Undersampled Radial Strips for Accelerated MRI
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Solution Overview
Problem
Radial strip scan techniques like PROPELLER are slower compared to other k-space trajectories due to oversampling the center of k-space, which is necessary for motion correction but increases scan time, and conventional acceleration methods introduce artifacts such as streaking.
Innovation Solution
The introduction of undersampled sections between radial strips, arranged such that no angular undersampled areas are diametrically opposite each other, allowing for improved reconstruction and reduced artifacts through Hermitian symmetry, and using fewer lines or strips to reduce echo train length and scan time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If radial strip scan techniques use full sampling of k-space center for motion correction, then motion correction capability is improved, but scan time increases
Solution Approach 1:
The patent segments k-space into distinct regions: a fully sampled central region for motion correction and peripheral regions with strategic undersampling. This segmentation allows the central portion to maintain full sampling for reliable motion correction while peripheral portions are undersampled to reduce overall scan time, directly resolving the contradiction between motion correction capability and scan duration.
Solution Approach 2:
The patent applies different sampling strategies to different regions of k-space: full sampling in the center for motion correction and reduced sampling in peripheral areas. This local quality differentiation ensures that the critical central region maintains high quality for motion correction while less critical peripheral regions contribute to scan time reduction, effectively balancing reliability and speed.
2Loss of time
If conventional acceleration methods undersample k-space uniformly, then scan time is reduced, but image artifacts such as streaking increase
Solution Approach 1:
The patent introduces asymmetric angular offsets for undersampled regions that are not diametrically opposite each other. This asymmetric arrangement prevents the formation of streaking artifacts that occur with symmetric uniform undersampling, while still achieving scan time reduction through strategic peripheral undersampling.
Solution Approach 2:
The patent moves from uniform one-dimensional undersampling to a two-dimensional asymmetric pattern in the angular domain. By distributing undersampled regions asymmetrically around the k-space perimeter rather than uniformly, the method eliminates artifact formation while maintaining acceleration benefits.
3Loss of time
If fewer radial strips are used to accelerate scanning, then scan time is reduced, but k-space coverage and image quality deteriorate
Solution Approach 1:
The patent performs preliminary motion correction using the fully sampled central k-space region before final image reconstruction. This preliminary action allows accurate motion correction to be applied even when fewer radial strips are used, thereby maintaining image quality while achieving scan acceleration through reduced strip count.
Solution Approach 2:
The fully sampled central k-space region acts as an intermediary that enables motion correction without requiring full peripheral k-space sampling. This intermediary central region provides the necessary motion information to compensate for the reduced number of radial strips, maintaining image quality while reducing scan time.
Data Source
AI summary
Magnetic resonance imaging (MRI) systems and methods to effect accelerated MR image reconstruction for undersampled data acquisitions with radial strip acquisitions of k-space are described. The improved MR image reconstruction is performed by acquiring k-space data in accordance with a data acquisition pattern which comprises a plurality of strips leaving a plurality of undersampled areas therebetween that do not have another undersampled area in a diametrically opposed position of k-space. The acquired k-space data is then used to generate an MR image.