X-ray Detector Signal Suppression via Sub-pixel Arbitration
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Solution Overview
Problem
Semiconductor X-ray detectors suffer from parasitic direct detection events where unabsorbed X-ray quanta interact with the imaging device, causing very bright pixels that disturb the intended image due to incomplete absorption in the conversion layer.
Innovation Solution
An X-ray detector apparatus with arbitration and switching arrangements that suppress signals from pixels affected by direct detection events by comparing signals from multiple radiation collection devices and adjusting the gate potentials of amplifier transistors to reduce the contribution of affected pixels to the output signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a scintillator or photoconductor is used to convert X-ray quanta, then X-ray detection is enabled, but not all X-ray quanta are absorbed causing parasitic direct detection events in the semiconductor imaging device
Solution Approach 1:
The pixel signal is segmented into multiple sub-pixel signals that are processed independently through arbitration circuits. By dividing the pixel into sub-pixels and processing their signals separately, the system can identify and suppress direct detection events that affect only specific sub-pixels, thereby resolving the contradiction between detecting X-rays and eliminating parasitic events.
Solution Approach 2:
An arbitration circuit is introduced as an intermediary between the pixel signal and the readout amplifier. This arbitration circuit receives signals from multiple sub-pixels, compares their characteristics, and selectively suppresses signals identified as direct detection events before they reach the final output, thus eliminating parasitic events while preserving genuine X-ray detection signals.
2Reliability
If arbitration arrangements are added to suppress direct detection events, then image quality improves, but device complexity increases
Solution Approach 1:
The pixel is divided into multiple sub-pixels with dedicated signal processing paths. This segmentation allows the arbitration circuit to work with smaller, more manageable signal components rather than processing the entire pixel signal at once, reducing the computational and circuit complexity while maintaining effective suppression of direct detection events.
Solution Approach 2:
The arbitration circuit applies signal suppression selectively only to sub-pixels exhibiting characteristics of direct detection events, rather than suppressing all pixel signals uniformly. This partial action approach maintains image quality by preserving genuine X-ray detection signals while eliminating only the parasitic events, avoiding excessive suppression that would degrade overall image quality.
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
Effectively suppresses parasitic direct detection events, minimizing the impact on the image quality without deteriorating the received image, by ensuring that signals from affected pixels contribute less to the output, thus improving image clarity.
Implementation Method 1
a scintillation layer for the conversion of X-rays into photons
Implementation Method 2
the light is converted in the semiconductor imaging device into electrical charges
Data Source
AI summary
According to an embodiment of the invention, signals coming from a number of pixels or sub-pixels are compared and those signals from pixels or sub-pixels, which are substantially brighter than the other pixels in the comparison, are excluded from contributing to the output signal, to suppress direct detection events in X-ray detectors. For this an X-ray detector apparatus (101) can comprise: —an array (102) of pixel arrangements (303), —each pixel arrangement (303) comprising at least one radiation collection device (311) for converting incident radiation into a collection device signal, —switching arrangements (313, 324, 314, 142; 313, 315, 314, 352, 142; 313, 315, 314; 361) for providing to respectively one output element (141) a signal derived from the collection device signals of a plurality of radiation collection devices (311) of at least one pixel arrangement (303).