Photon Counting CT Exposure Dose Estimation via Energy Spectrum Segmentation
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Solution Overview
Problem
Existing X-ray CT devices with photon counting mode struggle to accurately calculate exposure dose due to variations in X-ray energy spectrum caused by different filters, making it difficult to achieve precise radiation exposure control.
Innovation Solution
The implementation of a system that calculates exposure dose by obtaining photon counts in predetermined energy ranges, using exposure per band data and spectrum acquisition to estimate the radiation exposure dose, allowing for precise estimation irrespective of the X-ray spectrum shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If filters in various forms and thicknesses are used to attenuate X-rays outside the energy range, then the exposure dose to the patient is reduced, but the distribution of emitted X-ray energy values varies depending on the filter, resulting in variations of the exposure dose that make it difficult to calculate accurately
Solution Approach 1:
The patent changes the parameter for exposure dose calculation from using only current value variations to using a weighted sum of photon counts across multiple energy ranges. By introducing energy-range-specific weighting factors (exposure per band data), the system accurately calculates exposure dose despite variations in X-ray spectrum caused by different filters, thus resolving the contradiction between reducing exposure dose and maintaining calculation accuracy.
2Object-affected harmful factors
If photon counting mode is used to categorize X-ray photons by energy values, then the exposure dose can be reduced by attenuating X-rays outside the energy range, but the complexity of the system increases due to the need for energy spectrum analysis and multiple detector elements
Solution Approach 1:
The patent segments the X-ray energy spectrum into multiple predetermined energy ranges (e.g., 0-20 keV, 20-40 keV, etc.) and uses separate detector elements or detection channels for each energy range. This segmentation allows the system to categorize photons by energy while maintaining manageable complexity through structured organization of detection channels, enabling exposure dose reduction without excessive system complexity.
3Ease of manufacture
If the exposure dose is calculated based on current value variations with constant tube voltage, then the calculation is simple, but the accuracy is insufficient when filters are used because the spectrum shape changes
Solution Approach 1:
The patent adds the energy dimension to the exposure dose calculation. Instead of calculating based on current value alone (one-dimensional approach), the system uses photon counts across multiple energy ranges (multi-dimensional approach). By incorporating energy-range-specific weighting factors, the system achieves accurate exposure dose measurement while maintaining calculation simplicity through the use of pre-computed weighting data, thus resolving the contradiction between simplicity and accuracy.
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 precise estimation and control of radiation exposure dose in X-ray CT devices, improving imaging efficiency and patient safety by accounting for variations in X-ray energy spectrum.
Implementation Method 1
a photon counting type detector counts photons of X-rays (X-ray photons) that have passed through a subject, with respect to each detector element
Implementation Method 2
the X-rays falling outside the energy range are attenuated to a minimum, thereby reducing an exposure dose to a patient being the subject
Data Source
AI summary
Provided is a photon counting CT device for estimating an exposure dose to a subject, precisely in a simple configuration, irrespective of a spectrum shape of X-rays being applied. An exposure dose derived from the X-rays with predetermined intensity is obtained in every energy range provided in advance, and held as exposure per band data. When an imaging condition is provided, X-rays are applied in accordance with the imaging condition thus provided, and a photon count (intensity) of the incident X-rays as to each energy range is obtained, in the shape of spectrum of the X-rays applied to a detector without placing the subject. The intensity of the incident X-rays is multiplied by the exposure per band, and the results as to all the energy ranges are added up. Accordingly, the exposure dose caused by the X-rays being applied in accordance with the provided imaging condition is estimated.