C-arm Projection Data Subtraction for Rotational Angiography
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Solution Overview
Problem
Current medical diagnostic imaging techniques, such as rotational angiocardiography, face challenges in accurately removing background information without blurring the target object, especially when the C-arm is rotated, leading to motion artifacts and increased radiation dose due to longer acquisition times.
Innovation Solution
A method and system for subtracting background information from projection data acquired in a single rotational sweep of a C-arm, where the target is masked out, and the background is projected and subtracted from the original data, allowing for more accurate segmentation and motion compensation in 3D image reconstruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If background subtraction is performed using adjacent frames in rotational angiocardiography, then background information can be removed, but motion artifacts and blurring occur due to C-arm rotation
Solution Approach 1:
The patent applies preliminary action by first reconstructing a 3D volume from the rotational angiocardiogram data before performing background subtraction. This volume reconstruction captures the anatomical structures in their proper spatial relationships, allowing subsequent 2D background subtraction to be performed on accurate 3D-projected data rather than on blurred 2D frames, thus eliminating motion artifacts while maintaining background removal accuracy
Solution Approach 2:
The patent transitions from 2D frame-based processing to 3D volume-based processing. By reconstructing the data into a three-dimensional volume and then projecting it back to 2D planes for background subtraction, the method adds a dimensional intermediate step that resolves the contradiction between background removal and image sharpness, as the 3D reconstruction captures anatomical geometry without motion blur
2Measurement precision
If DSA is applied with C-arm swept at least twice for acquiring pre-contrast and contrast images, then accurate contrast visualization is achieved, but acquisition time increases requiring longer breath-holding and more radiation dose
Solution Approach 1:
The patent makes the single rotational sweep multi-functional by using it to simultaneously acquire both pre-contrast and post-contrast images. The same rotational trajectory and data acquisition protocol serve dual purposes: capturing anatomical structures without contrast and capturing structures with contrast enhancement, thereby eliminating the need for separate acquisition passes and reducing total acquisition time
Solution Approach 2:
The patent utilizes parameter changes in the contrast agent distribution over time. By acquiring images at different temporal phases during the contrast injection process, the system captures both pre-contrast and post-contrast states from a single rotational sweep, effectively using temporal parameter changes to achieve what would traditionally require spatial re-scanning
3Measurement precision
If DSA is applied to rotational angiography, then background subtraction can be performed, but synchronizing C-arm motion and cardiac motion is challenging causing misalignment
Solution Approach 1:
The patent applies preliminary action by performing motion compensation and registration algorithms on the reconstructed 3D volume before projecting it to 2D planes for background subtraction. This preliminary processing aligns the anatomical structures across different temporal phases, resolving motion misalignment issues before the actual background subtraction occurs, thus simplifying the overall synchronization complexity
Data Source
AI summary
Background information is subtracted from projection data in medical diagnostic imaging. The background is removed using data acquired in a single rotational sweep of a C-arm. The removal may be by masking out a target, leaving the background, in the data as constructed into a volume. For subtraction, the masked background information is projected to a plane and subtracted from the data representing the plane.