CT Motion Correction Around High-Absorption Image Distortion
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Solution Overview
Problem
Existing CT image reconstruction methods fail to accurately correct motion artifacts caused by high absorption substances like metal or contrast agents, leading to excessive movement correction and image distortion.
Innovation Solution
An X-ray CT apparatus and method that determines the presence of high absorption substances, adjusts pixel values, and selects appropriate image pairs to calculate movement vectors, thereby reducing excessive correction and maintaining image accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If noise reduction processing is performed on the first image and the second image to extract movement, then measurement precision of movement is improved, but manufacturing precision of the reconstructed image deteriorates due to excessive correction from high absorption bodies
Solution Approach 1:
The patent extracts and removes the harmful influence of high absorption bodies from the image pair before movement extraction. By identifying pixels with CT values exceeding a threshold and excluding them from movement calculation, the system separates the useful movement information from the harmful artifacts caused by high absorption substances like metal or contrast agents.
Solution Approach 2:
The patent applies different processing strategies to different regions of the image based on local characteristics. Pixels containing high absorption bodies are treated differently from normal pixels - specifically, their CT values are excluded from movement vector calculation. This local differentiation ensures that movement extraction is performed with high precision in healthy tissue regions while avoiding the distortion caused by high absorption materials.
2Reliability
If movement correction is performed using the image pair to correct motion artifacts, then reliability of motion artifact correction is improved, but object-generated harmful factors worsen due to distortion from high absorption bodies
Solution Approach 1:
The patent converts the harmful effect of high absorption bodies into a detectable condition that can be identified and excluded. By using the high CT values of high absorption bodies as identification markers, the system selectively excludes only those pixels from movement calculation, thereby transforming what would be sources of distortion into identifiable elements that trigger a protective exclusion mechanism.
Solution Approach 2:
The patent applies preliminary processing to the image pair before movement extraction to prevent the harmful effects of high absorption bodies. By pre-identifying and excluding pixels with abnormally high CT values, the system prevents these pixels from influencing the movement vector calculation, thereby avoiding the propagation of distortion into the final reconstructed image.
3Manufacturing precision
If pixel values are adjusted or image pairs are selected based on high absorption body detection, then manufacturing precision of the reconstructed image is improved, but device complexity increases
Solution Approach 1:
The patent changes the parameter threshold for pixel inclusion in movement calculation based on the detection of high absorption bodies. By setting a CT value threshold and dynamically excluding pixels that exceed this threshold, the system adjusts the composition of the image pair used for movement extraction. This parameter-based approach provides a simple yet effective mechanism to improve image quality without requiring complex processing algorithms.
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
The method effectively suppresses motion artifacts by minimizing excessive correction due to high absorption substances, enhancing diagnosis accuracy and efficiency.
Implementation Method 1
an X-ray source and an X-ray detector that are rotated around a subject, and acquires transmitted X-ray data of the subject
Data Source
AI summary
To reduce an unnatural distortion of an image that occurs in a case in which a high absorption body of X-rays is included in movement correction image reconstruction processing of a CT image.High absorption body presence or absence determination processing of determining whether or not a high absorption body of X-rays is included is added to movement correction image reconstruction processing, and processing of limiting pixel values of an image pair used for movement correction or processing of selecting an image pair used for calculating a movement vector is performed based on a result of the determination. An X-ray CT apparatus includes a high absorption body determination unit or a pixel value adjustment unit to perform these pieces of processing.