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YBCO SQUID 자력계를 이용한 자기심장검사장치 개발
김인선,오수호,임현균,이용호,이순걸,박용기,Kim, I.S.,Oh, S.H.,Lim, H.K.,Lee, Y.H.,Lee, S.G.,Park, Y.K. 한국초전도학회 2007 Progress in superconductivity Vol.8 No.2
YBCO do superconducting quantum interference device (SQUID) magnetometers based on bicrystal junctions have been fabricated for magnetocardiograph (MCG) measurements. We could fabricate YBCO SQUID magnetometers having magnetic field noise of about $20fT/Hz^{1/2}$ at white noise region. We have developed an MCG system employing the high performance SQUID magnetometers. The lightweight MCG system, requiring liquid nitrogen as a coolant, consists of 6-channel SQUID sensors, an adjustable patient bed with sliding motion, and data analyses software. The MCG system could record quite clear MCG signals in a room with moderate magnetic shielding. In normal operation with multi-position MCG measurements, we could obtain clear 48-point mappings of magnetic field map and current source map with high enough signal qualities far clinical trials.
강찬석,이용호,권혁찬,김진목,유권규,박용기,이순걸,Kang, C.S.,Lee, Y.H.,Kwon, H.,Kim, J.M.,Yu, K.K.,Park, Y.K.,Lee, S.G. 한국초전도학회 2007 Progress in superconductivity Vol.8 No.2
We developed a SQUID magnetometer based on Double Relaxation Oscillation SQUID(DROS) for measuring magnetocardiography(MCG). Since DROS provides a 10 times larger flux-to-voltage transfer coefficient than the conventional DC-SQUID, simple flux-locked loop electronics could be used for SQUID operation. Especially, we adopted an external feedback to eliminate the magnetic coupling with adjacent channels. When the DROS magnetometer was operated inside a magnetically shielded room, average magnetic field noise was about 5 $fT/^{\surd}Hz$ at 100 Hz. Using the DROS magnetometer, we constructed a multichannel MCG system. The system consisted of 61 magnetometers are arranged in a hexagonal structure and measures a vertical magnetic-field component to the chest surface. The distance between adjacent channels is 26 mm and the magnetometers cover a circular area with a diameter of 208 mm. We recorded the MCG signals with this system and confirmed the magnetic field distribution and the myocardinal current distribution.
다양한 기저선을 갖는 1차 및 2차 미분계의 신호크기 및 신호 대 잡음비 조사
강찬석,유권규,이용호,권혁찬,김진목,박용기,이순걸,Kang, C.S.,Yu, K.K.,Lee, Y.H.,Kwon, H.,Kim, J.M.,Park, Y.K.,Lee, S.G. 한국초전도학회 2007 Progress in superconductivity Vol.9 No.1
We investigated signal-to-noise ratios (SNRs) of magnetocardiography (MCG) signals using the first-order and the second-order gradiometers of different baselines. The MCG signals were recorded using a measurement system with 61 magnetometers which measured the normal magnetic component to the chest surface. The distance between the chest surface and the bottom of the dewar was changed from 0 cm to 15 cm, and the MCGs were measured for each distance. By subtracting the other signals (distance = 1 to 15 cm) from the reference signal (distance =0 cm), we could simulate the first-order and the second-order gradiometer signals with various baselines. In addition, to evaluate the reproducibility of the simulation, we fabricated the wire wound first-order and second-order gradiometers which measured a normal magnetic component to the chest surface. The baselines of the first-order gradiometers were, respectively, 50 mm, 70 mm and 100 mm and the baseline of the second-order gradiometer was 50 mm. Using these gradiometers, we recorded the MCG signal and compared the SNR between the simulation and the measurement.
권혁찬,김기웅,이용호,김진목,임현균,박용기,정남식,고영국,정보영,김진배,조정래,Kwon, H.,Kim, K.,Lee, Y.H.,Kim, J.M.,Lim, H.K.,Park, Y.K.,Chung, N.,Ko, Y.G.,Joung, B.,Kim, J.B.,Cho, J.R. 한국초전도학회 2007 Progress in superconductivity Vol.9 No.1
Myocardial ischemia causes heterogeneity of ventricular repolarization and sometimes produces changes of the ST-T wave in ECG. Therefore, morphological changes of ST-T waveform in ECG have a clinical significance in diagnosing myocardial ischemia. In this study, we investigated the ST-T changes caused by myocardial ischemia in magnetocardiography (MCG). We analyzed MCG patterns of biphasic T, ST segment deviations from baseline, main current angle of $T_{peak}$ and $T_{peak}$ dispersion in 300 CAD patients without ST elevation in ECG, 122 symptomatic patients and 48 normal subjects. MCGs were recorded by multichannel SQUID system in a magnetically shielded room. As results, we found that appearances of the abnormality were strongly correlated with the severity of myocardial ischemia. Also we found that the percentage of the patients showing MCG changes were higher than those in ECG. These results show that morphological changes of ST-T waveform in MCG can be used as a marker of myocardial ischemia.
권혁찬,김기웅,김진목,이용호,김태은,임현균,박용기,고영국,정남식,Kwon, H.,Kim, K.,Kim, J.M.,Lee, Y.H.,Kim, T.E.,Lim, H.K.,Park, Y.K.,Ko, Y.G.,Chung, N. 한국초전도학회 2006 Progress in superconductivity Vol.8 No.1
In emergency rooms, patients with acute chest pain should be diagnosed as quickly as possible with higher diagnostic accuracy for an appropriate therapy to the patients with acute coronary syndrome or for avoiding unnecessary hospital admissions. At present, electrocardiography(ECG) and biochemical markers are generally used to detect myocardial infarction and coronary angiography is used as a gold standard to reveal the degree of narrowing of coronary artery. Magnetocardiography(MCG) has been proposed as a novel and non-invasive diagnostic tool fur the detection of cardiac electrical abnormality associated with myocardial ischemia. In this study, we examined whether the MCG can be used fur the detection of coronary artery disease(CAD) in patients, who were admitted to the emergency room with acute chest pain. MCG was recorded from 36 patients admitted to the emergency room with suspected acute coronary syndrome. The MCG recordings were obtained using a 64-channel SQUID MCG system in a magnetically shielded room. In result, presence of CAD could be found with a sensitivity of 88.2 % in patients with acute chest pain without 57 elevation in ECG, demonstrating a possible use in the emergency room to screen CAD patients.
권혁찬,김기웅,김진목,이용호,김태은,임현균,박용기,고영국,정남식,Kwon, H.,Kim, K.,Kim, J.M.,Lee, Y.H.,Kim, T.E.,Lim, H.K.,Park, Y.K.,Ko, Y.G.,Chung, N. 한국초전도학회 2006 Progress in superconductivity Vol.8 No.1
Magnetocardiography(MCG) has been proposed as a novel and non-invasive diagnostic tool for the detection of cardiac electrical abnormality associated with myocardial ischemia. In our previous study, we have proposed a new classification method of MCG parameters, based on the different populations of the parameters between coronary artery disease(CAD) patients, symptomatic patients and healthy volunteers. We used four parameters, representing the directional changes of the electrical activity in the period of an R-ST-T interval. In patients with chest pain and without ST-segment elevation, who were selected consecutively from all patients admitted to the hospital in 2004, the patients with CAD could be classified with a higher sensitivity than conventional methods, showing that the proposed method can be useful for the diagnosis of CAD with MCG. In this study, we examined the validity of the algorithm with the prior probability distribution in diagnosis of new patients admitted to the hospital in 2005. In the results, presence of CAD could be found with sensitivity and specificity of 81.3% and 71.4%, respectively, in patients with chest pain and non-diagnostic ECG findings.
김병극,박용기 韓國非破壞檢査學會 1989 한국비파괴검사학회지 Vol.9 No.1
Piezoelectric elements, backing and shoe material are the important components of the ultrasonic transducer. In this study, characteristic constants in the domestic and the foreign PZT ceramic elements are investigated. The acoustic properties of the domestic and the foreign backing and shoes are characterized. The effects of components characteristics, the kinds of the piezoelectric elements and the thickness of the wear plates are investigated for the manufactured normal beam ultrasonic transducers.
회전 드럼의 공기 흡입원리를 이용한 토분에 포함된 이물질 제거장치에 관한 연구
서용권,허성규,박용기 동아대학교 생산기술연구소 2006 生産技術硏究所硏究論文集 Vol.11 No.-
In this paper, we present flow patterns and performance of an air-flow separator by using the numerical analysis. With this separator, particles of different density are to be separated by using the drag force from the air flow. The low-density particles are designed to be separated by using inhalation through holes on a rotating drum. To obtain the flow informations needed for determining the proper design parameters, we have performed numerical simulations by using a commercial code, ANSYS CFX. Various parameter set was tested and it was found that depending on the design of drums there exist critical.