Electric Current Imaging by Ultrasonography and SQUID Magnetometry

In this paper, we propose a new method for imaging the distribution of electric currents; this method involves a combination of ultrasonography and SQUID magnetometry. To evaluate this new method, we used a block of gelatin pierced through by a lead wire as a model of a biological object. An electric current was applied to the wire and the magnetic signal generated around the wire was measured by a superconducting quantum interference device (SQUID). At the same time, an ultrasound image of the wire was taken by means of an ultrasound imaging machine. Subsequently, the magnetic field image was aligned with the ultrasound image with respect to the position of marker coils relative to the ultrasound probe. The source of the magnetic signal was localized by solving the inverse problem and visualized on the ultrasound image of the wire. The position error was 2.9 mm. The results demonstrated the applicability of the new technique combining SQUID magnetometry with ultrasound imaging.