Spectral Grating Differential Phase Contrast Radiography
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Solution Overview
Problem
Conventional medical x-ray imaging techniques face challenges in providing sufficient contrast for soft tissues due to the reliance on x-ray attenuation, which results in poor imaging of tissues like vessels, cartilages, lungs, and breasts, as they have low absorption rates, leading to a lack of diagnostic information.
Innovation Solution
The implementation of a digital radiographic phase-contrast imaging system using an x-ray source, a beam shaping assembly, and an x-ray grating interferometer with a phase grating and analyzer grating to capture images at different relative beam energies, enabling spectral imaging and improved contrast through phase shift information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional x-ray attenuation imaging is used, then the imaging system is simple and fast, but soft tissue contrast is poor
Solution Approach 1:
The patent changes the imaging parameter from measuring only x-ray attenuation (absorption) to measuring phase shifts of x-rays. By using a grating-based interferometer, the system captures phase information that is approximately 1000 times more sensitive than attenuation for soft tissues, thereby dramatically improving soft tissue contrast without requiring complex additional hardware beyond the grating assembly
Solution Approach 2:
The patent introduces an x-ray grating interferometer as an intermediary device between the x-ray source and detector. This interferometer uses phase gratings to modulate and measure the phase shifts of x-rays passing through the object, converting invisible phase information into measurable intensity variations that can be captured by the detector, thus enabling soft tissue differentiation
2Measurement precision
If spectral imaging at multiple energies is implemented, then material differentiation is improved, but imaging time and complexity increase
Solution Approach 1:
The patent merges spectral imaging capability with phase contrast imaging by using the same grating-based interferometer setup to capture both phase information and energy-dependent attenuation information. The phase grating's transmission varies with x-ray energy, allowing the system to differentiate materials based on their energy-dependent phase shifts and attenuation characteristics simultaneously, eliminating the need for separate spectral imaging exposures
Solution Approach 2:
The patent utilizes the energy-dependent transmission characteristics of the phase grating to achieve spectral imaging. By analyzing how the phase grating's effective transmission changes with x-ray energy, the system can differentiate between materials with different atomic numbers and density, providing material-specific contrast enhancement without requiring multiple separate imaging acquisitions
3Measurement precision
If phase contrast imaging is used, then soft tissue visibility is improved, but patient radiation dose increases
Solution Approach 1:
The patent changes the detection parameter from measuring only absorption to measuring phase shifts, which are approximately 1000 times more pronounced for soft tissues. This parameter change allows achieving the same image quality with lower radiation doses because phase information provides much stronger contrast signals that require fewer photons to detect reliably
Solution Approach 2:
The patent replaces the conventional absorption-based detection mechanism with phase-shift-based detection using optical interference principles. By using the wave nature of x-rays and measuring phase differences through interferometric techniques, the system achieves high-contrast soft tissue imaging with improved signal-to-noise ratio, allowing for reduced radiation exposure
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 enhances diagnostic capabilities by providing improved contrast and detail in soft tissues, allowing for better differentiation and visualization of subtle details, particularly in mammography and orthopedic imaging, while reducing motion blur and patient dose.
Implementation Method 1
an x-ray grating interferometer comprising a phase grating G1 and an analyzer grating G2, offsetting a pitch of the analyzer grating G2 relative to a pitch of an interference pattern produced by the phase grating G1
Implementation Method 2
When an electromagnetic wave penetrates a medium, its amplitude is attenuated and its phase is shifted. In x-ray technology, the refractive index n of a material can be expressed by a complex number n=1−δ+iβ. The real part δ is responsible for the phase shift.
Implementation Method 3
an x-ray grating interferometer comprising a phase grating G1 and an analyzer grating G2, offsetting a pitch of the analyzer grating G2 relative to a pitch of an interference pattern produced by the phase grating G1
Data Source
AI summary
Embodiments of methods and apparatus are disclosed for obtaining a phase-contrast digital radiographic imaging system and methods for same that can include an x-ray source for radiographic imaging; a beam shaping assembly including a collimator and a source grating, an x-ray grating interferometer including a phase grating, and an analyzer grating; and an x-ray detector, where a single arrangement of the beam shaping assembly, the x-ray grating interferometer and a position of the detector is configured to provide spectral information (e.g. at least two images obtained at different relative beam energies).