MRI-Integrated Linear Accelerator Shielding for RF Interference
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Solution Overview
Problem
Combining linear accelerator radiotherapy with magnetic resonance imaging is challenging due to interference from magnetic fields and eddy currents generated by MRI systems, which can destroy imaging quality, and high-power RF from linac components can interfere with MRI functionality.
Innovation Solution
The system includes a gantry with shielding containers for linac components and RF waveguides oriented perpendicularly to MRI magnetic fields, using RF absorbing and reflecting materials, and cooling systems to minimize interference and maintain imaging quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If linear accelerator components are placed within MRI system, then integrated radiotherapy and imaging is achieved, but magnetic fields and eddy currents from MRI destroy imaging quality and interfere with linac components
Solution Approach 1:
The linear accelerator components are divided into separate shielded modules distributed around the gantry circumference, with each module containing specific components (RF power source, circulator, linac components) and connected via RF waveguides. This segmentation isolates interfering components while maintaining functional integration.
Solution Approach 2:
RF shielding containers and RF waveguides act as intermediaries between the linac components and the MRI environment, blocking harmful RF radiation from reaching the MRI system while allowing controlled RF transmission for linac operation.
2Power
If high-power RF is generated by linac components, then radiotherapy function is achieved, but RF radiation destroys MRI imaging capabilities
Solution Approach 1:
High-power RF-generating linac components are extracted from the central MRI bore and placed in separate shielded modules around the gantry periphery. This physical extraction removes the source of harmful RF radiation from the MRI imaging zone while preserving radiotherapy functionality.
Solution Approach 2:
RF shielding containers serve as intermediaries that contain and direct high-power RF radiation from linac components through controlled waveguides, preventing uncontrolled RF leakage into the MRI system while maintaining necessary RF transmission for radiotherapy.
3Measurement precision
If MRI main magnetic field is used for imaging, then imaging function is achieved, but magnetic field interferes with linear accelerator components
Solution Approach 1:
Linac components are segmented into separate shielded modules positioned at specific locations around the gantry where magnetic field interference is minimized. This spatial segmentation protects sensitive components from MRI magnetic field effects while maintaining imaging precision.
Solution Approach 2:
Magnetic shielding containers act as intermediaries that block and redirect MRI magnetic fields away from linac components, protecting sensitive RF and electronic components from magnetic interference while allowing the MRI magnetic field to maintain imaging precision in the patient treatment zone.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively shields linac components from MRI interference, allowing for simultaneous high-quality radiotherapy and imaging by minimizing eddy currents and RF disruption.
Implementation Method 1
The RF waveguide may be oriented to be substantially perpendicular to the magnetic field lines of a main magnet of the magnetic resonance imaging system
Implementation Method 2
the magnetic fields and eddy currents generated in ferromagnetic and conductive radiotherapy equipment through the MRI's main magnet and gradient coils
Implementation Method 3
The RF shielding may be an RF absorbing material, an RF reflecting material, or multiple layers of RF reflecting and absorbing materials
Implementation Method 4
The RF shielding may be an RF absorbing material, an RF reflecting material, or multiple layers of RF reflecting and absorbing materials
Implementation Method 5
The RF shielding may include water cooling or air cooling
Implementation Method 6
The RF shielding may include water cooling or air cooling
Data Source
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AI summary
Systems and methods for the delivery of linear accelerator radiotherapy in conjunction with magnetic resonance imaging in which components of a linear accelerator may be placed in RF shielding around a gantry, may be connected with RF waveguides, and may employ various systems and methods for magnetic and radio frequency shielding.