Flexible metasurface for improving brain imaging at 7T.

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Electromagnetics
• Materials Science

Background:

• Ultra-high field (7T) MRI provides exceptional detail for noninvasive brain imaging.
• Field inhomogeneity at 7T causes signal drop in temporal lobes and a bright center, complicating brain visualization.
• Existing methods for improving 7T brain imaging are often complex.

Purpose of the Study:

• To evaluate the efficacy of a metasurface for enhancing 7T brain MRI.
• To improve the homogeneity of the magnetic field distribution within the brain.
• To simplify the investigative workflow for 7T brain imaging.

Main Methods:

• Designed and optimized flexible metasurfaces using copper strips and capacitive elements on an ultra-thin substrate.
• Simulated electromagnetic performance and specific absorption rate (SAR) for metasurface placements near temporal and occipital lobes.
• Assessed in vivo signal-to-noise ratio (SNR) and diagnostic image quality in human volunteers.

Main Results:

• Metasurface placement increased transmit field homogeneity by up to 10.5% in targeted brain regions.
• Specific absorption rate (SAR) efficiency decreased by less than 8%, indicating minimal safety impact.
• In vivo studies confirmed improved field distribution and receive sensitivity in regions of interest.

Conclusions:

• Optimized metasurfaces effectively homogenize the transmit field distribution for 7T brain MRI.
• The lightweight, flexible metasurface design offers a promising approach for higher diagnostic value MR examinations.
• This technology has the potential to significantly improve clinical neuroimaging at ultra-high fields.