Magnetic Resonance Frequency Calibration Using Relaxation Time
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Solution Overview
Problem
Magnetic resonance tomography systems face challenges in accurate frequency calibration, particularly when substances other than water, such as fat or silicone, produce the highest peak value in the frequency spectrum, leading to faulty calibrations.
Innovation Solution
A method for frequency calibration in magnetic resonance systems involves exciting nuclear spins in a predetermined volume with RF pulses, acquiring multiple echo signals, converting them into spectral information, determining peak values and relaxation times, and assigning these values to specific substances based on relaxation times and resonance frequency differences, allowing for automatic identification and calibration without user specification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the highest peak value in the frequency spectrum is automatically assigned to water for frequency calibration, then the calibration process is simple and fast, but the calibration becomes faulty when fat or silicone produces a higher peak value than water
Solution Approach 1:
The patent changes the calibration parameter from simply using peak amplitude to using relaxation time (T2) as the distinguishing parameter. By measuring the relaxation time of different substances and comparing them against known reference values, the system can accurately identify water even when its peak amplitude is not the highest in the spectrum.
Solution Approach 2:
The patent introduces relaxation time as an intermediary parameter between the frequency spectrum and substance identification. Instead of directly using peak amplitude to identify substances, the system uses relaxation time measurements as an intermediate step to correctly identify water and other substances, thereby resolving the ambiguity in frequency calibration.
2Measurement precision
If multiple substances with different relaxation times are present in the frequency spectrum, then accurate substance identification is possible, but the complexity of determining which substance corresponds to which peak increases
Solution Approach 1:
The system performs self-identification of substances by automatically measuring relaxation times and comparing them against pre-stored reference values in a lookup table. The control device autonomously determines which substance corresponds to which peak without requiring manual intervention or complex user input, thereby reducing operational complexity while maintaining high identification accuracy.
Solution Approach 2:
The patent prepares reference data for multiple substances (water, fat, silicone) in advance, storing their characteristic relaxation times in a lookup table before the actual measurement. This preliminary preparation allows the system to quickly and accurately identify substances during calibration by simply comparing measured relaxation times against the pre-stored references, avoiding complex real-time analysis.
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 method enables robust and reliable frequency calibration, reducing user errors and measurement complexity, especially in applications like breast MR imaging, by accurately identifying and calibrating resonance frequencies for substances like water, fat, and silicone, thereby improving the quality of MR measurements.
Implementation Method 1
Nuclear spins in a predetermined volume section of a subject are excited, that contain an unknown number of predetermined substances, with RF pulses
Implementation Method 2
Multiple echo signals are acquired (detected) at different times after the respective excitation
Implementation Method 3
Each of the recorded echo signals is (as a rule by means of a Fourier transformation) converted into respective spectral information (i.e. in a frequency spectrum)
Data Source
AI summary
In a method for frequency calibration in a magnetic resonance system in a volume section containing an unknown number of determined substances, the predetermined volume section is excited with RF pulses and subsequent echo signals are recorded at different times and spectral information is determined for each of the echo signals, from which a peak value in the spectral information and an associated relaxation time are determined. Dependent on the relaxation time, a substance is determined for each peak value. A frequency adjustment substance dependent of the magnetic resonance system is then implemented. Multiple peak values in the spectral information of the echo signals can be determined.