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Effects of various typical electrodes and electrode gels combinations on MRI signal-to-noise ratio and safety issues in EEG-fMRI recording

Gao D., Li M., Li J., Liu Z., Yao D., Li G., Liu T.

Biocybernetics and Biomedical Engineering

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2016

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Vol. 36, no. 1

9--18

EN

To compare the effects of typical Ag/AgCl electrodes and electrode gels on MR images and assess safety hazards for patients during the electroencephalogram (EEG) data simultaneously with functional MRI (fMRI) recordings. So the measurements were conducted to compare the effects of three electrodes, three electrode gels and their combinations on the signal-to-noise ratio (SNR) of MR images at 3 T. Local temperature variation of the phantom for all conditions was also measured in the scanner. Results show that combination of silver-plated copper electrode and electrode gel (composed of carbomer as its main ingredient, with 85% moisture) is best for EEG-fMRI experiments. A sintered Ag/AgCl electrode could also be used as the material of EEG cap if infra-slow EEG-events need to be acquired in EEG-fMRI recording. Additionally, there is no significant heat induction detected. Overall, the methods and results of this study can be used for selecting appropriate EEG electrodes and electrode gels in EEG-fMRI experiments.

2

Absorption enhancement in 1D Ag/SiO2 metallic-dielectric photonic crystals

Chen S., Wang Y., Yao D., Song Z.

Optica Applicata

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2009

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Vol. 39, nr 3

473-479

EN

The one-dimensional Ag/SiO2 metallic-dielectric photonic crystals (PCs) have been prepared. The absorption enhancement effect over the corresponding metal of 1D Ag/SiO2 metallic-dielectric multi-layer structures has been measured. The enhancement effect increases with the number of layers increasing. The origin of this phenomenon and its effect on the transmittance and reflectance have been discussed.

3

Phase variation of fundamental field induced by cascaded second order nonlinear processes in KTP

Hu Y., Yao D.

Optica Applicata

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2005

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Vol. 35, nr 2

403-408

EN

In this paper it has been demonstrated by numerical simulation that the intense second harmonic field induces a nonlinear phase change on a fundamental field simultaneously through the cascaded second-order processes. It has been shown that the phase variation depends on both the propagation distance and the incident fundamental field E1. The phase variation strongly depends on the wavelength of the fundamental field. With the increase of the wavelength of the fundamental field, most of the phase variation induced by the second harmonic wave on the fundamental wave becomes smaller linearly. It has been also shown that there are some nonlinear regimes in the phase variation. For some wavelengths of the fundamental field, there are some peaks of the decrease or increase of the induced phase variation.