The MODEX-mTMS project aimed to move multi-locus transcranial magnetic stimulation, or mTMS, closer to practical use by developing a modular and expandable 3-channel system for adaptive and automated brain stimulation. The original need was clear: current TMS protocols are often user-dependent, not sufficiently personalized, stimulate only one brain target at a time, and target searches can take up to 30 minutes. The project therefore aimed to create a more affordable entry-level mTMS system that could later be expanded by adding electronic modules and new coil sets.
The main objectives were to design and specify a modular, expandable mTMS system; build a 3-channel prototype with matching electronics and a 3-coil set; and verify its performance through electronics testing, calibration, and E-field measurements on a spherical head model. We also aimed to demonstrate automated motor-hotspot and motor-threshold determination, targeting up to a 10-fold speed-up.
The project produced significant progress in system design, electronics architecture, coil development, calibration, and automated stimulation algorithms. The system specifications have been drafted and will be continuously updated from the user’s point of view, including the required number of pulses per second, safe operating duration before excessive heating, maximum electric field, and timing delays. The modular electronics architecture was defined, including improvements intended to reduce the number and cost of components. PCBs and system electronics bus architecture were designed, and ideas were developed for improve the IGBT power-switching circuitry. This work followed the original plan to create a system that can be expanded by adding further electronic modules and coil sets.
In prototype development, progress was more limited than originally planned. A benchtop module was only partly built, and a complete operational 3-channel stimulator prototype was not finished during the action although 3-coil transducers have been designed, manufactured and tested in a collaborative effort. The 3-coil concept remains central to the project: two orthogonal figure-of-eight coils can rotate the induced electric field, while the round coil can move the peak field location. The project also confirmed that product-level development requires higher robustness than a research demonstrator.
Several technical challenges affected the prototype schedule. Delays in obtaining IGBTs slow electronics work. Coil heating remains a challenge, especially for repetitive stimulation. Mechanical strength is another important issue: work with existing 5-coil sets showed that strong forces between stacked coil layers are a significant design challenge in multi-coil systems. These issues were already recognized as risks in the proposal, including possible component delays, coil heating, and the durability of curved coil sets. Manufacturability, rapid charging, power switching, and embedded software were not considered major blocking issues, although software refinements continued and extra effort had to be put on the methodology of calibration mTMS pulse strengths because of nonlinearities in the system when high electric currents are switched.
Human-subject algorithm development and testing were performed using the existing 5-coil mTMS system. Motor-evoked potentials were recorded from hand muscles, and the work demonstrated that a 10-fold increase in the speed of determining the cortical motor hotspot can be achieved with the new automated technology. This directly supports one of the main goals of the project, namely to reduce operator dependence and speed up TMS targeting.
Based on our understanding of dynamical system and control theories, we have reason to believe that repetitive multi-locus stimulation is more effective than single-target stimulation in modulating cortical excitability or connectivity and in depression and other therapies; however, this remains to be demonstrated. Manuscripts are currently under preparation.
The project advanced the technical basis for a modular and expandable mTMS system; we have also confirmed the value of automated stimulation algorithms. This project also helped in getting the technology previously developed in the ERC Synergy project ConnectToBrain and commercialization plans to a level that it was possible to found a startup company and get pre-seed funding for it. The company became fully operational in December 2025; it will continue the technical development that was done in the MODEX-mTMS project, with the aim of introducing a commericial mTMS system by the end of 2026.
