X-ray detector dual-mode sensor for saturated pixel signal estimation
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Solution Overview
Problem
Photon-counting based spectral CT systems face challenges with high count rates, leading to saturated detector pixels that cannot distinguish pulses or efficiently separate electron-hole pairs, resulting in corrupted energy information.
Innovation Solution
An x-ray detector with sensor elements that provide both energy-threshold counts and integrating measurement results, allowing for accurate estimation of count signals from saturated pixels using an object model and modeled x-ray beams, eliminating the need for scout scans and enabling reliable data reconstruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If photon-counting detectors are used in spectral CT systems, then energy information and material differentiation are improved, but detector saturation occurs at high count rates causing loss of measurement reliability
Solution Approach 1:
The patent applies dynamics by making the detector operate in two different modes dynamically: photon-counting mode for energy information and integration mode for total signal accumulation. The system automatically switches between these modes or combines them based on the counting rate conditions, allowing reliable operation across a wide range of x-ray flux conditions without saturation
Solution Approach 2:
The patent changes the operational parameter of the detector from fixed photon-counting mode to a flexible mode that adapts between photon-counting and integration based on the incident x-ray flux level. This parameter change allows the detector to handle high count rates by switching to integration mode while maintaining energy information capability through the dual-mode architecture
2Speed
If direct conversion material is used in detectors, then detection speed is improved, but pulse distinction capability deteriorates at high count rates leading to pixel saturation
Solution Approach 1:
The patent uses dynamics by implementing a dual-mode detector that can switch between photon-counting mode (for pulse distinction) and integration mode (for total signal) based on the incident flux level. This dynamic adaptation allows the system to maintain accurate pulse distinction at low count rates while avoiding saturation at high count rates through mode switching
3Measurement precision
If scout scans are performed to obtain object models, then accurate material composition determination is improved, but examination time and radiation dose increase
Solution Approach 1:
The patent applies universality by making the main imaging detector serve multiple functions: it simultaneously performs photon-counting for energy information, integration for total signal, and provides the data needed for object modeling. This eliminates the need for separate scout scans, as the same detector collects all necessary information during the primary examination
Solution Approach 2:
The patent implements preliminary action by using the integration mode data collected during the main scan to pre-process and create object models directly from the imaging data. This allows the system to have object models available without requiring preliminary scout scans, as the integration data is collected concurrently with the imaging process
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
Enables accurate and reliable measurement data even in saturated conditions, allowing for precise material composition and path length determination, and reduces the need for additional scans, improving image reconstruction in CT systems.
Implementation Method 1
said sensor unit comprises a direct-conversion sensing layer for directly converting incident x-ray radiation into electrical charge signals forming charge pulses
Implementation Method 2
said integrating layer being arranged on a side of the direct-conversion sensing layer facing away from the incident x-ray radiation for converting x-ray radiation reaching said integrating layer into said integration signals
Data Source
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AI summary
The present invention relates to an x-ray detector comprising a sensor unit (200, 300) for detecting incident x-ray radiation comprising a number of sensor elements (230, 311-314 ), a counting channel (240) per sensor element for obtaining a count signal by counting photons or charge pulses generated in response to the incident x-ray radiation since a beginning of a measurement interval, an integrating channel (250) per sensor element for obtaining an integration signal representing the total energy of radiation detected since the beginning of the measurement interval, and a processing unit (260) for estimating, from the integration signals of the sensor elements (321), count signals of sensor elements (311, 312) whose counting channel has been saturated during the measurement interval.