X-ray Interferometer Phase Grating Placement for Sensitivity and Field of View
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Solution Overview
Problem
Current x-ray phase contrast imaging systems face challenges in achieving high sensitivity and large field of view due to the requirement for small period and high aspect ratio x-ray analyzer gratings, which are difficult to fabricate and incompatible with large area medical detectors, limiting their clinical potential for applications like breast and lung imaging.
Innovation Solution
An x-ray phase contrast imaging system using an analyzer grating with a larger period and lower aspect ratio, compatible with polychromatic, low spatial coherence medical x-ray tubes and large area detectors, comprising a source grating and two phase gratings placed closer to the detector to form a universal moiré pattern that can be resolved by the detector, increasing interferometer sensitivity and field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Talbot-Lau interferometer uses a small period and high aspect ratio analyzer grating to achieve high sensitivity, then interferometer sensitivity is improved, but fabrication difficulty increases and compatibility with large area medical detectors deteriorates
Solution Approach 1:
The patent changes the key parameter of the analyzer grating from small period/high aspect ratio to large period/low aspect ratio. This parameter transformation allows the grating to be compatible with large area medical detectors while maintaining interferometer sensitivity through the use of two phase gratings that generate a universal moiré pattern with a larger, resolvable period.
Solution Approach 2:
The patent uses two phase gratings to create a universal moiré pattern that acts as an intermediate structure. This moiré pattern has a larger period than the original phase grating structures, effectively creating a 'copied' version of the fine structure that can be resolved by standard medical detectors without requiring fabrication of extremely fine analyzer gratings.
2Measurement precision
If a Talbot-Lau interferometer uses a small period analyzer grating to achieve high sensitivity, then interferometer sensitivity is improved, but field of view is reduced
Solution Approach 1:
The patent transforms the spatial frequency parameter from high (small period) to low (large period) by using the universal moiré pattern generated by two phase gratings. This allows the system to maintain sensitivity while expanding the field of view to cover large area medical detectors used in clinical applications like breast and lung imaging.
3Measurement precision
If the phase grating period is made small to achieve high sensitivity, then measurement precision is improved, but detector resolution requirements increase making clinical application difficult
Solution Approach 1:
The patent creates a universal moiré pattern that copies the phase modulation information but at a larger spatial scale. The two phase gratings generate interference fringes with a period that is the sum of their individual periods, creating a low spatial frequency pattern that can be easily detected by standard medical detectors while preserving the phase contrast measurement precision.
Solution Approach 2:
The patent changes the spatial frequency parameter of the detectable pattern from high to low by using the moiré effect. The universal moiré pattern has a larger period that is resolvable by medical detectors with typical spatial resolution, eliminating the need for ultra-high resolution detectors while maintaining measurement precision through the phase stepping method.
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
The system achieves high interferometer sensitivity and large field of view, compatible with clinical applications, by using a source grating or periodically structured x-ray source to meet spatial coherence requirements and optimize fringe visibility, allowing for effective imaging with large area detectors.
Implementation Method 1
Two x-ray phase gratings with period p1 and p2 form a universal moiré pattern at the plane of the analyzer grating
Implementation Method 2
The combination of the low spatial coherence x-ray source and the source grating is equivalent to an array of line sources. Each line source provides sufficient spatial coherence for Talbot self-imaging of the phase grating
Implementation Method 3
a Talbot interferometer, utilizing the Talbot self-imaging of an x-ray phase grating to allow the use of polychromatic x-ray sources. To resolve the fine pitch of the self-imaging pattern, an absorption grating with similar period as the self-image of the phase grating is placed in front of the detector and the resulting moiré fringe is recorded by the detector
Data Source
AI summary
Disclosed herein is an x-ray interferometer for x-ray phase contrast imaging including an x-ray source, an x-ray source grating, two x-ray phase gratings, an x-ray analyzer grating and an x-ray detector. An alternative interferometer includes a periodically structured x-ray source, two x-ray phase gratings, an x-ray analyzer grating and an x-ray detector. The phase gratings are placed much closer to the x-ray detector than to the x-ray source and the image object is positioned upstream and close to the phase gratings to achieve high sensitivity and large field-of-view simultaneously.