Forward-Scattering OCT Flow Quantification for Orthogonal Vessels
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Solution Overview
Problem
Existing optical coherence tomography (OCT) methods for quantifying blood flow are challenged by the anisotropic phase response of back-scattering, leading to unreliable flow calculations for vessels oriented approximately orthogonal to the OCT beam, particularly in the retina, and the influence of multiple scattering on decorrelation rates.
Innovation Solution
The approach focuses on dynamic forward scattering (DFS) signals from red blood cells, analyzing light forward-scattered from below the vessel to measure signal modulation rates, which are insensitive to vessel orientation and provide a robust estimate of blood flow, using interferometric data collection systems and controllers to determine flow parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If OCT methods use back-scattering signal for flow quantification, then the measurement can be obtained from within the vessel, but the phase response becomes anisotropic leading to unreliable flow calculations for vessels oriented orthogonal to the beam
Solution Approach 1:
The patent inverts the conventional approach by analyzing forward-scattered light signals from tissue below the vessel rather than back-scattered signals from within the vessel. This inversion makes the measurement insensitive to vessel orientation relative to the OCT beam, as forward scattering geometry fundamentally differs from back-scattering geometry in its phase response characteristics.
Solution Approach 2:
The patent uses tissue below the vessel as an intermediary medium to indirectly measure flow in the vessel above. By analyzing forward-scattered light that passes through the vessel and interacts with the underlying tissue, the system obtains flow information without requiring direct back-scattering from the vessel lumen, thereby eliminating orientation-dependent phase artifacts.
2Measurement precision
If OCT methods focus on single back-scattering within vessel, then the signal source is direct, but multiple scattering influences decorrelation rates reducing measurement robustness
Solution Approach 1:
The patent extracts the forward-scattering component of the optical signal and analyzes it separately from the conventional back-scattering signal. By focusing exclusively on forward-scattered light from below the vessel, the method isolates a signal component that is less susceptible to multiple scattering effects within the vessel lumen, thereby improving measurement robustness.
Solution Approach 2:
The patent changes the detection parameter from back-scattered intensity to forward-scattered intensity from below the vessel. This parameter change fundamentally alters the measurement physics, as forward scattering geometry provides different sensitivity to flow dynamics and reduced influence from multiple scattering events that plague back-scattering-based methods.
3Measurement precision
If OCT analyzes signals from choroidal blood vessels directly, then the measurement targets the vessel, but the signal-to-noise ratio is extremely weak
Solution Approach 1:
The patent uses the scleral tissue below choroidal vessels as an intermediary to enhance signal detection. By analyzing forward-scattered light from this highly scattering, bright tissue layer, the system indirectly measures flow in the choroidal vessels above, achieving much higher signal-to-noise ratio than direct choroidal imaging while still obtaining vessel-specific flow information.
Solution Approach 2:
The patent sacrifices direct imaging of the weak choroidal signal by using the brighter scleral tissue as a proxy measurement medium. This approach accepts indirect measurement in exchange for dramatically improved signal quality, analogous to using a surrogate marker when direct measurement is too weak to be useful.
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
DFS-based methods offer reliable blood flow measurement, especially for vessels with Doppler angles near 90°, providing higher signal-to-noise ratio and more voxels for analysis, and can be applied to various tissues including the posterior eye, skin, brain, gastrointestinal tissues, nerves, and precancerous/cancerous lesions.
Implementation Method 1
the movement of scatterers (e.g. red blood cells (RBCs)) which induces a modulation of the OCT signal
Implementation Method 2
obtain interferometric data from a sample adjacent to and outside of a distal side of the vessel
Implementation Method 3
the optical signals we focus on are modulated by the photons that are forward scattered from red blood cells in a blood vessel
Data Source
Figure 1(a)~1(d)
Figure 2(a)~2(d)
Figure 3(a)~3(b)
AI summary
An apparatus for measuring a blood flow parameter in a blood vessel, including: an interferometric data collection apparatus including a light source and a sensor coupled to a controller, the controller being configured to: direct the light source toward a proximal side of a blood vessel; obtain interferometric data from a tissue adjacent to and outside of a distal side of the blood vessel opposite the proximal side; determine a signal modulation rate based on the interferometric data; and estimate a blood flow parameter in the blood vessel based on the signal modulation rate.