Electromagnetic and RF pulse design simulation based optimization of an eight-channel loop array for 11.7T brain...

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Electromagnetics
• RF Engineering

Background:

• Ultra-high-field (UHF) MRI scanners (e.g., 11.7T) face challenges with radiofrequency (RF) losses and nonuniformity.
• Optimization of transmit array performance is critical for effective UHF MRI.

Purpose of the Study:

• To develop a novel workflow for investigating and minimizing RF coil losses in 11.7T MRI.
• To determine the optimal coil configuration for improved imaging.

Main Methods:

• Simulated an 8-channel transceiver loop-array at 499.415 MHz to analyze loss mechanisms.
• Developed a folded-end RF shield to reduce radiation loss and enhance efficiency.
• Utilized electromagnetic (EM) and RF pulse design (RFPD) simulations for optimization, followed by phantom validation.

Main Results:

• Conventional RF shields at 11.7T exhibited high radiation losses (18.4%).
• Optimized folded-end RF shields reduced radiation loss to 2.4% and increased absorbed power in tissue.
• The optimized array showed a 42% increase in peak efficiency compared to the reference array, validated by phantom measurements within 4%.

Conclusions:

• A validated workflow combining EM and RFPD simulations enables numerical optimization of transmit arrays.
• Optimizing RF shields in conjunction with array element design is essential for efficient excitation at 11.7T.
• The findings highlight the importance of RF shield design for UHF MRI performance.