X-Ray Scanner Geometry Calibration Using a Reference Tool
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Solution Overview
Problem
Existing x-ray scanning devices face uncertainties in the actual positions of sources and detectors due to manufacturing and assembly variations, leading to image quality issues and errors in algorithms, which conventional measurement methods cannot reliably address.
Innovation Solution
A calibration method and device using a geometric calibration tool with identifiable features, allowing for the determination of actual source and detector positions by analyzing images and performing measurements on the tool and the imaging device, without direct measurement of the sources and detectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional measurement methods are used to determine source and detector positions, then the measurement process is simple, but the measurement precision is insufficient to detect small position differences
Solution Approach 1:
The patent introduces a calibration device as an intermediary object with known geometric features (wires forming specific patterns) that can be scanned and imaged. By measuring the positions of these identifiable features in the images and comparing them to their known actual positions, the system can indirectly determine the source and detector positions with high precision without directly measuring the sources and detectors themselves.
Solution Approach 2:
The calibration device creates a known geometric pattern (copy) that can be imaged and analyzed. The wires and their arrangements serve as a reference copy with precisely known geometry, allowing the system to detect deviations in source and detector positions by comparing the imaged positions against the known reference positions.
2Ease of manufacture
If the sources and detectors are concealed in the scanning device, then the device structure is compact and protected, but direct measurement of their positions becomes impossible
Solution Approach 1:
The calibration device serves as a mediator that can be accessed and scanned separately. By placing the calibration device in the scanning chamber and scanning it with the concealed sources and detectors, the system can determine the positions of the hidden components through the images of the calibration features without needing to access or directly measure the sources and detectors.
Solution Approach 2:
The calibration device enables the scanning system to self-calibrate by providing its own measurement reference. The system uses the known geometry of the calibration device to automatically determine and correct its own source and detector positions without requiring external measurement equipment or disassembly.
3Ease of manufacture
If manufacturing and assembly tolerances are relaxed to reduce costs, then the manufacturing precision improves, but the actual positions of sources and detectors deviate from expected positions
Solution Approach 1:
The calibration process is performed as a preliminary action after assembly but before operation. By scanning the calibration device and determining the actual source and detector positions, the system can identify and compensate for manufacturing deviations before actual scanning operations begin, allowing relaxed manufacturing tolerances without sacrificing operational accuracy.
Solution Approach 2:
The system changes the parameters used for position determination from nominal design values to actual measured values obtained through calibration. By using the measured positions from scanning the calibration device, the system adapts to the actual manufacturing variations and operates with accurate position data despite relaxed manufacturing precision.
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 accurate calibration of x-ray scanning systems by determining the actual geometry, improving image quality and reducing errors in image output.
Implementation Method 1
x-rays are emitted in all directions from the source
Implementation Method 2
portions of each detector will be encountered by a plurality of x-rays to generate a pixel
Data Source
AI summary
A method of determining at least one x-ray scanning system geometric property includes the steps of positioning a calibration device inside a scanning chamber of the scanning device, the chamber being intersected by at least one fan beam of x-rays during a scanning operation, measuring a distance between the calibration device and at least one inner wall of the chamber, scanning the calibration device to produce an image of the calibration device, identifying pixels representing the a geometric feature of the calibration device in the image, determining a position and orientation of the pixels representing the geometric feature in the image and, determining a scanning system property based on the position and orientation of the pixels representing the geometric feature in the image. The position and orientation of the feature in the scanning chamber and the x-ray scanning system property may be determined simultaneously.