Parallel RF transmission with eight channels at 3 Tesla.

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Radiofrequency (RF) Engineering
• Biomedical Engineering

Background:

• B1 field inhomogeneity is a significant challenge in high-field MRI, affecting image quality and scan speed.
• Parallel excitation techniques aim to overcome these limitations by using multiple RF channels simultaneously.

Purpose of the Study:

• To design and demonstrate spatially selective RF waveforms for parallel excitation using an eight-coil transmit array.
• To achieve desired spatial target profiles for 2D and 3D k-space excitation with simultaneous RF transmission.

Main Methods:

• Utilized measured excitation profiles of individual coils in a dedicated eight-coil transmit array.
• Employed low-flip-angle pulse design for 2D and 3D k-space excitation with simultaneous eight-channel RF transmission.
• Validated experimental results against simulations based on measured coil maps.

Main Results:

• Successfully designed and demonstrated spatially selective RF waveforms for parallel excitation.
• Achieved high-resolution in-plane spatial patterns for 2D excitation and uniform slice selection for 3D excitation.
• Demonstrated acceleration of 2D excitation by factors of 2-8 with excellent agreement between experimental results and simulations.

Conclusions:

• Multichannel parallel RF excitation is effective in achieving desired spatial profiles and accelerating MRI scans.
• This technique shows promise for robust and routine human studies at very high field strengths, mitigating B1 inhomogeneity.
• Parallel RF transmission is a critical development for advanced MRI applications.