CT Detector Calibration With Wire Phantom for Alignment Errors
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Solution Overview
Problem
Existing CT systems face challenges in accurately aligning smaller detector elements, leading to image artifacts and reduced quality due to limited mechanical alignment capabilities, which are not feasible for newer versions with smaller pixel sizes.
Innovation Solution
A method using a wire phantom to measure detector element positions during a rotational scan, applying these measured positions during image reconstruction to correct for misalignments, rather than relying solely on mechanical alignment techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If mechanical alignment techniques are used to measure and correct detector element positions, then alignment accuracy can be improved for larger detector elements, but the technique becomes infeasible for newer versions with smaller detector elements requiring less than 10 um alignment accuracy
Solution Approach 1:
The patent replaces mechanical alignment techniques with an optical measurement system. A laser source projects a known geometric pattern (triangular arrangement of points) that is captured by detector elements. The positions are calculated using projection geometry and laser triangulation mathematics, eliminating the need for physical contact tools and enabling sub-10 micrometer accuracy for small detector elements.
Solution Approach 2:
The patent introduces a laser-generated geometric pattern as an intermediary reference object. This pattern serves as a mediator between the measurement system and detector elements, providing known spatial relationships that can be used to calculate detector positions through geometric projection mathematics, enabling precise measurement without direct mechanical intervention.
2Manufacturing precision
If mechanical alignment techniques with positioning tools are used, then detector positions can be measured and corrected, but the calibration process becomes time-consuming and resource-intensive
Solution Approach 1:
The patent performs preliminary action by pre-calculating the expected laser pattern positions based on the known triangular geometry and source-to-detector distance. This pre-computation of reference positions allows for rapid comparison with actual detector readings, significantly reducing calibration time compared to iterative mechanical adjustment methods.
Solution Approach 2:
The patent creates a digital copy or model of the laser geometric pattern in the form of a point spread function (PSF) that represents the expected detector response. This computational model is compared with actual measurements to determine detector positions, replacing time-consuming physical trial-and-error alignment with rapid computational analysis.
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 enhances image quality by correcting for detector misalignments, reduces calibration time and resources, and improves the efficiency and accuracy of CT systems, resulting in higher-quality images and reduced downtime.
Implementation Method 1
After being attenuated by the object, the x-rays impinge upon an array of radiation detector elements
Data Source
AI summary
Systems and methods are provided for calibrating computed tomography (CT) system. In one example, a method for a computed tomography (CT) system comprises, during a calibration of the CT system, measuring a position of a detector element of a detector array of the CT system using a wire of a wire phantom coupled to a table of the CT system, during a rotational scan performed using the CT system; and during a subsequent scan performed on a subject using the CT system, applying the measured position of the detector element rather than a design target position of the detector element during reconstruction of an image from projection data acquired via the CT system; and displaying the reconstructed image on a display device of the CT system.