MRT Local Coil Frequency Converter for Low-Field Movement Detection
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Solution Overview
Problem
Magnetic resonance tomography (MRT) systems with low static magnetic field strengths face challenges in reliably detecting patient movements, such as heartbeat, due to decreased modulation degree with frequency.
Innovation Solution
A local coil designed for MRT systems that acquires both magnetic resonance signals and pilot tone signals, with a frequency converter that brings the pilot tone signal into a common frequency range with the magnetic resonance signal, allowing for simultaneous processing and evaluation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a continuous wave magnetic field is used to detect patient movement, then the hardware complexity is reduced, but the modulation degree decreases strongly with frequency, making reliable detection difficult in low-field systems
Solution Approach 1:
The patent changes the frequency parameter of the pilot tone signal to be significantly higher than the Larmor frequency, and introduces a frequency converter to shift the pilot tone signal into a common frequency range with the magnetic resonance signal. This parameter transformation enables reliable movement detection in low-field systems while maintaining hardware simplicity.
2Ease of operation
If the pilot tone signal frequency is close to the magnetic resonance signal frequency, then the same receiver can evaluate both signals simultaneously, but the modulation degree decreases strongly with frequency
Solution Approach 1:
The patent applies frequency conversion to transform the pilot tone signal from a high frequency (significantly higher than Larmor frequency) into a common frequency range with the magnetic resonance signal. This allows both signals to be processed by the same receiver while maintaining high modulation degree and detection precision.
Solution Approach 2:
The frequency converter acts as an intermediary device that bridges the gap between the high-frequency pilot tone signal and the magnetic resonance signal, enabling both to be evaluated by the same receiver without compromising detection precision.
3Measurement precision
If the pilot tone signal frequency is significantly higher than the magnetic resonance signal frequency, then the modulation degree is improved, but the signals cannot be processed by the same receiver
Solution Approach 1:
The patent uses a frequency converter to change the frequency parameter of the pilot tone signal from a high frequency into a common frequency range with the magnetic resonance signal. This enables both signals to be processed by the same receiver while maintaining high modulation degree and detection precision.
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 solution enhances the reliability and stability of movement detection in low-field MRT systems by improving the signal-to-noise ratio of the pilot tone signal and allowing it to be processed by the same receiver as the magnetic resonance signal.
Implementation Method 1
Acquisition in this case, in particular, refers to the conversion of the magnetic or electromagnetic radio-frequency alternating field of the nuclear spins and of the pilot tone signal into an electrical signal by an antenna or induction loop
Implementation Method 2
The local coil has a frequency converter. The frequency converter of the local coil converts the acquired pilot tone signal into a common frequency range with the magnetic resonance signal
Implementation Method 3
Since most biological tissues are almost completely transparent to magnetic fields, the generated magnetic field penetrates the body of the patient almost unchanged
Implementation Method 4
However, most tissues are (weakly) conductive and hence the continuous wave magnetic field induces eddy currents
Implementation Method 5
These eddy currents then in turn generate a magnetic field superimposed on the excitation field, resulting in modulations in the received magnetic field in the receiving coil
Implementation Method 6
The magnetic resonance tomography system has a receiver designed simultaneously to receive and evaluate a pilot tone signal and a magnetic resonance signal
Data Source
AI summary
A local coil for a magnetic resonance tomography is designed to acquire a magnetic resonance signal and a pilot tone signal and to forward them to a receiver of the magnetic resonance tomography system for evaluation. The pilot tone signal lies in a first frequency range and the magnetic resonance signal in a second frequency range.