남녀 및 나이에 따른 심자도 변수 차이 분석

임현균,정남식,이용호,권혁찬,정보영,박용기,Lim, Hyun-Kyoon,Chung, Nam-Sik,Lee, Yong-Ho,Kwon, Hyuk-Chan,Joung, Bo-Young,Park, Yong-Ki 대한의용생체공학회 2007 의공학회지 Vol.28 No.4

Magnetocardiography (MCG) is a device to measure the magnetic field from the heart. It is a noninvasive device and takes only few minutes to record magnetocardiogram from a subject. In this study, we compared the difference of MCG data recorded from 56 normal subjects in early twenties (28 males and 28 females, mean $age=21.0{\pm}1.6$ years) and 36 elderly subjects (20 males and 16 females, mean $age=61.9{\pm}6.9$ years) for the analysis of the age and gender difference. A total of 24 parameters used in the analysis were derived from QRS complex, R-wave, T-wave, and ST-T period. As a result, seven parameters including maximum current angle and map angle showed the significant difference (p<0.01 and p<0.05, respectively) between young males and young females. Significant difference (p<0.05) between elderly males and elderly females was found from a parameter, pole distance at T-wave peak. In the comparison of age difference, seven parameters regarding current moment, pole distance, and dynamics showed the significant difference between young and elderly males. Eight parameters also showed significant difference (p<0.05) between two younger and elderly female groups. Results showed that parameters regarding current moment, pole distance, and dynamics might be changed when people get older. In conclusion, gender and age difference should be considered when MCG data are analyzed for certain parameters.

관상동맥질환을 진단하기 위한 R파와 T파의 크기에 대한 연구

임현균,유권규,김진목,김인선,강찬석,박용기,Lim, Hyun-Kyoon,Yu, Kwon-Kyu,Kim, Jin-Mok,Kim, In-Seon,Kang, Chan-Seok,Park, Yong-Ki 한국초전도학회 2008 Progress in superconductivity Vol.10 No.1

Multi-channel magnetocardiography (MCG) has been proposed to detect ischemic heart disease because its sensitivity is quite high comparing with other conventional diagnostic tools. Especially, current map and magnetic field map of MCG provide crucial information on whether myocardiac muscles maintain the normal conduction pathway. In addition, MCG parameters derived from repolarization are useful to detect coronary artery disease. Recently, there was a study reporting that R- and T- wave amplitude are highly correlated with ischemic heart disease. In this study, we studied R- and T-wave amplitude and their ratio as well as MCG parameters. MCG data from 20 young, 20 age-matched controls, and 20 myocardial infarction (MI) patients were analyzed. As a result, MCG parameters showed significant change in MI patients comparing to those of controls. R- and T-wave amplitude of MI patients showed a feature of severe ischemic heart disease even though it was difficult to find consistent values. Further study is needed to reveal the relations between small T-wave amplitude and coronary artery disease.

심자도의 P-Q 구간과 T-P 구간에서 설정한 베이스 라인의 효과에 대한 연구

임현균,권혁찬,김태은,이용호,김진목,김인선,김기웅,박용기,Lim, Hyun-Kyoon,Kwon, Hyuk-Chan,Kim, Tae-En,Lee, Yong-Ho,Kim, Jin-Mok,Kim, In-Seon,Kim, Ki-Woong,Park, Yong-Ki 한국초전도학회 2007 Progress in superconductivity Vol.9 No.1

The baseline selection is the first and important step to analyze magnetocardiography (MCG) parameters. There are no difficulties to select the baseline between P- and Q-wave peak (P-Q interval) of MCG wave recorded from healthy subjects because the P-Q intervals of the healthy subjects do not much vary. However, patients with ischemic heart disease often show an unstable P-Q interval which does not seem to be appropriate for the baseline. In this case, T-P interval is alternatively recommended for the baseline. However, there has been no study on the difference made by the baseline selection. In this study, we studied the effect of the different baseline selection. MCG data were analyzed from twenty healthy subjects and twenty one patients whose baselines were alternatively selected in the T-P interval for their inappropriate P-Q interval. Paired T-test was used to compare two set of data. Fifteen parameters derived from the R-wave peak, the T-wave peak, and the period, $T_{max/3}{\sim}T_{max}$ were compared for the different baseline selection. As a result, most parameters did not show significant differences (p>0.05) except few parameters. Therefore, there will be no significant differences if anyone of two intervals were selected for the MCG baseline. However, for the consistent analysis, P-Q interval is strongly recommended for the baseline correction.

심자도 센서의 위치 효과에 대한 연구

임현균,김기웅,권혁찬,이용호,Lim, Hyun-Kyoon,Kim, Ki-Woong,Kwon, Hyuk-Chan,Lee, Yong-Ho 한국초전도학회 2008 Progress in superconductivity Vol.10 No.1

Magnetocardiography (MCG) is a non-contact, non-invasive, and harmless diagnostic tool to detect the abnormal electrical conductivities of the heart caused by the various coronary artery disease or cardiac muscular disease. The purpose of this study is to identify whether MCG signals and MCG parameter values vary depending on the location of sensor assembly. It will be an important reference for the standard measurement. Four healthy male subjects (33.3$\pm$6.3 years) participated in this study. Basal recording was made at 20 mm apart from the chest surface. All subjects were requested to take a regular breathe while MCG was taken. The gap between the chest surface and the bottom of the sensor assembly was 20, 40, 60, and 80 mm. Recording was made using 64 channel MCG system (Axial type, first order gradiometer) developed by Korea Research Institute of Standards and Science (KRISS). After resting for two minutes in a supine position on the bed in magnetically shielded room, MCG were recorded for 30 s. As the sensor location is getting away from the chest surface signal, the amplitude of R and T wave peak decreases to 70% (at 40 mm gap), 50% (at 60 mm), and 37% (at 80 mm) of the reference strength measured (y = $1.3903e^{-0.0169x}$, $R^2$ = 0.99; where y=amplitude remained after reduction, x=distance between chest surface and sensor location). The regression equations may be used as a good reference to calculate how much strength will be decreased by the distance. In MCG parameters, most values of parameters were decreased as the gap was increased. As an example, the current moment at T-wave peak reduced to 52% (at 40 mm gap), 33% (at 60 mm), and 19% (at 80 mm). However, the difference caused by the gap could be reduced by considering the distance when the MCG parameters were calculated. The study results can be used as a useful reference to design the baseline and the sensor location.

시뮬레이터 개발 현황에 대한 연구

임현균 ( Hyun Kyoon Lim ),김진호 ( Jin Ho Kim ),박수찬 ( Soo Chan Park ),윤정선 ( Jung Sun Yoon ) 한국감성과학회 1999 추계학술대회 Vol.1999 No.-

본 연구에서는 웹 기반 감성데이터베이스구축 및 보급을 위한 연구의 일환으로 G72단계 연구결과 보고서에서 제시된 시뮬레이터 관련자료와 현재 인터넷에 등록된 시뮬레이터에 대한 자료들을 조사, 정리하고, Web 상에서 정보제공을 하기 위한 목적으로 수행되었다. 본 연구에서 제시하는 자료들은 1995년부터 1998년까지 수행된 ``선도기술 개발사업(G7)의 2단계 연구의 주요 결과에 대한 지표화 및 보급을 위한 연구`` 수행 중에 획득한 자료를 중심으로 정리되었다. 이들 지표 가운데에서 시뮬레이터에 관련된 소개물 및 Web site에 대한 연구결과가 1차적으로 정리되었고, 보다 많은 정보를 지원하기 위해 인터넷에서 시뮬레이터에 관련된 site가 keywords로 검색되어 정리되었다. 감성공학 2단계 연구에서 시뮬레이터의 개념은 종합적 감성측정평가를 하기 위한 통합적 의미의 시뮬레이터이며, 일본의 HQL (Research Institute of Human Engineering for Quality Life) 연구소의 시뮬레이터가 이것과 가장 근접한 형태라고 할 수 있다. 그 외의 시뮬레이터들은 통합 시뮬레이션 보다는 각각의 목적에 맞추어 제작, 개발된 형태가 주를 이루고 있었다. 본 고는 현재 http://www.gamsung.or.kr 내의 ``감성도서관``에서 제공하고 있는 시뮬레이터 관련 사이트에 대한 전반적인 소개와 세부항목에 대한 내용을 중심으로 기술하였다.

뇌파를 통한 어두운 시감효율함수 정량화 연구

임현균(Hyun Kyoon Lim),박세진(Se-Jin Park),황지수(Jisoo Hwang),박승남(Seung-Nam Park),김시경(Sikyung Kim),이근우(Geun Woo Lee),김승관(Seung Kwan Kim),박성종(Seongchong Park),오승빈(Seung Bin Oh),노기용(Ki Yong Noh),김원식(Wuon-Shik K 대한인간공학회 2010 대한인간공학회 학술대회논문집 Vol.2010 No.10

Lighting for home and road in modern society is one of the most important design factors. To date, standards for colors to human sensation are well made under the bright (=photopic vision) and dark (=scotopic vision) environment. However, the measurement method is not objective and therefore, new method is in need. In this study, we recorded electroencephalogram while a subject was watching light-emitting diode (LED) panel. Red, green, and blue color appeared sequentially from dark (=0) and to the most bright color level (=256) step by step. A subject was asked to press a button when he/she see any colors on the screen. EEG data from five subjects (34 ? 5.9 years) was analyzed. As results, subjects pressed button 37.1 seconds for red, 36.5 s for green, and 36.5 s for blue. Subjects showed also EEG changes by optical stimulation post onset of lighting stimulation. As a conclusion, EEG analysis may be a new objective measurement method to detect brain response by the optical stimulation. To get firm evidence for the response, additional subjects should be recruited more in the same test. Test-retest reliability should be also made for the evidence based standards of visual sensitivity.

자동혈압계 성능평가를 위한 인체혈압 시뮬레이터 개발

도일,임현균,안봉영,지영준,이종실,오재훈,Doh, Il,Lim, Hyun Kyoon,Ahn, Bongyoung,Chee, Youngjoon,Lee, Jongshill,OH, Jae Hoon 대한의용생체공학회 2017 의공학회지 Vol.38 No.3

Blood pressure is one of the important vital signs for monitoring the medical condition of a patient. Automated NIBP(non-invasive blood pressure) monitoring devices calculate systolic and diastolic blood pressures from the oscillation in cuff pressure caused by a pulsation of an artery. To validate the NIBP devices, we developed a simulator to supply the oscillometric waveforms obtained from human subjects. The simulator provided pressure pulses to device-under-test and device readings were compared to the auscultatory references. Fully automated simulation system including OCR(optical character recognition) were developed and used for NIBP monitoring devices. The validation results using the simulator agreed well with previous clinical validation. More validation studies using the standardized oscillometric waveforms would be required for the replacement of clinical trials to validate a new automated NIBP monitoring device.

Detection of Rapid Atrial Arrhythmias in SQUID Magnetocardiography

김기웅,권혁찬,김기담,이용호,김진목,김인선,임현균,박용기,김두상,임승평,Kim Kiwoong,Kwon Hyukchan,Kim Ki-Dam,Lee Yong-Ho,Kim Jin-Mok,Kim In-Seon,Lim Hyun-Kyoon,Park Yong-Ki,Kim Doo-Sang,Lim Seung-Pyung The Korean Superconductivity Society 2005 Progress in superconductivity Vol.7 No.1

We propose a method to measure atrial arrhythmias (AA) such as atrial fibrillation (Afb) and atrial flutter (Afl) with a SQUID magnetocardiograph (MCG) system. To detect AA is one of challenging topics in MCG. As the AA generally have irregular rhythm and atrio-ventricular conduction, the MCG signal cannot be improved by QRS averaging; therefore a SQUID MCG system having a high SNR is required to measure informative atrial excitation with a single scan. In the case of Afb, diminished f waves are much smaller than normal P waves because the sources are usually located on the posterior wall of the heart. In this study, we utilize an MCG system measuring tangential field components, which is known to be more sensitive to a deeper current source. The average noise spectral density of the whole system in a magnetic shielded room was $10\;fT/{\surd}Hz(a)\;1\;Hz\;and\;5\;fT/{\surd}Hz\;(a)\;100\;Hz$. We measured the MCG signals of patients with chronic Afb and Afl. Before the AA measurement, the comparison between the measurements in supine and prone positions for P waves has been conducted and the experiment gave a result that the supine position is more suitable to measure the atrial excitation. Therefore, the AA was measured in subject's supine position. Clinical potential of AA measurement in MCG is to find an aspect of a reentry circuit and to localize the abnormal stimulation noninvasively. To give useful information about the abnormal excitation, we have developed a method, separative synthetic aperture magnetometry (sSAM). The basic idea of sSAM is to visualize current source distribution corresponding to the atrial excitation, which are separated from the ventricular excitation and the Gaussian sensor noises. By using sSAM, we localized the source of an Afl successfully.

액체 헬륨 듀아의 온도 특성 연구

이정희(Jung-Hee Lee),이영신(Young-Shin Lee),임현균(Hyun-Kyoon Lim) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10

The techniques of cooling down cryogen are used to make superconductors superducting state at very low temperature, 4 K. This paper studied on the temperature characteristic of liquid helium dewar. The dewar has a 30 L liquid helium capacity, a hold time of 5 days. The dewar has two thermal shield, 150K and 40K. The temperature was measured at the end of thermal shield and was compared with the thermal analysis. The thermal analysis of helium dewar were carried out with a finite element method program, ANASYS 10. The simulation result has predicted similar temperature data in manufactured helium dewar.

심자도 장비의 냉각장치 특성 최적화를 위한 기하 설계 변수 연구

이정희(Jung-Hee Lee),이영신(Young-Shin Lee),이용호(Yong-Ho Lee),임현균(Hyun-Kyoon Lim),이성진(Sung-Jin Lee) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.2

인체의 심장 활동에 의해 발생되는 생체 자기 신호를 심자도(magnetocardio-gram, MCG)라고 부른다. 이러한 생체자기장은 극저온 상태에서 고감도 자장센서인 SQUID(Superconducting QUantum Interference Device)를 사용함으로서 측정할 수 있다. 이 심자도 장비의 냉각장치는 액체 헬륨을 냉매로 사용하며 이 냉매를 보관하는 방법이 장비의 성능을 좌우한다. 액체 저온 듀아가 극저온 4 K에서 초전도 특성을 유지하기 위하여 사용된다. 본 연구에서는 액체 헬륨 듀아의 온도분포 특성이 연구되었다. 본 연구에서 사용된 듀아는 액체헬륨 용량이 30 L이고 5일간 유지된다. 듀아에는 150 K와 40 K의 이중 차폐체가 설치되었다. 열차폐체 끝단에서의 온도가 측정되었으며 전산모델의 해석결과와 비교되었다. 기하 설계 변수에 대한 최적화 기법을 적용하여 냉각장치인 저온 듀아의 열전단율을 최소화하였으며 듀아의 응력분포에 영향을 갖는 설계 기하 변수들의 특성을 연구하였다. 냉각장치의 열해석 및 최적화해석을 위해 유한요소 코드 ANSYS 10을 사용하였다. 저온 듀아에 사용된 전산모델은 열복사에 의한 영향을 최소화 할 수 있는 분야에서 온도 분포를 예측하는데 유용하게 사용될 수 있다. A magnetocardiogram (MCG) is a recording of the biomagnetic signals generated by cardiac electrical activity. Biomagnetic instruments are based on superconducting quantum interference devices (SQUIDs). A liquid cryogenic Dewar flask was used to maintain the superconductors in a superconducting state at a very low temperature (4 K). In this study, the temperature distribution characteristics of the liquid helium in the Dewar flask was investigated. The Dewar flask used in this study has a 30 L liquid helium capacity with a hold time of 5 d. The Dewar flask has two thermal shields rated at 150 and 40 K. The temperatures measured at the end of the thermal shield and calculated from the computer model were compared. This study attempted to minimize the heat transfer rate of the cryogenic Dewar flask using an optimization method about the geometric variable to find the characteristics for the design geometric variables in terms of the stress distribution of the Dewar flask. For thermal and optimization analysis of the structure, the finite element method code ANSYS 10 was used. The computer model used for the cryogenic Dewar flask was useful to predict the temperature distribution for the area less affected by the thermal radiation.