Phase Contrast Imaging Grating Movement for Region of Interest
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Solution Overview
Problem
Traditional X-ray systems for medical applications face limitations in differential phase contrast imaging due to non-focused gratings, which result in reduced visibility of interference patterns, lower signal-to-noise ratio, and limited field of view, leading to increased radiation dose and noise issues, particularly with low-frequency noise being more annoying.
Innovation Solution
A device and method for phase contrast imaging that allows for the movement of the grating arrangement out of the X-ray beam, enabling focused imaging on a region of interest with a previous pure absorption scan, reducing X-ray dose exposure and enhancing image quality through local tomography and variable aperture adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If non-focused gratings are used in PCI system, then the FOV can be covered, but the visibility of interference pattern and signal-to-noise ratio decrease outside central region
Solution Approach 1:
The patent divides the imaging process into two separate scans: a first scan with the grating arrangement removed to capture the full FOV absorption image, and a second scan with the grating arrangement in place to capture the PCI image of a specific region of interest. This segmentation allows each scan to be optimized for its specific purpose, resolving the contradiction between full FOV coverage and high measurement precision.
Solution Approach 2:
The patent applies local quality by focusing the PCI imaging resources (grating arrangement) only on a specific region of interest rather than the entire FOV. The region of interest is determined from the absorption image, and the grating arrangement is positioned to image only that local area, thereby achieving high visibility and signal-to-noise ratio where needed without compromising overall FOV coverage.
2Measurement precision
If grating arrangement is placed in X-ray beam, then phase contrast imaging is enabled, but radiation dose must be increased to maintain image quality
Solution Approach 1:
The patent applies partial action by imaging only a region of interest rather than the entire FOV with the PCI system. Since the grating arrangement has limited FOV, the patent scans only the necessary local area to obtain the required diagnostic information, thereby reducing the total radiation dose while maintaining adequate contrast-to-noise ratio in the region of interest.
Solution Approach 2:
The patent performs a preliminary absorption scan without the grating arrangement to identify and determine the region of interest. This preliminary action allows the subsequent PCI scan to be targeted precisely, avoiding unnecessary radiation exposure to areas outside the region of interest while ensuring adequate dose for the area that requires phase contrast imaging.
3Reliability
If source grating thickness is increased to produce minimal absorption, then X-ray filtering is improved, but mean X-ray intensity and interference pattern visibility decrease
Solution Approach 1:
The patent changes the operational parameters by removing the source grating from the beam path during the first absorption scan. This parameter change allows the use of lower X-ray intensity during the preliminary scan, reducing radiation dose to the patient while still obtaining sufficient image quality for region of interest determination. The source grating is then used appropriately during the second PCI scan where its filtering function is needed.
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 allows for higher contrast-to-noise ratio imaging without increasing radiation dose, improves image quality by targeting specific regions of interest, and reduces noise, particularly low-frequency noise, while maintaining a large field of view.
Implementation Method 1
a diffracting grating G1 and an analyzer grating G2, wherein the source grating is located between the source and the object, and wherein the diffracting grating and the analyzer grating are located between the object and the detector
Implementation Method 2
resulting in a decreased visibility of an interference pattern
Data Source
AI summary
X-ray devices for Phase Contrast Imaging (PCI) are often built up with the help of gratings. For large field-of-views (FOV), production cost and complexity of these gratings could increase significantly as they need to have a focused geometry. Instead of a pure PCI with a large FOV, this invention suggests to combine a traditional absorption X-ray-imaging system with large-FOV with an insertable low-cost PCI system with small-FOV, The invention supports the user to direct the PCI system with reduced FOV to a region that he regards as most interesting for performing a PCI scan thus eliminating X-ray dose exposure for scanning regions not interesting for a radiologist. The PCI scan may be generated on the basis of local tomography.