Rotary Excitation based imaging of multi-frequency stimulus fields in the human brain: a method for optimization of deep brain stimulation?

Motivation: A Rotary Excitation (REX) based detection method was developed for field calibration of neurostimulation. In future, this non-invasive imaging technique could enable to localize brain regions under multi-frequency interference stimulation and thus to analyze correlation between stimulated cortical and subcortical regions and outcome. Goal(s): Investigate whether REX imaging enables frequency-specific field detection in the presence of multi-frequency magnetic fields. Approach: As a proof-of-concept the MRI gradient system was used to project two magnetic fields (f1=100Hz, f2=200Hz) of locally varying magnitudes onto brain tissue of a healthy subject. Results: Detection and discrimination of the magnetic fields was possible with a spatial resolution of 2x2x5mm. Impact: So far, non-invasive methods for patient-specific imaging of evoking fields induced by deep-brain-stimulation (DBS) do not exist. REX-based imaging could enable structured assessment of stimulation target regions via MRI and thus support the calibration and clinical testing of neurostimulation devices.