• 대한의사협회지
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• 제61권12호
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• pp.702-705
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• 2018

Advances in technology lead to advances in medical devices, and these advances have the positive effect of creating opportunities for beneficial developments in healthcare, such as innovating traditional healthcare processes or expanding opportunities for diagnosing and treating diseases. Nonetheless, device developers, suppliers, users, insurers, and patients all face the challenge of balancing patient safety and health effectiveness with a reasonable profit. In Korea, the New Health Technology Assessment system aims to introduce safe and effective health technology, but this is only effective for the entry of devices onto the healthcare market. This system is not enough for creating a healthy ecosystem in which high-quality technologies and devices survive in the market and naturally exit from the market if not successful. The nation must not lag in the rapid development of medical devices, but the concomitant requirement for patient safety is like two rabbits moving in different directions. There is not enough time to resolve each source of uncertainty for both developers and users. The early adoption of health technologies, including medical devices, offers new opportunities for treatment and diagnosis, but also poses unexpected health risks. Thus, we need to design a plan to generate scientific evidence related to medical devices after they introduced into practice. Additionally, regarding the use of individual medical devices, we believe that the creation of a healthy ecosystem for medical devices by implementing medical device surveillance culture is a way to manage the opportunities and risks of the early introduction of innovative medical devices.

• Korea-Australia Rheology Journal
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• 제19권3호
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• pp.157-164
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• 2007

Microencapsulation of cells within microfluidic devices enables explicit control of the membrane thickness or cell density, resulting in improved viability of the transplanted cells within an aggressive immune system. In this study, living cells (3T3 and L929 fibroblast cells) are encapsulated within a semi-permeable membrane (calcium crosslinked alginate gel) in two different device designs, a flow focusing and a core-annular flow focusing geometry. These two device designs produce a bead and a long microfibre, respectively. For the alginate bead, an alginate aqueous solution incorporating cells flows through a flow focusing channel and an alginate droplet is formed from the balance of interfacial forces and viscous drag forces resulting from the continuous (oil) phase flowing past the alginate solution. It immediately reacts with an adjacent $CaCl_2$ drop that is extruded into the main flow channel by another flow focusing channel downstream of the site of alginate drop creation. Depending on the flow conditions, monodisperse microbeads of sizes ranging from $50-200\;{\mu}m$ can be produced. In the case of the microfibre, the alginate solution with cells is extruded into a continuous phase of $CaCl_2$ solution. The diameter of alginate fibres produced via this technique can be tightly controlled by changing both flow rates. Cell viability in both forms of alginate encapsulant was confirmed by a LIVE/DEAD cell assay for periods of up to 24 hours post encapsulation.

• 한국자기학회지
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• 제16권4호
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• pp.216-220
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• 2006

10개의 다중 홀(Hall)소자를 이용하여 요골동맥에 놓여진 영구자석의 위치 변화에 따른 전압의 변화를 전기적 신호로 얻었다.전기적 신호는 맥의 파형 신호를 의미하며 이들을 다시 회로의 하드웨어를 통해 신호들을 미분하여 자장의 변화 신호만 얻었다.소프트웨어를 통해 위치 변화에 따른 자장 변화의 크기에 따라 그 형태를 3차원 영상을 얻어 착용형 맥진기로서의 개발 가능성을 보여주었다.

• 대한의용생체공학회:의공학회지
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• 제30권1호
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• pp.18-22
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• 2009

Laser has been widely used in various fields of medicine. Recently, noninvasive low-level laser therapeutic medical devices have been introduced in market. However, low-level laser cannot deliver enough photon density to expect positive therapeutic results in deep tissue layer due to the light scattering property in tissue. In order to overcome the limitation, this study was aimed to develop a negative pressure applied low-level laser probe to optimize laser transmission pattern and therefore, to improve photon density in soft tissue. In order to evaluate the possibility of clinical application of the developed laser probe, ex-vivo experiments were performed with porcine skin samples and laser transmissions were quantitatively measured as a function of tissue compression. The laser probe has an air suction hole to apply negative pressure to skin, a transparent plastic body to observe variations of tissue, and a small metallic optical fiber guide to support the optical fiber when negative pressure was applied. By applying negative pressure to the laser probe, the porcine skin under the metallic optical fiber guide is compressed down and, at the same time, low-level laser is emitted into the skin. Finally, the diffusion images of laser in the sample were acquired by a CCD camera and analyzed. Compared to the peak intensity without the compression, the peak intensity of laser increased about $2{\sim}2.5$ times and FWHM decreased about $1.67{\sim}2.85$ times. In addition, the laser peak intensity was positively and linearly increased as a function of compression. In conclusion, we verified that the developed low-level laser probe can control the photon density in tissue by applying compression, and therefore, its potential for clinical applications.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 2001년도 The Seoul International Simulation Conference
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• pp.231-236
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• 2001

Virtual Reality (VR) is a new technology that enables humans to communicate with a computer, It allows the user to see, hear, fuel and interact in a three-dimensional virtual world created graphically. Virtual Reality Therapy (VRT), based on this sophisticated technology, has been recently used in the treatment of subjects diagnosed with acrophobia. Acrophobia is a disorder that is characterized by marked anxiety upon exposure to heights, avoidance of heights, and a resulting impairment in functioning. Conventional virtual reality systems for the treatment of acrophobia have limitations, such as overly expensive devices or somewhat unrealistic graphic scenes. The goal of this study is to develop an inexpensive and more realistic virtual environment in which to perform an exposure therapy fur acrophobia. It runs on a personal computer, and a virtual scene ova bunge-jump tower in the middle of a large city. The virtual scenario includes an open tin surrounded by props beside a tower, which allows the patient to feel a sense of heights. The effectiveness of the VR environment was evaluated through the clinical treatment of a subject who was suffering from the fear of heights. Based on pre- and post- questionnaires and subjective comments from the subject. This virtual reality environment proved to be an effective and realistic tool fur the treatment of acrophobia.

• 대한의용생체공학회:의공학회지
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• 제29권5호
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• pp.371-375
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• 2008

In blood pressure measurement, the oscillometric method detects and analyzes the pulse pressure oscillation while deflating the cuff around the arm. For its principle, one has to inflate cuff pressure above the subject's systolic pressure and deflate below the diastolic pressure. Most of the commercialized devices inflate until the fixed target pressure and deflate until the fixed completion pressure because there is no way to know the systolic and diastolic pressure before measurement. Too high target pressure makes stress to the subject and too low target pressure makes big error or long measurement time because of re-inflation. There are similar problems for inadequate completion pressure. In this study, we suggest new algorithm to set proper target and completion pressure for each subject by analyzing pressure waveform while inflating period. We compared our proposed method and auscultation method to see the errors of estimation. The differences between the two measurements were -4.02$\pm$4.80mmHg, -10.50$\pm$10.57mmHg and -0.78$\pm$5.l7mmHg for mean arterial pressure, systolic pressure and diastolic pressure respectively. Consequently, we could set the target pressure by 30 mmHg higher than our estimation and we could stop at 20mmHg lower than our estimated diastolic pressure. Using this method, we could reduce the measurement time.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.391-394
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• 2002

There has recently been much interest and research in developing digital x-ray systems based on using amorphous selenium(a-Se) photoconductors as the image receptor. The amorphous selenium layer that is currently being studied for use as an x-ray photoconductor is not pure a-Se but rather amorphous selenium alloyed with arsenic. We fabricated samples using the selenium and arsenic alloy with various concentrations of the arsenic. In this work, x-ray photoconductor using amorphous selenium alloyed with arsenic were fabricated with different concentrations of the arsenic (0.1 wt.%, 0.3wt.%, 0.5wt.%, 1wt.%, 1.5wt.%, 3wt.%, 5wt.%). The seven kind of samples was fabricated with a-Se alloyed with arsenic through vacuum thermal evaporation. We also investigate the arsenic concentration dependence on the device performance in radiation detector. The electric characteristics of radiation detector devices with changing additive ratio of the arsenic is performed by measuring the x-ray induced photocurrent and integrating it over time to find the total charge. The thickness of a-Se is $100{\mu}m$. Bias voltages $3V/{\mu}m$, $6V/{\mu}m$， $9V/{\mu}m$ are applied at the samples. As results, the net charge of a-Se 0.3% As sample is $526.0pC/mR/cm^2$ at $9V/{\mu}m$ bias. The net charge is decreased as with the increasing additive ratio of arsenic.

• 대한인간공학회지
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• 제26권2호
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• pp.131-136
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• 2007

In this study, we developed an active ankle-foot orthosis(AAFO) which can control dorsi/ plantar flexion of the ankle joint to prevent foot drop and toe drag during walking. 3D gait analyses were performed on five healthy subjects under three different gait conditions: the normal gait without AFO, the SAFO gait with the conventional plastic AFO, and the AAFO gait with the developed AFO. As a result, the developed AAFO preeminently induced the normal gait compared to the SAFO. Additionally, AAFO prevented foot drop by proper plantarflexion during loading response and provided enough plantarflexion moment as a driving force to walk forward by sufficient push-off during pre-swing. AAFO also could prevent toe drag by proper dorsiflexion during swing phase. These results indicate that the developed AAFO may have more clinical benefits to treat foot drop and toe drag, compared to conventional AFOs, and also may be useful in patients with other orthotic devices.

• 대한의용생체공학회:의공학회지
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• 제29권1호
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• pp.40-45
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• 2008

Therapeutic ultrasound which is developed for rehabilitation therapy have already been used for healing joint contracture, synechia, acute and chronic inflammatory diseases. Medical devices for pain-relief and healing using therapeutic ultrasound are actively being developed. This study measured the change of PTT with the transmitted ultrasound through the human body to find out the increase of compliance of blood vessels. Measurement method of PTT in this study is employed as useful ways to acquire physiological information of patients in the clinical case in order to measure the change of mechanical characteristics of blood vessels. This study confirmed the PTT change of rehabilitation patients through the thermal effects of ultrasound by using PTT and also found that it is possible to increase PTT by adjusting the warm water and ultrasound. The increase of PTT means the decrease of the pulse wave velocity from the cardiovascular system to the peripheral arteries. The physiological effects occurred using the warm water and ultrasound.

• Transactions on Electrical and Electronic Materials
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• 제4권6호
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• pp.9-12
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• 2003

The electrical properties of stabilized amorphous selenium typical of the material used in direct conversion x-ray imaging devices are reported. Carrier mobility was measured using time-of-flight (TOF) measurements to investigate the transport properties of holes and electrons in stabilized a-Se film. A laser beam with pulse duration of 5 ns and wavelength of 350nm was illuminated on the surface of a-Se with thickness of 400 $\mu\textrm{m}$. The photo induced signals of a-Se film as a function of time were measured. The measured transit times of hole and electron were about 8.73${\mu}\textrm{s}$ and 229.17${\mu}\textrm{s}$, respectively. The hole and electron drift mobilities decreases with increase of electric field up to 4V/$\mu\textrm{m}$. Above 4V/$\mu\textrm{m}$, the measured drift mobilities exhibited no observable dependence with respect to electric field. The experimental results showed that the hole and electron drifting mobility were 0.04584 $\textrm{cm}^2$ V$\^$-1/s$\^$-1/ sand 0.00174 $\textrm{cm}^2$V$\^$-1/s$\^$-1/ at 10 V/$\mu\textrm{m}$.