MRI Phase Correction via Adaptive Smoothing
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Solution Overview
Problem
Magnetic resonance imaging (MRI) techniques face challenges in noise reduction while preventing artifacts in signal regions during the addition of complex images, particularly in diffusion weighted imaging (DWI), where phase alignment is disrupted by physiological motions, leading to inadequate noise reduction in low SNR regions.
Innovation Solution
The method involves applying two or more types of smoothing processing with different smoothing degrees to complex images, followed by weighted addition based on signal values, allowing for phase correction that balances noise reduction in background regions with artifact prevention in signal regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a filter with high smoothness degree is used for phase correction, then noise reduction effect is improved, but artifacts occur in signal regions
Solution Approach 1:
The patent applies different smoothing degrees to different regions of the image based on local SNR characteristics. Signal regions (high SNR) use filters with lower smoothness degree to prevent artifacts, while background regions (low SNR) use filters with higher smoothness degree to achieve noise reduction. This spatially varying filter strength resolves the contradiction by making the smoothing degree adaptive to local image characteristics rather than uniform across the entire image.
2Object-generated harmful factors
If a filter with low smoothness degree is used for phase correction, then artifact occurrence is reduced, but noise reduction effect is insufficient
Solution Approach 1:
The patent implements region-adaptive filtering where the smoothness degree is determined by local SNR measurements. In background regions with low SNR, a higher smoothness degree is applied to achieve sufficient noise reduction. In signal regions with high SNR, a lower smoothness degree is used to preserve signal integrity and avoid artifacts. This resolves the contradiction by matching filter strength to local noise characteristics.
3Ease of operation
If complex addition is performed without phase alignment, then processing simplicity is maintained, but phase misalignment reduces signal quality
Solution Approach 1:
The patent performs phase correction as a preliminary step before complex addition. By correcting phases of individual images using smoothing filters before they are added together, the method ensures that phase alignment is achieved in advance. This preliminary phase correction maintains signal quality while keeping the overall process relatively simple, as the phase correction is automatically applied during the image processing pipeline without requiring complex iterative alignment algorithms.
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 effectively reduces noise in low SNR regions while preventing artifacts in high SNR regions, achieving improved image quality by adapting smoothing intensity according to regional SNR characteristics.
Implementation Method 1
an imaging unit configured to measure a nuclear magnetic resonance signal generated from a subject
Data Source
AI summary
For a complex image to be complexly added, appropriate phase correction is executed by a simple method to prevent occurrence of an artifact in a signal region and to reduce noise in a background region. Two or more types of smoothing processing with different smoothing degrees are executed on a phase image of the complex image to obtain two or more types of smoothed phase images having different smoothing degrees. A weight for each of these smoothed phase images is calculated based on a signal value (SNR) of an intensity image, and addition is performed by a weight for each signal value to obtain a smoothed phase image for correction. After a phase of the complex image is corrected using the smoothed phase image, a phase-corrected complex image is complexly added. As a result, phase correction equivalent to phase correction in which a smoothing degree is weakened in the signal region and a smoothing degree is strengthened in the background region is realized.