MRI Image Reconstruction via Multiplexed Sensitivity Encoding Feedback
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Solution Overview
Problem
Multi-shot Echo Planar Imaging (EPI) in magnetic resonance imaging faces limitations in spatial resolution due to inter-shot motion-induced phase differences, and existing methods like SENSE and MUSE struggle to provide high-quality images, especially when the number of shots is high.
Innovation Solution
The method involves generating a first estimated phase through sensitivity encoding, reconstructing a multiplexed sensitivity encoded image, and then using regularized sensitivity encoding with feedback from the first reconstruction to improve the accuracy of the second estimated phase, thereby enhancing the quality of the final reconstructed image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multi-shot EPI is used to improve spatial resolution, then measurement precision is improved, but inter-shot motion causes phase differences that reduce image quality
Solution Approach 1:
The patent implements a feedback mechanism where the reconstructed image from the first shot is used as input for reconstructing subsequent shots. The phase information from previously reconstructed images is fed back to correct phase errors in current shot data, creating a cumulative refinement process that improves overall image quality while maintaining high spatial resolution
Solution Approach 2:
The patent performs preliminary reconstruction of the first shot to obtain initial phase information before processing subsequent shots. This preliminary action establishes a reference phase map that is then used to correct phase differences in following shots, preventing the propagation of phase errors throughout the multi-shot sequence
2Reliability
If SENSE method is used to reduce phase differences, then reliability is improved, but SNR is dramatically reduced
Solution Approach 1:
Instead of applying full SENSE reconstruction to all shots (which would preserve phase accuracy but lose SNR), the patent applies phase correction selectively and partially. Only the phase information from the first shot is used for correction, while retaining the full signal intensity from all shots, thus achieving phase accuracy without the severe SNR penalty of complete SENSE processing
3Loss of information
If MUSE method is used to increase SNR, then loss of information is reduced, but image quality deteriorates when number of shots is high
Solution Approach 1:
The patent introduces the reconstructed image from the first shot as an intermediary reference for phase correction. This intermediary serves as a mediator between the raw k-space data and the final composite image, providing phase information that improves image quality without requiring multiple SENSE operations that would degrade the result when shots are numerous
Data Source
AI summary
This invention provides an image processing method and apparatus for reconstructing an image of a site of a subject. The image processing method comprises: generating a first estimated phase of each shot of multiple shots of the site by sensitivity encoding based on shot data of the corresponding shot obtained for the site; reconstructing a first multiplexed sensitivity encoded image based on the first estimated phase of each shot and shot data of each shot; generating a second estimated phase of each shot of the multiple shots by regularized sensitivity encoding using the first multiplexed sensitivity encoded image; and reconstructing a second multiplexed sensitivity encoded image based on the second estimated phase of each shot and shot data of each shot. In this way, the quality of the finally reconstructed image in magnetic resonance imaging is further improved.