X-ray Detector Photoconductive Gain Compensation
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Solution Overview
Problem
X-ray detectors with direct conversion semiconductors like CdTe and CZT exhibit persistent currents due to hole traps, leading to baseline shifts in energy measurements, which existing correction methods like baseline restoration cannot effectively address, especially for high flux and fast-changing conditions.
Innovation Solution
A method to determine and compensate for photoconductive gain at each pixel of an X-ray detector, separating the persistent current from the photo current to correct energy estimations, using calibration and look-up tables for different X-ray flux and energy conditions, and integrating this compensation into readout electronics to accurately determine photon energies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If baseline restoration methods are used to correct persistent currents, then slowly changing baseline shifts can be compensated, but rapidly changing persistent currents and high flux conditions cannot be effectively addressed
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing correction factors in lookup tables before actual measurement. The system pre-characterizes the detector response under various flux conditions and stores these calibration data, enabling rapid correction during operation without real-time computation delays. This allows the system to handle fast-changing conditions effectively.
Solution Approach 2:
The patent replaces traditional electronic baseline restoration circuits with a computational approach using lookup tables and digital processing. Instead of using analog electronics to actively restore baselines, the system uses pre-computed correction factors stored in memory, which are applied digitally to correct measurements. This substitution enables faster response to changing conditions.
2Measurement precision
If photoconductive gain compensation is implemented, then accurate energy measurements can be achieved, but additional processing complexity is introduced
Solution Approach 1:
The patent reduces processing complexity by performing the complex calibration and correction factor calculation in advance. During actual operation, the system simply retrieves pre-computed correction factors from lookup tables based on measured flux levels and applies them to correct energy measurements. This eliminates the need for complex real-time calculations.
Solution Approach 2:
The patent introduces lookup tables as an intermediary structure between the detector and the measurement system. These tables store pre-computed correction factors that mediate between the raw detector signals and the final corrected energy values, simplifying the correction process while maintaining accuracy.
3Measurement precision
If persistent current separation is performed, then accurate photo current measurement is achieved, but additional correction steps are required
Solution Approach 1:
The patent performs the separation of persistent current effects in advance during calibration, storing the results as correction factors. During actual measurement, the system applies these pre-computed corrections directly to the photo current measurements, maintaining high throughput while achieving accurate separation of persistent current effects.
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 effectively corrects for persistent currents, even those changing rapidly, ensuring accurate energy measurements by isolating the persistent current's influence, thereby improving the precision of photon energy determination in X-ray imaging systems.
Implementation Method 1
X-ray detectors with direct conversion semiconductors like CdTe and CZT
Implementation Method 2
exhibit persistent currents due to hole traps
Data Source
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AI summary
The present invention relates to the correction of X-ray image information, e.g. the correction of X-ray image information regarding persistent currents in X-ray detector elements. X-ray detectors may be embodied as photoconductors with ohmic contacts, which output a photo current depending on the energy and amount of photons impinging on a respective photoconductor pixel. Such photoconductors may exhibit a photoconductive gain, i.e. the measured current when irradiated by X-ray is higher than the current, which would result from impinging photons only generating electron-hole pairs. To compensate for photoconductive gain a method (50) for image correction of X-ray image information is provided, comprising receiving (52) readout information of an X-ray detector element (14), wherein the readout information is dependent on impinging X-radiation (20) generating a photo current and compensating (54) the readout information for a photoconductive gain employing compensation information.