경 엑스선 존 플레이트(Zone Plate) 설계 및 제작

천권수 한국방사선학회 2010 한국방사선학회 논문지 Vol.4 No.3

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.

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.

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.

Usefulness of a Small-Field Digital Mammographic Imaging System Using Parabolic Polycapillary Optics as a Diagnostic Imaging Tool: a Preliminary Study

천권수,박정곤,박성훈,강성훈,김혜원,손현화,김혜원,김헌수,윤권하 대한영상의학회 2009 Korean Journal of Radiology Vol.10 No.6

Objective: To evaluate the efficacy for spatial resolution and radiation dose of a small-field digital mammographic imaging system using parabolic polycapillary optics. Materials and Methods: We developed a small-field digital mammographic imaging system composed of a CCD (charge coupled device) detector and an Xray source coupled with parabolic polycapillary optics. The spatial resolution and radiation dose according to various filters were evaluated for a small-field digital mammographic imaging system. The images of a test standard phantom and breast cancer tissue sample were obtained. Results: The small-field digital mammographic imaging system had spatial resolutions of 12 lp/mm with molybdenum and rhodium filters with a 25-μm thickness. With a thicker molybdenum filter (100 μm thick), the system had a higher spatial resolution of 11 lp/mm and contrast of 0.48. The radiation dose for a rhodium filter with a 25-μm thickness was 0.13 mGy within a 10-mm-diameter local field. A larger field image greater than 10 mm in diameter could be obtained by scanning an object. On the small-field mammographic imaging system, microcalcifications of breast cancer tissue were clearly observed. Conclusion: A small-field digital mammographic imaging system with parabolic polycapillary optics may be a useful diagnostic tool for providing high-resolution imaging with a low radiation dose for examination of local volumes of breast tissue. Objective: To evaluate the efficacy for spatial resolution and radiation dose of a small-field digital mammographic imaging system using parabolic polycapillary optics. Materials and Methods: We developed a small-field digital mammographic imaging system composed of a CCD (charge coupled device) detector and an Xray source coupled with parabolic polycapillary optics. The spatial resolution and radiation dose according to various filters were evaluated for a small-field digital mammographic imaging system. The images of a test standard phantom and breast cancer tissue sample were obtained. Results: The small-field digital mammographic imaging system had spatial resolutions of 12 lp/mm with molybdenum and rhodium filters with a 25-μm thickness. With a thicker molybdenum filter (100 μm thick), the system had a higher spatial resolution of 11 lp/mm and contrast of 0.48. The radiation dose for a rhodium filter with a 25-μm thickness was 0.13 mGy within a 10-mm-diameter local field. A larger field image greater than 10 mm in diameter could be obtained by scanning an object. On the small-field mammographic imaging system, microcalcifications of breast cancer tissue were clearly observed. Conclusion: A small-field digital mammographic imaging system with parabolic polycapillary optics may be a useful diagnostic tool for providing high-resolution imaging with a low radiation dose for examination of local volumes of breast tissue.

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.

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.

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.

모듈로 구성된 선형 검출기의 영상보정 방법

천권수,오석심,진왕연 한국방사선학회 2022 한국방사선학회 논문지 Vol.16 No.2

여러 모듈을 선형으로 배치하여 제작한 선형 검출기가 산업의 전수검사에 활용되고 있으나 선형 검출기로 획득한 2차원 영상에서 연결부위에 선 허상이 나타난다. 본 연구는 Flat-Field Correction 이후에 Wedge 팬텀 영상을 이용하여 선 허상을 제거하는 방법을 제시하였다. 통상적인 Flat-Field Correction을 수행하더라도 모듈의 연결부분에서 발생하는 선 허상을 제거하지 못하였다. 모듈의 연결부위에 위치한 양 엣지의 픽셀들이 Flat-Field Correction 이후 과도하게 보정되는 것을 확인하였고 이 픽셀들의 추가적인 보정을 위해 Wedge 영상을 이용하여 보정인자를 구하여 적용함으로써 선 허상이 완전히 제거된 영상을 획득하였다. 보정인자를 구하는 수동적인 절차를 자동화하여 산업에서 선 허상 제거를 쉽게 수행할 수 있도록 개선할 필요가 있다. Linear detectors composed of several modules have been widely used in industrial in-line inspection. Two dimensional image obtained from the linear detector shows line artifact at the connection part of each module. In this study, we proposed a method to remove the line artifact using the flat-field correction and a wedge phantom image. Conventional flat-field correction has been applied to remove the artifact, however there are still line artifacts even after applying correction. It was found that two edge pixels at the connection part of two modules were over-corrected after the flat-field correction. Those edge pixels was corrected by using the correction factor obtained from an image of the wedge phantom, and images removed line artifacts were obtained. It is necessary to improve the method obtained manually the correction factor from the image of the wedge phantom.

이중 적층 구조 표적을 갖는 투과형 엑스선관의 몬테카를로 전산모사

천권수 한국방사선학회 2023 한국방사선학회 논문지 Vol.17 No.1

엑스선형광분석은 비파괴적으로 시료에 포함된 원소와 농도를 분석할 수 있는 기법으로 과학 및 산업 분야에 광범위하게 사용되고 있다. 다양한 물질을 포함한 혼합물 또는 화합물 분석의 정밀도 향상을 위해 10 keV 근방의 저에너지와 20 keV 근방의 에너지 영역에 높은 강도 분포를 갖는 엑스선관이 요구된다. 두 에너지 영역에서 높은 강도 분포를 갖는 스펙트럼을 얻기 위하여 9.65 keV의 특성엑스선을 가지는 텅스텐과 17.48 keV의 몰리브덴 두 물질을 적층한 구조의 표적을 가지는 투과형 엑스선관을 몬테카를로 전산모사를 통해 스펙트럼을 분석하였다. W-Mo 구조의 표적을 통해 10 keV와 20 keV 근방의 강한 강도를 갖는 특성엑스선을 얻었다. 또한 4 μm 두께의 Mo-W multilayers 구조의 표적을 통해 최적의 강도 분포를 갖는 스펙트럼을 얻을 수 있음을 확인하였다. 다양한 표적 물질을 선택 조합하고 두께 최적화를 통해 원하는 에너지 대역에서 높은 강도 분포를 갖는 스펙트럼을 얻는 것이 가능하다.

X-선 튜브의 특성방사선을 이용한 영상획득

천권수 한국물리학회 2011 새물리 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.