Analysis and development of transcranial magnetic stimulation devices

Transcranial magnetic stimulation (TMS) is an emerging technique to stimulate neural tissue non-invasively by inducing electric field in the brain with pulsed high-intensity magnetic field. The advantages of stimulating neural tissue in this way have resulted in the technique being rapidly adopted for research and clinical purposes. Advances in the depth and localization of stimulation that TMS can achieve will allow new applications to be established that could replace surgical alternatives. To evaluate the performance of coils used for TMS it is necessary to understand how electric field is induced in neural tissue. To model this phenomenon, numerical methods and anatomically realistic human head models have been employed to accurately determine where neural stimulation will occur. The results of this analysis reveal the simplified homogeneous head models used in earlier studies are unable to correctly predict the distribution of induced electric field at depth in the brain. This method has subsequently been applied to develop novel coil designs to facilitate stimulation of deep-lying brain regions. Additionally, the mechanical stress experienced by TMS coils has been investigated to support further development of combined neuromodulation and neuroimaging systems

Deep brain transcranial magnetic stimulation using variable “Halo coil” system

Transcranial Magnetic Stimulation has the potential to treat various neurological disorders non-invasively and safely. The “Halo coil” configuration can stimulate deeper regions of the brainwith lower surface to deep-brain field ratio compared to other coil configurations. The existing “Halo coil” configuration is fixed and is limited in varying the site of stimulation in the brain. We have developed a new system based on the current “Halo coil” design along with a graphicaluser interface system that enables the larger coil to rotate along the transverse plane. The new system can also enable vertical movement of larger coil. Thus, this adjustable “Halo coil” configuration can stimulate different regions of the brain by adjusting the position and orientation of the larger coil on the head. We have calculated magnetic and electric fields inside a MRI-derived heterogeneous head model for various positions and orientations of the coil. We have also investigated the mechanical and thermal stability of the adjustable “Halo coil” configuration for various positions and orientations of the coil to ensure safe operation of the system

Transcranial magnetic stimulation of mouse brain using high-resolution anatomical models

Transcranial magnetic stimulation (TMS) offers the possibility of non-invasive treatment of braindisorders in humans. Studies on animals can allow rapid progress of the research including exploring a variety of different treatment conditions. Numerical calculations using animalmodels are needed to help design suitable TMS coils for use in animal experiments, in particular, to estimate the electric field induced in animal brains. In this paper, we have implemented a high-resolution anatomical MRI-derived mouse model consisting of 50 tissuetypes to accurately calculate induced electric field in the mouse brain. Magnetic field measurements have been performed on the surface of the coil and compared with the calculations in order to validate the calculated magnetic and induced electric fields in the brain.Results show how the induced electric field is distributed in a mouse brain and allow investigation of how this could be improved for TMS studies using mice. The findings have important implications in further preclinical development of TMS for treatment of human diseases

Transcranial magnetic stimulation: Improved coil design for deep brain investigation

This paper reports on a design for a coil for transcranial magnetic stimulation. The design shows potential for improving the penetration depth of the magnetic field, allowing stimulation of subcortical structures within the brain. The magnetic and induced electric fields in the human head have been calculated with finite element electromagnetic modeling software and compared with empirical measurements. Results show that the coil design used gives improved penetration depth, but also indicates the likelihood of stimulation of additional tissue resulting from the spatial distribution of the magnetic field

Focused and Deep Brain Magnetic Stimulation Using New Coil Design in Mice

Deep brain transcranial magnetic stimulation (TMS) offers promising treatment for neurological disorders that originate from deeper regions of the brain, such as Parkinson\u27s disease. Coils designed for the human head need significant redesigning to stimulate selective regions of the mouse brain for advanced TMS therapy analysis. We report a focused and deep brain TMS coil for mice that is based on a two coil configuration similar to the \u27Halo coil\u27. A heterogeneous MRI derived head model of mouse was used to obtain an electric field of about 150 V/m in selective deeper regions of the brain. Focality of stimulation was quantified using the ratio of half value volume to half value of depth of electric field. A prototype of the final coil design was fabricated and characterized to compare simulated and physical magnetic field profiles

Thermal and Mechanical Analysis of Novel Transcranial Magnetic Stimulation Coil for Mice

Transcranial magnetic stimulation (TMS) has potential to treat various neurological disorders noninvasively and safely. There has been significant work on coil designs for use on the human brain; however, there are fewer reports on the coil design for small animal brains, such as mice. Such work is essential to validate TMS treatment procedures on animals prior to clinical trials. We report thermal and mechanical analysis of a new small-animal coil system designed to produce focused electric fields resulting in more selective deep-brain stimulation. Thermal and magnetic force analyses conducted at experimental TMS operating conditions are used to determine the mechanical stability of the new coil system. Low magnetic linear attraction and rotational forces suggest mechanical stability of the coil. Small temperature increase over a simulated 60 s TMS therapy session indicates that the coil system operates within safe temperature limits. This coil configuration can be used on mice to stimulate selective regions of the brain to study various neurological disorders, such as Parkinson\u27s disease