Open AccessField Distribution of Transcranial Static Magnetic Stimulation in Realistic Human Head Model
Author(s) -
Tharayil Joseph J.,
Goetz Stefan M.,
Bernabei John M.,
Peterchev Angel V.
Publication year - 2018
Publication title -
neuromodulation: technology at the neural interface
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.296
H-Index - 60
eISSN - 1525-1403
pISSN - 1094-7159
DOI - 10.1111/ner.12699
Subject(s) - magnet , transcranial magnetic stimulation , magnetic field , field (mathematics) , human brain , head (geology) , nuclear magnetic resonance , physics , computational physics , stimulation , neuroscience , geology , mathematics , biology , quantum mechanics , geomorphology , pure mathematics
Objective The objective of this work was to characterize the magnetic field (B‐field) that arises in a human brain model from the application of transcranial static magnetic field stimulation (tSMS). Materials and Methods The spatial distribution of the B‐field magnitude and gradient of a cylindrical, 5.08 cm × 2.54 cm NdFeB magnet were simulated in air and in a human head model using the finite element method and calibrated with measurements in air. The B‐field was simulated for magnet placements over prefrontal, motor, sensory, and visual cortex targets. The impact of magnetic susceptibility of head tissues on the B‐field was quantified. Results Peak B‐field magnitude and gradient respectively ranged from 179–245 mT and from 13.3–19.0 T/m across the cortical targets. B‐field magnitude, focality, and gradient decreased with magnet–cortex distance. The variation in B‐field strength and gradient across the anatomical targets largely arose from the magnet–cortex distance. Head magnetic susceptibilities had negligible impact on the B‐field characteristics. The half‐maximum focality of the tSMS B‐field ranged from 7–12 cm 3 . Significance This is the first presentation and characterization of the three‐dimensional (3D) spatial distribution of the B‐field generated in a human brain model by tSMS. These data can provide quantitative dosing guidance for tSMS applications across various cortical targets and subjects. The finding that the B‐field gradient is high near the magnet edges should be considered in studies where neural tissue is placed close to the magnet. The observation that susceptibility has negligible effects confirms assumptions in the literature.