Integrated SSFP for functional brain mapping at 7T with reduced susceptibility artifact

Area of Science:

• Magnetic Resonance Imaging
• Neuroimaging Techniques
• Biophysics

Background:

• Balanced steady-state free precession (bSSFP) is a promising functional MRI (fMRI) tool, but susceptible to banding artifacts.
• Existing bSSFP methods for fMRI are limited by sensitivity to off-resonance effects, hindering widespread application.

Purpose of the Study:

• To introduce and evaluate a novel SSFP-FID sequence, termed integrated-SSFP (iSSFP), designed to overcome banding artifacts in fMRI.
• To demonstrate the feasibility of iSSFP for high-resolution fMRI at 7 Tesla, comparing its performance against standard GE-EPI and bSSFP techniques.

Main Methods:

• Developed the integrated-SSFP (iSSFP) sequence, compressing the SSFP profile to mitigate frequency shift sensitivity.
• Conducted visual stimulation fMRI studies at 7T using iSSFP with varying flip angles (4°, 25°) and TR (9.88ms).
• Employed simultaneous multi-slice (SMS) acquisition with CAIPIRIHNA and iSSFP for a semantic processing task fMRI, comparing against 2D GE-EPI.

Main Results:

• iSSFP demonstrated constant signal magnitude irrespective of frequency shift, effectively eliminating banding artifacts.
• Observed significant functional contrast with iSSFP: 2.48±0.53% (4° FA) and 2.96±0.87% (25° FA) signal changes in activated voxels.
• iSSFP with SMS successfully detected anterior temporal lobe activation, showing reduced susceptibility artifacts compared to 2D GE-EPI.

Conclusions:

• The integrated-SSFP (iSSFP) sequence is a feasible and effective tool for high-performance fMRI at 7T.
• iSSFP offers robust functional contrast while significantly reducing susceptibility artifacts, presenting a valuable alternative to conventional GE-EPI.
• This novel sequence holds potential for advancing neuroimaging research by enabling clearer visualization of brain activity.