The Spatial Filter Of Cardiac Magnetic Signals

Heart is a complicated physical system. Based on the research of cardiacmagnetism, it has become a new trend of science technology to diagnose heartdiseases via detecting the magnetocardiac signals on the body surface. Manycountries pay more and more attention to the research on cardiac magnetism theoryand signals processing.Nowadays, the magnetocardiac signals detected by SQUID are very weak, andthey can be easily affected by noises during the detected process. Not only regularfiltering methods which are based on time domain but also spatial influence ofenvironmental noises on the 36 measuring points over the thorax need to be involvedinto consideration. The research on magnetocardiac signal's spatial filter is veryimportant. Based on single magnetic dipole model and the signals detected by SQUID,two different spatial filter methods are deep researched in this paper. The followingstated are the main tasks of this paper:1. Analyze the characters of cardiac magnetic signals and the effect of environmentnoise on the basis of relevant works about spatial filter methods, and put forwardthe question of cardiac magnetic signal's spatial filter.2. Establish the algorithm of spatial filter on single magnetic dipole model. Estimatedifferent results of spatial filter after adding different magnitude noises on modelmagnetic signals. The SNR(Signal to Noise Ratio) and GOF(Goodness of Fit) arecomputed, and the results prove the validity of spatial filter of cardiac magneticsignals.3. Research the algorithm of spatial filter about wavelet transforms on the base ofsingle magnetic dipole model. Compare the results of three different wavelettransforms' spatial filter by using the cardiac magnetic signals of theory graphmodel. The result shows wavelet Sym7 is better.4. Expand the single time's spatial filter methods to the whole time domain. Giveout the arithmetic of continuous spatial filter. This method is proved by a computer simulation.5. The spatial filter module of magnetocardiac signals is programmed in theenvironment of MATLAB GUIDE. It includes spatial filter of single time point,spatial filter of real cardiac magnetic detecting signal and multi-channels cardiacmagnetic signal of theory model.6. Based on proving single magnetic dipole model, kinds of cardiac magnetic sourcemodel are researched with the help of magnetocardiac information analysissoftware.