OCT-Based FFR Estimation Using MLA and Branch-Specific Parameters
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Solution Overview
Problem
Current methods for diagnosing and monitoring coronary artery disease, such as angiography, face limitations in accurately measuring minimum lumen area (MLA) and predicting Fractional Flow Reserve (FFR) due to low spatial resolution, errors from X-ray projection angles, and failure to account for vessel dimensions and shape, leading to inadequate assessment of blood flow and pressure drops.
Innovation Solution
The use of optical coherence tomography (OCT) in conjunction with computational models to determine FFR by correlating MLA with FFR, accounting for branch-dependent hyperemic resistance and vessel type-specific parameters, enabling accurate measurement of vessel dimensions and flow dynamics to assess the physiological significance of lesions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If angiography is used to measure MLA, then the measurement can be obtained, but the spatial resolution is low (0.2-0.4 mm) leading to poor measurement precision
Solution Approach 1:
The patent replaces the mechanical/X-ray-based angiography imaging system with an optical coherence tomography (OCT) system that uses light waves to image coronary arteries. This substitution enables measurement precision of 10-20 micrometers, which is 10-20 times better than angiography's 0.2-0.4 mm resolution, while providing three-dimensional cross-sectional images of the vessel lumen and wall structure.
2Measurement precision
If simple linear regression is used to relate MLA and FFR, then the relationship can be established, but the prediction accuracy is poor
Solution Approach 1:
The patent transforms the simple linear relationship between MLA and FFR into a sophisticated non-linear computational model that incorporates multiple parameters including vessel geometry, blood flow dynamics, pressure gradients, and lesion characteristics. This model uses three-dimensional OCT-derived anatomical data to calculate FFR values with significantly improved accuracy compared to simple regression approaches.
Solution Approach 2:
The patent transitions from two-dimensional angiographic projections to three-dimensional OCT imaging, enabling comprehensive visualization of vessel cross-sections, plaque morphology, and lumen geometry. This dimensional enhancement allows the computational model to account for complex spatial relationships and hemodynamic factors that cannot be captured by simple linear regression on 2D angiographic measurements.
3Loss of information
If only minimum cross sectional area is measured, then the measurement is simple, but it is insufficient to characterize pressure drop across lesions with diffuse coronary disease
Solution Approach 1:
The patent divides the coronary artery into multiple cross-sectional segments along its length using OCT imaging. Instead of measuring only the minimum cross-sectional area, the system captures and analyzes the geometry, plaque composition, and lumen dimensions of numerous sequential vessel segments. This segmentation approach provides comprehensive information about diffuse coronary disease and enables accurate calculation of pressure drops across multiple lesions.
Solution Approach 2:
The patent transitions from single-point minimum area measurement to three-dimensional volumetric assessment of the entire vessel segment. OCT imaging provides cross-sectional area, circumference, wall thickness, and plaque burden measurements at multiple locations along the vessel, creating a comprehensive three-dimensional characterization that fully captures the extent and severity of diffuse coronary artery disease.
4Reliability
If conventional angiography is used, then the assessment can be performed, but errors increase due to X-ray projection angles and shadowing effects
Solution Approach 1:
The patent replaces the X-ray projection system with an optical coherence tomography system that uses near-infrared light to image coronary arteries. OCT provides cross-sectional views of the vessel lumen and wall, eliminating the projection angle and shadowing artifacts that plague angiography. This substitution fundamentally removes the source of measurement errors related to X-ray geometry.
Solution Approach 2:
The patent creates accurate three-dimensional optical copies of the coronary artery structure using OCT imaging. These virtual cross-sectional images and three-dimensional reconstructions serve as precise digital models of the vessel anatomy, allowing for accurate measurement of lumen area, plaque volume, and wall thickness without the geometric distortions inherent in projected two-dimensional angiographic images.
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 provides more accurate and reliable FFR predictions, improving diagnostic accuracy and decision-making for stent placement or revascularization by accounting for the complex geometry and dynamics of coronary arteries, reducing errors associated with conventional methods.
Implementation Method 1
Optical coherence tomography (OCT) imaging, applied in combination with new clinical parameters based on advanced analysis of lesion morphology, has the potential to overcome many of the limitations of conventional measures of lesion severity based on angiography.
Implementation Method 2
The relationship of these geometric measurements to ability of the artery to supply an adequate flow of blood to the myocardium when metabolic demands are high has been a long-standing area of investigation.
Data Source
AI summary
In one aspect, the invention relates to system comprising: a processor configured to receive a first optical coherence tomography (OCT) data set obtained during a pullback of a data collection probe along a first length of a first blood vessel; determine a minimum lumen area disposed along the first length using the first OCT data set; and determine a first FFR value along the first length based on the minimum lumen area. In one embodiment, the first FFR value is an estimated FFR. In another aspect, the invention relates to a method that includes measuring, using OCT, the area of a lumen of a vessel for which the vessel's FFR is to be determined; and calculating, using a computer, A2m/(A2m+k) or YA2min/(YA2min+k) as a FFR value. In one embodiment, k is about 0.7 mm2 and γ is patient-specific variable that depends on the coronary branch in which the images were obtained.