MRI RF Coil Pre-Amplifier Narrowband Filtering Against Oscillation
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Solution Overview
Problem
Traditional pre-amplifiers for magnetic resonance imaging radio-frequency coils suffer from oscillations and inadequate frequency selectivity, leading to unwanted gain at frequencies other than the magnetic resonance signal frequency, which affects image quality and stability.
Innovation Solution
Incorporating a narrow band filter, either an LC filter or a surface acoustic wave filter, into the pre-amplifier design to selectively amplify signals only near the magnetic resonance signal frequency, reducing gain at other frequencies and minimizing oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a traditional pre-amplifier with wide operation bandwidth is used, then great gain can be achieved within a wide frequency range, but the gain is also extremely high at frequencies other than the magnetic resonance signal frequency, causing oscillation
Solution Approach 1:
The patent changes the frequency response parameters of the pre-amplifier by introducing a narrow band filter. This filter modifies the gain characteristic from a wide bandwidth response to a narrow bandwidth response centered at the magnetic resonance frequency, thereby maintaining high gain at the target frequency while suppressing gain at other frequencies to prevent oscillation
Solution Approach 2:
The patent applies local quality by making the pre-amplifier's gain characteristic non-uniform across frequency. The narrow band filter creates a localized high-gain region at the magnetic resonance frequency while creating low-gain regions at other frequencies, allowing the system to have high sensitivity where needed while maintaining stability elsewhere
2Power
If the output matching circuit is designed for impedance matching with 50 ohm system load, then the gain is increased, but the Q value becomes extremely low and good frequency selectivity cannot be achieved
Solution Approach 1:
The patent merges the output matching circuit with a narrow band filter to create an integrated circuit. This combination allows the circuit to simultaneously achieve impedance matching with the 50 ohm system load and maintain high Q value for good frequency selectivity, as the filter is designed to work together with the matching components rather than in conflict
3Power
If the operation bandwidth is made extremely wide, then great gain can be achieved, but the pre-amplifier amplifies signals at frequencies other than the magnetic resonance frequency, affecting image quality
Solution Approach 1:
The patent changes the operational bandwidth parameter from wide to narrow by introducing the narrow band filter. This ensures that the pre-amplifier only amplifies signals within a narrow frequency range centered at the magnetic resonance frequency, preventing amplification of out-of-band noise and interference that would degrade image quality while maintaining sufficient gain for the target signal
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 pre-amplifier achieves the required gain only near the magnetic resonance signal frequency, significantly reducing the probability of oscillation and improving the stability and image quality by limiting amplification to a narrow frequency range.
Implementation Method 1
a narrow band filter used for filtering a magnetic resonance signal amplified by the amplification circuit
Implementation Method 2
The narrow band filter is an LC filter, and the LC filter and the output matching circuit form an integrated circuit
Implementation Method 3
The narrow band filter is a surface acoustic wave filter
Data Source
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AI summary
Disclosed is a pre-amplifier for a magnetic resonance imaging radio-frequency coil in the field of magnetic resonance imaging. The pre-amplifier comprises an input matching circuit, an amplification circuit, an output matching circuit and a narrow band filter used for filtering a magnetic resonance signal amplified by the amplification circuit. The pre-amplifier has the technical effect of the pre-amplifier for the magnetic resonance imaging radio-frequency coil generating the gain required for magnetic resonance imaging within an extremely narrow range near a magnetic resonance signal frequency point, but only generating an extremely small gain or having no amplification function at all at other frequency points, thereby significantly reducing the probability of oscillation of the magnetic resonance imaging radio-frequency coil. Further provided is a pre-amplifier for a magnetic resonance imaging radio-frequency coil, which can achieve the technical effect, comprising an input matching circuit, a first-level amplification circuit, a narrow band filter circuit, a second-level amplification circuit, and an output matching circuit.