• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.693-696
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• 2006

In this study, we made the system to measure variation of blood flow using bio-electrical impedance analysis method. The system, which could measure variation of impedance according to pressure change by artificial pressure, consists of pressure measurement and impedance measurement by 4-electrode method. Pressure measurement splits into semiconducting pressure sensor and electronic circuit for processing output signal. In addition, impedance measurement splits into constant current source circuit and lock-in amplifier for detection impedance signal. We experimented feature of impedance measurement using standard resistance to evaluate the system characteristic. As well as, we experimented to estimate variation of blood flow by measuring impedance and blood flow resistance ratio using mean arterial pressure and variation of blood flow with experimental group. As result of this study, blood flow resistance ratio and variation of blood flow were definitely in inverse proportion and were -0.96776 as correlation coefficient by correlation analysis.

• Proceedings of the KIEE Conference
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• 2008.10b
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• pp.197-198
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• 2008

본 논문은 Impedance plethysmography를 이용하여 당뇨병 및 동맥경화의 비침습적이고 고통없는 조기 진단을 위한 시스템 구성의 초기 단계로, 하지 동맥의 기계적 특징인 혈량 변화를 비침습적으로 측정하였다. 혈량과 혈압의 변화는 각각 Impedance plethysmograph와 mercury spbygmomanometer를 이용하여 측정되는데 탄성도는 혈량 변화값을 맥압(수축기압)의 변화량으로 나누어 계산한다. 이 논문에서는 하지 동맥의 탄성도를 비침습적으로 측정하기 위한 전초 단계로서 하지 동맥에서의 임피던스 변화만을 측정하였다. 회로는 50kHz Wien bridge 발진 회로, demodulation, 50kHz band past filter, 0.1Hz high pass filter, 20Hz low pass filter와 증폭기로 구성하였고, 생체 신호 획득 및 처리 과정을 거쳐 임피던스 변화량을 관찰하였다.

• Proceedings of the KSMRM Conference
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• 2004.09a
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• pp.19-19
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• 2004

• Journal of Biomedical Engineering Research
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• v.16 no.3
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• pp.353-358
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• 1995

The impedance pneumography which is widely used in monitoring respiration is simple to use and noninvasive, but it is sensitive to motion artifacts and insensitive to detect obstructive apnea. A 3-channel respiratory inductive plethysmography (RIP) developed in this study detects inductance change of the inductance band induced by cross-sectional area change of thorax or abdomen as one breathes. It was confirmed that RIP was less sensitive to various motion artifacts but more sensitive to detection of obstructive apnea than impedance pneumography.

• Journal of Biomedical Engineering Research
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• v.8 no.1
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• pp.57-62
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• 1987

A three-dimensional thoracic model was constructed using 8-node trilinear hexahedron elements. A three-dimensional steady-state finite element code was developed using FORTRAN. Its output consists of potential at each node. current In each element, and total current In each layer in the z-direction. The thoracic model was Implemented to calculate basal impedance(Zo) In Impedance CardiograPhy Generalized Laplace's equation was solved with Dirlchlet(constant potentials) and homogeneous Neumann(no flux) boundary conditions. It was found that the con structed thoracic model was reasonable since the calculated potential differences between the adjacent electrodes and basal impedance were about the same as the measured ones.

• Journal of Biomedical Engineering Research
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• v.23 no.6
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• pp.437-449
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• 2002

Coronary arteries are subjected to very different flow conditions compared to other arteries in systemic blood circulation. We Performed a computational fluid dynamic research to investigate influence of such flow conditions in coronary arteries on development and progress of atherosclerosis in the same. The results showed big differences in the flow field of the coronary artery compared to the abdominal and femoral arteries. The coronary artery showed higher wall shear stresses due to the small vessel diameter. On the other hand, it showed only one vortex distal to the stenosis throat during a whole pulse cycle. However. several vortices were observed in the abdominal and femoral arteries in both proximal and distal sides of the stenosis throat The wall shear stresses and extent of recirculation area were increased with impedance phase angle increasing toward more negative values. Therefore, cardiac contraction and the negative impedance phase angle as large as -110。 may induce a flow field that accelerates atherosclerosis.

• Journal of Biomedical Engineering Research
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• v.6 no.2
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• pp.63-68
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• 1985

Air pressure decay(APD) rate and ultrafiltration rate(UFR) tests were performed on new and saline rinsed dialyzers as well as those roused in patients several times. C-DAK 4000 (Cordis Dow) and CF IS-11 (Baxter Travenol) reused dialyzers obtained from the dialysis clinic were used in the present study. The new dialyzers exhibited a relatively flat APD, whereas saline rinsed and reused dialyzers showed considerable amount of decay. C-DAH dialyzers had a larger APD(11.70$\pm$1.32mmHg/min)compared to CF dialyzers(4.32$\pm$0.55mmHg/min)(p<0.05). However, there was no observable difference in the UFR between the two dialyzers. Neither APD nor UFR showed any significant increase with an increasing number of reuses for up to more than 20reuses. A substantial number of failures observed in APD(larger than 20mmHe/min)on the reused dialyzers(2 out of 40 CP and S out 26 C-DAK) were attributed to the Possible damage on the fibers. The CF 15-11 HFDs which failed APD test did not show changes in the UFR compared to normal dialyzers indicating that APD is a more sensitive test than UFR test to evaluate the integrity of the fibers.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.955-958
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• 2005

Bioelectrical Impedance Analysis(BIA) can measure body water amount and then body fat mass. The formula is used here FFM=-4.104+0.518H+0.231W+0.130X+4.229S is used, In this work, H is height, R is resistance value, W is weight, X is reactance and S is distinction of sex.

• Journal of Gastric Cancer
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• v.7 no.4
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• pp.228-236
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• 2007

Purpose: We have evaluated changes of body composition for patients that underwent a radical gastrectomy for stomach cancer by the use of available bioelectrical impedance analysis during the first year following surgery. We plan to utilize these findings in nutritional and physiological studies. Materials and Methods: We evaluated clinical changes in body composition in patients using the bioelectrical impedance method (Inbody 4.0, Biospace, Korea), between November 2003 to November 2004. A total of 98 patients agreed to enroll in this study among all of the patients that underwent a radical gastrectomy. Results: The average weight decreased by 6.7%, and 9.4%, within the first and 6 months after surgery, respectively (P<0.01). The fat free mass (FFM) dropped by 4.9% within the first month and there were no more changes after this period (P<0.01). The fat mass (FM) and visceral fat area (VFA) decreased 24.3% and 14.1% within the first 6 months (P<0.01), respectively. The reduction effects for female patients were greater than for male patients for weight, FFM and VFA (P<0.05). The edema index was higher in patients with stage III-IV disease than in patients with stage I-II disease (P<0.05). There were significant differences for Billroth I and Billrothl II patients as compared to patients that underwent an esophagojejunostomy for a reduction of the FM, as measured in the in the 12th month after surgery (27.6%, 22.1%, and 41.2%, respectively; P<0.05). Conclusion: Since nutritional supplementation and an improvement in body weight loss after a radical gastrectomy is significantly related with quality of life, nutritional and physiological studies should be greatly considered. In this study, bioelectrical impedance analysis was very useful in analyzing the diminution of body composition and we hope this study on the nutritional and physiological aspects related to a radical gastrectomy will be useful for later studies.

• Journal of Biomedical Engineering Research
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• v.25 no.4
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• pp.269-275
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• 2004

Different biological tissues have different values of electrical resistivity. In EIT (electrical impedance tomography), we try to provide cross-sectional images of a resistivity distribution inside an electrically conducting subject such as the human body mainly for functional imaging. However, it is well known that the image reconstruction problem in EIT is ill-posed and the quality of a reconstructed image highly depends on the measurement error. This requires us to develop a high-performance EIT system. In this paper, we describe the development of a 16-channel digital EIT system including a single constant current source, 16 voltmeters, main controller, and PC. The system was designed and implemented using the FPGA-based digital technology. The current source injects 50KHz sinusoidal current with the THD (total harmonic distortion) of 0.0029% and amplitude stability of 0.022%. The single current source and switching circuit reduce the measurement error associated with imperfect matching of multiple current sources at the expense of a reduced data acquisition time. The digital voltmeter measuring the induced boundary voltage consists of a differential amplifier, ADC, and FPGA (field programmable gate array). The digital phase-sensitive demodulation technique was implemented in the voltmeter to maximize the SNR (signal-to-noise ratio). Experimental results of 16-channel digital voltmeters showed the SNR of 90dB. We used the developed EIT system to reconstruct resistivity images of a saline phantom containing banana objects. Based on the results, we suggest future improvements for a 64-channel muff-frequency EIT system for three-dimensional dynamic imaging of bio-impedance distributions inside the human body.