Virtual Mask Imaging for Low-Dose Digital Subtraction Angiography
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Solution Overview
Problem
Existing digital subtraction angiography methods face challenges in reducing radiation exposure while maintaining image quality, as lower radiation doses lead to increased image noise and artifacts due to patient movement, and methods like digital variance angiography lack time-resolved representation of contrast agent filling.
Innovation Solution
Generate a virtual mask image from a sequence of fill images without recording a separate mask image, using extreme pixel values to create a virtual mask image that is subtracted from fill images, allowing for time-resolved representation of contrast agent filling without additional radiation exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate mask image is recorded before contrast agent injection, then the mask image can be used for subtraction to visualize blood vessels, but additional radiation exposure is required
Solution Approach 1:
The patent creates a virtual mask image by copying and processing information from existing fill images. Instead of recording a separate mask image with additional radiation, the system generates a virtual mask by selecting pixel values (e.g., minimum or extreme values) from the fill image sequence, thereby eliminating the need for an extra radiation exposure while still providing the necessary mask for subtraction angiography
Solution Approach 2:
The fill images serve multiple functions: they are used both for visualizing the contrast agent in blood vessels and for generating the virtual mask image. This multi-functionality eliminates the need for a separate mask image recording, reducing radiation exposure while maintaining the capability to perform subtraction angiography
2Object-affected harmful factors
If radiation dose is reduced to minimize harm, then radiation exposure is decreased, but image noise increases making vessel assessment difficult
Solution Approach 1:
The virtual mask is generated by copying and processing information from the existing low-dose fill images. By using statistical methods (selecting extreme pixel values) rather than direct recording, the system creates a usable mask without requiring additional radiation dose, thus maintaining image quality assessment capability while minimizing radiation exposure
Solution Approach 2:
The patent changes the parameter of mask image acquisition from direct recording (requiring additional radiation) to computational generation from existing images. This parameter change allows the system to maintain measurement precision in vessel assessment while reducing radiation exposure by using information already captured in the fill image sequence
3Object-affected harmful factors
If digital variance angiography is used to eliminate mask image requirements, then radiation exposure is reduced, but time-resolved representation of contrast agent filling is lost
Solution Approach 1:
The patent copies the essential function of the mask image (representing structures without contrast agent) from the fill image sequence itself. By selecting pixel values that represent the state without contrast agent from the temporal sequence, the system creates a virtual mask that preserves time-resolved information, unlike digital variance angiography which only provides an overall statistical image
Solution Approach 2:
The patent transitions from the temporal dimension (sequence of images over time) to create a virtual mask, while preserving the ability to perform time-resolved analysis. The virtual mask is generated by processing information across the temporal dimension of the fill image sequence, but the resulting subtraction images maintain temporal resolution for assessing contrast agent filling dynamics
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
Reduces radiation exposure by eliminating the need for a separate mask image, improves image quality through noise reduction, and enables time-resolved visualization of contrast agent filling in blood vessels.
Implementation Method 1
A sequence or time series of images, (e.g., time-resolved mappings), of the object may thus be obtained... The images may be obtained from a patient after injection of a contrast agent
Data Source
AI summary
The disclosure provides solutions for reducing exposure to radiation in digital subtraction angiography. For this, a method for generating a virtual mask image is proposed. A plurality of images of an object is captured by an angiography apparatus. For at least some of all pixel positions, an extreme pixel value of the pixels of the plurality of images in the respective pixel position is respectively ascertained. The virtual mask image is created from the extreme pixel values at the respective pixel positions.