MEMS Switch Decoupling for MRI Receive Coil Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing MRI systems face challenges in rapidly and efficiently decoupling receive coils from transmit coils to prevent noise and circuit losses during RF pulse transmission, as conventional methods like diode-activated detuning circuits are slow and lossy.
Innovation Solution
The implementation of a method and apparatus using MEMS switches and tuning circuits to control the coupling and decoupling of receive coils with transmit coils, allowing for rapid decoupling and coupling within a defined window of time, utilizing a control circuit to manage the MEMS switches and tuning elements to resonate or detune the receive coils accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a receive coil is electromagnetically coupled to the transmit coil during RF pulse transmission, then the receive coil can detect the full power RF pulse, but noise is produced within the auxiliary circuitry
Solution Approach 1:
The patent employs dynamic switching of the receive coil's electromagnetic coupling state with the transmit coil. A switch mechanism changes the receive coil's impedance characteristics between two states: a first state during RF pulse transmission that prevents noise generation, and a second state during signal reception that enables full-power pulse detection. This dynamic state transition resolves the contradiction by making the coupling characteristic adaptable to different operational phases.
2Object-generated harmful factors
If the receive coil is mechanically and electrically isolated from the transmit coil, then noise is avoided, but the receive coil cannot be electromagnetically coupled to resonate with the RF pulse
Solution Approach 1:
The patent employs dynamic switching of the receive coil's electromagnetic coupling state with the transmit coil. A switch mechanism changes the receive coil's impedance characteristics between two states: a first state during RF pulse transmission that prevents noise generation, and a second state during signal reception that enables full-power pulse detection. This dynamic state transition resolves the contradiction by making the coupling characteristic adaptable to different operational phases.
3Reliability
If conventional diode-activated detuning circuits are used to decouple the receive coil, then the receive coil is protected during transmission, but the decoupling process is slow and results in circuit losses
Solution Approach 1:
The patent replaces conventional diode-activated detuning circuits with an electrostatic switch mechanism that provides rapid, lossless decoupling. The electrostatic switch uses voltage-controlled capacitance changes to alter the receive coil's resonant frequency instantaneously, eliminating the slow mechanical or thermal decoupling processes inherent in diode-based systems. This substitution achieves both reliable protection and rapid response.
Solution Approach 2:
The patent utilizes voltage-controlled parameter changes in the electrostatic switch to rapidly alter the receive coil's electrical characteristics. By applying control voltages to the electrostatic switch, the receive coil's resonant frequency is instantly shifted away from the transmit frequency during pulse transmission, and then restored for signal reception. This parameter manipulation enables fast, lossless decoupling compared to conventional methods.
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 approach enables quick and low-loss decoupling of receive coils from transmit coils, reducing noise and circuit losses, thereby enhancing image quality and operational efficiency in MRI systems.
Implementation Method 1
a MEMS switch connected electrically in parallel with the tuning circuit, and operable to line up or to bypass the tuning circuit by opening or closing the MEMS switch
Implementation Method 2
coupling the receive coil to the transmit coil during a window of time... tune the receive coil to any of one or more non-receive frequencies for decoupling the receive coil from the transmit coil, or to a receive frequency for coupling the receive coil to the transmit coil
Data Source
AI summary
An apparatus for decoupling a receive coil from a transmit coil includes a tuning circuit connected electrically with the receive coil and a MEMS switch connected electrically in parallel with the tuning circuit, and operable to line up or to bypass the tuning circuit by opening or closing the MEMS switch. The apparatus further includes a control circuit operatively connected with the MEMS switch and operable to open or to close the MEMS within a window of time responsive to energization of the transmit coil to transmit a signal.