Cone Beam CT Parallax Correction via Weighted Projection Matrix
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Solution Overview
Problem
In cone beam CT imaging systems, the parallax in image output from flat-panel detectors leads to errors in projection matrices, resulting in deteriorated image quality of three-dimensional reconstructed images, especially in high-speed rotating systems or high-magnification applications.
Innovation Solution
The method involves obtaining a correction projection matrix by assigning weights to specific components of the center coordinates of beads in a geometric calibration phantom, using a component-weighted projection matrix calculated through singular value decomposition (SVD), and combining these matrices to correct errors caused by image output parallax.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a flat-panel X-ray detector is used in cone beam CT imaging, then the detector can capture projection images, but parallax occurs in the image output depending on the reading position, causing errors in the projection matrix
Solution Approach 1:
The patent applies local quality by treating different regions of the detector differently. Specifically, it identifies and corrects parallax errors in specific regions (rows or columns) of the detector based on their spatial positions. The correction involves adjusting projection matrix elements corresponding to different detector regions to compensate for position-dependent parallax effects, thereby improving measurement precision while maintaining the detector's overall coverage area.
2Speed
If high-speed rotating cone beam CT system or high-magnification cone beam CT system is used, then imaging speed or magnification is improved, but parallax errors in the projection matrix increase, resulting in deteriorated image quality
Solution Approach 1:
The patent applies preliminary action by performing projection matrix correction before the actual 3D image reconstruction. The correction is pre-calculated based on detector readout characteristics and parallax models, then applied to the projection images before back-projection. This preliminary correction ensures that even in high-speed or high-magnification systems where parallax effects are amplified, the projection matrix accurately represents the geometric relationships, thereby maintaining image quality.
3Reliability
If the rotational trajectory of the gantry is not accurately determined due to structural sagging or deformation, then the positional relationship between X-ray source, detector and object cannot be accurately determined, but correcting this requires complex calibration procedures
Solution Approach 1:
The patent applies self-service by enabling the system to automatically determine and correct geometric calibration parameters using the projection images themselves. Instead of requiring complex external calibration equipment or manual procedures, the system uses the detector's own readout characteristics and the known geometric relationships in the projection images to self-correct the projection matrix. This automatic correction process simplifies the overall calibration procedure while maintaining high reliability in determining the positional relationship between components.
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 errors in the projection matrix, leading to improved image quality of three-dimensional reconstructed images by accurately determining the positional relationship between the X-ray source, detector, and object, even in high-speed or high-magnification cone beam CT systems.
Implementation Method 1
A cone-beam computed tomography (CBCT) system includes an X-ray source and an X-ray detector. The X-ray source and the X-ray detector can acquire multiple two-dimensional projection images while rotating around an object.
Data Source
AI summary
The present disclosure relates to a cone beam computed tomography (CT) imaging system, an image processing method, and a device therefor. An image processing method performed by a cone beam computed tomography (CT) imaging apparatus including a source and a detector that rotate around an object may include: obtaining a plurality of projection images projected on the detector for the object; obtaining a correction projection matrix; and reconstructing a three-dimensional image by back-projecting the plurality of projection images based on the correction projection matrix.