X-ray Attenuation Correction for CT Boundary Artifacts
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Solution Overview
Problem
Current X-ray CT image reconstruction methods fail to adequately correct for X-ray beam attenuation at boundaries where the absorption rate changes, leading to image artifacts and degraded image quality.
Innovation Solution
An X-ray attenuation correction method that extracts boundary information, including positional and magnitude data, from projection or tomographic images, using differentiation and gain functions to correct for attenuation, thereby improving scattered X-ray correction and image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional scattered X-ray correction methods are used, then the correction is based on projection length, but the attenuation at boundaries where absorption rate changes is not corrected, leading to image artifacts
Solution Approach 1:
The patent segments the correction process into two distinct parts: (1) conventional scattered X-ray correction based on projection length, and (2) additional boundary attenuation correction. By dividing the correction into these segments, the patent addresses both the general scattered radiation and the specific boundary attenuation effects that cause artifacts.
Solution Approach 2:
The patent applies local quality by implementing position-dependent correction coefficients that vary according to the spatial location within the subject. The correction coefficient is determined based on the projection length and the specific position, allowing different regions (particularly boundaries) to receive customized correction tailored to their local attenuation characteristics.
2Measurement precision
If the projection length is increased to improve scattered X-ray correction, then the correction amount is increased, but the attenuation effect at boundaries becomes more pronounced, generating artifacts
Solution Approach 1:
The patent changes the correction parameters by introducing position-dependent correction coefficients that are functions of both projection length and spatial position. Instead of using a uniform correction approach, the correction coefficient varies based on the projection length and the specific location, allowing the system to adapt the correction amount to local conditions and prevent artifact generation.
3Device complexity
If simple projection length-based correction is applied, then the correction process is simple, but it cannot account for boundaries where absorption rate changes, degrading image quality
Solution Approach 1:
The patent performs preliminary action by pre-calculating correction coefficients based on projection length and position information before the actual image reconstruction. The correction coefficients are determined in advance using the relationship between projection length, position, and attenuation characteristics, so that during image reconstruction, the correction can be applied efficiently without adding significant computational complexity.
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 method effectively corrects for X-ray attenuation at boundaries, reducing artifacts and enhancing the quality of tomographic images by accurately accounting for changes in X-ray absorption rates.
Implementation Method 1
the attenuation of the X-ray beam on the boundary, in particular, may generate artifacts on an image in vicinity of the boundary where the X-ray absorption rate is changing
Data Source
AI summary
The present invention provides an X-ray attenuation correction method, image generating apparatus, X-ray CT apparatus, and image generating method for correcting for the attenuation of X-ray beam at the boundary where the X-ray absorption rate of a subject is changing. Boundary information comprised of the boundary position where the X-ray absorption rate is changing and the magnitude of change is extracted from the projection information of the subject, then the boundary information is used to multiply the amount of scattered X-ray by the amount corresponding to the magnitude of change at the boundary position, to correct for the attenuation of X-ray at the boundary position. The attenuation of X-ray at the boundary position may be corrected for along with the scattered X-ray correction of the projection information, allowing alleviating artifacts developed in a tomographic image.