• Journal of Radiation Protection and Research
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• 제48권3호
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• pp.117-123
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• 2023

Background: We investigated the impact of 0.35 T magnetic field on dose calculation for non-small cell lung cancer (NSCLC) stereotactic ablative radiotherapy (SABR) in the ViewRay system (ViewRay Inc.), which features a simultaneous use of magnetic resonance imaging (MRI) to guide radiotherapy for an improved targeting of tumors. Materials and Methods: Here, we present a comprehensive analysis of the effects induced by the 0.35 T magnetic field on various characteristics of SABR plans including the plan qualities and dose calculation for the planning target volume, organs at risk, and outer/inner shells. Therefore, two SABR plans were set up, one with a 0.35 T magnetic field applied during radiotherapy and another in the absence of the field. The dosimetric parameters were calculated in both cases, and the plan quality indices were evaluated using a Monte Carlo algorithm based on a treatment planning system. Results and Discussion: Our findings showed no significant impact on dose calculation under the 0.35 T magnetic field for all analyzed parameters. Nonetheless, a significant enhancement in the dose was calculated on the skin surrounding the tumor when the 0.35 T magnetic field was applied during the radiotherapy. This was attributed to the electron return effect, which results from the deviation of the electrons ejected from tissues upon radiation due to Lorentz forces. These returned electrons re-enter the tissues, causing a local dose increase in the calculated dose. Conclusion: The present study highlights the impact of the 0.35 T magnetic field used for MRI in the ViewRay system for NSCLC SABR treatment, especially on the skin surrounding the tumors.

• Journal of Radiation Protection and Research
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• 제45권1호
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• pp.11-15
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• 2020

Background: There have been various studies to investigate the mechanisms of DNA damage from low-energy electrons. To understand the mechanism of these strand breaks, it is necessary to investigate the dissociation mechanism of the DNA constituents, that is, bases, sugars, and phosphates. Materials and Methods: We studied the dissociation of thymine base upon interaction with low-energy electrons. For this experiment, thymine powder was pressed onto the indium base and irradiated by 5 eV electrons. Results and Discussion: Non-irradiated and irradiated thymine samples were compared and analyzed using the X-ray photoelectron spectroscopic technique to analyze the dissociation patterns of the molecular bonds after low-energy electron irradiation of thymine. Conclusion: With 5 eV electron irradiation, C-C and N-C = O bonds are the primary dissociations that occur in thymine molecules.

• 치과방사선
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• 제29권1호
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• pp.255-260
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• 1999

Purpose: The objective of this study was to evaluate the possibility of substitution of the zonography for the full-mouth periapical radiography in aspect of radiation protection. Materials and Methods: Rando phantom and LiF TLD chips were used for dosimetry. The absorbed doses at brain, skin above the TMJ. parotid gland. bone marrow in the mandibular body. and thyroid gland during the full-mouth periapical radiography. panoramic radiography. and zonography were measured. Resul ts: From the zonography. the absorbed doses to the brain. the skin over the TMJ. and the parotid gland were relatively high. but the absorbed doses to the bone marrow in the mandibular body and. especially. the thyroid gland were very low. Conclusion: The zonography can be an alternative to the full-mouth periapical radiography in aspect of radiation protection.

• Journal of Radiation Protection and Research
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• 제17권2호
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• pp.37-48
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• 1992

월성 원자력 발전소 2호기의 1차 종단 및 측면 차폐 계통의 각 차폐체에 대한 100% 출력 가동시 핵에너지 축적을 해석을 ANISN 코드를 이용하여 수행하였다. 본 해석 결과는 월성원자력 발전소 2호기 계통 설계시 고려 사항으로 이용될 수 있다.

• Nuclear Engineering and Technology
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• 제54권9호
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• pp.3440-3447
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• 2022

The accuracy of the photoatomic cross-section data is of great importance in the field of radiation protection, particularly in the characterization of radiation shielding materials. With the release of the latest and probably the most accurate photoatomic data library, EPDL2017, the need to re-evaluate all the existing and already established mass attenuation coefficients (MACs) of all radiation shielding materials arises. The MACs of several polymers, alloy-based, glasses, and building materials used in a nuclear medicine facility were investigated using the EPDL2017 library embedded in EpiXS software and were compared to MACs available in the literature. The relative differences between MAC_EpiXS and MACXCOM were negligible, ranging from 0.02% to 0.36% for most materials. However, for material like a glass comprising of elements Te and La evaluated near their corresponding K-edge energies, the relative differences in MACs increased up to 1.46%. On the other hand, a comparison with MACs calculated based on EPDL97 (a predecessor of EPDL2017) revealed as much as a 6.61% difference. Also, it would seem that the changes in MACs were more evident in the materials composed of high atomic number elements evaluated at x-ray energies compared to materials composed of low atomic number elements evaluated at gamma-ray energies.

• 패션비즈니스
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• 제11권6호
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• pp.52-61
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• 2007

To increase the ultraviolet radiation (UVR) protection of cotton fabric, ultraviolet protection (UVP) materials were treated onto cotton fabric using a new technique, UV-curing. A photocrosslinkablepolymer, poly(ethylene glycol) dimethacrylate was used as a UV-curable resin in the presence of a small amount of photoinitiator. Two kinds of UVP materials were used, UV-absorber, 2,2'-dihydroxy-4-methoxy benzophenone, and UV-scatterer, $TiO_2/ZnO$ Pad-dry-cure method in employing these materials onto cotton was also conducted to compare the effectiveness and the washfastness of UVP treatment between curing methods. UVP treated cotton fabric showed a moderate increase in UVP in case of 2,2'-dihydroxy-4-methoxy benzophenone treatment and a high increase in case of $TiO_2/ZnO$. UV-curing method increased the washfastness of UVP property of $TiO_2/ZnO$ treated cotton fabrics. However, in case of 2,2'-dihydroxy-4-methoxy benzophenone, similar wash fastnesses of UV-cured and pad-dry-cured cotton were observed. It can be presumed that 2,2'-dihydroxy-4-methoxy benzophenone was not significantly affected by water since its hydrophobicity. In short, UV-curing of UVP materials onto cotton was successfully done, and treated cotton fabrics showed the increased UVP properties and an increased washfastness in some extent.

• Journal of Radiation Protection and Research
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• 제43권1호
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• pp.1-9
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• 2018

Background: In this study, we investigate the image quality of virtual monochromatic images synthesized from dual-energy computed tomography (DECT) at voltages of 80/140 kV and 100/140 kV. Materials and Methods: Virtual monochromatic images of a phantom are synthesized from DECT scans from 40 to 70 keV in steps of 1 keV under the two combinations of tube voltages. The dose allocation of dual-energy (DE) scan is 50% for both low- and high-energy tubes. The virtual monochromatic images are compared to single-energy (SE) images at the same radiation dose. In the DE images, noise is reduced using the 100/140 kV scan at the optimal monochromatic energy. Virtual monochromatic images are reconstructed from 40 to 70 keV in 1-keV increments and analyzed using two quality indexes: noise and contrast-to-noise ratio (CNR). Results and Discussion: The DE scan mode with the 100/140 kV protocol achieved a better maximum CNR compared to the 80/140 kV protocol for various materials, except for adipose and brain. Image noise is reduced with the 100/140 kV protocol. The CNR values of DE with the 100/140 kV protocol is similar to or higher than that of SE at 120 kV at the same radiation dose. Furthermore, the maximum CNR with the 100/140 kV protocol is similar to or higher than that of the SE scan at 120 kV. Conclusion: It was found that the CNR achieved with the 100/140 kV protocol was better than that with the 80/140 kV protocol at optimal monochromatic energies. Virtual monochromatic imaging using the 100/140 kV protocol could be considered for application in breast, brain, lung, liver, and bone CT in accordance with the CNR results.

• Journal of Radiation Protection and Research
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• 제46권4호
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• pp.194-203
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• 2021

Background: Surface soil radiation monitoring around nuclear facilities is important to classify and characterize the contaminated areas. A scanning and direct measurement technique can survey the sites rapidly before starting sampling analysis. Materials and Methods: Regarding this, we test and suggest a measurement technique for gross alpha/beta and ⁹⁰Sr activities in surface soil based on a mobile ZnS(Ag)/PVT (polyvinyltoluene) array and a handheld PVT rod, respectively. To detect ⁹⁰Sr selectively in soil mixed with naturally occurring radioactive materials, chosen energy channel counts from the multichannel analyzers were used instead of whole channel counts. Soil samples contaminated with exempt liquid ⁹⁰Sr with 1 Bq·g^-1, 3 Bq·g^-1, and 10 Bq·g^-1 were prepared and hardened by flocculation. Results and Discussion: The mobile ZnS(Ag)/PVT array could discriminate gross alpha, gross beta, and gamma radiation by the different pulse-shaped signal features of each sensor material. If the array is deployed on a vehicle, the scan minimum detectable concentration (MDC) range will be about 0.11-0.17 Bq·g^-1 at 18 km·h^-1 speed, highly sensitive to actual sites. The handheld PVT rod with 12 mm (Φ) × 20 mm (H) size can directly measure ⁹⁰Sr selectively if channels on which energies are from 1,470 and 2,279 keV are gated, minimizing crossdetection of other radionuclides. These methods were verified by measuring soil samples fabricated with homogeneous ⁹⁰Sr concentrations, showing static MDC of 2.16 Bq·g^-1 at a measurement time of 300 seconds. Conclusion: Based on the results, comprehensive procedures using these detectors are suggested to optimize soil sites survey.

• Journal of Radiation Protection and Research
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• 제41권3호
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• pp.222-228
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• 2016

Background: We are developing a small size dosimeter for dose estimation in particle therapies. The developed dosimeter is an optical fiber based dosimeter mounting an radiation induced luminescence material, such as an OSL or a scintillator, at a tip. These materials generally suffer from the quenching effect under high LET particle irradiation. Materials and Methods: We fabricated two types of the small size dosimeters. They used an OSL material Eu:BaFBr and a BGO scintillator. Carbon ions were irradiated into the fabricated dosimeters at Heavy Ion Medical Accelerator in Chiba (HIMAC). The small size dosimeters were set behind the water equivalent acrylic phantom. Bragg peak was observed by changing the phantom thickness. An ion chamber was also placed near the small size dosimeters as a reference. Results and Discussion: Eu:BaFBr and BGO dosimeters showed a Bragg peak at the same thickness as the ion chamber. Under high LET particle irradiation, the response of the luminescence-based small size dosimeters deteriorated compared with that of the ion chamber due to the quenching effect. We confirmed the luminescence efficiency of Eu:BaFBr and BGO decrease with the LET. The reduction coefficient of luminescence efficiency was different between the BGO and the Eu:BaFBr. The LET can be determined from the luminescence ratio between Eu:BaFBr and BGO, and the dosimeter response can be corrected. Conclusion: We evaluated the LET dependence of the luminescence efficiency of the BGO and Eu:BaFBr as the quenching effect. We propose and discuss the correction of the quenching effect using the signal intensity ratio of the both materials. Although the correction precision is not sufficient, feasibility of the proposed correction method is proved through basic experiments.

• Journal of Radiation Protection and Research
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• 제48권1호
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• pp.44-51
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• 2023

Background: Aptamers are currently being used in various fields including medical treatments due to their characteristics of selectively binding to specific molecules. Due to their special characteristics, the aptamers are expected to be used to remove radionuclides from a large amount of liquid radioactive waste generated during the decommissioning of nuclear power plants. The radiological effects on the aptamers should be evaluated to ensure their integrity for the application of a radionuclide removal technique. Materials and Methods: In this study, Monte Carlo N-Particle transport code version 6 (MCNP6) and Monte Carlo damage simulation (MCDS) codes were employed to evaluate the radiological effects on the aptamers. MCNP6 was used to evaluate the secondary electron spectrum and the absorbed dose in a medium. MCDS was used to calculate the DNA damage by using the secondary electron spectrum and the absorbed dose. Binding experiments were conducted to indirectly verify the results derived by MCNP6 and MCDS calculations. Results and Discussion: Damage yields of about 5.00×10^-4 were calculated for 100 bp aptamer due to the radiation dose of 1 Gy. In experiments with radioactive materials, the results that the removal rate of the radioactive ⁶⁰Co by the aptamer is the same with the non-radioactive ⁵⁹Co prove the accuracy of the previous DNA damage calculation. Conclusion: The evaluation results suggest that only very small fraction of significant number of the aptamers will be damaged by the radioactive materials in the liquid radioactive waste.