Dynamic parallel imaging at 9.4 T using reconfigurable receive coaxial dipoles

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Radiofrequency (RF) Engineering
• Medical Physics

Background:

• Parallel imaging techniques in MRI accelerate image acquisition but often reduce signal-to-noise ratio (SNR) due to the geometrical factor (g-factor).
• Increasing channel count in MRI arrays can decrease element size, leading to insufficient coil loading and increased RF coil noise, further degrading SNR.
• Previous work introduced switchable sensitivities to enhance parallel imaging, where each element has two distinct spatial profiles.

Purpose of the Study:

• To develop and evaluate a novel eight-element human head receive-only reconfigurable coaxial dipole array for 9.4 Tesla (T) MRI.
• To assess the performance of dynamic sensitivity switching in reducing the g-factor compared to conventional static sensitivities.
• To enable scalable dynamic parallel imaging with a higher number of channels (32 and above).

Main Methods:

• Designed and optimized a novel eight-element reconfigurable coaxial dipole array for head imaging at 9.4 T.
• Utilized coaxial cables for DC voltage delivery to PIN diodes, eliminating direct current (DC) control wires to the dipoles.
• Experimentally tested the array, including in vivo studies, comparing dynamic sensitivity switching with conventional static sensitivities.

Main Results:

• The novel reconfigurable coaxial dipole design allows for scaling dynamic parallel imaging to 32 channels and beyond.
• Dynamic sensitivity switching resulted in an 8% lower mean g-factor and a 33% lower maximum g-factor for R_y × R_z = 2 × 2 acceleration.
• The new design avoids direct DC control wires, simplifying the architecture and enabling higher channel counts.

Conclusions:

• The developed reconfigurable coaxial dipole array significantly improves parallel imaging performance in high-field MRI.
• Dynamic sensitivity switching offers a promising approach to mitigate SNR loss associated with parallel imaging acceleration.
• This technology paves the way for more efficient and higher-resolution MRI scans, particularly in demanding applications like human head imaging at ultra-high fields.