Towards direct neuronal current imaging via ultra-low-field MR

TL;DR

This study explores the potential of ultra-low-field MRI for directly imaging neuronal currents, aiming to enhance localization accuracy beyond EEG and MEG, through phantom experiments simulating neuronal activity.

Contribution

The paper develops a measurement setup to detect neuronal magnetic fields with ultra-low-field MRI and identifies the need for doubling the SNR for feasible direct neuronal current imaging.

Findings

Phantom measurements show current SNR is insufficient for direct NCI.

Sensitivity needs to be increased by at least a factor of 2.

Ultralow-field MRI has potential but requires technical improvements.

Abstract

The feasibility of using ultra-low-field magnetic resonance (ULF MR) for direct neuronal current imaging (NCI) is investigated by phantom measurements. The aim of NCI is to improve the current localization accuracy for neuronal activity of established methods like electroencephalography (EEG) or magnetoencephalography (MEG) (~1 cm). A measurement setup was developed addressing the main challenge of reaching the necessary sensitivity in order to possibly resolve the faint influence of neuronal magnetic fields on 1H nuclear spin precession. Phantom measurements close to physiology conditions are performed simulating a specific long-lasting neuronal activity evoked in the secondary somatosensory cortex showing that the signal-to-noise ratio (SNR) of the setup needs to be further increased by at least a factor of 2.