CT Scanner Dual-Energy Material Decomposition
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional CT imaging systems face challenges in acquiring dual-energy data efficiently due to beam hardening artifacts, which result in errors in material decomposition and atomic number determination, especially when dealing with inhomogeneous objects, and require redundant scans or costly dual-source systems.
Innovation Solution
A method and apparatus that segment gantry rotations into low and high energy segments using a single x-ray source, allowing for dual-energy data acquisition in one or more gantry rotations, and employs image-based material decomposition with iterative beam hardening corrections to produce a composite image free of beam hardening artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sinogram-based material decomposition is used to obtain accurate atomic number information, then beam hardening errors are prevented, but the system architecture is greatly constrained and scan speed is reduced due to the requirement to identically register all source-to-detector angles in low and high energy projection views
Solution Approach 1:
The patent segments the CT scan process into separate low-energy and high-energy acquisition phases, allowing each to be optimized independently. The low-energy sinogram is acquired first, then the high-energy sinogram is acquired after the object has been repositioned to the same location, eliminating the need for identical registration of view angles while maintaining material decomposition accuracy.
Solution Approach 2:
The patent performs preliminary repositioning of the object to the same location before acquiring the high-energy sinogram data. This preliminary action ensures that the object is in the correct position for accurate material decomposition without requiring complex real-time registration algorithms, thereby improving scan speed while maintaining precision.
2Adaptability or versatility
If dual energy data is acquired by separate scans at two different kVP or spectral filter conditions, then material decomposition can be performed, but beam hardening artifacts occur due to mis-registered views acquired at different times and view angles
Solution Approach 1:
The patent employs preliminary repositioning of the object to the same location before acquiring the high-energy sinogram. This ensures that the object remains in the correct position throughout the dual-energy acquisition process, preventing mis-registration and beam hardening artifacts while enabling accurate material decomposition.
Solution Approach 2:
The patent uses feedback from the low-energy sinogram acquisition to guide the repositioning process before high-energy data acquisition. The system adjusts the object position based on the low-energy image information to ensure precise alignment, thereby eliminating beam hardening artifacts and improving material decomposition accuracy.
3Productivity
If a fast kVP switching circuit is used to acquire separate low and high energy images, then dual energy data can be obtained, but insufficient control of the x-ray source beam current and kVP is achieved due to long thermal time constants of the source filament and electrical time constants of the high voltage system reactance
Solution Approach 1:
The patent segments the dual-energy acquisition into distinct temporal phases: first the low-energy sinogram is acquired, then the object is repositioned, and finally the high-energy sinogram is acquired. This segmentation allows sufficient time for the x-ray source to stabilize at each energy level, achieving precise control of beam current and kVP while maintaining productive data acquisition.
Solution Approach 2:
The patent performs preliminary repositioning of the object between the low-energy and high-energy acquisitions. This preliminary action creates a deliberate time gap that allows the x-ray source to fully stabilize at each energy level, ensuring precise control of beam current and kVP while maintaining efficient overall scan time.
4Object-affected harmful factors
If conventional beam hardening correction using water parameters is applied to sinogram data, then cupping artifacts are eliminated in homogeneous objects, but artifacts remain in images of inhomogeneous objects with unknown composition
Solution Approach 1:
The patent changes the approach from using fixed water parameters for beam hardening correction to using energy-dependent parameters that are specifically optimized for the dual-energy acquisition. The low-energy and high-energy sinograms are processed with different parameter sets that account for their respective energy characteristics, thereby eliminating artifacts in inhomogeneous objects and improving material composition accuracy.
Solution Approach 2:
The patent treats the dual-energy sinogram data as a composite representation of the object's material composition. By processing the low-energy and high-energy data together using appropriate material decomposition algorithms, the system can accurately characterize inhomogeneous objects without relying on simplified water parameters, thereby eliminating artifacts and improving measurement precision.
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 efficient data acquisition and image reconstruction that provides accurate material composition information without substantial increases in scan time, reducing artifacts and costs associated with redundant scans or dual-source systems.
Implementation Method 1
The attenuation of x-rays by the object cannot be represented as a line integral across the object thickness. Rather, the attenuation results from a convolution across a broad spectrum of x-ray photon energies delivered by the x-ray source.
Implementation Method 2
detector array (18) on the opposite side of the gantry (12). Detector array (18) senses the projected x-rays that pass through an object (22).
Data Source
AI summary
A CT scanner acquires CT images at different energy levels and registers those images to provide a composite image that is substantially free of beam hardening artifacts and conspicuously provides atomic information of that imaged.