CT Image Reconstruction Using Continuous Weighting Functions
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Solution Overview
Problem
Existing image reconstruction methods for computed tomography (CT) using cone beam data suffer from artifacts due to data incompleteness and discontinuities in weighting functions, particularly when combining data from multiple axially offset radiation sources, leading to reduced dose efficiency and image quality.
Innovation Solution
A method for image reconstruction that employs a continuous weighting function defined by the boundaries between regions irradiated by different sources, eliminating the need for feathering and allowing for data combination on a per view basis, even with partial scan geometries, to produce a volumetric image with reduced artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If data from multiple axially offset radiation sources are combined using traditional weighting methods, then the completeness of acquired data is improved, but image artifacts increase due to discontinuities in weighting functions
Solution Approach 1:
The patent changes the parameter of the weighting function from traditional step-based or feathering methods to a continuous function defined by boundary equations. The weighting function w(z) is continuously differentiable and transitions smoothly between sources based on axial position z, eliminating discontinuities that cause artifacts while maintaining data completeness from multiple sources.
Solution Approach 2:
The patent introduces a continuous weighting function as an intermediary between multiple radiation sources and the final reconstructed image. This weighting function acts as a mediator that smoothly blends data from different axial positions, avoiding abrupt transitions and the resulting artifacts while preserving information from all sources.
2Object-affected harmful factors
If feathering is applied to reduce artifacts at boundaries between regions irradiated by different sources, then image quality is improved, but processing complexity and time increase
Solution Approach 1:
Instead of applying feathering as a post-processing step or complex boundary handling technique, the patent changes the fundamental parameter definition of the weighting function to be continuously differentiable by design. The boundary definitions and weighting function are formulated to be continuous from the start, eliminating the need for feathering operations and reducing processing time.
3Measurement precision
If only volume elements with sufficient angular coverage are used for reconstruction, then image quality is maintained, but dose efficiency is reduced as some acquired data is not used
Solution Approach 1:
The patent changes the parameter requirements for voxel reconstruction by introducing a continuous weighting function that can handle partial angular coverage. The weighting function continuously adjusts contributions from multiple sources based on axial position, allowing voxels with limited angular coverage to be reconstructed with optimized use of available data, thereby improving dose efficiency without sacrificing image quality.
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 method enhances image quality by reducing artifacts and processing time, achieving improved image reconstruction with fewer discontinuities and increased efficiency in combining data from multiple sources.
Implementation Method 1
Radiation emitted by the X-ray source is attenuated by the examination object and detected by the detector
Data Source
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AI summary
A method for volumetric image reconstruction of data collected from a plurality of radiation beams emitted from axially offset positions includes receiving projection data from at least two radiation beams emitted from axially offset positions, defining a first boundary between a first region irradiated only by a first beam of the at least two radiation beams and a second region irradiated by both the first beam and a second beam of the at least two radiation beams, defining a weighting function as a function of the first boundary, and reconstructing a volumetric image from the data that is weighted with the weighting function. Each beam moves on a circular trajectory and radiates at a plurality of view angles over the circular trajectory.