One-Dimensional Grid Modulation for X-Ray Tube Focal Spot Control
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Solution Overview
Problem
Existing x-ray imaging devices face challenges in achieving microsecond mA modulation of the electron beam while maintaining image quality, due to thermal distortions caused by heating and cooling of grids, which result in scatter and structural weakness.
Innovation Solution
A one-dimensional grid with rungs that expand and contract relative to attachment points without substantial distortion, attached to the cathode cup via flexible links or springs, allowing for rapid control of focal spot size and location without degrading image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a two-dimensional mesh grid is used to modulate mA, then beam compression in both width and length directions is achieved, but scatter increases in both directions
Solution Approach 1:
The two-dimensional mesh grid is segmented into two separate one-dimensional grids: a first one-dimensional grid with rungs extending in the width direction for beam compression in width, and a second one-dimensional grid with rungs extending in the length direction for beam compression in length. This segmentation allows independent optimization of each grid to minimize scatter while achieving the desired beam shape control.
2Object-generated harmful factors
If rung width is minimized and length is increased to reduce scatter, then scatter is reduced, but heat deposition increases
Solution Approach 1:
The grid structure is divided into two separate one-dimensional grids with different rung orientations. The first grid has narrow rungs optimized for reducing scatter in the width direction, while the second grid has rungs oriented to minimize heat deposition. This segmentation allows each grid to be optimized for its specific function without compromising the other.
Solution Approach 2:
The patent changes the geometric parameters of the grid rungs by creating two distinct sets: one with narrow width and long length for scatter reduction, and another with different dimensional characteristics for heat management. This parameter variation allows optimization of both scatter reduction and heat deposition simultaneously through the combined effect of the two grids.
3Object-generated harmful factors
If grid rungs are made thin to reduce scatter, then scatter is reduced, but structural strength decreases
Solution Approach 1:
The structural load is segmented between two separate one-dimensional grids. Each grid can use thinner rungs optimized for scatter reduction, while the combined structure of both grids provides the necessary structural strength. The first grid with narrow rungs handles scatter reduction in one direction, while the second grid provides complementary structural support.
4Speed
If grid is positioned in electron beam for mA modulation, then fast mA response is achieved, but heating of grid occurs
Solution Approach 1:
The two one-dimensional grids act as intermediaries that modulate the electron beam through electrostatic fields rather than direct thermal effects. By using electrostatic modulation with properly oriented rungs, the system achieves fast mA response while minimizing direct electron beam heating of the grid structure through optimized geometric configuration.
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
Enables microsecond mA modulation with reduced scatter and heat deposition, maintaining image quality by minimizing thermal distortions and structural weakness in the grid.
Implementation Method 1
gridding technologies are often used to control electron beam operation electrostatically and modulate the mA
Implementation Method 2
an x-ray tube cathode provides an electron beam from an emitter that is accelerated using a high voltage applied across a cathode-to-anode vacuum gap
Implementation Method 3
electrons that emit from the filament pass between the crosspieces of the one-dimensional grid when accelerated toward an anode
Implementation Method 4
produce x-rays upon impact with the anode
Implementation Method 5
the plurality of rungs are configured to expand and contract relative to the one or more attachment points without substantial distortion with respect to the emitter
Data Source
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AI summary
An x-ray imaging system (10) includes a detector (18) positioned to receive x-rays (14, 69), and an x-ray tube (12) coupled to a mount structure. The x-ray tube (12) is configured to generate x-rays (14, 69) toward the detector (18) and includes a target (57), a cathode cup (73), an emitter (55) attached to the cathode cup (73) and configured to emit a beam of electrons (67) toward the target (57), the emitter (55) having a length and a width, and a one-dimensional grid (70) positioned between the emitter (55) and the target (57) and attached to the cathode cup (73) at one or more attachment points (80). The one-dimensional grid (70) includes a plurality of rungs (72) that each extend in a direction of the width of the emitter (40), and the plurality of rungs (72) are configured to expand and contract relative to the one or more attachment points (80) without substantial distortion with respect to the emitter (55).