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Related Experiment Video

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Mouse Body Temperature Measurement Using Infrared Thermometer During Passive Systemic Anaphylaxis and Food Allergy Evaluation

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Passive magnetic shielding in MRI-Linac systems.

Brendan Whelan^1,2,3, Stefan Kolling¹, Brad M Oborn^4,5

¹Radiation Physics Laboratory, University of Sydney, Sydney (NSW), 2006, Australia.

Physics in Medicine and Biology

|March 27, 2018

Summary

Optimizing magnetic shielding for integrated MRI-Linac systems is crucial. Modifying shield shape improved shielding by 70% and reduced magnet impact by 10%, demonstrating effective design strategies.

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Area of Science:

Medical Physics
Electromagnetism
Materials Science

Background:

Passive magnetic shielding uses ferromagnetic materials to redirect magnetic fields.
Shielding is critical for integrated Magnetic Resonance Imaging (MRI) and linear accelerator (MRI-Linac) systems.
Shielding must minimize magnetic fields without degrading MRI imaging quality.

Purpose of the Study:

To assess magnetic shielding effectiveness for a 6 MV linac within a 1 Tesla MRI magnet.
To evaluate the impact of various shield parameters on shielding performance and MRI field homogeneity.
To compare in-line and perpendicular MRI-Linac configurations.

Main Methods:

Finite element modeling was employed to simulate magnetic fields.
Shielding parameters investigated included shape, thickness, length, openings, layering, and material.
Both in-line and perpendicular MRI-Linac configurations were analyzed.

Main Results:

Modifying shield shape increased shielding by ~70% and reduced magnet impact by ~10%.
Openings for RF ports and beam exit caused significant field leakage, but could be compensated.
Concentric layers were more effective in the perpendicular configuration; Mu-metal enhanced performance.

Conclusions:

Optimized shield design can significantly improve magnetic shielding effectiveness and minimize MRI impact.
Configuration (in-line vs. perpendicular) and specific design features greatly influence performance.
Careful material selection and design of openings are key for effective MRI-Linac shielding.