Numerical simulation of intracerebral hemorrhage detection using magnetic induction spectroscopy

Magnetic Induction Spectroscopy (MIS) is an emerging technique for contactless measurement of bioimpedance with promising application in intracerebral hemorrhage (ICH) detection. Here, we report numerical simulations of ICH detection based on the MIS. A novel MIS sensor using two planar rectangular spiral coils (TPRSC) as the exciter with frequency range 120 kHz-9 MHz is proposed for the first time. The exciter can generate an antisymmetric normal magnetic field at the detection sensor, and hence the primary voltage can be canceled theoretically. We construct symmetry-based and asymmetry-based ICH models with realistic anatomic structure and hexahedral discretization feature for numerical simulations. The numerical simulations based on the finite integration technique are conducted in the three-dimensional electromagnetic analysis software CST. The voltage phase spectrum, the phase change spectrum and the relative conductivity change spectrum at different hemorrhage volumes are calculated. We compare sensitivities between the TPRSC-based MIS sensor and the conventional type (CC MIS sensor) which uses the single planar rectangular spiral coil as the exciter. Using the constructed ICH models, the specific absorption rate (SAR) and the internal electric field strength are computed to evaluate the electromagnetic safety of the TPRSCbased MIS sensor. Results show that compared with the CC MIS sensor, the sensitivity of the TPRSC-based MIS sensor for measuring the voltage phase is improved by two orders of magnitude, and for measuring the phase change is improved by more than ten times. The phase change and relative conductivity change spectra for the TPRSC-based MIS sensor demonstrate good separability between different small-volume hemorrhages. In addition, the electromagnetic safety of the TPRSC-based MIS is also superior to that of the CC MIS sensor, which conforms to the IEEE standard and the ICNRP guidelines over a wide range of the amplitude of the excitation current.