X-ray CT Apparatus Spectrum Estimation for Material Decomposition
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Solution Overview
Problem
Conventional X-ray computed tomography (CT) techniques face challenges in accurately performing material decomposition due to discrepancies between the spectrum and image used for decomposition and the actual spectrum transmitted through a subject, leading to inaccurate calculations of material properties.
Innovation Solution
An X-ray CT apparatus that includes an X-ray generator, detector, and processing circuitry, which calculates an estimated spectrum by accounting for distortions in the X-ray transmission path, allowing for accurate determination of the X-ray transmission length through materials by comparing estimated and detected spectra.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional material decomposition is performed using measured spectrum and image, then the process is simple, but the accuracy of material decomposition is poor due to spectrum distortion
Solution Approach 1:
The patent applies preliminary action by calculating the estimated spectrum before performing material decomposition. The processing circuitry calculates an estimated spectrum based on an irradiation spectrum and estimated transmission lengths of materials, then uses this pre-calculated spectrum for decomposition. This preliminary spectrum calculation accounts for beam hardening effects and spectrum distortions that would otherwise compromise decomposition accuracy, thereby resolving the contradiction between simple processing and accurate results.
2Measurement precision
If the measured spectrum is used directly for material decomposition, then the processing is straightforward, but beam hardening effects cause estimation errors
Solution Approach 1:
The patent implements feedback by iteratively refining the estimated transmission lengths of materials based on comparing the estimated spectrum with the measured spectrum. The processing circuitry calculates an estimated spectrum using initial estimated transmission lengths, compares it with the actual measured spectrum, and then updates the transmission length estimates to reduce discrepancies. This feedback loop continuously improves measurement accuracy by accounting for beam hardening effects and spectrum distortions.
3Reliability
If conventional techniques are used, then the device structure is simple, but the calculated material properties deviate from actual values
Solution Approach 1:
The patent applies preliminary action by performing spectrum estimation before material decomposition. The processing circuitry calculates an estimated spectrum based on the irradiation spectrum and estimated transmission lengths, then uses this pre-processed spectrum as input for material decomposition. This preliminary step corrects for beam hardening effects and spectrum distortions, ensuring that the subsequent decomposition yields reliable material property values that accurately reflect the actual subject composition.
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 highly accurate material decomposition by minimizing estimation errors and accounting for beam hardening effects, resulting in precise calculations of material properties such as density and atomic number.
Implementation Method 1
The X-ray generator irradiates X-rays to a subject P. The X-ray detector detects the X-rays that have passed through the subject P.
Implementation Method 2
the fact that the interaction between the X-ray and the materials are different depending on the energy of the X-rays is used
Implementation Method 3
calculates an estimated spectrum based on an irradiation spectrum, an estimated length and information indicating a distortion of a spectrum occurring in a path of the X-rays passing through the subject
Data Source
AI summary
An X-ray computed tomography (CT) apparatus according to an embodiment includes an X-ray generator, an X-ray detector and processing circuitry. The X-ray generator irradiates X-rays to a subject. The X-ray detector detects the X-rays that have passed through the subject. The processing circuitry calculates an estimated spectrum based on an irradiation spectrum, an estimated length and information indicating a distortion of a spectrum occurring in a path of the X-rays passing through the subject, the estimated length representing an estimated value of an X-ray transmission length of a material of decomposition target. The processing circuitry determines an X-ray transmission length of the material of decomposition target based on the estimated spectrum and a detected spectrum that is a spectrum after the X-rays have passed through the subject and that is detected by the X-ray detector.