Tomographic Image Alignment via Marker-Based Position Correction
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Solution Overview
Problem
Current tomosynthesis imaging techniques face challenges in accurately aligning projection images due to mechanical errors and body motion, leading to degraded image quality, as existing methods struggle to effectively handle three-dimensional, non-linear positional misalignments.
Innovation Solution
A tomographic image generation device and method that corrects positional misalignment between slice plane projection images using affine transformation and regression analysis, projecting pixel values onto desired slice planes while preserving image values, and iteratively refining the alignment until convergence, to generate high-quality tomographic images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If projection images are aligned using calculated radiation source positions by equally dividing the range of movement or by calibration imaging, then the alignment process is simplified and can be performed without additional markers, but mechanical errors such as vibration during imaging or mechanical misalignment cause positional errors that hinder accurate alignment and degrade image quality
Solution Approach 1:
The patent introduces markers as intermediary objects that are imaged together with the subject to obtain projection images including marker images. These markers serve as reference points to accurately calculate radiation source positions and marker positions for each projection image, eliminating the influence of mechanical errors on alignment without requiring complex calibration procedures.
Solution Approach 2:
The patent replaces reliance on mechanical positioning accuracy with an image-based measurement system. Instead of trusting mechanical calculations of radiation source positions, the system uses actual marker positions captured in projection images to determine precise locations, substituting mechanical measurement with optical/image-based measurement that is less susceptible to mechanical errors.
2Adaptability or versatility
If tomosynthesis imaging is performed by moving the radiation source to different positions and reconstructing projection images, then three-dimensional tomographic images can be generated with emphasized slice planes, but the imaging operation takes several seconds during which subject body motion occurs, making accurate alignment difficult and degrading image quality
Solution Approach 1:
Markers serve as stable intermediary reference points that remain relatively fixed during the imaging process. By tracking marker positions across multiple projection images taken during the several-second imaging operation, the system can accurately determine radiation source positions and perform alignment even when the subject experiences body motion, maintaining measurement precision throughout the extended imaging time.
Solution Approach 2:
The system uses marker positions from actually acquired projection images to feedback and correct the calculated radiation source positions. This feedback mechanism allows the system to adapt to actual imaging conditions including subject motion, rather than relying solely on pre-calculated positions, thereby maintaining alignment accuracy despite the extended imaging time required for tomosynthesis.
3Device complexity
If affine transformation is used to align projection images by translating, rotating, and enlarging or reducing the images, then the alignment process is computationally simple, but it is difficult to remove the influence of three-dimensional non-linear mechanical errors and body motion from the tomographic image
Solution Approach 1:
The patent projects pixel values from three-dimensional projection images onto two-dimensional desired slice planes. This dimensionality reduction transforms the complex three-dimensional non-linear alignment problem into a more manageable two-dimensional correction problem on the slice plane, while still accurately representing the three-dimensional anatomical structures through the projection process.
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 effectively removes the influence of mechanical errors and body motion, improving the image quality of tomographic images by handling positional misalignments as two-dimensional corrections, resulting in clearer and more accurate images.
Implementation Method 1
a radiographic imaging apparatus using radiation, such as x-ray or γ-ray
Implementation Method 2
obtaining a plurality of projection images by imaging the subject with different radiation source positions
Data Source
AI summary
An image obtaining unit obtains a plurality of projection images by imaging a subject with different radiation source positions. A pixel value projecting unit projects pixel values of the projection images on coordinate positions on a desired slice plane of the subject based on the positional relationship between the radiation source position with which each projection image is taken and the radiation detector, while preserving pixel values of the projection images, to obtain a plurality of slice plane projection images. A positional misalignment correcting unit corrects positional misalignment between the slice plane projection images. A pixel value calculating unit generates a tomographic image from the slice plane projection images having been subjected to the correction of the positional misalignment.