Beam Hardening Correction in X-ray CT Devices
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Solution Overview
Problem
Current X-ray CT devices face challenges in achieving accurate beam hardening correction due to high operation and production costs, limited precision in polynomial fitting, and the inability to effectively remove ring-shaped and band-shaped artifacts, particularly when using simulation methods that lack accuracy in reproducing X-ray detection element variations.
Innovation Solution
The X-ray CT device employs a beam hardening correction method that calculates precise BH correction coefficients by comparing simulation-calculated and actually measured X-ray absorption characteristics, using a virtual water phantom to simulate different X-ray transmission path lengths and accounting for individual detection element variations, thereby improving accuracy and reducing the need for multiple phantom measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple phantoms with different materials and sizes are used for BH correction measurement, then the accuracy of BH correction coefficients is improved, but the operation cost and production cost increase
Solution Approach 1:
The patent uses simulation-calculated values to create virtual copies of phantom measurement data, replacing the need for multiple physical phantoms. The simulation generates X-ray absorption characteristic data for various phantom types (water, polyethylene, acrylic resin) and sizes without requiring actual physical specimens, thereby maintaining measurement accuracy while eliminating the costs and time associated with producing and measuring multiple physical phantoms.
Solution Approach 2:
The patent changes the parameter representation from physical phantom properties to simulated numerical data. By varying simulation parameters (material composition, phantom size, X-ray energy) rather than physically changing phantoms, the system achieves comprehensive BH correction coefficient calculation across different conditions without the operational burden of multiple physical measurements.
2Ease of operation
If simulation methods are used to calculate BH correction coefficients, then the number of phantom measurements is reduced, but the accuracy is insufficient due to inability to reproduce detection element variations
Solution Approach 1:
The patent merges simulation-calculated values with actually measured values in a hybrid approach. The simulation provides the baseline X-ray absorption characteristic data, which is then corrected by applying error terms derived from actual phantom measurements. This combination leverages the efficiency of simulation while incorporating the accuracy of real measurements, particularly for detecting individual detection element variations.
Solution Approach 2:
The patent implements a feedback mechanism where actually measured values from phantom measurements are used to evaluate and correct the simulation-calculated values. The error between simulated and actual measurements feeds back into the correction process, allowing the system to learn from real data and improve the accuracy of BH correction coefficients while maintaining the reduced measurement burden.
3Device complexity
If polynomial fitting is used for BH correction, then the correction process is simplified, but the precision is limited
Solution Approach 1:
The patent replaces the traditional polynomial fitting mathematical model with a physics-based simulation model. Instead of using empirical polynomial functions to approximate the relationship between projection data and path length, the system uses Monte Carlo simulation or ray-trace methods that are grounded in the actual physics of X-ray interactions, thereby achieving higher precision without increasing operational complexity.
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 enhances the quantitative determination of CT values, reduces artifacts, and lowers operational and production costs by standardizing measurements and using fewer phantoms, while maintaining high correction accuracy.
Implementation Method 1
there is induced the beam hardening (henceforth abbreviated as BH) phenomenon. The BH phenomenon is a phenomenon that energy of an X-ray passing through a subject and detected by an X-ray detector becomes higher as X-ray transmission path length of the X-ray in the subject becomes longer
Implementation Method 2
X-ray CT devices are devices for reconstructing a tomographic image (henceforth referred to as CT image) of a subject by using transmission X-ray data of the subject obtained by imaging the subject with revolving a pair of X-ray tube and X-ray detector
Data Source
AI summary
In X-ray CT devices, degradation of quantitative determination ability for CT values resulting from the beam hardening (BH) effect of X-ray is prevented. X-ray absorption characteristic S obtained by simulation and a target value T thereof are saved beforehand, the simulation value S is revised by using projection data measured by maintenance measurement for obtaining basic data required for BH correction, and a BH correction coefficient is calculated by using the revised X-ray absorption characteristic S and the target value T. With a few actually measured values, BH correction accuracy can be improved, and reduction of incorrect diagnosis resulting from inhomogeneity of the CT values and improvement in the diagnostic ability based on improvement in quantitative determination ability for the CT values can be realized.