Variable Resolution 4D DSA Reconstruction for Overlapping Vessels
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Solution Overview
Problem
In digital subtraction angiography, especially in four-dimensional DSA, the multiplicative back-projection method faces limitations when multiple vessels overlap, making it difficult to accurately assign x-ray signals to individual vessels, particularly when vessels are outside the reconstruction volume, leading to limited spatial resolution and potentially falsified results.
Innovation Solution
The method involves determining a first and second three-dimensional DSA dataset, normalizing x-ray datasets based on the first dataset, and segmenting the second dataset to calculate a four-dimensional DSA dataset with improved spatial resolution by back-projecting normalized data, while using confidence values and interpolation to accurately assign time information and intensity values, even in overlapping vessel projections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the reconstruction volume is made as large as possible to resolve overlapping vessels, then the coverage of vessels is improved, but the spatial resolution is limited by the fixed number of voxels
Solution Approach 1:
The patent divides the reconstruction process into two stages: first reconstructing a large-volume dataset with lower resolution to identify all vessels, then performing a second reconstruction of a smaller sub-volume with higher resolution. This segmentation allows the system to maintain both broad coverage and high detail in critical areas.
Solution Approach 2:
The patent applies different resolution qualities to different regions of the examination volume. The first reconstruction volume uses a coarser voxel grid for broad coverage, while the second reconstruction volume focuses computational resources on a smaller region to achieve finer spatial resolution where it is most needed.
2Manufacturing precision
If the reconstruction volume is made smaller to improve spatial resolution, then the resolution is improved, but vessels outside the reconstruction volume can falsify the results
Solution Approach 1:
The patent performs a preliminary reconstruction of a large-volume first DSA dataset before performing the second high-resolution reconstruction. This preliminary action identifies all vessels in the examination volume, including those outside the smaller second reconstruction volume, allowing the system to account for their influence and avoid falsified results.
Solution Approach 2:
The first DSA dataset serves as an intermediary that bridges the gap between the limited field of view of the second reconstruction volume and the complete examination volume. It provides contextual information about vessels outside the smaller volume that could otherwise contaminate the high-resolution results.
3Area of stationary object
If multiple vessels overlap in two-dimensional X-ray projections, then the field of view is maintained, but it becomes difficult to assign x-ray signals to individual vessels
Solution Approach 1:
The patent transitions from two-dimensional X-ray projection analysis to three-dimensional volumetric reconstruction. By adding the spatial dimension, the system can separate overlapping vessels that appear merged in 2D projections, allowing accurate signal assignment to individual vessels through their distinct spatial locations in the reconstructed volume.
Solution Approach 2:
The patent performs preliminary segmentation and identification of vessels in the first large-volume DSA dataset before attempting signal assignment in the second high-resolution dataset. This preliminary action establishes a spatial map of vessel locations that guides accurate signal assignment even when vessels overlap in projections.
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 a variable and improved spatial resolution, enabling accurate determination of hydrodynamic parameters and reducing errors in overlapping vessel projections, thereby enhancing the reliability of four-dimensional DSA data.
Implementation Method 1
In digital subtraction angiography (DSA for short), one or more vessels are represented by X-ray images
Implementation Method 2
normalized two-dimensional x-ray projections of an examination volume are back-projected into a volume element together with time information
Data Source
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AI summary
The invention relates to a method for calculating a four-dimensional DSA dataset from X-ray datasets, comprising receiving X-ray datasets relating to an examination volume via an interface, wherein each of the X-ray datasets comprises a two-dimensional X-ray projection of the examination volume with respect to a projection direction and a recording time of the X-ray projection, further comprising first determining a first three-dimensional DSA dataset of a first reconstruction volume based on the X-ray datasets by means of a computing unit, wherein the first reconstruction volume is a part of the examination volume or identical with it, further comprising second determining a second three-dimensional DSA dataset of a second reconstruction volume based on the X-ray datasets by means of the computing unit, wherein the second reconstruction volume is a part of the first reconstruction volume.further comprising segmenting the second three-dimensional DSA dataset using the computing unit, further comprising normalizing the X-ray datasets based on the first three-dimensional DSA dataset using the computing unit, further comprising calculating a four-dimensional DSA dataset by backprojecting the normalized X-ray datasets onto the segmented second three-dimensional DSA dataset using the computing unit, wherein the four-dimensional DSA dataset comprises several third three-dimensional DSA datasets as well as associated time information.