Photon-Counting CT Coincidence Circuit With Selective Pixel Decoupling
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Solution Overview
Problem
Conventional CT systems using photon-counting X-ray detectors face issues with coincidence events leading to image errors due to overlapping signals from adjacent detector pixels, which increase power consumption and interfere with sensitive analog circuits.
Innovation Solution
An electronic circuit for detecting coincidence events in CT systems that selectively decouples detector pixels for coincidence detection using switching units and logic circuits, reducing parasitic capacitance and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If coincidence detection is performed using multiple detector pixels and coincidence lines, then image errors from coincidence events are reduced, but power consumption increases due to parasitic capacitance in the cables
Solution Approach 1:
The patent divides the detector system into multiple independently controllable detector pixels, each with its own switching unit. This segmentation allows selective activation of coincidence detection for specific pixel pairs, reducing the overall number of active coincidence lines and associated parasitic capacitance, thereby lowering power consumption while maintaining image quality where needed.
Solution Approach 2:
The patent introduces dynamic control through switching units that can selectively connect or disconnect coincidence lines between detector pixels. This dynamic configuration allows the system to adapt the coincidence detection network based on actual imaging needs, activating detection only when and where coincidence events are likely to occur, thus reducing unnecessary power consumption from always-on coincidence lines.
2Reliability
If coincidence detection is performed using multiple detector pixels and coincidence lines, then image errors from coincidence events are reduced, but parasitic capacitance increases interfering with sensitive analog circuits
Solution Approach 1:
The patent segments the coincidence detection function into individual switching units for each detector pixel pair. This segmentation allows the system to limit the spatial extent of active coincidence lines, reducing the total parasitic capacitance and minimizing electromagnetic interference with adjacent sensitive analog circuits while maintaining coincidence detection capability where needed.
Solution Approach 2:
The patent extracts the coincidence detection function from a global, always-active system into localized, selectively activated units. By taking out only the necessary coincidence detection pairs from the full detector array and isolating them with individual switching units, the system reduces overall parasitic capacitance and minimizes crosstalk interference with surrounding analog circuits.
3Measurement precision
If direct conversion detectors are used instead of scintillation detectors, then signal-to-noise ratio is improved, but coincidence events between adjacent pixels increase causing image errors
Solution Approach 1:
The patent implements feedback through coincidence detection and switching units that monitor and respond to simultaneous detection events in adjacent pixels. When coincidence events are detected, the switching units can selectively disconnect affected pixels from the readout, providing a feedback mechanism that corrects for the increased coincidence probability in direct conversion detectors, thereby maintaining image accuracy despite the higher detection precision.
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
The solution effectively reduces image errors and power consumption by individually managing coincidence detection, enhancing signal-to-noise ratios and improving image quality.
Implementation Method 1
photon-counting X-ray detectors convert the X-ray photon directly into an electrical signal on the active surface (direct conversion). In this process, positive and negative electrical charges generated by incoming X-ray photons are separated by electric fields
Implementation Method 2
Conventional detectors for computed tomography systems (hereinafter CT systems) first convert incident X-ray photons into optical photons (scintillation)
Data Source
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AI summary
An electronic circuit (10) for detecting coincidence events of a computed tomography system, which has a photon-counting X-ray detector containing a detector pixel array, includes a first detection unit (1) configured to provide a first impact event signal. Furthermore, the electronic circuit (10) includes a further detection unit (1) for each additional detector pixel (12) of at least one further detector pixel (12) of the detector pixel array, which is configured to provide a further impact event signal. The electronic circuit (10) includes a logic circuit (2) that compares the first impact event signal with the at least one further impact event signal and provides a coincidence signal depending on the result of the comparison.A coincidence counter (3) of the electronic circuit (10) increments the coincidence counter value depending on the coincidence signal. Furthermore, the electronic circuit (10) contains a switching unit (4) for each additional detector pixel (12) of the at least one additional detector pixel (12), which is configured to disconnect the respective additional impact event signal from the logic circuit (2).