A comparison and evaluation of reduced-FOV methods for multi-slice 7T human imaging

Area of Science:

• Magnetic Resonance Imaging (MRI)
• High-Field Imaging
• Neuroimaging

Background:

• Reduced field-of-view (FOV) techniques are crucial for high-field MRI.
• Optimizing these methods at ultra-high fields (7T) presents unique challenges.
• Existing techniques require evaluation for efficacy and safety in human imaging.

Purpose of the Study:

• To implement, optimize, and evaluate diverse reduced FOV MRI techniques at 7T.
• To compare quantitative performance metrics including SNR, SAR, and artifact levels.
• To establish a foundation for localized small FOV human imaging at 7T.

Main Methods:

• Implementation and optimization of selective Inner-Volume Imaging (IVI) and Outer-Volume Suppression (OVS) methods.
• Utilized composite excitation, adiabatic refocusing RF pulses, and frequency-modulated pulses.
• Quantitative comparison in phantoms and in vivo using SNR, SAR, artifact assessment, and image quality.

Main Results:

• B1 inhomogeneity corrections improved SNR and reduced artifacts but increased SAR.
• Multi-slice IVI sequences with pulse reordering enhanced SNR compared to conventional methods.
• Evaluated signal losses in multi-slice IVI scans across varying slice numbers.

Conclusions:

• Optimized reduced FOV MRI techniques show promise for localized 7T human imaging.
• Careful pulse sequence design and B1 correction are key for high-field performance.
• This work provides a quantitative basis for selecting and applying reduced FOV methods at 7T.