• Title, Summary, Keyword: Surface Coil

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Fabrication of a Staircase Coil with Improved SNR and Image Uniformity by Structural Changes of a Conventional Birdcage Coil at 1.5T MRI

  • Ryang, Kyung-Seung;Shin, Yong-Jin
    • Journal of the Korean Magnetic Resonance Society
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    • v.7 no.1
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    • pp.25-36
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    • 2003
  • The performance of radio frequency (RF) coils, used in MRI units, is determined by the image uniformity and the signal-to-noise ratio (SNR). Birdcage and surface coils are commonly used. A birdcage coil provides a good image uniformity while a surface coil produces a high SNR. In this study, therefore, a staircase coil was designed from a standard version of a birdcage coil, with some structural changes to increase SNR while maintaining image uniformity. In phantom experiments, the improvement of the image to uniformity and the SNR increase of the staircase coil compared with the values for the birdcage coil were about 3.5% and 35%, respectively. In clinical experiment, the SNR increase of the staircase coil, compared with the value for the birdcage coil was about 40% in bone, muscle and blood-vessel tissues. These results show that the performance of the staircase coil was very improved over the standard birdcage coil in terms of SNR, and that image uniformity was maintained. Therefore, the staircase coil designed by this study should be useful in experimental and clinical l.5T MRI systems, and this coil offers an alternative method of quadrature detection.

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Coil Spring Inspection for Reliability Assurance of Automobile Suspension System using Guided Wave

  • Nohyu kim;Park, Woon-Yong
    • International Journal of Reliability and Applications
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    • v.5 no.1
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    • pp.37-46
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    • 2004
  • Coil spring of automobile suspension system is very important to safety and dynamics of passenger car and requires a highly advanced quality control during manufacturing processes. Surface cracks on the coil spring rod produced by mechanical machining and heat treatment may cause a severe accident and large cost to the manufacturer. In order to detect surface cracks of the rod, guided wave technique is applied for a fast total volumetric inspection. Pochhammer equation is studied to investigate the dispersion characteristics of the guided wave in the spring rod and optimal wave modes sensitive to the surface crack are selected experimentally to design the experimental arrangement for the generation of guided wave. Rod samples with different size of artificial axial EDM notch on the surface ranging from 50${\mu}{\textrm}{m}$ to 1 mm are examined by guided wave and inspection results discussed.

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Analysis of Distances for MRI Scan to Maintain Pptimal Signal Intensity in a Surface Coil (MRI 검사 시 코일내 최적의 신호강도를 유지할 수 있는 거리의 기준 분석)

  • Son, Soon-Yong
    • The Journal of the Korea Contents Association
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    • v.18 no.10
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    • pp.158-164
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    • 2018
  • The purpose of this study is to statistically analyze the signal intensity pattern according distance from the surface coil center and to maintain optimal signal intensity under clinical circumstances where the surface coil centers are not correctly positioned due to various causes. The cylindrical fluid phantom was placed and moved from the coil center in vertical direction with 1 cm increments. The signal intensities were measured and compared. As a result, the signal intensity showed no significant difference within 4 cm and 1 cm from in T1 weighted images while in T2 weighted images the signal intensity was maintained up to 5 cm and lower 3 cm in the upper and lower direction from the coil center. In conclusion, to maintain the optimal signal intensity the target region should be located within the reference distances proposed in this study.

Endovaginal and Endorectal Surface Coils for in-ViVo Human MR Imaging and Spectroscopy (자궁경부암 진단용 MR 질내표면코일과 전립선암 진단용 MR 경직장표면코일의 제작 : 인체에서의 MR 영상과 MR 분광)

  • 문치웅;조경식
    • Journal of Biomedical Engineering Research
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    • v.16 no.4
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    • pp.481-491
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    • 1995
  • Endovaginal and endorectal receiver only surface coils were designed for MR imaging (MRI) and $^1H$ MR spectroscopy (MRS) for the uterine cervix and the prostate. The shape of endovaginal coil wire was rectangular with round corner. Size of the coil wire was empirically determined for 7cm and 4cm along the long and short axis, respectively. The coil wire loop was supported by acryl handle and bent about $150^{\circ}$ at one side of the loop considering the average angle of the cervix to the vagina. We called this as a "spoon-type endovaginal coil". The wire of the endorectal coil was made of the flexible materials so that the wire loop became long elliptic shape by pushing the acryl handle into the plastic tube for the comfort of patients when the coil was inserted into the cervix. Then, the shape was maintained to be circle by popping out handle. Conventional spin echo (SE) and fast spin echo (FSE) sequences were used as 71 and 72 weighted imaging sequences, respectively. Matrix size was 128~$256{\times}256$. FOVs for surface coil and body coil were 14cm and 24cm, respectively. 3D volume localized in vivo $^1H$ MR spectroscopy of the human cervix and prostate was performed using PRESS or STEAM localization method with the following parameters . TR=3 sec, TE=135 msec for PRESS or 30 msec for STEAM, NEX=2, NS=48, Sl=2048, and SW=2500 Hz. Using home-built endovaginal and endorectal coils, excellent T1- and T2-images were obtained to visualize early cervical and prostate tumors. 3D volume localized in vivo IH MRS was useful to differentiate the cancerous tissue from the normal tissue.

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Lamb Wave Inspection for Crack Detection in Coil Spring of Automobile Suspension System (자동차 현가 장치용 스프링의 신뢰성 평가를 위한 Lamb Wave 크랙검사)

  • 문병준;김노유
    • Proceedings of the Korean Reliability Society Conference
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    • pp.227-233
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    • 2002
  • Suspension system is one of the most important components indespensible for stability and reliability of automobiles. The demands to more safe and durable suspension system have been increased as the automobiles get popular and improve in quality. The crack in the coil spring of the suspension system produced during manufacturing may grow under a fatigue load and cause a severe safety problems which lead to a catastrophic damage to the passengers. Many conventional NDT techniques including ET, RT, and UT are less sensitive or hard to apply to detect the surface breaking crack in the suspension coils partly because the techniques are point-to-point measurement methods, thus take too long time to inspect the coil spring longer than 1m. Contrary to this, Lamb wave technique is full-field measurement method that make it possible to examine the whole coil spring in real time. In this paper, the Lamb wave is applied to the coil spring to investigate the possibility to detect the cracks on the surface of the coil spring.

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An Evaluation Technique of Surface Roughness of Corroded Reinforcing Bar-in-Coils (코일철근의 표면 거칠기 물리량 평가 기술)

  • Roh, Young-Sook;Cho, Kang Woo
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.10
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    • pp.6551-6557
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    • 2015
  • This paper discusses the surface roughness of corroded reinforcement rebar-in-coil focusing on the quantitative measurement technique using 3D scanner. Reinforcement rebar-in-coil was stacked in site for 0 day, 3 days, 7 days, 14 days and 21 days. And rebar-in-coil was corroded 0.04%, 0.3367%, 0.6157%, 0.7898%, and 1.1965% respectively. Using 3-dimensional scanner, each surface profile of reinforcement rebar-in-coil was established, and surface roughness was measured. Through the tests and analyses of corroded rebar-in-coil, the increase of fractal dimension for each rebar-in-coil was measured as 0.0216, 0.0235, 0.028, 0.0319, and 0.0455 for different stacked periods. Therefore, surface assessment technique using fractal dimension showed similar results with the actual corrosion rate.

The Micro Coil Production through Research on the Additive Conditions of Electrochemical Metal 3D Printer (전기화학적 금속 3D 프린터의 적층 조건 연구를 통한 마이크로 코일 제작)

  • Kim, Young-Kuk;Kang, Donghwa;Kim, Sung-Bin;Yoo, Bongyoung
    • Journal of the Korean institute of surface engineering
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    • v.53 no.4
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    • pp.138-143
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    • 2020
  • In this study, we produced a coil of micro-pattern that can be used for electromagnetic wave absorber, heating material, wireless charging, sensor, antenna, etc. by using electrochemical additive manufacturing method. Currently, it contains research contents for manufacturing a micro pattern coil having practicality through control of process control variables such as applied voltage, distance between electrode, and nozzle injection. Circulation of the electrolyte through the nozzle injection control can significantly contribute to improving the surface characteristics of the coil because of minimizing voltage fluctuations that may occur during the additive manufacturing process. In addition, by applying the pulse method in the application of voltage, the lamination characteristics of the plated body were improved, which showed that the formation of a fine line width plays an important role in the production of a micro pattern coil. By applying the pulse signal to the voltage application, the additive manufacturing characteristics of the produced product were improved, and it was shown that the formation of a fine line width plays an important role in the production of a micro pattern coil.

Low-Power Design of the Surface Gradient Coil for Magnetic Resonance Imaging (자기공명영상촬영을 위한 표면경사자계코일의 저전력 설계)

  • Oh, Chang-Hyun;Lee, Jong-Kwon;Yi, Yun;Kim, Min-Gi
    • Proceedings of the KOSOMBE Conference
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    • v.1993 no.11
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    • pp.33-35
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    • 1993
  • A new low-power, high-order optimization scheme to design surface gradient coils (SGC) is proposed for magnetic resonance imaging (MRI). Although previous SGCs have been designed and constructed just to get strong linear gradients, this paper proposes more systematic ways of SGC design by minimizing electrical power consumption in the gradient coil and by removing unnecessary high-order field distortions in the imaging region. By assuming continuous current flow on the coil surface which may be or may not be planar, power consumption in the coil is minimized. According to the simulation results, the SGC designed by using the proposed scheme seems to produce much more uniform linear gradient field using less electrical power compared to the previously proposed SGCs.

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Insulation Design and Testing of HTS coil for 6.6 kV Class HTSFCL (6.6kV급 고온초전도 한류기용 HTS 코일의 절연 설계 및 시험)

  • 백승명;정종만;곽동순;류엔반둥;김상현
    • Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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    • pp.263-268
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    • 2003
  • The Electrical insulation design and testing of high temperature superconducting (HTS) coil for high temperature superconducting fault current limiter (HTSFCL) has been performed. Electrical insulating factors of HTS coil for HTSFCL are turn-to-turn, layer-to-layer. The electrical insulation of turn-to-turn depends on surface length, and the electrical insulation of layer-to-layer depends on surface length and breakdown strength of L$N_2$. Therefore, two basic characteristics of breakdown and flashover voltage were experimentally investigated to design electrical insulation for 6.6㎸ Class HTSFCL. We used Weibull distribution to set electric field strength for insulation design. And mini-model HTS coil for HTSFCL was designed by using Weibull distribution and was manufactured to investigate breakdown characteristics. The mini-model HTS coil had passed in AC and Impulse withstand test.

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Metallic Crack Detections by Planar Inductive Coil Sensor Under AC and DC Magnetic Fields

  • Lee, Joon-Sik;Nam, Baek-Il;Kim, Ki-Hyeon
    • Journal of Magnetics
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    • v.17 no.3
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    • pp.210-213
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    • 2012
  • To detect the surface and the opposite side cracks on iron specimen under AC and DC magnetic fields, the planar inductive coil sensors were employed. When the induced signals were measured, the planar inductive coil sensor and the magnetic field source were lifted off about 2 mm from the top surface of the specimen. AC magnetic fields and DC magnetic fields were applied to the specimens by single straight Cu coil and NdFeB permanent magnet, respectively. The detected signals at crack positions were good coincidence with those of the simulation results.