MRI Shimming via Multi-Slice Phase Data for Field Uniformity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current magnetic resonance imaging (MRI) systems face challenges in achieving uniformity of the static magnetic field, leading to non-uniformity artifacts, poor fat saturation, and longer pre-scan times due to limitations in existing shimming methods.
Innovation Solution
A shimming method that performs a scout scan to obtain phase data from multiple slice positions, determining three-dimensional static magnetic field information and calculating shimming values for each slice in a region of interest, reducing pre-scanning time and improving field uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a scout scan is performed to obtain phase data from multiple slice positions for determining three-dimensional static magnetic field information, then the accuracy of shimming value determination and fat saturation performance are improved, but the scanning time increases
Solution Approach 1:
The patent divides the magnetic field correction process into multiple slice positions within the region of interest, acquiring phase data separately for each slice. This segmentation allows precise measurement of magnetic field inhomogeneity at different locations, enabling accurate determination of shimming values for each slice while maintaining efficient scanning through the segmented approach.
Solution Approach 2:
The patent performs a scout scan as a preliminary action before the main diagnostic scan. During this scout scan, phase data from multiple slice positions are acquired to determine three-dimensional static magnetic field information and calculate optimal shimming values. This preliminary characterization of the magnetic field enables optimized scanning parameters to be set beforehand, improving both accuracy and efficiency in the subsequent diagnostic scan.
2Productivity
If existing shimming methods using central slice calculation are employed, then the pre-scan process is simpler and faster, but the fat saturation performance and field uniformity are degraded
Solution Approach 1:
The patent applies local quality by determining shimming values specifically for each slice within the region of interest rather than using a single central slice calculation. Phase data are acquired from multiple slice positions, and shimming values are calculated locally for each slice based on its specific magnetic field characteristics. This localized approach ensures optimal fat saturation and field uniformity for each slice while maintaining overall scanning efficiency.
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 enhances fat saturation performance and accurately corrects non-uniformities in the static magnetic field, reducing pre-scanning time while maintaining scanning sequence integrity.
Implementation Method 1
MRI utilizes the main magnet to generate a static magnetic field B0. When a subject to be examined is located in the static magnetic field B0, nuclei associated with hydrogen nuclei in a tissue of the subject to be examined spin and become polarized
Implementation Method 2
Magnetic resonance imaging (MRI) systems have been widely applied in the field of medical diagnosis. Magnetic resonance systems usually have a main magnet, a gradient radio-frequency amplifier, a gradient coil, a transmitting chain module, a transmitting/receiving coil, a receiving chain module, etc.
Implementation Method 3
After a radio-frequency field B1 intersecting the direction of the static magnetic field B0 is applied, the rotation direction of the protons changes, causing the tissue to be examined to produce a transverse magnetization vector macroscopically
Implementation Method 4
After the radio-frequency field B1 is removed, the transverse magnetization vector decays in a spiral manner until it returns to zero. A free induction decay signal is generated during the decay process. The free induction decay signal can be acquired as a magnetic resonance signal
Data Source
AI summary
Embodiments of the present application provide a magnetic resonance system and a shimming method and an imaging method thereof. The shimming method comprises: performing a scout scan on a subject to be examined, and obtaining phase data of a plurality of slice positions; determining three-dimensional space static magnetic field information according to the phase data of the plurality of slice positions; and determining a shimming value of a slice in a region of interest according to the three-dimensional space static magnetic field information.