MRI Circuit Board Mesh for Eddy Current Mitigation
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Solution Overview
Problem
Combined imaging systems, such as MRI-PET systems, face challenges with eddy currents induced by MRI magnetic fields, leading to heating issues, signal drift, and potential component damage.
Innovation Solution
Incorporating a mesh of holes into the conducting layers of printed circuit boards within the MRI magnetic field, which increases impedance in the kHz range relevant to eddy currents, thereby reducing heat induction without requiring additional components or space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If PET electronics are placed close to MRI gradient coils to meet design requirements, then patient bore diameter and power-to-field efficiency are improved, but eddy currents are induced in the PET electronics leading to heating
Solution Approach 1:
The conducting layer on the circuit board is segmented by creating a mesh of holes that divides the continuous conductive material into isolated regions. This segmentation interrupts the formation of large eddy current loops while maintaining local conductivity for signal transmission, thereby reducing overall eddy current heating in the PET electronics placed within the MRI gradient field.
2Temperature
If materials with lower electrical conductivity are used to reduce eddy current heating, then heating is reduced, but the functionality of the additional imaging system is compromised
Solution Approach 1:
Instead of reducing material conductivity, the invention segments the conducting layer by introducing a mesh of holes. This allows the use of highly conductive materials like copper while still reducing eddy currents through geometric disruption, thereby maintaining imaging system functionality without compromising reliability.
Solution Approach 2:
The conducting layer exhibits different properties in different regions: in areas with mesh holes, conductivity is reduced to minimize eddy currents, while in areas without holes (such as signal trace regions), full conductivity is maintained to ensure proper signal transmission and system functionality.
3Temperature
If capacitive segmentation is used to maximize impedance in the kHz range, then eddy current heating is reduced, but additional discrete components are required causing increased cost and complexity
Solution Approach 1:
The invention extracts the impedance-enhancing function from discrete capacitive components and integrates it directly into the circuit board's conducting layer through the mesh of holes. This eliminates the need for additional discrete components while achieving the desired impedance increase in the kHz range to reduce eddy current heating.
Solution Approach 2:
The mesh structure merges the functions of eddy current reduction and impedance enhancement into a single feature of the conducting layer, combining what were previously separate functions (conductive pathways and capacitive segmentation) into an integrated solution that reduces complexity.
4Temperature
If the orientation of electrically conductive surface is set to be non-perpendicular to the magnetic gradient field, then eddy current heating is reduced, but the degree of freedom in designing the electronics is limited
Solution Approach 1:
The mesh pattern can be applied selectively to specific regions of the circuit board where eddy current heating is most problematic, while leaving other regions with full conducting layers for signal traces and power connections. This localized application maintains design flexibility for electronic components while reducing heating in critical areas.
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
The mesh effectively reduces eddy current-induced heating, allowing for more flexible circuit board placement and design, while maintaining signal integrity and avoiding additional costs or complexity.
Implementation Method 1
electrically conductive materials that are positioned within the magnetic field of the MRI system may heat up due to eddy currents that are induced by the rapidly varying magnetic gradient field
Implementation Method 2
eddy currents that are induced by the rapidly varying magnetic gradient field
Implementation Method 3
electrically conductive materials that are positioned within the magnetic field of the MRI system may heat up due to eddy currents
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
An imaging system comprising a magnetic resonance imaging system with a gradient coil (3) arrangement configured to produce a varying magnetic gradient field during operation, the medical imaging system comprising one or several printed circuit boards arranged such that they are within the magnetic gradient field of the magnetic resonance imaging system during operation, each circuit board having at least one conducting layer (6), in particular a copper layer, wherein at least one of the circuit boards comprises a mesh (7) of holes that spreads over at least a partial region of the conducting layer (6).