Tomosynthesis Image Processing Reducing Ripple Artifacts
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Solution Overview
Problem
Tomosynthesis imaging is limited by artifacts such as ripple artifacts, leading to degraded quality in pseudo two-dimensional images generated from tomographic images, which existing techniques have not adequately addressed.
Innovation Solution
An image processing apparatus and method that acquires projection images from different irradiation angles, reconstructs tomographic images, and generates pseudo two-dimensional images by reducing or excluding noise pixels, particularly those with values differing less than a threshold from the mean, and decomposing images into low- and high-frequency components to mitigate artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If tomosynthesis imaging is used to generate pseudo two-dimensional images, then three-dimensional information can be obtained, but artifacts such as ripple artifacts are generated due to limited irradiation angles
Solution Approach 1:
The patent segments the projection images by decomposing them into multiple frequency components (low-frequency components and high-frequency components). This segmentation allows different processing to be applied to different frequency ranges, where low-frequency components are used to reduce ripple artifacts and high-frequency components are used to preserve edge information, thereby resolving the contradiction between obtaining 3D information and maintaining image quality.
Solution Approach 2:
The patent changes the parameter of irradiation angles by acquiring projection images at a plurality of different irradiation angles and selectively using certain angles for reconstruction. By adjusting which angles are used and how they are weighted in the reconstruction process, the patent reduces ripple artifacts while maintaining the ability to generate pseudo two-dimensional images from tomosynthesis data.
2Loss of information
If projection images are superimposed to reconstruct tomographic images, then tomographic information is obtained, but ripple artifacts indicating virtual images are generated in regions where no objects are originally present
Solution Approach 1:
The patent extracts and removes the harmful ripple artifact components from the reconstructed images. By decomposing projection images into frequency components and selectively processing low-frequency components separately, the patent isolates and eliminates the ripple artifacts that appear as virtual images in regions where no objects are originally present, while preserving the genuine tomographic information.
Solution Approach 2:
The patent converts the harmful effect of limited angle imaging (which causes ripple artifacts) into a benefit by using the frequency domain decomposition. The limited angle data, when processed through frequency-based reconstruction methods, allows the system to identify and suppress artifact-prone low-frequency components while preserving high-frequency edge information, thereby turning the limitation into an opportunity for artifact reduction.
3Quantity of substance
If noise pixels are included in pseudo two-dimensional image generation, then complete image data is obtained, but image quality is degraded by noise influence
Solution Approach 1:
The patent applies local quality processing by differently treating various regions and frequency components of the image data. Low-frequency components (which contain more noise) are processed with artifact reduction techniques, while high-frequency components (which contain edge information) are preserved with minimal filtering. This localized differential processing maintains image data completeness while improving overall image quality by reducing noise in appropriate regions.
Data Source
AI summary
Provided are an image processing apparatus, an image processing method, and a non-transitory recording medium storing an image processing program that can further improve the quality of a pseudo two-dimensional image generated using tomographic images. A control unit of a console acquires a plurality of projection images obtained by irradiating a subject disposed between a radiation source and a radiation detector with radiation emitted from the radiation source at different irradiation angles and capturing the radiation with the radiation detector at each of the irradiation angles. In addition, the control unit generates a pseudo two-dimensional image by reducing a weight of a noise pixel which is more affected by noise than a pixel of an object of interest or excluding the noise pixel, using a plurality of tomographic images reconstructed from the plurality of projection images.