Towards robust in vivo quantification of oscillating biomagnetic fields using Rotary Excitation based MRI

Area of Science:

• Neuroscience
• Biophysics
• Medical Imaging

Background:

• Functional magnetic resonance imaging (fMRI) offers potential for direct neuronal activity detection.
• Spin-lock techniques are crucial for enhancing sensitivity in fMRI.
• Understanding fundamental effects like Rotary EXcitation (REX) is key for advancing fMRI capabilities.

Purpose of the Study:

• To investigate the fundamental effect of Rotary EXcitation (REX) in spin-lock based fMRI.
• To establish experimental conditions for robust detection of ultra-weak magnetic field oscillations.
• To develop a novel method for emulating brain activity for REX sequence validation.

Main Methods:

• Simulations, phantom experiments, and in vivo studies were conducted to analyze REX.
• An empirical law was derived to predict optimal spin-lock pulse durations for maximum sensitivity.
• A novel concept using MRI gradient systems for brain activity emulation was developed and validated.

Main Results:

• An empirical law for optimizing spin-lock pulse durations was identified.
• Experimental conditions enabling robust detection of weak magnetic field oscillations were established.
• Transmission of Rotary EXcitation (tREX) successfully detected magnetic field oscillations in the nano-Tesla range in brain tissue.

Conclusions:

• REX is a fundamental effect with significant implications for fMRI.
• The developed tREX technique allows for the detection of biomagnetic fields in brain tissue.
• This work paves the way for quantifying biomagnetic fields using advanced fMRI techniques.