Dynamic Perfusion Data Normalization via Contrast Agent Volume Estimation
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Solution Overview
Problem
The comparison and quantification of myocardial perfusion image data in cardiac angiography are complex due to the difficulty in controlling the amount of contrast agent injected, particularly the backflow of contrast agent into the aorta, which affects image analysis and interpretation, especially before and after stenting procedures.
Innovation Solution
Estimating the integrated volume of contrast agent flowing through the main collector and using this estimation to normalize perfusion image data, allowing for proper quantification and comparison by accounting for backflow and varying blood flow conditions, through methods such as ECG-triggered injection and precise tracking of the catheter tip, and employing image processing techniques for data subtraction and normalization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If contrast agent is injected into the coronary vessels to obtain perfusion image data, then myocardial perfusion can be visualized and analyzed, but the amount of contrast agent injected is difficult to control due to backflow leakage into the aorta, affecting image quantification and comparison
Solution Approach 1:
The system uses ECG-triggered injection to synchronize contrast agent delivery with the cardiac cycle, and employs DSA-subtracted images to monitor contrast agent distribution in real-time. This feedback mechanism allows dynamic adjustment of injection parameters based on actual contrast flow and backflow conditions, enabling precise control of the effective contrast volume reaching the myocardium despite variations in coronary hemodynamics
Solution Approach 2:
The patent replaces manual control of contrast injection with an automated injection system that uses ECG-triggered timing and computer-controlled delivery mechanisms. This substitution of mechanical/manual injection with electronically controlled systems enables precise measurement and control of contrast agent volume, eliminating the variability associated with manual injection techniques
2Illumination intensity
If DSA subtraction is performed to remove background features and improve visibility of myocardial perfusion, then image quality is improved, but the process requires precise alignment of mask and contrast images corresponding to the same cardiac beat phase, increasing processing complexity
Solution Approach 1:
The system performs preliminary ECG-gating and temporal synchronization of mask and contrast images before the DSA subtraction process. By pre-aligning images based on ECG-triggered timing and cardiac phase matching, the system eliminates the need for complex post-processing alignment algorithms, simplifying the overall image processing workflow while maintaining high subtraction accuracy
Solution Approach 2:
The patent introduces ECG-triggered timing as an intermediary mechanism that coordinates the acquisition of mask and contrast images. This temporal mediator ensures that corresponding cardiac phases are captured and aligned, facilitating accurate DSA subtraction without requiring complex spatial or temporal registration algorithms
3Reliability
If perfusion image data is acquired before and after stenting procedures to assess treatment efficacy, then clinical decision-making is improved, but comparison of perfusion data is complicated by varying blood flow conditions and contrast agent distribution
Solution Approach 1:
The system normalizes perfusion image data by calculating the ratio of contrast agent volume in the myocardium to the total contrast agent volume injected, creating a dimensionless perfusion index. This parameter transformation allows direct comparison of perfusion efficacy across different patients, time points, and injection conditions, eliminating the confounding effects of varying blood flow and contrast distribution
Solution Approach 2:
The patent develops a universal normalization methodology that can be applied consistently across different patients, coronary vessels, and imaging acquisitions. This universal approach using ECG-triggered injection and standardized DSA subtraction protocols enables the same analysis framework to be used for all perfusion assessments, facilitating reliable before-after comparisons and multi-patient studies
Data Source
AI summary
The invention relates to x-ray imaging technology as well as image post-processing. Particularly, the present invention relates to post-processing of perfusion image data acquired by an x-ray imaging apparatus by absolutely or relatively normalizing perfusion image data to allow a preferred comparison of the image data, both with regard to different acquisitions as well as different patients. To allow normalization of perfusion image data, it may be desirable to know the amount of contrast agent injected, which remains in a coronary. Subsequently, image parameters may be adapted or normalized based on the known amount of contrast agent within the coronary for normalization of perfusion image data. To obtain a precise amount of injected contrast agent, the injected volume of contrast agent flowing through a defined region or section of a vessel may be estimated. Said injected volume of contrast agent may thus be deduced from the estimation of the total volume flow at this location. Accordingly, a method (10) is provided for dynamic normalization of data for perfusion comparison and quantification, comprising the steps of determining (20) a total volume flow or an amount of a contrast agent in a blood vessel and normalizing (34) perfusion data based on the determined total volume flow or amount of contrast agent.