Intra-coil interactions in split gradient coils in a hybrid MRI-LINAC system

Area of Science:

• Medical Physics
• Biomedical Engineering
• Electromagnetism

Background:

• MRI-LINAC systems integrate magnetic resonance imaging (MRI) with linear accelerators (LINAC) for real-time image-guided radiotherapy.
• Split gradient coil configurations in MRI-LINAC systems are susceptible to eddy currents due to their design.
• These eddy currents can degrade gradient field linearity and cause image distortion, crucial for precise tumor targeting.

Purpose of the Study:

• To investigate electromagnetic interactions between coils in a split gradient set for MRI-LINAC systems.
• To analyze the impact of varying gradient coil track widths and operating frequencies on induced eddy currents.
• To understand how conductor geometry and frequency influence inductive coupling effects.

Main Methods:

• Designed and analyzed a series of gradient coils with different track widths.
• Applied driving currents at frequencies ranging from 100 Hz to 10 kHz.
• Studied inductive coupling effects and quantified eddy current magnitudes and power loss.

Main Results:

• Eddy current induction in passive coils positively correlated with coil track width and driving frequency.
• Magnetic fields from eddy currents in wide-track passive coils were significantly larger than those from cryostat shields.
• Power loss in passive coils increased proportionally with track width.

Conclusions:

• Intra-coil interactions are a significant concern in MRI-LINAC split gradient coil design.
• Coil track width and operating frequency are critical parameters influencing eddy current generation.
• Accounting for intra-coil interactions during the design and analysis phase is essential for optimal MRI-LINAC performance.