Open-Source Coil Matching Toolbox for Magnetic Stimulation and Other Electromagnetics (COMATOSE)

The coil in transcranial magnetic stimulation (TMS) determines the spatial shape of the electromagnetic field in the head, which structures are concurrently activated, and how focal stimulation is. Most of the readily available coils have been designed intuitively instead of systematic mathematical-physical optimization as there were no methods available at the time. Previous research however demonstrated that these coils are far from optimum, e.g., for pulse energy or efficiency, and leave substantial room for lots of improvements. Techniques for rigorous mathematical optimization have been developed but are only available to very few groups worldwide. This paper presents an open-source toolbox, COMATOSE, to change that situation and make these methods available to a wider community. It incorporates the fundamental formalisms and offers vector space decomposition as well as base mapping as an explicit forward method, which is computationally less demanding than iterative computational optimization but can also form the initial solution for a subsequent optimization run if desired.