Magnetically compatible and fiberless fNIRS enables simultaneous multimodal imaging with optically pumped...

Area of Science:

• Neuroscience
• Biomedical Engineering
• Medical Imaging

Background:

• Simultaneous functional near-infrared spectroscopy (fNIRS) and magnetoencephalography (MEG) offer complementary insights into neurovascular coupling.
• Previous implementations used fiber-based fNIRS, which has limitations.
• Fiberless fNIRS is lighter and more flexible but faces magnetic compatibility challenges with MEG.

Purpose of the Study:

• To develop a magnetically compatible, fiberless fNIRS system for integration with optically pumped magnetometer (OPM) MEG.
• To overcome magnetic interference issues for robust multimodal neuroimaging.
• To enable flexible and non-invasive studies of neurovascular coupling.

Main Methods:

• Designed magnetically compatible source/detector optodes for fiberless fNIRS.
• Implemented a multipole moment flexible printed circuit design to suppress magnetic fields.
• Tested the system's magnetic compatibility and impact on OPM sensitivity.
• Demonstrated simultaneous fiberless fNIRS and OPM-MEG acquisition in a somatosensory paradigm.

Main Results:

• The developed optodes and cables generated minimal magnetic fields (<1 nT at ~1 cm), ensuring no measurable impact on OPM sensitivity.
• Achieved >1000-fold suppression of driving-current-induced magnetic fields.
• Successfully captured concurrent hemodynamic (fNIRS) and evoked magnetic (MEG) responses.
• Demonstrated the feasibility and robustness of the integrated fiberless fNIRS and OPM-MEG system.

Conclusions:

• This work presents a novel, magnetically compatible fiberless fNIRS system integrated with OPM-MEG.
• It addresses a key barrier, enabling flexible and non-invasive multimodal neuroimaging.
• Paves the way for advanced neurovascular coupling studies, wearable neuroimaging, and brain-computer interfaces.