Motion-Compensated Digital Subtraction Angiography for Medical Imaging
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Solution Overview
Problem
Medical imaging during interventions like embolization and TAVI often faces compromised image quality due to poor contrast and motion artifacts in fluoroscopic images, especially when dealing with complex backgrounds and cluttered environments.
Innovation Solution
An image processing system that includes a landmark identifier, motion estimator, and motion compensator to enhance image contrast and reduce artifacts by focusing on the region of interest, using a localized motion compensation technique that tracks and registers key landmarks within the image frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If traditional Digital Subtraction Angiography (DSA) is used to improve image contrast, then image contrast is enhanced, but motion artifacts are introduced due to complex motion patterns during intervention
Solution Approach 1:
The patent segments the image processing into multiple layers by identifying and tracking landmarks to define a region of interest (ROI). Motion compensation is then applied selectively to different layers: the background layer is compensated using landmark-based motion estimation, while the foreground (catheter, embolus) is processed separately. This segmentation allows motion artifact reduction in the background without compromising the visibility of moving medical devices.
Solution Approach 2:
The patent applies local quality enhancement by focusing motion compensation specifically on the background region within the ROI, rather than applying global motion compensation to the entire image. The landmark identifier tracks specific anatomical landmarks to define the ROI, and the motion compensator applies compensation only within this localized region, preserving the natural appearance of moving foreground objects while removing motion artifacts from the background.
2Productivity
If fluoroscopic images are acquired to monitor embolus position, then real-time monitoring is achieved, but image quality is compromised by poor contrast against complex background
Solution Approach 1:
The patent performs preliminary action by acquiring and storing a mask image before contrast injection, and by pre-identifying anatomical landmarks to define the region of interest. The landmark identifier and motion estimator prepare the background motion model in advance, so that when contrast images are acquired for real-time monitoring, the motion compensation can be applied immediately without delay, maintaining real-time capability while enhancing contrast.
3Illumination intensity
If mask image subtraction is performed to enhance contrast, then image contrast improves, but subtraction artifacts are introduced due to motion between mask and contrast images
Solution Approach 1:
The patent introduces an intermediary motion compensation step between mask image subtraction and contrast image enhancement. The motion compensator acts as an intermediary that transforms the mask image to match the motion of the contrast image using landmark-based motion estimation, or alternatively transforms the contrast image to match the mask image. This intermediary transformation eliminates misregistration artifacts while preserving the contrast enhancement benefits of DSA.
Data Source
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AI summary
An image processing method and related system to register projection images (AG, MI) only with respect to a motion of a landmark across said images. The motion of the landmark relates to a motion of a region of interest, ROI. The so registered images (AG, MI) are then subtracted from each other to arrive at a difference image that is locally motion compensated and that represents the ROI at good contrast whilst subtraction artifacts can be avoided.