Hasil untuk "Radioactivity and radioactive substances"

Ewerton Clementino Diniz, Luiz Da Silva Maia Neto, Mário Mardone Da Silva et al.

This study aimed to conduct a documentary analysis of federal legislation and regulations in Brazil regarding the irradiation of phytotherapeutic products. The research was carried out between April and June 2024 through a review of official documents, including regulations, resolutions, constitutional amendments, and decrees published between 1983 and 2018. Although the analysis revealed the existence of specific norms and resolutions related to food irradiation, no direct regulation concerning the use of ionizing radiation in phytotherapeutics was identified in Brazil. National legislation addresses the use of ionizing radiation in food, particularly for radio-sterilization, with emphasis on RDC No. 21/2001, which may be indirectly applicable to medicinal plants. Normative Instruction No. 44/2014 provides the most relevant guidelines regarding the application of ionizing radiation in pharmaceuticals. In contrast, international legislation—such as that from the FDA (USA) and FSSAI (India)—explicitly regulates the radio-sterilization of medicinal herbs and plants. The documentary analysis highlights the need for the expansion, regulation, and harmonization of Brazilian standards and protocols to ensure the safe application of ionizing radiation in phytotherapeutics.

Andreina Leon, Carlos Rodrígruez, José Alexander Durán Durán

At Secondary Standard Dosimetry Laboratory (SSDL) in Venezuela is the only one in the country that performs calibrations of dosimetry systems with an IAEA water phantom. However, SSDL has a PTW water phantom, for which there is no procedure for the calibration of dosimetry systems. Therefore, a methodology was developed for its validation using a cobalt-60 equipment, a secondary standard, an IAEA water phantom and a PTW phantom. The adapter for ionization chamber type NE 2561 was studied and designed to protect it from water. The methodology consisted of calculate of absorbed dose rate to water in IAEA water phantom and PTW water phantom. Subsequently, the absorbed dose rates to water were compared between both phantoms and finally, the validation of the new procedures and their respective uncertainties was performed. The adapter of ionization chamber was built with PMMA material. Comparisons between absorbed dose rates to water showed that there is no difference between the two phantoms. The absorbed dose rate to water was calculated with the procedure updates along with their associated uncertainties, obtaining =0.13482 ± 0.00292 Gy/min. Finally, the validation obtained a value of less than 0.7%, which means that the implementation of the new procedures for the calibration of dosimetry systems is valid and applied at the SSDL-Venezuela.

A. V. Vodovatov, E. A. Kosarlukova, A. M. Biblin et al.

Introduction: To successfully address the challenges of optimizing radiation protection during medical exposure, it is essential to have information on patient exposure levels and the structure of diagnostic radiology in medical organizations across the Russian Federation.   Materials and Methods: The primary source of data on patient exposure levels and the structure of diagnostic radiology is the Form No. 3-DOZ, a part of the Unified state statistical monitoring system for controlling and recording individual radiation doses of citizens.   The aim of this study was to comprehensively evaluate the results of completing Form No. 3-DOZ for 2023.   The study utilized data from the Form No. 3-DOZ at the level of the constituent entities of the Russian Federation, obtained from the Federal Database on Individual Radiation Doses of Citizens during medical diagnostic X-ray radiological procedures.   Results and Discussion: The collective dose from medical exposure among the adult population increased by 34 % in 2023 compared to 2022. The most significant increases in the collective doses were observed for radiographic (81 %), radionuclide (49 %), and interventional (57 %) procedures. For the first time in the past five years, the increase in collective doses for X-ray radiological procedures was not accompanied by a corresponding increase in the number of procedures, indicating a rise in average and individual effective doses for patients. The average effective dose per resident of the Russian Federation due to medical exposure in 2023 increased by more than one and a half times: 1.12 mSv compared to 0.86 mSv in 2022. The increase in collective doses for various types of diagnostic radiology is driven by the rise in average effective doses for different X-ray radiological procedures across regions of the Russian Federation. The greatest variations in average effective doses were observed for radiographic procedures (an increase of up to 2.5 times in 2023 compared to 2022).   Conclusion: These changes in average effective doses may be attributed to errors in calculating effective doses and completing the Form No. 3-DOZ, as well as to objective changes in the equipment fleet and/or protocols for conducting X-ray procedures. At the same time, several regions of the Russian Federation reported anomalously low average effective doses. To identify the reasons for abnormally high and/or low effective doses during diagnostic radiology procedures, it is necessary to develop and test a methodology for verifying the data submitted in the Form No. 3-DOZ.

Luiz Cavalcante Ferreira, Amanda Alves da Silva, Fernando Carlos Araujo Ribeiro et al.

Radionuclides occur naturally in the environment, exposing living organisms to ionizing radiation. In addition, human activities have introduced artificial radionuclides such as 137Cs, among others, into the environment. To better understand the occurrence and behaviour of radionuclides in soil, several countries have developed radiological studies and constructed maps. An effort has been made in Brazil to assess the radioactivity in the soils of the country. In this study, the activity concentrations of natural radionuclides 40K, 226Ra and 228Ra, and artificial 137Cs were determined in samples at a depth of 20 cm collected from the soils of the Brazilian State of Sergipe, in a regular grid of 25 km x 25 km. Samples were analysed by gamma-ray spectrometry with the use of hyperpure germanium detectors. The results were correlated with the type of soil, geology, and climate characteristics of the State. The median activity concentrations of 40K, 226Ra, and 228Ra were 210.4 Bq.kg-1, 12.33 Bq.kg-1, and 18.69 Bq.kg-1, respectively. The results are lower than those reported for soils from other Brazilian States in the same region. The activity concentration of 137Cs was lower than the minimum detectable activity. The activity concentration of 40K in young soils of the semi-arid region was higher than that found in most weathered soils of the rainy regions due to the very low pluviometry of the semi-arid area. Higher activity levels of 226Ra were found in Planosol and for 228Ra it was found in the weathered soils (Acrisol) of the coastal zone. Maps of the distribution of the studied radionuclides were designed. The median value of the outdoor absorbed dose rate in air (Dnat) calculated for the soils of the State of Sergipe is lower when compared with other Brazilian States and the UNSCEAR’s worldwide median value.

V. Yu. Golikov

The paper presents the values of the conversion coefficients from the operational quantity, HP(10)/ to the protection quantity, effective dose (E). The conversion coefficients were calculated in a number of points located at a depth of 10 mm under the surface of the torso of the computational model MIRD-5 of the body of an adult. The simulated irradiation conditions corresponded to both uniform and sharply non-uniform irradiation of the employee in the fields of photon radiation with the energy from 0.04 to 2 MeV. It was demonstrated that for the uniform radiation and the “typical” location of the individual dosimeter on the employee’s body, the E/HP(10) ratio is less than one in the entire range of radiation energies for the directions of its incidence in front and from the left side, i.e. Hp(10) is a conservative assessment of E. When the radiation falls on the back and for the “typical” location of an individual dosimeter on the employee’s body in the entire range of radiation energies, the ratio E/Hp(10) is significantly larger (for the energies <0.1 MeV) or close to one, i.e. Hp(10) is not a conservative assessment of E. In the spatial non-uniform fields of photon radiation with an increase in the degree of non-uniformity irradiation of the employee’s body, the values of the conversion coefficients decreased. When irradiation in front and from the left side an individual dosimeter placed in a “typical” position will be conservative estimate the value of an effective dose of the employee in the entire considered range of energies. When irradiation on the right side an individual dosimeter placed in a “typical” position will underestimate the value of an effective dose in the entire considered range of energy. It was demonstrated that the optimal location of the individual dosimeter on the surface of the employee’s body allows us to adequately assess according to his indications the value of an effective dose even with significantly changing geometry of its irradiation during a complete cycle of treatment with the source of ionizing radiation.

Shovi Sawe

Assessment of public exposure to background radiation was performed in Manyoni, Tanzania to address public concerns following the discovery of uranium deposits in their neighborhoods. Results show that the highest concentrations of radionuclides are 112, 95 and 463 Bq.kg-1 for 226Ra, 232Th and 40K, respectively. The highest annual effective dose to the public is 2.91 mSv.y-1 with a mean value of 1.29 mSv.y-1. Authorities may use these results to address public concerns as well as the baseline information. Further investigations on public exposures in Manyoni are recommended.

article Editorial

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Sérgio Augusto Santana de Souza, Felipe Monteiro Rodrigues, Allan Felipe Fattori Alves et al.

Computed Tomography (CT) has been one of the greatest innovations for medical diagnosis. Among the main features of CT is its ability to provide high-quality anatomical and functional images. Other important imaging modalities are the ones conducted in Nuclear Medicine (NM), which, with the use of radiotracers, makes it possible to obtain metabolic and molecular images in vivo. The union of NM and CT imaging modalities is possible through hybrid equipment. The purpose of this research is to evaluate the quality and quantity of tomographic exams that can be performed in hybrid equipment. To complete this research analyzes of the ability to perform CT exams in the room that holds a Single Photon Emission Computed Tomography/ Computed Tomography SPECT/CT equipment in an NM facility were carried out. The evaluation criteria were: equipment quality control, image quality assessment by a subjective method as per European Guidelines on Quality Criteria for Computed Tomography (EUR), and assessment of shielding of the room, as an indicator of how many exams can be performed. Considering the results of the barrier thickness, the Botucatu Medical School and Nuclear Medicine facility is capable of performing 100 tomography exams per week. According to information obtained in the facility, currently, approximately 20 scans are performed weekly, so there is an increased opportunity of up to 80 exams weekly. Therefore, the hybrid equipment is qualified to perform diagnostic tests with superior image quality, compared to those performed in CT equipment.

Van Hao Duong, Thanh Duong Nguyen, Erika Kocsis et al.

FELIPE DO CARMO AMORIM, PEDRO PACHECO DE QUEIROZ FILHO, Fernando Barcellos Razuck

With technological advances in several research areas of science, it is becoming increasingly common to use computer programs to solve problems. Some of these programs are based on statistical analysis and simulation of reality, such as the Monte Carlo Method (MC). The MC is a statistical tool widely used in different areas of knowledge, as a resource for simulating events that involve from financial assessments to the interaction of radiation with matter. Thereby, surveys with radiation sources, for example, are constantly evolving to study the question of radiation protection. In this sense, this paper has as main objective to verify the relevance of the MC for the area of radiation protection, analyzing the studies that apply the method in the Postgraduate Program (PPG) in Radiation Protection and Dosimetry of Institute of Radiation Protection and Dosimetry (IRD). This is because it is understood thatthrough the application of Scientific Knowledge Management (SKM) the construction of knowledge happens through an exchange of scientific information, that is, exchange of relevant contents that help in the preservation of knowledge.In this sense, a bibliometric analysis of the dissertations and theses deposited in Brazilian bank was made using the search term "Monte Carlo" and its respective programs (PENELOPE, GEANT4, EGSnrc, MCNP and Visual Monte Carlo), to be found in the title, abstract or keywords. With the identification of works carried out in all areas of concentration of the PPG, it is understood that the MC is extremely relevant for studies in the area of radiation protection.

José Luiz Horacio Faccini

Dynamic mode decomposition (DMD) has been used for experimental and numerical data analysis in fluid dynamics. Despite of its advantages, the application of the DMD methodology to investigate the natural circulation in nuclear reactors are very scarce in literature. In this paper it is applied the traditional DMD and its variation, the sparsity-promoting dynamic mode decomposition (SPDMD), for analysis of temperature and velocity fields data, generated by computational simulation of an experimental setup in reduced scale, similar to a heat removal system by natural circulation of a pool-type research reactor. Firstly the numerical data is partitioned, using a space-time correlation approach, in order to identify fundamental sequences to compute the dynamic modes. Next, the DMD and SPDMD methodologies are applied over each subsequence to obtain the dynamic modes of the temperature and velocity fields. Finally the flow fields are reconstructed and compared with the original numerical data. The conclusion is that the SPDMD performs better than DMD to represent both the temperature and velocity data.

João Henrique Hamann, José Guilherme Pereira Peixoto

Dosimetry by polymer gel associated with magnetic resonance imaging (MRI) is a promising technique for three-dimensional dose determination in radiotherapy. Understanding the effects of the interaction of radiation with the materials that make up the dosimetric solution and the mechanisms of the polymerization process are fundamental. Thus, studies associated with polymer gel dosimetry have been widely developed. The awakening to this type of work is due to the fact that dosimetry by polymer gel is a tool that allows, for example, the three-dimensional analysis of the dose distribution in a given volume. In this article, a literary review was carried out for a better understanding of the mechanisms responsible for the polymerization process of the dosimeter gel. Then, following the protocol presented in TRS 398, samples of the nPAG type dosimeter gel were irradiated in a medical linear accelerator with 6MeV X-ray beam energy. The response curve of these samples was obtained through the statistical analysis of magnetic resonance images.

Soroush Majlesi, Jukka Juutilainen, Tatiana Trubnikova et al.

Elicardo Alves de Souza Goncalves, Celio Simonacci Gomes, Luis Fernando Oliveira et al.

A well know way for best understanding of radiation scattering and radiation exposure rate during a procedure using ionizing radiation is to map exposure over the space around the source and sample. This map is done measuring exposure in points regularly spaced, it means, measurement will be placed in localization chosen by increasing a regular steps from a starting point, along the x, y and z axes or, in more efficient way, radial and angular coordinates. However, it is not always possible to maintain the accuracy of the steps throughout the entire space, or there will be regions of difficult access where the regularity of the steps will be impaired. In this work we use a high energy radiation source to simulate a common radiography setup and construct its exposure map. The arrangement of the points and the interpolation were used considering polar coordinates. Then with the same data, an interpolation using the Delaunay triangulation was made. The results show the advantages and disadvantages of each other besides the high coherence for the same data. To simulate the impossibility of regular points, the same procedures were performed in the absence of any point and compared. The results show a lower total variation when the map is calculated by triangulation. The computational and graphic treatment was performed with GNU OCTAVE software and its image processing package. The data were acquired from a bunker where a 6MeV betatron was used as a primary source. A well know way for best understanding of radiation scattering and radiation exposure rate during a procedure using ionizing radiation is to map exposure over the space around the source and sample. This map is done measuring exposure in points regularly spaced, it means, measurement will be placed in localization chosen by increasing a regular steps from a starting point, along the x, y and z axes or, in more efficient way, radial and angular coordinates. However, it is not always possible to maintain the accuracy of the steps throughout the entire space, or there will be regions of difficult access where the regularity of the steps will be impaired. In this work we use a high energy radiation source to simulate a common radiography setup and construct its exposure map. The arrangement of the points and the interpolation were used considering polar coordinates. Then with the same data, an interpolation using the Delaunay triangulation was made. The results show the advantages and disadvantages of each other besides the high coherence for the same data. To simulate the impossibility of regular points, the same procedures were performed in the absence of any point and compared. The results show a lower total variation when the map is calculated by triangulation. The computational and graphic treatment was performed with GNU OCTAVE software and its image processing package. The data were acquired from a bunker where a 6MeV betatron was used as a primary source.

Marcel Javier FREDERICO, Yolma Banguero, Hugo Cerecetto et al.

Radiological exams are increasingly used in clinic for diagnostic analysis of different types of pathologies. These tests are associated with a dose that is received by the patient. In addition, the risks in exposure to ionizing radiation are different according to the group which the individual belongs. According to age, the group of children is more radiosensitive than adults. In this work we have obtained values of the air-weighted kerma index for chest scans studies in a Genereal Electric Computed Tomography (CT) scanner model Discovery with 64-channels. Using an adult protocol, two scans have been performed, one using a cylinder standard PMMA phantom while the second one has used an oblong chest phantom designed for a two year old pediatric patient. Furthermore, other protocols have been selected by varying the X-ray tube current but maintaining the same voltage, in order to obtain a reduction in the dose received by the pediatric patient but maintaining the image quality. The use of the adult protocol in the child phantom has generated a value in the air-weighted kerma index 89.47% greater than that received using the adult phantom. As small patients receive higher doses, the use of specific protocols for children is important for the dose reduction in CT tests. Due to the different characteristics of CT scanners and in order to optimize these protocols with regard to dose and diagnostic image quality, there is a need to have pediatric phantoms in health centers

Juraci Passos Reis, Victor Gabriel Alves, Leandro Rodrigues Fairbanks

In recent years, there have been major changes in radiotherapy, particularly in dose delivery for treatments using the techniques of Three-Dimensional Conformal Radiation Therapy (3D-CRT), Intensity-Modulated Radiation Therapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT). However, in the literature, no workload results for radiation therapy treatments performed exclusively with the VMAT technique were found. In this study, a new workload and a new VMAT factor will be proposed. For such, patient data originating from management and planning systems were acquired, such as dose values, monitor units, numbers of arcs per patient and number of hypofractionated treatments. The average clinical workload values for conventional treatments were 328 Gy/week, resulting in a VMAT factor of 1.97; similarly, for hypofractionated treatments, the clinical workload was 33Gy/week and the VMAT factor was 1.54. The total workload has a value of 596 Gy/week, less than the value used in the facility shielding design, 1250 Gy/week, and the average value of VMAT factor for conventional and hypofractionated treatments showed that a smaller amount of C should be used at facilities that perform exclusive VMAT treatment.

Guilherme Soares Zahn, Iberê Souza Ribeiro Jr, Frederico Antonio Genezini

In conventional gamma-ray spectrometry, the probability of pile-up effects is considered to be proportional to the dead-time, and is usually neglected for low dead-times (below 4-5%). In gamma-gamma coincidence spectrometry, though, while the dead time takes into account only events that are actually digitized, the pile-up effects are proportional to the actual gamma-ray detection rate in each detector, not only to the ones that trigger the coincidence gate. Thus, the pile-up corrections may not be so easy to assess as in single spectrometry systems. In this work, a system composed of two HPGe detectors coupled to a CAEN v1724 digitizer is studied. A 3kBq 60Co source was analyzed, both alone and in the presence of other radioactive sources (137Cs, 133Ba and 152Eu), and the resulting coincidence peak areas were compared to assess the effectiveness of two distinct corrections: a simple normalization by the live time of acquisition and the normalization by the count rate obtained using a pulse generator. The results obtained stress the need to use the pulse generator in this specific setup in order to get accurate results.

Aleksander Nikolaevich Nikitin, Ihar Anatoljevich Cheshyk, Galina Zenonovna Gutseva et al.

L. D. Mikryukova, L. Yu. Krestinina, S. B. Epiphanova

Up to now there is no clear understanding of health risk and type of dose dependence for the population chronically exposed within a range of low and average dose levels (to 1Gy). In this respect studies performed in cohorts with a sufficient number of persons can have a significant potential in providing necessary information. Objective: to study peculiarities of lens opacity in exposed persons at later time after chronic radiation exposure with due account for dose impact and nonradiation factors. The study includes patients from the URCRM registry of exposed population examined by an ophthalmologist in the period 2016-2018 (total 1,377 persons). The same technique of medical examination with photofixation of lens opacity was applied to all examined individuals. A case-control technique was used to conduct the study. Individual exposure doses to lens were calculated on the basis of TRDS-2016 for the first time within the framework of the present study. As a result of the performed study among persons exposed to long-term ionizing low-dose radiation we have determined an exposure dose impact on risk growth of opacity in the posterior capsule and lens nucleus. No reliable statistical dependence of lens change with an increasing exposure dose in anterior capsule and cortical layers as well as colour change of the lens nucleus was obtained. Belonging to different ethnical groups showed no impact on priority opacification development in any lens layers.

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