S. Della Penna et al., The use of an inhomogeneous applied field improves the spatial sensitivityprofile of an in vivo SQUID susceptometer, PHYS MED BI, 44(3), 1999, pp. N21-N29
We present a SQUID susceptometer with a non-homogeneous magnetizing field w
hich is null at the sensing coil and increases towards the patient position
with a constant gradient plus a cubic term at large distances. Compared wi
th the magnetizing fields of similar instruments described in the literatur
e, our gradient field enhances the signal due to internal organs with respe
ct to the signal due to superficial tissue. Preliminary measurements have b
een performed on phantoms of known magnetic susceptibility. The advantage o
f using a non-homogeneous field compared with a uniform field has been inve
stigated in the case of a double-layer phantom.