)

Full Text Available This study presents result of outdoor absorbed dose rate and estimated annual effective dose rate from the naturally occurring radionuclides 238U, 232Th and 40K around BirninGwari artisanal goldmine using Instrumental Neutron Activation Analysis (INAA. The results showed that the mean absorbed dose rate is 96.52 nGy/h with a standard deviation of 33.3 nGy/h and the standard error of 9.62 nGy/h the range falls between 26.67-123.85 nGy/h. The mean effective dose rate was estimated to be 0.675 mSv/year with a standard deviation of 0.234 mSv and standard error of 0.068 mSv and in range between 0.183-0.867 mSv. The mean annual effective dose rate from this work is lower than the 1mSv/year recommended by ICRP for public radiation exposure control.

Y.I. Zakari

2013-05-01

269

Development of fluorescent, oscillometric and photometric methods to determine absorbed dose in irradiated fruits and nuts  

International Nuclear Information System (INIS)

To ensure suitable quality control at food irradiation technologies and for quarantine authorities, simple routine dosimetry methods are needed for absorbed dose control. Taking into account the requirements at quarantine locations these methods would require nondestructive analysis for repeated measurements. Different dosimetry systems with different analytical evaluation methods have been tested and/or developed for absorbed dose measurements in the dose range of 0.1-10 kGy. In order to use the well accepted ethanolmonochlorobenzene dosimeter solution and the recently developed aqueous alanine solution in small volume sealed vials, a new portable, digital, and programmable oscillometric reader was developed. To make use of the availability of the very sensitive fluorimetric evaluation method, liquid and solid inorganic and organic dosimetry systems were developed for dose control using a new routine, portable, and computer controlled fluorimeter. Absorption or transmission photometric methods were also applied for dose measurements of solid or liquid phase dosimeter systems containing radiochromic dye agents, which change colour upon irradiation. (author)

270

Regression models in the determination of the absorbed dose with extrapolation chamber for ophthalmological applicators  

International Nuclear Information System (INIS)

The absorbed dose for equivalent soft tissue is determined,it is imparted by ophthalmologic applicators, (90 Sr/90 Y, 1850 MBq) using an extrapolation chamber of variable electrodes; when estimating the slope of the extrapolation curve using a simple lineal regression model is observed that the dose values are underestimated from 17.7 percent up to a 20.4 percent in relation to the estimate of this dose by means of a regression model polynomial two grade, at the same time are observed an improvement in the standard error for the quadratic model until in 50%. Finally the global uncertainty of the dose is presented, taking into account the reproducibility of the experimental arrangement. As conclusion it can infers that in experimental arrangements where the source is to contact with the extrapolation chamber, it was recommended to substitute the lineal regression model by the quadratic regression model, in the determination of the slope of the extrapolation curve, for more exact and accurate measurements of the absorbed dose. (Author)

271

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 been minimized by achieving true quasi-adiabatic operation. 16 refs., 9 tabs., 11 figs

272

Utilization of radiation protection gear for absorbed dose reduction: an integrative literature review  

International Nuclear Information System (INIS)

Objective: The present study was aimed at evaluating the relation between the use of radiation protection gear and the decrease in absorbed dose of ionizing radiation, thereby reinforcing the efficacy of its use by both the patients and occupationally exposed personnel. Materials and Methods: The integrative literature review method was utilized to analyze 21 articles, 2 books, 1 thesis, 1 monograph, 1 computer program, 4 pieces of database research (Instituto Brasileiro de Geografia e Estatistica and Departamento de Informatica do Sistema Unico de Saude) and 2 sets of radiological protection guidelines. Results: Theoretically, a reduction of 86% to 99% in the absorbed dose is observed with the use of radiation protection gear. In practice, however, the reduction may achieve 88% in patients submitted to conventional radiology, and 95% in patients submitted to computed tomography. In occupationally exposed individuals, the reduction is around 90% during cardiac catheterization, and 75% during orthopedic surgery. Conclusion: According to findings of several previous pieces of research, the use of radiation protection gear is a low-cost and effective way to reduce absorbed dose both for patients and occupationally exposed individuals. Thus, its use is necessary for the implementation of effective radioprotection programs in radiodiagnosis centers. (author)

273

Utilization of radiation protection gear for absorbed dose reduction: an integrative literature review  

Energy Technology Data Exchange (ETDEWEB)

Objective: The present study was aimed at evaluating the relation between the use of radiation protection gear and the decrease in absorbed dose of ionizing radiation, thereby reinforcing the efficacy of its use by both the patients and occupationally exposed personnel. Materials and Methods: The integrative literature review method was utilized to analyze 21 articles, 2 books, 1 thesis, 1 monograph, 1 computer program, 4 pieces of database research (Instituto Brasileiro de Geografia e Estatistica and Departamento de Informatica do Sistema Unico de Saude) and 2 sets of radiological protection guidelines. Results: Theoretically, a reduction of 86% to 99% in the absorbed dose is observed with the use of radiation protection gear. In practice, however, the reduction may achieve 88% in patients submitted to conventional radiology, and 95% in patients submitted to computed tomography. In occupationally exposed individuals, the reduction is around 90% during cardiac catheterization, and 75% during orthopedic surgery. Conclusion: According to findings of several previous pieces of research, the use of radiation protection gear is a low-cost and effective way to reduce absorbed dose both for patients and occupationally exposed individuals. Thus, its use is necessary for the implementation of effective radioprotection programs in radiodiagnosis centers. (author)

Soares, Flavio Augusto Penna; Flor, Rita de Cassia [Instituto Federal de Santa Catarina (IFSC), Florianopolis, SC (Brazil); Pereira, Aline Garcia, E-mail: aalinegp@gmail.co [Sinan Project - Sistema de Informacao de Agravos de Notificacao, Florianopolis, SC (Brazil)

2011-03-15

274

?-ray survey meter for measuring absorbed dose rate independently of ?-ray energy  

International Nuclear Information System (INIS)

A new type of ?-ray survey meter has been developed which can be used for measuring absorbed dose rate from ?-rays almost independently of their maximum energy. This survey meter can be also used for monitoring surface contamination. The meter's detector is a plastic scintillator. When the survey meter is used for measuring absorbed dose rate, its response is constant to within +- 10% for ?-rays with maximum energy greater than 0.4 MeV. The measurable ranges of absorbed dose rate are 5 x 10-2 to 1 x 103 mrad/hr for skin (epidermal thickness: 7 mg/cm2) and 3 x 10-2 to 1 x 103 mrad/hr for fingers (epidermal thickness: 40 mg/cm2). In monitoring surface contamination, the measurable range is 3 x 10-1 to 1.7 x 103 ?-particles/cm2.sec [2? solid angle, natural uranium source covered by an aluminium filter (27 mg/cm2) for shielding low-energy ?-rays of 234Th and ?-rays]. (author)

275

Absorbed dose/melting heat dependence studies for the PVDF homopolymer  

International Nuclear Information System (INIS)

Differential Scanning Calorimetry (DSC) of gamma irradiated Poly (vinylidene Fluoride) [PVDF] homopolymer has been studied in connection with the use of material in industrial high gamma dose measurement. Interaction between gamma radiation and PVDF leads to the radio-induction of C=O and conjugated C=C bonds, as it can be inferred from previous infrared (FTIR) and ultraviolet-visible (UV-Vis) spectrometric data. These induced defects result in a decrease of the polymer crystallinity that can be followed with DSC scans, by measuring the latent heat during the melting transition (Hmelt). After a systematic investigation, we have found that Hmelt is unambiguously related to the delivered doses ranging from 100 to 2,000 kGy of gamma radiation. One the other hand, further fading investigation analysis has proved that the Hmelt x Dose relationship can be fitted by an exponential function that remains constant for several months. Both the very large range of dose measurement and also the possibility of evaluating high gamma doses until five months after irradiation make PVDF homopolymers very good candidates to be investigated as commercial high gamma dose dosimeters. The high gamma dose irradiation facilities in Brazil used to develop high dose dosimeters are all devoted to industrial and medical purposes. Therefore, in view of the uncertainties involved in the dose measurements related to the electronic equilibrium correction factors and backscattering in the isodose curves used at the irradiation setup, a validation process is required to correctly evaluate the delivered absorbed doses. The sample irradiations were performed with a Co-60 source, at 12kGy/h and 2,592 kGy/h, in the high gamma dose facilities at Centro de Desenvolvimento da Tecnologia Nuclear CDTN/CNEN, Belo Horizonte, Brazil. The comparison of the curve of the Hmelt vs Dose is presented in this paper. (author)

276

Absorbed dose/melting heat dependence studies for the PVDF homopolymer  

Energy Technology Data Exchange (ETDEWEB)

Differential Scanning Calorimetry (DSC) of gamma irradiated Poly (vinylidene Fluoride) [PVDF] homopolymer has been studied in connection with the use of material in industrial high gamma dose measurement. Interaction between gamma radiation and PVDF leads to the radio-induction of C=O and conjugated C=C bonds, as it can be inferred from previous infrared (FTIR) and ultraviolet-visible (UV-Vis) spectrometric data. These induced defects result in a decrease of the polymer crystallinity that can be followed with DSC scans, by measuring the latent heat during the melting transition (Hmelt). After a systematic investigation, we have found that Hmelt is unambiguously related to the delivered doses ranging from 100 to 2,000 kGy of gamma radiation. One the other hand, further fading investigation analysis has proved that the Hmelt x Dose relationship can be fitted by an exponential function that remains constant for several months. Both the very large range of dose measurement and also the possibility of evaluating high gamma doses until five months after irradiation make PVDF homopolymers very good candidates to be investigated as commercial high gamma dose dosimeters. The high gamma dose irradiation facilities in Brazil used to develop high dose dosimeters are all devoted to industrial and medical purposes. Therefore, in view of the uncertainties involved in the dose measurements related to the electronic equilibrium correction factors and backscattering in the isodose curves used at the irradiation setup, a validation process is required to correctly evaluate the delivered absorbed doses. The sample irradiations were performed with a Co-60 source, at 12kGy/h and 2,592 kGy/h, in the high gamma dose facilities at Centro de Desenvolvimento da Tecnologia Nuclear CDTN/CNEN, Belo Horizonte, Brazil. The comparison of the curve of the Hmelt vs Dose is presented in this paper. (author)

Batista, Adriana S.M.; Gual, Maritza R.; Pereira, Claubia, E-mail: adriananuclear@yahoo.com.br, E-mail: maritzargual@gmail.com, E-mail: claubia@nuclear.ufmg.br [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Departamento de Engenharia Nuclear; Faria, Luiz O., E-mail: farialo@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

2013-07-01

277

Clinical dosimetry with plastic scintillators - Almost energy independent, direct absorbed dose reading with high resolution  

International Nuclear Information System (INIS)

Clinical dosimetry is still far behind the goal to measure any spatial or temporal distribution of absorbed dose fast and precise without disturbing the physical situation by the dosimetry procedure. NE 102A plastic scintillators overcome this border. These tissue substituting dosemeter probes open a wide range of new clinical applications of dosimetry. This versatile new dosimetry system enables fast measurement of the absorbed dose to water in water also in regions with a steep dose gradient, close to interfaces, or in partly shielded regions. It allows direct reading dosimetry in the energy range of all clinically used external photon and electron beams, or around all branchytherapy sources. Thin detector arrays permit fast and high resolution measurements in quality assurance, such as in-vivo dosimetry or even afterloading dose monitoring. A main field of application is the dosimetric treatment planning, the individual optimization of brachytherapy applicators. Thus, plastic scintillator dosemeters cover optimally all difficult fields of clinical dosimetry. An overview about its characteristics and applications is given here. 20 refs, 1 fig

278

Emission properties of thermoluminescence from natural quartz - blue and red TL response to absorbed dose  

International Nuclear Information System (INIS)

The TL spectrometry of natural quartz exposed to a gamma radiation dose of 8.8 kGy proved that the red TL, mainly from volcanically originated quartz, has a broad emission band with a peak around 620 nm, while the blue TL from plutonically originated quartz also has a broad emission band giving a peak around 470 nm. These typical red or blue intrinsic colours were also confirmed on the thermoluminescence colour images (TLCI). Exceptionally, a pegmatite quartz changed its TLCI colour from red to blue when the absorbed dose was increased. By using colour filter assemblies, all these quartz samples were shown to emit mainly blue and red TLs, which have distinctly different TL responses to the absorbed dose; the blue invariably showed a supralinearity relation between 1 and 10 kGy dose. For the purpose of dating, the use of red TL, is preferable. The red TL component is related to the impurity Eu content in quartz minerals. (author)

279

Annual absorbed dose rate at the surface of 38 hot and mineral springs in Iran  

Energy Technology Data Exchange (ETDEWEB)

Full text of publication follows: Measurement of background radiation is very important from different points of view especially to human health. In some cases exposure rate near hot and mineral springs are higher than those of normal areas. The high background radiation of hot and mineral springs is primarily due to the presence of very high amounts of Ra 226 and its decay products. In this research, environmental gamma radiation of hot and mineral springs in Khorasan, Mazandaran and Sareeyn town in Ardabil province have been measured. Equipment used in this work included: a survey meter (R.D.S. -110), a tripod and an aluminium frame to hold the survey meter horizontally.R.D.S. -110 is a microprocessor controlled detector. This survey meter has been designed for monitoring X and rays and radiation. Measurements were carried out at one meter above water level in the vicinity of hot and mineral springs. Dose rates were recorded for one hour. The average of all recorded dose rates over one hour period was taken as the exposure rate for each station. The results indicate that in Khorasan province the highest and lowest annual absorbed dose rates were equal to 10.80 mSv/y at Shanigarmab and 0.52 mSv/y at Nasradin source respectively. In Mazandaran province maximum and minimum exposure rates equal to 54.4 and 0.53 mSv/y were obtained at the surface of Talleshmahalleh and Ghormerz sources. Exposure rates at the vicinity of Sarein sources were not very different and ranged from 1.39 to 1.59 mSv/y. The results indicate that in Khorasan province Shahingarmab hot spring has the highest annual absorbed dose rate (10.80 mSv/y) and Nasraddin in Sarbisheh has the lowest level of radiation (0.62 mSv/y). In Mazandaran province Taleshmahalleh hot mineral spring has the highest annual absorbed dose rate (54.41 mSv/y) and Ghormerz mineral spring has the lowest radiation level (0.53 mSv/y). Also in Sareeyn (in Ardabil province) Abechashm source has the highest annual absorbed dose rate (1.59 mSv/y) and Jeneral spring the lowest (1.39 mSv/y). (authors)

Bahreyni Toosi, M.; Orougi, M.H.; Sadeghzadeh, A.; Aghamir, A.; Jomehzadeh, A.; Zare, H. [Mashhad Univ. of Medical Sciences, Medical Physics Dep., Faculty of Medicine (Iran, Islamic Republic of)

2006-07-01

280

Annual absorbed dose rate at the surface of 38 hot and mineral springs in Iran  

International Nuclear Information System (INIS)

Full text of publication follows: Measurement of background radiation is very important from different points of view especially to human health. In some cases exposure rate near hot and mineral springs are higher than those of normal areas. The high background radiation of hot and mineral springs is primarily due to the presence of very high amounts of Ra 226 and its decay products. In this research, environmental gamma radiation of hot and mineral springs in Khorasan, Mazandaran and Sareeyn town in Ardabil province have been measured. Equipment used in this work included: a survey meter (R.D.S. -110), a tripod and an aluminium frame to hold the survey meter horizontally.R.D.S. -110 is a microprocessor controlled detector. This survey meter has been designed for monitoring X and 'rays and' radiation. Measurements were carried out at one meter above water level in the vicinity of hot and mineral springs. Dose rates were recorded for one hour. The average of all recorded dose rates over one hour period was taken as the exposure rate for each station. The results indicate that in Khorasan province the highest and lowest annual absorbed dose rates were equal to 10.80 mSv/y at Shanigarmab and 0.52 mSv/y at Nasradin source respectively. In Mazandaran province maximum and minimum exposure rates equal to 54.4 and 0.53 mSv/y were obtained at the surface of Talleshmahalleh and Ghormerz sources. Exposure rates at the vicinity of Sarein sources were not very different and rangedsources were not very different and ranged from 1.39 to 1.59 mSv/y. The results indicate that in Khorasan province Shahingarmab hot spring has the highest annual absorbed dose rate (10.80 mSv/y) and Nasraddin in Sarbisheh has the lowest level of radiation (0.62 mSv/y). In Mazandaran province Taleshmahalleh hot mineral spring has the highest annual absorbed dose rate (54.41 mSv/y) and Ghormerz mineral spring has the lowest radiation level (0.53 mSv/y). Also in Sareeyn (in Ardabil province) Abechashm source has the highest annual absorbed dose rate (1.59 mSv/y) and Jeneral spring the lowest (1.39 mSv/y). (authors)

 
 
 
 
281

Dose absorbed by technologists in positron emission tomography procedures with FDG  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese 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 diferen [...] ças 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. Abstract in english 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 significan [...] t 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.

Ademir, Amaral; Christian, Itié; Bernard, Bok.

2007-09-01

282

Absorbed dose due to radioiodine therapy by organs of patients with hyperthyroidism  

International Nuclear Information System (INIS)

The dose absorbed by organs of patients with hyperthyroidism treated with 131 I was estimated by using the MIRDOSE computer program and data from ICRP-53. The calculation were performed using effective half-life and uptake average values, which were determined for 17 patients treated with 370 MBq and 555MBq of 131 I. The results shown that the dose in the thyroid, for a 370 MBq administrated activity, was of 99 Gy and 49.5 Gy for 60 g and 80 g thyroid respectively. The average dose estimated in other organs were relatively low, presenting values lower than 0.1 Gy in the kidneys, bone marrow and ovaries and 0.19 Gy in the stomach

283

Do Only Small Uremic Toxins, Chromophores, Contribute to the Online Dialysis Dose Monitoring by UV Absorbance?  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of this work was to evaluate the contributions of the main chromophores to the total UV absorbance of the spent dialysate and to assess removal dynamics of these solutes during optical on-line dialysis dose monitoring. High performance chromatography was used to separate and quantify UV-absorbing solutes in the spent dialysate sampled at the start and at the end of dialysis sessions. Chromatograms were monitored at 210, 254 and 280 nm routinely and full absorption spectra were registered between 200 and 400 nm. Nearly 95% of UV absorbance originates from solutes with high removal ratio, such as uric acid. The contributions of different solute groups vary at different wavelengths and there are dynamical changes in contributions during the single dialysis session. However, large standard deviation of the average contribution values within a series of sessions indicates remarkable differences between individual treatments. A noteworthy contribution of Paracetamol and its metabolites to the total UV absorbance was determined at all three wavelengths. Contribution of slowly dialyzed uremic solutes, such as indoxyl sulfate, was negligible.

Fredrik Uhlin

2012-10-01

284

Estimation of absorbed gamma dose in air due to natural and artificial radioactivity of soil  

International Nuclear Information System (INIS)

This Ph. D. thesis is devoted to the measurements of air absorbed gamma doses due to natural and artificial radioactivity in soil. It contains four chapters, conclusions, acknowledge, and a reference list. The first chapter presents problems related to the measurement of natural and artificial radioactivity coming from soil contamination due to nuclear explosions or nuclear accidents. The natural and artificial radionuclides which usually contaminate the soil are reviewed. The chapter two presents the original contribution of the author in the field of the methods of soil sampling and NaI(Tl) gamma spectrometry analysis of radioactive samples. Also the results of the measurements carried out in 10 counties in Romania are here reported. The natural radionuclides measured were Ra-226, Th-232, and K-40, while the artificial radionuclides were Cs-137 and Cs-134. In the third chapter the radioactivity levels are reported as absorbed air gamma doses due to presence of 137 Cs and 134 Cs in soil. Also here the effective dose equivalents estimated for the population of the 10 counties are presented. In the chapter four a discussion is given concerning the dose levels measured following the Chernobyl nuclear accident as function of time elapsed from the accident and of depth of soil sampling and of soil type. It is shown that the dose levels which affected the population in the studied zones are within the values of radioprotection standards in Romania. Thf radioprotection standards in Romania. These data were used as input to solve the problem of the biological effects of low doses on the population health. (M.I.C.). 42 Figs., 54+15 Tabs., 216 Refs, 1 App

285

Quality control of diagnostic radiology to reduce absorbed dose of patients in Iran  

International Nuclear Information System (INIS)

In order to reduce absorbed dose, to increase the image quality and to reduce the numbers of rejected films various quality control parameters were applied to X ray machines. These parameter are Kilo Volt peak, Milli Ampere, Exposure Time Focal Film Distance, Inherent Filters, Additional Filters Half Value Layer, Processor Condition, Cassettes. To evaluate and to apply these parameters in diagnostic radiological centers, ten hospitals were selected and a total number of 12 X ray machines were kept under quality control program. Considering different kinds of diagnostic radiology examination and to compare the dose before and after implementation of a quality control program, two kinds of examinations include in chest and abdomen examinations were considered. For each X ray machine, ten patients and for all selected centers, 120 patients were selected for chest examination and 120 patients for abdomen examinations; before and after implementation of quality control program, a total of 480 patients were selected randomly to be controlled. Base on different examinations carried out, it was concluded that both exposure conditions and general situations in radiological centers were not acceptable. The dosimetry results show that the average ski dose for chest and abdomen examinations were 0.28 m Gy and 4.23 Gy respectively. Before implementation of quality control step to reduce the surface skin dose, quality control parameters were applied and the exposure conditions weree applied and the exposure conditions were imposed. On average the absorbed doses for chest and abdomen examination were decreased to 79% and 61% respectively after the implementation of the program. From dose reduction point of view, the results of a part of this project which made by co-operation of International Atomic Energy Agency showed that Iran acquired the first grade for chest examination and second grade for abdomen examination. Base on the results obtained, the number of patients under chest and abdomen examination were 4041588 and 1534148 persons respectively

286

Results of photon absorbed-dose measurements using the AAPM TG-21 protocol for accelerating potentials up to 26 MV.  

Science.gov (United States)

The AAPM Task Group 21 protocol for the calibration of high-energy photon and electron beams was produced to accomplish essentially two goals: (1) incorporate the latest physical data available for calculating absorbed dose from ionization measurements and (2) to eliminate inconsistencies in absorbed dose measurements made with various ion chamber and phantom combinations. The ability of the protocol was assessed to consistently determine x-ray absorbed dose from measurements made with four Farmer-type chambers and one parallel-plate chamber in water, polystyrene, and acrylic phantoms. The measurements were performed using seven high-energy x-ray beams from 60Co to 26-MV nominal accelerating potential. The absorbed dose to water calculated from measurements made with the various chamber and phantom combinations were found to be consistent. The doses calculated for the two most common phantom materials, water and polystyrene, were found to be in excellent agreement. This resolved a 1.6% discrepancy in the absorbed dose determined from the two phantoms using the SCRAD protocol. The doses for acrylic phantoms were found to be approximately 1.2%, low for nominal accelerating potentials less than 8.8 MV. For accelerating potentials of 8.8 MV or greater the agreement was considerably better. The mean dose determined for the parallel-plate chamber from measurements in polystyrene was found to be within 0.7% of the mean dose determined using Farmer-type ion chambers in all phantom materials. PMID:1753909

Hazle, J D; Kirby, T H; Gastorf, R J; Hanson, W F

1991-01-01

287

Assessment of absorbed dose to the ovaries of patients undergoing pelvic CT examination  

International Nuclear Information System (INIS)

Full text of publication follows: Introduction: Although Computed Tomography (CT) procedures constitute about 5% of the total diagnostic radiology procedures but are responsible for about 40% of the total ionizing radiation dose to the general population. As the dose is high especially in the CT of female pelvis, genetic radiation risk is also considerable. Materials and Methods: Radiation doses to the ovaries of the patients undergoing CT examination of the pelvis were measured from 9 different CT scanners available in Isfahan city. For each CT scanner 20 patients were selected. Measurement of organ dose was performed using TLD method. Results and Discussions: Mean and S.D. of absorbed dose to the ovaries from Shimadzo 2500 were 56.6 2.8; from GE Max 640 were 36.8 1.7; from GE Sytec 3000 were 36.6 1.8; from GE Sytec 4000 were 36.6 2.6; from Piker were 38.4 2.1; from Shimadzo 4500 were 36.4 1.2 and from Shimadzo 7800TE 28.2 1.5. Associated risks due to the measured dose are discussed. (author)

288

Data for absorbed dose calculations for external sources and for emitters within the body  

International Nuclear Information System (INIS)

Tables give data for the calculation of absorbed doses from radioactivity sources accumulated in individual body organs. The tables are arranged in such manner that the gamma energy (J) absorbed in 1 kg of target organ (19 organs and total body) are given for 18 source organs (16 different organs, total doby and surrounding air) resulting from 1 decay event, this for more than 250 radioisotopes evenly distributed in the source organ (1 J/kg=100 rad). Also given are the energies of alpha and beta radiations related to one decay. In tables having the surrounding air as the source it is assumed that the intensity of the external source is 1 decay per 1 m3 of surrounding air which is constant in the entire half-space. The tables are only elaborated for radioisotopes with a half-life of more than 1 min. (B.S.)

289

An algorithm for electron depth-dose distributions in multilayer slab absorbers  

International Nuclear Information System (INIS)

An algorithm to evaluate depth-dose distributions produced by plane-parallel electron beams normally incident on two- or three-layer slab absorbers has been developed. It is based on a simple model of electron penetration across the interface, and makes use of empirical equations previously formulated as well as ones newly developed. Distributions obtained by the algorithm have been compared with available experimental and Monte Carlo results for electrons of incident energies from 0.1 to 10 MeV, showing good agreement in most cases. The algorithm is considered to be valid for incident energies from 0.1 to 20 MeV and for absorbers consisting of slabs of atomic numbers from about 5.6 (polystyrene) to 82. (author)

290

Standard Guide for Selection and Use of Mathematical Methods for Calculating Absorbed Dose in Radiation Processing Applications  

CERN Document Server

1.1 This guide describes different mathematical methods that may be used to calculate absorbed dose and criteria for their selection. Absorbed-dose calculations can determine the effectiveness of the radiation process, estimate the absorbed-dose distribution in product, or supplement or complement, or both, the measurement of absorbed dose. 1.2 Radiation processing is an evolving field and annotated examples are provided in Annex A6 to illustrate the applications where mathematical methods have been successfully applied. While not limited by the applications cited in these examples, applications specific to neutron transport, radiation therapy and shielding design are not addressed in this document. 1.3 This guide covers the calculation of radiation transport of electrons and photons with energies up to 25 MeV. 1.4 The mathematical methods described include Monte Carlo, point kernel, discrete ordinate, semi-empirical and empirical methods. 1.5 General purpose software packages are available for the calcul...

American Society for Testing and Materials. Philadelphia

2010-01-01

291

Integral absorbed dose at optimal exposure condition in spiral CT for the temporomandibular joint  

International Nuclear Information System (INIS)

The purpose of the study was to optimize exposure condition on spiral CT for the temporomandibular joint and to calculate patient radiation dose under optimal exposure conditions. For measurement of exposure, a chamber was fixed on the detector of the spiral CT apparatus. The tube voltages used were 100 kV, 120 kV and 130 kV, and the tube currents were 25 mA, 50 mA, 1 mA, 200 mA and 300 mA. Exposure time was 1 second. The integral absorbed dose was calculated by the Energy Fluence method. The temporomandibular joint region of the phantom was scanned by CT at tube voltages of 100 kV, 120 kV and 130 kV, and tube currents of 25 mA, 50 mA, 75 mA, 100 mA, 125 mA and 150 mA. Table feed speed was fixed at 1 mm per rotation. Sagittal image of the temporomandibular joint was reconstructed from axial images. These images were assessed for their image quality using a five-point scale. The lowest exposure condition in clinical application was 120 kV, 75 mA and 1 mm per rotation. The integral absorbed dose during CT examination of the temporomandibular joint was 104 mJ under this condition. This was approximately three times greater than that of tomographic examination of the same region. (author)

292

Technique-dependent decrease in thyroid absorbed dose for dental radiography  

International Nuclear Information System (INIS)

A LiF thermoluminescent dosimetry (TLD) system, calibrated in the tissue of interest with the beam used for experimentation, was employed to investigate dosages (muGy) to the thyroid region of an anthropomorphic phantom resultant from two dental complete-mouth radiographic procedures. Both techniques were compared in terms of dosages associated with combinations of lead apron and thyroid collar shielding while using a 70-kVp or 90-kVp x-ray beam for a 20-film complete-mouth series. Lead shielding significantly decreased the dose to the thyroid using both techniques (p less than 0.05). The use of the 90-kVp beam resulted in a significant reduction in the thyroid absorbed dose when using the bisecting angle technique (p less than 0.05) but caused a significant increase in the thyroid absorbed dose when the paralleling technique was used (p less than 0.05). The implementation of higher kilovoltage techniques in dental offices must therefore be dependent on the radiographic technique employed

293

Selective fallopian tube catheterisation in female infertility: clinical results and absorbed radiation dose  

International Nuclear Information System (INIS)

Clinical results of fluoroscopic fallopian tube catheterisation and absorbed radiation doses during the procedure were evaluated in 30 infertility patients with unilateral or bilateral tubal obstruction documented on hysterosalpingography. The staged technique consisted of contrast injection through an intrauterine catheter with a vacuum cup device, ostial salpingography with the wedged catheter, and selective salpingography with a coaxial microcatheter. Of 45 fallopian tubes examined, 35 (78 %) were demonstrated by the procedure, and at least one tube was newly demonstrated in 26 patients (87 %). Six of these patients conceived spontaneously in the follow-up period of 1-11 months. Four pregnancies were intrauterine and 2 were ectopic. This technique provided accurate and detailed information in the diagnosis and treatment of tubal obstruction in infertility patients. The absorbed radiation dose to the ovary in the average standardised procedure was estimated to be 0.9 cGy. Further improvement in the X-ray equipment and technique is required to reduce the radiation dose. (orig.). With 3 figs., 3 tabs

294

Exchange of sources, beam flattening filters and jigs of a secondary standard for absorbed dose rates of beta radiation  

International Nuclear Information System (INIS)

A number of secondary standards for the absorbed dose rate of beta radiation have been examined to ascertain whether the exchange of beam flattening filters, jigs or beta sources requires a recalibration. In 56 of 57 exchanges the respective absorbed dose rates at the calibration distance differed by less than 1% if the different activities of the exchanged beta sources were taken into account. The relative changes observed were even less than 0.5% in 80% of all cases. (orig.)

295

Comparison of IAEA absorbe dose protocols TRS 277, TRS 381 and TRS 398 for different electron energies  

Digital Repository Infrastructure Vision for European Research (DRIVER)

OBJECTIVES: In this study, calculation of absorbed doses according to three different IAEA protocols for 6, 8, 10, 12, 15, and 18 MeV electron energies were compared. METHODS: Absorbe dose measurements were made at SSD=95 cm distance, 10 x 10 cm standart cone and reference depth. Electron energies was measured with five different cylindirical chambers and three different paralel plate chambers. Polarity and recombination effects were measured for all ionization chambers and energies before ab...

Acar, Hilal

2007-01-01

296

Discrimination of various contributions to the absorbed dose in BNCT: Fricke-gel imaging and intercomparison with other experimental results.  

Science.gov (United States)

A method is described for the 3D measurements of absorbed dose in a ferrous sulphate gel phantom, exposed in the thermal column of a nuclear reactor. The method, studied for Boron Neutron Capture Therapy (BNCT) purposes, allows absorbed dose imaging and profiling, with the separation of different contributions coming from different secondary radiations, generated from thermal neutrons. In fact, the biological effectiveness of the different radiations is different. Tests with conventional dosimeters were performed too. PMID:11003518

Gambarini, G; Agosteo, S; Marchesi, P; Nava, E; Palazzi, P; Pecci, A; Rosi, G; Tinti, R

2000-01-01

297

Response functions for computing absorbed dose to skeletal tissues from photon irradiation-an update  

Energy Technology Data Exchange (ETDEWEB)

A comprehensive set of photon fluence-to-dose response functions (DRFs) is presented for two radiosensitive skeletal tissues-active and total shallow marrow-within 15 and 32 bone sites, respectively, of the ICRP reference adult male. The functions were developed using fractional skeletal masses and associated electron-absorbed fractions as reported for the UF hybrid adult male phantom, which in turn is based upon micro-CT images of trabecular spongiosa taken from a 40 year male cadaver. The new DRFs expand upon both the original set of seven functions produced in 1985, and a 2007 update calculated under the assumption of secondary electron escape from spongiosa. In this study, it is assumed that photon irradiation of the skeleton will yield charged particle equilibrium across all spongiosa regions at energies exceeding 200 keV. Kerma coefficients for active marrow, inactive marrow, trabecular bone and spongiosa at higher energies are calculated using the DRF algorithm setting the electron-absorbed fraction for self-irradiation to unity. By comparing kerma coefficients and DRF functions, dose enhancement factors and mass energy-absorption coefficient (MEAC) ratios for active marrow to spongiosa were derived. These MEAC ratios compared well with those provided by the NIST Physical Reference Data Library (mean difference of 0.8%), and the dose enhancement factors for active marrow compared favorably with values calculated in the well-known study published by King and Spiers (1985 Br. J. Radiol. 58 345-56) (mean absolute difference of 1.9 percentage points). Additionally, dose enhancement factors for active marrow were shown to correlate well with the shallow marrow volume fraction (R{sup 2} = 0.91). Dose enhancement factors for the total shallow marrow were also calculated for 32 bone sites representing the first such derivation for this target tissue.

Johnson, Perry B; Bahadori, Amir A [Nuclear and Radiological Engineering, University of Florida, Gainesville, FL 32611 (United States); Eckerman, Keith F [Life Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Lee, Choonsik [Radiation Epidemiology Branch, National Cancer Institute, Bethesda, MD 20892 (United States); Bolch, Wesley E, E-mail: wbolch@ufl.edu [Nuclear and Radiological/Biomedical Engineering, University of Florida, Gainesville, FL 32611 (United States)

2011-04-21

298

Response functions for computing absorbed dose to skeletal tissues from photon irradiation--an update.  

Science.gov (United States)

A comprehensive set of photon fluence-to-dose response functions (DRFs) is presented for two radiosensitive skeletal tissues-active and total shallow marrow-within 15 and 32 bone sites, respectively, of the ICRP reference adult male. The functions were developed using fractional skeletal masses and associated electron-absorbed fractions as reported for the UF hybrid adult male phantom, which in turn is based upon micro-CT images of trabecular spongiosa taken from a 40 year male cadaver. The new DRFs expand upon both the original set of seven functions produced in 1985, and a 2007 update calculated under the assumption of secondary electron escape from spongiosa. In this study, it is assumed that photon irradiation of the skeleton will yield charged particle equilibrium across all spongiosa regions at energies exceeding 200 keV. Kerma coefficients for active marrow, inactive marrow, trabecular bone and spongiosa at higher energies are calculated using the DRF algorithm setting the electron-absorbed fraction for self-irradiation to unity. By comparing kerma coefficients and DRF functions, dose enhancement factors and mass energy-absorption coefficient (MEAC) ratios for active marrow to spongiosa were derived. These MEAC ratios compared well with those provided by the NIST Physical Reference Data Library (mean difference of 0.8%), and the dose enhancement factors for active marrow compared favorably with values calculated in the well-known study published by King and Spiers (1985 Br. J. Radiol. 58 345-56) (mean absolute difference of 1.9 percentage points). Additionally, dose enhancement factors for active marrow were shown to correlate well with the shallow marrow volume fraction (R(2) = 0.91). Dose enhancement factors for the total shallow marrow were also calculated for 32 bone sites representing the first such derivation for this target tissue. PMID:21427484

Johnson, Perry B; Bahadori, Amir A; Eckerman, Keith F; Lee, Choonsik; Bolch, Wesley E

2011-04-21

299

Response functions for computing absorbed dose to skeletal tissues from photon irradiation—an update  

Science.gov (United States)

A comprehensive set of photon fluence-to-dose response functions (DRFs) is presented for two radiosensitive skeletal tissues—active and total shallow marrow—within 15 and 32 bone sites, respectively, of the ICRP reference adult male. The functions were developed using fractional skeletal masses and associated electron-absorbed fractions as reported for the UF hybrid adult male phantom, which in turn is based upon micro-CT images of trabecular spongiosa taken from a 40 year male cadaver. The new DRFs expand upon both the original set of seven functions produced in 1985, and a 2007 update calculated under the assumption of secondary electron escape from spongiosa. In this study, it is assumed that photon irradiation of the skeleton will yield charged particle equilibrium across all spongiosa regions at energies exceeding 200 keV. Kerma coefficients for active marrow, inactive marrow, trabecular bone and spongiosa at higher energies are calculated using the DRF algorithm setting the electron-absorbed fraction for self-irradiation to unity. By comparing kerma coefficients and DRF functions, dose enhancement factors and mass energy-absorption coefficient (MEAC) ratios for active marrow to spongiosa were derived. These MEAC ratios compared well with those provided by the NIST Physical Reference Data Library (mean difference of 0.8%), and the dose enhancement factors for active marrow compared favorably with values calculated in the well-known study published by King and Spiers (1985 Br. J. Radiol. 58 345-56) (mean absolute difference of 1.9 percentage points). Additionally, dose enhancement factors for active marrow were shown to correlate well with the shallow marrow volume fraction (R2 = 0.91). Dose enhancement factors for the total shallow marrow were also calculated for 32 bone sites representing the first such derivation for this target tissue.

Johnson, Perry B.; Bahadori, Amir A.; Eckerman, Keith F.; Lee, Choonsik; Bolch, Wesley E.

2011-04-01

300

Response functions for computing absorbed dose to skeletal tissues from photon irradiation-an update  

International Nuclear Information System (INIS)

A comprehensive set of photon fluence-to-dose response functions (DRFs) is presented for two radiosensitive skeletal tissues-active and total shallow marrow-within 15 and 32 bone sites, respectively, of the ICRP reference adult male. The functions were developed using fractional skeletal masses and associated electron-absorbed fractions as reported for the UF hybrid adult male phantom, which in turn is based upon micro-CT images of trabecular spongiosa taken from a 40 year male cadaver. The new DRFs expand upon both the original set of seven functions produced in 1985, and a 2007 update calculated under the assumption of secondary electron escape from spongiosa. In this study, it is assumed that photon irradiation of the skeleton will yield charged particle equilibrium across all spongiosa regions at energies exceeding 200 keV. Kerma coefficients for active marrow, inactive marrow, trabecular bone and spongiosa at higher energies are calculated using the DRF algorithm setting the electron-absorbed fraction for self-irradiation to unity. By comparing kerma coefficients and DRF functions, dose enhancement factors and mass energy-absorption coefficient (MEAC) ratios for active marrow to spongiosa were derived. These MEAC ratios compared well with those provided by the NIST Physical Reference Data Library (mean difference of 0.8%), and the dose enhancement factors for active marrow compared favorably with values calculated in the well-known study published by King and Spiwell-known study published by King and Spiers (1985 Br. J. Radiol. 58 345-56) (mean absolute difference of 1.9 percentage points). Additionally, dose enhancement factors for active marrow were shown to correlate well with the shallow marrow volume fraction (R2 = 0.91). Dose enhancement factors for the total shallow marrow were also calculated for 32 bone sites representing the first such derivation for this target tissue.

 
 
 
 
301

Absorbed and effective dose from spiral and computed tomography for the dental implant planning  

Energy Technology Data Exchange (ETDEWEB)

To evaluate the absorbed and effective doses of spiral and computed tomography for the dental implant planning. For radiographic projection. TLD chips were placed in 22 sites of humanoid phantom to record the exposure to skin and the mean absorbed dose to bone marrow, thyroid, pituitary, parotid and submandibular glands and nesophages. Effective dose was calculated, using the method suggested by Frederiksen at al.. Patient situations of a single tooth gap in upper and lower midline region, edentulous maxilla and mandible were simulated for spiral tomography. 35 axial slices (maxilla) and 40 axial slices (mandible) with low and standard dose setting were used for computed tomography. All the radiographic procedures were repeated three times. The mean effective dose in case of maxilla was 0.865 mSv, 0.452 mSv, 0.136 mSv and 0.025 mSv, in spiral tomography of complete edentulous maxilla, computed tomography with standard mAs, computed tomography with low mAs and spiral tomography of a single tooth gap (p<0.05). That in case of mandible was 0.614 mSv, 0.448 mSv, 0.137 mSv and 0.036 mSv, in spiral tomography of complete edentulous mandible, computed tomography with standard mAs, computed tomography with low mAs and spiral tomography of a single tooth gap (p<0.05). Based on these results, it can be concluded that low mAs computed tomography is recommended instead of spiral tomography for the complete edentulous maxilla and mandible dental implant treatment planning.

Hong, Beong Hee; Han, Won Jeong; Kim, Eun Kyung [Dankook Univ. School of Dentistry, Seoul (Korea, Republic of)

2001-09-15

302

Evaluation of vibro-acoustography techniques to map absorbed dose distribution in irradiated phantoms.  

Science.gov (United States)

This work presents Vibro-acoustography (VA) as a tool to visualize absorbed dose distributions in a polymer gel dosimeter. VA uses the radiation force of focused ultrasound to vibrate a small region of the sample. Different modalities of VA were used to investigate the feasibility of this technique to evaluate dose distribution in irradiated 'MAGIC' polymer gel. A phantom was designed using this polymer with 2% w/w added glass microspheres having an average diameter range between 40-75 microm. The phantom was irradiated using conventional 10 MeV X-rays from a linear accelerator at a distance of 100 cm. An absorbed dose of 50 gray was delivered to the gel. To study the phenomena of dose distribution, continuous wave (CW), toneburst and multifrequency VA were applied to the phantom. Images were generated from the phase and magnitude of the emitted sound from the irradiated area. The comparative accuracy of the different VA results were validated using transverse relaxation rate (R2) image analysis by Magnetic Resonance Imaging (MRI) and a treatment planning system. A contour map of R2 was registered with the transverse CW images, obtained with the focal point on the top surface, and a good correlation was found between the images. The axial profile of irradiated inclusion from the toneburst VA image obtained with excitation frequency of 75 kHz showed the best accuracy compared to other VA modalities. The results show that VA imaging has potential to visualize dose distribution in a polymer gel dosimeter. PMID:19964244

Vieira, Silvio L; Kinnick, Randall R; Baggio, Andre L; Nicolucci, Patricia; Fatemi, Mostafa; Carneiro, Adilton O

2009-01-01

303

Absorbed doses to the main parts of eyeball due to use 90Sr + 90Y ophthalmic applicator  

International Nuclear Information System (INIS)

The ophthalmic radiotherapy dosimetry and some affecting factors are introduced. The distributions of absorbed doses to the main parts of a fresh eyeball such as the cornea, sclera, lens and anterior chamber, during the radiotherapy by using a 90Sr + 90Y ophthalmic applicator are presented. An tissue-equivalent extrapolation ionization chamber was used in the dose measurement. The reasonable doses during ophthalmic radiotherapy for different depths have been obtained. Therefore, the absorbed dose to the lens, the most sensitive organ, can be given. These data are useful for radiation protection in ophthalmic radiotherapy

304

99mTc Auger electrons - Analysis on the effects of low absorbed doses by computational methods  

International Nuclear Information System (INIS)

We describe here the use of computational methods for evaluation of the low dose effects on human fibroblasts after irradiation with Technetium-99m (99mTc) Auger electrons. The results suggest a parabolic relationship between the irradiation of fibroblasts with 99mTc Auger electrons and the total absorbed dose. Additionally, the results on very low absorbed doses may be explained by the bystander effect, which has been implicated on the cell's effects at low doses. Further in vitro evaluation will be worthwhile to clarify these findings.

305

Irradiation of ferrous ammonium sulfate for its use as high absorbed dose and low-temperature dosimeter  

International Nuclear Information System (INIS)

In the present paper, we study the response of crystalline ammonium ferrous sulfate as a function of the irradiation dose and temperature. The dose studied ranged from 33.5 to 546 kGy. The temperature regimen varied from 77 K (liquid nitrogen) to 311 K. The analysis of the samples was made by UV spectroscopy and EPR. The results show that the change in absorbance of the dosimeter was linear with respect to the absorbed dose in the range studied. There is a small influence of the irradiation temperature in the response of the iron salt. The dose rate and storage time after irradiation was of no importance in this application

306

Electron absorbed dose comparison between MCNP5 and Penelope Monte Carlo code for microdosimetry  

International Nuclear Information System (INIS)

The objective of the present work was to compare electron absorbed dose results between two widespread used codes in international scientific community: MCNP5 and Penelope-2003. Individual water spheres with masses between 10-9 g up to 10-3 g immersed in an infinite water medium (density of 1g/cm3) and monoenergetic electron sources with energy from 0.002 MeV to 0.1 MeV have been considered. The absorbed dose in the spheres was evaluated by both codes and the relative differences have been quantified. The results shown that Penelope gives, in general, higher results that, in some cases saturate or reach a maximum point and then rapidly drops. Particularly, for the 40 keV electron source we have done additional tests in three different scenarios: more points in the region of lower masses to a better definition of the curve behavior; MCNP used 200 substeps and Penelope was set to a full detail history methodology, and almost same parameters of case B but with the density of exterior medium increased to 10 g/cm3. The three cases show the influence of the backscattering that contribute with an important fraction of absorbed dose, finally we can infer a range of reliability to use the codes in this kind of simulations: both codes can calculate close results for up to 10-4 g.Even though MCNP5 uses the condensed history method, if simulation parameters are chosen carefully it can reproduce results very close to those obtained using detailed history mode. In some cases, the use of higher number of electron substeps causes significant differences in the result. (author)

307

BRIGITTE, Dose Rate and Heat Source and Energy Flux for Self-Absorbing Rods  

International Nuclear Information System (INIS)

1 - Nature of physical problem solved: Calculation of dose rate, heat sources or energy flux. The sources are self-absorbing radioactive rods. The shielding consists of blocks of which the cross section can be defined. 2 - Method of solution: Exponential attenuation and build-up factor between source points and detector points. Source integration with error estimate. Automatic or controlled build-up with monitor print-out. 3 - Restrictions on the complexity of the problem: Number of energy points, regions, detector points, abscissa points of the rod, vertical position of the rod, are all limited to ten. The maximum total number of vertical steps is 124

308

The 1998 calibration of Australian secondary standards of exposure and absorbed dose at 60Co  

International Nuclear Information System (INIS)

New calibration factors are reported for several of the ionization chambers maintained at the Australian Radiation Laboratory (ARL) and at the Australian Nuclear Science and Technology Organisation (ANSTO) as Australian secondary standards of exposure/air kerma and absorbed dose at 60Co. These calibration factors supplement or replace the calibration factors given in earlier reports. Updated 90Sr reference source data are given for the ARL chambers, and for two of the ANSTO chambers. These results confirm the stability of the secondary standards. A re-calibration of the ANSTO reference electrometer is reported. This was carried out using an improved method, which is fully described

309

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

International Nuclear Information System (INIS)

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

310

Estimation of the absorbed dose in radiation-processed food. 4. EPR measurements on eggshell  

International Nuclear Information System (INIS)

Fresh whole eggs were treated with ionizing radiation for Salmonellae control testing. The eggshell was then removed and examined by electron paramagnetic resonance (EPR) spectroscopy to determine if EPR could be used to (1) distinguish irradiated from unirradiated eggs and (2) assess the absorbed dose. No EPR signals were detected in unirradiated eggs, while strong signals were measurable for more than 200 days after irradiation. Although a number of OPR signals were measured,the most intense resonance (g = 2.0019) was used for dosimetry throughout the study. This signal was observed to increase linearly with dose (up to approximately 6 kGy), which decayed approximately 20 % within the first 5 days after irradiation and remained relatively constant thereafter. The standard added-dose method was used to assess, retrospectively, the dose to eggs processed at 0.2, 0.7, and 1.4 kGy. Relatively good results were obtained when measurement was made on the day the shell was reradiated; with this procedure estimates were better for shell processed at the lower doses

311

Specification of absorbed dose and radiation quality in heavy particle therapy (A review)  

International Nuclear Information System (INIS)

The introduction of heavy particles (hadrons) into radiation therapy aims at improving the physical selectivity of the irradiation (e.g. proton beams), or the radiobiological differential effect (e.g. fast neutrons), or both (e.g. heavy ion beams). Each of these new therapy modalities requires several types of information before prescribing doses to patients, as well as for recording and reporting the treatments: (i) absorbed dose measured in a homogeneous phantom in reference conditions; (ii) dose distribution computed at the level of the target volume(s) and the normal tissues at risk; (iii) radiation quality from which an evaluation on the RBE could be predicted; and (iv) RBE measured on biological systems or derived from clinical observation. The ICRU has published recommendations for fast neutrons and a similar report is in preparation for proton beams. These recommendations are now universally applied. The single beam isodoses and thus the dose distributions are similar in neutron and photon therapy. Similar algorithms can then be used for treatment planning and the same rules can be followed for dose specification for prescribing and reporting a treatment. In hadron therapy, the RBE of the different beams raise specific problems. radiation quality thus has to be taken into account when prescribing and reporting a treatment. (author)

312

Study on the ferrous sulfate dosimeter used as the province grade-Guangdong standard of absorbed dose  

International Nuclear Information System (INIS)

Ferrous sulfate dosimeter has been used as the province grade-Guangdong absorbed dose standard for 60Co-? ray. The molar extinction coefficient for Fe3+ at 303 nm is precisely determined to be 2174.3 l·mol-1·cm-1 (25 degree C). The conversion factor for absorbance-absorbed dose is obtained to be 280.2 Gy/ABS, and the overall uncertainty within 2.7%. Major factor effecting ferrous sulfate dosimeter is also studied. Comparing the ferrous sulfate dosimeter with the national standard dosimeter and assurance dosimeter of IAEA, the test results contrasting are quite good

313

CALDoseX: a software tool for absorbed dose calculations in diagnostic radiology  

International Nuclear Information System (INIS)

Conversion coefficients (CCs) between absorbed dose to organs and tissues at risk and measurable quantities commonly used in X-ray diagnosis have been calculated for the last 30 years mostly with mathematical MIRD5-type phantoms, in which organs are represented by simple geometrical bodies, like ellipsoids, tori, truncated cylinders, etc. In contrast, voxel-based phantoms are true to nature representations of human bodies. The purpose of this study is therefore to calculate CCs for common examinations in X-ray diagnosis with the recently developed MAX06 (Male Adult voXel) and FAX06 (Female Adult voXel) phantoms for various projections and different X-ray spectra and to make these CCs available to the public through a software tool, called CALDoseX (CALculation of Dose for X-ray diagnosis). (author)

314

The dose absorbed by lymphocytes irradiated in vitro with tritiated water  

International Nuclear Information System (INIS)

A simple method of irradiating cells in vitro with beta particles is to add the ?-emitter to a cell suspension; various dosimetric aspects of this procedure have been investigated. Is is shown that, due to the different water content of the various constituents of a blood cell suspension, the average dose Dsub(?) absorbed by a certain type of cells for a tritium nominal concentration C0 and an irradiation time t is given by Dsub(?)(t) = KEnC0etat. Typical values of the factor eta are calculated for lymphocytes. A series of experiments has demonstrated that whilst the uptake phase has negligible effect on the dose, a significant error may arise during washing-out because a proportion of the activity remains in the cells. (author)

315

Absorbed Dose Measurement by the MIRD System in the I-131 Treated Thyroid Cancer patients 61-7254-60  

International Nuclear Information System (INIS)

Medical Internal Radiation Dose(MIRD) schema was developed for calculating the absorbed dose from the administered radiopharmaceuticals. With the biological distribution data and the physical properties of the radionuclide we can estimate the absorbed dose by the MIRD schema. For the thyroid cancer patients received I-131 therapy, the absorbed dose to the bone marrow is the limiting factor to the administered dose, and the duration of admission is determined by the retained activity in the whole body. To monitor the whole body radioactivity, we used Eberline Smart 200 system using ionization chamber as a detector. With the time activity curve of the whole body, total body residence time was obtained. From the ICRP publication 53, the residence times of the source organs, such as kidney, urinary bladder content and stomach, were, used to calculate the absorbed doses of the target organs, such as stomach, red marrow, bladder wall and remainder total body. In 8 thyroid cancer patients with 175 mci of I-131 administered orally, the mean absorbed dose in the bladder wall was 375.1 in the stomach 285.1, red marrow 25.4 and total body 22.4 rad respectively. For the monitoring of the large administered activity, this method seemed to be quite useful.

316

Secondary absorbed doses from light ion irradiation in anthropomorphic phantoms representing an adult male and a 10 year old child  

Science.gov (United States)

Secondary organ absorbed doses were calculated by Monte Carlo simulations with the SHIELD-HIT07 code coupled with the mathematical anthropomorphic phantoms CHILD-HIT and ADAM-HIT. The simulated irradiations were performed with primary 1H, 4He, 7Li, 12C and 16O ion beams in the energy range 100-400 MeV/u which were directly impinging on the phantoms, i.e. approximating scanned beams, and with a simplified beamline for 12C irradiation. The evaluated absorbed doses to the out-of-field organs were in the range 10-6 to 10-1 mGy per target Gy and with standard deviations 0.5-20%. While the contribution to the organ absorbed doses from secondary neutrons dominated in the ion beams of low atomic number Z, the produced charged fragments and their subsequent charged secondaries of higher generations became increasingly important for the secondary dose delivery as Z of the primary ions increased. As compared to the simulated scanned 12C ion beam, the implementation of a simplified beamline for prostate irradiation with 12C ions resulted in an increase of 2-50 times in the organ absorbed doses depending on the distance from the target volume. Comparison of secondary organ absorbed doses delivered by 1H and 12C beams showed smaller differences when the RBE for local tumor control of the ions was considered and normalization to the RBE-weighted dose to the target was performed.

Hultqvist, Martha; Gudowska, Irena

2010-11-01

317

Thyroid absorbed dose for people at Rongelap, Utirik, and Sifo on March 1, 1954  

International Nuclear Information System (INIS)

A study was undertaken to reexamine thyroid absorbed dose estimates for people accidentally exposed to fallout at Rongelap, Sifo, and Utirik Islands from the Pacific weapon test known as Operation Castle BRAVO. The study included: (1) reevaluation of radiochemical analysis, to relate results from pooled urine to intake, retention, and excretion functions; (2) analysis of neutron-irradiation studies of archival soil samples, to estimate areal activities of the iodine isotopes; (3) analysis of source term, weather data, and meteorological functions used in predicting atmospheric diffusion and fallout deposition, to estimate airborne concentrations of the iodine isotopes; and (4) reevaluation of radioactive fallout, which contaminated a Japanese fishing vessel in the vicinity of Rongelap Island on March 1, 1954, to determine fallout components. The conclusions of the acute exposure study were that the population mean thyroid absorbed doses were 21 gray (2100 rad) at Rongelap, 6.7 gray (670 rad) at Sifo, and 2.8 gray (280 rad) at Utirik. The overall thyroid cancer risk we estimated was in agreement with results published on the Japanese exposed at Nagasaki and Hiroshima. We now postulate that the major route for intake of fallout was by direct ingestion of food prepared and consumed outdoors. 66 refs., 13 figs., 25 tabs

318

Absorbed dose rate conversion coefficients for reference terrestrial biota for external photon and internal exposures.  

Science.gov (United States)

The paper describes dosimetric models that allow the estimation of average radiation exposures to terrestrial biota due to environmental sources in the soil as well as internal uniform distributions of radionuclides. Simple three-dimensional phantoms for 13 faunal reference organisms are specified. The calculation of absorbed dose per unit source strength for these targets is based on photon and electron transport simulations using the Monte Carlo method. The presented absorbed dose rate conversion coefficients are derived for terrestrial reference species. This allows the assessment of internal exposure as well as external photon exposure depending on the nuclide, habitat, target size and environmental contamination. To enable the application of specific radiation weighting factors for alpha-, low energy beta- (E0 soil, as well as for a horizontally infinite volume source uniformly distributed to a depth of 10 cm. Furthermore, the coefficients are also presented for organisms living in a contaminated 50 cm thick soil layer. A multi-layer canopy model for plants is also described. The conversion coefficients are given for 3H, 14C, 40K, 36Cl, 59,63Ni, 89,90Sr, 94Nb, 99Tc, 106Ru, 129,131I, 134,135,137Cs, 210Po, 210Pb, 226Ra, 227,228,230,231,232,234Th, 234,235,238U, 238,239,240,241Pu, 241Am, 237Np and 242,243,244Cm, together with their PMID:15700697

Taranenko, V; Pröhl, G; Gómez-Ros, J M

2004-12-01

319

Estimation of absorbed dose rate of gamma radiation for compounds of dosimetric interest  

International Nuclear Information System (INIS)

The absorbed dose rate defines quantity of energy deposited per unit mass per unit time when a narrow beam of gamma radiation incident on the given compound. Hence this quantity has become a prerequisite for both radiation dosimetry and the selection of compound as radiation shielding material used in accelerators. In the present work we have made an attempt to estimate the absorbed dose rate for dosimetric compounds such as nucleobases, nucleosides and nucleotides by evaluating mass energy co-efficient and mass energy attenuation co-efficient for the given compound using WinXCom software in the wide energy range 1 keV - 100 GeV by giving input data such as types of elements and the data of mass attenuation co-efficient of these elements present in the given compound. These parameters for various compounds have been tabulated for wide gamma ray energy range. These values are found to vary with increasing of gamma energy. It is expected that these data are useful to know the magnitude of radiation hazards causing to the personnel working in the field of accelerator and to take radiation safety measures. (author)

320

Measurement of absorbed dose to water for low and medium energy x-rays  

International Nuclear Information System (INIS)

Full text: Over the last decade, the treatment of superficial or intercavitary malignancies with medium-energy x-rays has regained popularity. This development puts renewed and increased emphasis on the importance of accurate dosimetry in this energy range. An appreciable number of publications dealing with various aspects of dosimetry in medium-energy x-ray beams has appeared and several protocols for the dosimetry of medium-energy x-ray appeared which led to the publication of a comparison between the various protocols. Attempts were made to model x-ray radiotherapy units by Monte Carlo methods, a method originally developed for high-energy treatment systems. In-phantom dosimetry for medium-energy x-rays suffers from the lack of a primary standard which would allow direct determination of the water absorbed dose. Attempts at a direct measurement of the water absorbed dose were made employing water calorimetry. These attempts suffered from the unknown energy dependence of the chemical yield for ferrous sulfate dosimetry, or from insufficient knowledge of the calorimetric heat defect. In the absence of a direct method, two different approaches have mainly been made. In one of these an ionisation chamber calibrated in free air in terms of air kerma is positioned at reference depth inside the water phantom. The absorbed dose to water is obtained by conversion of the air kerma measured in the water phantom to water kerma or, which is essentially equivalent in this energy range, to absorbed dose to water. When this method is used, correction factors have to be applied, which have to take into account i) the differences in the properties of the radiation field used for calibration in free air and of that inside the phantom and ii) the modification of the in-phantom radiation field caused by the presence of the ionisation chamber with its air cavity and with non water-equivalent walls and chamber stem. The other approach is to start with the measurement of absorbed dose to graphite in a graphite phantom. A measurement of absorbed dose to graphite, traceable to the physical base quantities of length and charge, can be accomplished by means of a graphite extrapolation chamber. In the energy range considered and under conditions of secondary electron equilibrium, the absorbed dose to graphite is numerically identical to the graphite collision kerma. Thus, by making use of the spectral distribution of the photon fluence at the point of measurement, which can be obtained by Monte Carlo calculations, the graphite collision kerma can be converted to water collision kerma by means of the ratio of the mass-energy absorption coefficients averaged over the photon energy fluence spectrum. This allows the calibration of a transfer ionisation chamber in terms of water collision kerma inside the graphite phantom. This transfer chamber is then positioned at the reference point of a water phantom. On the assumption that the angular and spectral distributions of the photon fluence in the graphite and the water phantom are reasonably similar to each other, the ionisation chamber measures water collision kerma inside the water phantom, which, again under the conditions prevailing, is numerically identical to absorbed dose to water. Each of the two methods outlined above has its 'critical' steps. For the measurement based on air kerma calibration there are significant differences between the calibration conditions (essentially mono directional radiation) and the conditions of measurement characterised by abundant scattered radiation. This makes it difficult to find reliable values for the correction factors which have to be applied to take the difference in the response to the two radiation fields into account. On the other hand, for the measurements with the graphite extrapolation chamber the ratio of the mass-energy absorption coefficients graphite to water is to be determined. This factor depends quite strongly on photon energy. The accuracy of the results of the accompanying Monte Carlo calculations therefore plays a decisive role in the uncer

 
 
 
 
321

Absorbed dose measurements of mixed pile radiation in aqueous radiation chemistry  

International Nuclear Information System (INIS)

To use a nuclear reactor as a radiation source in the radiation chemistry of water and aqueous solutions, reliable routine dosimetry techniques are of basic importance. For this purpose we have tried to develop a calorimetric device and a chemical system. The differential calorimeter described here permits simultaneous measurements of energy absorption in different materials. From these values the relative contributions from gammas and non-thermalized neutrons to the total absorbed dose can be calculated. The possibility of inserting a liquid sample into the calorimeter makes it very convenient for radiation chemical studies of aqueous solutions or, generally, liquid systems. For a period of about two years, reliable values for the absorbed doses in different materials have been obtained, which are in good agreement with other physical measurements in the RA research reactor at Vinca. The chemical system described is an aqueous solution of oxalic acid. Its advantages are: the possibility of measurements in the multi-megarad region and negligible induced radioactivity. The results of calorimetric and chemical measurements are presented

322

A first order approximation of the tumor absorbed dose prior to treatment with Sr-89  

International Nuclear Information System (INIS)

A new technique developed for the estimation of the absorbed dose prior to treatment with Sr-89 is presented. This technique implies that patient undergoes bone scanning with Tc-99m-MDP, two days before the administration of Sr-89. A number of sequential quantitative images are to be obtained over the first 8 hours after the Tc-99m-MDP injection and data are used to derive St-89 time retention curve. For the development of this technique a simplified model for the kinetics of both Sr-89 and Tc-99m-MDP was assumed. Data on the time retention of the two radiopharmaceuticals for a compartment including bone surface and bone space of trabecular and cortical bone for normal adults were combined together. A linear relationship was derived between the time required for the same percentage uptake of the two radiopharmaceuticals after single injection. The absorbed dose in the principal metastases and normal bone, of the same type and volume with the metastases, for two patients who were treated with Sr-89 for metastasized prostatic carcinoma are reported. (authors)

323

Thyroid absorbed dose for people at Rongelap, Utirik, and Sifo on March 1, 1954  

Energy Technology Data Exchange (ETDEWEB)

A study was undertaken to reexamine thyroid absorbed dose estimates for people accidentally exposed to fallout at Rongelap, Sifo, and Utirik Islands from the Pacific weapon test known as Operation Castle BRAVO. The study included: (1) reevaluation of radiochemical analysis, to relate results from pooled urine to intake, retention, and excretion functions; (2) analysis of neutron-irradiation studies of archival soil samples, to estimate areal activities of the iodine isotopes; (3) analysis of source term, weather data, and meteorological functions used in predicting atmospheric diffusion and fallout deposition, to estimate airborne concentrations of the iodine isotopes; and (4) reevaluation of radioactive fallout, which contaminated a Japanese fishing vessel in the vicinity of Rongelap Island on March 1, 1954, to determine fallout components. The conclusions of the acute exposure study were that the population mean thyroid absorbed doses were 21 gray (2100 rad) at Rongelap, 6.7 gray (670 rad) at Sifo, and 2.8 gray (280 rad) at Utirik. The overall thyroid cancer risk we estimated was in agreement with results published on the Japanese exposed at Nagasaki and Hiroshima. We now postulate that the major route for intake of fallout was by direct ingestion of food prepared and consumed outdoors. 66 refs., 13 figs., 25 tabs.

Lessard, E.T.; Miltenberger, R.P.; Conrad, R.A.; Musoline, S.V.; Naidu, J.R.; Moorthy, A.; Schopfer, C.J.

1985-03-01

324

Fundamental measurement of absorbed dose in water for cobalt-60 gamma rays: Procedure and experimental instrumentation  

International Nuclear Information System (INIS)

The work is concerned with the set-up of a new standard expressed in terms of absorbed dose to water, at 5 g·cm-2 depth in a water phantom placed in a cobalt-60 gamma-ray field. The phantom is a parallelepiped with dimensions 30 cm x 30 cm x 20 cm. The irradiator is of the 'Alcyon' type, suitable for cobalt therapy applications. The procedure is based on a transfer method using three suitable dosimetry systems, namely: an ionometric system (using a 0.6 cm3 radiotherapy ionization chamber of the NE 2571 type), a spectrophotometry system based on the Fricke solution, and an ESR spectrometry system based on alanine. These systems are calibrated using the national primary standard of absorbed dose, which is the graphite calorimeter. The dosimetric interpretation of measurement results rests on a strict formalism, dealing in generalized terms with the cavity theory and with the perturbations, inherent to the measurement procedure. (author). 15 refs, 1 fig., 5 tabs

325

The relationship between absorbed dose and T2 in radiation dosimetry polymer gels  

International Nuclear Information System (INIS)

Full text: Changes in spin-spin relaxation times (T2) with absorbed radiation dose form the basis of polymer gel dosimetry. The detailed nature of those changes are still unknown. It is believed that this information will help in the design of new gel dosimeter formulations having desired characteristics. Radiation-sensitive polyacrylamide gels (PAG) were prepared under a nitrogen atmosphere in a glove box and kept in sealed glass vials. The composition of the PAG was acrylamide (AA) 3%, N,N'-methylenebisacrylamide (BIS) 3%, gelatin 5% and water 89%, by weight. The PAGs were irradiated with ?-rays from 60Co in a Gammacell-200. NMR spectroscopy at 300 MHz, FT-Raman spectroscopy and MRI (64 MHz) were used. Three proton pools in fast exchange of magnetization are considered. The mobile pool initially contains protons from water and AA and BIS. As irradiation proceeds, AA and BIS co-polymerize and protons are transferred to the initially empty polymer pool. The third pool contains the gelatin protons and remains unchanged. The amount of protons in the polymer pool is determined with FT-Raman spectroscopy and the amount of monomers remaining was monitored by 1H and 13C NMR spectroscopy. The model closely fits the non-linear variations of T2 (and R2 =1/T2) with absorbed dose. The model presented helps understanding the changes of T2 in PAG dosimeters. Copyright (2000) Australasian Colleters. Copyright (2000) Australasian College of Physical Scientists and Engineers in Medicine

326

Study of Some Factors Affecting the Absorbed Dose From Some Building Materials  

International Nuclear Information System (INIS)

Forty samples from thirteen different types of building materials such as cement, wood, marble, granite, gypsum, brick, sand, ceiling for ceramic, ceramic, iron, aluminum, insulators for water, and paints, were used in Jeddah and analyzer by a gamma spectrometer based on HPGe detector. Concentrations in Bq/kg dry weight for natural radioactivity such as Ra-226 and Th-232 series as well as K-40 and the fall out Cs-137 were measured. Also, the Raeq was determined (Bq/kg) for each sample (370 Bq/kg permissible limit of the dose rate 1.5 m Sv/y). The penetrability of Rn for some samples (cement, marble, granite, gypsum, brick, sand, ceramic, insulators for water) was checked using the equation of Bossew et al. (2003). The exposure and the dose rate one meter above the earth (nGy/h) and annual dose (mGy) were calculated for each sample, as well as the external burden factor (Hex) were checked. The concentrations for all the samples except one ceramic sample and two granite samples were relatively high and gives Raeq higher or around 370 Bq/kg. Also, the high concentrations of 40K in some wood samples (2109 Bq/kg) increases the absorbed dose. The results indicated that all the samples collected from the market used as building materials in Jeddah were safe in general for the radioactivity levels.

327

The absorbed dose to bone marrow in the treatment of polycythaemia by 32P  

International Nuclear Information System (INIS)

Measurements have been made of absorbed dose to bone marrow in the treatment of polycythaemia by 32P, based on the determination of activities in bone and marrow biopsies taken at various times from 1 to 27 days after injection of the radionuclide. Activities were measured in the cortex, trabeculation and marrow of biopsies taken from the iliac crest, and also in sternal marrow. The biological half-life of 32P in marrow from the iliac crest was found to be nine days; that derived for sternal marrow was lower, but the difference was not statistically significant; the value for trabecular bone was 27 days. The biological half life for 32P in the body, as measured by whole-body counting, was 39 days. Calculations of the dose-rate to trabecular marrow have been made by a method based on that of Whitwell and Spiers (1971, Proceedings of the Fifth Congress of the French Society for Radioprotection, Grenoble, France, 401), but modified to allow for the presence of 32P in the marrow as well as in trabecular bone. The dose-rates followed a single exponential decay with a half-life of 6.7 days. The integrated dose including that during the first day was 24 rad per mCi injected. (author)

328

Phantom dosimeters examined by NMR analysis: a promising technique for 3-D determinations of absorbed dose.  

Science.gov (United States)

Fricke-infused agarose gels examined by nuclear magnetic resonance (NMR) analysis are inspected, and their response to gamma-rays, thermal neutrons and protons, at radiotherapy dose levels, is examined. The gel composition is chosen with attention to the tissue equivalence for the radiation fields of interest; this problem is crucial, in particular, for thermal neutrons. The feasibility of three-dimensional determination of absorbed dose in Fricke-gel phantoms is investigated, and the possibility of employing the technique in conformal therapies, such as boron neutron capture therapy (BNCT) and proton therapy, is tested. Isodose curve determination in a cylindrical gel phantom exposed to thermal neutrons is presented. A method for depth-dose profiling in tissue exposed to protons is described, and some results are reported which show that the depth-dose data are determinable with millimetric precision. Results obtained with a spectrophotometer from gel augmented with a metal indicator are reported and discussed also. These results show the possibility of obtaining a very sensitive dosimetry technique consisting of spectrophotometric analysis of such a Fricke-gel. PMID:9463873

Gambarini, G; Monti, D; Fumagalli, M L; Birattari, C; Salvadori, P

1997-01-01

329

Ferrous sulphate polyvinyl alcohol MRI gel dosimeter: the manufacture and absorbed dose relaxation characteristics  

International Nuclear Information System (INIS)

Full text: Polyvinyl alcohol (PVA) gel has promising properties as a gelling agent in magnetic resonance imaging (MRI) ferrous sulphate gel dosimetry. It has been found to have a lower ferrous auto-oxidisation rate at room temperature compared with other gelling agents while maintaining a linear dose response and high sensitivity. Owing to the cross-linked PVA gel matrix produced through single or multiple freezing cycles, molecules and ions dissolved in the gel have a low diffusion coefficient. The aim of this study was to develop a reproducible bench-top manufacturing method for a ferrous sulphate polyvinyl alcohol MRI gel dosimeter and to examine the 1/T1 and 1/T2 nuclear magnetic resonance (NMR) relaxation rate response for an absorbed dose range up to 20 Gy. Three methods were investigated. Method (1) consisted of a single freezing at -18 deg C, the 20% PVA + 0.4 mM ferrous sulphate solution was then thawed before irradiation and MRI measurement (Siemens Vision, 1.5 T). Method (2) included a two-cycle freeze to enhance the extent of cross-linking in the PVA. Method (3) included re-oxygenation of the gel prior to freezing cycle to replace 02 evaporated off during heating. The dose response curves, 1/T1 versus absorbed dose from O to 20 Gy were linear and the range of sensitivity was 0.021 to 0.034 s-1/Gy. Method (1) was found to result in a dose response similar to previously reported results, slope 0.021 s-1/Gy. Our results indicate that method (2) produced a gel with a higher sensitivity compared to method (1). An increased extent of cross-linking in the PVA was also observed. Re-introduction of O2 into the gel prior to freezing increases the sensitivity. The results of the 1/T2 studies provided initial data suggesting that the T2 was of the order of 50 ms. We are currently investigating 1/T2 dose responses with NMR (300 MHz) to access details of the relaxation mechanisms of both PVA and water in the gel. The advantage demonstrated by this gel and the associated methods is ease of manufacture compared to previous publications while maintaining similar sensitivities. Further, the produced gels are suitable for storage in the freezer until required for use. Copyright (2000) Australasian College of Physical Scientists and Engineers in Medicine

330

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

International Nuclear Information System (INIS)

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

331

Absorbed dose rates in air due to U, Th and K in soils in parts of South-Western Nigeria  

International Nuclear Information System (INIS)

The absorbed dose rates in air due to the presence of radioisotopes 40K, 238U and 252Th in soils in Ondo State, South Western Nigeria have been determined by first estimating the concentration of these radionuclides in the soils of the area. The concentrations of the radionuclide were measured using a multichannel pulse-height analyser connected to a 7.6 cm. x 7.6 cm. NaI(TI) detector and by the use of appropriate conversion factors, the absorbed dose rates in air, at a height of 1.0 m. above the ground were computed from the concentrations. The concentrations of the radioisotopes are expressed in BqKg1 of dry weight and the corresponding absorbed dose rates in air are expressed in nGyh-1 with mean of the acceptable International Commission on Radiological Protection (ICRP) dose limit

332

VALIDATION OF A MOSFET DOSEMETER SYSTEM FOR DETERMINING THE ABSORBED AND EFFECTIVE RADIATION DOSES IN DIAGNOSTIC RADIOLOGY.  

Science.gov (United States)

This study aimed to validate a MOSFET dosemeter system for determining absorbed and effective doses (EDs) in the dose and energy range used in diagnostic radiology. Energy dependence, dose linearity and repeatability of the dosemeter were examined. The absorbed doses (ADs) were compared at anterior-posterior projection and the EDs were determined at posterior-anterior, anterior-posterior and lateral projections of thoracic imaging using an anthropomorphic phantom. The radiation exposures were made using digital radiography systems. This study revealed that the MOSFET system with high sensitivity bias supply set-up is sufficiently accurate for AD and ED determination. The dosemeter is recommended to be calibrated for energies 80 kVp. The entrance skin dose level should be at least 5 mGy to minimise the deviation of the individual dosemeter dose. For ED determination, dosemeters should be implanted perpendicular to the surface of the phantom to prevent the angular dependence error. PMID:25213263

Manninen, A-L; Kotiaho, A; Nikkinen, J; Nieminen, M T

2014-09-11

333

Absorbed radiation dose of the female breast during diagnostic multidetector chest CT and dose reduction with a tungsten-antimony composite breast shield: preliminary results  

International Nuclear Information System (INIS)

Aim: To determine the absorbed radiation dose to the female breast during chest computed tomography (CT), and whether a custom-designed breast shield can reduce that dose. Materials and methods: Bilateral breast phantoms were combined with an anthropomorphic torso phantom. Each breast phantom contained 20 thermoluminescent dosimeter (TLD) cavities. Eight cavities were used per phantom. Absorbed radiation was measured using TLD 100s. Three-stacked TLDs comprised a set. Three sets of three TLDs were positioned at eight designated locations and three depths (surface; 1 cm; 4 cm). One set of three TLDs was positioned at eight additional designations, 1 cm deep. Each breast was divided anatomically into quadrants. In total, 32 TLD sets/96 TLDs were deployed. The breast-torso phantom was consecutively imaged using a 16-detector array CT machine. Subsequently, 32 new TLD sets were similarly placed, the phantom re-imaged in a likewise manner, but with the application of a tungsten-antimony composite breast shield. TLD readings were averaged and calculated. Results: Average absorbed radiation doses for unshielded right and left breast phantoms ranged from 13.83-19.36 mGy, and 14-20.47 mGy, respectively. The absorbed dose in the shielded right and left breast was reduced to 6.64-8.12 mGy, and 6.7-8.03 mGy, respectively. Average absorbed radiation doses based on the depth for the unshielded breasts ranged from 15.4-18.3 mGy. Shielding reduced this dose to 7-7.9 mGy. Unshielded aduced this dose to 7-7.9 mGy. Unshielded absorbed radiation doses based on anatomic quadrants ranged from 17.5-18.9 mGy. Shielding reduced this dose to 7-7.5 mGy. Conclusions: The average absorbed radiation dose to the unshielded female breast phantom is approximately 14-20 mGy. An externally applied shield can reduce this absorbed dose by 56-61%

334

Reconstruction of absorbed dose by methods biological dosimetry inhabitans living in Semipalatinsk Nuclear Test Site  

International Nuclear Information System (INIS)

As a result perennial overland and atmospheric test the nucleus weapon on Semipalatinsk nucler test site (NTS) about 1,2 ml person were subjected to frequentative sharp and chronic irradiation in different range of doses. Besides a significant number of battle radioactive matters tests with radionuclei dispersion on soil surface and an atmosphere was realized also. All this activity has caused the significant radioactive contamination and damage to an environment, and the local population has received extra exposure to radiation. These circumstances have essentially complicated the economy development of the given region. Aim: Reconstruction of absorbed dose by modern methods biological dosimetry beside inhabitants living in region of influence Semipalatinsk NTS. The cytogenetically examination of population Semipalatinsk region, living in different zones radiation risk: s. Dolon, s. Sarzhal, s. Mostik. Installed that total frequency of chromosome aberrations forms 4,8/100; 2,1/100; 2,5/100 cells, accordingly. High level of chromosome aberrations is conditioned to account radiations markers - acentric fragments (2,1/100 cells in s. Dolon; 1,09/100 cells in s. Sarzhal; 0,79/100 cells in s. Mostik); dysenteric and ring chromosomes (0,6; 0,2; 0,11) and stable type chromosome aberrations (1,02; 0,3; 1,0, accordingly). Frequency and spectrum of chromosome aberrations are indicative of significant mutation action ionizing radiations on chromosome device of somatic cells. St on chromosome device of somatic cells. Studied dependency an cytogenetically of effects from dose of irradiation within before 0,5 Gr in vitro for calibrated curve standard when undertaking reconstruction efficient dose at the time of irradiations examined group of population. Dependency is described the model a*cos(x) 1 + sin (x), where x - correlation a dysenteric and ring chromosomes to acentric fragments. Dependence of cytogenetic parameters upon ESR-doses had been studied. Had been received dependences: for the total frequency of chromosomal aberrations a+b*cos(x)+c*sin(x), for acentric fragments and the sum of change aberrations - a*cos(x)+b*sin(x). Organized molecular-cytogenetically analysis (FISH), are used DNK-probe specific to chromosomes 1, 4 and 12. Analyzed 18500 metaphases. Frequency translocations on under investigation group has formed 0,14 on 100 metaphases. Share genomes has formed 19,2% ] (8,3+6,4+4,5). Frequency translocations on gene has formed - 0,45 on 100 cells. Cellular equivalent beside group of population p. Sarzhal is 318. Equivalent genome is 3,55. Organized reconstruction of absorbed dose with use the equation a regression, which is of the form of: y=0,0023+0,0067x+0,0017x2. Average absorbed dose has formed on group of population 2,8 Gr.

335

Absorbed dose measurements for kV-cone beam computed tomography in image-guided radiation therapy  

Science.gov (United States)

In this study, we develope a novel method to directly evaluate an absorbed dose-to-water for kilovoltage-cone beam computed tomography (kV-CBCT) in image-guided radiation therapy (IGRT). Absorbed doses for the kV-CBCT systems of the Varian On-Board Imager (OBI) and the Elekta X-ray Volumetric Imager (XVI) were measured by a Farmer ionization chamber with a 60Co calibration factor. The chamber measurements were performed at the center and four peripheral points in body-type (30?cm diameter and 51?cm length) and head-type (16?cm diameter and 33?cm length) cylindrical water phantoms. The measured ionization was converted to the absorbed dose-to-water by using a 60Co calibration factor and a Monte Carlo (MC)-calculated beam quality conversion factor, kQ, for 60Co to kV-CBCT. The irradiation for OBI and XVI was performed with pelvis and head modes for the body- and the head-type phantoms, respectively. In addition, the dose distributions in the phantom for both kV-CBCT systems were calculated with MC method and were compared with measured values. The MC-calculated doses were calibrated at the center in the water phantom and compared with measured doses at four peripheral points. The measured absorbed doses at the center in the body-type phantom were 1.96?cGy for OBI and 0.83?cGy for XVI. The peripheral doses were 2.36–2.90?cGy for OBI and 0.83–1.06?cGy for XVI. The doses for XVI were lower up to approximately one-third of those for OBI. Similarly, the measured doses at the center in the head-type phantom were 0.48?cGy for OBI and 0.21?cGy for XVI. The peripheral doses were 0.26–0.66?cGy for OBI and 0.16–0.30?cGy for XVI. The calculated peripheral doses agreed within 3% in the pelvis mode and within 4% in the head mode with measured doses for both kV-CBCT systems. In addition, the absorbed dose determined in this study was approximately 4% lower than that in TG-61 but the absorbed dose by both methods was in agreement within their combined uncertainty. This method is more robust and accurate compared to the dosimetry based on a conventional air-kerma calibration factor. Therefore, it is possible to be used as a standard dosimetry protocol for kV-CBCT in IGRT.

Hioki, Kazunari; Araki, Fujio; Ohno, Takeshi; Nakaguchi, Yuji; Tomiyama, Yuuki

2014-12-01

336

Evaluation of absorbed dose-distribution in the X-ray or gamma-irradiator for blood products  

Energy Technology Data Exchange (ETDEWEB)

Irradiation of blood products abrogates the proliferation of lymphocytes present in cellular component, which is currently the only accepted methodology to prevent transfusion-associated graft versus host disease (TA-GVHD). A range of irradiation dose levels between 15 Gy and 50 Gy is being used, but the majority of facilities are employing 15 Gy. It should, however, be recognized that the delivered dose in the instrument canister might differ from the actual dose absorbed by the blood bag. This study have evaluated the actual dose distribution under practical conditions where a container was loaded with blood products or water bags, or filled with distilled water. This approach provides data that the maximum attenuation occurred when the container was completely filled with a blood-compatible material. Thus, an error of approximately 20 percent should be considered in the dose measured in the in-air condition. A dose calibration in an in-air condition may lead to substantial underexposure of the blood products. A dose distribution study using adequately prearranged exposure period verified that the absorbed dose of 15 Gy was attained at any point in the container for both linear accelerator and gamma-irradiator. The maximal difference in the absorbed dose between measured points was 1.5- and 1.6-fold for linear accelerator and gamma-irradiator, respectively. In conclusion, using blood-compatible materials, a careful dose calibration study should be employed in which the absorbed dose of 15 Gy is obtained at the point where the lowest dose could be expected. (author)

Moriyama, Satoshi; Kurihara, Katsuhiko; Yokokawa, Nobuhiko; Satake, Masahiro; Juji, Takeo [Japanese Red Cross Central Blood Center, Tokyo (Japan)

2001-04-01

337

A Feasibility Study of Fricke Dosimetry as an Absorbed Dose to Water Standard for 192Ir HDR Sources  

Science.gov (United States)

High dose rate brachytherapy (HDR) using 192Ir sources is well accepted as an important treatment option and thus requires an accurate dosimetry standard. However, a dosimetry standard for the direct measurement of the absolute dose to water for this particular source type is currently not available. An improved standard for the absorbed dose to water based on Fricke dosimetry of HDR 192Ir brachytherapy sources is presented in this study. The main goal of this paper is to demonstrate the potential usefulness of the Fricke dosimetry technique for the standardization of the quantity absorbed dose to water for 192Ir sources. A molded, double-walled, spherical vessel for water containing the Fricke solution was constructed based on the Fricke system. The authors measured the absorbed dose to water and compared it with the doses calculated using the AAPM TG-43 report. The overall combined uncertainty associated with the measurements using Fricke dosimetry was 1.4% for k?=?1, which is better than the uncertainties reported in previous studies. These results are promising; hence, the use of Fricke dosimetry to measure the absorbed dose to water as a standard for HDR 192Ir may be possible in the future. PMID:25521914

deAlmeida, Carlos Eduardo; Ochoa, Ricardo; de Lima, Marilene Coelho; David, Mariano Gazineu; Pires, Evandro Jesus; Peixoto, José Guilherme; Salata, Camila; Bernal, Mario Antônio

2014-01-01

338

Comparison of skin absorbed radiation dose in thyroid gland area during panoramic radiography and spiral tomography techniques  

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Full Text Available Introduction: Thyroid gland is one of the critical organs during radiation in the head and neck region. The aim of this study was to compare absorbed radiation dose by skin in the thyroid area during spiral tomography and panoramic radiography by means of thermoluminance dosimetry (TLD.Materials and Methods: Thirty-six LiF (TLD-100 thermoluminescence dosimetry chips were utilized in this experimental in vitro study. One TLD chip was placed on the tube side and another was placed on the opposite side of the thyroid gland of a sliced anatomic Alderson head and neck phantom during panoramic radiography and spiral tomography. The dosimeters were read by a SOLARO 2A TLD reader twice followed by calculation of the absorbed dose. The results were analyzed by Wilcoxon’s test at a confidence interval of 95%.Results: The mean dose for screen-film panoramic radiographs was 34 µGy in the left thyroid and 39 on the right side. With spiral tomography the thyroid gland received a mean dose of 30?71 µGy. There were no statistically significant differences in the mean thyroid doses between anterior and posterior spiral tomography and panoramic examination (p value > 0.05.Conclusion: Skin absorbed radiation dose of a tomographic examination, which includes four sections with a specific thickness, are almost comparable to that with a panoramic radiographic technique. Key words: Absorbed dose, Spiral tomography, Panoramic radiography.

Najmeh Akhlaghi

2011-01-01

339

Measurements of spatial distribution of absorbed dose in proton therapy with Gafchromic EBT3  

Energy Technology Data Exchange (ETDEWEB)

A study of the response of EBT3 films has been carried out. Light transmittance images (around 630 nm) were acquired by means of a Ccd camera. The difference of optical density was assumed as dosimeter response. Calibration was performed by means of {sup 60}Co photons, at a radiotherapy facility. A study of the response variation during the time after exposure has been carried out. EBT3 films were exposed, in a solid-water phantom, to proton beams of various energies and the obtained depth-dose profiles were compared with those measured with a ionization chamber. As expected, in the Bragg peak region the values obtained with EBT3 films were lower than those obtained with the ionization chamber. The ratio of such values was evaluated, along dose profiles, for each utilized energy. A method for correcting the data measured with EBT3 has been proposed and tested. The results confirm that the method can be advantageously applied for obtaining spatial distribution of the absorbed dose in proton therapy. (author)

Gambarini, G.; Regazzoni, V.; Grisotto, S.; Artuso, E.; Giove, D. [Universita degli Studi di Milano, Department of Physics, via Celoria 16, 20133 Milano (Italy); Borroni, M.; Carrara, M.; Pignoli, E. [Fondazione IRCCS, Istituto Nazionale dei Tumori di Milano, Medical Physics Unit, via Giacomo Venezian 16, 20133 Milano (Italy); Mirandola, A.; Ciocca, M., E-mail: grazia.gambarini@mi.infn.it [Centro Nazionale Adroterapia Oncologica, Medical Physics Unit, Strada Campeggi 53, 27100 Pavia (Italy)

2014-08-15

340

Measurements of spatial distribution of absorbed dose in proton therapy with Gafchromic EBT3  

International Nuclear Information System (INIS)

A study of the response of EBT3 films has been carried out. Light transmittance images (around 630 nm) were acquired by means of a Ccd camera. The difference of optical density was assumed as dosimeter response. Calibration was performed by means of 60Co photons, at a radiotherapy facility. A study of the response variation during the time after exposure has been carried out. EBT3 films were exposed, in a solid-water phantom, to proton beams of various energies and the obtained depth-dose profiles were compared with those measured with a ionization chamber. As expected, in the Bragg peak region the values obtained with EBT3 films were lower than those obtained with the ionization chamber. The ratio of such values was evaluated, along dose profiles, for each utilized energy. A method for correcting the data measured with EBT3 has been proposed and tested. The results confirm that the method can be advantageously applied for obtaining spatial distribution of the absorbed dose in proton therapy. (author)

 
 
 
 
341

An assessment of absorbed dose and radiation hazard index from natural radioactivity  

International Nuclear Information System (INIS)

Naturally occurring radionuclides such as 40K, 226Ra and 228Ra which emit gamma radiation through their decaying process could reach the human in vicinity. The study area was chosen for its variety of surface conditions such as slope, flat land catchments and also forest area, which is used as a reference place. Soil samples were collected using hand auger, and the sampling positions were determined using a Global Positioning System (GPS). The amount of radioactivity concentration of these radionuclides is the important factor in assessing whether it is harmful or otherwise. In this study, the surface doses rate measurements were done in-situ using dose rate meter, and the radioactivity concentration levels were done by counting the soil samples using gamma spectrometer with HPGe detector in the laboratory. The amount of uranium, thorium and potassium in soil were determined using neutron activation analysis (NAA) technique. The results show a reasonably low radiation absorb dose and radiation hazard index, which is a good indication for the farmers to work in the area. (author)

342

Verification of absorbed dose calculation with XIO Radiotherapy Treatment Planning System  

International Nuclear Information System (INIS)

Modern radiotherapy relies on computerized treatment planning systems (TPS) for absorbed dose calculation. Most TPS require a detailed model of a given machine and therapy beams. International Atomic Energy Agency (IAEA) recommends acceptance testing for the TPS (IAEA-TECDOC-1540). In this study we present customization of those tests for measurements with the purpose of verification of beam models intended for clinical use in our department. Elekta Synergy S linear accelerator installation and data acquisition for Elekta CMS XiO 4.62 TPS was finished in 2011. After the completion of beam modelling in TPS, tests were conducted in accordance with the IAEA protocol for TPS dose calculation verification. The deviations between the measured and calculated dose were recorded for 854 points and 11 groups of tests in a homogenous phantom. Most of the deviations were within tolerance. Similar to previously published results, results for irregular L shaped field and asymmetric wedged fields were out of tolerance for certain groups of points.(author)

343

Absorbed dose distributions in a tissue-equivalent absorber for Bremsstrahlung produced at the beamlines of the European Synchrotron Radiation Facility  

CERN Document Server

The absorbed-dose distributions for Bremsstrahlung, incident on a tissue-equivalent phantom, were measured with LiF : Mg,Ti thermoluminescent dosimeters at two insertion device beamlines of the European Synchrotron Radiation Facility (ESRF). The measurements were carried out for two different electron beam energies of 4 and 6 GeV. The corresponding Bremsstrahlung spectra and power were measured using a high-resolution lead glass total absorption calorimeter. The results are compared with similar measurements carried out at other facilities. The normalized Bremsstrahlung absorbed dose in a cross-sectional area of 100 mm sup sup 2 , at a depth of 150 mm of the phantom, was measured as 6.1 and 3.6 kGy h sup sup - sup sup 1 W sup sup - sup sup 1 for the corresponding Bremsstrahlung spectra of 4 and 6 GeV.

Pisharody, M; Berkvens, P; Colomp, P

2000-01-01

344

Results of photon absorbed-dose measurements using the AAPM TG-21 protocol for accelerating potentials up to 26 MV  

International Nuclear Information System (INIS)

The AAPM Task Group 21 protocol for the calibration of high-energy photon and electron beams was produced to accomplish essentially two goals: (1) incorporate the latest physical data available for calculating absorbed dose from ionization measurements and (2) to eliminate inconsistencies in absorbed dose measurements made with various ion chamber and phantom combinations. The ability of the protocol was assessed to consistently determine x-ray absorbed dose from measurements made with four Farmer-type chambers and one parallel-plate chamber in water, polystyrene, and acrylic phantoms. The measurements were performed using seven high-energy x-ray beams from 60Co to 26-MV nominal accelerating potential. The absorbed dose to water calculated from measurements made with the various chamber and phantom combinations were found to be consistent. The doses calculated for the two most common phantom materials, water and polystyrene, were found to be in excellent agreement. This resolved a 1.6% discrepancy in the absorbed dose determined from the two phantoms using the SCRAD protocol. The doses for acrylic phantoms were found to be approximately 1.2%, low for nominal accelerating potentials less than 8.8 MV. For accelerating potentials of 8.8 MV or greater the agreement was considerably better. The mean dose determined for the parallel-plate chamber from measurements in polystyrene was found to be within 0.7% of the mean dose determined using Farmer-type ion chambere determined using Farmer-type ion chambers in all phantom materials

345

Radioactive caesium in a boreal forest ecosystem and internally absorbed dose to man  

International Nuclear Information System (INIS)

Different aspects dealing with water-soil, soil-plant and plant-herbivore interactions are studied. The study area is located to the Forest Research Station at Svartberget 50 km west of Umea in Vaesterbotten. An important topic in this study concerns the transport of caesium in food chains to man. Consumption of forest products by man i.e. game (primarily moose) and berries constitutes the major pathway of radioactive caesium to man. Moose meat contributes to about 30% of the total meat consumption in Vaesterbotten and the average over the Swedish population has remained at the level of 5-10% during the present decade. In order to assess the absorbed dose resulting from intake via these food products over a long period of time, knowledge about the long term behaviour of caesium in the biotic community is studied. (orig./HP)

346

Traceability of metrologic references of dose absorbed to water used in a Dosimetry Quality Assurance Program  

International Nuclear Information System (INIS)

Objective: to present the solidly established traceability structure for ionometric standards and for thermoluminescent dosimetry system that ensures reliability of the Dosimetry Quality Assurance Program and is aimed to certify the highest level of accuracy of the measurements. Materials and methods: thermoluminescent powder dosimeters (DTL 937) placed into plastic capsules and packed in specific kits for each intended application were mailed to the participant centers. Results: the results of the intercomparisons performed between 'Laboratorio de Ciencias Radiologicas da Universidade do Estado do Rio de Janeiro' and EQUAL-ESTRO for the beam of 60Co gamma rays, expressed for (1?), and the results of the dose absorbed measurements obtained with the chambers of the Program EQUAL and the chambers of the Dosimetry Quality Assurance Program were lower than 0.5%. Conclusion: based on these results we concluded that the Dosimetry Quality Assurance Program reached the desired level of reliability to allow its implementation. (author)

347

Response functions for computing absorbed dose to skeletal tissues from neutron irradiation  

International Nuclear Information System (INIS)

Spongiosa in the adult human skeleton consists of three tissues-active marrow (AM), inactive marrow (IM) and trabecularized mineral bone (TB). AM is considered to be the target tissue for assessment of both long-term leukemia risk and acute marrow toxicity following radiation exposure. The total shallow marrow (TM50), defined as all tissues lying within the first 50 ?m of the bone surfaces, is considered to be the radiation target tissue of relevance for radiogenic bone cancer induction. For irradiation by sources external to the body, kerma to homogeneous spongiosa has been used as a surrogate for absorbed dose to both of these tissues, as direct dose calculations are not possible using computational phantoms with homogenized spongiosa. Recent micro-CT imaging of a 40 year old male cadaver has allowed for the accurate modeling of the fine microscopic structure of spongiosa in many regions of the adult skeleton (Hough et al 2011 Phys. Med. Biol. 56 2309-46). This microstructure, along with associated masses and tissue compositions, was used to compute specific absorbed fraction (SAF) values for protons originating in axial and appendicular bone sites (Jokisch et al 2011 Phys. Med. Biol. 56 6857-72). These proton SAFs, bone masses, tissue compositions and proton production cross sections, were subsequently used to construct neutron dose-response functions (DRFs) for both AM and TM50 targets in each bone of the reference adult male. Kerma conditio the reference adult male. Kerma conditions were assumed for other resultant charged particles. For comparison, AM, TM50 and spongiosa kerma coefficients were also calculated. At low incident neutron energies, AM kerma coefficients for neutrons correlate well with values of the AM DRF, while total marrow (TM) kerma coefficients correlate well with values of the TM50 DRF. At high incident neutron energies, all kerma coefficients and DRFs tend to converge as charged-particle equilibrium is established across the bone site. In the range of 10 eV to 100 MeV, substantial differences are observed among the kerma coefficients and DRF. As a result, it is recommended that the AM kerma coefficient be used to estimate the AM DRF, and that the TM kerma coefficient be used to estimate the TM50 DRF below 10 eV. Between 10 eV and 100 MeV, the appropriate DRF should be used as presented in this study. Above 100 MeV, spongiosa kerma coefficients apply well for estimating skeletal tissue doses. DRF values for each bone site as a function of energy are provided in an electronic annex to this article available at http://stacks.iop.org/0031-9155/56/6873/mmedia.

348

Absorbed dose in ion beams: comparison of ionisation- and fluence-based measurements  

International Nuclear Information System (INIS)

A direct comparison measurement of fluorescent nuclear track detectors (FNTDs) and a thimble ionisation chamber is presented. Irradiations were performed using monoenergetic protons (142.66 MeV, ?=3x106 cm-2) and carbon ions (270.55 MeV u-1, ?=3x106 cm-2). It was found that absorbed dose to water values as determined by fluence measurements using FNTDs are, in case of protons, in good agreement (2.4 %) with ionisation chamber measurements, if slower protons and Helium secondaries were accounted for by an effective stopping power. For carbon, however, a significant discrepancy of 4.5 % was seen, which could not be explained by fragmentation, uncertainties or experimental design. The results rather suggest a W-value of 32.10 eV±2.6 %. Additionally, the abundance of secondary protons expected from Monte-Carlo transport simulation was not observed. FNTDs are able to yield correct dose estimation for protons. The assumption of a monoenergetic beam, even in the entrance channel, is invalid since slower protons and secondaries contribute significantly and an effective stopping power has to be employed. These corrections account for the discrepancies seen in the authors' previous experiments. Since the FNTD fluorescent track amplitude depends on the particle species and energy, the effective stopping power might be estimated from the intensity histogram of the particle tracks. For carbon ions, however, secondary particles did not fully account for the discrepancies found. Considering the detection efficiency of FNTD technology, it seems unlikely that a significant portion of tracks were not registered. This might stimulate discussions on the accuracy of the kQ,Q0 factor for carbon beams. Since the stopping power in this energy range is known quite accurately (1-2 %), one might question the currently used constant Wair value of 34.50 ± 0.52 eV (1.5 %)(14). The presented findings would imply a Wair value of 32.10±0.83 eV (2.6 %). This uncertainty includes all conceivable sources of errors including sFNTD, sFC and sTRS (except for the uncertainties given for long-term stability of user dosemeter, establishment of reference conditions, dosemeter reading relative to beam monitor and beam quality correction). More conclusive results are expected from absolute dose to water measurements in a carbon ion beam with a water calorimeter, which would allow to directly calibrate ionisation chambers in units of absorbed dose to water without applying radiation-field-dependent correction factors. (authors)

349

Determination of human absorbed dose of 201Tl(III)-DTPA-HIgG based on biodistribution data in rats  

International Nuclear Information System (INIS)

To estimate the absorbed dose in normal organs and inflamed tissue following i.v. administration of [201Tl](III)-DTPA-HIgG by using biodistribution data in inflammation-bearing rats was attempted. The percentages of injected dose per gram of each organ were calculated. The medical internal radiation dose formulation was applied to calculate the absorbed dose for various organs. The inflamed tissue to blood activity concentration ratios were about 19 and 23.3 at 24 and 28 h post-injection, respectively. A 185-MBq injection of 201Tl-DTPA-HIgG into the human body, might result in an estimated absorbed dose of 14.4 mGy for the total body and the highest absorbed dose was in the kidney with 1195 (mGy) and second to the Spleen were the liver, the lungs and the adrenals, which received 250.5 (mGy), 58.64 (mGy) and 56.44 (mGy), respectively. Biodistribution of [201Tl](III)-DTPA-HIgG demonstrated significant inflamed tissue uptake and low muscle and blood uptake, allowing for imaging of inflamed tissues. (authors)

350

Thermoluminescence-dosimetry (TLD) systems for determining absorbed dose in radiation-hardness testing of electronic devices  

International Nuclear Information System (INIS)

The practice covers procedures for the use of thermoluminescence dosimeters to determine the absorbed dose in a material irradiated by ionizing radiation. The specific area of concern is radiation-hardness testing of electronic devices in which the material of interest is usually silicon. The practice is applicable to the measurement of absorbed dose in materials irradiated by gamma rays, x rays, and electrons of energies up to 60 MeV. The range of absorbed dose covered is approximately from 10-2 to 104 Gy (1 to 1012 rad/s). The practice includes a discussion of apparatus, handling and readout procedures, requirements for performance testing, performance tests and correction factors, calibration, monitoring, and reporting results. Appendixes cover recommended procedures for application of CaF2:Mn CHIPS, energy absorption coefficients and collision stopping powers, electron equilibrium thickness, and determination of test sample size

351

Dosimetry audits based on NCS report 18: Assessment of absorbed dose to water in external beam therapy  

International Nuclear Information System (INIS)

In 2008 the Netherlands Commission for Radiation Dosimetry (NCS) published a new code of practice (NCS-18) for the absorbed dose determination in high energy photon and electron beams. NCS-18 replaces NCS-2 and NCS-5 for absolute dosimetry of clinical photon and electron beams, respectively. In contrast to NCS-2 and -5, it is based on absorbed dose to water calibration coefficients in 60Co beams. Most radiotherapy centres in Belgium and the Netherlands are currently implementing NCS-18. To monitor and verify the implementation of NCS-18, the Dutch Association of Medical Physics Engineers (NVKFM) in collaboration with the NCS established the NCS-subcommittee Dosimetry Audits. The aim of the audit is to verify local measurements of absorbed dose under reference conditions. Initially only clinical photon beams are being audited. In total 26 radiotherapy centres have been audited before the summer of 2010. In this study preliminary results of the audits until April 2010 are reported

352

Effect of some radio-modifying preparations on the doses absorbed by the thyroid glands in orally introduced iodine-131  

International Nuclear Information System (INIS)

In order to estimate the reduction dose rates of J131 absorbed by thyroid glands after preliminary administration of several chemical protectors, the experiments on 210 male Wistar rats were carried out. The protectors AET, VVR-2721, cysteamine hydrochloride, serotonin, creatine sulfate and Adeturon were applied intraperitoneally and after different periods of time J131 was introduced via stomach sounding . The results were shown as measured absorbed doses as well as calculated thyroid gland protection coefficients (PC). In all cases a sharp reduction of the absorbed doses in the first minutes after applications was found. The maximum PC of about 50-55% for serotonin, cysteamine and VVR-2721 was obtained. The protection effect gradually died down in the longer periods of time and practically it was missing in all cases in the 24th hour. The protection effect of radioprotectors was evaluated as unessential even in the most favourable cases

353

Optimal photon energies with respect to absorbed dose for visualization of soft tissue masses within adipose tissue  

International Nuclear Information System (INIS)

The photon energies which maximize the signal to noise ratio per unit absorbed dose (optimal photon energies) have been calculated for detection of soft tissue masses within adipose tissue 3-- 15 cm thick. The detection task simulates mammography in women with fatty breasts. Ideal, plain film and calcium tungstate screen--film systems were considered in the analysis. Net photographic density is not incorporated into this model; therefore, the optimal photon energy with respect to the signal to noise ratio per unit absorbed dose may not be the same as the photon energy which results in maximum film density per unit absorbed dose. Therefore, the model has limited applicability to film or screen--film systems. However, it is directly applicable to digital systems where brightness and contrast can be adjusted

354

Absorbed doses profiles vs Synovia tissue depth for the Y-90 and P-32 used in radiosynoviortesis treatment  

International Nuclear Information System (INIS)

The radiosynoviortesis treatment has been used during more of 40 years as an alternative to the chemical and surgical synovectomy to alleviate the pain and to reduce the inflammation in suffered patients of rheumatic arthropathies, haemophilic arthropathies and other articulation disorders. It consists on the injection of radioactive isotopes inside a synovial cavity. For to evaluate the dosimetry of the radiosynoviortesis treatment is of great interest to know the absorbed dose in the volume of the target (synovia). The precise calculation of the absorbed dose in the inflamed synovia it is difficult, for numerous reasons, since the same one will depend on the thickness of the synovial membrane, the size of the articular space, the structure of the synovial membrane, the distribution in the articulation, the nature of the articular liquid, etc. Also the presence of the bone and the articular cartilage, components also of the articulation, it even complicated more the calculations. The method used to evaluate the dosimetry in radioactive synovectomy is known as the Monte Carlo method. The objective of our work consists on estimating with the Monte Carlo code MCNP4B the absorbed dose of the Y-90 and the P-32 in the depth of the synovial tissue. The results are presented as absorbed dose for injected millicurie (Gy/mCi) versus depth of synovial tissue. The simulation one carries out keeping in mind several synovia areas, of 50 cm2 to 250 cm2 keeping in mind three states of progression of the illness. Those obtained values of absorbed dose using the MCNP4B code will allow to introduce in our country an optimized method of dose prescription to the patient, to treat the rheumatic arthritis in medium and big articulations using the Y-90 and the P-32, eliminating the fixed doses and fixed radionuclides for each articulation like it happens in many clinics of Europe, as well as the empiric doses. (Author)

355

Secondary absorbed doses from light ion irradiation in anthropomorphic phantoms representing an adult male and a 10 year old child  

International Nuclear Information System (INIS)

Secondary organ absorbed doses were calculated by Monte Carlo simulations with the SHIELD-HIT07 code coupled with the mathematical anthropomorphic phantoms CHILD-HIT and ADAM-HIT. The simulated irradiations were performed with primary 1H, 4He, 7Li, 12C and 16O ion beams in the energy range 100-400 MeV/u which were directly impinging on the phantoms, i.e. approximating scanned beams, and with a simplified beamline for 12C irradiation. The evaluated absorbed doses to the out-of-field organs were in the range 10-6 to 10-1 mGy per target Gy and with standard deviations 0.5-20%. While the contribution to the organ absorbed doses from secondary neutrons dominated in the ion beams of low atomic number Z, the produced charged fragments and their subsequent charged secondaries of higher generations became increasingly important for the secondary dose delivery as Z of the primary ions increased. As compared to the simulated scanned 12C ion beam, the implementation of a simplified beamline for prostate irradiation with 12C ions resulted in an increase of 2-50 times in the organ absorbed doses depending on the distance from the target volume. Comparison of secondary organ absorbed doses delivered by 1H and 12C beams showed smaller differences when the RBE for local tumor control of the ions was considered and normalization to the RBE-weighted dose to normalization to the RBE-weighted dose to the target was performed.

356

Long-term stability of liquid ionization chambers with regard to their qualification as local reference dosimeters for low dose-rate absorbed dose measurements in water  

International Nuclear Information System (INIS)

The long-term sensitivity and calibration stability of liquid ionization chambers (LICs) has been studied at a local and a secondary standards dosimetry laboratory over a period of 3 years. The chambers were transported several times by mail between the two laboratories for measurements. The LICs used in this work are designed for absorbed dose measurements in the dose rate region of 0.1-100 mGy min-1 and have a liquid layer thickness of 1 mm and a sensitive volume of 16.2 mm3. The liquids used as sensitive media in the chambers are mixtures of isooctane (C8H18) and tetramethylsilane (Si(CH3)4) in different proportions (about 2 to 1). Operating at a polarizing voltage of 300 V the leakage current of the chambers was stable and never exceeded 3% of the observable current at a dose rate of about 1 mGy min-1. The volume sensitivity of the chambers was measured to be of the order of 10-9 C Gy-1 mm-3. No systematic changes in the absorbed dose to water calibration was observed for any of the chambers during the test period (?<0.2%). Variations in chamber dose response with small changes in the polarizing voltage as well as sensitivity changes with accumulated absorbed dose were also investigated. Measurements showed that the LIC response varies by 0.15% per 1% change in applied voltage around 300 V. No significant change could be observed in the LIC sensitivity afuld be observed in the LIC sensitivity after a single absorbed dose of 15 kGy. The results indicate that the LIC can be made to serve as a calibration transfer instrument and a reference detector for absorbed dose to water determinations providing good precision and long-term reproducibility. (author)

357

Some views concerning the absorbed dose in the gamma-ray irradiation of traditional Chinese medicines and staple crops  

Energy Technology Data Exchange (ETDEWEB)

Several problems concerning the computation of absorbed dose from ionizing photon interactions with different organic materials have been studied. The mass energy-absorption coefficients for several traditional Chinese medicines and staple crops are reported. The linear relation between the percent by weight of hydrogen in animal and plant tissues and other organic materials and the mass energy-absorption coefficients values are tabulated, with a correlation coefficient 0.9999. The elemental constituents in organic ash content are analyzed quantitatively and their {mu}{sub en}/rho values are computed, so that the simple cavity theory correction to absorbed doses due to x and {gamma}-radiation may be applied. (author).

Zheng Zheng; Fang Jie; Dai Honggui; Tang Zhangxiong (Jiangsu Academy of Agricultural Sciences, Nanjing, JS (China). Inst. of Atomic Energy)

1991-01-01

358

90Y/90 Sr electron induced damages in an essential eucalyptus oil related to the absorbed dose  

International Nuclear Information System (INIS)

A good irradiation geometry was achieved in order to carry out the irradiation of an essential eucalyptus oil with a 90Y/90 Sr electron source. The Monte Carlo simulation code MCNP-4C was employed to determine the absorbed doses in this particular experimental configuration. It also helped us to understand which electrons (from an energetic point of view) were responsible for the damages. In order to identify the induced damages, the irradiated samples were studied by mass spectrometry. The obtained results were related to the absorbed doses determined by the computational simulation

359

Study of natural radionuclide and absorbed gamma dose in Ukhimath area of Garhwal Himalaya (India))  

International Nuclear Information System (INIS)

Natural radiation is the largest contributor to the collective radiation dose of the world population. It is widely distributed in different geological formations such as soil, rocks, air and groundwater. In the present investigation, 226Ra, 232Th and 40K were measured in soil samples of the Ukhimath region of Garhwal Himalaya (India)) using NaI(Tl) gamma-ray spectrometry. The activity concentrations of naturally occurring radionuclides 226Ra, 232Th and 40K were found to vary from 38.4±6.1 to 141.7±11.9 Bq kg-1 with an average of 80.5 Bq kg-1, 57.0±7.5 to 155.9±12.4 Bq kg-1 with an average of 118.9 Bq kg-1 and 9.0±3.0 to 672.8±25.9 Bq kg-1 with an average of 341 Bq kg-1, respectively. The total absorbed gamma dose rate varies from 70.4 to 169.1 nGy h-1 with an average of 123.4 nGy h-1. This study is important to generate a baseline data of radiation exposure in the area. Health hazard effects due to natural radiation exposure are discussed in details. (authors)

360

Monte Carlo Analysis of Pion Contribution to Absorbed Dose from Galactic Cosmic Rays  

Science.gov (United States)

Accurate knowledge of the physics of interaction, particle production and transport is necessary to estimate the radiation damage to equipment used on spacecraft and the biological effects of space radiation. For long duration astronaut missions, both on the International Space Station and the planned manned missions to Moon and Mars, the shielding strategy must include a comprehensive knowledge of the secondary radiation environment. The distribution of absorbed dose and dose equivalent is a function of the type, energy and population of these secondary products. Galactic cosmic rays (GCR) comprised of protons and heavier nuclei have energies from a few MeV per nucleon to the ZeV region, with the spectra reaching flux maxima in the hundreds of MeV range. Therefore, the MeV - GeV region is most important for space radiation. Coincidentally, the pion production energy threshold is about 280 MeV. The question naturally arises as to how important these particles are with respect to space radiation problems. The space radiation transport code, HZETRN (High charge (Z) and Energy TRaNsport), currently used by NASA, performs neutron, proton and heavy ion transport explicitly, but it does not take into account the production and transport of mesons, photons and leptons. In this paper, we present results from the Monte Carlo code MCNPX (Monte Carlo N-Particle eXtended), showing the effect of leptons and mesons when they are produced and transported in a GCR environment.

Aghara, S.K.; Battnig, S.R.; Norbury, J.W.; Singleterry, R.C.

2009-01-01

 
 
 
 
361

Dependence of TLD thermoluminescence yield on absorbed dose in a thermal neutron field.  

Science.gov (United States)

The emission from 6LiF and 7LiF thermoluminescence dosimeters (TLDs) exposed to the mixed field of thermal neutrons and gamma-rays of the thermal facility of a TRIGA MARK II nuclear reactor has been investigated for various thermal neutron fluences of the order of magnitude of those utilised in radiotherapy, with the purpose of investigating the reliability of TLD readouts in such radiation fields and of giving some information for better obtainment of the absorbed dose values. The emission after exposure in this mixed field is compared with the emission after gamma-rays only. The glow curves have been deconvoluted into gaussian peaks, and the differences in the characteristics of the peaks observed for the two radiation fields, having different linear energy transfers, and for different doses are shown. Irreversible radiation damage in dosimeters having high sensitivity to thermal neutrons is also reported, showing a memory effect of the previous thermal neutron irradiation history which is not restored by anneal treatment. PMID:9463872

Gambarini, G; Roy, M S

1997-01-01

362

Mathematical models of tumor growth: translating absorbed dose to tumor control probability  

International Nuclear Information System (INIS)

Full text: The dose-rate in internal emitter therapy is low and time-dependent as compared to external beam radiotherapy. Once the total absorbed dose delivered to a target tissue is calculated, however, most dosimetric analyses of radiopharmaceuticals are considered complete. To translate absorbed dose estimates obtained for internal emitter therapy to biologic effect, the growth characteristics, repair capacity, and radiosensitivity of the tumor must be considered. Tumor growth may be represented by the Gompertz equation in which tumor cells increase at an exponential growth rate that is itself decreasing at an exponential rate; as the tumor increases in size, the growth rate diminishes. The empirical Gompertz expression for tumor growth may be derived from a mechanistic model in which growth is represented by a balance between tumor-cell birth and loss. The birth rate is assumed to be fixed, while the cell loss rate is time-dependent and increases with tumor size. The birth rate of the tumors may be related to their potential doubling time. Multiple biopsies of individual tumors have demonstrated a heterogeneity in the potential doubling time of tumors. By extending the mechanistic model described above to allow for sub-populations of tumor cells with different birth rates, the effect of kinetic heterogeneity within a tumor may be examined. Model simulations demonstrate that the cell kinetic parameters of a tumor are predicted to change over time and measurements oted to change over time and measurements obtained using a biopsy are unlikely to reflect the kinetics of the tumor throughout its growth history. A decrease in overall tumor mass, in which each sub-population is reduced in proportion to its cell number, i.e., the log-kill assumption, leads to re-growth of a tumor that has a greater proliferation rate. Therapy that is linked to the potential doubling time or to the effective proliferation rate of the tumor may lead to re-growth of a tumor that is kinetically unchanged. The simplest model of cell loss due to irradiation, the log-kill model, therefore, predicts that incomplete treatment of a kinetically heterogeneous tumor will yield a more proliferative tumor. The probability of tumor control in such a simulation may be obtained from the nadir in tumor cell number. If the nadir is not sufficiently low to yield a high probability of tumor control, then the tumor will re-grow. Since tumors in each sub-population are assumed lost at the same rate, cells comprising the sub-population with the shortest potential doubling time will re-grow the fastest, yielding a recurrent tumor that is more proliferative. A number of assumptions and simplifications are both implicitly and explicitly made in converting absorbed dose to tumor control probability. The modeling analyses described above must, therefore, be viewed in terms of understanding and evaluating different treatment approaches with the goal of treatment optimization rather than outcome prediction

363

Secondary absorbed doses from light ion irradiation in anthropomorphic phantoms representing an adult male and a 10 year old child  

Energy Technology Data Exchange (ETDEWEB)

Secondary organ absorbed doses were calculated by Monte Carlo simulations with the SHIELD-HIT07 code coupled with the mathematical anthropomorphic phantoms CHILD-HIT and ADAM-HIT. The simulated irradiations were performed with primary {sup 1}H, {sup 4}He, {sup 7}Li, {sup 12}C and {sup 16}O ion beams in the energy range 100-400 MeV/u which were directly impinging on the phantoms, i.e. approximating scanned beams, and with a simplified beamline for {sup 12}C irradiation. The evaluated absorbed doses to the out-of-field organs were in the range 10{sup -6} to 10{sup -1} mGy per target Gy and with standard deviations 0.5-20%. While the contribution to the organ absorbed doses from secondary neutrons dominated in the ion beams of low atomic number Z, the produced charged fragments and their subsequent charged secondaries of higher generations became increasingly important for the secondary dose delivery as Z of the primary ions increased. As compared to the simulated scanned {sup 12}C ion beam, the implementation of a simplified beamline for prostate irradiation with {sup 12}C ions resulted in an increase of 2-50 times in the organ absorbed doses depending on the distance from the target volume. Comparison of secondary organ absorbed doses delivered by {sup 1}H and {sup 12}C beams showed smaller differences when the RBE for local tumor control of the ions was considered and normalization to the RBE-weighted dose to the target was performed.

Hultqvist, Martha; Gudowska, Irena, E-mail: martha.hultqvist@ki.s [Medical Radiation Physics, Department of Physics, Stockholm University, Box 260, SE-17176 Stockholm (Sweden)

2010-11-21

364

Measurements of TMR, absorbed dose using long SSD TBI dosimetry and calculation accuracy of treatment planning system  

International Nuclear Information System (INIS)

Over the last 50 years, total body irradiation (TBI) has become widely used in conditioning regimens for the treatment of hematological malignancies prior to bone marrow or peripheral blood stem cell transplantation. Many techniques and prescriptions have been proposed, and the use of a treatment planning system (TPS) may be best in terms of preventing toxicity to normal tissues and insufficient low dose in bone marrow. Since many measurement data in TPS can be applied at source axis distance (SAD) (1 m), absorbed dose at long source surface distance (SSD) calculated by TPS must be verified prior to clinical use. The aim of this study is to evaluate the difference between tissue maximum ratio (TMR) measured at long SSD (4 m) and TMR at SAD and the absorbed dose measured at long SSD and the absorbed dose calculated by TPS. TMR measured at long SSD agreed with TMR at SAD within 2.0%, while absorbed dose measured at long SSD agreed with that calculated by TPS within 2.5%. These verifications show that the CT-based treatment planning system of TBI can calculate prescription monitor unit (MU) within an acceptable tolerance. (author)

365

Study of the influence of gold particles on the absorbed dose in soft tissue using polymer gel dosimetry  

International Nuclear Information System (INIS)

The presence of high-Z material adjacent to soft tissue, when submitted to irradiation, enhances locally the absorbed dose in these soft tissues. Such effect occurs due to the outscattering of photoelectrons from the high-Z material. Polymer gel dosimeters have been used to investigate this effect. Analytic calculations to estimate the dose enhancement and Monte Carlo simulations have been performed. Samples containing polymer gel (PG) with 0.005 gAu/gPG and pure polymer gel have been irradiated using an X-rays beam produced by 150 kV, filtered with 4 mm Al and 5 mm Cu, which resulted in an approximately 20% higher absorbed dose in the samples with gold in comparison to those with pure polymer gel. The analytic calculations and the Monte Carlo simulation resulted in a dose enhancement factor of approximately 30%. (author)

366

Absorbed doses received by patients submitted to chest radiographs in hospitals of the city of Sao Paulo, Brazil  

International Nuclear Information System (INIS)

Medical irradiation contributes with a significant amount to the dose received by the population. Here, this contribution was evaluated in a survey of absorbed doses received by patients submitted to chest radiological examinations (postero-anterior (PA) and lateral (LAT) projections) in hospitals of the city of Sao Paulo. Due to the variety of equipment and procedures used in radiological examinations, a selection of hospitals was made (12, totalizing 27 X-ray facilities), taking into account their representativeness as medical institutions in the city, in terms of characteristics and number of radiographs carried out. An anthropomorphic phantom, provided with thermoluminescent dosemeters (TLD-1 00), was irradiated simulating the patient, and the radiographic image quality was evaluated. Absorbed doses were determined to the thoracic region (entrance and exit skin and lung doses), and to some important organs from the radiation protection point of view (lens of the eye, thyroid and gonads). The great variation on the exposure parameters (kV, mA.s, beam size) leads to a large interval of entrance skin doses-ESD (coefficients of variation, CV, of 60% and 76%, for PA and LAT projections, respectively, were found) and of organ doses (CV of 60% and 46%. for thyroid and lung respectively). Mean values of ESD for LAT and PA projections were 0.22 and 0.98 mGy, respectively. The average absorbed doses per exam (PA and LAT) to thyroid and lung, 0.15 and 0.24 mGy respectively,showed that the thyroid was irradiated by the primary beam in many cases. Values of lens of the eye and gonad absorbed doses were below 30 ?Gy. Comparison of the lung doses obtained in this study with values in the literature, calculated by Monte Carlo simulation, showed good agreement. On the other hand, the comparison shows significant differences in the dose values to organs outside the chest region (thyroid, lens of eye and gonads). The effective dose calculated for a chest examination, PA and LAT projections, was 47 ?Sv. An estimate of 5 million for the number of radiological examinations performed annually in Sao Paulo was achieved through information provided by the hospitals and by governmental institutions. Assuming that 40% of them refers to chest radiographs, it is possible to infer that radiological examinations contribute to the annual collective effective dose with 1,600 Sv-man. The large variation found in the dose values indicates that much can be done in order to reduce the patient doses without loss of image quality. In addition, more studies should be conducted for a substantial evaluation of doses received during other types of radiological examinations in Sao Paulo. (author)

367

Evaluation of absorbed dose rate and annual effective dose equivalent due to terrestrial gamma radiation in rocks in a part of Southwestern Nigeria  

International Nuclear Information System (INIS)

The average outdoor absorbed dose rate in air and the average annual effective dose equivalent due to terrestrial gamma radiation from 40K, 238U and 232Th in rocks in Ondo and Ekiti States, Southwestern Nigeria have been evaluated from measurements of the concentrations of these radionuclides in this environmental material. The concentration measurements were obtained using a very sensitive gamma spectroscopic system consisting of a 7.6x7.6 cm NaI(Tl) scintillation detector coupled to a computerised ACCUSPEC installation. The average absorbed dose rate and average annual effective dose equivalent was found to be 8.33±2.76 nGy.h-1 and 8.7±2.9 ?Sv.y-1 respectively. (author)

368

Method for calculating cobalt-60 primary absorbed dose in water using a forward and a backward electron diffusion equation  

International Nuclear Information System (INIS)

We have developed a method for calculating cobalt-60 primary absorbed dose in water. The method is based upon a kerma idea using a forward and a backward electron diffusion equation. It has been obtained that values of Co-60 primary dose within a water phantom including the regions near the entrance and the exit surface of a beam can be calculated by one expression derived from the method. (author)

369

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

International Nuclear Information System (INIS)

An investigation was carried out into the performance of parallel-plate chambers in 60Co and MV photon beams. The aim was to derive calibration factors, investigate chamber-to-chamber variability and provide much-needed information on the use of parallel-plate chambers in high-energy X-ray beams. A set of NE2561/NE2611 reference chambers, calibrated against the primary standard graphite calorimeter is used for the dissemination of absorbed dose to water. The parallel-plate chambers were calibrated by comparison with the NPL reference chambers in a water phantom. Two types of parallel-plate chamber were investigated - the NACP -02 and Roos and measurements were made at 60C0 and 6 linac photon energies (6-19 MV). Calibration factors were derived together with polarity corrections. The standard uncertainty in the calibration of a chamber in terms of absorbed dose to water is estimated to be ±0.75%. The results of the polarity measurements were somewhat confusing. One would expect the correction to be small and previous measurements in electron beams have indicated that there is little variation between chambers of these types. However, some chambers gave unexpectedly large polarity corrections, up to 0.8%. By contrast the measured polarity correction for a NE2611 chamber was less than 0.13% at all energies. The reason for these large polarity corrections is not clear, but experimental error and linac variations have been ruled out. By combining the calibration data for the different chambers it was possible to obtain experimental kQ factors for the two chamber types. It would appear from the data that the variations between chambers of the same type are random and one can therefore define a generic curve for each chamber type. These are presented in Figure 1, together with equivalent data for two cylindrical chamber types - NE2561/NE2611 and NE2571. As can be seen, there is a clear difference between the curves for the cylindrical chambers and those for the parallel-plate chambers, which is discussed below. The small difference (around 0.3%) between the NACP and Roos chambers at the highest photon energies is within the measurement uncertainties but may indicate a slight difference in chamber response. A number of chambers were recalibrated six months later to investigate chamber stability. It was found that the repeatability was generally better than 0.5% and the variations in time appear to be random. These differences are larger than for thimble chambers, where we have found stability at better than the 0.3% level over several years. Parallel-plate chambers in electron beams have also showed high stability (McEwen et al, 2001), which would indicate that parallel-plate chambers are sensitive to small variations in the beam quality of photon beams that do not affect thimble chambers. This data can also be used to derive relative wall correction factors for the Roos and NACP. Good agreement (within 0.3%) was found with previous data (Palm et al, 2000; Nystrom et al, 1993). These measurements would seem to confirm that pwall for the Roos chamber given in TRS-381 is too low by around 0.5%. Parallel-plate chambers can be calibrated in terms of absorbed dose to water, but with an uncertainty larger than for thimble chambers. Chamber stability also appears to be worse than for thimble chambers. Polarity corrections must always be measured and applied, as the polarity effect for a particular chamber is difficult to predict

370

Simulation of absorbed dose rate due to synchrotron radiation and shielding thickness for radiation safety at Indus-2 using FLUKA  

International Nuclear Information System (INIS)

Indus-2 is a 2.5 GeV electron synchrotron radiation source at Raja Ramanna Centre for Advanced Technology (RRCAT), India. 26 synchrotron radiation (SR) beam lines are planned in Indus-2 for various research applications, of several are in operation and many are in installation stage. For experiments SR beam is brought in air. Due to intense flux of SR and low energy, the dose rate in the direct beam is high and there is a potential for radiation exposure. Appropriate shielding hutches are needed to house the beamlines and protect the workers from the radiation hazard. Simulations were carried out using computer code FLUKA to find out the absorbed dose in water due to SR and required shielding thickness in the forward direction to reduce dose within acceptable limits. SR spectrum from Indus-2 in the range 4-100 keV was used for simulating the absorbed dose and shielding thickness. It was found that the absorbed dose rate is of the order of 105 Gy/h for the design parameters of Indus-2 (2.5 GeV and 300 mA). Forward shielding thickness of 3 mm lead was found to be sufficient to reduce the dose rate to acceptable level for continuously occupied area (<1?Sv/h). The details of the simulation and results are presented in the paper. (author)

371

Radiation-absorbed doses and energy imparted from panoramic tomography, cephalometric radiography, and occlusal film radiography in children  

International Nuclear Information System (INIS)

The absorbed doses and energy imparted from radiographic examinations of children, using panoramic tomography (PTG), cephalometric radiography (CPR), and maxillary frontal occlusal overview (FOO), were examined. The absorbed dose at various sites of the head were measured with TL dosimeters in a phantom and in patients. The energy imparted was calculated from measurements of areal exposure using a planparallel ionization chamber. The maximum absorbed doses for panoramic tomography were located around the lateral rotation center, for cephalometric radiography in the left (tube side) parotid region, and for frontal occlusal radiography in the nose. The absorbed doses in the eyes, thyroid gland, and skin are discussed and compared with previous reports and, for the most part, are found to be in agreement. The mean energy imparted from all three examination methods is 5 mJ with about 57 percent from panoramic, 33 percent from cephalometric, and 10 percent from frontal occlusal examinations. The energy imparted from cephalometric radiography can be reduced to about 10 percent with the use of an improved examination technique, leaving panoramic tomography responsible for contributing about 80 percent of the total energy imparted

372

Absorbed dose distribution patterns in the beagle thorax after inhalation of 90Sr--90Y fused clay particles. II  

International Nuclear Information System (INIS)

This experiment was designed to examine absorbed dose patterns in the Beagle dog thorax after inhalation of polydisperse fused montmorillonite clay particles labeled with 90Sr-90Y. Sixteen dogs were exposed nose-only to achieve initial lung burdens of 91 to 200 ?Ci. Dogs are being serially sacrificed and photographic data and autoradiographic data produced for a series of parallel planes approximately 1 cm apart through the thorax. Data analysis will include definition of absorbed dose patterns in the Beagle thorax at 8 days, 64 days, 1 year, 2 years, and 3 years post-exposure. To date, 8-day, 64-day, and 1-year animals have been sacrificed and partially analyzed. The result of this experiment will be a better understanding of deposition and absorbed dose patterns and allow a better correlation between absorbed dose and biological response for Beagle dogs exposed to relatively insoluble aerosols contaminated by energetic beta-emitting radionuclides. In addition, results will allow quantitating anomalies in deposition patterns, such as the striated pattern near ribs previously observed in this laboratory. (U.S.)

373

Absorbed dose to water standards established by water calorimetry at the LNE-LNHB for medium energy X-ray  

International Nuclear Information System (INIS)

Nowadays, the absorbed dose to water for kilo-voltage X-ray beams is determined from standards in terms of air-kerma by application of international dosimetry protocols. New standards in terms of absorbed dose to water have just been established for these beams at the LNE-LNHB. A specific calorimeter was developed to do measurements at low depth in water, in order to fulfill the reference conditions required by the international dosimetry protocols for medium-energy X-ray. This new calorimeter was used to measure the absorbed dose rate in water at a depth of 2 cm for six medium-energy X-ray reference beams with a tube potential from 80 kV to 300 kV. The relative standard uncertainty obtained on the absorbed dose rate by water calorimetry is lower than 0.8%, whereas the one given by application of protocols based on air kerma is around 2.5%. (authors)

374

Response functions for computing absorbed dose to skeletal tissues from neutron irradiation  

Energy Technology Data Exchange (ETDEWEB)

Spongiosa in the adult human skeleton consists of three tissues-active marrow (AM), inactive marrow (IM) and trabecularized mineral bone (TB). AM is considered to be the target tissue for assessment of both long-term leukemia risk and acute marrow toxicity following radiation exposure. The total shallow marrow (TM{sub 50}), defined as all tissues lying within the first 50 {mu}m of the bone surfaces, is considered to be the radiation target tissue of relevance for radiogenic bone cancer induction. For irradiation by sources external to the body, kerma to homogeneous spongiosa has been used as a surrogate for absorbed dose to both of these tissues, as direct dose calculations are not possible using computational phantoms with homogenized spongiosa. Recent micro-CT imaging of a 40 year old male cadaver has allowed for the accurate modeling of the fine microscopic structure of spongiosa in many regions of the adult skeleton (Hough et al 2011 Phys. Med. Biol. 56 2309-46). This microstructure, along with associated masses and tissue compositions, was used to compute specific absorbed fraction (SAF) values for protons originating in axial and appendicular bone sites (Jokisch et al 2011 Phys. Med. Biol. 56 6857-72). These proton SAFs, bone masses, tissue compositions and proton production cross sections, were subsequently used to construct neutron dose-response functions (DRFs) for both AM and TM{sub 50} targets in each bone of the reference adult male. Kerma conditions were assumed for other resultant charged particles. For comparison, AM, TM{sub 50} and spongiosa kerma coefficients were also calculated. At low incident neutron energies, AM kerma coefficients for neutrons correlate well with values of the AM DRF, while total marrow (TM) kerma coefficients correlate well with values of the TM{sub 50} DRF. At high incident neutron energies, all kerma coefficients and DRFs tend to converge as charged-particle equilibrium is established across the bone site. In the range of 10 eV to 100 MeV, substantial differences are observed among the kerma coefficients and DRF. As a result, it is recommended that the AM kerma coefficient be used to estimate the AM DRF, and that the TM kerma coefficient be used to estimate the TM{sub 50} DRF below 10 eV. Between 10 eV and 100 MeV, the appropriate DRF should be used as presented in this study. Above 100 MeV, spongiosa kerma coefficients apply well for estimating skeletal tissue doses. DRF values for each bone site as a function of energy are provided in an electronic annex to this article available at http://stacks.iop.org/0031-9155/56/6873/mmedia.

Bahadori, Amir A; Johnson, Perry; Bolch, Wesley E [Department of Biomedical Engineering, University of Florida, Gainesville, FL (United States); Jokisch, Derek W [Department of Physics and Astronomy, Francis Marion University, Florence, SC (United States); Eckerman, Keith F, E-mail: wbolch@ufl.edu [Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN (United States)

2011-11-07