Photon Counting Imaging Device Instant Retrigger Capability
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Solution Overview
Problem
Photon counting devices become paralyzed at high photon flux due to pulse pile-up, leading to incorrect detection and counting of individual photon pulses, resulting in a deviation from the actual photon rate and making precise count rate correction ambiguous.
Innovation Solution
Implementing an instant retrigger capability in the photon counting imaging device by introducing a dead time interval after each count, allowing the pixel to re-evaluate and re-enable counting if the amplified signal exceeds the threshold level, with adjustable dead time to compensate for pixel-to-pixel variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional photon counting is used to detect single x-ray photons, then single photon detection capability is achieved, but the device becomes paralyzed at high photon flux due to pulse pile-up
Solution Approach 1:
The patent applies dynamics by making the dead time adjustable rather than fixed. The dead time can be dynamically adapted based on operating conditions and pixel characteristics, allowing the system to optimize its response characteristics for different photon flux levels while maintaining single photon detection capability and preventing paralysis at high flux
Solution Approach 2:
The patent changes the parameter of dead time from a fixed value to an adjustable parameter. By allowing the dead time to be modified according to specific operating conditions and pixel variations, the system can maintain accurate counting at high photon flux levels while preserving single photon detection sensitivity
2Speed
If the discriminator output signal pulse width is reduced to improve time resolution, then time resolution capability is improved, but pulse pile-up occurs more frequently at high photon flux
Solution Approach 1:
The patent applies preliminary action by establishing a dead time period immediately following each detected photon event. This dead time prevents subsequent photons from being detected during the recovery period, proactively avoiding pulse pile-up before it can occur. The dead time acts as a preventive measure that ensures accurate counting even when photons arrive in rapid succession
3Measurement precision
If the dead time is made adjustable for each pixel, then pixel-to-pixel variations are compensated, but device complexity increases
Solution Approach 1:
The patent applies local quality by allowing each pixel to have its own adjustable dead time parameter tailored to its specific characteristics. This per-pixel customization compensates for manufacturing variations and performance differences between individual pixels, ensuring uniform response across the detector array while managing complexity through localized adjustment capabilities
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 prevents paralysis, ensuring a monotonically increasing count rate with the incoming photon rate, enabling precise count rate correction and improved high-rate counting performance.
Implementation Method 1
the output signal being proportional to a number of electron-hole pairs generated by a photon in the respective photodetector element
Data Source
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AI summary
A method for photon counting imaging with improved high-rate counting performance includes the step of applying an instant retrigger capability with adjustable dead time in cells of the detector array and operates an apparatus using a layer of photosensitive material, an L×K array of photodetector elements arranged in the layer of the photosensitive material, an N×M array of readout unit cells, including amplifying elements and at least one readout unit cells for at least one photodetector elements. The readout unit cells are controlled by signal processing elements with each readout unit cell having internal signal processing elements to generate a discriminator output signal representing an amplified signal of the electron-hole pairs generated by an incident photon or a number of incident photons in the respective photodetector element. The discriminator output signal is generated by comparing the amplified signal with a predetermined threshold level and the discriminator output signal is generated whenever the amplified signal exceeds the threshold level.