Collimator Assembly for Reducing Truncation Artefacts in CT Imaging
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Solution Overview
Problem
Current X-ray imaging methods, particularly in computed tomography (CT), face challenges in achieving high image quality of a limited target area while minimizing X-ray dose, often resulting in artefact-ridden images due to truncation artefacts.
Innovation Solution
The method involves taking a second part of projection images by irradiating marginal regions of the target area with X-ray radiation through secondary radiation openings of the collimator assembly, which surround the main radiation opening, to reduce truncation artefacts and enhance image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complete transillumination of the entire examination object is performed to avoid truncation artefacts, then image quality is improved, but X-ray dose increases
Solution Approach 1:
The collimator assembly is divided into multiple independent collimator elements (first, second, third, and fourth collimator elements) that can be independently controlled. This segmentation allows selective irradiation of different regions - the first and second elements irradiate the target area while the third and fourth elements irradiate the marginal regions, enabling region-specific dose optimization.
Solution Approach 2:
Different regions of the examination object receive different irradiation strategies. The target area receives full irradiation for high-quality imaging, while the marginal regions receive reduced or selective irradiation through the third and fourth collimator elements, optimizing the balance between image quality and dose reduction in different spatial locations.
2Use of energy by moving object
If only the target area is transilluminated to reduce X-ray dose, then X-ray dose is minimized, but truncation artefacts occur in the reconstructed image
Solution Approach 1:
The system performs preliminary irradiation of the marginal regions using the third and fourth collimator elements before or during the main imaging process. This preliminary action provides the reconstruction algorithm with advance information about the attenuation properties of the marginal regions, enabling accurate compensation for truncation artefacts without requiring complete transillumination.
Solution Approach 2:
The third and fourth collimator elements act as intermediaries that provide partial information about the marginal regions. These elements don't need to fully open like the first and second elements, but rather provide sufficient attenuation data to serve as a mediator between the limited target area irradiation and the complete object information needed for artefact-free reconstruction.
3Reliability
If the collimator assembly opens all elements to irradiate the entire object, then truncation artefacts are avoided, but the X-ray dose to the examination object increases
Solution Approach 1:
The collimator elements are dynamically controllable, allowing the system to adjust the opening state of each element based on the imaging requirements. The first and second elements can be fully opened for target area imaging, while the third and fourth elements are partially or selectively opened to provide marginal region information, creating a dynamic, adaptive irradiation pattern that optimizes the reliability-dose trade-off.
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 adaptive determination of the target area with sufficient image quality and minimizes X-ray dose, effectively reducing artefacts and achieving realistic Hounsfield values.
Implementation Method 1
the target area being irradiated with X-ray radiation by means of an X-ray device
Implementation Method 2
by means of motorized or manual positioning of lamellae made of a strongly X-ray-debilitating material
Implementation Method 3
projection images showing the target area are taken by means of an X-ray detector
Data Source
AI summary
The invention relates to a method for determining an X-ray image dataset of a target region of an object to be examined, wherein projection images showing the target region are captured by means of an X-ray detector and the X-ray image dataset is reconstructed from the projection images, wherein a first portion of the projection images is captured so as to be collimated onto the target region by the target region being irradiated with X-ray radiation by means of an X-ray device through at least one main radiation opening of a collimator assembly. The invention also relates to a corresponding apparatus for determining an X-ray image dataset of a target region of the object to be examined. The invention generally relates to the field of medical X-ray imaging, in particular with the aim of acquiring projections for reconstructing 2D computed-tomography images.