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RISS 인기검색어
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- 저자 : 이동훈(D. H. Lee) (검색결과 199 건)
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Keyhole Imaging기법을 적용한 위상대조도 자기공명 혈관조영기법
이동훈,홍철표,한봉수,이만우,Lee, D.H.,Hong, C.P.,Han, B.S.,Lee, M.W. 대한의용생체공학회 2012 의공학회지 Vol.33 No.2
Phase Contrast MR Angiography(PC MRA) is excellent MRA technique for measuring the velocity of vessels in the human body. PC MRA need to at least four images for angiogram reconstruction and it caused longer scan time. Therefore, we used keyhole imaging combined PC MRA to reduce the scan time. However, keyhole imaging can lead the erroneous effects as loss of phase information or frequency discontinuous. In this study, we applied the keyhole imaging combined 2D PC MRA for improving the temporal resolution and also measured the velocity to evaluate the accuracy of phase information. We used 0.32T MRI scanner(Magfinder II, Scimedix, Korea). Using the 2D PC MRA pulse sequence, the vascular images for a human brain targeted on the Superior Sagittal Sinus(SSS) were obtained. We applied tukey window function for keyhole images to minimize the ringing artifact and erroneous factors that are induced frequency discontinuous and phase information loss. We also applied zero-padded algorithm to peripheral missing k-space lines to compare keyhole imaging results and the artifact power(AP) value was measured on the complex difference images to validate the image quality. Consider as based on our results, heavy image distortions and artifacts were shown until using at least 50% keyhole factor. Using above the 50% keyhole factors are shown well reconstructed and matched for magnitude images and velocity information measurements. In conclusion, we confirmed the image quality and velocity information of keyhole technique combined 2D PC MRA. Especially, measured velocity information through the keyhole imaging combination was similar to the velocity information of full sampled k-space image despite of frequency discontinuous and phase information loss in the keyhole imaging reconstruction process. Consequently, the keyhole imaging combined 2D PC MRA will give some clinical usefulness and advantages as improving the temporal resolution and measuring the velocity information via selecting the appropriate keyhole factor at low tesla MRI system.
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선형적 위상배열 코일구조의 시뮬레이션을 통한 민감도지도의 공간 해상도 및 필터링 변화에 따른 MR-SENSE 영상재구성 평가
이동훈,홍철표,한봉수,김형진,서재준,김소현,이춘형,이만우,Lee, D.H.,Hong, C.P.,Han, B.S.,Kim, H.J.,Suh, J.J.,Kim, S.H.,Lee, C.H.,Lee, M.W. 대한의용생체공학회 2011 의공학회지 Vol.32 No.3
Parallel imaging technique can provide several advantages for a multitude of MRI applications. Especially, in SENSE technique, sensitivity maps were always required in order to determine the reconstruction matrix, therefore, a number of difference approaches using sensitivity information from coils have been demonstrated to improve of image quality. Moreover, many filtering methods were proposed such as adaptive matched filter and nonlinear diffusion technique to optimize the suppression of background noise and to improve of image quality. In this study, we performed SENSE reconstruction using computer simulations to confirm the most suitable method for the feasibility of filtering effect and according to changing order of polynomial fit that were applied on variation of spatial resolution of sensitivity map. The image was obtained at 0.32T(Magfinder II, Genpia, Korea) MRI system using spin-echo pulse sequence(TR/TE = 500/20 ms, FOV = 300 mm, matrix = $128{\times}128$, thickness = 8 mm). For the simulation, obtained image was multiplied with four linear-array coil sensitivities which were formed of 2D-gaussian distribution and the image was complex white gaussian noise was added. Image processing was separated to apply two methods which were polynomial fitting and filtering according to spatial resolution of sensitivity map and each coil image was subsampled corresponding to reduction factor(r-factor) of 2 and 4. The results were compared to mean value of geomety factor(g-factor) and artifact power(AP) according to r-factor 2 and 4. Our results were represented while changing of spatial resolution of sensitivity map and r-factor, polynomial fit methods were represented the better results compared with general filtering methods. Although our result had limitation of computer simulation study instead of applying to experiment and coil geometric array such as linear, our method may be useful for determination of optimal sensitivity map in a linear coil array.
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이동훈,정호열,김민호,임명은,김대희,한영웅,김영원,최재훈,김승환,Lee, D.H.,Jung, H.Y.,Kim, M.H.,Lim, M.E.,Kim, D.H.,Han, Y.W.,Lee, Y.W.,Choi, J.H.,Kim, S.H. 한국전자통신연구원 2016 전자통신동향분석 Vol.31 No.4
구글 딥마인드 알파고와 이세돌 선수와의 바둑대결 후 인공지능의 활용처로 의료분야가 거론되면서 임상의사결정지원시스템(Clinical Decision Support System: CDSS)이 최근 주목받고 있다. 기본적으로 CDSS는 환자 진료에 있어 예방, 진단, 치료, 처방 그리고 예후의 각 단계에서 임상의의 의사결정을 도와주는 시스템을 말한다. 본고에서는 CDSS의 국내외 도입 및 시장현황과 관련 기술현황을 검토하여 의료현장에서 CDSS의 활용이 활성화되기 위한 방안을 도출하고자 한다.
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역-솔레노이드 코일을 이용한 내부 영상용 핵자기공명 영상 탐침의 제작
이동훈,고락길,Lee, D.H.,Ko, R.K. 배재대학교 자연과학연구소 1995 自然科學論文集 Vol.8 No.1
Magnetic Resonance Imaging anti-solenoid probes have been constructed for the internal imaging. Signal-to-noise ratios of the images acquired by the anti-solenoid probes were compared with those obtained by commercial probes such as a head coil and a body coil. In terms of the internal imaging, the anti-solenoid probes, constructed in the present study, was performed better than the conventional commercial probes. Also, RF(radio-frequency)-field maps produced by the anti-solenoid probes have been simulated using computers. The possibility of human internal imaging using the anti-solenoid probes has been discussed as well.
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이동훈(D. H. Lee),유재환(J. H. Yu),김덕환(D. H. Kim) 한국재활복지공학회 2011 한국재활복지공학회 학술대회논문집 Vol.2011 No.11
This paper proposes a method for extraction of the gaze point on screen using EOG(Electrooculography) signal. Based on linear property of horizontal and vertical EOG signal, the proposed method corrects two dimensional distance error between coordinate of using EOG signal and coordinate on screen by using scaling, rotation and transformation. Experimental results show that the average distance errors at the gaze points are 3%(57pixels) at x-axis, 9%(90pixels) at y-axis on the monitor with 1680*1050 resolution. This method can be used to human computer interface of pointing device for general paralysis patients or VR games.
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