Temporal-Weighted MRI K-Space Trajectories Reduce Off-Resonance Artifacts
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Solution Overview
Problem
Existing accelerated MRI techniques using non-Cartesian k-space sampling are prone to off-resonance artifacts due to B0 inhomogeneities, which are challenging to correct and computationally intensive.
Innovation Solution
The MORE-SPARKLING method modifies SPARKLING trajectories by introducing temporal weighting in k-space to enforce smooth sampling, reducing sensitivity to off-resonance artifacts without complex corrections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If non-Cartesian k-space sampling is used for accelerated MRI, then acquisition time is reduced, but off-resonance artifacts increase due to B0 inhomogeneities
Solution Approach 1:
The patent modifies the SPARKLING trajectory parameters by introducing temporal weighting that enforces smooth sampling through k-space. This changes the sampling density distribution over time, reducing temporal variations that cause off-resonance artifacts while maintaining the accelerated non-Cartesian sampling approach
Solution Approach 2:
The patent introduces dynamic temporal weighting to the sampling trajectory, making the sampling density adaptive over time. The weighting scheme adjusts the sampling rate dynamically to ensure smooth progression through k-space, minimizing the temporal discontinuities that generate off-resonance artifacts
2Object-affected harmful factors
If conventional artifact correction methods are applied to non-Cartesian sampling, then off-resonance artifacts are reduced, but computational cost increases significantly
Solution Approach 1:
The patent applies preliminary action by pre-weighting the sampling trajectory with temporal weights before data acquisition. This preventive measure embeds the artifact reduction strategy into the sampling process itself, eliminating the need for complex post-processing correction algorithms
3Loss of time
If high acceleration factors are used in parallel MRI, then acquisition time is reduced, but image quality deteriorates rapidly
Solution Approach 1:
The patent changes the sampling trajectory parameters by applying temporal weighting that smooths the sampling density distribution. This parameter modification allows achieving higher acceleration factors while maintaining image quality by reducing the artifacts that normally deteriorate at high acceleration rates
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
MORE-SPARKLING significantly reduces off-resonance artifacts while maintaining acceleration benefits, improving image quality and reducing computational costs associated with artifact correction.
Implementation Method 1
positioning the body in a scanner bore where a static and substantially uniform magnetic field, called longitudinal field, oriented along a direction, called longitudinal direction, is established by the primary coil
Implementation Method 2
using all or part of the radio-frequency coils to transmit to said body at least one radio-frequency pulse adapted to excite nuclear spins inside said body
Implementation Method 3
using the gradient coils to apply to said body a time-varying magnetic field gradient defining a trajectory in k-space
Implementation Method 4
simultaneously using all or part of the radio-frequency coils to acquire samples of a magnetic resonance signal emitted by the excited nuclear spin
Data Source
AI summary
A method of performing magnetic resonance imaging of a body using a magnetic resonance imaging scanner the method includes applying to the body a time-varying magnetic field gradient (Gx, Gy, Gz) defining a continuous trajectory (ST) in k-space complying with a set of constraints including constraints on maximum amplitude and maximum slew rate of the time-varying magnetic field gradient, such that sampling points (KS) belonging to the trajectory define a pseudo-random sampling of the k-space, approximating a predetermined target sampling density, the trajectory in k-space minimizing, subject to the set of constraints, a cost function defined by the difference between a first term, called attraction term, promoting consistency of the distribution of sampling points in k-space with the predetermined target sampling density, and a second term, called repulsion term, promoting separation in k-space between sampling points, the repulsion term being expressed as a sum of contributions corresponding to respective pairs of sampling points; wherein each the contribution is weighted by a weight which increase with temporal separation of the sampling points along the trajectory in k-space.