Magnetic stimulation of excitable tissue: calculation of induced eddy-currents with a three-dimensional finite-element model

Author

Mouchawar, G.A. ; Nyenhuis, J.A. ; Bourland, J.D. ; Geddes, L.A. ; Schaefer, D.J. ; Riehl, M.E.

Author_Institution

Siemens Pacesetter, Sylmar, CA, USA

Volume

29

Issue

6

fYear

1993

fDate

11/1/1993 12:00:00 AM

Firstpage

3355

Lastpage

3357

Abstract

The eddy-current distribution in a 3-D inhomogeneous model of a dog´s thorax due to time varying fields in magnetic resonance imaging (MRI) x, y, and z-gradient coils and a pair of coplanar coils are calculated. From experimental data of cardiac threshold from a z-gradient coil for a 540 μs rectangular pulse, a current density of 21.5 A/m² was calculated. For a co-planar coil pair, the threshold current density for cardiac stimulation is 19.2 A/m² at a duration of 640 μs. The different conductivities of tissues in the thorax have a significant influence on the eddy-current flow. Calculations combined with measurements will help identify safe levels of pulsed gradient fields in future MRI systems

Keywords

bioelectric phenomena; biomagnetism; eddy currents; finite element analysis; physiological models; 3D finite element model; 3D inhomogeneous model; 540 mus; 640 mus; MRI safety; cardiac threshold; coplanar coils pair; dog thorax; excitable tissue; induced eddy-currents; magnetic resonance imaging; pulsed gradient fields; rectangular pulse; time varying fields; tissue conductivity; z-gradient coil; Biomedical imaging; Coils; Finite element methods; Geometry; Magnetic field measurement; Magnetic fields; Magnetic resonance imaging; Magnetic stimulation; Pulse measurements; Thorax;

fLanguage

English

Journal_Title

Magnetics, IEEE Transactions on

Publisher

ieee

ISSN

0018-9464

Type

jour

DOI

10.1109/20.281174

Filename

281174