Photon Counting X-ray Beam Hardening Correction via Atomic Number Estimation
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Solution Overview
Problem
Conventional beam hardening correction techniques in X-ray imaging are limited by a narrow range of effective atomic numbers, making it difficult to accurately correct for a wide range of substances, especially in medical and dental applications where various tissues with different atomic numbers are encountered, leading to incomplete and imprecise image data.
Innovation Solution
A method and apparatus that process X-ray data by calculating and normalizing attenuation values across multiple energy bins, using a preset range of effective atomic numbers to generate beam hardening correction functions, allowing for more precise correction across a wider range of atomic numbers without the need for multiple correction functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional beam hardening correction techniques are used with a single reference substance, then the correction function can be calculated, but the range of effective atomic numbers that can be accurately corrected is limited to a narrow range (Z=±2)
Solution Approach 1:
The patent creates a single beam hardening correction function that can accurately correct for a wide range of substances with different effective atomic numbers. By using multiple reference substances (water and iodine) and their respective attenuation characteristics across different energy bins, the correction function becomes universal and can handle various tissues and materials encountered in medical and dental imaging, rather than being limited to a narrow atomic number range.
Solution Approach 2:
The patent changes the parameters used in beam hardening correction by utilizing attenuation characteristics at multiple energy bins and incorporating effective atomic number as a variable. The correction function uses the relationship between attenuation coefficients at different energies and the effective atomic number to adapt to different substances, allowing accurate correction across a broad range of materials without requiring multiple separate correction functions.
2Measurement precision
If multiple correction functions are created to cover different atomic number ranges, then the correction precision for specific substances improves, but the calculation load and system complexity increase
Solution Approach 1:
Instead of creating multiple separate correction functions for different atomic number ranges, the patent develops a single universal correction function that can accurately handle all substances. This function uses the effective atomic number and attenuation characteristics at multiple energy bins to adapt to different materials, thereby reducing system complexity while maintaining high correction precision across all substance types.
Solution Approach 2:
The patent introduces effective atomic number as a key parameter in the correction function, allowing a single function to dynamically adapt to different substances. By incorporating the relationship between attenuation coefficients at different energies and the effective atomic number, the system achieves substance-specific precision without requiring multiple predefined correction functions, thus reducing computational complexity.
3Ease of manufacture
If beam hardening correction is performed without considering effective atomic number, then the calculation process is simpler, but the correction accuracy for different types of substances deteriorates
Solution Approach 1:
The patent incorporates effective atomic number as a parameter in the beam hardening correction process. By using the relationship between attenuation coefficients at different energy bins and the effective atomic number, the correction function can distinguish between different types of substances (such as soft tissue, bone, and contrast agents) and apply appropriate correction, thereby improving accuracy while maintaining a relatively simple calculation framework.
Solution Approach 2:
The patent replaces complex material-specific correction approaches with a unified physical model based on the relationship between X-ray attenuation and effective atomic number. This substitution allows the system to handle diverse substances through a single correction function that leverages fundamental physical relationships, maintaining calculation simplicity while achieving high correction accuracy across different material types.
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 beam hardening correction with reduced calculation load and higher precision, providing qualitative and quantitative image information for substance identification, effectively covering a broader range of effective atomic numbers and improving image accuracy.
Implementation Method 1
The detector detects the X-rays which have been transmitted through the object as a flow of photons, and outputs electric signals depending on energy of the photons
Implementation Method 2
when polychromatic X-rays are radiated to a substance, lower X-ray energy components are likely to be absorbed in the substance more than higher X-ray energy components so that components of the X-rays that have been transmitted are shifted in their ratios toward a higher X-ray energy side
Data Source
AI summary
A higher accuracy beam hardening correction with a low calculation load is performed with objects whose elements have a wider range of effective atomic numbers Zeff, thereby contributing to presentation of more quantitative X-ray images. Of two or more X-ray energy bins, two X-ray bins are selected to normalize X-ray attenuation amount μt in those bins such that one or more normalized X-ray attenuation amounts are obtained at each pixel areas. From reference information indicating a theoretical relationship of correspondence between the normalized X-ray attenuation amounts and effective atomic numbers of elements, one ore more effective atomic numbers are estimated every pixel area. Among the one or more effective atomic numbers (ZHigh, ZLow) and an effective atomic number (Zm) preset for the beam hardening correction, two or more atomic numbers are subjected to their equality determination.