Photon-Counting CT Detector Calibration via Multi-Energy X-Rays
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Solution Overview
Problem
Current photon counting CT detectors face challenges in accurate gain calibration due to the difficulty in using radioactive isotopes with sufficient radioactivity and the need for precise energy calibration across varying environmental conditions, especially since existing methods rely on single or limited characteristic X-rays from an imaging target.
Innovation Solution
A photon counting CT apparatus is designed with an X-ray source capable of generating a plurality of characteristic X-rays having different energies, allowing for the calibration of the detector's gain using these X-rays, which are produced by rotating an anode with multiple targets made of different elements, enabling accurate calibration across various energy bins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a radioactive isotope with high radioactivity (100 MBq or more) is used for detector gain calibration, then calibration accuracy is improved, but practical implementation becomes difficult due to safety and handling constraints
Solution Approach 1:
The patent replaces expensive and difficult-to-handle radioactive isotopes with inexpensive, non-radioactive contrast agents that can be safely administered to patients. The contrast agents (e.g., iodine-based compounds) provide sufficient signal for calibration without requiring high radioactivity levels, making the process practical and safe for clinical use.
2Device complexity
If a single characteristic X-ray energy is used for calibration, then the calibration process is simple, but accurate calibration across multiple energy bins cannot be achieved
Solution Approach 1:
The patent segments the calibration process by using multiple contrast agents with distinct K-edge energies (e.g., iodine at 33.2 keV, gadolinium at 50.2 keV, terbium at 56.9 keV). Each contrast agent calibrates a specific energy bin, allowing accurate multi-energy calibration. The segmentation is further applied by dividing the anode into multiple targets, each containing a different contrast agent element.
Solution Approach 2:
The patent changes the energy parameter by selecting contrast agents with different K-edge energies. This allows the calibration system to cover a broader energy range with multiple discrete energy points, enabling accurate calibration across multiple energy bins rather than relying on a single energy level.
3Measurement precision
If the anode is rotated to present different targets to the X-ray beam, then multiple characteristic X-rays with different energies are generated for better calibration, but the device complexity increases
Solution Approach 1:
The patent merges multiple calibration targets into a single rotating anode structure. Different contrast agent elements are deposited on different regions of the anode surface, combining multiple calibration functions into one component. This integration reduces the number of separate calibration devices needed while maintaining multi-energy calibration capability.
Solution Approach 2:
The patent introduces rotational motion to the anode, making it dynamic rather than static. The anode rotates to present different contrast agent targets to the X-ray beam at different angular positions. This dynamic approach allows sequential access to multiple energy levels without requiring multiple fixed targets or complex switching mechanisms.
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 and accurate gain calibration of the photon counting CT detector, improving the accuracy and quantitativeness of material discrimination in photon counting CT imaging by utilizing multiple characteristic X-rays with distinct energies.
Implementation Method 1
an anode including a plurality of targets configured to generate a plurality of characteristic X-rays having different energies
Implementation Method 2
a photon counting CT detector detects X-ray photons generated by the X-ray source
Data Source
AI summary
According to one embodiment, a photon counting CT apparatus includes an X-ray source, a photon counting CT detector, and a calibration unit. The X-ray source includes a cathode configured to generate electrons and an anode including a plurality of targets configured to generate a plurality of characteristic X-rays having different energies. The photon counting CT detector detects X-ray photons generated by the X-ray source. The calibration unit calibrates the gain of the photon counting CT detector based on the correspondence relationship between the photon energies of the plurality of characteristic X-rays and outputs from the photon counting CT detector.