Energy Subtraction Processing for Radiographic Image Separation
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Solution Overview
Problem
Existing energy subtraction processes in radiography struggle to accurately separate soft part and bone part images due to beam hardening effects, leading to residual structures in difference images, especially when the composition ratio of the subject varies and imaging apparatus characteristics change over time.
Innovation Solution
An energy subtraction processing device and method that acquires two radiographic images with different energy distributions, performs initial weighting subtraction, and iteratively derives new weighting coefficients based on pixel values from the bone part image, repeatedly refining the images to improve separation accuracy, while also removing scattered ray components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the same attenuation coefficient is used as the weighting coefficient in all pixels, then the calculation process is simple, but it is difficult to completely remove unnecessary structures in the difference image because the thickness of substance varies depending on location
Solution Approach 1:
The patent applies local quality by deriving different weighting coefficients for different pixel locations based on local thickness information. Instead of using a uniform attenuation coefficient across all pixels, the system calculates thickness-specific weighting coefficients that are applied locally to each pixel or region, thereby achieving complete removal of unnecessary structures while accounting for spatial variations in subject thickness.
2Ease of operation
If weighting coefficients are derived based on presumed attenuation coefficients, then the process is straightforward, but the bone part remains in the soft part image and soft part remains in the bone part image due to beam hardening effects
Solution Approach 1:
The patent implements feedback by using the initially derived soft part and bone part images to calculate thickness information, which then feeds back into the derivation of improved weighting coefficients. This iterative feedback loop allows the system to refine the weighting coefficients based on actual image data, thereby achieving accurate image separation despite beam hardening effects while maintaining a relatively straightforward process flow.
3Productivity
If a single subtraction process is performed with fixed weighting coefficients, then the processing time is short, but the accuracy of separating soft part and bone part images is insufficient when composition ratio varies
Solution Approach 1:
The patent applies dynamics by making the weighting coefficients adaptive rather than fixed. The system dynamically derives weighting coefficients based on thickness information obtained from the initial images, allowing the coefficients to adjust according to the actual composition and thickness variations in different regions. This dynamic approach enables accurate separation of soft part and bone part images across varying composition ratios while maintaining efficient processing through automated derivation.
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 more accurate removal of unnecessary structures in difference images, unaffected by changes in the imaging apparatus over time, ensuring precise extraction of soft and bone part images.
Implementation Method 1
two radiation detectors that include a plurality of pixels accumulating charge corresponding to the emitted radiation
Implementation Method 2
a so-called beam hardening phenomenon occurs in which the energy distribution of the detected radiation changes depending on the thickness of the substance
Data Source
AI summary
An image acquisition unit acquires two radiographic images based on radiation which has different energy distributions and has been transmitted through a subject including a soft part and a bone part. A subtraction unit performs weighting subtraction using a predetermined initial weighting coefficient between corresponding pixels of the two radiographic images to derive a soft part image obtained by extracting the soft part of the subject and a bone part image obtained by extracting the bone part of the subject. A weighting coefficient derivation unit derives a new weighting coefficient on the basis of a pixel value of the bone part included in the bone part image. The subtraction unit performs the weighting subtraction on the two radiographic images using the new weighting coefficient to derive a new soft part image and a new bone part image.