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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.
Subject(s)
Calibration , Electromagnetic Phenomena , Equipment Design , Magnetic FieldsABSTRACT
The objective of this study is to explore the possible ways to reduce defibrillation energy and further reveal the mechanism of electric defibrillation. A bidomain simulation study was performed on a rabbit whole-ventricle electrophysiological model and the feasibility of the defibrillation strategy with multi-electrodes stimulation was verified. Simulation results indicate that the new approach is effective in low-energy defibrillation.
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Electric Countershock , Animals , Electrodes , Heart , Heart Ventricles , RabbitsABSTRACT
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.
Subject(s)
Algorithms , Electromagnetic Fields , Phantoms, ImagingABSTRACT
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.
Subject(s)
Electric Countershock , Electric Stimulation Therapy , Electrophysiological Phenomena , Equipment DesignABSTRACT
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.
Subject(s)
Animals , Algorithms , Artificial Intelligence , Body Surface Potential Mapping , Methods , Electrophysiologic Techniques, Cardiac , Methods , Pericardium , Physiology , Signal Processing, Computer-Assisted , SoftwareABSTRACT
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.
Subject(s)
Animals , Dogs , Humans , Algorithms , Arrhythmias, Cardiac , Diagnosis , Electrocardiography , Methods , Entropy , Signal Processing, Computer-AssistedABSTRACT
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.
Subject(s)
Animals , Dogs , Atrial Fibrillation , Diagnosis , Body Surface Potential Mapping , Methods , Electrocardiography, Ambulatory , Electrodiagnosis , Methods , Pericardium , SwineABSTRACT
Objective To find a method for real-time measurement of epicardial electrical activity suitable for clinical application.Method Combined unipolar and bipolar mapping technique for recording epicardial electrical activity was applied to detect the propagation of depolarization wave over the epicardium.Epicardial signals from 4 pigs were sampled simultaneously during sinus rhythm or atrial fibrillation(AF).Result Active isopotential map showing the spread of excitation on epicardial surface was demonstrated and correlation analysis data were obtained.The difference in correlation coefficients between adjacent sites was evident during sinus rhythm(above 0.8) and AF(about(0.5).) Conclusion The result shows that combined unipolar and bipolar technique improves the electrode efficiency and the precision in epicardial mapping.Distribution of depolarization wave or the reentry pathway during complex arrhythmia may be revealed by correlation analysis.
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Objective To explore the mechanism underlying the superiority of the biphasic waveform to monophasic waveform in defibrillation.Method The Luo-Rudy model was adjusted so that it could be used to study defibrillation.Based on the adjusted model the effects of different defibrillation waveforms on cell action potential duration(APD) were studied.Result Biphasic electrical field pulse extended the APD longer than that with monophasic one.Moreover,biphasic waveforms with different strengths could prolong the APD almost equally,while monophasic pulses with different strengths showed different ability to prolong the APD and the spatial distribution of the APD became dispersed.It was also found that the strength of electrical fields pulse contributed much to the change of APD while the duration showed little effect.Conclusion The clinical superiority of biphasic pulses to monophasic pulses in defibrillation is resulted from its ability to prolong the time course of the APD and more importantly,it causes even spatial distribution of the APD.
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Objective To explore a method for real-time pretreatment and character extraction of epicardial signals and promote the research on the electrophysiological mechanism of atrial fibrillation (AF).Methods Firstly,an analysis was made to get the properties of epicardial signals. Then,a method based on template matching was used to extract atrial activities from epicardial signals. At last,the feature points of atrial activities could be recognized.Results The correctness of recognizing feature points of sinus rhythm and AF were 99.7% and 97.0% respectively. Furthermore,only 1~2 s were cost to compute a 10-second data record with this method.Conclusion The proposed method can extract crucial information about atrium depolarization from epicardial signals and is adequate for online analysis.
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Objective To study the complex restitution relation between the present action potential duration (APD) and its previous diastole interval (DI) and APD. Method The Luo-Rudy model was paced with different protocols to draw the coordinate curves between the present APD and its first previous DI. These curves were fit with the artificial neural network (ANN). Result Different pacing protocols caused different coordinate curves, and there was no one-to-one relation between pre-sent APD and its first previous DI. ANN fits these curves satisfactorily. Conclusion There is a complex relation between the present APD and the APDs and Dis of the first three previous beats. This relation can be modeled accurately with ANN.
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Some recently researches have showed that cardiac electrical activities are chaotic during ventricular fibrillation (VF) [1]. It is very difficult to realize the originations and evolvements of these complex activities by used of non-simultaneous mapping techniques. Simultaneous multiple sites epicardial mapping is one of the precise mapping techniques developed in recent years. Fudan University has designed a novel 64/176-channel epicardial mapping system [2]. The new design includes a multi-electrodes patch, 64-channel ECG (electrocardiogram) signal amplifier, 80-channel A/D converter and a PC (personal computer). It uses finite hardware resources to detect depolarization wave from any way, any direction wherever in the whole mapping area. In this article we will discuss the characteristics of the mapping system and some interesting results we have obtained from the animal trials by use of this system.
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Action potential duration (APD) alternans is believed to be a loss of stability and contributes much to the reentry arrhythmias. The purpose of this study is to analyze the stability conditions for one-dimension model and higher dimension model. These criterions are concluded by linear stability analysis in nonlinear dynamics. They should be useful for finding of cardiac control algorithms in low energy defibrillation and the designing of antiarrhythmic drug.
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This Paper brings forward a new technology of EEG Telemetry. Using two FDM channels, the signals can be transmitted through public telephone lines: the EEG signals are transmitted by TDM technology in one channel; the parametes are transmitted to the receiver for identification of data or synchronization in the other channel synchronously. This technology can satisfy almost any routine clinic needs, and also the quahty of transmission is nearly perfect: the distortion is little; distinct noise pollution and shift of base-line do not exist, which is valuable in medical application.