3D Image Reconstruction from 2D X-rays Using Projective Geometry Adjustment
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Solution Overview
Problem
Current X-ray imaging systems, particularly C-arms, face challenges in producing high-quality 3D images due to mechanical distortions and irreproducible positioning deviations, which limit the spatial resolution and accuracy of reconstructed images, especially in intra-operative settings where online calibration methods are hindered by occlusions and cumbersome phantom setups.
Innovation Solution
A method that involves computing an initial 3D image and adjusting projective geometry data using image-to-image registration techniques, allowing for online calibration and compensation of non-reproducible deviations, with the aid of a calibration phantom containing radiopaque markers that can be automatically detected in a subset of 2D images, enabling iterative refinement of the projective geometry for improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If C-arms are used for 3D imaging with automatic image acquisition, then intra-operative 3D imaging capability is achieved, but mechanical distortions and positioning deviations reduce spatial resolution and image accuracy
Solution Approach 1:
The patent replaces mechanical positioning measurement systems (encoders, mechanical sensors) with a vision-based optical measurement system. The method uses 2D marker projections captured by the X-ray detector to compute 3D positions and reconstruct the C-arm trajectory, substituting mechanical measurement with optical field-based measurement that is not affected by mechanical distortions of the C-arm structure.
Solution Approach 2:
The patent introduces radiopaque markers as intermediary objects placed on the patient's anatomy. These markers serve as mediators between the C-arm imaging system and the anatomical structures of interest, allowing precise tracking of anatomical positions and movements through their projections in the 2D X-ray images, thereby compensating for mechanical positioning deviations.
2Measurement precision
If online calibration methods are used during diagnostic scan, then real-time geometry adjustment is possible, but occlusions and cumbersome phantom setups hinder the calibration process
Solution Approach 1:
The patent extracts the calibration function from separate offline calibration procedures and integrates it into the diagnostic imaging workflow itself. The same 2D X-ray images used for diagnosis also serve for real-time calibration and trajectory reconstruction, eliminating the need for separate calibration phantoms and procedures during the diagnostic scan.
Solution Approach 2:
The system performs self-calibration by automatically detecting radiopaque markers in the acquired 2D images and computing the C-arm trajectory and projection geometry without requiring manual intervention or external calibration equipment. The diagnostic images themselves provide the information needed for calibration, making the system self-sufficient.
Data Source
AI summary
The present invention relates to a method for reconstructing a 3D image from 2D X-ray images acquired with an X-ray imaging system, said method comprising the steps of:a) receiving a set of 2D X-ray images of a region of a patient with said X-ray imaging system,b) computing an initial 3D image within the coordinate system of the X-ray imaging system by using at least part of said 2D X-ray images with their respective projective geometry data;c) projecting said initial 3D image on at least part of said 2D X-ray images and adjusting the respective projective geometry data of said images, said adjustment comprising registration of said images with the projection of the initial 3D image using an image-to-image registration technique;d) computing an updated 3D image using the complete set of 2D X-ray images with their respective adjusted projective geometry data.