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1

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

International Nuclear Information System (INIS)

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

2008-01-01

2

Calculation of absorbed glandular dose using a Fortran program based on Monte Carlo X-ray spectra in mammography  

International Nuclear Information System (INIS)

Average glandular dose calculation in mammography with Mo-Rh target-filter and dose calculation for different situations is accurate and fast. Material and Methods: In this research, first of all, x-ray spectra of a Mo target bombarded by a 28 keV electron beam with and without a Rh filter were calculated using the MCNP code. Then, we used the Sobol-Wu parameters to write a FORTRAN code to calculate average glandular dose. Results: Average glandular dose variation was calculated against the voltage of the mammographic x-ray tube for d = 5 cm, HVL= 0.35 mm Al, and different value of g. Also, the results related to average glandular absorbed dose variation per unit roentgen radiation against the glandular fraction of breast tissue for kV = 28 and HVL = 0.400 mmAl and different values of d are presented. Finally, average glandular dose against d for g = 60% and three values of kV (23, 27,35 kV) with corresponding HVLs have been calculated. Discussion and Conclusion: The absorbed dose computational program is accurate, complete, fast and user friendly. This program can be used for optimization of exposure dose in mammography. Also, the results of this research are in good agreement with the computational results of others.

2011-01-01

3

Evaluation of depth dose and glandular dose for digital mammography  

International Nuclear Information System (INIS)

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

2010-01-01

4

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

2007-01-01

5

Average glandular dose conversion coefficients for segmented breast voxel models  

International Nuclear Information System (INIS)

For 8 voxel models of a compressed breast (4-7 cm thickness and two orientations for each thickness) and 14 radiation qualities commonly used in mammography (HVL 0.28-0.50 mm Al), tissue dose conversion coefficients were calculated for a focus-to-film distance of 60 cm using Monte Carlo methods. The voxel models were segmented from a high-resolution (slice thickness of 1 mm) computed tomography data set of an ablated breast specimen fixated while being compressed. The contents of glandular tissues amounted to 2.6%, and were asymmetrically distributed with regard to the midplane of the model. The calculated tissue dose conversion coefficients were compared with the recent literature values. These earlier tissue dose conversion coefficients were also calculated using Monte Carlo methods and breast models of various thickness, but these consist of homogeneous mixtures of glandular and adipose tissues embedded in 5 mm pure adipose tissue both at the entrance and exit sides. The results show that the new glandular tissue dose conversion coefficients agree well with the literature values for those cases where the glandular tissue is predominantly concentrated in the upper part of the model. In the opposite case, they were lower by up to 40%. These findings reveal a basic problem in patient dosimetry for mammography: glandular dose is not only governed by the average breast composition, which could be derived from the breast thickness, but also by the local distribution of glandular tissue within the breast, which is not known. (authors)

2005-01-01

6

Media glandular dose in mammography;Dosis glandular media en mamografia  

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

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

2009-10-15

7

Dosimetric evaluation of average glandular absorption radiation dose in mammography  

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To evaluate the average glandular absorption radiation dose(AGARD) that results from tube voltage, target/filter material of the X-ray tube, enterance skin exposure, breast thickness and patterns in routine mammography. After obtaining craniocaudal views of left breast of 114 women, entrance skin exposure was measured by dosimetry. Under identical conditions of tube voltage and target/filter material of the X-ray tube, we obtained half value layer (HVL) and also calculated exposure-to-absorbed dose conversion factor (D{sub g}N) by Wu's methods. AGARD was calculated by entrance skin exposure multiplied by exposure-to-absorbed dose conversion factor. We analyzed AGARDs according to tube voltage, target/filter material, breast thickness and pattern using ANOVA method of the SPSS statistical packages. Breast patterns were divided into 4 groups such as DY (n=72), P1 (n=1), P2 (n=10), and N1 (n=31), respectively. Their AGARDs were 161.5, 180, 172.8, and 195.2 mrad respectively and showed no significant difference among groups. When divided by breast thickness into three groups, namely below 3 cm, 3 cm to 4.5 cm, and above 4.5 cm, the AGARD of each group was 178.3, 178.1, and 112.4 mrad respectively and the last one was significantly low. Concerning the effect of tube voltages, AGARDs gradually decreased by increasing kVp. Furthermore, AGARD was lower when rhodium (Rh) rather than when molybdenum (Mo) was used as filter/target materials. There was no difference in AGARDs by breast pattern. As more increasing KvP or using Rh/Rh as the target/filter material of the X-ray tube, we reduced AGARD for the patient with dense or thick breasts.

Kim, Tae Hoon; Oh, Ki Keun; Shin, Hyeong Cheol; Kim, Jai Keun; Choo, Sung Sil [Yonsei Univ. College of Medicine, Seoul (Korea, Republic of)

1996-12-01

8

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

International Nuclear Information System (INIS)

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

1993-10-01

9

Radiopharmaceutical absorbed dose considerations  

International Nuclear Information System (INIS)

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

1987-01-01

10

Mean glandular dose in a breast screening programme  

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

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

2012-10-23

11

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

International Nuclear Information System (INIS)

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

2005-01-01

12

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

International Nuclear Information System (INIS)

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

2006-01-01

13

Estimation of mean glandular dose for mammography of augmented breasts  

International Nuclear Information System (INIS)

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

2000-01-01

14

Estimation of mean glandular dose for mammography of augmented breasts  

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

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

2000-11-01

15

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 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.

2012-01-01

16

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

17

Dosimetry in Mammography: Average Glandular Dose Based on Homogeneous Phantom  

International Nuclear Information System (INIS)

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

2011-05-05

18

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)

19

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)

2000-01-01

20

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

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

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

2004-12-21

 
 
 
 
21

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 br...

Mowlavi A A

22

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

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

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

2010-04-15

23

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.

2010-01-01

24

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  

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

Vagner Ferreira Cassola; Gabriela Hoff

2010-01-01

25

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)

2011-01-01

26

Uncertainties involved in the estimation of mean glandular dose for women in the Norwegian Breast Cancer Screening Program (NBCSP).  

Science.gov (United States)

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 -0.05 mm (-9.0 %), uncertainty in the s-factor of ±2.1 % and changing the glandularity to an age-dependent glandularity distribution (+8.4 %). PMID:23188812

Hauge, I H R; Olerud, H M

2012-11-27

27

Uncertainties involved in the estimation of mean glandular dose for women in the Norwegian Breast Cancer Screening Program (NBCSP).  

UK PubMed Central (United Kingdom)

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 -0.05 mm (-9.0 %), uncertainty in the s-factor of ±2.1 % and changing the glandularity to an age-dependent glandularity distribution (+8.4 %).

Hauge IH; Olerud HM

2013-06-01

28

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

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

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

2006-01-01

29

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 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 voxel, sendo contabilizadas: a dose total absorvida no modelo, a dose absorvida pelo tecido glandular/material equivalente, e a dose absorvida e a fluência de fótons e (more) m 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 regarding total absorbed dose in the phantom, absorbed dose in the glandular tissue material-equivalent, absorbed dose and photons fluence at different depths in the phantoms. A (more) 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

Cassola, Vagner Ferreira; Hoff, Gabriela

2010-12-01

30

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  

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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; Manuel Villarreal U

2009-01-01

31

The MIRD method of estimating absorbed dose  

Energy Technology Data Exchange (ETDEWEB)

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.

Weber, D.A.

1991-01-01

32

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

33

Problems in measurement of absorbed dose  

International Nuclear Information System (INIS)

The present study surveyed theoretical or experimental problems in determining the absorbed dose of materials due to ionizing radiation. These are devided into four categories here. First, definition and meaning of ''absorbed dose'' are discussed. The word ''absorb'' is not still completely clear. Also ''dose'' itself has been used too broadly in Japan. Second, there is a problem in the absolute measurement of absorbed dose. The measurement includes three methods, i.e., calorimetry, ionometry and chemical method. The major theoretical problems are described. Third, problems in the practical relative measurement of absorbed dose are examined. The problems may be to obtain excellent accuracy and reproducibility. Last, other problems such as measuring absorbed neutron dose and improper use of the nomenclature ''dose'' are pointed out, and the addition of materials concerned should not be omitted for the unit ''rad''. However, even if only the above described problems were solved, it would advance considerably the research and application of the interaction of radiation with matters or the prevention of radiation hazard. (Wakatsuki, Y.)

1973-11-13

34

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

International Nuclear Information System (INIS)

Recently, patient radiation exposure in mammography has varied because of the great demand for mammography, the diffusion of special X-ray equipment, progress in CR, and improvement or study of mammography by the Japanese Society of Radiological Technology. Therefore, data on patient radiation exposure obtained with a 1998 questionnaire survey throughout Japan was analyzed. In addition, the average glandular dose in 1998 was compared with that in 1993. The doses at 782 institutions in 1998 were calculated from data obtained at 51 institutions in the Tokai and Hokuriku regions. The estimated dose in 1998 (1.422 mGy) was lower than that in 1993 (1.610 mGy). The target level for mammography with grid might be 1.5 mGy. (author)

2000-01-01

35

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)

2011-01-01

36

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

UK PubMed Central (United Kingdom)

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

Borg M; Badr I; Royle GJ

2013-01-01

37

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

Directory of Open Access Journals (Sweden)

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

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

2011-01-01

38

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

International Nuclear Information System (INIS)

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

2010-01-01

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

2004-01-01

40

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

International Nuclear Information System (INIS)

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

2010-01-01

 
 
 
 
41

Comparison of absorbed doses from cobalt sources  

International Nuclear Information System (INIS)

[en] Absorbed doses from medical cobalt beams were compared by all radiotherapeutic workplaces in Czechoslovakia using thermoluminiscence dosemeters. At most workplaces (58%), a the deviation from the reference primary standard at the Institute of Radiation Dosimetry of the Czechoslovak Academy of Sciences was below 3%. None of the workplaces exhibited a deviation greater than 5%, indicating a good clinical dosimetry standard. (author). 3 figs., 6 refs

1989-01-01

42

An absorbed dose calorimeter for IMRT dosimetry  

Science.gov (United States)

A new calorimeter for dosimetry in small and complex fields has been built. The device is intended for the direct determination of absorbed dose to water in moderately small fields and in composite fields such as IMRT treatments, and as a transfer instrument calibrated against existing absorbed dose standards in conventional reference conditions. The geometry, materials and mode of operation have been chosen to minimize detector perturbations when used in a water phantom, to give a reasonably isotropic response and to minimize the effects of heat transfer when the calorimeter is used in non-reference conditions in a water phantom. The size of the core is meant to meet the needs of measurement in IMRT treatments and is comparable to the size of the air cavity in a type NE2611 ionization chamber. The calorimeter may also be used for small field dosimetry. Initial measurements in reference conditions and in an IMRT head and neck plan, collapsed to gantry angle zero, have been made to estimate the thermal characteristics of the device, and to assess its performance in use. The standard deviation (estimated repeatability) of the reference absorbed dose measurements was 0.02 Gy (0.6%).

Duane, S.; Aldehaybes, M.; Bailey, M.; Lee, N. D.; Thomas, C. G.; Palmans, H.

2012-10-01

43

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

UK PubMed Central (United Kingdom)

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

Myronakis ME; Zvelebil M; Darambara DG

2013-04-01

44

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

Science.gov (United States)

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

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

2013-04-01

45

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

International Nuclear Information System (INIS)

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.

2011-01-01

46

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

Energy Technology Data Exchange (ETDEWEB)

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)

Horie, Tomohiko [Tokai Univ., Isehara, Kanagawa (Japan). Hospital

2000-10-01

47

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

Science.gov (United States)

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

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

2013-09-01

48

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

Science.gov (United States)

In many countries, computed radiography (CR) systems represent the majority of equipment used in digital mammography. This study presents a method for optimizing image quality and dose in CR mammography of patients with breast thicknesses between 45 and 75 mm. Initially, clinical images of 67 patients (group 1) were analyzed by three experienced radiologists, reporting about anatomical structures, noise and contrast in low and high pixel value areas, and image sharpness and contrast. Exposure parameters (kV, mAs and target/filter combination) used in the examinations of these patients were reproduced to determine the contrast-to-noise ratio (CNR) and mean glandular dose (MGD). The parameters were also used to radiograph a CDMAM (version 3.4) phantom (Artinis Medical Systems, The Netherlands) for image threshold contrast evaluation. After that, different breast thicknesses were simulated with polymethylmethacrylate layers and various sets of exposure parameters were used in order to determine optimal radiographic parameters. For each simulated breast thickness, optimal beam quality was defined as giving a target CNR to reach the threshold contrast of CDMAM images for acceptable MGD. These results were used for adjustments in the automatic exposure control (AEC) by the maintenance team. Using optimized exposure parameters, clinical images of 63 patients (group 2) were evaluated as described above. Threshold contrast, CNR and MGD for such exposure parameters were also determined. Results showed that the proposed optimization method was effective for all breast thicknesses studied in phantoms. The best result was found for breasts of 75 mm. While in group 1 there was no detection of the 0.1 mm critical diameter detail with threshold contrast below 23%, after the optimization, detection occurred in 47.6% of the images. There was also an average MGD reduction of 7.5%. The clinical image quality criteria were attended in 91.7% for all breast thicknesses evaluated in both patient groups. Finally, this study also concluded that the use of the AEC of the x-ray unit based on the constant dose to the detector may bring some difficulties to CR systems to operate under optimal conditions. More studies must be performed, so that the compatibility between systems and optimization methodologies can be evaluated, as well as this optimization method. Most methods are developed for phantoms, so comparative studies including clinical images must be developed. PMID:24002695

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

2013-09-04

49

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

UK PubMed Central (United Kingdom)

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

Jakubiak RR; Gamba HR; Neves EB; Peixoto JE

2013-09-01

50

Comparison of average glandular dose in screen-film and digital mammography using breast tissue-equivalent phantom  

Energy Technology Data Exchange (ETDEWEB)

In recent years, mammography system is changed rapidly from conventional screen-film system to digital system for application to screening and diagnosis. Digital mammography system provides several advantages over screen-film mammography system. According to the information provided by the manufacturer, digital mammography system offers radiation dose reduction in comparison with screen-film mammography system, because of digital detector, particularly direct digital detector has higher x-ray absorption efficiency than screen-film combination or imaging plate (IP). We measured average glandular doses (ADG) in screen-film mammography (SFM) system with slow screen-film combination, computed mammography (CM) system, indirect digital mammography (IDM) system and direct digital mammography (DDM) system using breast tissue-equivalent phantom (glandularity 30%, 50% and 70%). The results were shown as follows: AGD values for DDM system were highest than those for other systems. Although automatic exposure control (AEC) mode was selected, the curve of the AGD values against thickness or glandularity increased significantly for the SFM system with the uniform target/filter (Mo/Mo) combination. Therefore, the AGD values for the high energy examinations were highest in the SFM system, and those for the low energy examinations were highest in the DDM system. But the curve of the AGD values against thickness and glandularity increased gently for CM system with the automatic selection of the target/filter combination (from Mo/Mo to Mo/Rh or from Mo/Rh to Rh/Rh), and the AGD values were lowest. Consequently, the parameters in mammography for each exposure besides detection efficiency play an important role in order to estimate a patient radiation dose.

Shin, Gwi Soon; Kim, Jung Min; Kim, You Hyun; Choi, Jong Hak; Kim, Chang Kyun [College of Health Sciences, Korea University, Seoul (Korea, Republic of)

2007-03-15

51

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

International Nuclear Information System (INIS)

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

2009-01-01

52

The Australian Commonwealth standard of measurement for absorbed radiation dose  

International Nuclear Information System (INIS)

This report documents the absorbed dose standard for photon beams in the range from 1 to 25 MeV. Measurements of absorbed dose in graphite irradiated by a beam of cobalt-60 gamma rays from an Atomic Energy of Canada Limited (AECL) E1 Dorado 6 teletherapy unit are reported. The measurements were performed using a graphite calorimeter, which is the primary standard for absorbed dose. The measurements are used to calibrate a working standard ion chamber in terms of absorbed dose in graphite. Details of the methods, results and correction factors applied are given in Appendices. 13 refs., 6 tabs., 6 figs

1990-01-01

53

Absorbed dose measurements in mammography using Monte Carlo method and ZrO2+PTFE dosemeters  

International Nuclear Information System (INIS)

Mammography test is a central tool for breast cancer diagnostic. In addition, programs are conducted periodically to detect the asymptomatic women in certain age groups; these programs have shown a reduction on breast cancer mortality. Early detection of breast cancer is achieved through a mammography, which contrasts the glandular and adipose tissue with a probable calcification. The parameters used for mammography are based on the thickness and density of the breast, their values depend on the voltage, current, focal spot and anode-filter combination. To achieve an image clear and a minimum dose must be chosen appropriate irradiation conditions. Risk associated with mammography should not be ignored. This study was performed in the General Hospital No. 1 IMSS in Zacatecas. Was used a glucose phantom and measured air Kerma at the entrance of the breast that was calculated using Monte Carlo methods and ZrO2+PTFE thermoluminescent dosemeters, this calculation was completed with calculating the absorbed dose. (author)

2009-10-02

54

Graphite calorimeter for measurement of absorbed dose of electron beam  

International Nuclear Information System (INIS)

A multi-layer graphite calorimeter for the measurement of depth-map of the absorbed dose and the energy of the electron beams, and a device of the semi-adiabatic graphite calorimeter for the measurement of the absorbed dose and the calibration of film dosimeter were developed for the requirement to the standard method of the measurement of the absorbed dose of the electron beam. The construction of the two calorimeters and the researching result in the CIAE 14 MeV accelerator were introduced. (authors)

2009-01-01

55

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

56

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese OBJETIVO: Verificar o efeito da mudança no contraste do objeto, tempo de exposição e dose de radiação quando diferentes espessuras de filtração de molibdênio (Mo) e ródio (Rh) são empregadas em mamógrafos. MATERIAIS E MÉTODOS: Realizaram-se medidas da exposição na entrada da pele com uma câmara de ionização para diferentes espessuras para os filtros de Mo e Rh. Para determinar a dose glandular média foi utilizado simulador de BR12 (50% tecido adiposo e 5 (more) 0% tecido glandular) de diferentes espessuras (4 cm e 8 cm). Energias na faixa de 24 kVp a 34 kVp foram empregadas e filmes Kodak MinR 2000 foram utilizados. RESULTADOS: Os resultados evidenciaram dados de contraste do objeto, dose glandular e tempo de exposição para diferentes espessuras de filtros adicionais e diferentes tensões. Esses dados indicaram aumento nos valores de contraste do objeto e tempo de exposição, com o aumento da espessura dos filtros. A dose glandular apresentou comportamento com diferentes tendências para cada caso analisado. Equações foram definidas para possibilitar a estimativa do contraste do objeto, dose glandular e tempo de exposição para os casos estudados. CONCLUSÃO: Os resultados possibilitaram a estimativa de equações que auxiliam na verificação do comportamento do contraste do objeto e da dose glandular para simuladores com espessura de 4 cm e 8 cm e para os filtros de Rh e Mo. Dessa forma, torna-se possível estimar a figura de mérito (razão entre o contraste do objeto e a dose glandular), podendo auxiliar na análise da relação risco-benefício dos casos estudados. Abstract in english OBJECTIVE: Our purpose was to verify the effect of changes in subject contrast, exposure time and radiation dose when different thicknesses of molybdenum (Mo) and rhodium (Rh) filters are used in mammography equipments. MATERIALS AND METHODS: Entrance skin exposure measurements were performed with an ionization chamber for different thicknesses of Mo and Rh filters. Average glandular dose was determined with a BR12 simulator (50% fat tissue and 50% glandular tissue) of di (more) fferent thicknesses (4 cm and 8 cm). Energies in the range of 24 to 34 kVp and Kodak MinR 2000 films were used. RESULTS: Results have evidenced data on subject contrast data, glandular dose and exposure time for different thicknesses of additional filters and different kVp values. These data have indicated an increase both in values of subject contrast and exposure time when filters thickness is increased. The glandular dose has presented a different behavior tendency for each case analyzed. Equations were defined to allow us to estimate subject contrast, glandular dose and exposure time for the cases studied. CONCLUSION: The results have made possible to define equations to assist with the evaluation of subject contrast and glandular dose behavior in simulators with 4 cm and 8 cm thicknesses and for Rh and Mo additional filters. In this way, it is possible to estimate the figure of merit (subject contrast/glandular dose ratio) to assist in the risk-benefit analysis of the cases studied.

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

2006-06-01

57

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

Directory of Open Access Journals (Sweden)

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

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

2006-01-01

58

Absorbed dose in and out of radiation beam  

International Nuclear Information System (INIS)

[en] Data on the absorbed dose distribution in radiation beams and beyond it during radiotherapy of tumours are presented. Recommendations are given for the protection of organs and tissues from scattered radiation and leakage radiation from therapeutic apparatus

1987-01-01

59

The Australian Commonwealth standard of measurement for absorbed radiation dose  

International Nuclear Information System (INIS)

[en] As an agent of the Commonwealth Scientific and Industrial Research Organization, the Australian Atomic Energy Commission is responsible for the maintenance of the Australian Commonwealth standard of absorbed dose. A graphite calorimeter was designed and built at the AAEC Research Establishment to provide such a standard for the dose absorbed in carbon from ? and X-ray beams with maximum photon energies above 500 keV. The calorimeter measures the dose averaged over the volume of a thermally insulated absorber disc of diameter 20 mm, thickness 3 mm and mass 1.7 g. The absorber and associated adiabatic and temperature controlled jackets are contained within a small graphite phantom of diameter 15 cm. The depth to the centre of the absorber is adjustable between 2.1 and 10 cm. By using a modified vacuum chamber window, the minimum depth can be reduced to 5 mm for use with high energy electron beams. The calorimeter has been in operation for more than 12 months and no change in its response to a 60Co source has been detected in that time. The precision of dose measurements is +- 0.3 per cent at a dose rate of 4.2 mGy s-1 (25 rad min-1). Graphite and water phantoms have been made to enable portable working standards of absorbed dose in carbon and water to be calibrated against the primary standard

1978-01-01

60

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

Directory of Open Access Journals (Sweden)

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

Leili rahmatnezhad; Zhaleh Behrouzkia; Ahad Zeinali; Mir Hamid Mohammady; Nasrollah Jabbari

2012-01-01

 
 
 
 
61

High-temperature absorbed dose measurements in the megagray range  

International Nuclear Information System (INIS)

Organic conductors of the tetraselenotetracene family have been tested as ''high-temperature'' absorbed dose dosimeters. They were heated up to 1200C and irradiated at this temperature with 1-MeV electrons in order to simulate, in a short time, a much longer ?-ray irradiation. The electric resistance increase of the crystal can be considered a good measurement of the absorbed dose in the range 106 Gy to a few 108 Gy and presumably one order of magnitude more. This dosimeter also permits on-line (in-situ) measurements of the absorbed dose without removing the sensor from the irradiation site. The respective advantages of organic and inorganic dosimeters at these temperature and dose ranges are also discussed. In this connection, we outline new, but negative, results concerning the possible use of silica as a high-temperature, high-dose dosimeter. (author)

1988-01-01

62

Absorbed doses to patients from angioradiology  

International Nuclear Information System (INIS)

[en] 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)

2001-01-01

63

Phantoms for calculations of absorbed organ dose  

International Nuclear Information System (INIS)

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

1993-01-01

64

Evaluation of the absorbed dose in odontological computerized tomography  

International Nuclear Information System (INIS)

[en] 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

2011-01-01

65

Absorbed Doses to Patients in Nuclear Medicine  

International Nuclear Information System (INIS)

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

2007-01-01

66

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

2002-01-01

67

X-ray doses absorbed by patients during xeroxmammography  

International Nuclear Information System (INIS)

[en] Measurements and calculations have been carried out of doses absorbed by women during xeroxmammography. Although high, the mean doses were found to be of the order of those encountered in the literature. To lower the doses, the examinations should be made by pressing the breast and optimizing the image for various modes of the X-ray apparatus. 12 refs., 2 figs., 6 tabs. (author)

1988-01-01

68

Time improvement of photoelectric effect calculation for absorbed dose estimation  

Energy Technology Data Exchange (ETDEWEB)

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.

Massa, J M [INTIA, Facultad de Cs. Exactas, Universidad. Nac. del Centro de la Prov. de Bs As, Paraje Arroyo Seco, Campus Universitario, Tandil, Provincia de Buenos Aires (7000) (Argentina); Wainschenker, R S [INTIA, Facultad de Cs. Exactas, Universidad. Nac. del Centro de la Prov. de Bs As, Paraje Arroyo Seco, Campus Universitario, Tandil, Provincia de Buenos Aires (7000) (Argentina); Doorn, J H [INTIA, Facultad de Cs. Exactas, Universidad. Nac. del Centro de la Prov. de Bs As, Paraje Arroyo Seco, Campus Universitario, Tandil, Provincia de Buenos Aires (7000) (Argentina); Caselli, E E [IFAS, Facultad de Cs. Exactas, Universidad. Nac. del Centro de la Prov. de Bs As, Paraje Arroyo Seco, Campus Universitario, Tandil, Provincia de Buenos Aires (7000) (Argentina)

2007-11-15

69

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.

2007-01-01

70

Thyroid radiation absorbed dose from diagnostic procedures in US population  

International Nuclear Information System (INIS)

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 106 rad (18 x 104 Gy) in 1966 to 13.9 x 106 rad (13.9 x 104 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 106 rad (1.4 x 104 Gy). The number of radiation-induced cancer cases would also be reduced

1985-01-01

71

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

72

Absorbed dose to water reference dosimetry using solid phantoms in the context of absorbed-dose protocols.  

Science.gov (United States)

For reasons of phantom material reproducibility, the absorbed dose protocols of the American Association of Physicists in Medicine (AAPM) (TG-51) and the International Atomic Energy Agency (IAEA) (TRS-398) have made the use of liquid water as a phantom material for reference dosimetry mandatory. In this work we provide a formal framework for the measurement of absorbed dose to water using ionization chambers calibrated in terms of absorbed dose to water but irradiated in solid phantoms. Such a framework is useful when there is a desire to put dose measurements using solid phantoms on an absolute basis. Putting solid phantom measurements on an absolute basis has distinct advantages in verification measurements and quality assurance. We introduce a phantom dose conversion factor that converts a measurement made in a solid phantom and analyzed using an absorbed dose calibration protocol into absorbed dose to water under reference conditions. We provide techniques to measure and calculate the dose transfer from solid phantom to water. For an Exradin A12 ionization chamber, we measured and calculated the phantom dose conversion factor for six Solid Water phantoms and for a single Lucite phantom for photon energies between 60Co and 18 MV photons. For Solid Water of certified grade, the difference between measured and calculated factors varied between 0.0% and 0.7% with the average dose conversion factor being low by 0.4% compared with the calculation whereas for Lucite, the agreement was within 0.2% for the one phantom examined. The composition of commercial plastic phantoms and their homogeneity may not always be reproducible and consistent with assumed composition. By comparing measured and calculated phantom conversion factors, our work provides methods to verify the consistency of a given plastic for the purpose of clinical reference dosimetry. PMID:16266109

Seuntjens, Jan; Olivares, Marina; Evans, Michael; Podgorsak, Ervin

2005-09-01

73

Absorbed dose to water reference dosimetry using solid phantoms in the context of absorbed-dose protocols  

International Nuclear Information System (INIS)

[en] For reasons of phantom material reproducibility, the absorbed dose protocols of the American Association of Physicists in Medicine (AAPM) (TG-51) and the International Atomic Energy Agency (IAEA) (TRS-398) have made the use of liquid water as a phantom material for reference dosimetry mandatory. In this work we provide a formal framework for the measurement of absorbed dose to water using ionization chambers calibrated in terms of absorbed dose to water but irradiated in solid phantoms. Such a framework is useful when there is a desire to put dose measurements using solid phantoms on an absolute basis. Putting solid phantom measurements on an absolute basis has distinct advantages in verification measurements and quality assurance. We introduce a phantom dose conversion factor that converts a measurement made in a solid phantom and analyzed using an absorbed dose calibration protocol into absorbed dose to water under reference conditions. We provide techniques to measure and calculate the dose transfer from solid phantom to water. For an Exradin A12 ionization chamber, we measured and calculated the phantom dose conversion factor for six Solid WaterTM phantoms and for a single Lucite phantom for photon energies between 60Co and 18 MV photons. For Solid WaterTM of certified grade, the difference between measured and calculated factors varied between 0.0% and 0.7% with the average dose conversion factor being low by 0.4% compared with the calculation whereas for Lucite, the agreement was within 0.2% for the one phantom examined. The composition of commercial plastic phantoms and their homogeneity may not always be reproducible and consistent with assumed composition. By comparing measured and calculated phantom conversion factors, our work provides methods to verify the consistency of a given plastic for the purpose of clinical reference dosimetry

2005-01-01

74

A method study on absorbed dose determination of X (?) knife  

International Nuclear Information System (INIS)

[en] In this paper described is the absorbed dose determination of three types X (?) knives at isocenter point in different radiation fields by using a 160-mm diameter PMMA spherical phantom and a 0.015 cm3 PTW 31006 type pinpoint ionization chamber which can be inserted into the center of the phantom. The measured data were compared with those measured by a semiconductor detector (with sensitive volume of 1 mm x 1 mm x 0.5 mm). A comparative study on the applicability of the two detectors was carried out, and a method suitable for the absorbed dose determination of X(?) knife was put forward

2003-01-01

75

A measurement of kerma and absorbed dose in photon fields  

International Nuclear Information System (INIS)

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

1986-01-01

76

A sealed water calorimeter for measuring absorbed dose  

International Nuclear Information System (INIS)

The NIST sealed water calorimeter is intended for direct measurement of absorbed dose to water. This calorimeter was used for a series of approximately 3,700 measurements to investigate the so-called heat defect, that is, anomalous endothermic or exothermic effects caused by dissolved gases. The three systems investigated were high-purity water saturated with N2, H2, and mixtures of H2/O2. The repeatability of the measurements of absorbed dose rates for the 60Co teletherapy beam was studied with different water fillings and accumulated absorbed dose. Measurements with the H2/O2 system varied with accumulated absorbed dose. Based on the measurements and theoretical considerations, it appears that the H2-saturated system is the best choice for eliminating the heat defect. Measurements with both the N2- and H2-saturated systems are in good agreement with those determined with a graphite and graphite-water calorimeter (for which there is no heat defect).

1994-01-01

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

2008-01-01

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

Bone marrow and thyroid absorbed doses from mammography  

International Nuclear Information System (INIS)

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

1996-01-01

80

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)

1983-01-01

 
 
 
 
81

Absorbed dose optimization in the microplanar beam radiotherapy  

International Nuclear Information System (INIS)

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

1996-01-01

82

Absorbed dose optimization in the microplanar beam radiotherapy  

Energy Technology Data Exchange (ETDEWEB)

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

Company, F.Z.; Jaric, J. [University of Wetsern Sydney, Nepean, Kingswood, NSW, (Australia). Department of Physics; Allen, B.J. [St George Hospital, Kogarah, NSW, (Australia). Cancer Care Centre

1996-12-31

83

Absorbed doses due to mammography in various Dutch hospitals  

International Nuclear Information System (INIS)

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

1983-01-01

84

Absorbed dose measurements in mammography using Monte Carlo method and ZrO{sub 2}+PTFE dosemeters  

Energy Technology Data Exchange (ETDEWEB)

Mammography test is a central tool for breast cancer diagnostic. In addition, programs are conducted periodically to detect the asymptomatic women in certain age groups; these programs have shown a reduction on breast cancer mortality. Early detection of breast cancer is achieved through a mammography, which contrasts the glandular and adipose tissue with a probable calcification. The parameters used for mammography are based on the thickness and density of the breast, their values depend on the voltage, current, focal spot and anode-filter combination. To achieve an image clear and a minimum dose must be chosen appropriate irradiation conditions. Risk associated with mammography should not be ignored. This study was performed in the General Hospital No. 1 IMSS in Zacatecas. Was used a glucose phantom and measured air Kerma at the entrance of the breast that was calculated using Monte Carlo methods and ZrO{sub 2}+PTFE thermoluminescent dosemeters, this calculation was completed with calculating the absorbed dose. (author)

Duran M, H. A.; Hernandez O, M. [Departamento de Investigacion en Polimeros y Materiales, Universidad de Sonora, Blvd. Luis Encinas y Rosales s/n, Col. Centro, 83190 Hermosillo, Sonora (Mexico); Salas L, M. A.; Hernandez D, V. M.; Vega C, H. R. [Unidad Academica de Estudios Nucleares, Universidad Autonoma de Zacatecas, Cipres 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Pinedo S, A.; Ventura M, J.; Chacon, F. [Hospital General de Zona No. 1, IMSS, Interior Alameda 45, 98000 Zacatecas (Mexico); Rivera M, T. [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, IPN, Av. Legaria 694, Col. Irrigacion, 11500 Mexico D. F.(Mexico)], e-mail: hduran20_1@hotmail.com

2009-10-15

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)

1998-01-01

86

Electron absorbed dose measurements in LINACs by thermoluminescent dosimeters.  

UK PubMed Central (United Kingdom)

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

Cortés JR; Romero RA; Nieto JA; Montalvo TR

2013-06-01

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.

2010-01-01

88

The advantages of absorbed-dose calibration factors.  

UK PubMed Central (United Kingdom)

A formalism for clinical external beam dosimetry based on use of ion chamber absorbed-dose calibration factors is outlined in the context and notation of the AAPM TG-21 protocol. It is shown that basing clinical dosimetry on absorbed-dose calibration factors ND leads to considerable simplification and reduced uncertainty in dose measurement. In keeping with a protocol which is used in Germany, a quantity kQ is defined which relates an absorbed-dose calibration factor in a beam of quality Q0 to that in a beam of quality Q. For 38 cylindrical ion chambers, two sets of values are presented for ND/NX and Ngas/ND and for kQ for photon beams with beam quality specified by the TPR20(10) ratio. One set is based on TG-21's protocol to allow the new formalism to be used while maintaining equivalence to the TG-21 protocol. To demonstrate the magnitude of the overall error in the TG-21 protocol, the other set uses corrected versions of the TG-21 equations and the more consistent physical data of the IAEA Code of Practice. Comparisons are made to procedures based on air-kerma or exposure calibration factors and it is shown that accuracy and simplicity are gained by avoiding the determination of Ngas from NX. It is also shown that the kQ approach simplifies the use of plastic phantoms in photon beams since kQ values change by less than 0.6% compared to those in water although an overall correction factor of 0.973 is needed to go from absorbed dose in water calibration factors to those in PMMA or polystyrene. Values of kQ calculated using the IAEA Code of Practice are presented but are shown to be anomalous because of the way the effective point of measurement changes for 60Co beams. In photon beams the major difference between the IAEA Code of Practice and the corrected AAPM TG-21 protocol is shown to be the Prepl correction factor. Calculated kQ curves and three parameter equations for them are presented for each wall material and are shown to represent accurately the kQ curve for all ion chambers in this study with a wall of that specified material and a thickness less than 0.25 g/cm2. Values of kQ can be measured using the primary standards for absorbed dose in photon beams.

Rogers DW

1992-09-01

89

Additional radiation absorbed dose estimates for Zevalin radioimmunotherapy.  

UK PubMed Central (United Kingdom)

Zevalin (ibritumomab tiuxetan) radioimmunotherapy is a novel treatment for non-Hodgkin's lymphoma (NHL). The Zevalin regimen includes 5 mCi (111)In-labeled Zevalin on Day 1, followed by serial anterior and posterior planar gamma images for imaging or dosimetry. On Day 8, patients receive 0.4 mCi/kg (90)Y Zevalin for radioimmunotherapy. Both Zevalin doses are preceded by 250 mg/m(2) rituximab to clear peripheral B cells and improve biodistribution of the radiolabeled antibody. In a 143-patient, Phase III, randomized study, the Zevalin regimen produced a significantly higher overall response rate than rituximab for relapsed or refractory, low-grade, follicular, or transformed NHL (80% versus 56%, p = 0.02). Fifteen patients from the Zevalin arm of this study were randomly selected for additional radiation dosimetry. (90)Y residence times were calculated from (111)In image analysis data. MIRDOSE3.1 radiation absorbed dose estimates to normal tissues were highest for spleen, testes, and liver, with considerably lower doses reaching heart, lung, intestines, red marrow, and kidneys. Radiation absorbed doses to organs and marrow were within a safe range following administration of 0.4 mCi/kg (90)Y Zevalin.

Wiseman GA; Leigh BR; Dunn WL; Stabin MG; White CA

2003-04-01

90

Spatial distribution of absorbed dose onboard of International Space Station  

International Nuclear Information System (INIS)

The passive detectors (LD and PNTD) were exposed onboard of Russian Service Module Qn the International Space Station (ISS) from August 2004 to October 2005 (425 days). The detectors were located at 6 different positions inside the Service Module and also in 32 pockets on the surface of the spherical tissue-equivalent phantom located in crew cabin. Distribution of absorbed doses and dose equivalents measured with passive detectors, as well as LET spectra of fluences of registered particles, are presented as the function of detectors' location. The variation of dose characteristics for different locations can be up to factor of 2. In some cases, data measured with passive detectors are also compared with the data obtained by means of active instruments. (authors)

2009-01-01

91

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)

2011-01-01

92

Spatial distribution of absorbed dose onboard of International Space Station  

International Nuclear Information System (INIS)

The passive detectors (LD and PNTD) were exposed onboard of Russian Service Module Qn the International Space Station (ISS) from August 2004 to October 2005 (425 days). The detectors were located at 6 different positions inside the Service Module and also in 32 pockets on the surface of the spherical tissue-equivalent phantom located in crew cabin. Distribution of absorbed doses and dose equivalents measured with passive detectors, as well as LET spectra of fluences of registered particles, are presented as the function of detectors' location. The variation of dose characteristics for different locations can be up to factor of 2. In some cases, data measured with passive detectors are also compared with the data obtained by means of active instruments. (authors)

2008-01-01

93

The radon concentration and absorbed dose rate in Hungarian dwellings  

International Nuclear Information System (INIS)

A survey of indoor radiation in Hungarian homes has been carried out by measuring the radon concentration and the dose rate from external sources in a thousand dwellings using electret radon detectors (E-PERM) and thermoluminescence dosemeters (CaSO4:Tm). The measurements were performed in one year during 1993-1994. The resulting arithmetic mean of radon concentration is 128 Bq.m-3, the weighted mean value is 107 Bq.m-3. The mean value of absorbed dose rate, including terrestrial and cosmic rays, is 127 nGy.h-1 and the weighted mean is 109 nGy.h-1. The annual effective dose to the Hungarian population based on the weighted means are 1.3-1.8 mSv from radon inhalation and 0.4-0.6 mSv from external sources, according to the occupancy of 5008-7008 hours per annum. (author).

1996-01-01

94

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

UK PubMed Central (United Kingdom)

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.

Markou P

2006-09-01

95

Transfer from graphite absorbed dose to water absorbed dose for high energy photons at BNM-LPRI: case of cobalt 60  

International Nuclear Information System (INIS)

To derive the absorbed dose to water from a standard of absorbed dose to graphite, the metrology laboratories which apply that method usually make use of cavity ionization chambers as transfer instruments. The BNM-LPRI also tested, as such instruments, several Fricke dosimeters in its cobalt-60 beam. Both procedures are compared. Their results are in good agreement. Both procedures are then taken into account for the calculation of the reference value of absorbed dose to water. (authors).

1996-01-01

96

[Determination of absorbed doses of radiation during lateral cephalometric radiography].  

Science.gov (United States)

The aim of this study was to determine the absorbed doses of radiation in skin and deeper tissues as well as in critical organs, in vitro. For this purpose were used: a Siemens Orthoceph-10 cephalometric unit; a tissue equivalent Phantom head, type Rando; 43 thermoluminescencent dosimeters (T.L.D.), rare earth screens type, Siemens titan ZHS and Dupont Cronex-4 films 24 x 30 cm. Of the 43 T.L.D. 21 were places on the skin head, face and neck surface and 22 were places in deeper tissues and organs, and the exposure parameters were: 77 Kvp, 12 mA and 0.8 sec. The results of this study showed that: 1. doses on the left side towards focus were greater than the right side. 2. surface skin doses were ranged between 0.10 to 0.21 mGy. 3. Doses in deeper tissues or organs were varied and depended on the location and the consistency of tissue and were greater than the surface skin doses. Comparing our results with the results of other studies we can conclude that dose reduction to patient, can be achieved with use of rare earth screens in combination with fast speed film and the use of low exposure parameters. PMID:2640655

Patsakas, A J; Donta, C N; Tsiklakis, K D

1989-06-01

97

[Determination of absorbed doses of radiation during lateral cephalometric radiography  

UK PubMed Central (United Kingdom)

The aim of this study was to determine the absorbed doses of radiation in skin and deeper tissues as well as in critical organs, in vitro. For this purpose were used: a Siemens Orthoceph-10 cephalometric unit; a tissue equivalent Phantom head, type Rando; 43 thermoluminescencent dosimeters (T.L.D.), rare earth screens type, Siemens titan ZHS and Dupont Cronex-4 films 24 x 30 cm. Of the 43 T.L.D. 21 were places on the skin head, face and neck surface and 22 were places in deeper tissues and organs, and the exposure parameters were: 77 Kvp, 12 mA and 0.8 sec. The results of this study showed that: 1. doses on the left side towards focus were greater than the right side. 2. surface skin doses were ranged between 0.10 to 0.21 mGy. 3. Doses in deeper tissues or organs were varied and depended on the location and the consistency of tissue and were greater than the surface skin doses. Comparing our results with the results of other studies we can conclude that dose reduction to patient, can be achieved with use of rare earth screens in combination with fast speed film and the use of low exposure parameters.

Patsakas AJ; Donta CN; Tsiklakis KD

1989-06-01

98

Testing of the IAEA code: Absorbed dose determination at Co 60 gamma radiation  

International Nuclear Information System (INIS)

At several Primary Standard Dosimetry Laboratories measurements of absorbed dose to water have been performed with ionization chambers of different types. These ionization chambers are calibrated against both, primary standards of air kerma and water absorbed dose. Using the formalism of the IAEA Code of Practice the absorbed dose to water in Co 60 gamma beams was derived and compared with direct measurements of water absorbed dose. This yields a very valid test of the IAEA Code. (author). 18 refs, 7 tabs

1996-01-01

99

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

Directory of Open Access Journals (Sweden)

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

Keyhandokht Karimi Shahri; Hashem Miri Hakimabad; Lale Rafat Motavalli

2010-01-01

100

International comparison of calibration standards for exposure and absorbed dose  

International Nuclear Information System (INIS)

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

1990-01-01

 
 
 
 
101

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.

1999-01-01

102

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.

2008-01-01

103

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)

2011-01-01

104

Development of a prototype calorimeter for absorbed dose determination  

International Nuclear Information System (INIS)

As the final report of a three-year project carried out in the IAEA dosimetry laboratory on 'Design and construction of a portable graphite calorimeter', the construction, mode of operation, testing and performances of a prototype and four production units are presented. Results of extensive testing, by measuring the absolute absorbed dose with different 60Co sources, at the Seibersdorf Laboratory and the Hungarian National Office of Measures, Budapest, are given. Due to the improvements in the electronic circuitry, the introduction of a second core thermistor, and a new mode of operation under isothermic conditions, the sensitivity of the new apparatus was improved with one order of magnitude compared to the model started from, namely the one developed at the US National Bureau of Standards

1983-01-01

105

Scaling neutron absorbed dose distributions from one medium to another  

Energy Technology Data Exchange (ETDEWEB)

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

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

1982-11-01

106

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

1982-01-01

107

[The estimation of the absorbed dose with wedge fields  

UK PubMed Central (United Kingdom)

In the dose calculation at an arbitrary point in a water-equivalent homogeneous medium irradiated by an X-ray megavoltage wedged beam (w), several treatment planning systems (TPS) based on the Bently-Milan data processing procedure use algorithms which do not distinguish between wedged OF(s)w and open OF(s)o output factor or between field size dependent WF(s) and not WF wedge factor. This is equivalent to neglecting the difference between open (o) and wedged (w) fields both in relation to back-scattered radiation from secondary collimators to the beam monitor chamber and to scattered radiation generated by the water-phantom at the depth of measurement. The output factor can be expressed by: OF(s) = Sc(s)* Sp(s) where Sc(s) is the collimator scatter factor and Sp(s) is the phantom scatter factor. The approximation between wedged OF(s)w and open OF(s)o is thus equivalent to ignoring the fact that the insertion of the wedge in an open field modifies the back-scattered radiation from secondary collimators to the beam monitor chamber and the scattered radiation in the phantom. The lack of wedge factor's field size dependence WF(s) or the equivalent lack of wedged field output factor OF(s)w in the beam data installed in TPS is in appreciable source of systematic error in the calculation of the absorbed dose. This systematic uncertainty can be evaluated by measuring the wedge factor's field size dependence. In our study of WF(s) for 25-MV X-rays generated by our Linac "Saturne-43" (by GE), the relative wedge factor variation with respect to the reference value WF(so) ranges from (-.7%) for the smallest wedged field size (5 x 5) cm2 to (+2.6%) for the largest wedged field size (20 x 20) cm2. It is clear that the same relative variation reproduces itself identically as a systematic uncertainty in the calculation of the absorbed dose.

Ferri A; Ruggeri R

1997-10-01

108

'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 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

2013-06-03

109

90Y Bremsstrahlung imaging for absorbed-dose assessment in high-dose radioimmunotherapy.  

UK PubMed Central (United Kingdom)

UNLABELLED: This feasibility study demonstrates (90)Y quantitative bremsstrahlung imaging of patients undergoing high-dose myeloablative (90)Y-ibritumomab treatment. METHODS: The study includes pretherapy (111)In SPECT/CT and planar whole-body (WB) imaging at 7 d and therapy (90)Y SPECT/CT at 6 d and (90)Y WB imaging at 1 d. Time-activity curves and organ-absorbed doses derived from (90)Y SPECT images were compared with pretherapy (111)In estimates. Organ activities derived from (90)Y WB images at the first day were compared with corresponding pretherapy estimates. RESULTS: Pretherapy (111)In images from 3 patients were similar to the (90)Y images. Differences between absorbed-dose estimates from pretherapy (111)In and (90)Y therapy were within 25%, except for the lungs. Corresponding activity differences derived from WB images were within 25%. Differences were ascribed to incomplete compensation methods and real differences in pharmacokinetics between pretherapy and therapy. CONCLUSION: Quantitative bremsstrahlung imaging to estimate organ activities and absorbed doses is feasible.

Minarik D; Sjögreen-Gleisner K; Linden O; Wingårdh K; Tennvall J; Strand SE; Ljungberg M

2010-12-01

110

Indoor concentrations of Rn-222 and Rn-220 descendents: absorbed doses  

International Nuclear Information System (INIS)

Alpha activity due to Radon and Thorium B and their descendents in indoor air were measured and absorbed doses to the respiratory tract calculated. In the absence of ventilation the absorbed dose is very high, about 1500 mrem/year, while in normally ventilated rooms the dose is comparable to that due to outdoor exposure.

1982-01-01

111

Absorbed doses behind bones with MR image-based dose calculations for radiotherapy treatment planning.  

UK PubMed Central (United Kingdom)

PURPOSE: Magnetic resonance (MR) images are used increasingly in external radiotherapy target delineation because of their superior soft tissue contrast compared to computed tomography (CT) images. Nevertheless, radiotherapy treatment planning has traditionally been based on the use of CT images, due to the restrictive features of MR images such as lack of electron density information. This research aimed to measure absorbed radiation doses in material behind different bone parts, and to evaluate dose calculation errors in two pseudo-CT images; first, by assuming a single electron density value for the bones, and second, by converting the electron density values inside bones from T(1)?T(2)?-weighted MR image intensity values. METHODS: A dedicated phantom was constructed using fresh deer bones and gelatine. The effect of different bone parts to the absorbed dose behind them was investigated with a single open field at 6 and 15 MV, and measuring clinically detectable dose deviations by an ionization chamber matrix. Dose calculation deviations in a conversion-based pseudo-CT image and in a bulk density pseudo-CT image, where the relative electron density to water for the bones was set as 1.3, were quantified by comparing the calculation results with those obtained in a standard CT image by superposition and Monte Carlo algorithms. RESULTS: The calculations revealed that the applied bulk density pseudo-CT image causes deviations up to 2.7% (6 MV) and 2.0% (15 MV) to the dose behind the examined bones. The corresponding values in the conversion-based pseudo-CT image were 1.3% (6 MV) and 1.0% (15 MV). The examinations illustrated that the representation of the heterogeneous femoral bone (cortex denser compared to core) by using a bulk density for the whole bone causes dose deviations up to 2% both behind the bone edge and the middle part of the bone (diameter <2.5 cm), but in the opposite directions. The measured doses and the calculated ones in the standard CT image were within 0.4% (through gelatine only) and 0.9% (behind bones). CONCLUSIONS: This study indicates that the decrease in absorbed dose is not dependent on the bone diameter with all types of bones. Thus, performing dose calculation in a pseudo-CT image by assuming a single electron density value for the bones can lead to a substantial misrepresentation of the dose distribution profile. This work showed that dose calculation accuracy can be improved by using a pseudo-CT image in which the electron density values have been converted from the MR image intensity values inside bones.

Korhonen J; Kapanen M; Keyrilainen J; Seppala T; Tuomikoski L; Tenhunen M

2013-01-01

112

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

International Nuclear Information System (INIS)

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

1995-01-01

113

Dose enhancement in buildup region by lead, aluminum, and lucite absorbers for 15 MVp photon beam.  

UK PubMed Central (United Kingdom)

Changes in dose distributions in buildup region resulting from the presence of lead, aluminum, and lucite absorbers above the surface of a polystyrene phantom were evaluated. The surface dose, as a function of the absorber thickness, is presented as well as the influence of the air gap between the lead absorber and the phantom surface. It has been found that the surface dose does not depend on absorber thickness for absorbers thicker than the range of secondary electrons in the absorber material (after corrections for the attenuation of the primary beam in the absorber). Similarly, the depth dose curves in the phantom were elevated only at depths lower than the range of secondary electrons in the phantom. The applicability of the presented data in clinical radiotherapy is discussed.

Ciesielski B; Reinstein LE; Wielopolski L; Meek A

1989-07-01

114

Dose enhancement in buildup region by lead, aluminum, and lucite absorbers for 15 MVp photon beam  

Energy Technology Data Exchange (ETDEWEB)

Changes in dose distributions in buildup region resulting from the presence of lead, aluminum, and lucite absorbers above the surface of a polystyrene phantom were evaluated. The surface dose, as a function of the absorber thickness, is presented as well as the influence of the air gap between the lead absorber and the phantom surface. It has been found that the surface dose does not depend on absorber thickness for absorbers thicker than the range of secondary electrons in the absorber material (after corrections for the attenuation of the primary beam in the absorber). Similarly, the depth dose curves in the phantom were elevated only at depths lower than the range of secondary electrons in the phantom. The applicability of the presented data in clinical radiotherapy is discussed.

Ciesielski, B.; Reinstein, L. E.; Wielopolski, L.; Meek, A.

1989-07-01

115

Absorbed dose measurement by the MIRD system in the 131-I treated Thyroid Cancer patients  

Energy Technology Data Exchange (ETDEWEB)

Medical Internal Radiation Dose(MIRD) schema was developed for calculating the absorbed dose from the administrated radiopharmaceuticals. With the biological distribution data and physical properties of the radionuclide, we can estimated the absorbed dose by the MIRD schema. For the thyroid cancer patients received high dose 131-I therapy, the absorbed dose to the bone marrow is limiting factor to the administered dose and the duration of admission is determined by the retained activity in the whole body. To the monitoring of whole body radioactivity, we used Eberline Smart 200 system using ionization chamber as a detector. With the time activity (Author).

Hong, Seong Woon; Lim, Sang Mu; Kim, Chang Hui; Kim, Ki Sub; Cho, Jong Sio; Jeong, Jin Sung; Park, Heung Kyu; Kwon, Oh Jin [Korea Cancer Center Hospital, Seoul (Korea, Republic of)

1995-12-01

116

Absorbed dose determination in photon fields using the tandem method  

CERN Multimedia

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

117

Advances in absorbed dose measurement standards at the australian radiation laboratory  

Energy Technology Data Exchange (ETDEWEB)

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.

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

1996-12-31

118

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

International Nuclear Information System (INIS)

[en] 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)

2009-10-02

119

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

120

Measurement of absorbed dose in whole body; Examination by computed tomography  

Energy Technology Data Exchange (ETDEWEB)

The doses of radiation absorbed during computed tomography were measured with thermo-luminescence dosimeters (CaF[sub 2]) in selected organs in the head, neck, chest, and in the gonads of a Rando woman phantom. The pituitary gland, eye lenses, parotid glands, submandibular glands, sublingual glands, thyroid glands, breast, ovaries, testis, and surface of skin at the scanning area were the sites for the measurement. The maximum absorbed dose for head scanning was 36988 [mu]Gy in the pituitary gland. The maximum absorbed dose for maxillary scanning was 16625 [mu]Gy in the parotid gland. The maximum absorbed dose for mandibular scanning was 39958 [mu]Gy in the parotid gland. The maximum absorbed dose for coronal and axial scanning of the maxilla was 23816 [mu]Gy in the sublingual glands. The maximum absorbed dose for neck scanning was 50227 [mu]Gy in the thyroid glands. The maximum absorbed dose for chest scanning was 7692 [mu]Gy in the breast. The maximum absorbed dose for abdominal scanning was 6496 [mu]Gy in the breast. (author).

Okumura, Yasuhiko; Yoshitake, Teru; Yamada, Hidehiko; Suzuki, Seiji; Shigematsu, Hisao; Okada, Norihisa; Masuda, Tamuro (Meikai Univ., Saitama (Japan). School of Dentistry); Zhang, Gang

1994-03-01

 
 
 
 
121

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

International Nuclear Information System (INIS)

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

2002-01-01

122

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2008-12-15

123

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.

2008-01-01

124

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

International Nuclear Information System (INIS)

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

1993-01-01

125

Measurement of electron absorbed dose for J-2.5 MV proton accelerator using chemical method  

International Nuclear Information System (INIS)

[en] Combining the ferrous sulphate dosimeter with the radiochromic film dosimeter, the author measured electron absorbed dose, its depth dose distribution and range in water and polyethylenes. The measured maximum absorbed doses in water and polythylene are compared with those obtained with extrapolation ionization chamber, the results of the two methods agree within 2%. The total uncertainty of absorbed dose of water is within 2.1%; in polythylene and other materials are within 6.5%. The confidence level is not less than 95%

1996-01-01

126

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

UK PubMed Central (United Kingdom)

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 B; Wroe A; Kooy H; Depauw N; Flanz J; Paganetti H; Rosenfeld A

2010-01-01

127

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

Energy Technology Data Exchange (ETDEWEB)

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

Zenobio, M.A.F. [Centro de Desenvolvimento da Tecnologia Nuclear, Comissao Nacional de Energia Nuclear, Caixa Postal 941, CEP 30123-970 Belo Horizonte, MG (Brazil)]. E-mail: silvata@cdtn.br; da Silva, T.A. [Centro de Desenvolvimento da Tecnologia Nuclear, Comissao Nacional de Energia Nuclear, Caixa Postal 941, CEP 30123-970 Belo Horizonte, MG (Brazil)]. E-mail: madelon@cdtn.br

2007-06-15

128

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

UK PubMed Central (United Kingdom)

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

Zenóbio MA; da Silva TA

2007-06-01

129

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

UK PubMed Central (United Kingdom)

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 < 0.05). The mean percentage increase was 34 % (+17 %) in ESAK and 46 % (+16 %) in AGD. In the COMBO modality, the mean percentage increase in ESAK was 162 % (+41 %) and in AGD was 202 % (+61 %). Differences between MOSFET measurement and calculated values were <8 % for 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.

Cavagnetto F; Taccini G; Rosasco R; Bampi R; Calabrese M; Tagliafico A

2013-01-01

130

'IN VIVO' AVERAGE GLANDULAR DOSE EVALUATION: ONE-TO-ONE COMPARISON BETWEEN DIGITAL BREAST TOMOSYNTHESIS AND FULL-FIELD DIGITAL MAMMOGRAPHY.  

UK PubMed Central (United Kingdom)

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 < 0.05). The mean percentage increase was 34 % (+17 %) in ESAK and 46 % (+16 %) in AGD. In the COMBO modality, the mean percentage increase in ESAK was 162 % (+41 %) and in AGD was 202 % (+61 %). Differences between MOSFET measurement and calculated values were <8 % for 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.

Cavagnetto F; Taccini G; Rosasco R; Bampi R; Calabrese M; Tagliafico A

2013-06-01

131

Influence of CT number variations on absorbed dose calculations in CT based dose planning  

International Nuclear Information System (INIS)

[en] The present trend in radiotherapy treatment planning is towards increased use of CT picture information to plan and calculate the absorbed dose to the patient. As these calculations are not straightforward, complex algorithms and methods often have to be applied. This study approaches the calculation problems from another viewpoint, namely that of obtaining accurate values for the electron density of the object scanned. As the relationship between the CT numbers and the electron density is complex, any variation in CT numbers will result in less precise dose calculation. Using a specially constructed variable phantom with solution filled inserts, plots of CT number versus electron and mass density are presented. It is seen that these can be represented by a series of straight lines. The variation in CT numbers due to object size, shape, composition and position has been investigated for two different scanner systems, namely the EMI 7070 and Siemens SOMATOM DRH and marked deviations have been observed. Using this information, the influence of these variations on the calculated dose have been compared with the actual dose measured with an ionization chamber in the variable phantom and with TL dosimeters in four regions of an anatomical phantom. The calculation of the dose was performed on a GE RTPLAN II/TARGET treatment planning system. A dose deviation of up to 7% was observed in an extreme case and 4% deviation when standard tables alone were used. It is hoped that more attention will be paid to the measurement of the individual scanners, so that the relevant tables may be implemented in the treatment planning system, thereby improving dose calculation precision. (author). 3 refs, 3 figs, 5 tabs

1987-09-04

132

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)

2009-01-01

133

Direct absorbed dose to water determination based on water calorimetry in scanning proton beam delivery  

Energy Technology Data Exchange (ETDEWEB)

Purpose: The aim of this manuscript is to describe the direct measurement of absolute absorbed dose to water in a scanned proton radiotherapy beam using a water calorimeter primary standard. Methods: The McGill water calorimeter, which has been validated in photon and electron beams as well as in HDR {sup 192}Ir brachytherapy, was used to measure the absorbed dose to water in double scattering and scanning proton irradiations. The measurements were made at the Massachusetts General Hospital proton radiotherapy facility. The correction factors in water calorimetry were numerically calculated and various parameters affecting their magnitude and uncertainty were studied. The absorbed dose to water was compared to that obtained using an Exradin T1 Chamber based on the IAEA TRS-398 protocol. Results: The overall 1-sigma uncertainty on absorbed dose to water amounts to 0.4% and 0.6% in scattered and scanned proton water calorimetry, respectively. This compares to an overall uncertainty of 1.9% for currently accepted IAEA TRS-398 reference absorbed dose measurement protocol. The absorbed dose from water calorimetry agrees with the results from TRS-398 well to within 1-sigma uncertainty. Conclusions: This work demonstrates that a primary absorbed dose standard based on water calorimetry is feasible in scattered and scanned proton beams.

Sarfehnia, A.; Clasie, B.; Chung, E.; Lu, H. M.; Flanz, J.; Cascio, E.; Engelsman, M.; Paganetti, H.; Seuntjens, J. [Medical Physics Unit, McGill University, Montreal, Quebec, H3G-1A4 (Canada); Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114 (United States); Medical Physics Unit, McGill University, Montreal, Quebec, H3G-1A4 (Canada); Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114 (United States); Medical Physics Unit, McGill University, Montreal, Quebec, H3G-1A4 (Canada)

2010-07-15

134

Comparison of Absorbed Dose in Target Organs Using Conventional and Digital Panoramic Radiography  

Directory of Open Access Journals (Sweden)

Full Text Available Background and Aim: The objective of this study was to measure the absorbed dose in target organs using conventional and digital panoramic radiography.Materials and Methods: In this experimental cross-over study, the Rando phantom of the Atomic Energy organization of Iran(AEOI) was exposed 54 times using conventional (Cranex Tome -Sordex), and digital panoramic (Cranex D-Sordex). Radiography The absorbed doses were measured by a dosimeter (TLD’s) in the following areas: Thyroid gland, left and right Parotid and Submandibular glands, Sublingual gland , bone marrow of left and right maxilla and mandible . TLD’s were coded and the absorbed doses for each organ was determined under standard conditions in AEOI. Data was analyzed by using t-test and MANN-U-WHITNEY.Results: In this study, the total absorbed dose in conventional radiography was 0.82±0.06 ( mSiv) compared to 0.42±0.04 (mSiv) in digital radiography . The difference was statistically significant ( P< 1% )and the highest absorbed dose was reported to be in Submandibular glands The lowest absorbed dose was seen in the Thyroid gland. The difference was found to be statistically significant ( P< 0.01 ).Conclusion: Digital radiography can reduce the absorbed dose to critical organs. Keywords: Panoramic radiographies; Dental Digital Radiography; Dosimetry; Radiation

Talaeipour AR; Abbasi M; Sakhdari Sh; Valaii N; Jafari zadeh M

2013-01-01

135

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

136

Absorbed radiation doses in transcranial temporomandibular joint radiography  

Energy Technology Data Exchange (ETDEWEB)

Lateral transcranial radiographs are commonly used to evaluate TMJ morphology and function. This study evaluated the use of four TMJ positioners in controlling the amount of radiation absorbed at predetermined sites on a phantom head. Use of positioners and collimators can reduce the amount of radiation exposure.

Saini, T.S.; Fischer, W.G.; Verbin, R.S.

1986-05-01

137

Absorbed dose homogenizing devices for the 7 MeV NILPRP Linac  

International Nuclear Information System (INIS)

The 7 MeV Linac of the National Institute for Lasers Plasma and Radiation Physics is used for research works and materials irradiations for industry. In order to extend the application domain, two devices were designed and constructed for homogenizing the absorbed dose: one for 7 MeV electrons for absorbed dose and the other for 7 MeV photons. In this paper the device parameters and the transverse absorbed dose distributions are presented. They were measured by means of an ionization chamber (Klinisches Dosimeter 27012-70107). (authors)

2002-01-01

138

Aspects of pre-dose and other luminescence phenomena in quartz absorbed dose estimation  

International Nuclear Information System (INIS)

The understanding of all luminescence processes occurring in quartz is of paramount importance in the further development of robust absorbed dose estimation techniques (for the purpose of dating and retrospective dosimetry). The findings presented in this thesis, aid future improvements of absorbed dose estimation techniques using quartz by presenting investigations in the following areas: 1) interpretation of measurement results, 2) numerical modelling of luminescence in quartz, 3) phenomena needing inclusion in future physical models of luminescence. In the first part, the variability of properties of single quartz grains is examined. Through empirical and theoretical considerations, investigations are made of various problems of measurements of luminescence using multi-grain aliquots, and specifically areas where the heterogeneity of the sample at the inter-grain level may be misinterpreted at the multi-grain-aliquot level. The results obtained suggest that the heterogeneity of samples is often overlooked, and that such differences can have a profound influence on the interpretation of measurement results. Discussed are the shape of TL glow curves, OSL decay curves, dose response curves (including consequences for using certain signals as proxies for others), normalisation procedures and DE estimation techniques. Further, a numerical model of luminescence is proposed, which includes multiple R-centres and is used to describe the pre-dose sensitisation in quartz. The numerical model exhibits a broad-scale behaviour observed experimentally in a sample of annealed quartz. The shapes of TAC for lower (20 Gy) and higher doses (1 kGy) and the evolution with temperature of the isothermal sensitisation curves are qualitatively matched for the empirical and numerical systems. In the third area, a preliminary investigation of the properties of the '110 deg. C peak' in the 550 nm emission band, in annealed quartz is presented. These properties are in sharp contrast with the properties of the '110 deg. C peak' in the 360 nm emission band (e.g. significantly different saturation characteristic and thermal sensitisation characteristic). These differences in behaviour are difficult to incorporate into the band model of luminescence and remain unexplained. (author)

2000-01-01

139

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

140

Absorbed Dose Distributions in Irradiated Plastic Tubing and Wire Insulation  

DEFF Research Database (Denmark)

Plastic tubing and wire insulation were simulated by radiochromic dye dosimeter films having electron absorbing properties similar to the materials of interest (polyethylene and PVC). A 400-keV electron accelerator was used to irradiate from 1, 2, 3 and 4 sides simulating possible industrial irradiation situations. The results indicate that in most cases it is necessary but also sufficient to irradiate from two opposite sides.

Miller, Arne; McLaughlin, W. L.

1979-01-01

 
 
 
 
141

Glandular hypospadias repair.  

UK PubMed Central (United Kingdom)

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

Zaontz MR; Dean GE

2002-05-01

142

Comparison of two protocols for absorbed dose determination in high energy photon beam  

International Nuclear Information System (INIS)

In the FR Yugoslavia radiotherapy centers ICU R-14 protocol for absorbed dose measurements is more frequently used than IAA TR-277 protocol. Two dosimetric protocols (ICU R-14 and IAA TR-277) for absorbed dose measurements in radiotherapy are compared. Difference in determined absorbed dose for photon beams (energy range 1.25 - 1.8 MV) of 2-3% among two protocols originates from the difference of applied water to air stopping powers, and values of the mean energy expended in air per ion pair formation, as well as, perturbation correction factor applied solely in IAA protocol. Taking into account these corrections and effective point of measurement, the difference in absorbed dose obtained by these protocols are furred reduced (in range 1.5%). There is necessity for an unification of dosimetric protocols in the FR Yugoslavia radiotherapy centers on the basis of IAEA TR-277 protocol. (author)

1998-01-01

143

Estimation of absorbed dose due to gas bremsstrahlung from electron storage rings  

Energy Technology Data Exchange (ETDEWEB)

We have studied characteristics of the bremsstrahlung produced in electron storage rings by interactions with residual gas in vacuum chambers. Quantitative estimates of intensity, absorbed dose and shielding requirements are given.

Ban, S.; Hirayama, H.; Miura, S. (National Laboratory for High Energy Physics, Ibaraki-ken (Japan))

1989-09-01

144

Advances in absorbed dose measurement standards at the australian radiation laboratory  

International Nuclear Information System (INIS)

[en] 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

1996-01-01

145

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

Energy Technology Data Exchange (ETDEWEB)

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.).

Dinter, H.

1985-09-15

146

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.).

1985-01-01

147

Optically stimulated luminescence of some thermoluminescent detectors as an indicator of absorbed radiation dose  

Energy Technology Data Exchange (ETDEWEB)

Stimulation spectra of several TLD materials in the short-wave spectral region are measured using the optically stimulated afterglow (OSA) method for determination of absorbed dose. Optical stimulation spectra are studied in the region of wavelengths lower than those of emission spectra. The effective optical stimulation bands have been found for examined materials in the regions of wavelengths which overlap with fluorescence excitation bands. Application of short-wave OSA bands for determination of absorbed dose is analysed. (author)

Jaek, I.; Kerikmaee, M.; Lust, A

2002-07-01

148

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.

2001-01-01

149

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

Energy Technology Data Exchange (ETDEWEB)

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 melanogaster00.

Delfin, A. E-mail: adl@nuclear.inin.mx; Paredes, L.C.; Zambrano, F.; Guzman-Rincon, J.; Urena-Nunez, F

2001-11-01

150

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).

1996-01-01

151

Evaluation of mean glandular dose and modulation transfer function for different tube potentials and target-filter combinations in computed radiography mammography.  

UK PubMed Central (United Kingdom)

BACKGROUND: Different target-filter combinations in computed radiography have different impacts on the dose and image quality in digital radiography. This study aims to evaluate the mean glandular dose (MGD) and modulation transfer function (MTF) of various target-filter combinations by investigating the signal intensities of X-ray beams. METHODS: General Electric (GE) Senographe DMR Plus mammography unit was used for MGD and MTF evaluation. The measured MGD was compared with the dose reference level (DRL), whereas the MTF was evaluated using ImageJ 1.46o software. A modified Mammography Accreditation Phantom RMI 156 was exposed using different target-filter combinations of molybdenum-molybdenum (Mo-Mo), molybdenum-rhodium (Mo-Rh) and rhodium-rhodium (Rh-Rh) at two different tube voltages, 26 kV and 32 kV with 50 mAs. RESULTS: In the MGD evaluations, all target-filters gave an MGD value of < 1.5 mGy. The one-way ANOVA test showed a highly significant interaction between the MGD and the kilovoltage and target-filter material used (26 kV: F (2,12) = 49,234, P = 0.001;32 kV: F (2,12) = 89,972, P = 0.001). A Tukey post-hoc test revealed that the MGD for 26 kV and 32 kV was highly affected by the target-filter combinations. The test of homogeneity of variances indicates that the MGD varies significantly for 26 kV and 32 kV images (0.045 and 0.030 (P < 0.05), respectively). However, the one-way ANOVA for the MTF shows that no significant difference exists between the target-filter combinations used with 26 kV and 32 kV images either in parallel or perpendicular to the chest wall side F (2,189) = 0.26, P > 0.05). CONCLUSION: Higher tube voltage and atomic number target-filter yield higher MGD values. However, the MTF is independent of the X-ray energy and the type of target-filter combinations used.

Abdul Aziz SA; Mohd Saparudin AK; Harun AZ

2013-05-01

152

The absorbed dose in femur exposed to diagnostic radiography.  

UK PubMed Central (United Kingdom)

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

Salehi Z; Yusoff AL

2013-01-01

153

Estimation of the absorbed dose in gamma irradiated food containing bone by electron spin resonance spectroscopy  

International Nuclear Information System (INIS)

The use of electron spin resonance (ESR) spectroscopy to accurately evaluate the absorbed dose to radiationprocessed bones (and thus meats) is examined. The exposure of foodstuffs containing bone to a dose of ionizing radiation results in the formation of long lived free radicals which give rise to characteristics ESR signals. The yield of radicals was found to be proportional to absorbed dose. Additive re-irradiation of previously irradiated bone was used to estimate the absorbed dose in the irradiated chicken bone. Simple non-linear rational equation was found to fit to the data and yields good dose estimates for irradiated bone in the range of doses (1.0 - 5.0 kGy). Decay of the ESR signal intensity was monitored at different dose levels (2.0 and 7.0 kGy) up to 22 days. The absorbed dose in irradiated chicken (2.Om 3.0 and 6.0 kGy) was assessed at 2, 6 and 12 days after irradiation. Relatively good results were obtained when measurements were made within the following days (up to 12 days) after irradiation. The ability of the dose additive method to provide accurate dose assessments is tested here.

1997-01-01

154

Effects of body and organ size on absorbed dose: there is no standard patient  

International Nuclear Information System (INIS)

The problem of estimating the absorbed dose to organs and tissues of the human body due to the presence of a radiopharmaceutical in one or more organs is discussed. Complications are introduced by the fact that the body is not homogeneous and in many cases the organ shapes are not regular. Publications of the MIRD Committee have provided a direct means of estimating the absorbed dose (or absorbed fraction) for a number of radioisotopes. These estimates are based on Monte Carlo calculations for monoenergetic photons distributed uniformly in organs of an adult phantom. The medical physicist finds that his patient does not resemble the adult phantom. In addition, the absorbed fractions for the adult are not reasonable values for the child. This paper examines how these absorbed fraction estimates apply to a nonstandard patient

1976-04-26

155

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

International Nuclear Information System (INIS)

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

2012-01-01

156

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

157

Measurement of absorbed dose on radiation sterilization of medical articles  

International Nuclear Information System (INIS)

[en] In comparison to the results measured by Fricke dosimeter of national standard (called Fricke meter in the following text), Alanine Dosimeter of National Dose Assurance Service (called NDAS in the following text) and our dosimeter the errors were +-2.0% and +-0.5% respectively. Determined D10 values of indication bacillus E601(bacillus pumilus) and HBSAg (surface antigen) were 1.69 kGy and 47.1 kGy respectively. The dose homogeneous degree was 1.33-1.84

1995-01-01

158

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)

1994-01-01

159

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.

1996-01-01

160

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

Energy Technology Data Exchange (ETDEWEB)

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

Fisher, Darrell R.; Shen, Sui; Meredith, Ruby F.

2009-04-16

 
 
 
 
161

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

International Nuclear Information System (INIS)

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

2009-04-16

162

Absorbed radiation dose due to synchrotron radiation in the storage ring PETRA  

Energy Technology Data Exchange (ETDEWEB)

The spatial distribution of absorbed doses due to synchrotron radiation from the high-energy storage ring PETRA was measured using RPL glass dosimeters. The measured doses have been compared with the corresponding 'kerma' values calculated by the Monte Carlo code EGS. Good agreement has been obtained.

Dinter, H.; Tesch, K.; Yamaguchi, C. (Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany, F.R.))

1982-09-15

163

Development and evaluation of an independent system for absorbed dose calculations in radiotherapy  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The aim of this work was to develop, implement and evaluate an independent system with which to calculate the absorbed dose, delivered by high-energy X-ray beams, to the prescription point and the depth of dose maximum. The introduction of such a system in the clinical routine may help ensure high-q...

Johnsson, Stefan

164

Real-time measurement and monitoring of absorbed dose for electron beams  

Energy Technology Data Exchange (ETDEWEB)

The real-time method and system for measurement and monitoring of absorbed dose for industrial and research electron accelerators is considered in the report. The system was created on the basis of beam parameters method. The main concept of this method consists in the measurement of dissipated kinetic energy of electrons in the irradiated product, determination of number of electrons and mass of irradiated product in the same cell by following calculation of absorbed dose in the cell. The manual and automation systems for dose measurements are described. The systems are acceptable for all types of electron accelerators.

Korenev, Sergey E-mail: sergey_korenev@steris.com; Korenev, Ivan; Rumega, Stanislav; Grossman, Leon

2004-10-01

165

Real-time measurement and monitoring of absorbed dose for electron beams  

International Nuclear Information System (INIS)

The real-time method and system for measurement and monitoring of absorbed dose for industrial and research electron accelerators is considered in the report. The system was created on the basis of beam parameters method. The main concept of this method consists in the measurement of dissipated kinetic energy of electrons in the irradiated product, determination of number of electrons and mass of irradiated product in the same cell by following calculation of absorbed dose in the cell. The manual and automation systems for dose measurements are described. The systems are acceptable for all types of electron accelerators.

2004-01-01

166

Real-time measurement and monitoring of absorbed dose for electron beams  

Science.gov (United States)

The real-time method and system for measurement and monitoring of absorbed dose for industrial and research electron accelerators is considered in the report. The system was created on the basis of beam parameters method. The main concept of this method consists in the measurement of dissipated kinetic energy of electrons in the irradiated product, determination of number of electrons and mass of irradiated product in the same cell by following calculation of absorbed dose in the cell. The manual and automation systems for dose measurements are described. The systems are acceptable for all types of electron accelerators.

Korenev, Sergey; Korenev, Ivan; Rumega, Stanislav; Grossman, Leon

2004-09-01

167

Absorbed dose in polymers during a positron annihilation experiment  

Energy Technology Data Exchange (ETDEWEB)

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 {sup 22}Na have sufficient energy to induce radiation damage in polymers. In this study, the radiation dose induced by positrons emitted from {sup 22}Na 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).

Suzuki, T.; Namito, Y.; Oki, Y.; Numajiri, M.; Miura, T.; Hirayama, H.; Kondo, K. [National Lab. for High Energy Physics, Tsukuba, Ibaraki (Japan); Ito, Y.

1994-11-01

168

Radiation absorbed dose to the human fetal thyroid  

International Nuclear Information System (INIS)

The embryo/fetus is recognized to be particularly susceptible to damage from exposure to radiation. Many advisory groups have studied available information concerning radiation doses and radiation effects with the goal of reducing the risk to the embryo/fetus. Of particular interest are radioactive isotopes of iodine. Radioiodine taken into the body of a pregnant woman presents a possible hazard for the embryo/fetus. The fetal thyroid begins to concentrate iodine at about 13 weeks after conception and continues to do so throughout gestation. At term, the organic iodine concentration in the fetal blood is about 75% of that in the mother's blood. This paper presents a review the models that have been proposed for the calculation of the dose to the fetal thyroid from radioisotopes of iodine taken into the body of the pregnant woman as sodium iodide. A somewhat different model has been proposed, and estimates of the radiation dose to the fetal thyroid calculated from this model are given for each month of pregnancy from 123I , 124I , 125I , and 131I

1992-01-01

169

Intercomparison of absorbed doses in cobalt-60 therapy  

International Nuclear Information System (INIS)

[en] IAEA and WHO developed a postal intercomparison program to measure the output of Co-60 therapy units all over the world. The first results of modified postal intercomparison based on IAEA/WHO program are reported. A mailable 10x10x10,5 cm Mix-D phantom with embedded TLD dosimeters, films and field markers of lead and a questionaire were developed not only to obtain information regarding the output of Co-60 therapy machines but also to get information about alignment, field homogeneity, dose calculations, field size and surface dose. This program was tested in 10 differents Radiotherapy Centers. The results of this intercomparison gave a spread of the absorved dose from 78 rads to 127 rads for 5cm depth of the phantom and a reference value of 100 rads. Variation in the prescribed field size of 6 x 6cm were between 30cm2 and 100cm2. In half of the cases no homogeneity of the radiation field was spolted

1975-07-11

170

Absorbed dose calculations to blood and blood vessels for internally deposited radionuclides  

International Nuclear Information System (INIS)

At present, absorbed dose calculations for radionuclides in the human circulatory system use relatively simple models and are restricted in their applications. To determine absorbed doses to the blood and to the surface of the blood vessel wall, Monte Carlo calculations were performed using the code Electron Gamma Shower (EGS4). Absorbed doses were calculated for the blood and the blood vessel wall (lumen) for different blood vessel sizes. The radionuclides chosen for this study were those commonly used in nuclear medicine. No diffusion of the radionuclide into the blood vessel was or cross fire between blood vessels was assumed. Results are useful in assessing the doses to blood and blood vessel walls for different nuclear medicine procedures

1992-01-01

171

Calculation of absorbed doses in an organ using the MIRD method  

International Nuclear Information System (INIS)

[en] 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.)

1983-01-01

172

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.

1990-01-01

173

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

International Nuclear Information System (INIS)

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

2003-01-01

174

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

175

Absorbed dose in the full-mouth periapical radiography, panoramic radiography, and zonography  

Energy Technology Data Exchange (ETDEWEB)

The objective of this study was to evaluate the possibility of substitution of the zonography for the full-mouth periapical radiography in aspect of radiation protection. Rando phantom and LiF TLD chips were used for dosimetry. The absorbed doses at brain, skin above the TMJ, parotid gland, bone marrow in the mandibular body, and thyroid gland during the full-mouth periapical radiography, panoramic radiography, and zonography were measured. From the zonography, the absorbed doses to the brain, the skin over the TMJ, and the parotid gland were relatively high, but the absorbed doses to the bone marrow in the mandibular body and, especially, the thyroid gland were very low. The zonography can be an alternative to the full-mouth periapical radiography in aspect of radiation protection.

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

1999-02-15

176

Absorbed dose measurements in a close vicinity to a clinical proton beam  

International Nuclear Information System (INIS)

[en] The basic dosimetric characteristics of particles beyond the clinical proton beam profile are described. The experiments were performed at the clinical proton facility of the Joint Institute for Nuclear Research in Dubna, Russia, focusing on the absorbed dose and average linear energy transfer (LET) determinations. A combination of Al2O3:C and CaSO4:Dy thermoluminescent detectors was used. The relative thermoluminescent yield of the detectors depends on the LET and is different for the two detector types. In other words, different detector responses are obtained for the same absorbed dose. This difference was used to determine the average LET value. The data also enabled us to determine the absorbed dose uncertainty due to the change in the calibration beam radiation quality. (orig.)

2011-01-01

177

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 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

2012-01-01

178

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

International Nuclear Information System (INIS)

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

2005-01-01

179

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-12-15

180

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 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

2011-01-01

 
 
 
 
181

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

182

Absorbed XFEL Dose in the Components of the LCLS X-Ray Optics  

Energy Technology Data Exchange (ETDEWEB)

There is great concern that the short, intense XFEL pulse of the LCLS will damage the optics that will be placed into the beam. We have analyzed the extent of the problem by considering the anticipated materials and position of the optical components in the beam path, calculated the absorbed dose as a function of photon energy, and compared these doses with the expected doses required (i) to observe rapid degradation due to thermal fatigue, (ii) to reach the melting temperature, or (iii) to actually melt the material. We list the materials that are anticipated to be placed into the Linac Coherent Light Source (LCLS) x-ray free electron laser (XFEL) beam line, their positions, and the absorbed dose, and compare this dose with anticipated damage thresholds.

Hau-Riege, Stefan

2010-12-03

183

Dose absorbed by technologists in positron emission tomography procedures with FDG  

International Nuclear Information System (INIS)

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

2007-01-01

184

CCRI supplementary comparison of standards for absorbed dose to water in 60Co gamma radiation at radiation processing dose levels  

International Nuclear Information System (INIS)

Six national standards for absorbed dose to water in 60Co gamma radiation at the dose levels used in radiation processing have been compared over the range from 5 to 30 kGy using the alanine dosimeters of the NIST and the NPL as the transfer dosimeters. The standards are in agreement at the level of around 0.5%, which is significantly smaller than the stated standard uncertainties.

2006-01-01

185

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

UK PubMed Central (United Kingdom)

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

Wieser A

2012-03-01

186

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

2002-01-01

187

Absorbed dose measurement in low temperature samples: comparative methods using simulated material  

International Nuclear Information System (INIS)

There is a growing need to reliably measure absorbed dose in low temperature samples, especially in the pharmaceutical and tissue banking industries. All dosimetry systems commonly used in the irradiation industry are temperature sensitive. Radiation of low temperature samples, such as those packaged with dry ice, must therefore take these dosimeter temperature effects into consideration. This paper will suggest a method to accurately deliver an absorbed radiation dose using dosimetry techniques designed to abrogate the skewing effects of low temperature environments on existing dosimetry systems.

2004-01-01

188

State of the knowledge for electromagnetic absorbed dose in man and animals  

Energy Technology Data Exchange (ETDEWEB)

A study was conducted to: determine the effects of electromagnetic (EM) radiation on humans; establish radiation safety standards; and identify definitive hazard levels. The EM absorbed dose for humans and animals at various frequencies for the plane wave irradiation condition for different orientations of the body relative to incident fields was determined. Whole body absorption for conditions of electrical contact with ground and in the presence of reflecting surfaces of high conductivity and multiple animals is given. EM densitometry is not of primary importance; for a given power density, the absorbed dose can vary by orders of magnitude depending on the frequency, animal size and its orientation, and physical environment.

Gandhi, O.P.

1980-01-01

189

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

190

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.

1992-01-01

191

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

International Nuclear Information System (INIS)

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

2003-01-01

192

Monte Carlo calculated absorbed-dose energy dependence of EBT and EBT2 film.  

UK PubMed Central (United Kingdom)

PURPOSE: The absorbed-dose energy dependence of GAFCHROMIC EBT and EBT2 film irradiated in photon beams is studied to understand the shape of the curves and the physics behind them. METHODS: The absorbed-dose energy dependence is calculated using the EGSnrc-based EGS_chamber and DOSRZnrc codes by calculating the ratio of dose to water to dose to active film layers at photon energies ranging from 3 keV to 18 MeV. These data are compared to the mass energy absorption coefficient ratios and the restricted stopping power ratios of water to active film materials as well as to previous experimental results. RESULTS: In the photon energy range of 100 keV to 18 MeV the absorbed-dose energy dependence is found to be energy independent within +/- 0.6%. However, below 100 keV, the absorbed-dose energy dependence of EBT varies by approximately 10% due to changes in mass energy absorption coefficient ratios of water to film materials, as well as an increase in the number of electrons being created and scattered in the central surface layer of the film. Results are found to disagree with previous experimental studies suggesting the possibility of an intrinsic energy dependence at lower photon energies. For EBT2 film the absorbed-dose energy dependence at low photon energies varies by 50% or 10% depending on the manufacturing lot due to changes in the ratio of mass energy absorption coefficients of the active emulsion layers to water. CONCLUSIONS: Caution is recommended when using GAFCHROMIC EBT/EBT2 films at photon energies below 100 keV. It is recommended that the effective atomic number of future films be produced as close to that of water and that thicker active layers are advantageous.

Sutherland JG; Rogers DW

2010-03-01

193

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

Energy Technology Data Exchange (ETDEWEB)

Objective. We assessed the relative radiation load in patients undergoing hydrostatic and pneumatic reduction of childhood intussusception. Materials and methods. In a phantom study we simulated two situations occurring during reduction of intussusception. The absorbed radiation dose was measured at several positions in the phantom using either barium sulphate (BaSO{sub 4}) or air in the simulated reduction, combined with either automatic exposure control (AEC) or constant exposure rate (CER) at fluoroscopy. From these values the mean absorbed dose was calculated for different depth compartments within the phantom. Results. In the barium study the mean absorbed dose averaged over the total irradiated volume was 14-23 % lower when CER was used instead of AEC; in the air study the dose was 35-43 % lower when AEC was used instead of CER. The combination of air and AEC provided the lowest mean absorbed dose in the tissue. The barium enema created a low-radiation zone, which might be utilized for protecting radiation sensitive tissue. Conclusion. The use of BaSO{sub 4} or air in reduction of intussusception requires the proper combination with CER and AEC, respectively, to minimize the radiation load to the patient; the lowest radiation load is obtained by using air and AEC. (orig.). With 1 fig., 3 tabs.

Persliden, J. [Department of Radiation Physics, Faculty of Health Science, Linkoeping University, Linkoeping (Sweden); Schuwert, P. [Hospital Physics, The Karolinska Hospital, Stockholm (Sweden); Mortensson, W. [Department of Pediatric Radiology, The Karolinska Institute, St. Goeran`s Children`s Hospital, Box 12 500, S-112 81 Stockholm (Sweden)

1996-05-01

194

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

International Nuclear Information System (INIS)

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

1996-01-01

195

Status of air kerma and absorbed dose standards in India  

International Nuclear Information System (INIS)

Full text: The Radiation Safety Systems Division of Bhabha Atomic Research Centre, India maintains Primary and Secondary Standards of various parameters of radiation measurements and provides calibration services to various users of radiation in the country. This is an apex laboratory in India and plays a pivotal role in ensuring accurate radiological measurements. The laboratory coordinates national intercomparisons of radiation measurements to maintain their uniformity and traceability and is linked through various programmes with the other International organizations such as Bureau Internationale des Poids et Mesures (BIPM) Paris, International Atomic Energy Agency (IAEA) Vienna, Asia Pacific Metrology Programme (APMP) Taiwan. It is the recognized Regional Secondary Standards Dosimetry Laboratory (SSDL) of IAEA/WHO (World Health Organisation). This paper brings out the status of various primary and secondary standards for radiological measurements maintained at BARC. 1. Primary Exposure/Air-kerma standard at Co-60 energy (therapy level): The primary standard for exposure/ air-kerma measurements maintained at BARC is a graphite cavity chamber of volume 4.362 cc with an internal diameter of 1.8 cm, internal height of 1.78 cm and wall thickness of 704.3mg/cm2. Correction factors for the difference between electron stopping powers, photon mass energy absorption coefficients of air and graphite wall, correction for recombination, radiation field non-uniformity, stem scatter and polarity effect are applied and the maximum overall uncertainty in the realisation of exposure/air-kerma is around ±1%. This standard has been intercompared with IAEA and BIPM through transfer standard and the agreement in the results are better than ±1%. An intercomparison under the APMP programme is to be held during May, 2002. 2. Primary Exposure/Air-kerma standard at protection and brachytherapy level: A set of three spherical graphite-walled cavity chambers of different air-volumes are maintained as primary standards for protection level and brachytherapy measurements of Ir-192, Cs-137 and Co-60 sources. These chambers are made of high purity reactor-grade graphite of density 1700 kg/m3. The three chambers have different wall thickness, the external diameters of all the chambers being equal. A reference standard in the form of a re-entrant chamber developed at BARC, calibrated against this primary standard was intercompared with a reference standard from M.D Anderson Centre, Houston, U.S.A and the results showed a good agreement. Recently one of the chambers was used for the Cs-137 intercomparison with IAEA and showed an agreement of better than ± 1%. 3. Primary Standard for X-rays - the free air chamber (FAC): This facility is utilized in conjunction with a Philips RT-250 X-ray machine for calibrating secondary standard dosemeters at different X-ray qualities in the 75 to 250 kV range. The total uncertainty in the realization of air kerma is around ±1% using the free air chamber. Accuracy of calibration of the secondary standards is estimated to be better than ±2%. The FAC has been intercompared via transferable transfer standards with FACs at BIPM (1971), BNM (France) RCL (Canada) and Kriss (Korea), which showed good agreement within ±1% after necessary correction for the spectral differences in X-ray beams. BARC is just now taking part in intercomparisons of X-ray air kerma calibration factors organised by Institute of Nuclear Energy Research (INER), Taiwan under Asia Pacific Metrology Programme. In addition to the above-mentioned primary standards, the SSDL is also maintaining the following secondary standards. For air kerma measurements at Co-60 gamma energy, ionisation chambers of Exradin A3, NE2571, NE2577 and Victoreen 415 types are calibrated and maintained. For Co-60 radiation dose to water measurements, NE 2571 and NE 2577 chambers calibrated at BIPM in terms of ND,W are maintained. For air kerma at medium energy x-rays, chambers of the type Exradin A2, NE 2571, NE2577, Victoreen 415 B, Victoreen 415, Exradin A3 and NE 2581 are

2002-01-01

196

MCNP simulation of absorbed energy and dose by iodinated contrast agent  

Science.gov (United States)

The purpose of this study is to investigate the absorbed dose and energy by iodinated contrast medium in diagnostic radiology. A simulation geometry in which an inner sphere (d = 0.2cm, 1cm, 5cm) filled with iodinated contrast medium (or water) is located at the center of a 20cm diameter water sphere was used in simulations performed with MCNP5 codes. Monoenergetic x-rays with energies ranging from 40 to 80keV from a cone beam source were utilized and contrast medium concentration ranged from 100 to 1mg/ml. Absorbed dose ratio (RD) to inner sphere and total absorbed energies ratio (RE) to the whole phantom with and without iodinated contrast medium were investigated. The maximum RD was ~13 for the 0.2cm diameter sphere with 100mg/ml contrast medium. The maximum RE was ~1.05 for the 5cm diameter contrast sphere at 80keV with 100mg/ml contrast medium. Under the same incident photon energy, increasing the inner sphere size from 0.2cm to 5cm caused a ~63% increase in the RD on average. Decreasing the contrast medium concentration from 100 to 10 mg/ml caused a decrease of RD of ~ 76%. A conclusion was reached that although local absorbed dose increase caused by iodinated contrast agent could be high; the increase in total absorbed energy is negligible.

He, Wenjun; Mah, Eugene; Huda, Walter; Yao, Hai

2012-02-01

197

Dynamic dose-shaping by gravity-oriented absorbers for total lymph node irradiation  

International Nuclear Information System (INIS)

[en] Rotational therapy with gravity-oriented absorbers is proposed for better total lymph node irradiation (TLI). Two metal semicylinders are joined coaxially (face to face) to form a radiation absorber that is centrally suspended in the beam. During rotation this absorber is kept parallel to itself by gravity, like the riders of a Ferris wheel. The vertebrae remain continuously protected under the absorber's shadow. The circular full-dose region, achieved by ordinary rotation, is now transformed into a horse-shoe region embracing the spine anteriorly. The abdominal lymph nodes are thus irradiated while the spine and most of the normal tissue around the spine are protected. A similar technique is applied for the selective irradiation of the pelvic lymph nodes, which are confined in the two legs of an inverted V region

1981-01-01

198

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

Energy Technology Data Exchange (ETDEWEB)

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

Watts, J.W. Jr.; Parnell, T.A.; Akatov, Yu.A.; Dudkin, V.E.; Kovalev, E.E.; Benton, E.V.; Frank, A.L. [Institute of Biomedical Problems, Moscow (Russian Federation)]|[San Francisco Univ., CA (United States)

1995-03-01

199

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

International Nuclear Information System (INIS)

[en] The research on dose distribution in 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. Dmax/Dmin in this study was 1.45 irradiated in a commercial 60Co facility. The density of orange containers was about 0.391g/cm3. The evaluation of dosimeters showed that the PMMA-YL and clear PMMA dosimeters have linear 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. (author)

1998-04-03

200

Radiation absorbed dose to bladder walls from positron emitters in the bladder content  

Energy Technology Data Exchange (ETDEWEB)

A method to calculate absorbed doses at depths in the walls of a static spherical bladder from a positron emitter in the bladder content has been developed. The beta ray dose component is calculated for a spherical model by employing the solutions to the integration of Loevinger and Bochkarev point source functions over line segments and a line segment source array technique. The gamma ray dose is determined using the specific gamma ray constant. As an example, absorbed radiation doses to the bladder walls from F-18 in the bladder content are presented for static spherical bladder models having radii of 2.0 and 3.5 cm, respectively. Experiments with ultra-thin thermoluminescent dosimeters (TLD's) were performed to verify the results of the calculations. Good agreement between TLD measurements and calculations was obtained.

Powell, G.F.; Chen, C.T.

1987-11-01

 
 
 
 
201

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)

2005-01-01

202

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; M Sakhaee; M Vahabi-Moghaddam

2011-01-01

203

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 elec...

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

204

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.)

1999-01-01

205

Absorbed dose and collision kerma relationship for high-energy photons  

International Nuclear Information System (INIS)

Historically, exposure has been used as an important quantity to specify x- or ?-ray beams. For any photon beam the energy fluence is proportional to the exposure. Exposure can be calculated and/or measured if the spectrum of the beam is known and charged particle equilibrium (CPE) exists. For low energy photons (up to approximately 1 MeV), due to the existence of CPE, absorbed dose (D) is equal to the collision kerma (K/sub c/). For megavoltage photons this equality is lost due to CPE failure, which also restricts the measurement of exposure. It is possible, though, to find a relationship between the absorbed dose and collision kerma when transient charged particle equilibrium (TCPE) exists. This basic idea was originally proposed by Roesch in 1958 and its refinement has been discussed by Attix in 1979 and 1983. The modified Roesch's formula that enables measuring exposure even for high-energy photons is given by D = ? K/sub c/ approx. = K/sub c/ (1 + ?' ), where ?' is the effective linear attenuation coefficient and is the mean distance the secondary electrons carry kinetic energy in the direction of the photon beam while depositing it as absorbed dose. The symbol ? is the quotient of the absorbed dose and the collision kerma. Calculations were also performed for several photon energies and materials, using the Roesch method, which does not include photon scattering effects. Comparisons of measured and calculated values of show reasonable agreement.

1984-01-01

206

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

International Nuclear Information System (INIS)

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

2008-01-01

207

Estimation of absorbed dose levels at possible locations for LHCb detector electronics  

CERN Multimedia

2000-015 Absorbed dose levels are calculated for a model of the LHCb subdetector electronics and the fast electronics crates, located in the experimental cavern. The value of 1 MeV neutron equivalent flux is also estimated for a particular region of the detector.

Talanov, V

2000-01-01

208

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

International Nuclear Information System (INIS)

[en] 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)

1990-01-01

209

NPL's new absorbed dose standard for the calibration of HDR 192Ir brachytherapy sources  

Science.gov (United States)

A novel graphite calorimeter for absorbed dose rate measurements close to high dose rate (HDR) 192Ir brachytherapy sources has been designed and built at the UK National Physical Laboratory (NPL). The graphite calorimeter allows a more direct calibration of HDR 192Ir sources in terms of absorbed dose rate to water at a distance of 1 cm, \\dot {D}_{w, 1\\,cm} , compared with the current air kerma-based calibration method, where \\dot {D}_{w, 1\\,cm} is determined as the product of the measured air kerma strength and the dose rate constant, ?, resulting in overall standard uncertainties of up to 5%. With the new absorbed dose standard, \\dot {D}_{w, 1\\,cm} can be measured directly with standard uncertainties between 0.7% and 1.0%, depending on the operating mode of the calorimeter. A Nucletron microSelectron-v1 Classic HDR 192Ir source was calibrated with the calorimeter in terms of \\dot {D}_{w, 1\\,cm} . The same source was also calibrated with NPL's HDR 192Ir air kerma primary standard in terms of reference air kerma rate. Combining both measurements yielded the experimentally determined dose rate constant of the 192Ir source.

Sander, T.; Duane, S.; Lee, N. D.; Thomas, C. G.; Owen, P. J.; Bailey, M.; Palmans, H.

2012-10-01

210

Predictions of a stochastic model of bone marrow cell survival in high dose rate radiation fields with arbitrary neutron to gamma-ray absorbed dose rate ratios.  

UK PubMed Central (United Kingdom)

In this paper, a stochastic model of cell survival, which was developed by Cotlet and Blue, based on the work of Jones, is extended to describe bone marrow cell survival in high dose rate radiation fields with arbitrary neutron to gamma-ray absorbed dose rate ratios. Mathematical formulas are obtained that describe the interaction of the neutron and gamma-ray components of the absorbed dose, for radiation fields with arbitrary neutron to gamma-ray dose rate ratios, for exposures of cells to various absorbed doses, at various high dose rates.

Blue TE; Woollard JE

2000-10-01

211

Predictions of a stochastic model of bone marrow cell survival in high dose rate radiation fields with arbitrary neutron to gamma-ray absorbed dose rate ratios.  

Science.gov (United States)

In this paper, a stochastic model of cell survival, which was developed by Cotlet and Blue, based on the work of Jones, is extended to describe bone marrow cell survival in high dose rate radiation fields with arbitrary neutron to gamma-ray absorbed dose rate ratios. Mathematical formulas are obtained that describe the interaction of the neutron and gamma-ray components of the absorbed dose, for radiation fields with arbitrary neutron to gamma-ray dose rate ratios, for exposures of cells to various absorbed doses, at various high dose rates. PMID:11099209

Blue, T E; Woollard, J E

2000-10-01

212

[Radioiodine therapy for differentiated thyroid carcinoma: methods used to increase the radiation absorbed dose].  

UK PubMed Central (United Kingdom)

OBJECTIVES: Our aim was to analyze measures taken to increase the radiation absorbed dose (DOSE) during treatment of well-differentiated thyroid cancer (DTC) with iodine-131. METHODS: An increase in DOSE is achieved by: avoiding competition with non-radioactive iodine, stimulating cellular uptake/retention, increasing the administered activity. Basis and results of each one of these methods were reviewed. RESULTS: Although it is difficult to demonstrate an increase in survival, there is a direct relation between DOSE and tumoral response in DTC. Different approaches can be used aiming an increase in DOSE, with a possible improvement in tumoral response for treatment with iodine-131. Although DTC is a relatively benign disease, a better response to treatment is highly desirable in high-risk patients, who have few other options of therapy. CONCLUSIONS: An increase in DOSE during treatment of DTC can be achieved using the described interventions, which should be used in high-risk cases of DTC.

Sapienza MT; Endo IS; Campos Neto GC; Tavares MG; Marone MM

2005-06-01

213

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

International Nuclear Information System (INIS)

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

2010-01-01

214

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

International Nuclear Information System (INIS)

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

2001-01-01

215

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

International Nuclear Information System (INIS)

[en] 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)

1998-01-01

216

Assessment of effective absorbed dose of (111)In-DTPA-Buserelin in human on the basis of biodistribution rat data.  

UK PubMed Central (United Kingdom)

In this study, the effective absorbed dose to human organs was estimated, following intra vascular administration of (111)In-DTPA-Buserelin using biodistribution data from rats. Rats were sacrificed at exact time intervals of 0.25, 0.5, 1, 2, 4 and 24 h post injections. The Medical Internal Radiation Dose formulation was applied to extrapolate from rats to humans and to project the absorbed radiation dose for various human organs. From rat data, it was estimated that a 185-MBq injection of (111)In-DTPA-Buserelin into the human might result in an estimated absorbed dose of 24.27 mGy to the total body and the highest effective absorbed dose was in kidneys, 28.39 mSv. The promising results of this study emphasises the importance of absorbed doses in humans estimated from data on rats.

Lahooti A; Shanehsazzadeh S; Jalilian AR; Tavakoli MB

2013-04-01

217

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

Energy Technology Data Exchange (ETDEWEB)

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, approx. =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.

Chen, C.T.; Harper, P.V.; Lathrop, K.A.

1984-01-01

218

Dose absorbed by technologists in positron emission tomography procedures with FDG  

Scientific Electronic Library Online (English)

Full Text Available 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 diferenças significativas em sua organização e radioproteção. Esses centros aplicavam aproximadamente 300 MBq por exame PET/CT, embora apenas um deles correspondesse a um se (more) rviço 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 significant differences in their arrangements and radiation safety conditions. Both centers administered about 300 MBq per PET/CT study, although only one of them is a dedicated clinical (more) 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.

Amaral, Ademir; Itié, Christian; Bok, Bernard

2007-09-01

219

Microdosimetric measurements for neutron-absorbed dose determination during proton therapy.  

Science.gov (United States)

This work presents microdosimetric measurements performed at the Midwest Proton Radiotherapy Institute in Bloomington, Indiana, USA. The measurements were done simulating clinical setups with a water phantom and for a variety of stopping targets. The water phantom was irradiated by a proton spread out Bragg peak (SOBP) and by a proton pencil beam. Stopping target measurements were performed only for the pencil beam. The targets used were made of polyethylene, brass and lead. The objective of this work was to determine the neutron-absorbed dose for a passive and active proton therapy delivery, and for the interactions of the proton beam with materials typically in the beam line of a proton therapy treatment nozzle. Neutron doses were found to be higher at 45° and 90° from the beam direction for the SOBP configuration by a factor of 1.1 and 1.3, respectively, compared with the pencil beam. Meanwhile, the pencil beam configuration produced neutron-absorbed doses 2.2 times higher at 0° than the SOBP. For stopping targets, lead was found to dominate the neutron-absorbed dose for most angles due to a large production of low-energy neutrons emitted isotropically. PMID:22334761

Pérez-Andújar, Angélica; Deluca, Paul M; Thornton, Allan F; Fitzek, Markus; Hecksel, Draik; Farr, Jonathan

2012-02-14

220

Microdosimetric measurements for neutron-absorbed dose determination during proton therapy  

International Nuclear Information System (INIS)

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

2012-01-01

 
 
 
 
221

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. 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.

2010-01-01

222

An international dosimetry exchange for boron neutron capture therapy, Part I: Absorbed dose measurements  

International Nuclear Information System (INIS)

An international collaboration was organized to undertake a dosimetry exchange to enable the future combination of clinical data from different centers conducting neutron capture therapy trials. As a first step (Part I) the dosimetry group from the Americas, represented by MIT, visited the clinical centers at Studsvik (Sweden), VTT Espoo (Finland), and the Nuclear Research Institute (NRI) at Rez (Czech Republic). A combined VTT/NRI group reciprocated with a visit to MIT. Each participant performed a series of dosimetry measurements under equivalent irradiation conditions using methods appropriate to their clinical protocols. This entailed in-air measurements and dose versus depth measurements in a large water phantom. Thermal neutron flux as well as fast neutron and photon absorbed dose rates were measured. Satisfactory agreement in determining absorbed dose within the experimental uncertainties was obtained between the different groups although the measurement uncertainties are large, ranging between 3% and 30% depending upon the dose component and the depth of measurement. To improve the precision in the specification of absorbed dose amongst the participants, the individually measured dose components were normalized to the results from a single method. Assuming a boron concentration of 15 ?g g-1 that is typical of concentrations realized clinically with the boron delivery compound boronophenylalanine-fructose, systematic discrepancies in the specification of the total biologically weighted dose of up to 10% were apparent between the different groups. The results from these measurements will be used in future to normalize treatment plan calculations between the different clinical dosimetry protocols as Part II of this study.

2005-01-01

223

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

224

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

2008-01-01

225

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

226

Monte Carlo Assessments of Absorbed Doses to the Hands of Radiopharmaceutical Workers Due to Photon Emitters  

Energy Technology Data Exchange (ETDEWEB)

This paper describes the characterization of radiation doses to the hands of nuclear medicine technicians resulting from the handling of radiopharmaceuticals. Radiation monitoring using ring dosimeters indicates that finger dosimeters that are used to show compliance with applicable regulations may overestimate or underestimate radiation doses to the skin depending on the nature of the particular procedure and the radionuclide being handled. To better understand the parameters governing the absorbed dose distributions, a detailed model of the hands was created and used in Monte Carlo simulations of selected nuclear medicine procedures. Simulations of realistic configurations typical for workers handling radiopharmaceuticals were performedfor a range of energies of the source photons. The lack of charged-particle equilibrium necessitated full photon-electron coupled transport calculations. The results show that the dose to different regions of the fingers can differ substantially from dosimeter readings when dosimeters are located at the base of the finger. We tried to identify consistent patterns that relate the actual dose to the dosimeter readings. These patterns depend on the specific work conditions and can be used to better assess the absorbed dose to different regions of the exposed skin.

Ilas, Dan [ORNL; Eckerman, Keith F [ORNL; Karagiannis, Harriet [ORNL

2009-01-01

227

Monte Carlo Assessments of Absorbed Doses to the Hands of Radiopharmaceutical Workers Due to Photon Emitters  

International Nuclear Information System (INIS)

[en] This paper describes the characterization of radiation doses to the hands of nuclear medicine technicians resulting from the handling of radiopharmaceuticals. Radiation monitoring using ring dosimeters indicates that finger dosimeters that are used to show compliance with applicable regulations may overestimate or underestimate radiation doses to the skin depending on the nature of the particular procedure and the radionuclide being handled. To better understand the parameters governing the absorbed dose distributions, a detailed model of the hands was created and used in Monte Carlo simulations of selected nuclear medicine procedures. Simulations of realistic configurations typical for workers handling radiopharmaceuticals were performedfor a range of energies of the source photons. The lack of charged-particle equilibrium necessitated full photon-electron coupled transport calculations. The results show that the dose to different regions of the fingers can differ substantially from dosimeter readings when dosimeters are located at the base of the finger. We tried to identify consistent patterns that relate the actual dose to the dosimeter readings. These patterns depend on the specific work conditions and can be used to better assess the absorbed dose to different regions of the exposed skin.

2009-01-01

228

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

International Nuclear Information System (INIS)

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

2002-10-02

229

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

Directory of Open Access Journals (Sweden)

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

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

2012-01-01

230

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

International Nuclear Information System (INIS)

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

1987-01-01

231

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).

1987-01-01

232

Methodology for determination of absorbed dose by individuals irradiated with neutrons  

International Nuclear Information System (INIS)

In the present work an innovating methodology is proposed to estimate the absorbed dose received by individuals irradiated with neutrons. The method combines measurements of 24Na and 32P activated in the human body. A detailed study of papers published in the literature reporting neutron measurements in different facilities was combined to the results obtained after irradiation of an anthropomorphic phantom in the Argonauta reactor at the Institute de Engenharia Nuclear (IEN), Rio de Janeiro, Brazil. The results demonstrate that it is possible to correlate the measurements of those two activated elements (24Na e 32P) in order to assess the absorbed dose due to neutrons. A methodology was developed in which it is not necessary to know the neutron spectra inciding over the irradiated person or to use models to treat results of 32P measurements, as occurs with other theoretical and experimental proposed methods. (author)

1994-01-01

233

Absorbed dose from 7-GeV bremsstrahlung in a PMMA phantom.  

Energy Technology Data Exchange (ETDEWEB)

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 the Advanced Photon Source (APS), where the stored beam energy is 7 GeV, bremsstrahlung generated in the straight sections of the insertion devices comes down through the beamlines. The resulting absorbed dose distributions by, this radiation in a 300 mm x 300 mm x 300 mm tissue substitute phantom were measured with LiF:Mg,Ti (TLD-700) thermoluminescent dosimeters. The average normalized absorbed dose, in a cross sectional area of 100 mm{sup 2} at a depth of 150 mm of the PMMA phantom, was measured as 3.3 x 10{sup 6} mGy h{sup {minus}1}W{sup {minus}1} for a 7-GeV bremsstrahhmg spectrum.

Job, P. K.; Pisharody, M.; Semones, E.

1999-08-04

234

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)

1998-01-01

235

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

1983-01-01

236

Preliminary results from a polymer gel dosimeter for absorbed dose imaging in radiotherapy  

Science.gov (United States)

The reliability for radiotherapy applications of a normoxic-polymer gel dosimeter, analysed by means of optical methods, was studied. The optical transmittance was measured with a spectrophotometer and imaged with a CCD camera. The characteristics of sensitivity, spatial resolution, image stability, linearity of the response and reproducibility were investigated and analysed. Radiation induces a radical polymerisation in the gel matrix and the resulting macromolecules remain fixed in space making therefore possible the absorbed dose imaging.

Mariani, M.; Vanossi, E.; Gambarini, G.; Carrara, M.; Valente, M.

2007-08-01

237

The design of a calorimetric standard of ionising radiation absorbed dose  

International Nuclear Information System (INIS)

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

1981-01-01

238

Experimental studies on absorbed dose in radiation sterilization of pharmaceutical preparation  

Energy Technology Data Exchange (ETDEWEB)

For radiation sterilization, it is necessary to decide the irradiation conditions considering a balance between sterilization efficiency and chemical changes of samples by irradiation. These effects may be estimated by the product of two factors (D[sub 10] and G value) and absorbed dose. In this work, it has been found experimentally by using Fricke dosimeter that the absorbed doses of the samples in vessels different in size, material, volume, etc. are not equal under the same gamma-ray irradiation condition. The correction factor from exposure to absorbed dose was estimated to be 6-7% for organic vessels (a polyethylene bag and a polystyrene vial) and a 20-ml glass vial, 9% for a 10-ml glass vial, and 10% for the 5-ml glass vial. These values of the correction factor were confirmed by using the changes of enzymic activity of saccharated powder pepsin preparation. In the cases of using organic vessels and the 10-ml glass vial, G-values for the change of the enzymic activity were calculated to show similar values in the range from 0.79 to 0.82. However, in the case of a small glass vial (5-ml), the value was 0.93. (author).

Ohnishi, Tokuhiro; Okamoto, Shinichi (Osaka Prefectural Univ., Sakai (Japan). Research Inst. for Advanced Science and Technology); Kimura, Syojiro; Taimatsu, Meiko

1991-10-01

239

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

International Nuclear Information System (INIS)

[en] 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)

2011-01-01

240

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

International Nuclear Information System (INIS)

[en] 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

1989-01-01

 
 
 
 
241

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

Directory of Open Access Journals (Sweden)

Full Text Available OBJECTIVES: In this study, experimentally and theoretically determined absorbed dose to water calibration factors were compared. We used 6 MV photon and 12 MeV electron energies to compare experimentally and theoretically determined beam quality dependence factors. METHODS:Measurements were made at SSD=100 cm distance (LINAC), 10x10 cm standard field size and reference depth. Five different cylindrical and three parallel plate chambers were used. RESULTS: For absorbed dose to water calibration factor, the max difference between theoretical and experimental values was 2.8% for Marcus chamber. Beam quality dependence factors for 6 MV theoretical values of PTW 30001 (a) (-0.816%), NE 2571 (-0.1107%) were greater than their experimental values. For 12 MeV, the difference was 1.2371% for PTW 30001 (a), 1.6774% for PTW 30001 (b), 0.8758% for NE 2571, 0.8363% for NE 2581, 0.6071% for PTW 30002, and 0.6245% for Marcus ion chamber. CONCLUSION: As the protocol suggests, obtaining absorbed dose to water calibration factor directly from SSDL produces more accurate results.

Hilal ACAR

2008-01-01

242

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

International Nuclear Information System (INIS)

This paper evaluates the characteristics of ionization chambers for the measurement of absorbed dose to water for medium energy x-rays. The values of the chamber correction factor, kch, used in the IPEMB 1996 Code of Practice for the UK secondary standard (NE2561/NE2611) ionization chamber are derived. The comparison of the chamber responses in-air revealed that of the chambers tested, only the NE2561, NE2571 and NE2505 exhibit a flat (within 5%) energy response in air. Under no circumstances should the NACP, Sanders electron chamber or any chamber that has a wall made of high atomic number material be used for medium energy x-ray dosimetry. The measurements in water reveal that a chamber that has a substantial housing such as the PTW Grenz chamber, should not be used to measure absorbed dose to water in this energy range. The value of the perturbation correction, pu for a NE2561 chamber was determined by measuring the absorbed dose to water and comparing it with that for a NE2571 chamber, for which pu data has been published. The chamber correction factor varies from (1.023 ± 0.03) to (1.018 ± 0.001) for x-ray beams with HVL between 0.15 and 4 mm Cu. The values agree with that for a NE2571 chamber within the experimental uncertainty. (author)

1999-01-01

243

Monte Carlo estimation of absorbed dose to organs in diagnostic radiology  

International Nuclear Information System (INIS)

A method to estimate dose to parts of a head in diagnostic radiology, based on Monte Carlo technique, has been presented. It can be adapted to any type of x-ray examination. The absorbed dose per unit kerma in air during conventional x-ray examination for different parts of a head has been analyzed. Numerical experiment has been performed for mathematical model of head based on ADAM phantom and x-ray spectrums of various qualities (60-80 kV) (author)

2000-01-01

244

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

International Nuclear Information System (INIS)

[en] 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)

1992-01-01

245

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)

2003-01-01

246

Standard Guide for Absorbed-Dose Mapping in Radiation Processing Facilities  

CERN Document Server

1.1 This document provides guidance in determining absorbed-dose distributions in products, materials or substances irradiated in gamma, X-ray (bremsstrahlung) and electron beam facilities. Note 1—For irradiation of food and the radiation sterilization of health care products, other specific ISO and ISO/ASTM standards containing dose mapping requirements exist. For food irradiation, see ISO/ASTM 51204, Practice for Dosimetry in Gamma Irradiation Facilities for Food Processing and ISO/ASTM 51431, Practice for Dosimetry in Electron and Bremsstrahlung Irradiation Facilities for Food Processing. For the radiation sterilization of health care products, see ISO 11137: 1995, Sterilization of Health Care Products Requirements for Validation and Routine Control Radiation Sterilization. In those areas covered by ISO 11137, that standard takes precedence. ISO/ASTM Practice 51608, ISO/ASTM Practice 51649, and ISO/ASTM Practice 51702 also contain dose mapping requirements. 1.2 Methods of analyzing the dose map data ar...

American Society for Testing and Materials. Philadelphia

2003-01-01

247

Calculation of the internal radiation absorbed dose of 123I-Annexin V  

International Nuclear Information System (INIS)

To estimate absorbed doses by 123I-Annexin V in human, 125I-Annexin V was used as a radiotracer for measuring the distribution of radiolabeled Annexin V in mice. The standard Medical Internal Radiation Dose (MIRD) method was used by Mirdose-3 software in dosimetry estimation. The results show that liver and kidney received 2.77 x 10-3 and 2.71 x 10-3 mGy/MBq, respectively. The red marrow received 1.78 x 10-5 mGy/MBq, and the other organs received doses between 1.5 x 10-4 and 10.5 x 10-4 mGy/MBq. The effective dose was estimated at 5.55 x 10-4 mSv/MBq. Human radiation dosimetry can be performed by the mice biodistribution data and important data for clinical safe trial of 123I-Annexin V are provided. (authors)

2006-01-01

248

Absorbed dose calculations for gamma rays under non charged particle equilibrium conditions  

Energy Technology Data Exchange (ETDEWEB)

This research used the derived equations for secondary electron energy distributions in water irradiated by gamma rays and the generated electron spectra for different incident photon energies to calculate absorbed doses for non charged particle equilibrium conditions in the dose buildup regions. The pair production contribution is add to the Compton spectrum for 2 to 30 MeV photons. The generated electron spectral data and Spencer`s electron energy dissipation distribution data were used to calculate the buildup dose from the skin surface up to the range of the maximum energy electron. The authors then fit their calculated results and obtained the final buildup dose in one exponential form. They present the computed results of 1.25 MeV, 5 MeV and 10 MeV monoenergetic photons for {sup 60}Co, 10 MV and 26 MV Linac (Medical linear accelerator) radiations.

Chao, M.M.; Chabot, G.E. [Univ. of Massachusetts, Lowell, MA (United States)

1992-12-01

249

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-07-01

250

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)

2008-01-01

251

Influence of housing condition upon absorbed dose in peritoneal cavity of mouse chronically irradiated with low dose-rate 137Cs-?-rays  

International Nuclear Information System (INIS)

Full text: An accurate measurement of absorbed dose in mouse body is an essential prerequisite for success of the low dose whole-body exposure experiment. We have developed a specially designed small photoluminescence glass dosimeter (PLD), which is one of the most suitable systems for detecting low level exposures in individual mice monitoring. Using the PLD system, in the present study, we examined the subtle changes in the absorbed dose in mouse body depending on the caging conditions of mice, such as the number of mice housed together in a cage. Increasing number of mice kept in a cage from 1 to 5 reduced significantly the absorbed dose measured individually by PLD in the abdominal cavity to approximately 90%. The body weight of mice affected apparently the absorbed dose. The reduction in the dose by increasing mouse number in a cage is possibly explained in terms of the attenuation of ?-rays by the bodies of neighboring mice in the same cage

2003-01-01

252

Graphite calorimeter, the primary standard of absorbed dose at BNM-LNHB  

International Nuclear Information System (INIS)

The graphite calorimeter is the standard for absorbed dose to water at BNM-LNHB. The transfer from absorbed dose to graphite to absorbed dose to water is then performed by means of chemical dosimeters and ionisation chamber measurements. Therefore the quality of graphite calorimeter measurements is essential. The present graphite calorimeter is described. The characteristics of this calorimeter are pointed out. Special attention is given to the thermal feedback of the core, which is the main difference with the Domen-type calorimeter. The repeatability and reproducibility of the mean absorbed dose in the calorimeter core are presented in detail. As an example, individual measurements in the 20 MV photon beam from our Saturne 43 linac are given. The y-axis quantity is the mean absorbed dose in the core divided by the reference ionisation chamber charge. Both are normalised to the monitor ionisation chamber charge. The standard deviation (of the distribution itself) is 0.12 % for the first set of measurements performed in 1999. In 2002, for each different series, the standard deviation is 0.03%. The improvement on the 2002 standard deviation is mainly due to the change of the ionisation chamber used for the beam monitoring of the linac. Some benefit also comes from changes on the thermal control and measuring systems (nanovoltmeters, Wheatstone bridges, power supplies, determination of the measuring bridge sensitivity (V/?.The maximum difference between the means of the three series is 0.08%. This difference is due to the variation of not only the calorimetric measurements but also of the reference ionisation chamber response, of the position of the assembly and of the monitoring of the beam. The stability of the linac (electron energy, photon beam shape) has to be very good too in order to obtain this global performance. The correction factors necessary to determine the absorbed dose to graphite at the reference point in an homogeneous phantom from the measurement of the mean absorbed dose to the calorimeter core are examined including gradient correction factor. The uncertainties are analysed. The main uncertainty comes from the vacuum gaps correction factor determination. They are measured and calculated by Monte-Carlo code for cobalt 60, 6 MV, 12 MV and 20 MV photon beams. The influence of the irradiation on the sensitivity of the thermistor has been checked. A specific program was developed in order to perform the electrical calibration and the irradiation together. Recent measurements carried out in the 20 MV photon beam prove that there is no significant difference between the simultaneous measurement (irradiation + electrical power dissipation) and the sum of these two quantities measured separately. This confirms previous measurements in cobalt 60 beams. It is not possible to do this control with the water calorimeter because no electrical calibration is feasible. By using the same type of thermistor this result might be extrapolated to water calorimeters

2002-01-01

253

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.

Jürgen Arund; Risto Tanner; Fredrik Uhlin; Ivo Fridolin

2012-01-01

254

Do only small uremic toxins, chromophores, contribute to the online dialysis dose monitoring by UV absorbance?  

Science.gov (United States)

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. PMID:23162701

Arund, Jürgen; Tanner, Risto; Uhlin, Fredrik; Fridolin, Ivo

2012-10-18

255

Estimation of dose absorbed fraction for 131I-beta rays in rat thyroid.  

UK PubMed Central (United Kingdom)

The dose absorbed fraction of rat thyroid by internal deposit of 131I has been calculated as a function of effective diameter of thyroid. The calculations were done using two types of Monte Carlo simulations: one was by a simple energy-loss calculation in spherical volume according to the electron stopping power, and another by a more realistic simulation using Monte Carlo N-Particle Transport code system Version 4A (MCNP). These two calculations were consistent with each other within a deviation of 5%. The absorbed fractions in spherical thyroid were drastically changed up to 5 mm diameter, and then almost all energy was deposited within 10 mm diameter. For the practical application to the animal experiment, the absorbed fractions of ellipsoid-shaped thyroids were also calculated for 1-, 4- and 9-week-old rats, where the fractions were estimated to be 0.61, 0.67 and 0.68, respectively. It was also found that the absorbed fraction of the ellipsoid with various dimensions can be simulated by a calculation for spherical volume with a comparable effective diameter.

Endo S; Nitta Y; Ohtaki M; Takada J; Stepanenko V; Komatsu K; Tauchi H; Matsuura S; Iaskova E; Hoshi M

1998-09-01

256

Realisation of the absorbed dose to water for I-125 interstitial brachytherapy sources  

International Nuclear Information System (INIS)

A large air-filled parallel-plate extrapolation chamber in a phantom of water-equivalent material is used as a primary standard measuring device for low-energy interstitial brachytherapy sources from which the unit of absorbed dose to water can be derived. The chamber is suitable for low-energy photons with energies up to 50 keV. The method to determine the absorbed dose to water was newly developed based on radiation transport theory. It offers a clear analytical expression to determine Dw. A conversion factor C(xi, xi+1) has to be applied to the difference of ionization charges measured at two plate separations xi and xi+1. The details of the method are presented. The determination of Dw of an I-125 seed is demonstrated by the measurement of a 'BEBIG Symmetra I25.S16' - seed. Additional measurements of the reference air kerma rate with the PTB primary standard chamber GROVEX I allow to determine experimentally the dose rate constant of an I-125 seed by means of primary standards for the first time. Good agreement was found between the obtained dose rate constant and the published data.

2011-01-01

257

Determination of Absorbed and Effective Dose from Natural Background Radiation around a Nuclear Research Facility  

Directory of Open Access Journals (Sweden)

Full Text Available Problem statement: This study presents result of outdoor absorbed dose rate and estimated effective dose from the naturally occurring radionuclides 232Th and 238U series 40K, around a Nuclear Research Reactor at the Centre for Energy Research and Training (CERT), Zaria, Nigeria. Approach: A high-resolution in situ ?-ray spectrometry was used to carry out the study. CERT houses a 30Kw Research Reactor and other neutron and gamma sources for Research and Training. Results: The values of absorbed dose rate in air for 232Th, 238U and 40K range from 8.2 ± 2.5-24.5 ± 3.6 nGy h?1, 1.9 ± 1.2-4.6 ± 2.5 nGy h?1 and 12.2 ± 5-38 ± 6.7n Gy h?1 respectively . The estimated total annual effective dose outdoor for the sites range from 27.3-79.9 ?Sv y?1.Conclusions: This showed that radiation exposure level for the public is lower than the recommended value of 1 mSv y?1.Hence, the extensive usage of radioactive materials within and around CERT does not appear to have any impact on the radiation burden of the environment.

M. A. Musa; I. I. Funtua; S. P. Malam; A. S. Arabi

2011-01-01

258

A geochemical assessment of terrestrial gamma-ray absorbed dose rates.  

Science.gov (United States)

A survey of the geochemical literature and unpublished data has resulted in the classification of the concentrations of the naturally occurring radioelements U, Th, and K by their associated rock types. A data base of over 2500 entries has been compiled, permitting calculation of terrestrial gamma-ray absorbed dose rates. The general lithology of terrains may be distinguished by their radioelement ratios, relative abundances, and total gamma radioactivities. The gamma-ray absorbed dose rates in air above igneous rocks generally vary with their silica contents, and with the exception of shale, sedimentary rocks have lower K:U and K:Th ratios than most igneous rocks. The appreciable difference between the overall mean terrestrial gamma-ray dose rate for rock of the continental surface (approximately 7 X 10(-8) Gy h-1) and the mean dose rate from field measurements over soil (approximately 5 X 10(-8) Gy h-1) is explained by the substantial differences between radioelement concentrations of soil and rock, differences that may vary markedly with rock type. PMID:2404909

Wollenberg, H A; Smith, A R

1990-02-01

259

A geochemical assessment of terrestrial gamma-ray absorbed dose rates.  

UK PubMed Central (United Kingdom)

A survey of the geochemical literature and unpublished data has resulted in the classification of the concentrations of the naturally occurring radioelements U, Th, and K by their associated rock types. A data base of over 2500 entries has been compiled, permitting calculation of terrestrial gamma-ray absorbed dose rates. The general lithology of terrains may be distinguished by their radioelement ratios, relative abundances, and total gamma radioactivities. The gamma-ray absorbed dose rates in air above igneous rocks generally vary with their silica contents, and with the exception of shale, sedimentary rocks have lower K:U and K:Th ratios than most igneous rocks. The appreciable difference between the overall mean terrestrial gamma-ray dose rate for rock of the continental surface (approximately 7 X 10(-8) Gy h-1) and the mean dose rate from field measurements over soil (approximately 5 X 10(-8) Gy h-1) is explained by the substantial differences between radioelement concentrations of soil and rock, differences that may vary markedly with rock type.

Wollenberg HA; Smith AR

1990-02-01

260

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

International Nuclear Information System (INIS)

[en] 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)

2006-01-01

 
 
 
 
261

Comparison of graphite-to-water absorbed-dose transfers for 60Co photon beams using ionometry and Fricke dosimetry.  

UK PubMed Central (United Kingdom)

To derive the absorbed dose to water from a standard of absorbed dose to graphite, the metrology laboratories which apply such a method usually make use of cavity ionization chambers as transfer instruments. In addition, the BNM-LPRI has tested, as such instruments, two types of Fricke dosimeter in its cobalt-60 beam. The two procedures are compared and their results are found to be in good agreement (the difference is less than 0.1%). Both procedures are then taken into account for the calculation of the reference value of absorbed dose to water.

Chauvenet B; Baltès D; Delaunay F

1997-11-01

262

Comparison of graphite-to-water absorbed-dose transfers for 60Co photon beams using ionometry and Fricke dosimetry.  

Science.gov (United States)

To derive the absorbed dose to water from a standard of absorbed dose to graphite, the metrology laboratories which apply such a method usually make use of cavity ionization chambers as transfer instruments. In addition, the BNM-LPRI has tested, as such instruments, two types of Fricke dosimeter in its cobalt-60 beam. The two procedures are compared and their results are found to be in good agreement (the difference is less than 0.1%). Both procedures are then taken into account for the calculation of the reference value of absorbed dose to water. PMID:9394397

Chauvenet, B; Baltès, D; Delaunay, F

1997-11-01

263

Comparison of graphite-to-water absorbed-dose transfers for 60Co photon beams using ionometry and Fricke dosimetry  

International Nuclear Information System (INIS)

To derive the absorbed dose to water from a standard of absorbed dose to graphite, the metrology laboratories which apply such a method usually make use of cavity ionization chambers as transfer instruments. In addition, the Bn-LPRI has tested, as such instruments, two types of Fricke dosimeter in its cobalt-60 beam. The two procedures are compared and their results are found to be in good agreement (the difference is less than 0.1%). Both procedures are then taken into account for the calculation of the reference value of absorbed dose to water. (author)

1997-01-01

264

Transfer from graphite absorbed dose to water absorbed dose for high energy photons at BNM-LPRI: case of cobalt 60; Transfert de la dose absorbee dans le graphite a la dose absorbee dans l`eau pour les photons de haute energie au BNM-LPRI: cas du cobalt 60  

Energy Technology Data Exchange (ETDEWEB)

To derive the absorbed dose to water from a standard of absorbed dose to graphite, the metrology laboratories which apply that method usually make use of cavity ionization chambers as transfer instruments. The BNM-LPRI also tested, as such instruments, several Fricke dosimeters in its cobalt-60 beam. Both procedures are compared. Their results are in good agreement. Both procedures are then taken into account for the calculation of the reference value of absorbed dose to water. (authors). 12 refs.

Chauvenet, B.; Baltes, D.; Delaunay, F. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. des Applications et de la Metrologie des Rayonnements Ionisants

1996-12-31

265

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

International Nuclear Information System (INIS)

[en] 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)[fr] Les references actuelles, pour les rayons X de moyenne energie en radiotherapie, sont etablies au LNHB en termes de kerma dans l'air. La dose absorbee dans l'eau, grandeur d'interet pour la radiotherapie, est deduite de ces valeurs par transfert conformement aux protocoles internationaux. Ce travail de these a permis d'etablir les references en termes de dose absorbee dans l'eau dans les conditions de reference des protocoles en utilisant la methode de calorimetrie dans l'eau. La calorimetrie est la mesure de la dose absorbee a partir de l'elevation de temperature. Un 'calorimetre eau' a ete conçu et realise afin d'effectuer des mesures a 2 cm de profondeur: conditions de reference definies par le protocole AIEA TRS-398. Les debits de dose absorbee dans l'eau ainsi determines ont ete compares aux valeurs issues de l'application des protocoles fondes sur le kerma dans l'air. Un ecart maximum inferieur a 2.1 % a ete trouve par rapport a la calorimetrie. L'incertitude type associee aux valeurs calorimetriques etant inferieure a 0.8 % et celle associee aux valeurs issues des protocoles etant de l'ordre de 3.0 %, les resultats sont compatibles aux incertitudes des methodes pres. Grâce a ces nouvelles references, la determination de la dose absorbee dans l'eau dans ce type de faisceau pourra desormais etre realisee en appliquant le protocole AIEA TRS-398, conduisant ainsi a une forte reduction des incertitudes (facteur 3 par rapport au protocole AIEA TRS-277). Actuellement, aucun autre laboratoire primaire ne possede un tel instrument permettant l'etablissement direct de ces references dans les conditions recommandees par les protocoles

2012-01-01

266

Absorbed?dose estimation and quality attributes of gamma?irradiated fresh shiitake mushrooms  

UK PubMed Central (United Kingdom)

BACKGROUND: The general use of food irradiation requires reliable identification methods as well as extensive quality characterization. Shiitake (Lentinus edodes) mushrooms, packed in polystyrene trays and covered with polyvinylchloride film, were investigated for dose?dependent identification and quality characterization upon gamma irradiation (0, 1, 2, and 3 kGy). RESULTS: Thermoluminescence (TL) analysis of separated minerals provided excellent results to characterize the irradiated mushrooms. Low?dose re?irradiation (200?600 Gy), medium?dose re?irradiation (1?3 kGy) and high?dose re?irradiation (2?6 kGy) were performed and compared using an additive dose method. An electronic?nose analysis showed a difference in the volatile profiles of mushrooms following irradiation. One?kGy?irradiated mushrooms showed similar or better quality attributes to those of the control samples. Scanning electron microscopy revealed the dose?dependent degradation in microstructure of mushrooms upon irradiation. CONCLUSION: An absorbed dosed estimation was possible using TL analysis in which 1?3 kGy re?irradiation technique gave most promising results. An E?nose analysis effectively distinguished the samples based on irradiation history. The best quality attributes were observed at 1 kGy irradiation. However, the drastic effects of irradiation were prominent in 2 and 3 kGy?irradiated mushrooms. © 2012 Society of Chemical Industry

Akram K; Ahn J; Baek J; Yoon S; Kwon J

2013-02-01

267

Studies of the sensitivity dependence of float zone silicon diodes on gamma absorbed dose  

Energy Technology Data Exchange (ETDEWEB)

Full text: Several advantages of silicon diodes which include small size, low cost, high sensitivity and wide availability, make them suitable for dosimetry and for radiation field mapping. However, the small radiation tolerance of ordinary silicon devices has imposed constraints on their application in intense radiation fields such as found in industrial radiation processes. This scenario has been changed with the development of radiation hard silicon devices to be used as track detectors in high-energy physics experiments. Particularly, in this work it is presented the dosimetric results obtained with a batch of nine junction silicon diodes developed, in the framework of CERN RD50 Collaboration, as good candidates for improved radiation hardness. These diodes were produced with 300 micrometer n-type silicon substrate grown by standard float zone technique and processed by the Microelectronics Center of Helsinki University of Technology. The samples irradiation was performed using a Co-60 irradiator (Gammacell 220) which delivers a dose-rate of 2 kGy/h. During the irradiation, the unbiased diodes were connected through low-noise coaxial cables to the input of a KEITHLEY 617 electrometer, in order to monitor the devices photocurrent as a function of the exposure time. To study the response uniformity of the batch of nine diodes as well the sensitivity dependence on the absorbed dose, they were irradiated with different doses from 5 kGy up to 50 kGy. The sensitivity response of each device was investigated through the on-line measurements of the current signals as a function of the exposure time. For doses up to 5 kGy, all diodes exhibited a current decay of almost six percent in comparison with the value registered at the start-time of the irradiation. However, this decrease in the current sensitivity is much smaller than those observed with ordinary diodes for the same absorbed dose. The dose-response curves of the devices were also investigated through the plot of the charge generated in the depletion region of the diodes (obtained via integration of the current signals versus time) as a function of the absorbed dose. Similar dose-response curves (with second order polynomial fit) were obtained for all diodes. These results were used to verify both the uniformity and short-term repeatability of the devices. It still remains to be investigated the feasibility of using these float zone diodes for routine on-line radiation processing monitoring. (author)

Pascoalino, K.C.S.; Santos, T.C. dos; Barbosa, R.F.; Camargo, F. de; Goncalves, J.A.C.; Bueno, C.C. [Instituto de Pesquisas Energeticas e Nucleares (CTR/IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro de Tecnologia das Radiacoes

2011-07-01

268

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

1999-01-01

269

Effects of absorbed dose, storage time and temperature on 2-dodecylcyclobutanone in irradiated beef  

International Nuclear Information System (INIS)

As specific marker, 2-DCB could be used to detect whether the beef was irradiated or not, and evaluate the approximate absorbed doses if the storage temperature and time are known. The changes of the concentration of 2-dodecylcyclobutanone (2-DCB) with irradiation doses, storage time and temperature in irradiated beef were investigated. 2-DCB was extracted and separated by silica gel column and analyzed by capillary column gas chromatography-mass spectrometry (GC-MS). The results showed that there was a significant linear relationship between irradiation doses at the range 0.5 ? 5.0 kGy and the concentration of 2-DCB, and the amount of 2-DCB reduced during storage, but stored temperature did not effect it strongly. (authors)

2008-01-01

270

Biodistribution parameters and radiation absorbed dose estimates for radiolabeled human low density lipoprotein  

International Nuclear Information System (INIS)

The authors propose a model to generate radiation absorbed dose estimates for radiolabeled low density lipoprotein (LDL), based upon eight studies of LDL biodistribution in three adult human subjects. Autologous plasma LDL was labeled with Tc-99m, I-123, or In-111 and injected intravenously. Biodistribution of each LDL derivative was monitored by quantitative analysis of scintigrams and direct counting of excreta and of serial blood samples. Assuming that transhepatic flux accounts for the majority of LDL clearance from the bloodstream, they obtained values of cumulated activity (A) and of mean dose per unit administered activity (D) for each study. In each case highest D values were calculated for liver, with mean doses of 5 rads estimated at injected activities of 27 mCi, 9 mCi, and 0.9 mCi for Tc-99m-LDL, I-123-LDL, and In-111-LDL, respectively

1992-01-01

271

Intercomparison of extrapolation chamber measurements of the directional absorbed dose rate for 204Tl beta radiation  

International Nuclear Information System (INIS)

An intercomparison of directional absorbed dose rates, D'(0.07,?), at radiation protection levels in beta dosimetry was performed by five European laboratories in 1993 and 1994 using extrapolation chambers. For this purpose, a 204Tl beta ray source with an activity of about 6 MBq, constituent of the PTB Beta Secondary Standard, was sent to the five laboratories for intercomparison measurements. The dose rates, without a beam flattening filter, were determined at a distance of 20 cm for angles of incidence of the radiation, ?, of 0o and 60o. In the first stage of the intercomparison some unexpected differences of up to ± 5% in the results were obtained. These could be explained by the different methods used by the participants for measuring depth-dose curves. After applying a consistent method, the results of all participants agreed to within ± 2%. (author).

1996-01-01

272

[Estimation of absorbed dose of beta radiation into the critical tissues by a single injection of tritiated water].  

Science.gov (United States)

The biological effects of tritium in humans need to be clarified, because the chances of humans becoming exposed to tritium beta radiation may increase with the development of the nuclear fusion reactor. To evaluate the biological effects of tritium, it is necessary to estimate exactly the absorbed dose from the tritium beta rays in the tissue. In many reports, the absorbed dose of HTO in the tissues is estimated from the tritium content in body fluid and dose calculations are customarily based upon the water content of soft tissues, which is taken to be 0.7 to 0.8. However, these methods may not show the exact absorbed dose in the organs. In the present study, the radioactivity of the critical tissues was measured directly using a sample oxidizer and the absorbed dose was calculated from the radioactivity of tritium in the tissues. Details on the method for calculation of the absorbed dose in tissues of the mouse is shown in this report. The results suggest that the absorbed dose should be obtained from the radioactivity in the tissues. PMID:3212298

Tsuchiya, T; Norimura, T; Yamamoto, H; Hatakeyama, S; Dohi, S; Kunugita, N

1988-12-01

273

[Estimation of absorbed dose of beta radiation into the critical tissues by a single injection of tritiated water  

UK PubMed Central (United Kingdom)

The biological effects of tritium in humans need to be clarified, because the chances of humans becoming exposed to tritium beta radiation may increase with the development of the nuclear fusion reactor. To evaluate the biological effects of tritium, it is necessary to estimate exactly the absorbed dose from the tritium beta rays in the tissue. In many reports, the absorbed dose of HTO in the tissues is estimated from the tritium content in body fluid and dose calculations are customarily based upon the water content of soft tissues, which is taken to be 0.7 to 0.8. However, these methods may not show the exact absorbed dose in the organs. In the present study, the radioactivity of the critical tissues was measured directly using a sample oxidizer and the absorbed dose was calculated from the radioactivity of tritium in the tissues. Details on the method for calculation of the absorbed dose in tissues of the mouse is shown in this report. The results suggest that the absorbed dose should be obtained from the radioactivity in the tissues.

Tsuchiya T; Norimura T; Yamamoto H; Hatakeyama S; Dohi S; Kunugita N

1988-12-01

274

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)

2006-01-01

275

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

Energy Technology Data Exchange (ETDEWEB)

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.

Nakamura, K. [Department of Radiology, Nagoya University School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466 (Japan); Ishiguchi, T. [Department of Radiology, Nagoya University School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466 (Japan); Maekoshi, H. [Department of Radiological Technology, Nagoya University College of Medical Technology, Nagoya (Japan); Ando, Y. [Department of Radiology, Nagoya University School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466 (Japan); Tsuzaka, M. [Department of Radiological Technology, Nagoya University College of Medical Technology, Nagoya (Japan); Tamiya, T. [Department of Radiological Technology, Nagoya University College of Medical Technology, Nagoya (Japan); Suganuma, N. [Department of Obstetrics and Gynecology, Branch Hospital, Nagoya University School of Medicine, Nagoya (Japan); Ishigaki, T. [Department of Radiology, Nagoya University School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466 (Japan)

1996-08-01

276

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.

1996-01-01

277

Studying the absorbed dose in two-layer flat samples irradiated by fast neutrons  

International Nuclear Information System (INIS)

Fast neutron passage through two-layer fine structures is considered. Absorbed doses in quartz glass layer with polymeric coating of different thickness are calculated. The computerized calculations are carried out by means of the program permitting to apply the Monte-Carlo method for simulation of 0.1-14 MeV neutron irradiation of fine samples comprising plane layers of different materials. Accountancy of elastic ad inelastic neutron scattering as well as reactions with charged paticle escape is presupposed in the program. The calculations are performed for cases of normal drop of homogeneous neutron beams on a flat compostion of quartz glass of 2.21 g/cm3 density with polymeric caprone coating of 1.14 g/cm3 density or dacron coating of 1.38 g/cm3 density. Thickness of the glass layer is 1 mm. Thickness of the coating varied in the 0-2.5 mm range. Based on the analysis of the data obtained it is concluded that the absorbed dose in the surface layer increases several times as compared with the dose calculated for pure material under irradiation of materials with polymeric coatings by neutrons of the reactor spectrum (mean energy is 2 MeV).

1986-01-01

278

Evaluation of absorbed doses at the solid surface - tritiated water solution interface  

International Nuclear Information System (INIS)

Studies concerning the isotopic exchange H/D/T in the elemental hydrogen - water system: and in the presence of platinic metals on hydrophobic supports as catalyst were carried out at ICSI Rm. Valcea. Due to the very low energy of ? - radiation emitted by tritium, the direct measurements of dose absorbed by the isotopic exchange catalyst using classical methods is practically impossible. An evaluation model was built for this purpose. The volume of tritiated water which can irradiate the catalyst was represented by a sphere with the radius equal to the maximal rate of ? - radiation emitted by tritium. The catalyst surface is represented by a circle with a 0.2 m radius and the same centre as the circle of the hemisphere secant plane. Flow rate of absorbed dose is computed with the relation d (1/100)(? · Em/m), where d = dose flow rate, expressed in rad/s; ? = total radiation flux which interacts with the catalyst surface, expressed in erg; m = catalyst weight, in grams. Total flux of useful radiation, ?, was determined as a function of three parameters: a) total flow of tritium ?- radiation emitted in the hemisphere of tritiated water, dependent on the volume and radioactive concentration; b) emission coefficient on the direction of the catalyst surface; c) attenuation coefficient (due to self-absorption) of the tritium ? - radiation in the tritiated water body. (authors)

2002-01-01

279

Evaluation of absorbed doses at the solid surface-tritiated water solution interface  

International Nuclear Information System (INIS)

Studies concerning the isotopic exchange H/D/T in the elemental hydrogen - water system and in the presence of platinum metals on hydrophobic supports as catalyst were carried out at ICSI Rm. Valcea Romania. Due to the very low energy of ?-radiation emitted by tritium, direct measurements of the dose absorbed by the isotopic exchange catalyst using classical methods is practically impossible. For this purpose an evaluation model was developed. The volume of tritiated water which can irradiate the catalyst was represented by a hemi sphere with the radius equal to the maximal rate of ? - radiation emitted by tritium. The catalyst surface is a circle with a 0.2 ?m radius and the same centre as the circle of the hemisphere secant plane. Flow rate of absorbed dose is computed with the relation: d (1/100)(? · Em/m), where d = dose flow rate, expressed in rad/s; ? = total radiation flux which interacts with the catalyst surface, expressed in erg; Em = mean energy of tritium beta radiation and m = catalyst weight, in grams. Total flux of available radiation, ?, was determined as a function of three parameters: a) total flow of tritium ?-radiation emitted in the hemi sphere of tritiated water, depending on the volume and radioactive concentration; b) emission coefficient on the direction of the catalyst surface; c) attenuation coefficient (due to self-absorption) of the tritium ?-radiation in the tritiated water volume. (authors)

2003-01-01

280

Functional results of radioiodine therapy with a 300-GY absorbed dose in Graves' disease  

Energy Technology Data Exchange (ETDEWEB)

The aim of this study was to assess the results of high-dose radioiodine therapy given to 43 patients with recurrent hyperthyroidism due to Graves' disease between 1986 and 1992. We chose an intrathyroidal absorbed dose of 300 Gy and determined the applied activity individually, which ranged from 240 to 3120 MBq with a median of 752 MBq. Hperthyroidism was eliminated in 86% of cases after 3 months and in 100% after 12 months. No patient required a second radioiodine treatment. The incidnece of hyperthyroidism was 63% after 3 months and 93% after 18 months. Neither the pretherapeutic thyroid-stimulating immunoglobulin level nor the degree of co-existing endocrine ophthalmopathy was correlated with the time at which hypothyroidism developed. Patients with previous radioiodine therapy developed hypothyroidism earlier than patients with previous thyroid surgery. The results show that ablative radioiodine therapy with a 300-Gy absorbed dose is a very effective treatment of hyperthyroidism in Graves' disease, but it should be restricted to patients with recurrent hyperthyroidism combined with severe co-existing disorders or episodes of unfavourable reactions to antithyroid drugs. (orig.)

Willemsen, U.F. (Dept. of Nuclear Medicine, Dept. of Radiology, Muenchen (Germany)); Knesewitsch, P. (Dept. of Nuclear Medicine, Dept. of Radiology, Muenchen (Germany)); Kreisig, T. (Dept. of Nuclear Medicine, Dept. of Radiology, Muenchen (Germany)); Pickardt, C.R. (Dept. of Internal Medicine, Muenchen Univ. (Germany)); Kirsch, C.M. (Dept. of Nuclear Medicine, Dept. of Radiology, Muenchen (Germany))

1993-11-01

 
 
 
 
281

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

Energy Technology Data Exchange (ETDEWEB)

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{sup -9} g up to 10{sup -3} g immersed in an infinite water medium (density of 1g/cm{sup 3}) 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/cm{sup 3}. 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{sup -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)

Cintra, Felipe B. de; Yoriyaz, Helio, E-mail: fbcintra@ipen.b, E-mail: hyoriyaz@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

2009-07-01

282

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

International Nuclear Information System (INIS)

[en] 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)

2009-10-02

283

Influence of thermoplastic masks on absorbed skin dose for head and neck radiotherapy  

International Nuclear Information System (INIS)

The influence of thermoplastic masks used in clinical routine for patient immobilization in head and neck radiotherapy treatment on the absorbed skin dose has been investigated at Gustave-Roussy Institute. The measurements were performed in 60Co ?-rays, 4 and 6 MV X-rays and in 8 and 10 MeV electron beams. Initially, the measurements were performed with thermoluminescent dosimeters (LiF) and a NACP chamber on a polystyrene phantom in order to study the influence of physical parameters (distance, field size, energy...) on first millimeters depth variation dose. The study was completed with in vivo measurements on 14 patients using various dosimeters (thermoluminescent detectors, diodes) in order to assess the increase of dose on first millimeters depth and to verify the delivered dose during treatment sessions (quality control). In treatment conditions, masks lead to an important increase of dose on the first millimeter in 60Co ?-rays beams (dose value normalized to maximum of dose increase from 57.1% to 77.7% for 0.5 mm-water depth and from 78.5% to 88% for l mm-water depth); its contribution is less important in 4 and 6 MV X-rays beams (dose value normalized to maximum of dose increase from 49.5% to 63.2% for 0.5 mm-water depth and from 59% to 70.1 % for 1 mm-water depth). Concerning 8 and 10 MeV electron beams, the normalized dose value increase respectively from 78.4% to 81.7% and from 82.2% to 86.1% for 0.5 mm-water depth. In vivo dosimetry enabled the quality control of delivered dose during treatment. Measured dose is in agreement within ± 5% with the prescribed dose for 92.3% of cases. In routine, in vivo dosimetry allowed to quantify the increase of skin dose induced by thermoplastic masks for various energies of photon and electron beams as well as quality control. (authors)

2002-01-01

284

Determination of absorbed neutron dose of 241 Am-?-Be neutron source  

International Nuclear Information System (INIS)

A high-resolution semiconductor neutron spectrometer filled with 3He gas, in diode coincidence arrangement, is used for the neutron spectrum measurement of 241Am-?-Be neutron source. The neutron spectrum is evaluated from measured pulse-height distribution by using the HE3 computer code. Experiment results are compared with the spectra published by other authors. The measured spectrum provides a sufficient overlapping with the calculated one. Absorbed neutron dose rate (in tissue of standard man) is determined by measuring source neutron spectrum and absolute neutron flux and calculated conversion factors in given energy groups. (author)

1995-01-01

285

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

1998-01-01

286

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

1978-01-01

287

Influence of interface effect in the measurement of photon absorbed dose using TLDs  

International Nuclear Information System (INIS)

The absorbed dose in the TLDs between various thin foils was measured in the energy region of 30 keV to 200 keV. The results were compared with the values based on the cavity theory, which were 40% smaller than the measured in high Z material. The discrepancy is attributed to the accuracy of the attenuation of electron flux in the cavity theory because the attenuation is different from the calculated with EGS4 which agreed better with the measured. (author)

1993-01-01

288

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

International Nuclear Information System (INIS)

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

1993-01-01

289

Correction of effect of conditions in irradiating and storing irradiated thermoluminescence detectors (F11 glass) for absorbed dose determination  

International Nuclear Information System (INIS)

[en] A method is discussed of correcting the effects of temperature and time during storage and irradiation of thermoluminescent detectors of aluminophosphate glass F11 for the determination of the absorbed dose, based on the knowledge of the kinetic parameters of the detectors. A formula is proposed to determine the dose absorbed by the detector from the time and temperature of storage and irradiation and from integral thermoluminescence for the F11 glass. (author)

1981-01-01

290

Modeling the absorbed dose to the common carotid arteries following radioiodine treatment of benign thyroid disease.  

UK PubMed Central (United Kingdom)

INTRODUCTION: External fractionated radiotherapy of cancer increases the risk of cardio- and cerebrovascular events, but less attention has been paid to the potential side effects on the arteries following internal radiotherapy with radioactive iodine (RAI), i.e. 131-iodine. About 279 per million citizens in the western countries are treated each year with RAI for benign thyroid disorders (about 140,000 a year in the EU), stressing that it is of clinical importance to be aware of even rare radiation-induced side effects. In order to induce or accelerate atherosclerosis, the dose to the carotid arteries has to exceed 2 Gy which is the known lower limit of ionizing radiation to affect the endothelial cells and thereby to induce atherosclerosis. OBJECTIVE: To estimate the radiation dose to the carotid arteries following RAI therapy of benign thyroid disorders. METHODS: Assuming that the lobes of the thyroid gland are ellipsoid, that the carotid artery runs through a part of the lobes, that there is a homogeneous distribution of RAI in the lobes, and that the 24 h RAI uptake in the thyroid is 35 % of the (131)I orally administrated, we used integrated modules for bioassay analysis and Monte Carlo simulations to calculate the dose in Gy/GBq of administrated RAI. RESULTS: The average radiation dose along the arteries is 4-55 Gy/GBq of the (131)I orally administrated with a maximum dose of approximately 25-85 Gy/GBq. The maximum absorbed dose rate to the artery is 4.2 Gy/day per GBq (131)I orally administrated. CONCLUSION: The calculated radiation dose to the carotid arteries after RAI therapy of benign thyroid disorder clearly exceeds the 2 Gy known to affect the endothelial cells and properly induce atherosclerosis. This simulation indicates a relation between the deposited dose in the arteries following RAI treatment and an increased risk of atherosclerosis and subsequent cerebrovascular events such as stroke.

la Cour JL; Hedemann-Jensen P; Søgaard-Hansen J; Nygaard B; Jensen LT

2013-07-01

291

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

1993-01-01

292

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

Energy Technology Data Exchange (ETDEWEB)

Fresh whole eggs 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 EPR 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 reirradiated; with this procedure estimates were better for shell processed at the lower doses.

Desrosiers, M.F.; Le, F.G. (National Institute of Standards and Technology, Gaithersburg, MD (United States)); Harewood, P.M.; Josephson, E.S. (Univ. of Rhode Island, West Kingston, RI (United States)); Montesalvo, M. (Univ. of Massachusetts, Lowell, MA (United States))

1993-09-01

293

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

Energy Technology Data Exchange (ETDEWEB)

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.

Zeitz, L.; Laughlin, J.S.

1982-09-01

294

Study of Absorbed Dose and Effective Dose for Prostate Cancer Image Guided Radiation Therapy using kV Cone Beam Computed Tomography  

International Nuclear Information System (INIS)

To evaluate the results of absorbed and effective doses using two different modes, standard mode (A-mode) and low-dose mode (B-mode) settings for prostate cancer IGRT from CBCT. This experimental study was obtained using Clinac iX integrated with On Board Imager (OBI) System and CBCT. CT images were obtained using a GE Light Speed scanner. Absorbed dose to organs from ICRP recommendations and effective doses to body was performed using A-mode and B-mode CBCT. Measurements were performed using a Anderson and a phantom with TLD-100 (Thermoluminescent dosimeters). TLD-100 were widely used to estimate absorbed dose and effective dose from CBCT with TLD System 4000 HAWSHAW. TLD-100 were calibrated to know sensitivity values using photon beam. The measurements were repeated three times for prostate center. Then, Evaluations of effective dose and absorbed dose were performed among the A-mode and B-mode CBCT. The prostate absorbed dose from A-mode and B mode CBCT were 5.5 cGy 1.1 cGy per scan. Respectively Effective doses to body from A mode and B-mode CBCT were 19.1 mSv, 4.4 mSv per scan. Effective dose from A-mode CBCT were approximately 4 times lower than B-mode CBCT. We have shown that it is possible to reduce the effective dose considerably by low dose mode(B-mode) or lower mAs CBCT settings for prostate cancer IGRT. Therefore, we should try to select B-mode or low condition setting to decrease extra patient dose during the IGRT for prostate cancer as possible.

2009-01-01

295

Optimization of analyzer-based imaging systems for minimal surface absorbed dose.  

UK PubMed Central (United Kingdom)

Analyzer-based imaging has improved tissue X-ray imaging beyond what conventional radiography was able to achieve. The extent of the improvement is dependent on the crystal reflection used in the monochromator and analyzer combination, the imaging photon energy, the geometry of the sample and the imaging detector. These many factors determine the ability of the system to distinguish between various bone tissues or soft tissues with a specified statistical certainty between pixels in a counting detector before any image processing. The following discussion will detail changes in the required number of imaging photons and the resulting surface absorbed dose when the imaging variables are altered. The process whereby the optimal imaging parameters to deliver the minimum surface absorbed dose to a sample while obtaining a desired statistical certainty between sample materials for an arbitrary analyzer-based imaging system will be described. Two-component samples consisting of bone and soft tissue are discussed as an imaging test case. The two-component approach will then be generalized for a multiple-component sample.

Bewer BE

2013-05-01

296

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

Energy Technology Data Exchange (ETDEWEB)

With an increasing interest in using protons and light ions for radiation therapy there is a need for possibilities to simultaneously determine both absorbed dose (D) and linear energy transfer, LET, (L{sub {Delta}}). Potassium dithionate (K{sub 2}S{sub 2}O{sub 6}) tablets were irradiated in a conventional 6 MV linear accelerator photon beam and a N{sup 7+} beam (E = 33.5 MeV/u) respectively. The EPR spectrum of irradiated potassium dithionate is a narrow doublet consisting of two signals, R{sub 1} and R{sub 2}, with different microwave power saturation properties. On the basis of identification in related substances by EPR and ENDOR, these two signals are assigned to two non-equivalent SO{sub 3}{sup -} - radicals. Our experiments showed that the ratios of these two lines (R{sub 1}/R{sub 2}) were clearly connected to beam LET. Irrespective of the mechanistic details this investigation suggests a new method for measurement of absorbed dose and beam LET by using potassium dithionate EPR dosimetry.

Gustafsson, Hakan, E-mail: hakan.l.gustafsson@liu.se [Department of Medical and Health Sciences (IMH), Radiological Sciences, Linkoeping University, 581 85 Linkoeping (Sweden); Lund, Anders [Department of Physics Chemistry and Biology, Linkoeping University, 581 83 Linkoeping (Sweden); Lund, Eva [Department of Medical and Health Sciences (IMH), Radiological Sciences, Linkoeping University, 581 85 Linkoeping (Sweden)

2011-09-15

297

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 College of Physical Scientists and Engineers in Medicine

2000-01-01

298

Calculation of the internal radiation absorbed dose of 99mTc-TRODAT-1  

International Nuclear Information System (INIS)

To evaluate the radio-biodistribution and internal dosimetry of 99mTc-TRODAT-1 in human target organs. Three patients with Pakinson's disease (PD) and two patients with essential tremor (ET) were included. After injection of 99mTc-TRODAT-1 intravenously, serial whole body scans were acquired during the following 24h by dual-head SPECT. Radioactivity uptakes were estimated applying ROI technique and radioactivity-time curves in target organs were obtained with non-linear regression analysis in terms of Microcal Origin 5.0 software. Residence time was calculated from the accumulative activity. All data of the residence times were input to the MIRDOSE 3.1 software to create the organ-absorbed dose. Brain tomography for each patient was performed 3h post injection. The experimental results showed that the internal absorbed dose from 99mTc-TRODAT-1 in target organs was small and the striatum was clearly imaged. Also, demonstrates that 99mTc-TRODAT-1 is a safe and ideal radio tracer to visualize the changes of dopamine transporter in striatum

2002-01-01

299

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

300

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

International Nuclear Information System (INIS)

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

1998-01-01

 
 
 
 
301

[RBE/absorbed dose relationship of d(50)-Be neutrons determine for early intestinal tolerance in mice  

UK PubMed Central (United Kingdom)

RBE/absorbed dose realtionship of d(50)-Be neutrons (ref.: 60Co) was determined using intestinal tolerance in mice (LD50) after single and fractionated irradiation. RBE is 1.8 for a single fraction (about 1000 rad 60Co dose); it increases when decreasing dose and reaches the plateau value of 2.8 for a 60Co dose of about 200 rad. This RBE value is used for the clinical applications with the cyclotron "Cyclone" at Louvain-la-Neuve.

Gueulette J; Wambersie A

1978-01-01

302

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)

1976-01-01

303

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

UK PubMed Central (United Kingdom)

This paper reports the determination of absorbed dose to bone marrow in the treatment of polycythaemia by 32P, based on the measurement 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 slso 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), but modified to allow for the presence of32P in the marrow as well as in trabecular bone. The dose-rates follow a single exponetial decay with a half-life of 6.7 days. The intergrated dose including that during the first day is 24 rad per mCi injected.

Spiers FW; Beddoe AH; King SD

1976-02-01

304

A procedure for absorbed dose to water evaluation for photon beams  

International Nuclear Information System (INIS)

[en] In radiotherapy with external x and gamma ray beams, it is necessary to measure the radiation output in terms of absorbed dose to water. It is also essential to achieve a dose measurement accuracy of better than ± 3% for obtaining satisfactory cancer cure rates. In our country, majority of therapy level dosemeters used for dose measurements are of Bhabha Atomic Research Centre (BARC) make having Tufnol proximal wall and perspex build-up cap. In order to obtain nation wide uniformity and good accuracy in dose measurements for high energy x and gamma ray beams, a common evaluation procedure is to be adopted at all radiotherapy centers, based on detailed investigations. Such a common procedure for use is described with particular reference to BARC make dosemeters. This is similar to the one recommended by IAEA (TRS-277) for graphite, perspex or delrin walled chambers. Some experimental results are given which confirm the validity of the various factors calculated for Tufnol chamber. (author). 1 ref., 1 fig., 3 tabs

1993-01-01

305

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

International Nuclear Information System (INIS)

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

2005-01-01

306

Practical SPECT technique for quantitation of drug delivery to human tumors and organ absorbed radiation dose  

International Nuclear Information System (INIS)

A practical quantitative single photon emission computed tomographic (SPECT) technique based on an empirical threshold analysis permits accurate measurements in humans of drug delivery and absorbed radiation dose. The limits of the method have been explored using a wide range of phantom volumes, concentrations, and target-to-nontarget ratios. A threshold of 43% was found to give the best results using volumes of 30 to 3,800 cc. An excellent correlation (r = .99 with a standard error of estimate [SEE] of 41 cc) was found between SPECT measured volumes and actual phantom volumes. A similarly high correlation (r = .98, SEE = 260 counts/voxel) was found in 77 measurements of concentrations between 0.01 and 3.6 microCi/cc. There was a direct relationship between the target-to-nontarget ratio of phantoms and the accuracy of volume measurements. The technique has been validated by an excellent in vivo/in vitro correlation of uptake in human tumors. The tumor cumulative concentration and tumor-to-blood ratio were used for assessment of drug delivery. In vivo quantitative measurements of the pharmacokinetics of technetium-99m (99mTc) glucoheptonate, cobalt-57 (57Co) bleomycin and platinum-195m (195mPt) cisplatin in human tumors in vivo indicates that, in contrast with tumor models in animals, there is a marked variability in drug delivery even in tumors with the same histology. Future development of labeled drugs should make it possible to use quantitative SPECT for predicting tumor response to therapy and for tailoring chemotherapy for the individual patient under treatment. SPECT quantitation of organ concentration was used for Medical Internal Radiation Dose committee (MIRD) calculations of organ absorbed radiation dose from 99mTc-labeled RBCs. 48 references

1989-01-01

307

Evaluation of absorbed dose in thyroid follicles due to short-lived iodines irradiation using the Monte Carlo method  

International Nuclear Information System (INIS)

Thyroid cells are arranged in spheres called follicles of different sizes, in which most of the iodine in the body concentrates. For dose assessment in follicles, it is necessary to consider specific emissions of iodine isotopes in the calculation. Hence, the aim of this work was to evaluate the contribution of 131I and short-lived iodines to the absorbed dose in thyroid cells. Thus, the interaction of emissions from isotopes with follicles was carried out using the MCNP4C code. The results showed that the contribution of short-lived iodines for absorbed dose per disintegration is about 70%. (author)

2006-01-01

308

Dosimetric implications of age related glandular changes in screening mammography  

International Nuclear Information System (INIS)

The UK National Health Service Breast Screening Programme is currently organized to routinely screen women between the ages of 50 and 64, with screening for older women available on request. The lower end of this age range closely matches the median age for the menopause (51 years), during which significant changes in the composition of the breast are known to occur. In order to quantify the dosimetric effect of these changes, radiographic factors and compressed breast thickness data for a cohort of 1258 women aged between 35 and 79 undergoing breast screening mammography have been used to derive estimates of breast glandularity and mean glandular dose (MGD), and examine their variation with age. The variation of mean radiographic exposure factors with age is also investigated. The presence of a significant number of age trial women within the cohort allowed an extended age range to be studied. Estimates of MGD including corrections for breast glandularity based on compressed breast thickness only, compressed breast thickness and age and for each individual woman are compared with the MGD based on the conventional assumption of a 50:50 adipose/glandular composition. It has been found that the use of the conventional 50:50 assumption leads to overestimates of MGD of up to 13% over the age range considered. By using compressed breast thickness to estimate breast glandularity, this error range can be reduced to 8%, whilst age and compressed breast thickness based glandularity estimates result in an error range of 1%. (author)

2000-01-01

309

Supplementary comparison CCRI(I)-S2 of standards for absorbed dose to water in 60Co gamma radiation at radiation processing dose levels  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Eight national standards for absorbed dose to water in 60Co gamma radiation at the dose levels used in radiation processing have been compared over the range from 1 kGy to 30 kGy using the alanine dosimeters of the NIST and the NPL as the transfer dosimeters. The comparison was organized by the Bure...

Burns, D. T.; Allisy-Roberts, P. J.; Desrosiers, M. F.; Sharpe, P. H. G.; Pimpinella, M.; Lourenço, V.; Zhang, Y. L.

310

Influence of the neutron flux shape on the value of absorbed neutron dose  

International Nuclear Information System (INIS)

[en] This paper deals with the study od specific doses dependence on the type and approximation procedures of neutron spectra. Values of specific dose rates (dose per neutron cm2) were analysed for neutron spectra from RB reactor in Vinca, Crac facility in Valduc (France) and HPRR reactor in Oak Ridge (USA). Data used in this analysis were obtained by methods used in Harwell (AERE), Oak Ridge (ORNL), Chalk River (AECL), CEN de Cadarache (CEA) and in the Boris Kidric Institute (IBK). Specific absorbed neutron doses were determined for each of the estimated spectra and presented in the form of kerma/(n.cm-2) and rad/((n.cm-2) units. The obtained results have shown the influence of the flux approximation procedure on the values of conversion factors for obtaining neutron doses from neutron flux[sr] U okviru ovog rada radjeno je na ispitivanju zavisnosti specificnih doza od vrste i nacina aproksimacije neutronskog spektra. U radu su analizirane vrednosti specificnih doza (doza po n.cm-2) za neutronske spektre koji se dobijaju oko sledecih nuklearnih postrojenja: reaktora RB u Vinci, postrojenja CRAC u Valduc-u (Francuska), reaktora HPRR u Oak Ridge-u (SAD). Za analizu su korisceni podaci dobijeni metodama koje se koriste u nuklearnim centrima Harwell (AERE), Oak Ridge-u (ORNL), Chalk River-u (AECL), CEN de Cadarache (CEA) i Institutu Boris Kidric (IBK). Za svaki procenjeni spektar odredjene su specificne apsorbovane doze neutrona izrazene u kerma/(n.cm-2) i rad/(n.cm-2) jedinicama. Dobijeni rezultati su pokazali koliko nacin aproksimacije spektra utice na vrednost konverzionih faktora koji sluze za prelazak sa fluksa na dozu neutrona (author)

1974-01-01

311

Absorbed dose and image quality in examinations of the colon with digital and analogue techniques  

International Nuclear Information System (INIS)

Purpose: Image quality and the absorbed dose to the patient are issues of primary interest in the change-over from the conventional analogue technique to the digital technique in the examination of the colon by means of fluoroscopy. The aim of this study was to compare the incident radiation and to evaluate the image quality in two different X-ray equipment types, one digital and one analogue. Material and Methods: A kerma-area product meter was used to measure the incident radiation to the patient. Both fluoroscopy and total-examination times were measured as was the number of images. An evaluation of image quality was made and statistically analysed. Results and Conclusion: No significant difference in the irradiation dose was observed between the two techniques. The fluoroscopy time was significantly lower with the conventional technique but the total-examination time decreased by 18% with the digital technique. The total number of images taken was higher with the digital technique (25 images compared to 19) owing to the limited field of the image intensifier. Significantly more noise and less sharpness were observed with the digital system but there was no significant difference in contrast or image quality in the various anatomical structures. Although the change-over to the digital system produced a reduction in sharpness and an increase in noise, and no significant dose saving was measured, the digital system was faster to work with and could well be used for diagnostic purposes. (orig.).

1997-01-01

312

The sensitivity analysis of tooth enamel to the absorbed dose for the application to EPR dosimetry  

Energy Technology Data Exchange (ETDEWEB)

Electron Paramagnetic Resonance (EPR) spectroscopy is one of the methods applicable to retrospective dosimetry. The retrospective dosimetry is a process that is a part of dose reconstruction for estimation of exposed dose occurred years before the estimation. Many techniques can be used to the retrospective dosimetry. As a physical method, EPR analysis of biological material measures the quantity of free radicals generated in the material from the interaction of radiation and material. Since the later 80s, in many countries, EPR dosimetry with tooth enamel has been studied and applied for the retrospective dosimetry. In the consideration of the biological materials for EPR dosimetry, human fingernail, hair, bone and tooth are generally considered. The tooth can be separated as enamel, dentine and cementum. Among the three parts, enamel shows the best sensitivity to the absorbed dose and is most widely used. In this study, the characteristics of tooth enamel for EPR dosimetry is examined and experimented. At the experiment, for easy separation, tooth was cut into 4 parts and then each part is treated by ultrasonic vibration in NaOH liquid to reduce mechanically induced noise in the corresponding signal. After the separation of the enamel from dentine, background EPR signal is measured and then radiation-induced EPR spectrum is estimated.

Hong, Dae Seok; Lee, Kun Jai [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of); Cho, Young Hwan [KAERI, Taejon (Korea, Republic of)

2002-10-01

313

[Glandular cheilitis. 2 case reports  

UK PubMed Central (United Kingdom)

BACKGROUND: Glandular cheilitis (GC) is a rarely recognized disease of the accessory salivary glands of the lips, particularly of the lower lip. Clinically, three variants have been described: cheilitis glandularis simplex, cheilitis glandularis suppurativa, and cheilitis glandularis apostematosa. Most cases are diagnosed as the simple form of glandular cheilitis, which is characterized by enlarged excretory ducts, induration, and enlargement of the salivary glands as well as production of a rather mucopurulent saliva. CASE REPORTS: Two patients are described who revealed the characteristic changes of cheilitis glandularis simplex (case 1, 75-year-old male patient; case 2, 83-year-old female patient). In case 1 the patient developed a retention cyst of the upper lip probably as a consequence of GC. DIAGNOSIS: Histologically, ectasia of glandular ducts and chronic sialadenitis are typical features. Therapy formerly consisted of antibiotics and locally applied corticosteroids; an optimal oral hygiene, however, is mandatory. Advanced stages have to be treated surgically. Glandular cheilitis has been considered a precancerous lesion, although no definite scientific proof has ever been presented. Cheilitis granulomatosa, cheilitis exfoliativa, and self-induced changes (Munchausen syndrome) have to be considered in the differential diagnosis of glandular cheilitis.

Reichart PA; Scheifele Ch; Philipsen HP

2002-07-01

314

[Glandular cheilitis. 2 case reports].  

Science.gov (United States)

BACKGROUND: Glandular cheilitis (GC) is a rarely recognized disease of the accessory salivary glands of the lips, particularly of the lower lip. Clinically, three variants have been described: cheilitis glandularis simplex, cheilitis glandularis suppurativa, and cheilitis glandularis apostematosa. Most cases are diagnosed as the simple form of glandular cheilitis, which is characterized by enlarged excretory ducts, induration, and enlargement of the salivary glands as well as production of a rather mucopurulent saliva. CASE REPORTS: Two patients are described who revealed the characteristic changes of cheilitis glandularis simplex (case 1, 75-year-old male patient; case 2, 83-year-old female patient). In case 1 the patient developed a retention cyst of the upper lip probably as a consequence of GC. DIAGNOSIS: Histologically, ectasia of glandular ducts and chronic sialadenitis are typical features. Therapy formerly consisted of antibiotics and locally applied corticosteroids; an optimal oral hygiene, however, is mandatory. Advanced stages have to be treated surgically. Glandular cheilitis has been considered a precancerous lesion, although no definite scientific proof has ever been presented. Cheilitis granulomatosa, cheilitis exfoliativa, and self-induced changes (Munchausen syndrome) have to be considered in the differential diagnosis of glandular cheilitis. PMID:12242936

Reichart, P A; Scheifele, Ch; Philipsen, H P

2002-07-01

315

Determination of human absorbed dose of 67Ga-DTPA-ACTH based on distribution data in rats  

International Nuclear Information System (INIS)

The absorbed radiation dose to human organs has been estimated, following intravenous administration of 67Ga-labelled adrenocorticotropic hormone (ACTH) using distribution data from injected normal rats. Four rats were sacrificed at exact time intervals and the percentage of injected dose per gram of each organ was measured by direct counting from rat data. The Medical Internal Radiation Dose formulation was applied to extrapolate from rat to human and to project the absorbed radiation dose for various organs in a human. From rat data, it is estimated that a 185-MBq injection of 67Ga- diethylenetriaminepentaacetic acid-ACTH into a human might result in an estimated absorbed dose of 2.22 mGy to the whole body; the highest absorbed dose was in the bladder wall with 82.1 mGy and the organs that received the next highest doses were the lungs 31.8, liver 22.6 and spleen 8.72 mGy. These results suggest that it should be possible to perform early imaging of the lung anomalies. (authors)

2009-01-01

316

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; Ehsan Hekmatian

2011-01-01

317

Assessment of personnel absorbed dose at production of medical radioisotopes by a cyclotron  

International Nuclear Information System (INIS)

The medical radioisotope 20Tl is produced by a cyclotron through the 203Tl(p, 3n)201Pb reaction in the nuclear medicine research group of Agricultural, Medical and Industrial Research Schools in Iran. The produced 201Pb decays to 201Tl by electron capture. One of the most important problems that may occur is malfunction of a part of target or beam line, so that it needs the bombardment to be stopped and the problem fixed. In this work, induced radioactivity of the target, aluminium case of target, beam line and concrete walls of the thallium target room were calculated by Monte Carlo method. Then by using the results of the Monte Carlo simulation, the whole body absorbed dose to cyclotron personnel during repair and after stopping the bombardment, were assessed at different places of target room. (authors)

2011-01-01

318

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

International Nuclear Information System (INIS)

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

1968-01-01

319

Influence of initial electron beam parameters on Monte Carlo calculated absorbed dose distributions for radiotherapy photon beams.  

UK PubMed Central (United Kingdom)

Our aim in the present study was to investigate the effects of initial electron beam characteristics on Monte Carlo calculated absorbed dose distribution for a linac 6 MV photon beam. Moreover, the range of values of these parameters was derived, so that the resulted differences between measured and calculated doses were less than 1%. Mean energy, radial intensity distribution and energy spread of the initial electron beam, were studied. The method is based on absorbed dose comparisons of measured and calculated depth-dose and dose-profile curves. All comparisons were performed at 10.0 cm depth, in the umbral region for dose-profile and for depths past maximum for depth-dose curves. Depth-dose and dose-profile curves were considerably affected by the mean energy of electron beam, with dose profiles to be more sensitive on that parameter. The depth-dose curves were unaffected by the radial intensity of electron beam. In contrast, dose-profile curves were affected by the radial intensity of initial electron beam for a large field size. No influence was observed in dose-profile or depth-dose curves with respect to energy spread variations of electron beam. Conclusively, simulating the radiation source of a photon beam, two of the examined parameters (mean energy and radial intensity) of the electron beam should be tuned accurately, so that the resulting absorbed doses are within acceptable precision. The suggested method of evaluating these crucial but often poorly specified parameters may be of value in the Monte Carlo simulation of linear accelerator photon beams.

Tzedakis A; Damilakis JE; Mazonakis M; Stratakis J; Varveris H; Gourtsoyiannis N

2004-04-01

320

Magnetic resonance imaging-based radiation-absorbed dose estimation of 166Ho microspheres in liver radioembolization.  

UK PubMed Central (United Kingdom)

PURPOSE: To investigate the potential of magnetic resonance imaging (MRI) for accurate assessment of the three-dimensional (166)Ho activity distribution to estimate radiation-absorbed dose distributions in (166)Ho-loaded poly (L-lactic acid) microsphere ((166)Ho-PLLA-MS) liver radioembolization. METHODS AND MATERIALS: MRI, computed tomography (CT), and single photon emission CT (SPECT) experiments were conducted on an anthropomorphic gel phantom with tumor-simulating gel samples and on an excised human tumor-bearing liver, both containing known amounts of (166)Ho-PLLA-MS. Three-dimensional radiation-absorbed dose distributions were estimated at the voxel level by convolving the (166)Ho activity distribution, derived from quantitative MRI data, with a (166)Ho dose point-kernel generated by MCNP (Monte Carlo N-Particle transport code) and from Medical Internal Radiation Dose Pamphlet 17. MRI-based radiation-absorbed dose distributions were qualitatively compared with CT and autoradiography images and quantitatively compared with SPECT-based dose distributions. Both MRI- and SPECT-based activity estimations were validated against dose calibrator measurements. RESULTS: Evaluation on an anthropomorphic phantom showed that MRI enables accurate assessment of local (166)Ho-PLLA-MS mass and activity distributions, as supported by a regression coefficient of 1.05 and a correlation coefficient of 0.99, relating local MRI-based mass and activity calculations to reference values obtained with a dose calibrator. Estimated MRI-based radiation-absorbed dose distributions of (166)Ho-PLLA-MS in an ex vivo human liver visually showed high correspondence to SPECT-based radiation-absorbed dose distributions. Quantitative analysis revealed that the differences in local and total amounts of (166)Ho-PLLA-MS estimated by MRI, SPECT, and the dose calibrator were within 10%. Excellent agreement was observed between MRI- and SPECT-based dose-volume histograms. CONCLUSIONS: Quantitative MRI was demonstrated to provide accurate three-dimensional (166)Ho-PLLA-MS activity distributions, enabling localized intrahepatic radiation-absorbed dose estimation by convolution with a (166)Ho dose point-kernel for liver radioembolization treatment optimization and evaluation.

Seevinck PR; van de Maat GH; de Wit TC; Vente MA; Nijsen JF; Bakker CJ

2012-07-01

 
 
 
 
321

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.

1987-01-01

322

The analyses of the absorbed dose by the red marrow brain of wild hunting hoofed animals from incorporated 90Sr  

International Nuclear Information System (INIS)

[en] After research work has been valued the absorbed dose by the red marrow brain of wild hunting hoofed animals on the territory with different level of radioactive pollution was shown that the absorbed annual doses of incorporated Sr 90 by the red marrow brain on the territory of eviction and alienation zones formed for wild boar 19,5-28,3 mGy/year, roe deer european 8,0-24,2 mGy/year, and for elk 16,1-55,0 mGy/year. The absorber doses by the red marrow brain of wild hunting hoofed taken in the control regions fluctuated from 0,6 mGy/year roe deer european to 1,4 mGy/year wild boar. (authors)

2003-01-01

323

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)

2006-01-01

324

Monte Carlo analysis of pion contribution to absorbed dose from Galactic cosmic rays  

International Nuclear Information System (INIS)

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.

2009-04-15

325

Study of natural radionuclide and absorbed gamma dose in Ukhimath area of Garhwal Himalaya, India.  

UK PubMed Central (United Kingdom)

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, (226)Ra, (232)Th and (40)K 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 (226)Ra, (232)Th and (40)K 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.

Rautela BS; Yadav M; Bourai AA; Joshi V; Gusain GS; Ramola RC

2012-11-01

326

Absorbed dose estimates to structures of the brain and head using a high-resolution voxel-based head phantom  

International Nuclear Information System (INIS)

The purpose of this article is to demonstrate the viability of using a high-resolution 3-D head phantom in Monte Carlo N-Particle (MCNP) for boron neutron capture therapy (BNCT) structure dosimetry. This work describes a high-resolution voxel-based model of a human head and its use for calculating absorbed doses to the structures of the brain. The Zubal head phantom is a 3-D model of a human head that can be displayed and manipulated on a computer. Several changes were made to the original head phantom which now contains over 29 critical structures of the brain and head. The modified phantom is a 85x109x120 lattice of voxels, where each voxel is 2.2x2.2x1.4 mm3. This model was translated into MCNP lattice format. As a proof of principle study, two MCNP absorbed dose calculations were made (left and right lateral irradiations) using a uniformly distributed neutron disk source with an 1/E energy spectrum. Additionally, the results of these two calculations were combined to estimate the absorbed doses from a bilateral irradiation. Radiobiologically equivalent (RBE) doses were calculated for all structures and were normalized to 12.8 Gy-Eq. For a left lateral irradiation, the left motor cortex receives the limiting RBE dose. For a bilateral irradiation, the insula cortices receive the limiting dose. Among the nonencephalic structures, the parotid glands receive RBE doses that were within 15% of the limiting dose

2001-01-01

327

Secondary neutron dose measurement for proton eye treatment using an eye snout with a borated neutron absorber.  

UK PubMed Central (United Kingdom)

BACKGROUND: We measured and assessed ways to reduce the secondary neutron dose from a system for proton eye treatment. METHODS: Proton beams of 60.30 MeV were delivered through an eye-treatment snout in passive scattering mode. Allyl diglycol carbonate (CR-39) etch detectors were used to measure the neutron dose in the external field at 0.00, 1.64, and 6.00 cm depths in a water phantom. Secondary neutron doses were measured and compared between those with and without a high-hydrogen-boron-containing block. In addition, the neutron energy and vertices distribution were obtained by using a Geant4 Monte Carlo simulation. RESULTS: The ratio of the maximum neutron dose equivalent to the proton absorbed dose (H(10)/D) at 2.00 cm from the beam field edge was 8.79?±?1.28 mSv/Gy. The ratio of the neutron dose equivalent to the proton absorbed dose with and without a high hydrogen-boron containing block was 0.63?±?0.06 to 1.15?±?0.13 mSv/Gy at 2.00 cm from the edge of the field at depths of 0.00, 1.64, and 6.00 cm. CONCLUSIONS: We found that the out-of-field secondary neutron dose in proton eye treatment with an eye snout is relatively small, and it can be further reduced by installing a borated neutron absorbing material.

Kim DW; Chung WK; Shin J; Lim YK; Shin D; Lee SB; Yoon M; Park SY; Shin DO; Cho JK

2013-01-01

328

Measurement of ionization chamber absorbed dose k(Q) factors in megavoltage photon beams.  

UK PubMed Central (United Kingdom)

PURPOSE: Absorbed dose beam quality conversion factors (k(Q) factors) were obtained for 27 different types of ionization chamber. The aim was to obtain objective evidence on the performance of a wide range of chambers currently available, and potentially used for reference dosimetry, and to investigate the accuracy of the k(Q) calculation algorithm used in the TG-51 protocol. METHODS: Measurements were made using the 60Co irradiator and Elekta Precise linac facilities at the National Research Council of Canada. The objective was to characterize the chambers over the range of energies applicable to TG-51 and determine whether each chamber met the requirements of a reference-class instrument. Chamber settling, leakage current, ion recombination and polarity, and waterproofing sleeve effects were investigated, and absorbed dose calibration coefficients were obtained for 60Co and 6, 10, and 25 MV photon beams. Only thimble-type chambers were considered in this investigation and were classified into three groups: (i) Reference chambers ("standard" 0.6 cm3 Farmer-type chambers and their derivatives traditionally used for beam output calibration); (ii) scanning chambers (typically 0.1 cm3 volume chambers used for beam commissioning with 3-D scanning phantoms); and (iii) microchambers (very small volume ion chambers (< or = 0.01 cm3) used for small field dosimetry). RESULTS: As might be expected, 0.6 cm3 thimble chambers showed the most predictable performance and experimental k(Q) factors were obtained with a relative uncertainty of 0.1%. The performance of scanning and microchambers was somewhat variable. Some chambers showed very good behavior but others showed anomalous polarity and recombination corrections that are not fully explained at present. For the well-behaved chambers, agreement between measured and calculated k(Q) factors was within 0.4%; for some chambers, differences of more than 1% were seen that may be related to the recombination/polarity results. Use of such chambers could result in significant errors in the determination of reference dose in the clinic. CONCLUSIONS: Based on the experimental evidence obtained here, specification for a reference-class ionization chamber could be developed that would minimize the error in using a dosimetry protocol with calculated beam quality conversion factors. The experimental k(Q) data obtained here for a wide range of thimble chambers can be used when choosing suitable detectors for reference dosimetry and are intended to be used in the upcoming update/addendum to the AAPM TG-51 dosimetry protocol.

McEwen MR

2010-05-01

329

The PTB water calorimeter for the absolute determination of absorbed dose to water in 60Co radiation  

International Nuclear Information System (INIS)

The quantity to be measured in dosimetry for radiation therapy is the absorbed dose to water, Dw. At the Physikalisch-Technische Bundesanstalt a water calorimeter is established as the primary standard for Dw in 60Co radiation under reference conditions. The water calorimeter is capable of measuring the absorbed dose to water with a combined standard uncertainty of 0.20%. Some aspects of the design and operation of the water calorimeter are discussed. Detailed experimental and theoretical investigations for the different influence quantities affecting the calorimetric results are presented. (authors)

2006-01-01

330

Effect of tungsten absorption edge filter on diagnostic x-ray spectra, image quality and absorbed dose to the patient  

Energy Technology Data Exchange (ETDEWEB)

The X-ray spectra from a tungsten-target diagnostic tube were measured with a lithium-drifted silicon detector. Four characteristic X-ray peaks were clearly observed. When a 0.05-0.3 mm thick tungsten absorption edge filter was added to the tube, the number of photons in the spectra above the K-absorption edge decreased dramatically. The effect of the absorption edge filter on image quality and on the absorbed dose were investigated by both measurement and Monte Carlo calculation. The absorbed dose to the patient is reduced without image quality, being degraded.

Yamaguchi, C. (National Lab. for High Energy Physics, Oho, Ibaraki (Japan)); Yamamoto, T. (Osaka Univ., Suita (Japan). Inst. of Scientific and Industrial Research); Terada, H. (Osaka Univ. (Japan). Research Inst. for Microbial Diseases); Akisada, M. (Tsukuba Univ., Sakura, Ibaraki (Japan))

1983-03-01

331

Effect of tungsten absorption edge filter on diagnostic x-ray spectra, image quality and absorbed dose to the patient.  

UK PubMed Central (United Kingdom)

The X-ray spectra from a tungsten-target diagnostic tube were measured with a lithium-drifted silicon detector. Four characteristic X-ray peaks were clearly observed. When a 0.05-0.3 mm thick tungsten absorption edge filter was added to the tube, the number of photons in the spectra above the K-absorption edge decreased dramatically. The effect of the absorption edge filter on image quality and on the absorbed dose were investigated by both measurement and Monte Carlo calculation. The absorbed dose to the patient is reduced without image quality, being degraded.

Yamaguchi C; Yamamoto T; Terada H; Akisada M

1983-03-01

332

Effect of tungsten absorption edge filter on diagnostic x-ray spectra, image quality and absorbed dose to the patient  

International Nuclear Information System (INIS)

The X-ray spectra from a tungsten-target diagnostic tube were measured with a lithium-drifted silicon detector. Four characteristic X-ray peaks were clearly observed. When a 0.05-0.3 mm thick tungsten absorption edge filter was added to the tube, the number of photons in the spectra above the K-absorption edge decreased dramatically. The effect of the absorption edge filter on image quality and on the absorbed dose were investigated by both measurement and Monte Carlo calculation. The absorbed dose to the patient is reduced without image quality, being degraded. (author).

1983-01-01

333

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

Science.gov (United States)

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

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

2012-10-01

334

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

International Nuclear Information System (INIS)

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

2011-12-01

335

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)

2009-01-01

336

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

2002-01-01

337

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

International Nuclear Information System (INIS)

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

1995-01-01

338

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

International Nuclear Information System (INIS)

[en] 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)

2011-01-01

339

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)

2000-01-01

340

Dose absorbed in x-rays toraxicas executed in hospitals of the city of Sao Paulo Brazil  

International Nuclear Information System (INIS)

With the objective of evaluating the contribution of radiography exams in the dose received by the population of the city of Sao Paulo (Brazil), we made mensurations of the doses absorbed in toraxicas x-rays (projections PA and LAT) taken in several teams of rays X used in hospitals. The work is supplemented with demography data and the knowledge of the quantity of exams executed in each team

1998-01-01

 
 
 
 
341

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 (

2011-01-01

342

Perspectives in absorbed dose metrology with regard to the technical evolutions of external beam radiotherapy  

International Nuclear Information System (INIS)

This paper presents several R and D axes in absorbed close metrology to meet the needs resulting from the technical evolutions of external beam radiotherapy. The facilities in operation in France have considerably evolved under the impulse of the plan Cancer launched in 2003: replacements and increase of the number of accelerators, substitution of accelerators for telecobalt almost completed and acquisition of innovative facilities for tomo-therapy and stereotaxy. The increasing versatility of facilities makes possible the rapid evolution of treatment modalities, allowing to better delimit irradiation to tumoral tissues and spare surrounding healthy tissues and organs at risk. This leads to a better treatment efficacy through dose escalation. National metrology laboratories must offer responses adapted to the new need, i.e. not restrict themselves to the establishment of references under conventional conditions defined at international level, contribute to the improvement of uncertainties at all levels of reference transfer to practitioners: primary measurements under conditions as close as possible to those of treatment, characterization of transfer and treatment control dosimeters., metrological validation of treatment planning tools... Those axes have been identified as priorities for the next years in ionizing radiation metrology at the European level and included in the European. Metrology Research Programme. A project dealing with some of those topics has been selected in the frame of the Eranet+ Call EMRP 2007 and is now starting. The LNE-LAM is strongly engaged in it. (authors)

2009-01-01

343

Determination of absorbed dose in water for an electron beam below 10MeV using a Cylindrical Ionization chamber  

Energy Technology Data Exchange (ETDEWEB)

IAEA Technical Reports Series No. 398 (TRS-398) recommend to use only plane-parallel ionization chamber for beam output calibration under 10 MeV electron beam. But the cross calibration using ionization chamber which is calibrated at a PSDL (Primary standard Dosimetry Laboratories) at a reference beam quality Q{sub 0} is needed to use plane-parallel ionization chamber. The procedure of the cross calibration is very complex and it generate another errors such as p{sub wall}(factor that corrects for the non-medium equivalence of the chamber wall material). So generally the medical institutions of korea use cylindrical ionization chamber for all energy range. This study calculated calibration factors in terms of absorbed dose to water by Monte Carlo simulation for the use of cylindrical ionization chamber under 10 MeV electron beam. BEAMnrc code was used to simulate linear accelerator (the Varian Clinca 2100C) for 6 MeV, 9 MeV and 12 MeV. As the result Phase-space file which includes the information of the particles was generated. EGSPP code calculated the calibration factors in terms of absorbed dose to water using Phase-space file as a source. The calibration factors in terms of absorbed dose to water applied to cylindrical ionization chamber to determine the absorbed dose to water, and it was compared with the absorbed dose to water by plane-parallel ionization chamber in the same energy and conditions. For 9 MeV and 12 MeV relative standard uncertainty of two absorbed dose to water determined by cylindrical ionization and plane-parallel ionization was 1.3% and 1.5%. But for 6 MeV the relative standard uncertainty was 3.7%. This result shows that the calibration factors in terms of absorbed dose to water which is calculated in this study is possible to apply to the cylindrical ionization chamber for 9 MeV, and 12 MeV. But the more study are needed to apply to 6 MeV electron beam

Min, Chul Hee

2006-02-15

344

Status of the primary standard of water absorbed dose for high energy photon and electron radiation at the PTB  

International Nuclear Information System (INIS)

The national primary standard of water absorbed dose for high energy photon and electron radiation in Germany is based on ferrous sulphate dosimetry. The response of the solution is determined by total absorption of high energy electrons from a microtron with a known radiant energy. The energy dependence of the chemical yield of the solution at high energies is assumed to be negligible to within acceptable uncertainties. The calibrated Fricke solution therefore allows the beams of 60Co sources to be measured and to serve as standards of the Physikalisch-Technische Bundesanstalt (PTB) for the quantity 'water absorbed dose' under specified conditions. Besides the refinement of the present primary standard, the water calorimetric method is being developed as the standard of choice for the future. In contrast to the present method, it allows the water absorbed dose to be measured according to its definition. A major problem is the handling of the heat defect. To overcome it, the PTB chose an experimental, absolute determination using a total absorption calorimeter for the high energy electrons of the microtron. In this case the heat defect need not necessarily be zero - which is a crucial condition - but only stable. Investigation is under way of the heat defect of water containing chemical additives introduced to cause a stable heat defect, independent of possible impurities in the absorbed dose calorimeter. The water absorbed dose calorimeter is operated at a water temperature of 4 deg. C to avoid convection. It allows the quotient of temperature rise and irradiation period using a 60Co source to be measured with a relative standard deviation of about 0.1% for the mean of a daily set of measurements. The investigation of possible influences and influence quantities is pending. (author). 12 refs, 3 figs.

1994-01-01

345

Measurement of absorbed dose-to-water for an HDR (192)Ir source with ionization chambers in a sandwich setup.  

UK PubMed Central (United Kingdom)

PURPOSE: In this study, a dedicated device for ion chamber measurements of absorbed dose-to-water for a Nucletron microSelectron-v2 HDR (192)Ir brachytherapy source is presented. The device uses two ionization chambers in a so-called sandwich assembly. Using this setup and by taking the average reading of the two chambers, any dose error due to difficulties in absolute positioning (centering) of the source in between the chambers is cancelled to first order. The method's accuracy was examined by comparing measurements with absorbed dose-to-water determination based on the AAPM TG-43 protocol. METHODS: The optimal source-to-chamber distance (SCD) for (192)Ir dosimetry was determined from ion chamber measurements in a water phantom. The (192)Ir source was sandwiched between two Exradin A1SL chambers (0.057 cm(3)) at the optimal SCD separation. The measured ionization was converted to the absorbed dose-to-water using a (60)Co calibration factor and a Monte Carlo-calculated beam quality conversion factor, kQ, for (60)Co to (192)Ir. An uncertainty estimate of the proposed method was determined based on reproducibility of measurements at different institutions for the same type of source. RESULTS: The optimal distance for the A1SL chamber measurements was determined to be 5 cm from the (192)Ir source center, considering the depth dependency of kQ for (60)Co to (192)Ir and the chamber positioning. The absorbed dose to water measured at (5 cm, 90°) on the transverse axis was 1.3% lower than TG-43 values and its reproducibility and overall uncertainty were 0.8% and 1.7%, respectively. The measurement doses at anisotropic points agreed within 1.5% with TG-43 values. CONCLUSIONS: The ion chamber measurement of absorbed dose-to-water with a sandwich method for the (192)Ir source provides a more accurate, direct, and reference dose compared to the dose-to-water determination based on air-kerma strength in the TG-43 protocol. Due to the simple but accurate assembly, the sandwich measurement method is useful for daily dose management of (192)Ir sources.

Araki F; Kouno T; Ohno T; Kakei K; Yoshiyama F; Kawamura S

2013-09-01

346

Measurement of absorbed dose-to-water for an HDR (192)Ir source with ionization chambers in a sandwich setup.  

Science.gov (United States)

Purpose: In this study, a dedicated device for ion chamber measurements of absorbed dose-to-water for a Nucletron microSelectron-v2 HDR (192)Ir brachytherapy source is presented. The device uses two ionization chambers in a so-called sandwich assembly. Using this setup and by taking the average reading of the two chambers, any dose error due to difficulties in absolute positioning (centering) of the source in between the chambers is cancelled to first order. The method's accuracy was examined by comparing measurements with absorbed dose-to-water determination based on the AAPM TG-43 protocol.Methods: The optimal source-to-chamber distance (SCD) for (192)Ir dosimetry was determined from ion chamber measurements in a water phantom. The (192)Ir source was sandwiched between two Exradin A1SL chambers (0.057 cm(3)) at the optimal SCD separation. The measured ionization was converted to the absorbed dose-to-water using a (60)Co calibration factor and a Monte Carlo-calculated beam quality conversion factor, kQ, for (60)Co to (192)Ir. An uncertainty estimate of the proposed method was determined based on reproducibility of measurements at different institutions for the same type of source.Results: The optimal distance for the A1SL chamber measurements was determined to be 5 cm from the (192)Ir source center, considering the depth dependency of kQ for (60)Co to (192)Ir and the chamber positioning. The absorbed dose to water measured at (5 cm, 90°) on the transverse axis was 1.3% lower than TG-43 values and its reproducibility and overall uncertainty were 0.8% and 1.7%, respectively. The measurement doses at anisotropic points agreed within 1.5% with TG-43 values.Conclusions: The ion chamber measurement of absorbed dose-to-water with a sandwich method for the (192)Ir source provides a more accurate, direct, and reference dose compared to the dose-to-water determination based on air-kerma strength in the TG-43 protocol. Due to the simple but accurate assembly, the sandwich measurement method is useful for daily dose management of (192)Ir sources. PMID:24007170

Araki, Fujio; Kouno, Tomohiro; Ohno, Takeshi; Kakei, Kiyotaka; Yoshiyama, Fumiaki; Kawamura, Shinji

2013-09-01

347

Estimation of absorbed doses from paediatric cone-beam CT scans: MOSFET measurements and Monte Carlo simulations.  

Science.gov (United States)

The purpose of this study was to establish a dose estimation tool with Monte Carlo (MC) simulations. A 5-y-old paediatric anthropomorphic phantom was computed tomography (CT) scanned to create a voxelised phantom and used as an input for the abdominal cone-beam CT in a BEAMnrc/EGSnrc MC system. An X-ray tube model of the Varian On-Board Imager((R)) was built in the MC system. To validate the model, the absorbed doses at each organ location for standard-dose and low-dose modes were measured in the physical phantom with MOSFET detectors; effective doses were also calculated. In the results, the MC simulations were comparable to the MOSFET measurements. This voxelised phantom approach could produce a more accurate dose estimation than the stylised phantom method. This model can be easily applied to multi-detector CT dosimetry. PMID:19889800

Kim, Sangroh; Yoshizumi, Terry T; Toncheva, Greta; Frush, Donald P; Yin, Fang-Fang

2009-11-04

348

Estimation of absorbed doses from paediatric cone-beam CT scans: MOSFET measurements and Monte Carlo simulations  

International Nuclear Information System (INIS)

The purpose of this study was to establish a dose estimation tool with Monte Carlo (MC) simulations. A 5-y-old paediatric anthropomorphic phantom was computed tomography (CT) scanned to create a voxelised phantom and used as an input for the abdominal cone-beam CT in a BEAMnrc/EGSnrc MC system. An X-ray tube model of the Varian On-Board ImagerR was built in the MC system. To validate the model, the absorbed doses at each organ location for standard-dose and low-dose modes were measured in the physical phantom with MOSFET detectors; effective doses were also calculated. In the results, the MC simulations were comparable to the MOSFET measurements. This voxelised phantom approach could produce a more accurate dose estimation than the stylised phantom method. This model can be easily applied to multi-detector CT dosimetry. (authors)

2010-01-01

349

Estimation of absorbed doses from paediatric cone-beam CT scans: MOSFET measurements and Monte Carlo simulations.  

UK PubMed Central (United Kingdom)

The purpose of this study was to establish a dose estimation tool with Monte Carlo (MC) simulations. A 5-y-old paediatric anthropomorphic phantom was computed tomography (CT) scanned to create a voxelised phantom and used as an input for the abdominal cone-beam CT in a BEAMnrc/EGSnrc MC system. An X-ray tube model of the Varian On-Board Imager((R)) was built in the MC system. To validate the model, the absorbed doses at each organ location for standard-dose and low-dose modes were measured in the physical phantom with MOSFET detectors; effective doses were also calculated. In the results, the MC simulations were comparable to the MOSFET measurements. This voxelised phantom approach could produce a more accurate dose estimation than the stylised phantom method. This model can be easily applied to multi-detector CT dosimetry.

Kim S; Yoshizumi TT; Toncheva G; Frush DP; Yin FF

2010-03-01

350

Measurement of absorbed dose for high energy electron using CaSO4: Tm-PTFE TLD  

International Nuclear Information System (INIS)

In this study, the highly sensitive CaSO4: Tm-PTFE TLDs has been fabricated for the purpose of measurement of high energy electron. CaSO4: Tm phosphor powder was mixed with polytetrafluoroethylene(PTFE) powder and moulded in a disk type(diameter 8.5mm, thickness 90mg/cm2) by cold pressing. The absorbed dose distribution and ranges for high energy electron were measured by using the CaSO4: Tm-PTFE TLDs. The ranges determined were R100=3D14.5mm, R50=3D24.1mm and Rp=3D31.8mm, respectively and the beam flatness, the variation of relative dose in 80% of the field size, was 4.5%. The fabricated CaSO4: Tm-PTFE TLDs may be utilized in radiation dosimetry for personal, absorbed dose and environmental monitoring.=20

2000-01-01

351

Radiation doses from mammography in Portugal  

International Nuclear Information System (INIS)

[en] A survey of patient doses in mammography was conducted during 1988/1989 in Portugal. Information on frequency and techniques of mammography as well as on technical specifications of X ray units and imaging systems was collected from 46 centres in hospitals, private clinics and practices. Radiation measurements were carried out in every X ray unit to assess entrance and exit absorbed doses and average glandular doses for a compressed breast 5 cm thick with a standard composition. Large inter-centre variations in dose were analysed in terms of the technical specifications of the X ray units and 'speed' of individual components of the imaging system. The annual frequency of mammographies was estimated as 16.5 per thousand inhabitants, yielding patient breast glandular dose per image of 1.42 mGy and a collective breast dose equivalent per million inhabitants of 49.9 Sv. (author)

1991-01-01

352

Polymer gel - TPS radiotherapy dosimetry GeVero software for ionizing radiation absorbed dose 3D distribution calculations  

Energy Technology Data Exchange (ETDEWEB)

Implementation of polymer gel dosimetry in radiotherapy departments calls for: easily manufactured gel dosimeters of required physical-chemical properties, set-up procedures of irradiation, adaptation of three-dimensional scanning procedures and instruments as well as fast tool for calculation of 3D absorbed dose distribution in the polymer gel dosimeters and comparison with another treatment planning system calculated dose distribution. These challenges resulted in several propositions in polymer gel dosimetry area. In this work, however, a summary of results on construction of polymer gel dosimetry software facilitating usually laborious 3D dose distributions data processing is provided.

Kozicki, Marek; Karwowski, Andrzej C [Institute of Architecture of Textiles, Faculty of Material Technologies and Textile Design, Technical University of Lodz, Zeromskiego 116, 90-924 Lodz (Poland); Maras, Piotr [Medical Physics Department, Copernicus Hospital, Pabianicka 62, 93-513 Lodz (Poland); Jankowski, Jacek [Department of Strength of Materials and Structures, Faculty of Mechanical Engineering, Technical University of Lodz, Stefanowskiego 1/15, 90-924 Lodz (Poland)], E-mail: mkozicki@mitr.p.lodz.pl

2009-05-01

353

Polymer gel - TPS radiotherapy dosimetry GeVero® software for ionizing radiation absorbed dose 3D distribution calculations  

Science.gov (United States)

Implementation of polymer gel dosimetry in radiotherapy departments calls for: easily manufactured gel dosimeters of required physical-chemical properties, set-up procedures of irradiation, adaptation of three-dimensional scanning procedures and instruments as well as fast tool for calculation of 3D absorbed dose distribution in the polymer gel dosimeters and comparison with another treatment planning system calculated dose distribution. These challenges resulted in several propositions in polymer gel dosimetry area. In this work, however, a summary of results on construction of polymer gel dosimetry software facilitating usually laborious 3D dose distributions data processing is provided.

Kozicki, Marek; Maras, Piotr; Jankowski, Jacek; Karwowski, Andrzej C.

2009-05-01

354

Estimation of yttrium-90 Zevalin tumor-absorbed dose in ocular adnexal lymphoma using quantitative indium-111 Zevalin radionuclide imaging.  

UK PubMed Central (United Kingdom)

OBJECTIVE: The purpose of this investigation was to estimate radiation-absorbed dose in orbital tumors from yttrium-90 ibritumomab tiuxetan (Zevalin) radioimmunotherapy of ocular adnexal lymphoma. METHODS: Three patients participating in a prospective research protocol involving treatment of ocular adnexal lymphoma with yttrium-90 Zevalin consented to quantitative radionuclide imaging to estimate tumor radiation-absorbed doses. Each patient received 185 MBq of indium-111 Zevalin, followed by serial planar whole-body scanning, to derive an activity versus time curve for the tumor. Single photon emission computed tomography (SPECT) and computed tomography (CT) imaging, including a calibration source, were performed at 24 h on a SPECT/CT scanner, to obtain a SPECT estimate of the radioactivity (in megabequerels) in the tumor and correct the planar curve, as well as estimate the tumor mass (M) from CT. The curve was then converted to that for yttrium-90 at the prescribed activity, and absorbed dose estimated from the area under the curve multiplied by the Medical Internal Radiation Dose S value (Gy per MBq-h) for a sphere of mass M. RESULTS: A right orbital tumor in one patient was visualized in both the planar and SPECT/CT images, with an estimated absorbed dose of 3.57 Gy. Tumor uptake in the other two patients was not visualized. CONCLUSION: The radiation dose to the orbit and ocular structures during radioimmunotherapy of ocular adnexal lymphoma is well below the threshold for significant radiation-induced ocular toxicity and about 10 times lower than that delivered during external beam radiotherapy.

Erwin WD; Esmaeli B

2009-09-01

355

A robust method for determining the absorbed dose to water in a phantom for low-energy photon radiation  

International Nuclear Information System (INIS)

The application of more and more low-energy photon radiation in brachytherapy-either in the form of low-dose-rate radioactive seeds such as Pd-103 or I-125 or in the form of miniature x-ray tubes-has induced greater interest in determining the absorbed dose to water in water in this energy range. As it seems to be hardly feasible to measure the absorbed dose with calorimetric methods in this low energy range, ionometric methods are the preferred choice. However, the determination of the absorbed dose to water in water by ionometric methods is difficult in this energy range. With decreasing energy, the relative uncertainty of the photon cross sections increases and as the mass energy transfer coefficients show a steep gradient, the spectra of the radiation field must be known precisely. In this work two ionometric methods to determine the absorbed dose to water are evaluated with respect to their sensitivity to the uncertainties of the spectra and of the atomic database. The first is the measurement of the air kerma free in air and the application of an MC-based conversion factor to the absorbed dose to water. The second is the determination of the absorbed dose to water by means of an extrapolation chamber as an integral part of a phantom. In the complementing MC-calculations, two assortments of spectra each of which is based on a separate unfolding procedure were used as well as two kinds of databases: the standard PEGS and the recently implemented NIST database of EGSnrc. Experimental results were obtained by using a parallel-plate graphite extrapolation chamber and a free-air chamber. In the case when the water kerma in a phantom is determined from the measurements of air kerma free in air, differences in the order of 10% were found, according to which the database or the kind of spectrum is used. In contrast to this, for the second method, the differences found were about 0.5%.

2011-06-07

356

Estimation of kidney depth effective renal plasmatic flux and absorbed dose, from a radio isotopic renogram  

International Nuclear Information System (INIS)

A technique for the estimation of kidney depth is described. It is based on a comparison between the measurements obtained in a radioisotopic renogram carried out for two specific energies and the same measurements made with a phanto-kidney at different depths. Experiments performed with kidney and abdomen phantoms provide calibration curves which are obtained by plotting the photopeak to scatter ratio for 131I pulse height spectrum against depth. Through this technique it is possible to obtain the Hippuran-131I kidney uptake with external measurements only. In fact it introduces a correction in the measurements for the depth itself and for the attenuation and scattering effects due to the tissues interposed between the kidney and the detector. When the two kidneys are not equidistant from the detector, their respective renograms are different and it is therefore very important to introduce a correction to the measurements according to the organ depth in order to obtain the exact information on Hippuran partition between the kidneys. The significative influence of the extrarenal activity is analyzed in the renogram by monitoring the praecordial region after 131I-human serum albumin injection and establishing a calibration factor relating the radioactivity level of this area to that present in each kidney area. It is shown that it is possible to obtain the values for the clearance of each kidney from the renogram once the alteration in efficiency due to the organ depth and to non-renal tissue interference in the renal area is considered. This way, values for the effective renal plasma flow were obtained, which are comparable to those obtained with other techniques, estimating the total flow of the kidneys. Finally the mean absorbed dose of the kidneys in a renography is also estimated. (Author).

1979-01-01

357

In vivo absorbed dose messurements with mini-TLDS. Parameters affecting the reliability  

International Nuclear Information System (INIS)

Mini-TLDs have been proposed and widely used for in vivo measurements of absorbed doses in radionuclide therapies. The present investigation reports in detail on the signal dependence on different parameters and the accuracy of this method. Rodshaped Teflon-imbedded CaSO4:Dy or LiF thermoluminescent dosimeters (TLDs) with dimensions 0.2 x 0.4 x 5 mm3 were prepared from TLD-discs. To remove paraffin from the mini-TLDs after cutting in a microtome the TLDs were Xylene-treated, which does not affect the sensitivity. Irradiated mini-TLDs are sensitive to illumination. Fading effects in darkness were examined after 60Co-irradiation at temperatures 4, 22 and 37 C. For CaSO4:Dy mini-TLDs fading in air is small. The observed signal loss after implanting CaSO4:Dy mini-TLDs in gel and muscle tissue is the same at constant temperature and is increasing with the temperature. For LiF mini-TLDs the effect of signal loss in gel was smaller than for CaSO4:Dy dosimeters. For 60Co external irradiation supralinearity already starts between 0.5 and 1 Gy for both kinds of dosimeter material. There is a strong pH dependence of the signals from the mini-TLDs. For CaSO4:Dy dosimeters the loss of sensitivity in gel is smaller at higher pHs. For LiF dosimeters the loss of sensitivity is smallest for neutral pH. We conclude that using mini-TLDs for in vivo dosimetry requires careful handling and proper calibration for accuracy in the measurements. Without such calibration errors exceeding 65% for CaSO4:Dy and 40% for LiF may easily occur. (orig.)

1996-01-01

358

Evaluation of the absorbed dose of the thyroid gland in conventional spiral and spiral computed tomography techniques  

Directory of Open Access Journals (Sweden)

Full Text Available AbstractIntroduction: The use of sophisticated radiographic techniques is absolutely necessary in dentistry. The use of these techniques exposes the sensitive organs of head and neck to x-rays. The aim of the present study was to investigate the absorbed dose of the thyroid gland in conventional spiral and spiral computed tomography techniques. Materials and Methods: In this experimental study, 10 TLD GR-200 circular dosimeters (Thermoluminans Detector) were used in male RANDO-like phantom (head and neck segment, i.e. the first 10 segments) in order to determine the radiation dose absorbed by the thyroid gland. Then spiral computed tomographies were provided from the anterior and posterior regions of the maxilla and mandible along with a lateral Scout view as a guide. Conventional spiral tomographies were prepared from the maxilla, mandible and both jaws with a panoramic radiograph as a guide. Data was analyzed using Kruskal-Wallis and Mann-Whitney tests using SPSS 11.5 (a = 0.05). Results: The highest and lowest thyroid gland absorbed doses were observed with computed tomography of both jaws and conventional spiral tomography of the anterior maxilla, respectively (5.92 ± 0.01 and 0.79 ± 0.01 mSiv). The mean amount of the absorbed dose by the thyroid gland was lower in the conventional spiral tomography compared to computed tomography. The two techniques revealed significant differences in the absorbed doses except for conventional spiral tomography in the posterior and anterior regions of the mandible (p value = 0.276).Conclusion: According to results of the present study, the absorbed dose of the thyroid gland in the conventional spiral tomography in different regions of the jaws was less than CT scan techniques. As a result, it appears the use of conventional spiral tomography is preferred over CT scans in limited regions where three-dimensional and cross-sectional views are required.Key words: Thyroid gland, Film dosimetry, Spiral Computed Tomography.

Hamid Badrian; Mahnaz Sheikhi; Atefeh Mirzabagherian; Navid Khalighinejad

2012-01-01

359

Hematological toxicity in radioimmunotherapy is predicted both by the computed absorbed whole body dose (cGy) and by the administered dose (mCi)  

International Nuclear Information System (INIS)

Purpose/Objective: Radioimmunotherapy (RIT) has yielded encouraging response rates in patients with recurrent non-Hodgkin's lymphoma, but myelotoxicity remains the dose limiting factor. Dose optimization is theoretically possible, since a pretreatment biodistribution study with tracer doses allows for a fairly accurate estimate of the whole body (and by implication the bone marrow) dose in patients. It has been shown that the radiation dose as a function of the administered dose varies widely from patient to patient. The pretreatment study could therefore be used to determine the maximum tolerable dose for each individual patient. The purpose of this study was to examine whether the administered dose or the estimated whole body absorbed radiation dose were indeed predictors of bone marrow toxicity. Materials and Methods: We studied two cohorts of patients to determine if the computed integral whole body or marrow dose is predictive of myelotoxicity. The first cohort consisted of 13 patients treated with Yttrium-90 labeled anti-CD20 (2B8) monoclonal antibody. Those patients were treated in a dose escalation protocol, based on the administered dose, without correction for weight or body surface. The computed whole body dose varied from 41 to 129 cGy. The second cohort (6 patients) were treated with Iodine-131 labeled anti-CD20 (B1) antibody. In this group the administered dose was tailored to deliver an estimated 75 cGy whole body dose. The administered dose varied from 54 to 84 mCi of Iodine-131. For each patient, white blood cell count with differential, hemoglobin, hematocrit, and platelet levels were measured before and at regular intervals after RIT was administered. Using linear regression analysis, a relationship between administered dose, absorbed dose and myelotoxicity was determined for each patient cohort. Results: Marrow toxicity was measured by the absolute decrease in white blood cell (DWBC), platelet (DPLAT), and neutrophil (DN) values. In the Yttrium-90 anti-CD20 antibody treated group, in which the estimated whole body dose varied (D(cGy)), the decrease in these values was predicted by the linear (zero intercept) equations: DWBC = 0.01158 D(cGy) + 0.05247 D(mCi), DPLAT = 0.1476 D(cGy) + 3.043 D(mCi), and DN=0.0047 D(cGy)+0.0507D(mCi). In the Iodine-131 anti-CD20 antibody treated group, where D(cGy) was constant and equal to 75 cGy, the variation in toxicity was predicted by the linear equation DPLAT = -241 + 5.53 D(mCi), with F=12.184 (p

1997-01-01

360

The LundADose method for planar image activity quantification and absorbed-dose assessment in radionuclide therapy.  

UK PubMed Central (United Kingdom)

A new method for absorbed-dose assessment in radionuclide therapy is presented in this paper. The method is based on activity quantification by the conjugate-view methodology, applied to serial whole-body, anterior-posterior, scintillation-camera scans. The quantification method is an extension of previous studies, and includes separate corrections for attenuation, scatter, and overlapping organs. Further development has now been undertaken to take into account the capabilities of new dual-head camera systems with a built-in X-ray tube for anatomical imaging. Furthermore, the modeling of time-activity data is included, and dosimetric calculations based on the formalism by the Medical Internal Radiation Dose (MIRD) committee. To streamline absorbed-dose assessments for a large number of patient studies, the programs for quantification, image registration, and absorbed-dose calculations have been embedded in an envelop program termed LundADose, where calculations, to a great extent, are performed automatically. Evaluation of the whole-body activity quantification is performed for patients undergoing radioimmunotherapy by monoclonal antibodies labeled with (111)In or (90)Y.

Sjögreen K; Ljungberg M; Wingårdh K; Minarik D; Strand SE

2005-02-01

 
 
 
 
361

Absorbed dose estimation of gonads resulting from fault work of staff during injection of radiopharmaceuticals to the patients  

International Nuclear Information System (INIS)

Radiopharmaceuticals are used in nuclear medicine in a variety of diagnostic and therapeutic procedures and generally delivered to the patient via intravenous injection. 201Tl and 99mTc are the two most used radiopharmaceuticals in nuclear medicine. The maximum activity injected to the patient in nuclear medicine for 201Tl and 99mTc is 5 and 20-25 mCi respectively. In this research by using Monte Carlo method and MCNPX code the absorbed dose to Gonads due to drop of radiopharmaceutical on foot thigh during injection to the patient has been calculated. The activity of 201Tl and 99mTc has been considered 1 and 5mCi respectively. The amount of absorbed dose in gonads for 99mTc for male and female during 8 hours of work has been measured 0.37 and 0.055 ?Sv respectively. Also the amount of absorbed dose for201Tl during working hours at first day, second day and third day after work fault for male has been measured 0.387, 0.308 and 0.246 ?Sv and for female 0.06, 0.048 and 0.038 ?Sv respectively. The total dose in these three working days for male and female has been 0.941 and 0.146 ?Sv respectively. Since absorbed dose of gonads was far enough from the limits of ICRP, so it can be concluded that if a fault work occurs and even staff does not be aware there is no need to treat him. (authors)

2012-01-01

362

Fast neutron absorbed dose distributions in the energy range 0.5-80 MeV - a Monte Carlo study  

International Nuclear Information System (INIS)

[en] Neutron pencil-beam absorbed dose distributions in phantoms of bone, ICRU soft tissue, muscle, adipose and the tissue substitutes water, A-150 (plastic) and PMMA (acrylic) have been calculated using the Monte Carlo code FLUKA in the energy range 0.5 to 80 MeV. For neutrons of energies ?20 MeV, the results were compared to those obtained using the Monte Carlo code MCNP4B. Broad-beam depth doses and lateral dose distributions were derived. Broad-beam dose distributions in various materials were compared using two kinds of scaling factor: a depth-scaling factor and a dose-scaling factor. Build-up factors due to scattered neutrons and photons were derived and the appropriate choice of phantom material for determining dose distributions in soft tissue examined. Water was found to be a good substitute for soft tissue even at neutron energies as high as 80 MeV. The relative absorbed doses due to photons ranged from 2% to 15% for neutron energies 10-80 MeV depending on phantom material and depth. For neutron energies below 10 MeV the depth dose distributions derived with MCNP4B and FLUKA differed significantly, the difference being probably due to the use of multigroup transport of low energy (20 MeV, MCNP4B fails to describe dose build-up at the phantom interface and penumbra at the edge of the beam because it does not transport secondary charged particles. The penumbra width, defined as the distance between the 80% and 20% iso-dose levels at 5 cm depth and for a 10x10 cm2 field, was between 0.9 mm and 7.2 mm for neutron energies 10-80 MeV. (author)

2000-01-01

363

Reduction of uncertainties in radiotherapy assessed by Monte Carlo simulation: spectral analysis applied to absorbed dose correction  

International Nuclear Information System (INIS)

[en] Objective: to calculate spectra of cobalt-60 beam at water depth and correction factors for absorbed dose measurements obtained with lithium fluoride thermoluminescent dosimeters using Monte Carlo simulation. Materials and methods: the simulations of secondary spectra of clinical cobalt-60 sources were performed with the PENELOPE Monte Carlo code at different water depths. Experimental measurements of deep doses were obtained with thermoluminescent dosimeters and ionization chamber under reference conditions for radiotherapy. Correction factors for the thermoluminescent dosimeters detectors were obtained through the ratio between the relative energy absorption for the low energy spectrum and the total spectrum. Results: deep spectral analysis has demonstrated the presence of secondary low-energy spectra responsible for a significant portion of the dose deposition. Discrepancies of 3.2% were observed among the doses measured with ionization chamber and thermoluminescent dosimeters. The adoption of correction factors has allowed a reduction in the discrepancy among absorbed doses to a maximum of 0.3%. Conclusion: Simulated spectra allow the calculation of correction factors for reading of thermoluminescent dosimeters utilized in the measurement of deep doses, contributing for the reduction of uncertainties associated with quality control of clinical beams in radiotherapy. (author)

2010-01-01

364

Reduction of uncertainties in radiotherapy assessed by Monte Carlo simulation: spectral analysis applied to absorbed dose correction  

Energy Technology Data Exchange (ETDEWEB)

Objective: to calculate spectra of cobalt-60 beam at water depth and correction factors for absorbed dose measurements obtained with lithium fluoride thermoluminescent dosimeters using Monte Carlo simulation. Materials and methods: the simulations of secondary spectra of clinical cobalt-60 sources were performed with the PENELOPE Monte Carlo code at different water depths. Experimental measurements of deep doses were obtained with thermoluminescent dosimeters and ionization chamber under reference conditions for radiotherapy. Correction factors for the thermoluminescent dosimeters detectors were obtained through the ratio between the relative energy absorption for the low energy spectrum and the total spectrum. Results: deep spectral analysis has demonstrated the presence of secondary low-energy spectra responsible for a significant portion of the dose deposition. Discrepancies of 3.2% were observed among the doses measured with ionization chamber and thermoluminescent dosimeters. The adoption of correction factors has allowed a reduction in the discrepancy among absorbed doses to a maximum of 0.3%. Conclusion: Simulated spectra allow the calculation of correction factors for reading of thermoluminescent dosimeters utilized in the measurement of deep doses, contributing for the reduction of uncertainties associated with quality control of clinical beams in radiotherapy. (author)

Marques, Tatiana; Alva-Sanchez, Mirko; Nicolucci, Patricia, E-mail: tatiana.marques@usp.b [Universidade de Sao Paulo (USP), Ribeirao Preto, SP (Brazil). Dept. de Fisica e Matematica

2010-04-15

365

Activity of natural radionuclides and their contribution to the absorbed dose in the fish cubera snapper (lutjanus cyanopterus, cuvier, 1828) on the coast of Ceara, Brazil  

International Nuclear Information System (INIS)

A methodology was developed for converting the activity concentration of radionuclides (Bq kg-1) into absorbed dose rate (Gy y-1), aiming an approach to environmental radioprotection based on the concept of standard dose limit. The model considers only the internal absorbed dose rate. This methodology was applied to the cubera snapper fish (Lutjanus cyanopterus, Cuvier, 1828) caught off the coast of Ceara. The natural radionuclides considered were uranium-238, radium-226, lead-210, thorium-232 and radium-228. The absorbed dose rates were calculated for individual radionuclides and the type of emitted radiation. The average dose rate due to these radionuclides was 5.36 ?Gy y-1, a value six orders of magnitude smaller than the threshold value of absorbed dose rate used in this study (3.65 103 mGy y-1), and similar to that found in the literature for benthic fish. Ra-226 and U- 238 contributed 67% and 22% of the absorbed dose rate, followed by Th-232 with 10%. Ra-228 and Pb-210, in turn, accounted for less than 1% of the absorbed dose rate. This distribution is somewhat different from that reported in the literature, where the Ra-226 accounts for 86% of the absorbed dose rate. (author)