Whole brain, high resolution spin-echo resting state fMRI using PINS multiplexing at 7 T

Area of Science:

• Neuroimaging
• Magnetic Resonance Imaging
• Brain Activity Analysis

Background:

• Resting-state functional MRI (fMRI) is crucial for understanding brain function.
• High-field MRI (7 Tesla) offers enhanced signal-to-noise ratio but faces technical challenges.
• Gradient echo EPI sequences often suffer from signal voids in certain brain regions.

Purpose of the Study:

• To demonstrate the efficacy of spin-echo EPI for resting-state fMRI at 7 Tesla.
• To achieve whole-brain coverage with high spatial resolution.
• To overcome signal void limitations inherent in gradient echo acquisitions.

Main Methods:

• Utilized spin-echo EPI with a short repetition time (1860 ms) enabled by slice multiplexing.
• Employed the power independent of number of slices (PINS) technique to manage radiofrequency power deposition.
• Applied in-plane parallel imaging techniques to reduce image distortion and achieve high in-plane resolution (1.5 mm).
• Performed group-level independent component (IC) analysis and dual regression for single-subject analysis.

Main Results:

• Achieved whole-brain coverage with 84 slices of 1.6 mm thickness.
• Acquired data from six subjects in just over 15 minutes per subject.
• Identified 24 non-artefactual resting-state networks, including novel plausible networks.
• Successfully measured signal from regions typically affected by signal voids in gradient echo acquisitions.
• Demonstrated exquisite grey matter localisation of spatial IC maps at the single-subject level.

Conclusions:

• Spin-echo EPI at 7 Tesla provides high-resolution whole-brain coverage for resting-state fMRI.
• The technique overcomes signal void issues, enabling signal acquisition from previously inaccessible brain regions.
• This method shows significant potential for both resting-state and activation studies at ultra-high field strengths.