X-ray CT Apparatus Dual Energy Reconstruction via Projection Data Alignment
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Solution Overview
Problem
Conventional X-ray CT apparatuses face challenges in achieving high precision dual energy reconstruction based on projection data sets, particularly in non-helical scans, where accurate decomposition and alignment of image data sets at different tube voltages are necessary for generating reference-material images.
Innovation Solution
The X-ray CT apparatus incorporates a processing circuitry that controls the X-ray tube voltage to generate separate projection data sets at different energies during scans, performs image reconstruction, alignment processing, and transformation to create reference material images, enabling high-precision dual energy reconstruction by generating virtual projection data sets for specific imaging sections where actual data may not exist.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dual energy reconstruction is performed based on image data sets, then the reconstruction can be completed, but the precision is insufficient due to decomposition calculation on reconstructed images rather than raw projection data
Solution Approach 1:
The patent performs decomposition calculation on projection data sets before image reconstruction, rather than on reconstructed image data sets. This preliminary action on raw data preserves measurement precision while avoiding the complexity of post-reconstruction decomposition operations.
Solution Approach 2:
The patent replaces the conventional mechanical workflow of reconstructing images first then performing decomposition, with a computational substitution that performs decomposition directly on projection data in the frequency domain, achieving higher precision through mathematical transformation rather than sequential processing steps.
2Ease of manufacture
If decomposition calculation is performed on image data sets after reconstruction, then the process is simpler, but the precision of dual energy reconstruction deteriorates
Solution Approach 1:
The patent performs the computationally intensive decomposition calculation before final image reconstruction, when the data is still in the projection domain. This preliminary action maintains precision by avoiding information loss that occurs during image reconstruction, while the subsequent reconstruction step actually simplifies the final processing workflow.
3Ease of operation
If actual measured projection data sets are used for decomposition, then the data is readily available, but accurate alignment of data at the same slice center position is difficult due to patient movement and scanning variations
Solution Approach 1:
The patent introduces an alignment processing step that uses the first image data set as an intermediary reference to align the second image data set. This intermediary approach corrects misalignments caused by patient movement and scanning variations, achieving accurate correspondence between data sets from different tube voltages while maintaining ease of operation with available measured data.
4Ease of manufacture
If image data sets from different tube voltages are decomposed separately, then the calculation is straightforward, but the precision of reference-material image generation is insufficient without accurate alignment
Solution Approach 1:
The patent uses alignment processing with the first image data set as an intermediary to correct misalignments in the second image data set before decomposition. This ensures that decomposition is performed on accurately aligned data, achieving high precision reference-material image generation while maintaining straightforward calculation procedures.
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 allows for high-precision dual energy reconstruction based on projection data sets, improving image quality and reducing the effects of patient movement and other artifacts, thereby enhancing diagnostic accuracy.
Implementation Method 1
an X-ray tube configured to radiate X-rays
Implementation Method 2
images based on the intensity of X-rays transmitted through the object
Data Source
AI summary
An X-ray CT apparatus includes processing circuitry. The circuitry controls a voltage generator during non-helical scan to switch tube voltage, thereby causing an imaging to be performed separately with X-rays of a first energy and X-rays of a second energy. The circuitry generates first and second projection data sets, respectively. The circuitry performs image reconstruction based on the first and second projection data sets respectively, thereby generating first and second images respectively. The circuitry performs alignment processing to align the second image with the first image. The circuitry generates a third projection data set based on a processing result of the alignment processing. The circuitry performs transformation processing to transform the second and third projection data sets into projection data sets corresponding to reference materials. The circuitry performs image reconstruction based on the projection data sets after the transformation processing, thereby generating reference material images corresponding to reference materials.