Parallel PROPELLER MRI Sampling for Lower Noise and Artefacts
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Solution Overview
Problem
Existing PROPELLER MR imaging techniques suffer from extended scan times and significant noise and artefacts, particularly at high acceleration rates, which degrade image quality and motion correction accuracy.
Innovation Solution
A method combining PROPELLER imaging with parallel imaging, varying the subsampling density of k-space blades based on their rotation angles and spatial sensitivity profiles of RF receiving antennas to adapt to the capabilities of the RF coils, reducing artefacts and noise in the final MR image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If parallel imaging acceleration is applied to PROPELLER to reduce scan time, then scan time is reduced, but noise and artefacts increase significantly
Solution Approach 1:
The patent applies different acceleration factors to different k-space blades based on their orientation. Specifically, blades oriented along the major axis of the RF coil sensitivity variation are subsampled more aggressively than blades oriented along the minor axis. This local differentiation of sampling density adapts the parallel imaging reconstruction to the directional characteristics of the RF coils, reducing noise and artefacts in directions where the coils provide better conditioning.
Solution Approach 2:
The patent varies the acceleration factor parameter across different k-space blades rather than applying a uniform acceleration factor. The acceleration factor is set to be higher for blades oriented along the major axis and lower for blades oriented along the minor axis of the RF coil sensitivity pattern. This parameter variation optimizes the balance between scan time reduction and image quality preservation.
2Productivity
If uniform subsampling is applied to all k-space blades, then scan time is reduced, but artefacts and noise are amplified due to poor conditioning of parallel reconstruction
Solution Approach 1:
The patent differentiates the sampling density applied to different k-space blades according to their orientation relative to the RF coil sensitivity profiles. Blades oriented along the major axis receive higher subsampling ratios while blades oriented along the minor axis receive lower subsampling ratios. This local quality differentiation ensures that each blade is subsampled at an optimal rate that accounts for the directional characteristics of the RF coils, preventing noise and artefact amplification.
3Loss of time
If high acceleration rates are used to widen k-space blades, then scan time is reduced, but noise level and artefact level increase
Solution Approach 1:
The patent changes the acceleration factor parameter dynamically based on the orientation of each k-space blade. The acceleration factor is set to be higher for blades oriented along the major axis of the RF coil sensitivity variation and lower for blades oriented along the minor axis. This parameter adaptation allows the system to achieve high imaging speed where possible while preserving image quality where the RF coils provide better conditioning.
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
The method achieves reduced artefacts and noise in MR images while maintaining robustness against patient motion, enabling faster imaging with improved image quality and accuracy.
Implementation Method 1
Image-forming MR methods which utilize the interaction between magnetic fields and nuclear spins
Implementation Method 2
acquiring the MR signals in parallel via a number of RF receiving antennas having different spatial sensitivity profiles
Implementation Method 3
computing an MR image by combining the MR signals acquired via the different RF receiving antennas utilizing their spatial sensitivity profiles to perform a parallel image reconstruction
Data Source
Figure 1
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AI summary
The invention relates to a method of MR imaging of a body (10) of a patient. It is an object of the invention to provide a method that reduces the artefact level in parallel (accelerated) PROPELLER imaging. According to the proposed invention, MR signals are acquired in parallel via a number of RF receiving antennas (11, 12, 13) having different spatial sensitivity profiles, wherein the MR signals are acquired from a plurality of k-space blades (21-26) in temporal succession according to a PROPELLER scheme. The k-space blades (21-26) are rotated about the center of k-space, with the total acquired set of MR signals spanning a circle (28) in k-space and a common central region (27) of k-space being covered by all k-space blades (21-26). The MR-signal acquisition from the respective k-space blades (21-26) involves subsampling of k-space, wherein the density of k-space sampling is varied depending on the rotation angle. Finally, an MR image is computed by combining the MR signals acquired via the different RF receiving antennas (11, 12, 13) utilizing their spatial sensitivity profiles to perform a parallel image reconstruction. Moreover, the invention relates to an MR system (1) and to a computer program for an MR system (1).