New Designs for Deep Brain Transcranial Magnetic Stimulation

Abstract

New applications for transcranial magnetic stimulation are developing rapidly for both diagnostic and therapeutic purposes. Therefore, so is the demand for improved performance, particularly in terms of the ability to stimulate deeper regions of the brain and to do so selectively. The coil designs that are used presently are limited in their ability to stimulate the brain at depth and with high spatial focality. Consequently, any improvement in coil performance would have a significant impact in extending the usefulness of TMS in both clinical applications and academic research studies. New and improved coil designs have been developed, modeled, and tested as a result of this work. A large magnetizing coil, 300 mm in diameter and compatible with a commercial TMS system, has been constructed to determine its feasibility for use as a deep brain stimulator. This coil, used in a Helmholtz configuration, can produce 105 V/m at the surface of the head and 93 V/m at a depth of 15.2 mm compared to a single turn 60 mm coil which produces 82.6 V/m at the surface and only 15 V/m at 15.2 mm. The results of this work have suggested directions that could be pursued in order to further improve the coil designs.