X-ray Absorbing Encapsulation for Scintillator Pixel Protection
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Solution Overview
Problem
Conventional X-ray detector arrays in CT scanners face challenges in protecting underlying electronic circuitry from residual X-ray radiation, which can be harmful and cause damage, especially due to the transmission of X-rays through inter-scintillator regions and reflective layers.
Innovation Solution
An X-ray detector array with a highly X-ray absorbing layer composed of materials with an atomic number greater than 50, such as Bismuth oxide, is placed underneath the scintillator pixels to absorb transmitted X-rays, providing comprehensive protection to electronic circuitry while maintaining electrical insulation and allowing for easy integration with the scintillator pack.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a reflective layer is used to direct light into the photo detector, then light reflection efficiency is improved, but X-ray transmission through inter-scintillator regions increases causing harm to electronic circuits
Solution Approach 1:
The inter-scintillator region is segmented into multiple functional layers: a reflective layer for light direction and an underlying X-ray absorbing layer for radiation protection. This segmentation allows each layer to perform its specific function without interfering with the other, resolving the contradiction between light reflection efficiency and X-ray protection.
Solution Approach 2:
An X-ray absorbing layer is introduced as an intermediary between the reflective layer and the electronic circuits. This intermediary layer absorbs harmful X-rays while allowing the reflective layer above it to function effectively for light direction, thus protecting the circuits without compromising light reflection efficiency.
2Illumination intensity
If the reflective layer is made thicker to improve reflection efficiency, then light direction into photo detector is improved, but X-ray transmission through the layer increases
Solution Approach 1:
The protective function against X-rays is segmented from the reflective function by placing a dedicated X-ray absorbing layer beneath the reflective layer. This allows the reflective layer to be optimized for light reflection without concern for X-ray transmission, as the absorbing layer handles radiation protection independently.
Solution Approach 2:
The inter-scintillator region uses a composite structure combining a reflective layer (for light direction) with an X-ray absorbing layer (for radiation protection). This composite approach allows simultaneous optimization of both light reflection efficiency and X-ray absorption, resolving the contradiction between the two requirements.
3Object-affected harmful factors
If an X-ray absorbing layer is added to protect electronic circuits, then X-ray protection is improved, but device complexity increases
Solution Approach 1:
The X-ray absorbing layer is merged with the existing inter-scintillator region structure, utilizing the same spatial location where reflective material is already present. This integration approach adds X-ray protection functionality without requiring separate dedicated space or complex additional structures, thus minimizing the increase in device complexity.
Solution Approach 2:
The inter-scintillator region is designed to serve multiple functions: light reflection (via the reflective layer) and X-ray absorption (via the absorbing layer). This multi-functionality approach allows the structure to provide both optical and radiation protection functions within a single integrated region, avoiding the need for separate complex systems for each function.
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 X-ray absorbing layer effectively reduces X-ray transmission to nearly zero, ensuring the electronic circuitry is protected from damage, and allows for simple and cost-effective manufacturing with non-poisonous and electrically insulating materials, enhancing the reliability of CMOS-based integrated circuits.
Implementation Method 1
an X-ray absorbing layer, comprising a material which is highly X-ray absorbing due to its material comprised therein having an atomic number, also referred to as 'Z-Number', of more than 50
Implementation Method 2
X-ray radiation entering one of the scintillator pixels generates scintillation radiation, for example, light in the visible spectral range
Implementation Method 3
This light is detected using an array of associated photo detectors
Data Source
Figure 1~2
AI summary
A scintillator pack (2) and a CT X-ray detector array (1) comprising such scintillator pack (2) are proposed. The scintillator pack (2) comprises an array of scintillator pixels (3). At a bottom surface (31) of each scintillator pixel (3), an X-ray absorbing encapsulation(13) is provided. This encapsulation(13) comprises an electrically insulating highly X-ray absorbing material having an atomic number greater than 60 such as, for example, Bismuth oxide (Bi2O3 ). The X-ray absorbing encapsulation(13) is interposed between the scintillator pixels (3) and an electronic circuit (19). The electronic circuit (19) may be provided as an ASIC in CMOS technology and may therefore be sensitive to X-ray induced damage. The encapsulation(13) provides for good X-ray protection of such electronic circuit (19).