Phase Contrast X-ray Imaging Using Sample and Detector Masks
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Solution Overview
Problem
Conventional phase contrast x-ray imaging techniques face limitations such as reliance on expensive synchrotron sources, inefficient dose delivery, sensitivity to environmental vibrations, and limited applicability with commercial x-ray sources due to requirements for monochromatic and parallel radiation.
Innovation Solution
An x-ray imaging system using a combination of a sample mask and pixel edges at the detector to detect small variations in x-ray direction, allowing for the use of non-parallel, polychromatic radiation from conventional sources, which enhances image quality and reduces sensitivity to vibrations while maintaining efficiency and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If analyzer crystal-based phase contrast imaging is used, then image quality is improved, but the system requires monochromatic parallel radiation from expensive synchrotron sources and is highly sensitive to environmental vibrations
Solution Approach 1:
The patent replaces expensive, complex analyzer crystals with simple absorption masks that can be easily manufactured and replaced. These masks are made from常规 materials and do not require the sophisticated crystal growth processes needed for analyzer crystals, thereby reducing system complexity and cost while maintaining phase contrast imaging capability
Solution Approach 2:
The invention changes the detection parameter from angular sensitivity (using analyzer crystals) to intensity sensitivity (using absorption masks). By detecting intensity variations caused by phase shifts rather than angular deviations, the system eliminates sensitivity to environmental vibrations and removes the need for monochromatic parallel radiation, enabling use with conventional polychromatic sources
2Ease of manufacture
If conventional x-ray sources are used, then system cost and accessibility are improved, but the radiation is polychromatic and diverging which is incompatible with traditional phase contrast techniques
Solution Approach 1:
Instead of trying to make conventional diverging polychromatic radiation conform to the requirements of phase contrast imaging (parallel and monochromatic), the patent inverts the approach by adapting the detection method to work with the actual characteristics of conventional sources. The absorption masks are designed to detect phase shifts in diverging polychromatic beams, thereby enabling compatibility with readily available conventional x-ray sources
3Measurement precision
If synchrotron radiation is used, then phase contrast image quality is improved, but exposure time increases by two or more orders of magnitude when using conventional sources
Solution Approach 1:
The patent replaces the mechanical/optical system of analyzer crystals that requires precise angular alignment and monochromatic parallel beams with a simpler absorption mask system. This substitution allows direct detection of phase shifts in polychromatic diverging beams from conventional sources, eliminating the need for long exposure times required by synchrotron-based methods while maintaining image quality
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 image quality comparable to analyzer crystal-based approaches while using diverging, polychromatic radiation, delivering a more efficient dose and providing sensitivity to phase effects in both directions, thus overcoming the limitations of existing methods.
Implementation Method 1
Phase contrast is based on phase shift effects. The term responsible for phase effects is much bigger (∼1000 times) than the term accounting for absorption, hence the dramatically increased sensitivity of PC.
Implementation Method 2
the distortions of the x-ray wavefront due to phase shift result in local microvariations in the x-ray direction. In other words, after exiting the imaged sample, the direction of the x-rays has changed by a few tens of microradians
Implementation Method 3
a sample mask (8) is provided which, in use, absorbs a fraction of the x-rays incident on it and defines an illuminated area (22) on the sample (14). A detector mask (6) is provided which, in use, absorbs x-rays incident on it and defines an x-ray sensitive region (22) of a corresponding pixel (12)
Data Source
Figure 1~2
Figure 3~5
Figure 6~7
AI summary
Phase contrast imaging is achieved using a sample mask 8 and a detector mask (6). X- rays emitted from x-ray source (2) are formed into individual beams (16) by sample mask which pass through sample (14) and arrive at individual pixels (12) of the detector (4) through detector mask (6). The individual x-ray beams are arranged to hit the pixel edge (20) of individual rows of pixels, individual columns of pixels or individual pixels. Small deviations ? in the individual beams (16) cause a significant increase or decrease in the signal hitting the exposed area (22) of the pixel resulting in a significant phase contrast signal.