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Electromagnetic Fields in Biological Systems
via Fenton reaction, which is the iron-catalyzed oxidation of hydrogen peroxide (H 2 O 2 )
(Conner and Menzies 1995; Markesbery 1997; Koppenol 2001).
In addition to the radical pair mechanism, one of the other established physical
mechanisms is “magnetic induction” (van Rongen et al. 2007). This mechanism originates from the following two types of interaction:
1. Electrodynamic interactions with moving electrolytes: An SMF exerts Lorentz
forces on moving ionic charge carriers and thereby gives rise to induced electric
fields and currents. This interaction is the basis of magnetically induced potentials associated with flowing blood, which have been theoretically analyzed by
Kinouchi, Yamaguchi, and Tenforde (1996). The authors suggest that the sinoatrial node of the heart that controls cardiac pacing is the region most sensitive
to current and calculate that for a field of 5 T the current density in this region
is about 100 mA/m 2 , which is around 10% of the maximum endogenous current
from cardiac electrical activity and rises to around 20% for 10 T. A detailed assessment of the effects of electric fields on cardiac function using computational models of cardiac electrophysiology indicates that whereas fields up to 8 T are unlikely
to affect the heart rate and rhythm, this is not necessarily true for higher fields
(Holden 2005). More recently, however, using a uniform SMF of 0.2 T, Kainz et al.
(2010) successfully demonstrated the experimental and theoretical validation of a
magnetohydrodynamic (MHD) solver for blood flow analysis. The measured voltage value probably induced by MHD signal was 245 μV. The computational MHD
results can then be correlated with the actual measurements. The authors hope to
develop a MHD based biomarker to non-invasively estimate the blood flow for the
evaluation of heart failure.
2. Induced electric fields and currents: Time-varying magnetic fields induce electric
currents in living tissues in accordance with Faraday’s law of induction. Electric
currents may also be induced by movement in an SMF. In particular, motion along
a field gradient or rotational motion produces a change in flux linkage, which
induces an electric current, in contrast to linear motion of the body within a uniform SMF. For linear movement in a gradient field, the magnitudes of induced
currents and associated electric fields increase with velocity of the movement
and amplitude of the gradient. Calculations suggest that such induced electric
fields are substantial during normal movement around or within fields of 2–3 T
(Crozier and Liu 2005) and account for the numerous reports of vertigo, nausea,
and increased levels of magnetic phosphenes experienced by patients, volunteers,
and workers moving in such fields (Schenck et al. 1992; Chakeres and de Vocht
2005; de Vocht, Stevens, et al. 2006; de Vocht, van Drooge, et al. 2006). Glover and
Bowtell (2008) measured in situ surface electric fields induced by typical human
body movements such as walking or turning in the “fringe” magnetic fields of
a whole-body 3-T MRI scanner. These values were 0.15, 0.077, and 0.015 V/m
for the upper abdomen, head, and across the tongue, respectively. A peak electric field of 0.3 V/m was measured for the chest. The speed of movements was
not specified in this study. In a body moving at a constant speed of 0.5 m/s into
a 4-T magnet, Crozier and Liu (2005) estimated the maximum induced electric
Electromagnetic Fields in Biological Systems
via Fenton reaction, which is the iron-catalyzed oxidation of hydrogen peroxide (H 2 O 2 )
(Conner and Menzies 1995; Markesbery 1997; Koppenol 2001).
In addition to the radical pair mechanism, one of the other established physical
mechanisms is “magnetic induction” (van Rongen et al. 2007). This mechanism originates from the following two types of interaction:
1. Electrodynamic interactions with moving electrolytes: An SMF exerts Lorentz
forces on moving ionic charge carriers and thereby gives rise to induced electric
fields and currents. This interaction is the basis of magnetically induced potentials associated with flowing blood, which have been theoretically analyzed by
Kinouchi, Yamaguchi, and Tenforde (1996). The authors suggest that the sinoatrial node of the heart that controls cardiac pacing is the region most sensitive
to current and calculate that for a field of 5 T the current density in this region
is about 100 mA/m 2 , which is around 10% of the maximum endogenous current
from cardiac electrical activity and rises to around 20% for 10 T. A detailed assessment of the effects of electric fields on cardiac function using computational models of cardiac electrophysiology indicates that whereas fields up to 8 T are unlikely
to affect the heart rate and rhythm, this is not necessarily true for higher fields
(Holden 2005). More recently, however, using a uniform SMF of 0.2 T, Kainz et al.
(2010) successfully demonstrated the experimental and theoretical validation of a
magnetohydrodynamic (MHD) solver for blood flow analysis. The measured voltage value probably induced by MHD signal was 245 μV. The computational MHD
results can then be correlated with the actual measurements. The authors hope to
develop a MHD based biomarker to non-invasively estimate the blood flow for the
evaluation of heart failure.
2. Induced electric fields and currents: Time-varying magnetic fields induce electric
currents in living tissues in accordance with Faraday’s law of induction. Electric
currents may also be induced by movement in an SMF. In particular, motion along
a field gradient or rotational motion produces a change in flux linkage, which
induces an electric current, in contrast to linear motion of the body within a uniform SMF. For linear movement in a gradient field, the magnitudes of induced
currents and associated electric fields increase with velocity of the movement
and amplitude of the gradient. Calculations suggest that such induced electric
fields are substantial during normal movement around or within fields of 2–3 T
(Crozier and Liu 2005) and account for the numerous reports of vertigo, nausea,
and increased levels of magnetic phosphenes experienced by patients, volunteers,
and workers moving in such fields (Schenck et al. 1992; Chakeres and de Vocht
2005; de Vocht, Stevens, et al. 2006; de Vocht, van Drooge, et al. 2006). Glover and
Bowtell (2008) measured in situ surface electric fields induced by typical human
body movements such as walking or turning in the “fringe” magnetic fields of
a whole-body 3-T MRI scanner. These values were 0.15, 0.077, and 0.015 V/m
for the upper abdomen, head, and across the tongue, respectively. A peak electric field of 0.3 V/m was measured for the chest. The speed of movements was
not specified in this study. In a body moving at a constant speed of 0.5 m/s into
a 4-T magnet, Crozier and Liu (2005) estimated the maximum induced electric