Rotating Grating Cone Beam CT Reduces Scattered Photons
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Solution Overview
Problem
Cone beam CT imaging suffers from inaccurate image density due to scattered photons, with existing methods either limiting the imaging range, introducing noise, or requiring computationally intensive algorithms that are not clinically feasible for complex objects.
Innovation Solution
A rotating-grating cone beam CT apparatus that limits X-rays to narrow-angle cone or sector beams, using a rotating grating to reduce scattered photons by changing beam positions and employing interpolation algorithms to isolate main X-ray signals, allowing for high-definition image reconstruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a beam limitation device is adopted to limit the range of cone beams, then the influence of scattered photons is reduced, but the imaging range is also limited
Solution Approach 1:
The patent employs a rotating grating structure that dynamically changes the beam limitation pattern during acquisition. The grating rotates to sequentially limit different regions of the cone beam, allowing the imaging range to cover the entire object while maintaining narrow effective beam widths that reduce scattered photon influence in each measurement.
Solution Approach 2:
The patent divides the cone beam into multiple narrow-angle sub-beams using the rotating grating structure. Each sub-beam corresponds to a limited angular range, reducing scattered photon contamination. The complete image is reconstructed by combining measurements from all sub-beams acquired during grating rotation.
2Object-affected harmful factors
If a backscattering grid is added between the imaging object and the flat panel detector, then scattered photons are restrained, but noise is introduced
Solution Approach 1:
The patent extracts and removes scattered photons from the detection process by using the rotating grating to limit the beam angle. This prevents scattered photons from reaching the detector in the first place, rather than attempting to filter them afterward. The grating structure physically blocks scattered photons while allowing primary photons to pass through the limited angular range.
3Object-affected harmful factors
If the distance between the imaging object and the detector is increased, then the effect of the backscattering grid is improved, but the imaging range is limited
Solution Approach 1:
The rotating grating provides dynamic beam limitation that is independent of the object-detector distance. As the grating rotates, it continuously adjusts which angular ranges are transmitted, allowing the system to maintain effective scattered photon reduction regardless of the distance between object and detector.
4Measurement precision
If monte carlo algorithm is used for postprocessing, then scattered photon distribution is accurately estimated, but calculation time is excessive
Solution Approach 1:
The patent performs the scattered photon reduction action during the data acquisition phase rather than as a postprocessing step. The rotating grating physically limits the beam angle during acquisition, preventing scattered photons from being detected. This eliminates the need for computationally intensive monte carlo simulations to estimate and remove scattered photon effects afterward.
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 effectively reduces the influence of scattered photons, achieving higher image quality and accuracy comparable to sector beam CT while maintaining the open structure and convenience of cone beam CT.
Implementation Method 1
The rotating grating limits X-rays emitted from the X-ray source to a plurality of narrow-angle cone beams or sector beams
Implementation Method 2
the positions of the narrow-angle cone beams or sector beams are changed through the rotation of the grating, so that projection images of different regions of the imaging object are acquired
Data Source
AI summary
Disclosed is a rotating-grating cone beam CT imaging apparatus. This imaging apparatus is composed of a frame, a frame angle sensor, an X-ray source equipped with a rotating grating, a flat panel detector, a main controller and an image reconstruction workstation. Like a general cone beam CT imaging apparatus, this imaging apparatus also adopts an open structure. But unlike the general cone beam CT imaging apparatus, the rotating grating limits X-rays emitted from the X-ray source to a plurality of narrow-angle cone beams or sector beams. In the process that the X-ray source and the detector rotate around an imaging object, projection images of the narrow-angle cone beams or sector beams on the flat panel detector move back and forth continually through the rotation of the rotating grating, so as to acquire projection information about the imaging object in an entire scanning region. Finally, the projection information is reconstructed into a volume image in the image reconstruction workstation. In this manner of variable-focus scanning, the present invention not only can reserve the advantage of the open structure of the cone beam CT imaging apparatus, but also obtains the advantage that a sector beam CT imaging apparatus can restrain scattered photons so as to generate a high-quality image.