Stationary-Source CT Narrow Beam Collimation and Nonplanar Trajectory
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Solution Overview
Problem
Current stationary-source X-ray computed tomography (CT) systems face limitations in image acquisition due to scatter contamination and limited scan trajectories, leading to degraded image quality with artifacts such as scatter uptake and cone-beam artifacts, which affect diagnostic accuracy and measurement precision.
Innovation Solution
The implementation of a system with a stationary X-ray source and a pre-object or post-object collimator to form a narrow beam, combined with a narrow-field detector that oscillates to synchronize with the collimator, reduces scatter contamination to less than 5% and allows for nonplanar object trajectories, ensuring that projections are primarily composed of primary photons and fully representative of the object.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a stationary detector with large sensitive area is used to measure the object, then the object can be fully captured, but scatter radiation contamination increases
Solution Approach 1:
The detector is segmented into multiple detector elements that can be independently controlled. Only the detector elements within the narrow acceptance angle (within ±5 degrees of the central ray) are activated to detect primary photons, while other elements remain inactive or are used to detect and reject scattered photons. This segmentation allows the large detector area to be utilized without capturing excessive scatter radiation.
Solution Approach 2:
Different regions of the detector are assigned different functions: the central region within the narrow acceptance angle detects primary photons for image formation, while peripheral regions detect scattered photons for rejection. This local quality differentiation optimizes the detector performance by ensuring that only photons within the acceptable angular range contribute to the projection data.
2Device complexity
If the object rotates on a planar trajectory, then the scanning mechanism is simple, but image artifacts such as cone-beam artifacts occur
Solution Approach 1:
The object trajectory is changed from a static planar rotation to a dynamic nonplanar trajectory. The object rotates on the turntable while simultaneously undergoing vertical oscillation or translation, creating a three-dimensional scanning path. This dynamic trajectory ensures that rays from all detector elements intersect the object at different heights, satisfying the Tuy criterion and eliminating cone-beam artifacts while maintaining relatively simple scanning mechanics.
Solution Approach 2:
The scanning trajectory is extended from two-dimensional planar rotation to three-dimensional nonplanar motion by adding vertical displacement. This dimensional change allows the X-ray source and detector to sample the object from multiple heights, ensuring complete data acquisition for volumetric reconstruction and eliminating the zone of ignorance that causes cone-beam artifacts.
3Object-affected harmful factors
If a narrow beam is formed using collimator, then scatter contamination is reduced, but the detector must oscillate synchronously increasing system complexity
Solution Approach 1:
The turntable serves multiple functions: it rotates the object for angular sampling and simultaneously provides the vertical oscillation or translation motion needed for nonplanar trajectory. This multi-functionality eliminates the need for separate oscillation mechanisms and simplifies the synchronization requirements, as both motions are achieved through a single mechanical platform.
Solution Approach 2:
The system uses the existing turntable rotation mechanism to generate the nonplanar trajectory by incorporating vertical displacement, rather than requiring an independent oscillation system. The turntable's rotational motion combined with its vertical movement automatically creates the necessary three-dimensional scanning path, making the system self-sufficient and reducing overall complexity.
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 significantly reduces scatter contamination and cone-beam artifacts, resulting in improved image quality with enhanced diagnostic accuracy and precise measurements by minimizing scattered photons and ensuring complete data acquisition.
Implementation Method 1
a pre-object collimator positioned between the stationary X-ray source and an object of interest and comprising an opening configured to oscillate on a first translational arc
Implementation Method 2
a narrow-field X-ray detector configured to oscillate on a second translational arc having a second center of oscillation
Implementation Method 3
synchronizing a speed and a phase for the oscillatory translation of the narrow-field X-ray detector with the opening of the pre-object collimator
Implementation Method 4
a stationary X-ray source configured to generate a beam of X-ray photons
Data Source
AI summary
Described herein are X-ray-based CT systems, specifically those with a stationary X-ray source and a moving object of interest, and methods of using the same, that address limitations in current stationary-source CT, such as scatter contamination and limited scan trajectories. The described systems include a pre-object collimator to form a narrow beam. Scatter contamination is reduced to less than 5% of acquired projections, resulting in high-quality CT images with minimal artifacts, improving diagnostic accuracy and measurement precision. The described system also allows for nonplanar trajectories, providing complete sampling of an object along multiple degrees of freedom.