Ho-Dong Park

Stimulus Artifact Suppression Using the Stimulation Synchronous Adaptive Impulse Correlated Filter for Surface EMG Application

The voluntary EMG (vEMG) signal from electrically stimulated muscle is very useful for feedback control in functional electrical stimulation. However, the recorded EMG signal from surface electrodes has unwanted stimulation artifact and M-wave as well as vEMG. Here, we propose an event-synchronous adaptive digital filter for the suppression of stimulation artifact and M-wave in this application. The proposed method requires a simple experimental setup that does not require extra hardware connections to obtain the reference signals of adaptive digital filter. For evaluating the efficiency of this proposed method, the filter was tested and compared with a least square (LS) algorithm using previously measured data. We conclude that the cancellation of both primary and residual stimulation artifacts is enhanced with an event-synchronous adaptive digital filter and shows promise for clinical application to rehabilitate paretic limbs. Moreover because this algorithm is far simpler than the LS algorithm, it is portable and ready for real-time application.

New Cardiac MRI Gating Method Using Event-Synchronous Adaptive Digital Filter

When imaging the heart using MRI, an artefact-free electrocardiograph (ECG) signal is not only important for monitoring the patient’s heart activity but also essential for cardiac gating to reduce noise in MR images induced by moving organs. The fundamental problem in conventional ECG is the distortion induced by electromagnetic interference. Here, we propose an adaptive algorithm for the suppression of MR gradient artefacts (MRGAs) in ECG leads of a cardiac MRI gating system. We have modeled MRGAs by assuming a source of strong pulses used for dephasing the MR signal. The modeled MRGAs are rectangular pulse-like signals. We used an event-synchronous adaptive digital filter whose reference signal is synchronous to the gradient peaks of MRI. The event detection processor for the event-synchronous adaptive digital filter was implemented using the phase space method—a sort of topology mapping method—and least-squares acceleration filter. For evaluating the efficiency of the proposed method, the filter was tested using simulation and actual data. The proposed method requires a simple experimental setup that does not require extra hardware connections to obtain the reference signals of adaptive digital filter. The proposed algorithm was more effective than the multichannel approach.

Motion Artifact Reduction in Blood Pressure Signals Using Adaptive Digital Filter with a Capacitive Sensor

Motion artifacts can degrade the quality of data measured. In this paper, we suggest a capacitive sensor application which is able to be fabricated easily and employed for adaptive filtering. When the motion artifacts occur, the capacitance varies as well. Thereby, the capacitance data coincide with the motion artifacts. The capacitance data synchronous with the motion artifacts and the corrupted blood pressure signal were applied to the adaptive digital filter so that motion artifacts in blood pressure signal managed to be removed successfully.

A new noise reduction method for oscillometric blood pressure measurement

In this paper, a new noise reduction method was proposed for oscillometric blood pressure measurement. The proposed method uses a capacitive sensor and an adaptive filter to minimize blood pressure measurement error. Noise such as undesired external pressure applied to cuff was focused on. Three types of the distorted oscillation signals (no overlap, non-consecutive overlap, consecutive overlap between the noise and the oscillation) were used to compare the conventional method using linear interpolation and the proposed method using the adaptive filter. The proposed method outperformed the conventional method in the case of consecutive overlap between the noise and the oscillation. The proposed method could be useful for measuring blood pressure in such a noisy environment that the subject is being transported.

A New Acupuncture Point Detection Using the Impedance Measurement System Based on ANF and Phase-Space-Method

In this study, a new method for acupuncture point detection using the impedance measurement system based on the PSM (phase space method) is presented. The developed device has been developed as detectors for acupuncture points which are used for diagnosis and treatment in acupuncture. In this system, multi-frequency current injection and voltage measurements are both performed by the surface electrodes, which are controlled by a microcontroller. Also, the microcontroller process continuous time demodulation of the modulated signal by multi frequency components using the adaptive notch filter. After that, PSM is applied about each frequency using an acupuncture equivalent model which is proposed in the pre-study.

A correction method using a support vector machine to minimize hematocrit interference in blood glucose measurements

Point-of-care testing glucose meters are widely used, important tools for determining the blood glucose levels of people with diabetes, patients in intensive care units, pregnant women, and newborn infants. However, a number of studies have concluded that a change in hematocrit (Hct) levels can seriously affect the accuracy of glucose measurements. The aim of this study was to develop an algorithm for glucose calculation with improved accuracy using the Hct compensation method that minimizes the effects of Hct on glucose measurements. The glucose concentrations in this study were calculated with an adaptive calibration curve using linear fitting prediction and a support vector machine, which minimized the bias in the glucose concentrations caused by the Hct interference. This was followed by an evaluation of performance according to the international organization for standardization (ISO) 15197:2013 based on bias with respect to the reference method, the coefficient of variation, and the valid blood samples/total blood samples within the ±20% and 15% error grids. Chronoamperometry was performed to verify the effect of Hct variation and to compare the proposed method. As a result, the average coefficients of variation for chronoamperometry and the Hct compensation method were 2.43% and 3.71%, respectively, while the average biases (%) for these methods were 12.08% and 5.69%, respectively. The results of chronoamperometry demonstrated that a decrease in Hct levels increases glucose concentrations, whereas an increase in Hct levels reduces glucose concentrations. Finally, the proposed method has improved the accuracy of glucose measurements compared to existing chronoamperometry methods.

Minimization of artifact using adaptive digital filter during the oscillometric blood pressure measurement

Artifacts caused during the oscillometric blood pressure measurement can degrade the quality of data measured. In this paper, the stepped deflation artifact(SDA) and motion artifact have been dealt with. The former and the latter are due to the bleed valve switching and cuff movements, respectively. The adaptive impulse correlated filter (AICF) was applied to remove the stepped deflation artifact. This AICF is performed using a parametric method which use Finite Impulse Response(FIR) structure. A capacitive sensor was utilized in order to minimize the motion artifact caused by cuff movements. A control signal formed from the capacitance data with respect to the motion artifact was applied to the adaptive digital filter. The removal of artifact was worked almost perfectly without reducing the information in the blood pressure pulsation signal.

The Novel Method for the Fetal Electrocardiogram Extraction from the Abdominal Signal

In this paper, we have proposed a new method to extract the fetal ECG from a pregnant womans abdominal signal using least square acceleration (LSA) filter and adaptive impulse correlation (AIC) filter. To evaluate the performance, the proposed method and other fetal ECG extraction techniques were processed using the synthetic and real ECG data and then the results were compared. According to comparative results, the proposed method is powerful and successful for extracting the fetal ECG. It was able to separate perfectly even though the fetal beats overlap with the QRS wave of the maternal beats and to extract fetal ECG using any single-channel abdominal signal measured from pregnant womans abdominal surface. Also, it could be implemented easily by fast computation time and simple structure. It is sure that our method could be useful for portable fetal monitoring system.

Development of Mobile Units and Integrated System for Emergency

In this study, we developed six types of mobile units and an integrated system which can manage vital signs from each unit using Bluetooth wireless communication. The six kinds of mobile unit were so designed that each has different function to be applied according to the condition of patient properly. The mobile units can measure ECG signal of single or 12 channel, blood pressure, pulse and SpO2 signal from a patient. Also, to reduce the uncomfortable measurement, several types of units such as belt type, wrist type and necklace type were designed. Our proposed system can integrate and monitor several biological signals from different patients by using Bluetooth wireless communication simultaneously. The developed system was evaluated in the simulated emergent situation and showed the system can monitor 6 patients in maximum according to the data quality. It showed the possibilities that the developed system can be used effectively for emergency situation or in- or out-hospital transport of patient. In future, with the combination of mobile communication technique, a patient who is in emergency situation can be provided with proper first-aid and a doctor can pile the information of patient and give better diagnosis and treatments

Minimizing MR Gradient and RF pulse Artefacts on ECG Signals for MRI Gating based on an Adaptive real-time digital filter

In Magnetic resonance imaging(MRI), imaging a moving organ such as the heart requires a trigger so that successive scans can be synchronized. In the case of cardiac imaging, the QRS complex of ECG is used as a trigger signal for MRI scan. But, gradient and RF(radio frequency) artifacts which are caused to static and dynamic field in MRI scanner cause interference in the ECG. Also, the signal shape of theses artifacts can be similar to the QRS-complex, causing possible misinterpretation during patient monitoring and false gating of the MRI. In case of using general FIR or IIR band-pass filters for minimizing the artifacts, artifact-reduction-ratio is not excellent. So, an adaptive real-time digital filter is proposed for reduction of noise by gradient and RF(radio frequency) artifacts. The proposed filter for MRI-Gating is based on the noise-canceller with NLMS(Normalized Least Mean Square) algorithm. The reference signals of the adaptive noise canceller are a combination of the noisy three channel ECG signals. Various tests were done on normal volunteers in various scenarios[SE(spin echo), FSE(fast spin echo), TR(transition time), TX-Gain, RX-gain, Spin-echo-degree, soon]. The noise canceller’s performance was measured offline, simulating real-time processing by point-by-point operations. In conclusions, the proposed method showed the acceptable quality of ECG signal with sufficient SNR for gating the MRI and possibility of real time implementation