An AC magnetizing field biosusceptometer using a SQUID based sensor with additional compensation module

We present a new SQUID based susceptometer for liver iron concentration (LIC) assessment. The instrument is operated with an inhomogeneous AC magnetizing field. The susceptometer is based on 7 channels, each consisting of a sensing unit and of an additional unit for the compensation of the applied field residual and its variation. Each unit is a second order gradiometer and is coupled to a dc SQUID with a parallel washer configuration. The compensation module output is digitally processed and coupled to the sensing gradiometer by means of an additional feedback path. The estimation of LIC is based on a numerical model of the subject's torso obtained from the segmentation of ultrasound images.