A Comparative Study for Evaluating Passive Shielding of MRI Longitudinal Gradient Coil.

Area of Science:

• Medical Imaging Physics
• Computational Electromagnetics
• Applied Mathematics

Background:

• Gradient coils in Magnetic Resonance Imaging (MRI) generate eddy currents in metallic components, causing thermal, acoustic, and field distortion issues.
• Active shielding partially mitigates these effects, but passive shielding is a newer approach to further reduce eddy currents and acoustic noise.
• Accurate numerical computation is essential for assessing eddy current impacts and passive shielding effectiveness.

Purpose of the Study:

• To compare the computational performance of Network Analysis (NA) and an adapted Multilayer Integral Method (MIM) for eddy current analysis in MRI systems.
• To evaluate the efficacy of passive shielding configurations using these computational methods.
• To validate the results against Ansys Maxwell 3D simulations.

Main Methods:

• Harmonic and temporal eddy current analysis using Network Analysis (NA).
• Adapted Multilayer Integral Method (MIM) for simulating eddy currents in arbitrary geometries.
• Comparison with Ansys Maxwell 3D for validation.

Main Results:

• High agreement was observed in eddy ohmic loss profiles across NA, adapted MIM, and Ansys Maxwell 3D methods.
• Network Analysis (NA) demonstrated the highest computational efficiency but is limited by symmetry constraints.
• The adapted MIM method showed comparable accuracy to Ansys Maxwell 3D with improved computational efficiency.

Conclusions:

• A computationally efficient framework for eddy current analysis in MRI systems has been developed.
• The adapted MIM method provides a viable and efficient alternative to traditional methods like Ansys Maxwell 3D for evaluating passive shielding.
• This framework facilitates the design and optimization of passive shielding solutions for MRI gradient coils.