X-ray Image Reconstruction via Shift-and-Add and Focus Stacking
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Solution Overview
Problem
Conventional X-ray imaging techniques, particularly in dental panoramic imaging, face challenges in maintaining sharpness due to a narrow depth of field (DOF) and scale distortions, which are exacerbated by errors in patient positioning and anatomical variations, leading to reduced image quality.
Innovation Solution
The method combines shift-and-add and focus stacking techniques to generate multiple focal planes from X-ray images, allowing for improved 2D image reconstruction and correction of scale distortions, enabling a wider DOF that captures various anatomical variations without individual patient-specific adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional X-ray imaging uses a large Source-to-Image Distance (SID) to achieve a large Depth-of-Field (DOF), then the DOF is improved, but scale distortions and loss of relative object proportions occur due to diverging X-ray beam geometry
Solution Approach 1:
The patent transitions from conventional 2D projection imaging to 3D volumetric imaging by acquiring multiple X-ray images at different source-to-object distances and reconstructing focal planes at different depths. This dimensional transformation allows simultaneous capture of multiple focal planes, resolving the contradiction between DOF and scale accuracy by providing depth-resolved information.
Solution Approach 2:
The patent dynamically changes the source-to-object distance parameter during image acquisition to create images with different magnification factors. By varying this parameter and subsequently reconstructing focal planes at different depths, the system achieves both large DOF and accurate scale representation throughout the imaged volume.
2Measurement precision
If linear tomography is used to produce focused images of selected areas inside the object, then image sharpness at the focal plane is improved, but the Depth-of-Field is reduced compared to conventional area mode detection
Solution Approach 1:
The patent segments the 3D imaged volume into multiple discrete focal planes at different depths. Each focal plane is reconstructed with high sharpness using the shift-and-add method, while the collection of multiple focal planes provides extended DOF coverage throughout the volume, resolving the contradiction between sharpness and DOF.
Solution Approach 2:
The patent extends the single focal plane concept to multiple focal planes by adding the depth dimension to the traditional 2D image space. This allows simultaneous presentation of multiple in-focus planes, achieving both high sharpness at each plane and extended DOF across the volume.
3Measurement precision
If multiple images are acquired at different source-to-object distances to create multiple focal planes, then image sharpness and DOF are improved, but the device complexity and processing requirements increase
Solution Approach 1:
The patent makes the existing area detector serve multiple functions by operating it in continuous frame capture mode to acquire images for multiple focal planes simultaneously. This multi-functional use of the detector reduces the need for additional specialized hardware, thereby limiting the increase in device complexity while achieving improved sharpness and DOF.
Solution Approach 2:
The patent creates digital copies of the object at different focal depths through computational reconstruction rather than requiring physical sectioning or multiple specialized detectors. The shift-and-add method generates synthetic focal plane images from the acquired data set, reducing hardware complexity while maintaining high image quality.
4Measurement precision
If the X-ray source and detector are moved to capture multiple images, then image quality and DOF are improved, but the acquisition time and productivity are reduced
Solution Approach 1:
The patent implements continuous frame capture mode where the area detector continuously acquires X-ray images during the object's movement through the imaging zone. This continuous acquisition eliminates gaps between frames and maximizes the use of available data, improving acquisition efficiency while maintaining high image quality through subsequent focal plane reconstruction.
Solution Approach 2:
The patent performs preliminary image acquisition at high speed using continuous framing, capturing all necessary data before any processing occurs. The actual focal plane reconstruction and image quality enhancement are performed in post-processing, allowing rapid data collection followed by computationally intensive but time-independent reconstruction operations.
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 significantly enhances image sharpness and DOF, ensuring that all anatomical features are in focus, resulting in improved diagnostic quality and reduced complexity in X-ray system design.
Implementation Method 1
The TDI principle is also applicable to X-ray imaging. For example, an area mode X-ray detector can be operated in TDI mode and the sensitivity and SNR will be many times higher compared to a line-scan X-ray detector of the same native pixel size.
Implementation Method 2
a focus stacking method for generating a two-dimensional (2D) image from the plurality of focal planes
Data Source
Figure 1A~1B
Figure 2
Figure 3A~3B
AI summary
The present invention relates to a method and a system for producing X-ray images from an object. According to this invention, a shift-and-add method is used for generating a stack of linear tomography planes each associated with a different area inside the object. A set of shift values is defined from the consideration of ensuring that said stack of linear tomography planes fills in the tomographic volume with a spatial density adequate to the application. If so required by the application, some focal planes can be selectively processed for sharpness reduction in some areas to control the depth-of-field. A focus stacking method is used to synthesize a single 2D X-ray image from the tomographic stack of images. A depth map of in-focus areas from the linear tomography stack can be used for creating a 3D object model.