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Electromagnetic simulation software is being used to investigate the safety of an important research technique that integrates electroencephalography (EEG) with magnetic resonance imaging (MRI). The integration of these two analysis methods has the potential to improve investigations of brain activity because EEG offers high temporal resolution while MRI offers high spatial resolution. But concerns have arisen about temperature increases in sensitive brain tissues that could be caused by the current induced in the EEG electrodes by the radio frequency (RF) power generated by MRI. Leonardo Angelone and Dr. Giorgio Bonmassar, researchers at the Massachusetts General Hospital/Massachusetts Institute of Technology/Harvard Medical School Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts, simulated the RF power dissipated in the human head in an integrated MRI-EEG software simulation. Their results (Angelone et al. 2004) showed that in particular cases, such as high magnetic MRI fields and use of metallic EEG leads, the specific absorption rate (SAR), which measures tissue exposure to RF, is four to seven times higher than in MRI alone, indicating that power levels need to be reduced in integrated experiments.

One of the most important challenges in brain imaging is to model the sources of brain activity during different visual, auditory or motor tasks. Brain mapping with MRI has the highest spatial resolution of current noninvasive imaging techniques. The spatial resolution of MRI is typically millimeters in the case of human subjects. However, because MRI measures primarily a hemodynamic response with a time constant on the order of seconds, the precise mechanics of information exchange within the brain, which occur on a millisecond scale, remain hidden. EEG, on the other hand, can provide temporal accuracy in the required millisecond range but the spatial accuracy is only on the order of centimeters. Researchers have been working to integrate MRI and EEG in order to combine the spatial resolution available with MRI and the temporal resolution offered by EEG.

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