• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.6
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• pp.516-521
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• 2009

X-ray system which is usefully used in diagnosis of the patient, being bombed of radioactivity is a big weak point when irradiates a X-ray to the human body so that ICRP restricted the radiation exposure tolerance of the human body. In order to reduce being bombed, the many research and development is now advanced. A lots of diagnostic X-ray machines have currently used due to the increase of occurrence efficiency of X-ray and precisely the output control by using the inverter which is a high speed switching semiconductors. For getting the confidence of the X-ray machine, the same radiation occurrence, same evaluation, and same irradiation condition are necessary when evaluates X-ray irradiation. It is the most important part for the accuracy of the test result and the patient safety. This research has produced the high voltage occurrence system of full-wave rectification method by using the LC resonance inverter, and evaluated the irradiation reproducibility in order to use it in diagnosis of the patient.

• Investigative Magnetic Resonance Imaging
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• v.21 no.4
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• pp.233-241
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• 2017

Purpose: To report on the current practices in breast magnetic resonance imaging (MRI) in Korea. Materials and Methods: We invited the 68 members of the Korean Society of Breast Imaging who were working in hospitals with available breast MRI to participate in a survey on how they performed and interpreted breast MRI. We asked one member from each hospital to respond to the survey. A total of 22 surveys from 22 hospitals were analyzed. Results: Out of 22 hospitals, 13 (59.1%) performed at least 300 breast MRI examinations per year, and 5 out of 22 (22.7%) performed > 1200 per year. Out of 31 machines, 14 (45.2%) machines were 1.5-T scanners and 17 (54.8%) were 3.0-T scanners. All hospitals did contrast-enhanced breast MRI. Full-time breast radiologists supervised the performance and interpreted breast MRI in 19 of 22 (86.4%) of hospitals. All hospitals used BI-RADS for MRI interpretation. For computer-aided detection (CAD), 13 (59.1%) hospitals sometimes or always use it and 9 (40.9%) hospitals did not use CAD. Two (9.1%) and twelve (54.5%) hospitals never and rarely interpreted breast MRI without correlating the mammography or ultrasound, respectively. The majority of respondents rarely (13/21, 61.9%) or never (5/21, 23.8%) interpreted breast MRI performed at an outside facility. Of the hospitals performing contrast-enhanced examinations, 15 of 22 (68.2%) did not perform MRI-guided interventional procedures. Conclusion: Breast MRI is extensively performed in Korea. The indication and practical patterns are diverse. The information from this survey would provide the basis for the development of Korean breast MRI practice guidelines.

• Clinics in Shoulder and Elbow
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• v.20 no.4
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• pp.183-188
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• 2017

Background: To evaluate the clinical outcomes and associated repair integrity in patients treated with arthroscopic repair for a transtendinous rotator cuff tear followed by resection of the remnant rotator cuff tendon. Methods: Between July 2007 and July 2011, we retrospectively reviewed patients who were treated for transtendinous full-thickness tears in the tendinous portion of the rotator cuff by arthroscopic repair. Clinical outcomes were evaluated using the American Shoulder and Elbow Surgeons (ASES) score, the Shoulder Rating Scale of the University of California at Los Angeles (UCLA), the Constant-Murley score, a visual analogue scale (VAS) pain score, and range of motion (ROM). The repair integrity was determined by magnetic resonance imaging or ultrasonography. Results: There were 19 shoulders with transtendinous full-thickness tears in the tendinous portion of the rotator cuff. The ASES, UCLA, Constant-Murley, and VAS pain scores showed significant improvements in function and symptoms (all p<0.001). The active ROM for forward flexion and abduction was also significantly improved (p=0.002 and p<0.001, respectively). The postoperative radiological examination showed cuff integrity without a re-tear in 68.4% of patients. However, the UCLA, ASES, and Constant-Murley scores were not significantly different between healed and re-torn group (p=0.530, p=0.885, and p=0.262, respectively). Conclusions: Although repair of transtendinous rotator cuff tears followed by resection of the remnant rotator cuff tendon in the footprint has a relatively high re-tear rate, no significant difference was observed in the short-term clinical results between the re-tear and healed groups.

• Progress in Medical Physics
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• v.30 no.4
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• pp.139-149
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• 2019

Purpose: With neurodegeneration, the signal intensity of the cerebrospinal fluid (CSF) in the brain increases. The objective of this study was to evaluate chemical exchange saturation transfer (CEST) signals with and without the contribution of CSF signals in elderly human brains using two different 3T magnetic resonance imaging (MRI) sequences Methods: Full CEST signals were acquired in ten subjects (Group I) with a three-dimensional (3D)-segmented gradient-echo echo-planar imaging (EPI) sequence and in ten other subjects (Group II) with a 3D gradient and spin-echo (GRASE) sequence using two different 3T MRI systems. The segmented tissue compartments of gray and white matter were used to mask the CSF signals in the full CEST images. Two sets of magnetization transfer ratio asymmetry (MTR_asym) maps were obtained for each offset frequency in each subject with and without masking the CSF signals (masked and unmasked conditions, respectively) and later compared using paired t-tests. Results: The region-of-interest (ROI)-based analyses showed that the MTR_asym values for both the 3D-segmented gradient-echo EPI and 3D GRASE sequences were altered under the masked condition compared with the unmasked condition at several ROIs and offset frequencies. Conclusions: Depending on the imaging sequence, the MTR_asym values can be overestimated for some areas of the elderly human brain when CSF signals are unmasked. Therefore, it is necessary to develop a method to minimize this overestimation in the case of elderly patients.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.35 no.7
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• pp.272-277
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• 1986

The system that follows to the resonance frequency of high frequency MOSFET inverter and varies according to the changes of load characteristics is proposed. Also we suggested a method how to select the resonant load type between series and parallel circuit for a given inverter type. It leads to the conclusion that in the case of high impedance loads, parallel resonant circuits are preferable, on the other hand, for low impedance loads, series resonant circuits are more preferable. For frequency tracking, a PLL circuit is used as main control element to detect the phase difference of current and voltage of load. The realized apparatus composed of control circuit and voltage type full-bridged MOSFET elements as main parts of inverter. A stable frequency follow-up characteristics are obtained for 1.2MHz, 1.5KW high frequency output and power is always supplied to the load with unity power factor.

• Korean Journal of Veterinary Research
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• v.59 no.4
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• pp.213-217
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• 2019

Five paraplegic dogs were diagnosed with thoracolumbar intervertebral disc disease with more than 50% compression of spinal cord. Because the lesions were determined to be disc extrusion on magnetic resonance imaging, a hemilaminectomy was initially performed, however, protruded discs were confirmed during surgery. To remove the protruded disc, modified partial lateral corpectomy (mini-PLC) was additionally performed. All dogs recovered to full ambulation within a median of 44 days without temporary deterioration or vertebral instability. Mini-PLC as described here enables successful removal of the protruded disc, while preserving vertebral stability in dogs for whom the use of hemilaminectomy is inevitable.

• Journal of electromagnetic engineering and science
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• v.16 no.4
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• pp.235-240
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• 2016

In this paper, a low-profile planar inverted-F antenna (PIFA) for ultrawideband (UWB) applications is proposed. The antenna consists of a PIFA and a ground plane with a slot. The addition of the slot not only improves the impedance matching of the PIFA but also forms an additional resonance. Therefore, the proposed antenna has a wideband characteristic covering the full UWB frequency range (3.1 GHz to 10.6 GHz) and a stable and nearly omnidirectional radiation pattern. The antenna also has a smaller volume and thickness compared to previous UWB PIFAs.

• Journal of electromagnetic engineering and science
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• v.18 no.3
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• pp.206-211
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• 2018

In this paper, we proposed a two-level feature vector fusion technique to improve the performance of target classification. The proposed method combines feature vectors of the early-time region and late-time region in the first-level fusion. In the second-level fusion, we combine the monostatic and bistatic features obtained in the first level. The radar cross section (RCS) of the 3D full-scale model is obtained using the electromagnetic analysis tool FEKO, and then, the feature vector of the target is extracted from it. The feature vector based on the waveform structure is used as the feature vector of the early-time region, while the resonance frequency extracted using the evolutionary programming-based CLEAN algorithm is used as the feature vector of the late-time region. The study results show that the two-level fusion method is better than the one-level fusion method.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.8
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• pp.1222-1229
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• 2017

In this paper, a wireless power transfer system with semi-random magnetic flux is studied. Directions of semi-random magnetic flux are changing almost randomly which can induce voltages at coils irrelevantly to coil's posture. So, very convenient charging is possible. Semi-random magnetic flux can be generated by a coil system which has three coils perpendicular to each other and carrying currents with different frequencies. A prototype for charging mobile devices is constructed and tested, and the proposal is verified.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.6
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• pp.96-108
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• 2015

his study deals with a power conversion unit of an anti-start air conditioner compressor system for the commercial vehicle. In case of converter, to reduce the switching losses and current stresses of the device, applies LLC resonant topology. Transformer leakage inductance in the full-bridge converter is used for making the resonance with the capacitor of the voltage-doubler. Through this method we can increase power and decrease volume of system. Both circuit analysis and design guideline are described. So in this paper, power conversion unit is designed. 2.5kW anti-start air conditioner compressor system was implemented, and system operation and stability was verified through experiment.