Segmented X-ray Beam Filter for Spectral CT Intensity Control
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Solution Overview
Problem
Existing X-ray filters, such as those described in U.S. Pat. No. 6,157,703, modify the spectral shape of the X-ray beam, particularly attenuating low-energy photons, which is undesirable in spectrally resolved detection applications like spectral CT, where a known spectrum is required for accurate measurements.
Innovation Solution
A beam filter comprising a stack of absorbing sheets made from high atomic number materials like molybdenum, tungsten, or gold, arranged to mask different fractions of the radiation source at varying intensities across the detection area, ensuring intensity adjustment without spectral modification, achieved through partial total absorption of the X-ray beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a copper or beryllium plate with a matrix of apertures is used as an X-ray filter, then low-energy photons are attenuated and the beam spectrum is hardened, but the spectral shape of the X-ray beam is modified which is undesirable in spectrally resolved detection applications
Solution Approach 1:
The beam filter is segmented into multiple individual absorbing bodies (first, second, third absorbing bodies) that can independently mask different portions of the radiation source. This segmentation allows selective masking of specific source regions without affecting the overall spectral composition, as each absorbing body can be positioned to mask only certain angular ranges of the source.
Solution Approach 2:
Different regions of the detection area are provided with different masking degrees by positioning the absorbing bodies to create spatially varying intensity distributions. The first absorbing body masks central regions more strongly, the second masks intermediate regions, and the third masks peripheral regions, creating a tailored intensity profile that adapts to patient anatomy while preserving spectral integrity.
2Manufacturing precision
If absorbing bodies are used to mask different fractions of the radiation source at different points on the detection area, then precise intensity control is achieved, but the device complexity increases due to multiple absorbing bodies and positioning mechanisms
Solution Approach 1:
Multiple absorbing bodies with different masking characteristics are combined into a single integrated beam filter assembly. The first, second, and third absorbing bodies are positioned relative to each other to simultaneously create the desired intensity distribution across the detection area, merging multiple filtering functions into one device.
Solution Approach 2:
The absorbing bodies are designed to be movable relative to each other, allowing dynamic adjustment of the intensity distribution. This enables adaptation to different patient sizes and anatomical regions without requiring multiple fixed filters, as the absorbing bodies can be repositioned to create appropriate masking patterns for various clinical scenarios.
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 solution allows precise intensity control across the detection area with minimal spectral alteration, enhancing the accuracy of spectral CT measurements by maintaining the initial spectral configuration of the X-ray beam, thus supporting dose reduction and improved image interpretation.
Implementation Method 1
the absorbing body comprises however a material that is highly absorbing over the whole spectrum of the radiation emitted by the radiation source
Data Source
AI summary
The invention relates to a beam filter (10) that can particularly be used in spectral CT-applications for producing a desired intensity profile of a radiation beam without changing its spectral composition. In a preferred embodiment, the beam filter (10) comprises a stack of absorbing sheets (111) that are separated by wedge-shaped spaces (112) and focused to a radiation source (1). Furthermore, the absorbing sheets have a varying width in direct ion of the radiation. Different fractions of the radiation source (1) area are therefore masked by the beam filter (10) at different points (A, B) on a detector area (2). The absorbing sheets preferably comprise a material that is highly absorbing for the radiation to be filtered.