Self-Calibrating Digital Breast Tomosynthesis Imaging Geometry Correction
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Solution Overview
Problem
In digital breast tomosynthesis, geometric inaccuracies due to patient movement and mechanical limitations of existing devices lead to inconsistent projection image measurements, degrading image quality and requiring repeated scans, which is undesirable due to radiation dose considerations.
Innovation Solution
A data-driven algorithm using a rotating coordinate system to retrospectively estimate and correct the imaging geometry of X-ray source and detector positions based on X-ray projection image data, allowing for iterative refinement of geometric transformations to improve image consistency without the need for landmark-based calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional calibration methods are used to correct geometric inaccuracies, then manufacturing precision can be improved, but device complexity increases due to the need for calibration procedures and additional hardware components
Solution Approach 1:
The system performs self-calibration by automatically detecting calibration markers within the breast tissue and computing geometric corrections without requiring external calibration equipment or manual intervention. The tomosynthesis system uses its own acquired projection images to correct its imaging geometry, eliminating the need for separate calibration procedures and reducing device complexity.
Solution Approach 2:
The patent replaces mechanical calibration procedures with a computational approach. Instead of using physical calibration objects and manual measurement systems, the invention uses image processing algorithms to detect markers, compute geometric transformations, and correct projections automatically through software-based calibration.
2Measurement precision
If repeated scans are performed to improve image quality, then measurement precision can be improved, but loss of energy increases due to additional radiation dose
Solution Approach 1:
The system performs geometric calibration and correction during the initial scan acquisition, before the radiologist reviews the images. By detecting calibration markers and computing accurate geometric transformations in advance, the system ensures that the projection images are already corrected for geometric inaccuracies, eliminating the need for repeated scans and reducing radiation dose.
Solution Approach 2:
The calibration process uses the detected positions of calibration markers to compute geometric corrections that are fed back into the image reconstruction process. This feedback mechanism allows the system to automatically adjust and correct geometric inaccuracies in real-time, improving image quality without requiring repeated acquisitions.
3Measurement precision
If landmark-based calibration is used to correct projection geometry, then measurement precision can be improved, but device complexity increases due to the need for embedding and detecting calibration landmarks
Solution Approach 1:
The system embeds calibration markers within the breast tissue itself, using the patient's own anatomy as the calibration reference. This eliminates the need for separate external calibration objects and reduces the complexity of the calibration system, as the markers are integrated into the imaging process naturally.
Solution Approach 2:
The calibration markers serve multiple functions: they provide geometric calibration information, act as reference points for motion detection, and can be visualized in the final reconstructed images. This multi-functionality reduces the need for separate calibration systems and simplifies the overall implementation.
Data Source
AI summary
The invention relates to a calibration process specifically applicable for limited angle digital breast tomosynthesis (DBT). The method includes acquiring a set of X-ray projection exposure images, forming an initial estimate of the projection geometry corresponding to each of X-ray projection exposure images, computing an intermediate DBT reconstruction, establishing a set of rigid transformation parameters applied to an initial projection geometry estimate for each X-ray projection exposure image corresponding to calibration result, and computing a final DBT reconstruction using the set of X-ray projection exposure images and a final calibrated estimate of the projection geometry.