Gu-Young Jeong

Design of Ambulatory ECG Monitoring System to detect ST pattern change

In this paper, we describe the hardware configuration for the ambulatory ECG monitoring device and the algorithm for detection of ST pattern change. The ambulatory ECG recording are available for diagnosis of the heart diseases such as myocardial infarction, arrhythmia, etc. It especially is important to detect the transient ECG pattern change caused by the unbalance between the oxygen supply and the oxygen demand in the cardiac muscle that is called myocardial ischemia. This is one of the reasons why the ambulatory ECG monitoring system is necessary. We designed the portable ECG measurement device with the analysis algorithm. The algorithm analyzes the ECG signal and detects the transient ST changes. The detection of QRS complex is accomplished using its the morphological characteristics such as the steep slope and high amplitude. The developed algorithm detects the ST level change, and then classify the ST shape type using the polynomial approximation. The algorithm finds the least squares curve for the data between S wave and T wave in ECG. This curve is used for the classification of the ST shapes. ST type is classified by calculating the difference between the reference ST type and the least square curve. Through the result from the developed algorithm, we can know when the ST level change occurs and what the ST shape type is. The portable ECG device consists of instrumentation amplifier, multiplexer, micro-controller, filter and transmitter module. The designed ECG device measures ECG with four electrodes on the body and transmits the measured ECG signal to the receiver connected in PC by digital radio way. The available range of wireless communication is 70 m in building and 300 m in open ground

Generation of space grid map by 3D detection of obstacle distribution

In walking guide robot, a guide vehicle detects an obstacle distribution in walking space using range sensors, and generates a space grid map to mapping the obstacle information and the tactile display. And the obstacle information is transferred to a blind pedestrian using tactile feedback. Based on the obstacle information a user plans walking route and controls the guide vehicle. The algorithm of 3-D obstacle detection and the method of mapping the generated obstacle map and the tactile display device are proposed in this paper. The experiment for the 3-D detection of the obstacle distribution using ultrasonic sensors is performed and estimated. The experimental system consisted of ultrasonic sensors (SRF05, Devantech Co. Ltd.) and control system (PCI-6221 DAQ board & LabVIEW, National Instruments Co.). In the experiment, the detection of fixed obstacles on the ground and the detection of down step are performed. The performance for the 3D detection of obstacle distribution and mapping space is verified through the experiment.

ST shape classification in ECG by constructing reference ST set

Abnormal changes in the ST segment of an electrocardiogram (ECG) are very important diagnostic parameters for detecting myocardial ischemia. ST segment analysis requires a long-term ECG recording because of the transient change of the ST segment. Deviations of the ST segment are generally related to myocardial abnormality. In this study, we classify the ST segments by their morphology. First, a set of reference ST shapes is given. The ECG analysis algorithm developed in this study consists of feature point detection and ST shape classification. S wave and J-point detection are performed during the process of feature point detection, and the proposed algorithm classifies the STs into reference ST shapes. To improve the performance of ST shape classification, the rules for the trend of previous beats and the shape type of previous beats are used. The results from the proposed algorithm can provide information on the change in the ST shape. In our evaluation for classification of STs by their morphology using the test ECG data, the global correct rate was 83.14%. The best accuracy of existing ST level detection algorithms are 90% and over. However, considering that ST level detection algorithms cannot show the change of ST morphology; and that there are no studies about the classification of STs by their morphology using a reference ST set, the proposed algorithm is worthy of note.

Analysis of the assistance characteristics for the plantarflexion torque in elderly adults wearing the powered ankle exoskeleton

Ankle exoskeleton with an artificial pneumatic actuator, which is intended for the assistance and enhancement of muscular activity, was developed. In this study, the effectiveness of the system was investigated during plantarflexion motion of ankle joint. To find an effectiveness of the system, the subjects performed maximal voluntary isokinetic plantarflexion contraction on a Biodex-dynamometer. Plantarfexion torque of the ankle joint is assisted by subjects soleus muscle that is generated when ankle joint do plantarflexion motion. We used the muscular stiffness signal of a soleus muscle for feed-forward control of ankle-foot orthosis as physiological signal. For measurement of this signal, we made the muscular stiffness force sensor. We compared a muscular stiffness force of a soleus muscle between with feed-forward control and without it and a maximal plantarflexion torque between not wearing a ankle-foot orthosis, without feed-forward control wearing it and with feed-forward control wearing it in each ten elderly adults. The experimental result showed that a muscular stiffness force of a soleus muscle with feed-forward control was reduced and plantarflexion torque of an ankle joint only wearing ankle-foot orthosis was reduced but a plantarflexion torque with feed-forward control was increased. The amount of a increasing with feed-forward control is higher than the amount of a decreasing only wearing it. Therefore, we confirmed the effectiveness of the developed ankle-foot orthosis with feed-forward control.

Development of portable ECG measurement device and PC software for automatic ST analysis

ECG is used on purpose to keep good health or monitor cardiac function of aged person as well as on purpose to diagnose the disease of heart patients. The ambulatory ECG monitoring system under guarantee of safety and accuracy is very efficient to prevent the progress of heart disease and sudden death. These systems can detect the temporary change of ECG that is very significant to diagnose heart disease such as myocardial ischemia, arrhythmia and cardiac infarction. In this paper, we describe the ECG signal analysis algorithm and measurement system for ECG monitoring. The designed small-size portable ECG device consisted of instrumentation amplifier, micro-controller, filter and RF module. The developed device measures ECG with four electrodes in the body and detects QRS complex and ST level change in real-time. Also it transmits the measured signal to the personal computer. The developed software for ECG analysis in personal computer has the function to detect the feature points and ST level change.

3D detection of obstacle distribution and mapping for tactile stimulation

In walking guide system for a blind pedestrian, it is needed to detect an obstacle distribution in walking space not only 2D but space including pendent and/or protruded obstacles, and feedback to the blind for safe walking. The obstacle information is transferred to a blind pedestrian by a tactile stimulation. Based on the obstacle information a user plans walking route, and controls the walking guide system. In this paper, the methods for a 3D obstacle detection using ultrasonic sensors and mapping to an array type tactile stimulator are proposed. The experiment for the 3D detection of an obstacle distribution using ultrasonic sensors is performed and estimated. The experimental system consisted of ultrasonic sensors and control system. In the experiment, the detection of obstacles on the ground and the detection of down step are performed. The performance for the 3D detection of obstacle distribution and mapping for tactile stimulation are verified through the experiment.

Morphological Classification of ST segment using Reference STs Set

Morphological change of ECG is the important diagnostic parameter to finding the malfunction of a heart. An abnormal ST segment change especially is a very important for finding myocardial ischemia. Long-term ECG recording is needed because an ST change is transient. Accordingly, physicians try to find the transient change of the ST segment. The aim of this study is to classify ST according to its shape type using a polynomial approximation method and the reference STs set. The developed algorithm consists of feature point detection, ST level detection and ST shape classification. The first step of feature point detection is the detection of QRS complex, and this is accomplished using the morphological characteristics of QRS complex such as the steep slope and high amplitude. The other feature points are also detected using their morphological characteristics. The developed algorithm detects the ST level change, and then classifies the ST shape type using the polynomial approximation. The algorithm finds the least squares curve for the data between S wave and T wave in ECG. This curve is used for the classification of the ST shapes. ST type is classified by comparing the slopes between the reference ST type and the least square curve. We applied the developed algorithm to the ECG data in European ST database. Through the result from the developed algorithm, we can know when the ST level change occurs and what the ST shape type is.

Development of ambulatory ECG monitoring device with ST shape classification

In this paper, we describe the hardware configuration for ambulatory ECG monitoring device and the algorithm for detection of ST shape change. Ambulatory ECG recordings are available for diagnosis of heart diseases such as myocardial infarction, arrhythmia, etc. It especially is important to detect the transient ECG pattern changes. The detection of transient ST change caused by myocardial ischemia is one of the reasons why ambulatory ECG monitoring system is necessary. We designed a small-size portable ECG device that consisted of instrumentation amplifier, multiplexer, micro-controller, filter and transmitter module. The device measures ECG with four electrodes in the body and transmits the signal to receiver connected in PC by digital radio way. The developed algorithm detects the ST level change, and then classifies the ST shape type using the polynomial approximation. The algorithm finds the least squares curve for the data between S wave and T wave in ECG. This curve is used for the classification of the ST shapes. ST type is classified by comparing the slopes between the reference ST type and the least square curve. Through the result from the developed algorithm, we can know when the ST level change occurs and what the ST shape type is. And, the result of analysis is used to make control signal that decides when ECG recording begin and when stop.

A Polynomial Approximation Approach for Analyzing ST Shape Change

ST segment is the most important diagnostic parameter to finding myocardial ischemia. Generally physicians make theirs effort to find the change of ST level and shape in ECG to diagnose myocardial ischemia. Most of algorithms that have been developed until now place importance on the ST segment depression and elevation. However, ST change in shape is also good parameter to find a heart disease and it should be considered prudently. The aim of this study is to detect the change of ST in shape using a polynomial approximation method. The developed algorithm finds the least squares curve for the data between S wave and T wave in ECG and calculates the variance of ST shape. An approximate curve of ST is represented by one polynomial over the whole ST or three polynomials for the segmented ST by three parts. The algorithm considers only the relative change of ST shape based on the reference ST, normal shape typically. From the results of the developed algorithm, we can acquire visually the information about the place to include the change of ST shape in the test ECG provided by European ST database

Recognition of obstacle distribution via vibrotactile stimulation for the visually disabled

A tactile display is able to help the walking support system of a visually disabled person. A walking guide system must detect an obstacles distribution in walking space including hanging and/or protruding obstacles, and provide useful feedback for safe walking. In this study, we investigate the applicability of a tactile display to the walking guide. The obstacle information is transmitted to the palm by tactile stimulation. The three dimensional (3D) detection of an obstacles distribution using ultrasonic sensors, the fabrication of a tactile stimulator using vibration motors, and the mapping of the detected results to an array-type tactile stimulator are proposed. An experiment on the recognition of an obstacles distribution via tactile stimulation is performed to evaluate the possibility of a walking guide. In the experimental result, the average recognition rate was 95.14 % (5.73, standard error).