RF Coil Current Monitoring via Directional Couplers
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Solution Overview
Problem
Existing multi-channel transmit/receive RF systems for magnetic resonance examination systems require numerous electronic components to monitor specific absorption rate (SAR), which increases complexity and cabling, posing risks and inefficiencies.
Innovation Solution
A multi-channel RF system with directional couplers and a monitoring module to measure forward and reflected wave amplitudes, allowing calculation of individual coil element currents without additional pick-up coils, using a distribution matrix to estimate SAR directly from these measurements, reducing the need for extra components and cabling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional pick-up coils and cabling are used to monitor individual antenna element currents, then SAR monitoring accuracy is improved, but device complexity and cabling requirements increase
Solution Approach 1:
The patent extracts the current monitoring function from separate pick-up coils and integrates it into the existing directional couplers used for RF power monitoring. By measuring forward and reflected wave amplitudes at the directional couplers and calculating coil element currents from these measurements, the system eliminates the need for additional pick-up coils and their associated cabling, thereby reducing device complexity while maintaining measurement capability
Solution Approach 2:
The directional couplers in the RF system are made multi-functional by enabling them to perform both their original function of monitoring RF power and the additional function of measuring coil element currents for SAR calculation. This universal approach allows a single component to serve multiple purposes, reducing the total number of electronic components needed in the system
2Measurement precision
If numerous electronic components are used for SAR monitoring, then monitoring accuracy is improved, but reliability decreases due to increased failure points
Solution Approach 1:
By extracting the monitoring function from separate pick-up coils and integrating it into existing directional couplers, the patent reduces the number of electronic components that can fail. The calculation of coil element currents from forward and reflected wave measurements performed by the existing monitoring module eliminates additional sensors and their connection points, thereby reducing potential failure points while maintaining monitoring accuracy
Solution Approach 2:
The patent merges the SAR monitoring function with the existing RF power monitoring function performed by directional couplers. By combining these functions into a single integrated approach using existing components, the system reduces the total component count and interconnections, thereby improving reliability while maintaining the ability to accurately monitor SAR through mathematical calculation of coil currents
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 simplifies SAR monitoring by eliminating the need for additional pick-up coils and cabling, reducing common mode propagations and enabling accurate SAR estimation for magnetic resonance imaging, while minimizing electronic components on the coil or coil-array.
Implementation Method 1
directional couplers circuited between respective antenna elements and the power distributor, wherein a monitoring module is configured to measure forward electrical wave amplitude(s) and reflected electrical wave amplitude(s) at individual directional couplers
Data Source
AI summary
A multi-channel transmit/receive radio frequency (RF) system for a magnetic resonance examination system with an RF antenna array includes multiple antenna elements and an RF power supply to supply electrical RF power to the antenna elements. Directional couplers are circuited between respective antenna elements and a power distributor. A monitoring module is configured to measure forward electrical wave amplitude(s) and reflected electrical wave amplitude(s) at individual directional couplers. An arithmetic module is configured to compute individual coil element currents on the basis of the measured forward and reflected electrical wave amplitudes.