X-ray CT Filter with Spatially Varying Absorption for Dose Reduction
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Solution Overview
Problem
Current X-ray computed tomography (CT) systems face challenges in reducing radiation dose for live animals while maintaining high image quality, as existing filters either absorb too many X-rays, leading to low image intensity or high energy X-rays that can cause tissue damage.
Innovation Solution
A CT apparatus with a filter element having a spatially varying X-ray absorption capability, maximizing absorption near the rotation axis to reduce X-ray intensity and increase average energy, thereby minimizing radiation dose to sensitive areas without compromising image quality, using materials with high absorption coefficients for low energy X-rays and varying thickness or density along the cross direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a filter with uniform thickness is used to attenuate low energy X-rays, then the radiation dose is reduced, but the image quality deteriorates due to insufficient X-ray intensity
Solution Approach 1:
The filter element employs spatially varying thickness along the cross direction, with maximum thickness at the center (maximum absorption) and minimum thickness at the edges (minimum absorption). This local variation allows different regions of the filter to provide different levels of attenuation, reducing radiation dose in sensitive central areas while preserving sufficient intensity in peripheral areas to maintain image quality.
2Object-affected harmful factors
If the filter thickness is increased to absorb more X-rays, then the radiation dose is further reduced, but the X-ray intensity becomes too low leading to deteriorated image quality
Solution Approach 1:
The filter thickness is optimized locally: maximum thickness at the center for maximum dose reduction in sensitive regions, while minimum thickness at the edges to preserve sufficient X-ray intensity for maintaining image quality. This spatial optimization resolves the contradiction between dose reduction and intensity preservation.
3Object-affected harmful factors
If a filter with maximum absorption at the center is used, then the radiation dose is reduced in sensitive regions, but the X-ray intensity becomes non-uniform across the detection area
Solution Approach 1:
The filter creates intentional non-uniform intensity distribution with maximum absorption at the center and minimum absorption at the edges. This controlled non-uniformity allows dose reduction in sensitive central regions while preserving intensity in peripheral regions, and the overall effect is compensated during image reconstruction to achieve uniform image quality.
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 design reduces the overall radiation dose to the object, particularly in sensitive regions like bone marrow or intestines, while maintaining uniform image quality across cross-sections through back-projection reconstruction, effectively minimizing radiation-induced damage.
Implementation Method 1
the filter element has a spatially varying X-ray absorption capability along a cross direction (y) which is perpendicular to both the beam axis (z) and the rotation axis (x)
Data Source
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AI summary
An X-ray computed tomography (=CT) apparatus (10), comprising - an X-ray source (11) for emitting an X-ray beam (1), in particular a divergent X-ray beam (1), along a beam axis (z), - a filter element (2) for attenuating the X-ray beam (1), - a stage (14) for an object (3) to be investigated with the attenuated X-ray beam (1a), - a 2D X-ray detector (15) with a detection area (15a), - and a gantry system (16) capable of rotating either the entirety of the X-ray source (11), the filter element (2) and the 2D X-ray detector (15), or the stage (14) for the object (3) with respect to a rotation axis (x) which is perpendicular to the beam axis (z), wherein the filter element (2) has a spatially varying X-ray absorption capability along a cross direction (y) which is perpendicular to both the beam axis (z) and the rotation axis (x), is characterized in that the spatially varying X-ray absorption capability exhibits a maximum absorption along the cross direction (y) at a zero position (y0), wherein X-rays passing through the filter element (2) at the zero position (y0) intersect the rotation axis (x). The invention provides a CT apparatus which allows to further reduce the radiation dose for an object to be investigated, while retaining a high image quality at the same time.