Phase-Contrast X-Ray Imaging Grating System Beam Hardening Correction
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Solution Overview
Problem
Current phase-contrast x-ray imaging systems face challenges in achieving high-quality images and material discrimination, particularly at higher energies, due to issues with beam hardening and the difficulty in fabricating grids with fine feature sizes and large aspect ratios, which limits their ability to penetrate deeply and accurately distinguish materials.
Innovation Solution
The system employs a polychromatic x-ray source with a large spot size, a source grating, an object grating, and a detector grating, where the gratings are oriented orthogonally and have equivalent x-ray attenuation factors, allowing for beam hardening correction and improved scatter imaging by measuring visibility reductions in both object and detector gratings, enabling high-energy phase-contrast imaging with enhanced material discrimination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional phase-contrast x-ray imaging is used, then material discrimination is improved, but beam hardening effects and image artifacts worsen at higher energies
Solution Approach 1:
A beam hardening correction grating is introduced as an intermediary element between the object and detector. This grating specifically measures beam hardening effects through its visibility reduction, allowing the system to separate and correct beam hardening artifacts from actual scatter signals, thereby maintaining material discrimination accuracy at higher energies
Solution Approach 2:
The patent replaces purely mechanical/grid-based phase contrast measurement with a hybrid approach that incorporates computational correction based on visibility measurements. By substituting direct physical correction mechanisms with computational algorithms that process visibility data from multiple gratings, the system effectively compensates for beam hardening without requiring complex physical modifications
2Manufacturing precision
If grids with fine feature sizes and large aspect ratios are fabricated, then phase-contrast imaging quality is improved, but manufacturing difficulty increases
Solution Approach 1:
The imaging system is segmented into multiple functional gratings (object grating, detector grating, and beam hardening correction grating), each with optimized dimensions for its specific function. This segmentation allows each grating to be manufactured with practical aspect ratios while collectively achieving the desired imaging performance, avoiding the need for single gratings with excessively large aspect ratios
3Strength
If high energy x-ray sources are used, then material penetration is improved, but phase-contrast signal strength decreases
Solution Approach 1:
The system changes the measurement parameters by introducing multiple gratings with different orientations and transmission characteristics. By measuring visibility reductions across these multiple gratings and combining the data through computational algorithms, the system enhances the phase-contrast signal-to-noise ratio at high energies, effectively compensating for the inherent signal strength decrease
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 phase-contrast x-ray imaging at higher energies, correcting for beam hardening effects and improving material discrimination, allowing for the detection of sub-resolution textures and reducing false alarm rates in security screening and other applications.
Implementation Method 1
creating a series of periodically repeating apparent sources from the source x-rays using a source grating
Implementation Method 2
creating a series of periodically repeating apparent sources from the source x-rays using a source grating
Implementation Method 3
patterning the series of periodically repeating apparent sources into a patterned beam using an object grating
Implementation Method 4
patterning the series of periodically repeating apparent sources into a patterned beam using an object grating
Implementation Method 5
acquiring through the detector grating a first image with the object and a second image without the object
Data Source
AI summary
A system includes an x-ray source configured to emit an x-ray beam along a beam path and through an object arranged for inspection in a field of view of the x-ray source; and an object grating, an analyzer grating, a detector grating, and a detector arranged with respect to each other in the field of view, wherein the object grating includes object grating elements arranged in a first pattern, the detector grating includes detector grating elements arranged in a second pattern that is separable from the first pattern, and the analyzer grating includes analyzer grating elements that are arranged to correspond to a combination of the first pattern and second pattern, wherein the analyzer grating, and/or the object grating and detector grating, are configured to move relative to each other to different phase positions, and wherein the detector is configured to collect indirect moiré image data of the object at the different phase positions.