16 Channel magnetic induction tomography system featuring parallel readout

Abstract

Magnetic induction tomography (MIT) allows the reconstruction of conductivity distributions for a wide variety of industrial and medical applications. Philips is interested in using the MIT technique for acquiring information of conductivity distribution and conductivity changes in human tissue. The advantage of this technique is the contactless and non-invasive way of collecting information on the tissue. An MIT system consists of excitation coils that produce a primary magnetic field that causes eddy currents in a conductive object. The eddy current produces a secondary magnetic field that can be detected by an array of receiving coils. This paper presents the setup of a 16 channel MIT system featuring parallel readout of the 16 receiver coil array. To achieve the parallel readout the high-frequency signals used for the measurements are converted to a lower frequency by heterodyne downconversion and then sampled by high quality audio sampling equipment. The sampled low frequency signals are processed by digital signal processing algorithms in a standard computer. This allows the replacement of the commonly used lock-in amplifier and enables the processing of all 16 receiving channels in parallel. In addition to the detailed description of the system major parameters such as drift and noise as well as first reconstructed images are presented. © Springer-Verlag 2007.