• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.151-153
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• 1996

An optimal design approach is presented for high homogeneity superconducting magnet with superconducting active shield especially for use in magnetic resonance imaging system. This paper is investigated phenomena for the stray magnetic field to get a basic reduction techniques of the unwanted stray magnetic field from the magnet. The present method obtains optimal coil configuration considering constraints for magnetic field homogeneity and leakage field.

• Proceedings of the KIEE Conference
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• 2004.10a
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• pp.70-72
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• 2004

The ferromagnetic pole piece of permanent magnet assembly for magnetic resonance imaging(MRI) is optimally designed to get high homogenious magnetic field, taking into account the non-linearity of the magnetic materials. In the design, the pole face is kept smooth and axis-symmetric by using B-spline parameterization, and nonlinear design sensitivity analysis is used for search direction.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1996.06c
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• pp.314-324
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• 1996

A high speed NMR quality evaluation sensor was designed , constructed and tested . The device consists of an NMR spectrometer coupled to a conveyor system. The conveyor was run at speeds ranging from 0 to 250 mm/s. Spectral of avocado fruits and one-dimensional magnetic resonance images of pickled olives were acquired while the samples were moving on a conveyor belt mounted through a 20Tesla NMR magnet with a 20 mm diameter surface coil and a 150 mm diameter imaging coil respectively. Fro a magnetic resonance spectrum analysis, motion through variations in the magnetic field tends to narrow spectral line width just like using sample rotation in high resolution NMR to narrow spectral line width. Spectrum analysis was used to detect the dry weight of avocado fruits using the ratio oil and water resonance peaks. Good correlations maximum r=0.970@ 50 mm/s and minimum r=0.894@250mm/s ) between oil and water resonance peak ratio and dry weight of avocados were observed at speeds ra ging from0 to 250mm/s. For the application of magnetic resonance imaging (MRI) method, the projections were used to distinguish between pitted and non-pitted olives . Effect of fruit position in the coil was tested and coil degree effects were noticed when projects were generated under dynamic conditions. Various belt speeds (up to 250mm/s) were tested and detection results were compared to static measurements. Higher classification errors were occurred at dynamic conditions compared to errors while olives were at rest.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.517-527
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• 1997

Magnetic Resonance Spectroscopic Imaging is a methodology combining the imaging and spectroscopy. It can provide the spectrum of each areas of image so that one can easily compare the spectrum of one position to another position of the image. In this study, we developed pulse sequence or the spectroscopic imaging method, RF wave forms or the saturation of water signal, computer simulations to validate our method, and confirmed the methodology with phantom experiment. Then we applied the spectroscopic method to human subject and identified a few important metabolites in in vivo. To develope a water saturating RF waveform, we used Shinnar-Le-Roux algorithm and obtained maximum phase RF waveform. With this RF pulse, it could suppress the water signal to 1:1000. The magnet is shimmed to under 1.0ppm with auto-shimming technique. The saturation bandwidth is 80Hz(2ppm). The water and fat seperation is 3.3ppm(about 140Hz at 1 Tesla magnet), the bandwidth is enough to resolve the difference. But we are more concerned about the narrow window in between the two peaks, in which the small quantity of metabolites reside. We performed the computer simulation and phantom experiments in 8*8 matrix form and showed good agreement in the image and spectrum. Finally we applied spectroscopic imaging to the brain of human subject. Only the lipid signal was shown in the periphery region which agrees with the at distribution in human head surface area. The spectrum inside the brain shows the important metabolites such as NAA, Cr/PCr, Choline. We here have shown the spectroscopic imaging which is normally done above 1.5 Tesla machine can be performed in the 1 Tesla Magnetic Resonance Imaging Unit.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2001.02a
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• pp.80-83
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• 2001

We studied on effective quench protection method to prevent damage from unexpected quench of superconducting magnet for magnetic resonance imaging. And we suggested quench protection circuit that is combined with several protection techniques. This circuit has the capacity to maintain the symmetric nature of the magnetic field and the active shielding effect and to protect shim coils during a quench.

• Progress in Superconductivity and Cryogenics
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• v.25 no.4
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• pp.75-80
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• 2023

Rare earth barium copper oxide (REBCO) materials have shown the possibility of high-temperature superconductor (HTS) magnetic resonance imaging (MRI) magnets due to their elevated transition temperature. While numerous MRI magnet designs have emerged, there is a growing emphasis on estimating the cost before manufacturing. In this paper, we propose two designs of REBCO whole-body MRI magnets: (1) 1.5 T and (2) 3.0 T, the standard center field choices for hospital use, and compare their costs based on conductor usage. The basis topology of the design method is based on discretized solenoids to enhance field homogeneity. Magnetic stress calculation is done to further prove the mechanical feasibility of their construction. Multi-width winding technique and outer notch structure are used to improve critical current characteristic. We apply consistent constraints for current margins, sizes, and field homogeneities to ensure an equal cost comparison. A graph is plotted to show the cost increase with magnetic flux growth. Additionally, we compare our designs to two additional MRI magnet designs from other publications with respect to the cost and magnetic flux, and present the linear relationship between them.

• The Journal of Korean Physical Therapy
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• v.24 no.2
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• pp.66-72
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• 2012

Purpose: The purpose of this study is to explore the importance of the image distortion correction in the cross sectional area measurement for the iliopsas muscle, tensor fasciae latae muscle, gluteus maximus muscle and the knee extensor muscles, by using (magnetic resonance imaging) MRI. Methods: This study was performed using an open 0.32T MRI system. To estimate the image distortion, T1 images for an AAPM homogeneity/linearity phantom were acquired, and the region in which the maximum geometric distortion was less than or equal to the pixel size (1.6 mm) of the images, it was defined as the distortion correction-free region. The T2 images for a human subject's pelvis and thigh in normal positions were obtained. Then, after the regions of interest in the pelvis and thigh were moved into the distortion correction-free region, T2 images for the pelvis and thigh were scanned with the same imaging parameters used in the previous T2 imaging. The cross-sectional areas were measured in the two T2 images that were obtained in the normal position, and the distortion correction-free region, as well as the area error caused by geometric image distortion was calculated. Results: The geometrical distortion is gradually increased, from the magnet center to the outer region, in axial and coronal plane. The cross-sectional area error of gluteus maximus muscle and the knee extensors was as high as 9.27% and 3.16% in before and after distortion correction, respectively. Conclusion: The cross-sectional area of the muscles that suffered from the geometrical distortion is necessary to correct for the estimation of the intervention.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.41-43
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• 2001

We studied on effective quench protection method to prevent damage from unexpected quench of the inductively coupled superconducting magnet systems for magnetic resonance imaging. And we suggested quench protection circuit that is combined with several protection techniques. This circuit has the capacity to maintain the symmetric nature of the magnetic field and the active shielding effect and to protect shim coils during a quench.

• Progress in Superconductivity and Cryogenics
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• v.17 no.2
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• pp.31-35
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• 2015

Mapping is a useful tool in the magnetic field analysis and design. In some specific research area, such as the nuclear magnetic resonance (NMR) or the magnetic resonance imaging (MRI), it is important to map the magnetic field in the interesting space with high accuracy. In this paper, an indirect mapping method in the center volume of an air-core solenoid is presented, based on the solution of the Laplace's equation for the field. Through the mathematical analysis on the mapping calculation, we know that the condition number of the matrix, generated by the measurement points, can greatly affect the error of mapping result. Two different arrangement methods of the measurement points in field mapping are described in this paper: helical cylindrical line (HCL) method and parallel cylindrical line (PCL) method. According to the condition number, the HCL method is recommended to measure the field components using one probe. As a simple example, we mapped the magnetic fields in a MRI main magnet system. Comparing the results in the different methods, it is feasible and convenient to apply the condition number to reduce the error in the field mapping calculation. Finally, some guidelines were presented for the magnetic field mapping in the center volume of the air-core solenoid.

• Journal of radiological science and technology
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• v.15 no.2
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• pp.37-47
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• 1992

Magnetic Resonance Imaging(MRI) is one of the most expensive and sophisticated diagnostic tool and has been hailed as the most exciting event in medical imaging "since the introduction of X-rays", but a major disadvantage, high cost, is coming into focus especially in our country. To determine the status of distribution of MR imagers in Korea and to serve as a basic material for an efficient utilization of this Imaging machine, a retrospective survey of nationwide and regional(3 hospitals in Pusan) installations was performed. The results were as follows : 1. As of April 30, 1991, a total of 33 MRI units(24 for superconducting, 6 for permanent and 3 for resistive units) were set up and operated. 91% of the units were distributed in big cities with no one installation in 7 provinces among 12 provinces in our country. 85% of the units were imported. 2. Although 42.4% of the units were operated in Seoul, Taejeon had the best condition for the distribution of this imaging machine per population, hospital, and bed in Korea. 3. In Pusan : a) 5 units were operated with all superconducting magnet and medium magnetic field in type of machine. b) 80.1 % of the examinations were central nervous system(CNS). c) MRI examination occupied 1.4% of all radiographic examinations and the patients referred from other hospitals were composed of 23.4%% of all patients. 4. The average days under operating of MRI unit a week in Puasn were higher(5.5) than that of Seoul(4.5), but the average number of examinations and hours a week and a day, respectively(33, 8.4), was less than that of Seoul(57, 12.9). 5. The patients with positive MRI findings in a hospital(B) in Pusan was 74.5% on an average.