• Title/Summary/Keyword: gamma-radiation sensitivity

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Development of Sensitivity-Enhanced Detector using Pixelization of Block Scintillator with 3D Laser Engraving (3차원 레이저 각인으로 블록형 섬광체의 픽셀형화를 통한 민감도 향상 검출기 개발)

  • Lee, Seung-Jae;Baek, Cheol-Ha
    • Journal of the Korean Society of Radiology
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    • v.13 no.2
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    • pp.313-318
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    • 2019
  • To improve the sensitivity, a detector using a block scintillator was developed. In the pixelated scintillator, a reflector is located between pixels to move the light generated from the scintillator to the photosensor as much as possible, and sensitivity loss occurs in the reflector portion. In order to improve the sensitivity and to have the characteristics of the pixelated scintillator, the block scintillator was processed into a scintillator in pixel form through three-dimensional laser engraving. The energy spectra and energy resolution of each pixel were measured, and sensitivity analysis of block and pixel scintillator was performed through GATE simulation. The measured global energy resolution was 20.7%, and the sensitivity was 18.5% higher than that of the pixel scintillator. When this detector is applied to imaging devices such as gamma camera and positron emission tomography, it will be possible to shorten the imaging time and reduce the dose of patient by using less radiation source.

Induction of micronuclei in human, rabbit and dog lymphocytes irradiated in vitro with gamma radiation (사람, 토끼 및 개 유래 말초혈액 림프구의 미소핵을 이용한 방사선 피폭의 생물학적 선량측정)

  • Ryu, Si-yun;Kang, Bit-na;Kim, Ho-jun;Kim, Tae-hwan;Jeong, Kyu-sik;Kim, Se-ra;Lee, Hae-june;Kim, Sung-ho;An, Mi-Young
    • Korean Journal of Veterinary Research
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    • v.42 no.1
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    • pp.1-6
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    • 2002
  • The frequencies of gamma-ray-induced micronuclei (MN) in cytokinesis-blocked (CB) lymphocytes at several doses were measured in three donors of three species (human, rabbit, dog). Measurements performed after irradiation showed a dose-related increases in MN frequency in each of the donors studied. When analysed by linear-quadratic model the line of best fit was : human : $y=0.1184D+0.01867D^2+0.01$, rabbit : $y=0.0387D+0.00528D^2+0.01$ (y = number of MN/CB cells and D = irradiation dose in Gy). The relative sensitivity of rabbit lymphocytes compared with human lymphocytes was estimated by best fitting linear-quadratic model based on the radiation-induced MN data over the range from 0 Gy to 4 Gy. In the case of MN frequency with 0.2, the relative sensitivities of rabbit lymphocytes was 0.39. These data indicate that the induction of MN in rabbit CB cells following irradiation was much less sensitive to the MN induction effects of gamma-irradiation than those from human. The MN assay with dog lymphocytes was very difficult and time-consumed because the dog PHA-stimulated lymphocytes yielded cultures with very low level of CB cells formation in the condition of this experiment. Our in vitro radiobiological study confirmed that the cytogenetic response obtained in blood from rabbit can be utilized for application in environmental studies.

A Study on the Feasibility of Lead(II) Iodide and Gd2O2S:Tb Overlapping Sensors in Gamma Source Conditions using FLUKA Simulation (FLUKA 전산 모사를 통한 감마선원 조건에서의 요오드화납(II)과 Gd2O2S:Tb가 결합된 센서의 적용가능성 연구)

  • Yang, Seung-Woo;Park, Yoon-Hee;Park, Ji-Koon;Heo, Ye-Ji
    • Journal of the Korean Society of Radiology
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    • v.16 no.4
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    • pp.381-386
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    • 2022
  • Non-Destruction Test (NDT) is a method to check internal defects without destroying the product. Among them, radiographic testing (RT) uses high-energy radiation, so it is very important to prevent radiation exposure of workers. Therefore, in this study, in this study, a radiation sensor structure that improves radiation detection performance compared to the existing PbI2 and can immediately detect accidents in RT was presented. For evaluation, the conversion efficiency was analyzed in the gamma ray source through FLUKA simulation. PbI2 with overlapping Gd2O2S:Tb presented in this study showed a higher radiation sensitivity from 1.22 to 3.22 times than that of non-overlapping PbI2. This indicates that the presented sensor is suitable for use as a radiation sensor for source detection in RT.

Evaluation of DNA Damage and Repair Kinetics in the Earthworm (Eisenia fetida) Exposed to Radiation and Mercury (방사선과 수은에 의해 유도된 Eisenia fetida 체강세포의 DNA 손상 및 수복 평가)

  • Ryu, Tae-Ho;Nili, Mohammad;An, Kwang-Guk;Kim, Jin-Kyu
    • Korean Journal of Environmental Biology
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    • v.29 no.1
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    • pp.68-73
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    • 2011
  • The single cell gel electrophoresis (SCGE) assay is a microelectrophoretic technique for assessments of DNA damage at the level of the individual eukaryotic cell. The SCGE assay, due to its simplicity, sensitivity and need of a few cells, has advantages compared to other genomic damage assays such as sister chromatid exchange, chromosomal aberration and micronucleus test. In this study, investigated were the levels of DNA damage and the repair kinetics in the coelomocytes of Eisenia fetida treated with HgCl2 and ionizing radiation by means of the SCGE assay. For detecting DNA damage and repair in coelomocytes, earthworms (E. fetida) were irradiated with six doses of ${\gamma}$-rays (0, 2.5, 5, 10, 20 and 50 Gy) and in vivo exposed to mercuric chloride at 0, 80 and 160 mg $kg^{-1}$ for 48 hours. Then the Olive tail moments were measured during 0~12 hours after irradiation and 0~72 hours after Hg treatment. The results showed that the more the oxidative stress was induced by mercury and radiation, the longer the repair time was required. Also, the results suggest that the SCGE assay may be used as an important tool for comparison of the sensitivity of different species to oxidative stresses.

Preliminary Study on Performance Evaluation of a Stacking-structure Compton Camera by Using Compton Imaging Simulator (Compton Imaging Simulator를 이용한 다층 구조 컴프턴 카메라 성능평가 예비 연구)

  • Lee, Se-Hyung;Park, Sung-Ho;Seo, Hee;Park, Jin-Hyung;Kim, Chan-Hyeong;Lee, Ju-Hahn;Lee, Chun-Sik;Lee, Jae-Sung
    • Progress in Medical Physics
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    • v.20 no.2
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    • pp.51-61
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    • 2009
  • A Compton camera, which is based on the geometrical interpretation of Compton scattering, is a very promising gamma-ray imaging device considering its several advantages over the conventional gamma-ray imaging devices: high imaging sensitivity, 3-D imaging capability from a fixed position, multi-tracing functionality, and almost no limitation in photon energy. In the present study, a Monte Carlo-based, user-friendly Compton imaging simulator was developed in the form of a graphical user interface (GUI) based on Geant4 and $MATLAB^{TM}$. The simulator was tested against the experimental result of the double-scattering Compton camera, which is under development at Hanyang University in Korea. The imaging resolution of the simulated Compton image well agreed with that of the measured image. The imaging sensitivity of the measured data was 2~3 times higher than that of the simulated data, which is due to the fact that the measured data contains the random coincidence events. The performance of a stacking-structure type Compton camera was evaluated by using the simulator. The result shows that the Compton camera shows its highest performance when it uses 4 layers of scatterer detectors.

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Exploitation of the Dose/Time-Response Relationship for a New Measure of DNA Repari in the Single-Cell Gel Electrophoresis (Comet) Assay

  • Kim, Byung-Soo;Edler, Lutz;Park, Jin-Joo;Fournier, Dietrich Von;Haase, Wulf;Sautter-Bihl, Mare-Luise;Hagmuller, Egbert;Gotzes, Florian;Thielmann, Heinz Walter
    • Toxicological Research
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    • v.20 no.2
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    • pp.89-100
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    • 2004
  • The comet assay (also called the single-cell gel electrophoresis assay) has been widely used for detecting DNA damage and repair in individual cells. Since the conventional methods of evaluating comet assay data using frequency statistics are unsatisfactory we developed a new quantitative measure of DNA damage/repair that is based on all information residing in the dose/time-response curves of a comet experiment. Blood samples were taken from 25 breast cancer patients before undergoing radiotherapy. The comet assay was performed under alkaline conditions using isolated lymphocytes. Tail DNA, tail length, tail moment and tail inertia of the comet were measured for each patient at four doses of $\gamma$-rays (0, 2, 4 and 8 Gy) and at four time points after irradiation (0, 10, 20 and 30 min) using 100 cells each. The resulting three-dimensional dose-time response surface was modeled by multiple regression, and the second derivative, termed 2D, on dose and time was determined. A software module was programmed in SAS/AF to compute 2D values. We applied the new method successfully to data obtained from cancer patients to be assessed for their radiation sensitivity. We computed the 2D values for the four damage measures, i.e., tail moment, tail length, tail DNA and tail inertia, and examined the pairwise correlation coefficients of 2D both on the log scale and the unlogged scale. 2D values based on tail moment and tail DNA showed a high correlation and, therefore, these two damage measures can be used interchangeably as far as DNA repair is concerned. 2D values based on tail inertia have a correlation profile different from the other 2D values which may reflect different facets of DNA damage/repair. Using the dose-time response surface, other statistical models, e.g., the proportional hazards model, become applicable for data analysis. The 2D approach can be applied to all DNA repair measures, Le., tail moment, tail length, tail DNA and tail inertia, and appears to be superior to conventional evaluation methods as it integrates all data of the dose/time-response curves of a comet assay.

Evaluation of Radiation Effect on Damage to Nuclear Fuel of Spent Fuel Transport CASK due to Sabotage Attack (사보타주 공격으로 인한 사용후핵연료 운반용기 격납 실패시 핵연료 손상에 따른 방사선 영향 평가)

  • Ki Ho Park;Jong Sung Kim;Gun il Cha;Chang Je Park
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.18 no.2
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    • pp.43-49
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    • 2022
  • The purpose of this study is to evaluate the radiation effect on damage when the external shield of the spent nuclear fuel transport cask is damaged due to impact as the cause of an unexpected accident. The neutron and gamma-ray intensities and spectra are calculated using the ORIGEN-Arp module in the SCALE 6.2.4 code package(1) and then using MCNP6.2(2) code calculate the dose rate. In order to evaluate the radiation dose according to the size of damage caused by external impact, various sized holes of 0.3~13.7% are assumed in the outer shield of the cask to evaluate the sensitivity to the dose. In the case of radiation source leakage, damage to the nuclear fuel assembly is assumed to be up to 6% based on overseas test cases. When only the outer shield is damaged, the maximum surface dose is calculated as 3.12E+03 mSv/hr. However, if the radiation source is leaked due to damage to the nuclear fuel assembly, it becomes 7.00E+05 mSv/hr which is about 200 times greater than the former case.

Development of a TL pellet based on $CaSO_4:Dy$ for Neutron Measurement ($CaSO_4:Dy$ 물질 기반 중성자 측정용 TL소자 개발)

  • Yang, Jeong-Seon;Lee, Jeong-Il;Kim, Jang-Lyul;Kim, Bong-Hwan;Sou, Dong-Sup
    • Journal of Radiation Protection and Research
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    • v.31 no.3
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    • pp.129-134
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    • 2006
  • A TL pellet for a neutron dose measurement (KCT-306) by embedding a $^6Li$-compound into a $CaSO_4:Dy$ phohphor was developed based upon the technical information of KCT-300. The KCT-300 is an another kind of $CaSO_4:Dy$ TL detector shich was developed at KAERI, in which small amounts of $NH_4H_2PO_4$ have been emvedded as a binding material. This paper presented the optimized manufacturing condition of KCT-306 and compared its sensitivity with that of the commercialized neutron TL pellets. $CaSO_4:Dy$ Phosphor with grain size ranging less than $45{\mu}m$ are used for the KCT-306. The optimum $CaSO_4:Dy$ TL phosphor, $^6Li$-compounds and P-compound as the binding material are determined as 20-40wt%, 50-70wt% and 20wt%. The TL pellet combination of our KCT-306/KCT-300, TLD-600/TLD-700 and TLD-600H/TLD-700H(Harshaw) have been irradiated in the neutron/gamma mixed fields from a $D_2O$ moderated $^{252}Cf$ neutron source. The KCT-300, TLD-700 and TLD-700H were used at the same time as gamma ray discriminators in the neutron/gamma mixed fields. It was found that the neutron/gamma response ratios of KCT-306/KCT-300, which were developed in this study, were approximately 4 times higher than those of the commercial TLD-600H/TLD-700H.

Tackling range uncertainty in proton therapy: Development and evaluation of a new multi-slit prompt-gamma camera (MSPGC) system

  • Youngmo Ku;Sehoon Choi;Jaeho Cho;Sehyun Jang;Jong Hwi Jeong;Sung Hun Kim;Sungkoo Cho;Chan Hyeong Kim
    • Nuclear Engineering and Technology
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    • v.55 no.9
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    • pp.3140-3149
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    • 2023
  • In theory, the sharp dose falloff at the distal end of a proton beam allows for high conformal dose to the target. However, conformity has not been fully achieved in practice, primarily due to beam range uncertainty, which is approximately 4% and varies slightly across institutions. To address this issue, we developed a new range verification system prototype: a multi-slit prompt-gamma camera (MSPGC). This system features high prompt-gamma detection sensitivity, an advanced range estimation algorithm, and a precise camera positioning system. We evaluated the range measurement precision of the prototype for single spot beams with varying energies, proton quantities, and positions, as well as for spot-scanning proton beams in a simulated SSPT treatment using a phantom. Our results demonstrated high accuracy (<0.4 mm) in range measurement for the tested beam energies and positions. Measurement precision increased significantly with the number of protons, achieving 1% precision with 5 × 108 protons. For spot-scanning proton beams, the prototype ensured more than 5 × 108 protons per spot with a 7 mm or larger spot aggregation, achieving 1% range measurement precision. Based on these findings, we anticipate that the clinical application of the new prototype will reduce range uncertainty (currently approximately 4%) to 1% or less.

Development of simultaneous multi-channel data acquisition system for large-area Compton camera (LACC)

  • Junyoung Lee;Youngmo Ku;Sehoon Choi;Goeun Lee ;Taehyeon Eom ;Hyun Su Lee ;Jae Hyeon Kim ;Chan Hyeong Kim
    • Nuclear Engineering and Technology
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    • v.55 no.10
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    • pp.3822-3830
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    • 2023
  • The large-area Compton camera (LACC), featuring significantly high detection sensitivity, was developed for high-speed localization of gamma-ray sources. Due to the high gamma-ray interaction event rate induced by the high sensitivity, however, the multiplexer-based data acquisition system (DAQ) rapidly saturated, leading to deteriorated energy and imaging resolution at event rates higher than 4.7 × 103 s-1. In the present study, a new simultaneous multi-channel DAQ was developed to improve the energy and imaging resolution of the LACC even under high event rate conditions (104-106 s-1). The performance of the DAQ was evaluated with several point sources under different event rate conditions. The results indicated that the new DAQ offers significantly better performance than the existing DAQ over the entire energy and event rate ranges. Especially, the new DAQ showed high energy resolution under very high event rate conditions, i.e., 6.9% and 8.6% (for 662 keV) at 1.3 × 105 and 1.2 × 106 s-1, respectively. Furthermore, the new DAQ successfully acquired Compton images under those event rates, i.e., imaging resolutions of 13.8° and 19.3° at 8.7 × 104 and 106 s-1, which correspond to 1.8 and 73 μSv/hr or about 18 and 730 times the background level, respectively.