X-ray CT Pixel Offset for Uniform Interpolation
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Solution Overview
Problem
Conventional X-ray computed tomography systems using conic beam scanning experience uneven interpolation due to the spread of X-ray beams, leading to image degradation near the axis of rotation and central cross-section, resulting in artifacts in Maximum Intensity Projection (MIP) images.
Innovation Solution
An X-ray computed tomography apparatus and method that offsets the central positions of pixels in the imaging area from the corresponding centers of X-ray detection elements by a fraction of the image interval, specifically ¼ or ½ the slice thickness, during reconstruction processing to uniform the interpolation and reduce artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the central position of each pixel is set to correspond to the central position of the X-ray detection element, then the reconstruction process is simple, but interpolation becomes uneven and image quality degrades near the axis of rotation and mid-plane
Solution Approach 1:
The patent applies local quality by differentiating the treatment of pixel central positions based on their spatial location. For pixels not at the central position, the pixel central position is offset from the detection element central position to achieve uniform interpolation. This localized adjustment ensures that interpolation uniformity is improved in specific regions (away from the central axis) without complicating the overall reconstruction process excessively.
Solution Approach 2:
The patent changes the parameter of pixel central position offset from zero to a non-zero value (specifically 1/4 of the image interval) for pixels not located at the central position. This parameter modification transforms the interpolation behavior to achieve uniformity across the imaging area, thereby improving image quality while maintaining computational feasibility.
2Area of stationary object
If the X-ray beam spreads in the slice direction to cover the imaging area, then the coverage is improved, but the degree of interpolation varies depending on the position of detection elements
Solution Approach 1:
The patent addresses the varying interpolation degree by applying localized position adjustments. The offset is applied selectively to pixels not at the central position, ensuring that the interpolation uniformity is optimized in regions where the X-ray beam spread causes non-uniform sampling. This maintains comprehensive coverage while correcting the interpolation artifacts.
3Device complexity
If no offset is applied to pixel central positions, then the reconstruction algorithm is simpler, but artifacts occur in MIP images at the central position
Solution Approach 1:
The patent introduces localized offset adjustments for pixels not at the central position to eliminate artifacts in MIP images. This targeted approach removes the harmful artifacts while keeping the overall algorithm relatively simple, as the offset is only applied to specific pixel regions rather than requiring a complete redesign of the reconstruction methodology.
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 reduces noise and eliminates or minimizes artifacts in MIP images by ensuring consistent interpolation across the imaging area, enhancing image quality by optimizing the offsetting distance to ¼ the slice thickness.
Implementation Method 1
an X-ray source which irradiates an object with X-rays spreading in a slice direction
Implementation Method 2
an X-ray detector comprising a plurality of X-ray detection elements which are juxtaposed in the slice direction and detect X-rays transmitted through the object
Data Source
AI summary
An X-ray computed tomography apparatus includes, an X-ray source which irradiates an object with X-rays spreading in a slice direction, an X-ray detector including a plurality of X-ray detection elements which are juxtaposed in the slice direction and detect X-rays transmitted through the object, a reconstruction unit which includes a back-projection unit which obtains back-projection data relating to each of a plurality of pixels defined in an imaging area by performing back projection of data acquired by the X-ray detector and an interpolation unit which interpolates the data, and performs reconstruction processing for an image, and a setting unit which sets central positions of a plurality of pixels in the imaging area in the reconstruction processing to positions offset from positions corresponding to centers of the X-ray detection elements in the slice direction.