Rat brain MRI at 16.4T using a capacitively tunable patch antenna in combination with a receive array.

Area of Science:

• Medical Physics
• Magnetic Resonance Imaging
• RF Engineering

Background:

• Achieving a spatially homogeneous radiofrequency (RF) transmit field is a major challenge for Magnetic Resonance Imaging (MRI) at ultra-high fields (UHF) like 16.4T.
• Conventional volume coil designs struggle with size constraints and maintaining quadrature symmetry under varying loading conditions at high frequencies (698 MHz proton Larmor frequency).

Purpose of the Study:

• To address RF engineering challenges in UHF MRI by developing a novel coil design for improved transmit field homogeneity and reception sensitivity.
• To create additional space within the magnet bore for supplementary hardware by relocating RF components.

Main Methods:

• A capacitively tunable patch antenna was remotely placed to generate a homogeneous excitation field, mimicking a birdcage coil's profile.
• The patch antenna was integrated with an actively detunable 3-channel receive coil array to boost reception sensitivity.
• The system was tested for imaging quality using gradient echo and spin-echo sequences.

Main Results:

• The novel RF coil design produced a relatively homogeneous transmit field over a large imaging volume.
• The combined antenna and receive array system demonstrated increased signal-to-noise ratio (SNR) compared to a standard quadrature transceive surface coil.
• High-quality gradient echo and spin-echo images of the entire rat brain were acquired.

Conclusions:

• The proposed RF coil design offers a viable solution for UHF MRI, overcoming limitations of traditional volume coils.
• This approach enhances imaging performance and provides greater flexibility for hardware integration in narrow magnet bores.
• The technology facilitates high-resolution brain imaging in preclinical models at 16.4T.