X-ray focal spot motion estimation and correction
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Solution Overview
Problem
Mis-alignment of the X-ray focal spot with respect to collimating elements in X-ray imaging systems, such as CT imaging systems, leads to image artifacts due to differential gain changes in detector channels, which are particularly pronounced when the collimator blade pitch is larger than the pixel pitch, affecting clinical image quality.
Innovation Solution
A method to estimate and correct X-ray focal spot motion by characterizing the sensitivity of each channel to static and dynamic mis-alignment, using neighboring channels as a baseline, without requiring additional hardware, by incorporating the sensitivity into the image reconstruction process during data acquisition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the collimator blade pitch is made larger than the pixel pitch to improve spatial resolution, then the ability to distinguish fine structures is improved, but image artifacts increase due to differential gain changes in detector channels
Solution Approach 1:
The system continuously monitors detector channel responses and uses feedback to identify and correct focal spot misalignment. By comparing signal patterns across channels and detecting deviations from expected responses, the system real-time adjusts or compensates for misalignment effects, maintaining image quality while preserving the benefits of high spatial resolution
Solution Approach 2:
The invention dynamically adjusts reconstruction parameters based on detected misalignment conditions. When focal spot misalignment is detected, the system modifies imaging parameters such as beam angle corrections or channel gain adjustments to compensate for the misalignment, allowing the system to maintain accurate imaging despite the large collimator blade pitch
2Measurement precision
If additional hardware is added to detect focal spot drift, then measurement precision of focal spot position is improved, but device complexity and cost increase
Solution Approach 1:
The detector system performs self-diagnosis by using its own channel responses to detect focal spot misalignment. The system analyzes signal patterns from multiple detector channels to identify misalignment conditions without requiring external monitoring equipment, thereby achieving precise focal spot position detection while avoiding additional hardware complexity
Solution Approach 2:
The detector channels serve multiple functions: they not only detect X-ray signals for image formation but also simultaneously monitor for focal spot misalignment by analyzing their relative response patterns. This multi-functionality eliminates the need for separate detection hardware while maintaining precise measurement capabilities
Data Source
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AI summary
The techniques disclosed may be used to detect and correct channel gain errors resulting from X-ray focal spot mis-alignment during the course of a scan. One benefit of the present invention relative to conventional techniques is that additional hardware is not required for detection of focal spot drift. Instead, the static mis-alignment of each blade is taken into account as part of estimating and correcting X-ray focal spot drift or mis-alignment. In this manner, the risk of image artefacts due to focal spot motion is reduced and the need for costly hardware solutions to detect focal spot motion is avoided.