X-ray Detector Image Correction via Afterglow Signal Subtraction
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Solution Overview
Problem
Conventional x-ray systems, particularly those using analog technology, face challenges with low quantum efficiency, spatial resolution, and difficulty in reducing x-ray dose, leading to issues like shadow images due to high afterglow constants in scintillator detectors, which affect image quality and diagnostic accuracy.
Innovation Solution
A method to correct images by calculating and subtracting signal portions from preceding detector signals based on the detector's decay curve, allowing for real-time shadow-free image representation without hardware changes, using digital x-ray detectors like scintillator and photodetector systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If scintillator detectors are used to detect x-ray radiation, then detector sensitivity and quantum efficiency are improved, but shadow images appear in the acquired images due to high afterglow constant
Solution Approach 1:
The patent applies preliminary action by calculating and subtracting the expected afterglow signal from the current detector signal before image formation. The decay curve of the scintillator is measured in advance, and based on this pre-characterized decay behavior, the contribution of preceding x-ray pulses is calculated and removed from the current image data, preventing shadow images from appearing in the final image.
Solution Approach 2:
The patent changes the temporal parameter handling by introducing time-weighted subtraction based on the scintillator's decay constant. Instead of treating all detector signals equally, the system applies different weighting factors to signals from different time points, with the weighting determined by the exponential decay curve. This parameter-based differentiation allows separation of current x-ray signal from residual afterglow.
2Productivity
If the acquisition rate is increased to capture dynamic processes, then temporal resolution is improved, but shadow images become more pronounced due to overlapping decay curves
Solution Approach 1:
The patent implements feedback by using the known decay curve characteristics of the scintillator to continuously correct current measurements. The system feeds back the decay behavior information into the signal processing chain, allowing real-time calculation and removal of afterglow contributions even at high acquisition rates where multiple x-ray pulses overlap in time.
3Device complexity
If analog technology is used for x-ray imaging, then system complexity is reduced, but quantum efficiency and spatial resolution remain limited
Solution Approach 1:
The patent replaces the mechanical/analog signal processing approach with digital signal processing. Instead of using analog circuitry to handle detector signals, the system converts signals to digital form and applies computational methods including decay curve analysis and mathematical subtraction. This substitution enables superior spatial resolution and quantum efficiency while managing complexity through software-based solutions.
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 method enhances image quality by eliminating shadow images, improving spatial resolution, and reducing x-ray dose, enabling more accurate diagnostics and 3D applications with cost-effective implementation.
Implementation Method 1
If an x-ray quanta penetrates into a scintillator layer, among other things light emission is triggered by excitation and relaxation of luminophore centers in the scintillator layer
Implementation Method 2
This light emission is detected by photodiodes by being generated and collected
Implementation Method 3
The decay of the solid-state defects can lead to a re-excitation of the luminophore centers in the scintillator layer due to electron emission of the defect
Data Source
AI summary
In a method for correction of an image in a series of images acquired with an x-ray detector; wherein the x-ray detector is composed of a number of detector elements and an acquired image is composed of image elements associated with the detector elements, a series of detector signals is generated in a detector element by x-ray radiation, the detector signals respectively exhibiting a detector-specific temporal decay curve; and an image element to be corrected and acquired over a predetermined acquisition interval contains signal portions of the current and preceding detector signals acquired during this acquisition interval. By calculating signal portions of preceding detector signals acquired in the acquisition interval and subtracting them from the image element to be corrected, the image quality of an image from a series of images acquired with a digital image acquisition apparatus is improved.