Phase Grating Filler Material for X-ray Phase Contrast
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Solution Overview
Problem
Existing focus-detector arrangements for generating phase contrast recordings face challenges in achieving high signal-to-noise ratios due to unequal intensity contributions of interfering radiation components, primarily because the phase grating design does not equally attenuate radiation passing through bars and gaps, leading to suboptimal interference pattern formation.
Innovation Solution
The phase grating is designed such that the filler material in the gaps has a higher linear attenuation coefficient than the grating bars, with specific dimensions to achieve a π or λ/2 phase shift and equal attenuation, ensuring equal intensity contributions from both paths, thereby enhancing the interference pattern and signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional phase grating design is used with uniform bar and gap attenuation, then the structure is simple to manufacture, but the interference pattern strength and signal-to-noise ratio are suboptimal due to unequal intensity contributions
Solution Approach 1:
The patent applies local quality by making the filler material in the gaps have different attenuation properties than the grating bars. Specifically, the filler material is selected to have a higher linear attenuation coefficient, creating local variation in attenuation characteristics across different regions of the grating structure. This enables equalization of intensity contributions from bars and gaps, maximizing interference pattern strength and improving phase measurement accuracy.
2Measurement precision
If the filler material height is increased to achieve equal attenuation, then the interference pattern strength improves, but the manufacturing precision requirements increase
Solution Approach 1:
The patent employs parameter changes by carefully selecting and dimensioning the filler material to achieve specific attenuation characteristics. The height of the filler material is optimized to compensate for differences in linear attenuation coefficients between the filler material and grating bars, thereby equalizing the intensity contributions. This parameter optimization maximizes the interference pattern strength and signal-to-noise ratio while maintaining feasible manufacturing tolerances.
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 configuration maximizes the interference pattern strength and signal-to-noise ratio, allowing for more accurate phase measurements by ensuring equal intensity contributions from radiation passing through bars and gaps, thus improving the detection of phase shifts with position resolution.
Implementation Method 1
a phase grating arranged behind the subject, which generates an interference pattern of the X-radiation in a predetermined energy range
Implementation Method 2
The phase of an X-ray wave cannot be determined directly, rather only by interference with a reference wave. The phase shifts relative to reference waves or neighboring rays can be measured by using interferometric gratings.
Implementation Method 3
in the gaps between its bars, the phase grating comprises a filler material whose linear attenuation coefficient in the relevant energy range is greater than that of the bars
Implementation Method 4
the height of the filler material in the gaps should be dimensioned on the one hand so that the X-radiation with the energy used for measuring the phase shift generates a phase shift in the X-radiation such that, after the phase grating, the rays which pass through the bars are phase shifted by one half wavelength relative to the rays which pass through the gaps with the filler material
Data Source
AI summary
A focus-detector arrangement of an X-ray apparatus is disclosed for generating projective or tomographic phase contrast recordings with a phase grating. According to at least one embodiment of the invention, in the gaps between its bars, the phase grating includes a filler material whose linear attenuation coefficient in the relevant energy range is greater than that of the bars. The height of the filler material in the gaps is dimensioned on the one hand so that the X-radiation with the energy used for measuring the phase shift generates a phase shift in the X-radiation such that, after the phase grating, the rays which pass through the bars are phase shifted by one half wavelength relative to the rays which pass through the gaps with the filler material. Further, the height of the filler material in the gaps on the other hand is dimensioned so that the attenuation of the X-radiation, at least in relation to the energy used for measuring the phase shift, is the same when passing through the bars and when passing through the filler material.