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      • KCI등재

        몬테카를로 시뮬레이션을 이용한 선형가속기 구성요소 변화에 따른 후방산란에 관한 연구

        김회인,천권수 한국방사선학회 2015 한국방사선학회 논문지 Vol.9 No.4

        의료용 선형가속기의 헤드 구성요소인 표적물질과 일차 콜리메이터는 선속특징을 결정짓는데 가장 큰 영향을 미치며 이로 인해 발생하는 후방산란은 구조물 차폐와 장비 관리 관점에서 고려하여야 할 요소이다. 이에 본 연구에서는 몬테카를로 시뮬레이션 중 하나인 Geant4를 통해 선형가속기를 모델링하고 헤드 구성요소의 변화에 따른 후방산란 양상을 살펴보았다. 산란되어 발생한 전자의 경우, 표적물질이 위치한 일차 콜리메이터의 내부 반경에 대부분의 분포를 보였으며 이와 반대로 산란된 광자의 경우, 바깥쪽 영역에서 상대적으로 높은 에너지의 산란이 많음을 알 수 있었다. 산란된 양전자는 약 0.03%로 미미한 발생을 보였다. 일차 콜리메이터의 내부 반경이 달라짐에 따라 세 산란입자(전자, 광자, 양전자) 모두 반경 내부 쪽에서의 변화가 컸으며, 전체 반경의 변화에 따른 후방산란은 60 mm 이상에서부터 어느 정도의 영향을 보인다는 것을 알 수 있었다. 표적물질 두께의 변화에는 큰 영향을 받지 않는 것으로 나타났다. 이를 통하여 가속시킨 초기 전자에 대한 후방 쪽으로의 산란도 무시할 수 없음을 알 수 있었으며 주변 구성요소의 기하학적인 형태나 크기에 의해서도 후방산란의 양상이 달라질 수 있음을 알 수 있었다. 따라서 산란된 입자들의 에너지 분포를 통해 장비 관리의 관점에서도 고려하여야 할 결과라고 사료된다. It should be accurate dose calculation to increase the efficiency of radiation therapy, and it is priority to figure out the beam characteristics for this purpose. The target and primary collimator in head components of the linear accelerator have the greatest influence on determining the beam characteristics which is caused by backscatter and it is the factor to consider the shielding structures and equipment management. In this study, we made modeling of the linear accelerator through the Geant4 Monte Carlo simulation and investigated backscatter according to the change of the size and shape in head components. For the scattered electrons, it showed the greatest number of distributions inside of the inner radius at primary collimator. But, for the scattered photons which have the high energy, it was mostly located outside of the inner radius at primary collimator. Scattered positrons showed a small occurrence in about 0.03%. According to the change of the inner radius at primary collimator, it was great changes in the inside of inner radius for all three scattered particles. According to the change of the outer radius at primary collimator, it was shown some considerable effects from more than 60 mm outer radius. It was no significant effect according to the change of target thickness. In this study, we found that backscatter should be considered, and figured out that geometric size and shape of the peripheral components are the factors that influences the backscatter effect.

      • KCI등재

        Graded 다층박막거울을 이용한 단색 엑스선 획득

        유철우,최병정,손현화,권영만,김병욱,김영주,천권수 한국방사선학회 2015 한국방사선학회 논문지 Vol.9 No.4

        최근 의료영상기술에서 유방암 엑스선 진단기술의 주요 이슈는 정확한 조기암 진단과 환자의 피폭선량의 감소에 있다. 엑스선 영상대비도를 높이고 피폭선량을 줄이는 기술 중 하나로써 다층박막거울을 이용한 단색 엑스선을 획득하는 연구가 선행되어 왔다. 그러나 기존의 Uniform 다층박막거울은 거울면의 일부 반사영역에서만 원하는 파장대역의 단색 엑스선을 얻을 수 있어서 엑스선 영상기술 응용에 한계가 있다. 본 연구에서는 다층박막거울의 전 영역에 걸쳐 동일한 단색엑스선을 얻기 위해 거울에 입사하는 백색 엑스선의 입사각에 상응하는 선형적 기울기의 박막두께를 갖는 Graded 다층박막거울을 설계하였고, 기존 이온빔 스퍼터링 장치에 마스크 제어 장치를 추가 제작하여 100×100mm2 크기로 제작하였다. 제작된 Graded 다층박막거울은 17.5keV의 단색엑스선을 획득할 수 있도록 설계하였으며 박막두께주기는 2.88nm~4.62nm(Center 3.87nm)이다. 엑스선 반사율은 60% 이상이며, 단색 엑스선의 FWHM은 1.4keV 이하이고 엑스선 빔 폭은 3mm정도이다. 유방촬영에 적합한 몰리브덴 특성엑스선에 해당하는 17.5keV의 단색 엑스선을 얻음으로써 저선량·고감도 유방암 진단장치 개발에 응용할 수 있을 것으로 기대된다. At a recent medical imaging technology, the major issue of X-ray diagnosis in breast cancer is the early detection of breast cancer and low patient's exposure dose. As one of studies to acquire a monochromatic X-ray, Technologies using multilayer mirror had been preceded. However, a uniform multilayer mirror that consists of uniform thin-film thickness can acquire a monochromatic X-ray only in the partial area corresponds to angle of incidence of white X-ray, so there are limits for X-ray imaging technology applications. In this study, we designed laterally graded multilayer mirror(below GML) that reflects same monochromatic X-ray over the entire area of thin-film mirror, which have the the thickness of the linear gradient that correspond to angle of incidence of white X-ray. By using ion-beam sputtering system added the mask control system we fabricated a GML which has size of 100×100mm2. The GML is designed to achieve the monochromatic X-ray of 17.5kev energy and has thin-film thickness change from 4.62nm to 6.57nm(3.87nm at center). It reflects the monochromatic X-ray with reflectivity of more than 60 percent, FWHM of below 2.6keV and X-ray beam width of about 3mm. The monochromatic X-ray corresponded to 17.5keV using GML would have wide application in development of mammography system with high contrast and low dose.

      • KCI등재SCIESCOPUS

        Monochromatic X-ray Imaging System Using a W/C Multilayer Mirror

        천권수,Kwon-Ha,Yoon 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.6

        The possibility of monochromatic X-ray imaging using a conventional X-ray tube and a tungstencarbon (W/C) multilayer mirror was examined. The W/C multilayer mirror was designed to choose the characteristic X-ray (17.5 keV) generated from an X-ray tube with a molybdenum target and was fabricated by using an ion-beam sputtering deposition system. The X-ray reflectivity and the monochromaticity of the W/C multilayer mirror combined with the X-ray tube were 0.62 and 0.26 keV, respectively. Monochromatic X-ray slit images for a test sample were obtained from the monochromatic X-ray imaging system with a scanning stage. The slit images were combined together, and a full sample image was obtained. The monochromatic X-ray imaging system showed a spatial resolution of 26 lp/mm at 10% MTF, a better contrast, and a better signal-to-noise ratio compared with polychromatic X-ray imaging. The possibility of monochromatic X-ray imaging using a conventional X-ray tube and a tungstencarbon (W/C) multilayer mirror was examined. The W/C multilayer mirror was designed to choose the characteristic X-ray (17.5 keV) generated from an X-ray tube with a molybdenum target and was fabricated by using an ion-beam sputtering deposition system. The X-ray reflectivity and the monochromaticity of the W/C multilayer mirror combined with the X-ray tube were 0.62 and 0.26 keV, respectively. Monochromatic X-ray slit images for a test sample were obtained from the monochromatic X-ray imaging system with a scanning stage. The slit images were combined together, and a full sample image was obtained. The monochromatic X-ray imaging system showed a spatial resolution of 26 lp/mm at 10% MTF, a better contrast, and a better signal-to-noise ratio compared with polychromatic X-ray imaging.

      • KCI등재후보

        경 엑스선 존 플레이트(Zone Plate) 설계 및 제작

        천권수 한국방사선학회 2010 한국방사선학회 논문지 Vol.4 No.3

        '스콜라' 이용 시 소속기관이 구독 중이 아닌 경우, 오후 4시부터 익일 오전 7시까지 원문보기가 가능합니다.

        엑스선 영상의 공간분해능은 영상획득 장치에 사용되는 광학소자의 성능에 의해 결정된다. 8.5keV에서 높은 공간분 해능 달성이 가능한 존 플레이트를 설계하였다. 방사광을 이용하는 대신 엑스선 튜브를 사용하는 영상시스템에서는 80nm의 공간분해능을 달성할 수 있음을 광선추적 기법을 이용하여 예측하였다. 전자빔 석판인쇄술을 이용하여 최외곽 폭 40nm를 갖는 존 플레이트가 제작하였다. Spatial resolution is determined by the performance of x-ray optics used in the x-ray imaging system. A zone plate was designed for obtaining a high spatial resolution image at x-ray energy of 8.5keV. A spatial resolution of 80 nm was estimated by the ray tracing when an x-ray tube of tungsten targe was used instead of synchrotron radiation. The designed zone plate of outermost zone width of 40nm was successfully fabricated by the electron-beam lithography.

      • KCI등재

        X-선 튜브의 특성방사선을 이용한 영상획득

        천권수 한국물리학회 2011 New Physics: Sae Mulli Vol.61 No.1

        A characteristic X-ray that falls within the generated X-ray tube spectrum was examined for use in imaging soft tissue, for example, the breast, to reduce the radiation dose. A multilayer mirror was be applied to choose the characteristic X-ray from the X-ray tube spectrum. A multilayer mirror composed of tungsten (W) and carbon (C) was designed for an X-ray energy of 17.5 keV and was fabricated by using an ion-beam sputtering system. The reflectivity at 17.5 keV was 61.4%. A characteristic X-ray image of 50 mm×50 mm in size for the CDMAM phantom was obtained by using the imaging system with the W/C multilayer mirror. The results show that characteristic X-ray imaging should be useful in breast examination. 유방촬영과 같은 연부조직에 대한 방사선 피폭을 줄이기 위하여 X-선 튜브에서 발생되는 특성방사선을 이용하여 영상화 할 수 있는 가능성을 확인하였다. X-선 튜브에서 발생되는 몰리브덴 특성방사선을 얻기 위하여 W과 C 조합의 다층박막거울을 설계하고 ion-beam sputtering system을 이용하여 제작하였다. 제작된 다층박막거울은 17.5 keV에서 61.4 %의 반사효율을 보였다. 다층박막거울에서 반사된 슬릿빔을 이용하여 영상을 얻기 위하여 시료를 주사하였고, 50 mm×50 mm 크기의 CDMAM 팬텀의 특성방사선 영상을 획득하였다. X-선 튜브에서 발생된 특성방사선을 이용한 영상시스템은 유방촬영과 같은 연부조직 촬영에 적합할 것이다.

      • KCI등재

        Design study of hard X-ray tomography system to obtain a spatial resolution of 100 nm

        천권수,정선관,윤권하 한국물리학회 2012 Current Applied Physics Vol.12 No.1

        An optic-based X-ray tomography system of a high spatial resolution using a conventional X-ray tube was proposed. The system had several X-ray optics: multilayer mirror for monochromatic X-ray, capillary optic for focusing X-ray onto a sample, and objective zone plate. The X-ray tomography system was designed for obtaining a spatial resolution of 100 nm. Design parameters for each optic were determined and optimized by ray tracing in considering X-ray intensity and reflectivity. The X-ray tomography system with a spatial resolution of 100 nm will provide a good inspect tool in bio-medical field and semiconductor applications.

      • KCI등재SCOPUS

        Single-point diamond turning of electroless nickel for flat X-ray mirror

        천권수,Yoshiharu,Namba 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.8

        X-ray mirrors require a super-smooth surface to prevent strong X-ray scattering. We examined the fabrication possibility of the X-ray mirror by single-point diamond turning (SPDT) for electroless nickel. The stable and unstable cutting modes for the electroless nickel were obtained by observing the relative position of a diamond tool for machining. A super-smooth surface of 0.95 nm rms was achieved within the stable cutting mode. The surface roughness of the electroless nickel mirror measured with an optical profiler was compared with the X-ray reflectivity measurement. The electroless nickel mirror could be successfully used as a soft X-ray reflector and a low-pass filter for the hard X-rays.

      • KCI등재SCIESCOPUS

        Measurement of Roundness for an X-Ray Mono-Capillary Optic by Using Computed Tomography

        천권수 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.74 No.9

        X-ray computed tomography is a very useful tool for nondestructively imaging a cross section of a sample. By using a computed tomography beamline system of synchrotron radiation, we directly measured the radius of the inner reflection surface of a mono-capillary optic with an accuracy of 1.30~$\mu$m. The inner-surface deformation of a mono-capillary optic approximately 100 $\mu$m in diameter was first shown by combining radial profiles. The precise determination of the radius will contribute to an increase in fabrication precision for the mono-capillary optic.

      • KCI등재SCOPUS

        Trilayer model in design of W/C multilayer mirrors with a small period thickness

        천권수 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.12

        In the design of a W/C multilayer mirror, we applied a trilayer model to consider the interdiffusion of tungsten and carbon on the Won-C interface and investigated the first Bragg angle and its reflectivity. As the interdiffusion thickness of a W/C multilayer mirror increased, the first Bragg angle and the reflected X-ray energy increased. However, as the period thickness of the W/C multilayer mirror increased, the effects of the interdiffusion became less pronounced. The criteria for the use of either the bilayer or the trilayer models for the design of W/C multilayer mirrors were presented for various period thicknesses. The trilayer model would be useful for the design of multilayer mirrors with a small period thickness of less than approximately 4.0 nm at an interdiffusion of 0.28 nm.

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