X-ray CT Tube Current Modulation for Positional Displacement
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Solution Overview
Problem
In X-ray CT apparatuses, positional displacement between the subject and the compensation filter leads to reduced X-ray emission at the subject center, resulting in deteriorated image quality, especially when using CT-AEC, which is difficult to address with high-speed moving compensation filters due to technical and cost-related issues.
Innovation Solution
An X-ray CT apparatus that includes an X-ray source, a compensation filter, an X-ray detector, an image operation unit, a display unit, and a control unit, which compensates for image quality deterioration by adjusting the X-ray tube current modulation pattern and/or moving the subject position based on the displacement between the X-ray source rotation center and the desired subject position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the subject is positioned at the gantry center, then the image quality is optimized, but the subject position cannot be adjusted when there is displacement between the subject and compensation filter
Solution Approach 1:
The patent applies dynamics by making the tube current modulation pattern adjustable and adaptive. Instead of fixing the subject position or compensation filter position, the system dynamically adjusts the tube current distribution according to the actual displacement between the subject and compensation filter, allowing the system to adapt to different positioning scenarios while maintaining image quality.
Solution Approach 2:
The patent changes the parameter of tube current modulation to compensate for positional displacement. By calculating the displacement amount and adjusting the tube current distribution pattern accordingly, the system maintains optimal image quality without requiring physical repositioning of the subject or compensation filter.
2Device complexity
If the tube current is constant, then the control is simple, but the image quality deteriorates when there is positional displacement between subject and compensation filter
Solution Approach 1:
The patent implements feedback by calculating the displacement amount between the subject and compensation filter based on detected information, and then adjusting the tube current modulation pattern according to this calculated displacement. This closed-loop approach ensures image quality is maintained while adapting to positional variations.
Solution Approach 2:
The patent performs preliminary calculation of the displacement amount and determines the appropriate tube current modulation pattern before actual scanning. This preliminary adjustment ensures that when scanning occurs, the tube current is already optimized for the actual subject-position relative to the compensation filter, preventing image quality deterioration.
3Manufacturing precision
If the compensation filter is moved to align with the subject, then the image quality is improved, but high-speed moving means are technically difficult to provide and increase cost
Solution Approach 1:
The patent replaces the mechanical moving system with an electrical control system. Instead of physically moving the compensation filter or subject to achieve alignment, the system uses electronic adjustment of the tube current modulation pattern to compensate for positional displacement, eliminating the need for high-speed mechanical moving means.
Solution Approach 2:
The patent introduces the tube current modulation pattern as an intermediary between the subject position and the final image quality. Rather than directly moving the subject or compensation filter, the system uses the adjustable tube current distribution as a mediator to achieve the desired image quality outcome without requiring mechanical displacement.
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 the acquisition of high-quality CT images by appropriately setting the bed position and tube current change pattern during scanning, effectively maintaining target image quality despite positional displacement between the subject and the compensation filter.
Implementation Method 1
an X-ray source which emits X-rays while rotating around a subject; an X-ray detector which is disposed opposite to the X-ray source with the subject interposed therebetween, rotates together with the X-ray source, and detects the amount of X-rays transmitted through the compensation filter and the subject
Implementation Method 2
a compensation filter which adjusts at least one of output distribution and spectral distribution of the X-rays emitted from the X-ray source to the subject
Data Source
AI summary
An X-ray CT apparatus includes: an X-ray source which emits X-rays while rotating around a subject; a compensation filter which adjusts at least one of the output distribution and the spectral distribution of the X-rays emitted from the X-ray source to the subject; an X-ray detector which is disposed opposite to the X-ray source with the subject interposed therebetween, rotates together with the X-ray source, and detects the amount of X-rays transmitted through the compensation filter and the subject; an image operation unit which reconstructs a tomographic image of the subject on the basis of the detected amount of X-rays; a display unit which displays the tomographic image; a control unit which controls each of the constituent components; and a compensation unit which compensates for deterioration of image quality, which is based on the amount of displacement between the rotation center of the X-ray source and a desired position of the subject, by changing an X-ray tube current modulation pattern indicating a time-series change of emission of the X-rays and/or by moving the position of the subject.