X-ray Tube Focal Spot Control via Dynamic Bias Adjustment
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Solution Overview
Problem
Existing CT imaging systems face challenges in controlling focal spot size variations of x-ray tubes due to changes in mA and kV values, leading to artifacts in images, especially with increasing detector sizes and thin slices, as there is no effective method to manage these variations beyond using x-ray tubes designed within a specific focal spot range.
Innovation Solution
A method and system for dynamically controlling focal spot size by measuring and using a calibration table or transfer function based on x-ray tube operating parameters, such as mA, kV, and bias voltage, to maintain a consistent focal spot size, allowing the x-ray tube to operate at high peak power without limiting power due to spot size variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If x-ray tube operates at high mA and kV values to increase peak power, then tube performance and productivity are improved, but focal spot size varies substantially causing image artifacts and quality degradation
Solution Approach 1:
The patent applies dynamic focal spot control by making the focal spot size adjustable through control plates or magnetic fields. The system dynamically adapts the focal spot size based on operating conditions (mA, kV values) to maintain consistency during high power operation, resolving the contradiction between peak power and focal spot consistency.
Solution Approach 2:
The patent changes physical parameters (control plate voltages, magnetic field strength) to actively control and maintain focal spot size consistency across varying mA and kV operating conditions. This parameter adjustment allows the system to operate at high peak power while preventing focal spot size variation that would cause image artifacts.
2Manufacturing precision
If x-ray tube is designed with fixed focal spot range to control spot size variations, then focal spot consistency is improved, but tube performance and image quality are degraded due to limited operating range
Solution Approach 1:
The patent transforms the fixed focal spot design into a dynamic system where control plates or magnetic fields can adjust the focal spot size in real-time. This allows the x-ray tube to maintain focal spot consistency across a wide operating range of mA and kV values, eliminating the need to limit the operating range while preserving image quality.
Solution Approach 2:
The patent introduces adjustable parameters (control plate voltages, magnetic field strength) that enable the focal spot size to be maintained within specified limits across varying operating conditions. This resolves the contradiction by allowing both focal spot control and wide operating range through active parameter management.
3Manufacturing precision
If dynamic focal spot control is implemented using control plates or magnetic fields, then focal spot size consistency is improved, but device complexity increases
Solution Approach 1:
The patent introduces control plates or magnetic fields as intermediary elements between the power supply and the focal spot. These intermediaries provide a mechanism to influence electron beam focusing without fundamentally redesigning the x-ray tube, balancing the added complexity with the benefit of focal spot control.
Solution Approach 2:
The patent controls focal spot size by adjusting parameters of existing components (control plate voltages, magnetic field strength) rather than adding complex mechanical systems. This approach maintains focal spot consistency while minimizing the increase in device complexity through electrical parameter management.
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 maintaining focal spot size consistency over a wide range of mA and kV values, optimizing image quality and tube performance by adjusting bias voltages or magnetic field controls in real-time, thus preventing image degradation and allowing for higher peak power operation.
Implementation Method 1
an x-ray source, such as an x-ray tube, projects a fan-shaped beam
Implementation Method 2
X-ray tubes are generally required to produce currents varying from a few mA up to maximum currents near 1 Amp
Implementation Method 3
Due to space charge forces on the electron beam, focal spot size can vary substantial over the entire mA range
Implementation Method 4
These x-ray tubes use sets of control plates near the filament of the tube to shape and deflect the electron beam or a dynamic magnetic field
Data Source
AI summary
A method for controlling focal spot size changes of an x-ray source in an imaging system includes measuring focal spot sizes as a function of a plurality of x-ray source operating parameters, determining a calibration table or transfer function utilizing the measured focal spot sizes as a function of the plurality of x-ray tube operating parameters, and utilizing the calibration table or transfer function to control focal spot size variations during operation of the imaging system.