Development Of A Three-dimensional Electrophysiological Positioning System Based On Electric Field

The use of a three-dimensional electrophysiology mapping system as an auxiliary therapeutic tool for radiofrequency ablation is increasing year by year.The study shows that the introduction of a three-dimensional mapping system in the operation can effectively reduce the exposure time of X-ray and reduce the harm to the operator.The existing three-dimensional system of foreign countries is monopolized and cannot be compatible with similar products when interventional radiofrequency ablation is applied,resulting in a significant increase in the cost of surgery,this has played a serious impediment to the popularization and promotion of three-dimensional products.Therefore,it has great social benefit to develop a home-made three-dimensional electrophysiological mapping system with good compatibility and low cost.Compared with previous electrophysiology system,three-dimensional mapping system has the additional function of the positioning,which is the main focus of the research and development in our study.From the existing positioning technology,it is concluded that three-dimensional electric field positioning has the advantages of the best compatibility and the lowest cost of consumables,which is incomparable with other types of products.However,the technology of electric field positioning is also limited by the safety,stability and precision of electric field,and the electric signal is susceptible to interference.This paper mainly aims at the above shortcomings and analyzes the reasons and puts forward the method to solve the problem.In this way,a three-dimensional electrophysiological positioning system based on electric field is designed.The three-dimensional positioning system consists of an electric field generator,a signal amplifier and a main controller.The paper mainly discusses the work of these three parts separately:(1)Split frequency loading mode is designed based on the basic principle of three-dimensional electric field mapping,the electric field generator is realized through DDS(Direct Digital Synthesizer)and the constant current source technology.And isolation and protection circuit is used to limit the output of the electric field generator,so as to ensure the safety of the patients in the operation.In addition,in order to ensure the uniqueness of the electric field positioning,we proposed a phase calibration method to strictly control the initial phase of the output of the electric field generator.(2)The type of input signal amplifier are distinguished.According to the amplitude and frequency characteristics of the signal,the multilevel passive filtering scheme is used to attenuate the RF interference signal.At the same time,the multilevel amplification circuit is used to improve the location and ECG signal gain,and improve the signal-to-noise ratio of the useful signal.In this paper,a method of channel calibration was proposed,which solves the problem of consistency between channels of amplifier circuit,effectively improves the positioning accuracy,and reduces the cost of manufacturing.(3)the main controller of the three-dimensional positioning system is constituted by DSP(Digital Signal Processor)and FPGA(Field-Programmable Gate Array)combination.The basic peripherals of DSP and FPGA are designed and implemented to ensure the normal operation of the main controller.Combined with the rich logic gate resources in FPGA and the design idea of stratification in Verilog language,we have realized clock output,data sampling and data transmission modules.In DSP,the algorithm ideas and implementation process of DFT(Discrete Fourier Transform)to solve the signal amplitude and symbol are described.The paper tested the electric field generator,the signal amplifier and the whole system respectively.The test results show that the electric field generator frequency error in the range of about 0.02%;the error range is less than 1% when the constant current source is connected to the load of 20-1000 ohms;the SNR of the positioning signal is greater than 40db;the overall function of the three-dimensional positioning system is effective.The above tests are in conformity with the design standards,proving that the work carried out in the paper is practical and valuable.