• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.3
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• pp.269-274
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• 2002

(Sm/Y)-Ba-Cu-O system high Tc composite superconductors with/without $CeO_2$ additive were directionally grown by zone-melting process, haying large temperature gradient, In air atmosphere. Cylindrical green rods of $({Sm/y})_{1.8}Ba_{2.4}Cu_{3.4}O_x$ [(Sm/Y)1.8] composite oxides by cold isostatic pressing(CIP) method using rubber mold were fabricated. The microstructure and superconducting properties were investigated by XRD, SEM, TEM and SQUID magnetometer. The size of nonsuperconducting $({Sm/y})_2BaCuO_5$ inclusions of the melt-textured (Sm/Y)1.8 sample with CeO$_2$ additive were remarkably reduced and uniformly distributed within the superconducting (Sm/Y)1.8 matrix. Both samples, with/without $CeO_2$ additive, showed an onset Tc $\geq$ 90 K and sharp superconducting transition. The critical current density Jc value of the $CeO_2$ addictive were $1{\times}10^5A/\textrm{cm}^2$ in 77 K, 0 Tesla.

• Journal of Biomedical Engineering Research
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• v.22 no.3
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• pp.303-309
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• 2001

It is well known that the electrical impedance of biological tissues is very sensitive to their temperature. In this paper, we have analyzed the effects of temperature change on the phase of magnetic resonance images obtained with external current injection. It has been found that the local phase in the current injected magnetic resonance image can be changed noticeably when local temperature change appears at a part of the tissue. At the experiments with a 0.3 Tesla MRI system, we observed the local phase changes at the phantom images when the phantom temperature was varied between 25 -45$^{\circ}C$. We think that the current injection MRI technique can be used for in-vivo monitoring of the temperature inside biiological tissues if the relation between the local temperature and phase can be quantified.

• Progress in Medical Physics
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• v.20 no.4
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• pp.208-215
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• 2009

This study is to compare the accuracy of evaluation regarding the volume of the prostate, which three-dimensional volume rendering was produced the shape of protrusion, by measuring two kinds of craniocaudal length from the top of the protrusion and from the exclusion of the protrusion as the starting points. For the imaginary protrusion prostate models, total of 10 models were roughly made by using devils-tongue jelly and changing each of the 10 ml of capacity from 10 ml to 100 ml. For the protrusion prostate models aimed at estimating the real volume, through 64 cannel computed tomography (CT) and 3.0 tesla magnetic resonance image (MRI) were conducted by planimetry technique from three-dimensional volume rendering. And then we performed to evaluate on significance of these volumes by wilcoxon signed rank test. Also the obtained volumes data by ellipsoid volume formula were measured the volume of protrusion prostate models two times with each method using the two kinds of craniocaudal length from top of the protrusion and from exclusion of the protrusion as the starting points. Finally, the significance of differences using wilcoxon signed rank test was evaluated between the real volume by planimetry technique and the measured volume by ellipsoid volume formula from three-dimensional volume rendering. The average of the protrusion length on the models was $0.90{\pm}0.18\;mm$ in CT and was $0.75{\pm}0.11\;mm$ in MRI. There were not statistically significant difference between MRI and CT from the volume of protrusion prostate models (p=0.414). In MRI (p=0.139) and CT (p=0.057), there were not statistically significant difference between the real volume by planimetry technique and the measured volume by ellipsoid volume from exclusion of the protrusion as the starting points. While, there were statistically significant difference between the real volume by planimetry technique and the measured volume by ellipsoid volume from top of the protrusion as the starting points in MRI (p=0.005) and CT (p=0.005). For the accurate measurement of the protrusion prostate models, the craniocaudal length of the prostate should be measured from the exclusion of the protrusion as the starting points.

• Food Science and Biotechnology
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• v.15 no.6
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• pp.833-837
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• 2006

To determine whether alcohol-treated rat liver cells can be protected by a static magnetic field (SMF), we analyzed the blood chemistry and histology of hepatic tissue removed from alcohol-exposed rats that had been exposed to a static magnetic field. The rats were exposed to a 0.3 tesla (3,000 gauss) magnetic field (MF) for 24 hr daily for 5 weeks with appropriate controls. Glutamic pyruvic transaminase activity and the triglyceride levels in animals exposed to the north (N) or south (S) pole of the MF decreased significantly (p<0.01 and p<0.05, respectively) compared with negative control animals with alcohol exposure. A histological examination of hepatic tissue revealed a moderate to severe accumulation of fat vacuoles of various sizes in the cytoplasm of the hepatocytes of animals in the negative control group throughout the study; whereas in groups exposed to the MF poles, fewer fat vacuoles were seen compared with the negative control group. Electron microscopic observations showed that exposure to the N or S pole protected organelles, including the nucleus, from damage during exposure to this toxic agent, as indicated by the fact that the nucleus and the mithochondria virtually retained their shape throughout this study. These results suggest that exposure to a SMF could be an excellent way of protecting against alcohol-induced damage to the rat liver cell.

• Investigative Magnetic Resonance Imaging
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• v.20 no.2
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• pp.88-94
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• 2016

Purpose: Fluid-attenuated inversion recovery (FLAIR) imaging can be obtained faster with shorter repletion time (TR), but it gets noisier. We hypothesized that shorter-TR FLAIR obtained at 3 tesla (3T) with a 32-channel coil may be comparable to conventional FLAIR. The aim of this study was to compare the diagnostic value between conventional FLAIR (TR = 9000 ms, FLAIR9000) and shorter-TR FLAIR (TR = 6000 ms, FLAIR6000) at 3T in terms of diffusion-weighted imaging-FLAIR mismatch. Materials and Methods: We recruited 184 patients with acute ischemic stroke (28 patients < 4.5 hours) who had undergone 5-mm diffusion-weighted imaging (DWI) and two successive 5-mm FLAIR images (no gap; in-plane resolution, $0.9{\times}0.9mm$) at 3T with a 32-channel coil. The acquisition times for FLAIR9000 and FLAIR6000 were 108 seconds (generalized autocalibrating partially parallel acquisitions [GRAPPA] = 2) and 60 seconds (GRAPPA = 3), respectively. Two radiologists independently assessed the paired imaging sets (DWI-FLAIR9000 and DWI-FLAIR6000) for the presence of matched hyperintense lesions on each FLAIR imaging. The signal intensity ratios (area of DWI lesion to contralateral normal-appearing region) on both FLAIR imaging sets were compared. Results: DWI-FLAIR9000 mismatch was present in 39 of 184 (21.2%) patients, which was perfectly the same on FLAIR6000. Three of 145 patients (2%) with DWI-matched lesions on FLAIR9000 had discrepancy on FLAIR6000, showing no significant difference (P > 0.05). Interobserver agreement was excellent for both DWI-FLAIR9000 and DWI-FLAIR6000 (k = 0.904 and 0.883, respectively). Between the two FLAIR imaging sets, there was no significant difference of signal intensity ratio (mean, standard deviation; $1.25{\pm}0.20$; $1.24{\pm}0.20$, respectively) (P > 0.05). Conclusion: For the determination of mismatch or match between DWI and FLAIR imaging, there is no significant difference between FLAIR9000 and FLAIR6000 at 3T with a 32-channel coil.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.11a
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• pp.32-32
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• 2012

화석연료의 남용으로 지구 온난화가 심화되어 환경과 생태계변화가 가속화되고 있고, 급속한 산업의 발달과 인류 삶의 질 향상에 따른 에너지 수요가 급증하고 있는 실정에 있으며, 일본 후쿠시마 원전사태로 원자력 에너지의 위험성으로 지구 인류환경은 심각한 국면을 맞이 하고 있어 대체 에너지의 하나로 핵융합 에너지 필요성이 증대되고 있다. 핵융합 에너지 연구 개발은 우리나라에서 KSTAR가 1997년부터 건설하기 시작하여 지난 2007년에 완공되어 지금 운용 중에 있고, 국제적으로 미국, EU, 러시아, 중국, 한국, 일본 인도가 참여하는 ITER 국제 공동프로젝트가 2004년에 건설을 시작하여 프랑스 카다라쉬에 실증 플란트를 건설 중에 있다. 이러한 핵융합 반응을 위해서는 10e-7이상의 높은 진공과 1억$^{\circ}C$ 이상에서 중수소와 삼중수소가 반응하여 발생하는 플라즈마를 제어 할 필요가 있으며, 초고온의 핵융합 플라즈마를 가두고 가동시키기 위해서는 약 12Tesla이상의 고자장 마그넷이 필요하다. 현재 ITER 실증 플란트에 사용되는 고자장 마그넷은 TF (Toroidal Field)코일과 CS (Central Field)코일에 Nb3Sn 초전도선재가 핵심부품으로 사용되고 있으며 ITER프로젝트에서는 약 850톤의 Nb3Sn 초전도선재가 사용될 전망이다. 그 중에서 일본 25%, EU, 러시아와 한국이 각각 20%, 중국7%, 미국8% 할당되어 참여국 대부분은 초전도선재를 전략적으로 공급하고 있다. 초전도 선재의 크롬도금은 1~2 마이크로미터 이하의 균일하고 얇은 도금 두께와 밀착성이 우수한 품질이 요구된다. 일반적으로 크롬도금은 산업현장에서 컨베이어 벨트 방식으로 장식이나, 내식성 및 내마모성의 특성을 필요로 할 때 사용되고 있으나, 선재에 크롬도금을 릴투릴(Reel to Reel) 방식으로 적용되는 경우는 세계적으로 아주 드물다. 핵융합 마그넷의 CICC(Conduct In Cable Conduit)도체를 만들기 위해서는 초전도선재를 이용, 3(Sc 2+OFC 1)$^*3^*5^*5^*6$형태로 연선과 케이블링을 하게 되며, 초전도 선재를 연선하고 케이블링을 할 때 크롬 도금층이 박리될 가능성이 있어 크롬도금 방법과 프로세스를 특별히 고안할 필요가 있다. ITER핵융합로 마그넷의 TF코일은 높이 14m, 폭 9m 최대자장 12Tesla, 최대전류 68kA, CICC도체 직경이 40mm로서 그 초전도 조관/도체 내부에 0.82mm 직경의 Nb3Sn 초전도 선재가 약 1350가닥으로 연선과 케이블링으로 구성되어 있다. ITER 핵융합 마그넷용 초전도 선재의 크롬도금은 마그넷 권선 후 Nb3Sn 초전도물질을 형성하기 위해서 $650^{\circ}C$에서 500시간 열처리를 실시하며 열처리 시 초전도 선재의 소선들 사이에 발생할 수 있는 소착을 방지하고, 초전도 선재에서 발생하는 AC loss를 감소시키며, Quench시 발생되는 열을 쉽게 확산시킴으로써, 초전도 마그넷의 열적 안정성(Thermal Stability) 향상과 필요에 따라서 소선간 통전울 가능하게 한다. 고려제강의 자회사인 케이에이티는 크롬도금 밀착성이 우수하고 도금두께 0.1마이크로 미터 이내 제어가 가능한 얇고 균일한 도금품질을 개발하여 한국형 핵융합 실험로인 KSTAR에 65톤 전량 공급하였고, 크롬 도금된 무산소동 선재 32톤과 초전도 선재 93톤을 전량 ITER 프로젝트에 공급하고 있으며, 2013년도 상반기에는 공급을 마무리할 예정이다.

• Investigative Magnetic Resonance Imaging
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• v.11 no.2
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• pp.87-94
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• 2007

Purpose: The purpose of this study was to evaluate the usefulness of fast inversion recovery (FIR) and magnetization-prepared three dimensional gradient echo sequence (3D GRE) T1-weighted sequences for neonatal brain imaging compared with spin echo (SE) sequence in a 3T MR unit. Materials and Methods: T1-weighted axial SE, FIR and 3D GRE sequences were evaluated from 3T brain MR imaging in 20 neonates. The signal-to-noise ratio (SNR) of different tissues was measured and contrast-to-noise ratios (CNR) were determined and compared in each of the sequences. Visual analysis was carried out by grading gray-white matter differentiation, myelination, and artifacts. The Wilcoxon signed ranked test was used for evaluation of the statistical significance of CNR differences between the sequences. Results: Among the three sequences, the 3D GRE had the best SNRs. CNRs obtained with FIR and 3D GRE were statistically superior to those obtained with SE; these CNRs were better on the 3D GRE compared to the FIR. Gray to white matter differentiation and myelination were better delineated on the FIR and 3D GRE than the SE. However, motion artifacts were more commonly observed on the 3D GRE and flow-related artifacts of vessels were frequently seen on the FIR. Conclusion: FIR and 3D GRE are valuable alternative T1-weighted sequences to conventional SE imaging of the neonatal brain at 3T providing superior image quality.

• Korean Journal of Digital Imaging in Medicine
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• v.16 no.1
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• pp.27-33
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• 2014

The purpose of this study evaluated the hemo-dynamic information within 30 seconds clinically in 3D breast MRI. From January to March 2014, A total of 40 people were examined at 1.5 Tesla(Philips, Medical System, Achieva, The Netherlands) MRI equipments using 16 channel SENSE breast coil. The imaging parameters on vibrant are fellow as: $TR/TE/FA^{\circ}$/Matrix size/Slice thickness/Slab($5ms/2ms/10^{\circ}/180{\times}139{\times}2mm/80$). This study used a Gadovist and injected it with injection speed of 4 ml /sec by auto injector with 15 ml saline flushing. Firstly, for the delay time study, it divided three different delay time from immediately, 20 seconds, and 30 seconds. In quantitative analysis, the ROI signal intensities of tumor and surrounding tissues were measured retrospectively. In qualitative analysis, the image quality was scored from 1 to 5 point by one experienced radiological technologists as a visual test. The significance level of each delay time was evaluated with a one-way ANOVA(p<0.05). In the visual test, score levels on 30 seconds delay time was a little bit higher than others(p<0.05). The signal intensity of the tumor were $1445{\pm}360$, $1410{\pm}320$, $1510{\pm}415$ on immediately, 20 seconds, and 30 seconds and score levels were $4.18{\pm}0.85$, $3.54{\pm}0.94$, $4.45{\pm}0.74$(p<0.05). The data on immediate images showed better results than that others(p<0.05). Conclusively, Although it has been high scored in 30sec delay time for visual test in order to avoid failure in 20second, 30seconds delay time after contrast media administration, we recommend that the DCE 3D breast MRI commence immediately.

• Proceedings of the KOSOMBE Conference
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• v.1995 no.11
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• pp.173-176
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• 1995

We have developed a fast steady state free precession interferometry (SSFPI) technique which is useful for the fMRI (functional Magnetic Resonance Imaging). As is known, SSFP sequence with a suitable adjustment of gradient (readout) allows us to measure precession angle $\theta$ which is in turn related to the field inhomogeneity [1-3]. When the method is applied to the susceptibility effect based functional magnetic resonance imaging (fMRI), 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 also presented.

• Journal of Korean Neurosurgical Society
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• v.58 no.2
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• pp.155-158
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• 2015

The equipment and techniques associated with magnetic resonance imaging (MRI) have rapidly evolved. The development of 3.0 Tesla MRI has enabled high-resolution imaging of the intracranial vessel wall. High-resolution MRI (HRMRI) can yield excellent visualization of both the arterial wall and lumen, thus facilitating the detection of the primary and secondary features of intracranial arterial dissection. In the present report, we describe the manner in which HRMRI affected our endovascular treatment planning strategy in 2 cases with unruptured intracranial vertebral artery dissection aneurysm. HRMRI provides further information about the vessel wall and the lumen of the unruptured intracranial vertebral artery dissecting aneurysm, which was treated by an endovascular approach in the 2 current cases.