Multi-Channel RF Transmitter Optimization for MRI
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Solution Overview
Problem
Current multi-channel near-field RF transmitters for MRI struggle with maintaining optimal performance across various excitation modes and loads, leading to inefficiencies in RF field homogeneity and increased sensitivity to load variations, due to complex optimization procedures and lack of reliable real-time SAR monitoring.
Innovation Solution
A method employing multi-mode, multi-load, and multi-domain optimization that simultaneously optimizes time and frequency domain criteria to minimize reflected power across all excitation modes, ensuring minimal reflected power and maintaining optimal RF homogeneity and safety efficiency, using a novel set of optimization criteria and a two-stage optimization approach.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional single-mode, single-load optimization is used, then optimization simplicity is maintained, but transmitter performance degrades when operating with multiple loads or modes
Solution Approach 1:
The patent segments the optimization problem into two distinct stages: a first optimization stage that minimizes reflected power for each individual load independently, and a second optimization stage that optimizes the system for multiple loads simultaneously. This segmentation allows complex multi-load optimization to be broken down into manageable steps, improving adaptability while controlling procedure complexity.
Solution Approach 2:
The patent performs preliminary optimization for each individual load before performing the final multi-load optimization. This preliminary action ensures that each load is pre-optimized, which serves as a foundation for the subsequent multi-load optimization and improves overall transmitter performance across different operating conditions.
2Reliability
If multi-load optimization is performed, then load independence is improved, but optimization time increases
Solution Approach 1:
The patent divides the multi-load optimization into sequential stages: first optimizing each load individually, then performing a second optimization that considers all loads together. This segmentation reduces the computational complexity compared to performing a full multi-load optimization in a single step, thereby reducing optimization time while maintaining load independence.
Solution Approach 2:
By performing preliminary single-load optimizations before the final multi-load optimization, the patent establishes a good initial state for each load. This preliminary action reduces the iteration time required in the final optimization stage, thus reducing total optimization time while achieving improved load independence.
3Loss of energy
If reflected power is minimized for all modes, then RF power efficiency is improved, but the complexity of optimization criteria increases
Solution Approach 1:
The patent segments the reflected power minimization into two optimization stages: the first stage minimizes reflected power for each individual load mode independently using simple criteria, while the second stage performs multi-load optimization. This segmentation simplifies the optimization criteria at each step compared to attempting to minimize reflected power for all modes simultaneously in a single complex optimization.
Data Source
Figure 1A
Figure 1B
Figure 2A~2B
AI summary
The invention relates to a method for optimization of a performance of a multi-channel transmitter comprising several transmit elements, particularly in a magnetic resonance imaging device, wherein the method comprises the following steps: (a) Exciting the transmit elements of the multi-channel transmitter by electric excitation signals comprising a specific power, wherein the power of the excitation signals is partially reflected by the transmit elements of the multichannel transmitter, (b) Determining a reflected power which is reflected by the multi-channel transmitter during excitation of the transmit elements, (c) Determining reflection coefficients Sxx of the multi-channel transmitter, (d) Determining reflection coefficients Sxy of the multi-channel transmitter, (e) Calculating a performance criterion representing the performance of the multi-channel transmitter, wherein the performance criterion is based on el) the reflected power and e2) the reflection coefficients Sxx and e3) the reflection coefficients Sxy, (f) Tuning the multi-channel transmitter so that the performance criterion is optimized.