MagneticallyInduced Electric Fields and Currents in the Circulatory System

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Magnetically-Induced Electric Fields and Currents in the Circulatory System Thomas S. Tenforde National Council on Radiation Protection and Measurements Bethesda, Maryland (USA)

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Topics of Discussion Physical basis of magnetically-induced electric fields and currents associated with blood flow in a magnetic field Demonstration of induced voltages in the circulatory systems of rodents and primates Cardiovascular performance in strong magnetic fields Theoretical modeling of magnetic field interactions with blood flow

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Rat Electrocardiogram in Static Magnetic Fields up to 2.1 Tesla

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Rat Electrocardiogram in a 2 T Static Magnetic Field With Different Orientations

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Telemetered ECG Data From Rat in 1.5-Tesla Static Magnetic Field

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Static Magnetic Field Studies at Flux Densities up to 7.5 Tesla Phospholipid membrane permeability [Radiat. Res. 108, 102-111 (1986); J. Theor. Biol. 133, 385-396 (1988)] Thermoregulation in rodents [Bioelectromagnetics 7, 341-346 (1986)] Effects on electrically excitable tissues Nerve action potential conduction Induced blood flow potentials in rats

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Theoretical Analysis of Magnetic Field Interactions With the Cardiovascular System Using Physiological Parameters Relevant to Humans Kinouchi, Y., Yamaguchi, Y. and Tenforde, T.S. Bioelectromagnetics 17, 21-32 (1996)

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Theoretical Calculations Solve electrodynamic and magnetohydrodynamic equations using finite element analysis method to predict: magnetically-induced fields and currents in aorta (ascending and descending segments) magnetohydrodynamic slowing of blood flow leakage currents passing from aorta into the thoracic region (especially near the sinoatrial node of the heart)

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Induced Current Densities (J) and Magnetohydrodynamic Slowing of Blood Flow Rate

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Other Modeling Considerations in Static Magnetic Field Interactions With Aortic Blood Flow Offsetting effects of magnetically-induced fields associated with oppositely directed blood flows in ascending and descending aortic segments Effect of assuming an infinite versus finite length of the aortic vessel

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Conclusion from Modeling Combined Effects of Induced Fields Associated with Blood Flows in the Ascending and Descending Aortic Segments Offsetting effects on induced electric fields and current densities in nearby cardiac tissues are small (< 10%)

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Conclusions from Modeling Induced Current in Aorta as a Linear Dipole of Finite Length Effects on calculated fields and currents near the aorta are small At body surface effects are larger (predicted value of induced voltage is approximately two times less than the value calculated for an aorta of infinite length)

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Conclusions Based on Theoretical Modeling Magnetohydrodynamic slowing of blood flow rate is small at field levels up to about 10 T (maximum reduction of ~ 5% at 10 T and ~10% at 15 T) Induced voltages and current densities (J) in the aorta are large (maximum J ~ 2.2 A/m2 at 10 T and ~ 3.2 A/m2 at 15 T) Leakage current densities in tissue reach significant levels at > 5 T (maximum J > 100 mA/m2 at sinoatrial node)

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