Source Grating Alignment via Moiré Feedback in X-ray Phase Contrast
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Differential phase contrast imaging systems require precise alignment and adjustment of gratings, which is time-consuming and costly, especially in hospital environments, due to tight accuracy requirements for the movement and alignment of the gratings.
Innovation Solution
An X-ray imaging system with a grating arrangement and a processing unit that detects moiré patterns to compute a translation signal for adjusting the source grating, allowing for misalignment compensation in the sub-millimeter region, reducing the need for precise mechanical adjustments and stabilizing the interferometer unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If precise alignment and adjustment of gratings is performed to achieve accurate differential phase contrast imaging, then image quality is improved, but setup time and cost increase
Solution Approach 1:
The patent replaces complex mechanical alignment procedures with an automated optical feedback system. The detector captures moiré patterns that provide real-time information about grating alignment, allowing the system to self-correct positioning errors through computational algorithms rather than manual mechanical adjustment, thereby reducing setup time while maintaining precision
Solution Approach 2:
The system implements feedback by using the detector to monitor moiré fringe patterns generated by the interaction of X-rays with the grating structure. This feedback signal is processed to determine the actual positions of gratings relative to the source and detector, enabling real-time correction of alignment deviations without requiring pre-calibrated mechanical positioning systems
2Manufacturing precision
If tight accuracy requirements are imposed on the stepping device and grating alignment to achieve proper phase stepping, then phase retrieval accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent substitutes high-precision mechanical stepping devices with coarser mechanical components combined with computational correction. Instead of requiring the stepping device to achieve sub-micrometer precision mechanically, the system uses detector-based moiré pattern analysis to measure actual positions and applies digital corrections, thereby simplifying the mechanical subsystem while maintaining phase retrieval accuracy
Solution Approach 2:
The patent introduces an intermediary measurement and correction layer between the mechanical stepping device and the final image reconstruction. The detector captures moiré patterns that serve as an intermediary signal, allowing the system to indirectly measure grating positions with high precision even when the mechanical positioning is coarse, thus decoupling mechanical precision requirements from final measurement accuracy
3Measurement precision
If the distance between phase grating and analyser grating is precisely adjusted to achieve at least one interference fringe period across the detector, then phase contrast imaging quality is improved, but adjustment time and cost increase
Solution Approach 1:
The system uses feedback from detected moiré patterns to determine whether the distance between the phase grating and analyser grating produces the required interference fringe coverage across the detector. This feedback mechanism allows for post-assembly verification and correction, eliminating the need for extremely precise initial manufacturing tolerances and simplifying the assembly process
Solution Approach 2:
The patent performs preliminary alignment using easily achievable mechanical tolerances, then uses the moiré pattern detection to identify and correct any remaining deviations from the optimal grating distance. This preliminary action approach allows manufacturers to assemble the system with standard tolerances rather than requiring specialized high-precision assembly procedures
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 minimizes the number of tuning and adjustment procedures, shifting precision requirements from sub-micrometer to sub-millimeter, enabling faster and less costly setup and maintenance while maintaining image quality.
Implementation Method 1
The source grating is misaligned in respect to the interferometer unit such that moiré fringes are detectable in the plane of the detector
Implementation Method 2
a phase shift of at least one interference fringe period of the interferometer, i.e. the analyser grating G2 and the phase grating G1
Data Source
AI summary
An X-ray imaging method includes acquiring a differential phase contrast imaging X-ray scan with an X-ray imaging system having an X-ray source, an X-ray detector, and a grating arrangement having a source grating, a phase grating and an analyzer grating. The source grating is misaligned in respect to an interferometer such that moiré fringes are detectable in the plane of the detector. A translation signal is computed for translating the source grating for achieving a predetermined moiré pattern. The positioning of the source grating is adjusted in an X-ray projection direction based on the translation signal such that at least 2 pi of phase changes are covered with the Moiré fringes over the width of the detector. And a further differential phase contrast imaging X-ray scan is acquired.