Peripheral nerve stimulation by gradient switching fields in magnetic resonance imaging.
A heterogeneous model of the human body and the scalar potential finite difference method are used to compute electric fields induced in tissue by magnetic field exposures. Two types of coils are considered that simulate exposure to gradient switching fields during magnetic resonance imaging (MRI). These coils producing coronal (y axis) and axial (z axis) magnetic fields have previously been used in experiments with humans. The computed fields can, therefore, be directly compared to human response data. The computed electric fields in subcutaneous fat and skin corresponding to peripheral nerve stimulation (PNS) thresholds in humans in simulated MRI experiments range from 3.8 to 5.8 V/m for the fields exceeded in 0.5% of tissue volume (skin and fat of the torso). The threshold depends on coil type and position along the body, and on the anatomy and resolution of the human body model. The computed values are in agreement with previously established thresholds for neural stimulation.
So
Poman P M
PP
Department of Electrical and Computer Engineering, University of Victoria, Victoria, BC V8W 3P6, Canada.
Stuchly
Maria A
MA
Nyenhuis
John A
JA
D003198:Computer Simulation; D004558:Electric Stimulation / Q000009:adverse effects*; D004574:Electromagnetic Fields; D055590:Electromagnetic Phenomena; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000009:adverse effects*; D008959:Models, Neurological; D010525:Peripheral Nerves / Q000503:physiopathology* / Q000528:radiation effects*; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods*; D011874:Radiometry / Q000379:methods; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D014915:Whole-Body Counting