Analysis of MCG with spatial filter method

Magnetocardiogram (MCG) mapping is a new promising non-invasive tool for obtaining functional information concerning the electrical activities of the heart. Since MCG was first measured by Baule and McFee[1], the MCG has been studied worldwide. In particular, it is known that Cohen and his co-workers measured the MCG by use of a SQUID inside a magnetically shielded room[2] and the technique has been applied to the localization of various bio-electric events in the heart, such as the ventricular preexcitation site in Wolff-ParkinsonWhite (WPW) syndrome patients[3,4], or the late depolarization activity in arrhythmogenic tissue[5,6]. However, MCG has not been widely applied in clinics because the method for obtaining an MCG is cumbersome and the liquid helium coolant is expensive. For these reasons, high-Tc SQUID has been receiving attention as a diagnostic technique for observing the electrical activities of the heart. In the measurement of the High-Tc SQUID, the sensitivity is lower than the Low-Tc SQUID and the surrounding noise and the measurement errors will easily influence measured results and estimation of signal source. We try to use the spatial filter method (SFM) in signal analysis of MCG to reduce the influence of noise. The results were very satisfactory. In this paper, a 16-channel high-Tc SQUID magnetometer was used in the measurement of the current dipole and MCG of ten normal subjects and four patients with myocardial infarction. The results of the simulation and actual measurement demonstrate the SFM method is useful for researching of biomagnetic signals and is helpful in reducing the influence of noise and signal source error.