Measurement and Modelling of Electric Fields Induced in the Human Body by Temporally Changing Magnetic Fields

Lead Research Organisation: University College London
Department Name: Institute of Neurology

Abstract

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Publications

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Antunes A (2012) Magnetic field effects on the vestibular system: calculation of the pressure on the cupula due to ionic current-induced Lorentz force. in Physics in medicine and biology

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Glover PM (2014) A dynamic model of the eye nystagmus response to high magnetic fields. in Physics in medicine and biology

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Mian OS (2016) Effect of head pitch and roll orientations on magnetically induced vertigo. in The Journal of physiology

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Mian OS (2015) Reconciling Magnetically Induced Vertigo and Nystagmus. in Frontiers in neurology

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Mian OS (2013) On the vertigo due to static magnetic fields. in PloS one

 
Description We have made major contributions towards a deeper understanding of the phenomenon of vertigo that can be experienced by operators and patients in and around MRI scanners. The key findings to emerge from this research are:
• The vertigo is most likely caused by stimulation of the vestibular system of the inner ear.
• Contrary to our initial expectations, we have demonstrated that the mechanism of vestibular stimulation does not rely upon movement within the field or gradient magnetic fields.
• The mechanism is compatible with stimulation of the vestibular system by a homogeneous, static magnetic field causing fluid (endolymph) flow in the semicircular canals under the action of Lorentz forces. This movement of the endolymph mimics natural stimulation of the semicircular canals and gives rise to apparent rotation of the body (vertigo) and involuntary eye movements (nystagmus).
• We constructed a mathematical model of the Lorentz forces and their theoretical impact on fluid flow and pressure changes inside a realistic 3-D model of the vestibular labyrinth. The model predictions were in agreement with empirical data.
• We developed methods to quantify both the vertigo and nystagmus experienced by participants inside a high-field (7 Tesla) MRI scanner.
• The phenomena of vertigo and nystagmus have different properties related to their respective directions of rotation and adaptation with time.
• The directions and magnitudes of vertigo and nystagmus depend on head position with respect to the magnetic field. In the case of vertigo, the direction is modified further by contextual factors. When lying in the scanner, the vertigo is minimised with the neck flexed by about 20 degrees.
• Apparent differences between vertigo and nystagmus can be reconciled to invoke a common mode of stimulation.
Exploitation Route The findings of this research may be used in the future:
• To understand and minimise the discomfort associated with vertigo in patients and operators in a high-field MRI environment.
• To develop a novel physiological tool for investigating peripheral and central mechanisms of vestibular processing in health and disease.
• To inform the interpretation of neuroscience experiments that rely upon the method of functional magnetic resonance imaging (fMRI).
Sectors Healthcare,Pharmaceuticals and Medical Biotechnology
 
Title Lorentz force model 
Description Model of cupular pressure caused by endolymph flow through Lorentz forces produced by high-field magnets in MRI environment. 
Type Of Material Model of mechanisms or symptoms - human 
Provided To Others? No  
Impact Publications; 
 
Title Magnetic vestibular stimulation 
Description Assessment of perceptual effects arising from vestibular stimulation by high-field magnets inside MRI machine. 
Type Of Material Physiological assessment or outcome measure 
Provided To Others? No  
Impact Publications;