Tomosynthesis X-ray Image Reconstruction Using Synthetic Projection Alignment
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Solution Overview
Problem
Conventional tomosynthesis methods in mammography face challenges in generating reliable composite images due to angle deviations between low-energy and high-energy scans, leading to information loss during weighted subtraction processes.
Innovation Solution
Implementing two tomosynthesis scans with different x-ray energies, where a synthetic projection image is generated to align angles, allowing for the creation of a difference image for reconstruction without requiring precise angle matching, enabling continuous x-ray tube movement and reduced dose exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If weighted subtraction is performed on projection images acquired at different x-ray energies with angle deviations, then composite images can be generated, but information loss occurs due to misalignment
Solution Approach 1:
The patent applies preliminary action by generating synthetic projection images from the actual projection images before performing the weighted subtraction. These synthetic images are created by back-projecting the actual projection images to generate composite projection images that represent the breast structure at each projection angle, ensuring proper alignment before subtraction operations are performed.
Solution Approach 2:
The patent introduces synthetic projection images as intermediary objects between the actual projection images and the final difference images. These synthetic images serve as a mediator that aligns the low-energy and high-energy projection images at corresponding projection angles, enabling accurate weighted subtraction without direct angle matching requirements.
2Productivity
If tomosynthesis scans are performed with continuous x-ray tube movement, then scanning efficiency is improved, but angle alignment between different energy scans becomes difficult
Solution Approach 1:
The patent performs preliminary generation of synthetic projection images from the actual projection images acquired during continuous scanning. This preliminary processing creates aligned composite images that can be used for weighted subtraction without requiring the x-ray tube to be stopped or realigned between different energy scans.
Solution Approach 2:
The patent creates synthetic projection images that are copies or representations of the actual projection images, generated through back-projection algorithms. These synthetic copies allow for accurate alignment and weighted subtraction while the actual scanning continues without interruption, maintaining both efficiency and reliability.
3Loss of information
If slice images are used for weighted subtraction after tomosynthetic reconstruction, then three-dimensional imaging is achieved, but diagnostic quality deteriorates due to information loss during reconstruction
Solution Approach 1:
The patent performs the weighted subtraction operation on the actual projection images before the tomosynthetic reconstruction is completed. By conducting the subtraction in advance on the raw projection data, the method avoids the information loss that would occur if subtraction were performed on already-reconstructed slice images, thereby maintaining higher diagnostic quality.
Solution Approach 2:
The patent inverts the conventional sequence of operations by performing the weighted subtraction before the tomosynthetic reconstruction rather than after. This inverted approach allows the subtraction to be performed on the original projection images with full information content, and only then is the tomosynthetic reconstruction applied to create the final three-dimensional difference images.
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 eliminates the need for precise angle alignment and reduces patient dose while maintaining diagnostic quality by generating a tomosynthetic x-ray image through aligned synthetic projection images, improving the reliability of the imaging process.
Implementation Method 1
a first number n of first projection images P(1)i are generated with a first x-ray energy E(1) at different first projection angles a(1)i
Implementation Method 2
projection images (projection data sets) of an examination subject are acquired with a digital x-ray detector
Implementation Method 3
the high-energy x-ray beam is strongly absorbed by the contrast agent (for example iodine)
Data Source
AI summary
In a mammography method and apparatus to generate a tomosynthetic x-ray image of a breast of a patient, two tomosynthesis scans are successively implemented with different x-ray energies. In one of the scans, a synthetic projection image is generated from at least two projection images acquired in this scan, this synthetic projection image corresponding to a projection at a projection angle at which a projection image has been acquired in the other scan. A difference image, used to reconstruct the tomosynthesis x-ray image, is generated from this synthetic projection image and the projection image acquired in the other scan. Alternatively, in each scan a synthetic projection image is generated from at least two projection images acquired in that scan. Each synthetic projection image represents a projection at the same projection angle. A difference image, used to reconstruct the tomosynthesis x-ray image, is generated from these two synthetic projection images.