[Design of Electromagnetic Tracking System Using Rotating Magnetic Field Based on DSP].

This paper realized an electromagnetic tracking system based on electrically-controlled rotating magnetic field. A tracking system using the digital signal processor (DSP) as the control processing device was developed, including a controllable constant current source module, a magnetic field source module, a three-axis magnetic sensor and ADC interface circuit. The experimental results verified that each time the system could be stable positioning, average error of position was 0.282 cm, the average error of orientation was 0.696o, the positioning time was 1.572 s. Through calibration and further improvement of the hardware circuit, the performance of the system is expected to further improve.

[Research progress in electromagnetic tracking method].

Electromagnetic tracking is a method to track the position and space attitude of objects utilizing electromagnetic field. In this paper, the main methods during the development of Electromagnetic tracking are summarized and classified according to the magnetic field generation method, the number of magnetic sources and sensors used, the configuration and geometry of them. Tracking algorithm and calibration methods are also discussed. The critical issues during the development of electromagnetic tracking are analyzed, with the hope of helping the further research and application of electromagnetic tracking.

Influences of sites and protocols on inducing ventricular fibrillation: A computer simulation study.

In cardiac electrophysiological study, several electrical stimulation protocols have been employed to induce ventricular fibrillations (VF). In addition, sites of inducing may have different impacts on inducing results as well as different inducing protocols. To study whether VF inducing method is determinant of induced outcome, we simulated VFs induced with different protocols at different sites based on the Wei-Harumi whole heart model. Simulations showed that only certain combinations of pacing protocols and sites could induce sustainable VFs, which had similar frequency distributions. This result suggested that the interactions between protocols and sites determine the odds of successful inducing but once the VF was induced, the pattern was solely determined by inner cardiac properties.

[A design of electrophysiological stimulator].

Electrophysiological stimulator is widely used in study of biological electrical activities. This electrophysiological stimulator is capable of outputting both biphasic and monophasic waveforms with amplitudes within 0V and 30V. The sequence of the biphasic waveforms is alterable and their widths and interval can be respectively arbitrarily modified by the operator. The machine will inform the operator as soon as the charge completes through the indicator and buzzer. The safety of experimental objects is guaranteed by float ground thanks to battery power supply.

Implementation of a novel interpolating method to epicardial potential mapping for atrial fibrillation study.

Epicardial potential mapping is an efficient way to visualize the potential distribution on the epicardial surface. We found in our previous study, that the traditional linear interpolation used for the epicardial mapping may cause errors and distortions in reconstruction of the electric activities on the epicardial surface especially during the atrial fibrillation. In this study, we devoted on the implementation of a 3D interpolating method, and verified it in comparison with another interpolating method as well as studying of the mechanism of vagal atrial fibrillation (AF). In case studying, we analyzed the epicardial data from seven canine cardiac models using this method and found the macro-re-entry during the sustainable AF is more likely due to the dispersion of refractoriness in the myocardium and does not demonstrated the focal patterns at the beginning of AF. This indicated that the electrophysiological characteristics of myocardium might have been changed during the paroxysmal atrial fibrillation (PAF).

Successive ECG telemetry monitoring for preventing sudden cardiac death.

In this paper, a novel successive ECG telemetry monitoring prototype is developed to evaluate the effect of monitoring for those out-of-hospital patient who has serious arrhythmia and/or possesses the risk of sudden cardiac death (SCD). This system has such features as: real-time, continuous, telemetry monitoring, wide range, long distance, and long term etc. The developed prototype consists a pocket-size patient-side monitor and a monitoring center placed in a hospital, which continually collects every patient's ECG through GPRS mobile network and automatically analyzes it, if any danger found, instantly send medical warning message to patient. Based on the subsequent experiments on three volunteers in daily activity situation, the preliminary results indicate three-channel ECGs of each volunteer and his localization information can be real-timely and continuously monitored in the center.

A novel non-model-based 6-DOF electromagnetic tracking method using non-iterative algorithm.

Electromagnetic tracking, a non-fluoroscopic image navigation method most often used in minimally invasive therapy, has prominent advantages and features over the traditional X-ray radioscopy. Using two rotating coils and one 3-axis magnetic sensor, a novel 6 degree of freedom (DOF) electromagnetic tracking method is proposed in this paper. Two alternate rotating magnetic fields are generated in turns by these coils and the moving-around sensor simultaneously detects the magnetic filed flux density in 3 orthogonal directions. As the magnitude of a magnetic field comes to the maximum only when the rotating coil directly points toward the sensor, the spatial position and orientation of the sensor can be determined using triangulation measurement. An embodiment and the corresponding system framework of this method are developed and a non-model-based non-iterative algorithm is presented to calculate the 6-DOF of position and orientation. Moreover, simulation experiments are performed to validate the proposed method. The obtained results show that the averaged position error is 0.2365 cm and the averaged orientation error is below 1 degree away from low resolution area.

Analysis of epicardial mapping electrogram of sustained atrial fibrillation based on Shannon entropy.

The mechanisms of sustained atrial fibrillation (AF) are not well understood. And predicting the development of AF is a problem of great clinical interest. This paper proposed an AF analysis method by evaluating, based on Shannon entropy, the complexity of atrial activation in various AF stages. The first step was to preprocess and characterize electrograms. Then, Shannon entropy analysis and statistical analysis were applied to find the significance of interval entropy in sustained AF. Study results proved that interval entropy presented a degressive tendency in the process of sustained AF and some sites with high activation frequency but low entropy was possibly related to ectopic driver of AF.

[A method of real-time sampling and smooth scrolling in epicardial mapping system].

In order to control real-time sampling and achieve smooth scroll wave in the epicardial mapping system, which has 128 channels and a sampling rate of 2kHz/channel, we have designed a user interface using Direct-Draw in cooperation with multiple-thread technology and extracting method. This method has proven to be feasible in animal experiment.

[A method to automatically analyze and diagnose ambulatory ECG signals for telemonitoring system].

This paper proposes a method of automatic ECG analysis and arrhythmia diagnosis for telemonitoring system. A multi-buffer technique is applied to organize dispersive ECG data. Then, according to second order derivatives of ECG signals, peaks of R waves are automatically detected. Finally, real-time heart rhythm is decided by results of R wave detection. Tests prove that the proposed method is precise, efficient and stable to be applied in real-time ECG telemonitoring system.

[Battery and power management of portable telemonitoring system].

Biomedical Engineering of Electronic Engineering Deparment, Fudan University Shanghai, 200433 Based on the pulse-coded transmitting and wide-band receiving system, this paper describes a research of phase design a special power management circuit according to the particular demands of a real-time and continuously monitor system is essential. Combined with the requirement of voltage and current in separated module, three aspect must be considered, that is, how to select the functional component, how to accomplish voltage converting and how to carry on battery management. The test at last shows that, using this circuit and the 4400 mAh battery the energy utilization is more than 88%, and the work time is more than 20 hours.

[A new shockable rhythm detection algorithm for AED].

EMG, This paper introduces a slope variability algorithm which uses the CU Database and the AHA Database. The sensitivity, specificity, positive predictivity and accuracy are calculated and these values are compared with the results from two earlier detection algorithms. The results show this algorithm is more effective and fast than other algorithms.

[Detecting cardiac arrhythmias based on phase space analysis].

It is important for cardiac therapy devices such as the automated external defibrillator to discriminate different cardiac disorders based on Electrocardiogram analysis. A phase space analysis based algorithm is proposed to detect cardiac arrhythmias effectively. Firstly, the phase space of the signal is reconstructed. Then from the viewpoint of geometry and information theory, the distribution entropy of the point density in the two-dimensional reconstructed phase space is calculated as the features in the further classification. Finally the nearest-neighbour method based on Mahalanobis distance is used to classify the sinus rhythm (SR), supraventricular tachyarrhythmia (SVTA), atrial flutter (AFL) and atrial fibrillation (AF). To evaluate the sensitivity, specificity and accuracy of this proposed method in the cardiac arrhythmias classification, the MIT-BIH arrhythmias database and the canine endocardial database are studied respectively. Experiment results demonstrate that the proposed method can detect SR, SVTA, AFL and AF signals rapidly and accurately with the simple computation. It promises to find application in automated devices for cardiac arrhythmias therapy.

[Design of a flyback switch mode power supply for multichannel electrophysiological stimulators].

In order to supply the multichannel electrical stimulator, a DC-DC flyback switch mode power supply based on a high-performance current mode controller UC3845 has been designed. The experimental results indicate that the power supply has satisfied the demands and can supply the multichannel electrical stimulator and similar apparatuses.

[A denoising method of epicardial potential mapping signals based on ICA].

A new denoising method is presented in the paper, based on the independent component analysis(ICA) and the noise independent component selection measurement which is the dispersivity of the independent component's projection coefficients to each electrode. The results indicate that the method can denoise EPM signals with giving prominence to electrodes' true depolarization signals. So it' s fit well for the EPM system.

[Programmable multichannel electrophysiological stimulator based on MCU and CPLD platform].

According to the instruction of the operator, the designed programmable multichannel stimulator will deliver stimuli with an assigned amplitude and a proper width to the electrode-array in various modes. Each stimulation time is controlled by the internal timer of the MCU, while the stimulated electrodes' spatial parameter is controlled by the CPLD. Having abandoned conventional isolation using the transformer, we have adapted optical coupling and stable float ground connection to achieve the safety standard required by physiological measurements.

[Method and implementation of real-time QRS-waves detection based on wavelet transform].

A method based on wavelet transform has been developed for detecting QRS-waves.The MIT-BIH database is used to evaluate this method, and the accuracy is over 99.5%. Then the method is implanted into the embedded system to implement the real-time detection of ECG. This method has good performances in time-delay and computation.

[Initial study on the characterization of atrial fibrillation in epicardial mapping].

Atrial fibrillation (AF) is a complex and dangerous arrhythmia. The treatment method is still unefficient because of its unknown mechanism. The purpose of our research is to detect the electrical activity on the atria surface and therefore find the optimal technique to characterize AF for clinical application. All kinds of maps are presented clearly and the activity of sinus or AF rhythm can be seen quite differently. The active isopotential map can display the dynamic electrical conduction of the atrium as a movie. Sequentially the vectorgraph shows the direction of depolarization at every moment. Finally statistical results are also very useful for analysis on AF. Statistics of exciting frequency and correlation area show great difference in various channels during AF. "Source" or "sink" may be estimated by interval variance statistics. This study demonstrates the flexibility of the system in AF research. The statistical results can also be adopted to clearly express the characteristics of AF.

[Development of an embedded mobile terminal for real-time remote monitoring of out-of-hospital cardiac patients].

A kind of real-time remote monitoring embedded terminal which is combined with mobile communication technology and GPS localization technology, has been developed. The results of preliminary experiments show that the terminal can transmit ECG signals and localization information in real time and continuously, supply a real-time monitoring of out-of-hospital cardiac patients and trace the patients.

Study of the restitution of action potential duration using the artificial neural network.

It is widely accepted that the APD (action potential duration) restitution plays a key role in the initializing and maintaining of the reentry arrhythmias. The Luo-Rudy II models paced with different protocols showed that the current APD had a complex relation with the previous APDs and diastole intervals (DIs). This relation could not be accurately described by a single exponential function. We used an artificial neural network to formularize this relation. The results suggested that back-propagation (BP) network could predict the current APD from the information of the first three previous beats. This would help provide a target for potential anti-arrhythmic therapies.