LINAC Equatorial Mounting for Combined MRI Radiation Therapy
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Solution Overview
Problem
Existing combined MRI and radiation therapy equipment face challenges due to the sensitivity of linear accelerators to transverse magnetic fields, leading to beam deflection and reduced efficacy, and the impracticality of compact arrangements that require large main magnet coils and significant space.
Innovation Solution
The LINAC is positioned radially outside the main magnet, with active-shielded solenoidal magnets reducing stray fields and allowing a more compact design, enabling the main magnet coils to have a smaller diameter and reducing the influence of the magnetic field on the electron beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the LINAC is positioned inside the main magnet to achieve a compact design, then the system occupies less space, but the transverse magnetic field deflects the electron beam and destroys the efficacy of the radiation source
Solution Approach 1:
The LINAC is repositioned from an axial location to an equatorial position on the magnet's outer surface, changing the spatial dimension of integration. This allows the electron beam to travel parallel to the magnet's longitudinal axis, converting the beam path from a transverse to a longitudinal orientation relative to the magnet, thereby avoiding beam deflection while maintaining compact integration
Solution Approach 2:
A non-magnetic housing structure serves as an intermediary between the LINAC and the magnet, providing mechanical support and positioning while being transparent to both the electron beam and magnetic field. This housing allows the LINAC to be mounted on the magnet's outer surface without direct magnetic field interference
2Reliability
If the LINAC is positioned radially outside the main magnet to avoid beam deflection, then the radiation source efficacy is maintained, but the main magnet coils require larger diameter and the system becomes less compact
Solution Approach 1:
The LINAC is positioned in the equatorial plane on the magnet's outer surface rather than radially outward from the bore center, utilizing the magnet's longitudinal dimension. This arrangement allows the electron beam to travel parallel to the magnet axis, avoiding the need for large radial clearance while maintaining beam efficacy
Solution Approach 2:
The equatorial position of the LINAC serves multiple functions: it provides adequate space for electron beam acceleration and target interaction, maintains the beam path parallel to the magnet axis to avoid deflection, and integrates compactly with the magnet structure without requiring increased coil diameter
3Adaptability or versatility
If a radially-aligned LINAC is used to project radiation through the magnet aperture, then the LINAC can be integrated into the MRI system, but it requires a lot of space around the magnet making it impractical for many installations
Solution Approach 1:
The LINAC is merged with the magnet structure by mounting it on the equatorial outer surface of the magnet, combining two previously separate components into a single integrated unit. This eliminates the need for separate positioning of the LINAC around the magnet, reducing the overall installation footprint
Solution Approach 2:
The integration moves from a radial arrangement requiring circumferential space to an equatorial arrangement utilizing the magnet's longitudinal dimension. This dimensional change allows the radiation beam to pass through the patient bore along the magnet axis, eliminating the need for additional space around the magnet
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 allows for a more compact and practical installation of combined MRI and radiation therapy systems, minimizing beam deflection and providing more space for radiation beam shaping devices, while maintaining effective radiation delivery.
Implementation Method 1
Radiation generation by electron beam acceleration onto a suitable target
Implementation Method 2
produce higher-energy photons
Implementation Method 3
main magnet field coils
Implementation Method 4
magnetic resonance imaging part
Implementation Method 5
The magnetic field deflects the path of the electron beam within the accelerators
Data Source
AI summary
A combined MRI and radiation therapy system has MRI imaging equipment and radiation therapy equipment. The MRI imaging equipment includes a shielded solenoidal magnet including a number of main magnet coils arranged coaxially along an axis, and a shielding arrangement arranged coaxially with the axis, at a greater radius from the axis than the main magnet coils. The radiation therapy equipment includes a LINAC assembly, that includes a linear electron accelerator arranged with an electron beam path parallel to the axis, and electron beam deflection arrangement and a target for generating a beam of therapeutic radiation. The linear electron accelerator is located at a position radially between the main magnet coils and the shielding arrangement.