• 전기전자학회논문지
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• 제13권1호
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• pp.77-86
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• 2009

본 논문에서 이식형 심장 박동 조율기를 위한 심전도 검출기와 아날로그-디지털 변환기(ADC)를 설계한다. 제안한 웨이블렛 심전도 검출기는 웨이블렛 필터 뱅크 구조의 웨이블렛 변조기, 웨이블렛 합성된 심전도 신호의 가설 검정을 통한 QRS 신호 검출기와 0-교차점을 이용한 잡음 검출기로 구성된다. 저전력 소모의 동작을 유지하며 보다 높은 검출 정확도를 갖는 심전도 검출기의 구현을 위해, 다중스케일 곱의 알고리즘과 적응형의 임계값을 갖는 알고리즘을 사용하였다. 또한 심전도 검출기의 입력단에 위치하는 저전력 Successive Approximation Register ADC의 구현을 위해, 신호 변환의 주기 중, 매우 짧은 시간 동안에만 동작하는 비교기와 수동 소자로 구성되는 Sample&Hold를 사용하였다. 제안한 회로는 표준 CMOS $0.35{\mu}m$ 공정을 사용하여 집적 및 제작되었고, 99.32%의 높은 검출 정확도와 3V의 전원 전압에서 $19.02{\mu}W$의 매우 낮은 전력 소모를 갖는 것을 실험을 통해 확인하였다.

• 디지털융복합연구
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• 제10권2호
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• pp.141-146
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• 2012

최근 의료기술은 IT 기술과 융합하여 언제, 어디서나 의료 서비스를 받을 수 있는 유헬스케어 서비스가 각광을 받고 있다. 그러나, RFID 기술을 유헬스시스템에 적용한 체내삽입장치는 환자의 민감한 생체정보가 쉽게 제3자에게 유출되어 프라이버시 침해에 쉽게 노출될 수 있는 문제점이 있다. 이 논문에서는 체내삽입장체에 RFID 기술을 접목하여 환자의 생체정보가 불법적인 목적으로 시용되지 않는 RFID 기반의 유헬스케어 인증 프로토콜을 제안한다. 제안 프로토콜은 관리자와 병원관계자의 랜덤수를 조합하여 환자의 생체정보의 무결성을 보장하며, 연속번호 $SEQ$와 타임스탬프 $T$을 사용하여 체내삽입장치와 관리자, 관리자와 병원관계자를 서로 동기화하고 있다. 또한, 불법적인 공격자로부터 사용자의 프라이버시를 보호하도록 환자의 보안 인식자를 관리자(=위장자)에서 관리함으로써 환자의 생체정보 유출을 예방한다.

• 전자공학회논문지SC
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• 제41권5호
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• pp.49-56
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• 2004

완전 이식형 인공중이 시스템을 위한 음성 신호처리 및 제어 모듈을 소형 마이크로컨트롤러를 사용하여 저전력형으로 설계 하였다 설계된 모듈은 입력되는 음성신호를 난청자의 역치에 맞추어 이득을 조정하는 등의 신호처리를 수행함과 동시에 체내 이식부의 제어를 수행하게 된다. 설계된 마이크로컨트롤러는 전원이 켜지면 사용자의 청력 손실에 맞추어서 주파수별로 차등 되는 이득을 주도록 실시간으로 음성신호를 처리하게 된다. 그러나 체외에서 제어신호가 입력될 경우 수신된 제어 신호에 의해 마이크로컨트롤러는 인터럽트 서브루틴을 수행하여 전원 제어, 볼륨 조절과 같은 제어 명령을 수행한 후 다시 음성 신호를 처리하도록 하였다. 설계된 모듈을 구현한 후 구현된 시스템의 동작을 실험을 통하여 확인하였다.

• 한국정보통신학회논문지
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• 제14권10호
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• pp.2351-2357
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• 2010

최근 최첨단 IT 기술을 선도하는 USN은 사회 전반에 걸쳐 활용되고 있다. u-City, u-Home, u-Education, u-Farming 과 같은 다양한 USN 응용 서비스가 진행되고 있으며 도시를 지나 농촌에서도 유비쿼터스 기술이 '제 2의 농업 혁명'을 불러 오고 있다. 유비쿼터스 농업은 가축이나, 농작물 등의 생산 단계에서 USN 기술을 적용해 기온, 습도, 조도와 같은 생육 환경을 최적으로 조성하여 생산성과 안전성을 높이는데 있으며 기존 농업 환경에 많은 변화를 줄 수 있다. 본 논문에서 제안하는 이식형 소형 센서 노드는 센서 네트워크용 SoC(System-on-Chip)을 이용하여 설계하였으며 닭의 흉부에 이식하여 몸체의 체온을 직접적으로 모니터링 할 수 있도록 하였다. 또한 이를 이용한 여러 활용 방안 및 추가적인 고려사항에 대하여 논하였다.

• 대한의용생체공학회:의공학회지
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• 제31권5호
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• pp.401-406
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• 2010

Recently, many implantable medical devices have been developed and manufactured in many countries. In these devices, generally, energy is supplied by a transcutaneous method to avoid the skin penetration due to the power wires. As the most transcutaneous power transmission methods, the electromagnetic coupling between two coils and resonance at a specific frequency has been used widely. However, in case of a transcutaneous power transmitter with a fixed switching frequency to drive an electromagnetic coil, inefficient power transmission and thermal damage by the undesirable current variation may occur, because the electromagnetic coupling state between a primary coil and a secondary coil is very sensitive to skin thickness of each applied position and by person. In order to overcome these defects, a transcutaneous power transmitter of which operating frequency can be automatically tracked into the resonance frequency at each environment has been designed and implemented. Through the results of experiments for different coil surroundings, we have been demonstrated that the implemented transcutaneous power transmitter can track automatically into a varied resonance frequency according to arbitrary skin thickness change.

• 대한의용생체공학회:의공학회지
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• 제31권5호
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• pp.395-400
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• 2010

Hypertension is the chronic disease that the 16% of total population are suffering, and it needs to be studied to find alternative treatment because of the tolerance and side effect of medications that may bother some patients. in this paper, we verified practicality of implantable electrical stimulator that can readily change stimulus magnitude and frequency. And this device is possible to stimulate baroreflex or parasympathetic nerve. Therefore we performed in vitro tests and animal experiment for device's operating conditions. This device consist of implantable electrical stimulator and extracorporeal control/monitoring system. Stimulator was designed to make 1Hz~100Hz pulses and it can change continuous or periodic pulse train type. And this device can control stimulator's function and monitor stimulator's status and patients' blood pressure at exterior of body using ZigBee module as wireless telecommunication. We verified that stimulator have error rate under 5% at 50mm depth of organs and, stimulator makes high-efficiency energy with closer position of two electrodes. Also we can confirm the performance of device that decreasing blood pressure and heart rate of a rat by electrical stimulation.

• 대한의용생체공학회:의공학회지
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• 제37권5호
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• pp.168-177
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• 2016

In this paper we present an implantable pressure sensor to measure real-time blood pressure by monitoring mechanical movement of artery. Sensor is composed of inductors (L) and capacitors (C) which are formed by microfabrication and direct bonding on two biocompatible substrates (quartz). When electrical potential is applied to the sensor, the inductors and capacitors generates a LC resonance circuit and produce characteristic resonant frequencies. Real-time variation of the resonant frequency is monitored by an external measurement system using inductive coupling. Structural and electrical simulation was performed by Computer Aided Engineering (CAE) programs, ANSYS and HFSS, to optimize geometry of sensor. Ultrafast laser (femto-second) cutting and MEMS process were executed as sensor fabrication methods with consideration of brittleness of the substrate and small radial artery size. After whole fabrication processes, we got sensors of $3mm{\times}15mm{\times}0.5mm$. Resonant frequency of the sensor was around 90 MHz at atmosphere (760 mmHg), and the sensor has good linearity without any hysteresis. Longterm (5 years) stability of the sensor was verified by thermal acceleration testing with Arrhenius model. Moreover, in-vitro cytotoxicity test was done to show biocompatiblity of the sensor and validation of real-time blood pressure measurement was verified with animal test by implant of the sensor. By integration with development of external interrogation system, the proposed sensor system will be a promising method to measure real-time blood pressure.

• 대한의용생체공학회:의공학회지
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• 제28권4호
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• pp.539-548
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• 2007

In the paper, a wireless charger with the function of auto-shutdown for fully implantale middle ear hearing devices (F-IMEHD) has been designed. The wireless charger can communicate with an implant module to be turned off automatically shutdown after an internal rechargeable battery has been fully-charged by electromagnetic coupling using two coils. For the communication with an implant module, the wireless charger uses the load shift keying (LSK) method. But, the variation of the mutual inductance due to the different distance between two coils can cause the communication error in receiving the fully-charged signal from an implant module. To solve the problem, the implemented wireless charger has a variable reference generator for LSK communication. The wireless charger generates proper level of the reference voltage for a comparator using an ADC (analog-to-digital converter) and a DAC (digital-to-analog converter). Through the result of experiment, it has been confirmed that the presented wireless charger can detect signals from implantable module. And wireless charger can stop generating electromagnetic flux after an implanted battery has been fully charged in spite of variable coil distance according to different skin thickness.

• Journal of Pharmaceutical Investigation
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• 제25권2호
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• pp.109-116
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• 1995

For the administration of narcotic antagonist with short half-life and low patient compliance, the sustained release system using biodegradable matrix is effective. Polyphosphazenes are of considerable interest as biodegradable matrix systems for controlled release of drugs. In this study, biodegradable polyphosphazenes available for the sustained release implantable device were synthesized, and their application was examined. Poly[dichlorophosphazene] was synthesized by solution polymerization method and confirmed with IR spectrum. Poly[bis(ethyl glycinate) phosphazene] and poly[ (diethyl glutamate)-co-(ethyl glycinate)phosphazene] were then produced by substitution of amino acid alkyl esters for chloride side groups. Using these polymers, the implantable devices of 1 mm thickness and $10{\times}10\;mm$ size containing naloxone hydrochloride were prepared and their release and degradation profiles were measured. In the case of poly[bis(ethyl glycinate)phosphazene] with swelling characteristics, degradation rate was slower than the release rate, showing that the release rate is partly dependent on the swelling rate. In contrast, the degradation rate of polyl[(diethyl glutamate)-co-(ethyl glycinate)phosphazene] matrix was identical with release rate of naloxone hydrochloride. On the basis of these results, it is expected that these polymers can be applied to sustained release implantable systems delivering narcotic antagonist.

• Journal of Korean Neurosurgical Society
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• 제61권5호
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• pp.640-644
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• 2018

Objective : The purpose of this pilot study was to examine the safety and function of the newly developed cerebrospinal fluid (CSF) reservoir called the V-Port. Methods : The newly developed V-Port consists of a non-collapsible reservoir outlined with a titanium cage and a connector for the ventricular catheter to be assembled. It is designed to be better palpated and more durable to multiple punctures than the Ommaya reservoir. A total of nine patients diagnosed with leptomeningeal carcinomatosis were selected for V-Port insertion. Each patient was followed up for evaluation for a month after the operation. Results : The average operation time for V-Port insertion was 42 minutes and the average incision size was 6.6 cm. The surgical technique of V-Port insertion was found to be intuitive by all neurosurgeons who participated in the pilot study. There was no obstruction or leakage of the V-Port during intrathecal chemotherapy or CSF drainage. Also, there were no complications including post-operative intracerebral hemorrhage, infection and skin problems related to the V-Port. Conclusion : V-Port is a safe and an easy to use implantable CSF reservoir that addresses problems of other implantable CSF reservoirs. Further multicenter clinical trial is needed to prove the safety and the function of the V-Port.