X-ray CT Reconstruction Width Decision for Cone Beam Artifacts
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Solution Overview
Problem
Existing X-ray computed tomography apparatuses face challenges in reconstructing volume data when there are regions with incomplete projection data, leading to deteriorated image quality, especially at cone angle ends with large CT value changes, due to overlapping volume data in step and shoot scanning.
Innovation Solution
The apparatus includes a width decision unit that determines the end portion width of the reconstruction region based on the set radiation range, diameter, and imaging target portion, generating interpolation data to complete projection data for end portions, and reconstructs volume data using the Feldkamp method or cone beam reconstruction, allowing for approximation of a cylindrical shape while minimizing overlap and radiation exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If mask region reconstruction is performed to reduce overlap region and radiation exposure, then radiation dose is reduced, but image quality deteriorates at cone angle ends with large CT value changes
Solution Approach 1:
The patent applies local quality by differentiating the treatment of different regions within the scanning field. The reconstruction process selectively applies different algorithms or parameters to the central region versus the cone angle end regions. Specifically, the system identifies regions with large CT value changes at cone angle ends and applies specialized reconstruction techniques to those areas while using standard mask region reconstruction for other areas, thereby maintaining image quality where needed while still reducing overall radiation exposure.
Solution Approach 2:
The patent utilizes parameter changes by dynamically adjusting reconstruction parameters based on the specific characteristics of different regions. The system modifies reconstruction parameters such as interpolation methods, filtering techniques, or algorithm selection according to the local CT value variation characteristics. This allows the system to optimize image quality in problematic regions while maintaining radiation dose reduction benefits in other regions.
2Area of stationary object
If volume data is coupled along body axis direction to generate wide-volume, then imaging coverage is expanded, but overlap region increases leading to higher radiation exposure
Solution Approach 1:
The patent applies preliminary action by pre-calculating and identifying the overlap regions before performing the full coupling of volume data along the body axis direction. The system determines the optimal step size and positioning for acquiring successive volume data sets to minimize overlap. By planning the scanning trajectory and coupling strategy in advance, the system expands imaging coverage while avoiding excessive radiation exposure from redundant scanning of overlapping regions.
Solution Approach 2:
The patent implements partial action by selectively coupling volume data only in regions where it is necessary to achieve the desired wide-volume coverage. Instead of uniformly coupling all available volume data, the system identifies and couples only the essential portions that contribute to expanding imaging coverage, thereby reducing unnecessary radiation exposure from redundant data acquisition and coupling operations.
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 enables the reconstruction of high-quality volume data approximated to a cylindrical shape, reducing radiation dose and minimizing overlap between volume data sets, thereby maintaining image quality and reducing exposure.
Implementation Method 1
an X-ray generation unit that generates a cone-beam X-ray; an X-ray detection unit that detects the X-ray from the X-ray generation unit through an object on a top
Data Source
AI summary
According to one embodiment, an X-ray computed tomography apparatus includes an X-ray generation unit, an X-ray detection unit, a unit to reconstruct volume data for a reconstruction region having an operator-designated diameter based on projection data, a unit to generate interpolation data based on measurement data to complete projection data for end portions of the reconstruction region wherein the projection data required for reconstructing the volume data of a middle portion of the reconstruction region is acquired as the measurement data, and a unit to decide a width of the end portions based on the set radiation range along the top's longitudinal direction, reconstruction region's diameter, and object's imaging target portion.