InVesalius Navigator, a free and open-source software for navigated transcranial magnetic stimulation

Neuronavigation and transcranial magnetic stimulation (TMS) are valuable tools in clinical and research environment. Despite the well-accepted importance of both techniques, high-cost and low portability of neuronavigation systems, and limited spatial accuracy of TMS in targeting brain structures limit their applications. Furthermore, existing TMS neuronavigation software programs are not compatible with multiple tracking devices, and do not provide an easy-to-implement platform for custom tools. To overcome such limitations, we developed the open-source, free software InVesalius Navigator for navigated TMS (https://www.cti.gov.br/en/invesalius). A point-based, co-registration algorithm and a guiding interface were designed for tracking any TMS coil relative to an individual’s anatomy. The InVesalius Navigator provides communication with multiple tracking devices, tools for structural image processing, and online TMS coil tracking, all combined in a user-friendly interface. Localization, precision errors, and repeatability were measured for the spatial trackers Patriot (Polhemus Inc.) and MicronTracker Sx60 (ClaroNav Inc.). Additionally, errors were measured in commercial navigated TMS systems NBS 3.2 and 4.3 (Nexstim Plc.). InVesalius Navigator provided a localization error of about 1.5 mm, and repeatability of about 1 mm for translation and 1° for rotation angles. Our results are within the limits established in the literature and similar to those achieved with the NBS systems. The developed software provides a flexible platform aiming to fulfill the needs of research and clinical requirements, expanding the use of navigated TMS throughout the community. Finally, InVesalius Navigator might improve the reliability and spatial accuracy of non-invasive brain stimulation measurements.