C-Arm Air Calibration for Gain Drift and Image Artifact Reduction
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Solution Overview
Problem
C-arm X-ray systems suffer from gain drift of electrical and optical components, leading to undesirable artifacts in images, and require regular calibration to establish the relationship between X-ray technique and image detector output, compensating for non-ideal responses of the X-ray tube and detector.
Innovation Solution
An X-ray imaging system performs air calibration by measuring X-ray intensity with no object in the beam path, determining relationships between X-ray tube electrical parameters, detector entrance dose, and average pixel intensity, generating a normalized air map to reconstruct high-quality 3D images, compensating for X-ray field non-uniformity and detector gain non-uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If regular calibration is performed to compensate for gain drift and non-ideal response, then image quality and measurement precision are improved, but loss of time and productivity deteriorate due to calibration time requirements
Solution Approach 1:
The system performs air calibration measurements in advance to establish baseline detector response characteristics. By pre-determining the relationship between X-ray technique parameters and detector output in the absence of objects, the system creates reference data that can be used during actual imaging without requiring time-consuming calibration during patient scans.
Solution Approach 2:
The patent introduces air calibration measurements as an intermediary step between X-ray tube operation and object imaging. By measuring detector response in air (without objects present), the system creates a reference dataset that mediates the relationship between X-ray parameters and detector output, enabling accurate image reconstruction without repeated calibration during actual scans.
2Reliability
If air calibration is performed to establish relationship between X-ray technique and detector output, then reliability and measurement precision are improved, but device complexity and ease of operation worsen due to additional calibration procedures
Solution Approach 1:
The system performs self-calibration by automatically executing air calibration measurements and using the results to correct detector response. The calibration process is integrated into the normal operation workflow, allowing the system to calibrate itself without requiring separate manual calibration procedures or external reference objects.
Solution Approach 2:
The air calibration procedure serves multiple functions: it establishes the relationship between X-ray technique parameters and detector output, characterizes detector gain uniformity, and provides reference data for image reconstruction. By making the calibration process multi-functional, the system reduces the need for separate calibration routines for different imaging tasks.
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
The air calibration method effectively reduces artifacts and enhances the quality of 3D image reconstruction by normalizing scan data to unobstructed beam intensity, accurately determining object attenuation for precise 3D image generation.
Implementation Method 1
an X-ray source operative to transmit X-rays through the object
Implementation Method 2
a detector operative to receive the X-ray energy of the X-rays after having passed through the object and to generate corresponding object X-ray intensity
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A system for imaging an object includes an X-ray source operative to transmit X-rays through the object and a detector to receive the X-ray energy of the X-rays after passing through the object and to generate corresponding object X-ray intensity. The system also includes a controller to measure a detector entrance dose with no object being placed on the X-ray beam path and determine a relationship between an X-ray tube electrical parameter and the detector entrance dose. The controller further determines a relationship between the X-ray tube electrical parameter, the detector entrance dose and a detector average pixel intensity and obtains a normalized air map as a function of the X-ray tube electrical parameter based on calibration image data. The controller also generates an air map based on the normalized air map, the detector entrance dose and the detector average pixel intensity and reconstructs an image of the object based on the air map and the measured object X-ray intensity.