X-ray Imaging Misalignment Correction via Photon Counting
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Solution Overview
Problem
X-ray imaging systems, particularly CT systems, face challenges in managing geometric misalignment between the x-ray source, detector, and collimator structures, leading to errors in image acquisition, loss of photons, and non-linear spectral responses, which complicate image reconstruction and result in artifacts like ring artifacts.
Innovation Solution
A method and system that monitor output signals from a subset of pixels affected by shadowing due to geometric misalignment, estimate and correct for the misalignment using photon-counting and energy-discriminating detectors, and apply correction factors to photon counts in energy bins to address the geometric misalignment, enabling accurate image reconstruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional shielding is added to correct geometric misalignment, then image quality improves, but detection efficiency is sacrificed
Solution Approach 1:
The patent replaces physical shielding mechanisms with computational correction methods. Instead of adding mechanical shielding structures to block scattered photons, the system uses software-based algorithms to identify and correct artifacts caused by geometric misalignment, thereby improving image quality without sacrificing detection efficiency
Solution Approach 2:
The patent introduces correction factors as an intermediary computational element between the raw projection data and the final reconstructed image. These correction factors, derived from system geometry parameters, act as a mediator that compensates for misalignment effects without requiring physical modification to the imaging system or loss of photons
2Measurement precision
If geometric alignment is strictly maintained, then image reconstruction accuracy improves, but system complexity and adjustment difficulty increase
Solution Approach 1:
The patent transforms the geometric alignment problem from a physical adjustment task to a parameter-based computational task. By measuring and using system geometry parameters (source-to-detector distance, detector tilt angles, etc.) to calculate correction factors, the system maintains reconstruction accuracy without requiring complex mechanical alignment mechanisms or difficult physical adjustments
Solution Approach 2:
The patent replaces complex mechanical alignment systems with computational correction. Instead of using sophisticated mechanical devices to maintain strict geometric alignment, the system uses software algorithms that take measured geometry parameters and apply corresponding corrections to the projection data, thereby simplifying the physical system while maintaining accuracy
3Measurement precision
If geometric misalignment is corrected using traditional shielding methods, then artifacts are reduced, but photon loss increases
Solution Approach 1:
The patent replaces physical shielding methods with computational correction algorithms. Instead of using shielding materials to block scattered photons and reduce artifacts, the system uses software-based correction factors derived from system geometry to identify and correct artifact-causing data in the projection domain, thereby preserving all photons while still reducing artifacts
Solution Approach 2:
The patent converts the harmful effect of scattered photons (which cause artifacts) into beneficial information. By using the pattern of photon distribution and system geometry parameters to calculate correction factors, the system identifies which photons contribute to artifacts and corrects their contribution computationally, thereby utilizing all detected photons including scattered ones without requiring physical blocking
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 corrects for geometric misalignment, improving image quality by minimizing artifacts and maintaining high geometric efficiency, even during dynamic movements, without requiring additional shielding that would sacrifice detection efficiency.
Implementation Method 1
a photon-counting and energy-discriminating x-ray detector (20) and an intermediate collimator structure (22) in the x-ray path between the x-ray source (10) and the x-ray detector (20)
Data Source
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AI summary
There is provided a method for management of geometric misalignment in an x-ray imaging system having an x-ray source, a photon-counting x-ray detector and an intermediate collimator structure in the x-ray path between the x-ray source and the x- ray detector. The x-ray detector comprises a plurality of pixels, and the collimator structure comprises a plurality of collimator cells, wherein each of at least a subset of the collimator cells corresponds to a N x M matrix of pixels, where at least one of N and M is greater than one. The method comprises monitoring (S1), for a designated subset of pixels including at least two pixels that are affected differently by shadowing from the collimator structure due to geometric misalignment, output signals from the pixels of the designated subset of pixels, and determining (S2) the occurrence of geometric misalignment based on the monitored output signals from the pixels of the designated subset of pixels.