Hasil untuk "Radioactivity and radioactive substances"

Iasmin Nishibayaski, A. L. S Silveira, L. C. Meira-Belo

Fricke solution, composed of ferrous ammonium sulfate in an aqueous solution of sulfuric acid, is used as a chemical dosimeter for gamma rays, X-rays and high energy electrons. The three-dimensional dosimetry has several applications, such as in radiotherapy procedures, imaging diagnosis techniques and internal dosimetry. In this work, the response of Fricke gel dosimeter with two types of indicator was compared. Sodium thiocyanate, a salt not used in dosimetry, and xylenol orange, a well-established indicator, were analyzed as indicators. The studies were performed in a cobalt-60 source.  Dosimetric responses of Fricke gel with distinct indicators differ in their sensitivity, that is, the addition of sodium thiocyanate to the gel shifted the saturation point of the gel to an absorbed dose of approximately 300 Gy, while the Fricke gel with xylenol orange presents a saturation of around 30 Gy.

Andre Luiz de Carvalho Ribeiro, Alex Cristóvão Holanda de Oliveira, Leonardo Peres da Silva et al.

In recent decades, radiotherapy has advanced significantly due to the emergence of advanced clinical linear accelerators, enabling safer and faster treatments with reduced side effects. In this study, we present a Monte Carlo simulation of a 6 MV Varian Trilogy clinical linear accelerator using the Geant4 toolkit to analyze dosimetric parameters, with a focus on small photon fields. The simulation models phase-space files generated at key beam-modification stages. Validation was performed by comparing simulated depth dose curves (PDD) and dose profiles with experimental measurements for the 6 MV photon beam, employing the gamma index (3%/3 mm criteria) to quantify the degree of agreement in the PDDs. The results agreed within a 2% difference, with over 95% of points passing the gamma analysis for a 10 x 10 cm² field.  The developed framework allows for the calculation of correction factors for small-field dosimetry, addressing challenges such as lateral electronic disequilibrium in high-energy 6 MV beams, and comparing them with established values in the literature. These capabilities are particularly important for measurements of small fields used in advanced radiotherapy techniques, including Stereotactic Radiosurgery (SRS) and Stereotactic Body Radiotherapy (SBRT), where high precision in dose deposition is essential. Overall, this work establishes a robust and flexible Geant4-based platform for simulating clinical linear accelerators, contributing to the development of more accurate dosimetric protocols for high-energy photon therapy in small fields. Preliminary observations suggest notable output factor discrepancies in small photon fields (<3x3 cm2), indicating the potential need for detector-specific correction factors. Ongoing analysis aims to confirm these trends.

Abdollah Khorshidi, Mansour Ashoor

Breast cancer is one of the most common malignant diseases in women. After tumor mass surgery, radiation therapy is regularly taken into account the gold standard for the treatment. Kilo to Mega voltage photons have been suggested due to their characteristic depth dose build-up regime, reducing the dose to the breast skin to a fraction of the maximum dose exposure. During treatment, mean glandular dose is commonly used as a criterion for identifying radiation risks. Here, two outlines in cubic-rectangular (CR) and cylindrical- taper (CT) outlines were modelled together with corresponding assumptions using Monte-Carlo simulation and the recorded absorbed dose ratio (ADR) values were compared via defined a positron source by 511 keV energy. The results showed that the amounts of absorption and scattering cross-sections next to the ADR amount decreased as the height of the CR outline decreased. The average dose ratio amount in the CR outline was reduced by about 96% compared to that in the CT outline. By increasing the positron source distance from the nipple, the ADR amounts decreased for both outlines. The amount of accumulated dose ratio decreased harshly in the CR outline rather than in the CT outline. This study can be useful to examine breast tissue deformity in treatment planning.

Joel Charles Garcia, Marina de Arruda Botelho, Delano Valdivino Santos Baptista et al.

The objective of the TBI treatment is the ablation of the bone marrow and the destruction of the circulating leukemia cells, once they are widely distributed throughout the body. Using beam parameters acquired under conventional SSD in TBI treatments may add non-negligible uncertainties in the monitor units calculation or in the beam profiles. The study, aims to commission the 6 and 10 MV photon beams, of the Varian accelerator CX model. A slab phantom and dosimetric assembly were used under TBI conditions. The accuracy of the TPS was evaluated against the experimental data. A set of data were acquired, highlighting the TPR table and methodology for calculating MU has been implemented. The TPS has presented a statistical uncertainty of ± 2.7 % compared to the experimental data for monitor unit calculation. The use of an acrylic spoiler has been shown to be clinically advantageous where, for a 6 MV beam, the entrance PDD was 75 % without a spoiler and  99.5 % with a spoiler. For a 10 MV beam, it was verified that without a spoiler, the entrance PDD was about 55 %, but with a spoiler, it was about 93 %. For medium Heterogeneous the TPS underestimated dose values by up to - 3.5 % with a mean deviation of – 2.9 %, for 6 MV and for 10 MV, the TPS overestimated the dose values by up to 1.1 %, with an average deviation of 1.0 % using the acrylic thorax phantom. The data obtained can be used clinically.

Carla Daruich de Souza, Jong Bum Kim, Jin Joo Kim et al.

Demand for energy has increasing rapidly in the last decade. In 2021 an increase in 5% was observed. Half of this demand was covered by fossil fuels, increasing CO2 emissions to record levels. With the need for new reliable steady supply sources to be used in places where maintenance is difficult, Radioisotope Thermoelectric Generators (RTG) have been given renewed attention in the past 10 years. RTGs uses radioactive decay to generate electricity. This work presents in a simple manner, the basics of RTG operation, the requirements for construction, and is followed by an example developed at KAERI. Basic Radiation Physics Concepts, RTG configuration requirements, Thermoelectric effect and materials, and calculations for electric power were presented.

MARIA CANDIDA DOURADO PACHECO OLIVEIRA, Arno Heeren de Oliveira, Tarcísio Passos Ribeiro de Campos et al.

Radiotherapy (RT) plays an important role in the treatment of patients with head and neck cancer. Clinical changes in the surrounding healthy tissue are often inevitable. The deleterious effects on the bones of the jaws have been considered a contraindication for rehabilitation with dental implants. However, in recent years, the installation of implants in irradiated patients has been consolidated as a valuable treatment option. The aim of this study was to evaluate the effect of RT on the survival of osseointegrated dental implants in patients with head and neck cancer. The applied methodology involved an electronic search in the MEDLINE database during the last five years.  We identified 67 scientific documents related to the keywords: "radiotherapy", "dental implants" and "head and neck cancer", four articles were selected and reviewed, composing this analysis.  It is concluded that dental implants installed in irradiated bone in the oral cavity have a high survival rate, 97.37%, provided that rigorous monitoring is instituted in RT in order to be successful in the long term. The percentage of dental implant failures tended to be higher in the group of irradiated patients.

Ana Carolina Delgado Vieira, Yasko Kodama, Larissa Otubo et al.

Featherwork collections are usually stored and managed by ethnographic museums. Even though the featherwork manufacturing is still practiced by the indigenous communities, the offer of raw material and the contact with the surrounding society ended up reducing the production scale of such objects. Consequently, the preservation of the material culture is very important, particularly in museums. Biodegradation can affect featherworks mainly by xylophagous insects and moths’ action. The tropical Brazilian weather contributes to the contamination and proliferation of insects and fungi making the preservation conditions difficult. The use of gamma radiation for the disinfection of cultural heritage objects has shown to be a safe process and an excellent alternative to traditional methods usually involving toxic chemical pesticides. In this work are presented the preliminary results of the ionizing radiation effects on the color and morphological properties of a featherwork from the Museum of Archeology and Ethnology of the University of São Paulo (MAE/USP). Samples of feathers were selected from the artifact and irradiated with gamma rays at the Multipurpose Gamma Irradiation Facility at IPEN, applying absorbed doses between 0.5 kGy to 200 kGy. The results shown had no significant changes on color and morphological properties within the disinfection absorbed dose range applied.

Renato Pereira de Freitas Pereira de Freitas, Valter Souza Felix, Marcelo Oliveira Pereira

Analysis of historical artifacts, it's a multidisciplinary field of research known as archaeometry, has expanded greatly in recent years. One of the reasons for this expansion was the great effort of physicists and engineers, who focused on the development of portable instruments, that allow analyses in situ and non-destructive of these artifacts. The X-Ray Fluorescence (XRF) is techniques of the most used in this field of study. In this work the XRF was used to analysis the artwork "Passagem de Humaitá", by the Brazilian painter Victor Meirelles, dated 1872. The painting, which has dimensions of 268 cm x 405 cm, is exposed at National Historical Museum located in Rio de Janeiro. The analyses were carried out in situ with portable XRF system model TRACER IV from Bruker, which has Rh anode and can operate with maximum voltage and current of 40 kV and 200 μA. Spectra of more than 80 points of the painting were obtained, with the tube operating at voltage of 40 kV and a current of 10 μA, and the spectra were collected during 60 seconds. The results allowed to conclude that the painter used pigments such as vermilion and/or cinnabar [HgS], calcite [CaCO3], zinc white [ZnO], lead white [(PbCO3)2·Pb(OH)2], red ocher [Fe2O3], brown umbra [Fe2O3.MnO2].

V. Yu. Golikov

The paper is devoted to comparing the models and the doses of the population external exposure from radioactive fallout after the accident at the Chernobyl and Fukushima-1 NPPs estimated with their help. In the case of the Fukushima-1 accident, the model proposed by the UNSCEAR was used. Both the values of the doses of gamma radiation in the environment and the values of the effective doses of external exposure of comparable population groups normalized to the same surface activity of radionuclides were close for both accidents. The reasons for this are both the similarity of the isotopic compositions of the radioactive fallout and the fact that the “Japanese” model of external exposure was based on the “Chernobyl” model up to using the same numerical values for some parameters, due to the lack of specific Japanese post-accident data for the moment of the first dose estimates for the inhabitants of Japan. For a more accurate comparison of the external exposure of residents after two accidents it is necessary to verify the values of the parameters of the Japanese model using the results of measurements of gamma radiation dose rates in the environment and individual external doses of the residents after the accident at the Fukushima-1 NPP.

Baljeet Seniwal, Telma C. F. Fonseca, Ranjit Singh

Modeling of linac head (VARIAN Trilogy) for 6 MeV photon beam was performed using BEAMnrc code package (BEAMnrc 2017). The DOSXYZnrc code was used to determine the percentage depth dose (PDD profiles) and beam profiles for different symmetric square field sizes, i.e., 5cm X 5cm; and 40cm X 40cm. The DICOM images of Alderson Radiation Therapy (ART) RANDO Phantom was used. Four field 3D-CRT treatment plans were generated using AAA, PBC, and Monte-Carlo (MC). It was found that nominal energy of 5.7 MeV with FWHM of 1.2 mm provides best matching of modelled and working linac. All three 3D-CRT plans calculated with AAA, PBC and MC on a Pelvic Rando phantom, were compared using CERR (Computational Environment for Radiotherapy Research) and MATLAB 2013b. It was found that AAA and PBC have comparable results, although in case of tissue interfaces and inhomogeneous media AAA provides better accuracy in comparison to PBC. It can also be observed that AAA and PBC underestimate doses in comparison to MC in the soft muscle tissue which includes OARs such as bladder, bowel bag, and PTV TOTAL. It was found that both AAA and PBC fails to account for tissue air interface accurately and shows variation of 30-40% whereas for surface dose variation of +/-10% was observed. In homogeneous media (muscle tissue) AAA and PBC underestimate doses in comparison to MC. These commercially available algorithms overestimates and underestimates dose values as compared to MC based dose calculation for low and high dose regions specially.

N. K. Shandala, S. M. Kiselev, A. V. Titov

Today, Russia is implementing a national program for the remediation of legacy sites, resulting from the activities of the nuclear industry, the use of nuclear energy for military purposes, and due to radiation accidents and emergencies. Main priority is given to the health care provision issues of the workers and the population living in the vicinity of the targeted facilities. These tasks are under the regulatory responsibility of the FMBA of Russia. Since the beginning of the development of the nuclear industry in the country, the Institute of Biophysics, technical supporting organization of the FMBA of Russia (now the State Research Center – Burnasyan Federal Medical Biophysical Center Federal Medical Biological Agency (SRC-FMBC)), has been a leading institute in the scientific and methodological support of public radiation safety in the vicinity of radiation hazardous facilities serviced by the FMBA of Russia. In this regard, radiation-hygienic monitoring has always served as the main regulatory tool for more than 60 years. The paper describes the results of long-term monitoring (2005-2018) at the former coastal technical bases of the Russian Navy ( now – sites for temporary storage of SNF and RW in the Russian Northwest and Far East (nuclear legacy sites); sites of the uranium mining and milling facilities: Priargun Mountain Chemical Association and former Production Association “Almaz” (Lermontov, Stavropol Krai); and at uranium legacy sites of the Central Asia (Republic of Tajikistan and Kyrgyz Republic). The peculiarities of radiation situation at the sites are discussed, current challenges identified, and further regulatory improvements presented based on the gained experience.

Fábio Camargo, Carmen Cecília Bueno, Josemary A. C. Gonçalves

In this work, we report on the results obtained with rad-hard Standard Float Zone (STFZ) and Diffused Oxygenated Float Zone (DOFZ) silicon diodes in radiation processing dosimetry. The dosimetric probes were designed to operate in the direct current mode, as on-line radiation dosimeter. The irradiation of the samples was performed using a 60Co source with a dose rate of almost 2.4 kGy/h. The current response of each diode was measured as a function of the exposure time in steps from 5 kGy up to 50 kGy to achieve a total absorbed dose of 275 kGy. In this dose range it is observed a significant decrease in the photocurrent generated in both devices due to gamma radiation defects produced in their active volumes. To mitigate this effect, the samples were pre-irradiated with Co-60 gamma rays at 700 kGy. Despite of being less sensitive, these devices presented stable and reproducible current signals with a relative sensitivity decrease of about 19% within the whole range of dose studied. The dose-response curves of the pre-irradiated diodes showed quadratic behavior with correlation coefficient higher than 0.9999 for total absorbed dose up to 275 kGy. The comparison of the FZ and DOFZ responses evidenced that the latter was slightly superior to the first. However, it is important to note that all pre-irradiated diodes can be used as gamma dosimeters in radiation processing applications.

Gustavo Piriz, Yolma Banguero, Alejandro De Rosa et al.

The gynecological treatment with High Dose Rate (HDR) Brachytherapy imply deliver dose to the tumor and spare the dose in organs at risk. In this work we apply the recommendations for prescribing dose given by the International Commission of Radiation Units (ICRU) reports 38, 89 and the American Brachytherapy Society (ABS). With both schemes of optimization, recommendation of ICRU 38 or ABS with vaginal point from ICRU 89. Were analyze the dose received by the organs at risk, in this case rectum and bladder and also the irradiated volume for patients that receive HDR brachytherapy treatment. An afterloading technique is applying with a Eckert & Ziegler MultiSource® equipment using a Co-60 source, 30 patients with 4 applications with cervical cancer are planning with HDR brachytherapy. This work analyze 120 single applications with orthogonal images using the treatment planning system (TPS) HDRplus version 3.0.4 through “Auto dwell time determination” optimization method, using the recommendation for optimization dose from the ABS and vaginal point from ICRU 89 . The volume of the isodose curve of prescription is 15% less using ABS recommendation than ICRU 38. The bladder dose is 11% and rectum dose is 21% less using ABS recommendation than ICRU 38. The analysis of dose prescription using ICRU 38 and ABS recommendations in the patients analyzed shows less irradiated volume at the dose prescribed and also less mean dose in rectum and bladder of applications using ABS in contrast with ICRU 38 recommendations.

V. P. Ramzaev, A. N. Barkovsky, A. V. Gromov et al.

The study was conducted on Kunashir, Shikotan and Iturup Islands (Sakhalin Region of Russia) in order to evaluate the impact of the Fukushima accident on the “soil–grass–cow’s milk” exposure pathway. A total of 22 samples of cow’s milk were collected in the May 2011 – September 2012 period. Radiocaesium was isolated from thermally treated specimens using the antimony–iodide radiochemical method. The activity concentrations of 134Cs and 137Cs were measured by γ-ray spectrometry using high purity germanium detectors. Caesium-134 was detected in 18 of the total 22 samples of milk. The activity concentration of 134Cs in the samples varied from 0.08 Bq kg–1 to 2.00 Bq kg–1. Caesium-137 was quantified in all 22 samples: range = 0.088–2.43 Bq kg–1. On average, more than a half of the total 137Cs in the milk samples from Sakhalin Region was of Fukushima origin (mean = 60%, median = 57%, range = 13–95%). The highest activity concentrations and values of the soil–to–milk aggregated transfer coefficient, Tag, for 134Cs (and Fukushimaderived 137Cs) were observed in milk samples collected in mid-May 2011. The mean Tag values decreased in the May–October period of 2011 from 12 × 10−3 m2 kg–1 to 2.3 × 10−3 m2 kg–1. In September 2012, the Tag values remained unchanged (mean = 2.8 × 10−3 m2 kg–1) compared to those in September–October 2011. In the autumns of 2011 and 2012, the calculated values of Tag for Fukushima-derived radiocaesium were on average 17 times larger than the ones for pre-Fukushima 137Cs. The higher transfer of Fukushima-derived 137Cs (compared to pre-Fukushima 137Cs) for milk reflected the difference between the “new” and “aged” radiocaesium in the intensity of the radionuclide transfer from soil to grassland plants which were the major component of the cow’s diet in the area of our study. The ratio between the 137Cs activity concentration in the milk (fresh weight) and that in the grassland plants (dry weight) ranged from 0.028 to 0.11. The effective dose from ingestion of Fukushima-derived radiocaesium in locally produced cow’s milk for critical group of adult residents of the southern Kuril in the first year after the accident is conservatively estimated as 0.0027 mSv. The Fukushima accident has had a negligible impact on radiocaesium contamination of cow’s milk and the corresponding human exposure on the southern Kuril Islands: Shikotan, Kunashir and Iturup.

M. V. Kaduka, L. N. Basalaeva, T. A. Bekyasheva et al.

Institute of Radiation Hygiene carried out series of field studies because of possible dissemination of radioactive contamination in the territories of Far East regions of Russian Federation after the accident on “Fukushima-1” NPP. The aim of investigations was to clarify radiation situation in the territories of Sakhalin region. We carried out investigations during May-October of 2011 in the Sought-Eastern part of Sakhalin region including the territories of Korsakov district of Sakhalin Island and Kunashir and Shikotan Islands, which are located close to “Fukushima-1” NPP. In autumn of 2012, we carried additional investigation in the Islands Sakhalin, Iturup and Kunashir. In the frames of expedition investigations of 2011 – 2012, we carried out gamma-irradiation dose rate measurements, gamma-spectrometric investigations, sampling of soil, foodstuffs, environmental samples, and as well local population questionnaire survey with the aim of clarification of the food rations. We sampled 132 foodstuffs samples, which local population use to consume and implemented their gamma-spectrometric and radiochemical analysis. We carried out 99 questionnaire surveys of population to estimate the volume of consumption of different foodstuffs, clarification of food ration and its peculiarities. Carried survives revealed that practically all respondents consume milk, fish, mainly sea fish, seafood and/or edible algae. Local population consume freshly cooked, salt and pickled forest herbs: wild garlic, fern, and burdock. The consumption of cow milk, produced mainly in private farms, could reach 200 l/year, sea fish – 170 kg/year, seafood – 100 kg/year, edible algae – 50 kg/year. More than 50% of respondents rather actively consume forest mushrooms – up to 90 kg/year, 3% of respondents consume meat of game – up to 6 kg/year and feathered game – up to 15 kg/year. Carried survives revealed peculiarities of cattle ration: the cows gaze unorganized, feed meadow and forest grass and herbs, algae from a coast. Forestlands of the investigated region are located in the territories with prevailing of sandy, sandy loam and loamy soils. The values of caesium isotopes transfer factors from such soils to foodstuffs and environmental objects are much higher than the values of transfer factors from fertile black soils. Thus, the population of investigated territory actively consume the foodstuffs transfer of caesium isotopes to which is rather high.

статья Редакционная

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G. G. Onischenko

The paper presents data on the role and results of activities of Rospotrebnadzor bodies and institutions in the field of ensuring population radiation protection during various periods since accident at the Chernobyl NPP. Radiation hygienic characterization of territories affected by radioactive contamination from the accident, population exposure dose range, issues of ensuring radiological well-being of population and ways of their solution are being presented in the paper.

статья Редакционная

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Alex Cristóvão Holanda de Oliveira, José Wilson Vieira, Fernando Roberto Andrade Lima

Radiotherapy uses various techniques and equipment for local treatment of cancer. The equipment most often used in radiotherapy to the patient irradiation is linear accelerator (Linac). Among the many algorithms developed for evaluation of dose distributions in radiotherapy planning, the algorithms based on Monte Carlo (MC) methods have proven to be very promising in terms of accuracy by providing more realistic results. The MC simulations for applications in radiotherapy are divided into two parts. In the first, the simulation of the production of the radiation beam by the Linac is performed and then the phase-space is generated. In the second part the simulation of the transport of particles (sampled phase-space) in certain configurations of irradiation field is performed to assess the dose distribution. Accurate modeling of the Linac head is of particular interest in the calculation of dose distributions for intensity modulated radiation therapy (IMRT), where complex intensity distributions are delivered using a multileaf collimator (MLC). The objective of this work is to describe a methodology for modeling MC of MLCs using code Geant4. To exemplify this methodology, the Varian Millennium 120-leaf MLC was modeled. The dosimetric characteristics (i.e., penumbra, leakage, and tongue-and-groove effect) of this MLC were evaluated. The results agreed with data published in the literature concerning the same MLC.

Maria das Graças Anguera

RESUMO: Introdução: O fisioterapeuta utiliza-se de vários equipamentos eletro-eletrônicos que emitem radiação eletromagnética para fins terapêuticos. Entre esses, o equipamento de diatermia por micro-ondas de alta frequência, sendo essa de 2,45 GHz. Nesse procedimento terapêutico, é possível ter perdas variáveis da energia irradiada por reflexão e por dispersão, desde o aplicador até a área a ser tratada. Objetivo: Conhecer o padrão operacional de proteção radiológica relativa ao equipamento terapêutico de diatermia por micro-ondas por parte de fisioterapeutas. Metodologia: Utilizou-se de banco de dados construído em pesquisa anterior pela proponente deste estudo para extrair informações operacionais relativas ao equipamento terapêutico de diatermia por micro-ondas. Os dados obtidos foram fornecidos por fisioterapeutas por meio de questionário on line e foram descritos, analisados e apresentados em tabelas, com frequências absolutas e relativas. Resultados: Quando a questão é calibração de equipamento de diatermia por micro-ondas 65% dos profissionais não responderam. Quanto à tomada de alguma medida de segurança, 35% realizam algum tipo de segurança operacional. Desses 35% que realizam algum tipo de medida de segurança operacional, 42,85% relacionam segurança apenas com o paciente, 28,57% com o fisioterapeuta, 14,29% com ambos, ou seja, fisioterapeuta e paciente e 14,29% não especificou o tipo de medida. Conclusão: Conforme os resultados apresentados pode-se concluir que não existe estabelecido um padrão operacional de proteção radiológica relativa ao equipamento de diatermia por micro-ondas por parte de fisioterapeutas, tornando o ambiente de trabalho, bem como a si mesmo, passivos de situações de riscos não controlados.