Multi-Channel RF Antenna SAR Calculation via Q-Value Coupling
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Solution Overview
Problem
In MRI apparatuses with multiple channels, accurate Specific Absorption Rate (SAR) management is challenging due to coupling between channels, leading to overestimation or underestimation of object power consumption, which affects image quality and safety compliance.
Innovation Solution
An MRI apparatus with a radiofrequency antenna and a Q-value calculating unit that computes Q values using reflected signals from multiple channels, accounting for coupling effects, to accurately estimate SAR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If Q values are measured for each channel separately in a multi-channel RF antenna system, then the calculation is simplified, but coupling between channels causes overestimation or underestimation of object power consumption, reducing measurement precision
Solution Approach 1:
The patent divides the multi-channel RF antenna system into individual channel components, measuring Q values for each channel separately. By segmenting the system this way, the complex multi-channel coupling problem is broken down into manageable single-channel measurements, while still achieving accurate total object power consumption calculation through proper summation of individual channel contributions.
Solution Approach 2:
The patent incorporates a feedback mechanism where the measured Q values from each channel are used to calculate object power consumption, and this information feeds back into the SAR management system. The system continuously monitors and adjusts RF pulse parameters based on the calculated object power consumption to maintain accurate SAR levels, creating a closed-loop control system.
2Measurement precision
If SAR management is performed with coupling effects considered, then measurement precision improves, but device complexity increases due to need to compute reflected signals from multiple channels
Solution Approach 1:
The patent introduces a Q-value calculating unit as an intermediary component that handles the complex computations of reflected signals and coupling effects. This intermediary device processes the raw signal data from multiple channels, performs the necessary calculations including coupling effect compensation, and outputs the corrected object power consumption values, thereby managing the complexity in a dedicated computational module.
Solution Approach 2:
The patent replaces direct physical measurement of object power consumption with a computational approach using Q value measurements and mathematical calculations. Instead of attempting to directly measure the complex interacting fields from multiple channels, the system uses substitution of measurement quantities (Q values) and computational models to derive the desired information, simplifying the physical measurement process while maintaining accuracy.
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
Enables precise SAR management, ensuring safe irradiation power levels and maintaining image quality by accurately calculating object power consumption despite channel coupling, thereby adhering to safety standards.
Implementation Method 1
an object disposed in a homogenous magnetostatic field that is generated by a magnetostatic field magnet is irradiated with a radiofrequency pulse (hereinafter, referred to as an 'RF pulse') as an electromagnetic wave, nuclear spin is excited in the object, an NMR signal as the electromagnetic wave generated through the nuclear spin is received
Implementation Method 2
computes reflected signals of the plurality of channels of the radiofrequency antenna, respectively, in a case where transmission signals as electrical signals are simultaneously applied to the plurality of channels of the radiofrequency antenna, also including a signal that is a retrograde wave when the transmission signal supplied to one channel of the plurality of channels turns back from another channel
Data Source
AI summary
A radiofrequency antenna has a plurality of channels. A Q-value calculating unit computes reflected signals of the plurality of channels of the radiofrequency antenna, respectively, in a case where transmission signals as electrical signals are simultaneously supplied to the plurality of channels of the radiofrequency antenna, also including a signal obtained when the transmission signal supplied to one channel of the plurality of channels is reflected from another channel, and computes a Q value of the radiofrequency antenna using the reflected signal. An SAR calculating unit calculates a specific absorption rate (SAR) using the Q value.