• Investigative Magnetic Resonance Imaging
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• 제26권2호
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• pp.83-95
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• 2022

The purpose of this study was to establish and provide guidelines for the standardized acquisition and interpretation of diffusion-weighted magnetic resonance imaging (DW-MRI) to improve the image quality and reduce the variability of the results interpretation. The standardized protocol includes the use of high-resolution DW-MRI with advanced techniques and post-processing. The aim of the protocol is to increase the effectiveness of the medical image information exchange involved in the construction, activation, and exchange of clinical information for healthcare use. An organized interpretation form could make DW-MRIs' interpretation easier and more familiar. Herein, the authors briefly review the basic principles, optimized image acquisition, standardized interpretation guidelines, false negative and false positive cases of DW-MRI, and provide a standard interpretation form and examples of various cases to help users become more familiar with the DW-MRI.

• 한국의학물리학회지:의학물리
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• 제17권2호
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• pp.83-88
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• 2006

목적: 초고자장 MRI/MRS 장비를 이용하여 인체 피부조직의 고해상도 자기공명영상과 자기공명 스펙트럼을 얻고자 하였다. 또한 수분억제가 제외된 자기공명 스펙트럼을 이용하여 스킨로션(피부보습제)의 피부 보습효과가 측정가능한지 알아 보고자 하였다. 대상 및 방법: Bruker 14.1 T MRI/MRS 장비를 사용하였다. 자기공명영상을 얻기 위하여 Spin Echo 및 Fast Spin Echo 펄스시퀀스를 사용하였고 자기공명 스팩트럼을 얻기 위하여 PRESS 펄스시퀀스를 사용하였다. 결과: 초고자장 MRI/MRS 장비를 사용하여 인체 피부에 대한 고해상도의 자기공명영상과 자기공명 스펙트럼을 획득하였다. 수분 신호가 포함된 스펙트럼 분석을 통하여 스킨로션을 바르기 전에 비하여 스킨로션을 바른 후에 인체 피부조직의 수분 함유량이 상당히 증가함이 나타났다. 결론: 본 연구는 14.1 T 고자장 MRI/WRS 장비에서 얻은 피부 조직에 대한 고해상도 자기공명영상과 자기공명 스펙트럼이 보습효과를 측정하는 데 사용될 수 있음을 시사해 주고 있다.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2007년도 공동학술대회 논문집
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• pp.1-6
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• 2007

Two impedance imaging systems of multi-frequency electrical impedance tomography (MFEIT) and magnetic resonance electrical impedance tomography (MREIT) are described. MFEIT utilizes boundary measurements of current-voltage data at multiple frequencies to reconstruct cross-sectional images of a complex conductivity distribution (${\sigma}+i{\omega}{\varepsilon}$) inside the human body. The inverse problem in MFEIT is ill-posed due to the nonlinearity and low sensitivity between the boundary measurement and the complex conductivity. In MFEIT, we therefore focus on time- and frequency-difference imaging with a low spatial resolution and high temporal resolution. Multi-frequency time- and frequency-difference images in the frequency range of 10 Hz to 500 kHz are presented. In MREIT, we use an MRI scanner to measure an internal distribution of induced magnetic flux density subject to an injection current. This internal information enables us to reconstruct cross-sectional images of an internal conductivity distribution with a high spatial resolution. Conductivity image of a postmortem canine brain is presented and it shows a clear contrast between gray and white matters. Clinical applications for imaging the brain, breast, thorax, abdomen, and others are briefly discussed.

• 대한의용생체공학회:의공학회지
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• 제28권1호
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• pp.102-107
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• 2007

In molecular imaging studies via magnetic resonance imaging, in vivo cell tracking is an important issue for the observation of cell therapy or disease behavior. High resolution imaging and longitudinal study are necessary to track the cell movement. Since the field inhomogeneity extends over several voxels, we have performed the numerical analysis using the sub-voxel method dividing a voxel of MR image into several elements and the information about the field inhomogeneity distribution around the micro-beads. We imbedded ferrite-composite micro-beads with the size of $20-150{\mu}m$ in the subject substituted for cells to induce local field distortion. In the phantom imaging with the isotropic voxel size of $200{\mu}m^3$, we could confirm the feasibility of sub-voxel tracking in a 3.0 T MRI.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부 B
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• pp.597-599
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• 1998

The clinical acceptance of magnetic resonance imaging(MRI) system has been more rapid than that of the other medical image diagnosis system(X-ray, CT, etc) with the advantage of nonhazardous nature, high resolution capability, potential for chemically specified imaging. MRI system is composed of super conducting magnet, gradient fields, rf transceiver, system controller and imaging software technology. In this paper, introducing the principle of magnetic resonance imaging, it proposes the implementation of PC-based MRI system.

• 대한의용생체공학회:의공학회지
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• 제17권4호
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• pp.525-534
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• 1996

We have developed a fast steady state free precession interferometry (SSFPI) technique which is useful for the fMRl (functional Magnetic Resonance Imaging). As is known, SSFP sequence with a suitable adjustment of Vadient (readeut) allows us to measure precession angle 6 which in tw relates to the field inhomogeneity. Combining the two pulses (known as FID and Echo) in FADE (Fast Acquisition Double Echo) sequence, for example, one can obtain the interference term which is directly related to the precession angle It has been known that a fast high resolution magnetic field mapping is possible by use of the modified FADE sequence or SSFPI, and we have attempted to use the SSFPI technique for the susceptibility-induced fMRl. When the method is applied to the susceptibility effect based functional magnetic resonance imaging (fMRl), it was found that the direct susceptibility effect measurement was possible without perturbations such as the backgrounds and inflow effect. In this paper, simulation results and experimental results obtained with 2.0 Tesla MRI system are presented.

• 대한디지털의료영상학회논문지
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• 제17권1호
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• pp.43-48
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• 2015

Intracrnial 3D TOF MR angiography was performed in 30 normal volunteers with both 1.5 and 3.0 T MRI system with high resolutions. Used Voxel sizes were $0.39{\times}0.39{\times}0.2$(1.5 T) and $0.19{\times}0.19{\times}0.35$(3.0 T), respectively. High image quality and depiction of small vessel branches were equality demonstrated with 1.5 T and 3.0 T HR TOF MRA(p<0.05). Intracranial high resolution TOF MRA with 1.5 T and 3.0 T provides high diagnostic information with having merits and demerits in depiction of vascular branches.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.1-1
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• 2011

We developed a new generalized synthetic procedure, called as "heat-up process," to produce uniform-sized nanocrystals of many transition metals and oxides without a size selection process. We were able to synthesize uniform magnetite nanocrystals as much as 1 kilogram-scale from the thermolysis of Fe-oleate complex. Clever combination of different nanoscale materials will lead to the development of multifunctional nano-biomedical platforms for simultaneous targeted delivery, fast diagnosis, and efficient therapy. In this presentation, I would like to present some of our group's recent results on the designed fabrication of multifunctional nanostructured materials based on uniform-sized magnetite nanoparticles and their medical applications. Uniform ultrasmall iron oxide nanoparticles of <3 nm were synthesized by thermal decomposition of iron-oleate complex in the presence of oleyl alcohol. These ultrasmall iron oxide nanoparticles exhibited good T1 contrast effect. In in vivo T1 weighted blood pool magnetic resonance imaging (MRI), iron oxide nanoparticles showed longer circulation time than commercial gadolinium complex, enabling high resolution imaging. We used 80 nm-sized ferrimagnetic iron oxide nanocrystals for T2 MRI contrast agent for tracking transplanted pancreatic islet cells and single-cell MR imaging. We reported on the fabrication of monodisperse magnetite nanoparticles immobilized with uniform pore-sized mesoporous silica spheres for simultaneous MRI, fluorescence imaging, and drug delivery. We synthesized hollow magnetite nanocapsules and used them for both the MRI contrast agent and magnetic guided drug delivery vehicle.

• 응용통계연구
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• 제29권6호
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• pp.1129-1145
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• 2016

뇌기능 연결성 문제는 뇌의 신경역학적 현상과 밀접한 관련이 있다는 의미에서 뇌과학에서 주요 연구주제이다. 본 논문에서는 기능적 자기공명영상(fMRI)자료를 뇌활동에 대한 반응 자료의 주요 형태로써 선택하였는데, 이 fMRI자료는 높은 해상도 때문에 뇌과학 연구에서 선호되는 자료 형태이다. 뇌활동에 대한 생리학적 반응을 측정해서 자료로 사용한다는 전제하에서 뇌의 기능적 연결성을 분석하는 방법들을 고찰하였다. 여기서의 전제란 상태공간 및 측정 모형을 다룬다는것을 의미하는데, 여기서 상태공간 모형은 뇌신경역학을 표현한다고 가정한다. 뇌기능 영상자료의 분석은 무엇을 측정하였느냐에 따라서 분석방법과 그 해석이 조금씩 달라진다. 실제 fMRI자료를 고차원 자기회귀모형을 적용해서 분석한 결과를 논문에 포함하였는데, 이 결과를 통해서 서로 다른 도형문제를 푸는데 서로 다른 뇌신경 역학관계가 요구된다는 것을 엿볼 수 있었다.

• Investigative Magnetic Resonance Imaging
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• 제23권1호
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• pp.38-45
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• 2019

Purpose: To demonstrate the high-resolution numerical simulation of the respiration-induced dynamic $B_0$ shift in the head using generalized susceptibility voxel convolution (gSVC). Materials and Methods: Previous dynamic $B_0$ simulation research has been limited to low-resolution numerical models due to the large computational demands of conventional Fourier-based $B_0$ calculation methods. Here, we show that a recently-proposed gSVC method can simulate dynamic $B_0$ maps from a realistic breathing human body model with high spatiotemporal resolution in a time-efficient manner. For a human body model, we used the Extended Cardiac And Torso (XCAT) phantom originally developed for computed tomography. The spatial resolution (voxel size) was kept isotropic and varied from 1 to 10 mm. We calculated $B_0$ maps in the brain of the model at 10 equally spaced points in a respiration cycle and analyzed the spatial gradients of each of them. The results were compared with experimental measurements in the literature. Results: The simulation predicted a maximum temporal variation of the $B_0$ shift in the brain of about 7 Hz at 7T. The magnitudes of the respiration-induced $B_0$ gradient in the x (right/left), y (anterior/posterior), and z (head/feet) directions determined by volumetric linear fitting, were < 0.01 Hz/cm, 0.18 Hz/cm, and 0.26 Hz/cm, respectively. These compared favorably with previous reports. We found that simulation voxel sizes greater than 5 mm can produce unreliable results. Conclusion: We have presented an efficient simulation framework for respiration-induced $B_0$ variation in the head. The method can be used to predict $B_0$ shifts with high spatiotemporal resolution under different breathing conditions and aid in the design of dynamic $B_0$ compensation strategies.