Local-Coil Amplifier Bias Control for MRT Power Reduction
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Solution Overview
Problem
Local-coil apparatuses in magnetic resonance tomography (MRT) units face high power dissipation due to the need for high linearity in amplifier stages, leading to increased heating and power consumption, which is undesirable for patient comfort and efficiency.
Innovation Solution
The receive amplifier apparatus in the local-coil apparatus is designed to operate in high-current mode only near the center of k-space for maximum linear drive capability and in low-current mode elsewhere for minimum noise figure, with a switchover of bias current based on defined signal levels to reduce power dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If amplifier stages are operated at high bias current to ensure high linearity in the entire drive range, then signal distortions are prevented, but power dissipation and heating increase
Solution Approach 1:
The patent applies dynamics by making the bias current adjustable rather than fixed. The receive amplifier apparatus dynamically changes its operating mode between high-current mode (for high linearity near k-space center) and low-current mode (for minimum noise figure elsewhere), based on the signal level detected from the MRT signal. This dynamic adaptation resolves the contradiction by allowing high linearity only when needed while reducing power dissipation during most of the receive time.
Solution Approach 2:
The patent changes the operating parameters (bias current level) of the amplifier stages based on the signal characteristics. By detecting the signal level and switching between high-current mode and low-current mode, the system optimizes the balance between linearity and power dissipation. This parameter change approach allows the amplifier to maintain high linearity when high signal levels are detected while operating at lower currents for most other conditions.
2Reliability
If amplifier stages are operated at high bias current to prevent signal distortions, then image artifacts are avoided, but heating of the local-coil apparatus increases
Solution Approach 1:
The system dynamically adjusts the bias current based on the k-space position and signal level. Near the center of k-space, where high linearity is critical to avoid image artifacts, the amplifier operates at high bias current. In other regions, it operates at lower bias current, significantly reducing heating. This dynamic operation resolves the contradiction between preventing artifacts and minimizing temperature rise.
Solution Approach 2:
The patent applies local quality by providing different operating conditions for different regions of k-space. The receive amplifier apparatus is configured to operate in high-current mode specifically for the central region of k-space where linearity is most critical, while using low-current mode for peripheral regions. This localized optimization reduces overall heating while maintaining artifact-free imaging in the most important area.
3Adaptability or versatility
If high gain is used for central region of k-space, then signal dynamic range is accommodated, but power dissipation increases
Solution Approach 1:
The receive amplifier apparatus dynamically switches between high-gain and low-gain modes based on the signal level detected from the MRT signal. When high signal levels are detected (indicating central k-space region), high gain is applied to accommodate the full signal dynamic range. When lower signal levels are detected (peripheral k-space regions), the system switches to low-gain mode, reducing power dissipation. This dynamic gain adjustment resolves the contradiction between signal dynamic range coverage and energy consumption.
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 reduces power dissipation and heating, enabling more efficient operation, including potential wireless operation, while maintaining the full signal dynamic range required for MRT signal processing.
Implementation Method 1
the excited nuclei induce a voltage in a receive coil of the local-coil apparatus
Implementation Method 2
amplified by cascaded amplification, (e.g., a low noise preamplifier (LNA) and at least one amplifier additionally connected thereafter)
Data Source
AI summary
The disclosure relates to a method, a computer program, a data storage medium, a system, and a local-coil apparatus for a magnetic resonance tomography MRT unit having at least one receive coil configured to receive an MRT signal and a receive amplifier apparatus having at least one output amplifier unit and configured to amplify the received MRT signal in order to drive an analog-to-digital converter ADC. The at least one output amplifier unit is configured to amplify the MRT signal, below a signal-level threshold value, by a high gain, and, above the signal-level threshold value, by a low gain. The receive amplifier apparatus is configured to change a bias current of the at least one output amplifier unit according to a defined MRT signal level.