Resonator Barrier Suppressing Capacitive Coupling in MRI Systems
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Solution Overview
Problem
Magnetic resonance systems face challenges in suppressing unwanted capacitive couplings between the radio-frequency source and the examination subject, leading to heating issues due to eddy currents and capacitive couplings, which existing solutions like increasing distance or dividing resonance capacitors are inefficient or impractical.
Innovation Solution
A magnetic resonance system with individual resonators having two capacitor surfaces connected via a coil, where these surfaces are not directly connected to each other, forming a barrier that compensates displacement currents caused by the radio-frequency source, and can be arranged in various configurations including dielectric support or air gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the distance between the radio-frequency source and the examination subject is increased, then capacitive coupling is reduced, but the transmission antenna becomes over-dimensioned or spatial relationships are reduced
Solution Approach 1:
A barrier composed of individual resonators is introduced as an intermediary element between the radio-frequency source and the examination subject. Each resonator contains capacitor surfaces connected via a coil, creating a stationary wave barrier that blocks capacitive coupling without requiring increased distance. The barrier acts as a mediator that allows the desired magnetic field to pass while blocking the harmful electrical field coupling.
2Object-affected harmful factors
If resonance capacitors are divided (multiple reduction), then capacitive coupling is reduced, but capacitor losses increase and production expenditure increases
Solution Approach 1:
The barrier is segmented into multiple individual resonators, each containing capacitor surfaces and coils. This segmentation approach distributes the shielding function across multiple independent units rather than using a single large capacitor structure. The segmented design reduces capacitive coupling effectively while minimizing total capacitor losses compared to dividing a single resonance capacitor, and avoids the need for complex multiple reduction circuits that increase production costs.
3Object-affected harmful factors
If a barrier with individual resonators is introduced, then capacitive coupling is suppressed, but device complexity increases
Solution Approach 1:
The barrier is divided into multiple identical or similar individual resonators, each with a standardized structure containing capacitor surfaces and coils. This modular segmentation allows for simplified manufacturing and assembly compared to a single complex barrier structure, as the same components can be mass-produced and then assembled in an array to form the complete barrier.
Solution Approach 2:
The resonators are designed to resonate at the specific excitation frequency of the magnetic resonance system. By tuning the electrical parameters (capacitance and inductance) of each resonator to match the operating frequency, the barrier achieves effective capacitive coupling suppression without requiring overly complex structures. The parameter optimization allows simple resonator designs to perform the shielding function efficiently.
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
Effectively shields the examination volume from unwanted electrical fields, reducing heating and maintaining system sensitivity and efficiency without increasing production costs or complexity.
Implementation Method 1
each individual resonator has two capacitor surfaces, of which one faces toward the radio-frequency source and the other faces toward the examination volume, and that are connected with one another in an electrically-conductive manner via a coil
Implementation Method 2
The barrier essentially represents a further development of a known sheath wave barrier... individual resonators that are each naturally resonant at the excitation frequency
Implementation Method 3
Currents having electrical fields that are capacitively coupled into the examination subject and lead to a further heating of the examination subject... This arrangement causes currents in the barrier that compensate the displacement current caused by the radio-frequency source in the examination subject
Data Source
AI summary
A magnetic resonance system has a transmission antenna that excited magnetic resonance signals in an examination subject arranged in an examination volume, a radio-frequency source that is stationary or mobile in the examination volume or in its surroundings and by means of which an electrical field oscillating at the excitation frequency can be generated. A barrier is arranged between the radio-frequency source and the examination volume—the barrier formed of a number of individual resonators that are respectively inherently resonant at the excitation frequency. The examination volume is shielded by the barrier from the electrical field generated by the radio-frequency source. Each individual resonator has two capacitor surfaces of which one faces toward the radio-frequency source and the other faces the examination volume, and they are connected with one another in an electrically-conductive manner via a coil. The capacitor surface facing toward the radio-frequency source and/or the capacitor surface facing toward the examination volume are not directly connected with one another in an electrically-conductive manner.