The Research Of 12-Lead ECG Signal Acquisition And Analysis System

1. IntroductionSince the electrocardiograph(ECG) introduces medical science clinically, Nomatter in the biomedical respect, or in engineering, the recording,processing anddiagnosing technology of ECG have developed at a full speed, and abundantmaterials have been accumulated. In the clinical diagnosis of the heart disease theECG has important value, it can offer objective index for analyzing, diagnosing,treating and guarding of heart disease properly. It not only applies to routineinspection of the cardiovascular disease extensively, but also applies to thefoundation and clinical medical research for special professional personnel, such assportsman, aero-space aircrew, etc, it has very important social value and economicworth and get very extensive application in modern medical science. Nowadays,the processing of ECG signal is still one of the great research targets of biomedicalengineering.With the fast development of computer and medical digital signal processingtechnology, the traditional ECG machine is getting more and more difficult to meetmodern development need of medical science. Its leads are few, but we often need12-lead ECG synchronization record to diagnose the complex heart disease. Itmostly made by tape register and lack to take the files management of ECG datainto account. In display and printing model, it only can print while testing but can'tprint repeatedly. In the signal processing respect, it hasn't digital processing partand can't process well because of many errors existing. Especially, the traditionalECG machine hardly has expert-aided analyzing system and must analyze thesignal by medical expert's experience, without analyzing tools it increases thedifficulties for doctors.So it's a press of modern medical development to explore and researchECG-Signal Analyzing System with high performance.2. Research ContentThe design of ECG signal acquisition and processing system. It mainlyintroduces the characteristic of electrocardiogram signal and the acquisition method,the compound and filter of 12-lead signal, the design of the ECG signal acquisitionmodule, the design of sample module, the storage and communication module. Thearticle also has the study of the ECG signal digital processing method, it includesthe pre-processing of the ECG signal: the realize of the LMS arithmetic, thedetective of QRS, the analysis of arrhythmia. The design of ECG signal analysissoftware includes: the design of 12-lead ECG signal acquisition program, thedesign of storage program, the analysis of wave detective, the management ofpatient's documents and the printing of the ECG .The concrete implementations areas follows:The concrete implementations are as follows:Hardware Circuit design(1) ECG signal acquisition module, Based on the feature of ECG, thefront-level adopts instrument amplifier AD620 to amplify the original signal, it canrestrain the common mode disturbing and improving signal noise ratio. Based onthe feature of disturbing source, filter circuit adopts 50 Hz notch wave falling filterconfigured by double-T net and its Q can be adjusted to meet the need.(2) ECG signal sample module, We use CD4051s to finish the selectioncircuit of multi-path signal and the program-control gain circuit.8 ECG signals willbe sampled time-sharing. The gains will be adjusted according to the different ECGsignal level. We use MAX187 to sample signal. MAX187 is 12-bit serial A/D andhas fewer pins, so it's easy to get high precision and separate from digital circuit,it's the ideal A/D converter for ECG-Signal Analyzing System.(3) Data storage module. This system employed Dual-MCU control pattern.Dual-MCU could ride and write the dual port RAM the same time but not interfereeach other, which ensure the real-time data transmission and stability.(4) Data communication module design. MCU controlled communication andtransmission, employed serial port bus to exchange data with PC. The systemreduced costs and raised the performance -price ratio while the ECG signaltransmission is not distortion.The Studies of ECG Data Processing Method(1) Adaptive arithmetic restrained power line interference. This paperdesigned normalized adaptive arithmetic filter power line interference in ECGsignal.(2) ECG wave detection. The paper employed moving windows integralarithmetic to detect and identify QRS complex.(3) Arrhythmia analysis. This paper analyzed the results of detection withiatrology principle to conclude the arrhythmia, which provided diagnoses basis fordoctors and nurses.The Software Designing of ECG-Signal Analysis SystemThe designing of bottom data-acquisition board program and the real-timedata-acquisition module of ECG signal adopt timing-trigger mode to start A/Dconverting, adapt the interrupting mode to acquire data and serial interface toexchange data with computer. All these modules are written by assemble language.The designing of the bottom-driving program in system software, the part canaccomplish the transfer between serial interface and computer. The part combiningwith the assemble language of bottom board accomplish the data transfer. Thedesigning of user' graphical interfaces program, the part accomplish theestablishment,management,inquiry of patients' cases database and the display andplotting of patients' ECG.. The foundation of ECG waveform expert auto-analyzingsystem, it offers convenient and direct auto-measuring tools for doctors to read theECG, it implements computer-aided diagnosis and analysis function, it can offercase statistics analysis function for doctor.3. ConclusionThe paper finished the designing work for 2-Lead ECG-Signal Acquisitionand Analysis System by hardware and software design. The ECG signal samplingof the system not only meet the index of the hospital, but also the conceivingfunctions at the beginning of the design such as: displaying the ECG waveform,analyzing the waveform, judging the pathological changes, giving the diagnosisconclusion, helping expert to analyze cases, classifying and saving the patients'data.