Tilted X-ray Grating for High-Energy Phase Contrast Imaging
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Solution Overview
Problem
Current differential phase contrast X-ray imaging methods using Talbot-Lau interferometers face limitations at high X-ray energies above a few tens of keV due to difficulties in fabricating micron-period absorption gratings with the required thickness, leading to reduced contrast and inefficiency.
Innovation Solution
The use of micro-periodic gratings tilted at glancing incidence angles, combined with grazing incidence mirrors, to increase the effective absorber thickness and enhance interferometer contrast, allowing for efficient differential phase contrast imaging up to 100 keV or higher with conventional X-ray tubes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional absorption gratings are used at normal incidence, then the grating structure is simple to fabricate, but the effective absorber thickness is insufficient at high X-ray energies leading to reduced contrast
Solution Approach 1:
The patent tilts the absorption grating from normal incidence to glancing incidence angles, effectively changing the dimensional orientation of the grating relative to the X-ray beam. This angular transformation increases the path length of X-rays through the absorber material, thereby increasing the effective absorber thickness without requiring additional absorber material or changing the grating fabrication process.
Solution Approach 2:
The patent changes the incidence angle parameter of the grating from 0 degrees (normal incidence) to glancing angles, which transforms the effective interaction length between X-rays and the absorber material. This parameter change enables the same grating structure to provide sufficient absorption contrast at high X-ray energies where normal incidence gratings fail.
2Reliability
If the absorber thickness is increased to maintain contrast at high energies, then the interferometer contrast improves, but the fabrication difficulty increases due to micron-period requirements
Solution Approach 1:
By tilting the grating to glancing incidence, the patent effectively increases the absorber thickness in the X-ray path without increasing the physical thickness of the grating bars. This allows conventional fabrication methods to produce gratings with sufficient absorption contrast at high energies, avoiding the need to fabricate extremely thick micron-period structures.
Solution Approach 2:
The patent changes the operational parameter (incidence angle) rather than the structural parameter (absorber thickness), enabling the same easily-fabricated grating structure to achieve high contrast at high energies through angular transformation of the X-ray-beam-grating interaction geometry.
3Adaptability or versatility
If conventional X-ray optics are used, then the system works with conventional X-ray tubes, but the efficiency is less than a hundredth of a percent due to low transmission through thick absorbers
Solution Approach 1:
The patent uses glancing incidence geometry to increase the effective absorber thickness for contrast generation while simultaneously using grazing incidence mirrors to reflect and redirect X-rays, maintaining high transmission efficiency. This angular approach allows the system to work with conventional X-ray tubes while achieving practical imaging efficiency.
Solution Approach 2:
The patent introduces grazing incidence mirrors as intermediary optical elements that reflect X-rays at glancing angles, enabling the system to maintain high transmission efficiency while using thick absorbers for contrast generation. The mirrors act as mediators that preserve X-ray flux while allowing the absorption grating to function effectively at high energies.
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 high-resolution differential phase contrast imaging with improved contrast and larger fields of view, overcoming the limitations of traditional methods by effectively increasing the absorber thickness and maintaining high interferometer contrast across a broader range of X-ray energies.
Implementation Method 1
The beam splitter includes a splitter grating arranged to intercept an incident X-ray beam and provide an interference pattern of X-rays
Implementation Method 2
The beam splitter includes a splitter grating arranged to intercept an incident X-ray beam and provide an interference pattern of X-rays
Implementation Method 3
The analyzer grating is arranged to intercept and block at least portions of the interference pattern of X-rays prior to reaching the X-ray detection component
Implementation Method 4
The analyzer grating has a longitudinal dimension, a lateral dimension that is orthogonal to the longitudinal dimension and a transverse dimension that is orthogonal to the longitudinal and lateral dimensions. The analyzer grating includes a pattern of optically dense regions each having a longest dimension along the longitudinal dimension that are spaced substantially parallel to each other in the lateral dimension such that there are optically rare regions between adjacent optically dense regions. Each optically dense region has a depth in the transverse dimension that is smaller than a length in the longitudinal dimension. The analyzer grating is arranged with the longitudinal dimension at a shallow angle relative to incident X-rays and the shallow angle is less than 30 degrees.
Data Source
AI summary
A differential phase contrast X-ray imaging system includes an X-ray illumination system, a beam splitter arranged in an optical path of the X-ray illumination system, and a detection system arranged in an optical path to detect X-rays after passing through the beam splitter.