Flexible Resonant Trap Circuit for Bendable MRI Receive Coils
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Solution Overview
Problem
In Magnetic Resonance Imaging (MRI) systems, there is a need for flexible and comfortable RF receive coils that can be positioned close to a patient's anatomy without compromising their frequency trap behavior, to prevent coupling between the B1 field and transmission lines or inductive elements, ensuring safety and image uniformity.
Innovation Solution
A resonant trap circuit is designed with a conductor line featuring a helical winding portion formed by twisting two segments together, coupled with a capacitor to provide capacitance, which is applied to the transmission lines in the MRI system to prevent coupling with the magnetic field, maintaining frequency trap behavior even when bent or twisted.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rigid resonant trap circuits are used to block RF signals, then frequency filtering performance is improved, but flexibility and comfort for patient positioning deteriorates
Solution Approach 1:
The patent applies this principle by constructing the resonant trap circuit on a flexible substrate rather than using rigid lumped elements. The flexible substrate allows the circuit to be bent and positioned comfortably on patient anatomy while maintaining the electrical characteristics needed for RF signal filtering at the Larmor frequency.
Solution Approach 2:
The patent changes the physical state of the circuit from rigid to flexible by using flexible substrates and flexible capacitors. This parameter change allows the circuit to adapt to curved surfaces and patient positioning requirements while preserving the resonant frequency characteristics through careful design of the flexible components.
2Ease of operation
If receive coils are positioned close to patient anatomy for comfort and signal quality, then ease of operation is improved, but coupling with B1 field and transmission lines increases causing safety issues
Solution Approach 1:
The patent applies this principle by incorporating resonant trap circuits that create a preliminary blocking effect at the Larmor frequency. The trap circuits are designed to present a high impedance at the excitation frequency before harmful coupling can occur, thereby preventing common mode currents from developing on the transmission lines and cables.
Solution Approach 2:
The resonant trap circuit acts as an intermediary element between the receive coil and the transmission line. It provides a localized frequency-selective filtering function that blocks harmful RF signals at the Larmor frequency while allowing the receive coil to be positioned close to the patient for optimal signal quality.
3Adaptability or versatility
If flexible conductor lines are used to allow positioning, then adaptability is improved, but maintaining resonant trap behavior when bent or twisted becomes difficult
Solution Approach 1:
The patent uses flexible substrates to carry the resonant trap circuit components, allowing the entire assembly to be bent and positioned without compromising the electrical characteristics. The flexible nature of the substrate maintains the geometric relationships between components even when deformed.
Solution Approach 2:
The patent employs helical winding portions in the flexible conductor lines to create inductance. The helical structure maintains its inductive properties even when the flexible line is bent or twisted, as the helical geometry preserves the magnetic flux characteristics needed for resonant trap operation.
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 solution effectively blocks common mode currents at the Larmor frequency, reducing B1 perturbation and enhancing image uniformity while allowing the coils to be safely positioned close to the patient, thus improving MRI image quality and safety.
Implementation Method 1
A capacitor is arranged to provide capacitance between the first helical winding segment and the second helical winding segment
Implementation Method 2
Impedance of a typical resonant trap circuit becomes very high at its resonant frequency
Implementation Method 3
The inductance and capacitance of a trap can be determined by lumped elements, circuit board design, or cabling
Implementation Method 4
The precessing magnetization induces electric current in the receive coil via electromagnetic induction
Data Source
AI summary
A flexible resonant trap circuit is provided that includes a transmission line arranged to include a helical winding that has a first helical winding segment and a second helical winding segment; and a capacitor coupled between the first and second helical winding segments.