Laser-speckle contrast imaging system and method
Inventors
Patel, Dwani • Dhalla, Al Hafeez • Viehland, Christian B. • Lipinski, Daniel M.
Assignees
Coherence Consulting LLC • Medical College of Wisconsin
Publication Number
US-11974812-B2
Publication Date
2024-05-07
Expiration Date
2042-03-21
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Abstract
Laser-Speckle Contrast 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.
Core Innovation
This invention provides a laser-speckle contrast imaging (LSCI) system and method for non-contact, high-speed, wide-field mapping of motion, particularly blood flow in biological tissues such as the retina. The system employs an optical illumination arm with a set of apertures, each separated from the optical axis, often defined by a specially-structured optical fiber component. This configuration enables delivery of light to target surfaces, such as the retina, while substantially avoiding the illumination of the central axial region, resulting in annular or arcuately-shaped illumination patterns.
One central problem addressed is the inability of existing retinal imaging techniques, such as OCT and angiography, to quantitatively assess functional vascular changes over a large field of view, especially in early stages of diseases or without exogenous contrast. Moreover, related LSCI systems struggle to achieve uniform illumination or manage specular reflection and scattering artifacts, particularly in non-contact set-ups, limiting accurate quantification and reliable diagnosis.
Embodiments of this invention solve these challenges by combining a structured set of optical apertures with polarization gating between illumination and collection arms, allowing backscattered light from the object surface to be separated from specular reflections. The system further supports delivery of different optical parameters, including varying degrees of coherence or spectral contents, through the same optical train, enabling advanced imaging protocols such as multiplexed illumination or alignment procedures. Optional features include an auxiliary lens shared between arms and methods for forming images selectively from reflected light passing through specific designated regions of a target surface, enhancing image clarity and diagnostic capabilities.
Claims Coverage
The independent claim outlines multiple inventive features concerning the configuration, operation, and data processing methods of a laser-speckle contrast imaging (LSCI) system.
Dual-parameter optical fiber input for structured illumination
The method employs coupling two illuminating lights, each having a distinct optical parameter (such as wavelength, coherence, or polarization), into non-overlapping input facet areas of an optical fiber component that defines a set of optical apertures for illumination delivery. - Each aperture is separated from the optical axis. - The fiber's input areas are spatially distinct for each parameter. - This arrangement allows structured, selective illumination of the object.
Formation of arcuate or annular illumination at the target surface
An optical image of the set of apertures is formed at the target surface, resulting in an image area that is - arcuate and curved around the optical axis, and/or - bound by two curved lines, and/or - annularly-shaped. This spatially structured illumination defines a specific pattern for delivering and analyzing light interaction with the object.
Selective transmission and image formation through designated non-illuminated area
A portion of the first illuminating light, reflected from the object surface, is transmitted towards the optical detector only through a designated area of the target surface that is fully encircled by the image area of the apertures' optical image (e.g., through the central non-illuminated region in a ring pattern). - The collected image thus excludes the illuminated regions, decreasing interference from directly reflected light.
Processing for quantification of motion using speckle contrast
The method incorporates analyzing the speckle contrast characteristic from at least one optical image of the object surface formed using the collection system to determine an index of motion, such as a blood flow parameter in biological tissue. - The system can generate visually-perceivable outputs representing quantified changes in retinal hemodynamics or cardiac parameters (including systolic/diastolic peaks, crest time, and augmentation index).
Multiplexed and variable-parameter illumination with fiber structuring
Different illumination lights (e.g., with differing degrees of coherence, wavelength, or polarization) can be delivered simultaneously or in a time-multiplexed fashion through the same optical train via the optical fiber. The system's structure enables complete or spatially separated illumination at the output facet, and allows for system alignment using a second light with a differing optical parameter.
The claims cover structured illumination and collection to achieve spatially-selective, high-resolution, contrast-free motion and blood flow quantification, with unique dual-parameter optical fiber input, annular or arcuate illumination patterns, polarization gating, and programmable data processing for versatile imaging applications.
Stated Advantages
Enables non-contact, non-intrusive, high-speed, and wide-field imaging of blood flow and vascular function.
Provides spatially uniform and glare-free illumination while avoiding specular reflections and scattering artifacts.
Allows for quantitative assessment of both anatomical and functional changes in tissues, especially in the retina.
Supports the usage of different illumination parameters (wavelength, coherence, polarization) and multiplexed protocols in the same optical pathway.
Facilitates early detection, improved disease management, and identification of novel biomarkers for retinal, neurodegenerative, and systemic cardiovascular diseases.
Adaptable design permits use across varied species and anatomical differences by enabling easy adjustment of optical elements.
Documented Applications
Diagnosis, study, and management of neurodegenerative conditions such as mild cognitive impairment and Alzheimer's disease using retinal blood flow assessment.
Quantification and monitoring of systemic cardiovascular diseases, including athero- and arteriosclerosis, coronary artery occlusion, and hypertension.
Early detection and longitudinal monitoring of retinal vascular diseases and dysfunction, exemplified by branch retinal vein occlusion (BRVO) in animal models.
Assessment of cardiac and systemic vascular function parameters, such as heart rate, vessel stiffness, peripheral resistance, contractility, and pulse propagation, via retinal imaging.
Contrast-free, wide-field mapping of blood flow and vascular morphology in biological tissues for both clinical and pre-clinical studies.
Supplementary use in imaging processes employing fluorescence or for obtaining spectroscopic information, including non-contact determination of blood oxygenation.
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