Photon Counting Detector Pixel Correction Algorithm
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Solution Overview
Problem
Photon counting detectors face challenges in accurately counting photons due to pulse pileup and non-uniform pixel responses, leading to artifacts in images, particularly in high flux conditions where multiple photons strike pixels simultaneously, and pixel-to-pixel sensitivities vary, causing lines or streaks in images.
Innovation Solution
A computer-implemented method for correcting pixel counts in photon counting detectors involves determining actual and desired average count values, calculating multiplying and additive correction factors, and applying these to achieve uniform count values across pixels, thereby correcting for non-uniform responses and pulse pileup effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If photon counting detectors are used to count individual photons, then measurement precision is improved, but device complexity increases due to the need for pulse comparison electronics and threshold discrimination
Solution Approach 1:
The patent replaces complex electronic pulse comparison and threshold discrimination systems with a simplified detector design that directly outputs countable signals. The semiconductor detector elements generate electrical pulses proportional to photon energy, which can be directly counted without complex analog electronics, thereby reducing device complexity while maintaining measurement precision.
Solution Approach 2:
The patent introduces digital signal processing and calibration algorithms as intermediaries between the detector elements and the final count output. These digital intermediaries correct for non-uniform pixel responses and pileup effects through computational methods, replacing the need for complex analog electronics while maintaining accurate photon counting.
2Productivity
If the photon flux is increased to improve imaging speed, then productivity is improved, but measurement precision deteriorates due to pulse pileup from simultaneous photon arrivals
Solution Approach 1:
The patent applies preliminary calibration to each pixel to determine its specific response characteristics and pileup behavior before actual imaging. This pre-characterization allows the system to compensate for pileup effects during high-flux imaging by using pixel-specific correction factors, enabling accurate counting even at high photon fluxes where traditional detectors would fail.
Solution Approach 2:
The patent changes the operational parameters of the detector by allowing each pixel to have unique threshold and gain settings optimized for its specific response characteristics. This parameter customization enables the system to maintain accurate photon counting across a wider range of flux densities by adapting to each pixel's behavior rather than using fixed universal settings.
3Area of stationary object
If multiple pixels are used to increase detection area, then area of stationary object is improved, but manufacturing precision deteriorates due to pixel-to-pixel sensitivity variations causing image artifacts
Solution Approach 1:
The patent applies local quality correction by determining individual calibration factors for each pixel based on its specific response characteristics. Each pixel is characterized separately and assigned unique correction parameters that compensate for manufacturing variations. This localized approach maintains uniformity across large detector arrays without requiring perfect manufacturing precision.
Solution Approach 2:
The patent implements feedback through a calibration process where the actual response of each pixel is measured and used to generate correction factors. This feedback loop characterizes each pixel's non-uniform response and creates compensating parameters that are applied during imaging, thereby eliminating artifacts caused by manufacturing variations while maintaining large detector area.
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 method effectively corrects pixel count values, reducing artifacts and achieving uniformity in image output, ensuring accurate photon counting and improved image quality by accounting for varying pixel sensitivities and high flux conditions.
Implementation Method 1
The scintillation material converts high energy photons (x-rays and gamma rays) into visible or near visible light
Implementation Method 2
This light is then detected by photodiodes in the photodiode array. Scintillation light impinging on each photodiode of the photodiode array is converted thereby into an electrical signal
Data Source
AI summary
In a method of count correction for pixels of a pixilated photon counting detector, the average count value output by each of a plurality of pixels during a period of time is determined. A product is determined of the actual average count value and a multiplying correction factor. A corrected count value is then determined for the pixel equal to a sum of the product and an additive correction factor. The multiplying correction factor equals a square root of a quotient of a desired average count value to be output by each of the plurality of pixels during the period of time divided by the actual average count value. The additive correction factor equals a product of the multiplying correction factor and the actual average count value subtracted from the desired average count value.