X-ray Photon Counting Gating Mechanism for Pile-up Reduction
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Solution Overview
Problem
In computer tomography, the non-periodic and randomly distributed flux of X-ray photons leads to pile-up events, which reduce energy resolution and result in incorrect results due to the high and unpredictable nature of photon arrival times, making it challenging to accurately count and process photons without interfering with subsequent events.
Innovation Solution
An apparatus and method that utilize a sensor to convert photons into charge pulses, a processing element to convert these pulses into electrical pulses, and a gating mechanism to inhibit counting during pile-up events by activating and deactivating based on the state of the processing element, ensuring that each event is fully processed before allowing subsequent events to be counted.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If photon counting is performed without gating, then counting speed is high, but pile-up events occur and energy resolution deteriorates
Solution Approach 1:
The gating mechanism performs preliminary action by suppressing counting during the dead time period before pile-up events can occur. The gate is activated in advance based on the processing element state, preventing subsequent photons from being counted until the processing is complete, thus avoiding energy resolution deterioration while maintaining high counting speed.
2Measurement precision
If gating is applied to prevent pile-up, then energy resolution is maintained, but counting accuracy may be reduced due to dead time
Solution Approach 1:
The gating mechanism uses feedback from the processing element state to dynamically control counting suppression. The gate status is continuously monitored and adjusted based on the actual processing completion state, ensuring that only photons arriving during actual dead time are suppressed, while maintaining accurate counting of all other events.
3Device complexity
If simple counting is used, then device complexity is low, but pile-up events cause incorrect results
Solution Approach 1:
The gating mechanism acts as an intermediary component between the photon detection and counting stages. It mediates the interaction by selectively allowing or blocking counting based on the processing element state, preventing pile-up events from reaching the counter while adding minimal complexity to the overall detector structure.
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 prevents pile-up events from corrupting energy information, improving counting performance and energy resolution by ensuring that each photon is fully processed before subsequent photons are counted, thereby enhancing the accuracy of X-ray photon counting in computer tomography applications.
Implementation Method 1
when a photon impinges on the conversion material of a sensor, it creates a charge pulse
Implementation Method 2
a processing element adapted to convert the charge pulse into an electrical pulse
Implementation Method 3
a first discriminator adapted to compare the electrical pulse against a first threshold and to output an event if the first threshold is exceeded
Data Source
AI summary
The present invention relates to an apparatus (10) for counting X-ray photons (12, 14). The apparatus (10) comprises a sensor (16) adapted to convert a photon (12, 14) into a charge pulse, a processing element (18) adapted to convert the charge pulse (51) into an electrical pulse (53) and a first discriminator (20) adapted to compare the electrical pulse (53) against a first threshold (TH1) and to output an event (55) if the first threshold (TH1) is exceeded. A first counter (22) counts these events (55), unless counting is inhibited by a first gating element (24). The first gating element (24) is activated when the first discriminator (20) outputs the event (55), and it is deactivated, when the processing of a photon (12, 14) is found to be complete or about to be completed by a measurement or by the knowledge about the time that it takes to process a photon (12, 14) in the processing element (18). By activating and deactivating the first counter (22) pile-up events, i.e. pile-up of multiple electrical pulses (53), can be addressed. The invention also relates to a corresponding imaging device and a corresponding method.