Kwang Suk Park

Seoul National University, Sŏul, Seoul, South Korea

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Publications (168)164.06 Total impact

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    ABSTRACT: The standard assessment method for tremor severity in Parkinson's disease is visual observation by neurologists using clinical rating scales. This is, therefore, a subjective rating that is dependent on clinical expertise. The objective of this study was to report clinicians' tendencies to under-rate Parkinsonian tremors in the less affected hand. This was observed through objective tremor measurement with accelerometers. Tremor amplitudes were measured objectively using tri-axis-accelerometers for both hands simultaneously in 53 patients with Parkinson's disease during resting and postural tremors. The videotaped tremor was rated by neurologists using clinical rating scales. The tremor measured by accelerometer was compared with clinical ratings. Neurologists tended to under-rate the less affected hand in resting tremor when the contralateral hand had severe tremor in Session I. The participating neurologists corrected this tendency in Session II after being informed of it. The under-rating tendency was then repeated by other uninformed neurologists in Session III. Kappa statistics showed high inter-rater agreements and high agreements between estimated scores derived from the accelerometer signals and the mean Clinical Tremor Rating Scale evaluated in every session. Therefore, clinicians need to be aware of this under-rating tendency in visual inspection of the less affected hand in order to make accurate tremor severity assessments.
    PLoS ONE 06/2015; 10(6):e0131703. DOI:10.1371/journal.pone.0131703 · 3.23 Impact Factor
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    ABSTRACT: We established and tested a snoring detection method using a polyvinylidene fluoride (PVDF) sensor for accurate, fast, and motion-artifact-robust monitoring of snoring events during sleep. Twenty patients with obstructive sleep apnea participated in this study. The PVDF sensor was located between a mattress cover and mattress, and the patients' snoring signals were unconstrainedly measured with the sensor during polysomnography. The power ratio and peak frequency from the short-time Fourier transform were used to extract spectral features from the PVDF data. A support vector machine was applied to the spectral features to classify the data into either the snore or non-snore class. The performance of the method was assessed using manual labelling by three human observers as a reference. For event-by-event snoring detection, PVDF data that contained 'snoring' (SN), 'snoring with movement' (SM), and 'normal breathing' epochs were selected for each subject. As a result, the overall sensitivity and the positive predictive values were 94.6% and 97.5%, respectively, and there was no significant difference between the SN and SM results. The proposed method can be applied in both residential and ambulatory snoring monitoring systems.
    Physiological Measurement 05/2015; 36(7):1399-1414. DOI:10.1088/0967-3334/36/7/1399 · 1.62 Impact Factor
  • Soo Young Sim · Kwang Min Joo · Kwang Suk Park
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    ABSTRACT: Body temperature is an essential vital sign for assessing physiological functions. The double sensor method-based thermometer is a promising technology that may be applicable to body temperature monitoring in daily life. It continuously estimates deep tissue temperature from the intact skin surface. Despite its considerable potential for monitoring body temperature, its key design features have not been investigated. In this study, we considered four design factors: the cover material, insulator material, insulator radius, and insulator height. We also evaluated their effects on the performance of the double sensor thermometer in terms of accuracy, initial waiting time, and the ability to track changes in body temperature. The probe material and size influenced the accuracy and initial waiting time. Finite element analysis revealed that four thermometers of different sizes composed of an aluminum cover and foam insulator provided high accuracy (<0.1°C) under various ambient temperatures and blood perfusion rates: R=20mm, H=5mm; R=15mm, H=10mm; R=20mm, H=10mm; and R=15mm, H=15mm. The initial waiting time was approximately 10min with almost the same traceability of temperature change. Our findings may provide thermometer manufacturers with new insights into probe design and help them fabricate thermometers optimized for specific applications. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Journal of Thermal Biology 05/2015; 52. DOI:10.1016/j.jtherbio.2015.05.007 · 1.54 Impact Factor
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    Hong Ji Lee · Su Hwan Hwang · Hee Nam Yoon · Won Kyu Lee · Kwang Suk Park
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    ABSTRACT: In this study, we developed and tested a capacitively coupled electrocardiogram (ECG) measurement system using conductive textiles on a bed, for long-term healthcare monitoring. The system, which was designed to measure ECG in a bed with no constraints of sleep position and posture, included a foam layer to increase the contact region with the curvature of the body and a cover to ensure durability and easy installation. Nine healthy subjects participated in the experiment during polysomnography (PSG), and the heart rate (HR) coverage and heart rate variability (HRV) parameters were analyzed to evaluate the system. The experimental results showed that the mean of R-peak coverage was 98.0% (95.5%-99.7%), and the normalized errors of HRV time and spectral measures between the Ag/AgCl system and our system ranged from 0.15% to 4.20%. The root mean square errors for inter-beat (RR) intervals and HR were 1.36 ms and 0.09 bpm, respectively. We also showed the potential of our developed system for rapid eye movement (REM) sleep and wake detection as well as for recording of abnormal states.
    Sensors 05/2015; 15(5):11295-311. DOI:10.3390/s150511295 · 2.05 Impact Factor
  • Jeong Su Lee · Yong Gyu Lim · Sung Jun Kwon · Kwang Suk Park
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    ABSTRACT: Amyotrophic lateral sclerosis (ALS) patients can communicate via their residual capacity to voluntarily blink or move their eyes. Conventionally, electrooculography and video cameras have been used to detect blinks. However, these methods have several shortcomings for application to ALS patients. To overcome such weaknesses, a novel blink detection system that utilises transparent conductive films of indium tin oxide (ITO) is proposed. The ITO films, which are attached to the lenses of conventional glasses, detect blinks without obstructing the wearer's field of vision. The system was validated by a binary communication experiment conducted with six subjects. The results show that 100% of the blinks given by subjects correctly indicated their intended answers.
    Electronics Letters 03/2015; 51(5):382-384. DOI:10.1049/el.2014.3548 · 1.07 Impact Factor
  • 12/2014; 35(6):211-218. DOI:10.9718/JBER.2014.35.6.211
  • Jeong Su Lee · Won Kyu Lee · Yong Gyu Lim · Kwang Suk Park
    12/2014; 35(6):203-210. DOI:10.9718/JBER.2014.35.6.203
  • S.Y. Sim · H.S. Ryou · H.B. Kim · J.H. Jeong · S.J. Lee · S.M. Kim · Kwang Suk Park
    10/2014; 35(5):160-168. DOI:10.9718/JBER.2014.35.5.160
  • 10/2014; 35(5):169-176. DOI:10.9718/JBER.2014.35.5.169
  • Won Kyu Lee · Hong Ji Lee · Hee Nam Yoon · Gih Sung Chung · Kwang Suk Park
    08/2014; 35(4):87-94. DOI:10.9718/JBER.2014.35.4.87
  • 08/2014; 35(4):95-98. DOI:10.9718/JBER.2014.35.4.95
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    ABSTRACT: This study proposes the use of flexible capacitive electrodes for reducing motion artifacts in a wearable electrocardiogram (ECG) device. The capacitive electrodes have conductive foam on their surface, a shield, an optimal input bias resistor, and guarding feedback. The electrodes are integrated in a chest belt, and the acquired signals are transmitted wirelessly for ambulatory heart rate monitoring. We experimentally validated the electrode performance with subjects standing and walking on a treadmill at speeds of up to 7 km/h. The results confirmed the highly accurate heart rate detection capacity of the developed system and its feasibility for daily-life ECG monitoring.
    Sensors 08/2014; 14(8):14732-14743. DOI:10.3390/s140814732 · 2.05 Impact Factor
  • Kwang Suk Park · Su Hwan Hwang · Da Woon Jung · Hee Nam Yoon · Won Kyu Lee
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    ABSTRACT: Based on the its nonintrusive characteristics, ballistocardiography(BCG) has applied in the estimation of sleep structure without attaching any sensors to the subject's body. Loadcell or polyvinylidenefluoride (PVDF) film sensors are installed on the mattress for the monitoring of BCG. BCG peak was detected and heart rate variability parameters are derived. Parameters representing sleep structure and quality are estimated using these parameters. Sleep efficiency, four stages of sleep structure and sleep onset latency are estimated and results are compared with the results derived from polysomnographic recording.
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    Yong Gyu Lim · Jeong Su Lee · Seung Min Lee · Hong Ji Lee · Kwang Suk Park
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    ABSTRACT: The technology for measuring ECG using capacitive electrodes and its applications are reviewed. Capacitive electrodes are built with a high-input-impedance preamplifier and a shield on their rear side. Guarding and driving ground are used to reduce noise. An analysis of the intrinsic noise shows that the thermal noise caused by the resistance in the preamplifier is the dominant factor of the intrinsic noise. A fully non-contact capacitive measurement has been developed using capacitive grounding and applied to a non-intrusive ECG measurement in daily life. Many ongoing studies are examining how to enhance the quality and ease of applying electrodes, thus extending their applications in ubiquitous healthcare from attached-on-object measurements to wearable or EEG measurements.
    Annals of Biomedical Engineering 07/2014; 42(11). DOI:10.1007/s10439-014-1069-6 · 3.23 Impact Factor
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    ABSTRACT: Objective. Current electroencephalogram (EEG) monitoring systems typically require cumbersome electrodes that must be pasted on a scalp, making a private recording of an EEG in a public place difficult. We have developed a small, user friendly, biocompatible electrode with a good appearance for inconspicuous EEG monitoring. Approach. We fabricated carbon nanotube polydimethylsiloxane (CNT/PDMS)-based canal-type ear electrodes (CEE) for EEG recording. These electrodes have an additional function, triggering sound stimulation like earphones and recording EEG simultaneously for auditory brain-computer interface (BCI). The electrode performance was evaluated by a standard EEG measurement paradigm, including the detection of alpha rhythms and measurements of N100 auditory evoked potential (AEP), steady-state visual evoked potential (SSVEP) and auditory steady-state response (ASSR). Furthermore, the bio- and skin-compatibility of CNT/PDMS were tested. Main results. All feasibility studies were successfully recorded with the fabricated electrodes, and the biocompatibility of CNT/PDMS was also proved. Significance. These electrodes could be used to monitor EEG clinically, in ubiquitous health care and in brain-computer interfaces.
    Journal of Neural Engineering 06/2014; 11(4):046014. DOI:10.1088/1741-2560/11/4/046014 · 3.42 Impact Factor
  • Soo Young Park · Hyun Jae Baek · Kwang Suk Park · Yong Chul Kim
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    ABSTRACT: Objective: A prospective, observational study to investigate how photoplethysmography (PPG) signals change during lumbar sympathetic blockade (LSB), and whether these changes can predict sympathetically mediated pain (SMP). Methods: Patients with unilateral lower extremity pain and self-reported cold hyperalgesia underwent LSB. Bilateral temperature and PPG signals (AC and DC) were recorded. Power spectrum analysis (PSA) was performed. Results: Of the total patient cohort (n=38), eight patients (22.1%) had excellent pain-relief after LSB and were determined to have SMP. In all patients, the PPG AC signal changed immediately after drug administration, before any temperature change. DC signals decreased slowly in a linear fashion. PSA of DC signals showed significantly lower low-frequency/ high-frequency (LF/HF) ratios in the SMP group than the sympathetically independent pain group, both before and after LSB. A cut-off value of 2.92 for LF/HF resulted in sensitivity, specificity and positive predictive values for SMP of 75.0%, 76.7% and 3.21 [1.5, 6.9], respectively. Conclusions: PPG may be used as an early indicator of a successful LSB and could also be helpful in diagnosing SMP.
    The Journal of international medical research 06/2014; 42(4). DOI:10.1177/0300060514532619 · 1.10 Impact Factor
  • Yun-Kyoung Yim · Kwang Suk Park
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    ABSTRACT: The objective of this study is to investigate the effects of short-term bed rest on the radial pulse in healthy subjects. Twenty-one healthy volunteers participated in this study. Their radial pulse was measured at different measuring positions using a multi-step tonometry system. The participants took 30 minutes of bed rest and their radial pulse was measured before and after the bed rest. The effects of bed rest on the radial pulse were analyzed. The pulse area, the amplitudes of h4 and h5, the pulse period, and the diastolic pulse proportion increased with short-term bed rest, whereas the proportions of systolic and hightension pulse and the fundamental frequency of the pulse wave decreased with short-term bed rest. All the changes were in the same direction in both male and female participants at all measuring positions; however, some parameters changed more in women than in men, and some changed more at the distal position than at the proximal position. In shortly, Short-term bed rest induces significant changes in the radial pulse of healthy subjects. The results of this study could be used as a control reference for clinical acupuncture studies with participants lying on a bed for acupuncture treatment.
    Journal of Acupuncture and Meridian Studies 06/2014; 7(3):133-139. DOI:10.1016/j.jams.2013.12.001
  • Min Hye Chang · Hyun Jae Baek · Seung Min Lee · Kwang Suk Park
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    ABSTRACT: A high-frequency steady-state visual evoked potential (SSVEP) has been suggested for the reduction of eye fatigue for SSVEP-based brain-computer interfaces (BCIs). However, the poor performance of high-frequency SSVEP requires a novel stimulus of better performance even with low eye fatigue. As an alternative to the high-frequency SSVEP, we explore the SSVEP response to an amplitude-modulated stimulus (AM-SSVEP) to verify its availability for brain-computer interfaces (BCIs). An amplitude-modulated stimulus was generated as the product of two sine waves at a carrier frequency (fc) and a modulating frequency (fm). The carrier frequency was higher than 40Hz to reduce eye fatigue, and the modulating frequency ranged around the α-band (9-12Hz) to utilize low-frequency harmonic information. Four targets were used in combinations of three different modulating frequencies and two different carrier frequencies in the offline experiment, and two additional targets were added with one additional modulating and one carrier frequency in online experiments. In the AM-SSVEP spectra, seven harmonic components were identified at 2fc, 2fm, fc±fm, fc±3fm, and 2fc-4fm. Using an optimized combination of the harmonic frequencies, online experiments demonstrated that the accuracy of the AM-SSVEP was equivalent to that of the low-frequency SSVEP. Furthermore, subject evaluation indicated that an AM stimulus caused lower eye fatigue and less sensing of flickering than a low-frequency stimulus, in a manner similar to a high-frequency stimulus. The actual stimulus frequencies of AM-SSVEPs are in the high-frequency band, resulting in reduced eye fatigue. Furthermore, AM-SSVEPs can utilize both fundamental stimulus frequencies and non-integer harmonic frequencies including low frequencies for SSVEP recognition. The feasibility of AM-SSVEP with high BCI performance and low eye fatigue was confirmed through offline and online experiments. AM-SSVEPs combine the advantages of both low- and high-frequency SSVEPs - high power and low eye fatigue, respectively. AM-SSVEP-based BCI systems exploit these advantages, making them promising for application in practical BCI systems.
    Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology 12/2013; DOI:10.1016/j.clinph.2013.11.016 · 2.98 Impact Factor
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    ABSTRACT: We developed and tested a system for estimating body postures on a bed using unconstrained measurements of electrocardiogram (ECG) signals using 12 capacitively coupled electrodes and a conductive textile sheet. Thirteen healthy subjects participated in the experiment. After detecting the channels in contact with the body among the 12 electrodes, the features were extracted on the basis of the morphology of the QRS (Q wave, R wave, and S wave of ECG) complex using three main steps. The features were applied to linear discriminant analysis, support vector machines with linear and radial basis function (RBF) kernels, and artificial neural networks (one and two layers), respectively. SVM with RBF kernel had the highest performance with an accuracy of 98.4% for estimation of four body postures on the bed: supine, right lateral, prone, and left lateral. Overall, although ECG data were obtained from few sensors in an unconstrained manner, the performance was better than the results that have been reported to date. The developed system and algorithm can be applied to the obstructive apnea detection and analyses of sleep quality or sleep stages, as well as body posture detection for the management of bedsores.
    11/2013; 17(6):985-93. DOI:10.1109/JBHI.2013.2252911
  • Hyun Jae Baek · Hong Ji Lee · Yong Gyu Lim · Kwang Suk Park
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    ABSTRACT: Purpose Interest in brain computer interfaces (BCI) has recently increased due to the need for quality of life technologies for disabled people. While brain signal processing and its applications have been widely studied for many decades, BCI seldom requires attention to practical and efficient brain signal sensing methods. Noninvasive electroencephalogram (EEG) measurements using wet adhesive Ag/AgCl electrodes are universally employed for BCI, but have limitations in practical acceptability with regard to portability, comfort and aesthetic design. In order to translate the results of laboratory experiments into practical use, EEGs should be recorded easily without requiring scalp preparation and regardless of the presence of hair. Methods In this paper, general requirements for capacitive measurement of EEG are presented and four different frontends for capacitive EEG electrodes are evaluated: (a) basic voltage follower scheme with high value resistor bias network (Rb), (b) voltage follower scheme with active guarding (second op-amp), (c) reverse current of signal diodes to providing bias current, (d) electrode scheme without any external bias network. We explore the use of capacitively-coupled electrodes for BCI technologies through the use of current popular BCI paradigms such as steady state visual evoked potential, P300 and sensory motor rhythm. Results Our experimental results indicate that capacitive electrode technology allows the acquisition of spontaneous EEG signals through hair with average correlation coefficient of 0.7949, 0.7946, 0.6333, 0.6549 for each capacitive electrode at O2 and 0.8433, 0.7822, 0.6253, 0.5427 for each capacitive electrode at C4. Although signal quality is lower and the movement artifacts are larger than those of conventional electrodes, SSVEP was successfully recorded through hair without spectral difference between SSVEP peaks and stimulus peaks except low stimulus frequency (5.45 Hz). P300 responses was measured with significant coefficient of determination (>0.005) except electrode (d). Sensory motor rhythm was suppressed during right hand imagery movement with log ratio value less than zero for all electrodes. Conclusions Further studies are required to apply capacitive measurement technology to uses in diagnostic EEG, but the method can currently be used for simple BCI applications.
    09/2013; 3(3):158-169. DOI:10.1007/s13534-013-0099-6

Publication Stats

1k Citations
164.06 Total Impact Points

Institutions

  • 1997–2015
    • Seoul National University
      • Department of Biomedical Engineering
      Sŏul, Seoul, South Korea
  • 2007–2013
    • Sangji University
      • • College of Health Sciences
      • • Department of Oriental Medical Engineering
      Genshū, Gangwon, South Korea
  • 2001–2013
    • Seoul National University Hospital
      • • Department of Biomedical Engineering
      • • Department of Neurosurgery
      • • Department of Nuclear Medicine
      Sŏul, Seoul, South Korea