X-Ray Target Exit Bore Geometry for Secondary Image Suppression
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Solution Overview
Problem
Conventional X-ray target assemblies produce undesired secondary images due to scattered electrons, which degrade image sharpness and fidelity, and hinder reliable volumetric reconstructions in CT imaging.
Innovation Solution
A target assembly with a non-cylindrical exit bore, optionally conical and lined with a material of lower atomic number than the target housing, such as aluminum or beryllium, to absorb scattered electrons and reduce secondary image generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional target housing is used, then the target assembly is simple in structure, but secondary images are generated that reduce image sharpness and fidelity
Solution Approach 1:
The exit part of the target housing is segmented into multiple functional components: an exit bore for electron passage, a conical cavity for electron scattering containment, and an x-ray transmissive window for X-ray emission. This segmentation allows each component to perform its specific function optimally while collectively suppressing secondary image generation.
Solution Approach 2:
A conical cavity structure is introduced as an intermediary element between the exit bore and the external environment. This conical cavity acts as a mediator that captures and contains scattered electrons, preventing them from generating secondary X-rays, while allowing the primary X-ray beam to pass through the x-ray transmissive window unaffected.
2Measurement precision
If the exit bore is made cylindrical, then manufacturing is simpler, but electron scattering is not effectively limited
Solution Approach 1:
The exit bore is designed with a conical asymmetric geometry instead of a conventional cylindrical symmetric shape. The conical cavity has a specific cone angle that is optimized to match the scattering angle of electrons, creating an asymmetric structure that preferentially directs scattered electrons into the cavity while maintaining manufacturability through standard conical machining or molding processes.
3Measurement precision
If no liner is provided in the exit bore, then the structure is simpler, but scattered electrons continue to generate secondary images
Solution Approach 1:
A thin liner made of low atomic number material is inserted into the exit bore to absorb scattered electrons. The liner is designed as a relatively simple, inexpensive component that can be easily manufactured and installed, providing effective electron suppression without requiring complex structural modifications to the main target housing.
4Measurement precision
If the liner material has high atomic number, then electron absorption is better, but X-ray transmission is reduced
Solution Approach 1:
Different regions of the target assembly use materials with different atomic numbers optimized for their specific functions: high atomic number materials (such as tungsten or copper) are used in the target body for efficient X-ray generation, while low atomic number materials (such as aluminum, plastic, or carbon) are used for the liner in the exit bore for electron absorption with minimal X-ray attenuation. This local differentiation of material properties optimizes both electron suppression and X-ray transmission.
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 solution significantly reduces secondary image intensity, enhancing image contrast and fidelity, and improves the reliability of volumetric reconstructions in CT imaging by limiting electron scattering within the target assembly.
Implementation Method 1
electrons, which have been scattered or reflected from the target member
Implementation Method 2
The exit bore is provided with a liner predominantly composed of a material having lower atomic number than the atomic number of the predominant material of a surface of the exit part inward of the liner
Data Source
AI summary
Provided is a target assembly for an x-ray apparatus comprising a target housing and an entrance path formed in an entrance part of the target housing for accepting an incident electron beam, as well as a target member for generating x-rays under electron beam illumination through the entrance path and an exit path formed in an exit part of the target housing for allowing generated x-rays to exit the target assembly, the exit path being covered by an x-ray transmissive window. In the assembly, the exit path comprises an exit bore formed in the exit part which is configured to limit the generation of x-rays by impact of scattered electrons, which have been reflected from the target member, onto an inside of the bore. Also provided is a target assembly, an x-ray apparatus, a structure measurement apparatus, a structure measurement method, and a method of modifying a target assembly.