MRI Spoiler Gradient Fields for Coherence Path Suppression
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Solution Overview
Problem
Current magnetic resonance imaging (MRI) techniques face challenges in efficiently suppressing unwanted signal contributions due to the interaction of spoiler gradient fields and RF fields in different preparation modules, leading to unwanted coherence paths and the rapid growth of required gradient moments, which can be difficult to generate or result in limitations in measurement sequences.
Innovation Solution
A method and apparatus for MRI that utilizes spoiler gradient fields varying in multiple spatial dimensions, with iterative selection of spoiler gradient moments to satisfy threshold conditions for orthogonal spatial directions, effectively suppressing unwanted coherence paths while minimizing the growth of required gradient moments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional gradient spoiling with the same gradient moment is used in different preparation modules, then suppression of transverse magnetization is achieved, but unwanted coherence paths occur due to interaction of spoiler gradient fields
Solution Approach 1:
The patent applies dimensionality change by transitioning from single-direction gradient spoiling to multi-directional gradient spoiling. Specifically, gradient moments are applied along different spatial directions (e.g., phase encoding direction, frequency encoding direction, slice selection direction) in different preparation modules. This dimensional diversification prevents the coherent interaction that causes unwanted signal contributions while maintaining effective spoiling of transverse magnetization.
Solution Approach 2:
The patent implements local quality by making the spoiler gradient fields spatially variable in different directions for different preparation modules. Instead of using a uniform gradient moment throughout, the gradient moment is selectively applied along specific spatial directions depending on the preparation module, creating locally optimized spoiling that adapts to the specific coherence paths present in each module.
2Reliability
If gradient moments are increased to suppress unwanted coherence paths, then suppression effectiveness is improved, but the required gradient moments grow rapidly and become difficult to generate
Solution Approach 1:
The patent resolves the gradient moment growth problem by distributing the spoiling action across multiple spatial dimensions. Instead of increasing the magnitude of gradient moments in a single direction, the patent applies moderate gradient moments along different spatial directions in different preparation modules. This distributes the spoiling burden across dimensions, preventing the rapid growth of required gradient moment magnitude while maintaining suppression effectiveness.
3Adaptability or versatility
If multiple preparation modules are used for signal suppression, then specific signal contributions can be suppressed, but interaction of RF fields and gradient fields leads to unwanted rephasing
Solution Approach 1:
The patent prevents unwanted rephasing in multiple preparation modules by applying gradient moments along different spatial directions in each module. This dimensional differentiation ensures that the phase accumulation from gradient fields does not coherently add up across modules, even when RF fields are applied. The multi-directional approach disrupts the rephasing condition that would otherwise occur with identical gradient moments.
Solution Approach 2:
The patent applies local quality by customizing the gradient moment direction and magnitude for each specific preparation module. Instead of using a uniform gradient spoiling strategy, the patent selects appropriate spatial directions for gradient moments based on the specific suppression requirements of each preparation module, thereby locally optimizing suppression while preventing unwanted interactions.
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 allows for reliable suppression of unwanted coherence paths and efficient gradient spoiling with smaller gradient moments, maintaining effective suppression even for complex imaging voxel orientations and reducing the technical limitations of existing methods.
Implementation Method 1
a gradient field generation device to generate spoiler gradient fields in multiple preparation modules
Implementation Method 2
It based on the physical effect of nuclear magnetic resonance
Data Source
AI summary
In a method and apparatus for magnetic resonance (MR) imaging, a magnetization of nuclear spins in a subject is prepared in multiple preparation modules of an acquisition sequence. MR signals are acquired with at least one imaging module of the sequence. Spoiler gradient fields are generated in the multiple preparation modules in order to affect a transverse magnetization of the spins. The spoiler gradient fields that are applied in at least two different preparation modules are spatially varied along different directions. Spoiler gradient moments of the spoiler gradient fields are selected so that, for at least one of three orthogonal spatial directions, a weighted sum of the spoiler gradient moments that are applied along this spatial direction satisfies a threshold condition.