Functional MRI of the human motor cortex using single-shot, multiple gradient-echo spiral imaging.

Area of Science:

• Neuroimaging
• Magnetic Resonance Imaging (MRI)
• Functional Magnetic Resonance Imaging (fMRI)

Background:

• Accurate quantification of brain activity in fMRI is crucial.
• Distinguishing blood-oxygen-level-dependent (BOLD) signals from inflow effects remains a challenge.
• High magnetic field strengths offer improved signal-to-noise ratio but require advanced acquisition methods.

Purpose of the Study:

• To enhance the quantification of BOLD and inflow effects in functional brain imaging.
• To accurately estimate T2* relaxation times using a novel multi-slice spiral imaging approach.
• To validate a multiple gradient-echo sampling scheme at high magnetic field strength.

Main Methods:

• Combined a fast multi-slice spiral imaging approach with multiple gradient-echo sampling.
• Acquired eight echoes with echo times (TE) from 5 to 180 ms.
• Achieved an acquisition time of 25 ms per slice with a nominal resolution of 4 x 4 x 4 mm3.

Main Results:

• No significant activation was detected on inflow-sensitive spin-density images.
• Clear activation patterns were observed in the primary motor cortex (M1) and supplementary motor area (SMA) on BOLD-sensitive T2*-maps.
• Calculated average T2* of 46.1±4.5 ms and an average increase (ΔT2*) of 0.93±0.47 ms in activated areas.

Conclusions:

• The multiple gradient-echo approach effectively separates vascular contributions to brain activation in fMRI.
• This method improves the reliability of T2* quantification for functional brain imaging.
• Demonstrated the utility of advanced MRI techniques for precise neuroimaging analysis.