Slice-Specific Gradient Correction for MRI Inhomogeneity
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Solution Overview
Problem
In multi-contrast slice multiplexing magnetic resonance imaging, existing methods fail to adequately correct main magnetic field inhomogeneities of the first order, leading to inadequate fat saturation and contrast homogeneity, especially in regions with strong B0 distortions, as adjustments are typically averaged across all slices rather than being slice-specific.
Innovation Solution
A method that determines and applies slice-specific correction parameters for gradient pulses based on a main magnetic field map, allowing for direct correction of first-order magnetic field inhomogeneities in each slice during the excitation period, improving contrast homogeneity and fat saturation by using slice-specific adjustments for each slice, even when multiple slices are imaged simultaneously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If averaged correction parameters are used across all slices, then the complexity of the system is reduced, but the precision of magnetic field correction deteriorates, leading to inadequate fat saturation and contrast homogeneity
Solution Approach 1:
The patent divides the correction process into slice-specific segments. Instead of applying a single averaged correction parameter to all slices, the system determines and applies separate correction parameters for each slice based on its position and characteristics. This segmentation allows precise correction of first-order magnetic field inhomogeneities in each slice while maintaining manageable system complexity through automated parameter determination.
2Measurement precision
If slice-specific correction parameters are applied, then the precision of magnetic field correction is improved, but the device complexity increases
Solution Approach 1:
The system employs self-service mechanisms where the correction parameters are automatically determined based on the slice position and main magnetic field map, without requiring manual intervention. The automated determination process reduces the operational complexity despite the increased precision from slice-specific corrections, as the system self-adjusts based on predefined criteria and stored field maps.
3Productivity
If multiple slices are imaged simultaneously, then the productivity is improved, but the reliability of contrast homogeneity deteriorates due to inadequate correction of magnetic field inhomogeneities
Solution Approach 1:
The patent applies local quality corrections by tailoring correction parameters to each slice's specific characteristics and position. Each slice receives customized correction based on its location in the magnetic field and its individual inhomogeneity profile, ensuring reliable contrast homogeneity is maintained even when multiple slices are imaged simultaneously at high speed.
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 the quality of magnetic resonance data by providing slice-specific corrections that improve signal-to-noise ratio and contrast homogeneity, particularly in fat-suppression, by addressing the limitations of averaged corrections across all slices.
Implementation Method 1
the examination subject is positioned in a magnetic resonance apparatus in a comparatively strong static, homogeneous main magnetic field, also known as the B0-Feld, with field strengths of 0.2 tesla to 7 tesla and more, such that the nuclear spins thereof are orientated along the main magnetic field
Implementation Method 2
To trigger nuclear magnetic resonances, high frequency excitation pulses (also known as RF-pulses) are radiated into the examination subject. The nuclear magnetic resonances that are triggered are measured as what is known as k-space data
Implementation Method 3
For the spatial encoding of the magnetic resonance data, rapidly switched magnetic gradient fields are superimposed on the main magnetic field
Data Source
AI summary
A method for the simultaneous recording of magnetic resonance data relating to an examination subject from at least two different slices by a magnetic resonance sequence, wherein an excitation period of the magnetic resonance sequence that includes at least one sub-section that acts on only one of the slices, and that contains at least one high frequency pulse is used, wherein, to correct the main magnetic field inhomogeneities of the first order, for each slice affected by a sub-section, a correction parameter that modifies the gradient pulses that are to be emitted is determined, taking into account at least one main magnetic field map that describes the spatial distribution of the main magnetic field and a slice position of the affected slice and is applied in the emission of gradient pulses for the respective slice in the sub-section.