Deployable Barriers for Stray Magnetic Field Constraint in Mobile MRI
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Solution Overview
Problem
Current mobile MRI systems face challenges in constraining stray magnetic fields of high-strength magnets within conventional trailer dimensions, leading to impractical solutions such as excessive weight, size, or high costs due to additional shielding or larger trailers, which violate regulations and compromise stability.
Innovation Solution
Deployable barriers are integrated with the MRI system trailer to allow operation at a lower magnetic field intensity during transport and higher intensity at the site, with an interlock mechanism ensuring compliance with stray magnetic field regulations, using a conventional trailer size and minimizing weight and size issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If additional passive shielding (iron plates) is added to the trailer walls to constrain the stray magnetic field, then the magnetic field constraint is improved, but the trailer weight becomes excessively high making it impractical for road transport
Solution Approach 1:
The patent applies active shield coils that can dynamically adjust their current to compensate for stray magnetic field variations. Unlike static iron plates, the active shielding system can adapt to changes in magnet position, thermal expansion, and wind effects, providing effective magnetic field constraint without adding excessive weight to the trailer structure.
Solution Approach 2:
The patent replaces the mechanical/passive shielding approach (iron plates) with an electromagnetic approach (active shield coils). This substitution uses electromagnetic fields to counteract stray magnetic fields, achieving the same shielding effect with significantly reduced mass compared to thick iron plate construction.
2Object-affected harmful factors
If the trailer dimensions are increased to accommodate a 3 T magnet while keeping the 5 gauss contour within the walls, then the magnetic field constraint is improved, but the trailer size becomes too large for normal road transport
Solution Approach 1:
The active shield coils provide dynamic compensation that allows the use of a compact trailer design. By actively managing the magnetic field distribution through controllable coils, the system achieves effective magnetic field containment within standard trailer dimensions, avoiding the need for oversized trailers.
Solution Approach 2:
The patent changes the operational parameters of the magnetic field by using active shield coils to modify the field distribution. This allows the 5 gauss contour to be maintained within standard trailer dimensions through electromagnetic parameter control rather than relying solely on physical dimensional increases.
3Object-affected harmful factors
If superconducting magnets with magnetic field strength of 1.5 T or less are used, then the stray magnetic field can be constrained within the trailer using active shield coils and ferromagnetic shielding, but the image quality is limited compared to 3 T magnets
Solution Approach 1:
The patent employs dynamic active shielding with controllable superconducting coils that can adapt to the higher field strengths of 3 T magnets. This dynamic control system maintains effective magnetic field containment that was previously only achievable with lower field strengths, enabling high-quality imaging while meeting stray field regulations.
Solution Approach 2:
The patent combines active electromagnetic shielding with ferromagnetic shielding materials to create a composite shielding system. This hybrid approach leverages the strengths of both active control and passive materials to effectively constrain the stronger magnetic fields of 3 T magnets within standard trailer dimensions.
4Object-affected harmful factors
If additional shield coils are added within the magnet to reduce stray magnetic field, then the magnetic field constraint is improved, but the system cost, weight, and complexity increase significantly
Solution Approach 1:
The active shield coils are designed to serve multiple functions: they provide magnetic field shielding, enable field strength adjustment, and facilitate transport positioning. This multi-functionality reduces the need for separate dedicated shielding components, thereby limiting the increase in system complexity despite adding active shielding capability.
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
Enables the use of high magnetic field strength magnets in mobile MRI systems while adhering to existing stray magnetic field emission regulations, maintaining trailer size and reducing weight, and ensuring operational stability by deploying barriers only when necessary.
Implementation Method 1
the magnet of the MRI system can be operated to generate a magnetic field of a first field intensity
Implementation Method 2
ferromagnetic shielding of the trailer walls
Data Source
AI summary
An MRI system is housed within a housing that is provided with a set of deployable barriers that are attachable to the housing. The magnet in the MRI system may be operated at a first magnetic field intensity, such that the magnetic field outside of the housing remains below a safety limit when the barriers are not deployed. The magnet in the MRI system may be operated at a second magnetic field intensity, higher than the first, when the barriers are deployed, such that the magnetic field outside of the barriers remains below the safety limit.