Self-calibration procedure for digital breast tomosynthesis imaging apparatus
Inventors
LILJA, Mikko • Malm, Juhamatti • MOHSEN, Tarek
Assignees
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Publication Number
US-12056794-B2
Publication Date
2024-08-06
Expiration Date
Abstract
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.
Core Innovation
The invention relates to a self-calibration process for digital breast tomosynthesis (DBT) reconstruction using a limited number of two-dimensional X-ray projection images acquired over a limited tomographic angle. An initial projection geometry estimate describes the spatial positions and orientation of an X-ray source and an X-ray detector during acquisition, and an intermediate DBT reconstruction is computed using the X-ray projection images and the initial projection geometry estimate.
Projection-image-specific corrective rigid geometric transformations for the initial projection geometry estimate are determined based on the X-ray projection images, the initial projection geometry estimate, and the intermediate DBT reconstruction. The corrective rigid geometric transformations are determined in a projection image specific rotating coordinate system corresponding to the spatial positions and orientations of the X-ray source and X-ray detector during acquisition, by finding maximal similarity between the X-ray projection images and corresponding re-projected digitally reconstructed radiographs of the intermediate DBT reconstruction.
A final DBT reconstruction is computed using the X-ray projection images and a corrected estimate of the projection geometry corresponding to the determined corrective rigid geometric transformations. The invention applies self-calibration to refine projection geometry for DBT reconstruction in a limited-angle tomosynthesis problem, thereby improving the reconstruction quality of the final DBT reconstruction computed from the original X-ray projection images.
Claims Coverage
The patent provides two independent claims. Together, they cover a DBT self-calibration workflow that refines projection geometry by maximizing similarity between measured X-ray projection images and corresponding re-projected DRRs from an intermediate DBT reconstruction, with rigid corrective transformations applied in a projection image specific rotating coordinate system.
Self-calibration for limited-angle DBT using maximal similarity to re-projected DRRs
A self-calibration process for DBT reconstruction that acquires a plurality of two-dimensional X-ray projection images over a limited tomographic angle, defines an initial projection geometry estimate, computes an intermediate DBT reconstruction, determines projection-image-specific corrective rigid geometric transformations for the initial projection geometry estimate, and computes a final DBT reconstruction using a corrected estimate of the projection geometry corresponding to the determined corrective rigid geometric transformations, wherein the corrective rigid geometric transformations are determined by finding the maximal similarity between the X-ray projection images and corresponding re-projected digitally reconstructed radiographs of the intermediate DBT reconstruction.
DBT self-calibration using established rigid transformation geometric parameters to refine projection geometry
A method for a DBT self-calibration process comprising acquiring a set of X-ray projection exposure images over a limited tomographic angle, forming an initial estimate of the projection geometry corresponding to the set, computing an intermediate DBT reconstruction using the set and the initial estimate, establishing a set of rigid transformation geometric parameters applied to the initial estimate, and computing a final DBT reconstruction using the set and a final calibrated estimate of the projection geometry, wherein the corrective rigid transformation geometric parameters are determined by finding the maximal similarity between the X-ray projection exposure images and corresponding re-projected digitally reconstructed radiographs of the intermediate DBT reconstruction.
Both independent claims cover self-calibration for limited-angle digital breast tomosynthesis by computing an intermediate DBT reconstruction from an initial projection geometry estimate and determining corrective rigid transformation parameters by finding maximal similarity between measured projection images and corresponding re-projected DRRs, to obtain a corrected or refined projection geometry for the final DBT reconstruction.
Stated Advantages
Improved sharpness/contrast of the DBT reconstruction.
Reduced need for repeat scans.
Documented Applications
Applicability for software-upgrading existing 2D mammography systems to 3D tomosynthesis with limited numbers of projections and angles.
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