Abstract
Stimulation of deep brain structures by transcranial magnetic stimulation (TMS) is a method for activating deep neurons in the brain and can be beneficial for the treatment of psychiatric and neurological disorders. To numerically investigate the possibility for deeper brain stimulation (electric fields reaching the hippocampus, the nucleus accumbens, and the cerebellum), combined TMS coils using the double-cone coil with the Halo coil (HDA) were modeled and investigated. Numerical simulations were performed using MIDA: a new multimodal imaging-based detailed anatomical model of the human head and neck. The 3D distributions of magnetic flux density and electric field were calculated. The percentage of volume of each tissue that is exposed to electric field amplitude equal or greater than 50% of the maximum amplitude of E in the cortex for each coil was calculated to quantify the electric field spread (V50). Results show that only the HDA coil can spread electric fields to the hippocampus, the nucleus accumbens, and the cerebellum with V50 equal to 0.04%, 1.21%, and 6.2%, respectively.
Highlights
Transcranial magnetic stimulation (TMS) is a noninvasive and painless method for activating neurons in the brain and can be used as a probe of higher brain functions and an intervention for neurological and psychiatric disorders [1]
The Halo coil has been designed to increase the magnetic field at depth in the brain when used together with the existing Fo8 and circular coils typically used for TMS [9, 12]
The coil design will be a combination of two TMS coils mostly used to increase the deep penetration of the electric field: the double-cone coil and the Halo coil
Summary
Transcranial magnetic stimulation (TMS) is a noninvasive and painless method for activating neurons in the brain and can be used as a probe of higher brain functions and an intervention for neurological and psychiatric disorders [1]. Locations of activation in the brain are related to the area where the induced electric field is maximal These locations, in turn, depend on the coils’ placement and geometry as well as the head model for simulation studies [13]. Deng et al [15] published a BioMed Research International comprehensive study using spherical human head model to quantify the electric field focality and depth of penetration of various TMS coils. Guadagnin et al [14] recently published an extensive study providing a characterization of the induced E distributions in the brain of a realistic human model (Ella V1.3 from the Virtual population [21] containing consists of 76 different tissues in the whole body) due to various coil configurations. The new high resolution model (up to 500 μm) contains 153 structures in the head and the neck and provides detailed characterization of the deep brain tissues with an atlas-based segmentation, which makes the MIDA model among the most advanced imagebased models for anatomical models in the state of the art
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