Title :
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
fDate :
11/1/1993 12:00:00 AM
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;
Journal_Title :
Magnetics, IEEE Transactions on
