MRI Main Magnetic Field Correction via Variable Resonant Frequency Imaging
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Solution Overview
Problem
Conventional methods for correcting the main magnetic field in MRI systems are costly, complex, and time-consuming, especially in remote locations, and require manual operation and transportation of measuring devices, which can be damaging and inefficient.
Innovation Solution
A method involving a series of imaging sequences with variable resonant frequencies to estimate and pre-correct the main magnetic field, followed by accurate shimming based on phase differences in phantom images, allowing for automated correction and improved uniformity without the need for extensive manual handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetometers are used to measure magnetic field strength manually, then measurement precision is improved, but device complexity and operational complexity increase
Solution Approach 1:
The patent replaces the mechanical/manual measurement system (magnetometers requiring manual positioning and support structures) with an automated imaging-based system. The MRI scanner automatically acquires images at multiple resonant frequencies, and image processing algorithms computationally determine magnetic field uniformity, eliminating the need for complex mechanical measurement apparatus.
Solution Approach 2:
The patent creates a virtual representation (image) of the magnetic field distribution by acquiring MRI images at multiple resonant frequencies. This digital copy of the magnetic field state allows for analysis and correction without requiring direct physical measurement, simplifying the overall system while maintaining measurement capability.
2Measurement precision
If magnetometers are manually operated and transported, then measurement capability is maintained, but loss of time and transportation costs increase
Solution Approach 1:
The MRI scanner performs the measurement function autonomously without requiring external measurement devices or manual operation. The system automatically acquires images at multiple resonant frequencies, processes them to determine magnetic field uniformity, and generates correction information, eliminating time lost in device transportation and manual setup.
Solution Approach 2:
The system performs preliminary imaging at multiple resonant frequencies before final correction is applied. This preliminary action captures the magnetic field state in advance, allowing for computational analysis and correction planning without requiring time-consuming manual measurement procedures during the actual correction process.
3Device complexity
If conventional shimming is performed with poor magnetic field uniformity, then correction process is simplified, but manufacturing precision and correction accuracy worsen
Solution Approach 1:
The patent performs preliminary imaging at multiple resonant frequencies to accurately characterize the magnetic field uniformity before correction. This preliminary action provides comprehensive information about the field distribution, enabling precise correction even when initial uniformity is poor, rather than attempting correction under suboptimal conditions.
Solution Approach 2:
The system changes the resonant frequency parameter during imaging to capture magnetic field variations across different frequencies. By acquiring images at multiple resonant frequencies and analyzing the phase differences, the system accurately determines magnetic field uniformity and generates precise correction information, improving correction accuracy without increasing operational complexity.
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 and accelerates the correction process, achieving uniformity comparable to magnetometer-based methods while reducing costs and operational complexity, even in challenging geographical settings.
Implementation Method 1
When a part to be imaged of the human body is positioned in the static magnetic field B0, nuclear spin associated with hydrogen nuclei in human tissues is polarized
Implementation Method 2
A free induction decay signal is generated during decay of the transverse magnetization vector. The free induction decay signal can be acquired as a magnetic resonance signal
Implementation Method 3
imaging the phantom respectively based on a plurality of radio-frequency excitation pulses to obtain a plurality of images to be synthesized, the plurality of radio-frequency excitation pulses having different frequencies
Implementation Method 4
Shimming is subsequently performed on the basis of the measured magnetic field strength. For example, shimming pieces are added to the main magnet to adjust the magnetic field strength of a specific position
Data Source
AI summary
A main magnetic field correction method for a magnetic resonance imaging system includes: obtaining an estimated image of a phantom based on a first imaging sequence, the first imaging sequence having a variable resonant frequency; pre-correcting a main magnetic field based on the estimated image; obtaining a scanned image of the phantom based on the pre-corrected main magnetic field; and determining whether the quality of the scanned image is within an acceptable range, and if not, returning to the step of obtaining the estimated image.