Fan-Shaped Blade k-Space Sampling for MRI Motion Correction
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Solution Overview
Problem
In non-orthogonal system measurement for MRI, the contrast of reconstructed images decreases due to echo signals being arranged near the lower range of the k space, and body motion between blades complicates image quality and motion correction.
Innovation Solution
The use of fan-shaped blades in the k space, where each echo train is arranged with a fan-shaped region and an overlapping arc, ensures echo signals with desired TE are in the low spatial frequency region, allowing for body motion correction during image reconstruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-orthogonal system measurement is used to acquire data in k space, then the measurement is robust against motion artifacts, but the echo signals are arranged near the lower range of k space causing decreased image contrast
Solution Approach 1:
The patent divides the k space into multiple blades, where each blade contains a fan-shaped region and an overlapping arc region. This segmentation allows different regions to serve different purposes: the fan-shaped regions acquire data for image reconstruction while the overlapping arc regions are used for motion correction, thus resolving the contradiction between motion robustness and image contrast.
Solution Approach 2:
The patent performs motion correction using data from the overlapping arc regions before final image reconstruction. By preliminarily correcting motion artifacts using the redundant data in overlapping regions, the main image reconstruction can achieve both motion robustness and high contrast.
2Area of stationary object
If multiple blades are used to cover the k space, then complete k space coverage is achieved, but body motion between blades complicates image quality and requires motion correction
Solution Approach 1:
The patent merges multiple blades into a complete k space coverage, with each blade containing both fan-shaped and overlapping arc regions. The overlapping regions of adjacent blades are combined to provide redundant data for motion correction, thus achieving both complete k space coverage and motion correction capability.
Solution Approach 2:
The patent uses data from the overlapping arc regions as feedback to detect and correct body motion. The redundant data in overlapping regions provides information about motion that occurred between blade acquisitions, which is then used to correct the main image data.
3Manufacturing precision
If fan-shaped blades with overlapping arcs are used, then echo signals with desired TE are arranged in low spatial frequency region improving contrast, but device complexity increases
Solution Approach 1:
The patent uses fan-shaped regions with curved boundaries instead of straight-line k space trajectories. This curved geometry naturally positions echo signals with desired TE in the low spatial frequency region, improving image contrast while the curvature itself provides the overlapping arc regions needed for motion correction.
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 enhances image contrast and quality by correcting body motion quickly and efficiently, while maintaining high-speed imaging.
Implementation Method 1
measures an NMR signal (echo signal) to be generated by nuclear spins constituting an object
Implementation Method 2
The echo signal is given different phase encode and frequency encode as positional information depending on a gradient magnetic field
Implementation Method 3
The echo signal arranged in the k space is subjected to two-dimensional or three-dimensional Fourier transform, thereby reconstructing an image
Data Source
AI summary
In order to improve contrast and image quality in non-orthogonal measurement without sacrificing speed, in imaging which combines a fast imaging sequence for acquiring a plurality of echo signals in one shot with non-orthogonal system measurement, the shape of a blade in which an echo train of each shot is arranged includes a fan-shaped region having the radius and the arc of a circle centered on the origin of the k space, and a region overlapping an adjacent blade. During measurement, control is performed such that an echo signal for desired TE of each blade is arranged in a low spatial frequency region of a k space, and during image reconstruction, body motion between the blades is corrected using data of the overlapping regions.