Robust Phase Contrast CT Reconstruction via Reference Scan
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Solution Overview
Problem
Existing grating-based differential phase-contrast imaging methods are not robust to environmental changes such as mechanical and thermal fluctuations, leading to image artifacts and the need for frequent recalibration.
Innovation Solution
A signal processing system that models and fits the fluctuation of the reference phase in interferometric projection data, allowing for robust data acquisition and image reconstruction by incorporating a dedicated phase variable to account for phase drifts, thereby reducing image artifacts and increasing reproducibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional phase-stepping or fringe-scanning procedures are used to acquire interferometric data, then spatial distribution of physical properties can be obtained, but the system becomes sensitive to mechanical and thermal fluctuations causing image artifacts
Solution Approach 1:
The patent changes the parameter being measured from the absolute phase to the phase difference between object and reference scans. By formulating the reconstruction as a difference of interferometric projections, the method eliminates sensitivity to reference phase fluctuations caused by mechanical and thermal changes, while still recovering the spatial distribution of physical properties
Solution Approach 2:
The patent performs a reference scan without an object present, creating a reference interferometric projection that copies the environmental conditions (mechanical and thermal state) at that moment. This reference copy is then subtracted from the object scan to eliminate common-mode environmental artifacts
2Loss of information
If gratings are moved between successive detector readings to achieve different relative positions, then complete interferometric data can be acquired, but mechanical instability introduces phase drift and reduces reproducibility
Solution Approach 1:
The patent performs a preliminary reference scan to capture the interferometric pattern under current environmental conditions before introducing the object. This preliminary action establishes a baseline that accounts for any mechanical or thermal state, allowing subsequent object scans to be compared against this reference
3Measurement precision
If frequent recalibration is performed to maintain image quality, then measurement accuracy is preserved, but acquisition time increases and productivity decreases
Solution Approach 1:
The system performs self-calibration by using the reference scan to automatically compensate for environmental drifts. The phase difference calculation inherently corrects for mechanical and thermal changes without requiring external calibration procedures, making the system self-correcting and eliminating the need for frequent manual recalibration
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 proposed method enhances the robustness of grating-based phase contrast and dark field imaging, reducing sensitivity to mechanical and thermal-induced variations, and minimizing the need for recalibration, resulting in improved image quality and reduced artifacts.
Implementation Method 1
interferometric projection data derived from signals acquired by an X-ray detector, said signals caused by X-ray radiation after interaction of said X-ray radiation with an interferometer
Implementation Method 2
this method provides access to the spatial distribution of the electron density (via refraction)
Implementation Method 3
spatial distribution of the small-angle scattering power of the object
Data Source
AI summary
A system and related method for signal processing. Interferometric projection data reconstructed into one or more images for a spatial distribution of a physical property of an imaged object. The interferometric projection data is derived from signals acquired by an X-ray detector (D), said signals caused by X-ray radiation after interaction of said X-ray radiation with an interferometer and with the object (OB) to be imaged, said interferometer (IF) having a reference phase. A reconstructor (RECON) reconstructs for the image(s) by fitting said data to a signal model by adapting fitting variables, said fitting variables including i) one or more imaging variables for the one or more images and ii), in addition to said one or more imaging variables, a dedicated phase variable for a fluctuation of said reference phase.