X-ray Detector Calibration Using Light-Induced Noise Peaks
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Solution Overview
Problem
Current energy calibration methods for semiconductor x-ray detectors, such as those using gamma ray sources or K-edge filters, are impractical due to radiation safety concerns, variability, and long calibration times, and struggle with extracting accurate energy references, especially in polychromatic sources with complex spectral responses.
Innovation Solution
An x-ray detector system that includes a directly converting semiconductor layer and a light source emitting light above the semiconductor's band gap energy for simulation, with an evaluation unit to detect noise peaks in electrical signals generated at different light intensities, allowing for the determination of offset and gain, and a calibration unit to calibrate the detector without x-ray radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If gamma ray sources are used for energy calibration, then calibration accuracy can be achieved, but radiation safety issues and continuously changing source activity make the method problematic
Solution Approach 1:
The patent introduces light sources as an intermediary substance to replace gamma ray sources for calibration purposes. The light sources generate photons that interact with the semiconductor detector to produce electrical signals, enabling calibration without direct radiation exposure. This mediator approach maintains measurement capability while eliminating the harmful radiation aspect.
Solution Approach 2:
The patent creates a copy of the x-ray detection process using light instead of gamma rays. By generating light-induced electrical signals that mimic the response to x-ray photons, the system can perform calibration measurements without using actual ionizing radiation, thus preserving measurement characteristics while removing safety hazards.
2Measurement precision
If gamma ray sources are used for calibration, then energy calibration can be performed, but very close distance needs to be maintained which is unpractical for entire detector arrays
Solution Approach 1:
The patent makes the calibration system universal by using light sources that can illuminate entire detector arrays simultaneously. Unlike gamma ray sources that require close proximity and provide localized irradiation, light sources can cover large areas and are compatible with various detector array configurations, making the calibration process applicable to different imaging systems including CT and mammography.
3Measurement precision
If gamma ray sources are used for calibration, then calibration measurement can be performed, but low x-ray fluxes result in long calibration times
Solution Approach 1:
The patent changes the fundamental parameter of the calibration source from gamma rays to light, which has different interaction characteristics with the semiconductor material. Light sources can be operated at high intensities without the flux limitations of gamma ray sources, generating sufficient photon flux to produce strong electrical signals that enable rapid calibration measurements.
4Object-affected harmful factors
If K-edge filters are used for calibration, then no gamma ray sources are needed, but extraction of the K-edge attenuation feature is less trivial and often leads to erroneous measurements
Solution Approach 1:
The patent extracts the essential calibration function from the complex K-edge filter method. Instead of relying on the subtle K-edge attenuation feature that requires sophisticated spectral analysis and is prone to errors, the patent directly measures light-induced electrical signals to determine gain and offset, simplifying the extraction process and improving measurement reliability.
5Object-affected harmful factors
If polychromatic sources with K-edge filtration are used, then calibration can be performed without gamma rays, but difficult process of extracting the K-edge feature from measured spectra occurs
Solution Approach 1:
The patent replaces the complex spectral analysis mechanism required for K-edge feature extraction with a direct electrical signal measurement approach. Instead of analyzing pulse-height spectra to identify K-edge attenuation features, the system directly measures the electrical signals generated by light-induced charge carriers, eliminating the need for sophisticated spectral decomposition algorithms.
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 method enables rapid and repeatable calibration of x-ray detectors, reducing the need for x-ray radiation and improving accuracy by using light-induced noise peaks to determine gain and offset variations, thus overcoming the limitations of existing calibration methods.
Implementation Method 1
a directly converting semiconductor layer having a plurality of pixels for converting incident radiation into electrical measurement signals with a band gap energy characteristic of the semiconductor layer
Data Source
AI summary
An X-ray detector comprises a directly converting semiconductor layer having a plurality of pixels for converting incident radiation into electrical measurement signals with a band gap energy characteristic of the semiconductor layer, wherein said incident radiation is x-ray radiation emitted by an x-ray source or light omitted by at least one light source. An evaluation unit calculates evaluation signals per pixel or group of pixels from first electrical measurement signals generated when light from said at least one light source at a first intensity is coupled into the semiconductor layer, and second electrical measurement signals generated when light from said at least one light source at a second intensity is coupled into the semiconductor layer. A detection unit determines detection signals from electrical measurement signals generated when x-ray radiation is incident onto the semiconductor layer, and a calibration unit calibrates the detection unit on the basis of the evaluation signals.