MRI Image Artifact Suppression via Wavelet Noise Removal
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Solution Overview
Problem
MRI images suffer from artifacts when zero-fill reconstruction is combined with noise removal using the Wavelet transform, leading to a deterioration in image quality due to characteristic patterns appearing in high-frequency components.
Innovation Solution
The proposed solution involves pre-processing and post-processing techniques to prevent or eliminate artifacts caused by the Wavelet transform, including changing the matrix size of the reconstructed image before and after noise removal, and using a window function to predict and remove artifact signals during the noise removal process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If zero-fill reconstruction is performed to obtain a square reconstruction matrix, then image reconstruction is enabled, but characteristic patterns appear in high-frequency components causing artifacts
Solution Approach 1:
The patent applies a window function to the k-space data before zero-fill reconstruction to suppress the characteristic patterns that will appear in high-frequency components. This preliminary action prevents the formation of artifacts before they can affect the final image quality.
Solution Approach 2:
The window function acts as an intermediary between the k-space data and the zero-fill reconstruction process. It modifies the k-space data to eliminate the harmful characteristic patterns while preserving the useful imaging information, thereby mediating between the need for square matrix reconstruction and the avoidance of artifacts.
2Reliability
If noise removal using Wavelet transform is applied to the reconstructed image, then noise is reduced, but artifacts caused by zero-fill reconstruction are enhanced or created
Solution Approach 1:
The patent performs window function processing on the k-space data before zero-fill reconstruction and subsequent Wavelet transform noise removal. This preliminary suppression of characteristic patterns ensures that when noise removal is later applied, artifacts are not enhanced or created, allowing effective noise reduction without the harmful side effect of artifact enhancement.
3Productivity
If imaging time is shortened by asymmetric k-space filling, then productivity is improved, but artifacts may occur during reconstruction
Solution Approach 1:
The patent applies the window function to k-space data before asymmetric filling and zero-fill reconstruction. This preliminary action suppresses the characteristic patterns that would otherwise appear as artifacts, enabling faster asymmetric imaging without the harmful side effect of artifact formation in the reconstructed image.
Data Source
AI summary
Provided is a magnetic resonance imaging apparatus with no occurrence of artifacts, even after noise removal by applying Wavelet transform to a zero-fill reconstructed image. Nuclear magnetic resonance signals acquired by the magnetic resonance imaging apparatus are processed to perform reconstruction with a reconstruction matrix extended by zero-filling an acquisition matrix, and then a zero-fill reconstructed image is produced. This reconstructed image is subjected to an iterative operation combining the Wavelet transform and L1 norm minimization to remove noise. Before the noise removal, a pre-processing is performed to change the reconstruction matrix size so that an artifact does not occur in the image after noise removal, an artifact portion appears outside the reconstruction matrix after the noise removal, or cutting out is performed so that no artifact appears after the noise removal. The matrix size is restored to its original size in the post-processing after the noise removal.