Rigid Flux Filter for Photon Counting Detector Saturation
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Solution Overview
Problem
Computed tomography systems with direct conversion photon counting detectors face image quality degradation due to excessive x-ray flux at central detector elements, particularly when scanning objects with low or no attenuating structures between extremities, as existing beam shapers do not adequately reduce flux in these regions.
Innovation Solution
A rigid flux filter device, made of materials like polytetrafluoroethylene or aluminum, is positioned between the radiation source and detector array to uniformly attenuate x-ray radiation, ensuring a predetermined flux is incident on detector pixels, thereby reducing excessive flux and improving image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a beam shaper (bowtie filter) is used to attenuate x-ray beam periphery, then flux at peripheral detector elements is reduced, but flux at central detector elements remains excessive
Solution Approach 1:
The patent applies local quality by transitioning from a uniform beam shaper to a non-uniform flux filter with spatially varying attenuation properties. The flux filter is designed with different attenuation characteristics for different regions (central vs. peripheral) to match the specific needs of each detector element region, thereby resolving the contradiction between reducing peripheral flux and maintaining central flux reduction for objects with low attenuating structures.
Solution Approach 2:
The patent employs parameter changes by modifying the attenuation parameter of the flux filter across different spatial locations. The flux filter incorporates materials with varying atomic numbers or thicknesses in different regions to achieve the desired flux distribution pattern, allowing independent control of attenuation levels for central and peripheral detector elements.
2Ease of manufacture
If a uniform beam shaper is used across the entire beam, then manufacturing is simple, but it cannot adequately reduce flux in central regions for objects with gaps
Solution Approach 1:
The patent applies segmentation by dividing the flux filter into multiple regions with different attenuation properties. Instead of a uniform structure, the flux filter is segmented into central and peripheral zones, each with optimized attenuation characteristics. This segmentation allows precise control of flux distribution while maintaining manufacturability through modular design approaches.
Solution Approach 2:
The patent utilizes asymmetry by designing a flux filter with non-uniform attenuation distribution. The filter incorporates asymmetric material placement or thickness variations that create different attenuation levels for central versus peripheral regions, enabling precise flux control for objects with gaps while remaining manufacturable through targeted material placement.
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 rigid flux filter device effectively attenuates x-ray radiation across the beam, preventing detector pixel saturation and enhancing image quality by maintaining a consistent flux, especially in regions with low or no attenuating structures, thus improving the reconstructed volumetric image data.
Implementation Method 1
The rigid flux filter device is configured to filter the radiation traversing the examination region and incident thereon
Implementation Method 2
filtering the radiation that traverses the examination region with a rigid flux filter device
Data Source
AI summary
An imaging system includes a radiation source (108) configured to rotate about an examination region (106) and emit radiation that traverses the examination region. The imaging system further includes an array of radiation sensitive pixels (112) configured to detect radiation traversing the examination region and output a signal indicative of the detected radiation. The array of radiation sensitive pixels is disposed opposite the radiation source, across the examination region. The imaging system further includes a rigid flux filter device (130) disposed in the examination region between the radiation source and the radiation sensitive detector array of photon counting pixels. The rigid flux filter device is configured to filter the radiation traversing the examination region and incident thereon. The radiation leaving the rigid flux filter device has a predetermined flux.