Noninvasive room temperature instrument to measure magnetic susceptibility variations in body tissue

Abstract

A probe instrument using room-temperature sensor(s) that can measure magnetic susceptibilities variations. The instrument has sufficient resolution to monitor paramagnetic materials in a human body, and preferably iron in a human liver by noninvasively examining patients with iron-overload diseases. The instrument includes room temperature magnetic sensors, and detects the sample, that is the tissue response to an alternating current field applied by an applied field coil. The sensors that can be used include magnetoresistive, fluxgate and magnetoinductive sensors. The applied field coil dimensions are chosen so that the applied field is optimized for maximum response from the liver while minimizing the effects due to the overlying abdominal tissue and at the same time not unduly increasing the sensitivity of the instrument to the lung. To minimize noise introduced in the sensor due to fluctuations in the applied field, the applied field is canceled at the position of the sensor, i.e. the real and imaginary parts of the applied field are canceled. To overcome variations in the sensor output due to fluctuations in the applied field, change in the ambient temperature and mechanical relaxation of the instrument, the sensor-sample distance is modulated. The detector assembly is oscillated while the examined patient remains stationary. The detector's applied field coil is fabricated on a printed circuit board and is attached firmly to a solid nonmetallic support structure forming part of a detector. This improves mechanical and thermal stability, and makes for a precise and inexpensive fabrication of the applied field coil. The detector assembly forms part of a probe instrument for performing noninvasively the paramagnetic concentration of a patient.