7T Magnetic Compatible Multimodality Electrophysiological Signal Recording System

Abstract

This paper developed a comprehensive magnetic resonance imaging (MRI)-compatible electrophysiological (EP) acquisition system, which can acquire various physiological electrical signals, including electrocardiography (ECG), electromyography (EMG), electroencephalography (EEG) and electrocorticogram (ECoG), and EP recording combined with multimodal stimulation. The system is designed to be compatible with the 7-Tesla (7T) ultra-high field MRI environment, providing convenience for neuroscience and physiological research. To achieve MRI compatibility, the device uses magnetically compatible materials and shielding measures on the hardware and algorithm processing on the software side. Different filtering algorithms are adopted for different signals to suppress all kinds of interference in the MRI environment. The system can allow input signals up to ±0.225 V and channels up to 256. The equipment has been tested and proven to be able to collect a variety of physiological electrical signals effectively. When scanned under the condition of a 7T high-intensity magnetic field, the system does not generate obvious heating and can meet the safety requirements of MRI and EEG acquisition requirements. Moreover, an algorithm is designed and improved to efficiently and automatically remove the gradient artifact (GA) noise generated by MRI, which is a thousand-fold gradient artifact. Overall, this work proposes a complete, portable, MRI-compatible system that can collect a variety of physiological electrical signals and integrate more efficient GA removal algorithms.

Magnetically Compatible Brain Electrode Arrays Based on Single-Walled Carbon Nanotubes for Long-Term Implantation

“…As a result, these large-scale artifacts can overwhelm the LFP signal and are difficult to be removed directly by simple filtering. To mitigate the gradient artifacts, we employed the LOGDAE algorithm [25,29].…”

“…Each volume in the EPI sequence contains 32 slices. Below is the real LFP signal after removing the GA interference by the LOGDAE algorithm [25]. Figure 8b shows the LFP details after removing gradient artifacts from 20 to 25 s in Figure 8a.…”

“…However, there has been limited evaluation of the behavior of brain electrodes under these conditions. The fMRI needs a magnetically compatible brain electrode array, which is difficult because the electrodes can be heated by eddy induced by magnetic field during the MRI scanning, which will hurt brain cells and introduce artifacts into the fMRI images [25]. Zhao et al used graphene-encapsulated copper microwires as fMRI-compatible neural electrodes, which were unable to construct multiple channels due to their curved surfaces, and the copper has a magnetically compatible filament with large eddy currents, a powerful heating ramp-up, and significant artifacts [26].…”