Segmented RF shield design to minimize eddy currents for low-field Halbach MRI systems

Area of Science:

• Medical Imaging
• Electrical Engineering
• Biophysics

Background:

• Radiofrequency (RF) coils in MRI systems require shielding to minimize noise and coil coupling.
• Existing shields can impede gradient fields, leading to undesirable eddy currents.
• Low-field, point-of-care MRI devices present unique design challenges for effective shielding.

Purpose of the Study:

• To design and evaluate a novel segmented double-layer RF shield for low-field Halbach-based MRI systems.
• To minimize eddy currents while maintaining RF shielding effectiveness.
• To assess the impact of the new shield on image quality.

Main Methods:

• Eddy current simulations were performed to guide the shield design.
• A segmented double-layer shield was constructed based on simulation results.
• Shield performance was evaluated by measuring eddy current decay times and RF noise coupling.
• Turbo spin echo MRI scans of a phantom and a healthy volunteer brain were acquired.

Main Results:

• The segmented shield achieved a maximum reduction factor of 2.9 in eddy current decay time compared to a reference shield.
• The segmented shield exhibited comparable RF noise coupling to the unsegmented reference shield.
• MRI images demonstrated reduced blurring when using the segmented shield.

Conclusions:

• The developed segmented double-layer shield effectively reduces eddy currents in low-field MRI.
• This design offers improved image quality by minimizing blurring without compromising noise performance.
• The shield is suitable for low-field, point-of-care Halbach-based MRI applications.