Discussion of Biomagnetic Noise Processing with 3-D Reference Coil and Adaptive Filter

Somatosensory evoked field (SEF) using a 39-channel SQUID system was carried out. We proposed a new method for improving the signal-to-noise (SN) ratio. The proposed method, combining a reference coil (hardware) withadaptive filter (ADF) processing (software), was applied to the SEF data. First, independent component analysis (ICA) was applied to the SEF data, and correlation coefficient between each independent component and measureddata with the reference coil was calculated. Second, the adaptive noise processing was applied to frequencycomponents obtain by the discrete wavelet transform (DWT). The SN ratio of averaged SEF data obtained by proposed method was improved than ordinary averaging method. We confirmed that the proposed method, combining information of the hardware (reference coil) and the software technique (the ICA and the ADF) is useful to improve the SN ratio of the SEF data.