MRI Image Reconstruction via Direction-Specific Filter Sensitivity Synthesis
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Solution Overview
Problem
Magnetic resonance imaging (MRI) systems face challenges in maintaining image quality due to aliasing and noise artifacts caused by insufficient sampling rates, leading to inconsistent MR data across different read-out directions, which cannot be fully mitigated without compromising the signal-noise ratio (S/N) due to performance limitations.
Innovation Solution
An image generating apparatus that synthesizes filter sensitivity distributions and coil sensitivity distributions for each read-out direction, generating synthesis sensitivity distributions to produce high-quality MR images by performing sensitivity encoding (SENSE) or using regularization terms like compressed sensing (CS), thereby expanding the effective field of view without expanding the low-pass filter's passband.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a low-pass filter with a limited passband is used for MR signals in varying read-out directions, then the signal-noise ratio (S/N) is maintained, but the consistency of MR data in k-space deteriorates and streak artifacts occur
Solution Approach 1:
The patent segments the sensitivity information by separating filter sensitivity distributions (for different read-out directions) from coil sensitivity distributions. This segmentation allows independent optimization of direction-specific filtering while maintaining overall data consistency through separate sensitivity encoding.
Solution Approach 2:
The patent applies local quality by generating direction-specific filter sensitivity distributions tailored to each read-out direction. Each direction receives optimized filtering characteristics suited to its specific sampling pattern, rather than applying a uniform filter across all directions.
2Stability of the object's composition
If the passband of the low-pass filter is expanded to prevent streak artifacts, then consistency of MR data improves, but the signal-noise ratio deteriorates
Solution Approach 1:
The patent implements dynamic filtering by adjusting the passband width of the low-pass filter according to each specific read-out direction. The filter characteristics are not fixed but are dynamically adapted to match the sampling density and pattern of each direction, allowing optimal balance between artifact reduction and noise preservation.
Solution Approach 2:
The patent changes the filter parameters (cutoff frequency and passband width) based on the read-out direction. By modifying these parameters dynamically for each direction rather than using a fixed filter, the system achieves direction-appropriate filtering that maintains data consistency without excessive noise amplification.
3Device complexity
If a fixed low-pass filter is used for all read-out directions, then device complexity is reduced, but image quality deteriorates due to direction-specific inconsistencies
Solution Approach 1:
The patent performs preliminary action by pre-calculating and storing filter sensitivity distributions for each read-out direction before actual image reconstruction. These pre-computed sensitivity maps are then reused during reconstruction, avoiding the need for complex real-time filter adjustments while still achieving direction-specific optimization.
Solution Approach 2:
The patent introduces an intermediary element - the filter sensitivity distribution - that mediates between the fixed filter hardware and the varying read-out directions. This intermediary allows a single physical filter to effectively behave as multiple direction-specific filters through software-based sensitivity compensation.
Data Source
AI summary
An image generating apparatus according to the embodiment includes processing circuitry. The processing circuitry acquires MR data acquired in read-out directions including a first read-out direction and a second read-out direction intersecting the first read-out direction, filter sensitivity distributions corresponding to the read-out directions and indicating distributions of sensitivity of a low-pass filter, and coil sensitivity distributions corresponding to coil elements used to acquire the MR data. The processing circuitry generates synthesis sensitivity distributions for the respective read-out directions by synthesizing the filter sensitivity distributions and the coil sensitivity distributions for the respective read-out directions. The processing circuitry generates an MR image based on the synthesis sensitivity distributions and MR data.