Operator Safety and Field Focality in Aluminum Shielded Transcranial Magnetic Stimulation

This paper aims at verifying the effectiveness of the transcranial magnetic stimulation treatment when a passive shield is introduced for the nursing staff safety. The analysis is developed through a modeling approach, splitting the solution of the field problem into two successive steps. The Duke anatomical model of the Virtual Family dataset is used to model both the patient head and the operator body. The investigations are performed by considering stimulators equipped with a circular spiral coil or a figure-of-eight shaped (FoE or butterfly) winding. The addition of the shield slightly reduces the induced electric field values, while increasing the field focality in the patient brain (especially with the circular coil), preserving the effectiveness of the treatment, anyway. On the operators' side, the presence of a passive conductive shield significantly reduces the exposure levels.