Hyperreflective Dots in Central Fovea Visualized by a Novel Application of Visible-Light Optical Coherence Tomography.

Visible-light optical coherence tomography (vis-OCT) is a novel noninvasive retinal imaging system that offers improved resolution compared to conventional near-infrared (NIR) OCT systems. Here, we utilized vis-OCT to produce fibergrams (vis-OCTF) for the first time in human patients, enabling visualization and precise quantification of hyperreflective dots in the central fovea in two patients. We also directly compare the imaging qualities of conventional vis-OCT and NIR-OCT.

Freeform robotic optical coherence tomography beyond the optical field-of-view limit.

Imaging complex, non-planar anatomies with optical coherence tomography (OCT) is limited by the optical field of view (FOV) in a single volumetric acquisition. Combining linear mechanical translation with OCT extends the FOV but suffers from inflexibility in imaging non-planar anatomies. We report the freeform robotic OCT to fill this gap.

Adaptive balanced detection spectral domain optical coherence tomography.

Balanced detection optical coherence tomography (BD-OCT) enables near-shot noise-limited imaging by suppressing wavelength-dependent relative intensity noise (RIN) originating from the light source. In spectral-domain BD-OCT (SD-BD-OCT), the level of RIN suppression relies on the co-registration accuracy of the spectra simultaneously captured by two independent spectrometers. However, existing matching methods require careful pre-calibration using a RIN-dominated dataset or subjective post-processing using a signal-dominated dataset.

Adaptive spectroscopic visible-light optical coherence tomography for clinical retinal oximetry.

Background: Retinal oxygen saturation (sO) provides essential information about the eye's response to pathological changes that can result in vision loss. Visible-light optical coherence tomography (vis-OCT) is a noninvasive tool that has the potential to measure retinal sO in a clinical setting. However, its reliability is currently limited by unwanted signals referred to as spectral contaminants (SCs), and a comprehensive strategy to isolate true oxygen-dependent signals from SCs in vis-OCT is lacking.

High-Speed Balanced-Detection Visible-Light Optical Coherence Tomography in the Human Retina Using Subpixel Spectrometer Calibration.

Increases in speed and sensitivity enabled rapid clinical adoption of optical coherence tomography (OCT) in ophthalmology. Recently, visible-light OCT (vis-OCT) achieved ultrahigh axial resolution, improved tissue contrast, and provided new functional imaging capabilities, demonstrating the potential to improve clinical care further. However, limited speed and sensitivity caused by the high relative intensity noise (RIN) in supercontinuum lasers impeded the clinical adoption of vis-OCT.

Intrinsic spectrally-dependent background in spectroscopic visible-light optical coherence tomography.

Visible-light optical coherence tomography (vis-OCT) has enabled new spectroscopic applications, such as retinal oximetry, as a result of increased optical absorption and scattering contacts in biological tissue and improved axial resolution. Besides extracting tissue properties from back-scattered light, spectroscopic analyses must consider spectral alterations induced by image reconstruction itself. We investigated an intrinsic spectral bias in the background noise floor, which is hereby referred to as the spectrally-dependent background (SDBG).

Visible-Light Optical Coherence Tomography Fibergraphy for Quantitative Imaging of Retinal Ganglion Cell Axon Bundles.

Purpose: To develop a practical technique for visualizing and quantifying retinal ganglion cell (RGC) axon bundles .

Methods: We applied visible-light optical coherence tomography (vis-OCT) to image the RGC axon bundles, referred to as vis-OCT fibergraphy, of healthy wild-type C57BL/6 mice. After vis-OCT imaging, retinas were flat-mounted, immunostained with anti-beta-III tubulin (Tuj1) antibody for RGC axons, and imaged with confocal microscopy.

Spectrally dependent roll-off in visible-light optical coherence tomography.

Recent development of visible-light optical coherence tomography (vis-OCT) has introduced new applications for noninvasive spectroscopic imaging. However, the measured spectra may be altered by spectrally dependent roll-off (SDR). We formulated a mathematical model for SDR that accounted for nonuniform wavenumber spacing, optical aberrations, and misalignments in the spectrometer.

Longitudinal deep-brain imaging in mouse using visible-light optical coherence tomography through chronic microprism cranial window.

We longitudinally imaged both the superficial and deep cortical microvascular networks in brains of healthy mice and in a mouse model of stroke using visible-light optical coherence tomography (vis-OCT). We surgically implanted a microprism in mouse brains sealed by a chronic cranial window. The microprism enabled vis-OCT to image the entire depth of the mouse cortex.

Speckle reduction in visible-light optical coherence tomography using scan modulation.

We present a technique to reduce speckle in visible-light optical coherence tomography (vis-OCT) that preserves fine structural details and is robust against sample motion. Specifically, we locally modulate B-scans orthogonally to their axis of acquisition. Such modulation enables acquisition of uncorrelated speckle patterns from similar anatomical locations, which can be averaged to reduce speckle.

Designing visible-light optical coherence tomography towards clinics.

Background: The capabilities of visible-light optical coherence tomography (vis-OCT) in noninvasive anatomical and functional retinal imaging have been demonstrated by multiple groups in both rodents and healthy human subjects. Translating laboratory prototypes to an integrated clinical-environment-friendly system is required to explore the full potential of vis-OCT in disease management.

Methods: We developed and optimized a portable vis-OCT system for human retinal imaging in clinical settings.

Dual-wavelength photothermal optical coherence tomography for imaging microvasculature blood oxygen saturation.

A swept-source dual-wavelength photothermal (DWP) optical coherence tomography (OCT) system is demonstrated for quantitative imaging of microvasculature oxygen saturation. DWP-OCT is capable of recording three-dimensional images of tissue and depth-resolved phase variation in response to photothermal excitation. A 1,064-nm OCT probe and 770-nm and 800-nm photothermal excitation beams are combined in a single-mode optical fiber to measure microvasculature hemoglobin oxygen saturation (SO(2)) levels in phantom blood vessels with a range of blood flow speeds (0 to 17  mm/s).

Use of near-infrared luminescent gold nanoclusters for detection of macrophages.

We determined the effect of aggregation and coating thickness of gold on the luminescence of nanoparticles engulfed by macrophages and in gelatin phantoms. Thin gold-coated iron oxide nanoclusters (nanoroses) have been developed to target macrophages to provide contrast enhancement for near-infrared optical imaging applications. We compare the brightness of nanoroses luminescent emissions in response to 635 nm laser excitation to other nanoparticles including nanoshells, nanorods, and Cy5 conjugated iron oxide nanoparticles.

In vivo depth-resolved oxygen saturation by Dual-Wavelength Photothermal (DWP) OCT.

Microvasculature hemoglobin oxygen saturation (SaO2) is important in the progression of various pathologies. Non-invasive depth-resolved measurement of SaO2 levels in tissue microvasculature has the potential to provide early biomarkers and a better understanding of the pathophysiological processes allowing improved diagnostics and prediction of disease progression. We report proof-of-concept in vivo depth-resolved measurement of SaO(2) levels in selected 30 µm diameter arterioles in the murine brain using Dual-Wavelength Photothermal (DWP) Optical Coherence Tomography (OCT) with 800 nm and 770 nm photothermal excitation wavelengths.

Lamina-specific anatomic magnetic resonance imaging of the human retina.

Purpose: Magnetic resonance imaging (MRI) of the human retina faces two major challenges: eye movement and hardware limitation that could preclude human retinal MRI with adequate spatiotemporal resolution. This study investigated eye-fixation stability and high-resolution anatomic MRI of the human retina on a 3-Tesla (T) MRI scanner. Comparison was made with optical coherence tomography (OCT) on the same subjects.

Depth-resolved blood oxygen saturation measurement by dual-wavelength photothermal (DWP) optical coherence tomography.

Non-invasive depth-resolved measurement of hemoglobin oxygen saturation (SaO(2)) levels in discrete blood vessels may have implications for diagnosis and treatment of various pathologies. We introduce a novel Dual-Wavelength Photothermal (DWP) Optical Coherence Tomography (OCT) for non-invasive depth-resolved measurement of SaO(2) levels in a blood vessel phantom. DWP OCT SaO(2) is linearly correlated with blood-gas SaO(2) measurements.

Depth resolved photothermal OCT detection of macrophages in tissue using nanorose.

Application of photothermal Optical Coherence Tomography (OCT) to detect macrophages in ex vivo rabbit arteries which have engulfed nanoclusters of gold coated iron oxide (nanorose) is reported. Nanorose engulfed by macrophages associated with atherosclerotic lesions in rabbit arteries absorb incident laser (800nm) energy and cause optical pathlength (OP) variation which is measured using photothermal OCT. OP variation in polydimethyl siloxane tissue phantoms containing varying concentrations of nanorose match values predicted from nanoparticle and material properties.

Comparison of pulsed photothermal radiometry, optical coherence tomography and ultrasound for melanoma thickness measurement in PDMS tissue phantoms.

Melanoma accounts for 75% of all skin cancer deaths. Pulsed photothermal radiometry (PPTR), optical coherence tomography (OCT) and ultrasound (US) are non-invasive imaging techniques that may be used to measure melanoma thickness, thus, determining surgical margins. We constructed a series of PDMS tissue phantoms simulating melanomas of different thicknesses.

Effect on blood glucose monitoring of skin pressure exerted by an optical coherence tomography probe.

We proposed to use optical coherence tomography (OCT) for continuous noninvasive blood glucose monitoring, and recently we significantly improved the sensitivity of this technique. The accuracy of OCT glucose monitoring is limited by several factors, including variation of tissue pressure exerted by the OCT probe. We studied the influence of high (>10 kPa) and low (<1 kPa) pressure levels on OCT blood glucose monitoring.

Prediction capability of optical coherence tomography for blood glucose concentration monitoring.

Background: Optical coherence tomography (OCT) has been shown to be a promising optical approach to noninvasive monitoring of blood glucose concentration because of its capability of probing optical properties at different depths in tissue with high resolution. This article investigates the capability of OCT to predict changes in blood glucose concentration.

Methods: We varied blood glucose concentration in the physiological range in three sets of experiments.

Correlation between optical coherence tomography images and histology of pigskin.

Noninvasive imaging techniques such as optical coherence tomography (OCT) are being widely used for early diagnostics of a variety of pathologies. Traditional tissue preparation for histological evaluation alters the dimensions of histological images such that differences between the dimensions of histologic and OCT images can be as great as 2.5-fold.

Influence of osmolytes on in vivo glucose monitoring using optical coherence tomography.

Diabetes mellitus and its complications are the third leading cause of death in the world, exceeded only by cardiovascular disease and cancer. Tighter monitoring and control of blood glucose could minimize complications associated with diabetes. Recently, optical coherence tomography (OCT) for noninvasive glucose monitoring was proposed and tested in vivo.

In vivo study of glucose-induced changes in skin properties assessed with optical coherence tomography.

Recently, our in vivo studies demonstrated a strong correlation between blood glucose concentration and the slope of the optical coherence tomography (OCT) signal when the probing beam was scanned over a straight line. To improve the sensitivity of OCT for blood glucose monitoring, two-dimensional (2D) lateral scanning of the OCT probing beam was proposed. Depth-dependent changes in pig skin properties with variation of blood glucose concentration were revealed due to significant suppression of speckle noise and motion artefacts in 2D scanning mode.

In vivo visualization of Tradescantia leaf tissue and monitoring the physiological and morphological states under different water supply conditions using optical coherence tomography.

The optical coherence tomography (OCT) capabilities of plants were evaluated using leaves of Tradescantia pallida (Rose) D. Hunt. The internal structure of the leaf tissues was visualized in vivo and the physiological and morphological states of the tissues under different water supply conditions were monitored using OCT.