MRI Preamplifier Feedback Network for Oscillation Suppression
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Solution Overview
Problem
Magnetic Resonance Imaging (MRI) systems face preamplifier oscillation issues due to the placement of preamplifiers close to coil elements, leading to degraded imaging performance, which conventional methods attempt to address with additional devices like baluns and shielding, but these solutions increase cost and complexity and affect decoupling performance.
Innovation Solution
A preamplifier arrangement with a feedback network that generates frequency-selective negative feedback using a parallel resonator to suppress oscillations at specific frequencies, reducing gain peaks outside the clinically relevant band without using baluns or additional shielding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If preamplifiers are placed close to coil elements, then preamplifier-decoupling performance is improved and signal to noise ratio is improved, but preamplifier oscillation occurs and imaging performance is degraded
Solution Approach 1:
The patent applies feedback by introducing a feedback network connected to the preamplifier that detects oscillation signals and generates corrective feedback signals to suppress the oscillation. The feedback network includes components that sense the preamplifier output and feed back a portion to the input with appropriate phase and amplitude to cancel out the oscillation, thereby maintaining stable operation while keeping the preamplifier close to the coil elements.
2Reliability
If conventional devices like input baluns and additional shielding are used to reduce preamplifier feedback, then preamplifier oscillation is reduced, but device complexity and cost increase
Solution Approach 1:
The patent merges the oscillation suppression function with the existing preamplifier structure by integrating a feedback network that uses components already present in the preamplifier circuitry. Rather than adding separate shielding structures or baluns, the solution combines oscillation detection and suppression within the preamplifier's signal path, thereby reducing overall system complexity while maintaining reliability.
3Reliability
If input baluns are used to reduce preamplifier feedback, then oscillation is reduced, but preamplifier-decoupling performance is adversely affected
Solution Approach 1:
The patent applies local quality by implementing frequency-selective feedback that targets only the specific oscillation frequencies without affecting the broader frequency range used for signal reception. The feedback network is designed to provide oscillation suppression at problematic frequencies while maintaining high input impedance and decoupling performance across the clinical frequency band, thereby locally addressing the oscillation issue without globally degrading decoupling performance.
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 effectively reduces preamplifier oscillation while maintaining signal quality and decoupling performance, mitigating system instability without increasing complexity or cost.
Implementation Method 1
a feedback network connected to each of the plurality of preamplifier with each of the feedback networks configured to generate negative feedback at one or more oscillation frequencies
Implementation Method 2
the feedback networks each include a parallel resonator configured to provide selective negative feedback to the preamplifiers
Data Source
AI summary
A system and method for generating preamplifier feedback in magnetic resonance imaging (MRI) systems are provided. A preamplifier arrangement for the MRI system includes a plurality of preamplifiers with each of the preamplifiers connected to a different channel of a multi-channel coil array of the MRI system. The preamplifier arrangement further includes a feedback network connected to each of the plurality of preamplifiers with each of the feedback networks configured to generate negative feedback at one or more oscillation frequencies.