Optically tracked, single-coil, scanning magnetic induction tomography

Recent work has shown that single-coil, magnetic induction tomography (MIT) is useful for visualizing three-dimensional electrical conductivity distributions within biological targets. Coil-induced eddy currents and the associated secondary field are detected as an inductive loss while the coil is relocated to several unique positions and orientations near a target. Image reconstruction is then accomplished by inversion of a convolution integral that quantitatively maps inductive loss with conductivity. Previously, coil position and orientation had to be established by a template, which required assignment of fixed locations for the coil to visit. Here, our existing device is modified so that coil position and orientation are optically tracked while measuring inductive loss. Optical tracking is accomplished via a set of infrared reflective spheres mounted on the same enclosure that supports the coil. The coil center can be tracked with submillimeter accuracy while orientation angle is known to within a fraction of a degree. This work illustrates the use of single-coil MIT in full, position-orientation-tracked scan mode while imaging laboratory phantoms consisting of features having biologically relevant conductivity.