• 한국CDE학회논문집
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• 제17권6호
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• pp.436-442
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• 2012

Traumatic loading during car accidents or sports activities can lead to cervical spinal cord injury. Experiments in spinal cord injury research are mainly carried out on rabbit or rat. Finite element models that include the rat cervical spinal cord and adjacent soft tissues should be developed for efficient studies of mechanisms of spinal cord injury. Images of a rat were obtained from high resolution MRI scanner. Polygonal surfaces were extracted structure by structure from the MRI data using the ITK-SNAP volume segmentation software. These surfaces were converted to Non-uniform Rational B-spline surfaces by the INUS Rapidform rapid prototyping software. Rapidform was also used to generate a thin shell surface model for the dura mater which sheathes the spinal cord. Altair's Hypermesh pre-processor was used to generate finite element meshes for each structure. These processes in this study can be utilized in modeling of other biomedical tissues and can be one of examples for reverse engineering on biomechanics.

• Investigative Magnetic Resonance Imaging
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• 제23권3호
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• pp.179-201
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• 2019

Portable low-cost magnetic resonance imaging (MRI) systems have the potential to enable "point-of-care" and timely MRI diagnosis, and to make this imaging modality available to routine scans and to people in underdeveloped countries and areas. With simplicity, no maintenance, no power consumption, and low cost, permanent magnets/magnet arrays/magnet assemblies are attractive to be used as a source of static magnetic field to realize the portability and to lower the cost for an MRI scanner. However, when taking the canonical Fourier imaging approach and using linear gradient fields, homogeneous fields are required in a scanner, resulting in the facts that either a bulky magnet/magnet array is needed, or the imaging volume is too small to image an organ if the magnet/magnet array is scaled down to a portable size. Recently, with the progress on image reconstruction based on non-linear gradient field, static field patterns without spatial linearity can be used as spatial encoding magnetic fields (SEMs) to encode MRI signals for imaging. As a result, the requirements for the homogeneity of the static field can be relaxed, which allows permanent magnets/magnet arrays with reduced sizes, reduced weight to image a bigger volume covering organs such as a head. It offers opportunities of constructing a truly portable low-cost MRI scanner. For this exciting potential application, permanent magnets/magnet arrays have attracted increased attention recently. A magnet/magnet array is strongly associated with the imaging volume of an MRI scanner, image reconstruction methods, and RF excitation and RF coils, etc. through field patterns and field homogeneity. This paper offers a review of permanent magnets and magnet arrays of different kinds, especially those that can be used for spatial encoding towards the development of a portable and low-cost MRI system. It is aimed to familiarize the readers with relevant knowledge, literature, and the latest updates of the development on permanent magnets and magnet arrays for MRI. Perspectives on and challenges of using a permanent magnet/magnet array to supply a patterned static magnetic field, which does not have spatial linearity nor high field homogeneity, for image reconstruction in a portable setup are discussed.

• 디지털콘텐츠학회 논문지
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• 제11권3호
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• pp.283-290
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• 2010

1.5T에서 경직장 코일과 3.0T의 위상 배열 코일을 이용하여 신호대 잡음비를 비교하여 3.0T의 위상 배열 코일의 유용성을 제시한다. 전립선암으로 진단받은 환자 40명을 대상으로 1.5T MR scanner에서는 경직장 표면 코일과 3.0T MR scanner에서는 위상 배열 코일을 이용하여 T2 강조 영상, T1 강조영상, 확산 강조 영상을 각각 획득 후 전립선의 Central Zone(CZ)과 Peripheral Zone(PZ)에서 Right Peripheral Zone(PZ)과 Left Peripheral Zone(PZ) 세 부위에서 신호 강도(signal intensity)측정을 하였다. 정량적 분석방법으로 관심영역의 신호대 잡음비(signal to noise ratio)를 구하고 평균화 하여 1.5T MR scanner로 획득한 그룹과 3.0T MR scanner로 획득한 그룹에서의 신호대 잡음비를 비교하였다. 3.0T MR scanner에서 위상 배열 코일을 사용한 경우 1.5T MR scanner에서 경직장 코일을 사용한 경우보다 신호대 잡음비가 증가됨을 알 수 있었다.

• Investigative Magnetic Resonance Imaging
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• 제20권3호
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• pp.141-151
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• 2016

Purpose: Advances of magnetic resonance imaging (MRI), especially that of the Ultra-High Field (UHF) MRI will be reviewed. Materials and Methods: Diffusion MRI data was obtained from a healthy adult young male of age 30 using a 7.0T research MRI scanner (Magnetom, Siemens) with 40 mT/m maximum gradient field. The specific imaging parameters used for the data acquisition were a single shot DW echo planar imaging. Results: Three areas of the imaging experiments are focused on for the study, namely the anatomy, angiography, and tractography. Conclusion: It is envisioned that, in near future, there will be more 7.0T MRIs for brain research and explosive clinical application research will also be developed, for example in the area of connectomics in neuroscience and clinical neurology and neurosurgery.

• 디지털콘텐츠학회 논문지
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• 제12권2호
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• pp.157-164
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• 2011

유방암중 관상피내암으로 진단 받은 환자를 대상으로 조영제 주입전, 후의 감산된 영상과 3차원 재구성된 영상을 정량적으로 비교 분석하여 재구성된 영상의 효과와 유용성을 고찰 해보고자 한다. 조직학적으로 관상피 내암으로 진단 받은 환자 20명을 대상으로 3.0T MR scanner를 이용하여 감산된 영상과 3차원 재구성한 영상을 획득하였다. 분석 결과 감산 영상과 재구성한 영상에서 신호대 잡음비는 병변, 유관조직, 지방조직에서 재구성한 영상에서 높은 신호대 잡음비를 보였으며 두 영상에서의 대조 도대 잡음비는 차이를 보이지 않았다.

• 한국방사선학회논문지
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• 제5권3호
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• pp.149-154
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• 2011

유방암중 관상피 내암으로 진단 받은 환자를 대상으로 확산강조 영상을 정량적으로 비교 분석하여 확산강조영상의 효과와 유용성을 고찰 해보고자 한다. 조직학적으로 관상피 내암으로 진단 받은 환자 20명을 대상으로 3.0T MR scanner를 이용하여 확산강조영상과 ADC map 영상을 획득하였다. 정량적 분석 결과 병변 부위와 정상부위의 신호대 잡음비와 대조도대 잡음비는 병변 조직에서 높은 신호대 잡음비와 대조도대 잡음비를 보였으며 병변 부위와 정상부위의 현성확산계수는 병변 조직에서 낮은 현성확산계수를 보였다.

• 대한의용생체공학회:의공학회지
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• 제9권1호
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• pp.125-130
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• 1988

In the conventional infrared imaging system, complex infrared lens systems are usually used for directing collimated narrow infrared beams into the high speed 2-dimensional optic scanner. In this paper, a simple reflective infrared optic system with a 2-dimensional optic scanner is proposed for the realization of medical infrared thermography system. It has been experimentally proven that the intfrared thermography system composed of the proposed optic system has the temperature resolution of $0.1^{\circ}C$ under the spatial resolution of lmrad, the image matrix size of $256 {\times} 240, $ and tile imaging time of 4 seconds.

• 한국의학물리학회지:의학물리
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• 제21권4호
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• pp.348-353
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• 2010

임상적용 전 단계에서 마우스와 같은 작은 설치류를 이용한 신경학적 실험의 필요성이 높아지면서 임상용 3T MRI를 이용한 마우스 뇌 영상의 요구가 높아지고 있다. 본 연구에서는 임상용 3T MRI를 이용한 마우스 뇌 영상의 가능성과 기술적인 적용과 최적화에 대해 알아보고자 하였다. 20~25g 체중 마우스 3마리에서 임상용 3T MRI를 이용하여 T1 강조영상(T1WI), T2 강조영상(T2WI), FLAIR (Fluid Attenuated Inversion Recovery) 영상, 가돌리늄 조영 T1 강조영상(Gd-T1WI), 확산 강조영상(DWI)을 시행하였다. 대상이 되었던 마우스 1마리는 뇌 경색을 유발시키지 않았으며 2마리는 우측 중대뇌동맥을 결찰하여 일측 뇌경색을 유발하고 1시간, 24시간, 72시간에 각각의 MRI 영상을 시행하였으며 각 영상에서 마우스 뇌의 striatum, 뇌실, 대뇌 피질의 해부학적 구별, 뇌 경색 부위의 진단 가능성 등을 분석하였다. T2WI에서 마우스 뇌의 striatum, 뇌실, 대뇌 피질의 해부학적 구별이 모두 가능하였고 T1WI, FLAIR, DWI 영상에서는 위의 해부학적 경계부위의 해상도는 감소하였다. 뇌경색 부위는 경색 후 1시간, 24시간, 72시간 영상 모두에서 발견되었고 T2WI, FLAIR에서는 24시간, 72시간에서만 구분되었다. 임상용 3T MRI를 이용한 마우스 뇌 영상에서 해부학적 부위의 구별이 가능하였고 특히 DWI를 이용하여 급성기 뇌 경색의 진단이 가능하였다. 앞으로 기술적인 적용과 최적화를 위한 노력이 계속 진행된다면 임상 실험에 큰 도움을 줄 수 있을 것이라 생각된다.

• 대한의용생체공학회:의공학회지
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• 제27권1호
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• pp.30-37
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• 2006

Injecting currents into an electrically conducting subject, we may measure the induced magnetic flux density distributions using an MRI scanner. The measured data are utilized to reconstruct cross-sectional images of internal conductivity and current density distributions in Magnetic Resonance Electrical Impedance Tomography (MREIT). Injection currents are usually provided in a form of mono-polar or bi-polar pulses synchronized with an MR pulse sequence. Given an MRI scanner performing the MR phase imaging to extract the induced magnetic flux density data, the current source becomes one of the key parts determining the signal-to-noise ratio (SNR) of the measured data. Since this SNR is crucial in determining the quality of reconstructed MREIT images, special care must be given in the design and implementation of the current source. This paper describes a current source design for MREIT with features including interleaved current injection, arbitrary current waveform, electrode switching to discharge any stored charge from previous current injections, optical isolation from an MR spectrometer and PC, precise current injection timing control synchronized with any MR pulse sequence, and versatile PC control program. The performance of the current source was verified using a 3T MRI scanner and saline phantoms.

• 한국소음진동공학회논문집
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• 제24권1호
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• pp.62-68
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• 2014

Recently, MRI(magnetic resonance imager) scanner is continually used for medical diagnosis and many biomedical researches. When it operates, however, intense noise is generated. The SPL(sound pressure level) of the noise approaches 130 dB especially in 3 T(Tesla) MRI. Meanwhile, more than 3 T MRI scanners have been developed to get higher-resolution images, so louder noise is expected in the future. The intense noise makes patients feel nervous and uncomfortable. Moreover, it could possibly cause hearing loss to patient in extreme cases. For this reason, some active noise control systems have been researched. One of them used feedback Filtered-X LMS(FXLMS) algorithm which is able to control only narrowband noises and possible to diverge in severe case. In this paper, we determine the property of MRI noise. Using the property, we applied a method of open-loop and adaptive control for reducing MRI noise at target point inside bore. We verified performance of the method with computer simulation and preliminary experiment. The results demonstrate that the method can effectively reduce MRI noise at target point.