Suppression of Environmental Noise in Magnetopneumography by the Use of Higher Order Gradients

Magnetopneumography is a noninvasive method for examining contamination of metal workers' lungs by ferromagnetic dusts. Our aim is to estimate not only total amount but also spatial distribution of the dust. We use fluxgate magnetometer for measuring remanent field of contaminated volume (current experiments are mostly on phantoms). For earlier experiments we used a simple 6-channel magnetometer with improvised probe holder and we used multiple first order gradients. However, geometrical and other instabilities forced us to upgrade both the mechanical assembly and the fluxgate electronics. The environmental noise from relatively close sources is apparent even in first order gradients and thus—now with more stable electronics—we evaluated second order gradients in order to obtain a better signal.