인체의 위 조직 시료에서 자기공명영상장치를 이용한 확산계수 측정에 대한 기초 연구

문치웅,최기승,양영일,장희경,은충기,Mun Chi-Woong,Choi, Ki-Sueng,Nana Roger,Hu, Xiaoping P.,Yang, Young-Il,Chang Hee-Kyung,Eun, Choong-Ki 대한의용생체공학회 2006 의공학회지 Vol.27 No.5

The aim of this study is to investigate the feasibility of ex vivo MR diffusion tensor imaging technique in order to observe the diffusion-contrast characteristics of human gastric tissues. On normal and pathologic gastric tissues, which have been fixed in a polycarbonate plastic tube filled with 10% formalin solution, laboratory made 3D diffusion tensor Turbo FLASH pulse sequence was used to obtain high resolution MR images with voxel size of $0.5{\times}0.5{\times}0.5mm^3\;using\;64{\times}32{\times}32mm^3$ field of view in conjunction with an acquisition matrix of $128{\times}64{\times}64$. Diffusion weighted- gradient pulses were employed with b values of 0 and $600s/mm^2$ in 6 orientations. The sequence was implemented on a clinical 3.0-T MRI scanner(Siemens, Erlangen, Germany) with a home-made quadrature-typed birdcage Tx/Rx rf coil for small specimen. Diffusion tensor values in each pixel were calculated using linear algebra and singular value decomposition(SVD) algorithm. Apparent diffusion coefficient(ADC) and fractional anisotropy(FA) map were also obtained from diffusion tensor data to compare pixel intensities between normal and abnormal gastric tissues. The processing software was developed by authors using Visual C++(Microsoft, WA, U.S.A.) and mathematical/statistical library of GNUwin32(Free Software Foundation). This study shows that 3D diffusion tensor Turbo FLASH sequence is useful to resolve fine micro-structures of gastric tissue and both ADC and FA values in normal gastric tissue are higher than those in abnormal tissue. Authors expect that this study also represents another possibility of gastric carcinoma detection by visualizing diffusion characteristics of proton spins in the gastric tissues.

Image formation and system of MR

문치웅,이정한,Mun, Chi-Ung,Lee, Jeong-Han 대한디지털의료영상학회 1998 대한디지털의료영상학회논문지 Vol.4 No.1

Tailored RF 경자사계방향 (TRFGE} 자기공명영상(MRI)에서 유체에 의한 영상신호 변화 : 유체유입효과와 영상면내를 흐르는 유체의 효과에 대하여

문치웅,김상태,노용만,임태환,조장희,Mun, Chi-Ung,Kim, Sang-Tae,No, Yong-Man,Im, Tae-Hwan,Jo, Jang-Hui 대한의용생체공학회 1997 의공학회지 Vol.18 No.3

본 연구에서는 유체보상 경사자장 기법(flow-compensation-gradient of gradient-moment nulling method)을 이용하지 않은 Tailored RF를 이용한 TRFGE(tailored rf gradient echo) 영상에는 유체유입효과(in-flow effect)가 나타나지 않지만 절편(slice)내에서 판독경사자장(reading gradient)과 같은 방향으로 흐르는 유체는 신호가 강조가 됨을 이론과 실험으로 보였다. 절편 내에서 판독경사자장과 같은 방향으로 흐르는 유체의 신호가 TRFGE 영상에서 강조되는 이유를 이론적으로 설명하였으며 이 이론을 뒷받침 할 실험을 위해 유체 모형을 제작하였다. 원통 모양의 물 모형 중앙으로 유체 관을 통해 식염수(saline)가 주자장(B$B_0$)와 평행인 z 축 방향으로 흐를 수 있도록 하였다. 유체가 흐를 때와 흐르지 않을 때 CGE(conventional gradient echo) 영상과 TRFGE 영사을 얻어 각각 비교하였다. 유체 유입효과를 관찰하기 위해서는 횡단면(axial)의 영상을 얻었고 절편 내에서 판독경사자장과 같은 방향으로 흐르는 유체의 영상신호를 관찰하기 위해서 시상면(sagittal) 영상을 얻었다. In this paper, we have reported two interesting flow effects arising in the TRFGE sequence using water flow phantom. First, we have shown that the TRFGE sequence is indeed not affected by "in-flow" effect from the unsaturated spins flowing into the imaging slice. Second, the enhancement of "in-plane flow" signal in the readout gradient direction was observed when the TRFGE sequence was used without flow compensation. These two results have many interesting applications in MR imaging other than fMRI. Results obtained were also compared with the results obtained by the conventional gradient echo(CGE) imaging. Experiments were performed at 4.7T MRI/S animal system (Biospec, BRUKER, Switzerland). A cylindrical phantom was made using acryl and a vinyl tube was inserted at the center(Fig. 1). The whole cylinder was filled with water doped with $MnCl_2$ and the center tube was filled with saline which flows in parallel to the main magnetic field along the tube. Tailored RF pulse was designed to have quadratic ($z^2$) phase distribution in slice direction(z). Imaging parameters were TR/TE = 55~85/10msec, flip angle = $30^{\circ}$, slice thickness = 2mm, matrix size = 256${\times}$256, and FOV= 10cm. In-flow effect : Axial images were obtained with and without flow using the CGE and TRFGE sequences, respectively. The flow direction was perpendicular to the image slice. In-plane flow : Sagittal images were obtained with and without flow using the TRGE sequence. The readout gradient was applied in parallel to the flow direction. We have observed that the "in-flow" effect did not affect the TRFGE image, while "in-plane flow" running along the readout gradient direction enhanced the signal in the TRFGE sequence when flow compensation gradient scheme was not used.

핵자기공명분광법에 사용되는 D2O 및 TSP의 세포 독성 평가

문치웅 ( Chi Woong Mun ),곽소영 ( So Young Kwak ),장무영 ( Moo Young Jang ) 한국조직공학·재생의학회 2012 조직공학과 재생의학 Vol.9 No.2s

Nuclear magnetic resonance (NMR) spectroscopy has been being used to identify cell metabolite and differentiation with reference material (TSP) and locking solvent (D2O). The aim of this study is to evaluate the cytotoxicity of TSP and D2O which have been widely used for NMR research. MG-63 and hMSC were selected and cultured in 3-dimensions on alginate bead for cytotoxicity test. The statistical analysis was performed after identifying the cell viability in accordance with various concentrations and exposure time of TSP and D2O. There was significant difference of cell viability between two concentrations (40% and 100%) of locking solvent (D2O). Our results indicate that the increased concentration of D2O effects the reduction of cell viability on two different cell types (MG-63: 4%, hMSC:14~40%). However, there was no significant difference by concentration of TSP. The statistical significance and cytotoxicity of concentration were found on D2O but not on TSP except for exposed hMSC for 24 hours from TSP. No statistical significance was found according to exposure time of D2O and TSP. We concluded that TSP still can be used for NMR but the use of D2O should be prohibited when identifying cell metabolite and differentiation. So, another locking solvent except D2O is needed.

확산계수의 이방성을 이용한 자기공명 신경망조영술

이수열,문치웅,임태환,Lee, Su-Yeol,Mun, Chi-Ung,Im, Tae-Hwan 대한의용생체공학회 1994 의공학회지 Vol.15 No.4

A magnetic resonance neurography technique for exclusive imaging of nerve networks is proposed. In the proposed technique, the anisotropy of diffusion coefficients of the molecules inside nerve cells was utilized to effectively suppress the magnetic resonance signal radiating from ones other than nerve tissues. Two images were obtained with diffusionweighting magnetic field gradients applied in the parallel and perpendicular directions with respect to the nerve orientation. One image was then subtract- ted from the other to form the neurogram. Experimentally obtained neurograms of the squld are presented.

뇌 대사물질 팬텀을 이용한 뇌의 자기공명 온도측정법에 관한 기초 연구

한용희,장무영,문치웅,Han, Yong-Hee,Jang, Moo-Young,Mun, Chi-Woong 대한의용생체공학회 2010 의공학회지 Vol.31 No.5

In this study, we measured the chemical shift change of metabolite peaks in the brain-metabolite phantom according to the temperature variation using nuclear magnetic resonance(NMR). The temperature range in NMR system was controled from 25 to 80 (5 step) by internal temperature controller. Temperature coefficients of each metabolite peaks were also calculated from the measured chemical shift depending on the temperature. The chemical shift changes depending on temperature were validated by linear regression method for each metabolite peaks. The temperature coefficients of $_{tot}Cr$, Cho, Cr, NAA, and Lac were 0.0086, 0.0088, 0.0091, 0.0089, and 0.0088ppm/$^{\circ}C$, respectively. This study shows that chemical shift change of brain metabolite and temperature variation have linear relationship each other. This also makes authors believe that brain temperature measurement is possible using MR spectroscopic imaging technique.

자기공명촬영상에서 구한 내부 전류밀도를 이용한 임피던스 단층촬영법

이수열,우응제,문치웅,Lee, Su-Yeol,U, Eung-Je,Mun, Chi-Ung 대한의용생체공학회 1994 의공학회지 Vol.15 No.4

In electrical impedance tomography (EIT), we use boundary current and voltage measurements to provide the information about the cross-sectional distribution of electrical impedance or resistivity One of the major problems in EIT has been the inaccessibility of internal voltage or current data in finding the internal impedance values. We propose a new image reconstruction method using internal current density data measured by NMR. We obtained a two-dimensional current density distribution within a phantom by processing the real and imaginary MR images from a 4.7T NMR machine. We implemented a resistivity image reconstruction algorithm using the finite element method and sensitivity matrix. We presented computer simulation results of the image reconstruction algorithm and furture direction of the research.

PC를 이용한 단위용적/다용적 자기공명분광 신호처리 분석시스템의 개발

백문영(M.Y. Paik),문치웅(C.W. Mun) 대한전자공학회 2001 대한전자공학회 학술대회 Vol.2001 No.11

유한요소법에 의한 자기공명영상시스템에서의 와전류 영향 분석

이정한,강현수,조민형,문치웅,이강석,이수열,Lee, Jeong-Han,Gang, Hyeon-Su,Jo, Min-Hyeong,Mun, Chi-Ung,Lee, Gang-Seok,Lee, Su-Yeol 대한의용생체공학회 1999 의공학회지 Vol.20 No.1

Eddy current in MRI systems degrades gradient field linearity and distorts gradient waveform. When the waveform distortion is spatially variant, it is very difficult to perform special imaging techniques such as the echo planar imaging technique or the fast spin echo imaging technique. In this study, we have developed a new technique to estimate the distorted gradient waveforms at any points inside the imaging region using the finite element method. After obtaining the eddy-current-effect transfer function, which represents magnitude and phase characteristics of the gradient field at a particular point, we have used the transfer function to estimate the actual gradient waveforms at the point. To verify the proposed technique, we have compared the estimated gradient waveforms with the measured ones. 자기공명영상시스템에서 경사자계코일에 전류 펄스를 인가할 때 코일 주변의 도전성 구조물에 유도되는 와전류는 경사자계의 선형성을 열화 시킬 뿐만 아니라 경사자계의 파형을 왜곡시킨다. 특히 경사자계 파형의 왜곡 정도가 공간 위치에 따라 다를 경우 고속촬영법과 같은 고성능의 자기공명영상법을 실현하는 것이 어려워 진다. 본 연구에서는 촬영 공간 내 임의의 지점에서 와전류에 의해 경사자계 파형이 변형되는 정도를 알 수 있는 방법을 유한요소법을 이용해 구하였다. 경사자계코일에 정현파를 인가했을 때 임의의 지점에서 자계의 진폭 및 위상 특성이 주파수에 따라 어떻게 변하는지를 나타내는 와전류 영향 전달함수를 구하였고, 이 전달함수를 이용해 임의의 입력 전류 파형에 대한 출력 경사자계 파형을 예측하였다. 제안한 방법의 타당성을 검증하기 위해 실제로 측정한 경사자계 파형을 예측한 파형과 비교하여 제시하였다.

고속유속 NMR 영상과 넓은 다이나믹 영역을 위한 위상차 기법

김윤수(Y. S. Kim),문치웅(C. W. Mun),정관진(K. J. Jung),조장희(Z. H. Cho) 대한전자공학회 1986 대한전자공학회 학술대회 Vol.1986 No.9