X-ray focal spot alignment correction via electromagnetic steering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In X-ray imaging systems, particularly in CT imaging, focal spot misalignment due to the high aspect ratio of silicon detector elements and attenuating foils leads to data loss and image artifacts, as the focal spot shifts during operation, especially with the heating of the anode, which existing methods fail to adequately address.
Innovation Solution
The method involves using paired response data from sensor pairs with complementary response functions to determine the focal spot position and perform corrective actions, either in real-time using electromagnetic electron beam steering or through post-scan calibration, to maintain alignment and mitigate image artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicon detector elements with high aspect ratio are used to achieve high detection efficiency, then X-ray attenuation performance is improved, but focal spot misalignment occurs due to detector geometry and anode heating
Solution Approach 1:
The system performs preliminary calibration by acquiring projection data at multiple known focal spot positions before actual imaging. This pre-acquired calibration data is stored and later used to correct alignment errors, allowing the system to compensate for focal spot misalignment without requiring real-time mechanical adjustment of the high-aspect-ratio detector elements
Solution Approach 2:
The system establishes a feedback loop where projection data is continuously analyzed to determine actual focal spot positions. These measured positions are compared against expected positions, and correction factors are applied to subsequent imaging data, creating a closed-loop system that maintains alignment accuracy despite thermal drift in the anode
2Device complexity
If focal spot position is allowed to shift during operation, then device complexity is reduced, but image quality deteriorates due to data loss and artifacts
Solution Approach 1:
The system uses the detector itself to measure focal spot position by analyzing the projection data pattern. The detector elements detect the actual focal spot location, and this self-measured information is then used to correct the imaging data, eliminating the need for external alignment sensors or complex mechanical stabilization mechanisms
Solution Approach 2:
The patent introduces calibration projection data as an intermediary element that mediates between the focal spot position and the final image reconstruction. This calibration data serves as a reference that bridges the gap between actual and expected focal spot positions, allowing mathematical correction without mechanical intervention
3Manufacturing precision
If calibration procedures are made more comprehensive to address focal spot misalignment, then alignment accuracy is improved, but calibration time and complexity increase
Solution Approach 1:
The system acquires projection data at multiple focal spot positions (e.g., five positions) during calibration, which is more than the single-position calibration of conventional systems. However, this extended calibration is performed once and stored for reuse, so while the initial calibration time is longer, the per-scan calibration overhead is minimal, effectively averaging the time cost over many scans
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 effectively reduces focal spot motion-induced artifacts in CT images, ensuring high-quality imaging across various protocols and simplifying calibration procedures, while maintaining image quality and reducing the complexity and time required for calibration.
Implementation Method 1
X-rays are emitted from a focal spot of an X-ray source... The beam is typically attenuated by the object. Subsequently, the attenuated beam is incident on a CT detector having an array of detector elements
Implementation Method 2
perform corrective actions, either in real-time using electromagnetic electron beam steering
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present disclosure relates to determining the position of an X-ray focal spot in real time during an imaging process and using the focal spot position to ensure alignment of the focal spot and high-aspect detector elements or to correct for focal spot misalignment, thereby mitigating image artifacts. For example, the focal spot position may be monitored and may be adjusted in real-time using electromagnetic electron beam steering during a scan. Alternatively, previously determined functional relationships between focal spot position and measured data may be applied to address or correct for focal spot misalignment in the acquired data.