Small-bore gradient coil design with plate-rolling error correction for use in micro-MRI

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Biomedical Engineering
• Electromagnetism

Background:

• High-field MRI requires precise gradient coil performance for accurate spatial encoding.
• Conventional manufacturing methods, like copper-plate cutting and bending, introduce geometric distortions, leading to magnetic field deviations.
• These deviations compromise the fidelity between the designed and as-built gradient fields.

Purpose of the Study:

• To develop a high-precision engineering approach to minimize discrepancies between designed and as-built MRI gradient coil magnetic fields.
• To enhance the accuracy of gradient-field generation and spatial encoding in high-field MRI systems.
• To improve the consistency between gradient coil design and fabrication.

Main Methods:

• Proposed a mid-surface-based approach, defining 3D current paths directly on the cylindrical mid-surface of the conductor.
• Eliminated the need for planar unfolding and subsequent bending assumptions inherent in conventional methods.
• Demonstrated the methodology on an X-gradient coil for a 7T MRI magnet and validated with finite-element simulations.

Main Results:

• The mid-surface extrusion approach significantly improved magnetic field fidelity, reducing maximum field deviation from 10.92% to 3.71%.
• Simulations showed substantial improvements in magnetic field fidelity compared to conventional methods.
• Fabricated prototype coils for X, Y, and Z axes achieved coefficients of determination (R²) > 0.997, confirming high accuracy.

Conclusions:

• The mid-surface-based approach offers a higher-fidelity conversion from design patterns to manufacturable gradient coils.
• This method leads to improved as-built field accuracy and enhanced design-to-fabrication consistency.
• The findings are crucial for compact high-field MRI gradient systems demanding precise magnetic field generation.