Steady-state imaging with inhomogeneous magnetization transfer contrast using multiband radiofrequency pulses

Area of Science:

• Magnetic Resonance Imaging
• Biophysics

Background:

• Inhomogeneous magnetization transfer (ihMT) offers high specificity for myelinated tissue.
• Conventional MT sequences often require separate RF pulses for saturation and excitation.

Purpose of the Study:

• Investigate simultaneous off-resonance saturation and on-resonance excitation using nonselective multiband RF pulses.
• Generate ihMT contrast within rapid steady-state MRI sequences.

Main Methods:

• Developed a matrix-based signal modeling approach for balanced SSFP and spoiled GRE sequences.
• Performed phantom experiments and in vivo human brain imaging using SSFP sequences.
• Validated signal model against experimental data and predictions.

Main Results:

• Signal model accurately predicted phantom data with strong ihMT contrast (RMSE < 2.4%).
• In vivo ihMT ratio images demonstrated expected white matter contrast.
• Observed ihMT ratios aligned with model predictions.

Conclusions:

• Multiband RF pulses can be integrated into spoiled GRE and balanced SSFP sequences for ihMT contrast generation.
• The developed signal modeling approach aids in understanding acquired ihMT signals.