Capillary Oximetry via Visible Light OCT Segmentation
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Solution Overview
Problem
Current methods for retinal oximetry lack spatial resolution and cannot differentiate oxygen saturation levels between arteries and veins, making it difficult to assess localized alterations in ocular diseases, especially in retinal capillaries where pathologies may appear earlier than in major vessels.
Innovation Solution
The use of visible light optical coherence tomography (OCT) for capillary oximetry, which involves obtaining structural and angiography data, performing capillary segmentation, resampling and registering B-scans, determining capillary borders, and applying spectroscopic fitting to measure oxygen saturation in capillaries, providing high-resolution, non-invasive measurements of oxygen saturation in retinal capillaries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If pulse oximetry is used to measure blood oxygen saturation, then the measurement is simple and effective for systemic oxygen levels, but the technique lacks spatial resolution and cannot differentiate sO2 levels between arteries and veins
Solution Approach 1:
The patent applies segmentation by dividing the retinal vasculature into distinct arterial and venous segments using OCT angiography. The system segments capillary beds into arterial capillaries, venous capillaries, and mixed capillaries based on flow direction analysis, enabling separate oxygen saturation measurement for each vessel type while maintaining non-invasive operation.
Solution Approach 2:
The patent transitions from two-dimensional pulse oximetry to three-dimensional OCT-based measurement. By utilizing the depth-resolving capability of OCT, the system can differentiate vessels at different retinal layers and distinguish arterial from venous flow based on three-dimensional flow patterns, adding spatial dimensionality to the measurement.
2Measurement precision
If fundus photography or photoacoustic microscopy is used for retinal oximetry, then spatial capability is achieved, but these methods face difficulties separating signal from blood from other retinal pigments or have limited visualization of retinal capillaries
Solution Approach 1:
The patent extracts the blood flow signal from the complex retinal tissue background using OCT angiography. By utilizing motion contrast between sequential OCT scans, the system isolates flowing blood cells from static retinal pigments and structures, enabling specific measurement of hemoglobin oxygenation without interference from other retinal components.
Solution Approach 2:
The patent changes the measurement parameter from direct optical absorption (which confounds blood and pigment signals) to dynamic flow contrast. By measuring temporal changes in optical signal between sequential scans, the system selectively detects moving blood cells while ignoring stationary retinal pigments, resolving the signal separation problem.
3Measurement precision
If spectral domain OCT is used for capillary oximetry, then high-resolution imaging is achieved, but the system requires complex signal processing to separate oxy- and deoxy-hemoglobin absorption spectra
Solution Approach 1:
The patent employs periodic action by acquiring multiple sequential OCT scans at different time points. By periodically sampling the optical signal and analyzing temporal variations in absorption, the system can distinguish between oxy- and deoxy-hemoglobin based on their different absorption characteristics over time, simplifying spectral separation through time-domain analysis.
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 allows for accurate, non-invasive measurement of oxygen saturation in retinal capillaries, demonstrating physiological responses to changes in inhaled oxygen concentrations and providing valuable insights into retinal metabolism and ocular disease monitoring.
Implementation Method 1
obtain structural and angiography data using visible light optical coherence tomography (OCT)
Implementation Method 2
applying spectroscopic fitting to measure oxygen saturation in capillaries
Implementation Method 3
Measurement of blood oxygen saturation relies on the absorption contrast of oxy- and deoxy-hemoglobin
Data Source
AI summary
Disclosed herein are methods and systems for capillary oximetry (e.g., retinal capillary oximetry) using optical coherence tomography (OCT). The method may include obtaining an OCT angiography dataset, performing capillary segmentation based on the OCT angiography dataset to obtain capillary segments, resampling, registering, and/or averaging B-scans of the OCT angiography dataset that correspond to a first capillary segment of the capillary segments to obtain an averaged B-scan for the first capillary segment, determining an anterior and posterior border of the first capillary segment, and determining an oxygen saturation of the first capillary segment based on the averaged B-scan, the anterior border, and the posterior border. Other embodiments may be described and claimed.