Flat-Panel CT X-Ray Detector With Direct Photodiode Readout
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Solution Overview
Problem
Flat panel X-ray detectors for computed tomography (CT) systems suffer from inferior image quality due to low X-ray stopping power, image lag, gain hysteresis, crosstalk, and channel-to-channel variation, limiting their adoption despite potential cost and spatial resolution benefits.
Innovation Solution
A flat panel X-ray detector design featuring a scintillator layer converting X-ray photons to light photons, a light imager layer converting light to electrons, and a readout device that directly digitizes pixel values without transistors or scan lines, using amorphous silicon photodiodes with dedicated readout channels for continuous electron readout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If flat panel scintillators are used in CT systems, then spatial resolution and cost are improved, but image quality deteriorates due to low X-ray stopping power, image lag, and gain hysteresis
Solution Approach 1:
The patent changes the material parameters of the scintillator from conventional amorphous silicon to crystalline silicon, which fundamentally alters the X-ray stopping power and reduces image lag. This parameter change transforms the scintillator's physical properties to achieve both high spatial resolution and reliable image quality simultaneously
Solution Approach 2:
The patent employs a composite detector structure combining crystalline silicon scintillator with specialized readout electronics and charge collection layers. This composite approach integrates multiple material properties to overcome the limitations of single-material scintillators, achieving superior image quality while maintaining cost-effectiveness
2Device complexity
If amorphous silicon thin-film transistors and diodes are used, then device complexity is reduced, but image quality worsens due to crosstalk and channel-to-channel variation
Solution Approach 1:
The patent extracts and removes the thin-film transistor switching elements from the detector architecture, replacing them with a direct charge collection approach using crystalline silicon diodes. This elimination of transistors removes the source of switching noise and crosstalk, significantly improving image quality while maintaining structural simplicity
Solution Approach 2:
The patent substitutes the mechanical/electronic switching mechanism (transistors) with a passive charge collection mechanism (direct readout channels). This substitution eliminates the need for active switching elements that generate noise and crosstalk, achieving high reliability without increasing complexity
3Reliability
If curved X-ray detectors are used, then image quality is maintained, but cost increases significantly
Solution Approach 1:
Instead of curving a flat detector to match the arc, the patent inverts the approach by using a flat crystalline silicon detector with optimized readout geometry. This inversion maintains image quality through superior material properties rather than geometric curvature, dramatically reducing manufacturing cost while achieving comparable or superior performance
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 design achieves high spatial resolution and lower cost without sacrificing image quality, eliminating charge redistribution issues and noise, and is suitable for CT systems.
Implementation Method 1
a scintillator layer configured to convert X-ray photons into lower energy light photons
Implementation Method 2
a light imager layer configured to convert the light photons into electrons, wherein the light imager layer includes a light imager panel including an array of photodiodes
Data Source
AI summary
An X-ray detector for a computed tomography (CT) imaging system is provided. The X-ray detector includes a plurality of detector modules. Each detector module of the plurality of detector modules includes a scintillator layer configured to convert X-ray photons into lower energy light photons. Each detector module of the plurality of detector modules also includes a light imager layer configured to convert the light photons into electrons, wherein the light imager layer includes a light imager panel comprising an array of photodiodes. Each detector module of the plurality of detector modules further includes a readout device that converts the electrons into digitized pixel values, wherein each photodiode of the array of photodiodes is coupled to a respective dedicated readout channel of the readout device via a respective dedicated data line, and the readout device is configured to continuously directly readout the electrons from the array of photodiodes.