Local Coil Detuning and Preamplifier Voltage Management
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Solution Overview
Problem
Magnetic resonance tomography systems face challenges in optimizing local coil performance for both transmit and receive phases, particularly in managing signal forwarding and preamplifier voltage supply to minimize noise and ensure quick thermal and electrical settling.
Innovation Solution
The implementation of a local coil arrangement that uses PIN diodes and a λ/4 line in a resonant circuit for active detuning, with a control signal and supply voltage management system to maintain constant voltage to the preamplifier during both phases, preventing thermal and electrical settling issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the preamplifier is supplied with voltage during both transmit and receive phases, then thermal and electrical settling is ensured, but the device complexity increases due to additional voltage supply management
Solution Approach 1:
The voltage supply line is designed to serve multiple functions: it provides operating voltage to the preamplifier during receive phase and simultaneously serves as the signal transmission line during transmit phase. This multi-functionality eliminates the need for separate voltage supply and signal transmission lines, reducing device complexity while ensuring continuous voltage supply for thermal and electrical settling.
Solution Approach 2:
A switching mechanism acts as an intermediary to control the connection state of the voltage supply line based on the operational phase. During receive phase, the switching mechanism connects the voltage supply line to provide stable voltage to the preamplifier. During transmit phase, the switching mechanism reconfigures the connection to allow signal transmission while maintaining voltage supply through the same line.
2Measurement precision
If active detuning is implemented using PIN diode and λ/4 line, then signal-to-noise ratio is improved, but the device complexity increases due to additional detuning components
Solution Approach 1:
The detuning function is integrated into the existing resonant circuit structure by combining the PIN diode switching element with the λ/4 transmission line. This merging of functions allows the same structural elements to serve both as part of the resonant circuit and as the detuning mechanism, reducing the need for separate detuning components and minimizing overall device complexity.
Solution Approach 2:
The detuning mechanism works by changing the electrical parameters (conductance state) of the PIN diode between forward-biased and reverse-biased states. This parameter change allows the resonant circuit to switch between tuned and detuned states, improving signal-to-noise ratio during receive phase while maintaining simplicity through electrical control rather than mechanical or structural complexity.
3Object-affected harmful factors
If separate lines are used for voltage supply and signal transmission, then signal interference is reduced, but the device complexity and space requirements increase
Solution Approach 1:
The same transmission line is designed to perform dual functions: carrying voltage supply signals during receive phase and carrying RF signals during transmit phase. This multi-functional approach eliminates the need for separate voltage supply and signal transmission lines, reducing device complexity and space requirements while managing signal interference through phase-dependent connection control.
Solution Approach 2:
The system employs periodic switching to alternate between voltage supply mode and signal transmission mode on the same line. During receive phase, the line operates in voltage supply mode with the preamplifier powered. During transmit phase, the line switches to signal transmission mode. This periodic action allows a single line to serve multiple purposes, reducing overall system complexity.
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 enhances signal-to-noise ratio and allows for faster operation of the preamplifier, improving image quality and reducing noise interference during high-resolution imaging.
Implementation Method 1
Active detuning of the local coil takes place, for example, using a PIN diode and a lambda/4 line (e.g., a λ/4 line) in a resonant circuit of the local coil
Implementation Method 2
excited nuclei of an examination object (e.g., of a patient) induce a voltage by way of radiation emitted by the excited nuclei in an antenna of a local coil receiving the radiation
Data Source
AI summary
The present embodiments relate to a local coil for a magnetic resonance tomography system. The local coil includes a preamplifier for amplification of a signal received by the local coil from an examination object in a receive phase of the local coil. The local coil also includes a detuning device for detuning the local coil in a transmit phase of the local coil, and a rectification device for supplying voltage to the preamplifier.