MRI Phase Correction for Non-Orthogonal Sampling Blades
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Solution Overview
Problem
In MRI techniques using non-orthogonal sampling methods, phase differences between scanning trajectories (blades) lead to image quality degradation due to positional errors and phase mismatches, resulting in pixel value unevenness and image degradation.
Innovation Solution
A phase correction method is implemented during image reconstruction to match the phases at intersections between blades, using calculated shift amounts to adjust the phase differences, ensuring that the phases of all blades align at predetermined positions, thereby reducing phase changes and improving image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-orthogonal sampling method (radial scanning) is used, then resistance to body motion artifacts is improved, but phase difference at blade intersections degrades image quality
Solution Approach 1:
The patent applies preliminary action by calculating the phase difference at blade intersections before image reconstruction and correcting it in advance. The system calculates the phase difference using the formula φ = γ·G·Δx·T where γ is the gyromagnetic ratio, G is the gradient magnetic field strength, Δx is the positional deviation, and T is the echo time. This pre-correction prevents signal cancellation at intersections before the Fourier transform reconstruction, thereby maintaining both motion artifact resistance and image quality.
2Measurement precision
If blade arrangement position is corrected using gradient magnetic field output error data, then blade position accuracy is improved, but phase difference at intersections is not corrected
Solution Approach 1:
The patent introduces an intermediary correction step between blade positioning and image reconstruction. After blades are positioned according to gradient magnetic field output error data, an additional phase correction mechanism is applied as an intermediary layer. This mechanism calculates the phase difference φ = γ·G·Δx·T and applies phase compensation to ensure that both positional accuracy and phase consistency are achieved at blade intersections.
3Device complexity
If phase difference is not corrected at blade intersections, then processing complexity is reduced, but signal cancellation occurs causing pixel value unevenness
Solution Approach 1:
The patent applies parameter changes by modifying the phase parameter of the NMR signal at blade intersections. Instead of changing the fundamental sampling structure or blade arrangement, the system adjusts the phase parameter φ using the correction formula φ = γ·G·Δx·T. This minimal parameter adjustment prevents signal cancellation and pixel value unevenness while adding only a simple calculation step to the existing reconstruction process.
Data Source
AI summary
It is an object of the present invention to provide a technique for reducing the degradation of the image quality due to the phase difference between scanning trajectories (blades) in measurement using a non-orthogonal sampling method. Therefore, in the present invention, correction for reducing the phase difference between a plurality of scanning trajectories (blades) measured by using a non-orthogonal sampling method is performed at the time of image reconstruction. For example, the reduction of the phase difference is performed using a method of matching the phases at the intersections between blades, matching the phases of all blades at positions determined by considering the shift amount in the frequency direction, or canceling out the phase change amount of each blade obtained by calculation.