Cross-Grid Phase-Contrast CT for Beam Hardening Correction
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Solution Overview
Problem
Conventional x-ray imaging primarily relies on density and effective atomic number for material discrimination, lacking the ability to effectively utilize phase contrast for improved material differentiation, which leads to unwanted spectral effects and image artifacts, particularly in high penetration scenarios.
Innovation Solution
Employing a polychromatic x-ray source operating at energies above 100 keV, combined with a series of gratings to create patterned beams and orthogonal detector gratings, allowing for the measurement and correction of beam hardening to generate improved phase-contrast images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase contrast imaging is added to conventional x-ray imaging, then material discrimination is improved, but unwanted spectral effects and image artifacts increase
Solution Approach 1:
The patent introduces a detector grating as an intermediary component between the object and the detector. This grating serves as a mediator that enables the separation and correction of beam hardening effects from scatter signals. By placing the detector grating at a specific position and orientation, the system can measure and correct spectral effects without compromising the phase contrast information, thus resolving the contradiction between improved material discrimination and reduced image artifacts.
Solution Approach 2:
The patent implements a feedback mechanism by measuring the detector grating visibility reduction due to beam hardening and using this information to correct the object grating visibility measurements. The system continuously monitors the spectral effects through the detector grating and applies corrections to the final image, thereby maintaining high material discrimination while minimizing unwanted spectral effects and image artifacts.
2Strength
If high energy x-ray source is used to increase penetration, then material penetration is improved, but beam hardening effects increase
Solution Approach 1:
The detector grating acts as an intermediary that specifically targets beam hardening effects. By positioning the detector grating to measure visibility reduction caused by beam hardening, the system can separate this harmful effect from the useful signal. This allows the use of high energy x-ray sources for improved penetration while simultaneously correcting for the beam hardening artifacts through the feedback mechanism.
Solution Approach 2:
The patent converts the harmful beam hardening effect into a useful measurement signal. The beam hardening-induced visibility reduction of the detector grating is measured and used as feedback to correct the images. By doing so, the system turns the previously detrimental beam hardening effect into a correctable parameter, enabling high energy imaging with improved penetration while minimizing artifacts.
3Object-affected harmful factors
If scatter correction is applied to improve image quality, then image artifacts are reduced, but measurement complexity increases
Solution Approach 1:
The patent segments the imaging system into distinct functional components: an object grating for phase contrast imaging, a detector grating for scatter and beam hardening measurement, and a processing system for correction. This segmentation allows independent optimization of each component's function. The detector grating specifically measures scatter and beam hardening effects, while the object grating maintains phase contrast information, thereby reducing image artifacts without excessive complexity.
Solution Approach 2:
The detector grating serves as an intermediary measurement device that simplifies the scatter correction process. Instead of attempting to correct all scatter effects directly in the final image, the system uses the detector grating to measure scatter and beam hardening effects separately and applies corrections based on these measurements. This intermediary approach reduces the overall measurement complexity while effectively reducing image artifacts.
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
Enhances material discrimination by reducing scatter and beam hardening artifacts, resulting in higher quality x-ray images suitable for medical, security, and materials characterization 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
Implementation Method 6
measuring visibilities of the object grating from the first and second images to determine an object grating visibility reduction due to scatter and beam hardening
Implementation Method 7
emitting source x-rays from a polychromatic source operating at an endpoint energy greater than or equal to 100 keV
Implementation Method 8
emitting source x-rays from a polychromatic source operating at an endpoint energy greater than or equal to 100 keV
Data Source
AI summary
Systems include an x-ray optical arrangement that includes an x-ray source configured to emit an x-ray beam along a beam path and through an object placement location situated to receive an object for inspection, an object grating situated along the beam path, and a detector situated along the beam path to receive the x-ray beam after propagating through the object grating and object placement location and to detect image data, wherein the object grating includes object grating elements arranged in an object grating pattern; and a movement stage providing a plurality of computed tomography imaging positions for the object by the x-ray optical arrangement; wherein the object grating pattern and a positioning of the x-ray source, object grating, and detector in relation to each other are configured to provide a plurality of computed tomography detection modes in the image data.