Using PINS pulses to saturate inflow effects on fMRI data at 3 and 7 T

Area of Science:

• Magnetic Resonance Imaging
• Functional Magnetic Resonance Imaging (fMRI)
• Biomedical Engineering

Background:

• Inflow effects, caused by blood magnetization entering imaging slices, can contaminate fMRI signals.
• Existing methods to mitigate inflow effects often involve complex acquisition schemes or are less efficient.

Purpose of the Study:

• To develop and validate a novel method, Power Independent of Number of Slices (PINS) pulses, for suppressing magnetization inflow effects.
• To assess the efficacy of PINS pulses in reducing inflow artifacts in fMRI data at different magnetic field strengths (3T and 7T).

Main Methods:

• Designed and implemented PINS pulses to saturate magnetization in slice gaps prior to each excitation.
• Validated saturation and excitation profiles using simulations and phantom experiments.
• Evaluated inflow suppression using a flow phantom and conducted in vivo fMRI experiments at 3T and 7T.

Main Results:

• PINS pulses effectively saturated magnetization in slice gaps without degrading imaging slice profiles.
• PINS demonstrated superior suppression of through-plane inflow compared to no-gap acquisitions.
• fMRI experiments showed PINS reduced activated voxels by ~25% at 3T and ~10% at 7T, suggesting modulation of spin-echo BOLD signal.

Conclusions:

• PINS pulses provide an effective and efficient method for saturating inflow effects in fMRI.
• The PINS saturation module offers a valuable tool for investigating the contribution of inflow effects in fMRI data analysis.