MRI Coil Selection to Reduce Phase Wrap Artifact
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Solution Overview
Problem
Magnetic resonance imaging (MRI) systems face challenges in reducing the phase wrap artifact, particularly when imaging small regions of interest (ROI) or fields of view (FOV), as signals from outside the FOV can fold into the ROI, leading to image distortions without increasing scan time.
Innovation Solution
Selecting specific receive element groups (REGs) of the RF coil array based on their sensitivity within and outside the ROI, using sensitivity maps generated from calibration data to deactivate coil elements not contributing to the main scan, thereby reducing the phase wrap artifact without extending the scan time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If all coil elements are activated during MRI scanning, then signal coverage is maximized, but phase wrap artifact increases due to signals from outside the FOV folding into the ROI
Solution Approach 1:
The patent segments the RF coil array into multiple receive element groups (REGs), where each REG contains a subset of coil elements. By selectively activating only the REGs that contribute to the ROI while deactivating others, the system reduces phase wrap artifact from signals outside the FOV while maintaining adequate signal coverage within the ROI. This segmentation allows independent control of different coil element groups to eliminate harmful signals.
Solution Approach 2:
The patent applies local quality by determining sensitivity maps for each REG and evaluating their specific contribution to the ROI versus signals from outside the FOV. Each REG is assessed individually based on its local sensitivity characteristics, and only those with beneficial local quality (high sensitivity to ROI, low sensitivity to outside-FOV signals) are activated. This localized evaluation ensures optimal artifact reduction while preserving necessary signal coverage.
2Measurement precision
If REGs with high sensitivity outside ROI are activated, then signal-to-noise ratio improves, but phase wrap artifact increases
Solution Approach 1:
The patent changes the selection parameter from simply maximizing signal-to-noise ratio to a composite criterion that balances sensitivity within the ROI against sensitivity outside the ROI. By using a penalty parameter that weights outside-FOV sensitivity, the system selects REGs with optimal parameter combinations - those that provide sufficient signal-to-noise ratio while maintaining low sensitivity to signals that would cause phase wrap artifact. This parameter transformation enables simultaneous optimization of both competing objectives.
Data Source
AI summary
Various methods and systems are provided for a radio frequency coil array comprising a plurality of coil elements for magnetic resonance imaging. In one embodiment, a method includes grouping the plurality of coil elements into receive elements groups (REGs) according to REGs information, generating coil element sensitivity maps for the plurality of coil elements, generating REG sensitivity maps based on the REGs information and the coil element sensitivity maps, determining, for each REG, signals within a region of interest (ROI) and signals outside of the ROI based on the REG sensitivity maps, selecting one or more REGs based on the signals within the ROI and the signals outside of the ROI of each REG, and scanning the ROI with the coil elements in the selected REGs being activated and the coil elements not in any selected REGs being deactivated. In this way, phase wrap artifacts may be reduced.