Some Investigations For Optimizing Fronts Of Abdominal Potentials Detecting Systems

Success rate of existing abdominal potentials separation is too low to meet the clinical requirements.The fundamental cause for that lies in the very low signal-to-noise ratio(SNR)of the interested signal(such as fetal ECG)in the mixed abdominal potentials.To further improve the separation rate of abdominal potentials signal,we need to exploit potentialities in every steps of the detecting system.In general,bioelectricity detecting system mainly includes two parts:firstly,front part composed of the subject itself,the detection electrode and the interface between them;the other is rear part comprising amplifying and filtering circuit,ADC,various digital processing,storage,communication,display and so on.To address the problems in front part of abdominal potentials detection,some specific research works are carried out in this paper,shown as follows:(1)For optimizing front configuration schemes constituted by different kinds of electrode,conductive paste(liquid)and skin pretreatment,we conducted intensive comprehensive test and comparative study.Three different measuring and evaluating methods were designed;a)method one based on impedance measurement;b)method two based on adjacent points voltage measurement;c)method three based on LMS adaptive filter.Through the test and comparison using those three methods,the optimized scheme of bioelectricity detection front configuration is summarized.This is the second chapter.(2)The most typical clinical application in pregnant women's abdominal potentials detection is separating the fetal ECG.EMG noise is the key influencing factor for fetal ECG signal to noise ratio in pregnant abdominal potentials detection.All three main sources of EMG were:limb muscle,breathing muscle,and abdominal muscle.In Chapter 3,a test system was constructed by our self-developed high precision 8-channel fetal ECG monitor and PC,and was used to test the limb muscle EMG,breathing muscle EMG,and abdominal muscle EMG.By combining R wave detection and template method,we remove ECG signals from the recorded mixed signals.After the calculation and analysis of the residual signals' peak-to-peak values,EMG magnitude from subject's possible situation and its impact on fetal ECG separation could be evaluated.(3)The operation of traditional abdominal potentials detection is tedious.When the test channel number is large,whether the measuring points selection,electrode placing or electrodes loss detection would consume operators' and subjects' a lot of time.Based on a summary of existing various abdominal electrode placement schemes,an efficient,wearable,multi-channel electrode array placement scheme was designed for abdominal fetal ECG detection in Chapter 4.In the end,Chapter 5,the summary of this paper and the outlook of next work are given.