Finite-difference time-domain-based studies of MRI pulsed field gradient-induced eddy currents inside the human body

In modern magnetic resonance imaging (MRI), patients are exposed to strong, rapidly switching magnetic gradient fields that, in extreme cases, may be able to elicit nerve stimulation. This paper presents theoretical investigations into the spatial distribution of induced current inside human tissues caused by pulsed z-gradient fields. A variety of gradient waveforms have been studied. The simulations are based on a new, high-definition, finite-difference time-domain method and a realistic inhomogeneous 10-mm resolution human body model with appropriate tissue parameters. it was found that the eddy current densities are affected not only by the pulse sequences but by many parameters such as the position of the body inside the gradient set, the local biological material properties and the geometry of the body. The discussion contains a comparison of these results with previous results found in the literature. This study and the new methods presented herein will help to further investigate the biological effects caused by the switched gradient fields in a MRI scan. (C) 2002 Wiley Periodicals, Inc.

[1]  G. A. Mouchawar,et al.  Magnetic stimulation of excitable tissue: calculation of induced eddy-currents with a three-dimensional finite-element model , 1993 .

[2]  Jianming Jin.  Electromagnetic Analysis and Design in Magnetic Resonance Imaging , 1998 .

[3]  P Mansfield,et al.  Limits to neural stimulation in echo‐planar imaging , 1993, Magnetic resonance in medicine.

[4]  Ian Turner,et al.  The use of a coupled computational model for studying the microwave heating of wood , 2000 .

[5]  O. Gandhi,et al.  Specific absorption rates and induced current densities for an anatomy‐based model of the human for exposure to time‐varying magnetic fields of MRI , 1999, Magnetic resonance in medicine.

[6]  D Simunic,et al.  Analysis of Eddy Currents Originating from Switched Magnetic Gradient Fields in Magnetic Resonance Imaging. Analyse der Wirbelströme, verursacht durch geschaltete magnetische Gradientenfelder während der Kernspinresonanztomographie , 1996, Biomedizinische Technik. Biomedical engineering.

[7]  Michael B. Smith,et al.  SAR and B1 field distributions in a heterogeneous human head model within a birdcage coil , 1998, Magnetic resonance in medicine.

[8]  P R Harvey,et al.  Modular gradient coil: A new concept in high‐performance whole‐body gradient coil design , 1999, Magnetic resonance in medicine.

[9]  Stuart Crozier,et al.  Designs for an asymmetric gradient set and a compact superconducting magnet for neural magnetic resonance imaging , 1999 .

[10]  J.P. Reilly.  Maximum pulsed electromagnetic field limits based on peripheral nerve stimulation: application to IEEE/ANSI C95.1 electromagnetic field standards , 1998, IEEE Transactions on Biomedical Engineering.

[11]  J C Ehrhardt,et al.  Peripheral nerve stimulation in a whole‐body echo‐planar imaging system , 1997, Journal of magnetic resonance imaging : JMRI.

[12]  Pierre-Marie Robitaille,et al.  Biological effects and health implications in magnetic resonance imaging , 2000 .

[13]  Solomon R. Eisenberg,et al.  A three-dimensional finite element method for computing magnetically induced currents in tissues , 1994 .

[14]  L. Weixue,et al.  Computer simulation of epicardial potentials using a heart-torso model with realistic geometry. , 1996, IEEE transactions on bio-medical engineering.

[15]  D M Durand,et al.  Axonal stimulation under MRI magnetic field z gradients: A modeling study , 1997, Magnetic resonance in medicine.

[16]  An Analysis of the Finite-Difference Time-Domain Method for Modeling the Microwave Heating of Dielectric Materials Within a Three-Dimensional Cavity System , 1996 .