Distributing coil elements in three dimensions enhances parallel transmission multiband RF performance: A simulation...

Area of Science:

• Magnetic Resonance Imaging
• Radiofrequency Engineering

Background:

• Simultaneous multislice (SMS) imaging enables faster whole-brain coverage at high field strengths like 7 Tesla.
• Parallel transmission (pTx) techniques are crucial for advanced SMS pulse design.
• Optimizing radiofrequency (RF) coil arrays is key to managing specific absorption rate (SAR) and excitation performance in pTx SMS.

Purpose of the Study:

• To evaluate the advantages of a double-ring RF array for designing pTx multiband (MB) pulses for 7T whole-brain SMS imaging.
• To compare the performance of a double-ring array against single-ring arrays in terms of SAR and excitation fidelity.
• To investigate the impact of slice orientation on RF performance in pTx MB pulse design.

Main Methods:

• Modeled a 16-element double-ring head RF array and compared it with 8- and 16-element single-ring arrays.
• Designed band-specific pTx MB pulses with local SAR control for each array configuration.
• Assessed the influence of different slice orientations (axial, sagittal, coronal, oblique) on array performance.

Main Results:

• The double-ring array demonstrated superior performance, significantly reducing peak local SAR by up to 40% compared to single-ring arrays at a fixed excitation error.
• Excitation of sagittal or coronal slices resulted in better RF performance across all tested array types compared to axial or oblique slices.
• The double-ring design offers a better trade-off between SAR and excitation fidelity.

Conclusions:

• A double-ring RF array design is highly advantageous for pTx MB pulse design in 7T brain imaging, offering improved SAR and excitation fidelity over single-ring designs.
• Sagittal and coronal slice orientations are preferable for pTx MB pulse design with stripline arrays.
• The findings support the use of double-ring arrays for advanced biomedical applications utilizing pTx SMS imaging.