A Non-diffractive Radiating System for Safer Transcranial Magnetic Stimulation Treatments

In this paper, a radiative system for Transcranial Magnetic Stimulation (TMS) able to accomplish a focused treatment with a lower electromagnetic field exposure inside the brain tissue is introduced. The proposed radiating system comprises five actively fed and properly loaded RF coils able to shape the magnetic field distribution into a non-diffractive Bessel beam. In this work, we evaluate the Specific Absorption Rate (SAR, W/kg) within the investigated biological phantom, comparing the proposed radiating system against a traditional single-coil arrangement, achieving the same magnetic field amplitude within biological tissues. The numerical results obtained through accurate full-wave simulations show a significant SAR reduction with the focused radiating configuration. In addition, the exposed phantom region is more confined, strongly reducing the overall potential side effects on human health. Therefore, the preliminary results encourage future works, suggesting the possibility to reduce the invasiveness on the patient and improving clinical effectiveness of TMS treatments.