CT Data Processing for Cone Beam Artifact Suppression
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Solution Overview
Problem
Wide cone angle spectral CT images suffer from increased low-frequency noise when using the frequency split method for suppressing cone beam artifacts, which can degrade image quality and make it difficult to differentiate between gray and white matter.
Innovation Solution
A method that decomposes CT data in the projection domain to non-uniformly spread noise and inconsistencies, followed by applying the Frequency Split method using filter back projection, selectively adjusting the aggressiveness for different sinograms to reduce low-frequency noise and effectively suppress cone beam artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the frequency split method is applied to suppress cone beam artifacts in wide cone angle spectral CT, then cone beam artifacts are reduced, but low-frequency noise increases
Solution Approach 1:
The patent changes the parameter of noise distribution uniformity in the projection domain. By applying a non-uniform spreading transformation to the decomposed sinograms, the noise characteristics are modified before reconstruction, allowing the frequency split method to suppress cone beam artifacts while controlling low-frequency noise amplification
Solution Approach 2:
The patent performs preliminary noise redistribution in the projection domain before the actual image reconstruction process. By pre-processing the sinograms with non-uniform spreading, the subsequent frequency split reconstruction operates on already-optimized data, preventing excessive low-frequency noise generation while maintaining artifact suppression
2Reliability
If the frequency split method is applied to suppress cone beam artifacts, then image reconstruction quality improves, but residual low-frequency noise increases
Solution Approach 1:
The patent modifies the noise distribution parameter in the projection domain by applying non-uniform spreading to the decomposed sinograms. This parameter change ensures that when the frequency split method is applied, the reconstruction achieves high quality with suppressed cone beam artifacts while the amplification of residual low-frequency noise is controlled
Solution Approach 2:
The patent replaces the standard uniform noise distribution assumption in conventional frequency split methods with a non-uniform spreading model. This substitution transforms how noise is handled in the projection domain, allowing the system to achieve better reconstruction quality without excessive residual noise
Data Source
AI summary
The present invention relates to a method of processing CT data for suppressing image cone beam artefacts (CBA) in CT images, which are reconstructed from said CT data. For the reconstruction the Frequency Split method is used. However, a straightforward use of this method can lead to an un-desired increase of the residual low-frequency noise left in the basis image after applying image domain de-noising methods. This residual noise then propagates rather linearly to the spectral results. In order to avoid this increase of the noise, the method presented here uses the FS method selectively and yet effectively. Thus, in a first aspect of the invention there is provided a method of processing computer tomography (CT) data for suppressing image cone beam artefacts (CBA) in CT images to be reconstructed from said CT data. The method comprises the steps of obtaining CT data generated during a CT scan of a patient (step S1); decomposing the obtained CT data in the projection domain resulting in a plurality of decomposed sinograms (step S2); and non-uniformly spreading between said decomposed sinograms noise and/or inconsistencies that would lead to image cone beam artefacts (step S3).