Measuring cerebral hemodynamics with a modified magnetoencephalography system.

Area of Science:

• Neuroscience
• Biophysics
• Biomedical Engineering

Background:

• Magnetoencephalography (MEG) traditionally measures neural electrical activity via magnetic fields.
• Cerebral hemodynamics, crucial for brain function, are typically measured by other modalities.

Purpose of the Study:

• To investigate the feasibility of using a modified MEG system to measure cerebral hemodynamics.
• To develop and validate a forward model for simulating magnetic susceptibility changes.
• To assess the system's performance in controlled experiments and human studies.

Main Methods:

• Modification of an MEG system with dc electromagnets to measure magnetic susceptibility.
• Development of a forward model simulating magnetic field interactions with hemodynamic changes.
• Experimental validation using water-filled flask and human subject recordings during the Valsalva maneuver.
• Concurrent measurements with near-infrared spectroscopy (NIRS).

Main Results:

• The forward model accurately predicted experimental results (R(2) = 0.98).
• Significant correlation found between NIRS deoxyhemoglobin signals and modified MEG (SQUID) readouts in human subjects (R(2) = 0.84).
• Increased SQUID noise observed with applied magnetic fields, indicating a technical challenge.

Conclusions:

• The modified MEG system shows promise for noninvasively measuring cerebral hemodynamics.
• The developed forward model is a valuable tool for simulation and analysis.
• Further work is needed to mitigate SQUID noise for optimal performance.