Sensitivity Analysis of Circular and Helmet Coil Arrays in Magnetic Induction Tomography for Stroke Detection

Magnetic induction tomography (MIT) is harmless and contactless technique for measuring the conductivity of the biological tissue. MIT could be used for initial diagnosis and continuous monitoring of stroke. Different kinds of coil arrays have been proposed for MIT systems. Previous research results using a circular 16-channel MIT model reported difficulties with detection and measurement of small bioelectric signals. For stroke imaging, a system with a higher sensitivity is required. We aim to improve the sensitivity by increasing the number of coils and placing them closer to the head. In this paper, a helmet type coil array with 31 coils is introduced. For simplicity, the head is modelled as a sphere with white matter as a material. The stroke is simulated as a single inclusion with blood and assigned different sizes and positions. Sensitivity distribution and target response of the stroke were evaluated for the helmet model and compared with the circular MIT system. The simulations and analysis were performed at 10 MHz frequency with different coil pairs. Results from comparison of the two MIT models show that the Helmet coil array provides better spatial sensitivity, which has been estimated to be more than 20 times higher than the circular model. Further, when all coils are taken in account, the recorded sensitivity improvement was in the range of 13-90-fold.