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이수열,우응제,조민형,Lee, Soo-Yeol,Woo, Eung-Je,Cho, Min-Hyoung 대한의용생체공학회 1994 의공학회지 Vol.15 No.1
In the conventional infrared imaging system, complex infrared lens systems are usually used for directing collimated narrow infrared beams into the high speed 2-dimensional optic scanner. In this paper, a simple reflective infrared optic system with a 2-dimensionaloptic scanner is proposed for the realization of medical infrared thermography system. It has been experimentally proven that the infrared thermography system composed ofthe proposed optic system has the temperature resolution of $0.1{\circ}C$ under the spatial resolution of 1mrad, the image matrix size of $256{\times}240$, and the imaging time of 4 seconds.
자기공명 탄성계수 영상법을 위한 진동기의 개발 및 기초실험
이태휘,서용선,김영태,이병일,우응제,Lee, Tae-Hwi,Suh, Yong-Seon,Kim, Young-Tea,Lee, Byung-Il,Woo, Eung-Je 대한의용생체공학회 2007 의공학회지 Vol.28 No.1
Elasticity is an important physical property of biological tissues. Differences in elasticity can help facilitate the diagnosis of tumors and their extent. Magnetic Resonance Elastography (MRE) tries to visualize images of tissue elasticity by externally applying shear stress on the surface of an imaging object. Applied shear stress induces internal displacements that can be measured from MR phase images. In order to conduct MRE imaging experiments, we need to first develop a vibrator. We found that there does not exist enough technical information to design the MRE vibrator. In this paper, we describe the theory, design and construction of an MRE vibrator. We report the performance of the developed vibrator using two different test methods. We found that the vibrator successfully induces enough internal displacements that can be imaged using an MRI scanner. We suggest future studies of numerous MRE imaging experiments using the vibrator.
오동인,조성필,김상민,구환,우응제,Oh, Tong-In,Cho, Seong-Phil,Kim, Sang-Min,Koo, Hwan,Woo, Eung-Je 대한의용생체공학회 2007 의공학회지 Vol.28 No.1
We have developed a multi-channel, multi-frequency EIT system with operating frequency of 10Hz to 500KHz. The number of digital voltmeters using phase-sensitive demodulation can be varied from 8 to 64 and we found that 16 and 32-channels are most practical. This paper describes the design, implementation, and construction of 16 and 32-channel systems. The performance of the system was thoroughly tested and we found that CMRR of the developed voltmeter is about 85dB with $100{\Omega}$ unbalancing series resistor. The SNR is greater than 99.6dB and the output impedance of the constant current source is $1{\Omega}W$ at least for all frequencies. Imaging experiments using a banana with frequency-dependent conductivity and permittivity show that frequency-difference imaging is possible using the developed system. Future works of animal and human experiments are discussed.
도전율 및 유전율이 다른 병소의 검출을 위한 320-채널 다주파수 Trans-Admittance Scanner(TAS)
오동인,이민형,김희진,우응제,Oh, Tong-In,Lee, Min-Hyoung,Kim, Hee-Jin,Woo, Eung-Je 대한의용생체공학회 2007 의공학회지 Vol.28 No.1
In order to collect information on local distribution of conductivity and permittivity underneath a scan probe, we developed a multi-frequency trans-admittance scanner (TAS). Applying a sinusoidal voltage with variable frequency on a chosen distal part of a human body, we measure exit currents from 320 grounded electrodes placed on a chosen surface of the subject. The electrodes are packaged inside a small and light scan probe. The system includes one voltage source and 17 digital ammeters. Front-end of each ammeter is a current-to-voltage converter with virtual grounding of a chosen electrode. The rest of the ammeter is a voltmeter performing digital phase-sensitive demodulation. Using resistor loads, we calibrate the system including the scan probe to compensate frequency-dependent variability of current measurements and also inter-channel variability among multiple. We found that SNR of each ammeter is about 85dB and the minimal measurable current is 5nA. Using saline phantoms with objects made from TX-151, we verified the performance of the lesion estimation algorithm. The error rate of the depth estimation was about 19.7%. For the size estimate, the error rate was about 15.3%. The results suggest improvement in lesion estimation algorithm based on multi-frequency trans-admittance data.
나노웹 섬유형 전극 인터페이스와 KHU Mark2 EIT 시스템을 이용한 생체신호 동기 도전율 영상법
김태의,김현지,위헌,오동인,우응제,Kim, Tae-Eui,Kim, Hyun-Ji,Wi, Hun,Oh, Tong-In,Woo, Eung-Je 대한의용생체공학회 2012 의공학회지 Vol.33 No.1
Electrical impedance tomography(EIT) can produce functional images with conductivity distributions associated with physiological events such as cardiac and respiratory cycles. EIT has been proposed as a clinical imaging tool for the detection of stroke and breast cancer, pulmonary function monitoring, cardiac imaging and other clinical applications. However EIT still suffers from technical challenges such as the electrode interface, hardware limitations, lack of animal or human trials, and interpretation of conductivity variations in reconstructed images. We improved the KHU Mark2 EIT system by introducing an EIT electrode interface consisting of nano-web fabric electrodes and by adding a synchronized biosignal measurement system for gated conductivity imaging. ECG and respiration signals are collected to analyze the relationship between the changes in conductivity images and cardiac activity or respiration. The biosignal measurement system provides a trigger to the EIT system to commence imaging and the EIT system produces an output trigger. This EIT acquisition time trigger signal will also allow us to operate the EIT system synchronously with other clinical devices. This type of biosignal gated conductivity imaging enables capture of fast cardiac events and may also improve images and the signal-to-noise ratio (SNR) by using signal averaging methods at the same point in cardiac or respiration cycles. As an example we monitored the beat by beat cardiac-related change of conductivity in the EIT images obtained at a common state over multiple respiration cycles. We showed that the gated conductivity imaging method reveals cardiac perfusion changes in the heart region of the EIT images on a canine animal model. These changes appear to have the expected timing relationship to the ECG and ventilator settings that were used to control respiration. As EIT is radiation free and displays high timing resolution its ability to reveal perfusion changes may be of use in intensive care units for continuous monitoring of cardiopulmonary function.
3T MREIT 시스템을 이용한 실험견 사체의 두부 도전율 영상
정우철,김영태,김형중,이태휘,강병택,박희명,우응제,Jeong, Woo-Chul,Kim, Young-Tae,Minhas, Atul S.,Kim, Hyung-Joong,Lee, Tae-Hwi,Kang, Byeong-Teck,Park, Hee-Myung,Woo, Eung-Je 대한의용생체공학회 2009 의공학회지 Vol.30 No.2
Magnetic Resonance Electrical Impedance Tomography (MREIT) is a new bio-imaging modality providing cross-sectional conductivity images from measurements of internal magnetic flux densities produced by externally injected currents. Recent MREIT studies demonstrated successful conductivity image reconstructions of postmortem and in vivo canine brain. However, the whole head imaging was not achieved due to technical issues related with electrodes and noise in measured magnetic flux density data. In this study, we used a new carbon-hydrogel electrode with a large contact area and injected 30 mA imaging current through a canine head. Using a 3T MREIT system, we performed a postmortem canine experiment and produced high-resolution conductivity images of the entire canine head. Collecting magnetic flux density data inside the head subject to multiple injection currents, we reconstructed cross-sectional conductivity images using the harmonic $B_z$ algorithm. The conductivity images of the canine head show a good contrast not only inside the brain region including white and gray matter but also outside the brain region including the skull, temporalis muscle, mandible, lingualis proprius muscle, and masseter muscle.
우응제,박승훈 건국대학교 의과학연구소 1994 건국의과학학술지 Vol.4 No.-
We have developed biological signal measurement modules and PC-based data acquisition system. Biological signals included in this system are ECG, EEG, EMG, invasive blood pressure, respiration, and temperature. Parameters of each module can be controlled by PC through a data acquisition and control card. The data acquisition and control card can collect up to 16 channels of biological signals with sampling rate of 50~10,000Hz and 12-bit resolution. All measurement modules and data acquisition functions are controlled by microcontroller which receives commands from PC. All data transfers among PC, microcontroller, and ADC are done through a shared RAM access by polling method for real time operation. This system is being used in KKU BME Medical Instrumentation Laboratory in research areas such as ECG interpretation, high-resolution ECG, polysomnography, long-term monitoring of biological signals, design of intelligent alarm system, etc.
여성 요실금에서 Kontinence™와 Compact Elite™의 치료효과 비교
양상국,정상원,오미희,노용수,김홍섭,우응제,박승훈,이수열 건국대학교 의과학연구소 1999 건국의과학학술지 Vol.9 No.-
Biofeedback and pelvic floor electrical stimulation are new modalities that have been advocated for the treatment of female urinary incontinence. The aim of this study was to compare prospectively the therapeutic effect of Kontinence™(HMT Co., Korea) with Compact Elite™(ECL Co., France) in female urinary incontinence. All patients were evaluated with a complete history, physical examination, urinalysis, urine culture and urodynamic study. Eighteen patients were treated with Compact Elite™, and thirteen patients with Kontinence™. Enrolled patients had completed 8 office sessions consisting of biofeedback and intravaginal electrical stimulation according to the program of each machines. Overall treatment response was graded by patients on a scale of complete cure to aggravation. At two weeks after last session, overall improvement rate was 78% in Compact Elite™group and 92% in Kontinence™group(p>0.05). Overall patients' acceptability during treatment course was greater than 80% in both machines(p>0.05). There were no unexpected clinical findings during Kontinence™ treatment. After Kontinence™treatment, there were no laboratory changes including electrocardiography, complete blood count, liver function profile, and chest PA. These results showed that the biofeedback and electrical stimulation with Kontinence™was safe and moderately effective for female urinary incontinence comparable to Compact Elite™. However, long-term results of a larger patients are needed to ensure the therapeutic effect of Kontinence™.