Photon Counting Sub-Channels with Variable Shaping Times
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Photon counting x-ray detectors face a conflict between managing noise and pile-up, where large shaping times are needed to minimize noise but small shaping times are required to avoid pile-up, leading to suboptimal performance at varying radiation fluxes.
Innovation Solution
The implementation of an x-ray detector system with multiple photon counting sub-channels, each with different shaping times and comparator threshold levels, allowing for efficient counting of photons across various energy levels and flux rates, optimizing the signal-to-noise ratio and reducing pile-up by selectively switching between sub-channels based on flux rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If large shaping times are used in photon counting channels, then noise is minimized and signal-to-noise ratio is improved, but pile-up increases and detection accuracy deteriorates
Solution Approach 1:
The patent divides each photon counting channel into multiple sub-channels, where each sub-channel has a different shaping time constant. This segmentation allows the system to process photons with different energy levels simultaneously - sub-channels with longer shaping times handle low-energy photons with better noise performance, while sub-channels with shorter shaping times handle high-energy photons with better pile-up rejection
Solution Approach 2:
The system dynamically assigns photons to different sub-channels based on their energy level. The energy discrimination capability allows the system to adaptively route photons to the most appropriate sub-channel, optimizing the shaping time selection for each individual photon event rather than using a fixed shaping time for all photons
2Productivity
If small shaping times are used in photon counting channels, then pile-up is reduced and detection speed is improved, but noise increases and signal-to-noise ratio deteriorates
Solution Approach 1:
The patent segments the detection process into multiple sub-channels with different shaping time constants. Fast sub-channels with short shaping times handle high-count-rate scenarios and high-energy photons, maintaining high detection speed, while slow sub-channels with long shaping times handle low-count-rate scenarios and low-energy photons, maintaining high signal-to-noise ratio
Solution Approach 2:
The system changes the shaping time parameter across different sub-channels to optimize performance for different operating conditions. By having multiple sub-channels with different shaping time constants (e.g., 100 ns, 200 ns, 500 ns), the system can adapt to varying flux rates and energy levels without compromising either speed or precision
3Reliability
If multiple photon counting sub-channels with different shaping times are implemented, then both noise and pile-up are managed effectively, but device complexity increases
Solution Approach 1:
The patent merges multiple sub-channels with different shaping times into a unified readout unit. The readout unit integrates signals from all sub-channels and applies energy discrimination to route photons to the appropriate sub-channel, combining the advantages of multiple shaping times while maintaining a cohesive system architecture
Solution Approach 2:
The readout unit serves multiple functions: it receives signals from all sub-channels, performs energy discrimination, routes photons to appropriate sub-channels, and aggregates the final count. This multi-functional design reduces the need for separate dedicated circuits for each sub-channel, thereby reducing overall system complexity
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 robust and efficient detection of x-ray photons, optimizing the signal-to-noise ratio at different radiation fluxes and effectively managing both noise and pile-up, thereby improving the accuracy and quality of x-ray imaging.
Implementation Method 1
The x-ray photons, including also photons after Compton scattering, are converted to electron-hole pairs inside the semiconductor detector
Implementation Method 2
Compton scattering causes many x-ray photons to convert from a high energy to a low energy before conversion to electron-hole pairs in the detector
Implementation Method 3
the electrons created by the x-ray are creating electric charge in terms of electron-hole pairs which are collected through an applied electric field
Data Source
Figure 1
Figure 2
Figure 3
AI summary
There is provided an x-ray detector system (1) comprising a multitude of detector elements (2), each connected to a respective photon counting channel (4, PCC) for providing at least one photon count output, and a read-out unit (9) connected to the photon counting channels for outputting the photon count outputs. The x-ray detector system (1) is characterized in that each one of at least a subset of the photon counting channels (PCC, 4) comprises at least two photon counting sub-channels (40-1 to 40-M), each photon counting sub-channel providing at least one photon count output and having a shaping filter (6), wherein the shaping filters of the photon counting sub-channels are configured with different shaping times, and wherein the photon counting sub-channels, having shaping filters with different shaping times, are adapted for counting photons of different energy levels. Furthermore, the read-out unit (9) is configured to select, for each photon counting channel (PCC), photon count outputs from the photon counting sub-channels.