Minimizing k-Space Trajectory Lengths in MRI Echo Trains
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Solution Overview
Problem
In magnetic resonance imaging, the duration required to acquire MR data for three-dimensional turbo spin echo sequences remains a challenge, particularly with coherent and incoherent undersampling methods, leading to fluctuations and movements during echo trains, which can cause eddy currents and peripheral nerve stimulation, and affect image contrast.
Innovation Solution
A method is developed to distribute k-space lines among echo trains such that their trajectory lengths are minimized, with each k-space line intersecting a plane orthogonally, ensuring that each echo train scans k-space lines in an optimal order, reducing fluctuations and improving image contrast by associating k-space lines with echo trains in a way that minimizes the sum of their trajectory lengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If incoherent undersampling is used for compressed sensing, then acquisition time is reduced, but fluctuations and movements occur within echo trains causing eddy currents and peripheral nerve stimulation
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing optimal k-space line assignments for different echo trains before the actual MRI acquisition. The system determines the optimal trajectory length for each echo train in advance and assigns k-space lines accordingly, so that when acquisition occurs with compressed sensing undersampling, the harmful fluctuations are already minimized by the pre-optimized assignment strategy.
Solution Approach 2:
The patent changes the parameter of k-space line assignment by introducing a new optimization criterion: minimizing trajectory length. Instead of using conventional assignment methods, the system calculates trajectory lengths for different echo train assignments and selects the assignment that minimizes the sum of trajectory lengths, thereby reducing the harmful fluctuations and movements during accelerated acquisition.
2Productivity
If k-space lines are scanned with echo trains, then data acquisition is completed, but large trajectory lengths cause fluctuations and movements within echo trains
Solution Approach 1:
The system performs preliminary calculation of optimal k-space line assignments before data acquisition. By computing the trajectory lengths and determining the optimal assignment of k-space lines to echo trains in advance, the system ensures that when the actual scanning occurs, the trajectory lengths are minimized, thereby reducing fluctuations and maintaining stability during the acquisition process.
Solution Approach 2:
The patent introduces a new parameter optimization approach by minimizing the sum of trajectory lengths across all echo trains. This parameter change in the assignment strategy directly reduces the fluctuations and movements within echo trains while maintaining complete data acquisition, resolving the contradiction between productivity and stability.
3Speed
If strong gradients are used to accelerate acquisition, then scan speed is increased, but eddy currents and peripheral nerve stimulation are enhanced
Solution Approach 1:
The patent changes the assignment parameters of k-space lines to echo trains based on minimizing trajectory length. This parameter optimization reduces the total gradient switching and movement required during acquisition, thereby decreasing eddy currents and peripheral nerve stimulation even when strong gradients are used to maintain scan speed.
Data Source
AI summary
In a method to associate k-space lines with echo trains of raw magnetic resonance data, parallel k-space lines orthogonally intersect a plane at respective intersection points. Each echo train has a trajectory length, and the k-space lines are associated with the echo trains such that a sum of trajectory lengths of all echo trains is minimal. The trajectory length TL of an echo train is defined byTL=∑i=1L-1PiPi+1_wherein L is a sequence of k-space lines, Pi is an intersection point of the i-th k-space line of the echo train with the plane; and PiPi+1 is the length of the path from the i-th intersection point to the (i+1)-th intersection point.