Spectral Tomosynthesis Marker Detection for Geometry Calibration
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Solution Overview
Problem
Intraoral tomosynthesis systems face challenges in achieving accurate geometric calibration without mechanical coupling between the detector and radiation source, which complicates the alignment and reconstruction of 3D volume images due to the flexible positioning of the detector within the mouth, and radio-opaque markers used for calibration often obscure anatomy and compromise image quality.
Innovation Solution
A method involving a calibration phantom with radio-opaque markers is used to acquire 2D projection image data at different positional relationships of the x-ray source and detector, calculating source-to-detector geometry, and reconstructing a 3D volume image based on anatomy data from these projections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If radio-opaque markers are used for geometric calibration, then alignment accuracy is improved, but image quality deteriorates due to marker obscuration of anatomy
Solution Approach 1:
The patent separates the calibration marker detection process into distinct energy-based segments. By acquiring images at two different x-ray energy levels, the system segments the image data into anatomy-dominated and marker-dominated components, allowing independent optimization of each.
Solution Approach 2:
The patent changes the physical parameter of x-ray energy level to differentiate between marker and anatomy signals. By varying the energy level, the system exploits the different attenuation characteristics of radio-opaque markers versus biological tissues to achieve selective detection.
2Ease of operation
If the detector is flexibly positioned within the mouth, then ease of operation is improved, but geometric calibration difficulty increases due to lack of mechanical coupling
Solution Approach 1:
The patent replaces mechanical coupling between source and detector with an image-processing-based geometric calibration system. By using algorithmic detection of marker positions in multiple projection images, the system achieves geometric calibration without requiring rigid mechanical connections.
Solution Approach 2:
The patent introduces calibration markers as intermediary objects that mediate the geometric relationship between source and detector. These markers serve as reference points that allow the system to calculate and correct geometric parameters through image analysis.
3Object-affected harmful factors
If fewer x-ray projection images are used, then radiation exposure is reduced, but volume imaging capability deteriorates
Solution Approach 1:
The patent changes the energy parameter of x-ray imaging to extract additional information from fewer projection images. By utilizing dual-energy imaging, the system obtains both anatomical and calibration information from the same limited set of projections, maintaining volume imaging capability while reducing radiation dose.
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 enables accurate geometric calibration and reconstruction of 3D volume images with improved image quality by minimizing the impact of marker obscuration, allowing for precise alignment and reduced radiation exposure.
Implementation Method 1
acquiring 2D projection image data for the subject and the phantom, wherein the 2D projection image data distinguishes at least first and second x-ray energy distributions
Implementation Method 2
the phantom has a plurality of radio-opaque markers formed of a marker material
Data Source
AI summary
A method for geometric calibration of a volume imaging apparatus disposes calibration phantom in a radiation path that includes a subject positioned between an x-ray source and a detector. The phantom has a number of radio-opaque markers formed of a marker material. In a repeated sequence, at each of a number of positional relationships of the x-ray source to the detector: 2D projection image data is acquired for the subject and the phantom, wherein the 2D projection image data distinguishes at least first and second x-ray energy distributions; source-to-detector geometry of the imaging apparatus is calculated, corresponding to the acquired 2D projection image data for the first and second x-ray energy distributions. The method reconstructs and displays a 3D volume image of the subject according to acquired anatomy image data from the subject and source-to-detector geometry within the 2D projection images.