X-ray Tube Grid Potential Control for Rapid Current Adjustment

Solution Overview

Problem

Existing X-ray diagnostic apparatuses face challenges in quickly adjusting the tube current to achieve set X-ray conditions due to the time required for the filament temperature to change, affecting the generation of X-rays and the stability of X-ray image brightness.

Innovation Solution

The X-ray diagnostic apparatus incorporates a grid potential control circuitry that switches the grid potential to create a greater potential gradient around the filament, allowing for immediate adjustment of the tube current without relying on temperature changes, thereby enabling rapid switching to target tube currents and maintaining consistent X-ray image brightness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the tube current is adjusted by changing the filament temperature, then the X-ray characteristics are controlled, but it takes time for the filament temperature to change and achieve the set X-ray condition

Engineering Contradiction:

ImproveX-ray condition accuracyVSAvoidtime to achieve set X-ray condition

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The grid potential is adjusted in advance or simultaneously with filament current changes to pre-establish the electron flow conditions needed for the target tube current. This preliminary action on the grid potential compensates for the thermal inertia of the filament, allowing the system to reach the desired tube current faster than waiting for filament temperature alone.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The grid potential acts as an intermediary control mechanism between the filament heating and the actual electron emission. By controlling the grid potential, the system can modulate the electron flow from the filament to the target independently of the filament temperature changes, thereby decoupling the thermal response time from the tube current adjustment time.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Quantity of substance

If the filament temperature is increased to raise tube current, then more thermal electrons are emitted, but the response time is delayed due to thermal inertia

Engineering Contradiction:

Improvenumber of thermal electronsVSAvoidresponse speed of tube current change

Core Design Contradiction:

Quantity of substanceVSSpeed

Solution Approach 1:

The invention changes the control parameter from solely filament temperature to include grid potential. By adjusting the grid potential parameter, the system can control the number of electrons reaching the target without being constrained by the slow thermal response of the filament, thus improving response speed while maintaining the desired electron quantity.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention replaces part of the thermal-mechanical control system (filament heating) with an electrical control system (grid potential modulation). This substitution allows for faster response because electrical potential changes occur much more rapidly than thermal changes, enabling quick adjustment of tube current.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Adaptability or versatility

If the electric current through the filament is adjusted to change tube current, then the X-ray characteristics are modified, but the filament temperature changes slowly affecting the achievement time of target conditions

Engineering Contradiction:

ImproveX-ray characteristic adjustmentVSAvoidtime to achieve target tube current

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The grid potential is adjusted in advance or simultaneously with filament current changes to pre-establish the electron flow conditions needed for the target tube current. This preliminary action on the grid potential compensates for the thermal inertia of the filament, allowing the system to reach the desired tube current faster than waiting for filament temperature alone.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The grid potential acts as an intermediary control mechanism between the filament heating and the actual electron emission. By controlling the grid potential, the system can modulate the electron flow from the filament to the target independently of the filament temperature changes, thereby decoupling the thermal response time from the tube current adjustment time.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 for immediate adjustment of the tube current to achieve target X-ray conditions, reducing the time to stabilize X-ray image brightness and maintaining it at a constant level, even during changes in subject thickness or automatic brightness control.

Implementation Method 1

causing an electric current to flow through a filament to emit thermal electrons

Methodology Applied

Scientific EffectThermionic emission: Thermionic Emission

Implementation Method 2

a grid having a potential for adjusting a potential gradient around the filament

Methodology Applied

Scientific EffectElectric field: Electric Field

Data Source

PatentUS10412818B2X-ray diagnostic apparatus

Publication Date: 2019.09.10 CANON MEDICAL SYST CORP

AI summary

An X-ray diagnostic apparatus according to embodiments includes an X-ray tube assembly and a grid potential control circuitry. The X-ray tube assembly includes a filament that emits electrons, a target that generates X-rays by receiving the electrons, and a grid having a potential for adjusting a potential gradient around the filament. The grid potential control circuitry switches the potential of the grid to a potential where the potential gradient around the filament becomes greater than a potential gradient generated by a potential of the filament and a potential of the target.