X-ray CT Geometric Error Correction for Tomographic Image Accuracy
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Solution Overview
Problem
X-ray CT apparatuses face inaccuracies in tomographic image generation due to geometric errors such as eccentricity and surface tilt in the rotation axis of the rotary table, leading to blurry images and noise in the reconstruction process.
Innovation Solution
The apparatus corrects projection images using pre-observed geometric errors, such as eccentricity and surface tilt, to generate highly accurate tomographic images by employing a memory to store these errors and a corrector to adjust the images before reconstruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a rotary table is used to rotate the specimen during X-ray irradiation, then the specimen can be imaged from multiple angles for tomographic reconstruction, but geometric errors such as eccentricity and surface tilt in the rotation axis cause inaccuracies in the projection images and resulting tomographic images
Solution Approach 1:
The patent measures and stores the geometric errors (eccentricity and surface tilt) of the rotary table in advance before performing the actual CT measurement. This preliminary characterization of the rotation axis deviations allows the system to compensate for these errors during image reconstruction, thereby improving tomographic image accuracy while maintaining the reliability of projection images.
Solution Approach 2:
The patent modifies the reconstruction parameters by incorporating the measured geometric error values (eccentricity and surface tilt angles) into the image reconstruction algorithm. By changing the reconstruction parameters to account for the actual rotation axis deviations, the system compensates for the geometric errors and improves measurement precision without requiring perfect mechanical alignment.
2Ease of manufacture
If the rotary table has manufacturing imperfections in the rotation axis, then the device structure remains simple and cost-effective, but the projection images contain noise and the tomographic images become blurry
Solution Approach 1:
The patent converts the harmful effect of manufacturing imperfections in the rotary table into a beneficial correction process. By measuring the actual geometric errors (eccentricity and surface tilt) and using these measurements to correct the projection images during reconstruction, the system transforms the previously harmful manufacturing tolerances into actionable correction data, thereby improving image clarity while maintaining simple and cost-effective rotary table fabrication.
3Measurement precision
If geometric error correction is applied to projection images, then tomographic image accuracy improves, but additional processing steps and computational resources are required
Solution Approach 1:
The patent performs the geometric error measurement and stores the correction parameters in advance, before the actual CT measurement. This preliminary action separates the error characterization from the measurement process, allowing the correction to be applied efficiently during reconstruction without adding significant complexity to the real-time measurement system.
Solution Approach 2:
The patent implements geometric error correction by modifying the reconstruction parameters rather than fundamentally changing the reconstruction algorithm. By incorporating the measured eccentricity and surface tilt values as correction parameters in the existing reconstruction framework, the system improves accuracy while minimizing the increase in device and processing 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 approach enables the generation of highly accurate tomographic images and volume data by directly correcting projection images with known geometric errors, improving the precision of CT reconstruction and reducing noise and inconsistencies.
Implementation Method 1
an X-ray source 12 emitting X-rays 13 (shaped in a cone beam), an X-ray detection device 14 detecting the X-rays 13
Data Source
AI summary
When generating a tomographic image using a measuring X-ray CT apparatus that is configured to emit X-rays while rotating a specimen that is arranged on a rotary table and reconstruct a projection image thereof to generate a tomographic image of the specimen, an amount of geometric error that is included in the projection image is obtained in advance and stored; the projection image is corrected using the stored amount of geometric error; and a tomographic image is reconstructed using the corrected projection image.