Retinal Speckle Imaging With Polarization Gating for Wide-Field Flow Maps
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Solution Overview
Problem
Current retinal imaging modalities, such as OCT and OCT-angiography, are limited in their ability to provide quantitative assessments of vascular health and function over a small field-of-view, and lack strong correlations between anatomical and functional changes in retinal diseases like diabetic retinopathy and age-related macular degeneration, necessitating the development of a non-invasive imaging technique that can quantify early functional changes in retinal hemodynamics.
Innovation Solution
A laser-speckle contrast imaging (LSCI) system is designed with a customized optical illumination system and light-collecting system, utilizing a set of optical apertures defined by an optical fiber component to generate wide-field maps of blood flow with high spatial and temporal resolution, capable of quantifying retinal hemodynamics without contact, and incorporating polarization gating to block specular reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional imaging modalities (OCT, OCT-angiography) are used, then structural resolution is improved, but quantitative assessment of vascular function is limited
Solution Approach 1:
The LSCI system integrates multiple functions into a single imaging modality: it provides wide-field imaging coverage while simultaneously delivering quantitative blood flow measurements through speckle contrast analysis, eliminating the need for separate structural and functional imaging sessions
2Measurement precision
If Doppler-OCT is used for quantitative velocimetry, then blood flow measurement precision is improved, but sensitivity to vessel orientation complicates clinical use
Solution Approach 1:
The LSCI system converts the typically harmful speckle noise into a beneficial measurement tool by analyzing speckle contrast variations over time, where the speckle pattern fluctuations directly provide quantitative blood flow information without being affected by vessel orientation
3Measurement precision
If existing imaging modalities are applied, then anatomical resolution is improved, but correlation with functional changes is weak
Solution Approach 1:
The system merges anatomical imaging with functional blood flow measurement into a single LSCI modality, where the same optical path provides both structural visualization and quantitative hemodynamic data through speckle contrast analysis
4Measurement precision
If contact-based imaging methods are used, then measurement precision is improved, but invasiveness increases
Solution Approach 1:
The system replaces mechanical contact-based measurement methods with non-contact optical imaging, using laser illumination and camera-based detection to achieve precise blood flow measurements without physical contact or exogenous contrast agents
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
The LSCI system effectively measures early functional changes in retinal hemodynamics, enabling accurate characterization of anatomical and physiological dysfunction, and can assess cardiac and systemic vascular functions, potentially serving as a diagnostic tool for retinal vascular diseases and neurodegenerative conditions like Alzheimer's disease.
Implementation Method 1
an optical illumination system having an optical axis and including a group of lenses and a set of optical apertures dimensioned to deliver light to the group of lenses in transmission of such light through at least of these aperture(s)
Implementation Method 2
illuminating a rigid surface (e.g., a retinal blood vessel) with light generated by a coherent light source results in the formation of a random 'speckle pattern'
Implementation Method 3
Movement within the field-of-view, FOV (e.g., moving blood cells) causes temporal and spatial fluctuations in the speckle pattern
Implementation Method 4
incorporating polarization gating to block specular reflections
Data Source
AI summary
The imaging apparatus configured to assess and quantify motion associated with an object and, in a specific case of an eye—retinal vascular anatomy and hemodynamics and generate substantially contrast-free maps of retinal blood flow over a wide field-of-view at up to 590 fps and under short exposure durations (>50 μs), is applicable for diagnosis, study, and management of neurodegenerative conditions (i.e. mild cognitive impairment and Alzheimer's disease) and systemic cardiovascular diseases (i.e. athero- and arteriosclerosis, coronary artery occlusion, and hypertension). The apparatus employs a) a set of apertures substantially blocking light, delivered from a source of light to an illumination arm of the apparatus, from impinging onto an axial point of the front surface of the lens of the illumination arm, and b) polarization gating between the illumination and light-collecting arms of the apparatus. In one implementation, the apparatus is configured to allow for irradiation of the object with an optical field a degree of coherence and/or spectral content of which are varied delivered through the same optical train including the set of apertures.