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Objective To investigate the effects of prolonged low-dose neutron-γ radiation on peripheral blood lymphocytes of logging workers. Methods The health information of workers in a logging company was collected by on-site blood sample collection and questionnaire survey. Individual doses of γ and neutron radiation were recorded using LiF elements and CR-39, respectively. Lymphocyte count in peripheral blood was measured by blood cytometer. Cell cycle and cyclins were detected by flow cytometry. Results The annual dose of some logging workers exceeded 5 mSv. Lymphocyte counts showed a difference of 15% between the group exposed to the lowest annual dose of 0–1 mSv (mean: 2.45 × 109/L) and the group exposed to the highest annual dose of 5–25 mSv (mean: 2.08 × 109/L). In comparison to pre-shift workers, logging workers exhibited a G1-phase arrest in the lymphocyte cycle, along with increased expression of cyclins p21 and CDK2. Conclusion Prolonged exposure to low-dose neutron-γ radiation leads to reduced lymphocyte counts as well as changes in lymphocyte cycle and cyclin expression.
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Boron neutron capture therapy is a method based on 10B (n,α) 7Li reaction to achieve malignancy treatment. Upon entry into the human body, the 10B compound carrier can selectively enriched in tumor cells and reacts with external irradiation neutrons. Because 7Li (4 μm) and α particles (7 μm) will be deposited in a cell magnitude (10 μm), the purpose of directional local killing of tumor cells and causing less harm to normal tissue can be achieved successfully. So far, boron neutron capture therapy has been clinically studied in a variety of malignant diseases, including glioblastoma multiforme, meningeoma, head and neck cancer, lung cancer, etc. In this article, the clinical research progress of boron neutron capture treatment in head and neck carcinomas was mainly introduced.
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Boron neutron capture therapy (BNCT) is an emerging treatment modality. BNCT is performed by injecting patients with the boron containing drugs, which has strong affinity with cancer cells. After undergoing irradiation with neutrons, the boron containing drugs can yield alpha and lithium particles, which can kill tumor cells precisely. To date, clinical studies of BNCT have been conducted in a variety of tumors, including glioblastoma multiforme, meningioma, head and neck cancer, sarcoma, malignant skin tumor, malignant melanoma and recurrent cancers, etc. With continuous construction of BNCT treatment centers around the world, this new technology will be quickly and comprehensively spread. In this article, clinical research progress in the application of BNCT for glioma treatment was reviewed.
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Objective To investigate the natural penetrating radiation levels along the Qinghai-Tibet Railway, and to preliminarily evaluate the doses received by the railway employees and passengers. Methods Natural penetrating radiation was measured at 15 typical locations with different altitudes along the railway and in the carriages of a train from Lhasa to Xining using high-pressure ionization chamber RSS131, sodium iodide radiation dose rate meter MARS1561, and neutron ambient dose equivalent rate meter LB6411. Results The levels of terrestrial gamma radiation, cosmic ray ionization components, and neutron radiation were 21.5-246.6 nGy/h, 79.8-225.5 nGy/h, and 24.5-101 nSv/h, respectively. The effective dose of natural penetrating radiation received by passengers and crew on a train from Lhasa to Xining was 4.82 μSv. Conclusion Comparison with the empirical formula and verification of method reliability confirm the accuracy of the measurement. Our results provide a primary understanding of the radiation levels along the Qinghai-Tibet Railway and the radiation doses received by passengers, which can be used as a basis for the regulatory authorities.
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Objective To preliminarily compare 6LiF-7LiF and CR39 in individual neutron dose monitoring, and to provide a reference for improving individual neutron dose monitoring. Methods According to the GBZ 128-2019, 26 radiation workers from 7 institutions received individual neutron dose monitoring with 6LiF-7LiF and CR39 at the same time. The monitoring results were analyzed. Results For most of the workers, the personal neutron dose equivalent Hp(10) was less than the minimum detectable level. The results with the two monitoring methods differed in 6 of 26 workers. Conclusion Both 6LiF-7LiF and CR39 monitoring methods can be used for individual neutron dose monitoring for radiation workers, but the difference between 6LiF-7LiF and CR39 (in threshold energy, energy response, etc.) should be considered so that different types of radiation workers receive appropriate individual neutron dose monitoring.
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To summarize the progress in BNCT dose verification method in the world and discusses their development prospects. Boron neutron capture therapy (BNCT) utilizes the specific capture reaction between the neutrons and boron drugs enriched in tumor cells to selectively kill tumor cells. In order to verify the accuracy of the radiotherapy plan and ensure the therapeutic effect on patients, it is necessary to measure the dose before treatment and compare the experimental radiation dose with the planned dose. The current BNCT dose measurement method mainly include point dose measurement method based on ionization chambers, thermoluminescence dosimeters and activation foils, two-dimensional dose measurement method based on films, and three-dimensional dose measurement method based on gel dosimeters.
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Objective:To provide reference for establishing the testing method for quality control of neutron beam in boron neutron capture therapy (BNCT) equipment in China by testing the radiation characteristic parameters and dosimetry characteristic parameters of epithermal neutron beam in hospital neutron irradiator (IHNI).Methods:By comparing the uncertainties in the result of various test items with the deviation values recommended by the European Joint Research Center (EC-JRC), the feasibility of the relevant of testing method was analyzed and evaluated.Results:The uncertainty in epithermal neutron fluence rate was 2.7%. The uncertainty in ratio of thermal to epithermal neutron fluence rate was 3.1%. The uncertainty in ratio of fast neutron air kerma to epithermal neutron fluence rate was 9.3%. The uncertainty in ratio of gamma air kerma to epithermal neutron fluence rate was 8.7%. The uncertainty in spatial distribution of neutron fluence rate was 2.7%. The uncertainty in thermal neutron fluence rate in phantom was 1.8%. The uncertainty in neutron and gamma-ray dose rate in phantom was 17.1% and 4.0%, respectively.Conclusions:The uncertainty in neutron dose rate measurement result in phantom is higher, and further research is needed to improve the accuracy of the testing method. The uncertainty in the measurement result of other test items is lower, and the accuracy of the test result is expected to meet the allowable deviation value recommended by the European Joint Research Center, and the test method is feasible.
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With the extensive use of neutron sources in industry, medicine, and scientific research, the number of people exposed to neutron has been increasing, which highlights the importance of personal neutron dose monitoring in the field of radiation protection. In the past decades, researchers have developed and improved a variety of techniques and methods for personal neutron dose monitoring. This paper focuses on the problems and research progress of track dosimeters (solid-state nuclear track dosimeters and fluorescent nuclear track dosimeters), luminescent dosimeters (thermoluminescent dosimeters and optically stimulated luminescent dosimeters), and bubble dosimeters in personal neutron dose monitoring.
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Boron neutron capture therapy(BNCT), a promising radiotherapy, belongs to precision treatment for cancers. BNCT can accurately kill cancer cells and protect normal cells at the same time relying on 10B compounds with high efficacy. The research about developing new 10B compounds is in progress, and novel and efficient 10B compounds are emerging, which greatly facilitate broadening the advantages and efficacy of BNCT. Considering the mixed rays generated from the BNCT process, its biological effects on tumor cells are relatively complex, and related studies are still lacking. The molecular mechanisms underlying BNCT need to be elucidated further. BNCT has been applied in the treatment of malignant brain tumors, head and neck cancers, and malignant melanoma with favorable curative effects. This review mainly focuses on the development of 10B compounds, biological mechanisms, potential advantages, and clinical applications.
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Objective:To study the photoneutron radiation field caused by photonuclear reaction during the operation of high energy medical linac.Methods:Monte Carlo was used to simulate the photoneutron pollution of Clinic 2300CD medical electron accelerator in 15 MV X-ray mode. The photoneutron spectrum at different positions of the head and the variation in neutron ambient dose equivalent in different irradiation fields were investigated, and the dose distribution of photoneutron on the isocenter plane and the dose attenuation in the water model were analyzed.Results:When the collimator was closed, the average photoneutron energy at the lower surface of target, primary collimator, flattening filter and multi-leaf collimator was 1.08, 1.20, 0.35 and 0.30 MeV, respectively. The neutron ambient dose equivalent at the isocenter first increased and then decreased with the irradiation field expanding, reaching the maximum in about 30 cm × 30 cm irradiation field. With the increase in the depth of the measuring point in water phantom, the neutron fluent first increased and then decreased, while the neutron dose gradually decreased. In different irradiation fields, the photoneutron dose rate was almost close to the background when the depth of the water was 20 cm.Conclusions:By exploring the photoneutron spectrum and dose distribution characteristics of the high energy medical linac head, as well as the dose deposition mechanism of photoneutron in water phantom, this study provides data support for further research on the additional dose and secondary cancer effects on patients caused by photoneutron pollution from the high energy medical linac.
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Boron neutron capture therapy (BNCT) is an advanced method of precision radiotherapy for tumors. In BNCT, 10B enriched boron carriers enter and gather within tumor cells, then a thermal neutron beam triggers the 10B (n, α) 7Li reaction to release alpha and 7Li particle with low energy, which can kill tumor cells. Compared with conventional radiotherapy, BNCT has the characteristics of higher biological effect, more precise targeting, less damage to normal tissues and less treatment times. In this article, recent progress and existing problems of BNCT-related clinical research were reviewed.
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Objective To investigate the radiation dose to operators in the process of 241Am-Be neutron source logging, and discuss neutron source management and protective measures for operators in well logging. Methods Through on-site observation and measurement of 241Am-Be neutron source logging in a company, we obtained the surface γ dose rate and neutron dose rate of the neutron source, as well as the operating time and distance of various processes including source taking, transfer, and loading, calculated the radiation dose to operators in various processes, and analyzed the source and proportion of the personal effective dose to operators. Results The effective doses of neutron irradiation and γ irradiation were 94.17 μSv and 2.72 μSv, respectively, for the combined processes of source tank inspection, transfer, and detection; 36.66 μSv and 24.08 μSv, respectively, for source loading and unloading; and 130.83 μSv and 26.80 μSv, respectively, for the whole neutron source logging process. The total annual effective dose of neutron source logging was 15.78 mSv, as estimated by logging 100 times per year. Conclusion In the process of 241Am-Be neutron source logging in the company, the effective dose to operators mainly arises from neutron irradiation. Therefore, it is necessary to strengthen neutron source management and take effective protective measures against neutron radiation.
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The fusion neutron source based on Gas Dynamic Trap (GDT) device has the advantages of high neutron flux, large testing space and low construction cost, so it is an ideal solution for high-flux fusion volumetric neutron source. As a new type of radioactive facility, how to carry out radiation safety management under the current nuclear safety regulatory laws and regulations in China is an important issue that must be addressed before the construction of this facility. In this paper, the radiation safety characteristics of GDT fusion neutron source was analyzed and the main radiation terms of GDT fusion neutron source were expounded. Combined with the existing nuclear safety regulatory laws and regulations in China, the key points of radiation protection and safety management in the process of construction and application of GDT fusion neutron source were put forward. It is recommended that the GDT neutron source should be managed as a class I radiological device. Prior to operation, radiation safety permit and nuclear material permit should be obtained, and special attention should be paid to the safety protection of radioactive tritium. This study will pay the way for the radiation safety management of the international high flux fusion neutron source ALIANCE project, and also provide the reference for the related nuclear and radiation safety management departments in China.
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Objective To design and build a set of experimental equipment for neutron radiation irradiation by using the 241Am-Be neutron source. Methods In the preliminary work, the spatial distribution data of the neutron energy spectrum and the gamma energy spectrum inside and outside the device were simulated by Monte Carlo method, and the changes of radiation fluence rate with spatial distribution was studied. The model of the 241Am-Be neutron device was established, and the neutron transport process in the irradiation field was studied using the method of shadow cone, inverse square law and other data analysis methods. Results Based on the simulation results, the normalized effective does of fast neutron fluence at the measurement point is about 72.9 pSv/n, and the one of photon fluence is about 3.04 pSv/γ. The ratio of effective dose of photon fluence to neuteon is about 4.17%. Conclusion Using Monte Carlo method, a standard model of 241Am-Be neutron source was constructed, the shadow cone design was optimized, and the feasibility of using the shadow cone conversion method to establish a standard neutron source radiation device was discussed.
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Objective By measuring the induced radioactivity of the medical electron linear accelerator, and analyzing the measuring results and the measuring process, the cooling law of the induced radioactivity was studied, to provide basic data for evaluating additional doses to patients, medical staff and the public. Methods Five Medical Electron Linear accelerators were used to measure the induced radioactivity by using automes-6150AD6/H+6150AD-b/H x-γ radiation peripheral dose equivalent rate meter for environmental monitoring. Results The level of induced radioactivity of 5 medical electron linear accelerators is related to the factors such as measuring position and time: 10 second after the end of beam output, the maximum dose equivalent rate is 5.55 μSv/h around 5 cm on the surface of the head housing of the accelerator, and the maximum ambient dose equivalent rate at 1 m from the fixed point of the housing is 4.07 μSv/h, 5 minutes after the end of output, the maximum dose equivalent rate is 2.11 μSv/h around the 5 cm surface and 1.77 μSv/h around the 1 m fixed point. Conclusion The measured radioactivity induced by the medical electron linear accelerator gradually cools over time, the measurement valuesare maintained in a relatively fixed range, and the fluctuation range of the values is narrow.
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Pharmacoscintigraphy is a non-invasive technique for determining the fate of drugs after administration into humans. Collecting valuable information through the pharmacoscintigraphyabout absorption and release mechanisms of drugs from formulations, and thus proving to be an invaluable tool in developing newer and more effective formulations. Such studies can be used to determine the behavior of drugs, formulation as well as diagnostic agents that are administered. In this technique, radiolabelled formulations are administered to patients by their intended route of administration. Their transit through the body is monitored using sophisticated imaging cameras. Since the amount of radiotracer that is used is very low, this is a safe, efficient, and accurate method for studying the behavior of drugs in the human body. Preclinical studies of newer drugs have successfully been carried out using the pharmacoscintigraphic technique
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RESUMEN Se resumen las diferentes experiencias en la aplicación de las técnicas nucleares y conexas en el estudio de diversos problemas ambientales de la Ciudad de La Habana. El análisis medioambiental mediante las técnicas de Análisis por Activación Neutrónica (AAN) y Gamma (AAG), Fluorescencia de Rayos X (FRX), Espectrometría por Absorción Atómica (EAA) y por Inducción de plasma acoplado (ICP), así como la Espectrometría Gamma de Bajo Fondo (EGBF), han permitido obtener información muy relevante sobre el comportamiento de los metales pesados, antibióticos y radionúclidos en los sedimentos marinos y fluviales, suelos urbanos y agrícolas, aguas, arenas de balnearios, polvos urbanos y productos de la agricultura urbana de la ciudad de La Habana.
ABSTRACT Various nuclear and related analytical techniques applied to study different environmental problems in Havana city are presented. The environmental analysis by means of Neutron and Gamma Activation analyses, X-ray Fluorescence Atomic Abortion and Induced Coupled Plasma spectroscopies and Low Background , Gamma Spectrometry, have allowed to obtain important information about the behavior of heavy metals, antibiotics and radionuclides in sediments, urban and agricultural soils, waters, beach sands, urban dusts and agricultural products farmed in the Havana city.
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Introduction: This study aimed to calculate the photon and neutron doses received to the contralateral breast (CB) during breast cancer radiotherapy for various field sizes in the presence of a physical wedge. Materials and Methods: Varian 2100 C/D linear accelerator was simulated using a MCNP4C Monte Carlo code. Then, a phantom of real female chest was simulated and the treatment planning was carried out on tumoral breast (left breast). Finally, the received photon and neutron doses to CB (right breast) were calculated in the presence of a physical wedge for 18 MV photon beam energy. These calculations were performed for different field sizes including 11 cm × 13 cm, 11 cm × 17 cm, and 11 cm × 21 cm. Results: The findings showed that the received doses (both of the photon and neutron) to CB in the presence of a physical wedge for 11 cm × 13 cm, 11 cm × 17 cm, and 11 cm × 21 cm field sizes were 9.87%, 12.91%, and 27.37% of the prescribed dose, respectively. In addition, the results showed that the received photon and neutron doses to CB increased with increment in the field size. Conclusion: From the results of this study, it is concluded that the received photon and neutron doses to CB in the presence of a physical wedge is relatively more, and therefore, they should be reduced to as low as possible. Therefore, using a dynamic wedge instead of a physical wedge or field-in-field technique is suggested
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Resumen Con la finalidad de maximizar las posibilidades experimentales en el estudio de los núcleos exóticos utilizando el haz del sistema "Radioactive Ion Beams in Brasil" (RIBRAS), fue desarrollado un sistema modular de detectores centelleantes orgánicos con buena eficiencia y amplio ángulo sólido, conocido como Pared de Neutrones. La detección de los neutrones emitidos en coincidencia con los fragmentos de reacción incrementa las posibilidades experimentales y constituye una de las técnicas más usadas en el campo de la Astrofísica Nuclear. El obsoleto sistema de adquisición de datos de la Pared de Neutrones debe ser remplazado por un sistema basado en módulos del patrón Versa Module Euro Card (VME). El nuevo esquema será definido para incluir el arreglo de detectores de bandas para partículas cargadas y la Pared de Neutrones con el máximo de eficiencia de adquisición, sin tiempo muerto, con selección de datos y sincronización de eventos. Los módulos digitalizadores garantizan tareas como la supresión de ceros y la saturación en la lectura de la señal. Adicionando tarjetas FPGA (field programmable gate array) a la adquisición de datos se garantiza el procesamiento pre y post-algorítmico de los datos.
Abstract In order to potentiate the experiments for studying the exotic nuclei with Brazil Radioactive Ion Beam (RIBRAS), a modular organic scintillation detector (Neutron Wall), with good efficiency and extended solid angle was developed. The detection of neutrons emitted in coincidence with the reaction fragments increases the experimental possibilities and represents one of the most popular techniques in the Nuclear Astrophysics field. The data acquisition system used for the Neutron Wall is obsolete and should be replaced by Versa Module Euro Card Data Acquisition modules. The new scheme will be designed to include the Strip Array and Neutron Wall detectors with maximum readout efficiency, no dead time, data selection and event synchronization. The digitizer modules provide features like zero suppressed readout and overflow suppression. Zero suppression, once enabled, prevents conversion of value, which is lower than user defined threshold. Adding FPGA (field programmable gate array) cards to data acquisition provides pre- and post-algorithmic processing on data.
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Abstract Heavy-ion induced two-neutron transfer reactions (18O,16O) at 84 MeV were studied on several targets up to high excitation energy of the residual nucleus thanks to the use of the MAGNEX magnetic spectrometer to detect the ejectiles. The obtained results indicate of the important role played by the nuclear paring.
Resumen Se estudiaron reacciones de transferencia de dos neutrones inducidas por iones pesados (18O, 16O) a 84 MeV en varios blancos hasta una alta energía de excitación del núcleo residual gracias al uso del espectrómetro magnético MAGNEX para detectar los residuos eyectados. Los resultados obtenidos indican el importante papel desempeñado por el apareamiento nuclear.