Basis Material Decomposition Using Mass Conservation in Multi-Energy CT
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Solution Overview
Problem
Existing material decomposition methods in multi-energy CT, such as DECT and MECT, rely on volume conservation assumptions that are often violated, leading to biases in material quantification and noise issues, especially in solutions or mixtures, due to the lack of accurate proprietary information about x-ray spectra and detector responses.
Innovation Solution
A system and method for basis material decomposition that employs a general physical constraint, which can be represented as an unknown variable or obtained from reference data, allowing for improved image quality and reduced noise by eliminating the need for volume conservation assumptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If volume conservation assumption is used in material decomposition, then the decomposition can be performed with limited energy measurements, but the material quantification accuracy deteriorates due to violation of the assumption in solutions or mixtures
Solution Approach 1:
The patent changes the constraint parameter from volume conservation to mass conservation. By using mass fractions instead of volume fractions in the decomposition model, the method accounts for the actual physical behavior of materials in mixtures and solutions where volumes are not conserved but masses are. This parameter change resolves the contradiction by maintaining quantification accuracy while relying on a physically valid assumption.
Solution Approach 2:
The patent introduces an intermediary variable representing the mass fraction of basis materials in the mixture. This intermediary allows the decomposition to proceed without directly assuming volume conservation, instead using mass-based relationships that are always valid. The mass fraction acts as a mediator between the measured attenuation data and the material composition, eliminating the need for the flawed volume conservation assumption.
2Measurement precision
If proprietary x-ray spectrum and detector response information is used, then material decomposition accuracy improves, but the system complexity and access requirements worsen
Solution Approach 1:
The patent enables the system to determine its own x-ray spectrum and detector response characteristics through self-calibration procedures using phantom scans. Instead of requiring proprietary information from the manufacturer, the system performs autonomous measurements and calculations to characterize its own performance. This self-service approach eliminates the need for external proprietary data while maintaining decomposition accuracy.
Solution Approach 2:
The patent performs preliminary calibration measurements using phantom objects before actual material decomposition. These preliminary actions include acquiring transmission data at multiple energy levels and calculating the system's spectral and detector response characteristics. By performing these preparatory measurements in advance, the system establishes the necessary parameters for accurate decomposition without requiring complex proprietary information.
3Adaptability or versatility
If empirical spectrum estimation is performed, then the system can operate without proprietary information, but the spectrum accuracy deteriorates over time due to component aging
Solution Approach 1:
The patent implements a feedback mechanism where the system periodically performs calibration scans using phantom objects to update its spectrum and detector response characteristics. This feedback loop allows the system to detect and compensate for changes in component performance over time, such as anode material sputtering or detector aging. By continuously updating the spectral parameters based on actual measurements, the system maintains accuracy while remaining independent of proprietary information.
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 reduces bias and improves noise properties in material decomposition, providing more accurate quantitative analysis and enhanced image quality by using multi-energy measurements and reference data to determine basis material densities without relying on volume conservation.
Implementation Method 1
The intensity of the transmitted radiation is dependent upon the strength of the unattenuated beam emerging from the x-ray source and the attenuation of the x-ray beam by the object
Implementation Method 2
for materials without a measurable k-edge, interactions between X-rays and matter are limited to photoelectric and Compton effects
Implementation Method 3
for materials without a measurable k-edge, interactions between X-rays and matter are limited to photoelectric and Compton effects
Data Source
AI summary
A system and method is provided for performing material decomposition using a computed tomography (CT) system. The method includes acquiring CT imaging data of an object including data subsets corresponding to at least two different energy spectral bins and using the CT imaging data at each of the at least two different energy spectral bins to form a series of equations for basis material decomposition. The method also includes using a general physical constraint, which quantifies how each basis material in the object is mixed together to form the object, within the series of equations. The method also includes determining at least one basis material density of the object using the physical constraint and the CT imaging data and generating an image of the object using the CT imaging data and the mass densities of at least one basis material.