Remote RF excitation for small-bore MR imager at 15.2 T

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Bio-inspired Engineering
• Electromagnetics

Background:

• Preclinical ultra-high field (UHF) MRI requires specialized radiofrequency (RF) coils.
• Small-bore imager limitations restrict RF coil transmitter dimensions.
• Remote excitation offers a potential solution for overcoming coil size constraints.

Purpose of the Study:

• To report a novel method for remote RF signal excitation in preclinical UHF MRI.
• To design and validate a bio-inspired surface coil and waveguide system for small-bore MRI.
• To assess the imaging performance and simulation accuracy of the developed system.

Main Methods:

• Utilized a parallel-plate waveguide and a bio-inspired surface coil for remote excitation.
• Employed the Gielis super-formula for designing a compact RF coil suitable for small bores.
• Conducted electromagnetic simulations and radiation pattern analyses in a semi-anechoic chamber.
• Acquired images using spherical phantoms and formaldehyde-fixed mouse phantoms at 15.2 T.

Main Results:

• Radiation patterns demonstrated omnidirectional distribution with no side lobes and smooth behavior.
• Excellent correspondence between theoretical wave impedance and simulated results was observed.
• High-quality ex vivo mouse images showed clear anatomical structure delineation.
• Image data and B1 simulation results exhibited a strong correlation.

Conclusions:

• The developed remote excitation method, utilizing a bio-inspired coil and waveguide, is validated.
• This approach is effective for preclinical small-bore MRI at ultra-high fields.
• Numerical, theoretical, and experimental results confirm the system's viability and accuracy.