Yi-Li Tseng

Detection of the third and fourth heart sounds using Hilbert-Huang transform

BackgroundThe third and fourth heart sound (S3 and S4) are two abnormal heart sound components which are proved to be indicators of heart failure during diastolic period. The combination of using diastolic heart sounds with the standard ECG as a measurement of ventricular dysfunction may improve the noninvasive diagnosis and early detection of myocardial ischemia.MethodsIn this paper, an adaptive method based on time-frequency analysis is proposed to detect the presence of S3 and S4. Heart sound signals during diastolic periods were analyzed with Hilbert-Huang Transform (HHT). A discrete plot of maximal instantaneous frequency and its amplitude was generated and clustered. S3 and S4 were recognized by the clustered points, and performance of the method was further enhanced by period definition and iteration tracking.ResultsUsing the proposed method, S3 and S4 could be detected adaptively in a same method. 90.3% of heart sound cycles with S3 were detected using our method, 9.6% were missed, and 9.6% were false positive. 94% of S4 were detected using our method, 5.5% were missed, and 16% were false positive.ConclusionsThe proposed method is adaptive for detecting low-amplitude and low-frequency S3 and S4 simultaneously compared with previous detection methods, which would be practical in primary care.

Comparison of Support-Vector Machine and Sparse Representation Using a Modified Rule-Based Method for Automated Myocardial Ischemia Detection.

An automatic method is presented for detecting myocardial ischemia, which can be considered as the early symptom of acute coronary events. Myocardial ischemia commonly manifests as ST- and T-wave changes on ECG signals. The methods in this study are proposed to detect abnormal ECG beats using knowledge-based features and classification methods. A novel classification method, sparse representation-based classification (SRC), is involved to improve the performance of the existing algorithms. A comparison was made between two classification methods, SRC and support-vector machine (SVM), using rule-based vectors as input feature space. The two methods are proposed with quantitative evaluation to validate their performances. The results of SRC method encompassed with rule-based features demonstrate higher sensitivity than that of SVM. However, the specificity and precision are a trade-off. Moreover, SRC method is less dependent on the selection of rule-based features and can achieve high performance using fewer features. The overall performances of the two methods proposed in this study are better than the previous methods.

PORTABLE, REAL-TIME, 12-LEAD ECG MONITORING SYSTEM

This article introduces a wireless 12-lead electrocardiogram (ECG) recording system to monitor high-risk cardiovascular diseases. The design overcomes the limitation of wireless transmission by analog multiplexing. The proposed technique provides three leads of ECG at a time and requires less than 15 sec to display the total 12 leads ECG signals on a remote computer. This increases the chances to discover certain acute symptoms earlier. In addition, the synchronous display of three-lead ECG allows the clinician to survey the ECG from the same plane of the heart. The system is designed with low power consumption and is capable of long-term monitoring.

MINIATURE MODULES FOR MULTI-LEAD ECG RECORDING

Remote monitoring systems for home health care service have become one of the hottest topics recently. Biomedical signals recorded by portable devices can be wirelessly transmitted through the Internet. In this paper, a miniature signal-condition module for ambulatory recording of electrocardiogram (ECG) signals was designed with high input impedance, high common-mode rejection ratio (CMRR), low power, appropriate amplification and filtration, and automatic suppression of offset voltage. For early detection of acute myocardial infarction (AMI), this device is extended and 12-lead ECG recording is available. Due to the modular approach, the module is accommodated for other biomedical signals recording as well if the gain and pass-band of the module are modified.

PEG-TYPE TRANSDUCER FOR TENSION MEASUREMENT OF AN INTACT TENDON OR LIGAMENT IN OPEN REPAIR SURGERY

A suitable tension is critical to good prognoses of surgical repair of injured tendons or ligaments. The existing transducers have limiting roles in measuring the repair tension of intact tendons or ligaments. This study fabricated a sensor to assist surgeons in measuring tension during repair surgery. A peg-type force transducer made from stainless steel served the advantages of easy application and sterilizability. The electrical signals were stabilized by a bridge circuit coupled with two strain gauges. The performances of the system, which were tested by thin and thick silicon tubes, were linear to the applied forces. The results suggest that this system is reliable for force measurement and is beneficial for optimizing the tension of tendons or ligaments during repair surgeries.

MUSCLE FORCE MEASUREMENT SYSTEM FOR LONG-TERM MONITORING DURING DISTRACTION OSTEOGENESIS

Distraction osteogenesis is a procedure in orthopedics for skeletal lengthening. This operation sometimes causes clinical complications such as paralysis and pain related to the rate and extent of distraction. Therefore, a tension-force monitoring system is mandatory to control optimal lengthening. We developed a portable, low-power consumption system to continuously monitor the distracted tensions during the distraction osteogenesis period on the tibias of four male New Zealand white rabbits. The lengthening rate was 1mm per day at frequencies of once a day in one rabbit, and of three successive steps in the others. The system indicates the distraction measured by force, which is considered to be more physiological in nature rather than by distance. Radiographs were also taken for comparison. The results showed that the system was stable and approximate to being ideal. The measured distract-tension recovered to a steady state faster at the frequency of 1mm a day in three steps, rather than once per day. During the duration of the entire operation, each single lengthening induced more extensive force than that of one-day totals. The integer tension gradually increased until 15 days and tended to be stable. The radiographic examinations also revealed that the tibias healed well after the lengthening; consequently, a dispensable X-ray might be mostly replaced by the system monitoring. This system might be helpful to monitor force measurement for the improvement of distraction osteogenesis.

Time-frequency analysis of mismatch negativity in schizophrenia patients in Taiwan

Background: Event-related potentials (ERPs) are currently utilized to study information processing under the influence of neuropsychiatric disorders and are candidate endophenotypes of schizophrenia. However, the traditional ERP approach discards most oscillatory information in the EEG through grand averaging process. This study tried to focus on ERP component of mismatch negativity (MMN) between control and schizophrenia groups in Taiwan. In addition to traditional (grand average) ERP approach, we also compared the time-frequency analysis results of the mismatch negativity. Methods: MMN values were recorded in 55 schizophrenia patients and 42 controls using an auditory oddball paradigm for the duration of the MMN. Besides the traditional grand average approach, the continuous data files were also used for time-frequency analysis via ERP wavelab. Six parameters were explored: event-related spectral perturbation, WTav, avWT, induced activity, intertrial phase coherence and intertrial linear coherence. Results: Traditional ERP approach discovered that group difference occurred in MMN mean amplitude which was compatible with the previous literature. In time-frequency analysis, schizophrenia subjects have lower intertrial phase coherence than controls. Conclusion: Deficit in preattentive sensory information processing, such as MMN, is prominent in Taiwanese schizophrenia subjects. It may also play a role in the basic integrated neural network activity, which could be further explored by time-frequency approach.

Detection of the Third Heart Sound Using Hilbert-Huang Transform

Existence of the third heart sound is an indication of heart failure. In this paper, a novel method is proposed to detect the presence of the third heart sound. A timefrequency analysis method, Hilbert-Huang transform, was used to decompose the signal adaptively and to acquire the instantaneous frequency. Further extraction of the maximal instantaneous frequency and its magnitude is performed to a heart sound signal to distinguish the third heart sound which is usually with lower frequency as well as lower amplitude. A frequency-magnitude distribution was plotted, and the results showed the difference between a normal heart sound and a heart sound with the third heart sound.

PORTABLE ELECTRICAL STIMULATOR FOR URINARY INCONTINENCE

A versatile, low cost, low power electrical stimulator for urinary incontinence is described in this paper. The device is compact with a simple user interface. The device enables precise adjustments to the frequency, pulse width, mode (burst or continuous), and amplitude of the output current. It is valuable for experimental and clinical applications. Detailed circuit design, complete specification, and test are described.