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1

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

International Nuclear Information System (INIS)

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

2011-01-01

2

Monte Carlo calculation of normalized glandular dose in mammography  

International Nuclear Information System (INIS)

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

2005-06-01

3

Handbook of glandular tissue doses in mammography. Final report March 1985  

Energy Technology Data Exchange (ETDEWEB)

This Handbook contains data from which absorbed dose to glandular tissue in the breast (glandular tissue dose) can be estimated for mammographic procedures. The breast (excluding the skin) is a composite of adipose (i.e., fatty) and glandular (i.e., other soft) tissues. The glandular tissue is the tissue considered at risk for breast cancer. The intent of the Handbook is to permit the user to compute glandular tissue dose for various techniques in mammography as a function of breast compression, breast size, breast composition, and the quality of the x-ray beam. The method used to compute most of the basic data was a radiation transport calculation using a specialized version of a computer code developed at the Oak Ridge National Laboratory (Warner, 1973). The results of the calculations were then converted into the Handbook entries, using the specific characteristics of current mammographic techniques. Additional data are reproduced from previous work of others.

Rosenstein, M.; Anderson, L.W.; Warner, G.G.

1985-03-01

4

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

Directory of Open Access Journals (Sweden)

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

5

Average glandular dose conversion coefficients for segmented breast voxel models  

International Nuclear Information System (INIS)

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

2004-04-23

6

Media glandular dose in mammography;Dosis glandular media en mamografia  

Energy Technology Data Exchange (ETDEWEB)

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

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

2009-10-15

7

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

Science.gov (United States)

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

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

2014-02-01

8

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

International Nuclear Information System (INIS)

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

2008-06-01

9

Dosimetric evaluation of average glandular absorption radiation dose in mammography  

International Nuclear Information System (INIS)

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

1996-12-01

10

Mean glandular dose in a breast screening programme  

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-10-23

11

Mean glandular dose in a breast screening programme  

International Nuclear Information System (INIS)

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

2012-10-23

12

Absorbed dose water calorimeter  

Energy Technology Data Exchange (ETDEWEB)

An absorbed dose water calorimeter that takes advantage of the low thermal diffusivity of water and the water-imperviousness of polyethylene film. An ultra-small bead thermistor is sandwiched between two thin polyethylene films stretched between insulative supports in a water bath. The polyethylene films insulate the thermistor and its leads, the leads being run out from between the films in insulated sleeving and then to junctions to form a wheatstone bridge circuit. Convection barriers may be provided to reduce the effects of convection from the point of measurement. Controlled heating of different levels in the water bath is accomplished by electrical heater circuits provided for controlling temperature drift and providing adiabatic operation of the calorimeter. The absorbed dose is determined from the known specific heat of water and the measured temperature change.

Domen, S.R.

1982-01-26

13

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

International Nuclear Information System (INIS)

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

2006-01-01

14

Calculation of mean glandular dose for mammography practice in Bangladesh  

International Nuclear Information System (INIS)

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

2008-11-26

15

Dependence of mean glandular dose on compression plate position  

International Nuclear Information System (INIS)

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

2010-11-09

16

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; Yu, Ning Le

2014-05-01

17

Average glandular dose in digital mammography and breast tomosynthesis  

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-10-15

18

Average glandular dose in digital mammography and breast tomosynthesis  

International Nuclear Information System (INIS)

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

2012-10-01

19

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

International Nuclear Information System (INIS)

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

1996-01-01

20

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Mowlavi A A

2007-01-01

 
 
 
 
21

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2006-01-01

22

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

International Nuclear Information System (INIS)

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

2000-11-01

23

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

International Nuclear Information System (INIS)

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

2004-12-21

24

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

International Nuclear Information System (INIS)

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

2007-01-01

25

Investigation of mean glandular dose versus compressed breast thickness relationship for mammography  

International Nuclear Information System (INIS)

The relationship between the mean glandular dose (MGD) and the compressed breast thickness (CBT) is commonly used for the presentation of mammographic dose survey results and could also be useful for the assessment of individual breast doses retrospectively in case of lack of necessary dosimetric instrumentation. The high data scattering from the best fit reduces the reliability of this technique. The aim of this study was to investigate the accuracy of this relationship using the data collected from a patient survey and phantom experiment. Patients were divided into three different groups according to their breast glandularities, which were predicted from the inspection of previous mammograms. X-ray beam qualities that will be used in patient examinations were determined according to breast thickness and predicted glandularities. The MGD versus CBT relationship for all the examined patients resulted in a poor correlation (R2 = 0.28). This relationship was separately obtained for each glandularity group and also for sub-groups of specific beam qualities. The best correlation (R2 = 0.73) was obtained for the fatty breast group and Mo/Mo combination. A low correlation (R2 = 0.34) was observed in the mid-glandularity group due to inclusion of a wide range of glandularities in this group. In the case of the dense breast group, although the glandularity range was narrow, there were e still high data scattering (R2 = 0.25). This was probably due to the use of Mo/Rh and Mo/Mo combinations. This is validated by obtaining the MGD-CBT relationship specific to Mo/Mo combination (R2 = 0.61). (authors)

2007-04-18

26

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

Directory of Open Access Journals (Sweden)

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

Vagner Ferreira Cassola

2010-12-01

27

Method for the evaluation of a average glandular dose in mammography  

International Nuclear Information System (INIS)

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

2006-04-01

28

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1999-10-01

29

Absorbed dose of electron radiation  

International Nuclear Information System (INIS)

Interaction of the intense electron flux with the objects of complex composition is investigated. The process of electron energy absorption in uniform and nonuniform media is considered in the general form. An expression for determining the absorbed dose rate of electrons with account of electron spectrum, the matter braking ability and distribution of the electron soUrces is obtained. An error of the obtained expression is evaluated. It is connected with the fact, that participation of only low-energy electrons in the energy transport is taken into account. It is underlined that the choice of the energy limiting value at which the electrons are distributed in the matter without scattering determines only the relative error of the obtained formula. This error can be essential at the distances up to the interface of two media, much less than the extrapolated electron path and significant relation of ionization potentials of boundary matters

1978-01-01

30

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

Scientific Electronic Library Online (English)

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

Cassola, Vagner Ferreira; Hoff, Gabriela.

31

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

The aim of this study was to reflect on the estimation of the mean glandular dose for women in Norway aged 50–69 y. Estimation of mean glandular dose (MGD) has been conducted by applying the method of Dance et al. (1990, 2000, 2009). Uncertainties in the thickness of approximately ±10 mm adds uncertainties in the MGD of approximately ±10 %, and uncertainty in the glandularity of ±0 % will lead to an uncertainty in the MGD of ±4 %. However, the inherent uncertainty in the air kerma, give...

Hauge, Ingrid Helen Ryste; Olerud, Hilde Merete

2012-01-01

32

Impact of digitalization of mammographic units on average glandular doses in the Flemish Breast Cancer Screening Program  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The impact of digitalization on the average glandular doses in 49 mammographic units participating in the Flemish Breast Cancer Screening Program was studied. Screen-film was changed to direct digital radiography and computed radiography in 25 and 24 departments respectively. Average glandular doses were calculated before and after digitalization for different PMMA-phantom thicknesses and for groups of 50 successive patients. For the transition from screen-film to computed radiography both ph...

Hauwere, An; Thierens, Hubert

2012-01-01

33

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

Directory of Open Access Journals (Sweden)

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

Oswaldo Ramos N

2009-01-01

34

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

Scientific Electronic Library Online (English)

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

Oswaldo, Ramos N; Manuel, Villarreal U.

35

Absorbed Dose and Dose Equivalent Calculations for Modeling Effective Dose  

Science.gov (United States)

While in orbit, Astronauts are exposed to a much higher dose of ionizing radiation than when on the ground. It is important to model how shielding designs on spacecraft reduce radiation effective dose pre-flight, and determine whether or not a danger to humans is presented. However, in order to calculate effective dose, dose equivalent calculations are needed. Dose equivalent takes into account an absorbed dose of radiation and the biological effectiveness of ionizing radiation. This is important in preventing long-term, stochastic radiation effects in humans spending time in space. Monte carlo simulations run with the particle transport code FLUKA, give absorbed and equivalent dose data for relevant shielding. The shielding geometry used in the dose calculations is a layered slab design, consisting of aluminum, polyethylene, and water. Water is used to simulate the soft tissues that compose the human body. The results obtained will provide information on how the shielding performs with many thicknesses of each material in the slab. This allows them to be directly applicable to modern spacecraft shielding geometries.

Welton, Andrew; Lee, Kerry

2010-01-01

36

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

International Nuclear Information System (INIS)

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

2007-11-02

37

Absorbed dose uncertainty estimation for proton therapy  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Successful radiotherapy treatment depends on the absorbed dose evaluation and the possibility to define metrological characteristics of the therapy beam. Radiotherapy requires tumor dose delivery with expanded uncertainty less than ±5 %. It is particularly important to reduce uncertainty during therapy beam calibration as well as to apply all necessary ionization chamber correction factors. Absorbed dose to water was determined using ionometric method. Calibration was performed in refe...

2012-01-01

38

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2006-11-07

39

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

Science.gov (United States)

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

Koutalonis, M.; Delis, H.; Spyrou, G.; Costaridou, L.; Tzanakos, G.; Panayiotakis, G.

2006-11-01

40

Estimation of Absorbed Dose in Occlusal Radiography  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this study was to estimate absorbed dose of each important anatomic site of phantom (RT-210 Head and Neck Section R, Humanoid Systems Co., U.S.A.) head in occlusal radiography. X-radiation dosimetry at 12 anatomic sites in maxillary anterior topography, maxillary posterior topography, mandibular anterior cross-section, mandibular posterior cross-section, mandibular anterior topographic, mandibular posterior topographic occlusal projection was performed with calcium sulfate thermoluminescent dosimeters under 70 Kvp and 15 mA, 1/4 second (8 inch cone) and 1 second (16 inch cone) exposure time. The results obtained were as follows: Skin surface produced highest absorbed dose ranged between 3264 mrad and 4073 mrad but there was little difference between projections. In maxillary anterior topographic occlusal radiography, eyeballs, maxillary sinuses, and pituitary gland sites produced higher absorbed doses than those of other sites. In maxillary posterior topographic occlusal radiography, exposed eyeball site and exposed maxillary sinus site produced high absorbed doses. In mandibular anterior cross-sectional occlusal radiography, all sites were produced relatively low absorbed dose except eyeball sites. In Mandibular posterior cross-sectional occlusal radiography, exposed eyeball site and exposed maxillary sinus site were produced relatively higher absorbed doses than other sites. In mandibular anterior topographic occlusal radiography, maxillary sinuses, submandibular glands, and thyroid gland sites produced high absorbed doses than other sites. In mandibular posterior topographic occlusal radiography, submandibular gland site of the exposed side produced high absorbed dose than other sites and eyeball site of the opposite side produced relatively high absorbed dose.

Yoo, Young Ah; Choi, Karp Shick [Dept. of Oral Radiology, College of Dentistry, Kyungpuk National University, Daegu (Korea, Republic of); Lee, Sang Han [Dept. of Oral and Maxillofacial Surgery, College of Dentistry, Kyungpook National University, Daegu (Korea, Republic of)

1990-02-15

 
 
 
 
41

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

42

Determination of absorbed dose in water  

International Nuclear Information System (INIS)

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

1984-01-01

43

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

International Nuclear Information System (INIS)

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

2000-05-01

44

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

International Nuclear Information System (INIS)

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

2008-10-16

45

Evaluation of absorbed dose and image quality in mammography  

International Nuclear Information System (INIS)

Mammography refers to the X-ray examination of the human breast, and is considered the single most important diagnostic tool in the early detection of breast cancer, which is by far the most common cancer among women. There is good evidence from clinical trials, that mammographic screening can reduce the breast cancer mortality with about 30%. The side effects include a small and age related risk of carcinogenesis due to the exposure of the glandular tissues in the breast to ionising radiation. As for all X-ray examinations, and of special importance when investigating large populations of asymptomatic women, the relationship between radiation risk and diagnostic accuracy in mammography must be optimised. The overall objective of this thesis was to investigate and improve methods for average glandular dose (AGD) and image quality evaluation in mammography and provide some practical guidance. Dose protocols used for so-called reference dose levels in Sweden 1989 (Nordic) and 1998 (European) were compared in a survey of 32 mammography units. The study showed that the AGD values for a 'standard breast' became 5±2% (total variation 0-9%) higher at clinical settings, when estimated according to the European protocol. For the Sectra MDM, a digital mammography (DM) unit with a scanning geometry, it was impossible to follow procedures for characterisation of the X-ray beam (HVL=half value layer) specified in the European protocol. In an experimental setup, it was shown that non-invasive measurements of HVL can be performed accurately with a sensitive and well collimated semiconductor detector with simultaneous correction for the energy dependence. AGD values could then be estimated according to 3 different dose protocols. A dosimetry system based on radioluminescence and optically stimulated luminescence from Al2O3:C crystals was developed and tested for in vivo absorbed dose measurements. It was shown that both entrance and exit doses could be measured and that the dosemeters did not disturb the reading of the mammograms. A Monte Carlo study showed that the energy dependence could be reduced, primarily by reducing the diameter of the crystal. It is proposed that radiation scattered forward towards the breast from the compression paddle, a scanning device etc, should be considered with greater clarity in the breast dosimetry protocols, and be described with a forward-scatter factor, FSF, for the various geometries and conditions proposed. Low contrast-detail (CD) phantoms of simulated glandularity 30, 50 or 70%, and thickness 3, 5 or 7 cm, were used to compare three different mammography systems. The same number of perceivable objects was visible for the full-field DM system at 20-60% of the AGD necessary for the screen-film (SFM) system, with the largest dose reduction potential for the thickest phantoms with the highest glandularity. However, more recent research shows that CD phantoms with a homogeneous background, as used here, must be used with care due to the presence of 'anatomical noise' in the real clinical situation. Image quality criteria (IQC) recommended in a European Guideline 1996 for SFM were adjusted to be relevant also for DM images. The new set of IQC was tested in two different studies using clinical images from DM and SFM, respectively. The results indicate that the new set of IQC has a higher discriminative power than the old set. The results also suggest that AGD for the DM system used may be reduced

2009-01-01

46

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

International Nuclear Information System (INIS)

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

2010-01-01

47

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

48

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)

2012-06-01

49

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)

2010-01-01

50

Real-time estimation system for mean glandular dose in mammography  

International Nuclear Information System (INIS)

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

2003-01-01

51

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: "1"1C- acetate, "1"1C- methionine, "1"8F-DOPA, whole antibody labelled with either "9"9"mTc, "1"1"1In, "1"2"3I or "1"3"1I, fragment of antibody, F(ab')_2 labelled with either "9"9"mTc, "1"1"1In, "1"2"3I or "1"3"1I and fragment of antibody, Fab' labelled with either "9"9"mTc, "1"1"1In, "1"2"3I or "1"3"1I. The absorbed dose estimates for these substances have been made from published biokinetic information. For other substances of interest, e.g. "1"4C-urea (children age 3-6 years), "1"4C-glycocholic acid, "1"4C-xylose and "1"4C-triolein, sufficient literature data have not been available. Therefore, a large number of measurements on patients and volunteers have been carried out, in order to determine the biokinetics and dosimetry for these substances. Samples of breast milk from 50 mothers, who had been subject to nuclear medicine investigations, have been collected at various times after administration of the radiopharmaceutical to the mother. The activity concentration in the breast milk samples has been measured. The absorbed dose to various organs and tissues and the effective dose to the child who ingests the milk have been determined for 17 different radiopharmaceuticals. Based on these results revised recommendations for interruption of breast-feeding after nuclear medicine investigations are suggested

2004-01-01

52

Radiation absorbed dose from medically administered radiopharmaceuticals  

International Nuclear Information System (INIS)

The use of radiopharmaceuticals for medical examinations is increasing. Surveys carried out in West Berlin show a 20% average yearly increase in such examinations. This implies an increased genetic and somatic radiation exposure of the population in general. Determination of radiation exposure of the population as well as of individual patients examined requires a knowledge of the radiation dose absorbed by each organ affected by each examination. An extensive survey of the literature revealed that different authors reported widely different dose values for the same defined examination methods and radiopharmaceuticals. The reason for this can be found in the uncertainty of the available biokinetic data for dose calculations and in the application of various mathematical models to describe the kinetics and calculation of organ doses. Therefore, the authors recalculated some of the dose values published for radiopharmaceuticals used in patients by applying biokinetic data obtained from exponential models of usable metabolism data reported in the literature. The calculation of organ dose values was done according to the concept of absorbed fractions in its extended form. For all radiopharmaceuticals used in nuclear medicine the energy dose values for the most important organs (ovaries, testicles, liver, lungs, spleen, kidneys, skeleton, total body or residual body) were recalculated and tabulated for the gonads, skeleton and critical or examined organs respectively. These dose values are compared with those reported in the literature and the reasons for the observed deviations are discussed. On the basis of recalculated dose values for the gonads and bone-marrow as well as on the basis of results of statistical surveys in West Berlin, the genetically significant dose and the somatically (leukemia) significant dose were calculated for 1970 and estimated for 1975. For 1970 the GSD was 0.2 mrad and the LSD was 0.7 mrad. For 1975 the GSD is estimated at < 0.5 mrad and the LSD at < 1 mrad. (author)

1975-03-10

53

Determination of absorbed dose in external radiotherapy beams based on standards of absorbed dose to water  

International Nuclear Information System (INIS)

The International Atomic Energy Agency, in its last code of practice for dosimetry in radiotherapy, has changed the basis of absorbed dose determination in external therapeutic radiation beams from measurement standards of air kerma to those of absorbed dose to water. This radical change, which has been made within a short period after the similar decision of the American Association of Physicists in Medicine, provides medical physicists with a simple as well as accurate procedure for dosimetry of almost all kinds of currently radiation beams used external radiotherapy. In this work, using previous air kerma based and the new absorbed dose to water based procedures, we have determined absorbed dose to water in photon (gamma and x) and electron beams of a few Co-60 units and medical linear accelerators in some radiotherapy departments in Iran. The results of dosimetry in each case are then analyzed and compared, regarding the standard uncertainties associated with each method

2001-01-01

54

A polystyrene absorbed-dose-rate calorimeter  

International Nuclear Information System (INIS)

A simple portable calorimeter was constructed by embedding a calibrated thermistor on the axis of a polystyrene rod. This instrument was positioned on the axis of a cylindrical array of "6"0Co rods. The duration of the measurements was ?70 s. Absorbed dose rates of ?70 Gy/min were measured to a daily precision of several tenths of a percent standard deviation. The results are in good agreement with earlier measurements made with a graphite calorimeter. An absorbed dose of 620 kGy resulted in no detectable change in thermistor sensitivity. The specific heat capacity of the polystyrene presumably increased ?0.0024%/kGy. The use of a chart recorder was not necessary. (orig.)

1987-04-01

55

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-10-15

56

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

International Nuclear Information System (INIS)

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

2010-05-24

57

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

Science.gov (United States)

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

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

2013-09-21

58

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

International Nuclear Information System (INIS)

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

2013-09-21

59

Cistitis glandular Glandular cystitis  

Directory of Open Access Journals (Sweden)

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

Barbara Paula Piñera

2010-03-01

60

Cistitis glandular / Glandular cystitis  

Scientific Electronic Library Online (English)

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

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

 
 
 
 
61

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

62

Neutron absorbed dose in a pacemaker CMOS  

International Nuclear Information System (INIS)

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

2011-08-07

63

Determination of absorbed dose in reactors  

International Nuclear Information System (INIS)

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

1971-06-01

64

The BIPM Graphite Calorimeter Standard for Absorbed Dose to Water  

International Nuclear Information System (INIS)

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

2011-11-01

65

The Australian Commonwealth standard of measurement for absorbed radiation dose  

International Nuclear Information System (INIS)

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

1990-01-01

66

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

International Nuclear Information System (INIS)

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

2010-09-01

67

Absorbed dose calculation at cellular level in radionuclide therapy  

International Nuclear Information System (INIS)

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

2004-10-09

68

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

International Nuclear Information System (INIS)

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

2009-10-02

69

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)

1965-06-01

70

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

Directory of Open Access Journals (Sweden)

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

Gabriela Hoff

2006-06-01

71

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

Scientific Electronic Library Online (English)

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

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

72

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

2010-11-09

73

Variation of PM-355 properties by high gamma absorbed doses  

International Nuclear Information System (INIS)

PM-355 super grade nuclear track detectors were exposed to high gamma absorbed doses up to 5 x 105 Gy (50 Mrad), with an incremental dose of 2.5 x 104 Gy, from a 9.03 PBq (244 kCi) Co-60 source. Results indicate that each of the bulk etch rate (Vb), the track etch rate (Vt) and the sensitivity (V) of the detectors increases with the high gamma absorbed dose, but there is a drop in these parameters at the low gamma absorbed dose. The Vb's for all gamma absorbed doses decreased while their Vt's and V increased with increasing etching time. Signs of surface roughness were observed by increasing the gamma absorbed doses and changes in color observed for doses larger than 2 x 105 Gy. The temperature of the detectors during irradiation reached 40oC. The fission fragment tracks (from a Cf-252 source) disappeared quickly within the etching time (minutes), for total absorbed doses greater than 3 x 105 Gy, due to their high bulk etch rate. (author)

1997-02-01

74

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)

1985-01-01

75

Absorbed doses during a single bitewing projection  

International Nuclear Information System (INIS)

The doses that different anatomical structures receive around the head of a tissue-equivalent phantom during a single bitewing projection, were measured with calibrated lithium fluoride thermoluminescent powder. The mrad/mA.s-values were measured at different tube voltages and target-surface distances using two rontgen units of different make, namely GE 1000 and Asahi. The dose relationship between the various structures and the skin dose at the point of application were calculated

1980-01-01

76

Fetal absorbed doses by radiopharmaceutical administration  

International Nuclear Information System (INIS)

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)

2000-07-01

77

Specification of absorbed dose for reporting a therapeutic irradiation  

International Nuclear Information System (INIS)

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

1980-10-31

78

Absorbed dose effect on radiolysis of cyclohexene  

International Nuclear Information System (INIS)

The radiation chemical yield of hydrogen from irradiated cyclohexene is independent of the dose up to nearly 200 Mrad, whereas those of 1,3-butadiene, 1,3-cyclohexadiene and trans-1,3-hexadiene decrease with increasing dose. This can be explained by radical scavenging as well as by charge and excitation transfer. Equations have been calculated for the description of dose dependence of the yields of these three conjugated dienes. The significant influence of conjugated dienes produced from monoalkenes on the radiolysis has been reconfirmed. Irradiations were carried out using a 60Co ?-irradiation facility with a nominal activity of 80000 Ci, at a temperature of 30-35degC. The dose rate was equal to 1.5 Mrad h-1, the dose applied ranged from 6 to nearly 200 Mrad. (F.G.)

1975-01-01

79

Comparison of absorbed doses resulting from various intraoral periapical radiography  

Energy Technology Data Exchange (ETDEWEB)

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 (p<0.05). 4. No statistically significant reduction in the absorbed dose was found as cylinder length was change (p>0.05).

Kang, Mi Ae; Park, Tae Won [Dept. of Oral and Maxillofacial Radiology, Graduate School, Seoul National University, Seoul (Korea, Republic of)

1995-08-15

80

Absorbed dose and biological effect in light ion therapy  

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Radiation therapy with light ions improves treatment outcome for a number of tumor types. The advantageous dose distributions of light ion beams en-able exceptional target conformity, which assures high dose delivery to the tumor while minimizing the dose to surrounding normal tissues. The demand of high target conformity necessitates development of accurate methods to calculate absorbed dose distributions. This is especially important for heavy charged particle irradiation, where the patient...

2008-01-01

 
 
 
 
81

Depth absorbed dose distributions for electrons  

International Nuclear Information System (INIS)

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

1980-01-01

82

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-04-15

83

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

International Nuclear Information System (INIS)

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

2011-04-01

84

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

International Nuclear Information System (INIS)

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

1996-01-01

85

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

2010-05-28

86

Absorbed dose determination for tomographic implant site assessment techniques.  

Science.gov (United States)

A set of data to compare the absorbed dose delivered by tomographic implant site assessment techniques was generated. Absorbed doses were measured in fourteen anatomic sites from (1) computed tomography scans and (2) a series of tomographic cuts performed on a linear tomography unit. The doses to the thyroid gland, the active bone marrow, the brain, the salivary glands, and the eyes were determined with the use of a tissue-equivalent phantom with lithium fluoride thermoluminescent dosimeters at the appropriate locations. PMID:1574314

Kassebaum, D K; Stoller, N E; McDavid, W D; Goshorn, B; Ahrens, C R

1992-04-01

87

Determination of superficial absorbed dose based on experiment and theory  

International Nuclear Information System (INIS)

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

1994-01-01

88

Effect of backscatter factor on absorbed dose in radiotherapy  

International Nuclear Information System (INIS)

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

2011-01-01

89

Absorbed Doses to Patients in Nuclear Medicine  

International Nuclear Information System (INIS)

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

2007-01-01

90

X-ray doses absorbed by patients during xeroxmammography  

International Nuclear Information System (INIS)

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

1988-01-01

91

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

1979-01-01

92

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  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 profundi...

2010-01-01

93

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

International Nuclear Information System (INIS)

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

2009-10-02

94

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

1997-01-22

95

Evaluation of absorbed dose in mammography: monte carlo simulation studies.  

Science.gov (United States)

Computer programs for calculation of the backscatter factor and absorbed dose in breast phantoms are developed based on Monte Carlo simulation. Rad/roentgen conversion factors are calculated for water, fat, a mixture of 50% water and 50% fat, and lucite irradiated with monoenergetic and polyenergetic x rays from a tungsten or molybdenum anode x-ray tube. These factors can be used to estimate skin dose, average depth dose, or average integral dose in a breast when the beam quality, exposure in air at the skin position, and composition of the breast are known. Calculated backscatter factors are considerably greater than measured values reported previously. PMID:7360961

Doi, K; Chan, H P

1980-04-01

96

Absorbed dose rate levels around amang plant buildings  

International Nuclear Information System (INIS)

The measurements of absorbed dose rate in air around amang plant buildings were carried out using a scintillation detector. It was found that the mean radiation levels at seven amang plants were in the range of 1.6 - 5.5 ?Gyh-1. The individual maximum value measured was 56 ?Gyhr-1. The annual dose to a worker transporting the minerals to the plant was estimated to be 1.5 mSvy-1. (Author)

2008-12-01

97

A proposal concerning the absorbed dose conversion factor  

International Nuclear Information System (INIS)

New definitions of the absorbed dose conversion factors Csub(lambda) and Csub(E) are proposed. The absorbed dose in water is given by the product of absorbed dose conversion factor, exposure calibration factor, ionisation chamber reading, cap displacement correction factor and perturbation correction factor. At exposure calibration the material of the build-up cap must be the same as that of the chamber wall. An ionisation chamber of which the wall material is water-equivalent or air-equivalent may be used. In the latter case the wall must be thin. For these two cases absorbed dose conversion factors are introduced and it is recommended that either of the two sets should be adopted. Furthermore, if the chamber wall is neither water- nor air-equivalent, the factor by which these currently defined values should be multiplied is also given: again the wall must be thin. The ICRU definitions of Csub(lambda) and Csub(E) are inconsistent, as recently pointed out, while the definitions presented here are consistent. (author)

1978-01-01

98

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

99

Study of absorbed dose distribution to high energy electron beams  

International Nuclear Information System (INIS)

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

1983-01-01

100

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

 
 
 
 
101

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2009-10-15

102

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

Science.gov (United States)

Medical Internal Radiation Dose(MIRD) schema was developed for calculating the absorbed dose from the administrated radiopharmaceuticals. With the biological distribution data and physical properties of the radionuclide, we can estimated the absorbed dose...

S. W. Hong S. M. Lim C. H. Kim K. S. Kim J. S. Cho

1995-01-01

103

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 cm_3) simulating the breast. Dose determinations were made at 4.95, 24.5 and 44.05 mm depth with a Baldwin-Farmer ionisation chamber (BFIC) connected to a Keithley 616 digital electrometer and with thermoluminescent dosimeters (TLD). The measurements were made under conditions similar to those in routine mammography using the automatic phototimers. The doses received per mammoradiograph as derived from the ionisation chamber differed greatly among the different hospitals: between 2 and 21 mGy for the entrance dose, 0.1 and 0.3 mGy for the exit dose and 0.8 and 4 mGy for the mean tissue dose. The mean absorbed dose in the breast per investigation varies from 2 to 9 mGy. (Auth.)

1983-01-01

104

Absorbed dose to mice in prolonged irradiation by low-dose rate ionizing radiation  

International Nuclear Information System (INIS)

In this paper, the dose absorbed by mice was evaluated as a preliminary study of the late effects of prolonged continuous irradiation of mice with low-dose rate ionizing radiation. Eight-week-old male and female SPF C3H/HeN mice in three irradiation rooms were exposed to irradiation at 8000, 400, and 20 mGy, respectively, using a 137Cs ?-source. Nine racks were arranged in a circle approximately 2.5 m from the source in each room, and 10 cages were arranged on the 4 shelves of each rack. Dose distributions, such as in air at the source level, in the three rooms were estimated by using ionization chambers, and the absorbed dose distributions in the room and relative dose distributions in the cages in relation to the distance of the cage center were examined. The mean abdomen doses of the mice measured by TLD were compared with the absorbed doses in the cages. The absorbed dose distributions showed not only inverse-inverse-square-law behavior with distance from the source, but geometric symmetry in every room. The inherent scattering and absorption in each room are responsible for such behavior and asymmetry. Comparison of relative dose distributions revealed cage positions that are not suitable for experiments with high precision doses, but all positions can be used for prolonged continuous irradiation experiments if the position of the cages is rotated regularly. The mean abdomen doses of the mice were similar in each cage. The mean abdomen doses of the mice and the absorbed doses in a cage were almost the same in all cages. Except for errors concerning the positions of the racks and cages, the uncertainties in the exposure doses were estimated to be about ±12% for 8000 mGy group, 17% for 400 mGy group, and 35% for 20 mGy group. (K.H.)

1999-10-20

105

Electron absorbed dose measurements in LINACs by thermoluminescent dosimeters.  

Science.gov (United States)

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

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

2014-01-01

106

Absorbed dose assessment in newborns during x-ray examinations  

Science.gov (United States)

Often a newborn presents breathing problems during the early days of life, i.e. bronchopneumonia, wich are caused in most of cases, by aspirating a mixture of meconium and amniotic fluid. In these cases, it is necessary to make use of a radiograph, requested by the physician to reach a diagnosis. This paper seeks to evaluate the absorbed doses in neonates undergoing a radiograph. For this reason we try to simulate the real conditions in a X-ray room from Lima hospitals. With this finality we perform a simulation made according a questionnaire related to technical data of X-ray equipment, distance between the source and the neonate, and its position to be irradiated. The information obtained has been used to determine the absorbed dose by infants, using the MCNP code. Finally, the results are compared with reference values of international health agencies.

Taipe, Patricia K.; Berrocal, Mariella J.; Carita, Raúl F.

2012-02-01

107

Some comments on the concept of absorbed dose  

International Nuclear Information System (INIS)

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

1998-01-01

108

Multilayer detector for measuring absorbed dose in skin  

International Nuclear Information System (INIS)

A method of skin dosimetry using multilayer dosimeters is described that allows the skin-depth distribution of absorbed dose to be estimated. A method of quantitative estimation and prediction of the degree of skin radiation damage using a three-layer dosimeter is demonstrated. Dosimeters are holders of tissue-equivalent material that contain photographic film, a scintillator, thermoluminophor, or any other radiation-sensitive element

1985-11-01

109

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

110

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)

2002-08-01

111

Use of osseoequivalent mixtures to measure absorbed doses  

International Nuclear Information System (INIS)

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

1981-01-01

112

Estimation of absorbed doses on the basis of cytogenetic methods  

Energy Technology Data Exchange (ETDEWEB)

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 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.)

Shevchenko, V.A.; Rubanovich, A.V. [N.I. Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow (Russian Federation); Snigiryova, G.P.

1998-03-01

113

An NPL absorbed dose calibration service for electron beam radiotherapy  

International Nuclear Information System (INIS)

The electron beam graphite calorimeter developed at the National Physical Laboratory (NPL) covers the dose range down 1 Gy at the dose rates used in radiotherapy. The recent measurement at NPL of the specific heat capacity of the graphite core has reduced the uncertainty in the determination of graphite absorbed dose to less than ± 0.5% at the 95% confidence level. Intercomparison with the NPL high energy X ray primary standard shows agreement to within 0.2%. A formalism is presented for a direct electron beam calibration service in terms of absorbed dose to water, based on the graphite calorimeter and using Spencer-Attix cavity ionization theory. A principal feature of the proposed method is the Monte Carlo calculation of the effective electron stopping powers under the calibration conditions at NPL. Measurements of stopping powers and fluence correction factors are also in progress. It is anticipated that the overall uncertainty in the calibration of a user chamber will be around ± 1.7% at the 95% confidence level. The advantages of such a service include improved accuracy, simplicity, no requirement for 60Co or X radiation, and independence from external influences on the long term stability. (author). 18 refs, 2 figs

1994-05-01

114

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)

1992-10-01

115

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)

2010-05-28

116

Absorbed dose to the fetus during bone scintigraphy.  

Science.gov (United States)

The authors observed the uptake of radiopharmaceutical and calculated absorbed dose in fetuses of two patients who underwent bone scintigraphy with technetium-99m methylene diphosphonate. Dose estimates per administered activity were 17 mrad/mCi (4.6 microGy/MBq) for an 8-week-old fetus and 9.7 mrad/mCi (2.6 microGy/MBq) for an 18-week-old fetus. Neither fetus demonstrated radionuclide uptake above maternal background levels. The uterine activity showed rapid clearance, with an effective half-life of 12 minutes after reaching a maximum within 1 minute after injection. Major contribution to fetal dose comes from the presence of the radionuclide in the maternal bladder. The authors conclude that bone scintigraphy performed unknowingly in pregnant individuals presents negligible increased risk to the fetus. PMID:3380967

Hedrick, W R; DiSimone, R N; Wolf, B H; Langer, A

1988-07-01

117

Radon concentrations and absorbed dose measurements in a Pleistocenic cave  

International Nuclear Information System (INIS)

Radon concentration measurements were carried out using solid-state nuclear track-etch detectors (SSNTDs) type CA 80-15 cellulose nitrate films, in a Pleistocenic cave at Petralona, in Halkidiki, Northern Greece, at 55 km from the city of Thessaloniki. Radon levels as high as 88 kBqxm-3 (2.38 nCi x l-1) have been recorded inside the cave equivalent to 11.90 WL in terms of occupational exposure to radon and its decay products. Absorbed dose rates were performed using TL dosimeters, type TLD-200 (CaF2-Dy) in a continuous monitoring program (integrated measurements). Dose rate levels as high as 110 nGy x h-1 were recorded inside the cave. In interpreting the high levels of radiation doses, radioactivity measurements regarding the naturally occurring 238U, 232Th and 40K radionuclides were carried out in various speleothems found at different sites in the cave. (author)

2003-10-01

118

Patient absorbed dose for the Philips Tomoscan 350 CT scanner: a repeat study  

International Nuclear Information System (INIS)

The study shows the importance not only of knowing the absorbed dose from a CT scanner, but also of redetermining the values following upgrading, when the absorbed dose can be markedly changed. (author)

1988-01-01

119

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

Science.gov (United States)

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

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

2014-05-01

120

Relationship between dose-area product and incidence dose, surface dose, organ doses, integral absorbed dose and effective dose  

International Nuclear Information System (INIS)

A continuous determination and recording of the dose-area product during X-ray examinations and, particularly, fluoroscopic procedures performed on a routine basis is a very important step towards further technical refinements to such measures, since - methodological errors can be pinpointed immediately; -any breakdowns in the technical equipment are recognized sooner using this method than by constancy investigations performed monthly or at even greater intervals; - knowledge of the dose-area product permits a more reliable assessment of risk-loaded doses to patients; - the recording of the dose-area product ensures an easier and more accurate documentation of the data to be obtained according to Section 28 of the X-Ray Ordinance in order to determine doses to patients. (orig./VHE)

1995-01-01

 
 
 
 
121

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

Directory of Open Access Journals (Sweden)

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

Keyhandokht Karimi Shahri

2010-10-01

122

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)

2012-12-12

123

Miniature thermoluminescent dosimeter absorbed dose measurements in tumor phantom models  

International Nuclear Information System (INIS)

Miniature teflon-imbedded CaSO_4:Dy thermoluminescent dosimeter(s) (TLD) have been sized and cut to fit inside a syringe needle. These dosimeters have been shown to be linear in response to beta and high energy gamma radiation. This allows for their direct implantation into tumor-bearing animals undergoing radioimmunotherapy and subsequent measurement of dose deposition on a per organ basis. In order to perform these radiolabeled antibody dose measurements with sufficient accuracy, static calibration data must first be generated. Consequently, phantom models were constructed with artificial tumors of diameters ranging from 3-30 mm contained in a surrounding tissue equivalent medium. The TLD were used to characterize dose distributions in a radial direction from the center of the cylindrical tumor volumes containing "1"3"1I, "3"2P, or "9"0Y radionuclides. Absorbed dose measurements in the boundary region between tumor and outer medium were found to be dependent on the: tumor specific activity, average range of the beta radiation, and radial tumor dimensions

1986-01-01

124

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

International Nuclear Information System (INIS)

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

2011-10-01

125

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

1979-01-01

126

Determination of the Absorbed Doses in Shanks of Interventional Radiologists  

International Nuclear Information System (INIS)

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

2008-05-29

127

Calibration of film dosimeters by means of absorbed dose calorimeters  

International Nuclear Information System (INIS)

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

1980-01-01

128

'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

129

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

International Nuclear Information System (INIS)

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

2013-01-01

130

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

1985-11-05

131

Calibration problems in the direct measurement of radiation absorbed dose  

International Nuclear Information System (INIS)

Radiation absorbed dose calorimetry is a direct method for measuring radiation energy deposition in a nuclear reactor environment. It is superior to indirect dosimetry methods, although the validity of the calorimetry technique is crucially dependent on the calibration procedures that are employed. In this paper calorimeter calibration methods and measurement procedures are critically examined. Calibration problems are considered in the context of three aspects of calorimetry measurements. The first is concerned with the compatibility of the dosimeter with the radiation field. Radiation disequilibrium can lead to significant measurement errors. Errors of instrumentation are then considered, and the problems of temperature stability and electronic noise are emphasized. The bulk of the paper is devoted to an examination of heat transfer aspects of the calibration problem. This area is considered in terms of heat transfer mechanisms and conditions that may lead to significant measurement errors. Calorimeter calibration problems are illustrated with examples from practical calorimetry measurements

1987-06-05

132

Evaluation of absorbed dose and image quality in mammography  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Mammography refers to the X-ray examination of the human breast, and is considered the single most important diagnostic tool in the early detection of breast cancer, which is by far the most common cancer among women. There is good evidence from clinical trials, that mammographic screening can reduce the breast cancer mortality with about 30%. The side effects include a small and age related risk of carcinogenesis due to the exposure of the glandular tissues in the breast to ionising radiatio...

Hemdal, Bengt

2009-01-01

133

Radiation absorbed dose and expected risk in head and neck tissues after thyroid radioiodine therapy  

International Nuclear Information System (INIS)

Measurement of absorbed dose in head and neck phantom after applying I-131 therapeutic dose for the treatment of thyroid malignancies was conducted. The measurement were carried out at several sites of phantom using TL dosimeters. The absorbed doses were also measured on the skin of four patients during their administration of I-131 therapeutic doses 1.332 GBq (36 mci) I-131. The measurements were taken over 69 hours exposure at different sites of phantom. The same measurements were carried out on the four patients. At five sites of the patients head and neck, the absorbed dose were measured and compared with that measured on the phantom. The values measured are discussed in the light of the published individual absorbed doses in the organs by ICRP tables. High absorbed doses were absorbed in the different sites of the head and neck during the I-131 therapy (0.14-9.68 mGy/mCi). 3 figs., 2 tabs

1996-11-13

134

Implementation of an absorbed dose postal QA programme for radiosurgery  

International Nuclear Information System (INIS)

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

2006-11-13

135

A method for calculating absorbed dose in tissue by Cs-137 needle using EGS4  

International Nuclear Information System (INIS)

A method using dose rate constant and anisotropy function for calculating absorbed dose distribution in brachytherapy has been recommended by AAPM Report no.51. In 2003, the radiation treatment planning equipment with the method for obtaining the absorbed dose distribution in brachytherapy using Cs-137 needles was introduced into Department of Radiology, Nagoya University Hospital. The method beforehand requires radial dose functions g(r) and anisotropy functions F(r, ?). These functions are decided from known absorbed dose. However, it is difficult technologically to measure the absorbed dose distribution in the vicinity of the Cs-137 needle for brachytherapy. Therefore, we obtained these functions after the absorbed had been calculated using a conventional method. The absorbed dose distribution calculated by the conventional method must be compared with the measurement one. In order to verify the accuracy of this method, we compared the absorbed dose distribution obtained with this method and that obtained with EGS4 Monte Carlo simulation. Furthermore, we examined the influence of the geometry of the needle source to the absorbed dose distribution. As a result, both absorbed dose distributions obtained by two methods were good agreement with each other. In addition, there was little influence to the dose distribution on the basis of a difference of the geometry on both ends of the needle. (author)

2004-02-01

136

Scaling neutron absorbed dose distributions from one medium to another  

Energy Technology Data Exchange (ETDEWEB)

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

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

1982-11-01

137

Scaling neutron absorbed dose distributions from one medium to another  

International Nuclear Information System (INIS)

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

1982-01-01

138

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

International Nuclear Information System (INIS)

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

1982-06-11

139

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

International Nuclear Information System (INIS)

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

1995-01-01

140

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

1979-09-21

 
 
 
 
141

Absorbed dose measurement and LET determination with TLDs in space  

International Nuclear Information System (INIS)

For determination of the average LET in complex mixed radiation fields, a new method was developed using the LET dependent changes of the peak height ratios in thermoluminescence glow curves (HTR). Various types of standard and laboratory made TLDs were calibrated in alpha, beta, gamma and neutron fields and in heavy charged particles beams. These calibrated TL phosphors were used on space station MIR in order to determine the equivalent dose. During the long-term mission of 5 months in the summer of 1991 the dose rate was 0.24 ± 0.01 mGy.d-1 with an average LET (tissue) of 6.2 ± 0.25 keV.?m-1, and during an 8 day short-term mission October 1991 0.204 ± 0.003 mGy.d-1 with a LET of 6.5 ± 0.30 keV.?m-1. The new method was alos used for measurements carried out on satellite PHOTON-8 (1992) and on satellite BION-10 (1993) to obtain more information about the changes of the average LET of space radiation with the variation of the shielding. An increase in the average LET from 0.35 to 10 keV.?-1 dependent on the absorber thickness from 1.14 mg.cm-2 to 2.5 g.cm-2 was measured. The method was also used for determination of the characteristics of the low energy electron component of space radiation on BION-10 and for the determination of the average LET on board high altitude aircraft. (author)

1995-07-10

142

Scaling neutron absorbed dose distributions from one medium to another  

Energy Technology Data Exchange (ETDEWEB)

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

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

1983-07-01

143

Scaling neutron absorbed dose distributions from one medium to another  

International Nuclear Information System (INIS)

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

1983-01-01

144

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 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)

2007-01-01

145

Absorbed dose determination in photon fields using the tandem method  

CERN Document Server

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

Marques-Pachas, J F

1999-01-01

146

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

International Nuclear Information System (INIS)

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

2008-12-01

147

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

2002-12-01

148

Advances in absorbed dose measurement standards at the australian radiation laboratory  

Energy Technology Data Exchange (ETDEWEB)

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

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

1996-12-31

149

Advances in absorbed dose measurement standards at the australian radiation laboratory  

International Nuclear Information System (INIS)

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

1996-11-10

150

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 (105â??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 (1â??1014 rad sâ??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 (0.01â??10 MeV).

McLaughlin, W. L.; Miller, Arne

1977-01-01

151

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.)

1980-01-01

152

Absorbed dose measurements in photon and electron beams using AAPM TG-21 protocol  

International Nuclear Information System (INIS)

The AAPM TG-21 protocol takes into account the chamber dependent and radiation dependent parameters in determining the absorbed dose. Absorbed dose measurements are done for photon and electron beams using this protocol. Two cylindrical chambers of different wall materials and a flat chamber are made use of. The response of the chambers have been studied. (author). 2 refs., 3 figs., 4 tabs

1994-01-01

153

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

154

Shift in absorbed dose for megavoltage photons when changing to TRS-398 in Australia  

International Nuclear Information System (INIS)

Australian primary standards of air kerma and absorbed dose are realized in 60Co gamma rays. To calibrate the megavoltage photon beams from linear accelerators, radiotherapy centres have their ionization chamber calibrated in a 6 Co beam and then use a protocol to transfer this calibration to the higher energy. The radiotherapy community is in the process of changing from the ACPSEM Protocol (Second Edition 1998) based on an air kerma calibration to the IAEA's TRS-398 Code of Practice, based on an absorbed dose to water calibration. To evaluate the shift in absorbed dose resulting from the new protocol, the absorbed dose should be determined using both protocols and compared. We present a formula for this shift which can be used to check the result. To use this formula the centre needs to measure a displacement correction and know the ratio of the air kerma to absorbed dose to water calibration factors at 60)Co. We calculate the change they should expect by using the average ratio of the air kerma and absorbed dose to water calibration factors for NE2571 and NE2561 chambers, based on Australian standards, and by estimating the displacement correction from published depth dose data. We find the absorbed dose in a megavoltage photon beam to increase by between 0.1 and 0.6% for NE2571 chambers and between 0.7 and 1.1% for NE2561 chambers, for beams up to 35 MV. The dose measured using TRS-398 is always higher

2005-09-01

155

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 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.

2010-08-07

156

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

Science.gov (United States)

The performance of two digital mammography systems, Agfa CR75 and CRMM3 computed radiography (CR) and IMS Giotto MD direct digital radiography (DR), was assessed by applying a method recommended in the European protocol for quality control in mammography screening. The contrast-to-noise ratio (CNR) and mean glandular dose (MGD) values were measured and contrast detail (CD) analysis was performed. The CNRs for system CR were 21.9, 12.9, 9.5, 8.8, 7.4, 5.5 and 4.4 for 2, 3, 4, 4.5, 5, 6 and 7-cm polymenthylmethacrylate (PMMA) thickness, respectively. The respective CNRs for system DR were 10.4, 8.8, 6.3, 7.3, 7.2, 6.4 and 6.54. For the same phantom thickness sequence, the MGDs were 0.7, 1.1, 1.3, 1.6, 1.9, 2.5 and 3.4 mGy for system CR, whereas they were 0.7, 1.2, 1.1, 1.3, 1.8, 3.5 and 3.9 mGy for system DR. The CNR and MGD results satisfactorily correlate with CD analysis results. The MGD values compare well with the values recommended in the European protocol. Despite being simple, CNR and MGD can provide an effective system for performance assessment and constancy checks for related optimisations. PMID:18283065

Muhogora, W E; Devetti, A; Padovani, R; Msaki, P; Bonutti, F

2008-01-01

157

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

International Nuclear Information System (INIS)

In bone-equivalent materials two different calculations of absorbed dose are possible: the absorbed dose to soft tissue plastic (polystyrene) within bone-equivalent material and the dose to the bone-equivalent material itself. Both can be calculated from ionization measurements in phantoms. These two calculations result in significantly different doses in a heterogeneous phantom composed of polystyrene and aluminium (a bone substitute). The dose to a thin slab of polystyrene in aluminium is much higher than the dose to the aluminium itself at the same depth in the aluminium. Monte Carlo calculations confirm that the calculation of dose to polystyrene in aluminium can be accurately carried out using existing dosimetry protocols. However, the conversion of ionization measurements to absorbed dose to high atomic number materials cannot be accurately carried out with existing protocols and appropriate conversion factors need to be determined. (author)

1992-11-01

158

Determination of Absorbed Dose in Large 60-Co Fields Radiotherapy  

International Nuclear Information System (INIS)

Radiation in radiotherapy has selective impact on ill and healthy tissue. During the therapy the healthy tissue receives certain amount of dose. Therefore dose calculations in outer radiotherapy must be accurate because too high doses produce damage in healthy tissue and too low doses cannot ensure efficient treatment of cancer cells. A requirement on accuracy in the dose calculations has lead to improvement of detectors, and development of absolute and relative dosimetry. Determination of the dose distribution with use of computer is based on data provided by the relative dosimetry. This paper compares the percentage depth doses in cubic water phantoms of various dimensions with percentage depth doses calculated with use of Mayneord factor from the experimental depth doses measured in water phantom of large dimension. Depth doses in water phantoms were calculated by the model of empirical dosimetrical functions. The calculations were based on the assumption that large 6"0"Co photon field exceeds the phantom's limits. The experimental basis for dose calculations by the model of empirical dosimetrical functions were exposure doses measured in air and dose reduction factors because of finite phantom dimensions. Calculations were performed by fortran 90 software. It was found that the deviation of dosimetric model was small in comparison to the experimental data. (author)

2003-04-09

159

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

160

Gamma-ray absorbed dose measurements in media with plural thermoluminescent dosimeters having different atomic numbers  

International Nuclear Information System (INIS)

Corrective factors for thermoluminescent dosimeters to obtain the ?-ray dose in materials are examined systematically based on a general cavity ionization theory, and an experimental method; interpolation method, is presented for measuring the ?-ray absorbed dose in materials using thermoluminescent dosimeters with different atomic numbers. A characteristic feature of the method is to measure the ?-ray absorbed dose in materials without any ?-ray spectrum information. In order to examine the feasibility, the absorbed doses are measured in iron, lead and polyethylene media with a "6"0Co ?-ray source, and compared with a transport calculations whose accuracy is already verified. It is shown that the ?-ray absorbed doses measured using the present method agree with the calculated ones within +-5 to +-10%. (author)

1985-01-01

 
 
 
 
161

Determination of high level absorbed dose in a 60Co gamma ray field with ionization chambers  

International Nuclear Information System (INIS)

This paper relates to the principles and methods for determining the absorbed dose of high energy photons radiation with ionization chambers, and its shows the doserate results of high level 60Co ?-rays in water measured with Farmer chambers. The results with two kinds of chambers at a same point are consistent within 0.3%, and the total uncertainty is less than ± 4%. In the domestic intercomparison on determining high level absorbed dose in which 12 laboratories participated, the deviation of our result from the mean result of the intercomparison is -0.04% [Chen Yundong (1992). Summing up report on a high level absorbed dose intercomparison (in Chinese)]. (author)

1995-02-01

162

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1981-01-01

163

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1981-10-01

164

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

International Nuclear Information System (INIS)

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

1981-01-01

165

Simple approximation for estimating centerline gamma absorbed dose rates due to a continuous Gaussian plume  

International Nuclear Information System (INIS)

A simple approximation for estimating the centerline gamma absorbed dose rates due to a continuous Gaussian plume was developed. To simplify the integration of the dose integral, this approach makes use of the Gaussian cloud concentration distribution. The solution is expressed in terms of the I1 and I2 integrals which were developed for estimating long-term dose due to a sector-averaged Gaussian plume. Estimates of tissue absorbed dose rates for the new approach and for the uniform cloud model were compared to numerical integration of the dose integral over a Gaussian plume distribution

1987-01-01

166

Simple approximation for estimating centerline gamma absorbed dose rates due to a continuous Gaussian plume  

Energy Technology Data Exchange (ETDEWEB)

A simple approximation for estimating the centerline gamma absorbed dose rates due to a continuous Gaussian plume was developed. To simplify the integration of the dose integral, this approach makes use of the Gaussian cloud concentration distribution. The solution is expressed in terms of the I1 and I2 integrals which were developed for estimating long-term dose due to a sector-averaged Gaussian plume. Estimates of tissue absorbed dose rates for the new approach and for the uniform cloud model were compared to numerical integration of the dose integral over a Gaussian plume distribution.

Overcamp, T.J.; Fjeld, R.A.

1987-08-01

167

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, D(g).(N). These quantities were studied for different breast thicknesses and compositions, anode/filter combinations and tube potentials. Results showed that the S/P increases linearly with breast thickness, varying slightly with breast composition or the spectrum used. Evaluation of grid performance showed that the cellular grid provides the highest CIF with smaller BF. The SIF was also greater for the cellular grid, although both grids showed SIF < 1 for thin breasts. Results for D(g).(N) showed that it increases with the half-value layer (HVL) of the spectrum, decreases considerably with breast thickness and has a small dependence on the anode/filter combination. Inclusion of interference effects of breast tissues affected the values of S/P obtained with the grid up to 25%, while the energy broadening effect produced smaller variations on the evaluated quantities. PMID:20647608

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

2010-08-01

168

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

169

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

International Nuclear Information System (INIS)

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

1995-01-01

170

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

171

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

Energy Technology Data Exchange (ETDEWEB)

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

Neves, M.; Waerenborgh, F.; Patricio, L.

1987-01-01

172

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

International Nuclear Information System (INIS)

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

1987-01-01

173

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

International Nuclear Information System (INIS)

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

2010-09-22

174

Patient absorbed dose for Philips Tomoscan 300 CT scanner  

Energy Technology Data Exchange (ETDEWEB)

As part of a series of performance evaluation tests on the Philips Tomoscan 300 (T300) CT whole body scanner, at St. James's Hospital, Leeds, the authors have measured mean surface and core dose with anthropomorphic phantoms for all techniques regularly employed. Doses have been measured for a typical adult head and body section and a paediatric head and body section.

Jones, K.R. (Saint James' s University Hospital, Leeds (UK). Medical Physics Unit); Garrett, J.H. (Cookridge Hospital, Leeds (UK))

1985-04-01

175

Patient absorbed dose for Philips Tomoscan 300 CT scanner  

International Nuclear Information System (INIS)

As part of a series of performance evaluation tests on the Philips Tomoscan 300 (T300) CT whole body scanner, at St. James's Hospital, Leeds, the authors have measured mean surface and core dose with anthropomorphic phantoms for all techniques regularly employed. Doses have been measured for a typical adult head and body section and a paediatric head and body section. (author)

1985-01-01

176

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

International Nuclear Information System (INIS)

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

1985-09-15

177

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

Energy Technology Data Exchange (ETDEWEB)

A method to obtain the absorbed dose in Drosophila melanogaster irradiated in the thermal column facility of the Triga Mark III Reactor has been developed. The method is based on the measurements of neutron activation of gold foils produced by neutron capture to obtain the neutron fluxes. These fluxes, combined with the calculations of kinetic energy released per unit mass, enables one to obtain the absorbed doses in Drosophila melanogaster00.

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

2001-11-01

178

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

International Nuclear Information System (INIS)

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

2001-11-01

179

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 di...

2006-01-01

180

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)

2001-07-09

 
 
 
 
181

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2013-01-01

182

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, 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

2004-06-01

183

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

184

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

International Nuclear Information System (INIS)

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

1997-12-01

185

Biological indicators for radiation absorbed dose: a review  

International Nuclear Information System (INIS)

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

1996-01-01

186

Difference in radiation absorbed dose according to the panoramic radiographic machines  

International Nuclear Information System (INIS)

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

2000-03-01

187

Difference in radiation absorbed dose according to the panoramic radiographic machines  

Energy Technology Data Exchange (ETDEWEB)

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

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

2000-03-15

188

Calculation of absorbed dose from neutron irradiation by application of threshold-foil measurement data  

International Nuclear Information System (INIS)

The standard method outlines a procedure for calculating the absorbed dose in a material given the material composition, the neutron fluence, and threshold-foil data related to the neutron spectrum. The method is applicable to fast-pulsed reactors of the Godiva or TRIGA type, where a substantial fraction of the neutron fluence exceeds epithermal energies (that is, E > 0.01 MeV). A material exposed to the mixed neutron and gamma-ray radiation from such a reactor absorbs energy from both components. This method provides a procedure for calculating the neutron absorbed dose, and a companion standard, Method E 666, describes a technique for calculating the absorbed dose resulting from the gamma-ray component. The method is limited to materials for which tabulated kerma factors are available

1981-01-01

189

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 Ã? 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 â??430 nm.

McLaughlin, W.L.; Miller, Arne

1985-01-01

190

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 (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 x 10"6 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 lowintensity 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 about 430 nm

1984-01-01

191

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 10"6 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)

1984-10-21

192

Air kerma and absorbed dose on the torso of a patient during a mammography study;Kerma en aire y dosis absorbida en el torso de una paciente durante un estudio mastografico  

Energy Technology Data Exchange (ETDEWEB)

Two dosimetric magnitudes, due to the dispersed radiation, have been determined during a mammography study. The magnitudes that were determined are the kerma at the entrance of the torso and the absorbed dose by the torso. This determination was made in a paraffin phantom and with thermoluminescent dosemeters. One of the important parameters in the radiological protection of a patient to which is practiced a mammography is the value of the media glandular dose. However, during the taking of the X-ray a radiation portion that impacts on the mammary gland it is dispersed toward the patient's torso. In this work thermoluminescent dosemeters of ZrO{sub 2} has been used to determine the kerma at the entrance of the torso like the absorbed dose. The dosemeters was placed on the surface of the torso phantom while to the mamma phantom was made the mammography. As mamma phantom was used glucose serum to 5%. Of the obtained results we find that 3% of the air kerma at the entrance of the mamma it corresponds at the air kerma that receives the torso and 3.2% of the media glandular dose it is the absorbed dose of the same one. Another important result is the percentage value of the air kerma on the entrance of the thyroid area during a mammography, due to the dispersed radiation, it is 4% of the kerma at the entrance of the mamma. The air kerma at the entrance of the thyroid is of 0.41 +-0.07 mGy, 10% of this value corresponds to the absorbed dose by the thyroid. Therefore, it is observed that the media glandular dose and the air kerma at the entrance of the mamma they influence on the dispersed radiation toward the torso. Also, the superior part of the torso has less attenuation capacity to the dispersed radiation that those located in the inferior part. Therefore, the thyroid receives the major quantity of air kerma at the entrance. (Author)

Hernadez O, M.; Duran M, H. A.; Pinedo S, A.; Gonzalez G, R.; Guerra M, J. A.; Salas L, M. A.; Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Calle Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Rivera M, T. [IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Av. Legaria 694, 11500 Mexico D. F. (Mexico); Azorin N, J., E-mail: mar_h2o@hotmail.co [Universidad Autonoma Metropolitana, Unidad Iztapalapa, Av. San Rafael Atlixco 186, 09340 Mexico D. F. (Mexico)

2009-10-15

193

Absorb dose measurement on solid water phantom by TLD  

International Nuclear Information System (INIS)

The purpose of this study is to model the absorption of gamma rays by skin of head and neck cancer patients which are represented by solid water phantom. The absorptive doses by solid water phantom(1) with and without masked are measured by Thermoluminescence dosimeter (TLD; LiF). The two opposing field technique is utilised, using the dose of 90:90, 100:100, 125:125 and 150:150 cGy, respectively. The gamma source is Co-60 exposing to solid water phantom. The study shows that the skin dose in masked solid water phantom was higher than in unmasked condition with the ratio of 1.18:1.00. The results suggest a mean to aid radiation treatment technique planning

2003-06-19

194

Absorbed dose measurement on disprin tablets by ESR technique  

International Nuclear Information System (INIS)

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

1993-01-01

195

Absorbed dose and operation time as parameters of the P.I.BA operation  

Energy Technology Data Exchange (ETDEWEB)

The PIBA (BArros Irradiation Plant), a sewage irradiation plant has being built at Tucuman (Argentina) the National Commission of Atomic Energy. It is designed for insure an absorbed dose of 2 kGy (3 kGy without oxygenation) to 140 m{sup 3}/day of sludge by gamma irradiation from {sup 60} Co sources. To guarantee that almost all the volume of the irradiate sludge had absorbed at least the fixed dose is more important that its volume uniformity since the desired effect of the treatment is to produce a harmless sewage in respect to the risk diseases. The objective of this work is the calculation if the absorbed dose related to the irradiation time, the operation time and the sources geometry and activity. Mathematical models are developed for obtaining the volume distribution of the absorbed dose. An absorbed dose {>=} 2 kGy is required for the 99.8% of the irradiated sludge volume. Achieving the threshold dose depends upon the total activity which determines the daily time of operation. A numerical set of the major interrelated parameters is given for the efficient operation of the PIBA. (author). 5 refs., 3 figs., 1 tab.

Mangussi, M.J. [Universidad Tecnologica Nacional, Tucuman (Argentina); Graino, Jorge C. [Comision Nacional de Energia Atomica, Buenos Aires (Argentina). Centro Atomico Ezeiza

1997-10-01

196

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

International Nuclear Information System (INIS)

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

2002-04-17

197

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)

1998-11-11

198

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

International Nuclear Information System (INIS)

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

1982-09-15

199

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

International Nuclear Information System (INIS)

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

2009-07-08

200

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)

2000-01-01

 
 
 
 
201

Radiation absorbed dose to the human fetal thyroid  

International Nuclear Information System (INIS)

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

1992-05-01

202

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

203

Calculation of absorbed doses in an organ using the MIRD method  

International Nuclear Information System (INIS)

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

1983-01-01

204

The Relationship between Blood Injury and Absorbed Dose in Criticality Accidents  

International Nuclear Information System (INIS)

The neutron and gamma doses to individuals exposed in criticality accidents have been recalculated to yield the surface-absorbed dose to the trunk of the body. The relationship is examined between this dose estimate and blood-count profile scores that are based on the scoring system of N. Wald and G. E. Thoma for deviations from the normal of the lymphocyte, neutrophil and platelet-peripheral blood counts. It is shown that a quantity based on the surface-absorbed gamma dose and the Na24 activity in the blood shows a better correlation with the blood-count profile score and is a better prognostic guide for the degree of radiation injury than any of the conventional dose estimates. The R. B. E's of the heavy-particle recoil doses deduced from these observations are consistent in general with values obtained from experiments on dogs. (author)

1964-03-01

205

Analysis of absorbed dose distribution in head phantom in boron neutron capture therapy  

Energy Technology Data Exchange (ETDEWEB)

The absorbed dose rate from different reactions in a head phantom is investigated. The investigation involves both thermal and non-thermal neutrons. The calculation of absorbed dose rate was achieved by simulating the head by a slab containing a tumor-like volume. It was supposed that the elements constituting the head were H, O, N, C and Na with their natural density. Isotope {sup 10}B was introduced artificially with a concentration of 10 ppm in normal tissue and 30 ppm in tumor. The absorbed dose rate from {sup 1}H(n, {gamma}){sup 2}H, {sup 14}N(n, p){sup 14}C, {sup 10}B(n, {alpha}){sup 7}Li, proton recoil, {sup 1}H(n, {gamma}){sup 2}H and all (n, {gamma}) reactions both for thermal and non-thermal neutrons were considered. The major contribution to the total absorbed dose rate at the scalp surface was obtained to be due to the recoil protons (fast neutrons dose), whereas it has the least contribution in the tumor. Apart from the boron dose, the dose resulting from hydrogen capture gamma is the highest value in the tumor compared to those from other reactions.

Marashi, M.K

2000-02-01

206

Analysis of absorbed dose distribution in head phantom in boron neutron capture therapy  

International Nuclear Information System (INIS)

The absorbed dose rate from different reactions in a head phantom is investigated. The investigation involves both thermal and non-thermal neutrons. The calculation of absorbed dose rate was achieved by simulating the head by a slab containing a tumor-like volume. It was supposed that the elements constituting the head were H, O, N, C and Na with their natural density. Isotope 10B was introduced artificially with a concentration of 10 ppm in normal tissue and 30 ppm in tumor. The absorbed dose rate from 1H(n, ?)2H, 14N(n, p)14C, 10B(n, ?)7Li, proton recoil, 1H(n, ?)2H and all (n, ?) reactions both for thermal and non-thermal neutrons were considered. The major contribution to the total absorbed dose rate at the scalp surface was obtained to be due to the recoil protons (fast neutrons dose), whereas it has the least contribution in the tumor. Apart from the boron dose, the dose resulting from hydrogen capture gamma is the highest value in the tumor compared to those from other reactions

2000-02-01

207

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

1978-01-01

208

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

209

Absorbed dose calculations using mesh-based human phantoms and Monte Carlo methods  

International Nuclear Information System (INIS)

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

2010-09-07

210

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

International Nuclear Information System (INIS)

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

2001-12-01

211

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2001-12-15

212

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

International Nuclear Information System (INIS)

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

2007-03-01

213

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

214

Radiation absorbed dose from technetium-99m DTPA  

International Nuclear Information System (INIS)

The whole-body retention of intravenously administered [99mTc]DTPA was measured by urine analysis and whole-body counting in eight normal subjects. On average, the elimination of [99mTc]DTPA was faster in these subjects than in 11 patients under study for hypertension whose whole-body retention data were used in MIRD Dose Estimate Report No. 12. The average residence time for [99mTc]DTPA in total body, less bladder contents, was only 65% of the MIRD value. However, despite this difference, the dosimetry is similar in both cases largely owing to the influence of radioactivity in bladder contents. Approximately 2-3% of the administered radioactivity was retained in the body for a time that was long relative to the physical half-life of 99mTc, and probably reflects a small amount of protein binding of the DTPA preparation

1987-01-01

215

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-12-15

216

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

International Nuclear Information System (INIS)

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

2012-12-01

217

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

International Nuclear Information System (INIS)

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

1986-01-01

218

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

International Nuclear Information System (INIS)

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

2011-11-01

219

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

International Nuclear Information System (INIS)

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

1985-01-01

220

Absorbed dose in target cell nuclei and dose conversion coefficient of radon progeny in the human lung  

International Nuclear Information System (INIS)

To calculate the absorbed dose in the human lung due to inhaled radon progeny, ICRP focussed on the layers containing the target cells, i.e., the basal and secretory cells. Such an approach did not consider details of the sensitive cells in the layers. The present work uses the microdosimetric approach and determines the absorbed alpha-particle energy in non-spherical nuclei of target cells (basal and secretory cells). The absorbed energy for alpha particles emitted by radon progeny in the human respiratory tract was calculated in basal- and secretory-cell nuclei, assuming conical and ellipsoidal forms for these cells. Distributions of specific energy for different combinations of alpha-particle sources, energies and targets are calculated and shown. The dose conversion coefficient for radon progeny is reduced for about 2 mSv/WLM when conical and ellipsoidal cell nuclei are considered instead of the layers. While changes in the geometry of secretory-cell nuclei do not have significant effects on their absorbed dose, changes from spherical to conical basal-cell nuclei have significantly reduced their absorbed dose from ?4 to ?3 mGy/WLM. This is expected because basal cells are situated close to the end of the range of 6 MeV alpha particles. This also underlines the significance of better and more precise information on targets in the T-B tree. A further change in the dose conversion coefficient can be achieved if a different weighting scheme is adopted for the doses for the cells. The results demonstrate the necessity for better information on the target cells for more accurate dosimetry for radon progeny

2006-01-01

 
 
 
 
221

Absorbed dose in target cell nuclei and dose conversion coefficient of radon progeny in the human lung  

Energy Technology Data Exchange (ETDEWEB)

To calculate the absorbed dose in the human lung due to inhaled radon progeny, ICRP focussed on the layers containing the target cells, i.e., the basal and secretory cells. Such an approach did not consider details of the sensitive cells in the layers. The present work uses the microdosimetric approach and determines the absorbed alpha-particle energy in non-spherical nuclei of target cells (basal and secretory cells). The absorbed energy for alpha particles emitted by radon progeny in the human respiratory tract was calculated in basal- and secretory-cell nuclei, assuming conical and ellipsoidal forms for these cells. Distributions of specific energy for different combinations of alpha-particle sources, energies and targets are calculated and shown. The dose conversion coefficient for radon progeny is reduced for about 2 mSv/WLM when conical and ellipsoidal cell nuclei are considered instead of the layers. While changes in the geometry of secretory-cell nuclei do not have significant effects on their absorbed dose, changes from spherical to conical basal-cell nuclei have significantly reduced their absorbed dose from {approx}4 to {approx}3 mGy/WLM. This is expected because basal cells are situated close to the end of the range of 6 MeV alpha particles. This also underlines the significance of better and more precise information on targets in the T-B tree. A further change in the dose conversion coefficient can be achieved if a different weighting scheme is adopted for the doses for the cells. The results demonstrate the necessity for better information on the target cells for more accurate dosimetry for radon progeny.

Nikezic, D. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong (China); Faculty of Science, University of Kragujevac R. Domanovic 12, 34000 Kragujevac (Serbia and Montenegro); Lau, B.M.F. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong (China); Stevanovic, N. [Faculty of Science, University of Kragujevac R. Domanovic 12, 34000 Kragujevac (Serbia and Montenegro); Yu, K.N. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong (China)]. E-mail: appetery@cityu.edu.hk

2006-07-01

222

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

Energy Technology Data Exchange (ETDEWEB)

Absorbed dose in a liquid substitute for bone has been compared with absorbed dose in water for 9-, 12-, and 15-MeV electron beams using ionization chamber measurements. The ionization readings were converted to dose using collisional mass stopping power ratios. The collisional mass stopping powers for the liquid substitute of bone were calculated using the Monte Carlo Code PEGS4. The results of our study show that there is an increase in dose in the liquid bone substitute compared to water at shallow depths. The maximum increase in dose was 5%, 4%, and 2% at depths of 1.2, 1.5, and 2.0 cm, respectively, for 9-, 12-, and 15-MeV electrons. The density of the liquid bone substitute was 1360 kg/m/sup 3/ and the effective atomic number was 11.

Prasad, S.C.; Bassano, D.A.

1989-01-01

223

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

International Nuclear Information System (INIS)

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

1977-01-01

224

The standard absorbed dose in a medium ''M'' as a quantity to replace exposure  

International Nuclear Information System (INIS)

In order to replace exposure, at least as a calibration value, a more general dosimetric quantity is here proposed, namely the standard dose absorbed in a medium M, defined at any point in a photon field as 'the dose absorbed at the centre of a sphere filled with a material M, having its centre at the point under consideration and a radius equal to the maximum range of any electron brought into motion within it or incident upon it, and corrected for perturbation, by the sphere, of the energy fluence of the photons present at the point under consideration.' From the practical point of view, the absorbed dose thus specified possesses the following main advantages: its definition does not fix the reference material and leaves the choice thereof free depending on the field of application (for purposes of biomedical dosimetry this material would, of course, be water and the concept then concerns the 'standard dose in water'); the close and simple relationship with exposure would make it possible for metrology laboratories to establish calibration services in terms of standard dose unambiguously linked to the present exposure standards; calibration of a dose meter in terms of standard dose, for example in a cobalt-60 photon beam, would make it possible - for purposes of proceeding to mean dose calibration in the cavity - to apply a procedure fully analogous to that at present based on exposure calibration. (author)

1980-10-31

225

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)

2008-10-19

226

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

1992-01-01

227

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

1986-01-01

228

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1986-02-01

229

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

International Nuclear Information System (INIS)

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

1992-01-01

230

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)

2010-02-01

231

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

232

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)

2001-03-01

233

Measurement of absorbed dose during the phantom torso experiment on the International Space Station  

Science.gov (United States)

The Phantom Torso Experiment (PTE) was flown on the International Space Station (ISS) during Increment 2 (April-August 2001). The experiment was located in the US Lab module Human Research Facility (HRF) rack. The objective of the passive dosimetry portion of the experiment was to measure spatial distributions of absorbed dose in the 34, 1 inch sections of a modified RandoTM phantom. In each section of the phantom, thermoluminescent detectors (TLDs) were placed at various locations (depths) to provide the spatial measurement. TLDs were also located at several radiosensitive organ locations (brain, thyroid, heart/lung, stomach and colon) and two locations on the surface (skin). Active silicon detectors were also placed at these organ locations to provide time resolved results of the absorbed dose rates. Using these detectors, it is possible to separate the trapped and galactic cosmic ray components of the absorbed dose. The TLD results of the spatial and organ dose measurements will be presented and comparisons of the TLD and silicon detector organ absorbed doses will be made.

Semones, E.; Gibbons, F.; Golightly, M.; Weyland, M.; Johnson, A.; Smith, G.; Shelfer, T.; Zapp, N.

234

[A comparison of absorbed doses to water in photon beams in Japan Society of Medical Physics 01 and 12].  

Science.gov (United States)

A comparison of absorbed doses to water at a calibration depth determined by Japan Society of Medical Physics (JSMP) 12 and 01 was conducted, using a farmer type ionization chamber. The absorbed dose to water calibration factor (ND,W,Q0) and beam quality conversion factor (kQ,Q0) for JSMP 12 were smaller than the absorbed dose to water calibration factor and beam quality conversion factor for JSMP 01. Differences in absorbed doses at a calibration depth were -0.78% for 6 MV photon beam and -0.94% for 10 MV photon beam. In the present experiment, absorbed doses at a calibration depth were measured, using a farmer type ionization chamber. Further experiments at a larger number of facilities should be conducted to reveal the status of measurement of absorbed doses at a calibration depth using JSMP 12. PMID:23514857

Kinoshita, Naoki; Takemura, Akihiro; Nishimoto, Yasuhiro; Kita, Akinobu; Toi, Akiko; Murai, Emi; Shimada, Masato; Sasamoto, Kouhei; Adachi, Toshiki

2013-03-01

235

Absorbed doses from computed tomography for dental implant surgery: comparison with conventional tomography.  

Science.gov (United States)

Tomography is often needed prior to implant surgery to evaluate jaw bone dimensions. Computed tomography (CT) is advocated as an alternative. The purpose of this study was to measure the absorbed doses to radiosensitive organ in the head and neck region when CT is used. Measurements were made with extruded LiF thermoluminescent dosemeters within and on an anthropomorphic phantom examined with a Philips Tomoscan LX CT scanner. Axial scanning was performed for the maxilla and both frontal, perpendicular to the alveolus, and axial for the mandible. The highest absorbed doses were at the skin surface, 38 mGy with maxillary scans, and from axial and frontal scans of the mandible 35 mGy and 37 Gy, respectively. The parotid dose was 31 mGy from maxillary scans and in the mandible the submandibular gland dose was 27 mGy with axial scanning and 16 mGy with frontal. The eye lens received its highest dose (5.5 mGy) from frontal scans of the mandible. Although outside the scanning plane the pituitary and the thyroid glands received comparatively high absorbed doses of 0.6-4.0 mGy. All organ doses measured were considerably higher than those reported for conventional tomography. PMID:8508935

Ekestubbe, A; Thilander, A; Gröndahl, K; Gröndahl, H G

1993-02-01

236

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

International Nuclear Information System (INIS)

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

2005-01-01

237

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)

2001-11-01

238

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

Science.gov (United States)

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

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

2014-05-01

239

The distribution of absorbed dose-rates in humans from exposure to environmental gamma rays  

International Nuclear Information System (INIS)

The propagation of environmental ? rays through the human body was calculated using the 3-dimensional Monte-Carlo code DISDOS. These calculations were performed with the aim of determining the gonadal dose with a statistical accuracy of 10 % or less for each of the energies considered. The ratio of exposure to absorbed dose in the human body averages about 0.6. A mean annual gonadal dose produced by environmental ? rays in the U.S. was calculated to be 32 +- 4 % mrad/yr. The mean annual dose to the red marrow was calculated to be 29 +- 0.1 % mrad/yr (the errors cited being purely statistical). (author)

1976-01-01

240

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2013-01-01

 
 
 
 
241

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. D_m_a_x/D_m_i_n in this study was 1.45 irradiated in a commercial "6"0Co facility. The density of orange containers was about 0.391g/cm"3. 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)

2001-03-01

242

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

International Nuclear Information System (INIS)

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

2005-11-01

243

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1987-11-01

244

MCNP simulation of absorbed energy and dose by iodinated contrast agent  

Science.gov (United States)

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

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

2012-02-01

245

Status of air kerma and absorbed dose standards in India  

International Nuclear Information System (INIS)

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

2002-11-25

246

Dosimetry of interstitial brachytherapy using radiophotoluminescence glass. On absorbed dose of anterior wall of the rectum  

Energy Technology Data Exchange (ETDEWEB)

It has been almost impossible to perform in-vivo dosimetry of interstitial brachytherapy because of the lack of appropriate dosimeters. The newly developed photoluminescence dosimeter ''Dose Ace'' is suitable for interstitial brachytherapy dosimetry in terms of its small size, ease of handling, and good reproducibility. We performed dosimetry of the anterior rectal wall by suturing a Teflon tube containing photoluminescence dosimeters. We measured doses at 50 points in seven pelvic malignancy patients and calculated the dose at each point by planning computer. The mean ratio of measured dose to calculated dose was 1.108 to 0.213. The absorbed dose of the anterior rectal wall can be presumed from the calculated dose with about 10% deviation. (author)

Nose, Takayuki; Koizumi, Masahiko; Nishiyama, Kinji [Osaka Prefectural Center for Adult Diseases (Japan); Yoshida, Ken

2001-09-01

247

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

248

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

1981-01-01

249

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

250

Absorbed dose measurements using TLDS in biological samples from beta radiation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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,...

José Eduardo Manzoli; Valdir de Souza Carvalho; Eliomar Jacinto Gomes de Cerqueira

2006-01-01

251

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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. Res...

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

2011-01-01

252

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

International Nuclear Information System (INIS)

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

2012-10-01

253

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

Science.gov (United States)

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

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

2012-10-01

254

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

International Nuclear Information System (INIS)

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

1981-01-01

255

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)

1990-01-01

256

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.)

1981-01-01

257

Determination of gamma spectrum and absorbed dose in the center of the HERBE system  

International Nuclear Information System (INIS)

It is important to know the influence of neutron and gamma radiation on sample during irradiation in the centre of the reactor system HERBE. It was the reason for measuring the gamma energy spectrum as well as corresponding absorbed radiation dose. In this paper the results of measurements are shown.(author)

1995-06-06

258

Internal radiation absorbed dose estimation in human brain due to technetium-99m and iodine-131  

International Nuclear Information System (INIS)

Internal dosimetry is a branch of medical physics that deals with the measurement of the internally absorbed dose by an organ after applying isotopes. In this study, internal radiation absorbed dose has been calculated for 99mTc and 131I, which are frequently used for functioning tests and therapeutic treatments of thyroid, respectively in these cases, some amount of isotopes are accumulated in other tissues like brain, which are very soft and cannot be regenerated if they are damaged. Using ionizing radiation inside the body and to ensure the safety of brain, the internal radiation absorbed dose has been calculated applying direct counting measurement. Accumulation of isotopes to target organ has been measured and this target organ is considered as primary target organ; also this organ is considered as source with respect to other organs. These organ counts have, been measured by computer-based scintillation system. The amount of exposure in brain has been measured with the help of the data obtained from the special set-up equipment, including NaI detector, radiation survey meter and water phantoms of various sizes. Absorbed dose in brain for each isotope has been calculated by applying time-activity curve analysis. Finally, these results have been compared with the data in ICRP l Reports 53 and 71. (author)

2004-01-01

259

The Graphite Calorimeter as a Standard of Absorbed Dose for Cobalt-60 Gamma Radiation.  

Science.gov (United States)

Absorbed dose to water in a cobalt-60 gamma-ray beam has been determined using a thick-walled graphite ionization chamber. The chamber was calibrated in a graphite phantom against a graphite calorimeter, and the graphite calibration factor was converted t...

J. S. Pruitt S. R. Domen R. Loevinger

1981-01-01

260

Adiabatic Calorimeter for Measuring Absorbed Dose of IHEP Synchrotron Secondary Radiation.  

Science.gov (United States)

An adiabatic calorimeter for measuring the value of absorbed dose of mixed radiation generated by the 70-GeV proton synchrotron is described. The calorimetric system consists of a working body (a core) and a shell (a screen). The calorimeter adiabaticity ...

V. E. Borodin V. I. Bigaleev L. S. Ermolenko V. A. Rogov E. Y. Roinishvili

1978-01-01

 
 
 
 
261

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)

2009-10-02

262

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 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

1994-05-01

263

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 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)

2010-11-09

264

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 "6"0Co ? radiation, ten X-ray beam qualities between TPR_2_0_,_1_0=0.639 and 0.802 and ten electron beam qualities between R_5_0=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 "6"0Co to TPR_2_0_,_1_0 = 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 "6"0Co ? 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 k_Q factors listed in table 14. The comparison showed a maximum difference of 0.8% for the NE25611A and NE 2571A chambers. At "6"0Co ? 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)

2002-11-25

265

Absorbed breast dose: dependence on radiographic modality and technique, and breast thickness  

International Nuclear Information System (INIS)

The increased use of mammography has brought into focus the necessity for radiation dose reduction. In particular, the effect of radiographic technique on radiation dosimetry is not well documented. In this paper, the dependence of absorbed dose on radiographic modality, radiographic technique, and breast thickness is studied, with the following principal results: Breast thickness and incident half-value layer (HVL) are sufficient to characterize the normalized (mrad/incident roentgen) breast dose. The average breast dose depends on both beam HVL and kVp; the dependence on breast thickness is more pronounced for screen-film mammography, indicating the need for firm compression. Screen-film mammography shows substantial dose savings over xeromammography for thinner breasts imaged without a grid; this dose advantage disappears for thicker breasts and is generally reversed when a grid is used

1986-01-01

266

The experimental basis for absorbed dose calculations in medical uses of radionuclides  

International Nuclear Information System (INIS)

The report No. 83 (1985) of US NCRP, where the available information being generalyzed and recommendations on calculation and measurement of the absorbed doses in clinical application of radiopharmaceutical preparations (RPhP) being presented, is reviewed. It is marked that nowadays the radiation dose is estimated as the upper range of possible internal irradiation for the given quantity of RPhP administered into the organism. In this case three main methods are used: direct dose measurements in human body and organs; extrapolation of measurement results for animals and phantoms to a man; dose calculation using mathematical models. Main method developments are enumerated for the period since 1945. Special attention is paid to the method of dose calculation developed by the MIRD-committee (Medical Internal Radiation Dose Committee of the Society of Nuclear Medicine, USA)

1987-01-01

267

Absorbed breast dose: dependence on radiographic modality and technique, and breast thickness.  

Science.gov (United States)

The increased use of mammography has brought into focus the necessity for radiation dose reduction. In particular, the effect of radiographic technique on radiation dosimetry is not well documented. In this paper, the dependence of absorbed dose on radiographic modality, radiographic technique, and breast thickness is studied, with the following principal results: Breast thickness and incident half-value layer (HVL) are sufficient to characterize the normalized (mrad/incident roentgen) breast dose. The average breast dose depends on both beam HVL and kVp; the dependence on breast thickness is more pronounced for screen-film mammography, indicating the need for firm compression. Screen-film mammography shows substantial dose savings over xeromammography for thinner breasts imaged without a grid; this dose advantage disappears for thicker breasts and is generally reversed when a grid is used. PMID:3763877

Skubic, S E; Fatouros, P P

1986-10-01

268

Absorbed breast dose: dependence on radiographic modality and technique, and breast thickness  

Energy Technology Data Exchange (ETDEWEB)

The increased use of mammography has brought into focus the necessity for radiation dose reduction. In particular, the effect of radiographic technique on radiation dosimetry is not well documented. In this paper, the dependence of absorbed dose on radiographic modality, radiographic technique, and breast thickness is studied, with the following principal results: Breast thickness and incident half-value layer (HVL) are sufficient to characterize the normalized (mrad/incident roentgen) breast dose. The average breast dose depends on both beam HVL and kVp; the dependence on breast thickness is more pronounced for screen-film mammography, indicating the need for firm compression. Screen-film mammography shows substantial dose savings over xeromammography for thinner breasts imaged without a grid; this dose advantage disappears for thicker breasts and is generally reversed when a grid is used.

Skubic, S.E.; Fatouros, P.P.

1986-10-01

269

Comparison of absorbed and effective dose from two dental cone beam computed tomography scanners  

International Nuclear Information System (INIS)

This research compared the field of view with the tissue absorbed dose and effective doses using the two dental cone beam computed tomography (CBCT) scanners. Two CBCT devices, an Alphard VEGA and 3DX multi-image micro CT MCT-1, were used. Measurements were made using an Alderson RANDO phantom and thermoluminescence dosimeters (TLDs). The calculation of the effective dose was carried out according to ICRP Publication 60 and 103. The effective doses for Alphard VEGA D mode, I mode, P mode, and C mode were 86, 238, 413, and 323 ?Sv, respectively. The effective doses using 3DX for the maxillary incisor, maxillary molar, mandibular incisor, mandibular molar, TMJ, and mandibular molar scout images were 27, 30, 48, 60, 14, and 1 ?Sv, respectively. Both Alphard VEGA and 3DX values revealed salivary gland and oral mucosa doses much higher than those required for other tissues. It is necessary to select a small mode suitable in order to realize optimization. (author)

2012-03-01

270

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

271

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

Energy Technology Data Exchange (ETDEWEB)

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. The utility of these calculations for radiation dose calculations in nuclear medicine is discussed.

Eckerman, K.F.; Stabin, M.G.

2000-02-01

272

Study of the clinical thermoluminescent dosimeter in the direct measurement of radiation absorbed dose for radioimmunotherapy  

International Nuclear Information System (INIS)

One of the major obstacles facing radioimmunotherapy (RIT) is the lack of a device to measure directly tumor and normal tissue radiation absorbed dose. Calculations based on the clearance and imaging scans have several limitations; hence we design and fabricate a sheathed clinical thermoluminescent dosimeter (TLD) for the measurement of absorbed dose by implantation in humans. Preclinical studies are performed in nine normal rabbits. Complete blood count, body temperature monitoring, clinical observation and necropsy show no untoward effects from the TLD. Consistent bone marrow radiation doses are noted in the four rabbits receiving 131I-labeled monoclonal antibody A6H. By using up to 20 clinical TLDs in one sheath, it will be possible to determine macroscopic heterogeneities in organs undergoing RIT. (author)

1991-01-01

273

Estimation of absorbed dose for nonuniformly distributed I-131 in tumor  

International Nuclear Information System (INIS)

In internal emitter radiotherapy nonuniform activity distributions in geometrically irregular tumor volumes will be encountered. The conventional and established methodology for calculating the absorbed dose requires that individual source regions be uniform activity distribution. Any general dosimetry system should be able to account for the effects of tissue inhomogeneities. I-131 can eradicate small foci of remnant tissue in patient with differentiated thyroid cancer. In this study we present Monte Carlo simulation to evaluate detailed absorbed dose distributions in a homogeneous medium for any given activity distribution of I-131. Results are presented for the dose distribution in a 1 ml target volume with activity distribution which is uniform, limited by diffusion into target volume

2000-05-01

274

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)

1998-11-22

275

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

1988-02-01

276

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)

2006-06-12

277

Quality assurance in radiation therapy: ionization chamber calibration and intercomparison of absorbed doses  

International Nuclear Information System (INIS)

A secondary standard for calibration of ionization chambers used in radiotherapy was established by the Institute of Clinical Oncology in Bratislava in 1984. The secondary standard consists of 60Co treatment unit Chisobalt, a Baldwin-Farmer dosemeter and a Baldwin ionization chamber. The exposure and kerma rates of the primary dosimetry standard which is regularly checked are used. The parameters, uncertainties and stability of the secondary standard are discussed. A comparison of absorbed doses from 60Co gamma rays of therapy units in water phantom was performed for all radiotherapy centers in Czechoslovakia. The results showed that all observed doses were within ±3% from the absorbed dose specified. (author). 2 figs., 4 tabs., 8 refs

1987-08-01

278

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

International Nuclear Information System (INIS)

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

2010-01-01

279

Absorbed dose in a tumor and the efficacy of radiation therapy in cervical cancer  

Energy Technology Data Exchange (ETDEWEB)

The results of therapy of patients with cervical cancer are analysed. It has been established that doses of 50-70 Gy ensure high 5-year survival rates of patients with Stage 1 cervical cancer. In patients with Stage 2 and Stage 3 cervical cancer survival rates were the highest within the range of 50-70 Gy. A further increase in the absorbed dose level deteriorated the survival rates of the patients, the frequency of local tumor control was not elevated. It is recommended that optimum dose levels be adhered to even during treatment of patients with disseminated cervical cancer.

Zharinov, G.M. (Tsentral' nyj Nauchno-Issledovatel' skij Rentgeno-Radiologicheskij Inst., Leningrad (USSR))

1984-09-01

280

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

International Nuclear Information System (INIS)

We calculated the mean absorbed fractions, specific absorbed fractions and mean doses per unit of cumulated activity in source spheres 10 ?m-2 cm in radius for 22 beta-emitting radionuclides potentially useful in radioimmunotherapy. We considered two models of radionuclide distribution, either uniform at the surface of the source or throughout its volume. For each model, we calculated both the absorbed fractions in the spherical segments composing the source and the mean absorbed fractions. For surface distribution, we calculated the mean dose per unit of cumulated activity for a concentric sphere with a small radius (5 ?m) in order to determine the minimal dose delivered to the target. Calculations were performed using point kernels for monoenergetic emissions and then integrated into the beta spectra of the different emitters ("3"2P, "3"3P, "4"7Sc, "6"7Cu, "7"7As, "9"0Y, "1"0"5Rh, "1"0"9Pd, "1"1"1Ag, "1"2"1Sn, "1"3"1I, "1"4"2Pr, "1"4"3Pr, "1"4"9Pm, "1"5"3Sm, "1"5"9Gd, "1"6"6Ho, "1"7"7Lu, "1"8"6Re, "1"8"8Re, "1"9"4Ir and "1"9"9Au). Monoenergetic emissions were taken into account. (author)

1994-06-01

 
 
 
 
281

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2014-01-15

282

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

International Nuclear Information System (INIS)

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

2003-10-01

283

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

International Nuclear Information System (INIS)

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

1984-06-05

284

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1984-01-01

285

Dose absorbed by technologists in positron emission tomography procedures with FDG  

Directory of Open Access Journals (Sweden)

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

Ademir Amaral

2007-09-01

286

Comparison of the standards of absorbed dose to water of the OMH and the BIPM for 60Co ? rays  

International Nuclear Information System (INIS)

A comparison of the standards of absorbed dose to water of the Orszagos Meresugyi Hivatal (OMH), Budapest, Hungary and of the Bureau International des Poids et Mesures (BIPM) has been made in 60Co radiation. The results show that the OMH and the BIPM standards for absorbed dose to water are in close agreement, the difference being within the estimated uncertainty. (authors)

2003-01-01

287

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

288

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

1983-01-01

289

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)

1979-01-01

290

Absorbed Dose Determination Using Experimental and Analytical Predictions of X-Ray Spectra  

Science.gov (United States)

Electron beam welding in a vacuum is a technology that NASA is investigating as a joining technique for manufacture of space structures. This investigation characterizes the x-ray environment due to operation of an in-vacuum electron beam welding tool and provides recommendations for adequate shielding for astronauts performing the in-vacuum electron beam welding. NASA, in a joint venture with the Russian Space Agency, was scheduled to perform a series of welding in space experiments on board the U.S. Space Shuttle. This series of experiments was named the international space welding experiment (ISWE). The hardware associated with the ISWE was leased to NASA by the Paton Welding Institute (PWI) in Ukraine for ground-based welding experiments in preparation for flight. Two ground tests were scheduled, using the ISWE electron beam welding tool, to characterize the radiation exposure to an astronaut during the operation of the ISWE. These radiation exposure tests used thermoluminescence dosimeters (TLD's) shielded with material currently used by astronauts during extravehicular activities to measure the radiation dose. The TLD's were exposed to x-ray radiation generated by operation of the ISWE in-vacuum electron beam welding tool. This investigation was the first known application of TLD's to measure absorbed dose from x rays of energy less than 10 keV. The ISWE hardware was returned to Ukraine before the issue of adequate shielding for the astronauts was completely verified. Therefore, alternate experimental and analytical methods were developed to measure and predict the x-ray spectral and intensity distribution generated by ISWE electron beam impact with metal. These x-ray spectra were normalized to an equivalent ISWE exposure, then used to calculate the absorbed radiation dose to astronauts. These absorbed dose values were compared to TLD measurements obtained during actual operation of the ISWE in-vacuum electron beam welding tool. The calculated absorbed dose values were found to be in agreement with the measured TLD values.

Edwards, D. L.; Carruth, Ralph (Technical Monitor)

2001-01-01

291

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1996-12-31

292

Absorbed fraction and dose conversion coefficients of alpha particles for radon dosimetry  

International Nuclear Information System (INIS)

The sensitivity to different relevant parameters of the absorbed fraction of alpha particles emitted from the 222Rn chain in sensitive cells of the tracheo-bronchial tree have been investigated. The structure of the airway wall given by ICRP (ICRP66) has been adopted and employed in the present calculations. The source thickness (mucous gel and sol + cilia), target layer thickness and the depth of the sensitive layers have been varied within reasonable ranges around the default values recommended by ICRP66. The results have shown that the depth of the sensitive layers is the most important parameter in calculating the absorbed fraction. In addition, dose conversion coefficients were calculated and presented along with the absorbed fractions. (author)

2001-07-01

293

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

CERN Multimedia

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

Job, P K; Semones, E

1999-01-01

294

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)

2003-10-01

295

Experimental verification of the air kerma to absorbed dose conversion factor C_w_,_u  

International Nuclear Information System (INIS)

In a recently published code of practice for the dosimetry of high-energy photon beams, the absorbed dose to water is determined using an ionization chamber having an air kerma calibration factor and applying the air kerma to absorbed dose conversion factor C_w_,_u. The consistency of these C_w_,_u values has been determined for four commonly employed types of ionization chambers in photon beams with quality varying between "6"0Co gamma-rays and 25 MV X-rays. Using a graphite calorimeter, C_w_,_u has been determined for a graphite-walled ionization chamber (NE 2561) for the same qualities. The values of C_w_,_u determined with the calorimeter are within the experimental uncertainty equal to C_w_,_u values determined according to any of the recent dosimetry protocols. (Auth.)

1987-01-01

296

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

1961-01-01

297

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2007-09-21

298

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

Energy Technology Data Exchange (ETDEWEB)

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 ({rho}) and elemental weights ({omega}{sub 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 software (Image Converter Computed Tomography). It converts CT images in tissue parameters (mass densities ({rho}) and elemental weights ({omega}{sub i}). This work intended to verify if the estimate values by software ICCT of the tissue parameter and elemental weights ({omega}{sub i}) are plausible to estimate the absorbed dose with reasonable accuracy. (author)

Massicano, Felipe; Possani, Rafael G.; Yoriyaz, Helio [Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN/SP), Sao Paulo, SP (Brazil). Centro de Engenharia Nuclear; Cintra, Felipe B.; Massicano, Adriana V.F., E-mail: massicano@gmail.com [Instituto de Pesquisas Energeticas e Nucleares (DIRF/IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Diretoria de Radiofarmacia

2011-07-01

299

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 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)

2011-01-01

300

Absorbed dose estimates at the cellular level for 186Re and 188Re  

International Nuclear Information System (INIS)

Microdosimetric calculations of 186Re and 188Re have been evaluated at the cellular level. Stopping power, LET, range values and deposited energies per decay have been calculated for beta particles, Auger and conversion electrons. In addition, total absorbed doses have been calculated for the radionuclides distributed randomly with certain activities within the cell. Results indicate 186Re and 188Re to be promising radionuclides for therapy of tumors from millimeter through centimeter dimensions

2005-06-01

 
 
 
 
301

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

International Nuclear Information System (INIS)

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

1989-01-01

302

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

International Nuclear Information System (INIS)

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

2003-07-14

303

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

International Nuclear Information System (INIS)

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

2007-08-01

304

A brief look at absorbed dose measurements in the 60Co field  

International Nuclear Information System (INIS)

The main quantity of interest in radiotherapy is absorbed dose to water. For years, its determination has been obtained by indirect methods with an accuracy of 1 to 2%. A brief summary is given of the work undertaken by the national standardizing laboratories and the BIPM, to obtain better accuracy. Several methods are now available (calorimetry, ionometry, etc.) and the agreement between them is better than 1%. (orig.)

1995-07-01

305

Estimation and analysis of absorbed dose in high energy electron accelerators  

International Nuclear Information System (INIS)

The stem predicament, in radiation protection surveillance, posed by the secondary radiations like Bremsstrahlung photons and other particles emitted from unshielded and partially shielded portions of high energy electron particle accelerator facilities, has prompted to do the present simulation studies for the estimation of absorbed dose, in human equivalent water media. Simple empirical relations based on computer simulations using Monte-Carlo methods, are derived so that 'ready reckoners' can be prepared, for the estimation of dose to the persons exposed, by chance, around those facilities. (author)

2006-11-01

306

Mycosis Fungoides electron beam absorbed dose distribution using Fricke xylenol gel dosimetry  

Energy Technology Data Exchange (ETDEWEB)

Radiotherapy uses ionizing radiation to destroy tumor cells. The absorbed dose control in the target volume is realized through radiation sensors, such as Fricke dosimeters and radiochromic film, which permit to realize bi-dimensional evaluations at once and because of that, they will be used in this study as well. Among the several types of cancer suitable for ionizing radiation treatment, the Mycosis Fungoides, a lymphoma that spreads on the skin surface and depth, requires for its treatment total body irradiation by high-energy electrons. In this work the Fricke xylenol gel (FXG) was used in order to obtain information about the absorbed dose distribution induced by the electron interactions with the irradiated tissues and to control this type of treatment. FXG can be considered as an alternative dosimeter, since up to now only films have been used. FXG sample cuvettes, simulating two selected tomos (cranium and abdomen) of the Rando anthropomorphic phantom, were positioned along with radiochromic films for comparison. The phantom was subjected to Stanford total body irradiation using 6 MeV electrons. Tomographic images were acquired for both dosimeters and evaluated through horizontal and vertical profiles along the tomographic centers. These profiles were obtained through a Matlab routine developed for this purpose. From the obtained results, one could infer that, for a superficial and internal patient irradiation, the FXG dosimeter showed an absorbed dose distribution similar to the one of the film. These results can validate the FXG dosimeter as an alternative dosimeter for the Mycosis Fungoides treatment planning.

Silveira, Michely C. da [FFCLRP, Universidade de Sao Paulo, Ribeirao Preto, Sao Paulo (Brazil); Sampaio, Francisco G.A., E-mail: francisampaio@pg.ffclrp.usp.br [FFCLRP, Universidade de Sao Paulo, Ribeirao Preto, Sao Paulo (Brazil); Petchevist, Paulo C.D., E-mail: petchevist12@yahoo.com.br [FFCLRP, Universidade de Sao Paulo, Ribeirao Preto, Sao Paulo (Brazil); Instituto de Radioterapia e Megavoltagem, Ribeirao Preto, Sao Paulo (Brazil); Oliveira, Andre L. de [Servico de Radioterapia do Hospital das Clinicas da Unicamp, Campinas, Sao Paulo (Brazil); Almeida, Adelaide de, E-mail: dalmeida@ffclrp.usp.br [FFCLRP, Universidade de Sao Paulo, Ribeirao Preto, Sao Paulo (Brazil)

2011-12-15

307

Mycosis Fungoides electron beam absorbed dose distribution using Fricke xylenol gel dosimetry  

Science.gov (United States)

Radiotherapy uses ionizing radiation to destroy tumor cells. The absorbed dose control in the target volume is realized through radiation sensors, such as Fricke dosimeters and radiochromic film, which permit to realize bi-dimensional evaluations at once and because of that, they will be used in this study as well. Among the several types of cancer suitable for ionizing radiation treatment, the Mycosis Fungoides, a lymphoma that spreads on the skin surface and depth, requires for its treatment total body irradiation by high-energy electrons. In this work the Fricke xylenol gel (FXG) was used in order to obtain information about the absorbed dose distribution induced by the electron interactions with the irradiated tissues and to control this type of treatment. FXG can be considered as an alternative dosimeter, since up to now only films have been used. FXG sample cuvettes, simulating two selected tomos (cranium and abdomen) of the Rando anthropomorphic phantom, were positioned along with radiochromic films for comparison. The phantom was subjected to Stanford total body irradiation using 6 MeV electrons. Tomographic images were acquired for both dosimeters and evaluated through horizontal and vertical profiles along the tomographic centers. These profiles were obtained through a Matlab routine developed for this purpose. From the obtained results, one could infer that, for a superficial and internal patient irradiation, the FXG dosimeter showed an absorbed dose distribution similar to the one of the film. These results can validate the FXG dosimeter as an alternative dosimeter for the Mycosis Fungoides treatment planning.

da Silveira, Michely C.; Sampaio, Francisco G. A.; Petchevist, Paulo C. D.; de Oliveira, André L.; Almeida, Adelaide de

2011-12-01

308

Calorimetric measurement of the absorbed dose in a pulsed gamma radiation field  

International Nuclear Information System (INIS)

Modern weapon systems consist to a large extent of sophisticated and 'fighting-power-determining' electronic equipment which can be destroyed or influenced by radiation produced in a nuclear burst. An important quantity to describe such radiation-induced damage is the dose obsorbed by an electronic component in the nuclear radiation field. In this paper, measurements of absorbed dose in the elements lead, silicon and aluminium (produced by the radiation field of a Flash X-Ray machine) are reported. The measurements are performed using a semiadiabatic microcalorimeter operating at the temperature of liquid nitrogen. The described measuring technique draws its importance from the fact that it is an absolute and direct method to measure the absorbed dose that a pulsed gamma radiation field of unknown spectrum deposits in a given absorbing material. An absolute and spectrum-independent measurement is achieved by calibrating the measured quantities directly with a precisely determined amount of electric energy. The range of the reported measurements extends from approximately 0.5 to 1,000 rad. (orig.)

1974-01-01

309

Absorbed dose to water distribution measured around an HDR 192Ir brachytherapy source by thermoluminescent dosimeters  

Science.gov (United States)

The purpose of this work was to develop a procedure to directly estimate the spatial distribution of the absorbed dose rate to water, \\dot {D}_w , around an HDR 192Ir brachytherapy source. The methodology developed was based on Monte Carlo calculations and measurements in air and in water with thermoluminescent detectors. Variations in detector positioning had a significant influence near the brachytherapy source (20% at 1 cm). The method leads to a mean difference of about 7% with the CLRP TG-43 Parameter Database when the absorbed dose to water is characterized along the transverse plane to the source (from 1 cm to about 11 cm). This mean difference, however, is within an uncertainty of 7.7% over all distances. This method therefore can be used to provide direct estimates of the absorbed dose rate to water for HDR brachytherapy source irradiations which are more realistic than those which use other phantom materials. In addition, measurements are indicative of the source geometry and material composition.

Avilés Lucas, P.; Lourenço, V.; Vermesse, D.; Cutarella, D.; Aubineau-Lanièce, I.

2012-10-01

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 10"3 mrad/hr for skin (epidermal thickness: 7 mg/cm"2) and 3 x 10"-"2 to 1 x 10"3 mrad/hr for fingers (epidermal thickness: 40 mg/cm"2). In monitoring surface contamination, the measurable range is 3 x 10"-"1 to 1.7 x 10"3 ?-particles/cm"2.sec [2? solid angle, natural uranium source covered by an aluminium filter (27 mg/cm"2) for shielding low-energy ?-rays of "2"3"4Th and ?-rays]. (author)

1980-01-01

311

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

312

Basic evaluation of absorbed dose in the `mantle` field in radiotherapy for Hodgkin`s disease  

Energy Technology Data Exchange (ETDEWEB)

Hodgkin`s disease is one of the radiocurable disease. Avoiding overlap of dose from adjacent fields, megavoltage beams can be utilized at a treatment distance of 100 to 160 cm, making in possible to encompass all of the lymph node chains above the diaphragm in a single treatment field-the `mantle` field. In the mantle field, we use a set of lead blocks designed individually to spare lager parts of normal lung tissue. We made blocks with beam divergence from low melting lead alloy using lead shot. With these blocks, we measured the absorbed dose in the mantle field in a human phantom, using a thermoluminescent dosimetry system. The results demonstrate that the absorbed dose distribution calculated by the computer system in the axial slices at + 60, 0 and -70 mm from the middle of the radiation field were in good agreements with our dosimetric results in the same slices. An integral dose volume histogram (DVH) obtained from the axial slice in the middle of the radiation field showed quantitatively the irradiated normal lung tissue. In conclusion: first, a dose calculation system using a computer was available in the large irregular shaped field utilizing a long treatment distance such as the `mantle` field. Second, the DVH may be useful in the quantitative evaluation of lung injury resulting from radiotherapy using the `mantle` field. (author)

Fukutomi, Yukimi; Kawamura, Masashi; Kataoka, Masaaki; Fujii, Takashi; Kimura, Makoto; Kawakami, Toshiaki [Ehime Univ., Shigenobu (Japan). Hospital

1996-06-01

313

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

314

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

International Nuclear Information System (INIS)

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

2003-01-01

315

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

International Nuclear Information System (INIS)

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

2011-08-10

316

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)

2012-09-01

317

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)

2001-03-01

318

Absorbed dose intercomparison studies for Co-60 therapy units by the SSDL, Istanbul, Turkey  

International Nuclear Information System (INIS)

In 1989, CNAEM Secondary Standard Dosimetry Laboratory (SSDL) undertook a TLD intercomparison programme using the IAEA/WHO method for the user of Co-60 teletherapy units to raise the dosimetric accuracy in radiotherapy. For this purpose, the radiotherapy centres in Turkey are sent plastic capsules containing LiF by post and are asked to irradiate these capsules to an absorbed dose of 2.0 Gy at a depth of 5 cm in water. The irradiated TLD capsules are returned to the SSDL by the radiotherapy centres. The given dose to the capsule is determined by SSDL and this measured dose is compared with stated dose by the radiotherapy centre. In this intercomparison were found that the 9 radiotherapy centres have less than ±5% deviation and 3 radiotherapy centres have higher than ±5% deviation. 6 refs, 1 tab

1991-04-01

319

Ethanol-chlorobenzene dosimetry for absorbed doses below 1 kGy  

International Nuclear Information System (INIS)

The consistency of the ethanol-chlorobenzene dosimetry system is demonstrated with respect to the useful dose range of the radiation-chemical response (constant value of G(HCl)) and to the analytical methods of evaluation. The radiation chemical yield in terms of G(HCl) values is constant throughout the applicable absorbed dose range 0.1-100 kGy. The investigation of analytical methods (alkalimetric titration, coulometry and oscillometry) relative to mercurimetric titration shows that consistent results can be obtained routinely within + - 2.5% over this wide dose range. The importance of the calibration of oscillometric method is illustrated. A linear relationship between the radiolytical generation of HCl and the oscillometric reading makes possible the use of a simple expression for calculating the dose without relying on a calibration graph. (author)

1987-01-01

320

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

International Nuclear Information System (INIS)

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

2008-12-03

 
 
 
 
321

Code of practice for absorbed dose determination in photon and electron beams  

International Nuclear Information System (INIS)

An advisory group was set up by the IAEA to suggest measures to be taken for the production of a dosimetry protocol. The authors of the paper were chosen to be authors. The Agency was of the opinion that such a protocol would be of great value not only to the network of Secondary Standard Dosimetry Laboratories (SSDL) but also to hospitals providing radiation treatment for cancer patients. The report includes recommendations on the procedure for determining the absorbed dose at low and medium energy X-rays, and high energy photon and electron radiation. Advice on equipment, measurement geometry and quality assurance is given. It was decided that the symbols and formalism should follow the ICRU recommendations. The numerical data on interaction coefficients follow the recommendations of the standards laboratories (i.e. CCEMRI). Correction factors (i.e. k_a_t_t and k_m) to be applied for about 40 types of commercial ionization chambers were computed as it was considered that it would be difficult to restrict the use to a few types of chambers, as in the NACP protocol, or advise the users on how to carry out complicated computations, as in the AAPM protocol. A part of the report is devoted to conventional X-rays. In this case a very general type of formalism is suggested. It was found that there is a lack of information on the correction factors to be applied for different types of chambers. Furthermore, it was found that conventional dosimetry procedures, often used in determining the absorbed dose at the medium energy range of X-rays, underestimate the absorbed dose by several per cent. More work is needed in this field. An independent evaluation of the dosimetry resulting from the application of this protocol has been carried out for high energy photon and electron radiation using the FeSO_4 dosimeter as a reference. The agreement in absorbed dose values was generally within fractions of one per cent. The conclusion is, therefore, that use of this report can give an absorbed dose determination sufficiently accurate for practical applications in radiation therapy. (author)

1986-09-01

322

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

International Nuclear Information System (INIS)

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

2002-11-25

323

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

324

A geochemical assessment of terrestrial gamma-ray absorbed dose rates  

Energy Technology Data Exchange (ETDEWEB)

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.

Wollenberg, H.A.; Smith, A.R. (Lawrence Berkeley Laboratory, CA (USA))

1990-02-01

325

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

1990-01-01

326

Level of external natural radiation and absorbed dose to population in Shandong province  

International Nuclear Information System (INIS)

Two thousand sites over Shandong Province (one in each 10 km mesh) were chosen for determination of natural radiation level and the absorbed dose to the population. Crystal scintillation radiometers calibrated with spherical ionization chamber were used in the determination. The ranges and mean values of absorbed dose rates in air from natural penetrating radiation for indoors, outdoors and roads are (10.8-34.8) x 10-8 Gy.h-1 and 14.5 x 10-8 Gy.h-1; (4.8-25.8) x 10-8 Gy.h-1 and 10.8 x 10-8 Gy.h-1 and (5.9-16.9) x 10-8 Gy.h-1 and 10.2 x 10-8 Gy.h-1, respectively. The mean annual effective dose equivalent for each person in this province is estimated to be 9.18 x 10-4 Sv, and the annual collective dose equivalent 6.82 x 104 man.Sv

1985-01-01

327

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

International Nuclear Information System (INIS)

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

1987-01-01

328

Effect of diffuse radiation on the ratios of absorbed doses derived from ionization measurements and those obtained by Fricke dosimetry  

International Nuclear Information System (INIS)

An NPL secondary standard chamber (type NE-2561), two 0.6 cm3 Baldwin chambers (type NE-2505/3) and a Baldwin soft X-ray chamber (type NE-2536/3) were irradiated in Plexiglas and in water with Fricke dose meters from the National Physical Laboratory (NPL), Teddington, and from the laboratory where this work has been carried out. Within the experimental margins of error, no effect of field size or of depth in Plexiglas or in water on the absorbed dose ratios derived from measurements with both types of dose meter was found. Nevertheless, when the contribution of backscattered radiation to the absorbed dose at the point of measurement is removed, these absorbed dose ratios decrease by about 4% to 4.8% as the field size increases. Comparison of the absorbed dose ratios obtained with and without backscattered radiation shows that this secondary radiation component is responsible, with increasing field size, for a progressive increase in the ratios of the absorbed doses derived from measurements with Baldwin and NPL chambers and those obtained by ferrous sulphate dosimetry; when the soft X-ray chamber is used, the absorbed dose ratios vary differently. The study shows that, merely by increasing the number of measurements taken, it is possible, with the limited means available in a radiotherapy department, to define a correction factor for an ionization chamber with an accuracy better than 1%, and to specify its limits of validity. (author)

1977-12-09

329

Dose absorbed by technologists in positron emission tomography procedures with FDG  

Scientific Electronic Library Online (English)

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

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

330

Calculation of absorbed doses to water pools in severe accident sequences  

International Nuclear Information System (INIS)

A methodology is presented for calculating the radiation dose to a water pool from the decay of uniformly distributed nuclides in that pool. Motivated by the need to accurately model radiolysis reactions of iodine, direct application is made to fission product sources dissolved or suspended in containment sumps or pools during a severe nuclear reactor accident. Two methods of calculating gamma absorption are discussed - one based on point-kernal integration and the other based on Monte Carlo techniques. Using least-squares minimization, the computed results are used to obtain a correlation that relates absorbed dose to source energy and surface-to-volume ratio of the pool. This correlation is applied to most relevant fission product nuclides and used to actually calculate transient sump dose rate in a pressurized-water reactor (PWR) severe accident sequence

1991-01-01

331

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

International Nuclear Information System (INIS)

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

2008-12-01

332

Design of flattening filters based on intracavitary absorbed dose measurements in external radiation therapy  

International Nuclear Information System (INIS)

A method has been developed for the design of flattening filters on the basis of in-vivo oesophagus measurements of absorbed dose distribution in patients given external radiation therapy. The measurements were made by means of LiF-Teflon thermoluminescent dosimeters, read out by an automatic TL-system. A single filter was designed from the resultant dose distribution of parallel opposing fields. The method was checked clinically and was found to be convenient and reliable. The filters reduced the dose variation along the midline of the patients undergoing upper mantle treatments from about +- 20% to about +- 5%. The same limits of variation are believed to exist through the entire mid-plane of the body, though it was not possible to prove this by direct measurements. (author)

1980-01-01

333

Error in assessing the absorbed dose from the EPR signal from dental enamel  

International Nuclear Information System (INIS)

Dose measurements from EPR signals from dental enamel were analyzed in a random sampling of 100 teeth extracted in liquidators of the Chernobyl accident aftermath and the EPR spectra of dental enamel of 80 intact teeth from children studied. The mean square deviation of enamel sensitivity to ionizing radiation in some teeth is approximately 0.3 of the mean sensitivity value. The variability of the nature EPR spectrum of dental enamel limits in principle the lower threshold of EPR-measured 60 mGy doses. When assessing the individual absorbed doses from the EPR signal from dental enamel without additional exposure it is necessary to bear in mind the extra error of approximately 6-% at a confidence probability P=0.95 caused by the variability of enamel sensitivity to radiation in some teeth. This additional error may be ruled out by graduated additional exposure of the examined enamel samples

1997-01-01

334

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

2013-11-24

335

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

International Nuclear Information System (INIS)

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

1994-01-01

336

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 m"3 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.)

1976-01-01

337

Application of polystyrene - water calorimeter in determination of absorbed dose. Vol. 4  

International Nuclear Information System (INIS)

The polystyrene-water calorimeter was investigated as a modification of the water calorimeter, where the polystyrene has a low specific heat and negligible known heat defect. This calorimeter was designed, constructed and calibrated for measurement of radiation absorbed dose. The system utilizes a thermistor to detect the radiation-induced temperature rise in the polystyrene absorber at certain point from the radiation source. A temperature stability of as low as 0.0018 degree C/min in a 42.0 degree C environment, and a gamma-radiation sensitivity of as high as 1.9720 ohm/Gy were obtained. Comparisons of the results obtained by using the polystyrene-water calorimeter with those obtained by applying other types of calorimeters i.e., water and graphite calorimeters were also done to aid in the possible realization of an accurate and efficient instrument for use under widely different irradiation conditions. 4 figs., 1 tab

1996-03-01

338

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

International Nuclear Information System (INIS)

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

2006-05-15

339

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

Energy Technology Data Exchange (ETDEWEB)

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

340

Calorimetric determination of absorbed dose in water for 1-25 MeV X-rays  

International Nuclear Information System (INIS)

The calorimeter is becoming more and more used as a primary standard of absorbed dose. Because of an international agreement most calorimeters are made of graphite. The measured absorbed dose at a point in graphite has to be transferred to a value for absorbed dose at a point in water, the quantity of interest. Several procedures were recommended in the past; two of them were used in this study. The first method concerns the ICRU recommendation to use a thin-walled ionization chamber as a transfer instrument. We used the commercial NPL(UK) secondary standard therapy-level exposure meter. The second method is a much simpler procedure: the absorbed dose is calculated taking into account the difference in electron densities of the two media (the method of corresponding points). These absorbed dose determinations in water were compared with the ionometrically determined dose using the Csub(lambda)-concept or conversion factors according to the NACP(USA) protocol. The results show the dispersion of the conventional absorbed dose determination of 11 Dutch hospitals (from +3% to -5%), and a conclusion can be drawn about the undervaluation of Csub(lambda). According to this study the undervaluation amounts to 1% for 5-8 MeV, 2% for 16-18 MeV and 3% around 25 MeV. (author)

1980-10-31

 
 
 
 
341

Performance evaluation of graphite pancake ionization chamber by comparing the absorbed dose to water calibration  

International Nuclear Information System (INIS)

This paper describes modifications to an original design, correction factors and uncertainty evaluations for a graphite pancake ionization chamber constructed at the Institute of Nuclear Energy Research (INER, Taiwan). A bilateral comparison of the absorbed dose to water standards for 60Co using transfer chambers was performed to verify the graphite chamber experimental accuracy and measurement consistency. The comparison results showed a satisfactory agreement in the measurements within the combined standard uncertainties (k=1). This paper also compares the absorbed dose to water calibration in medical accelerator photon beams traceable to INER standards following the recommendations given in the AAPM TG-21 and TG-51 dosimetry protocols. For all types of linear accelerators and cylindrical chambers at 13 participating hospitals in Taiwan, the TG-51/TG-21 dose ratios were the same within +/-1.5%, less than the combined uncertainty, irrespective of the chamber make and model for each photon included here. A quality assurance guide for institutions switching from the TG-21 to TG-51 protocol was suggested based on the comparison results for the two dosimetry protocols

2006-03-01

342

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

International Nuclear Information System (INIS)

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

2002-09-01

343

Code of Practice for high-energy photon therapy dosimetry based on the NPL absorbed dose calibration service  

Energy Technology Data Exchange (ETDEWEB)

With the aim of improving the accuracy of photon dosimetry, NPL has launched a calibration service for high-energy photon beams in terms of absorbed dose to water, based on a graphite calorimeter as the primary standard (Burns et al 1988). It is expected that the 2 MV, C{sub {lambda}} derivation of absorbed dose to water and the absorbed dose calibration service will co-exist as alternative approaches to high-energy photon dosimetry for the foreseeable future and that NPL will continue to maintain the 2 MV primary standard. The purpose of this Code of Practice is to recommend procedures for calibrating field instruments using a secondary standard which has been calibrated by the NPL absorbed dose service, and procedures for measuring radiation output from a cobalt-60 unit or a high-energy accelerator. (author).

Lillicrap, S.C.; Owen, B.; Williams, J.R.; Williams, P.C. (Institute of Physical Sciences in Medicine, London (UK))

1990-10-01

344

Code of Practice for high-energy photon therapy dosimetry based on the NPL absorbed dose calibration service  

International Nuclear Information System (INIS)

With the aim of improving the accuracy of photon dosimetry, NPL has launched a calibration service for high-energy photon beams in terms of absorbed dose to water, based on a graphite calorimeter as the primary standard (Burns et al 1988). It is expected that the 2 MV, C? derivation of absorbed dose to water and the absorbed dose calibration service will co-exist as alternative approaches to high-energy photon dosimetry for the foreseeable future and that NPL will continue to maintain the 2 MV primary standard. The purpose of this Code of Practice is to recommend procedures for calibrating field instruments using a secondary standard which has been calibrated by the NPL absorbed dose service, and procedures for measuring radiation output from a cobalt-60 unit or a high-energy accelerator. (author)

1990-01-01

345

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

CERN Document Server

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

American Society for Testing and Materials. Philadelphia

2010-01-01

346

Evaluation of the absorbed dose, half-thickness layer and the yield of X-ray an diagnostic equipment  

International Nuclear Information System (INIS)

This work develops parametrization methods for evaluation the absorbed doses, the half-thickness and the effectiveness of a X-ray beams from a Shimadzu Radiotex and a SRO 2550 Philips models equipment

2004-09-26

347

The re-estimation of absorbed doses of less than 1 rad measured with lithium fluoride thermoluminescent dosemeters  

International Nuclear Information System (INIS)

The technique of ultraviolet light bleaching for the re-estimation of the absorbed dose of radiation received by lithium fluoride thermoluminescence dosemeters has been extended to the extruded ribbon and PTFE disc form of dosemeter. The threshold of detection for the re-estimation of absorbed dose was found to be 1.1 rad for the PTFE disc dosemeters and 2.8 rad for the extruded ribbon dosemeters. A further study of this technique has revealed that by raising the temperature of the dosemeter during bleaching the threshold for re-estimated absorbed doses may be substantially reduced. The optimum temperature was found to be 800C and the practical threshold for the re-estimation of absorbed dose using a PTFE disc dosemeter was determined as 750 mrad. (author)

1977-01-01

348

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)

2009-10-02

349

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2009-07-01

350

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

1984-06-05

351

SU-FF-T-390: In-Vivo Prostate Brachytherapy Absorbed Dose Measurements  

Energy Technology Data Exchange (ETDEWEB)

Purpose: In-vivo prostate brachytherapy absorbed dosimetrydetector using scintillating fibers. Method and Materials: Five pairs of 85.5 {+-} 0.05 cm long blue shifted scintillating fibers (model BCF-10) with 1 mm{sup 2} cross sectional area were placed in a mixture of gelatin (368.6 {+-} 0.5 grams) and water (3.78 {+-} 0.025 liters) to measured the absorbed dose delivered by a 12 Ci {sup 192}Ir HDR source. The fibers were held by a 7 x 7 cm{sup 2} template grid and optically connected to a 16-channel multianode photomultiplier tube (Hamamatsu, model H6568). Each pair consisted of one fiber 4 mm shorter than the other one to extract the dose by the subtraction method. A dose atlas was used for radiation delivered to the phantom. The plans followed delivered 5 and 7 Gy to a point located 2.0 centimeters away from the central dwelling positions. A total of 32 data points were acquired in a plan to assess the linearity and reproducibility of the measurements.Results: Reproducibility of the data was found to be within 5% and the overall accuracy of the system estimated to be {+-}5.5%. The linearity of the data for all 7 measureddose values (ranging from 0.6 to 7 Gy), gives a slope of 312 counts/Gy with a 1.4% relative deviation. Conclusion: This work indicates the possibility of measuring in real-time the dose effectively delivered to a biological system during prostate brachytherapy treatments. The availability of commercially thin (150 {micro}m) scintillating fibers opens the capability of using such system during clinical treatments (by embedding the fibers within the catheters) with the advantage of performing real-time adjustment of the dose delivery.

Gueye, Paul; Velasco, Carlos; Keppel, Cynthia; Murphy, B; Sinesi, C

2009-06-01

352

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

Energy Technology Data Exchange (ETDEWEB)

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.

Ryan, J.; Harper, P.; Stark, V.; Peterson, E.; Lathrop, K.

1984-01-01

353

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

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

2007-01-01

354

Intercomparison of absorbed dose to water calibration factors under WG5 of APMP programme  

International Nuclear Information System (INIS)

In 1999, Asia Pacific Metrology Programme Technical Committee on Ionizing Radiation (TCRI), initiated regional key comparisons among its member countries. Under this programme, BARC was chosen as the organizer for Working Group 5 (WG 5) for key comparison of absorbed dose in water in 60Co radiation (at a depth of 5 g cm-2). Five institutions namely, ARPANSA (Australia), NSCL (Syria), CSIR (South Africa), INER (Taiwan) and SIRIM (Malaysia) took part in the intercomparisons. This paper brings the materials and methods used and the results of the intercomparisons

2001-11-26

355

Importance of absorbed dose distribution in the body volume for the outcome of radiation injury  

Energy Technology Data Exchange (ETDEWEB)

The results of a 20-year study of 10 patients who had acute radiation disease in the past caused by absorbed dose distribution of various degree of uniformity, have shown that in uneven irradiation both a period of formation and a period of long-term aftereffects are characterized by a greater number of affected systems and more severe outcomes. The severity and time of the development of the most serious ones (amputation of the limb, cataracts) can be forecast by some early clinical signs.

Barabanova, A.V.; Gus' kova, A.K.

1982-11-01

356

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)

1988-01-01

357

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

Energy Technology Data Exchange (ETDEWEB)

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 (ED/sub 50/) 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 (ED/sub 50/) 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.

Dixon-Brown, A.; Hopewell, J.W.

1988-03-01

358

Powder state alanine/ESR dosimeter for measuring the absorbed dose of electron beam  

International Nuclear Information System (INIS)

This paper describes the application of a powder state alanine/ESR dosimeter for measurement of the absorbed dose of electron beam to monitor the dose standards and for quality control of the products processed by electron beam irradiation. The dosimeter is a sealed plastic container containing pre-treated alanine powder. Spectra of the internal standard and the alanine sample are measured simultaneously using dual cavity of an ESR spectrometer. The internal standard is a CuCl2.2H2O monocrystal which gives stable ESR signals. A diamond sample is used as working standard. With these two standards, the measurement accuracy can be improved. The standard dose value is determined with an electron beam calorimeter made in our laboratory for dose calibration purpose. The advantages and the dosimetry characteristics of the application of powder state alanine/ESR dosimeters are discussed. This method is accurate and easy to use. In the region of 10-104 Gy, the dose response shows a linear relationship and the precision is better than ± 2%. (Author)

1993-01-01

359

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

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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

360

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)

1964-03-01

 
 
 
 
361

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)

2008-10-19

362

Absorbed dose distribution visualization for superficial treatments through the Fricke Xylenol Gel dosimeter (FXG)  

Energy Technology Data Exchange (ETDEWEB)

Electrons, orthovoltage X-rays and betas are used for superficial treatments. It has been shown that it is practical to measure these three types of radiation using gel dosimetry, which is an accurate dosimetric tool, from which one can infer the absorbed dose. The Fricke Xylenol Gel (FXG) dosimeter has presented adequate results due to its spatial resolution, effective atomic number and density that are near to those of soft tissue. The aim of this work is to compare three types of radiation for skin treatments like orthovoltage (X-rays), brachytherapy (beta rays) and megavoltage (electrons) using the FXG-CCD dosimetric system to determine the calibration curves (CC), beam profiles (BP) and percentage depth dose curves (PDD), evidencing why for clinical applications a specific type of radiation is selected for superficial treatment. From the results obtained we can infer that the FXG-CCD system is adequate for linear, area and volume measurements.

Alva, M; Sampaio, F G A; Moreira, M V; Petchevist, P C D; De Almeida, A, E-mail: dalmeida@ffclrp.usp.b

2010-11-01

363

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

International Nuclear Information System (INIS)

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

1978-01-01

364

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

International Nuclear Information System (INIS)

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

1995-03-01

365

Absorbed decay-photon dose analysis of the IVVS/GDC plug in ITER  

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The In-Vessel Viewing System (IVVS) and the Glow Discharge Cleaning (GDC) unit share a common port at the equatorial level of the ITER tokamak. The plug consists mainly of the IWS probe, capable of performing the laser-based in-vessel viewing and metrology, the GDC electrode, capable of producing glow discharge in the vacuum vessel during intermediate maintenance and wall conditioning periods, and their respective deployment systems to move the electrodes. The plug extends over a length of about 11 m from the GDC tip to the rear end at the bioshield level. At the present stage of the conceptual design a neutronics analysis has been requested to provide valuable input to the design strategy. To this end, a first assessment has been performed focusing on operational loads on the GDC electrode head in the so-called shielding position and on absorbed decay-photon dose rate levels in the structural components of the entire system. In this contribution we are reporting on the absorbed dose rates after the ITER life time irradiation at several cooling times. Gamma sources from activated materials of the IVVS/GDC and surrounding structures, like blanket, vacuum vessel, toroidal and poloidal field coils, have been taken into account. (orig.)

Leichtle, D.; Serikov, A.; Fischer, U. [Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen (DE). Inst. for Neutron Physics and Reactor Technology (INR)

2011-07-01

366

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

International Nuclear Information System (INIS)

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

2002-11-01

367

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

International Nuclear Information System (INIS)

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

2000-12-01

368

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

Energy Technology Data Exchange (ETDEWEB)

The calculation of absorbed dose in skeletal tissues at radiogenic risk has been a difficult problem because the relevant structures cannot be represented in conventional geometric terms nor can they be visualized in the tomographic image data used to define the computational models of the human body. The active marrow, the tissue of concern in leukaemia induction, is present within the spongiosa regions of trabecular bone, whereas the osteo-progenitor cells at risk for bone cancer induction are considered to be within the soft tissues adjacent to the mineral surfaces. The International Commission on Radiological Protection (ICRP) recommends averaging the absorbed energy over the active marrow within the spongiosa and over the soft tissues within 10 {mu}m of the mineral surface for leukaemia and bone cancer induction, respectively. In its forthcoming recommendation, it is expected that the latter guidance will be changed to include soft tissues within 50 {mu}m of the mineral surfaces. To address the computational problems, the skeleton of the proposed ICRP reference computational phantom has been subdivided to identify those voxels associated with cortical shell, spongiosa and the medullary cavity of the long bones. It is further proposed that the Monte Carlo calculations with these phantoms compute the energy deposition in the skeletal target tissues as the product of the particle fluence in the skeletal subdivisions and applicable fluence-to-dose-response functions. This paper outlines the development of such response functions for photons. (authors)

Eckerman, K.F. [Life Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6480 (United States); Bolch, W.E. [Department of Nuclear and Radiological Engineering, University of Florida, Gainesville, FL 32611 (United States); Zankl, M.; Petoussi-Henss, N. [GSF-National Research Center for Environment and Health, Institute of Radiation Protection, Ingolstaedter Landstr, 1, 85764 Neuherberg (Germany)

2007-07-01

369

Response Funtions for Computing Absorbed Dose to Skeletal Tissues from Photon Irradiation  

Energy Technology Data Exchange (ETDEWEB)

The calculation of absorbed dose in skeletal tissues at radiogenic risk has been a difficult problem because the relevant structures cannot be represented in conventional geometric terms nor can they be visualised in the tomographic image data used to define the computational models of the human body. The active marrow, the tissue of concern in leukaemia induction, is present within the spongiosa regions of trabecular bone, whereas the osteoprogenitor cells at risk for bone cancer induction are considered to be within the soft tissues adjacent to the mineral surfaces. The International Commission on Radiological Protection (ICRP) recommends averaging the absorbed energy over the active marrow within the spongiosa and over the soft tissues within 10 mm of the mineral surface for leukaemia and bone cancer induction, respectively. In its forthcoming recommendation, it is expected that the latter guidance will be changed to include soft tissues within 50 mm of the mineral surfaces. To address the computational problems, the skeleton of the proposed ICRP reference computational phantom has been subdivided to identify those voxels associated with cortical shell, spongiosa and the medullary cavity of the long bones. It is further proposed that the Monte Carlo calculations with these phantoms compute the energy deposition in the skeletal target tissues as the product of the particle fluence in the skeletal subdivisions and applicable fluence-to-dose response functions. This paper outlines the development of such response functions for photons.

Eckerman, Keith F [ORNL; Bolch, W E [University of Florida, Gainesville; Zankl, M [Institute of Radiation Protection, GSF-National Reserach Center for Environ; Petoussi-Henss, N [Institute of Radiation Protection, GSF-National Reserach Center for Environ

2007-01-01

370