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김국배,이상준,김종현,이진평,장석상 한국물리학회 2006 새물리 Vol.53 No.4
Because the refractive index of X-rays in a medium is very weak, total reflection or diffraction cannot be used for deflecting the pathway or condensing X-rays as with visible light. Recently a compound refractive lens (CRL) for hard X-rays has been suggested as new X-ray optics. In this research, we designed many different CRLs with various parameters, such like various radii of curvature, lens thicknesses, lens heights, and so on. The CRL lenses were fabricated with PMMA by using the LIGA process. The effects of various design parameters on the performance of the CRLs were investigated. Through performance tests, the parameters were optimized to condene hard X-rays beam effectively. The radius of curvature and the thickness of the CRL were found not to have a large influence. However, increasing the lens height was found to improve the performance. X선은 매질에 대한 굴절률이 매우 작기 때문에 가시광처럼 빛의 경로를 바꾸거나 광을 집속하기 어렵다. 그러나 최근 들어 회절이나 다중굴절을 이용한 새로운 집속기법이 개발되고 있다. 본 연구에서는 물질에 대한 투과성이 우수하고 직진성이 강한 경 X선에 사용 가능한 복합굴절렌즈들을 설계, 제작하고, 이들의 성능을 비교, 분석하였다. 실험에 사용된 복합굴절렌즈는 폴리머 계열인 PMMA로 제작되었으며, 렌즈의 곡률반경, 렌즈의 두께 등의 변수들이 렌즈의 성능에 미치는 영향을 평가하였다. 성능 평가 결과, 렌즈의 두께와 곡률반경은 렌즈의 집속성능에 크게 영향을 미치지 않으며, 렌즈 높이는 최대한 크게 설계하여 광량을 많이 확보하는 것이 유리한 것으로 나타났다.
Three-Dimensional Printing: Basic Principles and Applications in Medicine and Radiology
김국배,이상욱,Haekang Kim,양동현,김영학,경윤수,김청수,최세훈,Bum Joon Kim,하호진,Sun U. Kwon,김남국 대한영상의학회 2016 Korean Journal of Radiology Vol.17 No.2
The advent of three-dimensional printing (3DP) technology has enabled the creation of a tangible and complex 3D object that goes beyond a simple 3D-shaded visualization on a flat monitor. Since the early 2000s, 3DP machines have been used only in hard tissue applications. Recently developed multi-materials for 3DP have been used extensively for a variety of medical applications, such as personalized surgical planning and guidance, customized implants, biomedical research, and preclinical education. In this review article, we discuss the 3D reconstruction process, touching on medical imaging, and various 3DP systems applicable to medicine. In addition, the 3DP medical applications using multi-materials are introduced, as well as our recent results.
김국배,이상준,윤화식,Jin Pyung Lee,Jong Hyun Kim,장석상,Tae Ju Sin 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.II
The majority of studies previously conducted on X-ray compound refractive lenses (CRLs) were related to synchrotron radiation (SR) facilities that had a relatively high photon energy level of several tens of keV. However, the performance of CRLs at an SR source with the main photon flux at a photon energy of 7 -- 9 keV, such as that of the Pohang Light Source (PLS), is still not very apparent. In this present study, to find the effective experimental conditions for CRL applications at the PLS, we focused the SR beam by using a CRL fabricated with poly methyl methacrylate (PMMA) under a photon energy of 8 keV. Various CRLs with different configurations were fabricated using the LIGA (LIthographie, Galvanoformung, Abformtechnik) process, and the focused beam size was measured at the PLS by using two different experimental methods. The size of the measured focused beam was 7.2 $\mu$m at a focal length of 298 mm. The CRLs developed in this study have a high potential and could eventually be used in real SR experiments at the PLS.
김국배(Guk Bae Kim),이상준(Sang Joon Lee) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
Synchrotron X-ray micro-imaging method has been used to observe various dynamics of internal structures inside organisms, industrial devices, and so on. However, it is not suitable for this imaging system to observe dynamics of flows inside a structure because tracer matters, such as seeding particles, dyes typically used in conventional optical flow visualization methods, cannot be detectable under X-ray light source any more. On the other hand, PIV (particle image velocimetry) method, which has recently been accepted as a reliable quantitative flow visualization technique, can extract instantaneous velocity fields by applying digital image processing technique to pairs of consecutive particle images captured with a small time interval. In this study, we composed a synchrotron X-ray PIV system combining the PIV method into a synchrotron X-ray micro-imaging system. At first, peculiar optical characteristics of blood were investigated by enhancing speckle patterns with a synchrotron X-ray imaging method. This pattern enhancement can be explained by propagation-based phase contrast enhancement via sample-to-scintillator distance and by interference-based enhancement via sample thickness. In addition, we quantitatively visualized real blood flow inside a tube without any contrast media. The measured velocity field data show typical features of blood flow such as the yield stress and are well matched with the Casson’s hemorheologic model. The X-ray PIV method has a strong potential for visualizing blood samples non-invasively to obtain detailed flow information such as flow rate, spatial distributions of velocity, and shear stress.
X선관을 이용한 불투명한 물체 내부 유동의 정량적 가시화 연구
김국배(Guk Bae Kim),임남윤(Nam Yun Lim),류재춘(Jae Chun Ryu),임대현(Dae Hyun Yim),이형구(Hyung Koo Lee),이상준(Sang Joon Lee) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
To diagnose circulatory diseases in the viewpoint of hemodynamics, we need to get quantitative hemodynamic information of blood flows related with the vascular diseases with high spatial resolution of tens micrometer and high temporal resolution in the order of millisecond. For investigating in-vivo hemodynamic phenomena, a new diagnosing technique combining medical radiography and PIV method was newly proposed and developed. This angiographic PIV technique consists of a medical X-ray tube, an X-ray CCD camera, a shutter module for double pulses of X-ray, and a synchronizer. The feasibility of the angiographic PIV technique was tested and quantitative flow velocity field distribution of a flow inside an opaque conduit was acquired by the developed system. It can be used for measuring flow phenomena of nontransparent fluids inside opaque conduits.
김국배(Guk Bae Kim),이상준(Sang Joon Lee) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
Conventional medical instruments for diagnosing vascular diseases such as an angiography and Doppler methods give rough information on the shape of blood vessels and point-wise blood speed. In this study, we developed a method called X-ray PIV technique for visualizing blood flow using a coherent synchrotron x-ray. Without any contrast agents or tracer particles, this X-ray PIV method can visualize the flow pattern of blood based on the diffraction and interference characteristics of blood cells. The quantitative velocity field information of blood flow inside an opaque tube was obtained by applying a 2-frame PIV (particle image velocimetry) algorithm to the x-ray images obtained. The velocity field data obtained are compared with various models for analyzing blood flows.