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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)

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.

3

Media glandular dose in mammography  

International Nuclear Information System (INIS)

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

4

Evaluation of depth dose and glandular dose for digital mammography  

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

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

2010-03-15

5

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

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

Mowlavi A A

2007-07-01

6

Average glandular dose in patients submitted to mammography exams  

International Nuclear Information System (INIS)

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

7

Average glandular dose in patients submitted to mammographic examinations  

International Nuclear Information System (INIS)

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

8

Evaluation of glandular dose in conventional and digital mammography systems  

International Nuclear Information System (INIS)

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

9

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

10

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 landular 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

11

Preliminary results of the average glandular dose to the breast with TLDS measure is computed as the conversion factors; Resultados preliminares da dose glandular media na mama medida com TLDS e calculada atraves de fatores de conversao  

Energy Technology Data Exchange (ETDEWEB)

At mammography exams there is a risk of a breast cancer induced from the absorbed dose by the glandular tissue. According to the National Institute of Cancer, INCA, breast cancer is the second type most frequent in the world and the most common among women, therefore the necessity of monitoring the mean glandular dose, D{sub G}. Measuring methods of D{sub G} were established by some authors. Among the established methods the method of Dance is one of the most known. In this study was utilized a measurement method realized with TL dosimeters inserted in a breast tissue equivalent phantom, BTE, with 46% of glandularity and exposed using Mo/Mo and Mo/Rh target/filter combination and 28kV. To ensure this measurement method the results were compared with a calculation method, used by Dance, of D{sub G} from the measurement of incident air kerma, K{sub i}, and conversion factors to consider mainly the beam quality, the compressed thickness and the glandularity of the breast. The results of the comparison of the D{sub G} measurement with the obtained dose by the method of Dance demonstrated that for the thickness of 4.0 and 6.0 cm the doses were consistent. For the thickness of 5.0 cm the difference was higher, indicating that the glandularity may influence, suggesting further investigation. (author)

Sardo, Luiz T.L.; Almeida, Claudio D.; Coutinho, Celia M.C., E-mail: ltsardo@yahoo.com.br, E-mail: claudio@ird.gov.br, E-mail: celia@ird.gov.br [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

2013-07-01

12

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 thee multi-slit pre-collimator device and the occurrence of a dose profile in the scanning direction. (authors)

13

Estimating the glandular average dose in some mammography labs  

International Nuclear Information System (INIS)

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

14

Investigation of mean glandular dose in diagnostic mammography in China.  

Science.gov (United States)

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

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

2014-05-01

15

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)

16

Average glandular dose in digital mammography and breast tomosynthesis  

International Nuclear Information System (INIS)

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

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

18

Dosimetry in Mammography: Average Glandular Dose Based on Homogeneous Phantom  

Science.gov (United States)

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

Benevides, Luis A.; Hintenlang, David E.

2011-05-01

19

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

OpenAIRE

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

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

2006-01-01

20

Average glandular dose and phantom image quality in mammography  

International Nuclear Information System (INIS)

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

21

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)

22

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

2010-12-01

23

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

International Nuclear Information System (INIS)

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

24

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

Science.gov (United States)

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

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

2014-11-11

25

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

International Nuclear Information System (INIS)

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

26

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)

27

A Methodology for Obtaining the Mean Glandular Dose in Mammography Exams  

Science.gov (United States)

This study proposes to validate measurements of mean glandular dose quantity (DG) for a given thickness and glandularity of compressed breast based in a PMMA phantom. 10 exposures were made in an ionization chamber in conventional mammographic equipment for a research. It obtained an average value for the incident air kerma, Ka,I = 9.59 mGy leading to a DG = 1.82 mGy. Experimental results too were obtained for the acquisition of this quantity in other mammography clinics and these results were also reported and discussed. After the comparison of the results the methodology was validated.

Feital, J. C.; Delgado, J. U.; Lopes, R. T.

2015-01-01

28

Absorbed dose in CT. Comparison by CT dose index  

Energy Technology Data Exchange (ETDEWEB)

Few reports have discussed the absorbed dose on CT units with increased scanning capacity even with the current widespread adoption of multi-slice CT units. To compare and investigate the dose indexes among CT units, we measured the absorbed dose on CT units operating in Nagano Prefecture Japan. The measurements showed proportionality between phantom absorbed dose and the exposured mAs values in conventional scanning operation. Further, the measurements showed that the absorbed dose in the center of the phantom differed by about 2.1-fold between the highest and lowest levels on individual CT units. Within a single company, multi-slice CT units of the same company gave absorbed doses of about 1.3 to 1.5 times those of conventional single-slice CT units under the same exposured conditions of conventional scanning. When the scanning pitch was reduced in helical scanning, the absorbed dose at the center of the phantom increased. (author)

Yamamoto, Kenji; Akazawa, Hiroshi [Toyoshina Red Cross Hospital, Nagano (Japan); Andou, Takashi [Shinshu Univ., Matsumoto, Nagano (Japan). Hospital

2002-04-01

29

Absorbed dose in CT. Comparison by CT dose index  

International Nuclear Information System (INIS)

Few reports have discussed the absorbed dose on CT units with increased scanning capacity even with the current widespread adoption of multi-slice CT units. To compare and investigate the dose indexes among CT units, we measured the absorbed dose on CT units operating in Nagano Prefecture Japan. The measurements showed proportionality between phantom absorbed dose and the exposured mAs values in conventional scanning operation. Further, the measurements showed that the absorbed dose in the center of the phantom differed by about 2.1-fold between the highest and lowest levels on individual CT units. Within a single company, multi-slice CT units of the same company gave absorbed doses of about 1.3 to 1.5 times those of conventional single-slice CT units under the same exposured conditions of conventional scanning. When the scanning pitch was reduced in helical scanning, the absorbed dose at the center of the phantom increased. (author)

30

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

International Nuclear Information System (INIS)

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

31

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

Science.gov (United States)

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

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

2014-12-01

32

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

Vagner Ferreira, Cassola; Gabriela, Hoff.

2010-12-01

33

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

34

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

Directory of Open Access Journals (Sweden)

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

F. Bouzarjomehri

2006-08-01

35

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

International Nuclear Information System (INIS)

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

36

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1999-06-01

37

Internal absorbed dose from administered radiopharmaceuticals  

International Nuclear Information System (INIS)

With the increasing application of radiopharmaceuticals in nuclear medicine an extensive knowledge of the absorbed doses to various organs is required. Therefore, dose values to gonads, red bone marrow, and critical or investigated organs have been calculated and tabulated for adults and for children of different ages. All tables for absorbed doses are given first in special radiation units and are then repeated in the recently introduced SI units. To enable the reader to understand the nature of these dose calculations, the fundamental biological and physical principles are first summarized. (author)

38

Estimate of average glandular dose (AGD) in national clinics of mammography  

International Nuclear Information System (INIS)

The breast cancer represents the second cause of death by cancer in the femme population of our country. The specialized equipment for the obtaining of the mammographic images is higher every day and its use increases daily. The quality of the radiographic study is linked to the dose that this tissue intrinsically sensible receives to the ionizing radiations. The present work makes the first national study to quantify the average glandular doses and to connect them with the diagnostic quality and the recommendations to international scale. (Author)

39

Mammography Dosimetry: Average Glandular Dose as a Function of X-Ray Equipment, Imaging Technique, Breast Composition, and Breast Thickness.  

Science.gov (United States)

Conversion factors relating entrance skin exposure to average glandular dose are presented for x-ray equipment, imaging techniques, breast compositions, and breast thicknesses encountered in modern clinical mammography. Using thermoluminescent dosimeters, dose conversion factors and average glandular dose were determined for grid screen-film mammography as a function of the x-ray tube target-filter materials, x -ray beam quality, breast composition, and breast thickness. These data allow more realistic dose estimates that are unique to the specific imaging technique and patient's anatomy. Based upon actual patient data and equipment performance data, the range of doses for typical clinical mammography examinations are better defined by this research.

Plott, Carmine Marie

1995-01-01

40

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

International Nuclear Information System (INIS)

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

41

Estimation of average glandular dose depending on the thickness of the breast; Estimativa da dose glandular media em funcao da espessura da mama  

Energy Technology Data Exchange (ETDEWEB)

Breast cancer is the most common type of cancer in women worldwide. Mammography is, to date, the most efficient method for detecting an abnormality in the patient's breast. It is a technique of imaging diagnostic that requires special care because radiographs without adequate quality may lead to a false diagnosis and lead to the need for a repeat examination, increasing the dose of radiation in the patient. This study aimed to evaluate the average glandular dose (AGD), depending on the breast thickness in patients undergoing routine tests, with a digital computer radiography processing system. Analyzed 30 exhibitions in patients aged (65 ± 12) years, in the right and left caudal skull projections, for breasts with thicknesses between 45 mm and 50 mm. The calculated value of the AGD for this track thickness was (1.600 ± 0.009) mGy. The performance of mammography quality control tests was satisfactory and the AGD values obtained for the chosen thickness range is acceptable, since the threshold achievable is 1.6 mGy and the acceptable is 2 mGy. In Brazil, it is only required the input dose calculation in skin for 45 mm breasts. However, the calculation of AGD is required for different thicknesses of the breast, to identify the best mammographic pattern aiming at better image quality at the lowest dose provided the patient.

Real, Jessica V.; Luz, Renata M. da, E-mail: jessica.real@pucrs.br, E-mail: renata.luz@pucrs.br [Hospital Sao Lucas (HSL/PUCRS), Porto Alegre, RS (Brazil); Fröhlich, Bruna D.; Pertile, Alessandra S.; Silva, Ana Maria Marques da, E-mail: bruna.frohlich@acad.pucrs.br, E-mail: lessandra.pertile@acad.pucrs.br, E-mail: ana.marques@pucrs.br [Pontificia Universidade Catolica do Rio Grande do Sul (PUCRS), Porto Alegre, RS (Brazil)

2014-07-01

42

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

Scientific Electronic Library Online (English)

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

Oswaldo, Ramos N; Manuel, Villarreal U.

43

Neutron absorbed dose in a pacemaker CMOS  

Energy Technology Data Exchange (ETDEWEB)

The neutron spectrum and the absorbed dose in a Complementary Metal Oxide Semiconductor (CMOS), has been estimated using Monte Carlo methods. Eventually a person with a pacemaker becomes an oncology patient that must be treated in a linear accelerator. Pacemaker has integrated circuits as CMOS that are sensitive to intense and pulsed radiation fields. Above 7 MV therapeutic beam is contaminated with photoneutrons that could damage the CMOS. Here, the neutron spectrum and the absorbed dose in a CMOS cell was calculated, also the spectra were calculated in two point-like detectors in the room. Neutron spectrum in the CMOS cell shows a small peak between 0.1 to 1 MeV and a larger peak in the thermal region, joined by epithermal neutrons, same features were observed in the point-like detectors. The absorbed dose in the CMOS was 1.522 x 10{sup -17} Gy per neutron emitted by the source. (Author)

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

2012-06-15

44

Neutron absorbed dose in a pacemaker CMOS  

International Nuclear Information System (INIS)

The neutron spectrum and the absorbed dose in a Complementary Metal Oxide Semiconductor (CMOS), has been estimated using Monte Carlo methods. Eventually a person with a pacemaker becomes an oncology patient that must be treated in a linear accelerator. Pacemaker has integrated circuits as CMOS that are sensitive to intense and pulsed radiation fields. Above 7 MV therapeutic beam is contaminated with photoneutrons that could damage the CMOS. Here, the neutron spectrum and the absorbed dose in a CMOS cell was calculated, also the spectra were calculated in two point-like detectors in the room. Neutron spectrum in the CMOS cell shows a small peak between 0.1 to 1 MeV and a larger peak in the thermal region, joined by epithermal neutrons, same features were observed in the point-like detectors. The absorbed dose in the CMOS was 1.522 x 10-17 Gy per neutron emitted by the source. (Author)

45

Criteria and measurements for the collection and validation of the mean glandular dose due to mammography exams  

Energy Technology Data Exchange (ETDEWEB)

This study proposes to validate measurements of mean glandular dose quantity (D{sub G}) for the compressed breast according to the representative's phantom measurements results. There were exposures in an ionization chamber and obtained an mean value for the absorbed dose or entrance surface air kerma (K{sub a,e}) and other results were obtained for this quantity. In addition to the value obtained of 1.84 mGy ± 0.2 % for D{sub G} at the two major experimental projections in mammography clinic, other results were reported and discussed. Regarding the level of uncertainty associated with the D{sub G}, it was proved to be 5 times greater than the measurements of uncertainties estimated in each clinic, based on quality control tests. However, this result was expected because other components of significant uncertainty in its composition were also considered, as consistent with the practices and negligible in relation to the ultimate given quantity. After the comparison of the representative dose value with the reference level (2.5 mGy), according to literature, such measurements were validated with appropriate recommendations. (author)

Feital, Joao Carlos da Silva; Delgado, Jose Ubiratan, E-mail: jfeital@ird.gov.br, E-mail: delgado@ird.gov.br [Instituto de Radioprotecao e Dosimetria (IRD/CNEN- RJ), Rio de Janeiro, RJ (Brazil)

2013-07-01

46

Criteria and measurements for the collection and validation of the mean glandular dose due to mammography exams  

International Nuclear Information System (INIS)

This study proposes to validate measurements of mean glandular dose quantity (DG) for the compressed breast according to the representative's phantom measurements results. There were exposures in an ionization chamber and obtained an mean value for the absorbed dose or entrance surface air kerma (Ka,e) and other results were obtained for this quantity. In addition to the value obtained of 1.84 mGy ± 0.2 % for DG at the two major experimental projections in mammography clinic, other results were reported and discussed. Regarding the level of uncertainty associated with the DG, it was proved to be 5 times greater than the measurements of uncertainties estimated in each clinic, based on quality control tests. However, this result was expected because other components of significant uncertainty in its composition were also considered, as consistent with the practices and negligible in relation to the ultimate given quantity. After the comparison of the representative dose value with the reference level (2.5 mGy), according to literature, such measurements were validated with appropriate recommendations. (author)

47

Evaluation of average glandular dose in digital and conventional systems of the mammography  

International Nuclear Information System (INIS)

Mammography is currently the most effective method of diagnosis and detection of breast pathologies. The main interest in this kid of exam comes from the high incidence rate of breast cancer and necessity of high quality images for accurate diagnosis. Digital mammography systems have several advantages compared to conventional systems, however the use of digital imaging systems is not always integrated to an image acquisition protocol. Therefore, it is questionable if digital systems truly reduce the dose received by the patient, because many times is introduced in the clinics without optimization of the image acquisition protocols. The aim of this study is to estimate the value of incident air Kerma and average glandular dose (AGD) in patients undergoing conventional and digital mammography systems in Recife. This study was conducted with 650 patients in three hospitals. The value of incident air Kerma was estimated from the measurement of the yield of equipment and irradiation parameters used for each patient. From these results and using the methodology proposed by Dance et al. the value of the average glandular dose was calculated. The results obtained show that the lowest value of AGD was found with conventional screen-film system, indicating that the parameters for image acquisition with digital systems are not optimized. It was also observed that the institutions with digital systems use lower breast compression values than the conventional. (author)

48

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)

49

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

50

A new dosimetric phantom for evaluation of glandular dose in conventional and digital mammography systems  

International Nuclear Information System (INIS)

Mammography is a screening method for early detection of breast cancer. Mammography aims to achieve a high image quality associated with a radiation dose in the patient as low as achievable where any existing abnormality or lesion is clearly visualized, ensuring the production of exams that enable a precise diagnosis. The mean glandular dose, DG, is defined as the energy deposited per unit mass of fibroglandular tissue (the most radiosensitive tissue in the breast) averaged over all the fibroglandular tissue in the breast. DG is calculated from values of entrance air kerma, the X ray beam quality (half- value layer), and compressed breast thickness. DG is the quantity that best characterizes the breast carcinogenic risk of ionizing radiation

51

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

International Nuclear Information System (INIS)

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

52

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

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

Irene Nsiah-Akoto

2011-08-01

53

Estimation of average glandular dose depending on the thickness of the breast  

International Nuclear Information System (INIS)

Breast cancer is the most common type of cancer in women worldwide. Mammography is, to date, the most efficient method for detecting an abnormality in the patient's breast. It is a technique of imaging diagnostic that requires special care because radiographs without adequate quality may lead to a false diagnosis and lead to the need for a repeat examination, increasing the dose of radiation in the patient. This study aimed to evaluate the average glandular dose (AGD), depending on the breast thickness in patients undergoing routine tests, with a digital computer radiography processing system. Analyzed 30 exhibitions in patients aged (65 ± 12) years, in the right and left caudal skull projections, for breasts with thicknesses between 45 mm and 50 mm. The calculated value of the AGD for this track thickness was (1.600 ± 0.009) mGy. The performance of mammography quality control tests was satisfactory and the AGD values obtained for the chosen thickness range is acceptable, since the threshold achievable is 1.6 mGy and the acceptable is 2 mGy. In Brazil, it is only required the input dose calculation in skin for 45 mm breasts. However, the calculation of AGD is required for different thicknesses of the breast, to identify the best mammographic pattern aiming at better image quality at the lowest dose provided the patient

54

Real-time estimation system for mean glandular dose in mammography  

International Nuclear Information System (INIS)

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

55

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

International Nuclear Information System (INIS)

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

56

Neutron absorbed dose in a pacemaker CMOS  

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-11-15

57

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

International Nuclear Information System (INIS)

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

58

Mean glandular doses for women undergoing mammographic breast screening in Oyo state, Nigeria  

International Nuclear Information System (INIS)

In this work, thermoluminescent dosimeters have been used to measure entrance surface doses (ESDs) of patients undergoing mammographic screening at the University College Hospital, Ibadan, Oyo state. The mean glandular doses (MGDs) were also calculated using the measured ESDs. The results showed that the ESDs ranged from 0.26 mGy to 21.26 mGy for the mediolateral oblique (MLO) views and 0.08 mGy to 5.36 mGy for the craniocaudal (CC) views. The calculated MGD ranged from 0.07 mGy to 3.57 mGy for the MLO views and 0.02 mGy to 0.98 mGy for the CC views. The possible reasons for the large variations in the individual ESD values and MGD values for both views are discussed using patients' data, equipment specific data and the technical parameters used for the examinations. Comparison showed that the mean ESD values and MGD values reported in this work are below published values. The mean of the calculated MGD values is also found to be lower than the recommended guidance level of 3.0 mGy when using grid. 92.5% of the patients had MGD values that are less than 2.5 mGy, hence a national reference MGD value of 2.5 mGy is proposed for Nigeria. Implementation of a dose reduction program in mammographic screening is also suggested because of the observed large variations in patients MGD values.

59

Mean glandular doses for women undergoing mammographic breast screening in Oyo state, Nigeria  

Energy Technology Data Exchange (ETDEWEB)

In this work, thermoluminescent dosimeters have been used to measure entrance surface doses (ESDs) of patients undergoing mammographic screening at the University College Hospital, Ibadan, Oyo state. The mean glandular doses (MGDs) were also calculated using the measured ESDs. The results showed that the ESDs ranged from 0.26 mGy to 21.26 mGy for the mediolateral oblique (MLO) views and 0.08 mGy to 5.36 mGy for the craniocaudal (CC) views. The calculated MGD ranged from 0.07 mGy to 3.57 mGy for the MLO views and 0.02 mGy to 0.98 mGy for the CC views. The possible reasons for the large variations in the individual ESD values and MGD values for both views are discussed using patients' data, equipment specific data and the technical parameters used for the examinations. Comparison showed that the mean ESD values and MGD values reported in this work are below published values. The mean of the calculated MGD values is also found to be lower than the recommended guidance level of 3.0 mGy when using grid. 92.5% of the patients had MGD values that are less than 2.5 mGy, hence a national reference MGD value of 2.5 mGy is proposed for Nigeria. Implementation of a dose reduction program in mammographic screening is also suggested because of the observed large variations in patients MGD values.

Ogundare, F.O. [Department of Physics, University of Ibadan, Ibadan (Nigeria)], E-mail: ogun_dare@yahoo.com; Odita, A.N. [Radiology Department, University College Hospital, PMB 5116, Ibadan (Nigeria); Obed, R.I. [Department of Physics, University of Ibadan, Ibadan (Nigeria); Balogun, F.A. [National Institute of Radiation Protection and Research, University of Ibadan, Ibadan (Nigeria)

2009-11-15

60

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

International Nuclear Information System (INIS)

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 selectiy 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

61

Displacement corrections used in absorbed dose determination  

International Nuclear Information System (INIS)

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

62

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2014-08-15

63

Absorbed doses modified by exposure settings with rotational panoramic radiography  

International Nuclear Information System (INIS)

Absorbed doses parotid gland, cervical vertebrae and thyroid gland were measured with various exposure settings of the tube voltage and tube current during use of a rotational panoramic radiographs, Veraview (J. Morita Corp., Kyoto, Japan) and PM 2002 CC (Planmeca Oy, Helsinki, Finland) using Rando phantom and thermoluminescence dosimeters. The magnitude of each absorbed dose was greatest in the parotid gland, followed in order by the cervical vertebrae and thyroid gland and was proportional to tube current. The increase of the thyroid gland absorbed dose with increasing tube voltage was steeper than were the increases in the absorbed doses in either the parotid gland or the cervical vertebrae. (author)

64

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

65

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-01-21

66

SU-E-I-04: A Mammography Phantom to Measure Mean Glandular Dose and Image Quality  

International Nuclear Information System (INIS)

Purpose: To evaluate mean glandular dose (MGD) and image quality in a selection of mammography systems using a novel phantom based on thermoluminescent dosemeters and the ACR wax insert. Methods: The phantom consists of two acrylic, 19 cm diameter, 4.5 cm thick, semicircular modules, used in sequence. The image quality module contains the ACR insert and is used to obtain a quality control image under automatic exposure conditions. The dosimetric module carries 15 TLD-100 chips, some under Al foils, to determine air kerma and half-value-layer. TL readings take place at our laboratory under controlled conditions. Calibration was performed using an ionization chamber and a Senographe 2000D unit for a variety of beam qualities, from 24 to 40 kV, Mo and Rh anodes and filters. Phantom MGD values agree, on the average, within 3% with ionization chamber data, and their precision is better than 10% (k=1). Results: MGD and image quality have been evaluated in a selection of mammography units currently used in Mexican health services. The sample includes analogic (screen/film), flexible digital (CR), and full-field digital image receptors. The highest MDG are associated to the CR technology. The most common image quality failure is due to artifacts (dust, intensifying screen scratches, and processor marks for film/screen, laser reader defects for CR). Conclusion: The developed phantom permits the MGD measurement without the need of a calibrated ionization chamber at the mammography site and can be used by a technician without the presence of a medical physicist. The results indicate the urgent need to establish quality control programs for mammography

67

Determination of Total Absorbed Dose Following Accidental and Chronic Exposure  

International Nuclear Information System (INIS)

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

68

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

International Nuclear Information System (INIS)

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

69

Absorbed dose from mammography in several Dutch hospitals  

International Nuclear Information System (INIS)

Absorbed doses and image quality in mammography units have been investigated at 12 institutes in the Netherlands. The dosimetry was performed in a mammary phantom with an ionisation chamber and thermoluminescence dosimeters. The dose received per mammoradiograph as derived from the ionisation chamber measurements differed greatly among the various hospitals. No correlation was found between the score of the image quality and the mean absorbed dose. A comparison of the two dosimetry methods revealed that the doses at the entrance surface derived from TLD were considerably lower than those from the ionisation chamber. The absorbed dose values determined are higher than those obtained by others. This might be due to an underestimate of the dose as measured by other groups with TLD but also to the use of an incorrectly low conversion factor from exposure in air to mean absorbed dose in the breast. For a number of hospitals the mean absorbed dose values are higher than the acceptable dose limit of 2 to 2.5 mGy per examination. Several hospitals have already made provisions to reduce the dose levels without loss of diagnostic information. (author)

70

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

International Nuclear Information System (INIS)

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

71

Fast neutron radiation inactivation of Bacillus subtilis: Absorbed dose determination  

International Nuclear Information System (INIS)

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

72

Specification of absorbed dose for reporting a therapeutic irradiation  

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

73

Fetal absorbed doses by radiopharmaceutical administration  

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The radiopharmaceutical administration with diagnostic or therapeutic purpose during pregnancy implies a prenatal radiation dose. The dose assessment and the evaluation of the radiological risks become relevant due to the great radiosensitivity of the fetal tissues in development. This paper is a revision of the available data for estimating fetal doses in the cases of the more frequently used radiopharmaceuticals in nuclear medicine, taking into account recent investigation in placental crossover. The more frequent diagnostic and therapeutic procedures were analyzed according to the radiation doses implied. (author)

74

Monte Carlo method absorbed dose evaluation under tomography investigation  

International Nuclear Information System (INIS)

Computer code PRIZMA based on Monte Carlo simulation was used for solving problems of medical physics. Our results were compared with the results of other authors in series of test calculations. The calculations of the spatial distribution of absorbed dose under tomographical examination were carried out. We numerically obtained the dependence of absorbed dose on scanning parameters: distance to the slice plane, slice thickness, penetration depth into a phantom etc. 5 refs., 6 figs., 2 tabs

75

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  

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

Gabriela Hoff

2006-06-01

76

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

Scientific Electronic Library Online (English)

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

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

2006-06-01

77

Absorbed doses to patients from angioradiology  

International Nuclear Information System (INIS)

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

78

Evaluation of the absorbed dose in odontological computerized tomography  

International Nuclear Information System (INIS)

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

79

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

80

Comparison of absorbed doses resulting from various intraoral periapical radiography  

International Nuclear Information System (INIS)

This study was designed to measure the absorbed dose to organs of special interest from full mouth with intraoral film (14 films) and to compare the five periapical techniques. Thermoluminescent crystals (TLD-100 chip) were located in brain, orbit, bone marrow of mandibular ramus, bone marrow of mandibular body, bone marrow of 4th cervical spine, parotid gland, submandibular gland and thyroid gland. X-ray machine was operated at 70 kVp and round collimating film holding device (XCP) and rectangular collimating film holding device (Precision Instrument) were used. The distance from the X-ray focus to the open end of the collimator was 8 inch, 12 inch and 16 inch. The following results obtained; 1. The absorbed dose was the highest in bone marrow of mandibular body (5.656 mGy) and the lowest in brain (0.050 mGy). 2. Generally, the lowest absorbed dose was measured from 16 inch cylinder, rectangular collimating film holding device with paralleling technique. But, in bone marrow of mandibular body and the floor of mouth, the highest absorbed dose was measured from 12 inch cylinder, rectangular collimating film holding device with paralleling techniques. 3. Comparing of five intraoral radiographic techniques, it was appeared statistically significant reduction of the absorbed doses measured with rectangualr collimating film holding device compared to XCP film holding device (p0.05).

81

166Ho absorbed dose distribution in water phantom  

International Nuclear Information System (INIS)

The radiation absorbed dose of tumor cells and dose distribution from radionuclide therapy is heterogeneous because of variability in tumor shape and differences in source characteristic. Many models of dose distribution have been constructed and calculated but it has been very difficult to confirm predictions with actual measured doses. The purpose of this study was to determine dose distribution and radiation absorbed dose using the TLD(thermoluminescent dosimetry). To investigate the relation between the dose and the distance from the source surface, TLD measurements were performed using the tissue equivalent water phantom. Radiation source used in this study was 166Ho, activated by the neutron flux of a HANARO nuclear reactor at KAERI(Korea Atomic Energy Research Institute). To measure the absorbed dose, small disc shape TLDs of 3.175mm (1/8') diameter and 0.13 mm thickness were made from discs of LiF(Teledyne Inc., NJ). Thirty TLDs were initially calibrated with ? ray from 60Co. Gamma ray dose was delivered at the maximum depth of 0.5 cm with a field size of 15X15cm2 and source to surface distance (SSD) of 49.5 cm. The TLDs were read with a TLD reader (Hawshaw, model 4000). The average output from the TLDs was 110.60nC/Gy. The standard deviation of these TLDs was the ± 2.7%. TLDs were inserted into the tissue equivalent water phantoms at different depth of 1,2,3,4 and 5 mm. Then source petri dish was positioned on the phantom. Sri dish was positioned on the phantom. Source activity was 740MBq/20cc. The relation between the dose and the distance from the source surface was shown semi-logarismically decreasing. Absorbed doses measured with TLDs at 1,2 and 3 mm were 219.7, 69.0 and 20.2Gy respectively

82

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

International Nuclear Information System (INIS)

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 th 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

83

Patient absorbed radiation doses estimation related to irradiation anatomy  

International Nuclear Information System (INIS)

Developed a direct equation to estimate the absorbed dose to the patient in x-ray examinations, using electric, geometric parameters and filtering combined with data from irradiated anatomy. To determine the absorbed dose for each examination, the entrance skin dose (ESD) is adjusted to the thickness of the patient's specific anatomy. ESD is calculated from the estimated KERMA greatness in the air. Beer-Lambert equations derived from power data mass absorption coefficients obtained from the NIST / USA, were developed for each tissue: bone, muscle, fat and skin. Skin thickness was set at 2 mm and the bone was estimated in the central ray of the site, in the anteroposterior view. Because they are similar in density and attenuation coefficients, muscle and fat are treated as a single tissue. For evaluation of the full equations, we chose three different anatomies: chest, hand and thigh. Although complex in its shape, the equations simplify direct determination of absorbed dose from the characteristics of the equipment and patient. The input data is inserted at a single time and total absorbed dose (mGy) is calculated instantly. The average error, when compared with available data, is less than 5% in any combination of device data and exams. In calculating the dose for an exam and patient, the operator can choose the variables that will deposit less radiation to the patient through the prior analysis of each combination of variables, using the ALARA principle in routine diagnostic radiology sector

84

Absorbed bone marrow dose in certain dental radiographic techniques  

International Nuclear Information System (INIS)

The absorbed dose of radiation in the bone marrow of the region of the head and neck was measured during intraoral, panoramic, and cephalometric radiography. Panoramic radiography results in a dose a fifth or less than that from an intraoral survey. The use of rectangular collimation reduces the bone marrow absorbed dose from an intraoral survey by about 60%. Comparison of the doses from dental radiography with natural environmental radiation shows that an intraoral set of films results in the same total dose to the bone marrow as 65 days of background exposure. The use of rectangular collimation reduces this value to 25 days. Panoramic radiography results in significantly less irradiation, as it reduces the value to 14 days or fewer. Dental radiography thus involves exposures in the range of variation of natural environmental background values

85

Absorbed dose and deterministic effects to patients from interventional neuroradiology.  

Science.gov (United States)

Following the presentation of radiation-induced skin effects by three patients who had undergone glue embolisation of intracranial arteriovenous malformation (AVM), measurements were made of absorbed dose to the skin of patients undergoing other interventional neuroradiological procedures that involve long fluoroscopy times. The maximum absorbed dose to the skin measured by thermoluminescent dosemeters during these procedures was 4 Gy. From these measurements and from records of fluoroscopy time and the number of digital runs acquired, estimates of the maximum absorbed skin dose were made for the AVM patients. The best estimate of maximum absorbed dose to the skin received by any of the AVM patients during a procedure was 5 Gy, which is consistent with the skin effects presented by the AVM patients, that is temporary epilation and main erythema. Maximum absorbed dose to the skull was estimated to be 45 Gy and to the outer table of the skull 55 Gy. Although it is unlikely that the AVM patients will suffer serious effects from these skin doses, there remains some uncertainty over the risk of long-term effects to the skull. Examination of the fluoroscopy unit showed that the image intensifier was not performing optimally in terms of entrance dose rate and resolution. Replacement of the unit with modern X-ray equipment designed for interventional radiology was prioritized. Operators should be aware of the potential risks to patients from complex interventional neuroradiology procedures and should optimize their procedures to minimize such risks. Patients undergoing prolonged and complex procedures should be counselled regarding the symptoms and risks of large doses of radiation. PMID:11089467

Mooney, R B; McKinstry, C S; Kamel, H A

2000-07-01

86

Computational determination of absorbed dose distributions from gamma ray sources  

International Nuclear Information System (INIS)

A biomedical procedure known as brachytherapy involves insertion of many radioactive seeds into a sick gland for eliminating sick tissue. For such implementations, the spatial distribution of absorbed dose is very important. A simulation tool has been developed to determine the spatial distribution of absorbed dose in heterogeneous environments where the gamma ray source consists of many small internal radiation emitters. The computation is base on integral transport method and the computations are done in a parallel fashion. Preliminary results involving 137Cs and 125I sources surrounded by water and comparison of the results to the experimental and computational data available in the literature are presented

87

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

Science.gov (United States)

The influence of anode and filter materials on the performance (image quality and dose) of a mammography system is investigated. The image quality is evaluated with the image quality index method. A computer simulation has been developed to calculate the physical parameters of the image quality index (contrast, resolution and noise) as well as the mean glandular dose. The calculations take into account the successive steps of the process: x-ray production, filtration, interaction with the test object, anti-scatter grid, interaction with the image detector (screen-film system). An excellent correlation is obtained between the results predicted by the model and those of experimental measurements, suggesting that the model may be used for the prediction of the performance of mammographic equipment. The experimental conclusions are confirmed: the use of a tungsten anode with a rhodium filter allows a dose reduction without a significant degradation of image quality. The computer program can also be used to simulate the influence of factors which are difficult to combine in practice, e.g., various anode and filter materials, monoenergetic x-rays, etc. PMID:1946601

Desponds, L; Depeursinge, C; Grecescu, M; Hessler, C; Samiri, A; Valley, J F

1991-09-01

88

Application of cytogenetic methods for estimation of absorbed dose  

International Nuclear Information System (INIS)

Accumulated data on the practical application of cytogenetic technique to evaluate the absorbed dose for men involved in activities to eliminate the effects of the Chernobyl NPP accident were analyzed. Those data were compared with the results of cytogenetic studies conducted in other Russia regions affected by radiation impacts (Muslyumovo settle., Chelyabinsk Region, the Altay Territory settlements near the Semipalatinsk test range) and with the examination results of population of the territory of the Three Mile Island NPP (Island, Pennsylvania, USA) where in 1975 the nuclear accident took place. The cytogenetic studies were carried out using the standard analysis technique evaluating the frequency of unstable aberrations of chromosomes (UA) and using FISH-technique designed to evaluate the frequency of stable aberrations of chromosomes. It was pointed out that UA-technique could not be used efficiently for the retrospective evaluation of the absorbed doses with no clear idea correlating the nature and the rate of elimination with cell life time, especially, in case of small doses of irradiation. Analysis of the stable translocation using FISH-technique enabled to evaluate the absorbed dose within 8-9 years following the accident. The range of the absorbed doses of the examined persons varied from the background ones up to 1 Gy

89

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)

90

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

91

Space radiation absorbed dose distribution in a human phantom  

Science.gov (United States)

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

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

2002-01-01

92

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)

93

Bone marrow and thyroid absorbed doses from mammography  

International Nuclear Information System (INIS)

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

94

The absorbed dose to blood from blood-borne activity  

Science.gov (United States)

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

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

2015-01-01

95

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

96

Absorbed doses due to mammography in various Dutch hospitals  

International Nuclear Information System (INIS)

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

97

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

International Nuclear Information System (INIS)

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

98

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

International Nuclear Information System (INIS)

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

99

International comparison of calibration standards for exposure and absorbed dose  

International Nuclear Information System (INIS)

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)

100

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)

101

Sensors of absorbed dose of ionizing radiation based on mosfet  

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

Perevertaylo V. L.

2010-10-01

102

Modeling gamma absorbed dose due to meandering plumes  

International Nuclear Information System (INIS)

A theory was developed to predict the average gamma absorbed dose rates due to a continuous Gaussian plume that meanders due to variations in the wind's direction caused by large-scale eddies. Such meandering often occurs under very stable, low-wind conditions. The theory is based on Gifford's fluctuating Gaussian plume model. Approximate calculations based on this theory were compared to traditional approaches based on an average concentration distribution

103

The weighting of absorbed dose in environmental risk assessments  

International Nuclear Information System (INIS)

Practical applications of using absorbed dose for radiation protection purposes forces consideration of the biological effectiveness of different types of radiation. For human radiation protection this is taken into account by applying dimensionless radiation weighting factors. Similarly, environmental dosimetry requires weighting factors, based on experimentally obtained RBE values, relevant for biota. The expected doses and dose rates in contaminated environments are low and the dose distribution is assumed to be highly heterogeneous. The identification of relevant RBE values for biota implies the recognition of critical end-points leading to reproductive disturbances. Concurrently, a mechanistic understanding of these end-points, whether they are of stochastic (single track) or deterministic origin, has to be elucidated. In a risk assessment framework it seems necessary to postulate the criteria for selecting appropriate RBE values, and to indicate a span for weighting factors applicable to different exposure situations and ecosystems. (author)

104

Analysis of absorbed dose to tooth enamel for ESR dosimetry  

International Nuclear Information System (INIS)

Absorbed dose to tooth enamel was quantitatively correlated to organ doses by Monte Carlo calculations using the Electron Gamma Shower Code Version 4 for the Electron Spin Resonance (ESR) dosimetry using teeth. A region for teeth was newly added to a mathematical human model. Kerma coefficients for whole tooth and enamel part were prepared to estimate the dose to tooth enamel. Experiments were also carried out with a physical head phantom, which is made of tissue equivalent materials. Tooth samples and thermo-luminescence dosimeters (TLDs) of CaSO4 crystal were set at the teeth position in the head phantom. Addition Monte Carlo calculations were performed to verify the results of the experiments by using a Voxel-type phantom reconstructed from computed tomographic (CT) images of the physical phantom. The obtained data are to be useful for retrospective dose assessments in past radiation events by the ESR dosimetry with teeth. (author)

105

Long-term high-dose proton pump inhibitor administration to Helicobacter pylori-infected Mongolian gerbils enhances neuroendocrine tumor development in the glandular stomach.  

Science.gov (United States)

Proton pump inhibitors (PPIs) are routinely used for control of upper gastrointestinal disorders, often with long-term application. However, there has been some concern about the long-term safety and the possibility of cancer induction and development of neuroendocrine tumors (NET) in the stomach. We therefore analyzed the influence of PPI use on tumor development histologically, immunohistochemically, and serologically in the glandular stomachs of Helicobacter pylori (Hp)-infected and uninfected Mongolian gerbils (MGs). 53 MGs were divided into 6 groups: Hp+25PPI, Hp+5PPI, Hp, 25PPI, 5PPI, and controls. The high-dose Hp+25PPI and 25PPI groups received the PPI (lansoprazole) at 25mg/kg/day, and the low-dose Hp+5PPI and 5PPI groups were given 5mg/kg/day. After 50 or 100 weeks, animals were sacrificed humanely, and the glandular stomach samples were evaluated histologically and phenotypically, using antibodies against chromogranin A (CgA), gastrin and gastric inhibitory polypeptide (GIP). Serum gastrin levels were also examined. NETs occurred in the Hp+25PPI, Hp+5PPI, Hp, and 25PPI groups, but there was no synergistic effect between Hp-infection and high-dose PPI administration. Serum gastrin was increased statistically by Hp infection and high-dose PPI administration, but not influenced by the low-dose. The NETs featured expression of CgA, but not gastrin or GIP. In conclusions, PPI at low dose had no influence on development of carcinomas and NETs in the Hp-infected and uninfected glandular MG stomach, suggesting clinical safety. However, PPI at high dose increased NET development and serum gastrin in the MG model. PMID:21790250

Tsukamoto, Hironobu; Mizoshita, Tsutomu; Sasaki, Makoto; Mizushima, Takashi; Tanida, Satoshi; Ozeki, Keiji; Hirata, Yoshikazu; Shimura, Takaya; Kataoka, Hiromi; Kamiya, Takeshi; Nojiri, Shunsuke; Tsukamoto, Tetsuya; Tatematsu, Masae; Joh, Takashi

2011-01-01

106

Estimation of absorbed doses on the basis of cytogenetic methods  

International Nuclear Information System (INIS)

Long-term studies in the field of radiation cytogenetics have resulted in the discovery of relationship between induction of chromosome aberrations and the type of ionizing radiation, their intensity and dose. This has served as a basis of biological dosimetry as an area of application of the revealed relationship, and has been used in the practice to estimate absorbed doses in people exposed to emergency irradiation. The necessity of using the methods of biological dosimetry became most pressing in connection with the Chernobyl accident in 1986, as well as in connection with other radiation situations that occurred in nuclear industry of the former USSR. The materials presented in our works demonstrate the possibility of applying cytogenetic methods for assessing absorbed doses in populations of different regions exposed to radiation as a result of accidents at nuclear facilities (Chernobyl, the village Muslymovo on the Techa river, the Three Mile Island nuclear power station in the USA where an accident occurred in 1979). Fundamentally, new possibilities for retrospective dose assessment are provided by the FISH-method that permits the assessment of absorbed doses after several decades since the exposure occurred. In addition, the application of this method makes it possible to restore the dynamics of unstable chromosome aberrations (dicentrics and centric rings), which is important for further improvement of the method of biological dosimetry based on the analysis iological dosimetry based on the analysis of unstable chromosome aberrations. The purpose of our presentation is a brief description of the cytogenetic methods used in biological dosimetry, consideration of statistical methods of data analysis and a description of concrete examples of their application. (J.P.N.)

107

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

International Nuclear Information System (INIS)

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

108

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

Science.gov (United States)

With the introduction of digital radiography, patients undergoing radiographic procedures are subject to being overexposed to radiation. Therefore, it is necessary to estimate the absorbed organ dose and the effective dose, which are significant for patient health, along with body type. During chest radiographic examinations conducted in 899 patients for screening, the absorbed dose of the 13 major organs, the average whole-body dose, and two effective doses weighted by factors published in ICRP 60 and ICRP 103 were calculated on the basis of patient information such as height, weight and examination condition, including kilovolt potential, focus-skin distance and entrance surface dose (ESD), using a PC-based Monte Carlo program simulation. It was found that dose per unit ESD had a tendency to decrease with body mass index (BMI). In particular, the absorbed dose for most organs was larger at high voltages (140 kVp) than at low voltages (120 kVp, 100 kVp). In addition, the effective dose which was based on ICRP 60 and ICRP 103 also represented the same tendency in respect of BMI and tube voltage. PMID:22772453

Kim, Hyunji; Park, MinSeok; Park, Songyi; Jeong, Hoiwoun; Kim, Jungmin; Kim, Youhyun

2013-01-01

109

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)

110

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)

111

The radon concentration and absorbed dose rate in Hungarian dwellings  

Energy Technology Data Exchange (ETDEWEB)

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 (CaSO{sub 4}:Tm). The measurements were performed in one year during 1993-1994. The resulting arithmetic mean of radon concentration is 128 Bq.m{sup -3}, the weighted mean value is 107 Bq.m{sup -3}. The mean value of absorbed dose rate, including terrestrial and cosmic rays, is 127 nGy.h{sup -1} and the weighted mean is 109 nGy.h{sup -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).

Nikl, I. [Orszagos Frederic Joliot-Curie Sugarbiologiai es Sugaregeszseguegyi Kutato Intezet, Budapest (Hungary)

1996-12-31

112

Measurement of absorbed dose rate in 14 MW TRIGA reactor  

International Nuclear Information System (INIS)

Almost all the energy absorbed in a material placed in the mixed radiation field of a reactor appears in the form of heat, since for the majority of materials the fraction of the energy that can result in light emission and chemical or structural change is very small. Therefore for determination of the absorbed dose essentially is the determination of the amount of heat which can be precisely determined with a calorimeter. For estimation of heat generated in different regions of the 14 MU TRIGA reactor and its experimental assemblies, two different calorimeters of heat flow calorimeter type were built. The first calorimeter is a rod type calorimeter where the heat generated in the sample is transmitted through a rod of aluminium towards cooling medium. The second calorimeter is a calorimeter with gas as heat transfer medium and uses thermal resistance of the gas and gas dumping. The sample of the both calorimeters is made of stainless steel. Outer diameter or the calorimeters is the same as the diameter of the fuel rod and their cooling is performed with water from the core. First, the calorimeters have been tested and reciprocal calibrated. Then they have been used for determination of absorbed dose rate in the core of the 14 MW TRIGA reactor. The principles of the both calorimeters were presented briefly and the results of the measurements in the reactor were discussed. (authors)

113

Variations in absorbed doses from 59Fe in different diseases  

International Nuclear Information System (INIS)

The biokinetics of radiopharmaceuticals administered in vivo may vary considerably with changes in organ functions. They studied the variations in absorbed doses from 59Fe in 207 patients with different diseases, in whom ferrokinetic investigations were performed for diagnostic purposes. Radiation doses to the bone marrow were highest in patients with deserythropoietic anemias (mean 38 nSv/Bq, range 19 - 57 nSv/Bq) and in hemolytic anemias (mean 21 nSv/Bq, range 7 - 35 nSv/Bq), whereas lower and rather constant values were found in other diseases (mean values between 9 and 13 nSv/Bq). The highest organ doses, the greatest differences with respect to diagnosis and also the largest variations within each group of patients were found for liver and spleen (e. g. in aplastic anemia; liver: 66 nSv/Bq, range 29 - 104 nSv/Bq; spleen: 57 nSv/Bq, range 34 - 98 nSv/Bq. In iron deficiency; liver: 13 nSv/Bq range 12 - 14 nSv/q; spleen: 19 nSv/Bq, range 18 - 20 nSv/Bq). Lower organ doses and smaller variations within and between the groups of patients were found for the gonads (means 3 - 7 nSv/Bq), the kidneys (means 10 - 13 nSv/Bq), the bone (means 4 - 7 nSv/Bq), the lung (means 8 - 12 nSv/Bq), and the total body (means 6 - 8 nSv/Bq). In patients with chronic bleeding absorbed doses decrease concomitantly to the extent of blood loss. The D/sub E/ is not markedly affected by the variations in organ doses but is fairly constant for different diseases. 16 references, 1 figr different diseases. 16 references, 1 figure, 3 tables

114

The measurement of the indoor absorbed dose rate in air in Beijing  

International Nuclear Information System (INIS)

This paper describes the indoor absorbed dose rate in air in Beijing. The average indoor absorbed dose rate in air is 8.29 ?rad/h. The ratio of indoor to outdoor absorbed dose rate for 849 buildings is 1.51

115

Nonisolated-sensor solid polystyrene absorbed dose measurements  

International Nuclear Information System (INIS)

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

116

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

International Nuclear Information System (INIS)

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

117

Measurement of absorbed dose and dose distribution of electron beam from microtron accelerator  

International Nuclear Information System (INIS)

Accelerators producing high energy particle beams and X-rays have a wide spectrum of applications in industry, medicine, defence and research. The Microtron is a compact cyclic accelerator intended solely for accelerating electrons to relativistic energies. The variable energy Microtron at Mangalore university has been used to study the effect of radiation on different materials and biological systems. While studying the effects of radiation, it is essential to have complete knowledge of absorbed dose. In the present study the dose due to 8 MeV electron beam from Microtron accelerator has been calculated using the chemical dosimeter Fricke. The uniformity of dose distribution at various points of the irradiation area also has been calibrated using Fricke dosimeter. From the dosimetry studies it is observed that there is a linear relation between dose and electron numbers over a wide range of absorbed doses. It is evaluated that the electron counts of about 1.15 x 1014 corresponds to an absorbed dose of 100 Gy and a field size of about 4 x 4 cm is available at 30 cm distance from the beam exit window over which the dose distribution is uniform. (author)

118

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

119

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

International Nuclear Information System (INIS)

A ? ray absorbed dose-rate meter is described for use in measuring the absorbed dose in the skin from contaminated sandy beaches. It consists of a plastic scintillator and pulse height analyser in order to obtain the best correlation between the instrument response and absorbed dose. Practical measurements are shown to be in agreement with theoretical calculations for various depths of dry sand. The measured dose appears to be almost entirely due to the naturally occurring radionuclide K40. It is concluded that the absorbed dose-rate meter has relatively high stability and sensitivity to measure skin doses and a program for future studies is outlined. (U.K.)

120

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

International Nuclear Information System (INIS)

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

121

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2009-07-01

122

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

International Nuclear Information System (INIS)

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

123

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2014-08-15

124

An absorbed dose map of bone tissue treated with a radiopharmaceutical in vivo.  

Science.gov (United States)

A beagle humerus treated with Ho-chelate radiopharmaceutical in vivo was examined by electron paramagnetic resonance (EPR) dosimetry. The bone was sectioned and the absorbed dose to each bone fragment was determined by additive re-irradiation of the bone tissue with calibrated doses of gamma radiation. The measured doses ranged from 4.3 Gy to 62 Gy. The highest doses were recorded in the predominately trabecular bone tissue and the lowest doses in the predominately cortical bone tissue. The mean absorbed dose for the entire bone was 17 Gy. The data from 50 bone fragments were combined to create an absorbed dose map of the interior bone surface. PMID:17220719

Desrosiers, M F; Fattibene, P; Le, F

2007-02-01

125

Influence of radioactive contaminants on absorbed dose estimates for radiopharmaceuticals  

International Nuclear Information System (INIS)

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

126

Impact of energy spread of electron beam on absorbed dose distribution  

International Nuclear Information System (INIS)

The results of numerical research on dependence of absorbed dose on energy spread of electron beam with two sided irradiation are presented in this paper. The dependence of change in value of absorbed dose in the critical point on spectrum width of electron beam is shown. The dependence of dose uptake ratio on energy spread of electron beam is found.

127

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

128

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

129

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

International Nuclear Information System (INIS)

An average absorbed dose of the tumour calculated by the MIRD formalism has not always a good correlation with the clinical response. The basic assumption of the MIRD schema is that a uniform spatial dose distribution is opposite to heterogeneity of intratumoral distribution of the administered radionuclide which can lead to a spatial nonuniformity of the absorbed dose. Therefore, in clinical practice, an absorbed dose of the tumour at the cellular level has to be calculated. The aim of this study is to define a referent 3D solid tumour model and using the direct Monte Carlo radiation transport method to calculate: a) absorbed fraction, b) spatial 3D absorbed dose distribution, c) absorbed dose and relative absorbed dose of cells or clusters of cells, and d) differential and accumulated dose volume histograms. A referent 3D solid tumour model is defined as a sphere which is randomly filled with cells and necrosis with defined radii and volumetric density. Radiolabelling of the tumour is defined by intracellular to extracellular radionuclide concentration and radio-labelled cell density. All these parameters are input data for software which generates a referent 3D solid tumour model. The modified FOTELP Monte Carlo code was used on this model for simulation study with beta emitters which were applied on the tumour. The absorbed fractions of Cu-67, I- 131, Re-188 and Y-90 were calculated for different tumour sphere masses and radii. Absorbed doses of cells and spatial adii. Absorbed doses of cells and spatial distributions of the absorbed doses in the referent 3D solid tumour were calculated for radionuclides I-131 and Y-90. Dose scintigram or voxel presentation of absorbed dose distributions showed higher homogeneity for Y-90 than for I-131. A differential dose volume histogram, or spectrum, of the relative absorbed dose of cells, was much closer to the average absorbed dose of the tumour for Y-90 than I-131. An accumulated dose volume histogram showed that most tumour cells received a lower dose than average, or prescribed, tumour absorbed dose. Those discrepancies between conventional and cellular approach show that dosimetry on the cellular level is necessary for a better selection of the radionuclide and optimal calculation of administered activity in the radionuclide therapy. (author)

130

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

International Nuclear Information System (INIS)

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

131

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

International Nuclear Information System (INIS)

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

132

Absorbed-dose/dose-rate dependence studies for the alanine-EPR dosimetry system  

International Nuclear Information System (INIS)

Over the course of the last decade, routine monitoring of the alanine dosimetry system revealed a small but significant observation that, after examination, led to the characterization of a previously unknown absorbed-dose-dependent, dose-rate effect for the alanine system. The newly discovered rate effect is of potential concern for electron-beam dosimetry, since electron-beam dosimetry typically derives its traceability to national standards through comparisons to gamma-ray calibrations of the dosimetry system. The largest discrepancy in source dose rates is between gamma-ray sources and electron-beam accelerators. Investigating the influence of temperature on the alanine rate effect is an important first step in preparation for a comparison study between electron-beam and gamma-ray dosimetry. Here, new data is presented on the influence of irradiation temperature (from -40 to +50 oC) on the dose-rate effect measured at 50 kGy.

133

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

International Nuclear Information System (INIS)

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

134

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

International Nuclear Information System (INIS)

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

135

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

136

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

International Nuclear Information System (INIS)

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

137

Uncertainty analysis for absorbed dose from a brain receptor imaging agent  

Energy Technology Data Exchange (ETDEWEB)

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

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

1999-01-01

138

'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

2013-11-01

139

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

International Nuclear Information System (INIS)

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 equthan 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.

140

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

International Nuclear Information System (INIS)

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

141

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

142

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

International Nuclear Information System (INIS)

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 192Ir 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.

143

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

Directory of Open Access Journals (Sweden)

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

Hilal ACAR

2006-01-01

144

Computational determination of absorbed dose distributions from multiple volumetric gamma ray sources  

International Nuclear Information System (INIS)

Determination of absorbed dose distributions is very important in brachytherapy procedures. The typical computation involves superposition of absorbed dose distributions from a single seed to compute the combined absorbed dose distribution formed by multiple seeds. This approach does not account for the shadow effect caused by the metallic nature of volumetric radioactive seeds. Since this shadow effect will cause deviations from the targeted dose distribution, it may have important implications on the success of the procedures. We demonstrated accuracy of our deterministic algorithms for isotropic point sources in the past. We will show that we now have the capability of computing absorbed dose distributions from multiple volumetric seeds and demonstrate that our results are quite close to the results published in the literature

145

Estimates of absorbed dose in different organs in children treated with radium for skin hemangiomas  

International Nuclear Information System (INIS)

Between 1930 and 1959, more than 10,000 infants were treated at Radiumhemmet, Stockholm, with radium (226Ra) needles and/or tubes for hemangioma of the skin. Absorbed dose to the brain, eye lenses, parotid glands, thyroid gland, breast enlarge, lungs, stomach, intestine, ovaries, testicles and bone marrow were calculated for each individual. The mean absorbed dose to the different organs ranged from 0.06 to 0.48 Gy. The highest absorbed dose was given to the breast (maximum 47.7 Gy). There was a wide dose range for each organ which was due mainly to differences in the distance between the applicator and the organ. The absorbed dose to all organs decreased on average by 32% during the study period. This was due to a 25% decrease in the treatment time and a change in the distribution of the treatment sites. 17 refs., 4 figs., 4 tabs

146

Importance of pre-treatment radiation absorbed dose estimation for radioimmunotherapy of non-Hodgkin's lymphoma  

International Nuclear Information System (INIS)

Non-Hodgkin's lymphoma I-131 radioimmunotherapy data were analyzed to determine whether a predictive relationship exists between radiation absorbed doses calculated from biodistribution studies and doses derived from patient size. Radioactivity treatment administrations scaled to patient size (MBq/kg or MBq/m2) or fixed MBq doses do not produce consistent radiation absorbed dose to critical organs. Treatment trials that do not provide dose estimates for critical normal organs are less likely to succeed in identifying a clinical role for radioimmunotherapy

147

Primary standard of absorbed dose to water in high-energy photon beam irradiation  

International Nuclear Information System (INIS)

In radiotherapy, accurate dose evaluation must be made. One of the most important things in dose evaluation is the measurement of absorbed dose to water. National Institute of Advanced Industrial Science and Technology developed the primary standard of absorbed dose to water in high-energy photon beam irradiation, and enabled the calibration of ionization chamber dosimeters, using the photon beam with nearly the same beam quality as high-energy photon beam used in the medical front. Firstly, this paper explains the principle of the measurement of absorbed dose to water using an ionization chamber dosimeter, as well as the purpose and significance of the calibration of ionization chamber dosimeters based on the standard for the 60Co-? beam measurement of absorbed dose to water. Secondly, it introduces graphite calorimeter as the primary standard of absorbed dose to water in high-energy photon beam irradiation, which was newly developed for enabling the calibration of ionization chamber dosimeters using high-energy photon beam, while omitting the necessity of correction with the beam quality transformation coefficient. The greater part of graphite calorimeter is an acrylic phantom, and three graphite elements as calorie absorption body are installed in its central part. Finally, it describes the future prospects for the standard for absorbed dose to water. (A.O.)

148

Effect of absorbed dose on post-irradiation chlorination of polyethylene  

International Nuclear Information System (INIS)

Investigation of the effect of p-radiation absorbed dose on post-irradiation chlorination of polyethylene show that only at the beginning of the process the degree of chlorination increases with dose increase, and then the dependence on the dose isn't observed. The mechanism of the process is given

149

Evaluation of the absorbed dose to the breast using radiochromic film in a dedicated CT mammotomography system employing a quasi-monochromatic x-ray beam  

Science.gov (United States)

Purpose: A dual modality SPECT-CT prototype system dedicated to uncompressed breast imaging (mammotomography) has been developed. The computed tomography subsystem incorporates an ultrathick K-edge filtration technique producing a quasi-monochromatic x-ray cone beam that optimizes the dose efficiency of the system for lesion imaging in an uncompressed breast. Here, the absorbed dose in various geometric phantoms and in an uncompressed and pendant cadaveric breast using a normal tomographic cone beam imaging protocol is characterized using both thermoluminescent dosimeter (TLD) measurements and ionization chamber-calibrated radiochromic film. Methods: Initially, two geometric phantoms and an anthropomorphic breast phantom are filled in turn with oil and water to simulate the dose to objects that mimic various breast shapes having effective density bounds of 100% fatty and glandular breast compositions, respectively. Ultimately, an excised human cadaver breast is tomographically scanned using the normal tomographic imaging protocol, and the dose to the breast tissue is evaluated and compared to the earlier phantom-based measurements. Results: Measured trends in dose distribution across all breast geometric and anthropomorphic phantom volumes indicate lower doses in the medial breast and more proximal to the chest wall, with consequently higher doses near the lateral peripheries and nipple regions. Measured doses to the oil-filled phantoms are consistently lower across all volume shapes due to the reduced mass energy-absorption coefficient of oil relative to water. The mean measured dose to the breast cadaver, composed of adipose and glandular tissues, was measured to be 4.2 mGy compared to a mean whole-breast dose of 3.8 and 4.5 mGy for the oil- and water-filled anthropomorphic breast phantoms, respectively. Conclusions: Assuming rotational symmetry due to the tomographic acquisition exposures, these results characterize the 3D dose distributions in an uncompressed human breast tissue volume for this dedicated breast imaging device and illustrate advantages of using the novel ultrathick K-edge filtered beam to minimize the dose to the breast during fully-3D imaging. PMID:21815398

Crotty, Dominic J.; Brady, Samuel L.; Jackson, D’Vone C.; Toncheva, Greta I.; Anderson, Colin E.; Yoshizumi, Terry T.; Tornai, Martin P.

2011-01-01

150

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

International Nuclear Information System (INIS)

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

151

Metabolic kinetics and absorbed doses of 137Cs in lactating rats and progeny during suckling  

International Nuclear Information System (INIS)

The transfer of 137Cs with maternal milk to progeny was studied in rats The rats were administered with 25 kBq/g of 137Cs nitrate (pH = 6) in a single oral dose immediately after delivery. Nonpregnant females served as control. Absorbed doses per activity unit to lactating rats were 23 % lover than to nonlactating ones. Over the suckling period absorbed doses to young rats amounted to about 35 % of the absorbed dose to the nursing female. For nonlactating females the internal dose approximately equalled the sum of doses to the nursing female and young rats. Lactating is the effective way for removal of 1'37Cs from organism of the rats. Content of 1'37Cs in lactating rat becomes on 42.9 % lower than in organism of nonlactating rat during period of lactating (near 20 days)

152

A comparison of mean glandular dose diagnostic reference levels within the all-digital irish national breast screening programme and the Irish symptomatic breast services  

International Nuclear Information System (INIS)

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

153

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)

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

154

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

International Nuclear Information System (INIS)

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

155

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-10-26

156

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

International Nuclear Information System (INIS)

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

157

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)

158

On the retention and absorbed dose following radiation synovectomy with yttrium-90 silicate colloid  

International Nuclear Information System (INIS)

Investigations on patients and on phantoms were performed to determine the retention and the absorbed dose in radiation synovectomy with 90Y silicate colloid. The electrons of 90Y are totally absorbed within the surrounding tissue and produce bremsstrahlung with a maximum intensity at about 110 keV. After application of 6 mCi 90Y the dose rate of the bremsstrahlung was measured at a distance of 10 cm over 13 knees in a total of 10 patients and was found to range between 0.6 and 1.3 mR/h. During a period of 3 hours up to 3 days after injection practically no removal of the material from the joint was observed. According to approximative calculations the mean dose absorbed in the knee ranged between 3,650 and 7,300 rad, and the absorbed dose in the synovium between 5,500 and 11,000 rad. (orig.)

159

Absorbed dose determination for interstitial 125I boost therapy  

International Nuclear Information System (INIS)

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

160

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

161

Standard method of test for absorbed gamma and electron radiation dose with the ceric sulfate dosimeter  

International Nuclear Information System (INIS)

The preparation and use of a ceric sulfate dosimeter for accurate measurement of the absorbed dose in water irradiated with x or ? rays or high-energy electrons are described. The ionizing radiation reduces the ceric to cerous ions, and the ceric ion concentration is measured spectrophotometrically. The method is accurate for absorbed doses in the range from 1 x 106 to 8 x 106 rd. The precision of the method is +-1 percent, and the accuracy is +-3 percent

162

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

International Nuclear Information System (INIS)

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)

163

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

164

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

OpenAIRE

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

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

2013-01-01

165

Dose-277 Program for the Determination of Absorbed Dose According to IAEA Technical Report Series No.277  

International Nuclear Information System (INIS)

High radiation doses are required to be delivered to patients with high accuracy in radiotherapy. The calibration of radiation beam, used for the cancer treatment, is based on rather complicated measurements and the application of several conversion and correction factors. In this work the development of a computer program (Dose277) is described. Dose277 program is designed to determine absorbed dose rate of high-energy photon, electron and x-ray beams from the electrometer reading by applying the necessary conversion and correction factors according to the IAEA TRS 277 protocol. Dose277 program runs under Microsoft Windows 95 and later versions. Setup of this program is available on three floppy diskettes. The program prints and stores calculated absorbed doses in water including measurement data from which correction factors have been calculated. The program has also support options for backup copy of library files for therapy units, electrometers, ionization chambers and some other dosimetric data

166

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

International Nuclear Information System (INIS)

The International Atomic Energy Agency published in 1987 an International Code of Practice entitled 'Absorbed Dose Determination in Photon and Electron Beams' (IAEA Technical Reports Series No. 277 (TRS-277)), recommending procedures to obtain the absorbed dose in water from measurements made with an ionization chamber in external beam radiotherapy. A second edition of TRS-277 was published in 1997 updating the dosimetry of photon beams, mainly kilovoltage X rays. Another International Code of Practice for radiotherapy dosimetry entitled 'The Use of Plane-Parallel Ionization Chambers in High Energy Electron and Photon Beams' (IAEA Technical Reports Series No. 381 (TRS-381)) was published in 1997 to further update TRS-277 and complement it with respect to the area of parallel-plate ionization chambers. Both codes have proven extremely valuable for users involved in the dosimetry of the radiation beams used in radiotherapy. In TRS-277 the calibration of the ionization chambers was based on primary standards of air kerma; this procedure was also used in TRS-381, but the new trend of calibrating ionization chambers directly in a water phantom in terms of absorbed dose to water was introduced. The development of primary standards of absorbed dose to water for high energy photon and electron beams, and improvements in radiation dosimetry concepts, offer the possibility of reducing the uncertainty in the dosimetry of radiotherapy beams. The dosimetry of kilovoltage X rays, ams. The dosimetry of kilovoltage X rays, as well as that of proton and heavy ion beams, interest in which has grown considerably in recent years, can also be based on these standards. Thus a coherent dosimetry system based on standards of absorbed dose to water is possible for practically all radiotherapy beams. Many Primary Standard Dosimetry Laboratories (PSDLs) already provide calibrations in terms of absorbed dose to water at the radiation quality of 60Co gamma rays. Some laboratories have extended calibrations to high energy photon and electron beams or are in the stage of developing the necessary techniques for these modalities. Following the recommendations in 1996 of the IAEA Standing Advisory Group Scientific Committee of the IAEA (WHO) SSDL Network, a Co-ordinated Research Project was undertaken during 1997-1999 with the task of producing a new international Code of Practice based on standards of absorbed dose to water. The Code is also endorsed by the World Health Organization, the Pan American Health Organization and the European Society of Therapeutic Radiology and Oncology (ESTRO). The final draft was reviewed by representatives of the organizations endorsing the Code and by a large number of scientists. This Code of Practice fulfils the need for a systematic and internationally unified approach to the calibration of ionization chambers in terms of absorbed dose to water and to the use of these detectors in determining the absorbed dose to water for the radiation beams used in radiotherapy. It provides a methodology for the determination of absorbed dose to water in the low, medium and high energy photon beams, electron beams, proton beams and heavy ion beams used for external radiation therapy. The officer at the IAEA responsible for this Code of Practice was P. Andreo of the Division of Human Health

167

Approximate calculation of patient skin absorbed dose in coronary angiography  

International Nuclear Information System (INIS)

A calculation method was devised to measure the amount of radiation exposure a patient receives during PTCA. The objective was to develop a plan to decrease exposure and help prevent the occurrence of any problems. Of 200 cases of coronary angiography studied, the average amount of radiation absorbed in the skin during angiography and fluoroscopy was calculated to be 2,028 mGy, with temporary redness on the skin. However, locally no overlapping skin area exceeded 2,000 mGy. The amount of radiation absorbed through the skin can be calculated during a procedure. As a result, during PTCA the operator will try to keep the patient's best interest in mind by making sure procedures are fast, simple, and safe by shortening cine and fluoroscopy time. (author)

168

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

169

Ferrous sulphate gels for determination of absorbed dose distributions using MRI technique: basic studies  

International Nuclear Information System (INIS)

Two gels were found suitable to load with ferrous sulphate solution. In these soft tissue equivalent phantoms, absorbed dose distribution can be measured after irradiation in clinically used MR imaging equipment. Studies were carried out using a 0.25 T NMR analyser without imaging properties. A ferrous sulphate solution, 0.05M with respect to sulphuric acid, can be gelled with 4% gelatin giving a dosemeter with a response linearly correlated (r=0.998) with absorbed dose in the interval 0-40 Gy. Ferrous sulphate solution can also be gelled with 1% agarose, but this gel has to be purged with oxygen to obtain a linear relationship (r=0.997) in the same absorbed dose interval. Ferrous sulphate loaded gels have a sensitivity which is a factor of 2.2 or 4.0 times higher for gelatin and agarose, respectively, than the ordinary dosemeter solution. Because the standard deviation of background measurements is higher for gels than for the dosemeter solution, the minimum detectable absorbed dose is about the same, or 1.0 Gy, for the two gels and the dosemeter solution. The sensitivity of the ferrous sulphate loaded gels shows no dependence on dose rate if the mean dose rate and absorbed dose per pulse are within limits normally used by accelerators for radiotherapy. (author)

170

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. Mediemainder 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.

171

The absorbed dose in femur exposed to diagnostic radiography  

International Nuclear Information System (INIS)

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

172

Plastic film materials for dosimetry of very large absorbed doses  

OpenAIRE

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 ...

Mclaughlin, W. L.; Miller, Arne; Abdel-rahim, F.; Preisinger, T.

2011-01-01

173

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

Science.gov (United States)

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

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

2010-08-01

174

Patient absorbed radiation doses estimation related to irradiation anatomy; Estimativa de dose absorvida pelo paciente relacionada a anatomia irradiada  

Energy Technology Data Exchange (ETDEWEB)

Developed a direct equation to estimate the absorbed dose to the patient in x-ray examinations, using electric, geometric parameters and filtering combined with data from irradiated anatomy. To determine the absorbed dose for each examination, the entrance skin dose (ESD) is adjusted to the thickness of the patient's specific anatomy. ESD is calculated from the estimated KERMA greatness in the air. Beer-Lambert equations derived from power data mass absorption coefficients obtained from the NIST / USA, were developed for each tissue: bone, muscle, fat and skin. Skin thickness was set at 2 mm and the bone was estimated in the central ray of the site, in the anteroposterior view. Because they are similar in density and attenuation coefficients, muscle and fat are treated as a single tissue. For evaluation of the full equations, we chose three different anatomies: chest, hand and thigh. Although complex in its shape, the equations simplify direct determination of absorbed dose from the characteristics of the equipment and patient. The input data is inserted at a single time and total absorbed dose (mGy) is calculated instantly. The average error, when compared with available data, is less than 5% in any combination of device data and exams. In calculating the dose for an exam and patient, the operator can choose the variables that will deposit less radiation to the patient through the prior analysis of each combination of variables, using the ALARA principle in routine diagnostic radiology sector.

Soares, Flavio Augusto Penna; Soares, Amanda Anastacio; Kahl, Gabrielly Gomes, E-mail: prof.flavio@gmail.com, E-mail: amanda-a-soares@hotmail.com, E-mail: gabriellygkahl@gmail.com [Instituto Federal de Eduacao, Ciencia e Tecnologia de Santa Catarina (IFSC), Florianopolis, SC (Brazil)

2014-07-01

175

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

176

Plastic film materials for dosimetry of very large absorbed doses  

International Nuclear Information System (INIS)

Most plastic films have limited response ranges for dosimetry because of radiation-induced brittleness, degradation, or saturation of the signal used for analysis 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 x 106 Gy 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, 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 approx. 430 nm. (author)

177

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

178

A Comparative Analysis of Expected and Measured Absorbed Dose in Total Body Irradiation  

International Nuclear Information System (INIS)

A simple and systematic method of semiconductor in-vivo dosimetry for absorbed dose determination in 60Co Total Body Irradiation (TBI) was presented. Also, a quality assurance of the whole procedure was investigated. The absorbed dose in the body midplane was based on the arithmetical mean of input and output dose readings corrected with factors which took into account the nonlinear dose decrease in tissue, anthropomorphic shape, tissue density and the source-patient geometry. An approximate theoretical model of human body (a number of cylindrical ellipsoids) made it possible to generalize the method to any individual case of the real patient's data). A quality assurance analysis of TBI as a condition for bone marrow transplantation of 260 patients who had undergone the method showed that the ratio of the mean measured dose values for all ten locations in all patients and the expected dose (12.45 Gy in 3 days, 3 fractions) was 0.998 (SD 0.033). A special attention was paid to the absorbed doses in head, lung and abdomen. It was found that the upper limit of the total combined uncertainty of TBI mid plane absorbed dose, including all locations and all sources of error, amounted to 9.4% (in accordance with the results of other authors). (author)

179

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

Science.gov (United States)

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

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

2014-02-01

180

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

International Nuclear Information System (INIS)

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

181

Applications of Monte-Carlo method in calculation of absorbed radiation dose  

International Nuclear Information System (INIS)

Monte-Carlo simulation is a powerful method to determine the absorbed dose at the point of interest caused by given radiation sources. Two commonly used codes (ITS and MCNP) are briefly described. Application examples of the two codes are demonstrated by calculations of the dose distributions from a 60Co ? and ? source and from a 240Pu neutron source. Point source kernels are calculated for two important ? isotopes (131I, 90Y) in nuclear medicine. The integral equation to calculate absorbed dose with point source kernel and an example are given

182

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

OpenAIRE

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-quality treatment and avoidance of errors which may jeopardise the clinical outcome of the treatment (i.e. under- or overdose). A set of equations for calculating the absorbed dose to the prescripti...

Johnsson, Stefan

2003-01-01

183

Dose absorbed in the fetus by radioactive drugs prescribed  

International Nuclear Information System (INIS)

This work aims to review existing guidelines on the hypothesis that must be taken into account when calculating impact from the dose on the fetus for widely employed radioactive drugs. Recent research is added giving data on placenta transference linked to pregnancy term. The most widely used diagnostic and therapeutic practices are analyzed comparing the dose impact on the fetus with limits internationally accepted. This will allow having the necessary tools to answer questions concerning radiological risks due to the administration of radioactive drugs to pregnant women

184

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

185

A study of estimation of absorbed dose determination in high energy electron beams for radiotherapy  

International Nuclear Information System (INIS)

The aim of electron beam dosimetry is to exactly deliver the prescribed absorbed dose at all points of interest is an irradiated patient. It is important to establish the procedure of dosimetry and to precisely make use of the technology for dosimetry in high electron beams for radiotherapy. In the West, the protocols absorbed dose determination in electron beams basal on ion chamber with absorbed-dose-to-water calibration factors is made by AAPM (American Association of Physicists in Medicine) TG-51 and IAEA (International Atomic Energy Agency) TPS-398. In Japan, the newest protocol ('01) is revised the former protocol of radiation dosimetry by JARP (Japan association Radiological Physics). In the West, absorbed-dose-to-water calibration factors of ion chamber is directly determined by using a water calorimeter. However, it dose not completely provide a laboratory with necessary calorimeter in Japan. Therefore the absorbed dose to water must to convert according to the theoretical estimation using irradiated calibration factor for 60Co ?-ray. Although the quality conversion factor of electron beam to convert absorbed dose to water is decided, the application of dose determination is restricted in calibration depth. The use of ion chamber is limited parallel-plate chamber to ignored electron fluence perturbatin effects. Consequently the procedure of absorbed dose determination in electron dosimetry is extremely complicated. In this report, we introduce a glicated. In this report, we introduce a general idea of calibration factor ratio (KD,X)E and quality conversion factor (KQ)E as against the depth to electron initial mean energy, and form an estimate of these factors for 43 kinds of commercial ion chamber. We propose a protocol based on simplified procedure for electron dosimetry using a table of which is calculated these factors in advance. The uncertainty of the these factors calculated with our protocol is estimated to be 2.87%, if the JARP's ('01) procedure lead the uncertainty to 2.86%. Therefore, our protocol has an almost equivalent tumor dose accuracy when compared with the JARP's ('01) one. We conclude that our protocol is quite simple for application for clinical purposes and can deliver high accuracy of the prescribed absorbed dose in a patient. In addition, we can prevent medical accidents caused overdosage and underdosage in high energy electron beam for radiotherapy. (author)

186

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1978-04-01

187

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

International Nuclear Information System (INIS)

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

188

Entrance absorbed dose measurements in clinical telecobalt beams  

International Nuclear Information System (INIS)

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

189

Review and status of absorbed dose standardization at therapy-level  

International Nuclear Information System (INIS)

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

190

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

International Nuclear Information System (INIS)

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

191

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

International Nuclear Information System (INIS)

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

192

Absorbed and effective dose from periapical radiography by portable intraoral x-ray machine  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this study was to measure the absorbed dose and to calculate the effective dose for periapical radiography done by portable intraoral x-ray machines. 14 full mouth, upper posterior and lower posterior periapical radiographs were taken by wall-type 1 and portable type 3 intraoral x-ray machines. Thermoluminescent dosemeters were placed at 23 sites at the layers of the tissue-equivalent ART woman phantom for dosimetry. Average tissue absorbed dose and radiation weighted dose were calculated for each major anatomical site. Effective dose was calculated using 2005 ICRP tissue weighted factors. On 14 full mouth periapical radiographs, the effective dose for wall-type x-ray machine was 30 Sv; for portable x-ray machines were 30 Sv, 22 Sv, 36 Sv. On upper posterior radiograph, the effective dose for wall-type x-ray machine was 4 Sv; for portable x-ray machines doses were 4 Sv, 3 Sv, 5 Sv. On lower posterior radiograph, the effective dose for wall type x-ray machine was 5 Sv; for portable x-ray machines doses were 4 Sv, 4 Sv, 5 Sv. Effective doses for periapical radiographs performed by portable intraoral x-ray machines were similar to doses for periapical radiographs taken by wall type intraoral x-ray machines.

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

2007-09-15

193

Absorbed and effective dose from periapical radiography by portable intraoral x-ray machine  

International Nuclear Information System (INIS)

The purpose of this study was to measure the absorbed dose and to calculate the effective dose for periapical radiography done by portable intraoral x-ray machines. 14 full mouth, upper posterior and lower posterior periapical radiographs were taken by wall-type 1 and portable type 3 intraoral x-ray machines. Thermoluminescent dosemeters were placed at 23 sites at the layers of the tissue-equivalent ART woman phantom for dosimetry. Average tissue absorbed dose and radiation weighted dose were calculated for each major anatomical site. Effective dose was calculated using 2005 ICRP tissue weighted factors. On 14 full mouth periapical radiographs, the effective dose for wall-type x-ray machine was 30 Sv; for portable x-ray machines were 30 Sv, 22 Sv, 36 Sv. On upper posterior radiograph, the effective dose for wall-type x-ray machine was 4 Sv; for portable x-ray machines doses were 4 Sv, 3 Sv, 5 Sv. On lower posterior radiograph, the effective dose for wall type x-ray machine was 5 Sv; for portable x-ray machines doses were 4 Sv, 4 Sv, 5 Sv. Effective doses for periapical radiographs performed by portable intraoral x-ray machines were similar to doses for periapical radiographs taken by wall type intraoral x-ray machines

194

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

195

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

International Nuclear Information System (INIS)

The purpose of this study was to estimate the distribution of absorbed doses of each important organs of head and neck region in panoramic radiography. Radiation dosimetry at internal anatomic sites and skin surfaces of phantom (RT-210 Humanoid Head and Neck Section R) was performed with lithium fluoride (TLD-100R) thermoluminescent dosimeters according to change of kilovoltage (65 kVp, 75 kVp and 85 kVp) with 4 miliamperage and 20 second exposure time. The results obtained were as follows; Radiation absorbed doses of internal anatomic sites were presented the highest does of 1.04 mGy, 1.065 mGy and 2.09 mGy in nasopharynx, relatively high doses of 0.525 mGy, 0.59 mGy and 1.108 mGy in deep lobe of parotid gland, 0.481 mGy, 0.68 mGy and 1.191 mGy in submandibular gland. But there were comparatively low doses of 0.172 mGy and 0.128 mGy in eyes and thyroid gland that absorbed dose was estimated at 85kVp. Radiation absorbed doses of skin surfaces were presented the highest doses of 1.263 mGy, 1.538 mGy and 2.952 mGy in back side of first cervical vertebra and relatively high doses of 0.267 mGy, 0.401 mGy and 0.481 mGy in parotid gland. But there were comparatively low doses of 0.057 mGy, 0.068 mGy and 0.081 mGy in philtrum and 0.059 mGy in middle portion of chin that absorbed dose was estimated at 85 kVp. According to increase of kilovoltage, the radiation absorbed doses were increased 1.1 times when kilovoltage changes from 65 kVp to 75 kVp and 1.9 times when kilovoltagep to 75 kVp and 1.9 times when kilovoltage changes from 75 kVp to 85 kVp at internal anatomic sites. According to increase of kilovoltage, the radiation absorbed doses were increased 1.3 times when kilovoltage changes from 65 kVp to 75 kVp and 1.6 times when kilovoltage changes from 75 kVp to 85 kVp at skin surfaces.

196

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

International Nuclear Information System (INIS)

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

197

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)

198

Determining absorbed dose of Ramsar people from natural radioactivity  

International Nuclear Information System (INIS)

Radiation exposure versus natural resources of environment is in external form. Especially, in some regions of the world radionuclides assembling in soils caused background of high radioactivity. Ramsar is one of these regions. The main purpose is to estimate gamma radiation exposure inside and outside of residential buildings in Ramsar and the suburbs and to present exposure map of Ramsar; also estimating internal exposure of radon gas and obtaining effective dose of Ramsar population. There for, SAPOS 90M gamma monitor and RSS-112 and Na I(Tl) scintillator were used. To determine the concentration of 226 Ra, 232 Th, 40 K in soil and building materials gamma spectrometer and Germanium detector were used. In addition to exposure rate of different sections of Ramsar and its suburbs, 200 residential houses with high exposure rate and more than 600 ones with normal exposure rate were determined. The results of measurement were respectively 11?Rh-1 to 3 ?Rh-1 in indoor region and 11?Rh-1 to 2?R-1 in indoor regions. Annual gamma exposure was 5.99+-18.01 mSv. Maximum of annual gamma exposure rate of this region is 131 mSv. The estimated radon dose, through previous measurement is approximated to 14.67+-39.14 mSv annually. normal exposure is respectively 8?Rh-1 to 17?Rh-1 in outdoor regions and 10?Rh-1 to 130?Rh-1 in indoor regions. Annual exposurein indoor regions. Annual exposure rate of gamma radiation is 0.68+-0.01 mSv and estimated radon gas from indoor and outdoor exposure for effective dose is 2.34+0.02 mSv

199

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

International Nuclear Information System (INIS)

As the breast cancer rate is increasing fast in Korean women, people pay more attention to mammography and number of mammography have been increasing dramatically over the last few years. Mammography is the only means to diagnose breast cancer early, but harms caused by radiation exposure shouldn't be overlooked. Therefore, it is important to calculate the radiation dose being absorbed into the breast tissue during the process of mammography for a protective measure against radiation exposure. Because it is impossible to directly measure the radiation dose being absorbed into the human body, statistical calculation methods are commonly used, and most of them are supposed to simulate the interaction between radiation and matter by describing the human body internal structure with anthropomorphic phantoms. However, a simulation using Geant4 Code of Monte Carlo Method, which is well-known as most accurate in calculating the absorbed dose inside the human body, helps calculate exact dose by recreating the anatomical human body structure as it is through the DICOM file of CT. To calculate the absorbed dose in the breast tissue, therefore, this study carried out a simulation using Geant4 Code, and by using the DICOM converted file provided by Geant4, this study changed the human body structure expressed on the CT image data into geometry needed for this simulation. Besides, this study attempted to verify if the dose calculation of Geant4 interlocking with the DICOM file is eant4 interlocking with the DICOM file is useful, by comparing the calculated dose provided by this simulation and the measured dose provided by the PTW ion chamber. As a result, under the condition of 28kVp/190mAs, the Difference(%) between the measured dose and the calculated dose was found to be 0.08 %?0.33 %, and at 28 kVp/70 mAs, the Difference(%) of dose was 0.01 %?0.16 %, both of which showed results within 2%, the effective difference range. Therefore, this study found out that calculation of the absorbed dose using Geant4 Simulation is useful in measuring the absorbed dose in the breast tissue for mammography

200

Absorbed dose measurement of 4 MV medical linear accelerator (LMR-4)  

International Nuclear Information System (INIS)

For the purpose of treating patients with malignant tumors we introduced a medical linear accelerator (LMR-4) in our hospital in April, 1982. In order to measure the radiation dose and the absorbed dose in a patient irradiated by this equipment, we carried out a experiment to obtain percentage depth dose (PDD) and tissue-peak dose ratio (TPR) by source-surface distance (SSD) and source-tumor distance (STD) methods, using a ionization chamber dosimeter and Mix-DP fantoms and compared the results with literatures and datas in other institutions. The results are as follows. 1) The reference depth was 1.3 cm. 2) There were a few variances of absorbed doses in both SSD and STD methods. 3) The PDD and TPR curves made by us were almost the same as those made by others, consequently, these PDD and TPR tables can be utilized for radiation therapy. (author)

201

Absorbed dose estimates in a prolonged cesium-137 gamma irradiation facility for mice  

International Nuclear Information System (INIS)

To study on late effects by continuous gamma irradiations, the absorbed dose in mice was estimated in detail. A Cs-137 source was used for exposures. Dosimetry was performed with an air ionization chamber and a thermoluminescence dosimeter (TLD). The absorbed dose mapping of the gamma irradiation room was carried out by using the ionization chamber. Arc-shaped racks with shelves made from wire net were designed on the basis of the dose map. The dose distributions in cages were measured under the racks and cages arrangements used during the experiments. Furthermore, by inserting TLD phosphors into abdomen of mice, exposure dose of the mice was actually measured under the experimental conditions. (author)

202

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

International Nuclear Information System (INIS)

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

203

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

204

Absorbed gamma and electron radiation dose with the ceric sulfate dosimeter  

International Nuclear Information System (INIS)

Ceric sulfate dosimetry is used for accurate measurement of the absorbed dose in water irradiated with x- or gamma-rays or high-energy electrons. It is based on the process of reduction of ceric to cerous ions by ionizing radiation. The method is most accurate for absorbed doses in the range from 1 x 106 to 8 x 106 rd, using spectrophotometric measurement of the ceric ion concentration. The method covers the preparation and procedure for the use of the ceric sulfate dosimeter and includes a discussion of interferences, equipment, reagents, standardization and preparation, determination of the molar extinction coefficient, dosimetry measurements, calculation of absorbed dose, determination of the G-value, precision, and accuracy

205

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

International Nuclear Information System (INIS)

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

206

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

207

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

International Nuclear Information System (INIS)

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.

208

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

International Nuclear Information System (INIS)

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

209

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

International Nuclear Information System (INIS)

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

210

A study on the absolute measurement of ?-ray absorbed dose in the skin depth  

International Nuclear Information System (INIS)

The absolute measurement of ? ray absorbed dose in the skin depth located at the certain distance from the radiation source (90Sr + 90Y, 204TI, 147Pm) recommended by the International Standardization Organization is performed by using an extrapolation chamber in the range of several mGy/h. Since one of critical points in measuring of absorbed dose is to make the environment in chamber similar to tissue, a new approach to the measurement of absorbed dose is proposed. The attenuation difference is minimized by deciding a window thickness such as the attenuation effect in chamber window becomes similar to that in the skin depth. A-150 tissue equivalent plastic, whose structure and density is very similar to tissue, is used for back material. The back scattering effect of both media is measured using the proposed method to calibrate the difference in back scattering effect between back material and tissue. For the measurement of back scattering effect of each material, an ionization chamber, whose structure is very similar to the extrapolation chamber and back material is replaceable, is made. Based on the results, ? ray absorbed dose in the skin depth of 70 ?m was measured as follows : 0.759 ?Gy/s (±3.78% ) for 90Sr + 90Y, 0.173 ?Gy/s (±4.17%) for 204TI and 0.088 ?Gy/s (±7.70%) for 147Pm. In order to evaluate the reliability of the proposed method, the absorbed dose measured in this study is compared to that measured in PTB (Physikalisch Technische Bundesanstalt) for the same ? ray source. Although the proposed method gives slightly higher value, the difference is within 1%. In conclusion, the proposed method seems to make the measuring environment closer to tissue, even though the calibration factor yielded by the proposed method has a little effect on evaluation of absorbed dose

211

Advance of the Austrian absorbed dose to water primary standardisation system  

International Nuclear Information System (INIS)

The Austrian absorbed dose to water primary standardisation system is based on a graphite calorimeter. It was developed at the Austrian Research Center Seibersdorf, based on the design by Domen, and is in operation since 1983. The calorimeter and the corresponding measuring devices are supervised by the Federal Office of Metrology and Surveying (BEV). The BEV is the National Metrology Institute (NMI) and national authority on legal metrology in Austria. The realisation of the unit absorbed dose to water is based upon absorbed dose to graphite measurements. The conversion from absorbed dose to graphite to absorbed dose to water is done by two methods based on the photon fluence scaling theorem. The calorimeter was originally designated for determination of absorbed dose to water in 60Co gamma ray beams. The progress in radiation therapy within the recent years forced increased demands on high energy photon dosimetry. To meet the needs the application range of our primary standard was extended, to enable field characterisation and calibration of medical accelerators. In order to operate the energy range and application enhancement a set of conversion and correction factors was needed. They were obtained via Monte Carlo simulations with PENELOPE code, and measurements - with the calorimeter itself and ionisation chambers. First of all measurements and simulation studies were carried out for 60Co gamma rays to achieve a well founded basis. The simulations include calorimeter geometry specific simulations to get radiation quality depended correction factors. These calculations are constitutive on photon fluence spectra determination of radiation facilities to enable the use of realistic input radiation fields. Furthermore cooperative measurements for the verification of simulation results at accelerators located in Austrian hospitals are in progress. The accomplishment of the BEV high energy calorimetry project was promoted by the Physico-technical Testing Service (PTP), which is a partial legal entity of BEV. (author)

212

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

Energy Technology Data Exchange (ETDEWEB)

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

Cunha, D M; Tomal, A; Poletti, M E, E-mail: poletti@ffclrp.usp.b [Departamento de Fisica e Matematica, FFCLRP, Universidade de Sao Paulo, 14040-901, Ribeirao Preto, Sao Paulo (Brazil)

2010-08-07

213

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

International Nuclear Information System (INIS)

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

214

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

Science.gov (United States)

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

Carlsson Tedgren, Åsa; Alm Carlsson, Gudrun

2013-04-01

215

Neutron absorbed dose rate with 252Cf sources for medical applications  

International Nuclear Information System (INIS)

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

216

Neutron absorbed dose rate with {sup 252}Cf sources for medical applications  

Energy Technology Data Exchange (ETDEWEB)

The {sup 252}Cf brachytherapy reduces the effect caused by the tumor hypoxia in photon radiotherapy and chemotherapy. The AAPM T G-43 modified formalism was used for the calculation of the fast neutron absorbed dose rate of {sup 252}Cf brachytherapy sources for normal tissues and malignant tumors. Three models of Hdr {sup 252}Cf sources; At, Vari Source and {mu}Selectron were simulated using spherical geometry, Watt fission spectrum and the MCNPX code. The results show that small variations in the elemental composition between the normal tissues and malignant tumors, produce variations in the reference fast neutron absorbed dose rate up to 14%. (Author)

Paredes, L.; Balcazar, M. [ININ, Carretera Mexico-Toluca s/n, Ocoyoacac 52750, Estado de Mexico (Mexico); Azorin, J. [Universidad Autonoma Metropolitana, Unidad Iztapalapa, Departamento de Fisica, Av. Michoacan y Purisima, Col. Vicentina, 09340 Mexico D. F. (Mexico); Francois, J. L., E-mail: lydia.paredes@inin.gob.m [UNAM, Facultad de Ingenieria, Departamento de Sistemas Energeticos, Circuito Interior, Ciudad Universitaria, 04510 Mexico D. F. (Mexico)

2010-02-15

217

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

218

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

International Nuclear Information System (INIS)

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

219

Neutron absorbed dose rate with 252 Cf sources for medical applications  

Directory of Open Access Journals (Sweden)

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

L. Paredes

2010-01-01

220

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

221

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

International Nuclear Information System (INIS)

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

222

Dose determination with nitro blue tetrazolium containing radiochromic dye films by measuring absorbed and reflected light  

DEFF Research Database (Denmark)

Tetrazolium salts as heterocyclic organic compounds are known to form highly coloured, water insoluble formazans by reduction, which can be utilized in radiation processing dosimetry. Radiochromic films containing nitro blue tetrazolium dissolved in a polymer matrix were found suitable for dose determination in a wide dose range both by absorbance and reflectance measurements. The concept of measuring reflected light from dose labels has been discussed earlier and emerged recently due to the requirement of introducing semiquantitative label dose indicators for quarantine control. The usefulness of the method was studied using the newly developed radiochromic dye films as well as already existing ones. (C) 2000 Elsevier Science Ltd. All rights reserved.

Kovács, A.; Baranyai, M.

2000-01-01

223

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

International Nuclear Information System (INIS)

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

224

Neutrons absorbed dose rate calculations for interstitial brachytherapy with {sup 252}Cf sources  

Energy Technology Data Exchange (ETDEWEB)

The AAPM TG-43 protocol was used to evaluate the neutron absorbed dose rate from {sup 252}Cf sources for two tissue substitute materials, five normal tissues and six malignant tumours. Three {sup 252}Cf source models (AT, VariSource and {mu}Selectron) were simulated using the Monte Carlo MCNPX code in spherical geometry for obtaining the following factors: (a) conversion coefficient of neutron air kerma strength, (b) neutron dose rate constant, (c) neutron radial dose function, (d) geometry function, (e) anisotropy function and (f) neutron absorbed dose rate. For the {sup 252}Cf AT source and a Watt fission spectrum, the calculated reference neutron dose rate in water was D{sup .}{sub N}(r{sub 0},{theta}{sub 0})=1.916 cGy h{sup -1} {mu}g{sup -1}. The results for the reference neutron dose rate in normal tissues and malignant tumours show how small variations in their elemental composition produce variations in the neutron absorbed dose rate up to 14.9% and 8.4%, respectively, when water and muscle are the reference medium.

Paredes, L. [Instituto Nacional de Investigaciones Nucleares, Carr. Mexico-Toluca s/n, La Marquesa, C.P. 52750 Ocoyoacac, Mex. (Mexico); Facultad de Medicina, Universidad Autonoma del Estado de Mexico, Paseo Tollocan s/n, C.P. 50180 Toluca, Mex. (Mexico)], E-mail: lpg@nuclear.inin.mx; Azorin, J. [Departamento de Fisica, Universidad Autonoma Metropolitana-Iztapalapa, Av. Michoacan y Purisima, C.P. 09340 Mexico D.F. (Mexico); Balcazar, M. [Instituto Nacional de Investigaciones Nucleares, Carr. Mexico-Toluca s/n, La Marquesa, C.P. 52750 Ocoyoacac, Mex. (Mexico); Francois, J.L. [Facultad de Ingenieria, Departamento de Sistemas Energeticos, Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, C.P. 04510 Mexico D.F. (Mexico)

2007-09-21

225

Uncertainties of organ-absorbed doses to patients from 18f-choline  

Science.gov (United States)

Radiation doses of radiopharmaceuticals to patients in nuclear medicine are, as the standard method, estimated by the administered activity, medical imaging (e.g. PET imaging), compartmental modeling and Monte Carlo simulation of radiation with reference digital human phantoms. However, in each of the contributing terms, individual uncertainty due to measurement techniques, patient variability and computation methods may propagate to the uncertainties of the calculated organ doses to the individual patient. To evaluate the overall uncertainties and the quality assurance of internal absorbed doses, a method was developed within the framework of the MADEIRA Project (Minimizing Activity and Dose with Enhanced Image quality by Radiopharmaceutical Administrations) to quantitatively analyze the uncertainties in each component of the organ absorbed doses after administration of 18F-choline to prostate cancer patients undergoing nuclear medicine diagnostics. First, on the basis of the organ PET and CT images of the patients as well as blood and urine samples, a model structure of 18F-choline was developed and the uncertainties of the model parameters were determined. Second, the model parameter values were sampled and biokinetic modeling using these sampled parameter values were performed. Third, the uncertainties of the new specific absorbed fraction (SAF) values derived with different phantoms representing individual patients were presented. Finally, the uncertainties of absorbed doses to the patients were calculated by applying the ICRP/ICRU adult male reference computational phantom. In addition to the uncertainty analysis, the sensitivity of the model parameters on the organ PET images and absorbed doses was indicated by coupling the model input and output using regression and partial correlation analysis. The results showed that the uncertainty factors of absorbed dose to patients are in most cases less than a factor of 2 without taking into account the uncertainties caused by the variability and uncertainty of individual human phantoms. The sensitivity study showed that the metabolic transfer parameter from the blood to soft tissues has a strong influence on blood sample collection from the beginning until 500 min. post administration; the transfer pathways between blood and liver impact strongly the liver imaging during the time course. The results of this study suggest that organ image acquisition of liver and kidneys after 100 min. as well as blood and urine sample collection are necessary for the reduction of uncertainties of absorbed dose estimates to patients.

Li, W. B.; Janzen, T.; Zankl, M.; Giussani, A.; Hoeschen, C.

2011-03-01

226

Absorbed dose distribution analyses in irradiation with adjacent fields  

International Nuclear Information System (INIS)

Because the special irradiation technique with adjacent fields is the most used in the case of medulloblastoma treatment, we consider very important to specify some general information about medulloblastoma. This malignant disease has a large incidence in children with age between 5-7 years. This tumor usually originates in the cerebellum and is referred to as primitive undifferentiated tumor. It may spread contiguously to the cerebellar peduncle, floor of the fourth ventricle, into the cervical spine. In addition, it may spread via the cerebrospinal fluid intracranially and/or to the spinal cord. For this purpose it is necessary to perform a treatment technique with cranial tangential fields combined with adjacent fields for the entire spinal cord to achieve a perfect coverage of the zones with malignant cells. The treatment in this case is an association between surgery-radio-chemotherapy, where the radiotherapy has a very important roll and a curative purpose. This is due to the fact that the migration of malignant cells in the body can't be controlled by surgery. Because of this special irradiation technique used in medulloblastoma treatment, we chase to describe in this paper this complex type of irradiation where the implications of the beams divergence in doses distribution are essentials

227

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

Directory of Open Access Journals (Sweden)

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

Gh Bagheri

2011-09-01

228

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

International Nuclear Information System (INIS)

Significant absorbed dose levels exceeding 1.0 Gy day-1 have been measured on the external surface of the Cosmos 1887 biosatellite as functions of depth in stacks of thin thermoluminescent detectors (TLDs) of U.S.S.R. and U.S.A. manufacture. The dose was found to decrease rapidly with increasing absorber thickness, thereby indicating the present 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. (author)

229

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

International Nuclear Information System (INIS)

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)

230

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

International Nuclear Information System (INIS)

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

231

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

International Nuclear Information System (INIS)

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

232

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

International Nuclear Information System (INIS)

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

233

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

DEFF Research Database (Denmark)

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

McLaughlin, W. L.; Miller, Arne

1980-01-01

234

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

International Nuclear Information System (INIS)

Tumor absorbed dose calculations in radionuclide therapy are presently based on the assumption of static tumor mass. This work examines the effect of dynamic tumor mass (growth and/or shrinkage) on the absorbed dose. Tumor mass kinetic characteristics were modeled with the Gompertz equation to simulate tumor growth and an additional exponential term to accommodate tumor shrinkage that may result as a consequence of therapy. Correction factors, defined as the ratio of the absorbed dose, which was calculated by considering tumor mass dynamics, to the absorbed dose, which was calculated by assuming static mass, are presented for 1- and 100-g tumors with different tumor mass kinetics. The dependence of the correction factor on the effective half-life Te of the radioactivity in the tumor and the tumor shrinkage half-time Ts was examined. The correction factors for the 1-g tumor were > 1 for short Ts and Te. In contrast, the correction factor was less than 1 for long Ts (> 9 days). The dose correction factors for the 100-g tumor were > 1 for all Ts and Te. Finally, the dosimetric method for dynamic masses is illustrated with experimental data on Chinese hamster V79 multicellular spheroids that were treated with 3H. Correction factors as high as about 10 are likely when Te and Ts are short. As Ts increases beyond 20 days, the importance of dynamic mass dim0 days, the importance of dynamic mass diminishes because most of the activity decays before the mass changes appreciably. In some cases, mass dynamics should be taken into account when the absorbed dose to tumors is estimated. 15 refs., 6 figs., 1 tab

235

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

International Nuclear Information System (INIS)

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

236

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)

237

The quotient of absorbed dose and the collision part of kerma for photon beams  

International Nuclear Information System (INIS)

With the conceptual definition of the quotient (?) of absorbed dose and the collision part of kerma for photon beams, the procedure of computing ? is briefly described. A series of calculations of ? was carried out for photons of 0.4, 0.5, 1 and 2 MeV in polystyrene, carbon, air and aluminium. Resultant values are tabulated and evaluated. (author)

238

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

International Nuclear Information System (INIS)

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

239

Ionization method of determining absorbed radiation dose of high energy electrons  

International Nuclear Information System (INIS)

A simple method is presented of determining the absorbed radiation dose based on the determination of the mass calibration factor and the ratio of the mass stopping powers of the material and the gas filling of the chamber cavity. Empirical relations were derived for calculating the mean electron spectrum energy and for determining the ratio of the stopping powers of water and air. Ionization chambers VAK 252.1 and VAK 251 were used for determining the dose absorbed in a phantom for electron beams of an energy of 5 to 40 MeV. The flow chart is given of calculating the absorbed dose in different phantom depths. The mass calibration factor (Nsub(g)) was determined using two methods. The maximum deviation was 2%. The experiments showed that individual calibration of the ionization chambers is necessary for accurate measurements while for routine measurements, the mean value of Nsub(g) calculated for the given type of chamber can be used. The main sources of inaccuracy include correction factors which, for the given procedure of calculating the absorbed dose, were defined as the ratio of fluencies in the middle of the ionization chamber. The procedure presented and the relations derived allow fast calculation with sufficient accuracy by small computers. (J.P.)

240

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

International Nuclear Information System (INIS)

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

241

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

242

Radiation absorbed dose distribution in a patient treated with yttrium-90 microspheres for hepatocellular carcinoma  

International Nuclear Information System (INIS)

We have implemented a three-dimensional dose calculation technique accounting for dose inhomogeneity within the liver and tumor of a patient treated with 90Y microspheres. Single-photon emission computed tomography (SPECT) images were used to derive the activity distribution within liver. A Monte Carlo calculation was performed to create a voxel dose kernel for the 90Y source. The activity distribution was convolved with the voxel dose kernel to obtain the three-dimensional (3D) radiation absorbed dose distribution. An automated technique was developed to accurately register the computed tomography (CT) and SPECT scans in order to display the 3D dose distribution on the CT scans. In addition, dose-volume histograms were generated to fully analyze the tumor and liver doses. The calculated dose-volume histogram indicated that although the patient was treated to the nominal whole liver dose of 110 Gy, only 16% of the liver and 83% of the tumor received a dose higher than 110 Gy. The mean tumor and liver doses were 163 and 58 Gy, respectively

243

An evaluation of absorbed doses of high energy electromagnetic radiation in radiotherapy of laryngeal cancer  

International Nuclear Information System (INIS)

When 60Co ? rays or high-energy X-rays are externally applied to treat laryngeal cancer, the absorbed dose at the laryngeal lumen is lower than given dose because of air space, which it should pass through, before reaching the lesion. Specially in case of high-energy X-rays, the loss of dose is considerable. Thus, the influence of the laryngeal air space on radiation dose was studied for 60Co? rays, 6 MV X-rays and 10 MV X-rays by thermoluminescent dosimetry using neck phantoms having an air cavity in the upper air way. At the anterior commissure, absorbed dose are apt to be reduced with 6 MV and 10 MV more than 60Co, but it is not affected by field size or anterior neck angle. In the vocal cord, the doses of 6 MV and 10 MV decrease in proportion to field size. In the posterior commissure, the reduction in dose varies according to field size and anterior neck angle, but it is not related with radiation energy. From the above results, it is concluded that 60Co is the most suitable for radiotherapy of laryngeal cancer of these three rays, and when high-energy X-rays above 6 MV are applied, the loss of dose more than 60Co in the anterior commissure and the vocal cord should be taken into account. (author)

244

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

International Nuclear Information System (INIS)

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

245

Measurement of absorbed dose with a bone-equivalent extrapolation chamber  

International Nuclear Information System (INIS)

A hybrid phantom-embedded extrapolation chamber (PEEC) made of Solid Water trade mark sign and bone-equivalent material was used for determining absorbed dose in a bone-equivalent phantom irradiated with clinical radiation beams (cobalt-60 gamma rays; 6 and 18 MV x rays; and 9 and 15 MeV electrons). The dose was determined with the Spencer-Attix cavity theory, using ionization gradient measurements and an indirect determination of the chamber air-mass through measurements of chamber capacitance. The collected charge was corrected for ionic recombination and diffusion in the chamber air volume following the standard two-voltage technique. Due to the hybrid chamber design, correction factors accounting for scatter deficit and electrode composition were determined and applied in the dose equation to obtain absorbed dose in bone for the equivalent homogeneous bone phantom. Correction factors for graphite electrodes were calculated with Monte Carlo techniques and the calculated results were verified through relative air cavity dose measurements for three different polarizing electrode materials: graphite, steel, and brass in conjunction with a graphite collecting electrode. Scatter deficit, due mainly to loss of lateral scatter in the hybrid chamber, reduces the dose to the air cavity in the hybrid PEEC in comparison with full bone PEEC by 0.7% to ?2% depending on beam quality and energy. In megavoltage photon and electron beams, graphite electrodes do not affect the dosraphite electrodes do not affect the dose measurement in the Solid Water trade mark sign PEEC but decrease the cavity dose by up to 5% in the bone-equivalent PEEC even for very thin graphite electrodes (<0.0025 cm). In conjunction with appropriate correction factors determined with Monte Carlo techniques, the uncalibrated hybrid PEEC can be used for measuring absorbed dose in bone material to within 2% for high-energy photon and electron beams

246

The NPL absorbed dose to water calibration service for high energy photons  

International Nuclear Information System (INIS)

The National Physical Laboratory (NPL) provides and absorbed dose to water calibration service for secondary standard dosimeters using 60Co? radiation and seven X ray qualities between 4 and 19 MV. The calibration service is based on a primary standard graphite calorimeter that is used to determine absorbed dose to graphite and to calibrate as 'working standards' three type 2561 ionization chambers in a graphite phantom. The calibration factors for the working standards are converted from graphite to water using both cavity ionization theory and measurements based on the photon fluence scaling theorem. Hospital dosimeters are compared with the working standards in water to give secondary standard calibration factors in absorbed dose to water with an uncertainty of 0.7% (1?). The calibration service was launched in 1988 and has undergone several developments that have shown calibration factors for a 2561 chamber to be dependent not only on quality index but also on electron accelerating potential and beam filtration. However, for radiotherapy beams, which are generally heavily filtered, the calibration factors depend only on quality index so the NPL filtrations have been increased to ensure that the calibration factors are applicable to radiotherapy beams. Chamber absorbed dose to water calibration factors measured by NPL have been compared with those derived from the Codes of Practice of the Hospital Physicists' Association and the International Atomic Enociation and the International Atomic Energy Agency. These Codes are based on 2 MV X ray or 60Co air kerma calibration of the chamber and the application of conversion factors to derive absorbed dose to water. The comparison showed a maximum difference of 1.6% between the three methods that is within the uncertainties for the methods. (author). 15 refs, 4 figs, 1 tab

247

Re-establishing the photon absorbed dose primary standard on the new NPL clinical linac  

International Nuclear Information System (INIS)

A new state-of-the-art clinical linac facility has recently been opened at the NPL in addition to the existing research linac facility, which is now over 40 years old. The new machine is an Elekta Synergy Digital Linac, with iViewGT portal and XVI 3D x-ray volumetric imaging that can be configured to deliver seven X-ray beam energies (instead of the usual maximum of three on any one hospital machine). This feature, together with the ability to provide up to ten electron beam energies, will enable NPL to provide absorbed dose calibrations for the full range of energies currently in therapeutic use in the UK. The NPL is responsible for maintaining the UK primary standards of absorbed dose to water in both high-energy photon and electron beams. For photons, the primary standard is a graphite calorimeter that directly measures absorbed dose to graphite, that is, the energy deposited in a small graphite core at the centre of the calorimeter, in 60Co gamma ray and MV X-ray beams, divided by the mass of the core. Reference standard ionisation chambers placed in a graphite phantom are then calibrated against the primary standard in terms of absorbed dose to graphite. These calibrations are then converted to absorbed dose to water using two possible methods: one through the application of the photon fluence scaling theorem and the second involving charge measurements at a constant target-chamber distance. Secondary standard instruments are then calibrated against thinstruments are then calibrated against these reference standards at either 5cm or 7cm depth in a water phantom. Chamber calibrations are normally given in terms of kQ, the ratio of the chamber calibration factor in a given quality, Q, to that in a reference quality, Qo (60Co at NPL) where the radiation quality is defined in terms of tissue-phantom ratio (TPR20/10)

248

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

International Nuclear Information System (INIS)

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

249

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1990-08-15

250

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

International Nuclear Information System (INIS)

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

251

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.

252

Electron absorbed fractions and dose conversion factors for marrow and bone by skeletal regions  

International Nuclear Information System (INIS)

The possible inductions of bone cancer and leukemia are the two health effects of primary concern in the irradiation of the skeleton. The relevant target tissues to consider in the dosimetric evaluation have been the cells on or near endosteal surfaces of bone, from which osteosarcomas are thought to arise, and hematopoietic bone marrow, which is associated with leukemia. The complex geometry of the soft tissue-bone intermixture makes calculations of absorbed doses to these target regions a difficult problem. In the case of photon or neutron radiations, charged particle equilibrium may not exist in the vicinity of a soft tissue-bone mineral interface. In this paper, absorbed fraction data are developed for calculations of the dose in the target tissues from electron emitters deposited within the volume or on the surfaces of trabecular bone. The skeletal average absorbed fractions presented are consistent with usage of this quantity in the contemporary dosimetric formulations of the International Commission on Radiological Protection (ICRP). Implementation of the new bone and marrow model is then developed within the context of the calculational schema of the Medical Internal Radiation Dose (MIRD) Committee. Model parameters relevant to the calculation of dose conversion factors (S values) for different regions of the skeleton of individuals of various age are described, and an example calculation is performed for a monoclonal antibody which localizes in the marrow. Thantibody which localizes in the marrow. The utility of these calculations for radiation dose calculations in nuclear medicine is discussed

253

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

Science.gov (United States)

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

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

2014-05-01

254

Development of beta-ray survey meter for measuring directly absorbed dose rate  

International Nuclear Information System (INIS)

A new type ?-ray survey meter was developed, which could be used for measuring the ?-ray absorbed dose rate of the skin (epidermal thickness is 7 mg/cm2) and of fingers (40 mg/cm2) almost independently of ?-ray maximum energy. The survey meter is also used for monitoring a surface contamination. The detector of the survey meter is a plastic scintillator (40 mm dia. x 2 mmt, effective opening diameter for ?-rays is 38 mm dia.). In dose rate measurement, the dose sensitivity of the survey meter (counting rate per absorbed dose rate) was constant within +-10% with maximum energy more than 0.4 MeV. The measurable ranges of the absorbed dose rate of the skin and of fingers were from 3.1 x 10-2 to 103 mrad/h and from 1.7 x 10-2 to 103 mrad/h, respectively. In surface contamination monitoring, the measurable range was from 1.9 x 10-1 to 1.7 x 103 ?-particles/cm2.s (2? solid angle), assuming the uniform contamination with natural uranium covered with an aluminum filter (27 mg/cm2) for shielding low energy ?-rays of 234Th and ?-rays. (author)

255

Adiabatic calorimeter for measuring absorbed dose of IHEP synchrotron secondary radiation  

International Nuclear Information System (INIS)

An adiabatic calorimeter for measuring the value of absorbed dose of mixed radiation generated by 70 GeV proton synchrotron is described. The calorimetric system consists of a working body (a core) and a shell (a screen). The calorimeter adiabaticity is provided by the absence of the core-shell heat exchange by maintaining the shell temperature equal to the core temperature and, consequently, the whole energy generated in the core goes for its heating. The work showed the possibility of carrying out the adiabatic calorimetric measurements of absorbed dose of secondary radiation generated by un accelerated proton beam under the conditions of alternating magnetic and electric fields at the IHEP proton synchrotron at the average dose rate not less than 5x10-3 Wxkg-1

256

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

International Nuclear Information System (INIS)

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

257

Monte Carlo estimates of absorbed dose rate in various tissues and organs  

International Nuclear Information System (INIS)

A computer program based on the Monte Carlo technique was developed for calculation of adsorbed dose rate in various tissues and organs. The accuracy of the program was tested by reproducing Berger's values of the specific absorbed fractions for point isotropic sources in water, and a good agreement with those obtained by the moments method was found within an error of several percent. In comparing with experiment and other Monte Carlo results, good agreement was also obtained within the range of statistical error. The absorbed dose rate for an 123I, 124I, 125I, 126I and 99mTc point source and their specific dose constants in various tissues and organs were calculated using this program. This computer program has the mass energy absorption and attenuation coefficients for 69 tissues and organs as a database file, and can be extended to various radionuclides used in nuclear medicine by adding their nuclear data to the program. (orig.)

258

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

259

Absorbed dose conversion coefficients for embryo and foetus in neutron fields  

International Nuclear Information System (INIS)

The Monte Carlo code MCNPX has been used to determine mean absorbed doses to the embryo and foetus when the mother is exposed to neutron fields. There are situations, such as on-board aircraft, where high-energy neutrons are often peaked in top down (TOP) direction. In addition to previous publications for standard irradiation geometries, this study provides absorbed dose conversion coefficients for the embryo of 8 weeks and the foetus of 3, 6 or 9 months at TOP irradiation geometry. The conversion coefficients are compared with the coefficients in isotropic irradiation (ISO). With increasing neutron energies, the conversion coefficients in TOP irradiation become dominant. A set of conversion coefficients is constructed from the higher value in either ISO or TOP irradiation at a given neutron energy. In cases where the irradiation geometry is not adequately known, this set of conversion coefficients can be used in a conservative dose assessment for embryo and foetus in neutron fields. (authors)

260

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

International Nuclear Information System (INIS)

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

261

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

International Nuclear Information System (INIS)

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

262

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

International Nuclear Information System (INIS)

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

263

Pain and Mean Absorbed Dose to the Pubic Bone After Radiotherapy Among Gynecological Cancer Survivors  

International Nuclear Information System (INIS)

Purpose: To analyze the relationship between mean absorbed dose to the pubic bone after pelvic radiotherapy for gynecological cancer and occurrence of pubic bone pain among long-term survivors. Methods and Materials: In an unselected, population-based study, we identified 823 long-term gynecological cancer survivors treated with pelvic radiotherapy during 1991-2003. For comparison, we used a non-radiation-treated control population of 478 matched women from the Swedish Population Register. Pain, intensity of pain, and functional impairment due to pain in the pubic bone were assessed with a study-specific postal questionnaire. Results: We analyzed data from 650 survivors (participation rate 79%) with median follow-up of 6.3 years (range, 2.3-15.0 years) along with 344 control women (participation rate, 72 %). Ten percent of the survivors were treated with radiotherapy; ninety percent with surgery plus radiotherapy. Brachytherapy was added in 81%. Complete treatment records were recovered for 538/650 survivors, with dose distribution data including dose-volume histograms over the pubic bone. Pubic bone pain was reported by 73 survivors (11%); 59/517 (11%) had been exposed to mean absorbed external beam doses <52.5 Gy to the pubic bone and 5/12 (42%) to mean absorbed external beam doses ?52.5 Gy. Thirty-three survivors reported pain affecting sleep, a 13-fold increased prevalence compared with control women. Forty-nine survivors reported functional impairment measured reported functional impairment measured as pain walking indoors, a 10-fold increased prevalence. Conclusions: Mean absorbed external beam dose above 52.5 Gy to the pubic bone increases the occurrence of pain in the pubic bone and may affect daily life of long-term survivors treated with radiotherapy for gynecological cancer.

264

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

International Nuclear Information System (INIS)

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

265

Absorbed doses from intraoral radiography with special emphasis on collimator dimensions  

International Nuclear Information System (INIS)

Thermoluminescence dosimeters were used in a phantom head and on patients to measure the absorbed dose to organs of special interest from full surveys with intraoral films (20 exposures) and single bitewing exposures. Two x-ray machines were used, operating at 65 kVp. The apertures of the circular tube collimators had diameters of 55 mm and 48 mm. Rectangular (35 mm x44 mm) tube collimators were also used. The distance from the x-ray focus to the open end of the collimators (FSD) was 0.20 and 0.35 m. Exposure values for Kodak Ultra-Speed film (speed group D) were used. The maximum skin dose measured from the full surveys decreased by 25 per cent on changing from the circular to the rectangular apertures. Using 0.35 m FSD and rectangular collimator the maximum skin dose was 13 mGy. The absorbed doses to the salivary glands and the thyroid gland were significantly reduced on changing from circular to rectangular apertures. The doses in the central part of the parotid and the thyroid glands were then 0.5 and 0.12 mGy, respectively, from a full survey with 20 intraoral films. With a leaded shield the thyroid dose was reduced to 0.05 mGy. All dose values could be further reduced by 40 per cent by using Kodak Ektaspeed film (speed group E)

266

Dose absorbed by technologists in positron emission tomography procedures with FDG  

Scientific Electronic Library Online (English)

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

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

2007-09-01

267

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

International Nuclear Information System (INIS)

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

268

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

International Nuclear Information System (INIS)

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

269

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

International Nuclear Information System (INIS)

Purpose: The precise determination of organ mass (mth) and total number of disintegrations within the thyroid gland (A~) are essential for thyroid absorbed-dose calculations for radioiodine therapy. Nevertheless, these parameters may vary according to the method employed for their estimation, thus introducing uncertainty in the estimated thyroid absorbed dose and in any dose–response relationship derived using such estimates. In consideration of these points, thyroid absorbed doses for Graves’ disease (GD) treatment planning were calculated using different approaches to estimating the mth and the A~. Methods: Fifty patients were included in the study. Thyroid131I uptake measurements were performed at 2, 6, 24, 48, 96, and 220 h postadministration of a tracer activity in order to estimate the effective half-time (Teff) of 131I in the thyroid; the thyroid cumulated activity was then estimated using the Teff thus determined or, alternatively, calculated by numeric integration of the measured time-activity data. Thyroid mass was estimated by ultrasonography (USG) and scintigraphy (SCTG). Absorbed doses were calculated with the OLINDA/EXM software. The relationships between thyroid absorbed dose and therapy response were evaluated at 3 months and 1 year after therapy. Results: The average ratio (±1 standard deviation) betweenmth estimated by SCTG and USG was 1.74 (±0.64) and that between A~ obtained by Teff and the integration of measured activity in the gland was 1.71 (±0.14). These differences affect the calculated absorbed dose. Overall, therapeutic success, corresponding to induction of durable hypothyroidism or euthyroidism, was achieved in 72% of all patients at 3 months and in 90% at 1 year. A therapeutic success rate of at least 95% was found in the group of patients receiving doses of 200 Gy (p = 0.0483) and 330?Gy (p = 0.0131) when mth was measured by either USG or SCTG and A~ was determined by the integration of measured 131I activity in the thyroid gland and based on Teff, respectively. No statistically significant relationship was found between therapeutic response and patients’ age, administered 131I activity (MBq), 24-h thyroid 131I uptake (%) or Teff (p ? 0.064); nonetheless, a good relationship was found between the therapeutic response and mth (p ? 0.035). Conclusions: According to the results of this study, the most effective thyroid absorbed dose to be targeted in GD therapy should not be based on a fixed dose but rather should be individualized based on the patient'smth and A~. To achieve a therapeutic success (i.e., durable euthyroidism or hypothyroidism) rate of at least 95%, a thyroid absorbed dose of 200 or 330?Gy is required depending on the methodology used for estimating mth and A~

270

Spatial dose distributions in water absorber irradiated with high energy nucleons  

International Nuclear Information System (INIS)

The technique of numerical calculation of the two-dimensional spatial distributions of full absorbed and equivalent dose in water phantom irradiated with high energy nucleon beams 0.05 <= E <= 10 GeV as well as its components distribution is described. Calculations are performed with the created MEDICA pro gram realizing the method of consecutive collisions copformably to narrow nucleon beams with an arbitrary energy spectrum incident onto the absorber. The calculation results satisfactorily (+-20%) agree with the measurement results and can be used as initial data for calculating microdosimetric energy distributions in the phantom for concrete cond.itions on similar beams

271

The contribution of secondary heavy particles to the absorbed dose from high-energy photon beams  

Science.gov (United States)

High-energy photon radiotherapy sources produce non-negligible numbers of secondary heavy particles (neutrons, protons and alphas) which contribute to the dose in a patient. They also present a radiation protection problem. The contribution of such particles to the absorbed dose in a tissue-like medium and to the equivalent dose is considered in this study experimentally. Track etch detectors were chosen as a basic type of measuring instrument: cellulose nitrate Kodak LR115 and polyallyldiglycol carbonate CR39 were used as detectors. Several methods of directly read datum (track density, track parameter, LET spectrum etc) interpretation have been analysed. It has been ascertained that the contribution of secondary heavy particles represents approximately 0.002 of the photon dose and 0.02 of the equivalent dose, both at 50 MeV as maximum photon energy. The contribution of a 20 MV bremsstrahlung beam is roughly one-fifth of that at 50 MV.

Spurný, Frantisek; Johansson, Lennart; Sätherberg, Anders; Bednár, Jirí; Turek, Karel

1996-12-01

272

The contribution of secondary heavy particles to the absorbed dose from high-energy photon beams  

International Nuclear Information System (INIS)

High-energy photon radiotherapy sources produce non-negligible numbers of secondary heavy particles (neutrons, protons and alphas) which contribute to the dose in a patient. They also present a radiation protection problem. The contribution of such particles to the absorbed dose in a tissue-like medium and to the equivalent dose is considered in this study experimentally. Track etch detectors were chosen as a basic type of measuring instrument: cellulose nitrate Kodak LR115 and polyallyldiglycol carbonate CR39 were used as detectors. Several methods of directly read datum (track density, track parameter, LET spectrum etc) interpretation have been analysed. It has been ascertained that the contribution of secondary heavy particles represents approximately 0.002 of the photon dose and 0.02 of the equivalent dose, both at 50 MeV as maximum photon energy. The contribution of a 20 MV bremsstrahlung beam is roughly one-fifth of that at 50 MV. (author)

273

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1983-04-01

274

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

International Nuclear Information System (INIS)

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

275

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

International Nuclear Information System (INIS)

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

276

New approach for standardizing absorbed dose from beta radioactive wires and seeds used for intravascular brachytherapy  

International Nuclear Information System (INIS)

A new method for standardizing beta particle emitting radioactive sources (in the form of wires or seeds) used in the intravascular brachytherapy of coronary disease has been devised and investigated. The method is based on the use of a new type of ionization chamber, called the ring ionization chamber (RIC).The RIC has a design that encompasses both a phantom and an ionization chamber. It has a cylindrical shape, and a catheter housing the source (a wire or seeds) passes through the chamber along its axis. Owing to its similarity to a cylindrical ionization chamber, the dosimetric protocol given in Technical Reports Series No. 277 can be applied for determining the absorbed dose to air chamber (and to water) calibration factors, ND, as well as the absorbed dose to water calibration factor, ND,w. Owing to this similarity, the overall uncertainty in the standardization of absorbed dose for beta radioactive sources used in intravascular brachytherapy could be substantially reduced compared with that presently achieved. The RIC can be used in a new code of practice for dose standardization and quality assurance in intravascular brachytherapy. (author)

277

Microdosimetric measurements for neutron-absorbed dose determination during proton therapy  

International Nuclear Information System (INIS)

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

278

Radiation dose absorbed in organs of rat after short time feeding with organically bound tritium (OBT)  

International Nuclear Information System (INIS)

Wistar rats aged 3 months were given for 5 days standard food supplemented with 126 kBq of OBT or tritiated water (TW). The animals were sacrificed in groups of three on the 1st 6, 11, 16, 31 and 61st day after the end of 5-day feeding. The specific radioactivity of wet and dry tissue of the following organs was determined: brain, lung, heart, kidney, liver, spleen, small intestine, femur and skin (without hair). The radiation doses absorbed in organs after OBT and TW administration were calculated by two methods: assuming that the half time of tritium excretion is constant and equal to the half time of tritiated water excretion from the rat body (method recommended by ICRP) and considering the experimentally determined curve of specific activity of wet and dry mass of the particular organ. It was found that after contamination with TW, the radiation doses calculated by both methods were very similar. The radiation doses absorbed in the wet tissues of rats given OBT were about two times higher than in those given TW. The radiation doses absorbed in the dry mass of organs after OBT were three times as high as after TW. (author)

279

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

International Nuclear Information System (INIS)

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

280

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

Energy Technology Data Exchange (ETDEWEB)

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.

Choi, Chang Heon; Kim, Jung In; Park, Jong Min; Park, Yang Kyun; Ye, Sung Joon [Medical Research Center, Seoul National University College of Medicine, Seoul (Korea, Republic of); Cho, Kun Woo; Cho, Woon Kap [Radiation Research, Korean Institute of Nuclear Safety, Daejeon (Korea, Republic of); Lim, Chun Il [Korea Food and Drug Administration, Seoul (Korea, Republic of)

2010-11-15

281

Estimate of absorbed dose based on two-dimensional autoradiographic information in internal radionuclide therapy  

International Nuclear Information System (INIS)

In radiation therapies using radionuclides emitting short-range particles, such as radioimmunotherapy or boron neutron capture therapy, the biological effects are strongly affected by the heterogeneity of the absorbed dose distribution delivered to tumor cells. The three-dimensional (3D) information of the source distribution at the cellular level is required to accurately determine the absorbed dose distribution to the individual tumor cells. Two-dimensional distribution of cell and nuclide with a resolution of 1 ?m can be obtained from individual tissue sections by microautoradiography. To obtain such information in 3D, an ideal approach would be to align the serial tissue sections from a block and analyze all of them. This is straightforward in theory, but extremely difficult in practice. Furthermore, every section in the block has to be processed and analyzed, and the usage of the data from this laborious work is very inefficient. An approach presented here is to estimate the absorbed dose based on individual sections without 3D reconstruction. It is realistically workable since it avoids the most difficult task of alignment for the serial tissue sections. In addition, the absorbed dose can be estimated based on a limited number of noncontiguous sections. The validity of this approach has been tested by a Monte Carlo simulation for two representative radionuclide configurations: (a) a uniform distribution of sources and (b) a cell membrane bound source distributi) a cell membrane bound source distribution. With only a limited number of sampling sections, the uncertainties in the dose estimation were estimated to ?15% for short-range particles

282

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

International Nuclear Information System (INIS)

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.

283

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

International Nuclear Information System (INIS)

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

284

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

285

Implementation of absorbed dose standardization at therapy-level in Brazil  

International Nuclear Information System (INIS)

At the present moment, IAEA presented the final document of the new International Code of Practice based on standards of absorbed dose to water, which will be implemented in Brazil gradually, making the transition from the existing Code of Practice (IAEA 1987) in the country. At Nuclear and Energy Research Institute (IPEN/CNEN/SP) and at National Laboratory for Metrology of Ionizing Radiation (IRD/CNEN/RJ), where the possibility of having an accelerator is remote, the approach used is to provide users with a calibration factor in terms of absorbed dose to water for the ionization chamber at the reference quality 60 Co and theoretically derived quality correction factors for that chamber type which must be applied for other beam qualities. (author)

286

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)

287

Absorbed dose to water secondary standard for brachytherapy sources in Austria  

International Nuclear Information System (INIS)

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

288

Absorbed dose to the human adrenals from iodomethylnorcholesterol (I-131) NP-59: concise communication  

International Nuclear Information System (INIS)

During the past 2 yrs, adrenal uptake percentage values were measured in more than 40 patients, using an external counting technique. They suggest that the absorbed dose to the adrenals is significantly less than the 150 rads/mCi previously estimated using concentration values from animal adrenals. The measured combined uptake percentage for both adrenals ranged from 0.15% to 0.52% in 21 patients without evidence of adrenal disease, with a mean of 0.33% +- 0.1%; also from 0.22% to 1.5% in 22 patients with Cushing's disease, with a mean uptake of 0.78% +- 0.35%. The absorbed dose to the adrenals was estimated to be 25 rads/mCi for patients without evidence of adrenal disease, and 57 rads/mCi for patients with Cushing's disease. Both values are calculated for the respective mean uptake percentages by using the MIRD formalism

289

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

Directory of Open Access Journals (Sweden)

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

Kneževi? Ivan D.

2012-01-01

290

Estimation of skin absorbed doses due to subcutaneous leakage of radioactive pharmaceuticals  

International Nuclear Information System (INIS)

Skin absorbed doses due to subcutaneous leakage of radioactive pharmaceuticals were estimated by three calculating methods. The radioactive pharmaceuticals used in calculation were 67Ga-citrate, 99mTc-HMDP, 111In-Cl, 123I-IMP, 131I-Adosterol, 201Tl-Chloride which are used frequently and in large amount in the daily examination. Time taken to remove contamination, range of contamination and ratio of leakage were assumed to be 30 minutes, 10 cm2 and 30% respectively. The skin absorbed doses calculated on this assumption were less than the threshold value that is found to cause skin disorders by Yamaguchi method. We confirmed the misprints of ICRU report 56 in the process of this calculation. (author)

291

Calorimeter measurements of absorbed doses at the heavy water enriched uranium reactor  

International Nuclear Information System (INIS)

Application of calorimetry measurements of absorbed doses was imposed by the need of good knowledge of the absorbed dose values in the reactor experimental channels. Other methods are considered less reliable. The work was done in two phases: calorimetry measurements at lower reactor power (13-80 kW) by isothermal calorimeter, and differential calorimeter constructions for measurements at higher power levels (up to 1 MW). This report includes the following four annexes, papers: Isothermal calorimeter for reactor radiation monitoring, to be published; Calorimeter dosimetry of reactor radiation, presented at the Symposium about nuclear fuel held in april 1961; Radiation dosimetry of the reactor RA at Vinca, published in the Bull. Inst. Nucl. Sci. 1961; Differential calorimeter for reactor radiation dosimetry

292

Influence of elemental weight of human tissues estimated by ICCT software in absorbed dose calculation  

International Nuclear Information System (INIS)

Therapeutic use of radiopharmaceuticals in Nuclear Medicine has been well established and presented good success rates against many forms of cancer. The biologic effects of radionuclide therapy are measured via a physical quantity, the absorbed dose, which is defined as per unit mass of tissue. Therefore, it is of great important an accurate dosimetry to assess the potential effects of treatment and to confirm or contradict the treatment predictions. The most common method used to estimate the absorbed dose at organ level was developed by Medical Internal Radiation Dose (MIRD) Committee, called MIRD system. However, this method does not have adequate patient data to obtain a dose estimate accurate in therapy. In recent years, internal radionuclide radiation dosimetry system evaluated spatial dose distribution. This system is based in Monte Carlo radiation transport codes with anatomical and functional information of the patient. The high accuracy is, at least in part, due to the Monte Carlo method allows human tissues to be characterized by elemental composition and mass density. Thus, a reliable estimation of human tissues (elemental composition and mass density) must be obtained. According to Schneider, Bortfield and Schlegel, the tissue parameters (mass densities (?) and elemental weights (?i)) can be obtained using Hounsfield units provided from Computed Tomography (CT) images. Based on this, the Nuclear Engineer Center of IPEN developed the ICCT softr Center of IPEN developed the ICCT software (Image Converter Computed Tomography). It converts CT images in tissue parameters (mass densities (?) and elemental weights (?i). This work intended to verify if the estimate values by software ICCT of the tissue parameter and elemental weights (?i) are plausible to estimate the absorbed dose with reasonable accuracy. (author)

293

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

International Nuclear Information System (INIS)

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

294

RESPONSE FUNCTIONS FOR COMPUTING ABSORBED DOSE TO SKELETAL TISSUES FROM PHOTON IRRADIATION – AN UPDATE  

OpenAIRE

A comprehensive set of photon fluence-to-dose response functions (DRFs) are presented for two radiosensitive skeletal tissues – active and total shallow marrow – within 15 and 32 bones sites, respectively, of the ICRP reference adult male. The functions were developed using fractional skeletal masses and associated electron absorbed fractions as reported for the UF hybrid adult male phantom, which in turn is based upon microCT images of trabecular spongiosa taken from a 40-year male cadav...

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

2011-01-01

295

Measurement of absorbed dose rate of gamma radiation for lead compounds  

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-07-21

296

Measurement of absorbed dose rate of gamma radiation for lead compounds  

Science.gov (United States)

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

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

2010-07-01

297

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

298

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

Energy Technology Data Exchange (ETDEWEB)

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. [Dipartimento di Ingegneria Nucleare, Politecnico di Milano, Via Ponzio 34/3, 20133 Milan (Italy); Vanossi, E. [Dipartimento di Ingegneria Nucleare, Politecnico di Milano, Via Ponzio 34/3, 20133 Milan (Italy); INFN-Istituto Nazionale di Fisica Nucleare, Via Celoria 16, 20133 Milan (Italy); Gambarini, G. [INFN-Istituto Nazionale di Fisica Nucleare, Via Celoria 16, 20133 Milan (Italy) and Dipartimento di Fisica, Universita di Milano, Via Celoria 16, 20133 Milan (Italy)]. E-mail: grazia.gambarini@mi.infn.it; Carrara, M. [Unita di Fisica Sanitaria, Istituto Nazionale dei Tumori, Via Venezian 1, 20133 Milan (Italy); Valente, M. [INFN-Istituto Nazionale di Fisica Nucleare, Via Celoria 16, 20133 Milan (Italy); Dipartimento di Fisica, Universita di Milano, Via Celoria 16, 20133 Milan (Italy)

2007-08-15

299

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

OpenAIRE

In 1945, within the frame of the Uranium Project for the production of nuclear weapons, the Mayak nuclear facilities were constructed at the Lake Irtyash in the Southern Urals, Russia. The nuclear workers of the Mayak Production Association (MPA), who lived in the city of Ozyorsk, are the focus of epidemiological studies for the assessment of health risks due to protracted exposure to ionising radiation. Electron paramagnetic resonance measurements of absorbed dose in tooth enamel have alread...

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

2014-01-01

300

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)

301

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

International Nuclear Information System (INIS)

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

302

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)

303

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)

304

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

International Nuclear Information System (INIS)

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

305

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

International Nuclear Information System (INIS)

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

306

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

Directory of Open Access Journals (Sweden)

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

Y.I. Zakari

2013-05-01

307

Calculation of absorbed doses in diagnostic and therapeutic use of monoclonal antibodies against malignant melanomas  

International Nuclear Information System (INIS)

The aim of this investigation was to derive the biokinetics for radiolabelled 96.5 antibodies in an animal model and estimate absorbed doses. As an experimental model, nude athymic rats transplanted with human melanoma were used. Whole antibody 96.5 was labelled with 125I and injected i.v. into the rats (n=52). Experiments were done for three different tumors, two patient tumors, called UM and KS, and one melanoma cell line, 1477. The tumors were inocculated on the thighs intramuscularly and subcutaneously and their final weight was between 0.02 and 11.5g. The uptake in tumor tissue always exeeded other normal tissues. The normal tissue dominating is the lungs with uptake values somewhat smaller than tumors. The ratio between the uptake values for tumors and muscle is 5.5 for UM, 4.0 for KS and 3.9 for 1477 tumor. The animal data for percentage uptake and halflife were used directly in the MIRD formalism to calculate the mean absorbed dose from 131I-96.5 antibodies. The absorbed dose to the tumor will be in the order of 0.1 Gy/MBq. This value, however, is strongly dependant on the tumor weight. The biokinetics for the different tumors also differed. (Author)

308

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-03-15

309

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

International Nuclear Information System (INIS)

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

310

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

International Nuclear Information System (INIS)

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

311

Assessment of indoor absorbed gamma dose rate from natural radionuclides in concrete by the method of build-up factors  

International Nuclear Information System (INIS)

The specific absorbed gamma dose rates, originating from natural radionuclides in concrete, were calculated at different positions of a detection point inside the standard room, as well as inside an example room. The specific absorbed dose rates corresponding to a wall with arbitrary dimensions and thickness were also evaluated, and appropriate fitting functions were developed, enabling dose rate calculation for most realistic rooms. In order to make calculation simpler, the expressions fitting the exposure build-up factors for whole 238U and 232Th radionuclide series and 40K were derived in this work, as well as the specific absorbed dose rates from a point source in concrete. Calculated values of the specific absorbed dose rates at the centre point of the standard room for 238U, 232Th and 40K are in the ranges of previously obtained data. (authors)

312

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

313

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

2011-01-01

314

A geochemical assessment of terrestrial gamma-ray absorbed dose rates  

International Nuclear Information System (INIS)

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.17 references

315

The estimation of absorbed dose rates for non-human biota: an extended intercomparison.  

Science.gov (United States)

An exercise to compare 10 approaches for the calculation of unweighted whole-body absorbed dose rates was conducted for 74 radionuclides and five of the ICRP's Reference Animals and Plants, or RAPs (duck, frog, flatfish egg, rat and elongated earthworm), selected for this exercise to cover a range of body sizes, dimensions and exposure scenarios. Results were analysed using a non-parametric method requiring no specific hypotheses about the statistical distribution of data. The obtained unweighted absorbed dose rates for internal exposure compare well between the different approaches, with 70% of the results falling within a range of variation of ±20%. The variation is greater for external exposure, although 90% of the estimates are within an order of magnitude of one another. There are some discernible patterns where specific models over- or under-predicted. These are explained based on the methodological differences including number of daughter products included in the calculation of dose rate for a parent nuclide; source-target geometry; databases for discrete energy and yield of radionuclides; rounding errors in integration algorithms; and intrinsic differences in calculation methods. For certain radionuclides, these factors combine to generate systematic variations between approaches. Overall, the technique chosen to interpret the data enabled methodological differences in dosimetry calculations to be quantified and compared, allowing the identification of common issues between different approaches and providing greater assurance on the fundamental dose conversion coefficient approaches used in available models for assessing radiological effects to biota. PMID:21113609

Vives i Batlle, J; Beaugelin-Seiller, K; Beresford, N A; Copplestone, D; Horyna, J; Hosseini, A; Johansen, M; Kamboj, S; Keum, D-K; Kurosawa, N; Newsome, L; Olyslaegers, G; Vandenhove, H; Ryufuku, S; Vives Lynch, S; Wood, M D; Yu, C

2011-05-01

316

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

Science.gov (United States)

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 D(w). A conversion factor C(x(i),x(i)(+1)) has to be applied to the difference of ionization charges measured at two plate separations x(i) and x(i)(+1). The details of the method are presented. The determination of D(w) 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. PMID:21924788

Schneider, Thorsten; Selbach, Hans-Joachim

2011-09-01

317

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.

318

Evaluation of variation of voltage (kV) absorbed dose in chest CT scans  

International Nuclear Information System (INIS)

Computed tomography (CT) is one of the most important diagnostic techniques images today. The increasing utilization of CT implies a significant increase of population exposure to ionizing radiation. Optimization of practice aims to reduce doses to patients because the image quality is directly related to the diagnosis. You can decrease the amount of dose to the patient, and maintain the quality of the image. There are several parameters that can be manipulated in a CT scan and these parameters can be used to reduce the energy deposited in the patient. Based on this, we analyzed the variation of dose deposited in the lungs, breasts and thyroid, by varying the supply voltage of the tube. Scans of the thorax were performed following the protocol of routine chest with constant and variable current for the same applied voltage. Moreover, a female phantom was used and thermoluminescent dosimeters (TLD-100), model bat, were used to record the specific organ doses. Scans were performed on a GE CT scanner, model 64 Discovery channels. Higher doses were recorded for the voltage of 120 kV with 200 mAs in the lungs (22.46 mGy) and thyroid (32.22 mGy). For scans with automatic mAs, variable between 100 and 440, this same tension contributed to the higher doses. The best examination in terms of the dose that was used with automatic 80 kV mAs, whose lungs and thyroid received lower dose. For the best breast exam was 100 kV. Since the increase in the 80 kV to 100 kV no impact so much the dose deposited in the lungs, it can be concluded that lowering the applied voltage to 100 kV resulted in a reduction in the dose absorbed by the patient. These results can contribute to optimizing scans of the chest computed tomography

319

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

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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

320

Influence of absorbed dose and deep traps on thermoluminescence response: A numerical simulation  

International Nuclear Information System (INIS)

Numerical simulations based on standard rate equations are carried out to study the dependence of the thermoluminescence (TL) response on the absorbed dose. The model, which includes thermally stimulated exo-electronic emission (TSEE), uses three electron traps - two active and one thermally disconnected (TD) - and one deep hole trap acting as a recombination centre. After instantaneous creation of a given dose of electron-hole pairs, one first follows isothermal recombination and trap filling before simulating the TL readout. Influence of TD traps and specific effects due to trap saturation are illustrated. A systematic study of the TL response is performed in wide ranges of the determining parameters. The dose dependence is found to be quadratic, linear or intermediate according to their relative values. Results are explained in terms of recombination-trapping competition, trap occupancy and in relation with the presence of TSEE. (authors)

321

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

322

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

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

Fredrik Uhlin

2012-10-01

323

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

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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)

Tavakoli, H.M.B. [Isfahan Univ. of Medical Sciences (Iran, Islamic Republic of)

2006-07-01

324

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)

325

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

International Nuclear Information System (INIS)

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

326

Assessment of absorbed dose and stopping power for 109Cd conversion electrons using a pressurized 4? proportional counter  

International Nuclear Information System (INIS)

The evaluation of the absorbed dose in external and internal contamination due to radionuclides is not easy, because of the difficulties in the assessment of the absorbed dose caused by electrons with energy less than 100 keV in skin and in mucous membrane. In this paper we work with a methodology for assessment of absorbed dose and stopping power in VYNS (co-polymer of polylvinyl chloride-acetate) absorbers, for the 32.5 keV and 84-88 keV energy 109 Cd conversion electrons, with a 4 ? proportional pressurized detector. In order to assure the reproducibility of measurement conditions, one of the detector halves was used to obtain a spectrum of a thin 109 Cd source, without absorber. The other half of the detector was used in concomitance to obtain spectra with different thicknesses of absorber. The absorbed energy was obtained subtracting each spectrum absorber from the spectrum without absorber and both were stored in a microcomputer connected to signal processing systems by a ACE type interface. The VYNS weight and thickness were evaluated using common radionuclide metrology procedures. As VYNS has characteristics similar to a tissue equivalent material, the results obtained are consistent with dosimetric concepts and have a good agreement with those of the literature. (author)

327

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.for prostate cancer as possible.

328

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

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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.

Na, Jong Eok; Lee, Do Geum; Kim, Jin Soo; Baek, Geum Mun; Kwon, Kyung Tae [Dept. of Radiation Oncology, Asan Medical Center, Seoul (Korea, Republic of)

2009-09-15

329

Radioiodine Therapy of Hyperthyroidism. Simplified patient-specific absorbed dose planning  

International Nuclear Information System (INIS)

Radioiodine therapy of hyperthyroidism is the most frequently performed radiopharmaceutical therapy. To calculate the activity of 131I to be administered for giving a certain absorbed dose to the thyroid, the mass of the thyroid and the individual biokinetic data, normally in the form of uptake and biologic half-time, have to be determined. The biologic half-time is estimated from several uptake measurements and the first one is usually made 24 hours after the intake of the test activity. However, many hospitals consider it time-consuming since at least three visits of the patient to the hospital are required (administration of test activity, first uptake measurement, second uptake measurement plus treatment). Instead, many hospitals use a fixed effective half-time or even a fixed administered activity, only requiring two visits. However, none of these methods considers the absorbed dose to the thyroid of the individual patient. In this work a simplified patient-specific method for treating hyperthyroidism is proposed, based on one single uptake measurement, thus requiring only two visits to the hospital. The calculation is as accurate as using the individual biokinetic data. The simplified method is as patient-convenient and time effective as using a fixed effective half-time or a fixed administered activity. The simplified method is based upon a linear relation between the late uptake measurement 4-7 days after intake of the test activity and the product take of the test activity and the product of the extrapolated initial uptake and the effective half-time. Treatments not considering individual biokinetics in the thyroid result in a distribution of administered absorbed dose to the thyroid, with a range of -50 % to +160 % compared to a protocol calculating the absorbed dose to the thyroid of the individual patient. Treatments with a fixed administered activity of 370 MBq will in general administer 250 % higher activity to the patient, with a range of -30 % to +770 %. The absorbed dose to other organs than the thyroid is also influenced. These doses should also be considered in estimating the risk of late radiation effects in the patients. This is becoming more important as an increasing number of younger patients are treated with radioiodine. If all Swedish hospitals considered the individual biokinetic data the total administrated activity of 131I would decrease by 10 % (100 GBq) corresponding to a yearly collective effective dose of 17 manSv, thyroid excluded. Seventeen different methods to determine the administered activity of 131I are in use in 23 Swedish hospitals. Only nine hospitals calculate the administered activity of 131I using individual biokinetic data. More effort should be done to consider the individual biokinetic data when calculating the administered activity of 131I and thus decrease unnecessary radiation dose to individual patients, their families and the public

330

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

331

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

International Nuclear Information System (INIS)

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

332

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

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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

333

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

International Nuclear Information System (INIS)

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

334

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

International Nuclear Information System (INIS)

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

335

Radiation absorbed dose estimate for Rb-82 using in vivo measurements in man  

International Nuclear Information System (INIS)

Radiation absorbed doses from intravenous Rb-82 (t 1/2 = 75 sec) were calculated by conjugate counting in 2 healthy adult men aged 27 and 23. Following an i.v. injection of a carefully calibrated amount of Rb-82, an organ of interest was imaged with a gamma camera equipped with a rotating tungsten collimator and data were collected in 10 second frames. Counts in the region of interest were corrected for adjacent background. Imaging was repeated from the opposite side of the body after a second injection. A calibrated reference source of Ge-68 placed on the body over the organ was similarly imaged in the absence of the rubidium activity. The integrated time activity curve in uCi-hours was obtained by comparing the observed kidney net conjugate counts with the reference source conjugate counts which represented a known number of uCi-hours. The organ self doses to the kidneys, liver, lungs, heart, and testes were determined by this technique which eliminated the effects of attenuation. Total absorbed doses to organs from all sources were calculated using the MIRD formulation and the averages of the 2 determinations (mrads/mCi) are as follows: heart (walls) 6.6; kidneys 31.3; liver 4.4; lungs 7.3; testes (1 subject only) 2.4; red marrow 1.7; and whole body 1.9. The highest dose is to the kidneys, but in an older subject (68 yr old man) the measured self dose to the left kidney was 16 mrads/mCi. These data are consistent with the decline in renal blood flow which occurs with increasing age and decreases renal exposure in older patients at increased risk of acute coronary disease who undergo myocardial perfusion imaging with Rb-82

336

Estimation of Absorbed Dose of Salivary Glands in Radioiodine Therapy and Its Reduction Using Pilocarpine  

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Full Text Available Introduction:  The use of radioactive iodine (131I has become an important adjunct to the treatment of thyroid cancer and hyperthyroidism. Salivary gland has the ability to concentrate radioactive iodine under normal circumstances. Salivary gland dysfunction and dry mouth are the common side effects of high-dose radioiodine therapy. The purpose of this study was to determine the absorbed dose of salivary glands. Methods: Twenty patients who were divided into two groups of 10 were studied (A group without pilocarpine and the B group received pilocarpine during treatment. The absorbed dose of parotid glands and the submandibular glands of patients was measured using thermoluminescent dosimeter (TLD at three different times (24 hours, 8 days and 3 months after treatment. The attenuation coefficient of patients and the effects of pilocarpine were also determined. Results: In group A total attenuation coefficient was 0.335, 0.323, and 0.357 for parotid glands and the right and left submandibular glands, respectively. In group B total attenuation coefficient was 0.462, 0.482, and 0.514 for parotid glands and the right and left submandibular glands, respectively. The results also showed the dose decreases to 1 cGy after 3 and 2 half life for A and B group, respectively. Conclusion: The findings showed that the dose decreases to 1 cGy after 3 half life of Iodine therapy. The exponential coefficient attenuation of salivary glands varied 3% to 4%.  Pilocarpine appears to be effective in increasing excretion of radioactive iodine and enhancing coefficient attenuation (up to 1.5 to 2 times.

Daryoush Shahbazi-Gahrouei

2007-09-01

337

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

International Nuclear Information System (INIS)

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

338

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

International Nuclear Information System (INIS)

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. To estimate the radiation dose to the carotid arteries following RAI therapy of benign thyroid disorders. 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 131I orally administrated, we used integrated modules for bioassay analysis and Monte Carlo simulations to calculate the dose in Gy/GBq of administrated RAI. The average radiation dose along the arteries is 4-55 Gy/GBq of the 131I 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 131I orally administrated. 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. (author)

339

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

International Nuclear Information System (INIS)

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

340

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

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Full Text Available OBJECTIVES: In this study, calculation of absorbed doses according to three different IAEA protocols for 6, 8, 10, 12, 15, and 18 MeV electron energies were compared. METHODS: Absorbe dose measurements were made at SSD=95 cm distance, 10 x 10 cm standart cone and reference depth. Electron energies was measured with five different cylindirical chambers and three different paralel plate chambers. Polarity and recombination effects were measured for all ionization chambers and energies before absorbed dose measurements. RESULTS: After the measurements, calculations were made according to three different protocols. For Marcus parallel plate chambers, the ratio of absorbe dose protocols was between -2.04% to 2.64%. Except from Marcus for other parallel plate chamber difference was between 0.11% to 3.38% for 6 MeV, 0.33% to 1.37% for 8 MeV, 0.12% to 1.71% for 10 MeV, 1.35% to 0.23% for 12 MeV, 1.69% to 0.24% for 15 MeV and 0.22% to 1.74% for 18 MeV. CONCLUSION: Contrary to photon energies, difference between absorbe dose protocols for electron beam energies was high. The reason of the difference was arise from the fact that TRS 277 assumes perturbation factor of parallel plate chambers was “1”. As a result, TRS 398 protocol enables us to calculate much more accurate absorbe dose.

Hilal ACAR

2007-01-01

341

Monte Carlo calculations and measurements of absorbed dose per monitor unit for the treatment of uveal melanoma with proton therapy  

OpenAIRE

The treatment of uveal melanoma with proton radiotherapy has provided excellent clinical outcomes. However, contemporary treatment planning systems use simplistic dose algorithms that limit the accuracy of relative dose distributions. Further, absolute predictions of absorbed dose per monitor unit are not yet available in these systems. The purpose of this study was to determine if Monte Carlo methods could predict dose per monitor unit (D/MU) value at the center of a proton spread-out Bragg ...

Koch, Nicholas; Newhauser, Wayne D.; Titt, Uwe; Gombos, Dan; Coombes, Kevin; Starkschall, George

2008-01-01

342

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

343

The future PTB primary standard for absorbed dose to water in 60Co-radiation  

International Nuclear Information System (INIS)

At the Physikalisch-Technische Bundesanstalt (PTB), a water calorimeter is being established as a primary standard realizing the unit of Gray (Gy) for absorbed dose to water, DW, in 60Co-?-radiation. The calorimeter is based on the design suggested by Domen. It consists of a water filled cubic phantom of 30 cm edge length, made of 1 cm thick polymethyl-methacrylate (PMMA) walls. The horizontally directed radiation enters the phantom through a 3 mm thick PMMA window. The phantom is thermally insulated by a 8 cm thick layer of polystyrene and is placed in a wooden container with an edge length of about 100 cm, in which active temperature stabilization is realized. The calorimeter is operated at a water temperature of 4 deg. C. The radiation induced temperature increase is measured inside a thin-walled plane-parallel glass cylinder in which two thin glass pipettes, each containing a thermistor sensor, are mounted opposite each other and perpendicular to the cylinder axis. The outer diameter of the glass cylinder is 95 mm, the wall thickness 2.5 mm and the outer length 41.5 mm, the front and rear walls being 0.75 mm in thickness. This design of the glass cylinder has been chosen to realize a well defined geometry for the proper modeling of heat transfer influences and to isolate a certain volume of specially prepared water from the water in the surrounding phantom. For the calorimetric determination of absorbed dose to water, various correction factors have to be applied to the measured radiation induced temperature increase at the point of measurement, i.e. for the heat defect, kHD, for the conductive heat transport processes, kC, and for the perturbations of the radiation field, kP. All these corrections have been determined by theoretical and experimental investigations. For example, in the case of heat transfer, detailed comparisons between finite element based calculations and calorimetric measurements yield a correction factor of kC=1.0009 to be applied to a single 120 s irradiation. The preliminary evaluation of the uncertainty budget for the determination of absorbed dose to water with the PTB water calorimeter leads to a relative combined standard uncertainty of less than 0.5 %. Measurements performed with the water calorimeter at the 60Co-?-radiation facility of the PTB serve to establish the radiation field in terms of absorbed dose to water under reference conditions. So far, the results indicate about a value 0.4 % larger value than that of the former PTB standard which is based on Fricke dosimetry

344

Terrestrial absorbed dose rate measurement in the Jhangar valley of Pakistan  

International Nuclear Information System (INIS)

Specific activity of natural radionuclides; 226Ra, 232Th and 40K were measured in the agricultural soil of eastern salt range of Pakistan using gamma-ray spectrometry. The soil samples were collected within the ploughing region (up to 12 cm depth) and processed before analysis. The average specific activities of different radionuclides in the dry mass of soil samples were: 40K, (666 Bq/kg), 226Ra (51 Bq/kg), and 232Th (59 Bq/kg). The average outdoor terrestrial absorbed dose rate in air from gamma-radiation one meter above ground surface was found to be 93 nGy/h. (author)

345

Analysis of absorbed dose to tooth enamel against external photon exposure  

International Nuclear Information System (INIS)

Absorbed dose to tooth enamel was examined against external photon exposure by measurements with thermoluminescence dosemeters (TLDs) and Monte Carlo calculations. TLDs were placed in a realistic physical phantom to measure dose to the teeth region in a head. A voxel-type phantom was constructed from computed tomography (CT) images of the physical phantom. Monte Carlo calculations with this voxel-type phantom were performed to analyse the results of the experiments. The data obtained were compared to the enamel doses, which were calculated with a modified MIRD-type phantom and already given in a previous paper. It was confirmed that the data derived with the MIRD-type phantom are applicable for retrospective individual dose assessments by electron spin resonance (ESR) dosimetry using teeth for the photon energy region above 300 keV. The analysis, however, indicated that the configuration of the head can affect the enamel dose relative to external exposure to photons with energy below 100 keV. (author)

346

The calculation of absorbed doses for radiobiological studies involving the use of small irradiation fields  

International Nuclear Information System (INIS)

It is suggested that irradiation with small slit fields clearly has a significant effect on absorbed dose. The effect of ignoring the field size correction factor in such situations can easily be demonstrated by reviewing the data presented by Hopewell et al (1987). In these studies the dose required to produce a specified incidence of late vascular damage (ED50) without correction would have been specified as 20.0 ± 0.5 Gy (16 mm field), 24.81 ± 0.66 Gy (8 mm field) and 31-58 ± 2.78 Gy (4 mm field). These differences are far more significant than those for the correct doses of 21.83 ± 0.66 Gy (8 mm field) and 25.58 ± 2.78 Gy (4 mm field); the dose specification for the 16 mm field remains unchanged. For the same reasons the slopes of the two lines presented in the same paper showing the relationship between isoeffect dose (ED50) and the length of rat spinal cord irradiated for vascular damage (> 30 weeks) and white-matter necrosis (< 30 weeks) would have been much steeper, thus over-emphasizing the field size effect. (author)

347

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

International Nuclear Information System (INIS)

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

348

A Method of Biological Measurement of Thermal- and Fast-Neutron Doses Absorbed by Living Organisms  

International Nuclear Information System (INIS)

After exposing young rats to a high thermal neutron flux the activated zones were determined by autoradiography at -195°C. The localization and nature of some of the activated elements were studied. Attention is drawn to the important role of P32 compared to other activation products. The authors compare the doses resulting from direct exposure to the neutron flux with those associated with local irradiation of bone and other tissue as a secondary effect of activation. The next step will be to study the possibility of using micro biopsy of bone tissue as a precise means of evaluating absorbed-neutron dose a posteriori in terms of different parts of the organism and different neutron energies. (Measurement of the samples specific P32 activity for thermal neutrons and calculation of the specific Si31 activity for fast neutrons). (author)

349

Radiobiologic risk estimation from dental radiology. Part I. Absorbed doses to critical organs.  

Science.gov (United States)

The aim of the present study was to generate one consistent set of data for evaluating and comparing radiobiologic risks from different dental radiographic techniques. To accomplish this goal, absorbed doses were measured in fourteen anatomic sites from (1) five different panoramic machines with the use of rare-earth screens, (2) a twenty-film complete-mouth survey with E-speed film, long round cone, (3) a twenty-film complete-mouth survey with E-speed film, long rectangular cone, (4) a four-film interproximal survey with E-speed film, long round cone, and (5) a four-film interproximal survey with E-speed film, long rectangular cone. The dose to the thyroid gland, the active bone marrow, the brain, and the salivary glands was evaluated by means of exposure of a tissue-equivalent phantom, fitted with lithium fluoride thermoluminescent dosimeters (TLDs) at the relevant locations. PMID:3165508

Underhill, T E; Chilvarquer, I; Kimura, K; Langlais, R P; McDavid, W D; Preece, J W; Barnwell, G

1988-07-01

350

Radiobiologic risk estimation from dental radiology. Part I. Absorbed doses to critical organs  

International Nuclear Information System (INIS)

The aim of the present study was to generate one consistent set of data for evaluating and comparing radiobiologic risks from different dental radiographic techniques. To accomplish this goal, absorbed doses were measured in fourteen anatomic sites from (1) five different panoramic machines with the use of rare-earth screens, (2) a twenty-film complete-mouth survey with E-speed film, long round cone, (3) a twenty-film complete-mouth survey with E-speed film, long rectangular cone, (4) a four-film interproximal survey with E-speed film, long round cone, and (5) a four-film interproximal survey with E-speed film, long rectangular cone. The dose to the thyroid gland, the active bone marrow, the brain, and the salivary glands was evaluated by means of exposure of a tissue-equivalent phantom, fitted with lithium fluoride thermoluminescent dosimeters (TLDs) at the relevant locations

351

Radiation-induced biomarkers for the detection and assessment of absorbed radiation doses  

Directory of Open Access Journals (Sweden)

Full Text Available Radiation incident involving living organisms is an uncommon but a very serious situation. The first step in medical management including triage is high-throughput assessment of the radiation dose received. Radiation exposure levels can be assessed from viability of cells, cellular organelles such as chromosome and different intermediate metabolites. Oxidative damages by ionizing radiation result in carcinogenesis, lowering of the immune response and, ultimately, damage to the hematopoietic system, gastrointestinal system and central nervous system. Biodosimetry is based on the measurement of the radiation-induced changes, which can correlate them with the absorbed dose. Radiation biomarkers such as chromosome aberration are most widely used. Serum enzymes such as serum amylase and diamine oxidase are the most promising biodosimeters. The level of gene expression and protein are also good biomarkers of radiation.

Rana Sudha

2010-01-01

352

Assessment of the absorbed dose to organs from bone mineral density scan by using TLDS and the Monte Carlo method  

Directory of Open Access Journals (Sweden)

Full Text Available Nowadays, dual energy X-ray absorptiometry is used in bone mineral density systems to assess the amount of osteoporosis. The purpose of this research is to evaluate patient organ doses from dual X-ray absorptiometry by thermoluminescence dosimeters chips and Monte Carlo method. To achieve this goal, in the first step, the surface dose of the cervix, kidney, abdomen region, and thyroid were measured by using TLD-GR 200 at various organ locations. Then, to evaluate the absorbed dose by simulation, the BMD system, patient's body, X-ray source and radiosensitive tissues were simulated by the Monte Carlo method. The results showed, for the spine (left femur bone mineral density scan by using thermoluminescence dosimeters, the absorbed doses of the cervix and kidney were 4.5 (5.64 and 162.17 (3.99(mGy, respectively. For spine (left femur bone mineral density scan in simulation, the absorbed doses of the cervix and kidney were 4.19 (5.88 and 175 (3.68(mGy, respectively. The data obtained showed that the absorbed dose of the kidney in the spine scan is noticeable. Furthermore, because of the small relative difference between the simulation and experimental results, the radiation absorbed dose may be assessed by simulation and software, especially for internal organs, and at different depths of otherwise inaccessible organs which is not possible in experiments.

Karimian Alireza

2014-01-01

353

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

International Nuclear Information System (INIS)

Dosimetry for low-energy interstitial brachytherapy sources is currently based on source calibrations in terms of the reference air-kerma rate (RAKR) or air-kerma strength (AKS). As patient dosimetry is based on the absorbed dose to water DW, a conversion formalism, as for example published by the American Association of Physicists in Medicine (AAPM), known as the TG-43 protocol and its update (TG-43U1), is required. The overall standard uncertainty in deriving DW at a point near the source from RAKR or AKS using the protocol is estimated to be about 8 % (k=1). Deviations of 8 % between prescribed and applied doses have to be regarded as clinically significant. A direct calibration in terms of the absorbed dose to water would reduce this uncertainty. A large, air-filled, parallel-plate extrapolation chamber in a phantom of water-equivalent material is under development for low energy photons as a primary standard for the realization of the absorbed dose to water. The entrance and the back plate of the extrapolation chamber are made of a water-equivalent material (RW1) with a measured density of 0.976 g/cm3. The thickness of the entrance plate (10.49 mm) defines the measurement depth within the water phantom (10.24 mm). Graphite was sprayed onto the inner side of the entrance plate. Biased at the potential U, this layer acts as the polarizing electrode and serves as the reference plane for the measurement. The back plate was chosen to beasurement. The back plate was chosen to be 60 mm in thickness. In front of the back plate, a polyethylene foil is located. A center collecting electrode and an outer guard ring - both at ground potential - are built, with this graphitized foil. The diameter of the collecting electrode amounts to 100 mm. The method of evaluation is described. It is based on a Monte Carlo-determined conversion factor C(xi, xi+1) to be applied to the difference of the ionization charge for the two plate separations xi and xi+1. In addition, the net energy fluence of the secondary electrons at the surface of the measuring volume must be taken into account. Both, this term and C(xi, xi+1) were calculated with the Monte Carlo simulation code EGSnrc. The spectra used in the calculation were obtained spectrometrically. The first measurements of an I-125 seed (BEBIG Symmetra I25.S06) with the chamber are presented. The absorbed dose to water rate in the chamber determined at various plate separations is shown. The results were compared to the results obtained by air-kerma rate measurements with the PTB primary standard chamber GROVEX I. For the comparison, two different conversion formalisms will be applied to obtain additional information about their effect on the results: a) the formalism according to TG-43U1 and b) a direct conversion of the air-kerma rate determined with the GROVEX I to the absorbed dose to water rate in the new chamber by an MC-based conversion factor. In the case of method a), a difference of 2.5 % was found and in the case of method b), a difference of 3.9 % was observed

354

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

International Nuclear Information System (INIS)

The paper describes dosimetric models that allow the estimation of average radiation exposures to terrestrial biota due to environmental sources in the soil as well as internal uniform distributions of radionuclides. Simple three-dimensional phantoms for 13 faunal reference organisms are specified. The calculation of absorbed dose per unit source strength for these targets is based on photon and electron transport simulations using the Monte Carlo method. The presented absorbed dose rate conversion coefficients are derived for terrestrial reference species. This allows the assessment of internal exposure as well as external photon exposure depending on the nuclide, habitat, target size and environmental contamination. To enable the application of specific radiation weighting factors for ?-, low energy ?- (E03H, 14C, 40K, 36Cl, 59,63Ni, 89,90Sr, up>59,63Ni, 89,90Sr, 94Nb, 99Tc, 106Ru, 129,131I, 134,135,137Cs, 210Po, 210Pb, 226Ra, 227,228,230,231,232,234Th, 234,235,238U, 238,239,240,241Pu, 241Am, 237Np and 242,243,244Cm, together with their progeny

355

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

356

A Comparison of Model Calculation and Measurement of Absorbed Dose for Proton Irradiation. Chapter 5  

Science.gov (United States)

With the increase in the amount of time spent EVA that is necessary to complete the construction and subsequent maintenance of ISS, it will become increasingly important for ground support personnel to accurately characterize the radiation exposures incurred by EVA crewmembers. Since exposure measurements cannot be taken within the organs of interest, it is necessary to estimate these exposures by calculation. To validate the methods and tools used to develop these estimates, it is necessary to model experiments performed in a controlled environment. This work is such an effort. A human phantom was outfitted with detector equipment and then placed in American EMU and Orlan-M EVA space suits. The suited phantom was irradiated at the LLUPTF with proton beams of known energies. Absorbed dose measurements were made by the spaceflight operational dosimetrist from JSC at multiple sites in the skin, eye, brain, stomach, and small intestine locations in the phantom. These exposures are then modeled using the BRYNTRN radiation transport code developed at the NASA Langley Research Center, and the CAM (computerized anatomical male) human geometry model of Billings and Yucker. Comparisons of absorbed dose calculations with measurements show excellent agreement. This suggests that there is reason to be confident in the ability of both the transport code and the human body model to estimate proton exposure in ground-based laboratory experiments.

Zapp, N.; Semones, E.; Saganti, P.; Cucinotta, F.

2003-01-01

357

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

International Nuclear Information System (INIS)

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

358

Total absorbed dose variations in different phantom materials of different neutron beam qualities  

International Nuclear Information System (INIS)

Percentage depth-dose data and output factors were studied for different phantom materials and different neutron beam qualities. In order to correct percentage depth-dose data from one phantom material to another, experimental and theoretical scaling factors (SF) are compared for different neutron beam qualities. The theoretical scaling factors are based on mean free path calculations and carried out at Fermilab, while the experimental scaling factors were collected from different European neutron therapy centers by means of a questionnaire. When comparing both scaling factors, for different phantom materials relative to water, diffences up to 10% were observed. In order to investigate these differences, SF/rho has been studied as a function of the H-concentration by mass, with rho being the mass density of the phantom material. It can be concluded that due to the uncertainty in the average total cross-sections of C and O experimental scaling factors will be more accurate than calculated values. A comparison of the absolute value of the absorbed dose at calibration depth (5cm) in a particular material relative to water shows a nearly linear variation with neutron energy. Determination of the output factor using these data and percentage depth-dose data yielded differences for polystyrene and TE-liquid which varied less than 3% for neutron beam qualities varying between d(14)+Be and p(65)+Be

359

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)

360

Absorbed dose measurements using TLDS in biological samples from beta radiation  

Directory of Open Access Journals (Sweden)

Full Text Available Irradiation of samples in peculiar experimental apparatus, subject to radiation spread, requires a special evaluation of absorbed dose implanted to the sample. Indirect calibration of the irradiation source, obtained in a different apparatus, and the spread, usually of very difficult theoretical evaluation, can cause very serious measurement errors, sometimes reaching 50%. In this work, the procedure for dose evaluation in an apparatus for beta irradiation of samples, usually biological ones,is presented, making use of calibration curves, obtained by irradiation in advance of thermoluminescent detectors in air, and so irradiating them in the same position of the sample. An application in blood sample irradiation is also presented.A irradiação de amostras em arranjos experimentais peculiares sujeitos a espalhamento necessita de uma determinação própria da dose absorvida que a amostra irá receber. A calibração indireta da fonte de irradiação, que ocorre em arranjo diferente, e o espalhamento, geralmente de difícil estimativa teórica, podem causar erros de medição muito elevados, não raro atingindo 50%. Neste trabalho é apresentado o procedimento para determinação da dose absorvida em um arranjo para irradiação beta de amostras, normalmente biológicas, utilizando curvas de calibração obtidas pela irradiação de dosímetros termoluminescentes no ar, e os irradiando na mesma posição das amostras. É apresentado um exemplo de aplicação para amostra irradiada de sangue.

José Eduardo Manzoli

2006-01-01

361

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

International Nuclear Information System (INIS)

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

362

Calculation of the effective UV dose absorbed by a flow of blood.  

Science.gov (United States)

Usually radiation damages in biological tissues are evaluated by the expose dose D(0) which is electromagnetic energy per unit area measured at the surface of a sample. We demonstrate that the appropriate measure of radiation damage is the effective dose D(a) which accounts for attenuation of electromagnetic field in the tissue. We treat a whole blood as strongly absorbing and viscous liquid and evaluate the ratio D(a)/D(0) in the process of UV irradiation of human blood perfused through a quartz cuvette. It is shown that because of absorption and parabolic profile of velocities of the blood flow in a rectangular cuvette, this ratio is small. An exponential decay of the intensity of the radiation means strong decrease of the probability of the damage a UV photon may produce on its mean free path. Numerical estimates done for the parameters of the procedure of blood retransfusion in ISOLDA device shows the decrease of the effective dose by up to 50 times as compared to the exposure dose. PMID:19959373

Vorontsova, I; Gumen, L N

2010-01-21

363

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

International Nuclear Information System (INIS)

A number of fast experimental neutron fields is created at the RB reactor. The intermediate and fast neutron spectra are measured by activation technique. The intermediate and fast neutron absorbed doses are compared at the basis of these experimental results. At the end the obtained doses are compared. (author)

364

Verification of absorbed dose to the lung SBRT treatments; Verificacion de dosis absorbida en los tratamientos de SBRT de pulmon  

Energy Technology Data Exchange (ETDEWEB)

The hypo fractionated stereotactic radiotherapy technique applied to the lung, also known as lung SBRT is a technique that small volumes irradiated to high doses using photon beams, usually not coplanar, with energies of 6 and 15 MV. Because of the uncertainties associated with the small field dosimetry calculation in heterogeneous media comes the need to verify the absorbed dose.

Gonzalez Gonzalez, J.; Modolell Farre, I.

2011-07-01

365

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

International Nuclear Information System (INIS)

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

366

A mathematical model for calculation of {sup 90}Sr absorbed dose in dental tissues: elaboration and comparison to EPR measurements  

Energy Technology Data Exchange (ETDEWEB)

A mathematical model for calculation of the {sup 90}Sr absorbed doses in dental tissues is presented. The results of the Monte-Carlo calculations are compared to the data obtained by EPR measurements of dental tissues. Radiometric measurements of the {sup 90}Sr concentrations, TLD and EPR dosimetry investigations were performed in animal (dog) study. The importance of the irregular {sup 90}Sr distribution in the dentine for absorbed dose formation has been shown. The dominant dose formation factors (main source-tissues) were identified for the crown dentine and enamel. The model has shown agreement with experimental data which allows to determine further directions of the human tooth model development.

Shishkina, E.A. E-mail: lena@urcrm.chel.su; Lyubashevskii, N.M.; Tolstykh, E.I.; Ignatiev, E.A.; Betenekova, T.A.; Nikiforov, S.V

2001-09-01

367

A mathematical model for calculation of 90Sr absorbed dose in dental tissues: elaboration and comparison to EPR measurements  

International Nuclear Information System (INIS)

A mathematical model for calculation of the 90Sr absorbed doses in dental tissues is presented. The results of the Monte-Carlo calculations are compared to the data obtained by EPR measurements of dental tissues. Radiometric measurements of the 90Sr concentrations, TLD and EPR dosimetry investigations were performed in animal (dog) study. The importance of the irregular 90Sr distribution in the dentine for absorbed dose formation has been shown. The dominant dose formation factors (main source-tissues) were identified for the crown dentine and enamel. The model has shown agreement with experimental data which allows to determine further directions of the human tooth model development

368

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

International Nuclear Information System (INIS)

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

369

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

Science.gov (United States)

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

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

2014-09-11

370

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

Science.gov (United States)

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

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

2014-12-01

371

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

OpenAIRE

High dose rate brachytherapy (HDR) using 192Ir sources is well accepted as an important treatment option and thus requires an accurate dosimetry standard. However, a dosimetry standard for the direct measurement of the absolute dose to water for this particular source type is currently not available. An improved standard for the absorbed dose to water based on Fricke dosimetry of HDR 192Ir brachytherapy sources is presented in this study. The main goal of this paper is to demonstrate the pote...

Dealmeida, Carlos Eduardo; Ochoa, Ricardo; Lima, Marilene Coelho; David, Mariano Gazineu; Pires, Evandro Jesus; Peixoto, Jose? Guilherme; Salata, Camila; Bernal, Mario Anto?nio

2014-01-01

372

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

Science.gov (United States)

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

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

2014-01-01

373

A feasibility study of Fricke dosimetry as an absorbed dose to water standard for 192Ir HDR sources.  

Science.gov (United States)

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

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

2014-01-01

374

Original paperEffects of absorbed dose of 131I isotope on the effectiveness of ablation of thyroid remnant tissue  

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Full Text Available Introduction: The aim of the study was the assesment of effective ablative dose of absorbed 131I radiation, based on dosimetric measurements. Material and methods: The study group comprised one hundred (100 patients in whom papillary thyroid carcinoma (PTC, 54 cases and follicular thyroid carcinoma (FTC, 46 cases had been diagnosed. The activities of 131I, administered to those patients, ranged from 1643 MBq (44.4 mCi to 4033 MBq (109 mCi. The following parameters were determined in the patients before radioiodine therapy: the mass of thyroid remnants [M (g], iodine uptake [U %], and the effective half-life of radioiodine [EHL (days]. After obtaining the results of measurements, the dose [D (Gy] absorbed by thyroid remnants was retrospectively calculated by means of our own modification of the Marinelli formula. Additionally the effect of the analyzed parameters on ablation effectiveness was assessed. Results: In 80 patients (80% the performed ablation was evaluated as effective. The most effective (91% was the ablation in the group of patients who received an absorbed dose of 2400 Gy or higher. A correlation was found between the absorbed dose and the effectiveness of ablation (rs=0.23; p1.5 ? (68% (p<0.03. Conclusions: A correlation has been demonstrated between ablation effectiveness and the 131I dose absorbed by thyroid remnants. The highest effectiveness of ablation was obtained after the administration of D ?2400 Gy.

Zbigniew Adamczewski

2007-06-01

375

Absorbed dose response of Al2O3 dosimeter irradiated by 60Co ? spectrum source capture and collimators  

International Nuclear Information System (INIS)

Objective: To investigated the absorbed dose response of Al2O3 dosimeter in water phantom irradiated by 60Co ? spectrum source. Methods: The EGSnrc simulation program code DOSRZnrc was used to calculate the absorbed dose of the Al2O3 dosimeter and that of the equivalent volume of water in the corresponding position, as well as the absorbed dose conversion factor, irradiated by 60Co photon beams in a water phantom. Simulations were done for a cylindrical geometry dosimeter (diameter 0.4 cm and height 0.1 cm) and the dosimeter was placed at the centre of the water phantom at different depths. Results: The average absorbed dose conversion factor is 1.143±0.006 and changes little with the depth of the dosimeter in the water phantom, and the deviation is less than 1.0%. Conclusion: The absorbed dose response of Al2O3 dosimeter irradiated by 60Co ? spectrum source is steady and is independent on the depth of the dosimeter in water phantom in this research. (authors)

376

Estimation of absorbed dose to thyroid in patients treated with radiotherapy for various cancers.  

Science.gov (United States)

This study is aimed at the evaluation of the absorbed dose to the thyroid gland from scattered/primary radiations in patients who have undergone radiotherapy. In this study, the skin entrance dose (SED) on the anterior neck at the level of the thyroid gland was measured using thermoluminescent dosimeters for 57 patients during radiotherapy with (60)Co teletherapy unit. Phantom dosimetry was also performed to find the correlation between the SED and the dose at the depth of the thyroid. SED of patients treated for breast cancer was 6.77±3.49 Gy and that of those with Hodgkin's disease and Ca. lung irradiation were 21.29±13.52 Gy and 28.80±14.94 Gy, respectively. SED at the level of the thyroid gland was found to be highest for patients whose thyroid gland was within the radiation field, while lowest for patients with skull irradiation. Thyroid gland is recommended to be shielded or excluded from the field whenever possible. PMID:23520201

Gul, Attia; Faaruq, Shafqat; Abbasi, Nadeem Zia; Siddique, Tariq; Ali, Akbar; Shehzadi, Nazia Neelam; Rahman, Mujeeb Ur; Khan, Amjad Aziz; Rizvi, Qaisar Abbas; Ahmad, Fayyaz

2013-01-01

377

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

International Nuclear Information System (INIS)

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

378

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

International Nuclear Information System (INIS)

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

379

Magnetic Resonance Imaging-Based Radiation-Absorbed Dose Estimation of {sup 166}Ho Microspheres in Liver Radioembolization  

Energy Technology Data Exchange (ETDEWEB)

Purpose: To investigate the potential of magnetic resonance imaging (MRI) for accurate assessment of the three-dimensional {sup 166}Ho activity distribution to estimate radiation-absorbed dose distributions in {sup 166}Ho-loaded poly (L-lactic acid) microsphere ({sup 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 {sup 166}Ho-PLLA-MS. Three-dimensional radiation-absorbed dose distributions were estimated at the voxel level by convolving the {sup 166}Ho activity distribution, derived from quantitative MRI data, with a {sup 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 {sup 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 {sup 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 {sup 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 {sup 166}Ho-PLLA-MS activity distributions, enabling localized intrahepatic radiation-absorbed dose estimation by convolution with a {sup 166}Ho dose point-kernel for liver radioembolization treatment optimization and evaluation.

Seevinck, Peter R., E-mail: p.seevinck@umcutrecht.nl [Image Sciences Institute, University Medical Center Utrecht, Utrecht (Netherlands); Maat, Gerrit H. van de [Image Sciences Institute, University Medical Center Utrecht, Utrecht (Netherlands); Wit, Tim C. de [Department of Nuclear Medicine, Amsterdam Medical Centre, Amsterdam (Netherlands); Vente, Maarten A.D.; Nijsen, Johannes F.W. [Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht (Netherlands); Bakker, Chris J.G. [Image Sciences Institute, University Medical Center Utrecht, Utrecht (Netherlands); Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht (Netherlands)

2012-07-01

380

Magnetic Resonance Imaging-Based Radiation-Absorbed Dose Estimation of 166Ho Microspheres in Liver Radioembolization  

International Nuclear Information System (INIS)

Purpose: To investigate the potential of magnetic resonance imaging (MRI) for accurate assessment of the three-dimensional 166Ho activity distribution to estimate radiation-absorbed dose distributions in 166Ho-loaded poly (L-lactic acid) microsphere (166Ho-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 166Ho-PLLA-MS. Three-dimensional radiation-absorbed dose distributions were estimated at the voxel level by convolving the 166Ho activity distribution, derived from quantitative MRI data, with a 166Ho 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 166Ho-PLLA-MS mass and activity distributions, as supported by a regression coefficient of 1.05 and a correlation coefficient of 0.99, relating locallation 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 166Ho-PLLA-MS in an ex vivo human liver visually showed high correspondence to SPECT-based radiation-absorbed