X-ray CT Image Reconstruction Using View Angle Segmentation
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Solution Overview
Problem
In X-ray computed tomography, helical scanning with a multi-array detector at a beam pitch of 1 or less, while reducing image noise, often degrades time resolution due to lung movement accompanying heartbeats, resulting in less sharp images.
Innovation Solution
An X-ray CT apparatus and image processing method that generates intermediate images from full and half projection data sets, applying weighting factors based on pixel value differences to improve time resolution and reduce noise, using a sigmoid function to calculate weighting factors for weighted addition of images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If beam pitch is set to 1 or less in helical scanning, then image noise is reduced, but time resolution is degraded due to lung movement accompanying heartbeats
Solution Approach 1:
The patent segments the projection data into multiple sets based on different view angle ranges. The first projection data set uses a wider view angle range to reduce image noise, while the second projection data set uses a narrower view angle range to improve time resolution. This segmentation allows the system to optimize for different quality metrics simultaneously.
Solution Approach 2:
The patent applies different quality characteristics to different regions of the image. By creating separate intermediate images with different noise and time resolution characteristics, and then applying weighted addition with region-specific weighting factors, the system achieves local optimization where lung fields (prone to movement) receive different processing than stable regions.
Solution Approach 3:
The patent changes the view angle range parameter to create different projection data sets. By adjusting this parameter, the system can trade off between noise reduction and time resolution, then combine the results through weighted addition to achieve an optimal balance that satisfies both requirements.
2Measurement precision
If all projection data corresponding to one or more rotations is used for image reconstruction, then image quality is improved, but time resolution is degraded due to lung movement
Solution Approach 1:
The patent divides the projection data into multiple categories based on view angle ranges. The first projection data set includes data from a wider view angle range for high image quality, while the second projection data set includes data from a narrower view angle range for high time resolution. This segmentation enables selective use of data based on reconstruction requirements.
Solution Approach 2:
The patent dynamically adjusts the weighting factors in the weighted addition process based on the specific imaging requirements and patient conditions. This dynamic adjustment allows the system to adaptively balance between image quality and time resolution, making the system responsive to different clinical scenarios.
3Productivity
If multi-array X-ray detectors are introduced to scan wide ranges, then scanning efficiency is improved, but image noise increases requiring slower beam pitch
Solution Approach 1:
The patent segments the projection data into multiple sets with different view angle ranges. This allows the system to utilize the high scanning efficiency of multi-array detectors while creating separate data sets that can be optimized for noise reduction, thereby maintaining both productivity and image quality.
Solution Approach 2:
The patent changes the view angle range parameter to create different projection data sets with different noise characteristics. By adjusting this parameter and applying weighted addition, the system can maintain low image noise while preserving the scanning efficiency benefits of multi-array detectors.
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 enhances time resolution and reduces image noise, particularly in lung fields, while maintaining data efficiency by adjusting the contribution of images based on target movement.
Implementation Method 1
an X-ray tube, an X-ray detector, a support mechanism, a control unit, an acquisition unit, an intermediate image generating unit, a weighting factor calculating unit, and a resultant image generating unit The X-ray tube generates X-rays
Implementation Method 2
The X-ray detector detects the X-rays which are generated by the X-ray tube and transmitted through a subject
Data Source
AI summary
According to one embodiment, An X-ray CT apparatus includes acquisition unit, intermediate image generating unit, weighting factor calculating unit, and resultant image generating unit. The intermediate image generating unit generates a first image based on a first projection data set and a second image based on a second projection data set. The first projection data set falls within a first view angle range of projection data acquired by the acquisition unit. The second projection data set falls within a second view angle range of the projection data. The second view angle range is narrower than the first view angle range. The weighting factor calculating unit calculates a weighting factor corresponding to a pixel value difference between the first image and the second image. The resultant image generating unit generates a resultant image associated with weighted addition of the first image and the second image based on the weighting factor.