X-ray CT Weighting Unit for Variable Speed Scanning Artifacts
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Solution Overview
Problem
In X-ray computed tomography (CT) apparatuses using helical scanning, artifacts occur due to the mismatch between the position of image data to be reconstructed and the view center of projection data, especially in variable speed scanning where the slice position does not match the view center.
Innovation Solution
An X-ray CT apparatus that includes a weighting unit to assign weights to projection data based on its distance from the slice position, using a shift-variant weighting function to correct data redundancy and ensure proper weighting of projection data, even when the scanning speed changes, thereby reducing artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If variable speed helical scanning is used to improve scanning efficiency and reduce examination time, then productivity increases, but artifacts occur due to mismatch between slice position and view center
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the weighting function based on the top speed at different viewing angles. The weighting function parameters are modified according to the instantaneous scanning speed, transforming the fixed weighting approach into a variable one that adapts to changing scan conditions, thereby resolving the mismatch between slice position and view center in variable speed scanning
Solution Approach 2:
The patent implements dynamics by making the weighting function time-dependent and speed-dependent. The weighting function is continuously adjusted according to the real-time top speed during scanning, allowing the system to adapt to variable scanning conditions. This dynamic adjustment ensures that the weighting function remains appropriate for the current scanning state, preventing artifact generation while maintaining high productivity
2Device complexity
If shift-invariant weighting function is applied to variable speed scanning, then data redundancy correction is simplified, but artifacts occur due to slice position mismatch with view center
Solution Approach 1:
The patent transitions from a static shift-invariant weighting function to a dynamic weighting function that varies with top speed and viewing angle. The weighting function is no longer fixed but continuously adjusts based on scanning conditions, maintaining complexity management while achieving accurate reconstruction in variable speed scanning scenarios
Solution Approach 2:
The patent modifies the weighting function parameters dynamically based on top speed and viewing angle. By changing the weighting function from a fixed form to a variable form that depends on scanning parameters, the system maintains appropriate complexity while achieving accurate data redundancy correction under varying scanning conditions
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
The solution effectively reduces artifacts caused by data mismatch during variable speed helical scanning, improving the quality of reconstructed image data by ensuring proper weighting and data redundancy correction.
Implementation Method 1
an X-ray tube configured to generates X-rays
Implementation Method 2
an X-ray detector configured to detects X-rays generated from the X-ray tube and transmitted through an subject
Data Source
AI summary
A control unit performs helical scanning an subject while moving a top along a direction substantially parallel to a body axis. An acquisition unit acquires projection data via an X-ray detector. A projection data extraction unit extracts a projection data set necessary for the reconstruction of image data associated with a predetermined slice position from the projection data. A weighting unit assigns a smaller weight to first projection data of the extracted projection data than a weight assigned to second projection data, the first projection data being acquired outside a predetermined period including a predetermined acquisition time of the projection data at the predetermined slice position, the second projection data being acquired within the predetermined period. A reconstruction processing unit reconstructs image data on the basis of the first projection data and the second projection data to which the weights are assigned.