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Influence of magnetically‐induced E‐fields on cardiac electric activity during MRI: A modeling study
Author(s) -
Liu Feng,
Xia Ling,
Crozier Stuart
Publication year - 2003
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.10639
Subject(s) - thorax (insect anatomy) , magnetic resonance imaging , electric field , magnetic field , work (physics) , sensitivity (control systems) , physics , nuclear magnetic resonance , biomedical engineering , cardiology , materials science , medicine , radiology , anatomy , electronic engineering , quantum mechanics , engineering , thermodynamics
In modern magnetic resonance imaging (MRI), patients are exposed to strong, time‐varying gradient magnetic fields that may be able to induce electric fields (E‐fields)/currents in tissues approaching the level of physiological significance. In this work we present theoretical investigations into induced E‐fields in the thorax, and evaluate their potential influence on cardiac electric activity under the assumption that the sites of maximum E‐field correspond to the myocardial stimulation threshold (an abnormal circumstance). Whole‐body cylindrical and planar gradient coils were included in the model. The calculations of the induced fields are based on an efficient, quasi‐static, finite‐difference scheme and an anatomically realistic, whole‐body model. The potential for cardiac stimulation was evaluated using an electrical model of the heart. Twelve‐lead electrocardiogram (ECG) signals were simulated and inspected for arrhythmias caused by the applied fields for both healthy and diseased hearts. The simulations show that the shape of the thorax and the conductive paths significantly influence induced E‐fields. In healthy patients, these fields are not sufficient to elicit serious arrhythmias with the use of contemporary gradient sets. However, raising the strength and number of repeated switching episodes of gradients, as is certainly possible in local chest gradient sets, could expose patients to increased risk. For patients with cardiac disease, the risk factors are elevated. By the use of this model, the sensitivity of cardiac pathologies, such as abnormal conductive pathways, to the induced fields generated by an MRI sequence can be investigated. Magn Reson Med 50:1180–1188, 2003. © 2003 Wiley‐Liss, Inc.