OCT Angiography Vessel Density Deviation Mapping
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Solution Overview
Problem
Traditional methods for imaging blood flow in the retina, such as fluorescein angiography, are invasive, require contrast agents, and struggle to accurately visualize small vessels and capillaries in a 3D manner, lacking a normative database for blood flow assessment.
Innovation Solution
The use of Optical Coherence Tomography Angiography (OCTA) to non-invasively quantify blood vessels and capillary flow in a 3D format, employing phase and amplitude information to detect motion and create vessel density maps, fractional deviation, and pattern deviation maps for comparison to a normative database.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fluorescein angiography is used to image blood flow in the retina, then blood vessel visualization is achieved, but the method is invasive and requires injection of contrast agents
Solution Approach 1:
The patent replaces the mechanical/invasive injection method with an optical non-contact method. OCT angiography uses light waves to detect blood flow through phase and amplitude variations in the OCT signal, eliminating the need for contrast agent injection while maintaining blood vessel visualization capability
Solution Approach 2:
The patent uses the OCT signal itself as an intermediary to detect blood flow. By analyzing phase and amplitude information from the OCT signal, the system can visualize blood vessels without requiring external contrast agents, thus avoiding the invasive nature of traditional angiography
2Measurement precision
If fluorescein angiography is used to image blood flow, then blood flow can be detected, but it cannot segment blood vessels into different layers for measurement
Solution Approach 1:
The patent applies segmentation by dividing the retina into multiple distinct layers (superficial capillary plexus, deep capillary plexus, outer retina, choriocapillaris) and generating separate OCTA images for each layer. This allows independent analysis and measurement of blood vessels in each specific layer, preserving layer-specific information that traditional 2D angiography loses
Solution Approach 2:
The patent transitions from 2D topographic viewing to 3D volumetric imaging by acquiring OCTA data along B-scans and segmenting into multiple depth layers. This dimensional enhancement allows simultaneous visualization of different vascular layers while maintaining the ability to detect blood flow through phase and amplitude analysis
3Measurement precision
If fluorescein angiography is used, then blood flow imaging is possible, but fluorescence emission is very weak in small vessels such as capillaries
Solution Approach 1:
The patent replaces the fluorescence emission mechanism with direct optical detection of blood flow through phase and amplitude variations in the OCT signal. This substitution eliminates the weakness of faint fluorescence in small vessels by using a detection method that is sensitive to the inherent optical properties of moving blood cells without requiring exogenous contrast agents
Solution Approach 2:
The patent enables the blood vessels themselves to serve as the detection target without requiring external contrast agents. By detecting phase and amplitude changes caused by blood cell motion directly in the OCT signal, the system allows the blood flow to reveal itself naturally, improving visibility of small vessels like capillaries
4Measurement precision
If traditional fluorescein angiography is used, then blood vessel imaging is achieved, but no normative database has been established for blood flow assessment
Solution Approach 1:
The patent establishes normative databases in advance by collecting and analyzing OCTA data from healthy individuals before clinical application. These pre-established reference databases include expected vessel density patterns and flow characteristics for different retinal layers, enabling immediate comparison and assessment of patient data against normal ranges
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
Enables accurate, non-invasive 3D assessment of blood vessel density and flow, providing clinically useful information by comparing patient data to a normative database, and highlighting focal losses and changes over time, improving visualization and diagnosis.
Implementation Method 1
Motion effects using OCTA can be detected either from the phase information
Implementation Method 2
from the amplitude information (see, for example, Yali Jia et al. [Split-spectrum amplitude-decorrelation angiography with optical coherence tomography, Optics Express, February 2012])
Data Source
AI summary
Optical Coherence Tomography Angiography (OCTA) image representation is obtained having OCTA pixels assigned respective OCTA values. A vessel density map is computed from the OCTA image representation. A fractional deviation map and/or a pattern deviation map is computed for the patient from the vessel density map and a normative database, wherein: (1) the fractional deviation map represents a percent loss of vessel density at each pixel location relative to an expected value based on the normative database; and (2) computing the pattern deviation map includes: computing a pattern map of the vessel density representing a normalized vessel density pattern of the vessel density map relative to an average value of the vessel density map; and computing the pattern deviation map using the pattern map. A loss is determined by using at least one of the fractional deviation map and the pattern deviation map. Other features are also provided.