Two-parametric beam model for dosimetry of the process of electron irradiation of materials with low density and atomic number

The work is devoted to studying the possibility of using a two-parametric model of an electron beam to describe the depth distributions of the electron dose in materials with a low density and an effective atomic number. In this model, the parameters are determined by fitting the semi-empirical mode...

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Дата:2021
Автори: Lazurik, V.T., Lazurik, V.M., Popov, G., Zimek, Z.
Формат: Стаття
Мова:English
Опубліковано: Національний науковий центр «Харківський фізико-технічний інститут» НАН України 2021
Назва видання:Вопросы атомной науки и техники
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Цитувати:Two-parametric beam model for dosimetry of the process of electron irradiation of materials with low density and atomic number / V.T. Lazurik, V.M. Lazurik, G. Popov, Z. Zimek // Problems of Atomic Science and Technology. — 2021. — № 6. — С. 34-37. — Бібліогр.: 11 назв. — англ.

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spelling nasplib_isofts_kiev_ua-123456789-1954642025-02-23T17:58:26Z Two-parametric beam model for dosimetry of the process of electron irradiation of materials with low density and atomic number Двопараметрична модель пучка для дозиметрії процесу електронного опромінення матеріалів з низькою щільністю і атомним номером Двухпараметрическая модель пучка для дозиметрии процесса электронного облучения материалов с малыми плотностью и атомным номером Lazurik, V.T. Lazurik, V.M. Popov, G. Zimek, Z. Interaction of relativistic particles with crystals and matter The work is devoted to studying the possibility of using a two-parametric model of an electron beam to describe the depth distributions of the electron dose in materials with a low density and an effective atomic number. In this model, the parameters are determined by fitting the semi-empirical model (PFSEM-method) to the results of measurements of the depth-dose distribution in a dosimetric wedge. The depth-dose distributions in a birchwood wedge were measured at the Institute of Nuclear Chemistry and Technology in Warsaw, Poland. The parameters of the electron beam incident on the wedge were determined by the PFSEM method. The Monte Carlo simulations of the depth-dose distribution in the wedge for the process of electron irradiation, the characteristics of which are determined by the PFSEM method, have been carried out. It is shown that there is a satisfactory agreement between the measurement results and the Monte Carlo simulation of the depth-dose distribution. The advantages of describing depth-dose distributions in a wedge based on a two-parametric model of an electron beam in comparison with traditional methods of polynomial approximation of measurement results are discussed. Робота присвячена дослідженню можливості використання двопараметричної моделі електронного пучка для опису розподілу дози електронів по глибині в матеріалах з низькою щільністю і ефективним атомним номером. У цій моделі параметри визначаються шляхом підгонки напівемпіричної моделі (PFSEM-метод) до результатів вимірювань розподілу дози по глибині в дозиметричному клині. Розподіл дози по глибині в клині з березової деревини було виміряно в Інституті ядерної хімії та технологій в Варшаві, Польща. Параметри падаючого на клин електронного пучка визначалися методом PFSEM. Проведено моделювання методом Монте-Карло розподілу дози по глибині в клині для процесу електронного опромінення, характеристики якого визначені методом PFSEM. Показано, що існує згода між результатами вимірювань і моделюванням методом Монте-Карло розподілу дози по глибині. Обговорюються переваги опису розподілу дози по глибині в клині на основі двопараметричної моделі електронного пучка в порівнянні з традиційними методами поліноміальної апроксимації результатів вимірювань. Работа посвящена исследованию возможности использования двухпараметрической модели электронного пучка для описания распределения дозы электронов по глубине в материалах с низкой плотностью и эффективным атомным номером. В этой модели параметры определяются путем подгонки полуэмпирической модели (PFSEM-метод) к результатам измерений распределения дозы по глубине в дозиметрическом клине. Распределение дозы по глубине в клине из березовой древесины было измерено в Институте ядерной химии и технологий в Варшаве, Польша. Параметры падающего на клин электронного пучка определялись методом PFSEM. Проведено моделирование методом Монте-Карло распределения дозы по глубине в клине для процесса электронного облучения, характеристики которого определены методом PFSEM. Показано, что существует удовлетворительное согласие между результатами измерений и моделированием методом Монте-Карло распределения дозы по глубине. Обсуждаются преимущества описания распределения дозы по глубине в клине на основе двухпараметрической модели электронного пучка по сравнению с традиционными методами полиномиальной аппроксимации результатов измерений. 2021 Article Two-parametric beam model for dosimetry of the process of electron irradiation of materials with low density and atomic number / V.T. Lazurik, V.M. Lazurik, G. Popov, Z. Zimek // Problems of Atomic Science and Technology. — 2021. — № 6. — С. 34-37. — Бібліогр.: 11 назв. — англ. 1562-6016 PACS: 87.53.Bn DOI: https://doi.org/10.46813/2021-136-034 https://nasplib.isofts.kiev.ua/handle/123456789/195464 en Вопросы атомной науки и техники application/pdf Національний науковий центр «Харківський фізико-технічний інститут» НАН України
institution Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection DSpace DC
language English
topic Interaction of relativistic particles with crystals and matter
Interaction of relativistic particles with crystals and matter
spellingShingle Interaction of relativistic particles with crystals and matter
Interaction of relativistic particles with crystals and matter
Lazurik, V.T.
Lazurik, V.M.
Popov, G.
Zimek, Z.
Two-parametric beam model for dosimetry of the process of electron irradiation of materials with low density and atomic number
Вопросы атомной науки и техники
description The work is devoted to studying the possibility of using a two-parametric model of an electron beam to describe the depth distributions of the electron dose in materials with a low density and an effective atomic number. In this model, the parameters are determined by fitting the semi-empirical model (PFSEM-method) to the results of measurements of the depth-dose distribution in a dosimetric wedge. The depth-dose distributions in a birchwood wedge were measured at the Institute of Nuclear Chemistry and Technology in Warsaw, Poland. The parameters of the electron beam incident on the wedge were determined by the PFSEM method. The Monte Carlo simulations of the depth-dose distribution in the wedge for the process of electron irradiation, the characteristics of which are determined by the PFSEM method, have been carried out. It is shown that there is a satisfactory agreement between the measurement results and the Monte Carlo simulation of the depth-dose distribution. The advantages of describing depth-dose distributions in a wedge based on a two-parametric model of an electron beam in comparison with traditional methods of polynomial approximation of measurement results are discussed.
format Article
author Lazurik, V.T.
Lazurik, V.M.
Popov, G.
Zimek, Z.
author_facet Lazurik, V.T.
Lazurik, V.M.
Popov, G.
Zimek, Z.
author_sort Lazurik, V.T.
title Two-parametric beam model for dosimetry of the process of electron irradiation of materials with low density and atomic number
title_short Two-parametric beam model for dosimetry of the process of electron irradiation of materials with low density and atomic number
title_full Two-parametric beam model for dosimetry of the process of electron irradiation of materials with low density and atomic number
title_fullStr Two-parametric beam model for dosimetry of the process of electron irradiation of materials with low density and atomic number
title_full_unstemmed Two-parametric beam model for dosimetry of the process of electron irradiation of materials with low density and atomic number
title_sort two-parametric beam model for dosimetry of the process of electron irradiation of materials with low density and atomic number
publisher Національний науковий центр «Харківський фізико-технічний інститут» НАН України
publishDate 2021
topic_facet Interaction of relativistic particles with crystals and matter
url https://nasplib.isofts.kiev.ua/handle/123456789/195464
citation_txt Two-parametric beam model for dosimetry of the process of electron irradiation of materials with low density and atomic number / V.T. Lazurik, V.M. Lazurik, G. Popov, Z. Zimek // Problems of Atomic Science and Technology. — 2021. — № 6. — С. 34-37. — Бібліогр.: 11 назв. — англ.
series Вопросы атомной науки и техники
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fulltext ISSN 1562-6016. ВАНТ. 2021. № 6(136) 34 https://doi.org/10.46813/2021-136-034 TWO-PARAMETRIC BEAM MODEL FOR DOSIMETRY OF THE PROCESS OF ELECTRON IRRADIATION OF MATERIALS WITH LOW DENSITY AND ATOMIC NUMBER V.T. Lazurik 1 , V.M. Lazurik 1 , G. Popov 1 , Z. Zimek 2 1 V.N. Karasin Kharkiv National University, Kharkov, Ukraine; 2 Institute of Nuclear Chemistry and Technology, Warsaw, Poland E-mail: lazurik@hotmail.com The work is devoted to studying the possibility of using a two-parametric model of an electron beam to describe the depth distributions of the electron dose in materials with a low density and an effective atomic number. In this model, the parameters are determined by fitting the semi-empirical model (PFSEM-method) to the results of meas- urements of the depth-dose distribution in a dosimetric wedge. The depth-dose distributions in a birchwood wedge were measured at the Institute of Nuclear Chemistry and Technology in Warsaw, Poland. The parameters of the electron beam incident on the wedge were determined by the PFSEM method. The Monte Carlo simulations of the depth-dose distribution in the wedge for the process of electron irradiation, the characteristics of which are deter- mined by the PFSEM method, have been carried out. It is shown that there is a satisfactory agreement between the measurement results and the Monte Carlo simulation of the depth-dose distribution. The advantages of describing depth-dose distributions in a wedge based on a two-parametric model of an electron beam in comparison with tradi- tional methods of polynomial approximation of measurement results are discussed. PACS: 87.53.Bn INTRODUCTION The practical use of a dosimetric wedge in radiation technologies is regulated by international standards, which define the procedures for measuring the depth distribution of the dose in the wedge, methods for pro- cessing the measurements and interpreting the results of processing measurements [1, 2]. The standards propose to determine the most probable energy EP and the aver- age energy EAv of electrons in the beam using the dosimetric wedge method. These characteristics of elec- trons in a beam are widely used to control the stability of the electron radiation flux in radiation-technological processes. However, the characteristics of electron radi- ation obtained using a standard dosimetric wedge, in some cases, are unsuitable for describing the spatial distribution of the dose in irradiated objects. Indeed, the spatial distribution of the dose substantially depends on the density and the effective atomic number of the mate- rials of the irradiated objects. As a rule, during radiation sterilization of medical devices and foodstuffs, the den- sity and effective atomic number of materials of irradi- ated objects are several times lower than for aluminum, on the basis of which a standard dosimetric wedge is made. In addition, for materials with low density, the spatial distribution of the dose in the irradiated objects depends significantly on the angular distribution of elec- trons in the beam. Therefore, for the further develop- ment of radiation technologies, dosimetric wedges cre- ated on the basis of materials with low density and ef- fective atomic number are of interest. A modern method for determining the characteristics of electron radiation is based on measurements of the depth distribution of the dose in a dosimetric wedge and using the parametric fitting method of the semi- empirical model (PFSEM method) [3 - 5]. This method has proven itself well in radiation sterilization technolo- gies in which aluminum dosimetric wedges are used [6 - 9]. In connection with the above, an urgent scientific and practical task is to test the PFSEM method using the results of measurements in dosimetric wedges created from materials with low density and effective atomic number. Therefore, for the further development of radiation technologies, dosimetric wedges created on the basis of materials with low density and effective atomic number are of interest, which was carried out at the radiation sterilization line of the Institute of Nuclear Chemistry and Technology in Warsaw, Poland [10]. The ad- vantages of describing depth dose distributions in a wedge on the basis of a semiempirical model with pa- rameters calculated by the PFSEM method in compari- son with traditional methods of polynomial approxima- tion of measurement results are discussed. 1. DEPTH-DOSE CURVE OF ELECTRON RADIATION IN A BIRCH WEDGE Measurements of the depth-dose curve of electron radiation were carried out using dosimetric films located in a wedge made of birch wood. The characteristics of the wedge are as follows: - density of birch wood: 0.536 g/cm 3 ; - effective atomic number: 6.28; - effective atomic weight: 11.86; - dimensions: 12.546.545.5 cm; - slope factor: 0.265. The method of irradiation and processing of dosimetric films is described in [6, 7]. The measurement results are shown in Fig. 1. The dose value D(x) is normalized to the calculated dose value D(0) on the wedge surface onto which the elec- tron beam falls. The depth in the wedge X is indicated in standard mass units of length [g/cm 2 ]. The vertical dashed lines indicate the boundaries of the depth regions that are used in the radiation sterilization process. Mark X1 indicates the depth range that is used for single-sided irradiation and X2 for double-sided irradiation. For com- mailto:lazurik@hotmail.com ISSN 1562-6016. ВАНТ. 2021. № 6(136) 35 parison, in Fig. 1 shows the depth-dose curve of elec- trons in the birch wedge, calculated using a semi- empirical model [5], the parameters of which were de- termined by the PFSEM method. X2 X1 0 0.5 1 1.5 0 1 2 3 4 5X, g/cm2 D(x)/D(0) Fig. 1. Dose distribution by depth in a wedge of birch. Points  results of measurements, a continuous curve  approximation of measurements by the PFSEM method When characterizing electron radiation by the PFSEM method, the absolute values of the measured dose are not used and, therefore, the method error is determined only by the reproducibility of measurement. Estimates of the reproducibility standard deviation of measurements Δ were made on the basis of calculating the standard deviation of the dose values measured on the first D1(xi) and second D2(xi) dosimetry films, for each of the recorded depths xi. For the areas of depths defined by marks X1 and X2, the estimates of the root- mean-square measurement errors are close and do not exceed values of 2%. As seen from Fig. 1, the error in approximating the measurement results using the PFSEM method is comparable to the error in the meas- urements 2. PROCESSING OF MEASUREMENT RESULTS BY USING THE PARAMETRIC FITTING METHOD OF THE SEMI- EMPIRICAL MODEL The processing of the results of dose measurements on two dosimetric films by the PFSEM method was carried out. For each of the films, using the PFSEM method, the model parameters of the electron beam of the radiation sterilization line, corresponding to the measurement results, were calculated. Model parame- ters of the electron beam calculated from the measure- ment data for the first Ex1 and the second Ex2 films are presented in Table. The line Av_Ex shows the model parameters of the electron beam obtained for the aver- aged data from these two measurements. The results of fitting the parameters of the semi-empirical model of the depth distribution of the dose of electron beam to the measurement results E1 [MeV] E0 [MeV] X0 [g/cm 2 ] Ex1 8.67 8.71 0.016 Ex2 8.7 8.82 0.056 Av_Ex 8.69 8.77 0.037 As can be seen from Table and Fig. 1, the model pa- rameter of the displacement X0 is small in comparison with the depths and the use of dose distributions in radi- ation technologies. This indicates the correct choice of the starting point when processing the depth distribution of the dose on the films. Note, that there is a small dif- ference in the model energy parameters for the one- parameter fit E1 and two-parameter fit E0 of the data obtained in these two measurements. The test results of the PFSEM method are illustrated in Fig. 2. In the figure, the dots show the values of the dose distribution averaged over two measurements. The solid curve is an approximation of the averaged values of the dose distribution using the PFSEM method and computer visualization of the semi-empirical model of the depth distribution of the absorbed energy of an elec- tron beam in matter [5]. Histogram  calculation using the ModeRTL software module of the RT-Office system [11] in accordance with the values of the characteristics of electron radiation E0 = 8.77 and X0 = 0.037 deter- mined by the PFSEM method (see Table 1) within the framework of the two-parameter model of the electron beam [7]. X1 X2 0 0.5 1 1.5 0 1 2 3 4 5X, g/cm2 D(x)/D(0) Fig. 2. Comparison of measurement and calculation results using the PFSEM method. Points  average depth distribution of the dose over two measurement results, a continuous curve  approximation of meas- urements by the PFSEM method, histogram  calcula- tion using ModeRTL module of the RT-Office system As seen in Fig. 2 satisfactory agreement: - between the measurement values and the calcula- tion results, using a computer visualization of a semi- empirical model [5] of the depth dose distribution in a wedge of birch wood irradiated with an electron beam, the parameters of which were determined by the PFSEM method; - between the measurement values and the calcula- tion results, using Monte Carlo simulation [11] of the depth dose distribution in a wedge of birch wood irradi- ated with an electron beam, the parameters of which were determined by the PFSEM method. 3. POLYNOMIAL APPROXIMATION OF MEASUREMENT RESULTS A numerical study of the possibilities of determining the dependences of the depth dose distribution on the basis of traditional methods of polynomial approxima- tion of the measurement results was carried out. Some ISSN 1562-6016. ВАНТ. 2021. № 6(136) 36 results of the numerical study of the polynomial approx- imation of measurements of the depth distributions of the electron radiation dose in a wedge made of birch wood are shown in Figs. 3 and 4. As can be find in Fig. 3 the dashed curve is the ap- proximation by a polynomial of the 2nd degree, the dashed-dotted curve is the approximation by the poly- nomial of the 3rd degree and the dashed curve is the approximation by the polynomial of the 4th degree. Sol- id curve according approximation by the PFSEM meth- od. X1 X2 0 0.5 1 1.5 0 1 2 3 4 5X, g/cm 2 D(x)/D(0) Fig. 3. Comparison of approximations of measurement results by polynomials of different degrees X1 X2 y2 (x)= -0.0734x 3 + 0.2863x 2 - 0.1217x + 1.1047 R 2 = 0.9869 y1 (x)= -0.0605x 3 + 0.2249x 2 - 0.0444x + 1.0835 R 2 = 0.9675 0 0.5 1 1.5 0 1 2 3 4 5X, g/cm2 D(x)/D(0) Fig. 4. Comparison of approximations of measurement results by degree 3 polynomials and using the PFSEM method. Points  measurement results, continuous curves  approximation by polynomials of degree 3, a dashed curve approximation of measurements by the PFSEM method According to that: - the results of measurements of dose distributions in the depth ranges (0-X1) and (0-X2) cannot be approxi- mated by polynomials below the 3rd degree with an accuracy comparable to the accuracy of the measure- ments; - polynomial approximation of measurement results cannot provide correct extrapolation to determine the dose value on the wedge surface, on which the electron beam falls. CONCLUSIONS Comparison of the depth dose distributions obtained as a result of measurements and calculations based on the parameters of the electron beam determined by the using the parametric fitting method of the semi- empirical modelallows us to draw the following conclu- sions: - the error in approximating the results of measure- ments of the depth dose distribution in a birch wood dosimetric wedge, made by the PFSEM method, is comparable to the error in the measurements; - there is satisfactory agreement between the results of measurements and Monte Carlo calculation of the depth distribution of the dose of electron radiation, the characteristics of which were determined by the PFSEM method; - in the depth ranges of practical interest, approxima- tion of the results of measurements of the depth distri- bution of the dose by polynomials above the 3rd degree allows us to describe the depth distribution of the dose with an accuracy comparable to the accuracy of the measurements; - the approximation of the results of measurements of the depth dose distribution performed by the PFSEM method coincides with the accuracy comparable with the accuracy of the polynomial approximation of these measurement results. Thus, the using the parametric fitting method of the semi-empirical model allows one to satisfactorily de- scribe the results of measurements of depth dose distri- butions using only two characteristics of the electron beam, in contrast to the polynomial approximation for which at least four formal parameters are required. REFERENCES 1. ISO/ASTM Standard 51649. Practice for Dosimetry in an E-Beam Facility for Radiation Processing at Energies between 300 keV and 25 MeV, Annual Book of ASTM Standards. 2005, v. 12.02. 2. Radiation Dosimetry: Electron Beams with Energies between 1 and 50 MeV, International Commission on Radiation Units and Measurements. 1984, report 35, Bethesda, MD, USA. 3. V.T. Lazurik, A.V. Pochynok. Dosimetry of elec- trons on the base of computer modeling the depth- dose distribution of irradiation, Journal of Kharkiv University //Mathematical modeling. Information technologies series. 2010, № 925, p. 114-122. 4. A.V. Pochynok, V.T. Lazurik, G.E. Sarukhanyan. 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Зимек Работа посвящена исследованию возможности использования двухпараметрической модели электронно- го пучка для описания распределения дозы электронов по глубине в материалах с низкой плотностью и эффективным атомным номером. В этой модели параметры определяются путем подгонки полуэмпириче- ской модели (PFSEM-метод) к результатам измерений распределения дозы по глубине в дозиметрическом клине. Распределение дозы по глубине в клине из березовой древесины было измерено в Институте ядерной химии и технологий в Варшаве, Польша. Параметры падающего на клин электронного пучка определялись методом PFSEM. Проведено моделирование методом Монте-Карло распределения дозы по глубине в клине для процесса электронного облучения, характеристики которого определены методом PFSEM. Показано, что существует удовлетворительное согласие между результатами измерений и моделированием методом Мон- те-Карло распределения дозы по глубине. Обсуждаются преимущества описания распределения дозы по глубине в клине на основе двухпараметрической модели электронного пучка по сравнению с традиционны- ми методами полиномиальной аппроксимации результатов измерений. ДВОПАРАМЕТРИЧНА МОДЕЛЬ ПУЧКА ДЛЯ ДОЗИМЕТРІЇ ПРОЦЕСУ ЕЛЕКТРОННОГО ОПРОМІНЕННЯ МАТЕРІАЛІВ З НИЗЬКИМИ ЩІЛЬНІСТЮ І АТОМНИМ НОМЕРОМ В.Т. Лазурик, В.М. Лазурик, Г. Попов, З. Зимек Робота присвячена дослідженню можливості використання двопараметричної моделі електронного пучка для опису розподілу дози електронів по глибині в матеріалах з низькою щільністю і ефективним атомним номером. У цій моделі параметри визначаються шляхом підгонки напівемпіричної моделі (PFSEM-метод) до результатів вимірювань розподілу дози по глибині в дозиметричному клині. Розподіл дози по глибині в кли- ні з березової деревини було виміряно в Інституті ядерної хімії та технологій в Варшаві, Польща. Параметри падаючого на клин електронного пучка визначалися методом PFSEM. Проведено моделювання методом Монте-Карло розподілу дози по глибині в клині для процесу електронного опромінення, характеристики якого визначені методом PFSEM. Показано, що існує згода між результатами вимірювань і моделюванням методом Монте-Карло розподілу дози по глибині. Обговорюються переваги опису розподілу дози по глиби- ні в клині на основі двопараметричної моделі електронного пучка в порівнянні з традиційними методами полиномиальной апроксимації результатів вимірювань.