X-ray CT Image Reconstruction Using Variable Back Projection Phase Width
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Solution Overview
Problem
Existing X-ray CT apparatuses face issues with noise irregularities and temporal resolution irregularities due to varying back projection phase widths, particularly in bilaterally symmetric sites like the breast or head, leading to potential misdiagnosis and increased exposure doses.
Innovation Solution
An X-ray CT apparatus that calculates a back projection phase width for each pixel based on its distance from a reference position on the axial plane, using this calculated phase width to determine a view weight for reconstructing CT images, thereby ensuring consistent noise characteristics across the image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant back projection phase width is used irrespective of image position, then noise is stabilized, but the use efficiency of data is relatively low and noise is increased
Solution Approach 1:
The patent applies local quality by setting different back projection phase widths for different regions of the image. Specifically, a first back projection phase width is used for a first region and a second back projection phase width is used for a second region, allowing optimization of noise characteristics and data efficiency for each region separately
2Device complexity
If a constant back projection phase width is used irrespective of FOV size, then the reconstruction process is simple, but the noise of the reconstructed image is increased and exposure dose is increased
Solution Approach 1:
The patent implements dynamics by making the back projection phase width variable rather than constant. The phase width is determined based on the FOV size and image position, allowing the system to adapt to different scanning conditions and optimize the balance between noise reduction and data efficiency
3Reliability
If the back projection phase width is set wider, then noise is reduced, but artifacts are generated due to extrapolation
Solution Approach 1:
The patent applies local quality by using different back projection phase widths for different regions. By carefully selecting the phase width for each region based on the FOV and position, the method reduces noise in regions where wider phase widths are beneficial while avoiding extrapolation artifacts in regions where narrower phase widths are more appropriate
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 enables proper image diagnosis by reducing noise irregularities and maintaining consistent image quality, especially in bilaterally symmetric sites, while also optimizing data use efficiency and reducing radiation exposure.
Implementation Method 1
an X-ray is irradiated to the subject to measure the X-ray penetrating the subject with an X-ray detector
Data Source
AI summary
To generate a reconstructed image suitable to characteristics of a bilaterally symmetric site and possible to an appropriate image diagnosis, a computation device: computes a back projection phase width at a rotational center and distance between the rotational center location which is a reference location and a pixel to be reconstructed; according to the distance between the rotational center location and the pixel to be reconstructed, sets a function (f1) changing the back projection phase width; computes a back projection phase width in the pixel to be reconstructed, substituting a value of the distance between the rotational center location and a pixel to be reconstructed in the function (f1); computes a view weighting, on the basis of the back projection phase width in the post-correction pixel to be reconstructed and a slope width of a view weighting function; and reconstructs a CT image, using the view weighting.