Biomagnetic Instrumentation

Within ITAB two different biomagnetic system have been developed, both using superconducting SQUID magnetometers. These systems have been implemented in the frame of an international co-operation among research institutions and companies. The first sensor features 74 sensors, 55 of which are placed on a planar surface, and is used mainly for cardiac measurements, but can be used also for the measurement of the peripheral nerve system; the second one features 165 sensors, 153 of which displaced on a helmet-like surface and is used for magnetoencephalography measurements. The sensing elements are integrated dc-SQUID magnetometers, featuring a field noise of about 5 fT Hz^-1/2. 

The systems, as shown in the figure, is located in a magnetic shielded room, in order to reduce the environmental magnetic noise. The magnetic field is recorded with sampling frequencies up to 10 kHz. The A/D converted data are processed on line by means of an array of DSP, allowing band-pass filtering, decimation and noise compensation.

In the frame of a project supported by the Ministery of University, Research and Technologies to enhance scientific and technological networks, further three new systems will be developed: a 500 channels whole-head neuromagnetometer, a biosusceptometer used to measure the iron concentration in patient organs and a susceptometer for in vitro measurements.

The design of the MEG system will be a advancement of the existing one; the sensing elements will be based on vector modules with the use of references to form software gradiometers.

Biosusceptometers are used  to the study of patients affected by diseases, such as thalassemia or hemocromatosis, that imply severe iron overload. In such instruments, the tissue under investigation is magnetised by an external applied field, while the magnetisation field is sensed by a SQUID, inductively coupled to a gradiometer coil. The shapes of the magnetising and of the sensing coils determine the quality of the spatial response. The design of the biosusceptometer is aimed at improving the instrument sensitivity in the region of the organ under study.