Field Emitter Cathode X-Ray Intensity Modulation
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Solution Overview
Problem
Conventional X-ray tubes have a slow thermal response, limiting the speed of X-ray intensity modulation, which is inadequate for instantaneous dose adjustment during CT scans, especially when used in sub-second rotation times.
Innovation Solution
The method employs a structured anode or field emitter cathode with a controller to quickly set X-ray intensity by aligning an electron beam to specific anode microstructures or applying emitter voltages, independent of heating current variations, allowing rapid dose modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If heating current is varied to modulate X-ray intensity in a conventional X-ray tube, then dose modulation is achieved, but the response speed is limited by thermal properties of the emitter
Solution Approach 1:
The patent changes the physical state of the emitter from thermal emission to field emission. By applying a strong electric field to the cathode tip, electrons are emitted via quantum tunneling rather than thermal excitation. This fundamental parameter change from thermal to electrical control enables instantaneous dose modulation without thermal lag, directly resolving the contradiction between response speed and dosing accuracy.
Solution Approach 2:
The patent replaces the thermal-mechanical system (heating current flowing through emitter material) with an electrical field system. The field emitter cathode uses an electric field to extract electrons directly from the cathode tip, eliminating the need for thermal heating. This substitution of the underlying physical mechanism achieves rapid response speed while maintaining reliable dose delivery to match patient needs instantaneously.
2Illumination intensity
If heating current is increased to achieve higher X-ray intensity, then intensity is improved, but thermal response time increases
Solution Approach 1:
The patent fundamentally changes the emission mechanism from thermal to field emission. The field emitter cathode generates high electron current density through quantum tunneling under strong electric fields, achieving high X-ray intensity without thermal heating. This parameter change eliminates the thermal time constant that normally limits intensity adjustment speed, allowing instantaneous transitions between intensity levels.
Solution Approach 2:
The patent enables rapid periodic modulation of X-ray intensity by controlling the electric field applied to the field emitter cathode. The electron beam can be switched on and off or modulated in intensity almost instantaneously by varying the cathode voltage, allowing the system to achieve high intensity when needed while minimizing exposure time, thus reducing overall radiation dose while maintaining diagnostic quality.
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 approach enables rapid adjustment of X-ray intensity, matching dose modulation to patient needs during imaging scans, improving diagnostic image quality and reducing radiation exposure.
Implementation Method 1
providing a field emitter cathode... applying the emitter voltage selected to the field emitter cathode, thereby setting the X-ray intensity
Implementation Method 2
aligning an electron beam of the X-ray tube to the first anode microstructure or to the second anode microstructure according to the first setpoint X-ray intensity number selected for generating the X-rays
Data Source
AI summary
A method, in an embodiment, is for setting an X-ray intensity using a structured anode or a field emitter cathode or a finger-shaped cathode head. Other embodiments include an associated X-ray device, an associated single X-ray tube CT scanner, an associated dual X-ray tube CT scanner, and an associated computer program product.