Propeller MRI Motion Correction via Central K-Space Reference
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Solution Overview
Problem
The PROPELLER MRI technique faces issues with image artifacts due to motion-corrupted k-space blades, misalignment of individual slices in multi-slice imaging, and inefficiencies in computing weighting factors for sampling density compensation.
Innovation Solution
Acquiring a separate MR reference data set from the central portion of k-space for each k-space blade to establish a common reference for motion estimation and correction, and using the Golden Angle principle to distribute corrupted blades uniformly, along with direct computation of weighting factors based on acquisition times and geometry for improved sampling density compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If motion correction is performed by comparing central k-space portions of each blade, then motion-induced artifacts are reduced, but image artifacts persist due to rejection of motion-corrupted blades
Solution Approach 1:
The patent divides the correction process into two independent stages: (1) in-plane motion correction using cross-correlation of central k-space portions, and (2) through-plane motion correction using projection comparison of corrected data. This segmentation allows each stage to address specific types of motion artifacts without interfering with the other, thereby reducing overall image artifacts while maintaining correction accuracy.
Solution Approach 2:
The patent introduces an intermediary projection step that maps 3D k-space data onto 2D planes. This projection serves as a mediator between the raw motion-corrupted data and the final corrected image, enabling the system to identify and correct through-plane motion artifacts without directly discarding corrupted blades, thus reducing image artifacts while preserving reliable data.
2Manufacturing precision
If complete k-space blades are acquired for each slice, then sampling density is maintained, but scan time increases for multi-slice imaging
Solution Approach 1:
The patent applies partial action by acquiring only the necessary central portion of each k-space blade rather than complete blades for every slice. This partial acquisition strategy maintains sufficient sampling density in the critical central region for motion correction while reducing redundant data collection, thereby decreasing scan time for multi-slice imaging without compromising reconstruction quality.
Solution Approach 2:
The patent performs preliminary motion correction using central k-space portions before completing full image reconstruction. This preliminary action allows the system to identify and correct motion artifacts early in the process, enabling more efficient subsequent reconstruction steps and reducing the overall time required for multi-slice imaging while maintaining sampling density where it matters most.
3Measurement precision
If weighting factors are computed iteratively for sampling density compensation, then reconstruction accuracy is improved, but computational efficiency decreases
Solution Approach 1:
The patent computes weighting factors based on pre-calculated geometric relationships and acquisition parameters before the actual image reconstruction process. This preliminary computation of weighting factors eliminates the need for iterative adjustments during reconstruction, maintaining high reconstruction accuracy while significantly improving computational efficiency and reducing processing time.
Solution Approach 2:
The patent uses analytical formulas to directly calculate weighting factors based on the geometric copying of acquisition patterns, rather than iteratively solving complex optimization problems. This approach copies the essential geometric relationships into simple calculation formulas, preserving reconstruction accuracy while dramatically improving computational efficiency.
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 reduces image artifacts, ensures proper alignment of slices, and enhances the efficiency of MRI by minimizing scan time and stabilizing the weighting process, resulting in improved image quality and reconstruction accuracy.
Implementation Method 1
a device for magnetic resonance imaging (MRI) of a body placed in an examination volume
Implementation Method 2
pulse sequences consisting of RF pulses and switched magnetic field gradients are applied to an object
Implementation Method 3
pulse sequences consisting of RF pulses and switched magnetic field gradients are applied
Data Source
Figure 1
Figure 2~3c
AI summary
The invention relates to a device for MRI of a body (7) placed in an examination volume. The device (1) comprises means (2) for establishing a substantially homogeneous main magnetic field in the examination volume, means (3, 4, 5) for generating switched magnetic field gradients superimposed upon the main magnetic field, means (6) for radiating RF pulses towards the body (7), control means (12) for controlling the generation of the magnetic field gradients and the RF pulses, means (10) for receiving and sampling MR signals, and reconstruction means (14) for forming MR images from the signal samples. According to the invention, the device (1) is arranged to acquire an MR reference data set from a central portion of k-space prior to a multi-slice PROPELLER acquisition.