Curved X-ray Grating Bars for Phase Contrast Imaging
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Solution Overview
Problem
Conventional focus-detector arrangements for X-ray phase contrast imaging suffer from inferior imaging quality towards the edge of the detector due to shadowing effects caused by high aspect ratios of grating bars, especially in fan and cone beam geometries, which impairs the diffraction and scan effects at larger angles.
Innovation Solution
The design includes X-ray optical gratings with bars oriented radially and curved to avoid shadowing, featuring a sinusoidal or trapezoidal height profile, and adaptable bar lengths and periods to maintain coherence and intensity, ensuring optimal alignment and curvature to prevent shadowing and enhance imaging across the entire detector region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional plane gratings with high aspect ratio bars are used, then the system can achieve sufficient absorption contrast, but shadowing effects occur at larger angles that impair diffraction and scan effects
Solution Approach 1:
The patent applies curvature to the grating structure by arranging grating bars along circular arcs centered on the X-ray source rather than using straight parallel bars. This curved configuration ensures that all grating bars remain perpendicular to the incident X-ray beams across the entire fan beam angle, eliminating shadowing effects while maintaining the necessary absorption and diffraction functions for phase contrast imaging.
2Area of stationary object
If the fan or cone angle is increased to achieve larger field of view, then the field of view is improved, but imaging quality deteriorates toward the edge of the detector
Solution Approach 1:
The curved grating configuration with bars arranged on circular arcs allows the system to maintain consistent optical performance across large fan and cone angles. This enables the use of wider beam angles to achieve larger field of view without the edge degradation that plagues conventional straight-bar gratings, as the curved geometry preserves perpendicularity between bars and incident beams throughout the extended angular range.
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 improves imaging quality across the entire off-axial region by preventing shadowing and maintaining coherence, allowing for effective phase contrast recordings with larger fan or cone angles, enhancing the field of view and diagnostic capabilities in medical and non-destructive testing applications.
Implementation Method 1
a phase grating arranged on the opposite second side of the subject in the beam path, which generates an interference pattern of the X-radiation
Implementation Method 2
an analysis-detector system which detects at least the interference pattern generated by the phase grating in respect of its phase shift with position resolution
Data Source
AI summary
A focus-detector arrangement includes a radiation source with a focus, arranged on a first side of the subject, for generating a fan-shaped or conical beam of rays; at least one X-ray optical grating arranged in the beam path, with at least one phase grating arranged on the opposite second side of the subject in the beam path generating an interference pattern of the X-radiation preferably, in a particular energy range; and an analysis-detector system which detects at least the interference pattern generated by the phase grating in respect of its phase shift with position resolution. According to at least one embodiment of the invention, at least one X-ray optical grating including bars which are free from overhangs form shadows in the beam path of the fan-shaped or conical beam of rays.