Energy-efficient Dual-site Transcranial Magnetic Stimulation System with Optimized Magnetic Coils

Dual-site transcranial magnetic stimulation (TMS) is a trending approach for the study of brain connectivity. The common setup of two commercial figure-8 coils for dual-site TMS faces potential limitations such as high energy dissipation, and geometrical intersections of coil bodies due to their large footprint. Furthermore, considering the diversified profundities and sizes of brain targets, it is necessary to customize the stimulation depth and focality of the coil for both targets. In this paper, a magnetic stimulation system with the capability of dual-site stimulation of the human brain is proposed, with optimized coil design for reduced magnetic energy and customizable depth and focality. A prototype coil is fabricated, whose stimulation depth and focality are comparable to the commercial figure-8 coil, with a three-fold energy reduction. The corresponding dual-channel stimulator is designed, with reconfigurable stimulus intensity and inter-channel pulse intervals. The electric field (E-field) on the 70-mm-radius spherical surface representing the human brain is measured with a measurement probe. The simulation and measurement results are in accord with each other. With the proposed system, dual-site TMS can be performed with improved energy efficiency and sufficient freedom on the configuration of E-field. 

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