The effect of applying orthogonal projection technique in short window segments to obtain fetal magnetocardiogram

Non-invasive recordings of fetal heart and brain have been possible for almost a decade with the advancement in biomagnetic sensors using the SQUID (Superconducting Quantum Interference Device) technology. Techniques such as orthogonal projection and ICA have been applied to attenuate interference from other biological sources such as maternal heart. Successful application of such techniques among other factors depend on the non-stationary characteristics of the signals. To minimize the effect of non-stationarity due to maternal and/or fetal movement in long duration datasets, we proposed to investigate the minimal time window that is needed to obtain averaging with good SNR to apply the orthogonal projection technique to attenuate maternal magnetocardiogram (MCG) and obtain fetal MCG. The quantifying measure is based on spectral power of signals from 151-channel SQUID array system.