MRI k-space echo arrangement control for phase error reduction
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Solution Overview
Problem
Existing MRI techniques using the fast spin echo method struggle with magnetic field errors that cause image artifacts due to varying errors across echoes in an echo train, requiring repeated pre-scans and extended imaging time, and cannot accurately address position-dependent error components.
Innovation Solution
An MRI apparatus controls the arrangement of echoes in k-space based on their phase characteristics after a single RF excitation, dispersing phase errors across the k-space to minimize image blurring by arranging echoes with smaller phase errors closer to the center of the k-space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pre-scans are repeated to perform highly accurate adjustment of pulse sequence, then measurement precision of phase error is improved, but imaging time is extended
Solution Approach 1:
The patent performs preliminary measurement of phase characteristics during the actual imaging process by using echoes with small phase errors as references, rather than requiring separate pre-scans. This preliminary action is integrated into the imaging sequence itself, allowing phase error characterization without extending total imaging time.
Solution Approach 2:
The imaging system uses its own acquired echoes (specifically those with small phase errors) as reference data for phase error measurement and correction, rather than requiring external reference scans. The system serves its own calibration needs using data already collected during imaging, eliminating the need for additional pre-scan time.
2Ease of operation
If pulse sequence adjustment is performed assuming uniform error for all echoes, then ease of operation is improved, but manufacturing precision of image quality deteriorates due to inability to handle position-dependent errors
Solution Approach 1:
The patent applies different correction strategies to different echoes based on their individual phase error characteristics. Instead of uniform correction, each echo is evaluated and corrected according to its specific phase error, allowing position-dependent errors to be addressed individually while maintaining operational simplicity through automated selection of reference echoes.
Solution Approach 2:
The patent dynamically adjusts the phase correction parameters for each echo based on measured phase characteristics. By changing the correction parameters individually for each echo rather than using a fixed uniform correction, the system achieves high image quality precision while maintaining ease of operation through automated parameter adaptation.
3Ease of manufacture
If echoes are arranged in conventional order in k-space, then ease of manufacture of pulse sequence is improved, but image quality deteriorates due to large discontinuities from position-dependent errors
Solution Approach 1:
The patent dynamically rearranges the order of echoes in k-space based on their phase error characteristics. Instead of a fixed conventional arrangement, the system adapts the echo ordering to minimize discontinuities, placing echoes with similar phase characteristics adjacent to each other while maintaining simple implementation through automated reordering algorithms.
Data Source
AI summary
To avoid discontinuities between echoes from becoming large level differences in a k-space and to reduce artifacts generated in a reconstructed image due to the discontinuities in the k-space, an MRI apparatus of the present invention uses phase characteristics of multiple echoes to be collected after a single RF excitation to control an arrangement order in the k-space where the multiple echoes are arranged when a pulse sequence of the fast spin echo method that collects the multiple echoes using a spin flip after a single RF excitation is executed. The arrangement is controlled so that echoes with small phase errors between the echoes at least near the center of the k-space are adjacent to each other.